Pyrazolyl Nitrogen Atoms Research Articles

The Influence of Aryl Substituents on the Supramolecular Structures and Photoluminescence of Cyclic Trinuclear Pyrazolato Copper(I) Complexes.

Cyclic trinuclear complexes with group 11 metal(I) ions are fascinating and important to coordination chemistry. One of the ligands known to form these cyclic trinuclear complexes is pyrazolate, which is a bridging ligand that coordinates many transition metal ions in a Npz–M–Npz linear mode (Npz = pyrazolyl nitrogen atom). In these group 11 metal(I) ions, copper is the most abundant metal. Therefore, polynuclear copper(I) complexes are very important in this field. The cyclic trinuclear copper(I) complex [Cu(3,5-Ph2pz)]3 (3,5-Ph2pz– = 3,5-diphenyl-1-pyrazolate anion) was reported in 1988 as a landmark complex, but its photoluminescence properties have hitherto not been described. In this study, we report the photoluminescence and two different polymorphs of [Cu(3,5-Ph2pz)]3 and its derivative [Cu(3-Me-5-Phpz)]3 (3-Me-5-Phpz– = 3-metyl-5-phenyl-1-pyrazale anion). The substituents in [Cu(3-Me-5-Phpz)]3 cause smaller distortions in the solid-state structure and a red-shift in photoluminescence due to the presence of intermolecular cuprophilic interactions.

Pincer-like pyrazole- and imidazole-pyridinyl compounds: Synthesis, characterisation, crystallographic and computational investigation

An array of pincer-like bis(pyrazole)pyridinyl (1–10) and bis(imidazole)pyridinyl compounds (11 and 12) with varying alkyl pendant arms was synthesised and spectroscopically characterised. The classic Knorr approach for the synthesis of pyrazoles was adopted to minimise experimental complications and to maximise yield. In general, the yield of compounds 1–8 increased as the n-alkyl arm length increased [1 (33.7%) < 2 (41.5%) < 3 (42.6%)…8 (80.5%)]. This was primarily attributed to the boiling points of their respective alkyl ketone reagents. In all cases tautomerism was evident in the 13C{1H} NMR spectra. The 13C resonances of the carbons adjacent to the pyrazolyl nitrogen atoms were broad and weak, revealing rapid pyrazolyl tautomerism in solution. Single crystal XRD analysis of 1 showed that, for the first time with the aid of an ethanol molecule, the compound was locked into a specific arrangement due to stabilisation via intermolecular hydrogen bonding. This was corroborated by DFT calculations which indicated mixed tautomer II (−497412 kcal.mol−1) to be further stabilised once it was brought in the presence of ethanol. Additionally, the energy gap between the HOMOs and LUMOs was computed and found to be 107.79, 111.22 and 116.29 kcal.mol−1 for structures I, II and III, respectively (265, 255 and 246 nm). This signifies that the π-π* electronic transition is red-shifted from structure III to I.

Synthesis and Structural Characterization of a Silver(I) Pyrazolato Coordination Polymer.

Coinage metal(I)···metal(I) interactions are widely of interest in fields such as supramolecular assembly and unique luminescent properties, etc. Only two types of polynuclear silver(I) pyrazolato complexes have been reported, however, and no detailed spectroscopic characterizations have been reported. An unexpected synthetic method yielded a polynuclear silver(I) complex [Ag(μ-L1Clpz)]n (L1Clpz− = 4-chloride-3,5-diisopropyl-1-pyrazolate anion) by the reaction of {[Ag(μ-L1Clpz)]3}2 with (nBu4N)[Ag(CN)2]. The obtained structure was compared with the known hexanuclear silver(I) complex {[Ag(μ-L1Clpz)]3}2. The Ag···Ag distances in [Ag(μ-L1Clpz)]n are slightly shorter than twice Bondi’s van der Waals radius, indicating some Ag···Ag argentophilic interactions. Two Ag–N distances in [Ag(μ-L1Clpz)]n were found: 2.0760(13) and 2.0716(13) Å, and their N–Ag–N bond angles of 180.00(7)° and 179.83(5)° indicate that each silver(I) ion is coordinated by two pyrazolyl nitrogen atoms with an almost linear coordination. Every five pyrazoles point in the same direction to form a 1-D zig-zag structure. Some spectroscopic properties of [Ag(μ-L1Clpz)]n in the solid-state are different from those of {[Ag(μ-L1Clpz)]3}2 (especially in the absorption and emission spectra), presumably attributable to this zig-zag structure having longer but differently arranged intramolecular Ag···Ag interactions of 3.39171(17) Å. This result clearly demonstrates the different physicochemical properties in the solid-state between 1-D coordination polymer and metalacyclic trinuclear (hexanuclear) or tetranuclear silver(I) pyrazolate complexes.

