Stereoselective synthesis of the first chatt-type bis(dinitrogen)- molybdenum(0) complex with a tetraphosphane ligand

Article abstract of DOI:10.1002/ejic.200800417

The first Chatt-type Mo⁰ dinitrogen complex with a tetraphosphane ligand has been prepared and characterized by NMR as well as infrared and Raman spectroscopy. Importantly, the employed reaction route allows the stereospecific synthesis of this complex as trans-[Mo(N₂) ₂(meso-prP₄)] (prP₄ = a tetraphos ligand with a central propylene bridge). The stereoselectivity in the reaction course is induced by the oxido-iodido-molybdenum(IV) precursor [Mo(O)I(prP ₄)]⁺ which directs both phenyl groups of the bridging P atoms of prP₄ into a meso configuration. The paper establishes a general strategy to synthesize mononuclear Mo⁰ dinitrogen and related molybdenum complexes with multidentate phosphane ligands which has not been possible to date. Moreover, the obtained molybdenum tetraphos N₂ complex should exhibit a higher thermodynamic stability in the reactions of the Chatt cycle of synthetic nitrogen fixation than the conventional bis(diphos) complexes, due to the linkage of the two diphosphane units by an alkyl bridge. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200800417

SHORT COMMUNICATION
DOI: 10.1002/ejic.200800417
Stereoselective Synthesis of the First Chatt-Type Bis(dinitrogen)-
Molybdenum(0) Complex with a Tetraphosphane Ligand
René Römer,[a] Gerald Stephan,[a] Carsten Habeck,[a] Christian Hoberg,[a] Gerhard Peters,[a]
Christian Näther,[a] and Felix Tuczek*[a]
Keywords: Dinitrogen / Molybdenum / Phosphane ligands
The first Chatt-type Mo0 dinitrogen complex with a tetra- strategy to synthesize mononuclear Mo0 dinitrogen and re-
phosphane ligand has been prepared and characterized by
NMR as well as infrared and Raman spectroscopy. Import-
antly, the employed reaction route allows the stereospecific
synthesis of this complex as trans-[Mo(N2)2(meso-prP4)] (prP4
= a tetraphos ligand with a central propylene bridge). The
stereoselectivity in the reaction course is induced by the ox-
ido-iodido-molybdenum(IV) precursor [Mo(O)I(prP4)]+ which
directs both phenyl groups of the bridging P atoms of prP4
into a meso configuration. The paper establishes a general
lated molybdenum complexes with multidentate phosphane
ligands which has not been possible to date. Moreover, the
obtained molybdenum tetraphos N2 complex should exhibit
a higher thermodynamic stability in the reactions of the Chatt
cycle of synthetic nitrogen fixation than the conventional
bis(diphos) complexes, due to the linkage of the two diphos-
phane units by an alkyl bridge.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Recently we have performed a complete quantum-chemical
investigation of the Chatt cycle and found a close mechan-
istic relationship to the Schrock cycle which has been theo-
retically treated before.[6,7] It is evident from this investiga-
tion and experimental studies,[3–5] that the basic problem of
the classic Chatt-type N2-Mo/W complexes with diphos-
phane coligands is the presence of two coordination sites
for external substrates which leads to the bonding of
Lewis bases deriving from the added acid or the solvent in
the course of the reactive cycle. These ligands either have
to be de-coordinated from the metal center in order to re-
bind N2 or even lead to complete deactivation of the cata-
lyst. It is therefore desirable to employ a polydentate
ligand which, in addition to a stable equatorial phosphane
ligation, also occupies the trans-position of the dinitrogen
ligand by a neutral donor atom (P or N). The coordination
of more than tridentate phosphane ligands to mono-
nuclear Mo0 centers, however, has not been achieved to
date.[8]
Introduction
One of the great challenges of bioinorganic and organo-
metallic chemistry is a biomimetic process of ammonia syn-
thesis under ambient conditions.[1] A major breakthrough
in this respect has been the synthesis and characterization
of the MoIII triamidoamine complex [Mo(HIPTN3N)] by
Schrock et al.[2] Employing decamethylchromocene as a re-
ductant and a special lutidinium salt as acid, this complex
allowed the catalytic synthesis of NH3 from N2 in 6 turn-
overs with an overall yield of 65%. In a pioneering study,
Pickett and Talarmin had already achieved a cyclic conver-
sion of N2 to NH3 on the basis of a phosphane-tungsten
complex many years before, however, only in three cycles
and with much smaller yield.[3] Nevertheless, the underlying
type of dinitrogen complexes provided the first rational and
complete reactive Scheme for synthetic nitrogen fixation,
the Chatt cycle,[4] and the realization of a truly catalytic
ammonia synthesis on the basis of phosphane-Mo/W com-
plexes still represents a significant goal.
