A zwitterionic phosphanyl-substituted phosphonio-benzo[c]phospholide as bridging ligand towards dinuclear transition metal carbonyls

Article abstract of DOI:10.1016/S0022-328X(01)01208-6

The zwitterionic 1-triphenylphosphonio-3-diphenylphosphanyl-benzo[c]phospholide (3) reacts with M₂(CO)₁₀ (M = Mn, Re) to form the dinuclear complexes [{M(CO)₄}₂(μ-3)] (7, 8) in which the metal-metal bond is retained and both metals are bound via the two phosphorus lone-pairs. In contrast, reaction of 3 with Cp₂Mo₂(CO)₄ (Mo≡Mo) proceeds with complete cleavage of the metal-metal bond to yield as final product a complex [{MoCp(CO)₂}₂(μ-3)] (10) in which both phosphorus lone-pairs of 3 co-ordinate to one metal atom, and the second metal atom is attached in a η²(π)-co-ordination mode to the benzophospholide π-electron system. All complexes 7, 8, and 10 were characterised by analytic and spectroscopic data and X-ray diffraction studies. The formation of 10 is preceded by that of an intermediate which could likewise be isolated and whose constitution was assigned on the basis of spectroscopic studies as an isomer of 10 which still contains a metal-metal single bond. The behaviour of 3 marks an interesting contrast to that of 2-phosphanyl-phosphinines which react under similar conditions exclusively under co-ordination via the phosphorus lone-pairs, and fail to induce any breakage of metal-metal bonds. The origin for the observed deviations is discussed in terms of the different π-acceptor properties of the two types of ligands.

Full text of DOI:10.1016/S0022-328X(01)01208-6

Journal of Organometallic Chemistry 643–644 (2002) 181–188
www.elsevier.com/locate/jorganchem
A zwitterionic phosphanyl-substituted
phosphonio-benzo[c]phospholide as bridging ligand towards
dinuclear transition metal carbonyls
Dietrich Gudat *, Stefan Ha¨p, Martin Nieger
Institut fu¨r Anorganische Chemie der Uni6ersita¨t Bonn, Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany
Received 25 June 2001; accepted 31 August 2001
Dedicated to Professor Franc¸ois Mathey on the occasion of his 60th birthday
Abstract
The zwitterionic 1-triphenylphosphonio-3-diphenylphosphanyl-benzo[c]phospholide (3) reacts with M2(CO)10 (M=Mn, Re) to
form the dinuclear complexes [{M(CO)4}2(m-3)] (7, 8) in which the metalꢀmetal bond is retained and both metals are bound via
the two phosphorus lone-pairs. In contrast, reaction of 3 with Cp2Mo2(CO)4 (MoꢁMo) proceeds with complete cleavage of the
metalꢀmetal bond to yield as final product a complex [{MoCp(CO)2}2(m-3)] (10) in which both phosphorus lone-pairs of 3
co-ordinate to one metal atom, and the second metal atom is attached in a h2(p)-co-ordination mode to the benzophospholide
p-electron system. All complexes 7, 8, and 10 were characterised by analytic and spectroscopic data and X-ray diffraction studies.
The formation of 10 is preceded by that of an intermediate which could likewise be isolated and whose constitution was assigned
on the basis of spectroscopic studies as an isomer of 10 which still contains a metalꢀmetal single bond. The behaviour of 3 marks
an interesting contrast to that of 2-phosphanyl-phosphinines which react under similar conditions exclusively under co-ordination
via the phosphorus lone-pairs, and fail to induce any breakage of metalꢀmetal bonds. The origin for the observed deviations is
discussed in terms of the different p-acceptor properties of the two types of ligands. © 2002 Elsevier Science B.V. All rights
reserved.
Keywords: Phosphorus heterocycles; Benzophospholides; Metal carbonyls; Metalꢀmetal bonds; Hybrid ligands
1. Introduction
latter—in which the ligand behaves as a pronounced
p-acceptor—being often energetically favoured [3]. Re-
cently, phosphinine and phospholide derivatives which
are capable to act as multidentate ligands have gained
particular attention. Beside 2,2%-bis-phosphinines [4]
and 2,2%-bis-phospholides [5], the emphasis is on mixed
ligands with additional phosphane [6] or nitrogen based
[7] donor sites whose electronic properties differ nota-
bly from that of the phosphinine or phospholide moi-
ety. ‘Hybrid’ ligands of this type are sought after
because the available electronic differentiation of the
binding sites allows significant improvements of selec-
tivity and activity in homogeneous catalysis. Lately,
first examples for the successful application of P,N-
chelating phosphinines as hydroformylation catalysts
were reported [7].
Aromatic phosphorus heterocycles like phosphinines
and phospholides are extremely versatile ligands [1–3].
Both types of compounds may bind transition metals
via the cyclic p-electron system and the phosphorus
lone-pair, but, owing to the different electronic situa-
tion, their disposition for a certain co-ordination mode
differs. Phospholides prefer to form p-complexes which
are isoelectronic and isolobal to metal cyclopentadi-
enyls [1,2], and as there, the metal–ligand interaction
appears to be dominated by L“M charge transfer
contributions [2]. For phosphinines, the formation of p-
and s(P)-complexes is frequently competitive, with the
We have recently found that reduction of the bis-
* Corresponding author. Tel.: +49-228-735334; fax: +49-228-
735327.
triphenylphosphonio-benzo[c]phospholide
(2-phos-
E-mail address: dgudat@uni-bonn.de (D. Gudat).
