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.     

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.     

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.     

The dicarbonylation of diiodomethane to malonate esters catalysed by triethylphosphine complexes of rhodium

Rhodium complexes, in the presence or absence of PEt₃, catalyse the carbonylation of CH₂I₂ to dialkylmalonates in the presence of alcohols (ROH, R=Me, Et, Pr¹, Bu) with side products from reactions in EtOH being CH₂(OEt)₂, EtI and traces of EtCO₂Et and EtOAc. The active species when using PEt₃ is shown to be [RhI(CO)(PEt₃)₂], formed via [Rh(OAc)(CO)(PEt₃)₂] from [Rh₂(OAc)₄ · 2MeOH] and PEt₃. Mechanistic studies show that the first step of the catalytic cycle is oxidative addition of CH₂I₂ to give [Rh(CH₂I)I₂(CO)(PEt₃)₂], but that insertion of CO into the Rh---CH₂I bond gives an iodoacyl complex which is unstable. The analogous [Rh(COCH₂X)X₂(CO)(PEt₃)₂], (X=Cl or Br) have been synthesised by oxidative addition of XCH₂COX to [RhX(CO)(PEt₃)₂] and fully characterised (by X-ray crystallography, for X=Cl). [Rh(COCH₂Br)Br₂(CO)(PEt₃)₂] has also been formed from reaction of [Rh(COCH₂Cl)Cl₂(CO)(PEt₃)₂] with excess NaBr. However, the analogous reaction with NaI does not give the iodoethanoyl complex, but rather [RhI₃(CO)(PEt₃)₂] and its decomposition products. It is proposed that [Rh(COCH₂I)I₂(CO)(PEt₃)₂] is unstable towards loss of I⁻ to form the ketene complex, [RhI₂(CH₂=C=O)(CO)(PEt₃)₂]I, which is transformed into [Rh(COCH₂CO₂Et)I₂(CO)(PEt₃)] by nucleophilic attack of ethanol at the central C atom, followed by CO insertion into the Rh---C bond. An analogue, [Rh(COCH₂CO₂Et)Cl₂(CO)(PEt₃)₂], has been isolated by oxidative addition of EtO₂CCH₂COCl across [RhCl(CO)(PEt₃)₂], and characterised both spectroscopically and crystallographically. In refluxing ethanol, [Rh(COCH₂CO₂Et)Cl₂(CO)(PEt₃)₂] produces diethylmalonate and [RhCl(CO)(PEt₃)₂], thus completing the catalytic cycle. Possible pathways of deactivation of the catalyst to give [RhI₃(CO)(PEt₃)₂] are discussed. One involves the reaction of ketene with ethanol to give EtOAc, whilst the others involve protonation of the Rh---Z bond in [RhZI₂(CO)(PEt₃)₂] (where Z =CH₂I, CH₂CO₂Et or H) by HI. The isolation of CH₂DCO₂Et, when carrying out the reaction in EtOD, is consistent with all of these deactivation pathways except protonation of [RhHI₂(CO)(PEt₃)₂].     

Nitrogen, sulfur and oxygen donor adducts with copper(II) complexes of antitumor 2-formylpyridinethiosemicarbazone analogs: Physicochemical and cytotoxic studies

