- Email: [email protected]
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II) complexes with η2 alkene, nitrogen and phosphorus and sulphur donor ligands
Polyhedron Vol. 7, No. 19/20, pp. 19531964, Printed in Great Britain
1988 0
0277-5387/88 S3.00+ .oO 1988 Pergarnon Press plc
SYNTHESIS AND SPECTROSCOPIC CHARACTERISTICS OF TRIMETHYLSILYLMETHYLPLATINUM(II) COMPLEXES WITH q* ALKENE, NITROGEN AND PHOSPHORUS AND SULPHUR DONOR LIGANDS S. KATHERINE
THOMSON
and G. BRENT YOUNG*
Inorganic Chemistry Labora.tories, Imperial College of Science and Technology, London SW7 2AY, U.K. Abstract-Various complexes cis-LzPtR2 (L = py, PMe3, PEt3, PMe,Ph, PMePh,, PPh3, L2 = bipy, Me,bipy, bipym, bipyz, Me4phen, Ph,phen, dppm, dppe, dppf, R = CH2SiMe,) have been synthesized by displacement of the diene from (cod)PtR, or (nbd)PtR2 or by sulphide replacement in [(dms)PtR2],. fTerpyPtR]BF, has been synthesized via (cod)Pt(R)(X), (X = Cl, I). The complexes have been characterized by IR, ‘H, 13CNMR and, where appropriate, 3‘P NMR and electronic spectroscopy. Trimethylsilylmethyl exerts a weaker trans-influence than neopentyl which, on NMR evidence, has the stronger Pt--C bond.
There is continued activity in evaluation of the rearrangement mechanistics of organo-transition metals as a route to greater understanding of their role in metal-mediated transformations of hydrocarbons. Common labilizing pathways for many alkylmetals feature hydrogen transfers, most often from a /?-carbon site. This feature, early recognized by Wilkinson and a few others, led to rapid development in alkyl transition metal chemistry using “j-elimination stabilized” ligands. ’ When this option is restricted, activation of more remote C-H bonds may occur.’ Again, the earlier examples were characterized by Wilkinson and co-workers. Neopentyl metals, for example, particularly lowvalent derivatives of the later d-block, have been observed widely to undergo such cyclizations to form metallacyclobutanes.3 The mechanistics have been elucidated elegantly for dineopentylplatinum(II).3” Trimethylsilylmethyl metals may also undergo y-C-H transfer, 3,4but, impressionistically, they are more inert.3 Other than a few thermochemical studies which document the thermodynamic differences in M-C bond strengths between M(CH,CMe3), and M(CH,SiMe3),4-which doubtless contribute to the rearrangement mechanistics where M-C homolysis is important-there has been little attempt to quantify and understand the kinetic effect of silicon on these intramolecular
*Author to whom correspondence should be ad-.
hydrogen transfers for d-block elements. An example in f-block chemistry has appeared.’ In parallel with our comparative studies of aromatic C-H activation in LzPt(CH2CMezPh)26 and L2Pt(CHzSiMezPh)2,7 we have now synthesized a wide variety of complexes, L2Pt(CH2SiMe3)2, for comparison with analogous neopentyl derivatives.3a Here we present some notable characteristics. A few of these complexes have been reported previously.8 In these cases, we present synthetic improvements and new spectroscopic data. EXPERIMENTAL General and instrumental
Elemental analyses were performed by Imperial College Microanalytical Laboratories. NMR spectra were recorded on Briiker WM 250 (‘H 250.13 MHz, 13C 62.9 MHz) and Jeol FX 90 Q (‘H 89.55 MHz, 31P 36.21 MHz) spectrometers. IR data were collected on a Perkin-Elmer 683 instrument as 4% KBr dispersions and electronic spectra were recorded on a Shimadzu UV-160 spectrometer. All reactions were carried out under argon, using standard anaerobic techniques.’ The apparatus was thoroughly flame-dried prior to use, and solvents were distilled from sodium under nitrogen. Diethyl ether and n-hexane were distilled from sodiumbenzophenone.
1953
1954
S. K. THOMSON and G. B. YOUNG
Chloromethyltrimethylsilane, 1,5-cyclooctadiene (cod), bicyclo[2.2.l]hepta-2,5-diene (nbd), dimethyl sulphide (dms), 2,2’-bipyridyl (bipy), 4,4’-dimethyl2,2’-bipyridyl (Mezbipy), 2,2’-bipyrazyl (bipyz), 1, lo-phenanthroline (phen), 4,7-diphenyl- 1, lophenanthroline (Ph,phen), 3,4,7,8_tetramethyll,lO-phenanthroline (Me,phen), 2,2’ : 62” terpyridyl (terpy), silver tetrafluoroborate, triphenylphosphine, bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), l,l’-bis(diphenylphosphino)ferrocene (dppf), toluene-ds and benzene-d6 were all used as supplied by the Aldrich Chemical Company. 2,2’-Bipyrimidyl (bipym) was obtained from Lancaster Synthesis. Trimethylphosphine, triethylphosphine, diphenylmethylphosphine and dimethylphenylphosphine were used as supplied by Strem Chemicals. Pyridine (py) was supplied by Rose Chemicals and distilled from sodium hydroxide under nitrogen prior to use. Dichloro( 1,5-cyclooctadiene) platinum(II), dichloro(bicyclo[2.2.l]hepta - 2,5 - diene)platinum(II) and cis-dichlorobis(dimethylsulphide)platinum(II) were prepared using published methods.‘W’2 Preparation of chloromagnesiomethyltrimethylsilane
A solution of chloromethyltrimethylsilane (5.0 g, 41 .Ommol) in Et,0 (40 cm3) was added dropwise to a suspension of magnesium shot (5.0 g, 206.0 mmol) in diethyl ether (10 cm3) previously activated by the introduction of 1,Zdibromoethane (0.25 cm’). After 2 h stirring at ambient temperature the resulting solution of Mg(CH,SiMe,)Cl was filtered off. (Yield, lOO%.) Preparation of bis(trimethylsilylmethyl)( 1,5-cyclooctadiene)platinum(II)
A solution of Mg(CHzSiMe3)C1 (30.0 cm3, 24.6 mmol) was added dropwise at -78°C to a stirred suspension of (cod)PtCl, (3.0 g, 8.02 mmol) in diethyl ether (20 cm3). The mixture was allowed to reach ambient temperature and stirred for 15 h. On cooling to -2O”C, saturated aqueous ammonium chloride (15 cm3) was added dropwise with stirring. The ether fraction, after separation, was dried over MgS04 and concentrated in vacua to yield large colourless crystals of the product. (Yield, 2.87 g, 75%.) IR: 2999w, 2994s, 2992sh, 2885s, 2855sh, 152Ow, 1475w, 1474sh, 145Ow, 1435m, 1405wb, 1365w, 134Om, 131Ow, 1305sh, 1285wb, 1255sh, 1235s, llSOw, 116Ow, 1085w, 1075w, lOlOmb, 99Ow, 98Ow, 950m, 840sb, 820sb, 785sh, 76Om, 745m, 712m, 675s, 605w, 535wb, 46Owb, 27Ow, 265m, 26Ow, 255w, 235m, 23Om, 215s, 210s.
Preparation of chloro(trimethylsilylmethyl)(1,5cyclooctadiene)platinum(II)
A solution of 0.42 M HCl in Et,0 (1.05 cm3, 0.42 mmol) was added dropwise to a stirred solution of (cod)Pt(CH,SiMe,), (0.20 g, 0.42 mmol) in diethyl ether (20 cm3) at - 78°C. The mixture was allowed to warm to ambient temperature and stirred for 24 h. The solvent was removed in vacua to yield colourless crystals of the product. (Yield, 0.16 g, 89%.) IR: 2945s, 2889m, 2843s, 27OOw, 1546w, 1475m, 1454w, 1436m, 1428m, 1408m, 1362m, 1344m, 1317w, 1262s, 1245s, 1183m, 1097sb, 1041s, 1023s, 987m, 96Om, 902w, 865s, 828s, 803sb, 776sb, 768m, 747w, 715m, 683m, 615w, 54Ow,479m, 432w, 392mb, 313m, 277~.
Preparation of iodo(trimethylsilylmethyl)( 1,5-cyclooctadiene)pZatimun(II)
(cod)Pt(CH$iMe,)Cl (0.30 g, 0.70 mmol) was dissolved with KI (0.83 g, 5.0 mmol) in acetone (20 cm3) and stirred for 24 h. The acetone was removed in vacua and the residue extracted into Et?0 (40 cm3). The solution was filtered, concentrated and cooled to - 25°C to yield pale yellow plates which were washed with cold hexane (2 cm’). (Yield, 0.28 g, 74%.) IR : 303 lw, 3006m, 2946m, 2923m, 2887m, 2872m, 2835w, 1481w, 1451w, 1428m, 1404w, 1386w, 1374m, 1340m, 1317w, 1292w, 1251m, 124Os, llSlw, 109Ow, 1075w, 1045m, 1002m, 987m, 961m, 902m, 876w, 838sh, 821s, 794m, 760m, 752w, 721m, 695w, 682m, 612w, 567w, 533w, 471w, 428w, 264w, 243m, 24Om, 229m.
Preparation of bis(trimethylsilylmethyr)(bicyclo [2.2.l]hepta-2,5-diene)pZatinum(II)
To a stirred suspension of (nbd)PtCIZ (1.36 g, 3.8 mmol) in diethyl ether (20 cm3) was added dropwise at - 78°C a solution of Mg(CH,SiMe,)Cl (13.9 cm3, 11.4 mmol). The mixture was allowed to reach ambient temperature and stirred for 15 h, then cooled to - 20°C and saturated aqueous NH&l (10 cm3) added dropwise. The ether layer was separated and dried over MgSO, and concentrated in vacua. The cream-coloured crystalline product was further recrystallized from a mixture of Et@-hexane. (Yield, 1.21 g, 69%.) IR: 3004w, 2948s, 2896m, 2850m, 2835m, 2789m, 1433m, 141Ow, 1369w, 1357w, 1308m, 1251m, 124Os, 1188m, 1154w, llOOw, 1098w, 1008m, 989m, 960m, 934m, 924w, 886m, 85Os, 827s, 757sh, 749m, 715m, 676m, 612w, 535w, 488w, 285w, 250m, 244m, 237s, 230s.
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II) Preparation of [bis(trimethylsilylmethyl)(dimethylsulphide)platinum(II)]~ (n = 2 or 3)
To a stirred suspension of (dms)zPtC1z (1.5 g, 3.84 mmol) in diethyl ether (10 cm’) at - 78°C was added dropwise a solution of Mg(CH$iMe,)Cl (14.0 cm3, 11.5 mmol). The mixture was stirred at ambient temperature for 2 h, then cooled to - 20°C and saturated aqueous NH&l (10 cm’) added. The ethereal layer was filtered onto MgSO, and activated charcoal, then after filtration, concentrated in vacua and cooled to -25”C, yielding a white solid. (Yield, 1.82 g, W!!.) IR: 2998m, 2946m, 2916m, 2895m, 2842m, 1458w, 1425w, 1413w, 1358w, 1262s, 1239s, 1096sbr, 1026s, 985s, 947w, 853s, 823s, SOOs,77Om, 747m, 715m, 679s, 609w, 545w, 453w, 408w, 283w, 275w, 266w, 261m, 256m, 252s, 245s, 23Os, 224s. Preparation of bis(trimethylsilylmethyl)(2,2’-bipyridyl)platinum(II)
[(dms)Pt(CH,SiMe,)J (n = 2 or 3) (0.10 g) was dissolved together with 2,2’-bipyridyl (0.04 g, 0.24 mmol) in dry deoxygenated toluene (5 cm’) and the solution kept at room temperature for two days. Any excess free ligand was removed by extraction with aqueous ferrous sulphate solution. The organic phase was then dried over MgS04 and concentrated in vacua, then cooled to - 25°C. The deep red crystals formed were filtered off and washed with cold n-hexane. (Yield, 0.11 g, 85% .) IR : 2942m, 2868m, 2829m, 1599w, 1468m, 1445m, 1306w, 1262m, 1237m, 1097mbr, IOllmbr, 955w, 849s, 821sbr, 757m, 745s, 728m, 712m, 672m, 555w, 254m, 248s, 24Os, 229s. Bis(trimethylsilylmethyl)(4,4’ ridyl)platinum(II)
- dimethyl - 2,2’ - bipy-
This was prepared according to the above procedure. Product: orange-red crystals from ether. (Yield, 87%.) IR: 2946m, 2869m, 2829m, 1616m, 1553w, 148Ow, 1446w, 1414w, 1298w, 1261w, 1233m, 1098wbr, lOlSmbr, 973w, 955w, 928w, 888w, 855s, 826s, 774w, 742w, 715w, 672m, 6OOw, 55Ow, 517w, 425w, 332w, 295w, 28Ow, 257w, 245w, 239m, 234m, 23Os, 224m. Preparation of bis(trimethylsilylmethyl)(2,2’-bipyrimidyl)platinum(II)
(cod)Pt(CH,SiMe,), (0.20 g, 0.42 mmol) was dissolved together with 2,2’-bipyrimidine (0.18 g, 0.84 mmol) in dry deoxygenated toluene (10 cm3). The solution was heated to 60°C for 14 days, then any
1955
complexes
excess free ligand removed by extraction with aqueous ferrous sulphate solution. The remaining organic phase was then concentrated, n-hexane (2 cm3) added and the mixture cooled. The claret crystals collected were washed with cold hexane. (Yield, 0.19 g, 86%.) IR: 3083w, 3042w, 2946m, 2877m, 2839m, 2729m, 1627wbr, 1572m, 1547m, 145Ow, 1405s, 1367w, 1332w, 1260sh, 1233m, 1199w, 1145w, 11 low, 1102w, 1076w, 1013m, lOOOw,956w, 854s, 826s, 815sh, 775m, 753s, 71Ow, 681m, 676m, 663m, 638w, 61Ow, 563w, 487w, 44Ow, 341w, 27Ow, 257~. Bis(trimethylGlylmethyl)(l,l0
- phenanthroline)plati-
num(I1) Product: red crystals from hot toluene. (Yield, 83%.) IR: 3057w, 2954m, 294Om, 2889w, 2868m, 2859m, 2824m, 1627w, 1578w, 1423w, 1415m, 1365m, 1338w, 1251m, 1236m, 1219m, 1202m, 1144w, 985m, 965m, 952w, 944m, 907w, 851s, 839s, 765m, 745m, 734w, 720m, 674m, 61 lw, 555w, 508w, 49Ow, 454w, 429w, 278w, 253~. Bis(trimethylsilylmethyl)(4,7 anthroline)platinum(II)
- diphenyl-
1,lO -phen-
Product : large red crystals from toluene. (Yield, 92%.) IR: 3058w, 303Ow, 2948m, 2861m, 2840m, 2725w, 1617w, 1592w, 1556w, 1494w, 1447w, 1435w, 1422m, 1415m, 1395w, 1362w, 126Ow, 1249m, 1236m, 1077wb, 102Om, 1003m, 962w, 949w, 907w, 854s, 824s, 764s, 748m, 736m, 717w, 7Ols, 676m, 632w, 585w, 548w, 465w, 407w, 255w, 246m, 238s. Bis(trimethyMylmethyl)(3,4,7,8 phenanthroline)platinum(II)
- tetramethyl - 1,lO -
Product: orange needles from toluene. (Yield, 86%.) IR: 2946m, 2888w, 2853m, 2835m, 161Ow, 1579w, 1514w, 1425m, 139Ow, 1263w, 1235m, 1093w, 1012w, 947w, 918w, 85Os, SlSs, 773w, 747w, 722w, 711w, 674m, 609w, 567w, 329~. Preparation of bis(trimethylsilylmethyl)(2,2’-bipyrazyl)platinum(II)
(nbd)Pt(CH$iMe3)* (0.20 g, 0.43 mmol) and 2,2’-bipyrazyl (0.07 g, 0.43 mmol) were dissolved together in toluene (10 cm’) in a grease-free sealed vessel, and the solution maintained at ambient temperature for 28 days. The purple product was recrystallized from toluenehexane. (Yield, 0.20 g, 88%.) IR: 3093w, 3058w, 2944m, 2878m, 2836m, 1635wb, 1580m, 1575m, 1469m, 1464m,
1956
S. K. THOMSON
and G. B. YOUNG
1407m, 1400m, 1368w, 1304w, 1261s, 1252s, 1237s, 1176m, 1166m, llOOmb, 1070m, 1034m, 1019m, 977wsh, 95Ow, 931w, 852s, 834s, 805sh, 765w, 713m, 679m, 623w, 558w, 395w, 267w, 252m.
