Revelations in Dinitrogen Activation and Functionalization by Metal Complexes

Relaxation and Dissociation Following Photoexcitation of the (μ-N2)[Mo(N[t-Bu]Ar)3]2 Dinitrogen Cleavage Intermediate

“…13 Using ultraviolet excitation, Kunkely and Volger recently demonstrated dissociation of the nitrogen bond in a μ-N 2 diosmium cation. 16 In the longest wavelength activation reported, Curley 3 ] 2 leads to breaking of both NN and Mo−NN bonds with roughly equal branching. 17,18 The three-coordinate molybdenum(III) complex Mo(N[tBu]Ar) 3 reacts readily at mild temperatures and pressures (−35 to 30°C, 1 atm) to cleave dinitrogen via the (μ-N 2 )[Mo(N[tBu]Ar) 3 ] 2 intermediate.…”

“…16 In the longest wavelength activation reported, Curley 3 ] 2 leads to breaking of both NN and Mo−NN bonds with roughly equal branching. 17,18 The three-coordinate molybdenum(III) complex Mo(N[tBu]Ar) 3 reacts readily at mild temperatures and pressures (−35 to 30°C, 1 atm) to cleave dinitrogen via the (μ-N 2 )[Mo(N[tBu]Ar) 3 ] 2 intermediate. 10,11,19 The complete reaction path, starting with N 2 and Mo(N[t-Bu]Ar) 3 , is illustrated in Scheme 1.…”

“…Experimentally, there have been three reports of photolytic nitrogen cleavage products from such complexes. Floriani and co-workers concluded that cleavage of the nitrogen bond was the initial step in the photochemical reaction of thermally stable (μ-N 2 )[Mo(Mes) 3 ] 2 (Mes = 2,4,6-Me 3 C 6 H 2 ) based on conversion to (Mes) 3 Mo−N−Mo(Mes) 3 under UV illumination. 13 Using ultraviolet excitation, Kunkely and Volger recently demonstrated dissociation of the nitrogen bond in a μ-N 2 diosmium cation.…”

“…17,18 The three-coordinate molybdenum(III) complex Mo(N[tBu]Ar) 3 reacts readily at mild temperatures and pressures (−35 to 30°C, 1 atm) to cleave dinitrogen via the (μ-N 2 )[Mo(N[tBu]Ar) 3 ] 2 intermediate. 10,11,19 The complete reaction path, starting with N 2 and Mo(N[t-Bu]Ar) 3 , is illustrated in Scheme 1. Recently, the (μ-N 2 )[Mo(N[t-Bu]Ar) 3 ] 2 intermediate was isolated and characterized via X-ray crystallography, and its electronic structure was studied using density functional theory.…”

“…17 Investigation of the compound's intense visible absorption band centered at 2.39 eV led to the discovery of a photochemical reaction that cleaves the metal nitrogen bond, with subsequent extrusion of N 2 and reformation of the starting complex. This reaction was determined to compete with photochemical NN cleavage based on bulk photolysis at −78°C that gives an approximate 1:1 mixture of NMo(N[tBu]Ar) 3 and Mo(N[t-Bu]Ar) 3 with a primary quantum yield of 0.05. Initial transient absorption spectroscopy has shown that the photoreaction is complete in less than 10 ns, the time resolution of the experiment.…”