Pyrrole Ligand Research Articles

Backbone Dehydrogenation in Pyrrole-Based Pincer Ligands.

Treatment of both [CoCl( tBuPNP)] and [NiCl( tBuPNP)] ( tBuPNP = anion of 2,5-bis((di- tert-butylphosphino)methyl)pyrrole) with one equivalent of benzoquinone affords the corresponding chloride complexes containing a dehydrogenated PNP ligand, tBudPNP ( tBudPNP = anion of 2,5-bis((di- tert-butylphosphino)methylene)-2,5-dihydropyrrole). Dehydrogenation of PNP to dPNP results in minimal change to steric profile of the ligand but has important consequences for the resulting redox potentials of the metal complexes, resulting in the ability to isolate both [CoH( tBudPNP)] and [CoEt( tBudPNP)], which are more challenging (hydride) or not possible (ethyl) to prepare with the parent PNP ligand. Electrochemical measurements with both the Co and Ni dPNP species demonstrate a substantial shift in redox potentials for both the M(II/III) and M(II/I) couples. In the case of the former, oxidation to trivalent Co was found to be reversible, and subsequent reaction with AgSbF6 afforded a rare example of a square-planar Co(III) species. Corresponding reduction of [CoCl( tBudPNP)] with KC8 produced the diamagnetic Co(I) species, [Co(N2)( tBudPNP)]. Further reduction of the Co(I) complex was found to generate a pincer-based π-radical anion that demonstrated well-resolved EPR features to the four hydrogen atoms and lone nitrogen atom of the ligand with minor contributions from cobalt and coordinated N2. Changes in the electronic character of the PNP ligand upon dehydrogenation are proposed to result from loss of aromaticity in the pyrrole ligand, resulting in a more reducing central amido donor. DFT calculations on the Co(II) complexes were performed to shed further insight into the electronic structure of the pincer complexes.

Exploring Basic Components Effect on the Catalytic Efficiency of Chevron-Phillips Catalyst in Ethylene Trimerization

In the present work, the effect of basic components on the energy pathway of ethylene oligomerization using the landmark Chevron-Phillips catalyst has been explored in detail, using density functional theory (DFT). Studied factors were chosen considering the main components of the Chevron-Phillips catalyst, i.e., ligand, cocatalyst, and halocarbon compounds, comprising (i) the type of alkyl substituents in pyrrole ligand, i.e., methyl, iso-propyl, tert-butyl, and phenyl, as well as the simple hydrogen and the electron withdrawing fluoro and trifluoromethyl; (ii) the number of Cl atoms in Al compounds (as AlMe2Cl, AlMeCl2 and AlCl3), which indicate the halocarbon level, and (iii) cocatalyst type, i.e., alkylboron, alkylaluminium, or alkylgallium. Besides the main ingredients, the solvent effect (using toluene or methylcyclohexane) on the oligomerization pathway was also explored. In this regard, the full catalytic cycles for the main product (1-hexene) formation, as well as side reactions, i.e., 1-butene release and chromacyclononane formation, were calculated on the basis of the metallacycle-based mechanism. According to the obtained results, a modification on the Chevron-Phillips catalyst system, which demonstrates higher 1-hexene selectivity and activity, is suggested.

A neutral auxiliary ligand enhanced dysprosium(iii) single molecule magnet.

An approximately equatorial three-coordinated dysprosium(iii) complex DyL2[N(SiMe3)2] (L = bis(2-(2,5-dimethyl-1H-pyrrol-1-yl)ethyl)amine) with an additional neutral auxiliary pyrrole ligand was synthesised and structurally characterized. The magnetic property measurement shows that it is an equatorial charge distributed field-induced single-molecule magnet. Ab initio calculations reveal that the neutral pyrrole ligand plays an important role in stabilizing the ground doublet and thus enhancing the magnetic anisotropy.