The preparation of N-, S- and O-donor ligand adducts with CuX⁺(HX=6-methyl-2-formylpyridinethiosemicarbazone (6HL); 2-formylpyridine-2^′-methylthiosemicarbazone (2′L); 2-formylpyridine-4′-methylthiosemicarbazone (4′HL)) is described. The N-donors, 2,2′-bipyridyl (bipy), 4-dimethylaminopyridine (dmap) give the complexes [Cu(6L)(bipy)]PF₆, [Cu(6L)(bipy)]Cl·5H₂O, [Cu(4′L)(bipy)]PF₆, [Cu(6L)(dmap)₂]PF₆·2.5 H₂O and [Cu(4′L)(dmap)₂]PF₆·H₂O which have been characterized by physical and spectroscopic techniques. Pentafluorothiophenolate (pftp) gives S-donor complexes [CuX(pftp)] (X=6L and 4′L) and thiolato co-ordination is proposed on the basis of spectroscopic evidence. Paratritylphenolate (ptp) and HPO²⁻₄ give O-donor complexes [Cu(6L)(ptp)], [Cu(4′L)(ptp)], [{Cu(6L)}₂HPO₄]·4H₂O, and [{Cu(4^′L)}₂HPO₄]·5H₂O which have been characterized by physical and spectroscopic techniques, as have the precursor complexes [Cu(6L)(CH₃COO)]·H₂O, [Cu(4′L)(CH₃COO)], Cu(6HL)(CF₃COO)](CF₃COO)·0.5H₂O, [Cu(4′HL)(CF₃COO)](CF₃COO), [Cu(2′L)Cl₂] and [Cu(2′L)(NO₃)₂]. Protonation constants for the ligands and some of their complexes have been determined. 2-Formylpyridinethiosemicarbazone (HL) complexes of silver, gold, zinc, mercury, cadmium and lead are also discussed. Cytotoxicity against the human tumor cell line HCT-8 and antiviral data for selected compounds are presented.     

Triphenylbismuth seven-coordinate complexes of molybdenum(II) and tungsten(II)

The seven-coordinate complexes [MI₂(CO)₃(NCMe)₂] (M = Mo and W) react with one equivalent of BiPh₃ in CH₂Cl₂ at room temperature to give the monoacetonitrile complexes [MI₂(CO)₃(NCMe)(BiPh₃)]. The molybdenum complex [MoI₂(CO)₃(NCMe)(BiPh₃)] after stirring in CH₂Cl₂ at room temperature for 5 h affords the iodide-bridged dimer [Mo(μ-I)I(CO)₃(BiPh₃)]₂, whereas the tungsten complex [WI₂(CO)₃(NCMe)(BiPh₃)] does not appear to dimerise even after stirring for 48 h in CH₂Cl₂ at room temperature. Reaction of [MI₂(CO)₃(NCMe)₂] with two equivalents of BiPh₃ gives the bistriphenylbismuth compounds [MI₂(CO)₃(BiPh₃)₂] in good yield. The new mixed ligand complexes [MI₂(CO)₃L(BiPh₃)] were prepared either by reaction of [MI₂(CO)₃(NCMe)(BiPh₃)]in situ with one equivalent of L(L = P(OPh)₃), or an in situ reaction of [MI₂(CO)₃(NCMe)L] (L = PPh₃ and SbPh₃; and L = AsPh₃ and PPh₂Cy (for M = Mo only) with an equimolar quantity of BiPh₃. Reaction of [MoI₂(CO)₃(NCMe)(BiPh₃)] with one equivalent of 2,2′-bipyridyl (bipy) in CH₂Cl₂ at room temperature afforded the cationic complexes [MoI(CO)₃(bipy)(BiPh₃)]I in good yield. The complex [WI₂(CO)₃(NCMe)(BiPh₃)] (prepared in situ) reacts with two equivalents of NaS₂CNMe₂·2H₂O to eventually give the non-triphenylbismuth containing product [W(CO)₃(S₂CNMe₂)₂] in high yield.     

Titanium-carbon functionalities on an oxo surface defined by a calix [4] arene moiety and its redox chemistry