A heterometallic Cd/Ag/Se complex incorporating 3-ferrocenyl-5-(2-pyridyl)pyrazolato (fcpp) ligands: synthesis and structure of [Cd2{Ag(SePh)}2(μ3-OH2)2(μ2,η3-fcpp)4]·2C3H6O

Abstract A self-assembly reaction of Cd(NO3)2 · 4H2O, 3-ferrocenyl-5-(2-pyridyl)-pyrazole (Hfcpp), [Ag(SePh)] n , and Et3N in a mixed acetone-water solvent resulted in the formation of a heterometallic complex [Cd2{Ag(SePh)}2 (μ 3-OH2)2(μ 2,η 3-fcpp)4] · 2C3H6O (1) with a phenylselenolate ligand. The two cadmium and two silver centers are linked by four [μ 2,η 3-fcpp]− ligands and two μ 3-OH2 water molecules. Each Cd atom is in a slightly distorted octahedral coordination environment, while each Ag atom shows a distorted tetrahedral coordination geometry, which is composed of two pyrazolyl nitrogen atoms, one selenium atom, and one oxygen atom.

Syntheses and Crystal Structures of Copper(II) Bis(pyrazolyl)acetic Acid Complexes

The reaction of bis(pyrazol-1-yl)acetic acid (L) with copper(II) bromide provides two new complexes: [Cu(L-H)Br(µ-Br)]2 (1) and [Cu(L)2]⋅4H2O (2). Complex 1 is prepared by the stoichiometric reaction of L-H with copper(II) bromide in tetrahydrofuran. Dissolution of 1 in methanol causes its conversion into the bis-ligated complex (2), a highly hygroscopic material. Complex 2 can also be synthesized directly by the stoichiometric reaction of L-H with CuBr2 in methanol. Complex 1 is dimeric, interlinked by two bridging bromide ligands, and possesses terminal bromide ligands on each copper atom. The two pyrazolyl ligands in 1 coordinate with the nitrogen atoms to complete the coordination sphere of copper, resulting in a highly distorted geometry that lies between a trigonal bipyramidal or square pyramidal geometry with wide bond angles between the trans-oriented pyrazolyl nitrogen atoms and bromide ligands. Complex 2 assumes a pseudo-trigonal prismatic geometry with the deprotonated carboxylic acid that interacts weakly with copper. Reaction of bis(pyrazol-1-yl)acetic acid (L-H) with copper(II) bromide provides two new complexes: [Cu(L-H)Br(µ-Br)]2 (1) and [Cu(L)2]⋅4H2O (2), these compounds represent the first, well-defined, independent copper(II) compounds supported by the base bis(pyrazolyl)acetic acid ligand.

Synthesis and structural studies of arene ruthenium and Cp*Rh/Cp*Ir complexes containing pyridylpyrazole- and pyridylthiazole-based ligands

The reactions of [(arene)RuCl2]2 (arene = p-cymene or benzene) and [Cp*MCl2]2 (M = Rh or Ir) with N,N′-bidentate chelating ligands 2-[3-(2-pyridyl)pyrazolyl]pyrimidine (L1) and 4-phenyl-(2-pyridyl)thiazole (L2) leads to the formation of mononuclear complexes of general formula [(arene)/Cp*M(L)Cl]PF6. Eight such complexes have been prepared and characterized by spectroscopic techniques. In addition, five of the complexes were also characterized by single-crystal X-ray diffraction. These complexes have typical piano-stool geometries around the metal center, with five-membered metellacycles in which L1 and L2 both act as N,N′-chelating ligands. Moreover, L1 prefers to coordinate through its pyrimidine and pyrazolyl nitrogen atoms, rather than the pyridine nitrogen.

The synthesis and characterisation of coordination and hydrogen-bonded networks based on 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid.

