Silicon transition-metal

Investigations of silicon-metal systems are of fundamental interest, since stable coordination compounds with low valent silicon are still rare [64], and furthermore, silicon transition-metal complexes have a high potential for technical applications. For instance, coordination compounds of Ti, Zr, and Hf are effective catalysts for the polymerization of silanes to oligomeric chain-silanes. The mechanism of this polymerization reaction has not yet been fully elucidated, but silylene complexes as intermediates have been the subject of discussion. Polysilanes find wide use in important applications, e.g., as preceramics [65-67] or as photoresists [68-83],... 

Some aspects of silicon-transition metal chemistry. B. J. Aylett, Adv. Inorg. Chem. Radiochem., 1982, 25, 1-133 (458). 

Organometallic Complexes with Silicon-Transition Metal or Silicon-Carbon-Transition Metal Bonds... 

B. The Synthesis of Compounds with Silicon-Transition Metal... 

E. Silicon-Transition Metal Complexes Having Special Structural... 

Reviews Relevant to Silicon-Transition Metal Chemistry... 

ORGANOMETALLIC COMPLEXES WITH SILICON-TRANSITION METAL BONDS... 

Silicon-transition metal chemistry is a relatively new area. The work of Hein and his associates (1941) on Sn—Co derivatives established the possibility of forming bonds between a Group IVB metal and a transition element 139), but it was another fifteen years before CpFe(CO)2SiMej 203), the first of many silyl derivatives, was synthesized. The interest in these compounds derives from (1) comparison with the corresponding alkyl- and Ge-, Sn-, and Pb- transition metal (M) complexes, including the role of ir-back-bonding from filled d orbitals of M into empty d orbitals on Si (or other Group IVB metal), and (2) expectation of useful catalytic properties from such heteronuclear derivatives. 

Silicon-Transition Metal Complexes with Special Structural Features... 

No new silicon-transition metal bonds are formed in these reactions, although new compounds containing such bonds are produced. Details are in Section II,C,l-3. 

Selected Distances and Angles eor Silicon-Transition Metal Complexes... 

It has been noted (Section II,B,1) that reactions between transition metal carbonyl anions and silicon halides often fail to produce species containing silicon-transition metal bonds, and that such failure has been ascribed to nucleophilic attack by carbonyl oxygen. It is therefore interesting that compounds containing Si—O—C—transition metal linkages have recently been isolated from such reactions [Eqs. (105) (R = Me, Ph) 183) and (106)... 

Hofler, F. The Chemistry of Silicon-Transition-Metal Compounds. 50, 129-165 (1974). 

More recently, it was the seminal work of Aitken, Harrod and Samuel which showed that Group IV metallocene compounds catalyzed the dehydrogenative coupling of primary silanes, RSiH3, to give polysilanes of relatively low molecular weight, [RSiH] [8], that attracted many others into the silicon/transition metal chemistry field [9],... 

Hofler, F, The Chemistry of Silicon-Transition-Metal Compounds. 50, 129-165 (1974). Hogeveen, H., and van Kruchten, E. M. G. A. Wagner-Meerwein Rearrangements in Long-lived Polymethyl Substituted Bicyclol3.2.0]heptadienyl Cations. 80, 89-124 (1979). 

The chromium complexes are proved to be silanediyl complexes, as shown by the silicon-transition metal bond lengths (Table 5) and by the extreme low field shift of the 29Si NMR signals (124.9 and 121.2) at 22 °C for R = H and CH2NMe2, respectively (Table 6). The 29Si NMR shifts of these complexes are temperature-dependent due to the hindered rotation of the phenyl ring and dynamic coordination of the nitrogens to the Si atom. 

It is possible to selectively cleave a Si—C(Cp )bond even in the presence of silicon-transition metal bonds as shown in reactions with nucleophiles, electrophiles and chlorinated hydrocarbons (equations 41 and 42)92,93. 

---