Acceleration of Nucleophilic CH Activation by Strongly Basic Solvents

Abstract

IPI)Ru(II)(OH) n (H 2 O) m , 2, where IPI is the NNN-pincer ligand, 2,6-diimidizoylpyridine, is shown to catalyze H/D exchange between hydrocarbons and strongly basic solvents at higher rates than in the case of the solvent alone. Significantly, catalysis by 2 is accelerated rather than inhibited by increasing solvent basicity. The evidence is consistent with the reaction proceeding by base modulated nucleophilic CH activation.

“Rollover” cyclometalation – early history, recent developments, mechanistic insights and application aspects

“…''Ligands with multiple personalities'' 196 have attracted some interest during the last years and such species exhibit perspectives for C-H bond activation reactions 197 or for the design of molecular devices.…”

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

“…However, it is necessary to emphasize that splitting the bond is actually a consequence of its activation [1]. Alternative definitions have been proposed by Periana and colleagues who "define CH activation as a facile CH cleavage reaction with an 'MX' species that proceeds by coordination of an alkane to the inner-sphere of 'M' (either via an intermediate 'alkane complex' or a transition state) leading to a M-C intermediate" ( [14]) and wrote about "the CH activation reaction as a coordination reaction with a reactive species 'M', that proceeds without the involvement of free radicals, carbocations, or carbanions to generate discrete M-R intermediates" ( [14][15][16][17]). …”

The Hydroxide‐Promoted Catalytic Hydrodefluorination of Fluorocarbons by Ruthenium in Aqueous Media

“…[10] Surprisingly, rather than observing rate inhibition, the rates of C À H activation are enhanced with increasing [KOH]. We postulate that reversible deprotonation of the non-innocent protic ligands leads to a coordinatively unsaturated, powerful p-donor that can interact more readily with the anti-bonding orbital (LUMO) of a C À H bond; leading to M À C bond formation (Scheme 1).…”

“…This result contrasts with the reactions of C À H bonds, where controls show that 6 shows no activity for H/D exchange in basic media. [10] No reaction was observed in either the absence of H 2 or KOH (in H 2 O), further demonstrating the necessity of KOH for turnover. Increasing the temperature to 50 8C resulted in the complete consumption of 2 with the fully hydrogenated 4 as the sole product (Scheme 3).…”

“…[10] To minimize issues related to mass transfer, we focused our efforts on para-fluorobenzoic acid, 2, as a base-soluble fluorocarbon. As can be seen in Table 1, treatment of 2 in 1 M KOH with 2 mol% 1 at 100 8C for 1 h under 400 psi H 2 resulted in the partial conversion of 2 (55%) to a mixture of BzOK, 3, and the fully hydrogenated product Cy-COOK, 4, as the major products (24% and 24%, respectively); along with minor amounts of the partially hydrogenated product 5 (6%) (Scheme 2; Table 1, entry 1).…”