Reactivity of the N-heterocyclic carbene complexes [Ru(IMes)2(CO)HX] (X = OH, Cl) with alkynes

Treatment of the 16-electron hydroxy hydride complex [Ru(IMes)₂(CO)H(OH)] (1, IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene) with HCCR affords the alkynyl species [Ru(IMes)₂(CO)H(CCR)] (R = Ph 3, SiMe₃, 4) and [Ru(IMes)₂(CO)(CCR)₂] (R = Ph, 5). Deuterium labelling studies show that the mono-alkynyl complexes are formed via hydrogen transfer from a coordinated alkyne ligand to Ru-OH, while bis-alkynyl formation is proposed to take place through hydrogen transfer to Ru-H. Both 3 and 5 readily coordinate CO to give the corresponding dicarbonyl species 6 and 7. Addition of HCCPh to the hydride chloride precursor [Ru(IMes)₂(CO)HCl] (2) results in a different reaction pathway involving alkyne insertion into the Ru-H bond to yield the alkenyl chloride complex [Ru(IMes)₂(CO)(CHCHPh)Cl] 8. Complexes 3-8 have been structurally characterised by X-ray crystallography.     

Synthesis and characterization of mixed-ligand ruthenium(III) complexes with oxalate and acetylacetonate ions

Two mononuclear mixed-ligand ruthenium(III) complexes with oxalate dianion (ox²⁻) and acetylacetonate ion (2,4-pentanedionate, acac⁻), K₂[Ru(ox)₂(acac)] (1) and K[Ru(ox)(acac)₂] (2), were prepared as a candidate for a building block. In fact, reaction of complex 2 with manganese(II) sulfate gave a heterometallic tetranuclear complex, TBA[Mn^II{(μ-ox)Ru^III(acac)₂}₃] (5) in the presence of tetrabutylammonium (TBA) bromide. The ¹H NMR, UV-Vis, selected IR and FAB mass spectral data of these complexes are presented. Both mixed-ligand ruthenium(III) complexes gave a Nernstian one-electron reduction step in 0.1 mol dm⁻³ Na₂SO₄ aqueous solution on a mercury electrode at 25 °C. Comparison of observed reversible half-wave potentials with calculated values for a series of [Ru(ox)_n(acac)_3 − n]ⁿ⁻ (n=0-3) complexes by using Lever’s ligand electrochemical parameters is presented.     

Synthesis, spectroscopic properties and structural characterisation of Pd(II) and Pt(II) complexes with 1,3,5-pyrazole derived ligands. Rotation around the metal-N bond

Reactions of ligands 1-ethyl-5-methyl-3-phenyl-1H-pyrazole (L¹) and 5-methyl-1-octyl-3-phenyl-1H-pyrazole (L²) with [PdCl₂(CH₃CN)₂ and K₂PtCl₄ gave complexes trans-[MCl₂(L)₂] (L = L¹, L²). The new complexes were characterised by elemental analyses, conductivity measurements, infrared, ¹H and ¹³C{¹H} NMR spectroscopies and X-ray diffraction. The NMR study of the complex [PdCl₂(L¹)₂], in CDCl₃ solution, is consistent with a very slow rotation of ligands around the Pd-N bond, so that two conformational isomers can be observed in solution (syn and anti). Different behaviour is observed for complexes [PdCl₂(L²)₂] and [PtCl₂(L)₂] (L = L¹, L²), which present an isomer in solution at room temperature (anti). The crystal structure of [PdCl₂(L¹)₂] complex is described, where the Pd(II) presents a square planar geometry with the ligands coordinated in a trans disposition.     

Iron-oxidation-state-dependent O-O bond cleavage of meta-chloroperbenzoic acid to form an iron(IV)-oxo complex

The mechanism of formation of [Fe^IV(O)(N4Py)]²⁺ (2, N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) from the reaction of [Fe^II(N4Py)(CH₃CN)]²⁺ (1) with m-chloroperbenzoic acid (mCPBA) in CH₂Cl₂ at −30 °C has been studied on the basis of the visible spectral changes observed and the reaction stoichiometry. It is shown that the conversion of 1 to 2 in 90% yield requires 1.5 equiv. peracid and takes place in two successive one-electron steps via an [Fe^III(N4Py)OH]²⁺(3) intermediate. The first oxidation step uses 0.5 equiv. peracid and produces 0.5 equiv. 3-chlorobenzoic acid, while the second step uses 1 equiv. peracid and affords byproducts derived from chlorophenyl radical. We conclude that the Fe^II(N4Py) center promotes O-O bond heterolysis, while the Fe^III(N4Py) center favors O-O bond homolysis, so the nature of O-O bond cleavage is dependent on the iron oxidation state.     

