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Chemistry of platinum(IV), platinum(II) and palladium(II) cyclometallates of benzylthio- or benzosulphinyl-substituted azobenzenes
421
Journal of Organometallic Chemistry, 414 (1991) 421-431 Elsevier Sequoia S.A., Lausanne
JOM 21935
Chemistry of platinum( IV), platinum( II) and palladium( II) cyclometallates of benzylthio- or benzosulphinyl-substituted azobenzenes Surajit Chattopadhyay, Chittaranjan Sinha, Partha Basu and Animesh Chakravorty * Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032 (India)
(Received February 21st, 1991)
Abstract
Cydometallated platinum(IV) complexes of the type [Pt(RL)CI 3 ) incorporating azobenzene (R = H) or 4-methylazobenzene (R = Me) with an SCH 2Ph (L = Ll) or an S(O)CH 2Ph (L = L2) substituent in an ortho position are described. These were obtained by oxidative addition of chlorine to [PtII(RL)Cl). Analogous palladium(I1) complexes, however, gave chloro-substituted azobenzenes upon reaction with chlorine. The platinum(IV) complexes show an irreversible cyclic voltammetric metal reduction peak near - 0.3 V vs SCE. Constant potential coulometric reduction at - 0.5 V or chemical reduction by hydrazine hydrate regenerated [PtII(RL)Cl). The structures of [Pt(HL1 )CI 3 ), [Pt(Mee)Cl) and [Pd(MeLl)Cl) have been determined by an X-ray diffraction study. The S(O)CH 2Ph group is coordinated via the sulphur atom.
Introduction
The platinum(II)-azobenzene system provided the first example of ortho-metalla tion [1] but the corresponding platinum(IV) organometallics have not been char acterised. Indeed, there are few authentic o-metallated platinum(IV) species of any type [2-10]. We report here the chemistry of several platinum(IV) azobenzene cyclometallates of the coordination type Pt(C,N,s)Cl 3 , along with their platinum(II) analogues of the type Pt(C,N,S)Cl. A PdlI(C,N,S)CI species is also discussed. Results and discussion Synthesis In the ortho-metallation reaction the azobenzene ligand is known to chelate platinum(II) in the bidentate (C,N) fashion [1]. The presence of a suitably posi tioned donor substituent has been found to be very effective in giving rise to stable platinum(IV) cyclometallates, the azobenzene ligand becoming potentially triden 0022-328X/91/$03.50
© 1991 - Elsevier Sequoia S.A.
422
tate. The azobenzenes used in the present contain the donor substituent PhCH 2S or PhCH2 S(O). Reaction of the azobenzenes with K 2PtCl 4 proceeds smoothly in hot aqueous ethanolic solution, to give the brown-coloured platinum(II) complexes in excellent yields. The platinum(IV) complexes are orange-yellow, and are formed in high yields upon oxidative addition of one molar proportion of chlorine to the platinum(II) complexes. The complexes synthesised are listed in Table 1. These belong to the types [PtII(RL1)CIJ (la and lb, [Pt II (RL2)CIJ (3a and 3b), [Ptlv(RLl)CI 3 J (2a and 2b), [Ptlv(RL2)CI 3 J (4a and 4b) where RLI and RL2 represent metallated azobenzenes bearing PhCH 2S and PhCH 2S(O) substituents respectively (R = H or Me). Spectral and structural characterisation The spectra of the platinum(II) and platinum(IV) species in the UV-Vis region are significantly different (Table 1). The absorption in the former species shows more structure and extends to longer wavelengths. The spectra of two representative pairs are shown in Fig. 1. The spectral differences are diagnostic of the oxidation state of the metal in the complexes. Two readily recognisable IR frequencies are p(PtCl) and p(SO). There is a single p(PtCI) band in the platinum(II) complexes; in the platinum(IV) species there are two such bands (Table 1). In the free ligands containing PhCH 2 S(O) substituents, p(SO) is observed as a strong band near 1040 cm -I, and upon complex formation this is shifted to higher energies. The specific frequencies are 1110 in 3a, 1120 in 3b, 1135 in 4a and 1140 cm- 1 in 4b. The shift to higher frequencies is indicative of
Table 1 UV-Vis, IR and IH NMR spectral data Compound
UV-Vis spectral data a (nm) «((dm3 mol-I em-I»
IR spectral data b ,,(PtCl) (em-I)
575 d (2930), 500 (3960), 405 (18900), 375 (23400), 355 (22370), 335 d (18250) 575 d (4390), 490 (4930), 410 (26280), 375 (24640), 358 (20810), 338 d (15880) 5255 d (2230), 490 (3090), 405 (12880), 370 (14420), 355 d (12190) 530 d (3350), 480 (4420), 410 (13710) 375 (12810), 360 d (9600) 465 (9790), 445 (10080), 385 (19580), 360 d (16700) 475 d (6433), 460 (6928), 400 (7918), 360 d (5444) 460 d (8180), 390 (18050), 360 d (14670)
340
4.54
340
4.52
Amax
[Pt(HLI )Cl) (la) [Pt(MeLI)Cl) (lb) [Pt(HL2 )Cl) (3a) [Pt(Mee)Cl) (3b) [Pt(HI!)CI 3 ) (2a) [Pt(MeLI )CI 3 ) (2b) [Pt(HL2 )CI 3 ) (4a) [Pt(MeL2 )CI 3 ) (4b)
475 360
d d
(11940), 455 (13620), 410 (15670), (9330)
340 350 350,325 345,330 350, 330 350, 335
8(CH 2 ) (ppm) eHNMR) (J (Hz»
4.92,4.97 (13.3) 4.90,4.95 (13.0) 4.60,4.90 (14.0) 4.58,4.89 (14.0) 5.12,5.43 (14.0) 5.10,5.41 (14.0)
a In dichloromethane solutions at 298 K. bIn KBr disk. C In CDCl 3 solvent at 298 K; the aromatic protons give rise a complex pattern at 7 to 8.5 ppm. d Shoulder.
423
I
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4.5
3.0
I
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\, 300
400
500
600
700
300
A/nm
400
500
600
A/nm
Fig. 1. Electronic spectra of (a) [Pt(HL1)Cl) (la) ( - - ) and [Pt(HL1)CI 3 ) (2a) (- - -) and (b) [Pt(MeL2 )Cl) (3b) ( - - ) and [Pt(MeL2 )CI 3 ) (4b) ( - - -) in dichloromethane at 298 K.
S-binding. A shift of v(SO) to lower frequencies (- 900 cm-I) is expected for O-binding [11-15]. In the IH NMR spectra in CDC1 3 the methylene protons of the complexes appear as a broad band for la and lb but as AB quartets for the other complexes (Table 1). The methylene chemical shifts of the coordinated PhCH 2 S(O) group in 3a, 3b, 4a and 4b lie 0.5-1.0 ppm downfield from free ligand values [11]. This is indicative of S-binding of the group [12-16]. The structures of one platinum(IV) complex and one platinum(II) complex viz. [Pt 1v(HL1 )C1 3 ] (2a) and [Pt II (MeL2 )CI] (3b) have been determined by an X-ray diffraction study. Molecular structures are shown in Figs. 2 and 3. (The complex [Pt(HL1 )CI 3 ] joins the very small group of structurally-characterised o-metallated
Fig. 2. Molecular structure and numbering scheme for [Pt(HL1)CI 3 ).
