Convenient synthesis of cationic allylplatinum(II) complexes with tertiary phosphines 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 easily displaced by mono- and bidentate tertiary phosphines. The solution behaviour of the cationic eta(3)-allyl platinum(II) complexes has been studied by multinuclear NMR spectroscopy. The solid state structures of the complexes [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-methylpropenyl ligand is symmetrically eta(3)-bound to platinum and assumes a unique orientation relative to the average coordination plane. In la, however, the propenyl ligand is disordered in two opposite orientations with occupation 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 the opposite orientation the C-C bond distances within the allyl group are considerably different [1.46(4) and 1.23(4) Angstrom] with the three allyl carbon atoms being at roughly equal distances from platinum. Even though the C3H5 group is affected by large anisotropic thermal motion, the observed asymmetry may also arise from a prevailing eta(1), eta(2) coordination of the ligand in the solid.