on a wide range of couplings has shown that consistent results are often obtained if A W is regarded as being constant within a series of similar compounds. The terms involved in A E are singlet-to-triplet excitation

Complexes cis- [PtR,(dmso),] and cis- [PtRCl(dmso),] (dmso = dimethyl sulphoxide) are readily obtained from K, [PtCI,] and SnMe,R (R = aryl or Me) in dmso at 70-90 "C. Hydrogen-1 n.m.r. spectra show that the dmso ligands are bound through sulphur in solution and that the dmso ligand trans to R in cis-[PtRCl(dmso),] undergoes dissociation and exchange a t ambient temperature. With anionic reagents X-(X = Br, I, or SCN) the complex cis- [PtPhCl(dmso),] forms bridged complexes [Pt,Ph,(p-X),(dmso),].In addition to the diaryl complex, SnMe,-(C,H,OMe-2) forms the cyclometallated complex [Pt(C6H,0dH,-2) (dmso),]. The dmso ligands of all the complexes are readily displaced by phosphorus donors, AsPh,, SbPh,, or 2,2'-bipyridyl ; 'H} n.m.r. parameters are reported for the phosphorus-containing complexes.L~KYLTHIMI-'l.HYLTIN compounds (Snhle,R) have been shown to react with a number of chloro-complexes of platinum( 11) and the reactions with [PtCl,(cod)] (cod = cyclo-octa-1 ,Tj-diene) provide a convenient route to the complexes [PtR,(cod)], [PtRCl(cod)], and complexes derived from them by displacement of cod by a variety of N, Y , and As donors.l This route can he of particular value when the corresponding aryl-lithium or Grignard reagent is not available [for example, R = Cr(q-C,H,)(CO),] or is not obtainable in a pure form [for example, R = 1,2-dihydrobenzocyclobutenyl] . , However, this and other methods of introducing alkyl and aryl ligands into platinum(I1) complexes have the disadvantage of requiring that the common starting material K,[PtCl,] must first be converted into a complex [PtCl,L2] (L = $cod, PR,, etc.) which is normally isolated before being treated with an organometallic reagent to give the organoplatinum( 11) complex.We have now found that platinum(I1) methyl and aryl complexes may be obtained by a very simple procedure from K2[PtC1,] and organotin compounds using dime thy1 sulphoxide (dmso) as solvent. This and the related method starting from [PtCl,(dmso),] are described here, and we also describe a number of comparisons between these routes and the previously described reaction between the organotin compounds and [PtCl,(cod)] ; a preliminary account of some of this work has a~p e a r e d .~ RESULTSA N D DISCUSSION In a typical procedure (method A), K,[PtCl,] (0.002 mol) was dissolved in dmso (8 cm3) at room temperature, an excess of SnMe,R (R = Me or aryl; 0.004-0.01 mol) added, and the mixture stirred for several hours at 70-90 "C. After removal of dmso under vacuum the complexes [PtR,(dmso),] were readily isolated. Use of equimolar proportions of K,[PtCl,] and SnMe,R gave the complexes [PtRCl(dmso),]. The reaction mixtures were initially red owing to the presence of [PtC1,I2-, and during the course of a few minutes became yellow because of formation of cis-[PtCl,(dmso),]. The course of the reaction and yield were similar irrespective of whether t No reprints available.the tin conq)ound was introduced before or after this colour change. W i t m the product was colourless, the mixture after complet...

