Synthesis and structural aspects of M-allyl (M = Ir, Rh) complexes

The synthesis, characterization and chemistry of novel η³-allyl metal complexes (M = Ir, Rh) are described. The structures of compounds (C₅Me₄H)Ir(PPh₃)Cl₂ (1), (C₅Me₄H)Ir(PPh₃)(η³-1-methylallyl)Br (3a), (C₅Me₄H)Ir(η⁴-1,3,5-hexatriene) (8), and (C₅Me₅)Rh(η³-1-ethylallyl)Br (5d) have been determined by X-ray crystallography. Structural comparisons among these complexes are discussed. It is found that the neutral metal allylic complex [Cp^∗IrCl(η³-methylallyl)] (5) ionizes in polar solvents to give [Cp^∗Ir(η³-methylallyl)]⁺Cl⁻ (6) and reaches equilibrium (5 ? 6) at room temperature. Addition of tertiary phosphine ligands to neutral complexes such as [Cp^∗Ir(η³-methylallyl)Cl], results in the formation of stable ionic phosphine adducts. Factors such as solvent, length of carbon chain, temperature and light are discussed with respect to the formation, stability and structure of the allyl complexes.     

Syntheses of new Mo(II) and W(II) mono(hydrosulfido) complexes and their conversion into di- and tetranuclear sulfido-bridged heterobimetallic complexes

Treatment of [Cp′MH(CO)₃] (M = Mo, W; Cp′ = η⁵-C₅H₅ (Cp), η⁵-C₅Me₅ (Cp*)) with 1/8 equiv of S₈ in THF, followed by the reaction with dppe under UV irradiation, gave new mono(hydrosulfido) complexes [Cp′M(SH)(CO)(dppe)] (Cp′ = Cp: M = Mo (5), W (6); Cp′ = Cp*: M = Mo (7), W (8); dppe = Ph₂PCH₂CH₂PPh₂). When 5 and 6 dissolved in THF were allowed to react with [RhCl(PPh₃)₃] in the presence of base, heterodinuclear complexes with bridging S and dppe ligands [CpM(CO)(μ-S)(μ-dppe)Rh(PPh₃)] (M = Mo (9), W(10)) were obtained. Semi-bridging feature of the CO ligands were also demonstrated. Upon standing in CH₂Cl₂ solutions, 9 and 10 were converted further to the dimerization products [(CpM)₂{Rh(dppe)}₂(μ₂-CO)₂(μ₃-S)₂] (M = Mo (13), W). Detailed structures of mononuclear 7 and 8, dinuclear 9 and tetranuclear 13 have been determined by the X-ray diffraction.     

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η⁶-arene)Ru(Ph-BIAN)Cl]BF₄ [η⁶-arene = benzene (1), p-cymene (2)], [(η⁵-C₅H₅)Ru(Ph-BIAN)PPh₃]BF₄ (3) and [(η⁵-C₅Me₅)M(Ph-BIAN)Cl]BF₄ [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η⁵-C₅Me₅)Ir(Ph-BIAN)Cl]BF₄ has been determined crystallographically. Complexes 1–5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH₃COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η⁵-C₅Me₅)Rh(Ph-BIAN)Cl]BF₄ (4) displays the most effective catalytic activity.     

(1,2,3,4,7-Pentamethylindenyl)rhodium complexes with arene ligands

The reaction of (η⁵-C₉H₂Me₅)Rh(1,5-C₈H₁₂) (1) with I₂ gives the iodide complex [(η⁵-C₉H₂Me₅)RhI₂]₂ (2). The solvate complex [(η⁵- C₉H₂Me₅)Rh(MeNO₂)₃]²⁺ (generated in situ by treatment of 2 with Ag⁺ in nitromethane) reacts with benzene and its derivatives giving the dicationic arene complexes [(η⁵-₉H₂Me₅)Rh(arene)]²⁺ [arene = C₆H₆ (3a), C₆Me₆ (3b), C₆H₅OMe (3c)]. Similar reaction with the borole sandwich compound CpRh(η⁵-C₄H₄BPh) results in the arene-type complex [CpRh(μ-η⁵:η⁶-C₄H₄BPh)Rh(η⁵-C₉H₂Me₅)]²⁺ (4). Treatment of 2 with CpTl in acetonitrile affords cation [(η⁵-C₉H₂Me₅)RhCp]⁺ (5). The structure of [3c](BF₄)₂ was determined by X-ray diffraction. The electrochemical behaviour of complexes prepared was studied. The rhodium-benzene bonding in series of the related complexes [(ring)Rh(C₆H₆)]²⁺ (ring = Cp, Cp^∗, C₉H₇, C₉H₂Me₅) was analyzed using energy and charge decomposition schemes.     

