Solvate-Dependent Polymorphism: Crystallization of [{Mn(CO)₃}₂{μ-(η⁵-C₆H₆-η⁵-C₆H₆)}] from CH₂Cl₂ as a Mono-Solvate in the Rare Tetragonal Space Group P4₂/mbc

Recrystallization from methylene chloride gives a tetragonal pseudo-polymorph of (μ-η⁵:η⁵-bicyclohexadienyl)bis(tricarbonylmanganese), [Mn₂(C₁₂H₁₂)(CO)₆].CH₂Cl₂, in the rare space group P4₂/mbc. Molecules in these crystals and in the monoclinic unsolvated form are virtually superimposable, and it is the inclusion of the methylene chloride solvate molecule which allows for crystallization in P4₂/mbc. The Mn dimers are packed in layers with fourfold symmetry, with disordered methylene chloride molecules filling interstices between the layers.

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