Reductive activation of tripod metal compounds: Identification of intermediates and preparative application

Article abstract of DOI:10.1002/ejic.200700873

[tripodCoCl₂] {tripod = CH₃C(CH₂PPh ₂)₃} when treated with KC₈ in THF solution under an argon atmosphere produces a reactive species ["tripodCo ⁰"] (A) which undergoes oxidative

Full text of DOI:10.1002/ejic.200700873

FULL PAPER
DOI: 10.1002/ejic.200700873
Reductive Activation of tripod Metal Compounds: Identification of
Intermediates and Preparative Application
Jürgen Mautz,[a] Katja Heinze,[a] Hubert Wadepohl,[a] and Gottfried Huttner*[a]
In memoriam Professor Dr. Ernst Otto Fischer
Keywords: Tripodal ligands / Cobalt / Nickel / Reductive activation / Oxidative addition / Silicon hydrides / Tin hydrides
[tripodCoCl2] {tripod = CH3C(CH2PPh2)3} when treated with
KC8 in THF solution under an argon atmosphere produces a
reactive species [“tripodCo0”] (A) which undergoes oxidative
additions with stannanes, [tripodCo(H)2(SnBu3)] (4), formed,
for example, by addition of Bu3SnH. Silanes, R3SiH, undergo
the same type of reaction producing [tripodCo(H)2(SiR3)] (R
= Et: 5a; R = Ph: 5b). The solid-state structures of all the com-
pounds [tripodCo(H)2(ER3)] (E = Si, R = Ph; E = Sn, R = Ph,
metal bonded hydrogen atoms leading to short H···E contacts
of only about 190 pm (E = Si) and 230 pm (E = Sn), respec-
tively. The generation of a reactive species [“tripodCo0”] (A)
was transferred to the synthesis of a reactive tripodnickel(0)
species by treating a THF solution of [(DME)NiBr2] with KC8
in the presence of tripod. This species reacts with two elec-
tron donor ligands L to produce the pseudo tetrahedral com-
pounds [tripodNi(L)] {L = PPh3 (6), AsPh3 (7), cHexNC (8),
Bu) are rather similar. While they contain six-coordinate co- tBuNC (9), C2H4 (10)}. The identity of the reactive nickel(0)
balt with the formal oxidation state of cobalt being +III the
coordination geometry is not octahedral: the heteroelement E
deviates from the position which it would have in octahedral
coordination by around 40° while the other five ligands, three
phosphorus and two hydrogen, have the expected interli-
gand angles of around 90° and 180°, respectively. The devia-
tion of the heteroelement E is such that it approaches the
species as unequivocally deduced from NMR experiments is
[tripod4Ni3] (12). All compounds were characterised by the
usual analytic techniques including X-ray analysis where ap-
plicable.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
The tripodal ligand [CH3C(CH2PPh2)3], henceforth
called tripod, has a peculiar coordination chemistry: tripod
metal templates have been shown to engage in coordination
of rather unconventional coligands.[1] In many cases re-
ductive activation of tripod metal precursors in the oxi-
dation state +II, either as in the preparation of [tri-
podCo(N2)Cotripod] by reduction of [CoCl2] with Na/Hg
in the presence of tripod under N2 atmosphere,[2] or in the
synthesis of [tripodCo(η3-P3)] from [Co(BF4)2·6H2O], tripod
and P4,[3] is a key step in the synthesis.
Scheme 1.
It has been reported that reduction of a solution of [tri-
podCoCl2] (1)[4] (Scheme 1) in THF by potassium graphit-
ate, KC8, in an atmosphere of argon leads to a compound
which behaves as expected for the species [“tripodCo0”] (A):
with HSnPh3 it reacts to produce [tripodCo(SnPh3)] (2),
which, under an atmosphere of H2 yields the cobalt(III)
species [tripodCo(H)2(SnPh3)] (3).[5] If HSnBu3 is used in-
stead of HSnPh3, [tripodCo(H)2(SnBu3)] (4), an analogue
of 3, is immediately obtained.[5]
The aim of the work reported here was to further investi-
gate the reactivity of the species presumed to be [“tri-
podCo0”] (A) and, if possible, to elucidate its constitution.
Results and Discussion
THF solutions of the species described as [“tripodCo0”]
(A) were prepared as reported.[5] From these solutions [tri-
podCo(H)2(SnBu3)] (4) was obtained following the pub-
lished procedures (Scheme 2).[5]
[a] Anorganisch-chemisches Institut, Universität Heidelberg,
69120 Heidelberg, Im Neuenheimer Feld 270, Germany
E-mail: g.huttner@urz.uni-heidelberg.de
Eur. J. Inorg. Chem. 2008, 1413–1422
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1413

J. Mautz, K. Heinze, H. Wadepohl, G. Huttner
FULL PAPER
the elements.[7] The position of the heteroatom E with re-
spect to the tripodcobalt entity is again similar for both
compounds 3 and 5b (Table 1; cf. angles P1–Co–E: 134.8°/
139.8°, P2–Co–E: 114.4°/110.8°, P3–Co–E: 118.5°/114.5°
for 5b/3). The Co–H distances are 134(3) pm and 132(3) pm
in 5b and 137(4) pm and 135(4) pm in 3.[5] As a cobalt(III)
compound, 5b is expected to show octahedral coordination.
The octahedron is, however, quite distorted (Figure 1,
Scheme 2.
4 had been fully characterised by standard analytical Table 1) as has also been found for 3.[5] The distortion is
techniques.[5] The solid-state structure of 4[6] referred to in such that the Si–H distances are only around 190 pm
this work (Table 1) was found to be analogous to that of 3 (Table 1) and thus only about 40 pm longer than a regular
in all comparable details.
Si–H single bond. Similarly short non-bonded contacts be-
Freshly prepared solutions of A were found to react as tween hydrogen and tin have been reported for 3.[5] In this
well with silanes of the type HSiR3. HSiEt3, when added to case coupling between the hydrogen nuclei and the tin nu-
a THF solution of A, produces [tripodCo(H)2(SiEt3)] (5a) cleus as observed by NMR experiments[5] has been taken as
(Scheme 3).
additional evidence for a kind of agostic interaction. Even
lacking this evidence for 5b the short Si–H distances are in
1
favour of this hypothesis. The H resonances of the metal
bonded hydrogen atoms appear as broad signals at δ =
–13.45 (5a) and δ = –13.10 (5b) The IR spectrum of 5b
shows two Co–H vibrations at 1928 cm–1 and 1916 cm–1.
The two bands are of equal intensity as expected for the
symmetric and asymmetric Co–H vibrations if the Co–H
bonds are at 90° to each other.[8] By X-ray analysis this
angle is found to be 87(2)°. The analytical data in a whole
(see Exp. Sect.) are in full agreement with the constitutions
and structures described.
Scheme 3.
While it was not possible to grow crystals of 5a, its ident-
The synthesis of 5b was in so far of special importance
as the yield of 5b was found to be above 60% in analytically
pure crystalline form. For the reactions reported so far the
isolated yields had generally been quite a bit below 40%
such that it could have been hypothesised that their forma-
tion might be due to the presence of some minor compo-
nent present in solution A. This hypothesis is definitely
ruled out by the high yield with which compound 5b is ob-
tained.
ity was unambiguously inferred from its mass spectrum and
1
its H and 31P signature (see Exp. Sect.).