Nickel promoted C-H, C-C and C-O bond activation in solution

Reaction of NiI₂ with the PCP-ligand {1-Et-2,6-(CH₂PⁱPr₂)₂-C₆H₃} (1) results in selective activation of the strong sp²-sp³ aryl-ethyl bond to afford the aryl-nickel complex [Ni{2,6-(CH₂PⁱPr₂)₂-C₆H₃}I] (2), whereas reaction of NiI₂ with {1,3,5-(CH₃)₃-2,6-(CH₂PⁱPr₂)₂-C₆H} (4) leads to the formation of the benzylic complex [Ni{1-CH₂-2,6-(CH₂PⁱPr₂)₂-3,5-(CH₃)₂-C₆H}I] (5) by selective C-H bond activation. Thermolysis of 5 results in formation of [Ni{2,6-(CH₂PⁱPr₂)₂-3,5-(CH₃)₂-C₆H}I] (6) by activation of the sp²-sp³ C-C bond. The identity of the new 16-electron complexes 2 and 6 was confirmed by reaction of NiI₂ with {1,3-(CH₂PⁱPr₂)₂-C₆H₄} (3) and {1,3-(CH₃)₂-4,6-(CH₂PⁱPr₂)₂-C₆H₂} (7), respectively, lacking the aryl-alkyl groups between the “phosphines arms” (alkyl=ethyl, methyl). Complexes 2 and 5 have been fully characterized by X-ray analysis. Nickel-based activation of an unstrained C-O single bond was observed as well. Reaction of the aryl-methoxy bisphosphine {1-OMe-2,6-(CH₂PⁱPr₂)₂-C₆H₃} (8) with NiI₂ results in the formation of the phenoxy complex [Ni{1-O-2,6-(CH₂PⁱPr₂)₂-C₆H₃}I] (9) by selective sp³-sp³ C-O bond activation.     

Synthetic and mechanistic studies on ruthenium dicarbonyl complexes containing PhP(CH2CH2CH2PCy2)2 (Cyttp) ligand

A synthetic and mechanistic study is reported on ligand substitution and other reactions of six-coordinate ruthenium(II) carbonyl complexes containing tridentate PhP(CH₂CH₂CH₂PCy₂)₂ (Cyttp). Carbonylation of cis-mer-Ru(OSO₂CF₃)₂(CO)(Cyttp) (1) affords [cis-mer-Ru(OSO₂CF₃)(CO)₂(Cyttp)]O₃SCF₃ (2(O₃SCF₃)) and, on longer reaction times, [cis-mer-Ru(solvent)(CO)₂(Cyttp)](O₃SCF₃)₂ (solvent = acetone, THF, methanol). 2(O₃SCF₃) reacts with each of NaF, LiCl, LiBr, NaI, and LiHBEt₃ to yield [cis-mer-RuX(CO)₂(Cyttp)]⁺ (X = F (3), Cl (4), Br (5), I (6), H (7)), isolated as 3-7(BPh₄). These conversions proceed with high stereospecificity to afford only a single isomer of the product that is assigned a structure in which the Ph group of Cyttp points toward the CO trans to X (anti when X = F, Cl, Br, or I; syn when X = H). Treatment of 2(O₃SCF₃) with NaOMe and CO generates the methoxycarbonyl complex [cis-mer-Ru(CO₂Me)(CO)₂(Cyttp)]⁺ (8), whereas addition of excess n-BuLi to 2(O₃SCF₃) in THF under CO affords mer-Ru(CO)₂(Cyttp) (9). The two ¹³C isotopomers [cis-mer-Ru(OSO₂CF₃)(CO)(¹³CO)(Cyttp)]O₃SCF₃ (2′(O₃SCF₃): ¹³CO trans to P_C; 2″(O₃SCF₃): ¹³CO cis to all P donors) were synthesized by appropriate adaptations of known transformations and used in mechanistic studies of reactions with each of LiHBEt₃, NaOMe/CO, and n-BuLi. Whereas LiHBEt₃ reacts with 2′(O₃SCF₃) and 2″(O₃SCF₃) to replace triflate by hydride without any scrambling of the carbonyl ligands, the corresponding reactions of NaOMe-CO are more complex. The methoxide combines with the CO cis to triflate in 2, and the resultant methoxycarbonyl ligand ends up positioned trans to the incoming CO in 8. A mechanism is proposed for this transformation. Finally, treatment of either 2′(O₃SCF₃) or 2″(O₃SCF₃) with an excess of n-BuLi leads to the formation of the same two ruthenium(0) isomers of mer-Ru(CO)(¹³CO)(Cyttp). These products represent, to our knowledge, the first example of a syn-anti pair of isomers of a five-coordinate metal complex.     

