Phenyl Complexes Research Articles

Synthesis and structure of tricarbonyl(η6-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

A series of 15 glycoside-derived tricarbonyl(η6-arene)chromium complexes were prepared in 19–87% yield by heating fully acetylated or methylated aryl O-, S-, N- and C-glycosides of D-glucopyranose and D-mannopyranose with hexacarbonylchromium. All tricarbonylchromium complexes were fully characterized. The structures of nine crystalline complexes were determined by X-ray diffraction, revealing unusual intra- and intermolecular nonclassical hydrogen bonds.

Preparation of a Family of Hexanuclear Rhenium Cluster Complexes Containing 5-(Phenyl)tetrazol-2-yl Ligands and Alkylation of 5-Substituted Tetrazolate Ligands

The preparation of two new families of hexanuclear rhenium cluster complexes containing benzonitrile and phenyl-substituted tetrazolate ligands is described. Specifically, we report the preparation of a series of cluster complexes with the formula [Re(6)Se(8)(PEt(3))(5)L](2+) where L = benzonitrile, p-aminobenzonitrile, p-methoxybenzonitrile, p-acetylbenzonitrile, or p-nitrobenzonitrile. All of these complexes undergo a [2 + 3] cycloaddition with N(3)(-) to generate the corresponding [Re(6)Se(8)(PEt(3))(5)(5-(p-X-phenyl)tetrazol-2-yl)](+) (or [Re(6)Se(8)(PEt(3))(5)(2,5-p-X-phenyltetrazolate)](+)) cluster complexes, where X = NH(2), OMe, H, COCH(3), or NO(2). Crystal structure data are reported for three compounds: [Re(6)Se(8)(PEt(3))(5)(p-acetylbenzonitrile)](BF(4))(2)•MeCN, [Re(6)Se(8)(PEt(3))(5)(2,5-phenyltetrazolate)](BF(4))•CH(2)Cl(2), and [Re(6)Se(8)(PEt(3))(5)(2,5-p-aminophenyltetrazolate)](BF(4)). Treatment of [Re(6)Se(8)(PEt(3))(5)(2,5-phenyltetrazolate)](BF(4)) with HBF(4) in CD(3)CN at 100 °C leads to protonation of the tetrazolate ring and formation of [Re(6)Se(8)(PEt(3))(5)(CD(3)CN)](2+). Surprisingly, alkylation of the phenyl and methyl tetrazolate complexes ([Re(6)Se(8)(PEt(3))(5)(2,5-N(4)CPh)](BF(4)) and [Re(6)Se(8)(PEt(3))(5)(1,5-N(4)CMe)](BF(4))) with methyl iodide and benzyl bromide, leads to the formation of mixtures of 1,5- and 2,5-disubstituted tetrazoles.

Formation of (Alkenylphosphonio)phenylruthenium Complexes from Diphenylacetylene and a [CpRu(dppm)] Cation: Experimental Evidence for the Equilibrium between η1-Disubstituted Vinylidene and η2-Internal Alkyne

The reaction of diphenylacetylene at a cationic ruthenium complex with a dppm (Ph2PCH2PPh2) ligand, [CpRu(dppm)]+, has been studied to reveal essentially for the first time the existence of an equilibrium between an η2-internal alkyne and η1-disubstituted vinylidene at a transition metal center. The reaction mixture at 70 °C for 69 h unexpectedly afforded a coupling product of diphenylacetylene and the dppm ligand, an (alkenylphosphonio)phenyl complex [CpRu{Ph2PCH2P(C6H4)Ph(η2-C(Ph)═CHPh)}]+ with the extremely rare coordination mode of κ1P,η1C,η2C,C′. The (alkenylphosphonio)phenyl complex further undergoes inversion of the coordination face of the alkene moiety at p-xylene reflux temperature. Both isomers of (alkenylphosphonio)phenyl complexes as well as the intermediary η2-internal alkyne and η1-disubstituted vinylidene complexes were fully characterized spectroscopically and crystallographically. By considering the structure of the (alkenylphosphonio)phenyl complexes obtained, the coupling reaction has been proposed to involve the attack of a phosphorus atom on the coordinated diphenylacetylene, which is in equilibrium with an η1-diphenylvinylidene ligand, and the C–H bond activation of a phenyl group on the cationic phosphorus atom leading to the products. Theoretical calculations support the proposed mechanism.

