Reactions of the tetrafluoroborate complex [Mo2Cp 2(k2-F2BF2)(μ-PPh 2)2(CO)]BF4 with mono- and bidentate ligands having E-H bonds (E = O, S, Se, N, P)

Article abstract of DOI:10.1021/ic300626y

The title compound reacted rapidly with CN^tBu at room temperature by displacing the BF₄^- ligand and incorporating three molecules of isocyanide to yield the electron-precise complex [Mo₂Cp₂(μ-PPh₂)₂(CN ^tBu)₃(CO)](BF₄)₂, which was obtained as a mixture of cis and trans isomers. Reaction with several HER_n molecules (HER_n = HSPh, HSePh, H₂PCy) took place with formal elimination of HBF₄ and spontaneous carbonylation to give the electron-precise cations [Mo₂Cp₂(μ-ER _n)(μ-PPh₂)₂(CO)₂]⁺. Reactions with several bidentate ligands (L₂H) having acidic E-H bonds (2-hydroxypyridine, 2-mercaptopyridine, cathecol, 2-aminophenol, and 2-aminothiophenol) proceeded analogously with deprotonation of these bonds with the preference E = S > O > N. The N,O-donor ligands yielded 32-electron chelate derivatives of the type [Mo₂Cp₂(O,N-L ₂)(μ-PPh₂)₂(CO)]BF₄ (L ₂ = OC₅H₄N, OC₆H₄NH ₂), whereas the S,N-donors yielded 34-electron, S-bridged complexes [Mo₂Cp₂(μ-S:S,N-L₂)(μ-PPh ₂)₂(CO)]BF₄ [L₂ = SC ₅H₄N (Mo-Mo = 2.8895(8) A), SC₆H ₄NH₂]. However, reaction with catechol gave a monodentate derivative [Mo₂Cp₂(O-OC₆H₄OH)(μ- PPh₂)₂(CO)]BF₄. In contrast, reactions of the title complex with several carboxylic acids and related species (acetic, benzoic, and thioacetic acids, acetamide, thioacetamide, and sodium diethyldithiocarbamate) were insensitive to the nature of the donor atoms and gave in all cases 32-electron chelate derivatives of type [Mo₂Cp ₂(k²-L₂)(μ-PPh₂) ₂(CO)]BF₄. All of the above cations having Mo-bound OH, NH, or NH₂ groups were easily deprotonated upon reaction with 1,8-diazabicycloundec-7-ene (DBU) or other bases to give neutral complexes which exhibited different coordination motifs depending on the donor atoms, including chelate complexes of the type [Mo₂Cp₂(k ²-L₂′)(μ-PPh₂)₂(CO)] (L₂′ = OC₆H₄O, OC₆H ₄NH), the bridged complexes [Mo₂Cp₂(μ-S,N:S, N-SC₆H₄NH)(μ-PPh₂)₂] and [Mo ₂Cp₂{μ-S,N-N(S)CMe}(μ-PPh₂)₂], and the terminal acetylimido complex [Mo₂Cp₂{N-N(O)CMe} (μ-PPh₂)₂(CO)].

Full text of DOI:10.1021/ic300626y

Article
pubs.acs.org/IC
Reactions of the Tetrafluoroborate Complex [Mo2Cp2(κ2-F2BF2)(μ-
PPh2)2(CO)]BF4 with Mono- and Bidentate Ligands Having E−H bonds
(E = O, S, Se, N, P)
Fernanda Cimadevilla,† M. Esther García,† Daniel García-Vivo,† Miguel A. Ruiz,*,† Claudia Graiff,‡
́
and Antonio Tiripicchio‡
†Departamento de Química Organ
́ ́
ica e Inorganica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain
‡Dipartimento di Chimica Generale e Inorganica, Chimica Analitica Chimica Fisica, Universita
I-43100 Parma, Italy
̀
di Parma, Viale delle Scienze 17/A,
S
* Supporting Information
ABSTRACT: The title compound reacted rapidly with CNtBu at room
temperature by displacing the BF4− ligand and incorporating three molecules
of isocyanide to yield the electron-precise complex [Mo2Cp2(μ-
PPh2)2(CNtBu)3(CO)](BF4)2, which was obtained as a mixture of cis and
trans isomers. Reaction with several HERn molecules (HERn = HSPh, HSePh,
H2PCy) took place with formal elimination of HBF4 and spontaneous
carbonylation to give the electron-precise cations [Mo2Cp2(μ-ERn)(μ-
PPh2)2(CO)2]+. Reactions with several bidentate ligands (L2H) having acidic
E−H bonds (2-hydroxypyridine, 2-mercaptopyridine, cathecol, 2-amino-
phenol, and 2-aminothiophenol) proceeded analogously with deprotonation
of these bonds with the preference E = S > O > N. The N,O-donor ligands
yielded 32-electron chelate derivatives of the type [Mo2Cp2(O,N-L2)(μ-PPh2)2(CO)]BF4 (L2 = OC5H4N, OC6H4NH2), whereas the
S,N-donors yielded 34-electron, S-bridged complexes [Mo2Cp2(μ-S:S,N-L2)(μ-PPh2)2(CO)]BF4 [L2 = SC5H4N (Mo−Mo =
2.8895(8) Å), SC6H4NH2]. However, reaction with catechol gave a monodentate derivative [Mo2Cp2(O-OC6H4OH)(μ-
PPh2)2(CO)]BF4. In contrast, reactions of the title complex with several carboxylic acids and related species (acetic, benzoic, and
thioacetic acids, acetamide, thioacetamide, and sodium diethyldithiocarbamate) were insensitive to the nature of the donor atoms and
gave in all cases 32-electron chelate derivatives of type [Mo2Cp2(κ2-L2)(μ-PPh2)2(CO)]BF4. All of the above cations having Mo-bound
OH, NH, or NH2 groups were easily deprotonated upon reaction with 1,8-diazabicycloundec-7-ene (DBU) or other bases to give
neutral complexes which exhibited different coordination motifs depending on the donor atoms, including chelate complexes of the
type [Mo2Cp2(κ2-L2′)(μ-PPh2)2(CO)] (L2′ = OC6H4O, OC6H4NH), the bridged complexes [Mo2Cp2(μ-S,N:S,N-SC6H4NH)(μ-
PPh2)2] and [Mo2Cp2{μ-S,N-N(S)CMe}(μ-PPh2)2], and the terminal acetylimido complex [Mo2Cp2{N-N(O)CMe}(μ-
PPh2)2(CO)].
Chart 1
INTRODUCTION
■
Organometallic compounds having weakly coordinating anions
−
−
−
(i.e., BF4 , PF6 , AsF6 , etc.) have been the subject of intense
research during the last decades mainly due to their use as
starting materials in synthetic organometallic chemistry1 or as
catalyst precursors.2 The reactivity of these complexes is
generally dominated by displacement of the coordinated anion
by other suitable ligands, a process typically taking place readily
under mild conditions. Recently, we reported the synthesis of
the unsaturated tetrafluoroborate complex [Mo2Cp2(κ2-F2BF2)-
(μ-PPh2)2(CO)]BF4 (1)3,4 (Chart 1) through a double
protonation process of the readily available oxo complex
[Mo2Cp2(O)(μ-PPh2)2(CO)].5 In the context of our studies
on the reactivity of highly electrophilic cations having metal−
metal multiple bonds,6 complex 1 seemed an ideal substrate to
further analyze the chemistry of these versatile but relatively
unexplored molecules, since it exhibits an uncommon
combination of features inducing electrophilic behavior: a
metal−metal double bond, a positive charge, and, above all, a
weakly coordinating anion occupying two coordination
positions. In fact, some preliminary experiments revealed that
complex 1 would easily undergo displacement of the
coordinated tetrafluoroborate ligand by nitriles, thus behaving
as a useful synthetic precursor of the highly unsaturated (28-
electron) cation [Mo2Cp2(μ-PPh2)2(CO)]2+, with an effective
Received: March 24, 2012
Published: June 20, 2012
© 2012 American Chemical Society
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deficiency of three vacant positions and six electrons. Of
particular interest was also the observation that 1 would readily
react with acetylacetone at room temperature to yield the
acetylacetonate derivative [Mo2Cp2(κ2-acac)(μ-PPh2)2(CO)]-
BF4,3 a process requiring activation of the relatively acidic C−H
bond of the organic molecule and presumably the release of
hydrated HBF4.
all attempts to isolate them as crystalline materials led to
their cocrystallization. Yet, the spectroscopic data obtained
from these mixtures (Table 1 and Experimental Section) were
Table 1. Selected IR and 31P{1H} NMR Data for New
Cationic Complexes
a
b
compound
ν(CO)
δP (JPP)
In this paper we analyze in detail the reactivity of complex 1
not only when faced with simple neutral donors (CO, CNR)
but also when confronted with monodentate ligands having E−H
bonds of different acidity (thiols, phosphines, etc.). Given the
κ2 coordination of the tetrafluoroborate ligand in 1 it was
also of interest to examine the reactions of this complex with
several bidentate ligands, and we thus studied the reactions
of 1 with simple organic molecules having donor groups
common in many biological molecules (OH, SH, NH2). As it
will be discussed, the presence of acidic E−H bonds in all these
molecules greatly facilitates their reactions with 1, but the
structures of the resulting complexes are strongly influenced by
the nature of the ligand (bidentate or monodentate) and of the
donor atoms (particularly the presence of S-donor centers)
involved in coordination to the dimetal center.
[Mo2Cp2(κ2-F2BF2)(μ-
PPh2)2(CO)]BF4 (1)
1921 (vs) 181.5
c
d
[Mo2Cp2(μ-PPh2)2(CNtBu)3(CO)] 1991 (w) 161.4, 144.7 (47)
(BF4)2 (cis-2)
[Mo2Cp2(μ-PPh2)2(CNtBu)3(CO)]
(BF4)2 (trans-2)
188.2, 178.6 (47)
[Mo2Cp2(μ-SPh)(μ-PPh2)2(CO)2] 2020 (vs) 102.5, 61.9 (77)
BF4 (3a)
[Mo2Cp2(μ-SePh)(μ-
PPh2)2(CO)2]BF4 (3b)
2019 (vs) 103.5, 70.2 (75)
[Mo2Cp2(μ-PHCy)(μ-
PPh2)2(CO)2]BF4 (3c)
2002 (vs) 75.4 (24, 94), 62.1 (94, 94),
e
42.5 (24, 94)
[Mo2Cp2(O,N-OPy)(μ-
PPh2)2(CO)]BF4 (4)
1914 (vs) 193.6, 177.8 (4)
1882 (vs) 183.5, 171.1 (6)
1989 (vs) 131.1, 105.1 (61)
1971 (vs) 129.2, 94.1 (67)
1918 (vs) 184.3
[Mo2Cp2{O,N-OC6H4NH2}(μ-
PPh2)2(CO)]BF4 (5)
[Mo2Cp2(μ-S:S,N-SPy)(μ-
PPh2)2(CO)]BF4 (6)
RESULTS AND DISCUSSION
■
[Mo2Cp2(μ-S:S,N-SC6H4NH2(μ-
PPh2)2(CO)]BF4 (7)
Reactions of Compound 1 with CO and CNtBu. In our
preliminary study we found that complex 1 would dissolve at
room temperature in acetonitrile or benzonitrile with full
displacement of the tetrafluoroborate ligand to yield unstable
electron-precise tris(nitrile) complexes [Mo2Cp2(μ-PPh2)2-
(CO)(NCR)3](BF4)2 (R = Me, Ph).3 We thus anticipated
that other simple donors such as CO or isocyanides would
react analogously. Indeed, addition of CNtBu to solutions
of complex 1 at room temperature led rapidly to the
tris(isocyanide) complex [Mo2Cp2(μ-PPh2)2(CNtBu)3(CO)]-
(BF4)2 (2), obtained as a mixture of cis and trans isomers
(Chart 2). Rather surprisingly, however, complex 1 failed to
[Mo2Cp2(O,O′-O2CPh)(μ-
PPh2)2(CO)]BF4 (8d)
[Mo2Cp2(O,O′-O2CMe)(μ-
PPh2)2(CO)]BF4 (8e)
1915 (vs) 184.6
[Mo2Cp2{O,S-S(O)CMe}(μ-
PPh2)2(CO)]BF4 (8f)
1914 (vs) 190.8, 179.3 (5)
1912 (vs) 185.0, 177.3 (6)
1906 (vs) 185.2
[Mo2Cp2{O,N-NH(O)CMe}(μ-
PPh2)2(CO)]BF4 (8g)
[Mo2Cp2(S,S′-S2CNEt2(μ-
PPh2)2(CO)]BF4 (8h)
[Mo2Cp2{S,N-NH(S)CMe}(μ-
PPh2)2(CO)]BF4 (8i)
1911 (vs) 182.9, 182.7 (3)
[Mo2Cp(O-OC6H4OH)(μ-
PPh2)2(CO)]BF4 (9)
1908 (vs) 187.2
a
b
Recorded in CH2Cl2 solution, data in cm−1. Recorded at room
Chart 2
c
temperature in CD2Cl2 solutions at 121.50 MHz. Data taken from
ref 3. ν (CN): 2164 (vs), 2150 (vs), 2131 (vs). Resonance
corresponding to the PHCy ligand, JHP = 402 Hz.
