Vanadium nitride functionalization and denitrogenation by carbon disulfide and dioxideElectronic supplementary information (ESI) available: synthetic, spectroscopic, analytical, and computational results for all new complexes. Fig. S1: frontier orbitals of model anions: See http://www.rsc.org/suppdata/cc/b1/b111550m/
Abstract:A dramatic difference in behavior is observed for the dithiocarbamate and carbamate complexes [Ar(But)N]3V(NCE2)Na(THF)2(E = S or O, respectively), prepared from the corresponding nitride species ([Ar(But)N]3V identical to NNa)2 by way of a nucleophilic addition reaction involving carbon disulfide or dioxide, and is rationalized with the aid of DFT calculations.
“…Proton NMR studies showed that the formation of 4 occurs immediately even at low temperature, and it was not possible to isolate any intermediate. Similar reactivity has been reported for a terminal V(V) nitride, but in that case the decomposition was slower and the dithiocarbamate intermediate was isolated . However, the formation of 4 involves oxidation of the metal center from U(III) to U(IV), and therefore, additional products must be formed that remain unidentified.…”
The reduction of the nitride-bridged diuranium(IV) complex Cs[{U(OSi(O t Bu) 3 ) 3 } 2 (μ-N)] affords the first example of a uranium nitride complex containing uranium in the +III oxidation state. Two nitride-bridged complexes containing the heterometallic fragments Cs 2 [ ------
“…Proton NMR studies showed that the formation of 4 occurs immediately even at low temperature, and it was not possible to isolate any intermediate. Similar reactivity has been reported for a terminal V(V) nitride, but in that case the decomposition was slower and the dithiocarbamate intermediate was isolated . However, the formation of 4 involves oxidation of the metal center from U(III) to U(IV), and therefore, additional products must be formed that remain unidentified.…”
The reduction of the nitride-bridged diuranium(IV) complex Cs[{U(OSi(O t Bu) 3 ) 3 } 2 (μ-N)] affords the first example of a uranium nitride complex containing uranium in the +III oxidation state. Two nitride-bridged complexes containing the heterometallic fragments Cs 2 [ ------
“…Thus is completed a synthetic cycle for element (P 4 ) activation, phosphaalkyne synthesis by metathetical P-atom transfer, and deoxygenative recycling of the ultimate niobium oxo product. As demonstrated previously for C−C and C−N ,, triple bonds, C−P triple-bond formation is now shown to be available via metathetical exchange on a low-coordinate, d 0 transition metal platform.…”
Reported herein is a new, metathetical P for O(Cl) exchange mediated by an anionic niobium phosphide complex that furnished phosphaalkynes (RCP) from acid chlorides (RC(O)Cl) under mild conditions. The niobaziridine hydride complex, Nb(H)(tBu(H)C=NAr)(N[Np]Ar)2 (1, Np = neopentyl, Ar = 3,5-Me2C6H3), has been shown previously to react with elemental phosphorus (P4), affording the mu-diphosphide complex, (mu2:eta2,eta2-P2)[Nb(N[Np]Ar)3]2, (2), which can be subsequently reduced by sodium amalgam to the anonic, terminal phosphide complex, [Na][PNb(N[Np]Ar)3] (3). It is now shown that treatment of 3 with either pivaloyl (t-BuC(O)Cl) or 1-adamantoyl (1-AdC(O)Cl) chloride provides the thermally unstable niobacyles, (t-BuC(O)P)Nb(N[Np]Ar)3 (4-t-Bu) and (1-AdC(O)P)Nb(N[Np]Ar)3 (4-1-Ad), which are intermediates along the pathway to ejection of the known phosphaalkynes t-BuCP (5-t-Bu) and 1-AdCP(5-1-Ad). Phosphaalkyne ejection from 4-t-Bu and 4-1-Ad proceeds with formation of the niobium(V) oxo complex ONb(N[Np]Ar)3 (6) as a stable byproduct. Preliminary kinetic measurements for fragmentation of 4-t-Bu to 5-t-Bu and 6 in C6D6 solution are consistent with a first-order process, yielding the thermodynamic parameters DeltaH = 24.9 +/- 1.4 kcal mol-1 and DeltaS = 2.4 +/- 4.3 cal mol-1 K-1 over the temperature range 308-338 K. Separation of volatile 5-t-Bu from 6 after thermolysis has been readily achieved by vacuum transfer in yields of 90%. Pure 6 is recovered after vacuum transfer and can be treated with 1.0 equiv of triflic anhydride (Tf2O, Tf = O2SCF3) to afford the bistriflate complex, Nb(OTf)2(N[Np]Ar)3 (7), in high yield. Complex 7 provides direct access to 1 upon reduction with magnesium anthracene, thus completing a cycle of element activation, small-molecule generation via metathetical P-atom transfer, and deoxygenative recycling of the final niobium(V) oxo product.
“…We postulated that bending of the linear acylimido moiety at nitrogen afforded an unobserved tungstacyclobutene species susceptible to retro-[2 + 2] fragmentation in a manner reminiscent of alkyne metathesis by Schrock-type alkylidyne complexes . A similar intramolecular mechanism was proposed for thiocyanate ion ([SCN] - ) formation upon reaction of the nitrido vanadium anion [N⋮V(N[ t -Bu]Ar) 3 ] - and CS 2 , in addition to the related phosphaalkyne synthesis mediated by anion [ 1a -P] - . The latter system was amenable to a kinetic study and was shown indeed to adhere to a unimolecular reaction profile.…”
Section: Resultsmentioning
confidence: 99%
“…Thus, we suggest the rapid metathetical exchange processes observed for the N[Np]Ar-ligated [ 1a -N] - can be inferred to be facilitated by a relatively unhindered coordination environment proximal to the Nb center. This line of thinking is further underscored by the observed formation of [SCN] - from CS 2 and [N⋮V(N[ t -Bu]Ar) 3 ] - , despite taking place on a smaller and seemingly unthinkably congested vanadium center. 7 …”
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