Imidazolium formation from the reaction of N-heterocyclic carbene stabilised group 13 trihydride complexes with organic acids

The reactions of the N-heterocyclic carbene (NHC) stabilised group 13 trihydride complexes [AlH₃(IMeMe)] (1) (IMeMe = 1,3,4,5-tetramethylimidazol-2-ylidene), [AlH₃(IⁱPrMe)] (2) (IⁱPrMe = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with three molar equivalents of phenol, and [InH₃(IMes)] (3) (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene) with one molar equivalent of 1,1,1,5,5,5-hexafluoropentan-2,4-dione (F₆acacH) are presented. These render the imidazolium tetraphenoxyaluminate species; [IMeMe · H][Al(OPh)₄] (4) and [IⁱPrMe · H][Al(OPh)₄] (5), and 1,3-bis(2,4,6-trimethylphenyl)imidazolium 1,1,1,5,5,5-hexafluoropentan-2,4-dionate; [IMes · H][CH{C(O)CF₃}₂] (6), the latter leading to metallohydride decomposition. The molecular structures of 4 and 6 are described.     

Ligand induced PH bond formation and a comparison of the reactivity of two isomers of the carbonyl hydride [Pt2(μ-PBu2)2(H)(CO)(PBu2H)]CF3SO3

The Pt₂ ^(II) isomeric terminal hydrides [(CO)(H)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)]CF₃SO₃ (1a), and [(CO)Pt(μ-PBu^t ₂)₂Pt(PBu^t ₂H)(H)]CF₃SO₃ (1b), react rapidly with 1 atm of carbon monoxide to give the same mixture of two isomers of the Pt₂ ^(I) dicarbonyl [Pt₂(μ-PBu^t ₂)(CO)₂(PBu^t ₂H)₂]CF₃SO₃ (3-Pt); the solid state structure of the isomer bearing the carbonyl ligands pseudo-trans to the bridging phosphide was solved by X-ray diffraction. A remarkable difference was instead found between the reactivity of 1a and 1b towards carbon disulfide or isoprene. In both cases 1b reacts slowly to afford [Pt₂(μ-PBu^t ₂)(μ,η²,η²-CS₂)(PBu^t ₂H)₂]CF₃SO₃ (4-Pt), and [Pt₂(μ-PBu^t ₂)(μ,η²,η²-isoprene) (PBu^t ₂H)₂]CF₃SO₃ (6-Pt), respectively. In the same experimental conditions, 1a is totally inert. A common mechanism, proceeding through the preassociation of the incoming ligand followed by the PH bond formation between one of the bridging P atoms and the hydride ligand, has been suggested for these reactions.     

Mixed chloride-phosphine complexes of the dirhenium core. Part 11. Reactions of [Re2Cl8] with secondary phosphines, PCy2H and PPh2H

The reaction between the dirhenium(III,III) anion, [Re₂Cl₈]²⁻, and the secondary phosphine, PCy₂H, yields a mixture of products as a result of disproportionation, namely, a dirhenium(II,III) chloride-phosphine complex 1,3,6-Re₂Cl₅(PCy₂H)₃ (1) and a dirhenium(IV) face-sharing bioctahedral compound with bridging phosphido groups, [Buⁿ ₄N][Re₂(μ-PCy₂)₃Cl₆] (2). The diphenylphosphine analogue of 2, [Buⁿ ₄N][Re₂(μ-PPh₂)₃Cl₆] (3) has been similarly prepared from the reaction of [Re₂Cl₈]²⁻ with PPh₂H. An interesting dirhenium(III,III) complex, [Buⁿ ₄N]₂[Re₂(μ-PPh₂)₂(PPh₂H)₂Cl₆] (4) having both neutral terminal phosphines and anionic phosphido bridges, has also been isolated as an intermediate in the latter system. Crystal structures of 1-4 have been determined by X-ray crystallography. The compounds were also characterized by cyclic voltammetry, IR and ³¹P NMR spectroscopy.     

