Synthesis,structure, and photochemistry of a rhenium(I) enolate complex

The rhenium(I) enolate complex fac-(CO)₃(P(CH₃)₃)₂Re(OC(CH₃)C₅H₄) (4 was prepared from the reaction of (η⁵-C₅H₄C(O)CH₃)Re(CO)₃ (3) with P(CH₃)₃. Compound 4 was characterized structurally in the solid state by X-ray crystallography and in solution by IR and ¹H, ¹³C, and ³¹P NMR spectroscopy. Photolysis of 4 at 337 nm in CH₂Cl₂ solution cleaves the ReO bond: smooth conversionto fac-(CO)₃(P(CH₃)₃)₂ReCl (5) is observed with a quantum yield of 0.04.     

Übergangsmetall-methylen-komplexe: LVI. Organoruthenium-komplexe mit offenkettigen und carbocyclischen alkyliden-brücken: Synthese,konstitution, isomerie,protonierung und thermolytischer abbau

The eighteen new μ-alkylidene ruthenium complexes 5a–r and 5t are very easily and cleanly obtained along the diazoalkane or the hydrazone routes that involve treatment of the dinuclear, metal-metal doubly bonded precursor compound [(η⁵-C₅H₅)Ru(μ-NO)]₂ (3) either with the diazoalkanes oxidizing agent (e.g., MnO₂), with the respective hydrazones. Similarly, sulfur dioxide adds cleanly to the RuRu double bond of 3, thus giving the complex (μ-SO₂)[(η⁵-C₅H₅)Ru(NO)]₂ (5s). Regardless of the nature of the carbene bridge ligands, the dimetallacyclopropanes exhibit, in contrast to their iron analogues, exclusively terminal nitrosyl ligands. cis/trans-Isomerism with predominating amounts of the trans-isomers is observed for the derivatives that display unsymmetrically substituted carbene bridges.Treatment of the μ-methylene- and μ-ethylidene complexes (μ-CH₂)[(η⁵-C₅H₅)Ru(NO)]₂ (5a) and (μ-CHCH₃)[(η⁵-C tetrafluoroboric acid or trifluoromethanesulfonic acid in diethyl ether yields, at ambient temperature, quantitatively the ionic complexes 6a,b and 7a,b, respectively, which were shown by ¹H NMR spectroscopy to contain metal-metal bridging hydrogen functionalities. The reaction of hydrogen bromide with 5a under the same conditions gives the neutral bromo(methyl) complex 6d. This latter compound results from the isolable ionic intermediate of composition [(μ-CH₂)(μ-H){(η⁵C₅H₅)Ru(NO)}₂]⁺Br^? (6c), which reaction stems from the nucleophilicity of the halide ion present in 6c.     

Mono and dinuclear iridium, rhodium and ruthenium complexes containing chelating carboxylato pyrazine ligands: Synthesis, molecular structure and electrochemistry

The mononuclear complexes [(η⁵-C₅Me₅)IrCl(L¹)] (1), [(η⁵-C₅Me₅)RhCl(L¹)] (2), [(η⁶-p-PrⁱC₆H₄Me)RuCl(L¹)] (3) and [(η⁶-C₆Me₆)RuCl(L¹)] (4) have been synthesised from pyrazine-2-carboxylic acid (HL¹) and the corresponding complexes [{(η⁵-C₅Me₅)IrCl₂}₂], [{(η⁵-C₅Me₅)RhCl₂}₂], [{(η⁶-p-PrⁱC₆H₄Me)RuCl₂}₂], and [{(η⁶-C₆Me₆)RuCl₂}₂], respectively. The related dinuclear complexes [{(η⁵-C₅Me₅)IrCl}₂(μ-L²)] (5), [{(η⁵-C₅Me₅)RhCl}₂(μ-L²)] (6), [{(η⁶-p-PrⁱC₆H₄Me)RuCl}₂(μ-L²)] (7) and [{(η⁶-C₆Me₆)RuCl}₂(μ-L²)] (8) have been obtained in a similar manner from pyrazine-2,5-dicarboxylic acid (H₂L²). Compounds isomeric to the latter series, [{(η⁵-C₅Me₅)IrCl}₂(μ-L³)] (9), [{(η⁵-C₅Me₅)RhCl}₂(μ-L³)] (10), [{(p-PrⁱC₆H₄Me)RuCl}₂(μ-L³)] (11) and [{(η⁶-C₆Me₆)RuCl}₂(μ-L³)] (12), have been prepared by using pyrazine-2,3-dicarboxylic acid (H₂L³) instead of H₂L². The molecular structures of 2 and 3, determined by X-ray diffraction analysis, show the pyrazine-2-carboxylato moiety to act as an N,O-chelating ligand, while the structure analyses of 5-7, confirm that the pyrazine-2,5-dicarboxylato unit bridges two metal centres. The electrochemical behaviour of selected representatives has been studied by voltammetric techniques.     

