A Nitridoniobium(V) Reagent That Effects Acid Chloride to Organic Nitrile Conversion:  Synthesis via Heterodinuclear (Nb/Mo) Dinitrogen Cleavage, Mechanistic Insights, and Recycling

Abstract

The transformation of acid chlorides (RC(O)Cl) to organic nitriles (RC[triple bond]N) by the terminal niobium nitride anion [N[triple bond]Nb(N[Np]Ar)3]- ([1a-N]-, where Np = neopentyl and Ar = 3,5-Me2C6H3) via isovalent N for O(Cl) metathetical exchange is presented. Nitrido anion [1a-N]- is obtained in a heterodinuclear N2 scission reaction employing the molybdenum trisamide system, Mo(N[R]Ar)3 (R = t-Bu, 2a; R = Np, 2b), as a reaction partner. Reductive scission of the heterodinuclear bridging N2 complexes, (Ar[R]N)3Mo-(mu-N2)Nb(N[Np]Ar)3 (R = t-Bu, 3b; R = Np, 3c) with sodium amalgam provides 1 equiv each of the salt Na[1a-N] and neutral N[triple bond]Mo(N[R]Ar)3 (R = t-Bu, 2a-N; R = Np, 2b-N). Separation of 2-N from Na[1a-N] is readily achieved. Treatment of salt Na[1a-N] with acid chloride substrates in tetrahydrofuran (THF) furnishes the corresponding organic nitriles concomitant with the formation of NaCl and the oxo niobium complex O[triple bond]Nb(N[Np]Ar)3 (1a-O). Utilization of 15N-labeled 15N2 gas in this chemistry affords a series of 15N-labeled organic nitriles establishing the utility of anion [1a-N]- as a reagent for the 15N-labeling of organic molecules. Synthetic and computational studies on model niobium systems provide evidence for the intermediacy of both a linear acylimido and niobacyclobutene species along the pathway to organic nitrile formation. High-yield recycling of oxo 1a-O to a niobium triflate complex appropriate for heterodinuclear N2 scission has been developed. Specifically, addition of triflic anhydride (Tf2O, where Tf = SO2CF3) to an Et2O solution of 1a-O provides the bistriflate complex, Nb(OTf)2(N[Np]Ar)3 (1a-(OTf)2), in near quantitative yield. One-electron reduction of 1a-(OTf)2 with either cobaltocene (Cp2Co) or Mg(THF)3(anthracene) provided the monotriflato complex, Nb(OTf)(N[Np]Ar)3 (1a-(OTf)), which efficiently regenerates complexes 3b and 3c when treated with the molybdenum dinitrogen anions [N2Mo(N[t-Bu]Ar)3]- ([2a-N2]-) or [N2Mo(N[Np]Ar)3]- ([2b-N2]-), respectively.

Molecular titanium nitrides: nucleophiles unleashed

“…A similar transformation involving N for O/Cl exchange was originally reported by Cummins using nitride complexes such as NW(N[ i Pr]Ar) 3 (Ar = 3,5-Me 2 C 6 H 3 ) or the salt [Na][NNb(N[Np]Ar) 3 ] (Np = CH 2 t Bu). 31,86 Likewise, Veige more recently reported N-atom transfer to various acid chlorides using {[ t BuOCO]MoN]Na(DMF)} 2 [ t BuOCO 3– = 2,6-C 6 H 3 (6- t BuC 6 H 3 O) 2 ]. In their studies the authors were able to isolate the acylimido intermediate [ t BuOCO]MoNC(O) t Bu, and mechanistically probe for an azametallacylobutene species en route to N for O exchange.…”

Early-Transition-Metal-Mediated Activation and Transformation of White Phosphorus

“…While much research has been targeted at the direct incorporation of N 2 -derived nitrogen atoms into main group molecules, the analogous chemistry with elemental phosphorus has been explored far less. [69][70][71][72][73][74] The incorporation of P 4 -derived phosphorus atoms into organic frameworks by P-atom transfer reactions mediated by transition-metal complexes could circumvent the need for PCl 3 …”

Dinitrogen‐Molybdenum Complex Induces Dinitrogen Cleavage by One‐Electron Oxidation

“…TheM o À Nb ond distances (1.653-(4), 1.640(5) )f or 2 are within the typical range for Mo N bonds (ca. 1.65 ), and MoÀP( 2.4386(9), 2.4927(8), 2.4568-(9), 2.3754 (11) )are also within the typical range for MoÀP (ca. 2.45 ).…”