Palladium(II) and Platinum(II) compounds of 1,1′-bis(phosphino) metallocene (m = fe, ru) ligands with metal-metal interactions

摘要

The reaction of [Pd(dtbpf)Cl_2] (dtbpf = 1,1′-bis(di-tert- butylphosphino)ferrocene) with a chemical oxidant led unexpectedly to the formation of [Pd(dtbpf)Cl]~+. Further study found that a variety of reagents could be used to abstract a chloride ligand from [Pd(dtbpf)Cl_2] to yield [Pd(dtbpf)Cl]~+. The solid-state structure suggests the formation of an Fe-Pd interaction. The presence of the bulky tert-butyl groups is essential, as similar reactions with [Pd(PP)Cl_2] (PP = other 1,1′-bis(phosphino)ferrocene ligands) results in the formation of [Pd(PP)(μ-Cl)]_2 ~(2+). The analogous platinum compounds have also been investigated and appear to behave in a similar manner. Similar compounds of the type [M′(PP)(PR_3)]~(2+) (M′ = Pd, Pt, R = Ph, Me) have been prepared, and a metal-metal interaction has also been observed. Steric and electronic effects dictate the formation of these compounds. X-ray crystal structures were obtained for eight of these compounds and were used as the basis for a computational analysis of the metal-metal interaction. DFT analysis indicates the presence of a weak, noncovalent interaction between the two metal centers. The electrochemical properties of these compounds were examined by cyclic voltammetry and typically show one oxidative wave and either one two-electron or two one-electron reductive waves.