Copper(II) and Nickel(II) Complexes of Dianionic and Tetraanionic Dinucleating Macrocycles
With nickel(II) or copper(II) acetate, 2,6-bis(acetoximato)-4-methylphenol (H2Damox) and 2,6-bis(acetoximato)-4-tert-butylphenol (H2Dabox) afford molecular dinuclear complexes [Cu2(Damox)2] (1), [Ni2(Damox)2(MeOH)2]· MeOH (2), [Cu2(Dabox)2] (5) and [Ni2(Dabox)2(H2O)2] (6). Salts of the macrocyclic tetraimine copper chelates from diacetylcresol with 1,3-diaminopropane and 1,4-diaminobutane, [Cu2(Dampn)]2+ and [Cu2(Dampn)]2+, were also examined. Pyridine solutions of 2 yielded pink crystals of [Ni2(Damox)2(Py)4]·(Py)2 (3a), which effloresce pyridine to form [Ni2(Damox)2(Py)2]·Py (3). The pseudomacrocyclic complexes 1, 5, and 6 react with BF3·Et2O to form BF2-bridged macrocyclic complexes [Cu2(Damfb)] (4), [Cu2(Dabfb)]·H2O (7), and [Ni2(Dabfb)] (8). Crystals of [Ni2(Damox)2(Py)4]·(Py)2 (3a) are monoclinic (space group P21ln), with a = 13.297(5) Å, b = 11.240-(5) Å, c = 17.396(6) Å, β= 109.03°, V = 2458(3) Å3, Z = 2, R = 0.050, and Rw = 0.052. The [Ni2(Dabfb] (8) crystals are orthorhombic (space group Pnma), with a = 11.558(6) Å, b = 17.200(5) Å, c = 16.058(2) Å, V = 3192(3) Å3, Z = 4, R = 0.057, and Rw = 0.057. The saddle-shaped molecules of 8 contain low-spin Ni(II). The copper(II) centers in 1, 5, 6, etc., are strongly antiferromagnetically coupled with -2J values in the range 550-800 cm-1. The nickel(II) centers in 2 and 3 are weakly (-2J = 3.2 cm-1) or moderately (-27 = 19.5 cm-1) antiferromagnetically coupled, whereas 6 shows a moderate ferromagnetic interaction with -2J = -5.1 cm-1. All the complexes are electrochemically reducible in two 1-electron steps. In CH3CN, the mixed-valence complexes [Cu2Dampn)]+ and [Cu2(Dambn)]+ are valence-localized. The nature of the carbon monoxide interactions with the M(I) centers is clearest for [Cu2(Dambn)]+/0, which in dimethylformamide solution binds two molecules of CO in a cooperative fashion.
K. K. Nanda et al., "Copper(II) and Nickel(II) Complexes of Dianionic and Tetraanionic Dinucleating Macrocycles," Inorganic Chemistry, American Chemical Society (ACS), Jan 1998.
The definitive version is available at https://doi.org/10.1021/ic9712434
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