Preparation of trimethylsilylmethyl(2,2 : 6’,2”-terpyridyl)platinum(II) tetrajluoroborate
(cod)Pt(1)(CH2SiMe3) (“.20 gy o.39 -01) was dissolved together with 2,2’ : 6’,2”-terpyridyl (0.09 g, 0.39 -01) in acetone (15 cm3) and the mixture stirred for 40 h to yield an orange solution. AgBF, (0.08 g, 0.39 mmol) in acetone (10 cm3) was added via a cannula and the solution filtered to yield an orange-yellow solution. On concentration in uacuo, bright yelloworange needles were formed. (Yield, 0.18 g, 76%.) IR: 3116w, 309Ow, 3075w, 2955m, 289Ow, 2853w, 1610m, 1599m, 1573w, 1472m, 1452m, 1401w, 1315w, 1289w, 1261m, 1239m, 1188w, 1169w, 1142s 1098s, 967w, 95Ow, 853m, 829m, 800m, 774m, 75Ow, 729w, 682w, 521w, 258w, 254w, 246w, 238s 23Ow, 223m.
Preparation of cis-bis(pyridine)bis(trimethylsilylmethyl)platinum(II)
(cod)Pt(CH2SiMe3)2 (0.20 g, 0.42 mmol) was dissolved in neat pyridine (5 cm3) and heated to 60°C for three days. The excess pyridine was removed in oacuo and the resulting oily solid recrystallized from ether-hexane to yield off-white crystals of the product. (Yield, 77%.) IR: 3077w, 2942s, 2887m, 2868m, 2823s 2712w, 1971w, 1915w, 16OOm, 1572w, 1479m, 1446s, 1402w, 1359w, 1348w, 1235s 1205w, 1149w, 1067m, 1045w, 1005m, 974w, 964w, 874s, 854s, 823s, 756s, 746m, 719m, 694s, 683m, 667m, 636w, 607w, 558w, 277w, 238m, 227s.
Prepared according to the same procedure were : cis - Bis(trimethylsilylmethyl)bis(triethylphosphine) platinum(I1) Product : large colourless crystals from toluene. (Yield, 95%.) IR : 2964s, 2947s 2936~, 2918m, 2893m, 1732w, 1633w, 1455m, 1433m, 1405w, 1381w, 1248m, 1235s 1099w, 1032s, 993w, 95Ow, 849s, 821s, 755s, 718s, 672m, 624w, 514w, 41Ow, 371w, 334w, 245m, 234s. cis - Bis(trimethylsilylmethyl)bis(dimethylphenylphosphine)platinum(II) Product : large colourless crystals from CH2C12/MeOH. (Yield, 82%.) IR: 3071w, 2982m, 2943m, 2922m, 2915m, 2884m, 1437m, 1421w, 1411w, 131Ow, 1294w, 1282w, 1275w, 1262m, 1246m, 1234m, llOOm, 1072w, 1052w, 1029w, lOOlw, 902s, 85Os, 823s 772w, 746m, 739m, 723w, 706m, 538w, 5Olw, 488w, 45Ow, 432w, 417w, 409m, 395w, 313w, 304w, 294w, 286w, 264m, 257s 248s, 240s 230s 224s. cis
- Bis(trimethylsilylmethyl)bis(diphenylmethylphosphine)platinum(II)
Product : colourless crystals from n-hexane. (Yield, 88%.) IR: 3075w, 3057w, 2983w, 2944m, 2920m, 2887m, 1963w, 1884w, 1588w, 1573w, 1483w, 1436s 142Ow, 137Ow, 1329w, 1307w, 1279w, 1248m, 1238m, 1231m, 1193w, 1156w, 1096m, 1077w, 1028w, 1013w, lOOOw,96Om, 914w, 894s, 884s, 875s, 851s 820s 75Os, 738s, 73Os, 698s 674m, 618w, 605w, 525m, 513s, 484m, 433m, 416m, 362w, 266w, 246w, 242m, 237m, 232s, 227s. cis - Bis(trimethylsilylmethyl)bis(triphenylphosphine)platinum(II)
Preparation of cis-bis(trimethylsilylmethyl)bis(trimethylphosphine)platinum(II)
To a solution of (cod)Pt(CH2SiMe3)2 (0.20 g, 0.42 mmol) in dry deoxygenated toluene (5 cm3) was added PMe3 (0.09 cm3, 0.86 mmol) via a syringe and the solution was heated to 60°C for 14 days. The solvent was then removed in uacuo and nhexane (2 cm’) added to the resultant colourless oil. Cooling to -25°C produced large colourless crystals of the product. (Yield, 0.22 g, loo%.) IR : 2946m, 2913m, 288Om, 1633vw, 1421w, 1301w, 1284m, 1262m, 1246m, 1235s, 1097mbr, 1022mbr, 963s, 943s, 85Os, 821s, 771w, 742w, 723m, 708m, 671m, 522w, 383w, 359w, 283w, 259w, 251w, 246m, 242m, 235s 23Os, 225s.
Product : cciourless crystals from toluene. (Yield, 84%.) IR: 3441w, 3055m, 3002m, 2938m, 2879m, 1746w, 1587w, 1484m, 1478m, 1438m, 1433m, 1313w, 1262w, 1249m, 1236m, 1182w, 1159w, 1119w, 1098m, 1091w, 1028w, 999w, 956w, 850s 825s, 751s 741m, 720m, 706s, 693sh, 619w, 54Os, 524s 512s, 491m, 464w, 453w, 432w, 421w, 281w, 268m, 251m, 243m, 237s 230s 225s. Bis(trimethylsi1ylmethyl)[bis(dipheny1phosphino)me thane]platinum(II)
Product : colourless crystals from toluene-n-hexane. (Yield, 83%.) IR: 3058w, 3005w, 2945m, 2875m, 2862m, 2836m, 1587w, 1572w, 1482m,
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II) complexes 1436s 1384w, 136Ow, 1329w, 1309w, 1277w, 1249s 1238s 1185w, 1098m, 1084m, 1028w, lOOOw,97Ow, 935w, 849s 822s 765m, 753s 737s, 724s 702s 692m, 674sh, 618w, 607w, 541m, 502s, 477m, 443w, 42Ow, 358w, 302w, 278w, 268w, 262w, 252m, 248m, 243m, 238s 230s 225s. Bis(trimerhylsilylmethyl)[l,2 - bis(diphenylphosphin0) ethune]plutinum(II) Product : colourless crystals from toluene. (Yield, 85%.) IR: 3445w, 3058m, 2942m, 2886m, 2855m, 1966w, 19OOw, 1825w, 1589w, 1573w, 1483m, 1436s 1407m, 131Ow, 1262s 1249m, 1236s, 1186w, 1101s 1027sh, 948s 857s, 846s 821s, 747s 713m, 694s 681m, 675m, 653w, 604w, 533s 482m, 469w, 436w, 4OOw,356w, 3Olw, 29Ow, 254w, 246w, 239m, 233m, 230s. Preparation of bis(trimethylsilylmethyl)[l,l’-bis(diphenylphosphinofirrocenelplatinum(I1)
(nbd)Pt(CH,SiMe3)z (0.20 g, 0.43 mmol) was dissolved together with dppf (0.23 g, 0.43 mmol) in dry deoxygenated toluene (10 cm3) and the solution maintained at 60°C for 20 days. The solvent was then removed in r~ucuo and the orange solid recrystallized from toluene (2 cm3) to yield orange crystals of the product. (Yield, 0.38 g, 96%.) IR: 3051m, 2942m, 2897m, 197Ow, 1618w, 1587w, 1571w, 148Om, 1434s 1384w, 1367w, 1308w, 1261m, 125Om, 1236s 1194w, 1181w, 1165m, 1097s, 107Ow, 1058w, 1038m, 1026m, lOOOw,959w, 850s 824s 744s, 719m, 694s 641w, 619w, 608w, 550s 527m, 514s 492s 477w, 468m, 459w, 449w, 439m, 348w, 278w, 27Ow, 26Ow, 247m, 238m, 233s 224m. RESULTS
AND DISCUSSION
Synthesis of L2PtR2
Where LZ = 1,5-cyclooctadiene the complex could be prepared in 75% yield as a colourless crystalline solid by reaction of the Grignard reagent with (cod)PtCl,. This is a considerable improvement on the method previously reported.8b The related new derivative, bis(trimethylsilylmethy1) (bicycle-[2.2.1]-hepta-2,5_diene)platinum(II) was prepared analogously. Treatment of (dms),PtCl, with trimethylsilyhnethyl magnesium chloride resulted in the formation of [@drns)Pt(CH,SiMe,)23,. Our spectroscopic observations (and those previously publishedsb) do not allow distinction between dimeric and trimeric structures. Subsequent replacement of the diene or dimethylsulphide ligands with a series of nitrogen
1957
donor ligands yielded highly coloured crystalline products, air-inert as solids. The displacement reaction with the diene complexes is generally complete in 1430 days at 60°C ; nbd is more labile than cod. Dms is replaced by 2,2’-bipyridyl and 4,4’-dimethyl-2,2’-bipyridyl in two days at room temperature and is clearly the most labile of the three. Deoxygenated solutions of these compounds in benzene and other hydrocarbon solvents are inert for indefinite periods. Reaction of the diene complexes with a series of phosphines yielded colourless, highly crystalline solids in almost quantitative yields. The ligand metathesis was generally complete within 14 days. These air-inert compounds do not decompose in deoxygenated hydrocarbon and chlorocarbon solvents. Colours and elemental compositions of all these complexes are detailed in Table 1. Spectroscopic characteristics
For numbering conventions employed, in accord with those previously used,6 see Fig. 1. (a) Electronic spectroscopy. The electronic spectra of complexes L2PtR, (LZ = N-donor ligand, R = trimethylsilylmethyl) were recorded as freshly prepared toluene solutions. They are characterized by two absorptions, I 1and &, attributable to dz-x* metal-ligand charge transfer (MLCT) transitions. ’ 3 The use of these bands in the analysis of the relative electronic effects of bidentate, heteroaromatic Ndonor ligands has been well documented. As the very intense x-x* transitions of the ligand often obscure the higher energy MLCT absorption &, the lower energy band, ;Zr, which reflects the energy difference between the metal (dz) HOMO and the (rc*) LUMO of the ligand, frequently features in comparisons within a series of such complexes. The energy of 1, increases in the order : bipyz < bipym < Ph,phen < bipy < Me,bipy < terpy < Me4phen. This is in full agreement with previous observations.6*1”‘6 MLCT transitions in complexes of this type occur at lower energies where the heteroaromatic ligands have electronegative ring atoms or substituents.” Proposedly, this arises from a lowering of the LUMO on the ligand, thus reducing the dx-n* energy gap. This explanation clearly accounts for the complexes of 2,2’-bipyrazyl and 2,2’-bipyrimidyl. An opposite effect can be invoked for the Mezbipy complex ; electron releasing substituents should raise the energy of the LUMO relative to that of bipy. As noted elsewhere, coordinated Ph,phen exhibits a lower energy absorption than phen, consistent with increased conjugation in the aromatic ligand.