Reactivity studies of highly electrophilic ruthenium complexes

The 16-electron, coordinatively unsaturated, dicationic ruthenium complex [Ru(P(OH)₂(OMe))(dppe)₂][OTf]₂ (1a) brings about the heterolysis of the C-H bond in phenylacetylene to afford the phenylacetylide complex trans-[Ru(CCPh)(P(OH)₂(OMe))(dppe)₂][OTf] (2). The phenylacetylide complex undergoes hydrogenation to give a ruthenium hydride complex trans-[Ru(H)(P(OH)₂(OMe))(dppe)₂][OTf] (3) and phenylacetylene via the addition of H₂ across the Ru-C bond. The 16-electron complex also reacts with HSiCl₃ quite vigorously to yield a chloride complex trans-[Ru(Cl)(P(OH)₂(OMe))(dppe)₂][OTf] (4). On the other hand, the other coordinatively unsaturated ruthenium complex [Ru(P(OH)₃)(dppe)₂][OTf]₂ (1b) reacts with a base N-benzylideneaniline to afford a phosphonate complex [Ru(P(O)(OH)₂)(dppe)₂][OTf] (5) via the abstraction of one of the protons of the P(OH)₃ ligand by the base. The phenylacetylide, chloride, and the phosphonate complexes have been structurally characterized. The phosphonate complex reacts with H₂ to afford the corresponding dihydrogen complex trans-[Ru(η²-H₂)(P(O)(OH)₂)(dppe)₂][OTf] (5-H₂). The intact nature of the H-H bond in this species was established using variable temperature ¹H spin-lattice relaxation time measurements and the observation of a significant J(H,D) coupling in the HD isotopomer trans-[Ru(η²-HD)(P(O)(OH)₂)(dppe)₂][OTf] (5-HD).     

Syntheses and structural characterizations of novel mono- and dinuclear iridium hydrido complexes with polydentate nitrogen donor ligands

New five mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, [Ir(H)₂(PPh₃)₂(tptz)]PF₆ (1), [Ir₂(H)₄(PPh₃)₄(tptz)](PF₆)₂ · 2H₂O (2 · 2H₂O), [Ir(H)₂(PPh₃)₂(tppz)]BF₄ (3), [Ir₂(H)₄(PPh₃)₄(tppz)](BF₄)₂ (4) and [Ir₂(H)₄(PPh₃)₄(bted)](BF₄)₂ · 6CHCl₃ (5 · 6CHCl₃), were systematically prepared by the reactions of the precursor Ir hydrido complex [Ir(H)₂(PPh₃)₂(Me₂CO)₂]X (X=PF₆ and BF₄) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 1,4-bis(2,2^′:6^′,2″-terpyridine-4^′-yl)benzene (bted), and their structures and properties were characterized in the solid state and in solution. Each of the Ir hydrido complexes with polydentate nitrogen ligands crystallographically described a unique coordination mode. Their ¹H NMR spectra demonstrated unusual ¹H NMR chemical shifts of pyridyl rings that are likely induced by the ring current effect of neighboring ligands.     

Synthesis, structure, and characterization of some ruthenium arene complexes of N-(arylmethylene)-2-(methylthio)anilines and 2-(methylthio)aniline

A series of cationic, half-sandwich ruthenium complexes with the general formula [(η⁶-p-cymene)RuCl(MeSC₆H₄2-NCHAr)][PF₆] (3a-h), have been prepared from the reaction of [(η⁶-p-cymene)RuCl₂]₂ with various N,S-donor Schiff base ligands derived from 2-(methylthio)aniline and several substituted benzaldehydes. The related aniline complex [(η⁶-p-cymene)RuCl(MeS-C₆H₄-2-NH₂)][PF₆] (4) was synthesized from 2-(methylthio)aniline. All of the ruthenium complexes were characterized by IR, ¹H NMR, and UV/Vis spectroscopies. The molecular structure of complex 4 was determined by X-ray crystallography.     

