Cluster Expansion Reactions of Group 6 and 8 Metallaboranes Using Transition Metal Carbonyl Compounds of Groups 7-9

The reinvestigation of an early synthesis of heterometallic cubane-type clusters has led to the isolation of a number of new clusters which have been characterized by spectroscopic and crystallographic techniques. The thermolysis of [(Cp*Mo)(2)B4H4E2] (1: E = S; 2: E = Se; Cp* = eta(5)-C5Me5) in presence of [Fe-2(CO)(9)] yielded cubane-type clusters [(Cp*Mo)(2)(mu(3)-E)(2)B2H(mu-H){Fe(CO)(2)}(2)-Fe(CO)(3)], 4 and 5 (4: E = S; 5: E = Se) together with fused clusters [(CP*Mo)(2)B4H4E2Fe(CO)(2)Fe(CO)(3)] (8: E = S; 9: E = Se). In a similar fashion, reaction of [(Cp*RuCO)(2)B2H6], 3, with [Fe-2(CO)(9)] yielded [(Cp*Ru)(2)(mu(3)-CO)(2)-B2H(mu-H){Fe(CO)(2)}(2)Fe(CO)(3)], 6, and an incomplete cubane cluster [(mu(3)-BH)(3)-(Cp*Ru)(2){Fe(CO)(3)}(2)], 7. Clusters 4-6 can be described as heterometallic cubane clusters containing a Fe(CO)(3) moiety exo-bonded to the cubane, while 7 has an incomplete cubane [Ru2Fe2B3] core. The geometry of both compounds 8 and 9 consist of a bicapped octahedron [MO2Fe2B3E] and a trigonal bipyramidal [Mo2B2E] core, fused through a common three vertex [Mo2B] triangular face. In addition, thermolysis of 3 with [Mn-2(CO)(10)] permits the isolation of arachno-[(Cp*RuCO)(2)B3H7], 10. Cluster 10 constitutes a diruthenaborane analogue of 8-sep pentaborane(11) and has a structural isomeric relationship to 1,2-[{Cp*Ru}(2)(CO)(2)B3H7].