Structures, preparation and catalytic activity of ruthenium cyclopentadienyl complexes based on pyridyl-phosphine ligand

Ruthenium complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) and [(η⁵-C₅H₅)Ru(κ²-P-N-PPh₂Py)(PPh₃)]⁺ (1a) containing diphenyl-2-pyridylphosphine (PPh₂Py) are reported. Coordinated PPh₂Py in the complex [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) exhibits monodentate behavior. In presence of NH₄PF₆ in methanol at room temperature it afforded chelated complex [(η⁵-C₅H₅)Ru(κ²-P,N-PPh₂Py)(PPh₃)]⁺ (1a). Further, 1 reacted with various species viz., CH₃CN, NaCN, NH₄SCN and NaN₃ to afford cationic and neutral complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L]⁺ and [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L] [L = CH₃CN (1b); CN⁻ (1c); N₃⁻ (1d) and SCN⁻ (1e)] and it’s reaction with N,N-donor chelating ligands dimethylglyoxime (H₂dmg) and 1,2-phenylenediamine (pda) gave cationic complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(κ²-N-N)]PF₆ [κ²-N-N = dmg (1f) and pda (1g)]. The complexes 1-1g have been characterized by physicochemical techniques and crystal structures of 1, 1a, 1c, 1e and 1f have been determined by single crystal X-ray analyses. Catalytic potential of the complex 1 has been evaluated in water under aerobic conditions. It was observed that the complex 1 selectively catalyzes reduction of aldehyde into alcohol.     

Mono and dinuclear rhodium, iridium and ruthenium complexes containing chelating 2,2′-bipyrimidine ligands: Synthesis, molecular structure, electrochemistry and catalytic properties

The mononuclear cations [(η⁵-C₅Me₅)RhCl(bpym)]⁺ (1), [(η⁵-C₅Me₅)IrCl(bpym)]⁺ (2), [(η⁶-p-PrⁱC₆H₄Me)RuCl(bpym)]⁺ (3) and [(η⁶-C₆Me₆)RuCl(bpym)]⁺ (4) as well as the dinuclear dications [{(η⁵-C₅Me₅)RhCl}₂(bpym)]²⁺ (5), [{(η⁵-C₅Me₅)IrCl}₂(bpym)]²⁺ (6), [{(η⁶-p-PrⁱC₆H₄Me)RuCl}₂(bpym)]²⁺ (7) and [{(η⁶-C₆Me₆)RuCl}₂(bpym)]²⁺ (8) have been synthesised from 2,2′-bipyrimidine (bpym) and the corresponding chloro complexes [(η⁵-C₅Me₅)RhCl₂]₂, [(η⁵-C₅Me₅)IrCl₂]₂, [(η⁶-PrⁱC₆H₄Me)RuCl₂]₂ and [(η⁶-C₆Me₆)RuCl₂]₂, respectively. The X-ray crystal structure analyses of [3][PF₆], [5][PF₆]₂, [6][CF₃SO₃]₂ and [7][PF₆]₂ reveal a typical piano-stool geometry around the metal centres; in the dinuclear complexes the chloro ligands attached to the two metal centres are found to be, with respect to each other, cis oriented for 5 and 6 but trans for 7. The electrochemical behaviour of 1-8 has been studied by voltammetric methods. In addition, the catalytic potential of 1-8 for transfer hydrogenation reactions in aqueous solution has been evaluated: All complexes catalyse the reaction of acetophenone with formic acid to give phenylethanol and carbon dioxide. For both the mononuclear and dinuclear series the best results were obtained (50 °C, pH 4) with rhodium complexes, giving turnover frequencies of 10.5 h⁻¹ for 1 and 19 h⁻¹ for 5.     

