Complex Mer Research Articles

New alkyl-cobalt(III) complexes containing chiral centers in the chelating system.

The complex mer-[Co(III)(L(1)Npy)(2)](+) (1') where the L(1)Npy(-) is the tridentate 3-[(2-pyridyl)methylimino]butan-2-one oximate ligand, gives alkyl-cobalt derivatives after reduction with NaBH(4)/Pd(2+) to the Co(I) and alkylation. The formation of the cobalt-carbon bond is accompanied by the reduction to the amino form of one or both imino ligands (depending on the experimental conditions) initially present in 1'. In one series of experiments, complexes of the type fac-[RCo(III)(L(1)Npy)(H-L(1)NHpy)](+) (R = Me, i-Pr, CH(2)Cl, CH(2)Br, CH(2)CF(3), and Bz) were obtained, in which only one of the two ligands was reduced to the amino form (H-L(1)NHpy). The saturation of one azomethine group causes the products to assume a fac configuration and induces the formation of one asymmetric carbon and one asymmetric nitrogen center in the chelating system. When an excess of reducing agent is used, both azomethine groups may be saturated, causing the introduction of one pair of chiral carbons and one pair of chiral nitrogens. Two isomers of the methyl derivative [MeCo(III)(L(1)NHpy)(H-L(1)NHpy)](+) were isolated. The X-ray analysis reveals that these isomers differ from one another in configuration of the C and N chiral centers. Possible reaction mechanisms leading to these different types of complexes are proposed.

Ruthenium-Catalyzed Isomerization of Allylic Alcohols: Oxidation State Determines Resistance Against Diene Inhibition

The novel complex mer-[RuCl3(dmso)(phen)] (1) has been prepared and characterized by X-ray diffraction. The ruthenium center is in a distorted octahedral environment with the three chloride ions coordinated in a mer-fashion and an S-bonded dmso ligand trans to one of the phen nitrogen atoms. Electrochemical experiments show two reversible waves in acetonitrile solution, corresponding to the couples RuIII/II (0.11 V) and RuIV/III (1.73 V). The analogous RuII complex cis,cis-[RuCl2(dmso)2(phen)] (2) shows one reversible wave at 1.08 V, corresponding to the RuIII/II couple. Both complexes exhibit high catalytic activity in the isomerization of 3-buten-2-ol to butanone. The initial turnover frequency (TOF) for 1 in diglyme/water at 130 °C is 295 h−1 with a first-order kini of 0.6 h−1, while 2 reaches an initial TOF of 260 h−1 and a kini of 0.5 h−1. A cumulative turnover number (TON) of 1025 has been obtained with 1 as a catalyst precursor. The activity of 1 and 2 has been compared to that of in situ mixtures with both RuIII and RuII precursors. All RuII complexes are deactivated before 100% conversion has been attained. RuCl3 is a good catalyst precursor with an initial TOF of 500 h−1. If RuCl3 is mixed in situ with one equivalent of phen, an induction period of 40 min results and the activity thereafter is much lower than without the addition of phen. With 2 equiv. of phen, no reaction is observed in the first 6 h and only a very low activity is obtained after that. An important difference between 1 and 2 becomes apparent when a conjugated diene is added to the reaction mixture; only 1 remains active. The results demonstrate that only RuIII complexes with one phen ligand are active catalyst precursors for the isomerization of allylic alcohols in the presence of conjugated dienes. The consequence of this observation is further demonstrated by applying both catalyst precursors in the direct one-pot conversion of 1,3-butadiene to butanone. In this reaction, complex 1 (TON = 2050, t = 6 h) forms a much more active precursor than complex 2 (TON = 1300, t = 7 h). (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Interactions at the Molecular Level between Biphosphine Ruthenium Complexes and Stearic Acid in Langmuir and Langmuir−Blodgett Films

