Reactions of Cp*(PMe 3 )Ir(Me)OTf with Silanes: Role of Base-Free Silylene Complexes in Rearrangements of the Resulting Silicon-Based Ligands
2002; American Chemical Society; Volume: 21; Issue: 16 Linguagem: Inglês
10.1021/om020191+
ISSN1520-6041
AutoresSteven R. Klei, T. Don Tilley, Robert G. Bergman,
Tópico(s)Organoboron and organosilicon chemistry
ResumoThe mechanisms of silicon−hydrogen activation by Cp*(PMe3)Ir(Me)OTf (Cp* = η5-C5Me5, 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 (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 ei...
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