Periodic Table |
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Lewis Acid/Base Interaction Matrix Database
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Type 5 Lewis Acid/Base Complexation Chemistry |
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Saline Hydrides | |
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Bonding: | Group I & II alkali and alkaline earth hydrides exist as ionic lattice solids. However, molecular 1:1 (LiH) and 1:2 (MgH2) complexes are formed in the vapor phase, although with difficulty as the compounds are liable to decompose back to elemental form. LiH is a much theoretically studied diatomic species. Studies show that bonding involves more than just s-LUMO/s-HOMO overlap. In valence bond (VB) terminology, the lithium’s 2s-LUMO mixes with (ie hybridizes with) a higher energy empty 2p orbital (ie the LUMO + 1 MO) to generate a directional sp hybrid bond. MO calculations show that the bonding in LiH involves 66% Li 2s/H1s overlap and 34% Li 2p/H 1s overlap. |
Charge: | The charge on a Type 5 complex is always neutral. |
Chemistry: | Saline hydride complexes either act as strong proton abstracting Bases or as donors of nucleophilic hydride ion. Organic chemists employ saline hydride complexes as proton abstracting Bases, with H2 being the conjugate Brønsted acid. Sodium hydride readily abstracts a proton from dimethyl sulfoxide (DMSO), pKa 35, to form sodium dimsyl: ![]() Inorganic chemists are more likely to use saline hydride reagents as a source of nucleophilic (and reducing) hydride ion, for example in the synthesis of sodium borohydride: ![]() |
Congeneric Series: | ![]() LiH NaH KH RbH CsH BeH2 MgH2 CaH2 SrH2 BaH2 |
Type 5 Lewis acid/base complex (generic)![]() |
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Barium hydride more here |
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Beryllium hydride more here |
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Calcium hydride more here |
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Cesium hydride more here |
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Lithium hydride more here |
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Magnesium hydride more here |
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Potassium hydride more here |
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Rubidium hydride more here |
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Sodium hydride more here |
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Strontium hydride more here |