The reactions of M(CO)(5)X (M = Mn, Re: X = Cl, Br) with {Ph2PCH2}(3)CCH3 (P-3) and {Ph2P(CH2)(2)}(3)P (P3P') are investigated, and the products are characterized by IR, NMR (P-31 and C-13), and electrospray mass spectrometric (ESMS) techniques. With P-3, the major products are fac-M(CO)(3)(eta (2)-P-3)X (syn and anti isomers) and ci,fac-M(CO)(2)(eta (3)-P-3)X, and with P3P', the major product for each metal is cis,mer-M(CO)(2)(eta (3)-P3P')X, but cis-[M(CO)(2)(eta (4)-P3P')]X and fac-[Re(CO)(3)(eta (3)-P3P')]X are also characterized. Addition of Mel to those complexes containing pendant phosphine groups produces the corresponding phosphonium cations without affecting the remainder of the molecule. On the voltammetric time scale, electrochemical oxidation of cis,fac-Mn(CO)(2)(eta (3)-P-3)X yields the corresponding 17e cation cis,fac-[Mn(CO)(2)(eta (3)-P-3)X](+), but on the longer time scale of exhaustive electrolysis or chemical oxidation, the product is fac-[Mn(CO)(3)(eta (3)-P-3)](+). In contrast, the rhenium cation; cis;fac-[Re(CO)(2)(eta (3)-P-3)X](+) is stable on the synthetic time scale, but upon oxidation of cis,fac-Re(CO)(2)(eta (3)-P-3)X With NOBF4, he final product is the 18e [Re(CO)(NO)(eta (3)-P-3)X](+). cis,mer-Mn(CO)(2)(eta (3)-P3P')X is reversibly oxidized to cis,mer-[Mn(CO)(2)(eta (3)-P3P')X](+) on the voltammetric time scale, but on the longer synthetic time scale, the product isomerizes to trans-[Mn(CO)(2)(eta (3)-P3P')X](+), which can be reduced to trans-Mn(CO)(2)(eta (3)-P3P')X. Upon voltammetric oxidation, the corresponding rhenium complexes show an initial irreversible response associated with the pendant phosphine group prior to the reversible oxidation of the metal on the synthetic time scale; spectroscopic data indicate formation of cis,mer-Re(CO)(2)(eta (3)-P3P'O)X. The complex cis,mer-[Re(CO)(2)(eta (3)-P3P'Me)X](+) shows only the reversible metal oxidation response. ESMS data are obtained directly for the methylated cationic complexes, and neutral complexes are either oxidized or adducted with sodium ions to produce cationic species.