Preparation, properties and reactions of metal-containing heterocycles: Part C: Tetraazatetraphosphadimolybdacyclophanes: Synthesis, isolation, characterization, and X-ray crystal structures

Article abstract of DOI:10.1016/S0022-328X(99)00587-2

The ditopic aminodiphosphines CH₂(4,4′-Ph₂PNHC₆H₄) ₂ (2) and CH₂(4,4′-Ph₂PCH₂NHC₆H ₄)₂ (5) are obtained by reaction of 4,4′-diaminodip

Full text of DOI:10.1016/S0022-328X(99)00587-2

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Journal of Organometallic Chemistry 595 (2000) 166–177
Preparation, properties and reactions of metal-containing
heterocycles
Part C: tetraazatetraphosphadimolybdacyclophanes: synthesis,
isolation, characterization, and X-ray crystal structuresꢀ
Ekkehard Lindner a,*, Markus Mohr a, Christiane Nachtigal a, Riad Fawzi a,
Gerald Henkel b
a Institut fu¨r Anorganische Chemie der Uni6ersita¨t Tu¨bingen, Auf der Morgenstelle 18, D-72076 Tu¨bingen, Germany
b Institut fu¨r Synthesechemie der Uni6ersita¨t (GH) Duisburg, Lotharstraße 1, D-47057 Duisburg, Germany
Received 14 July 1999; received in revised form 20 August 1999; accepted 9 September 1999
Dedicated to Professor Alfred Schmidpeter on the occasion of his 70th birthday.
Abstract
The ditopic aminodiphosphines CH2(4,4%-Ph2PNHC6H4)2 (2) and CH2(4,4%-Ph2PCH2NHC6H4)2 (5) are obtained by reaction of
4,4%-diaminodiphenylmethane with ClPPh2 and (i) (CH2O)n/NaOMe/(ii) HPPh2, respectively. Treatment of (h4-nbd)Mo(CO)4 with
2
and 5 under high-dilution conditions in CH2Cl2 affords the tetraazatetraphosphadimolybdaclophanes [CH2(4,4%-
(OC)4Mo(Ph2PNHC6H4)2)]2 (3) and [CH2(4,4%-(OC)4Mo(Ph2PCH2NHC6H4)2)]2 (6) in relatively high yields. The structures of 3
and 6 were investigated by X-ray crystal-structure analyses. Whereas the cavity of the molecular structure of 3 can be described
by a parallelogram, that of 6 has the shape of a boat in which the diphenylmethane building blocks form the hull and the
cis-(Ph2P)2Mo(CO)4 fragments represent the bow and stem, respectively. Because of the formation of only very weak hydrogen
bonds in 3 and 6, no binding to molecules like p-benzoquinone, 1,4-cyclohexanedione, 2,5-piperazinedione and trans-1,4-di-
aminocyclohexane could be detected. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Dimolybdacyclophanes; Molybdenum complexes; Aminophosphines; Macrocyclization; High dilution
redox activity [8], Lewis acidity [9], luminescence [10]
and paramagnetism [11]. These features may exert a
remarkable impact on the chemical and physical behav-
ior of such cyclophanes [12]. Furthermore the insertion
of complex moieties influences the structure of metalla-
cyclophanes because of their steric requirements and
they can serve as reactive centers for the binding of
molecules or as sensors for an included guest [13]. The
bis(triflate) method — a variant of cationic alkylation
— is an excellent method for the concomitant forma-
tion of several metal–carbon s bonds. It proved to be
suitable for the synthesis of several ferra- and osmacy-
clophanes [14]. However, this method cannot be suc-
cessfully applied if heteroatoms (S, N, O) are present in
the hydrocarbon framework [15].
1. Introduction
Cyclophanes play an important role in the develop-
ment of supramolecular chemistry [2]. However, re-
search has been mainly focused on cyclophanes with a
mere organic ring skeleton. Typical examples are pro-
vided by calixarenes [3] cryptophanes [4], carcerands
and hemicarcerands [5]. In recent years transition metal
centers have become the focal point of interest. The
incorporation of metal fragments not only enables the
phenomenon of self-assembly to occur [6], but also
affords cyclophanes with properties like catalytic [7] or
* Corresponding author. Tel.: +49-707-129-72039; fax: +49-707-
129-5306.
An alternative approach to metallacyclophanes refers
to the well-developed phosphine chemistry. The objec-
E-mail address: ekkehard.lindner@uni-tuebingen.de (E. Lindner)
1 Part IC: see Ref. [1].
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00587-2

E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
167
tive in this investigation was the synthesis of ditopic
phosphine ligands with secondary amino functionalities
and diphenylmethane building blocks that are known
to preorganize cavities. These novel ligands were re-
acted with a suitable transition metal precursor in a 2:2
cyclization reaction under high dilution conditions to
generate dimolybdacyclophanes with NH-binding sites.
Such cyclophanes have the potential to act as host
molecules [16].
spectrum, revealing the molecular peak at m/z=566.
Compound 2 is a colorless air-stable solid, which is
indefinitely storable at −18°C and dissolves readily in
organic solvents of medium polarity. In halogenated
solvents a slow decomposition takes place.
For access to the arylaminomethylphosphine 5 an
intermediate step has to be considered (Scheme 1). First
the diamine 1 is converted into the corresponding
methoxymethylamine 4 by reaction of paraformalde-
hyde with NaOMe in methanol. However, in contrast
to the monofunctional methoxymethylamines described
by Barluenga et al. [19], the bifunctional amine 4
cannot be isolated by removing the solvent, because
even at low temperatures a polymerization takes place.
