Platinum(II) and palladium(II) complexes containing a mixed donor `P2N' multidentate ligand

Ainscough, Eric W.; Brodie, Andrew M.; Burrell, Anthony K.; Derwahl, Andreas; Jameson, Geoffrey B.; Taylor, Steven K.

doi:10.1016/j.poly.2004.01.015

Cited by 12 publications

(11 citation statements)

References 36 publications

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“…P-C-C-N-C-C-C-P, -being any type of bond), and only one of them has palladium as the metal centre, 10a while all the four complexes contain the same P-N-P′-ligand used in this work. 7,10 Bond distances and angles around the metal ion in 1 well compare with those already reported, 11 including the Pd-C(38) distance. In particular, as found in related compounds, the M-P(1) distance (where M is the coordinated metal atom and P(1) belongs to the five-membered chelate ring) is usually shorter than the M-P(2) one (where P(2) is part of the six-membered chelate ring); the P-M-N angle belonging to the six-membered ring is always larger than that of the five-membered one, and finally the N-M-X and P-M-P angles are slightly less than 180°.…”

Section: Resultssupporting

confidence: 80%

“…The tridentate coordination of the ligand through the imino nitrogen and the phosphorus atoms is clearly indicated by the low-frequency shift of the ν(CvN) band (17-20 cm −1 ) relative to the free ligand [ν(CvN) = 1621 cm −1 ] in the IR spectra, and by the appearance of the 31 P signals as AB quartets in the range 26-34 ppm with 2 J(P-P) values of 312-362 Hz, which are typical of the non-equivalent 31 P nuclei in the trans position (Table 1). 7 The PNP coordination is also confirmed by the X-ray structural analysis of complex 1 (see further).…”

Section: Resultsmentioning

confidence: 63%

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η1-Allylpalladium complexes with a tridentate PNP ligand with different phosphino groups

et al. 2012

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3 = H: (1); R 1 = R 2 = Ph, R 3 = H: (2); R 1 = R 3 = H, R 2 = Ph: (3); R 1 = H, R 2 = R 3 = Me: (4)]. The P-N-P′ tridentate coordination and the η 1 -allyl bonding mode in the solid are confirmed by the X-ray structural analysis of 1. In solution, the complexes 1 and 2 undergo an η 1 -η 3 -η 1 rearrangement at 298 K interconverting the bonding site of the allyl group. A five-coordinate structure with the phosphine ligands in the axial position is proposed for the η 3 -allyl intermediate. For the dynamic process, a ΔG ≠ value of 53.8 kJ mol −1 is obtained from 1 H NMR data of 2. In 3 and 4, the allyl ligand is rigidly bound to the metal through the less substituted terminus, in line with the higher free energy content of the corresponding isomers: [Pd(η 1 -CHPhCHvCH 2 )(P-N-P′)] + +48.78 kJ mol −1 ; [Pd(η 1 -CMe 2 -CHvCH 2 )(P-N-P′)] + +69.35 kJ mol −1 . The complexes react with secondary amines in the presence of fumaronitrile at different rates yielding allylamines and the palladium(0) derivative [Pd(η 2 -fn)(P-N-P′)] (5). On the basis of charge distribution on the allylic carbon atoms and of steric factors, the difference in rate and the regioselectivity in the amination of 1-3 are better rationalized by a mechanism with nucleophilic attack at the η 3 -intermediate rather than by an S N 2 mechanism with nucleophilic attack at the Pd-CHR 1 carbon atom. The high regioselectivity in the reaction of 4 with piperidine implies an S N 2′ mechanism with nucleophilic attack at the CMe 2 allyl carbon. A dynamic process occurs also for the 18-electron complex 5 consisting in a dissociation-association equilibrium of the olefin.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 63%

