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-CNC ₅H₄CH=NC₆H₄R)] (R = H, NMe₂, SMe, CMe₃, NH₂, Br, Cl, OC_nH_2n+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.