Synthesis and characterization of polypyridineruthenium(II) complexes containing a linear ambidentate ligand, NCO or NCS, and reaction of isocyanato complexes under acidic conditions

Isocyanato and isothiocyanatopolypyridineruthenium complexes, [Ru(NCX)Y(bpy)(py)₂]ⁿ⁺ (bpy=2,2′-bipyridine, PY=pyridine; X=O, Y=NO₂ for n=0, and Y=py for n=1; X=S, Y=NO₂ for n=0, Y=NO for n=2, and Y=py for n=1), were synthesized by the reaction of polypyridineruthenium complexes with potassium cyanate or sodium thiocyanate salt. Isocyanatoruthenium(II) complexes, [Ru(NCO)(NO₂)(bpy)(py)₂] and [Ru(NCO)(bpy)(py)₃]⁺, react under acidic conditions to form the corresponding ammineruthenium complexes, [Ru(NO)(NH₃)(bpy)(py)₂]³⁺. The molecular structures of [Ru(NCO)(bpy)(py)₃]ClO₄, [Ru(NCS)(NO)(bpy)(py)₂](PF₆)₂ and [Ru(NO)(NH₃)(bpy)(py)₂](PF₆)₃ were determined by X-ray crystallography.     

Tricarbonyl(1,10-phenanthroline) (imidazole) rhenium(I): a powerful photooxidant for investigations of electron tunneling in proteins

The structure of [Re(CO)₃(phen)(im)]₂SO₄·4H₂O has been determined by X-ray crystallography. The yellow crystals are orthorhombic, space group Pccn (No. 56), with a=17.456(6), B=18.194(5), C=12.646(4) Å, R=0.063 for F_o²>0, R=0.032 for F_o²>3σ. The compound, which also has been characterized by IR, ¹H NMR, and UV---Vis spectroscopies, exhibits room temperature luminescence in aqueous solution (τ=120 ns) as well as reversible oxidation and reduction in acetonitrile solution (1.85 and −1.30 V versus SCE). The redox properties of the excited state of the complex (E⁰(Re^+*/0 = 1.2; E⁰(Re^2+/+*) = −0.7 V) are being exploited in studies of laser-induced electron tunneling in Re(CO)₃(phen)(histidine)-modified proteins.     

Nitrogen atom transfer and redox chemistry of terpyridyl phosphoraniminato complexes of osmium (IV)

