New interlocked molecules generated from a podand containing urea units and imidazolium salts using an anion template

A podand containing urea units (L) was found to form interlocked structures with 2,5-dihexylamide imidazolium salts (3·X), 2,5-dihexyl imidazolium salts (4·X), and 2,5-dihexyl benzoimidazolium salts (5·X), where X=Cl⁻, Br⁻, and PF₆⁻ using anions as templates. The binding ability of L and guest molecules was evaluated by ¹H NMR titrations in CDCl₃. It was found that L could form complexes with guest molecules in the following order, 3·X > 5·X > 4·X. Stabilities of the complexes also depended on shape of the templated anions: Cl⁻>Br⁻?PF₆⁻. Hydrogen bonding and π-π stacking interactions played an important role in the self-assembling of these interlocked molecules.     

Structural diversity in the self-assembly of Ag(I) complexes containing 2-amino-5-halopyrimidine

A series of Ag(I) complexes containing the 2-amino-5-halopyrimidine ligands have been synthesized and their structures characterized by X-ray crystallography. The isomorphous complexes Ag(L-Cl)₂(CF₃SO₃) (L-Cl = 2-amino-5-chloropyrimidine), 1, and Ag(L-Br)₂(CF₃SO₃) (L-Br = 2-amino-5-bromopyrimidine), 2, are mononuclear, while [Ag(L-Br)(CF₃SO₃)]₆·6C₄H₁₀O, 3, and [Ag(L-I)(CF₃SO₃)]₆ (L-I = 2-amino-5-iodopyrimidine), 4, show cyclic self-assembly of six Ag(Ι) atoms and six L-X ligands, resulting in 24-membered metallocycles. The complex [Ag(L-I)(CF₃SO₃)]_∞, 5, forms 1D zigzag chains which are linked through C-I?Ag and Ag?O interactions to form a 3D structure. The tetranuclear complexes [Ag(L-X)(NO₃)]₄ [X = Cl, 6; Br, 7] form 16-membered metallocycles, while [Ag(L-X)(ClO₄)]_∞ [X = Cl, 8; Br, 9] exhibit helical chains. The different structure of 5 from 1 and 2 appears to be due to the stronger nucleophilic character of the iodine atom. In these complexes, the relatively smaller NO₃⁻ anions lead to the formation of tetranuclear metallocycles and the larger CF₃SO₃⁻ anions support the hexanuclear metallocycles, whereas the ClO₄⁻ anions induce the helical chains.     

Preparation, characterization, and catalytic properties of ruthenium nitrosyl complexes with polypyrazolylmethane ligands

Ruthenium(II) nitrosyl complexes with polypyrazolylmethanes, [(Bpm)Ru(NO)Cl₃] [Bpm = bis(1-pyrazolyl)methane, 1], [(Bpm^∗)Ru(NO)Cl₃] [Bpm^∗ = bis(3,5-dimethyl-1-pyrazolyl)methane, 2], [(Tpm)Ru(NO)Cl₂][PF₆] [Tpm = tris(1-pyrazolyl)methane, 3], and [(Tpm^∗)Ru(NO)Cl₂][PF₆] [Tpm^∗ = tris(3,5-dimethyl-1-pyrazolyl)methane, 4], have been synthesized and characterized. The solid-state structures of [(Bpm^∗)Ru(NO)Cl₃] (2) and [(Tpm^∗)Ru(NO)Cl₂][PF₆] (4) were determined by single-crystal X-ray crystallographic analyses. These complexes have been tested as catalysts in the transfer hydrogenation of several ketones under mild conditions.     

