Complexes of manganese, iron, zinc, and molybdenum with a superbasic tris(guanidine) derivative of tris(2-ethylamino)amine (tren) as a tripod ligand

Article abstract of DOI:10.1002/1099-0682(200108)2001:8<1937::AID-EJIC1937>3.0.CO;2-I

The synthesis of the novel tripod ligand N[CH₂CH₂N=C(NMe₂)₂]₃, based on the tris(2-ethylamino)amine (tren) backbone and having a set of three superbasic tetramethylguanidine (TMG) donor atoms instead of the primary amine functionalities, is described. This ligand has been prepared by treating tren with the Vilsmeyer salt [(Me₂N)₂CCl]Cl in the presence of triethylamine as an auxiliary base and NaOH. Complexes of manganese(II), iron(II), and zinc(II) as biologically relevant transition metal ions as well as of molybdenum(0) have been synthesized and spectroscopically and structurally characterized. The electrochemical properties of selected complexes have been studied.

Full text of DOI:10.1002/1099-0682(200108)2001:8<1937::AID-EJIC1937>3.0.CO;2-I

FULL PAPER
Complexes of Manganese, Iron, Zinc, and Molybdenum with a Superbasic
Tris(guanidine) Derivative of Tris(2-ethylamino)amine (Tren) as a Tripod
Ligand
[
a]
[a]
[a]
[a]
Harald Wittmann, Volker Raab, Andrea Schorm, Jörn Plackmeyer, and
Jörg Sundermeyer*[
a]
Dedicated to Professor Herbert Roesky on the occasion of his 65th birthday
Keywords: Ligand design / N ligands / Tripodal ligands / Coordination chemistry / Manganese / Iron / Zinc / Molybdenum
The synthesis of the novel tripod ligand N[CH
2
CH
2
N=
the presence of triethylamine as an auxiliary base and
NaOH. Complexes of manganese(II), iron(II), and zinc(II) as
C(NMe , based on the tris(2-ethylamino)amine (tren)
2 2 3
) ]
backbone and having a set of three superbasic tetramethyl- biologically relevant transition metal ions as well as of mo-
guanidine (TMG) donor atoms instead of the primary amine lybdenum(0) have been synthesized and spectroscopically
functionalities, is described. This ligand has been prepared
by treating tren with the Vilsmeyer salt [(Me N) CCl]Cl in
2 2
and structurally characterized. The electrochemical proper-
ties of selected complexes have been studied.
Introduction
Peralkylguanidines belong to the strongest neutral or-
ganic bases known.[ They are several orders of magnitude
more basic than tertiary amines due to the excellent stabil-
ization of the positive charge over their resonance-stabilized
1]
[
2]
ϩ
Scheme 1. Guanidine-based complexes
cations. This trend is illustrated by the pKBH values
(
(
MeCN) of the 1,2,2,6,6-pentamethylpiperidinium cation
18.62), the parent guanidinium cation (23.00), and the pen-
[2c]
tamethylguanidinium cation (25.00). Therefore, in aque-
ous media, guanidines exist almost exclusively in the pro-
oxidation states of metals, e.g. in AgIII [12] and NiIII [13] com-
plexes (Scheme 1).
The focus of this investigation is the evaluation of the
[
3]
tonated form. Guanidines are currently attracting atten-
tion as anion receptors,[ both in enzymes and in model
4]
systems. Due to their hydrophilic nature, they also play an donor capabilities of tetradentate pentaalkylguanidine de-
important role in the mediation of solubility of natural rivatives. The basicities of these neutral ligands are interme-
[
5]
products and in the stabilization of protein conformations diate between those of tertiary amines and amido ligands,
through hydrogen bonding.[5Ϫ7] However, surprisingly little but the question remains as to how well they interact with
is known about the coordination chemistry of guanidines. Lewis acids. Indeed, the question arises as to whether, in
2
There is some indication that the guanidine functionality of addition to their strong σ-donor interaction sp -NǞM, gu-
arginine may play a role as a neutral donor towards various anidines may also be π-acidic like Schiff bases or π-basic
metal cations in the hydrophobic domains of cytochrome c like amido ligands. Various aspects of guanidine coordina-
enzymes and other such systems.[
2,5,6,8]
There have been a tion chemistry remain unexplored, such as the fine tuning
few reports on coordination compounds of monoguanid- of the basicity, donor strength, steric demand, and control
ines HNϭC(NRRЈ)2.[
5,6,8,9]
The first complexes of chelating of the solubility by variation of the substituents at the guan-
[10]
bis(guanidine)s have recently been reported by Kuhn and idine function. Following our study on guanidine derivat-
[
11a]
[11a]
ourselves.
We became interested in the coordination ives of the tmeda and tame backbones,
we wish to re-
chemistry of bis-, tris-, and oligoguanidines because of the port our first results on the synthesis and coordination
marked tendency of biguanides to stabilize unusually high chemistry of guanidine derivatives of the tren ligand family
2
(
Scheme 2). The target molecule 1,1,1-tris{2-[N -(1,1,3,3-
tetramethylguanidino)]ethyl}amine (1) (TMG tren) is struc-
3
[
a]
[14]
Fachbereich Chemie, Philipps-Universität Marburg,
Hans-Meerwein-Straße, 35032 Marburg, Germany
Fax: (internat.) ϩ 49-6421/28-28917
turally related to known Schiff bases, tris(pyridylmethyl)-
[15]
[16]
amine (tmpa), and other tripodal ligands based on the
well-known tren backbone (Scheme 2).
E-mail: jsu@chemie.uni-marburg.de
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948

WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0808Ϫ1937 $ 17.50ϩ.50/0
1937

H. Wittmann, V. Raab, A. Schorm, J. Plackmeyer, J. Sundermeyer
FULL PAPER
Scheme 2. Structural relationship between the target ligand 1 and
known tripods of the tren ligand family
Scheme 3. Preparation of peralkylated oligoguanidines
Results and Discussion
of the tris(hydrochloride) using a two-phase system of
MeCN/50% aqueous KOH.
Ligand Synthesis
The synthesis of the target ligand 1 was accomplished
The spectroscopic features of the protonated ligand 1A
following our general procedure that allows the transforma- are very similar to those of the free guanidine base 1. A
tion of primary bis-, tris-, or polyamines into the corres- difference can be seen in the IR spectra, where TMG tren
3
ponding tetramethylguanidino derivatives.[
11]
The main shows a single absorption at ν(CϭN) ϭ 1620 cm while
Ϫ1
problem associated with this synthesis is that polyguanid- the corresponding absorption of the tris(hydrochloride) is
Ϫ1
ines as well as their hydrochlorides are extremely hygro- split into two separate bands at 1627 and 1584 cm . This
scopic. Typically, they cannot be distilled/sublimed without splitting is a typical feature due the decreased molecular
decomposition and may not be purified by column chroma- symmetry in guanidinium cations. It is also observed for the
tography on polar phases (SiO , Al O ). Because of these hexamethylguanidinium cation.[ In order to avoid steric
21]
2
2
3
purification difficulties, it was imperative that the synthesis interactions, the Me N substituents adopt a mutually
2
involved selective reactions. A nearly quantitative trans- twisted propeller-like conformation[21,22] rather than a co-
formation of a primary amine functionality into the guanid- planar one. The UV/Vis spectrum of 1 in MeCN shows an
ine may be accomplished by reaction with the Vilsmeyer absorption at 216 nm with a molar extinction coefficient ε
4
salt [(Me N) CCl]Cl, a method first described by Eilings- of approximately 1·10 for each guanidinium unit, attribut-
2
2
[
17]
[23]
1
feld and Seefelder
al.
by reaction of tetramethylurea with phosgene
and later improved by Kantlehner et able to the πǞπ* transition of the CϭN bond.
for monoguanidines. The Vilsmeyer salt is obtained NMR spectrum of 1 features only one signal due to the
The H
[
18]
[19]
13
or oxalyl methyl groups, while the C NMR spectrum reveals the
chloride in toluene.[ Reaction of the latter with tren in presence of two chemically non-equivalent methyl groups.
20]
the presence of triethylamine as an auxiliary base leads to It is known from the literature that the barrier to rotation
the corresponding hydrochloride 1A (Scheme 3). Separation about the CϭN double bond of pentaalkylguanidines
from the by-product Et NHCl is accomplished by adding 1 (Scheme 4) leading to a syn-anti isomerization[
2b,24]
is mark-
3
equiv. of NaOH per guanidine functionality and removing edly lowered by protonation or by increased steric demand
the resulting Et N and NaCl by crystallization from aceto- of the alkyl groups. The bulkiness of the tren backbone
3
nitrile/diethyl ether. In the present case, the free base 1 was leads to a lower barrier, which is manifested in the equiva-
1
obtained in an overall yield of up to 86% by deprotonation lence seen in the H NMR spectrum.
1938
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948

