Protonation of zwitterionic manganese and rhenium phosphoniostyryl complexes (I·5-C5H5)(CO) 2M--C(+PR3)=C(H)Ph: Experimental and DFT study

Article abstract of DOI:10.1002/ejic.201000868

Stereoselective addition of tertiary phosphanes to manganese and rhenium phenylvinylidenes (I·⁵-C₅H₅)(CO) ₂M=C=C(H)Ph (1 M = Mn; 2 M = Re) gave the corresponding zwitterionic Z-phosphoniostyryl adducts (I·⁵

Full text of DOI:10.1002/ejic.201000868

FULL PAPER
DOI: 10.1002/ejic.201000868
Protonation of Zwitterionic Manganese and Rhenium Phosphoniostyryl
Complexes (η5-C5H5)(CO)2M––C(+PR3)=C(H)Ph: Experimental and DFT
Study
Vasily V. Krivykh,*[a] Dmitry A. Valyaev,[a] Kamil I. Utegenov,[a] Andrei M. Mazhuga,[a]
Elena S. Taits,[a] Oleg V. Semeikin,[a] Pavel V. Petrovskii,[a] Ivan A. Godovikov,[a]
Ivan V. Glukhov,[a] and Nikolai A. Ustynyuk*[a]
Keywords: Vinylidene complexes / Manganese / Rhenium / Protonation / Zwitterions / X-ray diffraction / Density
functional calculations
Stereoselective addition of tertiary phosphanes to manga-
nese and rhenium phenylvinylidenes (η5-C5H5)(CO)2-
M=C=C(H)Ph (1 M = Mn; 2 M = Re) gave the corresponding
zwitterionic Z-phosphoniostyryl adducts (η5-C5H5)(CO)2-
followed by C,H-reductive elimination in the intermediate
hydride cis-(η5-C5H5)(CO)2(H)MnϪC(+PMe3)=C(H)Ph (14) to
form the agostic complex (η5-C5H5)(CO)2Mn{η2-H–C-
(+PMe3)=C(H)Ph} (15) and subsequent isomerization of the
MϪϪC(+PR3)=C(H)Ph (3 M = Mn, PR3 = PPh2Me; 4 Mn, latter into the final η2-phosphonioalkene 10. In line with the
PPhMe2; 5 Mn, PMe3; 6 Re, PPh2Me; 7 Re, PMe3). Proton- theoretical data, the low-temperature protonation (–80°C) of
ation of 3–7 with HBF4·OEt2 resulted in the formation of the
3 with triflic acid in an NMR tube directly gave the corre-
sponding phosponioalkene complex 8. Unlike 3, the proton-
ation of their rhenium analogues 6 and 7 under the same
conditions revealed the quantitative formation of cis-hydride
intermediates cis-[(η5-C5H5)(CO)2(H)ReϪC(+PR3)=C(H)Ph]-
OTf (16, 17), which undergo conversion into the correspond-
ing η2-phosponioalkene complexes 11 and 12 at ca. –30°C
η2-phosponioalkene (η5-C5H5)(CO)2M(η2-E-
complexes
HC(+PR3)=C(H)Ph) (8 Mn, PPh2Me; 9 Mn, PPhMe2; 10 Mn,
PMe3; 11 Re, PPh2Me; 12 Re, PMe3) rather than in the corre-
sponding phosphoniocarbene complexes (η5-C5H5)(CO)2-
M=C(+PR3)CH2Ph. It was shown by DFT calculations (B3LYP/
6-31G*) that the protonation of 5 proceeds at the metal atom
to terminal alkynes displaying remarkably different stereo-
selectivity. Addition of PPh2H to propargyl alcohols
HCϵCC(OH)RRЈ catalyzed by (η5-C5Me5)Ru(Cl)L2 [L2 =
(PPh3)2, η4-cod] leads to the formation of Z-Ph2P(H)-
C=C(H)C(OH)RRЈ (Z-selectivity 75–95%),[6] whereas the
reaction of aliphatic and aromatic alkynes HCϵCR with
PPh3 in the presence of acid using (η4-cod)2RhCl or (PPh3)4-
RhH as catalyst precursors affords E-vinylphosphonium
salts E-Ph3P+(H)C=C(H)R (E-selectivity Ͼ 90%).[7]
Introduction
Highly selective addition of nucleophiles to Cα atoms in
neutral and cationic transition-metal vinylidene complexes
have been shown to serve as the key step in catalytic anti-
Markovnikov transformations of terminal alkynes.[1]
Depending on the nature of the starting vinylidene com-
plex I and the nucleophile (Nu), a wide variety of α-hetero-
atom-substituted σ-vinyl complexes II can be obtained
(Scheme 1). The transient formation of anionic IIa and neu-
tral IIc species have been postulated in some catalytic reac-
tions, e.g. cyclization of 1,ω-alkynols[2] and anti-Markovni-
kov addition of water[3] and carboxylic acids[4] to terminal
alkynes. The formation of betaine-type complexes IIb pre-
sumably takes place in the ruthenium-catalyzed addition of
Me2NNH2 to terminal alkynes,[5] and the occurrence of the
cationic intermediates IId has been proposed in the catalytic
anti-Markovnikov addition of PPh2H and PPh3/MeSO2OH
[a] A. N. Nesmeyanov Institute of Organoelement Compounds,
Russian Academy of Sciences,
28 Vavilov str., 119991 Moscow, Russian Federation
Fax: +7-499-135-01-76
Scheme 1. General scheme for the nucleophilic addition to transi-
tion-metal vinylidene complexes I.
E-mail: vkriv@ineos.ac.ru
ustynyuk@ineos.ac.ru
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000868.
Although the structure of intermediates II and the regu-
larities of their protonation are indeed responsible for the
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V. V. Krivykh, N. A. Ustynyuk et al
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regio- and stereoselectivity of these catalytic processes, the 2 in hexane at room temperature (Scheme 3). Under these
chemistry of such species have been quite poorly investi- conditions, the target products 3–7 precipitated in an ana-
gated to date. This is probably caused by the fact that only lytically pure state.
few stable adducts IIb and IId are known, mostly prepared
by the stoichiometric reactions of neutral[8] and cationic[9]
vinylidene complexes with tertiary amines and phosphanes.
Since the structure of α-phosphoniovinyl adducts IIb can
be represented as a hybrid of two resonance forms, the elec-
trophilic addition to them can proceed both at the metal
and the β-carbon atoms, which leads to the η2-alkene IV
and carbene V complexes, respectively (Scheme 2).
Scheme 3. Synthesis of σ-phosphoniostyryl complexes 3–7.
It was shown by IR and NMR spectroscopy that the sta-
bility of adducts 3–7 towards dissociation into the starting
materials in solution depends both on the metal and nucleo-
philicity of the phosphane. For example, the adduct of a
moderately nucleophilic triphenylphosphane (η5-C5H5)-
(CO)2Mn––C(+PPh3)=C(H)Ph strongly dissociates in
dichloromethane solution at room temperature (ca. 90%
based on the IR data), whereas only traces of vinylidene 1
and PPh2Me were detected in a dichloromethane solution
Scheme 2. Possible reactivity of α-phosphoniovinyl complexes IIb
towards electrophiles.
of manganese complex 3 under the same conditions. The
analogous rhenium PPh2Me adduct 6 shows no evidence of
dissociation, as well as complexes 4, 5, and 7 derived from
more nucleophilic phosphanes.
