4-COORDINATE MOLYBDENUM ALKENE AND ALKYNE COMPLEXES BEARING ANCILLARY IMIDO LIGANDS

Four coordinate molybdenum alkene complexes of the type Mo(NR)(2)(PMe(3)) (CH(2)CH(2)R') [R = Bu(t), R' = H (2a); R' = Me (2b); R = adamantyl, R' = H (2c)] have been synthesised by treatment of Mo(NR)(2)Cl-2(dme) [R = Bu(t) (1a); R = adamantyl (1b) with two equivalents of RMgCl (R = Et, n-Pr) in diethylether. The molecular structure of 2b is reported [triclinic, space group P ($) over bar 1, a = 9.312(2), b = 9.723(2), c = 11.203(2) Angstrom, alpha = 78.85(2), beta = 88.23(2), gamma = 85.94(2)degrees, U = 992.5(4) Angstrom(3), Z = 2, T = 293 K] The alkyne derivatives Mo(NR)(2)(PMe(3)) (R'C=CR'') [R = Bu(t), R' = R'' = Ph (3a); R = Bu(t), R' = Ph, R'' = H (3b); R = adamantyl, R' = R'' = Ph (3c)] are prepared from 2a and 2c by prolonged warming at 60-70 degrees C in heptane in the presence of one equivalent of the alkyne. The molecular structure of 3a [orthorhombic, space group Pbca (No. 61), a = 13.980(3), b = 15.333(6), c = 24.989(7) Angstrom, U= 5356(3) Angstrom(3), Z = 8, T= 120 K] reveals an analogous pseudo-tetrahedral geometry to that found for 2b. The relationship of these complexes to known zirconocene derivatives is discussed.