New Amides, Amidinides and Mixed-metal Derivatives Thereof in Magnesium Chemistry

Download or read book New Amides, Amidinides and Mixed-metal Derivatives Thereof in Magnesium Chemistry written by René B. Rowlings and published by . This book was released on 1998 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research has been directed towards the development of organonitrogen-magnesium chemistry, focusing on amide ligands mainly, and on amidinide ligands to a lesser extent. New compounds have been characterised by elemental analyses and NMR spectroscopic studies and seventeen of them have been crystallographically authenticated by X-ray diffraction. Within the area of dianionic ligands, it has been found that deprotonating 1,8-diaminonaphthalene twice with dibutylmagnesium leads to [{(1,8-C10H6(NH)2)Mg.HMPA}3.2THF], the first magnesium amide trimer, having an unprecedented N6Mg3 cage structure. In contrast, treating the diamines N,N'diphenylethylenediamine or N,N' -dibenzylethylenediamine with the same reagent in the same stoichiometry produces [{MgN(Ph)CH2CH2N(Ph).2THF(1.5THF)}2], [{MgN(CH2Ph)CH2CH2N(CH2Ph).HMPA}2], or [MgN(Ph)CH2CH2N(Ph).2HMPA], which adopt more conventional dimeric ring or monomeric structures. Also, the novel magnesium aluminate salt, [Mg(HMPA)4.2AlMe4], has been synthesised serendipitously from an attempt to make a mixed-metal diamide complex. Within the area of monoanionic ligands, two structurally related mixed lithium-magnesium amides, [{(Me3Si)2N}13LiMg] and [{(c-C6H11)2N}3LiMg.THF], based on discrete (NLiNMg) cyclic cores, have been prepared. Further exploration of the hexamethyldisilazide has opened up a remarkable new area of macrocyclic chemistry. Thus, magnesium-substituted derivatives of classical alkali metal amide ring structures, [{(Me3Si)2N}4Li2Mg2(02)x(O)y] and [{(Me3Si)2N}4Na2Mg2(02)x(O)y], having oxo or peroxo core dianions for charge balance, have been established. The tetramethylpiperidide analogue, [{Me2CCH2CH2CH2(Me)2CN}4Li2Mg2(O)], has also been made. In an extension of this work, a larger twelve-membered (N6Na4Mg2)2+ cationic ring system have been realised through [{Me2C(CH2)3(Me)2CN}6Na4Mg2{C6H3(CH3)}] and [{Me2C(CH2)3(Me)2CN}6}Na4Mg2(C6H4)}]. This ring acts as a templating host for the selective di-deprotonation of toluene and benzene respectively, the dianions of which occupy the ring centre. Possible insight into the mechanism of arene incorporation in these macro cycles is gained through the structure of [{(Me3Si)2N}6K2Mg2.4{C6H5(CH3)}], the first potassium amido magnesate species. Finally, two magnesium and one lithium-magnesium amidinide structures, [{PhNC(Ph)NPh}2Mg.2DMSO,C6H5CH3] [{PhNC(Ph)NPh}2Mg.2HMPA,C6H5CH3] and [{PhC(NSiMe3)2}4Li4Mg(O)] respectively, have been reported.