Solvato Complex Research Articles

Iridium(III) Complexes with Fluorinated Phenyl-tetrazoles as Cyclometalating Ligands: Enhanced Excited-State Energy and Blue Emission.

Five cationic iridium(III) complexes with fluorinated cyclometalating tetrazole ligands [Ir(dfptrz)2L]+, where Hdfptrz = 5-(2,4-difluorophenyl)-2-methyl-2H-tetrazole and L = 2,2'-bypiridine (1F), 4,4'-ditert-butyl-2,2'-bipyridine (2F), 1,10-phenantroline (3F), 4,4'-bis(dimethylamino)-2,2'-bipyridine (4F), and tert-butyl isocyanide (5F), were prepared following a one-pot synthetic strategy based on a bis-cyclometalated solvato complex obtained via silver(I)-assisted cyclometalation, which was then reacted with the proper ancillary ligand to get the targeted complexes. The X-ray crystal structures of 2F and 4F were determined, showing that the tetrazole ligands are in a trans arrangement with respect to the iridium center. Electrochemical and photophysical properties, along with density functional theory calculations, allowed a full rationalization of the electronic properties of 1F-5F. In acetonitrile solution at 298 K, complexes 1F-3F, equipped with bipyridine and phenanthroline ligands, exhibit strong vibronically structured luminescence bands in the blue region with photoluminescence quantum yields (PLQYs) in the range 56-76%. This behavior is radically different from the nonfluorinated analogues reported previously, which emits in the green region from 3MLCT excited states. 4F shows relatively strong emission (PLQY = 40%) of charge transfer character centered on the amino-bipyridine ancillary ligand, whereas the emission of 5F is very weak (PLQY = 0.6%), further blue-shifted and attributed to the lowest ligand-centered (3LC) triplet state of the tetrazolyl cyclometalated moiety. A similar photophysical behavior is observed in PMMA at 298 K, whereas in a 77 K matrix, all of the compounds are strong emitters. This novel fluorinated phenyl-tetrazole cyclometalating ligand provides the corresponding iridium(III) complexes with a combination of excited-state energy and redox potentials that make them very promising as photoredox catalysts.

Can a Nonorganometallic Ruthenium(II) Polypyridylamine Complex Catalyze Hydride Transfer? Mechanistic Insight from Solution Kinetics on the Reduction of Coenzyme NAD+ by Formate.

Application of organometallic ruthenium(II) arene complexes has been successful for the modulation of cellular redox processes via their interaction with species such as formate to control the NAD+/NADH balance in cells. Here we present the first evidence that similar effects can be reached with the application of a nonorganometallic ruthenium(II) polypyridyl complex. Kinetic studies performed demonstrate the ability of [RuII(terpy)(en)(H2O/EtOH)]2+ in water/ethanol (1:9, v/v) solution, where terpy = 2,2':6',2″-terpyridine and en = ethylenediamine, to catalyze the reduction of the NAD+ coenzyme to NADH in the presence of formate as hydride transfer source. In this case, terpy instead of arene is responsible for the labilization of coordinated solvent. The suggested catalytic cycle begins with the fast anation of the [RuII(terpy)(en)(H2O/EtOH)]2+ complex by formate. This is followed by the rate-determining formate-catalyzed decarboxylation of the generated ruthenium(II) formato complex to form [RuII(terpy)(en)H]+. Rapid hydride transfer to NAD+ from [RuII(terpy)(en)H]+ to form NADH and to regenerate the starting ruthenium(II) solvato complex, closes the overall catalytic cycle.

Solvent-Induced Encapsulation of Cobalt(II) Ion by a Boron-Capped tris-Pyrazoloximate.

Boron-cross-linked cobalt(II) pseudoclathrochelate was obtained by the template reaction of 2-acetylpyrazoloxime, phenylboronic acid, and a new DMF cobalt(II) solvato complex with a decachloro-closo-decaborate dianion. As confirmed by single-crystal X-ray diffraction, this complex crystallizes with two symmetry-independent cobalt(II) pseudoclathrochelate cations, one decachloro-closo-decaborate dianion, one benzene, one dichloromethane solvent molecule, and two molecules of DMF. The latter act as pseudocapping fragments to the monocapped tris-pyrazoloximate ligands by forming N-H···O hydrogen bonds with their pyrazole groups. The CoIIN6-coordination polyhedra adopt a nearly ideal TP geometry with distortion angles φ equal to 1.22(16) and 2.58(17)° for two symmetry-independent pseudoclathrochelate cations, both containing the encapsulated cobalt(II) ion in its high-spin state (Co-N 2.115(4)-2.198(3) Å). Magnetic properties of this complex were studied both by dc-magnetometry and by solution-state NMR spectroscopy to reveal a high magnetic anisotropy, thus suggesting a large magnetic susceptibility tensor anisotropy (25.8 × 10-32 m3 at 298 K) and a large negative zero-field splitting energy (-85 cm-1). The results of magnetometry studies in the ac magnetic field suggest a single molecule magnet behavior of this TP complex with an effective magnetization reversal barrier of approximately 130 cm-1. Its pseudocapping DMF molecules that form H-bonds with tris-pyrazoloximate fragments are easy to substitute by strong H-bond acceptors, such as chloride ions and di- and tetramethylureas, thus affecting the magnetic properties of a whole pseudomacrobicyclic paramagnetic system.

