The reaction of [Ru(η5-C7H11)2H]BF4 (1; (η5-C7H11) = η5-2,4-dimethylpentadienyl (DMP)) with 2-electron or cyclic 6-electron ligands gives the salts [Ru(η5-C7H11)L3]BF4 (L  CO, PMe3, P(OMe)3, CH3CN; L3 = 1,1,1-tris(diphenylphosphinomethyl)ethane) and [Ru(η5-C7H11)(ηn-ring)]BF4 ((ηn-ring) = η6-cyclohepta-1,3,5-triene, η-cycloocta-1,3,5,7-tetraene, η6-arene, η5-thiophene). In the presence of a halide salt, 1 reacts with 4-electron diene ligands to give neutral [Ru(η5-C7H11)(diene)X] complexes (X  I, Cl, and (diene) = η4-buta-1,3-diene; η4-2,3-dimethylbuta-1,3-diene, η2:η2- cycloocta-1,5-diene) and with 2-electron ligands to give neutral [Ru(η2-C7H11)L2X] complexes (X  I, Br, Cl and L  CO, P(OMe)3, PMe3; X  I and L2 = bis(diphenylphosphino)ethane; X  Cl and L2 = N,N,N′,N′-tetramethylethylenediamine). [Ru(η5-C6H7)(η4-C 6H8)I] is the product of the reaction of 1 with cyclohexa-1,3-diene and KI. The complexes [Ru(η5-C7H11)(P(OMe)3)3]BF4 and [Ru(η5-C7H11)L2I] (LCO, P(OMe)3) have been crystallographically characterized. Complexes of the type [Ru(η5-C7H11)L3]+ and [Ru(η5-C7H11)L2X] exhibit dynamic behaviour in solution due to rotation of the DMP ligand with respect to the RuL3 or RuL2X groups, and activation energies for twelve of the complexes have been evaluated. Exchange of free and coordinated acetonitrile in solutions of [Ru(η5-C7H11)(NCCH3)3]BF4 is non-stereospecific and associative in character.