d
e
informative enough to give support to the proposed structures,
which can be compared to those of the nitrile derivatives of 1
mentioned above and to those of the thiolate-bridged nitrile
complexes [Mo2Cp2(μ-SPh)(CO)4−x(NCR)x]2+ (x = 0, 1, 2;
R = Me, Ph).7 Incorporation of three isocyanide molecules in
both isomers was clearly evidenced by the number and intensity
t
of the resonances corresponding to the Bu groups in the
corresponding 1H NMR spectra. The major isomer presumably
retains the cisoid arrangement of the Cp ligands found in
precursor 1 (incidentally, the unique isomer observed for the
mentioned nitrile complexes), while the minor isomer would
display a transoid arrangement of these ligands (Chart 2).
Although the cis isomers seem to be the favored structures in
the mentioned dicationic complexes of the type [Mo2Cp2(μ-
SPh)(CO)4−x(NCR)x]2+,7 we note that cis/trans isomerism has
been previously observed in related isoelectronic but neutral
complexes of the type [Mo2Cp2(μ-H)(μ-SR)(CO)4]8 and
[Mo2Cp2(μ-H)(μ-PRR′)(CO)4].9
react with CO (by bubbling the gas (1 atm) through a dichloro-
methane solution of the complex, an observation that we
attribute, at least in part, to the low concentration of gas
actually present in the solution.
The ratio of isomers of complex 2 obtained in the above
reaction was somewhat dependent on the experimental
conditions but remained reproducibly at ca. cis/trans = 4
when using stoichiometric amounts (3 equiv) of isocyanide.
Unfortunately, we were unable to separate these isomers, and
Reactions of Compound 1 with HERn Molecules. The
tetrafluoroborate complex 1 reacts rapidly at room temperature
with PhSH, PhSeH, or PH2Cy to yield the new dicarbonyl
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complexes [Mo2Cp2(μ-ERn)(μ-PPh2)2(CO)2]BF4 [ERn = SPh
(3a), SePh (3b), PHCy (3c)] (Chart 2) in moderate yields.
Formation of these products necessarily follows from a
HSePh, H2PCy) is necessarily a multistep process. The
formation and geometry of the products can be rationalized by
assuming that the first step would be coordination of the
incoming ligand, possibly facilitated by a reduction in the
hapticity of the chelate tetrafluoroborate anion (A in Scheme 1),
−
multistep process involving displacement of the BF4 ligand
by the incoming molecule, activation of the E−H bond, release
of a proton, and spontaneous carbonylation to reach electronic
saturation (this requiring partial decomposition of some of the
unsaturated intermediates formed, see below). However, none
of the corresponding intermediate species could be detected in
these reactions. Expectedly, these complexes could be prepared
in better yields when the reactions were carried out under a CO
atmosphere.
Scheme 1
The IR spectra of complexes 3a−c in solution display just
one band shifted to frequencies significantly higher (by ca. 100 cm−1)
than that of the starting complex 1. This is consistent with the
presence of a cisoid M2(CO)2 oscillator in a cationic complex
having almost parallel CO ligands, for which the asymmetric
C−O stretch (at lower frequency) is expected to be of low to
negligible intensity.10 Indeed, this low-intensity band can be
observed as a shoulder of the symmetric stretch in the solid-
state IR spectra of these complexes when recorded in a Nujol
mull (see the Experimental Section).
The inequivalent PPh2 ligands in compounds 3 give rise to
two strongly coupled 31P NMR resonances [JPP = 77 (3a), 75
(3b), and 94 Hz (3c), Table 1], which is indicative of a relative
cisoid arrangement of these groups, if we take into account the
this being followed by release of a proton and the tetrafuoroborate
anion, most likely in the form of hydrated HBF4 (it should be
recalled that the solid material used for preparative purposes
actually is an hydrated phase of complex 1),4 to yield unsaturated
intermediates B which have not been detected (Scheme 1). We
must note that intermediates B are isostructural and isoelectronic
to the known hydroxo complexes [M2Cp2(OH)(μ-PPh2)2(CO)]+
(M = Mo, W), the latter being rather unstable cations which at
room temperature undergo spontaneous isomerization involving
cleavage of the O−H bond to yield the oxohydrides [M2Cp2(μ-
H)(O)(μ-PPh2)2(CO)]+.3,6f Obviously, the evolution of the
intermediates B to reduce its coordinative deficiency cannot
proceed analogously, since this would now require activation of
the more inert E−C or C−H bonds; instead, these intermediates
would undergo a spontaneous carbonylation followed by a
rearrangement of the ERn ligand into a bridging coordination
mode, then yielding the final products 3, which are both
electronically and coordinatively saturated. All this can take place
in the region of the space originally occupied by the chelate
tetrafluoroborate ligand and thus leads naturally to isomers having
the original PPh2 ligands placed in a cisoid arrangement. Finally,
we note that the carbonylation step is obviously possible only once
some of the above intermediates decompose, thus liberating the
required CO molecules. In agreement with this, addition of CO to
the reaction mixture led to improved yields of compounds 3.
Obviously, the use of bidentate ligands would likely suppress the
above spontaneous carbonylation, as discussed next.
Reaction of Compound 1 with Bidentate Ligands. The
tetrafluoroborate complex 1 reacts readily with a variety of
bidentate ligands combining O-, S-, and N-donor centers of
different nature: We studied two broad classes of ligands: (i)
molecules having an aromatic carbon skeleton, such as 2-
substituted pyridines and ortho-substituted phenols and
thiophenols, and (ii) carboxylic acids and related species,
including amides (Chart 3).
Reactions of 1 with the “aromatic” molecules (excluding
catechol, with a singular behavior to be discussed later on), take
place rapidly (5−30 min) at room temperature to yield the new
monocarbonyl derivatives 4−7 (Chart 4), which were isolated
2
general trends established for JXY in complexes of the type
[MCpXYL2] (|Jcis| > |Jtrans|).11 This is further supported by the
observation of quite different P−C couplings (JCP = 12, 4 Hz)
for the 13C NMR carbonyl resonance of complex 3a, which are
thus identified as cisoid and transoid couplings respectively. In
the case of compound 3c, the PPh2 resonances are
accompanied by a third resonance corresponding to the
cyclohexylphosphide ligand, which is easily identified in the
proton-coupled 31P NMR spectrum because of its large P−H
coupling (δ 42.5 ppm, JHP = 402 Hz). This resonance, as is the
case of one of the PPh2 resonances, displays one large (cisoid)
and one small (transoid) coupling (JPP = 94, 24 Hz), whereas
the second PPh2 ligand displays a large (cisoid) and identical
coupling (JPP = 94 Hz) to the other P nuclei. This explicitly
reveals that the PHCy group is part of the central flat Mo2P2
ring of the molecule. The proposed structure for compounds 3
is thus identical to that crystallographically determined for the
ditungsten complex [W2Cp2(μ-COMe)(μ-PPh2)2(μ-dmpm)]+
[dmpm = Me2PCH2PMe2]12 if we just replace the carbyne
ligand with the isoelectronic PHCy group and the dmpm ligand
with two CO ligands. The alternative arrangement of bridging
ligands for 3, that is, one with both PPh2 groups defining the
flat Mo2P2 ring of the cation, would be itself a sensible
alternative: for instance, this is the arrangement crystallo-
graphically determined for the dicarbonyl cations [W2Cp2(μ-X)-
(μ-PPh2)2(CO)2]+ (X = COMe,12 H),13 presumably more
favored on steric grounds, since it implies that the bulky PPh2
groups are positioned away from each other. The fact that this
isomer is not observed for compound 3c surely has a kinetic
origin (see below). We finally note that two conformers are
possible in each case for compounds 3a−c, depending on the
relative positioning (syn or anti) of the Ph or Cy substituents of
the new bridging ligand with respect to the closest PPh2 ligand.
Presumably, the observed molecules are anti conformers, more
favored on steric grounds.
Reaction Pathways in Formation of Complexes 3. As
noted above, reaction of 1 with H−ERn molecules (HERn = HSPh,
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analogous product [Mo2Cp2(S,S′-S2CNEt2)(μ-PPh2)2(CO)]-
BF4 (8h). The latter reaction illustrates a different approach
to the reactivity of 1, namely, nucleophilic substitution of the
chelate tetrafluoroborate ligand by a chelating bidentate anion
without any further structural change. This approach, however,
has a serious limitation: coordination of the added anion has to
compete with its protonation by the water molecules always
present in solutions of complex 1.4 When the latter process
dominates, then hydroxide ions are formed; these in turn
rapidly react with 1 to give the oxo complex [Mo2Cp2(O)(μ-
PPh2)2(CO)] (incidentally, the synthetic precursor of 1).3
Actually, this was the only observed reaction when using
strongly basic anions such as alkoxides (OR−), acetylides
(RCC−), and related species.
