Two novel organometallic diruthenium complexes, [Ru-2(II,II)](2+) and[Ru-2(III,III)](4+), containing a di-anionic biphenyl grouping that linearly bridges the two ruthenium centres, have been synthesized. In the solid state (X-ray structures) the biphenyl grouping of [Ru-2(III,III)](4+) is essentially planar indicating extensive pi-conjugation whereas in [Ru-2(II,II)](2+) the phenyl rings make an angle of 22.2 degrees with respect to each other. The complexes can also exist in the mixed valences state [Ru-2(II,III)] and have a K-C of 600 and 1250, respectively; the presence of strongly communicating metal centres is indicated by huge intervalence charge transfer bands at lambda 1820 nm (epsilon 27000 M(-1) cm(-1)) and 1875 nm (epsilon 33000 M(-1) cm(-1)), respectively.