Iridium complex-catalyzed highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes: 2:1 coupling versus 1:2 coupling

[reaction: see text] Highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes is achieved by using a catalytic amount of [Ir(cod)Cl](2) and ligand. The ligand had a considerable effect on the reaction. When 1,2-bis(diphenylphosphino)ethane was used, two molecules of dimethyl acetylenedicarboxylate (DMAD) reacted with one molecule of a monoyne to give the 2:1 coupling product. When 1,2-bis(dipentafluorophenylphosphino)ethane was used instead of dppe, one molecule of DMAD reacted with two molecules of a monoyne to give the 1:2 coupling product.     

Synthesis and near infrared electrochromic properties of metallodithiolene complexes

Four metallodithiolene complexes[4,8-bis(octyloxy)-1,3,5,7-tetrathia]?di[1,1′-bis(diphenylphosphino)ferrocene?palladium(II)](3),[4,8-bis(octyloxy)-1,3,5,7-tetrathia]di[1,3-bis(diphenylphosphino)propane?nickel(II)](4),[4,8-bis(octyloxy)-1,3,5,7-tetra-thia]?[1,1′-bis(diphenylphosphino)ferrocene?palladium(II)]?[1,3-bis(diphenylphosphino)propane·nickel(II)](5)and di[4,8-bis(octyloxy)-1,3,5,7-tetrathia]?[1,1′-bis(diphenylphosphino)ferrocene?palladium(II)]?nickel(II)(6)were synthesized and the near-infrared(NIR)electrochromic properties were studied.The spectroelectrochemical spectra and the electrochromic parameters such as optical contrast,switching time,optical density change,electrochromic efficiency and optical attenuation of complexes 3–6 were investigated in detail.The symmetric binuclear complex 4 showed relatively high electrochromic efficiency of63.0 and 75.4 cm~2/C both in the two oxidation states.The complexes exhibited excellent electroactive/electrochromic stability characterized by chronoamperometry(4000 cyclic switches).     

Bis(alkoxycarbonyl) complexes of platinum: preparation,reactivity and their role in carbonylation reactions

bis(alkoxycarbonyl) complexes of platinum of the type [Pt(COOR)₂L] [L = 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), l,4-bis(diphenylphosphino)butane (dppb), 1,1'-bis(diphenylphosphino)ferrocene (dppf) or 1,2-bis-(diphenylphosphino)benzene (dpb); R = CH₃, C₆H₅ or C₂H₅] were obtained by reaction of [PtCl₂L] with carbon monoxide and alkoxides. Palladium and nickel complexes gave only carbonyl complexes of the type [M(CO)L] or [M(CO)₂L]. The new complexes were characterized by chemical and spectroscopic means. The X-ray structure of [Pt(COOCH₃)₂(dppf] · CH₃OH is also reported. The reactivity of some alkoxycarbonyl complexes was also investigated.     

Cobalt-catalyzed cross-coupling reactions of alkyl halides with aryl Grignard reagents and their application to sequential radical cyclization/cross-coupling reactions

Reactions of alkyl halides with arylmagnesium bromides in the presence of cobalt(II)(diphosphine) complexes are discussed. Treatment of 1-bromooctane with phenylmagnesium bromide with the aid of a catalytic amount of CoCl₂(dppp) [DPPP=1,3-bis(diphenylphosphino)propane] yielded octylbenzene in good yield. The reaction mechanism would include single electron transfer from an electron-rich cobalt complex to alkyl halide to generate the corresponding alkyl radical. The mechanism was justified by CoCl₂(dppe)-catalyzed [DPPE=1,2-bis(diphenylphosphino)ethane] sequential radical cyclization/cross-coupling reactions of 6-halo-1-hexene derivatives that yielded benzyl-substituted cyclopentane skeletons.     