Rapid reactions occur between [Os^VI(tpy)(Cl)₂(N)]X (X = PF₆⁻, Cl⁻, tpy = 2,2′:6′,2″-terpyridine) and aryl or alkyl phosphi nes (PPh₃, PPh₂Me, PPhMe₂, PMe₃ and PEt₃) in CH₂Cl₂ or CH₃CN to give [Os^IV(tpy)(Cl)₂(NPPh₃)]⁺ and its analogs. The reaction between trans-[Os^VI(tpy)(Cl)₂(N)]⁺ and PPh₃ in CH₃CN occurs with a 1:1 stoichiometry and a rate law first order in both PPh₃ and Os^VI with k(CH₃CN, 25°C) = 1.36 ± 0.08 × 10⁴ M⁻ s⁻¹. The products are best formulated as paramagnetic d⁴ phosphoraniminato complexes of Os^IV based on a room temperature magnetic moment of 1.8 μ_B for trans-[Os^IV(tpy)(Cl)₂(NPPh₃)](PF₆), contact shifted ¹H NMR spectra and UV-Vis and near-IR spectra. In the crystal structures of trans-[Os^IV(tpy)(Cl)₂( NPPh₃)](PF₆)·CH₃CN (monoclinic, P2₁/n with a = 13.384(5) Å, b = 15.222(7) Å, c = 17.717(6) Å, β = 103.10(3)°, V = 3516(2) ų, Z = 4, R_w = 3.40, R_w = 3.50) and cis-[Os^IV(tpy)(Cl)₂(NPPh₂Me)]-(PF₆)·CH₃CN (monoclinic, P2₁/c, with a = 10.6348(2) Å, b = 15.146(9) ÅA, c = 20.876(6) Å, β = 97.47(1)°, V = 3334(2) ų, Z = 4, R = 4.00, R_w = 4.90), the long Os-N(P) bond lengths (2.093(5) and 2.061(6) Å), acute Os-N-P angles (132.4(3) and 132.2(4)°), and absence of a significant structural trans effect rule out significant Os-N multiple bonding. From cyclic voltammetric measurements, chemically reversible Os^V/IV and Os^IV/III couples occur for trans-[Os^IV(tpy)(Cl)₂(NPPh₃)](PF₆) in CH₃CN at +0.92 V (Os^V/IV) and −0.27 V (Os^IV/III) versus SSCE. Chemical or electrochemical reduction of trans-[Os^IV(tpy)(Cl)₂(NPPh₃)](PF₆) gives isolable trans-Os^III(tpy)(Cl)₂(NPPh₃). One-electron oxidation to Os^V followed by intermolecular disproportionation and PPh₃ group transfer gives [Os^VI(tpy)Cl₂(N)]⁺, [OS^III(tpy)(Cl)₂(CH₃CN)]⁺ and [Ph₃=N=PPh₃]⁺ (PPN⁺). trans-[Os^IV(tpy)(Cl)₂(NPPh₃)](PF₆) undergoes reaction with a second phosphine under reflux to give PPN⁺ derivatives and Os^II(tpy)(Cl)₂(CH₃CN) in CH₃CN or Os^II(tpy)(Cl)₂(PR₃) in CH₂Cl₂. This demonstrates that the Os^VI nitrido complex can undergo a net four-electron change by a combination of atom and group transfers.     

Manganese(II) complexes of an acyclic phenol-based dinucleating ligand with four methoxyethyl chelating arms: synthesis, structure, magnetism and electrochemistry

Dinuclear manganese(II) complexes [Mn₂(bomp)(PhCO₂)₂]BPh₄ (1), [Mn₂(bomp)(MeCO₂)₂]BPh₄ (2), and [Mn₂(bomp)(PhCO₂)₂]PF₆ (3) were synthesized with a dinucleating ligand 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol [H(bomp)]. Dinuclear zinc complex [Zn₂(bomp)(PhCO₂)₂]PF₆ (4) was also synthesized for the purpose of comparison. X-ray analysis revealed that the complex 1·CHCl₃ contains two manganese ions bridged by the phenolic oxygen and two benzoate groups, forming a μ-phenoxo-bis(μ-benzoato)dimanganese(II) core. Magnetic susceptibility measurements of 1–3 over the temperature range 1.8–300 K indicated antiferromagnetic interaction (J=−4 to −6 cm⁻¹). Cyclic voltammograms of 3 showed a quasi-reversible oxidation process at +0.9 V versus a saturated sodium chloride calomel reference electrode, assigned to Mn^IIMn^II/Mn^IIMn^III.     

The interaction of Lewis acidic boron derivatives with Re(CO)5−nH(PMe3)n complexes

