Metal Tetrahydroborates and Tetrahydroborato Metalates. 30 [1] Solvates of Alcoholato-, Phenolato-, and Bis(trimethylsilyl)amido-Magnesium Tetrahydroborates XMgBH4(Ln). Metall Tetrahydroborate und Tetrahydroborato Metallate, 30 [1]. Solvate der Alkoholato-, Phenolato- und Bis(trimethylsilyl)amino-magnesium-tetrahydroborate XMgBH4(Ln)

A series of alcoholato and phenolato magnesium tetrahydroborates have been prepared as solvates (RO)Mg(BH4)(OEt2) by 1:1 reactions of ROH (R = Me, Et, iPr, tBu, CH2CMe3, Et2(tBu)C, Ph3C, Ph, 2, 4, 6‐Me3C6H2, (2, 6‐iPr)2C6H3, (2, 6‐tBu2)C6H3, 2‐(iPrO)C6H4, 2, 6‐(MeO)2C6H3) with diethyl ether solutions of EtMg(BH4). Displacement of diethyl ether by thf, dme, and diglyme produced various solvates (RO)Mg(BH4)(L)n (L = thf, dme, diglyme, n = 1, 2, 3). Most of these compounds are centrosymmetric dimers with a central Mg2O2 four membered ring. Irrespective of the composition, the 11B NMR signals are 1:4:6:4:1 quintets showing that the hydrogen atoms of the BH4 groups are magnetically equivalent. The molecular structure of eight compounds [(RO)Mg(BH4)(OEt2)]2 (R = iPr, tBu, tBuCH2, Et3C, Me3Si), [(PhO)Mg(BH4)(thf)2]2, (2, 6‐tBu2C6H3O)Mg(BH4)(thf)2, (2, 6‐tBu2C6H3O)‐Mg(BH4)(thf)(dme)) have been determined. Typical for all compounds are hexacoordinated Mg atoms. The mononuclear complexes feature bidentate BH4 groups while dinuclear species show di‐ or tridentate BH4 groups depending on the number of coordinated O atoms. Mononuclear species are obtained only for compounds with bulky R groups, e. g. 2, 6‐(tBu2)(C6H3O)Mg(BH4)(thf)2 with tridentate BH4 groups. This compound has a linear O‐C‐Mg unit. In Me2SO the compound [(2‐iPrO)C6H4O]Mg(BH4)(OEt2) underwent ligand exchange to produce [(2‐iPrO)C6H4O]2Mg(OSMe2)]2. Reaction of EtMgBH4 with a stoichiometric amount (1:1) of (Me3Si)2NH gives [((Me3Si)2N)‐Mg(BH4)(OEt2)]2, 46 with a tridentate BH4 group. Its diethyl ether molecule can be replaced by thf, dme and diglyme. Amongst these solvates the compound [(Me3Si)2N]Mg(BH4)(diglyme) is mononuclear and its structure shows a bidentate BH4 group. Compound 46 on repeated crystallization from diethyl ether is transformed into [(Me3SiO)Mg(BH4)(OEt2)]2. No compound with a BH4 group bonded to two Mg atoms has so far been found.