Bulky N-phosphinomethyl-functionalized N-heterocyclic carbene chelate ligands: Synthesis, molecular geometry, electronic structure, and their ruthenium alkylidene complexes

Article abstract of DOI:10.1021/om300487r

A new, extremely bulky, and electron-rich N-phosphinomethyl-functionalized N-heterocyclic carbene ligand, 5a (^tBuNHCP^tBu), and a somewhat less bulky congener, 5b (^MesNHCP^tBu), forming five-membered chelate rings with metal centers, have been synthesized in four steps starting from the easily accessible di-tert-butyl(hydroxymethyl)phosphine oxide (1). 5a was isolated and fully characterized by spectroscopic methods including UV-photoelectron spectroscopy and X-ray diffraction. The reaction of 5a with [Ru(COD)Cl₂]_n under hydrogen pressure or with [Ru(p-cymene)Cl₂]₂ led to the formation of the unsaturated dinuclear complex [Ru(^tBuNHCP^tBu)(μ-Cl)(Cl)] ₂ (6), which serves as a precursor for a series of ruthenium carbene complexes (7a-f) using substituted phenyldiazomethanes (p-X-C₆H ₄(CH)N₂; X = H (a), Br (b), CF₃ (c), NO ₂, (d), CH₃ (e)) and trimethylsilyldiazomethane (f). Treatment of 6 with phosphine or pyridine ligands led to the formation of the mononuclear adducts, [Ru(^tBuNHCP^tBu)(Cl ₂)(PR₃)] (R = Me (8), Ph (9), Cy (10)) and [Ru( ^tBuNHCP^tBu)(Cl₂)(py)_n] (n = 1 (11), 2 (12); if (py)₂ = bipy (13)), which were synthesized in order to find alternative precursor complexes because the dimer 6 showed very low solubility in most organic solvents. Complex 7a was obtained analytically pure on a different route via transmetalation from a silver complex bearing ^tBuNHCP^tBu (15) to the first-generation Grubbs catalyst as the ruthenium precursor. Complexes 7a-c and 7e were characterized by X-ray diffraction analysis, revealing a geometry that can be viewed as both a distorted square pyramid and a distorted trigonal bipyramid with the two chloro ligands in a cis configuration. The steric bulk, especially of 5a with its N-tBu moiety, stabilizes 16 VE Ru complexes. In contrast to ligand 5a, the somewhat less bulky ^MesNHCP^tBu ligand 5b has allowed its direct metalation with two ruthenium alkylidene precursors, affording the two new carbene complexes 17 and 18.

Full text of DOI:10.1021/om300487r

Article
pubs.acs.org/Organometallics
Bulky N‑Phosphinomethyl-Functionalized N‑Heterocyclic Carbene
Chelate Ligands: Synthesis, Molecular Geometry, Electronic
Structure, and Their Ruthenium Alkylidene Complexes
Hiyam Salem,† Martin Schmitt,‡,§ Ulrike Herrlich (nee Blumbach),‡,⊥ Erik Kuhnel,‡ Marcel Brill,‡
́
̈
Philipp Nagele,‡ Andre Luiz Bogado,‡,∥ Frank Rominger,‡ and Peter Hofmann*,†,‡
́
̈
†Catalysis Research Laboratory (CaRLa), University of Heidelberg, Im Neuenheimer Feld 584, D-69120 Heidelberg, Germany
‡Organisch-Chemisches Institut, University of Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
S
* Supporting Information
ABSTRACT: A new, extremely bulky, and electron-rich N-
phosphinomethyl-functionalized N-heterocyclic carbene li-
gand, 5a (tBuNHCPtBu), and a somewhat less bulky congener,
5b (MesNHCPtBu), forming five-membered chelate rings with
metal centers, have been synthesized in four steps starting
from the easily accessible di-tert-butyl(hydroxymethyl)phosphine oxide (1). 5a was isolated and fully characterized by
spectroscopic methods including UV-photoelectron spectroscopy and X-ray diffraction. The reaction of 5a with [Ru(COD)Cl2]n
under hydrogen pressure or with [Ru(p-cymene)Cl2]2 led to the formation of the unsaturated dinuclear complex
[Ru(tBuNHCPtBu)(μ-Cl)(Cl)]2 (6), which serves as a precursor for a series of ruthenium carbene complexes (7a−f) using
substituted phenyldiazomethanes (p-X-C6H4(CH)N2; X = H (a), Br (b), CF3 (c), NO2, (d), CH3 (e)) and
trimethylsilyldiazomethane (f). Treatment of 6 with phosphine or pyridine ligands led to the formation of the mononuclear
adducts, [Ru(tBuNHCPtBu)(Cl2)(PR3)] (R = Me (8), Ph (9), Cy (10)) and [Ru(tBuNHCPtBu)(Cl2)(py)n] (n = 1 (11), 2 (12); if
(py)2 = bipy (13)), which were synthesized in order to find alternative precursor complexes because the dimer 6 showed very
low solubility in most organic solvents. Complex 7a was obtained analytically pure on a different route via transmetalation from a
silver complex bearing tBuNHCPtBu (15) to the first-generation Grubbs catalyst as the ruthenium precursor. Complexes 7a−c and
7e were characterized by X-ray diffraction analysis, revealing a geometry that can be viewed as both a distorted square pyramid
and a distorted trigonal bipyramid with the two chloro ligands in a cis configuration. The steric bulk, especially of 5a with its N-
tBu moiety, stabilizes 16 VE Ru complexes. In contrast to ligand 5a, the somewhat less bulky MesNHCPtBu ligand 5b has allowed
its direct metalation with two ruthenium alkylidene precursors, affording the two new carbene complexes 17 and 18.
crowded systems as the ones described within this work bearing
sterically demanding groups on both the phosphorus and at one
of NHC nitrogens has not yet been reported. By far, most
research related to the use of NHCPs as spectator ligands in
transition metal catalysis has focused on cross-coupling
reactions.5a,b,d,g,h,k,o,6a A few papers on ruthenium coordination
chemistry of NHCP ligands have been published, although
neither one deals with catalysis related to olefin metathesis.5s−v
In previous work we have reported the synthesis of cationic
ruthenium alkylidene complexes based on the bulky and
electron-rich bis(di-tert-butylphosphino)methane (dtbpm) li-
gand7 and their exceptionally high activity in ring-opening
metathesis polymerization (ROMP) of, for example, cyclo-
octene.8 Their neutral precursors (dtbpm)RuCl2(alkylidene)
resemble the square pyramidal first generation of Grubbs
catalysts, but the enforced cis coordination of the two chloro
ligands and thus their trans position to the phosphorus donors
of the cis-chelating dtbpm ligand results in a facile abstraction of
one of the chloro ligands even by TMS triflate. Ruthenium
INTRODUCTION
■
Since the development of the first generation of Grubbs
catalysts, a large variety of ruthenium alkylidene complexes for
olefin metathesis have been prepared by replacing one or both
of the phosphines with N-heterocyclic carbene ligands
(NHCs), pyridines, chelating Schiff bases, or pyridine-alkoxides
or by varying the alkylidene moiety.1 However, the employ-
ment of chelating NHC ligands in these systems has attracted
only little attention,2 with the exception of Hoveyda’s axially
chiral 1,1′-binaphthyl- or 1,1′-biaryl-substituted NHC-ruthe-
nium catalysts for asymmetric olefin metathesis3 and the very
recently introduced catalysts for Z-selective olefin metathesis by
Grubbs et al. featuring NHC ligands with C−H-activated N-
adamantyl groups, leading to sterically crowded five-membered
chelate complexes.4 We became interested in developing
analogues of the Grubbs second-generation catalysts with
sterically demanding bidentate hybrid ligands of phosphines
and N-heterocyclic carbenes. Although numerous phosphino-
functionalized NHC ligands have been published since the
synthesis of the first representative by Herrmann et al. in 1996,5
only two systems possess electron-rich dialkyl-substituted
phosphino groups.6 Moreover, the development of sterically
Received: June 1, 2012
Published: January 2, 2013
© 2013 American Chemical Society
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a
Scheme 1
a
(i) TsCl, NEt3, THF, 12 h, RT. (ii) 3a: N-tert-butylimidazole, 4 d, 100 °C; 3b: N-mesitylimidazole, toluene, 7 d, 120 °C. (iii) HSiCl3, C6H5Cl, 4a: 3
h, 120 °C; 4b: 2 d, 80 °C. (iv) KOtBu, THF, 2 h, RT.
Figure 1. ORTEP plots of the cation 4a and free NHCP 5a. Thermal ellipsoids are at the 50% probability level. Most hydrogen atoms and the
counterion are omitted for clarity. Selected bond lengths (Å) and angles (deg) of 4a: C1−N2 = 1.332(2); C1−N5 = 1.326(3); N2−C3 = 1.384(3);
N5−C4 = 1.380(3); C3−C4 = 1.353(3); N2−C1−N5 = 109.0(2); N2−C10−P1 = 111.81(14). Selected bond lengths (Å) and angles (deg) of 5a:
C1−N2 = 1.367(2); C1−N5 = 1.368(2); N2−C3 = 1.387(2); N5−C4 = 1.394(2); C3−C4 = 1.328(3); N2−C1−N5 = 101.94(15); N2−C10−P1 =
112.67(13).
alkylidene complexes of the same type with an enlarged P−
Ru−P bite angle were also prepared in our group based on
another bulky bisphosphine ligand, bis(di-tert-butylphosphino)-
ethane (dtbpe),9 and they have shown a decrease of activity in
ROMP reactions compared to their analogous dtbpm-based
systems.10 In light of the high activity of the cationic ruthenium
dtbpm-based complexes in ROMP reactions we have aimed at
the synthesis of comparably bulky and electron-rich chelating
hybrid ligands composed of an N-heterocyclic carbene moiety
and an N-connected phosphinomethyl functionality −CH2−
PR2 (called NHCP ligands in the following), appropriate for
producing cis analogues of the second generation of Grubbs
catalysts. We report herein the synthesis of such new, very
bulky bidentate NHCP ligands (RNHCPR′; R = tBu, Mes; R′ =
tBu) and their ruthenium alkylidene complexes. Complexes
based on the extremely bulky system tBuNHCPtBu (5a) were
prepared by two different routes, either by utilizing diazo
compounds and an electronically and coordinatively unsatu-
rated 16 VE ruthenium dimer (6) based on ligand tBuNHCPtBu
or via transmetalation from a silver adduct of 5a to the Grubbs
first-generation catalyst. A direct metalation of the slightly less
bulky ligand MesNHCPtBu (5b) with ruthenium alkylidene
complexes as precursors is also presented. Additionally, we have
studied the reactivity of dinuclear complex 6 towards
phosphines and pyridines.
RESULTS AND DISCUSSION
■
Synthesis of Bulky N-Phosphinomethyl-Functional-
ized NHC Ligands. We have developed a convenient synthetic
route to new chelating N-phosphinomethyl-functionalized N-
heterocyclic carbene ligands (NHCPs) 5a11 and 5b (Scheme
1), which were expected to form five-membered chelate rings
upon metal complexation. N-Substituted imidazolium salts
usually serve as precursors for N-heterocyclic carbenes and are
often synthesized by nucleophilic attack of an N-substituted
imidazole on an alkyl halide.12 Since these reactions often
require high temperatures and long reaction times, this
approach initially was considered limited since substances
such as R2PCH2X (X = leaving group) are unstable and tend to
polymerize at room temperature.13 Therefore, the correspond-
ing phosphine oxides tBu2P(O)CH2X were used for the
synthetic route outlined in Scheme 1. They additionally allow
a more convenient handling under noninert conditions.
To the best of our knowledge only three other examples of
NHCP ligands with a methylene bridge between the nitrogen
and the phosphorus atoms have been reported in the literature.
These compounds with much less bulky diphenyl-substituted
phosphine moieties were prepared from either Ph2P(O)CH2Br
or Ph2P(O)CH2Cl5n,r and the corresponding substituted
imidazoles or by the reaction of chloromethyl-substituted
benzimidazole with R2PLi5t,6b (R = Ph, Cy), also leading to
significantly less crowded systems than the ones described
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Table 1. Ionization Potentials (IPj) of tBuNHCPtBu (5a) from
the UV Photoelectron Spectrum Compared to the
Computed (HF/6-31G**) Orbital Energies (−εj)
herein, because one of the two NHC nitrogens remains
unsubstituted.
Our synthesis involves four steps starting from the known di-
tert-butyl(hydroxymethyl)phosphine oxide 1,14 which was
reacted with tosyl chloride in the presence of triethylamine to
give the tosylate 2 in reasonable yield. Compound 2 and the N-
substituted imidazole were coupled at high temperatures for
several days, affording the imidazolium salts 3a,b. In the case of
N-tert-butylimidazole a temperature higher than 100 °C led to
partial decomposition and a black product mixture resulting
also in a decrease of the yield. When applying tBu2P(O)CH2Cl
instead of 2, there was no reaction, indicating the necessity of a
better leaving group. Subsequent reduction of the phosphine
oxides 3a,b using an excess of HSiCl3 in chlorobenzene resulted
in the ligand precursors 4a,b in which the tosylate anions were
completely replaced by chloride anions due to the generation of
HCl during the course of the reaction.
PES
IPj
HF calculation
−εj
−εj − Δ1
assignment
7.7
8.12
8.61
9.15
9.84
7.7
8.2
8.7
9.4
(NHC-π3) − (P-σ(lp))
(NHC-π3) + (P-σ(lp))
(NHC-σ(lp))
HOMO
(7.9/8.2)
8.8
HOMO−1
HOMO−2
HOMO−3
9.4
(NHC-π2)
groups can act as potential electron reservoirs and are able to
efficiently delocalize the positive charge resulting from the
valence shell ionizations. A geometric relaxation after the
ionization process is less likely to happen, as it will be much
slower than the ionization process in the photoelectron
experiment. Therefore, the orbital energies can be correlated
to the ionization energies by shifting the values by the
differences between the HOMO energies and the first
ionization potentials; Δ1 = −ε1(SCF) − IP1 ≈ 0.4 eV. Thus,
the photoelectron spectrum is reproduced well, and the ligand
HOMO is attributed to a molecular orbital that is the
antibonding combination of the π3 orbital of the NHC ring
with the phosphorus lone pair π3NHC−lpP (with the larger
contribution of the NHC π-system to this MO, Figure 2). The
Deprotonation of the imidazolium salts 4a,b with KOtBu
resulted in the clean generation of the pure free carbenes 5a
and 5b, which could be isolated as a colorless solid or a slightly
yellow oil, respectively. These substances were stable under
argon at −20 °C for months. Apparently, the great steric bulk
created by the tBu groups at the phosphorus atom together
with the substituents on the imidazole moiety effectively shield
the carbene carbons and thus renders the stability of these
NHCP systems. The formation of the carbenes was confirmed
1
by the absence of the H1 protons in the H NMR and by the
characteristic chemical shift of the carbene carbon signals in the
13C{1H} NMR spectra as singlets at 215.2 (tBuNHCPtBu) and
219.5 ppm (MesNHCPtBu). In their 31P{1H} NMR spectra, 5a
exhibits a singlet at 23.5 and 5b one at 26.5 ppm. Crystals of 5a
suitable for X-ray diffraction analysis were grown by
recrystallization from pentane at −20 °C (Figure 1). The
bond lengths of the ring in 5a indicate less conjugation
compared to the imidazolium salt 4a. The C−C bond in 5a is
shorter, whereas the N−C bonds are longer. The angle around
C1 decreases from 109° in the imidazolium salt to 102° in the
free carbene. Unfortunately, for ligand 5b no crystal structure
has been obtained so far and the crystal structure analysis of its
ligand precursor 4b was of low quality and only serves as a
structural proof. The crystal structures of the imdazolium salt
4a and free NHCP 5a are shown in Figure 1.
UV Photoelectron Spectrum and Electronic Structure
of 5a. In a UV photoelectron spectrum (He−I) the first four
ionization potentials (IP) of 5a were measured. The first
ionization potential of 5a (7.7 eV) is close to the first IP of the
related electron-rich ligands bis(di-tert-butylphosphino)-
methane (7.8 eV)7d and 1,3-bis-tert-butylimidazol-2-ylidene
(7.68 eV).15 The second to fourth ionization potentials are
detected at 7.9, 8.8, and 9.4 eV, where the band at 7.9 eV is not
clearly resolved and could as well be at 8.2 eV. Assuming the
validity of Koopmans’ theorem, which equates ionization
potentials in UV-PES with the negative energies of the highest
occupied molecular orbitals (IPj = −εj(SCF)),16 a Hartree−Fock
single-point calculation (Gaussian03, HF/6-31G**)17 using the
crystal structure geometry of 5a was performed to help assign
the ionization potentials to the particular molecular orbitals.
