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High Mass Resolution Plasma Desorption and Secondary Ion Mass
Spectrometry of Neutral Nickel Thiolate Complexes.
Crystal Structure of [Ni6(SC3H7)12]
H erbert Feld, Angelika Leute, Derk Rading, and Alfred Benninghoven
Physikalisches Institut der U niversität Münster,
W ilhelm-Klemm-Straße 10, D-W-4400 Münster
G. Henkel
Fachgebiet Festkörperchemie der Universität Duisburg,
Lotharstraße 1, D-W-4100 D uisburg 1
Thom as K rüger and Bernt Krebs*
Anorganisch-Chemisches Institut der Universität Münster,
W ilhelm-Klemm-Straße 8, D-W-4400 M ünster
Z. N aturforsch.
47b,
929-936 (1992); received January 23, 1992
Plasma D esorption Mass Spectrometry, Secondary Ion Mass Spectrometry,
Nickel Thiolate Complexes, Crystal Structure
The use o f mass spectrometry for the analysis of transition metal complexes is dem onstrated
by combined high resolution Plasma Desorption Mass Spectrometry (PDM S) and Secondary
Ion Mass Spectrometry (SIMS) investigations of the neutral nickel thiolate complexes
[Ni4(SC3H 7)8] (1 ), [Ni4(SC6H n)8] (2 ), [Ni8(SCH2CO O Et)16] (3 ) and [Ni6(SC3H 7) ,J (4 ). The posi­
tive spectra are dominated by three kinds of SI-species: (a) molecular ions, (b) fragment ions
and (c) m olecular ions with one or more substrate atoms attached. The negative spectra show
mainly nickel sulfur cluster ions of the composition ( N i ^ ) - . In contrast to many Fast Atom
Bom bardm ent (FAB) spectra o f neutral metal complexes, SIMS and PDM S spectra provide
molecular weight as well as fragment ion information. Both techniques are m ost powerful
tools for the investigation of coordination compounds because the samples are easy to prepare
and the spectra are independent of matrix conditions. Additionally crystallographic studies
have been carried out for 4 . The hexanuclear complex 4 with square planar N i- S coordination
sites crystallizes in the trigonal space group R 3 with Z = 3 and a = 18.537(5), c = 13.966(3)Ä.
1. Introduction
Mass spectrom etry has proven to be a useful
tool for the investigation of coordination com­
pounds. As is well known the mass spectra provide
not only inform ation about the molecular weight
of parent ions but also structural inform ation by
the observation o f fragmentation patterns. The
predom inant part o f investigations concerning
metal complexes was done by fast atom bom bard­
ment (FAB) or field desorption (FD) mass spec­
trom etry [1-3]. On the other hand, little work has
been carried out with plasma desorption (PDMS)
[4] or secondary ion (SIMS) [5] mass spectrometry.
The former PD M S and SIMS investigations are
limited regarding mass resolution, mass range, or
* Reprint requests to Prof. Dr. B. Krebs.
Verlag der Zeitschrift für Naturforschung,
D-W-7400 Tübingen
0932-0776/92/0700-0929/$ 01.00/0
transmission o f the analyzers used (quadrupole,
magnetic sector field). To assess the analytical po­
tential of these desorption m ethods in com bina­
tion with a time-of-flight (TOF) mass analyzer we
have now perform ed for the first time a combined
PDM S/SIM S investigation of coordination com ­
pounds. PDM S and SIMS spectra have been ob­
tained for a series o f different kinds of metal com ­
plexes. According to their different behavior in the
desorption process the investigated complexes can
be divided into three groups: firstly neutral transi­
tion metal complexes, secondly 1 + and 2 + cation­
ic complexes and thirdly ligand stabilized metal
clusters. The results concerning the latter two
groups are described elsewhere [6, 7] whereas this
paper focusses on neutral transition metal com­
plexes.
In order to investigate the secondary ion (SI)
emission o f neutral metal complexes we measured
PDM S and SIMS spectra o f a series of group VIII
(Ni, Pd, Pt) coordination com pounds. In the last
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three decades a great num ber of complexes has
been synthesized with sulfur containing ligands.
