Trinuclear copper(I) acetylide complexes bearing carbonyl moiety: Synthesis, characterization, and photophysical properties

A series of trinuclear copper(I) acetylide complexes with carbonyl moiety, [Cu₃(μ-dppm)₃(μ₃-η¹-CCC(O)R)₂](ClO₄) (R = H (1), CH₃ (2), OCH₃ (3), NH₂ (4), NEt₂ (5)) (dppm = bis(diphenylphosphino)methane), have been synthesized and characterized. The crystal structures of [Cu₃(μ-dppm)₃(μ₃-η¹-CCC(O)CH₃)₂](ClO₄) (2) and [Cu₃(μ-dppm)₃(μ₃-η¹-CCC(O)NH₂)₂](ClO₄) (4) were determined by X-ray diffraction. The photophysical properties of complexes 1−5 have been studied. Complexes 1−5 show luminescence both in the solid state and in acetonitrile solution at 298 K, and their emission energies are in the order: 5 > 4 > 3 > 2 > 1. Density function theory (DFT) calculations at the hybrid Perdew, Burke, and Ernzerhof functional (PBE1PBE) level were performed on model complex 1 to elucidate the emission origin of complexes 1−5.     

Synthesis, electrochemistry, and spectroscopic characterization of bis-dirhodium complexes linked by axial ligands

The synthesis and electrochemical and spectroscopic properties of bis-dirhodium complexes containing ap or dpf bridging ligands, (ap)(4)Rh(2)(C triple bond C)(2)Rh(2)(ap)(4) (2) and (dpf)(4)Rh(2)(CNC(6)H(4)NC)Rh(2)(dpf)(4) (4), were investigated (where ap and dpf are the 2-anilinopyridinate and N,N'-diphenylformamidinate ions, respectively). The related "simple" dirhodium species, (ap)(4)Rh(2)(C triple bond C)(2)Si(CH(3))(3) (1) and (dpf)(4)Rh(2)(CNC(6)H(5)) (3), with the same set of bridging ligands were also synthesized and their properties compared to those of the analogous bis-dirhodium complexes. Compound 1 was obtained by mixing (ap)(4)Rh(2)Cl and Li(C triple bond C)(2)Si(CH(3))(3) in refluxing THF for 16 h under vacuum while compound 2 was prepared by a reaction between (ap)(4)Rh(2)(C triple bond C)(2)Li and (ap)(4)Rh(2)Cl under similar conditions. The reaction between (CF(3)COO)(4)Rh(2) and molten Hdpf under vacuum for 24 h leads to the generation of compound 3 with a yield of 65%. The red-orange compound 4 was obtained upon addition of 0.5 equiv of CNC(6)H(4)NC at room temperature to a CH(2)Cl(2) solution containing (dpf)(4)Rh(2) which was synthesized according to a method described previously in the literature. Compound 1 crystallizes in the triclinic space group P1, with a = 10.164(3) A, b = 13.881(3) A, c = 18.805(4) A, alpha = 73.55(2) degrees, beta = 77.89(2) degrees, gamma = 84.85(2) degrees, and Z = 2. Crystals of 2 were not good enough to collect adequate data for X-ray analysis, but the identity of this compound was confirmed, along with its P1; space group. Crystals of 3 and 4 belong to the monoclinic, P2(1)/c space group and the triclinic, P1; space group, respectively, with a = 13.5254(5) A, b = 13.7387(4) A, c = 27.2011(12) A, beta = 102.637(2) degrees, and Z = 4 for 3 and a = 13.866(8) A, b = 14.756(7) A, c = 15.008(6) A, alpha = 79.91(3) degrees, beta = 87.72(4) degrees, gamma = 89.19(4) degrees, and Z = 1 for 4. Compound 1 exhibits a single reversible oxidation at E(1/2) = 0.66 V and a single reversible reduction at E(1/2) = -0.44 V vs SCE in THF, 0.2 M TBAP. Both processes involve a one-electron transfer. Compound 2 undergoes a reversible oxidation at E(1/2) = 0.60 V and two separate one-electron-transfer reductions at E(1/2) = -0.52 and -0.65 V in THF, 0.2 M TBAP. The oxidation involves two overlapped one-electron-transfer processes. Compounds 3 and 4 undergo two reversible oxidations in CH(2)Cl(2), 0.1 M TBAP located at E(1/2) = 0.23 and 1.22 V (3) or 0.22 and 1.20 V (4). Each redox reaction of 3 involves a one-electron-transfer step while each redox reaction of 4 involves two overlapping one-electron transfers. Compound 2 shows interaction between the two dirhodium cores upon reduction, while 4 gives no evidence of electronic interaction between the two dirhodium units during either reduction or oxidation. An ESR signal with axial symmetry was obtained for the neutral compounds 1 and 2, and a similar spectrum was obtained for the singly oxidized products of compounds 3 and 4, thus suggesting the electronic configuration of (sigma)(2)(pi)(4)(delta)(2)(pi)(4)(delta)(1) for the neutral compounds 1 and 2 as well as for the oxidized compounds 3 and 4. The four compounds were also characterized by FTIR and UV-visible spectroscopy as well as by mass spectrometry.     

