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)] () (L = [CHC(NAr)CHC(CH)NCHCHN(CH)], Ar = 2,6-PrCH), with KC led to isolation of a dinuclear calcium azaallyl complex {[HCC(NAr)CHC(CH)(NCHCHN(CH))]Ca(THF)} (). Alternatively, reaction of with KC in the presence of azobenzene gives an azobenzenyl calcium complex LCa(PhNNPh)(THF) (). The electron paramagnetic resonance and UV-vis spectra of complex suggest that the (PhNNPh) moiety should be regarded as a radical anion. Complex can react with MeSiN, MeSiCHN, CS, W(CO), elemental sulfur, and AgBr, resulting in the formation of the azido complex [LCaN(THF)] (), isonitril complex {LCa[CNN(Si(CH))]} (), dimeric bis(thiolate) complex {[SCC(CMe(NAr))C(Me)NCHCHNMe]Ca(DME)} (), metallocyclic carbene complex {[OC(W(CO))N(CH)]Ca(THF)} (), bis(thiolate) complex {[SC(CMe(NAr))C(Me)NCHCHNMe]Ca(THF)} (), and bromide complex [LCaBr(THF)] (). Additional insights on the reaction process resulting in the formation of complex 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 acts as a low-valent calcium(I) synthon.