Hydrogenation and silylation of a double-cyclometalated ruthenium complex: Structures and dynamic behavior of hydrido and hydridosilicate ruthenium complexes

Article abstract of DOI:10.1021/om400574a

A double-cyclometalated ruthenium complex containing a chiral tripodal phospholane has been prepared by reaction with [Ru(η⁴-COD) (η³-methylallyl)₂] via elimination of isobutene. The ruthenium-carbon bonds of this compound were reversibly cleaved by H ₂, resulting in an equilibrium between a tri- and a tetrahydride (4 and 5). T₁ relaxation time measurements revealed the nonclassical nature of the fluctuating hydrides. Release of the gas led to complete re-formation of the cyclometalated compound. Reaction of 3 with D₂ afforded D₁₀-5, in which six ortho-phenyl protons and four hydrides were replaced by deuterium. Furthermore, diphenylsilane was found to readily insert into one Ru-C bond to form 6, containing a κ³- dihydridosilicate fragment. On the basis of deuterium labeling experiments, the fast exchange between the two hydrides was shown to include a reductive elimination/oxidative addition step involving the remaining metalated phenyl group. Again, pressurization of 6 with H₂ resulted in reversible cleavage of the remaining Ru-C bond, yielding the corresponding trihydride 7.

Full text of DOI:10.1021/om400574a

Article
pubs.acs.org/Organometallics
Hydrogenation and Silylation of a Double-Cyclometalated
Ruthenium Complex: Structures and Dynamic Behavior of Hydrido
and Hydridosilicate Ruthenium Complexes
Peter Scherl, Hubert Wadepohl, and Lutz H. Gade*
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: A double-cyclometalated ruthenium complex
containing a chiral tripodal phospholane has been prepared by
reaction with [Ru(η4-COD)(η3-methylallyl)2] via elimination
of isobutene. The ruthenium−carbon bonds of this compound
were reversibly cleaved by H2, resulting in an equilibrium
between a tri- and a tetrahydride (4 and 5). T1 relaxation time
measurements revealed the nonclassical nature of the
fluctuating hydrides. Release of the gas led to complete re-formation of the cyclometalated compound. Reaction of 3 with D2
afforded D10-5, in which six ortho-phenyl protons and four hydrides were replaced by deuterium. Furthermore, diphenylsilane
was found to readily insert into one Ru−C bond to form 6, containing a κ3-dihydridosilicate fragment. On the basis of deuterium
labeling experiments, the fast exchange between the two hydrides was shown to include a reductive elimination/oxidative
addition step involving the remaining metalated phenyl group. Again, pressurization of 6 with H2 resulted in reversible cleavage
of the remaining Ru−C bond, yielding the corresponding trihydride 7.
INTRODUCTION
RESULTS AND DISCUSSION
■
■
Synthesis of the Double-Cyclometalated Ruthenium
Intermediates containing ruthenium−carbon bonds play a vital
role in a variety of catalytic transformations.1 Of particular
interest in this context is the activation and functionalization of
C−H bonds,2 and cyclometalations, in particular, are among
the most convenient methods to establish Ru−C sigma-bonds.3
Most often, coordination of the heteroatom of a potentially
multidentate ligand facilitates the metalation of an attached
alkyl or aryl group to form a ruthenacycle.4 A large number of
monocyclometalated ruthenium complexes are known, whereas
there are far fewer examples of mononuclear bis-cyclo-
ruthenated structures.5
Complex. The 31P{1H} NMR spectrum recorded after heating
a solution of N(CH2DPP)3 (1) and [Ru(η4-COD)(η3-
methylallyl)2] to 80 °C overnight displayed the presence of
three species. A singlet at δ = 0.0 ppm corresponded to
unreacted ligand, and two singlet resonances (δ = −1.9 and
51.6 ppm, intensities of 1:2) indicated the formation of a
compound containing the ligand in its didentate binding mode
(complex 2, Scheme 1). An analogous complex was previously
isolated as an intermediate in the formation of the ruthenium
tmm complex of N(CH2DMP)3 (DMP = 2,5-dimethylphos-
pholane).7
Such compounds show a rich chemistry, as the ruthenium−
carbon bond can be transformed in reactions with various
substrates such as acetylenes, olefins, carbon monoxide, or
hydrogen.3b
Further heating of the reaction mixture to 125 °C for 2 d
resulted in complete conversion to the third species, which was
represented by three doublets of doublets (δ = 29.7, 60.1, and
107.6 ppm) in the 31P{1H} NMR spectrum with relative
intensities of 1:1:1. The formation of isobutene was observed
We recently developed the synthesis of tridentate phospho-
lanomethylamine ligands and investigated their coordination
chemistry and catalytic activity for rhodium and gold.6
Moreover, two tripodal ligands were subsequently reported to
form ruthenium η4-trimethylenemethane complexes.7 However,
as will be shown in this work, the chiral trisphospholane ligand
N(CH2DPP)3 (1, DPP = 2,5-diphenylphospholane) proved to
be “noninnocent” and exhibited a different reactivity.
