The reaction of [HRu 3 (CO) 1 1 ] - (1) with an excess of PCy 3 in refluxing THF gives the electron-deficient anion [HRu 3 (CO) 7 (PCy 3 ) 2 ] - (2) which has the rare electron count of 44e. As evidenced by the 1 H and 3 1 P NMR spectra, 2 exists in solution in the form of two isomers 2a and 2b, one of which crystallises from acetone as the tetraethylammonium salt. The single-crystal X-ray analysis shows a closed Ru 3 framework with the hydride ligand bridging the metal-metal bond between a phosphine-substituted and a phosphine-free ruthenium atom (isomer 2b).