Complexes of Mn, Fe, Zn, and Mo with a Superbasic Tris(guanidine) Derivative Tripod Ligand
FULL PAPER
B.M.; µ (4): 5.4 B.M., all with an uncertainty of Ϯ0.1,
eff
were determined by the Evans method.[
29]
Attempts to prepare well-defined complexes of 1 with
III
III
Fe and Mn salts have hitherto proved unsuccessful. It
Scheme 4. The syn-anti isomerization of pentasubstituted guanid- seems that, due to steric repulsion, the bite of the ligand is
ines
better matched with larger ions than with smaller, highly
charged ions. This interpretation is in accordance with the
electrochemical results discussed below, which reveal the
rapid decomposition of the oxidized iron species.
Synthesis of the Metal Complexes
The stabilities of compounds 2؊5 towards hydrolysis
were examined. All the complexes were found to be sensi-
tive to air and moisture, despite the extreme steric shielding
provided by the ligand. In general, it was observed that
metal hydroxides along with the protonated ligand were
formed when 2؊5 were exposed to aqueous solvent mix-
tures. These findings may be explained by the extremely
high proton affinity of guanidines. Deprotonation of an
aqua ligand irreversibly induces the hydrolytic cleavage of
the metalϪnitrogen bond, a pattern that is also typical for
amido complexes (Scheme 6).
The free guanidine base 1 is moderately stable in D O.
2
Due to slow hydrolysis, tetramethylurea is formed over a
period of several days by decomposition of the guanidinium
hydroxide. In contrast, the hydrochloride 1A is perfectly
stable in D O. In order to avoid side reactions due to hydro-
2
lysis of the ligand and of the metal salts, the latter were
dehydrated by the orthoester method[
25]
prior to com-
plexation. The complexes were synthesized in good yields
by combining the dehydrated metal salts with 1.05 equiv. of
TMG tren (1) in dry acetonitrile and stirring for 30 min
3
(
Scheme 5). The resulting ionic complexes 2؊5 proved to
be soluble in polar aprotic media such as MeCN, CH Cl ,
2
2
or acetone, but insoluble in diethyl ether and hydrocarbons.
Scheme 6. Hydrolytic cleavage of the metalϪnitrogen bond
Structural Characterization
Single crystals of all the ionic complexes suitable for X-
ray crystallography were grown by slow diffusion of diethyl
ether into acetonitrile solutions. The results of the structure
analyses are presented in Figures 1Ϫ6, while selected bond
lengths and angles are collected in Table 1 and parameters
relating to the data collection and refinement are listed in
Tables 7 and 8. Complexes 2 (Figures 1 and 2), 3 (Figure 3),
4
(Figure 4), and 5 (Figure 5) each possess a nearly C -sym-
3
Scheme 5. Complexation of M2ϩ salts with TMG
metrical trigonal-bipyramidal molecular geometry, with the
amine nitrogen atom located in one of the axial positions,
and N-coordinated acetonitrile (3, 4, 5) or chloride ion (2)
3
tren
The spectroscopic properties of the complexes resemble occupying the other.
those of the protonated ligand (1A). For example, two IR
absorptions are seen in the 1600 cm region due to ν(Cϭ the equatorial plane. The metal atom is slightly axially dis-
The imino nitrogen atoms of the guanidine groups define
Ϫ1
N). The UV/Vis maxima are shifted 5Ϫ10 nm to lower torted from the equatorial plane towards the acetonitrile
wavelengths. While the zinc(II) complex (5) is diamagnetic, molecule. As is evident from Table 2, this deviation is ac-
the manganese(II) (2, 3) and iron(II) (4) complexes are companied by a change in the ionic radius of the metal
paramagnetic with spin-only values of the order expected center. It also has an effect on the bond lengths between
5
6
[26]
for d and d high-spin complexes
comparable to those the amine and guanidine nitrogen atoms and the metal ion,
of known complexes: µ [Mn(Me tren)Br]Br: 6.01 B.M.; whereas the distance to the acetonitrile nitrogen atom re-
eff
6
µ [Fe(Me tren)Br]Br: 5.34 B.M.;[
27]
µ [Mn(ntb)Cl]Cl mains essentially the same. Other compounds containing
eff
eff
6
28]
[
ntb ϭ tris(2-benzimidazolylmethyl)amine]: 5.83 B.M.[
Mn, Fe, and Zn in similar tren ligand coordination spheres
Their magnetic susceptibilities, µ (2): 5.9 B.M.; µ (3): 5.8 are included in the table in order to correlate our results.
eff
eff
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948
1939

