Bis(phosphine)hydridorhodacarborane Derivatives of 1,1'-Bis(-carborane) and Their Catalysis of Alkene Isomerization and the Hydrosilylation of Acetophenone.

Deprotonation of [7-(1'--1',2'-CBH)--7,8-CBH] and reaction with [Rh(PPh)Cl] results in isomerization of the metalated cage and the formation of [8-(1'--1',2'-CBH)-2-H-2,2-(PPh)--2,1,8-RhCBH] (). Similarly, deprotonation/metalation of [8'-(7--7,8-CBH)-2'-(-cymene)--2',1',8'-RuCBH] and [8'-(7--7,8-CBH)-2'-Cp*--2',1',8'-CoCBH] affords [8-{8'-2'-(-cymene)--2',1',8'-RuCBH}-2-H-2,2-(PPh)--2,1,8-RhCBH] () and [8-(8'-2'-Cp*--2',1',8'-CoCBH)-2-H-2,2-(PPh)--2,1,8-RhCBH] (), respectively, as diastereoisomeric mixtures. The performances of compounds - as catalysts in the isomerization of 1-hexene and in the hydrosilylation of acetophenone are compared with those of the known single-cage species [3-H-3,3-(PPh)--3,1,2-RhCBH] () and [2-H-2,2-(PPh)--2,1,12-RhCBH] (), the last two compounds also being the subjects of Rh NMR spectroscopic studies, the first such investigations of rhodacarboranes. In alkene isomerization all the 2,1,8- or 2,1,12-RhCB species (-, ) outperform the 3,1,2-RhCB compound , while for hydrosilylation the single-cage compounds and are better catalysts than the double-cage species -.