Structural control in palladium(II)-catalyzed enantioselective allylic alkylation by new chiral phosphine-phosphite and pyridine-phosphite ligands

The ligands 6-[(diphenylphosphanyl)methoxy]-4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cycloheptene, 1, (S)-4-[(diphenylphosphanyl)methoxy]-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4a′]dinaphthalene, (S)-2, and (S)-4-[(diphenylphosphanyl)methoxy]-2,6-bis-trimethylsilanyl-3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalene, (S)-3, (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxymethyl)pyridine, (S)-4, and (S)-2-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yloxy)pyridine, (S)-5, have been easily prepared.The cationic complexes [Pd(η³-C₃H₅)(L-L′)]CF₃SO₃ (L–L′=1–(S)-5) and [Pd(η³-PhCHCHCHPh)(L–L′)]CF₃SO₃ (L–L′=(S)-2–(S)-4) were synthesized by conventional methods starting from the complexes [Pd(η³-C₃H₅)Cl]₂ and [Pd(η³-PhCHCHCHPh)Cl]₂, respectively. The behavior in solution of all the π-allyl- and π-phenylallyl-(L–L′)palladium derivatives 6–14 was studied by ¹H, ³¹P{¹H}, ¹³C{¹H} NMR and 2D-NOESY spectroscopy. As concerns the ligands (S)-4 and (S)-5, a satisfactory analysis of the structures in solution was possible only for palladium–allyl complexes [Pd(η³-C₃H₅)((S)-4)]CF₃SO₃, 11, and [Pd(η³-C₃H₅)((S)-5)]CF₃SO₃, 12, since the corresponding species [Pd(η³-PhCHCHCHPh)((S)-4)]CF₃SO₃, 13, and [Pd(η³-PhCHCHCHPh)((S)-5)]CF₃SO₃, 14, revealed low stability in solution for a long time. The new ligands (S)-2–(S)-5 were tested in the palladium-catalyzed enantioselective substitution of (1,3-diphenyl-1,2-propenyl)acetate by dimethylmalonate. The precatalyst [Pd(η³-C₃H₅)((S)-2)]CF₃SO₃ afforded the allyl substituted product in good yield (95%) and acceptable enantioselectivities (71% e.e. in the S form). A similar result was achieved with the precatalyst [Pd(η³-C₃H₅)((S)-3)]CF₃SO₃. The nucleophilic attack of the malonate occurred preferentially at allylic carbon far from the binaphthalene moiety, namely trans to the phosphite group. When the complexes containing ligands (S)-4 and (S)-5 were used as precatalysts, the product was obtained as a racemic mixture in high yield. The number of the configurational isomers of the Pd-allyl intermediates present in solution in the allylic alkylation and the relative concentrations are considered a determining factor for the enantioselectivity of the process.     

Synthesis of (+)-1,3,5,7 -tetrakis[2-(1S,3S,5R,6S,8R,10R)-D3-trishomocubanylbuta-1,3-diynyl]adamantane : The first optically active organic molecule with t symmetry and of known absolute configuration

(-)-(1S,3S,5R,6S,8R,10R)-Trishomocubanethanoic acid (5) of known absolute configuration and absolute rotation was converted into (+)-(1S,3S,5S,6S,8R,10R)-2-bromoethynyl-D₃-trishomocubane (27) of C₃ symmetry. 1,3,5,7-Tetraethynyladamantane (22), with Td symmetry, was prepared from 1,3,5,7-tetrakis(hydroxymethyl)adamantane(13). Coupling of the C₃-component 27 with the Td component 22 was successfully accomplished by Chodkiewicz and Cadiot's procedure providing (+)-1,3,5,7-tetrakis[2-(1S,3S,5R,6S,8R,10R)-D₃-trishomocubanylbuta-1,3-diynyl]adamantane(4) whose highest attainable static and time-averaged dynamic symmetry are T and (C₃)⁴ XXX T,respectively.     