Coordination compounds of N,N′-olefin functionalized imidazolin-2-ylidenes

N-Heterocyclic carbene ligands (NHC) were metalated with Pd(OAc)₂ or [Ni(CH₃CN)₆](BF₄)₂ by in situ deprotonation of imidazolium salts to give the N-olefin functionalized biscarbene complexes [MX₂(NHC)₂] 3-7 (3: M = Pd, X = Br, NHC = 1,3-di(3-butenyl)imidazolin-2-ylidene; 4: M = Pd, X = Br, NHC = 1,3-di(4-pentenyl)imidazolin-2-ylidene; 5: M = Pd, X = I, NHC = 1,3-diallylimidazolin-2-ylidene; 6: M = Ni, X = I, NHC = 1,3-diallylimidazolin-2-ylidene; 7: M = Ni, X = I, NHC = 1-methyl-3-allylimidazolin-2-ylidene). Molecular structure determinations for 4-7 revealed that square-planar complexes with cis (5) or trans (4, 6, 7) coordination geometry at the metal center had been obtained. Reaction of nickelocene with imidazolium bromides afforded the η⁵-cyclopentadienyl (η⁵-Cp) monocarbene nickel complexes [NiBr(η⁵-Cp)(NHC)] 8 and 9 (8: NHC = 1-methyl-3-allylimidazolin-2-ylidene; 9: NHC = 1,3-diallylimidazolin-2-ylidene). The bromine abstraction in complexes 8 and 9 with silver tetrafluoroborate gave complexes [NiBr(η⁵-Cp)(η³-NHC)] 10 and 11. The X-ray structure analysis of 10 and 11 showed a trigonal-pyramidal coordination geometry at the nickel(II) center and coordination of one N-allyl substituent.     

The first metallacarborane triple-decker complexes with a bridging borole ligand

The (borole)iodide complex [(η⁵-C₄H₄BPh)RhI]₄ reacts with the carborane anion [Carb′]⁻ (Carb′ = 9-SMe₂-7,8-C₂B₉H₁₀) giving (Carb′)Rh(η⁵-C₄H₄BPh) (2). Reactions of 2 with dicationic fragments [LM]²⁺ afford the μ-borole triple-decker complexes [(Carb′)Rh(μ-η⁵:η⁵-C₄H₄BPh)ML]²⁺ [LM = Cp^∗Ir (4), (Carb′)Rh (7)] or the arene-type complexes [(Carb′)Rh(μ-η⁵:η⁶-C₄H₄BPh)ML]²⁺ [LM = Cp^∗Rh (3), (Carb′)Ir (8)]. The structure of 4(BF₄)₂ was determined by X-ray diffraction.     

Functionalized cyclodiphosphazanes cis-[BuNP(OR)]2 (R=C6H4OMe-o, CH2CH2OMe, CH2CH2SMe, CH2CH2NMe2) as neutral 2e, 4e or 8e donor ligands