These com pounds have found an increasing inter­
est due to the impressive variety o f different struc­
tural principles [8] and their significance for bio­
logical systems [9—11]. Here we want to dem on­
strate the basic results of the mass spectrometric
investigation for a representative and typical selec­
tion of nickel thiolate complexes. As the neutral
complexes of this group are cyclic, the num ber of
metal centers can be changed without changing the
basic structure principle. Thus it is possible to ob­
serve the SI emission in dependence on the m o­
lecular size. We report on four complexes with a
nuclearity of four, six and eight. One o f the com ­
pounds investigated has been synthesized for the
first time. An X-ray structure determ ination was
carried out to assure both the empirical formula
and the structure o f the com pound.
2. Experimental Section
Instrumental
The mass spectra were obtained with a new
com bination PDM S/SIM S time-of-flight mass
spectrometer (T O F -M S ) developed in M ünster
[12]. In this instrum ent the sample can be bom ­
barded consecutively with prim ary ions in the keV
(SIMS) or MeV (PDM S) energy range. In the
SIMS mode, a continuous beam o f 10 keV X e+ions is chopped by a 90°-deflection unit resulting
in m ass-separated prim ary ion pulses. The pulse
width is about 1 ns with an intensity of 5000 ions/
pulse and a repetition rate o f 5 kHz. F or the
PDM S mode, fission fragments are delivered from
a retractable annular 252Cf-source that can be
placed between the target and the SI extractor. A
source activity o f 15 //Ci leads to about 300 single
desorption events per second in a sample area of
2 mm2. The beam diam eter in SIMS is adjusted to
this area.
In both cases the prim ary ions hit the same tar­
get area from the same side, thus allowing a direct
com parison o f both desorption m ethods in the
same instrum ent w ithout breaking the vacuum.
Secondary ions generated at the target surface are
extracted through the same secondary ion optics
and mass separated by the same analyzer. D epend­
ing on the special analytical problem, the TO F-analyzer can be operated as a linear-type or reflectron-type analyzer. Due to the initial kinetic ener­
gy distribution the mass resolution (R = m/zfm) of
H. Feld et al. • Mass Spectrometry of Nickel Thiolates
the instrum ent is small for the linear operation
mode (R ~ 500
1000), but high mass resolution
(R ~ 8000) can be achieved by energy focussing
with the reflectron-type analyzer. F urther details
are described elsewhere [12, 13].
Two ways of sample preparation were used. Ei­
ther the sample material was dissolved in C H 2C12
and some //I of this solution (about 10~3 m ol/ 1)
were deposited onto a substrate area o f about 0.4
cm2, or small crystals (crystal dimension < 0.1
mm) taken from the reaction recipient were direct­
ly put onto the substrate (crude sample). The sub­
strate was a thin aluminum foil (2 //m) with a silver
suspension on the sample side. By this suspension
the irradiated target is drastically enlarged. U sual­
ly thick samples (> 100 monolayer equivalents)
were investigated.
The prim ary ion dose density (PID D ) was var­
ied between IO10- - 1013 X e+ ions/cm 2 in SIMS and
106--10 9 fission fragments/cm 2 in PDM S, respec­
tively. Thus typical spectra accumulation times are
1 h for PDM S and 1 min for SIMS. Negative and
positive SIMS as well as PDM S spectra were taken
for all samples; the mass spectra in Figs. 2, 3, and 4
were carried out in the reflection mode. A ddition­
ally spectra were accumulated for different flight
paths of the secondary ions (linear and reflection
mode) to determine the stability of the SI. From
these measurements the rate constant for fragm en­
tation of the SI and their half life times are calculat­
ed [14]. The SI-yield is determined by dividing
Fig. 1. Structure of the [Ni6(SC3H 7)12] molecule in the
crystal (H-atoms omitted).
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H. Feld et al. ■Mass Spectrometry of Nickel Thiolates
(M -
S 3Ci 2H28)+
CV °
^
563.56
8 6°o - 5 6 3 .7 7 -
u
^ 400
(563.66)
D
O
U
565.66 (565.66)
i-— 5 6 7 .5 5 -5 6 7 .7 6 (567.66)
1-— 569.65 (569.65)
-j? 200
0
550
(c a lc u la ted )
0.1
?
< Nc
i'll.