The compound [tripodCo(H)2(SiPh3)] (5b), as a silicon
analogue of 3, is obtained if the solution A is treated with
HSiPh3 (Scheme 3). 5b has been characterised by the tradi-
tional analytic techniques including X-ray analysis (Table 1,
Figure 1). It crystallises in the same orthorhombic space
group Pna21 as 3.[5] The cell dimensions (5b: a = 1857 pm, b
= 1349 pm, c = 1900 pm) and volume (V = 4759ϫ106 pm3)
reflect the smaller radius of silicon as compared to tin
The experiments reported so far demonstrate that solu-
(3: a = 1919 pm, b = 1355 pm, c = 1905 pm; V = tions A contain a coordinatively unsaturated species, but
4959ϫ106 pm3).[5] Distances and angles (not implying sili- they shed no further light on the very nature of this species.
con and tin) are almost identical in 3[5] and 5b. The Co–Si All attempts to grow crystals of one of the species present
distance in 5b is 227.8(1) pm. The Co–Sn distance in 3 in solution A and thus to elucidate their composition by X-
amounts to 249.4(1) pm.[5] The difference in length being ray analysis did not meet with success. Although FAB+
well in accord with the difference of the covalent radii of mass spectrometric analysis of A shows strong signals for
Figure 1. The molecular structure of 5b in the crystal. Left: general view; right: projection onto the P3 plane.
1414
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1413–1422

Reductive Activation of tripod Metal Compounds
Table 1. Selected bond lengths [pm], bond angles [°] and torsion pod a yellow precipitate is formed first, which by referring
to literature data[10] should be [tripodNiBr]. This precipitate
angles [°] in 4 and 5b.
4[a,c]
5b[b,c]
gradually dissolves again to produce an intensely yellow
coloured solution, hereafter designated as solution B. This
solution B apparently contains a species behaving as ex-
pected for [“tripodNi0”]: it reacts with two electron donor
ligands L to form neutral nickel(0) complexes of the type
[tripodNiL] (Scheme 4).
Co–P1
Co–P2
Co–P3
Co–E
Co–H1
Co–H2
E–H1
E–H2
216.4(1)
216.4(1)
216.4(1)
246.6(1)
–
–
–
–
217.6(1)
217.9(1)
218.2(1)
227.8(1)
134(3)
132(3)
198(4)
189(4)
183(6)
96.1(1)
91.6(1)
91.6(1)
135.1(2)
114.4(1)
118.5(1)
88(2)
174(2)
91(2)
93(2)
89(2)
91(2)
60(2)
56(2)
87(2)
24.0
H1···H2
P1–Co–P2
P1–Co–P3
P2–Co–P3
P1–Co–E
P2–Co–E
P3–Co–E
P1–Co–H1
P2–Co–H1
P3–Co–H1
P1–Co–H2
P2–Co–H2
P3–Co–H2
H1–Co–E
H2–Co–E
H1–Co–H2
93.9(1)
93.9(1)
93.9(1)
139.8(1)
113.3(1)
112.2(1)
–
–
–
–
–
–
–
–
–
30.3
30.3
30.3
13.4
43.3
13.4
43.3
13.4
43.3
Scheme 4.
Addition of PPh3 and AsPh3 results in the formation of
the corresponding adducts 6 and 7, respectively. The isoni-
triles cHexNC and tBuNC yield 8 and 9. The ethylene de-
rivative 10 is obtained by performing the reduction process
of equimolar amounts of [(DME)NiBr2] and tripod with
KC8 in an atmosphere of C2H4 instead of argon. The com-
pounds 6–10 are obtained as yellow to orange coloured sol-
ids in fair yields in the range of 50–70% in analytically pure
crystalline form. Thus, they are not by-products formed by
the reaction of some minor component in solution B but
are derivatives of the main tripodnickel component present
in this solution.
The molecular structures of 6 to 10 were elucidated by
X-ray analysis. The coordination polyhedron is pseudo tet-
rahedral in each case. This principle is illustrated in Fig-
ure 2 with 8, 9 and 10 as examples. Two views are given in
each case, a general one demonstrating the pseudo tetrahe-
dral geometry (left) and another one which projects the
structure onto the plane of the three phosphorus atoms
(right side). This last view illustrates the torsion of the tri-
pod scaffolding τ and of the phenyl groups f, the numerical
values of which together with some relevant distances and
angles are presented in Table 2 for all compounds 6 to 10.
The Ni–P distances in 6–9 are 215 pm in the mean with
only small deviations of individual distances from this mean
value. For the ethylene derivative 10 larger Ni–P distances
[d]
τ1[d]
τ2[d]
τ3
10.8
13.8
10.9
60.6
27.8
37.0
40.5
21.0
[e]
f1[e]
f2[e]
f3[e]
f4[e]
f5[e]
f6
[a] E = Sn. The labelling Scheme used for the tripodcobalt entity
in 4 is the same as for 5a (see Figure 1). The position of the tin
atom in 4 is analogous to the position of the silicon atom in 5b.
The cobalt-bonded hydrogen atoms H1 and H2, which were found
and refined isotropically in the molecular structure of 5b in the
crystal could not be located in the case of 4. [b] E = Si. [c] The
values in parentheses are standard deviations in units of the last
decimals listed. [d] τ = torsion angles within the chelate cage: τ1 =
C4–C1–P1–Co, τ2 = C4–C2–P2–Co, τ3 = C4–C3–P3–Co. [e] The
torsion angles f involving Hz are defined as follows: f1 = Hz1–P1–
C100–C101, f2 = Hz1–P1–C106–C107, f3 = Hz2–P2–C200–C201,
f4 = Hz2–P1–C206–C207, f5 = Hz3–P3–C300–C301, f6 = Hz3–P3–
C306–C307; Hz–P designates a vector that is vertical to the plane
formed by the three tripod phosphorus donor atoms and points
towards the observer when, in a projection onto this plane, the
vector Co–C4 points away from the observer, such that C4 lies
below this plane.[9]
a species tripodCo at m/z = 683, this does not reveal the are observed throughout with a mean value of 218.7 pm.[11]
composition of A since many compounds of the type [tri- The angles suspended by the tripod phosphorus atoms at
podCo(L)n]n+ produce strong signals for [tripodCo]+ under nickel are definitely smaller than the ideal tetrahedral value
mass spectrometric conditions. As the solution A shows of 109.5°. The average value amounts to 96.0° with only
strongly paramagnetic properties NMR experiments are of minor deviations from this general mean value for the indi-
little help.
vidual values pertinent to each compound. Within the sets
The hope was therefore that by using nickel instead of of the three values of each compound the differences ob-
cobalt a diamagnetic compound might possibly be obtained served amount to maximally 4° (see Table 2). The P–Ni–E
under otherwise analogous conditions, such that, even if the angles – E referring to the heteroatom in the case of 6–9 or
compound could not be crystallised, NMR analysis might to the centre of the C=C bond in the case of 10 – average
help to clarify its constitution. When THF solutions of to 120.8°. The individual mean values of these angles refer-
[(DME)NiBr2] are treated with KC8 in the presence of tri- ring to each of the compounds 6 to 10 are equal to this
Eur. J. Inorg. Chem. 2008, 1413–1422
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1415

J. Mautz, K. Heinze, H. Wadepohl, G. Huttner
FULL PAPER
general mean value within Ϯ1°. Nevertheless, within each sector between P2 and P3 bending away from P1 (see Fig-
set of the three P–Ni–E angles pertinent to each compound, ure 2). Correspondingly, the largest P–Ni–E angle in 8 is
large differences are observed (see Table 2). The maximum observed for P1–Ni–E (see Table 2).
difference of close to 20° is observed for 9. The diagram of
The torsion τ of the tripod scaffolding spreads from a
the structure (see Figure 2) offers the explanation for this minimum average value of 6.5° for 7 to a maximum of 30.0°
finding: the tBuNC coligand with its bulky tButyl group for 10 (see Table 2). The sense of rotation was chosen for
points away from P3 bending towards the sector of P1 and each compound such that its τ values are positive, meaning
P2 corresponding to a large angle P3–Ni–E. A similar ori- that the torsion of the scaffolding corresponds to a right-
entation is observed for the cyclohexyl substituent of handed screw (see Figure 2, right-hand side). The orienta-
cHexNC in 8, as the cyclohexyl residue now occupies the tion of the phenyl groups as described by the f values has
Figure 2. The molecular structures of 8 (top), 9 (middle) and 10 (bottom) in the crystal. Left: General view; right: projection onto the
P3 plane.