The results are listed in Table 1.
Figure 2. Calculated (HF/6-31G**) HOMOs and orbital energies of
5a (eV).
HOMO−1 displays more P-lone-pair character, and the
HOMO−2 is represented mainly by the carbene carbon lone
pair in the NHC plane. We note that within the frame of
assigning the MO character as shown, the P-arm of NHCP 5a
may well be a somewhat stronger σ-donor center than the
NHC carbon in this system.
Synthesis of 16 VE Ruthenium(II) Dimer 6 Based on
NHCP 5a. A dinuclear ruthenium complex based on ligand 5a
was synthesized via two different routes. Similarly to a
procedure we reported earlier on the synthesis for the dinuclear
16 VE dihydride [(dtbpm)Ru(H)(μ-Cl)]2,18 our first route
involves the reaction of the precursor [Ru(COD)Cl2]n (COD =
1,5-cyclooctadiene) with 5a under hydrogen pressure in THF
at 80 °C, affording complex 6 in 79% yield (Scheme 2). Unlike
in the analogous reaction using the bisphosphine dtbpm, no
hydrido complex was obtained; thus no base (e.g., triethyl-
amine) was needed for the synthesis of 6. Complex 6 is
obtained both in the presence and absence of base. Moreover,
although 6 contains no hydrides or dihydrogen ligands, the
presence of H2 was necessary, presumably for hydrogenating off
the cyclooctadiene ligands. Indeed cyclooctane can be identified
in the reaction solution by NMR and GC. Most probably, COD
can interfere somehow with the formation of 6, as evidenced by
The differences Δj between the experimental ionization
energies IPj and the orbital energies −εj are around 0.4 eV,
which, like for a series of previously published diphosphino-
methanes,7d can be referred to an electronic relaxation after the
ionization process. The large and very electron-rich tert-butyl
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a
interpreted as an agostic bonding situation, involving a three-
center−two-electron M−H−C interaction.19,20 Yet, indications
of a strong agostic Ru−H−C bonding were not observed for 6.
The chemical shifts of all (NMR-equivalent) methyl units of
the N-tBu groups are in the range of uncoordinated C−H
bonds as reported in the literature. Unlike in a similar dinuclear,
cationic bisphosphine Ru complex reported by us some time
ago,8 where a substantially strong agostic interaction of the two
16 VE Ru centers with only one methyl group of two P-bound
tBu units was obvious from spectroscopic data and leads to a
frozen orientation of the tBu groups (even in solution) with
rotating agostic methyl units, free rotation of the N-tBu
substituents is observed for 6, even at low temperatures. It
therefore seems reasonable to view the relative stability of the
16 VE complex 6 as caused by the steric shielding of both
empty coordination sites of the ruthenium centers by weakly
interacting tBu groups, simply as a geometric consequence of
the NHCP-ruthenium chelate structure, which forces these
hydrocarbon fragments into their observed position. If one
optimizes the geometry of 6 by DFT [Turbomole 5.7, (BP86/
SV(P)] starting from the X-ray geometry, the final minimum
energy structure reproduces the structure in the crystal very
well, with a Ru−H9A distance of 2.37 Å and with all C−H
bonds of the N-tBu groups having indistinguishable lengths.
The bridging Ru−Cl bond lengths of 6 are 2.4382(4) and
2.5201(4) Å, with the Ru−Cl distance trans to the NHC
distinctly longer due to the stronger trans influence of the
better σ-donor NHC compared to the terminal chloride trans
to the other μ-Cl. As expected, the terminal Ru−Cl bond is
slightly shorter (2.3763(5) Å) than both bridging Ru−Cl
bonds.
Scheme 2
a
(i) [RuCl2(COD)]n, H2 (18 bar), THF, 80 °C, 3 d (79%). (ii)
[Ru(p-cymene)Cl]2, toluene, 80 °C, 18 h (68%).
the reaction of [Ru(COD)Cl2]n carried out in the absence of
H2, leading to substantial formation of unidentified byproducts.
In a second, more convenient route, the dinuclear [Ru(p-
cymene)Cl2]2 precursor was reacted with 5a in benzene at 80
°C, resulting in 6 with a slightly lower yield of 68% (Scheme 2).
Crystals of 6 suitable for X-ray diffraction analysis were
obtained by slow evaporation of its solution in dichloro-
methane. The crystal structure of 6 revealed molecules of Ci
symmetry with two unsaturated 16 VE ruthenium(II) centers,
where each ruthenium is in a square pyramidal coordination
geometry with the phosphines trans to the two empty
coordination sites in apical positions (Figure 2). Moreover,
the structure suggests an interaction between one of the C−H
bonds of the N-tBu groups and the ruthenium centers
(indicated by the dotted lines in Scheme 2 and Figure 3).
In its 31P{1H} NMR spectrum, complex 6 exhibits two
singlets at 133.5 and 131.7 ppm in a ratio of approximately
1
1.4:1. Two sets of signals are also observed in the H and
13C{1H} NMR spectra. This suggests the presence of at least
two diastereomers in solution, from which the achiral species 6
crystallizes preferentially. Variable-temperature 31P{1H} NMR
experiments (293−198 K) show a reversible variation in the
ratio of the two signals, reaching approximately the inverse ratio
of the room-temperature spectrum at the lowest accessible
temperature (198 K), suggesting a dynamic structural process
for the interconversion of diastereomers. If one considers how
many diastereomers of 6 are conceivable in principle (under the
sterically reasonable assumption of an apical P-coordination
trans to the tBu-shielded empty coordination site as in 6
above), then one can discuss the following structures 6a−c
(Scheme 3; other stereoisomers according to molecular models
suffer from severe steric repulsions).
6a has C2-symmetry and is racemic (C2 axis through the two
μ-Cl atoms), achiral 6b has Cs-symmetry, and 6c again is a
chiral structure of C2-symmetry (C2 axis perpendicular to the
(μ-Cl)2Ru2 plane), formed as a racemic mixture. In order to
qualitatively assess the relative energies of all diastereomers of
6, we have performed DFT calculations (Turbomole 5.7,
[BP86/SV(P)])21 for 6 and 6a−c. Geometry optimization
resulted only in energy minima for 6 and 6a; the latter is found
to be less stable than the isolated 6 by 36 kJ/mol (gas phase)
and 38 kJ/mol (CH2Cl2 as solvent, modeled through
COSMO22). The structural alternatives 6b and 6c do not
converge to local energy minima because in both diastereomers
apparently prohibitive steric repulsions between the tBu groups
of the phosphorus functionalities are present. The finding by
DFT of only 6 and 6a as reasonable structural proposals for
Figure 3. ORTEP plot of 6. Thermal ellipsoids are at the 50%
probability level. Most hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ru1−C1 = 1.9757(18);
Ru1−P1 = 2.2153(5); Ru1−Cl1 = 2.3763(5); Ru1−Cl2 = 2.4382(4);
Ru1−Cl2#1 = 2.5201(4); Ru1−Ru1#1 = 3.761; C1−Ru1−P1 =
82.20(5); C1−Ru1−Cl1 = 85.16(5); C1−Ru1−Cl2 = 100.27(5); C1−
Ru1−Cl2#1 = 173.47(5); P1−Ru1−Cl1 = 98.523(18); P1−Ru1−Cl2
= 102.599(16); P1−Ru1−Cl2#1 = 103.692(17); Cl1−Ru1−Cl2 =
158.705(17); Cl1−Ru1−Cl2#1 = 91.130(16); Cl2−Ru1−Cl2#1 =
81.337(15); Ru1−Cl2−Ru1#1 = 98.663(15).
The Ru−H9A and Ru−C9 distances are 2.39 and 3.07 Å,
respectively, and the H9A−Ru-C9 angle is 126°. Given the fact
that the Ru centers in 6 are coordinatively unsaturated and thus
electron deficient, and taking into account that the Ru atoms
are in a five-coordinate environment, which is the remnant of
an octahedron with one ligand missing (trans to the
phosphorus), the CH3/Ru interaction could be tentatively
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Scheme 3
Scheme 4
Scheme 5
species in solution, with 6 being more stable, is consistent with
our experimental results.
olefins formed from the phenyldiazomethanes used, which
could not be fully removed without product loss.25
Complexes 7a−e exhibit singlet signals in the range 130.7−
The mutual interconversion of 6 and 6a in solution could
occur through different mechanistic pathways. One possibility is
the intermediacy of triply chloro-bridged ruthenium dimers (as
intermediate or transition state), as displayed schematically in
Scheme 4. Similar structures have been suggested by James and
co-workers. These authors have prepared triply chloro-bridged
ruthenium dimers based on chelating bisphosphine ligands,23
which supports the potential existence of the triply chloro-
bridged intermediate of Scheme 4 in our system. Unfortunately,
when we attempted to redissolve crystals of samples, for which
the solid-state structure of 6 had been elucidated by X-ray
diffraction, their extremely low solubility in organic solvents
prevented us from drawing firm conclusions about the
postulated other isomer.
133.0 ppm in their 31P{1H} NMR spectra. The alkylidene
1
protons in the H NMR spectra appear as doublets at 14.97−
15.10 ppm with coupling constants between 8.4 and 8.8 Hz.
The signals for the alkylidene carbons are found at the expected
characteristic chemical shifts as doublets or broad singlets at
291.6−295.6 ppm in the 13C{1H} NMR spectra.
A ruthenium alkylidene complex (7f) bearing a trimethylsilyl-
substituted alkylidene moiety was obtained by the utilization of
the commercially available trimethylsilyl diazomethane. In
contrast to the usage of the phenyldiazomethanes the reaction
had to be carried out at 60 °C (Scheme 5). The proton and
carbon signals of the alkylidene moiety in complex 7f are
shifted downfield compared to complexes 7a−e; the alkylidene
1
proton appears at 18.93 ppm in the H NMR spectrum as a
New Ruthenium(II) Alkylidene Complexes Based on
tBuNHCPtBu (5a). Similarly to the synthesis of first-generation
Grubbs catalysts, which are accessible by the addition of phenyl
diazomethane to RuCl2(PPh3)3 followed by ligand exchange of
PPh3 with PCy3,24 we treated compound 6 with several
phenyldiazomethanes (p-X-C6H4(CH)N2; X = H (a), Br (b),
CF3 (c), NO2 (d), CH3 (e)), leading to the formation of the
corresponding alkylidene complexes 7a−e (Scheme 5). In the
case of phenyldiazomethane we were able to isolate the
ruthenium-NHCP complex (7a, Scheme 5). Using a different
route (vide infra) to prepare 7a, this Ru-carbene could be fully
characterized including elemental analysis and X-ray structure.
Although 7a−e when made on the phenyldiazomethane route
were contaminated with impurities, we were also able to obtain
suitable crystals for X-ray diffraction analysis for 7b,c,e,
revealing in all cases a geometry in between a square pyramid
and a trigonal bipyramid. Slow addition of solutions of the
phenyldiazomethanes to suspensions of 6 in dichloromethane
at 0 °C generally led to the best results. Due to the low
solubility and slow reaction of the dimer 6, the main
contaminants in these reactions were the corresponding E/Z
doublet (3JH,P = 3.4 Hz), and the alkylidene carbon appears as a
broad singlet at 354.9 ppm in the 13C{1H} NMR spectrum. In
the 31P{1H} NMR spectrum complex 7f exhibits a singlet at
124.6 ppm, which is slightly upfield compared to complexes
7a−e. Crystals of 7f suitable for X-ray analysis were obtained by
slow evaporation of its CH2Cl2 solution. The crystal structure
revealed, as for the previous cases, a distorted square pyramidal
geometry (see below, Figure 4).
For the ruthenium alkylidene complex 7c with the p-CF3
substituent the quality of the crystal structure (R1 = 0.1479)
only allows to safely confirm the overall structure as shown in
the Supporting Information, without enabling us to discuss
geometric details. In all systems, however, if considered as
square pyramids and octahedral fragments, the phosphorus
atom of the NHCP ligand is in the apical position and trans to
the empty coordination site. Similarly to the (dtbpm)-
RuCl2(alkylidene) systems previously reported by us,18 the
two chloro ligands are situated cis to each other; however for
7a−e the alkylidene fragment is not the apex of a square
pyramid as in the bisphosphine systems but is located trans to
one of the chlorides. Actually, a description of the molecular
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Figure 4. ORTEP plots of 7a,b,f. Thermal ellipsoids are at the 50% probability level. Hydrogen atoms are omitted for clarity. For 7f two orientations
are shown, exemplifying the two equally possible descriptions as square pyramid or as trigonal bipyramid. Structures of 7c,e are given in the
Supporting Information.
a
Table 2. Selected Bond Lengths (Å) and Angles (deg) of 7a−c,e,f
7a
7b
7c
7e
7f
Ru1−C1
Ru1−Cl1
Ru1−Cl2
Ru1−P1
2.035(3)
2.4339(8)
2.4864(8)
2.2175(8)
1.883(3)
178.70(9)
92.35(8)
87.89(3)
2.046(7)
2.031(16)
2.389(4)
2.452(5)
2.212(5)
1.833(17)
175.6(5)
112.61(17)
86.69(17)
2.045(2)
2.4182(7)
2.5024(7)
2.2236(7)
1.880(3)
177.79(7)
112.51(3)
86.33(3)
2.080(2)
2.4203(6)
2.4704(7)
2.2354(6)
1.849(3)
176.53(7)
118.39(3)
85.61(2)
2.4047(17)
2.4987(19)
2.2369(19)
1.887(8)
Ru1−C20
C1−Ru1−Cl1
C1−Ru1−Cl2
Cl1−Ru1−Cl2
178.57(19)
111.34(7)
86.36(6)
a
For 7c see text.
geometries as distorted trigonal bipyramids, with one Cl and
the NHC carbon being in the axial positions and the equatorial
positions being coordinated by the other Cl, the alkylidene, and
the phosphorus atom, is equally reasonable (as expected from
the location of both structure types on pseudorotation
itineraries of such d6-ML5 species). In this context we note
that the C1−Ru−Cl1 angles are all very close to 180°, in
agreement with our description (see Table 2). Starting from
eight different idealized coordination geometries of compound
7f, both square pyramidal and trigonal bipyramidal, we have
performed geometry optimizations by DFT calculations
[Turbomole 5.7, BP86/SV(P)]. The global minimum is
practically identical to the geometries found by X-ray
crystallography. Like dimer 6, complexes 7a,b,c,e,f also show
an interaction of one of the methyl groups of the N-tBu group
with the metal center. The corresponding bond distances are
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longer compared to those observed in complex 6 and are listed
in Table 3. In all structures 7a,b,c,e,f, the Ru−Cl bonds trans to
the NHC carbon are consistently shorter than those trans to
the alkylidene carbon.
and 108.3 ppm (2JP,P = 10.0 Hz). Crystals obtained from this
reaction have revealed a different square planar isomer than in
the case of PMe3 8 in the solid state. The PPh3 in complex 9b is
coordinated trans to one of the chlorides, which are positioned
cis to each other (Scheme 6, Figure 5). The overall geometry of
9b is similar to all previous complexes. The isolated complex 9b
can be the dominant isomer over 9a; however, this crystal
might also not be representative, if 9b just crystallizes
preferentially. Pyridine-functionalized phosphine ruthenium(II)
complexes resembling our systems were reported by Lavigne
and co-workers.26 They have observed two isomers as well, the
cis and trans dichlorides. In their case, the cis isomer is the
thermodynamic product, which would be consistent with our
result of obtaining crystals of 9b and not 9a.
Table 3. Distances and Angles for the Closest CH3/Ru
Contacts of Complexes 7a,b,c,e,f
7a
7b
7c
7e
7f
Ru1−H (Å)
Ru1−C (Å)
Ru1−H−C (deg)
2.57
3.27
128
2.67
3.24
117
2.63
3.28
123
2.57
3.21
123
2.57
3.27
128
Reactions of Complex 6 with Phosphines and
Pyridines. In view of the above-mentioned low solubility of
compound 6 and thus its sluggish reactivity, we have aimed at
breaking the dimeric structure and transforming it into
mononuclear complexes that might serve better for the
synthesis of NHCP ruthenium alkylidene complexes. For this
we have treated complex 6 with pyridine and also tested its
reactivity toward phosphines. Complex 6 does react with
phosphines PR3 (R = Me, Ph, Cy), resulting in the formation of
mononuclear complexes. In the case of PMe3, the clean
formation of complex 8 was observed (Scheme 6). It exhibits
Similarly, the addition of PCy3 to complex 6 has led to the
formation of two new sets of signals, in a 1:1 ratio, which
appear as singlets instead of displaying the expected doublets
(10a,b, Scheme 6). This reaction was less clean, and further
characterization could not be achieved. So in the case of the
much more bulky PCy3 we cannot safely assign the solution or
solid-state structure and tentatively assume 10a and 10b.
