Binuclear metal carbonyl dab complexes : VIII. The syntheses of Os 2(CO) 6(DAB) complexes (DAB = 1,4-diazabutadiene). Spectroscopic characterization and comparison with analogous iron and ruthenium complexes

Abstract

The reaction of Os 3(CO) 12 with glyoxalbis(alkylimine) (alkyl = i-Pr, t-Bu) yielded Os 2(CO) 6(DAB) complexes. The complexes have been characterized by field desorption mass spectrometry, 1H NMR and IR spectroscopy. They are isostructural with Fe 2(CO) 6(DAB) and Ru 2(CO) 6(DAB). In these complexes the DAB ligand is a six-electron donor system coordinated via two lone pairs and one pair of π electrons. The complex Os 3(CO) 9(i-PrNCHCHN-iPr) was also isolated. This is the first example of a trinuclear metal carbonyl DAB complex, in which the DAB ligand is σ-N,σ-N′,η 2-CN coordinated. The reactions of the metal carbonyl complexes of the iron triad with DAB ligands are compared, and the ruthenium system shown to be the most versatile.