Cyclodiphosphazanes having donor functionalities such as cis-[^tBuNP(OR)]₂ (R = C₆H₄OMe-o (2); R = CH₂CH₂OMe (3); R = CH₂CH₂SMe (4); R = CH₂CH₂NMe₂ (5)) were obtained in good yield by reacting cis-[^tBuNPCl]₂ (1) with corresponding nucleophiles. The reactions of 2-5 with [RuCl₂(η⁶-cymene)]₂, [MCl(COD)]₂ (M = Rh, Ir), [PdCl₂(PEt₃)]₂ and [MCl₂(COD)] (M=Pd, Pt) result in the formation of exclusively monocoordinated mononuclear complexes of the type cis-[{^tBuNP(OR)}₂ML_n-κP] irrespective of the reaction stoichiometry and the reaction conditions. In contrast, 2-5 react with [RhCl(CO)₂]₂, [PdCl(η³-C₃H₅)]₂, CuX (X=Cl, Br, I) to give homobinuclear complexes. Interestingly, CuX produces both mono and binuclear complexes depending on the stoichiometry of the reactants and the reaction conditions. The mononuclear complexes on treatment with appropriate metal reagents furnish heterometallic complexes.     

Half-sandwich binuclear carbaborane compounds: Closo-carbaboranes as good σ-donar ligands

The synthesis of half-sandwich binuclear transition-metal complexes containing the Cab^C,C chelate ligands (Cab^C,C = C₂B₁₀H₁₀ (1)) is described. 1Li₂ was reacted with chloride-bridged dimers [Cp∗RhCl(μ-Cl)]₂ (Cp∗ = η⁵-C₅(CH₃)₅), [Cp′RhCl(μ-Cl)]₂ (Cp′ = η⁵-1,3-^tBu₂C₅H₃), [Cp∗IrCl(μ-Cl)]₂ and [(p-cymene)RuCl(μ-Cl)]₂ to give half-sandwich binuclear complexes [Cp∗Rh(μ-Cl)]₂(Cab^C,C) (2), [Cp′Rh(μ-Cl)]₂(Cab^C,C) [3),[Cp∗Ir(μ-Cl)]₂(Cab^C,C) (4) and [(p-cymene)Ru(μ-Cl)]₂(Cab^C,C) (5), respectively. Addition reactions of the ruthenium complex 5 with air gave [(p-cymene)₂Ru₂(μ-OH)(μ-Cl)](Cab^C,C) (6), rhodium complex 2 with LiSPh gave [Cp∗Rh(μ-SPh)]₂(Cab^C,C) (7). The complexes were characterized by IR, NMR spectroscopy and elemental analysis. In addition, X-ray structure analysis were performed on complexes 2-7 where the potential C,C-chelate ligand was found to coordinate in a bidentate mode as a bridge.     

Organometallic dithiolene complexes of benzenedithiolate analogues with π-coordinating and π-interacting Cp* ligand

Organometallic dithiolene complexes, which were formulated as [Cp*M(dcbdt)] and [Cp*M(dcdmp)] (M = Co, Rh, Ir; Cp* = η⁵-pentamethylcyclopentadienyl, dcbdt = 4,5-dicyanobenzene-1,2-dithiolate, dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine) were prepared from a low valent Cp*Co^I or high valent Cp*M^III species (M^III = Co^III, Rh^III, Ir^III). The UV-Vis absorption spectral and electrochemical data of them were obtained. The lowest absorption (HOMO-LUMO) energies of them became redshift in order of the Co > Rh > Ir complexes. The reduction potentials suggested that the central metal modifies their LUMO levels. The molecular and crystal structures of [Cp*Co(dcbdt)] (3a), [Cp*Co(dcdmp)] (4a) and [Cp*Rh(dcdmp)] (4b) were determined by X-ray diffraction studies. The cobalt complexes 3a and 4a were monomeric, formally 16-electron complexes and have two-legged piano-stool geometries. The crystal structure of 3a indicated some plane-to-plane intermolecular interactions such as benzene?benzene interaction on the dcbdt ligand and two Cp*?benzene π-π stackings. 4a showed plane-to-plane interaction with a pseudo-4-fold-symmetry arrangement between the pyrazine moieties on the dcdmp ligand. The rhodium complex 4b was dimeric in the crystal to form a criss-cross arrangement and had a three-legged piano-stool geometry, but it was monomerized in solution. The dimer of 3b was observed in the oxidation process of the cyclic voltammogram.     