Lewis acid adducts of the hydrides cis- and trans-Re(CO)(PMe₃)₄H (1) and (2), mer-Re(CO)₂(PMe₃)₃H (3), fac-Re(CO)₂(PMe₃)₃H (4) and trans-Re(CO)₃(PMe₃)₂H (5) were studied with BH₃ and 9-borabicyclo[3,3,1] norbonane (BBNH). Using BH₃·THF and (BBNH)₂ 1 and 2 afforded Re(CO)(PMe₃)₃(η²-BH₄) (6) and Re(CO)(PMe₃)₃(η²-BBNH₂) (7) as stable and isolable products. VT IR studies established for the reaction to 7 that BBNH first attaches in a pre-equilibrium to the O_CO atom of 1 or 2. At higher temperatures ReH adduct formation occurs with instantaneous transformation to 7 and elimination of PMe₃·BBNH. In a similar way, the hydrides 3 and 4 were converted with BH₃·THF and (BBNH)₂ to yield the stable complexes Re(CO)₂(PMe₃)₂(η²-BH₄) (8) and Re(CO)₂(PMe₃)₂(η²-BBNH₂) (9). The intermediacy of the η¹-BH₄ adducts mer-/fac-Re(CO)₂(PMe₃)₃(η¹-BH₄) was confirmed by VT ¹H, ³¹P NMR and VT IR experiments. The conversion of 5 with BH₃·THF led to equilibria with adducts at the O_CO terminus in trans position to H and with H_Re as revealed by VT IR studies. Temperature dependent ³¹P equilibrium studies allowed to calculate ΔH=−4.9 kcal mol⁻¹ and ΔS=+0.034 e.u. for this reaction. These adducts could not be isolated. Compound 5 does not react with (BBNH)₂ even at elevated temperatures. DFT calculations were carried out to support the structures of the BH₃ adducts of 5. In addition a vibrational analysis helped to unravel the IR band assignments of the involved compounds. DFT calculations on 8 confirmed its C_2v structure. X-ray diffraction studies were carried out on single crystals of 6 and 7.     

The versatile coordination chemistry of tricyanoethenolate, [(NC)2C=C(CN)O]

The reaction of meso-tetrakis (4-dimethoxyphenyl) porphinatomanganese(II), MnTP_OMeP, with TCNE (TCNE = tetracyanoethylene) leads to the formation of [MnTP_OMeP]⁺ [TCNE]⁻ and [MnTP_OMeP]⁺[OC(CN)C(CN)₂]⁻. The single-crystal X-ray structures of the latter as well as [Cu(bipy)₂Cl]⁺ [OC(CN)C(CN)₂]⁻ were determined. The former has a disordered [OC(CN)C(CN)₂]⁻ bridging via C and O between a pair of Mn^III sites, whereas the latter has an isolated [OC(CN)C(CN)₂]⁻ unbound to Cu^II. The IR characterization for μ₂-C,O bound [OC(CN)C(CN)₂]⁻ is at 2219m and 2196s (νCN) cm⁻¹ and at 1558s (νCO) cm⁻¹ while for unbound [OC(CN)C(CN)₂]⁻ it is at 2210m, 2203m, 2181m (νCN) cm⁻¹ and at 1583s (νCO) cm⁻¹.     

Comparison in halide binding ability between the unsaturated clusters [Pd3(μ-dppm)3(CO)] and [PdPtCo(μ-dppm)2(CO)3(CNBu)] (dppm = Ph2PCH2PPh2)

The trinuclear clusters [Pd₃(μ-dppm)₃(CO)]²⁺ and [PtPdCo(μ-dppm)₂(CO)₃(CN^tBu)]⁺ exhibit a large and a small cavity, respectively, formed by the phenyl rings of the bridging diphosphine ligands. Their binding constants (K₁₁) with halide ions (X⁻) were obtained by UV-Vis spectroscopy. The binding ability varies as I⁻ > Br⁻ > Cl⁻, and [Pd₃(μ-dppm)₃(CO)]²⁺ > [ptPdCo(μ-dppm)₂-(CO)₃(CN^tBu)]⁺. The MO diagram for the related cluster [Pd₂Co(μ-dppm)₂(CO)₄]⁺ has been addressed theoretically in order to predict the nature of the lowest energy electronic bands. For this class of compounds, the lowest energy bands are assigned to charge transfers from the Co center to the Pd₂ centers.     

