A dirhodium complex bearing a newly-designed silyl-1,8-naphthyridine ligand (napySi), [Rh(kappa Si-2,N-napySi)(H)(mu-Cl)](2) (1), was synthesized. Reaction of complex 1 with excess BH3 center dot SMe2 afforded a mononuclear borane adduct Rh[kappa Si-4,N,H,H-napySi(BH3)](H)Cl (2), revealing that rhodium and the uncoordinated naphthyridine nitrogen cooperatively captured BH3 and weakened its two B-H bonds. Complex 2 contains a Rh(mu-H)(2)B core composed of two Rh-H-B-3-center 2-electron (3c-2e) bonds where one Rh-H interaction is considerably weakened by strong trans-influence of the silyl ligand moiety.