Search

Lewis bases react with borazine and polyborazylene, yielding borane adducts. In the case of NH3 (l), ammonia-borane (AB) is formed and quantified using NMR spectroscopy against an internal standard. Calculations indicate that the formation of B(NH2)3 may provide the driving force of this redistribution. Given the complexity and expense of currently known spent AB regeneration pathways, it is suggested that this redistribution chemistry be used to recover AB and improve regeneration methods.

The crystal structure of [RhCl(N2)(PPri3)2] has been redetermined at –160 °C. In contrast to the results of a previous structure determination, we conclude that a scattering model in which the N2 ligand is end-on (η1) co-ordinated is fully consistent with the data. Such end-on co-ordination is confirmed in solution at +30 °C from the 31P and 15N n.m.r. spectra of a 15N2 labelled sample. The material crystallizes in the space group P21/c(C52h) of the monoclinic system in a cell of dimensions a= 8.062(2), b= 8.883(2), c= 16.431(4)A, β= 92.45(1)°, Z= 2; the final R and R′ are 0.024 and 0.031, respectively, based on the full-matrix refinement of 124 variables and 3 597 observations. The 31P n.m.r. spectrum of the 15N2-labelled complex shows a doublet of doublets, JP – Rh 122.3 and Jp–15N 4.25 Hz, and proves the N2 co-ordination to be η1 in solution. The 15N n.m.r. spectrum of the labelled complex is also consistent with η1-co-ordination: J15N(1)–Rh 28, J15N(1)–15N(2) 4, J15N(1)–P 4, J15N(2)–Rh 4 Hz; δN(1) 269 and δN(2) 302 p.p.m.(downfield from external 15NH4+).