Oligodentate Phosphine Ligands with Phospholane End Groups: New Synthetic Access and Application to Molybdenum-Based Synthetic Nitrogen Fixation

Article abstract of DOI:10.1002/ejic.201901068

A new synthetic access to oligodentate phosphine ligands with phospholane end groups, starting from lithium phospholanide, is established. Based on this building block, the tridentate ligand prPP(Ph)P-pln was synthesized and used for the synthesis of [MoX₃{prPP(Ph)P-pln}] (X = Cl, Br, I) precursors. Sodium amalgam reduction in the presence of N₂ and either mono- or bidentate ligands leads to several molybdenum(0) mono- and bis(dinitrogen) complexes, respectively. With the diphosphine dppm a mixture of facial and meridional isomers of [Mo(N₂){prPP(Ph)P-pln}(dppm)] is formed. Using the monophosphines PMePh₂ and PMe₂Ph mer-[Mo(N₂){prPP(Ph)P-pln}(PMe₂Ph)₂] and trans-[Mo(N₂)₂{prPP(Ph)P-pln}(PMePh₂)] could be obtained. The spectroscopic properties and reactivity of the latter towards protonation was investigated, and a hydrazido complex could be obtained and characterized.

Full text of DOI:10.1002/ejic.201901068

DOI: 10.1002/ejic.201901068
Full Paper
Phospholanes
Oligodentate Phosphine Ligands with Phospholane End Groups:
New Synthetic Access and Application to Molybdenum-Based
Synthetic Nitrogen Fixation
Mareike Pfeil,[a] Tobias A. Engesser,[a] Alexander Koch,[a] Jannik Junge,[a] Jan Krahmer,[a]
Christian Näther,[a] and Felix Tuczek*[a]
Abstract: A new synthetic access to oligodentate phosphine phosphine dppm a mixture of facial and meridional isomers of
ligands with phospholane end groups, starting from lithium [Mo(N2){prPP(Ph)P-pln}(dppm)] is formed. Using the monophos-
phospholanide, is established. Based on this building block, the phines PMePh2 and PMe2Ph mer-[Mo(N2){prPP(Ph)P-pln}-
tridentate ligand prPP(Ph)P-pln was synthesized and used for (PMe2Ph)2] and trans-[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] could
the synthesis of [MoX3{prPP(Ph)P-pln}] (X = Cl, Br, I) precursors. be obtained. The spectroscopic properties and reactivity of the
Sodium amalgam reduction in the presence of N2 and either latter towards protonation was investigated, and a hydrazido
mono- or bidentate ligands leads to several molybdenum(0) complex could be obtained and characterized.
mono- and bis(dinitrogen) complexes, respectively. With the di-
Introduction
In the last years, our working group has investigated molyb-
denum dinitrogen complexes supported by oligodentate phos-
phine ligands (Figure 1). In order to increase the activation of
dinitrogen aryl phosphines were replaced by alkyl phosphines
which are better σ donors and weaker π acceptors.[24–29]
Since the discovery of the first dinitrogen complex,[1] the activa-
tion and (catalytic) conversion of highly inert dinitrogen into
ammonia has been one of the most demanding tasks in bio-
inorganic and organometallic chemistry.[2] In nature, this reac-
tion is catalyzed by the enzyme nitrogenase,[3] possessing the
FeMo cofactor as active site.[4] In the last decades, cyclic and
catalytic systems based on transition-metal complexes were de-
veloped to mimic this process.[5–10] In the field of synthetic
nitrogen fixation, molybdenum-phosphine complexes have
been exceedingly successful. The first molybdenum dinitrogen
complex supported by phosphine ligands, [Mo(N2)2(dppe)2],
was synthesized by Hidai et al. already in 1969,[11] and a few
years later, Chatt et al. achieved the first (non-catalytic) conver-
sion of dinitrogen into ammonia using complexes of the type
[M(N2)2(PR3)4] (M = W or Mo, PR3 = PMe2Ph or PMePh2).[10] In
the meantime, highly active catalysts have been developed for
the N2-to-NH3 conversion, some of which are based on molyb-
denum centers[7,9,12–18] and/or phosphine ligands,[6,7,13–22] al-
though other metals and ligands have been found to be effec-
tive as well.[5,6,9,19,21–23]
Figure 1. Selected molybdenum(0) dinitrogen complexes synthesized by our
working group and corresponding NN stretching frequencies.[24,25,27–30]
However, besides the electronic properties of the phosphine
donor groups, also the steric demand of their substituents has
to be taken into account.[25,26] Originally, we developed oligo-
dentate ligand systems with diisopropylphosphine end groups,
which turned out to be sterically too demanding for certain
applications.[25] In order to reduce steric bulk, we introduced
smaller substituents like methyl groups.[26–28] On the other
hand, experimental evidence exists that a certain degree of
shielding is beneficial to enhance the stability of the N2 ligand
and its protonated derivatives.[27,31] With these considerations
in mind we decided to explore the use of phospholane donor
groups as potentially suitable candidates to combine steric
[a] Institute of Inorganic Chemistry, Christian-Albrechts University Kiel,
Max-Eyth-Strasse 2, 24118 Kiel, Germany
E-mail: ftuczek@ac.uni-kiel.de
http://www.ac.uni-kiel.de/tuczek
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201901068.
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. ·
This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivs. License, which permits use and distri-
bution in any medium, provided the original work is properly cited, the use
is non-commercial and no modifications or adaptations are made.
Eur. J. Inorg. Chem. 2019, 1–13
1
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
shielding with the high donor strength of alkylphos- volatile liquid compound is difficult to handle and cannot be
phines.[25,32,33]
stored conveniently. Therefore, after the solvent diethyl ether
and the side product ethanol had been removed via distillation,
the product H-Pln was distilled directly in a solution of n-butyl-
In the literature, phospholane ligands have mostly been in-
vestigated in the field of asymmetric catalysis.[34] Ruthenium
and rhodium catalysts based on chiral bisphospholane ligands,
especially those belonging to the BPE or DuPHOS family,[34,35]
first published by Burk et al.,[36,37] have been well explored re-
garding the enantioselective hydrogenation of unsaturated
substrates.[34,38] Other ligand systems like tripodal or tridentate
PPP,[37,39] NP2,[40,41] NP3,[39–41] as well as PCP[42] or PNP[37,43–45]
pincer ligands have been developed. In the last decade, the
coordination of asymmetric phospholane ligands to metal cen-
ters like Pd(0),[46] Pd(II),[44] Ni(II),[44] Mn(I),[45,47] and Au(I)[41] has
become increasingly important. In comparison to chiral phos-
pholanes, the synthesis of achiral ligands containing phosphol-
ane groups and their coordination to transition metals is less
explored. Only few examples of bisphospholane ligands coordi-
nating to Fe(II),[48] Au(I),[49] Ag(I),[50] or Cu(I)[51] exist. Interest-
ingly, the coordination of phospholane donor groups to molyb-
denum is almost unknown. To the best of our knowledge, only
D'jakonov et al. demonstrated the coordination of mono-
dentate and bidentate phospholane ligands to molybdenum(0)
generating two molybdenum(0) carbonyl complexes.[52] In the
area of nitrogen fixation, phosphine ligands based on phos-
pholane donor groups have not been studied yet.
Herein, we first present the two-step synthesis of lithium
phospholanide (Li-Pln) which turned out to be a versatile build-
ing block for the synthesis of new non-chiral phospholane con-
taining ligands. As an example for this approach, we describe
the synthesis of the non-chiral tridentate ligand bis(3-phosphol-
anopropyl)phenylphosphine [prPP(Ph)P-pln]. In order to apply
this ligand in molybdenum-based synthetic nitrogen fixation,
we investigated its coordination behavior to molybdenum(III)
centers. The resulting molybdenum(III) precursors are reduced
to the corresponding molybdenum(0) mono(dinitrogen) or
bis(dinitrogen) complexes. Thereby, we explored the influence
of mono- (PMe2Ph, PMePh2) and bidentate (dppm, dmpm) co-
ligands on the coordination behavior of prPP(Ph)P-pln and the
activation of dinitrogen in the respective molybdenum(0) com-
plexes.
lithium in n-hexane (2.5
M). The lithium salt of phospholane
(Li-Pln) was obtained as colorless solid (in 28 % yield) which is
much easier to handle than liquid H-Pln.
Scheme 1. Synthesis of lithium phospholanide (Li-Pln) starting with ethyl
phospholanate.
Unexpectedly, more than one signal appears in the 31P{1H}
NMR spectrum of Li-Pln in [D8]THF (Figure 2, middle). The sin-
glet at –92.1 ppm can be assigned to PLi-Pln, the singlet at
–71.0 ppm to PH-Pln[54] and the triplet at –72.8 ppm to the phos-
phorus PD-Pln of deuterated phospholane (1JDP = 28.1 Hz). For
1
H-Pln a dm signal with a coupling constant of JHP = 180.1 Hz
is visible in the proton-coupled 31P NMR spectrum (see SI, Fig-
1
1
ure S3). The ratio of the JHP and JDP coupling constants (6.4)
is in accordance with the theoretical ratio [γ(H)/γ(D) ≈ 6.5]. Fur-
thermore, in the 31P{1H} NMR spectrum a singlet appears at
–28.3 ppm which is possibly associated with a lithium phos-
pholanide aggregate (PLi-Pln(aggregate)). This signal and the signal
at –71.0 ppm (PH-Pln) were found to decrease in intensity if
larger amounts of the product Li-Pln were dissolved in [D8]THF
(cf. Figure 2, top and middle). To verify the formation of Li-Pln
aggregates, the 31P NMR spectrum was measured in MeOD. This
results in a substitution of lithium by deuterium. As a conse-
quence, only one signal appears that can be assigned to the
deuterated phospholane [PD-Pln = –72.8 ppm (t), cf. Figure 2,
bottom]. To investigate if the Li-Pln aggregates were formed in
the NMR solvent [D8]THF the product Li-Pln was dissolved
again in [D8]THF and 0.1 mL MeOH were added. The solution
was investigated via NMR spectroscopy before and after adding
Results and Discussion
Synthesis of Lithium Phospholanide (Li-Pln)
As we found out, lithium phospholanide provides an easy and
versatile route for the introduction of achiral phospholane
groups in oligodentate ligand systems. However, as far as we
know, isolated lithium phospholanide (Li-Pln) has not been syn-
thesized before.
For the preparation of Li-Pln, ethyl dichlorophosphate was
converted to ethyl phospholanate via a Grignard reaction, fol-
lowing Polniaszek and Foster.[53] The following synthesis of
phospholane (H-Pln) was effected by the reduction of ethyl
phospholanate using LiAlH4 (Scheme 1). Obtained H-Pln was
purified via distillation (for NMR spectra of isolated H-Pln see
SI, Figure S1 and S2). However, this air-sensitive and extremely
Figure 2. 31P{1H} NMR spectra of lithium phospholanide (Li-Pln) in [D8]THF
(top, middle) and in MeOD (bottom).