Monodentate, didentate chelating, and bridging 1,8-naphthyridine complexes of pentamethylcyclopentadienyliridium(III): Syntheses and structures in the solid states and in solution

A series of new iridium(III) complexes containing pentamethylcyclopentadienyl (Cp^∗ = η⁵-C₅Me₅) and 1,8-naphthyridine (napy) have been prepared. X-ray crystallography revealed that napy acted as a monodentate, a didentate chelating, and a bridging ligand in complexes of [Cp^∗IrCl₂(napy)] (1), [Cp^∗IrCl(napy)]PF₆ (2), and [(Cp^∗IrCl)₂(H)(napy)]PF₆ (4), respectively. The crystal structure of [Cp^∗Ir(napy)₂](PF₆)₂ (3) has also been determined; the dicationic complex bore both monodentate and chelating napy ligands. Dinuclear Cp^∗Ir^III complex bridged by napy was only isolable if two Ir^III centers were supported by a hydride (H⁻) bridge. In complexes 2 and 3, the four-membered chelate rings formed by napy exhibited a large steric strain; in the rings the NIrN bond angles were only 60.5(2)-61.0(4)° and the IrNC angles were 94.7(8)-96.7(8)°. The bridging coordination of napy in complex 4 also afforded a large strain, i.e., the Ir^III centers were displaced by 0.84(3) Å from the napy plane, due to the steric interaction between two Cp^∗IrCl moieties. The monodentate napy complex 1 in CDCl₃ or CD₂Cl₂ at ambient temperature showed a rapid coordination-site exchange reaction, which gave two N sites of napy equivalent; at temperatures below −40 °C, the ¹H NMR spectra corresponded to the molecular structure of [Cp^∗IrCl₂(napy-κN)]. The analogous diazido complex of [Cp^∗Ir(N₃)₂(napy)] (5) has also been prepared, and the crystal structure has been determined. In contrast to the dichloro complex 1, the diazido complex 5 exhibited a dissociation equilibrium of coordinated napy in solution.     

Syntheses and structures of vinyl and aryl derivatives of carbonyl halide iron complexes

cis,trans-Fe(CO)₂(PMe₃)₂(p-Y-C₆H₄)X [X=Br, Y=H (4a), MeO (4b), Cl (4c), F (4d), Me (4e); X=I, Y=H (5); X=Cl, Y=H (6)] and cis,trans-Fe(CO)₂(PMe₃)₂(σ-CHCH₂)X [X=Br (7); X=I (8); X=Cl (9)] are prepared by reacting dihalide complexes cis,trans,cis- Fe(CO)₂(PMe₃)₂X₂ [X=Br (1), X=I (2), X=Cl (3)] with Grignard reagents p-Y-C₆H₄-MgBr (Y=H, OMe, Cl, F, Me) or CH₂CH-MgBr and with lithium reagents PhLi, CH₂CH-Li. With both reagents, the reaction proceeds following two parallel pathways: one is the metallation reaction which yields alkyl derivatives, the other affords 17 electron complexes [Fe(CO)₂(PMe₃)₂X] via monoelectron reductive elimination. The influence of the halides and organometallic reagents on the yield of the metallation reaction is discussed. The solution structure of the complexes is assigned on the basis of IR and ¹H, ¹³C, ¹⁹F, ³¹P NMR spectra. The solid state structure of complexes 4a, 5 and 6 is determined by single crystal X-ray diffractometric methods.     

Synthesis, molecular structure, substitution and C-C coupling reactions of ruthenium complexes containing (η-C9H7)Ru(PPh3) as a molecular unit