H. Wittmann, V. Raab, A. Schorm, J. Plackmeyer, J. Sundermeyer
FULL PAPER
Table 1. Selected bond lengths [pm] and bond angles [°] in complexes 2Ϫ6, with standard deviations in parentheses
II
[
Mn (TMG
3
tren)Cl]Cl (2)
217.7(1)
Mn(1)ϪN(1)
Mn(1)ϪN(10)
av.(NeqϪMnϪNeq
218.2(2)
237.8(1)
114.63(6)
Mn(1)ϪN(4)
Mn(1)ϪN(7)
219.1(2)
Mn(1)ϪCl(1)
av.(NaxϪMnϪNeq
243.0(1)
76.38(5)
)
)
N(10)ϪMn(1)ϪCl(1)
177.57(4)
II
[
Mn (TMG
3
tren)NCMe](ClO
4
)
2
(3)
Mn(1)ϪN(2)
Mn(1)ϪN(1)
av.(NeqϪMnϪNeq
212.7(3)
232.8(3)
115.79(11)
Mn(1)ϪN(5)
Mn(1)ϪN(11)
av.(NaxϪMnϪNeq
214.8(3)
221.5(3)
78.00(10)
Mn(1)ϪN(8)
213.1(3)
)
)
N(1)ϪMn(1)ϪN(11)
175.64(11)
II
[
Fe (TMG
3
tren)NCMe](ClO
4
)
2
(4)
Fe(1)ϪN(2)
Fe(1)ϪN(1)
av.(NeqϪFeϪNeq
207.3(3)
225.4(3)
116.95(14)
Fe(1)ϪN(5)
Fe(1)ϪN(11)
av.(NaxϪFeϪNeq
206.1(4)
215.1(4)
79.85(14)
Fe(1)ϪN(8)
208.4(4)
)
)
N(1)ϪFe(1)ϪN(11)
176.62(14)
II
[
Zn (TMG
3
tren)NCMe](ClO
)
4 2
(5)
Zn(1)ϪN(2)
Zn(1)ϪN(1)
av.(NeqϪZnϪNeq
203.4(2)
226.9(2)
117.46(10)
Zn(1)ϪN(5)
Zn(1)ϪN(11)
av.(NaxϪZnϪNeq
203.4(2)
218.7(3)
80.74(9)
Zn(1)ϪN(8)
205.1(3)
)
)
N(1)ϪZn(1)ϪN(11)
177.25(9)
0
[
Mo (TMG
3
tren)(CO)
3
] (6)
Mo(1)ϪN(1)
Mo(1)ϪC(22)
N(2)ϪC(3)
N(5)ϪC(10)
N(8)ϪC(17)
235.4(2)
193.0(3)
131.7(3)
131.1(3)
127.6(4)
175.64(10)
Mo(1)ϪN(2)
Mo(1)ϪC(23)
C(3)ϪN(3)
C(10)ϪN(6)
C(17)ϪN(9)
233.6(2)
192.4(3)
136.4(4)
137.2(4)
139.6(4)
174.64(10)
Mo(1)ϪN(5)
Mo(1)ϪC(24)
C(3)ϪN(4)
C(10)ϪN(7)
C(17)ϪN(10)
N(5)ϪMo(1)ϪC(22)
231.9(2)
192.4(3)
137.7(4)
137.2(4)
137.8(4)
167.41(10)
N(1)ϪMo(1)ϪC(23)
N(2)ϪMo(1)ϪC(24)
Figure 1. Molecular structure of 2[44]
However, an absolute comparison remains difficult because
the ligand properties differ significantly, e.g. in terms of
II
Figure 2. Molecular structure of [Mn (TMG
3
tren)Cl]Cl (2);
steric hindrance or considering the different neutral and an- SCHAKAL plot of a projection along the local C axis[44]
3
ionic coligands, which lead to different effective charges at
the metal atoms and hence to different bond lengths to the
equatorial nitrogen atoms.[30]
incorporates both basicity and steric hindrance, the
Comparing complex 2, which bears an anionic chloro li- TMG tren ligand can be estimated to be superior to
3
2
gand, with dicationic 3, which has a neutral acetonitrile li- Me tren in its donor ability. The guanidine sp -nitrogen
gand instead, the increased contraction of the TMG tren atom is much more basic than the amine sp -nitrogen atom
6
3
3
ligand can be directly attributed to the higher effective of Me tren and is also sterically less hindered. The net re-
6
charge at the metal center. As expected, the axial distortion sult is that the average bond length between the equatorial
decreases with decreasing ion radius of the central atom.
guanidine nitrogen atoms and the metal center is much
II
[48]
A comparison of 2 with [Mn (Me tren)Br]Br
(A) as smaller (218 pm) than the corresponding amineϪmetal dis-
6
II
regards the relative donor abilities of the amine and guanid- tance in [Mn Br(Me tren)]Br (A) (227 pm). A stronger
6
ine ligands is made difficult by the different steric require- donor component of the equatorial guanidines is also con-
ments of the two ligand regimes. In the case of 1, steric sistent with the longer distance to the axial amine in 2
repulsion is greatest at the periphery. Since donor ability (238 pm) compared to that in the corresponding Me tren
6
1940
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948

Complexes of Mn, Fe, Zn, and Mo with a Superbasic Tris(guanidine) Derivative Tripod Ligand
FULL PAPER
methylamino groups are not coplanar within the planar gu-
anidine CN unit but show out-of-plane torsion angles of
3
2
0Ϫ45° (Table 3). A similar distortion has been found for
[31]
the hexamethylguanidinium cation in its ground state.
In spite of these steric limitations to perfect π-conjuga-
tion in the outer ligand sphere, the superbasic tripod 1 effi-
ciently stabilizes dicationic complexes by delocalizing the
charge over the three perfectly planar guanidinium cations
(
sum of angles in representative 2: see Table 5).
According to a CCDC search,[ no structurally charac-
32]
terized complexes of iron and manganese with pentacoord-
ination by five neutral N donor ligands have hitherto been
1
0
2ϩ [33]
2ϩ [34]
reported. On the other hand, for d Zn
,
Cd
,
ϩ [35]
9
2ϩ [36]
Ag ,
and d Cu ,
this coordination mode is more
Figure 3. Molecular structure of 3[44]
common. Just a few representatives involving the tren li-
gand or its N-methyl derivatives and an anionic ligand have
been reported, for example the halide complexes of Di
[48]
[50]
Vaira et al.
and Templeton et al.,
and the pseudoha-
Ϫ
Ϫ
lide (OCN and SCN ) complexes investigated by Laskow-
ski and co-workers.[
37]
The Question of π-Bonding Contributions of Guanidine
Ligands
Because the CϭN valence vibrations of coordinated gu-
anidines do not seem to give a reliable measure of the donor
and acceptor qualities of TMG tren, we set out to synthe-
3
size a complex containing CO as an indicator ligand for elec-
tronic interactions of the coligands. The tris(acetonitrile)
complex [Mo(CH CN) (CO) ] was found to react cleanly
3
3
3
Figure 4. Molecular structure of 4[44]
with 1 to give compound 6 in 79% yield (Scheme 7). The
IR spectrum of 6 features more than two ν(CϭN) absorp-
tions in the region 1515Ϫ1580 cm , while in the C NMR
Ϫ1
13
spectrum two resonances due to guanidine CN moieties
3
are observed. Complex 6 proved to be stable under atmo-
spheric conditions for a short period of time, but ultimately
turned from yellow to brown. It showed a similar sensitivity
to oxidation in solution. While the TMG tren ligand is able
3
to displace even an anionic chloro ligand from 2, it is incap-
able of displacing more than three carbon monoxide ligands
from [Mo(CO) ] or derivatives thereof. It bonds in a facial
6
manner, leaving one guanidine functionality as a dangling
arm. This may be taken as an indication that 1 is not a
good π-acceptor, and furthermore that it is a ligand of con-
strained geometry, not being able to stabilize geometries
other than trigonal-bipyramidal in its tripodal coordination
mode. Figure 6 shows the results of an X-ray analysis of
single crystals of 6 obtained from acetonitrile/diethyl ether.
Figure 5. Molecular structure of 5[44]
The molecule of 6 exhibits local C symmetry in the crys-
s
complex A (219 pm). In the latter donorϪacceptor com- talline state with a mirror plane defined by Mo, N(1),
plex, the axial amine has to provide more electron density C(23), and C(24). The molybdenum atom is coordinated in
towards the overall charge compensation. As a con- a distorted octahedral manner. The inner ligand core is de-
sequence, the displacement of the manganese cation out of fined by three facial carbonyl ligands, one amine, and two
the equatorial plane is significantly greater in 2 (51 pm) guanidine ligands. One dangling guanidine arm points away
II
compared to that in [Mn (Me tren)Br]Br (A) (36 pm).
from the inner core. The amine is bonded with a slightly
6
A characteristic structural feature of all the complexes longer MoϪN(1) distance [235.4(2) pm] than the two guan-
2
؊5 is shown in Figure 2. In order to reduce steric repul- idines MoϪN(2) [233.6(2) pm] and Mo(1)ϪN(5) [231.9(2)
sion, the guanidine dimethylamino units are twisted by ap- pm]. However, this difference in bonding is not reflected in
proximately 40° into a propeller-like conformation. The di- specific bonding differences of the trans-CO ligands. On the
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948
1941

