Areneruthenium(II) Complexes Containing Bispyrazolylmethane Ligands: Effect of the Ligand Substituents on the Formation of an Isomer and on the Fluxional Behaviour

Abstract

Ruthenium derivatives of the type [RuCl(arene)(NN)][BPh4] (arene = benzene, 1; p‐cymene, 2) with NN = 2‐methoxyphenyl‐bis(3,5‐dimethylpyrazol‐1‐yl)methane (bpz*mArOCH3) have been synthesized and characterized. Two isomers were formed for both complexes and in each case the aryl ring was bonded to the methynic carbon with an axial disposition in the metallacycle. In the complexes either the chloro ligand (isomer A) or the arene (isomer B′) is oriented towards the pyrazolyl rings. Isomer B′ is reported here for the first time for these types of derivatives. The structure of 1 was determined by X‐ray diffraction and corresponds to isomer A. The fluxional behaviour of the new derivatives, along with that of other compounds previously synthesized by us that contain similar ligands, has been studied to evaluate the influence of the substitution in the pyrazolyl groups and in the aryl substituent of the central methynic carbon. Restricted rotation of the rings was found in complexes 1 and 2 and atropisomers were detected at low temperature. Complexes 1 and 2 were active precursors for the catalytic transfer hydrogenation of benzophenone with 2‐propanol as the hydrogen source in the presence of base and also under base‐free conditions. The results were compared with those obtained for other related derivatives. It was concluded that the simultaneous presence of the methyl and methoxy groups on the pyrazolyl and aryl rings, respectively, gives rise to worse results for the reactions with a base but an improvement was found for the reactions carried out in the absence of base.

Synthesis, characterisation and antibacterial activity of [(p-cym)RuX(L)]+/2+ (X = Cl, H2O; L = bpmo, bpms) complexes

“…The synthesis and 1 H NMR characterisation of BF 4 − salt of 1 + is reported elsewhere; however, the structural, spectral and electrochemical properties as well as its anticancer or antimicrobial activities have not yet been studied. 15 The chlorido complexes [1](ClO 4 ) and [2](PF 6 ) and their aqua derivatives [3] The electronic spectra of the complexes are recorded in CH 3 CN (Fig. S1 †).…”

Synthesis and In Vitro (Anticancer) Evaluation of η6-Arene Ruthenium Complexes Bearing Stannyl Ligands

“…The ongoing search for new metallodrugs has led to the discovery of several ruthenium-based drugs: NAMI-A and KP1019, both of which have completed phase I clinical trials, as well as RAPTA-C (Chart 1) [16][17][18][19][20][21][22][23]. In addition, ruthenium(II)-arene complexes are also considered promising drug candidates, owing to their demonstrated low toxicity and high antitumor activity [18][19][20][21][22][23][24][25][26][27][28][29][30]. The bioavailability of these compounds is controlled by the arene moieties facilitating the outreach in the intracellular region given their hydrophobic nature [29].…”

Cationic arene ruthenium(II) complexes bearing N, S chelating thiocarboxamides: Synthesis, structure, characterization and catalytic oxidation of alcohols

“…In particular, arene ruthenium complexes have emerged as versatile intermediates in organic synthesis as a consequence of the ease with which the arene ligand can be functionalized [6e8]. In recent years, half-sandwich arene ruthenium complexes have been proved to be extremely useful catalysts in organic synthesis such as DielseAlder reaction [9], olefin metathesis [10], CeC coupling reaction [11], transfer hydrogenation of ketones [12], oxidation [13] etc. Further, arene ruthenium(II) complexes have generated great interest in potential anticancer agents [14e18].…”