Addition of benzenethiol to terminal alkynes catalyzed by hydrotris(3,5-dimethylpyrazolyl)borate-Rh(III) bis(thiolate) complex: Mechanistic studies with characterization of the key intermediate

The Rh(III)-thiolate complex [Tp^∗Rh(SPh)₂(MeCN)] (2; Tp^∗ = hydrotris(3,5-dimethylpyrazolyl)borate) readily undergoes substitution of MeCN by XyNC (Xy = 2,6-dimethylphenyl) to give the isocyanide complex [Tp^∗Rh(SPh)₂(XyNC)] (3), whereas reaction of 2 with terminal alkynes results in the formation of the rhodathiacyclobutene complex [Tp^∗Rh(SPh){η²-CHCR(SPh)}] (4; R = aryl, alkyl). Molecular structures of 3 and 4 (R = CH₂Ph) have been determined by single crystal X-ray diffraction. Complex 2 as well as [Tp^∗Rh(cyclooctene)(MeCN)] have been found to catalyze regioselective addition of benzenethiol to terminal alkynes RCCH at 50 °C to give R(PhS)CCH₂ in moderate to high yields. The above products are selectively formed when R = CH₂Ph and n-C₆H₁₃, while cis-RCHCHSPh and RC(SPh)₂CH₃ are also obtained as by-products when R = p-MeOC₆H₄. Catalytic cycle involving 2 and 4 is proposed based on the mechanistic studies using NMR measurement.     

Heterobimetallic complexes as oxygen donor bidentate ligands: synthesis of early-late trinuclear complexes

The early-late heterometallic complexes [TiCp^∗((OCH₂)₂Py)(μ-O)M(COD)] (M = Rh, Ir) behave as four-electron donor ligands yielding the polynuclear cationic complexes [TiCp^∗(OCH₂)₂ Py(μ-O){M(COD)}₂]OTf (M = Rh (1), Ir (2)). The molecular structure of complex 1 has been established through an X-ray diffraction study.     

Synthesis and characterization of cyclometalated iridium(III) complexes containing pyrimidine-based ligands

New pyrimidine derivatives (pyr) have been synthesized using palladium-catalyzed Suzuki coupling reaction. These compounds can undergo cyclometalation with iridium trichloride to form bis-cyclometalated iridium complexes, (pyr)₂Ir(acac) (acac = acetylacetonate; pyr = cyclometalated pyr). The substituents at the both cyclometalated phenyl ring and pyrimidine ring were found to affect both electrochemical and photophysical properties of the complexes. Computation results on these complexes are consistent with the electrochemical and photophysical data. The complexes are green-emitting with good solution quantum yields at ∼0.30. Light-emitting devices using these complexes as dopants were fabricated, and the device performance at 100 mA/cm² are moderate: 9 (17 481 cd/m², 4.8%, 18 cd/A, 5.1 lm/W); 10 (18 704 cd/m², 4.9%, 18.9 cd/A, 4.7 lm/W); 13 (20 942 cd/m², 5.4%, 21.0 cd/A, 6.1 lm/W).     

Stepwise formation of metallo-prisms of iridium and rhodium complexes bearing pentamethylcyclopentadienyl ligands

Reactions of [M(Cp^∗)Cl(μ-Cl)]₂ (M = Ir(1a); M = Rh(1b)) with tridentate ligands tpt (tpt = 2,4,6-tripyridyl-1,3,5-triazine) gave the corresponding trinuclear complexes [M₃(Cp^∗)₃(μ₃-4-tpt-κN)Cl₆] (M = Ir(2a); M = Rh(2b)), which can be converted into hexanuclear complexes [M₆(Cp^∗)₆(μ₃-4-tpt-κN)₂(μ-Cl)₆](O₃SCF₃)₆ (M = Ir(3a); M = Rh(3b)) by treatment with AgO₃SCF₃, respectively. X-ray of 3b revealed that each of six pentamethylcyclopentadienyl metal moieties was connected by two μ-Cl-bridged atoms and a tridentate ligand to construct a cation triangular metallo-prism cavity with the volume of about 273 Å³ based on the distance of the two triazine moieties is 3.62 Å.     

