We have synthesized two new Eu-based compounds, EuSr2Bi2S4F4 and Eu2SrBi2S4F4, which are derivatives of Eu3Bi2S4F4, an intrinsic superconductor with Tc = 1.5 K. They belong to a tetragonal structure ...(SG: I4/mmm, Z = 2), similar to the parent compound Eu3Bi2S4F4. Our structural and 151Eu Mössbauer spectroscopy studies show that, in EuSr2Bi2S4F4, Eu-atoms exclusively occupy the crystallographic 2a-sites. In Eu2SrBi2S4F4, 2a-sites are fully occupied by Eu-atoms and the other half of Eu-atoms and Sr-atoms together fully occupy 4e-sites in a statistical distribution. In both compounds Eu atoms occupying the crystallographic 2a-sites are in a homogeneous mixed valent state ∼2.6-2.7. From our magnetization studies in an applied H ≤ 9 T, we infer that the valence of Eu-atoms in Eu2SrBi2S4F4 at the 2a-sites exhibits a shift toward 2+. Our XPS studies corroborate the occurrence of valence fluctuations of Eu and after Ar-ion sputtering show evidence of enhanced population of Eu2+-states. Resistivity measurements, down to 2 K, suggest a semimetallic nature for both compounds.
The FLP-mesityl azide addition products 5, formed by FLP-addition to the terminal azide nitrogen atom, undergo N-N bond cleavage in an unusual variant of the Staudinger reaction upon thermolysis or ...photolysis to give an internally borane stabilized P=NH phosphinimine and a dimethylindazole derivative.
Abstract
The plumbides
RE
ZnPb (
RE
=rare earth metals La–Nd and Sm–Tb) were synthesized by induction melting of the elements in sealed niobium ampoules. The samples were characterized by X-ray ...powder diffraction. The structures of the praseodymium and neodymium compound were refined from single-crystal X-ray diffractometer data: YPtAs type,
P
6
3
/
mmc
,
a
=461.32(8),
c
=1658.00(3) pm,
wR
2=0.0588, 267
F
2
values, 12 variables for PrZnPb and
a
=460.12(3),
c
=1642.7(1),
wR
2=0.0617, 243
F
2
values, 12 variables for NdZnPb. The plumbides with
RE
=La, Ce, Sm, Gd and Tb are isotypic while the Zintl phase EuZnPb crystallizes with the orthorhombic TiNiSi type,
Pnma
,
a
=796.6(2),
b
=482.53(9),
c
=822.9(2) pm. The zinc and lead atoms build up polyanionic networks: slightly puckered Zn
3
Pb
3
layers in AA′BB′ stacking sequence in the YPtAs type plumbides and a three-dimensional ZnPb
2−
network with distorted tetrahedral ZnPb
4/4
coordination in EuZnSn. The different crystal structures are a consequence of the valence electron count, i.e. 18 for EuZnSn and 19 for the hexagonal plumbides. The crystal chemical details and bonding peculiarities are discussed.
Abstract
The plumbides
RE
2
Rh
2
Pb (
RE
= La–Nd, Sm, Gd, Tb) were synthesized in sealed niobium ampoules by induction melting of the pure elements or directly via arc-melting. The characterization ...of the samples by X-ray powder diffraction confirmed their Mo
2
B
2
Fe-type structure (space group
P
4/
mbm
) at room temperature. The Sm
2
Rh
1.924
Pb structure was refined from single-crystal X-ray diffractometer data:
a
=760.02(5),
c
=378.20(3) pm,
wR
=0.0387, 292
F
2
values, 13 variables. The rhodium site shows small defects. The
RE
2
Rh
2
Pb plumbides are simple 1:1 intergrowth structures of AlB
2
and CsCl related slabs of compositions
RE
Rh
2
and
RE
Pb. The Rh
2
dumbbell in the SmRh
2
slab of Sm
2
Rh
2
Pb shows a Rh–Rh distance of 281 pm. Temperature-dependent magnetic susceptibility measurements of La
2
Rh
2
Pb, Pr
2
Rh
2
Pb and Nd
2
Rh
2
Pb showed that the rhodium atoms carry no localized magnetic moments. La
2
Rh
2
Pb exhibits Pauli-paramagnetic behavior induced by the conduction electrons. The ground state of the praseodymium compound is ferromagnetic below
T
C
=3.3 K while the neodymium compound shows a transition to an antiferromagnetic state at
T
N
=6.1 K and a metamagnetic transition at a critical field of ca. 1000 Oe.
