Reaction of iron and ruthenium halogenide complexes with GaCp and AlCp: Insertion, Cp transfer reactions and orthometallation

The reactions of the Fe(II) and Ru(II) halogenide complexes [Fe(PPh₃)₂Br₂], [Fe(NCCH₃)₂Br₂], [Ru(PPh₃)₃Cl₂], and [Ru(dmso)₄Cl₂] with GaCp^∗ and AlCp^∗, respectively, are investigated. The reactions of [FeBr₂L₂] with ECp^∗ exclusively proceed via Cp^∗ transfer, leading to [FeCp^∗(GaCp^∗)(GaBr₂)(PPh₃)] (1) (L = PPh₃, E = Ga), [FeCp^∗(GaCp^∗)₂ (GaBr₂)] (2) (L = NCCH₃, E = Ga) and [FeCp^∗(μ³-H)(κ²-(C₆H₄)PPh₂)(AlCp^∗)(AlBr₂)] (3) (L = PPh₃, E = Al), the latter of which is formed via orthometallation of one PPh₃ ligand. The reaction of [Ru(dmso)₄Cl₂] leads to the homoleptic complex [Ru(GaCp^∗)₆Cl₂] (4) in high yields, while [Ru(PPh₃)₃Cl₂] gives 4 in rather low yields. The reason for this difference in reactivity is investigated and it is shown that Cp^∗ transfer and orthometallation are the limiting side reactions of the reaction of [Ru(PPh₃)₃Cl₂] with GaCp^∗. All compounds were characterized by NMR spectroscopy, and single crystal X-ray diffraction studies were performed for 1, 3, and 4.     

Synthesis and structural characterization of dinuclear complexes of trivalent aluminum, gallium, indium and chromium derived from pyrazole-2-ethanol

The reaction of 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL) with anhydrous metal(III) halides (M = Al, Ga, In and Cr) results in the isolation of four novel dinuclear complexes [Al(μ-L)Cl₂]₂ (1), [Ga(μ-L)Cl₂]₂ (2), [In(μ-L)Br₂(H₂O)]₂·2thf (3) and [Cr(μ-L)Cl₂(H₂O)]₂·1.5thf (4) in good yields. The new complexes have been characterized with the aid of analytical and spectroscopic studies. A single crystal X-ray structure determination in each case confirms the dimeric structure for all the complexes in the solid-state. The pyrazole ethanol ligand binds to the metal through both pyrazole nitrogen and bridging alkoxide oxygen terminals with the formation of a central M₂O₂ core involving the ethoxide anion. The metal(III) center is pentacoordinated in compounds 1 and 2, while it is hexacoordinated in compounds 3 and 4.     

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.     

One-pot syntheses of alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III) bearing p-cymene or pentamethylcyclopentadienyl groups

Reaction of [(p-cymene)RuCl₂(PPh₃)] (1) or [Cp^∗MCl₂(PPh₃)] (Cp^∗ = C₅Me₅) (3a: M = Rh; 4a: M = Ir) with 1-alkynes and PPh₃ were carried out in the presence of KPF₆, generating the corresponding alkenyl-phosphonio complexes, [(p-cymene)RuCl(PPh₃){CHCR(PPh₃)}](PF₆) (2a: R = Ph; 2b: R = p-tolyl) or [Cp^∗MCl(PPh₃){CHCPh(PPh₃)}](PF₆) (5: M = Rh; 6: M = Ir). Similar reactions of complexes [Cp^∗RhCl₂(L¹)] (3a: L¹ = PPh₃; 3c: L¹ = P(OMe)₃) with L² (L² = PPh₃, PMePh₂, P(OMe)₃) gave [Cp^∗RhCl(L¹)(L²)](PF₆) (7bb: L¹ = L² = PMePh₂; 7ca: L¹ = P(OMe)₃, L² = PPh₃; 7cc: L¹ = L² = P(OMe)₃). Alkenyl-phosphonio complex 5 was treated with P(OMe)₃ or 2,6-xylyl isocyanide, affording [Cp^∗RhCl(L){CHCPh(PPh₃)}](PF₆) (8a: L = P(OMe)₃; 8b: L = 2,6-xylNC). X-ray structural analyses of 2a, 6 and 8a revealed that the phosphonium moiety bonded to the C_β atom of the alkenyl group are E configuration.     