Six novel complexes based on 5-Acetoxy-1-(6-chloro-pyridin-2-yl)-1H-pyrazole-3-carboxylic acid methyl ester derivatives: Syntheses,crystal structures,and anti-cancer activity

A novel 5-Acetoxy-1-(6-chloropyridin-2-yl)-1H-pyrazole-3-carboxylic acid methyl ester derivatives Htcdodtta (1), and it’s five complexes, [Cu₂(L¹)₂]·(CH₃CN) (2), [Cu₂(L²)_1.63(L³)_0.37]·(CH₃OH)_0.5 (3), [Cu₂(L³)(L⁴)]·(C₂H₅OH)_0.5·(CH₃OH)_0.5 (4), [Cu₂(L⁴)(L⁵)]·(H₂O) (5) and [Cu₂(L¹)_1.18(L²)_0.82] (6) have been synthesized. The Htcdodtta, HL¹-HL⁵ were formed in-situ reaction. HL¹-HL⁵ are homologues which possess two chiral carbons. Compounds 1–6 were characterized using single-crystal X-ray diffraction, IR, and elemental analysis. Compounds 2–6 are dinuclear copper complexes. The in vitro cytotoxicities of compounds 1–4 against a variety of cell lines were evaluated by MTT assays. Hela cancer cell apoptosis assay of 1 and 2 were examined by flow cytometry. The cell apoptosis in NP69, A549, Capan-2, Hela, HepG2, and HUVECs cell lines induced by compound 2 was further affirmed by cellular morphology observations.     

Structure of N,C,N-chelated organotin(IV) fluorides

The set of starting tri-, di- and monoorganotin(IV) halides containing N,C,N-chelating ligand (L^NCN = {1,3-[(CH₃)₂NCH₂]₂C₆H₃}⁻) has been prepared (1-5) and two compounds structurally characterized ([L^NCNPh₂Sn]⁺I₃⁻ (1c), L^NCNSnBr₃ (5)) in the solid state. These compounds were reacted with KF with 18-crown-6, NH₄F or L^CNnBu₂SnF to give derivatives containing fluorine atom(s). Triorganotin(IV) fluorides L^NCNMe₂SnF (2a) and L^NCNnBu₂SnF (3a) revealed monomeric structural arrangement with covalent Sn-F bond both in the coordinating and non-coordinating solvents, except the behaviour of 3a that was ionized in the methanol solution at low temperature. The products of fluorination of L^NCNSnPhCl₂ (4) and 5 were described by NMR in solution as the ionic hypervalent fluorostannates or the oligomeric species reacting with chloroform, methanol or moisture to zwitterionic monomeric stannate L^NCN(H)⁺SnF₄⁻ (5c), which was confirmed by XRD analysis in the solid state.     

Zur umsetzung von trimethylsilyl-methylen-dimethylsulfuran mit carbonylverbindungen : Reaktionen mit organosiliziumverbindungen, 1. mitt.

The first step in the reaction of trimethylsilylmethylene-dimethylsulfurane 1 (prepared from (CH₃)₃SiCH₂S?(CH₃)₂ī with 1 equivalent (CH₃)₃COK) with carbonyl compounds (R¹)(R²)CHCOCH₂R³2 leads Peterson-like way to the non-isolable vinylsulfoniumdimethylsilanolate-intermediate B or its recombined product A. Depending on the reaction conditions and the nature of the substituents R¹, R² and R³ there exist five different pathways to the end products 3–7. Frequently one can find an elimination of trimethylsilanole followed by a 2,3-sigmatropic rearrangement of an allyl-substituted methylene - sulfurane - intermediate to the 2,3,3 - trialkyl - 5 -thiahex -1 - enes 3 [CH₃SCH₂C(R¹)(R²)C(CH₂R³)=CH₂]. Sometimes this formation of 3 is suppressed by means of two equivalents of (CH₃)₃COK. In this case demethylation of the assumed precursor B arises yielding the E,Z-vinylsulfides 4 [CH₃SCH=C(CH₂R³)(CHR¹R²)], whereas the formation of the methylthiomethyl-dialkylcar-binoles 5 [CH₃SCH₂C(OH)(CH₂R³)(CHR¹R²)] can be explained by the demethylation of the precursor A. Treatment with five equivalents of (CH₃)₃COK yields in one case the 2,2,5,7 - tetramethyl - 5 - hydroxy - 3 - oxaoctane (7a) as

a consequence of a extrusion of dimethylsulfide. Frequently also epoxides of type 6 [CH₂-C(CH₂R³)(CHR¹R²)] can be isolated. Their formation is compared with the well-known preparation of epoxides by the dimethylsulfonium-methylide on the one and dimethylsulfoxoniummethylide on the other side.     

