Mo(0) carbonyl complexes bearing the bis(3,5-dimethylpyrazole) ligand: catalysis of the regioselective [2 + 2 + 2] cycloaddition of terminal alkynes to synthesize 1,3,5-isomers.

The reaction between 1,3-bis(3,5-dimethylpyrazolylmethyl)hexahydropyrimidine L and Mo(CO) in CHCN at 130 °C afforded a binuclear Mo(0) complex 1 containing a new macrocycle formed upon C-N bond cleavage in L in good yield. Conversely, a clean reaction takes place between L and [Mo(CO)(COD)] in THF at 60 °C to give a new metalloligand complex [Mo(CO)(κ-,-L)] 2 containing a spectator pyrazole arm in 83% yield. Their structures were determined by X-ray diffraction methods, and a plausible mechanism is proposed for the C-N bond cleavage leading to complex 1.

Selective synthesis of the missing tiara-like Ni, Ni and Ni thiolates by the C-S bond cleavage of bis(thioether) molecules with a DFT study.

A series of new bis(phenylthioether) and bis(benzylthioether) compounds (L1-L5) having hexahydropyrimidine, imidazolidine and dihydroperimidine backbones were synthesized. Instead of giving NHC complexes, these compounds undergo facile C-S bond cleavages upon treatment with Ni(II) salts to selectively give new toroidal Ni(II) thiolates: [Ni(SPh)] (1) and [Ni(SCHPh)] (5), and the known [Ni(SCHPh)] (8), as confirmed by single crystal X-ray diffraction studies. By-products such as RSSR (R = Ph and CHPh) and partially C-S bond cleaved starting compounds were isolated or detected as well from these reactions.

Copper(I) complexes bearing pyrrole-bridged S,N and N-donor ligands as catalysts for tandem hydroamination-alkynylation: effect of anions on product formation.

In this study, the reaction between 2-(3,5-dimethylpyrazolylmethyl)-5-(dimethylaminomethyl)pyrrole and thiophenol under heating conditions afforded the new ligand 2-(3,5-dimethylpyrazolylmethyl)-5-(phenylthiomethyl)pyrrole 2. The reaction of 2 with -chloroperbenzoic acid provided sulfoxide 3 and sulfone 4 group-containing ligands. The reaction of 2 with copper(I) halides provided the binuclear complexes [Cu(μ-X){μ-CHN-2-(CHMepz)-5-(CHSPh)-κ-S,N}] (X = Cl, Br and I, 5-7) in high yields.

Dipyrromethane-diphosphine: the effect of substituents on the formation of nickel complexes and on their performance in the transfer hydrogenation of ketones.

Three dipyrromethane-diphosphine ligands containing phenyl (L1H2), ethyl (L2H2) and cyclohexyl (L3H2) groups at their positions and their nickel complexes were synthesized and structurally characterized. Treatment of PhC(CHN)-1,9-(CHPPh) (L1H2) with [NiCl(DME)] gave complex [NiCl(κ-,-L1H2)] . Conversely, the analogous reactions of L2H2 and L3H2 with [NiCl(DME)] showed a mixture of products containing both a pyrrolide nitrogen coordinated complex of type [Ni(κ-,,,-L)] without an exogenous base and a chelated complex of type .

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

The reaction of PhPCHOH with PhPCl and PCl in the presence of EtN afforded new phosphonite compounds PhP(OCHPPh)1 and P(OCHPPh)2, respectively. The reaction between 1 and [NiCl(DME)] in dichloromethane gave the five-coordinate complex [NiCl(1-κ ,,)] 3. Conversely, 1 reacts with [NiCl(DME)] in the presence of NHPF in dichloromethane to yield the four coordinate ionic complex [NiCl(1-κ ,,)][PF] 4.

Synthesis, structural characterization, and bonding analysis of two-coordinate copper(I) and silver(I) complexes of pyrrole-based bis(phosphinimine): new metal-pyrrole ring π-interactions.

The reaction between 2,5-bis(diphenylphosphinomethyl)pyrrole and Me3SiN3 gave the new pyrrole-based bis(phosphinimine) L1H in an excellent yield. L1H reacts with [CuCl(COD)]2, AgBF4, or AgOTf to give the corresponding two-coordinate mononuclear ionic complex formulated as [M{(L1H)-κ2N,N}]+[X]- where M = Cu and Ag; X = [CuCl2], BF4 or OTf. Their single crystal X-ray diffraction studies confirmed the two-coordinate geometry formed by the chelate bonding mode of L1H.

Versatility of the bis(iminopyrrolylmethyl)amine ligand: tautomerism, protonation, helical chirality, and the secondary coordination sphere with halogen bonds in the formation of copper(II) and nickel(II) complexes.