A molecular-level interaction between biphosphine ruthenium complexes and stearic acid has been observed in Langmuir and Langmuir−Blodgett (LB) films. Similar results were obtained for the ruthenium complexes mer-[RuCl3(dppb)(4-Mepy)] (dppb = PPh2(CH2)4PPh2; 4-Mepy = 4-methylpyridine) (Rupic) and mer-[RuCl3(dppb)(py)], (pyridine) (Rupy), which differ by the substituent group in the pyridine ring. The interaction was manifested in the Langmuir films by a nonlinear increase in the area per molecule and in surface potential with the relative concentration of the ruthenium complex in the mixture. In the LB films, interaction with stearic acid occurred via complexation with Rupy or Rupic, even though the latter are not charged. It is suggested that one of the chlorides is labilized, thus promoting complexation and keeping the Ru(III) oxidation state for the complex. Complexation was confirmed through FTIR data. Interaction with stearic acid enhanced the color change characteristic of biphosphine ruthenium comp...

Molybdenum and tungsten complexes of sulfene (thioformaldehyde S,S-dioxide).

Propionitrile complexes fac-[M(CO)(3)(P-P)(NCEt)] (M = Mo (3), W (4); P-P = Ph(2)PCH(2)PPh(2) (a), Ph(2)PC(2)H(4)PPh(2) (b), Ph(2)PC(3)H(6)PPh(2) (c), (S,S)-Ph(2)PCHMeCHMePPh(2) (d), Fe(C(5)H(4)PPh(2))(2) (e)) were synthesized from [M(CO)(3)(NCEt)(3)] and the corresponding diphosphine. Reactions of 3 and 4 with sulfur dioxide initially gave complexes fac-[M(CO)(3)(P-P)(eta(2)-SO(2))] (M = Mo (5), W (6)), which slowly isomerized to mer-[M(CO)(3)(P-P)(eta(1)-SO(2))] (M = Mo (7), W (8)). The structures of 7b and 8b were determined by X-ray crystallography. Both compounds are isostructural (monoclinic, space group P2(1)/n (No. 14)) with almost identical unit cell dimensions (7b, a = 14.511(5) A, b = 12.797(2) A, c = 16.476(6) A, beta = 115.92(2); 8b, a = 14.478(8) A, b = 12.794(3) A, c = 16.442(9) A, beta = 116.01(2)) and molecular geometries. Treatment of either fac-[M(CO)(3)(P-P)(eta(2)-SO(2))] or mer-[M(CO)(3)(P-P)(eta(1)-SO(2))] with diazomethane yielded the sulfene complexes mer-[M(CO)(3)(P-P)(eta(2)-CH(2)SO(2))] (M = Mo (9), W (10)). The structure of 10a was determined crystallographically: monoclinic, space group P2(1)/n (No. 14), a = 11.719(2) A, b = 17.392(4) A, c = 13.441(3) A, beta = 95.58(2). The tungsten atom resides in the center of a distorted pentagonal bipyramid. The sulfene ligand occupies two adjacent equatorial sites with the bond distances W-C, 2.322(13) A, W-S, 2.353(3) A, and S-C, 1.721(12) A. The latter equals the S-C single bond distance in thiirane S,S-dioxide, indicating a high degree of charge density transfer into the LUMO of the sulfene ligand.

Synthesis, structure, DFT calculations, and full vibrational analysis of the prototypical thioformaldehyde complex mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)

