Syntheses and X-ray crystal structures of cis-[Mn(bipy)2Cl2] · 2H2O · EtOH and cis-[Mn(phen)2Cl2] (bipy = 2,2′-bipyridine; phen = 1,10-phenanthroline); catalysts for the disproportionation of hydrogen peroxide

MnCl2·4H2O reacts with 2,2′-bipyridine (bipy) to give cis-[Mn(bipy)2Cl2] (1), and recrystallisation of 1 from ethanol gives cis-[Mn(bipy)2Cl2]·2H2O·EtOH (2). MnCl2·4H2O and 1,10-phenanthroline (phen react to form cis-[Mn(phen)2Cl2] (3). In each case, the X-ray crystal structures of 2 and 3 show the manganese(II) atom to have a similar distorted octahedral geometry, and in both cases there is extended π-π stacking of the conjugated ring systems. Compared with MnCl2·4H2O, 1 and 3 are much more efficient catalysts for the disproportionation of hydrogen peroxide. The catalytically active species are believed to be [Mn(bipy)2(H2O)2]2+ and [Mn(phen)2(H2O)2]2+, respectively.