η1-Allylpalladium complexes with a tridentate PNP ligand with different phosphino groups

et al. 2012

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“…Fresh nitrobenzene and hexane-2,5-dione were then added into the catalyst-containing flask and the domino Pt-catalyzed reduction/Paal-Knorr reaction then proceeded under the same experimental conditions as described above. The conversion and selectivity measured for the consecutive runs were identical to those obtained for the initial one ( Table 2, run [26][27][28][29], indicative of both the robustness of the catalytic system and the absence of Ptparticles in the system. Neither significant loss of catalytic activity nor selectivity could be measured indicative of both the robustness of the catalytic system and the absence of Ptparticles in the system.…”

Section: Domino Pt-catalysed Reduction/paal-knorr Reactionsupporting

confidence: 61%

Cyclodextrin-based PNN supramolecular assemblies: a new class of pincer-type ligands for aqueous organometallic catalysis

et al. 2015

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Water-soluble cyclodextrins (CDs) bearing two nitrogen atoms as metal coordinating sites have been synthesized. An appropriate phosphane could be included within their cavity through the primary face to form self-assembled PNN supramolecular edifices. Once the PNN ligands were coordinated to platinum, the resulting complexes proved to be very effective as catalysts in a domino reaction, where a Pt-catalyzed reduction of nitrobenzene was followed by a Paal-Knorr pyrrole reaction. In the nitrobenzene reduction, the modified CDs acted both as first- and second-sphere ligands. Contrary to an acyclic glucopyranose-based NN ligand unable to interact with a phosphane ligand, the CD-based PNN ligands stabilized the catalytic species in water by supramolecular means. Interestingly, the product and the water-soluble Pt-catalyst could be recovered in two different phases once the reaction was complete.

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“…Crystallographic analysis of 3 showed a distorted tetrahedral geometry around the nickel center ( Figure 1 ). 27 The Ni(0) center is bound to 1 in a κ 4 (P,P,C,N)-fashion with an η 2 (C,N)-coordination of the imine backbone and to the PPh 3 coligand. The C–N distance of the imine moiety is clearly larger in 3 (1.364(5) Å) than in the Ni(II) complex 2 (1.294(5) Å), as a result of π-backdonation to the antibonding π* orbital of the imine C=N bond.…”

Section: Resultsmentioning

confidence: 99%

Versatile Coordination and C–C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0)

et al. 2018

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Ligands that can adapt their coordination mode to the electronic properties of a metal center are of interest to support catalysis or small molecule activation processes. In this context, the ability of imine moieties to bind in either an η1(N)-fashion via σ-donation of the lone pair or, less commonly, in an η2(C,N)-fashion via π-coordination is potentially attractive for the design of new metal–ligand cooperative systems. Herein, the coordination chemistry of chelating ligands with a diphosphine imine framework (PCNP) to nickel is investigated. The imine moiety binds in an η1(N)-fashion in a Ni(II)Cl2 complex. The uncommon η2(C,N)-interaction is obtained in Ni(0) complexes in the presence of a PPh3 coligand. Increasing the bulk on the phosphine side-arms in the Ni(0) complexes, by substituting phenyl for o-tolyl groups, leads to a distinct binding mode in which only one of the phosphorus atoms is coordinated. In the absence of a coligand, a mixture of two different dimeric Ni(0) complexes is formed. In one of them, the imine adopts an uncommon η1(N)η2(C,N) bridging mode of the ligand to nickel, while the second one may involve reactivity on the ligand by the formation of a new C–C bond by oxidative coupling. The latter is supported by the isolation and structural characterization of a crystalline bis-CO derivative featuring a C–C bond formed by oxidative coupling of two imine moieties.

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Platinum(II) and palladium(II) complexes containing a mixed donor `P2N' multidentate ligand

Cited by 12 publications

References 36 publications

η1-Allylpalladium complexes with a tridentate PNP ligand with different phosphino groups

η1-Allylpalladium complexes with a tridentate PNP ligand with different phosphino groups

Cyclodextrin-based PNN supramolecular assemblies: a new class of pincer-type ligands for aqueous organometallic catalysis

Versatile Coordination and C–C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0)

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