Reaction of PPN[W(CO)3(dmpe)(SH)] 2 (PPN = Ph3PNPPh3, dmpe = Me2PC2H4PMe2) with aqueous formaldehyde in the presence of trifluoroacetic acid gives the thioformaldehyde complex mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 3 in almost quantitative yield. The isotopomer mer-[W(CO)3(Me2PC2H4PMe2)(η2-SCD2)] 3-D22 was obtained analogously. 3 has a slightly distorted pentagonal-bipyramidal structure with one carbonyl group, two P atoms and the C and S atoms of the thioformaldehyde ligand spanning the pentagonal plane. In solution, 3 is in equilibrium with fac-[W(CO)3(Me2PC2H4PMe2)(η2-SCH2)] 4. The structures and energies of 3 and 4 and their rotamers 3′ and 4′ were calculated by DFT methods leading to a very good agreement with experimental data. FT-IR and FT-Raman spectra of 3 and 3-D22 were recorded and assigned with the aid of DFT calculations. Calculated vibrational amplitudes emphasize the extensive mixing of modes, particularly in the low-wavenumber region. The HOMO of 3 can approximately be described as a lone-pair at sulfur and is 0.38 eV higher in energy than that of isomer 4. The LUMOs of both isomers are highly delocalized with that of 4 being 0.45 eV lower in energy. On this basis it is expected that electrophiles will add preferentially at the sulfur atom of 3 while nucleophiles if at all will add to the thiocarbonyl carbon of 4.

Electrochemical characterization of Langmuir–Blodgett films from the ruthenium complex mer-[RuCl 3(dppb)(4-Mepy)

Ruthenium complexes containing diphenylphosphine ligands serve as good catalysts in hydrogenation reactions, and may be used as precursors for other Ru complexes. Their properties may also be exploited in Langmuir–Blodgett (LB) films, which is the focus of the present paper. We report on electrochemical properties of LB films from the pure ruthenium (III) complex, mer-[RuCl 3(dppb)(4-Mepy)] (dppb=PPh 2(CH 2) 4PPh 2; 4-Mepy=4-methylpyridine) (Ru–Pic), and from mixtures of stearic acid (SA) and Ru–Pic. Y-type LB films from these materials were deposited on indium tin oxide (ITO) substrates and analyzed using cyclic voltammetry. The overall shape of the voltammogram was the same for LB films of pure Ru–Pic and mixed with SA, with the redox peaks being ascribed to the Ru III/II conversion. However, in the mixed film, the potentials for the cathodic and anodic peaks were shifted toward more anodic and cathodic potentials, respectively, and this is attributed to the presence of SA within the coordination sphere of Ru, consistent with Fourier-transform infrared spectroscopy (FTIR) measurements. Even though Ru–Pic films at the air/water interface are not true monolayers, LB films from pure Ru–Pic display higher electroactivity than the mixed films, owing to the absence of the insulating stearic acid matrix and to the greater roughness of the pure films.

Molecular structures of iridium(III) complexes containing protonated (enH+) and non-protonated (en∗) monodentately bound 1,2-ethanediamine: mer-[Ir(en)(enH)Cl3]+ and mer-[Ir(en)(en∗)Cl3]. Comparative DFT and ab initio theoretical study

Extensive density functional theory (DFT) and correlated ab initio calculations are performed to study geometrical structures of the title Ir complexes. All the structures are fully optimized and the associated charge distribution is computed with the natural population analysis (NPA). For the cation mer-[Ir(en)(enH)Cl3]+ (1), two nearly degenerate geometrical isomers denoted (1a) and (1b) and differing by the conformation of the bidentately attached 1,2-ethanediamine (en) ligand have been found. The calculated conformation of en in mer-[Ir(en)(enH)Cl3]+ (1a) and in the non-protonated complex mer-[Ir(en)(en∗)Cl3] (2) are in a close agreement with the X-ray diffraction values by Galsbøl et al. The conformation of the monodentate enH+ ligand in the isolated cation is found to be stabilized via intramolecular N–H⋯Cl hydrogen bonds. For the complex (2), the theoretical predictions of the bond distances and bond angles involving the unique non-chelate 1,2-ethanediamine (en∗) are expected to be more reliable than the X-ray results. A good agreement between the DFT B3LYP and ab initio MP2 results is observed.

Molecular and electronic structures of bis(pyridine-2,6-diimine)metal complexes [ML2](PF6)n (n = 0, 1, 2, 3; M = Mn, Fe, Co, Ni, Cu, Zn).