To the best of our knowledge, the only clear example of
electrophilic addition to α-phosphoniovinyl adducts IIb was
noted for (η5-C5H5)(CO)2Mn––C(+PPh3)=C(H)Ph, which
was protonated to give the η2-alkene product [(η5-C5H5)-
(CO)2Mn[(η2-E-H(+PPh3)C=C(H)Ph]Cl.[8g] The proton-
ation of the structurally close β-phosphoniovinyl complexes
can proceed through both indicated reaction pathways: in
the case of (η5-C5H4R)(CO)2Mn––CH=CH(+PEt3) (R = H,
Me), the formation of the corresponding η2-alkene com-
plexes IV was observed,[10] whereas protonation of the re-
lated chromium complex (η6-1,3,5-C6H3Me3)(CO)2Cr––
CH=CH(+PnBu3) gave the phosphoniocarbene product
V.[11] The latter process is also characteristic of the proton-
ation of neutral transition-metal σ-vinyl complexes.[12]
Since regularities of protonation of transition-metal σ-
phosphoniovinyl complexes IIb remain unclear, we have
started a systematic study on the reactivity of these species
towards electrophiles. We report here the experimental and
theoretical studies of the protonation of the betaine-type σ-
phosphoniostyryl complexes (η5-C5H5)(CO)2M––C(+PR3)=
C(H)Ph (M = Mn, Re).
The molecular geometry of rhenium complex 6 was de-
termined by X-ray diffraction (Figure 1). Compound 6 has
a typical pseudo-octahedral piano-stool geometry. The Re–
C(8) and C(8)–C(9) distances of 2.151(3) and 1.362(5) Å,
respectively, in 6 are within the typical ranges for Re–C sin-
gle bonds and C=C double bonds. The C(8)–C(9) bond
length in betaine-type complex 6 is longer than the C=C
double bonds in the structurally similar iron cationic com-
plexes (η5-C5H5)(CO)(L)Fe–C(+PPh3)=C(H)R (L = CO, R
Results and Discussion
Synthesis of Manganese and Rhenium σ-Phosphoniostyryl
Complexes (η5-C5H5)(CO)2M––C(+PR3)=C(H)Ph (3–7):
Investigation of Their Stability and Structure
Figure 1.
Molecular
structure
of
(η5-C5H5)(CO)2Re––
C(+PPh2Me)=C(H)Ph (6) (thermal ellipsoids are shown with 30%
probability, hydrogen atoms are omitted for clarity.). Selected bond
lengths [Å] and angles [°]: Re(1)–C(1) 1.883(4), Re(1)–C(2)
1.873(4), Re(1)–C(8) 2.151(3), P(1)–C(8) 1.796, C(8)–C(9) 1.362(5);
C(1)–Re–C(2) 89.34(14), Re(1)–C(8)–P(1) 116.13(16), Re(1)–C(8)–
The betaine-type σ-phosphoniostyryl complexes 3–7
were prepared in good yields by addition of the correspond-
ing phosphane to solutions of vinylidene complexes 1 and C(9) 130.9(2).
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Protonation of Zwitterionic Manganese and Rhenium Phosphoniostyryl Complexes
= Ph, 1.35(1) Å;[9a] L = PPh3, R = H, 1.327(11) Å[9b]),
which is presumably a result of the contribution of the carb-
anionic resonance form (Scheme 2, right structure of IIb).
The Z geometry of all σ-phosphoniostyryl complexes 3–
1
7 was confirmed by H and 31P NMR spectroscopy. The
3
values of JH,P coupling constants observed (40–44 Hz) are
very close to those (3JH,P(cis) 40–43 Hz; 3JH,P(trans) 68–74 Hz)
reported for the structurally similar manganese betaine-
type α-phosphoniovinyl complexes (η5-C5MenH5–n)(CO)2-
Mn––C(+PR3)=CH2 (R = Me, Et; n = 0, 1, 5).[10a] The same
large difference between the coupling constants of the phos-
phorus atom with the vinylic cis- and trans-hydrogen atoms
was observed for the related cationic rhenium [(η5-
Scheme 4. Synthesis of η2-phosphonioalkene complexes 8–12.
3JH,P = 17–18 Hz, and 2JH,P = 7.5–7.7 Hz) clearly show that
the alkene ligands in 8–12 have the E configuration (see
ref.[10b]). NMR analysis of crude products shows no evi-
dence of the presence of the corresponding Z isomers of 8–
12. Though our attempts to get reasonable NMR 13C{1H}
data for the manganese complexes 3–5 and 8–10 failed, pre-
sumably because of the drastic loss of sensitivity caused by
the formation of traces of paramagnetic impurities during
the experiment, the related rhenium analogues 6, 7, 11 and
12 were fully characterized by NMR spectroscopy.
C5H5)(NO)(PPh3)Re–C(+PMe3)=C(H)Me]OTf
(3JH,P(cis)
3
36 Hz; JH,P(trans) 61 Hz),[9c] iron [(η5-C5H5)(CO)(PPh3)Fe–
3
C(+PR3)=CH2]BF4 (PR3 = PPh3, PPhMe2; JP,H(cis) 23 Hz,
3JP,H(trans) 46–53 Hz),[9b] andruthenium[(η5-C5H5)(Ph2Me)2-
Ru–C(+PPh2Me)=CH2]PF6 (3JP,H(cis) 39 Hz, JP,H(trans)
3
73 Hz) complexes.[9e] Importantly, the Z isomer of 5 was
calculated to be more stable by 13–14 kJ/mol than the cor-
responding E isomer (see below).
In the family of transition-metal π-alkene complexes,
phosphonioalkene ligands are quite rare.[8g,9e,10,15] Besides
the protonation of σ-vinylphosphonium adducts,[8g,10] these
compounds have been prepared by the innersphere phos-
phane/alkenyl coupling (for ruthenium[9e] and palladium[15]
complexes) or by direct coordination of alkenylphosphon-
ium salts (Pd complexes[15e]).
Stereoselective Protonation of σ-Phosphoniostyryl
Complexes 3–7 to the Cationic η2-Phosphonioalkene
Products [(η5-C5H5)(CO)2M(η2-E-H(+PR3)C=C(H)Ph)]-
BF4 (8–12)
We found in our initial experiments that the addition of
a strong protic acid (HBF4·OEt2) to the dichloromethane
solution of manganese σ-phosphoniostyryl complex 3 at
–70 °C afforded the η2-phosphonioalkene complex [(η5-
C5H5)(CO)2Mn(η2-E-H(+PPh2Me)C=C(H)Ph)]BF4 (8) in a
good yield. The purity of isolated 8 was confirmed by IR
spectroscopy and elemental analysis; however, 1H NMR
characterization of this compound was complicated by
traces of paramagnetic impurities. The appearance of these
unidentified admixtures is presumably caused by acid-in-
duced oxidation processes,[13] which results in persistent
DFT Study of the Protonation of the Manganese
Phosphoniostyryl Complex (η5-C5H5)(CO)2Mn––C-
(+PMe3)=C(H)Ph (5)
The transformation of α-phosphoniostyryl complexes 3–
7 into η2-phosphonioalkene derivatives 8–12 corresponds
formally to the direct protonation of the Mn–Cα bond. Be-
sides this straightforward route [Scheme 5, path (a) + (b)],
other reaction pathways could be proposed that involve ini-
paramagnetic radicals such as those recently reported [(η5-
[14]
C5H5)(CO)2Mn·–C(+PR3)=CHPh]PF6
or MnII and
MnIII salts as products of its further decomposition. The
separation of 8 from paramagnetic by-products was only
achieved by low-temperature chromatography (–20 to
–40 °C) on silica by using a polar eluent (CH2Cl2/acetone,
10:1).
However, a more convenient synthetic procedure for
these manganese η2-phosphonioalkene complexes that avo-
ids the use of chromatography was then discovered. It was
found that the protonation of solutions of 3–5 in ether at
–70 °C led to the precipitation of the target compounds 8–
10 in an analytically pure state free of paramagnetic admix-
tures (Scheme 4). The related rhenium complexes 11 and 12
were prepared similarly in high yields.
