Synthetic Applications of Synergism using Catalytic Binuclear Elimination Reactions. Further Examples of Rhodium‐Manganese and Rhodium‐Rhenium‐Catalyzed Hydroformylations

Abstract

Synergism has been previously observed in both rhodium-manganese-and rhodium-rhenium-catalyzed hydroformylation. Furthermore, detailed in situ spectroscopic investigations have conclusively shown that the phenomenological origin of this synergistic effect is catalytic binuclear elimination (J. Am. Chem. Soc. 2003, 125, 5540-5548; 2007, 129, 13327-13334). In the present contribution, further substrates are used in the hydroformylation reaction with both rhodium-manganese and rhodium-rhenium. In situ spectroscopic studies show that (i) significant rate enhancements occur in the mixed metal systems with the new substrates and (ii) the organometallics present in the active systems, and their concentration profiles are consistent with those present in the previously studied catalytic binuclear elimination reactions (CBER). It is therefore concluded that catalytic binuclear elimination is a rather general mechanism in mixed metal hydroformylations and is rather independent of the substrates used. Further discussion is given to mechanistic aspects, synthetic efficiency, and the possibility that such synergistic effects might be useful to other classes of organic syntheses.

Bimetallic Reductive Elimination from Dinuclear Pd(III) Complexes

“…The mechanisms of redox transformations at multinuclear complexes are less understood than the corresponding reactions of mononuclear complexes . Stoichiometric oxidative addition to and reductive elimination from dinuclear complexes have been observed, and dinuclear intermediates have been proposed as intermediates in catalysis. , The potential of utilizing metal-metal redox synergy to accomplish challenging transformations has long been recognized, and while proposals of mechanisms involving metal-metal cooperation have been posited, identification of the intimate role of each metal center during redox transformations at dinuclear complexes is difficult to establish experimentally. − , Understanding how metal-metal redox synergy can be used in catalysis requires insight into the role of each metal during redox chemistry.…”

A Review of BTEM Analysis for Catalytic Studies and a Recent Homogeneous Catalytic Example

“…Recently, BTEM was used to identify a new homogeneous catalytic reaction mechanism that involves both mononuclear and dinuclear intermediates simultaneously. This mechanism is now called ''catalytic binuclear elimination'' [26][27][28][29][30]. In the following example, some unpublished details from a recent study are presented [30].…”

The Catalytic Binuclear Elimination Reaction: Importance of Non-linear Kinetic Effects and Increased Synthetic Efficiency

“…is typically initiated by the combined application of HRe(CO) 5 and Rh 4 (CO) 12 as catalyst precursors to a n-hexane solution containing an alkene, hydrogen and CO at ambient temperature [75][76][77][78]. The structure of the system is shown in Fig.…”

“…In situ spectroscopic analysis was not available/reported. In a series of studies, HMn(CO) 5 [61][62][63]74], HRe(CO) 5 [75][76][77][78], HMoCp(CO) 3 [77,78] and HWCp(CO) 3 [79] the complexes were added individually to unmodified rhodium-catalysed alkene hydroformylations. In situ FTIR spectroscopy was performed on all systems, and detailed modelling was performed on the more well-behaved systems containing HMn(CO) 5 and HRe(CO) 5 .…”