- 2-Pyridyl-phosphine and -diphosphine complexes of nickel(0), their reactivity (including aqueous solution chemistry), and some related, incidental methylphosphonium iodides
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The chemistry of Ni0-dicarbonyl(pyridylphosphine) complexes of the type Ni(CO)2L2, where L is either P-bonded PPh3-npyn (n = 1-3, py = 2-pyridyl; abbreviated PNx, x = 1-3, species 1a-c), or L2 is (P-P)-chelated py2P(CH2)2Ppy2 or, is further developed from earlier studies by our group [the P-P ligands are abbreviated, respectively, as d(py)pe and d(py)pcp]. The complexes are synthesized from C6H6 solutions of Ni(CO)2(PPh3)2, and the Ni(CO)2(PPh3)(PNx) intermediates (1a-c) are detected; Ni(CO)2[d(py)pcp] (2b) is shown by X-ray analysis to have a distorted tetrahedral structure; and the NiII species [Ni2(CO)4(μ-PN2)2]Cl4 is isolated from a light-induced reaction in CDCl3 solution. Complex 2b dissolves in water at ambient conditions via a net double protonation of pyridyl N-atoms, the {Ni(CO)2[2H-d(py)pcp]}2+ being isolated as the bis(triflate) salt; the dication decomposes in minutes with formation of [Ni(H2O)6]2+, CO, the phosphine dioxide, and deprotonated d(py)pcp. Some twenty-two Ni0 complexes, exemplified by Ni(P-P)2, Ni(PNx)2(P-P), Ni(PNx)4, and related PPh3- and Ph2P(CH2)2PPh2 (dppe)-containing species, are synthesized from Ni(1,5-COD)2 and their reactivity studied; for example, oxidative addition of MeI generates trans-Ni(Me)(I)(PN3)2 and trans-Ni(Me)(I)(P-P)2 but, with non-pyridyl containing reactants such as Ni(PPh3)4 and Ni(dppe)2, only (monomethyl)phosphonium iodides are formed. Such iodides, and the bis(methyl) analogues [(CH3)2(diphosphine)]I2, are then studied for clarification of some observed Ni chemistry. The NMR trends (a)-(d) are noted within the series of Ni0 complexes, and are rationalized: (a) the 2JPP values in 1a-c, and the separation between the two doublets, parallel the number of N-atoms present; (b) the 31P{1H} signals in the Ni(PNx)4 and Ni(PNx)2(P-P) complexes shift downfield in the order PN1 2 3 within linear dependences; (c) the 2JPP values for the Ni(PR3)2(P-P) complexes (R = Ph and PNx) decrease in the order R = Ph > PN1 > PN2 > PN3; (d) and the separation between the two 31P{1H} triplets of the Ni(PNx)2(P-P) complexes generally depends on the relative numbers of phenyl and pyridyl groups.
- Le Page, Matthew D.,Patrick, Brian O.,Rettig, Steven J.,James, Brian R.
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p. 276 - 288
(2015/06/02)
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- Halogenolysis of a nickelalactone complex produces β-halo-anhydrides
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Nickelalactone complex [(dppe)Ni{κ2-C,O-CH2CH2C(=O)O}] {dppe = 1,2-bis(diphenylphosphino)ethane} reacts with halogens to form 3-halo-propionic anhydrides, [(dppe)NiX2], and [(dppeO2)3Ni][NiX4] (X = Cl, Br, I). Studies of model complexes [(dppe)Ni(O2CtBu)2] and [(dppe)NiBr(O2CtBu)] suggest that oxidation to NiIII and P-O reductive elimination are key steps in this reaction.
- Zarkesh, Ryan A.,Hopkins, Michael D.,Jordan, Richard F.
