Presence Of NH4PF6 Research Articles

Four- and five-coordinate nickel(ii) complexes bearing new diphosphine-phosphonite and triphosphine-phosphite ligands: catalysts for N-alkylation of amines.

The reaction of Ph2PCH2OH with PhPCl2 and PCl3 in the presence of Et3N afforded new phosphonite compounds PhP(OCH2PPh2)21 and P(OCH2PPh2)32, respectively. The reaction between 1 and [NiCl2(DME)] in dichloromethane gave the five-coordinate complex [NiCl2(1-κ3P,P,P)] 3. Conversely, 1 reacts with [NiCl2(DME)] in the presence of NH4PF6 in dichloromethane to yield the four coordinate ionic complex [NiCl(1-κ3P,P,P)][PF6] 4. The reactions between 1, [NiCl2(DME)] and KPF6 in the presence of RNC (R = Xylyl, tBu and iPr) in dichloromethane yielded the five coordinate monocationic [NiCl(1-κ3P,P,P)(RNC)][PF6] (R = Xylyl) and dicationic [Ni(1-κ3P,P,P)(RNC)2][PF6]2 (R = tBu and iPr) complexes, respectively. The analogous reaction of 2 with [NiCl2(DME)] in the presence of KPF6 gave complex [NiCl(2-κ4P,P,P,P)][PF6], 8. The structures of all complexes were determined by single crystal X-ray diffraction studies and supported by spectroscopic methods. To demonstrate their catalytic application, N-alkylation reactions between primary aryl amines, benzyl and 4-methoxy benzyl alcohols were found to proceed smoothly in the presence of 2.5 mol% of complexes bearing ligand 1 and <0.5 mmol of KOBut in toluene at 140 °C. The C–N coupled products were formed in very good yields. Its substrate scope includes sterically encumbered, heterocyclic amines and aliphatic alcohol.

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Diastereoselection and induced chirality at-metal in distorted-tetrahedral bis[(R or S)-1-(p-R1-C6H4)-N-(phenyl(pyridin-2-yl)methylene)ethanamino-κ2N,N]-Δ/Λ-copper(PF6)2

The enantiopure Schiff bases (R or S)-1-(p-R1-C6H4)-N-(phenyl(pyridin-2-yl)methylene)ethanamine (R1 = H and OCH3) are synthesized from reaction between the 2-benzoyl-pyridine and chiral-amine (R or S)-1-(p-R1-C6H4)ethylamine, respectively. These Schiff bases react with the copper(II) acetate to give distorted-tetrahedral bis[(R or S)-1-(p-R1-C6H4)-N-(phenyl(pyridin-2-yl)methylene)ethanamino-κ2N,N]-Δ/Λ-Cu(PF6)2 in the presence of NH4PF6. A conformational change from cis- to trans-isomer occurs in solution and thereby, the copper(II) coordinates to the solely trans-form to provide the complexes. Cyclic voltammograms demonstrate two quasi-reversible one electron charge transfer processes for the Cu2+/Cu+ and Cu+/Cu0 couples in acetonitrile. ECD spectra reveal expected mirror-image relationships and indicate enantiopurity or enantiomeric excess of the R or S-ligands and their associated complexes in solution. Comparisons of experimental and simulated ECD spectra suggest induced chirality at-metal center, which diastereoselectively provides the Δ-Cu-R or Λ-Cu-S diastereomer as major product in solution. DFT/TDDFT optimized structures and excited state properties correspond well to the experimental results.

Synthesis, Hirshfeld surface analysis, luminescence and thermal properties of three first‐row transition metal complexes containing 4′‐hydroxy‐2,2′:6′,2″‐terpyridine: Application for preparation of nano metal oxides

