Preparation and characterization of a vanadium (III) dinitrogen complex supported by a tripodal anionic amide ligand

Desmangles, Nathalie; Jenkins, Hilary A.; Ruppa, Kamalesh B. P.; Gambarotta, Sandro

doi:10.1016/s0020-1693(96)05323-6

Cited by 35 publications

(32 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One option is to replace the amine cap with a group which does not have a strong interaction with the metal, for example the CMe cap in the H 3 C-CA C H T U N G T R E N N U N G (CH 2 NHR) 3 ligand (R = CH 3 , C 2 H 5 or CHA C H T U N G T R E N N U N G (CH 3 ) 2 ). [54] This ligand system has been used to synthesise the N 2 À{VA C H T U N G T R E N N U N G [(iPrHNCH 2 ) 3 CMe]} 2 dimer with N 2 bridging the metal centres [55] but no NÀN cleavage was reported. Based on our earlier study of the metal dependence of N 2 activation in M[N(R)Ar] 3 complexes, [48] we predict that N À N cleavage should be favourable in the N 2 À {M-A C H T U N G T R E N N U N G [(iPrHNCH 2 …”

Section: Resultsmentioning

confidence: 99%

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

Christian¹,

Stranger²,

Yates³

2008

Chemistry A European J

View full text Add to dashboard Cite

The four-coordinate Mo[N(3)N] complex, [N(3)N] = [{RNCH(2)CH(2)}(3)N], R = 3,5-(2,4,6-iPr(3)C(6)H(2))(2)C(6)H(3) (HIPT), which is capable of converting N(2) to ammonia catalytically, reacts with N(2) in a similar manner to Mo[N(R)Ar](3) (R = tBu, Ar = 3,5-C(6)H(3)Me(2)) to form a dinitrogen-bridged dimer intermediate, but unlike its three-coordinate counterpart, N(2) cleavage is not observed. To rationalise these differences, the reaction of N(2) with the model Mo[NH(2)](3)[NH(3)] and full ligand Mo[N(3)N] systems was explored using density functional theory and compared with the results of an earlier study involving the model three-coordinate Mo[NH(2)](3) system. Although the overall reaction is exothermic, the final N-N cleavage step is calculated to be endothermic by 75 kJ mol(-1) for the model system when the Mo-amine cap bond length is fixed to mimic the constraints of the ligand straps, but exothermic by 14 kJ mol(-1) for the full ligand system. In the latter case, the slightly exothermic cleavage step can be attributed to the destabilization of the N(2) bridged dimer relative to the nitride product owing to the steric effects of the bulky R groups. The activation barrier for N-N cleavage is estimated at 151 kJ mol(-1) for the model system, more than twice the calculated value for Mo[NH(2)](3), and even greater, 213 kJ mol(-1), for the full ligand [N(3)N]Mo system. A bonding analysis shows that although the binding of the amine cap helps to stabilize the intermediate dimer, at the same time it destabilizes the metal d-orbitals involved in backbonding to the pi* orbitals on N(2). As a result, backdonation is less efficient and N-N activation reduced compared to the three-coordinate system. Thus, the increased stability of the intermediate dimer on binding of the amine cap combined with the reduced level of N-N activation and higher kinetic barrier, explain why N-N cleavage has not been observed experimentally for the four-coordinate Mo[N(3)N] system.

show abstract

Section: Resultsmentioning

confidence: 99%

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

Christian¹,

Stranger²,

Yates³

2008

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…The V-N2 distance in 5 (1.757 (3) ) [18] is imide-like, suggesting that each metal center significantly backbonds to both nitrogen atoms composing the N 2 unit, and the VN 2 V metrical parameters are comparable to other reduced dinitrogen complexes of vanadium. [19,20] In the structure of 5, each {(PNP)V(=CHtBu)(N)} fragment is related by symmetry, and its alkylidene functionalities are essentially orthogonal with respect to each other. The gross structural features of 5 closely resemble a Ta V analogue prepared previously by Schrock by the two-electron reduction of a Ta V alkylidene-dichloride precursor under an atmosphere of N 2 .…”

mentioning

confidence: 99%

“…[21] The packing diagram of 5 (space group R3 c) also merits highlighting. In the unit cell, three large voids or channels along the N 2 vector are observed with dimensions (14), V1-P1 2.4711(5), V1-P2 2.4554(6), N2-N3 1.3216 (19); P1-V1-P2 149.127 (19), V1-C27-C28 150.03 (14). 3: V1-C27 1.894(5), V1-N1 2.093(3), V1-O1 1.595(4), V1-P1 2.4811(10), V1-P2 2.4752(9); P1-V1-P2 152.28(4), V1-C27-C28 140.5 (7).…”

mentioning

confidence: 99%

A Transient V^III–Alkylidene Complex: Oxidation Chemistry Including the Activation of N₂ to Afford a Highly Porous Honeycomb‐Like Framework