Synthesis and Structure of Unprecedented Samarium Complex with Bulky Bis‐iminopyrrolyl Ligand via Intramolecular C=N Bond Activation

An unprecedentate samarium complex of the molecular composition [{κ3‐{(Ph2CH)N=CH}2C4H2N)}{κ3‐{(Ph2CHN=CH)(Ph2CHNCH)C4H2N}Sm}2] (2), which was isolated by the reaction of a potassium salt of 2,5‐bis{N‐(diphenylmethyl)‐iminomethyl}pyrrolyl ligand [K(THF)2{(Ph2CH)N=CH}2C4H2N)] (1) with anhydrous samarium diiodide in THF at 60 °C through the in situ reduction of imine bond is presented. The homoleptic samarium complex [[κ3‐{(Ph2CH)–N=CH}2C4H2N)]3Sm] (3) can also be obtained from the reaction of compound 1 with anhydrous samarium triiodide (SmI3) in THF at 60 °C. The molecular structures of complexes 2 and 3 were established by single‐crystal X‐ray diffraction analysis. The molecular structure of complex 2 reveals the formation of a C–C bond in the 2,5‐bis{N‐(diphenylmethyl)iminomethyl}pyrrole ligand moiety (Ph2Py–). However, complex 3 is a homoleptic samarium complex of three bis‐iminopyrrolyl ligands. In complex 2, the samarium ion adopts an octahedral arrangement, whereas in complex 3, a distorted three face‐centered trigonal prismatic mode of nine coordination is observed around the metal ion.

The effect of pyridinic- and pyrrolic-nitrogen in nitrogen-doped carbon nanotubes used as support for Pd-catalyzed nitroarene reduction: an experimental and theoretical study

Nitrogen-doped carbon nanotubes (N-CNTs) containing different nitrogen species were synthesized via a chemical vapour deposition technique. This was archived by use of ferrocene and ferrocenyl-2-(4-cyanophenyl)acrylonitrile as catalysts. The N-CNTs were acid-treated and then used as Pd nanoparticle supports (Pd/N-CNTs). Both N-CNTs and Pd/N-CNTs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and other spectroscopic techniques. The selective reduction of nitroarenes to anilines was used as a model reaction to test the effect of pyridinic- and pyrrolic-nitrogen species on the catalytic performance of Pd/N-CNTs. A larger number of pyridinic-nitrogens in the N-CNTs increased nitroarene conversion and enhanced the selectivity towards anilines as opposed to the pyrrolic-nitrogens. Also, pyridinic-nitrogens favoured the nucleation of Pd nanoparticles with higher surface areas than those nucleated in the presence of pyrrolic-nitrogens. Density functional theory calculations were employed to determine the band-gap energy and optimal geometry of Pd complexed to pyridine and pyrrole ligands. These results showed that the pyridine complex had a lower band-gap energy (5.804 eV) than the pyrrole complex (6.406 eV) implying that the former complex is more reactive than the later. Thus, the inclusion of pyridinic-nitrogens in the N-CNTs, used as support, favours Pd-catalyzed nitroarene reductions.

Ethylene oligomerization over chromium(III) complexes with pyrrole derivatives

The effect of the nature of a chromium(III) coordination compound and various substituted pyrrole ligands on ethylene oligomerization in the presence of a Cr(III) complex–pyrrole ligand (L)/AlEt3 catalyst system (CS), where Cr(III) is Cr(EH)3, Cr(асас)3, or CrCl3(THF)3 and L is pyrrole, 2-phenylpyrrole, 2-formylpyrrole, N-methylpyrrole, or N-vinyl-2-phenylpyrrole, has been studied. It has been shown that the most significant effect on the behavior of the CS is exerted by the nature of the ligand involved in the formation of the CS. The acid–base properties of the employed ligands have been determined by quantum-chemical calculations. The data obtained have revealed that selectivity of the catalyst system depends on the ligand basicity.

Selective Palladium-Catalyzed Aminocarbonylation of Olefins to Branched Amides.