Subsequently the in situ product 4 was immediately
reacted with excess diphenylphosphine in dichloro-
methane to give the arylaminomethylphosphine 5,
which after work up precipitates as a colorless, air-sta-
ble solid. The diphos ligand 5 readily dissolves in
solvents of medium polarity, but ethers induce polymer-
ization. An FD mass spectrum corroborated the ex-
pected composition of this ligand, showing the
molecular peak at m/z=595.
2. Results and discussion
2.1. Synthesis of ligands 2 and 5
For a largely quantitative reaction the treatment of
the diamine 1 with ClPPh2 has to be carried out in the
presence of the auxiliary base NEt3 [17] (Scheme 1).
Stronger bases, like n-butyllithium, are not successful,
because the lithiated diamine 1 deprotonates 2 as soon
as it is formed, leading to undesired by-products. Be-
cause of its thermal and hydrolytic sensitivity, the aryl-
aminophosphine 2 cannot be purified by common
methods (distillation, chromatography) [18], hence it
must be washed with a dilute aqueous solution of
NaHCO3. The ligand 2 crystallizes with 1 mol of water
and its composition was established by an FD mass
The 31P{1H}-NMR spectra of the diphosphines 2 and
5 (in CDCl3) exhibit a singlet at l 29.5 and −17.9,
respectively. In the low- and high-field region both
1H-NMR spectra (CDCl3) display one AB pattern (2: l
7.0 and 6.9; 5: l 7.0 and 6.5) and a singlet (l 3.7),
which are assigned to the aromatic and methylene
protons of the diphenylmethane unit. A doublet in the
spectrum of 5 at l 3.8 is attributed to the protons of the
methylene group between nitrogen and phosphorus.
1
Whereas the H-NMR spectrum of 2 is characterized
by a doublet for the NH function at l 4.2, the NH
group in 5 gives rise to a broad singlet at l 3.5. The IR
spectra of the ligands 2 and 5 (THF) show absorptions
at 3289 and 3351 cm−1, respectively, which are as-
cribed to NꢀH stretching vibrations.
2.2. Synthesis of the dimolybdacyclophanes 3 and 6
To promote the formation of the dinuclear dimolyb-
dacyclophanes 3 and 6 (Scheme 1) two preconditions
have to be fulfilled. (i) The divergent properties of the
diphosphine ligands 2 and 5 require a convergent metal
fragment that prearranges the coordination geometry
precisely. (ii) The thermal lability of the employed
ligands 2 and 5 necessitates a coreactant that reacts as
fast as possible at ambient temperature. Both prerequi-
sites are best complied with the application of (h4-
nbd)Mo(CO)4.
The reactions between (h4-nbd)Mo(CO)4 and 2 and
5, respectively, are carried out under high-dilution con-
ditions in dichloromethane [20]. To meet this require-
ment a computer-controlled dosing apparatus was
constructed, which allows a highly synchronous addi-
Scheme 1. Synthesis of the aminophosphines 2 and 5 and the di-
molybdacyclophanes 3 and 6.

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E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
tion of the solutions of two sensitive reactants into a
reaction flask in any desired rate and under exclusion of
light [21]. With the aid of such an apparatus it was
possible to double the yields of the expected
tetraazatetraphosphadimolybdacyclophanes.
and 1880 cm−1 the IR spectra of 3 and 6 exhibit four
CO absorptions (3 in CCl4, 6 in acetone), which is
consistent with the presence of cis-Mo(CO)4 arrange-
ments. The NH stretching vibration in the IR spectrum
of 6 is found in the same region as that of the ligand 5.
In the case of the smaller dimolybdacyclophane 3 two
NH absorptions are observed: a sharp peak at 3389 and
a broad band at 3245 cm−1, indicating NꢀH···N hydro-
gen bonds [24]. Dilution experiments did not change
the intensity ratio of these two absorptions, i.e. the
hydrogen bonds were not cleaved revealing their in-
tramolecular character.
The separated remainders of the reaction mixtures
showed absorptions of cis-Mo(CO)4 groups in the IR
spectra and low-field shifted signals in the 31P{1H}-
NMR spectra, which are in a similar range as those for
3 and 6. These observations point to higher nuclear or
polynuclear species. According to the MPLC chro-
matograms, several small fractions were observed. With
increasing retention time these fractions become smaller
and their separation becomes more complicated.
The favored formation of the dinuclear molybdacy-
clophanes 3 and 6 may be rationalized by the following
course of reaction: in a first step a diphosphine ligand
attacks nucleophilically (h4-nbd)Mo(CO)4 to give an
open-chain mononuclear intermediate with one phos-
phine and one (h2-nbd)Mo(CO)4 end group each [22].
Owing to the steric conditions of the diphosphines 2
and 5, both phosphorus donors are not able to coordi-
nate to a single transition metal fragment. Thus ring
closure is not possible at this stage and the formation of
cyclic mononuclear species is unlikely. In a second
SN-type reaction two mononuclear units react with each
other to give a dinuclear open-chain intermediate with
the same above-mentioned end groups. In principle this
dinuclear species can undergo an intramolecular cy-
clization or it reacts intermolecularly either with a
further diphosphine and a (h4-nbd)Mo(CO)4 molecule,
respectively, or with itself to give open-chain products.
The formation of non-cyclic compounds or ring sys-
tems of higher nuclearity is partially or largely sup-
pressed if the dilution principle is adhered to as strictly
as possible by employing the mentioned dosing appara-
tus. Only in this case do the ends of the dinuclear
chains have enough time to approach each other in a
cyclic conformation. Once a tri- or tetranuclear chain is
formed it will react to give oligo- or polynuclear rings
or open-chain by-products.
2.3. X-ray crystal structures of the
dimolybdacyclophanes 3 and 6
To get a more detailed structural information about
the dimolybdacyclophanes, X-ray structural analyses
were performed. ORTEP drawings of the molecular
structures of 3 and 6 with atom labeling are depicted in
Fig. 1 (top) and 4 (top). A listing of selected bond
lengths and angles is summarized in Tables 1 and 2.
The cavity of the molecular structure of 3 can be
described by a parallelogram. The vertices of this paral-
lelogram are occupied by the atoms Mo(3), C(12),
Mo(3A), and C(12A). The lengths of the edges are
Unlike the ligands 2 and 5, the corresponding color-
less dimolybdacyclophanes 3 and 6 are rather stable
toward oxygen and moisture and dissolve slowly in
dichloromethane and chloroform, respectively. The so-
lutions are slightly sensitive to light and the purification
of 3 and 6 succeeded via middle-pressure liquid chro-
matography (MPLC).
,
9.278(7) (Mo(3)ꢀC(12)) and 9.162(6) A (Mo(3)ꢀC(12A))
with angles of 93.47(5)° (P(2)ꢀMo(3)ꢀP(4)) and
112.0(5)° (C(13)ꢀC(12)ꢀC(9A)). The diagonals of this
parallelogram, which represent the Mo(3)ꢀMo(3A) and
C(12)ꢀC(12A) distances, have lengths of 15.106(2) and
Compared to the 31P{1H}-NMR spectra of 2 and 5,
the 31P{1H} signals of the dimolybdacyclophanes (3 in
CDCl3; 6 in CD2Cl2) are shifted to lower field [23]. The
1H-NMR spectra of 3 and 6 are quite similar to those
of the ligands 2 and 5. The observation of a degenerate
AA%BB% system is a consequence of the fast rotation of
the phenylene rings within the diphenylmethane units.
Even at −55°C this effect could not be frozen out. A
doublet of triplets is observed in the spectrum of the
dimolybdacyclophane 6 at l 3.5, which is attributed to
,
10.58(1) A. Both diphenylmethane units in 3 are ori-
ented face-to-face and generate a cylindrical cavity,
because the opposite carbon atoms are connected by a
center of inversion. Within a diphenylmethane building
block the phenylene rings are not perpendicular to the
plane, which is defined by the atoms C(9A), C(12), and
C(13). The deviations from the vertical orientation are
7.4(2) and 11.8(2)°.
A space-filling model (Fig. 1, bottom) demonstrates
that the interior of the cyclophane framework is big
enough to include guest molecules with an adequate
dimension. Indeed, one disordered CHCl3 molecule is
included inside this cavity, and five disordered CHCl3
molecules are located outside. Each phenyl substituent
of the four P(C6H5)2 units is partially shielding the
entrance of the cavity. Consequently the NH functions
1
the NH protons. A H{31P}-NMR experiment reduces
the spectrum to a simple triplet, typical for a coupling
of the NH to the vicinal CH2 protons. In the case of the
smaller dimolybdacyclophane 3 only a complex multi-
plet at l 4.6 is observed for the NH protons. This
multiplet is generated by an AA%XX% spin system. 31P
decoupling results in the expected singlet. Between 2025

E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
169
Fig. 1. Top: ORTEP plot of the molecular structure of compound 3. Thermal ellipsoids are drawn at 20% probability level, except for H atoms.
Phenyl rings are numbered cyclically. Bottom: space-filling representation of 3. Solvent molecules are omitted for clarity.
the molecules of 3 (Fig. 2). Along the a axis these
molecules form continuous channels with their cavities
and the above-mentioned phenyl rings point to the
centers of the channels, thus impeding free passage. The
smallest distance between these phenyl rings is 5.177(2)
are completely hidden by these phenyl rings. Further-
more it is remarkable that both NH groups at each side
of a diphenylmethane unit are either oriented above or
below the cavity, but not inside. To bind guest
molecules inside the cavity via hydrogen bonding, a
change in the conformation of 3 would be necessary.
The shielding of the cavity by the P-phenyl rings is
corroborated by an inspection of the packing mode of
,
A (C(21A)ꢀC(49)).
To demonstrate the influence of both cis-
(Ph2P)2Mo(CO)4 fragments on the geometry of the

170
E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
Table 1
result if the
a
bonds in the diosma[5.1.5.1]-
,
Selected interatomic distances (A) and interbond angles (°) for 3
paracyclophane being rotated by 180°. From this it
follows that in 3 the b bonds are oriented inwards,
which lengthens the Mo(3)ꢀMo(3A) and narrows the
C(12)ꢀC(12A) distances, thus the cavity of 3 is con-
tracted. In contrast to 3 in the diosma[5.1.5.1]para-
cyclophane the b bonds are oriented outwards, which
shortens the Os(1)ꢀOs(2) and lengthens the C(17)ꢀC(34)
distance. In this case the cavity nearly adopts the shape
of a rectangle. The reason for this rotation is quite
obvious. The orientation of the b bonds in the
diosma[5.1.5.1]paracyclophane suggests that the sub-
stituents at the a-carbon atoms (two hydrogen atoms)
are located inside the cavity. This conformation is
impossible in the case of 3, because each a-phosphorus
atom is provided with two bulky phenyl groups, which
repel each other. These phenyl rings adopt the optimum
distance by such a rotation of the a bonds, that one
phenyl ring is oriented either above or below and the
other one sidewards away from the cavity.
