Cationic complexes of platinum and palladium of the type [MCl(p-CH3C6H4NC)L2]ClO4 (M = Pt, Pd; L = p-tolyl3P, o-tolyl3P, Cy3P, Ph2MeAs, Ph2EtAs, Ph2PrAs, Cy3As; Cy = cyclohexyl) have been isolated. These show a v(CN) band at ca. 2200 cm-1 compared with 2130 cm-1 for the free isocyanide ligand, suggesting weak π-character in the metal-carbon bond. The PMR spectra of the cationic complexes indicate trans configurations for the complexes. © 1977

Gowda, N.M.N.

Nagasundara, K.R.

Reddy, G.K.N.

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121 Journal of Organometallic Chemistry. 129 (19’77) 121-126 @ Elsevier Sequoia S-A.. Lausanne - Printed in The Netherlands CATIONIC COMPLEXES OF PLATINUM AND PALLADIUM WITH p-TOLYL ISOCYANIDE K.R. NAGASUNDARA. N.M. NANJE GOWDA and G.K.N. REDDY * Department of Chemistry. Bangalore University. Bnngalore-560001 (India) (Received September 14th. 1976) Summary Cationic complexes of platinum and palladium of the type [MCI@-CH&H,NC)- L,]ClO, (M = Pt, Pd; L = p-tolylsP, o-toly13P, Cy,P, Ph&ieAs, PhzEtAs, Ph,PrAs, Cy,As; Cy = cyclohexyl) have been isolated_ These show a v(CN) band at ca. 2200 cm-’ compared with 2130 cm-’ for the free isocyanide ligand, suggesting weak r-character in the metal-carbon bond. The PMR spectra of the cationic complexes indicate trans configurations for the complexes. Introduction Several cationic complexes of platinum(II) containing carbon monoxide and/ or an isocyanide as a ligand have been isolated, and their properties have been extensively investigated [l--8]. Invariably such complexes are stabilised by terti- ary phosphine or arsine ligands. Very few of the analogous complexes of palla- dium have been synthesised. In fact, the unstable compound trans-[PdCl(CO)- (EtJP)z]BF, [ 21 seems to be the only cationic carbonyl species of palladium previously made. Clark and coworkers [S], however, have prepared several iso- cyanide complexes of palladium of the type tmns-[PdCl(RNC)L2]’ (R = CH3, C,,HS, OCH&,H4, CHJCeH4; L = Ph&s or tertiary phosphine). Busetto et al. [S] have isolated two cations of the formulae truns-[PdCl {C(NHPh)NHGH, I- (PhNC)J and trans-[PdCl(C(NH-p-N02C6H4)NHC7H7}@-N02C6HJNC)2]C. They suggest that the presence of the carbene ligand helps to stabilise these compounds. These workers also reported that they were unable to isolate cationic palladium- (II) isonitrile complexes analogous to plat.inum(II) complexes of the type truns- [PtX(RNC)(Et3P)&104 (X = Cl, Br; R = Me, Ph) which they isolated. We have previously described the synthesis of several complexes of platinum _ and palladium of the general formulae MX2L2 (M = Pd, Pt; X = halogen; L = ter- tiary amine), PtX& and trarzs-[PtCl(CO)LJClO, [S]. We have extended these studies, and have irive&igated the possibility of isolating new cationic carbonyl and isocyanide complexes of both platinum and palladium- ThatI? 1 ’ PHYSICI\LPROPERTIESANDhNhLYTlCALI)hTh FOl~CA'~IONICCOL~PL~SESO1"PALLADIUMAND PLhTINUhl Compound 0 Mop, or r’(CN) JJ t\ c Annlylicnl duln (founcl (caIcd,)) (Fig dec, p. (cm-1 ) __,..S” .._._..__. _-_..-._ . . . . .._.._..._._._... ___.._..__ . . . . . . .._._...... . .,..._.. . . . . ....___..,....._1 (“a C II N X M p_I_.- _w_.- _.., -_..-.- ,.S._.__._.. _...“.._._._ ..“. . . . .._ _,.I . . . . _..“.... .