1416
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1413–1422

Reductive Activation of tripod Metal Compounds
Table 2. Selected bond lengths [pm], bond angles [°] and torsion the instrumentation was as well too low for allowing the
angles [°] for 6–10.
observation of the quaternary carbon atoms of the co-
1
6[a]
7[a]
8[a]
9[a]
10[a]
ligands. H NMR spectroscopic data are as expected, with
the exception of the signals for the cyclohexyl moiety in 8.
At 303 K broad signals are observed for all 11 protons of
the C6H11 residue. Well separated from the signals gener-
ated by the CH2 groups between δ = 1.54 and δ = 2.1, a
broad signal corresponding to the proton of the CH group
is observed at δ = 3.89 ppm. Upon lowering the tempera-
ture this signal broadens and vanishes in the background at
233 K. Further lowering the temperature down to 183 K
causes the signal to reappear at δ = 4.15 ppm. This behav-
iour is typical for a dynamic equilibrium between two con-
formations of the cyclohexyl group, one, in which the C–H
group points in an axial direction and the other one, in
which its orientation is equatorial. From the coalescence
temperature together with the frequency difference in the
shift of the proton signal[14] the free activation energy of the
process is estimated as ∆G2϶33 = 47Ϯ1 kJmol–1. This value
is well in agreement with the values expected for ring inver-
sions of cyclohexyl derivatives.[15]
L = PPh3 L = AsPh3 L = cHexNC L = tBuNC L = C2H4
Ni–P1
Ni–P2
Ni–P3
Ni–E
215.7(2)
216.1(2)
215.5(2)
217.1(2)
214.7(1)
215.0(2)
213.6(1)
228.5(1)
214.4(1)
215.5(1)
214.8(1)
181.7(3)
214.3(1)
215.4(1)
215.7(1)
180.6(2)
219.1(1)
220.2(1)
216.7(1)
207.1(5)[e]
210.7(5)[e]
95.0(1)
95.8(1)
93.4(1)
120.2(2)
118.7(2)
126.5(2)
30.9
P1–Ni–P2 96.1(1)
P1–Ni–P3 95.5(1)
P2–Ni–P3 99.4(1)
P1–Ni–E[b] 121.5(1)
P2–Ni–E[b] 119.6(1)
97.3(1)
97.7(1)
97.4(1)
118.5(1)
123.0(1)
117.7(1)
6.9
97.7(1)
95.4(1)
93.8(1)
123.9(1)
118.1(1)
121.2(1)
18.8
96.1(1)
96.7(1)
92.3(1)
119.4(1)
112.1(1)
132.2(1)
27.1
P3–Ni–E[b] 119.4(1)
[c]
τ1
τ2
τ3
8.7
[c]
[c]
11.0
3.3
7.0
5.6
12.5
16.0
22.5
30.0
29.3
31.0
[d]
[d]
[d]
[d]
[d]
[d]
f1
f2
f3
f4
f5
f6
45.0
25.4
45.1
33.5
50.2
28.6
42.5
27.4
42.2
16.7
50.4
35.0
20.7
59.0
17.5
32.3
21.2
33.0
50.9
6.7
36.7
7.6
15.6
1.3
59.5
27.3
36.1
3.3
37.2
7.5
[a] The values in parentheses are standard deviations in units of
the last decimals listed. [b] E = atom of L coordinating to nickel;
in the case of 10: centre of C=C-bond. [c] τ = torsion angles within
the chelate cage: τ1 = C4–C1–P1–Ni, τ2 = C4–C2–P2–Ni, τ3 = C4–
C3–P3–Ni. [d] The torsion angles f involving Hz are defined as
follows: f1 = Hz1–P1–C100–C101, f2 = Hz1–P1–C106–C107, f3 =
Hz2–P2–C200–C201, f4 = Hz2–P1–C206–C207, f5 = Hz3–P3–
C300–C301, f6 = Hz3–P3–C306–C307; Hz–P designates a vector
that is vertical to the plane formed by the three tripod phosphorus
donor atoms and points towards the observer when, in a projection
onto this plane, the vector Co–C4 points away from the observer,
such that C4 lies below this plane.[12] [e] Distance to ethylene car-
bon atoms.
While all the results above suggest that solution B con-
tains a species reacting as would be expected for “tri-
podNi0” they give no hint, neither to the structure nor to
the composition of such a tripodnickel(0) species. Referring
to the rule of thumb that a nickel(0) species should have a
tetrahedral environment it might well be expected that the
solvent THF could play the role of the fourth ligand sta-
bilising [“tripodNi0”] by its coordination. If no coligands
were present the structure of [“tripodNi0”] should be oligo-
meric or polymeric in order to allow for a coordination
number of four at nickel supplied by tripod ligands alone.
Highly polymeric structures are ruled out by the observa-
tion that the compound is well soluble in THF. Fortunately
one and the same sense for all of the six phenyl groups of enough [“tripodNi0”] is diamagnetic such that NMR spec-
all six compounds (see Table 2). The individual f values troscopic data can be collected. To this end, in order to
within each compound alternate systematically in so far as have a clean sample of solution B, the reduction of [(DME)-
for each diphenylphosphane unit there is a phenyl group NiBr2] by KC8 in [D8]THF was performed in an NMR tube
with a large f value while the other one has a small value (f using glove box techniques. The 31P{1H} NMR spectrum
= 0° means orientation parallel to the pseudotrigonal axis obtained with this sample is shown in Figure 3 (left).
i.e. minimum visibility in the projection plane). The se-
A spectrum of this type has been repeatedly reproduced
quence of f values in each compound follows the pattern and it was shown by DOSY[16] experiments (Figure 3; right)
large–small, large–small, large–small in cyclic order (see that the observed signals most probably belong to just one
Table 2).
chemical species since all of them are affected by diffusion
The 31P{1H} NMR spectroscopic data of compounds 6 to the same degree. There are four prominent multiplet sig-
to 10 show one sharp singlet signal in the range of δ = 2.5 nals at δ = 3.3, δ = 5.5, δ = 12.0 and δ = 28.1 with an
to δ = 7.4 for the three tripod phosphorus atoms of each integral ratio close to 3:1:1:1. The structure of the signal at
compound, demonstrating that all three nuclei are equiva- δ = 3.3 is that of a doublet with a coupling constant of
lent in the time average. Observations of this kind have oc- 15 Hz. Intensity and chemical shift are appropriate to the
casionally been made in the examination of tripodcobalt de- interpretation of this signal as originating from a tripod li-
rivatives in the past.[5,13] As a consequence of this, it is evi- gand κ3-coordinated to nickel(0); its doublet structure and
dent that – down to the lowest achievable temperatures the observed coupling constant indicate the coordination of
(183 K) – the coligands are free to rotate around their one additional phosphorus atom to this tripodnickel entity.