Rh(II) and Rh(I) two-legged piano-stool complexes: structure,reactivity, and electronic properties

The ligand 1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene, 3, was used to synthesize a mononuclear Rh(II) complex [(eta(1):eta(6):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh][PF(6)](2), 6+, in a two-legged piano-stool geometry. The structural and electronic properties of this novel complex including a single-crystal EPR analysis are reported. The complex can be cleanly interconverted with its Rh(I) form, allowing for a comparison of the structural properties and reactivity of both oxidation states. The Rh(I) form 6 reacts with CO, tert-butyl isocyanide, and acetonitrile to form a series of 15-membered mononuclear cyclophanes [(eta(1):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh(CO)(3)][PF(6)] (8), [(eta(1):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh(CNC(CH(3))(3))(2)][PF(6)] (10), and [(eta(1):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh(CO)(CH(3)CN)][PF(6)] (11). The Rh(II) complex 6+ reacts with the same small molecules, but over shorter periods of time, to form the same Rh(I) products. In addition, a model two-legged piano-stool complex [(eta(1):eta(6):eta(1)-1,4-bis[3-(diphenylphosphino)propoxy]-2,3,5,6-tetramethylbenzene)Rh][B(C(6)F(5))(4)], 5, has been synthesized and characterized for comparison purposes. The solid-state structures of complexes 5, 6, 6+, and 11 are reported. Structure data for 5: triclinic; P(-)1; a = 10.1587(7) A; b = 11.5228(8) A; c = 17.2381(12) A; alpha = 96.4379(13) degrees; beta = 91.1870(12) degrees; gamma = 106.1470(13) degrees; Z = 2. 6: triclinic; P(-)1; a = 11.1934(5) A; b = 12.4807(6) A; c = 16.1771(7) A; alpha = 81.935(7) degrees; beta = 89.943(1) degrees; gamma = 78.292(1) degrees; Z = 2. 6+: monoclinic; P2(1)/n; a = 11.9371(18) A; b = 32.401(5) A; c = 12.782(2) A; beta = 102.890(3) degrees; Z = 4. 11: triclinic; P(-)1; a = 13.5476(7) A; b = 13.8306(7) A; c = 14.9948(8) A; alpha = 74.551(1) degrees; beta = 73.895(1) degrees; gamma = 66.046(1) degrees; Z = 2.     

Functionalised trimethylsilyl reagents in cluster synthesis: reactions of Ph2P(S)SSiMe3 with group 11 salts

A series of complexes, ranging from the small cluster 1/infinity[Ag(Ph2PS2)(dppe)](infinity) [dppe=1,2-bis(diphenylphosphino)ethane] to [Cu48S20(O(t)Bu)2(Ph2PS2)2(dppm-)4(dppm)4][dppm=1,2-bis(diphenylphosphino)methane] (the largest Cu cluster containing phosphinodithioato ligands), has been synthesised. The structural evidence presented here indicates that in these reactions initially small cyclic aggregates or one-dimensional coordination polymers are formed. The growth of these intermediates to larger aggregates can take up to several months and could proceed via cationic intermediates.     

The cyclic "silver-diphos" motif [Ag2(mu-diphosphine)2]2+ as a synthon for building up larger structures

