Synthesis, Structure, and Transformation of Novel Osmium Azine and Ylide Complexes

Three novel triosmium complexes with unusual coordination characteristics are reported. Treatment of the
hydridotriosmium cluster (μ-H)2Os3(CO)10 with CNNPPh3 in CH2Cl2 gave complexes (μ-H)Os3(CO)10(μ2-η2-C(H)NNPPh3) (1) and (μ-H)Os3(CO)10(μ2-η1-CHPPh3) (2). Complex 1 represents the first example of the existence of
a coordinated phosphinazine ligand. An in-situ 1H NMR study showed that the reaction of (μ-H)2Os3(CO)10 with
CNNPPh3 produced complex 1 as the initial product in 100% conversion. The latter is not stable in solution and
slowly eliminates nitrogen to form an unusual ylide complex 2 in quantitative yield. The thermolysis of 2 in refluxing
toluene afforded (μ-H)3Os3(CO)9(μ3-η1-CCO2CH2Ph) (3) as a colorless compound. Complexes 1−3 were characterized
by spectroscopic methods and single-crystal X-ray diffraction analysis. The interesting feature of structure 3 is the
presence of a μ3-alkylidyne ligand where the symmetrically triply bridged CCO2CH2Ph fragment lies perpendicular
to and above the triosmium triangle.