Interatomic distances
Mo(3)ꢀC(12)
Mo(3)ꢀC(12A)
Mo(3)ꢀMo(3A)
C(12)ꢀC(12A)
C(21A)ꢀC(49)
Mo(3)ꢀP(2)
9.278(7)
9.162(6)
15.106(2)
10.58(1)
5.177(2)
2.500(2)
2.510(1)
P(2)ꢀN(1)
P(4)ꢀN(5)
N(1)ꢀC(16)
N(5)ꢀC(6)
C(9)ꢀC(12A)
C(12)ꢀC(13)
1.689(5)
1.689(5)
1.414(8)
1.412(7)
1.512(8)
1.512(9)
Mo(3)ꢀP(4)
Interbond angles
P(2)ꢀMo(3)ꢀP(4)
C(13)ꢀC(12)ꢀC(9A)
C(33)ꢀMo(3)ꢀC(37)
P(2)ꢀMo(3)ꢀP(4)
N(1)ꢀP(2)ꢀMo(3)
C(16)ꢀN(1)ꢀP(2)
93.47(5)
112.0(5)
177.7(2)
93.47(5)
114.5(2)
131.7(4)
C(45)ꢀP(4)ꢀMo(3)
C(39)ꢀP(4)ꢀMo(3)
N(1)ꢀP(2)ꢀC(19)
N(1)ꢀP(2)ꢀC(25)
C(19)ꢀP(2)ꢀC(25)
C(45)ꢀP(4)ꢀC(39)
115.3(2)
115.6(2)
106.3(3)
102.6(3)
105.2(3)
104.5(3)
cavity, it is appropriate to compare 3 with the likewise
28-membered diosma[5.1.5.1]paracyclophane [14a].
Similar to 3 this macrocycle contains two 4,4%-substi-
tuted diphenylmethane units, which are connected to
two cis-Os(CO)4 fragments via two methylene groups.
The absence of the voluminous diphenylphosphino
groups in the diosma[5.1.5.1]paracyclophane affects the
shape of the cavity: the Os(1)ꢀOs(2) distance (12.334(4)
A comparison of the axial CO ligands is quite inter-
esting. Whereas in the diosma[5.1.5.1] paracyclophane
they are inclined toward the cavity (COaxꢀCOax=
165.2(4)°) due to the electropositive alkyl chains [25],
they are inclined in the opposite direction in 3
(COaxꢀCOax=177.7(2)°).
In contrast to 3, the molecular structure of the
,
A) is smaller and the distance between the methylene
32-membered dimolybdacyclophane
6
represents
carbon atoms bridging the phenylene rings (12.224(1)
roughly the shape of a boat in which the diphenyl-
methane building blocks form the hull and the cis-
(Ph2P)2Mo(CO)4 fragments the bow and stem,
respectively (Fig. 4, top). The Mo(4)ꢀMo(4A) and
,
A) is larger as compared to the corresponding distances
,
in 3 (15.106(2) and 10.58(1) A). In other words, the
cavity in 3 is extended along the Mo(3)ꢀMo(3A) axis.
This can be explained as follows: on the basis of X-ray
structural data Fig. 3 displays a schematic view of the
transition metal fragments of both the diosma-
[5.1.5.1]paracyclophane and 3 along the axial CO lig-
ands. The depicted orientations of the b bonds in 3
,
C(14)ꢀC(14A) distances are 15.338(4) and 6.397(3) A.
Again the phenylene rings are not perpendicular to the
plane in which the atoms C(11), C(14) and C(15) are
located. The deviations from the vertical position are
25.0(2) and 7.8(2)°. Unlike in 3, the diagonally opposite
phenylene rings that are connected by a C2 axis are not
parallel, but include angles of 69.4(2) and 78.6(1)°,
respectively.
Table 2
,
Selected interatomic distances (A) and interbond angles (°) for 6
Inspection of the space-filling representation (Fig. 4,
bottom) offers an impression of the steric conditions:
the entrance into the boat is of sufficient size for the
passage of smaller molecules like C2H4Cl2, which is
embedded tightly inside the cavity. An additional
C2H4Cl2 and a water molecule are located outside the
cavity. It should be mentioned that from a solvent
mixture consisting of C2H4Cl2, (n-butyl)2O, and H2O,
the chlorinated hydrocarbon is selected to be incorpo-
rated as a guest into the cavity of 6.
Similar to 3 the macrocycles 6 are stacked in such a
manner that they form channels with their cavities
along the b axis (Fig. 5). However, in contrast to 3 the
P-phenyl rings are located outside the channels, which
have the shape of a flattened rhombus. Thus the pas-
sage through the channels is impeded. All four NH
Interatomic distances
Mo(4)ꢀMo(4A)
C(14)ꢀC(14A)
Mo(4)ꢀP(3)
Mo(4)ꢀP(5)
P(3)ꢀC(2)
15.338(4)
6.397(3)
2.524(1)
2.537(2)
1.859(6)
1.854(5)
N(1)ꢀC(2)
N(7)ꢀC(6)
N(1)ꢀC(19)
N(7)ꢀC(8)
C(11)ꢀC(14)
C(14)ꢀC(15)
1.439(7)
1.432(8)
1.396(8)
1.405(7)
1.529(7)
1.500(8)
P(5)ꢀC(6)
Interbond angles
P(3)ꢀMo(4)ꢀP(5)
C(2)ꢀP(3)ꢀMo(4)
C(6)ꢀP(5)ꢀMo(4)
N(1)ꢀC(2)ꢀP(3)
C(41)ꢀP(5)ꢀMo(4)
C(47)ꢀP(5)ꢀMo(4)
N(7)ꢀC(6)ꢀP(5)
C(19)ꢀN(1)ꢀC(2)
91.54(4)
111.7(2)
120.3(2)
107.9(3)
113.6(2)
116.6(2)
110.1(4)
120.5(4)
C(8)ꢀN(7)ꢀC(6)
C(15)ꢀC(14)ꢀC(11) 114.3(5)
C(33)ꢀMo(4)ꢀC(39) 175.3(3)
C(27)ꢀP(3)ꢀC(21)
C(47)ꢀP(5)ꢀC(41)
C(27)ꢀP(3)ꢀMo(4)
C(21)ꢀP(3)ꢀMo(4)
121.2(5)
96.7(3)
104.7(3)
120.1(2)
120.2(2)

E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
171
Fig. 2. Four channels of molecules in the crystal structure of 3 viewed along the a axis. Solvent molecules are omitted for clarity, unit cell is shown.
