Ruthenium(II) Complexes Bearing Carboxylato and 2‐Oxocarboxylato Ligands

Abstract

The syntheses of ruthenium(II) acetato and benzoato complexes [Ru(bdmpza)(O2CCH3)(PPh3)] (6) and [Ru(bdmpza)(O2CPh)(PPh3)] (7) [bdmpza = bis(3,5‐dimethylpyrazol‐1‐yl)acetate] are reported. The complexes 6 and 7 are synthesized in high yield from [Ru(bdmpza)Cl(PPh3)2] (1) and thallium acetate (2) or thallium benzoate (3). In a similar substitution reaction a benzoylformate complex [Ru(bdmpza){O2CC(O)Ph}(PPh3)] (8) is obtained from 1 and thallium benzoylformate (4). Reaction of 6 or 7 with benzoylformic acid also yields 8. In analogous reactions several 2‐oxocarboxylato ruthenium(II) complexes [Ru(bdmpza){O2CC(O)R}(PPh3)] (9: R = CH2CH2CO2H, 10: R = Me, 11: R = Et) can be obtained. The low‐spin ruthenium(II) complexes 8 to 11 exhibit a purple or brownish‐red colour caused by MLCT transitions and thus a HOMO−LUMO gap which is almost identical to that of high‐spin 2‐oxoglutarate dependent iron oxygenases. 6 crystallises as a water adduct, 6·H2O and 8 forms an acetonitrile adduct 12. Crystal structures of the water adduct 6·H2O and 8 were obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Novel N,N,O Scorpionate Ligands and Transition Metal Complexes Thereof Suitable for Polymerisation

“…1 H, 13 C and 2D NMR spectra: Bruker DPX300, δ values relative to TMS or the deuterated solvent. EPR spectroscopy: JEOL JES-FA 200, internal 55 Mn standard.…”

“…[5] Similar to our recent report on [Re(bdmpzap)(CO) 3 ], [15] this chirality is not only observed in the X-ray structure analyses of 4, but also in case of complex 5 in solution. This is indicated by an AB system in the 1 H NMR spectra of 5 for the -CH 2 O-group at δ = 5.31 and 5.79 ppm, causing coupling between the diastereotopic protons and a set of two signals for each pyrazole carbon atom in the 13 C NMR spectrum. Broad signals in the 1 H NMR spectra do not allow to resolve the 3 J(H,H) coupling constants of the AB system.…”

“…[5,6,9,10] The N,N,O binding motif is of particular interest not only as tripodal ligand in organometallic and coordination chemistry but as mimic of the active site of enzymes with a 2-His-1-carboxylate motif as well. [6,[11][12][13] Transition metal complexes of Hbdmpza with zinc and iron have proven to be good structural mimics for such metalloenzymes. [6,12] Due to their binding behaviour was evidenced by IR spectra of the polymer supported transition metal complexes and the uptake of manganese was proven by AAS measurements.…”

Bis(3,5‐dimethyl‐4‐vinylpyrazol‐1‐yl)acetic Acid: A New Heteroscorpionate Building Block for Copolymers that Mimic the 2‐His‐1‐carboxylate Facial Triad

“…[1][2][3][4][5] Especially, the 2-His-1-carboxylate facial triad of 2-oxoglutarate (2-OG) dependent iron oxygenases (Figure 1) is well resembled by these ligands in which the pyrazole donors mimic the two histidines and the carboxylate emulates the aspartate. Unfortunately, due to their high binding affinity, sterically less-demanding bis(pyrazol-1-yl)-acetic acids such as bis(3,5-dimethylpyrazol-1-yl)acetic acids (Hbdmpza) form rather unreactive bisligand complexes which do not allow any further reactions with additional ligands or potential substrates.…”

N,N,O Ligands Based on Triazoles and Transition Metal Complexes Thereof

“…[2,3] Examples for transition metal complexes with manganese and ruthenium are [Mn(bdmpza)(CO) 3 ] and [Ru(bdmpza)(PPh 3 ) 3 ] {bdmpza: bis(3,5-dimethyl-1H-pyrazol-1-yl)acetate}. [4][5][6] Furthermore, model complexes with biorelevant transition metals such as iron(II) and zinc(II) support the concept of bis(1H-pyrazol-1-yl)acetic acids to be good structural mimics for the active site of metalloenzymes with an 2-His-1-carboxylate motif.…”