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On the unprecedented level of dinitrogen activation in the calix[4]arene complex of Nb(III)


Terrett, R and Cavigliasso, G and Stranger, R and Yates, BF, On the unprecedented level of dinitrogen activation in the calix[4]arene complex of Nb(III), Dalton Transactions, 40, (42) pp. 11267-11275. ISSN 1477-9226 (2011) [Refereed Article]

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Copyright Statement

Copyright 2011 The Royal Society of Chemistry

DOI: doi:10.1039/C1DT11091H


The calix[4]arene niobium(III) complex ([L]NbNNNb[L] where [L] = p-tert-butylcalix[4]arene), reported to bind N2 in a μ2-linear dimeric capacity and to activate the N2 triple bond to 1.39 , corresponding to the longest N2 bond known in the end-on coordination mode, was subjected to a computational investigation involving both density functional and wavefunction based methods to establish the basis for the unprecedented level of activation. Replacement of the calix[4]arene ligand with hydroxide or methoxide ligands reveals that the organic backbone structure of the calix[4]arene ligand exerts negligible electronic influence over the metal centre, serving only to geometrically constrain the coordinating phenoxide groups. A fragment bonding analysis shows that metal-to-dinitrogen π* backbonding is the principal NbN interaction, providing a strong electronic basis for analogy with other well-characterised three- and four-coordinate complexes which bind N2 end-on. While the calculated structure of the metallacalix[4]arene unit is reproduced with high accuracy, as is also the NbNb separation, the calculated equilibrium geometry of the complex under a variety of conditions consistently indicates against a 1.39 activation of the N2 bond. Instead, the calculated NN distances fall within the range 1.261.30 , a result concordant with closely related three- and four-coordinate μ2N2 complexes as well as predictions derived from trends in NN stretching frequency for a number of crystallographically characterized linear N2 activators. A number of potential causes for this bond length discrepancy are explored.

Item Details

Item Type:Refereed Article
Research Division:Chemical Sciences
Research Group:Theoretical and computational chemistry
Research Field:Theoretical quantum chemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the chemical sciences
UTAS Author:Yates, BF (Professor Brian Yates)
ID Code:76874
Year Published:2011
Funding Support:Australian Research Council (DP0986529)
Web of Science® Times Cited:8
Deposited By:Chemistry
Deposited On:2012-03-14
Last Modified:2012-07-10

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