Syntheses, structures and redox properties of {Os(PPh3)2Cp}2{μ-(CC)x} (x = 2, 3, 4): Comparisons with the Ru analogues

The syntheses of {Os(PPh₃)₂Cp}₂{μ-(CC)_x} (x = 2, 3, 4) from reactions between OsBr(PPh₃)₂Cp* and Me₃Si(CC)_xSiMe₃ in the presence of KF/NaBPh₄ are described. The molecular structure of x = 3 has been determined by a single-crystal XRD study. Comparison of the redox properties of {M(PPh₃)₂Cp}₂{μ-(CC)_x} (M = Ru, Os) shows that the oxidation potentials of the osmium complexes are invariably lower (by between 0.16 and 0.64 V) than those of the Ru analogues.     

Stable radical adducts of diisopropylphosphoryl radicals with fullerene complexes (η2-C60)Os(CO)(PPh3)2(CNBut) and (η2-C70)Os(CO)(PPh3)2(CNBut)

It was determined by ESR spectroscopy that the UV irradiation of toluene solutions containing Hg[P(O)(OPrⁱ)₂ and the complex (²-C₆₀)Os(CO)(PPh₃)₂(CNBu^t) produces six stable regioisomeric adducts of phosphoryl radicals with complexes, which are not demetallated under UV irradiation and do not dimerize in the absence of UV irradiation. This is caused by the addition of the phosphoryl radicals to the carbon atoms of fullerene localized near the metal-containing moiety. The addition of the phosphoryl radicals to (²-C₇₀)Os(CO)(PPh₃)₂(CNBu^t) gives rise to the formation of nine stable regioisomeric radical adducts. A comparison of the composition of regioisomers of the radical adducts of C₇₀ with the phosphoryl radicals, which were formed directly from C₇₀ and from the radical adducts of ²-C₇₀)Os(CO)(PPh₃)₂(CNBu^t) by the demetallation of the latter, revealed an orienting effect of the osmium-containing moiety on the addition of the phosphoryl radicals to the fullerene complex.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1968–1972, September, 2004.     

Spin fluctuations and orbital ordering in quasi-one-dimensional α-Cu(dca)2(pyz) {dca = dicyanamide = N(CN)2; pyz = pyrazine}, a molecular analogue of KCuF3

The magnetic properties of α-Cu(dca)₂(pyz) were examined by magnetic susceptibility, magnetization, inelastic neutron scattering (INS), muon-spin relaxation (μSR) measurements and by first-principles density functional theoretical (DFT) calculations and quantum Monte Carlo (QMC) simulations. The χ versus T curve shows a broad maximum at 3.5 K, and the data between 2 and 300 K is well described by an S = 1/2 Heisenberg uniform chain model with g = 2.152(1) and J/k_B = −5.4(1) K. μSR measurements, conducted down to 0.02 K and as a function of longitudinal magnetic field, show no oscillations in the muon asymmetry function A(t). This evidence, together with the lack of spin wave formation as gleaned from INS data, suggests that no long-range magnetic order takes place in α-Cu(dca)₂(pyz) down to the lowest measured temperatures. Electronic structure calculations further show that the spin exchange is significant only along the Cu–pyz–Cu chains, such that α-Cu(dca)₂(pyz) can be described by a Heisenberg antiferromagnetic chain model. Further support for this comes from the M versus B curve, which is strongly concave owing to the reduced spin dimensionality. α-Cu(dca)₂(pyz) is a molecular analogue of KCuF₃ owing to d_x2-y2${\text{d}}_{x^2-y^2}$ orbital ordering where nearest-neighbor magnetic orbital planes of the Cu²⁺ sites are orthogonal in the planes perpendicular to the Cu–pyz–Cu chains.     

A general route for the synthesis of hydrido-carboxylate complexes of the type MH(CO)(κ-OCOR)(PPh3)2 [M = Ru,Os; R = CH3, CH2Cl,C6H5, CH(CH3)2] and their use as precatalysts for hydrogenation and hydroformylation reactions