Synthesis and characterization of platinum diimine bis(acetylide) complexes containing easily derivatizable aryl acetylide ligands

New Pt(II) diimine bis(acetylide) complexes where the diimine is a substituted bipyridine or phenanthroline and the arylacetylide is 4-ethynylbenzaldehyde have been prepared in good to excellent yields. Spectroscopic characterization supports a square planar coordination geometry with cis-alkynyl ligands, and the crystal structure of one of the complexes, Pt(phen)(Ctbd1;CC(6)H(4)CHO)(2) (1), confirms the assignment. The new diimine bis(acetylide) complexes exhibit an absorption band ca. 400 nm that corresponds to a Pt(d) --> pi diimine charge transfer transition and are brightly emissive in fluid solution, with excited state lifetimes in the range 100-800 ns. Correlation of diimine substituent with lambda(max) for the 400 nm absorption band gives strong support to the MLCT assignment. Complex 1 undergoes electron transfer quenching, showing good Stern-Volmer behavior with a variety of oxidative and reductive quenchers. Quenching studies conducted with DNA nucleosides (A, T, C, G) were also investigated. Silyl-protected adenosine and guanosine were found to quench the luminescence of 1 better than similarly protected cytidine or thymidine. Since the former are the more easily oxidized bases, the results suggest that the Pt(II) diimine bis(acetylide) complexes are more powerful photooxidants than photoreductants with regard to electron transfer to DNA bases.     

Preparation and characterization of diruthenium(II,III) compounds containing terminal olefin groups

4-Vinylbenzoic acid reacted with Ru₂(D(3,5-Cl₂Ph)F)₃(OAc)Cl and cis-Ru₂(D(3,5-Cl₂Ph)F)₂(OAc)₂Cl (D(3,5-Cl₂Ph)F is N,N′-bis(3,5-dichlorophenyl)formamidinate) to yield Ru₂(D(3,5-Cl₂Ph)F)₃(4-vinylbenzoate)Cl (1) and cis-Ru₂(D(3,5-Cl₂Ph)F)₂(4-vinylbenzoate)₂Cl (2), respectively. Ru₂(D(3,5-Cl₂Ph)F)₃(OAc)Cl reacted with 5-hexenoic acid and 6-heptenoic acid to afford Ru₂(D(3,5-Cl₂Ph)F)₃(5-hexenoate)Cl (3) and Ru₂(D(3,5-Cl₂Ph)F)₃(6-heptenoate)Cl (4), respectively. All new compounds were characterized using voltammetric and Vis–NIR spectroscopic techniques, and the structures of 1 and 2 were also established through X-ray single crystal diffractions.     

Synthesis of linked metal acetylide complexes for nonlinear optics

Treatment of [Mn(CO)₅Br] (1) with a slight excess of Me₃SnCCPh affords the known species [(CO)₅Mn(CCPh)] (2), whereas reaction between 1 and Me₃SnCCRCCSnMe₃ (R = p-C₆H₄C₆H₄) gives the bimetallic complex [(CO)₅MnCCRCCSnMe₃] (3). This latter species is a good precursor for other syntheses, and treatment of 3 with a further equivalent of 1 gives [(CO)₅MnCCRCCMn(CO)₅] (4), while 3 with trans-[Pd(PBu₃)₂Cl₂] affords [(CO)₅MnCCRCCPd(PBu₃)₂Cl] (5).     

