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)).     

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.     

Synthesis and characterization of Cu(I) chelate complexes with 1,3-bis(diphenylphosphino)propane, 1,2-bis(diphenylphosphino)benzene and perfluorinated carboxylates

Cu(I) complexes with 1,3-bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)benzene (dppB) and perfluorinated carboxylates of the general formula [Cu(diphosphine)₂](RCOO), R=C₂F₅, C₄F₉, C₆F₁₃, C₈F₁₇, C₉F₁₉, have been prepared and characterized with MS, IR and ¹H, ³¹P, ¹³C, ¹⁹F, ⁶³Cu NMR spectroscopy. The presence of distinct bis-chelated cations of [Cu(diphosphine)₂]⁺ type and uncoordinated carboxylate anions has been proposed.     

Synthesis and VT-NMR studies of cationic hydride platinum clusters

The synthesis of three trinuclear platinum hydrides [Pt₃(L-L)₃(H)₃]⁺ (L-L = 1,2-bis(diphenylphosphino)ethane, dppe, l; 1-diphenylphosphino-2-diphenylarsinoethane, dppae. 2; 1,2-bis(diphenylarsino)ethane, dpae, 3) is reported. The complexes were characterized by IR, FAB-MS, and NMR (¹H,³¹P and¹⁹⁵Pt) spectroscopic techniques. The fast exchange of the hydride ligands, observed at ambient temperature, is frozen out at low temperature. The low-temperature¹H and³¹P NMR spectra are consistent with an open array of Pt atoms in the clusters, in keeping with a 16-electron configuration on each platinum atom. Two of the hydride ligands are terminally bonded to two metal centers, whereas the third one is µ₃-coordinated, interacting more tightly with the unique platinum atom.     

New Pentacoordinated Rhodium Species as Unexpected Products during the In Situ Generation of Dimeric Diphosphine‐Rhodium Neutral Catalysts

Dimeric rhodium complexes of the type [Rh(PP)(μ₂‐Cl)]₂ (PP=diphosphine) are often used as precatalysts and are generated “in situ” from the corresponding diolefin complexes by exchange of the diene with the desired diphosphine. Herein, we report that the “in situ” procedure also leads to unexpected monomeric pentacoordinated neutral complexes of the type [RhCl(PP)(diolefin)], for the first time herein characterized by NMR spectroscopy and X‐ray crystallography for the ligands 1,4‐bis(diphenylphosphino)propane (DPPP), 1,4‐bis(diphenylphosphino)butane (DPPB), and 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP). The pentacoordinated complexes are in equilibrium with the dimeric target compound [Rh(PP)(μ₂‐Cl)]₂. The equilibrium is influenced by the rhodium‐diolefin precursor, the solvent and the temperature. Based on the results of NMR and UV/Vis spectroscopic analysis (kinetics) it could be shown that the pentacoordinated complex [RhCl(PP)(diolefin)] may arise both from the “in situ”‐generated neutral complex [Rh(PP)(μ₂‐Cl)] by reaction with the free diolefin and, more surprisingly, directly from [Rh(diolefin)(μ₂‐Cl)]₂ and the diphosphine.     

Bis(metallo) Capsules Based on Two Ionic Diphosphines

Self‐assembly and characterization of heterodimeric diphosphine capsules formed by multiple ionic interactions are described. The first type of capsules is composed of one novel tetrasulfonato‐xantphos ligand and one complementary tetraammonium calix[4]arene. Encapsulation of a transition metal is achieved by self‐assembly of a rhodium complex containing the tetraanionic diphosphine ligand and a tetracationic calix[4]arene. The second type of capsules is composed of two oppositely charged diphosphine ligands: one tetrasulfonato‐xantphos and one tetraammonium‐diphosphine (of the xantphos‐, DPEphos‐, and 1,2‐bis(diphenylphosphino)ethane (dppe)‐type). Bis(metallo) capsules, that is, simultaneous encapsulation of two different transition metals, are created by self‐assembly of a palladium or platinum complex containing a tetracationic ligand and a rhodium complex containing a tetraanionic ligand. Diphosphine ligands with different flexibilities and shapes assemble into metallocapsules with a proper capsular structure, as is indicated by ¹H NMR and 1D‐NOESY spectroscopy, ESIMS, and modeling studies.     

