Synthesis and reactivity of monocarbollide carbonyl complexes of iron and molybdenum with icosahedral frameworks

The [NEt4](+) (1a), [NHMe3](+) (1b), and [N(PPh3)(2)](+) (1c) salts of the monoanion [Fe(CO)(3)(eta(5)-7-CB10H11)](-) have been prepared via the reaction between [Fe-3(CO)(12)] and [NHMe3][nido-7-CB10H13] in THF (tetrahydrofuran). The complexes [N(PPh3)(2)][Fe(CO)(2)(L)(eta(5)-7-CB10H11)] (L = PPh3 (2), CNBut (3)) were obtained by treating 1c in THF with PPh3 and CNBut respectively, in the presence of Me3NO. The compound [N(PPh3)(2)][Mo(CO)(4)(eta(5)-7-CB10H11)] (4) has been synthesized from [Na](3)[nido-7-CB10H11] and [Mo(CO)(3)(NCMe)(3)] in the presence of CO and with addition of HBF4. Et2O and [N(PPh3)(2)]Cl. An X-ray diffraction study established that in the anion of 4 the Mo atom is coordinated on one side by the four CO molecules and on the other by a nido-7-CB10H11 carborane in a eta(5) manner. In reactions with PPh3 and CNBut, the salt 4 gives the species [N(PPh3)(2)][Mo(CO)(3)(L)(eta(5)-7-CB10H11)] (L = PPh3 (5a), CNBut (6)). Salts of the anions [Fe(CO)(3)(eta(5)-7-CB10H11)](-) and [Mo(CO)(3)(PPh3)(eta(5)'-7-CB10H11)](-) react with donor molecules (THF, OEt2, SMe2) in the presence of acids and other hydride abstracting reagents to give zwitterionic complexes: [Fe(CO)(3)(eta(5)-9-L-7-CB10H10)] (L = O(CH2)(4) (7), OEt2 (8), SMe2 (9)) and [Mo(CO)(3)(PPh3)(eta(5)-9-L-7-CB10H10)] (L = O(CH2)(4) (10), OEt2 (11)), formed as single isomers. That the donor molecules L are bonded to a boron atom which lies in a beta-site with respect to the carbon in the CBBBB ring ligating the metal was established by X-ray diffraction studies on 7 and 10. In the latter the PPh3 molecule is transoid to the BO(CH2)(4) group, presumably for steric reasons. Alkyne-molybdenum complexes [N(PPh3)(2)][Mo(CO)(2)((BuC)-C-t=CH)(eta(5)-7-CB10H11)] (13) and [N(PPh3)(2)]- [Mo(CO)(2)(PhC=CR)(eta(5)-7-CB10H11)] (R = H (14), Ph (15)) have also been prepared.