The Construction of (Salophen)ruthenium(II) Assemblies Using Axial Coordination

Abstract

Mononuclear and binuclear carbonylruthenium(II) complexes with N2O2 Schiff base ligands based on 3,5-di-tert-butylsalicylaldehyde and three different ortho-diamines have been prepared. The mononuclear Ru(BSP)(CO) [BSP = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-phenylenediamine] complex 4 acts as a versatile supramolecular synthon, as illustrated by the fact that it spontaneously forms linear and three-dimensional assemblies through axial coordination with pyridyl Lewis bases. Using this motif, neutral and charged assemblies 6, 9, and 12 were prepared. The versatility of the salophen ligand was highlighted by the preparation of bimetallic carbonylruthenium(II) compounds 14−17 from 1,2,4,5-tetraaminobenzene and 2,3,7,8-tetraaminodibenzo[1,4]dioxin. The bimetallic complexes were isolated as a mixture of cis and trans diastereomers with respect to the spatial relationship between the two axially bound carbon monoxide ligands. The electronic spectral and electrochemical properties of the pyridyl adducts 5, 15, and 17 were compared. The properties of 17 closely resembled 5 due to the insulating effect of the extended central tetraamino fragment, while 15 behaved as a single, novel chromophore. The electrochemical studies revealed that the central tetraamino linker regulates the communication between the two metal centers of 15 and 17. It was found that the two metal atoms of 15 sense each other to a larger extent than those of 17.