The synthesis and solid-state IR, ¹H and ³¹P{¹H} NMR spectroscopic characterization of complexes of the type MH(CO)(κ³-OCOR)(PPh₃)₂ [M = Ru, Os; R = CH₃, CH₂Cl, C₆H₅ and CH(CH₃)₂] are reported in this paper. These compounds were obtained by reaction of the respective cationic complex [MH(CO)(NCMe)₂(PPh₃)₂]BF₄ with the sodium salt of the corresponding carboxylic acid in a 1:1 v/v dichloromethane/methanol solution at room temperature. The spectroscopic data of these complexes and some DFT calculations reveal an octahedral geometry with a bidentated carboxylate, two equivalent triphenylphosphines in a mutually trans positions, a linear hydride and a linear carbonyl both in the cis-positions of the coordination sphere. The catalytic results indicate that these complexes are efficient and regioselective precatalysts for the quinoline hydrogenation and for the hydroformylation of 1-hexene, under mild reaction conditions (130 °C and 4 atm H₂ and 120 °C and 15 atm H₂/CO, respectively). For benzothiophene hydrogenation, the osmium complexes showed low activities whereas the analogous ruthenium complexes were catalytically inactive under somewhat more drastic reaction conditions to those of the quinoline hydrogenation (140 °C and 10 atm H₂).     

Synthesis and X-ray crystal structure of the dinuclear copper(I) complex [Cu2((Me-Pk)2En)(PPh3)4](ClO4)2 · 2CHCl3

The new dinuclear copper(I) complex, [Cu₂((Me-Pk)₂En)(PPh₃)₄](ClO₄)₂ · 2CHCl₃ (I), where (Me-Pk)₂En = N,N′-bis(1-pyridin-2-yl-ethylidene)ethane-1,2-diamine), has been synthesized and characterized by elemental analyses, FT-IR, and single-crystal X-ray diffraction method. In this complex, two Cu(PPh₃)₂ units are connected by one (Me-Pk)₂En bridging ligand. The coordination geometry around each copper(I) atom is a distorted tetrahedron formed by two N atoms from (Me-Pk)₂En and two P atoms from the PPh₃ ligands. The distance between two copper atoms is 7.06(1) ?.     

Synthesis, X-ray crystal structure, and reactivity of Pd2(μ-dotpm)2 (dotpm = bis(di-ortho-tolylphosphino)methane)

Alkylation of PdCl₂(dotpm) (dotpm = bis(di-ortho-tolylphosphino)methane) with n-butyllithium produces the binuclear Pd(0) complex Pd₂(μ-dotpm)₂ and the elimination byproducts 1-butene, cis-2-butene, trans-2-butene, butane, and octane. The dibutyl complex, Pd(dotpm)(n-Bu)₂, is presumed to be the reaction intermediate. The crystal structure of Pd₂(μ-dotpm)₂ reveals that the methylene groups of the bridging dotpm ligands are located on opposite sides of the Pd₂P₄ unit, forming an 8-membered ring that is in an elongated chair conformation. The four phosphorus atoms are not coplanar, and the P1-P2-P3-P4 ring has a torsion angle of 13.8°, which minimizes the spatial interactions among the o-tolyl rings. The Pd-Pd bond distance is 2.8560(6) Å, which indicates that there is a weak “closed-shell” bonding interaction between the d¹⁰-d¹⁰ metal centers. Each palladium atom has a nearly linear geometry, and the eight methyl groups of the dotpm ligands shield the open coordination sites on the metal centers. Four methyl groups shield the metal atoms above and below the Pd₂P₄ ring cavity, and four methyl groups block the open metal sites outside of the Pd₂P₄ ring. The Pd₂(μ-dotpm)₂ complex readily undergoes oxidative addition of dichloromethane to form the rigid A-frame complex Pd₂Cl₂(μ-CH₂)(μ-dotpm)₂.     

Synthesis and structural characterisation of five copper(I) and silver(I) complexes with 2-aminopyridine (2-APy), [Cu(μ-Cl)(2-Apy)(PPh3)]2, [Ag(μ-X)(2-Apy)(PPh3)]2 (X = Cl,Br), [Ag(μ-ONO2)(2-Apy)(EPh3)]2 (E = P,As)

Five new copper(I)/silver(I) complexes containing 2-aminopyridine, [Cu(μ-Cl)(2-Apy)(PPh₃)]₂(1), [Ag(μ-Cl)(2-Apy)(PPh₃)]₂(2), [Ag(μ-Br)(2-Apy)PPh₃)]₂(3), [Ag(μ-ONO₂)(2-Apy)(PPh₃)]₂(4), [Ag(μ-ONO₂)(2-Apy)(AsPh₃)]₂(5) have been synthesised for the first time. Complexes 1–5 are obtained by the reactions of MX (MX = CuCl for 1; M = Ag for 2–5; X = Cl, Br for 2–3; X = NO₃ for 4–5) with the monodentate ligands EPh₃ (E = P for 1–4; E = As for 5) and 2-Apy in the molar ratio of 1:1:2 in the mixed solvent of CH₂Cl₂ and MeOH. Complexes 1–5 are characterised by IR and X-ray diffraction. In 1–5, chloride, bromide and nitrate ions bridge two metal atoms to form dinuclear complexes containing the parallelogram cores M₂X₂ (M = Cu, Ag).     