Herein the stereospecific synthesis of the first bis(dini-
trogen)molybdenum(0) complex with a tetraphosphane li-
gand, [Mo(N2)2(prP4)] (4; prP4 = 1,1,4,8,11,11-hexaphenyl-
1,4,8,11-tetraphosphaundecane), is presented. Compound 4
corresponds to the classic Chatt-type N2 complex [Mo(N2)2-
(dppe)2] {dppe = 1,2-bis(diphenylphosphanyl)ethane} but
has a propylene bridge between the two 1,2-phosphanyl-
ethane moieties (Scheme 1, top). The intermediates and the
product of the synthesis are characterized by 31P NMR,
vibrational and UV/Vis spectroscopy as well as X-ray struc-
ture analysis.
Our group has been involved in the spectroscopic charac-
terization of the intermediates of the Chatt cycle and the
investigation of their reactivities for a number of years.[5]
[a] Institut für Anorganische Chemie der Christian-Albrechts-
Universität Kiel,
Otto-Hahn-Platz 6/7, 24098 Kiel, Germany
E-mail: ftuczek@ac.uni-kiel.de
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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Chatt-Type Bis(dinitrogen)-Molybdenum(0) Complex
mer-cis [Mo(O)Cl2(PMe3)3] (1) is able to exchange two
PMe3 groups and one chloro ligand for two dmpe ligands,
giving trans-[Mo(O)Cl(dmpe)2]Cl [dmpe = 1,2-bis(dimethyl-
phosphanylethane)]. The 31P NMR spectrum of 1 exhibits
an AX2 coupling Scheme with a JAX coupling constant of
–21.6 Hz, and its infrared and Raman spectra show the
Mo=O stretch vibration at 952/951 cm–1. In contrast to the
reaction with dmpe, however, treatment of 1 with the steri-
cally more demanding ligand dppe did not lead to a single
product, but to a mixture of the starting complex and the
di- and mono-substituted derivatives [Mo(O)Cl(dppe)2]+
and [Mo(O)Cl2(PMe3)(dppe)], respectively. Due to the
equivalence of all P-donors, the 31P-NMR spectrum of di-
substituted complex shows one line. The spectrum of the
monosubstituted complex corresponds to an AMX pattern
with JAX (cis) and JMX (trans) coupling constants of –20.5
and +203.2 Hz, respectively. JAM is vanishingly small as the
A and M atoms are coupled via the metal and the ethylene
bridge of dppe with coupling constants of equal magnitude,
but opposite signs.[12] Reaction of 1 with the tetradentate
ligand prP4, finally, did not lead to an isolable product at
all.
In order to make the MoIV oxido precursor more reactive
towards the coordination of prP4, the chloro ligands of 1
were subsequently exchanged for iodides, leading to the
complex mer-cis [Mo(O)I2(PMe3)3] (2) which had been pre-
pared and characterized by Poli et al. recently (Scheme 1,
center).[13] Like its chloro congener, 2 exhibits an AX2
coupling Scheme in the 31P NMR spectrum, this time with
a JAX coupling constant of –22.7 Hz. In the infrared spec-
trum the Mo=O stretch is found at 948 cm–1. In contrast
Scheme 1.