phaindenide) (1) gives access to neutral phosphonio-
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01208-6

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D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
benzophospholides (2, 3) and anionic phosphanyl-ben-
zophospholides (4, Scheme 1) [8]. First studies of the
co-ordination chemistry of the neutral and cationic
derivatives revealed that the phosphonio-groups de-
crease the p-nucleophilicity and enhance the p-acidity
of the benzophospholide moiety. The zwitterion 2 thus
showed a balanced co-ordination behaviour, being ca-
pable to bind a chromium carbonyl fragment both via
the phosphorus lone pair in [Cr(h1(P)-2)(CO)5] or the
p-electron system in [Cr(h5-2)(CO)3] [8b]. A still in-
creased p-acceptor quality for a bis-phosphonio-ben-
zophospholide was illustrated by the synthesis of
complexes 5, 6 whose spectroscopic data suggested that
the two co-ordinate phosphorus atom in the ligand is
electronically similar to a phosphite [9].
In the present work, we report on a first co-ordina-
tion chemical study of the phosphanyl-substituted zwit-
terion 3. In contrast to the bidentate ligand in 5, 6, the
PꢀCꢀP backbone between the donor sites is less flexible
and imposes similar geometrical constraints as in bis-
diphenylphosphino-methane (dppm) or 2-phosphanyl-
phosphinines [6]. Similar as for these systems, a wide
range of dinuclear complexes, either with or without
metalꢀmetal bonds, may thus likewise accessible for 3.
Focussing on two possible routes to the target com-
plexes, viz. (a) ligand displacement at a suitable precur-
sor with a metalꢀmetal single bond, or (b) formal
addition of 3 to a metalꢀmetal multiple bond, we now
present some results concerning the reactions of 3 with
[M2(CO)10] (M=Mn, Re) and Cp2Mo2(CO)4,
respectively.
ambient temperature. Both products were isolated in
good yield and their constitution established by elemen-
tal analysis and spectroscopic (NMR, IR, FAB-MS)
studies. Even under forcing conditions (prolonged
refluxing in xylene), 3 failed to produce detectable
amounts of
a Mn2(CO)5 complex analogous to
[(dppm)2Mn2(CO)5] which was obtained from dppm
under similar conditions [10].
The k2(P, P%)-co-ordination of the ligand 3 in the
complexes 7 and 8 was deduced from the characteristic
co-ordination shifts (Dlcoord=l(complex)−l(ligand))
of the 31P-NMR signals of the phosphorus atoms in the
Ph2P group (Dlcoord= +35.5 (7), −22.5 (8)) and in
the ring (Dlcoord= +6.1(7), −65.1 (8)). The upfield
shift of d31P induced by the formal replacement of the
Mn by Re atoms is in accord with a general trend of
co-ordination shifts in complexes of phosphorus ligands
[11]. The presence of two chemically inequivalent
M(CO)4 moieties was inferred from the number of
signals in the 13C{1H}-NMR spectra. The IR spectra
(in CH2Cl2 solution) displayed five (7) or six (8) bands
between 2070 and 1900 cm−1 attributable to w(CO)
vibrational modes of terminal carbonyl ligands. The
absence of w(CO) bands at lower wavenumbers ruled
out the presence of bridging carbonyls. Considering
that a single cis-configurated M(CO)4-unit has four
IR-active w(CO) vibrations, we interpret the occurrence
of excess bands as a result of vibrational coupling
between two M(CO)4-moieties which are still connected
by a metalꢀmetal bond. The proposed molecular struc-
tures of 7, 8 were confirmed by the results of single
crystal X-ray diffraction studies (see below).
2. Results
2.2. Reaction with Cp2Mo2(CO)4 (MoꢁMo)
2.1. Reactions with manganese and rhenium carbonyls
Expecting that 3 should in analogy to 2-phosphanyl-
phosphinines or dppm undergo addition to metalꢀmetal
multiple bonds, we investigated its interaction with an
equimolar amount of Cp2Mo2(CO)4. The reaction pro-
ceeded smoothly at ambient temperature, however, a
31P-NMR spectroscopic assay indicated that it followed
actually a two-step mechanism and was thus more
Reactions of zwitterion 3 with [Mn2(CO)10] in boiling
toluene or with [Re2(CO)10] in boiling xylene proceeded
cleanly with quantitative formation of the dinuclear
complexes 7, 8 which precipitated as orange or yellow
crystalline solids after cooling the reaction mixtures to
Scheme 1.

D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
183
downfield shift (Dlcoord= +58.0) whose size is typical
for co-ordinated phosphanyl groups [11]. The ring
phosphorus atom displayed, in contrast, a large nega-
tive co-ordination shift (Dlcoord= −340.6) whose mag-
nitude strongly suggests p-co-ordination of the
benzophospholide moiety. This hypothesis was further
supported by large negative co-ordination shifts of the
carbon atoms in 1- and 3-position of the annulated ring
system (Dlcoord= −32.9 (C-1), −88.1 (C-8)).
Even if the available spectroscopic data can be con-
sistently interpreted by assuming that the ligand 3 binds
two CpMo(CO)2-fragments via the Ph2P-group and a
PꢂC-double bond of the benzophospholide moiety, a
complete structural assignment proved unfeasible since
no decision regarding the presence or absence of a
metalꢀmetal bond could be made. This remaining as-
signment problem was finally solved by an X-ray dif-
fraction study which revealed the presence of a complex
10 (Scheme 2) with two separate CpMo(CO)2-units.
Scheme 2.
