Organometallic oxides: Oxidation of the cubane [(eta-C5R5)Cr(mu(3)-O)](4) and the structures and magnetic properties of the salts {[(eta-C5R5)Cr(mu(3)-O)](4)}{tcnq} and {[(eta-C5R5)Cr(mu(3)-O)](4)}{BF4}

Differential pulse and current voltammetry for the cubane-like clusters [(e ta -C5R5)Cr(mu (3)-O)](4) (R = H, Me; R-5 = H4Me) showed that [(eta -C5H4Me )Cr(mu (3)-O)](4) and [(eta -C5Me5)Cr(mu (3)-O)](4) were oxidized to {[(eta -C5R5)Cr(mu (3)-O)](4)}(+) and then to {[(eta -C5R5)Cr(mu (3)-O)](4)}(2+), but [(eta -C5H5)-Cr(mu (3)-O)](4) was oxidized only to {[(eta -C5H5)Cr(mu (3)-O)](4)}(+). Oxidation of [(eta -C5Me5)Cr(mu (3)-O)](4) (1) by AgBF4 or tcnq gave {[(eta -C5Me5)Cr(mu (3)-O)](4)}{BF4} (2) {[(eta -C5Me5)Cr(mu (3)- O)](4)}{tcnq} (3). It was shown by X-ray diffraction that the average Cr-Cr , Cr-O, and Cr-Cp* distances in 2 and 3 were 0.034(2), 0.007(5), and 0.02(1 ) Angstrom shorter than those in 1, respectively. Compounds 1 2, and 3 were antiferromagnetic., with similar intracluster exchange coupling constants, J (-262(23), -211(34), and -266(46) cm(-1), respectively). There was coupl ing between unpaired electrons on {[(eta -C5Me5)Cr(mu (3)-O)](4)}(+) and {t cnq}(-) in 3 at temperatures below 110 Ii.