Regioselectivity of the Insertion of 4,4-Dimethyl-2-Pentyne into the Pd-C Bond of Cyclopalladated Complexes

Spencer, John; Pfeffer, Michel; Kyritsakas, Nathalie; Fischer, Jean

doi:10.1021/om00005a022

Cited by 86 publications

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“…The Pd-N(pyridine) bond length [Pd-N(2) = 2.120(2) Å] is similar to those found in related arrangements (pyridine trans to aryl carbon). [51,52] This distance is longer than those found in related Pd II complexes in which the pyridine fragment is trans to an atom with a smaller trans influence; for instance, the Pd-N(py) bond length in [Pd(C 6 H 4 CH 2 NMe 2 )(Ph 3 PNC(O)-2-NC 5 H 4 )]ClO 4 is 2.056(3) Å, and in this complex the pyridine is trans to the aminic N atom of the NMe 2 group. [30] The P( [37] This clear elongation of the P-N bond in 11 is due to two main facts: the coordination of the N atom and the presence of the carbonyl group, which delocalizes the charge density through the P-N-C-O system.…”

Section: X-ray Structure Of Complex 11mentioning

confidence: 99%

Synthesis, Structure, Reactivity, and Catalytic Activity of C,N‐ and C,N,N‐Orthopalladated Iminophosphoranes

et al. 2005

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The orthopalladated complexes [Pd(μ‐Cl)(C6H4‐2‐PPh2=NPh‐κ‐C,N)]2 (1) and [Pd(C6H4‐2‐PPh2=N‐C(O)‐2‐NC5H4‐κ‐C,N,N)Cl] (11) have been obtained by reaction of Pd(OAc)2 (OAc = acetate) with the iminophosphoranes Ph3P=NPh and Ph3P=N‐C(O)‐2‐NC5H4, respectively, in the presence of excess LiCl. Complex 11 has been characterised by X‐ray diffraction methods. The orthoplatinated derivative [Pt(C6H4‐2‐PPh2=N‐C(O)‐2‐NC5H4‐κ‐C,N,N)Cl] (12) can be obtained by reaction of [PtCl2(NCPh)2] with Ph3P=N‐C(O)‐2‐NC5H4 in refluxing 2‐methoxyethanol. Complex 1 shows the typical reactivity of C,N‐orthopalladated complexes, while complex 11 shows that the C,N,N‐orthometallated ligand is strongly bonded to the Pd atom and cannot be easily displaced. The catalytic activity of the complexes [Pd(μ‐Cl)‐(C6H4‐2‐PPh2=NPh‐κ‐C,N)]2 (1), [Pd(C6H4‐2‐PPh2=NPh‐κ‐C,N)(Cl)(py)] (4), [Pd(C6H4‐2‐PPh2=N‐C(O)‐2‐NC5H4‐κ‐C,N,N)Cl] (11) and [Pd(C6H4‐2‐PPh2=N‐C(O)‐2‐NC5H4‐κ‐C,N,N)(NCMe)]ClO4 (13) in the Mizoroki–Heck (MH) reaction between methyl acrylate and different haloarenes has been examined. All complexes behave as moderate to good catalysts, yielding turnover numbers (TON) up to 526000. Their role as catalysts or precatalysts and the formation of nanoparticles is also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Section: X-ray Structure Of Complex 11mentioning

confidence: 99%

Synthesis, Structure, Reactivity, and Catalytic Activity of C,N‐ and C,N,N‐Orthopalladated Iminophosphoranes

et al. 2005

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“…This latter reaction afforded an unusual example of formation of an eight-membered cyclopalladated compound by monoinsertion of an alkyne into the C-Pd r bond of its precursor six-membered palladacycle [19][20][21][22][23][24][25]. In addition, in the experimental section, we describe an adaptation of the previously reported method of synthesis of compound 2 [18] that produces this compound in high yield and improved purity.…”

Section: Introductionmentioning

confidence: 95%

Reactivity of cyclopalladated compounds derived from biphenyl-2-ylamine towards carbon monoxide, tbutyl isocyanide and alkynes