metal–ligand axis and the relative orientation of the tripod This interpretation is corroborated by comparing the data
ligand with respect to the coligands is dynamic. 13C NMR with the 31P{1H} NMR spectroscopic data obtained for
spectroscopic data are as well consistent with the formula- [tripodNi(PPh3)] (6): the tripod phosphorus atoms give rise
tions given. For the isocyanide derivatives 8 and 9, the solu- to a signal at δ = 6.0 with a coupling constant to the phos-
bility of the compounds was too low and the sensitivity of phorus atom of the coligand PPh3 of 15 Hz. The 31P NMR
Eur. J. Inorg. Chem. 2008, 1413–1422
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1417

J. Mautz, K. Heinze, H. Wadepohl, G. Huttner
FULL PAPER
Figure 3. 31P{1H} NMR spectrum (left) and DOSY spectrum (right) of [“tripodNi0”] (B).
signal of the PPh3 coligand appears at δ = 38.5 with an
apparent quartet structure. In the 31P{1H} NMR spectrum
of the compound analysed, the signal at δ = 28.1 likewise
appears as a quartet with the same coupling constant as
found for the prominent doublet at δ = 3.3 (see above). The
origin of the signals at δ = 5.5 and δ = 12.0 was, however,
still unclear. It was hypothesised that the signals might be
Figure 4. Constitution of the reactive species [tripod4Ni3] (12).
due to phosphorus atoms of two pairs of PPh2 groups, each
one being part of a tripod ligand.
To possibly falsify this hypothesis [tripod2Ni] (11) was
synthesised by adding two equivalents of tripod to a solu-
tion of [(DME)NiBr2] in THF and subsequent reduction by
KC8 (Scheme 5). This experiment was as well performed in
[D8]THF on an NMR scale, using glove-box techniques.
The 31P{1H} NMR spectrum of [tripod2Ni] (11) shows two
broad signals for the coordinated phosphorus atoms in the
ratio of 1:1 at δ = 6.8 and δ = 12.2 ppm. The non-coordi-
nated arms of the two κ2-coordinated tripod ligands give
rise to a sharp singlet at δ = –26.7 ppm. The magnetic in-
equivalence of the four coordinated phosphorus atoms in
two pairs is due to the axial chirality of the compound. The
assignment of the signals is in full accord with the consti-
tution of 11, as unequivocally elucidated by X-ray analysis
(Table 4).
This constitution with its stoichiometry of tripod/nickel
of 4:3 is at the same time the most simple solution to the
problem satisfying the coordination number of four by the
tripod ligand having only three donor groups such that all
donor groups and all metal atoms engage in coordination.
Conclusions
Treating a THF solution of [tripodCoCl2] with KC8 un-
der an argon atmosphere leads to a reactive species which
reacts with HER3 (E = Si, R = Et, Ph; E = Sn, R = Bu,
Ph) to produce the cobalt(III) compounds [tripodCo(H)2-
(ER3)] (4, 5). The coordination mode of these six-coordi-
nate cobalt(III) complexes deviates strongly from octahe-
dral coordination in that the Co–E bond bends towards the
cobalt bonded hydrogen atoms. The nature and exact com-
position of the reactive species itself, which undergoes the
oxidative addition reactions leading to 4 and 5, is not
known in this case.
In the case of nickel, by reduction of a THF solution of
[(DME)NiBr2] with KC8 in the presence of tripod under an
argon atmosphere, a reactive species is likewise obtained. It
reacts with two electron donor ligands L to produce dia-
magnetic, pseudo tetrahedral nickel(0) complexes [tri-
podNiL] {L = PPh3 (6), AsPh3 (7), cHexNC (8), tBuNC (9),
Scheme 5.
Based on the comparison of the 31P{1H} NMR spectra C2H4 (10)}. In this case the nature of the reactive species
of [tripodNi(PPh3)] (6) and [tripod2Ni] (11) the 31P{1H} could be elucidated since, in contrast to the reactive cobalt
NMR spectroscopic data obtained for the solution of [“tri- species, the nickel(0) compound is diamagnetic. By NMR
podNi0”] (B) allow for only one interpretation: the signals experiments its composition was unequivocally deduced to
are due to a compound of the constitution [tripod4Ni3] (12) be [tripod4Ni3] (12). It is tempting to assume that the reac-
(Figure 4).
tive tripodcobalt(0) species has an analogous constitution.
1418
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1413–1422

Reductive Activation of tripod Metal Compounds
crystalline powder was obtained. The compound was further puri-
fied by crystallisation from diethyl ether/petroleum ether (boiling
range 40–60 °C); yield 224 mg (0.28 mmol, 28%).
5a:[19] 1H NMR (CD2Cl2): δ = –13.45 (br. s, 2 H, Co-H), 0.88–1.00
(m, 15 H, Si-CH2CH3), 1.56 (m, 3 H, tripod-CH3), 2.35 (m, 6 H,
tripod-CH2), 6.90–7.22 (m, 30 H, arom. H) ppm. 31P{1H} NMR
(CD2Cl2): δ = 41.5 (s) ppm. MS (FAB+); m/z (%) [fragment]: 936
(30) [M+ + matrix], 821 (70) [tripodCo+ + matrix], 683 (20)
[tripodCo+] UV/Vis (THF), λmax [nm] (ε) [–1 cm–1]: 490 (sh), 520
(1250), 1034 (sh), 1310 (400).
Experimental Section
General: All manipulations were performed under an inert atmo-
sphere of dry argon using standard Schlenk techniques or by work-
ing in a glove box. Solvents were dried with potassium (THF,
DME) or CaH2 (CH2Cl2, Et2O, PE 40/60), distilled, and thor-
oughly degassed prior to use. Deuterated solvents were dried with
potassium ([D8]THF) or CaH2 (CD2Cl2), vacuum distilled, de-
gassed by three successive “freeze-pump-thaw”-cycles and stored in
teflon valve ampoules under argon.
NMR: Bruker Avance DPX 200 at 200.120 MHz (1H), 50.323 MHz
[13C(1H)], 81.015 MHz {31P{1H}}; T = 303 K unless otherwise
stated; chemical shifts (δ) in ppm referenced to (residual proton)
peaks of CD2Cl2 (1H: δ = 5.32; 13C: δ = 53.8 ppm) and [D8]THF
(1H: δ = 1.73, 3.58; 13C: δ = 25.5, 67.7) as internal standards; 31P
chemical shifts (δ) in ppm with respect to 85% H3PO4 (31P: δ =
0 ppm) as external standard. FAB-/HR-FAB-MS: Finnigan MAT
8400 spectrometer, xenon, matrix: 4-nitrobenzyl alcohol. LIFDI-
MS: JEOL JMS-700 double-focusing magnetic sector mass spec-
trometer.[17] IR: BioRad Excalibur FTS 3000 spectrometer using
CsI discs. UV/Vis: Perkin–Elmer Lambda 19; 0.2 cm cells (Hellma,
suprasil). Cyclic Voltammetry (CV): Metrohm “Universal Meß-
und Titriergefäß”, Metrohm GC electrode RDE 628, platinum
electrode, SCE electrode, EG&G Princeton Applied Research po-
tentiostate Model 273, potentials in mV vs. SCE at 25 °C, sample
10–3  in 0.1  nBu4NPF6/CH2Cl2. – Differential Scanning calo-
rimetry (DSC): Mettler DSC 30, argon, 30–600 °C, heating rate:
10 Kmin–1. Thermogravimetric Analysis (TGA): Mettler TC 15,
argon, 30–600 °C, heating rate: 10 Kmin–1. Elemental analyses:
Department of Chemistry, University of Heidelberg.
