The Methanol−Methanolate CH3OH···OCH3- Bridging Ligand: Tuning of Exchange Coupling by Hydrogen Bonds in Dimethoxo-Bridged Dichromium(III) Complexes

Two bis(mu-methoxo)dichromium(III) complexes, [L(Se)(2)Cr(2)(mu-OCH(3))(2)(CH(3)OH)(2)] 1 and [L(Se)(2)Cr(2)(mu-OCH(3))(2)(CH(3)OH)(CH(3)O)](-) 2, where L(Se) represents the dianion of 2,2'-selenobis(4,6-di-tert-butylphenol), have been reported to demonstrate the effect of hydrogen bonding on the exchange coupling interactions between the chromium(III) centers. The corresponding sulfur analogue of the ligand, i.e., 2,2'-thiobis(4,6-di-tert-butylphenol), also yields the analogous [L(S)(2)Cr(2)(mu-OCH(3))(2)(CH(3)OH)(2)] 3 and [L(S)(2)Cr(2)(mu-OCH(3))(2)(CH(3)O)(CH(3)OH)](-) 4, which exhibit similar exchange coupling parameters. An acid-base dependent equilibrium between 1 and 2 or 3 and 4 has been established by electronic spectral measurements.