Homo- and heteroleptic alkoxycarbene f-element complexes and their reactivity towards acidic N-H and C-H bonds

Arnold, P. L., Cadenbach, T., Marr, I. H., Fyfe, A. A., Bell, N. L. , Bellabarba, R., Tooze, R. P. and Love, J. B. (2014) Homo- and heteroleptic alkoxycarbene f-element complexes and their reactivity towards acidic N-H and C-H bonds. Dalton Transactions, 43(38), pp. 13436-14358. (doi: 10.1039/C4DT01442A) (PMID:24920060)

Abstract

The reactivity of a series of organometallic rare earth and actinide complexes with hemilabile NHC-ligands towards substrates with acidic C–H and N–H bonds is described. The synthesis, characterisation and X-ray structures of the new heteroleptic mono- and bis(NHC) cyclopentadienyl complexes LnCp2(L) 1 (Ln = Sc, Y, Ce; L = alkoxy-tethered carbene [OCMe2CH2(1-C{NCHCHNiPr})]), LnCp(L)2 (Ln = Y) 2, and the homoleptic tetrakis(NHC) complex Th(L)44 are described. The reactivity of these complexes, and of the homoleptic complexes Ln(L)3 (Ln = Sc 3, Ce), with E–H substrates is described, where EH = pyrrole C4H4NH, indole C8H6NH, diphenylacetone Ph2CC(O)Me, terminal alkynes RC[triple bond, length as m-dash]CH (R = Me3Si, Ph), and cyclopentadiene C5H6. Complex 1-Y heterolytically cleaves and adds pyrrole and indole N–H across the metal carbene bond, whereas 1-Ce does not, although 3 and 4 form H-bonded adducts. Complexes 1-Y and 1-Sc form adducts with CpH without cleaving the acidic C–H bond, 1-Ce cleaves the Cp–H bond, but 2 reacts to form the very rare H+–[C5H5]−–H+ motif. Complex 1-Ce cleaves alkyne C–H bonds but the products rearrange upon formation, while complex 1-Y cleaves the C–H bond in diphenylacetone forming a product which rearranges to the Y–O bonded enolate product.

• Item Type: Articles
• Additional Information: The authors are grateful for the support of the Technische Universität München – Institute for Advanced Study, funded by the German Excellence Initiative, Sasol Technology, the University of Edinburgh, and the EPSRC.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Bell, Dr Nicola
• Authors: Arnold, P. L., Cadenbach, T., Marr, I. H., Fyfe, A. A., Bell, N. L., Bellabarba, R., Tooze, R. P., and Love, J. B.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Dalton Transactions
• Publisher: Royal Society of Chemistry
• ISSN: 1477-9226
• ISSN (Online): 1477-9234
• Published Online: 11 June 2014
• Copyright Holders: Copyright © 2014 The Royal Society of Chemistry
• First Published: First published in Dalton Transactions 43(38): 13436-14358
• Publisher Policy: Reproduced under a Creative Commons License