Synthesis and characterization of homologous nickel(II) and palladium(II) complexes with biphosphine monoxide ligands Ph2P(CH2)nP(O)Ph2 (n = 1–3) and pTol2P(CH2)P(O)pTol2

A series of cationic nickel complexes [(η³-methally)Ni(PP(O))]SbF₆ (1–4) [PP(O) = Ph₂P(CH₂)P(O)Ph₂ (dppmO) (1), Ph₂P(CH₂)₂P(O)Ph₂ (dppeO) (2), Ph₂P(CH₂)₃P(O)Ph₂ (dpppO) (3), pTol₂P(CH₂)P(O)pTol₂ (dtolpmO) (4)] has been synthesized in good yields by treatment of [(η³-methally)NiBr]₂ with biphosphine monoxides and AgSbF₆. The ligands are coordinated in a bidentate way. Starting from [(η³-all)PdI]₂ the cationic complexes [(η³-all)PP(O))]Y (8–14). [PP(O) = dppmO, dppeO, dpppO, dtolpmO;Y = BF₄, SbF₆, CF₃SO₃, pTolSO₃] were synthesized in good yields. The coordination mode of the ligand is dependent on the backbone and the anion, revealing a monodentate coordination with dppmO for stronger coordinating anions. The intermediates [(η³-all)Pd(I)(PP(O)-κ¹-P)] (5–7) [PP(O) = dppmO (5), dppeO (6), dtolpmO (7)] were isolated and characterized. Neutral methyl complexes [(Cl)(Me)Pd(PP(O))] (15–18). [PP(O) = dppmO (15), dppeO (16), dpppO (17), dtolpmO (18)] can easily be obtained in high yields starting from [(cod)PdCl₂]. For dppmO two different routes are presented. The structure of [(Me)(Cl)Pd{;Ph₂P(CH₂-P(O)Ph₂-κ²-P,O};] · CH₂Cl₂ (15) with the chlorine atom trans to phosphorus was determined by X-ray diffraction.     

Hetero-polynuclear complexes containing bridging diphenylphosphino-alkenes and -alkynes. The crystal structure of an Rh2{μ−ν:ν−P(Ph2) (CH2)3C≡CR}Co2 complex

The phosphinoalkenes Ph₂P(CH₂)_nCH=CH₂ (n= 1, 2, 3) and phosphinoalkynes Ph₂P(CH₂)_n C≡CR (R = H, N = 2, 3; R = CH₃, N = 1) have been prepared and reacted with the dirhodium complex (η−C₅H₅)₂Rh₂(μ−CO) (μ−η²−CF₃C₂CF₃). Six new complexes of the type (ν−C₅H₅)₂(Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃)L, where L is a P-coordinated phosphinoalkene, or phosphinoalkyne have been isolated and fully characterized; the carbonyl and phosphine ligands are predominantly trans on the Rh---Rh bond, but there is spectroscopic evidence that a small amount of the cis-isomer is formed also. Treatment of the dirhodium-phosphinoalkene complexes with (η−CH₃C₅H₄)Mn(CO)₂thf resulted in coordination of the manganese to the alkene function. The Rh₂---Mn complex [(η−C₅H₅)₂Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃) {Ph₂P(CH₂)₃CH=CH₂} (η−CH₃C₅H₄)Mn(CO)₂] was fully characterized. Simi treatment of the dirhodium-phosphinoalkyne complexes with Co₂(CO)₈ resulted in the coordination of Co₂(CO)₆ to the alkyne function. The Rh₂---Co₂ complex [(η−C₅H₅)₂Rh₂(CO) (μ−η¹:η¹−CF₃C₂CF₃) {Ph₂PCH₂C≡CCH₃}Co₂(CO)₂], C₃₇H₂₅Co₂F₆O₇PRh₂, was fully characteriz spectroscopically, and the molecular structure of this complex was determined by a single crystal X-ray diffraction study. It is triclinic, space group (C_i¹, No. 2) with a = 18.454(6), B = 11.418(3), C = 10.124(3) Å, = 112.16(2), β = 102.34(3), γ = 91.62(3)°, Z = 2. Conventional R on |F| was 0.052 fo observed (I > 3σ(I)) reflections. The Rh₂ and Co₂ parts of the molecule are distinct, the carbonyl and phosphine are mutually trans on the Rh---Rh bond, and the orientations of the alkynes are parallel for Rh₂ and perpendicular for Co₂. Attempts to induce Rh₂Co₂ cluster formation were unsuccessful.     

