4-Chloro-3,5-dimethyl-1H-pyrazole (cas: 15953-73-8) belongs to pyrazole derivatives. Pyrazole is a weak base, with pKb 11.5 (pKa of the conjugated acid 2.49 at 25 °C).Pyrazole used as a ligand to prepare organometallic compounds. Protonation of pyrazole in strong acid leads to pyrazolium cations, which undergo electrophilic substitution preferentially at C3 rather than C4. The pyrazole anion is not reactive toward nucleophiles but is mostly reactive to electrophiles.Computed Properties of C5H7ClN2
Transition metal organometallic complexes containing 3-substituted poly(pyrazolyl)borate ligands. Part 1. Formation of η2-aroyl, η1-halocarbyne or sterically crowded aryldiazenide ligands in the reactions of ring-substituted tricarbonyl[hydrotris(pyrazolyl)borato]molybdate and -tungstate anions with arenediazonium cations and related oxidants was written by Lalor, Fergus J.;Desmond, Timothy J.;Cotter, Gerard M.;Shanahan, Claire A.;Ferguson, George;Parvez, Masood;Ruhl, Barbara. And the article was included in Journal of the Chemical Society, Dalton Transactions: Inorganic Chemistry in 1995.Computed Properties of C5H7ClN2 This article mentions the following:
Although the hydrotris(pyrazolyl)borato complex [Mo{HB(pz)3}(CO)3]– reacted with 3- or 4-substituted arenediazonium cations [R’N2]+ yielding carbonyl-substitution (i.e. aryldiazenido) products [Mo{HB(pz)3}(CO)2(N2R’)], reaction of the Me-substituted analog [ML*(CO)3]– [L* = tris(3,5-dimethylpyrazolyl)hydroborate; M = Mo or W] led, via oxidative formation of aryl radicals and [ML*(CO)3]•, to η2-aroyl complexes [ML*(CO)2(η2-COR’)] [R’ = C6H4X-4 (X = NO2, CN, COMe, CF3, H, Me, OMe or NMe2) or C6H4X-3 (X = NO2 or OMe)] in MeCN or to the halocarbyne complexes [ML*(CO)2(CX)] (X = Cl, Br or I) in the presence of the haloalkanes CH2Cl2 or CHX3 (X = Br or I). [MoL*(CO)3]– reacted similarly with diphenyliodonium or triphenylsulfonium cations, but in the latter case anion-cation redox is very slow in the dark but rapid upon irradiation with sunlight. Comparison of these results with those obtained for [ML*(CO)3]– analogs with different substituents in the pyrazolyl rings demonstrates that oxidation of the former by arenediazonium cations occurs in response to the steric rather than the electronic effect of the 3-Me substituents. However, further steric crowding in either the hydrotris(pyrazolyl)borate ligand or the diazonium cation promotes a reversion to the carbonyl-substitution pathway. A mechanism to account for these observations is proposed. Attempts to extend the chlorocarbyne synthesis to systems other than [ML*(CO)3]– met with only limited success. Spectroscopic data for the new complexes are reported and discussed. Two aryldiazenido complexes, [MoL*(CO)2(N2R’)] (R’ = 2,6-Me2C6H3 or 2,3-dimethyl-5-oxo-1-phenyl-3-pyrazolin-4-yl) were characterized by single-crystal x-ray diffraction studies and were found to differ in the manner in which the aryldiazenide ligand accommodates to steric crowding in the Mo coordination sphere. In the experiment, the researchers used many compounds, for example, 4-Chloro-3,5-dimethyl-1H-pyrazole (cas: 15953-73-8Computed Properties of C5H7ClN2).
4-Chloro-3,5-dimethyl-1H-pyrazole (cas: 15953-73-8) belongs to pyrazole derivatives. Pyrazole is a weak base, with pKb 11.5 (pKa of the conjugated acid 2.49 at 25 °C).Pyrazole used as a ligand to prepare organometallic compounds. Protonation of pyrazole in strong acid leads to pyrazolium cations, which undergo electrophilic substitution preferentially at C3 rather than C4. The pyrazole anion is not reactive toward nucleophiles but is mostly reactive to electrophiles.Computed Properties of C5H7ClN2
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics