SYNTHESIS AND CHARACTERIZATION OF AIR-STABLE SIGMA-BONDED ORTHO-CARBORANE MANGANESE METAL-COMPLEXES 1-[MN(CO)(5)]-2-R-1,2-CLOSO-(SIGMA-C2B10H10) AND THEIR CONVERSION TO THE STABLE ORTHO-CARBORANE SUBSTITUTED FISCHER-TYPE CARBENE COMPLEXES 1-[(CO)(4)MN=C(OCH3)(CH3)]-2-R-1,2-CLOSO-C2B10H10 (R=CH3, C6H5)

The metal-carbon sigma-bond cluster complexes 1-Mn(CO)(5)-2-R-1,2-C2B1 0H10 (R=CH3 Ia, C6H5 Ib) have been prepared in good yields from readil y available carboranyl lithium complexes, 1-Li+-2-R-1,2-C2B10H10- (R=C H3, C(6)H5()), by direct reaction with (CO)(5)MnBr. These manganese me tal complexes are rapidly converted to the corresponding manganese met al carbene complexes, 1-[(CO)(4)Mn=C(OCH3)(CH3)]-2-R-1,2-C2B10H10 (R=C H3 IIIa, C6H5 IIIb), via alkylation with methylithium followed by O-me thylation with CF3SO3CH3. The crystal structure of IIIb was determined by X-ray diffraction. Thus, complex IIIb crystallizes in the orthorho mbic space group P2(1)2(1)2(1) With cell parameters a=15.5537(5), b=19 .0697(5), c=7.4286(3) Angstrom, V=2203.4(1) Angstrom(3), and Z=4. Of t he reflections measured a total of 3805 unique reflections with F-2>3 sigma(F-2) was used during subsequent structure refinement. Refinement converged to R(1)=0.053 and R(2)=0.091. Structural studies showed tha t the manganese atom had a slightly distorted pseudo-octahedral config uration about the metal center with the carbene and ortho-carborane oc cupying the equatorial plane cis-orientation to each other.