A large variety of cationic η3-allylplatinum(II) complexes of the type [Pt(η3-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(η2-C2H4)(PPh3)2]. A similar reaction of [NEt3CH2C(R)=C(R′)2]+ with [Pt(cod)2] yields the related complexes [Pt(η3-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,c can be easily displaced by mono- and bidentate tertiary phosphines. The solution behaviour of the cationic η3-allyl platinum(II) complexes has been studied by multinuclear NMR spectroscopy. The solid state structures of the complexes [Pt(η3-CH2CHCH2)(PPh3)2]+ (1a) and [Pt(η3-CH2C(Me)CH2)(PPh3)2]+ (1b) have been determined by X-ray analyses. In 1b, the 2-methylpropenyl ligand is symmetrically η3-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 η3-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) Å] 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 η1, η2 coordination of the ligand in the solid.
|Titolo:||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|
|Autori interni:||MENEGHETTI, FIORELLA (Penultimo)|
|Settore Scientifico Disciplinare:||Settore CHIM/08 - Chimica Farmaceutica|
|Data di pubblicazione:||2000|
|Digital Object Identifier (DOI):||10.1016/S0022-328X(00)00251-5|
|Appare nelle tipologie:||01 - Articolo su periodico|