Synthesis of Oxorhenium Acetyl and Benzoyl Complexes Incorporating Diamidopyridine Ligands: Implications for the Mechanism of CO Insertion

A series of oxorhenium alkyl, phenyl, and vinyl complexes of the form [(DAP)Re(O)(R)] (R = aryl, vinyl, alkyl) was reported, and their reactivity with CO was examined. The methyl complex 5a reacts with CO at a significantly faster rate (2.5 h) than the phenyl complex 7a (24 h). Computational (B3PW91) studies reveal that although the acyl complex is the least stable (ΔG353 = −11.2 kcal/mol) with respect to CO insertion compared to the benzoyl complex (ΔG353 = −14.5 kcal/mol), the activation energy for CO insertion is lower for the methyl complex (ΔG⧧353 = 14.6 kcal/mol) than for the phenyl complex (ΔG⧧353 = 17.4 kcal/mol). This is consistent with the previously proposed mechanism, where CO inserts directly into the Re–R bond without prior formation of a CO adduct. The X-ray crystal structures of complexes 6, 7a, 8a, and 9a are reported.

Aryl and NHC Compounds of Technetium and Rhenium

Air- and water-stable phenyl complexes with nitridotechnetium(V) cores can be prepared by straightforward procedures. [TcNPh(2)(PPh(3))(2)] is formed by the reaction of [TcNCl(2)(PPh(3))(2)] with PhLi. The analogous N-heterocyclic carbene (NHC) compound [TcNPh(2)(HL(Ph))(2)], where HL(Ph) is 1,3,4-triphenyl-1,2,4-triazol-5-ylidene, is available from (NBu(4))[TcNCl(4)] and HL(Ph) or its methoxo-protected form. The latter compound allows the comparison of different Tc-C bonds within one compound. Surprisingly, the Tc chemistry with such NHCs does not resemble that of corresponding Re complexes, where CH activation and orthometalation dominate.

Side-on Bound Complexes of Phenyl- and Methyl-diazene

Treatment of trans-[FeCl(2)(dmpe)(2)] with phenylhydrazine and 1 equiv of base afforded the side-on bound phenylhydrazido complex cis-[Fe(η(2)-NH(2)NPh)(dmpe)(2)](+). Further deprotonation of the phenylhydrazido complex afforded the side-on bound phenyldiazene complex cis-[Fe(η(2)-HN═NPh)(dmpe)(2)] as a mixture of diastereomers. Treatment of cis-[RuCl(2)(dmpe)(2)] with phenylhydrazine or methylhydrazine afforded the end-on bound phenylhydrazine or methylhydrazine complexes cis-[RuCl(η(1)-NH(2)NHR)(dmpe)(2)](+) (R = Ph, Me). Treatment of the substituted hydrazine complexes with base afforded the side-on bound phenylhydrazido complex cis-[Ru(η(2)-NH(2)NPh)(dmpe)(2)](+) as well as the phenyldiazene and methyldiazene complexes cis-[Ru(η(2)-HN═NR)(dmpe)(2)] (R = Ph, Me). cis-[RuCl(η(1)-NH(2)NHR)(dmpe)(2)](+) (R = Ph, Me), cis-[M(η(2)-NH(2)NPh)(dmpe)(2)](+) (M = Fe, Ru) and cis-[Ru(η(2)-HN═NPh)(dmpe)(2)] were characterized structurally by X-ray crystallography. cis-[Ru(η(2)-HN═NPh)(dmpe)(2)] is the first side-on bound phenyldiazene complex to be structurally characterized. In the structure of cis-[Ru(η(2)-HN═NPh)(dmpe)(2)], the geometry of the coordinated diazene fragment is significantly nonplanar (CNNH angle 137°) suggesting that the complex is probably better described as a Ru(II) metallodiaziridine than a Ru(0) diazene π-complex.