Vanadium complexes with 2-pyridineformamide thiosemicarbazones: In vitro studies of insulin-like activity

Reaction of VOCl₂ with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives in ethanol gave as products [VO(H2Am4DH)Cl₂] (1), [VO(H2Am4Me)Cl₂] · 1/2HCl (2), [VO(H2Am4Et)Cl₂] · HCl (3) and [VO(2Am4Ph)Cl] (4). Upon the dissolution of 1-4 in water, oxidation immediately occurs with the formation of [VO₂(2Am4DH)] (5), [VO₂(2Am4Me)] (6), [VO₂(2Am4Et)] (7) and [VO₂(2Am4Ph)] (8). The crystal and molecular structures of 5 and 6 were determined. Complexes 5-8 inhibited glycerol release in a similar way to that observed with insulin but showed a low enhancing effect on glucose uptake by rat adipocytes.     

Synthesis, structure, and formation mechanism of the halogen-bridged tricobalt clusters, [Co3Cp3(μ3-CPh)2(μ-X)] (X=Cl, Br, and I)

Reactions of a benzylidyne-capped tricobalt cluster, [Co₃Cp₃(μ₃-CPh)₂] (1), with halogens (X₂ = Cl₂, Br₂, and I₂) in CH₂Cl₂ afforded halogen-adducts of 1. The structure of four isolated salts [Co₃Cp₃(μ₃-CPh)₂(μ-Cl)]PF₆ · MeCN (2PF₆ · MeCN), [Co₃Cp₃(μ₃-CPh)₂(μ-Br)]SbF₆ (3SbF₆), [Co₃Cp₃(μ₃-CPh)₂(μ-I)]SbF₆ · CH₂Cl₂ (4SbF₆ · CH₂Cl₂), and [Co₃Cp₃(μ₃-CPh)₂(μ-I)]I₃ (4I₃) determined by X-ray diffraction can be regarded formally as halide-adducts of 1²⁺. The halogen atom in each structure lies in the Co₃ plane. The halogen-bridged Co-Co edge was elongated (in 2PF₆ · MeCN = 2.6072(4), in 3SbF₆ = 2.6106(7), in 4SbF₆ · CH₂Cl₂ = 2.622(2), and in 4I₃=2.6718(9) Å), and the Co-Co distances that had no halogen-bridge remained unchanged from the Co-Co distance of 1 (2.382(8) Å), (in 2PF₆=2.4037(8) and 2.3948(7), in 3SbF₆=2.3888(6) and 2.4017(7), in 4SbF₆ · CH₂Cl₂ = 2.393(2) and 2.388(1), and in 4I₃ = 2.397(1) and 2.3868(9) Å). The UV-Vis absorption spectra of 2⁺, 3⁺, and 4⁺ had characteristic absorption peaks at 796, 819, and 844 nm, respectively. Cyclic voltammograms of 2PF₆ in CH₂Cl₂ with 0.1 M ⁿBu₄NPF₆ as the supporting electrolyte showed a chemically reversible oxidation (at a potential of 0.75 V versus Fc/Fc⁺), and an irreversible reduction wave at −0.57 V. The irreversible reduction resulted in the recovery of 1. The redox properties of 3⁺ and 4⁺ are very similar to that of 2⁺. Cyclic voltammetry of 1 in 0.1 M ⁿBu₄NCl/MeCN indicates that the formation of 2⁺ is a multi-step reaction. Initially, 1 is oxidized to 1⁺, and then, 1⁺ is coordinated by Cl⁻ followed by immediate oxidation to 2⁺.     

