Steric effects of bulky diazolylmethane ligands (N-N) on synteses and structures of

Article abstract of DOI:10.1016/0022-328X(94)88070-0

The N-N ligands of PhHC(3,5-Me2Pz)2, H2C(3,5-Me2;4-BzPz)2, H2C(3-t-BuPz)2 and H2C(3(5)-PhPz)2 were prepared readily from PhHCCl2 or CH2Cl2 by the same procedure as for H2C(3,5-Me2Pz)2 (Pz=pyrazol-1-yl).Subsequent reactions with either (pip=piperidine) or , however, gave only (CO)4> (1), (CO)4> (2) and (CO)4> (3).The structural characteristics of 1-3, (CO)4>, (CO)4> and (CO)4>, reported previously, suggest firstly that the presence of a bulky substituent such as a phenyl or tert-butyl group at the pyrazolyl skeleton may afford strong nonbonded interaction in and inhibit the formation of the stable complexes, (CO)4> or (CO)4> and secondly, that the phenyl substituent at the carbon end of the six-membered boat metallacyle, formed by the N-N ligand and the central metal atom, is cis to the most distorted carbonyl in 1.This explains the facile formation of the η²-arene compound, (CO)3> as well as the regiospecific formation of (CO)2(η³-allyl)(Br)>. 1, mono-clinic, P 2₁/n, a=9.718(2), b=14.198(4), c=16.076(4) Angstroem, β=96.62(2), Z=4, R=0.034, R_w=0.037, based on 2538 reflections with I > 3?(I); 2, monoclinic, P 2₁/n, a=18.093(12), b=13.138(4), c=18.745(6) Angstroem, β=98.79(6), Z=8, R=0.040, R_w=0.031, based on 4465 reflections with I > 2?(I); and 3, orthorhombic, Pbca, a=12.2387(18), b=22.525(4), c=20.028(5) Angstroem, Z=8, R=0.035, R_w=0.032, based on 2095 reflections with I > 2?(I).Key words: Molybdenum; Diazolylmethane