The trans influence of F, Cl, Br and I ligands in a series of square-planar Pd(II) complexes. Relative affinities of halide anions for the metal centre in trans-[(Ph3P)2Pd(Ph)X]

Single crystal X-ray diffraction studies of trans-[(Ph₃P)₂Pd(Ph)X] (X = F (1), Cl (2), Br (3), and I (4) were carried out. The four structures split in two isostructural and isomorphous groups, namely orthorhombic for 1 and 2 (space group Pbca, Z = 8) and triclinic for 3 and 4 (space group P-1, Z = 2). According to the Pd---C bond length, the trans influence of X within these pairs follows the trend Cl>F and 1>Br. However, the trans influence of Cl is slightly stronger than that of Br. Both structural and ¹³C NMR studies revealed that electron-donating effects of (Ph₃P)₂PdX increase along the series X=I− for the Pd centre in [(Ph₃P)₂Pd(Ph)]⁻ were studied by ³¹P NMR in rigorously anhydrous CH₂Cl₂ solutions, and equilibrium constants and ΔG values were obtained for all possible combinations. The sequence F⁻ > Cl⁻ > Br⁻ > I⁻ is characteristic of halide preference for the Pd complexes. Dissolving 1 and PPN Cl in dry CH₂Cl₂ resulted in the release of ‘naked’ F⁻ which fluorinated the solvent smoothly to give a mixture of CH₂ClF and CH₂F₂ in high yield. When chloroform was used instead of CH₂Cl₂, dichlorocarbene was generated slowly, forming the corresponding cyclopropane in the presence of styrene. All observations were rationalized successfully in terms of the filled/filled effect and push/pull interactions.     

The kinetics and energetics of formation of a molecular hydrogen complex involving a dinuclear ruthenium(II) centre

The reversible equilibrium conversion under H₂ of [RuCl(dppb) (μ-Cl)]₂ (1) to generate (η²-H₂) (dppb) (μ-Cl)₃RuCl(dppb) in CH₂Cl₂ (dppb = Ph₂P(CH₂)₄PPh₂) has been studied at 0–25 °C by UV-Vis and ³¹P{¹H} NMR spectroscopy, and by stoppe kinetics; the equilibrium constant and corresponding thermodynamic parameters, and the forward and reverse rate constants at 25 °C have been determined. A measured ΔH° value of 0 kJ mol⁻¹ allows for an estimation of an exothermicity of 60 kJ mol⁻¹ for binding an η²-H₂ at an Ru(II) centre; a ΔS° value of 60 J mol⁻¹ K⁻¹ indicates that in solution 1 contain s coordinated CH₂Cl₂. The kinetic and thermodynamic data are compared to those obtained from a previously studied hydrogenation of styrene catalyzed by 1. Preliminary findings on related systems containing Ph₂P(CH₂)₃PPh₂ and (C₆H₁₁)₂P(C₆H₁₁)₂ are also noted.     

Reactions of the haloalcohols HO(CH2)nCl (n = 2, 3) with platinum(II) - alkynyl and -alkyne complexes. X-ray crystal structure of trans-[Pt(Me) {C(OCH2CH2Cl) (CH2Ph)} (PPh3)2] [BF4]

