Communication
Heteroleptic lead and aluminium complexes ligated by a bulky non-symmetrical triazenide

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Abstract

The sterically bulky non-symmetrical triazene, DmpN3(H)Dipp∗, was prepared. Amido lead triazenide and dimethyl aluminium triazenide complexes were readily prepared by metalation of the parent triazene. The former is a rare example of a stable heteroleptic lead triazenide complex. Analogous compounds are inaccessible when smaller triazenes are employed under these conditions, as they readily form homoleptic bis(aryl)triazenide complexes. Quantification of the bulk of this and other bidentate monoanionic N,N′-donor ligands, using the solid-state structures of model dimethyl aluminium complexes, help to rationalize the superior stability of the amido lead triazenide complex reported herein with regards to subsequent metalation.

Introduction

Bidentate monoanionic N,N′-donor ligands are widely deployed in coordination chemistry because these chelating ligands are able to stabilize and shield reactive sites [1,2]. Of this ligand class the most widely employed are the β-diketiminates (Fig. 1) [[3], [4], [5], [6]]. However, several recent studies have shown these ligands may not behave as simple spectators, specifically there are several examples of this ligand set displaying redox non-innocence [7]. Amidinate ligands (Fig. 1) are widely utilized alternatives [[8], [9], [10], [11], [12]]. A frequently overlooked ligand class, isoelectronic to formamidinates, are the triazenides (Fig. 1) [13]. As demonstrated by Niemeyer and others, a notable feature of this ligand subclass is the ease of which sterically demanding substituents can be added [[14], [15], [16], [17], [18]]. There has been renewed interest in developing sterically demanding N,N′-ligands to stabilize reactive complexes by kinetically preventing ligand redistributions [[19], [20], [21], [22], [23]]. Notable examples are the development of amidinate [[24], [25], [26]], guanidinate [27] and β-diketiminates [28,29] bearing N-2,6-dibenzhydrylphenyl- substituents.

We are interested in the stabilization of reactive low coordinate main group metal complexes by sterically demanding neutral and anionic ligands [[30], [31], [32], [33], [34]]. Several heteroleptic lead complexes featuring amidinate [35,36], iminoanilide [37] and β-diketiminate [[38], [39], [40], [41], [42], [43], [44], [45], [46]] ligands have been reported. By contrast there is only a single example of a heteroleptic lead triazenide complex, [(AdN3Si(SiMe3)3)Pb{Si(SiMe3)3}] [47]. Recent attempts by Fox and Johnson to prepare a heteroleptic amido lead triazenide complex, [(Dipp2N3)Pb{N(SiMe3)2}], by treating the parent triazene with an equimolar amount of [Pb{N(SiMe3)2}2] afforded the bis(triazenide) complex, Pb(N3Dipp2)2, as the only isolable product [48]. There are few heteroleptic triazenide complexes of the lighter Group 14 metals [33,49,50]. In each instance, a triazenide bearing bulky N-substituents is deployed, which likely hinders the formation of bis(triazenide) species.

In this contribution we prepare a new bulky non-symmetrically substituted triazene. We demonstrate its size by isolating a heteroleptic amido lead triazenide complex. Subsequently, we attempt to quantify the steric bulk of this triazenide using readily prepared model aluminium complexes.

Section snippets

Results and discussion

Niemeyer has reported the large-scale preparation of triazenes bearing bulky substituents by reacting lithiated aryls with aryl azides followed by hydrolysis [14]. Utilizing an analogous synthetic route, we have prepared a new bulky non-symmetrically substituted triazene, DmpN3(H)Dipp∗ (1) in excellent yield (94%) on an 8.6 mmol scale (Scheme 1). This incorporates a Dmp (2,6-dimesitylphenyl-) at one nitrogen terminus and a Dipp∗ (2,6-dibenzhydryl-4-methylphenyl-) at the other. The 1H and 13C{1

Conclusions

In summary, we have prepared and structurally characterized, with the help of a very bulky aryl-substituted triazenide ligand, a stable heteroleptic amido lead complex. The steric bulk introduced by this ligand was further quantified using metrics taken from the solid-state structures of model dimethyl aluminium complexes.

General information

All manipulations were performed using conventional Schlenk or glovebox techniques under an atmosphere of high purity argon in flame-dried glassware. Diethyl ether, THF and n-hexane were dried over sodium wire and purged with nitrogen prior to distillation from sodium benzophenone ketyl. Benzene-d6 (C6D6) was dried over sodium and freeze-thaw degassed prior to use. Infrared spectra were recorded as Nujol mulls using sodium chloride plates on a Nicolet Avatar 320 FTIR spectrophotometer. Spectra

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to thank the Australian Research Council (DP110104759) for financial support of this research and the Australian Government for funding postgraduate scholarships. The authors would like to thank Dr. Matthew R. Gyton for insightful comments and for the generous gift of Dipp∗2N3H.

References (74)

  • Y.-C. Tsai

    Coord. Chem. Rev.

    (2012)
  • F.T. Edelmann
  • F.T. Edelmann
  • C. Jones

    Coord. Chem. Rev.

    (2010)
  • A. Causero et al.

    Organometallics

    (2016)
  • G. Ballmann et al.

    Organometallics

    (2019)
  • T.X. Gentner et al.

    Organometallics

    (2019)
  • B. Freitag et al.

    Organometallics

    (2018)
  • E.C.Y. Tam et al.

    Polyhedron

    (2015)
  • M.J. Taylor et al.

    Organometallics

    (2015)
  • K. Klinkhammer

    Polyhedron

    (2002)
  • M.L. Cole et al.

    Polyhedron

    (2019)
  • L. Falivene et al.

    Organometallics

    (2016)
  • D.L. Kays

    Chem. Soc. Rev.

    (2016)
  • R. Kretschmer, Chem. Eur J., DOI:...
  • L. Bourget-Merle et al.

    Chem. Rev.

    (2002)
  • C. Chen et al.

    Dalton Trans.

    (2015)
  • S.P. Sarish et al.

    Acc. Chem. Res.

    (2011)
  • C. Camp et al.

    Dalton Trans.

    (2016)
  • D.A. Kissounko et al.

    Russ. Chem. Rev.

    (2006)
  • M. Asay et al.

    Chem. Rev.

    (2010)
  • P. Gantzel et al.

    Inorg. Chem.

    (1998)
  • S.O. Hauber et al.

    Angew. Chem. Int. Ed.

    (2005)
  • H.S. Lee et al.

    Inorg. Chem.

    (2006)
  • S. Balireddi et al.

    Acta Crystallogr.

    (2007)
  • H.S. Lee et al.

    Inorg. Chem.

    (2008)
  • A. Hinz et al.

    J. Am. Chem. Soc.

    (2015)
  • T.X. Gentner et al.

    Angew. Chem. Int. Ed.

    (2019)
  • G. Ballmann et al.

    Eur. J. Inorg. Chem.

    (2019)
  • E.W.Y. Wong et al.

    Aust. J. Chem.

    (2013)
  • C. de Bruin Dickason et al.

    Chem. Commun.

    (2018)
  • A.K. Maity et al.

    Inorg. Chem.

    (2014)
  • M. Arrowsmith et al.

    Inorg. Chem.

    (2014)
  • M.-t. Ma et al.

    Chin. J. Inorg. Chem.

    (2016)
  • S.G. Alexander et al.

    Dalton Trans.

    (2009)
  • A.R. Leverett et al.

    Dalton Trans.

    (2015)
  • A.R. Leverett et al.

    Dalton Trans.

    (2019)
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