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
2
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
methanol. The signal at –92.1 ppm (PLi-Pln) disappeared, 12 h at room temperature afforded the corresponding molyb-
whereas that at –28.3 ppm (PLi-Pln(aggregate)) was still present. denum(III) complexes in reasonable yields (41–74 %). The com-
Adding higher amounts of MeOH showed no change. These plexes were characterized by elemental analysis and IR spectro-
observations indicate that Li-Pln in fact is prone to form aggre- scopy (see Experimental Section). Comparing the FIR spectra of
gates in THF, a behavior which is also known from LiPPh2.[55] [MoX3{prPP(Ph)P-pln}] (1-X, X = Cl, Br, I; Figure 3) a successive
Additional peaks due to aggregate formation also appear in the shift of the Mo–X vibrations to lower wavenumbers from
1H and 13C NMR spectra (NMR spectra see SI, Figure S4 and S5). [MoCl3{prPP(Ph)P-pln}] (1-Cl) over [MoBr3{prPP(Ph)P-pln}] (1-Br)
to [MoI3{prPP(Ph)P-pln}] (1-I) is apparent which can be ex-
plained by the increasing mass of the halide ligands.
Bis(3-phospholanopropyl)phenylphosphine [prPP(Ph)P-pln]
The tridentate ligand prPP(Ph)P-pln was synthesized by addi-
tion of Li-Pln to bis(3-chloropropyl)phenylphosphine in the
presence of n-butyllithium in THF (Scheme 2).
Scheme 2. Synthesis of the tridentate ligand prPP(Ph)P-pln.
Starting with the reduction of dichlorophenylphosphine by
LiAlH4 as described by Kuchen et al.[56] and Nagel et al.,[57]
phenylphosphine as the central building block was obtained.
Phenylphosphine was lithiated using lithium diisopropylamide
and subsequently converted with 1-bromo-3-chloropropane to
bis(3-chloropropyl)phenylphosphine (Scheme 2). This reaction
was performed as described by Green and Meek.[58] As the
final step, bis(3-chloropropyl)phenylphosphine reacted with
Li-Pln to form bis(3-phospholanopropyl)phenylphosphine
[prPP(Ph)P-pln] in an excellent yield (91 %). In order to break
up the present Li-Pln aggregates (cf. previous section), n-BuLi
was added to the solution of Li-Pln in THF before adding this
mixture to bis(3-chloropropyl)phenylphosphine. This addition is
necessary for the complete substitution of the chlorine groups
by phospholanide giving the tridentate ligand prPP(Ph)P-pln
(NMR spectra see SI, Figure S6–S8).
Figure 3. FIR spectra of the molybdenum(III) complexes 1-Cl, 1-Br and 1-I.
Crystals of [MoCl3{prPP(Ph)P-pln}] (1-Cl) suitable for a X-ray
structure determination could be obtained by slow evaporation
of the solvent THF and dichloromethane. [MoCl3{prPP(Ph)P-pln}]
(1-Cl) crystallizes in the space group P21/c and shows a slightly
distorted octahedral coordination geometry whereby the trident-
ate ligand prPP(Ph)P-pln coordinates in a meridional fashion to
the molybdenum(III) center (Figure 4). In the literature, only a
few crystal structures of molybdenum(III) complexes with the
constitution [MoCl3(PPP)] {PPP
=
PhP(CH2CH2CH2PPh2)2,[59]
MeP(CH2CH2CH2PMe2)2,[59]
PhP(CH2CH2PCy2)2
and
[60]
P(CH2CH2PCy2)3[61]} are known. In these molybdenum(III) com-
plexes the tridentate PPP ligands coordinate meridionally to the
molybdenum(III) center as well. To the best of our knowledge, no
crystal structure of a molybdenum complex with a phospholane
donor group is known so far. The Mo–Cl bond lengths amount
to 2.426 Å [Mo–Cl(1)], 2.426 Å [Mo–Cl(2)] and 2.384 Å [Mo–Cl(3)]
where Cl(2) and Cl(3) coordinate trans to each other. Therefore,
it is surprising that the bond lengths [Mo–Cl(2)] and [Mo–Cl(3)]
are different whereas the bond lengths of [Mo–Cl(1)] and
Molybdenum(III) Complexes
In order to obtain information about the coordination behavior
of prPP(Ph)P-pln to molybdenum centers, the Mo(III) com-
plexes [MoX3{prPP(Ph)P-pln}] (1-X, X = Cl, Br and I) were synthe-
sized according to Scheme 3. These complexes were subse-
quently reduced to molybdenum(0) dinitrogen complexes (see
below).
Scheme 3. Synthesis of the molybdenum(III) complexes [MoX3{prPP(Ph)P-pln}]
(1-X, X = Cl, Br, I).
Stirring of prPP(Ph)P-pln and [MoX3(thf)3] (1-X, X = Cl, Br
Figure 4. Crystal structure of [MoCl3{prPP(Ph)P-pln}] (1-Cl), shown in two dif-
and I) in THF or in a mixture of THF and dichloromethane for
ferent perspectives. Hydrogen atoms are omitted for clarity.
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
3
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[Mo–Cl(2)] are similar. A possible explanation could be the 1929 cm–1)[27] which to date exhibited the lowest NN stretching
stronger steric influence of the phenyl ring of the tridentate frequency of a molybdenum mono(dinitrogen) complex with a
ligand on Cl(3) as compared to Cl(2) (Figure 4, right). The same pentaphosphine environment.
effect was observed for the complexes of the type [MoCl3(PPP)]
[59]
with PPP = PhP(CH2CH2CH2PPh2)2 or PhP(CH2CH2PCy2)2.[60]
Of particular interest are the conformation(s) and bond
lengths of the phospholane groups. Both phospholane rings
exhibit an envelope conformation meaning that in each case
one carbon atom stands out of the ring plane [endo position:
C(3) and C(13)]. The bond lengths P(3)–C(14) (1.842 Å) and P(3)–
C(11) (1.843 Å) are nearly identical, whereas the bond lengths
P(1)–C(1) (1.846 Å ) and P(1)–C(4) (1.831 Å) differ from each
other. Also the bond lengths C(1)–C(2) (1.557 Å) and C(3)–C(4)
(1.518 Å) differ more from each other than the bond lengths
C(11)–C(12) (1.511 Å) and C(13)–C(14) (1.524 Å). Again, the small
differences between both phospholane rings may be caused by
the steric influence of the phenyl ring.
Figure 5. IR (ATR) spectrum of the product of the sodium amalgam reduction
of [MoI3{prPP(Ph)P-pln}] (1-I) in the presence of one equivalent dppm.
The 31P NMR spectrum of the product mixture (Figure 6 and
S9) shows the formation of the three isomeric molybdenum(0)
dinitrogen complexes, fac1-[Mo(N2){prPP(Ph)P-pln}(dppm)]
Synthesis of Dinitrogen Complexes Containing the
Tridentate Ligand prPP(Ph)P-pln
To gain insight into the ability of the molybdenum(0) com-
plexes supported by prPP(Ph)P-pln to bind and activate di-
nitrogen, the molybdenum(III) precursors 1-Br and 1-I were re-
duced by sodium amalgam in the presence of monodentate
(PMePh2, PMe2Ph) or bidentate phosphine coligands (dppm,
dmpm). Because the molybdenum(III) complex 1-Cl was ob-
tained with much lower yield in comparison to 1-Br and 1-I,
this precursor was not used for the sodium amalgam reduc-
tions. The results are presented in the following sections.
(fac1-2) (Figure 6, blue), mer1-[Mo(N2){prPP(Ph)P-pln}(dppm)]
(mer1-2) (red) and fac2-[Mo(N2){prPP(Ph)P-pln}(dppm)] (fac2-2)
(green), which exist in a ratio of 10:6:1. The remaining signals
belong to free ligands and a side product (*) which is possibly
[Mo(dppm)3][62] (see below).
The molybdenum-containing isomers and signals could be
1
assigned on the basis of 31P-, 31P, 31P-COSY- and H,31P-HMBC-
NMR spectra (Figure S10 and S11). For the isomer fac1-
[Mo(N2){prPP(Ph)P-pln}(dppm)] (fac1-2) a set of four dddd-
signals located at 31.9, 27.2, 12.7, 10.3 ppm, and one pseudo-
“dtd” signal at 19.5 ppm appear in the 31P NMR spectrum (Fig-
ure 6, blue). The coupling between these P nuclei can be ob-
served in the 31P, 31P-COSY NMR spectrum (Figure S10). The sig-
nal at 31.9 ppm is assigned to the equatorial phospholane P
atom (Pa) and the signal at 27.2 ppm to the axial phospholane
P atom (Pb) which is coordinated to the molybdenum center in
trans position to the N2 ligand. The latter assignment is also
supported by a missing large coupling constant in the range of
90–110 Hz. The pseudo-“dtd”-signal at 19.5 ppm can be as-
signed to the central P atom Pd of prPP(Ph)P-pln. The coupling
constants between Pd and Pg or Pa (2JPP = 27.8 and 27.7 Hz) are
nearly identical leading to the observed pseudo-“dtd” instead
of a “dddd” pattern. The signal at 12.7 ppm is attributed to Pg,
the PPh2 group of the coligand dppm which is in trans position
to the phospholane P atom Pa (2JPaPg = 95.7 Hz). Finally, the
signal at 10.3 ppm is assigned to Ph, the PPh2 group of the
coligand which coordinates trans to the central ligand P atom
Pd (2JPdPh = 91.3 Hz).
Synthesis of Molybdenum(0) Dinitrogen Complexes in the
Presence of Bidentate Coligands (dppm, dmpm)
For the synthesis of a molybdenum(0) dinitrogen complex
[MoI3{prPP(Ph)P-pln}] (1-I) and one equivalent of dppm [bis(di-
phenylphosphino)methane] as coligand were stirred with so-
dium amalgam in THF for 12 h (Scheme 4). The reaction prod-
uct was highly sensitive to vacuum and could not be precipi-
tated by addition of MeOH. Therefore, the solvent was removed
by a stream of nitrogen and the obtained sticky oil was charac-
terized by IR and NMR spectroscopy.
Scheme 4. Sodium amalgam reduction of [MoI3{prPP(Ph)P-pln}] (1-I) with one
equivalent dppm. A mixture of isomers (fac1-2, mer1-2, fac2-2) was obtained.
For the isomer mer1-[Mo(N2){prPP(Ph)P-pln}(dppm)] (mer1-2)
a set of two dddd-signals located at 22.0 and 17.9 ppm and
The product exhibits a broad and intense NN stretching two dtd-signals located at 13.3 and 4.5 ppm are observed in
band at 1929 cm–1 as well as three shoulders at 1955, 1986 the 31P NMR spectrum (Figure 6, red). The coupling of these P
and 1997 cm–1 (Figure 5). The presence of more than one NN nuclei among each other is shown in the 31P, 31P-COSY NMR
stretching vibration indicates the formation of several com- spectrum (Figure S10). The signal at 22.0 ppm can be assigned
plexes. The intense band at 1929 cm–1 has the same frequency to both phospholane nuclei Pc and Pc′ which coordinate trans
as the NN stretch of the complex [Mo(N2)(P2MePP2Ph)] (ν = to each other. Of course, magnetically equivalent phosphorus
˜
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
4
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[Mo(N2){prPP(Ph)P-pln}(dppm)] (fac1-2). These findings suggest
formation of the isomer fac2-[Mo(N2){prPP(Ph)P-pln}(dppm)]
(fac2-2), in which the central P(Ph)-moiety of the tridentate li-
gand coordinates trans to N2.
