SiSi Double Bonds: Synthesis of an NHC‐Stabilized Disilavinylidene

An efficient two‐step synthesis of the first NHC‐stabilized disilavinylidene (Z)‐(SIdipp)SiSi(Br)Tbb ( 2 ; SIdipp=C[N(C₆H₃‐2,6‐iPr₂)CH₂]₂, Tbb=C₆H₂‐2,6‐[CH(SiMe₃)₂]₂‐4‐tBu, NHC=N‐heterocyclic carbene) is reported. The first step of the procedure involved a 2:1 reaction of SiBr₂(SIdipp) with the 1,2‐dibromodisilene (E)‐Tbb(Br)SiSi(Br)Tbb at 100 °C, which afforded selectively an unprecedented NHC‐stabilized bromo(silyl)silylene, namely SiBr(SiBr₂Tbb)(SIdipp) ( 1 ). Alternatively, compound 1 could be obtained from the 2:1 reaction of SiBr₂(SIdipp) with LiTbb at low temperature. 1 was then selectively reduced with C₈K to give the NHC‐stabilized disilavinylidene 2 . Both low‐valent silicon compounds were comprehensively characterized by X‐ray diffraction analysis, multinuclear NMR spectroscopy, and elemental analyses. Additionally, the electronic structure of 2 was studied by various quantum‐chemical methods.     

A Bis(silaselenone) with Two Donor‐Stabilized SiSe Bonds from an Unexpected Stereoconvergent Hydrolysis of a Diselenadisiletane

SiSe matters : Diselenadisiletane 2 , formed from direct reaction of a racemic silylene 1 with elemental selenium, gives the first bis(silaselenone) upon hydrolysis with water ( 3 ; see picture, C gray, H white, N blue, O red, Se purple, Si green; d(Si?Se)=215 pm). The reaction is stereoconvergent: only racemic forms of 3 are obtained from a mixture of racemic and meso forms of 2 .