Electrochemical studies of bi- and polymetallic complexes featuring acetylide based bridging ligands

Acetylide-based bridging ligands have been widely used in the preparation of complexes that display a degree of electronic interaction between metal-based redox groups located at the ligand termini. The electrochemical response of these systems has been selectively reviewed, with a focus on the variation in properties that accompany changes in the structure of the bridging ligand and the nature of the metal groups.

Synthesis and characterization of trimetallic complexes with a borazine core

Treatment of [Cp*Ru(dppe)]⁺ with B-triethynyl-N-trimethylborazine and piperidine produces the trimetallic complex [Cp*Ru(dppe)(CC)]₃B₃N₃Me₃, the structure of which has been confirmed by X-ray diffraction. Reaction of RuHCl(CO)(PPh₃)₃ with B-triethynyl-N-trimethylborazine produces the trimetallic complex [RuCl(CO)(PPh₃)₂(CH=CH)]₃B₃N₃Me₃.     

Synthesis, electrochemistry and structural characterization of luminescent rhenium(I) monoynyl complexes and their homo- and hetero-metallic binuclear complexes

A series of luminescent rhenium(I) monoynyl complexes, [Re(N---N)(CO)₃(CC---R)] (N---N=bpy, ^tBu₂bpy; R=C₆H₅, C₆H₄---Cl-4, C₆H₄---OCH₃-4, C₆H₄---C₈H₁₇-4, C₆H₄---C₆H₅, C₈H₁₇, C₄H₃S, C₄H₂S---C₄H₃S, C₅H₄N), together with their homo- and hetero-metallic binuclear complexes, {Re(N---N)(CO)₃(CC---C₅H₄N)[M]} (N---N=bpy, ^tBu₂bpy; [M]=[Re{(CF₃)₂-bpy}(CO)₃]ClO₄, [Re(NO₂-phen)(CO)₃]ClO₄, W(CO)₅) have been synthesized and their electrochemical and photoluminescence behaviors determined. The structural characterization and electronic structures of selected complexes have also been studied. The luminescence origin of the rhenium(I) alkynyl complexes has been assigned as derived states of a [dπ(Re)→π*(N---N)] metal-to-ligand charge transfer (MLCT) origin mixed with a [π(CCR)→π*(N---N)] ligand-to-ligand charge transfer (LLCT) character. The assignments are further supported by extended Hückel molecular orbital (EHMO) calculations, which show that the LUMO mainly consists of π*(N---N) character while the HOMO is dominated by the antibonding character of the Re---CCR moiety resulted from the overlap of the dπ(Re) and π(CCR) orbitals.     

New diruthenium vinyliminium complexes from the insertion of alkynes into bridging aminocarbynes

Primary alkynes R′CCH [R′ = Me₃Si, Tol, CH₂OH, CO₂Me, (CH₂)₄CCH, Me] insert into the metal-carbon bond of diruthenium μ-aminocarbynes [Ru₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] [R = 2,6-Me₂C₆H₃ (Xyl), 1a; CH₂Ph (Bz), 1b; Me, 1c] to give the vinyliminium complexes [Ru₂{μ-η¹:η³-C(R′)CHCN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] [R = Xyl, R′ = Me₃Si, 2a; R = Bz, R′ = Me₃Si, 2b; R = Me, R′ = Me₃Si, 2c; R = Xyl, R′ = Tol, 3a; R = Bz, R′ = Tol, 3b; R = Bz, R′ = CH₂OH, 4; R = Bz, R′ = CO₂Me, 5a; R = Me, R′ = CO₂Me, 5b; R = Xyl, R′ = (CH₂)₄CCH, 6; R = Xyl, R′ = Me, 7a; R = Bz, R′ = Me, 7b; R = Me, R′ = Me, 7c]. The related compound [Ru₂{μ-η¹:η³-C[C(Me)CH₂]CHCN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃], (9) is better prepared by reacting [Ru₂{μ-CN(Me)(Xyl)}(μ-CO)(CO)(Cl)(Cp)₂] (8) with AgSO₃CF₃ in the presence of HCCC(Me)CH₂ in CH₂Cl₂ at low temperature.In a similar way, also secondary alkynes can be inserted to give the new complexes [Ru₂{μ-η¹:η³-C(R′)C(R′)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = Bz, R′ = CO₂Me, 11; R = Xyl, R′ = Et, 12a; R = Bz, R′ = Et, 12b; R = Xyl, R′ = Me, 13). The reactions of 2-7, 9, 11-13 with hydrides (i.e., NaBH₄, NaH) have been also studied, affording μ-vinylalkylidene complexes [Ru₂{μ-η¹:η³-C(R′)C(R″)C(H)N(Me)(R)}(μ-CO)(CO)(Cp)₂] (R = Bz, R′ = Me₃Si, R″ = H, 14a; R = Me, R′ = Me₃Si, R″ = H, 14b; R = Bz, R′ = Tol, R″ = H, 15; R = Bz, R′ = R″ = Et, 16), bis-alkylidene complexes [Ru₂{μ-η¹:η²-C(R′)C(H)(R″)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (R′ = Me₃Si, R″ = H, 17; R′ = R″ = Et, 18), acetylide compounds [Ru₂{μ-CN(Me)(R)}(μ-CO)(CO)(CCR′)(Cp)₂] (R = Xyl, R′ = Tol, 19; R = Bz, R′ = Me₃Si, 20; R = Xyl, R′ = Me, 21) or the tetranuclear species [Ru₂{μ-η¹:η²-C(Me)CCN(Me)(Bz)}(μ-CO)(CO)(Cp)₂]₂ (23) depending on the properties of the hydride and the substituents on the complex. Chromatography of 21 on alumina results in its conversion into [Ru₂{μ-η³:η¹-C[N(Me)(Xyl)]C(H)CCH₂}(μ-CO)(CO)(Cp)₂] (22). The crystal structures of 2a[CF₃SO₃] · 0.5CH₂Cl₂, 12a[CF₃SO₃] and 22 have been determined by X-ray diffraction studies.     

Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes

The VO(IV) complexes of tridentate ONO Schiff ligands were synthesised and characterized by IR, UV–vis and elemental analysis. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO < H < Br < NO₂ and H < Cl. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20–700 °C. The VOL¹(OH₂) decomposed in two steps whereas the remaining six complexes decomposed in three steps. The thermal decomposition of these complexes is closely related to the nature of the Schiff base ligands and proceeds via first order kinetics.     

Synthesis, characterization, and electrochemistry of diruthenium(III,II) and monoruthenium(III) complexes containing pyridyl-substituted 2-anilinopyridinate ligands

Reaction of the metal-metal bonded complex Ru(2)(O2CCH3)4Cl with 2-anilino-4-methylpyridine leads to the (3,1) isomer of the diruthenium(III,II) complex Ru2(ap-4-Me)4Cl, 1 while the same reaction with 2-anilino-6-methylpyridine gives the monoruthenium(III) derivative Ru(ap-6-Me)3, 2. Both compounds were examined as to their structural, electrochemical, and UV-visible properties, and the data were then compared to that previously reported for (4,0) Ru2(2-Meap)4Cl and other (3,1) isomers of Ru2(L)4Cl with similar anionic bridging ligands. ESR spectroscopy indicates that the monoruthenium derivative 2 contains low-spin Ru(III), and the presence of a single ruthenium atom is confirmed by an X-ray structure of the compound. The combined electrochemical and UV-vis spectroelectrochemical data indicate that the diruthenium complex 1 is easily converted to its Ru2(4+) and Ru2(6+) forms upon reduction or oxidation by one electron while the monoruthenium derivative 2 also undergoes metal-centered redox processes to give Ru(II) and Ru(IV) complexes under the same solution conditions. The reactivity of 1 with CO and CN- was also examined.     

The synthesis and electrochemistry of CpTiCl2(OR) (R = alkyl, aryl) complexes

The syntheses of several new CpTiCl₂(OR) (R = alkyl, aryl) complexes are described. It was possible to isolate pure product when the R group is substituted such as to cause steric crowding at the metal centre; for example, particularly good yields of the phenolate complexes were obtained when there were isopropyl substituents in the 2 and 6 positions of the phenolate. Electrochemical studies of the complexes in dry THF show that the Ti^III complexes are relatively stable, but only a diol complex could be reduced further to a Ti^II species. In general, the Ti^IV complexes undergo a reversible 1e⁻ reduction reaction. The chemistry is more complex if the electrolyte contains added water: both the Ti^IV and Ti^III complexes can react with water, the OR group being replaced by OH. The reaction is particularly rapid for the Ti^III alkoxide complexes.     