Mono and dinuclear complexes of half-sandwich platinum group metals (Ru, Rh and Ir) bearing a flexible pyridyl-thiazole multidentate donor ligand

The mononuclear cationic complexes [(η⁶-C₆H₆)RuCl(L)]⁺ (1), [(η⁶-p-ⁱPrC₆H₄Me)RuCl(L)]⁺ (2), [(η⁵-C₅H₅)Ru(PPh₃)(L)]⁺ (3), [(η⁵-C₅Me₅)Ru(PPh₃)(L)]⁺ (4), [(η⁵-C₅Me₅)RhCl(L)]⁺ (5), [(η⁵-C₅Me₅)IrCl(L)]⁺ (6) as well as the dinuclear dicationic complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (7), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (8), [{(η⁵-C₅H₅)Ru(PPh₃)}2(L)]²⁺ (9), [{(η⁵-C₅Me₅)Ru(PPh₃)}₂(L)]²⁺ (10), [{(η⁵-C₅Me₅)RhCl}₂(L)]²⁺ (11) and [{(η⁵-C₅Me₅)IrCl}₂(L)]²⁺ (12) have been synthesized from 4,4′-bis(2-pyridyl-4-thiazole) (L) and the corresponding complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂, [(η⁶-p-ⁱPrC₆H₄Me)Ru(μ-Cl)Cl]₂, [(η⁵-C₅H₅)Ru(PPh₃)₂Cl)], [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl], [(η⁵-C₅Me₅)Rh(μ-Cl)Cl]₂ and [(η⁵-C₅Me₅)Ir(μ-Cl)Cl]₂, respectively. All complexes were isolated as hexafluorophosphate salts and characterized by IR, NMR, mass spectrometry and UV-vis spectroscopy. The X-ray crystal structure analyses of [3]PF₆, [5]PF₆, [8](PF₆)₂ and [12](PF₆)₂ reveal a typical piano-stool geometry around the metal centers with a five-membered metallo-cycle in which 4,4′-bis(2-pyridyl-4-thiazole) acts as a N,N′-chelating ligand.     

C2-Bridged sandwich and half-sandwich entities with Ti(IV) and Cr(0) centers

The intense purple colored bi- and trimetallic complexes {Ti}(CH₂SiMe₃)[CC(η⁶-C₆H₅)Cr(CO)₃] (3) ({Ti}=(η⁵-C₅H₅)₂Ti) and [Ti][CC(η⁶-C₆H₅)Cr(CO)₃]₂ (5) {[Ti]=(η⁵-C₅H₄SiMe₃)₂Ti}, in which next to a Ti(IV) center a Cr(0) atom is present, are accessible by the reaction of Li[CC(η⁶-C₆H₅)Cr(CO)₃] (2) with {Ti}(CH₂SiMe₃)Cl (1) or [Ti]Cl₂ (4) in a 1:1 or 2:1 molar ratio. The chemical and electrochemical properties of 3, 5, {Ti}(CH₂SiMe₃)(CCFc) [Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄)] and [Ti][(CC)_nMc][(CC)_mM′c] [n, m=1, 2; n=m; n≠m; Mc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); M′c=(η⁵-C₅H₅)Ru(η⁵-C₅H₄); Mc=M′c; Mc≠M′c] will be comparatively discussed.     

Synthesis, characterization, and reactivity of new types of constrained geometry group 4 metal complexes derived from picolyl-substituted dicarbollide ligand systems