Results and Discussion
The synthesis of the tetraphos ligand is outlined in to its chloro analog 1, complex 2 reacts cleanly with the
Scheme 1, bottom.[9] In a first step (2-chloroethyl)diphenyl- tetradentate prP4 ligand in thf, affording crystalline [Mo(O)I-
phosphane is prepared by reaction of lithium diphenylphos- (prP4)]BPh4 (3) after addition of NaBPh4 to the reaction
phide with dichloroethane. This precursor is reacted with mixture. Importantly, 31P NMR spectroscopy shows the
1,3-dilithium diphenylphosphide obtained from 1,3-bis(di- presence of only one isomer, indicating that the reaction
phenylphosphanyl)propane (dppp) by treatment with Li in product either contains the meso or the rac ligand but not a
THF to give a mixture of meso- and rac-prP4. Note that mixture of both. Moreover, single crystals could be grown,
the meso isomer has the two phenyl rings of the central allowing to perform a X-ray structure determination of
phosphorus atoms oriented to the same side whereas in the 3.[14] The structure of the complex cation shown in Figure 1
rac isomer these two phenyl rings are located on the oppo- reveals that the reaction product contains the meso and not
site sides of the ligand.[10] Correspondingly the 31P NMR the rac ligand. These findings can be attributed to the steric
spectrum of the reaction product exhibits two (AX)2 influence of the iodo ligand which prevents formation of
schemes with equal chemical shifts for the terminal but the rac complex in which one of the phenyl substituents on
slightly different chemical shifts for the central phosphorus
atoms (see Supporting Information). The JAX coupling con-
stants for both isomers are 28.5 Hz. No coupling between
the central P atoms is observed, indicating that spin–spin
interaction via the propylene bridge of the prP4 ligand is
negligible.
The crucial synthetic hurdle associated with the coordi-
nation of a tetraphos ligand to a low-valent, mononuclear
molybdenum complex can be cleared by choosing the
proper precursor. Our approach of synthesizing the Mo0–
N2 prP4 complex 4 builds upon the ligand exchange chemis-
try of oxido-halide molybdenum(IV) complexes with PMe3
coligands established by Carmona, Galindo et al.[11] As
Figure 1. Crystal structure of the complex cation of [Mo(O)I(prP4)]
demonstrated by these authors the neutral MoIV complex BPh4 (3).
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F. Tuczek et al.
SHORT COMMUNICATION
the central phosphorus atoms would point to this ligand tral phosphorus atoms (see Supporting Information), the
(see below). The Mo–P distances are within the usual range spectrum now exhibits an AAЈXXЈ pattern (A = central, X
(2.50 to 2.57 Å); the Mo=O and Mo–I bond lengths are = terminal P). The trans JAX coupling constant is 110.4 Hz.
1.69 and 2.95 Å, respectively.[15] The Mo0 central atom ap- The central and the terminal phosphorus atoms couple
pears to tightly fit into the cavity provided by the tetraphos among each other with constants JAA and JXX of –18.4 and
ligand. A small steric strain can be inferred from the bend- –28.2 Hz. We assume that the cis-interaction with the larger
ing of the terminal P atoms out of the equatorial plane. absolute value (28.2 Hz) corresponds to the interaction be-
This causes an increase of the P–Mo–P angle between the tween the central P atoms where the bonding angle is al-
terminal P atoms to 108° whereas the angle between the most exactly 90°; about the same coupling constant is ob-
central P atoms is about 90°. The angles between the central served between the central P atoms of the ligand dppp [1,2-
and the terminal P atoms are ca. 80°, as known from Mo0 bis(diphenylphosphanyl)propane] in the complex [Mo(CO)4-
complexes with dppe or depe ligands.[16]
(dppp)].[17] For the terminal P atoms where the bonding
The 31P NMR spectrum of complex 3 is shown in Fig- angle is increased to 108° the absolute value of the coupling
ure 2, top. As mentioned above, the spectrum corresponds constant is decreased and thus corresponds to the smaller
to one isomer which, on the basis of the X-ray structure coupling constant, –18.4 Hz. The terminal and bridging P
information, contains the meso-ligand. In contrast to the atoms, finally, are coupled via the metal and the ethylene
free prP4 ligand which shows no coupling between the cen- bridge whence the resulting coupling constant is small (see
Figure 2. 31P{1H}NMR spectra of trans-[Mo(O)I(meso-prP4)]BPh4 (3; top) and trans-[Mo(N2)2(meso-prP4)] (4; bottom).