The chloro complexes trans-[Pt(Me)(Cl)(PPh₃)₂], after treatment with AgBF₄, react with 1-alkynes HC---C---R in the presence of NEt₃ to afford the corresponding acetylide derivatives trans-[Pt(Me) (C---C---R) (PPh₃)₂] (R = p-tolyl (1), Ph (2), C(CH₃)₃ (3)). These complexes, with the exception of the t-butylacetylide complex, react with the chloroalcohols HO(CH₂)_nCl (n = 2, 3) in the presence of 1 equiv. of HBF₄ to afford the alkyl(chloroalkoxy)carbene complexes trans-[Pt(Me) {C[O(CH₂)_nCl](CH₂R) } (PPh₃)₂][BF₄] (R = p-tolyl, N = 2 (4), N = 3 (5); R=Ph, N = 2 (6)). A similar reaction of the bis(acetylide) complex trans-[Pt(C---C---Ph)₂(PMe₂Ph)₂] with 2 equiv. HBF₄ and 3-chloro-1-propanol affords trans-[Pt(C---CPh) {C(OCH₂CH₂CH₂Cl)(CH₂Ph) } (PMe₂Ph)₂][BF₄] (7). T alkyl(chloroalkoxy)-carbene complex trans-[Pt(Me) {C(OCH₂CH₂Cl)(CH₂Ph) } (PPh₃)₂][BF₄] (8) is formed by reaction of trans-[Pt(Me)(Cl)(PPh₃)₂], after treatment with AgBF₄ in HOCH₂CH₂Cl, with phenylacetylene in the presence of 1 equiv. of n-BuLi. The reaction of the dimer [Pt(Cl)(μ-Cl)(PMe₂Ph)]₂ with p-tolylacetylene and 3-chloro-1-propanol yields cis-[PtCl₂{C(OCH₂CH₂CH₂Cl)(CH₂C₆H₄-p-Me}(PMe₂Ph)] (9). The X-ray molecular structure of (8) has been determined. It crystallizes in the orthorhombic system, space group Pna2₁, with a = 11.785(2), B = 29.418(4), C = 15.409(3) Å, V = 4889(1) ų and Z = 4. The carbene ligand is perpendicular to the Pt(II) coordination plane; the PtC(carbene) bond distance is 2.01(1) Å and the short C(carbene)-O bond distance of 1.30(1) Å suggests extensive electronic delocalization within the Pt---C(carbene)---O moietry.     

The ReH6[P(C6H5)3]2 ion as a ligand: complexes with M(CO)3 fragments (M = Cr, Mo, W)

The reactions of [(H₅C₆)₃P]₂ReH₆⁻ with (CH₃CN)₃Cr(CO)₃, (diglyme)Mo(CO)₃ or (C₃H₇CN)₃W(CO)₃ led to the formation of [(H₅C₆)₃P]₂ReH₆M(CO)₃⁻ (M = Cr, Mo, W) complexes. These have been characterized by IR and NMR spectroscopies, as well as elemental analyses. A single crystal X-ray diffraction study has also been carried out for the M = Cr complex as a K(18-crown-6)⁺ salt. The complex crystallizes as a THF monosolvate in the monoclinic space group P2₁/n with a = 22.323(6), B = 9.523(2), C = 27.502(5) Å, β = 104.98(2)⁰ and V = 5648 ų for Z = 4. The Re---Cr separation is 2.5745(12) Å, and the two phosphine ligands are oriented unsymmetrically. Although the hydride ligands were not found, the presence of three bridging hydrides and a dodecahedral coordination geometry about rhenium could be inferred. Low temperature ¹H and ³¹P NMR spectroscopic studies did not reveal the low symmetry of the solid state structure.     

Studies of the oxovanadium(IV)—oxalate system: syntheses and crystal structures of binuclear (Ph4P)2[(VO)2(H2O)2(C2O4)3]·4H2O and of the one-dimensional chain material, (Ph4P)[VOCl(C2O4)]

The hydrothermal reactions of (Ph₄P)[VO₂Cl₂] and H₂C₂O₄ at 150 and 125°C yield (Ph₄P)₂[V₂O₂(H₂O)₂(C₂O₄)₃]·4H₂O (1) and (Ph₄P)[VOCl(C₂O₄)] (2), respectively. The structure of the molecular anion of 1 consists of a binuclear unit of oxovanadium(IV) octahedra bridged by a bisbidentate oxalate group. The VO₆ coordination geometry at each vanadium site is defined by a terminal oxo group, an aquo ligand, and four oxygen donors — two from the bisbidentate bridging oxalate and two from the terminal bidentate oxalate. The structure of 2 consists of discrete Ph₄P⁺ cations occupying regions between [VOCl(C₂O₄)]⁻_∞ spiral chains. The structure of the one-dimensional anionic chain exhibits V(IV) octahedra bridged by bisbidentate oxalate groups. Crystal data: 1·4H₂O, monoclinic P2₁/n, A = 12.694(3), B = 12.531(3), C = 17.17(3) Å, β = 106.32(2)°, V = 2621.3(13) ų, Z = 2, D_calc = 1.501 g cm⁻³, structure solution and refinement converged at a conventional residual of 0.0518; 2, tetragonal P4₃, A = 12.145(2), C = 15.991(3) Å, V = 2358.7(12) ų, Z = 4, R = 0.0452.     