424
elll)
ellS) Fig. 3. Molecular structure and numbering scheme for [Pt(MeL2 )Cl].
platinum(IV) complexes [3-7].) Selected bond parameters for the two complexes are listed in Tables 2 and 3. The azobenzene ligands act in the meridional tridentate (C,N,S) fashion in both complexes. In [Pt(MeL2)CI] the PhCH 2S(O) group is S-coordinated and with exclusion of the sulphoxide oxygen and the CH 2Ph group the molecule is planar (mean deviation 0.053 A). In [Pt(HL1 )CI 3 ], the platinum(IV) coordination sphere, Pt(C,N,S)CI 3 , is distorted octahedral, and except for the benzyl group the metallated azobenzene ligand lies in a plane with mean deviation of only 0.035 A. The CI(3) atom also lies in this plane. . The Pt-C distances in the two compounds are equal within experimental error and this also applies to the Pt-N distances. The Pt-CI distances are slightly longer in [Pt(HL1 )CI 3 ]. These observations are in agreement with the very similar radii of platinum(II) (square planar) and platinum(IV) (octahedral) [17,18]. The Pt-S dis tances cannot be compared because of the different nature of the two sulphur atoms. The normal Ptll-S (sulphoxide) distance is 2.22 A [19,20]. In Pt(MeL2)CI the distance is longer, 2.309 A, probably as a result of the trans influence of the coordinated carbon centre [21,22].
Table 2 Selected bond lengths (A) and angles (0) in [Pt(HL1 )CI 3 ] (28) Pt-C(2) Pt-N(2) Pt-S Pt-Cl(1) S-Pt-Cl(l) S-Pt-Cl(2) Cl(1)-Pt-Cl(3) S-Pt-C(2) Cl(2)-Pt-C(2) S-Pt-N(2) Cl(2)-Pt-N(2) C(2)-Pt-N(2) Pt-S-Cl(3)
2.007(15) 1.961(16) 2.441(5) 2.357(5) 86.8(2) 94.4(2) 90.8(2) 164.5(6) 87.9(5) 85.3(4) 91.1(4) 79.4(7) 111.0(6)
Pt-Cl(2) Pt-Cl(3) N(1)-N(2) Cl(1)-Pt-Cl(2) S-Pt-Cl(3) Cl(2)-Pt-Cl(3) Cl(1)-Pt-C(2) Cl(3)-Pt-C(2) Cl(1)-Pt-N(2) Cl(3)-Pt-N(2) Pt-S-C(8) C(8)-C-Cl(13)
2.334(4) 2.317(6) 1.280(20) 178.2(1) 98.2(2) 90.3(2) 90.6(5) 97.1(6) 87.7(4) 176.2(5) 94.6(6) 101.0(9)
425 Table 3 Selected bond lengths (A) and angles (0) in [Pt(MeL2 )CI] (3b) 2.006(20) 1.964(18) 2.286(6)
Pt-C(2) Pt-N(2) Pt-CI
Pt-S N(I)-N(2) S-O(I)
96.8(2) 85.7(2) 165.2(6) 79.5(8) 176.9(6) 98.0(6)
S-Pt-CI S-Pt-N(2) S-Pt-C(2) N(2)-Pt-C(2) N(2)-Pt-CI C(2)-Pt-CI
Pt-S-O(I) Pt-S-C(9) Pt-S-C(14) C(9)-S-C(14) 0(1)-S-C(9) O(I)-S-C(14)
2.309(6) 1.295(25) 1.454(16) 125.3(7) 96.1(7) 113.1(7) 104.1(10) 110.7(9) 105.4(10)
Electrochemical and chemical reduction of platinum(IV) complexes
In acetonitrile solution each platinum(lV) complex shows an irreversible (no anodic peak) cyclic voltammetric metal reduction peak (platinum working electrode; tetraethylammonium perchlorate supporting electrolyte). Specific peak potentials versus saturated calomel electrode are: 2a, -0.26 V; 2b, -0.38 V; 4a, -0.28 V and 4b, - 0.40 V. Methyl-substitution in the metallated benzene ring increases the electron density and shifts the potential substantially to more negative values (compare 2a and 2b or 4a and 4b). Upon constant potential coulometry at -0.5 V two electrons are consumed, and the corresponding platinum(II) complex is quanti tatively produced. Thus the electrode reaction involving metal reduction is associ ated with spontaneous and rapid chloride loss, as in eq. 1. This also accounts for the irreversible nature of the voltammogram, since Pt(RL)Cl is not electroactive in the voltage range ± 0.7 V.
(1)
R
R
cA
cA
N
N
PtCl n ~N/ \
(::rS"I~ 1
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CH 2Ph
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PtlRL2)Cl n R
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3
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14b)
Me
3
426
Cl1l1
Fig. 4. Molecular structure and numbering scheme for [Pd(Mer! )Cl].
When solutions of the platinum(IV) complexes in ethanol were heated they converted into their platinum(II) analogous. The reduction can be brought about more smoothly in acetonitrile at room temperature by use of a stoichiometric proportion of hydrazine hydrate. Comparison with palladium(II) complexes The synthesis of the palladium(II) complexes of type [Pd(RLI)CI] and [Pd(RL2 )CI] were described previously [11,23]. The structure of [Pd(MeL1 )CI] has now been determined and confirms the presence of a planar Pd(C,N,S)CI coordination sphere. A view of the molecule is shown in Fig. 4, and selected bond parameters are listed in Table 4. The behavior of the palladium(II) complexes towards chlorine is entirely differ ent from that of the platinum(II) analogues. The latter undergo oxidative addition at the metal site but with the former chlorine cleaves the Pd-C bond to give chloro-coordinated palladium(II) species and a chlorinated ligand. The observed reactions are represented by eqs. 2, 3. No evidence was found for the formation of a tetravalent palladium(lV) intermediate. The cleavage of the Pd-C bond by chlorine has been reported previously for related organometallics [24,25]. PtII(RL)CI + Cl 2 -+ Pt IV (RL)CI 3 (2) II PdII(RL)CI + Cl -+ Pd Cl + RLCl (3) 2
2
Table 4 Selected bond lengths (A) and angles ( 0) in [Pd(MeL1)Cl] Pd-C(2) Pd-N(2) Pd-Cl S-Pd-Cl S-Pd-N(2) S-Pd-C(2) N(2)-Pd-C(2) N(2)-Pd-Cl
1.988(6) 1.970(4) 2.300(2) 96.5(1) 85.1(2) 163.9(2) 79.6(2) 178.1(2)
Pd-S N(I)-N(2) C(2)-Pd-Cl Pd-S-C(9) Pd-S-C(14) C(9)-S-C(14)
2.375(2) 1.285(7) 98.9(2) 96.3(2) 113.4(2) 103.2(3)
427
Experimental Dipotassium tetrachloroplatinate(II) [26], 2-(benzylthio)azobenzene [11] and 2 (benzylsulphinyl)azobenzene [23] were prepared as previously described. Purifica tion of solvents and the preparation of tetraethylammonium perchlorate for electro chemical work were carried out as described previously [27]. All other chemicals and solvents used for the preparative work were of reagent grade, and were used without further purification. UV-Vis spectra were recorded on a Hitachi spectrophotometer and IR (4000-200 em-I) spectra on a Perkin-Elmer 783 spectrophotometer. Proton NMR spectra were recorded for CDCl 3 solutions on Varian XL 200 and Bruker 270 MHz FT NMR spectrometers. Electrochemical studies were carried out with PAR Model 370-4 electrochemistry apparatus as described elsewhere [28]. Elemental analyses were performed with a Perkin-Elmer 240C elemental analyser. Synthesis Chloro((2 -(benzylthio)phenyl)azo)phenyl-C 2 ,N,S )platinum(II), [Pt(H LI)el] (Ia)
To an aqueous solution (10 cm3 ) of K 2 PtCl 4 (0.10 g, 0.24 mmol) was added slowly a hot ethanolic solution of 2-(benzylthio)azobenzene (0.067 g, 0.22 mmol).
