Synthesis, crystal structures and properties of quasi-one-dimensional platinum compounds

Article abstract of DOI:10.1016/S0020-1693(01)00551-5

Quasi-one-dimensional complexes of the type [Pt(NH₂R)₄][Pt(mnt)₂], where mnt designates maleodinitriledithiolate and R an ethyl (Et) or octyl (Oc) group, were synthesized and characterized. Single-crystal X-ray diffraction revealed that both compounds crystallized in the triclinic space group P1. The platinum atoms were arranged in linear arrays in both compounds; while the Pt-Pt distances were equal in [Pt(NH₂Et)₄][Pt(mnt)₂] (3.96 ?), surprisingly, two different intermetallic spacings (3.86 and 4.01 ?) were observed in [Pt(NH₂Oc)₄][Pt(mnt)₂]. The Pt-Pt distances in the [Pt(NH₂R)₄][Pt(mnt)₂] compounds are large compared to those in the typical Magnus-salt-type complexes (3.15-3.62 ?). An uncommon, reversible solid-state phase transition was detected for [Pt(NH₂Oc)₄][Pt(mnt)₂] at 70°C, which might be related to a change in the packing of the octyl chains. The platinum stacks decayed when in solution, yielding predominantly ion pairs. The UV-Vis absorption spectra of such solutions were dominated by characteristics associated with [Pt(mnt)₂]^2- units, and UV emission maxima were found at 345 and 363 nm upon excitation with light of wavelengths between 250 and 340 nm.

Full text of DOI:10.1016/S0020-1693(01)00551-5

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 322 (2001) 23–31
Synthesis, crystal structures and properties of
quasi-one-dimensional platinum compounds
Juliane Bremi, Volker Gramlich, Walter Caseri *, Paul Smith
Eidgeno¨ssische Technische Hochschule (ETH), Zentrum, CH-8092 Zurich, Switzerland
Received 5 May 2001; accepted 6 June 2001
Abstract
Quasi-one-dimensional complexes of the type [Pt(NH2R)4][Pt(mnt)2], where mnt designates maleodinitriledithiolate and R an
ethyl (Et) or octyl (Oc) group, were synthesized and characterized. Single-crystal X-ray diffraction revealed that both compounds
(
crystallized in the triclinic space group P1. The platinum atoms were arranged in linear arrays in both compounds; while the PtꢀPt
,
,
distances were equal in [Pt(NH2Et)4][Pt(mnt)2] (3.96 A), surprisingly, two different intermetallic spacings (3.86 and 4.01 A) were
observed in [Pt(NH2Oc)4][Pt(mnt)2]. The PtꢀPt distances in the [Pt(NH2R)4][Pt(mnt)2] compounds are large compared to those in
the typical Magnus-salt-type complexes (3.15–3.62 A). An uncommon, reversible solid-state phase transition was detected for
,
[Pt(NH2Oc)4][Pt(mnt)2] at 70 °C, which might be related to a change in the packing of the octyl chains. The platinum stacks
decayed when in solution, yielding predominantly ion pairs. The UV–Vis absorption spectra of such solutions were dominated
by characteristics associated with [Pt(mnt)2]2− units, and UV emission maxima were found at 345 and 363 nm upon excitation
with light of wavelengths between 250 and 340 nm. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Platinum complexes; Amine complexes; One-dimensional complexes
,
platinum atoms separated by distances of 3.15–3.62 A
1. Introduction
(Table 2). The observed PtꢀPt distances exceed those in
,
more common PtꢀPt bonds (2.6–2.8 A), although these
One of the first quasi-one-dimensional compound
synthesized is the platinum(II)–amine complex
[Pt(NH3)4][PtCl4], prepared by Magnus around 1830
[1,2] and still referred to as Magnus’ green salt. Re-
markably, its quasi-one-dimensional structure of linear
arrays of platinum atoms remained unresolved for
roughly a century. For long, it was regarded as a
stoichiometric mixture of [Pt(NH3)4]Cl2 and PtCl2 [3,4]
and as late as in 1930, discussions about the general
structure of platinum complexes had not been closed
[5]. In the course of time, many compounds of the type
spacings allow a certain overlap of metal orbitals [6]. It,
therefore, appears likely that the PtꢀPt distances in the
Magnus-salt-type compounds are determined by elec-
trostatic forces between the oppositely charged coordi-
nation units and their packing in the crystalline state
[6]. It should be noted that a platinum chain structure
is not necessarily present in each [PtL4]2+[PtL%]2− com-
pound. For example, a pink isomer of Magnus’ green
salt is known [6–9] with an interplatinum distance that
exceeds 5 A, and which most likely does not display the
4
,
[PtL4]2+[PtL%]2− (L is ligand) have been described, a
chain structure [7].
4
In the present work, we describe the preparation,
structural analysis and selected properties of quasi-one-
dimensional compounds of type [Pt(NH2R)4]2+, where
R is alkyl, and bis(maleodinitriledithiolato)platinum-
(II), i.e. [Pt(mnt)2]2− units (cf. Scheme 1). Previously, a
quasi-one-dimensional complex has been described with
[Pt(mnt)2]2− and [Pt(CNCH3)4]2+ as the counterion,
selection of which is presented in Table 1. Only a few of
them have been subject to a complete structural charac-
terization by X-ray diffraction, which revealed indeed a
structure comprised linear backbones of equally spaced
* Corresponding author. Tel.: +41-1-632 2218; fax: +41-1-632
1178.
,
having an intermetallic distance of 3.33 A [10]. It will
E-mail address: wcaseri@ifp.mat.ethz.ch (W. Caseri).
