The crystal structure of fa c-tricarbonyl(bis(3,5-dimethyl-4 H -pyrazole)- κ 1 N )-((nitrato)- κ 1 O )- rhenium(I) — 3,5-dimethyl-4 H -pyrazole(1/1), C 18 H 23 N 7 O 6 Re

C 18 H 23 N 7 O 6 Re, triclinic, P 1 (no. 2), a = 10.527(2) Å, b = 10.849(2) Å, c = 11.215(2) Å, α = 72.798(2) ° , β = 69.767(2) ° , γ = 87.496(10) ° , V = 1145.52(4) Å 3 , Z = 2, R gt ( F ) = 0.0273, w R ref ( F 2 ) = 0.0727, T = 150(2) K.


Source of material
The title compound was crystallized from the intermediate fac-[Re I (CO) 3 (OCH 3 ) 3 ]NO 3 in the presence of excess pyrazole ligand during the reaction indicated in the literature. 5The title compound was crystallized from the methanol filtrate in high purity.IR (ATR, cm −1 ): ν (CO) 2020, 1892, 1879.

Experimental details
All hydrogen atoms were positioned geometrically using a riding model, with fixed C-H aromatic = 0.97 Å.The H atoms isotropic displacement parameters were fixed; U iso (H) = 1.2U eq (C) for aromatic, allowing them to ride on the parent atom.The graphics were obtained using the mercury program with 50 % probability ellipsoids.All the H-atoms on the title structure were omitted for clarity.

Comment
The radionuclide 99m Tc is the most significant radioisotope in radiopharmaceutics mainly for imaging purposes. 5his isotope has first to be stabilized by chelator ligands with substituents containing dominant physico-chemical properties.However, ligands providing enough stability to this radionuclide core under physiological conditions are limited. 6This simply signifies that, tuning the resulting complex properties by introducing various ligands is not favourable. 6Therefore, our interest in rhenium chemistry is the ability of this metal ion to form stable octahedral complexes with various suitable chelator ligands. 7,8urthermore, this metal ion has two radioisotopes, 186 Re and 188 Re which exhibit favourable nuclear properties (beta emitters with emission energies of 1.01 and 2.12 MeV, respectively) since it is the analogue of technetium-99m.[10][11][12][13] The ligand employed in this study is a neutral heterocyclic Schiff base pyrazole that can accommodate chelation with a metal ion.The ability of these type of pyrazole ligands to coordinate with one or both nitrogen atoms to form monometallic and bimetallic complexes respectively is what make these chelator ligands special.
The title complex presented herein consists of three facial carbonyl ligands, a nitrato and one pyrazole ligand coordinated in the equatorial plane, and another pyrazole occupying the axial position, together with a pyrazole guest molecule in the outer coordination sphere.The crystal structure exhibits an octahedral distortion for rheniumtricarbonyl-based complexes as indicated by the N1-Re1-N3 bond angle of 86.45 (12)°and O4-Re1-N1 bond angle of 78.15 (11)°.The rhenium bond distances for rhenium-carbonyl (Re-C) interactions are typical and within an average of 1.913(4) Å. 8,12,13 The bond distance between the rhenium (Re1) and the oxygen (O4) of the nitrato moiety is 2.170(3) Å which is in accordance with literature related structures. 14,15This title compound is further stabilized by N-H … O, N-H … N, C-H … O, and C-H … N intra-and inter-molecular hydrogen contacts.[16][17] Author contribution: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: National Research Foundation of South Africa (Grant No. 129468 and TTK2204193773), Tshwane University of Technology, University of the Western Cape and the University of Pretoria.Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

Table  :
Data collection and handling.

Table  :
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å  ).