The Ru−H8 and Ru1−C8 distances (for the numbering see
Figure 5) are 2.61 and 3.14 Å for 8 and 2.84 and 3.50 Å for 9b,
respectively. The Ru1−H−C8 angle is 114° for 8 and 126° for
9b. Compared to the case of complex 6, the CH3/Ru
interaction for 8 and 9b is even weaker. For compound 9b
one might have expected that the Ru−Cl bond trans to the
NHC should be lengthened compared to the one trans to the
PPh3 ligand, but within experimental error they are
indiscernible.
Other mononuclear complexes starting from compound 6
could be synthesized by the addition of pyridine ligands. Upon
dissolving complex 6 in pyridine, the dimer breaks up to give an
octahedral complex (11, Scheme 7) with two coordinated
pyridine molecules, as revealed by the crystal structure (Figure
6). Crystals suitable for X-ray analysis were obtained by
concentration of a solution of 11 in pyridine followed by slow
evaporation. The chlorides are positioned trans to each other,
and the pyridines are positioned cis to each other, where one
pyridine is trans to the NHCP phosphine and the other trans to
the NHC carbon. The Ru1−N21 and Ru1−N31 bond lengths
are 2.169(4) and 2.186(4) Å, respectively. In contrast to what
one might have expected, but not contradicting our conclusions
from the UV-PES of 5a, the Ru1−N21 bond that is trans to the
σ-donor NHC ligand is slightly shorter than the Ru1−N31
bond that is trans to the phosphine unit PtBu2. In this context,
two doublets at −3.5 (2JP,P = 19.2 Hz) and 122.2 ppm (2JP,P
=
19.2 Hz) in its 31P{1H} NMR spectrum for the two different
phosphorus atoms. The protons of the bridging methylene and
of the tBu groups on the phosphine are not split by additional
coupling with a second phosphine, even at low temperatures
(−60 °C). At those temperatures the system must still be so
dynamic that on average it displays Cs symmetry with an on
average planar chelate ring. The solid-state structure of 8 was
confirmed by X-ray diffraction analysis, revealing a geometry
described best as a distorted square pyramid, where the
phosphine of the NHCP ligand is again trans to the empty
coordination site. The two chloro ligands, however, are trans to
each other (angle Cl−Ru−Cl = 155.3°), resulting in a less
sterically hindered configuration. In the 31P{1H} NMR
spectrum of analytically pure complex 8 another minor set of
signals was observed (in approximately a 1:50 ratio to 8) as
doublets at −5.5 and at 120.7 ppm (2JP,P = 19.2 Hz), which
most likely belongs to the cis isomer, which could not be
isolated.
When treating complex 6 with PPh3 instead of PMe3, two
sets of doublets are observed in the 31P{1H} NMR spectrum in
a 5:3 ratio at 34.1 and 126.0 ppm (2JP,P = 32.3 Hz) and at 24.5
Scheme 6
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Figure 5. ORTEP plots of 8 and 9b. Thermal ellipsoids are at the 50% probability level. Hydrogen atoms are omitted for clarity, except for the
methyl groups of the N-tBu group blocking the empty coordination site of the ruthenium atom. Selected bond lengths (Å) and angles (deg) of 8:
Ru1−C1 = 2.049(2); Ru1−P1 = 2.2153(7); Ru1−P2 = 2.3586(7); Ru1−Cl1 = 2.3990(7); Ru1−Cl2 = 2.4239(7); C1−Ru1−P1 = 82.12(7); P2−
Ru1−Cl1 = 88.50(3); C1−Ru1−P2 = 172.13(7); C1−Ru1−Cl2 = 93.21(7); P1−Ru1−P2 = 105.67(3); P1−Ru1−Cl2 = 103.52(3); C1−Ru1−Cl1
= 88.83(7); P2−Ru1−Cl2 = 86.15(3); P1−Ru1−Cl1 = 101.16(3); Cl1−Ru1−Cl2 = 155.28(3). Selected bond lengths (Å) and angles (deg) of 9b:
Ru1−P2 = 2.3164(14); Ru1−Cl1 = 2.4416(15); Ru1−Cl2 = 2.4364(14); Ru1−C1 = 2.036(5); Ru1−P1 = 2.2380(15); C1−Ru1−P1 = 80.95(15);
P2−Ru1−Cl2 = 152.09(5); C1−Ru1−P2 = 89.14(15); C1−Ru1−Cl1 = 175.99(15); P1−Ru1−P2 = 102.71(5); P1−Ru1−Cl1 = 97.85(5); C1−
Ru1−Cl2 = 93.00(15); P2−Ru1−Cl1 = 94.87(5); P1−Ru1−Cl2 = 105.10(5); Cl1−Ru1−Cl2 = 83.60(5).
A mononuclear complex that bears only one pyridine
molecule was obtained by addition of one equivalent of
pyridine per ruthenium center of complex 6. The resulting
complex 12 could also be obtained by long-term drying of 11
under vacuum or by addition of CH2Cl2 to 11. We have also
observed a conversion of 11 to 12 in low-temperature NMR
experiments. Crystals of 12 could not be obtained. The
geometry is most likely similar to that of the mononuclear
complexes 8 and 9b, as evidenced from the NMR data. The
presence of only one pyridine molecule is further confirmed by
mass spectroscopy.
Scheme 7
Disappointingly, treatment of the monopyridine complex 12
with phenyldiazomethanes did not result in the desired
alkylidene complexes. The pyridine molecule is apparently
too strongly bound to the metal center; its replacement with an
alkylidene fragment does not take place. To address this
problem, substituted pyridines such as 2,6-dibromo- and 2,6-
dimethylpyridine were also applied, hoping for a weaker
coordination of only one pyridine molecule per ruthenium
center induced by their increased steric bulk. Upon treatment
of complex 6 with these substituted pyridines, we have obtained
only mixtures of undefined products.
we note here that Furstner et al. have structurally characterized
̈
a Grubbs II type ruthenium benzylidene complex with two cis-
ligated chloro ligands and with one NHC and one PCy3 ligand,
both also cis to each other.2a In this compound the Ru−Cl
bond trans to the NHC unit is also shorter than Ru−Cl trans to
PCy3. Furthermore, we note parenthetically that as with
phosphines and pyridines the Ru dimer 6 also reacts with
CO to yield an octahedral trans-dichloro complex
[RuCl2(tBuNHCPtBu)(CO)2] with a CO ligand trans to the
NHC-carbon and the other trans to the tBu2P unit, respectively.
Its X-ray structure (given in the Supporting Information,
compound A) also points to the P-arm of 5a to have the
stronger trans influence.
The bidentate ligand 2,2′-bipyridine reacts with 6, resulting
in the formation of complex 13, the structure of which was
confirmed by X-ray analysis (Figure 6). The crystal structure
revealed a distorted octahedral geometry where the two
chlorides are positioned cis to each other and trans to one of
the pyridine rings and the phosphine. According to NMR data,
only this isomer is present in solution. In the 31P{1H} NMR
spectrum complex 13 exhibits one singlet at 119.4 ppm and in
1
the H NMR spectrum two different sets of signals for the
bipyridine protons are present, supporting the nonequivalence
of the two rings. An isomer of 13 where the two chlorides are
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Figure 6. ORTEP plots of 11 and 13. Thermal ellipsoids are at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg) of 11: Ru1−P1 = 2.3139(11); Ru1−C1 = 2.086(4); Ru1−N21 = 2.169(4); Ru1−N31 = 2.186(4); Ru1−Cl1 =
2.4488(10); Ru1−Cl2 = 2.4319(10); C1−Ru1−N31 = 99.90(15); N31−Ru1−Cl2 = 88.47(9); N21−Ru1−N31 = 82.56(13); P1−Ru1−Cl2 =
97.36(4); C1−Ru1−P1 = 80.85(12); C1−Ru1−Cl1 = 85.73(11); N21−Ru1−P1 = 96.29(10); N21−Ru1−Cl1 = 90.65(9); N31−Ru1−P1 =
173.99(9); N31−Ru1−Cl1 = 83.91(9); C1−Ru1−Cl2 = 97.21(11); P1−Ru1−Cl1 = 90.21(4); C1−Ru1−N21 = 175.37(14); N21−Ru1−Cl2 =
86.75(9); Cl2−Ru1−Cl1 = 172.21(4). Selected bond lengths (Å) and angles (deg) of 13: Ru1−P1 = 2.2962(6); Ru1−C1 = 2.094(2); Ru1−Cl1 =
2.5217(5); Ru1−Cl2 = 2.4292(6); Ru1−N21 = 2.0924(18); Ru1−N31 = 2.0372(19); N31−Ru1−N21 = 79.10(8); N31−Ru1−C1 = 91.59(7);
N21−Ru1−C1 = 170.34(8); N31−Ru1−P1 = 96.85(5); N21−Ru1−P1, 97.03(5); N31−Ru1−Cl2 = 164.54(5); N21−Ru1−Cl2 = 92.15(6); C1−
Ru1−Cl2 = 97.50(6); C1−Ru1−P1 = 81.40(6); P1−Ru1−Cl2 = 96.85(2); N31−Ru1−Cl1 = 81.27(5); N21−Ru1−Cl1 = 79.25(5); C1−Ru1−Cl1
= 102.06(6); P1−Ru1−Cl1 = 176.072(19); Cl2−Ru1−Cl1 = 84.604(18).
Scheme 8
positioned trans apparently is sterically unfavorable. Unlike in
the case of complex 11, where the pyridine rings can freely
rotate, decreasing the steric hindrance, the bidentate 2,2′-
bipyridine ligand imposes a coordination mode that would
create significant steric hindrance, if the two chlorides would go
trans. It is also noteworthy that an attempt to synthesize an
adduct complex of type 13 with 6,6′-bis(trifluoromethyl)-2,2′-
bipyridine was not successful. This more electron-deficient
bipyridine ligand was expected to coordinate less strongly to
ruthenium than 2,2′-bipyridine. The steric bulk brought by the
CF3 groups and the lower donor capacity, however, is
apparently sufficient to prevent such a coordination. In complex
13 the Ru1−N21 and Ru1−N31 bond lengths are 2.0924(18)
and 2.0372(19) Å, respectively. The Ru1−N21 bond that is
trans to the NHC carbon is the longer one but is shorter than
the corresponding bond in 11 (2.169(4) Å), but for 13 a direct
comparison of the trans influences of the NHC and the tBu2P
arm is of course not possible.
New NHCP-Ruthenium Alkylidene Complexes Using
Ruthenium Alkylidene Precursors. Several alkylidene
complexes so far have been prepared from different ruthenium
alkylidene precursors.27 For example, the synthesis of the
second-generation Grubbs catalysts was achieved by simply
exchanging a phosphine ligand from the first-generation catalyst
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Figure 7. ORTEP plots of 16a and 16b. Thermal ellipsoids are at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg) of 16a: Ag1−P1 = 2.4255(6); Ag1−C1 = 2.164(2); Ag1−I1 = 2.9697; Ag1−Ag1 = 3.1028(4); C1−Ag1−P1 =
150.15(6); C1−Ag1−I1 = 92.38(6); P1−Ag1−I1 = 114.410(16). Selected bond lengths (Å) and angles (deg) of 16b: Ag1−P1 = 2.367(3); Ag1−C1
= 2.144(11); Ag1−I1 = 2.8980(13); Ag1−Ag1 = 3.1951(17); C1−Ag1−P1 = 151.2(3); C1−Ag1−I1 = 105.5(3); P1−Ag1−I1 = 103.30(8).
Scheme 9
MesNHCPtBu (16a) and a chiral NHCP (tBuNHCPtBuMe) with a
with a stronger σ-donating N-heterocyclic carbene ligand.
Therefore, a straightforward rational approach for obtaining
ruthenium alkylidene complexes based on ligand 5a seemed to
be its exchange with a phosphine or NHC ligand of a suitable
ruthenium alkylidene precursor. Surprisingly, the application of
several ruthenium precursors, such as the first-, second-, and
third-generation Grubbs catalysts, and the vinyl alkylidene
complex [RuCl2(PPh3)2(CH−CHCMe)2]28 with ligand
5a in different solvents and at variable temperatures did not
lead to well-defined reaction products or resulted in the
decomposition of either the NHCP ligand or the ruthenium
precursor.
As an alternative we investigated the use of silver carbene
complexes, which, as described by Wang and Lin,29 can easily
be prepared by deprotonating imidazolium salts with Ag2O to
generate powerful transmetalation reagents. This procedure has
already been applied for chiral phosphino-functionalized NHCs
and their subsequent transmetalation to rhodium precursors.30
Interestingly, in the case of 4a it was necessary to change the
counterion to iodide (14) in order to achieve full conversion of
the imidazolium salt to the desired silver-NHCP complex 15
(Scheme 8). So far, it was not possible to obtain crystals of 15
suitable for X-ray diffraction analysis. Our postulated structure
is based upon the structures of related silver complexes bearing
tBu and methyl substitution on the phosphorus atom (16b),
which were synthesized analogously in our group using the
corresponding imidazolium iodide salts and Ag2O. The
formation of the silver carbene complex 15 is indicated by
the absence of the H1 signal in the 1H NMR spectrum and by a
weak signal at 186.1 ppm for the Ag−C carbon in the 13C{1H}
1
NMR spectrum. The characteristic signals in the H, 31P{1H},
and 13C{1H} NMR spectra are in good accordance with those
detected for the analogous silver-NHCP complexes 16a and
16b (Figure 7).
The reaction of 15 with the first-generation Grubbs catalyst
led to the formation of the ruthenium carbene complex 7a
(Scheme 8) in 40% yield. In contrast to the reaction of
phenyldiazomethane with dimer 6 this conversion shows much
fewer side products. This transmetalation route is a convenient
and less dangerous alternative to the reaction of diazo
compounds with dimer 6.
While our attempts to obtain complexes 7a−e by direct
metalation of ligand 5a with different ruthenium alkylidene
complexes as precursors were not successful, a direct ligand
exchange of the first-generation Grubbs catalyst and Umicore
M131 with the less bulky ligand MesNHCPtBu (5b) resulted in
the formation of the desired products (Scheme 9).
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Complex 17 exhibits in the 31P{1H} NMR spectrum a singlet
at 107.2 ppm and in the 1H NMR spectrum a doublet at 14.97
ppm (3JH,P = 12.5 Hz) of the benzylidene carbon proton.
Further spectral data are given in the Experimental Section. 18
exhibits a singlet at 102.4 ppm in the 31P{1H} NMR spectrum.
system. Deuterated solvents were purchased from Deutero GmbH or
Aldrich. CD2Cl2 was stirred over CaH2 and then degassed three times
through freeze−pump−thaw cycles prior to use. Celite was dried at
150 °C in the oven for 1 week. NMR spectra were recorded on a
Bruker AC200-300, Bruker ARX250, Bruker DRX300, Bruker
DRX500, or Bruker DRX600 spectrometer. The chemical shifts are
given in parts per million and are referenced to the deuterated solvent
1
Its H NMR spectrum shows a doublet at 8.94 ppm, which is
1
used for H and 13C NMR and relative to 85% H3PO4 for 31P NMR.
characteristic for the indenylidene proton of the five-membered
ring. The carbene carbon of the alkylidene fragment is observed
in the 13C{1H} NMR at 284.4 ppm as a doublet (2JC,P = 12.1
Hz), and the carbon of the NHC appears at 181.2 ppm as a
doublet (2JC,P = 9.1 Hz).
We believe that the reduced steric bulk in 5b compared to 5a
facilitates the approach of the ruthenium center to the NHC
carbene carbon, in contrast to 5a, with its rotationally invariant
bulky N-tBu group. On the basis of molecular models of 17 and
18 we assume that the N-Mes unit also exerts a stabilizing
influence by shielding the empty coordination sites of
ruthenium, but so far we have not been able to grow X-ray
quality crystals of these ruthenium-carbenes.
Infrared spectra were measured on a Bruker FT-IR Equinox 55
spectrometer in KBr pellets. Mass spectra were recorded on a JEOL
JMS-700 or a Finnigan TSQ700 spectrometer and Bruker ApexQe
Apollo II FT-ICR instrument. The photoelectron spectrum was
measured on a Perkin-Elmer PS18 spectrometer and calibrated with
2
argon. The resolution of the P3/2 argon line is 20 meV. Elemental
analyses were performed in the “Mikroanalytisches Laboratorium der
Chemischen Institute der Universitat Heidelberg”.