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00551-5

24
J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
Table 2
be evident, however, that the novel [Pt(NH2R)4]-
[Pt(mnt)2] complexes prepared in this work exhibit
Reported PtꢀPt distances in the Magnus-salt-like compounds
,
Compounds
d (A)
References
Table 1
Selection of the Magnus-salt-type compounds described in the litera-
ture
[Pt(NH3)4][PtCl4] (Magnus’ green salt) 3.23–3.25
[7,32,33]
[15,32,33]
[15]
[32]
[32]
[32]
[15]
[32]
[Pt(NH2CH3)4][PtCl4]
3.24–3.29
3.62
[Pt(NH2CH2CH3)4][PtCl4]
[Pt(H2NCH2CH2NH2)2][PtCl4]
[Pt(NH3)4][PtBr4]
Compounds
References
3.41 a
3.31 a
3.37 a
3.35 a
3.51 a
[Pt(NH2CH3)4][PtCl4]
[Pt(NH2CH2CH3)4][PtCl4]
[Pt(NH2CH2CH2CH3)4][PtCl4]
[Pt(NH2CH2CH2CH2CH3)4][PtCl4]
[Pt(NCxH2x+1)4][PtCl4], x=7, 8, 9, 10, 12, 14
[Pt(py)4][PtCl4]
[15,32–38]
[15,32,36,38,40]
[38,40]
[6,38,40]
[6,41]
[Pt(NH2CH3)4][PtBr4]
[Pt(NH2CH2CH3)4][PtBr4]
[Pt(H2NCH2CH2NH2)2][PtBr4]
[Pt(bipy)2][Pt(CN)4]
ca. 3.3 a [24]
[Pt(p-CN-iso-C3H7)4][Pt(CN)4]
[Pt(CNMe)4][Pt(mnt)2]
3.15
3.33
[60]
[10]
[40]
[Pt(bipy)2][PtCl4]
[Pt(bipy)(mhb)][PtCl4]
[42,43]
[40]
Only the structures of [Pt(NH3)4][PtCl4], [Pt(NH2CH3)4][PtCl4],
Pt(NH2CH2CH3)4][PtCl4], [Pt(p-CN-iso-C3H7)4][Pt(CN)4], and [Pt(C-
NMe)4][Pt(mnt)2] have been determined entirely.
[Pt(H2NCH2CH2NH2)2][PtCl4]
[Pt(H2NCH2NHCH2NH2)(NH3)2][PtCl4]
[Pt{H2NCH(CH3)CH(CH3)NH2}2][PtCl4]
[Pt(H2NCH2CH2CH2NH2)2][PtCl4]
[32,35,37,44]
[35]
[35]
a Estimated from the unit cell dimensions.
[45]
[Pt(H2NCH2CH2NHCH2CH2NH2)(NH3)][PtCl4] [46]
[Pt(CNC6H5)4][PtCl4]
[47,48]
[48]
[48]
[48]
rather different structural features of the backbone
formed by the metal ions, depending on the length of
the alkyl substituents.
[Pt(o-CNC6H4CH3)4][PtCI4]
[Pt(p-CNC6H4CH2CH3)4][PtCl4]
[Pt(p-CNC6H4OCH3)4][PtCl4]
[Pt(CH3SCH3)2(H2NCH2CH2NH2)][PtCl4]
[Pt(CH3SCH3)4][PtCl4]
[Pt(CH3CH2SCH2CH2SCH2CH3)4][PtCl4]
[Pt{Sb(CH3)3}4][PtCl4]
[Pt(NH3)4][PtBr4]
[49]
[49–51]
[50,52]
[53]
[32,36,42,50,54]
[32,36,39]
[32]
2. Experimental
[Pt(NH2CH3)4][PtBr4]
[Pt(H2NCH2CH2NH2)2][PtBr4]
[Pt{CH3SCH3}4][PtBr4]
2.1. General
[50]
[Pt(CH3CH2SCH2CH2SCH2CH3)2][PtBr4]
[Pt(NH3)4][Pt(CN)4]
[Pt(H2NCH2CH2NH2)2][Pt(CN)4]
[Pt(py)4][Pt(CN)4]
[Pt(bipy)2][Pt(CN)4]
[Pt(bipy)(mhb)][Pt(CN)4]
[Pt(phen)2][Pt(CN)4]
[Pt(CN-iso-C3H7)4][Pt(CN)4]
[Pt(p-CNC6H4-n-CxH2x+1)4][Pt(CN)4], x=l, 6, [61]
10, 12, 14
[Pt(CN-cyclo-C11H25)4][Pt(CN)4]
[Pt(CH3CH2CH2SCH2CH2SCH2CH2CH3)2]-
[Pt(CN)4]
[Pt(NH3)4][Pt(SCN)4]
[Pt(py)4][Pt(SCN)4]
[50]
[42,55–57]
[5]
[58]
[24,42,43,59]
[43]
All chemicals were obtained from commercial
sources (Fluka, Aldrich, Johnson Matthew) and used as
received. For UV measurements in acetone and acetoni-
trile, UV grade was used (Fluka).
The elemental contents of carbon, hydrogen, nitro-
gen, and chlorine were determined by the microelemen-
tal service of the Laboratorium fu¨r Organische Chemie
at ETH Zu¨rich. Differential scanning calorimetry
(DSC) and thermogravimetric analyses (TGA) were
performed with equipment from Netzsch (DSC 200 and
TG 209, respectively) under nitrogen atmosphere at
heating rates of 10 °C min−1, if not otherwise indi-
cated. IR spectra were recorded with CsCl pellets in a
Bruker IFS 66v spectrometer. UV–Vis spectra were
recorded in a Perkin–Elmer Lambda 900 and NMR
spectra in a 300 MHz Bruker spectrometer.
[24]
[60]
[58]
[58]
[58]
[58]
[10]
[Pt(CNMe)4][Pt(mnt)2]
py=pyridine, bipy=2,2%-bipyridine, mhb=4-methyl-4%-heptyl-2,2%-
bipyridine, phen=1,10-phenanthroline, mnt=maleodinitriledithio-
late. An early report on [Pt(NH3)4][PtI4] and [Pt(NH3)4][Pt(CN)4] [25]
is not included since elemental analysis is not available, and the
synthetic procedures do not appear to be reproducible. Regarding the
nomenclature used in original articles before 1860, the following has
to be considered: the element symbol ‘Pt’ frequently corresponded
effectively to Pt0.5; i.e. the chemical composition of, e.g. Magnus’
green salt was then designated ‘PtClNH3’. In addition, it was occa-
sionally assumed that the element platinum existed in two forms
referred to as platinosum (Pt) and platinicum (pt), with molecular
weights of Pt:pt=2:1 [26–28]. Further, it was suggested that platinum
may substitute hydrogen atoms in an NH3 or N2H6 molecule [26–31]
resulting in NH2Pt (platosamine), N2H5Pt (diplatosamine), NHpt2
(platinamine), and N2H4pt2 (diplatinamine) as basic units of plat-
inum–amine compounds (such as Magnus’ green salt) [27–29].
In the following syntheses, filtrations were performed
with sintered-glass funnels, type N4, of diameter 2, 4,
or 6 cm. The products were dried at l0−2 mbar for 24
h, if not otherwise indicated.
