MIXED-VALENCE COMPLEXES CONTAINING THE RH-2(5+) CORE - X-RAY CRYSTAL-STRUCTURE OF THE DIMER-OF-DIMERS [RH-2(FORM)2(O2CCF3)3-(AGO2CCF3)2]2 (FORM = N,N'-DI-PARA-TOLYLFORMAMIDINATE ANION)

The chemical oxidation of the Rh2(4+) formamidinate derivative Rh2(form)2(O2CCF3)2(H2O)2 (form = N,N'-di-p-tolylformamidinate) with the appropriate silver salt leads to the formation of the paramagnetic complexes [Rh2(form)2(O2CCF3)3(AgO2CCF3)2]2 (1), [Rh2(form)2(O2CCF3)2(H2O)2]ClO4 (2) and [Rh2(form)2(O2CCF3)](NO3)2 (3). The complexes were characterized by EPR spectroscopy and X-ray analysis. The EPR spectra in frozen solution consist of two absorption lines. The low-field one is unresolved while the high-field one is split into a triplet. The pattern is interpreted in terms of hyperfine magnetic interaction between the unpaired electron and two equivalent Rh-103 nuclei (I = 1/2). Complex 1, which consists of two Rh2(form)2(O2CCF3)3 radicals axially linked by CF3COOAg molecules, crystallizes in the monoclinic space group C2/c, with a = 32.981(4), b = 16.286(2), c = 18.642(3) angstrom, beta = 94.32(4)-degrees, V = 9984.3(4) angstrom3, Z = 4 and D(calc) = 1.92 g cm-3.