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One or both chloride ligands of [Pt(cod)CI,] (cod = cyclo-octa-1.5-diene) can be readily and selectively replaced by aryl groups by treatment of the complex with aryltrimethyistannanes in dichloromethane or syrn-tetrachloroethane. Use of 1 mol of SnMe,R usually gives the monoaryl comptexes in high yield [e.g. R = 2-furyl, 2-thienyl, benzofuran-2-yl, 2-benzothienyl, 1.2-dihydrobenzocyclobuten-3-yl, or C6H,X (X = H, p-Me0.p-CI, p-F, p-Me,Si, orp-Me)], but for R = ~6-p-MeC6H4Cr(CO), the diaryl complex is formed. Use of 3 2 mol of SnMe,R gives the diaryl complexes in,good yield [e.g. R as above, plus C6H,X (X = o-MeO, rn-MeO, rn-F,C, p-Br, rn-F, rn-CI, and p-O,N)], but, for steric reasons, with R = C6H,Me,-2,4,6 only the monoaryl complex is formed. The reactivity of the SnMe,R compounds generally parallels the ease of electrophilic substitution at the corresponding R-H bonds. The arylation method has substantial advantages over those using aryl Grignard or lithium reagents. Aryl .cornpounds, MMe,R, of other Group 4 metals undergo analogous reactions, the reactivity decreasing in the sequence (M =) Pb > Sn S= Ge > Si. While mixed diaryl complexes can sometimes be made in good yield (e.g. [Pt(cod)-(2-C4H,S) (2-C,H30)] from [Pt(cod) (2-C4H,S)CI] and SnMe3(2-C,H,O)}, such preparations can be complicated by exchange of aryl groups between platinum centres; e.g. ( i ) reaction of [Pt(cod) (2-C4H,S),] with [Pt(cod)CI,J followed by addition of 1.2-bis(dipheny1phosphino)ethane (dppe) gives [Pt(2-C4H,S)Cl(dppe)] in ca. 100% yield, ( i i ) [Pt(cod)(2-C8H,0),] and [Pt(cod) (C6H,CI-rn),] similarly give some [Pt(2-C,H50) (C,H,CI-m) (dppe)], and (I;;) [Pt(cod) (3-C8H7)CI] and SnMe,(C,H,Me-p) similar!y give some [Pt(3-C,H,),(dppe)] and [Pt(C6H4Me-p),-(dppe)] (3-C,H = 1.2-dihydrobenzocyclobuten-3-yl). The olefin ligand is readily displaced from the aryl complexes by neutral ligands, and a wide range of [PtR(CI)L,] and [PtR,L,] complexes with L = 3 dppe or PPh, have been made. The i.r. and lH, 13C-{lH}, and 31P-(1H} n.m.r. spectra of the products are discussed. For cis-[Pt(C6H4X-p),(PPh3),] complexes the values of lJ( Pt-P) show a good correlation with crI constants. The norbornadiene (nbd) complex [Pt(nbd)CI,] reacts with SnMe3(2-C,H,O) to give [Pt(2-C,H,O)(nbd)CI]in 91% yield, but the corresponding palladium complex [Pd(nbd)CI,] reacts with SnMe,R (R = C6H40Me-p or C6HaMe-p) to give a dimeric chloride-bridged complex in which the aryl group is attached to the organic ligand. DICHLOROBIS(TRIORGANOPHOSPHINE)PLATINUMThe ease of reaction increases in the order (R =) CH,=CH, < CF=CF, < C-CPh [and this order applies also to oxidative addition of SnMe,-R species to platinum( 0) complexes] .2 No reaction takes place between cis-[PtCl,(PMe,Ph),] and SnMe,(CH,SiMe,) even on prolonged refluxing in tetrahydr0furan.lWe were interested in the possibility of utilizing aryltin compounds for attaching aryl groups to platinum, and we have found that while SnMe,R (R = aryl) compounds do not react (or react only very slowly) with bis(phosphine) complex...

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The parameters from the l H and 31P n.m.r. spectra are reported for trans-[PtMeX(Et,P),] (X = CI, Br, I, NO,, N3. NCS, NCO, NO,, CN), cis-[PtMeX(Et,P),] (X = CI, Br, N3, NCS, Me), and some related complexes. The platinumphosphorus coupling constant depends mainly on the covalency and s-character of the Pt-P bond, and this is used to investigate the mutual influence of the ligands in these complexes. The Pt-P bonds are weakened by the inductive effect of a methyl group in the trans-position, and it is argued that phosphines also inductively weaken bonds in the trans-position. The effects of varying the anionic ligands are similar to those produced in platinum hydrides and in methyl mercury compounds.1 : 2 : 1).