DFT calculations show that the fac1- and mer1-isomers, in-
deed, are more stable than the fac2-isomer, which is present in
solution as a minor product (Figure 7). However, the calculated
mer1-structure is more stable than the fac1-isomer, in contrast
to the experiment where fac1 exhibits the highest concentra-
tion. This may reflect a kinetic control of the formation of these
complexes, affected by the sterically demanding residues.
Figure 7. Calculated free energies (B3LYP/def2-TZVPP) of the different isomers
of [Mo(N2){prPP(Ph)P-pln}(dppm)] (2) with (blue, D3BJ) and without (red) dis-
persion correction. (For more details see SI, Figure S25 and S26).
Besides the described molybdenum(0) dinitrogen complexes
fac1-2, mer1-2 and fac2-2 a singlet appears at 15.5 ppm which,
according to the 1H,31P-HMBC spectrum (Figure S11), can be
assigned to [Mo(dppm)3].[62] To confirm the formation of
[Mo(dppm)3] we reduced [MoCl3(thf)3] in the presence of three
equivalents dppm via sodium amalgam according to the litera-
ture.[62] The NMR spectra (Figure S12 and S13) and the missing
NN stretching vibration in the IR spectrum (Figure S23) support
our assumption that [Mo(dppm)3] was formed. However, it is
known that the complex [Mo(dppm)3] is labile,[63] which may
explain the large amount of dppm (cf. Figure S9 and S12). This
also indicates that the formation of a dinitrogen complex sup-
ported by the tridentate ligand prPP(Ph)P-pln and dppm is not
particularly favorable. In order to investigate whether the steric
demand of dppm has a negative impact on the formation of
[Mo(N2){prPP(Ph)P-pln}(dppm)] (2), dmpm was employed as a
coligand. However, no well-defined and stable complexes could
be isolated in this case. The 31P NMR spectrum and the calcu-
lated free energies of different isomers of the complex
[Mo(N2){prPP(Ph)P-pln}(dmpm)] are given in the SI, Figure S14
and S26, respectively.
Figure 6. 31P{1H} NMR spectrum of [Mo(N2){prPP(Ph)P-pln}(dppm)] (2) meas-
ured in C6D6: Bottom: Structure formulae; middle: 31P{1H} NMR spectrum be-
tween 36 ppm and 4 ppm; top: comparison of the measured and simulated
spectra for the fac1- and mer1-isomer of 2 (enlarged sections).
nuclei are not supposed to show a coupling to each other. Nev-
ertheless, a coupling constant of 1.1 Hz is observable. This be-
havior can be explained by different conformations of the phos-
pholane rings. Already in the crystal structure of the molyb-
denum(III) complex [MoCl3{prPP(Ph)P-pln}] (1-Cl) different bond
lengths within the phospholane rings were observed (see
above and Figure 4). The dddd-signal at 17.9 ppm is assigned
to the central P atom Pe of the tridentate ligand whereas the
dtd-signal at 13.3 ppm is attributed to the PPh2 group of the
coligand dppm that is coordinated in trans position to the N2
ligand (Pf). For the other PPh2 group of the coligand (Pi) a dtd-
signal is observed at 4.5 ppm (2JPePi = 94.5 Hz).
Synthesis of Molybdenum(0) Dinitrogen Complexes in the
Presence of Monodentate Coligands (PMePh2, PMe2Ph)
and Investigation of their Reactivities towards Acids
Finally, the 31P NMR spectrum of the product mixture result-
ing from the sodium amalgam reduction of [MoI3{prPP(Ph)P-
pln}] (1-I) in the presence of one equivalent dppm exhibits a
third isomer (Figure 6, green), albeit with little intensity. The To explore whether it is possible to synthesize a molyb-
signal at 35.5 ppm is probably the AA′ part of an AA′XX′M pat- denum(0) bis(dinitrogen) complex supported by the tridentate
tern. In the 31P, 31P-COSY NMR spectrum (NMR spectra see SI, ligand prPP(Ph)P-pln [MoBr3{prPP(Ph)P-pln}] (1-Br) was sub-
Figure S10) a coupling to two other signals is visible, but these jected to a sodium amalgam reduction in the presence of N2
signals are hidden by the signals of Pd and Ph of fac1- and the monodentate ligands PMePh2 and PMe2Ph which have
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
5
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
different steric demands {1-Br turned out to be easier accessi- which is assigned to the symmetric NN stretching vibration of
ble in pure form than [MoI3{prPP(Ph)P-pln}] (1-I)}. In the follow- the two N2 ligands. The Raman spectrum exhibits the corre-
ing, the results of these investigations are described in more sponding bands at 2000 cm–1 and 1930 cm–1 but with an oppo-
detail.
site intensity ratio compared to the IR spectrum.
Synthesis of [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3)
Employing one equivalent of PMePh2 yielded the bis(dinitro-
gen) complex trans-[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3;
Scheme 5). The complex could be obtained as an orange-col-
ored solid by precipitation with methanol and was character-
ized by IR, Raman and NMR spectroscopy as well as by elemen-
tal analysis. Employing two equivalents of PMePh2 also afforded
3 along with one equivalent of uncoordinated PMePh2 instead
of a mono(dinitrogen) complex (see below). However, it was
not possible to precipitate the product in this case.
Figure 8. IR (ATR) (top, black) and Raman spectrum (bottom, red) of the bis(di-
nitrogen) complex [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3).
The formation of trans-[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3)
is further supported by 31P NMR spectroscopy (Figure 9, bot-
tom). A set of signals located at 25.0, 22.8 and 18.0 ppm for the
trans-[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] complex (3) are ob-
Scheme 5. Synthesis of [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3) via sodium
amalgam reduction of [MoBr3{prPP(Ph)P-pln}] (1-Br) in the presence of one
or two equivalent(s) PMePh2.
The IR and Raman spectra of 3 indicate the formation of served. The signal at 25.0 ppm is assigned to both phospholane
a trans-bis(dinitrogen) complex (Figure 8). Specifically, the IR P atoms Pa and Pa′ which are in trans position to each other
spectrum shows an intense band at 1924 cm–1 which is as- [Figure 9 (bottom), Scheme 5]. For the coordinated coligand
signed to the antisymmetric and a small band at 2005 cm–1 PMePh2 a dt-signal pattern at 22.8 ppm is observed [Pb, Figure 9
Figure 9. 31P{1H} NMR spectra of [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3) measured in [D8]THF (bottom) and [Mo(NNH2)(OTf){prPP(Ph)P-pln}(PMePh2)]OTf (4)
measured in CD2Cl2 (top). Furthermore, enlarged signals (measured and simulated) of the complexes 3 and 4 are shown. Full 31P NMR spectra see SI (Figure
S15 and S17).
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
6
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
(bottom), Scheme 5]. The central PPh group of prPP(Ph)P-pln IR spectrum shows two weak bands at 3246 and 3103 cm–1
(Pc) coordinates in trans position to PMePh2 (Pb) and gives rise which can be assigned to the NH stretching vibrations of the
to a dt-signal at 18.0 ppm [Figure 9 (bottom), Scheme 5]. Fur- NNH2 group.
thermore, a large trans coupling between the central PPh (Pc)
Synthesis of [Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2] (5)
and PMePh2 (Pb) is observed (2JPbPc = 100.8 Hz).
In order to investigate whether formation of the bis(dinitrogen)
complex [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3) is influenced by
Synthesis of [Mo(NNH2)(OTf){prPP(Ph)P-pln}(PMePh2)]OTf (4)
the steric demand of the monophosphine, we also employed
PMe2Ph as a coligand which exhibits a smaller Tolman cone
angle (122°)[33] than PMePh2 (136°).[33] If the sodium amalgam
reduction of [MoBr3{prPP(Ph)P-pln}] (1-Br) was performed
in the presence of two equivalents of the monophosphine
PMe2Ph, the mono(dinitrogen) complex [Mo(N2){prPP(Ph)P-pln}-
(PMe2Ph)2] (5) was obtained (Scheme 6). Using one equivalent
of PMe2Ph did not lead to the corresponding bis(dinitrogen)
complex, but to the mono(dinitrogen) complex 5 as well; how-
ever, not in a pure form.
The formation of a hydrazido complex by protonation of bis(di-
nitrogen) complexes represents the first step towards the gen-
eration of ammonia (Chatt cycle).[10,64] In fact, conversion of the
bis(dinitrogen) complex [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3)
to the hydrazido complex [Mo(NNH2)(OTf){prPP(Ph)P-pln}-
(PMePh2)]OTf (4) could be effected by addition of triflic acid
(TfOH) in a NMR experiment performed in [D10]Et2O and CD2Cl2.
The orange-colored bis(dinitrogen) complex 3 was dissolved
in [D10]Et2O and 2.5 equivalents of TfOH were added, leading to
precipitation of a grey solid. The solvent was removed in vacuo
and the solid was dissolved in CD2Cl2 whereby the solution be-
came red. After the addition of the acid NMR spectra were meas-
ured immediately. The 31P{1H} NMR spectrum proves the reten-
tion of the tetraphosphine ligand sphere. Compared to the
bis(dinitrogen) complex [Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3) all
signals are shifted to higher field by 10 – 14 ppm (cf. Figure 9).
The signal of the phospholane P atoms Pa and Pa′ of complex 4
appears at 15.0 ppm whereby the signal of the coordinated co-
ligand PMePh2 (Pb) can be found at 10.9 ppm. The signal of the
P(Ph) group (Pc) of the tridentate ligand prPP(Ph)P-pln has been
shifted to 4.00 ppm. Moreover, the trans-coupling constant of
the P nuclei Pb and Pc (2JPbPc = 135.6 Hz) has significantly been
increased by the formation of the hydrazido complex 4.
Scheme 6. Synthesis of the mono(dinitrogen) complex [Mo(N2){prPP(Ph)P-
pln}(PMe2Ph)2] (5) via sodium amalgam reduction of [MoBr3{prPP(Ph)P-pln}]
(1-Br) in the presence of two equivalents PMe2Ph.
By precipitation with MeOH 5 could be isolated as a red
solid. The corresponding IR spectrum (Figure 11, top, black) ex-
hibits an intense NN stretching band at 1931 cm–1 and a shoul-
der at 1944 cm–1 whereas the Raman spectrum exhibits a
strong peak at 1944 cm–1 and a smaller one at 1933 cm–1 (Fig-
ure 11, bottom, red). In contrast to the bulk, the liquid IR spec-
trum reveals only one broad NN stretching band at 1945 cm–1
(Liquid IR spectrum see SI, Figure S24). The absence of the
shoulder in the liquid IR reveals that the second band is due
the solid state effect (Davydov splitting).[65]
1
The H NMR spectrum of the solution after protonation re-
veals a singlet at 8.9 ppm that corresponds to the NNH2 protons
(Figure S18). In the 19F NMR spectrum one intense singlet at
–79.3 ppm associated with the fluorine atoms of TfO– is visible
(Figure S19). It seems that ligand exchange occurs between co-
ordinated and solvated TfO– at a temperature of 300 K.