Rhodium(III) and iridium(III) complexes of thioarylazoimidazoles: Synthesis,structure, spectral characterization,electrochemistry and DFT calculation

[M(SRaaiNR′)Cl₃] (M = Rh(III), Ir(III) and SRaaiNR′ = 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazole) complexes are described in this article. The single crystal X-ray structure of one of the complexes, [Rh(SMeaaiNEt)Cl₃] (3b), shows a tridentate chelation of SMeaaiNEt via N(imidazole), N(azo) and S(thioether) donor centres. Spectral characterization has been done by IR, UV–Vis and ¹H NMR data. The electronic structure, redox properties and spectra are well supported by DFT and TDDFT computation on the complexes.     

Functionalized pentamethylferrocenes: Synthesis, structure, and electrochemistry

The advantageous properties of the Cp^* ligand — intensified electron donation, steric bulk, and enhanced solubility in comparison to the ubiquitous Cp ligand — are finding increasing use in organometallic chemistry. A systematic evaluation of synthetic routes to pentamethylferrocene compounds with a wide range of functionalities, including carboxyl, carbonyl, aminomethyl, vinyl, ethynyl, fulvenyl, cyclopentadienylmethyl, and others is reported. Spectroscopic, structural, and electrochemical properties of such functionalized pentamethylferrocenes Fc^*/2—R are compared to those of non-methylated ferrocenes Fc—R. The electronic influence of the Cp^* ligand in these unsymmetricalferrocenes Fc^*/2—R has been studied by cyclic voltammetry measurements, demonstrating a decrease in oxidation potential of −0.276 V in direct comparison to non-methylated ferrocenes Fc—R.     

Synthesis, electrochemistry, and photophysical properties of binuclear ruthenium(II)-terpyridine complexes comprising redox-active ferrocenyl spacer

In attempting to perturb the electronic properties of the spacer, we now describe an interesting example of Ru²⁺-tpy (tpy = terpyridine) complexes with 1,1′-bis(ethynyl)polyferrocenyl moiety attached directly to the 4′-position of the tpy ligand (tpy-CC-(fc)_n-CC-tpy; fc = ferrocenyl;n = 2-3). Complexes of Ru²⁺-tpy have room-temperature luminescence in H₂O/CH₃CN (4/1) solution. The ground-state HOMO and LUMO energies were probed by electrochemical measurements and the excited-state photophysical properties were probed by UV-Vis absorption spectroscopy and luminescence spectroscopy. The redox behavior of [(tpy)Ru^II-tpy-CC-(fc)_n-CC-tpy-Ru^II(tpy)]⁴⁺ complex is dominated by the Ru²⁺/Ru³⁺ redox couple (E_1/2 from 1.35 to 1.39 V), Fe²⁺/Fe³⁺ redox couples (E_1/2 from 0.4 to 1.0 V) and tpy/tpy⁻/tpy²⁻ redox couples (E_1/2 from −1.3 to −1.5 V). Electrochemical data, UV absorption and emission spectra indicate that the π-delocalization in the spacer is enhanced by the insertion of ethynyl unit. Interestingly, the insertion of ethynyl unit into the main chain causes a dramatic increase of phosphorescence yield (1.48 × 10⁻⁴ for n = 2; 1.13 × 10⁻⁴ for n = 3), triplet lifetime (67 ns for n = 2; 24 ns for n = 3), and emission intensity. The biferrocenyl spacer can be converted into mixed-valence biferrocenium spacer, which gives a more effective π-delocalization along main chain, by selective chemical oxidation of ferrocenyl unit. In deoxygenated H₂O/CH₃CN (4/1) solution at 25 °C, the oxidized complex of [(tpy)Ru^II-tpy-CC-(fc)₂-CC-tpy-Ru^II(tpy)]⁵⁺ is nonemissive. The presence of lower energy ferrocenium-centered excited-state provides an additional channel for excited-state decay. The mixed-valence biferrocenium center acts as an efficient quencher for the MLCT excited-state.     