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

An efficient route to the novel tridentate phosphine ligands RP[CH₂CH₂CH₂P(OR′)₂]₂ (I: R = Ph; R′ = i-Pr; II: R = Cy; R′ = i-Pr; III: R = Ph; R′ = Me and IV: R = Cy; R′ = Me) has been developed. The corresponding ruthenium and iron dicarbonyl complexes M(triphos)(CO)₂ (1: M = Ru; triphos = I; 2: M = Ru; triphos = II; 3: M = Ru; triphos = III; 4: M = Ru; triphos = IV; 5: M = Fe; triphos = I; 6: M = Fe; triphos = II; 7: M = Fe; triphos = III and 8: M = Fe; triphos = IV) have been prepared and fully characterized. The structures of 1, 3 and 5 have been established by X-ray diffraction studies. The oxidative addition of MeI to 1-8 produces a mixture of the corresponding isomeric octahedral cationic complexes mer,trans-(13a-20a) and mer,cis-[M(Me)(triphos)(CO)₂]I (13b-20b) (M = Ru, Fe; triphos = I-IV). The structures of 13a and 20a (as the tetraphenylborate salt (21)) have been verified by X-ray diffraction studies. The oxidative addition of other alkyl iodides (EtI, i-PrI and n-PrI) to 1-8 did not afford the corresponding alkyl metal complexes and rather the cationic octahedral iodo complexes mer,cis-[M(I)(triphos)(CO)₂]I (22-29) (M = Ru, Fe; triphos = I-IV) were produced. Complexes 22-29 could also be obtained by the addition of a stoichiometric amount of I₂ to 1-8. The structure of 22 has been verified by an X-ray diffraction study. Reaction of 13a/b-20a/b with CO afforded the acetyl complexes mer,trans-[M(COMe)(triphos)(CO)₂]I, 30-37, respectively (M = Ru, Fe; triphos = I-IV). The ruthenium acetyl complexes 30-33 reacted slowly with 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) even in boiling acetonitrile. Under the same conditions, the deprotonation reactions of the iron acetyl complexes 34-37 were completed within 24-40 h to afford the corresponding zero valent complexes 5-8. It was not possible to observe the intermediate ketene complexes. Tracing of the released ketene was attempted by deprotonation studies on the labelled species mer,trans-[Fe(COCD₃)(triphos)(CO)₂]I (38) and mer,trans-[Fe(¹³COMe)(triphos)(CO)₂]I (39).     

Synthesis and electrochemical properties of new cobalt and manganese phthalocyanine complexes tetra-substituted with 3,4-(methylendioxy)-phenoxy

The synthesis and electrochemical properties of new cobalt and manganese phthalocyanine complexes, tetra-substituted with 3,4-(methylendioxy)-phenoxy at the peripheral (complexes 3 and 5) and non-peripheral (complexes 4 and 6) positions, are reported. Complexes 3 and 4 showed Q-band absorption, in DMF, at 668 and 686 nm, respectively while Q-band due to complexes 5 and 6 appeared at 732 and 760 nm, respectively in CHCl₃. All the complexes showed well resolved redox processes attributed to both metal and ring based processes. Complexes 3 and 4 showed four redox processes, labeled I, II, III and IV. For complex 3, process I (Co^IPc⁻²/Co^IPc⁻³) was observed at −1.45 V, II (Co^IIPc⁻²/Co^IPc⁻²) at −0.38 V, III (Co^IIIPc⁻²/Co^IIPc⁻²) at +0.49 V and IV (Co^IIIPc⁻¹/Co^IIIPc⁻²) at +0.97 V versus Ag|AgCl. Similar processes were observed for complex 4 at −1.36 V, −0.27 V, +0.56 V, +1.03 V versus Ag|AgCl, respectively. Complexes 5 and 6 showed two redox processes (I and II). For complex 5, these processes appeared at −0.79 V (Mn^IIPc⁻²/Mn^IIPc⁻³, I) and −0.07 V versus Ag|AgCl (Mn^IIIPc⁻²/Mn^IIPc⁻², II), while for complex 6, they were observed at −0.86 V and −0.04 V versus Ag|AgCl. Spectroelectrochemistry was used to probe and confirm the origin of these processes.     