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Chatt-Type Bis(dinitrogen)-Molybdenum(0) Complex
above; |JAX| = 4.9 Hz). The infrared and Raman spectra ated interaction between the terminal P atoms whereas the
of 3, finally, show the MoO stretch at 954 and 958 cm–1, smaller one (AAЈ) corresponds to a spin–spin interaction
respectively (see Supporting Information).
between the central P atoms. The smallest cis-coupling con-
The hypothesis that the orientation of the phenyl substit- stant (AX) is the result of a metal-mediated and another
uents on the bridging phosphane groups of the prP4 ligand interaction through the ethylene bridge (vide supra).
is decisively influenced by the iodo ligand also supported by
A second, independent spectroscopic proof of the ident-
the reactivity of the complex [Mo(O)I2(PMe3)3] (2) towards ity of 4 as trans-[Mo(N2)2(meso-prP4)] is provided by vi-
diphosphanes. In particular, 2 does not react with dppe, in brational spectroscopy. The comparison of the infrared and
contrast to the corresponding oxido-chlorido complex mer- Raman spectrum (Figure 3) shows the existence of two N–
cis [Mo(O)Cl2(PMe3)3] (1) where reaction with dppe was N vibrations, a symmetric combination at 2044 cm–1 and
hindered (as evident from the resulting mixture of non-, an antisymmetric combination at 1961 cm–1, indicating the
mono- and disubstituted products), but did occur. This in- coordination of two dinitrogen ligands. In the presence of a
dicates that coordination of a bis(phenylphosphanyl)ethane center of inversion the symmetric combination is Raman-
moiety with two phenyl groups pointing towards the halide allowed and the antisymmetric combination IR allowed.
ligand is even more disfavoured in the oxido-iodido com- The intensities of νs and νas as shown in Figure 2 clearly
plex 2 than in its chloro congener 1. On the other hand, reflect these relations, although the selection rules are
Bendix et al. found that a MoIV oxido-iodido complex with slightly relaxed in comparison with the higher-symmetric
two dppe ligands, [Mo(O)I(dppe)2]+, can be prepared by complexes [Mo(N2)2(dppe)2] (νs = 2030, νas = 1970 cm–1)
reaction of the trans-dioxido complex [Mo(O)2(dppe)2] with and [W(N2)2(dppe)2] (2005 and 1950 cm–1, resp.; cf. Sup-
HI.[18] The observed steric influence of the iodo ligand thus porting Information).[5a,20] For bis(dinitrogen) complexes
is a kinetic and not a thermodynamic effect, which also ex- with a cis-configuration, in contrast, no vibrational ex-
plains the observation that the prP4 complex 3 tolerates the clusion principle applies and νs as well as νas are observed
presence of four phenyl substituents at the terminal posi- with comparable intensities both in the IR and in the Ra-
tions of the tetraphosphane ligand. On the basis of these man spectrum. Complex 4 therefore is unambiguously asso-
observations, the coordination of the prP4 ligand to the Mo ciated with a bis(dinitrogen) complex exhibiting a trans-
oxido-iodido complex 3 may proceed in the following way: configuration, as already inferred from 31P-NMR spec-
first, one of the (more nucleophilic) central phosphorus troscopy. This is further corroborated by the UV/Vis ab-
atoms binds – probably after exchange of the PMe3 ligand sorption spectrum of 4 (Figure 4) showing the same absorp-
in trans-position – to the equatorial iodo ligand. Then, in a tion features as Mo(N2)2(dppe)2 and W(N2)2(dppe)2.[5a,5b]
second step, the other bridging phosphorus atom is coordi- In particular, the characteristic absorption band of the trans
nated in a stereoselective fashion with formation of the cen- metal-bis(dinitrogen) unit is found at about 300 nm (for 4:
tral meso unit of the ligand. Finally, the terminal phos- 318 nm). This band has been assigned to the transition
phane groups are bound in the equatorial plane, which from the metal dxz and dyz orbitals to the dinitrogen π*x
completes the metalation of prP4.
