1,3,2‐Diselena‐ and 1,3,2‐Ditelluraphospholanes with an Annelated 1,2‐Dicarba‐closo‐dodecaborane(12) Unit

Abstract

AbstractThe exchange reactions of phosphorus dihalides RPX2 [R = iPr, cyclohexyl (Cy), tBu, (3,5‐Me2‐C6H3)CH2, Ph; X = Cl, Br], EtOPCl2, Et2NPCl2, Cl2PCH2PCl2, and Cl2PCH2CH2PCl2 with 2,2‐dimethyl‐4,5‐[1,2‐dicarba‐closo‐dodecaborano(12)]‐1,3‐diselena‐2‐silacyclopentane provide a straightforward route to 1,3,2‐diselenaphospholanes. Some tellurium analogues were prepared from the dilithium salt [1,2‐(LiTe)2‐1,2‐C2B10H10] and were more difficult to characterize. For the selenium compounds, some of the P‐organosubstituted five‐membered rings dimerize to give ten‐membered rings, most readily with the more bulky alkyl groups such as tBu. This was not observed for the tellurium compounds. The conformations of the five‐membered rings were studied by NMR spectroscopy and DFT methods. Striking structural differences were clear for the 2‐phenyl‐1,3,2‐diselenaphospholane derivative in solution and in the solid state. All reactions were monitored by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 31P, 77Se, and 125Te NMR), and solution‐state structures could be proposed. Remarkably large secondary isotope effects as isotope‐induced chemical shifts 2Δ12/13C(31P) exerted by the carborane carbon atoms were observed; this is apparently a special property of the five‐membered ring. The gas‐phase structures were optimized by DFT methods [B3LYP/6‐311+G(d,p) level of theory], and the NMR parameters were calculated. Two 1,3,2‐diselenaphospholanes and one dimer were characterized by X‐ray analysis.