Rhenium and manganese carbonyl compounds incorporating tridentate chelating pyrazolyl gallate ligands

Abstract

The coordinating properties of a variety of unsymmetrical uninegative tridentate chelating "pyrazolylgallate" ligands have been studied using the tricarbonyl moieties "M(CO)3", where M = Mn or Re, as acceptor species. A series of monomeric, pseudo octahedral complexes has been characterized and a fac mode of coordination established for the tridentate gallate ligands from 1H nmr, ir measurements, and X-ray structure determinations. Nitrosylation of a selection of the rhenium tricarbonyl compounds has yielded a number of cationic rhenium mononitrosyl dicarbonyl species. The reactivity of these cations towards reducing agents has been investigated.

Synthesis and characterization of transition metal complexes containing novel, unsymmetric tridentate organogallate ligands

“…The position ofthe COMe signal (7.587, CDCl,), compares nicely with those reported for similar rhodium acetyl compounds (30,31,35) and the square pyramidal arrangement proposed for the present complex has been established by X-ray crystallography for the closely related [Me2Gapz(OCH2CH2- The mass spectrum of the [Me2GapzO(C9H6N)]Rh(COMe)I complex displayed signals corresponding to the parent, P+, P -M e + , P -M e -I + , P -2 M e -I + , a n d P -M e -CO+ ions, but no P -CO+ signals were observed. Signals arising from the latter ion are usually characteristic of transition metal carbonyl compounds containing terminally bound CO groups.…”

“…The pyrazolyl proton resonances appeared as two sets again providing additional supporting evidence for the presence of both isomers in solution. The ir and 'H nrnr results discussed here, together with results for related compounds (4,14), strongly support the presence of both fac and rner isomers in solution for the L,M(C0)3 complexes.…”

“…However, in all octahedral transition metal carbonyl compounds studied thus far, coordination of the unsymmetric tridentate organogallate ligand has been found to be exclusively facial (4,14). The present manganese and rhenium tricarbonyl compounds incorporating the ligand [Me2Ga(N2C3H3).…”

Syntheses and reactivity of square-planar Rh(I) complexes, LRh(CO) (L = unsymmetric tridentate chelating pyrazolylgallate ligand). X-ray crystal structures of [Me2Gapz(OCH2CH2NH2)]Rh(CO) and [Me2Gapz(OCH2CH2NMe2)]Rh(COMe)I (pz = pyrazolyl, N2C3H3)

“…Numerous carbonyl compounds incorporating tridentate pyrazolylgallate ligands of the type 1 have been reported for Cr, Mo, W, Mn, and Re (4,(14)(15)(16)(17)(18). In each of these complexes the pyrazolylgallate anions were found to coordinate exclusively in a fac mode, even though the chelating ligands are capable of meridional coordination.…”

“…Dihalogens (Fisher Scientific) were used as supplied. Sodium salts of the unsymmetrical tridentate pyrazolylgallate ligands were prepared as standard THF solutions as described earlier (4).…”