Synthesis of [tripodCo(H)2(SiPh3)] (5b): To a THF solution con-
taining A, prepared from 1[4] (754 mg, 1 mmol) and KC8 (297 mg,
2.2 mmol) (see above) a solution of HSiPh3 (780 mg, 3 mmol) in
THF (10 mL) was added. HSiPh3 was purified/dried by sublima-
tion prior to use. After stirring overnight, the solvent was removed
in vacuo. The residue was suspended in petroleum ether (boiling
range 40–60 °C) and transferred to a column containing silica gel
(Ø = 3 cm, l = 5 cm), conditioning with petroleum ether (boiling
range 40–60 °C) via a cannula. After elution by 100 mL of petro-
leum ether (boiling range 40–60 °C), the product was eluted by
20 mL of dichloromethane as a yellow-orange band. Having re-
moved the solvent in vacuo, a yellow microcrystalline powder was
obtained. Yield: 590 mg, 0.62 mmol, 62%. Orange crystals of 5b,
suitable for X-ray structural analysis, were obtained by layering a
saturated dichloromethane solution of 5b with diethyl ether.
5b: C59H56P3CoSi (944.27): calcd. C 74.99, H 5.97, P 9.83; found
C 74.67, H 5.97, P 9.83. 1H NMR (CD2Cl2): δ = –13.10 (br. s, 2
H, Co-H), 1.58 (s, 3 H, tripod-CH3), 2.40 (s, 6 H, tripod-CH2),
6.90–7.68 (m, 45 H, arom. H) ppm. 31P{1H} NMR (CD2Cl2): δ =
39.3 (s) ppm. 13C{1H} NMR (CD2Cl2): δ = 38.0 (br. s, tripod-CH3),
39.5 (br. s, tripod-CH2), 126.9–150.7 (aromatic C) ppm. MS
(LIFDI); m/z (%) [fragment]: 944 (100) [M+], 683 (60) [tripodCo+].
MS (FAB+); m/z (%) [fragment]: 821 (100) [tripodCo+ + matrix],[b]
Materials: 1,1,1-Tris[(diphenylphosphanyl)methyl]ethane (tripod)
was prepared according to literature procedures.[18] All other rea-
gents were obtained from commercial sources and used as received
unless explicitly stated. Silica gel (Kieselgel z.A., 0.06–0.20 mm, J.
T. Baker Chemicals B.V.) used for chromatography and kieselgur
(Erg. B.6, Riedel-de Haën AG) used for filtration were degassed at
10–2 mbar for 48 h and saturated with argon.
683 (60) [tripodCo+]. IR (CsI, ν): ν (Co–H) = 1928 (m), ν (Co–H)
˜
s
as
= 1916 (m) cm–1. UV/Vis (THF), λmax [nm] (ε) [–1 cm–1]: 320
(6680), 360 (sh), 680 (90), 790 (80), 1060 (270), 1170 (sh). CV: EAp
= –60 mV (reverse scan: –1230 mV); EAp = 680 mV (reverse scan:
–640 mV). DSC/TGA: endothermic melting process (m.p. 260 °C)
initiates exothermic decomposition, which is complete at 600 °C;
exp. final weight: 11.2%; calcd. final weight [Co2P3]: 11.2%.
General Procedure for the Synthesis of Solutions Containing A or B:
KC8 (297 mg, 2.2 mmol), prepared by heating potassium (86 mg,
2.2 mmol) with graphite (211 mg, 17.6 mmol) was added to a solu-
tion of [tripodCoCl2] (1)[4] (754 mg, 1 mmol) in THF (20 mL) or
[tripodNiBr2] (840 mg, 1 mmol). [tripodNiBr2] was prepared by tre-
ating [(DME)NiBr2] (308 mg, 1 mmol) with equimolar amounts of
tripod (624 mg, 1 mmol). The suspension resulting in each case was
sonicated until the colour changed to orange brown [“tripodCo0”]
(A) or yellow brown [“tripodNi0”] (B), respectively. The reduction
was monitored by UV/Vis spectroscopy until the spectra indicated
Synthesis of [tripodNi(L)] (L = PPh3: 6, L = AsPh3: 7, L = cHexNC:
8, L = tBuNC: 9, L = C2H4: 10): To a THF solution containing B
prepared from [tripodNiBr2] (840 mg, 1 mmol) and KC8 (297 mg,
2.2 mmol) (see above) a solution of L (1 mmol) in THF (10 mL)
was added. After stirring overnight, the solvent was removed in
vacuo. The residue was suspended in petroleum ether (boiling range
40–60 °C) and transferred to a column containing silica gel [Ø =
3 cm, l = 5 cm, conditioning with petroleum ether (boiling range
40–60 °C)] via a cannula. After elution with 100 mL of petroleum
ether (boiling range 40–60 °C), the products were eluted by 20 mL
of DME as yellow brown bands. Having removed the solvent in
vacuo, yellow to orange coloured microcrystalline powders were
obtained. Orange red crystals, suitable for X-ray structural analysis,
were obtained by layering saturated DME solutions of the respec-
tive compound with petroleum ether (boiling range 40–60 °C).
Yields for 6: 410 mg, 0.43 mmol, 43%; 7: 375 mg, 0.38 mmol, 38%;
8: 340 mg, 0.43 mmol, 43%; 9: 370 mg, 0.48 mmol, 48%; 10:
400 mg, 0.56 mmol, 56%.
completeness of the reaction showing a strong band at λmax
=
680 nm in the case of A and λmax = 380 nm in the case of B. The
reaction mixture was then filtered through kieselgur by means of a
syringe to remove the remaining graphite.
Synthesis of [tripodCo(H)2(SiEt3)] (5a): To a THF solution contain-
ing A, prepared from 1[4] (754 mg, 1 mmol) and KC8 (297 mg,
2.2 mmol) (see above) a solution of HSiEt3 (349 mg, 3 mmol) in
THF (10 mL) was added. After stirring overnight, the solvent was
removed in vacuo. The residue was suspended in petroleum ether
(boiling range 40–60 °C) and transferred to a column containing
silica gel (Ø = 3 cm, l = 5 cm), conditioning was performed with
petroleum ether (boiling range 40–60 °C) via a cannula. After elu-
tion with 100 mL of petroleum ether (boiling range 40–60 °C), the
product was eluted by 100 mL of diethyl ether as an orange col-
oured band. Having removed the solvent in vacuo, a yellow micro-
6: C59H54P4Ni (944.25): calcd. C 74.94, H 5.76, P 13.10; found C
74.79, H 5.87, P 12.82. 1H NMR ([D8]THF): δ = 1.42 (s, 3 H,
4
tripod-CH3), 2.57 (d, JPH = 2 Hz, 6 H, tripod-CH2), 6.65–7.42 (m,
2
45 H, arom. H) ppm. 31P{1H} NMR ([D8]THF): δ = 6.0 (d, JPP
Eur. J. Inorg. Chem. 2008, 1413–1422
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1419

J. Mautz, K. Heinze, H. Wadepohl, G. Huttner
FULL PAPER
= 15 Hz, tripod-PPh2), 38.5 (q, 2JPP = 15 Hz, PPh3) ppm. 13C{1H}
NMR ([D8]THF): δ = 37.2 (br. s, tripod-CH3), 43.9–43.6 (m, tripod-
58Ni], 767.2333 [M+, 60Ni] (calcd. m/z: 765.2353, 767.2336). UV/
Vis (THF), λmax [nm] (ε) [–1 cm–1]: 360 (6700). CV: E1/2 = –540 mV
CH2), 126.8 (s, arom. tripod-Cp), 127.1–127.3 (m, arom. tripod-Cm),
(rev. ox., ∆E = 120 mV), EAp = 1130 mV, EAp = 1740 mV, ECp
=
2
127.5 (s, PPh3-Cp), 127.7 (d, JCP = 6 Hz, PPh3-Cm), 132.8–133.3 –2110 mV (reverse scan: –50 mV). DSC/TGA: endothermic melting
(m, arom. tripod-Co), 133.9 (d, 2JCP = 9 Hz, PPh3-Co), 141.5–142.0 process (m.p. 204 °C) initiates exothermic decomposition, which is
(m, arom. Cq), 143.8 (m, arom. Cq) ppm. MS (HR–FAB+); m/z
[fragment]: 944.2552 [M+, 58Ni], 946.2544 [M+, 60Ni] (calcd. m/z:
944.2529, 946.2525) UV/Vis (THF), λmax [nm] (ε) [–1 cm–1]: 380
(4600), 580 (150). CV: E1/2 = –550 mV (qrev. ox., ∆E = 170 mV),
EAp = 600 mV, EAp = 1500 mV. DSC/TGA: endothermic melting
process (m.p. 274 °C) initiates exothermic decomposition, which is
complete at 600 °C; exp. final weight: 11.3%; calcd. final weight
[Ni2P3]: 11.1%.