1
The H-, 31P-, and 95Mo- (l95Mo= −1001, −1514)
NMR spectra of the reaction intermediate displayed the
same number of signals as those of 10, and the (+)-Xe-
FAB mass spectrum showed an identical molecular ion
peak, suggesting that both complexes are isomers. The
co-ordination shift of the phosphorus atom in the Ph2P
moiety (Dlcoord= +53.2) is similar as in 10 whereas
the ring phosphorus atom exhibits a negative co-ordi-
nation shift (Dlcoord= −137.5) which is smaller than
in 10, but comparable to that of other p-complexes of
phosphonio-benzophospholides [8b,12]. The IR spec-
trum displayed three bands in the w(CO) region (w¯ =
1969, 1911, 1867 cm−1) which appear in contrast to
those of 10 at higher frequencies as compared to
Cp2Mo2(CO)4 (w¯ =1954, 1892, 1833 cm−1). Combining
the available information, and assuming that by anal-
ogy to the reaction of 2-phosphanyl-phosphinines with
Cp2Mo2(CO)4 [6e] the initial reaction step should in-
volve most likely co-ordinative addition of 3 to the
metalꢀmetal triple bond, we assign the molecular struc-
ture of the intermediate as 9 (Scheme 2). The h2(PꢂC)-
co-ordination of the benzophospholide unit has
precedence in that of a bis-phosphonio-benzophospho-
lide ligand in the Co-complex 11 [12] (Scheme 3). An
attempt to confirm this assignment by an X-ray diffrac-
tion study failed since 9 rearranged into 10 during the
crystallisation process.
Scheme 3.
complicated than anticipated. The spectroscopic data
revealed that the first reaction step was complete within
a couple of hours, whereas conversion of the detected
intermediate into the final product required several
days. The final product was isolated by precipitation
with hexane after completion of the reaction. Isolation
of the intermediate was likewise feasible since selective
precipitation of this product was observed when the
reaction was carried out in a THF–toluene mixture.
The composition of both compounds was determined
by analytic and spectroscopic studies.
The (+)-Xe-FAB mass spectrum of the final product
displayed a molecular ion peak whose relative mass
(m/e=1014) and isotope pattern is in accord with the
formation of an 1:1 addition product [(3)Cp2Mo2-
(CO)4]. This composition was confirmed by the 1H-,
13C-, and 31P-NMR spectra which showed a set of
signals attributable to co-ordinated 3 together with
further resonances pointing at the presence of two
chemically inequivalent cyclopentadienyl and four in-
equivalent carbonyl moieties. The presence of two
metal atoms with different co-ordination spheres was
further substantiated by the observation of two equally
intense signals in the 95Mo-NMR spectrum (l95Mo=
−1007, −1309). The IR spectrum displayed three
strong bands (w¯ =1952, 1873, 1792 cm−1) attributable
to w(CO) vibrations of terminal carbonyls, thus disclos-
ing as in 7, 8 the absence of bridging CO moieties.
Comparison of the 31P chemical shifts with those of 3
revealed for the phosphorus atom in the Ph2P-moiety a
2.3. Crystal structure studies
The Mn and Re complexes 7, 8 crystallise as solvates
with one molecule of solvent (7: toluene, 8: CH2Cl2) per
formula unit. An ORTEP-style drawing of the molecular
structure of 8 is depicted in Fig. 1 together with selected
bond distances and angles. The molecular structure of 7
deviates not significantly from that of 8, and a separate
illustration has therefore been omitted. Important bond

184
D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
distances and angles are given in brackets together with
the corresponding data of 8 in Fig. 1.
The geometry of the benzophospholide ligand in 7
and 8 is normal and deserves no special comments. The
,
Mn1[Re1]ꢀP1 bond (2.287(3) [2.323(2)] A) involving the
ring phosphorus atom is shorter than the Mn2[Re2]–
,
P2(phosphanyl) bond (2.331(3) [2.457(2)] A). This devi-
ation is attributable to the different formal
hybridisation of the phosphorus atoms and allows no
direct comparison of bond orders. The sum of valence
angles at the ring phosphorus atom P1 (355° in both 7
and 8) indicates a deviation from planar co-ordination
geometry which is larger than in other complexes con-
taining s(P)-co-ordinated phosphonio-benzophospho-
lides (ꢀÚ\358° [8b,13]) but still by far smaller as in
the s-phospholyl complex [CpW(CO)3(h1-PC4Me2)]
(ꢀÚ 320° [14]). The metal co-ordination geometries can
be described as interpenetrating distorted octahedrons
