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Este artículo se refiere al documental “La Caja de Arriba del Ropero”. Su realizadora analiza y comparte reflexiones sobre la fotografía. Las imágenes son construcciones ideológicas que tienen que ver con su momento histórico, en este caso es un fotógrafo quien deja un legado, aunque las narradoras en la película y las que conservan el patrimonio, son todas mujeres. Pero además una película es un viaje en el tiempo y en ese hace un recorrido por episodios de la vida de Juan Pi, el fotógrafo que retrató San Rafael desde el momento en que llegó el tren a esa ciudad de Mendoza (Argentina). El viaje al pasado, va hasta la etapa prehispánica en esa zona, describiendo lo que en las fotos se omite, la ocupación de tierras, la campaña de exterminio de nativos. La construcción de un fortín como maquinaria que terminó por desterrar de las ciudades, a los pueblos nativos. Finalmente destaca la participación como mediadora, de una mujer del pueblo Pehuenche, La Cacica María Josefa Roco.

A new strategy for tuning the electronic properties of 1,2,3-triazol-5-ylidene metal complexes is reported using {Mo(η3-C4H7)(bipy)(CO)2} or {Re(bipy)(CO)3} fragments as substituents at the triazole N3 atom. The reaction of cationic molybdenum(II) and rhenium(I) 1-methyl-1,2,3-triazole compounds with the strong base KN(SiMe3)2 in the presence of electrophilic metal fragments, such as AgOTf (OTf = trifluoromethanesufonate) or [CuCl(IPr)] [IPr = 2,6-(diisopropyl)phenylimidazol-2-ylidene] affords a new type of 1,2,3-triazol-5-ylidene complexes. For silver(I) cationic bis(triazolylidene), [Ag(tzNHCM)2]OTf (M = [Mo], 2; [Re], 4), complexes are obtained, whereas in the case of Cu(I) mixed normal/mesoionic NHC, [Cu(IPr)(tzNHCM)]OTf (M = [Mo], 7; [Re], 8) complexes are formed. This special type of mesoionic N-heterocyclic carbenes bear a metal fragment at the N3 atom of the 1,2,3-triazole moiety, showing notable enhancement of the carbene electron donor ability compared to conventional alkyl-substituted analogues. Transmetalation from cationic silver bis(triazolylidene) complexes 2 and 4, prepared using this methodology, has proven to be very efficient toward [M′Cl(cod)]2 (M′ = Rh, Ir; cod = 1,5-cyclooctadiene), affording the corresponding cationic bis(triazolylidene) [M′(cod)(tzNHCM)2]OTf (9–12) complexes. A subsequent reaction with CO(g) easily produces substitution of the diene ligand, affording the corresponding cis-dicarbonyl [M′(CO)2(tzNHCM)2]OTf (13–16) compounds., This work was supported by Ministerio de Ciencia, Innovación y Universidades/FEDER (Grant PGC2018-100013-B-I00).

Pyridine ring-opening of a metal-coordinated 1,10-phenanthroline has been demonstrated for the first time. The reaction of stable, well-defined cis,trans-[Re(CO)(N-N)(N-RIm)(PMe)]OTf [N-N = 2,2′-bipyridine (bipy), N-RIm = N-alkylimidazole] compounds with KN(SiMe) followed by the addition of an excess of electrophile (MeOTf) afforded bipy ring-opening products easily at room temperature. The new, electron rich analogous 1,10-phenanthroline (phen) cis-{Re(CO)} complexes allowed also, under mild conditions, the ring-opening of phen, which can be regarded as a model of coordinated quinoline, one of the impurities in fuels most difficult to eliminate by the hydrodenitrogenation (HDN) process. The phenanthroline ring-opening products are regiochemically different from those obtained with bipy, and the results of computational calculations suggest that the difference can be traced to the avoidance of a larger loss of aromaticity. The new ring-opening products have been spectroscopically characterized in solution and by means of X-ray diffraction in the solid state., This work was supported by Ministerio de Ciencia, Innovación y Universidades/FEDER (grant PGC2018-100013-B-I00). The authors thank Servicios Científico-Técnicos de la Universidad de Oviedo for technical support and the use of RIAIDT-USC analytical facilities.

The reactions of [Re(N‐N)(CO)3(PMe3)]OTf (N‐N=2,2′‐bipyridine, bipy; 1,10‐phenanthroline, phen) compounds with tBuLi and with LiHBEt3 have been explored. Addition to the N‐N chelate took place with different site‐selectivity depending on both chelate and nucleophile. Thus, with tBuLi, an unprecedented addition to C5 of bipy, a regiochemistry not accessible for free bipy, was obtained, whereas coordinated phen underwent tBuLi addition to C2 and C4. Remarkably, when LiHBEt3 reacted with [Re(bipy)(CO)3(PMe3)]OTf, hydride addition to the 4 and 6 positions of bipy triggered an intermolecular cyclodimerization of two dearomatized pyridyl rings. In contrast, hydride addition to the phen analog resulted in partial reduction of one pyridine ring. The resulting neutral ReI products showed a varied reactivity with HOTf and with MeOTf to yield cationic complexes. These strategies rendered access to ReI complexes containing bipy‐ and phen‐derived chelates with several C(sp3) centers., The authors thank Ministerio de Ciencia, Innovación y Universidades, and EU (Grants PGC2018‐100013‐B‐I00 and PGC2018‐093451‐B‐I00, both including FEDER funds) for funding, and Servicios Científico‐Técnicos de la Universidad de Oviedo for technical support. R.A. thanks the Ministerio de Educación, Cultura y Deporte for an FPU predoctoral fellowship.

The reactions of [Re(N-N)(CO)

This article belongs to the Special Issue Theoretical Inorganic Chemistry., A comparative theoretical study on the reactivity of the complexes [ReY(CO)3(bipy)] (Y = NH2, NHMe, NHpTol, OH, OMe, OPh, PH2, PHMe, PMe2, PHPh, PPh2, PMePh, SH, SMe, SPh; bipy = 2,2′-bipyridine) towards methyl propiolate was carried out to analyze the influence of both the heteroatom (N, O, P, S) and the alkyl and/or aryl substituents of the Y ligand on the nature of the product obtained. The methyl substituent tends to accelerate the reactions. However, an aromatic ring bonded to N and O makes the reaction more difficult, whereas its linkage to P and S favour it. On the whole, ligands with O and S heteroatoms seem to disfavour these processes more than ligands with N and P heteroatoms, respectively. Phosphido and thiolato ligands tend to yield a coupling product with the bipy ligand, which is not the general case for hydroxo, alcoxo or amido ligands. When the Y ligand has an O/N and an H atom the most likely product is the one containing a coupling with the carbonyl ligand, which is not always obtained when Y contains P/S. Only for OMe and OPh, the product resulting from formal insertion into the Re-Y bond is the preferred., This research was funded by the Ministerio de Ciencia, Innovación y Universidades (MCIU) of Spain, grant number PGC2018-100013-B-I00.