Table 5 Crystallographic data for [Pt(HL1 )CI 3) (2a), [Pt(MeL2)Cl) (3b) and [Pd(MeLI)Cl)
Formula Formula weight Crystal size, mm3 Crystal system Space group
a,A b,A c,A {3, °
V,A3 Z No. centering reflections Centering 29 Dc, g.cm 3 JL(Mo-K ), cm- I a
29 limits h, k, I range No. unique reflections Observed data I> 3(J(I) Parameters refined Ra Rw b g in weighting scheme C Largest peak in final Fourier map, eA - 3
CI9HI5N2Cl3PtS 604.8 0.12xO.18xO.22 Monoclinic
C 20 H 17 N 2OClPtS 564.0 0.06 x 0.14 x 0.12 Monoclinic
C 2o H 17 N 2ClPdS 459.3 0.11 x 0.13 xO.27 Monoclinic
P2J1n
P2J1a
P2J1n
11.773(3) 11.205(4) 15.099(7) 99.48(3) 1964.7(12) 4 25 15 < 29 < 31° 2.045 77.36 2-52 15,14, ± 19 3785 1699 235 0.0518 0.0519 0.000300
9.782(8) 13.932(8) 14.038(10) 98.76(7) 1891(2) 4 15 10 < 29 < 25° 1.981 7u.57 2-50 12,17, ± 17 3329 1418 165 0.0550 0.055 0.000500
11.062(3) 10.963(4) 15.409(4) 100.47(2) 1837.6(9) 4 25 15<28<27° 1.660 12.56 2-55 14,14, ±20 4199 2403 226 0.0412 0.0509 0.000400
0.78
1.00
0.23
a R =L(IFo 1- IFe I)/LIFo I. b Rw=[LW(IFo 1- IFe 1)2;Lw1Fo 12)1/2.
C
1/[(J2(IFo 1)+ glFo 12).
428
The mixture was stirred for 24 h, then the brown-red solution was evaporated in air and the residue washed thoroughly with water and then with ethanol-water (1: 1 vIv). The dark brown residue was chromatographed on silica gel with acetonitrile benzene (1 : 9 vIv) as eluent. A brown band was collected which yielded [Pt(HL1)Cl] in 74% yield (found: C, 42.65; H, 2.79; N, 5.36. Cl9Hl5N2SClPt calcd.: C, 42.73; H, 2.81; N, 5.25%). [Pt(MeL1)Cl (lb), [Pt(HL2)Cl] (3a) and [Pt(MeL2)Cl] (3b) were prepared similarly in 70-80% yield (lb: found: C, 43.61; H, 2.93; N, 5.29. C 20 H 17 N 2SClPt calcd.: C, 43.83; H, 3.10; N, 5.11%. 3a: found: C, 40.97; H, 2.67; N, 4.98. Cl9Hl5N2S0ClPt calcd.: C, 41.49; H, 2.73; N, 5.10%. 3b: found: C, 42.45; H, 2.98; N, 4.67. C 20 H 17 N 2SOClPt calcd.: C, 42.59; H, 3.02; N, 4.97%). Trichloro(((2-(benzylthio)phenyl)azo)phenyl-C 2 ,N,s)platinum(/V), [Pt(HL 1)C131 (2a) To an acetonitrile solution (50 cm3) of Pt(HL1)Cl (0.10 g, 0.19 mmol) was added dropwise 20 cm3 of acetonitrile saturated with chlorine. The mixture was stirred for 0.5 h and then evaporated in the air. The solid was dissolved in dichloromethane and the solution (10 cm3) chromatographed on silica gel with benzene as eluent. An orange yellow band was collected and yielded 0.080 g (70%) of [Pt(HL1)C1 3] (found: C, 37.34; H, 2.52; N, 4.70. Cl9H15N2SCl3Pt calcd.: C, 37.72; H, 2.48; N, 4.63%). [Pt(MeL1)C1 3] (2b), [Pt(HL2)C1 3] (4a) and [Pt(MeL2)C1 3] (4b) were prepared
Table 6 Atomic coordinates (X 10 4 ) for [Pt(HL1 )CI 3 1 Atom
x
y
z
Pt S Cl(l) Cl(2) Cl(3) N(l) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19)
2891(1) 197894) 1140(3) 4655(3) 2384(4) 3878(13) 3326(11) 4103(15) 3700(13) 3890(16) 4494(20) 4890(17) 4666(18) 3015(16) 2345(13) 2002(20) 2321(20) 2961(18) 3329(16) 2862(15) 2277(16) 1234(17) 690(18) 1193(22) 2247(19) 2761(17)
1199(1) 369(5) 829(4) 1541(4) 3178(5) -731(16) -454(15) 294(20) 1415(18) 2426(20) 2249(25) 1192(31) 194(25) -1417(16) -1149(19) -2077(24) -3245(24) -3472(17) -2634(19) 623(18) 192(19) 659(21) 236(22) -648(26) ~ 1095(22) -686(19)
1055(1) - 381(3) 1571(3) 586(3) 779(3) 2150(10) 1374(10) 2670(13) 2323(10) 2836(13) 3717(13) 4059(13) 3550(14) 748(12) -75(12) -674(14) -469(17) 343(17) 982(13) -1248(12) -2143(12) -2560(13) -3372(13) -3792(14) 3445(13) -2597(13)
429
similarly in 60-70% yield (2b: found: C, 38.61; H, 2.80p N, 4.32. C2oH17N2SC13Pt calcd.: C, 38.81; H, 2.75; N, 4.53%. 4a: found: C, 36.49; H, 2.50; N, 4.32. C19HlSN2S0Cl3Pt calcd.: C, 36.75; H, 2.42; N, 4.51%. 4b: found: C, 37.64; H,2.59; N, 4.37. C2oH17N2S0C13Pt calcd.: 37.83; H, 2.68; N, 4.91 %). Reaction of [Pd(MeL1)CI] with chlorine Chlorine gas was passed slowly into an acetonitrile solution (50 cm3) of Pd(MeLl)CI (0.10 g, 0.22 mmol) for 0.5 h and the mixture then stirred for an additional 1 h. The orange yellow solution was evaporated in air and the residue washed thoroughly with water. The aqueous extract contained chloro-coordinated palladium(II). The residue from water was dissolved in dichloromethane (10 cm3) and chromatographed on silica gel with benzene as eluent. An orange yellow band was collected and yielded 0.060 g (71 %) of 2-(benzylthio)azo-o,0' -dichloro-p-toluene (found: C, 61.85; H, 3.90; N, 7.51. C2oH16N2SCl2 calcd.: C, 62.03; H, 4.14; N, 7.24%). X-Ray crystal structure and analysis Crystals suitable for X-ray work were grown by slow diffusion of hexane into dichloromethane solutions at 298 K. Data collection was performed on a Nicolet
Table 7 Atomic coordinates (X 10 4 ) for [Pt(MeL2 )CI] Atom
x
y
z
Pt S CI 0(1) N(l) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(l8) C(19) C(20)
957(1) - 393(6) 2272(7) 105(17) 101(20) -169(20) 1195(23) , 1838(21) 2911(23) 3281(24) 2643(34) 1601(30) 4465(34) -1287(22) -1533(20) -2632(26) -3457(24) - 3218(24) -2142(24) -1485(22) -2129(23) -1488(26) - 2128(25) -3477(27) -4124(25) -3482(23)
212(1) 1445(4) 1131(4) 2235(9) -1541(12) -631(13) -1777(16) -1061(15) -1346(17) -2318(22) -2997(20) -2749(17) -2579(22) -250(19) 708(15) 1117(17) 530(15) -444(15) -844(15) 1993(15) 1290(13) 938(17) 331(18) -2(17) 345(19) 967(15)
2304(1) 1573(5) 3445(5) 1043(11) 1367(14) 1377(14) 2009(16) 2675(15) 3339(15) 3427(20) 2821(21) 2067(22) 4253(24) 753(15) 797(14) 155(18) -483(16) - 519(17) 112(16) 2359(15) 2932(16) 3787(19) 4388(17) 4035(19) 3185(18) 2631(16)
430
Table 8 Atomic coordinates (X 10 4 ) for [Pd(MeL1 )Cl] Atom
x
Y
z
Pd S Cl N(l) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20)
4503(1) 3325(1) 4222(2) 5470(4) 4748(4) 5986(5) 5668(5) 6196(5) 6970(5) 7244(5) 6762(5) 7526(6) 4151(5) 3434(5) 2870(6) 2978(6) 3678(6) 4266(6) 1669(5) 1067(5) 1127(6) 528(7) -145(7) -217(6) 392(6)
2471(1) 4281(2) 2264(2) 1852(5) 2590(5) 1043(6) 1099(6) 275(6) 658(6) -717(6) 125(7) -1587(7) 3502(6) 4362(6) 5286(6) 5362(7) 4494(7) 3599(6) 4053(6) 3102(6) 1883(7) 1023(7) 1341(9) 2532(10) 3439(8)
3274(1) 3281(1) 1766(1) 5064(3) 4570(3) 4550(4) 3616(4) 3130(4) 3537(4) 4459(4) 4962(4) 3003(4) 4990(3) 4455(3) 4830(4) 5733(4) 6256(4) 5897(4) 2876(4) 3339(4) 3125(4) 3520(5) 4i36(5) 4385(5) 3979(4)
R3m/V automated diffractometer using graphite monochromated Mo-Ka radiation
(;\ = 0.71073 A). Crystal data and data collection parameters are listed in Table 5.
