Breaking and\nEntering: Diazene Cleavage and Insertion\ninto U(III)–Si Bonds

Treatment of trivalent [K(18-crown-6)][U(I)<sub>2</sub>{(Si(SiMe<sub>3</sub>)<sub>2</sub>SiMe<sub>2</sub>)<sub>2</sub>O}]\n(<b>1-crown</b>) with aryl diazenes generated a series of uranium(IV)\nspecies of\nthe form [(THF)U(I)<sub>2</sub>{N(R/R′)Si(SiMe<sub>3</sub>)<sub>2</sub>SiMe<sub>2</sub>}<sub>2</sub>O] (R = R′ = Ph (<b>2-Ph</b>), 4-FC<sub>6</sub>H<sub>4</sub> (<b>2-F</b>), 4-MeC<sub>6</sub>H<sub>4</sub> (<b>2-Tol</b>), 4-OMeC<sub>6</sub>H<sub>4</sub> (<b>2-Mes</b>), and R = 4-MeC<sub>6</sub>H<sub>4</sub>, R′ = Ph (<b>2-TolPh</b>). Activation of an ortho-substituted\ndiazene, (2,4,6-Me<sub>3</sub>C<sub>6</sub>H<sub>2</sub>N)<sub>2</sub> (MesNNMes), forms <b>2-Mes</b>, [K(18-crown-6)][U(I)<sub>3</sub>{N(Mes)Si(SiMe<sub>3</sub>)<sub>2</sub>SiMe<sub>2</sub>}<sub>2</sub>O] (<b>2-MesKI</b>), and ([K(18-crown-6][U(I)(NMes)(N[Mes]-3,3,5,5-Me<sub>4</sub>2,2,6,6-(SiMe<sub>3</sub>)<sub>4</sub>-tetrasil-3-oxane)])\n(<b>3-Mes</b>). The increased sterics of this <i>ortho</i>-substituted substrate slowed insertion, facilitating the observation\nof <b>3-Mes</b> by in situ NMR spectroscopy. The redox potentials\nof the aryl diazenes (R–NN–R′) were studied\nusing cyclic voltammetry to elucidate their electronic contributions\ntoward their reactivity with <b>1-crown</b>. The reaction of <b>1-crown</b> and (<i>Z</i>)-11,12-dihydrodibenzo[<i>c</i>,<i>g</i>][1,2]diazocine is also described, forming\nthe [(THF)U(I)<sub>2</sub>{[N(C<sub>7</sub>H<sub>6</sub>)]<sub>2</sub>Si(SiMe<sub>3</sub>)<sub>2</sub>SiMe<sub>2</sub>}<sub>2</sub>O] (<b>2-diazonine</b>) and {(THF)<sub>2</sub>U(I)<sub>2</sub>[N(C<sub>7</sub>H<sub>6</sub>)]<sub>2</sub>}<sub>2</sub> (<b>4</b>)\ndimers.