Here we report the formation of a pentacoordinate
ruthenium complex of 1 containing two cyclometalated phenyl
groups along with its reactions with dihydrogen and
diphenylsilane.
1
by in situ H NMR spectroscopy. In addition, the spectrum
displayed aromatic proton resonances at unusual chemical shifts
of δ = 5.23 (2 H), 8.65 (1 H), and 8.90 ppm (1 H), indicating
that two phenyl rings had been transformed. Moreover the
presence of two quaternary 13C{1H} NMR resonances at low
field (δ = 178.7 and 185.3 ppm) exhibiting multiplet carbon−
phosphorus couplings was indicative of the formation of Ru−C
bonds. These observations led to the suggestion of structure 3
Received: June 18, 2013
Published: July 22, 2013
© 2013 American Chemical Society
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Scheme 1. Formation of Double-Cyclometalated Ruthenium Complex 3 via Intermediate 2
(Scheme 1), in which two of the phospholane-bound phenyl
rings were ortho-metalated.
Scheme 2. Complex 3 Reacted with H2 to Reversibly Form
Trishydride 4 and Tetrahydride 5
This was in accordance with the full set of 1D and 2D NMR
data as well as mass spectrometry (HR-FAB) and elemental
analysis. Compound 3 was isolated as a yellow powder in 91%
yield after workup.
Reactivity of 3 with H2. It is known that the Ru−C bond
in cyclometalated complexes can be cleaved by hydrogen to
form ruthenium hydride species.4c,d,8 Consequently a solution
of 3 was pressurized with H2 (2 bar) in a high-pressure NMR
tube. The yellow color of the solution faded immediately upon
shaking, indicating a very rapid reaction. The 31P{1H} NMR
spectrum exhibited the formation of two new species
represented by a singlet (79%) at δ = 46.4 ppm and a set of
2
three doublets of doublets (21%) at δ = 40.7 (1 P, J(P,P) =
2
28.8 Hz), 42.2 (1 P, J(P,P) = 28.3 Hz), and 78.6 ppm (1 P,
2J(P,P) = 29.2 Hz). The equilibrium between the two
compounds was shifted toward the main component by
increasing the H2 pressure. At 10 bar, a ratio of 95:5 in favor
of the singlet species was observed. The pressure dependence
of the relative amounts in solution is presented in Figure 1.
resonances similar to the one found for 3 were observed,
confirming that both Ru−C bonds were cleaved.
As mentioned above, the minor species present in solution
was represented by three doublets of doublets in the 31P NMR
1
spectrum. A H NMR signal at δ = −4.82 ppm (3 H) was
attributed to this complex. One single quaternary multiplet at δ
= 175.9 ppm in the 13C{1H} NMR spectrum characteristic for a
ruthenium-coordinated aromatic carbon atom was assigned to
this compound.
These findings are consistent with the structure 4 shown in
Scheme 2. Cleavage of one Ru−C bond followed by η2-
coordination of a second equivalent of dihydrogen led to the
formation of the trishydride.
Remarkably, release of the hydrogen pressure and purging
with argon led to complete recovery of the initial complex 3.
Such reversibility of a Ru−C bond cleavage by hydrogen or
deuterium has been observed before4d,8,9 and is most likely due
to both entropic effects and steric properties of the ligand. The
phospholane-bound phenyl groups are preorientated toward
the metal center, facilitating metalation.
Figure 1. Hydrogen pressure dependence of the molar fractions of
complexes 4 and 5 in solution, determined by 31P{1H} NMR. Broad
signals of residual 3 were observed at p(H2) = 1 bar. These were not
accounted for in the determination of the molar fractions of 4 and 5.
