Azobenzenyl Calcium Complex: Synthesis and Reactivity Studies of a Ca(I) Synthon.

Attempted preparation of a low-valent Ca(I) complex by reduction of Ca iodide precursor [LCaI(THF)] 2 ( 1 ) (L = [CH 3 C(NAr)CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ] - , Ar = 2,6- i Pr 2 C 6 H 3 ), with KC 8 led to isolation of a dinuclear calcium azaallyl complex {[H 2 CC(NAr)CHC(CH 3 )(NCH 2 CH 2 N(CH 3 ) 2 )]Ca(THF)} 2 ( 2 ). Alternatively, reaction of 1 with KC 8 in the presence of azobenzene gives an azobenzenyl calcium complex LCa(PhNNPh)(THF) ( 3 ). The electron paramagnetic resonance and UV-vis spectra of complex 3 suggest that the (PhNNPh) moiety should be regarded as a radical anion. Complex 3 can react with Me 3 SiN 3 , Me 3 SiCHN 2 , CS 2 , W(CO) 6 , elemental sulfur, and AgBr, resulting in the formation of the azido complex [LCaN 3 (THF)] 2 ( 5 ), isonitril complex {LCa[CNN(Si(CH 3 ) 3 )]} 2 ( 6 ), dimeric bis(thiolate) complex {[S 2 CC(CMe(NAr))C(Me)NCH 2 CH 2 NMe 2 ]Ca(DME)} 2 ( 7 ), metallocyclic carbene complex {[OC(W(CO) 5 )N(C 6 H 5 )]Ca(THF) 3 } 2 ( 8 ), bis(thiolate) complex {[S 2 C(CMe(NAr))C(Me)NCH 2 CH 2 NMe 2 ]Ca(THF)} 2 ( 9 ), and bromide complex [LCaBr(THF)] 2 ( 10 ). Additional insights on the reaction process resulting in the formation of complex 7 are provided by density-functional theory studies. These results demonstrate that the (PhNNPh) •- radical anion can serve as a very potent one-electron donor, and 3 acts as a low-valent calcium(I) synthon.