Syntheses, structures and magnetic properties of mono- and di-manganese inclusion compounds

Mono- and di-manganese inclusion compounds 1 and 2 are reported. Two mono-manganese molecules Mn(bpy)₂(NO₃)₂ (bpy=2,2′-bipyridine) and [Mn(bpy)₂(NO₃)(H₂O)]·NO₃ coexist in the mole ratio of 1:1 in the structure of 1, while two di-manganese molecules [Mn₂O(bpy)₂(phtha)₂(H₂O)₂]·(NO₃)₂ (phtha=phthalate) and [Mn₂O(bpy)₂(phtha)₂(NO₃)(H₂O)]·NO₃ in the structure of 2. Refluxing Mn(NO₃)₂/bpy/phthalic acid reaction mixtures in CH₃CN leads to the isolation of 1, further concentration of the reaction solution in raising temperature results in 2. The Mn₁ and Mn₂ units in the inclusion compounds 1 and 2 are similar to other reported Mn₁ and Mn₂ analogs, respectively. The Jahn–Teller distortion was observed to give rise to the elongation along the O_terminal---Mn---O_carboxyl axes for all the four Mn(III) sites in 2, leading to unexpected longer Mn(III)---O_aqua than Mn(II)---O_aqua in 1. Extensive hydrogen bonding interactions among H₂O, NO₃ ⁻ and COOH were observed in the two inclusion compounds. Cyclic voltammetry of 2 in DMF displays two quasi-reversible redox couples at +0.10/+0.22 and −0.43/−0.36 V assigned to the Mn(III)Mn(IV)/2Mn(III) and 2Mn(III)/Mn(III)Mn(II), respectively. Variable temperature magnetic susceptibilities of 1 and 2 were measured. The data were fit to a model including axial zero-field splitting term and a good fit was found with D=1.77 cm⁻¹, g=1.98 and F=1.48×10⁻⁵ for 1. For 2, the least-squares fitting of the experimental data led to J=2.37 cm⁻¹, g=2.02 and D=0.75 cm⁻¹ with R=1.45×10⁻³.     

Nickel(II) and copper(II) complexes of mixed benzene-triazolehemiporphyrazines

The kinetics of substitution reactions of [η-CpFe(CO)₃]PF₆ with PPh₃ in the presence of R-PyOs have been studied. For all the R-PyOs (R = 4-OMe, 4-Me, 3,4-(CH)₄, 4-Ph, 3-Me, 2,3-(CH)₄, 2,6-Me₂, 2-Me), the reactions yeild the same product [η⁵-CpFe(CO)₂PPh₃]PF₆, according to a second-order rate law that is first order in concentrations of [η⁵-CpFe(CO)₃]PF₆ and of R-PyO but zero order in PPh₃ concentration. These results, along with the dependence of the reaction rate on the nature of R-PyO, are consistent with an associative mechanism. Activation parameters further support the bimmolecular nature of the reactions: ΔH^≠ = 13.4 ± 0.4 kcal mol⁻¹, ΔS^≠ = −19.1 ± 1.3 cal k⁻¹ mol⁻¹ for 4-PhPyO; ΔH^≠ = 12.3 ± 0.3 kcal mol⁻¹, ΔS^≠ = 24.7 ±1.0 cal K⁻¹ mol⁻¹ for 2-MePyO. For the various substituted pyridine N-oxides studied in this paper, the rates of reaction increase with the increasing electron-donating abilities of the substituents on the pyridine ring or N-oxide basicities, but decrease with increasing ¹⁷O chemical shifts of the N-oxides. Electronic and steric factors contributing to the reactivity of pyridine N-oxides have been quantitatively assessed.     

