Exploring the mechanism of the hydroboration of alkenes by amine–boranes catalysed by [Rh(xantphos)]⁺

Abstract

The [Rh(xantphos)]+ fragment acts as an effective catalyst for the hydroboration of the alkene TBE (tert-butyl ethene) using the amine–borane H3B·NMe3 at low (0.5 mol%) catalyst loadings to give the linear product.

Elusive Reaction Intermediates in Solution Explored by ESI‐MS: Reverse Periscope for Mechanistic Investigations

“…[50] Several rhodium-containing intermediates responsible for B À Ha ctivation through the metal were intercepted at the early stage of the reaction progress. Interestingly,t heir signals decrease very quickly over time, and thus explain why they cannot be detected by NMR spectroscopy.P SI-ESI-MS,i na greement with other experimental data, indicates release of the hydroboration product as the rate-determining step of the reaction.…”

“…Rhodium-mediated transformations constitute another group of highly intriguing reactions.M cIndoe,W eller,a nd co-workers very recently reported on the investigation of two reactions in this field by using PSI-ESI-MS. [16,50] They investigated the hydroboration of tert-butylethene (TBE) with amine-boranes,c atalyzed by [Rh(xantphos)] + ,b yu sing ESI-MS online monitoring. [50] Several rhodium-containing intermediates responsible for B À Ha ctivation through the metal were intercepted at the early stage of the reaction progress. Interestingly,t heir signals decrease very quickly over time, and thus explain why they cannot be detected by NMR spectroscopy.P SI-ESI-MS,i na greement with other experimental data, indicates release of the hydroboration product as the rate-determining step of the reaction.…”

PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes

“…However, the precise structure of this active species remains unclear. Complex 1 also promotes the stoichiometric B–B homocoupling of H 3 B⋅NMe 3 to form [Rh(κ 2 ‐ P,P ‐xantphos)(H 4 B 2 ⋅2NMe 3 )][BAr F 4 ] 2 alongside the dihydride complex [Rh(κ 3 ‐ P,O,P ‐xantphos)(H) 2 (η 1 ‐H 3 B⋅NMe 3 )][BAr F 4 ] 3 (Scheme )5 and also promotes the hydroboration of alkenes using H 3 B⋅NMe 3 6…”

Elektrospray‐Massenspektrometrie: ein umgekehrtes Periskop zur Erforschung von Reaktionsmechanismen in Lösung

“…Eine weitere Gruppe von hochinteressanten Reaktionen ist die Rhodiumkatalyse. Zwei solche Reaktionen untersuchten McIndoe, Weller und Mitarbeiter jüngst mit ihrer PSI‐ESI‐MS‐Technik . Durch Online‐ESI‐MS‐Monitoring verfolgten sie die Hydroborierung von tert ‐Butylethen (TBE) mit Aminboranen, die durch [Rh(Xantphos)] + katalysiert wird .…”

“…Zwei solche Reaktionen untersuchten McIndoe, Weller und Mitarbeiter jüngst mit ihrer PSI‐ESI‐MS‐Technik . Durch Online‐ESI‐MS‐Monitoring verfolgten sie die Hydroborierung von tert ‐Butylethen (TBE) mit Aminboranen, die durch [Rh(Xantphos)] + katalysiert wird . Sehr früh in der Reaktion konnten sie mehrere Rhodium‐Intermediate abfangen, die an der B‐H‐Aktivierung durch das Metall beteiligt waren.…”