Reactions of nido-7,8-C2B9H13 with pentacarbonyl(methyl)manganese: Crystal structure of the charge-compensated complex [Mn(CO)(3){eta(5)-7,8-C2B9H10-10-O(CH2)(4)}]

The reaction between nido-7,8-C2B9H13 and [MnMe(CO)(5)] in THF (tetrahydrofuran) at reflux temperatures over a period of several hours affords the zwitterionic mononuclear manganese complex [Mn(CO)(3){eta(5)-7,8-C2B9H10- 10-O(CH2)(4)}]double dagger (1), the structure of which has been established by X-ray diffraction. In the molecules of 1 the manganese atom is coordinated on one side by three linearly bound CO groups and on the other by a neutral nido-10-O(CH2)(4)-7,8-C2B9H10 ligand in a pentahapto manner. The C2B9H10 cage-framework is anionic but the ligand is charge-compensated since a THF molecule replaces hydrogen at the boron atom at the beta-site with respect to the carbon atoms in the pentagonal CCBBB ring coordinated to the manganese atom. Reactions of 1 with donor molecules L (PPh(3), NEt(3) or NC(5)H(4)Me-4) cleaves a C-O bond in the THF ring with the formation of the complexes [Mn(CO)(3){eta(5)-7,8-C2B9H10-10-O(CH2)(3)CH(2)L}]. A similar process occurs on treatment of 1 with [NEt(4)]I, yielding the unstable salt [NEt(4)][Mn(CO)(3){eta(5)-7,8-C4B9H10-10-O(CH2)(4)I}]. NMR data (H-1, C-13{H-1}, B-11{H-1}) for the new compounds are reported.