Dimeric cyclopalladated azobenzenes: structural differences between 2-hydroxypyridine and 2-mercaptopyridine bridged complexes

Binuclear chloro-bridged cyclopalladated azobenzenes [Pd(A)Cl](2) (A = ortho-metallated azobenzene or its derivatives) have been reacted with aqueous (aq.) AgNO3 followed by the addition of 2-hydroxypyridine (2-PyOH; donor centres of deprotonated form abbreviated N,O)/2-mercaptopyridine (2-PySH; donor centres of deprotonated form abbreviated N,S) in presence of Et3N to synthesise bridged dinuclear compound [Pd(A)(mu-N,S)](2)-[Pd(A)(mu-N,S)](2). The compositions of the complexes have been established by elemental analyses, IR, UV-vis, H-1 and C-13-NMR spectral data. The structural confirmation has been carried out by X-ray crystallography. The structures show anti-symmetric metallacycle in the dimer and N,O[N,S bridging arrangement. The dimer [Pd(A(1))(mu-N,X)](2) shows strong (PdPd)-Pd-. . . interaction (A(1) = 2-(phenylazo)benzene). The coordination mode in [Pd(A(1))(mu-N,O)](2) shows trans pyridine-N to Pd-N(azo) bond while in [Pd(A(1))(mu-N,S)](2) pyridine-N is trans to the Pd-C bond. The square planes are convergent towards heterocyclic bridging side. (C) 2002 Rublished by Elsevier Science B.V.