̈
Di-tert-butyl(tosylmethyl)phosphine Oxide (2). Under an air
atmosphere in a 500 mL three-necked flask equipped with a dropping
funnel, a reflux condenser, and a pressure relief valve, triethylamine
(14.2 mL, 105 mmol) was added to a solution of tBu2P(O)CH2OH
(1) (13.40 g, 70 mmol) in THF (210 mL), and the mixture was cooled
to −15 °C. A solution of tosyl chloride (14.68 g, 77 mmol) in THF
(70 mL) was added dropwise over a period of 40 min. The reaction
mixture was allowed to warm to room temperature and stirred
overnight. Water (100 mL) and dichloromethane (50 mL) were
added, and the layers were separated (brine was added when
separation was difficult). The aqueous phase was extracted with
dichloromethane (2 × 50 mL). The combined organic phases were
washed with brine and dried over MgSO4. The solvent was removed
under vacuum, and the residue was purified by column chromatog-
raphy (SiO2; dichloromethane−ethanol, 20:1) to give tBu2P(O)-
CH2OTs (2) as a white crystalline solid in 65% (15.6 g) yield. Mp:
SUMMARY
■
A series of new ruthenium alkylidene complexes (7a−f) based
on stable and isolatable, chelating N-phosphinomethyl-
functionalized N-heterocyclic carbene ligands were synthesized
applying two different methods. A coordinatively unsaturated
16 VE ruthenium dimer (6) served as a precursor for the
synthesis of these ruthenium alkylidenes utilizing a variety of
aryl diazomethanes. In only two of these cases were we able to
fully purify and characterize the products (7b, 7f) spectroscopi-
cally. Complex 7a could alternatively be prepared in fair yield
by transmetalation from a NHCP silver complex to the first-
generation Grubbs catalyst and was isolatable in analytically
pure form. Five of the novel ruthenium carbene complexes due
to their propensity to crystallize could be characterized by X-ray
diffraction, revealing a distorted square pyramidal (or distorted
trigonal bipyramidal) geometry, where the two chlorides are
positioned cis to each other. The direct metalation by ligand
substitution was successful only for the reaction of the less
bulky free NHCP ligand (5b) with Grubbs-type ruthenium
alkylidene precursors, which led to the formation of two
additional NHCP ruthenium alkylidene complexes (17 and
18). A number of other ruthenium complexes bearing
phosphine- or pyridine-type ligands were also prepared from
complex 6. Following up the chemistry of cationic bisphosphine
ruthenium alkylidene complexes formed by chloride abstraction
from cis-dichloro alkylidene precursors, which we have reported
earlier2 and which we have shown to be extremely active
ROMP catalysts working in ppm catalyst concentrations for
various cycloolefins, the investigation of the reactivity of the
new alkylidene complexes in halide abstraction reactions and as
cationic catalysts in ROMP reactions is under way.
1
3
73.4−74.0 °C. H NMR (300.13 MHz, CDCl3): 7.80 (d, JH,H = 8.3
Hz, 2H, Ts-H), 7.38 (d, 3JH,H = 8.3 Hz, 2H, Ts-H), 4.26 (d, 2JH,P = 6.8
3
Hz, 2H, PCH2), 2.46 (s, 3H, Ts-CH3), 1.28 (d, JH,P = 13.9 Hz, 18H,
PC(CH3)3). 13C{1H} NMR (75.48 MHz, CDCl3): 145.7 (s, TsC),
1
131.1 (s, Ts-C), 130.1 (s, Ts-CH), 128.2 (s, Ts-CH), 61.5 (d, JC,P
=
1
61 Hz, PCH2), 35.6 (d, JC,P = 58 Hz, P(C(CH3)3)2), 26.2 (s,
P(C(CH3)3)2), 21.7 (s, Ts-CH3). 31P{1H} NMR (101.26 MHz,
CDCl3): 54.3 (s). IR (KBr), ν (cm−1): 750 (s), 814 (s), 977 (s, νC−O),
998 (s), 1151 (s), 1175 (s, PO), 1188 (s, PO), 1371 (s), 1477
(m), 1596 (m), 1917 (w), 2872 (m), 2932 (m), 2971 (m), 3042 (w),
3057 (w). MS (EI+), m/z (%): 347.3 (1) [M+1]+, 289.2 (2) [M −
tBu]+, 233.1 (100) [M − 2(tBu) + 1]+, 155.1 (50) [SO2 − C6H4 −
CH3]+, 139.1 (29) [C6H4SO2]+, 91.1 (40) [C6H4CH3]+. Anal. Calcd
for C16H27O4PS: C, 55.47; H, 7.86; P, 8.94; S, 9.26. Found: C, 55.49;
H, 7.82; P, 8.92; S, 9.10.
3-tert-Butyl-1-(di-tert-butylphosphinooxymethyl)-
imidazolium Tosylate (3a). Into a 50 mL flask equipped with a
reflux condenser and a pressure relief valve, 2 (15.6 g, 46 mmol) and
N-tert-butylimidazole (5.7 g, 46 mmol) were added and heated at 100
°C for 4 days. After cooling to room temperature the oily product was
dissolved in a minimum amount of dichloromethane and precipitated
with diethyl ether. The white solid was washed with diethyl ether and
recrystallized from hot THF to give a white crystalline solid as a pure
1
product in 74% (16.0 g) yield. Mp: 192 °C. H NMR (250.13 MHz,
3
CDCl3): 10.32 (bs, 1H, NCHN), 8.03 (t, JH,H = 1.7 Hz, 1H,
N(CH)2N), 7.80 (d, 3JH,H = 8.1 Hz, 2H, Ts-H), 7.24 (t, 3JH,H = 2.0 Hz,
1H, N(CH)2N), 7.16 (d, 3JH,H = 7.6 Hz, 2H, Ts-H), 5.21 (d, 2JH,P = 4.2
Hz, 2H, PCH2), 2.35 (s, 3H, Ts-CH3), 1.69 (s, 9H, NC(CH3)3), 1.29
(d, 3JH,P = 14.3 Hz, 18H, P(C(CH3)3)2). 13C{1H} NMR (75.48 MHz,
CDCl3): 143.7 (s, Ts-C), 139.1 (s, Ts-C), 137.0 (s, NCHN), 128.5 (s,
Ts-CH), 126.0 (s, Ts-CH), 124.4 (s, N(CH)2N), 117.8 (s, N(CH)2N),
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were carried out under an
atmosphere of dry argon in a glovebox (MBraun) or using standard
Schlenk techniques, unless stated otherwise. N-tert-Butylimidazole,32
N-mesitylimidazole,33 di-tert-butyl(hydroxymethyl)phosphine oxide14
(1), and the phenyldiazomethanes34 were prepared according to
literature procedures. (Trimethylsilyl)diazomethane, the first-gener-
ation Grubbs catalyst, and the Umicore M1 catalyst were purchased
from Aldrich and used as obtained. Pentane and diethyl ether were
distilled over benzophenone sodium-ketyl and stored under argon.
Chlorobenzene was distilled over CaH2. Toluene, hexane, CH2Cl2, and
THF were dried using an MBraun SPS-800 solvent purification
1
1
60.4 (s, NC(CH3)3), 41.2 (d, JC,P = 47.0 Hz, PCH2), 36.2 (d, JC,P
=
59.0 Hz, P(C(CH3)3)2), 29.9 (s, NC(CH3)3), 26.0 (s, P(C(CH3)3)2),
21.2 (s, Ts-CH3). 31P{1H} NMR (101.26 MHz, CDCl3): 57.5 (s). IR
(KBr), ν (cm−1): 815 (m), 1114 (s), 1131 (s), 1192 (s), 1377 (m),
1398 (m), 1476 (m), 1557 (m), 2871 (w), 2915 (m), 2946 (m), 2979
(w), 3076 (w), 3144 (w), 3196 (w). MS (ESI+), m/z (%): 299.43
(100) [M]+, 243.40 (8) [M − (tBu) + 1]+. Anal. Calcd for
39
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Organometallics
Article
C23H39N2O4PS: C, 58.70; H, 8.35; N, 5.95; P, 6.58; S, 6.81. Found: C,
58.50; H, 8.37; N, 5.94, P, 6.42, S, 6.76.
heated for 24 h at 80 °C. The volatiles were removed under vacuum,
and the residue was extracted with dichloromethane (3 × 10 mL),
filtered, and dried again. The residue was washed with diethyl ether (3
× 20 mL) and pentane (20 mL) and finally dried under vacuum,
affording a white solid in 94% (1.34 g) yield. Crystals suitable for X-ray
analysis were obtained by slow condensation of pentane into a
saturated solution of 4b in CHCl3. Mp: 235 °C (dec). 1H NMR
(500.13 MHz, CDCl3): 11.04 (s, 1H, NCHN), 8.23 (s, 1H,
N(CH)2N), 7.15 (s, 1H, N(CH)2N), 6.97 (s, 2H, Mes-CH), 5.44
(s, 2H, PCH2), 2.31 (s, 3H, Mes-p-CH3), 2.02 (s, 6H, Mes-o-CH3),
1.32 (d, 3JH,P = 12.9 Hz, 18H, P(C(CH3)3)2). 13C{1H} NMR (125.77
MHz, CDCl3): 141.2 (s, Mes-C), 139.4 (s, NCHN), 134.0 (s, Mes-C),
130.7 (s, Mes-C), 129.8 (Mes-CH), 123.5 (s, N(CH)2N), 122.6 (s,
N(CH)2N), 43.8 (d, JC,P = 14.2 Hz, PCH2), 32.7 (d, JC,P = 12.5 Hz,
P(C(CH3)3)2), 29.1 (2JC,P = 11.0 Hz, P(C(CH3)3)2), 21.0 (Mes-p-
CH3), 17.5 (Mes-o-CH3). 31P{1H} NMR (101.26 MHz, CDCl3): 33.3
(s). IR (KBr), ν (cm−1): 2950 (vs), 2864 (vs), 2360 (w), 1608 (w),
1546 (m), 1471 (s), 1369 (m), 1261 (w), 1206 (s), 1161 (s), 1102
(m), 1039 (m), 968 (w), 855 (w), 811 (m), 749 (w), 669 (w). MS
(ESI+), m/z (%): 725.46 (45) [2M − Cl]+, 345.25 (100) [M]+. HRMS
(ESI+): m/z calcd 725.46023, 345.24541; found 725.46011,
345.24547.
3-Mesityl-1-(di-tert-butylphosphinooxymethyl)imidazolium
Tosylate (3b). In a 50 mL two-necked flask equipped with a reflux
condenser and a pressure relief valve a mixture of 2 (2.20 g, 6.35
mmol) and N-mesitylimidazole (1.18 g, 6.35 mmol) was suspended in
dry toluene (10 mL), and then the reaction mixture was heated at 120
°C for 7 days. The solvent was removed on a rotary evaporator, and
the yellow residue was dissolved in dichloromethane (5 mL). Diethyl
ether (50 mL) was added, resulting in the precipitation of a yellow
solid, which was filtered, washed with diethyl ether (3 × 20 mL), and
then recrystallized from hot THF. The product was finally dried under
vacuum, affording a white solid in 74% (2.5 g) yield. Crystals suitable
for X-ray diffraction were obtained by slow evaporation of a
1
1
1
concentrated solution of 3b in chloroform. Mp: 230 °C. H NMR
3
(300.13 MHz, CDCl3): 9.67 (s, 1H, NCHN), 8.40 (t, JH,H = 1.5 Hz,
3
1H, N(CH)2N), 7.70 (d, 3JH,H = 8.0 Hz, 2H, Ts-CH), 7.09 (t, JH,H
=
1.6 Hz, 1H, N(CH)2N), 7.06 (d, 3JH,H = 7.7 Hz, 2H, Ts-CH), 6.79 (s,
2H, Mes-CH), 5.32 (d, 2JH,P = 4.0 Hz, 2H, PCH2), 2.32 (s, 3H, Mes-p-
CH3), 2.29 (s, 3H, Ts-p-CH3), 2.00 (s, 6H, Mes-o-CH3), 1.28 (d, 3JH,P
= 14.3 Hz, 18H, P(C(CH3)3)2). 13C{1H} NMR (75.48 MHz, CDCl3):
143.4 (Ts-C), 141.1 (s, Mes-C), 139.0 (s, Ts-C), 138.4 (s, NCHN),
134.1 (s, Mes-C), 130.6 (s, Mes-C), 129.7 (s, Mes-CH), 128.4 (s, Ts-
CH), 125.8 (s, Ts-CH), 125.5 (s, N(CH)2N), 121.9 (s, N(CH)2N),
3-tert-Butyl-1-(di-tert-butylphosphinomethyl)imidazol-2-yli-
dene, tBuNHCPtBu (5a). Into a 10 mL Schlenk flask 4a (100 mg, 0.31
mmol) was suspended in 6 mL of THF, and KOtBu (41.0 mg, 0.35
mmol, 1.1 equiv) was added in portions. The reaction mixture was
stirred for 2 h, and all volatiles were removed under vacuum. The
residue was extracted with pentane (5 × 10 mL), and the filtrate was
dried under vacuum, affording a white solid in 72% (63 mg) yield. 5a
is stored in the glovebox at −20 °C. Mp: 79 °C. Crystals suitable for
X-ray analysis were obtained from a saturated solution of 5a in pentane
1
1
41.4 (d, JC,P = 46.0 Hz, PCH2), 36.2 (d, JC,P = 58.1 Hz,
P(C(CH3)3)2), 25.9 (s, P(C(CH3)3)2), 21.2 (s, Ts-p-CH3), 21.0 (s,
Mes-p-CH3), 17.3 (s, Mes-o-CH3). 31P{1H} NMR (101.26 MHz,
CDCl3): 59.4 (s). IR (KBr): ν (cm−1) 3078 (m), 3072 (m), 2971 (m),
2954 (m), 1608 (w), 1552 (m), 1479 (m), 1373 (w), 1233 (vs), 1210
(s), 1177 (vs), 1155 (s), 1120 (s), 1034 (s), 1010 (s), 850 (m), 815
(s), 756 (w), 681 (s), 667 (w), 635 (m). MS (ESI+), m/z (%): 361.24
(100) [M]+. HRMS (ESI+), m/z: calcd 361.24033; found 361.24037.
Anal. Calcd for C28H41N2O4PS: C, 63.13; H, 7.76; N, 5.26; P, 5.81; S,
6.02. Found: C, 62.94; H, 7.55; N, 5.45; P, 5.77; S, 6.21.
1
at −20 °C. H NMR (300.13 MHz, C6D6): 7.21 (d, J = 1.4 Hz, 1H,
2
N(CH)2N), 6.74 (s, 1H, N(CH)2N), 4.49 (d, JH,P = 2.1 Hz, 2H,
3
PCH2), 1.49 (s, 9H, NC(CH3)3), 1.08 (d, JH,P = 10.8 Hz, 18H,
PC(CH3)3). 13C{1H} NMR (75.48 MHz, C6D6): 215.2 (s, NCN),
118.8 (d, J = 9 Hz, N(CH)2N), 116.3 (s, N(CH)2N), 56.1 (s,
3-tert-Butyl-1-(di-tert-butylphosphinomethyl)imidazolium
Chloride (4a). Into a 2 L four-necked flask equipped with a stopcock
olive tap, a reflux condenser with a pressure relief valve, and a pressure-
equalizing dropping funnel was added phosphine oxide 3a (9.30 g,
19.8 mmol), and the mixture was then dissolved in dry chlorobenzene
(280 mL) by heating to reflux temperature. The temperature was then
maintained at 120 °C, and HSiCl3 (35.0 mL, 251 mmol, 17-fold
excess) was added dropwise. When the addition was complete, the
reaction mixture was heated at 120 °C overnight. If necessary, an
additional 5 equiv of HSiCl3 was added, and the mixture was stirred
until a full conversion was detected by 31P NMR spectroscopy. After
cooling to room temperature the volatiles were removed under
vacuum and the residue was extracted with dichloromethane (3 × 10
mL), filtered, and dried again. The residue was washed with diethyl
ether (3 × 20 mL) and finally dried under vacuum, affording a white
1
1
NC(CH3)3), 47.0 (d, JC,P = 20 Hz, PCH2), 32.0 (d, JC,P = 22 Hz,
2
PC(CH3)3), 31.8 (s, NC(CH3)3), 30.1 (d, JC,P = 13 Hz, PC(CH3)3).
31P{1H} NMR (121.49 MHz, C6D6): 23.5 (s). IR (KBr), ν (cm−1):
735 (s), 809 (m), 822 (m), 1019 (w), 1099 (m), 1127 (m), 1204 (m),
1230 (s), 1365 (s), 1391 (s), 1463 (s), 1475 (s), 1551 (w), 2859 (s),
2896 (s), 2941 (s), 2973 (s), 3051 (s). MS (LIFDI), m/z (%): 283.3
(100) [M + 1]+.
