title: First dinuclear B(II) monocations with bridging guanidinate ligands: synthesis and properties.
abstract: Reaction between the diborane (4) B2Cl2(NMe2)2 and Li(hpp) (hpp-=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) leads to [(Me2N)B(mu-hpp)] 2. This species can be protonated by HCl.OEt2 to give [(Me2HN)B(mu-hpp)]2Cl2 featuring two B(II) cations with direct B-B bonding. The unsymmetrical monocation [(Me2N)B2(mu-hpp)2(NHMe2)]+ is also obtained. [(Me2HN)B(mu-hpp)]2Cl2 eliminates NHMe2 in a slow reaction leading to [ClB2(mu-hpp)2(NHMe2)]Cl and ultimately, presumably, to [ClB(mu-hpp)]2. We report the crystal structures of the two monocations [ClB2(mu-hpp)2(NHMe2)]Cl and [(Me2N)B2(mu-hpp)2(NHMe2)]Cl. The experimental results are accompanied by some quantum chemical density-functional theory calculations.
authors.affiliation: Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany.
authors.forename: Oxana
authors.initials: O
authors.lastname: Ciobanu
authors.forename: Dimitri
authors.initials: D
authors.lastname: Emeljanenko
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kaifer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Mautz
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Himmel