Synthesis and Reactivity of Monocarbollide Carbonyl Complexes of Iron and Molybdenum with Icosahedral Frameworks

The [NEt 4 ] + ( 1a ), [NHMe 3 ] + ( 1b ), and [N(PPh 3 ) 2 ] + ( 1c ) salts of the monoanion [Fe(CO) 3 ( η 5 -7-CB 10 H 11 )] - have been prepared via the reaction between [Fe 3 (CO) 12 ] and [NHMe 3 ][ nido -7-CB 10 H 13 ] in THF (tetrahydrofuran). The complexes [N(PPh 3 ) 2 ][Fe(CO) 2 (L)( η 5 -7-CB 10 H 11 )] (L = PPh 3 ( 2 ), CNBu t ( 3 )) were obtained by treating 1c in THF with PPh 3 and CNBu t, respectively, in the presence of Me 3 NO. The compound [N(PPh 3 ) 2 ][Mo(CO) 4 ( η 5 -7-CB 10 H 11 )] ( 4 ) has been synthesized from [Na] 3 [ nido -7-CB 10 H 11 ] and [Mo(CO) 3 (NCMe) 3 ] in the presence of CO and with addition of HBF 4 ·Et 2 O and [N(PPh 3 ) 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-CB 10 H 11 carborane in a η 5 manner. In reactions with PPh 3 and CNBu t, the salt 4 gives the species [N(PPh 3 ) 2 ][Mo(CO) 3 (L)( η 5 -7-CB 10 H 11 )] (L = PPh 3 ( 5a ), CNBu t ( 6 )). Salts of the anions [Fe(CO) 3 ( η 5 -7-CB 10 H 11 )] - and [Mo(CO) 3 (PPh 3 )( η 5 -7-CB 10 H 11 )] - react with donor molecules (THF, OEt 2, SMe 2 ) in the presence of acids and other hydride abstracting reagents to give zwitterionic complexes: [Fe(CO) 3 ( η 5 -9-L-7-CB 10 H 10 )] (L = O(CH 2 ) 4 ( 7 ), OEt 2 ( 8 ), SMe 2 ( 9 )) and [Mo(CO) 3 (PPh 3 )( η 5 -9-L-7-CB 10 H 10 )] (L = O(CH 2 ) 4 ( 10 ), OEt 2 ( 11 )), formed as single isomers. That the donor molecules L are bonded to a boron atom which lies in a β -site with respect to the carbon in the ring ligating the metal was established by X-ray diffraction studies on 7 and 10 . In the latter the PPh 3 molecule is transoid to the BO(CH 2 ) 4 group, presumably for steric reasons. Alkyne−molybdenum complexes [N(PPh 3 ) 2 ][Mo(CO) 2 (Bu t C⋮CH)( η 5 -7-CB 10 H 11 )] ( 13 ) and [N(PPh 3 ) 2 ][Mo(CO) 2 (PhC⋮CR)( η 5 -7-CB 10 H 11 )] (R = H ( 14 ), Ph ( 15 )) have also been prepared.