Decarbonylnitrosyltriruthenate, [Ru3(CO)10(NO)]-, exhibits reactivity at both the nitrosyl ligand and the metal core. The NO bond can be cleaved in a thermal reaction to give [Ru5N(CO)14]- in low yield, whereas [Ru3(NCO)(CO)11]- can be formed quantitatively when [Ru3(CO)10(NO)]- is photolyzed under CO. The carbonyl ligands of the cluster are readily substituted by triphenylphosphine and trimethylphosphite giving [Ru3(CO)9L(NO)]- (where L = PPh3, P(OCH3)3). Under an atmosphere of 13CO complete exchange with the carbonyl ligands is observed. The substituted clusters have been characterized by infrared and NMR spectroscopies as well as by their reactions with acids to give HRu3(CO)9L(NO). With the anionic nucleophile, PPN(NO2), [Ru3(CO)10(NO)]- photochemically reacts under a CO atmosphere to form [Ru(CO)3NO)]-. This new nitrosyl carbonylmetalate can also be prepared from PPN (NO2) and Ru(CO)5.