Dinuclear palladium complexes incorporating amidato, carbamato and urea bridging groups

Abstract

Dipalladium complexes of the pentadentate, benzenethiolate-hinged binucleating ligand 2,6-bis[(cyclohexyl)-hydroxymethylenehydrazonomethyl]-4-methylbenzenethiol (H₃L), incorporating amidato and alkyl-substituted urea and carbamato moieties at the exogenous bridging site, have been prepared. The conjugate bases of acetamide, acrylamide, maleimide, N,N-dimethylurea and urethane bridge the two palladium atoms in a three-atom N–C–O mode, and the conjugate base of O-methylisourea is co-ordinated via a N–C–N bridging mode, at the bridging site of LPd₂⁺. A dinuclear complex cation is generated when O-methylisourea is incorporated as a neutral species at the bridging site, although the nature of the co-ordination mode is not clear. The structure of an amidato-N,O bridged complex has been established by a single-crystal X-ray diffraction study. It is the first example of a complex containing co-ordinated maleimide, [Pd₂L(C₄H₂NO₂)]. The relevance of these complexes to possible intermediates for the urease-catalysed hydrolysis of urea is discussed.