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Application of spectroscopic techniques to the complexes formed by reaction of zeise's salt derivatives with carbon monoxide
86
P. S. HALL et al.
of chloroform using a stream of warm dry air. On addition of dry n-hexane (20 cm3) to the point of cloudiness, the product was precipitated. The products, truns-[PtX,(CO)(L)] (X = Cl or Br ; L = an or Him) were isolated by vacuum filtration, washed with n-hexane and stored over silica gel in a vacuum desiccator (< 0.1 mmHg) at - 5°C. (b) Preparation oftrans-ptX,(CO)(py)]
(X = Cl or
Br) trans-[PtX,(CO)(py)] (X = Cl or Br) was prepared from trans-[PtX,(C,H&py)] (X = Cl or Br) as described in (a), except that n-hexane (10 cm3) was added before the cloudiness occurred, and the resulting solution was placed over silica gel in a large partly evacuated desiccator and stored at -5°C overnight, during which time the solvent evaporated resulting in the formation of needlelike crystals of truns-[PtX,(CO)(py)] (X = Cl or Br) which were collected and stored as described in (a).
(c) Attempted preparation o( = Cl or Br)
of trans-[PtX,(CO)(pz)]
(1) Attempts to prepare trans-[PtX,(CO)(pz)] (X = Cl or Br) from trans-ptX,(C,H&pz)] using the method described in (a) resulted in the formation of the bridged complex trans-[Pt2X,(CO),(pz)] in quantitative yield. (2) H[Pt(CO)X,] (X = Cl or Br) (1 mmol), prepared as described by Gribov et a1.,6 was dissolved in chloroform. Reaction of this solution with pyrazine in various molar ratios always resulted in the
formation of truns-[Pt,X,(CO),(pz)], while the addition of a large excess of pyrazine (> 10 mmol) resulted in the formation of trans-[ptxZ(pz)J. 7 (3) Crystals of [ptCl,(CO)&, prepared as described in the literature8*9 were dissolved in chloroform and allowed to react with pyrazine, in various molar ratios. All attempts resulted either in no reaction or in the formation of either transfPt2C14(CO),(pz)] or trans-[ptC12(pz)J. (4) The salts [NR,][PtX,(CO)] (X = Cl or Br, R = Pe or Bu:) were prepared as described by Browning et al. lo Reaction of these salts with pyrazine, in various molar ratios, resulted either in no reaction or in the formation of truns-ptX&z)d. (d) Preparation or Br)
of trans-[Pt2X,(CO),(
(X = Cl
was prepared from l?Gww2cPa [Pt,X,(C,H&(pz)] as described in (a), except for the fact that larger volumes of chloroform (- 70 cm’) are required to dissolve the ethylene complexes. The purity and composition of all the compounds were determined by microanalysis (C, H and N) (Table 1). The deuterated complexes were similarly prepared using the following labelled compounds supplied by Merck, Sharp & Dohme (Canada) Ltd (isotopic purity in parentheses) : ammonia-d, (99%), aniline-d, (98%), and imidazole-d, (98%) ; and the following compounds supplied by BOC Prochem Ltd: pyridine-d, (99%) and pyridine-d, N-oxide (98%). The deuteroimine groups of 1,2,4,5-tetradeuteroimidazole (Him-d,) undergo rapid exchange
Table 1. Analytical data Found
Calculated % c
%H
%N
% C
% H
% N
Molecular weight (mass spectrum)
trurzs-[PtCl,(CO)(an)] trans-[PtCl,(CO)@yO)]
21.7 18.5
1.8 1.3
3.6 3.6
21.8 18.6
1.9 1.3
3.7 3.5
386 b
trans-[PtCl,(CO)@y)] trans-[PtCl,(CO)(NH,)] trans-[PtCl,(CO)(Him)]
19.3 3.9 3.3
1.4 1.0 1.1
3.8 4.5 7.7
19.2 4.0 13.3
1.4 1.0 1.1
3.8 4.5 7.7
372 310 361
trans-[PtBrz(CO)(an)] trans-[PtBr,(CO)@yO)] trans-[PtBr,(CO)@y)] trarzs-PtBr,(CO)(NH,)] trans-[PtBr,(CO)(Him)]
7.7 5.1 5.6 3.0 10.7
1.5 1.1 1.1 0.8 0.9
2.9 2.9 3.0 3.5 6.2
17.6 15.1 15.7 3.0 10.7
1.5 1.1 1.1 0.8 0.9
2.9 2.9 3.1 3.5 6.2
474 460 398 449
tram-[Pt,CI,(CO),(pz)] trans-[PtzBr,(CO),(pz)]
10.8 8.5
0.6 0.5
4.2 3.3
10.9 8.7
0.6 0.6
4.2 3.3
666 842
Compound
“Based on 19’Pt “Cl and 79Br. ‘Greater m/z odserved.
6
Reaction of Zeise’s salt derivatives with carbon monoxide in aqueous or ethanolic solution to yield complexes
containing 2,4,5&ideuteroimidazole (Him-d,). The ‘H NMR spectra were run at ambient temperature on a Bruker WH-90 spectrometer using CD,COCD3 as the solvent and TMS as reference. The IR spectra were determined as Nujol mulls (4000-1500 and 1300-300 cm-‘) or hexachlorobutadiene mulls (4000-l 700 and 150&l 300 cm- ‘) between CsBr plates on a Perkin-Elmer 983 s~trophotometer, and as Nujol mulls between polyethylene plates (500-80 cm- ‘) on a Digilab FTS-16 B/D interferometer. The W spectra were determined on a Varian Superscan 3 spectrophotometer using CH30H as solvent. Mass spectra were measured on a VG Micromass 16/F instrument operating in the electron impact mode, with electron beam energy = 70 eV, ion-accelerating voltage = 3 kV, and with ion source temperatures in the range lOO-195°C. Microanalyses were performed by Mr W. R. T. Hemsted of the University of Cape Town.
