First Dinuclear B(II) Monocations with Bridging Guanidinate Ligands: Synthesis and Properties
摘要:
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 center dot OEt2 to give [(Me2HN)B(mu-hpp)](2)Cl(2)featudng two B(II) cations with direct B-B bonding. The unsymmetrical monocation [(Me2N)B-2(mu-hpp)(2)(NHMe2)](+) is also obtained. [(Me2HN)B(mu-hpp)](2)Cl-2 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)B-2(mu-hpp)(2)(NHMe2)]Cl. The experimental results are accompanied by some quantum chemical density-functional theory calculations.