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Phosphorus Monoxide Coordination Chemistry:  Synthesis and Structural Characterization of Tetranuclear Clusters Containing a PO Ligand

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journal contribution
posted on 11.06.1996 by Weibin Wang, John F. Corrigan, Simon Doherty, Gary D. Enright, Nicholas J. Taylor, Arthur J. Carty
The clusters Ru4(CO)13(PNPri2) (1) and Os4(CO)13(PNPri2) (4) have been prepared via the reactions of Cl2PNPri2 with respectively [Ru4(CO)13]2- and the reaction product of Na2[Os(CO)4] and Os3(CO)12. The successful synthesis of 4 suggests that the reaction of Na2[Os(CO)4] with Os3(CO)12 generates [Os4(CO)13]2-, thus providing a relatively easy route for the preparation of this dianion. Thermal decarbonylation of 1 and 4 affords the tetranuclear clusters M4(CO)12(PNPri2) (M = Ru, 2, and Os, 5), which upon chromatography and subsequent metathesis with Et4N[Cl] afford the [H2NPri2]+ and [Et4N]+ salts of [M4(CO)12(PO)]- (M = Ru, 3, and Os, 6), respectively. The structures of 1, 2, 3[H2NPri2], 4, and 6[Et4N] were determined by X-ray crystallography. The M4P frameworks in 1 and 4 form a square pyramidal arrangement with the P atom occupying a basal position. The molecular structure of 2 reveals a five-vertex polyhedron with the PNPri2 ligand capping one face of a Ru4 tetrahedron. The arrangement of metal and phosphorus atoms in 3[H2NPri2] and 6[Et4N] remains similar to that in 2. The phosphorus monoxide ligand, in each case, triply bridges a M3 face of the tetrahedral M4 skeleton with the P−O vector essentially perpendicular to this face. The interatomic P−O distances in 3[H2NPri2] and 6[Et4N] suggest double-bond character for the P−O moiety. Cleavage of the PN bond of an aminophosphinidene ligand followed by P−O bond formation may have general applicability for the preparation of metal clusters containing a PO ligand.