The syntheses of group 4 metal complexes containing the picolyldicarbollyl ligand Dcab^PyH [nido-7-HNC₅H₄(CH₂)-8-R-7,8-C₂B₉H₁₀] (2) are reported. New types of constrained geometry group 4 metal complexes (Dcab^Py)MCl₂, [{(η⁵-RC₂B₉H₉)(CH₂)(η¹-NC₅H₄)}MCl₂] (M = Ti, 3; Zr, 4; R = H, a; Me, b), were prepared by the reaction of 2 with M(NMe₂)₂Cl₂ (M = Ti, Zr). The reaction of 2 with M(NMe₂)₄ in toluene afforded (Dcab^Py)M(NMe₂)₂, [{(η⁵-RC₂B₉H₉)(CH₂)(η¹-NC₅H₄)}M(NMe₂)₂] (M = Ti, 5; Zr, 6; R = H, a; Me, b), which readily reacted with Me₃SiCl to yield the corresponding chloride complexes (Dcab^Py)MCl₂ (M = Ti, 3; Zr, 4; R = H, a; Me, b). The structures of the diamido complexes (Dcab^Py)M(NMe₂)₂ (M = Ti, 5; Zr, 6) were established by X-ray diffraction studies of 5a, 5b, and 6a, which verified an η⁵:η¹-bonding mode derived from the dicarbollylamino ligand. Related constrained geometry catalyst CGC-type alkoxy titanium complexes, (Dcab^Py)Ti(OⁱPr)₂ (7), were synthesized by the reaction of 2 with Ti(OⁱPr)₄. Sterically less demanding phenols such as 2-Me-C₆H₄OH replaced the coordinated amido ligands on (Dcab^Py)Ti(NMe₂)₂ (5a) to yield aryloxy stabilized CGC complexes (Dcab^Py)Ti(OPh^Me)₂(Ph^Me  =  2- Me-C₆H₄, 8). NMR spectral data suggested that an intramolecular Ti-N coordination was intact in solution, resulting in a stable piano-stool structure with two aryloxy ligands residing in two of the leg positions. The aryloxy coordinations were further confirmed by single crystal X-ray diffraction studies on complexes (Dcab^Py)Ti(OPh^Me)₂ (8).     

Organo-aluminum,zinc and magnesium derivatives of the imidotris(amido)phosphate Me3SiNP(NHtBu)3

Reactions of (^tBuHN)₃PNSiMe₃ (1) with the alkyl-metal reagents dimethylzinc, trimethylaluminum and di-n-butylmagnesium yield the monodeprotonated complexes [MeZn{(N^tBu)(NSiMe₃)P(NH^tBu)₂}] (2), [Me₂Al{(N^tBu)(NSiMe₃)P(NH^tBu)₂}] (3) and [Mg{(N^tBu)(NSiMe₃)P(NH^tBu)₂}₂] (4), respectively. Attempts to further deprotonate complex 2 with n-butyllithium or di-n-butylmagnesium result in nucleophilic displacement of the methylzinc fragment by lithium or magnesium. The two remaining amino protons of 3 are removed by reaction with di-n-butylmagnesium to give a heterobimetallic complex in which the coordination sphere of magnesium is completed by two molecules of THF (5 · 2THF) or one molecule of TMEDA (5 · TMEDA). Reaction of complex 3 with 1 equiv. of n-butyllithium followed by treatment of the product with di-n-butylmagnesium yields the complex {Me₂Al[(N^tBu)(NSiMe₃)P(N^tBu)₂]MgBu} Li · 4THF (6 · 4THF), the first example of a triply deprotonated complex of 1 containing three different metals. Reaction of complex 5 with iodine results in cleavage of an Al–Me group to give {MeIAl[(N^tBu)(NSiMe₃)P(N^tBu)₂Mg]} (7). Complexes 5 · 2THF, 5 · TMEDA, 6 · 4THF and 7 have been characterized in solution by multinuclear (¹H, ¹³C, ³¹P and ⁷Li) NMR spectroscopy, while the solid-state structures of 2, 4 and 5 · 2THF have been determined by X-ray crystallography.     

Dimethyl-, diphenyl- and cyclotetramethylene silylchloride derivatives of guanidine,their synthesis and structure. Formation of pentacoordinated silicon compounds and an unexpected diionic disila-diguanidinium dichloride

The reaction of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2a]pyrimidinyl potassium, [hpp]⁻K⁺ (1), with dimethyldichlorosilane, diphenyldichlorosilane or cyclotetramethylenedichlorosilane (1,1-dichloro silolane) in THF resulted in the formation of the in solid-state unexpected diionic dimer λ⁴Si-[Me₂SiCl(hpp)]₂ (2) (76%), as well as λ⁵Si-Ph₂SiCl(hpp) (3) (87%) and λ⁵Si-(CH₂)₄SiCl(hpp) (4) (28%). Compounds 3 and 4 are the first synthesised examples of four ring (–λ⁵Si–N–CN–) guanidine structures. ¹H and ¹³C NMR show the compounds to have a symmetric guanidine unit in solution. ²⁹Si NMR analysis shows the structures, in selected solvents, to be of λ⁵Si-type for 3 and to the major part for 2. Compound 4, on the other hand, is of ionic λ⁴Si-type. The syntheses and molecular structures of the compounds are discussed.     