After removing the solvent from the protonation solution an
IR spectrum [Figure 10, red (bottom)] was measured from the
obtained yellow oil. No bands for the NN-vibrations of
[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3) are visible. However, the
Figure 11. IR (ATR) (black, top) and Raman (red, bottom) spectrum of
[Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2] (5).
The 31P NMR spectrum of [Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2]
(5; cf. Figure 12; full spectrum see SI, Figure S20) proves that
only one complex is formed; i.e., the spectrum exhibits a set of
four signals relating to the mono(dinitrogen) complex 5 and a
Figure 10. Comparison of the IR (ATR) spectra of [Mo(N2)2{prPP(Ph)P-pln}-
(PMePh2)] (3) (black, top) and [Mo(NNH2)(OTf){prPP(Ph)P-pln}(PMePh2)]OTf (4)
(red, bottom).
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
7
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
singlet relating to a small amount of uncoordinated coligand dentate ligand prPP(Ph)P-pln to molybdenum(III) centers as
PMe2Ph.
well as formation of molybdenum mono(dinitrogen) or bis-
(dinitrogen) complexes by sodium amalgam reduction of the
molybdenum(III) precursors. The constitution of the final prod-
uct was, however, found to strongly depend on the applied
coligands. Using monodentate coligands, only a meridional co-
ordination of prPP(Ph)P-pln and the formation of one isomer
was observed. Using two equivalents of PMePh2 as coligand,
the reduction of [MoBr3{prPP(Ph)P-pln}] (1-Br) via sodium amal-
gam led to the bis(dinitrogen) complex [Mo(N2)2{prPP(Ph)P-
pln}(PMePh2)] (3), which could be converted into the hydrazido
complex [Mo(NNH2)(OTf){prPP(Ph)P-pln}(PMePh2)]OTf (4). Ap-
plying less sterically demanding PMe2Ph as coligand the
mono(dinitrogen) complex [Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2]
(5) supported by the tridentate ligand prPP(Ph)P-pln was ob-
tained which, however, could not be protonated.
If bidentate dppm was employed as a coligand in the de-
scribed syntheses a mixture of isomers was formed whereby
prPP(Ph)P-pln coordinates in a meridional or facial fashion. Be-
cause of the large amount of uncoordinated dppm found in
the product, it appears that this ligand is only weakly bound in
this type of complexes. Using less sterically demanding dmpm
as coligand, however, no well-defined complex was obtained.
To conclude, we have presented the first molybdenum di-
nitrogen complexes supported by a tridentate ligand with
phospholane end groups, employing lithium phospholanide as
a useful and versatile building block for the synthesis of such
multidentate ligands. Further studies will be devoted to explore
the application of phospholane end groups in tripods or ligands
of higher denticity such as pentadentate tetrapodal (pentaPod)
ligands which we have recently employed in synthetic nitrogen
fixation.[27]
Figure 12. Measured and simulated 31P NMR spectra of [Mo(N2){prPP(Ph)P-
pln}(PMe2Ph)2] (5).
A ddd-signal pattern located at 25.0 ppm can be assigned
to the two phospholane P atoms Pa and Pa′ which are in trans
position to each other (Figure 12, Scheme 6). In comparison to
the complex mer1-[Mo(N2){prPP(Ph)P-pln}(dppm)] (mer1-2) the
31P nuclei of both phospholanes seem to be magnetically
equivalent as no trans coupling is visible. The dtd-signal at
15.3 ppm can be assigned to the central P(Ph) group of the
tridentate ligand prPP(Ph)P-pln (Pb, Figure 12, Scheme 6). One
coligand PMe2Ph (Pd) is coordinated trans to Pb (2JPbPd
=
85.9 Hz). The corresponding signal is located at 3.7 ppm and
exhibits a dtd-signal pattern. The second coligand PMe2Ph (Pc,
Scheme 6), which coordinates trans to N2, gives rise to a dtd-
signal at 9.4 ppm (Figure 12). Unfortunately, the elemental anal-
ysis of [Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2] (5) exhibits too low
values for nitrogen and carbon (cf. experimental section) indi-
cating that decoordination of both the N2 ligand and the co-
ligand PMe2Ph occurs. The instability of [Mo(N2){prPP(Ph)P-pln}-
(PMe2Ph)2] (5) could also be observed in solution via NMR spec-
troscopy since we repeated the measurement of the same NMR
sample after two weeks, showing that new signals had ap-
peared and the amount of free coligand PMe2Ph had increased
(cf. SI, Figure S22).
Experimental Section
General Information: Commercially available starting materials
were used as received. Water- and oxygen-sensitive reagents were
handled in a M. Braun Labmaster 130 Glovebox under N2. All syn-
theses were performed in dried solvents under a N2 atmosphere by
using Schlenk techniques. Solvents were dried with CaH2 (dichloro-
methane, n-hexane, n-pentane), LiAlH4 (THF, diethyl ether) or mag-
nesium methoxide (methanol) under Ar and freshly distilled prior
to use. [MoCl3(thf)3],[67] [MoBr3(thf)3],[68] [MoI3(thf)3],[69] ethyl phos-
pholanate,[53] phenylphosphine[56,57] as well as bis(3-chloropropyl)-
phenylphoshine[58] were prepared as described in the literature. Ele-
mental analyses were performed using a EuroVector CHNSO-ele-
ment analyzer (Euro EA 3000) or a vario MICRO cube (Co. Elementar
Analysensysteme). Samples were burned in sealed tin containers in
a stream of oxygen. NMR spectra were recorded with a Bruker
Avance 400 Pulse Fourier Transform spectrometer operating at fre-
quencies of 400.13 MHz (1H), 376.46 MHz (19F) 161.98 MHz (31P),
155.51 MHz (7Li) and 100.62 MHz (13C). Referencing was performed
either using the solvent residue signal (7.26 ppm for CDCl3,
5.32 ppm for CD2Cl2, 3.58 ppm for [D8]THF, 3.31 ppm for CD3OD).
7Li NMR spectra were referenced to LiCl in D2O [δ(7Li) = 0 ppm],
19F NMR spectra were referenced to CFCl3 in CDCl3 [δ(19F) = 0 ppm]
and 31P NMR spectra were referenced to H3PO4 85 % [δ(31P) =
0 ppm] as substitutive standard. Infrared spectra were recorded on
In analogy to compound 3, we also attempted to protonate
[Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2] (5) by adding two equiva-
lents of different acids {HBArF and [LutH]BArF with the non-
4
4
coordinating anion BArF – = tetrakis[3,5-bis(trifluoromethyl)-
4
phenyl]borate or [LutH]OTf with the coordinating anion TfO–} to
a solution of 5 in [D8]THF. These experiments were performed
in a young tube to investigate the reaction immediately by NMR
spectroscopy. Nevertheless, only a decomposition of the molyb-
denum(0) mono(dinitrogen) complex [Mo(N2){prPP(Ph)P-pln}-
(PMe2Ph)2] (5) was observed, which was ascribed to the fact
that the monodentate phosphine ligands are substituted by,
e.g., coordinating anions or hydrides.[66]
Conclusion
We established a new access to oligodentate ligands with phos-
pholane end groups and demonstrated coordination of the tri- a Bruker Alpha FT-IR Spectrum with Platinum ATR setup. Solution-
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
8
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
phase IR spectroscopy was performed with a Bruker Vertex 70 spec-
trometer at a resolution of 2 cm–1. Raman spectra were recorded at
room temp. on a Bruker RAM II FT-Raman spectrometer using a
tion at 0 °C. The solution was stirred for 60 h at room temperature.
Degassed water (10 mL) was added and it was stirred for 30 min.
The organic layer was separated with a syringe and the aqueous
liquid nitrogen cooled, highly sensitive Ge detector, 1064 nm radia- layer was extracted three times with diethyl ether (5 mL). The sol-
tion and 3 cm–1 resolution.
vent was removed in vacuo. The residue was redissolved in di-
chloromethane (5 mL), filtered through basic aluminum oxide and
washed with dichloromethane (50 mL) to give the product as color-
less oil (735 mg, 2.00 mmol, 91 %). Anal.: C20H33P3 (366.40): C 65.6,
H 9.1; found C 65.6, H 9.4.31P{1H} NMR: (161.98 MHz, CDCl3, 300 K):
δ = –25.5 (s, 1 P, PPh2), –27.0 (s, 2 P, PPln) ppm. 1H-NMR (400.13 MHz,
CDCl3, 300 K): δ = 7.52–7.46 (m, 2 H, CHphenyl), 7.37–7.29 (m, 3 H,
CHphenyl), 1.84–1.71 (m, 8 H, CH2), 1.70–1.57 (m, 8 H, CH2), 1.53–1.32
(m, 12 H, CH2) ppm. 13C{1H} NMR (100.62 MHz, CDCl3, 300 K): δ =
Single Crystal Structure Analysis of 1-Cl: Data collection was per-
formed with an Imaging Plate Diffraction System (IPDS-2) from
STOE A numerical absorption correction was performed (Tmin/max:
0.8061/0.8725). All non-hydrogen atoms were refined anisotropic.
The C-H H atoms were positioned with idealized geometry and
were refined isotropic with Uiso(H) = 1.2 Ueq(C) using a riding model.
Selected crystal data and details of the structure refinement can be
found in Table S1 and an ORTEP plot as well as lists with bond
lengths and angles can be found in Figure S27 and Table S2.