2.2. (NBu4)2[Pt(mnt)2]
This compound was prepared in analogy to the cor-
responding nickel complex described in the literature
[11]. An aqueous solution of K2[PtCl4] (5 ml, 415.2 mg,
1.0 mmol) was slowly added to a 5 ml solution of

J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
25
Na2mnt in ethanol–water (1:1 v/v). The deep red solu-
tion was filtered, and tetrabutylammonium chloride
(555.8 mg, 2.0 mmol) dissolved in 2 ml ethanol was
added to the filtrate, whereupon red crystals precipi-
tated. After precipitation, the resulting crystals were
collected by filtration, washed with 10 ml of water and
10 ml of an ethanol–water (1:1 v/v) mixture and dried
in the filter by conduction of air through the filter. The
solids were then dissolved in 30 ml acetone at 60 °C
followed by filtration through a Teflon® filter (pore
diameter 1 mm). The filtered solution was heated to its
boiling temperature, and acetone was evaporated until
a volume of 15–20 ml was left. After cooling to room
temperature (r.t.), approximately 15 ml of isobutanol
was slowly added. The solution was allowed to stand at
r.t. whereupon large, red crystals formed. The product
was filtered-off, washed with 10 ml isobutanol and 10
ml n-pentane in the filter, and dried (yield 80%). IR
(CsCl, cm−1): 2963s, 2935m, 2875m, 2186s, 1479s,
1382m, 1152s, 1048w, 1025w, 1010w, 885m, 868m,
799w, 738m, 511m, 332w, and 318w.
of the mnt unit were not visible due to the high
relaxation times of the carbon atoms involved).
2.4. In situ preparation of [Pt(NH2Et)4]Cl2
A solution of K2[PtCl4] (10 ml, 300.0 mg, 0.72 mmol)
in water was cooled with ice, and thereafter 1-
aminoethane (2 ml, 14.4 mmol) was added. The solu-
tion was heated to 65 °C for 1 h under reflux
conditions. A pink solid that precipitated after approx-
imately 15 min dissolved after heating to 100 °C for 1
h. Afterwards, the clear solution was cooled and kept at
r.t. for 1 h, allowing some 1-aminoethane to evaporate.
The volume of the solution was reduced to approxi-
mately 65% with a rotary evaporator at 50 °C and 60
mbar. This solution was used for the preparation of
[Pt(NH2Et)4][Pt(mnt)2].
2.5. [Pt(NH2Et)4][Pt(mnt)2]
K2[Pt(mnt)2] (398.3 mg, 0.72 mmol) was dissolved in
12.2 ml water and then 2.2 ml ethanol was added. The
resulting solution was poured to the in situ prepared
[Pt(NH2Et)4]Cl2 solution described above, whereupon a
red precipitate formed rapidly. The suspension was
cooled with ice, filtered through a Teflon® filter (pore
diameter 1 mm), and the remaining solids were dried
(yield 88%). The product was recrystallized from a
mixture of 8 ml dimethyl sulfoxide, 10 ml diethyl ether
and 20 ml n-butanol (yield 56%). IR (CsCl, cm−1):
3257s, 3226s, 2972m, 2205s, 1591s, 1573s, 1474s, 1445s,
1383m, 1370m, 1259m, 1235m, 1154s, 1106w, 1078s,
1028m, 867m, 744s, 730s, 600w, 508s, 334m, 322m,
291m and 257m. Elemental composition: Anal. Found:
C, 22.66; H, 3.09; N, 12.92; S, 14.93. Calc. for
C16H28N8S4Pt2: C, 22.59; H, 3.32; N, 13.17; S, 15.07%
(w/w).
2.3. [Pt(NH2Oc)4][Pt(mnt)2]
A solution of [Pt(NH2Oc)4]Cl2 (15 ml, 329.8 mg, 0.42
mmol, prepared according to the literature [6]) in etha-
nol was added to a 25 ml solution of (NBu4)2[Pt(mnt)2]
(403.9 mg, 0.42 mmol) in acetone. The resulting solu-
tion was filtered through a Teflon® filter (pore diameter
1 mm). Water (30 ml) was added to the filtrate, where-
upon an orange precipitate formed rapidly. The
product was finally collected by filtration through a
Teflon® filter (pore diameter 1 mm) and dried. Yield
95%. IR (CsCl, cm−1): 3245s, 3127w, 2927s, 2856s,
2205s, 1579s, 1482s, 1468m, 1378w, 1207w, 1153s,
1042w, 883w, 729m, 508m, 322w and 271w. Elemental
composition: Anal. Found: C, 40.66; H, 6.28; N, 9.33;
S, 10.52. Calc. for C40H76N8S4Pt2: C, 40.46; H, 6.45; N,
1
9.44; S, 10.80%. H NMR (CD3COCD3, 300 MHz, l
2.6. Crystal structures of [Pt(NH2Oc)4][Pt(mnt)2] and
[Pt(NH2Et)4][Pt(mnt)2]
ppm): 0.87 (t, 3H), 1.29 (m, 10H), 1.72 (qn, 2H), 2.94
(qn, 2H), 4.95 (m, 2H). 13C NMR (CD3COCD3, 75
MHz, l ppm): 14.4, 23.3, 27.4, 32.1, 32.6, 48.4 (signals
For X-ray crystal structure analysis, a [Pt(NH2Oc)4]-
[Pt(mnt)2] crystal of dimensions 0.2×0.05×0.02 mm
and a [Pt(NH2Et)4][Pt(mnt)2] crystal of extension 0.5×
0.2×0.1 mm was used. Due to the small crystal dimen-
sions, the data of the former complex were generated
with graphite monochromated Cu Ka radiation on a
Picker–Stoe diffractometer; for the latter complex a
Syntex P21 diffractometer with graphite monochro-
mated Mo Ka radiation was used. Crystallographic
data and details of the structure refinement are summa-
rized in Table 3. Only independent reflections were
collected. Absorption correction was applied to the
data using integration. The structures were solved using
the program SHELXS-86 [12] and refined by full-matrix
least-squares on F2 using SHELXL-93 [13]. The H atoms
Scheme 1. Synthesis of [Pt(NH2R)4][Pt(mnt)2] with R=octyl (Oc).

26
J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
Table 3
2.7. Electrical conducti6ity
Crystallographic data and structure refinement parameters for
[Pt(NH2Oc)4][Pt(mnt)2] and [Pt(NH2Et)4][Pt(mnt)2]
The electrical conductivity of [Pt(NH2Oc)4][Pt(mnt)2]
and [Pt(NH2Et)4][Pt(mnt)2] was measured on pellets of
a diameter of 1.3 cm of the pure substances, pressed
under a load of 10 t. In all cases the values were below
[Pt(NH2Et)4]-
[Pt(mnt)2]
[Pt(NH2Oc)4]-
[Pt(mnt)2]
Empirical formula
Formula weight
Temperature (K)
Space group
C
850.88
293(2)
P1
triclinic
16H28N8Pt2S4
C40H76N8Pt2S4
1187.51
293(2)
10−10 S cm−1
.