RESULTS AND DISCUSSION
IR spectra The spectrum of each compound was determined twice, firstly in the unlabelled form and secondly with the ligand (L) in the deuterated form. The frequency data and assignments for the internal ligand modes of the complexes are listed in Table 2, while the far-IR frequencies are given in Table 3. The internal vibrations of the ligands, L, are assigned to those bands which shift significan~y on deuteration of L, with more specific assigmnents made from their vD/vH ratios. ” Assignments are made in relation to the analogous ethylene compounds’ and earlier use of the vD/vHratio in complexes of aniline, ’ I pyridine ’ ’ and imidazole, ’ * while the assignments for the pyridine N-oxide complexes follow those reported from a normal coordinate analysis of the free ligand. I 3-I 5 The v(C=G) frequencies were determined in chlorofo~, as well as in Nujol mulls. The former resulted in a single sharp band, while the latter sometimes resulted in splittings which may arise from rotational fine structure in the solid state.6 The simplicity of the IR spectrum in the v(C&) region is consistent with truns coordination. The far-IR assignments are in good accord with previous work “3 ’ 6**? on related complexes and the 6(Pt--C=O) band is at higher frequency than that of v(Pt-C) as expected in metal carbonyls.‘8,‘9 Only one previous IR study of complexes of this type has been reported,6 in which Gribov and
87
co-workers reported the IR spectrum of trans~~Cl~(CO)~~)]. Two bands were observed in the skeletal region, at 532 and 477 cm-‘, both of which were attributed to S(Pt-C%O) deformations. We now attribute these to the defo~ation &P&--C&G) and stretching v(pt--C), respectively. As expected, the v(Pt-N) frequency is substantially lower in the complexes trans-[PtzX,(CO)(pz)] (where the pyrazine is bridging) than in the complexes where similar ligands are terminal, e.g. trms[PtXZ(CG)(PY)l.
‘H NMR spectra The *H NMR data for the complexes are given in Table 4. Exa~~tion of the data reveals that some of the complexes show 19’Pt-H coupling. The complexes trans+PtX,(CO)(Him)] fx = Cl or Br) and drub-[PtBr*(CO)~y)] exhibit coupling at ambient temperature while trans-[PtCl,(CO)(py)] exhibits coupling at reduced temperatures. This suggests that ligand exchange is relatively slow in the former three complexes, with pyridine being more labile in the latter. The above is in direct contrast to the analogous ethylene complexes, ‘,*’ trff~-FtX*(C*H~)(L)], where exchange is rapid at ambient temperature as indicated by an absence of 19’Pt-H coupling. This emphasizes the weaker “tram effect” of carbon monoxide relative to C2H4. “‘Pt-H coupling was not observed in the complexes trans-[PtX,(CO)(L)] (X = Cl or Br, L = py0 or an), probably because the protons are separated by at least four bonds from the platinum atom, The absence of coupling in the complexes trans[Pt2X4(C0)2(pz)] may indicate rapid exchange but this is not easy to verify since all four protons are equivalent when the pyrazine plays a bridging role.
~~e~~ronicspectra The electronic spectral data are listed in Tables 5 and 6. By analogy with similar complexes previously studied21-23 we expect to observe the IE--, n*(CO) transition as well as the SdPt -+ x*(CO) inverse-charge-transfer and the X- -+ Pt*+ chargetransfer bands. In addition, in complexes where L is a ligand which has n-electrons present, there is the possibility of a 5~Pt-~*~~gand) inversecharge-transfer transition. Since some of the transitions overlap, giving rise to broad bands, some of the assignments are tentative. We observe the previously reportedz3 red shift in the Sd(Pt) -+ rc* transition which results from the replacement of Cl by Br in the complexes.
88
P. S. HALL et al. Table 2. Internal ligand frequencies (cm-‘) and assignments for the complexes trans-[PtX,(CO)(L)] and trans-[PtzX,(CO),(pz)] x = Cl
X = Br
L
Unlabelled
L-deuterated
Unlabelled
NH3
3292
3280 3201
2145 2139 (2129)b 1636 1535 1294 784
2459 2427 2377 2145 2138 (2130) 1296 1210 1073 505
3122 3110 3059
2603 2479 2359
2123
2121
(2133) 1612 1483 ‘1451 1354 1242 1218 1213 1157
(2133) 1571 1536 1327 1238 894 845 839 835 830
1072 1022 941 760
983 1030 804 778
PY
PYO
3200
688 685 660 507 503 433
631 503 498 397
3134 3109 3083 3055 2108
