Tuning the electronic properties of cyclopentadienyl analogs with CB2N2 frameworks: 1,2-diphenyl-1,2-diaza-3,5-diborolyl ligands and their alkali metal salts
作者:Hanh V. Ly、Jari Konu、Masood Parvez、Roland Roesler
DOI:10.1039/b802930j
日期:——
Two heterocyclic cyclopentadienyl analogs with a CB2N2 skeleton, 4-methyl-1,2,3,5-tetraphenyl-1,2-diaza-3,5-diborolidine and 4-methyl-3,5-dimethylamino-1,2-diphenyl-1,2-diaza-3,5-diborolidine were prepared through cyclocondensation of the corresponding 1,1-bis(organochloroboryl)ethane with 1,2-diphenylhydrazine. The former diazadiborolidine featured a cyclopentadiene-like structure with short B–N bonds and a planar ring framework, while in the latter the B–N bonds were noticeably longer and the ring framework was considerably folded as a result of the interaction between boron and the electron donating NMe2 groups. The dimethylamino substituted diazadiborolidine could not be deprotonated due to the reduced acidity of the ring proton, however, the B-phenylated analog was easily deprotonated and the lithium, sodium and potassium 1,2-diaza-3,5-diborolyls were isolated and structurally characterized. The solid state structures of the lithium and sodium salts were similar, with an η1-coordinated π ligand and three THF molecules completing the coordination sphere of the metal. The potassium salt featured a highly unusual mono-dimensional polymeric structure with the metal π-coordinated by the CB2N2 ligand and two of the phenyl groups on boron and nitrogen, and σ-coordinated by one THF molecule.
两种具有CB2N2骨架的杂环环戊二烯类类似物,4-甲基-1,2,3,5-四苯基-1,2-二氮-3,5-双博烯和4-甲基-3,5-二甲氨基-1,2-二苯基-1,2-二氮-3,5-双博烯,通过相应的1,1-双(有机氯硼基)乙烷与1,2-二苯肼的环缩合反应制备而成。前者的二氮双博烯具有类环戊二烯的结构,B–N键较短,环框架呈平面状;而后者的B–N键明显较长,环框架由于硼和供电子的NMe2基团之间的相互作用而显著折叠。由于环质子的酸性降低,二甲氨基取代的二氮双博烯无法去质子化,然而,B-苯基化的类似物却能轻易去质子化,锂、钠和钾的1,2-二氮-3,5-双博烯盐被分离并进行了结构表征。锂和钠盐的固态结构相似,具有η1-配位的π配体和三个THF分子完成金属的配位层。钾盐则具有一种非常不寻常的一维聚合物结构,金属通过CB2N2配体进行π配位,同时氮和硼上的两个苯基也与金属σ配位,并与一个THF分子σ配位。