Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of B18H22

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the syn- and antiisomers of B18H22 with powdered selenium in THF variously give new macropolyhedral selenaboranes: 19-vertex [SeB18H19](-) anion 1, 19-vertex [SeB18H21](-) anion 2, 20-vertex [Se2B18H19](-) anion 3, and 19-vertex [Se2B17H18](-) anion 4. Single-cluster [hypho-Se2B6H9](-) anion 5 and neutral arachno-Se2B7H9 6 also result. All of the macropolyhedrals 1, 2, 3, and 4 are characterized by NMR spectroscopy and mass spectrometry, and by single-crystal X-ray diffraction analyses. Anions 1 and 2 each consist of an 11-vertex subcluster joined by a common two-boron edge to a 10-vertex subcluster. Anion 3 consists of an 11-vertex subcluster joined by a common boron atom and an interboron link to an arachno-type 10-vertex subcluster. Unusually, anion 3 incorporates a hexagonal pyramidal intracluster structural motif in its 11-vertex subcluster. Anion 4 entails two arachno-type 10-vertex subclusters joined by a common boron atom, and with an additional intercluster boron-boron link. NMR data for syn-B18H22 and its mono- and dianions 7 and 8 and single-crystal X-ray diffraction results for these anions and also the monoanion 9 of anti-B18H22 are also reported. The oxaborane [mu-(8,9)-O-syn-B18H20](2-) dianion 10 was serendipitously formed during the work and also characterized by a single-crystal X-ray diffraction study. Experimental NMR and structural findings are supported by DFT calculations throughout.

Automated summary

High yields of novel macropolyhedral selenaboranes have been synthesized and characterized. These selenaboranes exhibit unique structural features, including different numbers of vertices, connectivity between subclusters, and the presence of special structural motifs within the subclusters.