Synthesis, Reactions, and Rearrangement of X(PR′3)2M[C(=PR)X] (M = Pt, Pd; X = Cl, Br; R′ = Et, Ph; R = 2,4,6-Tri-tert-butylphenyl): Mechanism of the Transition Metal Promoted Conversion of X2C=PR to R—C≡P

Hyoung Jun, Victor G. Young, Robert J. Angelici

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Abstract

Oxidative addition reactions of X2C=PR (X = Cl, Br; R = 2,4,6-tri-tert-butylphenyl) with M(PEt3)4 (M = Pt, Pd) or (C2H4)Pt(PPh3)2 initially yield the cis isomer of square planar (X)-(PR′3)2M[C(=PR)X] (II); these complexes (IIa-IId), where PR′3 is PEt3, rearrange rapidly in the presence of free PEt3 to give the trans isomers (Ia‒Id). In contrast, the cis isomers (IIe and IIf), where PR′3 is PPh3 and M is Pt, react further to give R—C≡P and cis-X2Pt(PPh3)2. In polar solvents (CH2Cl2 and CHCl3), all the addition products (I and II) convert to R—C≡P and cis- or trans-X2M(PR′3)2 via the surprising phosphabicyclo intermediate (X)(PR′3)2Pt(X—PBC) (III and IV); the structure of IIIa was established crystallographically. In the presence of H2O, (X)(PEt3)2Pt[C(=PR)X] (Ia and Ib where X = Cl, Br) give the oxophosphabicyclo complex (X) (PEt3)2Pt[(H) O=PBC] (Va and Vb) which was characterized by X-ray diffraction. A mechanism for the conversion of (X)(PR′3)2M[C(=PR)X] to R—C≡P and X2M-(PR′3)2 is proposed.

Original languageEnglish (US)
Pages (from-to)2444-2453
Number of pages10
JournalOrganometallics
Volume13
Issue number6
DOIs
StatePublished - Jun 1 1994

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