Structure and photoluminescence of Ge nanoparticles with different sizes embedded in SiO2 glasses fabricated by a sol–gel method

Metalloid Cluster Compounds of Germanium: Synthesis – Properties – Subsequent Reactions

“…The reaction of the GeBr emulsion, described before, with LiN(SiMe 3 ) 2 leads to the metalloid cluster compound Ge 8 [N(SiMe 3 ) 2 ] 6 (1), [19] where six ligand-bound and two naked germanium atoms are present in the cluster core. The eight germanium atoms in 1 are arranged in the form of a distorted cube, as two different Ge-Ge distances of 250 and 267 pm are found inside the cluster core ( Figure 3).…”

“…Hence, the bonding situation inside the anionic compound 7 is comparable to that found in the Zintl anions or in the metalloid cluster compounds 3 and 4 depending on whether the transition-metal ligand is counted as a neutral Cr(CO) 5 or as a dianionic [Cr(CO) 5 ] 2-ligand. Nevertheless, this first result reveals that transition-metal ligands can be used for the synthesis of germanium cluster compounds, and very recently the first metalloid cluster compound of germanium, (thf) 18 Na 6 Ge 10 [Fe(CO) 4 ] 8 (8), was synthesized by the reaction of a GeBr solution with Collmann's reagent, Na 2 Fe(CO) 4 . [36] The arrangement of the ten germanium atoms in the cluster core of 8 is totally different from that of the two other Ge 10 compounds, 5 and 6, showing that an adamantine-like arrangement must not necessarily occur when ten germanium atoms are present in the cluster core of a metalloid cluster compound.…”

“…Eight of the ten germanium atoms inside the cluster core of 8 are bound to one Fe(CO) 4 ligand each and the Fe(CO) 4 ligands are bound through the CO molecules to six sodium cations, which surround the cluster in a pseudooctahedral fashion. The sodium cations are coordinatively saturated by three thf molecules each, leading to the neutral compound (thf) 18 Na 6 Ge 10 [Fe(CO) 4 ] 8 (8), which can be dissolved and recrystallized from thf. A closer look into the bonding situation inside the cluster core was taken with the aid of quantum chemical calculations on the model compound {Ge 10 [Fe(CO) 4 ] 8 } 6-(8Ј), which revealed that inside the different sides of the centaur polyhedra different bonding situations are also present (Figure 7).…”

“…Taking a look at the space-filling models of the metalloid cluster compounds Ge 8 [N(SiMe 3 ) 2 ] 6 (1), Ge 6 Ar 2 (3) (Ar = C 6 H 3 Dipp 2 ; Dipp = C 6 H 3 -2,6-iPr 2 ), {Ge 9 (6), as shown in Figure 8 reveals that the naked germanium atoms are well shielded by the ligand shell in nearly all cases. However, in the anionic compound {Ge 9 [Si(SiMe 3 ) 3 ] 3 } -(4), the three Si(SiMe 3 ) 3 ligands shield the cluster core only incompletely against the exterior, and the three-membered rings of naked germanium atoms are not protected by the ligand shell.…”

“…[7] Such small nanoparticles exhibit a molecular character and can no longer be seen as a small crystalline piece of germanium having a diamond lattice. [8] They are better described as molecular metalloid cluster compounds, featuring the general molecular formula Ge n R m (n Ͼ m), where R is any ligand or substituent bound to the surface germanium atoms. In contrast to the ligandbound germanium atoms at the surface, the internal germanium atoms only form Ge-Ge bonds.…”