In order to further investigate the optical activity of the asymmetric manganese atom, a large number of complexes of the type [C5H5Mn(CO)(NO)L]+ [PF6]- is needed. These compounds were prepared by the reaction of [C5H5Mn(CO)2NO]+[PF6]- with several neutral donors. According to the equation [C5H5Mn(CO)2NO]+[PF6]- + L → [C5H5Mn(CO)(NO)L]+ [PF6]- + CO monosubstituted products were formed with L = P(C4H9)3, P(C6H11)3, P(CH2C6H5)3, P(OC6H5)3, P(OC2H5)3, As(C6H5)3 and CNC6H11. In acetone the reactions proceed at room temperature. When L = Sb(C6H5)3, S(C6H5)2, C5H8 and C6H10 a reaction was also observed, but the corresponding monosubstitution products could not be isolated. PCl3 did not react with [C5H5Mn(CO)2NO]+[PF6]-. The new compounds were investigated by IR and 1H NMR spectroscopy. © 1969.