The synthesis, structural and thermal characterisation of a number of coordination complexes featuring the N,O-heteroditopic ligand 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate, HL are reported. The reaction of H2L with cobalt(II) and nickel(II) nitrates at room temperature in basic DMF/H2O solution gave discrete mononuclear coordination complexes with the general formula {[M(HL)2(H2O)4]·2DMF} (M = Co (1), Ni (2)), whereas the reaction with zinc(II) nitrate gave [Zn(HL)2]∞, 3, a coordination polymer with distorted diamondoid topology and fourfold interpenetration. Coordination about the tetrahedral Zn(II) nodes in 3 are furnished by two pyrazolyl nitrogen atoms and two carboxylate oxygen atoms to give a mixed N2O2 donor set. Isotopological coordination polymers of zinc(II), {[Zn(HL)2]·2CH3OH·H2O}∞, 4, and cobalt(II), [Co(HL)2]∞, 5, are formed when the reactions are carried out under solvothermal conditions in methanol (80 °C) and water (180 °C), respectively. The reaction of H2L with cadmium(II) nitrate at room temperature in methanol gives {[Cd(HL)2(MeOH)2]·1.8MeOH}∞6, a 2-D (4,4)-connected coordination polymer, whereas with copper(II) the formation of green crystals that transform into purple crystals is observed. The metastable green phase [Cu3(HL)4(μ2-SO4)(H2O)3]∞, 7, crystallises with conserved binding domains of the heteroditopic ligand and contains two different metal nodes: a dicopper carboxylate paddle wheel motif, and, a dicopper unit bridged by sulfate ions and coordinated by ligand pyrazolyl nitrogen atoms. The resultant purple phase {[Cu(HL)2]·4CH3OH·H2O}∞, 8, however, has single copper ion nodes coordinated by mixed N2O2 donor sets with trans-square planar geometry and is threefold interpenetrated. The desolvation of 8 was followed by powder X-ray diffraction and single crystal X-ray diffraction which show desolvation induces the transition to a more closely packed structure while the coordination geometry about the copper ions and the network topology is retained. Powder X-ray diffraction and microanalysis were used to characterise the bulk purity of the coordination materials 1–6 and 8. The thermal characteristics of 1–2, 4–6 and 8 were studied by TG-DTA. This led to the curious observation of small exothermic events in networks 4, 6, and 8 that appear to be linked to their decomposition. In addition, the solid state structures of H2L and that of its protonated salt, H2L·HNO3, were also determined and revealed that H2L forms a 2-D hydrogen bonded polymer incorporating helical chains formed through N–HO and O–HN interactions, and that [H3L]NO3 forms a 1-D hydrogen-bonded polymer.

Ethylene and Styrene Carbon Monoxide Copolymerization Catalyzed by Pyrazolyl Palladium(II) Complexes

The pyrazolyl pyridylimine ligands [2-(3,5-dimethylpyrazol-1-yl)ethyl]pyridin-2-ylmethyleneimine (L1) and [2-(3,5-di-tert-butylpyrazol-1-yl)ethyl]pyridin-2-ylmethyleneimine (L2) and pyrazolyl thienylimine ligands [2-(3,5-dimethylpyrazol-1-yl)ethyl]thiophen-2-ylmethyleneimine (L3), [2-(3,5-di-tert-butyl-pyrazol-1-yl)ethyl]thiophen-2-ylmethyleneimine (L4), [2-(3,5-dimethylpyrazol-1-yl)ethyl]-2-bromothiophen-2-ylmethyleneimine (L5), and [2-(3,5-di-tert-butyl-pyrazol-1-yl)ethyl]-2-bromothiophen-2-ylmethyleneimine (L6) were synthesized by condensation of the appropriate pyrazolylamine and the corresponding aldehyde. Reactions of L1–L6 with [PdCl(Me)(cod)] gave the corresponding palladium(II) complexes [PdCl(Me)(L)] (where L = L1 (1a), L2 (2a), L3 (3a), L4 (4a), L5 (5a), L6 (6a)) in very good yields. The pyridylimine ligands L1 and L2 were found to coordinate via the imine and pyridine nitrogen atoms, while the thienylimine ligands L3–L6 coordinate via imine and pyrazolyl nitrogen atoms to the palladium. The ca...

