S. Basu, Rama Acharyya, F. Basuli
Oct 15, 2010
Citations
0
Influential Citations
22
Citations
Journal
Inorganica Chimica Acta
Abstract
Reaction of five 4 - R -benzaldehyde thiosemicarbazones (R = OCH 3 , CH 3 , H, Cl and NO 2 ) with [Ir(PPh 3 ) 3 Cl] in refluxing ethanol in the presence of a base (NEt 3 ) affords complexes of three different types, viz . 1 - R , 2 - R and 3 - R . In the 1 - R complexes the thiosemicarbazone is coordinated to iridium as a monoanionic bidentate N,S-donor forming a four-membered chelate ring. Two triphenylphosphines, a hydride and a chloride are also coordinated to the metal center. The 2 - R complexes are very similar in composition and stereochemistry to the corresponding 1 - R complexes, except that a second hydride is bound to iridium instead of the chloride. In the 3 - R complexes, the thiosemicarbazones are coordinated to iridium as dianionic tridentate C,N,S-donors forming two adjacent five-membered chelate rings. Two triphenylphosphines and a hydride are also coordinated to the metal center. Structures of the 1 - NO 2 , 2 - NO 2 and 3 - NO 2 complexes have been determined by X-ray crystallography. Reaction of the same 4 - R -benzaldehyde thiosemicarbazones with [Ir(PPh 3 ) 3 Cl] in refluxing toluene in the presence of NEt 3 affords complexes of two types, viz . 3 - R and 4 - R . The 4 - R complexes are very similar in composition and stereochemistry to the corresponding 3 - R complexes, except that a chloride is bound to iridium instead of the hydride. Structure of the 4 - CH 3 complex has been determined by X-ray crystallography. In all the complexes the two PPh 3 ligands are trans. All the complexes show intense MLCT transitions in the visible region. Cyclic voltammetry on the complexes shows an Ir( III )–Ir( IV ) oxidation on the positive side of SCE followed by an oxidation of the coordinated thiosemicarbazone. A reduction of the coordinated thiosemicarbazone is also observed on the negative side of SCE.