Variable deprotonation of an aromatic amino ligand by molybdenum(VI). Crystal and molecular structure of mer-Bis[2,2'-{1,2-phenylenebis(iminomethylene)}-bis(phenol)ato(3–)]molybdenum(VI)

Abstract

The ligand 2,2'-[1,2-phenylenebis(iminomethylene)]bisphenol, H₄L, features two phenolic and two aromatic secondary amino functions. Reaction of H₄L with [MoO₂(acac)₂] in MeOH leads to cis-[MoO₂(H₂L)] in which the two phenolic protons are displaced and H₂L^2- acts as a quadridentate ligand. Reaction of H₄L with (pyH) [MoOBr₄and NaOMe in MeOH precipitates a brown solid. Extraction with fresh MeOH provides low yields of mer-[Mo(HL)₂].MeOH which was characterized structurally by X-ray crystallography. The compound features the tridentate ligand HL₃- where two deprotonated amino nitrogens and one deprotonated phenolic oxygen are ligand atoms and the other phenolic oxygen is protonated and not bound to the metal. The steric requirements of the ligands impose a distorted octahedral stereochemistry which also permits effective metal-ligand multiple bonding revealed by short metal-ligand bond lengths. Crystal data: a 9.963(5); b 17.244(4); c 20.703(8)Å; β 93.32(4)º; P2₁/c; Z 4.