Search

Femtosecond pump–probe absorption spectroscopy in tetrahydrofuran solution has been used to investigate the dynamics of a metalloid cluster compound {Ge9[Si(SiMe3)3]3}−1. Upon UV photoexcitation, the transients in the near-infrared spectral region showed signatures reminiscent of excess electrons in THF (bound or quasi-free) whereas in the visible part excited state dynamics of the cluster complex dominates. [ABSTRACT FROM AUTHOR]

A chemically assisted top-down method for the synthesis of MOF-nanoplates was developed applying amine based delamination agents. Applied on a well described model structure, the layered MOF Cu 2 (bdc) 2 (DMF) 2 (bdc - 1,4-benzenedicarboxylate), two different strategies of amine assisted delamination turned out to be successful to obtain nanoplates. Particles with thicknesses of around 70 nm were obtained by direct delamination of crystals using octylamine. The surfactant (polyvinylpyrrolidone) assisted synthesis combined with a post-synthetic amine delamination step enabled a further reduction of the thickness of the MOF nanoplates down to 4-14 nm.

A high yield synthesis of a new, extremely bulky anionic gallium(I) N-heterocyclic carbene analogue, [(DAB*)Ga:](-) (DAB* = {N(Ar*)C(H)}(2), Ar* = C(6)H(2){C(H)Ph(2)}(2)Me-2,6,4) has been developed and four monomeric sodium complexes of the heterocycle have been crystallographically characterised. The gallium(I) heterocycle has been utilised in the preparations of the heteroleptic zinc and cadmium gallyl complexes, [(DAB*)GaMX(tmeda)] (M = Zn or Cd, X = Br or I), which were crystallographically characterised. In addition, [(DAB*)Ga:](-) was oxidatively coupled to give the diamagnetic digallane(4), [(DAB*)GaGa(DAB*)]. The moderate yield synthesis of the six-membered gallium(I) heterocycle, [((But)MesNacnac)Ga:] ((But)MesNacnac = [(MesNCBu(t))(2)CH](-), Mes = mesityl), is described, and the compound found to be a monomer in the solid state by an X-ray crystallographic analysis. A low yield by-product from this synthesis, [Ga(5)I(4)((But)MesNacnac)(3)], was also isolated and shown by X-ray crystallography to be a rare example of a compound bearing a group 13 metal-metal bonded chain stabilised by β-diketiminate ligands. A preliminary analysis of the bonding in the compound was carried out using DFT calculations.

Reductions of the β-diketiminato group 14 metal(II) chloride complexes, [((But)MesNacnac)ECl] ((But)MesNacnac = [(MesNCBu(t))(2)CH](-); Mes = mesityl; E = Ge, Sn or Pb), with a magnesium(I) dimer have led to differing outcomes, which include the formation of the first β-diketiminato group 14 metal(I) dimer, [{((But)MesNacnac)Sn}(2)]., (This journal is © The Royal Society of Chemistry 2012)

The preparation of a series of extremely bulky secondary amines, Ar*N(H)SiR(3) (Ar* = C(6)H(2){C(H)Ph(2)}(2)Me-2,6,4; R(3) = Me(3), MePh(2) or Ph(3)) is described. Their deprotonation with either LiBu(n), NaH or KH yields alkali metal amide complexes, several monomeric examples of which, [Li(L){N(SiMe(3))(Ar*)}] (L = OEt(2) or THF), [Na(THF)(3){N(SiMe(3))(Ar*)}] and [K(OEt(2)){N(SiPh(3))(Ar*)], have been crystallographically characterised. Reactions of the lithium amides with germanium, tin or lead dichloride have yielded the first structurally characterised two-coordinate, monomeric amido germanium(II) and tin(II) chloride complexes, [{(SiR(3))(Ar*)N}ECl] (E = Ge or Sn; R = Me or Ph), and a chloride bridged amido-lead(II) dimer, [{[(SiMe(3))(Ar*)N]Pb(μ-Cl)}(2)]. DFT calculations on [{(SiMe(3))(Ar*)N}GeCl] show its HOMO to exhibit Ge lone pair character and its LUMO to encompass its Ge based p-orbital. A series of bulky amido silicon(IV) chloride complexes have also been prepared and several examples, [{(SiR(3))(Ar*)N}SiCl(3)] (R(3) = Me(3), MePh(2)) and [{(SiMe(3))(Ar*)N}SiHCl(2)], were crystallographically characterised. The sterically hindered group 14 complexes reported in this study hold significant potential as precursors for kinetically stabilised low oxidation state and/or low coordination number group 14 complexes.