A series of mononuclear, octahedral first-row transition metal ion complexes mer-[M(II)L0(2)](PF6)2 containing the tridentate neutral ligand 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine (L0) and a Mn(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II) ion have been synthesized and characterized by X-ray crystallography. Cyclic voltammetry and controlled potential coulometry show that each dication (except those of Cu(II) and Zn(II)) can be reversibly one-electron-oxidized, yielding the respective trications [M(III)L0(2)]3+, and in addition, they can be reversibly reduced to the corresponding monocations [ML2]+ and the neutral species [ML2]0 by two successive one-electron processes. [MnL2]PF6 and [CoL2]PF6 have been isolated and characterized by X-ray crystallography; their electronic structures are described as [Mn(III)L1(2)]PF6 and [Co(I)L0(2)]PF6 where (L1)1- represents the one-electron-reduced radical form of L0. The electronic structures of the tri-, di-, and monocations and of the neutral species have been elucidated in detail by a combination of spectroscopies: UV-vis, NMR, X-band EPR, Mossbauer, temperature-dependent magnetochemistry. It is shown that pyridine-2,6-diimine ligands are noninnocent ligands that can be coordinated to transition metal ions as neutral L0 or, alternatively, as monoanionic radical (L1)1-. All trications are of the type [M(III)L0(2)]3+, and the dications are [M(II)L0(2)]2+. The monocations are described as [Mn(III)L1(2)]+ (S = 0), [Fe(II)L0L1]+ (S = 1/2), [Co(I)L0(2)]+ (S = 1), [Ni(I)L0(2)]+ (S = 1/2), [Cu(I)L0(2)]+ (S = 0), [Zn(II)L1L0]+ (S = 1/2) where the Mn(II) and Fe(II) ions are low-spin-configurated. The neutral species are described as [Mn(II)L1(2)]0, [Fe(II)L1(2)]0, [Co(I)L0L1]0, [Ni(I)L0L1]0, and [Zn(II)L1(2)]0; their electronic ground states have not been determined.

Rhodium(III)‐Assisted Nucleophilic Addition of Ammonia to Metal‐Bound Benzyl Cyanide: Crystal Structures of mer‐[RhCl3(PhCH2CN)3]·1/2 C6H5CH3 and mer‐[RhCl3{PhCH2C(NH2)=NH}3

Heating of [RhCl3(MeCN)3] in benzyl cyanide at 100 °C gives the substitution product mer-[RhCl3(PhCH2CN)3] (90% yield), whose recrystallization from an acetone/toluene mixture leads to formation of the toluene solvate mer-[RhCl3(PhCH2CN)3]·1/2 C6H5Me. The crystal structure of the latter, determined by X-ray single-crystal diffractometry, shows an unusual self-assembly due to intermolecular CH···Cl hydrogen bonding with concomitant clathration of toluene. Diffusion of ammonia into a solution of mer-[RhCl3(PhCH2CN)3] in neat benzyl cyanide brings about a facile rhodium(III)-assisted addition of NH3 to the coordinated nitrile species to produce the amidine complex mer-[RhCl3{PhCH2C(NH2)=NH}3] (83% yield). Both starting material and the product were characterized by elemental analyses, FAB-MS, IR and 1H and 13C{1H} NMR spectroscopy. The crystal structure of mer-[RhCl3{PhCH2C(NH2)=NH}3] provides the first example of a rhodium(III) complex with a monodentate amidine ligand.