Metal cation- and anion-induced assembly: structures and luminescent properties

Three complexes HgLBr2 (1), [HgLI2]·CH3CN (2) and HgL(SCN)2 (3) were synthesized by self-assembly of a multidentate ligand containing pyridyl and pyrazolyl groups, namely, 6-phenyl-4-(4-(1H-pyrazolyl)phenyl)-2,2′-bipyridine (abbreviated as L), with corresponding mercury(II) salts. While the ligand reacted with Cd(NCS)2 and Co(NCS)2, complexes [CdL2(NCS)2]·H2O (4) and [CoL2(NCS)2]·CH3OH (5) were obtained. The structures of these complexes were determined by X-ray crystallography. In 1 and 3, the hydrogen bonding or C–H⋯π interactions based on the anions and the pyrazolyl nitrogen atom contribute to the 2-D and 3-D structures, respectively. Compared with 1 and 3, no hydrogen bonding interaction based on the I− anion can be found in 2. As a result, only the C–H⋯N hydrogen bonding interactions based on the pyrazolyl nitrogen atom link the molecules to form a 1-D structure. In complexes 3–5, the difference in their structures is attributed to the different metal center ions with diverse coordination modes. The results reveal that the anions and metal ions have great impact on the final structures of the supramolecular architectures. The relationships between the structures and luminescent properties were investigated in detail.

Synthesis and catalytic activity of N-heterocyclic carbene silver complexes derived from 1-[2-(pyrazol-1-yl)phenyl]imidazole

Six mono- and dinuclear N-heterocyclic carbene (NHC) silver complexes based on 1-[2-(pyrazol-1-yl)phenyl]imidazole have been synthesized and characterized by elemental analysis and NMR spectroscopy, and their structures have been confirmed by single crystal X-ray diffraction. The N-functionalized carbene ligands exhibit versatile coordination modes in these silver complexes. N-[2-(3,5-Dimethylpyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene (L) acts as a monodentate ligand through the carbene carbon in mononuclear LAgCl. While in dinuclear L2Ag2(PF6)2 and L′2Ag2(PF6)2 (L′ = N-[2-(pyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene), L and L′ act as bridging bidentate ligands through the pyrazolyl nitrogen and the carbene carbon atoms to two silver atoms. Though, these two silver atoms have different coordination environments. In the former, one silver atom coordinates with two carbene carbons, the other coordinates with two pyrazolyl nitrogen atoms. In the latter, each silver atom coordinates with one carbene carbon and one pyrazolyl nitrogen atom, respectively. A dinuclear macrocyclic structure is observed in m-xylyl bridging tetradentate bis-NHC complexes L2Ag2(BF4)2 and (L)CH2C6H4CH2(L)Ag2(BF4)2, in which the coordination mode of carbene ligands is similar with that in L2Ag2(PF6)2. Preliminary catalytic tests show that all these complexes exhibit highly effective catalytic activity in the three-component coupling reaction of alkyne, aldehyde and amine forming propargylamines.

Synthesis, structure, and magnetic properties of the halide-bridged dimeric complex [(bpmaL1)Fe(μ-Cl)Cl

Complexation of FeCl2·4H2O with N,N-Bis{(1-H pyrazole-1-yl)methyl}aniline [bpmaL1] gave air-stable dichloro-bridged binuclear iron(II) species (1a) having five-coordinated iron, which was characterised by X-ray crystallography and magnetic susceptibility. The geometry at each iron centre of 1a is a distorted trigonal bipyramid with two equivalent half-molecules providing overall Ci symmetry. One of the pyrazolyl nitrogen atoms (N1) and a chlorine atom (Cl2)# form one apex of the distorted trigonal bipyramid. The magnetic parameters indicated only a weak antiferromagnetic coupling, despite the presence of two chloro ions, and dominant zero-field-splitting parameters. The relatively long Fe⋯Fe distance of 3.8118(6)Å within the chloro-bridged dimer excludes direct interaction between the iron(II) ions. Thus, the antiferromagnetic coupling between the two iron(II) ions of 1a is attributed to superexchange through the chloride ions. Compared to the analogous cobalt complexes, the activity of α-olefin polymerization towards ethylene, norbornene, 1-octene and methyl methacrylate (MMA) was virtually zero, 1a is the first bis-pyrazole based dinuclear and five-coordinated iron(II) complex.

