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(N<i>t</i>Bu)₂SiCl (<b>1</b>) with CH­(SiMe₃)­N₂ resulted in the formation of colorless [PhC­(N<i>t</i>Bu)₂Si­(Cl)­{N₂CH­(SiMe₃)}]₂ (<b>2</b>), which consists of a four-membered Si₂N₂ ring. Surprisingly, N₂ 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 <b>A</b> as an intermediate, which is formed during the reaction and dimerized under [2 + 2] cycloaddition to <b>2</b>. In contrast, treatment of <b>1</b> with dichloromethane afforded a 2:1 product, [{PhC­(N<i>t</i>Bu)₂Si­(Cl₂)}₂CH₂] (<b>3</b>), 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 <b>3</b> are five-coordinate. Compounds <b>2</b> and <b>3</b> were characterized by single-crystal X-ray studies, multinuclear NMR spectroscopy, and EI-mass spectrometry

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(N<i>t</i>Bu)₂SiCl (<b>1</b>) with CH­(SiMe₃)­N₂ resulted in the formation of colorless [PhC­(N<i>t</i>Bu)₂Si­(Cl)­{N₂CH­(SiMe₃)}]₂ (<b>2</b>), which consists of a four-membered Si₂N₂ ring. Surprisingly, N₂ 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 <b>A</b> as an intermediate, which is formed during the reaction and dimerized under [2 + 2] cycloaddition to <b>2</b>. In contrast, treatment of <b>1</b> with dichloromethane afforded a 2:1 product, [{PhC­(N<i>t</i>Bu)₂Si­(Cl₂)}₂CH₂] (<b>3</b>), 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 <b>3</b> are five-coordinate. Compounds <b>2</b> and <b>3</b> were characterized by single-crystal X-ray studies, multinuclear NMR spectroscopy, and EI-mass spectrometry