Synthesis, Spectroscopic and Structural Characterization of New RuII and RuIII Complexes Containing Triazole- and Thiadiazole-Type Ligands

The chemical behavior of triazole, thiadiazole, and triazoline derivatives of thiocarbonohydrazide towards cis-[RuCl2(DMSO)4] (2) was studied. Reaction of 4-amino-5-methylthio-3-(2-pyridyl)-1,2,4-triazole (L1) with 2 gave two diastereomeric complexes, trans,cis-[RuCl2(DMSO)2(L1)] (3) and chiral cis,cis-[RuCl2(DMSO)2(L1)] (4). Reaction of 2 with 2-(2-formylhydrazino)-1,3,4-thiadiazole in MeOH gave the complex trans,cis-[RuCl2(DMSO)2(L2)] (5) with concomitant deformylation of the starting ligand. The process was catalyzed by RuII in very low yield. Synthesis of the Ru complexes of 4-amino-3-methyl-1,2,4-Δ2-triazoline-5-thione (L3) and 4-amino-3-ethyl-1,2,4-Δ2-triazoline-5-thione (L4) resulted in an interesting oxidation of the metal promoted by DMSO. Reaction of 2 with these ligands in a 6 N HCl solution led to the isolation of the complexes mer-[RuCl3(DMSO)(L3)]·1/2 H2O (6) and mer-[RuCl3(DMSO)(L4)]·1/2 H2O (7). The complex mer-[RuCl3(DMSO)(L4)]·CH3COOH·H2O (7′) was obtained by recrystallization of 7 from ethyl acetate. The complexes 6, 7, and 7′ were highly stable in HCl solutions and acetone but not in neutral aqueous solution. To the best of our knowledge this is the first report of RuIII complexes with an N–N–C–S chelating system.

Synthesis, structures and hypoxia-selective cytotoxicity of cobalt(III) complexes containing tridentate amine and nitrogen mustard ligands

Cobalt(III) complexes containing the tridentate nitrogen mustard ligand N,N-bis(2-chloroethyl)diethylenetriamine (DCD) and the non-alkylating analogs N,N-diethyldiethylenetriamine (DED) and diethylenetriamine (dien) have been synthesised and the mustard complexes evaluated as potential hypoxia-selective anticancer drugs. The complexes were prepared from the precursor trans-K2[Co(acac)(CO3)(NO2)2]·H2O in a charcoal-catalyzed substitution reaction. Reaction of this precursor with dien·3HCl in water resulted in the isolation of two isomeric products, mer- and s-fac-[Co(dien)(acac)(NO2)]+. Reaction in methanol with DED·3HCl gave one product, mer-[Co(DED)(acac)(NO2)]ClO4, while from the reaction with DCD·3HCl both the tridentate mustard complex mer-[Co(DCD)(acac)(NO2)]ClO4 and, in low yield, a complex containing DCD coordinated in a bidentate fashion, trans-Co(η2-DCD)(acac)(NO2)2, were isolated. The two DCD complexes were characterized by X-ray structure determinations, which confirm the tridentate coordination with a long cobalt–tertiary nitrogen bond distance in the former, and bidentate coordination with the mustard nitrogen as a pendant arm in the latter. The bidentate complex, which contains a free nitrogen mustard, had cytotoxicity similar to that of the free ligand, but cytotoxicity was successfully masked in the tridentate complex, which showed modest hypoxic selectivity (five-fold) in a clonogenic assay.

Synthesis, structure and kinetics of Group 6 metal carbonyl complexes containing a new ‘P2N’ mixed donor multidentate ligand †

