Copper Complexes with New Pyridylpyrazole Based Ligands

Abstract

We report the synthesis, characterization, and crystal structures of new ligands of the pyridinylpyrazole type, i.e., 3,5-bis(4-butoxyphenyl)-1-(pyridin-2-yl)-1H-pyrazole (L 1 ) and 3,5-bis(4-phenoxyphenyl)-1-(pyridin-2-yl)-1H-pyrazole (L 2 ) (Scheme 1), and the study of their coordination behavior towards Cu I and Cu II . The versatility of this type of ligand, which can give access to different coordination spheres about the metal center, depending on the nature of the copper starting material used in the preparation of the complexes (Scheme 2), is illustrated. Thus, pseudo-tetrahedral Cu I as well as six-coordinated tetragonal and distorted tetragonal pyramidal Cu II derivatives were obtained for [Cu(L) 2 ]PF 6 , [Cu(Cl) 2 (L) 2 ] (L L 1 , L 2 ), and [Cu(Cl)(L 1 ) 2 ]PF 6 , respectively. We also present a crystallographic support of a distorted octahedral cis-bis(tetrafluoroboratokF)copper(II) compound found for [Cu(BF 4 ) 2 (L 1 ) 2 ] (3).Introduction. ± Chelating ligands based on the pyrazole ring have been developed extensively in the last years [1] [2]. Most of the actual work deals with pyrazole rings bearing one or two bulky N-heterocycle substituents at the 3 and/or 5 position, as this type of ligand often produces multimetallic compounds [1 ± 6]. By constrast, related 1-substituted pyrazoles with heterocyclic substituents, which can act as bidentate ligands, have received less attention [7 ± 9]. They are, however, versatile ligands whose coordinative abilities could be influenced by the nature of additional substituents at the 3 and/or 5 position of the pyrazole ring.In this context, it is interesting to note that a (pyridinylpyrazole)-type ligand such as 5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carboxamide (L c ) formed Cu II compounds of formula [CuX 2 (L c ) 2 ¥ H 2 O] (X Cl, Br, NO 3 , ClO 4 ) with a distorted octahedral geometry [10]. To achieve that, one of the two L c ligands acted in a N,N'-bidentate and the other in a N,N',O-tridentate fashion with the amide O-atom participating in the latter case and the sixth apical coordination site being occupied by a H 2 O molecule or a X counterion [10]. However, a related [Cu(La) 2 ] 2 complex with the 3-(2,5-dimethoxyphenyl)-1-(pyridin-2-yl)-1H-pyrazole (L a ) ligand showed a tetrahedrically distorted planar geometry in which, in addition to the CuN 4 core, CuÀO interactions with the MeO groups of each ligand were observed [11].From these results, it appears that O-containing substituents at the 3 and 5 positions of the pyrazole ring of the pyridinylpyrazole ligands can play an important role in the stereochemistry of the copper derivatives.Following these precedents, we are now interested in using O-containing 3,5-disubstituted pyridinylpyrazole ligands in metal complexes to produce different geometries that might allow access to certain types of supramolecular arrangements.

Reactivity of bis(long chain substituted β-diketonato)palladium(II) [Pd(OOR2)2] towards HBF4: formation of luminescent [BF2(OOR2)] derivatives. X-ray structure of [1,3-di(4-n-butoxyphenyl)propane-1,3-dionato]difluoroboron(III)

“…In a previous work, we have described the liquid crystal behaviour of the 3,5-bis(4-n-alkyloxyphenyl)-1-(pyridin-2-yl)-1H-pyrazol ligands (pypz R2 ; R = C 6 H 4 OC n H 2n+1 , n = 12, 14,16,18) In order to understand the role of the palladium in these reactions, we have also explored the reactivity of the free b-diketones or the sodium b-diketonates towards HBF 4 or NaBF 4 [10] (Scheme 2). All of these essays gave rise to the corresponding adducts [BF 2 (OO R2 )] (1-3), which were clearly identified by their yellow luminescence in the solid state, and characterized by spectroscopic and analytical techniques [7].…”

Crystal structure of 2-[3,5-bis(4-octyloxyphenyl)pyrazol-1-yl]pyridine, C36H47N3O2

“…The larger dihedral angle corresponds to the substituent at the 5-position, which is attributed to steric effect with the pyridine ring. As characteristic feature, die N-donor atoms (N1 and N3) present an onA'-disposition (as reflected by the N2-N1-C6-N3 torsion angle of-118.2(4)°), possibly due to repulsion between their respective lone pairs as it has already been observed in related derivatives [5,7]. Also, in agreement with this fact, the dihedral angle between the pyrazole and pyridine rings is 57.2(2)°.…”

“…We describe herein the crystal structure of one of these ligands, 2-[3,5-bis(4-octyloxyphenyl)pyrazol-l-yl]pyridine. As in other pyrazoles [2,[4][5][6], the bond distances of the pyrazole, pyridine and benzene-substituent groups evidence a delocalized π system, which is extended to the four rings. However, the dihedral angles between the pyrazole ring and their benzene-substituents rings (23.1(1)° and 32.4(1)°) indicate the absence of planarity.…”

“…Also, in agreement with this fact, the dihedral angle between the pyrazole and pyridine rings is 57.2(2)°. However, upon complexation this ligand-type adopts a ^-conformation necessary for a chelation [5]. The lateral alkyl chains located in the substituents at the 3-and 5-position of die pyrazole show the characteristic single C-C distances, both chains being responsible for an elongated molecular shape.…”

Electrochemical and liquid crystal properties of ferrocene-based β-diketonato copper(II) and zinc(II) complexes

“…bdiketones incorporating transition metals have been extensively studied due to their easier preparation, as well as known chemistries and/or rich structural varieties. Numerous b-diketonate compounds with calamitic as well as non-calamitic structures, generated by a combination of the metal incorporated and the numbers of flexible chains, have been prepared and their mesomorphic properties investigated in detail [23][24][25][26][27][28][29][30]. However, ferrocene-containing b-diketones, widely used in conjugate chemistry [31] and medicinal chemistry, [32] etc., are rarely applied in the studies of metallomesogenic systems.…”