A quartet at δ = −7.34 ppm (4 H) in the 1H NMR spectrum
was attributed to the major 31P NMR resonance. This suggests
the formation of the tetrahydride 5, as shown in Scheme 2, in
which the four hydrides rapidly interchange, resulting in a
pseudo-C3-symmetric structure. The multiplicity of the hydride
resonance (2J(H,P) = 10 Hz) which is completely resolved
above −30 °C was explained by the coupling to the three
chemically equivalent phosphorus donors. Accordingly, the
The NMR spin−lattice relaxation time (T1) has proved to be
an important criterion for the distinction between classical and
nonclassical hydrides.10 The presence of η2-H2 in fluxional
min
ruthenium polyhydrides usually gives rise to a short T1 of
<100 ms.11 The temperature dependence of T1 of complexes 4
and 5 was determined by inversion−recovery measurements at
1
min
quartet simplified to a singlet in the H{31P} NMR spectrum.
400 MHz. Trishydride complex 4 exhibited a T1 of 15 ms,
1
The H and 13C{1H} NMR resonances are in accordance
strongly suggesting the presence of a fluxional nonclassical
structure. In the case of 5, a minimum of the relaxation time
with the proposed structure. No extreme low-field carbon
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was not reached even at temperatures as low as −90 °C.
interactions.17 There are only a few other examples of
structures containing this H2Si motif.18 A common feature of
these compounds is the presence of phosphorus coligands.
Given the structural similarity of Tilley’s tridentate
phosphine ligand19 with our trisphospholane 1 and the
observation that the Ru−C bonds in complex 3 are easily
cleaved by dihydrogen, we investigated its reactivity toward
hydrosilanes.
min
However, given that the actual T1 will be shorter than the
lowest observed T1 value of 50 ms, one can confidently assume
a nonclassical nature of the hydrido ligands.
The spectral data and relaxation time of of 5 are comparable
to the well-known analogue [Ru(H2)H2(PPh3)3].9,10,11e,12
Further derivatives of this system including various coligands
have been reported.10c,11c,13
Deuteration Experiment. Due to the reversible nature of
the formation of the hydrido complexes 4 and 5, these species
cannot be isolated and characterized by any technique other
than NMR spectroscopy. Deuterium labeling has proved to be a
valuable tool for structural and mechanistic investigations
related to such species.14 In order to provide additional
evidence for the assumed structures of complex 3 and
tetrahydride 5, a solution of 3 was pressurized with 10 bar of
D2.
Indeed, reaction of 3 with diphenylsilane proceeded
smoothly at room temperature. Insertion into one of the two
Ru−C bonds affords the ruthenium silyl dihydrido complex 6
(Scheme 4). The 31P{1H} NMR spectrum exhibited three
Scheme 4. Insertion of Diphenylsilane into One Ru−C Bond
to Form 6
Compared to the spectra of nondeuterated tetrahydride
complex 5, the NMR data of d10-5 (Scheme 3) lack one very
Scheme 3. Reaction of Cyclometalated Complex 3 with D2 to
Form Deuterated Complexes d10-5 and d4-3
doublets of doublets, owing to the P−P coupling of the three
inequivalent phosphorus nuclei. Compound 6 was isolated as
an off-white powder in a yield of 72% and fully characterized by
NMR spectroscopy, mass spectrometry, and elemental analysis.
Its molecular structure determined by X-ray diffraction is
depicted in Figure 2. The ruthenium center is coordinated in a
1
broad H resonance at δ = 8.11 ppm and one broad 13C{1H}
signal at δ = 129.9 ppm. This was explained by the H/D
exchange of the aromatic ortho-protons of three phenyl groups
oriented toward the ruthenium. This was backed up by the
observation of a hydridic 1H resonance of low intensity despite
the use of pure D2. As a result of the fast equilibrium between 5,
starting complex 3, and trihydride 4, four aromatic protons are
distributed statistically within the available positions in the
complex and the deuterium gas. The 2H NMR spectrum of d10-
5 provided additional evidence, showing a broad aromatic
resonance at 7.37 ppm (6 ortho-D) and a deuteride signal at
−7.35 ppm (4 D). Release of D2 afforded the deuterated
compound d4-3 (Scheme 3). The disappearance of three
aromatic proton resonances respectively clearly showed that H/
D exchange occurred in the ortho positions of all three phenyl
groups that are oriented toward the metal. Again, this was
expected, as compounds d4-3 and d10-5 are in equilibrium
under a hydrogen atmosphere. The three phenyl groups that,
due to the chirality, are located on the opposite side of the
phospholane rings with respect to the ruthenium, thus pointing
away from the metal center, do not undergo H/D exchange.