Intensities were corrected for Lorentz and polarization effect. An empirical absorption correction was made on the basis of "'-scans [29]. All calculations, data reduction, and structure solution were carried out on a MicroVAX II computer with the SHELXTL-PLUS programs [30]. The positions of metal atom in both [Pt(HLl)CI 3 ] and [Pt(MeL2 )Cl] were determined by heavy atom methods. All nonhydrogen atoms were located from subsequent difference Fourier maps. All nonhydrogen atoms were treated anisotropically for [Pt(HL1 )CI 3 ]. For [Pt(MeL2 )Cl], the atoms within the coordination sphere and those constituting the ortho-metallated benzene ring were treated anisotropically. The structure of [Pd(MeL1 )CI] was solved by direct methods and all the nonhydrogen atoms were refined anisotropically. For all three complexes hydrogen atott\s were included at calculated positions with fixed thermal parameters. Atomic coordinates are collected in Tables 6-8. Tables of H-atom coordinates and thermal parameters, complete lists of bond distances and angles, and lists of structure factors are available from the authors. Acknowledgements We thank the Department of Science and Technology, New Delhi for establish ing a National Single Crystal Diffractometer Facility at· the Department of In
431
organic Chemistry, Indian Association for the Cultivation of Science. Financial support from the Council of Scientific and Industrial Research, New Delhi, is also acknowledged. References 1 Ae. Cope and R.W. Siekman, J. Am. Chern. Soc., 87 (1965) 3272. 2 G. Wilkinson, F.G.A Stone and E.W. Abel (Eds.), Comprehensive Organometallic Chemistry, Pergamon, New York, 1982. 3 G. van Koten, J. Terheijden, J.AM. von Beek, I.C.M.W. Ooyevaar, F. Muller and e.H. Stam, Organornetallics, 9 (1990) 903. 4 E. Wehman, G. van Koten, C.T. Knaap, H. Ossor, M. Pfeffer and AL. Spek, Inorg. Chern., 27 (1988) 4409 and references therein. 5 e.M. Anderson, R.J. Puddephatt, G. Ferguson and AJ. Lough, J. Chern. Soc., Chern. Commun., (1989) 1297. 6 N.W. Alcock, K.H. Brayars and P.G. Pringle, J. Chern. Soc., Dalton Trans., (1990) 1433. 7 I.e.M.W. Ooyevaar, D.M. Grove, P. van der Sluis, AL. Spek and G. van Koten, J. Chern. Soc., Chern. Commun., (1990) 1367. 8 C.C. Deuschel and A von Zelewsky, Inorg. Chern., 26 (1987) 3354 and references therein. 9 D. Sandrini, M. Maestri, V. Balzani, L. Chassot and A von Zelewsky, J. Am. Chern. Soc., 109 (1987) 7720. 10 L. Chassot and A. von Zelewsky, Helv. Chim. Acta., 69 (1986) 1855. 11 C. Sinha, D. Bandyopadhyay and A. Chakravorty, Inorg. Chern., 27 (1988) 1173. 12 J.A. Davies, Adv. Inorg. Chern. Radiochern., 24 (1981) 115. 13 J.H. Price, A.N. Williamson, R.F. Schramm and B.B. Wayland, Inorg. Chern., 11 (1972) 1280. 14 G. Anniback, L. Cattalini, L. Canoverse, B. Pitteri, A Tiripicchio, M.T. Carnellini and M.L. Tobe, J. Chern. Soc., Dalton Trans., (1986) 1101. 15 M.J. Root and E. Deutsch, Inorg. Chern., 24 (1985) 1464. 16 W. Kitching, e.J. Moore and D. Doddrell, Aust. J. Chern., 22 (1969) 1149. 17 R.D. Shanon, Acta Crystallogr., Sect. A, 32 (1976) 751. 18 F.R. Hartley, The Chemistry of Platinum and Palladium, Applied Science Publishers Ltd., London, 1973. 19 P. Bitha, G.O. Morton, T.S. Dunne, E.F. Delos Santos, Y. Lin, S.R. Boone, R.C. Haltiwagner and e.G. Pierpont, Inorg. Chern., 29 (1990) 645. 20 F.D. Rochon, P.e. Kong and R. Melanson, Inorg. Chern., 29 (1990) 1352. 21 T.G. Appleton, H.e. Clark and L.E. Manzer, Coord. Chern. Rev., 10 (1973) 335 22 R.e. Elder, R.D.P. Curea and R.F. Morrison, Inorg. Chern., 15 (1976) 1623. 23 A.K. Mahapatra, D. Bandyopadhyay, P. Bandyopadhyay and A. Chakravorty, Inorg. Chern., 25 (1986) 2214. 24 D.R. Fahey, J. Organornet. Chern., 27 (1971) 283. 25 A.D. Ryabov, Synthesis, (1985) 233. 26 S.E. Livingstone, Synth. Inorg. Met.-Org. Chern., 1 (1971) 1. 27 G.K. Lahiri, S. Bhattacharya, M. Mukherjee, AK. Mukherjee and A Chakravorty, Inorg. Chern., 26 (1987) 3359. 28 N. Bag, G.K. Lahiri and A Chakravorty, J. Chern. Soc., Dalton Trans., (1990) 1557. 29 Ae.T. North, D.e. Phillips and F.S. Mathews, Acta Crystallogr., Sect. A, 24 (1968) 351. 30 G.M. Sheldrick, SHELXTL-PLUS 88, Structure Determination Software Programs, Nicolet Instrument Corp., Madison, WI, 1988.