Phosphonioalkene complexes 8–12 are bright to pale yel-
low crystalline substances stable in air for a long time when
solids; this is especially relevant to the rhenium compounds.
Scheme 5. Possible reaction pathways for the protonation of the σ-
phosphoniostyryl complex (η5-C5H5)(CO)2Mn––C(+PMe3)=C-
The values of the coupling constants (3JH,H = 11–12 Hz, (H)Ph (5).
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tial protonation either at the Cβ atom of the σ-phos- The Properties of the HOMO Orbital of Z-5: Impossibility
phoniostyryl ligand or at the metal atom in complexes 3–7 of Direct Protonation Across the Mn–Cα Bond in Z-5
[path (c) and (e), respectively]. To get a better insight into
The protonation site in betaine-type complex Z-5 should
be determined mainly by the charges of the potential reac-
tion centers (the metal atom and the Cα, and Cβ atoms of
the σ-phosphonioalkenyl ligand) and by the contribution of
the center orbitals to the HOMO of the molecule. The
charge distribution in Z-5 was calculated in terms of the
NBO approach, which reveals the following charge density
values for the Mn (–0.31), Cα (–0.50), and Cβ (–0.26) atoms,
and therefore show the Cα atom as the preferred proton-
ation site in a charge-controlled reaction.
the mechanism of the protonation, the possible reaction
pathways (Scheme 5) were calculated for manganese com-
plex 5 by using Becke–Lee–Young–Parr density functional
hybrid approach. The main part of calculations was per-
formed by using the 6-31+G* basis set, which was extended
in some cases to 6-31++G** one (see Experimental Section
for details).
The Relative Stability of the Regioisomers and Conformers
for Manganese σ-Phosphoniostyryl Complex 5
However, the analysis of the orbital population for Z-5
reveals the most significant contribution of the metal atom
orbitals in the HOMO (Figure 2), whereas the participation
of the Cα atom orbitals is negligibly small. Thus, proton-
ation of Z-5 at this atom, which leads to the formation of
the agostic complex 15, cannot proceed, irrespective of its
high negative charge [Scheme 5, path (a) + (b)].
Phosphoniostyryl complexes 3–7 can exist as conforma-
tionally stable E and Z isomers at room temperature, as was
experimentally found for the structurally related rhenium
complexes
(η5-C5H5)(NO)(PPh3)Re–C(+PMe3)=C(H)-
CH3.[9c] According to our calculations, the most stable is
the experimentally observed Z isomer of 5, which has the
phosphane and the phenyl group in a trans disposition to
each other (Table 1). Complex Z-5 displays the degenerated
rotation across the Mn–Cα bond with an activation barrier
of 32.2 kJ/mol. The less stable E isomer has two conformers
E-5a and E-5b, which differ in the values of the dihedral
angle between the phenyl ring and the σ-phosphoniostyryl
ligand planes.
Table 1. Formation energies and relative stabilities of the isomers
of 5 (in kJ/mol).
Figure 2. HOMO orbital geometry of Z-5.
The protonation of Z-5 can thus proceed either at the Cβ
atom or at the manganese atom [Scheme 5, path (c) and
(e), respectively]. The latter pathway seems more preferable
when orbital control is taken into account.
[a] [M] = (η5-C5H5)(CO)2Mn. [b] Δ1E0 and Δ2E0 – formation ener-
gies of isomers 5 from vinylidene complex 1 and PMe3 for 6-31G*
and 6-31++G** basis sets, respectively, in kJ/mol. [c] ΔEZ – thermo-
dynamic stability with respect to complex Z-5. [d] N/A – the corre-
sponding stationary point was not found.
General Calculation Details on the Protonation of Z-5
Since the protonation of σ-phosphoniostyryls (Scheme 4)
was carried out by using HBF4·OEt2 in dichloromethane or
ether, the dimethyloxonium cation [HOMe2]+ was consid-
According to both calculation and experimental data, the ered as a protic acid model in the gas phase for the calcula-
E isomers of 5 are not present in the reaction mixture in tion. At the B3LYP/6-31++G** level of theory, a proton
noticeable amounts; therefore, their protonation was ex- transfer from [HOMe2]+ either to the manganese atom or
cluded from consideration.
to the Cβ atom was shown to be barrier free, which is quite
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Protonation of Zwitterionic Manganese and Rhenium Phosphoniostyryl Complexes
similar to the typical proton transfer processes to O, N, F Hydride complexes 14a and 14b are conformers that differ
and S centers.[16] On the other hand, the impossibility of in the disposition of the PMe3 fragment to the hydride li-
determining the barrier for proton addition may be caused gand (syn- and anti-, respectively). Importantly, they cannot
by the fact that [HOMe2]+ is not a fully appropriate proton interconvert easily because of a relatively high rotation bar-
model for the reaction conditions used in the synthesis of rier of the phosphoniostyryl group around the Mn–Cα
8–12 (Scheme 4). It should also be noted that the small mo- bond (31.8 kJ/mol), which noticeably exceeds their barriers
lecule [HOMe2]+, which has a localized positive charge, is for further reductive elimination processes. Complexes 14a
highly destabilized in the gas phase relative to the proton- and 14b result from direct protonation of complex Z-5 from
ation products 13 and 14 in which the positive charge is the side of the PMe3 and the styryl group, respectively
largely delocalized. Therefore, high protonation energies (Scheme 7).
obtained for the transformations Z-5 Ǟ 13 (ΔE =
–208.9 kJ/mol) and Z-5 Ǟ 14a,b (ΔE = –158.8 and
–148.4 kJ/mol, respectively) are not fully reliable for the real
protonation process in solution. The utilization of other
proton models including an increased number of solvent
molecules such as [H(OMe2)2]+ is very time consuming and
was not performed in this work. Nevertheless, one can be-
lieve that the activation barriers to proton addition at both
reaction sites (Mn and Cβ) are small, and, therefore, the
outcome of the protonation process should be determined
by subsequent reaction steps.
Protonation of Complex Z-5 at the Cβ Atom
The formation of η2-phosphonioalkene complex 10
through the initial protonation of Z-5 at the Cβ atom in-
cludes the formation of the phosphoniocarbene complex 13
and the concerted intramolecular 1,2-hydrogen shift in the
latter complex[17] [Scheme 5, (c) + (d) + (b)]. The first step
(c), i.e. the formation of the phosphoniocarbene 13, is
highly exothermic (ΔE = –208.9 kJ/mol). The conversion of
13 into the agostic complexes 15 (path c) is also thermody-
namically feasible (ΔE = –9.9 and + 1.8 kJ/mol for the for-
mation of 15a and 15b, respectively; see Scheme 7), but,
very importantly, it is forbidden because of the high acti-
vation barrier (173.1 kJ/mol for the transformation 13 Ǟ
15a). Thus, the only possible pathway for the phospho-
niocarbene Ǟ phosphonioalkene isomerization 13 Ǟ 10 is
the base-catalyzed rearrangement of Fischer-type carbene
complexes[18] including the protonation of σ-phospho- Scheme 7. Two possible reaction pathways for protonation of Z-5
at the metal atom. The formation energies (ΔEX) of complexes aris-
ing from the protonation process Z-5 + HOMe2 Ǟ Me2O + X
are given in parenthesis. The activation barriers are given near the
niostyryl complex 5 at the metal atom, which is considered
below.
+
reaction arrows.
