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 η3-propenyl- and η3-2-methylpropenyl-bis(triphenylphosphine)platinum(II)perchlorates

Abstract A large variety of cationic η 3 -allylplatinum(II) complexes of the type [Pt(η 3 -CH 2 C(R)C(R′)(R″)(PPh 3 ) 2 ] + ( 1a – f ) are prepared in high yield by oxidative allyl transfer from the ammonium cations [NEt 3 CH 2 C(R)C(R′)(R″] + to [Pt(η 2 -C 2 H 4 )(PPh 3 ) 2 ]. A similar reaction of [NEt 3 CH 2 C(R)C(R′) 2 ] + with [Pt(cod) 2 ] yields the related complexes [Pt(η 3 -CH 2 C(R)C(R′) 2 (cod)] + ( 2a – c ), indicating a rather general feasibility of such synthetic route. The 1,5-cyclooctadiene ligand of complexes 2a , c can be easily displaced by mono- and bidentate tertiary phosphines. The solution behaviour of the cationic η 3 -allyl platinum(II) complexes has been studied by multinuclear NMR spectroscopy. The solid state structures of the complexes [Pt(η 3 -CH 2 CHCH 2 )(PPh 3 ) 2 ] + ( 1a ) and [Pt(η 3 -CH 2 C(Me)CH 2 )(PPh 3 ) 2 ] + ( 1b ) have been determined by X-ray analyses. In 1b , the 2-methylpropenyl ligand is symmetrically η 3 -bound to platinum and assumes a unique orientation relative to the average coordination plane. In 1a , 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 η 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) A] with the three allyl carbon atoms being at roughly equal distances from platinum. Even though the C 3 H 5 group is affected by large anisotropic thermal motion, the observed asymmetry may also arise from a prevailing η 1 , η 2 coordination of the ligand in the solid.