Phosphorescent Imaging of Living Cells Using a Cyclometalated Iridium(III) Complex

A cell permeable cyclometalated iridium(III) complex has been developed as a phosphorescent probe for cell imaging. The iridium(III) solvato complex [Ir(phq)2(H2O]2)] preferentially stains the cytoplasm of both live and dead cells with a bright luminescence.

Rate Studies on the Release of Terminal Alkynes from Indenylruthenium(II) Vinylidene Complexes. Implications on the Mechanism of η1-Vinylidene into η2-Alkyne Isomerization

The indenylruthenium(II) vinylidene complexes [Ru{═C═C(H)R}(η5-C9H7)(PPh3)2][PF6] [R = Ph (1), 4-MeOC6H4 (2), 4-MeC6H4 (3), 4-PhC6H4 (4), 4-FC6H4 (5), 4-ClC6H4 (6), 4-IC6H4 (7), 4-MeCOC6H4 (8), 4-O2NC6H4 (9), nBu (10), (η5-C5H4)Fe(η5-C5H5) (11, Fc)] have been synthesized from [RuCl(η5-C9H7)(PPh3)2] and RC≡CH, in a methanolic solution of NaPF6 at room temperature. The complexes, when dissolved in acetonitrile-d3, release the vinylidene ligand upon thermal activation in the form of the corresponding terminal alkyne, with formation of the solvato complex [Ru(N≡CCD3)(η5-C9H7)(PPh3)2][PF6] (1a). The reactions, followed by 31P{1H} NMR spectroscopy, exhibit first-order behavior in the vinylidene substrates, and the activation parameters ΔH⧧ = 24 ± 1 kcal mol−1 and ΔS⧧ = −3 ± 2 cal mol−1 K−1 for complex 1 (36−54 °C). The Hammett plot derived from the aryl-substituted complexes yields the reaction parameter ρ = −1.5, indicating a rate enhancement effect by electron-donor substituents on the β-C atom. Formation of ...

N-Dimethoxyphenylation of highly basic pyrazoles during undivided electrolysis

The reactions of pyrazole, 3,5-dimethylpyrazole, and its 4-nitro derivatives with 1,4-dimethoxybenzene during undivided amperostatic electrolysis in MeCN (CH2Cl2) were studied. The basicity of the medium, which depends on the solvent nature, the nature and concentration of pyrazole and the acid-base properties of additives, and the amount of electricity passed determine the yield and relative content of the target products, viz., 1,4-dimethoxy-2-(pyrazol-1-yl)benzenes (1) and 1,4-dimethoxy-1,4-di(pyrazol-1-yl)cyclohexa-2,5-dienes (2). The process occurs mainly through the interaction of the nonionized solvato complex of pyrazole with the 1,4-dimethoxybenzene radical cation and affords radical intermediates structurally similar to compounds 1 and 2. The key stage of the process determining the 1 : 2 ratio is the rearrangement of the intermediately produced 1,4-dimethoxy-1-(pyrazol-1-yl)arenonium cation to the 1-(pyrazol-1-yl)-2,5-dimethoxyarenonium cation.

Synthesis and reactivity of PtII complexes containing the orthometallated ligand [C6H4-2-PPh2C(H)COCH2PPh3

