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.



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© 1998 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jan 1998