The reaction of fac-[M(OTf)(CO)3(N–N)](M = Mn, Re; N–N = 2,2′-bipyridine, 1,10-phenanthroline) complexes with in situ generated LiSEt afforded immediately, in THF at low temperature, the corresponding mononuclear terminal thiolato complexes fac-[M(SEt)(CO)3(N–N)](1-2a,b). Using an analogous synthetic strategy, tungsten and molybdenum (II) alkyl- and arylthiolatos of formula cis-[M(SR)(η3-allyl)(CO)2(N–N)] (3-6a,b) have been obtained. Preliminary reactions of the more reactive molybdenum thiolato complexes towards dimethylacetylenedicarboxylate led to Z-alkenyl products (7a,b), resulting from the insertion of the organic unsaturated electrophile into the Mo–S bond. For each new type of compound, one representative has been characterized in the solid state by X-ray diffraction., Financial support from Ministerio de Economía y Competitividad/FEDER (grant CTQ2015-70231-P), Ministerio de Ciencia, Innovacion y Universidades (grant PGC2018-097366-B-100), and Principado de Asturias (grant GRUPIN14-103, and Severo Ochoa predoctoral fellowship to S. F.) is gratefully acknowledged. S. Z. participated in this work during her stay at Universidad de Oviedo as an Erasmus exchange student from University of Heidelberg.

Unsupported 1-methyl-1,2,3-triazole has been coordinated to {Mo(η

The first examples for the rhenium-catalysed hydroboration of aldehydes, ketones and aldimines, including heteroaromatic quinoline, are reported herein. Reactions are remarkably chemoselective and tolerant of several functional groups. A wide array of rhenium complexes were efficient pre-catalysts for these hydroborations, including new low-valent complexes of the formula [Re(N-N)(CO)(L)]X (N-N = bipy derivative, L = labile ligand/solvent, and X = [BAr ] and [B(3,5-di-tBu-cat)]), which have been characterized fully including an X-ray diffraction study for [Re(bipy)(CO)(quin)][BAr ] (2). A new silver spiroboronate ester Ag[B(3,5-di-tBu-cat)](NCCH) (3) was prepared and characterized fully, including an X-ray diffraction study, and used to make one of the new rhenium complexes., The Oviedo authors thank MINECO and FEDER (grant CTQ2015-70231-P) and Principado de Asturias (grant FC-15-GRUPIN14-103) for funding, and Ministerio de Educación for an FPU predoctoral fellowship (to RA). SAW is grateful to the Natural Sciences and Engineering Research Council, the CRC programme and Mount Allison University for funding.

Intramolecular C-C coupling between N-bonded 1,2-dimethylimidazole, 2-methyloxazoline, or 2-methylpyridine and either 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) ligands results from α-methyl group deprotonation in the coordination sphere of Re(CO) fragments. The nucleophilic CH group generated by the deprotonation attacks the 6 (bipy) or 2 (phen) positions of the diimines, dearomatizing the involved pyridine ring and generating new asymmetric, fac-capping tridentate ligands., The authors thank MINECO and FEDER (Grant CTQ2015-70231-P) and Principado de Asturias (Grant FC-15-GRUPIN14-103) for funding and the Ministerio de Educación for an FPU predoctoral fellowship (to R.A.).

Herein we present a theoretical study on the reaction of [Re(PPh) (CO)(phen)] (phen = 1,10-phenanthroline) and [Re(PPh) (CO)(bipy)] (bipy = 2,2′-bipyridine) toward methyl propiolate. In agreement with experimental results for the phen ligand, the coupling of the substituted acetylenic carbon with the nonsubstituted ortho carbon of the phen ligand is the preferred route from both kinetic and thermodynamic viewpoints with a Gibbs energy barrier of 18.8 kcal/mol and an exoergicity of 11.1 kcal/mol. There are other two routes, the insertion of the acetylenic fragment into the P-Re bond and the coupling between the substituted acetylenic carbon and a carbonyl ligand in cis disposition, which are kinetically less favorable than the preferred route (by 2.8 and 1.9 kcal/mol, respectively). Compared with phen, the bipy ligand shows less electrophilic character and also less π electron delocalization due to the absence of the fused ring between the two pyridine rings. As a consequence, the route involving the coupling with a carbonyl ligand starts to be kinetically competitive, whereas the product of the attack to bipy is still the most stable and would be the one mainly obtained after spending enough time to reach thermal equilibrium., The authors thank Ministerio de Economia y Competitividad (Grant No. CTQ2015-70231-P) and Principado de Asturias (Grant No. FC-15-GRUPIN14-103) for financial support. We also acknowledge financial support from CONICYT/CHILE under the Project PAI No. 79150043 (G.I.C.-J. and R.M.-A.) and computing resources from the Fundacion Computacion y Tecnologias Avanzadas de Extremadura (J.D.).

Unsupported 1-methyl-1,2,3-triazole has been coordinated to {Mo(η3 -methallyl)(CO)2 (N-N)} (N-N=2,2'-bipyridine, bipy; or 1,10-phenanthroline, phen) fragments, yielding cationic complexes that can be regarded as metalated triazolium salts. Their reactivity towards a strong base led to the deprotonation of the C5-H group of the triazole moiety, followed by an intermolecular nucleophilic attack to the ortho CH group of a bipy or phen ligand affording cyclic, bimetallic dearomatized C-C coupling products. The reaction of the neutral bipy derivative with an acid led to the formation of dihydropyridyl units by protonation of a CH group of the dearomatized rings, the dimeric nature of complexes being mantained upon protonation., Financial support from Ministerio de Economía y Competitividad/FEDER (grant CTQ2015‐70231‐P) and Principado de Asturias (grant GRUPIN14‐103, and Severo Ochoa fellowship to S.F.) is gratefully acknowledged.

