Ring-shaped phosphinoamido-magnesium-hydride complexes : syntheses, structures, reactivity, and catalysis

A.S. is grateful to the Australian Research Council for project support and a fellowship.A series of magnesium(II) complexes bearing the sterically demanding phosphinoamide ligand, L−=Ph2PNDip−, Dip=2,6-diisopropylphenyl, including heteroleptic magnesium alkyl and hydride complexes are described. The ligand geometry enforces various novel ring and cluster geometries for the heteroleptic compounds. We have studied the stoichiometric reactivity of [(LMgH)4] towards unsaturated substrates, and investigated catalytic hydroborations and hydrosilylations of ketones and pyridines. We found that hydroborations of two ketones with pinacolborane using various Mg precatalysts is very rapid at room temperature with very low catalyst loadings, and ketone hydrosilylation using phenylsilane is rapid at 70 °C. Our studies point to an insertion/σ-bond metathesis catalytic cycle of an in situ formed “MgH2” active species.PostprintPostprintPeer reviewe

Extremely bulky β-diketiminate complexes of calcium(II) and ytterbium(II)

This research was supported by the Australian Research Council.The potassium salt of an extremely bulky β-diketiminate, [K(Ar*Nacnac)] (Ar*Nacnac = [(Ar*NCMe)2CH]-; Ar* = C6H2Me{C(H)Ph2}2-4,2,6) was reacted with either CaI2 or YbI2(THF)2, which afforded [(Ar*Nacnac)MI] (M = Ca or Yb). These are the first examples of structurally characterised, donor solvent free, N-arene substituted β-diketiminato calcium/ytterbium complexes that incorporate a terminal iodide ligand. Reduction of [(Ar*Nacnac)CaI] with sodium metal gave a complex product mixture, from which a few crystals of the β-diketiminate C-H activated product, [{Ca(μ-Ar*Nacnac-H)}2], were obtained and crystallographically characterised. In an attempt to form a terminal ytterbium hydride compound, treatment of [(Ar*Nacnac)YbI] with K[HBEt3] gave a good yield of the contact ion pair compound [(Ar*Nacnac)Yb(HBEt3)].Publisher PDFPeer reviewe

A molecular aluminium fulleride

Funding: The project was financially supported by the Deutsche Forschungsgemeinschaft (DFG, KR4782/3-1), the EPSRC (PhD studentship for S. R. L.; EP/N509759/1), and the Chemnitz University of Technology.The reaction of alumylene [(Dippnacnac)Al] (1) with C60 fashions the first example of a structurally characterised aluminium-fulleride complex, [{(Dippnacnac)Al}3C60] (2), in which the Al centres are covalently bound to significantly elongated 6:6 bonds. Hydrolysis of 2 yields C60H6 and the reaction of 2 with [{Mesnacnac)Mg}2] cleaved the Al fragments by affording the fulleride [{Mesnacnac)Mg}6C60].PostprintPeer reviewe

Synthesis and attempted reductions of bulky 1,3,5-triazapentadienyl groups 2 and 13 halide complexes

This research was supported by the Australian Research Council and the US Air Force Asian Office of Aerospace Research and Development (grant FA23861141114043 to CJ).Three extremely bulky 1,3,5-triazapentadienes, ArNNNH (ArNNN = N{C(But)=N(Ar)}2; Ar = Mes (mesityl), Dep (2,6-diethylphenyl) or Dip (2,6-diisopropylphenyl)) have been prepared and structurally characterized. These are readily deprotonated, yielding a series of lithium and potassium triazapentadienyl complexes, one of which, (DipNNN)Li, has been structurally characterized. Similarly, three monomeric triazapentadienyl magnesium iodide complexes, (ArNNN)MgI(OEt2), and a dimeric calcium counterpart, {(MesNNN)Ca(THF)(μ-I)}2, have been prepared. Attempts to reduce the former gave homoleptic bis(triazapentadienyl) magnesium complexes, (ArNNN)2Mg (Ar = Mes or Dep) as the main products. One reaction also gave a very low yield of the magnesium(I) dimer, {(DepNNN)Mg−}2, which was structurally characterized. In related chemistry, two triazapentadienyl boron difluoride compounds, (ArNNN)BF2 (Ar = Mes or Dep), have been synthesized, and unsuccessful attempts made to reduce these to boron(I) heterocycles. For sake of comparison, attempts have been made to prepare a series of related amino-substituted β-diketiminato group 13 element(I) heterocycles. While these were also not successful, several group 13 element(III) halide complexes incorporating this ligand class, and related amino-substituted β-diketiminates, have been characterized.PostprintPeer reviewe