Synthesis, solution behaviour and molecular structures of 16-electron closo-2-(Ph3P)-1-N,2-[μ-(η-CH2CH=Ch2)]-1-N-(σ-CH2CH=CH2)-2,1- RhCB10H10, the first η-olefinic monocarbon metallacarborane

The first η²-olefinic monocarbon metallacarbone closo-2-(Ph₃P)-1-N,2-[μ-(η²-CH₂CH=Ch₂)]-1-N-(σ-CH₂CH=CH₂)-2,1- RhCB₁₀H₁₀ has been prepared by the reaction of the dimeric anion {[Ph₃PRhB₁₀H₁₀CNH₂]₂-μ-H}⁻[PPN]⁺ with allyl bromide and characterized by a combination of spectroscopic methods and a single-crystal X-ray diffraction study. The variable temperature ¹H and ¹³C NMR studies revealed the fluxional behavior of the η²-olefinic complex in CD₂Cl₂ solution which is associated with the allyl side-chain exchange process.     

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.     

The synthesis of the tripodal phosphine CH3C{CH2P(m-CF3C6H4)2}3 and its rhodium coordination chemistry

The new tripodal phosphine CH₃C{CH₂P(m-CF₃C₆H₄)₂}₃, CF₃PPP, was prepared by reacting CH₃C(CH₂Br)₃ with Li⁺P(m-CF₃C₆H₄)₂⁻, the latter being best obtained by adding Li⁺NⁱPr₂⁻ to PH(m-CF₃C₆H₄)₂. The rhodium complexes [RhCl(CO)(CF₃PPP)], [Rh(LL)(CF₃PPP)](CF₃SO₃) (LL = 2 CO or NBD), [RhX₃(CF₃PPP)], [RhX(MeCN)₃(CF₃PPP)](CF₃SO₃)₂ (X = H and Cl), [RhCl₂(MeCN)(CF₃PPP)](CF₃SO₃) and [Rh(MeCN)₃(CF₃PPP)](CF₃SO₃)₃ were prepared and characterized. The X-ray crystal structure of [Rh(NBD)(CF₃PPP)](CF₃SO₃) is reported. The lower oxygen sensitivity of the CF₃PPP rhodium(I) complexes, relative to the corresponding species with the parent ligand CH₃C(CH₂PPh₂)₃, is attributed to the higher effective nuclear charge on the metal centers caused by the presence of the six CF₃ substituents on the terdentate phosphine. A similar effect may be responsible for the easier hydrolysis of the CF₃PPP-containing, cationic rhodium(III) complexes relative to the corresponding compounds of the parent ligand.     

Kinetics and mechanisms of ligand substitution reactions of molybdenum SO2 complexes. Synthesis and X-ray structure of trans-Mo(CO)2 (dmpe) (PPh3) (SO2)

Kinetic results are reported for intramolecular PPh₃ substitution reactions of Mo(CO)₂(η¹-L)(PPh₃)₂(SO₂) to form Mo(CO)₂(η²-L)(PPh₃)(SO₂) (L = DMPE = (Me)₂PC₂H₄P(Me)₂ and dppe=Ph₂PC₂H₄PPh₂) in THF solvent, and for intermolecular SO₂ substitutions in Mo(CO)₃(η²-L)(η²-SO₂) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH₂Cl₂ solvent. Activation parameters for intramolecular PPh₃ substitution reactions: ΔH^≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; ΔS^≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO₂ in MO(CO)₃(η²-L)(η²-SO₂) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO₂ to accept a pair of electrons from the metal, with its bonding transformations of η²-SO₂ to η¹-pyramidal SO₂, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO)₂(dmpe)(PPh₃)(SO₂) was determined crystallographically: P2₁/c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) ų, Z=4, R(F)=3.49%.     

Water soluble platinum(II) and palladium(II) complexes of alkyl sulfonated phosphines

The reactions of the alkylsulfonated phosphines LM=Ph₂P(CH₂)_nSO₃Na/K (n=2, 3, 4) with K₂PtCl₄ and K₂PdCl₄ have been studied in homogeneous aqueous solution as a function of pH. In homogeneous acidic solution the protonated phosphines react to give cis- and trans-PtCl₂(LH)₂. The biphasic reaction between 1,5-cyclooctadiene platinum(II) chloride in dichloromethane and acidified aqueous LNa/K gives a higher proportion of the cis isomer. In neutral solution the initial reaction to give [PtCl(LNa/K)₃]⁺Cl⁻ is followed by slow formation of cis-PtCl₂(LNa/K)₂. K₂PdCl₄ reacts more rapidly to give PdCl₂(LNa/K)₂. In homogeneous alkaline solution rapid oxidation of the phosphine occurs with only small amounts of platinum complex being observable. The biphasic reaction yields phosphine oxide in the aqueous layer and a small amount of the chelate complexes PtL₂ in the organic. Representative complexes have been isolated and characterised and the mechanisms for the reactions discussed. The electrospray mass spectra of solutions of the isolated complexes have been recorded in both positive and negative ionisation modes. The positive ionisation spectra are complicated, but platinum and palladium containing ions derived from loss of chloride, H⁺ and HCl are observed in the negative ionisation spectra.     