Reactivity with Silanes. Hydrosilanes react with most
transition metals to form stable metal silyl complexes.15 The
scope of bonding modes ranges from nonclassical σ-complexes
to classical structures containing two-center-two-electron M−Si
bonds. A wide variety of isolated intermediates exist in which
the Si−H bond cleavage is “arrested” along the oxidative
addition pathway.16 Tilley and co-workers have recently
published η3-silane complexes [(PhBPPh3)RuH(η3-H2SiRR′)]
(RR′ = PhMe, Ph2) containing two M−H−Si σ-bonding
Figure 2. Thermal ellipsoids (50% probability level; nonhydridic
hydrogen atoms omitted for clarity) of the molecular structure of
complex 6. Principal bond lengths [Å] and angles [deg]: Ru−P(1)
2.3076(5), Ru−P(2) 2.3586(4), Ru−P(3) 2.2952(5), Ru−C(47)
2.1324(17), Ru−HA 1.58(3), Ru−HB 1.60(3), Ru−Si 2.3850(5),
Si−HA 1.84(3), Si−HB 1.87(3), P(1)−Ru−P(2) 89.53(2), P(3)−
Ru−P(1) 87.90(2), P(3)−Ru−P(2) 91.27(2), Si−Ru−HA 50.3(10),
Si−Ru−HB 51.5(9).
slightly distorted octahedral fashion, the two agostic hydrogen
atoms being cis to the metalated carbon atom C(47). The η3-
H2Si moiety is symmetrically bound to the metal, the Ru−H−
Si angles being very similar. The Ru−H distances are in accord
with those found previously in ruthenium complexes containing
a hypervalent [H2SiPh3]− fragment (1.47(4)−1.568(16) Å).18e,j
Both the Si−H and Ru−Si bond lengths are in the range of the
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literature data (Si−H: 1.72(3)−2.016(14); Ru−Si 2.3816(5)−
2.4006(5) Å). The five-membered ring formed by coordination
of the cyclometalated phenyl group (Ru−P(3)−C(39)−
C(46)−C(47)) is virtually planar (RMSD = 0.0150 Å).
however coalescence was not observed even at −90 °C. Given a
min
T1 of 38 ms at 0 °C (400 MHz), the hydrides were again
considered to be of fluctuating nonclassical nature. This is in
accordance with the T1 value of 22 ms (250 MHz) found for
[(η2-H2)(PCy3)2RuH(η3-H2SiPh3)].18c−f
1
In the H NMR spectrum of 6, only one broad hydridic
As in the case of 5, release of the hydrogen and purging with
argon led to complete backreaction to the initial dihydrido
complex 6.
Mechanism of Hydride Exchange in 6. A mechanism
rendering the two hydrides in complex 6 equivalent was
considered to consist in a fast reductive elimination−oxidative
addition process involving the metalated phenyl group.
Consequently, H/D scrambling was expected to occur when
employing d2-diphenylsilane in the synthesis of d2-6 (Scheme
6). Indeed, the low-field hydride signal also detected for 6
resonance was observed at δ = −6.08 ppm, equivalent to two
protons. Given the C1 symmetry of the complex, a fast
exchange must account for the equivalence of the two bridging
hydrides. As the silicon moiety is covalently attached to one
phospholane ring via a phenyl group, exchange between the
two hydride atoms by simple rotation of the silyl fragment18g is
min
not possible (see discussion below). A T1 of 424 ms was
found at 0 °C (400 MHz). This is well in the characteristic
range of classical hydride structures10d and in agreement with
the value of 436 ms (400 MHz) found for [TpRu(PPh3)-
(η3H2SiR3)].18g,j 1H NMR spectra acquired at various temper-
atures showed coalescence of the hydride signal at −20 °C
(ΔG⧧ = 46 kJ/mol). Two doublets of doublets are observed at
lower temperature, and one doublet of doublets represented
the high-temperature limit. The multiplicities are due to the
coupling to two nonequivalent phosphorus nuclei. Accordingly,
the 1H{31P} NMR spectra displayed singlet hydride signals with
1J(Si,H) values of 47 Hz.