The 2-methallyl complex [(η⁵-C₉H₇)Ru(η³-2-MeC₃H₄)(PPh₃)] (3), prepared from [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] (2) and 2-MeC₃H₄MgCl, reacts with HX (X = Cl, CF₃CO₂) in the presence of ethene to give the chiral-at-metal compounds [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)X] (4, 5) in nearly quantitative yields. Treatment of 2 with AgPF₆ and ethene affords [(η⁵-C₉H₇)Ru(C₂H₄)(PPh₃)₂]PF₆ (6), which reacts with acetone to give the substitution product [(η⁵-C₉H₇)Ru(OCMe₂)(PPh₃)₂]PF₆ (7). The molecular structure of 7 has been determined crystallographically. Whereas treatment of 4 with CH(CO₂Et)N₂ yields the olefin complex [(η⁵-C₉H₇)Ru{η²-(Z)-C₂H₂(CO₂Et)₂}(PPh₃)Cl] (8), the reactions of 4 and 5 with Ph₂CN₂, PhCHN₂ and (Me₃Si)CHN₂ lead to the formation of the carbeneruthenium(II) derivatives [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)Cl] (9-11) and [(η⁵-C₉H₇)Ru(CRR′)(PPh₃)(κ¹-O₂CCF₃)] (12-14), respectively. Treatment of 9 (R = R′ = Ph), 10 (R = H, R′ = Ph) and 11 (R = H, R′ = SiMe₃) with MeLi produces the hydrido(olefin) complexes [(η⁵-C₉H₇)RuH(η²-CH₂CPh₂)(PPh₃)] (15), [(η⁵-C₉H₇)RuH(η²-CH₂CHPh)(PPh₃)] (18a,b) and [(η⁵-C₉H₇)RuH(η²-CH₂CHSiMe₃)(PPh₃)] (19) via C-C coupling and β-hydride shift. The analogous reactions of 11 with PhLi gives the η³-benzyl compound [(η⁵-C₉H₇)Ru{η³-(Me₃Si)CHC₆H₅}(PPh₃)] (20). The η³-allyl complex [(η⁵-C₉H₇)Ru(η³-1-PhC₃H₄)(PPh₃)] (17) was prepared from 10 and CH₂CHMgBr by nucleophilic attack.     

Synthesis of dimethylcobalt(III) complexes containing trimethylphosphine and 2-formyl-phenolato- or 2-formyl-enolato(O:O) ligands

Substituted salicylaldehydes [C₆HR¹R²R³(CHO)(OH)] react with CoMe₃(PMe₃)₃ to afford 6-coordinate (cis-dimethyl)(2-formyl-phenolato)trans-bis(trimethylphosphine)cobalt(III) compounds Co[C₆HR¹R²R³(CHO)(O)Me₂](PMe₃)₂ (1: R¹ = H; R² = Me; R³ = tert-Bu; 2: R¹, R² = C₆H₄; R³ = H). Accordingly, substituted enolated malonic dialdehydes (CHO-CR⁴CR⁵-OH) react with CoMe₃(PMe₃)₃ to afford 6-coordinate (cis-dimethyl)(2-formyl-enolato)trans-bis(trimethylphosphine)cobalt(III) compounds Co[(CHO-CR⁴CR⁵-O)(Me)₂](PMe₃)₂ (3: R⁴, R⁵ = (CH₂)₂C₆H₄; 4: R⁴ = R⁵ = C₆H₅). In the molecular structure of 4, the cobalt atom is centred in an octahedral coordination geometry brought about by a six-membered chelate ring (O:O-ligand), cis-dimethyl and trans-trimethylphosphine groups. A reaction mechanism is suggested.     

Dimeric palladium and platinum complexes isolated in Lewis-acidic media

The synthesis and X-ray characterization of binuclear dipalladium(I) and diplatinum(I) p-xylene complexes [Pd₂(η⁶-C₈H₁₀)₂(μ-Cl/Br)₂(GaCl₃)₂] (1) and [Pt₂(η⁶-C₈H₁₀)₂(Ga₂Br₇)₂] (5) are reported. It was established that the toluene ligands in the palladium complex [Pd₂(η⁶-C₇H₈)₂(GaCl₄)₂] (3) can be substituted by naphthalene without disruption of the metal-metal bond. The reaction of 3 with Pd(PPh₃)₄ leads to the formation of a dipalladium(II) μ-diphenylphosphido compound [Pd₂(μ-PPh₂)(PPh₃)₄] (GaCl₄)₂ · 4(C₇H₈) (4), most likely also involving a bridging μ-H⁻ ligand.     

Dinuclear alkoxo-bridged copper(II) coordination polymers: Syntheses, structural and magnetic properties

The alkoxo-bridged dinuclear copper(II) complexes [Cu₂(ap)₂(NO₂)₂] (1), [Cu₂(ap)₂(C₆H₅COO)₂] (2) and [Cu₂(ap)₂μ-1,3-C₆H₄(COO)₂(dmso)₂]·dmso (3) (ap = 3-aminopropanolato and dmso = dimethyl sulfoxide) have been synthesized via self-assembly from copper(II) perchlorate, 3-aminopropanol as main chelating ligand and nitrite and isophthalate anions as spacers and benzoate anion as auxiliary ligand. Complexes 1 and 3 crystallize as 2D and 1D coordination polymers, respectively, and their structures consist of dinuclear [Cu₂(ap)₂]²⁺ units connected with nitrite and isophthalate ligands. The adjacent dinuclear units of 2 and 1D polymers of 3 are further connected by hydrogen bonds resulting in the formation of 2D layers. The variable temperature crystallographic measurements of 1 at 100, 173 and 293 K indicate the static Jahn-Teller distortion with librational disorder in the nitrite group. Experimental magnetic studies showed that complexes 1-3 exhibit strong antiferromagnetic couplings. The values of the magnetic exchange coupling constant for 1-3 are well reproduced by the theoretical calculations.     

