Hafnium complexes silyl

F. Hoffmann und G. Roewer reported on reactions of cyclohexasilylpotassium with transition metal compounds, and C. Marschner described a Cp-fiee hafnium silyl-substituted complex. A series of four papers from the group of W. Malisch deal with the description of silanol functionalities in organometallic iron and tungsten complexes and the synthesis of perchlorinated metallo siloxanes. 

The reaction of 1 with hafnium- or zirconium tetrachloride in toluene gave octahedrally coordinated hafnium- (3) and zirconium- (4) trichlorotris(trimethylsilyl)silyl tmen complexes (Eq.3) [3]. 

Eq.3. Synthesis of hafnium and zirconium trichlorotris(tiimethylsilyl)silyl complexes (3,4). 

Product 5 was subjected to X-ray diffraction analysis (Fig. 2 and Table 2) [6]. The structure was found to be an octahedrally coordinated metal dichloro complex with the two bidentate ligands occupying the equatorial positions. The observed stereochemistry can be considered to be caused by the trans-effect of the tmen group [3], which activates the two chloro atoms of the hafnium tetrachloride in equatorial position and makes them susceptible to the nucleophilic attack by the silyl dianion. 

This reaction has been extended to the reaction between aldehydes and alkenyl complexes of boranes, silanes, and stannes to give allylic alcohols, " where the reaction with alkenyl complexes of silanes is known as the silyl-Prins reaction. In addition, several Lewis acids-mediated or -promoted Prins reactions have recently been developed, including the application of TMSI, hafnium (IV) bis(perfluorooctanesulfonyl)amides (in fluorous biphase system),iron (III) species," and 2,6-di-f rf-butylphenoxy(difluoro)borane. J... 

Sadow AD, Tilley TD (2003) Cationic hafnium silyl complexes and their enhanced reactivity in c-bond metathesis processes with Si-H and C-H bonds. J Am Chem Soc 125 9462... 

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