Protonation of Complex Z-5 at the Metal Atom
The protonation of Z-5 at the metal atom can lead to
On the basis of the shape of the HOMO of Z-5 (Fig-
the formation of hydride species having a cis- (14a and 14b)
ure 2), trans-hydride 14c cannot be formed by direct pro-
and trans- (14c) four-leg piano-stool geometry (Scheme 6).
tonation because of the absence of the space between the
two carbonyl ligands for proton-to-metal binding and can
arise from the rearrangement of the initially formed cis-hy-
drides 14a and 14b only. Since 14c is an unproductive com-
pound, unable to undergo the reductive elimination (depro-
tonation or rearrangement to 14a are only possible), it was
excluded from consideration.
The conversion of hydrides 14a and 14b into the corre-
sponding η2-phosphonioalkene complex 10 was found to
Scheme 6. Structure and relative energies of isomers of the manga-
nese hydride complex 14.
proceed in two steps [Scheme 5, (f) + (b)] rather than one
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V. V. Krivykh, N. A. Ustynyuk et al
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[Scheme 5, (g)]. The intermediate agostic structures 15a and
15b were identified on the potential energy surface
(Scheme 7), and the activation barriers to their formation
were calculated to be 6.2 and 2.7 kJ/mol, respectively. The
further transformations of agostic compounds 15 are also
fast and selectively afford two different rotamers of η2-
phosphonioalkene complex 10a and 10b. Importantly, the
nature of the rotamer formed from Z-5 is a function of the
side on which the initial protonation takes place (from the
PMe3 side or the styryl side in Z-5 for the formation of 10a
or 10b, respectively). Finally, the less stable conformer 10b
should undergo rotation along the alkene ligand to afford
10a as a single or predominant product.
Scheme 8. Low-temperature protonation of rhenium complexes 6
and 7.
The calculated rotational barrier for 10 (17.5 kJ/mol) is
significantly lower than the experimental values found for
manganese η2-alkene complexes (η5-C5H5)(CO)2Mn(η2-
H(R)C=C(R)H) (35–50 kJ/mol; R = H, Br, OMe, CO-
OMe).[19] Variable-temperature NMR studies of η2-phos- responds probably to the carbonyl group trans-disposed to
phonioalkene rhenium complexes 11 and 12 reveal an in- the σ-phosphoniovinyl moiety because of the presence of
crease in the rotational barrier for the alkene ligand bearing 3JC,P coupling. The 2D NOESY spectrum of complex 16
the more bulky phosphonio moiety. Complex 12, having a reveals a strong cross-peak between the Me and Ph substit-
small PMe3 fragment, displays one set of NMR signals even uents of the PPh2Me moiety, as well as weak cross-peaks
at –100 °C in CD2Cl2 solution, whereas for 11, which has a of the hydride ligand with the PPh2Me and Cp groups. This
1
3
PPh2Me moiety, decoalescence of both H and 31P signals data together with the absence of the JH,P coupling in the
is observed at –70 °C to afford clearly the slow-exchange signals of the hydride ligands lead us to propose that hy-
NMR pattern at –100 °C. The estimated rotational barrier dride complexes 16 and 17 have a syn-conformation as in
ΔG# = 35.5 kJ/mol is again lower than those observed for the calculated manganese complex 14a.
coordinated E- and Z-alkene ligands in [(η5-C5H5)(NO)-
To the best of our knowledge, complexes 16 and 17 repre-
sent the first examples of half-sandwich rhenium cis-organ-
ylhydrides of the type (η5-C5H5)(CO)2(X)ReH that are
stable at low temperature and fully characterized. The for-
mation of cis-phosphonioallenylhydride intermediate by
protonation of the related γ-phosphonioallenyl complex
(PPh3)Re(η2-H(R)C=C(R)H)]BF4 (R = alkyl, aryl; ΔG#
=
46.2–78.1 kJ/mol).[20]
Low-Temperature Protonation of σ-Phosphoniostyryl
(η5-C5H5)(CO)2Re––C(Tol)=C13=C13(Ph)+PPh2Me
was
Complexes 3, 6, and 7 with Triflic Acid
proposed by Casey et al.[21] on the basis of H, 31P, 13C
1
On the basis of the calculation data, the reductive elimi- (labeled atoms) NMR spectroscopy. This complex proved
nation process in the manganese hydrides 14 proceeds very to be highly thermolabile (τ1/2 30 min at –80 °C) and readily
easily; thus the probability of NMR detection of the initial undergoes conversion into the corresponding η2-phospho-
protonation products [(η5-C5H5)(CO)2(H)Mn–C(+PR3)= nioallene complex [(η5-C5H5)(CO)2Re(η2-HC(Tol)=C13=
C(H)Ph]OTf is rather unlikely. In line with this expectation, C13(Ph)PPh2Me)]OTf. The transient formation of the cis-
the addition of CF3SO2OH (TfOH, 1.1 equiv.) to a CD2Cl2 hydridoacyl
cis-(CO)2(H)Re–C(=O)CH2CH2(η5-C5H4)
solution of the manganese complex (η5-C5H5)(CO)2Mn–– from the corresponding trans precursor was also proposed
C(+PPh2Me)=C(H)Ph (3) at –80 °C led to its gradual trans- to explain the results of its thermal reaction with PPh3 to
formation into η2-phosphonioalkene product 8 without any form (η5-C5H4CH2CH2CHO)(CO)2Re(PPh3).[22]
detectable hydride intermediates. Gratifyingly, the proton-
It is noteworthy that dicarbonyl trans-organylhydride
ation of the related rhenium complexes 6 and 7 under the rhenium complexes are generally more stable than their cis
same conditions resulted in the hydride species 16 and 17, isomers, as was evidenced both experimentally[23] and by
respectively, as only products (Scheme 8). Complex 16 un- DFT calculations (cis isomers are 18–20 kJ/mol less stable)
dergoes reductive elimination above –30 °C, whereas for its [24] for a series of σ-arylhydride complexes (η5-C5R5)(CO)2-
less bulky PMe3 analogue 17, this process proceeds slowly (H)Re–Ar (R = H, Me; Ar = C6F5, 2,3,5,6-C6F4H, 2,4-
even at –40 °C (ca. 30% conversion after two hours).
C6H3F2). The NMR spectra of the cis-σ-phosphoniovi-
1
The H and 31P{1H} NMR spectroscopic data show un- nylhydrides 16 and 17 in a temperature region of –100 to
ambiguously that rhenium hydride complexes 16 and 17 ex- –40 °C show no traces of an isomeric hydride species. We
ist in solution as single regioisomers. The presence of two suppose that for complexes 16 and 17 selectively formed at
different CO groups in the 13C{1H} NMR spectra [16: low temperature, as well as for the related cis-σ-phosphonio-
3
195.8 (d, JC,P = 7.8 Hz), 192.5 (s); 17: 198.5 (br. s), 191.1 allenylhydride complex reported by Casey,[21] the reductive
(s)] allows us to clearly attribute the observed compounds elimination process is much easier than the isomerization
to cis-hydrides. The upfield CO resonance in each case cor- into the potentially more stable trans-hydride compounds.
206
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 201–211

Protonation of Zwitterionic Manganese and Rhenium Phosphoniostyryl Complexes
An additional DFT study on the relative stability of the cis- L2Ru+=C=C(H)C(OH)RRЈ (E-alkene selectivity 55–65%),
and trans isomers and on the reductive elimination process in which the formation of Z-IId becomes even more prefer-
for such rhenium hydride complexes may shed light on this able than E-IId. The regularities of phosphane addition to
phenomenon.
vinylidene complexes are not completely understood yet,
and additional studies are required to gain a better insight
into such type of processes.
