The first example of tetraosmium carbonyl clusters containing (mu(3)-NH) nitrene ligands: Syntheses and crystal structures

The reaction of [Os-4(mu-H)(4)(CO)(12)] with o-tent-butylhydroxylamine hydrochloride ((BuONH2)-Bu-t . HCl) in the presence of trimethylamine-N-oxide (Me3NO) in dichloromethane afforded [OS4(-)(mu-H)(4)(CO)(11){eta(1)-(NH2OBu)-Bu-t}] (1) in high yield. Upon the addition of tetrafluoroboric acid (HBF4) into the solution of 1 in acetonitrile, the novel cationic cluster [OS4(mu-H)(4)(CO)(11)(mu-NH2)(NCMe)] [BF4] (2) formed. Reaction of 1 with HBF4 in the presence of diphenylacetylene gave two geometric isomers, [Os-4(mu-H)(2)(CO)(11)(mu-NH2){mu-eta(3)-Ph(CHC)Ph}] (3) and [Os-4(mu-H)(2)(CO)(11)(mu-NH2)(eta(1)-Ph(CH=C)Ph)] (4). Treatment of 2 with excess Me3NO in acetonitrile gave [Os-4(mu-H)(4)(CO)(12)(mu-NH2)(NCMe)(2)] [BF4] (5). The carbonylation of 2 in the refluxing chloroform afforded the neutral clusters [Os-3(mu-H)(2)(CO)(9)(mu-NH2)Cl] (6) and [Os-4(mu-H)(3)(CO)(12)(mu-NH2)] (7). Protonation of 7 with trifluoromethylsulfonic acid, CF3SO3H, gave another cationic cluster, [Os-4(mu-H)(4)(CO)(12)(mu-NH2)] [CF3SO3] (8), which is an analogue of 2. Refluxing of 7 in toluene under an argon atmosphere afforded [Os-4(mu-H)(2)(CO)(12)(mu3-NH)] (9), which is the first example of (mu(3)-NH) nitrene ligands containing tetraosmium carbonyl clusters. The solid-state structures of 2-9 were established by X-ray analysis. The H-1 NMR properties of these clusters were studied, and a correlation between the chemical shift and the structural geometry was established