(
(
P1
Crystal system
triclinic
3. Results and discussion
Unit cell dimensions
,
a (A)
7.906(14)
9.753(10)
9.755(12)
113.77(10)
103.21(11)
103.18(11)
625(2)
10.477(5)
15.157(8)
17.028(9)
83.280(10)
85.80(2)
73.08(2)
2567.(2)
2
Quasi-one-dimensional compounds of the type
[Pt(NH2R)4][Pt(mnt)2] with R=Et (ethyl) or R=Oc
(octyl) were prepared according to Scheme 1. The com-
pounds were finally obtained by precipitation upon
combination of solutions containing [Pt(mnt)2]2− and
[Pt(NH2R)4]2+, respectively. The elemental analyses
(see Section 2) fit well with the proposed composition
of the products.
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
3
,
Z (formula units)
1
Dcalc (g cm−3
)
2.259
11.526
400
1.536
11.820
1184
v (mm−1
F(000)
)
[
min, [max
2.44, 20.04
1179
2.61, 49.98
5266
integration
0.784, 0.214
full-matrix
3.1. Crystal structures
Independent reflections
Absorption correction
Max/min transmission
Refinement method
integration
0.28, 0.13
full-matrix
X-ray analysis of a single crystal of [Pt(NH2Oc)4]-
[Pt(mnt)2] revealed that this compound crystallized in a
triclinic unit cell in the space group P1. All ligand
atoms were arranged in a square planar coordination
sphere, and SꢀPtꢀS and NꢀPtꢀN bond angles between
89.2 and 90.8° were found (Table 4). The PtꢀS bond
lengths in [Pt(mnt)2]2− were equal within the experi-
mental precision (2.29–2.30 A) and corresponded to
the values of other mnt complexes (2.28 A) [14], and the
lengths of the PtꢀN bonds (2.04–2.08 A, cf. Table 4)
were close to those in trans-[PtCl2(NH2R)4] (R=octyl
least-squares on least-squares on F2
(
F2
Data/restraints/
parameters
1179/27/75
5266/0/490
Goodness-of-fit on F2
Final R indices
[I\2|(I)]
1.016
1.049
R1=0.0588,
wR2=0.1462
R1=0.0627,
wR2=0.1522
4.468 and
−4.051
R1=0.0406,
wR2=0.1015
R1=0.0559,
wR2=0.1128
0.908 and −0.671
,
R indices (all data)
,
,
Largest difference peak
−3
,
and hole (e A
)
,
or decyl) and [Pt(NH2Et)4][PtCl4] (2.0–2.1 A) [6,15].
Adjacent anions and cations were staggered by 45°,
analogous to the structure of [Pt(CNMe)4][Pt(mnt)2]
[10]. The positively and negatively charged complex
ions were linearly arranged in alternating sequence. The
coordination planes of equally charged units were par-
allel, but the oppositely charged coordination planes
were tilted by 28.6° to each other, similar to the related
inclination of 29° reported for [Pt(NH2Et)4][PtCl4] [15].
Surprisingly, two different [Pt(NH2Oc)4]2+ entities ap-
peared in the crystal structure of [Pt(NH2Oc)4]-
[Pt(mnt)2] in alternating succession (Fig. 1). In one of
these entities, all alkyl chains were extended parallel to
the coordination plane, while in the other [Pt-
(NH2Oc)4]2+ units, two centrosymmetric pairs of alkyl
chains turned aside from the respective coordination
plane. Two different PtꢀPt distances have been found in
[PtL][PtCl4], where L is the tetradentate ligand N,N%-
bis(2-aminoethyl)-N,N%-bis(2-ethylammonium)ethylene-
diamine [16]. This complex can appropriately be viewed
as a linear assembly of ion pairs which probably form
as a result of H-bonds between the amine groups and
the chlorine atoms. The PtꢀPt distance in such
were included in calculated positions and treated as
‘riding atoms’. It is evident from the lattice parameters
of [Pt(NH2Et)4][Pt(mnt)2] that a transformation from
(
triclinic P1 to monoclinic C2/m is possible. In fact,
structure analysis and refinement in the monoclinic
symmetry showed that the molecules are then (again) in
special positions of 2/m site symmetry with the twofold
rotation axes going through Pt and the centers of the
CꢀC bonds of [Pt(mnt)2]2− and through one of the
CꢀCꢀNꢀPtꢀNꢀCꢀC chains of [Pt(NH2Et)4]2+. The lat-
ter situation can only be described with disorder in
(
C2/m or with twinning in P1. A twinned description
was arbitrarily chosen. The fractional contributions of
the twin components did not deviate significantly from
a 50–50% distribution. In order to reduce correlation
effects due to the extreme monoclinic pseudosymmetry,
only the heavy atoms Pt and S of this structure were
refined anisotropically.

J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
Table 4 (Continued)
27
Table 4
,
Selected bond lengths (A) and bond angles (°) for [Pt(NH2Et)4]-
[Pt(mnt)2] and [Pt(NH2Oc)4][Pt(mnt)2]
C(2)ꢀS(2)ꢀPt(1)
C(5)ꢀS(3)ꢀPt(1)
C(6)ꢀS(4)ꢀPt(1)
C(9)ꢀN(5)ꢀPt(2)
C(17)ꢀN(6)ꢀPt(2)
C(25)ꢀN(7)ꢀPt(3)
C(33)ꢀN(8)ꢀPt(3)
101.5(4)
102.3(4)
102.5(4)
119.7(6)
115.2(6)
115.4(6)
119.0(7)
[Pt(NH2Et)4][Pt(mnt)2]
Bond lengths
Pt(1)ꢀS(1)
2.280(8)
2.280(8)
2.283(8)
2.283(8)
2.06(2)
Pt(1)ꢀS(1)c1
Pt(1)ꢀS(2)
Pt(1)ꢀS(2)c1
Pt(2)ꢀN(3)c2
Pt(2)ꢀN(3)
The standard deviations of the last digits are given in brackets.
Symmetry operations used to generate equivalent atoms in
[Pt(NH2Et)4][Pt(mnt)2]: c1 −x, −y, −z, c2 −x+1, −y, −z; and
in [Pt(NH2Oc)4][Pt(mnt)2]: c1 −x−1, −y, −z, c2 −x, −y+1,
−z.
