Tungsten-silene complex

In 1988, Tilley and coworkers first succeeded in the synthesis of a ruthenium-silene complex by the reaction of Cp Ru(PR3)Cl with a Grignard reagent, and the structure was confirmed by X-ray crystallography (Eq. 9) [10]. They later synthesized an iridium complex in a similar manner (Eq. 10) [11]. Berry synthesized a tungsten-silene complex by treatment of a tungsten-chloride complex with Mg (Eq. 11) [12]. Although reactions of transition metal-silene complexes with Mel, HX, and MeOH have been reported, little is known about their reactivities [11,12]. 

Since silene is an unstable species, various transition metal-silene complexes coordinated by the silicon-carbon double bond have been reported. In 1970, Pannel reported the formation of silene by irradiation of an iron complex (Eq. 6) [8]. He obtained an iron-TMS complex that was apparently formed from silene and an iron-hydride complex generated from the starting iron complex by /3-hydrogen elimination [8]. Wrighton confirmed the existence of tungsten-and iron-silene complexes by examination of NMR spectra obtained at low temperature (Eqs. 7 and 8) [9]. 

Silene-transition metal complexes were proposed by Pannell121 for some iron and tungsten systems, and such species were observed spectroscopically by Wrighton.122,123 Thus intermediates such as 33 have been proposed in the preparation of carbosilane polymers from hydrosilanes,124 both as intermediates in the isotope scrambling observed to occur in similar ruthenium hydride systems125 126 and in the 5N2 addition of alkyllithium species to chlorovinylsilanes.47... 

The chemistry of silylene-metal complexes has developed in quite another direction, however, from reactions of disilyl-metal complexes, leading to complexes of otherwise unstable disilenes such as Me2Si=SiMe2. Molybdenum and tungsten complexes have been particularly well investigated by Berry and co-workers,103 and platinum complexes have also been isolated.104 Readers interested in this field are directed to a 1992 review of silylene, silene, and disilene-metal complexes.105... 

While the germanium-containing tungsten complex 166 rearranged to 167 on photolysis, the isomeric species 168 directly eliminated the silene Me2Si=CH2 yielding 169 (Scheme 26)80. 

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