A series of new mono‐ and bis‐terpyridine complexes [Mn(tpyOH)Cl2] (1), [Ni(tpyOH)2](PF6)2 (2) and [Zn(tpyO)(η1‐OCOCH3)(H2O)]⋅3H2O (4) containing 4′‐hydroxy‐2,2′:6′,2″‐terpyridine (tpyOH) were synthesized and structurally characterized using elemental analysis, infrared spectroscopy and single‐crystal X‐ray diffraction. The reaction of MnCl2 with tpyOH in a mixture of methanol and CH2Cl2 resulted in the formation of 1. The X‐ray crystal structure of 1 reveals that Mn(II) is penta‐coordinated by three nitrogen atoms from tpyOH and two Cl− in a slightly distorted trigonal bipyramidal geometry. Complex 2 was also prepared by the reaction of nickel(II) chloride with tpyOH in a methanolic medium in the presence of NH4PF6. Notably, the complex [Ni(tpyOH)(tpyO)]PF6 (3), obtained during the crystallization of 2 from dichloromethane, was characterized using X‐ray crystallography which shows that six nitrogen atoms from terpyridine ligands occupy the coordination sites around the Ni(II) centre in a distorted octahedral geometry with four longer bonds and two shorter NiN bonds. The reaction of zinc(II) acetate with tpyOH in a mixture of methanol and CH2Cl2 led to the formation of 4. The crystal structure of 4 reveals the formation of penta‐coordinated Zn(II) complex containing three nitrogen atoms from tpyO, a monodentate acetate ligand and one coordinated water molecule. Hirshfeld surface analyses and two‐dimensional fingerprint plots show that the main interactions are O…H/H…O contacts in 1, 3 and 4. The thermal decomposition reactions of 1, 2 and 4 were studied using thermogravimetric analysis in detail due to their different structures. The solution luminescence features of 1, 2 and 4 include high‐energy intense π → π* intraligand and low‐energy metal‐to‐ligand charge transfer transitions at room temperature. The calcination of the coordination complexes led to the formation of corresponding nano metal oxides. The products were structurally characterized using infrared spectroscopy, scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. The average particle size using Scherrer's equation was calculated to be below 50 nm.

Synthesis and characterization of iridium hydride complexes with meso-Ph2PCH2P(Ph)CH2P(Ph)CH2PPh2 (meso-dpmppm) as an unsymmetric pincer ligand

Reaction of [IrCl(CO)(PPh3)2] with meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso-dpmppm) afforded a mononuclear IrI complex, [Ir(meso-dpmppm−κ3)(CO)2]Cl (1), which showed excellent reactivity towards HX, H2, HCOOH, and R3SiH to yield a series of IrIII hydride complexes, [IrH(meso-dpmppm−κ3)(CO)2]X2 (X = Cl (2), PF6 (2*)), [Ir(H)2(meso-dpmppm−κ3)(CO)]Cl (4), and [IrH(SiR3)(meso-dpmppm−κ3)(CO)]Cl (R3 = Me2Ph (5a), Ph2H (5b)). The hydride IrIII complexes with isocyanides, [IrH(meso-dpmppm−κ3)(RNC)2](PF6)2 (R = Xyl (2,6-xylyl) (3a), Mes (2,4,6-mesityl) (3b), Cy (cyclohexyl) (3c), tBu (tert-butyl) (3d)), were also prepared by reacting [IrCl(cod)]2 with meso-dpmppm and RNC in the presence of NH4PF6. Complexes 2–5 were characterized by 1H and 31P NMR and ESI−MS spectroscopies and X-ray diffraction analyses (3a, 4, 5a,b) to have distorted octahedral IrIII structures supported by a meso-dpmppm in meridional mode as an unsymmetrical PPP−κ3 pincer ligand, coordinating with two outer and one inner phosphorus atoms to form fused six- and four-membered chelate rings and bearing an uncoordinate inner phosphine unit. The terminal hydride occupied the axial open site surrounded by the equatorially oriented phenyl groups of meso-dpmppm and is trans to the carbonyl (2, 4) and isocyanide ligands (3) nested in the closed site with respect to the {Ir(meso-dpmppm−κ3)} pincer plane. The remaining equatorial site is coordinated by CO (2), RNC (3), hydride (4), and silyl (5) ligand. These structural features demonstrated that oxidative additions of H+, H2, and R3SiH occurred at the axial open site of 1. The uncoordinate inner phosphine of 1 is readily reacted with [Cp*IrCl2]2 to give [Ir(μ−meso-dpmppm−κ3)(η5−Cp*IrCl2)(CO)2]Cl (1∙Cp*IrCl2, Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl), which further transformed by oxidative addition of H2 and HCl to [Ir(H)2(μ−meso-dpmppm−κ3)(η5−Cp*IrCl2)(CO)]Cl (4∙Cp*IrCl2) and [IrH(μ−meso-dpmppm−κ3) (η5−Cp*IrCl2)(CO)2]Cl2 (2∙Cp*IrCl2), respectively, and however addition of bulky Me2PhSiH resulted in a disproportionation mixture of [IrH(Me2PhSi)(μ−meso-dpmppm−κ3)(η5-Cp*IrCl2)(CO)]Cl (5a∙Cp*IrCl2) as well as 4∙Cp*IrCl2, indicating an allosteric influence by attaching Cp*IrCl2 unit on the uncoordinate phosphine of the {Ir(meso-dpmppm−κ3)} unsymmetric pincer unit in 1.