On the synthesis and structures of the complexes [RuCl(L)(dppb)(N–N)]PF6 (L = CO,py or 4-NH2py; dppb = 1,4-bis(diphenylphosphino)butane; N–N = 2,2′-bipyridine or 1,10-phenanthroline) and [(dppb)(CO)Cl2-Ru-pz-RuCl2(CO)(dppb)] (pz = pyrazine)

The “Ru(P–P)” unit (P–P = diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl₂Ru-pz-RuCl₂(CO)(dppb)] (pz = pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF₆ (N–N = diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF₆ were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl₂(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and ³¹P{¹H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography.     

Effect of solvent on reactions of Cp2Zr{(μ-H)2BHR}2 and Cp2ZrH{(μ-H)2BHR} (R = CH3, Ph) with B(C6F5)3

The effect that a solvent has on reactions of Cp₂Zr{(μ-H)₂BHR}₂ and Cp₂ZrH{(μ-H)₂BHR} (R = CH₃, Ph) with B(C₆F₅)₃ has been studied. From the reaction in benzene the metathesis product Cp₂Zr{(μ-H)₂B(C₆F₅)₂}₂, 2, was isolated. In the case of diethyl ether, different hydride abstraction products, including [Cp₂Zr(OEt₂){(μ-H)₂BHPh}][HB(C₆F₅)₃], 3, [Cp₂Zr(OEt₂){(μ-H)₂BHCH₃}][HB(C₆F₅)₃], 4, [Cp₂Zr(OEt₂){(μ-H)₂BH₂}][HB(C₆F₅)₃], 5, and [Cp₂Zr(OEt)(OEt₂)][HB(C₆F₅)₃], 6, were isolated depending on the starting zirconocene complex. The diethyl ether molecules of 3-6 are weakly coordinated to Zr and displaced in THF solution. Isolation of 3 and 4 is attributed to their fast precipitation from the reaction mixture, which prevented further reactions from occurring. In addition to the hydride abstraction, a hydride metathesis was also involved in the formation of 5. Time-elapsed ¹¹B NMR studies indicate that 3 and 4 are the intermediates on the pathway to 5 and 6. The molecular structures of 2-6 were determined by single-crystal X-ray diffraction.     

Palladium nitrosyl carboxylate clusters: Synthesis and reactivity. X-ray structures of Pd4(μ-CO)2(μ-NO)(μ-RCO2)5 (R = Pr, Bu)

New palladium nitrosyl carboxylate complexes Pd₈(CO)_4−m(NO)_m(NO₂)₄(RCO₂)₈ (m = 2, 4) were obtained by the treatment of palladium carbonyl carboxylates clusters cyclo-Pd_n(μ-CO)_n(μ-RCO₂)_n (n = 6) (1) with gaseous nitrogen monoxide. These complexes are the products of CO substitution in early described Pd₈(CO)₄(NO₂)₄(RCO₂)₈ clusters. By adding an excess of corresponding acid to reaction mixture Pd₄(CO)₂(NO)(RCO₂)₅ complexes were obtained, their structures were determined by X-ray diffraction analysis. These clusters are intermediate products of transformation of 6-nuclear initial clusters into various 8-nuclear complexes. This fact demonstrates that carboxylate ligands can be used as stabilizers for intermediate unstable polynuclear palladium compounds.     

Reactions of Ru3(CO)12 with 2-pentynal-diethyl-acetal. The crystal structure of Ru2(CO)6[μ-η-{EtC2C(H)(OEt)2}CO{EtC2C(H)(OEt)2}] and its reactivity towards tetraethyl-orthosilicate

The title compound has been obtained in considerable yield by reacting Ru₃(CO)₁₂ with 2-pentynal-diethyl-acetal [CH₃CH₂CCC(H)(OEt)₂] (PDA) in hydrocarbon solvents. The X-ray analysis shows that the title complex belongs to the well known family of the flyover derivatives. Some X-ray structural studies have been reported, many years ago, on di-iron flyover complexes; in contrast only a few examples of diruthenium derivatives have been structurally characterized.The complex contains ethoxy-groups which could potentially undergo hydrolysis in the presence of tetraethyl-orthosilicate (TEOS) in the presence of catalysts. Reactions of complex Ru₂(CO)₆[μ-η⁴-{EtC₂C(H)(OEt)₂}CO{EtC₂C(H)(OEt)₂}] with TEOS in the presence of HCl or of NaF (as catalysts) have been attempted. An inorganic-organometallic sol-gel material containing the skeleton of the complex has been obtained and characterized with IR-Raman, XRD on powders and SEM microscopy.     

