Equilibrium Coordination of NHCs to Si(IV) Species and Donor Exchange in Donor–Acceptor Stabilized Si(II) and Ge(II) Compounds

Abstract

We report the reversible coordination of the N-heterocyclic carbene (NHC), NHC i Pr 2 Me 2 (NHC iPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), to silicon­(IV)-halides, SiCl4, MeSiCl3, Me2SiCl2, and Me3SiCl. Predicted as well as experimentally determined thermodynamic parameters of these equilibria confirm that the complexation constant increases with the Lewis acidity of the silicon halides. In contrast, the more σ-donating N-heterocyclic carbene, NHC Me 4 (NHCMe 4 = 1,3,4,5-tetramethylimidazol-2-ylidene), does not show any signs of dissociation from the corresponding SiCl4 and Me2SiCl2 adducts even at higher temperatures. As a consequence, NHC i Pr 2 Me 2 in donor–acceptor stabilized Si­(II)- and Ge­(II)-dimethyl complexes, NHC i Pr 2 Me 2 ·GeMe 2 ·Fe­(CO) 4 and NHC i Pr 2 Me 2 ·SiMe 2 ·Fe­(CO) 4 , is readily replaced by NHC Me 4 .

Single‐Source Precursors for the Chemical Vapor Deposition of Iron Germanides

“…Jutzi and Steiner described the sole formation of the solvent‐stabilized germylene complex thf ⋅ GeCl 2 ⋅ Fe(CO) 4 1 upon reaction of GeCl 2 /1,4‐dioxane complex with Fe 2 (CO) 9 in thf (Scheme 1). [15] The analogous reaction of $${{^{{\rm Me}{_{2}}{\rm iPr}{_{2}}}}}$$ NHC ⋅ GeCl 2 results in the corresponding $${{^{{\rm Me}{_{2}}{\rm iPr}{_{2}}}}}$$ NHC ⋅ GeCl 2 ⋅ Fe(CO) 4 [16] ( 3 ), which can be further derivatized by substitution of the chlorides using methyl lithium [17] and by reduction either to an NHC‐substituted [GeFe 3 ] cluster III through further treatment with Fe 2 (CO) 9 [18] or to the dimer [$${{^{{\rm Me}{_{2}}{\rm iPr}{_{2}}}}}$$ NHC ⋅ Ge ⋅ Fe(CO) 4 ] 2 IV using potassium/graphite [16b] . Larger iron‐germanium clusters are accessible by the reaction of organylgermanes with ironcarbonyls as part of typically complex reaction mixtures from which propellane‐stuctured V and VI , [19,20] the trigonal‐bipyramidal VII [19] and the spiro ‐clusters VIII [21] and 4 [19,21] were isolated.…”