SOLVATE-DEPENDENT POLYMORPHISM - CRYSTALLIZATION OF [(MN(CO)(3))(2)(MU-(ETA(5)-C6H6-ETA(5)-C6H6))] FROM CH2CL2 AS A MONO-SOLVATE IN THE RARE TETRAGONAL SPACE GROUP P4(2) MBC/

Recrystallization from methylene chloride gives a tetragonal pseudo-po lymorph of ta(5)-bicyclohexadienyl)bis(tricarbonylmanganese), [Mn-2(C1 2H12)(CO)(6)]CH2Cl2, in the rare space group P4(2)/mbc. Molecules in t hese crystals and in the monoclinic unsolvated form are virtually supe rimposable, and it is the inclusion of the methylene chloride solvate molecule which allows for crystallization in P4(2)/mbc. The Mn dimers are packed in layers with fourfold symmetry, with disordered methylene chloride molecules filling interstices between the layers. (C) 1996 I nternational Union of Crystallography.