1
138.5 (d, JPC = 14.8 Hz, 1 C, Ci,phenyl), 132.6 (d, JPC = 18.7 Hz, 2 C,
CHphenyl), 128.9 (s, 1 C, CHphenyl), 128.4 (d, JPC = 6.9 Hz, 2 C, CHphenyl),
30.7 (dd, JPC = 11.0, 16.3 Hz, 2 C, pr-CH2), 29.9 (t, JPC = 11.6 Hz, 2 C,
pr-CH2), 27.9 (dd, JPC = 1.3, 3.9 Hz, 4 C, (CH2)Pln), 26.0 (dd, JPC = 9.1,
11.3 Hz, 4 C, (CH2)pln), 23.5 (dd, JPC = 14.6, 16.5 Hz, 2 C, pr-CH2)
CCDC 1955603 (for 1-Cl) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre.
ppm. IR (ATR): ν = 3070 (w), 3049 (w), 2925 (s), 2884 (s), 2855 (s),
Lithium Phospholanide (Li-Pln): To a solution of ethyl phosphol-
anate (22.9 g, 155 mmol) in diethyl ether (30 mL) were added a
solution of lithium aluminium hydride in diethyl ether (1 M, 353 mL,
˜
2349 (vw), 2324 (vw), 1867 (vw), 1806 (vw), 1589 (vw), 1570 (vw),
1484 (w), 1463 (sh), 1448 (m), 1433 (m), 1414 (br m), 1378 (w), 1338
(w), 1318 (w), 1301 (w), 1257 (w), 1239 (w), 1207 (vw), 1174 (vw),
1156 (w), 1107 (m), 1099 (sh), 1057 (w), 1053 (w), 1028 (m), 1000
(sh), 980 (w), 971 (w), 942 (br w), 865 (w), 837 (m), 803 (br m), 740
(s), 695 (s), 673 (m), 658 (m), 511 (sh), 486 (m), 469 (w), 447 (vw),
353 mmol) within 2.5 h at 0 °C. The reaction mixture was stirred for
14 h at room temperature followed by a very slow addition of de-
gassed water (13.5 mL), of a 15 % degassed sodium hydroxide solu-
tion (13.5 mL) and again of degassed water (40 mL) at 0 °C. It was
stirred for 1 h at room temperature, the white precipitate was fil-
tered and washed with diethyl ether (80 mL). Most of the diethyl
ether was removed using a distilling link. Afterwards, the product
H-Pln could be obtained via distillation (7 × 10–3 mbar, 0–70 °C).
This extremely volatile liquid compound is difficult to handle and
cannot be stored conveniently. Therefore, H-Pln was distilled di-
430 (vw), 403 (w) cm–1
.
[MoCl3{prPP(Ph)P-pln}] (1-Cl): The ligand prPP(Ph)P-pln (301 mg,
822 μmol) was dissolved in dichloromethane (4 mL). This solution
was added to a suspension of [MoCl3(thf)3] (344 mg, 822 μmol),
THF (4 mL) and dichloromethane (4 mL). After adding further THF
(4 mL) it was stirred for 19 h at room temperature. The suspension
was reduced in vacuo to a quantity of 20 mL, n-hexane (5 mL) was
added, the precipitate was filtered, washed with THF (6 mL), n-hex-
ane (6 mL) and diethyl ether (6 mL) and dried in vacuo. The product
was obtained as yellow solid (192 mg, 338 μmol, 41 %). Anal. calcd.
rectly in a solution of n-butyllithium in n-hexane (2.5
M, 56 mL,
140 mmol) which was cooled to –78 °C to obtain Li-Pln. It was
stirred for 16 h at room temperature. The colorless precipitate was
filtered, washed with 60 mL n-hexane and dried in vacuo. The prod-
uct Li-Pln was obtained as colorless solid (4.05 g, 43.1 mmol, 28 %).
C20H33Cl3MoP3 (568.72): C 42.2, H 5.9; found C 42.1, H 5.8. IR (ATR):
ν = 3056 (w), 2984 (sh), 2936 (w), 2904 (vw), 2895 (vw), 2860 (w),
˜
Note: The product contains a little amount of n-hexane. It wasn't
possible to remove it completely by drying in vacuo.
2326 (br vw), 1982 (br vw), 1883 (br vw), 1810 (br w), 1588 (vw),
1573 (br vw), 1488 (br vw), 1460 (sh), 1447 (m), 1435 (m), 1420 (br
m), 1404 (br m), 1389 (m), 1340 (w), 1316 (sh), 1304 (w), 1256 (br
w), 1234 (sh), 1196 (sh), 1183 (w), 1158 (w), 1149 (w), 1133 (sh),
1117 (br m), 1100 (sh m), 1163 (m), 1147 (w), 1027 (m), 995 (m),
959 (sh), 951 (br m), 924 (w), 915 (br w), 855 (m), 830 (m), 804 (w),
788 (br w), 762 (m), 738 (s), 695 (s), 669 (m), 637 (m), 617 (w), 600
(w), 517 (m), 491 (s), 480 (sh), 450 (br w), 414 (m), 400 (w), 371 (w),
Isolated H-Pln: Anal.: Because of the pyrophoric property no ele-
mental analysis was possible. 31P{1H} NMR (161.98 MHz, [D8]THF,
300 K): δ = –70.9 ppm. 1H-NMR (400.13 MHz, [D8]THF, 300 K): δ =
2.96–2.41 (dm, 1 H, 1JPH = 180.1 Hz, H-Pln), 1.95–1.85 (m, 2 H, CH2),
1.81–1.67 (m, 4 H, CH2), 1.48–1.33 (m, 2 H, CH2) ppm.
Li-Pln: Anal.: Because of the pyrophoric property no elemental anal-
ysis was possible. 31P{1H} NMR (161.98 MHz, [D8]THF, 300 K): δ =
–92.1 (s, 1 P, Li-Pln) ppm. 31P{1H} NMR: (161.98 MHz, CD3OD, 300 K):
313 (s), 296 (s), 275 (s), 263 (sh) cm–1
.
[MoBr3{prPP(Ph)P-pln}] (1-Br): The ligand prPP(Ph)P-pln (401 mg,
1.09 mmol) was dissolved in THF (10 mL). This solution was added
to [MoBr3(thf)3] (603 mg, 1.09 mmol) and further THF (10 mL) was
added. It was stirred for 16 h at room temperature. The suspension
was reduced to a quantity of 5 mL and diethyl ether (20 mL) was
added. The precipitate was filtered, washed with n-hexane (20 mL)
and diethyl ether (2 × 20 mL) and dried in vacuo. The product was
obtained as yellow solid (422 mg, 601 μmol, 55 %). Anal. calcd.
C20H33Br3MoP3 (702.08): C 34.2, H 4.7; found C 34.2, H 4.8. IR (ATR):
1
δ = –72.8 (t, 1 P, D-Pln) ppm. H-NMR (400.13 MHz, [D8]THF, 300 K):
δ = 2.00–1.98 (m, 4 H, CH2 (Li-Pln)), 1.68–1.67 (m, 4 H, CH2 (Li-Pln))
1
ppm. H-NMR (400.13 MHz, CD3OD, 300 K): δ = 1.96–1.86 (m, 2 H,
CH2 (D-Pln)), 1.83–1.69 (m, 4 H, CH2 (D-Pln)), 1.49–1.36 (m, 2 H, CH2
(D-Pln)) ppm. 13C{1H} NMR (100.62 MHz, [D8]THF, 300 K): δ = 33.2
(s, 2 C, CH2 (Li-Pln)), 22.2 (d, JPC = 23.9 Hz), 2 C (CH2 (Li-Pln)) ppm.
13C{1H} NMR (101 MHz, CD3OD, 300 K): δ = 31.2 (d, JPC = 5.5 Hz,
2 C, CH2 (D-Pln)), 20.3 (d, JPC = 8.0 Hz, 2 C, CH2 (D-Pln)) ppm.
7Li-NMR (156 MHz, [D8]THF, 300 K): δ = 1.60 (s, 1 Li) ppm.
ν = 3054 (w), 2932 (br m), 2893 (sh), 2858 (m), 2326 (vw), 1587 (vw),
˜
Bis(3-phospholanopropyl)phenylphosphine [prPP(Ph)P-pln]: To 1572 (vw), 1484 (w), 1456 (sh), 1446 (m), 1434 (m), 1410 (br m), 1392
a solution of bis(3-chloropropyl)phenylphosphine in THF (1.22 m
1.80 mL, 2.20 mmol) THF (15 mL) was added. To a solution of lith-
ium phospholanide (436 mg, 2.20 mmol) in THF (15 mL) a solution
M
,
(sh), 1340 (w), 1316 (sh), 1304 (w), 1255 (br w), 1239 (sh), 1181 (w),
1158 (w), 1134 (w), 1114 (m), 1102 (sh), 1062 (m), 1027 (m), 993 (m),
953 (m), 924 (w), 912 (w), 868 (sh), 852 (m), 830 (m), 806 (w), 787 (w),
763 (m), 743 (sh), 738 (m), 694 (s), 667 (m), 636 (m), 615 (vw), 512
(br m), 489 (br m), 480 (sh), 452 (vw), 415 (m), 373 (w), 355 (vw), 311
(br w), 302 (w), 279 (w), 247 (br s), 222 (br s), 206 (sh) cm–1.
of n-butyllithium in n-hexane (2.5
M, 4.60 mL, 11.5 mmol) was
added. Within 30 min the lithium phospholanide/n-butyllithium so-
lution was added to the bis(3-chlorpropyl)phenylphosphine solu-
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
9
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[MoI3{prPP(Ph)P-pln}] (1-I): The ligand prPP(Ph)P-pln (400 mg,
suspension of [MoBr3{prPP(Ph)P-pln}] (1-Br, 290 mg, 413 μmol) and
1.09 mmol) was dissolved in THF (10 mL). This solution was added PMePh2 (83 mg, 413 μmol) in THF (5 mL). Further THF (15 mL)
to [MoI3(thf)3] (750 mg, 1.08 mmol). After adding further THF was added and the reaction mixture was stirred for 16 h at room
(10 mL) it was stirred for 18 h at room temperature. The suspension
was reduced in vacuo to a quantity of 5 mL, diethyl ether (20 mL)
was added. The precipitate was filtered, washed with n-hexane
(10 mL) and diethyl ether (2 × 20 mL) and dried in vacuo. The
product was obtained as orange-brown solid (680 mg, 807 μmol,
74 %). Anal. calcd. C20H33I3MoP3 (843.08): C 28.5, H 4.0; found C
temperature under nitrogen atmosphere. The solution was sepa-
rated with a syringe from amalgam. After reducing the solvent in
vacuo, the residue was dissolved in diethyl ether (10 mL) and the
solution was filtered through neutral aluminum oxide. The solvent
was reduced in vacuo to a quantity of 5 mL and methanol (5 mL)
was added. The solvent was reduced in vacuo to a quantity of 5 mL
again and further methanol (5 mL) was added to precipitate the
29.2, H 4.2. IR (ATR): ν = 3076 (vw), 3052 (vw), 3012 (vw), 2936 (m),
˜
2898 (sh), 2847 (vw), 2352 (vw), 2325 (vw), 2291 (vw), 1984 (vw), product. The precipitate was filtered, washed with methanol
1931 (w), 1848 (br w), 1612 (br w), 1586 (w), 1571 (w), 1485 (w),
1446 (m), 1433 (m), 1409 (br m), 1400 (sh), 1341 (vw), 1320 (sh),
1302 (w), 1255 (br w), 1234 (sh), 1179 (w), 1159 (vw), 1129 (sh),
(10 mL) and dried in vacuo to obtain the product as an orange
solid (110 mg, 153 μmol, 37 %). Anal. calcd. C33H46MoN4 (718.6): C
55.2, H 6.5, N 7.8 found C 55.0, H 6.8, N 2.0. The nitrogen value is
1112 (m), 1100 (sh), 1061 (m), 1027 (m), 992 (m), 987 (m), 953 (m), too low because of the thermal instability of the product. 31P{1H}
2
923 (w), 912 (sh), 851 (m), 829 (w), 808 (vw), 788 (w), 760 (w), 739
(m), 693 (s), 669 (sh), 631 (m), 617 (w), 608 (w), 560 (vw), 551 (vw),
510 (sh), 486 (s), 466 (sh), 444 (vw), 413 (m), 405 (sh), 373 (vw), 349 18.0 Hz, 1 P, Pb), 18.0 (dt, JPbPc = 100.8 Hz, JPa/a′Pc = 29.0 Hz, 1 P,
NMR (161.98 MHz, [D8]THF, 300 K): δ = 25.0 (dd, JPa/a′Pc = 29.0 Hz,
2
2
2JPa/a′Pb = 18.0 Hz, 2 P, Pa/a′), 22.8 (dt, JPbPc = 100.8 Hz, JPa/a′Pb
=
2
2
(vw), 334 (vw), 307 (vw), 290 (vw), 275 (vw), 256 (vw), 233 (sh), 212
Pc) ppm. 1H-NMR (400.13 MHz, [D8]THF, 300 K): δ = 7.81–7.77 (m,
CHphenyl (PhPR2)), 7.58–7.54 (m, CHphenyl (PMePh2)), 7.45–7.41 (m,
CHphenyl), 7.40–7.32 (m, CHphenyl), 7.29–7.25 (m, CHphenyl (PMePh2)),
7.21–7.16 (m, CHphenyl), 2.11–1.15 [5xm, CH2 (phospholane and
(br s), 201 (br s), 183 (m), 171 (sh), 162 (sh), 145 (m) cm–1
.