C60-fullerenides of ytterbium and lutetium

Cp^#₂Yb (Cp^#=C₅H₄(CH₂)₂NMe₂) has been obtained by reaction of YbI₂(THF)₂ with 2 equiv. of C₅H₄(CH₂CH₂NMe₂)K in THF. The X-ray structure analysis shows a bent structure with intramolecular coordination of both nitrogen atoms to ytterbium. The reaction of C₆₀-fullerene with Cp^#₂Yb leads to the formation of the fullerenide derivative [Cp^#₂Yb]₂C₆₀, which shows an ESR signal in the solid state and in THF solution at room temperature (solid: ΔH = 50 G, G = 1.9992; solution: ΔH = 10 G, G = 2.0001) and a magnetic moment of 3.6 BM. The lutetium fullerenides CpLu(C₆₀)(DME) (3) and Cp^*Lu(C₆₀)(DME)(C₆H₅CH₃) (4), (Cp = η⁵−C₅H₅, Cp^* = η⁵−C₅Me₅), were obtained by reaction of C₆₀ with CpLu(C₁₀H₈) (DME) and Cp^*Lu(C₁₀H₈) (DME) in toluene. Both complexes are paramagnetic (μ_eff = 1.4 and 0.9 BM) and exhibit temperature-dependent ESR signals (293 K: g = 1.992 and 2.0002 respectively).     

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.     

Hydroformylation of alkenes and alkynes using a heterobinuclear Rh---W catalyst

Hydroformylation reactions of a series of alkenes and alkynes have been carried out using the heteronuclear Rh---W catalyst, (CO)₄ hH(CO)(PPh₃) (1). The results of these reactions have been compared with corresponding reactions using [Rh(OAc)₂]₂ as catalyst. Catalysis of a reaction of styrene using 1 gave a very high yield of the branched chain aldehyde containing only a trace of the straight chain isomer. Reactions of the phosphinoalkene, Ph₂P(CH₂)₃CH=CH₂ (7) and the corresponding alkyne, Ph₂P(CH₂)₃CCH (11) gave similar products using either catalyst system with the alkryne reaction being significantly slower. Reaction of the alkenyl dithiane, H---CH₂CH=CH₂ (2), using the Rh---W catalyst (1) gave a higher ratio of linear to branched aldehydes (47 linear:53 branched) than the corresponding reaction using [Rh(OAc)₂]₂ (25 linear:75 branched). Reactions of vinyl acetate using 1 as catalyst gave a significant amount of linear aldehyde in contrast to reactions using [Rh(OAc)₂]₂ but reactions of allyl acetate gave similar products for both catalyst systems.     

Mono-η complexes of chromium(II) and chromium(0). Electron demanding substituents, structural and spectroscopic data comparisons

Using thermal and photochemical methods a series of new chromium complexes has been prepared: (ν⁶-p-C₆H₄F₂)Cr(CO)₃; (ν⁶-C₆H₅CF₃)Cr(CO)₃; [m-C₆H₄(CF₃)₂]Cr(CO)₃; (ν⁶-C₆H₅F)Cr(CO)₂H(SiCl₃); (ν⁶-C₆H₅F)Cr(CO)₂(SiCl₃)₂; (p-C₆H₄F₂)Cr(CO)₂-H(SiCl₃); (C₆H₅CF₃)Cr(CO)₂H(SiCl₃(p-C₆H₄F₂)Cr(CO)₂(SiCl₃)₂; C₆H₅CF₃)Cr(CO)₂(SiCl₃)₂; [m-C₆H₄(CF₃)₂]Cr(CO)₂-H(SiCl₃); [m-C₆H₄(CF₃)₂]Cr(CO)₂(SiCl₃)₂. Two compounds were structurally characterized by X-ray diffraction. These data combined with IR and ¹H NMR have allowed assessment of some of the electronic and steric effects. The Cr-arene bond is considerably longer in the Cr(II) derivatives than in the Cr(0) species. Also the Cr center, as might be expected, is less electron rich in the Cr(II) dicarbonyl disilyl derivatives. The ν⁶-p-C₆H₄F₂ ligands are slightly folded so that the C---F carbons are moved further away from the Cr center. Comparison of structural and electronic effects is made with a series of similar chromium compounds reported in the literature. These new (arene)Cr(II) derivatives possess more labile ν⁶-arene ligands, which promise a rich chemistry at the chromium center.     