-... . . . . _ .._... _. _ . . .._ __._ ._ . . . . . ..,._ _ _,._,. __,__. ___,_.,__ --I 11-G (12.0) 11,l f11.8) 10.3 (l&G) [PdCl(p,tNC)(PhzhreAa)* JClO4 ’ 98 2214 22,B 47.7 41 2.2 G,l (492) (389) (LB) (93) [PtC1(pStNC)(Ph~MeAs)2]CI04 100-101 2203 32,B 43,3 39 2,l 7.2 (J3.G) (3,5) fl,G) (7.6) ~PdCl@~tNC)(Ph2EtAs)2~ClO4 AO-I33 2218 22,l 48.9 .&PI 1.8 (49.4) t&3) (I,G) ~~PtCI@.tNC)(Ph2EtAs)2lClO4 95-100 2207 244 44,G .I,1 1,7 (445) (3,9) (101) iPdCl(p.tNC)fPh2PrAs)2 ICI04 79-81 2213 22,9 51.4 *I,9 2,fl 0.2 tGO.6) (4.G) (PtCi(p~tNC)(Ph2PrAsb2lCfO4 fl,G) (73, 74-76 2210 2G,9 <If%9 d,l 1.G 5.8 , f4G.O) (482) (104) (7.1) [PdCl(ptNC)(CyjAs)~lClO4 12t 2200 21,4 D2.3 7,5 I,3 7,G (52.5) (79) (10l) (7.0) [PtCI@.lNC)(Cy~As)2ICl04 217 2197 31,o 47,3 O,G 1,7 59 (492) 67) 11,:~) fG.G) [PdCI@tNC)fCy5P)2lClO4 228-230 2200 27.6 57.3 7,9 1Si (57.8) W-0 f1,5) [PdCI@~tNC)~o~tolyl~P~~lClO4 131, 2204 22.7 (il.4 5.2 3,5 G ‘2 ~PdCI@~tNC)~p~tolyl~P~~lClO4 tG2.1) (5,l) (1.5) c7:3, 123-l 2G 2213 2601 GO.2 4,lI 1.2 (62.1) (5,l) fl,G) [PtCl0l.lNC)@~tolyljP)Z)CIOJ 236-238 2210 25.0 6G.l *I, 0 1.f WLG) (4.7) (13) _______.__...-.- . .._.__. “_..“.” . . .._ _..__ _._ ._.......... .._.. . _ 0 Compounds are white or palo yellow, G r(CN) (forptNC) 2130 cm -1 , r Mtrlw contlucli~~we (ohm” cm2 molc’~ ) of w. IV3 JJ solullons in nltrobonzenc (cn, 25”C), 10.2 (11.0) II,2 fll,O) -. . - ..-__.__ . . .._ ____ Results and discussion 123 Cationic carbonyl complexes of platinum can be made by bubbling carbon monoxide through a solution of PtCIZLz (& = tertiary phosphine or arsine) in a polar solvent such as acetone, in the presence of an anion such as ClO,; BF,- or PF,- (as sodium salt) [ 11. The corresponding isocyanide complexes may be made by using isocyanide in place of CO_ Our attempts to prepare carbonyl compleses of palladium analogous to the platinum compleses we made earlier by this method were unsuccessful (the metal slowly separates out from the system). The method does, however, give four-coordinate cationic complexes of platinum and palladium of the composition [MCl@-tNC)L,]ClO, (M = Pd. Pt: p-tNC = p- CH,C,H,NC; L = tertiary arsine or phosphine): trans-R;IC12Lz + p-tNC E trans-[ MCl(p-tNC)L2 ]ClO, + NaCl The new isocyanide complexes behave as 1 : 1 electrolytes in nitrobenzene, and show a Y(CN) band around 2200 cm-’ and a perchlorate stretch at ca. 1100 cm -’ in their infrared spectra. The analytical results support the proposed for- mulae (Table 1). Details of the PMR spectra of the cationic complexes con- taining the ligands Ph,MeAs, PhlEtAs and p-toly13P are shown in Table 2. All the spectra show a s’inglet resonance due to the methyl of the p-tolyl isocyanide ligand at 7 ca. 7.7 ppm. Further the PhzEtAs-containing complexes show an ad- ditional single ethyl pattern suggesting that the two arsine ligands are located trans to each other. Similarly the complexes containing PhzMeAs and p-toly13P ligands show only a single resonance peak due to the methyl groups of these ligands. However, in these complexes there is a coincidental overlap of the res- onance due to the methyl groups of the arsine (or phosphine) with that from the methyl group of the p-tolyl isocyanide ligand. These results suggest a tram con- figuration for the cationic complexes. -4s espected for cationic complexes of this type, the value of v(CN) for the coordinated isocyanide is higher than that of the free ligand, indicating an in- crease in the bond order of the CN group and hence a poorer r-character in the TABLE 2 PMR DATA FOR LIGANDS AND CONPLEXES __ ________I__ __------- __- Compound chemical shift (7. pssm) * _--.