Fig. 3. Schematic view onto the transition metal fragments of compound 3 and the diosma[5.1.5.1]paracyclophane along the axial CO ligands.
functions are oriented outwards from the cavity and
like in 3 a change in the conformation is a necessary
precondition for the inclusion of guests via hydrogen
bonding.

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E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
Fig. 4. Top: ORTEP plot of the molecular structure of compound 6. Thermal ellipsoids are drawn at 20% probability level, except for H atoms.
Phenyl rings are numbered cyclically. Bottom: space-filling representation of 6. Solvent molecules that are located outside the cavity are omitted
for clarity.
3. Conclusions
none, 1,4-cyclohexanedione, 2,5-piperazinedione and
trans-1,4-diaminocyclohexane. However, none of
1
With regard to the possibility of forming host–guest
complexes, two novel tetraphosphadimolybdacyclo-
phanes with different ring sizes and four NH binding
sites were introduced in this investigation. Satisfactory
yields of the macrocycles 3 and 6 are only achieved if
the aminodiphosphines 2 and 5 are reacted with (h4-
nbd)Mo(CO)4 under high-dilution conditions, which is
enabled by employing a computer-controlled dosing
apparatus. In consideration of the fact that solvent
molecules are included in the cavities of molecules 3
and 6, inclusion experiments with hydrogen acceptors
were performed in solution applying NMR titration
methods [15]. The guests tested were p-benzoqui-
these potential guests gave rise to separate H-NMR
peaks or to
a
change in the chemical shift
of the respective proton signals attributed to the
formation of a host–guest complex. In contrast, a
similar macrocyclic system without transition metals,
which was described by Hunter and co-workers,
clearly features molecular recognition [16a]. The main
difference between both systems is the low tendency of
the molybdacyclophanes 3 and 6 to form hydrogen
bonds. Because of the presence of peptide functions,
the macrocycles described by Hunter and co-workers
are able to provide hydrogen bonds even in water
[2f].

E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
173
Fig. 5. Four channels of molecules of 6 viewed along the b axis. Solvent molecules are omitted for clarity, unit cell is shown.
4. Experimental
P4O10. Chlorodiphenylphosphine (Fluka) was distilled
and stored under argon at 4°C.
4.1. General procedures
4.2. Dosing apparatus
All manipulations were carried out under an atmo-
sphere of argon by use of standard Schlenk techniques.
Solvents were dried with appropriate reagents, distilled,
degassed, and stored under argon. IR data were ob-
tained with Bruker IFS 48 FTIR and Bruker IFS 25
FTIR spectrometers. FD mass spectra were taken on a
Finnigan MAT 711 A instrument, modified by AMD;
FAB mass spectra were recorded on a Finnigan MAT
TSQ 70. Elemental analyses were performed with a
Elementar Vario EL analyzer; Mo was analyzed ac-
cording to the literature [26]; AAS was performed on a
The dosing apparatus consists of two 50 ml Hamilton
gastight syringe barrels mounted on a carrier. The
plungers are precisely and simultaneously moved by a
step motor via a spindle. Each of the syringes is con-
nected via a Teflon pipe to a magnetic valve with three
entries that controls the direction of the flow of the
solutions of the educts. Two further entries of the
magnetic valves are connected to storing vessels which
can be refrigerated. Another set of entries is connected
to cannulas, which are penetrating compact Teflon
blocks. These Teflon blocks fit into the ground joints of
the reaction vessel. The step motor and the magnetic
valves are computer controlled.
1
Varian Spectra AA20 Plus spectrometer. H-, 31P{1H}-,
31P- and 13C{1H}-NMR spectra were recorded on a
Bruker DRX 250 spectrometer at 250.13, 101.25, and
62.90 MHz, respectively, and at 25°C. 1H and 13C
chemical shifts were measured relative to partially
deuterated solvent peaks and to deuterated solvent
peaks, respectively, which are reported relative to TMS.
31P chemical shifts were measured relative to 85%
H3PO4 (l=0). (h4-nbd)Mo(CO)4 was obtained
analogous to a literature method [27] and sublimed at
75°C (1.5×10−3 mbar). The diamine 1 (Merck–
Schuchardt) was purified by distillation and precipi-
4.3. Chromatography
Chromatography was performed on a preparative
scale with a Bu¨chi MPLC system consisting of a B-681
chromatography pump equipped with
a six-way
changeover valve, a UV–vis filter–photometer and a
Knauer strip chart recorder. A standard column (Ø=
49 mm, l=460 mm) equipped with a precolumn and a
PrepElut dry application column, for sample injection,
were used. The columns were filled using a dry packing
tated from
a
CH2Cl2 solution with n-pentane.
Paraformaldehyde (Merck) was dried in vacuo over

174
E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
technique (Bu¨chi dry-filling set). Unmodified non-
the reaction mixture was pumped onto 250 ml of
degassed ice-water. The aqueous phase was extracted
(0°C) with 75 ml of CH2Cl2. This procedure was re-
peated twice with 25 ml of CH2Cl2. The CH2Cl2 phases
were collected and dried with degassed Na2SO4. This
CH2Cl2 solution was added dropwise at 0°C to a solu-
tion of diphenylphosphine (3.72 g, 20.00 mmol) in 20
ml of CH2Cl2. After the addition was completed, stir-
ring was continued for 2 h at ambient temperature.
