η3-Allyl rhodium complexes with azolate ligands. Crystal structures of the trinuclear 1,2,4-triazolate (tz) complexes [Rh3(µ-tz)3(η3-C3H5)6] and [Rh3(µ3-tz)(µ-Cl)Cl(η3-C3H5)2(CO)4]·0.5C2H4Cl2

Abstract

The η³-allyl rhodium compound [Rh(acac)(η³-C₃H₅)₂](acac = acetylacetonate) reacts with azole ligands to give the new azolate complexes [Rh₃(µ-az)₃(η³-C₃H₅)₆][az = tetrazolate (ttz)(1), 1,2,4-triazolate (tz)(2), benzotriazolate (btz)(3), or imidazolate (im)(4)]. A single-crystal X-ray diffraction study on complex (2) has established that its structure consists of discrete trinuclear complexes in which each rhodium atom is bridged by the 1,2,4-triazolate ligands through the non-adjacent nitrogen atoms to form a multiatomic ring. Complexes (2) and (1) react with [Rh₂(µ-Cl)₂(CO)₄] to give the mixed-valence trinuclear complexes [Rh₃(µ₃-az)(µ-Cl)Cl(η³-C₃H₅)₂(CO)₄][az = tz (10) or ttz (11)]. The crystal structure of complex (10) has confirmed the existence of trinuclear molecules in which a chlorine atom and a triazolate bridge Rh(CO)₂ and Rh(η³-C₃H₅)₂ moieties; in addition the remaining nitrogen atom of the triazolate ligand completes the square-planar co-ordination of a RhCl(CO)₂ unit. In the crystal, there is an intermolecular Rh–Rh distance of 3.393(1)Å. Complex (2) reacts with [Rh₂(µ-Cl)₂(η³-C₃H₅)₄] to give the trinuclear complex [Rh₃(µ₃-tz)(µ-Cl)Cl(η³-C₃H₅)₆]. Heterobridged binuclear pyrazolate (pz) complexes of formula [Rh₂(µ-pz)(µ-X)(η³-C₃H₅)₄](X = Cl, OH, or N₃) have also been prepared.