Intermolecular Dehydrative Coupling and Intramolecular Cyclization of Ruthenium Vinylidene Complexes Formed from Aromatic Propynes Containing Carbonyl Functionalities.

A remarkable intermolecular dehydrative coupling reaction with the formation of a C-C bond was found for the vinylidene complex 2 a, yielding the dinuclear bisvinylidene complex 4 a. Complex 2 a containing 1-hydroxyindan moiety was first formed from the reaction of o-propynyl benzaldehyde 1 a with [Ru]-Cl ([Ru]=Cp(PPh3 )2 Ru) by a cyclization process. For analogous aldehyde 1 b containing an additional 1,3-dioxolane group on the aryl ring, similar intermolecular coupling yields the dinuclear bisvinylidene complex 4 b. However, the fluoro group on the aryl ring in aldehyde 1 c inhibits the coupling reaction, giving only the vinylidene complex 2 c. For the reactions of [Ru]-Cl in MeOH with compounds 1 f, 1 g and 1 h, each with a ketone functionality, cyclization gives vinylidene complexes 2 f, 2 g and 2 h, respectively. However, no similar intermolecular coupling was observed, instead, the intramolecular dehydration yields 8 f, 8 g and 8 h, respectively. In CDCl3 , catalytic cyclization is observed for the o-propynylphenyl ketone 1 h with [Ru]-Cl at 50 °C giving the isochromene products 14 h. Furthermore, treatment of the o-propynylaryl α,β-unsaturated ketones 1 k-m and 1 n with [Ru]-Cl in MeOH affords the corresponding vinylidene complexes 10 k-m and 11 n each with 1-benzosuberone moiety in the presence of NH4 PF6 . These intramolecular cyclization products were formed by the addition of Cβ onto the terminal carbon of the alkene moiety. All these reaction products were characterized by spectroscopic methods. In addition, structures of complexes 4 a, and 10 l were confirmed by single crystal X-ray diffraction analysis.

Synthesis and structural characterization of Ni(II) complexes with the chiral CpH(PNMent) tripod ligand

Treatment of NiCl2 with the tripod ligand (LMent,SC)-1H led to (LMent,SC)-[Cp(PNMent)NiCl] in which the potentially tridentate ligand coordinated to the metal center in a bidentate way via the cyclopentadienyl system and the phosphorus atom. In the presence of NH4PF6 [(LMent,SC)-[Cp(PNMent)NiCl] readily underwent Cl/PPh3 exchange to give (LMent,SC)-[Cp(PNMent)NiPPh3]PF6. Reaction of (LMent,SC)-[Cp(PNMent)NiCl] with 0.5 eq. of dppe afforded [{(LMent,SC)-[Cp(PNMent)Ni]}2dppe](PF6)2. (LMent,SC)-[Cp(PNMent)NiPPh3]PF6 and [{(LMent,SC)-[Cp(PNMent)Ni]}2dppe](PF6)2 were characterized by NMR and MS spectroscopy, and also by single crystal X-ray diffraction. The cyclopentadienyl ligand of (LMent,SC)-[Cp(PNMent)NiPPh3]PF6 shows a distortion intermediate between the ene-allyl and diene types, while the two cyclopentadienyl ligands of [{(LMent,SC)-[Cp(PNMent)Ni]}2dppe](PF6)2 have intermediate and diene distortions, respectively. According to the temperature dependent NMR spectra of (LMent,SC)-[Cp(PNMent)NiPPh3]PF6 and [{(LMent,SC)-[Cp(PNMent)Ni]}2dppe](PF6)2 two different conformations of the tether in the Cp(PNMent)Ni system could be frozen out at low temperatures.