Synthesis, Characterization, and X-Ray Structures of 2-(3,5-Dimethylpyrazol-1-Yl)Phenyl-Based Organoselenium Compounds and Their Glutathione Peroxidase (Gpx) Like Activity

The synthesis of a series of 2-(3,5-dimethylpyrazol-1-yl)phenyl-based organoselenium compounds, (dmpzC6H4Se)2 (1), dmpzC6H4SeR (dmpz = 3,5-dimethylpyrazol-1-yl; R = (CH2)nY; Y = OH, NH2, and COOH), and dmpzC6H4SeX (X = Cl, Br, or I) is described. The compounds are characterized by IR, NMR (1H, 13C{1H}, 77Se{1H}), and mass spectral (MS) data. The molecular structures of (dmpzC6H4Se)2, dmpzC6H4SeCH2COOH, and dmpzC6H4SeCH2CH2OH have been established by X-ray crystallography. The two latter compounds are associated in the solid state through intermolecular hydrogen bonding between the OH proton and the pyrazolyl nitrogen atom of the adjacent molecule. Glutathione peroxidase (GPx) like catalytic activity of these compounds has been evaluated by using hydrogen peroxide (H2O2) as substrate and dithiothreitol (DTTred) as thiol cofactor in CD3OD, and the progress of the reaction was monitored by 1H NMR spectroscopy. All the compounds exhibited the GPx-like catalytic activity. Among these, the ones containing alkylamino groups showed the best activity. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Synthesis and reactivity of bis(3,5-dimethylpyrazol-1-yl)methanes functionalized by 2-halophenyl groups on the methine carbon

Three new bis(3,5-dimethylpyrazol-1-yl)methanes [(2-XC6H4)CH(3,5-Me2Pz)2, X = F, Cl and Br] functionalized by 2-halophenyl groups on the methine carbon atom have been synthesized. Upon heating (2-XC6H4)CH(3,5-Me2Pz)2 with Mo(CO)6 or W(CO)5THF in THF at reflux, complexes (2-XC6H4)CH(3,5-Me2Pz)2M(CO)4 (X = F or Cl, M = Mo or W) were obtained. While the similar reaction of (2-BrC6H4)CH(3,5-Me2Pz)2 led to the oxidative addition of the C–Br bond to the Mo or W center to give complexes (C6H4)CH(3,5-Me2Pz)2M(CO)3Br (M = Mo or W). In addition, 2-ImC6H4CH(3,5-Me2Pz)2 (Im = imidazol-1-yl) has been obtained by the reaction of (2-BrC6H4)CH(3,5-Me2Pz)2 with imidazole, which subsequently reacted with PhCH2Cl to form 1-{2-[bis(3,5-dimethylpyrazol-1-yl)methyl]phenyl}-3-benzylimidazium chloride. Treatment of this imidazole salt with Ag2O and succeedingly with W(CO)5THF or Ru3(CO)12 yielded N-heterocylic carbene complexes LW(CO)5 and LRu3(CO)8(μ-H)(μ-Cl) (L = 1-{2-[bis(3,5-dimethylpyrazol-1-yl)methyl]phenyl}-3-benzylimidazol-2-ylidene), respectively. In the former, L acts as a monodentate ligand by the carbene carbon to the tungsten atom, and two pyrazolyl nitrogen atoms do not take part in the coordination to the metal center. While in the latter, L serves as a bridging bidentate ligand by one pyrazolyl nitrogen and the carbene carbon atoms to a Ru–Ru bond, and a hydride along with a chloride ligand bridges this metal–metal bond.

Steric Effects on Uranyl Complexation: Synthetic, Structural, and Theoretical Studies of Carbamoyl Pyrazole Compounds of the Uranyl(VI) Ion

New bifunctional pyrazole based ligands of the type [C(3)HR(2)N(2)CONR'] (where R = H or CH(3); R' = CH(3), C(2)H(5), or (i)C(3)H(7)) were prepared and characterized. The coordination chemistry of these ligands with uranyl nitrate and uranyl bis(dibenzoyl methanate) was studied with infrared (IR), (1)H NMR, electrospray-mass spectrometry (ES-MS), elemental analysis, and single crystal X-ray diffraction methods. The structure of compound [UO(2)(NO(3))(2)(C(3)H(3)N(2)CON{C(2)H(5)}(2))] (2) shows that the uranium(VI) ion is surrounded by one nitrogen atom and seven oxygen atoms in a hexagonal bipyramidal geometry with the ligand acting as a bidentate chelating ligand and bonds through both the carbamoyl oxygen and pyrazolyl nitrogen atoms. In the structure of [UO(2)(NO(3))(2)(H(2)O)(2)(C(5)H(7)N(2)CON {C(2)H(5)}(2))(2)], (5) the pyrazole ligand acts as a second sphere ligand and hydrogen bonds to the water molecules through carbamoyl oxygen and pyrazolyl nitrogen atoms. The structure of [UO(2)(DBM)(2)C(3)H(3)N(2)CON{C(2)H(5)}(2)] (8) (where DBM = C(6)H(5)COCHCOC(6)H(5)) shows that the pyrazole ligand acts as a monodentate ligand and bonds through the carbamoyl oxygen to the uranyl group. The ES-MS spectra of 2 and 8 show that the ligand is similarly bonded to the metal ion in solution. Ab initio quantum chemical studies show that the steric effect plays the key role in complexation behavior.