A reversible NO complex of Fe(TIM): an S = 1/2FeNO nitrosyl

[Fe(TIM)(CH₃CN)₂](PF₆)₂ (1) (TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclodeca-1,3,8,10-tetraene) forms a complex with NO reversibly in CH₃CN (53±1% converted to the NO complex) or 60% CH₃OH/40% CH₃CN (81±1% conversion). Quantitative NO complexation occurs in H₂O or CH₃OH solvents. The EPR spectrum of [Fe(TIM)(solvent)NO]²⁺ in frozen 60/40 CH₃OH/CH₃CN at 77 K shows a three line feature at g=2.01, 1.99 and 1.97 of an S=1/2FeNO⁷ ground state. The middle line exhibits a three-line N-shf coupling of 24 G indicating a six-coordinate complex with either CH₃OH or CH₃CN as a ligand trans to NO. In H₂O [Fe(TIM)(H₂O)₂]²⁺ undergoes a slow decomposition, liberating 2,3-butanedione, as detected by ¹H NMR in D₂O, unless a π-acceptor axial ligand, L=CO, CH₃CN or NO is present. An equilibrium of 1 in water containing CH₃CN forms [Fe(TIM)(CH₃CN)(H₂O)]²⁺ which has a formation constant K_CH3CN=320 M⁻¹. In water K_NOK_CH3CN since NO completely displaces CH₃CN. [Fe(TIM)(CH₃CN)₂]²⁺ binds either CO or NO in CH₃CN with K_NO/K_CO=0.46, sigificantly lower than the ratio for [Fe^II(hemes)] of 1100 in various media. A steric influence due to bumping of β-CH₂ protons of the TIM macrocycle with a bent S=1/2 nitrosyl as opposed to much lessened steric factors for the linear Fe---CO unit is proposed to explain the lower K_NO/K_CO ratio for the [Fe(TIM)(CH₃CN)]²⁺ adducts of NO or CO. Estimates for formation constants with [Fe(TIM)]²⁺ in CH₃CN of K_NO=80.1 M⁻¹ and K_CO=173 M⁻ are much lower than to hemoglobin (where K_NO=2.5×10¹⁰ M⁻¹ and K_CO=2.3×10⁷) due to a reversal of steric factors and stronger π-backdonation from [Fe^II(heme)] than from [Fe^II(TIM)(CH₃CN)]²⁺.     

In situ IR and NMR study of the interactions between proton donors and the Re(I) hydride complex [{MeC(CH2PPh2)3}Re (CO)2H]. ReH…H bonding and proton-transfer pathways

The reactions of various proton donors (phenol, hexafluoro-2-propanol, perfluoro-2-methyl-2-propanol, monochloroacetic acid, and tetrafluoroboric acid) with the rhenium (I) hydride complex [(triphos)Re(CO)₂H] (1) have been studied in dichloromethane solution by in situ IR and NMR spectroscopy. The proton donors from [(triphos)Re(CO)₂H…HOR] adducts exhibiting rather strong H…H interactions. The enthalpy variations associated with the formation of the H-bonds (−ΔH = 4.4–6.0 kcal mol⁻¹) have been determined by IR spectroscopy, while the H…H distance in the adduct [(triphos)Re(CO)₂H…HOC(CF₃)₃] (1.83 Å) has been calculated by NMR spectroscopy through the determination of the T_1min relaxation time of the Re---H proton. It has been shown that the [(triphos)Re(CO)₂H…HOR] adducts are in equilibrium with the dihydrogen complex [(triphos)Re(CO)₂(η²-H₂)]⁺, which is thermodynamically more stable than any H-bond adduct.     

Fluoro-hydrido-oxo and other fluoro-oxo complexes of rhenium (V) containing a triphosphine ligand

The fluoro-hydrido-oxo complex [Re(F)(H)(O)Cyttp]⁺ (3, Cyttp = PhP(CH₂CH₂CH₂PCy₂)₂) was prepared in high yield from [Re(H₂)H₄Cyttp]SbF₆ (1(SbF₆), NaSbF₆ and acetone in toluene at reflux. Reaction chemistry of 3 has been studied and, where appropriate, compared with that of the related dihydrido-oxo complex [ReH₂(O)Cyttp]⁺ (2). Unlike 2, which readily reacts with both CO and SO₂, 3 was found to be inert to these reagents under comparable conditions. However, 3(SbF₆) reacts with NaSbF₆ at elevated temperature to afford the difluoro-oxo complex [ReF₂(O)Cyttp]⁺ (4). 4 undergoes fluoride substitution by Cl⁻ or Br⁻ to yield [Re(X)(F)(O)Cyttp]⁺ (X = Cl (5, Br (6)). 5 can also be obtained by treatment of 6(BPh₄) with LiCl. All of these complexes contain mer-Cyttp, and 3–6 contain trans fluoride and oxide ligands as inferred from spectroscopic data.     

