The stability of the complex (μ-H)Os3(μ-OCNMe2)(CO)9PPh2CH2CH=CH2 (1), which contains a free unsaturated functional group in the terminal ligand PPh2CH2CH=CH2, with respect to isomerization, chelation of the ligand, and other transformations in solutions was examined. No transformations of complex1 were observed in the course of synthesis from (μ-H)Os3(μ-OCNMe2)(CO)9NMe3 or upon heating in solution. Complex1 as well as complexes (μ-H)Os3(μ-OCNMe2)(CO)9PHPh2 and (μ-H)Os3(μ-OCNMe2)(CO)9PPh3, which were formed as admixtures, were isolated in the solid state and identified by1H,1H-{31P}, and1H-{1H} NMR, IR, and Raman spectroscopy and mass spectrometry.