[Mo(N2){prPP(Ph)P-pln}(dppm)] (fac1-2, mer1-2, fac2-2): To so-
dium amalgam (201 mg, 8.70 mmol Na, 2 mL of Hg) and THF
(10 mL) was added a suspension of [MoI3{prPP(Ph)P-pln}] (1-I,
330 mg, 390 μmol) and dppm (150 mg, 390 μmol) in THF (10 mL)
and further THF (10 mL) was added. The reaction mixture was
stirred for 23 h at room temperature under nitrogen atmosphere.
The solution was decanted from amalgam, filtered and the solvent
was evaporated by passing a steady stream of nitrogen over the
solution at room temperature. The sticky oil was dissolved in diethyl
ether (20 mL) and the solution was filtered through neutral alumi-
num oxide. The solvent was removed via a stream of nitrogen. The
product was obtained as red oil. [MoBr3{prPP(Ph)P-pln}] (1-Br) can
also be used as precursor. Anal.: For [Mo(N2){prPP(Ph)P-pln}(dppm)]
an elemental analysis could not be obtained because of the oily
character of the material, the large amount of the coligand dppm,
the presence of solvent (diethyl ether) and a side product. 31P{1H}
NMR (161.98 MHz, C6D6, 300 K): fac1-[Mo(N2){prPP(Ph)P-pln}-
2
propyl chains)], 2.06 (d, JHP = 4.2 Hz, CH3 (PMePh2)) ppm. 13C{1H}
NMR (100.62 MHz, [D8]THF, 300 K): δ = 146.7 (dt, JCP = 1.9, 21.3 Hz,
2 C, Cipso (PMePh2)), 139.1 (d, JCP = 18.3 Hz, 1 C, Cipso (PhPR2)), 132.8
(s, CHphenyl (PhPR2)), 131.9 (d, JCP = 11.0 Hz, CHphenyl (PMePh2)), 129.1
(d, JCP = 1.56 Hz, CHphenyl), 128.9–128.8 (m, CHphenyl), 128.5 (s,
CHphenyl), 128.5 (s, CHphenyl), 128.4 (s, CHphenyl), 128.3 (d, JCP = 1.2 Hz,
CHphenyl), 31.4–31.2 (m, CH2), 31.0 (m, CH2), 30.3–30.1 (m, CH2), 27.4
(s, CH2), 27.1 (s, CH2), 26.0 (t, JCP = 7.4 Hz, CH2), 20.7 (d, JCP = 3.0 Hz,
CH2), 15.8 (d, JCP = 17.8 Hz, CH3 (PMePh2)) ppm. IR (ATR): ν = 3073
˜
(w), 3051 (w), 3019 (vw), 2998 (vw), 2961 (sh), 2918 (br m), 2903
(sh), 2853 (m), 2005 (w, sym-NN), 1924 (s, asym-NN), 1810 (sh), 1761
(vw), 1584 (w), 1570 (w), 1479 (w), 1463 (sh), 1447 (w), 1430 (m),
1418 (br m), 1377 (sh), 1326 (br sh), 1304 (w), 1278 (sh), 1260 (br
m), 1175 (w), 1155 (w), 1144 (w), 1104 (m), 1089 (m), 1069 (w), 1055
(w), 1027 (m), 1017 (sh), 987 (w), 977 (sh), 949 (w), 922 (sh), 911 (w),
876 (br m), 863 (br m), 845 (m), 821 (sh), 803 (sh), 789 (m), 739 (m),
694 (s), 675 (s), 660 (m), 615 (br m), 550 (m), 503 (s), 492 (sh), 472
2
(dppm)]: δ = 31.9 (dddd, JPP = 95.7, 29.3, 22.8, 16.3 Hz, 1 P, Pa),
2
27.2 (dddd, JPP = 27.7, 22.8, 20.4, 17.4 Hz, 1 P, Pb), 19.5 (pseudo-
(s), 447 (m), 424 (sh) cm–1. Raman: ν = 3056 (m), 2977 (sh), 2963
“dtd”, 2JPP = 91.3, 27.8, 27.7, 16.3 Hz, 1P, Pd), 12.7 (dddd, 2JPP = 95.7,
˜
(sh), 2942 (sh), 2934 (sh), 2926 (sh), 2915 (m), 2901 (m), 2885 (sh),
2877 (sh), 2852 (sh), 2000 (s), 1930 (vw), 1587 (m), 1572 (w), 1451
(w), 1418 (br w), 1308 (br vw), 1257 (br vw), 1196 (sh), 1187 (w),
1159 (w), 1104 (br w), 1030 (m), 1000 (s), 964 (br vw), 917 (m), 870
(br w), 751 (br vw), 702 (vw), 683 (m), 670 (w), 645 (vw), 637 (vw),
2
27.8, 17.4, 15.2 Hz, 1 P, Pg), 10.3 (dddd, JPP = 91.3, 29.3, 20.4,
15.2 Hz, 1 P, Ph) ppm. mer1-[Mo(N2){prPP(Ph)P-pln}(dppm)]: δ = 22.0
2
2
(dddd, JPP = 38.8, 17.6, 14.8, 1.1 Hz, 2 P, Pc/Pc′), 17.9 (dddd, JPP
=
94.5, 38.8, 38.8, 22.9 Hz, 1 P, Pe), 13.3 (dtd, 2JPP = 22.9, 14.8, 11.9 Hz,
1 P, Pf), 4.5 (dtd, JPP = 94.5, 17.6, 11.9 Hz, 1 P, Pi) ppm. fac2-
2
619 (w), 494 (br w), 432 (vw), 415 (w) cm–1
.
[Mo(N2){prPP(Ph)P-pln}(dppm)]: δ = 35.5 (AA′, 2 P, Ppln), 19.6 (M, 1 P,
P(Ph), this signal is covered by a signal of fac1-[Mo(N2){prPP(Ph)P-
pln}(dppm)]), 10.3 (XX′, 2 P, PPh2, this signal is covered by a signal
of fac1-[Mo(N2){prPP(Ph)P-pln}(dppm)]) ppm. Side product (*): δ =
15.5 (s) ppm. Uncoordinated dppm: δ = –23.0 (s, 2 P, PPh2) ppm. IR
[Mo(NNH2)(OTf){prPP(Ph)P-pln}(PMePh2)]OTf (4): The complex
[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3, 20.0 mg, 27.8 μmol) was dis-
solved in 0.45 mL [D8]Et2O and 2.5 equivalents TfOH (6.1 μL,
69.5 μmol) were added. A grey solid precipitated wherefore the
solvent was removed in vacuo and the residue was dissolved in
CD2Cl2. The solution became red and 2.5 equiv. of. TfOH (6.1 μL,
69.5 μmol) were added. The solution was transferred in a young
tube and characterized via NMR spectroscopy immediately. 31P{1H}
(ATR): ν = 3138 (w), 3065 (sh), 3049 (br m), 3027 (sh), 3013 (w), 2997
˜
(w), 2957 (sh), 2924 (br s), 2902 (sh), 2853 (s), 2800 (w), 1997 (m,
NN), 1986 (w, NN), 1955 (sh, NN), 1929 (br s, NN), 1881 (br sh), 1841
(w), 1818 (vw), 1806 (vw), 1775 (w), 1660 (br w), 1618 (vw), 1582
(m), 1570 (m), 1547 (w), 1510 (vw), 1479 (m), 1449 (m), 1431 (vs),
1417 (sh), 1378 (br m), 1350 (w), 1324 (br w), 1303 (m), 1270 (sh),
1260 (m), 1233 (br sh), 1202 (w), 1180 (m), 1152 (m), 1105 (s), 1086
(br s), 1070 (s), 1048 (sh), 1024 (s), 999 (m), 986 (w), 871 (sh), 947
(br m), 911 (br m), 861 (m), 845 (br m), 823 (w), 806 (w), 789 (m),
740 (s), 690 (vs), 659 (sh), 614 (s), 552 (vw), 523 (s), 499 (vs), 475
2
NMR (161.98 MHz, CD2Cl2, 300 K): δ = 15.0 (dd, JPa/a′Pb = 21.3 Hz,
2
2
2JPa/a′Pc = 30.0 Hz, Pa/a′), 10.9 (dt, JPbPa/a′ = 21.3 Hz, JPbPc
=
2
2
1
135.6 Hz), 4.0 (dt, JPcPa/a′ = 30.0 Hz, JPcPb = 135.6 Hz, Pc) ppm. H-
NMR (400.13 MHz, CD2Cl2, 300 K): δ = 8.9 (br s, N-H), 7.85–7.29
(6xm, CHphenyl), 2.55 (d, J = 14.7 Hz), 2.21–1.43 (4xm) ppm. IR (ATR):
ν = 3246 (w, N-H), 3103 (w, N-H), 3065 (w), 2999 (vw), 2951 (sh),
˜
(vs), 419 (s), 393 (s) cm–1
.
2942 (sh), 2926 (w), 2869 (w), 1589 (vw), 1485 (vw), 1454 (sh), 1440
(w), 1417 (w), 1327 (sh), 1304 (sh), 1282 (m), 1252 (sh), 1231 (s),
1200 (s), 1155 (s), 1114 (m), 1073 (vw), 1027 (s), 1013 (s), 979 (sh),
[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] (3): To sodium amalgam
(220 mg, 9.61 mmol Na, 2 mL of Hg) and THF (5 mL) was added a
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
10
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
F. Tuczek, Eur. J. Inorg. Chem. 2018, 1337; d) H. Broda, F. Tuczek, Angew.
Chem. Int. Ed. 2014, 53, 632; Angew. Chem. 2014, 126, 644; e) M. D.
