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

Abstract

The clusters Ru 4 (CO) 13 (PNPr i 2 ) (1) and Os 4 (CO) 13 (PNPr i 2 ) (4) have been prepared via the reactions of Cl 2 PNPr i 2 with respectively [Ru 4 (CO) 13 ] 2and the reaction product of Na 2 [Os-(CO) 4 ] and Os 3 (CO) 12 . The successful synthesis of 4 suggests that the reaction of Na 2 [Os-(CO) 4 ] with Os 3 (CO) 12 generates [Os 4 (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 M 4 (CO) 12 (PNPr i 2 ) (M ) Ru, 2, and Os, 5), which upon chromatography and subsequent metathesis with Et 4 N[Cl] afford the [H 2 NPr i 2 ] + and [Et 4 N] + salts of [M 4 (CO) 12 (PO)] -(M ) Ru, 3, and Os, 6), respectively. The structures of 1, 2, 3[H 2 NPr i 2 ], 4, and 6[Et 4 N] were determined by X-ray crystallography. The M 4 P 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 PNPr i 2 ligand capping one face of a Ru 4 tetrahedron. The arrangement of metal and phosphorus atoms in 3[H 2 NPr i 2 ] and 6[Et 4 N] remains similar to that in 2. The phosphorus monoxide ligand, in each case, triply bridges a M 3 face of the tetrahedral M 4 skeleton with the P-O vector essentially perpendicular to this face. The interatomic P-O distances in 3[H 2 NPr i 2 ] and 6[Et 4 N] 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.

Synthesis and Structural Characterization of Two Tetraruthenium Bis(phosphinidene) Clusters with 62- and 64-Electron Counts: Ru4(CO)11(μ4-PPh)(μ4-PNPri2) and Ru4(CO)12(μ4-PNPri2)2

“…Whether this reflects a better π-acceptor capability for PPh vs PNPr i 2 or greater steric repulsion between the metal-ligand envelope and the PNPr i 2 ligand is uncertain. These distances are both significantly longer, however, than the Ru−P bond lengths observed for 2 (2.332(1) Å) and Ru 4 (CO) 13 (μ 3 -PNPr i 2 ) (2.348(1) Å).

2 Molecular structure of Ru 4 (CO) 10 (μ-CO)(μ 4 -PPh)(μ 4 -PNPr i 2 ) ( 6 ).

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Synthesis and characterization of a tetraruthenium butterfly cluster containing a quadruply-bridging ligand derived from an N,N′-dipyrid-2-ylurea

“…The latter always have a bridging ligand that spans two or three metal atoms, e.g. [Ru 4 (l-SR 2 )(l-CO)(CO) 12 ] [9] and [Ru 4 (l 3 -PR) (CO) 13 ] [10].…”

Interconversion of tetrahedranes containing naked phosphorus ligands; synthesis of the trimetallic complexes [MonW(3−n) Cp3(CO)6(μ3-P)] (n = 0–3, Cp = η5-C5H5) and their air oxidation to the corresponding complexes of the μ3-PO ligand

“…2 By contrast with its first row congener NO, 3 there are only a very small number of transition-metal complexes of the PO ligand; the first of these, [Ni 2 WCp 2 (CO) 4 (µ 3 -PO) 2 ] (Cp = η 5 -C 5 H 5 ), was obtained by Scherer et al, 4 by oxidation of a P 2 ligand using bis(trimethylsilyl) peroxide. Subsequent examples have been provided by Carty and co-workers 5 via hydrolysis of a capping aminophosphinidene ligand and by Butenschön and coworkers 6 who reported a series of tricobalt clusters capped by µ 3 -P, µ 3 -PO and µ 3 -PS ligands formed by oxidation using atmospheric oxygen or elemental sulfur. Examples of complexes containing the closely related PS ligand are also rare; to our knowledge, the examples of Butenschön and co-workers 6 and Visi-Orosz et al, 7 are the only examples of µ 3 -PS complexes, with a solitary example of a complex containing a terminal PS ligand being given by Cummins and co-workers.…”