Intra- and Intermolecular C–H Activation by Bis(phenolate)pyridineiridium(III) Complexes

A bis(phenolate)pyridine pincer ligand (henceforth abbreviated as ONO) has been employed to support a variety of iridium complexes in oxidation states I, III, and IV. Complexes (ONO)IrL_2Me (L = PPh_3, PEt_3) react with I_2 to cleave the Ir–C bond and liberate MeI, apparently via a mechanism beginning with electron transfer to generate an intermediate Ir(IV) complex, which can be isolated and characterized for the case L = PEt_3. The PPh_3 complex is transformed in benzene at 65 °C to the corresponding phenyl complex, with loss of methane, and subsequently to a species resulting from metalation of a PPh_3 ligand. Labeling and kinetics studies indicate that PPh_3 is the initial site of C–H activation, even though the first observed product is that resulting from intermolecular benzene activation. C–H activation of acetonitrile has also been observed.

Cyclopentadiene Alkylation and Nickel Complexes with Tri-, Tetra-, or Pentaisopropylcyclopentadienide or an Even Bulkier Lithium Alkylcyclopentadienide

Phase transfer catalysis has been adapted to the synthesis of triisopropylcyclopentadiene isomers 1 in high yield and purity. Alkylation of sodium triisopropylcyclopentadienides with isopropyl bromide in tetrahydrofuran has been shown to be the currently most efficient way to generate tetraisopropylcyclopentadiene isomers 2, which give sodium tetraisopropylcyclopentadienide (3) upon metalation. The crucial step for the introduction of the fifth isopropyl group, the selective attack of an iminium salt at the tetraisopropylcyclopentadienide anion in the 5-position with generation of the corresponding 1,2,3,4-tetraisopropyl(6-dimethylamino)fulvene (4), has been carried out according to a published procedure. Addition of 1-naphthyllithium to the dimethylaminofulvene 4 yielded extremely bulky lithium dimethylamino(1-naphthyl)methyltetraisopropylcyclopentadienide (7). Pure 1,2,4,1′,2′,4′-hexaisopropylnickelocene (8) was obtained from sodium triisopropylcyclopentadienide and nickel(II) bromide. The tetraisopropylcyclopentadienylnickel(II) bromide [(C5iPr4H)Ni(μ-Br)]2 (9) added triphenylphosphine, trimethylphosphine, trimethyl phosphite, and triisopropylphosphine with formation of the diamagnetic phosphine complexes [(C5iPr4H)NiBr(PPh3)] (10), [(C5iPr4H)NiBr(PMe3)] (13), [(C5iPr4H)NiBr{P(OMe)3}] (14), and [(C5iPr4H)NiBr(PiPr3)] (15), respectively. The triphenylphosphine derivative 10 displays a dissociation equilibrium with small amounts of 9 in deuteriobenzene solution and could be converted to the methylnickel(II) derivative [(C5iPr4H)NiMe(PPh3)] (11) or to the phenyl complex [(C5iPr4H)NiPh(PPh3)] (12), respectively. Substitution reactions of the bromide 9 yielded a dinuclear complex with two bridging 2,6-dimethylphenolate ligands, [(C5iPr4H)Ni(μ-2,6-OC6Me2H3)]2 (16), with potassium 2,6-dimethylphenolate and methylene-bridged dinuclear [{(C5iPr4H)Ni}2(μ-CH2)] (18) with methylmagnesium chloride and concomitant methane formation. Partial hydrolysis converted the phenolate 16 to the monohydroxy derivative [{(C5iPr4H)Ni}2(μ-2,6-OC6Me2H3)(μ-OH)] (17). Crystal structure analyses have been carried out on complexes 8, 11, 13, 14, 16–18, and 20. Lithium pentaisopropylcyclopentadienide (6) reacted with nickel(II) bromide dimethoxyethane adduct in pentane to form the bromo-bridged [(C5iPr5)Ni(μ-Br)]2 (19), and the new bulky dimethylamino(naphthyl)methyl-carrying cyclopentadienide 7 reacted with the dimethoxyethane adduct of nickel(II) bromide in pentane to give the diamagnetic alkylcyclopentadienylnickel bromide monomer [{C5iPr4CH(NMe2)(1-naphthyl)}NiBr] (20). The crystal structure of 20 shows no sign of electron donation from the dimethylamino nitrogen lone pair to the nickel center. The paramagnetism of 19 is in line with similar findings for the pentamethylcyclopentadienyl, tetraisopropylcyclopentadienyl, and 1,2,4-tri-tert-butylcyclopentadienyl analogues of 19. The diamagnetism of 20 is most probably due to an empty dz2 orbital, which is high in energy because of the combined electron donation from the five-membered ring and the bromo ligand on the z axis.

