Preparation of rhenium hydride complexes with pyrazole and pyrazolato ligands

Abstract

Hydride-pyrazolato ReH( Rpz)(H Rpz)(NO)(PPh 3) 2 complexes ( R = H ( 1), 5-Me ( 2)) were prepared by allowing the ReH 2(NO)(PPh 3) 3 derivative to react with pyrazole (H Rpz) 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)(PPh 3) 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)(PPh 3) 2] + cation. Acetylide-pyrazolato Re(C CAr)( Rpz)(H Rpz)(NO)(PPh 3) 2 ( 3, 4) complexes (Ar = Ph, p-tolyl; R = H, 5-Me) were also prepared by reacting hydride ReH( Rpz)(H Rpz)(NO)(PPh 3) 2 species with terminal alkynes HC CAr in refluxing 1,2-dichloroethane.