Synthetic studies have been carried out for the addition or substitution of phosphorus nucleophiles to the cation <tex>$[(exo-6-R-{eta}^ {5_-}2-MeO-C_6H_5)Mn(CO)_2NO]PF_6,$</tex> 2. $PPh_3$ reacts with 2 to yield the CO displaced product and $MePPh_2$ attacks the dienyl ring of 2 to yield the phosphonium adduct or the metal to give the CO displaced depending upon the reaction temperatures. Nucleophilic addition of HPPh2 to the dienyl ring of 2 gives a neutral substituted product. $P(OMe)_3$ reacts with 2 to yield a mixture of ring adduct and CO displaced product at room temperature. $At - 20^{circ}C,;P(OMe)_3$ attacks the dienyl ring of 2 to give a posphonium adduct, which underwent Arbuzov reaction. This reaction affords a new route to the phosphonate complexes.