1319205-95-2Relevant articles and documents
Thermal decomposition of mono- and bimetallic magnesium amidoborane complexes
Spielmann, Jan,Piesik, Dirk E.-J.,Harder, Sjoerd
experimental part, p. 8307 - 8318 (2010/09/10)
Complexes of the type [(DIPPnacnac)MgNH(R)BH3] have been prepared (DIPPnacnac=CH{(CMe)(2,6-iPr2C6H 3N)}2). The following substituents R have been used: H, Me, iPr, DIPP (DIPP = 2,6-diisopropylphenyl). Complexes [(DIPPnacnac)MgNH 2BH3]·THF, [{(DIPPnacnac)MgNH(iPr)BH 3}2] and [(DIPPnacnac)MgNH(DIPP)BH3] were structurally characterised. The Mg amidoborane complexes decompose at a significantly higher temperature (90-110°C) than the corresponding Ca amidoborane complexes (20100°C). The complexes with the smaller R substituents (H, Me) gave a mixture of decomposition products of which one could be structurally characterised as [{(DIPPnacnac)Mg}2(H 3BNMe-BH-NMe)·THF. [{(DIPPnacnac)MgNH(iPr)BH3} 2] cleanly decomposed to [(DIPPnacnac)MgH], which was characterised as a dimeric THF adduct. The amidoborane complex with the larger DIPP-substituent decomposed into a borylamide complex [(DIPPnacnac)MgN (DIPP)BH2], which was structurally characterised as its THF adduct. Bimetallic Mg amidoborane complexes decompose at lower temperatures (60-90°C) and show a different decomposition pathway. The dinuclear Mg amidoborane complexes presented here are based on DIPPnacnac units that are either directly coupled through N-N bonding (abbreviated NN) or through a 2,6-pyridylene bridge (abbreviated PYR). Crystal structures of [PYR-{Mg(nBu)}2], [PYR-(MgNH(iPr)BH3}2], [NN{MgNH(iPr)BH3}2]·THF and the decomposition products [PYR-Mg2(iPrN-BH-iPrN-BH3)] and [NN-Mg 2(iPrNBH-iPrN-BH3)]·THF are presented. The following conclusions can be drawn from these studies: i)The first step in the decomposition of a metal amidoborane complex is β-hydride elimination, which results in formation of a metal hydride complex and R(H)N=BH2, ii) depending on the nature of the metal, the metal hydride is either stable and can be isolated or it reacts further, iii) amidoborane anions with small R substituents decompose into the dianionic species (RN-BHRN-BH3) 2-, whereas large substituents result in formation of the borylamide RN=BH2- and iv) enforced proximity of two Mg amidoborane units results in decomposition at a significantly lower temperature and cleanly follows the BNBN pathway.