1958
S. K. THOMSON and G. B. YOUNG Table 1. Physical data for LzPt(CH,SiMeJz Analytical data” H
Compound
C
(cod)Pt(Cl)(CH,SiMe,) (cod)Pt(I)(CH,SiMe,) (nbd)Pt(CHzSiMeS)z (bipy)Pt(CH,SiMe,), (Me,bipy)Pt(CH,SiMe,), (bipym)Pt(CHzSiMe3)2 (phen)Pt(CH,SiMe,), (Ph,phen)Pt(CH,SiMe& (Me,phen)Pt(CH,SiMe,), (bipyz)Pt(CH2SiMe& [(terpy)PtCH$iMe,]BF, (&Pt(CH$iMe& (Me3P)2Pt(CH,SiMeJ2 (Et3P)2Pt(CHzSiMes)z (Me,PhP),Pt(CH,SiMe,)(MePh,P),Pt(CH,SiMe,), (Ph,P),Pt(CHzSiMeS)z (dppm)Pt(CH,SiMe& (dppe)Pt(CH,SiMe,), (dppf)Pt(CH&Me&
33.6(33.8) 27.7(28.0) 39.1(39.0) 41.0(41.1) 43.3(43.4) 36.2(36.4) 43.4(43.7) 54.9(54.7) 47.2(47.6) 36.7(36.4) 37.4(37.8) 40.6(41.O) 32.2(32.2) 39.q39.q 44.5(44.6) 53.2(53.0) 59.3(59.7) 52.9(52.6) 53.6(53.2) 54.2(54.6)
5J5.4) 4.4(4.1) 6.6(6.5) 5.3(5.7) 6.3(6.2) 5.3(5.3) 5.5(5.5) 5.6(5.5) 6.0(6.3) 5.3(5.3) 4.0(3.8) 6.2(6.1) 7.6(7.7) 8.8(8.6) 6.9(6.9) 6.2(6.3) 5.9(5.9) 5.9(5.8) 6.1(6.0) 5.0(5.5)
N -
5.1(5.3) 4.8(5.1) 10.3(10.6) 5.1(5.1) 3.8(4.0) 4.4(4.6) 10.7(10.6) 6.3(7.0) 4.7(5.3) -
-
Colour Colourless Pale yellow Cream Red Orange-red Wine red Deep red Deep red Orange Deep purple Orange-yellow Cream Colourless Colourless Colourless Colourless Colourless Colourless Colourless Yellow
a Calculated values in parentheses.
The MLCT transition for bipy occurs at lower energy than that for phen, however, and so the extent of conjugation is not the only factor governing the energies of these transitions. (b) NMR spectroscopy. (i) ‘H NMR. Common features of all these spectra are the characteristic singlet near 0 ppm (S) for the Si(CH3)3 hydrogens, and the 1 : 4 : 1 “triplet” for
+/ z
the methylene hydrogens, as a result of spin-spin coupling to 19?t (I = &34% abundant). ‘J(Pt-H) is generally of the order of 9&94 Hz in all the dialkyl complexes. Replacement of one R group by halide causes a reduction of 15-20 Hz. 2J(Pt-H) associated with the coordinated diene protons are 73 and 35 Hz for those tram to Cl and R, respectively. A distinctive feature of the ‘H spectra of these complexes is the broadening of the ‘95Pt satellites
6
4
3
6
ON\ f 2
3’
R
YN'
0
d
5’
/
1‘\\
-PPh
0 5 6
2
4”
Fig. 1.
b
3
4
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II)
complexes
1959
Table 2. ‘H NMR characteristics of LPtRX (R = CH,SiMe,) Complex L
X
6 ‘H ppm CH$i(CH& (JR-n) CH, CH3
6 ‘H ancillary ligand(s) L (JR-n) [Assignment]
1.14(93.6 Hz)
0.31
1.34-l .89m [CH,], 4.46(41.5 Hz) [CH]
cod
R” Cl”
1.35(76.4 Hz)
0.39
1.331.84m [CH& 3.96(73.0 Hz) [CH trans to Cl], 5.29(34.6 Hz) [CH trans to R]
cod
Ib
1.47(76.9 Hz)
0.10
1.94-2.45m [CHA, 4.67(74.2 Hz) [CH trms to I], 5.44(39.8 Hz) [CH truns to R]
nbd
1.27(102.7 Hz)
0.29
l.Ot [CHJ, 3.27m [CH], 4.52m (40.6 Hz) [CH=CH]
bipy
R” R”
1.28(89.7 Hz)
0.35
6&m 6.66d
Me,bipy
R’
1.23(81.6 Hz)
0.37
bipym
R”
1.45(91.6 Hz)
0.46
phen
R’
1.45(90.1 Hz)
0.36
cod
D&lVHrH, = 5.7 Hz), (Jnrn, = 1.3 Hz), W,l &+.I, = 8.0 Hz), 7.OOm[H4], 9.09(27.5 Hz)
[Hd (-&+H~ =
5.0 Hz) 1.54 [CH,], 6.32dd [HJ, 6.74 [H3], 8.98dd [H,] (Jn6uI = 5.7 Hz) 6.05t [H,], 8.28dd [H4], 8.99(21.4 Hz) [H6] (Jn,n, = nrub = 5.7 Hz) 6.72m [H,,] (JscstYsj = 5.1 Hz), 6.87s [H, J, 7.44dd
D-L.,1(Jq~~~~~ = 8.0 Hz), 9.32dd[Hz,1Vy9bq7)= 1.2 Hz) Ph,phen
R
1.57(90.8 Hz)
0.47
Me,phen
R” R”
1.60(90.2 Hz)
0.58
bipyz
1.75(90.8 Hz)
0.42
(PY)2
R
0.77(89.2 Hz)
0.19
terpY
BF,d
0.91(77.7 Hz)
0.01
6.83d [H3,*] (Js(st2(9j = 5.4 Hz), 7.05-7.17m [ph], 7.31 Wd9.46d (23.0 Hz) D32.91 1.71, 1.88 [CH,], 7.36 [H& 9.30(23.1 Hz) [H,,] 8.92(20.2 Hz) 7.92d P-U V~+,s = 2.9 Hz), 8.12 11-13], [HJ 6.25m [H,], 6.74m [Hd (Ju,_n,,, = 7.6 Hz), (JH~H, = 1.6 Hz), 8.32m (20.9 Hz) [H2] (JHrH, = 6.4 Hz) 7.97(11.4 Hz) [HS,Y], 8.51(15.7 Hz) [H4,4”],8.59-8.65 obs [Hs,Y,Y,v,Y].9.06(52.8 Hz) [Hs,6”]
(PMG2
R”
0.36(72.9 Hz)
0.19
0.86m (20.4 Hz) [CH,] (‘J,-,
PW2
R
0.64(73.0 Hz)
0.33
0.77-0.88 [CH,], 1.44-1.53m [CHJ
PMe2W2
Rb
0.50(76.2 Hz)
0.03
1.32m (19.9 Hz) [CH,] (2Jp_H= 7.6 Hz), 7.43-7.55m [H,,], 7.65-7.74m [Hz]
PPh2M42
R”
1.06(78.6 Hz)
0.36
1.55m (19.7 Hz) [Me] (“J,-, [H3,.,], 7.47-7.54m [H,]
0.38
6.94m [H3,.,], 7.57-7.65m [H2]
WW2
R”
1.14m
dwm
Rb
0.93(85.6 Hz)
-0.25
dppe
Rb
0.72(82.5 Hz)
-0.36
dmf
R’
0.95br
a Run bRun ‘Run d Run
in in in in
0.15
= 7.6 Hz)
= 7.0 Hz), 7.01-7.05m
4.21m [CHd (‘J&_u = 18.4 Hz), 7.25-7.43m [H,,d, 7.51-7.59m [H2] 2.12m [CH,], 7.367.39 [H,,J, 7.55-7.62m [H2] 3.77 [H3.,& 4.10 [H,:,,], 7.05m [H+,], 7.83br [H2]
benzene-d,. chloroform-d ,. toluene-d,. acetone-d,.
of the methylene resonance upon coordination of nitrogen donor ligands. This phenomenon appears to be a general feature of alkylplatinum complexes of this type and is attributed 14,’’ to quadrupolar relaxation of ‘95Pt by “N. A similar effect has been
noted previously in the ‘H spectra of MeHgI complexes where efficient relaxation of ‘99Hg by “‘1 broadens the satellite peaks to the extent that they cannot be resolved. ’ * Slight broadening of the central methylene resonance is sometimes discernible
1960 Table
S. K. THOMSON 3. 3LP NMR
characteristics CH,Si(CH,),)
Complex L We3Ph
(WP), (PhMezP)2C (Ph,MeP),’ (Ph3P)z’ dPPm’ dPpe’ dPpfb
6 3‘P” ppm -26.31 5.13 - 14.78 2.81 24.98 -42.38 43.61 19.55
“Referenced to external H,PO,/D,O bRun in benzene-d,. ’ Run in chloroform-d ,.
of LPtR,
(R =
JR-+.
1945.1 1987.1 1989.4 1998.2 2004.9 1575.1 1938.4 2020.4
Hz Hz Hz Hz Hz Hz Hz Hz
and G. B. YOUNG Table 4. Ring contributions
Compound L*
&pm dpPe dPPf (Ph,MeP),
6P
6F”
-42.4 43.6 91.6 2.8
-22.7 -13.2 -17.1 -28.1
for L,Pt(CH,Si(CH,),), Chelate ring size -19.7 56.8 36.7 30.9
-50.6 25.9 5.8 0.0
4 5 7 -
a Free phosphine chemical shifts obtained from ref. 15.
85%.
for these complexes, due, presumably to enhancement of ‘H relaxation by ’ 'N but this is clearly a
less significant effect. (ii) 31P NMR. The 3’P NMR spectra show the expected 1 : 4 : 1 “triplet” as a result of spin-spin coupling concoupling of 31P to 195Pt. ‘J(Pt-P) stants are generally in the range 194&2000 Hz, typical for cis-bis(phosphine)platinum(II) complexes. As has been previously noted for complexes with different alkyl groups, I9 ‘J(Pt-P) for (dppm)PtR2 has an appreciably lower value. This reduction originates from the angular constraints around P and Pt due to the four-membered ring.lga A ring contribution, AR, to the chemical shift results upon coordination of phosphorus nuclei in chelate rings, with the magnitude and direction of this shift dependent on ring substitution and size. The value of AR = A -A: has been measured for LzPtMe, (L2 = dppm, dppe, dppp, dppb) where A is the change in shift upon coordination and 8: is a standard ring contribution.20 Comparison with the values obtained for the trimethylsilyhnethyl complexes (Table 4) shows them to be in accord with these findings. We have noted similar trends for related silylmethylplatinum complexes. I4 A further notable aspect which emerges from these 31Pspectra is that the magnitude of ‘J(Pt-P) is consistently greater (by ca 300 Hz) than for neopentyl analogues (see Section iv). (iii) 13CNMR. All the compounds have been characterized by 13C{‘H} NMR. Assignments are in * Sample of (Et3P)ZPt(CH2CMe3)2prepared according to Whitesides et ~1.~”
accord with those discussed elsewhere, particularly in related bis(ethenyldimethylsilylmethy1) l4 and bis(phenyldimethylsilylmethy1) ’ 5 complexes. Variation of the N-donor ligands produces little change in the chemical shifts or 3J(Pt-C) values for the trimethylsilylmethyl group, an indication of the similar electronic and steric environments conferred by this series of ancillary ligands. From these spectra it emerges that ‘J(Pt-C) is uniformly smaller than in comparable neopentyl complexes (aide infru) . (iv) General implications. Compared with analogous neopentylplatinum(I1) derivatives with diene,3” N-donor I and P-donor3a ligands, trimethylsilylmethylplatinum(II) complexes exhibit several notable characteristics. First of all, ‘J(Pt-C) for the q ‘-alkyl is significantly lower (by 170180 Hz) for trimethylsilylmethyl. This trend is paralleled in ‘H NMR spectra by decreased ‘J(Pt-H) in the neopentyl case. On the other hand, ‘J(Pt-C) for the diene ligand in, for example, (cod)Pt(CH2SiMe3)2 is correspondingly larger than for (cod)Pt(CH,CMe,), (Fig. 2). The same trend is evident in 2J(Pt-H methine) values for the q2-alkene. For phosphine complexes, for instance triethylphosphine (Fig. 3), the reduction (178 Hz) in ‘J(Pt-C) for (Et3P)2Pt(CH2SiMe3)2* is matched by an increase in ‘J(Pt-P) of 349 Hz, which is in the typical range for analogues for which comparative data are available. The extent of change in ‘J(Pt-C) and ‘J(Pt-P) is comparable (ca 23%). We have noted closely similar trends in comparisons of neophylplatinum complexes with silaneophyl-” and (related) sila-neohexenylplatinum14 analogues. Based on the assumption of Fermi contact dominance of ‘J magnitudes,23 we ascribe the variations to greater attraction by the carbon than by the silicon containing ligand for the platinum 6s orbitals. This, in turn, is as a result of deployment of greater 2s character in the Pt-C bond by a ligating carbon with a more electronegative alkyl
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II)
complexes
1961
Fig. 2.