The synthesis and crystal structures of new trinuclear and hexanuclear nickel complexes with metallodithiolate ligands

ABSTRACTTwo nickel complexes with metallodithiolate ligands, which can be regarded as the active site models of the acetyl coenzyme A synthase, were prepared and structurally characterized by X-ray crystallography. Reactions of Ni(PPh3)2Cl2 with Ni(bme-dach) [bme-dach = N,N'-bis(mercaptoethyl)-1,4-diazacycloheptane] or Ni(bme-dach*) [bme-dach* = N,N'-bis(mercaptoethyl)-1,4-diazacyclohexane] in MeCN in the presence of NH4PF6 resulted in the formation of a trinuclear nickel complex {Ni[Ni(bme-dach)]2}[PF6-]2 (1) and a hexanuclear nickel complex {Ni2[Ni(bme-dach*)]4}[PF6−]4 (2). The crystal structure of 1·2MeCN shows a square planar geometry of nickel atom that is coordinated by four sulfur atoms of the metallodithiolate ligands Ni(bme-dach). The crystal structure of 2·4MeCN reveals that each of the two nickel atoms is ligated by four sulfur atoms of the metallodithiolate ligands Ni(bme-dach*) to form a square planar coordination sphere.

Selective Aerobic C-H Amination of Phenols with Primary Amines over Copper toward Benzoxazoles.

Using O2 as the oxidant, the benzoxazole frameworks can be directly constructed from the readily available phenols and primary amines in the presence of NH4PF6 over copper under mild conditions. Mechanistic studies showed that a novel mechanism involving biphenyldiols and o-quinones very possibly takes effect in the reaction, because both can selectively give the benzoxazoles under the reaction conditions. An unprecedented unstrained Caryl-Caryl bond cleavage takes place in the reaction.

Influence of calcium(II) and chloride on the oxidative reactivity of a manganese(II) complex of a cross-bridged cyclen ligand.

Available data from different laboratories have confirmed that both Ca(2+) and Cl(-) are crucial for water oxidation in Photosystem II. However, their roles are still elusive. Using a manganese(II) complex having a cross-bridged cyclen ligand as a model, the influence of Ca(2+) on the oxidative reactivity of the manganese(II) complex and its corresponding manganese(IV) analogue were investigated. It has been found that adding Ca(2+) can significantly improve the oxygenation efficiency of the manganese(II) complex in sulfide oxidation and further accelerate the oxidation of sulfoxide to sulfone. Similar improvements have also been observed for Mg(2+), Sr(2+), and Ba(2+). A new monomeric manganese(IV) complex having two cis-hydroxide ligands has also been isolated through oxidation of the corresponding manganese(II) complex with H2O2 in the presence of NH4PF6. This rare cis-dihydroxomanganese(IV) species has been well characterized by X-ray crystallography, electrochemistry, electron paramagnetic resonance, and UV-vis spectroscopy. Notably, using the manganese(IV) complex as a catalyst demonstrates higher activity than the corresponding manganese(II) complex, and adding Ca(2+) further improves its catalytic efficiency. However, adding Cl(-) decreases its catalytic activity. In electrochemical studies of manganese(IV) complexes with no chloride ligand present, adding Ca(2+) positively shifted the redox potential of the Mn(IV)/Mn(III) couple but negatively shifted its Mn(V)/Mn(IV) couple. In the manganese(II) complex having a chloride ligand, adding Ca(2+) shifted both the Mn(IV)/Mn(III) and Mn(V)/Mn(IV) couples in the negative direction. The revealed oxidative reactivity and redox properties of the manganese species affected by Ca(2+) and Cl(-) may provide new clues to understanding their roles in the water oxidation process of Photosystem II.