2.06(2)
Pt(2)ꢀN(4)c2
2.063(12)
2.063(12)
Pt(2)ꢀN(4)
Bond angles
S(1)ꢀPt(1)ꢀS(1)c1
180.0
90.3(2)
89.7(2)
89.7(2)
90.3(2)
180.0
179.999(2)
92.5(9)
87.5(9)
S(1)ꢀPt(1)ꢀS(2)
,
an ion pair amounts to 3.41 A and that between
S(1)c1ꢀPt(1)ꢀS(2)
S(1)ꢀPt(1)ꢀS(2)c1
S(1)c1ꢀPt(1)ꢀS(2)c1
S(2)ꢀPt(1)ꢀS(2)c1
N(3)c2ꢀPt(2)ꢀN(3)
N(3)c2ꢀPt(2)ꢀN(4)c2
N(3)ꢀPt(2)ꢀN(4)c2
N(3)c2ꢀPt(2)ꢀN(4)
N(3)ꢀPt(2)ꢀN(4)
,
adjacent ion pairs 3.96 A. The two different PtꢀPt
,
spacings (3.86 and 4.01 A) in [Pt(NH2Oc)4][Pt(mnt)2] in
alternating sequence arise as a result of the structurally
diverse [Pt(NH2Oc)4]2+ moieties. The distance of 3.8 A
,
is large compared to those in the other Magnus-salt-
type structures (3.15–3.62 A, cf. Table 2). Intermetallic
distances in this range (3.94 A) appear in the Magnus-
,
87.5(9)
92.5(9)
,
N(4)c2ꢀPt(2)ꢀN(4)
179.998(2)
101.8(11)
101.5(10)
115.8(12)
114.9(10)
salt structure in the unusual co-crystal [Ptꢀ(pzH)4]-
[PtCl4]·2[cis-PtCl2(pzH)2] (pzH=pyrazole) [17]. It con-
tains two types of perpendicularly oriented, quasi-one-
dimensional chains composed of [cis-PtCl2(pzH)2] and
[Pt(pzH)4][PtCl4], respectively. Both chains are stabi-
lized by H-bonds between the chloride ions and the
NꢀH units of pyrazole.
The proposed crystal structure of [Pt(NH2Et)4]-
[Pt(mnt)2] is shown in Fig. 2. Here, the ligand atoms are
arranged virtually in a square planar coordination
sphere, although the NꢀPtꢀN bond angles deviate by
4–6° from the ideal coordination geometry (Table 4).
In contrast, the SꢀPtꢀS bond angles are close to 90°
(Table 4). Similar to [Pt(NH2Oc)4][Pt(mnt)2], neighbor-
ing coordination planes are staggered by 45° and tilted,
however, to a somewhat lesser extent (18.4°). In con-
trast to [Pt(NH2Oc)4][Pt(mnt)2], all PtꢀPt distances in
C(1)ꢀS(1)ꢀPt(1)
C(3)ꢀS(2)ꢀPt(1)
C(5)ꢀN(3)ꢀPt(2)
C(7)ꢀN(4)ꢀPt(2)
[Pt(NH2Oc)4][Pt(mnt)2]
Bond lengths
Pt(1)ꢀS(4)
Pt(1)ꢀS(1)
Pt(1)ꢀS(3)
Pt(1)ꢀS(2)
Pt(2)ꢀN(5)
Pt(2)ꢀN(5)c1
Pt(2)ꢀN(6)c1
Pt(2)ꢀN(6)
2.289(3)
2.290(3)
2.292(3)
2.296(3)
2.035(7)
2.035(7)
2.080(7)
2.081(7)
2.050(8)
2.051(8)
2.078(8)
2.078(8)
Pt(3)ꢀN(8)
Pt(3)ꢀN(8)c2
Pt(3)ꢀN(7)c2
Pt(3)ꢀN(7)
Bond angles
S(4)ꢀPt(1)ꢀS(1)
S(4)ꢀPt(1)ꢀS(3)
S(1)ꢀPt(1)ꢀS(3)
S(4)ꢀPt(1)ꢀS(2)
S(1)ꢀPt(1)ꢀS(2)
S(3)ꢀPt(1)ꢀS(2)
N(5)ꢀPt(2)ꢀN(5)c1
N(5)ꢀPt(2)ꢀN(6)c1
N(5)c1ꢀPt(2)ꢀN(6)c1
N(5)ꢀPt(2)ꢀN(6)
N(5)c1ꢀPt(2)ꢀN(6)
N(6)c1ꢀPt(2)ꢀN(6)
N(8)ꢀPt(3)ꢀN(8)c2
N(8)ꢀPt(3)ꢀN(7)c2
N(8)c2ꢀPt(3)ꢀN(7)c2
N(8)ꢀPt(3)ꢀN(7)
,
[Pt(NH2Et)4][Pt(mnt)2] are equal (3.96 A). They corre-
spond to the average intermetallic length in
[Pt(NH2Oc)4][Pt(mnt)2] (3.93 A) and are, therefore,
again unusually large for the Magnus-salt-type com-
plexes. The PtꢀS and the PtꢀN bond lengths are close
to those in [Pt(NH2Oc)4][Pt(mnt)2] (Table 4).
179.30(9)
90.02(9)
89.63(9)
90.26(9)
90.09(10)
179.57(9)
180.0
89.6(3)
90.4(3)
90.4(3)
89.6(3)
180.0
,
3.2. Infrared spectra
An assignment of the IR absorption bands of
[Pt(NH2R)4][Pt(mnt)2] (R=ethyl, octyl) was performed
with the help of related substances reported in the
literature [18], and the corresponding absorption fre-
quencies were compared with those in [Pt(NH2Oc)4]-
[PtCl4] and (NBu4)2[Pt(mnt)2] (Table 5). The IR absorp-
tions of the CꢁC, CꢀS and CꢀCN bonds of the mnt
group were sensitive to the charge and the oxidation
180.0
89.2(3)
90.8(3)
90.8(3)
89.2(3)
180.0
N(8)c2ꢀPt(3)ꢀN(7)
N(7)c2ꢀPt(3)ꢀN(7)
C(1)ꢀS(1)ꢀPt(1)
102.3(4)

28
J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
,
Fig. 1. Crystal structure of [Pt(NH2Oc)4][Pt(mnt)2] (ORTEP); the PtꢀPt distances are 3.86 and 4.01 A, respectively.
state, respectively, of mnt. The typical w(CꢁC) of the
mnt dianion at 1480 cm−1 differed from that of the
mnt monoanion which appeared at 1435 cm−1, and in
fact the related vibrations at 1474–1482 cm−1 in
[Pt(NH2R)4][Pt(mnt)2] indicated that mnt was present
as a dianion in those complexes [18–20]. Generally, the
positions of the bands characteristic for the Pt–mnt
unit emerged in the region of those in (NBu4)2[Pt(mnt)2]
and those characteristic for the Pt–NH2Oc unit in the
area of the related vibrations in [Pt(NH2Oc)4][PtCl4].
both complexes, the remaining mass at 900 °C ex-
ceeded that of the initially present platinum; obviously,
the coordinated ligands did not decompose completely
into volatile products. In comparison with the case of
(NBu4)2[Pt(mnt)2], the residual mass corresponded to
the mass of the initially present platinum.