Journal of Organometallic Chemistry, 414 (1991) 421-431 Elsevier Sequoia S.A., Lausanne
JOM 21935
Chemistry of platinum( IV), platinum( II) and palladium( II) cyclometallates of benzylthio- or benzosulphinyl-substituted azobenzenes Surajit Chattopadhyay, Chittaranjan Sinha, Partha Basu and Animesh Chakravorty * Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032 (India)
(Received February 21st, 1991)
Abstract
Cydometallated platinum(IV) complexes of the type [Pt(RL)CI 3 ) incorporating azobenzene (R = H) or 4-methylazobenzene (R = Me) with an SCH 2Ph (L = Ll) or an S(O)CH 2Ph (L = L2) substituent in an ortho position are described. These were obtained by oxidative addition of chlorine to [PtII(RL)Cl). Analogous palladium(I1) complexes, however, gave chloro-substituted azobenzenes upon reaction with chlorine. The platinum(IV) complexes show an irreversible cyclic voltammetric metal reduction peak near - 0.3 V vs SCE. Constant potential coulometric reduction at - 0.5 V or chemical reduction by hydrazine hydrate regenerated [PtII(RL)Cl). The structures of [Pt(HL1 )CI 3 ), [Pt(Mee)Cl) and [Pd(MeLl)Cl) have been determined by an X-ray diffraction study. The S(O)CH 2Ph group is coordinated via the sulphur atom.
Introduction
The platinum(II)-azobenzene system provided the first example of ortho-metalla tion [1] but the corresponding platinum(IV) organometallics have not been char acterised. Indeed, there are few authentic o-metallated platinum(IV) species of any type [2-10]. We report here the chemistry of several platinum(IV) azobenzene cyclometallates of the coordination type Pt(C,N,s)Cl 3 , along with their platinum(II) analogues of the type Pt(C,N,S)Cl. A PdlI(C,N,S)CI species is also discussed. Results and discussion Synthesis In the ortho-metallation reaction the azobenzene ligand is known to chelate platinum(II) in the bidentate (C,N) fashion [1]. The presence of a suitably posi tioned donor substituent has been found to be very effective in giving rise to stable platinum(IV) cyclometallates, the azobenzene ligand becoming potentially triden 0022-328X/91/$03.50
© 1991 - Elsevier Sequoia S.A.
422
tate. The azobenzenes used in the present contain the donor substituent PhCH 2S or PhCH2 S(O). Reaction of the azobenzenes with K 2PtCl 4 proceeds smoothly in hot aqueous ethanolic solution, to give the brown-coloured platinum(II) complexes in excellent yields. The platinum(IV) complexes are orange-yellow, and are formed in high yields upon oxidative addition of one molar proportion of chlorine to the platinum(II) complexes. The complexes synthesised are listed in Table 1. These belong to the types [PtII(RL1)CIJ (la and lb, [Pt II (RL2)CIJ (3a and 3b), [Ptlv(RLl)CI 3 J (2a and 2b), [Ptlv(RL2)CI 3 J (4a and 4b) where RLI and RL2 represent metallated azobenzenes bearing PhCH 2S and PhCH 2S(O) substituents respectively (R = H or Me). Spectral and structural characterisation The spectra of the platinum(II) and platinum(IV) species in the UV-Vis region are significantly different (Table 1). The absorption in the former species shows more structure and extends to longer wavelengths. The spectra of two representative pairs are shown in Fig. 1. The spectral differences are diagnostic of the oxidation state of the metal in the complexes. Two readily recognisable IR frequencies are p(PtCl) and p(SO). There is a single p(PtCI) band in the platinum(II) complexes; in the platinum(IV) species there are two such bands (Table 1). In the free ligands containing PhCH 2 S(O) substituents, p(SO) is observed as a strong band near 1040 cm -I, and upon complex formation this is shifted to higher energies. The specific frequencies are 1110 in 3a, 1120 in 3b, 1135 in 4a and 1140 cm- 1 in 4b. The shift to higher frequencies is indicative of
Table 1 UV-Vis, IR and IH NMR spectral data Compound
UV-Vis spectral data a (nm) «((dm3 mol-I em-I»
IR spectral data b ,,(PtCl) (em-I)
575 d (2930), 500 (3960), 405 (18900), 375 (23400), 355 (22370), 335 d (18250) 575 d (4390), 490 (4930), 410 (26280), 375 (24640), 358 (20810), 338 d (15880) 5255 d (2230), 490 (3090), 405 (12880), 370 (14420), 355 d (12190) 530 d (3350), 480 (4420), 410 (13710) 375 (12810), 360 d (9600) 465 (9790), 445 (10080), 385 (19580), 360 d (16700) 475 d (6433), 460 (6928), 400 (7918), 360 d (5444) 460 d (8180), 390 (18050), 360 d (14670)
340
4.54
340
4.52
Amax
[Pt(HLI )Cl) (la) [Pt(MeLI)Cl) (lb) [Pt(HL2 )Cl) (3a) [Pt(Mee)Cl) (3b) [Pt(HI!)CI 3 ) (2a) [Pt(MeLI )CI 3 ) (2b) [Pt(HL2 )CI 3 ) (4a) [Pt(MeL2 )CI 3 ) (4b)
475 360
d d
(11940), 455 (13620), 410 (15670), (9330)
340 350 350,325 345,330 350, 330 350, 335
8(CH 2 ) (ppm) eHNMR) (J (Hz»
4.92,4.97 (13.3) 4.90,4.95 (13.0) 4.60,4.90 (14.0) 4.58,4.89 (14.0) 5.12,5.43 (14.0) 5.10,5.41 (14.0)
a In dichloromethane solutions at 298 K. bIn KBr disk. C In CDCl 3 solvent at 298 K; the aromatic protons give rise a complex pattern at 7 to 8.5 ppm. d Shoulder.
423
I
'5.0
I
(a)
/ I
: I
12.0 'E
I
o
!.... 13.5 o E
I
,.,
E
,., E
'~\."""
- "0
I
,.,W
I I
I I
I
\
\
'"
(b)
\\ \
I
:
I
:
I
I
/
\
I
,
\\ ,/
\I
~
"0
I I
- UJ
II
'$2
I
,.,
I
'~
E
9.0
,
'
I
'E
o
,-,
I
,
I
I
I
4.5
3.0
I
I \ \
I
\, 300
400
500
600
700
300
A/nm
400
500
600
A/nm
Fig. 1. Electronic spectra of (a) [Pt(HL1)Cl) (la) ( - - ) and [Pt(HL1)CI 3 ) (2a) (- - -) and (b) [Pt(MeL2 )Cl) (3b) ( - - ) and [Pt(MeL2 )CI 3 ) (4b) ( - - -) in dichloromethane at 298 K.
S-binding. A shift of v(SO) to lower frequencies (- 900 cm-I) is expected for O-binding [11-15]. In the IH NMR spectra in CDC1 3 the methylene protons of the complexes appear as a broad band for la and lb but as AB quartets for the other complexes (Table 1). The methylene chemical shifts of the coordinated PhCH 2 S(O) group in 3a, 3b, 4a and 4b lie 0.5-1.0 ppm downfield from free ligand values [11]. This is indicative of S-binding of the group [12-16]. The structures of one platinum(IV) complex and one platinum(II) complex viz. [Pt 1v(HL1 )C1 3 ] (2a) and [Pt II (MeL2 )CI] (3b) have been determined by an X-ray diffraction study. Molecular structures are shown in Figs. 2 and 3. (The complex [Pt(HL1 )CI 3 ] joins the very small group of structurally-characterised o-metallated
Fig. 2. Molecular structure and numbering scheme for [Pt(HL1)CI 3 ).