Lithiation of [p-Bu^t-calix[4]-(OMe)₂(OH)₂] (1), followed by reaction with TiCl₃(thf)₃ or TiCl₄(thf)₂, led to the corresponding titanium-calix[4]arene complexes [p-Bu^t-calix[4]-(OMe)₂(O)₂]TiCl] (2) and [p-Bu^t-calix[4]-(OMe)₂(O)₂]TiCl₂] (3), respectively. Reaction of 1 with TiCl₄(thf)₂ results in demethylation of the calix[4]arene and the obtention of [p-Bu^t-calix[4]-(OMe)₂(O)₃]TiCl] (4), whose hydrolysis led to [p-Bu^t-calix[4]-(OMe)(OH)₃] (6). The preparation of 6 can be carried out as a one-pot synthesis. Both 2 and 4 undergo alkylation reactions using conventional procedures, thus forming surprisingly stable organometallic species, namely [p-Bu^t-calix[4]-(OMe)₂(O)₂Ti(R)] (R = Me (7); CH₂Ph (8), p-MeC₆H₄ (9) and [p-Bu^t-calix[4]-(OMe)(O)₃Ti(R)] (R = Me (10); CH₂Ph (11); p-MeC₆H₄ (12)). Complexes 7 and 9 undergo a thermal oxidative conversion into 10 and 12, occurring with the demethylation of one of the methoxy groups. A solid state structural property of 9 and 12 has been revealed by X-ray analysis showing a self-assembly of the monomeric units into a columnar polymer, where the p-tolyl substituent at the metal functions as a guest group for an adjacent titanium-calixarene. Reductive alkylation of 3 with Mg(CH₂Ph)₂ gave 8 instead of forming the corresponding dialkyl derivative. Two synthetic routes have been devised for the synthesis of the Ti(III)-Ti(III) dimer [p-Bu^t-calix[4]-(OMe)(O)₃Ti]₂] (13): the reduction of 4 and the reaction of TiCl₃(thf)₃ with the lithiated form of 6. A very strong antiferromagnetic coupling is responsible for the peculiar magnetic behavior of 13. The proposed structures have been supported by the X-ray analyses of 4, 9, 12 and 13.     

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.     

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.     

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.     

Intramolecular and intermolecular C-H activation at a cationic Pt center

Syntheses and C-H bond activation reactions of the novel electrophilic Pt^II complexes [(tmeda)Pt(CH₃)(OEt₂)][BAr₁], [(tmeda)Pt(CH₃)(THF)][BAr_f], and [(tmeda)Pt(CH₃)(NC₅F₅)][BAr_f] are described {[BAr_f]⁻ = [(3,5-C₆H₃(CF₃)₂)₄B]⁻} (tmeda is N,N,N′,N′-tetramethylethylenediamine), [(tmeda)Pt(CH₃)(OEt₂)][BAr_f] and [(tmeda)Pt(CH₃)(THF)][BAr_f] are unstable at room temperature, yielding methane and the Fischer carbene Pt^II hydrides, [(tmeda)Pt(=C(CH₃)(OCH₂CH₃))(H)][BAr_f] and . The methane liberated from [(tmeda)Pt(CH₃)(OEt₂-d₁₀)][BAr_f] consists of an isotopomeric mixture, (CH₄, CH₃D, CH₂D₂ and CHD₃), indicating a multiple H/D exchange reaction following the C-D activation and prior to methane loss. [(tmeda)Pt(CH₃)(THF-d₈)][BAr] liberates CH₄ and CH₃D. Methane-¹³C, cyclohexane, toluene, and benzene react with [(tmeda)Pt(CH₃)(NC₅F₅)][BAr_f] to yield methane and new organoplatinum complexes. Deuterated alkanes and arenes react with [(tmeda)Pt(CH₃)(NC₅F₅] [BAr_f] to give a mixture of methane isotopomers. The relevance of these results to the oxidation of alkanes by aqueous platinum complexes is discussed.     

Slippage of η-allenyl/propargyl to an η structure and tautomerization of η-propargyl to η-allenyl in ligand addition and substitution reactions of platinum(II) complexes

Reactions of [(PPh₃)₂Pt(η³-CH₂CCPh)]OTf with each of PMe₃, CO and Br⁻ result in the addition of these species to the metal and a change in hapticity of the η³-CH₂CCPh to η¹-CH₂CCPh or η¹-C(Ph)=C=CH₂. Thus, PMe₃ affords [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺, CO gives both [trans-(PPh₃)₂Pt(CO)(η¹-CH₂CCPh)]⁺ and [trans-(PPh₃)₂Pt(CO)(η¹-C(Ph)=C=CH₂)]⁺, and LiBr yields cis-(PPh₃)₂PtBr(η¹-CH₂CCPh), which undergoes isomerization to trans-(PPh₃)₂PtBr(η¹-CH₂CCPh). Substitution reactions of cis- and trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) each lead to tautomerization of η¹-CH₂CCPh to η¹-C(Ph)=C=CH₂, with trans-(PPh₃)₂PtBr(η¹-CH₂CCPh) affording [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]⁺ at ambient temperature and the slower reacting cis isomer giving [trans-(PPh₃)(PMe₃)₂Pt(η¹-C(Ph)=C=CH₂)]⁺ at 54 °C . All new complexes were characterized by a combination of elemental analysis, FAB mas spectrometry and IR and NMR (¹H, ¹³C{¹H} and ³¹P{¹H}) spectroscopy. The structure of [(PMe₃)₃Pt(η¹-C(Ph)=C=CH₂)]BPh₄·0.5MeOH was determined by single-crystal X-ray diffraction analysis.     