Fig. 3. Table 5. 13CNMR characteristics of LPtRX (R = CH,Si(CH,),) Complex L
X
6 13Cppm CH2Si(CHJ3 (Jpt--c) CHz CH3
6 13C ancillary ligand(s) L (&& [Assignment]
cod
R”
13.89(712.4 Hz)
3.58(31.0 Hz)
29.99 [CH,], 97.53(62.8 Hz) [CH]
cod
Clb
16.39(529.0 Hz)
255(16.5 Hz)
28.15(22.1 Hz), 31.92(22.8 Hz) [CHJ, 83.47(215.9 Hz), 111.12(35.2 Hz) [CH]
cod
Ib
12.64(570.0 Hz)
3.51(17.0 Hz)
28.72t18.0 Hz), 31.28(21.0 Hz) [CHA, 89.31(181.0 Hz), 109.21(39.0 Hz) [CI-Ij
nbd
Rb
16.88(754.0 Hz)
3.22(33.0 Hz)
48.79(41.0 Hz) [CH), 72.85(51.0 Hz) [CHJ, 84.84(54.0 Hz) [CH==CH]
bipy
R”
- 6.27(793.4 Hz)
3.29(36.4 Hz)
121.86(10.8 Hz) [C,], 126.12(20.1 Hz) [C,], 134.65 [C,], 147.26(32.8 Hz) [C J, 156.17 [Cd
Me,bipy
R”
- 7.44(747.5 Hz)
3.37(36.2 Hz)
21.10 [CH,], 122.72(11.6 Hz) [C,], 127.01(20.5 Hz) [C,], 146.36 [C,], 146.85(33.2 Hz) [Cd, 156.19 [Cd
bipym
R”
- 7.00(762.2 Hz)
3.22(36.2 Hz)
123.07(16.0 Hz) [&I, 152.52(28.8 Hz) [C,], 155.29 [C,,], 162.90 [CA
1962
Table 5 (continued) Complex L
X
6 13CPPm CH&(CH3)3 CHz
6 ’ 3C ancillary ligand(s) L (&__,-) [Assignment]
(Jpt--c) CH3
phen
R”
- 7.59(754.0 Hz)
3.34(36.6 Hz)
Ph,phen
R”
-6.97(747.7
Hz)
3.51t35.7 Hz)
Me,phen
R”
-7.96(749.1
Hz)
3.52(36.4 Hz)
14.37, 16.96 [CH,], 122.50 [C,,,], [C13,14 obs], 133.27(20.0 Hz) [C& 140.70 [Cd,,], 147.17 [C ,,,, 2], 148.30(33.9 Hz) [C,,,]
terry
BF,,’
4.89(733.0 Hz)
2.48(18.1 Hz)
125.05 [C,,.], 126.60(30.2 Hz) [C,,..], 129.57(43.9 Hz) [C,,..], 141.51 [C,.], 142.51 [C,,..], 153.01(31.2 Hz) [C,:.], 153.34 [C,,..], 161.17 [C,:,.]
bipyz
R”
Hz)
3.08(35.0 Hz)
139.85(29.8 Hz) [C,], 144.37(9.2 Hz) [CS], 149.17 [C2], 149.23 [C,]
(PY)z
Rd
- 11.22(749.1 Hz)
2.86(37.6 Hz)
125.18(20.5 Hz) [C& 126.51 [&I. 130.50 [C,3,,4], 134.09 [C& 147.0(33.4 Hz) [Cw], 148.38
[C,,,,,l
124.7 [C4’], 125.88(20.9 Hz) [C,,,], [(& obs], 128.91 [C,,], 129.21 [C,.], 137.82 [C& 146.62(33.3 Hz) [&,I, 147.23
[C,,l, 148.91[C,,,,,l
-3.92(708.7
124.75 [C,,,], 134.71 [C,], 150.90(14.9 Hz)
G,el
(PMe,),
Rb
6.35(528.2 Hz) (JPSG = 7.7 Hz) = 94.1 Hz) (JP<,
3.98(29.8 Hz)
17.56(29.2 Hz) [CH,] (Jp4
(PJ%),
Rb
5.80(544.5 Hz) (JP-G = 8.1 Hz)
4.36(28.7 Hz)
18.31(18.1 Hz) [CH,], 17.00(22.5 Hz) [CHJ (Jp< = 27.9 Hz)
(PMezPh)z
Rb
4.00(29.2 Hz)
15.2q27.5 Hz) [CH,] (Jp4 = 31.5 Hz), 128.0 [C,] (Jp4 = 8.9 Hz), 129.26 [C.,], 131.04(16.1 Hz) [Cd (Jp4 = 10.9 Hz), 139.10(16.9 Hz) [C,] (Jp4 = 43.6 Hz)
(PMePh&
Rb
7.41(552.9 Hz)
3.95(29.3 Hz)
14.63(23.0 Hz) [CHJ (Jp4 = 31.6 Hz), 127.86(14.4 Hz) [C,] (Jp4 = 8.8 Hz), 129.19 [C,], 132.99(14.5 Hz) [Cd (JP-c = 10.7 Hz), 136.43(18.7 Hz) [C,] (Jp-c = 44.3 Hz)
Rb
8.53
4.04(28.9 Hz)
127.39(8.6 Hz) [C,] (Jpx = 8.7 Hz), 129.16 [C,], 133.90(18.5 Hz) [C,] - 43.9 Hz), 134.84(10.8 Hz) [CJ 22 = 10.9 Hz)
(JP-c,
= 30.5 Hz)
obs)
6.45(538.3 Hz) = 7.5 Hz) = 93.2 Hz) zz_
(JP+, = 6.7 Hz) (JPQk.= 91.6 Hz) Rb
5.41(572 6 Hz) (JP<<~ = 6.7 Hz) (JP-c,, = 94.1 Hz)
3.75(30.6 Hz)
49.09(11.4 Hz) [CHZ] (Jpx = 51.2 Hz), 128.49(10.9 Hz) [C,] (Jpx = 9.9 Hz), 130.20 [C.,], 132.80(19.2 Hz) [Cd - 30.0 Hz), 133.00(12.6 Hz) [Cd gz = 12.6 Hz)
dppe
Rb
1.94(551.1 Hz) (JP-G~ = 5.5 Hz) (JP--c,, = 89.3 Hz)
3.58(28.9 Hz)
28.1Om [CHJ, 128.30 [C,] (Jp4 = 9.7 Hz), 130.10 [C,], 133.03 (25.5 Hz) [Gl, (JP-c = 40.2 Hz), 133.57 [CJ (JPX = 11.0 Hz)
dppf
Rd
8.53(568.0 Hz) (JP-G = 7.3 Hz) (JP+_ = 93.7 Hz)
4.58(28.5 Hz)
72.19 [C,:,.], 75.28 [C,:,.] (Jc_p = 8.8 Hz), 79.46 [C,.] (Jp< = 47.8 Hz), 127.82 [C,], 130.09 [C,], [C, obs], 135.70(11.7 Hz) [C,] (Jp4 = 11.2 Hz)
aRun in benzene-d, b Run in chloroform-d,. ‘Run in acetone-d,. dRun in toluene-d *.
Synthesis and spectroscopic characteristics of trimetbylsilylmethylplatinum(II)
complexes
1963
Table 6. r3C NMR characteristics of nitrogen donor ligands 6 i3C ppm [Assignments]
Ligand 2,2’-bipyridine”
156.8 [CJ, 149.65 [C J, 137.40 [C,], 124.15 [C3], 121.34 [C,]
2,2’-bipyrimidine”
161.0 [Cd, 156.7 [C.,, Cd, 120.3 [C,]
1, lo-phenanthrolineb
150.1 [C2, C,], 146.1 [Cr,, C&-J, 135.9 [C4, C,], 128.5 [C13. C,,], 126.4 ]C,, C,I, 122.9 ]C3, Cd 149.8 [C,, C,], 148.4 [C, ,, C12], 138.0 [C,, C,], 126.4 (C,3, C,,], 128.4 [Cs, C,], 123.4 [C,, C,], 146.8, 129.5, 128.5, 123.9 [C,H,] - -
4,7diphenyl-
1,IO-phenanthroline’
0From ref. 2 1. bFrom ref. 22. ‘From ref. 6.
Table 7. First MLCT absorption 1, for L,PtR,” Complex bipyPtR, MezbipyPtR, bipymPtRz bipyzPtR, pheriPtR, PhzphenPtR2 Me,phenPtR,
[terpP’WBF4
&
(nm) 516.0 507.5 539.5 564.0 511.0 519.0 480.0 482.0
a Measured in toluene.
(as opposed to silaalkyl) substituent, in accord with isovalent hybridization. ’ 4*24 A corollary is that trimethylsilylmethyl appears to exert a lesser (bond-weakening) truns-influence than does neopentyl. Ancillary hgand dissociation is often a prerequisite for thermolytic rearrangements in complexes of this type. Such a ground state energetic difference may have a kinetic influence on lability and contribute (in part at least) to the readier reactivity of neopentyl (and neophy16) complexes relative to their silicon analogues. ’ * We shall report in due course on our mechanistic observations. An apparent paradox in these ‘.Z data, however, is the implication that the neopentyl-platinum bond is stronger than that in complexes, trimethylsilylmethyl-platinum the which contradicts previous thermochemical indications.4*5 We are also investigating this aspect.
REFERENCES 1 For reviews, see (a) R. R. Schrock and G. W. Parshall, Chem. Reu. 1976, 76, 243 ; (b) P. J. Davison, M. F. Lappert and R. Pearce, Chem. Rev. 1976,76,219; (c) M. C. Baird, J. Orgunomet. Chem.
1974, 64, 289 ; (d) P. S. Brateman and R. J. Cross,
Chem. Sot. Rev. 1973,2,271; Seealso, for example, (e) G. M. Whitesides, J. F. Gaasch and E. R. St&on&y, J. Am. Chem. Sot. 1972,94, 5258 ; (f) R. G. Nuzzo, T. J. McCarthy and G. M. Whitesides, J. Am. Chem. Sot. 1981, 103, 3396 ; (g) S. Komiya, Y. Morimoto, A. Yamamoto and T. Yamamoto, Organometallics
1982, 1, 1528.
2. See, for example, (a) S. D. Chapell and D. J. ColeHamilton, PoZyhedron 1982, 1, 739 ; (b) I. P. Rothwell, Polyhedron 1985,4,2; (c) J. C. Calabrese, M. C. Colton, T. Hershovitz, U. Kablunde, G. W. Parshall, D. L. Thorn and T. H. Tulip, Annu. N.Y. Acad. Sci. 1983,415, 302; (d) G. B. Young, in Znorganic Reactions and Methods (Edited by J. J. Zuckerman). Springer, Berlin, in press. 3. (a) P. Foley, R. DiCosimo and G. M. Wbitesides, J. Am. Chem. Sot. 1980,102,6713 ; (b) R. A. Andersen, R. A. Jones and G. Wilkinson, J. Chem. Sot., Dalton Trans. 1978, 446 ; (c) P. Diversi, G. Ingrosso, A. Lucherini and D. Fasse, J. Chem. Sot., Chem. Commun. 1982,945 ; (d) T. H. Tulip and D. L. Thorn, J. Am. Chem. Sot. 1981,103,2448 ; (e) J. W. Bruno, T. J. Marks and V. W. Day, J. Organomet. Chem. 1983,250,237.
4. (a) J. C. Baldwin, M. F. Lappert, J. B. Pedley and J. S. Pollard, J. Chem. Sot., Dalton Trans. 1972, 1943 ; (b) J. C. Baldwin, M. F. Lappert, J. B. Pedley and J. A. Treverton, J. Chem. Sot. (A) 1967,198O ; (c) I. E. Giimrtikciioglii, J. Jeffery, M. F. Lappert, J. B. Pedley and A. K. Rai, J. Organomet. Chem., in press. 5. J. W. Bruno, T. J. Marks and L. R. Morss, J. Am. Chem. Sot. 1983,105,6824. 6. (a) D. C. Griffiths and G. B. Young, Polyhedron 1983,2, 1095 ; (b) D. C. Griffiths and G. B. Young, OrganometaIlics, in press. 7. B. Ankianiec, D. J. Wilkes and G. B. Young, unpublished results. 8. (a) M. M. Truelock, D.Pbil. thesis, University of Sussex (1971); (b) B. Wozniak, J. D. Ruddick and G. Wilkinson, J. Chem. Sot. (A) 1971, 3116. 9. D. F. Shriver, The Manipulation of Air Sensitive Compounds. McGraw-Hill, New York (1969). 10. J. X. McDermott, J. F. White and G. M. Wbitesides, J. Am. Gem.
Sot. 1976,98,6521.
S. K. THOMSON 11. C. R. Kistner, J. H. Hutchinson, J. R. Doyle and J. C. Storlie, Inorg. Chem. 1963,2, 1255. 12. E. G. Cox, H. Saerger and W. Wardlaw, J. Chem. Sot. 1934, 182. 13. N. Chaudhury and R. J. Puddephatt, J. Organomet. Chern. 1975,84,105. 14. R. D. Kelly and G. B. Young, Polyhedron, in press. 15. B. Ankianiec and G. B. Young, Polyhedron, in press. 16. V. Christou and G. B. Young, to be published. 17. R. R. Rumininski and J. D. Petersen, Znorg. Chem. 1982, 21, 3706 ; V. F. Sutcliffe and G. B. Young, Polyhedron 1984,3, 87. 18. D. N. Ford, P. R. Wells and P. C. Lauterbur, J. Chem. Sot., Chem. Commun. 1967,616. 19. (a) P. S. Braterman, R. J. Cross, L. Manjlovic-Muir,
and G. B. YOUNG
20. 21. 22. 23.
24.
K. W. Muir and G. B. Young, J. Organomet. Chem. 1975, 84, 0; (b) T. G. Appleton, M. A. Bennett and I. B. Tompkins, J. Chem. Sot., Dalton Trans. 1976,439 ; (cl M. Bochman, G. Wilkinson and G. B. Young, J. Chem. Sot., Dalton Trans. 1980, 1879. P. E. Garrou, Chem. Rev. 1981,81,229. C. A. Overton and J. A. Connor, Polyhedron 1982, 1, 53. A. Kiinnecke, E. Lipmann, J. Mlochowski and W. Sliwa, Org. Mag. Res. 1979, 12,696. P. S. Pregosin, Annu. Rep. NMR Spectrosc. 1986, 17, 285 ; A. Pidcock, A.C.S. Adv. Chem. Ser. 1982, 196, 1 and refs cited in both. H. A. Bent, Chem. Rev. 1961,61,275.