600
0.2
iso to p ic d istrib u tio n
c\
.N( A
/c
7c sN A ,s cN
C
Nix ^Ni
C
-C
931
650
| It
iso to p ic d istrib u tio n
(from
spectrum )
_______ J
700
750
800
850
mass / u — —
Fig. 2. Positive PDM S spectrum (high-mass range, PID D = 2.3- 108/cm2) of [Ni4(SC3H 7)g] and calculated isotopic
peak distribution. The fragment ion peak is shown with measured and calculated (in brackets) mass values.
Fig. 3. Positive SIMS spectrum of [Ni6(SC3H 7)12], (highmass range, PID D = 4- 10'°/cm2).
Fig. 4. Negative SIMS spectrum o f [Ni4(SC3H 7)g],
(PID D = 6.9- 10n/cm2).
the background corrected integrated peak area by
the prim ary ion dose, whereas the yield ratio Y' is
defined by the ratio of SI-yields in PDM S and
SIMS: Y' = Y(PDM S)/Y(SIM S).
com pounds are often formed as the main products
besides cyclic complexes. The num ber of metal
centers in the ring probably depends on the size of
the ligands and the packing forces in the crystal
lattice. The com pounds [Ni4(SC 3H 7)8] (1),
[Ni4(SC 6H n )8] (2) and [Ni8(SCH 2C O O Et)16] (3)
were prepared as reported in the literature
[15-17].
Materials
Nickel(II)chloride and 1-propanethiol
used as commercially available compounds.
were
Preparation o f [ Ni 6(S C 3H 7) 12] (4)
Synthesis
Due to the high affinity of Ni(II) ions to sulfur
generally high reaction rates occur with sulfur con­
taining ligands. During the synthesis of nickel
thiolate com pounds insoluble polymeric chain
1-Propanethiol (1.52 g, 20 mmol) was added u n ­
der a stream o f nitrogen to a solution of sodium
methylate obtained from sodium (0.46 g, 20 mmol)
in 40 ml of methanol. NiCl 2 (0.65 g, 5 mmol) was
added and the resulting solution was filtered after
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H. Feld et al. • Mass Spectrometry of Nickel Thiolates
stirring for 1 d. The dark precipitate was washed
with m ethanol and dissolved in 20 ml of C H 2C12.
After stirring for 3 h, the dark red solution was fil­
tered and evaporated to a volume o f 10 ml. At
-2 0 °C black crystals suitable for X-ray diffrac­
tion were formed within 3 d. All operations were
carried out in degassed solvents under a pure ni­
trogen atmosphere. Elemental analysis gave satis­
factory results.
gram package SHELXTL PLUS. An empirical ab­
sorption correction was carried out. All non-hydrogen atoms were treated anisotropically, where­
as the hydrogen atoms were calculated at idealized
positions ( C - H 0.96 Ä) assuming an isotropic
tem perature factor coefficient of 0.08 Ä2. The final
coordinates together with the equivalent isotropic
tem perature factors are given in Table II [28].
3. Results
Collection and reduction o f X-ray data
Crystal and molecular structure o f [ Ni 6(SC 3H 7) I2]
Crystals of 4 were obtained from the reaction
mixture. X-ray diffraction data were collected at
room tem perature on a Siemens R 3 four-circle dif­
fractom eter equipped with a M oK a source, a
graphite m onochrom ator and a scintillation
counter. Details o f data collection are given in
Table I.
Table I. [Ni6(SC3H 7)12]: Details o f data collection and
structure refinement.
Form ula
Mol. wt.
a[M
c[Aj
^"36^84^*6^12
V[A3]
Crystal system
Z
dcalc>[g Cm“3]
Space group
Crystal dimensions
// [cm"1] (M oK a)
Scan speed [deg/min] in 2 6
Scan mode
20max,[deg.]
No. of unique data measd.
