Abstract
Diazo compounds, >C═N═N, typically undergo C═N bond cleavage to form carbenes and N(2), whereas direct N═N bond breaking remains exceedingly rare in main-group chemistry. We report the N═N bond scission of diazodiarylmethanes, Ar(2)C═N═N (Ar = phenyl, Ar(2)C = 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-C(2)B(10)H(10)) engenders complete N═N bond cleavage to afford isolable disilicon nitrido imino species containing a Si═N─Si─N═CAr(2) unit that hydrolyzes to Ar(2)C═NH, NH(3), SiO(2), C(2)B(10)H(12), 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.