Intermolecular propargyl/allenyl group transfer from Pd(II) to Pt(0) and Pt(II) to Pd(0). Key reaction in metal-catalyzed isomerization between propargyl and allenyl metal complexes

Isomerization of phenyl-substituted propargylplatinum(II) complex, trans-Pt (CH2C=CPh)(Cl)(PPh3)(2) (1) to allenyl complex, trans-Pt(CPh=C=CH2)(Cl)(PPh 3)(2) (2) was found to be catalyzed by zerovalent complex Pd(PPh3)(4). The reaction was proposed to proceed through the transfer of the propargyl/alle nyl ligand both from Pt(II) to Pd(0) and Pd(II) to Pt(0). The former transf er, which seemingly has a thermodynamic disadvantage, has unambiguously bee n confirmed to take place; treatment of 1 with Pd(PPh3)(4) or a mixture of Pd-2(dba)(3) and PPh3 resulted in the formation of Pd(I) complex, Pd-2(mu - PhCCCH2)(mu -Cl)(PPh3)(2) which lies in equilibrium with a mixture of propa rgyl/allenylpalladium(II) and Pd(0) complexes. (C) 2001 Elsevier Science B. V. All rights reserved.