Convenient synthesis of cationic allylplatinum(II) complexes with tertiaryphosphines by oxidative allyl transfer from ammonium cations to platinum(0) substrates. Crystal and molecular structures of eta(3)-propenyl- and eta(3)-2-methylpropenyl-bis-(triphenylphosphine)platinum(II)perchlorate

A large variety of cationic eta(3)-allylplatinum(II) complexes of the type [Pt(eta(3)-CH2C(R)C(R')(R ")(PPh3)(2)](+)(1a-f) are prepared in high yield by oxidative allyl transfer from the ammonium cations [NEt3CH2C(R) C(R')(R ")](+) to [Pt(eta(2)-C2H4)(PPh3)(2)]. A similar reaction of [NEt3CH2C(R)-C( R')(2)](+) with [Pt(cod)(2)] yields the related complexes [Pt(eta(3)-CH2C(R )C(R')(2)(cod)](+) (2a-c), indicating a rather general feasibility of such synthetic route. The 1,5-cyclooctadiene ligand of complexes 2a,e can be eas ily displaced by mono- and bidentate tertiary phosphines. The solution beha viour of the cationic eta(3)-allyl platinum(II) complexes has been studied by multinuclear NMR spectroscopy. The solid state structures of the complex es [Pt(eta(3)-CH2CHCH2)(PPh3)(2)](+) (1a) and [Pt(eta(3)-CH2C(Me)CH2)(PPh3) (2)](+) (1b) have been determined by X-ray analyses. In Ib, the 2-methylpro penyl ligand is symmetrically eta(3)-bound to platinum and assumes a unique orientation relative to the average coordination plane. In la, however, th e propenyl ligand is disordered in two opposite orientations with occupatio n factors of 0.65 and 0.35. In the orientation with 0.65 occupation factor, the allyl ligand is symmetrically eta(3)-bound to the metal, whereas, in t he opposite orientation the C-C bond distances within the allyl group are c onsiderably different [1.46(4) and 1.23(4) Angstrom] with the three allyl c arbon atoms being at roughly equal distances from platinum. Even though the C3H5 group is affected by large anisotropic thermal motion, the observed a symmetry may also arise from a prevailing eta(1), eta(2) coordination of th e ligand in the solid. (C) 2000 Elsevier Science S.A. All rights reserved.