Chemistry of in-plane coordinated double bonds. Coordinated alkyl and aryl migration to adjacent exocyclic olefin in alkyl(or aryl)halo(5-methylenecyclooctene)platinum(II)

Article abstract of DOI:10.1021/om00100a011

The complexes dichloro[(1,2,5,9-η⁴)-5-methylenecyclooctene]platinum(II) (4a) and dibromo[(1,2,5,9-η⁴)-5-methylenecyclooctene]platinum(II) (4b), each of which has an unusual in-plane coordinated olefin (C5C9), show marked reactivity enhancements compared to typical dihalo(η⁴-diene)platinum(II) models. The second-order reaction of 4a or 4b with (aryl)Sn(CH₃)₃ results in aryl transfer to platinum with rate enhancement approaching 1000 compared to dichloro[(1,2,5,6-η⁴)-cycloocta-1,5-diene]platmum(II) (5). The aryl or alkyl transfers to 4a or 4b are followed by rupture of the Pt(C5C9) π-olefin bond to form halide-bridged dimers, e.g. bis(μ-chloro)bis[(1,2-η ²)-5-methylenecydooctene]diphenyldiplatmum(II) (8). The aryl groups transfer quantitatively from platinum to C9, with half-lives ranging from 7 to 110 min and with concomitant formation of a Pt-CS σ bond (olefin insertion into Pt-aryl). Simultaneous coordination of olefinic C5C9 and aryl to Pt(II) is not observed directly; however, simultaneous coordination is observed when the transferred group is methyl. In the latter case the methyl group is observed to be trans to coordinated C5C9 and the subsequent methyl transfer to C9 has a methyl transfer half-life of 1.5 × 10⁴ min (from 4a) or 3 × 10⁴ min (from 4b). Also reported is the facile reaction of 4a with sodium methoxide which results in formal insertion of C5C9 into Pt-OCH₃ (Pt-C5-C9-OCH₃). In the course of this work the crystal structures of derivatives of two final insertion products were determined. Crystal data for (benzylamine)chloro-[(1,4,5-η ³)-1-(phenylmethyl)-4-cycloocten-1-yl]platinum(II) (12): C₂₂H₂₈ClNPt, space group P1 with a = 10.613 (4) A?, b = 13.380 (5) A?, c = 7.969 (1) A?, α = 107.21 (2)°, β = 96.70 (2)°, γ = 108.56 (6)°, V = 996 (1) A?³, Z = 2. Crystal data for chloro[(1,4,5-η ³)-1-(methoxymetnyl)-4-cycloocten-1-yl](pyridine)platinum(II) (16): C₁₅H₂₂ClNOPt, space group P2₁/n with a = 7.932 (3) A?, b = 17.619 (2) A?, c = 11.145 (2) A?, β = 101.16 (2)°, V = 1528 (1) A?³, Z = 4.