H. Wittmann, V. Raab, A. Schorm, J. Plackmeyer, J. Sundermeyer
FULL PAPER
Table 2. Ionic radii of Mn, Fe, and Zn; structural features of complexes 2؊5 and literature counterparts
Ion radius[47] [pm] Axial distortion[a] [pm] d(MϪNax) [pm] d(MϪNeq)[b] [pm] d(MϪLax) [pm]
Complex Metal atom
1
II
ϩ [48]
ϩ [28]
A
AЈ
B
[L Mn ϪBr]
89
89
85
82
82
82
89
89
36
63
32
27
64
39
51
44
37
33
219
252
221
219
248
227
216
215
211
205
249
236
248
245
225
2
II
[L Mn ϪCl]
1
II
ϩ [48]
ϩ [48]
ϩ [49]
ϩ [50]
ϩ
[L Fe ϪBr]
1
II
C
CЈ
CЈЈ
2
[L Zn ϪBr]
2
II
[L Zn ϪCl]
3
II
[L Zn ϪCl]
232
206
231
II
[(1)Mn ϪCl]
237.8(1)
232.8(3)
225.4(3)
226.9(2)
218.3(2)
213.5(3)
207.3(4)
204.0(2)
243.0(1)
221.5(3)
215.1(4)
218.7(3)
II
ϩϩ
3
[(1)Mn (NCMe)]
II
ϩϩ
ϩϩ
[c]
4
[(1)Fe (NCMe)]
85
82
II
5
[(1)Zn (NCMe)]
[
a]
[b]
Distance of M from the equatorial plane defined by the three equatorial nitrogen atoms. Ϫ Average distance of the three equatorial
[c]
2ϩ
[47]
nitrogen atoms from the metal center. Ϫ Average radius of Fe for coordination numbers of 4 and 6 (high spin). Standard deviations
in parentheses. L ϭ Me
1
2
3
6
6
tren, L ϭ tris(2-benzimidazolylmethyl)amine (ntb), L ϭ tren.
II
Table 3. Torsion angles [°] in complex [Mn (TMG
3
tren)Cl]Cl (2)
longer as compared to those in the amine complex [Mo(C-
O) (dien)] (Table 4).
3
Mn(1)ϪN(1)ϪC(3)ϪN(2/3)
N(1)ϪC(3)ϪN(2)ϪC(4/5)
N(1)ϪC(3)ϪN(3)ϪC(6/7)
Ϫ42.7/140.3
Ϫ22.4/139.9
Ϫ40.6/147.2
Table 4. Comparison of bond lengths in 6 and [Mo(CO)
dien ϭ cis-diethylenetriamine
3
(dien)];
6
[Mo(CO)
3
(dien)][38]
av.(MoϪNamine) [pm]
av.(MoϪNimine) [pm]
av.(MoϪC) [pm]
av.(CϪO) [pm]
av.(CϪMoϪC) [°]
235.4
232.7
192.6
117.8
84.8
232.3
Ϫ
194.3
115.3
85.3
Carbonyl stretching frequencies are often used as an ad-
ditional criterion for evaluating the donor/acceptor quali-
ties of coligands. There is no clear trend when guanidine 6
Ϫ1
(
1883 cm ) is compared to complexes of amines that act
Ϫ1 [39]
as pure σ-donors such as [Mo(CO) (tacn)] (1850 cm
or [Mo(CO) (dien)] (1887 cm ).
)
3
Scheme 7. Facial coordination of TMG
3
tren to [Mo(CO)
3
] in 6
Ϫ1 [38]
On the basis of struc-
3
tural and IR spectroscopic evidence, it appears that there is
no π-interaction between the metal center and ligand 1.
Finally, the comparison of CϪN bond lengths in guanid-
ines, guanidinium hydrochlorides, and guanidine complexes
(
Lewis acid adducts) allows us to estimate the extent of elec-
tron density donation to a proton or a Lewis acid, respect-
ively. The greater the donation, the more the imino
nitrogenϪcarbon bond length should become equivalent to
the peripheral CϪNMe2 bond lengths. In the dangling
guanidine group of 6, a short CϪNguanidine bond [127.6(4)
pm] and two long bonds to the peripheral CϪNMe groups
2
[
139.6(4) and 137.8(4) pm] are observed. The differences be-
tween these three guanidine CϪN bond lengths become
much smaller when the guanidine is coordinated to a Lewis
acid (e.g. 2), and become negligible upon protonation as a
result of complete charge delocalization (Table 5).
Figure 6. Molecular structure of 6[48]
other hand, a comparison of the structural parameters of
[38]
Cyclic Voltammetric Measurements
the closely related complexes 6 and [Mo(CO) (dien)],
in
3
which cis-diethylenetriamine (dien) acts as a pure σ-donor,
In order to gain additional information about the synthe-
indicates slightly stronger donation by the guanidine ligand. sized compounds, cyclic voltammetry experiments were car-
Back-donation in 6 is slightly stronger; the MoϪC bonds ried out. A reversible Mnϩ3/ϩ2 couple could be observed
