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 (H 2 Damox) and 2,6-bis(acetoximato)-4- tert -butylphenol (H 2 Dabox) afford molecular dinuclear complexes [Cu 2 (Damox) 2 ] ( 1 ), [Ni 2 (Damox) 2 (MeOH) 2 ]· MeOH ( 2 ), [Cu 2 (Dabox) 2 ] ( 5 ) and [Ni 2 (Dabox) 2 (H 2 O) 2 ] ( 6 ). Salts of the macrocyclic tetraimine copper chelates from diacetylcresol with 1,3-diaminopropane and 1,4-diaminobutane, [Cu 2 (Dampn)] 2+ and [Cu 2 (Dambn)] 2+, were also examined. Pyridine solutions of 2 yielded pink crystals of [Ni 2 (Damox) 2 (Py) 4 ]·(Py) 2 ( 3a ), which effloresce pyridine to form [Ni 2 (Damox) 2 (Py) 2 ]·Py ( 3 ). The pseudomacrocyclic complexes 1, 5, and 6 react with BF 3 ·Et 2 O to form BF 2 -bridged macrocyclic complexes [Cu 2 (Damfb)] ( 4 ), [Cu 2 (Dabfb)]·H 2 O ( 7 ), and [Ni 2 (Dabfb)] ( 8 ). Crystals of [Ni 2 (Damox) 2 (Py) 4 ]·(Py) 2 ( 3a ) are monoclinic (space group P 2 1 / n ), with a = 13.297(5) Å, b = 11.240(5) Å, c = 17.396(6) Å, β = 109.03°, V = 2458(3) Å 3, Z = 2, R = 0.050, and R w = 0.052. The [Ni 2 (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) Å 3, Z = 4, R = 0.057, and R w = 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 −2 J values in the range 550−800 cm - 1 . The nickel(II) centers in 2 and 3 are weakly (−2 J = 3.2 cm - 1 ) or moderately (−2 J = 19.5 cm - 1 ) antiferromagnetically coupled, whereas 6 shows a moderate ferromagnetic interaction with −2 J = −5.1 cm - 1 . All the complexes are electrochemically reducible in two 1-electron steps. In CH 3 CN, the mixed-valence complexes [Cu 2 (Dampn)] + and [Cu 2 (Dambn)] + are valence-localized. The nature of the carbon monoxide interactions with the M(I) centers is clearest for [Cu 2 (Dambn)] +/0, which in dimethylformamide solution binds two molecules of CO in a cooperative fashion.