Chart 3
Chart 4
We note the different structures of complexes 6 and 8i, even
if both of them have S- and N-donor atoms separated by an sp2-
hybridized carbon atom. We attribute this structural difference
to the distinct spatial distribution of thr lone electron pairs at
the S atom in each case (Chart 5). In complex 6 the tetrahedral
Chart 5
distribution of pairs around the S atom facilitates its
coordination to the second metal center. However, in the
carboxylic complex 8i there is a delocalized π-bonding
interaction along the S−C−N chain involving one of the sulfur
electron pairs, then implying a trigonal distribution of the
remaining pairs around the S atom. This leaves just a
nonbonding pair at sulfur pointing away from the second
metal center, thus preventing the ligand from acting efficiently
as an S-bridging group.
as microcrystalline solids in high yields. These can be grouped
in two different structural types which seem to be dictated by
the nature of the donor atoms present. Thus, in the complexes
containing only N- and O-donor atoms, namely, [Mo2Cp2-
(O,N-OPy)(μ-PPh2)2(CO)]BF4 (4) and [Mo2Cp2(O,N-
OC6H4NH2)(μ-PPh2)2(CO)]BF4 (5), the new ligand displays
a κ2-chelate coordination mode comparable to those found in
the parent complex 1 and its acetylacetonate derivative
[Mo2Cp2(O,O′-acac)(μ-PPh2)2(CO)]BF4.3 However, in the
complexes having an S-donor atom, namely, [Mo2Cp2(μ-
S:S,N-SPy)(μ-PPh2)2(CO)]BF4 (6) and [Mo2Cp2(μ-S:S,N-
SC6H4NH2)(μ-PPh2)2(CO)]BF4 (7), the new ligand displays
a different coordination mode, since the S atom is now
additionally bound to the second metal atom, thus achieving
full coordinative and electronic saturation of the dimetal center.
As a result, a single M−M bond should be formulated for the
latter cations, in agreement with the structural data of complex
6 to be discussed later. We finally note that in all of the above
reactions deprotonation of the incoming ligand takes place
following the order of acidity of the corresponding E−H bonds
(S−H > O−H > N−H), as expected.
Structural Characterization of the Chelate Complexes
4, 5, and 8. The structure of the benzoate complex 8d was
confirmed by a single-crystal X-ray diffraction study. The very
poor quality of the crystals prevented us from obtaining
accurate structural results, even if the general geometrical
features of the complex could be confirmed.14 A PLUTO view
of the cation is shown in Figure 1. The complex is formed by
two cisoid MoCp fragments bridged by two PPh2 ligands, and
the coordination spheres of the metal atoms are completed with
either a terminal carbonyl or a bidentate benzoate ligand, the
latter effectively acting as a four-electron donor to the Mo(2)
atom. As a result, a double intermetallic bond might be formally
proposed for this 32-electron cation, in agreement with the
relatively short intermetallic separation of 2.828(2) Å.
This structure actually is very similar to those of the tetra-
fluoroborate complex 1 and the acetylacetonate complex
[Mo2Cp2(O,O′-acac)(μ-PPh2)2(CO)]BF4, which also are 32-
electron complexes and display short intermetallic lengths of
2.841(2) and 2.831(2) Å, respectively.3 Yet all these values are
significantly longer than those in the isoelectronic complex
[Mo2Cp2(μ-PPh2)2(CO)2] (2.713(1) Å),5 a difference that can
be attributed to the presence in the above cations of two
(instead of one) terminal donors at one of the MoCp moieties.
A comparable lengthening effect can be appreciated in the
neutral complex [Mo2Cp2(μ-PPh2)2(η2-MeCCMe)(CO)]
In a similar way, compound 1 reacted readily with several
carboxylic acids and related species (acetic, benzoic, and
thioacetic acids, acetamide, thioacetamide, thiobenzamide), but
the products were in all cases 32-electron chelate derivatives of
type [Mo2Cp2(κ2-L2)(μ-PPh2)2(CO)]BF4 (8d−i) irrespective
of the nature of the donor atoms (Chart 4). The sodium salt of
the diethyldithiocarbamate anion also reacted with 1 to give an
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Figure 1. PLUTO diagram of the cation in compound 8d with Ph
rings (except the C1 atoms) and H atoms omitted for clarity.
Figure 2. ORTEP diagram of the cation in compound 6, with Ph rings
(except the C1 atoms) and H atoms omitted for clarity.
having an alkyne molecule η2-bound to one of the metal atoms
(Mo−Mo = 2.865(1) Å).15
Table 2. Selected Bond Lengths (Angstroms) and Angles
(degrees) for Compound 6
The spectroscopic data in solution for the carboxylic
complexes 8 (Table 1 and Experimental Section) are similar
to each other and fully consistent with retention of a κ2
coordination of the carboxylate ligands. The presence of the
terminal carbonyl ligand in all these complexes is clearly
denoted by the appearance of one C−O stretching band in the
corresponding IR spectra (1906−1918 cm−1). The frequency of
these bands is intermediate between the values found for the
starting complex 1 (1921 cm−1) and that of the acetylacetonate
derivative (1898 cm−1).3 This is the expected trend after
consideration of the better donor ability of the carboxylate
ligands when compared to that of a tetrafluoroborate anion and
the less favorable geometry (for electron pair donation) of the
four-membered chelate rings formed when compared to the six-
membered ring present in the acetylacetonate complex.
Complexes 8d−i give rise to 31P NMR resonances around
180 ppm, these chemical shifts being comparable to those of 1
and the mentioned acetylacetonate complex. As expected, only
one resonance is observed for complexes having identical
donors in the chelate ligand (8d,e,h), while two resonances are
observed for complexes having two different donors (8f,g,i).
These resonances appear as weakly coupled doublets (JPP = 3−
6 Hz), which is consistent with the relatively large P−Mo−P
angles (ca. 105° in 8d) within the rather flattened Mo2P2
central core of these cations.
Complexes 4 and 5 also display in each case two weakly
coupled 31P NMR resonances around 180 ppm, in agreement
with the presence of chelating O,N-donors in these cations.
The most salient spectroscopic feature here is the low C−O
stretching frequency of the aminophenol derivative 5 (1882
cm−1), some 30 cm−1 lower than the values measured for the
carboxylate complexes 8 and the hydroxypyridine derivative 4,
even if the latter has analogous N,O-donor centers. This is
again a reflection of the more favorable geometry (for electron
pair donation) of the five-membered chelate rings (5) over the
four-membered ones (4 and 8).
Mo(1)−Mo(2)
Mo(1)−P(1)
Mo(2)−P(1)
Mo(1)−P(2)
Mo(2)−P(2)
Mo(2)−S(1)
Mo(1)−S(1)
N(1)−Mo(2)
2.8895(8)
2.491(2)
2.396(2)
2.448(2)
2.401(2)
2.501(2)
2.542(2)
2.258(6)
Mo(1)−P(1)−Mo(2)
Mo(1)−P(2)−Mo(2)
N(1)−C(2)−S(1)
Mo(1)−S(1)−Mo(2)
C(2)−S(1)−Mo(2)
P(1)−Mo(1)−P(2)
P(1)−Mo(1)−S(1)
S(1)−Mo(1)−N(1)
S(1)−Mo(1)−P(2)
72.5(1)
73.2(1)
108.8(5)
69.91(5)
82.7(2)
76.2(1)
72.3(1)
65.2(2)
105.4 (1)
being placed in a cisoid, almost parallel arrangement. While the
overall geometry of 6 is comparable to that of the dicarbonyl
complexes 3 and those of different thiolate-bridged complexes
of the type [Mo2Cp2(μ-SR)2(μ-X)L2]n+,7b the μ-S:S,N coordi-
nation mode is somewhat unusual for the Spy− anion. In fact, a
search in the Cambridge Structural Database16 reported only 10
examples of compounds with this coordination mode which,
excluding a couple of cationic polymeric silver compounds,17 are
reduced to [Re2(μ-SMePy)2(CO)6],18 [Et4N][Mo2(μ-SPy)(CO)9],19
[ M o2 (μ -S P y) 2 (CO)4 ( P P h3 )2 ], 2 0 [Mo 3 (μ-SPy)-
(μ3-SPy)2(CO)6],20 [Ru2Cp2(μ-SPy)2][PF6]2,21 [MnMoCp-
(μ-SPy)(μ-κ1-SPy)(μ-CO)(CO)3],22 [Ru2(μ-SPy)3(κ2-SPy)2]-
[CF3SO3],23 and [Co5(μ3-S)3(μ-SPy)4(κ2-SPy)3(CO)2].24 The
P and S atoms in 6 bridge the metal atoms asymmetrically,
being closer to the MoN center, as expected from the different
donor ability of the CO and N(py) ligands. This effect is
particularly strong for the P(1) atom (Δd ca. 0.1 Å), reflecting
the different trans influence of the carbonyl and pyridine
ligands. We finally note that the intermetallic distance of
2.8895(8) Å is relatively short for a molecule having a single
metal−metal bond (cf. 2.974(1) Å in [Mo2(μ-SPy)2(CO)4-
(PPh3)2])20 and in fact only ca. 0.06 Å longer than that
measured in the 32-electron complex 8d (formally with a
double metal−metal bond). This relative shortening of the
intermetallic length in 6 can be attributed to the presence
of three, rather than two, bridging atoms, a circumstance that
has been also found to cause a systematic decrease of inter-
metallic distances in related thiolate-bridged systems.7b The
covalent radius of the bridging atoms (P > S) is another factor
influencing the intermetallic separations in these dimetal
complexes; an extreme example of the shortening influence of
the S-bridging ligands is found in the 34-electron complex
Structural Characterization of Complexes 6 and 7.
The structure of complex 6 was determined by a single-crystal
X-ray diffraction study (Figure 2 and Table 2). The structure of
the cation is built from two cisoid MoCp fragments bridged by
three ligands: two cisoid PPh2 groups and the S atom of a
deprotonated mercaptopyridine molecule. The piano-stool
coordination geometry around each metal center is completed
with a carbonyl and the N atom of the pyridine ring, these
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[Mo2Cp2(μ-SMe)3(CO)2]Br·H2O, which displays an intera-
tomic separation of only 2.785(2) Å for its Mo−Mo single
bond.25
product, this being isolated as a green microcrystalline material
in a conventional way.
The proposed structure for 10 is based on the corresponding
spectroscopic data (Table 3 and Experimental Section) and
The spectroscopic data available for complexes 6 and 7
(Table 1 and Experimental Section) are similar to each other
and indicative of the retention of the bridging coordination
mode of the S,N-donor ligands found in the solid-state
structure of 6 while being significantly different from the data
for the chelate complexes 4, 5, and 8. First, these S-bridged
complexes exhibit C−O stretching bands significantly shifted to
higher frequencies [1989 (6) and 1971 cm−1 (7)] with respect
to those of the κ2-chelate complexes (most of them around
1915 cm−1). In fact, the frequency of these bands is
intermediate between those of the κ2-chelate complexes and
those of the dicarbonyl complexes 3, which seems a reasonable
position for cations sharing structural features with both type of
complexes. As noted for the couple 4/5, the C−O stretch of 7
is considerably less energetic (now by ca. 20 cm−1) than that of
6, as a result of the better-suited geometry (for electron
donation) of its five-membered ring.
Table 3. Selected IR and 31P{1H} NMR Data for New
Neutral Complexes
a
b
compound
ν(CO)
1876 (vs) 177.8
187.3
δP (JPP)
[Mo2Cp2(μ-PPh2)2(O,O’-O2C6H4)(CO)] (10)
[Mo2Cp2(O,N- OC6H4NH)(μ-PPh2)2(CO)] (11) 1848 (s)
c
176.6 (5)
91.3
[Mo2Cp2(μ-S,N:S,N-SC6H4NH)(μ-PPh2)2] (12)
c
82.6 (60)
164.6
[Mo2Cp2{N-N(O)CMe}(μ-PPh2)2(CO)] (13)
[Mo2Cp2{μ-S:N-N(S)CMe}(μ-PPh2)2] (14)
1867 (s)
83.1
a
b
Recorded in CH2Cl2 solution; data in cm−1. Recorded at room
temperature in CD2Cl2 solutions at 161.97 MHz, unless otherwise
stated, with coupling to phosphorus (in Hertz) indicated in brackets.
c
Recorded at 213 K.