in which the two phosphorus atoms of 3 occupy equa-
torial (with respect to the M–M axis) sites. The equato-
rial ligands at adjacent metal atoms adopt a staggered
conformation similar as in M2(CO)10, [15] but the dihe-
dral angles between corresponding equatorial CO lig-
ands on adjacent metal atoms (38–41° (7), 38–42° (8))
are significantly larger than the P1ꢀMꢀMꢀP2 angles
(29.5° (7), 30.3° (8)). As a consequence, the Mn1[Re1]
atom which carries the benzophospholide unit displays
a more pronounced deviation from regular octahedral
co-ordination geometry than the Mn2[Re2] atom. We
attribute both this distortion and the notable pyrami-
dalisation at the P1 atom to steric interference between
the bulky Ph3P-substituent in 3 with the adjacent axial
CO ligand rather than electronic effects. Comparison of
M–C distances to carbonyl ligands reveals no signifi-
cant differences between the bonding situation at both
metal atoms. This is in accordance with the fact that a
s(P)-co-ordinated zwitterionic phosphonio-benzophos-
pholide should be electronically similar to a phosphane
type ligand [8b]. The metalꢀmetal bonds (Mn1–Mn2
Fig. 1. Molecular structure of 8 in the crystal, ORTEP view thermal
ellipsoids are at the 50% probability level, H atoms omitted for
,
clarity. Selected bond distances (A) (corresponding values for 7 are
given in brackets: Re(1)ꢀRe(2) 3.0365(4) [Mn(1)ꢀMn(2) 2.917(2)],
Re(1)ꢀP(1) 2.423(2) [Mn(1)ꢀP(1) 2.287(3)], Re(1)ꢀC(1A) 1.961(10)
[Mn(1)ꢀC(1A) 1.785(12)], Re(1)ꢀC(1B) 1.929(9) [Mn(1)ꢀC(1B)
1.808(12)],
Re(1)ꢀC(1D) 1.987(9) [Mn(1)ꢀC(1D) 1.772(11)], Re(2)ꢀP(2)
2.4569(19) [Mn(2)ꢀP(2) 2.331(3)], Re(2)ꢀC(2A) 1.966(8)
[Mn(2)ꢀC(2A) 1.723(11)], Re(2)ꢀC(2B) 1.930(8) [Mn(2)ꢀC(2B)
1.788(12)], Re(2)ꢀC(2C) 1.971(9) [Mn(2)ꢀC(2C) 1.773(12)],
Re(1)ꢀC(1C)
1.994(9)
[Mn(1)ꢀC(1C)
1.790(13)],
Re(2)ꢀC(2D) 1.981(9) [Mn(2)ꢀC(2D) 1.783(11)], P(1)ꢀC(2) 1.729(7)
[P(1)ꢀC(2) 1.715(9)], P(1)ꢀC(9) 1.729(7) [P(1)ꢀC(9) 1.743(8)],
C(2)ꢀC(3) 1.445(9) [C(2)ꢀC(3) 1.430(11)], C(3)ꢀC(8) 1.422(9)
[C(3)ꢀC(8) 1.450(11)], C(8)ꢀC(9) 1.469(9) [C(8)ꢀC(9) 1.482(11)]
C(2)ꢀP(2) 1.770(7) [C(2)ꢀP(2) 1.781(9)], C(9)ꢀP(3) 1.748(8) [C(9)ꢀP(3)
1.727(9)].
,
2.917(2) (7), Re1–Re2 3.037(1) A (8)) compare well to
those of the corresponding decacarbonyls [15] (M–M:
,
2.904 (Mn2(CO)10), 3.042 A (Re2(CO)10)).
The dimolybdenum complex 10 crystallises as solvate
with one molecule of THF per formula unit. An ORTEP
-
style representation of the molecular structure is shown
in Fig. 2 together with selected bond distances and
angles.
The absence of a metalꢀmetal bond is clearly evi-
Fig. 2. Molecular structure of 10 in the crystal, ORTEP view thermal
ellipsoids are at the 50% probability level, H atoms omitted for
denced by observation of an Mo1ꢀMo2 distance of
,
,
clarity. Selected bond distances (A) (Z(PC) and Z(cp1,2) denote the
4.409(2) A. The co-ordination environment at the metal
centroids of the P1ꢀC2 bond and the Cp rings on the Mo1 and Mo2
atoms, respectively): Mo(1)ꢀC(1A) 1.930(2), Mo(1)ꢀC(1B) 1.953(2),
Mo(1)ꢀZ(PC) 2.222(1), Mo(1)ꢀZ(cp1) 2.034(1), Mo(2)ꢀP(1) 2.5746(5),
Mo(2)ꢀP(2) 2.4804(5), Mo(2)ꢀC(2A) 1.950(2), Mo(2)ꢀC(2B) 1.969(2),
Mo(2)ꢀZ(cp2) 2.011(1), P(1)ꢀC(9) 1.7944(18), P(1)ꢀC(2) 1.8113(18),
C(2)ꢀC(3) 1.488(2), C(3)ꢀC(8) 1.426(3), C(8)ꢀC(9) 1.459(3), C(2)ꢀP(2)
1.8059(18), C(9)ꢀP(3) 1.7119(18).
atoms can be described as three (Mo1) or four legged
(Mo2) piano-stool geometry, respectively. The distances
between the metal atoms and the centroid of the cy-
,
clopentadienyl rings (CpꢀMo1 2.03, CpꢀMo2 2.01 A)
,
and the carbon atoms of CO ligands (1.93–1.97 A) are
similar for both metal atoms and display no peculiari-

D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
185
Mn2(CO)10 and Re2(CO)10 matches that of 2-phos-
phanyl-substituted phosphinines which was investigated
by Mathey and co-workers [6e]. As there, the phospho-
rus compound acts as bidentate bridging ligand via the
lone-pairs of two phosphorus atoms, and the reaction
stops after substitution of one carbonyl ligand at each
metal atom. Even if the reason for the failure to
observe poly-substituted complexes of similar constitu-
tion as (dppm)2Mn2(CO)5 is not yet totally clear, it may
be argued that the different formal hybridisation of the
ring phosphorus atoms (sp2) as compared to a phos-
phane centre (sp3) renders phosphinine- and phospho-
Scheme 4.
