Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of B 18 H 22 .

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the syn - and anti -isomers of B 18 H 22 with powdered selenium in THF variously give new macropolyhedral selenaboranes: 19-vertex [SeB 18 H 19 ] - anion 1 , 19-vertex [SeB 18 H 21 ] - anion 2 , 20-vertex [Se 2 B 18 H 19 ] - anion 3 , and 19-vertex [Se 2 B 17 H 18 ] - anion 4 . Single-cluster [ hypho -Se 2 B 6 H 9 ] - anion 5 and neutral arachno -Se 2 B 7 H 9 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 -B 18 H 22 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 -B 18 H 22 are also reported. The oxaborane [μ-(8,9)-O- syn -B 18 H 20 ] 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.