A general and efficient protocol for iso-selective aminocarbonylation of olefins with aliphatic amines has been developed for the first time. Key to the success for this process is the use of a specific 2-phosphino-substituted pyrrole ligand in the presence of PdX2 (X=halide) as a pre-catalyst. Bulk industrial and functionalized olefins react with various aliphatic amines, including amino-acid derivatives, to give the corresponding branched amides generally in good yields (up to 99 %) and regioselectivities (b/l up to 99:1).

Selective Palladium‐Catalyzed Aminocarbonylation of Olefins to Branched Amides

AbstractA general and efficient protocol for iso‐selective aminocarbonylation of olefins with aliphatic amines has been developed for the first time. Key to the success for this process is the use of a specific 2‐phosphino‐substituted pyrrole ligand in the presence of PdX2 (X=halide) as a pre‐catalyst. Bulk industrial and functionalized olefins react with various aliphatic amines, including amino‐acid derivatives, to give the corresponding branched amides generally in good yields (up to 99 %) and regioselectivities (b/l up to 99:1).

Synthesis, structural characterization and catalysis of ruthenium(ii) complexes based on 2,5-bis(2'-pyridyl)pyrrole ligand.

Treatment of the 2,5-bis(2'-pyridyl)pyrrolato (PDP-) anion with {Ru(COD)Cl2}n in THF readily yielded [Ru(PDP)(COD)Cl] (1) in almost quantitative yield. Anion metathesis of 1 in organic solvent by NO3- and OTf- (OTf- = triflato) gave [Ru(PDP)(COD)(NO3)] (2) and [Ru(PDP)(COD)(OTf)] (3), and in aqueous solution by BF4- and PF6- afforded aqueous complexes [Ru(PDP)(COD)(H2O)](BF4) (4+·BF4-) and [Ru(PDP)(COD)(H2O)](PF6) (4+·PF6-), respectively. Treatment of 1 with PhICl2 in CH2Cl2 afforded 5 with halogenated pyrrole. These complexes exhibit similar structure, including one Ru(ii) atom, one 2,5-bis(2'-pyridyl)pyrrole and one monodentate anion or aqua ligand. Each Ru(ii) tightly binds to three adjacent coplanar sites of PDP- ligand to form a meridional configuration. Complex 1 with NaIO4 as the oxidant in EtOAc-CH3CN-H2O (ratio = 3 : 1 : 2) proved to be highly effective in the catalytic oxidation of olefins to carbonyl products.

Regulating ancillary ligands of Ru(ii) complexes with square-planar quadridentate ligands for more efficient sensitizers in dye-sensitized solar cells: insights from theoretical investigations

In this work, we designed three dyes (Ru1, Ru2, and Ru3) by modifying the square-planar quadridentate ligand of the experimental Ru(ii) complex K1, [RuL(trans-NCS)2] with L = dimethyl-6,60-bis(methyl-2-pyridylamino)-2,20-bipyridine-4,40-dicarboxylate, from a theoretical viewpoint. As is known, K1 shows obvious advantages over the famous dye N749 in light absorption ability because of its highly conjugated ancillary ligands. Density functional theory and time-dependent density functional theory methods were used to determine the geometrical structures, electronic structures and absorption spectra of the dye complexes. A quantum dynamics method in conjunction with extended Hückel theory was used to simulate the interfacial electron transfer process at the dye-TiO2 interface. The calculated results suggest that Ru1, which contains arylmethane groups, presents improved light absorption and efficient interfacial electron transfer compared with the reference dye K1. We also verified that the position of the anchoring carboxylic acid groups could largely guide the rate of interfacial electron transfer. Ru3, whose anchoring groups are attached to pyridine rings, would have significantly faster interfacial electron transfer than Ru2, whose anchoring groups are attached to the pyrrole ligands; this is because varying the position of the anchoring group results in a difference in the extent of electron donor-acceptor orbital interactions. We expect that the current study will provide some theoretical guidelines for the experimental synthesis of novel Ru(ii) complex dyes.