1988 0
0277-5387/88 S3.00+ .oO 1988 Pergarnon Press plc
SYNTHESIS AND SPECTROSCOPIC CHARACTERISTICS OF TRIMETHYLSILYLMETHYLPLATINUM(II) COMPLEXES WITH q* ALKENE, NITROGEN AND PHOSPHORUS AND SULPHUR DONOR LIGANDS S. KATHERINE
THOMSON
and G. BRENT YOUNG*
Inorganic Chemistry Labora.tories, Imperial College of Science and Technology, London SW7 2AY, U.K. Abstract-Various complexes cis-LzPtR2 (L = py, PMe3, PEt3, PMe,Ph, PMePh,, PPh3, L2 = bipy, Me,bipy, bipym, bipyz, Me4phen, Ph,phen, dppm, dppe, dppf, R = CH2SiMe,) have been synthesized by displacement of the diene from (cod)PtR, or (nbd)PtR2 or by sulphide replacement in [(dms)PtR2],. fTerpyPtR]BF, has been synthesized via (cod)Pt(R)(X), (X = Cl, I). The complexes have been characterized by IR, ‘H, 13CNMR and, where appropriate, 3‘P NMR and electronic spectroscopy. Trimethylsilylmethyl exerts a weaker trans-influence than neopentyl which, on NMR evidence, has the stronger Pt--C bond.
There is continued activity in evaluation of the rearrangement mechanistics of organo-transition metals as a route to greater understanding of their role in metal-mediated transformations of hydrocarbons. Common labilizing pathways for many alkylmetals feature hydrogen transfers, most often from a /?-carbon site. This feature, early recognized by Wilkinson and a few others, led to rapid development in alkyl transition metal chemistry using “j-elimination stabilized” ligands. ’ When this option is restricted, activation of more remote C-H bonds may occur.’ Again, the earlier examples were characterized by Wilkinson and co-workers. Neopentyl metals, for example, particularly lowvalent derivatives of the later d-block, have been observed widely to undergo such cyclizations to form metallacyclobutanes.3 The mechanistics have been elucidated elegantly for dineopentylplatinum(II).3” Trimethylsilylmethyl metals may also undergo y-C-H transfer, 3,4but, impressionistically, they are more inert.3 Other than a few thermochemical studies which document the thermodynamic differences in M-C bond strengths between M(CH,CMe3), and M(CH,SiMe3),4-which doubtless contribute to the rearrangement mechanistics where M-C homolysis is important-there has been little attempt to quantify and understand the kinetic effect of silicon on these intramolecular
*Author to whom correspondence should be ad-.
hydrogen transfers for d-block elements. An example in f-block chemistry has appeared.’ In parallel with our comparative studies of aromatic C-H activation in LzPt(CH2CMezPh)26 and L2Pt(CHzSiMezPh)2,7 we have now synthesized a wide variety of complexes, L2Pt(CH2SiMe3)2, for comparison with analogous neopentyl derivatives.3a Here we present some notable characteristics. A few of these complexes have been reported previously.8 In these cases, we present synthetic improvements and new spectroscopic data. EXPERIMENTAL General and instrumental
Elemental analyses were performed by Imperial College Microanalytical Laboratories. NMR spectra were recorded on Briiker WM 250 (‘H 250.13 MHz, 13C 62.9 MHz) and Jeol FX 90 Q (‘H 89.55 MHz, 31P 36.21 MHz) spectrometers. IR data were collected on a Perkin-Elmer 683 instrument as 4% KBr dispersions and electronic spectra were recorded on a Shimadzu UV-160 spectrometer. All reactions were carried out under argon, using standard anaerobic techniques.’ The apparatus was thoroughly flame-dried prior to use, and solvents were distilled from sodium under nitrogen. Diethyl ether and n-hexane were distilled from sodiumbenzophenone.
1953
1954
S. K. THOMSON and G. B. YOUNG
Chloromethyltrimethylsilane, 1,5-cyclooctadiene (cod), bicyclo[2.2.l]hepta-2,5-diene (nbd), dimethyl sulphide (dms), 2,2’-bipyridyl (bipy), 4,4’-dimethyl2,2’-bipyridyl (Mezbipy), 2,2’-bipyrazyl (bipyz), 1, lo-phenanthroline (phen), 4,7-diphenyl- 1, lophenanthroline (Ph,phen), 3,4,7,8_tetramethyll,lO-phenanthroline (Me,phen), 2,2’ : 62” terpyridyl (terpy), silver tetrafluoroborate, triphenylphosphine, bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), l,l’-bis(diphenylphosphino)ferrocene (dppf), toluene-ds and benzene-d6 were all used as supplied by the Aldrich Chemical Company. 2,2’-Bipyrimidyl (bipym) was obtained from Lancaster Synthesis. Trimethylphosphine, triethylphosphine, diphenylmethylphosphine and dimethylphenylphosphine were used as supplied by Strem Chemicals. Pyridine (py) was supplied by Rose Chemicals and distilled from sodium hydroxide under nitrogen prior to use. Dichloro( 1,5-cyclooctadiene) platinum(II), dichloro(bicyclo[2.2.l]hepta - 2,5 - diene)platinum(II) and cis-dichlorobis(dimethylsulphide)platinum(II) were prepared using published methods.‘W’2 Preparation of chloromagnesiomethyltrimethylsilane
A solution of chloromethyltrimethylsilane (5.0 g, 41 .Ommol) in Et,0 (40 cm3) was added dropwise to a suspension of magnesium shot (5.0 g, 206.0 mmol) in diethyl ether (10 cm3) previously activated by the introduction of 1,Zdibromoethane (0.25 cm’). After 2 h stirring at ambient temperature the resulting solution of Mg(CH,SiMe,)Cl was filtered off. (Yield, lOO%.) Preparation of bis(trimethylsilylmethyl)( 1,5-cyclooctadiene)platinum(II)
A solution of Mg(CHzSiMe3)C1 (30.0 cm3, 24.6 mmol) was added dropwise at -78°C to a stirred suspension of (cod)PtCl, (3.0 g, 8.02 mmol) in diethyl ether (20 cm3). The mixture was allowed to reach ambient temperature and stirred for 15 h. On cooling to -2O”C, saturated aqueous ammonium chloride (15 cm3) was added dropwise with stirring. The ether fraction, after separation, was dried over MgS04 and concentrated in vacua to yield large colourless crystals of the product. (Yield, 2.87 g, 75%.) IR: 2999w, 2994s, 2992sh, 2885s, 2855sh, 152Ow, 1475w, 1474sh, 145Ow, 1435m, 1405wb, 1365w, 134Om, 131Ow, 1305sh, 1285wb, 1255sh, 1235s, llSOw, 116Ow, 1085w, 1075w, lOlOmb, 99Ow, 98Ow, 950m, 840sb, 820sb, 785sh, 76Om, 745m, 712m, 675s, 605w, 535wb, 46Owb, 27Ow, 265m, 26Ow, 255w, 235m, 23Om, 215s, 210s.
Preparation of chloro(trimethylsilylmethyl)(1,5cyclooctadiene)platinum(II)
A solution of 0.42 M HCl in Et,0 (1.05 cm3, 0.42 mmol) was added dropwise to a stirred solution of (cod)Pt(CH,SiMe,), (0.20 g, 0.42 mmol) in diethyl ether (20 cm3) at - 78°C. The mixture was allowed to warm to ambient temperature and stirred for 24 h. The solvent was removed in vacua to yield colourless crystals of the product. (Yield, 0.16 g, 89%.) IR: 2945s, 2889m, 2843s, 27OOw, 1546w, 1475m, 1454w, 1436m, 1428m, 1408m, 1362m, 1344m, 1317w, 1262s, 1245s, 1183m, 1097sb, 1041s, 1023s, 987m, 96Om, 902w, 865s, 828s, 803sb, 776sb, 768m, 747w, 715m, 683m, 615w, 54Ow,479m, 432w, 392mb, 313m, 277~.
Preparation of iodo(trimethylsilylmethyl)( 1,5-cyclooctadiene)pZatimun(II)
(cod)Pt(CH$iMe,)Cl (0.30 g, 0.70 mmol) was dissolved with KI (0.83 g, 5.0 mmol) in acetone (20 cm3) and stirred for 24 h. The acetone was removed in vacua and the residue extracted into Et?0 (40 cm3). The solution was filtered, concentrated and cooled to - 25°C to yield pale yellow plates which were washed with cold hexane (2 cm’). (Yield, 0.28 g, 74%.) IR : 303 lw, 3006m, 2946m, 2923m, 2887m, 2872m, 2835w, 1481w, 1451w, 1428m, 1404w, 1386w, 1374m, 1340m, 1317w, 1292w, 1251m, 124Os, llSlw, 109Ow, 1075w, 1045m, 1002m, 987m, 961m, 902m, 876w, 838sh, 821s, 794m, 760m, 752w, 721m, 695w, 682m, 612w, 567w, 533w, 471w, 428w, 264w, 243m, 24Om, 229m.
Preparation of bis(trimethylsilylmethyr)(bicyclo [2.2.l]hepta-2,5-diene)pZatinum(II)
To a stirred suspension of (nbd)PtCIZ (1.36 g, 3.8 mmol) in diethyl ether (20 cm3) was added dropwise at - 78°C a solution of Mg(CH,SiMe,)Cl (13.9 cm3, 11.4 mmol). The mixture was allowed to reach ambient temperature and stirred for 15 h, then cooled to - 20°C and saturated aqueous NH&l (10 cm3) added dropwise. The ether layer was separated and dried over MgSO, and concentrated in vacua. The cream-coloured crystalline product was further recrystallized from a mixture of Et@-hexane. (Yield, 1.21 g, 69%.) IR: 3004w, 2948s, 2896m, 2850m, 2835m, 2789m, 1433m, 141Ow, 1369w, 1357w, 1308m, 1251m, 124Os, 1188m, 1154w, llOOw, 1098w, 1008m, 989m, 960m, 934m, 924w, 886m, 85Os, 827s, 757sh, 749m, 715m, 676m, 612w, 535w, 488w, 285w, 250m, 244m, 237s, 230s.
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II) Preparation of [bis(trimethylsilylmethyl)(dimethylsulphide)platinum(II)]~ (n = 2 or 3)
To a stirred suspension of (dms)zPtC1z (1.5 g, 3.84 mmol) in diethyl ether (10 cm’) at - 78°C was added dropwise a solution of Mg(CH$iMe,)Cl (14.0 cm3, 11.5 mmol). The mixture was stirred at ambient temperature for 2 h, then cooled to - 20°C and saturated aqueous NH&l (10 cm’) added. The ethereal layer was filtered onto MgSO, and activated charcoal, then after filtration, concentrated in vacua and cooled to -25”C, yielding a white solid. (Yield, 1.82 g, W!!.) IR: 2998m, 2946m, 2916m, 2895m, 2842m, 1458w, 1425w, 1413w, 1358w, 1262s, 1239s, 1096sbr, 1026s, 985s, 947w, 853s, 823s, SOOs,77Om, 747m, 715m, 679s, 609w, 545w, 453w, 408w, 283w, 275w, 266w, 261m, 256m, 252s, 245s, 23Os, 224s. Preparation of bis(trimethylsilylmethyl)(2,2’-bipyridyl)platinum(II)
[(dms)Pt(CH,SiMe,)J (n = 2 or 3) (0.10 g) was dissolved together with 2,2’-bipyridyl (0.04 g, 0.24 mmol) in dry deoxygenated toluene (5 cm’) and the solution kept at room temperature for two days. Any excess free ligand was removed by extraction with aqueous ferrous sulphate solution. The organic phase was then dried over MgS04 and concentrated in vacua, then cooled to - 25°C. The deep red crystals formed were filtered off and washed with cold n-hexane. (Yield, 0.11 g, 85% .) IR : 2942m, 2868m, 2829m, 1599w, 1468m, 1445m, 1306w, 1262m, 1237m, 1097mbr, IOllmbr, 955w, 849s, 821sbr, 757m, 745s, 728m, 712m, 672m, 555w, 254m, 248s, 24Os, 229s. Bis(trimethylsilylmethyl)(4,4’ ridyl)platinum(II)
- dimethyl - 2,2’ - bipy-
This was prepared according to the above procedure. Product: orange-red crystals from ether. (Yield, 87%.) IR: 2946m, 2869m, 2829m, 1616m, 1553w, 148Ow, 1446w, 1414w, 1298w, 1261w, 1233m, 1098wbr, lOlSmbr, 973w, 955w, 928w, 888w, 855s, 826s, 774w, 742w, 715w, 672m, 6OOw, 55Ow, 517w, 425w, 332w, 295w, 28Ow, 257w, 245w, 239m, 234m, 23Os, 224m. Preparation of bis(trimethylsilylmethyl)(2,2’-bipyrimidyl)platinum(II)
(cod)Pt(CH,SiMe,), (0.20 g, 0.42 mmol) was dissolved together with 2,2’-bipyrimidine (0.18 g, 0.84 mmol) in dry deoxygenated toluene (10 cm3). The solution was heated to 60°C for 14 days, then any
1955
complexes
excess free ligand removed by extraction with aqueous ferrous sulphate solution. The remaining organic phase was then concentrated, n-hexane (2 cm3) added and the mixture cooled. The claret crystals collected were washed with cold hexane. (Yield, 0.19 g, 86%.) IR: 3083w, 3042w, 2946m, 2877m, 2839m, 2729m, 1627wbr, 1572m, 1547m, 145Ow, 1405s, 1367w, 1332w, 1260sh, 1233m, 1199w, 1145w, 11 low, 1102w, 1076w, 1013m, lOOOw,956w, 854s, 826s, 815sh, 775m, 753s, 71Ow, 681m, 676m, 663m, 638w, 61Ow, 563w, 487w, 44Ow, 341w, 27Ow, 257~. Bis(trimethylGlylmethyl)(l,l0
- phenanthroline)plati-
num(I1) Product: red crystals from hot toluene. (Yield, 83%.) IR: 3057w, 2954m, 294Om, 2889w, 2868m, 2859m, 2824m, 1627w, 1578w, 1423w, 1415m, 1365m, 1338w, 1251m, 1236m, 1219m, 1202m, 1144w, 985m, 965m, 952w, 944m, 907w, 851s, 839s, 765m, 745m, 734w, 720m, 674m, 61 lw, 555w, 508w, 49Ow, 454w, 429w, 278w, 253~. Bis(trimethylsilylmethyl)(4,7 anthroline)platinum(II)
- diphenyl-
1,lO -phen-
Product : large red crystals from toluene. (Yield, 92%.) IR: 3058w, 303Ow, 2948m, 2861m, 2840m, 2725w, 1617w, 1592w, 1556w, 1494w, 1447w, 1435w, 1422m, 1415m, 1395w, 1362w, 126Ow, 1249m, 1236m, 1077wb, 102Om, 1003m, 962w, 949w, 907w, 854s, 824s, 764s, 748m, 736m, 717w, 7Ols, 676m, 632w, 585w, 548w, 465w, 407w, 255w, 246m, 238s. Bis(trimethyMylmethyl)(3,4,7,8 phenanthroline)platinum(II)
- tetramethyl - 1,lO -
Product: orange needles from toluene. (Yield, 86%.) IR: 2946m, 2888w, 2853m, 2835m, 161Ow, 1579w, 1514w, 1425m, 139Ow, 1263w, 1235m, 1093w, 1012w, 947w, 918w, 85Os, SlSs, 773w, 747w, 722w, 711w, 674m, 609w, 567w, 329~. Preparation of bis(trimethylsilylmethyl)(2,2’-bipyrazyl)platinum(II)
(nbd)Pt(CH$iMe3)* (0.20 g, 0.43 mmol) and 2,2’-bipyrazyl (0.07 g, 0.43 mmol) were dissolved together in toluene (10 cm’) in a grease-free sealed vessel, and the solution maintained at ambient temperature for 28 days. The purple product was recrystallized from toluenehexane. (Yield, 0.20 g, 88%.) IR: 3093w, 3058w, 2944m, 2878m, 2836m, 1635wb, 1580m, 1575m, 1469m, 1464m,
1956
S. K. THOMSON
and G. B. YOUNG
1407m, 1400m, 1368w, 1304w, 1261s, 1252s, 1237s, 1176m, 1166m, llOOmb, 1070m, 1034m, 1019m, 977wsh, 95Ow, 931w, 852s, 834s, 805sh, 765w, 713m, 679m, 623w, 558w, 395w, 267w, 252m.
