Dinitrogen Fixation versus Metal-Metal Bond Formation in the Chemistry of Vanadium(II) Amidinates

Berno, Pietro; Hao, Shoukang; Minhas, Ravinder K.; Gambarotta, Sandro

doi:10.1021/ja00095a059

Cited by 94 publications

(45 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The VV bond length within the {V 2 (hpp) 4 } ( L ) unit of the [( L )Li(μ‐Cp)Li(μ‐Cp)Li( L )] + ion of 1 (1.933(1) Å) is identical to that observed in the previously reported structure of [V 2 (hpp) 4 ] (1.932(1) Å) 11e. The chelation to Li(3) of both of the V‐bonded N centers of two of the hpp ligands results in some elongation of the VN bonds in 1 (range 2.057(4)–2.116(4) Å) compared to the free [V 2 (hpp) 4 ] complex (2.058(4)–2.076(3) Å);11e the longest of VN bonds in 1 are found at the Li‐bonded atoms N(41) and N(12) (2.111(4) and 2.116(4) Å, respectively). This coordination, together with the η 5 ‐coordination by a Cp ligand, produces a distorted square‐based pyramidal geometry for Li(3).…”

Section: Methodssupporting

confidence: 81%

Trapping of Oligomeric Cyclopentadienyllithium Cationic and Anionic Fragments by a VV‐Bonded Ligand

Fernández-Cortabitarte

Garcı́a

Morey

et al. 2007

Angewandte Chemie

View full text Add to dashboard Cite

Main-group cyclopentadienyl compounds are typically far more ionic than their transition-metal relatives. [1][2][3] This difference is apparent not only in their reactivity patterns but also, in particular, in the frequent formation of electrostatically bonded polymeric structures for many main-group cyclopentadienyl species. Owing to the similar ionic sizes and charges of the metals, analogous infinite polymeric structures [M(h 5 -Cp)] 1 are found for the parent cylopentadienyl compounds of the alkali metals (M = Li, Na, K, Rb, Cs) [4] and for the heavier Group 13 metals (M = In, Tl).[5] As a consequence of Cp···M or M···M interactions, these polymers can be either linear or bent at the metal atoms (Scheme 1). The structures of the alkaline earth complexes and those of the heaviest Group 14 metal Pb can also be regarded as similarly related. [2] An important focus of research in this area in recent years has been the investigation of multidecker cations and anions. [3,6] These species can be conceived of as representing fragments of the parent cyclopentadienyl lattices and are produced by a number of routes. As outlined in Scheme 2 for Group 1 and Group 13 metals, these methods include formal+ cations, [7] and restricted solvation in the presence of bulky Cp ligands to give salts of the type[8]Our recent interests in this field have concerned attempts to extend the ionic chemistry of main-group cyclopentadienyl compounds to the transition metals, with a particular aim of obtaining new magnetic molecules and lattices. [9,10] We have shown that manganocene [Cp 2 Mn], the most ionic transitionelement metallocene, exhibits similar chemistry to maingroup metallocenes. Herein, we report for the first time that vanadocene [Cp 2 V] displays similar reactivity with the lithiated amide (hpp)Li (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine); the reaction results in substitution of the Cp ligands (as CpLi) and formation of the known VV-bonded compound [V 2 (hpp) 4 ] (L).[11f] Remarkably, the product crystallizes with five units of CpLi to form the ionic species ions are paired. [11,12] The spectrum shows a series of poorly resolved multiplets for the hpp ligand in the region d = 3.57-1.74 ppm and a singlet C 5 H 5 resonance (d = 5.70 ppm). The complicated appearance of the spectrum and its temperatureand concentration-dependent behavior can be attributed to the presence of dynamic equilibria in solution. On changing from 300 to 190 K, the 1 H NMR spectrum exhibits several changes, including the appearance of an additional Cp resonance (d = 6.20 ppm). The temperature-dependent 7 Li NMR Scheme 1. Schematic representation of the structures of [CpM] 1 (M = Li, Na, K, Rb, Cs, In, Tl).Scheme 2.

show abstract

Section: Methodssupporting

confidence: 81%

Trapping of Oligomeric Cyclopentadienyllithium Cationic and Anionic Fragments by a VV‐Bonded Ligand

Fernández-Cortabitarte

Garcı́a

Morey

et al. 2007

Angewandte Chemie

View full text Add to dashboard Cite

show abstract

“…672 Amides and amidinate ligands (RNC(R′)NR -) have been employed as versatile precursors for dinuclear compounds with metal-metal bonds such as the N 2 bridged dinuclear V-complexes shown in 150-154. 676 The diazenido(2-)-bridged complex in 150 has V-N and N-N bond lengths of 1.76 and 1.24 Å, respectively, but these dinuclear complexes cleave upon the addition of thf. Coordination of other donor ligands, such as thf, results in the release of N 2 gas and the formation of a monomeric complex with the formula [V(RNC(R′)NR) 2 (thf) 2 ].…”

Section: Activation Of Nitrogenmentioning

confidence: 99%

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

et al. 2004

View full text Add to dashboard Cite

“…Since two of the examples of Step 2 involve a vanadium supported nitride, 6,7 we sought to prepare a low-valent V complex with the requisite number of electrons such that two equivalents can reduce N 2 by 6 electrons. [32][33][34][35] There is precedent for N 2 activation by low valent V II complexes included in the work from the groups of Gambarotta, [32][33][34] Cloke, 36 and Mindiola. 35 (12) was prepared by treating VCl 3 (THF) 3 with two equivalents of the ligand in a frozen Et 2 O slurry.…”

Section: Design Of a New V Ii System For N 2 Activationmentioning

confidence: 99%

Experimental and computational studies on the formation of cyanate from early metal terminal nitrido ligands and carbon monoxide

et al. 2014

View full text Add to dashboard Cite

An important challenge in the artificial fixation of N2 is to find atom efficient transformations that yield value-added products. Here we explore the coordination complex mediated conversion of ubiquitous species, CO and N2, into isocyanate. We have conceptually split the process into three steps: (1) the six-electron splitting of dinitrogen into terminal metal nitrido ligands, (2) the reduction of the complex by two electrons with CO to form an isocyanate linkage, and (3) the one electron reduction of the metal isocyanate complex to regenerate the starting metal complex and release the product. These steps are explored separately in an attempt to understand the limitations of each step and what is required of a coordination complex in order to facilitate a catalytic cycle. The possibility of this cyanate cycle was explored with both Mo and V complexes which have previously been shown to perform select steps in the sequence. Experimental results demonstrate the feasibility of some of the steps and DFT calculations suggest that, although the reduction of the terminal metal nitride complex by carbon monoxide should be thermodynamically favorable, there is a large kinetic barrier associated with the change in spin state which can be avoided in the case of the V complexes by an initial binding of the CO to the metal center followed by rearrangement. This mandates certain minimal design principles for the metal complex: the metal center should be sterically accessible for CO binding and the ligands should not readily succumb to CO insertion reactions.

show abstract

Dinitrogen Fixation versus Metal-Metal Bond Formation in the Chemistry of Vanadium(II) Amidinates

Cited by 94 publications

References 0 publications

Trapping of Oligomeric Cyclopentadienyllithium Cationic and Anionic Fragments by a VV‐Bonded Ligand

Trapping of Oligomeric Cyclopentadienyllithium Cationic and Anionic Fragments by a VV‐Bonded Ligand

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

Experimental and computational studies on the formation of cyanate from early metal terminal nitrido ligands and carbon monoxide

Contact Info

Product

Resources

About