Structural comparison of (pentamethylcyclopentadienyl)iridium(III) azido complexes containing potentially N,S-bidentate N-heterocyclic thiolates: 2- or 8-quinolinethiolate and benzimidazole-2-thiolate

The crystal structures of mononuclear (azido)(pentamethylcyclopentadienyl)iridium(III) complexes bearing 2- or 8-quinolinethiolate (n-Sqn⁻), [Cp^∗Ir(N₃)(n-Sqn)] {n = 2 (1) or 8 (2); Cp^∗ = η⁵-C₅Me₅} have been determined by X-ray analysis. The 2-Sqn complex, 1, acquires severe steric strains in the four-membered κ²N,S chelate ring, while the 8-Sqn isomer, 2, forms a strain-free five-membered planar κ²N,S chelate ring. It has also been revealed that the corresponding benzimidazole-2-thiolate (Hbimt⁻) complex, which was obtained similarly to the above n-Sqn complexes from [Cp^∗Ir(N₃)₂]₂ and Na(Hbimt), takes an unsymmetrical dinuclear structure bridged by two Hbimt⁻ ligands with different bonding modes, [Cp^∗Ir(N₃){μ(S:N¹)-Hbimt}{μ(S:S)-Hbimt}Ir(N₃)Cp^∗] · MeOH (3).     

Mononuclear and polynuclear halide and nitrate Cu(II) compounds with 1,4,5-triazanaphthalene as a ligand: Characterization, magnetism and X-ray structures

Using the ligand 1,4,5-triazanaphthalene (abbreviated as tan) in combination with Cu(II) salts, three mononuclear compounds, Cu(tan)₂Cl₂ (1), Cu(tan)₂Br₂ (3), Cu(tan)₂(NO₃)₂ (5) and three polynuclear compounds, [Cu(tan)Cl₂]_n (2), [Cu(tan)Br₂]_n (4), [Cu(tan)(NO₃)₂]_n (6) have been synthesized and characterized by UV-Vis, EPR, FTIR and Far-FTIR spectroscopies. The crystal structures of compounds 1, 3, 5 and 6 are reported, as well as that of the dioxane adduct of compound 4, [Cu(tan)Br₂(C₄H₈O₂)](C₄H₈O₂) (4A).The structure of (2) was solved by X-ray powder diffraction. The coordination geometry around the Cu(II) atoms is tetrahedral for (1) and (3), square-pyramidal for (4A) and distorted octahedral for (5) and (6). Magnetic susceptibility measurements on the polynuclear compounds revealed weak antiferromagnetic interactions between the Cu(II) atoms with interaction constants (J) of J = −9.1 and −10.5 cm⁻¹, for 4 and 6, respectively. For compound 2 two options for possible interactions were considered, with interaction constants which vary for J_rung −22.0 to −13.5 cm⁻¹ and J_rail −19.6 to −17.0 cm⁻¹. These figures are discussed in the light of relevant structural parameters and literature.     

Synthesis and characterization of CpMCl(PR3)(S or W-η-butadienesulfonyl) compounds of rhodium and iridium

A metathesis reaction of [Cp^∗MCl₂(PR₃)] [M = Rh, R = Ph (1), Me (3); M = Ir, R = Ph (2), Me (4)] takes place in the presence of potassium butadienesulfinate (SO₂CHCHCHCH₂)K (9) to afford the mononuclear compounds [Cp^∗M(Cl)(PR₃)(η¹-SO₂CHCHCHCH₂)] [M = Rh, R = Ph (11S), (11W); M = Rh, R = Me (13S), (13W)] and [M = Ir, R = Ph (12S); M = Ir, R = Me (14S), (14W)] under different reaction conditions. The addition of PR₃ (R = Ph, Me) to Cp^∗Ir(Cl)[(1,2,5-η)-SO₂CHCHCHCH₂] (7) affords the corresponding iridium isomers 12S, 12W and 14S, in a non-selective reaction, along with the corresponding dichloride compounds 2 or 4. The ¹H and ¹³C{¹H} NMR data are consistent with the butadienesulfonyl ligands coordinated exclusively through the sulfur atom, and they show the presence of two isomers, described as the S and W conformers, which can be isolated separately. There is clear evidence that these isomers correspond to the kinetic and thermodynamic derivatives, respectively.     