Cytotoxic half-sandwich rhodium(III) complexes: Polypyridyl ligand influence on their DNA binding properties and cellular uptake

The DNA binding of polypyridyl (pp) (η⁵-C₅Me₅)Rh^III complexes of the types [(η⁵-C₅Me₅)RhCl(pp)](CF₃SO₃) (2-6) (pp = bpy, phen, dpq, dppz, dppn), [(η⁵-C₅Me₅)Rh{(Me₂N)₂CS}(pp)](CF₃SO₃)₂ (7-9) (pp = dpq, dppz, dppn) and [(η⁵-C₅Me₅)Rh(L)(pp)](CF₃SO₃) (10) (L = C₆H₅S⁻) and (11) (L = C₁₀H₇S⁻) has been studied by UV/Vis spectroscopy, circular dichroismus and viscosity measurements. Complexes 3-11 are cytotoxic towards the human MCF-7 breast and HT-29 colon cancer cell lines and exhibit IC₅₀ values in the range 0.56-10.7 μM. Stable intercalative binding into CT-DNA is indicated for the dpq and dppz complexes by large increases ΔT_m of 6-12 °C in the DNA thermal denaturation temperature for r = [complex]/[DNA] = 0.1 and by induced CD bands and large viscosity increases. In contrast, significant DNA lengthening is not observed after incubation of the biopolymer with the dppn complexes 2 and 9 at molar ratios of r < 0.08. Pronounced hypochromic shifts for the π-π^∗ transitions of the dppn ligands in the range 320-425 nm indicate the possible presence of surface stacking. The in vitro cytotoxicities of the chloro complexes 4-6 and the (Me₂N)₂CS complexes 7-9 are dependent on the size of the polypyridyl ligand with IC₅₀ values decreasing in the order dpq > dppz > dppn. For instance, IC₅₀ values of 5.3, 1.5 and 0.91 μM were determined for 7-9 against MCF-7 cells. Rapid Cl⁻/H₂O exchange leads the formation of aqua dications for 4-6, whose levels of cellular uptake and cytotoxicities are similar to those established for 7-9. Intramolecular interactions between the aromatic thiolate and dppz ligands of 10 and 11 prevent significant DNA intercalation. X-ray structural determinations have been performed for 2-7 and 11.     

Substituted cyclopentadienylchromium(III) complexes containing neutral donor ligands. Synthesis, crystal structures and reactivity in ethylene polymerization

Lithium derivatives of substituted cyclopentadiene ligands reacted with CrCl₃(THF)₃ in THF solution to afford homodinuclear complexes of the type [{(η⁵-RCp)CrCl(μ-Cl) }₂] [R=SiMe₃ (1), CH₂C(Me)CH₂ (2)]. Complex 1 reacts with pyrazole (C₃H₄N₂) to yield the mononuclear half-sandwich complex [(η⁵-Me₃SiCp)CrCl₂(pyrazole)] (3). The similar complex [Cp*CrCl₂(pyrazole)] (4) was synthesised by reaction of [{Cp*CrCl(μ-Cl)}₂] with pyrazole. Complex 2 reacts with bidentate ligands to give binuclear complexes of the type [{(η⁵-CH₂C(Me)CH₂Cp)CrCl₂ }₂(μ-L-L)] [L-L=Ph₂PCH₂CH₂PPh₂ (5), trans-Ph₂P(O)CHCHP(O)Ph₂ (6)]. All complexes were structurally characterised by X-ray diffraction. After reaction with methylaluminoxane these complexes are active in the polymerization of ethylene. At 25 °C and 4 bar of ethylene, complex 3 yields polyethylene with a bimodal molecular weight distribution centred at 155,000 and 2000 g/mol. Complex 4 shows similar activity, yielding only the low molecular weight fraction. On the other hand, the binuclear complexes 5 and 6 under the same conditions were three times more active than mononuclear complexes. The melting point of the polymers indicates the formation of linear polyethylene.     