424
elll)
ellS) Fig. 3. Molecular structure and numbering scheme for [Pt(MeL2 )Cl].
platinum(IV) complexes [3-7].) Selected bond parameters for the two complexes are listed in Tables 2 and 3. The azobenzene ligands act in the meridional tridentate (C,N,S) fashion in both complexes. In [Pt(MeL2)CI] the PhCH 2S(O) group is S-coordinated and with exclusion of the sulphoxide oxygen and the CH 2Ph group the molecule is planar (mean deviation 0.053 A). In [Pt(HL1 )CI 3 ], the platinum(IV) coordination sphere, Pt(C,N,S)CI 3 , is distorted octahedral, and except for the benzyl group the metallated azobenzene ligand lies in a plane with mean deviation of only 0.035 A. The CI(3) atom also lies in this plane. . The Pt-C distances in the two compounds are equal within experimental error and this also applies to the Pt-N distances. The Pt-CI distances are slightly longer in [Pt(HL1 )CI 3 ]. These observations are in agreement with the very similar radii of platinum(II) (square planar) and platinum(IV) (octahedral) [17,18]. The Pt-S dis tances cannot be compared because of the different nature of the two sulphur atoms. The normal Ptll-S (sulphoxide) distance is 2.22 A [19,20]. In Pt(MeL2)CI the distance is longer, 2.309 A, probably as a result of the trans influence of the coordinated carbon centre [21,22].
Table 2 Selected bond lengths (A) and angles (0) in [Pt(HL1 )CI 3 ] (28) Pt-C(2) Pt-N(2) Pt-S Pt-Cl(1) S-Pt-Cl(l) S-Pt-Cl(2) Cl(1)-Pt-Cl(3) S-Pt-C(2) Cl(2)-Pt-C(2) S-Pt-N(2) Cl(2)-Pt-N(2) C(2)-Pt-N(2) Pt-S-Cl(3)
2.007(15) 1.961(16) 2.441(5) 2.357(5) 86.8(2) 94.4(2) 90.8(2) 164.5(6) 87.9(5) 85.3(4) 91.1(4) 79.4(7) 111.0(6)
Pt-Cl(2) Pt-Cl(3) N(1)-N(2) Cl(1)-Pt-Cl(2) S-Pt-Cl(3) Cl(2)-Pt-Cl(3) Cl(1)-Pt-C(2) Cl(3)-Pt-C(2) Cl(1)-Pt-N(2) Cl(3)-Pt-N(2) Pt-S-C(8) C(8)-C-Cl(13)
2.334(4) 2.317(6) 1.280(20) 178.2(1) 98.2(2) 90.3(2) 90.6(5) 97.1(6) 87.7(4) 176.2(5) 94.6(6) 101.0(9)
425 Table 3 Selected bond lengths (A) and angles (0) in [Pt(MeL2 )CI] (3b) 2.006(20) 1.964(18) 2.286(6)
Pt-C(2) Pt-N(2) Pt-CI
Pt-S N(I)-N(2) S-O(I)
96.8(2) 85.7(2) 165.2(6) 79.5(8) 176.9(6) 98.0(6)
S-Pt-CI S-Pt-N(2) S-Pt-C(2) N(2)-Pt-C(2) N(2)-Pt-CI C(2)-Pt-CI
Pt-S-O(I) Pt-S-C(9) Pt-S-C(14) C(9)-S-C(14) 0(1)-S-C(9) O(I)-S-C(14)
2.309(6) 1.295(25) 1.454(16) 125.3(7) 96.1(7) 113.1(7) 104.1(10) 110.7(9) 105.4(10)
Electrochemical and chemical reduction of platinum(IV) complexes
In acetonitrile solution each platinum(lV) complex shows an irreversible (no anodic peak) cyclic voltammetric metal reduction peak (platinum working electrode; tetraethylammonium perchlorate supporting electrolyte). Specific peak potentials versus saturated calomel electrode are: 2a, -0.26 V; 2b, -0.38 V; 4a, -0.28 V and 4b, - 0.40 V. Methyl-substitution in the metallated benzene ring increases the electron density and shifts the potential substantially to more negative values (compare 2a and 2b or 4a and 4b). Upon constant potential coulometry at -0.5 V two electrons are consumed, and the corresponding platinum(II) complex is quanti tatively produced. Thus the electrode reaction involving metal reduction is associ ated with spontaneous and rapid chloride loss, as in eq. 1. This also accounts for the irreversible nature of the voltammogram, since Pt(RL)Cl is not electroactive in the voltage range ± 0.7 V.
(1)
R
R
cA
cA
N
N
PtCl n ~N/ \
(::rS"I~ 1
PtIRL )Cl n ~
(!l!.l
~N/
CH 2Ph
PtCl n \
(::r11"I 0
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PtlRL2)Cl n R
'2
H
(~
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Me
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H
3
(4g1
H
3
(2bl
Me
3
14b)
Me
3
426
Cl1l1
Fig. 4. Molecular structure and numbering scheme for [Pd(Mer! )Cl].
When solutions of the platinum(IV) complexes in ethanol were heated they converted into their platinum(II) analogous. The reduction can be brought about more smoothly in acetonitrile at room temperature by use of a stoichiometric proportion of hydrazine hydrate. Comparison with palladium(II) complexes The synthesis of the palladium(II) complexes of type [Pd(RLI)CI] and [Pd(RL2 )CI] were described previously [11,23]. The structure of [Pd(MeL1 )CI] has now been determined and confirms the presence of a planar Pd(C,N,S)CI coordination sphere. A view of the molecule is shown in Fig. 4, and selected bond parameters are listed in Table 4. The behavior of the palladium(II) complexes towards chlorine is entirely differ ent from that of the platinum(II) analogues. The latter undergo oxidative addition at the metal site but with the former chlorine cleaves the Pd-C bond to give chloro-coordinated palladium(II) species and a chlorinated ligand. The observed reactions are represented by eqs. 2, 3. No evidence was found for the formation of a tetravalent palladium(lV) intermediate. The cleavage of the Pd-C bond by chlorine has been reported previously for related organometallics [24,25]. PtII(RL)CI + Cl 2 -+ Pt IV (RL)CI 3 (2) II PdII(RL)CI + Cl -+ Pd Cl + RLCl (3) 2
2
Table 4 Selected bond lengths (A) and angles ( 0) in [Pd(MeL1)Cl] Pd-C(2) Pd-N(2) Pd-Cl S-Pd-Cl S-Pd-N(2) S-Pd-C(2) N(2)-Pd-C(2) N(2)-Pd-Cl
1.988(6) 1.970(4) 2.300(2) 96.5(1) 85.1(2) 163.9(2) 79.6(2) 178.1(2)
Pd-S N(I)-N(2) C(2)-Pd-Cl Pd-S-C(9) Pd-S-C(14) C(9)-S-C(14)
2.375(2) 1.285(7) 98.9(2) 96.3(2) 113.4(2) 103.2(3)
427
Experimental Dipotassium tetrachloroplatinate(II) [26], 2-(benzylthio)azobenzene [11] and 2 (benzylsulphinyl)azobenzene [23] were prepared as previously described. Purifica tion of solvents and the preparation of tetraethylammonium perchlorate for electro chemical work were carried out as described previously [27]. All other chemicals and solvents used for the preparative work were of reagent grade, and were used without further purification. UV-Vis spectra were recorded on a Hitachi spectrophotometer and IR (4000-200 em-I) spectra on a Perkin-Elmer 783 spectrophotometer. Proton NMR spectra were recorded for CDCl 3 solutions on Varian XL 200 and Bruker 270 MHz FT NMR spectrometers. Electrochemical studies were carried out with PAR Model 370-4 electrochemistry apparatus as described elsewhere [28]. Elemental analyses were performed with a Perkin-Elmer 240C elemental analyser. Synthesis Chloro((2 -(benzylthio)phenyl)azo)phenyl-C 2 ,N,S )platinum(II), [Pt(H LI)el] (Ia)
To an aqueous solution (10 cm3 ) of K 2 PtCl 4 (0.10 g, 0.24 mmol) was added slowly a hot ethanolic solution of 2-(benzylthio)azobenzene (0.067 g, 0.22 mmol).