Positioning of Single Co Atoms Steered by a Self-Assembled Organic Molecular Template

The bonding and organization of cobalt atoms on a self-assembled organic molecular template are investigated by low-temperature scanning tunneling microscopy. In a first step, N,N′-diphenyl oxalic amide is deposited on the Ag(111) surface with submonolayer and monolayer coverage, leading to the formation of supramolecular nanogratings and a dense-packed layer, respectively. These templates are exposed to evaporated cobalt at different substrate temperatures in the range of 110 to 240 K. We find that Co always binds on top of the phenyl rings, and thus the realization of Co–phenyl complexes is preferred over metal cluster growth on the bare Ag(111) surface. In the case of the dense-packed template, a large fraction of the provided Co is engaged in the formation of well-defined, uniform monomeric Co-half-sandwich structures. At optimal temperatures in the 180–200 K range, the fraction of monomeric Co species on the template exceeds 80% of the total amount of Co deposited. The temperature-dependent adsorptio...

1,2-C−H Activation of Benzene Promoted by (Arylimido)vanadium(V)-Alkylidene Complexes: Isolation of the Alkylidene, Benzyne Complexes

Reactions of the (arylimido)vanadium(V) dialkyl complex containing an imidazolin-2-iminato ligand, V(NAr)(CH2SiMe3)2(L) [2, Ar = 2,6-Me2C6H3; L = ImDIPPN = 1,3-(2′,6′-diisopropylphenyl)imidazolin-2-iminato], with C6D6 or C6H6 took place affording the phenyl complex V(NAr)(CH2SiMe3)(C6H5)(L) (3) or V(NAr)[CH(D)SiMe3](C6D5)(L) (3-d6) by 1,2-C−H or C−D activation of benzene via a vanadium(V)-alkylidene intermediate. The reaction of 2 in n-hexane in the presence of PMe3 afforded the vanadium(V)alkylidene complex V(CHSiMe3)(NAr)(ImDIPPN)(PMe3) (4), and the structure of 4 has been determined by X-ray crystallography. The reaction of 3 or 3-d6 with C6D6 or C6H6 took place to afford the diphenyl complex V(NAr)(C6H5)2(L) (5) or V(NAr)(C6D5)2(L) (5-d10). The same reaction in the presence of PMe3 afforded the proposed intermediate, the PMe3-trapped benzyne complex V(NAr)(η2-C6D4)(L)(PMe3) (6), and the structure of 6 has been determined by X-ray diffraction analysis.

Amidate Iridium(III) Bis(2-pyridyl)phenyl Complexes: Application Examples of Amidate Ancillary Ligands in Iridium(III)-Cyclometalated Complexes

The syntheses, structures, and photophysical properties of a series of iridium(III) bis(2-pyridyl)phenyl complexes, (ppy)2Ir(LX) (LX = amide ligands), are described. The complex (ppy)2Ir(N-phenylmethacrylamide) (5), bearing an acrylamidate ligand, has been further employed for polymerization to generate the metal-containing homopolymer poly((ppy)2Ir(N-phenylmethacrylamide)) (6). In addition, the complexes (ppy)2Ir(acetylaniline) (2) and (ppy)2Ir(N-phenylbenzamide) (3) have been structurally characterized by X-ray crystallography. It was found that the amidate ligand binds to the Ir center in an imine/alkoxide mode via a four-membered, nearly planar ring (N−Ir−O−C); the limited delocalization is supported by the lengthened C−O bond compared to the C−N bond length in the amidate backbone and no strong absorption around 1650 cm−1 in the infrared spectra. The photophysical and electrochemical properties of these complexes were then studied. The maximum emission wavelengths ranging from 510 to 548 nm as well as the ΔEp values varying from 2.55 to 2.77 V can be attributed to the different effects of ancillary amide ligands tolerating different electronic characters. The HOMO and LUMO energy levels and compositions of the iridium complexes were investigated by DFT calculations. The amidate ancillary ligands affect the absorption and emission energies of these complexes by tuning the HOMO energies.

