Ruthenium Alkylidenes:  Fast Initiators for Olefin Metathesis

Abstract

A family of ruthenium alkylidene complexes, (H 2 IMes)RuCl 2 (dCHR)(3-bromopyridine) 2 , where R ) Me, Et, nPr, as well as the corresponding PCy 3 complexes, (H 2 IMes)RuCl 2 (dCHR)(PCy 3 ), have been prepared. The PCy 3 alkylidene complexes exhibit much higher stoichiometric reactivity than does the analogous benzylidene complex, reflecting faster dissociation of PCy 3 from the alkylidene complexes.

Catalytic transformation of phenylacetylene mediated by phosphine-free ruthenium alkylidene complexes

“…We speculated that those new peaks might be attributed to 3-bromopyridine coordinated to the ruthenium center of the new complex formed after the alkylidene ligand loss. Proton signals in the same range were observed after the decomposition of [RuCl 2 (¼CHR)(3-Br-py) 2 (IMesH 2 )], where R ¼ Me, Et, n Pr, in the presence of 1-alkenes [50] and assigned by Hong unsuccessful, and unidentified products were obtained. In order to prove the formation of a pyridine-based complex of ruthenium together with the vinylidene species at the initial stage of the reaction, some 1 H NMR studies of phenylacetylene reaction with complex [RuCl 2 (¼CHPh)(py) 2 (IMesH 2 )] were carried out.…”

Probing the Mechanism of Olefin Metathesis in Grubbs–Hoveyda and Grela Type Complexes

“…Clearly, there is no saturation behavior, which on the other hand is well‐established for Grubbs second‐generation complexes 2a. 14 At this concentration of DEDAM, fading of the 378 nm absorbance in complex 1 occurs in less than 100 s. Fitting of the absorbance versus time plot with an exponential function (pseudo‐first‐order condition) A =( A 0 − A ∞ ) exp(− k obs t )+ A ∞ yields k obs and follows the same linear regression as for the lower concentrations 15…”

Olefin metathesis for metal incorporation: Preparation of conjugated ruthenium-containing complexes and polymers

“…With this complex, preparation of 8 was accomplished very quickly: reaction of G2B with excess hexatriene for a few minutes, followed by addition of PCy 3 . We recently reported that the alkylidenes 9 (R = Me, Et, Pr) also offer faster initiation [11]. While the first-generation ethylidene 5 offers advantages for OMMI based on metathesis equilibrium and volatile propene byproduct (see above), the analogous second-generation complexes are also of value for their faster dissociation of PCy 3 .…”

“…Derivatives of the Grubbs first-generation catalyst (PCy 3 ) 2 C1 2 Ru@(CHPh), G1) including the Hoveyda-Grubbs catalyst [8], heterobimetallic complexes [9], and several different alkylidene complexes [10,11] have been prepared using this strategy. OMMI has also been reported in sulfur-rich Ru complexes [12] and on ruthenium surfaces [13].…”