Cyclidene complexes with bulky substituents

Abstract Unbridged Ni(II) cyclidene complexes have been prepared with bulky substituents at the terminal nitrogen atoms (R2 = -C(Me)2CH2N(Me)2; -CH(Ph)2; -CH2C(Me)3; -CH2CH(Ph)2) (substituent R3 at the adjoining carbon = Me). Complexes containing the last two substituents and bridged with m-xylylene and (CH2)6 have also been synthesised. The effects of the bulky substituents on 13C n.m.r spectra, electrochemical behaviour and oxygen binding ability are examined. The crystal structures of the m-xylylene-bridged complexes with R2 = CH2C(Me)3, R3 = Me (I) and R2 = Me, R3 = Ph (II) have been determined; both are monoclinic, P21\c, with (I) a = 13.463(1); b = 14.506(2); c = 26.72492)A, β = 91.45(1), R = 0.082 for 3895 observed (I/σ(I)> = 2.0) reflections; (II) a = 24.721(6), b = 10.934(3), c = 16.321(5)A, β = 97.30(2)°, R = 0.074 for 2992 observed (I/σ(I)> = 3.0) reflections

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