The inequivalent PPh2 groups in complexes 6 and 7 exhibit
two distinct 31P NMR resonances as expected, at a chemical
shift significantly lower than those of the κ2-chelate complexes,
actually closer to those of the electron-precise dicarbonyls 3. In
addition, these resonances display large P−P couplings as
observed for 3, in agreement with the cisoid arrangement of the
PPh2 ligands and the acute P−Mo−P angle implied by this
crystallographic analysis of its ditungsten analogue.26 In fact,
the IR spectrum of 10 exhibits a C−O stretch at 1876 cm−1, a
position ca. 10 cm−1 above that of the ditungsten analogue
(1865 cm−1), as expected when comparing isostructural
molybdenum and ditungsten complexes,27 while being lower
than the frequencies of all cationic complexes discussed above,
due to the increased electron density at the dimetal center in
this neutral complex. The 31P NMR spectrum of 10 displays a
single resonance at 177.8 ppm, and its diolate ligand gives rise
to an AA′XX′ multiplet in the 1H NMR spectrum, thus
confirming the symmetrical coordination of both O atoms to a
single metal center.
1
arrangement (ca. 78° for 6). In the case of 7, the H NMR
spectrum confirms the presence of an NH2 group, also revealed
by the observation of two N−H stretches at 3278 and 3256 cm−1
in the corresponding solid-state IR spectra. All of this confirms
that, upon reaction with 1, deprotonation of the aminothiophenol
takes place specifically at the S−H bond, as expected on the basis
of the higher acidity of that bond compared to that of the N−H
bonds.
Reaction of Complex 1 with Catechol. The tetrafluor-
oborate complex 1 reacts with a slight excess of catechol to give
solutions containing the catecholate complex [Mo2Cp2(O-
OC6H4OH)(μ-PPh2)2(CO)]BF4 (9) as the major species,
along with small amounts of the diolate derivative
[Mo2Cp2(O,O′-O2C6H4)(μ-PPh2)2(CO)] (10) (Chart 6) and
Complex 9 displays a C−O stretch at 1908 cm−1, a frequency
significantly higher than that of 10 and comparable to those of
the κ2-chelate complexes 8 (Table 1). However, the proposal of
a similar κ2-chelate coordination for 9 (B in Chart 6) must be
discarded on the basis of the equivalence of the P nuclei
deduced from the 31P NMR spectra, instead suggesting
coordination of the ligand through only the deprotonated O
atom (A in Chart 6). In fact, such a structure would be
analogous to the one proposed for the hydroxo complex
[Mo2Cp2(OH)(μ-PPh2)2(CO)]+, a cation detected in proto-
nation of cis-[Mo2Cp2(O)(μ-PPh2)2(CO)] and displaying
similar spectroscopic parameters (ν(CO) = 1821 cm−1, δP
176.3 ppm).3 Finally, we note that the κ1-coordination mode of
the catecholate ligand has been crystallographically charac-
terized in a number of cases.28
Chart 6
Pathways in the Reactions of 1 with Bidentate Ligands.
Reactions of complex 1 with the bidentate ligands discussed
above should follow a mechanism (Scheme 2) not very dif-
ferent from that proposed for the monodentate ligands
(Scheme 1). The coordination of the incoming ligand to the
metal center would be again facilitated by a change in the
hapticity of the tetrafluoroborate anion to yield an intermediate
C having the bidentate ligand presumably coordinated through
its better donor group present (the nitrogen atom or, in the
carboxylic derivatives, the carbonyl group; L in Scheme 2). This
would be followed by deprotonation of the uncoordinated E−H
bond in the incoming ligand (except, perhaps, in the reaction
other minor species that could not be identified. Unfortunately,
all attempts to isolate complex 9 as a pure material from these
mixtures led to its progressive decomposition. However,
addition of a strong base such as 1,8-diazabicycloundec-7-ene
(DBU) to the above mixture gave compound 10 as the major
−
with catechol) and displacement of the BF4 ligand to yield a
chelate derivative D stable enough in the case of the carboxylic
ligands (compounds 8) or the O,N-donors (compounds 4 and 5).
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when recorded at 213 K (at other temperatures this signal is
masked by the resonances of the PPh2 groups). The IR spec-
trum of 11 in solution displays a C−O stretch at 1848 cm−1,
almost 30 cm−1 lower than that of the diolate complex 10,
reflecting the excellent donor properties of the amido (vs
alkoxo) ligand. As expected, 11 displays two 31P{1H} NMR
resonances at around 180 ppm, but these are somewhat broad
at room temperature. On cooling the solution at 213 K they
resolve into two weakly coupled doublets (JPP = 5 Hz), in
agreement with the proposed chelate structure, implying a
relatively large P−Mo−P bond, as noted above. The observed
broadening of the 31P NMR resonances is due to the
occurrence of a mutual exchange process, as confirmed by
the observation of the pertinent cross peaks in a standard
31P{1H} EXSY NMR spectrum of the complex at room
temperature. Our proposal for that process implies exchange
between O and N positions (Scheme 3), probably through a
Scheme 2
In the case of the noncarboxylic S,N-donors, the chelate com-
plexes D would be intermediate species rapidly rearranging into
their μ-S:S,N-bridged forms (compounds 6 and 7), thus achiev-
ing full electronic and coordinative saturation of the dimetal
center.
Scheme 3
Deprotonation of the Aminocomplexes 5 and 7. The
cationic nature of compounds 5−9 increases the acidity of the
E−H bonds still remaining in the bidentate ligands so as to
allow for a second deprotonation. This takes place easily in the
case of catechol (i.e.. the transformation 9 → 10), as noted
above, and it can be also induced in ligands having NH2 and
even NH groups upon addition of the appropriate base (DBU,
NaOH, or Na2CO3) to dichloromethane solutions of the
cationic complexes, then yielding neutral derivatives with
composition and structures strongly dependent on the
particular bidentate ligand present (Chart 7).
Chart 7
zwitterionic intermediate E in which the chelate ring opens by
cleaving the weaker Mo−O bond while retaining the stronger
Mo−N bond. This is consistent with the observation of sharp
resonances for the Cp and C6H4 protons at all temperatures
analyzed.
In contrast, deprotonation of the aminothiolate complex 7
with DBU was accompanied by spontaneous decarbonylation
to yield the amidothiolate derivative [Mo2Cp2(μ-S,N:S,N-
SC6H4NH)(μ-PPh2)2] (12) (Chart 7), having both the S and
the N atoms at bridging positions. This coordination mode of
the amidothiolate ligand has been previously characterized
crystallographically in the diiron complex [Fe2{μ-S,N:S,N-
SC6H4NH}(CO)6].30 Deprotonation of the amino group in 7
is confirmed by the appearance of just one N−H stretch in the
solid-state IR spectrum of 12 and of a P-coupled resonance at
1
Deprotonation of the aminophenolate complex 5 with DBU
yields the neutral derivative [Mo2Cp2{O,N-OC6H4NH}(μ-
PPh2)2(CO)] (11) (Chart 7), which still retains a chelate
coordination of the organic ligand. This type of coordination is
well established for the amidophenolate dianion. We can quote
the complex [Et4N]2[W(CO)3{NH(O)C6H4}], which was
prepared analogously by deprotonation of the aminophenolate
precursor [Et4N][W(CO)4{NH2(O)C6H4}].29 Deprotonation
of the amino group in 5 is confirmed by the appearance of just
one N−H stretch in the solid-state IR spectrum of 11 and of a
1.92 ppm (JHP = 13 Hz) in its H NMR spectrum. Note the
strong shielding of this resonance (ca. 5 ppm) compared to the
corresponding one in 11, an effect possibly derived from the
bridging coordination of the NH group. The latter is also
denoted by the equivalence of the Cp ligands, otherwise
impossible. The μ-S,N:S,N-coordination of the amidophenolate
ligand in 12 renders inequivalent P atoms, which accordingly
give rise to two strongly coupled resonances (JPP = 60 Hz) in
the 31P{1H} NMR spectrum when recorded at 213 K. However,
these resonances broaden in the spectra recorded at higher
temperatures and eventually disappear in the baseline when the
1
deshielded singlet at 7.26 ppm in its H{31P} NMR spectrum
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spectrum is recorded at room temperature. At the same time,
significant broadening was observed in the 1H NMR spectra for
the Ph resonances but not for the Cp or C6H4 ones, which
remained sharp at the different temperatures analyzed. All of
this reveals the operation of a fluxional process accomplishing
the mutual exchange of the NH and S positions (Scheme 4),
presence of a unique resonance in the 31P NMR spectrum of
14, excludes a μ-S,N:S,N coordination mode of the S,N-ligand
comparable to that observed for 12. This leaves as the only
reasonable possibility a μ-S:N coordination mode, with the S
and N atoms terminally bound to different metal atoms. To
the best of our knowledge, this type of coordination is
unprecedented for the dianionic thioimidate ligand, although
we can quote three thioamidate complexes having this
coordination mode verified crystallographically, namely, the
trinuclear clusters [Co3{μ-S:N-NH(S)CMe}(μ-S)3(CO)7],33
[Co2Fe{μ-S:N-NH(S)CMe}(μ-S)3(CO)7],34 and the dimolyb-
denum complex[Mo2(DAniF)3]2[μ-S:N-S:N-HN(S)CC(S)-
NH] (DAniF = N,N′-di-p-anisylformamidinate).35 In contrast,
this is a quite common coordination mode for binuclear
complexes having acetate or amidate ligands.
Scheme 4
The donor ability of a thioimidate ligand (RC(S)N2−) is not
obvious, since there are electron pairs involved in the π-
bonding interaction along the S−C−N chain that could be also
involved in π(X−Mo) bonding interactions (X = S, N; see the
canonical forms in Chart 8). Depending on the extent of the
possibly involving an intermediate F having each donor atom
terminally bound to one of the metal centers. We note that
the structure of F would be analogous to that of the deproto-
nated derivative of the thioamidate complex 8i to be discussed
later on.
Chart 8
Deprotonation of Amidate Complexes. Removal of a
proton from the NH group in the amidate complexes of type 8
also yielded different structures for N,O- and N,S-donors.
Deprotonation of the amidate complex 8g with DBU gave the
acetylimido derivative [Mo2Cp2(μ-PPh2)2{N-N(O)CMe}-
(CO)] (13) (Chart 7) with its dianionic ligand terminally
bound through its nitrogen atom. This transformation is
reversible, so that 13 could be converted quantitatively into 8g
upon reaction with (NH4)PF6 in dichloromethane solution.
