Boron-nitrogen compounds. CXX. Complexes of B-triethylboroxin with ethylenediamine and derivatives thereof

Article abstract of DOI:10.1016/0022-328X(89)88001-5

B-Triethylboroxin forms colorless 1/1 molar complexes of the type (C2H5BO)3.L with L=ethylenediamine (1) and various derivatives of the latter, i.e., N,N-dimethylethylenediamine (2), N,N,N',N'-tetramethylethylenediamine (3), piperazine (4), 1,4-diazabicyclo<2.2.2>octane (5), diethylenetriamine (6), and tris(2-aminoethyl)amine (7).The cited boroxin also forms 2/1 molar complexes, 2(C2H5BO)3.L, with L=ethylenediamine (8) and those derivatives of the latter which may be considered as symmetrical species, i.e., N,N,N',N'-tetramethylethylenediamine (9), piperazine (10), 1,4-diazabicyclo<2.2.2>octane (11), and diethylenetriamine (12).NMR spectroscopic data suggest that the complexes are fluxional in solution at room temperature with a single nitrogen coordinating to the three boron atoms of a given boroxin ring and where, in solution, the 1/1 molar complexes of symmetrical amines appear to exchange their donor sites.There seem to be no principal differences in the complexing of (RBO)3 with R=C2H5 or C6H5.Two species of the unusual composition 3(RBO)3.2H2NCH2NH2 were also identified.