The reaction of N,N-di(2,6-bis(isopropyl)phenylimino-pyrrolyl-α-methyl)-N-methylamine H2L1 with copper(i) sources such as CuX (X = Cl (1), Br (2), and I (3)) afforded bis(chelated) ionic copper(ii) complexes of the type [CuL1H]X. A similar type of mononuclear structure was obtained with Cu(NO3)2·(H2O)3. Conversely, binuclear copper(ii) complexes [Cu2(μ-L1)(μ-OOCCH3)(μ-OH)](4) and [Cu2(μ-L1H)(μ-OOCPh)(μ-O)] (5) were obtained from the reaction of Cu(O2CR)2·H2O with H2L1.

Crystal structure and DFT analyses of a pentacoordinated PCP pincer nickel(II) complex.

The reaction of NiCl with 1,3-bis[(diphenylphosphanyl)methyl]hexahydropyrimidine in the presence of 2,6-dimethylphenyl isocyanide and KPF afforded a new pentacoordinated PCP pincer Ni complex, namely {1,3-bis[(diphenylphosphanyl)methyl]hexahydropyrimidin-2-yl-κN}(2,6-dimethylphenyl isocyanide-κC)nickel(II) hexafluoridophosphate 0.70-hydrate, [Ni(CHN)(CHClNP)]PF·0.7HO or [NiCl{C(NCHPPh)(CH)-κP,C,P'}(Xylyl-NC)]PF·0.

Nickel(II) and Palladium(II) Complexes Bearing an Unsymmetrical Pyrrole-Based PNN Pincer and Their Norbornene Polymerization Behaviors versus the Symmetrical NNN and PNP Pincers.

Unsymmetrical pincers have been shown to be better than the corresponding symmetrical pincers in several catalysis reactions. A new unsymmetrical PNN propincer, 2-(3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole (1), was synthesized from pyrrole through Mannich bases in a good yield. In addition, the new byproduct 2-(3,5-dimethylpyrazolylmethyl)-5-(dimethylaminomethyl)- N-(hydroxymethyl)pyrrole was also isolated.

Facile synthesis of Pd(ii) and Ni(ii) pincer carbene complexes by the double C-H bond activation of a new hexahydropyrimidine-based bis(phosphine): catalysis of C-N couplings.

Hexahydropyrimidine-based bis(phosphine), a pro-NHC ligand, was synthesized in one step and excellent yield. It underwent spontaneous double C-H bond activation to give cationic pincer NHC complexes of the type [(PCP)MCl]X (M = Pd, Ni and X = Cl, BF4) in the absence of any external reagents. Their structures were determined by X-ray diffraction methods and the mechanism of formation of palladium carbene complexes as analyzed by DFT calculations showed two transition states.

Enantiomers and Structural Isomers of Sodium and Palladium Complexes Bearing ortho-Bis(3,5-dimethylpyrazolylmethyl)phenolate: Fluxional Property and Highly Active Catalysts for Norbornene Polymerization.

2,6-Bis(3,5-dimethylpyrazoylmethyl)-4-methylphenol LH was readily synthesized by the reaction between 2,6-bis[(dimethylamino)methyl]-4-methylphenol and 3,5-dimethylpyrazole. The X-ray structure of the trisodium complex of LH showed the benzene-like planar NaO ring with alternative shorter (2.181-2.

The pyrrole ring η-hapticity bridged binuclear tricarbonyl Mo(0) and W(0) complexes: catalysis of regioselective hydroamination reactions and DFT calculations.

Following the report of the ferrocene structure, metal complexes containing the heteroatom-substituted cyclopentadienyl (Cp) analogue, that is the η pyrrolyl ligand, have been reported. While the Cp ligand continues to be a favorite ligand in organometallics, the transition metal chemistry of the pyrrolyl ligand is still in the developing stage. In view of this, we carried out the reaction between the multidentate ligand 2,3,4,5-tetrakis(3,5-dimethylpyrazolylmethyl)pyrrole (LH) and Mo(CO) or [W(CO)(CHCN)] and isolated two new binuclear tricarbonyl Mo(0) and W(0) complexes, [Mo(CO)(μ-η:η-LH-κN)] (1) and [W(CO)(μ-η:η-LH-κN)] (2).

Synthesis and structural characterization of anion complexes with azacalix[2]dipyrrolylmethane: effect of anion charge on the conformation of the macrocycle.