2335 2315 2308 2284 2108
(2117) 1615
(2117) 1571 1549 1353 1141 1248 1196
1473 1259 1245 1197
638
L-deuterated
2128
2420 2369 2331 2126 I
(2126) 1626 1529 1289 782
(2125) 1 1287 1202 1 1067 772
3098 3075 3048 3041 2126 2111 (2128) 1609 1599 1483 1451 1352 1243
2599 2476 2359 2331 I 2126 2111 (2128) I 1568 1534 1325 1238 1 789 739
1213
641
1160 1092 1076 1020 870 762 758 692 689 660 507
678 I 1042 982 1033 1
440 437
403 1
3113 3078 3063 3036 2097 2052 (2113) 1612
2395 2331 2307 2284 I 2101 2049 (2113) 1 1569 1547 I 1351 1145
1473 1262 1194
739 733 1 532 529 } 559 504
1195
Assignment”
W--H)
NH2 scissor NH2 twist NH, wag
v(C-H)
v(-) (84 @b) (194 VW
v(fing)
(14) (3)
&C-H)
(9a) (15) (18b)
&-b> (12) (10’4 (11)
Y(C--H)
Wng) 1/K--HI
(4) (6a)
Wing) y(r&s)
(16b)
v(C-H)
v(ring) + v(Nv@ng) v(N--o) v(ring)
-0)
(4) (5) (6)
89
Reaction of Zeise’s salt derivatives with carbon monoxide Table 2. (Cont.) x = Cl
X = Br
L
Unlabelled
L-deuterated
Unlabelled
L-deuterated
PYO
1186 1173 1156 1153 1094
875 859 844 830 817
1171 1159 1156 1095 1070
875 858 843 829 787
1068 1053 1027 1004
782 1040 1009 989
935 831
765 567
776 669
531 657
598
567
1056 1033 1026 1004 967 933 830 814 804 773 673 637 591
1040 1017 994 988 1 778 764 573 564 545 531 I 655 636 573 I
3229 3182 3123 3051 3025
3262 3213 3108 3045 3007
3263 3214 3102 I 2359 2331 I 2122
1575
3229 3184 3118 2390 2366 2331 2144 2120 (2130) 1581 1573 1563
1493 1471 1216 1191 1178
1424 1380 1206 1137 1173
1073 1028
842 822
767 756 691 643 580 530
769 757 657 617 574 531
3550 3179 3157 3136 2965 2847
3348 2597 2369 2338 2883 2597
an
2121 (2130) 1599
Him
2119
Assignment” (7) (18) 6(C-H) (19) (8)
(2125) 1599 1595 1569 1561 1493 1466 1198 1180 1162 1145 1069 1029 973 909 798 760 742 691 578 554 483
(2125) 1 1579 I 1559 )
3345 3173 3153 3131 2964 2849
3343 2597 2366 2336
1377 1299 1166 1135 1 1158 1022 842 822 790 765 i 749 764 738 1 534 529 465
Wnf4
Y(C--HI (27) (28) Wxit) VW-H) v(C-H)
v(-) v@h) NH2 scissor
vG-&d NH2 twist
6(C-H)
vbhi9 IQ% wag v(C-H) &ring) NH z rock y(rW VW-H)
v(C-H) I
P. S. HALL et al. Table 2. (Cont.) x = Cl L Him
X = Br
Unlabelled
L-deuterated
Unlabelled
L-deuterated
2129 2116 (2127) 1545 1516 1510
2129 2116 (2127) 1493 1471 1452
2122 2109 (2121) 1491
1483 1428 1328 1272 1261 1225 1183 1131 1096 1073 1067 853 837 753 744 708 653 646 613 504
1429 1400 1193 1283 945 978 896 876 867 828 820 772 739
2123 2109 (2121) 1545 1515 1510 1495 1479 1429 1328 1271 1265 1221 1191 1131 1102 1072 1068 852 835 751 742 695 653 645 611 504
3146 3115 3101 3068 3051 2136 2089 (2138) 1493 1433 1426 1172 1126 1120 1104 1091
2359 2341 2323 2297 2277 2135 2089 (2139) 1297 1189 1180 1174 886 860
729 707 589 582 521 497
1473
I
v(W)
I
1417 1404 1373 1291
Assignment”
v(r%r)
i
1278
&N-H)
977 894 875
&C-H)
867 828 945 821 774 738
1 1
727 695 587 581 564 502
I
~~~-Fbx4w%bz)l 3120 3094 3045 3023 2993 2131 2082 (2134) 1490 1437 1422 1166 1131 1122 1103 1090 1013 977 823
2331 2312 2299 2287 2273 2131 2082 (2136) 1291 1172 1160 1136 884 850 1095 1060 1011 976 662
742 552 472 460
724 536
973 824 816 761 552
452
472
’ Band numbers refer to those given in Ref. 1. bValues in parentheses are those obtained in chloroform solution.
v(C-H) I
I
v6-W 1 6(C-H)
v(rW
91
Reaction of Zeise’s salt derivatives with carbon monoxide
Table 3. Metal-ligand
frequencies and ligand isotopically-induced shifts (cm-‘) in the IR spectra of the complexes frans-[PtXz(CO)Q] and rrans-[ptzX,(CO),(pz)]
VW--c>
VW--N)
v(Pt--cl)
Other
or v(Pt-0)
NH,, Cl
531(O)
465(6)
479(7)
349( 1)
208(3) 168(3) 152(l) 123(O)
PY. Cl
541(3)
479(O)
226(13)
353(O)
215(2) 159(l) 124(l)
PYO, Cl
580(5)
508( 1)
440(23) 413(20)
352( 1)
216(2) 158(l) 129( 1)
an, Cl
557(O)
484(4)
477(17) 369(11)
345(O)
215(-) 172(5) 132(O)
Him, Cl
543(3) 485(2)
538(2)
lOY-) 252( 13)
350(O)
162(O) 128(O) 99(l) 84(l)
~~~~-Fw,oMP~01
510(7)
486(2)
186(l)
357( 1)
151(4) 126(2)
NH,, Br
528(O)
481(3)
466(8)
254(O)
205(4) 174(2) 99(l) 90(l)
PY, Br
544(4) 507(3)
488(O)
230(19)
261(l)
185(10) 102(O)
PYQ Br
576(6) 490(8)
511(l)
436(19) 402(14)
258( 1)
222(6) 180( -) 134(3)
an, Br
530(3)
493(2)
434(20)
254(O)
219( -) 207(6) 165(-) 149(5)
Him, Br
538(O)
479(O)
229(8)
271(6)
196(6)
80(2)
97(2) 85(-) 510(6)
493( 1)
174(6)
259( 1)
144(2) 100(O) 88(O)
aNumbers in parentheses are the shifts (cm- ‘) induced by ligand deuteration.
