Bis[(trimethylsilyl)methyl]manganese: structural variations of its solvent-free and tmeda-, pyridine-, and dioxane-complexed forms

First synthesized in 1976 and recently taking on a new significance as a key precursor to heterobimetallic alkali-metal-manganese(II) complexes, bis[(trimethylsilyl)methyl] manganese has been structurally characterized by X-ray crystallography. It forms a polymeric chain structure of formula [{Mn(CH2SiMe3)(2)}(infinity)], 1, in which distorted tetrahedral, spiro Mn atoms are linked together via mu(2)-bonding alkyl ligands. The structure is notable for displaying two distinct categories of Mn-C bond lengths with a mean size differential of 0.225 angstrom and for being the first fully crystallographically characterized polymeric manganese(II) dialkyl compound. Magnetic measurements of 1 indicate a surprisingly strong spin exchange coupling of J approximate to -45 cm(-1) between the manganese ions aligned along the chain. Four Lewis base complexes of bis[(trimethyl silyl)methyl] manganese have also been subjected to X-ray crystallographic studies. Previously known [TMEDA center dot Mn(CH2SiMe3)(2)], 2, and [(pyridine)(2)Mn(CH2SiMe3)(2)], 3, both adopt a simple monomeric arrangement with C2N2 distorted tetrahedral coordinations of the metal atom. Synthesized by direct addition of the Lewis base to 1, two further, new complexes, [{(dioxane)-[Mn(CH2SiMe3)(2)](2)}(infinity)], 4, and [{(dioxane)[Mn(CH2SiMe3)(2)]}(infinity)], 5, are also reported. Hemisolvate 4 displays dimeric [(Me3SiCH2)Mn(mu-CH2SiMe3)(2)Mn(CH2SiMe3)] subunits, whereas 1:1 solvate 5 consists of monomeric subunits of [{Mn(CH2SiMe3)(2)}(infinity)]; in both cases these subunits are linked together via O(CH2CH2)(2)O bridges to generate one-dimensional polymers.