Nickel(II) complexes with mono(imino)pyrrole ligands: preparation, structure and ethylene polymerization behavior

A series of unsymmetrical mono(imine)pyrroles (L1–L3) were synthesized by microwave irradiation from 2-acetylpyrrole and a series of dimethylanilines with two methyl groups at different positions on the aniline ring. A simplified synthetic method was initiated to prepare the corresponding nickel complexes NiL2 (1–3) with direct condensation of mono(imine)pyrrole and nickel chloride. The compounds were determined using a suite of techniques (i.e. 1H NMR, 13C NMR, IR, EA, MS). L1–L3 and 3 were further characterized by X-ray crystal diffraction. The structure of 3 showed that the ligand chelated to nickel with 2 : 1 M ratio, in spite of a 1 : 1 rate of charge. Application of 1–3 in ethylene polymerization indicated that mono(imino)pyrrole nickel complexes showed low activities. The polymerization reaction time and temperature, as well as the ligand structure, influenced the catalytic performance to some extent. Experimental data showed higher activity as –CH3 on the aniline ring is closer to the imine group.

New types of bi- and tri-dentate pyrrole-piperazine ligands and related zinc compounds: Synthesis, characterization, reaction study, and ring-opening polymerization of ε-caprolactone

Reactions of one or two equivalents of formaldehyde and phenylpiperazine with pyrrole in methanol or ethanol generated substituted pyrrole ligands C4H3NH-[2-CH2N(CH2CH2)2NPh] (1) and C4H2NH-{2,5-[CH2N(CH2CH2)2NPh]2} (2), respectively. Reacting 1 with one equivalent of ZnMe2 in toluene generated a di-zinc compound 3, {ZnMe{C4H3N-[2-CH2N(CH2CH2)2NPh]}}2, in moderate yield. Further reacting 3 with two equivalents of p-cresol in toluene overnight afforded pheoxide bridged di-zinc compound 4, {Zn(μ-O-C6H4-4-Me){C4H3N-[2-CH2N(CH2CH2)2NPh]}}2. Similarly, the reactions of one and two equivalents of tridentate substituted pyrrole ligand 2 with ZnMe2 afforded Zn compounds ZnMe{C4H2N-{2,5-[CH2N(CH2CH2)2NPh]2}} (5) and Zn{C4H2N-{2,5-[CH2N(CH2CH2)2NPh]2}}2 (6), respectively, in moderate yield. All of these compounds were characterized using 1H and 13C NMR spectroscopy. Compound 5 is relatively air and moisture sensitive and decomposes during the recrystallization process to yield a tri-Zn cluster, {Zn(μ2-OH){C4H2N-{2,5-[CH2N(CH2CH2)2NPh]2}}}3 (7). The molecular geometries of compounds 1, 3, 4, 6, and 7 were also determined using single crystal X-ray diffractometric analysis. Compounds 3, 4, and 6 were used as initiators for the ring opening polymerization of ε-caprolactone, and all of the zinc compounds showed high conversion with broad or bimodal molecular weight distributions.

Exploring the sensitization properties of thienyl-functionalized tripyrrole Ru(II) complexes on TiO2 (101) surface: a theoretical study

