Synthesis, characterization, and thermolytic behaviour of η3-allyl(methyl)(tertiary phosphine)palladium(II), and X-ray structure of the cluster [Pd4(µ-C3H5)2(µ-Cl)2(µ-dppm)2]·4C4H8O (dppm = Ph2PCH2PPh2)

Abstract

Complexes of the type [Pd(η³-allyl) Me(L)][allyl = C₃H₅ or 2-MeC₃H₄; L = P(C₆H₁₁)₃, PPh₃, PPh₂Me, PPhMe₂, or PBuⁿ₃] have been synthesized and characterized by ¹H, ¹³C n.m.r. and mass spectroscopy. The [Pd (η³-C₃H₅) Me(L)] complexes thermally decompose with preferential evolution of ethane rather than but-1-ene, the allylic alkylation product. The participation of the binuclear methyl-bridged intermediate [Pd₂(η³-allyl)₂(µ-Me)₂](3) is supposed. Indirect support for this is given by the thermolysis of a toluene solution of (3). The effects of phosphines, alkenes, and other additives on the thermolysis products are discussed. The structure of a complex isolated from the [Pd₂(η³-allyl)₂(µ-Cl)₂]–LiMe–Ph₂PCH₄PPh₄(dppm) reaction system in tetrahydrofuran was revealed by X-ray analysis as two µ-chloro-µ-allyl-dipalladium(I) units bridged by two dppm ligands.