Group IV-B Derivatives Si, Ge, Sn of o-Carborane

A primary objective of the syntheses of 1,2-bis(chlorodimethylsilyl)carborane 2 has been the incorporation of the B10C2 carborane nuclei into the backbone of essentially inorganic polymers. Heying etal.26 has prepared compound 2 through the reaction of o-CioH10C2Li2 and 2 equiv. of Me2SiCl2. 

When 1,2-bis(chlorodimethylsilyl)carborane 2 was treated with ammonia, an amminolysis reaction occurred to give the cyclic tetramethyldisilaazane 3. The ease with which this reaction occurs to form five-membered ring bears notice. Hydrolysis of 2 gives cyclic siloxane compound 4. Utilization of the same general 

Complex 12 was found to be a good reactant in the double-silylation reaction. Thus, thermolysis of a toluene solution of 12 and diphenylacetylene at 120°C for 12 h afforded 5,6-carboranylene-1,1,4,4-tetramethyl-2,3-diphenyl-1,4-disilacyclohex-2-ene 13. When 1-hexyne was employed in the reaction with 12 under the same reaction conditions, the five-membered disila ring compound 18 was isolated. A key feature in the h NMR spectrum of 18 includes a singlet at 6.24 ppm assigned to the vinyl proton. A characteristic high-frequency 13C NMR resonance at 138.50ppm provides evidence for a tethered sp2 carbon atom between the two silicon atoms. 

Thermolysis of 12 with frans-cinnamaldehyde afforded the insertion compound 19, formed through the di-insertion of two carbonyl ligands into the C—Si bond of 12. The reaction of 12 with fumaronitrile yielded the cyclization product 20. X-ray study revealed 20 to be a cyclization product which contains two types of disilyl moieties, imino and N,N-bis(silyl)amino, which are connected by a five-membered ring. 

The disilanickela compound 21 is not effective in the nickel-catalyzed double silylation reaction with styrene. However, the stoichiometric reaction of 21 with styrene afforded 4,5-carboranylene-l,l,3,3-tetramethyl-2-phenylmethylene-1,3-disilacyclopentane 29. A key feature in the 111 NMR spectmm of 29 includes a singlet at 7.71 ppm assigned to the vinyl proton. A characteristic low-frequency 13C NMR resonance at 139.75 ppm provides evidence for a tethered carbon atom of the two silicon moieties. Unambiguous confirmation was provided by X-ray crystallographic analysis of 29. 

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