The ‘P2N’ mixed donor ligand 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]aniline (PNCHP) reacted with [Cr(CO)4(NBD)] and [M(CO)4(C5H11N)2] (M = Mo or W; NBD = norbornadiene; C5H11N = piperidine) to yield cis-[Cr(CO)4(PNCHP-κ2N,P)] and cis-[M(CO)4(PNCHP-κ2P,P′)] respectively. PNCHP behaves as a ‘P,N’ bidentate ligand when M is Cr and a ‘P,P’ bidentate ligand when M is Mo or W. Heating cis-[Cr(CO)4(PNCHP-κ2N,P)] or cis-[M(CO)4(PNCHP-κ2P,P′)] (M = Mo or W) in toluene affords the complexes mer-[M(CO)3(PNCHP-κ3P,N,P′)] (M = Cr, Mo or W). Reaction of PNCHP with [Mo(CO)3(CHT)] (CHT = 1,3,5-cycloheptatriene) in cold toluene yields fac-[Mo(CO)3(PNCHP-κ3P,N,P′)] which readily isomerises to mer-[Mo(CO)3(PNCHP-κ3P,N,P′)] in solution. PNCHP reacts with UV-irradiated tetrahydrofuran solutions of [M(CO)6] (M = Cr or W) to yield phosphorus bound co-ordination isomers of [M(CO)5(PNCHP-κ1P)]. The same reaction when carried out with one half equivalent of PNCHP yields the PNCHP bridged dinuclear species [{M(CO)5}2(PNCHP-κ2P,P′)]. The compounds have been characterised by spectroscopic means and the single crystal structures of cis-[Cr(CO)4(PNCHP-κ2N,P)], cis-[W(CO)4(PNCHP-κ2P,P′)], mer-[Mo(CO)3(PNCHP-κ3P,N,P′)] and [{W(CO)5}2(PNCHP-κ2P,P′)] determined. In addition, the isomerisation kinetics of fac- to mer-[Mo(CO)3(PNCHP-κ3P,N,P′)] has been studied to determine rate constants and thermodynamic activation parameters.

Synthesis and structures of tungsten ferrocenyldiazoalkane complexes derived from a dinitrogen complex.: Part 58. Preparation and properties of molybdenum and tungsten dinitrogen complexes

Reaction of the hydrazido(2-) complex cis, mer-[WCl 2(NNH 2)(PMe 2Ph) 3], derived from a dinitrogen complex cis-[W(N 2) 2(PMe 2Ph) 4], with formylferrocene or acetylferrocene gave ferrocenyldiazoalkane complexes cis, mer-[WCl 2(NNCRFc)(PMe 2Ph) 3] ( 2: R = H, Me; Fc = (η 5-C 5H 4)Fe(η 5-C 5H 5)). Treatment of 2 with π-acceptor ligands L such as CO, CH 2CH 2, p-MeC 6H 4CHO, p-MeC 6H 4CCH and Bu tNC afforded a series of ferrocenyldiazoalkane complexes cis, trans-[WCl 2(NNCRFc)(L)(PMe 2Ph) 2] ( 4), while upon treatment with CH 2Cl 2 2 gave the W(V) complexes mer, trans-[WCl 3(NNCRFc)(PMe 2Ph) 2] ( 5). The X-ray analyses have been undertaken to determine the detailed structures for 2a (R = H) and 5b (R = Me).

Rhodium(III)-mediated oxime–nitrile coupling giving chelated iminoacylated species †

Treatment of the acetonitrile complex mer-[RhCl3(MeCN)3] with cyclopentanone oxime (C4H8)CNOH resulted in the formation of two rhodium(III) products that contain newly formed chelated iminoacyl ligands, i.e. [RhCl3{NHC(Me)ONC(C4H8)}{HONC(C4H8)}] and [RhCl2{NHC(Me)ONC(C4H8)}2]Cl·1.5H2O. Only one iminoacylated product, i.e. the rhodium(III) complex [RhCl2{NHC(Ph)ONC(C4H8)}2]Cl·H2O·EtOH, has been isolated in the reaction between the oxime and the benzonitrile complex mer-[RhCl3(PhCN)3] in ethanol. A formally reverse reaction between [RhCl3{HONC(C4H8)}3], prepared on treatment of RhCl3·4H2O with the oxime in EtOH, and free organonitrile has also been carried out. All products were characterized by elemental analyses (C, H, N, Cl, Rh), FAB+-MS, IR, 1H and 13C-{1H} NMR spectroscopies. X-Ray single-crystal analyses were performed for [RhCl3{NHC(Me)ONC(C4H8)}{HONC(C4H8)}], [RhCl2{NHC(Me)ONC(C4H8)}2]Cl·1.5H2O, [RhCl2{NHC(Ph)ONC(C4H8)}2]Cl·H2O·2EtOH and mer-[RhCl3{HONC(C4H8)}3].