Catalyst structural effects in titanocene-catalyzed pinacol coupling: activity,stereoselectivity and mechanistic implications

The effects of catalyst structural variation on the activity and selectivity of titanocene-catalyzed pinacol coupling of cyclohexane carboxaldehyde by Mn/TMSCl have been evaluated. Complexes which have been tested include: Cp₂TiCl₂ (1), Cp₂TiBr₂ (2), (C₅Me₅)₂TiCl₂ (3), (1,3-t-Bu₂C₅H₃)₂TiCl₂ (4), (1,3-t-Bu₂C₅H₃)(Cp)TiCl₂ (5), ansa-[(η⁵-tetrahydroindenyl)CH₂CH₂(η⁵-tetrahydroindenyl)]TiCl₂ (6), and ansa-[(η⁵-Cp)CH₂CH₂(η⁵-fluorenyl)]TiCl₂ (7). Cp₂TiCl₂ (1) is the most active (pre)catalyst for pinacol silylether (8a) formation, but Brintzinger's complex 6 provides the best dl/meso diastereoselectivity (5:1). Complexes 2, 4 and 7 slowly catalyze the predominant formation of the corresponding pinacol acetal 9a as a secondary product. Comparative stoichiometric reactions of benzaldehyde/Me₃SiCl with [Cp₂TiCl·MnCl₂(THF)₂·Cp₂TiCl] (10) and [Cp₂TiCl]₂ (11) result in highly diastereoselective pinacol silylether formation with binuclear 11 (29:1), but primarily the production of pinacol acetal (9b) from trimetallic 10, suggesting a dominant role for the binuclear complex (or derived mononuclear species) in the catalytic systems employing Cp₂TiCl₂/M/TMSCl, contrary to previous suggestions.     

Displacement,reduction, and ligand redistribution reactivity of the cationic mono-C5Me5 Ln2+ complexes (C5Me5)Ln(BPh4) (Ln = Sm,Yb)

The reactivity of the mono(pentamethylcyclopentadienyl) divalent lanthanide tetraphenylborate complexes, (C₅Me₅)Ln(BPh₄) (Ln = Sm, 1; Yb, 2), was investigated to determine how Ln²⁺ and (BPh₄)^1? reactivity would combine in these species. The (BPh₄)^1? ligand in (C₅Me₅)Yb(BPh₄) can be displaced with KN(SiMe₃)₂ to form the heteroleptic divalent dimer, {(C₅Me₅)Yb[μ-N(SiMe₃)₂]}₂ (3). Both 1 and 2 reduce phenazine to give the bis(pentamethylcyclopentadienyl) ligand redistribution products, [(C₅Me₅)₂Ln]₂(μ-C₁₂H₈N₂). 2,2-Bipyridine is reduced by 1 to yield the ligand redistribution product, (C₅Me₅)₂Sm(C₁₀H₈N₂) (4), while 2 does not react with bipyridine. Tert-butyl chloride is reduced by 1 to form the trimetallic pentachloride complex [{(C₅Me₅)(THF)Sm}₃(μ-Cl)₅][BPh₄] (6), in a reaction that appears to use the reductive capacity of both Sm²⁺ and (BPh₄)^1?.     

Iridium(I) complex of chelating pyridine-2-thiolate ligand: Synthesis, reactivity, and application to the catalytic E-selective terminal alkyne dimerization via C-H activation

A novel iridium(I) complex bearing a chelate-coordinated pyridine-2-thiolate ligand [Ir(η²-SNC₅H₄)(PPh₃)₂] (2) was prepared by the reaction of iridium ethylene complex [IrCl(C₂H₄)(PPh₃)₂] (1) with lithium salt of pyridine-2-thiol (Li[SNC₅H₄]). On the treatment of iridium(I) complex 2 with chloroform, iridium(III) dichloro-complex [IrCl₂(η²-SNC₅H₄)(PPh₃)₂] (3) was formed. Reactions of complex 2 with methyldiphenylsilane, acetic acid, and p-tolylacetylene afforded iridium(III) hydride complexes [IrH(SiMePh₂)(η²-SNC₅H₄)(PPh₃)₂] (4), [IrH(O₂CCH₃)(η²-SNC₅H₄)(PPh₃)₂] (5), and [IrH(CC(p-tolyl))(η²-SNC₅H₄)(PPh₃)₂] (6), respectively. Complex 2 catalyzed dimerization of terminal alkynes leading to enynes (7) with high E-selectivity via C-H bond activation.     

