Preparation of rhenium hydride complexes with pyrazole and pyrazolato ligands

Hydride-pyrazolato ReH(Rpz)(HRpz)(NO)(PPh3)2 complexes (R = H (1), 5-Me (2)) were prepared by allowing the ReH2(NO)(PPh3)3 derivative to react with pyrazole (HRpz) in refluxing toluene. The complexes were characterised spectroscopically (IR and NMR data) and by the X-ray crystal structure determination of the ReH(5-Mepz)(H-5-Mepz)(NO)(PPh3)2 derivative. An intramolecular hydrogen bond N–H⋯N between the pyrazolato and the pyrazole ligands was established both in the solid state and in solution. Protonation reaction with Brønsted acid of compound 1 was studied and led to the unstable bis(pyrazole) [ReH(Hpz)2(NO)(PPh3)2]+ cation. Acetylide-pyrazolato Re(Ctriple bond; length of mdashCAr)(Rpz)(HRpz)(NO)(PPh3)2 (3, 4) complexes (Ar = Ph, p-tolyl; R = H, 5-Me) were also prepared by reacting hydride ReH(Rpz)(HRpz)(NO)(PPh3)2 species with terminal alkynes HCtriple bond; length of mdashCAr in refluxing 1,2-dichloroethane.