Conclusions
Experimental Section
The protonation of manganese and rhenium σ-phos-
phoniostyryl complexes Z-(η5-C5H5)(CO)2M––C(+PR3)=
C(H)Ph (3–7) results in stereoselective formation of the η2-
phosphonioalkene complexes [(η5-C5H5)(CO)2M(η2-E-
All operations were carried out under an argon atmosphere by
using standard Schlenk techniques. Solvents were purified by using
standard procedures and distilled under argon prior to use. IR
H(+PR3)C=C(H)Ph)]BF4 (8–12), and no phosphoniocar- spectra were recorded on a Specord 75 IR spectrophotometer (Carl
Zeiss, Jena) and are given in cm–1 with relative intensity in paren-
bene by-products (η5-C5H5)(CO)2M=C(+PR3)CH2Ph re-
sulting from the protonation at the Cβ atom were detected.
DFT calculations of the reaction pathways for manganese
complex (η5-C5H5)(CO)2Mn––C(+PMe3)=C(H)Ph (5) re-
veals the initial proton addition at the metal atom to afford
the cis-hydride intermediate cis-(η5-C5H5)(CO)2(H)Mn–
C(+PPh2Me)=C(H)Ph (14), followed by its subsequent low-
barrier transformations into the agostic complex [(η5-
C5H5)(CO)2Mn(η2-(C,H)-E-H–C(+PPh2Me)=C(H)Ph)] (15),
and finally to the η2-phosphonioalkene product 10. In
line with these calculation data, all attempts to detect the
manganese hydride intermediate in the low-temperature
protonation of 3 with triflic acid failed, but the protonation
of their rhenium analogues 6 and 7 resulted in quantitative
formation of the corresponding cis-hydrides, cis-(η5-
C5H5)(CO)2(H)Re–C(+PR3)=C(H)Ph (16, 17), which are
stable below –50 °C and readily undergo reductive elimi-
nation above –40 °C. Complexes 16 and 17 represent the
first examples of fully spectroscopically characterized half-
sandwich rhenium cis-hydrides of the type (η5-C5H5)-
(CO)2(X)ReH.
As was briefly mentioned in the introduction the proton-
ation of transition-metal σ-phosphonioalkenyl complexes is
a likely final step of the catalytic addition of tertiary and
secondary phosphanes to terminal alkynes.[6,7] Our results
show clearly that the protonation of σ-phosphoniovinyl
complexes of the type IIb and IId (see Scheme 1) only fixes
the geometry of the alkenyl moiety, which is determined
for half-sandwich vinylidene complexes by the phosphane
addition step. Having these data in mind, one can assume
that the opposite stereoselectivity (E and Z products,
respectively) in the catalytic addition of PPh3/MeSO2OH[7]
and PPh2H[6] to terminal alkynes is caused by the different
structure of the reaction intermediates IId. The Z-stereose-
lective addition of PPh3 to rhodium cationic vinylidene
complexes followed by rapid protonation of Z-IId with acid
to give E-alkene products[7] corresponds ideally to the same
processes studied here for manganese and rhenium phenyl-
vinylidenes. The E-stereoselective PPh2H addition to the ru-
thenium vinylidene intermediates (η5-C5Me5)L2Ru+=C=
C(H)C(OH)RRЈ to form E-IId is probably caused by the
bulkiness of both the metal fragment and substituents at
the Cβ atom of the vinylidene ligand, which destabilizes the
usual addition product Z-IId. This assumption is well con-
1
thesis. H, 13C{1H}, and 31P{1H} NMR spectra were recorded on
Bruker Avance 300, Bruker Avance 400, and Bruker Avance 600
instruments at 25 °C and referenced to the residual deuterated sol-
vent signals (1H and 13C NMR) and external 85% H3PO4, respec-
tively. Vinylidene complexes 1[25] and 2[26] and phosphanes
[29]
PPh2Me,[27] PPhMe2,[28] and PMe3
literature procedures.
were prepared according to
Synthesis of Z-(η5-C5H5)(CO)2Mn––C(+PPh2Me)=C(H)Ph (3):
PPh2Me (160 mg, 0.8 mmol) was added to a solution of 1 (112 mg,
0.4 mmol) in hexane (10 mL) at room temperature, and the mixture
was stirred for 2 h. The yellow precipitate formed was filtered off,
washed with hexane, and dried in vacuo to yield 3 as a yellow solid.
Yield: 172 mg (90%). IR (CH Cl ): ν = 1890 (s, CO), 1814 (s, CO)
˜
2
2
cm–1. 1H NMR (300.1 MHz, C6D6, 25 °C): δ = 8.04–7.00 (m, 15
3
H, C6H5), 7.73 [d, JH,P = 43.9 Hz, 1 H, =C(H)Ph], 4.27 (s, 5 H,
2
C5H5), 2.23 (d, JH,P = 12.9 Hz, 3 H, PCH3) ppm. 31P{1H} NMR
(121.5 MHz, C6D6, 25 °C): δ = 11.7 (s) ppm. C28H24MnO2P (478):
calcd. C 70.30, H 5.06; found C 70.51, H 5.02.
Synthesis of Z-(η5-C5H5)(CO)2Mn––C(+PMe2Ph)=C(H)Ph (4):
Similarly, from a solution of 1 (56 mg, 0.2 mmol) in hexane (5 mL)
and PPhMe2 (55 mg, 0.4 mmol), complex 4 was obtained as a yel-
low solid. Yield: 71 mg (85%). IR (CH Cl ): ν = 1888 (s, CO), 1814
˜
2
2
1
(s, CO) cm–1. H NMR (300.1 MHz, C6D6, 25 °C): δ = 7.98–7.00
3
(m, 10 H, C6H5), 7.69 [d, JP,H = 41.4 Hz, 1 H, =C(H)Ph], 4.13
(br. s, 5 H, C5H5), 1.37 [br. s, 6 H, P(CH3)2] ppm. 31P{1H} NMR
(121.5 MHz, C6D6, 25 °C): δ = 8.0 (s) ppm. C23H22MnO2P (416):
calcd. C 66.35, H 5.33, Mn 13.2; found C 66.17, H 5.21, Mn 13.4.
Synthesis of Z-(η5-C5H5)(CO)2Mn––C(+PMe3)=C(H)Ph (5): Simi-
larly, from a solution of 1 (55 mg, 0.2 mmol) in hexane (5 mL) and
a solution of PMe3 (18 mg, 0.24 mmol) in diethyl ether (2 mL),
complex 5 was obtained as a yellow solid. Yield: 61 mg (87%). IR
(CH Cl ): ν = 1896 (s, CO), 1811 (s, CO) cm–1. 1H NMR
˜
2
2
(300.1 MHz, [D6]acetone, 25 °C): δ = 7.94 [d, 3JH,P = 42.5 Hz, 1 H,
3
3
=C(H)Ph], 7.75 (d, JH,H = 7.4 Hz, 2 H, Hortho Ph), 7.36 (t, JH,H
3
= 7.6 Hz, 2 H, Hmeta Ph), 7.21 (t, JH,H = 7.7 Hz, 1 H, Hpara Ph),
2
4.07 (s, 5 H, C5H5), 1.93 [d, JH,P = 12.4 Hz, 9 H, P(CH3)3] ppm.
31P{1H} NMR (121.5 MHz, [D6]acetone, 25 °C): δ = 13.1 (s) ppm.
