SYNTHESIS AND CHARACTERIZATION OF TETRACARBONYL COMPLEXES OF MOLYBDENUM AND TUNGSTEN WITH FUNCTIONALIZED IMINES - CRYSTAL-STRUCTURE OF CIS-MO(CO)(4)[(CH3)(C6H5)C=N(CH2)](2)

A series of octahedral cis-iminetetracarbonyl molybdenum and tungsten complexes of the general formula [M(CO)(4)L(2)], where L(2)=R(1)R(2)C= N(CH2)CH(R(3))N=CR'(1)R(2) have been prepared and characterized by IR, H-1 and C-13 NMR spectroscopies. These imine chelates complexes of mo lybdenum and tungsten have exocyclic double bonds. A consistent struct ural feature of these complexes appears to be the chelate bonding of t he imine ligand with consequent rotation around the carbon-nitrogen bo nd. This phenomenon leads to isomeric compounds: 4 and 5; 8 and 9; 11 and 12. NMR data analysis established unambiguously the configuration of the following nine complexes: M(CO)(4)L(2) [R(1)=R'(2)=CH3, R'(1)=R (2)=C6H5, R(3)=H, M=Mo (4), M=W (8)]; [R(1)=R'(1)=C6H5, R(2)=R'(2)=CH3 , R(3)=H, M=Mo (5), M=W (9)]; [R(1)=R'(1)=R(2)=R'(2)=C6H5, R(3)=H, M=M o (6), M=W (10)]; [R(1)=R'(1)=R(2)=R'(2)=CH3, R(3)=H, M=Mo (7)]; [R(1) =R'(2)=C6H5, R'(1)=R(2)=CH3, R(3)=CH3, M=Mo (11)]; [R(1)=R'(1)=C6H5, R (2)=R'(2)=CH3, R(3)=CH3, M=Mo (12)]. Long-range coupling constants (5) J(H-H) have confirmed the configuration and chemical shifts assignment s for complexes 11 and 12. The C-13 chemical shifts of the carbonyl gr oups are particularly useful in the characterization of the molybdenum compounds. Single-crystal X-ray diffraction studies of 4 confirm the formation of the nonsymmetric complex l-3,6-diaza-2,6-octadiene]tetrac arbonylmolybdenum. The complex crystallizes in the space group P2(1)/n with the unit cell parameters a = 11.112(1) Angstrom; b = 19.345(1) A ngstrom; c = 11.680(1) Angstrom; beta = 102.89(6)degrees; V = 2447.5(3 ) Angstrom(3); Z = 4, D-X = 1.39 g cm(-3). The structure was solved by direct methods and refined by full-matrix least-squares techniques to R and R(W) values of 0.052 and 0.064, respectively, for 4706 observed reflections. The data obtained show that the structure has been solva ted with half a molecule of benzene. Evidence of monocoordination of i mine 1 to Mo(CO)(4)(NBD) has been obtained by C-13 NMR spectroscopy an d some insight into the mechanism of complex formation is provided.