92
P. S. HALL et al.
Table 4. ‘H NMR data
JR-H
Chemical shift @pm) X
Complex
Cl Br
H,
Hb
H,
Jm-H,
JR-IS,, JR-~
Multiplet at 7.36 Multiplet at 7.42
“b
Cl Br
8.73 8.71
7.97 7.98
8.23 8.23
Cl Br
8.78 8.78
7.76 7.72
8.22 8.18
“b
“b
(III)
o=c-Pt-NH,
i
4.46 broad 4.47 broad
Cl Br
I i (IV)
OIC-Pt-
N
Cl Br
8.48 8.51
Cl Br
9.26 9.17
(V)
X
HI,
osc--Pt-
i
N’
“a
i
‘N-Pt-CsO
X
“Not observed. bCoupling observed at 270 K.
7.52 7.53
7.40 7.40
17 18
18 18
D 0
Table
5. UV
data for
the complexes
Ft2XmMPzll
truns-[PtX,(CO)(L)]
and
truns-
o( = Cl) Assignment
NH3
200 240 278
16,605 5766 3228
Cl- -# Pt2+ a * n*(CO) Sd(Pt) + 7qCO)
PY
201 239 254 284
14,942 3704 4342 894
Cl- -+ pt*+ 71 -) n*(CO) x --) x’k)y) Sd(Pt) + n*(CO), Sd(Pt) -+ n*(py)
PYO
204 263b
23,322 14,730
Cl- + pt*+ 7c+ n*(CO), II --r x*(pyo),
an
201 234 278
19,233 7659 2042
Cl- --f PtZ+ 7r+ a*(CO), 7c+ x*(an) sd(Pt) -+ 7qCO)
Him
201 236 247 278
15,748 4209 4480 2444
Cl- + PtZ+ II + n*(CO) x --t s*(Him) Sd(Pt) + x*(CO). 5d(Pt) + n*(Him)
209 265 320’
28,012 17,336 2930
Sd(Pt) + n*(CO)
~r~dR2WC~)2Wl Cl- + Ptz+ 7c+ s*(pz), ‘II+ x*(CO) sd(Pt) + x*(co), sd(Pt) + x*@z)
LICH,OH used as the solvent. bBroad band. Table
6. UV
data for
the complexes
Ft2XdWb41 L
0
truw[PtX,(CO)(L)]
and truns-
(x = Br) Assignment
E
-
NH3
205 240 290
34,55 1 2675 1115
Br- -+ Pt2+ 7r+ s*(co) Sd(Pt) + 7?(CO)
PY
203 249 255 295
29,571 4743 4902 1107
Br- + Pt2+ K + n*(CO)
PYO
206 263b
38,350 14,792
Br- + Pt*+ R --, n*(CO), It + n*(pyO), Sd(Pt) -+ n*(CO)
an
202 238 282
34,273 8047 2077
Br- + Pt*+ R + x*(co), II + s*(co) 5cqPt) + n*(co)
Him
206 242 255 290
31,187 2859 2079 780
Br- + Pt*+ x --t 7qCO) R + n*(Him) Sd(Pt) --t n*(CO), Sd(Pt) + n*(Him)
x + x*(l-JY) S&J%) -+ n*(CO), Sd(Pt) + 7rQy)
@~-[Pt2Br&Wpx)l 213 263 318’
33,005 18,803 2725
Br- + Pt*+ n + ?F(pz), n + nZ(CO) Sd(Pt) -+ n*(CO), Sff(Pt) + s*@z)
0 CHSOH used as the solvent. bBroad band. 93
P. S. HALL et al.
94
AcknowIe&ement-We Research Development ance
thank the Foundation for of the CSIR for financial assist-
REFERENCES 1. T. P. Auf der Heyde, G. A. Foulds and D. A. Thornton, J. Mol. Struct. 1983,!%, 11. 2. W. H. Clement and M. Orchin, J. Organomet. Chem. 1965,3, 98. 3. F. Basolo and R. G. Pearson, Mechanisms of Inorganic Reactions, 2nd Edn, p. 376. Wiley, New York (1967). 4. G. A. Foulds, D. A. Thornton and J. Yates, J. Mol. Strut. 1983,98,315. 5. M. Orchin and P. J. Schmidt, Znorg. Chim. Acta, Rev. 1968,1,123. 6. L. A. Gribov, A. D. Gel’man, F. A. Zakhavova and M. M. Orlova, Russ. J. Znorg. Chem. 1960,5,473. 7. G. A. Foulds and D. A. Thornton, Spectrochim. Acta 1981,37A, 917. 8. R. J. Irving and E. A. Magnusson, J. Chem. Sot. 1956, 1860. 9. F. Mylius and F. Foerster, Chem. Ber. 1891, 24, 2424. 10. J. Browning, P. L. Goggin, R. J. Goodfellow, M. G. Norton, A. J. M. Rattray, B. F. Taylor and J. Mink, J. Chem. Sot., Dalton Trans. 1977,206l.
Il. G. A. Foulds, J. B. Hodgson, A. T. Hutton, G. C. Percy, P. E. Rutherford and D. A. Thornton, Spectrosc. Lett. 1979, 12, 25. 12. J. B. Hodgson, G. C. Percy and D. A. Thornton, J. Mol. Struct. 1980,66, 75. 13. A. Gambi and S. Ghersetti, Spectrosc. Lett. 1977,8, 627. 14. V. Tabaick, V. Pellegrin and M. Gonthard, Spectrochim. Actu 1979,35A, 1055. 15. M. Cordes and J. L. Walter, Spectrochim. Acta 1968, 24A, 237. 16. M. J. Cleare and W. P. Griffith, J. Chem. Sot. 1969, 37. 17. P. L. Goggin and R. J. Goodfellow, J. Chem. Sot., Dalton Trans. 1973, 2355. 18. K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, 2nd Edn, p. 197. Plenum Press, New York. 19. F. Carderazzo, R. Ercoli and G. Natta, Organic Syntheses via Metal Carbonyls, p. 1. Wiley Interscience, New York (1968). 20. G. A. Foulds, G. E. Jackson and D. A. Thornton, J. Mol. Strut. 1983, 98,232. 21. D. Sutton, Electronic Spectra of Transition Metal Complexes. McGraw-Hill, London (1968). 22. G. A. Foulds and D. A. Thornton, J. Mol. Struct. 1983,98, 309. 23. M. A. M. Meesters, D. J. St&kens and K. Vriese, Znorg. Chim. Acta 1975, 14,25.