Syntheses and characterization of mono and dinuclear complexes of platinum group metals bearing benzene-linked bis(pyrazolyl)methane ligands

Reaction of the benzene-linked bis(pyrazolyl)methane ligands, 1,4-bis{bis(pyrazolyl)-methyl}benzene (L1) and 1,4-bis{bis(3-methylpyrazolyl)methyl}benzene (L2), with pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh and Ir) in the presence of NH₄PF₆ results under stoichiometric control in both, mono and dinuclear complexes, [(η⁵-C₅Me₅)RhCl(L)]⁺ {L = L1 (1); L2 (2)}, [(η⁵-C₅Me₅)IrCl(L)]⁺ {L = L1 (3); L2 (4)} and [{(η⁵-C₅Me₅)RhCl}₂(μ-L)]²⁺ {L = L1 (5); L2 (6)}, [{(η⁵-C₅Me₅)IrCl}₂(μ-L)]²⁺ {L = L1 (7); L2 (8)}. In contrast, reaction of arene ruthenium complexes [(η⁶­arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me and C₆Me₆) with the same ligands (L1 or L2) gives only the dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(μ-L)]²⁺ {L = L1 (9); L2 (10)}, [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(μ-L)]²⁺ {L = L1 (11); L2 (12)} and [{(η⁶-C₆Me₆)RuCl}₂(μ-L)]²⁺ {L = L1 (13); L2 (14)}. All complexes were isolated as their hexafluorophosphate salts. The single-crystal X-ray crystal structure analyses of [7](PF₆)₂, [9](PF₆)₂ and [11](PF₆)₂ reveal a typical piano-stool geometry around the metal centers with six-membered metallo-cycle in which the 1,4-bis{bis(pyrazolyl)-methyl}benzene acts as a bis-bidentate chelating ligand.     

Half-sandwich Ru(II), Ir(III) and Rh(III) complexes with bridging or chelating N-heterocyclic bis-carbene ligand: Synthesis and characterization

N-heterocyclic bis-carbene ligand (bis-NHC) which was derived from 1,1′-diisopropyl-3,3′-ethylenediimidazolium dibromide (L·2HBr) via silver carbene transfer method, reacted with [(η⁶-p-cymene)RuCl₂]₂ and [Cp^∗MCl₂]₂ (Cp^∗ = η⁵-C₅Me_5, M = Ir, Rh) respectively, afforded complexes [(η⁶-p-cymene)RuCl₂]₂(L) (1), [Cp^∗IrCl₂]₂(L) (2) and [Cp^∗RhCl(L)][Cp^∗RhCl₃] (3). When [Cp^∗IrCl₂]₂ was treated with 2 equiv AgOTf at first, and then reacted with bis-NHC ligand, [Cp^∗IrCl(L)]OTf (4) was obtained. The molecular structures of complexes 1-4 were determined by X-ray single crystal analysis, showing that 1 and 2 adopted bridging coordination mode, 3 and 4 adopted chelating coordination mode. All of these complexes were characterized by ¹H, ¹³C NMR spectroscopy and element analysis.     

Synthesis of 2-picolyl functionalized η-cyclopentadienyl derivatives of rhodium(I) and iridium(I) and preliminary study of their reaction with ruthenium(II) for assembling hetero-bimetallic complexes

