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(BH 4 )(OEt 2 ) by 1:1 reactions of ROH (R = Me, Et, i Pr, t Bu, CH 2 CMe 3 , Et 2 ( t Bu)C, Ph 3 C, Ph, 2, 4, 6‐Me 3 C 6 H 2 , (2, 6‐iPr) 2 C 6 H 3 , (2, 6‐tBu 2 )C 6 H 3 , 2‐( i PrO)C 6 H 4 , 2, 6‐(MeO) 2 C 6 H 3 ) with diethyl ether solutions of EtMg(BH 4 ). Displacement of diethyl ether by thf, dme, and diglyme produced various solvates (RO)Mg(BH 4 )(L) n (L = thf, dme, diglyme, n = 1, 2, 3). Most of these compounds are centrosymmetric dimers with a central Mg 2 O 2 four membered ring. Irrespective of the composition, the 11 B NMR signals are 1:4:6:4:1 quintets showing that the hydrogen atoms of the BH 4 groups are magnetically equivalent. The molecular structure of eight compounds [(RO)Mg(BH 4 )(OEt 2 )] 2 (R = i Pr, t Bu, t BuCH 2 , Et 3 C, Me 3 Si), [(PhO)Mg(BH 4 )(thf) 2 ] 2 , (2, 6‐ t Bu 2 C 6 H 3 O)Mg(BH 4 )(thf) 2 , (2, 6‐ t Bu 2 C 6 H 3 O)‐Mg(BH 4 )(thf)(dme)) have been determined. Typical for all compounds are hexacoordinated Mg atoms. The mononuclear complexes feature bidentate BH 4 groups while dinuclear species show di‐ or tridentate BH 4 groups depending on the number of coordinated O atoms. Mononuclear species are obtained only for compounds with bulky R groups, e. g. 2, 6‐( t Bu 2 )(C 6 H 3 O)Mg(BH 4 )(thf) 2 with tridentate BH 4 groups. This compound has a linear O‐C‐Mg unit. In Me 2 SO the compound [(2‐iPrO)C 6 H 4 O]Mg(BH 4 )(OEt 2 ) underwent ligand exchange to produce [(2‐ i PrO)C 6 H 4 O] 2 Mg(OSMe 2 )] 2 . Reaction of EtMgBH 4 with a stoichiometric amount (1:1) of (Me 3 Si) 2 NH gives [((Me 3 Si) 2 N)‐Mg(BH 4 )(OEt 2 )] 2 , 46 with a tridentate BH 4 group. Its diethyl ether molecule can be replaced by thf, dme and diglyme. Amongst these solvates the compound [(Me 3 Si) 2 N]Mg(BH 4 )(diglyme) is mononuclear and its structure shows a bidentate BH 4 group. Compound 46 on repeated crystallization from diethyl ether is transformed into [(Me 3 SiO)Mg(BH 4 )(OEt 2 )] 2 . No compound with a BH 4 group bonded to two Mg atoms has so far been found.