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...