The presence of the acetylimido ligand in 13 was denoted by
the absence of NH resonances in its 1H NMR spectrum and by
the presence in the 13C{1H} NMR spectrum of characteristic
resonances at 22.3 (Me) and 178.9 ppm [N(C)O], which are
comparable to those previously reported for a decade of
complexes crystallograpically characterized31 with this coordi-
nation mode of the ligand (cf. 24.8 and 181.8 ppm for
[{HB(Me2pz)3}W{NC(O)Me}I(CO)]).31b The solid-state IR
spectrum of 13 also displays diagnostic bands for this ligand at
1599 (m) and 1248 (vs) cm−1 that can be assigned,
respectively, to the corresponding C−O and C−N stretches,
the somewhat low frequency of the C−O stretch possibly
reflecting the presence of substantial delocalization of the π-
bonding interactions along the Mo−N−C−O chain. Com-
pound 13 displays a carbonyl stretch at 1867 cm−1 and a 31P
NMR resonance for the equivalent P nuclei at 164.9 ppm, these
being spectroscopic parameters almost identical to those of the
oxo complex cis-[Mo2Cp2(O)(μ-PPh2)2(CO)] (1859 cm−1 and
163.3 ppm),5 thus further supporting the proposal of a cisoid
arrangement of the pairs of CO/NR and Cp ligands in this
molecule.
latter interactions, the formal contribution of the anion to the
complex would go from 4 to 6 electrons, thus yielding formal
Mo−Mo bond orders of 3 and 2, respectively. In the absence of
structural data is difficult to ascertain the exact nature of the
above interactions. Yet, by considering the relatively low 31P
NMR shifts of the PPh2 ligands in compound 14 (83.1 ppm),
which is much lower than those of 30-electron complexes of the
type [Mo2Cp2(μ-PPh2)(μ-PR′2)(μ-CO)],27 (in the range 190−
200 ppm), we tentatively propose this compound as a 32-
electron complex with an intermetallic double bond. Note,
however, that complex 14 is a Mo(III) rather than a Mo(II)
species.
Structural Preferences in the Neutral Complexes 12
and 14. As noted above, these complexes display quite
different coordination modes of their S,N-donor ligands
(amidothiophenolate vs thioamidate, Chart 7). The observed
difference can be attributed to the distinct distribution of
electron pairs at the donor atoms, as already noted when
rationalizing the structural differences between the cationic
complexes 5 (or 7) and 8h,i. The μ-S,N:S,N- coordination
mode is easily adopted by the amidothiophenolate dianion
thanks to the tetrahedral distribution of electron pairs around
the S and N atoms. In contrast, because of the electron
delocalization of the π-bonding interaction along the S−C−N
chain in the thioimidate anion and the implied trigonal
distribution of the remaining electron pairs around the donor
atoms (Chart 8), fewer electron pairs would be available for
metal binding in the μ-S,N:S,N- coordination mode, thus
disfavoring it.
The thioacetamidate complex 8i could be deprotonated even
with Na2CO3. This reaction proceeds slowly at room
temperature with spontaneous loss of carbon monoxide to
give the thioimidate-bridged complex [Mo2Cp2{μ-S:N-N(S)-
CMe}(μ-PPh2)2] (14) (Chart 7).32 Unfortunately, all attempts
to obtain suitable crystals for X-ray analysis of this unusual pro-
duct were unsuccessful. The observation of two independent
1H NMR resonances for the Cp ligands, along with the
CONCLUDING REMARKS
■
Complex 1 undergoes easy displacement of its tetrafluoroborate
ligand by different donors, therefore acting as a useful synthetic
precursor of the highly unsaturated 28-electron cation
[Mo2Cp2(μ-PPh2)2(CO)]2+ with an effective unsaturation
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ether (2 × 10 mL) and dried under vacuum. The solid was then
dissolved in dichloromethane and layered with toluene and petroleum
ether. Slow diffusion of the top layers at room temperature gave a red
crystalline material which was washed with petroleum ether and dried
under vacuum (0.049 g, 77%). This material contains an inseparable
mixture of the isomers cis-2 and trans-2 in a ratio of ca. 4:1, as
determined by 1H NMR spectroscopy. Anal. Calcd for
C51H59N3B2Cl2F8Mo2OP2 (2·CH2Cl2): C, 49.86; H, 4.84; N, 3.42.
equivalent to three vacant positions and six electrons, as
illustrated by its reaction with CNtBu to yield the saturated
cation [Mo2Cp2(μ-PPh2)2(CNtBu)3(CO)](BF4)2. Even quite
weak donors are able to react with 1 provided they have E−H
bonds of moderate to low acidity (E = O, S, Se, N, P); in those
cases, the incoming ligand is deprotonated while the
tetrafluoroborate ligand of 1 is displaced as HBF4 (possibly
in a hydrated form). In the case of monodentate ligands, this
reaction takes place with spontaneous incorporation of an extra
CO ligand (originated from partial decomposition of
intermediate species) to give the electron-precise dicarbonyls
of the type [Mo2Cp2(μ-PPh2)2(μ-E)(CO)2], which retain the
cisoid arrangement of the original Mo2Cp2(μ-PPh2)2 core of
the parent cation. As expected, such a spontaneous carbon-
ylation is suppressed when using bidentate ligands L2H having
at least one E−H bond, with most of the resulting complexes
being of the type [Mo2Cp2(κ2-L2)(μ-PPh2)(CO)]+, displaying a
κ2-chelate coordination of the deprotonated ligand identical to
1
Found: C, 49.47; H, 4.98; N, 3.46. Spectroscopic data for cis-2: H
NMR (400.13 MHz): δ 7.82−6.19 (m, 20H, Ph), 5.68, 5.58 (2s, 2 ×
t
5H, Cp), 1.53, 1.22, 1.13 (3s, 3 × 9H, Bu). 13C{1H} NMR (100.61
MHz): δ 230.0 (d, JPC = 12, CO), 150.6, 152.1, 155.5 (3d, JPC = 18, 14,
15, CN), 144.5 [dd, JPC = 37, 4, C1(Ph)], 144.3 [dd, JPC = 40, 6,
C1(Ph)], 142.3 [d, JPC = 28, C1(Ph)], 141.9 [d, JPC = 26, C1(Ph)],
134.2−128.6 (m, Ph), 92.0, 91.3 (2s, Cp), 61.3, 61.2, 60.5 [3s,
C1(tBu)], 30.1, 29.7, 29.5 [3s, C2(tBu)]. Spectroscopic data for trans-2:
1H NMR (400.13 MHz) δ 7.82−6.19 (m, 20H, Ph), 5.72, 5.64
t
(2s, 2 × 5H, Cp), 1.26, 1.22, 1.13 (3s, 3 × 9H, Bu). 13C{1H} NMR
(100.61 MHz): δ 134.2−128.6 (m, Ph), 96.8, 91.9 (2s, Cp), 61.4, 60.6,
60.4 [3s, C1(tBu)], 32.1, 23.2, 22.8 [3s, C2(tBu)]. Other resonances of
this minor isomer could not be assigned unambiguously due to overlap
with those of the major isomer.
−
that of the displaced BF4 ligand and still being 32-electron
complexes. Exceptions to this κ2-coordination mode were
observed for (a) ligands having S-donor atoms with tetrahedral
distribution of electron pairs, instead giving S-bridged 34-
electron complexes of the type [Mo2Cp2(μ-S:S,N-L2)(μ-
PPh2)(CO)]+, and (b) the cathecolate ligand, unable to
adopt the chelate coordination mode because of the poor
donor ability of its hydroxyl group. The N−H bonds remaining
in some of these cations can be further deprotonated to yield
neutral derivatives displaying distinct coordination modes of
their dianionic ligands, including the more common κ2-chelate
mode of the cationic precursors, κ1-imido coordination, and
either μ-S:N or μ-S,N:S,N- bridging coordination modes. Most
of the above differences can be rationalized by considering the
distinct spatial distribution of the electron pairs in the ligands
under study.
Preparation of [Mo2Cp2(μ-SPh)(μ-PPh2)2(CO)2]BF4 (3a).
Freshly distilled methanol (2 drops, excess) was added to a suspension
of compound 1 (0.050 g, 0.052 mmol) in dichloromethane (10 mL).
The reaction vessel was cooled at 77 K, degassed under vacuum, and
then refilled with CO. The solution was allowed to reach room
temperature, then thiophenol (50 μL, 0.47 mmol) was added, and the
mixture was stirred for 3 h to give a red-yellowish solution. Petroleum
ether (10 mL) was then added, and the solvents were partially
removed under vacuum until most of the product precipitated. The
remaining solution was discarded, and the resulting orange solid was
washed with petroleum ether (2 × 10 mL) and dried under vacuum
(0.042 g, 82%). Anal. Calcd for C42.5H36BClF4Mo2O2P2S (3a·1/
2CH2Cl2): C, 51.71; H, 3.64. Found: C, 52.0; H, 3.50. IR (Nujol):
ν(CO) 2011 (s), 1990 (w, sh); ν(BF) 1046 (s, br). 1H NMR (400.13
MHz): δ 7.44, 7.06, 6.69, 6.58 (4 m, 4 × 2H, PPh), 7.30−7.15 (m,
12H, PPh), 6.99 (m, 2H, SPh), 6.77 (m, 3H, SPh), 6.04 (s, 10H, Cp).
13C{1H} NMR (100.61 MHz): δ 224.8 (dd, JPC = 12, 4, 2CO), 145.9
[m, C1(PPh)], 142.6 [d, JPC = 22, C1(PPh)], 137.4 [d, JPC = 34,
2C1(PPh), 134.6 [s, C1(SPh)], 135.0, 134.0, 133.2, 132.6 [4d, JPC = 9,
9, 9, 8, C2(PPh)], 132.1 [s, C2,3(SPh)], 130.1, 129.9, 129.6, 129.1, [4d,
JPC = 3, 2, 3, 2, C4(PPh)], 130.9−128.5 (m, PPh and SPh), 128.1 [s,
C4(SPh)], 90.1 (s, Cp).
EXPERIMENTAL SECTION
■
General Procedures. All reactions and manipulations were carried
out under a nitrogen atmosphere using standard Schlenk techniques.
Solvents were purified according to literature procedures36 and
distilled under nitrogen prior to use. Petroleum ether refers to that
fraction distilling in the range 338−343 K. Complex [Mo2Cp2(κ2-
F2BF2)(μ-PPh2)2(CO)]BF4 (1) was prepared in its hydrated form
(1·1/2CH2Cl2·H2O) as described previously.3,4 All other reagents
were obtained from the usual commercial suppliers and used as
received. Filtrations were carried out through diatomaceous earth.
Chromatographic separations were carried out using jacketed columns
cooled by tap water (ca. 288 K) or with a cryostat. Commercial
aluminum oxide (Aldrich, activity I, 150 mesh) was degassed under
vacuum prior to use. The latter was mixed under nitrogen with the
appropriate amount of water to reach the desired activity. IR stretching
frequencies of CO, CN, NH, and BF bonds were measured either in
solution (using CaF2 windows) or in Nujol mulls (using NaCl
windows), are referred to as ν(CO), ν(CN), ν(NH), or ν(BF), and are
given in cm−1. Nuclear magnetic resonance (NMR) spectra were
routinely recorded at 300.13 (1H), 121.50 (31P{1H}), and 75.47 MHz
(13C{1H}) at 290 K in CD2Cl2 solutions unless otherwise stated.
Chemical shifts (δ) are given in ppm, relative to internal
tetramethylsilane (1H and 13C) or external 85% aqueous H3PO4
solutions (31P). Coupling constants (J) are given in Hertz.