tend to be shorter and the CϪO bonds tend to be slightly for 2 (E1/2 ϭ ϩ0.47 V, ∆E1/2 ϭ 0.11 V, i /i ϭ 1), along with
a
c
1942
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948

Complexes of Mn, Fe, Zn, and Mo with a Superbasic Tris(guanidine) Derivative Tripod Ligand
FULL PAPER
Table 5. Bond angle sums [°] and selected guanidine CϪN distances [pm] in the non-coordinated guanidine of 6, the coordinated guanidine
in 2, and the protonated guanidine in bis(tetramethylguanidino)ethane hydrochloride
[
3 3
Mo(TMG tren)(CO) ] (6)
Σ° N(8)
C(17)ϪN(8)
Ϫ
Σ° N(9/10)
C(17)ϪN(9)
344.5/358.8
139.6(4)
Σ° C(17)
C(17)ϪN(10)
359.9
137.8(4)
127.6(4)
II
[
Mn (TMG
3
tren)Cl]Cl (2)
Σ° N(1)
C(3)ϪN(1)
359.4
131.9(2)
Σ° N(2/3)
C(3)ϪN(2)
357.8/359.6
135.5(2)
Σ° C(3)
C(3)ϪN(3)
359.9
136.9(2)
TMG
Σ° N(1/2)
C(5)ϪN(1)
2
en·2HCl[11a]
359.9/359.9
134.2(2)
Σ° N(3)
C(5)ϪN(3)
358.1
133.6(2)
Σ° C(5)
C(5)ϪN(2)
360.0
133.8(2)
an additional wave (E1/2 ϭ ϩ0.92 V, ∆E1/2 ϭ 0.22 V, ia/ tion potential than the corresponding step for 3 owing to
ϩ4/ϩ3
ic ϭ 4) for the couple Mn
. The latter was irreversible, the presence of the anionic chloro ligand, which facilitates
III
pointing to rapid decomposition of the oxidized species the oxidation of 2. The oxidation potential of Mn
Ǟ
IV
(Figure 7).
Mn does not lie within the window of 0 to 1.5 V.
Complex 4 displays a potential of E ϭ ϩ0.52 V
1/2
II
III
(
∆E1/2 ϭ 0.11 V) for the Fe Ǟ Fe electron transfer, ia/
i ϭ 1 (Figure 8). The irreversible wave in the cathodic re-
c
II
gion (Ϫ 2.09 V) can only cautiously be assigned to an Fe
Ǟ Fe reduction because of its low intensity and position
I
near the border of the electrochemical window.
The values of the normal potentials can only be com-
pared indirectly due to the different recording conditions
(
solvent, temperature) but can still be used to draw qualita-
tive conclusions. All the complexes display lower oxidation
potentials compared to the redox potentials of the aqua
complexes Mn (II Ǟ III): ϩ1.54 V; Fe (II Ǟ III): ϩ0.77
[40]
V
as a result of the electron-donating TMG tren ligand.
3
As expected, the monocationic complex 2 is more easily ox-
idized than the dicationic compound 3 (Table 6).
Table 6. Selected redox potentials
3
Figure 7. Cyclic voltammograms of 2 and 3 (CH CN/TBAP, 2 mm
Ϫ1
glassy carbon/SCE/Pt, v ϭ 100 mV s , 20 °C)
[
40]
Metal complex
]2ϩ (ϩ3/ϩ2)
E
1/2
[V]
Complex 3 shows only a single wave in the anodic region
at E1/2 ϭ ϩ0.88 V (∆E1/2 ϭ 0.09 V, i /i ϭ 1), corresponding [(1)Mn(NCMe)] (ϩ3/ϩ2)
[a]
[Mn(H
2
O)
6
ϩ1.54
ϩ0.88
ϩ0.47
ϩ0.77
ϩ0.52
2
ϩ
[b]
a
c
ϩ3/ϩ2
II
III
ϩ
[b]
to the reversible couple Mn
ition for compound 2 was found to occur at a lower oxida-
. The Mn Ǟ Mn trans- [(1)MnϪCl] (ϩ3/ϩ2)
2
ϩ
[a]
[
[
Fe(H
2
O)
6
]
(ϩ3/ϩ2)
ϩ
2
[b]
(1)Fe(NCMe)] (ϩ3/ϩ2)
[a]
Recorded in H
2
O. Ϫ [b] Recorded in MeCN.
Besides the inherent donor abilities of a given ligand,
steric factors cannot be neglected with regard to the re-
sulting oxidation potential and stability of the oxidized spe-
[
41]
cies.
This statement is related to the investigations of
Ray[ and Schrock,
42]
[43]
who commented on the oxidation
potentials of various transition metal complexes with tren-
like amido ligands possessing varying degrees of steric
strain. We believe that the instability of our oxidized com-
plexes is due to the steric strain of the ligand periphery
imposed by the reduced radius of the cation in its oxidized
form.
3
Figure 8. Cyclic voltammogram of 4 (CH CN/TBAP, 2 mm glassy
Ϫ1
carbon/SCE/Pt, v ϭ 100 mV s , 20 °C)
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948
1943

