Insertion of CO and Strained Olefins into Organometallic (Ferrocenylmethyl)phosphane Palladium Complexes

Abstract

AbstractThe reaction of [Pd(cod)(CH3)Cl] (cod = 1,5‐cyclooctadiene) with the primary phosphane (ferrocenylmethyl)phosphane (PH2CH2Fc, 1, 2 equiv.) affords trans‐[Pd(PH2CH2Fc)2(CH3)Cl] (2) in 95 % yield. The intermediate chlorido‐bridged dinuclear complex [Pd(PH2CH2Fc)(CH3)(μ‐Cl)]2 (3) is traversed along the formation of 2. Complex 3 may be isolated as a mixture of anti‐3a and syn‐3b isomers by treating [Pd(cod)(CH3)Cl] with 1 (1 equiv.). For comparison, the analogous reactions of 1 with [Pt(cod)(CH3)Cl] gives [Pt(PH2CH2Fc)2(CH3)Cl] as a mixture of cis‐4a and trans‐4b geometric isomers, regardless of the P/Pt molar ratio used. The insertion (at 1 atm and 253 K) of CO into the methyl–Pd bonds of either 2 or 3 gives the acetyl Pd complexes trans‐[Pd(PH2CH2Fc)2(COCH3)Cl] (5) and anti‐[Pd(PH2CH2Fc)(COCH3)(μ‐Cl)]2 (6), respectively. The process leading from 3 to 6 occurs without fragmentation of the dinuclear core of the complexes, lending support to an associative mechanism with CO binding to the metal. Complex 6 undergoes facile insertion of strained olefins, such as norbornadiene or norbornene, into the acetyl–palladium bond, giving the complexes [Pd(κ2C,O‐C7H8C(O)CH3)(Cl)(PH2CH2Fc)] (7) and [Pd(κ2C,O‐C7H10C(O)CH3)(Cl)(PH2CH2Fc)] (8), respectively. Complexes 3 were tested as precatalysts for the vinylic polymerization of norbornene at 253 K, as well as for the alternate copolymerization of carbon monoxide with norbornene.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)