The dinuclear, cyclic structural motif [Ag2(diphosphine)2](2+), here termed the "silver-diphos" motif, previously observed in many diphosphine-silver complexes, has been investigated as a synthon for building up larger structures such as coordination cages and polymers. A series of ligands containing one to four meta-substituted diphosphine groups, attached via a central core, has been synthesized from the corresponding fluoroarenes by reaction with KPPh2. Upon reaction with silver salts, the target synthon is adopted by meta-substituted diphosphines 1,3-bis(diphenylphosphino)benzene (L1), 2,6-bis(diphenylphosphino)benzonitrile (L2), and 3,5-bis(diphenylphosphino)benzamide (L3), each of which gives a single species in solution consistent with the expected dimeric complexes [Ag2L2(anion)2]. X-ray crystal structures of [Ag2(L1)2(OTf)2] and [Ag2(L2)2(SbF6)2] confirm the adoption of the silver-diphos motif in the solid state. Amide-functionalized diphosphine L3 forms a hydrogen-bonded chain structure in the solid state via the amide group. A discrete boxlike cage [Ag4(L4)2][SbF6]4 based on two silver-diphos synthons is formed when the tetraphosphine Ph2Sn{3,5-bis(diphenylphosphino)benzene}2 (L4) reacts with silver(I). Its single-crystal X-ray structure reveals a central cavity of minimum diameter, ca. 5.0 A, which contains a single SbF6(-) counterion disordered over two sites. In contrast to the highly selective behavior of the di- and tetra-phosphines L1-L4, the heptaphosphine P{3,5-bis(diphenylphosphino)benzene}3 L5 and the hexaphosphine PhSn{3,5-bis(diphenylphosphino)benzene}3 L6 give dynamic mixtures upon reaction with silver salts in solution. This nonspecific behavior is rationalized by the fact that their diphosphine groups are not appropriately disposed to form stable discrete structures based on the silver-diphos synthon. By contrast, the octaphosphine Sn{3,5-bis(diphenylphosphino)benzene}4 L7 does selectively form a single, discrete, highly symmetrical product in solution, [Ag4(L7)(OTf)4]. In this case, the ligand unexpectedly adopts an interarm tetra-chelating coordination mode, resulting in a continuous 24-membered ring around the periphery of the molecule. To understand the adoption of this unusual coordination mode, the alternative diphosphine Ph2Sn(3-diphenylphosphinobenzene)2 L8, which models a single interarm chelating site of L7, was also investigated. By contrast to L7, its coordination was nonspecific, giving mixtures of silver complexes upon reaction with AgOTf. The selective interarm chelation by L7 may therefore be stabilized by the continuous coordination ring in [Ag4(L7)(OTf)4]; that is, the four chelating sites can be thought of as acting in a cooperative manner. Alternatively, interarm steric repulsions between phenyl groups may favor interarm chelation. Overall, we conclude that, if the diphosphine groups are appropriately articulated to act independently (i. e., they are adequately separated and oriented), the silver-diphos synthon can be a useful tool for the coordination-based self-assembly of larger structures.     

Investigations of olefin hydrogenation catalysts. The major species present in solutions containing rhodium(I) complexes of chelating diphosphines

¹H and ³¹P NMR spectroscopy are used to determine the nature of the species present in catalytically active solutions prepared by treating [RhCl(C₂H₄)₂]₂ with diphosphines and [Rh(norbornadiene)diphosphine]BF₄ with hydrogen (diphosphine = 1,3-bis(diphenylphosphino)propane (dppp) and isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane (diop)).     

Coordination chemistry of dinucleating P2N2S ligands: preparation and characterization of cationic palladium complexes

The thioethers (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylimino)methyl)phenyl)(tert-butyl)sulfane (tBuL3) and (4-tert-butyl-2,6-bis((2-(diphenylphosphino)ethylamino)methyl)phenyl)(tert-butyl)sulfane (tBuL4) react readily with [Pd(NCMe)2Cl2] to give the dinuclear palladium thiophenolate complexes [(L3)Pd2(Cl)2]+ and [(L4)Pd2(micro-Cl)]2+ (HL3=2,6-bis((2-(diphenylphosphino)ethylimino)methyl)-4-tert-butylbenzenethiol, HL4=2,6-bis((2-(diphenylphosphino)ethylamino)methyl)-4-tert-butylbenzenethiol). The chlorides in could be replaced by neutral (MeCN) and anionic ligands (NCS-, N3-, I-, CN-) to give the dinuclear PdII complexes [(L3)Pd2(NCMe)2]3+, [(L3)Pd2(SCN)2]+, [(L3)Pd2(N3)2]+, [(L3)Pd2(I)2]+, and [(L3)Pd2(CN)2]+. The acetonitrile ligands in are readily hydrated to give the corresponding amidato complex [(L3)Pd2(NHCOMe)]2+. All complexes were isolated as perchlorate salts and studied by infrared, 1H, and 31P NMR spectroscopy. In addition, complexes [ClO4].EtOH, [ClO4]2, [ClO4], [ClO4].EtOH, and [ClO4]2.MeCN.MeOH have been characterized by X-ray crystallography. The dipalladium complex was found to catalyse the vinyl-addition polymerization of norbornene in the presence of MAO (methylalumoxane) and B(C6F5)3/AlEt3.     