Bulky and Modular 3,3′‐Bipyrazoles as Ligands: Synthesis, Characterization, and Catalytic Activity of Pd Complexes

AbstractIn the present study, the properties of a new bidentate N,N′‐chelating ligand class that bears an electron‐excessive 3,3′‐bipyrazole core have been investigated. The ligands are easily accessible in a three‐step procedure by condensation with diethyl oxalate followed by tandem condensation with hydrazine hydrate and finally by aryl‐ or alkylation exclusively at the N‐1,1′‐pyrazole positions to furnish overall eleven new ligands with different electronic properties. After structural analysis of the ligands, their coordination to palladium, copper, and cobalt has been studied. These ligands coordinate the 2,2′‐pyrazolyl nitrogen atoms in a bidentate fashion to the metals to realize complexes with an (L)MX2 motif. We present two crystal structures of Pd and Cu complexes, which to the best of our knowledge represent the first d8 and d9 2,2′‐bipyrazole compounds coordinated through bidentate complexation. Initial catalytic experiments have been performed with palladium complexes with three bipyrazole ligands of this new class; the palladium‐catalyzed copper‐free Wacker oxidation of different alkenes showed superior activity compared to 2,2′‐bipyridines. We attribute this to a higher redox potential of the 3,3′‐bipyrazoles, which are ― besides electronic effects ― also strongly influenced by steric effects. These might be enforced by the extended ligand backbone, the choice of the wingtip substitution, and the smaller coordination cavity within the N2,N2′ atoms compared to 2,2′‐bipyridine ligands.

Carbophosphazene-Supported Ligand Systems Containing Pyrazole/Guanidine Coordinating Groups

Carbophosphazene-based coordination ligands [{NC(NMe(2))}(2){NP(3,5-Me(2)Pz)(2)}] (1), [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(3,5-Me(2)Pz)(2)}] (2), [NC(3,5-Me(2)Pz)](2)[NP(3,5-Me(2)Pz)(2)] (3), [{NCCl}(2){NP(NC(NMe(2))(2))(2)}] (4), and [{NC(p-OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}] (5) were synthesized and structurally characterized. In these compounds, the six-membered C(2)N(3)P ring is perfectly planar. The reaction of 1 with CuCl(2) afforded [{NC(NMe(2))}(2){NHP(O)(3,5-Me(2)Pz)}·{Cu(3,5-Me(2)PzH)(2)(Cl)}][Cl] (6). The ligand binds to Cu(II) utilizing the geminal [P(O)(3,5-Me(2)Pz)] coordinating unit. Similarly, the reaction of 2 with PdCl(2) afforded, after a metal-assisted P-N hydrolysis, [{NC(NEt)(2)}{NC(3,5-Me(2)Pz)}{NP(O)(3,5-Me(2)Pz)}·{Pd(3,5-Me(2)PzH)(Cl)}] (7). In the latter, the [P(O)(3,5-Me(2)Pz)] unit does not coordinate; in this instance, the Pd(II) is bound by a ring nitrogen atom and a carbon-tethered pyrazolyl nitrogen atom. The reaction of 3 with PdCl(2) also results in P-N bond hydrolysis affording [{NC(3,5-Me(2)Pz)(2)}{NP(O)(3,5-Me(2)Pz)}{Pd(Cl)}] (8). In contrast to 7, however, in 8, the Pd(II) elicits a nongeminal η(3) coordination from the ligand involving two carbon-tethered pyrazolyl groups and a ring nitrogen atom. Metalated products could not be isolated in the reaction of 3 with K(2)PtCl(4). Instead, a P-O-P bridged carbodiphosphazane dimer, [{NC(3,5-Me(2)Pz)NHC(3,5-Me(2)Pz)}{NP(O)}](2) (9), was isolated as the major product. Finally, the reaction of 5 with PdCl(2) resulted in [{NC(OC(5)H(4)N)}(2){NP(NC(NMe(2))(2))(2)}·{PdCl(2)}] (10). In the latter, the exocyclic P-N bonds are quite robust and are involved in binding to the metal ion. Compounds 6-10 have been characterized by a variety of techniques including X-ray crystallography. In all of the compounds, the bond parameters of the inorganic heterocyclic rings are affected by metalation.

