Ligand Exchange Reaction Between an Alkylzinc Primary Amide and a Dialkylmagnesium Compound:  Crystal Structures of [(thf)MeMg-μ-N(H)SiiPr₃]₂ and (tmeda)Mg[N(H)SiiPr₃]₂

Abstract

The reaction of alkylzinc triisopropylsilylamide with dialkylmagnesium leads to a ligand exchange. Besides the starting materials, heteroleptic alkylmagnesium triisopropylsilylamide and homoleptic magnesium bis(triisopropylsilylamide) are detected by NMR spectroscopy. After the addition of 1,2-bis(dimethylamino)ethane (TMEDA) to the reaction mixture, (tmeda)Mg[N(H)SiiPr3]2 (1) precipitates as colorless cuboids (C24H60MgN4Si2, a = 2269.6(2), b = 1029.58(5), c = 1593.2(1) pm, beta = 120.826(8) degrees , monoclinic, C2/c, Z = 4). The amide nitrogen atoms are coordinated planarily with strongly widened Mg-N-Si bond angles of 139.2(1) degrees . The metalation of triisopropylsilylamine with dimethylmagnesium in THF yields quantitatively heteroleptic [(thf)MeMg-N(H)SiiPr3]2 (2) which crystallizes as colorless needles (C28H66Mg2N2O2Si2, a = 1982.4(2), b = 2034.1(1), c = 907.22(6) pm, beta = 95.021(9), monoclinic, P2(1)/n, Z = 4). Because of the bridging position of the triisopropylsilylamide anion, the tetracoordinate nitrogen atoms show rather long Mg-N bond lengths of 210.7 pm (average value).

Recent developments in the field of organic heterobimetallic compounds of the alkaline-earth metals

“…Even though a dialkylamidozincate has to be an intermediate it was not possible to detect a zincate species in the course of this reaction. 73 The electronegativity difference between magnesium and mercury (D(EN) = 0.69) is larger than for zinc and similar to the D(EN) value between lithium and zinc. Despite this larger difference magnesium mercurates have no significant importance in application.…”

Advances in alkaline earth-nitrogen chemistry

“…A similar approach was used by Westerhausen et al with the use of bidentate TMEDA to isolate Mg[N(H)(Si i Pr 3 )] 2 (tmeda) [93]. The aforementioned compounds are all monomeric in nature, however when pentafluroaniline, H 2 N(Ar F ) is employed in the presence of THF, a trimer is obtained where each Mg atom is bridged by three 2 -anions, [{(Ar F NH) 6 Mg 3 ·(thf) 6 }·2Tol·THF] [94].…”

Lewis Base Assisted Magnesium Complexes Incorporating Pyrrolyl and Ketiminate Ligands: Synthesis, Structural Diversity and Characterization

“…However, magnesium complexes incorporating all nitrogen or heteroatom coordinated ligands are less explored. [10][11][12][13][14][15][16][17] In this regard, we are trying to develop new organomagnesium complexes with non-carbon coordinated ligands and searching its vast application in organic synthesis.…”