Dinuclear sulfide–thiolate complexes [Pt2(μ-S)(μ-SR)(PPh3)4] as cationic metalloligands

The cationic monoalkylated derivatives of the well-known metalloligand [Pt₂(μ-S)₂(PPh₃)₄], viz. [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ (R = n-Bu, CH₂Ph) are themselves able to act as metalloligands towards the Ph₃PAu⁺ and R′Hg⁺ (R′ = Ph or ferrocenyl) fragments, by reaction with Ph₃PAuCl or R′HgCl, respectively. The resulting dicationic products [Pt₂(μ-SR)(μ-SAuPPh₃)(PPh₃)₄]²⁺ and [Pt₂(μ-SR)(μ-SHgR′)(PPh₃)₄]²⁺ are readily isolated as their hexafluorophosphate salts, and have been fully characterised by spectroscopic techniques and an X-ray structure determination on [Pt₂(μ-SR)(μ-SHgFc)(PPh₃)₄](PF₆)₂.     

Heterobimetallic chloro bridgedcomplexes of (η:η−C10H16)-ruthenium(IV) with palladium(II), platinum(II), rhodium(III), iridium(III), copper(I) and rhodium(I)

Metathesis of [(η³:η³−C₁₀H₁₆)Ru(Cl) (μ−Cl)]₂ (1) with [R₃P) (Cl)M(μ-Cl)]₂ (M = Pd, Pt), [Me₂NCH₂C₆H₄Pd(μ-Cl)]₂ and [(OC)₂Rh(μ-Cl)]₂ affords the heterobimetallic chloro bridged complexes (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂M(PR₃)(Cl) (M = Pd, Pt), (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂PdC₆H₄CH₂NMe₂ and (η³:η³-C₁₀H₁₆) (Cl)Ru(μ-Cl)₂Rh(CO)₂, respectively. Complex 1 reacts with [Cp^*M(Cl) (μ-Cl)]₂ (M = Rh, Ir), [p-cymene Ru(Cl) (μ-Cl]₂ and [(Cy₃P)Cu(μ-Cl)]₂ to give an equilibrium of the heterobimetallic complexes and of educts. The structures of (η³:η³-C₁₀H₁₆)Ru(μ-Cl)₂Pd(PR₃) (Cl) (R = Et, Bu) and of one diastereoisomer of (η³:η³-C₁₀H₁₆)Ru(μ-Cl)₂IrCp^*(Cl) were determined by X-ray diffraction.     

The synthesis and reactions of A-ring aromatic steroid complexes of manganese tricarbonyl

Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO)₅⁺BF₄⁻ in CH₂Cl₂ yields the corresponding [(steroid)Mn(CO)₃]BF₄ salts 1 and 2 as mixtures of and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO)₃]BF₄ · CH₂Cl₂ (1) having the Mn(CO)₃ moiety on the side of the steroid is reported: space group P2₁ with a=10.3958(9), b=10.9020(6), c=12.6848(9) Å, β=111.857(6)°, Z=2, V=1334.3(2) ų, _calc=.481 cm⁻³, R=0.0508, and wR=0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear Mn---C---O linkages. The nucleophiles NaBH₄ and LiCH₂C(O)CMe₃ add to [(β-estradiol 3,17-dimethyl ether)Mn(CO)₃]BF₄ (2) in high yield to give the corresponding - and β-cyclohexadienyl manganese tricarbonyl complexes (3). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo-CH₂C(O)CMe₃ substituent is reported (complex 4): space group P2₁2₁2₁ with a=7.5154(8), b=15.160(2), c=25.230(3) Å, Z=4, V=2874.4(5) ų, _calc=1.244 g cm⁻³, R=0.0529 and wR2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 Å out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths.     