Preparation of [Mo2Cp2(μ-SePh)(μ-PPh2)2(CO)2]BF4 (3b). The
procedure is analogous to that described for 3a but using PhSeH (60
μL, 0.548 mmol) and a reaction time of 3 h with no added methanol
to give a brown solution which was filtered. Workup as described for
3a gave a solid that was dissolved in a minimum amount of
dichloromethane and layered with toluene and petroleum ether. Slow
diffusion of the top layers at 253 K gave brown crystals of compound
3b, which were washed with petroleum ether and dried under vacuum
(0.044 g, 85%). Anal. Calcd for C42H35BF4Mo2O2P2Se: C, 50.89; H,
3.56. Found: C, 52.52; H, 3.21. IR (Nujol): ν(CO) 2012 (s), 1982 (w,
1
sh). H NMR (200.13 MHz): δ 7.37, 7.08, 6.69, 6.58 (4 m, 4 × 2H,
PPh), 7.31−7.14 (m, 12H, Ph), 6.77 (m, 3H, SePh), 6.95 (m, 2H,
SePh), 6.03 (s, 10H, Cp).
Preparation of [Mo2Cp2(μ-PHCy)(μ-PPh2)2(CO)2]BF4 (3c). The
procedure is analogous to that described for 3a but using PH2Cy (15
μL, 0.110 mmol) and a reaction time of 20 min to give a yellow
solution. Workup as described for 3a (using diethyl ether instead of
petroleum ether) gave compound 3c as an orange solid (0.042 g,
85%). Anal. Calcd for C42H42BF4Mo2O2P3: C, 53.07; H, 4.45. Found:
C, 52.69; H, 4.18. IR (Nujol): ν(CO) 1995 (s), 1952 (w, sh); ν(BF)
1069 (s, br). 1H NMR (200.13 MHz): δ 7.90−6.50 (m, 20H, Ph), 5.86
(s, 10H, Cp), 1.49−1.08 (m, 11H, Cy). The resonance of the P-bound
hydrogen atom was obscured by other resonances in the spectrum.
Preparation of [Mo2Cp2(O,N-OPy)(μ-PPh2)2(CO)]BF4 (4).
Freshly distilled methanol (2 drops, excess) was added to a suspension
of compound 1 (0.050 g, 0.052 mmol) in dichloromethane (10 mL),
Reaction of 1 with CNtBu. Neat CNtBu (18 μL, 0.156 mmol) was
added to a suspension of compound 1 (0.050 g, 0.052 mmol) in
dichloromethane (10 mL), and the mixture was stirred for 30 min to
give a brown-reddish solution. Petroleum ether (10 mL) was then
added, and the solvents were partially removed under vacuum until
most of the product precipitated as a red solid. The remaining solution
was discarded, and the resulting solid was washed with petroleum
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and the mixture was stirred for 5 min to give a red solution. Then solid
2-hydroxypyridine (0.050 g, 0.53 mmol) was added, and the mixture
was stirred for 10 min to give a red solution which was filtered.
Workup as described for 3a gave compound 4 as a red solid (0.040 g,
80%). Anal. Calcd for C41H36NBClF4Mo2O2P2 (4·CH2Cl2): C, 49.93;
H, 3.68; N, 1.42. Found: C, 49.52; H, 3.31; N, 1.41. IR (Nujol):
142.9 [d, JCP = 36, C1(PPh)], 132.7 [d, JCP = 53, C1(PPh)], 137.0−
127.0 (m, Ph), 99.2, 92.9 (2s, Cp), 25.8 (s, Me).
Preparation of [Mo2Cp2{O,S-S(O)CMe}(μ-PPh2)2(CO)]BF4 (8f).
The procedure and workup is analogous to that described for 4 but
using thioacetic acid (10 μL, 0.140 mmol) and a reaction time of 3 h.
This yielded compound 8f as an orange solid (0.045 g, 89%). Anal.
Calcd for C38H35BCl2F4Mo2O2P2S (8f·CH2Cl2): C, 47.18; H, 3.65.
Found: C, 46.86; H, 3.71. IR (Nujol): ν(CO) 1904 (s); ν(BF) 1053
(s, br). 1H NMR (400.13 MHz): δ 7.79−6.50 (m, 20H, Ph), 5.89, 5.10
(2s, 2 × 5H, Cp), 1.43 (s, 3H, Me).
Preparation of [Mo2Cp2{O,N-NH(O)CMe}(μ-PPh2)2(CO)]BF4
(8g). The procedure and workup is analogous to that described for
4 but using acetamide (0.003 g, 0.051 mmol) and a reaction time of 5
h. This yielded compound 8g as a red solid (0.032 mg, 71%). Anal.
Calcd for C37H34BF4Mo2O2P2N: C, 51.36; H, 3.96; N, 1.62. Found: C,
51.02; H, 3.58; N, 1.75. IR (Nujol): ν(CO) 1901 (s); ν(BF) 1054 (s);
ν(NH) 3320 (w). 1H NMR: δ 7.81−7.56 (m, 11H, Ph and NH), 7.34
(m, 6H, Ph), 6.63, 6.50 (2 m, 2 × 2H, Ph), 5.83, 5.06 (2s, 2 × 5H,
Cp), 2.19 (s, 3H, Me).
Preparation of [Mo2Cp2(S,S′-S2CNEt2)(μ-PPh2)2(CO)]BF4 (8h).
The procedure and workup is analogous to that described for 4 but
using sodium diethyl dithiocarbamate trihydrate previously dried by
heating under vacuum (12 mg, 0.053 mmol) and a reaction time of 10
min. This yielded compound 8h as a red solid (0.041 g, 82%). Anal.
Calcd for C40H40NBF4Mo2OP2: C, 50.28; H, 4.22; N, 1.47. Found: C,
49.96; H, 3.94; N, 1.44. IR (Nujol): ν(CO) 1886 (s); ν(BF) 1043 (s,
br). 1H NMR: δ 7.84 (m, 4H, Ph), 7.63, 7.36 (2 m, 2 × 6H, Ph), 6.79
(m, 4H, Ph), 5.65, 4.92 (2s, 2 × 5H, Cp), 3.19, 3.02 [2dq, JHH = 14, 7,
4H, C1(Et)], 0.76 [t, JHH = 7, 6H, C2(Et)].
1
ν(CO) 1890 (s); ν(BF) 1046 (s). H NMR: δ 8.09−5.95 (m, 24H,
PPh and OPy), 5.71, 5.28 (2s, 2 × 5H, Cp).
Preparation of [Mo2Cp2(O,N-OC6H4NH2)(μ-PPh2)2(CO)]BF4
(5). The procedure and workup is analogous to that described for 4
but using 2-aminophenol (0.006 g, 0.055 mmol) and a reaction time of
10 min. This yielded compound 5 as a red solid (0.047 g, 83%). Anal.
Calcd for C43H40NCl4BF4Mo2OP2 (5·2CH2Cl2): C, 47.59; H, 3.72; N,
1.29. Found: C, 47.68; H, 3.72; N, 1.24. IR (Nujol): ν(CO) 1873 (s);
1
ν(BF) 1085 (s, br); ν(NH) 3262 (w), 3221 (w). H NMR (200.13
MHz): δ 8.27, 7.71, 7.63 (3 m, 3 × 2H, PPh), 7.37 (m, 6H, PPh), 7.87,
6.89 (2 m, 2 × 4H, PPh), 6.71 (m, 2H, C6H4), 6.35 (td, JHH = 9, 1, 1H,
C6H4), 5.70 (dd, JHH = 8, 1, 1H, C6H4), 5.77, 5.10 (2s, 2 × 5H, Cp).
The resonances of the NH2 group could not be located unambiguously
in the spectrum.
Preparation of [Mo2Cp2(μ-S:S,N-SPy)(μ-PPh2)2(CO)]BF4 (6).
The procedure and workup is analogous to that described for 4 but
using 2-mercaptopyridine (0.007 g, 0.063 mmol) and a reaction time
of 5 min. This yielded compound 6 as a brown solid (0.039 g, 81%).
The crystals used in the X-ray study were grown by the slow diffusion
of a layer of a petroleum ether/diethyl ether mixture into a
dichloromethane solution of the complex at room temperature.
Anal. Calcd for C41H36NBCl2F4Mo2OP2S (6·CH2Cl2): C, 49.13; H,
1
3.62; N, 1.40. Found: C, 48.73; H, 3.67; N, 1.82. H NMR (400.13
Preparation of [Mo2Cp2{S,N-NH(S)CMe}(μ-PPh2)2(CO)]BF4
(8i). The procedure and workup is analogous to that described for 4
but using thioacetamide (0.004 g, 0.053 mmol) and a reaction time of
15 min. This yielded compound 8i as an orange solid (0.045 g, 90%).
Anal. Calcd for C38H36NBCl2F4Mo2OP2S (8i·CH2Cl2): C, 47.23; H,
3.76; N, 1.45. Found: C, 46.87; H, 3.64; N, 1.37. IR (Nujol): ν(CO)
1903 (s); ν(BF) 1097 (s); ν(NH) 3318 (w). 1H NMR (200.13 MHz):
δ 8.01−7.40 (m, 10H, Ph), 7.38−7.30 (2 m, 2 × 3H, Ph), 6.74−6.53
(m, 5H, Ph and NH), 5.74, 5.10 (2s, 2 × 5H, Cp), 1.36 (s, 3H, Me).
Preparation of Solutions of [Mo2Cp2(O-OC6H4OH)(μ-
PPh2)2(CO)]BF4 (9). The procedure is analogous to that described
for 4 but using catechol (0.045 mg, 0.55 mmol) and a reaction time of
1 h, yielding a deep purple solution containing complex 9 as the major
organometallic product. Compound 9 could not be isolated as a pure
material, and all spectroscopic data were obtained from this crude
MHz): δ 7.53 (m, 1H, SPy), 7.45 (m, 2H, PPh), 7.35−7.22 (m, 7H,
PPh and SPy), 6.96 (m, 4H, PPh), 6.79 (m, 5H, PPh and SPy),
6.71 (m, 2H, PPh), 6.62 (m, 1H, SPy), 6.35 (m, 2H, PPh), 5.81, 5.59
(2s, 2 × 5H, Cp).
Preparation of [Mo2Cp2(μ-S:S,N-SC6H4NH2)(μ-PPh2)2(CO)]BF4
(7). The procedure and workup is analogous to that described for 4
but using 2-aminothiophenol (0.007 g, 0.055 mmol) and a reaction
time of 30 min. This yielded compound 7 as an orange solid (0.045 g,
93%). Anal. Calcd for C41H36NBF4Mo2OP2S (7): C, 52.87; H, 3.90;
N, 1.50. Found: C, 53.01; H, 3.92; N, 1.45. IR (Nujol): ν(CO) 1964
1
(s); ν(BF) 1054 (s); ν(NH) 3278 (w), 3256 (w). H NMR: δ 7.17−
6.72 (m, 15H, Ph and C6H4), 7.36 (dd, JHH = 7, 2, 1H, C6H4), 7.51,
7.29, 6.59, 6.35 (4 m, 4 × 2H, Ph), 5.69 (d, JHH = 16, 1H, NH2), 5.63,
5.51 (2s, 2 × 5H, Cp), 2.86 (d, JHH = 16, 1H, NH2).
Preparation of [Mo2Cp2(O,O′-O2CPh)(μ-PPh2)2(CO)]BF4 (8d).
