Metallo siloxane

Generation, Structural Characterization, and Transformation to Metallo-Siloxanes ... 

Metallo-Silanols and Metallo-Siloxanes, Part 5. - Part 4 W. Malisch, K. Grun, N. Gunzelmaim, S. Moller, R. Lankat, J. Reising, M. Neumayer, O. Fey, in Selective Reactions of Metal Activated Molecules (Eds. H. Werner, J. Sundermeyer), Vieweg Verlag, Braunschweig, in press in addition Part 30 of the series Synthesis and Reactivity of Silicon Transition Metal Complexes. 

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 silanol 3 shows the expected reactivity toward di- and trimethylchlorosilane, respectively. In the presence of NEt3 as an auxiliary base, the corresponding metallo-siloxanes 4a,b are obtained in good yields [72% (4a), 63% (4b)] as pale yellow powders (Eq. 1). 

Synthesis of Polychlorinated Metallo-Siloxanes via Metalation of Polychlorosiloxanes... 

The metallo-siloxane 3a bears the possibility of a regiospecific exchange reaction as the electrophilicity of the a-Si-atoms is decreased due to the electron donating influence of the transition metal fragment. For this reason, the methanolysis reaction of 5a with three equivalents of MeOH involves the y-silicon-atom to yield preferentially the metallo-trimethoxydisiloxane 6, which can be converted into the pentamethoxydisiloxane 7 by using methanol as solvent. 

Synthesis of Polychlorinated Metallo-Siloxanes via Reaction of the Ferrio-Silanol Cp(0C)2SiMe20H (12) with Hexachlorodisiloxane (2a)... 

Metallo-Siloxanes with three or more Si-atoms in the siloxane ftamework are in addition accessible by reaction of the ferrio-dimethylsilanol 12 with hexachlorodisiloxane (2a) in diethylether. 13 is obtained in a yield of 75%. 

Part 34 of the series MetalloSilanoIs and Metallo-Siloxanes . In addition. Part 63 of the series "Synthesis and Reactivity of Silicon Transition Metal Complexes. Part 62/33, see [1]. 

Part 16 in the series "Metallo-Silanols and Metallo-Siloxanes". In addition. Part 42 of the series "Synthesis and Reactivity of Silicon Transition Metal Complexes". Part 15/41, see W. Malisch, M. Neumayer, K. Perneker, N. Gunzelmann, K. Roschmann, in Organosilicon Chemistry III From Molecules to Materials (Eds. N. Auner, J. Weis), VCH, Weinheim, 1997, p. 407. 

The condensation of metallo-silanols with organochlorosilanes [4] is a common method of preparing metallo-siloxanes. It has now been applied to gain diastereomerically pure ferrio-siloxanes RS,SR)-3a-c by interaction of the ferrio-silanol (RS,SR)-1 with the organochlorosilanes 2a-c in ether or benzene at room temperature (Eq. 1),... 

Keywords Metallo-Siloxanes / Photoinduced Cyclization / Photoinduced Metallation... 

Metal-fragment substituted silanols are known to be stable towards self-condensation due to the strongly reduced acidity of the Si-OFI proton [2], However, these species show ready reaction with organochlorosilanes RsSiCl, which gives access to metallo-siloxanes [2], constituting attractive models for transition metal complexes anchored on silica surfaces. 

Introduction of Si-H functionality at the y-silicon of these metallo-siloxanes promises a rich area concerning consecutive reactions, especially oxidative addition to coordinatively unsatured metal centers [3],... 

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