Pd(DIPHOS)2-catalyzed cross-coupling reactions of organoborons with free or polymer-bound aryl halides

Bis[1,2-bis(diphenylphosphino)ethane]palladium(0) [Pd(DIPHOS)2] catalyzes cross-coupling reactions of free or polymer-bound aryl halides with organoboron compounds to produce biaryls in overall yields of 60-96%.     

Ruthenium dihydrogen complexes with wide bite angle diphosphines

The wide bite angle diphosphines homoxantphos (10,11-dihydro-4,5,-bis(diphenylphosphino)dibenzo[b,f]oxepine), sixantphos (4,6-bis(diphenylphosphino)-10,10-dimethylphenoxasilin), and thixantphos (2,8-dimethyl-4,6-bis(diphenylphosphino)phenoxathiin) were used to prepare cis[MH(2)(diphosphine)(2)] complexes (1a-f) by reaction of [Ru(cod)(cot)] (cod = cyclo-octa-1,5-diene, cot = cyclo-octa-1,3,5-triene) with 2 equiv of the diphosphine under dihydrogen pressure. The electronic properties of the thixantphos ligand were varied. Complexes 1a-f can be protonated with HBF(4) or CF(3)COOH to yield hydrido(dihydrogen) complexes cis[MH(H(2))(diphosphine)(2)](+) (2a-f), which were characterized by VT (variable temperature) NMR and T(1) measurements. These complexes show fast hydrogen atom exchange between the eta(2)-H(2) and the terminal hydride at all temperatures studied. They are thermally unstable toward dihydrogen loss yielding the cationic monohydride complexes cis[MH(diphosphine)(2)](+) (3a-f). Coordination of the eta(2)-H(2) is dominated by sigma --> d donation, and hence, the H-H distance is hardly influenced by the electronic properties of the ligands.     

Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids: a new access to triarylmethanes

Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids proceeded in the presence of [Pd(eta3-C3H5)Cl]2-DPPPent (1,5-bis(diphenylphosphino)pentane) catalyst, yielding a variety of triarylmethanes.     

Asymmetric synthesis catalyzed by chiral ferrocenylphosphine-transition metal complexes VII. New chiral ferrocenylphosphines with C2 symmetry

A new chiral ferrocenylphosphine ligand, 2,2′-bis[1-N,N-dimethylamino)ethyl]-1,1′-bis(diphenylphosphino)ferrocene (2), which has C₂ symmetry and a functional group on the side chain, was prepared by ortho-lithiation and phosphination of 1,1′-bis[1-N,N-dimethylamino)ethyl]ferrocene followed by optical resolution; recrystallization of the diammonium salt with tartaric acid. An X-ray diffraction study of PdCl₂[(+)-2] showed that the complex has square-planar geometry with two cis chlorine and two phosphorus atoms and ligand (+)-2 has an (S) configuration on the 1-dimethylaminoethyl side chain and (R) ferrocene planar chirality.     

Arsinophosphonium cations from arsenium-phosphine and -bisphosphine coordination chemistry

A new 14pi-electron tricyclic organoarsenium cation (5-hydrophenarsazinium, AN, C12H9AsN+) has been prepared in situ and used as a Lewis acceptor with trimethylphosphine, triphenylphosphine, bis(diphenylphosphino)methane (dppm), bis(dimethylphosphino)methane (dmpm), and 1,4-bis(diphenylphosphino)benzene (dppb) ligands. Solid-state structures and spectroscopic characterization data are reported for complexes of the general formula [AN-PMe3]+, [AN-PPh3]+, [AN-dppm]+, [AN-dppm-AN]2+, [AN-dmpm-AN]2+, and [AN-dppb-AN]2+ as tetrachlorogallate salts. Depending on reaction stoichiometry, dppm forms adducts at one or both of the donor sites. Structural comparisons with analogous complexes of phosphenium cations provide interesting similarities and differences.     

Synthesis, structure and photoluminescence of [Cu(acac)(dppe)]n with novel 1D zigzag chain-like motif

A novel complex [Cu(acac)(dppe)]_n (1) [acac = acetylacetone; dppe = 1,2-bis(diphenylphosphino)ethane] was obtained by solution reactions and structurally characterized by X-ray diffraction. The crystal structure analysis indicates that the title complex is characteristic of a polymeric chain formed by the dppe ligands bridging neighboring copper centers. The copper atom is in a distorted tetrahedral geometry. Photoluminescent investigation reveals that the title complex displays a strong emission in bluelight region.     