H. Wittmann, V. Raab, A. Schorm, J. Plackmeyer, J. Sundermeyer
FULL PAPER
Chlorotetramethylformamidinium Chloride:[19] In a flask fitted with
a reflux condenser cryostatted at Ϫ30 °C, phosgene was passed
through a solution of tetramethylurea (50.00 g, 430 mmol) in tolu-
ene (200 mL) kept at 0 °C for 2 h. The phosgene inlet was then
closed and the solution was allowed to warm to room temperature
under stirring for a period of 24 h, with the reflux condenser being
maintained at Ϫ30 °C. The precipitate formed was collected by
Conclusions
Peralkyloligoguanidines are an unexplored class of mul-
tidentate nitrogen ligands within the large family of chelat-
ing N-donors typically containing amines, imines (Schiff
bases), and azaaromatic building blocks. The novel tripod
ligand TMG tren (1), a derivative of tren with three su- filtration, washed three times with dry diethyl ether, and dried in
3
perbasic pentaalkylguanidine donor functions and a geo- vacuo. Yield ca. 95%.
metry constrained to coordinate metal ions preferably in a
2
1
,1,1-Tris{2-[N -(1,1,3,3-tetramethylguanidino)]ethyl}amine (1): To
trigonal-bipyramidal mode, has been introduced. Due to its
ability to delocalize positive charge over the three guanidin-
ium moieties, 1 stabilizes cationic and even dicationic com-
plexes, which are not so common for the corresponding
parent compounds with tren ligands. However, increasing
steric strain on the ligand periphery as a consequence of
a solution of tris(2-aminoethyl)amine (14.62 g, 100 mmol) and tri-
ethylamine (30.36 g, 41.6 mL, 300 mmol) in acetonitrile (50 mL), a
solution of [(Me
150 mL) was slowly added under cooling in an ice bath. After the
exothermic reaction had occurred, the mixture was refluxed for 3 h,
in the course of which a clear solution was produced. NaOH
2 2
N) CCl]Cl (51.32 g, 300 mmol) in acetonitrile
(
the decreased ionic radii of highly oxidized metal cations (12.00 g, 300 mmol) in water (30 mL) was subsequently added un-
seems to limit the stability of such high-valent species. Ini- der vigorous stirring in order to deprotonate the Et NHCl. After
, TMG tren (1) was
3
tial evidence that larger cations are coordinated more fa- evaporation of the solvents and excess NEt
3
3
obtained by deprotonation of 1A [tris(hydrochloride)] with 50%
vourably than smaller ones was provided by the bite angle
and steric constraints of the tripodal ligand sphere of 1.
Our current interest is focused on the Lewis acid activation
of small molecules other than acetonitrile and their trans-
formations in the molecular pocket imposed by the guanid-
ine ligand environment. Furthermore, we are extending our
investigation of this class of ligands to other metals and
other guanidine building blocks.
KOH (50 mL) and extracting the aqueous phase with MeCN
(
3 ϫ 50 mL). The combined extracts were concentrated to dryness
and the residue was taken up in warm hexane. The resulting solu-
tion was dried with MgSO , stirred with activated charcoal while
4
still warm to eliminate impurities, and then filtered through Celite.
Finally, removal of the solvent and drying of the residue in vacuo
gave TMG
yield (38.03 g, 86 mmol). Ϫ M.p. 59Ϫ60 °C. Ϫ H NMR
200.1 MHz, CDCl , 25 °C, CDCl ): δ ϭ 3.23 (m, 6 H, CH ),
.84Ϫ2.59 (m, 42 H, CH ϩ CH ). Ϫ C NMR (50.3 MHz,
CDCl , 25 °C, CDCl ): δ ϭ 160.4 (CN ), 58.2, 48.3 (CH ), 39.6,
8.8 (CH
). Ϫ IR (film): ν˜ ϭ 2880 s, 2839 sh, 1620 s [ν(CϭN)],
3
tren (1) as a pale-yellow slowly crystallizing oil in 86%
1
(
2
3
3
2
1
3
2
3
3
3
3
2
Experimental Section
3
1
3
Ϫ1
495 m, 1453 w, 1364 s, 1236 w, 1130 m, 1062 w, 989 w cm . Ϫ
Materials and Methods: All experiments were carried out in glass-
ware that was assembled while hot and cooled under vacuum. Inert
gas argon 4.8 was dried with granulated P O10. Solvents were puri-
4
UV/Vis (MeCN): λmax (ε) ϭ 216 nm (24000 mol dm cmϪ1). Ϫ
Ϫ1
3
ϩ
MS (70 eV, EI): m/z (%) ϭ 439.0 (1) [M Ϫ H] , 312.0 (100)
ϩ
ϩ
ϩ
[
(
(
C
54) [C
80) [C
15
H
34
N
7
] , 210.0 (73) [C11
H
22
N
4
] , 142.0 (43) [C
7
H
16
N
3
] , 128.0
fied according to literature procedures and were also kept under an
inert gas. Tris(2-aminoethyl)amine and the metal salts were used as
purchased from Fluka. Triethylamine was freshly distilled and
stored under argon prior to use. Substances sensitive to air and
moisture were kept in a nitrogen-flushed glove-box (Braun, Type
MB 150 BG-1). Ϫ Spectra were recorded with the following spec-
ϩ
ϩ
ϩ
6 14 3 4 9 2 3 8 2
H N ] , 85.0 (82) [C H N ] , 72.0 (26) [C H N ] , 58.0
ϩ
2
H
6
N
2
] . Ϫ C21
48
H N10 (440.7): calcd. C 57.24, H 10.98, N
3
1.78; found C 56.87, H 10.83, N 31.45.
2
1
,1,1-Tris{2-[N -(1,1,3,3-tetramethylguanidinium)]ethyl}amine Tri-
chloride (1A; 1·3HCl): The hydrochloride salt could be obtained by
treating the free oligoguanidine base (0.57 g, 1.13 mmol) dissolved
in EtOH (10 mL) with the requisite amount of 1  HCl (3.5 mL).
13
trometers: NMR: Bruker AM 400 ( C: gated-decoupled). Ϫ IR:
Bruker IFS 88 FT. Ϫ MS (EI, 70 eV): Varian MAT CH-7a. Ϫ
Elemental analysis: Heraeus CHN-Rapid. Ϫ Melting points: Büchi
MP B-540 apparatus (uncorrected values). Ϫ X-ray crystallo-
graphy: EnrafϪNonius CAD4 and Siemens P4. Ϫ Magnetic sus-
ceptibility: Momentum apparatus, using the Evans method.[
2
Recrystallization from EtOH/Et O gave strongly hygroscopic, col-
orless crystals that analyzed as the trihydrate. Yield 0.51 g
(
(
0.84 mmol, 74%). Following our synthesis of 1, the TMG
hydrochloride) 1A could also be obtained without isolation of
NHCl with an equimolar
3
tren tris-
29]
the free base. After deprotonation of Et
3
Electrochemical Measurements: Cyclic voltammetry (CV) was per-
formed with electrochemical equipment from AMEL (Milano) con-
sisting of a Model 552 potentiostat, a Model 563 multipurpose
unit, a Nicolet Model 3091 storage oscilloscope, and a Kipp &
Zonen Model BD 90 x/y recorder. The electrochemical cell was
operated under argon, with glassy carbon, platinum rod, and satur-
ated calomel (SCE) serving as working, counter, and reference elec-
trodes, respectively. For temperature control, the cell was immersed
amount of NaOH dissolved in the minimum volume of water and
removing all volatiles in vacuo, the crude tris(hydrochloride) was
redissolved in warm MeCN. The resulting solution was dried with
MgSO , treated with activated charcoal, passed through Celite, and
4
the solvent was evaporated. The residue was washed with dry di-
ethyl ether and dried in vacuo to yield the tris(hydrochloride) 1A
as a colorless, strongly hygroscopic solid that analyzed as the tri-
1
hydrate. Ϫ M.p. 153 °C (dec.). Ϫ H NMR (200.1 MHz, CD
3
CN,
),
O). Ϫ C NMR (50.3 MHz,
CN): δ ϭ 161.3 (CN ), 51.7 (CH ), 39.5 (CH ),
). Ϫ IR (KBr): ν˜ ϭ 3431 s, 1627 s, 1584 s [ν(CϭN)], 1457
m, 1406 s, 1311 w, 1233 w, 1176 w, 1136 w, 1067 w, 900 m, 668 br
in a thermostatted cooling bath. CV curves were obtained at a scan
Ϫ1
3 2
25 °C, CD CN): δ ϭ 8.91 (br. s, 3 H, NH), 3.76 (br., 12 H, CH
4 4
rate of 100 mV s working at 20 °C in MeCN/0.1  nBu NClO .
1
3
2
.92 (s, 36 H, CH
3
), 2.55 (br., 6 H, H
2
Caution! Phosgene is a severe toxic agent that can cause pulmonary
embolism and in cases of heavy exposure may be lethal. It should 39.3 (CH
only be used in a well-ventilated fume hood. Perchlorate salts are
potentially explosive and should be handled with care.
CD
3
CN, 25 °C, CD
3
3
2
3
2
Ϫ1
Ϫ1
3
cm . Ϫ UV/Vis (H
2
O): λmax (ε) ϭ 213 nm (34000 mol dm
1944
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948