Then 20 ml of toluene was added and CH2Cl2 and
methanol were removed in vacuo. The toluene solution
was filtered (P3) with a 2 cm column containing basic
Al2O3, which was subsequently rinsed twice with 20 ml
of toluene. The filtrate was transferred via a Teflon
pipe to 200 ml of vigorously stirred n-hexane at
−50°C and allowed to precipitate for 2 h. The super-
natant solution was removed via a Teflon pipe and the
precipitate was washed with 10 ml of n-pentane and
dried overnight in vacuo to give 4.3 g (72%) of 5 as a
colorless sticky material; m.p. 36.7°C. MS (FD, 30°C):
m/z 595.6 [M+]. Anal. Calc. for C39H36N2P2 (594.73):
C, 78.77; H, 6.10; N, 4.71. Found: C, 78.72%; H, 6.35;
,
regular silica gel (pore size 60 A, particle size 25–40
mm) was purchased from Machery–Nagel (‘Polygoprep
60–30’), degassed and used as stationary phase.
Samples were eluted isocratically by a mobile phase
consisting of a 2:5 ethyl acetate–n-hexane mixture and
the solvents were purified as described in Section 4.1.
The mobile phase flow rate was fixed at 29 ml min−1
.
4.4. N,N%-Bis(diphenylphosphino)4,4%-diaminodiphenyl-
methane (2)
A solution of chlorodiphenylphosphine (3.40 g, 15.40
mmol) in 50 ml of THF was added dropwise at
−10°C to a solution of 1 (1.53 g, 7.70 mmol), triethyl-
amine (2.14 ml, 15.44 mmol) and 4-(dimethylamino)-
pyridine (DMAP) (40 mg, 0.32 mmol) in 50 ml of
THF. After the addition was completed precipitated
HNEt3Cl was filtered (P3) and washed twice with 20
ml of THF. The solvent was evaporated in vacuo and
replaced by 20 ml of CH2Cl2. This mixture was washed
three times with 5 ml of an aqueous NaHCO3 solution
(5%) and then dried twice with Na2SO4. The product
precipitated with addition of 40 ml of n-pentane. The
remainder of the filtrate (P3) was washed twice with 10
ml of n-pentane and dried overnight under reduced
pressure to give 4.41 g (98%) of 2·H2O as a colorless
powder; m.p. 74.2°C (dec.). MS (FD, 30°C): m/z 566
[M+]. Anal. Calc. for C37H32N2P2·H2O (584.63): C,
76.01; H, 5.86; N, 4.79. Found: C, 76.04; H, 6.01; N,
N, 4.80%. IR (THF): w(NH)=3351 (m) cm−1
.
31P{1H}-NMR (101.26 MHz, CDCl3, 22°C): l=
1
−17.9 (s). H-NMR (250.13 MHz, CDCl3, 22°C): l=
3.5 (s, 2H, NH), 3.7 (s, 2H, C6H4ꢀCH2ꢀC6H4), 3.8 (d,
3J(PH)=3.8 Hz, NꢀCH2ꢀP), 6.5, 7.0 (AB pattern,
3J(HH)=8.3 Hz, 8H, C6H4), 7.3–7.5 (m, 20H, PPh2).
13C{1H}-NMR (62.90 MHz, CDCl3, 22°C): l=41.4 (s,
2
C6H4ꢀCꢀC6H4), 45.0 (d, J(PH)=11.4 Hz, NꢀCH2ꢀP),
4.63%. IR (THF): w(NH)=3289 (m) cm−1
.
31P{1H}-
114.5 (s, 3,3%,5,5%-C of C6H4), 130.0 (d, 3J(PC)=6.4
Hz, m-C of PPh2), 130.2 (s, p-C of PPh2), 130.8 (s,
2,2%,6,6%-C of C6H4), 132.7 (s, 1,1%-C of C6H4), 134.2 (d,
2J(PC)=18.5 Hz, o-C of PPh2), 137.6 (d, 1J(PC)=
1
NMR (101.26 MHz, CDCl3, 22°C): l=29.5 (s). H-
NMR (250.13 MHz, CDCl3, 22°C): l=3.7 (s, 2H,
2
C6H4ꢀCH2ꢀC6H4), 4.2 (d, J(PH)=8.2 Hz, 2H, NH),
6.9, 7.0 (AB pattern, 3J(HH)=8.5 Hz, 8H, C6H4),
7.3–7.4 (m, 20H, PPh2). 13C{1H}-NMR (62.90 MHz,
CDCl3, 22°C): l=40.7 (s, C6H4ꢀCꢀC6H4), 116.5 (d,
3J(PC)=12.8 Hz, 3,3%,5,5%-C of C6H4), 128.9 (d,
3J(PC)=8.1 Hz, m-C of PPh2), 129.5 (s, p-C of PPh2),
12.8 Hz, ipso-C of PPh2), 147.6 (d, J(PC)=6.4 Hz,
3
4,4%-C of C6H4).
4.6. General procedure for the formation of the
dimolybdacyclophanes 3 and 6
4
130.0 (d, J(PC)=1.4 Hz, 2,2%,6,6%-C of C6H4), 131.7
2
5
(d, J(PC)=20.2 Hz, o-C of PPh2), 133.2 (d, J(PC)=
A reaction vessel was charged with 500 ml of
CH2Cl2. With the aid of a dosing apparatus, solutions
of the ligands 2 or 5 and (h4-nbd)Mo(CO)4 in 200 ml of
CH2Cl2 were slowly added within 72 h under vigorous
stirring and exclusion of light at ambient temperature.
