Synthesis of hydridotriosmium complexes containing isomeric μ-carboxamido, {μ( O, C)-OC(NHR)}, μ-formamido, {μ( O, N)-OC(H)N(R)}, and μ-iminyl, {μ( C, N)-C(OR′)=NR}, groups. Crystal and molecular structure of Os 3{μ-H,μ-C(OR′)=NCH 3}(CO) 10, R′ = C (=O)NHCH 3

Abstract

Primary or secondary aliphatic amines are observed to react with Os 3(CO) 12 in excess amine or other polar solvents at temperatures in the range −10 to 25 ° C. One mole of CO is evolved and a μ( O, C)-carboxamido complex ( 1) is isolated in high yield: Os 3{μ-H,μ-OCNR′R}(CO) 10 ( 1a, R = Me, R′= H; 1b, R = R′ = Me; 1c, R = n-Pr, R′ = H, 1d, R = n-Bu, R′ = H; 1e, R = Et, R′ = H). The 1H NMR spectrum of 1e indicates the existence of two isomers due to the restricted rotation around the CN bond of the μ-carboxamido group. Reaction of methyl or ethyl isocyanate with Os 3{μ-H} 2(CO) 10 at room temperature under N 2 gives three principal products: a μ( O, N)-formamido complex, Os 3{μ-H,μ-OC(H)NR}(CO) 10 ( 2), the μ( O, C)-carboxamido complex, 1, and a μ( C, N)-iminylurethane complex, Os 3{μ-H,μ-C(OR′)=NR}(CO) 10, ( 4, R′ = C(=O)NHR). Product 1 in this reaction arises from isomerization of an intermediate μ( C, N)-hydroxyiminyl complex, Os 3{μ-H,μ-C(OH)=NR)(CO) 10 ( 3). This complex is isolated upon initial chromatography of the reaction mixture. For the isomerization of 3 to 1, t 1 2 17.5 d in CDCl 3 solution, E a 92 kJ/mol. Spectroscopic data indicate that 3 is a mixture of tautomers in ratio of 19 1 in CDCl 3: Os 3{μ-H,μ-C(OH)NCH 3}(CO) 10 ( 3-enol) and Os 3{μ-H,μ-C(=O)N(H)CH 3}(CO) 10 ( 3-keto). The structure of 4 has been determined at −158 °C using a Syntex P 1 computer-automated diffractometer and graphite-monochromatized Mo- K α radiation. Some 2936 unique reflections with I > 3σ( I) were used in the refinement to give final discrepancy indices of R = 0.030 and R w = 0.037. The complex crystallizes in the monoclinic space group P2 1/ c in a cell having the dimensions of a 13.413(3) Å, b 16.712(3) Å, c 9.400(3) Å, and β 95.01(2)°. The calculated density is 3.06 g cm −3. The location of the three Os atoms was determined from the Patterson map. All other nonhydrogen atoms were then located by difference maps. The two hydrogen atoms, one bridging the edge of the cluster and the other attached to the nitrogen atom, were located after all but the two methyl carbon atoms were refined anisotropically; the latter two atoms were included in the refinement as members of rigid methyl groups. The crystal consists of discrete molecules. Three osmium atoms form a nearly isosceles triangle (Os(1)-Os(2) 2.882(1) Å, Os(1)-Os(3) 2.881(1) Å, Os(2)-Os(3) 2.923(1) Å). An N-methyl-iminyl group with a urethane derivative on the carbon atom is bridging across Os(2) and Os(3) through the carbon and nitrogen atoms, respectively. The two metal atoms Os(2) and Os(3) are also bridged by a hydrogen atom outside the trimetal plane and away from the bridging iminyl group. The metal bonded carbonyl groups are all terminal.