and π*y orbitals. Likewise at lower energy, the typical ab-
The conversion of the [Mo(O)I(prP4)]+ precursor 3 to the sorption feature connected with phenylphosphane ligands
corresponding dinitrogen complex was achieved by electro- (shoulders at 380 nm) is found. At 470 nm, finally, a weak
chemical reduction in the presence of dinitrogen and phe- absorption deriving from the lowest-energy spin-allowed li-
nol, following the method of Pickett et al. (Scheme 1, gand-field transition of the Mo0 d6 configuration (1A1g
top).[19] The latter reagent was added as a weak acid to 1T1g) can be observed.
induce protonation of the oxido group and subsequent eli-
mination as water. Four-electron reduction was effected by
electrolysis in thf using a mercury pool electrode. The blue
solution of the oxido-molybdenum complex thereby turned
yellow, indicating the formation of the dinitrogen complex.
The 31P NMR spectrum of the yellow-orange reaction
product, [Mo(N2)2(prP4)] (4), is shown in Figure 2, bottom.
In analogy with complex 3, it exhibits a single AAЈXXЈ
pattern, indicating the presence of only one isomer and a
trans-geometry of the complex. On the basis of the struc-
tural information obtained on the precursor 3, the dinitro-
gen complex 4 contains the meso ligand. The 31P NMR
spectrum of 4 can be fully analyzed, leading to the follow-
ing parameters: JAX (trans) = 105.2, |JAX| (cis) = 3.8, JAAЈ
= –15.3 and JXXЈ = –29.8 Hz. Importantly, the derived pa-
rameters are very similar to those of the precursor 3, cor-
Ǟ
Figure 3. Infrared (top) and Raman spectrum (bottom) of trans-
[Mo(N2)2(prP4)] (4), indicating the positions of the symmetric and
antisymmetric N–N stretching vibrations [νs(NN) and νas(NN),
roborating the retention of the trans-meso configuration in
the conversion to the dinitrogen complex. Again, the largest
cis-coupling constant (XXЈ) is derived from the metal-medi- respectively].
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F. Tuczek et al.
SHORT COMMUNICATION
NMR spectra were recorded on a Bruker Avance 400 pulse Fourier
transform spectrometer operating at a 1H frequency of 400.13 MHz
(31P: 161.98 MHz) using a 5 mm inverse triple-resonance probe
head. References as substitutive standards: H3PO4 85% pure, δ(31P)
= 0 ppm.
Elemental analyses were performed using a Euro Vector CHNS-O-
element analyzer (Euro EA 3000). Samples were burned in sealed
tin containers by a stream of oxygen.
Cyclic voltammograms were recorded with a Metrohm Autolab
PGstat 30 potentiostat controlled by the VA computrace or GPES
software in a three-electrode cell with a mercury hanging drop
working electrode and a silver rod as a pseudo-reference electrode.
A solution of [MoOI(prP4)]BPh4 (0.5 m), TBABF4 (0.2 ) and
10 mmol phenol in THF was recorded at 25 °C. The scan rate was
set to 100 mVs–1. The potentials are referenced against ferrocen-
ium/ferrocene.
Figure 4. UV/Vis spectra trans-[Mo(N2)2(prP4)] in KBr (dotted
line) and in CH2Cl2 (solid line).
The electrochemical syntheses were carrier out in a three-electrode
cell. The working-electrode was a mercury pool with a surface of
about 7 cm2. A coiled platinum wire counter electrode was sepa-
rated from the working-electrode by a diaphragm made of clay. A
silver rod was used as reference electrode. Potentiostatic control
was effected by an EG&G PAR model 273A potentiostat con-
trolled by the EG&G PAR M270 software.
Conclusions
In summary, the first Chatt-type Mo0 dinitrogen complex with a
tetraphosphane ligand has been prepared and characterized by
NMR, infrared and Raman IR spectroscopy. Importantly, the em-
ployed reaction route allows the stereospecific synthesis of this
complex as trans-[Mo(N2)2(meso-prP4)] and nowhere requires the
use of chromatographic separation techniques. The stereoselectivity
in the reaction course is induced by the oxido-iodido-molybde-
num(IV) precursor [Mo(O)I(prP4)]+ which directs both phenyl
groups of the bridging P atoms of prP4 into a meso configuration.
