Some (η 3 -crotyl) (2,5-dichlorophenyl)palladium(II) complexes containing phosphine and phosphite ligands Pd(η 3 -CH 2 CHCHMe)(Ar)(PR 3 ) (Ar = C 6 H 3 Cl 2 -2,5) were isolated as crystalline solids or generated in solution. These existed as a mixture of two geometrical isomers arising from a different way of relative disposition of the crotyl-methyl group and the aryl ligand. The electronic nature of the PR 3 ligand controlled the relative rates of the interconversion between the two isomers and the reductive elimination of the complexes which released MeCH=CHCH 2 Ar and CH 2 =CHCH(Me) (Ar). Electron-withdrawing phosphite ligands were particularly effective in enhancing the reductive elimination rate, making the contribution of the isomerization path almost negligible and allowing the formation of two coupling products to be followed separately by spectroscopic means. These observations demonstrated the occurrence of C-C coupling between mutually cis carbon ligands in (η 3 -allyl)(hydrocarbyl)palladium(II) complexes. The η 1 -crotyl complex, Pd(η 1 -CH 2 CH=CHMe)(Ar)(dppen) (dppen = cis-Ph 2 PCH=CHPPh 2 ) was isolated and shown to exist as a sole regio-isomer in solution. Reductive elimination of this η 1 -crotyl complex gave MeCH=CHCH 2 Ar exclusively.