title: A boron-boron coupling reaction between two ethyl cation analogues.
abstract: The design of larger architectures from smaller molecular building blocks by element-element coupling reactions is one of the key concerns of synthetic chemistry, so a number of strategies were developed for this bottom-up approach. A general scheme is the coupling of two elements with opposing polarity or that of two radicals. Here, we show that a B-B coupling reaction is possible between two boron analogues of the ethyl cation, resulting in the formation of an unprecedented dicationic tetraborane. The bonding properties in the rhomboid B₄ core of the product can be described as two B-B units connected by three-centre, two-electron bonds, sharing the short diagonal. Our discovery might lead the way to the long sought-after boron chain polymers with a structure similar to the silicon chains in β-SiB₃. Moreover, the reaction is a prime textbook example of the influence of multiple-centre bonding on reactivity.
authors.affiliation: Institute of Inorganic Chemistry, Ruprecht-Karls-University Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Litters
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kaifer
authors.forename: Markus
authors.initials: M
authors.lastname: Enders
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Himmel