complete at 600 °C; exp. final weight: 19.1%; calcd. final weight
[Ni2P3]: 13.8%.
10: C43H43P3Ni (711.43): C 72.60, H 6.09, P 13.06; found C 72.05,
1
H 5.98, P 13.12. H NMR ([D8]THF): δ = 1.49 (br. s, 3 H, tripod-
CH3), 2.32 (br. s, 6 H, tripod-CH2), 3.25 (s, 4 H, C2H4), 6.86–7.07
(m, 30 H, arom. H) ppm. 31P{1H} NMR ([D8]THF): δ = 2.5 (s)
2
ppm. 13C{1H} NMR ([D8]THF): δ = 36.5–36.9 (q, JCP = 7 Hz,
3
CH3-Cq), 37.0–37.6 (q, JCP = 10 Hz, tripod-CH3), 37.8–38.2 (m,
tripod-CH2), 43.1 (m, C2H4), 127.1 (s, arom. tripod-Cp), 127.5–
127.7 (m, arom. tripod-Cm), 131.7–132.0 (m, arom. tripod-Co),
142.3–143.1 (m, arom. Cq) ppm. 13C DEPT NMR ([D8]THF): δ =
37.4–38.0 (m, tripod-CH3), 38.2–38.6 (m, tripod-CH2), 43.4 (br. s,
C2H4), 127.1 (s, arom. tripod-Cp), 127.4–127.6 (m, arom. tripod-
Cm), 131.6–131.9 (m, arom. tripod-Co) ppm. MS (LIFDI); m/z
[fragment]: 710 [M+] (100). UV/Vis (THF), λmax [nm] (ε) [–1 cm–1]:
340 (5660), 430 (3460). CV: E1/2 = –290 mV (rev. ox., ∆E =
120 mV), EAp = 1100 mV, EAp = 1520 mV, ECp = –1010 (reverse scan:
–610 mV). DSC/TGA: endothermic melting process (m.p. 223 °C)
initiates exothermic decomposition, which is complete at 600 °C;
exp. final weight: 21.0%; calcd. final weight [Ni2P3]: 14.8%.
7: C59H54P3AsNi (989.61): C 71.61, H 5.50, P 9.39; found C 71.23,
1
4
H 5.75, P 9.39. H NMR ([D8]THF): δ = 1.44 (d, JPH = 2 Hz, 3
2
H, tripod-CH3), 2.58 (d, JPH = 6 Hz, 6 H, tripod-CH2), 6.65–7.47
(m, 45 H, arom. H) ppm. 31P{1H} NMR ([D8]THF): δ = 7.4 (s)
2
ppm. 13C{1H} NMR ([D8]THF): δ = 36.9 (q, JCP = 7 Hz, CH3-
Cq), 37.5 (q, 3JCP = 10 Hz, tripod-CH3), 42.6–43.0 (m, tripod-CH2),
126.4 (s, arom. tripod-Cp), 126.7–126.8 (m, arom. tripod-Cm), 127.4
(s, AsPh3-Cp), 127.6 (s, AsPh3-Cm), 132.3–132.4 (m, arom. tripod-
Co), 133.5 (s, AsPh3-Co), 143.0–143.5 (m, arom. Cq) ppm. MS
(FAB+); m/z (%) [fragment]: 988 (1) [M+], 820 (5) [tripodNi+ + ma-
trix], 682 (20) [tripodNi+]. UV/Vis (THF), λmax [nm] (ε) [–1 cm–1]:
380 (21500). CV: E1/2 = –260 mV (qrev. ox., ∆E = 100 mV), ECp
=
–1600 mV (reverse scan –500 mV), EAp = 1690 mV. DSC/TGA: en-
dothermic melting process (m.p. 256 °C) initiates exothermic de-
composition, which is complete at 600 °C; exp. final weight: 15.9%;
calcd. final weight [Ni2P3]: 21.4%.
Synthesis of [tripod2Ni] (11): [(DME)NiBr2] (31 mg, 0.1 mmol) and
tripod (125 mg, 0.2 mmol) are dissolved in [D8]THF (2 mL). This
solution was treated with KC8 (30 mg, 0.22 mmol) and sonicated.
Within 10 min a yellow solid precipitates which dissolves again
whereby a yellow brownish solution is obtained. The reaction mix-
ture was then filtered through kieselgur by means of a syringe to
remove the remaining graphite. The resulting solution was used for
NMR experiments. Yellow crystals, suitable for X-ray structural
analysis, were obtained after concentrating and storing this solu-
8: C48H50P3NNi (792.55): C 72.74, H 6.36, P 11.72, N 1.77; found
1
C 72.51, H 6.37, P 11.88, N 1.80. H NMR ([D8]THF, 303 K): δ =
4
1.40 (d, JPH = 2 Hz, 3 H, tripod-CH3), 1.54 (br. s, 4 H, cHex-
2
CH2), 2.00 (br. s, 6 H, cHex-CH2), 2.18 (d, JPH = 5 Hz, 6 H,
tripod-CH2), 3.89 (br. s, 1 H, cHex-CH), 6.84–7.40 (m, 30 H, arom.
H) ppm. 1H NMR ([D8]THF, 183 K): δ = 1.34 (m, 8 H, tripod-
CH3, cHex-CH2), 2.11–2.43 (m, 10 H, tripod-CH2, cHex-CH2), 3.14
(br. s, 1 H, cHex-CH2), 4.15 (br. s, 1 H, cHex-CH), 6.84–7.40 (m,
30 H, arom. H) ppm. 31P{1H} NMR ([D8]THF): δ = 7.3 (s) ppm.
13C{1H} NMR ([D8]THF): δ = 23.2 (s, cHex-CH2), 26.1 (s, cHex-
CH2), 34.2 (s, cHex-CH2), 37.1–37.8 (m, tripod-CH3, tripod-CH2),
53.6 (s, cHex-CH), 126.9 (s, arom. tripod-Cp), 127.0–127.3 (m,
arom. tripod-Cm), 131.8–132.1 (m, arom. tripod-Co), 142.9–143.0
(m, arom. Cq) ppm. 13C DEPT NMR ([D8]THF): δ = 23.2 (s, cHex-
CH2), 26.1 (s, cHex-CH2), 34.2 (s, cHex-CH2), 37.1 (m, tripod-
CH2), 37.2–37.8 (m, tripod-CH3), 53.6 (s, cHex-CH), 128.9 (s,
arom. tripod-Cp), 127.0–127.3 (m, arom. tripod-Cm), 131.8–132.1
(m, arom. tripod-Co) ppm. MS (HR–FAB+); m/z [fragment]:
791.2565 [M+, 58Ni], 793.2508 [M+, 60Ni] (calcd. m/z: 791.2510,
793.2495). UV/Vis (THF), λmax [nm] (ε) [–1 cm–1]: 360 (4900). CV:
E1/2 = –530 mV (rev. ox., ∆E = 200 mV), EAp = 760 mV (reverse
scan: –220 mV). DSC/TGA: endothermic melting process (m.p.