The reaction of PtCl2(NCPh)2 with the ylide [Ph3PC(H)COCH2PPh3]ClO4 (1:1 molar ratio, refluxing CHCl3) affords trans-[PtCl2(NCPh){C(H)PPh3C(O)CH2PPh3}]ClO41. However, the reaction of PtCl2 (CH2Cl2, r.t.) or PtCl2(NCMe)2 (2-methoxyethanol, reflux) with the ylide [Ph3PC(H)COCH2PPh3]ClO4 (1:1 molar ratio) affords the orthometallated [Pt{C6H4-2-PPh2C(H)COCH2PPh3}(μ-Cl)]2(ClO4)2, 2, as a mixture of diastereoisomers 2a–d. Treatment of 2 with PPh3 (1:2 molar ratio) affords [PtCl{C6H4-2-PPh2C(H)COCH2PPh3}(PPh3)](ClO4), 3, as a single geometric isomer. The reaction of 2 with AgClO4 (1:2 molar ratio) in NCMe gives the solvato complex [Pt{C6H4-2-PPh2C(H)COCH2PPh3}(NCMe)2](ClO4)2, 4, while the reaction of 2 with Tl(acac) (1: 2 molar ratio) gives [Pt{C6H4-2-PPh2C(H)COCH2PPh3}(acac)](ClO4), 5. The dicationic complexes [Pt{C6H4-2-PPh2C(H)COCH2PPh3}(dppe)](ClO4)2, 6, and [Pt{C6H4-2-PPh2C(H)COCH2PPh3}(phen)](ClO4)2, 7, can be obtained by reaction of 2 with AgClO4 followed by addition of the appropiate ligand (1: 2:2 molar ratio). The reaction of 6 with NaH gives [Pt{C6H4-2-PPh2C(H)COCHPPh3}(dppe)](ClO4), 8, while the reaction of 4 with PPh3 and NaH gives [Pt{C6H4-2-PPh2C(H)COCHPPh3}(PPh3)2](ClO4), 9. Complexes 8 and 9, which contain a “free ylide” functionality, react with ClAu(tht) to give [Pt{C6H4-2-PPh2C(H)COCH(AuCl)PPh3}(dppe)](ClO4), 10, and [Pt{C6H4-2-PPh2C(H)COCH(AuCl)PPh3}(PPh3)2](ClO4), 11. In the heterobimetallic complexes 10 and 11 the ylide ligand acts as a C,C,C-terdentate ligand and, in spite of the presence of two chiral centers, only one diastereoisomer (as the mixture of two enantiomers) is observed. All complexes were characterized on the basis of their spectroscopical and analytical parameters.

Electroinduced and Spontaneous Metal−Halide Bond Dissociation in [Co(η5-C5H5)(η3-2-MeC3H4)I

The electrochemical behavior of the species [Co(η5-C5H5)(η3-2-MeC3H4)I] and [Co(η5-C5H5)(η3-2-MeC3H4)(ACN)]+ in ACN solutions, at 25 °C, is described. The kinetic analysis of the cyclic voltammetry curves indicates that the introduction of one electron in the former complex is concerted with the dissociation of the Co−I bond. The ensuing radical undergoes fast solvation to yield the solvato complex [Co(η5-C5H5)(η3-2-MeC3H4)(ACN)]•, which then acts as an efficient electron donor toward the starting material with the formation of [Co(η5-C5H5)(η3-2-MeC3H4)(ACN)]+; finally, the cation is electroreduced at the working potentials to conclude an overall autocatalytic sequence. The solvato complex [Co(η5-C5H5)(η3-2-MeC3H4)(ACN)]•, formed as a product of the above reduction process, can be reversibly reduced to the corresponding anion at more negative potentials. Confirmation of the above mechanism and of the fact that the solvato complex can act as a solution electron donor toward the starting material was obtain...

The coordination ability of the organometallic sulfur ligand [Pd 3( μ-OAc) 3( μ-MeSCHCO 2Et- C, S) 3] and the XRD structure of its palladium(II) complex [Pd 4( μ-OAc) 3( μ-MeSCHCO 2Et- C, S)( μ3-MeSCHCO 2Et- C, κ2S) 2( η2-MeSCHCO 2Et- C, S)]BF 4

The trimetric mixed sphere complex of palladium(II) [Pd 3( μ-OAc) 3( μ-MeSCHCO 2Et- C, S) 3]( 1) affords [Pd 4( μ-OAc) 3( μ-MeSCHCO 2Et- C, S)( μ 3-MeSCHCO 2Et- C, κ 2 S) 2( η 2-MeSCHCO 2Et- C, S)]BF 4 ( 2) by reaction with the equimolar amount of HBF 4 in CH 2Cl 2. The solvato complex 2-Me 2CO crystallizes as monoclinic, space group P2 1/ n, a=13.315(2), b=24.138(2), c=15.049(2) Å, β=105.4(1)°, U=4663(3) Å 3, Z=4. Its structure ( R w=0.049) is characterized by the presence of four (ethoxycarbonyl)(methylthio)methanide ligands, with chiral methine carbon and sulfur atoms. The latter display three different coordination modes: κ 1 in a three membered chelate ring and μ 2 bridges and κ 2 in μ 3 bridges. The tetranuclear cation formally stems from the addition of the chelate cationic fragment [Pd(MeSCHCO 2Et- C, S)] + to a molecule of the starting compound. The formation of 2 highlights the coordination ability of 1 through its sulfur atoms, which is confirmed by the successful synthesis of [Pd{[Pd 3( μ-OAc) 3( μ-MeSCHCO 2Et- C, S)( μ 3-MeSCHCO 2Et- C, κ 2 S) 2]} 2](BF 4) 2 ( 3) and of [Cu{[Pd 3( μ-OAc) 3( μ-MeSCHCO 2Et- C, S)( μ 3-MeSCHCO 2Et- C, κ 2 S) 2]} 2]PF 6 ( 4), by simple addition of 1 to the tetrakis acetonitrile complexes of palladium(II) and copper(I), respectively.