4,4’-Disubstituted-2,2′-bipyridine ligands coordinated to Mo and Re cationic fragments become dearomatized by an intramolecular nucleophilic attack from a deprotonated N-alkylimidazole ligand in cis disposition. The subsequent protonation of these neutral complexes takes place on a pyridine carbon atom rather than at nitrogen, weakening an aromatic C−C bond and affording a dihydropyridyl moiety. Computational calculations allowed for the rationalization of the formation of the experimentally obtained products over other plausible alternatives., Financialsupport from Ministerio de Economía y Competitividad/FEDER (grant CTQ2015-70231-P) and Principado de Asturias (grant GRUPIN14-103) is gratefully acknowledged. J.D.thanks COMPUTAEX for granting access to LUSITANIA supercomputing facilities.

Rhenium(I) compounds [Re(CO) 3(Hdmpz) 2(ampy)] BAr′ 4 and [Re(CO) 3(N-MeIm) 2(ampy)] BAr′ 4 (Hdmpz = 3,5-dimethylpyrazole, N-MeIm = N-methylimidazole, ampy = 2-aminopyridine or 3-aminopyridine) have been prepared stepwise as the sole reaction products in good yields. The cationic complexes feature two different types of hydrogen bond donor ligands, and their anion binding behavior has been studied both in solution and in the solid state. Compounds with 2-ampy ligands are labile in the presence of nearly all of the anions tested. The X-ray structure of the complex [Re(CO) 3(Hdmpz) 2(ampy)] + (2) shows that the 2-ampy ligand is metal-coordinated through the amino group, a fact that can be responsible for its labile character. The 3-ampy derivatives (coordinated through the pyridinic nitrogen atom) are stable toward the addition of several anions and are more selective anion hosts than their tris(pyrazole) or tris(imidazole) counterparts. This selectivity is higher for compound [Re(CO) 3(N-MeIm) 2(MeNA)]BAr′ 4 (5·BAr′ 4, MeNA = N-methylnicotinamide) that features an amido moiety, which is a better hydrogen bond donor than the amino group. Some of the receptor-anion adducts have been characterized in the solid state by X-ray diffraction, showing that both types of hydrogen bond donor ligands of the cationic receptor participate in the interaction with the anion hosts. DFT calculations suggest that coordination of the ampy ligands is more favorable through the amino group only for the cationic complex 2, as a consequence of the existence of a strong intramolecular hydrogen bond. In all other cases, the pyridinic coordination is clearly favored. © 2011 American Chemical Society., Financial support from the Ministerio de Ciencia e Innovación (MICINN, project number CTQ2009-12366) and Principado de Asturias (project number IB08-104) is gratefully acknowledged.

El pdf del artículo es el manuscrito de autor.-- et al., Two birds, one stone: A deprotonation–protonation sequence using only one molar equivalent of base and acid transforms two N-alkylimidazole molecules into N-heterocyclic carbene ligands (see scheme; black C, gray H, green F, blue N, red O, cyan Re, yellow S)., Financial support from the Ministerio de Ciencia e Innovación (MICINN, No. CTQ2009-12366) and Principado de Asturias (No. IB08-104) is gratefully acknowledged.

This Microreview deals with the supramolecular chemistry of pyrazole metal complexes, in particular, complexes of pyrazoles with a nonsubstituted N–H group, which are able to engage in hydrogen bonding. The most pertinent general features of pyrazoles, in comparison with other heterocycles that are also popular ligands, and some aspects of the supramolecular chemistry of free pyrazoles are also included. In addition to the general supramolecular chemistry of pyrazole complexes, sections of this Microreview are devoted to liquid crystals, self-assembled species, and hosts for anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

KN(SiMe3)2 reacts with [Re(CO)3(phen)(PMe3)]OTf via reversible addition to the phen ligand and irreversible deprotonation of the PMe3 ligand followed by intramolecular attack to phen by the deprotonated phosphane, whereas MeLi irreversibly adds to phen. The addition of MeLi has been shown to be intermolecular, unlike previously known nucleophilic additions to pyridines., The authors thank MINECO and FEDER (grant CTQ2015-70231-P) and Principado de Asturias (grantFC-15-GRUPIN14-103) forfunding, and Ministerio de Educación for an FPU predoctoral fellowship (to R.A.).

Chapter Two., 2,2′-Bipyridine (bipy) and 1,10-phenanthroline (phen), employed for a long time in all areas of coordination chemistry, are archetypical auxiliary ligands that stabilize metal fragments but are not themselves the site of the reactivity. Several examples of dearomatization of one of the pyridine rings of coordinated bipy and phen are discussed, including one example of ring opening. The highly reactive species resulting from deprotonation of coordinated N-alkylimidazoles can result, besides of the mentioned dearomatization, in other intramolecular C–C coupling reactions involving monodentate pyridines, other N-alkylimidazoles, imine, nitrile, isonitrile, and carbonyl ligands. In some examples, the products of these couplings, and of those between two pyridines, can be oxidatively rearomatized, affording pyridylimidazoles and bipyridines. Similar reactions leading to C–C couplings have been demonstrated for deprotonation of dimethylsulfide and methylphosphane ligands. In some instances, the deprotonation of coordinated N-alkylimidazoles produces complexes with rare N-alkylimidazol-2-yl ligands. The protonation or alkylation of the nonsubstituted nitrogen of the latter affords coordinated N-heterocyclic carbenes., The authors gratefully acknowledge funding from Ministerio de Economía y Competitividad and FEDER (grants CTQ2012-37379-C02-01 and CTQ2012-37379-C02-02, and FPI graduate studentships to M.E.V. and M.A.H.) and Principado de Asturias (grant FC-15-GRUPIN14-103, administered by FICYT) and Ministerio de Educación Cultura y Deporte (FPU graduate studentship to R.A.).

DNA damage by MoCH3(eta3-allyl)(CO)2(phen) complexes has been shown to occur by two mechanisms: by backbone cleavage via the abstraction of H1' and/or H5' from the deoxyribose moiety and by base modification, resulting in G-specific cleavage via the formation of base-labile residues methylguanine, methoxyguanine, and 8-oxo-G.

