Silicon compounds metal derivatives

The cobalt compound R3Si Co(CO)4 (LXXI) was historically the first optically active silicon-transition-metal derivative to be prepared 407), using the route of Eq. (133). 

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. 

The second class consists of molecular compounds containing one or more silicon-transition-metal bonds. The first example, Me3SiFe(CO)2-(tjs-CbHb), was prepared in 1956 (359), but nearly 10 years then elapsed before other compounds were described (26, 94). These heralded many more, and now examples are known in which silicon is bonded to almost every transition metal (Fig. 1). Curiously, no Si-Ag compounds have been described there are also no reports of derivatives of lanthanides or actinides. Most work has involved Fe, Co, Pt, Mn, Re, Mo, Ru, and Ni, in roughly decreasing order of frequency. Almost all well-characterized molecular silicon-transition-metal compounds known at present are diamagnetic some possible exceptions are noted in Section II,F. The most recent comprehensive reviews of the area were published in 1973 (134) and 1974 (235), covering the literature until 1971 and 1972, respectively these contain details of earlier reviews. Other surveys of certain aspects have also appeared, two of them very recently (24, 25, 201). 

The method is of limited applicability, since although silyl alkali metal compounds RaSiM are known when RaSi is H2n+iSin (n = 1-5), Me2n+iSi in = 1, 3, 4), and Me Ph3-nSi (n = 0-2), and several dilithium derivatives Li(SiPh2) Li (n = 4-6) have also been described, all are rather difficult to prepare and handle (24). It will be seen that only some of them have yet been used to prepare silicon-transition-metal compounds. 

Entry Metal derivative Silicon compound ment Silicon-metal product... 

Up to the end of 1972, more than 350 compounds containing silicon-transition-metal bonds had been synthesized, but their distribution among the d-block elements is by no means uniform. It can be inferred that the stability of such complexes decreases from right to left in a transition series and with increasing oxidation state of the transition metal. Nevertheless, it is remarkable that no silyl derivatives of the vanadium group have been prepared and that there are few nickel or palladium derivatives, as can be seen in the complete list of compounds given in Section 6. 

Silicon halides (especially the readily available chlorides) are probably the most synthetically useful and versatile monomeric inorganic silicon compounds. They may readily be reduced to hydrides, hydrolyzed to silanols (and subsequently to siloxanes), treated with other protic species such as alcohols, carboxylic acids, amines, and thiols to give SiA)R, Si-0C(0)R, Si NR2, and Si SR species respectively, used to make sUyl pseudohalogen derivatives by treatment with silver or alkali metal salts, for example, treated with sodium... 

The intermediate of the reaction may be the sUyl-alkali metal species, so that the reaction of the silyl-alkah metal derivatives with chlorosUane resulted in the formation of the silicon-silicon bonded compound (equation 58). 

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