Structure, physical, chemical and photophysical properties of Pt(bph) (CO)2, where bph is the biphenyl dianion

The complex Pt(bph) (CO)₂ crystallizes in the space group Cmcm with a = 18.647(6), B = 9.566(2) and C = 6.4060(5) Å. The geometry of the molecule is slightly distorted from square planar with a Pt---C(CO) bond distance of 1.98(2) Å and a Pt---C(bph) bond distance of 2.04(2) Å. The Pt(bph)(CO)₂ complex serves as a precursor for the preparation of a wide variety of Pt(bph)X₂ complexes, where X = monodentate ligands such as acetonitrile, pyridine, etc., and X₂ = bidentate ligands such as bypyridine, 1,10-phenanthroline, etc. In the solid state, the complex exhibits a green color, but when ground with an alkali metal salt turns deep blue to purple. In CH₂Cl₂, the color disappears but optical transitions are observed at 271 nm (2.7 × 10⁴ M⁻¹ cm⁻¹), 303 nm (1.1 × 10⁴ M⁻¹ cm⁻¹) and 330 nm (5.5 × 10³ M⁻¹ cm⁻¹). The complex is a weak emitter exhibiting a structured spectrum in CH₂Cl₂ at r.t. with maxima located at 562 and 594 nm and an emission lifetime of 3.1 μs when excited at 337 nm.     

Mixed-metal butterfly acetamidediato clusters derived from a highly reactive ruthenium oxo cluster: synthesis and characterization of [(PPh3)2N][MRu3(CO)12(η-μ3-NC(μ-O)CH3)], (M = Mn or Re)

Analogy with the isolable oxo cluster [Fe₃(CO)₉(μ₃-O)]²⁻, which is structurally interesting and synthetically useful, prompted the present attempt to synthesize its ruthenium analog. Although the high reactivity of [Ru₃(CO)₉(μ₃-O)]²⁻ (I) prevented its isolation, the reaction of this species with [M(CO)₃(NCCH₃)]⁺, where M = Mn or Re, yields [PPN][MRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃]⁻. The high nucleophilicity of the oxo ligand in [Ru₃(CO)₉(μ₃-O)]²⁻ (I) appears to be responsible for the conversion of acetonitrile to an acetamidediato ligand and for the instability of I. The crystal structure of [PPN][MnRu₃(CO)₁₂(η²-μ₃-NC(μ-O)CH₃)]] reveals a hinged butterfly array of metal atoms in which the acetamidediato ligand bridges the two wings with μ₃-N bonding to an Mn and two Ru atoms, and μ-O bonding to an Ru atom.     

Synthesis and characterization of organomolybdenum and organotungsten halides containing the η-pentabenzylcyyclopentadienyl ligand η-Bz5C5M(CO)3X (M = Mo, W; X = Cl, Br, I). The X-ray molecular structure of η-Bz5C5Mo(CO)3I

An improved synthetic procedure for pentabenzylcyclopentadiene Bz₅C₅H was developed. Six new organomolybdenum and organotungsten halides η⁵-Bz₅C₅M(CO)₃X(M = Mo, W; X = Cl, Br, I) were syntesized through the reaction of η⁵-Bz₅C₅M(CO)₃Li (derived from Bz₅C₅H, n-BuLi and M(CO)₆) with PCl₃, PBr₃ or I₂ and characterized by elemental analysis, IR and ¹H NMR spectroscopy. The structure of η⁵-Bz₅C₅Mo(CO)₃I was determined by single-crystal X-ray diffraction techniques. It crystallized in the monoclinic space groupp P2/c with cell parameters a = 13.294(4), B = 15.147(4), C = 19.027(3) Å, β = 108.32(2)°, V = 3637(2) ų, Z = 4 and D_x = 1.50 g cm⁻³. The final R value was 0.035 for 4564 observed reflections.     