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supporting information
p. 5491 - 5494
(2015/03/30)
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- σ-bond metathesis between M-X and RC(O)X′ (M = Pt, Pd; X, X′ = Cl, Br, I): Facile determination of the relative Δ G values of the oxidative additions of RC(O)X to an M(0) complex, evidence by density functional theory calculations, and synthetic applications
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The novel utility of the ligand exchange reaction between M-X and RC(O)X′ (X, X′ = halogen; R = aryl, alkyl) is described. The relative ΔGs (ΔΔGs) of the oxidative additions of acid halides RC(O)X to M(PPh3)2Ln (M = Pt, Pd) were determined using the halogen-exchange reactions between X of trans-M(X)[C(O)R](PPh3)2 and X′ of RC(O)X′. Experimental thermodynamics data are reasonably consistent with those obtained by density functional theory (DFT) calculations. Activation parameters obtained by experiments as well as a systematic DFT study supported the fact that reactions occurred through slightly distorted quadrangular pentacoordinated σ-bond metatheses, in which the Cl atom underwent a more indirect course than the Br atom. Moreover, exchange reactions were employed as the accessible prototype for the conversion of halogen ligands of nickel triad complexes into heavier halogen ligands.
- Kuniyasu, Hitoshi,Sanagawa, Atsushi,Nakane, Daisuke,Iwasaki, Takanori,Kambe, Nobuaki,Bobuatong, Karan,Lu, Yunpeng,Ehara, Masahiro
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supporting information
p. 2026 - 2032
(2013/05/09)
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- Active-site models for the nickel-iron hydrogenases: Effects of ligands on reactivity and catalytic properties
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Described are new derivatives of the type [HNiFe(SR) 2(diphosphine)(CO)3]+, which feature a Ni(diphosphine) group linked to a Fe(CO)3 group by two bridging thiolate ligands. Previous work had described [HNiFe(pdt)(dppe)(CO) 3]+ ([1H]+) and its activity as a catalyst for the reduction of protons (J. Am. Chem. Soc.2010, 132, 14877). Work described in this paper focuses on the effects on properties of NiFe model complexes of the diphosphine attached to nickel as well as the dithiolate bridge, 1,3-propanedithiolate (pdt) vs 1,2-ethanedithiolate (edt). A new synthetic route to these Ni-Fe dithiolates is described, involving reaction of Ni(SR) 2(diphosphine) with FeI2(CO)4 followed by in situ reduction with cobaltocene. Evidence is presented that this route proceeds via a metastable μ-iodo derivative. Attempted isolation of such species led to the crystallization of NiFe(Me2pdt)(dppe)I2, which features tetrahedral Fe(II) and square planar Ni(II) centers (H 2Me2pdt = 2,2-dimethylpropanedithiol). The new tricarbonyls prepared in this work are NiFe(pdt)(dcpe)(CO)3 (2, dcpe = 1,2-bis(dicyclohexylphosphino)ethane), NiFe(edt)(dppe)(CO)3 (3), and NiFe(edt)(dcpe)(CO)3 (4). Attempted preparation of a phenylthiolate-bridged complex via the FeI2(CO)4 + Ni(SPh)2(dppe) route gave the tetrametallic species [(CO) 2Fe(SPh)2Ni(CO)]2(μ-dppe)2. Crystallographic analysis of the edt-dcpe compund [2H]BF4 and the edt-dppe compound [3H]BF4 verified their close resemblance. Each features pseudo-octahedral Fe and square pyramidal Ni centers. Starting from [3H]BF4 we prepared the PPh3 derivative [HNiFe(edt)(dppe)(PPh3)(CO)2]BF4 ([5H]BF 4), which was obtained as a ~2:1 mixture of unsymmetrical and symmetrical isomers. Acid-base measurements indicate that changing from Ni(dppe) (dppe = Ph2PCH2CH2PPh2) to Ni(dcpe) decreases the acidity of the cationic hydride complexes by 2.5 pK aPhCN units, from ~11 to ~13.5 (previous work showed that substitution at Fe leads to more dramatic effects). The redox potentials are more strongly affected by the change from dppe to dcpe, for example the [2]0/+ couple occurs at E1/2 = -820 for [2]0/+ vs -574 mV (vs Fc+/0) for [1]0/+. Changes in the dithiolate do not affect the acidity or the reduction potentials of the hydrides. The acid-independent rate of reduction of CH 2ClCO2H by [2H]+ is about 50 s-1 (25 °C), twice that of [1H]+. The edt-dppe complex [2H]+ proved to be the most active catalyst, with an acid-independent rate of 300 s-1.