Zinc(II) complexes with 1,8-naphthyridine-based ligand: Crystal structures and luminescent properties

The reactions of 2,4-dimethyl-7-(2-pyridylamino)-1,8-naphthyridine (L1) with Zn(ClO₄)₂ · 6H₂O, and bis(5,7-dimethyl-1,8-naphthyrid-2-yl)amine ligand (L2) with Zn(OAc)₂ · 2H₂O, ZnCl₂ or Zn(ClO₄)₂ · 6H₂O afforded four blue luminescent zinc(II) complexes, [Zn(L1)₂](ClO₄)₂ · 2CH₂Cl₂ (1), [Zn(L2)(OAc)₂] · CH₂Cl₂ (2), [Zn(L2)₂][ZnCl₄] · 3.5CH₂Cl₂ (3) and [Zn(L2)₂](ClO₄)₂ (4), respectively. Crystal structures of complexes 1-3 have been determined by X-ray structural analyses as mononuclear complexes with pseudo-tetrahedral geometry. The crystal packing of 1 reveals the coordination cation which is self-assembled to stair chains through aromatic π-π interactions. The intermolecular N-H?O hydrogen bond in 2 generates a centrosymmetric H-bonded dimer. However, the crystal lattice of 3 shows that the molecules are linked by extensive intermolecular hydrogen bonds between the amino groups and the anions, resulting in a one-dimensional zigzag chain. Furthermore, these molecular pairs or chains were self-assembled to two-dimensional sheets or three-dimensional networks through aromatic π-π interactions. All the zinc(II) complexes display intense intraligand ¹(π-π^∗) fluorescence with λ_max at 380 and 393 nm for 1, 385 and 404 nm for 2-4 in methanol at room temperature, respectively. Emission quantum yields of these complexes are in the range from 0.41 to 0.57. The broad emission bands in their solid-state emission spectra are attributed to intraligand ¹(π-π^∗) transition and aromatic π-π interactions as well.     

Syntheses and characterization of titanium malonato and amino acid complexes: [Ti(cp)2(OOCCH2NMe2)] - The first structurally characterized α-amino acid titanium(III) complex

The reaction of [Ti(cp^∗)₂(BTMSA)] (1) (cp^∗ = η⁵-C₅Me₅, BTMSA = bis(trimethylsilyl)acetylene) with malonic acids ((HOOC)₂CR₂, R = H, Me) and N,N-dimethylglycine resulted in the formation of titanium(IV) dicarboxylato complexes [Ti(cp^∗)₂{(OOC)₂CR₂}] (R = H, 2; R = Me, 3) and an α-amino acid titanium(III) complex [Ti(cp^∗)₂(OOCCH₂NMe₂)] (4). The identities of complexes 2-4 were confirmed by microanalysis, ¹H and ¹³C NMR spectroscopy (2, 3), ESI-MS and CID experiments (2, 3) as well as by ESR and magnetic measurements (μ_eff = 1.81, 298 K) for 4. Single X-ray diffraction analyses of 2 and 4 exhibited monomolecular complexes in which the titanium atom is distorted tetrahedrally coordinated by two η⁵-C₅Me₅ rings and by the chelating bound malonato-κ²O,O′ (2) and N,N-dimethylglycinato-κ²O,O′ ligand (4).     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

Synthesis, characterizations and crystal structures of antimony(III) complexes with nitrogen-containing ligands