Complexes of Mn, Fe, Zn, and Mo with a Superbasic Tris(guanidine) Derivative Tripod Ligand
FULL PAPER
cmϪ1). Ϫ MS (70 eV, EI): m/z (%) ϭ 440.0 (1) [M Ϫ 3 HCl] , 312.0 Ϫ IR (KBr): ν˜ ϭ 2947 m, 2881 m, 1618 s, 1573 s [ν(CϭN)], 1553
ϩ
ϩ
ϩ
ϩ
(
2
95) [C15
H
34
N
7
] , 255.0 (28) [C12
H
27
N
6
] , 222.0 (17) [C10
H
18
N
6
] ,
vs, 1427 m, 1395 m, 1342 w, 1164 sh, 1151 s, 1075 m, 891 m, 764
ϩ
ϩ
Ϫ1
Ϫ1
3
22 4 21 4
10.0 (67) [C11H N ] , 197.0 (28) [C10H N
] , 142.0 (91) m cm . Ϫ UV/Vis (MeCN): λmax (ε) ϭ 226 nm (49000 mol dm
ϩ
ϩ
ϩ
Ϫ1
ϩ
[
[
[
C
C
7
H
H
16
N
3 6 14 3 6 34 7
] , 128.0 (94) [C H N ] , 97.0 (45) [C H11N] , 85.0 (94) cm ). Ϫ MS (70 eV, EI): m/z ϭ 312.0 (60) [C15H N ] , 210.0 (33)
ϩ
ϩ
ϩ
ϩ
ϩ
ϩ
4
9
N
2
] , 71.0 (64) [C
3
H
7
N
2
] , 58.0 (95) [C
O (604.1): calcd. C 41.75, H 9.51, N
3.19; found C 41.69, H 9.86, N 22.83.
2
H
6
N
2
] , 36.0 (100) [C11
(100) [C
(80) [CH
5 °C): µ
Pt, v ϭ 100 mV s , 20 °C): E1/2(ϩ3/ϩ2) ϭ 0.47 V, ∆E1/2(ϩ3/ϩ2) ϭ
.11 V, Ipa/pc ϭ 1; E1/2(ϩ4/ϩ3) ϭ 0.92 V, ∆E1/2(ϩ4/ϩ3) ϭ 0.22 V,
pa/pc ϭ 4. Ϫ C21 48Cl MnN10 (566.5): calcd. C 44.52, H 8.54, N
H
22
N
4
] , 142.0 (32) [C
7
H
16
N
3
] , 128.0 (43) [C
] , 58.0 (74) [C
6
H
14
N
3
] , 85.0
ϩ
ϩ
ϩ
ϩ
HCl] . Ϫ C21
H
51Cl
3
N
10·3H
2
4
H
9
N
2
] , 71.0 (31) [C
3
H
7
N
2
2
H
6
N
2
] , 28.0
ϩ
2
2
N] . Ϫ µeff (Evans method, 5% [D
6 3
]benzene in CD CN,
2
B
/mol ϭ 5.9Ϯ0.1. Ϫ CV (MeCN/TBAP, 2 mm GC/SCE/
General Procedure for the Synthesis of the TMG
3
tren Complexes:
Ϫ1
The metal salts were first dehydrated by the orthoester method.[
Thus, the hydrated salts were stirred in dry EtOH containing twice
the molar amount, with respect to the water present in the salt, of
triethyl orthoformate at 60 °C for 1 h. Equimolar amounts of the
dehydrated metal salt and 1 were separately dissolved in 5-mL por-
tions of dry MeCN under argon. These solutions were then com-
bined and the resulting mixture was stirred for 30 min. at 40Ϫ50
25]
0
I
H
2
2
4.72; found C 44.06, H 8.53, N 23.73.
2
Acetonitrile(1,1,1-tris{2-[N -(1,1,3,3-tetramethylguanidino)]-
ethyl}amine)manganese(II) Diperchlorate (3): The general procedure
was followed using Mn(ClO
.90 mmol). Yield 1.30 g (1.77 mmol, 95%) as colorless crystals. Ϫ
IR (KBr): ν˜ ϭ 2893 m, 2275 w [ν(CϵN)], 1616 sh, 1565 vs, 1535 s
ν(CϭN)], 1463 m, 1427 m, 1398 s, 1346 w, 1257 w, 1164 m, 1092
4 2
) (0.47 g, 1.86 mmol) and 1 (0.84 g,
1
°
3
C, filtered through Celite, and concentrated to a volume of ca.
mL. The complex was then precipitated by the addition of dry
diethyl ether (10 mL), washed with absolute diethyl ether, and dried
in vacuo. Single crystals suitable for X-ray analysis could be grown
by slow diffusion of diethyl ether into the respective acetonitrile so-
lutions.
[
Ϫ1
vs [ν(ClϭO)], 906 w, 892 w, 769 m, 624 s cm . Ϫ MS (70 eV, EI):
m/z (%) ϭ 128.0 (24) [C
[
[
ϩ
ϩ
6
H
14
N
3
4 9 2
] , 85.0 (100) [C H N ] , 71.0 (25)
H N] . Ϫ µeff (Evans method, 5%
2 6
]benzene in CD CN, 25 °C): µ /mol ϭ 5.8Ϯ0.1. Ϫ CV (MeCN/
ϩ
ϩ
C
D
3
H
7
N
2
] , 44.0 (46) [C
6
3 B
2
Ϫ1
Chloro{1,1,1-tris[N -(1,1,3,3-tetramethylguanidino)ethyl]amine} TBAP, 2 mm GC/SCE/Pt, v ϭ 100 mV s , 20 °C): E1/2(ϩ3/ϩ2) ϭ
manganese(II) Chloride (2): The general procedure was followed us-
ing MnCl (0.15 g, 1.12 mmol) and 1 (0.66 g, 1.15 mmol). Yield (735.6): calcd. C 37.56, H 6.99, N 20.95; found C 37.42, H 6.95,
.59 g (1.04 mmol, 93%) as colorless crystals. Ϫ M.p. 230 °C (dec.). N 20.62
2 8
0.88 V, ∆E1/2(ϩ3/ϩ2) ϭ 0.09 V, Ipa/pc ϭ 1. Ϫ C23H51Cl MnN11O
2
0
Table 7. Crystal data and details of the structure refinement for 2, 3, and 4
II
II
II
Complex
[Mn (TMG
3
tren)Cl]Cl (2) [Mn (TMG
3
tren)NCMe](ClO
4
)
2
(3) [Fe (TMG
3
4 2
tren)NCMe](ClO ) (4)
Empirical formula
C
21
H
48Cl
607.59
223(2)
2
MnN10
C
23
H
51Cl
735.59
198(2)
2
MnN11
O
8
C
23
H
51Cl
736.50
198(2)
2
FeN11
O
8
Molecular mass [g molϪ1]
Temperature [K]
Crystal system
Space group
a [pm]
b [pm]
c [pm]
triclinic
monoclinic
P2 /c
monoclinic
P2 /c
1614.4(1)
1329.3(1)
1641.7(1)
90
94.460(10)
90
3512.7(4)
4
¯
P1
1
1
1174.6(3)
1227.4(2)
1298.1(2)
92.451(9)
96.182(10)
117.907(10)
1635.1(5)
2
1619.1(1)
1333.6(1)
1651.1(1)
90
α [°]
β [°]
94.669(10)
90
γ [°]
Volume [A ]
˚
3
3553.1(5)
4
1.375
0.580
1556
Z
ρ [Mg mϪ3]
1.234
0.598
650
1.393
0.640
1560
Ϫ1
µ [mm
F(000)
]
Crystal size [mm]
Diffractometer
Scan technique
0.40 ϫ 0.30 ϫ 0.20
Siemens P4
ω-scan
0.39 ϫ 0.33 ϫ 0.15
Enraf Nonius CAD4
ω-scan
0.28 ϫ 0.21 ϫ 0.10
Enraf Nonius CAD4
ω-scan
θ range for data collection [°]
Index ranges
1.89Ϫ27.71
0 Յ h Յ 13
Ϫ14 Յ k Յ 14
Ϫ14 Յ l Յ 14
5996
2.48Ϫ24.99
0 Յ h Յ 19
0 Յ k Յ 15
Ϫ19 Յ l Յ 19
6462
3.06Ϫ24.98
Ϫ19 Յ h Յ 0
Ϫ15 Յ k Յ 0
Ϫ19 Յ l Յ 19
6379
Reflections collected
Independent reflections
5720
0.0461
6227
0.0169
6150
0.0309
R
int
Observed reflections [F Ն 4σ(F)]
5230
5720/0/366
1.033
0.0327
0.0916
0.8898/0.7959
0.364/Ϫ0.316
5272
6227/0/430
1.106
0.0487
0.1655
0.9181/0.0855
0.532/Ϫ0.448
3741
6150/0/430
1.032
0.0599
0.1490
0.9388/0.8412
0.529/Ϫ0.364
Data/restraints/parameters
2
Goodness of fit on F
[
a]
R1 [F
wR (all data)
Transmission (min./max.)
Largest diff. peak and hole [eAϪ3]
0
Ն 4σ(F)]
[
a]
2
˚
[
a]
ϭ {Σ[w(F2 ) ]}1/2.
2 2
2 2
R
1
ϭ Σ||F
o
| Ϫ |F
c
o
||/Σ|F |; wR
2
o c o
Ϫ F ) ]/Σ[w(F
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948
1945