230 °C) initiates exothermic decomposition, which is complete at
600 °C; exp. final weight: 6.8%; calcd. final weight [Ni2P3]: 13.3%.
Table 3. Crystal data for 4 and 5b.
Compound
4
5b
Empirical formula
Molecular mass [g]
Crystal size [mm]
Crystal system
Space group (No.)
a [pm]
b [pm]
c [pm]
α [°]
C53H68P3CoSn
975.69
0.15ϫ0.05ϫ0.05 0.50ϫ0.25ϫ0.25
C59H56P3CoSi
944.97
cubic
orthorhombic
Pna21 (3 3)
1857.1(4)
1349.1(3)
1899.7(4)
90
90
90
4760
4
1.319
200
3.7° Յ 2θ Յ
55.0°
¯
I43d (220)
2688.1(3)
2688.1(3)
2688.1(3)
90
β [°]
90
90
19425
16
1.294
200
γ [°]
V [106 pm3]
Z
dcalcd. [g cm–3]
T [K]
Scan range
3.7° Յ 2θ Յ
50.1°
Method
ω scan, ∆ω = 1° ω scan, ∆ω = 1°
9: C46H48P3NNi (766.51): C 72.08, H 6.31, P 12.12, N 1.83; found
Scan speed [s frame–1]
60
8
C 71.99, H 6.34, P 12.22, N 1.92. 1H NMR ([D8]THF): δ = 1.40
No. of reflections measured 32884
10942
10522
9371
I Ն 2σ
585
2
(br. s, 3 H, tripod-CH3), 1.63 (s, 9 H, tBu-CH3), 2.18 (d, JPH
=
No. of unique reflections
No. reflections observed
Observation criterion
2874
2288
I Ն 2σ
196
5 Hz, 6 H, tripod-CH2), 6.85–7.41 (m, 30 H, arom. H) ppm.
31P{1H} NMR ([D8]THF): δ = 7.3 (s) ppm. 13C{1H} NMR ([D8]-
THF): δ = 31.6 (s, tBu-CH3), 36.7–37.3 (m, tripod-CH2), 37.6–38.0
(m, tripod-CH3), 127.0 (s, arom. tripod-Cp), 127.1–127.3 (m, arom.
tripod-Cm), 131.7–132.3 (m, arom. tripod-Co), 142.4–143.2 (m,
arom. Cq) ppm. MS (HR–FAB+); m/z [fragment]: 765.2299 [M+,
No. of parameters refined
Resididual electron density 0.54
0.26
[10–6 epm–3]
R1/Rw (%) (F2 refinement) 4.9/13.1
3.6/7.9
1420
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1413–1422

Reductive Activation of tripod Metal Compounds
Table 4. Crystal data for 6, 7, 8, 9, 10 and 11.
Compound
6
7
8
9
10
11
Empirical formula
Molecular mass
Crystal size [mm]
Crystal system
Space group (No.)
Lattice constants:
a [pm]
b [pm]
c [pm]
α [°]
β [°]
C59H54P4Ni·DME C59H54P3AsNi
1035.73 989.61
0.25ϫ0.25ϫ0.20 0.50ϫ0.50ϫ0.30 0.50ϫ0.50ϫ0.25 0.30ϫ0.30ϫ0.20 0.25ϫ0.20ϫ0.20 0.22ϫ0.13ϫ0.05
C48H50P3NNi
792.55
C46H48P3NNi
766.51
C43H43P3Ni
711.43
C82H78P6Ni·2THF
1452.27
triclinic
P1(2)
monoclinic
P21/c (14)
monoclinic
P21/n (14)
monoclinic
P21/c (14)
monoclinic
P21/n (14)
monoclinic
P21/n (14)
¯
1187.4(2)
1591.7(3)
1661.0(3)
75.15(3)
82.31(3)
74.95(3)
2923
2647.9(5)
1827.2(4)
2172.1(4)
90
113.15(3)
90
1299.0(3)
1422.6(3)
2144.1(4)
90
91.59(3)
90
3961
4
1944.6(4)
1242.2(3)
1728.3(4)
90
108.00(3)
90
3971
4
1021.8(2)
2019.6(4)
1738.0(4)
90
97.72(3)
90
3554
4
1520.3(3)
2178.8(4)
2539.5(5)
90
99.26(3)
90
8302
4
γ [°]
V [106 pm3]
Z
9663
2
8
dcalcd. [g cm–3
]
1.177
1.360
1.329
1.282
1.330
1.162
T [K]
200
200
200
200
200
100
Scan range
Method
2.5° Յ 2θ Յ 59.8°
ω scan, ∆ω = 1°
10
2.8° Յ 2θ Յ 55.1°
ω scan, ∆ω = 1°
10
3.4° Յ 2θ Յ 55.0°
ω scan, ∆ω = 1°
10
4.1° Յ 2θ Յ 55.0°
ω scan, ∆ω = 1°
10
3.1° Յ 2θ Յ 55.0°
ω scan, ∆ω = 1°
30
2.5° Յ 2θ Յ 46.5°
ω scan, ∆ω = 1°
15
Scan speed [s frame–1
]
No. of reflections measured 19635
40626
21984
11966
I Ն 2σ
1163
16613
9054
6043
I Ն 2σ
526
16856
9037
6542
I Ն 2σ
468
10098
7966
4451
I Ն 2σ
429
12303
11922
5484
I Ն 2σ
745
No. of unique reflections
No. reflections observed
Observation criterion
13212
7943
I Ն 2σ
662
No. of parameters refined
Resididual electron density 1.63
[10–6 epm–3
R1/Rw [%]F2 refinement
0.87
0.39
0.47
0.83
1.83
]
8.9/30.0
6.0/16.1
4.7/10.5
4.2/10.2
7.6/21.5
13.8/38.7
tion at –10 °C. 31P{1H} NMR ([D8]THF): δ = –26.7 (s, 2 P), 6.8
(br. s, 2 P), 12.2 (br. s, 2 P) ppm.
plementary publication nos. CCDC-657981 (for 4), -657982 (for
9), -657983 (for 8), -657984 (for 7), -657985 (for 6), -657986 (for
11), -657987 (for 5b) and -657988 (for 10). Copies of the data can
be obtained free of charge on application to the CCDC, 12 Union
Road, Cambridge CB2 1EZ, U.K., Fax: +44 (0)1223/336033; E-mail:
deposit@ccdc.cam.ac.uk.
Synthesis of [tripod4Ni3] (12): Synthesis follows the procedure de-
scribed for the synthesis of solutions containing B. [(DME)NiBr2]
(31 mg, 0.1 mmol) and tripod (62 mg, 0.1 mmol) are dissolved in
[D8]THF (2 mL). This solution was treated with KC8 (30 mg,
0.22 mmol) and sonicated. Within 10 min a yellow solid precipi-
tates which dissolves again whereby a yellow brownish solution is
obtained. The reaction mixture was then filtered through kieselgur
by means of a syringe to remove the remaining graphite. The re-
sulting solution was used for NMR experiments. 31P{1H} NMR
Acknowledgments
We are indebted to T. Jannack for mass spectrometric measure-
ments and to the crew of the microanalytical laboratory of the
chemical institutes, University of Heidelberg, for elemental analy-
ses. We thank Dr. J. Gross and co-workers of the Mass Spectrome-
try Laboratory of the Institute of Organic Chemistry, University of
Heidelberg, for measuring the LIFDI mass spectrum.
