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 (tetrah ydrofuran) at reflux temperatures over a period of several hours affor ds 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 mang anese atom is coordinated on one side by three linearly bound CO group s and on the other by a neutral nido-10-O(CH2)(4)-7,8-C2B9H10 ligand i n a pentahapto manner. The C2B9H10 cage-framework is anionic but the l igand is charge-compensated since a THF molecule replaces hydrogen at the boron atom at the beta-site with respect to the carbon atoms in th e pentagonal CCBBB ring coordinated to the manganese atom. Reactions o f 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 (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.