Synthesis of Z-(η5-C5H5)(CO)2Re––C(+PMePh2)=C(H)Ph (6):
Similarly, from a solution of 2 (64 mg, 0.16 mmol) in hexane
(15 mL) and PPh2Me (0.043 mL, 0.24 mmol), complex 6 was ob-
tained as a pale yellow solid. Yield: 89 mg (96%). IR (CH Cl ): ν
˜
2
2
= 1880 (s, CO), 1806 (s, CO) cm–1. 1H NMR (300.1 MHz, CD2Cl2,
3
25 °C): δ = 7.64–7.51 (m, 12 H, PPh2, Hortho Ph), 7.41 [d, JH,P
=
41.1 Hz, 1 H, =C(H)Ph], 7.29 (m, 2 H, Hmeta Ph), 7.20 (m, 1 H,
Hpara Ph), 4.66 (s, 5 H, C5H5), 2.58 (d, 2JH,P = 12.6 Hz, 3 H, PCH3)
ppm. 31P{1H} NMR (121.5 MHz, CD2Cl2, 25 °C): δ = 20.1 (s)
firmed by the results obtained for less bulky (η5-C5H5)- ppm. 13C{1H} NMR (150.9 MHz, CD2Cl2, 25 °C): δ = 208.9 (d,
Eur. J. Inorg. Chem. 2011, 201–211
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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207

V. V. Krivykh, N. A. Ustynyuk et al
FULL PAPER
3JC,P = 19.8 Hz, Re–CO), 159.2 (d, JC,P = 12.5 Hz, Cipso =CPh),
Synthesis of [(η5-C5H5)Mn(CO)2(η2-E-HC(P+Me3)=C(H)Ph)]BF4
3
1
146.5 (d, JP,C = 36.7 Hz, Cipso PPh2), 136.2–132.1 (CPh, PPh2), (10): Similarly, from
5
(70 mg, 0.2 mmol) and HBF4·Et2O
(0.028 mL, 0.2 mmol) in the ether (5 mL), complex 10 was obtained
as a yellow solid. Yield: 78 mg (89%). IR (CH Cl ): ν = 1983 (s,
1
130.4 (d, JC,P = 74.8 Hz, PC=CPh), 129.5 (s, PC=CPh), 87.7 (s,
C5H5), 15.8 (d, 1JC,P = 71.9 Hz, PCH3) ppm. C28H24O2PRe (609.2):
calcd. C 55.28, H 4.09, P 5.01; found C 55.16, H 3.97, P 5.08.
˜
2
2
CO), 1916 (s, CO) cm–1. 1H NMR (300.1 MHz, [D6]acetone,
3
3
25 °C): δ = 7.52 (d, JH,H = 7.4 Hz, 2 H, Hortho Ph), 7.32 (t, JH,H
Synthesis of Z-(η5-C5H5)(CO)2Re––C(+PMe3)=C(H)Ph (7): Simi-
larly, from a solution of 2 (30 mg, 0.07 mmol) in hexane (7 mL)
and a solution of PMe3 (7.6 mg, 0.1 mmol) in diethyl ether (1 mL),
complex 7 was obtained as a pale yellow solid. Yield: 27 mg (76%).
3
= 7.4 Hz, 2 H, Hmeta Ph), 7.22 (t, JH,H = 7.4 Hz, 1 H, Hpara Ph),
4.83 (s, 5 H, C5H5), 4.26 [m, 1 H, =C(H)P], 4.15 [m, 1 H, =C(H)
Ph], 2.08 (d, JH,P = 12.5 Hz, 9 H, PCH3) ppm. 31P{1H} NMR
2
(121.5 MHz, [D6]acetone, 25 °C):
δ
=
35.1 (s) ppm.
IR (C H ): ν = 1890 (s, CO), 1808 (s, CO) cm–1. 1H NMR
˜
6
6
C18H21BF4MnO2P (442): calcd. C 48.90, H 4.79, Mn 12.43; found
C 48.72, H 4.68, Mn 12.48.
(400.1 MHz, [D6]acetone, 25 °C): δ = 7.82 [d, 3JH,P = 40.2 Hz, 1 H,
3
3
=C(H)Ph], 7.72 (d, JH,H = 7.4 Hz, 2 H, Hortho Ph), 7.31 (t, JH,H
Synthesis of [(η5-C5H5)Re(CO)2(η2-E-HC(P+Ph2Me)=C(H)Ph)]-
BF4 (11): Similarly, from 6 (61 mg, 0.1 mmol) and HBF4·Et2O
(0.014 mL, 0.1 mmol) in the ether (5 mL), complex 11 was obtained
3
= 7.6 Hz, 2 H, Hmeta Ph), 7.21 (t, JH,H = 7.3 Hz, 1 H, Hpara Ph),
2
4.67 (s, 5 H, C5H5), 2.00 [d, JH,P = 12.5 Hz, 9 H, P(CH3)3] ppm.
31P{1H} NMR (162.0 MHz, [D6]acetone, 25 °C): δ = 20.1 (s) ppm.
13C{1H} NMR (100.6 MHz, CD2Cl2, 25 °C): δ = 209.7 (s, Re–CO),
as a white powder. Yield: 69 mg (99%). IR (CH Cl ): ν = 1982 (s,
˜
2
2
CO), 1906 (s, CO) cm–1. H NMR (600.2 MHz, CD2Cl2, 25 °C): δ
1
2
1
149.1 (d, JC,P = 10.6 Hz, PC=CPh), 143.6 (d, JC,P = 35.1 Hz,
3
1
= 7.80–7.34 (m, 10 H, PPh2), 7.24 (d, JH,H = 7.7 Hz, 2 H, Hortho
PC=CPh), 129.2–126.2 (Ph), 84.6 (s, C5H5), 12.7 [d, JC,P
57.3 Hz, P(CH3)3] ppm.
=
3
3
CPh), 7.15 (t, JH,H = 7.7 Hz, 2 H, Hmeta CPh), 6.99 (t, JH,H
=
3
7.3 Hz, 1 H, Hpara CPh), 5.08 (s, 5 H, C5H5), 4.33 [dd, JH,H(trans)
= 10.4, JH,P(cis) = 15.9 Hz, 1 H, =C(H)Ph], 4.03 [dd, JH,H(trans)
10.3, JH,P = 6.9 Hz, 1 H, =C(H)P], 2.14 (d, JH,P = 12.7 Hz, 3 H,
PCH3) ppm. 31P{1H} NMR (243.0 MHz, CD2Cl2, 25 °C): δ = 32.6
(s) ppm. 13C{1H} NMR (150.9 MHz, CD2Cl2, 25 °C): δ = 201.4
Preparation of [(η5-C5H5)(CO)2Mn(η2-E-HC(P+Ph2Me)=C(H)-
Ph)]BF4 (8) in a Dichloromethane Solution: An ethereal solution of
HBF4 (54%, 0.04 mL, 0.3 mmol) was added to a solution of 8a
(113 mg, 0.24 mmol) in CH2Cl2 (4 mL) cooled to –70 °C, with stir-
ring. The reaction mixture was stirred for 30 min at this tempera-
ture, and ether (20 mL) was added. The yellow precipitate formed
was filtered off, washed with diethyl ether, and dried to afford crude
8, which was further purified by column chromatography on silica
at low temperature (–20 to –40 °C). The light yellow fraction was
eluted with a CH2Cl2/acetone (10:1) mixture. The eluate was evapo-
rated in vacuo to afford 8 as a yellow powder. Yield: 96 mg (74%).
3
3
=
2
2
3
(d, JC,P = 9.3 Hz, Re–COtrans), 201.2 (s, Re–COcis), 143.4–122.3
1
(Ph, PPh2), 91.2 (s, C5H5), 38.0 [s, =C(H)Ph], 7.9 [d, JC,P
80.6 Hz, =C(H)P], 7.2 (d, JC,P
=
1
= 61.3 Hz, PCH3) ppm.
C28H25BF4O2PRe (697.2): calcd. C 48.22, H 3.61, P 4.44; found C
48.36, H 3.70, P 4.40.