The 2-picolylcyclopentadienyl derivatives of rhodium(I) and iridium(I) of formula [M{η⁵-C₅H₄(2-CH₂C₅H₄N)}(η⁴-C₈H₁₂)] (3) (M = Rh) and (4) (M = Ir) are obtained in good yields by reacting 2-picolylcyclopentadienyllithium (7) with [RhCl(η⁴-C₈H₁₂)]₂ and [IrCl(η⁴-C₈H₁₂)]₂, respectively. The corresponding dicarbonyl derivatives, [M{η⁵-C₅H₄(2-CH₂C₅H₄N)}(CO)₂] (5) (M = Rh) and 6 (M = Ir), are obtained in good yields by reacting 2-picolylcyclopentadienylthallium(I) (8) with [RhCl(CO)₂]₂ and [IrCl(C₅H₅N)(CO)₂], respectively. 5 has already been reported in the literature. The new complexes were characterized by elemental analysis, mass spectrometry, ¹H NMR, FT-IR, and UV-Vis (210-330 nm) spectroscopy. The UV-Vis spectra indicate the existence of some electronic interaction between the 2-picolinic chromophore and the cyclopentadienyl-metal moiety. The study of the electrochemical behaviour of 3-6 by cyclic voltammetry (CV) allows the interpretation of the electrode processes and gives information about the location of the redox sites. Moreover, various synthetic strategies were tested in order to try to coordinate the complexes 3-6 to a ruthenium(II) centre, but most of them failed. Instead, the hetero-bimetallic complex bis(2,2′-bipyridine)[(η⁵-2-picolylcyclopentadienyl)(η⁴-cycloocta-1,5-diene)rhodium(I)]chlororuthenium(II)-(hexafluorophosphate) (13), was obtained, although in poor yields (10%), by reacting the nitrosyl complex [RuCl(bipy)₂(NO)][PF₆]₂14 (bipy = 2,2′-bipyridine) first with potassium azide and then with the rhodium(I) complex 3. The analogous complex bis(2,2′-bipyridine)(2-picoline)chlororuthenium(II)-(hexafluorophosphate) (15), that carries a ruthenium-bonded 2-picoline molecule instead of 3, has prepared in the same way. 13 and 15 were characterized by elemental analysis, mass spectrometry, and ¹H NMR.     

Cationic half-sandwich complexes (Rh, Ir, Ru) containing 2-substituted-1,8-naphthyridine chelating ligands: Syntheses, X-ray structure analyses and spectroscopic studies

Reactions of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me) and [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh, Ir) with 2-substituted-1,8-naphthyridine ligands, 2-(2-pyridyl)-1,8-naphthyridine (pyNp), 2-(2-thiazolyl)-1,8-naphthyridine (tzNp) and 2-(2-furyl)-1,8-naphthyridine (fuNp), lead to the formation of the mononuclear cationic complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ {L = pyNp (1); tzNp (2); fuNp (3)}, [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ {L = pyNp (4); tzNp (5); fuNp (6)}, [(η⁵-C₅Me₅)Rh(L)Cl]⁺ {L = pyNp (7); tzNp (8); fuNp (9)} and [(η⁵-C₅Me₅)Ir(L)Cl]⁺ {L = pyNp (10); tzNp (11); fuNp (12)}. All these complexes are isolated as chloro or hexafluorophosphate salts and characterized by IR, NMR, mass spectrometry and UV/Vis spectroscopy. The molecular structures of [1]Cl, [2]PF₆, [4]PF₆, [5]PF₆ and [10]PF₆ have been established by single crystal X-ray structure analysis.     

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

Reactions of 0.5 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = η⁶-C₆H₆, η⁶-p-ⁱPrC₆H₄Me) and [(Cp∗)M(μ-Cl)Cl]₂ (M = Rh, Ir; Cp∗ = η⁵-C₅Me₅) with 4,6-disubstituted pyrazolyl-pyrimidine ligands (L) viz. 4,6-bis(pyrazolyl)pyrimidine (L1), 4,6-bis(3-methyl-pyrazolyl)pyrimidine (L2), 4,6-bis(3,5-dimethyl-pyrazolyl)pyrimidine (L3) lead to the formation of the cationic mononuclear complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ (L = L1, 1; L2, 2; L3, 3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ (L = L1, 4; L2, 5; L3, 6), [(Cp∗)Rh(L)Cl]⁺ (L = L1, 7; L2, 8; L3, 9) and [(Cp∗)Ir(L)Cl]⁺ (L = L1, 10; L2, 11; L3, 12), while reactions with 1.0 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ and [(Cp∗)M(μ-Cl)Cl]₂ give rise to the dicationic dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (L = L1, 13; L2, 14; L3, 15), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (L = L1, 16; L2, 17; L3, 18), [{(Cp∗)RhCl}₂(L)]²⁺ (L = L1, 19; L2, 20; L3, 21) and [{(Cp∗)IrCl}₂(L)]²⁺ (L = L1 22; L2, 23; L3 24). The molecular structures of [3]PF₆, [6]PF₆, [7]PF₆ and [18](PF₆)₂ have been established by single crystal X-ray structure analysis.