Compound cis,fac-[Mo(eta3-allyl)(CO)2(Hdmpz)3]BAr'4 (1) (Hdmpz = 3,5-dimethylpyrazole, Ar' = 3,5-bis(trifluoromethyl)phenyl) undergoes rapid substitution of one of the pyrazole ligands by anions, including the low nucleophilic ReO4-, a reaction that afforded [Mo(OReO3)(eta3-allyl)(CO)2(Hdmpz)2] (2), structurally characterized by X-ray diffraction. The new compounds fac-[Mn(CO)3(Hdmpz)3]BAr'4 (4a) and fac-[Mn(CO)3(HtBupz)3]BAr'4 (4b) (HtBupz = 3(5)-tert-butylpyrazole) also undergo pyrazole substitution with most anions, and the product from the reaction with nitrate was crystallographically characterized. Compounds 4a,b were found to be substitutionally stable toward perrhenate, and the adducts [Mn(CO)3(Hdmpz)3].[ReO4] (7a) and [Mn(CO)3(HtBupz)3].[ReO4].[Bu4N].[BAr'4] (7b), crystallographically characterized, display hydrogen bonds between one of the perrhenate oxygens and the N-H groups of two of the pyrazole ligands. The structurally similar adduct [Re(CO)3(Hdmpz)3].[ReO4] (8) was found to result from the interaction of [Re(CO)3(Hdmpz)3]BAr'4 with perrhenate. The reaction of [Re(OTf)(CO)5] with 3,5-dimethylpyrazole (Hdmpz) afforded [Re(CO)5(Hdmpz)]OTf (9). The reaction of 9 with Hdmpz and NaBAr'4 yielded [Re(CO)4(Hdmpz)2]BAr'4 (10), which was found to be unstable toward chloride anion. In contrast, the new compound fac,cis-[Re(CO)3(CNtBu)(Hdmpz)2]BAr'4 (11) is stable in solution in the presence of different anions. Binding constants for 11 with chloride, bromide, and nitrate are 1-2 orders of magnitude lower than those found for these anions and rhenium tris(pyrazole) hosts, indicating that the presence of the third pyrazole ligand is crucial. Compounds fac-[Re(CO)3(HPhpz)3]BAr'4 (14) (HPhpz = 3(5)-phenylpyrazole) and fac-[Re(CO)3(HIndz)3]BAr'4 (15) (HIndz = indazole) are, in terms of anion binding strength and selectivity, inferior to those with dimethylpyrazole or tert-butylpyrazole ligands.

Complexes [Re(ONCMe2)(CO)3(bipy)] (1) and [Re(ONCMe2)(CO)3(phen)] (2), synthesized by reaction of the respective triflato precursors [Re(OTf)(CO)3(N-N)] (N-N = bipy, phen) with KONCMe2, feature O-bonded monodentate oximato ligands. Compound [Re(CO)3(phen)(HONCMe2)]BAr'4 (3), with a monodentate N-bonded oxime ligand, was prepared by reaction of [Re(OTf)(CO)3(phen)], HONCMe2, and NaBAr'4. Deprotonation of 3 afforded 2. The oximato complexes reacted with p-tolylisocyanate, p-tolylisothiocyanate, maleic anhydride, and tetracyanoethylene, affording the products of the insertion of the electrophile into the Re-O bond, compounds 4-7. One representative of each type of compound was fully characterized, including single-crystal X-ray diffraction. The reactions of 1 and 2 with dimethylacetylenedicarboxylate were found to involve first an insertion as the ones mentioned above but followed by incorporation of water, loss of acetone, and formation of the charge-separated neutral amido complexes 9 and 10. The structure of 9 and 10 was determined by X-ray diffraction, and key features of their electronic distribution were studied using a topological analysis of the electron density as obtained from the Fourier map.

New N-methylimidazole (N-MeIm) complexes of the {Mo(η3-allyl)(CO)2(N–N)} fragment have been prepared, in which the N,N-bidentate chelate ligand is a 2-pyridylimine. The addition of a strong base to the new compounds deprotonates the central CH group of the imidazole ligand and subsequently forms the C–C coupling product that results from the nucleophilic attack to the imine C atom. This reactivity contrasts with that previously found for the analogous 2,2′-bipyridine compounds [Mo(η3-allyl)(CO)2(bipy)(N-RIm)]OTf [N-RIm = N-MeIm, N-mesitylimidazole (N-MesIm, Mes= 2,4,6-trimethylphenyl); OTf = trifluoromethanesulfonate) which afforded imidazol-2-yl complexes upon deprotonation. Density Functional Theory (DFT) computations uncover that the reactivity of the imine C atom along with its ability to delocalize electron density are responsible for the new reactivity pattern found for the kind of molybdenum complexes reported herein., Financial support from the Ministerio de Economia y Competitividad (Projects CTQ2010-18231, CTQ2012-37370-C02-01, and CTQ2012-37370-C02-02) is gratefully acknowledged.

The reactions of the hydroxo complexes [Mo(OH)(η3-methallyl)(CO)2(phen)] (1) and [Re(OH)(CO)3(Me2-bipy)] (2) (phen = 1,10-phenanthroline, Me2-bipy= 4,4‘-dimethyl-2,2‘-bipyridine) with maleic anhydride, phenyl(ethyl)ketene, diphenylketene, and rac-lactide afford new carboxylato complexes. The molybdenum and rhenium hydroxo complexes react in the same way, and their reactions are quantitative. The products, some of which have been characterized by X-ray diffraction, feature monodentate O-bonded carboxylato ligands, and their treatment with triflic acid yields the triflato complexes [Mo(OTf)(η3-methallyl)(CO)2(phen)] and [Re(OTf)(CO)3(Me2-bipy)] and the corresponding free carboxylic acid.

The behavior of the receptors [Re(CO)3(Hdmpz)3]BAr'4 (Hdmpz = 3,5-dimethylpyrazole) (1) and [Re(CO)3(HtBupz)3]BAr'4 (HtBupz = 3(5)-tert-butylpyrazole) (2; Ar' = 3,5-bis(trifluoromethyl)phenyl) toward the anions fluoride, chloride, bromide, iodide, hydrogensulfate, dihydrogenphosphate, nitrate, and perrhenate was studied in CD3CN solution. In most cases, the receptors were stable. Anion exchange was fast, and binding constants were calculated from the NMR titration profiles. The structure of the adduct [Re(CO)3(HtBupz)3] x NO3 (3) was determined by X-ray diffraction. Two pyrazole moieties are hydrogen-bonded to one nitrate oxygen atom, and the third pyrazole moiety is hydrogen-bonded to an oxygen atom of an adjacent nitrate, leading to infinite chains. The structure of the adduct [Re(CO)3(Hdmpz)3]BAr'4acetone (4), also determined by X-ray diffraction, showed a similar interaction of two pyrazole N-H groups with the acetone oxygen atom. F- and H2PO4(-) deprotonate the receptors, and HSO4(-) decomposed 1. The structure of one of the decomposition products (5), determined by X-ray diffraction, is consistent with pyrazole protonation and substitution by sulfate.

