Dynamic behaviour of carbon metallated palladium hydrazone complexes. Crystal structure of {Pd[CH2CMe2C(=N-NMePh)MeCl}2] and [{Pd[CH2C(=N-NMePh)But]Cl}2]

The carbon-palladated species [{Pd[CH2CMe2C(=NMePh)Me]Cl}2](1a) and [{Pd[CH2C(=NMePh)But]Cl}2] (2) have in the solid state a trans geometry and are planar; their crystal structures have been determined by X-ray methods. These species, as well as the bromo- and iodo-derivatives of (1a) and the complex [{Pd[CH2C(=N-NMe2)But]Cl}2], exhibit temperature-dependent n.m.r. spectra which have been interpreted on the basis of cis-trans isomerization of the complexes and of hindered rotation about the N-N single bond of the hydrazone. The latter process is also present in the mononuclear species obtained from (1a) by bridge-splitting reactions with triphenylphosphine, pyridine, and acetylacetonate. Crystals of (1a) are triclinic, space group P1, a = 10.642(8), b = 11.793(9), c = 6.269(6) Å, α = 98.05(6), β = 97.46(6), γ = 111.91(7)°, and Z = 1. Crystals of (2) are monoclinic, space group P21/a, a = 24.059(12), b = 10.035(8), c = 6.018(5) Å, β = 95.39(5)°, and Z = 2.