3-Mesityl-1-(di-tert-butylphosphinomethyl)imidazol-2-yli-
dene, MesNHCPtBu (5b). 4b (305 mg, 0.80 mmol) was suspended in
THF (10 mL); then KOtBu (108 mg, 0.96 mmol, 1.2 equiv) was
added in portions. The reaction mixture was stirred for 2 h at room
temperature, and then all volatiles were removed under vacuum. The
residue was extracted with pentane (3 × 8 mL), filtered through Celite,
and dried under vacuum, affording a yellow, viscous oil in 65% (180
mg) yield. The oil was stored under argon at −20 °C. 1H NMR
(300.13 MHz, THF-d8): 7.31 (d, 3JH,H = 1.5 Hz, 1H, N(CH)2N), 6.87
1
solid in 60% (3.80 g) yield. H NMR (300.13 MHz, CD2Cl2): 10.82
(s, 1H, NCHN), 7.60 (d, 3JH,H = 1.3 Hz, 1H, N(CH)2N), 7.25 (t, 3JH,H
= 1.8 Hz, 1H, N(CH)2N), 4.80 (s, 2H, PCH2), 1.71 (s, 9H,
3
3
NC(CH3)3), 1.20 (d, JH,P = 12.0 Hz, 18 H, P(C(CH3)3)2). 13C{1H}
(s, 2H, Mes-CH), 6.87 (d, JH,H = 1.5 Hz, 1H, N(CH)2N), 4.55 (d,
2JH,P = 1.6 Hz, 2H, PCH2), 2.28 (s, 3H, Mes-p-CH3), 1.96 (s, 6H, Mes-
o-CH3), 1.21 (d, 3JH,P = 11.0 Hz, 18H, P(C(CH3)3)2). 13C{1H} NMR
(75.48 MHz, THF-d8): 219.5 (s, NCN), 141.7 (s, Mes-C), 137.6 (s,
Mes-C), 136.0 (s, Mes-C), 129.4 (s, Mes-CH), 121.7 (s, N(CH)2N),
NMR (125.78 MHz, CD2Cl2): 137.7 (s, NCHN), 122.7 (s,
1
N(CH)2N), 119.2 (s, N(CH)2N), 45.2 (d, JC,P = 24 Hz, PCH2),
1
32.6 (d, JC,P = 19 Hz, P(C(CH3)3)2), 30.3 (s, NC(CH3)3), 29.7 (d,
2JC,P = 14 Hz, P(C(CH3)3)2), 26.4 (s, NC(CH3)3). 31P{1H} NMR
119.8 (s, N(CH)2N), 46.9 (d, 1JC2,P = 20.7 Hz, PCH2), 32.4 (d, 1JC,P
=
(202.47 MHz, CD2Cl2): 29.2 (s). IR (KBr), ν (cm−1): 1370 (w), 1380
(w), 1469 (w), 1555 (m), 2862 (m), 2895 (m), 2937 (m), 2977 (m),
3049 (m), 3080 (w), 3134 (w). MS (ESI+), m/z (%): 283.5 (70)
[M]+, 159.5 (100) [CH2PtBu]+.
21.8 Hz P(C(CH3)3)2), 20.2 (d, JC,P = 13.2 Hz, P(C(CH3)3)2), 21.2
(s, Mes-p-CH3), 18.3 (s, Mes-o-CH3). 31P{1H} NMR (101.26 MHz,
THF-d8): 26.5 (s). MS (LIFDI), m/z (%): 345.12 (100) [M + 1]+.
[RuCl(tBuNHCPtBu)2-(μ-Cl)2] (6). Method a: In a glovebox a 20 mL
glass autoclave was charged with [RuCl2(COD)]n (430 mg, 1.54 mmol
Ru), 5a (475 mg, 1.68 mmol), and dry THF (15 mL). The vessel was
pressurized with hydrogen (18 bar), and the reaction mixture was
stirred at 80 °C for 72 h, after which the hydrogen pressure had
dropped to 12 bar. The autoclave was cooled to room temperature,
and the pressure was released. The formed slurry was allowed to settle,
and the dark brown solution was decanted. The green solid was
washed with diethyl ether (4 × 8 mL) and dried under vacuum,
3-Mesityl-1-(di-tert-butylphosphinomethyl)imidazolium
Chloride (4b). Into a 500 mL four-necked flask equipped with a
dropping funnel, a reflux condenser, a stopcock olive tap, and a
pressure relief valve was added 3a (2.00 g, 3.75 mmol), and the system
was put under argon flow. Dry chlorobenzene (70 mL) was then
added, and the solution was heated to 80 °C. At this temperature,
HSiCl3 (7.5 mL, 75 mmol, 20 equiv) was added dropwise and the
reaction mixture was stirred for 24 h. An additional 7 equiv of HSiCl3
(2.5 mL, 25 mmol) was then added, and the reaction mixture was
40
dx.doi.org/10.1021/om300487r | Organometallics 2013, 32, 29−46

Organometallics
Article
1
resulting in 79% (553 mg) yield. H NMR (600.13 MHz, CD2Cl2),
178.8 (d, 2JC,P = 10.3 Hz, NCN), 151.0 (d, JC,P = 1.9 Hz, Ar) 131.6 (bs,
3
first set of signals: 7.25 (d, JH,H = 1.9 Hz, 2H, N(CH)2N), 7.20 (d,
Ar), 131.3 (s, Ar), 129.6 (s, Ar), 120.9 (s, N(CH)2N), 119.6 (d, JC,P =
1
3JH,H = 2.1 Hz, 2H, N(CH)2N), 4.14−4.17 (m, 2H, PCH2), 3.78−3.81
8.8 Hz, N(CH)2N), 59.8 (s, NC(CH3)3), 44.2 (d, JC,P = 27.1 Hz,
PCH2), 38.74 (d, 1JC,P = 22.0 Hz, PC(CH3)3), 37.2 (d, 1JC,P = 24.0 Hz,
PC(CH3)3), 32.0 (s, NC(CH3)3), 29.3 (d, 2JC,P = 3.3 Hz, PC(CH3)3),
3
(m, 2H, PCH2), 1.85 (s, 18H, NC(CH3)3), 1.37 (d, JH,P = 13.6 Hz,
3
18H, P(C(CH3)3)2), 1.16 (d, JH,P = 12.8 Hz, 18H, P(C(CH3)3)2);
2
29.1 (d, JC,P = 2.0 Hz, PC(CH3)3). 31P{1H} NMR (242.94 MHz,
second set of signals: 7.23 (d, 3JH,H = 2.1 Hz, 2H, N(CH)2N), 7.17 (d,
3JH,H = 2.1 Hz, 2H, N(CH)2N), 4.18−4.21 (m, 2H, PCH2), 3.79−3.83
CD2Cl2): 131.4 (s). HRMS (FAB+), m/z: calcd for C23H37ClN2PRu
509.1430; found 509.1440. Anal. Calcd for C23H37Cl2N2PRu: C,
50.73; H, 6.85; N, 5.14. Found: C, 45.90; H, 6.44; N, 4.36. Analysis:
The results obtained from three samples suit an additional molecule of
dichloromethane per molecule in the solid. Anal. Calcd for
C23H37Cl2N2PRu·CH2Cl2: C, 45.80; H, 6.25; N, 4.45.
3
(m, 2H, PCH2), 1.83 (s, 18H, NC(CH3)3), 1.51 (d, JH,P = 13.6 Hz,
3
18H, P(C(CH3)3)2), 1.29 (d, JH,P = 12.7 Hz, 18H, P(C(CH3)3)2).
13C{1H} NMR (150.90 MHz, CD2Cl2), first set of signals: 191.3 (d,
2JC,P = 12.7 Hz, NCN), 119.3 (s, N(CH)2N), 119.3 (d, 3JC,P = 8.0 Hz,
N(CH)2N), 58.4 (s, NC(CH3)3), 46.6 (d, 1JC,P = 27.2 Hz, PCH2), 39.8
1
1
[RuCl2(tBuNHCPtBu)(4-bromobenzylidene)] (7b). Complex 6
(100 mg, 110 μmol) was suspended in dichloromethane (8 mL).
Freshly prepared p-bromophenyldiazomethane (70.0 mg, 355 μmol)
was dissolved in dichloromethane (1.5 mL) and added at 0 °C via
syringe pump (∼2 mL/h). After complete addition, the reaction
mixture was warmed to room temperature, filtered, and concentrated
to ca. 0.5 mL. Diethyl ether (5 mL) was added, resulting in
precipitation of a solid, and the supernatant was decanted. The
resulting green solid was washed with diethyl ether (2 × 5 mL), and
the residue was dried under vacuum, affording a green solid in 65%
(89 mg) yield. 1H NMR (600.13 MHz, CD2Cl2): 14.86 (d, 3JH,P = 8.4
(d, JC,P = 18.4 Hz, P(C(CH3)3)2), 38.9 (d, JC,P = 18.7 Hz,
P(C(CH3)3)2), 33.4 (s, NC(CH3)3), 31.1 (d, JC,P = 2.5 Hz,
2
P(C(CH3)3)2), 29.6 (bs, P(C(CH3)3)2); second set of signals, 191.0
(d, 2JC,P = 13.2 Hz, NCN), 119.4 (d, 3JC,P = 7.4 Hz, N(CH)2N), 119.1
1
(s, N(CH)2N), 58.2 (s, NC(CH3)3), 46.4 (d, JC,P = 27.0 Hz, PCH2),
37.3 (d, JC,P = 21.5 Hz, P(C(CH3)3)2), 37.1 (d, JC,P = 21.2 Hz,
1
1
1
P(C(CH3)3)2), 33.4 (s, NC(CH3)3), 31.5 (d, JC,P = 2.5 Hz,
P(C(CH3)3)2), 29.7 (d, JC,P = 2.5 Hz, P(C(CH3)3)2). 31P{1H}
1
NMR (242.94 MHz, CD2Cl2): 132.3 (s), 130.5 (s). IR (KBr), ν
(cm−1): 3132 (w), 2962 (s), 1630 (m), 1475 (m), 1362 (s), 1231 (s),
1046 (m, 682 (m). MS (FAB+), m/z (%): 910.1 (35) [M]+, 454.0
(100) [1/2M]+, 383.1 (90) [Ru(NHCP)]+. HRMS (FAB+), m/z:
calcd for C32H62Cl4N4P2Ru2 908.1291; found 908.1349. Anal. Calcd
for C32H62Cl4N4P2Ru2: C, 42.29; H, 6.88; N, 6.17; P, 6.82. Found: C,
42.12; H, 6.92; N, 6.30; P, 6.80.
Method b: In the glovebox a 10 mL glass autoclave was charged
with [RuCl2(cymene)]2 (100 mg, 0.163 mmol) and toluene (5 mL).
Ligand 5a (96.8 mg; 0.343 mmol) was added, slowly leading to a color
change from orange to green. Then the reaction mixture was heated at
80 °C for 20 h. After cooling to room temperature pentane (10 mL)
was added for a better precipitation. The brown solution was decanted,
and the green residue was washed with pentane (3 × 10 mL). The
green solid was dried under vacuum, affording a 68% (100 mg) yield.
Mp: 192 °C. 1H NMR (250.1 MHz, CD2Cl2): 7.28 (s, 2H,
Hz, 1H, RuCH), 8.32 (bs, 2H, Ar), 7.58 (d, 3JH,H = 8.4 Hz, 2H, Ar),
2
7.37 (s, 1H, N(CH)2N), 7.07 (s, 1H, N(CH)2N), 4.45 (dd, JH,H
14.1 Hz, 2JH,P = 10.1 Hz, 1H, PCH2), 4.39 (dd, 2JH,H = 14.1 Hz, 2JH,P
=
=
2.8 Hz, 1H, PCH2), 1.48 (d, 3JH3,P = 14.3 Hz, 9H, P(C(CH3)3)2), 1.19
(s, 9H, NC(CH3)3), 1.11 (d, JH,P = 14.7 Hz, 9H, P(C(CH3)3)2).
13C{1H} NMR (150.90 MHz, CD2Cl2): 292.2 (d, JC,P = 15.7 Hz,
2
RuCH), 178.3 (d, 2JC,P = 10.0 Hz, NCN), 149.5 (d, J = 1.6 Hz, Ar),
132.9 (s, Ar), 132.8 (bs, Ar), 125.9 (s, Ar), 121.0 (s, N(CH)2N), 119.7
3
1
(d, JC,P = 8.4 Hz, N(CH)2N), 59.9 (s, NC(CH3)3), 44.3 (d, JC,P
=
27.0 Hz, PCH2), 38.4 (d, 1JC,P = 21.8 Hz, P(C(CH3)3)2), 37.2 (d, 1JC,P
= 23.8 Hz, P(C(CH3)3)2), 32.1 (s, NC(CH3)3), 29.3 (d, 2JC,P = 2.7 Hz,
P(C(CH3)3)2), 29.1 (d, 2JC,P = 1.4 Hz, P(C(CH3)3)2); contains traces
of Et2O and 4,4′-dibromostilbene. 31P{1H} NMR (242.94 MHz,
CD2Cl2): 131.2 (s). IR (KBr), ν (cm−1): 2955 (s), 1571 (m), 1479 (s),
1368 (m), 1178 (s), 1070 (m), 1007 (m), 871 (m), 808 (m), 694 (w),
508 (m). MS (FAB+), m/z (%): 624.1 [M]+ (1), 589.1 [M − Cl]+
(100). HRMS (FAB+), m/z (%): calcd for C23H36BrCl2N2PRu
622.0220; found 622.0205.
3
N(CH)2N), 7.14 (d, JH,H = 11.8 Hz, 2H, N(CH)2N), 4.22 (bs, 2H,
CH2P), 3.68 (d, JH,H = 11.9 Hz, 2H, CH2P), 1.76 (s, 12H,
2
NC(CH3)2), 1.45 (s, 6H, NC(CH3)2), 1.42−1.00 (m, 36H, P(C-
(CH3)3)2). 31P{1H} NMR (101.2 MHz, CD2Cl2): 133.5 (s), 131.7 (s).
MS (FAB+), m/z (%): 909.0 (20) [M]+, 873.0 (10) [M − Cl]+, 454.1
(70) [1/2M]+, 383.2 (60) [1/2M − 2Cl]+. Anal. Calcd for
C32H62Cl4N4P2Ru2: C, 42.29; H, 6.88; N, 6.17. Found: C, 42.70; H
6.90; N, 6.12.
[RuCl2(tBuNHCPtBu)(4-(trifluoromethyl)benzylidene)] (7c).
Complex 6 (10 mg, 11 μmol) was suspended in dichloromethane (5
mL), and then (4-(trifluoromethyl)diazomethane (7.0 mg, 38 μmol)
was added to the mixture as a solid. The reaction mixture was stirred
for 1.5 h at room temperature, showing a slight evolution of a gas. The
resulting green solution was filtered and concentrated to ca. 1 mL, and
the product was precipitated by addition of pentane (2 mL). The
precipitate was washed again with pentane (2 mL) and dried under
vacuum, affording a greenish-brown solid. The yield could not be
determined as a result of contamination with byproducts and with E/
Z-stilbene, and a full spectral characterization could not be achieved.
1H NMR (600.13 MHz, CD2Cl2): 15.10 (d, 3JH,P = 8.4 Hz, 1H, Ru
CH), 8.54 (d, 3JH,H = 7.4 Hz, 2H, Ar), 7.69 (d, 3JH,H = 8.1 Hz, 2H, Ar),
7.38 (s, 1H, N(CH)2N), 7.09 (s, 1H, N(CH)2N), 4.45−4.52 (m, 1H,
[RuCl2(tBuNHCPtBu)(benzylidene)] (7a). Method a: Into an NMR
tube were added complex 6 (10.0 mg, 11 μmol), phenyldiazomethane
(5.0 mg, 42 μmol), and CD2Cl2 (0.5 mL), affording a green solution.
Complex 7a was contaminated with byproducts and therefore could
not be fully characterized. Mp: 152 °C (dec). Selected spectral data:
31P{1H} NMR: (101.26 MHz, THF-d8): 133.4 (s, P(C(CH3)3)2). H
1
3
NMR (250.13 MHz, THF-d8): 14.82 (d, JH,P = 8.6 Hz, 1H, Ru
CH). MS (FAB+), m/z (%): 509.2 [M − Cl]+ (100), 454.1
[RuCl2(NHCP)]+ (15), 383.1 [Ru(NHCP)]+ (35). HRMS (FAB+),
m/z: calcd for C23H37ClN2PRu 509.1426; found 509.1446. Method b:
Into a Schlenk tube were added complex 15 (100 mg, 193 μmol) and
first-generation Grubbs catalyst (159 mg, 193 μmol) and suspended in
toluene (5 mL). The slurry was stirred under heating at 80 °C for 2 h,
resulting in a color change from violet to brown and in a precipitated
green solid. The slurry was filtered through a cotton and Celite pad
and washed with toluene (5 mL). The green solid on the pad was
dissolved with dichloromethane (10 mL), leaving a violet material.
