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Synthesis, structural authentication, and structurally defined metalation reactions of lithium and sodium DA-zincate bases (DA = diisopropylamide) with phenylacetylene

Lookup NU author(s): Emeritus Professor Bill Clegg, Dr Ross Harrington, Dr Luca Russo

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Abstract

In a study aimed at developing the diisopropylamido (DA) chemistry of zincates, the new lithium DA-zincate [(TMEDA) · Li(tBu)(DA) Zn(tBu)] (4) has been synthesized by an interlocking cocomplexation approach comprising mixing of its three component chemicals, LDA, tBu2Zn, and TMEDA, in a 1:1:1 ratio in hexane solution. Previously made by transamination from the corresponding TMP-zincate, the known sodium congener [(TMEDA)-Na(tBu)(DA)Zn(tBu)] (2) was also synthesized by this approach, substituting NaDA for LDA. Closely resembling each other, their molecular structures determined by X-ray crystallography can be categorized as contact ion-pair ates of TMEDA-chelated alkali metal cations linked to trigonal-planar dialkyl-Zn anions via bridging DA ligands. Reaction of 4 and 2 with phenylacetylene affords the bimetallic acetylides [((TMEDA)·Li(C≡CPh)2Zn(tBu)} 2·(TMEDA)] (5) and [((TMEDA)·Na(C≡CPh) 2Zn(tBu)}2] (6), respectively. X-ray crystallographic studies reveal 5 is a pseudodimer (tetranuclear) with two (LiCZnC) rings linked at the Zn atoms by a bridging, nonchelating TMEDA ligand; in contrast 6 adopts a distorted cubane of alternating PhC≡C and metal (2 Na, 2 Zn) corners. For comparison, the synthesis and crystal structures of the neutral zinc complexes [(TMEDA)·Zn(C≡CPh)2] (7) and [(TMEDA)·Zn(tBu)(C≡CPh)] (8), formally components of the ate complexes 5 and 6, are also reported. In addition, the 1H and 13C NMR spectra of 2, 4, 5, 6, 7, and 8 recorded from solutions in C6D6 are disclosed. © 2008 American Chemical Society.


Publication metadata

Author(s): Clegg W, Garcia-Alvarez J, Garcia-Alvarez P, Graham DV, Harrington RW, Hevia E, Kennedy AR, Mulvey RE, Russo L

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2008

Volume: 27

Issue: 11

Pages: 2654-2663

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om8001813

DOI: 10.1021/om8001813


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