Ytterbocenes as one- and two-electron reductants in their reactions with diazadienes: Yb-III mixed-ligand bent-sandwich complexes containing a dianion of diazabutadiene

Ytterbocene [Yb(C5MeH4)(2)(thf)(2)] reacts with diazabutadiene 2,6-iPr(2)C(6)H(3)-N=CH-CH=N-C(6)H(3)iPr(2)-2,6 (DAD) as a one-electron reductant to afford a bis(cyclopentadienyl) Yb-III derivative containing a DAD radical anion [Yb(C5MeH4)(2)(dad(-center dot))]. However, ytterbocenes [YbCp*(2)(thf)(2)] (Cp* = C5Me5, C5Me4H) coordinated by sterically demanding cyclopentadienyl ligands act as two-electron reductants in their reactions with DAD. These reactions occur by abstraction of one Cp* ring and result in the formation of novel Yb-III. mixed-ligand bent-sandwich complexes, [YbCp*(dad)(thf)], in which the dianion of DAD has an uncommon terminal eta(4)-coordination to the ytterbium atom. The variable-temperature magnetic measurements of complex [Yb(C5Me5) (dad) (thf)] suggest the existence of redox tautomerism for this compound.