Tetrahomodiazacalix[2]dipyrrolylmethane 1, [-CH2(C4H3N)CR2(C4H3N)CH2N(Me)-]2 an expanded version of the calix[4]pyrrole system, has the tendency to change its ring conformation (1,3-alternate) upon anion binding analogous to calix[4]pyrrole. However, owing to its tertiary amine nitrogen atoms in the ring, it can be protonated and becomes a powerful cationic receptor for anions, besides its inherent hydrogen bonding features. Macrocycle 1 binds with a series of monoanions BF4(-), Cl(-), PhCOO(-) and ClO4(-), and their X-ray structures showed that the ring conformation constitutes the 1,2-alternate form.

Synthesis and structural characterization of silver(I), copper(I) coordination polymers and a helicate palladium(II) complex of dipyrrolylmethane-based dipyrazole ligands: the effect of meso substituents on structural formation.

A new class of multidentate dipyrrolylmethane based ditopic tecton, 1,9-bis(3,5-dimethylpyrazolylmethyl)dipyrrolylmethane, containing diethyl (L1) or cyclohexylidene (L2) substituents at the meso carbon atom were readily synthesized in 28-45% yields in two different ways starting from dipyrrolylmethanes. A one dimensional coordination polymer structure ([(L2)Ag][BF4])n was obtained when L2 was treated with AgBF4, whereas the analogous reaction between L1 and AgBF4 afforded the dicationic binuclear metallacycle complex [(L1)2Ag2][BF4]2. In addition, yet another coordination polymeric structure [(L1)CuI]n was obtained from the reaction between L1 and CuI.

Exhibition of the Brønsted acid-base character of a Schiff base in palladium(II) complex formation: lithium complexation, fluxional properties and catalysis of Suzuki reactions in water.

The reaction of the dialdehyde N,N-di(α-formylpyrrolyl-α-methyl)-N-methylamine with two equiv. of 2,6-diisopropylaniline yielded two Schiff bases: bis(iminopyrrolylmethyl)amine () and its hydrolyzed monoimino compound () after column separation. The dimeric lithium complex [(HL)Li]2 () containing the monoanionic form of was obtained by treating with (n)BuLi.

Single-step substitution of all the α, β-positions in pyrrole: choice of binuclear versus multinuclear complex of the novel polydentate ligand.

The α and β-positions of pyrrole were substituted with 3,5-dimethylpyrazolylmethyl groups in a single step that involved the reaction between 2,5-dimethylaminomethylpyrrole and 3,5-dimethylpyrazole-1-carbinol, affording 2,3,4,5-tetrakis(3,5-dimethylpyrazol-1-ylmethyl)pyrrole LH in 40% yield. The coordination chemistry of this new polydentate ligand LH was explored by synthesizing several Pd(II), Cu(I), and Ag(I) complexes. When LH was used as a neutral ligand with [Pd(COD)Cl2], AgBF4, and CuX (X = Cl and I), compartmental type binuclear Pd(II) and Ag(I) complexes such as [Pd2Cl4(μ-C4HN-2,3,4,5-(CH2Me2pz)4-N,N,N,N)] and [Ag2(μ-C4HN-2,3,4,5-(CH2Me2pz)4-N,N,N,N)(CH3CN)2](2+)[BF4(-)]2 and cage-like copper(I) complexes [Cu2(μ-X)(μ-C4HN-2,3,4,5-(CH2Me2pz)4-N,N,N,N)](+)[CuX2](-) (X = Cl and I) containing a halide ion bridging in a bent fashion were obtained, respectively.

Structural diversity of copper(I) complexes formed by pyrrole- and dipyrrolylmethane-based diphosphine ligands with cu-X···HN hydrogen bonds.

Metal complexes containing hydrogen bond donor/acceptor groups are interesting because of their applications in several areas. In the course of our investigation on the synthesis of metal complexes using newly developed pyrrole-based diphosphine ligands, a few structurally interesting copper(I) complexes containing the pyrrolic NH hydrogen bond donors were synthesized. The reaction of 2,5-bis(diphenylphosphinomethyl)pyrrole (PNP) with an equimolar quantity of CuX (X = Cl, Br, and I) afforded the binuclear copper(I) complexes [Cu(μ-X)(μ-PNP-P,P)]2 (1-3) in very good yields (87-90%).

Synthesis of novel polyazacryptands for recognition of tetrahedral oxoanions and their X-ray structures.

The Mannich reaction of tris(pyrrolyl-α-methyl)amine (H3tpa) with a mixture of formaldehyde and primary amine hydrochloride (methyl or ethyl) gave two novel macrobicyclic molecules: a hexapyrrolic pentaazacryptand and an unusual pentapyrrolic tetraazacryptand, which were separated by column chromatography and their structures were determined by X-ray diffraction method. The analogous reaction using benzylamine hydrochloride yielded the encapsulated chloride anion complex in 16% yield even after neutralization with aqueous K2CO3, which was also characterized by X-ray diffraction. In addition, the anion binding properties of these macrobicycles were investigated by NMR titration methods, and the binding constants for halides and oxoanions were determined with the EQNMR program.