In order to obtain further information on the en-
dothermic transition at 70 °C of [Pt(NH2Oc)4]-
[Pt(mnt)2], powder X-ray diffraction studies were per-
formed at various temperatures between 30 and 80 °C
in steps of 10 °C. The results clearly indicated that the
distances between the lattice planes and relative intensi-
ties of the individual reflexes changed between 60 and
70 °C (Table 8). Hence, it appeared likely that a solid-
state phase transition is responsible for the enthalpy
change observed around 70 °C although it was not
possible to elucidate the detailed structural changes
with our measurements.
3.3. Thermal analyses
Careful recrystallization was carried out to obtain
reproducible DSC thermograms of [Pt(NH2Oc)4]-
[Pt(mnt)2]. Various endothermal transitions appeared
upon heating (Table 6). The first at 70 °C, accompa-
nied with an enthalpy change of 21 J g−1, was found to
be reversible and appeared, as a consequence, as an
exothermal peak upon cooling. Additional transitions
around 220 °C and above were irreversible. In an
optical microscope, no changes were noted around
70 °C, while decomposition was evident around
220 °C. [Pt(NH2Et)4][Pt(mnt)2] displayed only one en-
dothermal transition, which was irreversible and ap-
peared at 240 °C. At this temperature a color change
from red to brown was observed in the optical micro-
scope which was attributed to decomposition. Charac-
teristic data obtained with TGA are presented in Table
7. The maximum decomposition rate was found to
depend on the heating rate; the values at 10 °C min−1
were 231 °C for [Pt(NH2Et)4][Pt(mnt)2] and 200 °C for
[Pt(NH2Oc)4][Pt(mnt)2]; the latter corresponded to the
high temperature transitions observed in DSC and the
decomposition observed in the optical microscope. For
Fig. 2. Crystal structure of [Pt(NH2Et)4][Pt(mnt)2], the PtꢀPt distance
,
is 3.96 A.

J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
29
Table 5
IR frequencies (cm−1) of [Pt(NH2R)4][Pt(mnt)2], [Pt(NH2R)4][PtCl4] with R=(CH2)7CH3, and (NBu4)2[Pt(mnt)2]
Assignment
w(NꢀH)
[Pt(NH2Et)4][Pt(mnt)2]
[Pt(NH2Oc)4][Pt(mnt)2]
(NBu4)2[Pt(mnt)2]
[Pt(NH2R)4][PtCl4]
3257s
3226s
2987m
2972m
2930m
2205s
2197sh
1591s
1573s
1474s
1445s
1383m
1154s
1106w
867m
730s
3245s
3127m
2956s
2927s
2856s
2210s
2205s
1579s
3210
3133
2957
2924
2853
w(CꢀH)
w(CN)
2197sh
2186s
l(NH2)
1586
w(CꢁC)
l(CH2)
l(CH3)
1482s
1468s
1378m
1153s
1108w
883m
729s
1479s
1467
1378
w(CꢀS)+w(CꢀC)
y(CꢀCN)
w(CꢀS)
1151s
1109m
885m
k(CH2)
724
Ring deformation
y(CꢀCN)
w(PtꢀS)
508s
508s
511s
498 sh
330m
322m
334m
322s
332m
318m
3.4. Vapor phase osmometry
L–M, and M–L transitions as described in the litera-
ture [21]. Accordingly, the respective umax are close to
those in (NBu4)2[Pt(mnt)2] (Table 9). The weak absorp-
tion maxima of the d–d transitions, as far as de-
tectable, in (NBu4)2[Pt(mnt)2] and [Pt(NH2R)4]-
[Pt(mnt)2] do not agree (Table 9), which might indicate
a Pt–Pt interaction in the dissolved [Pt(NH2R)4]-
[Pt(mnt)2] ion pairs.
Emission of [Pt(NH2Oc)4][Pt(mnt)2] in acetonitrile
was measured between 200 and 800 nm. Excitation was
performed with wavelengths between 220 and 500 nm
at every 10 nm. Significant emission was found at
excitation wavelengths between 250 and 340 nm. The
emission spectra obtained at these excitation wave-
lengths did not differ considerably. Emission maxima
arose at 345 and 363 nm, and the Stokes shift
amounted to 28 nm. It is unlikely that emission was due
to a d–d transition [22] or an L–L transition because
mnt itself is not photoemitting [23]. Hence, the ob-
(
The number average molecular weight (Mn) of
[Pt(NH2Oc)4][Pt(mnt)2] was determined with vapor
phase osmometry in acetone at 25 °C. The resulting
value of 1000 g mol−1 was in the range of that of the
formula unit (1188 g mol−1), and we ascribe the
difference to the limited precision of the measurement
method or to impurities such as solvent molecules
(
which decrease Mn. Hence, [Pt(NH2Oc)4][Pt(mnt)2]
appeared to be present in solution predominantly as an
ion pair, and not as individually dissolved complex ions
or oligomeric or polymeric structures. The limited
solubility of [Pt(NH2Et)4][Pt(mnt)2] did not allow to
obtain reliable values by vapor phase osmometry.
3.5. UV–Vis absorption and emission spectra
UV–Vis absorption spectra of [Pt(NH2R)4][Pt(mnt)2]
(R=ethyl or octyl) were measured in acetonitrile
(Table 9) and acetone; in the latter, however, UV light
was essentially quantitatively absorbed below approxi-
mately 350 nm. The absorption spectrum of the two
compounds did not considerably differ from each other.
Table 6
Reversible (r) and irreversible (i) transitions observed in DSC under
nitrogen atmosphere at different heating rates (°C min−1
)
Heating rate
10
[Pt(NH2Et)4][Pt(mnt)2] [Pt(NH2Oc)4][Pt(mnt)2]
In acetonitrile, pronounced absorption maxima (umax
)
T
Type
i
T
DH Type
or shoulders in the range of 250–1500 nm appeared
around 520, 470 (480 nm in acetone, and 472 nm in the
solid state, respectively, for R=octyl), 340 (340 nm in
the solid state, R=octyl), and 315 nm. Since these
absorptions are characteristic for [Pt(mnt)2]2− [21] and
[Pt(NH2Oc)4]Cl2 shows only one strong absorption
maximum at 237 nm (in ethanol), the umax mentioned
for [Pt(NH2R)4][Pt(mnt)2] originate most likely in L–L,
240
72
22
r
i
ꢀ200
221
71
i
1
0.2
21
21
r
r
70
Transition temperatures (T) are given in °C and enthalpy changes
(DH) of the reversible transitions in J g−1
.