Molecular structure and iodine oxidative-thermal decarbonylation of the seven-coordinate complex [MoI2(CO)3(NCMe)2] to give the crystallographically characterised complex mer-[MoI3(NCMe)3

The X-ray crystal structure of the seven-coordinate complex [MoI2(CO)3(NCMe)2] (1) has been determined and shows discrete molecules. The geometry of the metal coordination sphere conforms to a distorted capped octahedron with a carbonyl group in the unique capping position. The capped face contains two carbonyl ligands and an iodo group, the uncapped face two MeCN ligands and an iodo group. The low temperature 13C n.m.r. spectrum (−70 °C, CD2Cl2) shows a single band at δ = 222.8 ppm, which suggests that the complex is rearranging more rapidly than the n.m.r. timescale at this temperature. Refluxing a 2:1 mixture of [MoI2 (CO)3(NCMe)2] and I2 in MeCN for 2h gives the crystallographically characterised molybdenum(III) complex mer-[MoI3(NCMe)3] (2) in quantitative yield.

Hydrocarbyl derivatives of dppm- or dppa-bridged alkoxysilyl heterobimetallic Fe–Pd complexes and CO insertion reactions. Crystal structures of [(OC)3{(MeO)3Si}Fe(μ-dppm)Pd(8-mq)] (dppm = Ph2PCH2PPh2), [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppa)PdCl] and [(OC)3Fe{μ-Si(OMe)2(OMe)}(μ-dppa)PdPh] (dppa = Ph2PNHPPh2) †

The complexes [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppm)PdR] (R = alkyl, aryl) have been obtained either by treatment of [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppm)PdCl] 1a with organolithium or Grignard reagents or, in the case where R = Me, by reaction of [PdCl(Me)(COD)] (COD = 1,5-cyclooctadiene) with the metallate K[Fe{Si(OMe)3}(CO)3(dppm-P)] 2a. When dppa was used as an assembling ligand, reaction of the hydrido complex mer-[HFe- {Si(OMe)3}(CO)3(dppa-P)] 7b with [PdCl(Me)(COD)] or [Pd(η3-allyl)(µ-Cl)]2 proceeded via elimination of methane or propene, respectively, to afford [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppa)PdCl] 1b and not via HCl elimination which would have resulted in hydrocarbyl complexes. However, reaction of 7b with [PdX(R)(TMEDA)] (X = Cl, R = Me; X = I, R = Ph; TMEDA = Me2NCH2CH2NMe2) afforded the hydrocarbyl complexes [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppa)PdMe] 3b or [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppa)PdPh] 5b. The latter and [(OC)3{(MeO)3Si}Fe(µ-dppa)Pd(η3-allyl)] 8b were obtained by reaction of the carbonylmetallate 2b with [PdCl(Me)(COD)], [PdI(Ph)(TMEDA)] or [Pd(η3-allyl)(µ-Cl)]2, respectively. The stabilizing but labile four-membered µ-η2-SiO→Pd bridging interaction facilitates CO insertion into the Pd–Me bond of 3a or 3b to afford the corresponding acetyl complexes. For comparison, [(OC)3{(MeO)3Si}Fe(µ-dppm)Pd(8-mq)] 6a which contains a stable five-membered (C,N) chelate at Pd did not insert CO under similar conditions. The reaction of CO with the benzyl derivative [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppm)Pd(CH2Ph)] 4a was more complex since the resulting acyl [(OC)3Fe{µ-Si(OMe)2(OMe)}(µ-dppm)Pd{C(O)CH2Ph}] 11a rearranged into the µ-siloxycarbene complex [(OC)3Fe{µ-C(CH2Ph)OSi(OMe)3}(µ-dppm)Pd(CO)] 12a. Comparisons are made between complexes containing dppm or dppa and different R groups. The structures of complexes 1b, 5b·THF and 6a·hexane have been determined by X-ray diffraction.

