A Remarkable End-On Activation of Diazoalkane and Cleavage of Both C-Cl Bonds of Dichloromethane with a Silylene to a Single Product with Five-Coordinate Silicon Atoms

The 1:1 reaction of benzamidinato-stabilized chlorosilylene PhC(NtBu)(2)SiCl (1) with CH(SiMe3)N-2 resulted in the formation of colorless [PhC(NtBu)(2)Si(Cl){N2CH(SiMe3)}}(2) (2), which consists of a four-membered Si2N2 ring. Surprisingly, N-2 elimination from the diazoalkane did not occur, but rather an end-on activation of the nitrogen was observed. For the mechanism, we propose the formation of a silaimine complex A as an intermediate, which is formed during the reaction and dimerized under [2 + 2] cydoaddition to 2. In contrast, treatment of 1 with dichloromethane afforded a 2:1 product, [{PhC(NtBu)(2)Si(Cl-2)}(2)CH2} (3), which is obviously formed by oxidative addition under cleavage of both C-Cl bonds and formation of two Si-Cl and two Si-C bonds. Both silicon atoms in 3 are five-coordinate. Compounds 2 and 3 were characterized by single-crystal X-ray studies, multinuclear NMR spectroscopy, and El-mass spectrometry.