C–H activation of benzene by platinum(II) complexes with cyclometalated phosphine ligands

The bulky phosphine ligands di- tert-butyl(1-naphthyl)phosphine ( 1) or di- tert-butyl( N-indolyl)phosphine ( 2) react at room temperature with [( μ-SMe 2)PtMe 2] 2. Coordination of the phosphine and C–H bond activation at an sp 2 carbon of the ligand with the release of methane takes place to form the PC cyclometalated products [(PC)PtMe(SMe 2)] ( 3 or 4, respectively). The cyclometalated complexes 3 and 4 have both been characterized by X-ray crystallography. Complexes 3 and 4 were each observed to undergo intermolecular activation of arene C–H bonds. Upon thermolysis in benzene, complexes 3 and 4 react to eliminate methane and yield isolable platinum(II)–phenyl complexes.

ChemInform Abstract: Asymmetric Direct Alkynylation Catalyzed by Chiral Ru—Bis(oxazolinyl)phenyl Complexes.

Propargylic alcohols were obtained with excellent enantioselectivities in the asymmetric direct alkynylation of aldehydes using 5 mol % of chiral ruthenium complexes containing the chiral bis(oxazolinyl)phenyl ligand.

A Beneficial Kinetic Effect of an η5-C5Me4H Ligand

C-H activation of benzene at 26 °C by (η(5)-C(5)Me(5))W(NO)(CH(2)CMe(3))(η(3)-CH(2)CHCHMe) results after 4 h in the production of five new organometallic complexes, only two of which are isomers of the desired (η(5)-C(5)Me(5))W(NO)(C(6)H(5))(η(3)-CH(2)CHCHMe) compound. In contrast, the identical reaction involving the η(5)-C(5)Me(4)H analogue affords only the phenyl complexes during the first 24 h, thereby facilitating their isolation in good yields. This striking difference in reactivity can be attributed to the lesser steric demands of the η(5)-C(5)Me(4)H ligand that result in its complexes reacting at a significantly slower rate.

ChemInform Abstract: Combination of Vinyl, Phenyl and Carbonyl Ligands in Ruthenium(II) Complexes: A Route to Vinyl Ketones.

Conversion of chloride complexes [Ru(CO)2(CHCHR)Cl(PMe2Ph)2](R = CMe3 or Ph) into the corresponding phenyl complexes [Ru(CO)2(CHCHR)Ph(PMe2Ph)2] by low-temperature treatment with LiPh is accompanied by a change in the ligand arrangement around the metal. At 20 °C the products undergo two competing rearrangement processes, one a simple isomerisation back to a ligand arrangement analogous to that in [Ru(CO)2(CHCHR)Cl(PMe2Ph)2] and the other a remarkably facile combination of phenyl, carbonyl and vinyl ligands to yield the ketone complexes [Ru(CO)(η4-PhCOCHCHR)(PMe2Ph)2], from which the ketone may be liberated by treatment with Me3CNC.

Asymmetric Direct Alkynylation Catalyzed by Chiral Ru−Bis(oxazolinyl)phenyl Complexes

Propargylic alcohols were obtained with excellent enantioselectivities in the asymmetric direct alkynylation of aldehydes using 5 mol % of chiral ruthenium complexes containing the chiral bis(oxazolinyl)phenyl ligand.