Fulvene–Ruthenium and Cp–Ruthenium Complexes via [2 + 2 + 1] Cyclotrimerization of Phenylacetylene with [RuCl(Tp)(1,5-cod)

The complex [RuCl(Tp)(1,5-cod)], which bears the labile 1,5-cod ligand, was prepared from a high-yielding route involving the reaction of [RuCl2(1,5-cod)(CH3CN)2] with KTp (Tp = HB(pz)3). The reaction of [RuCl(Tp)(1,5-cod)] with phenylacetylene in either ethanol or methanol gave anti-Markovnikov alkoxide-adduct complexes [Ru(Tp)(η6-C5H2Ph2-CH(Ph)R)] (R = OMe, OEt). These adducts were formed by [2 + 2 + 1] cyclotrimerization reactions of phenylacetylene mediated by the precursor complex, [RuCl(Tp)(1,5-cod)]. The ruthenium(II)–fulvene complex, [Ru(Tp)(η6-C5H2Ph2-CH(Ph))]+, involved in these transformations was successfully isolated in the presence of NH4PF6. These complexes were fully characterized by 1H NMR, 13C NMR, DEPT, HSQC, IR, and ESI-MS spectroscopy. The molecular structures of [Ru(Tp)(η6-C5H2Ph2-CH(Ph)R)] (R = OMe/OEt) and [Ru(Tp)(η6-C5H2Ph2-CH(Ph))]PF6 have been determined by X-ray single-crystal diffraction. These complexes have piano-stool structures around the ruthenium center where half of the...

Hydroxylation of azomethine carbon: isolation of complexes of η5 and η6-cyclic hydrocarbon platinum group metals with a new Schiff-base ligand

A new Schiff base, (pyridin-2-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine, (L), was synthesized. Reaction of [(η6-arene)Ru(µ-Cl)Cl]2 and [Cp*M(µ-Cl)Cl]2 (M = Rh and Ir) with one equivalent of L in the presence of NH4PF6 in methanol yielded dinuclear complexes, [(η6-arene)2Ru2(L-OH)Cl](PF6)2 {arene = C6H6 (1), p-iPrC6H4Me (p-cymene) (2) and C6Me6 (3)}, and [Cp*2M2(L-OH)Cl](PF6)2 [M = Rh (4) and Ir (5)], respectively, leading to the formation of five new chiral complexes with –OH on the azomethine carbon. L is a pentadentate ligand where one of the metal centers is coordinated to two nitrogen atoms in a bidentate chelating fashion while the other metal is bonded tridentate to three nitrogen atoms. Although the ligand is neutral before coordination, after complexation it is anionic (uni-negative) with negative charge on the azo nitrogen {see the structures: N(5) in 2[PF6]2 and N(3) for 4[PF6]2}. The complexes have been characterized by various spectroscopic methods including infrared and 1H NMR and the molecular structures of the representative complexes are established by single-crystal X-ray diffraction studies.

Cyclometallated Palladium Diphosphane Compounds Derived from the Chiral Ligand (S)‐PhCH(Me)NMe2. Michael Addition Reactions to the Vinylidene Double Bond

AbstractTreatment of (S)‐PhCH(Me)NMe2 (1) with palladium(II) acetate in toluene gave the dinuclear cyclometallated complex [Pd{(S)‐C6H4CH(Me)NMe2‐C2,N}(μ‐OAc)]2 (2), inwhich the ligand is bonded to the palladium atom through the nitrogen phenyl carbon atoms. The reaction of 2 with aqueous sodium chloride gave the chloro‐bridged complex 3. The reaction of 3 with (R,R)‐DIOP [(4R,5R)‐4,5‐bis(diphenylphosphanylmethyl)‐2,2‐dimethyl‐1,3‐dioxolane], in a complex/phosphane 1:1 molar ratio, gave [{Pd[(S)‐C6H4CH(Me)NMe2‐C2,N]Cl}2(μ‐(R,R)‐DIOP)] (4). The reaction of 3 with (Ph2P)2C=CH2 (vdpp) in a 1:2 molar ratio in the presence of NH4PF6 or NaClO4 afforded [Pd{(S)‐C6H4CH(Me)NMe2‐C2,N}{(Ph2P)2C=CH2‐P,P′}][Y] [Y = PF6– (5); Y = ClO4– (6), respectively]. The treatment of 5 with acetylacetone in the presence of anhydrous sodium carbonate or with methanol afforded the addition products, [Pd{(S)‐C6H4CH(Me)NMe2‐C2,N}{(Ph2P)2CHCH2R‐P,P′}][PF6] [R = CH(COMe)2 (7); R = OMe (8), respectively], in good yield. The treatment of 6 with methyl acetoacetate and anhydrous sodium carbonate afforded the addition derivative [Pd{(S)C6H4CH(Me)NMe2C2,N}{(Ph2P)2CHCH2CH‐(COMe)(COOMe)‐P,P′}][ClO4] (9). The NMR spectra of the addition products showed that some of the resonances were duplicated due to the existence of optical isomers. The X‐ray crystal structure of complexes 2, 5, and 7 were determined by single‐crystal X‐ray diffraction analysis.

