Copper(II) complexes of tetradentate thioether-oxime ligands

Two dinuclear copper(II) thioether-oxime complexes ([Cu(DtdoH)]2(ClO4)2 and [Cu(DtudH)]2(ClO4)2 Æ 2CH3OH) have been synthesized. [Cu(DtdoH)]2(ClO4)2 reacted with excess BF3 Æ OEt2 to yield [Cu(Thyclops)]ClO4, a BF2 þ-macrocyclized di-oxime. [Cu(DtdoH)]2(ClO4)2 and [Cu(DtudH)]2(ClO4)2 Æ 2CH3OH are the first representatives of copper(II) thioether oximes which exhibit the classical out-of-plane oximate oxygen-metal dimer structure. [Cu(DtdoH)]2(ClO4)2 and [Cu(Thyclops)]ClO4 have been structurally characterized by single-crystal X-ray diffraction. The geometry about each copper(II) in [Cu(DtdoH)]2(ClO4)2 is a distorted square pyramid (s = 0.14). The average copper–nitrogen(oxime) bond length is 1.984 Å longer ( 0.03 Å) than the average copper–nitrogen(oxime) bonds in copper(II) bis-glyoximates. The geometry of [Cu(Thyclops)]ClO4 reveals an almost perfect square pyramid (s = 0.03) of N2S2O donors. Solution, cryogenic glass, and powder ESR spectra show a typical axial pattern, except for the powder spectrum of [Cu(DtudH)]2(ClO4)2 Æ 2CH3OH which displays a small rhombic distortion. Variable-temperature magnetic susceptibility measurements indicate very weak ferromagnetic interactions in [Cu(DtdoH)]2(ClO4)2, where J = +0.52 cm 1 and very weak antiferromagnetic interactions in [Cu(DtudH)]2(ClO4)2 Æ 2CH3OH, where J = 0.59 cm . Electrochemical measurements reveal that the mixed thioether-oxime coordination environment tends to stabilize Cu(II), as all electrochemical reductions were quasi-reversible or irreversible. [Cu(Thyclops)]ClO4 is more oxidizing than [Cu(DtdoH)]2(ClO4)2 by 0.14 V. 2005 Elsevier B.V. All rights reserved.