After the addition was completed the solvent and nor-
bornadiene were removed in vacuo. The remainder was
suspended in 20 ml of CH2Cl2 (3) or CHCl3 (6) and the
suspension was filtered (P3) over a 5 cm layer of silica,
which was subsequently rinsed with 300 ml of CH2Cl2
(3) or CHCl3 (6). To the filtrates 8.0 g of silica gel was
added and the solvent was removed in vacuo. The
remaining silica was filled into a PrepElut dry applica-
tion column and compressed at 10 bar (N2) according
to a Bu¨chi procedure using a dry-filling set [28]. After
MPLC the eluent was removed in vacuo. The remain-
1.4 Hz 1,1%-C of C6H4), 140.8 (d, 2J(PC)=12.1 Hz,
1
4,4%-C of C6H4), 145.0 (d, J(PC)=17.5 Hz, ipso-C of
PPh2).
4.5. N,N%-Bis[(diphenylphosphino)methyl]4,4%-diamino-
diphenylmethane (5)
Sodium (2.30 g, 100.00 mmol) was dissolved in 30 ml
of methanol. A solution of 1 (1.98 g, 10.00 mmol) in
10 ml of methanol was added via a Teflon pipe. This
mixture was stirred for 15 min giving a colorless sus-
pension. The suspension was added to another suspen-
sion of anhydrous paraformaldehyde (0.84 g, 28.00
mmol) in 20 ml of methanol via a Teflon pipe and was
stirred for a further 5 h at ambient temperature. Then

E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
175
der was dissolved in 100 ml of CH2Cl2 (3) or CHCl3
(6), precipitated with 200 ml of n-pentane and finally
the products were washed with 10 ml of n-pentane.
2J(PH)=5.6 Hz, 8H, NꢀCH2ꢀP), 6.1, 6.8 (AB pattern,
3J(HH)=8.3 Hz, 16H, C6H4), 7.3–7.4 (m, 40H, PPh2).
1H{31P}-NMR (250.13 MHz, 101.26 CDCl3, 22°C):
3
l=3.5 (t, J(HH)=5.5 Hz, 4H, NH). 13C{1H}-NMR
(62.90 MHz, CDCl3, 22°C): l=41.7 (s, C6H4ꢀCꢀ
C6H4), 32.3 (s, NꢀCH2ꢀP), 115.0 (s, 3,3%,5,5%-C of
C6H4), 130.4 (m, N=9.1 Hz3 [29], m-C of PPh2), 130.9
(s, p-C of PPh2), 131.6 (s, 1,1%-C of C6H4), 133.7 (s,
2,2%,6,6%-C of C6H4), 133.8 (m, N=11.5 Hz3 [29], o-C
of PPh2), 136.4 (m, N=32.7 Hz3 [29], ipso-C of PPh2),
147.2 (m, N=7.7 Hz3 [29], 4,4%-C of C6H4), 211.4 (t,
2J(PC)=9.1 Hz, COax), 216.0 (m, N=16.2 Hz3 [29],
COeq).
4.7. 3,3,3,3,21,21,21,21-Octacarbonyl-2,2,4,4,20,20,
22,22-octaphenyl-1,5,19,23-tetraaza-2,4,20,22-tetraphosp
ha-3,21-dimolybda[5.1.5.1]paracyclophane (3)
Starting materials: 2 (1.98 g, 3.50 mmol) and (h4-
nbd)Mo(CO)4 (1.05 g, 3.50 mmol). Purification by
MPLC afforded 3 as the fraction with the highest peak
intensity (tR=17 min). Yield: 1.41 g (26%) of 3; color-
less powder; m.p. 199.9°C. MS (FAB, 30°C, negative
ions): m/z 1548.7 [M+]. Anal. Calc. for C82H64Mo2-
N4O8P2·H2O (1567.22): C, 62.84%; H, 4.24%; Mo,
12.24%; N, 3.57%. Found: C, 62.54%; H, 4.24%; Mo,
11.76%; N, 3.56%. IR (THF): w(NH)=3389 (w), 3245
(w) cm−1. IR (CCl4): w(CO)=2023 (m), 1930 (s), 1899
4.9. Crystallographic analysis
Colorless single crystals suitable for X-ray structural
determinations were obtained by slow evaporation of a
solution of 3 in CHCl3 and diffusion of di-n-butyl
ether into a solution of 6 in dichloroethane, respec-
tively. The crystals were mounted on a glass fiber and
transferred to a P4 Siemens diffractometer, using
graphite-monochromated MoꢀKa radiation. Random
searches were performed to find suitable reduced cells.
The lattice constants were determined by 25 (3) and 29
(6) precisely centered high-angle reflections and refined
by least-square methods. The final cell parameters for 3
and 6 are summarized in Table 3. Intensities were
collected via the ꢀ-scan technique. Absorption correc-
tions were applied (C-scan). The resultant data of 3 fit
(s), 1880 (vs) cm−1
.
31P{1H}-NMR (101.26 MHz,
CDCl3, 22°C): l=72.5 (s). 1H-NMR (250.13 MHz,
CDCl3, 22°C): l=3.4 (s, 4H, C6H4ꢀCH2ꢀC6H4), 4.7
(m, N=20.7 Hz2 [29], 4H, NH), 6.0, 6.6 (AB pattern,
3J(HH)=8.3 Hz, 16H, C6H4), 7.4–7.7 (m, 40H, PPh2).
