Studies of a series of [Ni(P(R)2N(Ph)2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production: substituent variation at the phosphorus atom of the P2N2 ligand

A series of [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes containing the cyclic diphosphine ligands [P(R)(2)N(Ph)(2) = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(P(Bn)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) and [Ni(P(n-Bu)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(P(Bn)(2)N(Ph)(2))(2)] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(P(Cy)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2), all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H(2) in acidic acetonitrile solutions. The heterolytic cleavage of H(2) by [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(P(R)(2)N(Ph)(2))(2)](BF(4)) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H(2), suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate.     

Synthesis and crystal structure of [(Ph3P)2N] [Ni2(CO)6H]

The interstitial dihydride dianion [Ni₁₂(CO)₂₁H₂]^2? is readily converted by carbon monoxide (25°C, 1 atm) into a mixture of tetracarbonylnickel and a new colourless hydride carbonyl monoanion, which has been characterized by X-ray diffraction as [Ni₂(CO)₆H]^?.     

Reactions of S4N4 with diphosphines,Ph2P(X)PPh2 (X = NC4H8N,CH2CH2)

Reactions of S₄N₄ with diphosphines, Ph₂P(X)PPh₂ (X = NC₄H₈N, CH₂CH₂) have resulted in the isolation of N₃S₃? NPPh₂(X)Ph₂PN? S₃N₃ (X = NC₄H₈N, CH₂CH₂), (S)PPh₂(CH₂CH₂)Ph₂PN? S₃N₃, and (S)PPh₂NC₄H₈NPh₂P(S) as new compounds. These heterocycles have been characterized by analytical and spectroscopic (IR, UV-VIS, ¹H and ³¹P-NMR, and MS) techniques.     

Intensely green quinonoid [Cr(CO)4(Ph2P)2C-C6H4-C(R)O2CR-P,P] complexes

Summary Ph₂PCH(Ph)PPh₂, prepared by treating Ph₂PCH₂Ph successively with n-BuLi and Ph₂PCl, reacts with group VI metal hexacarbonyls to give [M(CO)₄{Ph₂PCH(Ph)-PPh₂}], where M = Cr, Mo or W. The Cr complex [Cr(CO)₄{Ph₂PCH(Ph)PPh₂}] was deprotonated with MeLi and the resulting carbanion [Cr(CO)₄(Ph₂-PCPhPPh₂)]^– acylated with RCOCl (R = Ph or p-tolyl) to give the intensely green title compounds in which an aromatic ring has become a quinonoid.Author to whom all correspondence should be directed.     

Synthese und Struktur von [(Ph3C6H2)Te]2, [(Ph3C6H2)Te(AuPPh3)2]PF6 und [(Ph3C6H2)TeAuI2]2

Synthesis and Structure of [(Ph₃C₆H₂)Te]₂, [(Ph₃C₆H₂)Te(AuPPh₃)₂]PF₆ and [(Ph₃C₆H₂)TeAuI₂]₂ [(2,4,6-Ph₃C₆H₂)Te]₂ reacts with Ph₃PAu⁺ to yield [2,4,6-Ph₃C₆H₂TeAuPPh₃₂]PF₆ which can be oxidized by I₂ to form the gold(III) complex [(2,4,6-Ph₃C₆H₂)TeAuI₂]₂. [(2,4,6-Ph₃C₆H₂)Te]₂ crystallizes in the monoclinic space group P2₁/c with a = 810.6(2); b = 2026.5(5); c = 2260.6(7) pm; β = 99.23(3)° and Z = 4. In the crystal structure the ditelluride exhibits a dihedral angle C11? Te1? Te2? C21 of 66.1(2)°. The distance Te1? Te2 is 269.45(6) pm. In the cation of the triclinic complex [(2,4,6-Ph₃C₆H₂)Te(AuPPh₃)₂]PF₆ (space group P1 ; a = 1197.4(3); b = 1457.2(4); c = 1680.0(6) pm; α = 84.69(3)°; β = 85.11(3)°; γ = 75.54(3)°; Z = 2) a pyramidal skeleton RTeAu₂ with distances Te? Au = 259.2(1) and 257.8(2) pm and Au? Au = 295.3(1) pm is present. [(2,4,6-Ph₃C₆H₂)TeAuI₂]₂ crystallizes in the triclinic space group P1 with a = 1086.3(3); b = 1462.9(6); c = 1654.2(2) pm; α = 85.25(2)°; β = 87.44(1)°; γ = 80.90(3)°; Z = 2. In the centrosymmetrical dinuclear complex [(2,4,6-Ph₃C₆H₂)TeAuI₂]₂ the Au atoms exhibit a square-planar coordination by two iodine atoms and two tellurolate ligands. The tellurolate ligands form symmetrical bridges with distances Te? Au = 260.0 pm. The distances Au? I are in the range of 260.3(1) and 263.7(1) pm.     