Synthesis of [(η5-C5H5)Re(CO)2(η2-E-HC(P+Me3)=C(H)Ph)]BF4
(12): Similarly, from
(0.007 mL, 0.05 mmol) in the ether (5 mL), complex 12 was ob-
tained as a white solid. Yield: 39 mg (89%). IR (CH Cl ): ν = 1987
6 (27 mg, 0.05 mmol) and HBF4·Et2O
IR (CH Cl ): ν = 1982 (s, CO), 1924 (s, CO) cm–1. 1H NMR
˜
2
2
(300.1 MHz, [D6]acetone, 25 °C): δ = 8.35–7.23 (m, 10 H, C6H5),
˜
2
2
4.82 [dd, 3JH,H(trans) = 11.65, 2JH,P = 7.7 Hz, 1 H, =C(H)P], 4.74 (s,
(s, CO), 1903 (s, CO) cm–1. 1H NMR (600.2 MHz, [D6]acetone,
3
3
5 H, C5H5), 4.58 [dd, JH,H(trans) = 12.5, JH,P(cis) = 17.8 Hz, 1 H,
3
3
25 °C): δ = 7.36 (d, JH,H = 7.4 Hz, 2 H, Hortho Ph), 7.30 (t, JH,H
2
=C(H)Ph], 2.47 (d, JH,P = 12.9 Hz, 3 H, PCH3) ppm. 31P{1H}
3
= 7.3 Hz, 2 H, Hmeta Ph), 7.16 (t, JH,H = 7.2 Hz, 1 H, Hpara Ph),
NMR (121.5 MHz, [D6]acetone, 25 °C):
C28H25BF4MnO2P (566): calcd. C 59.40, H 4.45; found C 59.50, H
4.61.
δ = 32.1 (s) ppm.
5.52 (s, 5 H, C5H5), 4.38 [dd, 3JH,H(trans) = 10.9, 3JH,P(cis) = 16.8 Hz,
3
2
1 H, =C(H)Ph], 4.27 [dd, JH,H(trans) = 10.6, JH,P = 6.8 Hz, 1 H,
=C(H)P], 2.07 (d, JH,P = 12.5 Hz, 9 H, PCH3) ppm. 31P{1H}
2
NMR (243.0 MHz, [D6]acetone, 25 °C): δ = 35.1 (s) ppm. 13C{1H}
NMR (150.9 MHz, CD2Cl2, 25 °C): δ = 202.0 (br. s, Re–CO), 201.2
(s, Re–CO), 143.4–129.0 (Ph), 90.9 (s, C5H5), 38.4 [s, =C(H)Ph],
Preparation of [(η5-C5H5)Mn(CO)2(η2-E-HC(P+Ph2Me)=C(H)-
Ph)]BF4 (8) in an Ethereal Solution: Complex 3 (48 mg, 0.1 mmol)
was added as a solid to a solution of HBF4·OEt2 (0.014 mL,
0.1 mmol) in diethyl ether (5 mL) cooled to –70 °C, and the reac-
tion mixture was slowly warmed to room temperature. Within the
temperature interval 12–15 °C, the bright orange color of the start-
ing solution changed to light yellow of the η2-phosphonioalkene
product. The mixture was then stirred for additional hour at room
temperature. The precipitate 8 was filtered off, washed twice with
ether, and dried first in an argon stream and then in vacuo. Yield:
1
10.2 [d, 1JC,P = 76.3 Hz, =C(H)P], 10.1 (d, JC,P = 56.4 Hz, PCH3)
ppm.
Variable-Temperature 1H and 31P{1H} NMR Spectroscopy Data for
[(η5-C5H5)Re(CO)2(η2-E-HC(P+Ph2Me)=C(H)Ph)]OTf ([11]OTf):
The activation energy barrier was calculated by using the approxi-
mation of the Eyring equation: ΔG# = RTc(22.96 + lnTc/δν), where
Tc [K] is the estimated coalescence temperature of two signals sepa-
rated by δν [Hz].
57 mg (100%). IR (CH Cl ): ν = 1982 (s, CO), 1924 (s, CO) cm–1.
˜
2
2
Synthesis of [(η5-C5H5)Mn(CO)2(η2-E-HC(P+PhMe2)=C(H)- [11]OTf: 1H NMR (400.1 MHz, CD2Cl2, 25 °C): δ = 7.86–7.38 (m,
3
Ph)]BF4 (9): Similarly, from 4 (42 mg, 0.1 mmol) and HBF4·Et2O
(0.014 mL, 0.1 mmol) in the ether (5 mL), complex 9 was obtained
10 H, PPh2), 7.32 (d, JH,H = 7.5 Hz, 2 H, Hortho CPh), 7.18 (t,
3JH,H = 7.5 Hz, 2 H, Hmeta CPh), 7.02 (t, 3JH,H = 7.3 Hz, 1 H, Hpara
CPh), 5.13 (s, 5 H, C5H5), 4.61 [dd, JH,H(trans) = 10.4, JH,P(cis)
15.9 Hz, 1 H, =C(H)Ph], 4.06 [dd, JH,H(trans) = 10.3, JH,P
3
3
as a yellow solid. Yield: 43 mg (85%). IR (CH Cl ): ν = 1984 (s,
=
=
˜
2
2
CO), 1924 (s, CO) cm–1. 1H NMR (300.1 MHz, [D6]acetone,
3
2
2
25 °C): δ = 8.13–7.23 (m, 10 H, C6H5), 4.82 (s, 5 H, C5H5), 4.45 6.9 Hz, 1 H, =C(H)P], 2.17 (d, JH,P = 12.7 Hz, 3 H, PCH3) ppm.
[dd, JH,H(trans) = 10.8, JH,P = 7.6 Hz, 1 H, =C(H)P], 4.36 [dd, 1H NMR (400.1 MHz, CD2Cl2, –100 °C): δ = 8.15–7.10 (m, 15 H,
3
2
3JH,H(trans) = 10.8, 3JH,P(cis) = 17.0 Hz, 1 H, =C(H)Ph], 2.56 (d, 2JH,P
PPh2, Ph), 5.22 (s, 5 H, C5H5), 4.82 [br. s, =C(H)Ph major isomer],
= 13.4 Hz, 3 H, PCH3), 2.21 (d, 2JH,P = 13.3 Hz, 3 H, PCH3) ppm. 4.37 [br. s, =C(H)P major isomer], 4.01 [br. s, =C(H)Ph minor iso-
31P{1H} NMR (121.5 MHz, [D6]acetone, 25 °C): δ = 33.1 (s) ppm.
C23H23BF4MnO2P (504): calcd. C 54.80, H 4.60, Mn 10.9; found
C 54.45, H 4.61, Mn 10.4.
mer], 3.57 [br. s, =C(H)P minor isomer], 2.70 (br. s, PCH3 minor
isomer), 2.01 (br. s, PCH3 major isomer) ppm. 31P{1H} NMR
(162.0 MHz, CD2Cl2, 25 °C): δ = 31.65 (s) ppm. 31P{1H} NMR
208
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 201–211

Protonation of Zwitterionic Manganese and Rhenium Phosphoniostyryl Complexes
(162.0 MHz, CD2Cl2, –100 °C): δ = 34.05 (s, minor isomer), 31.6
(s, major isomer) ppm.
