Fluorosubstituted rhodacarboranes 3,4-(R3P)2-3-H-3,1,2-RhC2B9H11−n F n (n=1, 2, 4): Synthesis, molecular structure, and catalytic properties in hydrosilylation of styrene and phenylacetylene

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

“…However, we believe that, to a first approximation, V serves as an appropriate substitute for XI because in both the {RhH­(PPh 3 ) 2 } fragment is bonded to a CB 4 face of the carborane ligand (Figure ). Note that the use of I and V as a catalyst for alkene isomerization , and I as a catalyst for hydrosilylation has already been reported by Hawthorne, and that Balagurova et al have used I and analogs of I to extend the scope of catalytic hydrosilylation …”

“…It is believed that this, in turn, is in equilibrium with an exo Rh III species III, the result of oxidative insertion of the metal into a B−H bond, and that dissociation of one PPh 3 from III affords the active catalyst. 3 Although neither III nor an analog have ever been isolated it has been possible to stabilize and fully characterize (including a crystallographic study) an analog of the exonido species II with a 1′,2′-CH 2 C 6 H 4 CH 2 − bridge on the cage C atoms and a mixed PPh 3 /PCy 3 ligand set on Rh. 4 There have been relatively few studies in which the catalytic activity of I is tuned by modification.…”

“…2b,4 Of relevance to the present work is the observation that one such derivative, [1-n Bu-3-H-3,3-(PPh 3 ) 2 -closo-3,1,2-RhC 2 B 9 H 10 ], isomerizes to the less-sterically crowded isomer [8-n Bu-2-H-2,2-(PPh 3 ) 2closo-2,1,8-RhC 2 B 9 H 10 ] under mild conditions. 2b Other notable modifications to the parent catalyst precursor I include partial B-fluorination 5 and its incorporation into phosphazenebased polymers. 6 Recent years have witnessed significant interest in the synthesis and applications of derivatives of bis(carboranes).…”

“…The 2,1,7-RhC 2 B 9 ( IV ) and 2,1,12-RhC 2 B 9 ( V ) isomeric analogs of I (Figure ) have been studied, as have compounds in which various substituents are attached to one or both cage C atoms, , and/or the exopolyhedral ligand set is altered. , Of relevance to the present work is the observation that one such derivative, [1- n Bu-3-H-3,3-(PPh 3 ) 2 - closo -3,1,2-RhC 2 B 9 H 10 ], isomerizes to the less-sterically crowded isomer [8- n Bu-2-H-2,2-(PPh 3 ) 2 - closo -2,1,8-RhC 2 B 9 H 10 ] under mild conditions . Other notable modifications to the parent catalyst precursor I include partial B -fluorination and its incorporation into phosphazene-based polymers …”

“…Note that the use of I and V as a catalyst for alkene isomerization 2a,3a and I as a catalyst for hydrosilylation 2a has already been reported by Hawthorne, and that Balagurova et al have used I and analogs of I to extend the scope of catalytic hydrosilylation. 5 Scheme 4 depicts the isomerization of 1-hexene, and the results are displayed graphically in Figure 11. Here "yield" represents the combined yields of trans-2-hexene, cis-2-hexene, trans-3-hexene, and cis-3-hexene (a breakdown of these components is given in the SI).…”