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

The bis-β-diketimine with a meta-phenylene bridge (META-H(2): DIPPN(H)CMeCHCMeN-C(6)H(4)-NCMeCHCMeN(H)DIPP; DIPP = 2,6-iPr-C(6)H(3)) reacted with two equivalents of nBu(2)Mg to give the bis-β-diketiminate complex META-(MgnBu)(2). The latter binuclear magnesium complex was converted to META-MgNH(iPr)BH(3) by reaction with H(2)N(iPr)BH(3). The thermal decomposition of this binuclear iPr-substituted magnesium amidoborane complex has been investigated. In benzene it starts to eliminate H(2) at 90 °C. Two decomposition products could be obtained by fractional crystallization of the residue. The first product is the trinuclear magnesium complex META-Mg(3)iPrNB(H)N(iPr)BH(3) and the second product is (META-Mg)(2). These products have been formed by ligand exchange reactions of the expected complex META-Mg(2)[iPrNB(H)N(iPr)BH(3)] and were characterized by single crystal X-ray diffraction. The central Mg(2+) ion in META-Mg(3)iPrNB(H)N(iPr)BH(3) 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)BH(3)(2-) ion.