Synthesis,spectral and electrochemical properties of mixed-ligand ruthenium(II) complexes of bis(pyrid-2-yl)- and bis(benzimidazol-2-yl)-dithioether ligands: Effect of an asymmetric diimine co-ligand

Two new mixed-ligand Ru(II) complexes [Ru(pdto)(dppt)](ClO₄)₂ (1) and [Ru(bbdo)(dppt)](ClO₄)₂ (2), where pdto = 1,8-bis(pyrid-2-yl)-3,6-dithiaoctane, bbdo = 1,8-bis(benzimidazol-2-yl)-3,6-dithiaoctane and dppt = 3-(pyridin-2-yl)-5,6-diphenyl-1,2,4-triazine, have been isolated and characterised by elemental analysis. NMR and electronic absorption and emission spectral and electrochemical techniques have been used to investigate the solution structures and electronic properties of the complexes. The ¹H and ¹³C spectra of the complexes in solution reveal that the N₂S₂ donor set of the pdto and bbdo ligands is “cis-α” coordinated and the dppt ligand is chelated to Ru(II) through both triazine N2 and pyridine nitrogen atoms. The proton chemical shifts of the phenyl rings of dppt are not affected much upon coordination, supporting the triazine N2 rather than N4 coordination. The anomalous upfield shifts of the H₆₁ and H₆₂ (1) and H₇₂ and H₈₁ (2) protons are caused by the shielding magnetic anisotropy due to the ring currents of the py and tra rings of dppt, which are forced to be coplanar by coordination. The py and bzim rings of pdto and bbdo are obliged to rotate away from dppt and the Ru–N_py and Ru–N_bzim bonds lengthen in order to minimise the steric clashes with dppt. The c.i.s values for 1 are less positive than those for 2 suggesting that the ligand bzim nitrogens of bbdo rather than the py nitrogens of pdto are involved in stronger σ-bonding with Ru(II). Both the complexes display a strong MLCT transition (1, 470; 2, 515 nm) along with intense intraligand transitions in the UV region, and when excited in the MLCT band an emission band (650 nm) is observed for both 1 and 2. In acetonitrile solution they show a quasi-reversible Ru(II)/Ru(III) redox couple (E_1/2, 1, 1.18; 2, 0.90 V). Two more redox processes (E_1/2, 1, −0.97, −1.09; 2, −1.06, −1.42 V) involving the coordinated dppt ligand are also observed. A plot of the difference between the metal oxidation and ligand reduction potentials of the complexes versus the absorption or emission maxima is linear, illustrating that the lowest π^∗ orbitals of dppt are involved in the redox, absorption and emission processes in the complexes. Electrochemical parameterisation of the Ru(II)/Ru(III) redox potentials of the present complexes has been carried out using Lever’s method and the calculated ligand reduction potential E_L(L) correlates well with the observed Ru(II)/Ru(III) redox potentials.     

Anion recognition by 2,2′-binaphthalene derivatives bearing urea and thiourea groups at 8- and 8′-positions by UV-vis and fluorescence spectroscopies

Synthesis and anion recognition properties of 2,2′-binaphthalene derivatives bearing two thiourea (1) and urea (2) groups at 8- and 8′-positions were studied. The structure of receptor 1 was determined by X-ray crystallography. UV-vis spectra of the receptors showed characteristic changes around 300-400 nm through isosbestic points upon the addition of biologically relevant anions such as acetate, dihydrogenphosphate, and chloride in MeCN and DMSO due to restriction of the rotation around the single bond connecting two naphthyl moieties by cooperative guest binding of two recognition sites. Job’s plots showed 1:1 complexation for guest anions. The fluorescence quantum yields of free form of 1 and 2 in MeCN were determined to be 0.021 and 0.57, respectively. The fluorescence intensities of the receptors diminished upon the addition of anions in MeCN. The association constants of receptors 1 and 2 were one or two orders of magnitude greater than the corresponding monothiourea and urea receptors 3 and 4 indicating cooperative hydrogen bonding with guest anions. The selectivity trends of association of anions were F⁻>AcO⁻>H₂PO₄⁻>Cl⁻>>HSO₄⁻≈NO₃⁻≈Br⁻≈I⁻ for 1, and F⁻>AcO⁻≈Cl⁻>H₂PO₄⁻>Br⁻>HSO₄⁻>I⁻≈NO₃⁻ for 2. Receptor 2 showed remarkable Cl⁻ selectivity presumably owing to suitable orientation for effective hydrogen bond formation with Cl⁻.     

