Synthesis, characterization and crystal structures of some tungsten and triosmium carbonyl complexes with monopyridyl and dipyridyl azo ligands

Abstract

Substitution reactions of [W(CO) 5(THF)] with the azo-functionalized monopyridyl and dipyridyl ligands, namely, 4-phenylazopyridine L 1 and 4,4′-azopyridine L 2 , readily afford two tungsten carbonyl complexes [W(CO) 5(NC 5H 4NNC 6H 5)] ( 1) and [(CO) 5W(μ-NC 5H 4NNC 5H 4N)W(CO) 5] ( 2) in good yields. Ligation of L 1 and L 2 with the activated triosmium carbonyl cluster [Os 3(CO) 10(NCMe) 2] by ortho-metallation reaction provides [Os 3(μ-H)(CO) 10(μ-NC 5H 3NNC 6H 5)] ( 3) and the linking cluster [Os 3(μ-H)(CO) 10(μ-NC 5H 3NNC 5H 3N)Os 3(μ-H)(CO) 10] ( 4) in satisfactory yields. All of the complexes have been fully characterized by IR, 1H-NMR, UV–vis spectroscopies, fast atom bombardment (FAB) mass spectrometry and electrochemical measurements. The solid-state molecular structures of 1– 4 have been ascertained by single-crystal X-ray diffraction methods. The structures of 1 and 3 involve the coordination of L 1 to one {W(CO) 5} and {Os 3(CO) 10} moieties, respectively. In the case of 2 and 4, two identical metal cores are linked together by the bridging ligand L 2 . Spectroscopic investigations revealed that the metal-to-ligand charge transfer (MLCT) transitions of 1 and 2 demonstrate strong solvent dependency, displaying a large negative solvatochromism in a wide range of organic solvents.