Multifunctional Dithiocarbamates: Synthesis and Ring-Closing Metathesis of Diallyldithiocarbamate Complexes

The complex cis-[RuCl2(dppm)2] reacts with the diallyldithiocarbamate KS2CN(CH2CH═CH2)2 to form [Ru{S2CN(CH2CH═CH2)2}(dppm)2]+. The same ligand was also used to prepare the alkenyl complexes [RuR{S2CN(CH2CH═CH2)2}(CO)(PPh3)2] (R = CH═CHBut, CH═CHC6H4Me-4, C(C≡CBut)═CHBut) from the corresponding precursors [RuRCl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) and [Ru(C(C≡CBut)═CHBut)Cl(CO)(PPh3)2]. The complexes [Ni{S2CN(CH2CH═CH2)2}(dppp)]+ (dppp =1,3-bis(diphenylphosphino)propane) and [M{S2CN(CH2CH═CH2)2}(dppf)]+ (M = Ni, Pd, Pt; dppf = 1,1′-bis(diphenylphosphino)ferrocene) were prepared from the respective precursors [MCl2(L2)] (L2 = dppp, dppf) and KS2CN(CH2CH═CH2)2 in the presence of NH4PF6. In a similar manner, treatment of the cyclometalated dimer [Pd(C,N-CH2C6H4NMe2)Cl]2 with the dithiocarbamate ligand yielded [Pd(C,N-CH2C6H4NMe2){S2CN(CH2CH═CH2)2}]. The homoleptic literature complexes [Ni{S2CN(CH2CH═CH2)2}2] and [Co{S2CN(CH2CH═CH2)2}3] were also prepared and characterized. Ring-closing metathesis...

Lotus-Root-like One-Dimensional Polymetallocages with Drastic Void Adaptability Constructed from 4,4′-Bis(1,2,4-triazol-1-ylmethyl)biphenyl and Zn(II) or Co(II) and Their Fluorescein Encapsulation Properties

The reaction of 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl (L) with Zn(NO3)2·6H2O or Co(NO3)2·6H2O in the presence of NH4PF6 in water−methanol or water−acetone produced both {[ZnL3](PF6)2(H2O)2}n (1) or {[CoL3](PF6)2(H2O)2}n (2). The metal ions in both complexes coordinate with six identical N atoms from six different ligands in an ideal octahedral environment where each ligand binds to two metal ions. Both complexes are one-dimensional triple-helical chains each containing an empty lotus-root-structured polymetallocage. The metallocage in 1 is fully empty, while the cage in 2 contains two water molecules. However, metallocages in 1 have a void volume of ∼200 A3, which is much smaller than the 1020 A3 void in 2. The void in 2 is comparable to the size of fluorescein. Both complexes are capable of encapsulating fluorescein anion in pH 9 aqueous solution to form {C20H10O5 ⊂ [ML3]}n, where C20H10O52− is fluorescein dianion, and M is Zn or Co. The encapsulation occurs via anion exchange. The cages in 1 are in...