The behavior of the new cationic complex [Re(CNtBu)(CO)3(N–N)]+ (N–N = 1,2-phenylenediamine) toward several inorganic anions (X−) has been investigated both in solution (by 1H NMR) and in the solid state (by X-ray diffraction), and the results show the formation of supramolecular adducts featuring N–H⋯X hydrogen bonds.

Cationic complexes [Mo(η3-allyl)(CO)2L3]+ (L3 = either nitrogen-donor tridentate ligand or three monodentate ligands) were prepared in high yield and under mild conditions using as precursors either the triflato complex [Mo(η3-allyl)(OTf)(CO)2(NCMe)2] or the combination of the chloro complex [Mo(η3-allyl)Cl(CO)2(NCMe)2] and the salt NaBAr′4 (Ar′ = 3,5-bis(trifluoromethyl)phenyl). The tridentate ligands employed were 2,2′:6′,2′-terpyridine (terpy) and cis,cis-1,3,5-cyclohexanetriamine (CHTA), whereas the monodentate ligands imidazole (im) and 3,5-dimethylpyrazole (dmpz) were chosen. In order to stabilize the labile intermediates, an excess of acetonitrile was used in most of the syntheses. However, the pyrazole complex was prepared through a nitrile-free route to avoid reactions at the coordinated nitrile. The solid state structures of [Mo(η3-methallyl)(CO)2(terpy)]OTf (2), [Mo(η3-methallyl)(CO)2(CHTA)]BAr′4 (3), [Mo(η3-methallyl)(CO)2(NCMe)3]BAr′4 (4), [Mo(η3-allyl)(CO)2(im)3]OTf (5) and [Mo(η3-allyl)(CO)2(dmpz)3]BAr′4 (6) were determined by means of single-crystal X-ray diffraction.

The reaction of the complex [Mo(OTf)(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (1) (OTf = trifluoromethylsulfonate; phen = 1,10-phenanthroline) with tetrabutylammonium fluoride trihydrate afforded the fluoride complex [MoF(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (2). The IR spectrum and the oxidation potential of 2 reflect the fact that its metal center is more electron-rich than that of the chloro analogue [MoCl(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)]. Compound 2 reacted with 1 affording the homobinuclear complex [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](2)(mu-F)][OTf] (3), with a fluoride bridge. Compound 2 also reacts with the species generated in situ by triflate abstraction from [M(OTf)(CO)(3)('N-N')] (M = Mn, Re; 'N-N' = 2,2'-bipyridine (bipy), phen) using NaBAr'(4) (Ar' = 3,5-bis(trifluoromethyl)phenyl), affording the heterobinuclear complexes [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](mu-F)[M(CO)(3)('N--N')]][BAr'(4)] (M = Mn, 'N-N' = bipy (4); M = Re, 'N-N' = phen (5)). All new compounds have been characterized by spectroscopic methods (IR and NMR) and, in the case of 1, 2, 3, and 4, also by means of X-ray diffraction analysis.

The hydroxo compounds [Re(OH)(CO)(3)(N-N)] (N-N=bipy, 2 a; Me(2)-bipy, 2 b) were prepared in a biphasic H(2)O/CH(2)Cl(2) medium by reaction of [Re(OTf)(CO)(3)(N-N)] with KOH. In contrast, when anhydrous CH(2)Cl(2) was used, the binuclear hydroxo-bridged compound [[Re(CO)(3)(bipy)](2)(mu-OH)]OTf (3-OTf) was obtained. Compound [Re(OH)(CO)(3)(Me(2)-bipy)] (2 b) reacted with phenyl acetate or vinyl acetate to afford [Re(OAc)(CO)(3)(Me(2)-bipy)] (4) and phenol or acetaldehyde, respectively. The reactions of [Mo(OH)(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (1), 2 a, and 2 b toward several unsaturated organic electrophiles were studied. The reaction of 1 with (p-tolyl)isocyanate afforded an adduct of N,N'-di(p-tolyl)urea and the carbonato-bridged compound [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](2)(mu-eta(1)(O),eta(1)(O)-CO(3))] (5). In contrast, the reaction of 2 a with phenylisocyanate afforded [Re(OC(O)NHPh)(CO)(3)(bipy)] (6); this results from formal PhNCO insertion into the O-H bond. On the other hand, compounds [Mo[SC(O)NH(p-tolyl)](eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (7), [Re[SC(O)NH(p-tolyl)](CO)(3)(Me(2)-bipy)] (8 a), and [Re[SC(O)NHEt](CO)(3)(Me(2)-bipy)] (8 b) were obtained by reaction of 1 or 2 b with the corresponding alkyl or aryl isothiocyanates. In those cases, RNCS was inserted into the M-O bond. The reactions of 1, 2 a, and 2 b with dimethylacetylenedicarboxylate (DMAD) gave the complexes [Mo[C(OH)-C(CO(2)Me)C(CO(2)Me)-O](eta(3)-C(3)H(4)-Me-2)(CO)(phen)] (9) and [Re[C(OH)C(CO(2)Me)C(CO(2)Me)O](CO)(2)(N-N)] (N-N=bipy, 10 a; Me(2)-bipy, 10 b). The molecules of these compounds contain five-membered metallacycles that are the result of coupling between the hydroxo ligand, DMAD, and one of the CO ligands. The new compounds were characterized by a combination of IR and NMR spectroscopy, and for [[Re(CO)(3)(bipy)(2)(mu-OH)]BF(4) (3-BF(4)), 4, 5, 6, 7, 8 b, 9, and 10 b, also by means of single-crystal X-ray diffraction.

