Synthesis, molecular structure and reactivity of the dimethyl sulfide adduct of a 1,3,2-diselenaborolane with an annelated dicarba-closo-dodecaborane(12) unit

A Spirocyclic Borate and a Dihydroborate Derived from the 1,2‐Diselenolato‐1,2‐dicarba‐closo‐dodecaborane(12) Dianion [1,2‐(1,2‐C2B10H10)Se2]2–: Structures, NMR Spectroscopy, and DFT Calculations

“…Some examples with BSe 4 structures are known from solid-state chemistry. [19] The structural data (Table 3) of the carborane moiety and of the C 2 Se 2 B rings are similar to those found previously for A [10] and they are similar to those reported for B, although the standard deviations in the latter are fairly large. [8] To the best of our knowledge, the borate anion 9 is the first example of this type of borate that has been structurally characterized.…”

“…Deboronation of one or both carborane cages in anion 4 -to give novel di-and trianions was not observed. Treatment of 4a with methanol (Scheme 4) proceeded expectedly to give B(OMe) 3 along with diselenol 6 [10] and the parent ortho-carborane 1. The formation of 1 indicates that cleavage of the B-Se bonds leading to 6 is accompanied by cleavage of the C-Se bonds as well.…”

“…80 %), the ether adduct of the 2-chloro-4,5-[1,2-dicarba-closo-dodecaborano(12)]-1,3-diselena-2-borolane (ca. 10 %), [10] and some unidentified products. The other conceivable product, the borate anion 4, was not observed.…”

“…[8][9][10][11][12][13][14] The selenium derivative 3 is particularly attractive, since the 77 Se nucleus (natural abundance 7.58 %; I = ½) possesses favorable NMR spectroscopic properties, and thus 77 Se NMR spectroscopy is well suited to monitor reactions and characterize products, even in mixtures. [15] We have shown that it is advisable for many purposes to use 3 after careful isolation [10,12,14] instead of Scheme 1. Dilithiation of ortho-carborane (1) to give 2, and insertion of selenium into the C-Li bonds.…”

“…The products observed here were characterized by NMR spectroscopy, in two cases by X-ray structural analysis, and gas-phase geometries were optimized by DFT methods, which also served for the calculation of NMR spectroscopic parameters (chemical shits and spin-spin coupling constants). So far, solely the dimethyl sulfide borane adduct A has been isolated and structurally characterized, [10] and one diborate B derived from the 1,2-diselenolato-1,2-dicarba-closo-dodecaborane (12) dianion in 3 has been reported. [8] Using the sulfur analogue of 3, [1,2- (1,2-C 2 B 10 H 10 )S 2 ] 2-, in reactions with boron halides, the formation of a spiroborate anion {[1,2-(1,2-C 2 B 10 H 10 )S 2 ] 2 B} -has been proposed mainly on the basis of the 11 B NMR spectroscopic signal (δ 11 B = 13.4 ppm) of the central tetracoordinate boron atom.…”