H. Wittmann, V. Raab, A. Schorm, J. Plackmeyer, J. Sundermeyer
FULL PAPER
2
2
Acetonitrile(1,1,1-tris{2-[N -(1,1,3,3-tetramethylguanidino)]ethyl} Tricarbonyl(fac-tris{2-[N -(1,1,3,3-tetramethylguanidino)]-
amine)iron(II) Diperchlorate (4): The general procedure was fol-
lowed using Fe(ClO (0.32 g, 1.26 mmol) and (0.57 g, lowed using [Mo(CH
.30 mmol). Yield 0.83 g (1.13 mmol, 89%) as light-yellow crystals. (0.88 g, 2.00 mmol). Yield 0.69 g (1.11 mmol, 79%) as a yellow
ethyl}amine)molybdenum(0) (6): The general procedure was fol-
4
)
2
1
3
CN) (CO) ] (0.42 g, 1.40 mmol) and 1
3
3
1
1
Ϫ IR (KBr): ν˜ ϭ 2893 m, 2270 w [ν(CϵN)], 1614 sh, 1558 vs, 1533 powder. Ϫ H NMR (300.1 MHz, CD
sh [ν(CϭN)], 1463 m, 1427 m, 1399 s, 1346 m, 1257 w, 1166 m, 3.50 (m, 2 H, CH ), 3.16 (m, 6 H, CH
). Ϫ C NMR (75.5 MHz, CD CN, 25 °C, CD
/mol ϭ 5.4Ϯ0.1. Ϫ 232.7, 230.1 (CO), 166.5 (CN , coordinated TMG), 160.8 (CN
free TMG), 66.1, 57.2, 50.7, 46.2 (CH ), 39.8, 39.3 (CH ). Ϫ IR
ϭ 2889 s, 1883 s, 1740 vs, 1730 sh [ν(CϭO)], 1619 s, 1577
CN, 25 °C, CD
), 2.70 (m, 40 H, CH
CN): δ ϭ
3
CN): δ ϭ
3
2
2
3
ϩ
Ϫ1
13
1
090 vs [ν(ClϭO)], 908 w, 894 m, 772 m, 623 s cm . Ϫ µeff (Evans
method, 5% [D ]benzene in CD CN, 25 °C): µ
CV (MeCN/TBAP, 2 mm GC/SCE/Pt, v ϭ 100 mV s , 20 °C): E1/
(ϩ3/ϩ2) ϭ 0.52 V, ∆E1/2(ϩ3/ϩ2) ϭ 0.11 V, Ipa/pc ϭ 1, E1/2(ϩ2/ (KBr): ν
ϩ1) ϭ Ϫ2.09 V. Ϫ C23 51Cl FeN11 (736.5): calcd. C 37.51, H s, 1553 sh, 1515 s [ν(CϭN)], 1455 m, 1424 w, 1390 s, 1236 m, 1142
.98, N 20.92; found C 36.90, H 7.03, N 20.52.
CH
2
3
3
6
3
B
3
3
,
Ϫ1
2
3
˜
2
H
2
O
8
Ϫ1
6
m, 1060 w, 1026 w, 976 w, 895 w, 763 w cm . Ϫ MS (70 eV, EI):
ϩ
ϩ
m/z (%) ϭ 621.0 (1) [M] , 594.0 (2) [M Ϫ CO] , 312.0 (98)
2
Acetonitrile(1,1,1-tris{2-[N -(1,1,3,3-tetramethylguanidino)]-
ethyl}amine)zinc(II) Diperchlorate (5): The general procedure was
(0.41 g, 1.54 mmol) and 1 (0.71 g,
.60 mmol). Yield 0.96 g (1.29 mmol, 84%) as colorless crystals. Ϫ
ϩ
ϩ
ϩ
[C
15
H
34
N
7
] , 255.0 (17) [C11
H
25
N
7
22 4
] , 210.0 (52) [C11H N ] ,
ϩ
ϩ
1
7 16 3 6 14 3
42.0 (60) [C H N ] , 128.0 (64) [C H N ] , 101.0 (40)
followed using Zn(ClO
4
)
2
ϩ
ϩ
ϩ
[
[
C
5
H
H
13
N
2
] , 85.0 (96) [C
] , 44.0 (37) [C
4
H
9
N
2
] , 72.0 (53) [C
3
H
8
N
2
] , 58.0 (100)
1
ϩ
ϩ
ϩ
C
2
6
N
2
2
H
6
N] , 28.0 (72) [CH
2
N] .
Ϫ
1
H NMR (200.1 MHz, CDCl
m, 48 H, CH ϩ CH ), 2.04 (s, 3 H, NCCH
50.3 MHz, CDCl , 25 °C, CDCl ): δ ϭ 165.9 (CN
6.6 (CH ), 39.3 (CH
). Ϫ IR (KBr): ν˜ ϭ 2948 w, 2894 w, 2251 w X-ray Structure Analysis: Crystal data and experimental conditions
ν(CϵN)], 1620 sh, 1571 s, 1555 s [ν(CϭN)], 1463 w, 1427 m, 1398 are listed in Tables 7 and 8. The molecular structures are illustrated
3 3
, 25 °C, CDCl ): δ ϭ 3.02Ϫ2.77 (br.
21
C H
48MoN10
O
3
(620.7): calcd. C 46.45, H 7.80, N 22.57; found C
). Ϫ 1 C NMR
3
3
2
3
4
5.89, H 8.07, N 22.29.
(
4
[
3
3
3
), 53.8 (CH ),
2
2
3
as SCHAKAL[ plots in Figures 1Ϫ6. Selected bond lengths and
] , angles with standard deviations in parentheses are presented in
Zn Table 1. Intensity data were collected with graphite-monochrom-
44]
s, 1348 w, 1250 w, 1165 m, 1146 m, 1096 vs [ν(ClϭO)], 894 w, 766
w, 625 m cm . Ϫ MS (70 eV, EI): m/z (%) ϭ 85.0 (100) [C
Ϫ1
ϩ
4
H
9
N
2
ϩ
ϩ
7
1.0 (33) [C
3
H
7
N
2
] , 44.0 (60) [C
2
H
6
N] . Ϫ C23
H
51Cl
2
N
11
O
8
α
(746.0): calcd. C 37.03, H 6.89, N 20.65; found C 36.88, H 7.09, ated Mo-K radiation (λ ϭ 71.069 pm). The collected reflections
N 20.53.
were corrected for Lorentz and polarization effects. The structures
Table 8. Crystal data and details of the structure refinement for 5 and 6
II
0
Complex
[Zn (TMG
3
tren)NCMe](ClO
4
)
2
(5)
[Mo (TMG
3
tren)(CO)
3
] (6)
Empirical formula
C
23
H
51Cl
746.02
193(2)
2
N
11
O
8
Zn
C
21
H
661.72
48MoN10
O
3
Molecular mass [g molϪ1
]
Temperature [K]
Crystal system
Space group
a [pm]
b [pm]
c [pm]
223(2)
monoclinic
P2 /c
1618.2(10)
1320.4(9)
1634.3(6)
90
triclinic
¯
P1
1
1006.0(2)
1259.5(2)
1529.3(2)
66.470(12)
75.237(9)
76.840(15)
1700.3(5)
2
α [°]
β [°]
94.63(4)
90
3481(3)
4
1.424
0.918
γ [°]
Volume [A ]
˚
3
Z
ρ [Mg mϪ3]
1.292
0.429
700
Ϫ1
µ [mm
F(000)
]
1576
Crystal size [mm]
Diffractometer
Scan technique
θ range for data collection [°]
Index ranges
0.25 ϫ 0.25 ϫ 0.25
Enraf Nonius CAD4
ω-scan
0.45 ϫ 0.35 ϫ 0.25
Siemens P4
ω-scan
1.78Ϫ25.04
0 Յ h Յ 11
Ϫ13 Յ k Յ 13
Ϫ14 Յ l Յ 14
5789
2.30Ϫ26.01
Ϫ19 Յ h Յ 19
Ϫ16 Յ k Յ 0
0
Յ l Յ 20
7086
Reflections collected
Independent reflections
6834
0.0194
5251
5483
0.0281
4982
R
int
Observed reflections [F Ն 4σ(F)]
Data/restraints/parameters
6834/0/418
1.038
0.0418
0.1192
0.8030/0.8030
0.595/Ϫ0.537
5483/0/403
1.010
0.0334
0.0907
0.9004/0.8305
0.722/Ϫ0.619
2
Goodness of fit on F
[
a]
R1 [F
wR (all data)
Transmission (min./max.)
Largest diff. peak and hole [eAϪ3]
0
Ն 4σ(F)]
[
a]
2
˚
[
a]
ϭ {Σ[w(F2 ) ]}1/2.
2 2
2 2
R
1
o
ϭ Σ||F | Ϫ |F
c o
||/Σ|F |; wR
2
o c o
Ϫ F ) ]/Σ[w(F
1946
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948

Complexes of Mn, Fe, Zn, and Mo with a Superbasic Tris(guanidine) Derivative Tripod Ligand
FULL PAPER
[
12]
of 2, 5, and 6 were solved by direct methods and refined by full-
matrix least-squares methods on F , while those of 3 and 4 were
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[
[
13]
14]
[
45]
solved using SIR-92.
and isotropically refined except for those of H23A, B, C of 3 and
, which were found and then isotropically refined. An empirical
absorption correction based on the ψ-scans of 9 reflections (Tmin
.4508, Tmax ϭ 0.5098) was performed for 4.[46]
Hydrogen atom positions were calculated
4
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45] [45a]
G. M. Sheldrick, SHELXS-97 (resolution), University of
Göttingen, 1997; SHELXL-97 (refinement), University of
Göttingen, 1997; SHELXTL 5.06, Siemens Analytical
Received December 19, 2000
[I00478]
1948
Eur. J. Inorg. Chem. 2001, 1937Ϫ1948