454485-17-7Relevant academic research and scientific papers
Stoichiometric and catalytic behavior of cationic silyl and silylene complexes
Klei, Steven R.,Tilley, T. Don,Bergman, Robert G.
, p. 4648 - 4661 (2008/10/08)
Reactions of Ir(III) silyl and silylene complexes with a variety of unsaturated substrates were investigated. The reactivity of these complexes toward small molecules was also examined, and this led to the discovery of a nitrile carbon-carbon bond cleavage under mild conditions. Both silyl and silylene complexes of Ir(III) are precatalysts for catalytic hydrosilylation of ketones, and the mechanism of this reaction is discussed. In the course of studying the catalytic reaction mechanism, analogous new ruthenium silylene complexes of the form [Cp*(PMe3)2Ru(SiR2)] [B(C6F5)4] (Cp* = η5-C5Me5, R = iPr, SPh) were prepared. A comparison of [Cp*(PMe3)Ir(SiPh2)(H)] [B(C6F5)4] and the known Lewis acid hydrosilylation catalyst B(C6F5)3 is also made.
Reactions of Cp*(PMe3)Ir(Me)OTf with silanes: Role of base-free silylene complexes in rearrangements of the resulting silicon-based ligands
Klei, Steven R.,Don Tilley,Bergman, Robert G.
, p. 3376 - 3387 (2008/10/08)
The mechanisms of silicon-hydrogen activation by Cp*(PMe3)Ir(Me)OTf (Cp* = η5-C5-Me5, OTf = OSO2CF3; 1) and rearrangements of the resulting silyliridium complexes were investigated. The scope of this reaction has been studied for silanes with a variety of substituents. Silylene complexes of the type [Cp*(PMe3)Ir(SiR2)(H)] [X] (X = OTf, R = Mes, 6; X = B(C6F5)4, R = Ph, 16) have been isolated, and the likelihood of their involvement in the rearrangements is discussed. The kinetics of the isomerization reaction of the cyclometalated iridium(V) complex {Cp*(PMe3)Ir(H)[κ2-SiH(Mes)(2-CH2-4 ,6-Me2C6H2)]}[OTf] (5) to the iridium silylene [Cp*(PMe3)Ir(SiMes2)(H)] [OTf] (6) were examined using NMR spectroscopic techniques. The primary kinetic isotope effect (Si-H vs Si-D bond) for this process was determined to be 1.4 ± 0.1, implying a rate-limiting hydride migration from silicon to iridium. The activation parameters for this isomerization have also been measured: ΔH? = 23 ± 2 kcal/mol and ΔS? = 0.1 ± 0.01 eu. Slow hydride migration to produce a silylene complex from either Cp*(PMe3)Ir(Me)OTf (1) or [Cp*(PMe3Ir(Me)(CH2Cl2)][BC6F 5)4] (17) is observed for large substituents on silicon. However, production of the sterically less crowded complex [Cp*(PMe3)Ir(SiPh2)(H)] [B(C6F5)4] (16) is extremely rapid upon reaction of 17 with H2SiPh2. This argues for the intermediacy of a three-coordinate silicon species.