The syn and anti isomers of the porphyrinogen-like precursor of calix[4]phyrin: isolation, X-ray structure, anion binding and fluoride-ion-mediated proton-deuterium exchange studies.

Porphyrinogen-like precursors of calix[4]phyrins are presumed to be unstable owing to their auto-oxidation. In contrast to this, the syn and the anti isomers of a calix[4]pyrrole molecule containing pyridine moieties at the meso positions were isolated and their structures were determined by single crystal X-ray diffraction studies. Both the isomers gave the same calix[4]phyrin molecule upon oxidation.

Pyrrole-based new diphosphines: Pd and Ni complexes bearing the PNP pincer ligand.

A new class of diphosphine PNP pincer ligand, 2,5-bis(diphenylphosphinomethyl)pyrrole 2, was synthesized by the reaction between Ph2PH and 2,5-bis(dimethylaminomethyl)pyrrole in 90% yield. The analogous reaction of Ph2PH with 1,9-bis(dimethylaminomethyl)diphenyldipyrrolylmethane readily afforded a PNNP type diphosphine ligand, 1,9-bis(diphenylphosphinomethyl)diphenyldipyrrolylmethane 5 in 92% yield. These phosphine compounds were oxidized with H2O2 and S8 to give the corresponding phosphoryl and thiophosphoryl compounds 6-9 in very good yields.

A tripyrrolylmethane-based macrobicyclic triazacryptand: X-ray structure, size-selective anion binding, and fluoride-ion-mediated proton-deuterium exchange studies.

A new class of tripyrrolylmethane-based triazacryptand with bridgehead carbons and acyclic molecules were synthesized by the Mannich reaction of tripyrrolylmethane with primary or secondary amine hydrochloride and formaldehyde, respectively. The structure of the triazacryptand was determined by X-ray diffraction (XRD) method. The anion binding properties of both the bicyclic and acyclic receptors were studied by (1)H NMR titration method.

Synthesis and X-ray structures of novel macrocycles and macrobicycles containing N,N-di(pyrrolylmethyl)-N-methylamine moiety: preliminary anion binding study.

The [2 + 2] Schiff base condensation reactions between the newly synthesized dialdehyde, N,N-di(α-formylpyrrolyl-α-methyl)-N-methylamine), and ethylenediamine or p-phenylenediamine dihydrochloride readily afforded the 30- and 34-membered large size macrocycles in very high yields. Subsequent reduction reactions of these macrocycles with NaBH(4) gave the corresponding saturated macrocyclic hexaamines in good yields. The analogous reaction of the new dialdehyde with a triamine molecule afforded the [3 + 2] Schiff base macrobicycle in high yield, which was then reduced by reaction with NaBH(4) to give the saturated macrobicycle.

Mononuclear, helical binuclear palladium and lithium complexes bearing a new pyrrole-based NNN-pincer ligand: fluxional property.

A new pyrrole based NNN-pincer ligand, 2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrole 2, was readily synthesized in two steps from pyrrole in 56% yield. The lithiation of the pincer ligand 2 using n-BuLi led to isolation of the dimeric lithium complex, [Li{μ-C(4)H(2)N-2,5-(CH(2)Me(2)pz)(2)-N,N,N}](2) 4, in 23% crystalline yield. The transmetalation reaction of 4 with [Pd(PhCN)(2)Cl(2)] afforded the mononuclear Pd(II) complex, [PdCl{C(4)H(2)N-2,5-(CH(2)Me(2)pz)(2)-N,N,N}] 5, containing one chloride ion in 45% yield.

Dipyrrolylmethane-based macrobicyclic azacryptand: synthesis, X-ray structures, conformational and anion binding properties.

A new class of macrobicyclic azacryptand containing dipyrrolylmethane subunits with nitrogen bridgeheads was synthesized by the Mannich reaction of the dipyrrolylmethane in the presence of aqueous ammonia. The azacryptand exhibits a staggered conformation in the solid state, but is in a dynamic equilibrium with the eclipsed conformation in solution studied by the variable-temperature (1)H NMR methods. The azacryptand has a specific size suitable only for fluoride ion; large anions such as NO(3)(-) bind in the clefts of the macrobicycle as shown by the X-ray structures of its fluoride ion inclusion and the nitrate anion complexes.

Macrocyclic and acyclic molecules synthesized from dipyrrolylmethanes: receptors for anions.

A new class of macrocyclic and acyclic molecules was synthesized by the Mannich reactions of dipyrrolylmethanes to investigate anion recognition. The X-ray structures of the macrocycle and sulfate complexes are reported.