Seven-Vertex Phosphinohalometallacarboranes of Iron, Cobalt, and Nickel: Syntheses, Structures, and Reactions.

摘要

The reaction of the nido-2, 3-Et2C2B4H5- ion with (Ph3P)2NiBr2 in THF at room temperature gave purple, crystalline 1-Br-1, 5-(Ph3P)2-1, 2, 3-Ni(Et2CB4H3) (1), whose phosphino ligands are attached to nickel and boron, respectively. The same carborane in reacted with (Ph2PCH2)w and MC12 (M = Co, Fe) in THF to give the crystalline metallacarboranes 1,1-(Ph2PCH2)2-1-C1-1, 2, 3-M(Et2C2B4H4) (2, M=Co;3,M = Fe). Products 1-3 were structurally chracterized by single-crystal X-ray diffraction and by IR, UV-visible, and mass spectra; in addition, high-field NMR spectra were obtained for the diamgnetic species 1 and 2, while paramagnetic 3 was examined via ESR and magnetic susceptibiltiy measurements, which support the presence of low-spin FE(III) in 3. The MC2B4 cages in all three compounds have normal closo seven-vertex (pentagonal-bipyramidal) geometry. Although 3 has one less electron than 2, its cage shows no significant distortion; hence, the unpaired electron appears to be localized in a nonbonding orbital on iron.