Table 5 Crystallographic data for [Pt(HL1 )CI 3) (2a), [Pt(MeL2)Cl) (3b) and [Pd(MeLI)Cl)
Formula Formula weight Crystal size, mm3 Crystal system Space group
a,A b,A c,A {3, °
V,A3 Z No. centering reflections Centering 29 Dc, g.cm 3 JL(Mo-K ), cm- I a
29 limits h, k, I range No. unique reflections Observed data I> 3(J(I) Parameters refined Ra Rw b g in weighting scheme C Largest peak in final Fourier map, eA - 3
CI9HI5N2Cl3PtS 604.8 0.12xO.18xO.22 Monoclinic
C 20 H 17 N 2OClPtS 564.0 0.06 x 0.14 x 0.12 Monoclinic
C 2o H 17 N 2ClPdS 459.3 0.11 x 0.13 xO.27 Monoclinic
P2J1n
P2J1a
P2J1n
11.773(3) 11.205(4) 15.099(7) 99.48(3) 1964.7(12) 4 25 15 < 29 < 31° 2.045 77.36 2-52 15,14, ± 19 3785 1699 235 0.0518 0.0519 0.000300
9.782(8) 13.932(8) 14.038(10) 98.76(7) 1891(2) 4 15 10 < 29 < 25° 1.981 7u.57 2-50 12,17, ± 17 3329 1418 165 0.0550 0.055 0.000500
11.062(3) 10.963(4) 15.409(4) 100.47(2) 1837.6(9) 4 25 15<28<27° 1.660 12.56 2-55 14,14, ±20 4199 2403 226 0.0412 0.0509 0.000400
0.78
1.00
0.23
a R =L(IFo 1- IFe I)/LIFo I. b Rw=[LW(IFo 1- IFe 1)2;Lw1Fo 12)1/2.
C
1/[(J2(IFo 1)+ glFo 12).
428
The mixture was stirred for 24 h, then the brown-red solution was evaporated in air and the residue washed thoroughly with water and then with ethanol-water (1: 1 vIv). The dark brown residue was chromatographed on silica gel with acetonitrile benzene (1 : 9 vIv) as eluent. A brown band was collected which yielded [Pt(HL1)Cl] in 74% yield (found: C, 42.65; H, 2.79; N, 5.36. Cl9Hl5N2SClPt calcd.: C, 42.73; H, 2.81; N, 5.25%). [Pt(MeL1)Cl (lb), [Pt(HL2)Cl] (3a) and [Pt(MeL2)Cl] (3b) were prepared similarly in 70-80% yield (lb: found: C, 43.61; H, 2.93; N, 5.29. C 20 H 17 N 2SClPt calcd.: C, 43.83; H, 3.10; N, 5.11%. 3a: found: C, 40.97; H, 2.67; N, 4.98. Cl9Hl5N2S0ClPt calcd.: C, 41.49; H, 2.73; N, 5.10%. 3b: found: C, 42.45; H, 2.98; N, 4.67. C 20 H 17 N 2SOClPt calcd.: C, 42.59; H, 3.02; N, 4.97%). Trichloro(((2-(benzylthio)phenyl)azo)phenyl-C 2 ,N,s)platinum(/V), [Pt(HL 1)C131 (2a) To an acetonitrile solution (50 cm3) of Pt(HL1)Cl (0.10 g, 0.19 mmol) was added dropwise 20 cm3 of acetonitrile saturated with chlorine. The mixture was stirred for 0.5 h and then evaporated in the air. The solid was dissolved in dichloromethane and the solution (10 cm3) chromatographed on silica gel with benzene as eluent. An orange yellow band was collected and yielded 0.080 g (70%) of [Pt(HL1)C1 3] (found: C, 37.34; H, 2.52; N, 4.70. Cl9H15N2SCl3Pt calcd.: C, 37.72; H, 2.48; N, 4.63%). [Pt(MeL1)C1 3] (2b), [Pt(HL2)C1 3] (4a) and [Pt(MeL2)C1 3] (4b) were prepared
Table 6 Atomic coordinates (X 10 4 ) for [Pt(HL1 )CI 3 1 Atom
x
y
z
Pt S Cl(l) Cl(2) Cl(3) N(l) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19)
2891(1) 197894) 1140(3) 4655(3) 2384(4) 3878(13) 3326(11) 4103(15) 3700(13) 3890(16) 4494(20) 4890(17) 4666(18) 3015(16) 2345(13) 2002(20) 2321(20) 2961(18) 3329(16) 2862(15) 2277(16) 1234(17) 690(18) 1193(22) 2247(19) 2761(17)
1199(1) 369(5) 829(4) 1541(4) 3178(5) -731(16) -454(15) 294(20) 1415(18) 2426(20) 2249(25) 1192(31) 194(25) -1417(16) -1149(19) -2077(24) -3245(24) -3472(17) -2634(19) 623(18) 192(19) 659(21) 236(22) -648(26) ~ 1095(22) -686(19)
1055(1) - 381(3) 1571(3) 586(3) 779(3) 2150(10) 1374(10) 2670(13) 2323(10) 2836(13) 3717(13) 4059(13) 3550(14) 748(12) -75(12) -674(14) -469(17) 343(17) 982(13) -1248(12) -2143(12) -2560(13) -3372(13) -3792(14) 3445(13) -2597(13)
429
similarly in 60-70% yield (2b: found: C, 38.61; H, 2.80p N, 4.32. C2oH17N2SC13Pt calcd.: C, 38.81; H, 2.75; N, 4.53%. 4a: found: C, 36.49; H, 2.50; N, 4.32. C19HlSN2S0Cl3Pt calcd.: C, 36.75; H, 2.42; N, 4.51%. 4b: found: C, 37.64; H,2.59; N, 4.37. C2oH17N2S0C13Pt calcd.: 37.83; H, 2.68; N, 4.91 %). Reaction of [Pd(MeL1)CI] with chlorine Chlorine gas was passed slowly into an acetonitrile solution (50 cm3) of Pd(MeLl)CI (0.10 g, 0.22 mmol) for 0.5 h and the mixture then stirred for an additional 1 h. The orange yellow solution was evaporated in air and the residue washed thoroughly with water. The aqueous extract contained chloro-coordinated palladium(II). The residue from water was dissolved in dichloromethane (10 cm3) and chromatographed on silica gel with benzene as eluent. An orange yellow band was collected and yielded 0.060 g (71 %) of 2-(benzylthio)azo-o,0' -dichloro-p-toluene (found: C, 61.85; H, 3.90; N, 7.51. C2oH16N2SCl2 calcd.: C, 62.03; H, 4.14; N, 7.24%). X-Ray crystal structure and analysis Crystals suitable for X-ray work were grown by slow diffusion of hexane into dichloromethane solutions at 298 K. Data collection was performed on a Nicolet
Table 7 Atomic coordinates (X 10 4 ) for [Pt(MeL2 )CI] Atom
x
y
z
Pt S CI 0(1) N(l) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(l8) C(19) C(20)
957(1) - 393(6) 2272(7) 105(17) 101(20) -169(20) 1195(23) , 1838(21) 2911(23) 3281(24) 2643(34) 1601(30) 4465(34) -1287(22) -1533(20) -2632(26) -3457(24) - 3218(24) -2142(24) -1485(22) -2129(23) -1488(26) - 2128(25) -3477(27) -4124(25) -3482(23)
212(1) 1445(4) 1131(4) 2235(9) -1541(12) -631(13) -1777(16) -1061(15) -1346(17) -2318(22) -2997(20) -2749(17) -2579(22) -250(19) 708(15) 1117(17) 530(15) -444(15) -844(15) 1993(15) 1290(13) 938(17) 331(18) -2(17) 345(19) 967(15)
2304(1) 1573(5) 3445(5) 1043(11) 1367(14) 1377(14) 2009(16) 2675(15) 3339(15) 3427(20) 2821(21) 2067(22) 4253(24) 753(15) 797(14) 155(18) -483(16) - 519(17) 112(16) 2359(15) 2932(16) 3787(19) 4388(17) 4035(19) 3185(18) 2631(16)
430
Table 8 Atomic coordinates (X 10 4 ) for [Pd(MeL1 )Cl] Atom
x
Y
z
Pd S Cl N(l) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20)
4503(1) 3325(1) 4222(2) 5470(4) 4748(4) 5986(5) 5668(5) 6196(5) 6970(5) 7244(5) 6762(5) 7526(6) 4151(5) 3434(5) 2870(6) 2978(6) 3678(6) 4266(6) 1669(5) 1067(5) 1127(6) 528(7) -145(7) -217(6) 392(6)
2471(1) 4281(2) 2264(2) 1852(5) 2590(5) 1043(6) 1099(6) 275(6) 658(6) -717(6) 125(7) -1587(7) 3502(6) 4362(6) 5286(6) 5362(7) 4494(7) 3599(6) 4053(6) 3102(6) 1883(7) 1023(7) 1341(9) 2532(10) 3439(8)
3274(1) 3281(1) 1766(1) 5064(3) 4570(3) 4550(4) 3616(4) 3130(4) 3537(4) 4459(4) 4962(4) 3003(4) 4990(3) 4455(3) 4830(4) 5733(4) 6256(4) 5897(4) 2876(4) 3339(4) 3125(4) 3520(5) 4i36(5) 4385(5) 3979(4)
R3m/V automated diffractometer using graphite monochromated Mo-Ka radiation
(;\ = 0.71073 A). Crystal data and data collection parameters are listed in Table 5.