2
([D8]THF): δ = 3.3 (d, JPP = 15 Hz, 3 P), 5.5 (m, 1 P), 12.0 (m,
2
1 P), 28.1 (q, JPP = 15 Hz, 1 P) ppm. For more detailed NMR
spectroscopic data see Figure 3.
X-ray Crystallographic Study: Suitable crystals were taken directly
out of the mother liquor, immersed in perfluorinated polyether oil,
and fixed on top of a glass capillary. Measurements were made on
a Nonius-Kappa CCD diffractometer with low-temperature unit
using graphite-monochromated Mo-Kα radiation. The temperature
was set to 200 K. The data collected were processed using the stan-
dard Nonius software.[20] All calculations were performed using the
SHELXT-PLUS software package. Structures were solved by direct
methods with the SHELXS-97 program and refined with the
SHELXL-97 program.[21,22] Graphical handling of the structural
data during solution and refinement was performed with
XPMA.[23] Structural representations were generated using Winray
32.[24] Atomic coordinates and anisotropic thermal parameters of
non-hydrogen atoms were refined by full-matrix least-squares cal-
culations. Data relating to the structure determinations are com-
piled in Tables 3 and 4.
[1] a) L. Sacconi, F. Mani in Transition Metal Chemistry, (Eds:
G. A. Melson, B. N. Figgis), Marcel Decker, New York, 1982,
vol. 8, p. 179; b) D. A. Buckingham, C. R. Clark in Comprehen-
sive Coordination Chemistry (Eds.: S. G. Wilkinson, R. D. Guil-
lard, J. A. McCleverty), Pergamon, New York, 1987, vol. 4,
p. 635; c) L. Sacconi, F. Mani, A. Bencini in Comprehensive
Coordination Chemistry (Eds.: S. G. Wilkinson, R. D. Guillard,
J. A. McCleverty), Pergamon, New York, 1987, vol. 5, p. 1.
[2] F. Cecconi, C. A. Ghilardi, S. Midollini, S. Moneti, A. Orland-
ini, M. Bacci, J. Chem. Soc. Chem. Commun. 1985, 731.
[3] a) M. D. Vaira, C. A. Ghilardi, S. Midollini, L. Sacconi, J. Am.
Chem. Soc. 1978, 100, 2550; b) C. A. Ghilardi, S. Midollini, A.
Orlandini, L. Sacconi, Inorg. Chem. 1980, 19, 301.
[4] K. Heinze, G. Huttner, L. Zsolnai, P. Schober, Inorg. Chem.
1997, 36, 5457.
[5] U. Winterhalter, L. Zsolnai, P. Kircher, K. Heinze, G. Huttner,
Eur. J. Inorg. Chem. 2001, 89.
Crystallographic data (excluding structure factors) have been de-
posited with the Cambridge Crystallographic Data Centre as sup-
Eur. J. Inorg. Chem. 2008, 1413–1422
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1421

J. Mautz, K. Heinze, H. Wadepohl, G. Huttner
FULL PAPER
[6]
[14] M. Hesse, H. Meier, B. Zeeh, Spektroskopische Methoden in der
organischen Chemie, 4. Auflage, G. Thieme Verlag, Stuttgart,
1991.
[15] K. Schwendlick, Organikum, 18th ed., VEB Deutscher Verlag
der Wissenschaften, Berlin, 1990.
[16] N. E. Schlörer, E. J. Cabrita, S. Berger, Angew. Chem. 2002,
114, 115; Angew. Chem. Int. Ed. 2002, 41, 107.
[17] J. H. Gross, N. Nieth, H. B. Linden, U. Blumbach, F. J. Richter,
M. E. Tauchert, R. Tompers, P. Hofmann, Anal. Bioanal.
Chem. 2006, 386, 52.
[18] a) W. Hewertson, H. R. Watson, J. Chem. Soc. 1962, 1490; b)
A. Muth, O. Walter, G. Huttner, A. Asam, L. Zsolnai, C. Em-
merich, Z. Naturforsch. Teil B 1994, 48, 149.
The molecular structure of 4 in the crystal was solved in space
¯
group I43d. While it is accurately determined (see Tables 1
and 3) there is an appearing disorder of the orientation of the
SnBu3 group over three positions since the cobalt atom occu-
pies a position at a crystallographic trigonal axis. This appear-
ing disorder problem – which does not affect the accuracy of
the determination of the molecular structure to a great extent –
might be due to a twin problem or to an overstructure phenom-
enon. No attempt has been made to untangle this problem.
A. Bondi, J. Phys. Chem. 1964, 68, 441.
A. Sacco, R. Ugo, J. Chem. Soc. 1964, 3, 3274.
S. Beyreuther, J. Hunger, G. Huttner, S. Mann, L. Zsolnai,
Chem. Ber. 1996, 129, 745.
[7]
[8]
[9]
[19] With the techniques used, problems arise with the highly air-
and moisture-sensitive compound 5a. Owing to decomposition
during the preparation and measurement of the samples 13C
NMR spectra, microanalytical data and IR spectra were of lit-
tle help.
[10] a) L. Sacconi, S. Midollini, J. Chem. Soc. Dalton Trans. 1972,
1213; b) J. Ellermann, J. Organomet. Chem. 1975, 94, 201; c) J.
Ellermann, J. F. Schindler, Chem. Ber. 1976, 109, 1095.
[11] Compound 10 crystallises in the space group P21/n. The solu-
tion of the molecular structure in the crystal was straightfor-
ward and the agreement factors are satisfactory (see Table 4).
A peculiarity is, however, that the ethylene C–C distance was
determined as only 116.4(8) pm. Inspection of the size and ori-
entation of the thermal ellipsoids of the ethylene carbon atoms
gives a clue to a rational interpretation of this seemingly short
C–C distance: the thermal ellipsoids are oriented such that
their longest axes almost lie in the C–Co–C plane. This could
mean that there are two positions available for the ethylene
entity, both of them in the C–Co–C plane, but slightly dis-
placed from the observed position on either side. Further re-
finement using an appropriate model of disorder, for instance
starting with a physically realistic contrained C–C distance, was
not considered necessary.
[20] DENZO-SMN, Data processing software, Nonius, 1998; http://
www.nonius.com.
[21] a) G. M. Sheldrick, SHELXS-97, Program for Crystal Struc-
ture Solution, University of Göttingen, 1997; http://shelx.uni-
ac.gwdg.de/SHELX/index.html; b) G. M. Sheldrick, SHELXL-
97, Program for Crystal Structure Refinement, University
of Göttingen, 1997; http://shelx.uni-ac.gwdg.de/SHELX/in-
dex.html.
[22] International Tables for X-ray Crystallography, vol. 4, Kynoch
Press, Birmingham, U.K., 1974.
[23] L. Zsolnai, G. Huttner, XPMA, University of Heidelberg,
1994; http://www.uni-heidelberg.de/institute/fak12/AC/huttner/
software/software.html.
[24] R. Soltek, Winray 32, University of Heidelberg, 2000; http://
www.uni-heidelberg.de/institute/fak12/AC/huttner/software/
software.html.
[12] S. Beyreuther, J. Hunger, G. Huttner, S. Mann, L. Zsolnai,
Chem. Ber. 1996, 129, 745.
[13] K. Heinze, G. Huttner, L. Zsolnai, A. Jacobi, P. Schober,
Chem. Eur. J. 1997, 3, 732.
Received: August 21, 2007
Published Online: February 5, 2008
1422
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1413–1422