Six antimony adducts with N-donor neutral ligands (1,10-phenanthroline, 4,4′-bipyridine) have been obtained following the reaction of antimony halides with phenanthroline and 4,4′-bipyridine. By changing the solvent and stoichiometry, we obtained six different complexes, Sb(phen)Cl₃ (1), Sb(phen)Br₃ (2), Sb₂(phen)₄Br₈ (3) and Sb(bpy)Cl₃ (4), Sb(bpy)₂Cl₃ (5), Sb(bpyH · bpyH₂)Br₆ (6) (where phen = 1,10-phenanthroline, bpy = 4,4′-bipyridine). All the complexes have been characterized via elemental analysis, FT-IR and NMR (¹H, ¹³C) spectroscopy. The crystal structures of complexes 2, 3 and 6 have been determined by X-ray single crystal diffraction.The structural analysis show that the coordination sphere around antimony atom in complex 2 is a distorted square pyramid, coordinated by three bromine atoms and two nitrogen atoms from phen. In complex 3, the central antimony atom is six-coordinated through four bromine atoms and two nitrogen atoms forming a distorted octahedral geometry. Besides that, there are also uncoordinated 1,10-phenanthroline bonded by hydrogen bonds and π-π stacking interactions, which is rarely observed in previous reports. The crystal structure of complex 6 consists of bpyH · bpyH₂ trications and hexabromoantimonate trianions. The antimony atom in the anion has a distorted octahedral environment. Additionally, all complexes present a 3D framework built up by N-H?Br, C-H?Br and C-H?Cl weak hydrogen bonds interactions.     

Structural variations and spectroscopic properties of copper(I) complexes with bis(schiff base) ligands

Six copper(I) complexes {[Cu₂(L1)(PPh₃)₂I₂] · 2CH₂Cl₂}_n (1), {[Cu₂(L2)(PPh₃)₂]BF₄}_n (2), [Cu₂(L3)(PPh₃)₄I₂] · 2CH₂Cl₂ (3), [Cu₂(L4)(PPh₃)₄I₂] (4), [Cu₂(L5)(PPh₃)₂I₂] (5) and [Cu₂(L6)(PPh₃)₂I₂] (6) have been prepared by reactions of bis(schiff base) ligands: pyridine-4-carbaldehyde azine (L1), 1,2-bis(4′-pyridylmethyleneamino)ethane (L2), pyridine-3-carbaldehyde azine (L3), 1,2-bis(3′-pyridylmethyleneamino)ethane (L4), pyridine-2-carbaldehyde azine (L5), 1,2-bis(2′-pyridylmethyleneamino)ethane (L6) with PPh₃ and copper(I) salt, respectively. Ligand L1 or L2 links (PPh₃)₂Cu₂(μ-I)₂ units to form an infinite coordination polymer chain. Ligand 3 or 4 acts as a monodentate ligand to coordinate two copper(I) atoms yielding a dimer. Ligand 5 or 6 chelates two copper(I) atoms using pyridyl nitrogen and imine nitrogen to form a dimer. Complexes 1-4 exhibit photoluminescence in the solid state at room temperature. The emission has been attributed to be intraligand π-π* transition mixed with MLCT characters.     

Addition compounds of MoO2Cl2 with chiral sulfoxides. First molecular structures of dioxomolybdenum complexes bearing chiral non-racemic sulfoxide as ligand

MoO₂Cl₂(L)₂ [L = (R)-(+)-methyl-p-tolylsulfoxide (R-MeTolSO) (1), methyl-p-tolylsulfoxide (MeTolSO) (2), 2-benzenesulfinyl-1,1-diphenylethanol (BSDPE) (3), 1-benzenesulfinyl-2-methyl-2-propanol (BSMP) (4), benzenesulfinylmethyl 4-methylphenyl ketone (BSMMPK) (5)], and MoO₂Cl₂(L) [L = BSDPE (6), BSMP (7), BSMMPK (8), (S,S)-bis(p-tolylsulfinyl)methane (S,S-TolSOCH₂SOTol) (9), bis(methylsulfinyl)methane (MeSOCH₂SOMe) (10), bis(phenylsulfinyl)methane (PhSOCH₂SOPh) (11)] have been synthesized by reacting a solution of MoO₂Cl₂(H₂O)₂ in diethyl ether with the corresponding ligand. The crystal and molecular structures of 1, 2, and 9 have been established by X-ray diffraction analysis. The ability of 1 and 9 as catalysts for the enantioselective reduction of sulfoxides to sulphides and the oxidation of sulphides to sulfoxides has been examined.     