No. of obsd. data (I > 1.96er(I))
No. of variables
R/R w
1253.99
18.537(5)
13.966(3)
4156.0
trigonal
3
1.50
R3
0.4x0.4x0.3
24.7
4 -2 9
6126 scan
54
2021 (+h, +k, ± 0
1829
82
0.027/0.034
Solution and refinement o f the structure
The structure was solved by direct methods and
refined by full m atrix least squares using the p ro ­
Atom
X
Ni
S(l)
S(2)
C (l)
C(2)
C(3)
C(4)
C(5)
C(6)
0.18136(1)
0.17204(3)
0.17028(3)
0.12683(15)
0.13498(17)
0.09884(21)
0.26270(14)
0.34337(15)
0.37669(16)
y
0.07934(1)
-0.01486(3)
-0.01420(3)
-0.01071(14)
-0.06579(17)
-0.06121(20)
-0.02573(15)
0.05204(17)
0.12097(19)
z
0.00053(2)
0.10250(3)
-0.10473(4)
0.21703(14)
0.29093(16)
0.38647(18)
-0.09141(18)
-0.12228(18)
-0.05104(21)
According to the X-ray structure determ ination
the unit cell contains three cyclic [Ni6(SC 3H 7)12]
molecules (point symmetry 3) which are composed
of nearly perfect hexagons of nickel atom s with
two doubly bridging thiolate ligands between each
adjacent pair (Fig. 1). The resulting metal coordi­
nation is approximately square planar (Table III).
The N i-N i distances of 2.919Ä, excluding strong
m etal-m etal interactions, and the N i-S bond
lengths with a mean of 2.201 Ä are com parable to
the corresponding values in other known cyclic
hexanuclear nickel thiolate complexes [18- 23].
S I emission
Since both dried sample solutions and crystals
of all investigated compounds lead to the same
spectra no distinction between both preparation
methods is necessary. The PDM S and SIMS spec­
tra do not show any significant differences. In gen­
eral the positive mass spectra can be divided into
two parts: the mass region below and above m ~
300 u. The low mass region is dom inated by sec­
ondary ions originating from the ligands and
hydrocarbon contamination. In the mass range
> 300 u mainly three types of SI species are found:
(a) molecular ions, (b) fragment ions and (c) m o­
lecular ions with one or more substrate atom s a t­
tached.
U eq *
0.03064(12)
0.03557(22)
0.03579(22)
0.0459(11)
0.0588(13)
0.0852(18)
0.0501(11)
0.0587(13)
0.0752(15)
Table II. [Ni6(SC3H 7)12]: Positional param ­
eters and equivalent isotropic thermal pa­
rameters.
*
The isotropic equivalent tem perature
factor is defined as one-third of the trace
of the orthogonalized
tensor.
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H. Feld et al. • M ass Spectrometry of Nickel Thiolates
Table III. [Ni6(SC3H 7)12]: Selected distances and angles3.
Distances (Ä)
N i- N i'
N i- S ( l)
N i-S (2 )
2.919(1)
2.192(1)
2.203(1)
N i'- N i- N i"
S ( l) - N i—S(l')
S (l) - N i-S (2 )
S ( l) - N i—S(2')
N i - S ( l) - N i'
120.0( 1)
N i- S ( l')
N i-S (2 ')
2.204(1)
2.206(1)
Angles (deg)
178.4(1)
82.4(1)
98.1(1)
83.2(1)
S (2 ) -N i- S (l')
S (2 )-N i-S (2 ')
S (2 ')- N i- S ( l')
N i-S (2 )-N i'
97.3(1)
176.6(1)
82.0(1)
82.9(1)
a Symmetry transform ation: ('): +x-y, +x, -z; ("): +y,
-x+ y, -z.
(a) and (b)
The first and m ost im portant SI species is the
m olecular ion o f the metal complex, observed
from all samples with the exception o f 3. The sec­
ond SI species is a relatively heavy fragment ion
that is formed by a rearrangem ent under ion bom ­
bardm ent. Both SI species are shown in the PDMS
spectrum of 1 (Fig. 2), which is dom inated by two
peaks at 565 u and 836 u. Besides the molecular
ion peak at higher mass, the lower mass ion is
probably due to a fragm entation of the complex
and subsequent rearrangem ent o f the molecular
structure. From a chemical point of view several
suggestions for this fragment ion are possible. By
the high mass resolution and accuracy of the ob­
tained mass spectrum the num ber of possible ex­
planations for this previously unknown rearrange­
ment product is drastically reduced. The com pari­
son o f calculated and measured isotopic peak
pattern suggests a ( M - S 3C 12H 28)+ secondary ion
as shown in Fig. 2. This ion can be formed by
the splitting o f three complete ligands and the
alkyl group o f a fourth ligand. The remaining
sulfur atom may be situated above the center of
the nickel ring bridging all adjacent Ni atoms.