- Carroll, Maria E.,Barton, Bryan E.,Gray, Danielle L.,MacK, Amanda E.,Rauchfuss, Thomas B.
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p. 9554 - 9563
(2011/10/31)
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- Reactions between Bis(O-alkyl dithiocarbonato)nickel(II) Complexes and Phosphines. Formation of a Dithiocarbonate Complex of Nickel(II):
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The behaviour of O-alkyl dithiocarbonato complexes, , towards several phosphines has been studied.Depending on the S2COR derivative and phosphine (L) used, octahedral complexes , paramagnetic five-co-ordinate complexes , and square-planar (R=Et or cyclo-C6H11) and complexes have been obtained.The reaction of (R=Me, Et, or cyclo-C6H11) with an excess of dppe gives which is the first NiII-dithiocarbonate complex described.This compound reacts with MeI and C3H5Br to give (X=I or Br).There is no reaction with Lewis-base N donors or with carbon monoxide.
- Perpinan, Maria F.,Ballester, Loreto,Gonzalez-Casso, Maria E.,Santos, Amelia
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p. 281 - 284
(2007/10/02)
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- Co-ordination Chemistry of Higher Oxidation States. Part 11. The Reaction of Nickel(II) Iodo-complexes with Molecular Iodine; Crystal and Molecular Structure of 2>2*2I2
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The reaction of excess of elemental iodine with the nickel(II) iodo-complexes in CH3CN-CH2Cl2 solution produces diamagnetic Ni(L-L)2I6 materials formulated as II(L-L)2>2 and containing tri-iodide(1-) anions.From neat CH2Cl2 solution the complex Ni2I10 was obtained, and has been shown by single-crystal X-ray studies to be triclinic, space group P1, with unit-cell dimensions a = 9.672(2), b = 12.369(2), c = 9.574(3) Angstroem, α = 106.55(2), β = 107.70(2), γ = 99.48(1) deg, and Z = 1.2914.Observed reflections 4?(F)> refined to R 0.032.The complex contains planar 2>(2+) cations , linear I3(1-) anions , and di-iodine .Weak secondary interactions between the iodine atoms of I3(1-) and I2 lead to the formation of bifurcated chains.Other nickel(II) polyiodides obtained include the paramagnetic (L-L = MeSCH2CH2SMe or MeSeCH2CH2SeMe) and the diamagnetic and .The reaction of the nickel-(III) and -(IV) species 2Cl2>(n+) (n = 1 or 2) with I(1-) gives a compound of composition 2I3> which is considered to be a nickel(II) derivative.The complexes have been characterised by electronic and e.s.r. spectroscopy, magnetic and conductance measurements.No evidence for the formation of nickel(III) iodo-complexes has been obtained.
- Gray, Leslie R.,Higgins, Simon J.,Levason, William,Webster, Michael
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p. 1433 - 1440
(2007/10/02)
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- Ditertiary phosphine complexes of nickel. Spectral, magnetic, and proton resonance studies. A planar-tetrahedral equilibrium
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A number of complexes of nickel in oxidation states 0, II, and III with the ditertiary phosphines (C6H5)2P(CH2)nP(C 6H5)2 (n = 1, 2, or 3) are reported and studied by spectral and magnetic methods. In solution in organic solvents complexes of the type Ni[(C6H5)2P(CH2)nP(C 6H5)2]X2 where X = Br or I and n = 2 remain diamagnetic. The analogous complexes with n = 3 show a square-planar (diamagnetic)-tetrahedral (paramagnetic) equilibrium in solution. Isotropic proton magnetic resonance shifts were observed in these systems and thermodynamic parameters for the equilibrium were obtained from the temperature dependences of these shifts. The epr spectrum of polycrystalline Ni[(C6H5)2P(CH2)3P(C 6H5)2]Br3 shows an isotropic signal at g = 2.218.
- Van Hecke, Gerald R.,Horrocks Jr., William DeW.
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p. 1968 - 1974
(2008/10/08)
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