SYNTHESIS AND CHARACTERIZATION OF THE DINUCLEAR COPPER(II) COMPLEXES [CU(HB(3,5-ME2PZ)3)]2X (X = O2-, (OH)2(2-), CO3(2-), O2(2-))

The synthesis and characterization of a series of dinuclear copper(II) complexes ligated by HB(3,5-Me2PZ)3 (hydrotris(3,5-dimethyl-1-pyrazolyl)borate) are presented. Displacement of the carbonyl group in a mononuclear copper(I) complex Cu(CO)(HB(3,5-MC2PZ)3) (1) with PPh3 affords Cu(PPh3)(HB(3,5-Me2PZ)3) (2), quantitatively. The reaction of 2 with an excess amount of PhIO results in the formation of a novel-mu-oxo dinuclear copper(II) complex [Cu(HB(3,5-Me2PZ)3)]2O (3). Complex 3 is readily converted to a bis(mu-hydroxo) dinuclear complex [Cu(HB(3,5-Me2PZ)3)]2(OH)2 (4) in the presence of a trace amount of water. CO2 reacts with 3 to give an adduct [Cu(HB(3,5-Me2PZ)3)]2(CO3) (5). Treatment of 3 with H2O2 yields the mu-peroxo dinuclear copper(II) complex [Cu(HB(3,5-Me2PZ)3)]2(O2) (6), which shows many similarities to oxyhemocyanin in its physicochemical properties: diamagnetic; UV-vis 338 nm (epsilon-20800), 530 nm (epsilon-840); nu(O-O) 731 cm-1. The resonance Raman spectroscopic study with mixed labeled hydrogen peroxide establishes that the coordination mode of the peroxide ion in 6 is symmetric as in oxyhemocyanin. Crystallography was performed on 2, 4.2C6H6, and 5. Compound 2 crystallizes in the monoclinic space group C2/c with alpha = 26.951 (4) angstrom, b = 18.003 (2) angstrom, c = 18.363 (3) A, beta = 124.53 (1)-degrees, V = 7340 (1) angstrom3, and Z = 8. The refinement converged with a final R (R(W)) value of 8.72% (8.53%) for 4213 reflections with F(o) greater-than-or-equal-to 3-sigma(F(o)). Compound 4.2C6H6 crystallizes in the triclinic space group P1BAR with a = 11.051 (3) angstrom, b = 11.296 (3) angstrom, c = 10.121 (2) angstrom, alpha = 103.03 (2)-degrees, beta = 103.51 (2)-degrees, gamma = 105.45 (2)-degrees, V = 1127.0 (5) angstrom3, Z = 1, and a final R (R(W)) value of 10.83% (11.00%) for 3243 reflections with F(o) greater-than-or-equal-to 6-sigma(F(o)). Compound 5 crystallizes in the monoclinic space group P2(1) with a = 8.068 (1) angstrom, b = 31.008 (5) angstrom, c = 8.064 (1) angstrom, beta = 113.59 (1)-degrees, V = 1849.7 (5) angstrom3, Z = 2, and a final R (R(W)) value of 5.88% (5.18%) for 2735 reflections with F(o) greater-than-or-equal-to 3-sigma(F(o)).