Polytopic cation receptor functional phthalocyanines: Synthesis,characterization, electrochemistry and metal ion binding

Our efforts toward the development of the synthesis of a novel type of receptor ligand and its tetrasubstituted phthalocyanines, 2,9,16,23-tetrakis(6-hydroxyhexylsulfanyl) phthalocyanine, M[Pc(S–C₆H₁₃OH)₄] (M = Zn(II), Cu(II), Co(II)), bearing sulfur and oxygen donor atoms on the periphery together with hexyl moieties, have been carried out together with spectroscopic and electrochemical characterization. The newly synthesized functional phthalocyanines were soluble in MeOH, EtOH, THF, DMF, CNP (α-chloronapthalene), DMSO and quinoline, and less soluble in i-PrOH and CH₃CN. Cation binding abilities of the functional phthalocyanines with Ag⁺, Pd²⁺, Hg²⁺ and Cd²⁺, resulting in the formation of polynuclear phthalocyanine complexes, were evaluated by UV–Vis spectroscopic techniques. The spectroscopic properties of the complexes were affected strongly by the electron-donating sulfanyl units on the periphery. The cyclic voltammetry of the complexes were examined on a platinum electrode in DMSO. The new synthesized compounds have been characterized by elemental analysis, FTIR, ¹H and ¹³C NMR, MS (ESI and MALDI-TOF) and UV–Vis spectral data.     

Synthesis,characterization and thermal stability of new dumbbell-shaped isobutyl-substituted POSSs linked by aromatic bridges

Five new dumbbell-shaped polyhedral oligomeric silsesquioxanes (POSSs), in which two identical silicon cages R₇(SiO_1.5)₈ (with R = isobutyl), linked to various aromatic bridges (Ar, Ar–Ar, Ar–O–Ar, Ar–S–Ar and Ar–SO₂–Ar, where Ar = p-C₆H₄) were prepared through a literature method opportunely modified by us to make easier preparation and increase yield, which was higher than 70 % in all cases. The obtained products were the expected ones, as supported by the results of elemental analysis and ¹H NMR spectra. Their resistance to the thermal degradation in both flowing nitrogen and static air atmosphere was checked by degrading samples at 10 °C min^?1 and determining temperatures at 5 % mass loss (T _5%) and residues at 700 °C. The T _5% values in air were lower than the corresponding ones in nitrogen, but the trend among the various POSSs investigated was the same in both used atmospheres, with the most high value for the compound having the Ar–O–Ar aromatic bridge. The residues at 700 °C in air of the compounds having not hetero-atoms (O or S) in the aromatic bridge were higher than those in nitrogen, whilst no substantial difference was observed for the other ones.     

Synthesis, characterization, and electrochemistry of biorelevant photosensitive low-potential orthometalated ruthenium complexes

Redox potentials of photosensitive cyclometalated RuII derivatives of 2-phenylpyridine or 2-(4-tolyl)pyridine are controllably decreased by up to 0.8 V within several minutes. This is achieved by irradiation of the ruthena(II)cycles cis-[Ru(o-X-2-py)(LL)(MeCN)2]PF6 (2, X = C6H4 (a) or 4-MeC6H3 (b), LL = 1,10-phenanthroline or 2,2'-bipyridine). The cis geometry of the MeCN ligands has been confirmed by the X-ray structural studies. The sigma-bound sp2 carbon of the metalated ring is trans to LL nitrogen. Complexes 2 are made from [Ru(o-X-2-py)(MeCN)4]PF6 (1) and LL. This "trivial" ligand substitution is unusual because 1a reacts readily with phen in MeCN as solvent to give cis-[Ru(o-C6H4-2-py)(phen)(MeCN)2]PF6 (2c) in a 83% yield, but bpy does not afford the bpy-containing 2 under the same conditions. cis-[Ru(o-C6H4-2-py)(bpy)(MeCN)2]PF6 (2e) has been prepared in CH2Cl2 (74%). Studies of complexes 2c,e by cyclic voltammetry in MeOH in the dark reveal RuII/III quasy-reversible redox features at 573 and 578 mV (vs Ag/AgCl), respectively. A minute irradiation 2c and 2e converts them into new species with redox potentials of -230 and 270 mV, respectively. An exceptional potential drop for 2c is accounted for in terms of a photosubstitution of both MeCN ligands by methanol. ESR, 1H NMR, and UV-vis data indicate that the primary product of photolysis of 2c is an octahedral monomeric low-spin (S = 1/2) RuIII species, presumably cis-[RuIII(o-C6H4-2-py)(phen)(MeOH)2]2+. The primary photoproduct of bpy complex 2e is cis-[RuII(o-C6H4-2-py)(bpy)(MeCN)(MeOH)]+, and this accounts for a lower decrease in the redox potential. Irradiation of 2c in the presence of added chloride affords [(phen)(o-C6H4-2-py)ClRuIIIORuIVCl(o-C6H4-2-py)(phen)]PF6, a first mu-oxo-bridged mixed valent dimer with a cyclometalated unit. The structure of the dimer has been established by X-ray crystallography.     