Scheme 6. Deuterium Labeling Experiment with d2-
Diphenylsilane
Reactivity of 6 with Hydrogen. It was expected that in
analogy with the reaction of 3 with dihydrogen the remaining
Ru−C bond of 6 might be easily cleaved upon pressurization.
Indeed, the in situ 31P{1H} NMR spectrum of a solution of 3
under 2 bar of H2 revealed a mixture of starting complex (22%)
and a new species (78%). The relative amount of the latter
went up to 96% upon increasing the pressure to 10 bar (Figure
1
appeared in the H NMR spectrum. This proved the proposed
exchange of the deuterides and the aromatic protons. A relative
intensity of this resonance of 2/3 would be indicative of an H/
D exchange involving one proton in the ortho position of the
metalated phenyl ring. The observed intensity of around 6/5
led to the conclusion that also the previously noncoordinating
phenyl group pointing toward the metal takes part in the
process.
1
3). H, 13C{1H}, and 31P{1H} NMR spectra recorded under
these conditions agreed with structure 7 shown in Scheme 5.
In order to further corroborate this hypothesis, a solution of
d2-6 was pressurized with D2. Subsequent gas release led to the
formation of a species that was identified as d5-6 by NMR
spectroscopy. Two 13C{1H} resonances corresponding to the
nonequivalent aromatic ortho-carbons that underwent H/D
exchange converted from doublets in nondeuterated 6 (124.9
and 131.7 ppm) to broad quaternary signals in d5-6 (124.6 and
131.4 ppm). Given these findings, participation of the
phospholane-bound phenyl groups in the fast exchange
between the hydride ligands in 6 is likely.
Addition of an excess of d2-diphenylsilane to 3 led to the
1
detection of HDSiPh2 and H2SiPh2 in the H NMR spectrum.
Obviously, exchange occurs between hydridic protons in 6 on
the one hand and deuterides in noncoordinated silane on the
other hand. No reaction was observed upon heating solutions
of 3 and tris(isopropyl)silane or triphenylsilane at elevated
temperatures of 80 or 95 °C, respectively.
Figure 3. Hydrogen pressure dependence of the molar fraction of
complex 7 in solution, determined by 31P{1H} NMR.
Scheme 5. Reaction of the Dihydridosilicato Complex 6 with
H2 to Reversibly Form the Trihydride 7
CONCLUSION AND OUTLOOK
■
In summary, we have provided a rare example of a ruthenium
complex including a double-cyclometalated ligand. Moreover a
hydridosilicate complex comprising a κ3-H2Si fragment was
synthesized, again exhibiting reversible incorporation of
dihydrogen. Ruthenium hydride species are involved in a
variety of catalytic carbon−carbon bond formations,1a,b and
investigations into the activity of these compounds with
particular focus on asymmetric transformations are currently
under way. The reversibility of the formation of 5 might be
beneficial for future applications of this compound as a catalyst
A series of low-temperature 1H NMR spectra of 7 exhibited a
broadening of the hydridic resonance at δ = −7.48 ppm;
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70.17; H, 6.00; N, 1.60. Found: C, 69.93; H, 6.48; N, 1.64. HRMS
(ESI): m/z calcd for C51H53NP3Ru ([M + H]) 874.2434, found
874.2485.
in stereoselective reactions. Many catalyst precursors need to be
activated by irreversible elimination of a leaving group such as
COD. As a consequence, after complete conversion of the
substrate, these catalysts may decompose due to the absence of
coordinating species. In principle, the cyclometalated ligand
itself might act as an internal protecting group, which might
prove useful in terms of catalyst recovery.
Synthesis of [(N(CH2DPP)3-κ3P)RuH4] (5). A solution of 5 (6.2
mg, 0.0071 mmol) in C6D6 (0.45 mL) was pressurized with H2 (10
bar) in a pressure NMR tube. The product forms within seconds upon
shaking. The reaction is reversible, and the product is in equilibrium
with complex 4 (5% based on 31P{1H} NMR). Purging of the NMR
tube with argon leads to the back-formation of the starting complex.