The filtrate was dried under vacuum, affording a green solid in 40%
(42 mg) yield. 1H NMR (600.13 MHz, CD2Cl2): 14.97 (d, 3JH,P = 8.2
Hz, 1H, RuCH), 8.40 (d, 3JH,H = 7.7 Hz, 2H, Ar), 7.68 (t, 3JH,H = 7.4
3
PCH2), 4.40−4.44 (m, 1H, PCH2), 1.49 (d, JH,P = 14.3 Hz, 9H,
P(C(CH3)3)2), 1.19 (s, 9H, NC(CH3)3), 1.12 (d, 3JH,P = 14.9 Hz, 9H,
P(C(CH3)3)2). 13C{1H} NMR (150.90 MHz, CD2Cl2): 291.6 (d, 2JC,P
2
= 4.6 Hz, RuCH), 177.6 (d, JC,P = 9.4 Hz, NCN), 152.2 (bs, Ar),
131.2 (s, Ar), 129.7 (s, Ar), 126.6 (bs, Ar), 126.2 (bs, CF3), 121.2 (s,
N(CH)2N), 119.9 (d, 3JC,P = 8.3 Hz, N(CH)2N), 60.0 (s, NC(CH3)3),
1
1
44.5 (d, JC,P = 26.6 Hz, PCH2), 38.3 (d, JC,P = 21.7 Hz,
1
P(C(CH3)3)2) 37.1 (d, JC,P = 24.0 Hz, P(C(CH3)3)2), 32.1 (s,
NC(CH3)3), 29.3 (bs, P(C(CH3)3)2), 29.0 (bs, P(C(CH3)3)2).
31P{1H} NMR (242.94 MHz, CD2Cl2): 130.7 (s). 19F NMR (376.27
MHz, CD2Cl2, RT): −63.7 (s, CF3). MS (FAB+), m/z (%): 612.5
[M]+ (2), 577.2 [M − Cl]+ (100), 454.1 [RuCl2(NHCP)]+ (8), 383.2
[Ru(NHCP)]+ (10). HRMS (FAB+), m/z (%): calcd for
C24H36Cl2F3N2PRu 577.1300; found 577.1313.
3
3
Hz, 1H, Ar), 7.45 (t, JH,H = 7.8 Hz, 2H, Ar), 7.36 (d, JH,H = 1.9 Hz,
1H, N(CH)2N), 7.05 (d, 3JH,H = 1.9 Hz, 1H, N(CH)2N), 4.42 (d, 2JH,P
= 5.8 Hz, 2H, PCH2), 1.48 (d, 3JH,P =14.3 Hz, 9H, PC(CH3)3), 1.19 (s,
9H, NC(CH3)3), 1.13 (d, JH,P = 14.6 Hz, 9H, PC(CH3)3). 13C{1H}
3
2
NMR (150.90 MHz, CD2Cl2): 295.4 (d, JC,P = 15.9 Hz, RuCH),
41
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Organometallics
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[RuCl2(tBuNHCPtBu)(4-nitrobenzylidene)] (7d). Complex 6 (10
mg, 11 μmol) was suspended in dichloromethane (4 mL), and to it
was added (4-nitrophenyl)diazomethane (4.0 mg, 25 μmol) as a solid.
The reaction mixture was stirred for 1.5 h at room temperature while
observing a slight evolution of a gas. The resulting green solution was
concentrated to 1 mL, and to it was added pentane (2 mL), resulting
in the precipitation of a green solid. The supernatant was decanted,
and the solid was washed with pentane (2 mL). The residue was dried
under vacuum, affording a brownish-green solid. The yield could not
be determined as a result of contamination, and a full spectral
characterization could not be achieved. 1H NMR (250.14 MHz,
CD2Cl2): 15.10 (d, 3JH,P = 8.8 Hz, 1H, RuCH), 8.57 (d, 3JH,H = 8.8
added to precipitate the product. The mother liquor was removed, and
the solid was washed again with pentane (5 mL). The residue was
dried under vacuum, affording a green solid in a 68% (45 mg) yield.
1H NMR (300.13 MHz, CD2Cl2): 7.36 (m, 1H, N(CH)2N), 7.27 (m,
2
2
1H, N(CH)2N), 4.12 (d, JH,P = 6.4 Hz, 2H, PCH2), 1.65 (d, JH,P
=
3
7.0 Hz, 9H, P(CH3)3), 1.52 (s, 9H, NC(CH3)3), 1.16 (d, JH,P = 12.9
Hz, 18H, P(C(CH3)3)2). 13C{1H} NMR (75.48 MHz, CD2Cl2): 191.4
(s, NCN), 119.5 (s, N(CH)2N), 119.4 (s, N(CH)2N), 59.1 (s,
NC(CH3)3), 47.9 (d, 1JC,P = 25.1 Hz, PCH2), 39.2 (d, 1JC,P = 20.4 Hz,
2
P(C(CH3)3)2), 32.1 (s, NC(CH3)3), 30.1 (d, JC,P = 2.4 Hz,
1
P(C(CH3)3)2), 15.0 (d, JC,P = 21.5 Hz, P(CH3)3). 31P{1H} NMR:
2
2
(121.50 MHz, CD2Cl2): −5.5 (d, JP,P = 17.8 Hz), 120.7 (d, JP,P
=
3
17.8 Hz). IR (KBr), ν (cm−1): 3125 (w), 2963 (m), 2908 (m), 1393
(s), 1276 (s), 952 (s), 727 (m). MS (FAB+), m/z (%): 530.2 [M]+
(75), 495.2 [M − Cl]+ (80), 454.1 [RuCl2(NHCP)]+ (100), 383.1
[Ru(NHCP)]+ (30). HRMS (FAB+), m/z: calcd for C19H40Cl2N2P2Ru
530.1087; found 530.1116. Anal. Calcd for C19H40Cl2N2P2Ru: C,
43.02; H, 7.60; N, 5.28; P, 11.68. Found: C, 43.06; H, 7.60; N, 5.36; P,
11.38.
Hz, 2H, Ar), 7.10 (d, JH,H = 2.2 Hz, 1H, N(CH)2N), 4.37−4.58 (m,
3
2H, PCH2), 1.48 (d, JH,P = 14.5 Hz, 9H, P(C(CH3)3)2), 1.18 (s, 9H,
NC(CH3)3), 1.12 (d, 3JH,P = 15.1 Hz, 9H, P(C(CH3)3)2); as a result of
contamination missing signals are probably covered, and signals at
around 7.38 (1H, N(CH)2N), 7.69 (2H, Ar) can be assigned. 31P{1H}
NMR (101.26 MHz, CD2Cl2): 131.2 (s). MS (FAB+), m/z (%): 554.2
[M − Cl]+ (100), 454.1 [RuCl2(NHCP)]+ (25). HRMS (FAB+), m/z
(%): calcd for C23H36ClN3O2PRu 554.1277; found 554.1403.
[RuCl2(MesNHCPtBu)(PPh3)] (9a,b). In a Schlenk tube complex 6
(50.0 mg, 54.8 μmol) and PPh3 (27.0 mg, 100 μmol, 2 equiv) were
dissolved in dichloromethane (6 mL). The reaction mixture was
stirred for 1.5 h at room temperature, resulting in a color change to a
red solution. After filtration of the solution pentane (5 mL) was added
to precipitate the product. The mother liquor was decanted, and the
solid was washed with hexane (3 × 5 mL). The residue was dried
[RuCl2(tBuNHCPtBu)(4-methylbenzylidene)] (7e). Complex 6
(40.0 mg, 44 μmol) was suspended in chloroform (3.5 mL); then
(4-tolyl)diazomethane (30.0 mg, 230 μmol) was added. The reaction
mixture was stirred for 1.5 h at room temperature and then for
additional 1.5 h at 60 °C, leading to the slight evolution of a gas. The
resulting brownish-green solution was concentrated to ca. 0.7 mL, and
pentane (2 mL) was added, resulting in the product precipitation. The
solid was washed with pentane (2 mL) and dried under vacuum,
affording a brownish-green solid. The yield could not be determined as
a result of contamination, and a full spectral characterization could not
be achieved. Selected spectral data: 1H NMR (500.13 MHz, CD2Cl2):
14.85 (m, 1H, RuCH). 31P{1H} NMR (101.26 MHz, CD2Cl2):
133.0 (s). IR (KBr), ν (cm−1): 2962 (s), 1951 (s), 1597 (m), 1477 (s),
1369 (s), 1233 (m), 1178 (s), 1019 (m), 810 (m), 691 (w), 506 (m).
MS (FAB+): NBA-matrix, m/z (%), 523.2 [M − Cl]+ (70), 454.1
[RuCl2(NHCP)]+ (15), 383.2 [Ru(NHCP)]+ (55), 208.1 [dimethyl-
stilbene] (100). HRMS (FAB+), m/z (%): calcd for C24H39ClN2PRu
523.1583; found 523.1524.
1
under vacuum, affording a red solid in 67% (48 mg) yield. H NMR
(300.13 MHz, CD2Cl2), first set of signals: 7.13−7.44 (m, 15H, Ar),
6.98 (d, 3JH,H = 2.2 Hz, 1H, N(CH)2N), 6.57 (d, 3J H,H = 2.0 Hz, 1H,
N(CH)2N), 3.27−3.40 (m, 1H, PCH2), 2.45−2.54 (m, 1H, PCH2),
3
1.37 (s, 9H, NC(CH3)3), 1.36 (d, JH,P = 14.2 Hz, 9H, PC(CH3)3),
3
1.20 (d, JH,P = 13.3 Hz, 9H, P(C(CH3)3)2); second set of signals:
7.79−7.93 (m, 6H, Ar), 7.33 (m, 1H, N(CH)2N), 7.24 (m, 1H,
2
N(CH)2N), 7.13−7.44 (m, 12H, Ar-H), 4.09 (d, JH,P = 6.4 Hz, 2H,
3
PCH2), 1.41 (s, 9H, NC(CH3)3), 1.07 (d, JH,P = 13.3 Hz, 18H,
P(C(CH3)3)2). The sample contains free PPh3. 13C{1H} NMR (75.47
MHz, CD2Cl2), first set of signals: 183.1 (s, NCN), 129.5 (m, Ar),
129.0 (d, 2J
= 6.8 Hz, Ar), 128.3−128.8 (m, Ar), 121.0 (s,
C,P
[RuCl2(tBuNHCPtBu)(CH-SiMe3)] (7f). Complex 6 (76.0 mg, 110
μmol) was suspended in dichloromethane (8 mL), and then
(trimethylsilyl)diazomethane (180 μL, 2 M in THF, 350 μmol) was
added slowly via syringe. The reaction mixture was stirred for 30 min
at room temperature, and then it was heated at 60 °C for 2.5 h,
resulting in the formation of a brown solid. The solution was then
concentrated to 0.5 mL, and pentane (3 mL) was added for complete
product precipitation. The greenish-brown solution was decanted, and
the brown solid was washed with pentane (4 × 2 mL). The product
was dried under vacuum, affording a brown solid in 60% (54 mg)
N(CH)2N), 120.1 (d, 3JC,P = 7.1 Hz, N(CH)2N), 59.8 (s, NC(CH3)3),
1
1
45.4 (d, JC,P = 24.8 Hz, PCH2), 39.5 (d, JC,P = 19.3 Hz,
1
P(C(CH3)3)2), 36.4 (d, JC,P = 21.6 Hz, P(C(CH3)3)2), 32.2 (s,
2
NC(CH3)3), 31.8 (bs, P(C(CH3)3)2), 29.7 (d, JC,P = 2.9 Hz,
P(C(CH3)3)2); second set of signals: 192.2 (s, NCN), 135.8 (d, 2JC,P
=
10.3 Hz, Ar), 129.6 (d, 3JC,P = 1.3 Hz, Ar), 129.3 (s, Ar), 128.3−128.8
(m, Ar), 119.8 (d, 4JC,P = 3.9 Hz, N(CH)2N), 119.3 (dd, 3JC,P = 7.6 Hz,
4JC,P = 2.1 Hz, N(CH)2N), 58.8 (s, NC(CH3)3), 47.9 (d, JC,P = 29.9
1
1
Hz, CH2), 39.8 (d, JC,P = 18.7 Hz, P(C(CH3)3)2), 32.8 (s,
2
NC(CH3)3), 30.3 (d, JC,P = 2.6 Hz, P(C(CH3)3)2). (The sample
3
yield. 1H NMR (600.13 MHz, CD2Cl2): 18.93 (d, JH,P = 3.4 Hz, 1H,
contains free PPh3.) 31P{1H} NMR (121.49 MHz, CD2Cl2, 223 K),
RuCH), 7.34 (d, 3JH,H = 2.1 Hz, N(CH)2N), 7.06 (d, 3JH,H = 2.1 Hz,
first set of signals: 34.1 (d, 2JP,P = 32.3 Hz, PPh3), 126.0 (d, 2JP,P = 32.3
2
2
2
1H, N(CH)2N), 4.40 (dd, JH,H = 14.0 Hz, JH,P = 10.3 Hz, 2H,
PCH2), 4.29 (dd, 2JH,H = 14.0 Hz, 2JH,P = 3.2 Hz, 2H, PCH2), 1.41 (d,
3JH,P = 14.2 Hz, 9H, P(C(CH3)3)2), 1.31 (s, 9H, NC(CH3)3), 1.07 (d,
Hz, P(C(CH3)3)2); second set of signals: 24.5 (d, JP,P = 10.0 Hz,
PPh3), 108.3 (d, 2JP,P = 10.0 Hz, P(C(CH3)3)2). (The sample contains
free PPh3 in a 2:1 ratio.) IR (KBr), ν (cm−1): 3053 (w), 2960 (m),
2908 (m), 1480 (m), 1434 (s), 1366 (m), 744 (m), 697 (s), 527 (m).
MS (FAB+), m/z (%): 716.2 [M]+ (5), 681.2 [M − Cl]+ (55), 454.1
[Ru(NHCP)(Cl)2]+ (50), 383.1 [Ru(NHCP)]+ (48), 262.1 [PPh3]+
(100). HRMS (FAB+), m/z: calcd for C34H46Cl2N2P2Ru 716.1557;
found 716.1650. Anal. Calcd for C34H46Cl2N2P2Ru: C, 56.98; H, 6.47;
N, 3.91; P, 8.64. Found: C, 56.93; H, 6.85; N, 3.95; P, 8.02.
3JH,P = 14.9 Hz, 9H, P(C(CH3)3)2), 0.42 (s, 9H, Si(CH3)3). 13C{1H}
2
NMR (150.90 MHz, CD2Cl2): 354.9 (bs, RuCH), 175.4 (d, JC,P
=
3
9.4 Hz, NCN), 121.2 (s, N(CH)2N), 119.5 (d, JC,P = 8.6 Hz,
N(CH)2N), 59.6 (s, NC(CH3)3), 44.8 (d, 1JC,P = 28.2 Hz, PCH2), 38.5
1
1
(d, JC,P = 21.3 Hz, P(C(CH3)3)2), 34.6 (d, JC,P = 24.5 Hz,
2
P(C(CH3)3)2), 32.7 (s, NC(CH3)3), 29.3 (d, JC,P = 3.2 Hz,
[RuCl2(MesNHCPtBu)(PCy3)] (10a,b). In a Schlenk tube complex 6
(30.2 mg, 33 μmol) and PCy3 (5.2 mg, 66 μmol, 2 equiv) were
dissolved in dichloromethane (6 mL). The reaction mixture was
stirred at room temperature for 2 h, resulting in a color change to a red
solution, which was filtered and concentrated under vacuum to ca. 0.5
mL. Diethyl ether (1 mL) was added, resulting in the product
precipitation. The mother liquor was decanted, and the solid was
washed again with diethyl ether (2 mL). The residue was dried under
vacuum, affording a red solid in 87% (42 mg) yield. Mp: 127 °C (dec).
31P{1H} NMR (202.46 MHz, CD2Cl2): 33.4 (s, PCy3), 39.6 (s, PCy3),
94.0 (s, P(C(CH3)3)2), 116.0 (s, P(C(CH3)3)2). The two species are
2
P(C(CH3)3)2), 28.6 (d, JC,P = 2.3 Hz, P(C(CH3)3)2), −0.9 (s,
Si(CH3)3). 31P{1H} NMR (242.94 MHz, CD2Cl2): 124.6 (s). IR
(KBr), ν (cm−1): 3101 (w), 2951 (s), 2900 (s), 1936 (w), 1477 (s),
1370 (m), 1199 (m), 842 (s). MS (FAB+), m/z (%): 540.1 [M]+ (9),
505.2 [M − Cl]+ (100), 454.1 [RuCl2(NHCP)]+ (15). HRMS (ESI+),
m/z: calcd for C20H41Cl2N2PRuSi 540.1197; found 540.1166.
