Nickel-Ruthenium mixed-metal carbonyl clusters. Syntheses and solid state structures of the two tetrahedral clusters [PPh4][NiRu3(\uf06d3-H)(CO)9(\uf06d-CO)3] and [NEt4]2[NiRu3(CO)9(\uf06d-CO)4].

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) \uc5, b = 12.335(3) \uc5, c = 13.3080) \uc5, a = 91.89(2)\ub0, \u3b2 = 93.35(1)\ub0,y = 96.41(2)\ub0, Z = 2, V= 1926.9(7) \uc5'. 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 \uc5, Ru-Ni = 2.640 \uc5, Ru-C, = 1.910 A,Ru-Cb = 2.084 \uc5, Ni-Cb = 2.022 \uc5, Ru-H = 1.77 \uc5, C-0, = 1.135 \uc5, C-Ob = 1.159 \uc5, M-C-O, = 176.3\ub0,M-C--Ob = 139.3\ub0;other distances are: Ni-C1 = l.758(7) \uc5, Ni-H= 1.85(7) \uc5. [NEt4]2[NiRu3(CO)12] crystallizes in the orthorhombic space group Pnma (no. 62) with unit cell dimensions of a=20.247(5) \uc5, b = 15.038(4)\uc5, c = 12.079(3) \uc5, 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 \uc5, Ru-Ct= 1.878 \uc5, Ru-Cb2.045 \uc5, Ni-Cb= 2.055 \uc5, C-Ot= 1.145 \uc5, C-01,=1.157 \uc5, M-C-O,= 176.9\ub0, M-C-Ob = 138.6\ub0; other distance is: Ni-Ct = 1.754(10) \uc5, t = terminal, b = bridging

Bimetallic Iron-Rhodium anionic carbonyl clusters [Fe2Rh(CO)x]- (x= 10 or 11), [FeRh4(CO)15]2-, [Fe2Rh4(CO)16]2- and [FeRh5(CO)16]-.

The syntheses and interconversions of mixed iron-rhodium carbonyl clusters are described; a combination of X-ray analysis and multinuclear n.m.r. measurements allowed the structural characterisation of [FeRh 4(CO)15]2-, [FeRh5(CO) 16]-, and [Fe2Rh4(CO) 16]2-, which can all be obtained from the unstable cluster, [Fe2Rh(CO)x]- (x = 10 or 11)