Synthesis and characterisation of bis(2,2′-bipyridine)(4-carboxy-4′-(pyrid-2-ylmethylamido)-2,2′-bipyridine)ruthenium(II) di(hexafluorophosphate): Comparison of spectroelectrochemical properties with related complexes

The new complex, [Ru^II(bpy)₂(4-HCOO-4′-pyCH₂ NHCO-bpy)](PF₆)₂ · 3H₂O (1), where 4-HCOO-4′-pyCH₂NHCO-bpy is 4-(carboxylic acid)-4′-pyrid-2-ylmethylamido-2,2′-bipyridine, has been synthesised from [Ru(bpy)₂(H₂dcbpy)](PF₆)₂ (H₂dcbpy is 4,4′-(dicarboxylic acid)-2,2′-bipyridine) and characterised by elemental analysis and spectroscopic methods. An X-ray crystal structure determination of the trihydrate of the [Ru(bpy)₂(H₂dcbpy)](PF₆)₂ precursor is reported, since it represented a different solvate to an existing structure. The structure shows a distorted octahedral arrangement of the ligands around the ruthenium(II) centre and is consistent with the carboxyl groups being protonated. A comparative study of the electrochemical and photophysical properties of [Ru^II(bpy)₂(4-HCOO-4′-pyCH₂NHCO-bpy)]²⁺ (1), [Ru(bpy)₂(H₂dcbpy)]²⁺ (2), [Ru(bpy)₃]²⁺ (3), [Ru(bpy)₂Cl₂] (4) and [Ru(bpy)₂Cl₂]⁺ (5) was then undertaken to determine their variation upon changing the ligands occupying two of the six ruthenium(II) coordination sites. The ruthenium(II) complexes exhibit intense ligand centred (LC) transition bands in the UV region, and broad MLCT bands in the visible region. The ruthenium(III) complex, 5, displayed overlapping LC bands in the UV region and a LMCT band in the visible. 1, 2 and 3 were found, via cyclic voltammetry at a glassy carbon electrode, to exhibit very positive reversible formal potentials of 996, 992 and 893 mV (versus Fc/Fc⁺) respectively for the Ru(III)/Ru(II) half-cell reaction. As expected the reversible potential derived from oxidation of 4 (−77 mV (versus Fc/Fc⁺)) was in excellent agreement with that found via reduction of 5 (−84 mV (versus Fc/Fc⁺)). Spectroelectrochemical experiments in an optically transparent thin-layer electrochemical cell configuration allowed UV-Vis spectra of the Ru(III) redox state to be obtained for 1, 2, 3 and 4 and also confirmed that 5 was the product of oxidative bulk electrolysis of 4. These spectrochemical measurements also confirmed that the oxidation of all Ru(II) complexes and reduction of the corresponding Ru(III) complex are fully reversible in both the chemical and electrochemical senses.     

Reactions of the hexaaquarhodium(III) cation with bis(benzimidazol-2-ylmethyl)methylamine and PPh3: syntheses and properties of new hydrido- and carbonylrhodium complexes

Hexaaquarhodium(III) perchlorate has been found to be an interesting starting material for the preparation of rhodium compounds. New mononuclear hydrido- and carbonylrhodium compounds with bis(benzimidazol-2-ylmethyl)methylamine (L) and PPh₃ of the type [Rh(H)L(PPh₃)₂](ClO₄)₂ (1) and [Rh(CO)L(PPh₃)₂](ClO₄) (2) have been synthesized. The monomeric Rh(II) compound was identified as an intermediate. Complexes 1 and 2 were characterized by elemental analysis, mass spectrometry and IR, and NMR spectroscopies. The fluxional behaviour of 2 was studied by variable-temperature ¹H and ³¹P{H} NMR experiments.