Synthesis, structural characterization and solvatochromic studies of a series of Schiff base-containing triosmium alkylidyne carbonyl clusters

A series of new Schiff base-containing triosmium alkylidyne carbonyl clusters [Os3(μ-H)2(CO)9(μ3-CNC5H4CH=NC6H4R)] (R = H, NMe2, SMe, CMe3, NH2, Br, Cl, OCnH2n+1, n = 1, 6, 7 or 9) have been prepared by reaction of [Os3(μ-H)3(CO)9(μ3-CCl)] with one equivalent of 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a ten-fold excess of the Schiff base ligands NC5H4CH=NC6H4R at room temperature. Analogous triosmium carbonyl clusters bearing 4′-methoxy-4-stilbazole or 4-(4-nitrobenzyl)pyridine moiety at the apical carbon centre have also been synthesized using a similar deprotonation method. The molecular structures of selected complexes have been established by X-ray crystallography. UV-vis spectroscopy suggests that this class of compounds displays significant negative solvatochromic effect in an organic medium.