ABS program.[32] The structure was solved by direct methods and
refined by full-matrix least-squares against F2 in anisotropic (for
non-hydrogen atoms) approximation. All H(C) atoms were placed
in geometrically calculated positions and refined in isotropic
approximation with a riding model. All calculations were per-
formed on an IBM PC/AT by using the SHELXTL software.[33]
Crystallographic data and refinement parameters for 6 are given in
Table 2. CCDC-742639 contains the supplementary crystallo-
graphic data for the structure of 6. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Low-Temperature Protonation of Complex Z-(η5-C5H5)(CO)2Re––
C(+PMePh2)=C(H)Ph (6) in the NMR Tube: Complex 6 (30 mg,
0.05 mmol) was dissolved in CD2Cl2 (ca. 0.5 mL), and the solution
was filtered through Celite directly into an NMR tube. The NMR
tube was capped with a rubber septum, and the sample was cooled
to –80 °C. At this temperature, the solution of TfOH (5 μL,
0.055 mmol) in CD2Cl2 (0.1 mL) was added by a syringe, which
led, after gentle shaking, to a change in the color of the solution
from yellow to light rose. The NMR tube was rapidly inserted into
the precooled NMR spectrometer probe (–80 °C), and the rhenium
hydride complex cis-[(η5-C5H5)(CO)2(H)Re–C(+PMePh2)=C(H)-
Ph]OTf (16) was observed as the only product. Complex 16 was
shown to be absolutely stable for hours below –50 °C. The re-
ductive elimination process in 16 started at ca. –30 °C and was
completed at about –10 to 0 °C to form quantitatively the η2-phos-
phonioalkene complex 11.
Table 2. Crystallographic details of 6.
Compound
6
Molecular formula
Crystal color, habit
Crystal size [mm]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C28H24O2PRe
Yellow, prism
0.18ϫ0.12ϫ0.11
monoclinic
P21/c
15.8201(16)
12.1554(17)
11.9825(16)
90
1
16: H NMR (400.1 MHz, CD2Cl2, –80 °C): δ = 7.87–7.50 [m, 11
H, PPh2, =C(H)Ph], 7.42 (t, 3JH,H = 7.3 Hz, 2 H, Hmeta CPh), 7.35
3
3
(t, JH,H = 7.3 Hz, 1 H, Hpara CPh), 7.29 (d, JH,H = 7.7 Hz, 2 H,
2
Hortho CPh), 5.07 (s, 5 H, C5H5), 2.72 (d, JH,P = 12.7 Hz, 3 H,
PCH3), –8.87 (s, 1 H, Re–H) ppm. 31P{1H} NMR (162.0 MHz,
β [°]
97.034(3)
90
2286.9(5)
4
1.771
54
CD2Cl2, –80 °C): δ = 36.35 (s) ppm. 13C{1H} NMR (100.6 MHz,
γ [°]
V [Å3]
3
CD2Cl2, –80 °C): δ = 195.8 (d, JC,P = 7.8 Hz, Re–COtrans), 192.5
(s, Re–COcis), 169.3 (d, 2JC,P = 9.1 Hz, PC=CPh), 141.2 (d, 1JC,P
=
Z
Dcalcd. [gcm–3]
2θmax [°]
29.8 Hz, PC=CPh), 134.2–127.6 (Ph, PPh2), 88.0 (s, C5H5), 9.9 (d,
1JC,P = 64.8 Hz, PCH3) ppm.
Absorption coefficient, μ(Mo-Kα) [mm–1] 5.407
Low-Temperature Protonation of Complex Z-(η5-C5H5)(CO)2Re––
C(+PMe3)=C(H)Ph (7) in the NMR Tube: Complex 7 (25 mg,
0.05 mmol) was dissolved in CD2Cl2 (ca. 0.5 mL), and the solution
was filtered through Celite directly into an NMR tube. The NMR
tube was capped with rubber septum, and the sample was cooled
to –80 °C. At this temperature, a solution of TfOH (5 μL,
0.055 mmol) in CD2Cl2 (0.1 mL) was added by a syringe, which
led, after gentle shaking, to a change in the color of the solution
from yellow to light rose. The NMR tube was rapidly inserted into
the precooled NMR spectrometer probe (–80 °C), and the rhenium
hydride complex cis-[(η5-C5H5)(CO)2(H)Re–C(+PMe3)=C(H)Ph]-
OTf (17) was observed as the only product. The reductive elimi-
nation process in 17 proceeded slowly at –40 °C (30% conversion
into 12 after 2 h) and was completed at –20 °C to form quantita-
tively the η2-phosphonioalkene complex 12.
No. reflections collected
Completeness
No. independent reflections
No. observed reflections [I Ͼ2σ (I)]
Absolute structure parameters
No. of parameters
R1 (on F for observed reflections)
wR2 (on F2 for all reflections)
Weighting scheme
16879
1.000
4994 (Rint = 0.0366)
3494
290
0.0326
0.0424
2
w–1 = σ2(Fo ) + (aP)2 + bP
P = 1/3(Fo + 2Fc2)
2
a
b
0.01
1.00
1192
1.043
F(000)
GOF
Largest diff. peak and hole [eÅ–3]
0.923 and –0.543
3
17: 1H NMR (400.1 MHz, CD2Cl2, –60 °C): δ = 8.11 [d, JP,H
=
Computational Details: Calculations were carried out for the gas
phase by the Becke–Lee–Young–Parr density functional approach
(B3LYP) by using the GAUSSIAN 03 program. Full geometry op-
timizations were performed with the 6-31G* basis set[34,35] for all
the structures studied. The structures corresponding to local min-
ima on the PES were also studied with the 6-31++G** basis
set.[36,37] The procedure for location and calculation of transition-
state structures was made with QST2[38] and/or Opt(CalcAll,TS)
methods. All stationary points were characterized by frequency cal-
culations in the 6-31G* basis set to give positive definite Hessian
matrices (minima on the PES) and a sole negative eigenvalue in
their diagonalized force constant matrices (transition states). ZPE
correction of the internal energy was performed for all minima and
transition states in the 6-31G* basis set. The natural bonding or-
bital method[39] was used to analyze the electronic structures of the
stable compounds.
35.2 Hz, 1 H, =C(H)Ph], 7.49–7.36 (m, 5 H, C6H5), 5.03 (s, 5 H,
C5H5), 2.72 (br. d, 2JH,P = 11.0 Hz, 9 H, PCH3), –8.61 (s, 1 H, Re–
1
H) ppm. H NMR (400.1 MHz, CD2Cl2, –100 °C): δ = 8.05 [br. d,
3JP,H = 34 Hz, 1 H, =C(H)Ph], 7.48–7.25 (m, 5 H, C6H5), 4.96 (s,
5 H, C5H5), 1.96 (br. s, 9 H, PCH3), –8.59 (s, 1 H, Re–H) ppm.
31P{1H} NMR (162.0 MHz, CD2Cl2, –100 °C): δ = 34.6 (s) ppm.
13C{1H} NMR (100.6 MHz, CD2Cl2, –80 °C): δ = 198.5 (br. s, Re–
2
COtrans), 191.1 (s, Re–COcis), 162.6 (d, JC,P = 6.6 Hz, PC=CPh),
140.9 (d, JC,P = 28.0 Hz, PC=CPh), 128.8–128.1 (s, Ph), 88.2 (s,
1
1
C5H5), 11.5 (d, JC,P = 56.8 Hz, PCH3) ppm.
Single-Crystal X-ray Diffraction Analysis: Single-crystal X-ray dif-
fraction experiments for 6 were carried out with a Bruker SMART
APEX II area detector diffractometer, by using graphite monochro-
mated Mo-Kα radiation (λ = 0.71073 Å, ω-scans) at 100 K. The
low temperature of the crystal was maintained with a Cryostream
(Oxford Cryosystems) open-flow N2 gas cryostat. Reflection inten-
sities were integrated by using the SAINT software,[30,31] and ab-
sorption correction was applied semiempirically by using the SAD-
Supporting Information (see footnote on the first page of this arti-
cle): Energies and Cartesian coordinates of all calculated interme-
diates and transition states.
Eur. J. Inorg. Chem. 2011, 201–211
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
209

V. V. Krivykh, N. A. Ustynyuk et al
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Received: August 12, 2010
Published Online: November 12, 2010
Eur. J. Inorg. Chem. 2011, 201–211
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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211