An infrared and raman spectroscopic study of metal(II) Di(2-methylpyridine) tetracyanonickelate complexes: Ni(C6H7N)2Ni(CN)4 and Cd(C6H7N)2Ni(CN)4

The results of an infrared and Raman spectroscopic study are reported for two new metal 2-methylpyridine tetracyanonickelate complexes, M(C₆H₇N)₂Ni(CN)₄, M=Ni or Cd. Their structure consists of corrugated polymeric layers of {M-Ni(CN)₄} with 2-methylpyridine molecules bound directly to the metal (M). These complexes can act as host lattices in the formation of inclusion compounds with dioxane guest molecules.     

Chloro- und Polyselenoselenate(II) Darstellung,Struktur und Eigenschaften von [Ph3(C2H4OH)P]2[SeCl4] · MeCN, [Ph4P]2[Se2Cl6] und [Ph4P]2[Se(Se5)2]

Chloro- and Polyselenoselenates(II): Synthesis, Structure, and Properties of [Ph₃(C₂H₄OH)P]₂[SeCl₄] · MeCN, [Ph₄P]₂[Se₂Cl₆], and [Ph₄P]₂[Se(Se₅)₂] By symproportionation of elemental selenium and SeCl₄ in polar protic solvents the novel chloroselenates(+II), [SeCl₄]^2? and [Se₂Cl₆]^2?, could be stabilized; they were crystallized with voluminous organic cations. They were characterized from complete X-ray structure analysis. Yellow-orange [Ph₃(C₂H₄OH)P]₂[SeCl₄] · MeCN (space group P1 , a = 10.535(4), b = 12.204(5), c = 16.845(6) Å, α = 77.09(3)°, β = 76.40(3)°, γ = 82.75(3)° at 140 K) contains in its crystal structure monomeric [SeCl₄]^2? anions with square-planar coordination of Se(+II). The mean Se? Cl bond length is 2.441 Å. In yellow [Ph₄P]₂[Se₂Cl₆] (space group P1 , a = 10.269(3), b = 10.836(4), c = 10.872(3) Å, α = 80.26(3)°, β = 79.84(2)°, γ = 72.21(3)° at 140 K) a dinuclear centrosymmetric [Se₂Cl₆]^2? anion, also with square-planar coordinated Se(+II), is observed. The average terminal and bridging Se? Cl bond distances are 2.273 and 2.680 Å, respectively. From redox reactions of elemental Se with boranate/thiolate in ethanol/DMF the bis(pentaselenido)selenate(+II) anion [Se(Se₅)₂]^2? was prepared as a novel type of a mixed-valent chalcogenide. In dark-red-brown [Ph₄P]₂[Se(Se₅)₂] (space group P2₁/n, a = 12.748(4), b = 14.659(5), c = 14.036(5) Å, β = 108.53(3)° at 140 K) centrosymmetric molecular [Se(Se₅)₂]^2? anions with square-planar coordination of the central Se(+II) by two bidentate pentaselenide ligands is observed (mean Se? Se bond lengths: 2.658 Å at Se(+II), 2.322 Å in [Se₅]_2?). The resulting six-membered chelate rings with chair conformation are spirocyclically linked through the central Se(+II). The vibrational spectra of the new anions are reported.     

Synthesis and Characterisation of Two Examples of Unsymmetrically Disubstituted Cyclotetrathiazenes, 1,5-(X)(Y)S4N4[X = Ph3PN- and Y = i) (p-CH3C6H4) Ph2PN- and ii) (P-CH3C6H4)2PhPN-]

Abstract

1,5- [(p-tolyl)diphenylphosphinimino] (triphenylphosphinimino)tetrasulphurtetranitride, (I) and 1,5-[di(p-tolyl)phenylphosphinimino] (triphenylphosphinimino)tetrasulphurtetranitride, (II) are the first examples of heterodisubstituted tetrasulphurtetranitride derivatives to be made. Their synthesis and structural characterization are described.     

