| The triosmium (mu)-hydrido-(mu)-carboxamido cluster complexes, HOs(,3)(O=CNR'R)(CO)(,10) (1), (R = Me, R' = H; R = R' = Me; R = Et, R' = H; R = Pr, R' = H and R = Bu, R' = H) are synthesized in high yield, from the direct reaction of Os(,3)(CO)(,12) with neat primary or secondary amines at temperatures of -10(DEGREES) to 25(DEGREES)C. ('1)H magnetic resonance indicates the presence of two types of isomers: optical isomers derived from the attachment of the carboxamido group to the cluster complex and geometrical isomers derived from placement of the R group(s) on the nitrogen of the carboxamido complex. A basis for the unprecedented low temperature syntheses is suggested.; Reaction of H(,2)Os(,3)(CO)(,10) with alkyl isocyanate at room temperature yields two novel products, HOs(,3)(HOC=NR)(CO)(,10) (3) and HOs(,3)(R''OC=NR)(CO)(,10) (4), (R'' = C(O)N(H)R), in addition to HOs(,3)(OC(H)NR)(CO)(,10) (2) as the major product. Complex 3 is unstable in solution and is observed to isomerize to 1 with an energy of activation E(,a) = 92 kJ/mol.; The low temperature crystal structure of 4, R = Me and R'' = C(O)N(H)Me, has been determined confirming an edge bridging iminyl ligand. The hydrogen bridging on the edge of the metal triangle was located and refined.; Phosphorus ligands substitution of 1 and 2 gives contrasting results. With 1c, substitution with P(OMe)(,3) is observed in a normal fashion to give HOs(,3)(O=CN(H)n-Pr)(CO)(,9)(P(OMe)(,3)), (7c), while the more basic ligand PEt(,3) leads to removal of amine in formation of Os(,3)(CO)(,11)(PEt(,3)). A PEt(,3) substituted carboxamido complex can, however, be obtained as a major product in the reaction of H(,2)Os(,3)(CO)(,9)(PMe(,3)) with methyl isocyanate. Different isomers of the above is obtained by reaction of Os(,3)(CO)(,11)(P(OMe)(,3)) with n-propyl amine; these arise from the nucleophilic attack of the amine at the carbonyl group remote from the P(OMe)(,3) group. A pair of substituted complexes HOs(,3)(O=CN(H)n-Pr)(CO)(,9)(P(OMe)(,3)), i and/or ii (ax and/or eg) are obtained where phosphite ligand is remoted from the edge bridged by the carboxamido group and the hydrogen atom. These assignments are derived from the ('31)P-('1)H coupling constants which are larger in 7c than that in i and/or ii. The latter two are seen to interconvert rapidly and have not been separated from one another. By constrast, for 2, both phosphite and phosphine substituted complexes HOs(,3)(O=C(H)-NR)(CO)(,9)L, L = P(Et)(,3) or P(OMe)(,3), are obtained in refluxing cyclohexane.; Pyrolysis of 1 leads to the formation of the amido complex HOs(,3)((mu)-NHR)(CO)(,10), (9), which can also be obtained as a minor product in the thermal reaction of 2 at 150(DEGREES)C. Pyrolysis of 2 gives a series of osmium cluster complexes containing triply bridging nitrene and iminyl ligands. At 150(DEGREES)C, H(,2)Os(,3) ((mu)(,3)-NR)(CO)(,9), (5), is obtained as a major product. For complex 2 having (beta)-hydrogen in the alkyl group, a complex containing (mu)(,3)-(eta)('2)-CH(,3)CH=N ligand is isolated. Higher temperature pyrolysis (192(DEGREES)C) leads to the formation of tetranuclear cluster, Os(,4)((mu)(,3)-NR)(CO)(,12), (6), while the nitrene ligand is kept intact.; Two triply bridging nitrene cluster complexes, 5 and 6 have been characterized by X-ray crystal structure determinations. A mirror plane is found to lie on a symmetry element of 5. Complex 6 is an electron precise tetranuclear cluster with slightly distorted tetrahedron frame work. |