,
ties [16]. The P2ꢀMo2 distance (2.480(1) A) is close to
,
A in complexes [Cp-
the value of 2.4690.09
,
Mo(CO)2(PR3)X] [16]. The P1ꢀMo2 bond (2.575(1) A)
is nearly 10 pm longer and lies near the upper limit of
known bond distances in molybdenum complexes con-
taining m2-bridging phosphides (MoꢀP(m-PR2) 2.306–
nio-benzophospholide
nucleophiles than dppm. The carbonyl stretching fre-
quencies of 7 (w¯ =2054, 1992, 1969, 1946, 1911 cm−1
based
ligands
weaker
)
,
2.689, mean 2.456 A [16]). The distance between Mo2
appear all at lower wavenumbers as those of
[Mn2(CO)8{3,4 - dimethyl - 2 - (3%,4% - dimethyl - 1% - phos-
,
and the centre of the P1ꢀC1 bond (2.222(2) A) is close
to the corresponding distance in [{m2(h1:h2)-Ph-
pholyl)-phosphinine}]
(12)
(w¯ =2059, 1997, 1974,
,
PCMe}Cp2Mo2(CO)2] (2.240 A [17]). The geometry of
1951, 1925 cm−1) [6e], suggesting the zwitterion 3 to
be a less efficient p-acceptor than the phospholyl-phos-
phinine ligand in 12.
the phosphonio-benzophospholide fragment in 10 dif-
fers significantly from those of the k2(P,P%)-co-ordi-
nated ligands in 7, 8 and that of free 3, but resembles
closely that of the h2(p)-co-ordinated bis-phosphonio-
benzophospholide unit in the Co-complex 11. The most
remarkable structural features comprise the pyramidali-
sation at the C2 carbon atom (sum of intraꢀligand
bond angles 326°) which is even more pronounced than
for the corresponding atom in 11 (ꢀÚ 337° [12]), and
the lengthening (relative to 3 [8c]) of the exocyclic
The formation of the molybdenum complex 9 via
co-ordinative addition of 3 to the metalꢀmetal triple
bond in Cp2Mo2(CO)4 still mirrors in a formal sense
the behaviour of 2-phosphanyl-phosphinines [6e], but
differs insofar as the heterocyclic ligand fragment is
bound via the p-electron system and not the phospho-
rus lone-pair. The shift from s(P)- (in 7, 8) to p-co-or-
dination of the benzophospholide unit coincides with
,
P2ꢀC2 (1.806(2) A) and the endocyclic P1ꢀC2 (1.812(2)
an increased p-basicity of the CpMo(CO)2 as com-
−
,
,
,
A), P1ꢀC9 (1.794(2) A), and C2ꢀC3 (1.488(2) A) bonds
pared to an isolobal Mn[Re](CO)4-fragment and paral-
lels the observation of p(PꢂC)-co-ordination of a
bis-phosphonio-substituted benzophospholide to an
electron rich Cobalt atom in 11 [12]. The h2(p)-co-ordi-
nation of the fused ring system implies a partial p-bond
localisation which is presumably facilitated by the com-
paratively low aromatic stabilisation energies in phos-
phonio-benzophospholides [8c,18] and the possibility to
compensate for the loss of resonance energy by in-
creased ylidic character of the exocyclic CꢀP(phos-
phonio) bond [12].
in the phospholide ring.
The discussed structural features suggest that the
bonding situation in 10 may be explained by assuming
that the phosphanyl-benzophospholide 3 binds via the
h2(p)-co-ordinated P1ꢀC2 double bond to the Mo1
atom and via the lone-pairs at the P1 and P2 atoms to
the Mo2 atom. As in the complex 11 [12], the lengthen-
ing of the co-ordinated double bond and the pro-
nounced pyramidalisation at the C2 atom point in the
frame of the Dewar–Chatt–Duncanson model to a
high degree of d(M)“p*(L) charge-transfer and thus
considerable metallacycle character. Taking this into
account, the electronic situation in 10 may be described
in terms of a resonance between two canonical struc-
tures 10% and 10%% (Scheme 4). Presuming that both
metal atoms obey the 18e-rule, the metal atoms in 10%
are then assigned formal oxidation states of −1 (Mo1)
and +1 (Mo2), whereas in 10¦ both metal atoms are
assigned a formal oxidation state of +1, and a formal
reduction of the ligand has taken place.
The rearrangement 9“10 with concomitant cleavage
of the metalꢀmetal bond is unprecedented in the chem-
istry of phosphanyl-phosphinines. Considering the con-
tribution from canonical structure 10%% in the bonding
description, the rupture of the metalꢀmetal bond is
accompanied by a net d(M)“p*(L) charge-transfer, or
in other words, a (partial) reduction of the phosphonio-
benzophospholide moiety. This point being taken into
account, the different reactivities of 3 and phosphanyl-
phosphinines towards complexes with electron rich
metal atoms can be explained by assuming that the
former is more prone to undergo reduction processes.
Even if this argument seems surprising in the light of
the higher p-acceptor character of phosphanyl-phos-
phinines in Mn2(CO)8 complexes (vide supra), the ap-
3. Discussion
The presented results merit some comments. The
observed reactivity of the zwitterion
3 towards

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D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
parent contradiction can be resolved: whereas the rela-
tive p-acceptor powers of ligands bound to metal atoms
of low p-back-donating power (e.g. in 7, 12) are in the
first place determined by the relative LUMO energies,
the situation may change with increasing ex-
tent of M“L charge-transfer under the influence of
different charge-capacities. In this context, the observed
metalꢀmetal bond cleavage in 10 suggests that the
10p-electron system of a phosphonio-benzophospholide
is easier polarisable, and may accommodate a larger
amount of excess electronic charge, than the 6p-elec-
tron system of a phosphinine.