P. S. HALL et al.
of chloroform using a stream of warm dry air. On addition of dry n-hexane (20 cm3) to the point of cloudiness, the product was precipitated. The products, truns-[PtX,(CO)(L)] (X = Cl or Br ; L = an or Him) were isolated by vacuum filtration, washed with n-hexane and stored over silica gel in a vacuum desiccator (< 0.1 mmHg) at - 5°C. (b) Preparation oftrans-ptX,(CO)(py)]
(X = Cl or
Br) trans-[PtX,(CO)(py)] (X = Cl or Br) was prepared from trans-[PtX,(C,H&py)] (X = Cl or Br) as described in (a), except that n-hexane (10 cm3) was added before the cloudiness occurred, and the resulting solution was placed over silica gel in a large partly evacuated desiccator and stored at -5°C overnight, during which time the solvent evaporated resulting in the formation of needlelike crystals of truns-[PtX,(CO)(py)] (X = Cl or Br) which were collected and stored as described in (a).
(c) Attempted preparation o( = Cl or Br)
of trans-[PtX,(CO)(pz)]
(1) Attempts to prepare trans-[PtX,(CO)(pz)] (X = Cl or Br) from trans-ptX,(C,H&pz)] using the method described in (a) resulted in the formation of the bridged complex trans-[Pt2X,(CO),(pz)] in quantitative yield. (2) H[Pt(CO)X,] (X = Cl or Br) (1 mmol), prepared as described by Gribov et a1.,6 was dissolved in chloroform. Reaction of this solution with pyrazine in various molar ratios always resulted in the
formation of truns-[Pt,X,(CO),(pz)], while the addition of a large excess of pyrazine (> 10 mmol) resulted in the formation of trans-[ptxZ(pz)J. 7 (3) Crystals of [ptCl,(CO)&, prepared as described in the literature8*9 were dissolved in chloroform and allowed to react with pyrazine, in various molar ratios. All attempts resulted either in no reaction or in the formation of either transfPt2C14(CO),(pz)] or trans-[ptC12(pz)J. (4) The salts [NR,][PtX,(CO)] (X = Cl or Br, R = Pe or Bu:) were prepared as described by Browning et al. lo Reaction of these salts with pyrazine, in various molar ratios, resulted either in no reaction or in the formation of truns-ptX&z)d. (d) Preparation or Br)
of trans-[Pt2X,(CO),(
(X = Cl
was prepared from l?Gww2cPa [Pt,X,(C,H&(pz)] as described in (a), except for the fact that larger volumes of chloroform (- 70 cm’) are required to dissolve the ethylene complexes. The purity and composition of all the compounds were determined by microanalysis (C, H and N) (Table 1). The deuterated complexes were similarly prepared using the following labelled compounds supplied by Merck, Sharp & Dohme (Canada) Ltd (isotopic purity in parentheses) : ammonia-d, (99%), aniline-d, (98%), and imidazole-d, (98%) ; and the following compounds supplied by BOC Prochem Ltd: pyridine-d, (99%) and pyridine-d, N-oxide (98%). The deuteroimine groups of 1,2,4,5-tetradeuteroimidazole (Him-d,) undergo rapid exchange
Table 1. Analytical data Found
Calculated % c
%H
%N
% C
% H
% N
Molecular weight (mass spectrum)
trurzs-[PtCl,(CO)(an)] trans-[PtCl,(CO)@yO)]
21.7 18.5
1.8 1.3
3.6 3.6
21.8 18.6
1.9 1.3
3.7 3.5
386 b
trans-[PtCl,(CO)@y)] trans-[PtCl,(CO)(NH,)] trans-[PtCl,(CO)(Him)]
19.3 3.9 3.3
1.4 1.0 1.1
3.8 4.5 7.7
19.2 4.0 13.3
1.4 1.0 1.1
3.8 4.5 7.7
372 310 361
trans-[PtBrz(CO)(an)] trans-[PtBr,(CO)@yO)] trans-[PtBr,(CO)@y)] trarzs-PtBr,(CO)(NH,)] trans-[PtBr,(CO)(Him)]
7.7 5.1 5.6 3.0 10.7
1.5 1.1 1.1 0.8 0.9
2.9 2.9 3.0 3.5 6.2
17.6 15.1 15.7 3.0 10.7
1.5 1.1 1.1 0.8 0.9
2.9 2.9 3.1 3.5 6.2
474 460 398 449
tram-[Pt,CI,(CO),(pz)] trans-[PtzBr,(CO),(pz)]
10.8 8.5
0.6 0.5
4.2 3.3
10.9 8.7
0.6 0.6
4.2 3.3
666 842
Compound
“Based on 19’Pt “Cl and 79Br. ‘Greater m/z odserved.