Borane and monoiodoborane derivatives of some bis(diphenylphosphino)alkanes

A series of borane and monoiodoborane derivatives of bis(diphenylphosphino)alkanes. (C₆H₅)₂P--- (CH₂)_n---P(C₆H₅)₂ in which n has values of 2 through 4 has been synthesized. Only compounds with the formulae [(C₆H₅)₂P]₂(CH₂)_n · (BH₃)₂ and (C₆H₅)₂P]₂CH₂)_n · BH₂I were isolable, the latter being boronium iodides. The compounds were characterized by their melting points, elemental analyses, molar conductivities, infrared spectroscopy, and ¹H and ¹¹B nuclear magnetic resonance spectroscopy. The relationship between the length of the carbon chain and the ¹¹B NMR chemical shift is discussed.     

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.     

Lightinduced sulfur-dealkylation of phosphino-thioether nickel(0) complexes

The observation of homolytic S---CH₃ bond cleavage in (Ph₂P(o-C₆H₄)SCH₃)₂Ni⁰ under photochemical conditions has prompted further investigation of nickel(0) complexes and their stability. Tetradentate P₂S′₂ donor ligands (S′ = thioether type S donor) with aromatic rings incorporated into the P to S links, Ph₂P(o-C₆H₄)S(CH₂)₃S(o-C₆H₄)PPh₂ (arom-PSSP), or the S to S links, Ph₂P(CH₂)₂SCH₂(o-C₆H₄)CH₂S(CH₂)₂PPh₂ (PS-xy-SP), have been used to form four-coordinate, square planar nickel(II) complexes, [(arom-PSSP)Ni](BF₄)₂ (2) and [(PS-xy-SP)Ni](BF₄)₂ (3). The bidentate and tetradentate ligands, Ph₂P(o-C₆H₄)SCH₂CH₃ (arom-PSEt) and Ph₂P(CH₂)₂S(CH₂)₃S(CH₂)₂PPh₂ (PSSP), give similar complexes, [(arom-PSEt)₂Ni](BF₄)₂ (1) and [(PSSP)Ni](BF₄)₂ (4), respectively. Cyclic voltammograms of the Ni¹¹ complexes in CH₃CN show two reversible redox events assigned to and . The one-electron reduction product produced by stoichiometric amounts of Cp₂Co can be characterized by EPR. At 100 K rhombic signals show hyperfine coupling to two phosphorus atoms. Complete bulk chemical reduction of complexes 1, 2, 3 and 4 with Na/Hg amalgam provided the corresponding nickel(0) complexes 1^R, 2^R, 3^R and 4^R which were isolated as red solutions or solids characterized by magnetic resonance properties and reaction products. Photolysis of these nickel(0) complexes leads to S-dealkylation to produce alkyl radicals and dithiolate nickel(II) complexes. Complex 3 crystallized in the monoclinic space group P_2t/c with a=20.740(5), B=9.879(3), C=17.801(4) åA, ß=92.59(2)°, V=3644(2) ų and Z=4; complex 4: P2₁/c with A=13.815(4), B=13.815(4), C=15.457(5) åA, V=3365.4(14) ų and Z=4.     

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⁺.     

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.     