Structure of a new binuclear complex of tungsten [W2S4Cl2(dppe)2]·2CH3CN

Journal of Structural Chemistry - In the reaction of (Et4N)2[W2S4Cl4] with 1,2-bis(diphenylphosphino)ethane in acetonitrile a new binuclear complex of tungsten(V) [W2S4Cl2(dppe)2]·2CH3CN is...     

1,2-Bis(diphenylphosphino)carborane as a dual mode ligand for both the Sonogashira coupling and hydride-transfer steps in palladium-catalyzed one-pot synthesis of allenes from aryl iodides

[reaction: see text] One-pot allene synthesis from aryl iodides 1 and propargyldicyclohexylamine 2 proceeded in the presence of Pd(2)(dba)(3).CHCl(3) catalyst (2.5 mol %), 1,2-bis(diphenylphosphino)carborane 5 (10 mol %), CuI (15 mol %), and Et(3)N (150 mol %) to give the corresponding allenes 4 in good to high yields. Electron-deficient bidentate phosphines, such as 1,2-bis(diphenylphosphino)carborane 5 and (C(6)F(5))(2)PC(2)H(4)P(C(6)F(5))(2), play the role of a dual mode ligand for both the Sonogashira coupling and hydride-transfer reactions.     

Preparation of enantiopure norbornane ligands bearing both (2S,3S)-bis(phosphinomethyl) and 7-syn-oxygen functional groups and an application to rhodium-catalyzed asymmetric hydrogenation

Enantiopure bicyclo[2.2.1]heptane derivatives having both (2S,3S)-bis[(diphenylphosphino)methyl] and 7-syn-oxygen functional groups were synthesized by using diastereoselective Diels-Alder reaction of di-(1R)-menthyl fumarate and 5-trimethylsilylcyclopentadiene followed by silver-promoted stereospecific frame rearrangement of a bromolactone intermediate. Rhodium-catalyzed asymmetric hydrogenations were carried out using the diphosphines as a chiral ligand.     

Extended-chain, multinuclear transition metal complexes bridged by cyanodiazenido(1-), [N=N-C[triple bond, length as m-dash]N]-, ligands

Extended-chain complexes containing multiple transition metal centres linked by conjugated micro-cyanodiazenido(1-) ligands [N=N-C[triple bond, length as m-dash]N]- have been obtained by reaction of trans-[BrW(dppe)2(N2CN)], , [dppe=1,2-bis(diphenylphosphino)ethane] with dirhodium(II) tetra-acetate, bis(benzonitrile)palladium(II) dichloride, and bis(aqua)M(II) bis(hexafluoroacetylacetonate) (M=Mn, Ni, Cu, Zn): stronger Lewis acids such as tetrakis(acetonitrile)palladium(II) tetrafluoroborate and boron trifluoride promote hydrolysis of complex , leading to the isolation of a novel carbamoylhydrazido(2-) complex, trans-[BrW(dppe)2(N2HC=ONH2)]+[BF4]-.     

Silicon hydrides and nickel complexes : II. Mechanism of the hydrosilylation catalyzed by nickel-phosphine complexes

Two ethylene-nickel(0) complexes, viz., [1,2-bis(diphenylphosphino)ethane]-(ethylene)nickel(0) and bis(triphenylphosphine)(ethylene)nickel(0) have been used in a comparison of their catalytic activities in hydrosilylation reactions with those of the corresponding nickel(II) complexes, viz., dichloro [1,2-bis(diphenylphosphino)-ethane]nickel(II) and dichlorobis(triphenylphosphine)nickel(II). The reaction profiles are similar, apart from a significant difference in the induction period; the nickel(II) catalysts requiring a substantially longer time. A mechanism involving a nickel(0) species is proposed for the hydrosilylation.The interchange of hydrogen and chlorine on silicon accompanying the hydrosilylation is related to a high electron density at the nickel atom bearing the phosphine, olefin, and silicon hydride ligands.