Bis(silylene)-Mediated N═N Bond Scission of Diazo Compounds.

Diazo compounds, >C═N═N, typically undergo C═N bond cleavage to form carbenes and N2, whereas direct N═N bond breaking remains exceedingly rare in main-group chemistry. We report the N═N bond scission of diazodiarylmethanes, Ar2C═N═N (Ar = phenyl, Ar2C = 9,9-fluorendiyl), mediated by a chelating bis-NHSi (NHSi = N-heterocyclic silylene). Three bis-NHSi scaffolds with tunable Si···Si distances were examined: While XT(LSi:)2 (XT = 9,9-dimethyl-9H-xanthene-4,5-diyl, L = PhC(tBuN)2) and PhN(LSi:)2 lead to end-on addition products with partial N═N bond activation, the carborane-based CB(LSi:)2 (CB = 1,2-C2B10H10) engenders complete N═N bond cleavage to afford isolable disilicon nitrido imino species containing a Si═N─Si─N═CAr2 unit that hydrolyzes to Ar2C═NH, NH3, SiO2, C2B10H12, and LH. According to density functional theory (DFT) calculations, the N═N cleavage stems from a unique cooperative interaction of the two divalent silicon centers.