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

Thermal rearrangement of a 1,2-bis(silylene) : synthesis and crystal structure of a silyl-silylene

This research was supported by the Australian Research Council.Thermal rearrangement of the 1,2-bis(silylene), [{(4-ButPh)C(NDip)2}Si−]2 (Dip = 2,6-diisopropylphenyl, leads to the silyl-silylene, {(4-ButPh)C(NDip)2}Si−Si(H) {N(Dip)C(=NDip)(4-ButPh-H)}, via an intramolecular C−H activation reaction. The X-ray crystal structure, and limited spectroscopic data, for the compound are reported. The structure of the silyl-silylene incorporates an exocyclic imine fragment, which is unprecedented for this compound class.Publisher PDFPeer reviewe

A facile synthesis of Robinson’s NHC-stabilised diborane(4)

Reactions of bis(pinacolato)diboron (B2pin2) with [(IDip)AlH3] (IDip = (HCNDip)2C:, Dip = 2,6-iPr2C6H3) afforded both the new diborane [(IDip)BH2B(pin)] and the known compound [(IDip)BH2BH2(IDip)] in a facile one-pot procedure; the latter reaction is improved by the addition of free IDip. [(IDip)AlH3] transfers both IDip and hydride ligands to the diborane moiety in a halide-free approach. [(IDip)BH2B(pin)] was structurally and spectroscopically characterised and additional spectroscopic data for [(IDip)BH2BH2(IDip)] is reported.Publisher PDFPeer reviewe

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Si la adolescencia fue descubierta a finales del siglo XIX, y se democratizó en la primera mitad del XX, la segunda mitad del siglo ha presenciado la irrupción de la juventud, ya no como sujeto pasivo sino como actor protagonista en la escena pública

Low coordinate magnesium sulfide and selenide complexes

Funding: Authors thank the University of St Andrews and the EPSRC doctoral training grant (EP/N509759/1) for support. We gratefully acknowledge computational support via the EaStCHEM Research Computing Facility.The reactions of [{(iPrDipNacNac)Mg}2] 1 (iPrDipnacnac = HC(iPrCNDip)2) with Ph3P═O at 100 °C afforded the phosphinate complex [(iPrDipNacNac)Mg(OPPh3)(OPPh2)] 3 . Reactions of 1 with Ph3P═E (E = S, Se) proceeded rapidly at room temperature to low-coordinate chalcogenide complexes [{(iPrDipNacNac)Mg}2(μ-S)] 4 and [{(iPrDipNacNac)Mg}2(μ-Se)] 5 , respectively. Similarly, reactions of RNHC═S ((MeCNR)2C═S with R = Me, Et, or iPr) with 1 afforded NHC adducts of magnesium sulfide complexes, [{(iPrDipNacNac)Mg(RNHC)}(μ-S){Mg(iPrDipNacNac)}] 6 , that could alternatively be obtained by adding the appropriate RNHC to sulfide complex 4 . Complex 4 reacted with 1-adamantylazide (AdN3) to give [{(iPrDipNacNac)Mg}2(μ-SN3Ad)] 7 and can form various simple donor adducts in solution, of which [(iPrDipNacNac)Mg(OAd)}2(μ-S)] 8a (OAd = 2-adamantanone) was structurally characterized. The nature of the ionic Mg–E–Mg unit is described by solution and solid-state studies of the complexes and by DFT computational investigations.Publisher PDFPeer reviewe