Synthesis, crystal structures, and DFT calculations of tungsten (IV) and tungsten (VI) phosphino polyhydrides

Abstract

We present here the synthesis, crystal structures, and DFT calculations of tungsten (IV) and tungsten (VI) phosphino polyhydrides. These polyhydrides have the potential of demonstrating intriguing non-classical η2-H2 interactions. The subject compounds have been synthesized previously, however, the crystal structures (with the location of all hydrogen atoms) have yet to be reported. We have used high quality X-ray diffraction at low temperature to assist in locating, for the first time, the hydrides in these complexes. The polyhydrides each contain four phosphine ligands with the general formula PRPh2 (where R = Me or Et) making very intriguing eight and nine-coordinate complexes. The eight-coordinate complexes [tungsten (IV)] resemble a slightly distorted dodecahedron while the nine-coordinate complex [tungsten (VI)] resembles a tricapped trigonal prism. Optimized DFT geometries showing the position of the hydrides for all three compounds that were crystallographically characterized have also been calculated. The combination of our results indicate that these compounds are best described as classical metal hydrides. The structures are also compared to similar structures reported in the literature.