This suggestion is supported by the fact that the
same rearrangem ent principle is observed in
the mass spectra of [Ni4(SC 6H n)8] and
[Ni8(SCH 2C O O Et)16],
(c)
The third type o f secondary ions observed in
the positive mass spectra are molecular ions with
one or m ore substrate atom s (Ag) attached. This
secondary ion kind is only observed in the spectra
of 1 and 4. Fig. 3 shows the peaks of the molecular
and quasim olecular ions in the positive SIMS
spectrum o f com pound 4. Due to the high mass re­
solution and accuracy o f the corresponding signal,
the peak centered at about 1360 u was unam big­
uously derived to correspond to (M + A g)+ with
M = [Ni6(SC 3H 7) 12] by com paring the calculated
and measured isotopic peak distribution. The very
rare case of an attachm ent of eight silver atom s to
the molecular ion is only obtained by keV ion
bom bardm ent of 1. The corresponding peak is
centered at 1699.1 u. O ther substrate materials do
not show any attachm ents to the molecular ion so
that in some cases an enhancement o f the molecu­
lar ion peak is observed.
The negative SIMS and PDM S spectra of all
com pounds are dom inated by nickel sulfur cluster
ions o f the com position (Ni^S^)- . F or most of
these ions an excess of metal atom s is observed: i.e.
x > y. The distribution o f these cluster ions ranges
from x, y = 4 up to x, y « 30. The highest intensity
is observed for the peaks o f the symmetric cluster
ions (Ni 4S4)~ and (Ni 4S4)2_. Fig. 4 shows the nega­
tive SIMS spectrum o f 1. The whole series o f sig­
nals is due to ions of the com position N ixS;c_2,
NiA - i and N ixSx.
All spectra show a similar mass resolution for
peaks resulting from the same SI species. High
mass resolution is obtained for the molecular ion
peaks whereas the fragm ent ion peaks are not well
resolved. F or all complexes investigated the yields
Y o f all characteristic secondary ions are signifi­
cantly higher in PDM S than in SIMS. The abso­
lute yields range from 0.01 to 0.4% in PDM S and
between 0.001 and 0.08% in SIMS. The exact val­
ue depends on the special complex and the consid­
ered SI species. The yield o f molecular ions de­
creases with increasing diam eter o f the metal thiolate ring, whereas the yields o f fragm ent ions
increase. The yield ratio Y' = Y(PDM S)/Y(SIM S),
however, is mainly determined by the kind o f SI
species. Y' varies between four (fragment ions) and
eight (molecular ions).
The stabilities of the generated secondary ions
are estimated by m easuring their half life times.
Values from about 100 //s (fragment ions) up to
one ms (molecular ions) are found. Generally the
stabilities o f these ions are only slightly higher in
PDM S than in SIMS. Especially the molecular ion
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934
of 4 with one silver atom attached, (M + Ag)+, has
a very high stability, even as com pared to the m o­
lecular ion itself. The half life times t 1/2 of these SI
species in SIMS are 190 //s for M + and 640 ^s for
(M + A g )\
4. Discussion
The yield ratio Y' (Y' ~ 5) and the dependence
of the absolute SI-yield Y on the mass (respectively
size) is relatively small for this group of metal com ­
plexes com pared to other classes o f com pounds, e.g.
cationic metal complexes [7], peptides [24] or poly­
mers [25] (Y' ~ 20 " 100). This behavior is typical
for substances with a low interm olecular binding
energy. Due to the fact that the desorption-active
area is distinctly higher in PDM S than in SIMS,
the molecular size o f strongly bonded molecules
has a stronger effect on the decrease o f the SI-yield
in SIMS than in PDM S. By contrast, this phenom ­
enon is not observed for molecular solids with low
binding energies. As the sample material was de­
posited in thick layers or small crystallites onto the
target, completely neutral complexes occupy lat­
tice points and therefore the binding energy is
dom inated by the weak van der W aals interaction.
In this way both the relative independence of the
absolute yield o f m olecular ions in PDM S and
SIMS and the small value o f Y' can be explained.
Our results fit very well to observations on poly­
mers where the yield relation can be determ ined for a
broad spectrum o f binding energies [25], e.g. Y ' is
about 10 for the fragment ions of the thoroughly
fluorinated polymer polytetrafluorethylene over a
large mass range whereas for the secondary ions of
polymers that build hydrogen bonds (higher bind­
ing energies) Y' is about 100.
Possible explanations for the observation o f sil­
ver atom attachm ent (although thick layers have
been used) are: the solvent C H 2C12 dissolves the sil­
ver suspension resulting in a m ixture o f complex
molecules and silver particles or simply inhom o­
geneities in the target coverage. The stability of the
secondary ion (M + Ag)+, only observed in the
mass spectrum of 4, can be well explained from the
interatomic distances o f the metal atoms, if a posi­
tion of the attached substrate atom in the center of
the ring is assumed. Calculation o f the hypotheti­
cal N i-A g distances gives: 1.9Ä for 1 and 2, 2.9 Ä
for 4 and 4.1 Ä for 3. Only the size of the hexanu-
H. Feld et al. • Mass Spectrometry of Nickel Thiolates
clear ring 4 results in N i-A g distances com parable
to those in a metal lattice. For the (M + A g)+ quasimolecular ion of 4 a half life time more than three
times higher was found as com pared to the molec­
ular ion. If this new complex ion (M + A g)+ is sta­
bilized through the silver atom in the ring center,
the six nickel atoms together with the silver atom
form a section of a closed packed layer, as it is pre­
sent in both crystal structures of Ni and Ag. A ddi­
tionally the correlation between the fragm ent ion
yield and the diameter of the metal thiolate ring
may be attributed to the lower m echanical solidity
of the larger rings. Due to steric effects the attach­
ment of eight silver atom s to a molecular ion only
occurs at complex 1. We assume these silver atom s
to be built in between the sulfur functions o f the
eight thiolate ligands.
The nickel-sulfur cluster ions ( N i ^ ) - have been
observed for the first time in the gas phase. The re­
lated signals are present in the negative spectra of
all investigated complexes. The appearance in the
mass spectra of different com pounds indicates a
strong formation tendency and stability o f these
ions. Since we observe all nuclearities one can as­
sume structures of the gas phase species based on
fragments of solid state com pounds such as NiS.
The observed different mass resolution for frag­
m ent and molecular ion peaks is not due to instru­
m ental conditions. The resolution of the mass ana­
lyzer is mainly determined by the initial kinetic en­
ergy distribution. Thus we postulate that the
desorbed molecular ions as well as the quasimolecular ions, e.g. (M + Ag)+, have a lower kinetic
energy as compared to the fragment ions. This is
probably caused by the different desorption p ro ­
cesses which are responsible for the creation of
these secondary ions. The form ation o f a fragment
ion requires more initial energy because it is neces­
sary to overcome not only the weak van der Waals
forces (lattice binding energy) but also the inner
molecular forces (covalent binding energy). There­
fore the fragment ions are probably formed in a
target area where a higher energy density has been
deposited by the primary ion. As this energy is
divided into internal and kinetic energy of the frag­
m ent ions, both the lower stability and the lower
mass resolution are explained.
All spectra show that SIMS and PD M S are able
to yield highly significant molecular as well as
fragment ion inform ation of neutral metal com-
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H. Feld et al. • Mass Spectrometry of Nickel Thiolates
plexes with high accuracy. The observed fragment
ions give useful data for structural characteriza­
tion and additionally the stability o f different frag­
ment ions can be com pared by determining their
half life times. The sample preparation is not criti­
cal and only a small am ount of m aterial is neces­
sary, e.g. some small crystallites (sub ng-range) are
sufficient. By multilayer preparation the substrate
influence is negligible or very small. Only under
special conditions matrix effects, e.g. an attach­
ment o f substrate atoms, are observed. Neverthe­
less, in no case a degradation o f the complex or li­
gand loss due to matrix effects were observed. This
is in strong contrast to F A B -M S , the mass spectrom etric technique m ost frequently used in the in­
vestigation of metal complexes. Here the draw ­
backs are mainly due to the problems o f solubility
and stability of the complexes in the liquid matrix
[26]. Therefore one has to find out suitable matrix
conditions, but the enhancement o f ion form ation
without degrading the metal complex is critical
[27]. Even if these conditions are found, the inten­
sities o f quasimolecular ions are small com pared
to the matrix signal. In many cases FAB does not
Support of this work by the Fonds der Che­
mischen Industrie and the Deutsche Forschungs­
gemeinschaft (D FG ) is gratefully acknowledged.