3JP,C=1.8 Hz, 12.1 Hz, C-4], 124.4 [dd, 1JP,C=90.0
3
3
Hz, JP,C=1.5 Hz, i-C(PPh3)], 128.3 [d, JP,C=9.7 Hz,
4
m-C(PPh2)], 129.6 [d, JP,C=1.9 Hz, p-C(PPh2)], 130.0
[d, 3JP,C=12.6 Hz, m-C(PPh3)], 132.2 [d, 2JP,C=9.9
Hz, o-C(PPh2)], 134.0 [d, 4JP,C=2.7 Hz, p-C(PPh3)],
2
1
134.8 [d, JP,C=10.3 Hz, o-C(PPh3)], 135.6 [d, JP,C
=
42.6 Hz, i-C(PPh2)], 141.4 [ddd, 1JP,C=4.3 Hz, 14.7
Hz, JP,C=4.3 Hz, C-3], 147.4 [dd, JP,C=8.2 Hz, 16.3
Hz, C-7a], 147.9 [ddd, JP,C=34.5 Hz, 46.8 Hz, JP,C
3
2
2
3
=
10.4 Hz, C-3a], 220.2 [br, CO], 221.2 [br, CO], 223.4
[br, CO], 224.9 [br, 2CO], 225.9 [br, CO], 227.9 [br,
2CO]. FAB-MS: m/z (%)=913 (10) [M+], 800 (20)
[M+−Mn(CO)4], 745 (20) [M+−Mn(CO)4], 717 (100)
[M+−Mn(CO)5]. IR (CH2Cl2, CaF2): w(CO)=2054,
4. Experimental
1992, 1969, 1946, 1911 cm−1
. Anal. Calc. for
C46H29Mn2O8P3 (912.5): C, 60.55; H, 3.20. Found: C,
60.0; H, 3.2%.
4.1. General remarks
All manipulations were carried out under dry argon.
Solvents were dried by standard procedures. Com-
pound 3 [8b] was prepared as described. NMR spectra:
Bruker AMX300 (1H: 300.1 MHz, 31P: 121.5 MHz, 13C:
75.4 MHz, 95Mo: 19.5 MHz). Chemical shifts were
referenced to ext. Me4Si (1H, 13C), 85% H3PO4 (]=
40.480747 MHz), aq. MO42− (]=6.516926 MHz); pos-
itive signs of chemical shifts denote shifts to lower
frequencies, and coupling constants are given as abso-
lute values. Prefixes i-, o-, m-, p- denote atoms of
phenyl substituents, and atoms in the benzophospholide
ring are denoted as 4-C, 5-H, etc. assignment of reso-
nances were derived in ambiguous cases from analysis
4.1.2. Preparation of octacarbonyl-{v-(3-diphenyl-
phosphino-1-triphenylphosphonio-benzo[c]phospholide)-
1sP,2sP%}dirhenium (ReꢀRe) (8)
A mixture of 200 mg (0.33 mmol) of 3 and 220 mg
(0.34 mmol) of Re2(CO)10 was dissolved in 10 ml of
p-xylene in a 25 ml Schlenk tube and refluxed for 18 h.
The resulting brownish–yellow solution was then
cooled to ambient temperature and stored in a refriger-
ator at 2 °C. A yellow crystalline precipitate formed
which was collected by filtration, washed with little cold
pentane, and dried in high vacuum. Yield: 380 mg (0.32
1
mmol, 97%), m.p. 281 °C (dec.). H-NMR (THF-d8):
6.44–6.68 [4 H, 4-H to 7-H], 7.3–8.1 [25 H, C6H5].
1
2
of 2D H,13C-HMQC and HMBC NMR spectra. MS:
31P{1H}-NMR (THF-d8): 157.4 [dd, JP,P=166.6, 57.9
Kratos Concept 1H, Xe-FAB, m-NBA matrix. FT-IR
spectra: Nicolet Magna 550, in CH2Cl2 solution. Ele-
mental analyses: Heraeus CHNO-Rapid. Melting
points were determined in sealed capillaries.
Hz, P-2], 13.9 [dd, 2JP,P=166.6 Hz, 4JP,P=7.6 Hz,
–P+Ph3], −22.5 [dd, 2JP,P=57.9 Hz, 4JP,P=7.6 Hz,
1
PPh2]. 13C{1H}-NMR (THF-d8): 93.4 [ddd, JP,C=13.2
3
3
Hz, 104.0 Hz, JP,C=3.2 Hz, C-1], 119.2 [dd, JP,C
=
=
4
4.4 Hz, 5.2 Hz, C-4], 119.7 [s, C-5/6], 120.4 [d, JP,C
3
4.1.1. Preparation of octacarbonyl-{v-(3-diphenyl-
phosphino-1-triphenylphosphonio-benzo[c]phospholide)-
1sP,2sP%}dimanganese (Mn–Mn) (7)
2.9 Hz, C-5/6], 120.9 [d, JP,C=2.4 Hz, C-7], 124.2 [dd,
1JP,C=90.2 Hz, 3JP,C=1.9 Hz, i-C(PPh3)], 128.4 [d,
3JP,C=10.1 Hz, m-C(PPh2)], 129.8 [d, JP,C=2.1 Hz,
4
A mixture of 200 mg (0.33 mmol) of 3 and 150 mg
(0.38 mmol) of Mn2(CO)10 was dissolved in 9 ml of
toluene in a 25 ml Schlenk tube and refluxed for 6 h.
