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The reaction of the benzothiazolate-capped triosmium clusters Os 3 (CO) 9 (μ 3 ,η 2 -C 7 H 3 NSR)(μ-H) ( 1a , R = H; 1b , R = Me) with PPh 3 proceeds readily at room temperature with a μ 3 ,η 2 → μ,η 2 hapticity change in the benzothiazolate heterocycle to furnish Os 3 (CO) 9 (PPh 3 )(μ,η 2 -C 7 H 3 NSR)(μ-H) ( 2a , R = H; 2b , R = Me) in high yields. X-ray crystallography has confirmed the regiospecific nature of this reaction where the PPh 3 ligand is bound to the osmium atom that serves as the coordination site for the hydride and the metalated-carbon atom associated with the edge-bridged benzothiazolate ligand. The thermolysis of 2a and 2b in boiling toluene affords several new Os 3 clusters as a result of ligand isomerization, decarbonylation, and ortho metalation of the ancillary PPh 3 ligand. The new products have been isolated and characterized by a combination of spectroscopic methods and X-ray crystallography in the case of 3b , 4b , 5b and 6b . Clusters 3b and 4b are isomers of 2b and differ in the location of the hydride and PPh 3 ligands relative to the benzothiazolate moiety. Electronic structure calculations on the isomeric clusters 2b , 3b , and 4b confirm that 2b is the kinetic product of ligand substitution, accounting for its rearrangement to the latter two isomers upon heating. Cluster 5b contains a face-capping benzothiazolate moiety and is shown by DFT calculations to derive from a site-selective loss of an axial CO group in 4b . Cluster 6a,b formed from 5a,b as a result of further decarbonylation with concomitant ortho metalation of one of the phenyl groups of the coordinated PPh 3 ligand. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of the electronically unsaturated cluster [(μ-H)Os3(CO)8(Ph2PCH2P(Ph)C6H4)] (1) with HCl gas at ambient temperature in dichloromethane afforded (μ-H)Os3(CO)8(μ-Cl)(μ-dppm) (2) and [(μ-H)Os3(CO)7(η1-Cl)(μ-Cl)2(μ-dppm)] (3). Thermolysis of 2 at 110 °C led to an isomer of 2, 4. A similar reaction of 1 with HBr gas gave [(μ-H)Os3(CO)8(μ-Br)(μ-dppm)] (5) as the only product which does not isomerize at 110 °C. In sharp contrast, treatment of 1 with HF gas gave the protonated species [(μ-H)2Os3(CO)8(Ph2PCH2P(Ph)C6H4)]+ (6). Treatment of 1 with CF3CO2H also gave cation 6 whereas CH3CO2H yielded [(μ-H)Os3(CO)8(μ-η2-CH3CO2)(μ-dppm)] (7). Structures of 2, 3, 4 and 6 were established crystallographically. In 2, both the chloride and the hydride ligands simultaneously bridge the same Os–Os edge and the dppm spans another Os–Os bond whereas in 4, all the three ligands bridge the same Os–Os edge. Compound 3 is comprised of an open Os3 arrangement in which one chloride bridges the open Os⋯Os edge, another chloride and a hydride mutually bridge an Os–Os bond and the third chloride is terminally coordinated to one of the Os atoms of the dppm bridged edge. The cation 6 consists of a triangle of osmium atoms in which the shortest Os–Os edge is bridged by a hydride and the metallated phenyl ring and the longest edge is bridged by another hydride and the diphosphine ligand. [Copyright &y& Elsevier]