Redox condensation of [Ru3H(CO)11]- with Ni(CO)4, in tetrahydrofuran solution, under a nitrogen atmosphere, yields the tetranuclear anion [NiRuH(CO)11)-. Subsequent deprotonation with Bu'OK in acetonitrile solution leads to the formation of the related dianion. Both anions have been characterized by spectroscopic techniques, elemental analysis and single crystal X-ray diffraction. [PPh4][NiRu3H(CO)12] crystallizes in the triclinic space group PI with unit cell dimensionsof a = 11.842(2) A,b = 12.335(3) A, c = 13.3080) A,a = 91.89(2)°,β = 93.35(1)°,y = 96.41(2)°, Z = 2, V= 1926.9(7) A'. The NiRu3, metal core of the molecule defines a distorted tetrahedron with nine terminal and three edge bridging carbonyl groups. The hydrido ligand was located by difference Fourier techniques and was found to bridge the NiRu2 basal triangle at a distance of 0.88(6) A from this plane. Selected average distances and angles are: Ru-Ru = 2.839 A, Ru-Ni = 2.640 A, Ru-C, = 1.910 A,Ru-C b = 2.084 A, Ni-C b = 2.022 A, Ru-H = 1.77 A, C-0, = 1.135 A, C-O b = 1.159 A, M-C-O, = 176.3°,M-C--O b = 139.3°;other distances are: Ni-C1 = l.758(7) A, Ni-H= 1.85(7) A. [NEt4]2[NiRu3(CO)12] crystallizes in the orthorhombic space group Pnma (no. 62) with unit cell dimensions ofa=20.247(5) A,b = 15.038(4)A,c = 12.079(3) A, Z=4, V=3678(2) A'. The molecule contains a tetrahedral NiRu3 core with eight terminal and four edge bridging carbon monoxide groups which bridge the three Ni-Ru and one Ru-Ru bond. Average distances and angles are: Ru -Ru =2.3050A Ru-Ni 2.648 A, Ru-C t = 1.878 A, Ru-C b 2.045 A, Ni-C b = 2.055 A, C-O t = 1.145 A, C-01,=1.157 A, M-C-O,= 176.9°, M-C-O b = 138.6°; other distance is: Ni-C t = 1.754(10) A,t = terminal,b = bridging.