Reactions of diferrocenyl dichalcogenides with [W(CO)5(THF)]: X-ray crystal structures of Fc2Te2 and [W2(μ-SeFc)2(CO)8] (Fc = [Fe(η-C5H5)(η-C5H4)])

Treatment of [W(CO)₅THF] with diferrocenyl diselenide, Fc₂Se₂, yielded the novel metal-metal bonded tungsten(I) complex, [W₂(μ-SeFc)₂(CO)₈] (1: Fc = ferrocenyl, [Fe(η⁵-C₅H₅)(η⁵-C₅H₄)]), which was characterised by NMR and IR spectroscopy, mass spectrometry, and X-ray crystallography. The corresponding tellurium derivative could not be prepared by an analogous route. The X-ray crystal structure of Fc₂Te₂ has also been determined.     

The structurally characterised silyl complexes, Os(κ-S2CNMe2)(SiMeCl2)(CO)(PPh3)2 and Os(κ-S2CNMe2)(SiCl3)(CO)(PPh3)2, which have remarkably unreactive Si-Cl bonds

Treatment of Os(κ²-S₂CNMe₂)H(CO)(PPh₃)₂ with HSiMeCl₂ or HSiCl₃ gives in high yield Os(κ²-S₂CNMe₂)(SiMeCl₂)(CO)(PPh₃)₂ (1) or Os(κ²-S₂CNMe₂)(SiCl₃)(CO)(PPh₃)₂ (2), respectively. The crystal structures of both compounds have been determined and the Os-Si distances are 2.3672(10) Å for 1 and 2.3449(12) Å for 2. In solution, and under forcing conditions, both compounds are extraordinarily unreactive towards hydroxide ions.     

Supramolecular assemblages through metal-η-arene π-interactions: Synthesis and X-ray characterization of {Hg[NNN(PhR)2]2}n (R = NO2, F), a bis diaryl-substituted triazenide complex polymer of Hg(II)

3-(2-fluorophenyl)-1-(3-nitrophenyl)triazene reacts with mercury(II) acetate in tetrahydrofuran in the presence of 2,2′-bipyridilamine to give yellow crystalline blocks of polymeric {Hg^II[NNN(PhR)₂]₂}_n (R = NO₂, F). The new triazenide complex belongs to the triclinic space group . In a molecule of {Hg^II[NNN(PhR)₂]₂} two deprotonated 1,3-diaryl-substituted triazenide ligands are coordinated in an opposite way to one Hg(II) ion by means of primary and secondary bonds. The Hg(II) ions are placed on the inversion centers of translation operated {Hg[NNN(PhR)₂]₂} moieties which are stacked along the crystallographic a-axis forming infinite unidimensional chains linked through metalocene alike Hg-η²,η²-arene π-interactions.     

A new versatile binuclear seven-coordinate complex of molybdenum(II), [(μ-Cl)2{Mo(μ-Cl)(SnCl3)(CO)3}2]

The two new seven-coordinate anionic complexes of molybdenum(II), binuclear [(μ-Cl)₂{Mo(μ-Cl)(SnCl₃)(CO)₃}₂]²⁻ and mononuclear [MoCl₃(GeCl₃)(CO)₃]²⁻, have been synthesized and characterized by single-crystal X-ray diffraction studies. The binuclear complex exhibits a unique mode of reactivity towards norbornene. In a strictly anhydrous atmosphere the binuclear complex effectively initiates the ring-opening metathesis polymerization reaction of norbornene, but in the presence of water norbornene is efficiently transformed to the binorbornyl ether (C₇H₁₁)₂O.     

[M(dipicH2)(H2O)3], M = Ni,Cu, Zn (dipicH2 = dipicolinic acid) – A combined crystallographic,spectroscopic and computational study

Cationic metal complexes of dipicolinic acid (dipicH₂) are stabilized by [Ce(dipic)₃]²⁻ ions in the three isomorphous crystals [M(dipicH₂)(OH₂)₃][Ce(dipic)₃] · 3H₂O (M = Ni, 1; Cu, 2; Zn, 3). Magnetic dilution provided by the bulky anions leads to well-resolved EPR spectra in polycrystalline samples of 2. The cations have 4+2 coordination, the carbonyl atom of the carboxylic acid groups coordinating weakly from trans positions. In the case of 2 this steric distortion is augmented by Jahn–Teller distortion. All the three structures are satisfactorily modelled by calculations based on density functional theory (DFT). The switch of the Jahn–Teller axis upon deprotonation of the complex, leading to the neutral species Cu(dipic)(H₂O)₃, is also reproduced by DFT. Electronic transition energies as well as the g-tensor component of the d⁹ complex obtained are in good agreement with experiment. However, the calculated hyperfine coupling constants are in error. DFT also fails to satisfactorily account for the electronic transition in the d⁸ ion in 1.     

