Macropolyhedral Chalcogenaboranes: Insertion of Selenium into the Isomers of B₁₈H₂₂

Abstract

High yields of novel macropolyhedral selenaboranes are reported. Reactions of the monoanions of the syn- and anti-isomers 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 [μ-(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.

Expanding Luminescence Horizons in Macropolyhedral Heteroboranes

“…Compound 1 was characterised by a single‐crystal X‐ray diffraction study [23] (Figure 1), by multinuclear NMR (Nuclear Magnetic Resonance) spectroscopy (Figures 2, S1, S2 and Table S1), and by mass spectrometry (Figure S3). The cluster compound comprises a nido ‐11‐vertex subcluster conjoined with an arachno‐ 10‐vertex subcluster and is thus very different from the anti‐ octadecaborane species from which its conjugated base is derived, [22] and which contains two identical conjoined nido‐ 10‐vertex subclusters.…”

“…Se 2 B 17 H 17 ( 1 ) . Low‐temperature protonation with concentrated sulphuric acid of dichloromethane solutions of [Se 2 B 17 H 18 ] − , [22] the selenium analogue of the known [S 2 B 17 H 18 ] − , [14] affords Se 2 B 17 H 17 1 (see Supporting Information for full experimental details). Compound 1 was characterised by a single‐crystal X‐ray diffraction study [23] (Figure 1), by multinuclear NMR (Nuclear Magnetic Resonance) spectroscopy (Figures 2, S1, S2 and Table S1), and by mass spectrometry (Figure S3).…”

Expanding Luminescence Horizons in Macropolyhedral Heteroboranes

“…SeB 18 H 20 (4). We have previously described the synthesis of anionic 19-vertex [SeB 18 H 19 ] À [22] and we therefore examined the addition of concentrated H 2 SO 4 to this compound also. Thus, acidification of pale yellow dichloromethane solutions of the anion, which is prepared from the addition of selenium to [syn-B 18 H 21 ] À , results in an immediate loss of colour and the formation of a single product as shown from 11 B NMR spectroscopy (Figure S10).…”

“…Se 2 B 17 H 17 (1). Low-temperature protonation with concentrated sulphuric acid of dichloromethane solutions of [Se 2 B 17 H 18 ] À , [22] the selenium analogue of the known [S 2 B 17 H 18 ] À , [14] affords Se 2 B 17 H 17 1 (see Supporting Information for full experimental details). Compound 1 was characterised by a single-crystal X-ray diffraction study [23] (Figure 1), by multinuclear NMR (Nuclear Magnetic Resonance) spectroscopy (Figures 2, S1, S2 and Table S1), and by mass spectrometry (Figure S3).…”

The metal-mediated coupling of the diselenaundecaborate anion [Se2B9H10]−

“…New macropolyhedral [1] heteroborane cluster species have been synthesised by the addition of selenium to the preformed macropolyhedral anions syn-and anti-[B18H21] − , to afford the anionic species [Se2B17H18] − , [SeB18H19] − , [SeB18H21] − and [Se2B19H81] − in good yields [2]. However, the starting borane anti-B18H22 is quite expensive and we are therefore interested in exploring the possibility of synthesising macropolyhedral boron species by fusing smaller selenanonaborane clusters.…”