Ruthenium(II) complexes, as the dye sensitizer in the solar cell system, has attracted great interests. In the present study, based on the ruthenium(II) complex N749, new sensitizers have been designed theoretically to increase the stability and the efficiency of dye-sensitized solar cell (DSSC). By investigating the ground state geometries, electronic structures, and spectroscopic properties by density functional theory (DFT) and time-dependent DFT, the orbital components and absorption transition have been obtained. The effect of tripyrrin ligand in the designed new sensitizers can be demonstrated from our results. The results show that the absorption spectra are systematically broadened and red-shifted with the increase sizes of the pyrrole ligands. The important unoccupied orbitals referred to charge transfer are mainly from di/tripyrrin derivative groups. Consequently, the charge transfer to the di/tripyrrin derivative groups has been strengthened. According to our study, the di/tripyrrin derivative ligand is more efficient than the NCS− ligand in absorbing visible light. The calculation results also indicate that the electronic structures of the N749 derived sensitizers are significantly influenced by the different substituted positions of the thienyl groups on di/tripyrrin ligands. Thus, the efficiency of DSSCs would be different. Our research predicted that the Ru(II) complexes containing 5,10-(2-thienyl)-4,6,9,11-tripyrrin ligand may enhance the visible light absorption of DSSC. This is in accordance with the corresponding experiment. These results are expected to assist the molecular design for new dyes in future DSSCs.

Synthesis, Characterization, and Reactivity of Lanthanide Amides Incorporating Neutral Pyrrole Ligand. Isolation and Characterization of Active Catalyst for Cyanosilylation of Ketones

A series of lanthanide amido complexes incorporating a neutral pyrrole ligand were synthesized and characterized, and their catalytic activities were studied. Treatment of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 1 equiv of [(2,5-Me2C4H2N)CH2CH2] 2NH (1) in toluene afforded the corresponding lanthanide amides with the formula [η5:η1-(2,5-Me2C4H2N)CH2CH2]2NLn[N(SiMe3)2]2 (Ln = La (2), Nd (3)). Reaction of 2 or 3 with N,N′-dicyclohexylcarbodiimide (CyN═C═NCy) gave the carbodiimide selectively inserted into the appended Ln–N bond products formulated as CyNC{[N,N-(2,5-Me2C4H2N)CH2CH2]2N}NCyLn[N(SiMe3)2]2 (Ln = La (4), Nd (5)). Reactions of the lanthanide amides with Me3SiCN were also examined. A mixed reaction of [(Me3Si)2N]3La(μ-Cl)Li(THF)3, [(2,5-Me2C4H2N)CH2CH2]2NH (1), and Me3SiCN in toluene at room temperature produced the novel cyano bridged dinuclear lanthanum complex η5:η1:η3-[(2,5- Me2C4H2NCH2CH2)2N]La[N(SiMe3)2](μ-CN)La[N(SiMe3)2]3 (6). The stoichiometric reactions of lanthanide amides 2 or 3 with Me3SiCN produced the novel trinuclear lanthanum and neodymium complexes {(η5:η1-[(2,5-Me2C4H2NCH2CH2)2N]Ln[N(SiMe3)2](μ-CN)}3 (Ln = La (7), Nd (8)) through selective σ-bond metathesis reaction of the terminal Ln–N (N(SiMe3)2) bond with the Si–C bond of Me3SiCN. On the basis of the stoichiometric reactions of complexes 2, or 3 with Me3SiCN, complexes 2, 3, 4, 5, 7, and 8 as catalysts for cyanosilylation of ketones were investigated. Results indicated that these complexes displayed a high catalytic activity on addition of Me3SiCN to ketones, and the activity of the complexes has the order of 7 ∼ 8 > 2 ∼ 3 ∼ 4 ∼ 5. Thus, complex 7 or 8 was proposed as the active catalyst in the catalytic reaction for the precatalysts of 2 and 3.

Mechanistic DFT Study on Ethylene Trimerization of Chromium Catalysts Supported by a Versatile Pyrrole Ligand System

To elucidate fundamental mechanistic aspects of the landmark Chevron–Phillips ethylene trimerization system, a detailed theoretical study has been carried out by DFT methods on an aluminum pyrrolyl chromium catalyst. Reaction pathways for selective ethylene oligomerization have been successfully located on the basis of the metallacycle mechanism. Consistent with experimental results, for the model system ethylene trimerization was proven to be energetically preferred in comparison to ethylene dimerization or further ring expansion toward the formation of higher α-olefins. The Cr(I/III) redox couple was found to be the most likely for the catalytic ethylene trimerization. A careful electronic configuration analysis has been conducted, and the ground state of all active species involved in the catalytic cycle is identified to be S = 3/2 except for the bare active species, which favors a high spin state of S = 5/2. The role of a pendant chlorine functionality has been investigated as well. Variable Cr–Cl bond distance and NBO charge analysis of every intermediate clearly exhibit the hemilabile behavior of the chlorine. This unique hemilability is considered to be a key factor for the selectivity toward 1-hexene formation.

