Abstract
A number of paramagnetic silylated d1 group 4 metallates were prepared by reaction of potassium tris(trimethylsilyl)silanide with group 4 metallates of the type K[Cp2MCl2] (M = Ti, Zr, Hf). The outcomes of the reactions differ for all three metals. While for the hafnium case the expected complex [Cp2Hf{Si(SiMe3)3}2]− was obtained, the analogous titanium reaction led to a product with two Si(H)(SiMe3)2 ligands. The reaction with zirconium caused the formation of a dinuclear fulvalene bridged complex. The desired [Cp2Zr{Si(SiMe3)3}2]− could be obtained by reduction of Cp2Zr{Si(SiMe3)3}2 with potassium. In related reactions of potassium tris(trimethylsilyl)silanide with some lanthanidocenes Cp3Ln (Ln = Ce, Sm, Gd, Ho, Tm) complexes of the type [Cp3Ln Si(SiMe3)3]− with either [18-crown-6·K]+ or the complex ion [18-crown-6·K·Cp·K·18-crown-6] as counterions were obtained. Due to d1 or fn electron configuration, unambiguous characterization of all obtained complexes could only be achieved by single crystal XRD diffraction analysis.
Highlights
Investigations on the chemistry of group 4 silyl complexes were started in the late 1960s, with some work on silyl titanium chemistry1−6 and Lappert’s contributions of zirconocene and hafnocene complexes.7−10 Systematic studies of zirconocene and hafnocene silyl complexes were carried out by Tilley and co-workers,11−17 who especially studied aspects of σ-bond metathesis and the catalytic dehydrocoupling polymerization of hydrosilanes catalyzed by these compounds.16−19 While in the initial papers by Harrod and co-workers20−23 on the dehydrocoupling polymerization of hydrosilanes titanium was acting as the catalytically active element, Tilley’s mechanistic studies were carried out using hafnium or zirconium
Starting out from CpCp*M(Cl)Si(SiMe3)3 (M = Zr, Hf) it was shown that σ-bond metathesis reaction with a hydrosilane leads to (Me3Si)3SiH and a new metal silyl complex, which in reaction with another hydrosilane forms a disilane and a metal hydride
In order to study the chemistry of silylated Cp2Ti(III) complexes, we reacted α,ω-oligosilanyldiides with (18-crown-6)·K[Cp2TiCl2] or·Li[Cp2TiCl2] to titanacyclosilanes with titanium in the oxidation state +3.25 Further investigations revealed that analogous metallacyclosilanes could be obtained with Zr(III) and Hf(III)
Summary
Investigations on the chemistry of group 4 silyl complexes were started in the late 1960s, with some work on silyl titanium chemistry− and Lappert’s contributions of zirconocene and hafnocene complexes.− Systematic studies of zirconocene and hafnocene silyl complexes were carried out by Tilley and co-workers,− who especially studied aspects of σ-bond metathesis and the catalytic dehydrocoupling polymerization of hydrosilanes catalyzed by these compounds.− While in the initial papers by Harrod and co-workers− on the dehydrocoupling polymerization of hydrosilanes titanium was acting as the catalytically active element, Tilley’s mechanistic studies were carried out using hafnium or zirconium. In order to study the chemistry of silylated Cp2Ti(III) complexes, we reacted α,ω-oligosilanyldiides with (18-crown-6)·K[Cp2TiCl2] or (tmeda)·Li[Cp2TiCl2] to titanacyclosilanes with titanium in the oxidation state +3.25 Further investigations revealed that analogous metallacyclosilanes could be obtained with Zr(III) and Hf(III).. In the current paper we wish to report on reactions of (Me3Si)3SiK with (18-crown-6)·K[Cp2MCl2] (M = Ti, Zr, Hf) to obtain d1-complexes of the type K[Cp2M{Si(SiMe3)3}2]. Among all 4f-elements, samarium and the late lanthanide metals ytterbium and lutetium are best investigated for this class of compounds In their landmark contributions, Schumann and co-workers were the first to employ a common method for the preparation of early transition-metal complexes, treating rare-earth halide complexes with the lithium silanide Me3SiLi. Reactions with complexes of the type Cp2Ln(μ-Cl)2Na provided atecomplexes = Sm, Lu, of the type Dy, Ho, Er, a[nLdi(TDmM.2E6)−32]8[Cp2Ln(SiMe3)2].
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