Adamantane-dipyrromethanes: novel anion receptors

New adamantane-dipyrromethanes (AdD 1-4) were synthesized and their anion binding properties investigated. AdD 1-3 form 2:1 complexes with F⁻ (AdD:F = 2:1) characterized by high association constants, and 1:1 complexes with Cl⁻, Br⁻, and . The binding of Cl⁻, Br⁻, and by AdD 1-3 is 2-3 times stronger than for the reference compound, meso-phenyldipyrromethane (5). However, AdD 4 forms complexes with F⁻ characterized by 1:1 and 1:2 stoichiometry (AdD:F = 1:2).     

The supramolecular chemistry of metal complexes with heavily substituted imidazoles as ligands: Cobalt(II) and zinc(II) complexes of 1-methyl-4,5-diphenylimidazole

An investigation of the M^II/X⁻/L [M^II = Co, Ni, Cu, Zn; X⁻ = Cl⁻, Br⁻, I⁻, NCS⁻, NO₃⁻, N₃⁻, CH₃COO⁻; L = 1-methyl-4,5-diphenylimidazole] general reaction system towards the detailed study of the intermolecular interactions utilized for controlling the supramolecular organization and the structural consequences on the structures produced has been initiated. Three representative complexes with the formulae [Co(NO₃)₂(L)₂] (1), [Zn(NO₃)₂(L)₂] (2) and [Co(NCS)₂(L)₂]·EtOH (3·EtOH) have been synthesized and characterized by spectroscopic methods and single-crystal X-ray analysis. Compounds 1 and 2 are isomorphous (tetragonal, I4₁cd) with their metal ions in a severely distorted octahedral Co/ZnN₂O₄ environment, while 3·EtOH crystallizes in P2₁/c with a tetrahedral CoN₄ coordination. The structural analysis of 1, 2 and 3·EtOH reveals a common mode of packing among neighbouring ligands (expressed through intramolecular π–π interactions between the 4,5-diphenylimidazole moieties), enhancing thus the rigidity and stability of the complexes. The bent coordination of the two isothiocyanates in 3 [Co–NCS angles of 173.8(2) and 160.8(2)°] seems to be caused by intermolecular hydrogen bonding and crystal packing effects.     

Calix[4]arenes containing urea and crown/urea moieties: effects of the crown ether unit and Na towards anion binding ability

Calix[4]arenes containing urea and crown/urea moieties, 7 and 10, respectively have been synthesized. ¹H NMR titrations of 7 and 10 with anions in DMSO-d₆ showed that 7 and 10 formed complexes with Cl⁻, Br⁻, NO₃⁻ and H₂PO₄⁻ to a different extent. The association constants of 7 and 10 towards anions were calculated and found to vary as H₂PO₄⁻>Cl⁻>Br⁻>NO₃⁻. However, compared to 7 the presence of the crown unit in 10 resulted in a slightly higher affinity to Cl⁻ and Br⁻, but a lower affinity to H₂PO₄⁻. Upon addition of Na⁺, the binding ability of 10 towards H₂PO₄⁻ is increased due to ion-pair enhancement.     

Zinc(II) complexes derived from di-2-pyridyl ketone N-phenyl-3-semicarbazone: Crystal structures and spectral studies

Six zinc(II) complexes, Zn(HL)Br₂ (1), Zn(HL)Cl₂ (2), ZnL(OAc) (3), ZnLN₃ (4), ZnL₂ (5) and ZnL₂ · H₂O (6), have been synthesized and characterized by different physicochemical techniques. Complex 1 is five coordinated and has a distorted square pyramidal geometry. Complexes 5 and 6 are six coordinated and have distorted octahedral geometries. In complexes 1 and 2, the ligand moieties are coordinated in the neutral form (HL), and in the other complexes they are monoanionic (L⁻).     

