Molecular and electronic structure of two linear thiophenolate-bridged heterotrinuclear complexes [LFeRuFeL](2+/3+) (L=1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane)

The reaction of [(FeL)-L-III] with [(RuCl2)-Cl-II(dmso)(4)] in methanol und er argon, affords, upon addition of NaPF6, brown crystals of [LFeRuFeL](PF6 )(2) . 3 CH3OH (1). Its one-electron oxidation product [LFeRuFeL](PF6)(3) ( 2) [L = 1,4,7-(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane] was generated by using one equivalent of [NO]BF4. The crystal structure determi nation of [LFeRuFeL](BPh4)(2) . CH3CN . 3 (CH3)(2)CO shows that 1 contains a trinuclear, face-sharing thiolato-bridged dication. Mossbauer spectroscop y established that the oxidation state distribution of 1 can best be descri bed by (FeRuFe2.5)-Ru-2.5-Fe-III and 2 by (FeRuFeIII)-Ru-III-Fe-III. Comple x 1 possesses a diamagnetic (S-t = 0) and 2 an S-t = 1/2 ground state. The electronic structures of 1 and 2 are rationalized by an MO picture involvin g Fe-Ru metal-metal bonds of bond order 0.5 in both species. Complex 1 is f ormally a mixed valence compound with complete delocalization of the "exces s electron" (class III).