“…The present R 6 (Os)I 14 structural network is a notable contrast to the well-known Nb 6 Cl 14 , ANb 6 Cl 14 , and over 40 zirconium halide cluster systems with a wide range of interstitials, all with the same Nb 6 Cl 14 -type linkage. ,, These clusters are all interbonded by two trans X i-a and four X a-a functions to produce a unique three-dimensional network (M 6 Z)X i 10 X i-a 2/2 X a-i 2/2 X a-a 4/2 . A single alkali-metal cation per cluster may occupy one of two different sites depending on its size. , The present K 4 R 6 I 14 Os is to date the halogen-richest among all rare-earth-metal cluster halides. In addition, each cluster therein contains just 16 skeletal electrons (4·1 + 6·3 − 14 + 8), not the 18-e - optimum .…”
The title compounds are obtained from reactions of KI, RI3, R, and Os at 750−850 °C in sealed Nb or Ta containers.
The structure was established by single-crystal X-ray diffraction studies (tetragonal, P4/mnc, Z = 2; a = 10.044(4), 9.879(3) Å and c = 21.825(4), 21.86(1) Å for La, Pr, respectively) for three samples, La and Pr at 23 °C and
La at −100 °C. This particular combination of large R, interstitial Z, and halogen results in the highest X:R ratio
known among rare-earth-metal cluster halides and an unprecedented structure type. The cluster units are
interconnected according to the pattern [(R6Os)Ii
8Ii-a
4/2Ia-i
4/2Ia
2]4- in which four R in the waist of each cluster,
the Os, and four bridging Ii-a,a-i pairs generate a planar 2D network of geometrically nearly ideal, 16-electron
R6Os octahedra. This contrasts with the tetragonal compression found for many other 16-e- examples with the
parallel disappearance of Curie−Weiss paramagnetism. Powdered α-K4La6I14Os exhibits an exceptionally low
resistivity for a cluster halide (∼120 μΩ·cm) over 110−280 K and a small paramagnetism over about 35 to
∼250 K associated with a probable Mott−Hubbard state that changes to a temperature-independent (presumably
Pauli) paramagnetism above about 300 K. EHTB band calculations show that a significant broadening of the
HOMO (∼t1u) states takes place in the plane of the intercluster bridging. The unique structure, properties, and
band picture for the compound indicate a transition to a delocalized (band) state.
“…The present R 6 (Os)I 14 structural network is a notable contrast to the well-known Nb 6 Cl 14 , ANb 6 Cl 14 , and over 40 zirconium halide cluster systems with a wide range of interstitials, all with the same Nb 6 Cl 14 -type linkage. ,, These clusters are all interbonded by two trans X i-a and four X a-a functions to produce a unique three-dimensional network (M 6 Z)X i 10 X i-a 2/2 X a-i 2/2 X a-a 4/2 . A single alkali-metal cation per cluster may occupy one of two different sites depending on its size. , The present K 4 R 6 I 14 Os is to date the halogen-richest among all rare-earth-metal cluster halides. In addition, each cluster therein contains just 16 skeletal electrons (4·1 + 6·3 − 14 + 8), not the 18-e - optimum .…”
The title compounds are obtained from reactions of KI, RI3, R, and Os at 750−850 °C in sealed Nb or Ta containers.
The structure was established by single-crystal X-ray diffraction studies (tetragonal, P4/mnc, Z = 2; a = 10.044(4), 9.879(3) Å and c = 21.825(4), 21.86(1) Å for La, Pr, respectively) for three samples, La and Pr at 23 °C and
La at −100 °C. This particular combination of large R, interstitial Z, and halogen results in the highest X:R ratio
known among rare-earth-metal cluster halides and an unprecedented structure type. The cluster units are
interconnected according to the pattern [(R6Os)Ii
8Ii-a
4/2Ia-i
4/2Ia
2]4- in which four R in the waist of each cluster,
the Os, and four bridging Ii-a,a-i pairs generate a planar 2D network of geometrically nearly ideal, 16-electron
R6Os octahedra. This contrasts with the tetragonal compression found for many other 16-e- examples with the
parallel disappearance of Curie−Weiss paramagnetism. Powdered α-K4La6I14Os exhibits an exceptionally low
resistivity for a cluster halide (∼120 μΩ·cm) over 110−280 K and a small paramagnetism over about 35 to
∼250 K associated with a probable Mott−Hubbard state that changes to a temperature-independent (presumably
Pauli) paramagnetism above about 300 K. EHTB band calculations show that a significant broadening of the
HOMO (∼t1u) states takes place in the plane of the intercluster bridging. The unique structure, properties, and
band picture for the compound indicate a transition to a delocalized (band) state.
“…So far, only one example of a bromide supported zirconium cluster is known, which is obtained by solution chemical methods: (H 3 O) 3 [(Zr 6 B)Br 16 (H 2 O) 2 ] containing coordinated water molecules . Further compounds, containing molecular bromide cluster anions, obtained by solid-state chemical procedures, are K 4 [(Zr 6 C)Br 18 ] (an isostructural iron centered version is also mentioned, but not structurally fully characterized) and (A I 4 Br) 2 [(Zr 6 Z)Br 18 ] with A I = Na−Cs, Z = H, Be, B, Mn , 1 Molecular structure of the [(Zr 6 Fe)Br 18 ] 4- cluster anion in crystals of (EMIm) 4 [(Zr 6 Fe)Br 18 ] with 50% thermal probability ellipsoids showing the atom labeling scheme. 2 Molecular structure of the [(Zr 6 Be)Br 18 ] 4- cluster anion in crystals of (EMIm) 4 [(Zr 6 Be)Br 18 ] with 50% thermal probability ellipsoids showing the atom labeling scheme. …”
Section: Resultsmentioning
confidence: 99%
“…Comparing these values with those of other iron centered, bromide supported zirconium clusters proved rather difficult, because no detailed structural data has been published so far on any Fe-centered zirconium bromide (to the best of the author's knowledge). The only phases mentioned so far in the literature are [(Zr 6 Fe)Br 14 ], Cs[(Zr 6 Fe)Br 15 ], and the above referenced K 4 [(Zr 6 Fe)Br 18 ] …”
The solid-state precursor cluster chlorides Na(4)[(Zr(6)Be)Cl(16)] and K[(Zr(6)Fe)Cl(15)] readily dissolve in Lewis-basic ionic liquids consisting of mixtures of EMIm-Br and AlBr(3) (EMIm: 1-ethyl-3-methyl-imidazolium) to give dark colored solutions. From these solutions, the cluster phases (EMIm)(4)[(Zr(6)Fe)Br(18)] (1) and (EMIm)(4)[(Zr(6)Be)Br(18)] (2) were obtained in acceptable yields. Crystallographic data of the isostructural phases are the following: monoclinic, P2(1)/c, Z = 2. The data for 1 follow: a = 10.5746(4) Angstrom, b = 22.6567(9) Angstrom, and c = 13.0260(5) Angstrom, beta = 111.279(2) degrees. The data for 2 follow: a = 10.574(2) Angstrom, b = 22.681(4) Angstrom, and c = 13.041(2) Angstrom, beta = 111.31(2) degrees. Compound 1 is the first detailed structurally characterized molecular Fe-centered zirconium bromide cluster phase. In the bromide based ionic liquid, a complete exchange of all the outer and inner chlorides by bromide takes place. Since the inverse reaction, the exchange of all bromides by chlorides, was reported before, this complete ligand exchange can be considered as reversible, with the equilibrium being largely determined by the free ligand concentration. The electronic spectra of a chloride supported cluster precursor in different ionic liquids were measured and analyzed.
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