Preparation of trimethylsilylmethyl(2,2 : 6’,2”-terpyridyl)platinum(II) tetrajluoroborate
(cod)Pt(1)(CH2SiMe3) (“.20 gy o.39 -01) was dissolved together with 2,2’ : 6’,2”-terpyridyl (0.09 g, 0.39 -01) in acetone (15 cm3) and the mixture stirred for 40 h to yield an orange solution. AgBF, (0.08 g, 0.39 mmol) in acetone (10 cm3) was added via a cannula and the solution filtered to yield an orange-yellow solution. On concentration in uacuo, bright yelloworange needles were formed. (Yield, 0.18 g, 76%.) IR: 3116w, 309Ow, 3075w, 2955m, 289Ow, 2853w, 1610m, 1599m, 1573w, 1472m, 1452m, 1401w, 1315w, 1289w, 1261m, 1239m, 1188w, 1169w, 1142s 1098s, 967w, 95Ow, 853m, 829m, 800m, 774m, 75Ow, 729w, 682w, 521w, 258w, 254w, 246w, 238s 23Ow, 223m.
Preparation of cis-bis(pyridine)bis(trimethylsilylmethyl)platinum(II)
(cod)Pt(CH2SiMe3)2 (0.20 g, 0.42 mmol) was dissolved in neat pyridine (5 cm3) and heated to 60°C for three days. The excess pyridine was removed in oacuo and the resulting oily solid recrystallized from ether-hexane to yield off-white crystals of the product. (Yield, 77%.) IR: 3077w, 2942s, 2887m, 2868m, 2823s 2712w, 1971w, 1915w, 16OOm, 1572w, 1479m, 1446s, 1402w, 1359w, 1348w, 1235s 1205w, 1149w, 1067m, 1045w, 1005m, 974w, 964w, 874s, 854s, 823s, 756s, 746m, 719m, 694s, 683m, 667m, 636w, 607w, 558w, 277w, 238m, 227s.
Prepared according to the same procedure were : cis - Bis(trimethylsilylmethyl)bis(triethylphosphine) platinum(I1) Product : large colourless crystals from toluene. (Yield, 95%.) IR : 2964s, 2947s 2936~, 2918m, 2893m, 1732w, 1633w, 1455m, 1433m, 1405w, 1381w, 1248m, 1235s 1099w, 1032s, 993w, 95Ow, 849s, 821s, 755s, 718s, 672m, 624w, 514w, 41Ow, 371w, 334w, 245m, 234s. cis - Bis(trimethylsilylmethyl)bis(dimethylphenylphosphine)platinum(II) Product : large colourless crystals from CH2C12/MeOH. (Yield, 82%.) IR: 3071w, 2982m, 2943m, 2922m, 2915m, 2884m, 1437m, 1421w, 1411w, 131Ow, 1294w, 1282w, 1275w, 1262m, 1246m, 1234m, llOOm, 1072w, 1052w, 1029w, lOOlw, 902s, 85Os, 823s 772w, 746m, 739m, 723w, 706m, 538w, 5Olw, 488w, 45Ow, 432w, 417w, 409m, 395w, 313w, 304w, 294w, 286w, 264m, 257s 248s, 240s 230s 224s. cis
- Bis(trimethylsilylmethyl)bis(diphenylmethylphosphine)platinum(II)
Product : colourless crystals from n-hexane. (Yield, 88%.) IR: 3075w, 3057w, 2983w, 2944m, 2920m, 2887m, 1963w, 1884w, 1588w, 1573w, 1483w, 1436s 142Ow, 137Ow, 1329w, 1307w, 1279w, 1248m, 1238m, 1231m, 1193w, 1156w, 1096m, 1077w, 1028w, 1013w, lOOOw,96Om, 914w, 894s, 884s, 875s, 851s 820s 75Os, 738s, 73Os, 698s 674m, 618w, 605w, 525m, 513s, 484m, 433m, 416m, 362w, 266w, 246w, 242m, 237m, 232s, 227s. cis - Bis(trimethylsilylmethyl)bis(triphenylphosphine)platinum(II)
Preparation of cis-bis(trimethylsilylmethyl)bis(trimethylphosphine)platinum(II)
To a solution of (cod)Pt(CH2SiMe3)2 (0.20 g, 0.42 mmol) in dry deoxygenated toluene (5 cm3) was added PMe3 (0.09 cm3, 0.86 mmol) via a syringe and the solution was heated to 60°C for 14 days. The solvent was then removed in uacuo and nhexane (2 cm’) added to the resultant colourless oil. Cooling to -25°C produced large colourless crystals of the product. (Yield, 0.22 g, loo%.) IR : 2946m, 2913m, 288Om, 1633vw, 1421w, 1301w, 1284m, 1262m, 1246m, 1235s, 1097mbr, 1022mbr, 963s, 943s, 85Os, 821s, 771w, 742w, 723m, 708m, 671m, 522w, 383w, 359w, 283w, 259w, 251w, 246m, 242m, 235s 23Os, 225s.
Product : cciourless crystals from toluene. (Yield, 84%.) IR: 3441w, 3055m, 3002m, 2938m, 2879m, 1746w, 1587w, 1484m, 1478m, 1438m, 1433m, 1313w, 1262w, 1249m, 1236m, 1182w, 1159w, 1119w, 1098m, 1091w, 1028w, 999w, 956w, 850s 825s, 751s 741m, 720m, 706s, 693sh, 619w, 54Os, 524s 512s, 491m, 464w, 453w, 432w, 421w, 281w, 268m, 251m, 243m, 237s 230s 225s. Bis(trimethylsi1ylmethyl)[bis(dipheny1phosphino)me thane]platinum(II)
Product : colourless crystals from toluene-n-hexane. (Yield, 83%.) IR: 3058w, 3005w, 2945m, 2875m, 2862m, 2836m, 1587w, 1572w, 1482m,
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II) complexes 1436s 1384w, 136Ow, 1329w, 1309w, 1277w, 1249s 1238s 1185w, 1098m, 1084m, 1028w, lOOOw,97Ow, 935w, 849s 822s 765m, 753s 737s, 724s 702s 692m, 674sh, 618w, 607w, 541m, 502s, 477m, 443w, 42Ow, 358w, 302w, 278w, 268w, 262w, 252m, 248m, 243m, 238s 230s 225s. Bis(trimerhylsilylmethyl)[l,2 - bis(diphenylphosphin0) ethune]plutinum(II) Product : colourless crystals from toluene. (Yield, 85%.) IR: 3445w, 3058m, 2942m, 2886m, 2855m, 1966w, 19OOw, 1825w, 1589w, 1573w, 1483m, 1436s 1407m, 131Ow, 1262s 1249m, 1236s, 1186w, 1101s 1027sh, 948s 857s, 846s 821s, 747s 713m, 694s 681m, 675m, 653w, 604w, 533s 482m, 469w, 436w, 4OOw,356w, 3Olw, 29Ow, 254w, 246w, 239m, 233m, 230s. Preparation of bis(trimethylsilylmethyl)[l,l’-bis(diphenylphosphinofirrocenelplatinum(I1)
(nbd)Pt(CH,SiMe3)z (0.20 g, 0.43 mmol) was dissolved together with dppf (0.23 g, 0.43 mmol) in dry deoxygenated toluene (10 cm3) and the solution maintained at 60°C for 20 days. The solvent was then removed in r~ucuo and the orange solid recrystallized from toluene (2 cm3) to yield orange crystals of the product. (Yield, 0.38 g, 96%.) IR: 3051m, 2942m, 2897m, 197Ow, 1618w, 1587w, 1571w, 148Om, 1434s 1384w, 1367w, 1308w, 1261m, 125Om, 1236s 1194w, 1181w, 1165m, 1097s, 107Ow, 1058w, 1038m, 1026m, lOOOw,959w, 850s 824s 744s, 719m, 694s 641w, 619w, 608w, 550s 527m, 514s 492s 477w, 468m, 459w, 449w, 439m, 348w, 278w, 27Ow, 26Ow, 247m, 238m, 233s 224m. RESULTS
AND DISCUSSION
Synthesis of L2PtR2
Where LZ = 1,5-cyclooctadiene the complex could be prepared in 75% yield as a colourless crystalline solid by reaction of the Grignard reagent with (cod)PtCl,. This is a considerable improvement on the method previously reported.8b The related new derivative, bis(trimethylsilylmethy1) (bicycle-[2.2.1]-hepta-2,5_diene)platinum(II) was prepared analogously. Treatment of (dms),PtCl, with trimethylsilyhnethyl magnesium chloride resulted in the formation of [@drns)Pt(CH,SiMe,)23,. Our spectroscopic observations (and those previously publishedsb) do not allow distinction between dimeric and trimeric structures. Subsequent replacement of the diene or dimethylsulphide ligands with a series of nitrogen
1957
donor ligands yielded highly coloured crystalline products, air-inert as solids. The displacement reaction with the diene complexes is generally complete in 1430 days at 60°C ; nbd is more labile than cod. Dms is replaced by 2,2’-bipyridyl and 4,4’-dimethyl-2,2’-bipyridyl in two days at room temperature and is clearly the most labile of the three. Deoxygenated solutions of these compounds in benzene and other hydrocarbon solvents are inert for indefinite periods. Reaction of the diene complexes with a series of phosphines yielded colourless, highly crystalline solids in almost quantitative yields. The ligand metathesis was generally complete within 14 days. These air-inert compounds do not decompose in deoxygenated hydrocarbon and chlorocarbon solvents. Colours and elemental compositions of all these complexes are detailed in Table 1. Spectroscopic characteristics
For numbering conventions employed, in accord with those previously used,6 see Fig. 1. (a) Electronic spectroscopy. The electronic spectra of complexes L2PtR, (LZ = N-donor ligand, R = trimethylsilylmethyl) were recorded as freshly prepared toluene solutions. They are characterized by two absorptions, I 1and &, attributable to dz-x* metal-ligand charge transfer (MLCT) transitions. ’ 3 The use of these bands in the analysis of the relative electronic effects of bidentate, heteroaromatic Ndonor ligands has been well documented. As the very intense x-x* transitions of the ligand often obscure the higher energy MLCT absorption &, the lower energy band, ;Zr, which reflects the energy difference between the metal (dz) HOMO and the (rc*) LUMO of the ligand, frequently features in comparisons within a series of such complexes. The energy of 1, increases in the order : bipyz < bipym < Ph,phen < bipy < Me,bipy < terpy < Me4phen. This is in full agreement with previous observations.6*1”‘6 MLCT transitions in complexes of this type occur at lower energies where the heteroaromatic ligands have electronegative ring atoms or substituents.” Proposedly, this arises from a lowering of the LUMO on the ligand, thus reducing the dx-n* energy gap. This explanation clearly accounts for the complexes of 2,2’-bipyrazyl and 2,2’-bipyrimidyl. An opposite effect can be invoked for the Mezbipy complex ; electron releasing substituents should raise the energy of the LUMO relative to that of bipy. As noted elsewhere, coordinated Ph,phen exhibits a lower energy absorption than phen, consistent with increased conjugation in the aromatic ligand.
