Metalltetrahydridoborate und Tetrahydridometallate, 11 1 Zur Kristall- und Molekülstruktur von Magnesiumtetrahydridoborat Mg(BH4)2 • 3 THF / Metal Tetrahydridoborates and Tetrahydridoborato Metallates, 11 1 The Crystal and Molecular Structure of Magnesium Tetrahydridoborate Mg(BH4)2 • 3 THF

Mg(BH 4 ) 2 • 3 THF was prepared from MgHo and B 2 H 6 in tetrahydrofuran. It crystallizes monoclinically, space group C2/c, Z = 4. The crystal structure reveals that the molecule contains a seven-coordinate Mg center. Its BH 4 groups form double hydrogen bridges to magnesium. The geometry at Mg corresponds to a slightly distorted trigonal bipyramid for the O 3 B 2 (Mg)-coordination polyhedron, with two THF molecules in apical and one in equatorial position. A two-fold crystallographic axis passes through Mg and the equatorial oxygen atom thus posing C 2 symmetry on the molecule