1H{31P}-NMR (250.13 MHz, 101.26 CDCl3, 22°C):
l=4.7 (s, 4H, NH). 13C{1H}-NMR (62.90 MHz,
CDCl3, 22°C): l=41.2 (s, C6H4ꢀCꢀC6H4), 120.9 (s,
3,3%,5,5%-C of C6H4), 131.1 (m, N=10.0 Hz3 [29], m-C
of PPh2), 131.3 (s, p-C of PPh2), 132.4 (s, 1,1%-C of
C6H4), 133.6 (m, N=12.8 Hz3 [29], o-C of PPh2),
136.8 (s, 2,2%,6,6%-C of C6H4), 138.7 (m, N=38.4 Hz3
[29], ipso-C of PPh2), 142.6 (m, N=11.4 Hz3 [29],
(
best with the triclinic space group P1 with one formula
2
unit per unit cell (Z=1) and six distorted chloroform
molecules. 6 crystallizes in the monoclinic space group
C2 (Z=2) with two molecules of 1,2-dichloroethane
and one molecule of water. The structures were solved
by direct methods with SHELXS [30] and refined by
least squares using SHELXTL with anisotropic thermal
parameters for all non-hydrogen atoms except the sol-
vent molecules (based on F2) [31]. Hydrogen atoms
were included in calculated positions (riding model)
with exception of water and the distorted CHCl3
molecules. The maximum and minimum peaks in the
final difference synthesis were 1.894, −2.224 (3), and
4,4%-C of C6H4), 209.5 (t, J(PC)=9.8 Hz, COax), 214.6
(m, N=19.5 Hz [29]3, COeq).
4.8. 4,4,4,4,24,24,24,24-Octacarbonyl-3,3,5,5,23,23,25,
25-octaphenyl-1,7,21,27-tetraaza-3,5,23,25-tetraphospha-
4,24-dimolybda[7.1.7.1]paracyclophane (6)
Starting materials: 5 (2.08 g, 3.50 mmol) and (h4-
nbd)Mo(CO)4 (1.05 g, 3.50 mmol). Purification by
MPLC afforded 6 as the fraction with the highest peak
intensity (tR=29 min). Yield: 1.32 g (23.5%) of 6;
colorless powder; m.p. 164.3°C. MS (FD, 30°C): m/
z=1606.1 [M+]. Anal. Calc. for C86H72Mo2N4O8·
1.5CH2Cl2 (1732.7): C, 60.65; H, 4.36; Cl, 6.14; Mo,
11.07; N, 3.23. Found: C, 60.96; H, 4.50; Cl, 5.88; Mo,
1.133, −1.586 (6) e A−3, respectively.
,
10.80; N, 3.23%. IR (THF): w(NH)=3380 (m) cm−1
IR (acetone): w(CO)=2021 (m), 1920 (s), 1907 (vs),
1884 (s) cm−1 31P{1H}-NMR (101.26 MHz, CDCl3,
22°C): l=29.2 (s). 1H-NMR (250.13 MHz, CDCl3,
.
5. Supplementary material
Crystallographic data for the structures reported in
this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publi-
cation nos. CCDC 130862 for 3 and CCDC 130863 for
6. Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge,
CB2 1EZ, UK (Fax: +44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk).
.
3
4
22°C): l=3.4 (dt, J(HH)=5.5 Hz, J(PH)=4.9 Hz,
4H, NH), 3.6 (s, 4H, C6H4ꢀCH2ꢀC6H4), 3.7 (d,
2
2 AA%XX% spin system, N=ꢀ J(PH)+4J(PH)ꢀ.
m
3 A part of an AXX% spin system, N=ꢀ J(AX)+nJ(AX%)ꢀ.

176
E. Lindner et al. / Journal of Organometallic Chemistry 595 (2000) 166–177
Table 3
Crystallographic data and refinement details for 3 and 6
Compound 3·6CHCl3
Compound 6·2C2H4Cl2·H2O
Empirical formula
Formula weight
Temperature (K)
C88H70Cl18Mo2N4O8P4
2265.34
173(2)
C90H82Cl4Mo2N4O9P4
1821.16
173(2)
,
Wavelength, MoꢀKa (A)
Crystal system
0.71073
Triclinic
0.71073
Monoclinic
(
Space group
P1
11.235(2)
C2
17.935(3)
10.097(3)
24.220(4)
90
105.78(1)
,
a (A)
,
b (A)
13.154(2)
17.218(2)
105.33(1)
94.27(1)
,
c (A)
h (°)
i (°)
k (°)
90.80(1)
2445.7(6)
1
1.538
0.868
1140
90
4221(2)
2
1.433
0.560
1868
3
,
V (A )
Z
Dcalc. (g cm−3
)
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
q Range for data collection (°)
Index ranges
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameters
Goodness of fit on F2
Final R indices [I\2|(I)]
R indices (all data)
0.30×0.20×0.20
2–27.5
−145h514, −165k516, −225l522
14553
889 (Rint=0.0227)
Full-matrix least-squares on F2
8891/0/541
0.30×0.20×0.10
2–27.5
−235h523, −135k51, −315l530
11275
5686 (Rint=0.1070)
Full-matrix least-squares on F2
5686/3/487
1.671
1.878
R1=0.0867 a, wR2=0.2229 b
R1=0.0980 a, wR2=0.2417 b
1.894 and −2.224
0.8455 and 0.7807
R1=0.0529 a, wR2=0.1301 b
R1=0.0601 a, wR2=0.1400 b
1.133 and −1.586
0.3707 and 0.3253
−3
,
Largest diff. peak and hole e A
Max. and min. transmission
a R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ.
b wR2=[S[w(Fo2−Fc2)2]/S[w(F2o)2]]0.5
.
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Acknowledgements
Support of this research by the Deutsche
Forschungsgemeinschaft and the Fonds der Chemis-
chen Industrie is gratefully acknowledged. We are also
indebted to Priv.-Doz. Dr H.A. Mayer, Institut fu¨r
Anorganische Chemie II, University of Tu¨bingen, for
helpful discussions regarding the interpretation of the
NMR spectra.
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