Reactivity of copper(I) complexes with tripodal ligands towards O2: Structures of a precursor L3CuI(NCCH3)(BF4), L3 = tris(3-isopropyl-4,5-trimethylenepyrazolyl)methane and of its oxidation product L3CuII(m-OH)2CuIIL3(BF4)2 with strong antiferromagnetic spin-spin coupling
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Zeitschrift fuer Anorganische und Allgemeine Chemie 631 (13-14): 2568--2574 (2005)

The mol. structure of the highly oxygen-sensitive complex L3CuI(NCCH3)(BF4) (1, L3 = tris(3-isopropyl-4,5-trimethylenepyrazolyl)methane) reveals approx. sym. coordination by the fac-tridentate (tripodal) ligand and a rather short CuI-N(acetonitrile) distance of 1.865(5) \AA. In CH2Cl2 at -78° the colorless compd. reacts with O2 to yield a labile purple intermediate (lmax 517 nm) - presumably a peroxodicopper(II) complex - which decomps. at -30°. No such intermediate was obsd. on reaction of the CuI complex of bis(2-pyridylmethyl)benzylamine with O2 at -80°. However, an EPR spectrum with g‖ = 2.17 and g$\bot$ = 2.03 without 63,65Cu hyperfine splitting was obsd. at low temps. Exposure of the precursor 1 to air under ambient conditions yields dinuclear L3CuII(m-OH)2CuIIL3(BF4)2 (2), which exhibits an EPR detectable dissocn. into monomers in CH2Cl2 soln. The structure of the hexakis(dichloromethane) solvate of 2 with Cu-Cu and Cu-O distances of 3.055 and 1.94 \AA, resp., is typical for dihydroxo-bridged dicopper compds. with square-pyramidal CuII configuration (t = 0.03), adopting an anti arrangement. In agreement with the relatively wide Cu-O-Cu angles of 103.5°, an anal. of the temp. dependence of the magnetic susceptibility revealed a rather strong (J = -633 cm-1) antiparallel spin-spin coupling. The effect is ascribed to the steric bulk of the ligand L3. on SciFinder(R)
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