The resulting red solution was then cooled to ambient
temperature and stored in a refrigerator at 2 °C. An
orange crystalline precipitate formed which was col-
lected by filtration, washed with little cold toluene, and
dried in high vacuum. Yield: 280 mg (0.31 mmol, 94%),
p-C(PPh2)], 130.0 [d, 3JP,C=12.6 Hz, m-C(PPh3)], 132.2
2
4
[d, JP,C=10.7 Hz, o-C(PPh2)], 134.1 [d, JP,C=2.9 Hz,
p-C(PPh3)], 134.9 [d, JP,C=10.3 Hz, o-C(PPh3)], 136.6
2
1
3
[dd, JP,C=47.2 Hz, JP,C=8.7 Hz, i-C(PPh2)], 143.5
[ddd, 2JP,C=7.3 Hz, 2.1 Hz, 3JP,C=14.7 Hz, C-3a],
2
146.7 [dd, JP,C=8.7 Hz, 17.2 Hz, C-7a], 148.9 [ddd,
1JP,C=56.0 Hz, 54.7 Hz, 3JP,C=10.1 Hz, C-3], 189.3 [d,
2JP,C=6.7 Hz, CO], 190.4 [d, 2JP,C=7.4 Hz, CO], 195.6
[dd, 2JP,C=45.6 Hz, 3JP,C=5.3 Hz, CO], 197.2 [dd,
1
m.p. 252 °C (dec.). H-NMR (THF-d8): 6.40–6.60 [4
H, 4-H to 7-H], 7.06–8.12 [25 H, C6H5]. 31P{1H}-NMR
2JP,C=58.8 Hz, JP,C=1.7 Hz, CO], 198.2 [dd, JP,C
=
3
2
2
3
2
(THF-d8): 228.6 [dd, JP,P=170.2, 57.2 Hz, P-2], 13.9
13.0 Hz, JP,C=2.3 Hz, 2 CO], 202.9 [dd, JP,C=9.6
2
4
3
[dd, JP,P=170.2 Hz, JP,P=8.3 Hz, ꢀP+Ph3], 35.5 [dd,
Hz, JP,C=4.5 Hz, 2 CO]. FAB-MS: m/z (%)=1176
2JP,P=57.2 Hz, JP,P=8.3 Hz, PPh2]. 13C{1H}-NMR
(THF-d8): 98.5 [ddd, JP,C=15.3 Hz, 103.1 Hz, JP,C
6.4 Hz, C-1], 118.9 [dd, JP,C=4.3, 4.3 Hz, C-7], 119.6
[s, C-5/6], 119.9 [d, JP,C=2.5 Hz, C-5/6], 120.4 [dd,
(100) [M+]; 1064 (50) [M+−4CO]. IR (CH2Cl2, NaCl):
4
1
3
=
w(CO)=2069, 2017, 1983, 1975, 1951, 1907 cm−1
.
3
Anal. Calc. for C46H292O8P3Re (1175.1): C, 50.62; H,
3.07. Found: C, 50.06; H, 3.08%.
4

D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
187
4.1.3. Preparation of complex 9
4.1.4. Preparation of [v-(3-diphenylphosphino-1-
A mixture of 200 mg (0.33 mmol) of 3 and 150 mg
(0.33 mmol) of Cp2Mo2(CO)4 was dissolved in 2 ml of
THF and 10 ml of toluene in a 25 ml Schlenk tube and
stirred for 56 h at ambient temperature. The resulting
red crystalline precipitate was collected by filtration,
washed with hexane, and dried in high vacuum. Yield:
210 mg (0.21 mmol, 64%), m.p. 199 °C (dec.). 1H-
NMR (THF-d8): 4.56 [s, 5H, Cp], 4.65 [s, 5H, Cp],
triphenylphosphonio-benzo[c]phospholide)-1s2P,P%,2s-
(p2-PꢂC)-bis-(p5-cyclopentadienyl–dicarbonyl–
molybdenum)] (10)
A mixture of 200 mg (0.33 mmol) of 3 and 150 mg
(0.33 mmol) of Cp2Mo2(CO)4 was dissolved in 10 ml of
THF in a 25 ml Schlenk tube and stirred for 4 days at
ambient temperature. The resulting mixture was filtered
and the filtrate evaporated in vacuum. The residue was
dissolved in 3 ml of THF and the solution layered with
20 ml of hexane. A dark brown precipitate formed
slowly which was collected by filtration, and dried in
high vacuum. Complex 10 was likewise formed in quan-
titative yield (by 31P-NMR spectroscopy) when a THF
solution of 9 was stirred for 24 h at ambient tempera-
ture. Yield: 250 mg (0.25 mmol, 76%), m.p. 208 °C
6.3–6.7 [4 H, 4-H to 7-H], 7.0–8.1 [25 H, C6H5].
31P{1H}-NMR (THF-d8, −20 °C): 89.7 [dd, JP,P
=
2
189.5 Hz, 97.9 Hz, P-2], 32.5 [dd, 2JP,P=189.5 Hz,
4JP,P=3.5 Hz, –PPh2], −16.0 [dd, 2JP,P=97.9 Hz,
4JP,P=3.5 Hz, –P+Ph3]. 95Mo-NMR (THF): −1001,
−1514. FAB-MS: m/z (%)=1014 (100) [M+]. IR
(CH2Cl2, NaCl): w(CO)=1969, 1911, 1867 cm−1
.
