Studies of dirhodium(II) tetrakis(trifluoroacetate)

The interaction of benzene, p-xylene, and naphthalene with a strong two-ended Lewis acid, Rh2(O2CCF3)4, led to one-dimensional linear polymers of 1:1 composition, [Rh2(O2CCF3)4·L], where L C6H6 (1), p-(CH3)2C6H4 (2), and C10H8 (3). Compounds 1‐3 have been characterized by elemental analysis and IR spectroscopy and their structures have been determined by X-ray diffraction. In the crystal structures of the compounds the alternating arrangement of the dirhodium(II) tetrakis(trifluoroacetate) units with the aromatic ligands coordinated to their axial positions forms infinite chains extended along one direction of the unit cell. The rare bridging off-centered, h 2 :h 2 coordination of arene groups by the Rh(II) centers was found to be preferred in all three cases with the two closest RhCarene distances averaged to 2.662(6) A, in the benzene complex (1), to 2.684(7) A, in the p-xylene analogue (2), and to 2.588(9) A, in the naphthalene product (3). © 2000 Elsevier Science Ltd. All rights reserved.