30
J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
Table 7
Decomposition temperatures obtained with thermogravimetric analysis (TGA) under nitrogen atmosphere at different heating rates (in °C min−1
)
Compound
Heating rate
Ton
Tmax
m900
mPt
[Pt(NH2Et)4][Pt(mnt)2]
[Pt(NH2Oc)4][Pt(mnt)2]
10
10
0.2
185
118
113
231
200
154
53
42
46
33
a
a
Ton is the temperature at the onset of mass loss (in °C), Tmax the temperature at maximum mass loss rate (in °C), m900 the mass remaining at
900 °C (in %w/w), and mPt the initial mass of platinum in the respective metal complexes (in %w/w).
a Not determined.
Table 8
dynamic processes in the ligand sphere of the platinum
complexes.
2q Reflections (hkl in °) and relative intensities (I in %) observed in
powder X-ray diffraction spectra of [Pt(NH2Oc)4][Pt(mnt)2] at differ-
ent temperatures (T)
hkl
T=30 °C
2q
T=80 °C
2q
4. Conclusions
I
I
[Pt(NH2Et)4][Pt(mnt)2] and [Pt(NH2Oc)4][Pt(mnt)2]
contain linearly stacked platinum atoms, but a pro-
nounced distinction is the number of formula units per
unit cell, which was found to be two in the case of
[Pt(NH2Oc)4][Pt(mnt)2] and one for [Pt(NH2Et)4]-
[Pt(mnt)2]—the latter being usual for compounds of the
Magnus-salt-type which have been structurally charac-
terized so far. As a result of its uncommon structure,
[Pt(NH2Oc)4][Pt(mnt)2] displayed two different inter-
001
111
002
−1−11
113
5.08
10.02
10.23
10.91
15.62
22.69
22.91
100
47
46
39
32
45
44
4.70
9.60
10.01
100
43
38
16.98
21.06
23.14
26
26
35
−130
−131
The spectra at temperatures of 30, 40, 50, and 60 °C on the one hand
and those at 70 and 80 °C on the other hand are essentially identical.
,
metallic spacings (3.86 and 4.01 A), the average of
which is close to the related value of [Pt(NH2Et)4]-
,
served fluorescence is probably caused by M–L or
L–M transitions. Other luminescent Magnus-salt-like
compounds, [Pt(bipy)2][Pt(CN)4] and [Pt(phen)2]-
[Pt(CN)4], unlike the present materials, contain the
typical luminescence-promoting ligands 2,2%-bipyridine
(bipy) or 1,10-phenanthroline (phen) [24]. These com-
pounds exhibit an emission maximum at 620 and 650
nm, respectively [24].
[Pt(mnt)2] (3.96 A). Generally, the PtꢀPt distances in
the [Pt(NH2R)4][Pt(mnt)2] complexes were established
to be large compared to those in the typical Magnus-
,
salt-like complexes (3.15–3.62 A). It appears that pack-
ing of the alkyl chains determined the PtꢀPt distance,
rather than the electrostatic interactions between the
oppositely charged complex ions. In addition, an un-
usual solid-state phase transition was observed in
[Pt(NH2Oc)4][Pt(mnt)2], but not in [Pt(NH2Et)4]-
[Pt(mnt)2], which could originate in a reversible change
in the packing of the octyl chains.
The platinum stacks of [Pt(NH2Oc)4][Pt(mnt)2] de-
cayed in solution in acetone, yielding predominantly
ion pairs. In the absence of a crystalline packing of the
alkyl chains, the electrostatic forces apparently were
not sufficient to maintain the ion pairs in close proxim-
1H and 13C NMR spectra of [Pt(NH2Oc)4][Pt(mnt)2]
showed the characteristic signals of the 1-aminooctyl
group (cf. Section 2). Peaks of mnt were absent in the
13C NMR spectrum at the acquisition parameters used
here due to the large relaxation times of the carbon
atoms in mnt. Also, no signals were found in 195Pt
NMR spectra, as in the case of [Pt(NH2Oc)4][PtCl4] [6],
probably due to very short relaxation times or to
Table 9
Absorption maxima (in nm) in UV–Vis spectra measured in acetonitrile
Transition
[Pt(NH2Et)4][Pt(mnt)2]
[Pt(NH2Oc)4][Pt(mnt)2]
(NBu4)2[Pt(mnt)2] [21]
d–d
M–L and d–d
M–L
L–L
L–M
855 (20)
521 a
474 (4000)
339 (15 000)
311 a
865 (19)
517 a
469 (6500)
337 (25 000)
317 a
694, 639
541
476
337
310
Molar extinction coefficients (in M−1 cm−1) are given in brackets.
a Shoulder.

J. Bremi et al. / Inorganica Chimica Acta 322 (2001) 23–31
[25] J. Reiset, C. R. Acad. Sci. Paris 18 (1844) 1100.
31
ity. Pronounced absorption maxima found in UV–Vis
spectra of the dissolved [Pt(NH2R)4][Pt(mnt)2] com-
plexes are characteristic for the [Pt(mnt)2]2− units, and
emission maxima were observed at 345 and 363 nm
upon excitation between 250 and 340 nm.
[26] H. Buff, E. Dieffenbach, C. Ettling, F. Knapp, H. Will, F.
Zamminer, Jahresber. Fortschr. rein. pharm. techn. Chem. Phys.
Mineral. Geol. (1850) 335.
[27] C. Gerhardt, J. Prakt. Chem. 53 (1851) 345.
[28] C. Gerhardt, C. R. Acad. Sci. Paris 31 (1850) 241.
[29] F. Wo¨hler, J. Liebig, Ann. Chem. Pharm. (Liebig’s Ann.) 76
(1850) 307.
[30] W. Olding, Chem. News 21 (1870) 289.
[31] J. Reiset, J. Prakt. Chem. 33 (1844) 21.
Acknowledgements
[32] M.L. Rodgers, D.S. Martin, Polyhedron 6 (1987) 225.
[33] J.R. Miller, J. Chem. Soc. (1965) 713.
We are indebted to A. Ha¨ne and Y Sta¨dler for
[34] A. Wurtz, Ann. Chim. Phys. Se´r. 3 30 (1850) 443.
[35] V.I. Belova, Ya.K. Syrkin, L.I. Baranova, Zh. Neorg. Khim. 6
(1961) 625; Engl. Transl. Russ. J. Inorg. Chem. 6 (1961) 319.
