The Formation of Hemiacetal Complexes of Rhenium(V) by Degradation of a Schiff Base

Mono‐ and dinuclear oxidorhenium(V) complexes with hemiacetal ligands were isolated from a reaction of (NBu 4 )[ReOCl 4 ] with a potentially tetradentate Schiff base prepared from (1 R ,2 R )‐cyclohexane‐1, 2‐diamine and (2‐formylphenyl)diphenylphosphine in methanol. The hemiacetal is formed by solvolysis of first one imine functionality of the Schiff base, whereas the second remains intact. The resulting amine/iminophosphine coordinates as a tridentate N , N, P ligand in a dinuclear compound. Ongoing degradation of the Schiff base gives more hemiacetal (HL 1a ) and the final product, the monomeric complex [ReOCl(L 1a ) 2 ] is formed. Cleavage of the organic framework is not observed during the reaction of (NBu 4 )[ReOCl 4 ] with a related Schiff base derived from ethylene‐1, 2‐diamine and (2‐formylphenyl)diphenylphosphine. The Schiff base reacts as a bis‐bidentate N, P ligand and a dinuclear oxorhenium(V) compound with a central ethylene bridge is formed.