Synthesis, Characterization, and Solution Properties of a Novel Cross-Bridged Cyclam Manganese(IV) Complex Having Two Terminal Hydroxo Ligands

A novel monomeric tetravalent manganese complex with the cross-bridged cyclam ligand 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (Me2EBC), [Mn(IV)(Me2EBC)(OH)2](PF6)2, was synthesized by oxidation of Mn(II)(Me2EBC)Cl2 with H2O2 in the presence of NH4PF6)in aqueous solution. The X-ray crystal structure determination of this manganese(IV) compound revealed that it contains two rare terminal hydroxo ligands. EPR studies in dry acetonitrile at 77 K show two broad resonances at g = 1.96 and 3.41, indicating that the manganese(IV) exists as a high-spin d3 species. Resonance Raman (rR) spectra of this manganese(IV) species reveal that the dihydroxy moiety, Mn(IV)(OH)2, is also the dominant species in aqueous solution (pH < 7). pH titration provides two pK(a) values, 6.86(4) and 10.0(1), associated with stepwise removal of the last two oxygen-bound protons from [Mn(IV)(Me2EBC)(OH)2](2+). The cyclic voltammetry of this manganese(IV) complex in dry acetonitrile at 298 K demonstrates two reversible redox processes at +0.756 and -0.696 V (versus SHE) for the Mn4+/Mn3+ and Mn3+/Mn2+ couples, respectively. This manganese(IV) complex is relatively stable in weak acidic aqueous solution but easily degrades in basic solution to manganese(III) derivatives with an 88 +/- 1% yield.

Syntheses and Characterization of Oxygen/Sulfur-Bridged Incomplete Cubane-Type Clusters, [Mo3S4Tp3]+and [Mo3OS3Tp3]+, and a Mixed-Metal Cubane-Type Cluster, [Mo3FeS4ClTp3]. X-ray Structures of [Mo3S4Tp3]Cl, [Mo3OS3Tp3]PF6, and [Mo3FeS4ClTp3

The reaction of [Mo3S4(H2O)9]4+ (1) with hydrotris(pyrazolyl)borate (Tp) ligands produced [Mo3S4Tp3]Cl x 4 H2O ([3]Cl x 4 H2O) in an excellent yield. An X-ray structure analysis of [3]Cl x 4 H2O revealed that each molybdenum atom bonded to the Tp ligand. We report four salts of 3, [3]Cl x 4 H2O, [3]tof x 2 H2O, [3]PF6 x H2O, and [3]BF4 x 2 H2O in this paper. The solubility and stability of the chloride salt in organic solvents differ completely from those of the other salts. We have also prepared a new compound, [Mo3OS3Tp3]PF6 x H2O ([4]PF6 x H2O), via the reaction of [Mo3OS3(H2O)9]4+ (2) with KTp in the presence of NH4PF6. All the molybdenum atoms bonded to Tp ligand. 1H NMR signals corresponding to nine protons bonded to three pyrazole rings in one Tp were observed in a spectrum (at 253 K) of [3]BF4 x 2 H2O. It shows that cluster 3 has a 3-fold rotation axis in CD2Cl2 solution. Twenty-one 1H NMR signals corresponding to twenty-seven protons bonded to nine pyrazole rings in three Tp ligands were observed in a spectrum (at 233 K) of [4]PF6 x H2O; obviously, 4 has no 3-fold rotation axis, in contrast to 3. The short CH...mu3S distance caused large upfield chemical shifts in the 1H NMR spectra of 3 and 4. The reaction of 3 with metallic iron in CH2Cl2 produced [Mo3FeS4XTp3] (X = Cl (5), Br (6)). X-ray structure analysis of 5 has revealed the existence of a cubane-type core Mo3FeS4. Complex 3 functions as a metal-complex ligand for preparing a novel mixed-metal complex even in nonaqueous solvents. The cyclic voltammogram of 5 shows two reversible one-electron couples (E(1/2) = -1.40 and 0.52 V vs SCE) and two irreversible one-electron oxidation processes (E(pc) = 1.54 and 1.66 V vs SCE).