[36] J.R. Miller, Proc. Chem. Soc. (1960) 318.
[37] S.M. Jo¨rgensen, S.P.L. So¨rensen, Z. Anorg. Chem. 48 (1906)
441.
experimental assistance.
References
[1] G. Magnus, Pogg. Ann. 14 (1828) 239.
[38] S. Yamada, R. Tsuchida, Bull. Chem. Soc. Jpn. 31 (1958) 813.
[39] J.R. Miller, J. Chem. Soc. (1961) 4452.
[40] S.M. Jo¨rgensen, J. Prakt. Chem. 141 (1886) 489.
[41] W. Heffels, J. Friedrich, C. Darribe`re, J. Teisen, K. Interewicz,
C. Bastiaansen, W. Caseri, P. Smith, Recent Res. Dev. Macro-
mol. Res. 2 (1997) 143.
[2] G. Magnus, Ann. Chim. Phys. Se´r. 2 40 (1829) 110.
[3] M. Peyrone, Ann. Chim. Phys. Se´r. 3 12 (1844) 193.
[4] M. Peyrone, Ann. Chem. Pharm. (Liebig’s Ann.) 51 (1844) 1.
[5] A. Hantzsch, F.Z. Rosenblatt, Z. Anorg. Allg. Chem. 187 (1930)
241.
[6] J. Bremi, D. Brovelli, W. Caseri, G. Ha¨hner, P. Smith, T.
Tervoort, Chem. Mater. 11 (1999) 977.
[42] K. Honda, K. Chiba, E. Tsuchida, A.J. Frank, J. Mater. Sci.
Lett. 24 (1989) 4004.
[7] M. Atoji, J.W. Richardson, R.E. Rundle, J. Am. Chem. Soc. 79
(1957) 3017.
[8] S.M. Jo¨rgensen, S.P.L. So¨rensen, Z. Anorg. Chem. 48 (1906)
441.
[9] E. Hertel, K.Z. Schneider, Anorg. Chem. 202 (1931) 77.
[10] H. Bois, N.G. Connelly, J.G. Crossley, J. Guillorit, G.R. Lewis,
A.G. Orpen, P. Thornton, J. Chem. Soc., Dalton Trans. (1998)
2833.
[11] A. Davison, R.H. Holm, R.E. Benson, W. Mahler, Inorg. Synth.
8 (1979) 16.
[43] V.H. Houlding, A.J. Frank, Inorg. Chem. 24 (1985) 3664.
[44] H.D.K. Drew, J. Chem. Soc. 2 (1932) 2328.
[45] H.D.K. Drew, H.J. Tress, J. Chem. Soc. (1933) 1335.
[46] G.W. Watt, W.A. Cude, Inorg. Chem. 7 (1968) 335.
[47] L. Tschugaeff, P. Teearu, Ber. Deutsch. Chem. Ges. 47 (1914)
568.
[48] H.J. Keller, R. Lorentz, Z. Naturforsch., Teil B 31 (1976) 565.
[49] E.G. Cox, H. Saenger, W. Wardlaw, J. Chem. Soc. (1934) 182.
[50] L. Tchougaeff, D. Fraenkel, C. R. Acad. Sci. Paris 154 (1912)
33.
[12] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[13] G.M. Sheldrick, SHELXL93, Program for Crystal Structure Refin-
ement, University of Go¨ttingen, Go¨ttingen, Germany.
[14] W. Gu¨ntner, G. Gliemann, U. Klement, M. Zabel, Inorg. Chim.
Acta 165 (1989) 51.
[15] M.E. Cradwick, D. Hall, R.K. Phillips, Acta Crystallogr. 27
(1971) 480.
[16] K. Sakai, Y. Tanaka, T. Tsubomura, Acta Crystallogr., Sect. C
52 (1996) 541.
[17] K. Sakai, Y. Tomita, T. Ue, K. Goshima, M. Ohminato, T.
Tsubomura, K. Matsumoto, K. Ohmura, K. Kawakami, Inorg.
Chim. Acta 297 (2000) 64.
[18] C.W. Schla¨pfer, K. Nakamoto, Inorg. Chem. 14 (1975) 1338.
[19] J.A. McCleverty, Prog. Inorg. Chem. 10 (1968) 86.
[20] J.A. McCleverty, Prog. Inorg. Chem. 10 (1968) 96.
[21] S.I. Shupack, E. Billig, R.J.H. Clark, R. Williams, H.B. Gray, J.
Am. Chem. Soc. 86 (1964) 4594.
[22] W. Tuszynski, G. Gliemann, Z. Naturforsch., Teil A 34 (1979)
211.
[23] C.E. Johnson, R. Eisenberg, T.R. Evans, M.S. Burberry, J. Am.
Chem. Soc. 105 (1983) 1795.
[51] L. Tschugaeff, W. Subbotin, Ber. Deutsch. Chem. Ges. 43 (1910)
1200.
[52] L. Tschugaeff, A. Kobljanski, Z. Anorg. Allg. Chem. 83 (1913)
8.
[53] G.T. Morgan, V.E. Yarsley, J. Chem. Soc. 127 (1925) 184.
[54] S. Yamada, J. Am. Chem. Soc. 1579 (1951) 73.
[55] G.B. Buckton, Ann. Chem. Pharm. 78 (1851) 328.
[56] I.I. Chernyaev, N.N. Zhekigovskaya, A.V. Babkov, Zh. Neorg.
Khim. 6 (1961) 2627; Engl. Transl. Russ. J. Inorg. Chem. 6
(1961) 1328.
[57] O.N. Estav’eva, I.B. Baranovskii, A.V. Babaeva, Zh. Neorg.
Khim. 10 (1965) 27; Engl. Transl. Russ. J. Inorg. Chem. 10
(1965) 14.
[58] Yu.N. Kukushkin, L.V. Vrublevskaya, S.I. Bakjireva, E.N. Ka-
lyukova, Zh. Neorg. Khim. 25 (1980) 1302; Engl. Transl. Russ.
J. Inorg. Chem. 25 (1980) 723.
[59] P.D. Harvey, K.D. Truong, K.T. Aye, M. Drouin, A.D. Ban-
drauk, Inorg. Chem. 33 (1994) 2347.
[60] C.E. Buss, C.E. Anderson, M.K. Pomije, C.M. Lutz, D. Britton,
K.R. Mann, J. Am. Chem. Soc. 120 (1998) 7783.
[61] C.A. Daws, C.L. Exstrom, J.R. Sowa Jr., K.R. Mann, Chem.
Mater. 9 (1997) 363.
[24] V.M. Miskowski, V.H. Houlding, Inorg. Chem. 30 (1991) 4446.
.