Chaplin, Adrian B. and Weller, Andrew S.. (2010) C−C bond activation of a cyclopropyl phosphine : isolation and reactivity of a tetrameric rhodacyclobutane. Organometallics, Vol.29 (No.10). pp. 2332-2342. ISSN 0276-7333

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Abstract

Reaction of the functionalized phosphine P(t)Bu(2)CH(2)(C(3)H(5)) with [Rh(C(8)H(14))(2)Cl](2) (C(8)H(4) = ciscyclooctene) resulted in selective C C bond activation of the cyclopropyl group and formation of a tetrameric rhodacyclobutane, [RhCl(kappa(3)-P(t)Bu(2)CH(2)CH(CH(2))2)]4, which was characterized in the solid state by X-ray crystallography. This complex acts as a latent source of the [Rh(kappa(3)-P(t)Bu(2)CH(2)CH(CH(2))(2))](+) fragment, forming a range of new complexes by salt metathesis with NaCp, [RhCp(kappa(3)-P(t)Bu(2)CH(2)CH(CH-chloride abstraction in the presence of arenes, [Rh(eta(6)-arene)(kappa(3)-P(t)Bu(2)CH(2)CH(CH(2))2)][BAr(4)(F)] [arene = C(6)H(5)F, C(6)H(3)Me(3); Ar(F) = 3,5-C(6)H(3)(CF(3)),], or fragmentation by addition aphosphine ligands, trans-[RhCl(PR(3))(kappa(3)-P(t)Bu(2)CH(2)CH(CH(2))(2))] (R = (t)Bu, Cy). In contrast, reaction with carbon monoxide results in the reductive elimination of the tethered cyclopropane, demonstrating reversible C C bond activation, and formation of cis-[RhCl(CO)(2)(P(t)BuCH(2)(C(3)H(5)))]. These complexes were characterized in solution by NMR spectroscopy and in the solid state by X-ray diffraction. Chloride abstraction from [RhCl(B(t)Bu(3))(kappa(3)P(t)Bu(2)CH(2)CH(CH(2))(2))] resulted in the regioselective isomerization of the tethered cyclopropane to a terminal alkene, viz., the formally 14-electron complex [Rh(P(t)Bu(3))(kappa(3)-P(t)Bu(2)CH(2)CH(2)CH=CH(2))][BAr(4)(F)], notable for the presence of a strong agostic interaction with a phosphine (t)Bu substituent, apparent both from the solid-state structure and in solution by (1)H NM R spectroscopy. Addition of hydrogen to this complex resulted in hydrogenation of the alkene and formation of [Rh(H)(2)(P(t)Bu(3))(P(t)Bu(2)(II)Bu)][BAr(4)(F)]. These steps overall correspond to selective C C bond frinctionalization (hydrogenation) of the tethered cyclopropane and are of direct significance to a related catalytic process [J Am. Chem. Soc. 2003, 125, 886] and, more generally, to the rhodium-mediated transformation of alkalies.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Activation (Chemistry), Phosphine, Chemical bonds, Cyclopropane, Chemical reactions
Journal or Publication Title:	Organometallics
Publisher:	American Chemical Society
ISSN:	0276-7333
Date:	24 May 2010
Volume:	Vol.29
Number:	No.10
Page Range:	pp. 2332-2342
Identification Number:	10.1021/om100105p
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Engineering and Physical Sciences Research Council (EPSRC), University of Oxford
URI:	http://wrap.warwick.ac.uk/id/eprint/40517

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