As the product is stable only under a hydrogen atmosphere, it cannot
be isolated. 1H NMR (C6D6, 600.13 MHz, 295 K): δ −7.34 (q,
2J(H,P) = 9.8 Hz, 4 H, hydride), 1.37−1.48 (m, 6 H, CH, CH2), 1.99
(m, 3 H, CH2), 2.46−2.55 (m, 6 H, NCH2P, CH2), 2.65 (m, 3 H,
CH2), 3.02 (d, 2J(H,H) = 15.3 Hz, 3 H, NCH2P), 3.45 (m, 3 H, CH),
6.79 (t, 3J(H,H) = 7.3 Hz, 3 H, HAr), 6.82 (d, 3J(H,H) = 7.7 Hz, 6 H,
HAr), 7.00 (b, 6 H, HAr), 7.06 (t, 3J(H,H) = 7.3 Hz, 3 H, HAr), 7.15 (m,
6 H, HAr), 8.11 ppm (b, 6 H, HAr). 13C{1H} NMR (C6D6, 150.92 Hz,
295 K): δ 26.7 (m, CH2), 30.0 (m, CH2), 42.8 (m, CH), 46.6 (m,
NCH2P), 52.1 (m, CH), 125.9 (s, CHAr), 126.7 (s, CHAr), 128.0 (s,
CHAr), 128.9 (s, CHAr), 129.1 (b, CHAr), 129.9 (b, CHAr), 140.1 (s,
CAr), 143.4 ppm (m, CAr). 31P{1H} NMR (C6D6, 242.92 Hz, 295 K): δ
46.4 ppm (s).
EXPERIMENTAL SECTION
■
General Experimental Methods and Procedures. All reactions
were carried out in air- and moisture-free conditions. Argon was used
as inert gas after drying over Granusic phosphorus pentoxide
granulate. Standard Schlenk and glovebox techniques were employed
to handle the substances. Solvents were dried according to literature
known procedures,20 degassed by several successive freeze−pump−
thaw cycles, and stored under argon in Teflon-capped glass ampules.
Tris((2S,5S)-2,5-diphenylphospholanomethyl)amine (1) was prepared
according to a literature method.6a All other chemicals were received
from commercial suppliers and used without further purification.
Nuclear magnetic resonance spectra were recorded on Bruker
Avance II (400 MHz) and Bruker Avance III (600 MHz) instruments.
Chemical shifts are given in parts per million (ppm) and are
referenced to the residual proton solvent signals (1H: C6D6 = 7.16
ppm) or carbon resonances (13C: C6D6 = 128.06 ppm).21 H3PO4 (31P
NMR) and SiMe4 (29Si NMR) were used as external standards. The
appearance of the signals was described using the following
abbreviations: s (singlet), d (doublet), dd (doublet of doublets), t
(triplet), q (quartet), m (multiplet), b (broad signal). T1 relaxation
data were recorded by inversion−recovery experiments at 400 MHz,
and relaxation times were calculated using the standard nonlinear
three-parameter fitting routine provided by the spectrometer
software.22 Mass spectra were acquired on Bruker ApexQe hybrid
9.4 T FT-ICR (HR-ESI) and JEOL JMS-700 magnetic sector (HR-
FAB) spectrometers at the mass spectrometry facility of the Institute
of Organic Chemistry of the University of Heidelberg. Elemental
analyses were carried out in the Microanalysis Laboratory of the
Heidelberg Chemistry Department.
Synthesis of [(N(CH2DPP)3SiPh2H2-κ3P,κ1C,κ2SiH2)Ru] (6). To a
solution of [Ru(C3DPP)] (50.1 mg, 0.0574 mmol) in THF (2 mL)
was added diphenylsilane (11 μL, 0.0593 mmol). After stirring for 20
min at room temperature, the solvent was removed in vacuo. Addition
of diethyl ether to the oily residue produced a solid, which was washed
with diethyl ether and dried in vacuo (43.9 mg, 0.0415 mmol, 72%).