The procedure and workup is analogous to that described for 4 but
using benzoic acid (0.010 g, 0.082 mmol) and a reaction time of
30 min. This yielded compound 8d as a green-yellowish solid
(0.042 g, 87%). The crystals used in the X-ray study were grown by
slow diffusion of a layer of petroleum ether into a dichloromethane
solution of the complex at room temperature. Anal. Calcd for
C40.5H36BClF4Mo2O3P2 (8d·1/2CH2Cl2): C, 52.58; H, 3.74. Found:
C, 52.42; H, 3.63. IR (Nujol): ν(CO) 1918 (vs), 1602 (s), 1505 (s);
1
reaction mixture. H NMR (400.13 MHz, 288 K): δ 7.96−7.42 (m,
PPh, 20H), 6.46 (m, C6H4, 2H), 5.74, 5.18 (2s, 2 × 5H, Cp). The
resonance of the other two hydrogen atoms of the catecholate group
could not be identified, possibly due to its broadness. 1H NMR
(400.13 MHz, 223K): δ 8.04−7.43 (m, PPh, 20H), 6.61 (s, br, C6H4,
1H), 6.55, 6.37 (2t, JHH = 6, 2 × 1H, C6H4), 6.28 (d, JHH = 6, 1H,
C6H4), 5.80, 5.15 (2s, 2 × 5H, Cp).
Preparation of [Mo2Cp2(O,O′-O2C6H4)(μ-PPh2)2(CO)] (10). The
procedure is analogous to that described for 4 but using catechol (12
mg, 0.110 mmol) and a reaction time of 1 h, yielding a deep purple
solution of complex 9. Neat 1,8-diazabicycloundec-7-ene (DBU, 25
μL, 0.167 mmol) was then added, and the mixture was stirred for 10
min to give a deep green solution. The solvent was then removed
under vacuum, and the residue was chromatographed on alumina
(activity IV) at 288 K. Elution with dichloromethane gave a green
fraction yielding, after removal of the solvent, compound 10 as a green
solid (0.040 g, 93%). Anal. Calcd for C41H34Mo2O3P2: C, 59.43; H,
4.14. Found: C, 58.98; H, 4.03. 1H NMR: δ 8.03 (m, 4H, PPh), 7.54, 7.29
1
ν(BF) 1058 (vs, br). H NMR: δ 7.88 (m, 4H, PPh), 7.67 (m, 6H,
PPh), 7.41 (m, 7H, PPh and Ph), 7.11 (ft, JHH + JHH′ = 8, 2H, Ph),
6.75 (m, 2H, Ph), 6.65 (m, 4H, PPh), 5.94, 5.20 (2s, 2 × 5H, Cp).
13C{1H} NMR (100.61 MHz, Me2CO-d6): δ 187.5 (s, O2CPh), 143.4
[d, JCP = 35, C1(PPh)], 137.2, [m, C2,3(PPh)], 135.1 [s, C1(Ph)],
131.4 [m, C2,3(PPh)], 131.3 [s, C4(PPh)], 131.1 [s, C4(Ph)], 130.8
[s, C4(PPh)], 129.8, 129.2 [2 m, 2C2,3(PPh)], 129.1, 128.6 [2s,
2C2,3(Ph)], 100.3, 93.8 (2s, Cp). The resonance of the Mo-bound
carbonyl could not be located due to the low solubility of complex 8d.
Preparation of [Mo2Cp2(O,O′-O2CMe)(μ-PPh2)2(CO)]BF4 (8e).
The procedure and workup is analogous to that described for 4 but
using acetic acid (10 μL, 0.173 mmol) and a reaction time of 50 min.
This yielded compound 8e as an orange solid (0.040 g, 88%). Anal.
Calcd for C37.5H34BClF4Mo2O3P2 (8e·1/2CH2Cl2): C, 49.56; H 3.68.
(2 m, 2 × 6H, PPh), 7.02 (m, 4H, PPh), 6.17, 5.76 (2 m, AA′XX′, JAX
+
JAX′ = 9, 2 × 2H, C6H4), 5.47 (s, 5H, Cp), 4.78 (t, JPH = 1, 5H, Cp).
Preparation of [Mo2Cp2(O,N-OC6H4NH)(μ-PPh2)2(CO)] (11).
Neat DBU (50 μL, 0.334 mmol) was added to a solution of compound
5 (50 mg, 0.046 mmol) in dichloromethane (10 mL), and the mixture
was stirred for 10 min to give a deep green solution. Workup as
described for 10 gave compound 11 as a green solid (0.039 g, 92%).
Anal. Calcd for C42H37Cl2NMo2O2P2 (11·CH2Cl2): C, 55.28; H, 4.09;
1
Found: C, 49.52; H, 3.63. H NMR (200.13 MHz): δ 8.00−6.40 (m,
20H, Ph), 5.96, 5.17 (2s, 2 × 5H, 2Cp), 1.14 (s, 3H, Me). 13C{1H}
NMR (75.48 MHz): δ 234.4 (t, JCP = 10, MoCO), 196.0 (s, O2CMe),
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N, 1.54. Found: C, 54.95; H, 4.07; N, 1.49. IR (Nujol): ν(CO) 1853
(s), ν(NH) 3352 (w). 31P{1H} NMR (161.97 MHz, 288 K): δ 187.7,
176.8 (2s, br, Δυ1/2 = 14 Hz, μ-PPh2). 31P{1H} NMR (161.97 MHz,
213 K): δ 187.3, 176.6 (2d, JPP = 5, μ-PPh2). 1H NMR (288 K): δ 8.03
(m, 4H, PPh), 7.66−7.17 (m, 17H, PPh and NH), 6.19 (m, 2H,
C6H4), 5.80 (m, 1H, C6H4), 5.74 (t, JHH = 4, 1H, C6H4), 5.22, 4.70
(2s, 2 × 5H, Cp).
Preparation of [Mo2Cp2(μ-S,N:S,N-SC6H4NH)(μ-PPh2)2] (12).
Neat DBU (50 μL, 0.334 mmol) was added to a solution of compound
7 (0.050 mg, 0.054 mmol) in dichloromethane (10 mL), and the
mixture was stirred for 12 h to give a brown solution which was
filtered. The filtrate was then concentrated under vacuum and layered
with petroleum ether. Slow diffusion of the top layer at room
temperature gave orange crystals of compound 12, which were washed
with petroleum ether and dried under vacuum (0.038 g, 79%). Anal.
Calcd for C41H37Cl2NMo2P2S (12·CH2Cl2): C, 54.68; H, 4.14; N,
1.56. Found: C, 54.36; H, 4.22; N, 1.62. IR (Nujol): ν(NH) 3316 (w).
1H NMR (288 K): δ 7.15 (m, 10H, PPh), 6.76 (m, 7H, PPh and
C6H4), 6.56 (m, 4H, PPh), 6.19, 5.99 (2t, JHH = 7, 2 × 1H, C6H4), 5.71
(d, JHH = 7, 1H, C6H4), 5.56 (s, 10H, Cp), 1.94 (d, JHP = 13, 1H, NH).
1H NMR (243 K): δ 7.26 (m, 2H, PPh), 7.12 (m, 8H, PPh), 6.76 (m,
7H, PPh and C6H4), 6.58 (m, 4H, PPh), 6.22, 6.02 (2t, JHH = 7, 2 ×
1H, C6H4), 5.75 (d, JHH = 7, 1H, C6H4), 5.57 (s, 10H, Cp), 1.92 (d,
JHP = 13, 1H, NH).
Preparation of [Mo2Cp2{μ-S:N-N(S)CMe}(μ-PPh2)2] (14). Solid
sodium carbonate (ca. 0.050 g, excess) was added to a solution of
compound 8i (0.040 g, 0.041 mmol) in dichloromethane (10 mL),
and the mixture was stirred for 12 h to give a yellow solution which
was filtered. The solvent was then removed from the filtrate under
vacuum, and the residue was chromatographed on alumina (activity
IV) at 288 K. Elution with dichloromethane gave a yellow fraction,
yielding, after removal of the solvents, compound 14 as a yellow solid
(0.030 g, 86%). Anal. Calcd for C37H35Cl2NMo2P2S (14·CH2Cl2): C,
52.25; H, 4.15; N, 1.65. Found: C, 52.56; H, 4.65; N, 1.61. 1H NMR: δ
7.01 (m, 4H, Ph), 6.94, 6.71 (2 m, 2 × 6H, Ph), 6.55 (m, 4H, Ph),
5.69, 5.67 (2s, 2 × 5H, Cp), 1.45 (s, 3H, Me).
X-ray Structure Determination of Compound 6·CH2Cl2. The
intensity data of compound 6·CH2Cl2 were collected on a Bruker
SMART 1000 single-crystal diffractometer using a graphite-mono-
chromated Mo Kα radiation. Crystal data are reported in Table 4. The
structure was solved by Fourier methods and refined by full-matrix
least-squares procedures, first with isotropic thermal parameters and
then with anisotropic thermal parameters in the last cycles of
refinement for all non-hydrogen atoms.37 Hydrogen atoms were
introduced into the geometrically calculated positions and refined
riding on the corresponding parent atoms.
ASSOCIATED CONTENT
* Supporting Information
■
S
Preparation of [Mo2Cp2(μ-PPh2)2{N-N(O)CMe}(CO)] (13). Neat
DBU (50 μL, 0.334 mmol) was added to a solution of compound 8g
(0.050 g, 0.058 mmol) in dichloromethane (10 mL), and the mixture
was stirred for 10 min to give a deep red solution. The solvent was
then removed under vacuum, and the residue was chromatographed
on alumina (activity III) at 288 K. Elution with dichloromethane gave
a violet fraction, yielding, after removal of the solvents, compound 13
as a red solid (0.039 g, 92%). Anal. Calcd for C37H33NMo2P2O2 (13):
C, 57.16; H, 4.28; N, 1.80. Found: C, 57.27; H, 4.32; N, 1.94. IR
CIF file giving crystallographic data for structural analysis of
compound 6·CH2Cl2. This material is available free of charge
via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: mara@uniovi.es.
■
1
(Nujol): ν(CO) 1858 (vs), 1599 (m); ν(CN) 1247 (vs). H NMR
Notes
(400.13 MHz): δ 8.10−6.60 (m, 20H, Ph), 5.31 (s, 5H, Cp), 5.07 (s,
5H, Cp), 0.66 (s, 3H, Me). 13C{1H} NMR (100.63 MHz): δ 236.4 (t,
JCP = 10, MoCO), 178.9 [s, NC(O)Me], 148.8 [d, JCP = 10, C1(Ph)],
141.9 [d, JCP = 10, C1(Ph)], 136.0−127.3 (m, Ph), 98.3, 87.3 (2s, Cp),
22.3 (s, Me).
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank the DGI of Spain (Project CTQ2009-09444) for
supporting this work and the Consejeria de Educacion
Asturias for a postdoctoral reintegration grant (to D.G.V.). We
also thank Dr. M. T. Rueda for initial preparation of
compounds 8e and 13.
■
́
́
de
a
Table 4. Crystal Data for Compound 6·CH2Cl2
mol formula
mol wt
C41H36BCl2F4Mo2NOP2S
1002.30
REFERENCES
cryst syst
monoclinic
■
space group
radiation (λ, Å)
a, Å
P21/c
(1) (a) Seppelt, K. Angew. Chem., Int. Ed. Engl. 1993, 32, 1025.
(b) Strauss, S. H. Chem. Rev. 1993, 93, 927. (c) Beck, W.; Sunkel, K.
Chem. Rev. 1988, 88, 1405.
0.71073
̈
9.2349(6)
(2) (a) Rach, S. F.; Kuhn, F. E. Chem. Rev. 2009, 109, 2061.
(b) Chen, E. Y. X.; Marks, T. J. Chem. Rev. 2000, 100, 1391.
