Binuclear magnesium amidoborane complexes: characterization of a trinuclear thermal decomposition product

Abstract

The bis-β-diketimine with a meta-phenylene bridge (META-H₂: DIPPN(H)CMeCHCMeN–C₆H₄–NCMeCHCMeN(H)DIPP; DIPP = 2,6-iPr-C₆H₃) reacted with two equivalents of nBu₂Mg to give the bis-β-diketiminate complex META-(MgnBu)₂. The latter binuclear magnesium complex was converted to META-[MgNH(iPr)BH₃]₂ by reaction with H₂N(iPr)BH₃. The thermal decomposition of this binuclear iPr-substituted magnesium amidoborane complex has been investigated. In benzene it starts to eliminate H₂ at 90 °C. Two decomposition products could be obtained by fractional crystallization of the residue. The first product is the trinuclear magnesium complex META-Mg₃[iPrNB(H)N(iPr)BH₃]₂ and the second product is (META-Mg)₂. These products have been formed by ligand exchange reactions of the expected complex META-Mg₂[iPrNB(H)N(iPr)BH₃] and were characterized by single crystal X-ray diffraction. The central Mg²⁺ ion in META-Mg₃[iPrNB(H)N(iPr)BH₃]₂ is not connected to the ligand system and its coordination geometry could be representative of that in a solid-state magnesium salt containing the RNB(H)N(R)BH₃²⁻ ion.