Synthesis, characterization, and computational analysis of the dialanate dianion, [H3Al-AlH3]2− : a valence isoelectronic analogue of ethane

C.J. and A.S. gratefully acknowledge financial support from the Australian Research Council, while C.J. thanks the U.S. Air Force Asian Office of Aerospace Research and Development (FA2386-14-1-4043) for funding. G.F. acknowledges financial support from the Deutsche Forschungsgemeinschaft.The first example of a well-defined binary, low-oxidation-state aluminum hydride species that is stable at ambient temperature, namely the dianion in [{(DepNacnac)Mg}2(μ-H)]2[H3Al-AlH3] (DepNacnac=[(DepNCMe)2CH]−, Dep=2,6-diethylphenyl), has been prepared via a magnesium(I) reduction of the alanate complex, (DepNacnac)Mg(μ-H)3AlH(NEt3). An X-ray crystallographic analysis has shown the compound to be a contact ion complex, which computational studies have revealed to be the source of the stability of the aluminum(II) dianion.PostprintPeer reviewe

Anion stabilised hypercloso-hexaalane Al6H6

The authors gratefully acknowledge financial support from the Australian Research Council (C.J. and A.S.), the U.S. Air Force Asian Office of Aerospace Research and Development (grant FA2386-18-1-0125 to C.J.), Deutsche Forschungsgemeinschaft (FR 641/25-2) (G.F.), and Director, Bragg Institute, ANSTO, 2011 approval of DB 1959 (A.J.E. and C.J.).Boron hydride clusters are an extremely diverse compound class, which are of enormous importance to many areas of chemistry. Despite this, stable aluminium hydride analogues of these species have remained staunchly elusive to synthetic chemists. Here we report that reductions of an amidinato-aluminium(III) hydride complex with magnesium(I) dimers lead to unprecedented examples of stable aluminium(I) hydride complexes, [(ArNacnac)Mg]2[Al6H6(Fiso)2] (ArNacnac = [HC(MeCNAr)2]-, Ar = C6H2Me3-2,4,6 Mes; C6H3Et2-2,6 Dep or C6H3Me2-2,6 Xyl; Fiso = [HC(NDip)2]-, Dip = C6H3Pri2-2,6), which crystallographic and computational studies show to possess near neutral, octahedral hypercloso-hexaalane, Al6H6, cluster cores. The electronically delocalised skeletal bonding in these species is compared to that in the classical borane, [B6H6]2-. Thus, the chemistry of classical polyhedral boranes is extended to stable aluminium hydride clusters for the first time.Publisher PDFPeer reviewe

Normal and abnormal NHC coordination in cationic hydride iodide complexes of aluminium

We thank the University of St Andrews and the EPSRC UK National Mass Spectrometry Facility (NMSF) at Swansea University.The mixed N-heterocyclic carbene (NHC) complexes NHCAlHxI3-x, where NHC is IDip or IMes ((HCNAr)2C:, Ar = 2,6-iPr2C6H3 = Dip (IDip); or 2,4,6-Me3C6H2 = Mes (IMes)), x = 1 or 2, were either prepared from NHCAlH3 and NHCAlI3 or by halogenation of NHCAlH3 with MeI. Reaction of [(IDip)AlHxI3-x], with x = 0-3, with another equivalent of a IDip afforded either fluxional equilibria in benzene solution for x = 0, no reaction for x = 3, or the new mixed normal-abnormal NHC-coordinated ionic complexes [(IDip)AlH2(aIDip)]I ( 9 ) and [(IDip)AlHI(aIDip)]I ( 10 ), where aIDip is the abnormal IDip carbene tautomer bonded through its 4-position. The molecular structures of 9 and 10 were determined and show slightly shorter Al–C(aIDip) than Al–C(IDip) distances. In addition, a complex containing [(IDip)AlI2(aIDip)]I ( 11 ) was structurally characterized though could not intentionally be synthesised. Possible formation mechanisms for 9 - 11 are discussed and the normal and abnormal IDip coordination to the aluminium(III) centre is believed to occur for steric reasons.PostprintPeer reviewe

Activation of CO by Hydrogenated Magnesium(I) Dimers: Sterically Controlled Formation of Ethenediolate and Cyclopropanetriolate Complexes

International audienceThis study details the formal hydrogenation of two magnesium(I) dimers {(Nacnac)Mg}2 (Nacnac = [{(C6H3R2-2,6)NCMe}2CH]−; R = Pri (DipNacnac), Et (DepNacnac)) using 1,3-cyclohexadiene. These reactions afford the magnesium(II) hydride complexes, {(Nacnac)Mg(μ-H)}2. Their reactions with excess CO are sterically controlled and lead cleanly to different C–C coupled products, viz. the ethenediolate complex, (DipNacnac)Mg{κ1-O-[(DipNacnac)Mg(κ2-O,O-O2C2H2)]}, and the first cyclopropanetriolate complex of any metal, cis-{(DepNacnac)Mg}3{μ-C3(H3)O3}. Computational studies imply the CO activation processes proceed via very similar mechanisms to those previously reported for related reactions involving f-block metal hydride compounds. This work highlights the potential magnesium compounds hold for use in the “Fischer–Tropsch-like” transformation of CO/H2 mixtures to value added oxygenate products

Cobalt(II) Complex of a Diazoalkane Radical Anion

β-Diketiminate cobalt­(I) precursors react with diphenyldiazomethane to give a compound that is shown by computational studies to be a diazoalkane radical anion antiferromagnetically coupled to a high-spin cobalt­(II) ion. Thermolysis of this complex results in formal N–N cleavage to give a cobalt­(II) ketimide complex. Experimental evaluation of the potential steps in the mechanism suggests that free azine is a likely intermediate in this reaction