6
Reaction of Zeise’s salt derivatives with carbon monoxide in aqueous or ethanolic solution to yield complexes
containing 2,4,5&ideuteroimidazole (Him-d,). The ‘H NMR spectra were run at ambient temperature on a Bruker WH-90 spectrometer using CD,COCD3 as the solvent and TMS as reference. The IR spectra were determined as Nujol mulls (4000-1500 and 1300-300 cm-‘) or hexachlorobutadiene mulls (4000-l 700 and 150&l 300 cm- ‘) between CsBr plates on a Perkin-Elmer 983 s~trophotometer, and as Nujol mulls between polyethylene plates (500-80 cm- ‘) on a Digilab FTS-16 B/D interferometer. The W spectra were determined on a Varian Superscan 3 spectrophotometer using CH30H as solvent. Mass spectra were measured on a VG Micromass 16/F instrument operating in the electron impact mode, with electron beam energy = 70 eV, ion-accelerating voltage = 3 kV, and with ion source temperatures in the range lOO-195°C. Microanalyses were performed by Mr W. R. T. Hemsted of the University of Cape Town.
RESULTS AND DISCUSSION
IR spectra The spectrum of each compound was determined twice, firstly in the unlabelled form and secondly with the ligand (L) in the deuterated form. The frequency data and assignments for the internal ligand modes of the complexes are listed in Table 2, while the far-IR frequencies are given in Table 3. The internal vibrations of the ligands, L, are assigned to those bands which shift significan~y on deuteration of L, with more specific assigmnents made from their vD/vH ratios. ” Assignments are made in relation to the analogous ethylene compounds’ and earlier use of the vD/vHratio in complexes of aniline, ’ I pyridine ’ ’ and imidazole, ’ * while the assignments for the pyridine N-oxide complexes follow those reported from a normal coordinate analysis of the free ligand. I 3-I 5 The v(C=G) frequencies were determined in chlorofo~, as well as in Nujol mulls. The former resulted in a single sharp band, while the latter sometimes resulted in splittings which may arise from rotational fine structure in the solid state.6 The simplicity of the IR spectrum in the v(C&) region is consistent with truns coordination. The far-IR assignments are in good accord with previous work “3 ’ 6**? on related complexes and the 6(Pt--C=O) band is at higher frequency than that of v(Pt-C) as expected in metal carbonyls.‘8,‘9 Only one previous IR study of complexes of this type has been reported,6 in which Gribov and
87
co-workers reported the IR spectrum of trans~~Cl~(CO)~~)]. Two bands were observed in the skeletal region, at 532 and 477 cm-‘, both of which were attributed to S(Pt-C%O) deformations. We now attribute these to the defo~ation &P&--C&G) and stretching v(pt--C), respectively. As expected, the v(Pt-N) frequency is substantially lower in the complexes trans-[PtzX,(CO)(pz)] (where the pyrazine is bridging) than in the complexes where similar ligands are terminal, e.g. trms[PtXZ(CG)(PY)l.
‘H NMR spectra The *H NMR data for the complexes are given in Table 4. Exa~~tion of the data reveals that some of the complexes show 19’Pt-H coupling. The complexes trans+PtX,(CO)(Him)] fx = Cl or Br) and drub-[PtBr*(CO)~y)] exhibit coupling at ambient temperature while trans-[PtCl,(CO)(py)] exhibits coupling at reduced temperatures. This suggests that ligand exchange is relatively slow in the former three complexes, with pyridine being more labile in the latter. The above is in direct contrast to the analogous ethylene complexes, ‘,*’ trff~-FtX*(C*H~)(L)], where exchange is rapid at ambient temperature as indicated by an absence of 19’Pt-H coupling. This emphasizes the weaker “tram effect” of carbon monoxide relative to C2H4. “‘Pt-H coupling was not observed in the complexes trans-[PtX,(CO)(L)] (X = Cl or Br, L = py0 or an), probably because the protons are separated by at least four bonds from the platinum atom, The absence of coupling in the complexes trans[Pt2X4(C0)2(pz)] may indicate rapid exchange but this is not easy to verify since all four protons are equivalent when the pyrazine plays a bridging role.
~~e~~ronicspectra The electronic spectral data are listed in Tables 5 and 6. By analogy with similar complexes previously studied21-23 we expect to observe the IE--, n*(CO) transition as well as the SdPt -+ x*(CO) inverse-charge-transfer and the X- -+ Pt*+ chargetransfer bands. In addition, in complexes where L is a ligand which has n-electrons present, there is the possibility of a 5~Pt-~*~~gand) inversecharge-transfer transition. Since some of the transitions overlap, giving rise to broad bands, some of the assignments are tentative. We observe the previously reportedz3 red shift in the Sd(Pt) -+ rc* transition which results from the replacement of Cl by Br in the complexes.