The reaction of [ClP(μ-NtBu)]2 (1) with H2O (1 : 2 equivalents) in the presence of excess Et3N gives the new chain compound [(μ-O){P(μ-NtBu)2P(H)O}2] (3), consisting of two P2N2 rings linked by a μ-O atom and terminating in PV(H)O groups. A similar chain species is obtained from the reaction of the lithiate of [(tBuNH)P(μ-NtBu)2P(H)O] (5) with [ClP(μ-NtBu)2P(NHtBu)] (2), the product being [(μ-O){P(μ-NtBu)2P(NHtBu)}2] (6). Compounds 3 and 6 are the first examples of O-bridged chain phosphazanes and potential precursors to new phosphorus-nitrogen macrocycles. The syntheses and X-ray structures of 3, 5 and 6 are reported.

Inorganic macrocycles, possessing molecular frameworks composed entirely of elements other than carbon, are rare. Even rarer are species analogous to classical organic macrocycles (like crown ethers) that possess the potential ability to coordinate metal ions within their cavities. Recent studies reveal an emerging structural class of valence-isoelectronic main-group ligands of general formula [{E(µ-E′R)}2Y]nx−, which possess fascinating coordination characteristics. Such species can coordinate metal ions within their cavities (using the donor centres Y and E′), their peripheral donor centres (E′) (in an exo fashion) and are also capable of coordinating anions (where Y = N−H). This short review highlights the recent synthetic and structural studies of these unusual ligand systems and pinpoints potential future areas of development. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The reactions of the complexes [MCl(η3-C3H4-R)(CO)2(phen)] (1a−c; M = Mo, W) with KCH2C(O)Ar afford the O-bound enolato complexes [M(η3-C3H4-R){OC(CH2)Ar}(CO)2(phen)] (2a−d). On the other hand, the...

The molybdenum alkynyl complexes [Mo(CCPh)(η3-allyl)(CO)2(bipy)] (1) and [Mo(CCH)(η3-allyl)(CO)2(N–N)] (N–N=2,2′-bipyridine, 2a; 1,10-phenanthroline, 2b) react with dicobalt octacarbonyl to give the new tetrahedrane trimetallic complexes [Co2(CO)6(μ-η2:η2-M–CCPh)], M={Mo(η3-C3H5)(CO)2(bipy)} (3) and [Co2(CO)6(μ-η2:η2-M–CCH)], M={Mo(η3-C3H5)(CO)2(N–N)} (N–N=bipy, 4a; phen, 4b), respectively. These new compounds were characterized by analytical (C, H, N), spectroscopic (IR, 1H NMR) and crystallographic (single crystal X-ray diffraction) means.

Treatment of [MoCl(eta(3)-allyl)(CO)(2)(phen)] with NaCN in CH2Cl2/MeOH afforded [Mo(CN)(eta(3)-allyl)(CO)(2)(phen)] [allyl = C3H5 (1a); 2-MeC3H4 (1b)] as the sole products (no products of cyanide attack on the allyl group were detected). Treatment of 1a,b with [Mo(OTf)(eta(3)-C3H5)(CO)(2)(phen)] and NaBAr'(4) in CH2Cl2 yielded the compounds [{Mo(eta(3)- allyl)(CO)(2)(phen)}(mu-CN){Mo(eta(3)-C3H5)(CO)(2)(phen)}]BAr'(4) (2a,b). Analogous treatment of 1a with fac-[M(OTf)(CO)(3)(bipy)] (M = Mn, Re) and NaBAr'(4) resulted in the synthesis of [{Mo(eta(3)-C3H5)(CO)(2)(phen)}(mu-CN){M(CO)(3)(bipy)}]BAr'(4) (3, 4), in which the C and N atoms of the cyano bridge are bonded to Mo and M (M = Mn, Re), respectively. The linkage isomer of 4 (C and N atoms of the cyano group bonded to Re and Me, respectively) (6) was prepared by treatment of [Re(CN)(CO)(3)(bipy)] (5) with [Mo(OTf)(eta(3)-C3H5)(CO)(2)(phen)] and NaBAr'(4). Compounds 1a, 2b, 3, and 6 were characterized by X-ray diffraction. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

The reaction of fac-[Re(bipy)(CO)3(PMe3)][OTf] (bipy = 2,2′-bipyridine) with KN(SiMe3)2 affords two neutral products: cis,trans-[Re(bipy)(CO)2(CN)(PMe3)], and a thermally unstable compound, which features a new C-C bond between a P-bonded methylene group (from methyl group deprotonation) and the C6 position of bipy. The solid-state structures of more stable 1,2-bis[(2,6-diisopropylphenyl) imino]acenaphthene analogs, resulting from the deprotonation of PMe3, PPhMe2, and PPh2Me ligands, are determined by X-ray diffraction., Financial support from the Ministerio de Economía y Competitividad (grants CTQ2012-37379-C02-01 and CTQ2012-37379-C02-02) is gratefully acknowledged. R.A. thanks the Ministerio de Educación, Cultura y Deporte for an FPU graduate studentship.

The reaction of [Mo(η3-C3H4-Me-2)Cl(CO)2(phen)] with NaBAr‘4 (Ar‘ = 3,5-bis(trifluoromethyl)phenyl) and H2O allowed the isolation of the aquo complex [Mo(η3-C3H4-Me-2)(OH2)(CO)2(phen)]BAr‘4·2Et2O (1). Deprotonation of 1 afforded a neutral monomeric hydroxo compound isolated as [{Mo(η3-C3H4-Me-2)(OH)(CO)2(phen)}2(μ-H2O)] (2), which could be also obtained by reaction of [Mo(η3-C3H4-Me-2)Cl(CO)2(phen)] with KOH in a biphasic CH2Cl2/H2O medium. The reaction of 1 and 2 afforded the binuclear hydroxo-bridged compound [{Mo(η3-C3H4-Me-2)(CO)2(phen)}2(μ-OH)]BAr‘4 (3b) via nucleophilic substitution of water by the hydroxo ligand.

