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“Chiral-at-Metal” Hemilabile Nickel complexes with a latent d10-ML2Configuration: Receiving substrates with open arms


Linden, Anthony; Llovera, Ligia; Herrera, Julio; Dorta, Reto; Agrifoglio, Giuseppe; Dorta, Romano (2012). “Chiral-at-Metal” Hemilabile Nickel complexes with a latent d10-ML2Configuration: Receiving substrates with open arms. Organometallics, 31(17):6162-6171.

Abstract

Complexes with highly reactive stereogenic metal centers are of great interest to asymmetric synthesis. Thus, by reacting [Ni(COD)2] with 2 equiv of the P-alkene ligand (S)-5 ((S)-(+)-N-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yl)dibenz[b,f]azepine) or (SP,SC)-6 ((2S,5S)-(-)-N-(aza-3-oxa-2-phosphabicyclo[3.3.0]octan-4-on-2-yl)dibenz[b,f]azepine), the diastereomerically and enantiomerically pure tetrahedral complexes (Δ,S,S)-[Ni(5-κP,η2-alkene)2] (2a) and (Δ,SP,SC,SP′,SC′)-[Ni(6-κP,η2-alkene)2] (2b) were obtained in almost quantitative yields on multigram scales. The Ni atoms showed in both cases stable Δ configurations. Even though these Ni(0) complexes were air stable in the solid state, once dissolved, complex 2a readily activated CS2, alkynes, and enones as the formal d10-ML2 fragment [Ni(5-κP)2] (4) to form adducts 8–11. This is possible thanks to the decoordination of the hemilabile alkene arms of the P-alkene ligands, and the X-ray crystal structures of the CS2 and 4-ethynyltoluene adducts confirmed the η2 coordination modes of the substrates and the concomitant opening up of the alkene arms of ligand 5. The coordination of α,β-unsaturated carbonyl compounds in complexes 11a–c was reversible.

Abstract

Complexes with highly reactive stereogenic metal centers are of great interest to asymmetric synthesis. Thus, by reacting [Ni(COD)2] with 2 equiv of the P-alkene ligand (S)-5 ((S)-(+)-N-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yl)dibenz[b,f]azepine) or (SP,SC)-6 ((2S,5S)-(-)-N-(aza-3-oxa-2-phosphabicyclo[3.3.0]octan-4-on-2-yl)dibenz[b,f]azepine), the diastereomerically and enantiomerically pure tetrahedral complexes (Δ,S,S)-[Ni(5-κP,η2-alkene)2] (2a) and (Δ,SP,SC,SP′,SC′)-[Ni(6-κP,η2-alkene)2] (2b) were obtained in almost quantitative yields on multigram scales. The Ni atoms showed in both cases stable Δ configurations. Even though these Ni(0) complexes were air stable in the solid state, once dissolved, complex 2a readily activated CS2, alkynes, and enones as the formal d10-ML2 fragment [Ni(5-κP)2] (4) to form adducts 8–11. This is possible thanks to the decoordination of the hemilabile alkene arms of the P-alkene ligands, and the X-ray crystal structures of the CS2 and 4-ethynyltoluene adducts confirmed the η2 coordination modes of the substrates and the concomitant opening up of the alkene arms of ligand 5. The coordination of α,β-unsaturated carbonyl compounds in complexes 11a–c was reversible.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2012
Deposited On:19 Oct 2012 11:49
Last Modified:07 Dec 2017 15:30
Publisher:American Chemical Society
ISSN:0276-7333
Funders:Fonacit (Projects S1-2001000851 and G- 2005000433), UZH
Additional Information:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organometallics, copyright © American Chemical Society after peer review and technical editing by the publisher.
Publisher DOI:https://doi.org/10.1021/om300484z

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