Synthesis, structure and bonding of cadmium(II) thiocyanate systems featuring nitrogen based ligands of different denticity

Complexes catena-[di(4-amino-pyridine)di(mu-S,N-thiocyanato)cadmium(II)], (1)(infinity)[Cd(mu-SCN)(2)(L-1)(2)] (1), catena-[{(1-pyridine-2-yl-e thylene)-hydrazine} di(mu-S,N-thiocyanato)cadmium(II)], (1)(infinity)[Cd(mu-SCN)(2)(L-2)] (2), and di-mu-S,N-thiocyanatobis{(N,N-diethyl- N-1-(1-pyridine-2-yl-ethylidene)-ethane-1,2-diamine)(N-thiocyanato)cadmium(II)}, [Cd(NCS)(mu-SCN)(L-3)](2) (3) have been synthesized by reacting cadmium acetate/NH4SCN with 4-amino-pyridine (L-1), C5H4N-C(CH3)=NNH2 (L-2), and C5H4N-C(CH3)= N-CH2-CH2-N(C2H5)(2) (L-3), respectively, in methanol. Characterization by single-crystal X-ray crystallography shows that in compounds 1 and 2 the cadmium atoms have a 4N2S-hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1-D polymeric chains. Compound 3 is a centrosymmetric dimeric complex, with the cadmium atom pseudo octahedrally surrounded by a 5N1S coordination sphere. In compound I the crystal packing is controlled mainly by interchain N-(HN)-N-... and C-H(...)pi interactions between the aminopyridine moieties, whereas in complexes 2 and 3 pi-stacking interactions between the pyridyl planes stabilize the interchain or intermolecular packing, respectively. Thiocyanate and pyridylimine chelation to metal center is also scrutinized with EHMO analysis. (C) 2004 Elsevier B.V. All rights reserved.