635702-17-9Relevant articles and documents
Mechanistic study on the cross-coupling of alkynyl stannanes with aryl iodides catalyzed by η2-(dimethyl fumarate)palladium(0) complexes with iminophosphine ligands
Crociani, Bruno,Antonaroli, Simonetta,Beghetto, Valentina,Matteoli, Ugo,Scrivanti, Alberto
, p. 2194 - 2202 (2003)
The reactions of [Pd(η2-dmfu)(P-N)] [dmfu = dimethyl fumarate; P-N = 2-(PPh2)C6H4-1-CH=NR, R = C6H4OMe-4 (1a), CHMe2 (2a)] and [Pd(η2-dmfu)(P-N)2] with IC6H 4CF3-4, ISnBu3 and PhC≡SnBu3 have been studied under pseudo-first-order conditions. The oxidative addition of IC6H4CF3-4 yields [PdI(C6H 4CF3-4)(P-N)] (1b or 2b). No reaction takes place with PhC≡CSnBu3 and also with ISnBu3 in the presence of an excess of PhC≡CSnBu3. In the presence of fumaronitrile (fn), 1b and 2b undergo transmetalation by PhC≡CSnBu3 followed by fast reductive elimination to yield [Pd(η2-fn)(P-N)]. The same reaction sequence occurs for the system [PdI(C6H4CF 3-4)(P-N)]/P-N (1: 1 molar ratio) to give [Pd(η2-fn) (P-N)2]. The palladium(0) complexes are active catalysts in the cross-coupling of PhC≡CSnBu3 with aryl iodides ArI (Ar = C 6H4CF3-4, Ph). The catalytic efficiency depends on the complex: [Pd(η2-dmfu)(P-N)2] > [Pd(η2-dmfu)(P-N)], and on the substituent R: C6H 4OMe-4 > CHMe2. The reactivity and spectroscopic data suggest a catalytic cycle involving initial oxidative addition of ArI to a palladium(0) species, followed by transmetalation of the product and by fast reductive elimination to regenerate the starting palladium(0) compound. For [Pd(η2-dmfu)(P-N)] as catalyst, the oxidative addition is the rate-determining step, while for [Pd(η2-dmfu)(P-N)2] the oxidative addition and the transmetalation steps occur at comparable rate. The Royal Society of Chemistry 2003.
Kinetic studies of the oxidative addition and transmetallation steps involved in the cross-coupling of alkynyl stannanes with aryl iodides catalysed by η2-(dimethyl fumarate)(iminophosphane)palladium(0) complexes
Crociani, Bruno,Antonaroli, Simonetta,Canovese, Luciano,Uguagliati, Paolo,Visentin, Fabiano
, p. 732 - 742 (2007/10/03)
The complexes [Pd(η2-dmfu)(P-N)] {dmfu = dimethyl fumarate; P-N = 2-(PPh2)C6H4-1-CH=NR, R = C 6H4OMe-4 (1a), CHMe2 (2a), C6H 3Me2-2,6 (3a), C6H3(CHMe 2)2-2,6 (4a)} undergo dynamic processes in solution which consist of a P-N ligand site exchange through initial rupture of the Pd-N bond at lower energy and an olefin dissociation-association at higher energy. According to equilibrium constant values for olefin replacement, the complex [Pd(η2-fn)(P-N)] (fn = fumaronitrile, 1b) has a greater thermodynamic stability than its dmfu analogue 1a. The kinetics of the oxidative addition of ArI (Ar = C6H4CF3-4) to 1a and 2a lead to the products [PdI(Ar)(P-N)] (1c, 2c) and obey the rate law, k obs = k1A k2A[ArI]. The k1A step involves oxidative addition to a reactive species [Pd(solvent)(P-N)] formed from dmfu dissociation. The k2A step is better interpreted in terms of oxidative addition to a species [Pd(η2-dmfu)(solvent) (κ1-P-N)] formed in a pre-equilibrium step from Pd-N bond breaking. The complexes 1c and 2c react with PhC≡CSnBu3 in the presence of an activated olefin (ol = dmfu, fn) to yield the palladium(0) derivatives [Pd(η2-ol)(P-N)] along with ISnBu3 and PhC≡CAr. The kinetics of the transmetallation step, which is rate-determining for the overall reaction, obey the rate law: kobs = k2T[PhC≡CSnBu3]. The k2T values are markedly enhanced in more polar solvents such as CH3CN and DMF. The solvent effect and the activation parameters suggest an associative S E2 mechanism with substantial charge separation in the transition state. The kinetic data of the above reactions in various solvents indicate that, for the cross-coupling of PhC≡CSnBu3 with ArI catalysed by 1a or 2a, the rate-determining step is represented by the oxidative addition and that CH3CN is the solvent in which the highest rates are observed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
