Chemistry of CS(2) and CS(3) Bridged Decaborane Analogues: Regular Coordination Versus Cluster Expansion

In an effort to synthesize metallaheteroborane clusters of higher nuclearity, the reactivity of metallaheteroboranes, nido-[(Cp*M)(2)B(6)S(2)H(4)(CS(3))] (Cp* = C(5)Me(5)) (1: M = Co; 2: M = Rh) with various metal carbonyls have been investigated. Photolysis of nido-1 and nido-2 with group 6 metal carbonyls, M’(CO)(5).THF (M’ = Mo or W) were performed that led to the formation of a series of adducts [(Cp*M)(2)B(6)S(2)H(4)(CS(3)){M’(CO)(5)}] (3: M = Co, M’ = Mo; 4: M = Co, M’ = W; 5: M = Rh, M’ = Mo; 6: M = Rh, M’ = W) instead of cluster expansion reactions. In these adducts, the S atom of C=S group of di(thioboralane)thione {B(2)CS(3)} moiety is coordinated to M’(CO)(5) (M = Mo or W) in η(1)-fashion. On the other hand, thermolysis of nido-1 with Ru(3)(CO)(12) yielded one fused metallaheteroborane cluster [{Ru(CO)(3)}(3)S{Ru(CO)}{Ru(CO)(2)}Co(2)B(6)SH(4)(CH(2)S(2)){Ru(CO)(3)}(2)S], 7. This 20-vertex-fused cluster is composed of two tetrahedral {Ru(3)S} and {Ru(2)B(2)}, a flat butterfly {Ru(3)S} and one octadecahedron {Co(2)RuB(7)S} core with one missing vertex, coordinated to {Ru(2)SCH(2)S(2)} through two boron and one ruthenium atom. On the other hand, the room temperature reaction of nido-2 with Co(2)(CO)(8) produced one 19-vertex fused metallaheteroborane cluster [(Cp*Rh)(2)B(6)H(4)S(4){Co(CO)}(2){Co(CO)(2)}(2)(μ-CO)S{Co(CO)(3)}(2)], 8. Cluster 8 contains one nido-decaborane {Rh(2)B(6)S(2)}, one butterfly {Co(2)S(2)} and one bicapped square pyramidal {Co(6)S} unit that exhibits an intercluster fusion with two sulfur atoms in common. Clusters 3–6 have been characterized by multinuclear NMR and IR spectroscopy, mass spectrometry and structurally determined by XRD analyses. Furthermore, the DFT calculations have been carried out to gain insight into electronic, structural and bonding patterns of the synthesized clusters.