88
P. S. HALL et al. Table 2. Internal ligand frequencies (cm-‘) and assignments for the complexes trans-[PtX,(CO)(L)] and trans-[PtzX,(CO),(pz)] x = Cl
X = Br
L
Unlabelled
L-deuterated
Unlabelled
NH3
3292
3280 3201
2145 2139 (2129)b 1636 1535 1294 784
2459 2427 2377 2145 2138 (2130) 1296 1210 1073 505
3122 3110 3059
2603 2479 2359
2123
2121
(2133) 1612 1483 ‘1451 1354 1242 1218 1213 1157
(2133) 1571 1536 1327 1238 894 845 839 835 830
1072 1022 941 760
983 1030 804 778
PY
PYO
3200
688 685 660 507 503 433
631 503 498 397
3134 3109 3083 3055 2108
2335 2315 2308 2284 2108
(2117) 1615
(2117) 1571 1549 1353 1141 1248 1196
1473 1259 1245 1197
638
L-deuterated
2128
2420 2369 2331 2126 I
(2126) 1626 1529 1289 782
(2125) 1 1287 1202 1 1067 772
3098 3075 3048 3041 2126 2111 (2128) 1609 1599 1483 1451 1352 1243
2599 2476 2359 2331 I 2126 2111 (2128) I 1568 1534 1325 1238 1 789 739
1213
641
1160 1092 1076 1020 870 762 758 692 689 660 507
678 I 1042 982 1033 1
440 437
403 1
3113 3078 3063 3036 2097 2052 (2113) 1612
2395 2331 2307 2284 I 2101 2049 (2113) 1 1569 1547 I 1351 1145
1473 1262 1194
739 733 1 532 529 } 559 504
1195
Assignment”
W--H)
NH2 scissor NH2 twist NH, wag
v(C-H)
v(-) (84 @b) (194 VW
v(fing)
(14) (3)
&C-H)
(9a) (15) (18b)
&-b> (12) (10’4 (11)
Y(C--H)
Wng) 1/K--HI
(4) (6a)
Wing) y(r&s)
(16b)
v(C-H)
v(ring) + v(Nv@ng) v(N--o) v(ring)
-0)
(4) (5) (6)
89
Reaction of Zeise’s salt derivatives with carbon monoxide Table 2. (Cont.) x = Cl
X = Br
L
Unlabelled
L-deuterated
Unlabelled
L-deuterated
PYO
1186 1173 1156 1153 1094
875 859 844 830 817
1171 1159 1156 1095 1070
875 858 843 829 787
1068 1053 1027 1004
782 1040 1009 989
935 831
765 567
776 669
531 657
598
567
1056 1033 1026 1004 967 933 830 814 804 773 673 637 591
1040 1017 994 988 1 778 764 573 564 545 531 I 655 636 573 I
3229 3182 3123 3051 3025
3262 3213 3108 3045 3007
3263 3214 3102 I 2359 2331 I 2122
1575
3229 3184 3118 2390 2366 2331 2144 2120 (2130) 1581 1573 1563
1493 1471 1216 1191 1178
1424 1380 1206 1137 1173
1073 1028
842 822
767 756 691 643 580 530
769 757 657 617 574 531
3550 3179 3157 3136 2965 2847
3348 2597 2369 2338 2883 2597
an
2121 (2130) 1599
Him
2119
Assignment” (7) (18) 6(C-H) (19) (8)
(2125) 1599 1595 1569 1561 1493 1466 1198 1180 1162 1145 1069 1029 973 909 798 760 742 691 578 554 483
(2125) 1 1579 I 1559 )
3345 3173 3153 3131 2964 2849
3343 2597 2366 2336
1377 1299 1166 1135 1 1158 1022 842 822 790 765 i 749 764 738 1 534 529 465
Wnf4
Y(C--HI (27) (28) Wxit) VW-H) v(C-H)
v(-) v@h) NH2 scissor
vG-&d NH2 twist
6(C-H)
vbhi9 IQ% wag v(C-H) &ring) NH z rock y(rW VW-H)
v(C-H) I
P. S. HALL et al. Table 2. (Cont.) x = Cl L Him
X = Br
Unlabelled
L-deuterated
Unlabelled
L-deuterated
2129 2116 (2127) 1545 1516 1510
2129 2116 (2127) 1493 1471 1452
2122 2109 (2121) 1491
1483 1428 1328 1272 1261 1225 1183 1131 1096 1073 1067 853 837 753 744 708 653 646 613 504
1429 1400 1193 1283 945 978 896 876 867 828 820 772 739
2123 2109 (2121) 1545 1515 1510 1495 1479 1429 1328 1271 1265 1221 1191 1131 1102 1072 1068 852 835 751 742 695 653 645 611 504
3146 3115 3101 3068 3051 2136 2089 (2138) 1493 1433 1426 1172 1126 1120 1104 1091
2359 2341 2323 2297 2277 2135 2089 (2139) 1297 1189 1180 1174 886 860
729 707 589 582 521 497
1473
I
v(W)
I
1417 1404 1373 1291
Assignment”
v(r%r)
i
1278
&N-H)
977 894 875
&C-H)
867 828 945 821 774 738
1 1
727 695 587 581 564 502
I
~~~-Fbx4w%bz)l 3120 3094 3045 3023 2993 2131 2082 (2134) 1490 1437 1422 1166 1131 1122 1103 1090 1013 977 823
2331 2312 2299 2287 2273 2131 2082 (2136) 1291 1172 1160 1136 884 850 1095 1060 1011 976 662
742 552 472 460
724 536
973 824 816 761 552
452
472
’ Band numbers refer to those given in Ref. 1. bValues in parentheses are those obtained in chloroform solution.
v(C-H) I
I
v6-W 1 6(C-H)
v(rW
91
Reaction of Zeise’s salt derivatives with carbon monoxide
Table 3. Metal-ligand
frequencies and ligand isotopically-induced shifts (cm-‘) in the IR spectra of the complexes frans-[PtXz(CO)Q] and rrans-[ptzX,(CO),(pz)]
VW--c>
VW--N)
v(Pt--cl)
Other
or v(Pt-0)
NH,, Cl
531(O)
465(6)
479(7)
349( 1)
208(3) 168(3) 152(l) 123(O)
PY. Cl
541(3)
479(O)
226(13)
353(O)
215(2) 159(l) 124(l)
PYO, Cl
580(5)
508( 1)
440(23) 413(20)
352( 1)
216(2) 158(l) 129( 1)
an, Cl
557(O)
484(4)
477(17) 369(11)
345(O)
215(-) 172(5) 132(O)
Him, Cl
543(3) 485(2)
538(2)
lOY-) 252( 13)
350(O)
162(O) 128(O) 99(l) 84(l)
~~~~-Fw,oMP~01
510(7)
486(2)
186(l)
357( 1)
151(4) 126(2)
NH,, Br
528(O)
481(3)
466(8)
254(O)
205(4) 174(2) 99(l) 90(l)
PY, Br
544(4) 507(3)
488(O)
230(19)
261(l)
185(10) 102(O)
PYQ Br
576(6) 490(8)
511(l)
436(19) 402(14)
258( 1)
222(6) 180( -) 134(3)
an, Br
530(3)
493(2)
434(20)
254(O)
219( -) 207(6) 165(-) 149(5)
Him, Br
538(O)
479(O)
229(8)
271(6)
196(6)
80(2)
97(2) 85(-) 510(6)
493( 1)
174(6)
259( 1)
144(2) 100(O) 88(O)
aNumbers in parentheses are the shifts (cm- ‘) induced by ligand deuteration.