Moreover, the prP4 ligand appears to have the right size to accom-
modate the Mo0 center. Although this result does not yet solve
the basic problem of Chatt-type complexes, the possibility for the
coordination of Lewis-basic ligands in trans-position to N2, it has
established a first pathway for the rational synthesis of mononu-
clear molybdenum dinitrogen complexes with tetraphosphane li-
gands which now can be applied to corresponding complexes with
other polyphosphane or polydentate, mixed P/N ligands.[21] Never-
theless, the obtained molybdenum prP4/N2 complex is of significant
interest by itself as it should exhibit a higher thermodynamic sta-
bility in the reactions of the Chatt cycle than the conventional
bis(diphos) complexes, due to the linkage of the two diphosphane
units by an alkyl bridge. This is of particular relevance for the inter-
mediates of higher oxidation states where the metal–phosphane
bonds become labile,[5c] and will be checked in further studies prob-
ing the reactivity of [Mo(N2)2(prP4)] and its derivatives towards
acids and reductants.
[MoOI(prP4)]BPh4 (3): [MoOI2(PMe3)3] (593 mg, 1 mmol), prP4
(684 mg,1 mmol) and NaBPh4 (342 mg, 1 mmol) were refluxed for
6 h in 30 mL of THF. The solvent was removed in vacuo. The resi-
due was extracted with 20 mL of acetone. The solution was filtered
and cooled overnight at –42 °C. The violet solid was filtered and
dried in vacuo yielded 844 mg (68%). A cyclovoltammogram of the
product is shown in FigureS6 (Supporting Information). A small
amount of the solid was solved in 5 mL of CH2Cl2 and recrystal-
ized by slow vapour diffusion of diethyl ether. The obtained deep
blue crystals were suitable for X-ray diffraction studies. Elemental
analysis calcd. for C67H64BIMoOP4 (1242.77): C 64,75, H 5.19, I
10.21; found
NMR(161.975 MHz,CD2Cl2): δ = 46.01 (Jab = –28.2 Hz, |Jac/bd| =
4.9 Hz, Jad/bc = 110.8 Hz, Jcd = –18.4 Hz, 2P; Pa/b), 41.06 (Jab
C
64.51,
H
5.23,
I
10.10%. 31P{1H}
=
–28.2 Hz, Jac/bd = –4.9 Hz, Jad/bc = 110.8 Hz, Jcd = –18.4 Hz, 2P;
Pc/d) ppm.
[Mo(N2)2(prP4)] (4): [MoOI(prP4)]BPh4 (700 mg, 0.56 mmol) and
phenol (94 mg, 10 mmol) were dissolved in 15 mL of THF. The
solution was transferred into a bulk electrolysis cell described above
containing 35 mL of a 0.2  TBABF4 solution in THF. A constant
stream of nitrogen was bubbled into the stirred solution all the
time. The oxido complex was reduced at –2.1 V vs. the reference
electrode (vide supra). The orange solution was transferred by sy-
ringe into a Schlenk flask. The solvent was removed in an atmo-
sphere of nitrogen. The residue was extracted with benzene and
filtered. The solution was concentrated and layered with ethanol.
Cooling overnight gave 256 mg (39%) of a yellow-orange solid,
which corresponds to a mixture of the product and the supporting
electrolyte, [NBu4][BF4]. In order to free the sample from the con-
ducting salt, the mixture was repeatedly extracted with ethanol, as
described in the literature.[23] In further analogy with this pro-
cedure, the identity of the product of the electrosynthesis was
shown spectroscopically. 31P{1H} NMR(161.975 MHz,C6D6): δ =
Experimental Section
General: All reactions were performed under an inert gas atmo-
sphere using Schlenk techniques. The solvents were dried and
freshly distilled under inert gas. Using the following drying agents
during distillation: THF and diethylether, lithium aluminium hy-
dride; benzene and dichloromethan, calcium hydride; ethanol, so-
dium; acetone, calcium sulfate. Sodium tetraphenylborate 99.5+%
(ACS) was used as obtained from Strem Chemicals. Tetrabutylam-
monium tetrafluoroborate puriss. was used as obtained from Fluka
Riedel-de Haën. All other reagents were used without further puri-
fication. The ligand prP4 was prepared by the reaction of (C6H5)2P-
(CH2)2Cl[22] with Lippp.[9] [MoOCl2(PMe3)3] and [MoOI2(PMe3)3]
were prepared using the literature procedures.