-~ .- CH3 (p.1NC) CR3 ‘332 ___ _. _____ ___-__ Ph= McAs 8.45s PhzEtAs 8.85t 7.99q P-Tolyl3P 7.67~ p-CH&jH4NC 7.24s [PdCl(p-tNC)(Ph2hleAs)zlClO4 7.70s 7=iOS LPtCI~-tNC)(Ph2Me~)~lC104 7.76s 7.68s [PdClCp-tNC)(Ph,EtAs),)21C104 7.72s 8.63t _ 7.08q [PtCl(p-tNC)<PhzEtAt>zlC104 7.70s 8.57t 7.03q [PdCl(p-tNC)(p-tolyl3P)2lClDq 7.64s 7.64s .[PtCUp-tNC)~-tolyl3P)z~lO4 7.67s 7.67s 0 5 &&et; t. triplet; 9. quartet; em. iomplu mutt&let. C6& 29-2.4 cm 3.2-2.0 cm 2.9-2.2 cm 3.6-2.4 cm 3.6-2.0 cm 3.6-2-O cm 3.6-2-O cm 3.8-2.1 cm 3.8-2.4 cm 3.9-2-4 cm metal-carbon bond of the comples [4,10,11]. In a series of analogous com- pleses of the type [MC1(RNC)L2]’ (M = Ni, Pd, Pt; R = p-CH&.H,,p-0CH1C6H4, Ph; L = Ph2MeP, PhMezP), Clark et al. [ 4,6] found that v(CN) uniformly increases in the order Ni < Pd < Pt. In contrast, with our compounds the Y(CN) values of the cationic platinum complexes are a little lower than those of the corresponding palladium compleses. A similar trend is apparent in the neutral complexes PtCl,- ( RNC)2 and PdCl,(RNC)2 (R = CeHS, C,H, ,) [ 12-141. These results suggest that the antibonding orbit& of carbon of the CN group have a higher electron den- sity in the platinum complexes than in the palladium complexes probably due to greater back-bonding in the former_ Similar results were noted with com- plexes of Ru and OS of the type MC1,(RNC)z(Ph-n-BuzP), (M = Ru, OS; R = p- NO,C,H,, p-OCH,C,H, [ 151. The compounds MXzL2 used for the preparation of cationic complexes were prepared by refluxing stoichiometric quantities of the metal halide and ligand in an alcoholic medium [S]. The CyJAs-containing complexes (Cy = cyclohexyl) have been made for the first time, and some of their properties are listed in Table 3. The far-infrared spectra of these compounds were recorded in the range 50 to 450 cm-‘, and show a single v(M-X) band, suggesting a trans configuration for these compounds as expected [ 16-191. Esperimental The platinum and palladium salts were supplied by Messrs Johnson Matthey Chemicals Ltd, London. The tertiary at-sines, phosphines and p-tolyl isocyanides were prepared as described elsewhere [ 201. Microanalyses (C, H and N) were car- ried out at the Universities of hlanchester and Surrey (England). Halogen was estimated by sodium hydroxide fusion and subsequent titration by the Vohl- hard’s method [ 211. Palladium was determined gravimetrically (as palladium dimethyl glyoximate) as follows: a known amount of the complex was digested with cont. H,SO, (Kjeldahl method) and was diluted with water. The metal was precipitated as sulphide and then taken up into nitric acid from which palladium dimethyl glyoximate was isolated according to the usual procedure [21,22]. Conductivity measurements were made with a Toshniwal conductivity bridge type Cl 01.02. Infrared spectra (in nujol mull) were recorded on a Carl Zeiss UR 10 spectrophotometer. Far-infrared spectra (in polyethylene powder) were recorded on a Polytec FIR 30 Fourier spectrometer. NMR spectra were recorded on a Varian T-60 instrument using CDQ as solvent and Si(CH3)4 as internal standard. tram+Chloro-p-tolyl isocyanide bis(tertiary arsine or phosphine)-paliadium(II) or -platinum(H) perchtomte compounds, trans-[MCl(p-tNCjLJCIOJ (M = Pd. Pt; L = PhlMeAs, PhzEtAs, Ph#rAs, Cygls, Cyp, p-tolyl& o-tolylPI To an acetone solution (25 ml) (acetone/benzene mixture in the case of Cy&s and Cy,P) of MCl& (0.2 mmol) and p-tNC (0.2 mmol), sodium per- chlorate was added in excess. The mixture was stirred at room temperature for 6 h. The NaCI was filtered off and the filtrate was concentrated to dryness under reduced pressure_ The white or pale yellow pasty residue was washed successive- ly witi ether and water to give a solid, which was dried in vacua. 