Syntheses, spectroscopic and structural studies of indenyl ruthenium complexes incorporating amine and nitrile ligands: molecular structures of [(η5-C9H7) Ru(η2-dppe)(CH3CN)]PF6 and [(η5-C9H7)Ru(η2-dppe)(NH3)]PF6

The reaction of [(η5-C9H7)Ru(η2-dppe)Cl] (1) with monodentate nitriles, (L) in the presence of NH4PF6 afforded the complexes [(η5-C9H7)Ru(η2-dppe)(L)]PF6, with L = CH3CN (2a), CH3CH=CHCN (2b), NCC6H4CN (2c), C6H5CH2CN (2d), respectively. However, reaction of 1 with NH4PF6 in methanol yielded an amine complex of the type [(η5-C9H7) Ru(η2-dppe)(NH3)]PF6 (3a). The complexes were fully characterized by spectroscopy and analytical data. The molecular structures of the complexes [(η5-C9H7)Ru(η2-dppe) (CH3CN)]PF6 (2a) and [(η5-C9H7)Ru(η2-dppe)(NH3)]PF6 (3a) have been determined by single crystal X-ray analyses.

Enhanced hydrolytic activity of Cu(ii) and Zn(ii) complexes in highly cross-linked polymers

The chelate ligand tris[(1-vinylimidazol-2-yl)methyl]amine (5) was synthesized in five steps from commercially available starting materials. Upon reaction with ZnCl2 or CuCl2 in the presence of NH4PF6, the complexes [Zn5Cl]PF6 (6) and [Cu5Cl]PF6 (7) were obtained. The structure of both complexes was determined by single-crystal X-ray crystallography. Immobilization of 6 and 7 was achieved by co-polymerization with ethylene glycol dimethacrylate. The supported complexes P6-Zn and P7-Cu were found to be efficient catalysts for the hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) at 50 degrees C. At pH 9.5, the heterogeneous catalyst P7-Cu was 56 times more active than the homogeneous catalyst 7. Partitioning effects, which increase the local concentration of BNPP in the polymer, are shown to contribute to the enhanced activity of the immobilized catalyst.

Structurally characterized acylruthenium organometallics bearing a pendant aldehyde function

By reacting [Ru(RL1)(PPh3)2(CO)Cl], (1) (R = C6H4Me, Et) with an excess of CNBu t in the presence of NH4PF6, organometallics of the type [Ru(RL2)(PPh3)2(CNBu t )2]PF6, (2) have been isolated in excellent yield [RL1 = C6H2O-2-CHNHR(p)-3-Me-5, RL2 = C6H2(CO)-O-2-CHNHR(p)-3-Me-5]. These organometallics, on controlled hydrolysis, produce [Ru(L3)(PPh3)2(CNBu t )2], (3) in very good yield (L3 = C6H2(CO)-O-CHO-3-Me-5). In both ([2(C6H4Me)] · 2H2O) and ([3] · 2CH2Cl2) the two phosphine ligands lie in trans positions. In ([2(C6H4Me)] · 2H2O) the Ru(C6H4MeL2) fragment, excluding the pendant tolyl ring, is a near perfect plane (mean dev ~ 0.02A) which makes a dihedral angle of 5.2° with the tolyl plane. The acyl chelate ring in ([2(C6H4Me)] · 2H2O) is excellently planar with a mean deviation of 0.006°. In ([3] · 2CH2Cl2) the Ru(L3) fragment defines a crystallographic plane of symmetry, the coordinates of the atom being of the type x, 1/4z. The complex ([2C6H4Me)] · 2H2O) displays N–HȮFO (iminium-phenolato) hydrogen bonding while in ([3] · 2CH2Cl2) C–H...O hydrogen bonding is present. Characteristic spectral data (u.v.–vis, i.r. and 1H n.m.r.) of the complexes are reported. A notable feature is that an allowed band near 500 nm due to the t2g → π*(azomethine) charge transfer transition, which is diagnostic of the coordinated iminium-phenolato function, is present in (3) but this band is absent in the aldehydic acyl complex (2). In the 1H n.m.r. spectrum the N+–H signal in (2) (near 13.5 ppm) is split into a doublet due to transcoupling with the azomethine proton. The aldehydic proton of (3) resonates as a sharp singlet near 10 ppm. In CH2Cl2 solution (2) and (3) display quasireversible a Ru III /Ru II cyclic voltammetric response with E1/2 near 0.9 and 0.5 V versuss.c.e. The conversion (2) → (3) is accompanied by the nucleophilic attack of water. The complex (3) is also obtained directly from (1) by reaction with CNBu t in the presence of H2O. The aldehyde function in (3) is deactivated by the existing acyl moiety; as a result further decarbonylation does not take place.