Rebuttal to the article Pathological crystal structures

Abstract

A section in the Acta Crystallographica Section C article by Raymond & Girolami [Acta Cryst. (2023), C79, 445–455] stated that the product of the reaction of [(Cp*Rh)2(μ-OH)3]+ (Cp* is 1,2,3,4,5-pentamethylcyclopentadiene) with 1-methylthymine (1-MT) at pH 10 and 60 °C, to synthesize the anionic component [RhI(η1-N 3-1-MT)2]−, was not an RhI complex, but rather an AgI complex, due to the use of silver triflate (AgOTf) to remove Cl− from [Cp*RhCl2]2 to synthesize [Cp*Rh(H2O)3](OTf)2, a water-soluble crystalline complex. We will clearly show that this premise, as stated, is invalid, while the authors have simply avoided several important facts, including that Cp*OH, a reductive elimination product, at pH 10 and 60 °C, was unequivocally identified, thus leading to the RhI anionic component [RhI(η1-N 3-1-MT)2]−. More importantly, AgOH, from the reaction of NaOH at pH 10 with any potentially remaining AgOTf, after the AgCl was filtered off, would be insoluble in water. Furthermore, a control experiment with the inorganic complex Rh(OH)3, reacting with 1-methylthymine at pH 10, provided no product, and this bodes well for a similar fate with AgOTf and 1-methylthymine, i.e. at pH 10, AgOTf would again be converted to the water-insoluble AgOH; therefore, no reaction would occur! Finally, a 1H NMR spectroscopy experiment was carried out with synthesized and crystallized [Cp*Rh(H2O)3](OTf)2 in D2O at various pD values; at pD 8.65 no reaction took place, while at pD 13.6, and at 60 °C for 2 h, a reductive elimination reaction caused the precipitation of Cp*OH. The subsequent 1H NMR spectrum clearly demonstrated, in the absence of any AgI complexes, that the solution structure and the X-ray crystals in D2O were similar. A postulated mechanism for this novel anionic component structure, as published previously [Smith et al. (2014). Organometallics, 33, 2389–2404], will be presented, along with the experimental data, to insure the credibility of our results. We will also answer the comments in the response of Drs Raymond and Girolami to this rebuttal.