Paramagnetic phosphine shift reagents. 2. Study of the structures of (substituted-allyl)palladium complexes in solution

Faller, J. W.; Blankenship, Craig; Whitmore, Bryan C.; Sena, Salvador

doi:10.1021/ic00220a013

Cited by 35 publications

(14 citation statements)

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“…On the contrary, coordination of π-acceptor ligands involves charge transfer from the metal to the ligand through back-donation that leads to orbital contraction and as a consequence a lowering of the 2a‘‘ level. The ligand effects on the MO interactions are reflected, for example, by the Pd−C bonding: in (π-allyl)PdL 2 complexes with σ-donor ligands the Pd−C bond lengths are 2.08−2.15 Å, while with π-acceptor ligands the Pd−C bonds are much longer and weaker, 2.19−2.22 Å. 4a, This is consistent with the higher reactivity toward nucleophiles of the (π-allyl)palladium complexes with π-acceptor ligands compared to those with σ-donor ligands.…”

Section: Resultsmentioning

confidence: 61%

Central versus Terminal Attack in Nucleophilic Addition to (π-Allyl)palladium Complexes. Ligand Effects and Mechanism

et al. 1997

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Nucleophilic addition to (η3-2-chloropropenyl)palladium complexes 1 with stabilized carbanions such as dialkyl malonates was studied. These complexes are used as probes to determine whether nucleophilic attack occurs at the central or terminal carbon of the π-allyl group. Attack at the central carbon leads to substitution of chloride via a palladacyclobutane intermediate. The regiochemistry of the reaction (central versus terminal attack) is controlled by proper choice of ligands. Thus, σ-donor ligands direct the attack of the nucleophile to the central carbon (C-2) of the allyl group whereas π-acceptor ligands direct the attack to the terminal carbons (C-1 or C-3). It was found that there is a correlation between the relative rate of central versus terminal attack and the 13C NMR shifts of the allyl group. The shift difference between the central and terminal carbons, Cc − Ct, can be used to predict the site of attack. Ab initio calculations were performed on (π-allyl)palladium complexes as well as on the postulated palladacyclobutane. The calculations support the experimental results, and for the π-allyl complexes with the σ-donor ligands the LUMO from the calculations is the symmetrical orbital with a large coefficient at the central carbon.

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Section: Resultsmentioning

confidence: 61%

Central versus Terminal Attack in Nucleophilic Addition to (π-Allyl)palladium Complexes. Ligand Effects and Mechanism

et al. 1997

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“…The phenyl protons of the η 6 - p -cymene fragment are at δ = 5.0 ppm, while the resonances assignable to the methyl and isopropyl (C H 3 and H ) protons of the p -cymene are at δ = 1.88, 1.13, and 3.0 ppm, respectively. Note that the resonances of the organometallic fragments are broadened, indicating the effect of the remote aminoxyl radical on each proton, but only slightly shifted with respect to the corresponding PPh 3 derivative. , …”

Section: Resultsmentioning

confidence: 99%

Stable Organopalladium(II) and Organoruthenium(II) Complexes with Spin-Labeled Phosphine Ligands