The Stereospecific Ligand Exchange at a Pseudo‐Benzylic T‐4 Iridium Centre in Planar‐Chiral Cycloiridium (η6‐Arene)tricarbonylchromium Complexes

The stereospecificity of ligand exchange at the Ir(III) centre of a cycloiridium arenetricarbonylchromium complex has been established experimentally by various analytical methods as well as by X-ray diffraction structural analysis and computational investigations. Two new cases of phenyl and methyl iridium(III) complexes have been prepared by reaction of (S(P)*,R(Ir)*-chlorido{2-[(tricarbonyl)(eta(6)-phenylene-kappaC(1'))chromium(0)]pyridine-kappaN}(pentamethylcyclopentadienyl)iridium(III) with PhMgBr and MeMgBr. The determining influence of electrostatic repulsion has been established by means of density functional theory at the Becke-Perdew/TZP(ZORA) level by using, among other means, energy partitioning analysis. It is also shown that the Cr(CO)(3) fragment is likely to ease the ionic cleavage of the Ir-Cl bond in chlorido cycloiridium tricarbonylchromium complexes in a way similar to that already established for the solvolysis of benzyl halide complexes, that is, through a direct interaction of the Cr(0) centre with the cationic Ir(III) centre.

Suzuki reaction catalysed by a PC sp3P pincer Pd(II) complex: Evidence for a mechanism involving molecular species

{ Cis-1,3-bis[(di- tert-butylphosphino)methyl]cyclohexyl}palladium(II)trifluoroacetate ( 1) acts as a precatalyst for the Suzuki reaction of aryl halides with phenylboronic acid in the absence or presence of mercury to give the product in modest to reasonably good yields. The reaction was monitored by 31P- and 1H NMR spectroscopy in a stepwise fashion, concluding that complex 1 reacts with activated boronic acids in the first reaction step to yield the corresponding phenyl complex 2. Complex 2 thereafter generates the Suzuki cross-coupling product upon addition of aryl halide. This shows that (PCP)Pd complexes, in addition to the previously demonstrated Pd(0)/Pd(II) mechanism, can mediate cross-coupling reactions using molecular species in a non-zero oxidation state.

Amidinate-ligated iridium(iii) bis(2-pyridyl)phenyl complex as an excellent phosphorescent material for electroluminescence devices

Highly efficient, low driving-voltage, and emitter concentration insensitive phosphorescent EL devices are established for the first time by using an amidinate-ligated iridium(III) complex as an emitting component.

Synthesis of phenyl substituted bisphosphonates and crystal structures and characterization of Cd complexes of (dichloromethylene)bisphosphonic acid phenyl and alkyl ester derivatives

Two novel phenyl esters and partial phenyl esters of (dicloromethylene)bisphosphonic acid were synthesised. Three new layered Cd complexes of (dichloromethylene)bisphosphonic acidP,P-diphenyl, monophenyl and monoethyl esters were prepared. The complexes, [Cd3{(Cl2CP2O6Ph)2(H3COH)(H2O)5}(H2O)2]n (7), [{Cd(Cl2CP2O6Ph2)(H2O)3}(H2O)]n (8) and [{Cd1.5(Cl2CP2O6Et)(H2O)2}(C3H6O)0.5(H2O)4.5]n (9), were characterized by single crystal X-ray diffraction, IR spectroscopy, solid-state 31P- and 113Cd-CP/MAS NMR and elemental analysis. Also their thermal behaviour was investigated. Compound 7 consists of 1D chains with four independent octahedral Cd atoms joined by two L1 ligands, L1 = (Cl2CP2O6Ph)3−. The chains are connected into layers by phosphonate O atoms, and the adjacent layers are held together by face-to-face π–π stacking interactions. Compound 8 shows a new type of layered structure for metal bisphosphonates, where the L2 ligand, L2 = (Cl2CP2O6Ph2)2−, coordinates tridentately to three Cd2+ ions. Each CdO6 octahedron is connected to three CPO3 tetrahedra and each tetrahedron to three octahedra leading to a 2-D framework consisting of 12-membered cyclic cores. The layers are held together by edge-to-face CH/π interactions. In compound 9, the asymmetric unit contains two independent Cd2+ cations connected by L3 ligands, L3 = (Cl2CP2O6Et)3– and aqua ligands, to form a Cd–bisphosphonate layer. The layers are further interconnected into a 3-D supramolecular network by extensive hydrogen bonds.