Symmetric Ni(II) dithiocarbamates with bidentate phosphines ligands

Ni(II) mononuclear dithiocarbamate complexes with bidentate P,P ligands of composition [Ni(R₂dtc)(P,P)]X {R?=?pentyl (pe), benzyl (bz); dtc?=?S₂CN^?; P,P?=?1,2-bis(diphenylphosphino)ethane (dppe), 1,4-bis(diphenylphosphino)butane (dppb), 1,1′-bis(diphenylphosphino) ferrocene (dppf); X?=?ClO₄, Cl, Br, NCS} and binuclear complexes of composition [Ni₂(μ-dpph)(R₂dtc)₂]X₂ with a P,P-bridging ligand {P,P?=?1,6-bis(diphenylphosphino)hexane (dpph); X?=?Cl, Br, NCS} have been synthesized. The complexes have been characterized by elemental and thermal analysis, IR, electronic and ³¹P{¹H}-NMR spectroscopy, magnetochemical and conductivity measurements. Single crystal X-ray analysis of [Ni(pe₂dtc)(dppf)]ClO₄ confirmed a distorted square planar coordination in the NiS₂P₂ chromophore. For selected samples, the catalysis of graphite oxidation was studied.     

A conformational study of [3.3](3,5)pyridinophane

A variable temperature ¹H NMR study of the [3.3](3,5)pyridinophane indicated that the syn(chair/chair) is more stable than syn(chair/boat) by 0.2 kcal/mol in solution, whereas the trimethylene bridges show disorder even at −150 °C in the solid state. A transition state search by ab initio MO calculations suggested two competitive conformational changes for syn(chair/chair)-syn(chair/boat) conversion via a bridge wobble or a ring inversion in the [3.3](3,5)pyridinophane.     

Synthesis,characterization, and spectroscopic studies of novel transition metal complexes with N,N′-bis(salicylaldehydene)-1,4-bis(4-chloro-2-aminophenoxy)butane

The metal complexes of Co(II), Cu(II), Ni(II), and Zn(II) with novel quadridentate Schiff base derived from 1,4-bis(4-chloro-2-aminophenoxy)butane and salicylaldehyde have been synthesized in DMF. These complexes have been characterized by microanalytical data, elemental analysis, magnetic measurements. ¹H NMR, ¹³C NMR, UV-vis and IR-spectra as well as conductance measurements were used to confirm the structures. On the basis of these observations it is suggested that these complexes exhibit the coordination number four. The text was submitted by the authors in English.     

Enantioselective Alternating Copolymerization of Propylene with Carbon Monoxide Using Cationic Palladium-Chiral Diphosphine Catalyst

Alternating copolymerization of (-olefins with carbon monoxide (CO) catalyzed by cationic palladium-chiral ligand complexes is of great interest due to the potential use of the resulting polymer as a new material1. Recently, enantioselective alternating copolymerization of CO with styrene has been reported by us using PdCl_2-CuCl2-chiral phosphine catalyst2. Here, we first report enantioselective alternating copolymerization of CO with propylene (P) using [(DDPPI)Pd(CH3CN)4](BF4)2 as …     

Synthesis,characterization and mass spectral studies on acrocyclic schiff base complexes of Pb(II), Zn(II) and La(III)

Six new macrocyclic complexes were synthesized by template reaction of (±)-1,4-bis(3-aminopropoxy)butane with metal(II) nitrate and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane or 1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane and their structures were proposed on the basis of elemental analysis, FT-IR, UV-Vis, molar conductivity measurements, ¹H NMR and mass spectra. The metals to ligand molar ratios of the complexes were found to be 1: 1. The complexes are 1: 2 electrolytes for Pb(II) and Zn(II) complexes and 1: 3 electrolytes for La(III) as shown by their molar conductivities (Λ_m) in DMSO at 10⁻³ mol L⁻¹. Due to the existence of free ions in these complexes, such complexes are electrically conductive. The configurations of La(III) and Zn(II) complexes were proposed to probably octahedral.     

Dependence of the product on the P–P ligand in reactions of [RuCl3(NO)(P–P)] complexes (P–P = aromatic diphosphines) with 2-mercaptopyridine

This study presents the syntheses and characterization of 2-mercaptopyridine (pyS⁻) complexes containing ruthenium(II) with the following general formula [Ru(pyS)₂(P–P)], P–P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl₃(NO)(P–P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P–P ligand. The reaction of pyS⁻ with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)₂(NO)(η¹-dppbO-P)]PF₆(5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1–5, and report the X-ray structures for 1 and 5.     