Intensities were corrected for Lorentz and polarization effect. An empirical absorption correction was made on the basis of "'-scans [29]. All calculations, data reduction, and structure solution were carried out on a MicroVAX II computer with the SHELXTL-PLUS programs [30]. The positions of metal atom in both [Pt(HLl)CI 3 ] and [Pt(MeL2 )Cl] were determined by heavy atom methods. All nonhydrogen atoms were located from subsequent difference Fourier maps. All nonhydrogen atoms were treated anisotropically for [Pt(HL1 )CI 3 ]. For [Pt(MeL2 )Cl], the atoms within the coordination sphere and those constituting the ortho-metallated benzene ring were treated anisotropically. The structure of [Pd(MeL1 )CI] was solved by direct methods and all the nonhydrogen atoms were refined anisotropically. For all three complexes hydrogen atott\s were included at calculated positions with fixed thermal parameters. Atomic coordinates are collected in Tables 6-8. Tables of H-atom coordinates and thermal parameters, complete lists of bond distances and angles, and lists of structure factors are available from the authors. Acknowledgements We thank the Department of Science and Technology, New Delhi for establish ing a National Single Crystal Diffractometer Facility at· the Department of In
431
organic Chemistry, Indian Association for the Cultivation of Science. Financial support from the Council of Scientific and Industrial Research, New Delhi, is also acknowledged. References 1 Ae. Cope and R.W. Siekman, J. Am. Chern. Soc., 87 (1965) 3272. 2 G. Wilkinson, F.G.A Stone and E.W. Abel (Eds.), Comprehensive Organometallic Chemistry, Pergamon, New York, 1982. 3 G. van Koten, J. Terheijden, J.AM. von Beek, I.C.M.W. Ooyevaar, F. Muller and e.H. Stam, Organornetallics, 9 (1990) 903. 4 E. Wehman, G. van Koten, C.T. Knaap, H. Ossor, M. Pfeffer and AL. Spek, Inorg. Chern., 27 (1988) 4409 and references therein. 5 e.M. Anderson, R.J. Puddephatt, G. Ferguson and AJ. Lough, J. Chern. Soc., Chern. Commun., (1989) 1297. 6 N.W. Alcock, K.H. Brayars and P.G. Pringle, J. Chern. Soc., Dalton Trans., (1990) 1433. 7 I.e.M.W. Ooyevaar, D.M. Grove, P. van der Sluis, AL. Spek and G. van Koten, J. Chern. Soc., Chern. Commun., (1990) 1367. 8 C.C. Deuschel and A von Zelewsky, Inorg. Chern., 26 (1987) 3354 and references therein. 9 D. Sandrini, M. Maestri, V. Balzani, L. Chassot and A von Zelewsky, J. Am. Chern. Soc., 109 (1987) 7720. 10 L. Chassot and A. von Zelewsky, Helv. Chim. Acta., 69 (1986) 1855. 11 C. Sinha, D. Bandyopadhyay and A. Chakravorty, Inorg. Chern., 27 (1988) 1173. 12 J.A. Davies, Adv. Inorg. Chern. Radiochern., 24 (1981) 115. 13 J.H. Price, A.N. Williamson, R.F. Schramm and B.B. Wayland, Inorg. Chern., 11 (1972) 1280. 14 G. Anniback, L. Cattalini, L. Canoverse, B. Pitteri, A Tiripicchio, M.T. Carnellini and M.L. Tobe, J. Chern. Soc., Dalton Trans., (1986) 1101. 15 M.J. Root and E. Deutsch, Inorg. Chern., 24 (1985) 1464. 16 W. Kitching, e.J. Moore and D. Doddrell, Aust. J. Chern., 22 (1969) 1149. 17 R.D. Shanon, Acta Crystallogr., Sect. A, 32 (1976) 751. 18 F.R. Hartley, The Chemistry of Platinum and Palladium, Applied Science Publishers Ltd., London, 1973. 19 P. Bitha, G.O. Morton, T.S. Dunne, E.F. Delos Santos, Y. Lin, S.R. Boone, R.C. Haltiwagner and e.G. Pierpont, Inorg. Chern., 29 (1990) 645. 20 F.D. Rochon, P.e. Kong and R. Melanson, Inorg. Chern., 29 (1990) 1352. 21 T.G. Appleton, H.e. Clark and L.E. Manzer, Coord. Chern. Rev., 10 (1973) 335 22 R.e. Elder, R.D.P. Curea and R.F. Morrison, Inorg. Chern., 15 (1976) 1623. 23 A.K. Mahapatra, D. Bandyopadhyay, P. Bandyopadhyay and A. Chakravorty, Inorg. Chern., 25 (1986) 2214. 24 D.R. Fahey, J. Organornet. Chern., 27 (1971) 283. 25 A.D. Ryabov, Synthesis, (1985) 233. 26 S.E. Livingstone, Synth. Inorg. Met.-Org. Chern., 1 (1971) 1. 27 G.K. Lahiri, S. Bhattacharya, M. Mukherjee, AK. Mukherjee and A Chakravorty, Inorg. Chern., 26 (1987) 3359. 28 N. Bag, G.K. Lahiri and A Chakravorty, J. Chern. Soc., Dalton Trans., (1990) 1557. 29 Ae.T. North, D.e. Phillips and F.S. Mathews, Acta Crystallogr., Sect. A, 24 (1968) 351. 30 G.M. Sheldrick, SHELXTL-PLUS 88, Structure Determination Software Programs, Nicolet Instrument Corp., Madison, WI, 1988.