(3) Cimadevilla, F.; García, M. E.; García-Vivo, D.; Ruiz, M. A.;
́
̈
b, Å
16.7867(11)
c, Å
26.6004(17)
α, deg
90.0
Rueda, M. T.; Halut, S. J. Organomet. Chem. 2012, 699, 67.
(4) Complex 1 can be prepared as a red, soluble solid solvated with
1/2CH2Cl2, as determined by an X-ray study, but it readily transforms
into an orange insoluble hydrate of composition 1·1/2CH2Cl2·H2O.
Use of this insoluble material is preferred over that of anhydrous 1 for
preparative purposes, and its dissolution can be achieved easily by
addition of small amounts of methanol to the corresponding
suspension in dichloromethane (see ref 3).
β, deg
94.0780(10)
γ, deg
V, Å3
90.0
4113.2(5)
Z
4
calcd density, gcm−3
abs coeff, mm−1
temp., K
1.619
0.921
293
(5) Adatia, T.; McPartlin, M.; Mays, M. J.; Morris, M. J.; Raithby, P.
R. J. Chem. Soc., Dalton Trans. 1989, 1555.
θ range (deg)
reflns collected
independent reflns
reflns with I > 2σ(I)
R indexes [data with I > 2σ(I)]
R indexes (all data)
GOF
1.44−28.48
24 825
(6) (a) Alvarez, M. A.; Anaya, Y.; García, M. E.; Riera, V.; Ruiz, M. A.
J. Organomet. Chem. 2007, 692, 983. (b) Alvarez, M. A.; Anaya, Y.;
García, M. E.; Riera, V.; Ruiz, M. A. Organometallics 2005, 24, 2452.
(c) Alvarez, M. A.; Anaya, Y.; García, M. E.; Ruiz, M. A.
Organometallics 2004, 23, 3950. (d) Alvarez, M. A.; Anaya, Y.;
García, M. E.; Riera, V.; Ruiz, M. A. Organometallics 2004, 23, 433.
(e) Alvarez, M. A.; García, G.; García, M. E.; Riera, V.; Ruiz, M. A.;
9259
4870
R1 = 0.0577, wR2 = 0.1314
R1 = 0.1345, wR2 = 0.1666
0.949
a
R1 = Σ||Fo| − |Fc||/Σ|Fo|. wR2 = [Σw(|Fo|2 − |Fc|2)2/Σw|Fo|2]1/2
.
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Inorganic Chemistry
Article
Lanfranchi, M.; Tiripicchio, A. Organometallics 1999, 18, 4509.
(f) García, M. E.; Riera, V.; Rueda, M. T.; Ruiz, M. A. J. Am. Chem.
Soc. 1999, 121, 1960. (g) Alvarez, M. A.; García, M. E.; Riera, V.; Ruiz,
M. A.; Bois, C.; Jeannin, Y. Angew. Chem., Int. Ed. Engl. 1993, 32, 1156.
(7) (a) El Khalifa, M.; Gueguen, M.; Mercier, R.; Petillon, F. Y.;
Saillard, J. Y.; Talarmin, J. Organometallics 1989, 8, 140. (b) Petillon, F.
Y.; Schollhammer, P.; Talarmin, J.; Muir, K. W. Coord. Chem. Rev.
1998, 178−180, 203.
number CCDC 236733. (e) Dulatas, L. T.; Brown, S. N.; Ojomo, E.;
Noll, B. C.; Cavo, M. J.; Holt, P. B.; Wopperer, M. M. Inorg. Chem.
2009, 48, 10789. (f) Chaudhary, A.; Patra, R.; Rath, S. P. Eur. J. Inorg.
Chem. 2010, 5211. (g) Benedict, J. B.; Coppens, P. J. Am. Chem. Soc.
2010, 132, 2938.
(29) Darensbourg, D. J.; Klausmeyer, K. K.; Reibenspies, J. H. Inorg.
Chem. 1996, 35, 1535.
(30) Le Borgne, G.; Grandjean, D. Acta Crystallogr., Sect. B 1973, 29,
1040.
(31) (a) Nielson, A. J.; Hunt, P. A.; Rickard, C. E. F.; Schwerdtfeger,
P. J. Chem. Soc., Dalton Trans. 1997, 3311. (b) Thomas, S.; Lim, P. J.;
Gable, R. W.; Young, C. G. Inorg. Chem. 1998, 37, 590. (c) Clough, C.
R.; Greco, J. B.; Figueroa, J. S.; Diaconescu, P. L.; Davis, W. M.;
Cummins, C. C. J. Am. Chem. Soc. 2004, 126, 7742. (d) Sceats, E. L.;
Figueroa, J. S.; Cummins, C. C.; Loening, N. M.; Van der Wel, P.;
Griffin, R. G. Polyhedron 2004, 23, 2751. (e) Figueroa, J. S.; Piro, N.
A.; Clough, C. R.; Cummins, C. C. J. Am. Chem. Soc. 2006, 128, 940.
(f) Watanabe, D.; Gondo, S.; Seino, H.; Mizobe, Y. Organometallics
2007, 26, 4909. (g) Sarkar, S.; Abboud, K. A.; Veige, A. S. J. Am. Chem.
́
(8) Muir, K. W.; Girdwood, S. E.; Petillon, F. Y.; Pichon, R.; Poder-
Guillou, S.; Schollhammer, P.; Talarmin, J. J. Organomet. Chem. 1995,
486, 183.
(9) (a) Alvarez, C. M.; Alvarez, M. A.; García-Vivo, D.; García, M. E.;
́
Ruiz, M. A.; Saez, D.; Falvello, L. R.; Soler, T.; Herson, P. Dalton
Trans. 2004, 4168. (b) Alvarez, C. M.; Alvarez, M. A.; Alonso, M.;
García, M. E.; Rueda, M. T.; Ruiz, M. A. Inorg. Chem. 2006, 45, 9593.
(10) Braterman, P. S. Metal Carbonyl Spectra; Academic Press:
London, U.K., 1975.
(11) (a) Jameson, C. J. In Phosphorus-31 NMR Spectroscopy in
Stereochemical Analysis; Verkade, J. G., Quin, L. D., Eds.; VCH:
Deerfield Beach, FL, 1987; Chapter 6. (b) Wrackmeyer, B.; Alt, H. G.;
Maisel, H. E. J. Organomet. Chem. 1990, 399, 125.
Soc. 2008, 130, 16128. (h) Clough, C. R.; Muller, P.; Cummins, C. C.
̈
Dalton Trans. 2008, 4458.
(32) We have not detected the neutral carbonyl complex presumably
preceding formation of 14 after initial deprotonation of 8i.
Interestingly, an unstable carbonyl complex could be identified in a
related reaction using the thiobenzamidate analogue of complex 8i.
Unfortunately, all thiobenzamide derivatives were unstable and could
not be properly isolated as pure materials.
(33) Benoit, A.; Darchen, A.; Le Marouille, J.-Y.; Mahe, C.; Patin, H.
Organometallics 1983, 2, 555.
(34) Wantao, Z.; Shin, G.; Suy-Tin, S. Russ. J. Inorg. Chem. (Zh.
Neorg. Khim.) 1997, 42, 1107.
(35) Cotton, F. A.; Li, Z.; Liu, C. Y.; Murillo, C. A. Inorg. Chem.
2007, 46, 7840.
(36) Armarego, W. L. F.; Chai, C. Purification of Laboratory
Chemicals, 5th ed.; Butterworth-Heinemann: Oxford, U.K., 2003.
(37) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.
(12) García, M. E.; García-Vivo,
Organometallics 2008, 27, 3879.
(13) Alvarez, M. A.; García, M. E.; Martinez, M. E.; Ramos, A.; Ruiz,
M. A.; Saez, D. Inorg. Chem. 2006, 45, 6965.
(14) The crystals, all of poor quality, diffracted very weakly, so the
ratio between the observed and the unique reflections was very low.
Moreover, one of the two Cp rings was found disordered in two
positions and two phenyl groups disordered in two and three
positions. Crystal data of 8d: mol formula C42H35O3P2Mo2·BF4, mol
wt 928.33, monoclinic, space group P21/n, a = 17.045(4) Å, b =
10.885(3) Å, c = 22.433(5) Å, β = 93.10(3)°, V = 4156.0 (18) Å3, Z =
4, calcd density = 1.484 g cm−3.
́
D.; Ruiz, M. A.; Herson, P.
́
(15) Conole, G.; McPartlin, M.; Mays, M. J.; Morris, M. J. J. Chem.
Soc., Dalton Trans. 1990, 2359.
(16) Allen, F. H. Acta Crystallogr., Sect. B 2002, 58, 380.
(17) (a) Hong, M.; Su, W.; Cao, R.; Zhang, W.; Lu, J. Inorg. Chem.
1999, 38, 600. (b) Su, W. P.; Hong, M. C.; Weng, J. B.; Liang, Y. C.;
Zhao, Y. J.; Cao, R.; Zhou, Z. Y.; Chen, A. S. C. Inorg. Chim. Acta
2002, 331, 8.
(18) Deeming, A. J.; Karim, M.; Bates, P. A.; Hursthouse, M. B.
Polyhedron 1988, 7, 1401.
(19) Yu, P.; Huang, L.; Zhuang, B. Acta Crystallogr., Sect. C 1994, 50,
1191.
(20) Shi, Y. M.; Lu, S. W.; Guo, H. F.; Wu, Q. J.; Hu, N. H. J.
Organomet. Chem. 1996, 514, 183.
(21) (a) Becker, E.; Mereiter, K.; Schmid, R.; Kirchner, K.
Organometallics 2004, 23, 2876. (b) The analogous complex
[Ru2Cp*2(μ-SPy)2][BPh4]2 has also been reported recently:
Jimenez−Tenorio, M.; Puerta, M. C.; Valerga, P. Inorg. Chem. 2011,
́
50, 12399.
(22) Begum, N.; Kabir, S. E.; Hossain, G. M. G.; Rahman, A. F. M.
M.; Rosenberg, E. Organometallics 2005, 24, 266.
(23) Sokolov, M.; Sasaki, Y.; Umakoshi, K. Inorg. Chem. Commun.
2001, 4, 142.
(24) Zhuang, B. T.; Yu, P. H.; Huang, L. G.; He, L. J.; Pan, G. H.
Polyhedron 1997, 16, 1425.
(25) De Lima, M. B. G.; Guerchais., J. E.; Mercier, R.; Pet
Organometallics 1986, 5, 1952.
́
illon, F. Y.
(26) Cimadevilla, F.; García, M. E.; García-Vivo,
Tiripicchio, A. Unpublished results.
́
D.; Ruiz, M. A.;
(27) García, M. E.; Riera, V.; Ruiz, M. A.; Rueda, M. T.; Sae
́
z, D.
Organometallics 2002, 21, 5515.
(28) (a) Sacconi, L.; Orioli, P. L.; di Vaira, M. J. Chem. Soc., Chem.
Commun. 1967, 849. (b) Heistand, R. H.; Roe, A. L.; Que, L., Jr. Inorg.
Chem. 1982, 21, 676. (c) Dilworth, J. R.; Griffiths, D. V.; Parrott, S. J.;
Zheng, Y. F. J. Chem. Soc., Dalton Trans. 1997, 2931. (d) Kooijman,
H.; Alsters, P. L.; Baesjou, P. J.; van Koten, G.; Spek, A. L. Private
communication to the Cambridge Structural Database 2004, deposition
7295
dx.doi.org/10.1021/ic300626y | Inorg. Chem. 2012, 51, 7284−7295