M - B distances for r 3 - BH4 third-row transition metal complexes. In grey, complexes with one r 3 -BH4, in blacky complexes with two r 3 -BH4 , in white with black linesy complexes with more than two r 3 -BH4 and in black with white lines, complexes combining r 2 and r 3 ligands. Squared bands show the average values of a data group