[RuCl2(MesNHCPtBu)(PMe3)] (8). In a Schlenk tube complex 6 (60.0
mg, 65.8 μmol) was suspended in dichloromethane (6 mL), and a
solution of PMe3 in THF (125 μL, 125 μmol, 1 M) was added. The
reaction mixture was stirred at room temperature for 1.5 h, resulting in
the formation of a green solution. After filtration pentane (5 mL) was
42
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Organometallics
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3
in a 1:1 ratio. IR (KBr), ν (cm−1): 2933 (w), 2857 (m), 1447 (m),
1371 (m), 1238 (w), 1098 (s), 806 (m). MS (FAB+), m/z (%): 699.5
[M]+ (30), 454.1 [Ru(NHCP)(Cl)2]+ (80), 383.1 [Ru(NHCP) ]+
(90). Anal. Calcd for C34H64Cl2N2P2Ru: C, 55.57; H, 8.78; N, 3.81.
Found: C, 54.57; H, 8.57; N, 1.71.
6.5 Hz, 1H, bipy), 7.28 (d, JH,H = 1.8 Hz, 1H, N(CH)2N), 4.48 (d,
2JH,P = 14.0 Hz, 1H, PCH2), 4.28 (dd, JH,P = 10.5 Hz, 1H, PCH2),
2
1.25 (s, 9H, NC(CH3)3), 0.54 (d, 3JH,P = 13.8 Hz, 18H, P(C(CH3)3)2).
31P{1H} NMR (101.20 MHz, CDCl3): 119.4 (s). MS (FAB+), m/z
(%): 575.2 [M − Cl]+ (95). Anal. Calcd for C26H40Cl2N4PRu: C,
51.06; H, 6.59; N, 9.16. Found: C, 50.90; H, 6,51; N, 9.01.
[RuCl2(MesNHCPtBu)(py2)] (11). In a Schlenk tube complex 6 (10.3
mg, 11 μmol) and pyridine (3.0 mg, 38 μmol, 3.6 equiv) were
dissolved in CD2Cl2 (0.5 mL), affording a green solution, which upon
cooling to −30 °C became brown. Crystals suitable for X-ray analysis
were obtained by slow evaporation of a concentrated solution of
3-tert-Butyl-1-(di-tert-butylphosphinomethyl)imidazolium
Iodide (14). To a suspension of 4a (50.0 mg, 161 μmol) in acetone (5
mL) was added NaI (23.5 mg, 157 μmol) as a solid, and the reaction
mixture was stirred for 16 h at room temperature. The reaction
mixture was filtered through Celite, and the solvent removed in vacuo.
The product was dried under vacuum, affording a white solid in 99%
(64 mg) yield. 1H NMR (300.08 MHz, CD2Cl2): 10.44 (s, 1H,
1
complex 6 in pyridine. H NMR (300.13 MHz, pyridine-d5): 7.53 (d,
3
3JH,H = 2.1 Hz, 1H, N(CH)2N), 7.39 (d, JH,H = 2.1 Hz, 1H,
2
N(CH)2N), 4.76 (d, JH,P = 4.7 Hz, 2H, PCH2), 1.49 (s, 9H,
3
3
NCHN), 7.67 (s, 1H, N(CH)2N), 7.41 (t, JH,H = 1.9 Hz, 1H,
NC(CH3)3), 1.33 (d, JH,P = 11.3 Hz, 18H, P(C(CH3)3)2), signals of
N(CH)2N), 4.78 (bs, 2H, CH2P), 1.70 (s, 9H, NC(CH3)3), 1.21 (d,
3JH,P = 11.8 Hz, 18H, PC(CH3)3). 13C{1H} NMR (75.46 MHz,
CD2Cl2): 136.1 (d, 3JC,P = 5.2 Hz, NCHN), 123.1 (d, 3JC,P = 10.3 Hz,
the coordinated pyridines were not detected because of exchange with
the solvent. 13C{1H} NMR (75.47 MHz, pyridine-d5): 192.2 (d, 2JC,P
=
9.9 Hz, NCN), 129.8 (s, py), 129.0 (s, py), 122.4 (s, N(CH)2N), 120.9
1
3
1
N(CH)2N), 119.4 (s, N(CH)2N), 45.5 (d, JC,P = 26.4 Hz, CH2P),
(d, JC,P = 5.5 Hz, N(CH)2N), 60.4 (s, NC(CH3)3), 48.6 (d, JC,P
=
32.7 (d, 1JC,P = 19.0 Hz, PC(CH3)3), 30.5 (s, PC(CH3)3), 29.8 (d, 1JC,P
= 13.2 Hz, PC(CH3)3), 26.4 (s, PC(CH3)3). 31P{1H} NMR (121.47
MHz, CD2Cl2): 29.1 (s). MS (ESI), m/z (%): 283.23 [M]+ (100).
Anal. Calcd for C16H32IN2P: C, 46.83; H, 7.86; N, 6.83. Found: C,
45.16; H, 7.65; N, 6.62.
1
23.6 Hz, PCH2), 37.6 (d, JC,P = 11.5 Hz, P(C(CH3)3)2), 32.4 (s,
NC(CH3)3), 31.0 (d, JC,P = 2.7 Hz, P(C(CH3)3)2), signals of the
2
coordinated pyridines were not detected because of exchange with the
solvent. 31P{1H} NMR (121.50 MHz, pyridine-d5): 84.9 (s). Partial
NMR data in CD2Cl2: 1H NMR (500.13 MHz, CD2Cl2, 193 K): 9.36
(bs, 1H, py), 9.05 (bs, 1H, py), 8.44 (bs, 1H, py), 8.06 (bs, 1H, py),
7.65 (d, 3JH,H = 4.7 Hz, 2H, py), 7.19−7.32 (m, 3H, py), 7.15 (bs, 1H,
[AgI(tBuNHCPtBu)]2 (15). Into a Schlenk tube under argon were
added ligand 8 (200 mg, 487 μmol) and Ag2O (56.5 mg, 244 μmol) as
solids, and then CH2Cl2 (5 mL) was added. The reaction mixture was
heated at 50 °C under stirring for 2 h, resulting in a light yellow
solution. The solution was filtered through Celite. The filtrate was
dried under vacuum, affording a light brown solid in 89% (174 mg)
yield. 1H NMR (300.19 MHz, CD2Cl2): 7.39 (s, 1H, N(CH)2N), 7.25
py) 7.03 (bs, 1H, N(CH)2N), 6.95 (bs, 1H, N(CH)2N), 4.62 (d, 2JH,P
3
= 11.5 Hz, 1H, PCH2), 4.07−4.17 (m, 1H, PCH2), 1.57 (d, JH,P
=
13.1 Hz, 3H, P(C(CH3)3)2), 1.31 (bs, 3H, P(C(CH3)3)2), 1.22 (bs,
3
9H, NC(CH3)3), 0.98 (d, JH,P = 8.8 Hz, 9H, P(C(CH3)3)2), 0.44 (d,
3JH,P = 9.8 Hz, 3H, P(C(CH3)3)2). 31P{1H} NMR (200.46 MHz,
CD2Cl2, 193 K): 80.5 (s). MS (FAB+), m/z (%): 622.4 [M]+ (10),
587.4 [M − Cl]+ (7), 538.4 [M − py]+ (40).
3
(t, JH,H = 1.9 Hz, 1H, N(CH)2N), 4.42 (s, 2H, CH2P), 1.70 (s, 9H,
NC(CH3)3) 1.23 (d, 3JH,P = 12.4 Hz, 18H, PC(CH3)3). 13C{1H} NMR
(75.48 MHz, CD2Cl2): 186.1 (bs, NCN), 121.8 (s, N(CH)2N), 119.3
(d, JC,P = 4.0 Hz, N(CH)2N), 46.7 (d, 1JC,P = 4.6 Hz, CH2P), 33.6 (d,
[RuCl2(MesNHCPtBu)(py)] (12). In a Schlenk tube complex 6 (60.0
mg, 66 μmol) and a solution of pyridine in THF (260 mL, 13 μmol,
0.5 M, 1 equiv) were dissolved in THF (5 mL). The green solution
was heated for 1 h at 50 °C and then filtered and concentrated under
vacuum to ca. 0.5 mL. Pentane (8 mL) was added, resulting in the
product precipitation. The residue was then washed with pentane (3 ×
8 mL) and dried under vacuum, affording a green solid in 68% (47
mg) yield. 1H NMR (500.13 MHz, CD2Cl2): 9.60 (dd, 3JH,H = 6.4 Hz,
1JC,P =12.1 Hz, PC(CH3)3), 31.9 (s, NC(CH3)3), 30.0 (d, JC,P =10.9
2
Hz, PC(CH3)3), 27.0 (s, NC(CH3)3). 31P{1H} NMR (121.47 MHz,
CD2Cl2): 30.44 (bs). HRMS (FAB+), m/z (%): calcd for
C16H31AgN2P: 389.1276 (100); found 389.1278 (93). Anal. Calcd
for C16H31AgIN2P: C, 37.16; H, 6.04; N, 5.42. Found: C, 35.52; H,
5.76; N, 5.12.
[RuCl2(MesNHCPtBu)(benzylidene)] (17). First-generation Grubbs
catalyst (47.8 mg, 58 μmol) was dissolved in toluene (1 mL), and to it
was added 5b (20.0 mg, 58 μmol) in toluene (1 mL). The reaction
mixture was stirred for 16 h at room temperature, resulting in a color
change to brownish-green and the formation of a green solid. The
slurry was filtered through a short plug of Celite, and the solid on the
plug was washed with toluene (2 × 2 mL). The solid was eluted with
THF (3 mL), dried under vacuum, and then redissolved in THF (1
mL). The solution was passed through a silica gel plug and washed out
with another 3 mL of THF, leaving a brown material on the plug. The
green solution was dried under vacuum, affording a green solid in 29%
4JH,H = 1.4 Hz, 2H, Py), 7.87 (t, JH,H = 7.6 Hz, 1H, Py), 7.41−7.46
3
(m, 2H, Py), 7.28 (d, 3JH,H = 2.2 Hz, 1H, N(CH)2N), 7.22 (d, 3JH,H
=
2
2.2 Hz, 1H, N(CH)2N), 4.02 (d, JH,P = 6.4 Hz, 2H, PCH2), 1.67 (s,
3
9H, NC(CH3)3), 1.15 (d, JH,P = 13.1 Hz, 18H, P(C(CH3)3)2).
13C{1H} NMR (125.76 MHz, CD2Cl2): 194.7 (d, JC,P = 12.5 Hz,
2
NCN), 155.1 (s, Py), 137.1 (s, Py), 124.4 (s, Py), 119.2 (d, 3JC,P = 7.7
Hz, N(CH)2N), 119.1 (s, N(CH)2N), 58.8 (s, NC(CH3)3), 47.4 (d,
1JC,P = 26.9 Hz, PCH2), 38.9 (d, JC,P = 20.2 Hz, P(C(CH3)3)2), 32.2
1
(s, NC(CH3)3), 30.3 (d, 2JC,P = 2.9 Hz, P(C(CH3)3)2). 31P{1H} NMR
(202.46 MHz, CD2Cl2): 122.4 (s). 15N{1H} NMR (50.70 MHz,
CD2Cl2): −190.0 (Im-N3), −167.2 (Im-N1), −107.5 (coordinated
pyridine), −64.7 (contains noncoordinated pyridine). IR (KBr), ν
(cm−1): 2962 (m), 2899 (w), 1598 (w), 1482 (m), 1443 (s), 1368 (s),
1235 (s), 699 (s). MS (FAB+), m/z (%): 533.2 [M]+ (40), 454.1
[Ru(NHCP)(Cl)2]+ (100). HRMS (FAB+), m/z: calcd for
C21H36Cl2N3PRu: 533.1067. Found: 533.1093. Anal. Calcd for
C21H36Cl2N3PRu: C, 47.28; H, 6.80; N, 7.88. Found: C, 47.97; H,
6.93; N, 7.73.
1
(10 mg) yield of an unclean product. Partial spectral data: H NMR
3
(200.15 MHz, acetone-d6): 14.97 (d, JH,P = 12.5 Hz, 1H, RuCH),
8.42 (d, J = 7.8 Hz, 2H, Ar), 7.96 (d, J = 2.0 Hz, 1H, N(CH)2N), 7.59
(t, J = 7.6 Hz, 1H, Ar), 7.32 (d, J = 7.3 Hz, 2H, Ar), 6.91 (dd, J = 2.1,
0.6 Hz, 1H, N(CH)2N), 6.75 (bs, 1H, Mes), 6.51 (bs, 1H, Mes), 5.19
(dd, J = 14.7, 10.8 Hz, 1H, PCH2), 4.91 (dd, J = 14.7, 1.7 Hz, 1H,
PCH2), 4.29 (t, J = 7.0 Hz, 1H), 2.17 (s, 3H, Mes-CH3), 1.98 (s, 3H,
Mes-CH3), 1.47 (d, J = 12.7 Hz, 9H, PC(CH3)3), 1.19 (d, J = 14.4 Hz,
9H, PC(CH3)3), 1.16 (s, 3H, Mes-CH3). 31P NMR (81.02 MHz,
acetone-d6): 107.2 (s).
[RuCl2(MesNHCPtBu)(bipy)] (13). In a Schlenk tube complex 6
(30.0 mg, 32.9 μmol) was dissolved in CH2Cl2 (5 mL), and 2,2′-
bipyridine (10.8 mg, 69.2 μmol) was added. The reaction mixture was
stirred at 40 °C for 20 h, affording a deep red solution. The solvent
was removed under vacuum, and the residue was washed with pentane
[RuCl2(tBuNHCPtBu)(3-phenyl-1H-inden-1-ylidene)] (18). In a
Schlenk tube ligand 5b (20.0 mg, 58.1 μmol) and Umicore M1 catalyst
(53.6 mg, 58.1 μmol) were dissolved in toluene (4 mL). The reaction
mixture was heated at 80 °C for 10 h, resulting in a color change from
reddish-brown to red and in the formation of a red solid. The slurry
was filtered through cotton and a Celite plug. The solid on the plug
was washed with toluene (4 mL) and then dissolved partially with
THF (2 mL) and completely dissolved with dichloromethane (5 mL).
The combined solutions were dried under vacuum, affording a red
(4 × 10 mL) and then dried under vacuum, affording the product in
1
87% (35 mg) yield. H NMR (250.10 MHz, CDCl3): 9.65 (d, 3JH,H
=
=
2
3
5.1 Hz, 1H, bipy), 8.79 (d, JH,H = 8.4 Hz, 1H, bipy), 8.69 (d, JH,H
8.4 Hz, 1H, bipy), 8.20 (t, 3JH,H = 8.4 Hz, 1H, bipy), 7.88 (t, 3JH,H = 8.4
Hz, 1H, bipy), 7.76 (d, 3JH,H = 1.8 Hz, 1H, N(CH)2N), 7.68 (t, 3JH,H
=
=
3
3
6.5 Hz, 1H, bipy), 7.45 (d, JH,H = 6.0 Hz, 1H, bipy), 7.35 (t, JH,H
43
dx.doi.org/10.1021/om300487r | Organometallics 2013, 32, 29−46

Organometallics
Article
solid in 60% (25 mg) yield. 1H NMR (600.13 MHz, CD2Cl2): 8.94 (d,
6. Brown crystals (polyhedron), 0.30 × 0.19 × 0.17 mm3,
monoclinic, P21/n, Z = 2, a = 11.8023(1) Å, b = 18.0801(1) Å, c =
12.1946(1) Å, α = 90°, β = 116.5820(10)°, γ = 90°, V = 2327.10(3)
Å3, ρ = 1.539 g/cm3, θmax = 27.42°, 22 349 reflections measured, 5300
unique (Rint = 0.0315), 4831 observed (I >2σ(I)), μ = 1.21 mm−1, Tmin
= 0.71, Tmax = 0.82, 246 parameters refined, goodness of fit 1.06 for
observed reflections, final residual values R1(F) = 0.023, wR(F2) =
0.056 for observed reflections, residual electron density −0.41 to 0.50
e Å−3.