Albert

D’Andrea

Granell

et al. 2007

Journal of Organometallic Chemistry

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“…For example, reaction of PhCCMe with [NiMe(acac)(PPh 3 [45]. It is interesting to note that, in a similar study of the insertion of t BuCCMe into various palladacycles [PdX(o-C 6 H 4 CH 2 Y-kC,Y)] 2 (X Cl, I; Y NMe 2 , SMe, S t Bu), the same regioselectivity prevailed [29]; steric interaction between the large t Bu group with the HÀC(6) of the cyclometallated aromatic ring was thought to prevent the formation of the alternative isomer (see Scheme 2).…”

Section: Insertion Reactions Of Phosphanickelacyclesmentioning

confidence: 99%

“…Both electronic and steric effects have been invoked to explain the regioselectivities observed for the insertions of alkynes into PdÀaryl bonds, but, although the latter argument is generally preferred, neither could satisfactorily be applied in all cases [16] [17] [28]. For example, two investigations of the insertions of were under steric control [24] [29], whereas the regioselectivities of the reactions of ester-activated alkynes with nickelaindenes are better accounted for by invoking electronic factors [30]. Studies over the last ten years have revealed the existence of a series of nickelacycles, containing the units shown in 1 ± 5, which readily undergo insertions with a range of alkynes.…”

mentioning

confidence: 99%

Insertions of Unsymmetric Alkynes into the Metal−Carbon Bonds of Nickelacycles: What Determines the Regiochemistry?

Bennett

Macgregor

Wenger

2001

HCA

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In memoriam Professor Luigi M. Venanzi, who contributed so much to coordination and organometallic chemistryAlthough the insertion of alkynes into transition-metalÀcarbon bonds plays an important role in synthesis, the regioselectivities observed with unsymmetric alkynes have usually been interpreted on the basis of steric effects. In this perspective paper, we review the available data for such reactions with nickelacycles and present the results of some preliminary theoretical (DFT) calculations. These suggest that, even for unactivated alkynes, the regiochemistry may also be controlled by electronic factors such as frontier-orbital interactions between the triple-bond of the alkyne and the polarized metalÀcarbon bond.1. Introduction. ± The insertion of an unsaturated molecule into a metalÀcarbon (MÀC) bond is a fundamental reaction in organometallic chemistry that has been exploited in both organic syntheses and industrial processes. Detailed experimental studies have been carried out on alkene and CO insertions [1] [2], and these have been underpinned by extensive theoretical investigations [3]. Alkyne insertion reactions have also received considerable attention, especially in the context of transition-metalcatalysed cyclotrimerization and oligomerization reactions [4 ± 8]. The insertion of an alkyne into the MÀC s-bond of a metallacycle provides a synthetically useful process, because cyclometallated compounds can often be prepared directly by cleavage of a CÀH bond close to a suitable donor atom [9 ± 11]. In particular, alkyne reactions with palladacycles have found wide application in the synthesis of important polycyclic and heterocyclic molecules [12 ± 18]; a stoichiometric process based on cyclomanganated complexes derived from aromatic ketones [19] [20] and a process based on a-tetralone catalysed by [RuH 2 (CO)(PPh 3 ) 3 ] [21] have also been reported.If unsymmetric alkynes are to be used in such reactions, good regioselectivity or even complete regiocontrol is essential. Although several mechanistic studies of the insertions of alkynes into NiÀC and PdÀC bonds have been reported [22 ± 27], little is known about the factors governing the regiochemistry of alkyne insertions into MÀC bonds. Both electronic and steric effects have been invoked to explain the regioselectivities observed for the insertions of alkynes into PdÀaryl bonds, but, although the latter argument is generally preferred, neither could satisfactorily be applied in all cases [16] [17] [28]. For example, two investigations of the insertions of

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Regioselectivity of the Insertion of 4,4-Dimethyl-2-Pentyne into the Pd-C Bond of Cyclopalladated Complexes

Cited by 86 publications

References 0 publications

Synthesis, Structure, Reactivity, and Catalytic Activity of C,N‐ and C,N,N‐Orthopalladated Iminophosphoranes

Synthesis, Structure, Reactivity, and Catalytic Activity of C,N‐ and C,N,N‐Orthopalladated Iminophosphoranes

Reactivity of cyclopalladated compounds derived from biphenyl-2-ylamine towards carbon monoxide, tbutyl isocyanide and alkynes

Insertions of Unsymmetric Alkynes into the Metal−Carbon Bonds of Nickelacycles: What Determines the Regiochemistry?

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