DINUCLEAR COPPER(II) COMPLEXES WITH THE NEW [CU-2(MU-OR)(MU-OAC)(2)](- PREPARATION AND CHARACTERIZATION OF [CU-2(OR)(OAC)(2)(BPY)(2)](+) (R=ME, ET, PR-11) SALTS() (R=ALKYL) CORE )

Procedures are described for the synthesis of complexes containing the cations [Cu-2(mu-OR)mu O(2)CME)(2)(bpy)(2)](+) (R = Me, Et, Pr-n). Tr eatment of Cu-2(O(2)CMe)(4)(H2O)(2) with 2 equivs of bpy and 1 equiv. of NaOH in anhydrous EtOH, followed by addition of NBu(4)(n)PF(6) in M eCN gave highly crystalline blue [Cu-2(OEt) (O(2)CMe)(2)(bpy)(2)](PF6) (1a) in similar to 70% yield. The corresponding reaction in dry MeOH- MeCN led to green crystals of the methoxo analogue [Cu-2(OMe)(O(2)CMe) (2)(bpy)(2)](PF6) (2a), also in similar to 70% yield. Layering of a me thanolic solution of 1a with a mixture of Et(2)O and hexanes led to cl ean, high-yield conversion to complex 2a. Complexes 1a, 2a and [Cu-2(O Prn)(O(2)CMe)(2)(bpy)(2)] (PF6) (3) were also prepared from the reacti ons of the compound [Cu-2(OH)(O(2)CMe)(2) (bpy)(2)](PF6). 3DMF with an excess of the appropriate alcohol. In order to study the influence of the counterion on the structure of the [Cu-2(OR)(O(2)CMe)(2)(bpy)(2)] (+) ions, the blue-turquoise complex [Cu-2(OEt)(O(2)CMe)(2)(bpy)(2)](C lO4) (1b) and the corresponding green methoxo-bridged compound [Cu-2(O Me) (O(2)CMe)(2)(bpy)(2)](ClO4) (2b) were obtained in the same manner as complexes 1a and 2a, respectively. The structure of the cations of both complexes determined by X-ray diffraction consisted of triply-bri dged pairs of copper (II) atoms. Two of the bridging ligands are syn,s yn eta(1):eta(1):mu(2), acetate groups, the third being the OR(-) ion, a terminal bpy molecule completes five-coordination at each metal ato m. The Cu ... Cu separations are 3.093(1) and 3.230(1) Angstrom for 2a and 1a, respectively. In 1a, the metal coordination geometry is best described as square pyramidal; the oxygen atoms [O(30) and O(32)] of o ne acetate occupy basal positions while the oxygens of the other aceta te [O(34) and O(36)] occupy the apical positions of the two square pyr amids. The cation of 2a consists of two distorted trigonal bipyramids sharing the methoxo oxygen as a common apex. The solid-state electroni c and IR spectra of the complexes are discussed in terms of the nature of the bonding and structures of 1a and 2a. A cyclic voltammetry stud y of 1a and 2a in MeCN reveals a quasireversible reduction at similar to- 0.75 V vs ferrocene, and an irreversible reduction at E(p) = -1.83 V for 1a and - 1.63 V for 2a, yielding copper metal, which deposits o n the electrode.