Octahedral (cyclopentadienyl)rhodium clusters [Rh6Cp6(μ6-C)] and [Rh6Cp6(μ3-CO)2]: Synthesis, structures and electrochemistry

The 86-electron dicationic octahedral rhodium clusters containing Cp (Cp = C₅H₅) ligands and either an interstitial carbon atom, [Rh₆Cp₆(μ₆-C)]²⁺ ([1]²⁺), or two carbonyl groups, [Rh₆Cp₆(μ₃-CO)₂]²⁺ ([2]²⁺), were synthesized in low yields by reactions of Rh₃Cp₃(μ-CO)₃ with RhCp(C₂H₄)₂ or [RuCp^∗(MeCN)₃]⁺ (Cp^∗ = C₅Me₅), respectively. The structures of [1]²⁺ and [2]²⁺ were determined by X-ray diffraction. Their electrochemical behavior proved that they possess a rather extended electron transfer activity. In accordance with DFT calculations, the nearly octahedral structure of [1]²⁺ and [2]²⁺ is retained both upon oxidation (2+/3+) and the first reduction (2+/+); however, the second reduction (+/0) results in the breaking of one (for [1]⁰) or two (for [2]⁰) Rh-Rh bonds. In the case of the related Dahl’s nickel cluster Ni₆Cp₆ the nearly octahedral structure is retained upon all redox steps (3+/2+/+/0/−/2−).     

Products of the reaction of 9-nickelafluorenyllithium with iodine and different cyclopentadienyl-metal complexes

9-Nickelafluorenyllithium (1) reacted with iodine and then with various Cp_xM complexes (Cp_x = Cp, Cp^∗, M = Na, Mg, Li) in different solvents. The products (π-allyl complexes), isolated from these reactions, were formed via addition of the biphenyl ligand to the Cp ring originally bonded to the Ni atom. Stereospecifity of the reactions depended on the used solvent. π-Allyl compounds 2, 3 and 4 were characterized by X-ray single crystal analysis.     

Synthesis, photoluminescence and electrochemiluminescence of ruthenium(II) polypyridyl complexes based on bipyridine derivatives with carbazole moieties

Six complexes (1-6) with the type of [Ru(bpy)₂L]X₂ (1-3: L = L1-L3, X = Cl⁻; 4-6: L = L1-L3, X = PF₆⁻) were synthesized based on 2,2′-bipyridine and three 2,2′-bipyridine derivatives L1, L2 and L3 (L1 = 5,5′-dibromo-2,2′-bipyridine, L2 = 5-bromo-5′-carbazolyl-2,2′-bipyridine, L3 = 5,5′-dicarbazolyl-2,2′-bipyridine). The complexes 1-6 were characterized by ¹H NMR, MS(ESI) and IR spectra, along with the X-ray crystal structure analysis for 1, 5 and 6. Their photophysical properties and electrochemiluminescence (ECL) properties were investigated in detail. In the UV-Vis absorption spectra, all complexes 1-6 show strong intraligand (π → π^∗) transitions and metal-ligand charge transfer (MLCT, dπ (Ru) → π^∗) bands. Upon the excitation wavelengths at ∼508 nm, all complexes 1-6 exhibit typical MLCT emission of ruthenium(II) polypyridyl complexes. The introduction of carbazole moieties improves the MLCT absorption and emission intensity. The ruthenium(II) complexes 1-6 exhibit good electrochemiluminescence (ECL) properties in [Ru(bpy)₂L]²⁺/tri-n-propylamine (TPrA) acetonitrile solution and the complexes with PF₆⁻ showed higher ECL emission intensity than that of the complexes with Cl⁻ based on the same ligands.     