Dinuclear silver(I) complexes of 24-membered bibracchial tetraimine Schiff base macrocycles derived from 2,5-diformylthiophene

The cyclocondensation of 2,5-diformylthiophene and the amines N,N-bis-(2-aminoethyl)-2-phenylethylamine, N,N-bis-(2aminoethyl)-t-butyl-amine and N,N-bis-(2-aminoethyl)-t-butyl-amine in the presence of silver(I) salts yields homodinuclear bibracchial tetraimine Schiff base macrocyclic complexes. The structures of two such complexes are also reported. The complex Ag₂L⁴(NO₃)(PF₆) (2) crystallises in the triclinic space group , No. 2) and has unit-cell dimensions a = 12.834(6), B = 13.183(6), C = 14.588(7) Å, = 64.86(4), β = 79.77(4), γ = 69.44(3)° with Z = 2; there is a monodentate and singly bridging nitrate anion present and the Ag---Ag separation is 4.161 Å. The complex Ag₂L⁴(CH₃CN)₂(BF₄)₂·CH₃CN (9) crystallises in the triclinic space group , No. 2) and has unit-cell dimensions a = 9.297(4), B = 12.985(3), C = 21.770(5) Å, = 91.570(10), β = 92.33(3), γ = 97.92(3) ° with Z = 2; there is a strongly bonded acetonitrile molecule coordinated to each silver atom and the Ag---Ag separation is 4.920 Å.     

Ruthenium complexes containing tertiary phosphines and imidazole or 2,2′-bipyridine ligands

Complexes RuCl₃(PPh₃)L₂ (L = MeIm (1a, Im (1b)) and [RuCl₂(PPh₃)₂(bipy)]Cl·4H₂O (2) have been synthesized via the ruthenium(III) precursor RuCl₃(PPh₃)₂ (DMA), and characterized, including an X-ray structural analysis for 1a (MeIm = N-methylimidazole, Im = imidazole, bipy = 2,2′-bipyridyl, and DMA = N, N′-dimethylacetamide). Crystals of 1a are monoclinic, space group P2₁/n, A = 10.5491(5), B = 20.4934(9), C = 12.8285(4) Å, β = 90.166(4)°, Z = 4. The structure, which reveals a mer configuration for the chlorides, and cis-methylimidazoles, was solved by conventional heavy atom methods and was refined by full-matrix least-square procedures to R = 0.041 and R_w = 0.042 for 3328 reflections with I 3σ(I). From the RuCl₂(PPh₃)₃ precursor, the ruthenium(II) complexes RuCl₂(PPh₃)₂L₂ and [RuCl(PPh₃)L₄]Cl have been made (L = Im or MeIm), while [RuCl(dppb)Im₃]Cl has been made from [RuCl₂(dppb)]₂(μ-dppb) (dppb = Ph₂P(CH₂)₄PPh₂).     

Synthesis and structural characterization of two cis-dioxorhenium(V) ReO2[SN][P] mixed-ligand complexes

Two novel five-coordinate cis-dioxorhenium(V) complexes of the general formula ReO₂[R₂NCH₂CH₂S][PPh₃] (R₂N=Et₂N, complex 1 and R₂N=(o-CH₃O---C₆H₄N(CH₂CH₂)₂N, complex 2) have been synthesized by reacting ReOCl₃(PPh₃)₂ with the respective bidentate ligands R₂NCH₂CH₂SH. The complexes have been characterized by elemental analysis, IR, NMR spectroscopies and X-ray crystallography. X-ray crystallographic studies showed that the coordination geometry around rhenium is distorted trigonal bipyramidal. The basal plane is defined by the two doubly bonded oxygen atoms and the sulfur of the bidentate ligand, while the nitrogen of the ligand and the phosphorus occupy the apical positions.