Isotope effect in Ni + C2H4 (C2D4) association reaction

The association reactions of atomic nickel with ethene and fully deuterated ethene in carbon dioxide buffer gas at 295 K have been investigated in the pressure range 5–100 torr, using a laser photolysis-laser fluorescence technique. By comparison with results of ab initio quantum chemistry calculations for the complex Ni[C₂H₄], the data are shown to be consistent with reaction on both ground and excited state potential energy surfaces. A simple rate equations treatment is described which shows the form of the pressure dependence of the second-order recombination rate coefficient in this case. Under conditions which are expected to hold for the Ni + C₂H₄ (C₂D₄) reaction, the pressure dependence has the standard Lindemann-Hinshelwood form, with the limiting high pressure rate constant given by an apparent value which reflects the degree to which the participating electronic states are coupled by nonadiabatic transitions. The limiting high pressure behavior of the recombination rate coefficient for Ni + C₂H₄ is not strongly affected by deuterium isotope substitution. However, the effect on the low pressure rate constant is large and consistent with RRKM unimolecular reaction theory. This validates the use of RRKM calculations for estimating the binding energy of the complex from kinetic data. The binding energy of Ni[C₂H₄] is estimated to be 35.2 ± 4.2 kcal mol^?1. © 1994 John Wiley & Sons, Inc.     

Synthesis of Diaminophosphonium Salts [Ph2(ArNH)2P]+Br− (Ar = o-MeC6H4, p-MeC6H4, p-Pr i C6H4, p-EtO2CC6H4, p-MeOC6H4)

The behavior of different anilines H₂NC₆H₄R (R = o-Me, p-Me, o-, m- and p? ⁱ Pr, p-OMe, p-CO₂Et) and 2,6-Me₂C₆H₃NH₂ towards trihalophosphoranes was studied. 2,6-Me₂C₆H₃NH₂ failed to form the diaminophosphonium salt [Ph₂PNH(2,6-Me₂C₆H₃)₂]Br, and the aminophosphine oxide Ph₂(2,6-Me₂C₆H₃NH)PO was the only isolated product. Both o- and p-toluidine gave the corresponding diaminophosphonium salts; however in the case of o-toluidine, the yield was low and a mixture with the respective aminophosphine oxide was observed. Anilines containing methoxy and ethoxycarbonyl groups in para-position form the diaminophosphonium salts in reasonable yields.     

Heteroatom effects on allenic seven-membered ring X2C4H4C (X = CH,N, P,and As)

Stable configurations of seven-membered rings X₂C₄H₄C (1 _X , X = CH, N, P, and As) in the singlet (s) and triplet (t) states are found at B3LYB/6-311++G** level of theory. Thermal energy gaps, ΔE _s-t; enthalpy gaps, ΔH _s-t; Gibbs free energy gaps, ΔG _s-t, between the singlet and triplet states of 1 _X were estimated at the same level of theory. The ΔG _s-t gap between the singlet and triplet states of 1 _X changes in the order: 1 _P > 1 _As > 1 _N , respectively.     

Reactions of the perfluoroalkyltriazapentadiene Ph2N3C2(C3F7)2H with acids,bases, and water

Treatment of the bis(perfluoroalkyl)triazapentadiene PhN=C(C(3)F(7))-N=C(C(3)F(7))-NHPh, 2, with bases affords salts of the conjugate base. Alkylation of the Na(+) salt with CH(3)I yields PhN=C(C(3)F(7))-N=C(C(3)F(7))-NMePh. The crystal structure of [Bu(4)N][Ph(2)N(3)C(2)(C(3)F(7))(2)] demonstrates a twisted, zigzag geometry for the anion in the solid state, but in solution, it is conformationally unstable. Both compounds are stable in aqueous methanol, but hydrolysis occurs under acidic conditions. Protonation with CF(3)SO(3)H acid occurs at the sp(2) nitrogen to give [PhN-(H) HC(C(3)F(7))-C(C(3)F(7))-NHPh][CF(3)SO(3)]. Heating 2 in CF(3)SO(3)H produces 2,4-bis(heptafluoropropyl)-1,3-quinazoline.     

Deprotonation of 1,1′-methylenebis[4-tert-butyl-2-(diphenylphosphino)-benzene] and its analogues: synthesis and crystal structure of {5-But-2-[4-But-2-(Ph2P)C6H3(Ph)CH]C6H3P(Ph)K(OEt2)}2

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