3
JH,P = 6.9 Hz, 1H, Ind-CH), 7.66 (s, 1H, N(CH)2N), 7.58 (d, JH,H
=
7.4 Hz, 2H, Ind-Ar), 7.51 (t, 3JH,H = 7.5 Hz, 1H, Ind-Ar), 7.41 (m, 3H,
3
Ind-Ar), 7.24 (t, JH,H = 7.4 Hz, 1H, Ind-Ar), 7.16 (m, 2H, Ind-Ar),
6.81 (s, 1H, Mes-CH), 6.76 (s, 1H, N(CH)2N), 6.62 (s, 1H, Mes-
2
2
CH), 4.90 (dd, JH,P = 14.4 Hz, JH,H = 10.6 Hz, 1H, PCH2), 4.45 (d,
2JH,P = 14.4 Hz, 1H, PCH2), 2.23 (s, 3H, Mes-o-CH3), 1.88 (s, 3H,
3
Mes-o-CH3),1.47 (d, JH,P = 13.0 Hz, 9H, P(C(CH3)3), 1.41 (s, 3H,
Mes-p-CH3), 1.14 (d, JH,P = 14.7 Hz, 9H, P(C(CH3)3). 13C{1H}
3
2
7a. Dark orange crystals (polyhedron), 0.18 × 0.09 × 0.08 mm3,
trigonal, space group P3121, Z = 6, a = 12.4946(11) Å, b =
12.4946(11) Å, c = 31.855(4) Å, α = 90°, β = 90°, γ = 120°, V =
4306.8(7) Å3, ρ = 1.456 g/cm3, θmax = 28.35°, 45 832 reflections
measured, 7137 unique (Rint = 0.0615), 6633 observed (I >2σ(I)), μ =
0.99 mm−1, Tmin = 0.84, Tmax = 0.93, 289 parameters refined, Flack
absolute structure parameter 0.07(3), goodness of fit 1.10 for observed
reflections, final residual values R1(F) = 0.035, wR(F2) = 0.072 for
observed reflections, residual electron density −0.37 to 0.73 e Å−3.
7b. Green crystals (polyhedron), 0.22 × 0.14 × 0.04 mm3,
monoclinic, P21/n, Z = 4, a = 9.6909(1) Å, b = 26.8891(1) Å, c =
12.5386(2) Å, α = 90°, β = 103.3680(10)°, γ = 90°, V = 3178.78(6)
Å3, ρ = 1.569 g/cm3, θmax = 24.71°, 24 728 reflections measured, 5424
unique (Rint = 0.0866), 3792 observed (I >2σ(I)), μ = 2.24 mm−1, Tmin
= 0.64, Tmax = 0.92, 319 parameters refined, goodness of fit 1.08 for
observed reflections, final residual values R1(F) = 0.063, wR(F2) =
0.126 for observed reflections, residual electron density −1.27 to 1.37
e Å−3.
NMR (150.90 MHz, CD2Cl2): 284.4 (d, JC,P = 12.1 Hz, RuCH),
2
181.2 (d, JC,P = 9.1 Hz, NCN), 148.7 (s, Ind), 140.5 (s, Ind), 138.79
(s, Ind), 137.3 (d, 3JC,P = 6.0 Hz, Ind), 137.1 (s, Ind), 136.3 (d, 4JC,P
=
3
1.5 Hz, Ind), 130.7 (s, Ind), 130.3 (d, JC,P = 7.5 Hz, Ind), 129.6 (s,
Ind), 129.5 (d, 4JC,P = 1.5 Hz, Ind), 128.8 (s, Ind), 128.7 (d, 4JC,P = 3.0
3
Hz, Ind), 126.8 (s, Ind), 126.5 (s, Ind), 121.1 (d, JC,P = 7.5 Hz,
N(CH)2N), 118.3 (s, N(CH)2N), 45.3 (d, 1JC,P = 9.0 Hz, PCH2), 38.1
(d, 1JC,P = 18.1 Hz, P(C(CH3)3), 36.6 (d, 1JC,P = 18.1 Hz, P(C(CH3)3),
2
2
30.7 (d, JC,P = 3.0 Hz, P(C(CH3)3), 29.5 (d, JC,P = 3.0 Hz,
P(C(CH3)3), 21.3 (s, Mes-CH3), 18.8 (s, Mes-CH3), 17.9 (s, Mes-
CH3). 31P{1H} NMR (242.94 MHz, CD2Cl2): 102.4 (s). HRMS
(FAB+), m/z: calcd for C36H43ClN2PRu: 671.1903; found 671.1887.
Anal. Calcd for C36H43Cl2N2PRu: C, 61.18; H, 6.13; N, 3.96. Found:
C, 59.12; H, 6.57; N, 3.75.
X-ray Diffraction Studies. For the X-ray diffraction studies data
sets were collected on Bruker CCD diffractometers (“Smart CCD” for
3b, 5a, 6, 7b, 7e, 7f, 8, 12 and “APEX” for 4a, 7a, 7c, 9b, 13, 16a, 16b
with Mo Kα radiation (λ = 0.71073 Å) at 200 K (100 K for 4a, 13)). A
complete sphere in reciprocal space was covered by 0.3 deg ω-scans in
all cases. For all data sets the intensities were corrected for Lorentz and
polarization effects, and an empirical absorption correction, based on
the Laue symmetry of the reciprocal space, was applied using SADABS
(2008/1).31 All structures were solved by direct methods and refined
against F2 with a full-matrix least-squares algorithm using the
SHELXTL (Version 2008/4) software package.32 If not noted
differently below hydrogen atoms were treated using appropriate
riding models. CCDC 643287 (2), 643288 (3a), 887432 (3b), 643289
(4a), 643291 (5a), 887433 (6), 887434 (7a), 887435 (7b), 887436
(7c), 887437 (7e), 887438 (7f), 887439 (8), 887440 (9b), 887441
(12), 887442 (13), 887443 (16a), and 887444 (16b) contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
7c. Green crystals (needles), 0.77 × 0.04 × 0.03 mm3, monoclinic,
P21/n, Z = 8, a = 9.5624(13) Å, b = 27.160(4) Å, c = 23.802(3) Å, α =
90°, β = 99.976(3)°, γ = 90°, V = 6088.1(15) Å3, ρ = 1.441 g/cm3, θmax
= 22.55°, 37 093 reflections measured, 7971 unique (Rint = 0.1432),
6469 observed (I >2σ(I)), μ = 0.87 mm−1, Tmin = 0.55, Tmax = 0.97,
636 parameters refined, goodness of fit 1.35 for observed reflections,
final residual values R1(F) = 0.147, wR(F2) = 0.255 for observed
reflections, residual electron density −1.59 to 1.45 e Å−3.
7e. Green crystals (polyhedron), 0.18 × 0.18 × 0.10 mm3,
monoclinic, P21/n, Z = 4, a = 10.0971(1) Å, b = 21.0977(2) Å, c =
11.9795(2) Å, α = 90°, β = 96.5740(10)°, γ = 90°, V = 2535.16(5) Å3,
ρ = 1.463 g/cm3, θmax = 27.49°, 25 082 reflections measured, 5794
unique (Rint = 0.0839), 4607 observed (I >2σ(I)), μ = 0.91 mm−1, 284
parameters refined, the “carbene H” H20 was refined isotropically,
goodness of fit 1.05 for observed reflections, final residual values R1(F)
= 0.035, wR(F2) = 0.079 for observed reflections, residual electron
density −0.57 to 0.60 e Å−3.
3b. Colorless crystals (polyhedron), 0.17 × 0.11 × 0.05 mm3,
triclinic, P1, Z = 2, a = 8.5358(2) Å, b = 13.0227(3) Å, c = 15.8524(4)
̅
Å, α = 101.698(1)°, β = 98.601(1)°, γ = 91.077(1)°, V = 1703.94(7)
Å3, ρ = 1.271 g/cm3, θmax = 20.83°, 9487 reflections measured, 3568
unique (Rint = 0.0683), 2286 observed (I >2σ(I)), μ = 0.41 mm−1, Tmin
= 0.93, Tmax = 0.98, 415 parameters refined, goodness of fit 1.03 for
observed reflections, final residual values R1(F) = 0.068, wR(F2) =
0.131 for observed reflections, residual electron density −0.35 to 0.47
e Å−3.
7f. Colorless crystals (polyhedron), 0.26 × 0.24 × 0.14 mm3,
orthorhombic, P212121, Z = 4, a = 10.9174(1) Å, b = 16.107 Å, c =
16.7379(1) Å, α = 90°, β = 90°, γ = 90°, V = 2943.38(3) Å3, ρ = 1.412
g/cm3, θmax = 27.49°, 29 950 reflections measured, 6745 unique (Rint
=
=
0.0475), 6272 observed (I >2σ(I)), μ = 1.00 mm−1, Tmin = 0.78, Tmax
0.87, 315 parameters refined, hydrogen atom H20 at C20 was refined
isotropically, Flack absolute structure parameter 0.03(2), goodness of
fit 1.10 for observed reflections, final residual values R1(F) = 0.027,
wR(F2) = 0.060 for observed reflections, residual electron density
−0.54 to 0.53 e Å−3.
4a. Colorless crystals (polyhedron), 0.21 × 0.18 × 0.17 mm3,
triclinic, P1, Z = 2, a = 8.8210(10) Å, b = 11.2465(13) Å, c =
̅
13.8864(16) Å, α = 79.030(2)°, β = 72.245(2)°, γ = 87.263(2)°, V =
1287.9(3) Å3, ρ = 0.983 g/cm3, T = 100(2) K, θmax = 28.31°, 13 037
reflections measured, 6243 unique (Rint = 0.0232), 5400 observed (I
>2σ(I)), μ = 0.25 mm−1, Tmin = 0.95, Tmax = 0.96, 294 parameters
refined, the “carbene H” H1 was refined isotropically, goodness of fit
1.11 for observed reflections, final residual values R1(F) = 0.066,
wR(F2) = 0.181 for observed reflections, residual electron density
−0.30 to 0.60 e Å−3.
8. Green crystals (polyhedron), 0.42 × 0.24 × 0.10 mm3,
orthorhombic, Pca21, Z = 4, a = 13.1234(2) Å, b = 15.9143(2) Å, c
= 12.1529(1) Å, α = 90°, β = 90°, γ = 90°, V = 2538.13(5) Å3, ρ =
1.388 g/cm3, θmax = 27.47°, 25 223 reflections measured, 5794 unique
(Rint = 0.0398), 5129 observed (I >2σ(I)), μ = 0.96 mm−1, Tmin = 0.69,
Tmax = 0.91, 247 parameters refined, Flack absolute structure
parameter 0.02(2), goodness of fit 1.05 for observed reflections, final
residual values R1(F) = 0.026, wR(F2) = 0.049 for observed
reflections, residual electron density −0.41 to 0.34 e Å−3.
5a. Colorless crystals (polyhedron), 0.38 × 0.2 × 0.2 mm3,
monoclinic, P21/c, Z = 4, a = 12.4480(1) Å, b = 14.2069(3) Å, c =
11.5696(2) Å, α = 90°, β = 116.6650(10)°, γ = 90°, V = 1828.45(5)
Å3, ρ = 1.026 g/cm3, θmax = 25.35°, 15 701 reflections measured, 3332
unique (Rint = 0.0621), 2334 observed (I >2σ(I)), μ = 0.14 mm−1, 189
parameters refined, the hydrogen atoms H3 and H4 at the NHC ring
were refined isotropically, goodness of fit 1.02 for observed reflections,
final residual values R1(F) = 0.042, wR(F2) = 0.082 for observed
reflections, residual electron density −0.23 to 0.16 e Å−3.
9b. Violet crystals (plates), 0.23 × 0.15 × 0.01 mm3, monoclinic,
P21/c, Z = 4, a = 13.3716(8) Å, b = 14.0724(9) Å, c = 21.8737(14) Å,
α = 90°, β = 99.899(2)°, γ = 90°, V = 4054.7(4) Å3, ρ = 1.452 g/cm3,
θmax = 28.36°, 41 839 reflections measured, 10 107 unique (Rint
=
=
0.0892), 8446 observed (I >2σ(I)), μ = 0.89 mm−1, Tmin = 0.82, Tmax
0.994 33 parameters refined, goodness of fit 1.36 for observed
44
dx.doi.org/10.1021/om300487r | Organometallics 2013, 32, 29−46

Organometallics
Article
reflections, final residual values R1(F) = 0.102, wR(F2) = 0.150 for
observed reflections, residual electron density −1.59 to 0.96 e Å−3.
12. Orange crystals (polyhedron), 0.22 × 0.12 × 0.08 mm3,
monoclinic, P21/n, Z = 4, a = 18.1448(6) Å, b = 9.1268(3) Å, c =
19.6120(6) Å, α = 90°, β = 93.8720(10)°, γ = 90°, V = 3240.41(18)
Å3, ρ = 1.418 g/cm3, θmax = 27.49°, 32 713 reflections measured, 7426
unique (Rint = 0.1334), 5517 observed (I >2σ(I)), μ = 0.73 mm−1, Tmin
= 0.86, Tmax = 0.943 71 parameters refined, goodness of fit 1.13 for
observed reflections, final residual values R1(F) = 0.052, wR(F2) =
0.105 for observed reflections, residual electron density −0.85 to 0.69
e Å−3.
DEDICATION
■
Dedicated to Prof. Roald Hoffmann on the occasion of his 75th
birthday.
REFERENCES
■
(1) For recent reviews, see: (a) Vougioukalakis, G. C.; Grubbs, R. H.
Chem. Rev. 2010, 110, 1746. (b) Lozano-Vila, A. M.; Monsaert, S.;
Bajek, A.; Verpoort, F. Chem. Rev. 2010, 110, 4865. (c) Samojłowicz,
C.; Bieniek, M.; Grela, K. Chem. Rev. 2009, 109, 3708. (d) Die-
sendruck, C. E.; Tzur, E.; Lemcoff, N. G. Eur. J. Inorg. Chem. 2009,
4185.
(2) For hydroxyalkyl-NHC-coordinated ruthenium alkylidene
complexes, see: (a) Pruhs, S.; Lehmann, C. W.; Furstner, A.
Organometallics 2004, 23, 280.
13. Black crystals (polyhedron), 0.28 × 0.23 × 0.17 mm3,
monoclinic, P21/n, Z = 4, a = 12.6218(14) Å, b = 16.0062(17) Å, c
= 16.0036(17) Å, α = 90°, β = 99.837(2)°, γ = 90°, V = 3185.6(6) Å3,
ρ = 1.450 g/cm3, T = 100(2) K, θmax = 28.33°, 33 225 reflections
measured, 7905 unique (Rint = 0.0261), 7151 observed (I >2σ(I)), μ =
0.90 mm−1, Tmin = 0.79, Tmax = 0.86, 400 parameters refined, goodness
of fit 1.08 for observed reflections, final residual values R1(F) = 0.033,
wR(F2) = 0.076 for observed reflections, residual electron density
−0.71 to 1.71 e Å−3.
̈
̈
For aryloxy-NHC-coordinated
ruthenium alkylidene complexes, see: (b) Occhipinti, G.; Bjørsvik,
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5527.
(d) C
Bruneau, C.; Dixneuf, P. H. New J. Chem. 2001, 25, 519. (e) C
For arene-NHC-coordinated allenylidene complexes, see:
triclinic, P1, Z = 1, a = 9.7387(9) Å, b = 11.1342(10) Å, c =
̅
̈
̧
etinkaya, B.; Demir, S.; Ozdemir, I.; Toupet, L.; Sem
́
eril, D.;
etinkaya,
13.2867(16) Å, α = 65.277(2)°, β = 77.942(2)°, γ = 85.113(2)°, V =
1279.8(2) Å3, ρ = 1.599 g/cm3, T = 200(2) K, θmax = 28.3°, 13 678
reflections measured, 6314 unique (Rint = 0.0521), 5470 observed (I
>2σ(I)), μ = 2.07 mm−1, Tmin = 0.72, Tmax = 0.76, 283 parameters
refined, goodness of fit 1.03 for observed reflections, final residual
values R1(F) = 0.027, wR(F2) = 0.072 for observed reflections,
residual electron density −1.20 to 1.00 e Å−3.
̧
̈
B.; Demir, S.; Ozdemir, I.; Toupet, L.; Sem
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24.619(5) Å, α = 90°, β = 90°, γ = 90°, V = 9694(4) Å3, ρ = 1.60 g/
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unique (Rint = 0.0577), 6847 observed (I >2σ(I)), μ = 2.184 mm−1,
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ASSOCIATED CONTENT
■
S
* Supporting Information
This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: ph@oci.uni-heidelberg.de.
Present Addresses
§Sandoz AG, Frankfurt, Germany.
⊥Freudenberg, Weinheim, Germany.
∥Faculdade de Cien
̂
cias Integradas do Pontal, Brazil.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
H.S. and P.H. work at CaRLa (Catalysis Research Laboratory)
of Heidelberg University, being cofinanced by the University of
Heidelberg, the State of Baden-Wuerttemberg, and BASF SE.
We gratefully acknowledge generous support from these
institutions. Dr. Rommy Haufe has contributed valuable advice
for NHCP ligand synthesis, worked out in the context of her
studies of NHCP complexes of the nickel triad.33 A.L.B. thanks
DAAD, FAPESP, CNPq, CAPES, and FAPEMIG for financial
support and fellowships.
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