We report observations on the reactivity of the dinuclear bridged metal-metal-bonded carbonyl [Rh-II(CO)(mu-CpPPh(2))](2+)(2) (2(2+)) and of the bis(solvate) cations [Rh-II(solv)(mu-CpPPh(2))](2+)(2) (3(2+)) with nitriles, amines and pyridine and in general with nitrosyl cation and nitrite anion. By reaction of nitriles and pyridine with 2(2+) we obtained monosubstituted [Rh-2(CO)L(mu-CpPPh(2))(2)](2+) (4(2+)) and disubstituted [Rh(L)(mu-CpPPh(2))](2+)(2) (5(2+)) (L = MeCN, PhCN, pyridine). These complexes (5(2+)) were also obtained directly from 3(2+). In the reactions with 2(2+) the difference in reactivity of the two rhodium(II) sites suggests a specific role of the metal-metal bond. With secondary and primary amines, reductions of 2(2+) to [Rh-I(CO)(mu-CpPPh(2))](2) (1) were also observed, and the selectivity with respect to substitution or reduction was strongly solvent dependent. Lithium diisopropylamide induces quantitatively the reduction of 2(2+) to 1 and apparently the substitution of the solvent in 3a(2+). Finally, the new compounds [Rh-II(THF)(mu-CpPh(2))](2+)(2) (3a(2+)), [Rh-II(mu-H2NC5H4N)(mu-CpPh(2))(2)](2+) (6(2+)) and [Rh-II(NO2)(mu-CpPh(2))](2) (7(2+)) were obtained from 2(2+) and PhIO, from 3(2+) and aminopyridine, and from 2(2+) and nitrite anion, respectively. The compounds were characterized by elemental analysis and the usual spectroscopic methods including COSY NMR experiments. Reaction of NOBF4 with 1 led efficiently to the compound 2(2+) again through a redox process, instead of a substitution.