Two interlocking Au6 rings, whose individual metal atoms are linked through ethynyl ligands, are present in the title compound [{Au(C  CtBu)}6]2. This novel homoleptic organometallic [2]catenane spontaneously self‐assembles in the reaction of [Au(NH3)2]BF4 with tBuC  CH. Weak AuAu interactions may contribute to the self‐assembly of the structure. The bonding in one ring is shown schematically on the right.

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The [Au(NCPh) 2 ] + cation has been isolated and synthesized in high yields by the oxidation of gold powder in the presence of NOBF 4 . It represents a labile form of gold(), which has been shown to be a valuable synthon for the synthesis of a wide range of gold() complexes and especially of a variety of gold() amines which have opened new synthetic routes for the isolation of organometallic gold() complexes.

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We prepared a series of Mg 1Ϫx Zr x B 2 bulk samples with different x values by the solid-state reaction at ambient pressure and investigated the effects of the Zr doping on phase compositions, microstructure, and flux pinning behavior. The results indicate that the a axis increases with the increase of the Zr doping and the c axis remains unchanged. ZrB 2 phases form and a small amount of Zr atoms may substitute Mg in Zr-doped samples. Critical temperature drops with increasing the Zr doping. It is found that critical current density J c can be significantly enhanced by the Zr doping and the best data are achieved in Mg 0.9 Zr 0.1 B 2 . For this sample, J c values are remarkably improved to 1.83ϫ10 6 A/cm 2 in the self field and 5.51ϫ10 5 A/cm 2 in 1 T at 20 K. Also, the irreversibility field is increased by the Zr doping. The high density, fine grain size of MgB 2 , and small ZrB 2 particles in Zr-doped samples may be responsible for the enhancement of J c . Also, the field dependence of J c at different temperatures was briefly discussed.