Synthesis and Reactivity of 10- and 12-Vertex Cobalt−Monocarborane Anions Containing Multiple Metal Centers

Treatment of [closo-1-CB7H8]- with [Co2(CO)8] in THF at room temperature affords the 10-vertex
dicobalt−monocarbollide anion [6,10-(μ-CO)-6,6,10,10-(CO)4-closo-6,10,1-Co2CB7H8]-, isolated as the
[N(PPh3)2]+ salt (6). The analogous 12-vertex species [N(PPh3)2][2,3-(μ-CO)-2,2,3,3-(CO)4-closo-2,3,1-Co2CB9H10] (7) is obtained similarly from [arachno-6-CB9H14]- and [Co2(CO)8] heated to 50 °C. Both
6 and 7 contain a cobalt−cobalt bond that is bridged by one CO ligand. In contrast, the same cobalt
reagent with [closo-4-CB8H9]- at room temperature gives the tricobalt species [6,7,10-{Co2(μ-CO)(CO)5}-7-(μ-H)-6,6-(CO)2-closo-6,1-CoCB8H7]-, similarly isolated as its [N(PPh3)2]+ salt (8a). The latter contains
a V-shaped tricobalt unit, part of a {Co3B} butterfly that is edge-fused to a {CoCB8} cluster. Compounds
6 and 7 with CF3SO3Me in CH2Cl2−THF (1:1) give the zwitterionic, B-substituted complexes [6,10-(μ-CO)-6,6,10,10-(CO)4-8-{O(CH2)4}-closo-6,10,1-Co2CB7H7] (9) and [2,3-(μ-CO)-2,2,3,3-(CO)4-12-{O(CH2)4}-closo-2,3,1-Co2CB9H9] (10), respectively, the latter of which reacts further with PPh3,
undergoing THF ring opening to give [2,3-(μ-CO)-2,2,3,3-(CO)4-12-{O(CH2)4PPh3}-closo-2,3,1-Co2CB9H9] (11). In addition, compounds 6 and 8 react with [CuCl(PPh3)]4 in the presence of Tl[PF6], affording
trimetallic [7,8,10-{Cu(PPh3)}-7,8-(μ-H)2-6,10-(μ-CO)-6,6,10,10-(CO)4-closo-6,10,1-Co2CB7H6] (12) and
tetrametallic [6,7,8,9,10-{Co2Cu(μ-CO)(CO)3(PPh3)2}-6-(μ-CO)-7,8,9-(μ-H)3-6,6-(CO)2-closo-6,1-CoCB8H5]
(13), respectively. The novel features in the structures of compounds 6−10 and 13 have been confirmed
by X-ray diffraction experiments.

将[closo-1-CB7H8]^-与[Co2(CO)8]在四氢呋喃(THF)中于室温下反应，得到10顶点二钴-单碳硼烷阴离子[6,10-(μ-CO)-6,6,10,10-(CO)4-closo-6,10,1-Co2CB7H8]^-，以双(三苯基膦)亚铵([N(PPh3)2]+)盐的形式分离得到（化合物6）。以类似方法，由[arachno-6-CB9H14]^-与[Co2(CO)8]在50℃下加热反应，得到同构的12顶点物种[N(PPh3)2][2,3-(μ-CO)-2,2,3,3-(CO)4-closo-2,3,1-Co2CB9H10]（化合物7）。化合物6和7均含有一条由一个桥连CO配体桥联的钴-钴键。与之相反，在室温下将同一钴试剂与[closo-4-CB8H9]^-反应，得到三钴类物种[6,7,10-{Co2(μ-CO)(CO)5}-7-(μ-H)-6,6-(CO)2-closo-6,1-CoCB8H7]^-，同样以其双(三苯基膦)亚铵盐形式分离得到（化合物8a）。该物种包含一个V形三钴单元，属于与{CoCB8}簇边稠合的{Co3B}蝶形结构的一部分。化合物6和7分别与三氟甲磺酸甲酯(CF3SO3Me)在二氯甲烷(CH2Cl2)-四氢呋喃(THF)体积比1:1的混合溶剂中反应，得到两性离子型B位取代配合物[6,10-(μ-CO)-6,6,10,10-(CO)4-8-{O(CH2)4}-closo-6,10,1-Co2CB7H7]（9）和[2,3-(μ-CO)-2,2,3,3-(CO)4-12-{O(CH2)4}-closo-2,3,1-Co2CB9H9]（10）；其中化合物10可进一步与三苯基膦(PPh3)反应，伴随四氢呋喃开环，得到[2,3-(μ-CO)-2,2,3,3-(CO)4-12-{O(CH2)4PPh3}-closo-2,3,1-Co2CB9H9]（11）。此外，化合物6和8分别在六氟磷酸亚铊(Tl[PF6])存在下与[CuCl(PPh3)]4反应，得到三金属配合物[7,8,10-{Cu(PPh3)}-7,8-(μ-H)2-6,10-(μ-CO)-6,6,10,10-(CO)4-closo-6,10,1-Co2CB7H6]（12）和四金属配合物[6,7,8,9,10-{Co2Cu(μ-CO)(CO)3(PPh3)2}-6-(μ-CO)-7,8,9-(μ-H)3-6,6-(CO)2-closo-6,1-CoCB8H5]（13）。化合物6~10及13的结构中的新颖特征已通过X射线衍射实验得到证实。