Synthesis,structural characterisation and reactivity of molybdenum half-sandwich complexes containing keto- and amido-phosphines

The keto-functionalised N-pyrrolyl phosphine ligand PPh₂NC₄H₃{C(O)CH₃-2} L¹ reacts with [MoCl(CO)₃(η⁵-C₅R₅)] (R=H, Me) to give [MoCl(CO)₂(L¹-κ¹P)(η⁵-C₅R₅)] (R=H 1a; Me 1b). The phosphine ligands PPh₂CH₂C(O)Ph (L²) and PPh₂CH₂C(O)NPh₂ (L³) react with [MoCl(CO)₃(η⁵-C₅R₅)] in an analogous manner to give the compounds [MoCl(CO)₂(L-κ¹P)(η⁵-C₅R₅)] (L=L², R=H 2a, Me 2b; L=L³, R=H 3a, Me 3b). Compounds 1–3 react with AgBF₄ to give [Mo(CO)₂(L-κ²P,O)(η⁵-C₅R₅)]BF₄ (L=L¹, R=H 4a, Me 4b; L=L², R=H 5a, Me 5b; L=L³, R=H 6a, Me 6b) following displacement of chloride. The X-ray crystal structure of 4a revealed a lengthening of both Mo–P and CO bonds on co-ordination of the keto group. The lability of the co-ordinated keto or amido group has been assessed by addition of a range of phosphines to compounds 4–6. Compound 4a reacts with PMe₃, PMe₂Ph and PMePh₂ to give [Mo(CO)₂(L¹-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₃ 7a; PMe₂Ph 7b; PMePh₂ 7c) but does not react with PPh₃, 5a reacts with PMe₂Ph, PMePh₂ and PPh₃ to give [Mo(CO)₂(L²-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₂Ph 8b; PMePh₂ 8c; PPh₃ 8d), and 6a reacts with PMe₃, PMe₂Ph, PMePh₂ and PPh₃ to give [Mo(CO)₂(L³-κ¹P)(L)(η⁵-C₅H₅)]BF₄ (L=PMe₃ 10a; PMe₂Ph 10b; PMePh₂ 10c; PPh₃ 10d). No reaction was observed for the pentamethylcyclopentadienyl compounds 4b–6b with PMe₃, PMe₂Ph, PMePh₂ or PPh₃. These results are consistent with the displacement of the co-ordinated oxygen atom being influenced by the steric properties of the P,O-ligand, with PPh₃ displacing the keto group from L² but not from the bulkier L¹. In the reaction of [Mo(CO)₂(L²-κ²P,O)(η⁵-C₅H₅)]BF₄ (5a) with PMe₃ the phosphine does not displace the keto group, instead it acts as a base, with the only observed molybdenum-containing product being the enolate compound [Mo(CO)₂{PPh₂CHC(O)Ph-κ²P,O}(η⁵-C₅H₅)] 9. Compound 9 can also be formed from the reaction of 2a with BuLi or NEt₃, and a single crystal X-ray analysis has confirmed the enolate structure.     

Organometallic polymorphism. Synthesis and structural characterization of two forms of [Ru(η6-C6H6)(η6-C6H4(CH3)COOCH3)][BF4]2 and the phase transition in [Ru(η5-C5H5)(η6-C6H5OH)][PF6]

The synthesis and structural characterization of the complex [Ru(η⁶-C₆H₆)(η⁶-C₆H₄(CH₃)COOCH₃)] [BF₄]₂ (2) and of its precursor [Ru(η⁶-C₆H₄(CH₃)COOCH₃)Cl₂]₂ (1) are reported. Compound (2) has been characterized in two polymorphic modifications (2a and 2b) and the molecular organization in the solid state has been investigated. The complex [Ru(η⁵-C₅H₅)(η⁶-C₆H₅OH)][PF₆] (3) has also been investigated; it has been shown to possess a disorder similar to that observed in the high temperature phase of related systems such as [Ru(η⁵-C₅H₅)(η⁶-C₆H₆)][PF₆].