A quantum chemical study on the mechanism of S-coordinated tetrazole-thiolato formation by the reaction of organic isothiocyanates with metal azido complexes of Pt(II), Pd(II), and Sn

Chiral N-Fmoc-β-Amino Alkyl Isonitriles Derived from Amino Acids: First Synthesis and Application in 1-Substituted Tetrazole Synthesis

“…As an example to demonstrate the reactions of the isocyano group in case of the newly prepared isonitriles, we proceeded with synthesis of the 1-substitued tetrazoles from compound 3 . Amino acid derived tetrazoles are being used as carboxylic acid isosteres, catalysts in asymmetric organic synthesis, pharmaceutical compounds, and stabilizers of metallopeptides . 5-Substituted tetrazoles have been synthesized from 2 + 3 dipolar cycloaddition of azide with nitriles obtained from N -urethane-protected amino acids, but the isomeric 1-substituted tetrazole analogues of N -protected amino acids are yet to be described.…”

Azide Chemistry – An Inorganic Perspective, Part II[‡][3+2]‐Cycloaddition Reactions of Metal Azides and Related Systems

“…As main driving force for the overall process the high affinity between sulfur and metals was identified which considerably lowers the barrier to step 1. In case of the cycloaddition between isothiocyanates and hydrazoic acid, this barrier is not lowered by an affinity between S and H, so here a single‐step mechanism to the N‐protonated thiotetrazole is favoured over the above two‐step process, both kinetically and thermodynamically 56. This reaction path is very similar to the concerted [3+2]‐cycloaddition of an organic azide and an organic nitrile,24,25 yet excluded for azidometal complexes in its turn. …”

“…As for the coordination modes VI vs. VII (Scheme ), a more recent quantum chemical study on the reactions of azido complexes of Pd II , Pt II and Sn IV (as well as of HN 3 ) with isothiocyanates implies that the formation of the N 4 ‐bound tetrazoline‐5‐thion‐1‐ate VI (N 4 H tautomer) is favoured over the production of the S‐bonded tetrazole‐5‐thiolate VII (S H tautomer), both kinetically and thermodynamically 56. This is in accord with the experimental results in the case of hydrazoic acid – free 1‐substituted mercaptotetrazoles have been proved to exist only as the thione tautomer [388] – and also with previously (erroneously(!))…”

“…The above‐mentioned discrepancy between the calculations of the relative stabilities of the two possible linkage isomers VI and VII (Scheme ) which clearly favour N 4 coordination,56 and the recent accumulated experimental evidence of ‘S‐coordination without exception', [52, 53, 55, 60, 61, 64, 65, 390–392, 396–398] has been resolved by a detailed study of the reaction mechanisms 56. According to that, a two‐step process occurs in which the isothiocyanate S‐atom first approaches the metal with simultaneous attack by the azide N α ‐ on the isothiocyanate C‐atom to give an intermediate S‐bonded imidoyl azide, XVI , strongly reminiscent of the imidoyl azide intermediate previously found in the theoretical study on the mechanism of azidometal to nitrile [3+2]‐cycloadditions (cf.…”

Facile formation of tetrazole–thiolato Pd(ii) and Pt(ii) complexes through deprotonation or oxidative addition using organic tetrazole–thiones

“…The formation of transition-metal tetrazole–thiolato compounds from organic tetrazole–thiones has received continuous research attention owing to the structural or coordinative behavior of transition metals, which includes N -, S -, and N , S -coordination to the tetrazole–thiolato moiety (as shown in I–IV in Chart 1), 1,2 their abilities to inhibit metal corrosion, 3–5 and antibacterial (or anticancer) activities, 6–8 and theoretical studies. 6,9…”