Palladium and half sandwich ruthenium(II) complexes of selenated and tellurated benzotriazoles: Synthesis, structural aspects and catalytic applications

1-(Phenylselenomethyl)-1H-benzotriazole (L¹) and 1-(4-methoxyphenyltelluromethyl)-1H-benzotriazole (L²) have been synthesized by reacting 1-(chloromethyl)-1H-benzotriazole with in situ generated nucleophiles PhSe⁻ and ArTe⁻, respectively. The complexes of L¹ and L² with Pd(II) and Ru(II)(η⁶-p-cymene) have been synthesized. Proton, carbon-13, Se-77 and/or Te-125 NMR spectra authenticate both the ligands and their complexes. The single crystal structures of L¹, L² and [RuCl(η⁶-p-cymene)(L)][PF₆] (L = L¹: 3, L = L²: 4) have been solved. The Ru-Se and Ru-Te bond lengths have been found 2.4801(11) and 2.6183(10) Å, respectively. The palladium complexes, [PdCl₂(L)] (L = L¹: 1, L = L²: 2) have been explored for Heck and Suzuki-Miyaura C-C coupling reactions. The TON values are upto 95,000. The Ru-complexes have been found promising for catalytic oxidation of alcohols (TON ∼ 7.8-9.4 × 10⁴). The complexes of telluroether ligands are as efficient catalysts as those of selenoether ones and in fact better for catalytic oxidation.     

2-Oxazoline/benzoxazole-1,10-phenanthrolinylmetal (iron, cobalt or nickel) dichloride: Synthesis, characterization and their catalytic reactivity for the ethylene oligomerization

Series of 2-benzoxazole-1,10-phenanthrolines (L1-L4) and 2-oxazoline-1,10-phenanthrolines (L5-L8) were synthesized and used as tridentate N^N^N ligands in coordinating with metal (nickel, cobalt or iron) chlorides. Their metal complexes, nickel(II) (Ni1-Ni8), cobalt(II) (Co1-Co8) and iron(II) (Fe1-Fe8), were characterized by elemental and IR spectroscopic analyses. The molecular structures of the ligand L2 and the complexes Ni3, Co1, Co3 and Fe2 have been determined by the single-crystal crystallography. The nickel complex Ni3 and iron complex Fe2 display an octahedral geometry, whereas cobalt complex Co1 is with a distorted bipyramidal geometry and Co3 as square pyramidal geometry. At 10 atm ethylene, all the complexes showed good activities in ethylene dimerization upon activation with appropriate aluminum cocatalysts; the nickel complexes gave the activity up to 3.11 × 10⁶ g mol⁻¹(Ni) h⁻¹ upon activation with diethylaluminum chloride (Et₂AlCl), meanwhile the cobalt and iron complexes showed activities up to 1.51 × 10⁶ g mol⁻¹(Co) h⁻¹ and 1.89 × 10⁶ g mol⁻¹(Fe) h⁻¹, individually, upon activation with modified methylaluminoxane (MMAO).     

Organotin compounds: an ionophore system for fluoride ion recognition

Ion-selective properties were established for membrane electrodes prepared by using organotin compounds of type (L^CNRSnF₂)_n, (R = n-Bu (I), = Ph (II)) and (L^CNSnF₃)_n (III) (L^CN = C₆H₄(CH₂NMe₂)-2). Electrodes formulated with the optimized membranes containing the organotin compounds I-III as ionophores and sodium tetraphenylborate (10-30%) exhibited high selectivity for fluoride over other anions. An electrode prepared with ionophore II using dibutyl phthalate as the plasticizer and 15% sodium tetraphenylborate (NaTPB) as anion additive, possesses the best potentiometric response characteristics. It shows a detection limit of 7.9 × 10⁻⁷ M with a slope of 62.7 mV decade⁻¹ of activity in buffer solutions of pH 5.5. The interference from other anions is suppressed under this optimized measurement conditions. An entirely non-Hofmeister selectivity sequence (F⁻ > CH₃COO⁻ > Cl⁻ > I⁻ ∼ Br⁻ >ClO₄⁻ > NO₂⁻ > NO₃⁻ > SCN⁻) with remarkable preference towards fluoride is obtained. The influence on the electrode performances by anion additive was studied, and the possible response mechanism was investigated by UV-vis spectra. The electrode has been used for direct determination of fluoride in drinking mineral water with satisfactory results.     

A new heteroditopic receptor and sensor highly selective for bromide in the presence of a bound cation

The heteroditopic receptor 2 containing a crown ether and amidoferrocence groups was synthesized and the binding abilities with various anions are reported in the presence and absence of metal cations. In the presence of Na⁺, 2 showed positive co-operative binding towards Br⁻ with the binding affinity K_ass = 16,096 M⁻¹. Therefore, receptor 2 showed a switched-on binding for Br⁻ in the presence of Na⁺ and a switched-off binding in the absence of Na⁺. Compound 2 was also found to sense Cl⁻ and Br⁻ electrochemically.     

Synthesis,crystal structure and DNA-binding properties of ruthenium(II) polypyridyl complexes with dicationic 2,2′-dipyridyl derivatives as ligands

New Ru(II) complexes with dicationic ligand, [Ru(phen)₂L¹]⁴⁺(1) and [Ru(phen)₂L²]⁴⁺(2) (phen = 1,10-phenanthroline; L: L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation) have been synthesized and structurally characterized. The interaction of these complexes with calf thymus DNA (CT-DNA) has been investigated. The intrinsic binding constants (K_b: 1, 7.73 × 10⁴ M⁻¹; 2, 2.50 × 10⁴ M⁻¹) determined by absorption spectral titrations of these complexes with CT-DNA indicate the DNA-binding affinity of 1 is stronger than that of 2. Both complexes can display luminescence either alone in aqueous solution or in the presence of DNA. Equilibrium dialysis experiments monitored by CD spectroscopy reveal the preferential binding of the Δ-enantiomer to the right-handed CT-DNA. DNA-viscosity studies suggest that the binding modes are different, 1 may partially intercalate between DNA base-pairs while 2 most likely interact with DNA in an electrostatic binding mode.     

Oligothiophene-2-yl-vinyl bridged mono- and binuclear ruthenium(II) tris-bipyridine complexes: Synthesis, photophysics, electrochemistry and electrogenerated chemiluminescence

A series of mono- and binuclear ruthenium(II) tris-bipyridine complexes tethered to oligothienylenevinylenes have been synthesized and characterized by ¹H NMR, ¹³C NMR and TOF-MS spectrometry. Photophysics, electrochemistry and electrogenerated chemiluminescence (ECL) properties of these complexes are investigated. The electronic absorption spectra of the mononuclear ruthenium complexes show a significant red shift both at MLCT (metal-to-ligand charge transfer) and π-π^∗ transitions of oligothienylenevinylenes with increase in the number of thiophenyl-2-yl-vinyl unit. For the binuclear complexes these two absorption bands are overlapped. All the metal complexes have very weak emission compared to that of the reference complex Ru(bpy)²⁺₃. The first reduction potentials of all mononuclear ruthenium complexes are less negative than that of Ru(bpy)²⁺₃, due to the moderate electron-withdrawing effect of oligothienylenevinylenes. For binuclear ruthenium complexes, only one Ru(II/III) oxidation peak (E_1/2 = 0.96 V vs. Ag/Ag⁺) was observed, suggesting a weak interaction between two metal centers. Three successive reduction processes of bipyridine ligands are similar among all ruthenium complexes except for RuTRu, which has a very sharp peak owing to the accumulation of neutral product on the electrode surface. All these ruthenium complexes exhibited different ECL property in CH₃CN solution without any additional reductant or oxidant. For three mononuclear ruthenium complexes, the ECL intensity strengthens with increase in the number of thiophene-2-yl-vinyl unit. However, the ECL efficiency dramatically decreased in the binuclear ruthenium complexes. The ECL efficiencies of all the reported complexes do not exceed that of Ru(bpy)²⁺₃, where the ECL efficiency decreases in the order of RuTRu > Ru3T > Ru2T > RuT > Ru2TRu (RuT,bis-2,2′-bipyridyl-(4-methyl-4′-(2-thienylethenyl)-2,2′-bipyridine) ruthenium dihexafluorophosphate; Ru2T, bis-2,2′-bipyridyl-(4-methyl-4′-{(E)-2-[5-((E)-2-thienylethenyl)-thienylethenyl]}-2,2′-bipyridine) ruthenium dihexafluorophosphate; Ru3T, bis-2,2′-bipyridyl-(4-methyl-4′-{(E)-2-{(E)-2-[5-((E)-2-thienylethenyl)-thienylethenyl]}}-2,2′-bipyridine) ruthenium dihexafluorophosphate; RuTRu, bis-2,2′-bipyridyl-ruthenium-bis-[2-((E)-4′-methyl-2, 2′-bipyridinyl-4)-ethenyl]-thienyl-bis-2,2′-bipyridyl-ruthenium tetrahexafluorophosphate; Ru2TRu, bis-2,2′-bipyridyl-ruthenium-(E)-1,2-bis-{2-[2-((E)-4′-methyl-2,2′-bipyridinyl-4)-ethenyl]-thienyl}-ethenyl-bis-2,2′-bipyridyl-ruthenium tetrahexafluorophosphate).     