Alkoxo complexes [Re(OR)(CO)(3)(N-N)] (R=Me, Et, tBu; N-N=2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'bipyridine (bipy'), 1,10-phenanthroline (phen)) and [M(OMe)(eta(3)-allyl)(CO)(2)(phen)] (M=Mo, W) have been synthesized in good yields and using mild conditions by the reaction of sodium alkoxides with [Re(OTf)(CO),(N-N)] and [MCl(eta(3)-allyl)(CO)(2)-(phen)] precursors. These have been characterized by IR and NMR spectroscopy as well as by X-ray diffraction for [W(OMe)(eta(3)-allyl)(CO)(2)(phen)] (10). The reactions of the molybdenum and rhenium alkoxo complexes with isocyanates, R'NCO, yield [LnM{N(R')C(O)-OR}] complexes; the carbamate ligand, which results from an R'NCO insertion into the M-OR bond, is monodentate through the nitrogen atom. The solid-state structures of Mo and Re examples have been determined by X-ray diffraction. The geometry around the carbamate nitrogen of these compounds is planar, and the distances indicate delocalization of the nitrogen lone pair involving mainly the carbonyl groups. Experiments carried out with the Re complexes showed that aryl isocyanates are more reactive than their alkyl counterparts, and that bulky R' groups led to slow rates of insertion. Insertion reactions were also observed with isothiocyanates, although here it is the S-C bond that inserts into the M-OR bond, and the resulting ligand is bound to the metal by sulfur. Competition experiments with the Re compounds indicate that isocyanates are more reactive than isothiocyanates towards the Re-OR bonds. Tetracyanoethylene inserts into the Re-OMe bond of [Re(OMe)(CO)(3)(bipy')], forming a complex with a 2-methoxytetracyanoethyl ligand; the structure of which was determined by X-ray diffraction. The formation of the xanthato complex [Re(SC(S)OtBu)(CO)(3)(bipy)] (20) by reaction of [Re(OTf)(CO)3(bipy)] with CS2 and NaO-tBu, but not by the reaction of CS, and [Re(OtBU)(CO)(3)(bipy)] (5a), suggests that the insertion reactions do not take place by ionization of the alkoxo complexes to give the free alkoxide ion.

The complex [MoCl(η3-C3H5)(CO)2(phen)] was prepared in a one-pot manner from Mo(CO)6, allyl chloride, and 1,10-phenanthroline (phen). This complex reacted with AgOTf to afford [Mo(OTf)(η3-C3H5)(CO)2(phen)] (1). The reaction of 1 with NaBAr‘4 (Ar‘ = 3,5-bis(trifluoromethyl)phenyl) in CH2Cl2 yielded a solution that catalyzed (1% load of the catalyst) the reaction of ethyl diazoacetate with N-benzylideneaniline to give a mixture of cis-(carboxyethyl)-1,3-diphenylaziridine and two enamines. Replacement of phen by chiral ligands based on trans-1,2-diaminocyclohexane failed to induce asymmetry on the obtained aziridine.

The ligands [nBuSn(2-pyridyl)3] and [RSn(methylthiomethyl)3] (R = nBu, Me) have been prepared in a one-pot, two-step procedure from the corresponding alkyltin trichloride and 2-pyridyl or methylthi...

A new family of cationic rhenium tricarbonyl complexes with either two N-alkylimidazole (N-RIm) and one pyridine (Py) ligand, or two pyridine and one N-RIm ligand, [Re(CO)3(N-RIm)(3-x)(Py)x] +, has been prepared. The reaction of these complexes with a strong base, followed by an oxidant, selectively afforded 2,2'-pyridylimidazole complexes as the result of intramolecular dehydrogenative C-C coupling reactions. For tris(pyridine) complexes [Re(CO)3(Py) 3]+ the reaction pattern upon a deprotonation/oxidation sequence is maintained, which allows the generation of complexes with 2,2'-bipyridine ligands. In the particular combination of two different types of pyridine ligand in the cationic fac-Re(CO)3 complexes only the cross-coupling products with asymmetric 2,2'-bipyridine ligands were obtained; the homocoupling products were not observed., Financial support from the Ministerio de Economía y Competitividad (project numbers CTQ2012–37370-C02–01 and CTQ2012–37370-C02–02), Principado de Asturias (project number SV-PA-13-ECOEMP-11), and EU Fondos FEDER is gratefully acknowledged.

Deprotonation of the dimethyl sulfide ligand in [Re(bipy)(CO) 3(SMe2)][OTf] (1) by KN(SiMe3)2 afforded a mixture of two diastereomers (2M and 2m) in which a C-C bond has been formed between the S-bonded CH2 group and the 2 position of 2,2′-bipyridine. The solid-state structure of the more stable 2,6- iPr-BIAN analogue could be determined by X-ray diffraction. © 2013 American Chemical Society., Financial support from Ministerio de Ciencia e Innovación (Grant CTQ2009-12366) and Ministerio de Economía y Competitividad (Grants CTQ2012-37379-C02-01 and CTQ2012-37379-C02-02) is gratefully acknowledged. R.A. thanks the Universidad de Oviedo (Beca de Excelencia del Campus de Excelencia Internacional), Principado de Asturias (Beca Severo Ochoa), and Ministerio de Educación, Cultura y Deporte (Beca FPU), for graduate studentships.

Ligand activation: Deprotonation of the nitrile or isonitrile complexes [Re(CO)3(N-RIm)2(L)]+ (N-RIm=N-alkylimidazole; L=Nï£CtBu, Cï£NtBu) selectively afforded alkylidenamido or iminoacyl derivatives, respectively, in which C-C coupling has occurred. Protonation of the latter complex leads to aminocarbene products. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., We gratefully acknowledge the Ministerio de Economía y Competitividad (project numbers CTQ2012-37379-C02-01 and CTQ2012-37379-C02-02) and Principado de Asturias (project number SV-PA-13-ECOEMP-11) for financial support.

Rhenium tricarbonyl complexes with three N-heterocyclic ligands (N-alkylimidazoles or pyridines) undergo deprotonation with KN(SiMe3)2 and then oxidation with AgOTf to afford complexes with pyridylimidazole or bipyridine bidentate ligands resulting from deprotonation, C–C coupling and rearomatization., Financial support from the Ministerio de Ciencia e Innovacion (MICINN, No. CTQ2009-12366), CSIC (PIE No. 201080I038) and EU Fondos FEDER is gratefully acknowledged.

El pdf del artículo es el manuscrito de autor., Make it a double¡ A coordinated N-methylimidazole has been transformed, by double activation, into a bridging ligand that is simultaneously an abnormal N-heterocyclic carbene (NHC) and a Fischer carbene., The authors gratefully acknowledge the Spanish Ministry of Science and Innovation (MICINN)/FEDER (project number CTQ2009-12366), the Principality of Asturias (project number IB08-104) and the Spanish National Research Council (CSIC) (project number PIE-201080I038) for financial support.

Amido complexes of Mo(II) allyl carbonyl fragments containing monodentate amido ligands, prepared by reaction of suitable chloro precursors with potassium amides, react (for the N(H)(p-tolyl) derivative) with tetracyanoethylene to give a 1-azaallenylidene complex.

