Dirhodium(II) carboxylates as building blocks. Macrocyclic dimers with vertically stacked Rh-2(4+) units

摘要

Reaction of Rh-2(OAc)(4) and H2L (=2,7-di- tert-butyl-9,9-dimethyl-4,5-xanthenedicarboxylic acid) in N,N-dimethylaniline gave the singly bridged dimer (AcO)(3)Rh2LRh2(OAc)(3) and three doubly bridged dimers, (AcO)(2)Rh2L2Rh2(OAc)(2), (HL)(AcO)Rh2L2Rh2(OAc)(2), and (HL)(AcO)Rh2L2Rh2(OAc)(HL). Crystal structures of the last two compounds showed a macrocyclic core with a trans arrangement of bridging dicarboxylates, with one or two of the four remaining acetate ligands replaced by a bridging ligand bound through one carboxylate only. The rhodium cages are separated by 4.5 Angstrom in the direction of the Rh-Rh axes, and offset horizontally by 2.5 Angstrom so that a rhodium atom of one cage lies over a carboxylate oxygen of the other, with Rh . . .O distances of 2.248-2.286 Angstrom. [References: 16]