Polynuclear and polymeric metal complexes based upon 1,2,4-triazolyl functionalized adamantanes

A series of coordination compounds [Cd₂(trad)₇Br₂][Cd(trad)Br₃]₂ (1), [Cd₃(trad)₆{N(CN)₂}₄(H₂O)₂](N(CN)₂)₂ (2), [{Cd₂(trad)₅}{Cd(N(CN)₂)₆}]·3CH₃OH (3), [{Cd₃(trad)₆(SeCN)₂}{Cd(SeCN)₄}₂] (4), [Cd₂(trad)₃(NCS)₄] (5), [Cd₃(tr₂ad)₃(μ-NCS)₃](NCS)₃ (6), [Cd₃(tr₂ad)₆](NO₃)₆·22H₂O (7), [Cu₃(tr₂ad)₄(SO₄)(H₂O)₃](SO₄)₂·34H₂O (8) and [Cu₂(OH)(tr₂ad)₂](NO₃)₃·4H₂O (9) (trad = 4-(adamantan-1-yl)-1,2,4-triazole; tr₂ad = 1,3-bis(1,2,4-triazol-4-yl)-adamantane) revealed the potential of 1,2,4-triazolyl functionalized adamantanes for design of metal-organic polymers incorporating polynuclear coordination units as multiconnected nodes. Structures 1-5 are based upon characteristic di- and trinuclear clusters involving triple triazole bridges [M(μ₂-trad)₃M] (M = Cd), while doubling of the ligand functionality (tr₂ad) allows integration of the clusters into 3D polymeric frameworks 6-9 (M = Cd, Cu).     

Unexpected structural and electronic effects of internal rotation in diruthenium paddlewheel complexes containing bulky carboxylate ligands

A series of complexes containing the bulky carboxylate ligand 2,4,6-triisopropylbenzoate (TiPB) of type trans-[Ru₂(TiPB)₂(O₂CCH₃)₂X] [X = Cl (1), PF₆ (2)] and [Ru₂(TiPB)₄X] [X = Cl (3), PF₆ (4)] have been synthesised. The corresponding complexes trans-[Ru₂(TiPB)₂(O₂CCH₃)₂] (5) and [Ru₂(TiPB)₄] (6) were also isolated. Magnetic susceptibility measurements indicate that the diruthenium cores have the expected three (1-4) or two (5 and 6) unpaired electrons consistent with σ²π⁴δ²(δ^∗π^∗)³ and σ²π⁴δ²δ^∗2π^∗2 electronic configurations. Compounds 1-4 and 6 were structurally characterised by X-ray crystallography, and show the expected paddlewheel arrangement of carboxylate ligands around the diruthenium core. The diruthenium cores of complexes 3, 4 and 6 are all distorted to minimise steric interactions between the bulky carboxylate ligands. The Ru-Ru bond length in the complex 6 [2.2425(6) Å] is the shortest observed for a diruthenium tetracarboxylate and, surprisingly, is 0.014 Å shorter than in the analogous complex 4, despite an increase in the formal Ru-Ru bond order from 2.0 (6) to 2.5 (4). This is rationalised in terms of the extent of internal rotation, or distortion, about the diruthenium core. This was supported by density functional theory calculations on the model complexes [Ru₂(O₂CH)₄] and [Ru₂(O₂CH)₄]⁺, that demonstrate the relationship between Ru-Ru bond length and internal rotation. Electrochemical and electronic absorption data were recorded for all complexes in solution. Comparison of the data for the ‘bis-bis’ (1, 2 and 5) and tetra-substituted (3, 4 and 6) complexes indicates that the shortening of the Ru-Ru bond length results in a small increase in energy of the near-degenerate δ^∗ and π^∗ orbitals.