Alkynyl Ti-M complexes with M = Cd and Hg: Synthesis, characterization, and reaction chemistry

The synthesis and properties of heterobimetallic Ti-Cd complexes of type {[Ti](μ-η¹:η²-CCR)₂}CdX₂ ([Ti] = Ti(η⁵-C₅H₄SiMe₃)₂; R = SiMe₃: 3a, X = Cl; 3b, X = Br; 3c, X = I; R = Fc: 3d, X = Br; Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅) is reported. These compounds were accessible by treatment of [Ti](CCR)₂ (1a, R = SiMe₃; 1b, R = Fc) with the cadmium salts CdX₂ (2a, X = Cl; 2b, X = Br; 2c, X = I) in a 1:1 M ratio in diethyl ether. Dissolving, for example, 3b in tetrahydrofuran afforded coordination polymer [Cd(μ-Br)₂(thf)₂]_n (4) along with the tweezer molecule 1a. Treatment of 3b with two equiv of LiCCFc (5) gave {[Ti](μ-η¹:η²-CCSiMe₃)₂}Cd(CCFc)₂ (6) which eliminated at ambient temperature the all-carbon buta-1,3-diyne FcCC-CCFc (7) producing 1a and elemental Cd. The same reaction behavior was observed, when 2b was reacted with 5. The thus obtained bis(alkynyl) cadmium complex Cd(CCFc)₂ (8) is redox-active at low temperature producing 7 and Cd(0). When mercury halides HgX₂ (9a, X = Cl; 9b, X = Br) are used, then the titanocene dihalides [Ti]X₂ (10a, X = Cl; 10b, X = Br) together with Me₃SiCC-CCSiMe₃ (11) and Hg(0) were formed. Nevertheless, mercury acetylides were available by treatment of Hg(OAc)₂ (12) with HCCFc (13) in a 1:2 M ratio. Thus obtained Hg(CCFc)₂ (14) gave with [CuBr] (15) coordination polymer [{Hg(η²-CCFc)₂}(Cu₂(μ-Br)₂]_n (16), while with [AgPF₆] oxidation of the ferrocenyl moieties took place affording dicationic [Hg(CCFc)₂]²⁺ (18).The structures of 3b and 4 in the solid state are reported. Compound 3b shows the typical characteristics for heterobimetallic organometallic π-tweezer complexes with cadmium in a tetrahedral environment, while 4 corresponds to a one-dimensional coordination polymer in which the Cd(II) ions are linked in a edge-sharing fashion by bromide bridges in the pseudo-equatorial plane. The appropriate tetrahydrofuran molecules are completing the pseudo-octahedral coordination sphere at cadmium.The cyclic voltammogram of 14 is reported showing a single reversible redox event at E⁰ = 0.108 V with ΔE_p = 76 mV indicating that there is no communication between the Fc termini along the mercury acetylide unit.     

Organometallic complexes for nonlinear optics: Part 31. Cubic hyperpolarizabilities of ferrocenyl-linked gold and ruthenium complexes

The complexes [Fe{η-C₅H₄---(E)---CH=CH---4-C₆H₄CCX}₂] [X=SiMe₃ (1), H (2), Au(PCy₃) (3), Au(PPh₃) (4), Au(PMe₃) (5), RuCl(dppm)₂ (7), RuCl(dppe)₂ (8)] and [Fe{η-C₅H₄---(E)---CH=CH---4-C₆H₄CH=CRuCl(dppm)₂}₂](PF₆)₂ (6) have been prepared and the identities of 1 and 7 confirmed by single-crystal X-ray structural studies. Complexes 1–8 exhibit reversible oxidation waves in their cyclic voltammograms attributed to the Fe^II/III couple of the ferrocenyl groups, 6–8 also showing reversible (7, 8) or non-reversible (6) processes attributed to Ru-centered oxidation. Cubic nonlinearities at 800 nm by the Z-scan method are low for 1–5; in contrast, complexes 6 and 7 exhibit large negative γ_real and large γ_imag values. A factor of 4 difference in γ and two-photon absorption cross-section σ₂ values for 6 and 7 suggest that they have potential as protically switchable NLO materials.