Acid hydrolysis of [Ru-5(CO)(15)(mu(4)-PN/Pr-2)] (2) or protonation of the anionic PO cluster [Ru-5(CO)(15)(mu(4)-PO)](-) (3) affords the hydroxyphosphinidene complex [Ru-5(CO)(15)(mu(4)-POH)]center dot 1 center dot[H2N/Pr-2][CF3SO3], which cocrystallizes with a hydrogen-bonded ammonium triflate salt. Reaction of [Ru-5(CO)(15)(mu(4)-PN/Pr-2)] (2) with bis(cliphenylphosphino)methane (dppm) leads to [Ru-5(CO)(13)(mu-dppm)(mu(4)-PN/Pr-2)] (4). Acid hydrolysis of 4 leads to the dppm-substituted hydroxyphosphinidene [Ru-5(CO)(13)(mu-dppm)(mu(4)-POH)] (5), which is analogous to 1, but unlike 1, can be readily isolated as the free hydroxyphosphinidene acid. Compound 5 can also be formed by reaction of 3 with dppm and acid. The cationic hydride cluster [Ru-5(CO)(13)(mu-dppm)(mu(3)-H)(mu(4)center dot POH)][CF3SO3] (6) can be isolated from the same reaction if chromatography is not used. Compound 4 also reacts with HBF4 to form the fluorophosphiniclene cluster [Ru-5(CO)(13)(mu-dppm)(mu(4)-PF)] (7), while reaction with HCl leads to the mu-chloro, mu(5)-phosphide cluster [Ru-5(CO)(13)(mu-dppm)(u-Cl)(u(5)-P)] (8).