Mono- and dinuclear palladium(II) cyclometallates with 4-R-N'-(mesitylidene)benzohydrazides and mono- and diphosphines

Abstract

Reactions of PdCl2, LiCl, 4-R-N'-(mesitylidene)benzohydrazides (H2Ln; n = 1 and 2 for R = H and OMe, respectively) and NaOAc·3H2O in 1:2:1:1 mol ratio in methanol produce [Pd(HLn)Cl] (1 (n = 1) and 2 (n = 2)) in ∼77% yields. Reactions of [Pd(HLn)Cl] (1 and 2) with PPh3 in 1:2 mol ratio in acetone provide [Pd(Ln)(PPh3)] (3 (n = 1) and 4 (n = 2)) in ∼76% yields. Whereas, treatment of 2 mol equivalents of [Pd(HLn)Cl] (1 and 2) with 1 mol equivalent of 1,4-bis(diphenylphosphino)butane (dppb) in acetone affords the dinuclear [Pd2(μ-dppb)(Ln)2] (5 (n = 1) and 6 (n = 2)) in ∼74% yields. Analogous reaction between [Pd(HL2)Cl] (2) and 1,1'-bis(diphenylphosphino)ferrocene (dppf) provides [Pd2(μ-dppf)(L2)2] (7) in 67% yield. Elemental (CHN) analysis, X-ray crystallographic and spectroscopic (IR, UV-Vis and NMR) measurements have been used to characterize all the complexes. In these complexes, the metal centers are in square-planar CNOCl or CNOP coordination geometry formed by the 6,5-membered fused chelate rings forming methylene-C, azomethine-N and amide- or amidate-O donor (HLn)- or (Ln)2- and the ancillary ligand chloride or phosphine. The spectroscopic properties of the complexes are consistent with the corresponding molecular structures established by X-ray crystallography.