Fryzuk, Chem. Commun. 2013, 49, 4866; f) M. D. Fryzuk, Science 2013,
340, 1530; g) Y. Tanabe, Y. Nishibayashi, Coord. Chem. Rev. 2013, 257,
2551; h) H. Broda, S. Hinrichsen, F. Tuczek, Coord. Chem. Rev. 2013, 257,
587.
a) F. Mus, A. B. Alleman, N. Pence, L. C. Seefeldt, J. W. Peters, Metallomics
2018, 10, 523; b) N. S. Sickerman, K. Tanifuji, Y. Hu, M. W. Ribbe, Chem.
Eur. J. 2017, 23, 12425; c) R. D. Milton, S. Abdellaoui, N. Khadka, D. R.
Dean, D. Leech, L. C. Seefeldt, S. D. Minteer, Energy Environ. Sci. 2016, 9,
2550; d) B. M. Hoffman, D. Lukoyanov, Z.-Y. Yang, D. R. Dean, L. C. See-
feldt, Chem. Rev. 2014, 114, 4041; e) M. W. Ribbe, Y. Hu, K. O. Hodgson,
B. Hedman, Chem. Rev. 2014, 114, 4063.
a) K. M. Lancaster, M. Roemelt, P. Ettenhuber, Y. Hu, M. W. Ribbe, F. Neese,
U. Bergmann, S. DeBeer, Science 2011, 334, 974; b) T. Spatzal, M. Aksoyo-
glu, L. Zhang, S. L. A. Andrade, E. Schleicher, S. Weber, D. C. Rees, O.
Einsle, Science 2011, 334, 940.
L. R. Doyle, A. J. Wooles, L. C. Jenkins, F. Tuna, E. J. L. McInnes, S. T. Liddle,
Angew. Chem. Int. Ed. 2018, 57, 6314; Angew. Chem. 2018, 130, 6422.
J. S. Anderson, J. Rittle, J. C. Peters, Nature 2013, 501, 84.
K. Arashiba, Y. Miyake, Y. Nishibayashi, Nat. Chem. 2011, 3, 120.
C. J. Pickett, K. S. Ryder, J. Talarmin, J. Chem. Soc., Dalton Trans. 1986,
1453.
959 (sh), 938 (m), 923 (m), 889 (w), 863 (w), 850 (w), 834 (vw), 814
(w), 790 (w), 744 (m), 718 (vw), 690 (m), 629 (s), 585 (sh), 573 (m),
515 (s), 490 (m), 467 (w) cm–1
.
[Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2] (5): To sodium amalgam
(200 mg, 8.70 mmol Na, 2 mL of Hg) and THF (5 mL) was added
[MoBr3{prPP(Ph)P-pln}] (1-Br, 300 mg, 427 μmol) and further THF
(25 mL). After adding the coligand PMe2Ph (119 mg, 861 μmol), it
was stirred for 16 h at room temperature under nitrogen atmos-
phere. The solution was separated by filtration from amalgam. After
reducing the solvent in vacuo to a quantity of 10 mL, the solution
was filtered through neutral aluminum oxide. The solvent was re-
duced in vacuo to a quantity of 5 mL and methanol (10 mL) was
added. The precipitate was filtered, washed with methanol (10 mL)
and dried in vacuo to obtain the product as a red solid (120 mg,
157 μmol, 37 %). Anal. calcd. C36H55MoN2P5 (766.68): N 3.7 C 56.4,
H 7.2; found N 1.5, C 54.8, H 7.6. The C and N values are presumably
too low due to decoordination of the N2 ligand and the coligand
PMe2Ph. 31P{1H} NMR (161.98 MHz, [D8]THF, 300 K): δ = 25.0 (ddd,
[3]
[4]
[5]
[6]
[7]
[8]
2
2JPP = 30.1, 19.3, 18.4 Hz, 2 P, Pa/a′), 15.3 (dtd, JPP = 85.9, 30.1,
2
13.6 Hz, 1 P, Pb), 9.4 (dtd, JPP = 19.3, 18.4, 13.6 Hz, 1 P, Pc), 3.7
2
(“dq”= dtd, JPP = 85.9, 19.3, 19.3 Hz, 1 P, Pd) ppm. 1H-NMR
[9]
[10]
[11]
D. V. Yandulov, R. R. Schrock, Science 2003, 301, 76.
(400.13 MHz, [D8]THF, 300 K): δ = 7.65–7.63 (m, 2 H, CHortho (PhPR2)),
7.59–7.55 (m, 4 H, CHortho (PMe2Ph)), 7.36–7.34 (m, 2 H, CHmeta
(PhPR2)), 7.30–7.23 (m, 4 H, CHmeta (PMe2Ph)), 7.22–7.12 (m, 3 H,
CHpara (PhPR2, PMe2Ph)), 2.41–2.33 (m, 2 H, CH2), 1.89–1.77 (m, 8 H,
CH2), 1.68–1.57 (m, 2xd, 14 H, 4 × CH2, 2 × CH3), 1.55–1.34 (m, 14 H,
CH2),1.13–1.06 (m, 2 H, CH2) ppm. 13C{1H} NMR (100.62 MHz,
[D8]THF, 300 K): δ = 153.7 (dt, JCP = 2.5, 13.8 Hz, 1 C, Cipso (PMe2Ph)),
J. Chatt, A. J. Pearman, R. L. Richards, Nature 1975, 253, 39.
a) M. Hidai, K. Tominari, Y. Uchida, J. Am. Chem. Soc. 1972, 94, 110; b) M.
Hidai, K. Tominari, Y. Uchida, A. Misono, J. Chem. Soc., D 1969, 1392.
a) L. A. Wickramasinghe, T. Ogawa, R. R. Schrock, P. Müller, J. Am. Chem.
Soc. 2017, 139, 9132; b) M. R. Reithofer, R. R. Schrock, P. Müller, J. Am.
Chem. Soc. 2010, 132, 8349; c) R. R. Schrock, Angew. Chem. Int. Ed. 2008,
47, 5512; Angew. Chem. 2008, 120, 5594; d) R. R. Schrock, Acc. Chem. Res.
2005, 38, 955.
[12]
151.8 (dd, JCP = 5.4, 17.0 Hz, 1 C, Cipso (PMe2Ph)), 138.6 (dd, JCP
3.7, 19.1 Hz, 1 C, Cipso (PhPR2)), 132.4 (d, JPC = 9.3 Hz, 2 C, Cortho
(PhPR2)), 131.1 (d, JCP = 8.9 Hz, 2 C, Cortho (PMe2Ph)), 130.2 (d, JCP
8.5 Hz, 2 C, Cortho (PMe2Ph)), 128.5 (d, JCP = 6.0 Hz, 2 C, Cmeta
(PMe2Ph)), 128.2 (d, JCP = 6.1 Hz, 2 C, Cmeta (PMe2Ph)), 127.7 (d, JCP
=
[13]
[14]
[15]
[16]
[17]
[18]
S. Kuriyama, K. Arashiba, K. Nakajima, H. Tanaka, N. Kamaru, K. Yoshizawa,
Y. Nishibayashi, J. Am. Chem. Soc. 2014, 136, 9719.
=
K. Arashiba, E. Kinoshita, S. Kuriyama, A. Eizawa, K. Nakajima, H. Tanaka,
K. Yoshizawa, Y. Nishibayashi, J. Am. Chem. Soc. 2015, 137, 5666.
A. Eizawa, K. Arashiba, H. Tanaka, S. Kuriyama, Y. Matsuo, K. Nakajima,
K. Yoshizawa, Y. Nishibayashi, Nat. Commun. 2017, 8, 14874.
K. Arashiba, A. Eizawa, H. Tanaka, K. Nakajima, K. Yoshizawa, Y. Nishibaya-
shi, Bull. Chem. Soc. Jpn. 2017, 90, 1111.
Y. Ashida, K. Arashiba, K. Nakajima, Y. Nishibayashi, Nature 2019, 568,
536.
Y. Ashida, K. Arashiba, H. Tanaka, A. Egi, K. Nakajima, K. Yoshizawa, Y.
Nishibayashi, Inorg. Chem. 2019, 58, 8927.
S. E. Creutz, J. C. Peters, J. Am. Chem. Soc. 2014, 136, 1105.
N. X. Gu, G. Ung, J. C. Peters, Chem. Commun. 2019, 55, 5363.
J. Higuchi, S. Kuriyama, A. Eizawa, K. Arashiba, K. Nakajima, Y. Nishibaya-
shi, Dalton Trans. 2018, 47, 1117.
Y. Sekiguchi, K. Arashiba, H. Tanaka, A. Eizawa, K. Nakajima, K. Yoshizawa,
Y. Nishibayashi, Angew. Chem. Int. Ed. 2018, 57, 9064; Angew. Chem.
2018, 130, 9202.
a) M. J. Chalkley, T. J. Del Castillo, B. D. Matson, J. C. Peters, J. Am. Chem.
Soc. 2018, 140, 6122; b) J. Fajardo, J. C. Peters, J. Am. Chem. Soc. 2017,
139, 16105; c) M. J. Chalkley, T. J. Del Castillo, B. D. Matson, J. P. Roddy,
J. C. Peters, ACS Cent. Sci. 2017, 3, 217; d) T. J. Del Castillo, N. B. Thomp-
son, J. C. Peters, J. Am. Chem. Soc. 2016, 138, 5341.
=
7.3 Hz, 2 C, Cmeta (PhPR2)), 127.6 (dd, JCP = 1.3 Hz, 1 C, Cpara (PhPR2)),
127.4 (br s, 1 C, Cpara (PMe2Ph)), 127.3 (br s, 1 C, Cpara (PMe2Ph)),
37.3 (m, 2 C, CH2), 34.2–34.0 (m, 2 C, CH2), 32.2 (d, JCP = 16.8 Hz,
2 C, CH2), 28.2–28.0 (dm, 2 C, CH3), 27.5 (s, 2 C, CH2), 27.2 (s, 2 C,
CH2), 23.3–23.1 (m, 2 C, CH2), 21.7 (d, 2 C, JCP = 2.5 Hz), 21.6 (br s,
1 C, CH3 (PMe2Ph)), 21.4 (br s, 1 C, CH3 (PMe2Ph)) ppm. IR (ATR): ν =
˜
3086 (vw), 3072 (vw), 3047 (w), 3017 (vw), 2995 (vw), 2959 (m), 2934
(sh), 2911 (m), 2889 (sh), 2853 (br m), 2804 (sh), 2008 (br w), 1944
(sh, NN), 1931 (s, NN), 1755 (vw), 1584 (w), 1569 (vw), 1487 (w),
1464 (vw), 1449 (w), 1430 (w), 1421 (sh), 1408 (w), 1375 (vw), 1319
(vw), 1306 (vw), 1287 (w), 1260 (m), 1181 (vw), 1156 (vw), 1145 (w),
1095 (br m), 1072 (sh), 1056 (m), 1019 (br m), 989 (sh), 972 (sh), 945
(sh), 929 (m), 923 (m), 889 (m), 863 (br w), 844 (br w), 817 (sh), 799
(br m), 773 (sh), 746 (sh), 739 (m), 704 (sh), 695 (br m), 657 (br m),
614 (m), 551 (vw), 519 (sh), 506 (m), 490 (m), 474 (m) cm–1. Raman:
[19]
[20]
[21]
[22]
[23]
ν = 3051 (m), 2970 (br sh), 2940 (m), 2908 (s), 2861 (sh), 2000 (vw),
˜
1944 (m), 1933 (m), 1812 (vw), 1585 (m), 1568 (w), 1488 (vw), 1450
(w), 1423 (w), 1413 (w), 1400 (w), 1269 (w), 1251 (w), 1186 (w), 1156
(w), 1100 (br m), 1028 (m), 1001 (s), 931 (w), 920 (w), 895 (vw), 874
(vw), 747 (vw), 738 (vw), 706 (vw), 691 (w), 661 (m), 618 (m), 521
[24]
[25]
J. Krahmer, H. Broda, C. Näther, G. Peters, W. Thimm, F. Tuczek, Eur. J.
Inorg. Chem. 2011, 4377.