Synthesis and reactivity of bis(3,5-dimethylpyrazol-1-yl)ethane tetracarbonylmolybdenum and tungsten X-ray crystal structureof bis(3,5-dimethylpyrazol-1-yl)ethane tetracarbonyltungsten

Bis(3,5-dimethylpyrazol-1-yl)ethane tetracarbonylmolybdenum (1a) and tungsten (1b) have been synthesized by the direct reaction of bis(3,5-dimethylpyrazolyl)ethane (bmpze) with M(CO)₆ (M = Mo or W). The molecular structure (1b), determined by x-ray crystallography, showed the seven-membered ring W–N–N–C–C–N–N to be in the boat conformation. Upon treatment with RSnCl3 (R=Ph or Cl) in CH₂Cl₂ at room temperature, complexes (1a) and (1b) gave the seven-coordinate oxidative-addition products [(bmpze)M(CO)₃(SnCl₂R)Cl] [M = Mo, R = Ph, (2a); M = W, R=Ph, (2b); M = Mo, R = Cl, (2c); M = W, R = Cl, (2d)]. When complexes (1b) and (2b) were heated under reflux with 1,2-bis(diphenylphosphino)ethane (dppe), the ligand, bmpze, in these complexes was easily removed. The novel compounds were characterized by ¹H-n.m.r., i.r. and elemental analysis.     

The formation of Pt(P–P)(X)(COAr) (X=Cl, I; Ar=Ph, 2-Tioph) complexes via insertion of carbon monoxide

Pt(diphosphine)X(aryl) complexes [diphosphine = 1,3-bis(diphenylphosphino)propane (dppp); aryl=phenyl, 2-thiophenyl; X=Cl, I] have been reacted with carbon monoxide in chloroform. It has been revealed by in situ NMR studies that the starting compounds insert carbon monoxide into the Pt-aryl group resulting in Pt(diphosphine)X{C(O)aryl} complexes. It has been found that the phenyl complexes are much more reactive than the corresponding 2-thiophenyl complexes. Similarly, higher reactivity has been observed with iodo than with the chloro complexes.     

Ru(II)/bisphosphine/diimine/amino acid complexes: diastereoisomerism,cytotoxicity, and inhibition of tumor cell adhesion to collagen type I

We herein report the synthesis and characterization of Ru(II)/amino acid complexes with general formula [Ru(AA-H)(dppb)(4-mebipy)](PF₆), where AA-H means the deprotonated amino acids Gly, Ala, Val, Met, Trp, Tyr, and Ser; dppb is 1,4-bis(diphenylphosphino)butane and 4-mebipy = 4,4′-dimethyl-2,2′-bipyridine. The complexes were characterized by ³¹P{¹H}, ¹³C, and ¹H NMR spectroscopy, as well as X-ray crystallographic analysis of [Ru(DL-Ala-H)(dppb)(4-mebipy)]⁺, suggesting the presence of diastereoisomers. The complexes exhibit IC₅₀ values against breast tumor cells (MDA-MB-231) comparable with cisplatin. In addition, the Ru(II)-based complex with tryptophan inhibited tumor cell adhesion to collagen type I. Therefore, the use of ruthenium complexes containing amino acids can be an interesting tool for development of new therapeutic agents.     

Synthesis and conformational behaviour of ditosyldiaza[2.2]orthometacyclophanes

Summary The N,N-ditosyl-diaza[2.2]orthometacyclophanes5a, b were synthesized from N,N-ditosyl-metaphenylenediamine by reaction with (Z)-1,4-dichlorobutene and 1,2-bis-bromomethylbenzene, respectively. Low temperature NMR studies showed that the compound5b exists as a 1:1 mixture of chair and boat form of the strained (E,Z)-diazanonadiene ring. At room temperature all corresponding resonances are averaged on the NMR time scale (including all four ethylene bridge protons). Going to lower temperatures, in a first step the methylene bridge inversion is frozen (giving twoexo H and twoendo H, G ca. 52kJmol^–1). In a second step the chair and boat form can be observed separately (G ca. 43.5 kJ mol^–1 for the chair/boat flip). The assignments were confirmed by 2D NMR experiments.Dedicated to Prof. Dr. E. L. Eliel on the occasion of his 70th anniversary     

Chelating and bridging diphosphinoamine (PPh2)2N(iPr) complexes of copper(I)