1958
S. K. THOMSON and G. B. YOUNG Table 1. Physical data for LzPt(CH,SiMeJz Analytical data” H
Compound
C
(cod)Pt(Cl)(CH,SiMe,) (cod)Pt(I)(CH,SiMe,) (nbd)Pt(CHzSiMeS)z (bipy)Pt(CH,SiMe,), (Me,bipy)Pt(CH,SiMe,), (bipym)Pt(CHzSiMe3)2 (phen)Pt(CH,SiMe,), (Ph,phen)Pt(CH,SiMe& (Me,phen)Pt(CH,SiMe,), (bipyz)Pt(CH2SiMe& [(terpy)PtCH$iMe,]BF, (&Pt(CH$iMe& (Me3P)2Pt(CH,SiMeJ2 (Et3P)2Pt(CHzSiMes)z (Me,PhP),Pt(CH,SiMe,)(MePh,P),Pt(CH,SiMe,), (Ph,P),Pt(CHzSiMeS)z (dppm)Pt(CH,SiMe& (dppe)Pt(CH,SiMe,), (dppf)Pt(CH&Me&
33.6(33.8) 27.7(28.0) 39.1(39.0) 41.0(41.1) 43.3(43.4) 36.2(36.4) 43.4(43.7) 54.9(54.7) 47.2(47.6) 36.7(36.4) 37.4(37.8) 40.6(41.O) 32.2(32.2) 39.q39.q 44.5(44.6) 53.2(53.0) 59.3(59.7) 52.9(52.6) 53.6(53.2) 54.2(54.6)
5J5.4) 4.4(4.1) 6.6(6.5) 5.3(5.7) 6.3(6.2) 5.3(5.3) 5.5(5.5) 5.6(5.5) 6.0(6.3) 5.3(5.3) 4.0(3.8) 6.2(6.1) 7.6(7.7) 8.8(8.6) 6.9(6.9) 6.2(6.3) 5.9(5.9) 5.9(5.8) 6.1(6.0) 5.0(5.5)
N -
5.1(5.3) 4.8(5.1) 10.3(10.6) 5.1(5.1) 3.8(4.0) 4.4(4.6) 10.7(10.6) 6.3(7.0) 4.7(5.3) -
-
Colour Colourless Pale yellow Cream Red Orange-red Wine red Deep red Deep red Orange Deep purple Orange-yellow Cream Colourless Colourless Colourless Colourless Colourless Colourless Colourless Yellow
a Calculated values in parentheses.
The MLCT transition for bipy occurs at lower energy than that for phen, however, and so the extent of conjugation is not the only factor governing the energies of these transitions. (b) NMR spectroscopy. (i) ‘H NMR. Common features of all these spectra are the characteristic singlet near 0 ppm (S) for the Si(CH3)3 hydrogens, and the 1 : 4 : 1 “triplet” for
+/ z
the methylene hydrogens, as a result of spin-spin coupling to 19?t (I = &34% abundant). ‘J(Pt-H) is generally of the order of 9&94 Hz in all the dialkyl complexes. Replacement of one R group by halide causes a reduction of 15-20 Hz. 2J(Pt-H) associated with the coordinated diene protons are 73 and 35 Hz for those tram to Cl and R, respectively. A distinctive feature of the ‘H spectra of these complexes is the broadening of the ‘95Pt satellites
6
4
3
6
ON\ f 2
3’
R
YN'
0
d
5’
/
1‘\\
-PPh
0 5 6
2
4”
Fig. 1.
b
3
4
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II)
complexes
1959
Table 2. ‘H NMR characteristics of LPtRX (R = CH,SiMe,) Complex L
X
6 ‘H ppm CH$i(CH& (JR-n) CH, CH3
6 ‘H ancillary ligand(s) L (JR-n) [Assignment]
1.14(93.6 Hz)
0.31
1.34-l .89m [CH,], 4.46(41.5 Hz) [CH]
cod
R” Cl”
1.35(76.4 Hz)
0.39
1.331.84m [CH& 3.96(73.0 Hz) [CH trans to Cl], 5.29(34.6 Hz) [CH trans to R]
cod
Ib
1.47(76.9 Hz)
0.10
1.94-2.45m [CHA, 4.67(74.2 Hz) [CH trms to I], 5.44(39.8 Hz) [CH truns to R]
nbd
1.27(102.7 Hz)
0.29
l.Ot [CHJ, 3.27m [CH], 4.52m (40.6 Hz) [CH=CH]
bipy
R” R”
1.28(89.7 Hz)
0.35
6&m 6.66d
Me,bipy
R’
1.23(81.6 Hz)
0.37
bipym
R”
1.45(91.6 Hz)
0.46
phen
R’
1.45(90.1 Hz)
0.36
cod
D&lVHrH, = 5.7 Hz), (Jnrn, = 1.3 Hz), W,l &+.I, = 8.0 Hz), 7.OOm[H4], 9.09(27.5 Hz)
[Hd (-&+H~ =
5.0 Hz) 1.54 [CH,], 6.32dd [HJ, 6.74 [H3], 8.98dd [H,] (Jn6uI = 5.7 Hz) 6.05t [H,], 8.28dd [H4], 8.99(21.4 Hz) [H6] (Jn,n, = nrub = 5.7 Hz) 6.72m [H,,] (JscstYsj = 5.1 Hz), 6.87s [H, J, 7.44dd
D-L.,1(Jq~~~~~ = 8.0 Hz), 9.32dd[Hz,1Vy9bq7)= 1.2 Hz) Ph,phen
R
1.57(90.8 Hz)
0.47
Me,phen
R” R”
1.60(90.2 Hz)
0.58
bipyz
1.75(90.8 Hz)
0.42
(PY)2
R
0.77(89.2 Hz)
0.19
terpY
BF,d
0.91(77.7 Hz)
0.01
6.83d [H3,*] (Js(st2(9j = 5.4 Hz), 7.05-7.17m [ph], 7.31 Wd9.46d (23.0 Hz) D32.91 1.71, 1.88 [CH,], 7.36 [H& 9.30(23.1 Hz) [H,,] 8.92(20.2 Hz) 7.92d P-U V~+,s = 2.9 Hz), 8.12 11-13], [HJ 6.25m [H,], 6.74m [Hd (Ju,_n,,, = 7.6 Hz), (JH~H, = 1.6 Hz), 8.32m (20.9 Hz) [H2] (JHrH, = 6.4 Hz) 7.97(11.4 Hz) [HS,Y], 8.51(15.7 Hz) [H4,4”],8.59-8.65 obs [Hs,Y,Y,v,Y].9.06(52.8 Hz) [Hs,6”]
(PMG2
R”
0.36(72.9 Hz)
0.19
0.86m (20.4 Hz) [CH,] (‘J,-,
PW2
R
0.64(73.0 Hz)
0.33
0.77-0.88 [CH,], 1.44-1.53m [CHJ
PMe2W2
Rb
0.50(76.2 Hz)
0.03
1.32m (19.9 Hz) [CH,] (2Jp_H= 7.6 Hz), 7.43-7.55m [H,,], 7.65-7.74m [Hz]
PPh2M42
R”
1.06(78.6 Hz)
0.36
1.55m (19.7 Hz) [Me] (“J,-, [H3,.,], 7.47-7.54m [H,]
0.38
6.94m [H3,.,], 7.57-7.65m [H2]
WW2
R”
1.14m
dwm
Rb
0.93(85.6 Hz)
-0.25
dppe
Rb
0.72(82.5 Hz)
-0.36
dmf
R’
0.95br
a Run bRun ‘Run d Run
in in in in
0.15
= 7.6 Hz)
= 7.0 Hz), 7.01-7.05m
4.21m [CHd (‘J&_u = 18.4 Hz), 7.25-7.43m [H,,d, 7.51-7.59m [H2] 2.12m [CH,], 7.367.39 [H,,J, 7.55-7.62m [H2] 3.77 [H3.,& 4.10 [H,:,,], 7.05m [H+,], 7.83br [H2]
benzene-d,. chloroform-d ,. toluene-d,. acetone-d,.
of the methylene resonance upon coordination of nitrogen donor ligands. This phenomenon appears to be a general feature of alkylplatinum complexes of this type and is attributed 14,’’ to quadrupolar relaxation of ‘95Pt by “N. A similar effect has been
noted previously in the ‘H spectra of MeHgI complexes where efficient relaxation of ‘99Hg by “‘1 broadens the satellite peaks to the extent that they cannot be resolved. ’ * Slight broadening of the central methylene resonance is sometimes discernible
1960 Table
S. K. THOMSON 3. 3LP NMR
characteristics CH,Si(CH,),)
Complex L We3Ph
(WP), (PhMezP)2C (Ph,MeP),’ (Ph3P)z’ dPPm’ dPpe’ dPpfb
6 3‘P” ppm -26.31 5.13 - 14.78 2.81 24.98 -42.38 43.61 19.55
“Referenced to external H,PO,/D,O bRun in benzene-d,. ’ Run in chloroform-d ,.
of LPtR,
(R =
JR-+.
1945.1 1987.1 1989.4 1998.2 2004.9 1575.1 1938.4 2020.4
Hz Hz Hz Hz Hz Hz Hz Hz
and G. B. YOUNG Table 4. Ring contributions
Compound L*
&pm dpPe dPPf (Ph,MeP),
6P
6F”
-42.4 43.6 91.6 2.8
-22.7 -13.2 -17.1 -28.1
for L,Pt(CH,Si(CH,),), Chelate ring size -19.7 56.8 36.7 30.9
-50.6 25.9 5.8 0.0
4 5 7 -
a Free phosphine chemical shifts obtained from ref. 15.
85%.
for these complexes, due, presumably to enhancement of ‘H relaxation by ’ 'N but this is clearly a
less significant effect. (ii) 31P NMR. The 3’P NMR spectra show the expected 1 : 4 : 1 “triplet” as a result of spin-spin coupling concoupling of 31P to 195Pt. ‘J(Pt-P) stants are generally in the range 194&2000 Hz, typical for cis-bis(phosphine)platinum(II) complexes. As has been previously noted for complexes with different alkyl groups, I9 ‘J(Pt-P) for (dppm)PtR2 has an appreciably lower value. This reduction originates from the angular constraints around P and Pt due to the four-membered ring.lga A ring contribution, AR, to the chemical shift results upon coordination of phosphorus nuclei in chelate rings, with the magnitude and direction of this shift dependent on ring substitution and size. The value of AR = A -A: has been measured for LzPtMe, (L2 = dppm, dppe, dppp, dppb) where A is the change in shift upon coordination and 8: is a standard ring contribution.20 Comparison with the values obtained for the trimethylsilyhnethyl complexes (Table 4) shows them to be in accord with these findings. We have noted similar trends for related silylmethylplatinum complexes. I4 A further notable aspect which emerges from these 31Pspectra is that the magnitude of ‘J(Pt-P) is consistently greater (by ca 300 Hz) than for neopentyl analogues (see Section iv). (iii) 13CNMR. All the compounds have been characterized by 13C{‘H} NMR. Assignments are in * Sample of (Et3P)ZPt(CH2CMe3)2prepared according to Whitesides et ~1.~”
accord with those discussed elsewhere, particularly in related bis(ethenyldimethylsilylmethy1) l4 and bis(phenyldimethylsilylmethy1) ’ 5 complexes. Variation of the N-donor ligands produces little change in the chemical shifts or 3J(Pt-C) values for the trimethylsilylmethyl group, an indication of the similar electronic and steric environments conferred by this series of ancillary ligands. From these spectra it emerges that ‘J(Pt-C) is uniformly smaller than in comparable neopentyl complexes (aide infru) . (iv) General implications. Compared with analogous neopentylplatinum(I1) derivatives with diene,3” N-donor I and P-donor3a ligands, trimethylsilylmethylplatinum(II) complexes exhibit several notable characteristics. First of all, ‘J(Pt-C) for the q ‘-alkyl is significantly lower (by 170180 Hz) for trimethylsilylmethyl. This trend is paralleled in ‘H NMR spectra by decreased ‘J(Pt-H) in the neopentyl case. On the other hand, ‘J(Pt-C) for the diene ligand in, for example, (cod)Pt(CH2SiMe3)2 is correspondingly larger than for (cod)Pt(CH,CMe,), (Fig. 2). The same trend is evident in 2J(Pt-H methine) values for the q2-alkene. For phosphine complexes, for instance triethylphosphine (Fig. 3), the reduction (178 Hz) in ‘J(Pt-C) for (Et3P)2Pt(CH2SiMe3)2* is matched by an increase in ‘J(Pt-P) of 349 Hz, which is in the typical range for analogues for which comparative data are available. The extent of change in ‘J(Pt-C) and ‘J(Pt-P) is comparable (ca 23%). We have noted closely similar trends in comparisons of neophylplatinum complexes with silaneophyl-” and (related) sila-neohexenylplatinum14 analogues. Based on the assumption of Fermi contact dominance of ‘J magnitudes,23 we ascribe the variations to greater attraction by the carbon than by the silicon containing ligand for the platinum 6s orbitals. This, in turn, is as a result of deployment of greater 2s character in the Pt-C bond by a ligating carbon with a more electronegative alkyl
Synthesis and spectroscopic characteristics of trimethylsilylmethylplatinum(II)
complexes
1961
Fig. 2.
