Synthesis, solution behavior and molecular structure of the new sandwich-type cobaltacarborane cluster closo,nido-[CoH(2,4-C2B8H10) (7,8-C2B8H11)](1-)

摘要

Treatment of an anhydrous CoCl2 with the [Na][C2B8H11] (1) generated in situ from the neutral ten-vertex dicarbon carborane [5,6-nido-C2B8H12] (2) with NaH in THF at ambient temperature affords the new cobaltacarborane commo cluster closo,nido-[CoH(2,4-C2B8H10)(7,8-C2B8H11)](1-) isolated as its air-stable [Ph4P](+) (3) and [Ph3PMe](+) (4) salts. As was found from the crystallographically determined structure of 4 and based on the H-1 NMR spectroscopic data for both 3 and 4, these anionic salts are composed of the Co-H unit that is sandwiched between two {C2B8} cages; one of these cages, the formally doubly charged [C2B8H10](2-) ligand, is involved in the eta(6)-coordination to the metal center, but another singly charged [7,8-C2B8H11](1-) ligand, which retains one bridged B-H-B hydrogen atom, is involved through its CB3-open face in the eta(4)-coordination to the cobalt atom. At room temperature, complexes 3 and 4 exhibited fluxional behavior in solution where the exchange between terminal Co-H and bridging B-H -B hydrogen atoms occurs. This is discussed in detail based on the comparable room- and low-temperature H-1 NMR spectra of 3. (C) 2015 Elsevier B.V. All rights reserved.