Aluminum Compounds Containing Pyrrole–Imine Ligand Systems – Synthesis, Characterization, Structure Elucidation, Ring‐Opening Polymerization, and Catalytic Meerwein–Ponndorf–Verley Reaction

AbstractThe reactions of AlMe3 with the tridentate pyrrole ligand precursor C4H3NH(2‐CH=NCH2Py) and subsequent treatment of the derivatives with small organic molecules such as 2,6‐diisopropylphenol or dibenzoylmethane were conveniently performed, and the products were characterized. The reaction between 1 equiv. of AlMe3 and 1 equiv. of a pyrrole–imine–pyridine ligand in toluene affords [Al{C4H3N(CHNCH2Py)Me2}] (1) in high yield. In addition, the use of 2 equiv. of AlMe3 with the same tridentate precursor results in the formation of a dialuminum compound [AlMe3{C4H3N(CHNCH2‐Py)AlMe2}] (2) in moderate yield. Furthermore, the combination of 1 with either 1 or 2 equiv. of 2,6‐diisopropylphenol or 2 equiv. of dibenzoylmethane in toluene yields aluminum monophenoxide or diphenoxide compounds [Al{C4H3N(CHNCH2‐Py)Me(O‐2,6‐iPr2C6H3)}] (3) and [Al{C4H3N(CHNCH2‐Py)}(O‐2,6‐iPr2C6H3)2] (4), respectively, as well as an aluminum bis‐diketonate compound, [Al{C4H3N(CHNCH2‐Py)}(PhCOCHCOPh)2] (5). All of the aforementioned derivatives were characterized by 1H and 13C NMR spectroscopy, and their solid‐state molecular structures were determined by single‐crystal X‐ray diffraction. The geometries of 1–5 show that the pyrrole ligand exists in the pyrrolyl–imine and azafulvene–amido resonance forms. Compounds 1, 3, 4 and 5 were used in the ring‐opening polymerization of ϵ‐caprolactone in the presence of BnOH and in the catalytic Meerwein–Ponndorf–Verley (MPV) reaction of 1‐naphthalenemethanol and 2‐naphthalenecarbaldehyde.

Highly active half-sandwich chromium(iii) catalysts bearing bis(imino)pyrrole ligands for ethylene (co)polymerization

A series of novel half-sandwich chromium(iii) complexes bearing bis(imino)pyrrole complexes was synthesized, characterized, and investigated as catalyst precursors for ethylene polymerization and ethylene/norbornene copolymerization.

Synthesis and structural aspects of gallium compounds containing tridentate pincer type pyrrolyl ligands: Intramolecular hydrogen bonding of gallium aryloxides

A series of gallium derivatives incorporating with pincer type tridentate symmetric and asymmetric pyrrolyl ligands are conveniently synthesized. Compilation of a symmetrical tridentate pyrrole ligand, [C4H2NH-(2,5-CH2NHtBu)2] (1) with one equiv of n-BuLi in heptane generates lithiated 1 that turns to Ga[C4H2N-(2,5-CH2NHtBu)2]Cl2 (2) subjecting the addition of GaCl3/ether suspension into diethyl ether. Reacting 2 with two equiv of lithium reagents (LiR) in same solvent originates a series of gallium compounds Ga[C4H2N-(2,5-CH2NHtBu)2]R2 (3, R = Me; 4, R = O–C6H4–4-Me; 5, R = O–C6H3–2,6-Me2) in moderate yield through metathesis reactions. Furthermore, the combination of a tridentate asymmetrical pyrrole ligand, [C4H2NH(2-CH2NHtBu)(5-CH2NMe2)] and n-BuLi initiates the lithiated 6 that undergoes the formation of a penta-coordinated gallium compound GaCl2[C4H2N(2-CH2NHtBu)(5-CH2NMe2)] (7) while reacting with GaCl3. Furthermore, reacting 7 with two equivs of MeLi affords the gallium-alkyl compound, GaMe2[C4H2N(2-CH2NHtBu)(5-CH2NMe2)] (8) in high yield. The Ga-derivatives are characterized by 1H and 13C NMR spectroscopy and the molecular structures of 2, 3, 4, 5 and 7 are determined by single crystal X-ray diffractometry in solid state.

