Lithium tetrahydroborate reaction with

Alkali-metal tetrahydraborate reduction of phosphorus halides is of limited utility . Lithium tetrahydroborate reaction with PClj or PClj in Et20 at — 80°C produces PHj, but yields are low" ... 

Zirconium(IV) and hafnium(IV) tetrakis(tetrahydroborates) M(BH4)4 are of interest as extremely volatile, covalent complexes that contain tridentate BH ligands and exhibit rapid intramolecular exchange of bridging and terminal hydrogen atoms. 4,615 These compounds were prepared initially from NaMF5 (M = Zr or Hf) and excess A1(BH4)3 (equation 53),616 but they are obtained more conveniently from the reaction of the anhydrous metal tetrachloride with excess lithium tetrahydroborate (equation 54), either in the solid state617,618 or in the presence of a small amount of diethyl ether.619... 

The chemical reactions of M(BH )4 complexes have received very little attention. Both compounds behave as Lewis adds in reactions with tetraalkylammonium and lithium tetrahydroborates, yielding [(C8Hi7)3NPr][M(BH4)5], [NBu4][M(BH4)5] and LiM(BH4)5.620 Zr(BH4)4 reacts with LiAlH4 in ether to give Zr(AlH4)4, an unstable white solid, which decomposes within several hours at room temperature to a pyrophoric black solid.617... 

The reaction of boron trifluoride etherate with a solution of lithium tetrahydroborate in a simple ether or in dioxan (278, 280) is of importance, not only as the first reaction of this kind to be discovered, but also as the first reaction of any kind found to produce... 

Treatment of thiiranes with lithium aluminum hydride gives a thiolate ion formed by attack of hydride ion on the least hindered carbon atoms (76RCR25), The mechanism is 5n2, inversion occurring at the site of attack. Polymerization initiated by the thiolate ion is a side reaction and may even be the predominant reaction, e.g. with 2-phenoxymethylthiirane. Use of THF instead of ether as solvent is said to favor polymerization. Tetrahydroborates do not reduce the thiirane ring under mild conditions and can be used to reduce other functional groups in the presence of the episulfide. Sodium in ammonia reduces norbornene episulfide to the exo thiol. 

Long and Wallbridge 120> report the preparation of mixed methyl derivatives of diborane(6) from the reaction of trimethylborane with lithium or sodium tetrahydroborate(— 1) and hydrogen chloride in the presence of suitable Lewis acid. 

Volatile hydrides may be prepared from ether solutions by the reaction of the appropriate chlorides with lithium tetrahydroaluminate. In this general method, it is necessary to work with strictly anhydrous reagents and solvents because of the great reactivity of lithium tetrahydro-aluminate toward water. The procedures described below are believed to be much more convenient because the reducing agent employed is potassium tetrahydroborate, which is relatively insensitive toward water. Since only aqueous solutions are involved, there are no solvent-purification steps and there is no dissolution or contamination of stopcock grease, etc. 

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