We previously reported the reaction of the hydride HRu3(CO)&But (I) [ 11 with [(n-C,Hs)Ni(CO)] z, which yielded the tetranuclear compound (r&H,)-NiRus(CO)&*C(H)Bu' (II) [2] , until now the first ruthenium-nickel cluster described.
We give now a preliminary report on the synthesis and crystal structure of a new tetranuclear ruthenium-nickel complex, (&Hs)NiRua(CO)a(C~H~) (III), which was obtained by treating [(&Hs)Ni-(CO)12 with the hydride HRu~(CO)~(C$H~) [3] (IV), 'allyl' isomer, in refluxing n-octane, purified by preparative t.l.c., and crystallized from n-heptane/ CHCls at -10 "c. The i.r. spectrum of (III) in the CO stretching region (n-heptane solution) shows bands at 2049 s, 2013 vs, 1981 s, 1964 s, 1859 m, 1837 s, cm-'. The mass spectrum shows the molecular ion at 735 m/e, gradual loss of 8 CO groups, then demolition of the organic moiety; doubly charged ions, corresponding to CO loss, are observed. The crystals of (III) are monoclinic,a = 10.525(9), b = 20.487(13), c = 9.891(7) A, /I = 92.1 l(7)', V = 2131 A', Z = 4, d& = 2.29 g cm-', space group Q/n. 4918 reflections in the range 3 < 8 < 27' were recorded on an AED singlecrystal diffractometer using the Zr-filtered MoKa! radiation; 2963 of these (having Z > 20 (Z)) were used in the structure analysis. The structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.062.
The structure of (III), represented in Fig. 1, is characterized by a butterfly arrangement of three Ru and one Ni atoms, bonded to eight carbonyls (through the Ru atoms only), to a cyclopentadienyl