Kinetics of ligand substitution in bis(N-alkylsalicylaldiminato)nickel(II) complexes: A search for kinetically-effective aromatic ring stacking

The square-planar bis chelate complexes Ni(R-sal)₂ (= bis(N-alkyl)salicylaldiminato)nickel(II)) with R = (CH₂)₂Ph (I; Ph = phenyl), (CH₂)₃Ph (II), (CH₂)₄Ph (III) and (CH₂)₂(4-hydroxyphenyl) (IV) were prepared and characterized. ComplexesII and III meet the steric requirements for intramolecular aromatic ring stacking. Stopped-flow spectrophotometry was used to study the kinetics of ligand substitution in complexesI–IV by H₂salen (=N,N′-disalicylidene-ethylenediamine) in acetone. For the substitution of the two bidentate ligands in Ni(R-sal)₂ only one step is kinetically observed which follows a second-order rate law, rate =k[H₂salen] [Ni(R-sal)₂], with k = 43.4 (I), 64.0 (II), 87.0 (III) and 49.5 (IV) M⁻¹ s⁻¹ at 298 K. It is found, therefore, that the size of k does not change significantly upon lengthening of the alkane chain in Ni(Ph(CH₂)_nsal)₂ from n = 2 to 4 and that there is no kinetic evidence for intramolecular stacking interactions. The equilibrium constants and thermodynamic parameters for the formation of the bis adductsIII·(py)₂ and III·(MeOH)₂ in acetone are reported.     

Reactivity of cationic carbonyl/phosphine ruthenium(II) compounds

Cis(or trans)-[RuCl₂(CO)₂(PPh₃)₂] react with two and one equivalents of AgBF₄ to give the recently reported [Ru(CO)₂(PPh₃)₂][BF₄]₂·CH₂Cl₂ (1) and novel [RuCl(CO)₂(PPh₃)₂][BF₄] · 1/2 CH₂Cl₂ (2), respectively. Cis-[RuCl₂(CO)₂(PPh₃)₂] also reacts with two equivalents of AgBF₄ in the presence of CO to give [Ru(CO)₃(PPh₃)₂][BF₄]₂ (3). Reactions of 1 and 2 with NaOMe and CO at 1 atm produce the carbomethoxy species [Ru(COOMe)₂(CO)₂(PPh₃)₂] (4) and [RuCl(COOMe)(CO)₂(PPh₃)₂] (5), respectively. Complex 4 can also be formed from the reaction of 3 with NaOMe and CO. Alternatively, 4 is formed from cis-[RuCl₂(CO)₂(PPh₃)₂] with NaOMe and CO at elevated pressure (10 atm); if these reactants are refluxed under 1 atm of CO, [Ru(CO)₃(PPh₃)₂] is the product. The reaction of [RuCl(CO)₃(PPh₃)₂][AlCl₄] with NaOMe provides an alternative route to the preparation of 5, but the product is contaminated with [RuCl₂(CO)₂(PPh₃)₂]. Compounds 1. 2, 4 and 5 have been characterised by IR, ¹H NMR and analysis, whilst the formulation of 3 is proposed from spectroscopic data only. This account also examines the reactivity of [Ru(CO)₂(PPh₃)₂][BF₄]₂ · CH₂Cl₂ with NaBH₄, conc. HCl, KI and, finally, MeCOONa in the presence of CO. The products of these reactions, namely cis-[RuH₂(CO)₂(PPh₃)₂], cis-[RuCl₂(CO)₂(PPh₃)₂], cis-[RuI₂(CO)₂(PPh₃)₂] and [Ru(OOCMe)₂(CO)₂(PPh₃)₂], have been identified by comparison of their spectra with previous literature.     

Synthesis, immobilization and catalytic activity of some silylated cyclopentadienyl rhodium(I) complexes

The mixture of isomers of silylated cyclopentadiene derivative C₅H₅CH₂CH₂Si(OMe)₃ (1) has been used for the syntheses of the mononuclear Rh(I) complexes [η⁵-C₅H₄(CH₂)₂Si(OMe)₃]Rh(CO)₂ (3). [η⁵-C₅H₄(CH₂)₂Si(OMe)₃]Rh(COD) (4) and [η⁵-C₅H₄(CH₂)₂Si(OMe)₃]Rh(CO)(PPh₃) (5). Upon entrapment of 3–5 in silica sol-gel matrices, air stable, leach-proof and recyclable catalysts 6–8 resulted. Their catalytic activities in some hydrogenation processes were compared with those of the non-immobilized complexes 3–5, as well as with those of homogeneous and heterogenized non-silylated analogs, 9–14.