Linear‐ and Cyclo‐Hexa(amino)hexaboranes: New Routes to Synthesis of B6 Chain and B6 Ring

In this work, a linear‐hexaborane(8) B6(NMe2)6(CH2SiMe3)2 was synthesized using a new method. By replacing one chlorine atom of Cl2B3(NMe2)3 with CH2SiMe3 group, compound ClB3(NMe2)3CH2SiMe3 was prepared. Reductive dehalogenative coupling of ClB3(NMe2)3CH2SiMe3 led to linear‐hexaborane(8). Moreover, the six‐membered boron ring, cyclo‐hexaborane B6(NEt2)6 was synthesized by reductive dehalogenation of Br2BNEt2. The first linear‐hexaborane(8) and cyclo‐hexaborane B6(NEt2)6 crystal structures were fully characterized by X‐ray structural analysis and 11B, 1H, and 13C NMR spectroscopy. While the B1⋅⋅⋅B6 chain in linear‐hexaborane(8) is strongly twisted at all B−B bonds, the B6 ring cyclo‐hexaborane B6(NEt2)6 has a chair conformation similar to cyclohexane. Linear‐ and cyclo‐Hexaboranes have been synthesized and characterized using single crystal X‐ray diffraction analysis and 11B, 1H, and 13C NMR Spectroscopy. Reductive dehalogenative coupling of triborane(5) ClB3(NMe2)3CH2SiMe3 with Li powder in thf dimerized triborane(5) to produce B6 Chain. The B6 Ring was obtained by reductive dehalogenation of Et2NBBr2 with k/Na alloy. While the B1⋅⋅⋅B6 Chain is strongly twisted at all B−B bonds, the B6 Ring has a chair conformation similar to cyclohexane.