SYNTHESIS OF HYDRIDOTRIOSMIUM COMPLEXES CONTAINING ISOMERIC μ-CARBOXAMIDO, , AND μ-IMINYL, , GROUPS. CRYSTAL AND MOLECULAR STRUCTURE OF Os3(CO)10, R' = C(=O)NHCH3

Article abstract of DOI:10.1016/0022-328X(84)80467-2

Primary or secondary aliphatic amines are observed to react with Os3(CO)12 in excess amine or other polar solvents at temperatures in the range -10 to 25 deg C.One mole of CO is evolved and a μ(O,C)-carboxamido complex (1) is isolated in high yield: Os3<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 Os3<μ-H>2(CO)10 at room temperature under N2 gives three principal products: a μ(O,N)-formamido complex, Os3<μ-H,μ-OC(H)NR>(CO)10 (2), the μ(O,C)-carboxamido complex, 1, and a μ(C,N)-iminylurethane complex, Os3<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, Os3(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 CDCl3 solution, E_a 92 kJ/mol.Spectroscopic data indicate that 3 is a mixture of tautomers in ratio of 19/1 in CDCl3: Os3<μ-H,μ-C(OH)=NCH3>(CO)10 (3-enol) and Os3<μ-H,μ-C(=O)N(H)CH3>(CO)10 (3-keto). The structure of 4 has been determined at -158 deg C using a Syntex P<*> computer-automated diffractometer and graphite-monochromatized Mo-K_α radiation.Some 2936 unique reflections with I >3?(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 P2₁/c in a cell having the dimensions of a 13.413(3) Angstroem, b 16.712(3) Angstroem, c 9.400(3) Angstroem, and β 95.01(2) deg.The calculated density is 3.06 g cm^-3.