Organometallic Complexes of Uracil and Orotic Acid Derivatives: Coordination Mode, Structure, and Reactivity

Abstract

Carbonyltungsten derivatives of uracilates and orotates, where the metal center is bound to a nitrogen atom of the pyrimidine ring, are described. There organometallic complexes were synthesized by the reaction of either W(CO)5THF or W(CO)5MeOH with the tetraethylammonium salt of the deprotonated monoanion of dihydrouracil (1), 5‐methyluracil (2), 6‐methyluracil (3), methylorotic acid (4), and N,N‐dimethylorotic acid (5). The complexes were all characterized in solution by IR and 13C NMR spectroscopy, and in select instances in the solid‐state by X‐ray crystallography. The structures of complexes 1 and 3 consist of octahedrally coordinated anions of pentacarbonyltungsten uracilate, where the uracilate ligand is bound to the metal center by the N3 atom of the pyrimidine ring, and the tetraethylammonium cation for charge balance. In contrast, the anion of complex 2 reveals that the uracilate ligand is bound to the W(CO)5 fragment by the N1 atom of the pyrimidine ring. The ν(CO) vibrational modes and 13C NMR chemical shifts for the carbonyl ligands of complexes 1 and 3 indicate that the metal centers are more electron‐rich than those of complex 2. This conclusion is further substantiated by the rates of intermolecular CO exchange in these carbonylmetal anions with 13CO. The facile CO exchange observed in complexes 1 and 3 is faster than that seen in complex 2. The rapid CO dissociation process measured in these derivatives is attributed to the π‐donation of electron density from the pyrimidine ring to the tungsten center in the transition state as the M−CO bond is broken.

Effects of the ionization in the tautomerism of uracil: A reaction electronic flux perspective

“…Uracil molecule, as a part of the RNA helix, is one of the most studied compounds due to its relevance in pharmacy and biochemistry . Consequently, its acidity, basicity solvation by water molecules, its fragmentation in mass spectrometry, and its reactivity with respect to different reactants and metal ions have been investigated. Their tautomeric forms attracted the attention of many scientists along the years as they are suspected to be behind the genetic mutations .…”

Synthesis and Spectroscopic Characterization of Group 6 Pentacarbonyl(4-substituted pyridine)metal(0) Complexes

“…2-substituted pyridine derivatives such as 2-cyanopyridine, 2-methylpyridine or 2-phenylpyridine form also complexes of M(CO) 5 L type [9,10,11]. Similar complexes of uracil and thymine derivatives are also known [12]. All these studies show that a non-bulky substituent in position 2-does not hinder the coordination of pyridine to the central atom.…”

Synthesis, Spectroscopic Investigations, Thermal Analysis And DFT Calculations Of Some Pentacarbonyl(Mercaptopyrimidine)Metal(0) Complexes Of Group VI B Elements

“…Metal carbonyl complexes where one or more carbonyl ligand bonded to a single metal center show intense FTIR-bands between 2200 and 1800 cm -1 due to the polarization of CO on binding metal atom [11], [12]. The coordination chemistry of heterocyclic ligands is a field of growing interest in coordination chemistry since they have multiple sites, allowing the use of various coordination modes [13]- [16]. Pentacarbonyl(pyridine)metal(0) complexes (M: Cr, Mo, W) have been known for a long time [13].…”