et al. 1999

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Palladium(II) and ruthenium(II) complexes containing aminoxyl radical-substituted triphenylphosphine ligands are reported. The novel spin-labeled phosphine ligands [(p-(4,4,5,5,-tetramethylimidazolinyl-1-oxyl-3-oxide)phenyl)diphenylphosphine] (1) and [(p-(Noxyl-tert-butylamino-2-)phenyl)diphenylphosphine] (2) react with PdCl 2 to yield trans-Pd[1] 2 Cl 2 and trans-Pd [2] 2 Cl 2 (complexes 3 and 4, respectively), which show exchange-coupled EPR spectra. This through-space, intramolecular coupling provides a method of determining the number of radical phosphines coordinated to the Pd(II) center. Systems with only one coordinated phosphine show EPR spectra typical of the ligand. Phosphine 2 reacts with [(η 3 -C 3 H 5 )PdCl] 2 and [(η 6 -p-cymene)RuCl 2 ] 2 to form the mononuclear metal phosphine adducts (η 3 -C 3 H 5 )Pd[2]Cl ( 5) and (η 6 -p-cymene)Ru[2]Cl 2 (6). All complexes show broad, shifted 1 H NMR spectra, and magnetic susceptibility measurements confirm the presence of one (complexes 5, 6) or two (complexes 3, 4) radicals per complex accordingly. The X-ray crystal structures of Pd[2] 2 Cl 2 and (η 3 -C 3 H 5 )Pd[2]Cl are also reported. Complexes 5 and 6 are unusual examples of stable organometallic systems with peripheral free radicals, i.e., spin-labeled organometallics.

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“…The P2-Pd1 and Co1-N2 lines form an angle of 68.10(7) • . Surprisingly, to the best of our knowledge, only one example of a P,N-bridged Pd/Co complex has been reported before 12 and there are only three precedents for a bridging behaviour of ligand 1, in a Fe/Co, 13 Fe/Cu 14 and Co/Co complex. 11 The reaction leading to 2 features (i) the cleavage of the parent dinuclear cobalt complex, (ii) a chloride transfer from Pd to Co, and (iii) P-migration from cobalt to palladium.…”

Section: Resultsmentioning

confidence: 87%

A phosphino-oxazolineligand as a P,N-bridge in palladium/cobalt or P,N-chelate in nickel complexes: catalytic ethylene oligomerization

et al. 2012

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The Pd(II) complex [PdCl(2)(1)] [1 = ({oxazolin-2-yl}methyl)diphenylphosphine] was obtained by the 1:1 reaction of 1 with [PdCl(2)(NCPh)(2)]. Although this neutral complex is stable in the solid-state and in solution, it reacts with the dinuclear complex [CoCl(2)(μ-1)](2) to afford the heterometallic zwitterionic complex [{PdCl(1)}(+)(μ-1)(CoCl(3))(-)] (2). Under inert atmosphere, two equivalents of 1 reacted with [NiCl(2)(dme)] to give trans-[NiCl(2)(1)(2)] (3) in CH(2)Cl(2) but cis-[NiCl(2)(1)(2)] (4) in CHCl(3). When the latter reaction was performed in air, trans-[NiCl(2)(5)(2)] (6) [5 = ({oxazolin-2-yl}methyl)diphenylphosphine oxide] was obtained. All metal complexes, 2, 3, 4 and 6, have been structurally characterized by X-ray diffraction. Complexes 3, 4 and 6 have been evaluated as precatalysts for ethylene oligomerisation in the presence of AlEtCl(2) as cocatalyst. Complexes 3 and 6 yielded a turnover frequency (TOF) of 60,700 and 62,600 mol of C(2)H(4)/((mol of Ni)·h), respectively, in the presence of 10 equiv. of AlEtCl(2). In the presence of only 6 equiv. of cocatalyst, these Ni complexes yielded TOF values of 41,500 and 58,000 mol of C(2)H(4)/((mol of Ni)·h), respectively.

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Paramagnetic phosphine shift reagents. 2. Study of the structures of (substituted-allyl)palladium complexes in solution

Cited by 35 publications

References 0 publications

Central versus Terminal Attack in Nucleophilic Addition to (π-Allyl)palladium Complexes. Ligand Effects and Mechanism

Central versus Terminal Attack in Nucleophilic Addition to (π-Allyl)palladium Complexes. Ligand Effects and Mechanism

Stable Organopalladium(II) and Organoruthenium(II) Complexes with Spin-Labeled Phosphine Ligands

A phosphino-oxazolineligand as a P,N-bridge in palladium/cobalt or P,N-chelate in nickel complexes: catalytic ethylene oligomerization

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