Synthesis, characterization, and structural study of iron-sulfur core {Cp2Fe2(μ-SEt)2} complexes

The known complexes [Cp₂Fe₂(μ-SEt)₂(MeCN)₂](PF₆)₂ (1) and Cp₂Fe₂(μ-SEt)₂(CN)₂ (2) are prepared to investigate their reactivity. The reaction of complex 2 with equimolar amounts of MeOTf yields a monomethylation product [Cp₂Fe₂(μ-SEt)₂(CN)(CNMe)](OTf) (3). Dimethylation of complex 2 by 2 equiv. MeOTf gives a complex [Cp₂Fe₂(μ-SEt)₂(CNMe)₂](OTf)₂ (4). Complex 1 containing two labile MeCN ligands reacts with several bidentate phosphine ligands, such as dppm, dppa, and dppf, to afford complexes [Cp₂Fe₂(μ-SEt)₂(dppm)](PF₆)₂ (5), [Cp₂Fe₂(μ-SEt)₂(dppa)](PF₆)₂ (6), and [Cp₂Fe₂(μ-SEt)₂(dppf)](PF₆)₂ (7), respectively. The spectroscopic, electrochemical, and reactivity studies of iron-sulfur core complexes are performed. The structures of complexes 1-7 were confirmed by X-ray crystallography.     

Synthesis and reactivity of rhodium(III) pentamethylcyclopentadienyl complexes of N-B-PTA(BH3): X-ray crystal structures of [CpRhCl2{N-B}-PTA(BH3)] and [CpRh{N-B-PTA(BH3)}(η-CH2 = CHPh)]

The reaction between 1-boranyl-1,3,5-triaza-7-phosphaadamantane ligand N-B-PTA(BH₃) and [Cp^∗RhCl(μ-Cl)]₂ affords [Cp^∗Rh{N-B-PTA(BH₃)}Cl₂] (3) or [Cp_∗Rh{N-B-PTA(BH₃)}₂Cl]Cl (5) containing one or two P-bonded boronated PTA ligands. The hydride [Cp_∗Rh{N-B-PTA(BH₃)}H₂] (8) was also obtained by reaction of 3 with NaBH₄ and alternatively by direct hydroboration of [Cp^∗Rh(PTA)Cl₂] with excess NaBH₄. Moderately slow hydrolysis of the N-boranyl rhodium complexes affords dihydrogen, H₃BO₃ and the corresponding PTA derivatives, including the water-soluble dihydride [Cp^∗Rh(PTA)H₂] (9). Finally, the reaction of 8 with electron poor alkynes gives the alkene complexes [Cp^∗Rh{N-B-PTA(BH₃)}(η²-CH₂ = CHR)] (R = Ph, 10; C(O)OEt, 11) as a mixture of rotamers η²-coordinated to rhodium without affecting the N-BH₃ moiety. The X-ray crystal structures of 3 and 10 were also obtained and are here discussed.     

Quantification of steric interactions in phosphine ligands from single crystal X-ray diffraction data. Crystal structures of (η-C5H4Me)Mo(CO)2(PR3)I (R3 = PhMe2, PhEt2, Et3)

Distorted square pyramidal complexes of molybdenum (η⁵-C₅H₄Me)Mo(CO)₂(PR₃)I (R₃ = PhMe₂ (2a); PhEt₂ (3a) and Et₃ (4a)) have been synthesized and the structures of the lateral (cis) isomers have been determined by X-ray diffraction. The cone (Θ) and solid (Ω) angles as well as the angular profiles of the phosphine ligands in the complexes have been computed using the program steric. Values for the crystallographic cone and solid angles calculated for 2a, 3a and 4a are Θ (129°, 135° and 139°) and Ω (2.73, 2.99 and 2.93 sr), respectively. A search of the Cambridge Structural Database (CSD) was made for piano stool, 5- and 6-coordinate complexes containing the title phosphine ligands. Results from this study show a wide range of sizes for each of the ligands and even the seemingly simple PPhMe₂ ligand exhibited a wide range of values for the cone (113-137°) and solid (2.49-3.07 sr) angles. These observations have been rationalized and related to the possible group conformations from the crystallographic data.