Two-Electron Reduction of a Vanadium(V) Nitride by CO To Release Cyanate and Open a Coordination Site

Abstract

We report herein that the terminal nitride complex Na[NV(N[t-Bu]Ar)(3)] (Na[1-VN], Ar = 3,5-Me(2)C(6)H(3)) reacts with CO over the course of 24 h to generate V(N[t-Bu]Ar)(3) (1-V) and sodium cyanate in an isolated yield of 77%. The reaction products were identified using a combination of NMR and IR spectroscopy, and cyanate formation was further confirmed by performing a (13)C labeling experiment. In addition, we report on the synthesis and structural characterization of the isocyanate complex (OCN)V(N[t-Bu]Ar)(3) (1-V(NCO)) to compare its redox chemistry with that of (OCN)Nb(N[t-Bu]Ar)(3) (1-Nb(NCO)). Electrochemical studies of 1-Nb(NCO) and 1-V(NCO) revealed large differences in the M(5+)/M(4+) and M(4+)/M(3+) reduction potentials. Complex 1-V(NCO) displays two redox events in the cyclic voltammogram: a quasireversible event -0.11 V vs Fc/Fc(+) and a reversible event at -1.56 V vs Fc/Fc(+). Complex 1-Nb(NCO) displays two redox events as well: a quasireversible event at -1.1 V and an irreversible event at -2.9 V vs Fc/Fc(+).

DFT Studies on Reactions of CO2 with Niobium and Vanadium Nitride Complexes

“…These calculation results are in good agreement with the experimental observation of (OCN)V(N t BuAr) 3 (4V) + Na → V(N t BuAr) 3 (5V triplet ) + NaOCN. 23 In Figure 7, we see that [Na]1-V + CO lies higher in energy than 6A-V. This calculation result explains the experimental observation that reaction of [Na]1V with CO gives V(N t BuAr) 3 (5V triplet ) + NaOCN.…”

“…The other pathway is related to the isocyanate ligand dissociation, a pathway observed experimentally in the vanadium analogue only (vide infra). 23 The energy profiles calculated for these two pathways are shown in Figure 5. Clearly, the CO extrusion from the triplet species 6A-Nb triplet is energetically inaccessible.…”

“…Experimental results indicated that 4Nb and Na were allowed to stir about 7−8 h to give [Na]1Nb and CO, in which CO was trapped and monitored by Cp*RuCl-(PCy 3 ). 21,23 The equilibrium mentioned above requires interconversion between 6C-Nb and (5-Nb triplet + NaOCN). The interconversion between the two requires an intersystem crossing between the singlet and triplet potential energy surfaces.…”

A journey into the electrochemistry of vanadium compounds

“…V(V) compound was prepared, with one OCN and three anions of (3,5-dimethylphenyl)-tert-butylamine ( t Budman) [190]. The CV of ( t Budman) 3 V(OCN) is marked by two electrochemical events.…”

Formation and Reactivity of the Terminal Vanadium Nitride Functionality

“…A few exemplary and unique reactions mediated by metal nitrides include direct insertion into C-H bonds, [12-14a] bioinspired hydrogenation to form the parent metal amide and ammonia, [6,15,16] complete and incomplete N-atom transfer to form C-N bonds from π-acids (CO, CNR), [16][17][18][19][20] and multi-electron reductive coupling reactions to render metal-dinitrogen complexes. [13,21] Moreover, a new and synthetically important application of molybdenum nitrides is the generation of molybdenum alkylidyne catalysts for alkyne metathesis geared towards the formation of carbon-carbon triple bonds for the synthesis of polymers and other organic commodity reagents.…”