71.98 (Jab = –29.8 Hz, |Jac/bd| = 3.8 Hz, Jad/bc = 105.2 Hz, Jcd
=
–15.3 Hz, 2 P; Pa/b), 63.74 (Jab = –29.8 Hz, Jac/bd = 3.8 Hz, Jad/bc
= 105.2 Hz, Jcd = –15.3 Hz, 2P; Pc/d) ppm. IR/Raman νs(NN) =
2044, νas(NN) = 1964 cm–1.
IR spectra were obtained from KBr pellets using a Bruker IFS v66/
S FT-IR-Spectrometer. UV/Vis spectra were recorded on a Cary 5
UV/Vis/NIR-Spectrometer using quartz cuvettes with d = 1 cm.
Supporting Information (see footnote on the first page of this arti-
cle): 31P NMR spectrum of the prP4 ligand, spectroscopic and cy-
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Chatt-Type Bis(dinitrogen)-Molybdenum(0) Complex
[10] M. T. Bautista, K. A. Earl, P. A. Maltby, R. H. Morris, Can. J.
Chem. 1994, 72, 547.
[11] E. Carmona, A. Galindo, Ch. Guille-Photin, L. Sanchez, Poly-
hedron 1988, 7, 1767–1771.
clovoltammetric characterization of compound 3 and reference vi-
brational spectra of dinitrogen complexes.
[12] K.Klatt, G. Stephan, G. Peters, F. Tuczek, Inorg. Chem. 2008,
Acknowledgments
##in press.
[13] J. A. Mata, S. Maria, J.-C. Daran, R. Poli, Eur. J. Inorg. Chem.
2006, 2624–2633.
FT thanks Deutsche Forschungsgemeinschaft (DFG) Project Tu58/
13-2 (SPP1118 “Sekundäre Wechselwirkungen”) for support of this
research.
[14] STOE IPDS-1, Mo-Kα radiation, structure determination:
SHELXS-97, refinement: SHELXL-97. 3: C68H65BCl3IMoOP4
(mol. mass 1362.08), a = 17.9343(11) Å, b = 14.7008(6) Å, c
= 23.8189(13) Å, β = 98.423(7)°, 6212.1(6) Å3 (170 K), ρcalc
=
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1.456 gcm–3, monoclinic, P21/n, Z = 4, STOE IPDS-1, µ =
0.983 mm–1, 49191 measured (5° Յ 2θ Յ 54°) and 13436 inde-
pendent reflections (Rint = 0.0313%), 713 parameters, R1 for
11067 reflections with IϾ2σ (I) = 0.0346, wR2 for all data =
0.0931, GOF = 1.029, residual electron density: 1.00/–1.27 e/
Å3. CCDC-681498 (for 3) contains the supplementary crystal-
lographic data. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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Mo(1)–I(1) 2.9526, Mo(1)–P(1) 2.4960, Mo(1)–P(2) 2.4999,
Mo(1)–P(3) 2.5357, Mo(1)–P(4) 2.5693. The most relevant
bond angles [°] are: I(1)–Mo(1)–O(1) 172.56, P(1)–Mo(1)–P(2)
87.69, P(1)–Mo(1)–P(3) 157.74, P(1)–Mo(1)–P(4) 80.25, P(2)–
Mo(1)–P(3) 78.27, P(2)–Mo(1)–P(4) 161.59, P(3)–Mo(1)–P(4)
108.51.
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Received: April 23, 2008
Published Online: June 18, 2008
Eur. J. Inorg. Chem. 2008, 3258–3263
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3263