Synthesis, spectroscopic and catalytic properties of cationic Rh(I) complexes bound to phosphine functionalized water-soluble polymers

Coupling of phosphine moieties to water-soluble polymers yields macromolecular ligands, L = PAA-PNH (phosphinated polyacrylic acid) and PEI-PNH (phosphinated polyethyleneimine) which are water-soluble at basic and acidic pH values, respectively. Preparation of and spectroscopic characterization ( 31P-NMR) of [(NBD)RhL 2] + complexes 1 (L = PAA-PNH) and 2 (L = PEI-PNH) demonstrate the complex forming properties of the ligands. Reaction of 1 and 2 with H 2 results in the formation of a solvato complex [RhL 2S 2] + (S = H 2O) for 1, whereas 2 gives a mixture of [RhL 2S 2] + and [RhL 2(H) 2] +, and this difference is an effect of pH. Hydrogenations using water-miscible (acrylic acid, 4-propenoic acid, and 1-buten-4-ol) and water-insoluble (1-hexen) olefins as substrate using 1 and 2 as catalyst precursors demonstrate inhibiting interaction of the acrylate anion while 1-buten-4-ol give normal first order kinetics in olefin. 1-hexene requires addition of surfactants (anionic as SDS in the case of 1 and cationic as DTA or non-charged as Tween 80 in the case of 2) because of slow diffusion of into the water-phase.

New Synthetic Approach to Cyclic Oxycarbene Complexes from Platinum(II)−Alkynyl and −Alkyne Complexes and Oxirane. X-ray Crystal Structure oftrans-[Pt(Me){CCH(p-tolyl)CH2CH2O}(PPh3)2][BF4]·0.25CH2Cl2

The cyclic five-membered platinum(II) oxycarbene complex trans-[Pt(Me){CCH(p-tolyl)CH2CH2O}(PPh3)2][BF4] (1) can be prepared in good yield under very mild conditions either by reaction of trans-[Pt(Me)(C⋮C-p-tolyl)(PPh3)2] with oxirane in the presence of 1 equiv of HBF4 or by reaction of the cationic solvato complex trans-[Pt(Me)(PPh3)2(solv)][BF4] with oxirane and 1.5 equiv of p-tolylacetylene. The X-ray crystal structure of 1 is reported.

Mixed phosphito–phosphonato rhodium(I) complexes

O,O′-3,3′-Di-tert-butyl-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl phosphonate (HL)I was prepared by hydrolysis of (3,3′-di-tert-butyl-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl)phosphorus chloride. Its tautomeric equilibrium with the corresponding phosphite form was completely shifted toward the phosphonate form. The reaction of I with the solvato complex [Rh(C8H12)(thf)2]ClO4(C8H12= cycloocta-1,5-diene, thf = tetrahydrofuran), in thf, in the molar ratio 2 : 1, afforded the rhodium(I) complex [Rh(HL)L(C8H12)] containing I co-ordinated both as a phosphonate and phosphite ligand. Carbon monoxide replaces the C8H12 ligand of 1 to afford the corresponding dicarbonyl species 2. The latter was better obtained by treating [Rh(acac)(CO)2](acac = acetylacetonate) with I, in benzene solution, in the molar ratio 1 : 2. The 31P-{1H} NMR spectra indicate for 1 and 2 the existence either of a P–OH to PO proton-exchange process faster than the NMR time-scale or of a symmetrical O ⋯ H ⋯ O bridge. The existence of a symmetrical O ⋯ H ⋯ O bridge was confirmed by treating 2 with BF3·Et2O. The acidic character of the hydrogen of the O ⋯ H ⋯ O framework was also confirmed treating 2 with NaOH. The reaction of the resulting anionic species with the solvato species [Rh(C8H12)(thf)2]ClO4 afforded a binuclear dirhodium(I) zwitterionic compound [Rh2L2(C8H12)2] containing bridging phosphonate ligands both bonded to a rhodium(I) centre through the phosphorus atoms and to the other one through the oxygen atoms. Attempts to crystallize 1 from a dilute diethyl ether–dichloromethane (4 : 1) solution also afforded the binuclear complex in low yield. Its crystal structure has been determined by single-crystal X-ray diffraction. Under catalytic hydroformylation conditions, the complexes lose the phosphorus-containing moieties to give the catalyst [RhH(CO)4].