El pdf del artículo es la versión de autor.-- et al., Both manganese and rhenium complexes of the type [M(bipy)(CO)3(N-RIm)]+ (bipy=2,2’-bipyridine) undergo deprotonation of the central CH group of the N-alkylimidazole (N-RIm) ligand when treated with a strong base. However, the outcome of the reaction is very different for either metal. For Mn, the addition of the equimolar amount of an acid to the product of the deprotonation affords an N-heterocyclic carbene (NHC) complex, whereas for Re, once the deprotonation of the central imidazole CH group has occurred, the bipy ligand undergoes a nucleophilic attack on an ortho carbon, affording the C--C coupling product. The extension of these studies to pseudo-octahedral [Mo(η3-allyl)(bipy)(CO)2(N-RIm)]+complexes has allowed us to isolate cationic NHC complexes (MnI-type behavior), as well as their neutral imidazol-2-yl precursors. Theoretical studies of the reaction mechanisms using DFT computations were carried out on the deprotonation of [Mn(bipy)(CO)3(N-PhIm)]+, [Re(bipy)(CO)3(N-MesIm)]+, and [Mo(η3-C4H7)(bipy)(CO)2(N-MesIm)]+ complexes (Mes=mesityl) at the B3LYP/6-31G(d) (LANL2DZ for Mn, Re, and Mo) level of theory. Our results explain why different products have been found experimentally for Mn, Mo, and Re complexes. For Re, the process leading to a C_C coupling product is clearly more favored than those forming an imidazol-2-yl product. In contrast, for Mn and Mo complexes, the lower stabilizing interaction between the central imidazole and ortho bipy C atoms, along with the higher lability of the ligands, make the formation of an NHC-type product kinetically more accessible, in good agreement with experimental findings., Financial support from the Ministerio de Ciencia e Innovación (MICINN, project number CTQ2009–12366) and Principado de Asturias (project number IB08–104) is gratefully acknowledged.

8 páginas, 3 figuras, 1 tabla, 4 esquemas., Compounds [Re(bipy)(CO)3(HIm)]OTf (1) and [Mo(η3-C3H4-R-2)(CO)2(HIm)(phen)]BAr′4 [R = Me (2a), H (2b); Ar′ = 3,5-bis(trifluoromethyl)phenyl; HIm = 1H-imidazole] were prepared from 1H-imidazole and either [Re(OTf)(bipy)(CO)3] or [MoCl(η3-C3H4-R-2)(CO)2(phen)]. Compounds 1, 2a, and 2b were deprotonated to afford the terminal κ-N-imidazolate complexes [Re(bipy)(CO)3(Im)] (3) and [Mo(η3-C3H4-R-2)(CO)2(Im)(phen)] [R = Me (4a), H (4b)], which were fully characterized, including an X-ray structural determination of 3. The topological analysis of the electron density (obtained from the X-ray diffraction study) and its Laplacian were used to characterize the differences in the electron density at the five-membered ring ligand between the imidazole and imidazolate complexes 1 and 3. The reaction of complexes 3, 4a, and 4b with the appropriate organometallic complexes afforded the bimetallic imidazolate-bridged compounds [{Re(bipy)(CO)3}2(μ-Im)]OTf (5), [{Mo(η3-C4H7)(CO)2(phen)}2(μ-Im)]OTf (6), and [{Mo(η3-C3H5)(CO)2(phen)}(μ-Im){Re(phen)(CO)3}]OTf (7). The reaction of [Mo(η3-C4H7)(CO)2(Im)(phen)] (4a) with SnClPh3 led to the formation of the trinuclear complex [{Mo(η3-C4H7)(CO)2(phen)(μ-Im)}2{SnPh3}]BAr′4 (8)., We thank the Ministerio de Educación y Ciencia (Ramón y Cajal contract to L.R. and Grant CTQ2006-07036/BQU) and the Principado de Asturias (FICYT, Grant IB08-104) for financial support.

Complexes [Re(CO)(3)(N-RIm)(3)]OTf (N-RIm=N-alkylimidazole, OTf=trifluoromethanesulfonate; 1a-d) have been straightforwardly synthesised from [Re(OTf)(CO)(5)] and the appropriate N-alkylimidazole. The reaction of compounds 1a-d with the strong base KN(SiMe(3))(2) led to deprotonation of a central C-H group of an imidazole ligand, thus affording very highly reactive derivatives. The latter can evolve through two different pathways, depending on the nature of the substituents of the imidazole ligands. Compound 1a contains three N-MeIm ligands, and its product 2a features a C-bound imidazol-2-yl ligand. When 2a is treated with HOTf or MeOTf, rhenium N-heterocyclic carbenes (NHCs) 3a or 4a are afforded as a result of the protonation or methylation, respectively, of the non-coordinated N atom. The reaction of 2a with [AuCl(PPh(3))] led to the heterobimetallic compound 5, in which the N-heterocyclic ligand is once again N-bound to the Re atom and C-coordinated to the gold fragment. For compounds 1b-d, with at least one N-arylimidazole ligand, deprotonation led to an unprecedented reactivity pattern: the carbanion generated by the deprotonation of the C2-H group of an imidazole ligand attacks a central C-H group of a neighbouring N-RIm ligand, thus affording the product of C-C coupling and ring-opening of the imidazole moiety that has been attacked (2c, d). The new complexes featured an amido-type N atom that can be protonated or methylated, thus obtaining compounds 3c, d or 4c, d, respectively. The latter reaction forces a change in the disposition of the olefinic unit generated by the ring-opening of the N-RIm ligand from a cisoid to a transoid geometry. Theoretical calculations help to rationalise the experimental observation of ring-opening (when at least one of the substituents of the imidazole ligands is an aryl group) or tautomerisation of the N-heterocyclic ligand to afford the imidazol-2-yl product.

This Microreview deals with the supramolecular chemistry of pyrazole metal complexes, in particular, complexes of pyrazoles with a nonsubstituted N–H group, which are able to engage in hydrogen bonding. The most pertinent general features of pyrazoles, in comparison with other heterocycles that are also popular ligands, and some aspects of the supramolecular chemistry of free pyrazoles are also included. In addition to the general supramolecular chemistry of pyrazole complexes, sections of this Microreview are devoted to liquid crystals, self-assembled species, and hosts for anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)