Quantum chemistry studies on the Ru-M interactions and the P NMR in [Ru(CO)3(Ph2Ppy)2(MCl2)] (M = Zn, Cd, Hg)

To study the Ru-M interactions and their effects on ³¹P NMR, complexes [Ru(CO)₃(Ph₂Ppy)₂] (py = pyridine) (1) and [Ru(CO)₃(Ph₂Ppy)₂MCl₂] (M = Zn, 2; Cd, 3; Hg, 4) were calculated by density functional theory (DFT) PBE0 method. Moreover, the PBE0-GIAO method was employed to calculate the ³¹P chemical shifts in complexes. The calculated ³¹P chemical shifts in 1-3 follow 2 > 3 > 1 which are consistent to experimental results, proving that PBE0-GIAO method adopted in this study is reasonable. This method is employed to predict the ³¹P chemical shift in designed complex 4. Compared with 1, the ³¹P chemical shifts in 2-4 vary resulting from adjacent Ru-M interactions. The Ru → M or Ru ← M charge-transfer interactions in 2-4 are revealed by second-order perturbation theory. The strength order of Ru → M interactions is the same as that of the P-Ru → M delocalization with Zn > Cd > Hg, which coincides with the order of ³¹P NMR chemical shifts. The interaction of Ru → M, corresponding to the delocalization from 4d orbital of Ru to s valence orbital of M²⁺, results in the delocalization of P-Ru → M, which decreases the electron density of P nucleus and causes the downfield ³¹P chemical shifts. Except 2, the back-donation effect of Ru ← M, arising from the delocalization from s valence orbital of M²⁺ to the valence orbital of Ru, is against the P-Ru → M delocalization and results in the upfield ³¹P chemical shifts in 4. Meanwhile, the binding energies indicate that complex 4 is stable and can be synthesized experimentally. However, as complex [Ru(CO)₃(Ph₂Ppy)₂HgCl]⁺5 is more stable than 4, the reaction of 1 with HgCl₂ only gave 5 experimentally.     

Synthesis of di-, tri-, tetra- and pentacyclic arene complexes of ruthenium(II):[Ru(η-polycyclic arene)-(1-5-η-cyclooctadienyl)]PF6 and their reactions with NaBH4

The phenanthrene complex of ruthenium(II), [Ru(η⁶-phenanthrene)(1,5-η⁵-cyclooctadienyl)]PF₆ (2c), is prepared by the reaction of Ru(η⁴-1,5-COD)(η⁶-1,3,5-COT) (1) with phenanthrene and HPF₆ in 65% yield. Similar treatments with di- tri-, tetra- and pentacyclic arenes give corresponding polycyclic arene complexes, [Ru(η⁶-polycyclic arene)(1-5-η⁵-cyclooctadienyl)]PF₆ [polycyclic arene = naphthalene (2b), anthracene (2d), triphenylene (2e), pyrene (2f) and perylene (2g)] in 46-90% yields. The molecular structure of the perylene complex 2g is characterized by X-ray crystallography. Reaction of 2c with NaBH₄ gives a mixture of the 1,5- and 1,4-COD complexes of ruthenium(0), Ru(η⁶-phenanthrene)(η⁴-1,5-COD) (3c) and Ru(η⁶-phenanthrene)(η⁴-1,4-COD) (4c) in 76% in 1:8 molar ratio. The arene exchange reactions among cationic complexes [Ru(η⁶-arene)(1-5-η⁵-cyclooctadienyl)]PF₆ (2) showed the coordination ability of arenes in the following order: benzene ∼ triphenylene > phenanthrene > naphthalene > perylene ∼ pyrene > anthracene, suggesting the benzo fused rings, particularly those of acenes, decreasing thermal stability of the arene complex.