126 Dihaio bk(tri&?tohexyL arsine)-platinum(II) or -palladium(U) compounds, trans-MX,(Cy,As)z (M = Pd7 Pt; X = Cl, Br; Cy = cyclohexyl) The metal halide (PdC& or KrPtC&; 0.2 mmol) was treated with Cy3As (0.4 mmol) in alcohol (25 ml) and hydrochloric or hydrobromic acid (2 ml). The mixture was refluxed for 5 h, and the solid which separated was washed with water and alcoho1, and dried in vacua. Acknowledgements The authors are indebted to Drs. D.J. Machin and G.A. Webb (England), for micro-analyses, the authorities of the Indian Institute of Science, Bangalore for infrared and PMR spectra and Prof. S. Chandrasekhar and Dr. S. Venugopal of the Raman Research Institute, Bangalore for far-infrared spectra. One of the authors (KRN) is grateful to the CSIR, Govt. of India, for financial assistance. References 1 2 10 11 12 13 14 15 16 17 18 19 20 21 22 M.J. Church and M.J. B¶PYS_ J_ Chem. Sot. A. (1968) 3074: (1970) 1938. H.C. Clark and K.R. Dixon. .I_ Amer. Chem. Sot.. 91 (1969) 596: W-J. Chcrwinski and H-C. Clark. Inorg. Chem.. 10 (1971) 2263. P.M. ~rekhd. W.J. KnebeI and R.W. Hess. J. Amer. Chem. Sot.. 93 (1971) 5424. H.C. Clark and L-E. Manzer. Inolg. Chcm.. 11 (1972) 503. P_M_ Treichel and W-J_ Knebcl. Inorp. Chem.. I1 (1972) 1289. W.J. Cherwinski. H.C. Clark and L.E. Mlanzer. Inorg. Chcm.. 11 (1972) 1511. P.M. Treichel. K.P. Wagner and R-W. Hess. Inork Chem.. 12 (1973) 1471. N.M. Nanie Gowda and G.K.N. Reddy. Aust. J. Chem.. 27 (1974) 2557. L. Busetto. A. PaIazzi. B_ Cro+ni. U_ BeIluco. E.M. Badley. B.J.L. KiIby and R.L. Richards. J. Cbem. Sot. DaItoq (1972) 1800. L. MaIatesta and F. Bona& Isocyanide complexes of Metals. Wiley Interscience. New York. 1969. J-W_ Dart. IW_K_ Lloyd. R. Mason and J-A_ BlcCIeverty. J. Chem. Sot. Dalton. (1973) 2039. B_ Crociani. T_ Bochi and U. BeIIuco. Inor& Chem.. 9 (1970) 2021. . F_ Bonati and G. MingbettI. J. OrganometaI. Chem.. 24 (lSi’O> 251. R-R. Cooke and J-L. Burmeister. .I_ OrganometaL Chem.. 63 (1973) 471- J. Cbatt, R-L. Richards and G.H.D. Royston. J. Chem. Sot. Dalton. (1973) 1433. F.G. Moers. J.AX De Jong and P.M.H. Beaumont, J. Inorg. Nucl. Chem.. 35 <I9731 1915. F-R. Hartley. The Chemistry of Platinum and Palladium. Applied Science PubIisber?r Ltd. London. 1973. p. 242. RJ_ Goodfellow. J-G. Evans, P-L_ Coggin and D-A_ DuddeII. J. Chem Sot. A. (1968) 1604- S-H_ Biaztin. Inorg Chem.. 13 (1974) 1003. N-M- Nank Gowda. Some Tertiary arsine and phosphine complexes of Platinum group metals. Ph.D. Thesis. Bangalore University, 1975. A-I. Vogel. A Textbook of Quantitative Inorganic Analysis. ELBS k Longman. London. Third Edi- tton. 1975. P_ 266. 512. F-E. Beamisb. The Analytical Chemistry of tbe Noble Metals. Pergamon Press. London. 1966. P. 263. . . . _ ._ :_ : . . 

Cationic complexes of platinum and palladium with p-tolyl isocyanide

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Cationic complexes of platinum and palladium with p-tolyl isocyanide

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