Novel Lanthanide Amides Incorporating Neutral Pyrrole Ligand in a Constrained Geometry Architecture: Synthesis, Characterization, Reaction, and Catalytic Activity

The first series of lanthanide amido complexes incorporating a neutral pyrrole ligand in a constrained geometry architecture were synthesized, and their bonding, reactions, and catalytic activities were studied. Treatment of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 1 equiv of (N-C6H5NHCH2CH2)(2,5-Me2C4H2N) (1) afforded the first example of bisamido lanthanide complexes having the neutral pyrrole η5-bonded to the metal formulated as [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]Ln[N(SiMe3)2]2 (Ln = La (2) and Nd (3)). Reaction of [(Me3Si)2N]3Sm(μ-Cl)Li(THF)3 with 2 equiv of 1 produced the complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)][η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]]SmN(SiMe3)2 (4). Treatment of 3 with 2 equiv of 1 gave the sandwich neodymium complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]2Nd[η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)] (5), in which two neutral pyrroles bonded with metal in an η5 mode. Complex 5 could also be prepared by reaction of [(Me3Si)2N]3Nd(μ-Cl)Li(THF)3 with 3 equiv of 1. Reactivities of the lanthanide bisamido complexes were further investigated. Reaction of complex 2 with pyrrolyl-functionalized imine [2-(2,6-iPr2C6H3N═CH)C4H3NH] afforded a mixed η5-bonded neutral pyrrole and η1-bonded anionic pyrrolyl lanthanum complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]{η1-2-[(2,6-iPr2C6H3)NCH]C4H3N}La[N(SiMe3)2] (6). Reactions of complexes 2 and 3 with pyrrolyl-functionalized secondary amine afforded the mixed η5-bonded neutral pyrrole and the η1-bonded anionic pyrrolyl lanthanide complexes [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)][(η1-2-tBuNCH)C4H3N]2Ln (Ln = La (7), Nd (8)) with dehydrogenation of the secondary amine. Investigation of the catalytic properties of complexes 2–8 indicated that all complexes exhibited a high activity with a high chemo- and regioselectivity on the addition of dialkyl phosphite to α,β-unsaturated carbonyl derivatives. An interesting result was found that 1,2-hydrophosphonylation substrates could be catalytically converted to 1,4-hydrophosphinylation products when the substrates are the substituted benzylideneacetones by controlling the reaction conditions.

Thermal oxidative degradation of the functionally substituted 2,2′-dipyrrolylmethenes hydrobromides and difluoroborates

Thermal oxidative decomposition of samples of crystalline hydrobromide and borofluoride complexes (BODIPY) of a series of 2,2′-dipyrrolylmethenes (HL) was studied by means of thermogravimetry in an atmosphere of air oxygen. An increase in the degree and symmetry of substitution, aromaticity, and the length of the substituents in 4,4′-positions of the pyrrole ligand rings increases stability of the BODIPY-dyes to oxidative degradation. A comparative analysis of the influence of structural factors on the thermolability of hydrobromdes (HL·HBr), d-metal (ML2) and boron(III) complexes with 2,2′-dipyrrolylmethenes was carried out.