Activation of the (Trimethylsilyl)tetramethylcyclopentadienyl Ligand in the [C₅Me₄(SiMe₃)]₂TiCl₂/Mg System, Yielding Intramolecular Si−CH₂−Mg and Si−CH₂−Ti Bonds. Molecular Structures of {[η⁵-C₅Me₄SiMe₂(μ-CH₂{Mg,Mg})][η⁵-C₅Me₄(SiMe₃)]Ti^III(μ-H)₂Mg(THF)}₂ and [η⁵:η¹-

Abstract

The reduction of [C5Me4(SiMe3)]2TiCl2 by excess Mg in THF yields the paramagnetic compound {[η5-C5Me4SiMe2(μ-CH2{Mg,Mg})][η5-C5Me4(SiMe3)]TiIII(μ-H)2Mg(THF)}2 (3). In the presence of Me3SiC⋮CSiMe3 the same system affords the paramagnetic compound [η5:η1-C5Me4SiMe2CH2][η5-C5Me4(SiMe3)]TiIII (4) in 75% yield. The crystal structures of 3 and 4 reveal that one SiMe3 group in each of the compounds has been activated by hydrogen abstraction. In centrosymmetric dimer 3, two titanocene−magnesium hydride-bridged units are held together by two methylene groups which link the two Mg atoms via a two-electron−three-center Mg−C−Mg bond. In the mononuclear 4, a regular Ti−CH2 σ-bond (2.204(5) Å) binds the central Ti atom to the η5:η1-C5Me4SiMe2CH2 ligand.

A Non-Metallocene Hydride of Titanium(III)

“…The presence of the hydride was corroborated by infrared spectroscopy. The IR spectrum of 3 displayed a broad absorption at 1274 cm -1 , overlapping with those due to the [NN 2 ] ligand and which can be assigned to the asymmetric stretch of the bridging hydride by comparison with absorptions previously observed for the dimeric titanocenes [μ-η 5 :η 5 -(C 5 H 4 ) 2 ][(η 5 -C 5 H 5 )Ti(μ-H)] 2 , [μ-η 5 :η 5 -(C 5 HMe 3 ) 2 ][(η 5 -C 5 H 2 Me 3 )Ti(μ-H)] 2 , and {[η 5 -C 5 Me 4 SiMe 2 (μ-CH 2 { Mg, Mg })][η 5 -C 5 Me 4 SiMe 3 ]Ti(μ-H) 2 Mg(THF)} 2 . To confirm this assignment, we synthesized the deuteride 3 - ( 2 H) in a manner similar to that of the hydride 3 ; in the mass spectrum, the molecular ion of the deuteride was observed at 734 amu along with an appropriate fragmentation pattern.…”

Bis[η5-tetramethyl(trimethylsilyl)cyclopentadienyl]titanium(II) and Its π-Complexes with Bis(trimethylsilyl)acetylene and Ethylene

“…The starting complex 1 was obtained by the reduction of the titanocene dichloride [{η 5 -C 5 Me 4 (SiMe 3 )} 2 TiCl 2 ] with activated magnesium in THF in the presence of a large excess of bis(trimethylsilyl)acetylene (BTMSA) at −18 °C (Scheme ). At elevated temperature (60 °C), which is commonly used in the synthesis of the nonsilylated analogues of 1 , [(η 5 -C 5 H 5 - n Me n ) 2 Ti(η 2 -Me 3 SiC⋮CSiMe 3 )] ( n = 0−5), 8d, the paramagnetic complexes [{η 5 :η 1 -C 5 Me 4 (SiMe 2 CH 2 )}{η 5 -C 5 Me 4 (SiMe 3 )}Ti III ] ( 4 ) and [{{η 5 -C 5 Me 4 SiMe 2 (μ-CH 2 (Mg,Mg))}{η 5 -C 5 Me 4 (SiMe 3 )}Ti III (μ-H) 2 Mg(THF)} 2 ] ( 5 ) are obtained instead as the major and the minor products, respectively . To avoid the formation of these and some other byproducts, complex 1 , resulting in the form of a THF/BTMSA solution by the low-temperature reduction, has to be separated from excess magnesium at low temperature, as well.…”

“…Compound 2 can be obtained by the reduction of [{η 5 -C 5 Me 4 (SiMe 3 )} 2 TiCl 2 ] by active Mg in THF at room temperature, however, it is strongly contaminated by the impurity described in ref , by the hydride 5 , or by [{η 5 -C 5 Me 4 (SiMe 3 )} 2 TiCl] …”

Effect of the Trimethylsilyl Substituent on the Reactivity of Permethyltitanocene

“…At 60 °C, the temperature which is advantageously used to produce the titanocene−btmse complexes from the titanocene dichlorides in the presence of btmse, , the reaction afforded instead of the btmse complex the intramolecular silylmethylene-bridged paramagnetic complex [Ti III {η 5 :η 1 -C 5 Me 4 (SiMe 2 CH 2 )}{η 5 -C 5 Me 4 (SiMe 3 )}] ( 4 ) as the main product (see Chart ). In the absence of btmse, the reduction afforded mainly the trinuclear paramagnetic complex [{{η 5 -C 5 Me 4 SiMe 2 (μ-CH 2 ( Mg , Mg ))}{η 5 -C 5 Me 4 (SiMe 3 )}Ti III (μ-H) 2 Mg(THF)} 2 ] . Reactions leading to both of the main products have not been elucidated; however, the exclusive activation of the trimethylsilyl groups is their common feature.…”