The reaction of uranium tetrachloride, UCl 4, with sodium N,N-dimethylaminodiboranate, Na(H 3BNMe 2BH 3), in refluxing 1,2-dimethoxyethane (dme) yields small amounts of a new complex, which we formulate as (μ-oxo)hexakis(tetrahydroborato)bis(1,2- dimethoxyethane)diuranium(IV), toluene solvate, U 2(μ-O)(BH 4) 6(dme) 2·C 7H 8, 1. Most likely, the formation of BH 4 - groups from H 3BNMe 2BH 3 - occurs with the elimination of [Me 2NBH 2] 2, and the formation of the oxo group involves adventitious hydrolysis. Each uranium center in 1 adopts a fac octahedral geometry (counting the BH 4 - groups as occupying one coordination site); the bridging oxygen atom and the two coordinated oxygen atoms of the dme ligand occupy positions trans to the three BH 4 - groups. The hydrogen atom positions were located in the electron density difference maps and reveal that all three BH 4 - groups are bound in a κ 3H fashion. The U⋯B distances to the two BH 4 - groups that are cis to the bridging oxygen atom are 2.574(6) and 2.584(6) , whereas the U⋯B distance of 2.635(7) to the BH 4 - group that is trans to the bridging oxygen is distinctly longer. Thus, the bridging oxygen atom exerts a noticeable trans influence. The crystallographic and 1H NMR data strongly suggest that the previously reported uranium hydride complex U 2(μ-H) 2(BH 4) 6(dme) 2 should be reformulated as this oxo complex U 2(μ-O)(BH 4) 6(dme) 2.
- Crystal structure
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry