Nucleophilic Magnesium Silanide and Silaamidinate Derivatives

Bibian Okokhere-Edeghoghon, Maximilian Dehmel, Michael Hill, Robert Kretschmer, Mary Mahon, Claire McMullin, Louis Morris, Nasir Rajabi

OAI: oai:purehost.bath.ac.uk:openaire_cris_publications/b6eecc5c-39a1-453a-a5be-492d92a37ee8 • DOI: https://doi.org/10.1021/acs.inorgchem.0c02034

Density functional theory (DFT) calculations demonstrate that the previously reported reaction of [(BDI)Mgn-Bu] (BDI = HC{(Me)CN-Dipp}2; Dipp – 2,6-di-iso-propylphenyl) with the silaborane, Me2PhSi-Bpin, provides the magnesium silanide derivative, [(BDI)MgSiMe2Ph], through the intermediacy of a short lived silyl-pinacolato-organoborate species. The nucleophilic character of the resultant silanide anion is assayed through a series of reactions with RN=C=NR (R = i-Pr, Cy, t-Bu) and p-tolN=C=Np-tol. When performed in a strict 1:1 stoichiometry, all four reactions result in silyl addition to the carbodiimide carbon center and formation of the corresponding beta-diketiminato magnesium sila-amidinate complexes. Although performance of the reaction of [(BDI)MgSiMe2Ph] with two equivalents of p-tolylcarbodiimide also results in the formation of a sila-amidinate anion, the second equivalent is observed to engage with the nucleophilic gamma-methine carbon of the BDI ligand to provide a tripodal di-imino-iminoamidate ligand. This behaviour is judged to be a consequence of the enhanced electrophilicity of the N-aryl substituted carbodiimide reagent, a viewpoint supported by a further reaction with the N-isopropyl sila-amidinate complex, [(BDI)Mg(i-PrN)2CSiMe2Ph]. This latter reaction not only provides an identical di-imino-iminoamidate ligand but also results in twofold insertion of p-tolN=C=Np-tol into a Mg-N bond between the magnesium center and the sila-amidinate anion.