Abstract
The equiatomic plumbides
RE
RhPb (
RE
=Y, La–Nd, Sm, Gd–Lu) were synthesized by induction melting of the elements in sealed niobium ampoules. The samples were characterized by X-ray powder ...diffraction, confirming their ZrNiAl-type structure, space group
P
6̅2
m
. Four structures were refined from single-crystal X-ray diffractometer data:
a
=769.42(5),
c
=415.60(3) pm,
wR
=0.0415, 343
F
2
values, 15 variables for LaRhPb,
a
=767.91(6),
c
=369.37(4) pm,
wR
=0.0798, 284
F
2
values, 15 variables for ErRhPb,
a
=767.01(8),
c
=366.21(4) pm,
wR
=0.0380, 341
F
2
values, 15 variables for YbRhPb and
a
=766.9(1),
c
=363.42(6) pm,
wR
=0.0699, 290
F
2
values, 15 variables for LuRhPb. The
RE
RhPb plumbides contain two crystallographically independent rhodium atoms, both in tricapped trigonal prismatic coordination: Rh1@Pb
3
RE
6
and Rh2@
RE
6
Pb
3
. Short Rh–Pb distances (277 and 284 pm in ErRhPb) are indicative of covalent Rh–Pb bonding. The crystal chemical details of the
RE
RhPb series are compared with the silver plumbides
RE
AgPb which show different transition metal-lead coloring. Temperature dependent magnetic susceptibility data show Pauli paramagnetism for YRhPb, LaRhPb and LuRhPb. An antiferromagnetic ground state below the Néel temperatures of 13.5, 21.0 and 6.9 K was found for PrRhPb, TbRhPb and DyRhPb, respectively. HoRhPb exhibits Curie-Weiss behavior in the observed temperature range.
The indide EuPtIn2 (MgCuAl2 type, Cmcm, a = 448.23(4), b = 1068.64(11), c = 784.09(8) pm, wR2 = 0.0432, 466 F2 values, 16 variables) was synthesized by induction-melting of the elements and ...subsequent annealing. The platinum and indium atoms built up a three-dimensional PtIn22- polyanionic network (278-282 pm Pt-In) which contains channels that are filled with the europium cations. These bind to the network through shorter Eu-Pt contacts (302-323 pm). Temperature dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic data manifest divalent europium down to 4.2 K. EuPtIn2 orders ferromagnetically at 32.5 K. EuPtIn2 and SrPtIn2 form a complete solid solution Eu1-xSrxPtIn2 with Vergard type behavior for the lattice parameters. Divalent europium is proven through magnetic data and Mössbauer spectroscopy. The Curie temperature decreases monotonically from 32.5 to 3.1 K in going to Eu0.1Sr0.9PtIn2.
The indide EuPtIn
2
(MgCuAl
2
type,
Cmcm
,
a
= 448.23(4),
b
= 1068.64(11),
c
= 784.09(8) pm, w
R
2
= 0.0432, 466
F
2
values, 16 variables) was synthesized by induction-melting of the elements and ...subsequent annealing. The platinum and indium atoms built up a three-dimensional PtIn
2
2−
polyanionic network (278-282 pm Pt-In) which contains channels that are filled with the europium cations. These bind to the network through shorter Eu-Pt contacts (302-323 pm). Temperature dependent magnetic susceptibility and
151
Eu Mössbauer spectroscopic data manifest divalent europium down to 4.2 K. EuPtIn
2
orders ferromagnetically at 32.5 K. EuPtIn
2
and SrPtIn
2
form a complete solid solution Eu
1−
x
Sr
x
PtIn
2
with Vergard type behavior for the lattice parameters. Divalent europium is proven through magnetic data and Mössbauer spectroscopy. The Curie temperature decreases monotonically from 32.5 to 3.1 K in going to Eu
0.1
Sr
0.9
PtIn
2
.