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Meyer, Anal. Chem. 55, 1954 (1983).
[3] J. M. Miller, Mass. Spectrom. Rev. 9, 319 (1989).
[4] L. K. Panell, H. M. Fales, J. P. Scovell, D. L. Klagman, D. X. West, and R. L. Tate, Trans. Met.
Chem. 10, 141 (1985).
[5] J. L. Pierce, K. L. Busch, R. G. Cooks, and R. A.
Walton, Inorg. Chem. 21, 2597 (1982).
[6] a) H. Feld, A. Leute, D. Rading, A. Benninghoven,
and G. Schmid, Z. Phys. D 17, 73 (1990);
b) H. Feld, A. Leute, D. Rading, A. Benninghoven,
and G. Schmid, J. Am. Chem. Soc. 112, 8166 (1990).
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Reusmann, and B. Krebs, Int. J. Mass. Spectrom.
and Ion Proc. 110, 225 (1991).
[8] B. Krebs and G. Henkel, in H. W. Roesky (ed.):
Rings, Clusters and Polymers of M ain G roup and
Transition Elements, S. 439, Elsevier, Amsterdam
(1989).
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(1991); Angew. Chem. Int. Ed. Engl. 30, 769 (1991).
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istry of Nickel; VCH Verlagsgesellschaft, Weinheim
(1988).
[12] H. Feld, D octoral Thesis, M ünster (1991).
[13] H. Feld, A. Leute, R. Zurm ühlen, and A. Benning­
hoven, Anal. Chem. 63, 903 (1991).
[14] B. Schueler, R. Beavis, G. Bolbach, W. Ens, D. E.
Main, and K. G. Standing, in A. Benninghoven,
R. J. Colton, D. S. Simons, and H. W. W erner
(eds): Secondary Ion Mass. Spectrometry, SIMS V,
S. 57, Springer Series in Chemical Physics 44, Springer-Verlag, Berlin-H eidelberg (1986).
[15] T. Krüger, B. Krebs, and G. Henkel, Angew. Chem.
101, 54 (1989); Angew. Chem., Int. Ed. Engl. 28, 61
(1989).
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Crosse, J. Am. Chem. Soc. 87, 5251 (1965).
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provide molecular ion inform ation of neutral com­
plexes [2]. Also signals due to fragm entation pro­
cesses are small so that it is difficult to get structur­
al inform ation.
5. Conclusion
PDM S as well as SIMS are well suited for an ef­
ficient determ ination of molecular weight with
high accuracy and establishing of the molecular
form ula of unknown coordination compounds.
The results do not critically depend on the sample
preparation; crystallites, powder and dried solu­
tions can be investigated without any sample pre­
treatm ent. Spectra are obtained in minutes. Both
desorption techniques are an appropriate tool for
the analysis of neutral transition metal complexes.
Because of the relatively small yield ratio Y' and
the com parable results for PDM S and SIMS there
is an advantage for SIMS concerning the spectra
accum ulation time.
Unauthenticated
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936
[25] H. Feld, R. Zurmühlen, A. Leute, B. Hagenhoff, A.
Benninghoven, in A. Benninghoven, C. A. Evans,
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(eds): Secondary Ion Mass Spectrometry, SIMS
VII, S. 219, John Wiley & Sons, New York (1990).
[26] J. Cleareboudt, B. De Spiegeleer, E. A. De Bruijn,
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25,415(1990).
H. Feld et al. ■Mass Spectrometry o f Nickel Thiolates
[28] Further details o f the crystal structure determina­
tion may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft für wissenschaft­
lich-technische Inform ation mbH. D-W-7514 Eggenstein-Leopoldshafen 2, Germany, on quoting
the depository number CSD 56407, the names of
authors, and the journal citation.
Unauthenticated
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