Syntheses and characterisation of rhenium-(III) and -(V) complexes containing aminophosphine ligands. Crystal structures of [ReVOCl2(OMe)L] and [ReIIICl3L(PPh3)], L = o-(diphenylphosphino)-N ,N′-dimethylaniline

Abstract

Substitution reactions of labile rhenium(V) precursors with o-(diphenylphosphino)-N,N′ -dimethylaniline, L, gave a series of monooxorhenium(V) complexes of general formula [ReOX 2 Y(L)] (X = Y = Cl 1; X = Cl, Y = OMe 2) and [ReOX 2 (OEt)L] (X = Cl 3, Br 4 or I 5). These complexes, which contain only one aminophosphine chelate, have a distorted-octahedral geometry, as evidenced by a crystal structure determination of 2. Reactions conducted in basic media, or treatment of 2 in the presence of the weakly co-ordinating trifluoromethanesulfonic acid, gave the bis(chelate) cationic complexes [ReO 2 L 2 ] + 6 and [ReCl 2 L 2 ] + 7, respectively. Similar ligand-exchange reactions between the lower-oxidation-state precursor [Re III Cl 3 (MeCN)(PPh 3 ) 2 ] and L or L′ [o-(diphenylphosphino)aniline] still produced mono-substituted aminophosphine complexes, i.e. [Re III Cl 3 L(PPh 3 )] 8 or [Re III Cl 3 L′(PPh 3 )] 9 in which there is a meridional arrangement of chloride ligands along with a cis-phosphorus co-ordination. The crystal structure of 8 was determined. On the contrary, treatment of [Re III X 3 (MeCN)(PPh 3 ) 2 ] (X = Cl or Br) with L′ in the presence of co-ordinating hydrohalogenic acid gave bis-substituted cationic complexes [ReX 2 L′ 2 ] + (X = Cl 10 or Br 11). In spite of the paramagnetism of the low-spin d 4 ion, all of the rhenium(III) complexes can be conveniently characterised in solution by proton NMR spectroscopy.