Coordination geometry of tetradentate Schiff’s base nickel complexes: the effects of donors, backbone length and hydrogenation

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The X-ray crystal structures of ( N, N′-bis-( o-amidobenzilidene)-1,3-diaminopropane)nickel (Niambpr), ( N, N′-bis-( o-amidobenzilidene)-1,4-diaminobutane)nickel (Niambut), ( N, N′-bis-( o-thiobenzilidene)-1,4-diaminobutane)nickel(II) (Nitsalbut), {bis-acetonitrile-( N, N′-bis-( o-aminobenzyl)-1,2-diaminoethane)}nickel(II) tetrafluoroborate [Ni(H 4amben)(MeCN) 2] [BF 4] 2, {bis- O-acetato-( N, N′-bis-( o-aminobenzyl)-1,2-diaminoethane)}nickel(II) [Ni(H 4amben)(OAc) 2 · H 2O] and {bis- O-acetato-( N, N′-bis-( o-aminobenzyl)-1,3-diaminopropane)}nickel(II) [Ni(H 4ambpr)(OAc) 2] are presented. These structures complete the structural characterisation of the simple unsubstituted Schiff’s base complexes with N 4 and N 2S 2 donor sets and allow us to assess the effects of donor groups and polymethylene chain length on the coordination geometries of nickel(II). The hydrogenated N 4 complexes offer an insight into the effects of increased flexibility and character of the internal nitrogen donors. Unlike the parent N 4 imine species the hydrogenated amine species do not deprotonate at the peripheral nitrogen donors and do not seem to be restricted to the meridial plane of the nickel.