Tetramethylcyclobutadienecobalt(I) complexes containing pyrazolate or tetrazolate ligands with various coordination modes

Treatment of Cb ∗Co(CO) 2I (Cb ∗ = η 4-C 4Me 4) with one equivalent of potassium 3,5-dimethylpyrazolate (Me 2pzK) or potassium 3,5-bis(trifluoromethyl)pyrazolate ((CF 3) 2pzK) in tetrahydrofuran at 0 °C afforded (η 4-C 4Me 4(Me 2pz))Co(CO) 2 and Cb ∗Co((CF 3) 2pz)(CO) 2 in 90 and 71% yields, respectively. Treatment of Cb ∗Co(CO) 2I with one equivalent of Me 2pzH followed by the addition of one equivalent Me 2pzK in tetrahydrofuran afforded Cb ∗Co(Me 2pzH)(Me 2pz)(CO) in 74% yield. The reaction of Cb ∗Co(CO) 2I with one equivalent of potassium phenyl tetrazolate (PhtetzK) in tetrahydrofuran at 0 °C afforded [Cb ∗Co(Phtetz)(CO)] 2 in 44% yield. The solid state structure of (η 4-C 4Me 4(Me 2pz))Co(CO) 2 revealed nucleophilic addition of a pyrazolate nitrogen atom to a Cb ∗ ligand carbon atom to afford a novel tetradentate ligand that bonds to the cobalt ion through an η 3-π-allyl interaction and one pyrazolyl nitrogen atom. Two carbonyl ligands are also present. An X-ray crystal structure determination of Cb ∗Co((CF 3) 2pz)(CO) 2 showed η 1-coordination of the (CF 3) 2pz ligand and η 4-coordination of the Cb ∗ ligand. The solid state structure of Cb ∗Co(Me 2pz)(Me 2pzH)(CO) is monomeric with one η 1-Me 2pz, one η 1-Me 2pzH, two carbonyl, and one η 4-Cb ∗ ligands. The η 1-Me 2pz and η 1-Me 2pzH ligands are linked by a hydrogen bond involving the uncoordinated nitrogen atoms. The X-ray crystal structure determination of [Cb ∗Co(Phtetz)(CO)] 2 showed a dimeric molecular structure with two μ:η 1,η 1-Phtetz ligands connected to the cobalt ions through the 2- and 3-nitrogen atoms, one η 4-Cb ∗ ligand, and one carbonyl ligand per cobalt center. (η 4-C 4Me 4(Me 2pz))Co(CO) 2 is highly volatile and sublimes at 60 °C/0.03 Torr.

Synthesis, structure and biological activity of diorganotin derivatives with pyridyl functionalized bis(pyrazol‐1‐yl)methanes

AbstractThree pyridyl functionalized bis(pyrazol‐1‐yl)methanes, namely 2‐[(4‐pyridyl)methoxyphenyl] bis(pyrazol‐1‐yl)methane (L1), 2‐[(4‐pyridyl)methoxyphenyl]bis(3,5‐dimethylpyrazol‐1‐yl)methane (L2) and 2‐[(3‐pyridyl)methoxyphenyl]bis(pyrazol‐1‐yl)methane (L3) have been synthesized by the reactions of (2‐hydroxyphenyl)bis(pyrazol‐1‐yl)methanes with chloromethylpyridine. Treatment of these three ligands with R2SnCl2 (R = Et, n‐Bu or Ph) yields a series of symmetric 2:1 adducts of (L)2SnR2Cl2 (L = L1, L2 or L3), which have been confirmed by elemental analysis and NMR spectroscopy. The crystal structures of (L2)2Sn(n‐Bu)2Cl2·0.5C6H14 and (L3)2SnEt2Cl2 determined by X‐ray crystallography show that the functionalized bis(pyrazol‐1‐yl)methane acts as a monodentate ligand through the pyridyl nitrogen atom, and the pyrazolyl nitrogen atoms do not coordinate to the tin atom. The cytotoxic activity of these complexes for Hela cells in vitro was tested. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The modification of ArSCH 2(3,5-Me 2Pz) (Ar = phenyl or 2-pyridyl, Pz = pyrazol-1-yl) by organotin group and related reactions

