Triosmium carbonyl complexes with multiple 1,3,5-triaza-7-phosphaadamantane (PTA) ligands: Synthesis of a new water-soluble Os3 cluster

Abstract

Microwave heating has been used to substitute carbonyl ligands for 1,3,5-triaza-7-phosphaadamantane (PTA) ligands on the Os3(CO)12 molecule. Os3(CO)11(PTA) (1) has been prepared in 66% yield by the reaction of Os3(CO)12 with MeCN, followed by reaction with one mole equivalent of PTA. Os3(CO)10(PTA)2 (2) has been prepared in 65% yield via a three-step reaction. First, Os3(CO)12 was heated in MeCN. Next, one mole equivalent of PTA was added to this reaction mixture. Finally, one mole equivalent of trimethylamine-N-oxide was added followed by another mole equivalent of PTA. Additionally, Os3(CO)9(PTA)3 (3) has been prepared in 85% yield by the reaction of Os3(CO)12 with 3.5mol equivalents of PTA in 1,2-dichlorobenzene, and Os3(CO)8(PTA)4 (4) has been prepared in 36% yield by the reaction of Os3(CO)12 with 8mol equivalents of PTA in a mixture of acetonitrile and 1,2-dichlorobenzene. The solubilities of clusters 1–4 in water at various pH levels have been studied, and 4 was found to be soluble in water with a neutral pH. X-ray diffraction has been used to determine the crystal structures of clusters 1 and 3. The X-ray crystal structure of a protonated form of 3, [Os3(CO)9(PTAH)3]Cl3 (5), has also been determined. All PTA ligands occupy equatorial coordination sites on the triangular Os3 units.