The indide EuPtIn
2
(MgCuAl
2
type,
Cmcm
,
a
= 448.23(4),
b
= 1068.64(11),
c
= 784.09(8) pm, w
R
2
= 0.0432, 466
F
2
values, 16 variables) was synthesized by induction-melting of the elements and subsequent annealing.
The plumbides
Rh
Pb (
= La–Nd, Sm, Gd, Tb) were synthesized in sealed niobium ampoules by induction melting of the pure elements or directly via arc-melting. The characterization of the samples by ...X-ray powder diffraction confirmed their Mo
Fe-type structure (space group
4/
) at room temperature. The Sm
Rh
Pb structure was refined from single-crystal X-ray diffractometer data:
=760.02(5),
=378.20(3) pm,
=0.0387, 292
values, 13 variables. The rhodium site shows small defects. The
Rh
Pb plumbides are simple 1:1 intergrowth structures of AlB
and CsCl related slabs of compositions
Rh
and
Pb. The Rh
dumbbell in the SmRh
slab of Sm
Rh
Pb shows a Rh–Rh distance of 281 pm. Temperature-dependent magnetic susceptibility measurements of La
Rh
Pb, Pr
Rh
Pb and Nd
Rh
Pb showed that the rhodium atoms carry no localized magnetic moments. La
Rh
Pb exhibits Pauli-paramagnetic behavior induced by the conduction electrons. The ground state of the praseodymium compound is ferromagnetic below
=3.3 K while the neodymium compound shows a transition to an antiferromagnetic state at
=6.1 K and a metamagnetic transition at a critical field of ca. 1000 Oe.
The plumbides
ZnPb (
=rare earth metals La–Nd and Sm–Tb) were synthesized by induction melting of the elements in sealed niobium ampoules. The samples were characterized by X-ray powder diffraction. ...The structures of the praseodymium and neodymium compound were refined from single-crystal X-ray diffractometer data: YPtAs type,
,
=461.32(8),
=1658.00(3) pm,
2=0.0588, 267
values, 12 variables for PrZnPb and
=460.12(3),
=1642.7(1),
2=0.0617, 243
values, 12 variables for NdZnPb. The plumbides with
=La, Ce, Sm, Gd and Tb are isotypic while the Zintl phase EuZnPb crystallizes with the orthorhombic TiNiSi type,
,
=796.6(2),
=482.53(9),
=822.9(2) pm. The zinc and lead atoms build up polyanionic networks: slightly puckered Zn
Pb
layers in AA′BB′ stacking sequence in the YPtAs type plumbides and a three-dimensional ZnPb
network with distorted tetrahedral ZnPb
coordination in EuZnSn. The different crystal structures are a consequence of the valence electron count, i.e. 18 for EuZnSn and 19 for the hexagonal plumbides. The crystal chemical details and bonding peculiarities are discussed.
Abstract
Phase-pure samples of the antimonides PrPdSb and NdPdSb were prepared by arc-melting pieces of the elements and subsequent annealing. The samples were investigated by powder and single ...crystal X-ray diffraction: NdPtSb type, space group
P
6
3
mc
,
a
= 458.70(5),
c
= 780.55(6) pm,
wR
2 = 0.0272, 244
F
2
values, 11 variable parameters for PrPdSb and
a
= 458.18(4),
c
= 771.25(6) pm,
wR
2 = 0.0317, 229
F
2
values, 11 variable parameters for NdPdSb. The palladium and antimony atoms form slightly puckered Pd
3
Sb
3
hexagons which are rotated by 60° in every other layer. The rare earth (
RE
) atoms are coordinated by two Pd
3
Sb
3
hexagons with the
RE
–Pd shorter than the
RE
–Sb contacts. The
121
Sb Mössbauer spectra at
T
= 5 K confirm the antimonide character with isomer shifts of −7.55 (PrPdSb) and −7.47 mm · s
−1
(NdPdSb). In agreement with the crystal structures, each spectrum could be fitted with one quadrupole split signal.
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