Metalladiboranes of the Iron Subgroup: K[M(CO)₄(η²-B₂H₅)] (M = Fe, Ru, Os) and M′(η⁵-C₅H₅)(CO)₂(η²-B₂H₅) (M′ = Fe, Ru). Analogues of Metal-olefin Complexes

The metal carbonylates [M(CO)4]2- (M = Fe, Ru, Os) and [(η5-C5H5)M′(CO)2] - (M′ = Fe, Ru) react with L·BH3 (L = THF, Me2O) to yield the metalladiborane complexes [M(CO)4(η2-B2H5)]- and (η5-C5H5)M′-(CO) 2(η2-B2H5). The molecular structure of (η5-C5H5)Fe(CO)2(η 2-B2H5) was determined from single-crystal X-ray data. This structure can be described as that of a diborane(6) molecule with a (η5-C5H5)Fe(CO)2 unit replacing a bridge hydrogen. Distances and angles within the B2H5 unit are consistent with those observed for B2H6. Crystal data for (η5-C5H5)Fe(CO)2(η 2-B2H5): space group Pnam, orthorhombic, a = 11.955 (3) Å, b = 6.425 (1) Å, c = 11.552 (3) Å, V = 887.44 Å3, mol wt 204.04, ρcalcd = 1.524 g/cm3, for Z = 4. For Mo Kα 1355 unique reflections were collected at -174°C over the range 5° < 2θ < 55° with 1100 reflections greater than 2.33σ(I) used in the final refinement. RF = 0.0254 and RwF = 0.0303. Boron-11 and proton NMR spectra also indicate diborane-like structures for [M(CO)4(η2-B2H5)]- (M = Fe, Ru, Os) and (η5-C5H5)M′(CO) 2(η2-B2H5). Mössbauer spectra as well as the X-ray diffraction data support a three-center, two-electron bond representation between the metal center and the two borons of the B2H5 moiety. © 1989 American Chemical Society.