Syntheses and structures of Zr₄tetrahedral clusters containing direct Zr–Zr bonds: the missing cluster in the series Zr_n(n = 2–6)

Abstract

The reduction of [(μ(2)-H)( μ(3)-H)(Cp*ZrCl)](4) by excess Na/Hg led to the isolation of the mixed-valence Zr(III)/Zr(IV) Zr(4) cluster [(μ(2)-H)(8)(μ(2)-Cl)(2)(Cp*Zr)(4)], 1, and the Zr(II)/Zr(III) Zr(4) cluster [(μ(2)-H)(6)(Cp*Zr)(4)], 2. The proton NMR data supports the diamagnetic property of both clusters in solution and the solid state structure of each cluster revealed a distorted tetrahedral skeleton comprised of four Zr atoms and the presence of direct Zr-Zr bonds. The hydride-bridged Zr-Zr bond distances are in the range of 3.0516(6)-3.0585(6) Å in 1 and 3.0525(13)-3.0864(13) Å in 2. The chloride-bridged Zr-Zr distances in 1 are 3.5514(6) and 3.5643(6) Å. The existence of Zr-Zr bonds in both clusters was further confirmed by DFT calculations. 1 and 2 represent the first examples of Zr(4) tetrahedrons containing direct Zr-Zr bonds.

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

“…Although, those will not be further discussed except for some examples. 5–10 Apart from that, there is one species with lithium coordinated by oxygen atoms.…”

“…The adamantane-type compound [(Cp*Zr) 4 H 6 ] ( 5 , Cp* = pentamethylcyclopentadienyl) was found as the final piece in a row of tetrahedral compounds with fewer hydrides by reduction of [(μ-H)(μ 3 -H)(Cp*ZrCl)] 4 with Na amalgam. 5 This led to a mixed-valence Zr II /Zr III situation in the cluster core.…”