Table 1
Crystallographic data, structure solution and refinement parameters of 7, 8, and 10
7
8
10
Empirical formula
Formula weight
Temperature (K)
C46H29Mn2O8P3·1/2toluene
958.55
123(2)
C46H292O8P3Re·CH2Cl2
1259.93
123(2)
C52H39Mo2O4P3·THF
1084.73
123(2)
,
Wavelength (A)
0.71073
Monoclinic
P21/c (No.14)
0.71073
Monoclinic
P21/c (No.14)
0.71073
Triclinic
Crystal system
Space group
(
P1 (No.2)
Unit cell dimensions
,
a (A)
12.815(1)
24.678(3)
14.989(2)
13.0944(7)
24.6514(13)
15.0265(7)
11.2592(2)
11.4543(2)
19.5723(3)
84.923(1)
83.897(1)
68.871(1)
2337.70(7)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
112.59(1)
113.678(3)
3
,
4376.6(9)
4
1.455
0.74
1956
4442.2(4)
4
1.884
0.74
Z
zcalc. (g cm−3
)
1.541
0.69
1104
v (mm−1
F(000)
)
2424
Dimensions (mm)
Diffractometer
Radiation
0.40×0.10×0.02
Nonius Kappa CCD
Mo–Ka
45.0
0.20×0.10×0.03
Nonius Kappa CCD
Mo–Ka
0.35×0.20×0.10
Nonius Kappa CCD
Mo–Ka
2q max. (°)
50.0
50.0
−135h511
−235k526
−125l516
20 481
5705
0.201
−155h513
−205k529
−175l517
25 432
7773
0.099
−135h513
−135k512
−235l523
30 137
8212
0.041
Measured data
Unique data
Rint
Absorption correction
None
Empirical from multiple
reflections
F2
559/0
0.038
Empirical from multiple
reflections
F2
595/6
0.024
Refinement method
Parameters/restraints
Final R indices [I\2|(I)]
R indices (all data)
F2
549/7
0.072
0.166
0.072
0.063
Max./min. difference peak
0.43 and −0.53
1.95 and −1.12
−0.58 and −0.55
−3
,
(e A
)

188
D. Gudat et al. / Journal of Organometallic Chemistry 643–644 (2002) 181–188
1
(dec.). H-NMR (THF-d8): 4.74 [s, 5H, Cp], 5.25 [d,
3JP,H=0.7 Hz, 5H, Cp], 6.01 [m, 1H, 4/7-H], 6.18 [m,
1H, 5/6-H], 6.26 [m, 1H, 5/6-H], 6.58 [m, 1H, 4/7-H],
6.70–8.26 [25 H, C6H5]. 13C{1H}-NMR (THF-d8): 55.5
[ddd, 1JP,C=24.7 Hz, 24.7 Hz, 3JP,C=5.1 Hz, C-3],
Acknowledgements
Financial support by the Deutsche Forschungsge-
meinschaft is gratefully acknowledged.
1
60.3 [dd, JP,C=22.0 Hz, 110.9 Hz, C-1], 91.6 [s, Cp],
92.7 [dd, JP,C=5.3 Hz, 0.7 Hz, Cp], 117.0 [s, C-4/7],
References
2
118.6 [dd, JP,C=4.1 Hz, 4.1 Hz, C-4/7], 122.4 [s, C-5/6],
125.5 [s, C-5/6], 147.7 [ddd, JP,C=9.7 Hz, 7.1 Hz, 12.0
[1] F. Mathey, Coord. Chem. Rev. 137 (1994) 1.
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2
Hz, C-3a], 148.5 [dd, JP,C=2.7 Hz, 17.7 Hz, C-7a],
233.9 [dd, 2JP,C=10.8 Hz, 2.6 Hz, CO], 241.5 [d,
2JP,C=20.6 Hz, CO], 250.1 [dd, 2JP,C=33.8 Hz, 2.5 Hz,
2
CO], 256.3 [d, JP,C=32.8 Hz, CO]; signals attributable
to C6H5 groups could not be unambiguously assigned
due to severe dynamic broadening, presumably owing
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2
(THF-d8): −118.1 [dd, JP,P=67.1 Hz, 53.1 Hz, P-2],
2
4
37.3 [dd, JP,P=67.1 Hz, JP,P=2.5 Hz, –PPh2], 11.7
[dd, 2JP,P=53.1 Hz, 4JP,P=2.5 Hz, –P+Ph3]. 95Mo-
NMR (THF): −1007, −1309. FAB-MS: m/z (%)=
1014 (100) [M+]. IR (CH2Cl2, NaCl): w(CO)=1952,
1873, 1792 cm−1. Anal. Calc. for C52H39Mo2O4P3
(1012.7)·hexane: C, 63.40; H, 4.86. Found: C, 63.70; H,
4.95%.
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4.1.5. Crystal structure determinations of complexes 7, 8,
and 10
Single crystals of 7×0.5 toluene, 8×CH2Cl2, and
10×THF were grown from toluene–CH2Cl2 (7, 8) or
toluene–THF (10) solutions. The diffraction data were
collected on a Nonius Kappa CCD diffractometer at
−150 °C using Mo–Ka radiation. The structures were
solved by direct methods (SHELXS-97 19a). The non-hy-
drogen atoms were refined anisotropically, H atoms
were refined using a riding model (full-matrix least-
(b) D. Gudat, S. Ha¨p, L. Szarvas, M. Nieger, Chem. Commun.
(2000) 1637;
(c) S. Ha¨p, L. Szarvas, M. Nieger, D. Gudat, Eur. J. Inorg. Chem.
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2269.
squares refinement on F2
(SHELXL-97 [19b]). The sol-
vent molecule in the crystal structure of 7 is disordered.
Details of data collection and refinement are given in
Table 1.
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5. Supplementary material
Crystallographic data (excluding structure factors)
for the structures reported in this work have been
deposited with the Cambridge Crystallographic Data
Centre as publication no. CCDC 164401 (7), CCDC
164402 (8), and CCDC 164403 (10), respectively.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
[16] A quest in the CCSD database for molecules containing the frag-
ment {CpMo(CO)2(PR3)} yielded the following average distance
ranges
:
Mo–Cp(centroid) 2.0190.015, Mo–C(carbonyl)
,
1.96090.036, Mo–P 2.4690.09 A.
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mun. (1999) 2455.
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therein.
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many, 1997.