Modeling the Kinetics of Hydrosilylation Based Polyaddition

Rh(1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) tetrafluoroborate, an unsymmetrical Rh-homoazallylcarbene: synthesis, X-ray structure and reactivity in carbonyl arylation and hydrosilylation reactions

“…The distance Rh(1)-C(9) is 204.0(4) pm, somewhat shorter than the one found in 2 (206.5(8)) [21]. However, the cationic Rh-center is stabilized by a homoazallyl bonding to the arene, as evidenced by a comparably short distance Rh(1)-C(13) of 237.7(4) pm.…”

“…However, the cationic Rh-center is stabilized by a homoazallyl bonding to the arene, as evidenced by a comparably short distance Rh(1)-C(13) of 237.7(4) pm. In due consequence, the angle N(1)-C(9)-Rh(1) is reduced to 101.5(3)°, compared to 119.6(5)°in 2 [21]. Table 2 Bond lengths (pm) and angles (°) for 1…”

“…Among the various transition metals most commonly employed in hydrosilylation reactions [33][34][35][36][37], Rh is certainly a prominent one. Various NHC complexes of Rh have been used so far, however, with the exception of 2 [21], Rh-1,3-R 2 -imidazol-2-ylidenes (R = mesityl, etc.) have been used almost exclusively [10,12,[38][39][40][41][42][43][44][45][46][47].…”

“…Yields and turn over numbers (TONs) were determined by GC-MS using both the conversion of the educts and the peak areas of standard solutions of the products. Isolation and properties of the products is described elsewhere [20,21]. For the alkyne compounds the ratio of the product isomers was determined by integration of the GC-MS peaks.…”

“…Recently, our group [15][16][17][18][19][20][21] reported on novel NHC complexes of Ag (I), Pd (II), Rh (I), Ir (I), and Ru (II) based on 1,3-R 2 -3,4,5,6-tetrahydropyrimidin-2-ylidenes (R = mesityl, 2-propyl). For carbonyl arylation and hydrosilylation reactions the novel NHC-complexes MX(1,3-R 2 -3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (M = Rh, Ir; X = Cl, Br; R = 2-Pr, mesityl; COD = g 4 -1,5-cyclooctadiene) have been used and were found to possess excellent activity [20,21]. However, inspired by fruitful discussions in course of the International Symposium on Homogeneous Catalysis (ISHC) in Munich, 2004, we were interested whether the corresponding cationic complexes would allow for even enhanced reactivity and/or selectivity in these reactions.…”