et al. 2008

View full text Add to dashboard Cite

Terminal vanadium alkylidenes [1][2][3][4] still constitute a rare class of complexes, and this type of functional group, when combined with this metal, has been far less explored than its heavier congeners niobium [5,6] and tantalum. [6] Part of this limitation revolves around the ability of vanadium to populate low-valent oxidation states, especially the + 3 state. As a result, alkylation reactions stemming from the high-valent metal complex often lead to reduction as opposed to the more prototypical transmetalation/a-hydrogen abstraction processes encountered in Nb V and Ta V alkylidenes.[6] Out of the few terminal vanadium alkylidene complexes known (e.g. V III ,[1] V IV , [3] and V V[4] ), only the high-valent system appears to be highly reactive for ring-opening metathesis polymerization (ROMP).[4] Therefore, an entry to the V V alkylidene group directly from a V III precursor would represent an attractive synthetic strategy for this metal given the vast quantity of low-valent vanadium halide precursors available. In general, heat, photolysis, Lewis bases, or Brønsted bases can incite a-hydrogen abstraction to form Schrock-like MÀC multiple bonds. [6,7] More recently, a one-electron oxidation step has been also shown to promote a-hydrogen abstraction. [7] When the metal is in a highoxidation state, powerful Lewis acids such as Al(CH 3 ) 3 can also instigate a-hydrogen abstraction as well as trap the MÀC multiple bond.[ [8][9][10] Although a handful of vanadium alkylidenes have been generated by treatment of a bis-alkyl precursor with PR 3 , [1] the concept of using two-electron oxidants to promote a-hydrogen abstraction, to the extent of providing a facile entry to the V V alkylidene unit, has not been realized.Herein we demonstrate that p acids or two-electron oxidants can ultimately lead to a-hydrogen abstraction when the metal in question is a low-valent V III bis-neopentyl species. As a result, a transient, four-coordinate V III neopentylidene can be generated and trapped with a series of two-electron oxidants to afford a family of V V alkylidenes. In the case where the p acid promoting the a-hydrogen abstraction is sterically crowded, N 2 becomes the substrate of choice to afford the first vanadium bridging end-on dinitrogenalkylidene species. The solid state packing diagram for this complex displays a highly "porous" honeycomb-like framework along the activated N 2 unit. During the course of our investigation, we also discovered that the elusive V III alkylidene generated in these set of reactions can be trapped with a chelate p acid such as 2,2'-bipyridine (bpy).When the bis-alkyl precursor, readily prepared from a one-pot reaction of Li(PNP) and [VCl 3 (thf) 3 ] followed by alkylation with the appropriate stoichiometry of LiCH 2 tBu, [11] was treated with N 2 CPh 2 in diethyl ether, a gradual reaction ensued over a period of 12 h to afford the V V alkylidenediphenylmethylene hydrazido [12] complex [(PNP)V( = CHtBu)(N 2 CPh 2 )] (2) in 62 % yield after workup of the reaction mixture (Scheme 1). Li...

show abstract

“…88 In the following years, the group of Gambarotta studied N based ligands to obtain V-N 2 complexes, such as amide, polydentate amides 89 and amidinate. 90 In 1995, the same group synthesized an anionic V-nitride dimer [((SiMe 3 ) 2 N) 2 V(μ-N)] 2 via hydrogenolysis of a vanadacyclobutane complex under N 2 , N 2 being the source of the bridging nitride ligands. 91 Few years later, in 1999, Cloke also observed direct N 2 cleavage upon reduction of a V III complex featuring a tridentate diamidoamine ligand (scheme 22).…”

Section: Vanadium Complexes: Synthesis and Reactivitymentioning

confidence: 99%

Reactivity and Structure of Complexes of Small Molecules: Dinitrogen

Mézailles

2021

Comprehensive Coordination Chemistry III

View full text Add to dashboard Cite

show abstract

Preparation and characterization of a vanadium (III) dinitrogen complex supported by a tripodal anionic amide ligand

Cited by 35 publications

References 44 publications

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

A Transient V^III–Alkylidene Complex: Oxidation Chemistry Including the Activation of N₂ to Afford a Highly Porous Honeycomb‐Like Framework

Reactivity and Structure of Complexes of Small Molecules: Dinitrogen

Contact Info

Product

Resources

About

Preparation and characterization of a vanadium (III) dinitrogen complex supported by a tripodal anionic amide ligand

Cited by 35 publications

References 44 publications

A Comparison of N2 Cleavage in Schrock's Mo[N3N] and Laplaza–Cummins' Mo[N(R)Ar]3 Systems

A Comparison of N2 Cleavage in Schrock's Mo[N3N] and Laplaza–Cummins' Mo[N(R)Ar]3 Systems

A Transient VIII–Alkylidene Complex: Oxidation Chemistry Including the Activation of N2 to Afford a Highly Porous Honeycomb‐Like Framework

Reactivity and Structure of Complexes of Small Molecules: Dinitrogen

Contact Info

Product

Resources

About

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

A Comparison of N₂ Cleavage in Schrock's Mo[N₃N] and Laplaza–Cummins' Mo[N(R)Ar]₃ Systems

A Transient V^III–Alkylidene Complex: Oxidation Chemistry Including the Activation of N₂ to Afford a Highly Porous Honeycomb‐Like Framework