92
P. S. HALL et al.
Table 4. ‘H NMR data
JR-H
Chemical shift @pm) X
Complex
Cl Br
H,
Hb
H,
Jm-H,
JR-IS,, JR-~
Multiplet at 7.36 Multiplet at 7.42
“b
Cl Br
8.73 8.71
7.97 7.98
8.23 8.23
Cl Br
8.78 8.78
7.76 7.72
8.22 8.18
“b
“b
(III)
o=c-Pt-NH,
i
4.46 broad 4.47 broad
Cl Br
I i (IV)
OIC-Pt-
N
Cl Br
8.48 8.51
Cl Br
9.26 9.17
(V)
X
HI,
osc--Pt-
i
N’
“a
i
‘N-Pt-CsO
X
“Not observed. bCoupling observed at 270 K.
7.52 7.53
7.40 7.40
17 18
18 18
D 0
Table
5. UV
data for
the complexes
Ft2XmMPzll
truns-[PtX,(CO)(L)]
and
truns-
o( = Cl) Assignment
NH3
200 240 278
16,605 5766 3228
Cl- -# Pt2+ a * n*(CO) Sd(Pt) + 7qCO)
PY
201 239 254 284
14,942 3704 4342 894
Cl- -+ pt*+ 71 -) n*(CO) x --) x’k)y) Sd(Pt) + n*(CO), Sd(Pt) -+ n*(py)
PYO
204 263b
23,322 14,730
Cl- + pt*+ 7c+ n*(CO), II --r x*(pyo),
an
201 234 278
19,233 7659 2042
Cl- --f PtZ+ 7r+ a*(CO), 7c+ x*(an) sd(Pt) -+ 7qCO)
Him
201 236 247 278
15,748 4209 4480 2444
Cl- + PtZ+ II + n*(CO) x --t s*(Him) Sd(Pt) + x*(CO). 5d(Pt) + n*(Him)
209 265 320’
28,012 17,336 2930
Sd(Pt) + n*(CO)
~r~dR2WC~)2Wl Cl- + Ptz+ 7c+ s*(pz), ‘II+ x*(CO) sd(Pt) + x*(co), sd(Pt) + x*@z)
LICH,OH used as the solvent. bBroad band. Table
6. UV
data for
the complexes
Ft2XdWb41 L
0
truw[PtX,(CO)(L)]
and truns-
(x = Br) Assignment
E
-
NH3
205 240 290
34,55 1 2675 1115
Br- -+ Pt2+ 7r+ s*(co) Sd(Pt) + 7?(CO)
PY
203 249 255 295
29,571 4743 4902 1107
Br- + Pt2+ K + n*(CO)
PYO
206 263b
38,350 14,792
Br- + Pt*+ R --, n*(CO), It + n*(pyO), Sd(Pt) -+ n*(CO)
an
202 238 282
34,273 8047 2077
Br- + Pt*+ R + x*(co), II + s*(co) 5cqPt) + n*(co)
Him
206 242 255 290
31,187 2859 2079 780
Br- + Pt*+ x --t 7qCO) R + n*(Him) Sd(Pt) --t n*(CO), Sd(Pt) + n*(Him)
x + x*(l-JY) S&J%) -+ n*(CO), Sd(Pt) + 7rQy)
@~-[Pt2Br&Wpx)l 213 263 318’
33,005 18,803 2725
Br- + Pt*+ n + ?F(pz), n + nZ(CO) Sd(Pt) -+ n*(CO), Sff(Pt) + s*@z)
0 CHSOH used as the solvent. bBroad band. 93
P. S. HALL et al.
94
AcknowIe&ement-We Research Development ance
thank the Foundation for of the CSIR for financial assist-
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Il. G. A. Foulds, J. B. Hodgson, A. T. Hutton, G. C. Percy, P. E. Rutherford and D. A. Thornton, Spectrosc. Lett. 1979, 12, 25. 12. J. B. Hodgson, G. C. Percy and D. A. Thornton, J. Mol. Struct. 1980,66, 75. 13. A. Gambi and S. Ghersetti, Spectrosc. Lett. 1977,8, 627. 14. V. Tabaick, V. Pellegrin and M. Gonthard, Spectrochim. Actu 1979,35A, 1055. 15. M. Cordes and J. L. Walter, Spectrochim. Acta 1968, 24A, 237. 16. M. J. Cleare and W. P. Griffith, J. Chem. Sot. 1969, 37. 17. P. L. Goggin and R. J. Goodfellow, J. Chem. Sot., Dalton Trans. 1973, 2355. 18. K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, 2nd Edn, p. 197. Plenum Press, New York. 19. F. Carderazzo, R. Ercoli and G. Natta, Organic Syntheses via Metal Carbonyls, p. 1. Wiley Interscience, New York (1968). 20. G. A. Foulds, G. E. Jackson and D. A. Thornton, J. Mol. Strut. 1983, 98,232. 21. D. Sutton, Electronic Spectra of Transition Metal Complexes. McGraw-Hill, London (1968). 22. G. A. Foulds and D. A. Thornton, J. Mol. Struct. 1983,98, 309. 23. M. A. M. Meesters, D. J. St&kens and K. Vriese, Znorg. Chim. Acta 1975, 14,25.