Hydrosilylation and Silane Polymerization Catalyzed by Group 4 Amidometallocene Cations

Abstract

Four cationic amidotitanocene complexes [Cp2Ti­(NRR′)]­[B­(C6F5)4] (Cp = η5-C5H5; 1a: R = R′ = p-anisyl; 1b: R = p-fluorophenyl, R′ = p-anisyl; 1c: R = p-fluorophenyl, R′ = phenyl; 1d: R = phenyl, R′ = 2-pyridyl) were synthesized. Complexes 1a–d undergo Ti–N bond homolysis under visible light irradiation. Complexes 1a–c catalyze the polymerization of phenylsilane to yield branched polysilane polymers with molecular weights (Mw) up to approximately 3000 and dispersity indexes (Đ) of 1.4–1.6. Previously reported Group 4 cationic amidometallocene complexes [Cp2Ti­(NPh2)]­[B­(C6F5)4] (Ia) and Cp2Zr­(NPh2)]­[MeB­(C6F5)3] (IIa) were also tested in the hydrosilylation of carbonyl compounds with triethylsilane (Et3SiH). In some cases, complex Ia afforded completely reduced products (e.g., ethylbenzene from acetophenone), while IIa was generally more selective (e.g., (1-phenylethoxy)­triethylsilane from acetophenone) but also more active. Complex IIa could also convert anisole derivatives to phenoxysilanes with high efficiency (TON = 2000).

Poly(vinyl chloride) Dechlorination Catalyzed by Zirconium

“…Interestingly, LP and its derivatives underwent complete loss of the ester function of PVA (this is especially visible in the IR spectra, Figures S51–S53), in line with the known ester hydrosilylation activity of 1 b ; [16] however, no significant PVC reduction was observed.…”

“…Interestingly, while 1 b does not react with Et 3 SiH alone, [16] mixing 1 b in C 6 D 5 Br with 3 eq of chlorocyclohexane alone immediately afforded a complex mixture in which both DHC and HDC products were observed. A new signal was observed in the Cp region of the 1 H NMR spectrum, suggesting the clean formation of a single Zr species.…”

“…[14] During the past decade, we have investigated the catalytic properties of cationic group 4 amidometallocene complexes (such as 1 a and 1 b, Figure 1) in hydrogenation, [15] dehydrocoupling, [15b] and hydrosilylation reactions. [16] It occurred to us that the high Lewis acidity of these species makes them ideal candidates for the dehalogenation of various substrates, including PVC. In this contribution, we show that Zr complex 1 b indeed converts PVC into a PE-like polymer under mild conditions, and hence report the proof-of-concept of PVC dechlorination with a non-precious metal under mild conditions.…”

“…During the past decade, we have investigated the catalytic properties of cationic group 4 amidometallocene complexes (such as 1 a and 1 b , Figure 1) in hydrogenation, [15] dehydrocoupling, [15b] and hydrosilylation reactions [16] . It occurred to us that the high Lewis acidity of these species makes them ideal candidates for the dehalogenation of various substrates, including PVC.…”

Porous Silicone Rubber Composite Supported 1,4-Diphenylethynyl Benzene for Hydrogen Absorption with Pd/C Catalyst

“…Generally, SR is obtained by cross-linking liquid polysiloxane, and the most common cross-linking method is use of the hydrosilylation reaction. The hydrosilylation reaction is an addition reaction between the vinyl group on polysiloxane and the functional Si-H groups on the oligomer under the catalysis of the organometallic complexes of Pt or Rh [12]. The main chain of the obtained silicone rubber is composed of silicon and oxygen atoms alternately, and the organic functional groups in the side chain are attached to both sides of the silicon atoms after modification [13][14][15][16].…”