L. Söncksen, C. Gradert, J. Krahmer, C. Näther, F. Tuczek, Inorg. Chem.
2013, 52, 6576.
(vw), 498 (m), 488 (m), 442 (m) cm–1
.
[26]
[27]
H. Broda, J. Krahmer, F. Tuczek, Eur. J. Inorg. Chem. 2014, 3564.
S. Hinrichsen, A. Kindjajev, S. Adomeit, J. Krahmer, C. Näther, F. Tuczek,
Inorg. Chem. 2016, 55, 8712.
H. Broda, S. Hinrichsen, J. Krahmer, C. Näther, F. Tuczek, Dalton Trans.
2014, 43, 2007.
S. Hinrichsen, A.-C. Schnoor, K. Grund, B. Flöser, A. Schlimm, C. Näther, J.
Krahmer, F. Tuczek, Dalton Trans. 2016, 45, 14801.
S. L. Foster, S. I. P. Bakovic, R. D. Duda, S. Maheshwari, R. D. Milton, S. D.
Minteer, M. J. Janik, J. N. Renner, L. F. Greenlee, Nat. Catal. 2018, 1, 490.
Keywords: Nitrogen fixation · Phospholanes ·
Molybdenum · Synthesis design
[28]
[29]
[30]
[1] A. D. Allen, C. V. Senoff, Chem. Commun. 1965, 621.
[2] a) Y. Nishibayashi, Transition metal-dinitrogen complexes. Preparation and
reactivity, 1. Aufl., Wiley-VCH, Weinheim, Germany, 2019; b) Y. Nishibaya-
shi, Dalton Trans. 2018, 47, 11290; c) N. Stucke, B. M. Flöser, T. Weyrich,
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
11
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[31] M. T. Mock, A. W. Pierpont, J. D. Egbert, M. O′Hagan, S. Chen, R. M.
Bullock, W. G. Dougherty, W. S. Kassel, R. Rousseau, Inorg. Chem. 2015,
54, 4827.
[49] M. Streitberger, A. Schmied, E. Hey-Hawkins, Inorg. Chem. 2014, 53, 6794.
[50] M. Streitberger, A. Schmied, R. Hoy, E. Hey-Hawkins, Dalton Trans. 2016,
45, 11644.
[32] a) J. A. Bilbrey, A. H. Kazez, J. Locklin, W. D. Allen, J. Comput. Chem. 2013,
34, 1189; b) R. A. Baber, M. F. Haddow, A. J. Middleton, A. G. Orpen, P. G.
Pringle, A. Haynes, G. L. Williams, R. Papp, Organometallics 2007, 26, 713;
c) T. E. Müller, D. M. P. Mingos, Trans. Met. Chem. 1995, 20, 533.
[33] C. A. Tolman, Chem. Rev. 1977, 77, 313.
[51] P. Boar, M. Streitberger, P. Lönnecke, E. Hey-Hawkins, Inorg. Chem. 2017,
56, 7285.
[52] V. A. D′yakonov, A. L. Makhamatkhanova, R. A. Agliullina, L. K. Dilmukha-
metova, T. V. Tyumkina, U. M. Dzhemilev, Beilstein J. Org. Chem. 2016, 12,
406.
[34] M. J. Burk, Acc. Chem. Res. 2000, 33, 363.
[53] R. P. Polniaszek, A. L. Foster, J. Org. Chem. 1991, 56, 3137.
[54] R. A. Aitken, W. Masamba, N. J. Wilson, Tetrahedron Lett. 1997, 38, 8417.
[55] H. J. Reich, R. R. Dykstra, Organometallics 1994, 13, 4578.
[56] W. Kuchen, H. Buchwald, Chem. Ber. 1958, 91, 2296.
[57] U. Nagel, A. Bublewitz, Chem. Ber. 1992, 125, 1061.
[58] L. M. Green, D. W. Meek, Polyhedron 1990, 9, 35.
[59] B. Pietsch, L. Dahlenburg, Inorg. Chim. Acta 1988, 145, 195.
[60] Q. Liao, N. Saffon-Merceron, N. Mézailles, ACS Catal. 2015, 5, 6902.
[61] Q. Liao, N. Saffon-Merceron, N. Mézailles, Angew. Chem. Int. Ed. 2014, 53,
14206; Angew. Chem. 2014, 126, 14430.
[35] a) T. V. RajanBabu, Y.-Y. Yan, S. Shin, J. Am. Chem. Soc. 2001, 123, 10207;
b) J. Holz, M. Quirmbach, U. Schmidt, D. Heller, R. Stürmer, A. Börner, J.
Org. Chem. 1998, 63, 8031.
[36] a) M. J. Burk, J. E. Feaster, W. A. Nugent, R. L. Harlow, J. Am. Chem. Soc.
1993, 115, 10125; b) M. J. Burk, J. Am. Chem. Soc. 1991, 113, 8518; c)
M. J. Burk, J. E. Feaster, R. L. Harlow, Organometallics 1990, 9, 2653.
[37] M. J. Burk, J. E. Feaster, R. L. Harlow, Tetrahedron: Asymmetry 1991, 2,
569.
[38] a) T. Clark, C. Landis, Tetrahedron: Asymmetry 2004, 15, 2123; b) J. Al-
brecht, U. Nagel, Angew. Chem. Int. Ed. 1996, 35, 407; Angew. Chem.
1996, 108, 444.
[62] M. W. Anker, J. Chatt, G. J. Leigh, A. G. Wedd, J. Chem. Soc., Dalton Trans.
1975, 2639.
[63] N. A. Buang, D. L. Hughes, N. Kashef, R. L. Richards, J. Organomet. Chem.
1987, 323, C47.
[39] M. J. Burk, R. L. Harlow, Angew. Chem. Int. Ed. 1990, 29, 1462; Angew.
Chem. 1990, 102, 1511.
[64] a) M. Tamizmani, C. Sivasankar, Eur. J. Inorg. Chem. 2017, 4239; b) B. M.
Flöser, F. Tuczek, Coord. Chem. Rev. 2017, 345, 263; c) K. H. Horn, N. Böres,
N. Lehnert, K. Mersmann, C. Näther, G. Peters, F. Tuczek, Inorg. Chem.
2005, 44, 3016; d) K. H. Horn, N. Lehnert, F. Tuczek, Inorg. Chem. 2003,
42, 1076; e) N. Lehnert, F. Tuczek, Inorg. Chem. 1999, 38, 1671; f) C. J.
Pickett, J. Biol. Inorg. Chem. 1996, 1, 601; g) C. J. Pickett, J. Talarmin,
Nature 1985, 317, 652.
[65] a) H. C. Wolf, Z. Naturforsch. A 1956, 797; b) A. S. Davydov, J. Exp. Theor.
Phys. 1948, 210.
[66] a) T. A. George, L. Ma, S. N. Shailh, R. C. Tisdale, J. Zubieta, Inorg. Chem.
1990, 29, 4789; b) J. Chatt, A. J. Pearman, R. L. Richards, J. Chem. Soc.,
Dalton Trans. 1978, 1766.
[40] J. Lloret Fillol, A. Kruckenberg, P. Scherl, H. Wadepohl, L. H. Gade, Chem.
Eur. J. 2011, 17, 14047.
[41] L.-I. Rodríguez, T. Roth, J. Lloret Fillol, H. Wadepohl, L. H. Gade, Chem.
Eur. J. 2012, 18, 3721.
[42] S. K. Gibbons, Z. Xu, R. P. Hughes, D. S. Glueck, A. L. Rheingold, Organo-
metallics 2018, 37, 2159.
[43] a) R. Sablong, C. Newton, P. Dierkes, J. A. Osborn, Tetrahedron Lett. 1996,
37, 4933; b) T. Morimoto, N. Ando, K. Achiwa, Synlett 1996, 1211.
[44] N. Grüger, L.-I. Rodríguez, H. Wadepohl, L. H. Gade, Inorg. Chem. 2013,
52, 2050.
[45] M. Garbe, K. Junge, S. Walker, Z. Wei, H. Jiao, A. Spannenberg, S. Bach-
mann, M. Scalone, M. Beller, Angew. Chem. Int. Ed. 2017, 56, 11237;
Angew. Chem. 2017, 129, 11389.
[46] Y.-Y. Yan, T. V. RajanBabu, Org. Lett. 2000, 2, 199.
[47] L. Zhang, Y. Tang, Z. Han, K. Ding, Angew. Chem. Int. Ed. 2019, 58, 4973;
Angew. Chem. 2019, 131, 5027.
[67] F. Stoffelbach, D. Saurenz, R. Poli, Eur. J. Inorg. Chem. 2001, 2699.
[68] B. E. Owens, R. Poli, A. L. Rheingold, Inorg. Chem. 1989, 28, 1456.
[69] a) F. A. Cotton, R. Poli, Inorg. Chem. 1987, 26, 1514; b) W. Strohmeier,
Chem. Ber. 1961, 94, 3337.
[48] a) L. D. Field, I. P. Thomas, T. W. Hambley, P. Turner, Inorg. Chem. 1998,
37, 612; b) L. D. Field, I. P. Thomas, Inorg. Chem. 1996, 34, 2546.
Received: October 2, 2019
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
12
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Phospholanes
M. Pfeil, T. A. Engesser, A. Koch,
J. Junge, J. Krahmer, C. Näther,
F. Tuczek* .......................................... 1–13
Oligodentate Phosphine Ligands
with Phospholane End Groups: New
Synthetic Access and Application to
Molybdenum-Based Synthetic Nitro-
gen Fixation
The tridentate phosphine ligand and either mono- or bidentate coli-
prPP(Ph)P-pln with phospholane end gands led to molybdenum(0) mono-
groups is synthesized and used for the and bis(dinitrogen) complexes and
synthesis of MoX3 (X = Cl, Br, I) precur- subsequent protonation to a hydraz-
sors. Reduction in the presence of N2 ido complex.
DOI: 10.1002/ejic.201901068
Eur. J. Inorg. Chem. 2019, 1–13
www.eurjic.org
13
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim