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

Substitution reactions of [W(CO)(5)(THF)] with the ate-functionalized monop yridyl and dipyridyl ligands, namely, 4-phenylazopyridine L-1 and 4,4'-azop yridine L-2, readily afford two tungsten carbonyl complexes [W(CO)(5)(NC5H4 -N=N-C6H5)] (1) and [(CO)(5)W(mu-NC5H4-N=N-C5H4N)W(CO)(5)] (2) in good yiel ds. 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(mu-H)(C O)(10)(mu-NC5H3-N=N-C6H5)] (3) and the linking cluster [Os-3(mu-H)(CO)(10)( mu-NC5H3-N=N-C5H3N)Os-3(mu-H)(CO)(10)] (4) in satisfactory yields. All of t he complexes have been fully characterized by IR, H-1-NMR, UV-vis spectrosc opies, fast atom bombardment (FAB) mass spectrometry and electrochemical me asurements. The solid-state molecular structures of 1-4 have been ascertain ed by single-crystal X-ray diffraction methods. The structures of 1 and 3 i nvolve the coordination of L-1 to one {W(CO)(5)} and {Os-3(CO)(10)} moietie s, respectively. In the case of 2 and 4, two identical metal cores are link ed together by the bridging ligand L-2. Spectroscopic investigations reveal ed that the metal-to-ligand charge transfer (MLCT) transitions of 1 and 2 d emonstrate strong solvent dependency, displaying a large negative solvatoch romism in a wide range of organic solvents. (C) 2000 Elsevier Science S.A. All rights reserved.