Syntheses and redox properties of the first phosphirene–dinitrogen and phosphirene–diazenide complexes

The first mixed phosphirene–dinitrogen and phosphirene–diazenide complexes mer-[ReCl(N2)(PPhCPhCPh)L3] (L = PMe2Ph 1a or PMePh2 1b) and [ReBr(NNPh)2(PPhCPhCPh)2(PPh3)] 2 have been prepared by treatment of the corresponding thf solutions of trans-[ReCl(N2)L4] or [ReBr3(NNPh)(PPh3)2] with PPhCPhCPh. Their redox properties have been investigated by cyclic voltammetry in an aprotic medium, at a platinum electrode, and the electrochemical EL and PL parameters estimated for the phosphirene ligand indicating that its overall electron donor/acceptor properties are similar to those of PMePh2.

Synthesis and NMR investigation on mer-[ReIIICl3(L)3] and mer-[ReIIICl3(L)2(PPh3)] complexes (L = pyridine-like ligand). X-ray structure of mer-[ReIIICl3(3,5-lut)3

The co-ordination geometry of the monomeric rhenium complexes mer-[ReIIICl3(L)3] (L = py 1, 3,5-lut 2, 4-pic 3) has been determined in the solid state by single X-ray diffraction of the representative complex 2 and in solution by proton NMR spectroscopy. Only a single stable conformation has been found in the solid state and in solution, under the experimental conditions utilised. The NMR spectra of the related complexes mer-[ReIIICl3(L)2(PPh3)] (L = py 4, 3,5-lut 5, 4-vinpy 6) have also been reported for comparison purposes.

Darstellung und Kristallstruktur von /wer-[Os(NCS)3Py3] / Synthesis and Crystal Structure of mer-[Os(NCS)3Py3

By reaction of K3[Os(NCS)3(SCN)3] with pyridine and glycerine the complex mer- [Os(NCS)3Py3] is formed. The X-ray structure determination on a single crystal (monoclinic, space group C2/c, a = 18.6156(12), b = 15.9448(7), c = 19.555(2) Å, β = 94.657(7)°, Z = 8) reveals that the nearly linear thiocyanate groups are exclusively bonded via the N atoms with Os-N-C angles ranging from 169.9° to 177.7°.

Syntheses and properties of organocyanamide, cyanoguanidine and dinitrogen complexes of rhenium. Crystal structure of mer-[ReCl 2(NCNEt 2) (PMePh 2) 3

Treatment of a THF solution of trans-[ReCl(N 2)L 4] (L  PMePh 2) with a cyanamide, NCNR 2 (R  Me, Et or H) or with cyanoguanidine, NCNC(NH 2) 2 , yields mer-[ReCl(N 2)(NCNR 2)L 3] ( 1) or mer-[Re(N 2)[Re(N 2){NCNC(NH 2) 2} 2L 3]Cl ( 2), respectively, which, to our knowledge, are the first mixed dinitrogen-cyanamide-type complexes to be reported. The former products ( 1, RMe or Et) can also be obtained from reaction of the benzoyldiazenido complex [ReCl 2(NNCOPh)L 3] with NCNR 2 in refluxing methanol; the Re(II) complex mer-[ReCl 2(NCNEt 2)L 3] ( 3) is also formed (conceivably via an unusual homolysis of the CN bond of the benzoyldiazenido ligand) and its crystal structure is reported. It shows an unusual pyramidal conformation at the amine N atom of the diethylcyanamide ligand which also exhibits a significant structural trans influence on the phosphine, behaving as a stronger net electron donor than the latter ligand.