Fig. 3. Table 5. 13CNMR characteristics of LPtRX (R = CH,Si(CH,),) Complex L
X
6 13Cppm CH2Si(CHJ3 (Jpt--c) CHz CH3
6 13C ancillary ligand(s) L (&& [Assignment]
cod
R”
13.89(712.4 Hz)
3.58(31.0 Hz)
29.99 [CH,], 97.53(62.8 Hz) [CH]
cod
Clb
16.39(529.0 Hz)
255(16.5 Hz)
28.15(22.1 Hz), 31.92(22.8 Hz) [CHJ, 83.47(215.9 Hz), 111.12(35.2 Hz) [CH]
cod
Ib
12.64(570.0 Hz)
3.51(17.0 Hz)
28.72t18.0 Hz), 31.28(21.0 Hz) [CHA, 89.31(181.0 Hz), 109.21(39.0 Hz) [CI-Ij
nbd
Rb
16.88(754.0 Hz)
3.22(33.0 Hz)
48.79(41.0 Hz) [CH), 72.85(51.0 Hz) [CHJ, 84.84(54.0 Hz) [CH==CH]
bipy
R”
- 6.27(793.4 Hz)
3.29(36.4 Hz)
121.86(10.8 Hz) [C,], 126.12(20.1 Hz) [C,], 134.65 [C,], 147.26(32.8 Hz) [C J, 156.17 [Cd
Me,bipy
R”
- 7.44(747.5 Hz)
3.37(36.2 Hz)
21.10 [CH,], 122.72(11.6 Hz) [C,], 127.01(20.5 Hz) [C,], 146.36 [C,], 146.85(33.2 Hz) [Cd, 156.19 [Cd
bipym
R”
- 7.00(762.2 Hz)
3.22(36.2 Hz)
123.07(16.0 Hz) [&I, 152.52(28.8 Hz) [C,], 155.29 [C,,], 162.90 [CA
1962
Table 5 (continued) Complex L
X
6 13CPPm CH&(CH3)3 CHz
6 ’ 3C ancillary ligand(s) L (&__,-) [Assignment]
(Jpt--c) CH3
phen
R”
- 7.59(754.0 Hz)
3.34(36.6 Hz)
Ph,phen
R”
-6.97(747.7
Hz)
3.51t35.7 Hz)
Me,phen
R”
-7.96(749.1
Hz)
3.52(36.4 Hz)
14.37, 16.96 [CH,], 122.50 [C,,,], [C13,14 obs], 133.27(20.0 Hz) [C& 140.70 [Cd,,], 147.17 [C ,,,, 2], 148.30(33.9 Hz) [C,,,]
terry
BF,,’
4.89(733.0 Hz)
2.48(18.1 Hz)
125.05 [C,,.], 126.60(30.2 Hz) [C,,..], 129.57(43.9 Hz) [C,,..], 141.51 [C,.], 142.51 [C,,..], 153.01(31.2 Hz) [C,:.], 153.34 [C,,..], 161.17 [C,:,.]
bipyz
R”
Hz)
3.08(35.0 Hz)
139.85(29.8 Hz) [C,], 144.37(9.2 Hz) [CS], 149.17 [C2], 149.23 [C,]
(PY)z
Rd
- 11.22(749.1 Hz)
2.86(37.6 Hz)
125.18(20.5 Hz) [C& 126.51 [&I. 130.50 [C,3,,4], 134.09 [C& 147.0(33.4 Hz) [Cw], 148.38
[C,,,,,l
124.7 [C4’], 125.88(20.9 Hz) [C,,,], [(& obs], 128.91 [C,,], 129.21 [C,.], 137.82 [C& 146.62(33.3 Hz) [&,I, 147.23
[C,,l, 148.91[C,,,,,l
-3.92(708.7
124.75 [C,,,], 134.71 [C,], 150.90(14.9 Hz)
G,el
(PMe,),
Rb
6.35(528.2 Hz) (JPSG = 7.7 Hz) = 94.1 Hz) (JP<,
3.98(29.8 Hz)
17.56(29.2 Hz) [CH,] (Jp4
(PJ%),
Rb
5.80(544.5 Hz) (JP-G = 8.1 Hz)
4.36(28.7 Hz)
18.31(18.1 Hz) [CH,], 17.00(22.5 Hz) [CHJ (Jp< = 27.9 Hz)
(PMezPh)z
Rb
4.00(29.2 Hz)
15.2q27.5 Hz) [CH,] (Jp4 = 31.5 Hz), 128.0 [C,] (Jp4 = 8.9 Hz), 129.26 [C.,], 131.04(16.1 Hz) [Cd (Jp4 = 10.9 Hz), 139.10(16.9 Hz) [C,] (Jp4 = 43.6 Hz)
(PMePh&
Rb
7.41(552.9 Hz)
3.95(29.3 Hz)
14.63(23.0 Hz) [CHJ (Jp4 = 31.6 Hz), 127.86(14.4 Hz) [C,] (Jp4 = 8.8 Hz), 129.19 [C,], 132.99(14.5 Hz) [Cd (JP-c = 10.7 Hz), 136.43(18.7 Hz) [C,] (Jp-c = 44.3 Hz)
Rb
8.53
4.04(28.9 Hz)
127.39(8.6 Hz) [C,] (Jpx = 8.7 Hz), 129.16 [C,], 133.90(18.5 Hz) [C,] - 43.9 Hz), 134.84(10.8 Hz) [CJ 22 = 10.9 Hz)
(JP-c,
= 30.5 Hz)
obs)
6.45(538.3 Hz) = 7.5 Hz) = 93.2 Hz) zz_
(JP+, = 6.7 Hz) (JPQk.= 91.6 Hz) Rb
5.41(572 6 Hz) (JP<<~ = 6.7 Hz) (JP-c,, = 94.1 Hz)
3.75(30.6 Hz)
49.09(11.4 Hz) [CHZ] (Jpx = 51.2 Hz), 128.49(10.9 Hz) [C,] (Jpx = 9.9 Hz), 130.20 [C.,], 132.80(19.2 Hz) [Cd - 30.0 Hz), 133.00(12.6 Hz) [Cd gz = 12.6 Hz)
dppe
Rb
1.94(551.1 Hz) (JP-G~ = 5.5 Hz) (JP--c,, = 89.3 Hz)
3.58(28.9 Hz)
28.1Om [CHJ, 128.30 [C,] (Jp4 = 9.7 Hz), 130.10 [C,], 133.03 (25.5 Hz) [Gl, (JP-c = 40.2 Hz), 133.57 [CJ (JPX = 11.0 Hz)
dppf
Rd
8.53(568.0 Hz) (JP-G = 7.3 Hz) (JP+_ = 93.7 Hz)
4.58(28.5 Hz)
72.19 [C,:,.], 75.28 [C,:,.] (Jc_p = 8.8 Hz), 79.46 [C,.] (Jp< = 47.8 Hz), 127.82 [C,], 130.09 [C,], [C, obs], 135.70(11.7 Hz) [C,] (Jp4 = 11.2 Hz)
aRun in benzene-d, b Run in chloroform-d,. ‘Run in acetone-d,. dRun in toluene-d *.
Synthesis and spectroscopic characteristics of trimetbylsilylmethylplatinum(II)
complexes
1963
Table 6. r3C NMR characteristics of nitrogen donor ligands 6 i3C ppm [Assignments]
Ligand 2,2’-bipyridine”
156.8 [CJ, 149.65 [C J, 137.40 [C,], 124.15 [C3], 121.34 [C,]
2,2’-bipyrimidine”
161.0 [Cd, 156.7 [C.,, Cd, 120.3 [C,]
1, lo-phenanthrolineb
150.1 [C2, C,], 146.1 [Cr,, C&-J, 135.9 [C4, C,], 128.5 [C13. C,,], 126.4 ]C,, C,I, 122.9 ]C3, Cd 149.8 [C,, C,], 148.4 [C, ,, C12], 138.0 [C,, C,], 126.4 (C,3, C,,], 128.4 [Cs, C,], 123.4 [C,, C,], 146.8, 129.5, 128.5, 123.9 [C,H,] - -
4,7diphenyl-
1,IO-phenanthroline’
0From ref. 2 1. bFrom ref. 22. ‘From ref. 6.
Table 7. First MLCT absorption 1, for L,PtR,” Complex bipyPtR, MezbipyPtR, bipymPtRz bipyzPtR, pheriPtR, PhzphenPtR2 Me,phenPtR,
[terpP’WBF4
&
(nm) 516.0 507.5 539.5 564.0 511.0 519.0 480.0 482.0
a Measured in toluene.
(as opposed to silaalkyl) substituent, in accord with isovalent hybridization. ’ 4*24 A corollary is that trimethylsilylmethyl appears to exert a lesser (bond-weakening) truns-influence than does neopentyl. Ancillary hgand dissociation is often a prerequisite for thermolytic rearrangements in complexes of this type. Such a ground state energetic difference may have a kinetic influence on lability and contribute (in part at least) to the readier reactivity of neopentyl (and neophy16) complexes relative to their silicon analogues. ’ * We shall report in due course on our mechanistic observations. An apparent paradox in these ‘.Z data, however, is the implication that the neopentyl-platinum bond is stronger than that in complexes, trimethylsilylmethyl-platinum the which contradicts previous thermochemical indications.4*5 We are also investigating this aspect.
REFERENCES 1 For reviews, see (a) R. R. Schrock and G. W. Parshall, Chem. Reu. 1976, 76, 243 ; (b) P. J. Davison, M. F. Lappert and R. Pearce, Chem. Rev. 1976,76,219; (c) M. C. Baird, J. Orgunomet. Chem.
1974, 64, 289 ; (d) P. S. Brateman and R. J. Cross,
Chem. Sot. Rev. 1973,2,271; Seealso, for example, (e) G. M. Whitesides, J. F. Gaasch and E. R. St&on&y, J. Am. Chem. Sot. 1972,94, 5258 ; (f) R. G. Nuzzo, T. J. McCarthy and G. M. Whitesides, J. Am. Chem. Sot. 1981, 103, 3396 ; (g) S. Komiya, Y. Morimoto, A. Yamamoto and T. Yamamoto, Organometallics
1982, 1, 1528.
2. See, for example, (a) S. D. Chapell and D. J. ColeHamilton, PoZyhedron 1982, 1, 739 ; (b) I. P. Rothwell, Polyhedron 1985,4,2; (c) J. C. Calabrese, M. C. Colton, T. Hershovitz, U. Kablunde, G. W. Parshall, D. L. Thorn and T. H. Tulip, Annu. N.Y. Acad. Sci. 1983,415, 302; (d) G. B. Young, in Znorganic Reactions and Methods (Edited by J. J. Zuckerman). Springer, Berlin, in press. 3. (a) P. Foley, R. DiCosimo and G. M. Wbitesides, J. Am. Chem. Sot. 1980,102,6713 ; (b) R. A. Andersen, R. A. Jones and G. Wilkinson, J. Chem. Sot., Dalton Trans. 1978, 446 ; (c) P. Diversi, G. Ingrosso, A. Lucherini and D. Fasse, J. Chem. Sot., Chem. Commun. 1982,945 ; (d) T. H. Tulip and D. L. Thorn, J. Am. Chem. Sot. 1981,103,2448 ; (e) J. W. Bruno, T. J. Marks and V. W. Day, J. Organomet. Chem. 1983,250,237.
4. (a) J. C. Baldwin, M. F. Lappert, J. B. Pedley and J. S. Pollard, J. Chem. Sot., Dalton Trans. 1972, 1943 ; (b) J. C. Baldwin, M. F. Lappert, J. B. Pedley and J. A. Treverton, J. Chem. Sot. (A) 1967,198O ; (c) I. E. Giimrtikciioglii, J. Jeffery, M. F. Lappert, J. B. Pedley and A. K. Rai, J. Organomet. Chem., in press. 5. J. W. Bruno, T. J. Marks and L. R. Morss, J. Am. Chem. Sot. 1983,105,6824. 6. (a) D. C. Griffiths and G. B. Young, Polyhedron 1983,2, 1095 ; (b) D. C. Griffiths and G. B. Young, OrganometaIlics, in press. 7. B. Ankianiec, D. J. Wilkes and G. B. Young, unpublished results. 8. (a) M. M. Truelock, D.Pbil. thesis, University of Sussex (1971); (b) B. Wozniak, J. D. Ruddick and G. Wilkinson, J. Chem. Sot. (A) 1971, 3116. 9. D. F. Shriver, The Manipulation of Air Sensitive Compounds. McGraw-Hill, New York (1969). 10. J. X. McDermott, J. F. White and G. M. Wbitesides, J. Am. Gem.
Sot. 1976,98,6521.
S. K. THOMSON 11. C. R. Kistner, J. H. Hutchinson, J. R. Doyle and J. C. Storlie, Inorg. Chem. 1963,2, 1255. 12. E. G. Cox, H. Saerger and W. Wardlaw, J. Chem. Sot. 1934, 182. 13. N. Chaudhury and R. J. Puddephatt, J. Organomet. Chern. 1975,84,105. 14. R. D. Kelly and G. B. Young, Polyhedron, in press. 15. B. Ankianiec and G. B. Young, Polyhedron, in press. 16. V. Christou and G. B. Young, to be published. 17. R. R. Rumininski and J. D. Petersen, Znorg. Chem. 1982, 21, 3706 ; V. F. Sutcliffe and G. B. Young, Polyhedron 1984,3, 87. 18. D. N. Ford, P. R. Wells and P. C. Lauterbur, J. Chem. Sot., Chem. Commun. 1967,616. 19. (a) P. S. Braterman, R. J. Cross, L. Manjlovic-Muir,
and G. B. YOUNG
20. 21. 22. 23.
24.
K. W. Muir and G. B. Young, J. Organomet. Chem. 1975, 84, 0; (b) T. G. Appleton, M. A. Bennett and I. B. Tompkins, J. Chem. Sot., Dalton Trans. 1976,439 ; (cl M. Bochman, G. Wilkinson and G. B. Young, J. Chem. Sot., Dalton Trans. 1980, 1879. P. E. Garrou, Chem. Rev. 1981,81,229. C. A. Overton and J. A. Connor, Polyhedron 1982, 1, 53. A. Kiinnecke, E. Lipmann, J. Mlochowski and W. Sliwa, Org. Mag. Res. 1979, 12,696. P. S. Pregosin, Annu. Rep. NMR Spectrosc. 1986, 17, 285 ; A. Pidcock, A.C.S. Adv. Chem. Ser. 1982, 196, 1 and refs cited in both. H. A. Bent, Chem. Rev. 1961,61,275.