Macropolyhedral boron-containing cluster chemistry. A synthetic approach via the auto-fusion of [6,9-(SMe2)2-arachno-B10H12]

Abstract

In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe₂)₂-arachno-B₁₀H₁₂] 1 in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe₂)-nido-B₁₀H₁₂] 2 (30%), but also the two two-cluster species [6,9-(SMe₂)₂-arachno-B₁₀H₁₁-1-(6′-nido-B₁₀H₁₃)] 3 (20%) and [1,6′-(nido-B₁₀H₁₃)₂] 6 (ca. 0.5%) and the two three-cluster species [6,9-(SMe₂)₂-arachno-B₁₀H₁₀-1,5-(6′-nido-B₁₀H₁₃)₂] 4 (5%), characterized crystallographically, and [6,9-(SMe₂)₂-arachno-B₁₀H₁₀-1,3-(6′-nido-B₁₀H₁₃)₂] 5 (<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe₂)-nido-B₁₀H₁₂] 2 is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe₂)₂-arachno-B₁₀H₁₂] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre-σ-linked two-cluster compounds as starting substrates, two-cluster [5-(SMe₂)-4-(2′-nido-B₁₀H₁₃)-nido-B₁₀H₁₁] 7 (0.6%) has been isolated from the reaction of SMe₂ with [1,5′-(nido-B₁₀H₁₃)₂], other identified products being compound 1 (39%) and compound 3 (10.5%).