η and η olefin complexation by S, S-[Ru(Me2edda)]: a structural change to accommodate bidentate dienes

[Ru^II(Me₂edda)(H₂O)₂] (1), Me₂edda²⁻ = N,N′-dimethylethylenediaminediacetate, exhibits a sterically-controlled molecular recognition in forming η² and η⁴ olefin complexes. 1 exists with an N₂O₂ in-plane set of chelate donors and axial H₂O ligands. The two CH₃ functionalities of Me₂edda²⁻ are poised above and below the N₂O₂ plane of the glycinato rings. Studies herein of the 2,2′-bipyridine complex, [Ru^II(Me₂edda)(bpy)], with bidentate bpy chelation as established via ¹H NMR and electrochemical methods show 1 to be ligated in the S,S configuration with the glycinato rings in-plane as a cis-O form. 1 is sterically discriminating in forming η² complexes with smaller olefins (ethylene, 2-propene, cis-2-butene, methyl vinyl ketone and 3-cyclohexene-1-methanol), but rejects larger decorated ring structures and branched olefins (1,2-dimethyluracil, cyclohexene-1-one 2-methyl-2-propene). η² complexes of 1 have characteristic Ru^II/III DPP waves near 0.55 V which vary slightly with olefin structure. Potentially bidendate dienes (1,3-butadiene, 1,3-cyclohexadiene and 2,5-norbornadiene (nbd) form η⁴ complexes as shown by Ru^II/III waves between 0.94 and 1.30 V, indicate of a highly stabilized Ru^II center by π-backboning. An η²η⁴ ‘equilibrium’ with apparent K = 22 at 25 °C is observed for nbd coordinated to 1. (The η² and η⁴ distribution may be a kinetic one and not a thermodynamic one). To allow formation of the cis η⁴ complexes, 1 must undergo a shift of one or both glycinato donors from the N₂O₂ plane into the axial site away from the dimethyl functionalities. η⁴ chelation by 1,3-butadiene has been confirmed by ¹H NMR spectral assignments of two [Ru^II(Me₂edda)] isomers, one in the axial rans-O glycinato configuration, e.g. 1,3-butadiene is bidentate in the original N₂O₂ plane and a second unsymmetrical glycinato arrangement with in-plane and axial glycinato as well as in-plane and axial η⁴-1,3-butadiene coordination. [Ru^II(hedta)(H₂O)]⁻ (2), hedta³⁻ = N-hydrpxyethylenediaminetriacetate, is less discriminating for olefin structures, forming η² complexes with all eleven olefins and dienes mentioned for studies with 1. However, 2 does not undergo displacement of a carboxylate donor by the second olefin unit of a diene [Ru^II(hedta)(diene)]⁻ complexes possess a pendant non-coordinated olefin and on η²-bound olefin in the complex, indicated by a normal Ru^II(pac)(olefin)Ru^II/III wave near 0.55 V.     

Ammonia ruthenium complexes for the access to new hydrido, carbonyl and isocyanide ruthenium-alkynyl derivatives

The potential in preparative chemistry of the precursors trans-[Ru(NH₃)(CC---R¹)(Ph₂PCH₂CH₂PPh₂)₂]PF₆ (3) has been studied. They offer a convenient access, by NH₃ displacement, to new functional alkynyl-ruthenium derivatives. Complexes 3 react with alkynes HCC---R² to give unsymmetrical trans-Ru(---CC---R¹)(---CC---R²)(dppe)₂ compounds 4a-c, and with sodium methoxide in methanol they open the route to a variety of mixed hydride complexes 5a-c, trans-Ru(H)(---CC---R¹)(dppe)₂. In contrast, with carbon monoxide or isocyanides CN---R³ (R³:CH₂Ph, C₆H₁₁, Me₃C) they allow the preparation of cationic derivatives trans-(Ru(CO)(---CC---R¹)(dppe)₂]PF₆ (6a-c) or trans-[Ru(CNR³)(---CC---R¹)(dppe)₂]PF₆ (7a-d).