Benzannulated N-heterocyclic germylenes and stannylenes with sterically demanding N,N'-substituents.

Four N,N'-disubstituted 1,2-diaminobenzes (1a: R = t-Bu, 1b: R = adamantyl, 1c: R = Ph, 1d: R = Dipp) have been prepared and reacted with E[N(SiMe3)2]2 (E = Ge, Sn) to give the benzannulated N-heterocyclic germylenes 2a-d and stannylenes 3a-d. Germylene 2d and stannylenes 3a, 3c and 3d have been characterized by X-ray diffraction showing different types of intermolecular interactions in the solid state. Deprotonation of 1b with n-BuLi yields the lithium stannyl anion Li[4] with an n-Bu group bound to the tin(II) center.

Metastable 11 K superconductor Na(1-y)Fe(2-x)As2.

The topochemical deintercalation of Na(+) ions from solid NaFeAs at room temperature in THF with iodine yields the superconducting phase Na(1-y)Fe(2-x)As(2) (T(c) ≈ 11 K). This metastable iron arsenide decomposes at 120 °C and is not accessible by high-temperature solid-state synthesis. X-ray powder diffraction confirms the ThCr(2)Si(2)-type structure, but reveals very small coherently scattering domains with a mean composition Na(0.9(2))Fe(1.7(1))As(2). HRTEM investigations show crystalline as well as strongly distorted areas with planar defects. The latter are probably due to sodium loss and disorder which is also detected by (23)Na solid state NMR. The (57)Fe-Mössbauer spectrum of Na(1-y)Fe(2-x)As(2) shows one type of iron atoms in tetrahedral coordination. All results point to one crystallographic phase with very small domains due to fluctuations of the chemical composition. From electronic reasons we suggest the superconducting phase is presumably NaFe(2)As(2) in the ordered fractions of the sample.

Doped semimetal clusters: ternary, intermetalloid anions [Ln@Sn7Bi7]4- and [Ln@Sn4Bi9]4- (Ln = La, Ce) with adjustable magnetic properties.

Two K([2.2.2]crypt) salts of lanthanide-doped semimetal clusters were prepared, both of which contain at the same time two types of ternary intermetalloid anions, [Ln@Sn(7)Bi(7)](4-) and [Ln@Sn(4)Bi(9)](4-), in 0.70:0.30 (Ln = La) or 0.39:0.61 (Ln = Ce) ratios. The cluster shells represent nondeltahedral, fullerane-type arrangements of 14 or 13 main group metal atoms that embed the Ln(3+) cations. The assignment of formal +III oxidation states for the Ln sites was confirmed by means of magnetic measurements that reveal a diamagnetic La(III) compound and a paramagnetic Ce(III) analogue. Whereas the cluster anions with a 14-atomic main-group metal cage represent the second examples in addition to a related Eu(II) cluster published just recently, the 13-atomic cages exhibit a yet unprecedented enneahedral topology. In contrast to the larger cages, which accord to the Zintl-Klemm-Busmann electron number-structure correlation, the smaller clusters require a more profound interpretation of the bonding situation. Quantum chemical investigations served to shed light on these unusual complexes and showed significant narrowing of the HOMO-LUMO gap upon incorporation of Ce(3+) within the semimetal cages.

Surprising luminescent properties of the polyphosphates Ln(PO3)3:Eu (Ln = Y, Gd, Lu).

The optical emission properties of the lanthanoid catena-polyphosphates Ln(PO(3))(3) (Ln = Y, Gd, Lu) doped with europium were investigated. Incommensurately modulated ß-Y(PO(3))(3):Eu (super space group Cc (0|0.364|0)0) and Gd(PO(3))(3):Eu (space group I2/a) show the usual emission characteristics of Eu(3+), while in Lu(PO(3))(3):Eu (space group Cc) the europium is unprecedentedly partially reduced to the divalent state, as proven by both a broad emission band at 406 nm excited at 279 nm and an EPR spectroscopic investigation. (151)Eu-Mössbauer spectroscopy showed that only a very small part of the europium is reduced in Lu(PO(3))(3):Eu. An explanation for this unusual behaviour is given.

Indium flux-growth of Eu2AuGe3: a new germanide with an AlB2 superstructure.

The germanide Eu(2)AuGe(3) was obtained as large single crystals in high yield from a reaction of the elements in liquid indium. At room temperature Eu(2)AuGe(3) crystallizes with the Ca(2)AgSi(3) type, space group Fmmm, an ordered variant of the AlB(2) type: a = 857.7(4), b = 1485.5(10), c = 900.2(4) pm. The gold and germanium atoms build up slightly distorted graphite-like layers which consist of Ge(6) and Au(2)Ge(4) hexagons, leading to two different hexagonal-prismatic coordination environments for the europium atoms. Magnetic susceptibility data showed Curie-Weiss law behavior above 50 K and antiferromagnetic ordering at 11 K. The experimentally measured magnetic moment indicates divalent europium. The compound exhibits a distinct magnetic anisotropy based on single crystal measurements and at 5 K it shows a metamagnetic transition at ∼10 kOe. Electrical conductivity measurements show metallic behavior. The structural transition at 130 K observed in the single crystal data was very well supported by the conductivity measurements. (151)Eu Mössbauer spectroscopic data show an isomer shift of -11.24 mm/s at 77 K, supporting the divalent character of europium. In the magnetically ordered regime one observes superposition of two signals with hyperfine fields of 26.0 (89%) and 3.5 (11%) T, respectively, indicating differently ordered domains.

Synthesis and reactivity of ferrocenyl functionalized Sn/S cages.

Depending on the solvent used, the mono-stannylated FcSnCl(3) (1) reacts with Na(2)S to give ionic [Na(6)(Me(2)CO)(4)(OH(2))(6)] [(FcSn)(3)S(6)](2) (2), with a yet unprecedented thiostannate anion, or the adamantane-type Sn/S-cluster [(FcSn)(4)S(6)] (3). Complex 2 reacts readily with [Ni(acac)(2)], yielding the mixed-metallic complex [{Na(thf)(3.5)}(2){(FcSn)(8)Ni(3)S(16)}] x 2 THF (4 x 2 THF); the structures of 1-4 are discussed as well as Mössbauer spectra.

The formation of a metalloid Sn(10)[Si(SiMe(3))(3)](6) cluster compound and its relation to the alpha<-->beta tin phase transition.

Very recently it was shown that Sn monohalides can be prepared in preparative scale applying a preparative co-condensation technique. Here, a first reaction of Sn(i)Br is presented leading to the metalloid cluster compound Sn(10)[Si(SiMe(3))(3)](6) 1. This reaction can be seen as a first step to metalloid cluster compounds applying the disproportionation reaction of a metastable Sn monohalide. The ten tin atoms in 1 are arranged in the form of a centaur polyhedron, representing a novel structural motif in tin chemistry. The structural and electronic properties of 1 and its relation to the phase transition alpha<-->beta tin are discussed with the aid of quantum chemical calculations as well as (119)Sn Mössbauer spectroscopy.