The ligand bis(diphenylphosphino)isopropylamine (dppipa) has been shown to be a versatile ligand sporting different coordination modes and geometries dictated by copper(I). Most of the molecular structures were confirmed by X-ray crystallography. It is found in a chelating mode, in a monomeric complex when the ligand to copper ratio is 2:1. A tetrameric complex is formed when low ratios of ligand to metal (1:2) were used. But with increasing ratios of ligand to metal (1:1 and 2:1), a trimer or a dimer was obtained depending on the crystallization conditions. Variable temperature ³¹P{¹H} NMR spectra of these complexes in solution showed that the Cu–P bond was labile and the highly strained 4-membered structure chelate found in the solid state readily converted to a bridged structures. On the other hand, complexes with the ligand in a bridging mode in the solid state did not form chelated structures in solution. The effect of adding tetra-alkylammonium salts to solutions of various complexes of dppipa were probed by ³¹P{¹H} NMR and revealed the effect of counter ions on the stability of complexes in solution.     

Carborane complexes of ruthenium with long-chain diphosphine ligands as effective catalysts of controlled radical polymerization

Catalytic systems based on carborane complexes of ruthenium with long-chain diphosphine ligands, such as 1,4-bis(diphenylphosphino)butane and 1,5-bis(diphenylphosphino)pentane, are prepared for the controlled radical polymerization of methyl methacrylate. It is found that the used metallacarboranes can catalyze polymerization initiated by both carbon tetrachloride and 2,2′-azo-bis(isobutyronitrile). It is shown that closo-ruthenacarborane with 1,5-bis(diphenylphosphino)pentane 3,3-[PPh₂(CH₂)₅PPh₂]-3-Cl-3,1,2-closo-RuC₂B₉H₁₁ and its o-phenylenecycloborated derivatives make it possible to conduct polymerization at higher rates than those attained with the use of previously synthesized complexes based on diphosphines with a smaller length of the hydrocarbon fragment. The relationship between the redox potential of the complex and the efficiency of control over molecular-mass characteristics of the polymers is analyzed. Experiments reveal that the addition of small amounts of aliphatic amines causes a considerable increase in the rate of polymerization and leads to a decrease in the concentration of the catalyst with retention of a high degree of control over the process.     

Regioselective cyclotrimerization of phenylacetylenes to 1,2,4-triarylbenzenes catalyzed by iridium-diphosphine complexes

The organoiridium derivatives HIr(cod)(P-P) (cod=1,5-cyclooctadiene; P-P=dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane), dppb (1,4-bis(diphenylphosphino)butane)) catalyze the regioselective cyclotrimerization of phenylacetylene as well as of its derivatives p-CH₃OC₆H₄CCH and p-CF₃C₆H₄CCH. The catalytic activity of the precursors as well as the selectivity towards formation of the 1,2,4-triarylbenzenes (up to 100%) are influenced by the diphosphine, and both increase by decreasing the size of the phosphine-iridium chelate ring.     

Effect of Gold(I) on the Room-Temperature Phosphorescence of Ethynylphenanthrene

The synthesis of two series of gold(I) complexes with the general formulae PR₃-Au-C≡C-phenanthrene (PR₃=PPh₃ ( 1 a / 2 a ), PMe₃ ( 1 b / 2 b ), PNaph₃ ( 1 c / 2 c )) or (diphos)(Au-C≡C-phenanthrene)₂ (diphos=1,1-bis(diphenylphosphino)methane, dppm ( 1 d / 2 d ), 1,4-bis(diphenylphosphino)butane, dppb ( 1 e / 2 e )) has been realized. The two series differ in the position of the alkynyl substituent on the phenanthrene chromophore, being at the 9-position (9-ethynylphenanthrene) for the L1 series and at the 2-position (2-ethynylphenanthrene) for the L2 series. The compounds have been fully characterized by ¹H, ³¹P NMR, and IR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction resolution in the case of compounds 1 a , 1 e , 2 a , and 2 c . The emissive properties of the uncoordinated ligands and corresponding complexes have been studied in solution and within organic matrixes of different polarity (polymethylmethacrylate and Zeonex). Room-temperature phosphorescence (RTP) is observed for all gold(I) complexes whereas only fluorescence can be detected for the pure organic chromophore. In particular, the L2 series presents better luminescent properties regarding the intensity of emission, quantum yields, and RTP effect. Additionally, although the inclusion of all the compounds in organic matrixes induces an enhancement of the observed RTP owing to the decrease in non-radiative deactivation, only the L2 series completely suppresses the fluorescence, giving rise to pure phosphorescent materials.