Abstract
In this thesis, a series of low-coordinate α-diimine cobalt and nickel complexes were successfully synthesized and characterized. Reduction of (o,o’-iPr2C6H3-DAB)CoCl2 (o,o’-iPr2C6H3-DAB = 2.3-dimethyl-1,4-bis- (2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene) by one equivalent of KC8 in toluene afforded a dicobalt complex [(o,o’-iPr2C6H3-DAB)Co(μ-Cl)]2 (1). However, when the amount of KC8 was increased from one to two equivalent, a half-sandwich complex [(o,o’-iPr2C6H3-DAB)Co(η6-C7H8)] (2) was generated. Interestingly, two dimeric complexes [(o,o’-R2C6H3-DAB)Co]2 (R = iPr (3), Et (4)) were isolated, if the reduction of (o,o’-R2C6H3-DAB)CoCl2 (R = iPr, Et) was carried out in ether or THF. Both 2 and 3 reacted with white phosphorus to lead to the isolation of a P4-bridged dicobalt complex (μ-η4: η4-P4)[Co(o,o’-iPr2C6H3-DAB)]2 (5), where the bridging square planar P4 coordinate to each cobalt atom in an □4 fashion. Furthermore, treatment of both complexes 2 and 3 with elemental selenium produced [(o,o’-iPr2C6H3-DAB)Co(μ-Se)]2 (6), in which two elemental selenium atoms bridge two cobalt atoms. Reduction of (o,o’-iPr2C6H3-DAB)NiI2 by two equivalent of KC8 in toluene led to the isolation of an inverted-sandwich complex (μ-η3:η3-C7H8)[Ni(o,o’-iPr2C6H3-DAB)]2 (7). Interestingly, when the reduction was carried out in ether or THF, a Ni-Ni bonded complex [(o,o’-iPr2C6H3-DAB)Ni]2 (8) (Ni-Ni, 2.2946(8) A) was obtained. Notably, when the amount of KC8 was increased from two to three equivalent, an inverted-sandwich complex (μ-η3:η3-C6H6)[Ni(o,o’- iPr2C6H3-DAB)]2(Et2O)2(THF)2 (9) was obtained. Upon reduction of the less hindered (o,o’-Et2C6H3-DAB)NiI2 by two equivalent of KC8, a mononuclear distorted tetrahedral complex [Ni(o,o’-Et2C6H3-DAB)2] (10) was isolated. Reaction of complex 8 with white phosphorus yielded a P4-bridged dinuclear complex (μ-η4:η4-P4)[Ni(o,o’-iPr2C6H3-DAB)]2 (11), in which the structure is similar to 5. Treatment of 8 with COT (COT = 1,3,5,7-cyclooctatetraene) yielded trans-(η2,2,η2,2-COT)[Ni(o,o’- iPr2C6H3-DAB)]2 (12), where COT coordinates to each nickel atom by 1,5 and 3,7 position π-bond. Diphenylacetylene, phenylacetylene and benzonitrile were reduced to double bond by 8 upon coordination to nickel atom forming mononuclear square planar complexes (η2-X)[Ni(o,o’-iPr2C6H3-DAB)] (X = PhCCPh (13), HCCPh (14), NCPh (15)).