Reaction of 1-arylthiomethyl-3,5-dimethylpyrazole [ArSCH 2(3,5-Me 2Pz), Ar = phenyl or 2-pyridyl, Pz = pyrazol-1-yl] with Mo(CO) 6 produces complexes ArSCH 2(3,5-Me 2Pz)Mo(CO) 4, while similar reaction with W(CO) 6 yields analogous complexes ArSCH 2(3,5-Me 2Pz)W(CO) 4 and concomitant desulfurized complex (3,5-Me 2PzH)W(CO) 5 in the reaction of PhSCH 2(3,5-Me 2Pz). Succedent treatment of complexes PhSCH 2(3,5-Me 2Pz)M(CO) 4 with SnCl 4 gives heterobimetallic complexes PhSCH 2(3,5-Me 2Pz)M(CO) 3(Cl)(SnCl 3) (M = Mo or W) in good yields. ArSCH 2(3,5-Me 2Pz) act as S,N chelating bidentate ligands through the sulfur and the pyrazolyl nitrogen atoms in the aforementioned complexes. The modification of ArSCH 2(3,5-Me 2Pz) by organotin group at the methylene group has been successfully carried out, which yields functionalized ligands Ph 3SnCH(SAr)(3,5-Me 2Pz). Markedly different reactions are observed, upon treatment of Ph 3SnCH(SPh)(3,5-Me 2Pz) and Ph 3SnCH(SPy)(3,5-Me 2Pz) (Py = 2-pyridyl) with W(CO) 5THF. The former yields complex Ph 3SnCH(SPh)(3,5-Me 2Pz)W(CO) 4, as well as PhSCH 2(3,5-Me 2Pz)W(CO) 4 with a partial loss of the organotin moiety, while no reaction takes place in the latter. In addition, reaction of Ph 3SnCH(SPy)(3,5-Me 2Pz) with Mo(CO) 6 results in the oxidative addition reaction of the Sn–C sp3 bond to the molybdenum(0) atom to yield novel heterometallacyclic complex CH(SPy)(3,5-Me 2Pz)Mo(CO) 3SnPh 3, in which [(2-pyridyl)thiomethyl](3,5-dimethylpyrazol-1-yl)methide acts as a tridentate κ 3-[N,C,N] chelating ligand through the carbon atom, the pyrazolyl and the pyridyl nitrogen atoms, as the sulfur atom does not coordinate to the molybdenum atom anymore. Interestingly, treatment of this heterometallacyclic complex with P(OR) 3 (R = Ph or Et) gives rise to the isomerization of the C–S bond to the C–N bond, generating the thione–S coordinated complex CH(NC 4H 4C = S)(3,5-Me 2Pz)Mo(CO) 2(P(OR) 3)SnPh 3, in which the ligand binds in a novel tridentate, monoanionic κ 3-[N,C,S] chelating mode to the molybdenum atom.

New organotin(IV) complexes with a potentially multi-site ligand based on the cyclotriphosphazene platform: Synthesis and spectral studies

A functionalized cyclotriphosphazene with four pyrazolyl substituents, N3P3(MeNC2H4O)(dmp)4 where dmp = 3,5-dimethylpyrazole, has been synthesized and characterized. The reaction of this potentially multi-site coordinating cyclotriphosphazene with diorganotin(IV) dichlorides, SnR2Cl2 (R = Ph, Me), leads to dinuclear [(SnPh2Cl2)2{N3P3(MeNC2H4O)(dmp)4}] (1) and mononuclear [(SnMe2Cl2){N3P3(MeNC2H4O)(dmp)4}] (2) complexes. These new compounds were characterized by elemental analysis and IR, 1H, 31P and 119Sn NMR spectroscopy. On the basis of these data, in the complex 1 pyrazolylcyclotriphosphazene acts as a bis-bidentate ligand and coordinates to two SnPh2Cl2 molecules via two geminal pyrazolyl nitrogen atoms. As for complex 2, coordination to one SnMe2Cl2 molecule occurs through two nongeminally substituted pyrazolyl nitrogens. The 119Sn NMR data are consistent with the increasing of coordination number of tin(IV) in solution.