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-)1 can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. So the reaction of 1 with Cr(CO)(3)(CH(3)CN)(3) leads to a cluster enlargement where the chromium atom is incorporated into the cluster core. Here further applications of 1 as a flexible ligand in coordination chemistry are presented where the reaction of 1 with Mo(CO)(3)(EtCN)(3) and W(CO)(3)(CH(3)CN)(3) leads to [(CO)(3)MoGe(9)R(3)](-)4 and [(CO)(3)WGe(9)R(3)](-)5 respectively (R = Si(SiMe(3))(3)), showing that 1 can indeed be used as a flexible ligand in coordination chemistry. Structural and electronic properties of the Ge(9)M clusters 4 and 5 are discussed as well as mechanistic aspects of their formation., (This journal is © The Royal Society of Chemistry 2011)

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-) can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. So the reaction of with M(+) sources of group 11 metals gives metalloid cluster compounds of the formulae {MGe(18)[Si(SiMe(3))(3)](6)}(-) (M = Au, Ag, Cu). These reactions can be seen as first steps into a supramolecular chemistry with metalloid cluster compounds. However, further build-up reactions lead to insoluble products, thus better soluble starting materials are needed for further build-up reactions. Here the first neutral MGe(18)[Si(SiMe(3))(3)](6) (M = Hg, Cd, Zn) compounds are described, exhibiting a strongly enhanced solubility in inert solvents. Beside the synthesis, the structural properties as well as the bonding situations in these cluster compounds are discussed.

The reactions of the metalloid cluster {Ge9[Si(SiMe3)3]3}- with Cr(CO)5COE (COE=cyclooctene) and Cr(CO)3(CH3CN)3 lead to the new cluster compounds {Ge9[Si(SiMe3)3]3Cr(CO)5}- and {Ge9[Si(SiMe3)3]3Cr(CO)3}-, whose structural and electronic properties are presented.

The reaction of Ar(3)GeBr (Ar = 2,6-(OtBu)(2)C(6)H(3)), which is the side product of the synthesis of the metalloid germanium cluster compound Ge(8)Ar(6), with the silver salt of the weakly coordinating anion (WCA) [Al(OR(f))(4)](-) (R(f) = C(CF(3))(3)) gives the free germyl cation Ar(3)Ge(+). Quantum chemical calculations open an insight into the bonding situation of this first free cation exhibiting aryl ligands and a first reaction leading to Ar(3)GeOH is presented.

The reaction of GeBr with LiGe(SiMe(3))(3) yields the largest metalloid cluster compound of germanium Ge(14)[Ge(SiMe(3))(3)](5)Li(3)(THF)(6), in which 14 germanium atoms are arranged as a hollow sphere in the cluster core, showing that in the case of germanium also fullerene-like compounds might be present in the borderland between the molecular and solid states.

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-) can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. Here further reactions of with M(+) sources of group 11 metals are described, leading to metalloid cluster compounds of the formula {MGe(18)[Si(SiMe(3))(3)](6)}(-) (M = Ag, Cu). These reactions can be seen as first steps into a supramolecular chemistry with metalloid cluster compounds. Beside this feature, the structural properties as well as the bonding situations in these cluster compounds are discussed.

Cluster compounds of germanium exhibiting germanium-germanium bonds, where the germanium atoms are additionally bound to transition metal ligands, are rare. Here a synthetic pathway to such cluster compounds is described, starting from metastable Ge I halide solutions leading to the two cluster compounds Ge4Br4[Mn(CO)5]4 and Ge6Br2[Mn(CO)5]6, being the first examples of germanium cluster compounds bearing Mn(CO)5 ligands. The Ge6 compound exhibits a novel arrangement of germanium atoms that has not been previously observed in ligand stabilized cluster compounds of germanium, neither with organic nor with transition metal ligands. The bonding situation inside the cluster compounds is discussed, together with a possible reaction pathway that opens the way to metalloid cluster compounds of germanium exhibiting Mn(CO)5 ligands.