Effect of phenyl substitution on bonding in η3-benzyl complexes of platinum
Abstract
Reaction of the platinum(0) styrene complexes [Pt(η2-CH2CHC6H4X){But2P(CH2)3PBut2}]1a–1f(X = Br-3, Br-4, Me-4, F-4, F-3 or MeO-4) with HBF4 in diethyl ether afforded the η3-methylbenzyl complexes [Pt(η3-MeCHC6H4X){But2P(CH2)3PBut2}][BF4]2a–2f. The effect of phenyl substitution on the asymmetry of the η3-methylbenzyl interaction was measured by 31P-{1H} NMR spectroscopy and it was found that, in general, the more electron releasing the substituent, X, the more asymmetric is the bonding. Complexes 2a–2f lose styrene reversibly to form the hydride-bridged dinuclear platinum complex [Pt2(µ-H)2{But2P(CH2)3PBut2}2][BF4]2. Displacement of styrenes from 2a–2f by ethene and bicyclo[2.2.1]hept-2-ene affords known complexes stabilized by a three-centre, two-electron (agostic) bond.