Grubbs group

Grubbs group reported a series of cross-linkable triarylamine-containing poly(norbor-nenes) (51) and investigated them as the HTMs in a bilayer OLED (Scheme 3.19) [94]. However, cross-linking was found to decrease the device performance due to the low Ts of the polymers and the poor film quality after UV irradiation. 

Most recently, Grubbs group demonstrated that some neutral salicylaldiminato nickel(II) complexes, whose skeleton structure appears as lb in Figure 1, show catalytic activities rivaling those of the bisimine complexes [9], This potentially opens the door to a new class of catalysts as the active sites derived from these nickel complexes are neutral, thus reducing the ion-pairing problems encountered in the current catalysts. 

Grubbs group [31, 32] developed another type of Ni-based catalyst. This neutral Ni-catalyst, based on salicylaldimine ligands, is active in ethene polymerisation without any co-activator and originated from the Shell higher olefin process (SHOP). Shortly thereafter another active neutral P,0-chelated nickel catalysts for polymerisation of ethene in emulsion was developed by Soula et al. [33, 34, 35]. The historical development of single site catalysts is represented in Fig. 1. 

With the experimental tools of Grubbs group, SonBinh Nguyen discovered in a short period of time that 81 did not only catalyze the metathesis of acyclic olefins but was also competitive with Schrock s molybdenum carbenes in ringclosing metathesis (RCM) [171]. Compared with Schrock s compounds, the ruthenium carbenes had the advantage that they were only moderately sensitive... 

Living ring opening metathesis polymerization methods (ROMP) were first employed to synthesize LC-coil diblock copolymers by Komiya and Shrock [80] in 1993. The structure of their polymer system is shown in Scheme 7D. Recent work from Grubbs group also used a novel ruthenium catalyst which can tolerate more functional groups [81] to synthesize well-defined LC-coil block copolymers [82]. The ROMP polymer backbone can be hydrogenated to create saturated structure to improve its stability. 

Despite the high Z selectivity exhibited by catalysts 10 and 26 in ROMP, neither catalyst showed an ability to control the tacticity of the formed polymer. Catalysts based on Mo and W are often capable of tacticity control, but Ru-based catalysts have traditionally struggled with this type of selectivity [56]. However, the Grubbs group recently reported that a C-H-activated Ru catalyst, where the adamantyl has been replaced with a tert-butyl group, was capable of tacticity control (Scheme 3.8) [57]. The syndiotactic microstructure of the resulting polymers was confirmed using NMR spectroscopy. 

The Grubbs group used the same type of catalyst in the asymmetric ringopening cross-metathesis (AROCM, Scheme 3.2). For the transformation of... 

Much effort has been expended recendy to understand how Hoveyda-type precatalysts initiate. Originally, it was simply assumed that the initiation mechanism was dissociative and data to support this was pubHshed by Love et al., in which no dependence of the initiation rate of GH2 on substrate concentration was observed. No entropy change was required to reach the transition state (AH = 19.9(5) kcal moH and AS = 1(2) cal mol for the initiation of GH2 with EVE in toluene). However, activation parameters collected during a later study, also by the Grubbs group, suggested a nondissociative mechanism, due to the negative entropy of activation (AH = 15.2(8) kcal mol and AS = —19(3) cal moH for the... 

By using mesityl-substituted NHCs, Grubbs and Nolan disclosed, practically simultaneously, the synthesis of the Ru-alkylidene complexes 19 (NHC = l,3-dimesitylimidazol-2-ylidene) soon thereafter, the Grubbs group firther introduced complexes 20 (Cy = cyclohexyl) and 21 (Cp = cyclopentyl) containing a saturated NHC (l,3-dimesityl-4,5-dihydroimidazol-2-ylidene). 

---