A Simple Route to Calcium and Strontium Hydride Clusters.

The first strontium hydride complex has been obtained by simply treating Sr[N(SiMe ) ] with PhSiH in the presence of PMDTA. The Sr complex Sr H [N(SiMe ) ] ⋅(PMDTA) crystallizes as an "inverse cryptand": an interstitial H is surrounded by a Sr H cage decorated with amide and PMDTA ligands. The analogous Ca complex could also be obtained and both retain their solid-state structures in solution: H NMR spectra in C D show two doublets and one nonet (4:4:1). Up to 90 °C, no coalescence is observed. The Ca cluster was investigated by DFT calculations and shows atypically low charges on Ca (+1.14) and H (-0.59) which signifies an unexpectedly low ionicity. AIM analysis shows hydride⋅⋅⋅hydride bond paths with considerable electron densities in the bond critical point. The clusters thermally decompose into larger, undefined, metal hydride aggregates.