CYCLIDENE COMPLEXES WITH BULKY SUBSTITUENTS

Unbridged Ni(II) cyclidene complexes have been prepared with bulky sub stituents at the terminal nitrogen atoms (R(2) = -C(Me)(2)CH2N(Me)(2); -CH(Ph)(2); -CH2C(Me)(3); -CH2CH(Ph)(2)) (substituent R(3) at the adj oining carbon = Me). Complexes containing the last two substituents an d bridged with (m) under bar-xylylene and (CH2)(6) have also been synt hesised, The effects of the bulky substituents on C-13 n.m.r spectra, electrochemical behaviour and oxygen binding ability are examined, The crystal structures of the (m) under bar-xylylene-bridged complexes wi th R(2) = CH2C(Me)3, R(3) = Me (I) and R(2)= Me, R(3) = Ph (II) have b een determined; both are monoclinic, P2(1)/c, with (I) a = 13.463(1); b = 14.506(2); c = 26.72492)A, beta = 91.45(1), R = 0.082 for 3895 obs erved (I/sigma(I)> = 2.0) reflections; (II) a = 24.721(6), b = 10.934( 3), c = 16.321(5)Angstrom, beta = 97.30(2)degrees, R = 0.074 for 2992 observed (I/sigma(I)> = 3.0) reflections.