The Influence of Substituents at C2 Carbon of Thiosemicarbazones on the Bonding Pattern of Bis(diphenylphopshano)alkanes in Palladium(II) Complexes

Reactions of trans-PdCl2(PPh3)(2) with acetone thiosemicarbazone (Hactsc) and benzaldehyde thiosemicarbazone (Hbtsc) in a 1:1 molar ratio in the presence of Et3N yielded the neutral complexes [Pd(eta(2)-N-3,S-actsc)(PPh3)Cl] (1) and [Pd(eta(2)-N-3,S-btsc)(PPh3)Cl] (2) respectively. In contrast, reactions of cis-PdCl2(dppe) (dppe = bis(diphenylphosphanyl)ethane) and cis-PdCl2(dppp) (dppp = bis(diphenylphosphanyl)propane) with Hbtsc gave the ionic complexes [Pd(eta(2)-N-2,S-btsc)(eta(2)-dppe)]Cl (3) and [Pd(eta(2)-N-3,S-btsc)(eta(2)-dppp)]Cl (4) because of the chelation effect. The reaction of salicylaldehyde thiosemicarbazone (H(2)stsc) with cis-PdCl2(dppm) (dppm = bis(diphenylphosphanyl)methane)- and cis-PdCl2(dppp) yielded the dinuclear complexes [Pd-2(eta(3)-O,N-3,S-stsc)(2)(mu-dppm)] (5) and [Pd-2(eta(3)-O,N-3,S-stsc)(2)(mu-dppp)] (6). Complexes 1-6 were characterized with spectroscopic techniques [IR, H-1, P-31{H-1} NMR], and single-crystal X-ray crystallography The ligands are negative bidentate in complexes 1-4 and di-negative tridentate (O, N-3, S) in complexes 5 and 6. Diphosphanes exhibited both chelating (eta(2); 3, 4) as well as bridging (mu; 5, 6) modes.