1H NMR (C6D6, 600.13 MHz, 295 K): δ −6.08 (b, 2 H, hydrides),
1.15−1.30 (m, 2 H, 2 × CH2), 1.30−1.50 (m, 5 H, 4 × CH2), 1.52−
1.62 (m, 2 H, CH2, NCH2P), 1.75 (d, 2J(H,H) = 15.2 Hz, 1 H,
NCH2P), 1.78−1.85 (m, 2 H, CH2, NCH2P), 1.90 (m, 1 H, CH2),
2.00 (m, 1 H, CH2), 2.21 (m, 1 H, CH2), 2.32 (m, 1 H, CH2), 2.50 (m,
1
1 H, CH), 2.62 (d, J(H,H) = 5.5 Hz, 1 H, CH), 3.15−3.24 (m, 2 H,
1
CH, NCH2P), 3.35 (d, J(H,H) = 10.8 Hz, 1 H, CH), 3.42 (m, 1 H,
CH), 3.65 (d, 2J(H,H) = 15.2 Hz, 1 H, NCH2P), 3.72 (m, 1 H, CH),
3.78 (d, 2J(H,H) = 15.5 Hz, 1 H, NCH2P), 6.77−7.76 ppm (m, 38 H,
2
HAr). 13C{1H} NMR (C6D6, 150.92 Hz, 295 K): δ 32.4 (d, J(C,P) =
Synthesis of [(N(CH2DPP)3-κ3P,κ2C)Ru] (3). A solution of ligand
N(CH2DPP)3 (1) (482 mg, 0.623 mmol) and [(COD)Ru-
(methylallyl)2] (209 mg, 0.654 mmol) in toluene was heated to 125
°C for 2 days in an ACE pressure tube, whereupon a yellow precipitate
formed. Removal of the solvent in vacuo and addition of pentane (6
mL) to the oily residue produced a yellow solid, which was washed
with pentane (3 × 5 mL) and dried in vacuo (496 mg, 0.568 mmol,
91%). 1H NMR (C6D6, 600.13 MHz, 295 K): δ 1.18−1.54 (m, 5 H, 4
× CH2, CH), 1.55−1.77 (m, 4 H, 3 × CH2, NCH2P), 1.90 (m, 1 H,
CH2), 1.96−2.07 (m, 3 H, 2 × CH2, NCH2P), 2.12 (m, 1 H, CH2),
9.2 Hz, CH2), 34.6 (s, CH2), 37.0 (s, CH2), 37.1 (m, CH2), 38.7 (s,
CH2), 39.0 (s, CH2), 44.2 (m, CH), 48.6 (m, CH), 49.0 (m, NCH2P),
50.4 (m, CH), 50.7 (m, NCH2P), 52.1 (m, CH), 54.2−54.4 (m, CH,
NCH2P), 54.7 (m, CH), 122.2 (s, CHAr), 124.9 (d, J(C,P) = 17.9 Hz,
CHAr), 125.1 (s, CHAr), 125.3 (m, CHAr), 126.4 (s, CHAr), 126.7 (s,
CHAr), 126.8 (s, CHAr), 127.0−127.1 (m, 2 × CHAr), 127.5 (s, CHAr),
127.9 (m, CHAr), 128.1−128.3 (m, 4 × CHAr), 128.7 (s, CHAr), 129.1
(s, CHAr), 129.3 (m, CHAr), 130.7 (b, 2 × CHAr), 131.1 (d, J(C,P) =
9.3 Hz, CHAr), 131.7 (d, J(C,P) = 9.6 Hz, CHAr), 135.4 (s, CHAr),
137.1 (b, CHAr), 137.5 (m, CHAr), 141.7 (d, J(C,P) = 1.8 Hz, CAr),
141.9 (d, J(C,P) = 6.7 Hz, CAr), 142.6 (d, J(C,P) = 4.6 Hz, CAr), 142.8
(d, J(C,P) = 5.1 Hz, CAr), 143.8 (m, CAr), 147.1−147.3 (m, 2 × CAr),
147.8 (m, CHAr), 148.1 (d, J(C,P) = 6.9 Hz, CAr), 156.0 (m, CAr),
170.2 ppm (m, CAr). 31P{1H} NMR (C6D6, 242.92 Hz, 295 K): δ 20.2
2
2.26 (d, J(H,H) = 15.4 Hz, 1 H, NCH2P), 2.37−5.52 (m, 2 H, CH2,
2
NCH2P), 2.88 (d, J(H,H) = 15.4 Hz, 1 H, NCH2P), 2.91 (m, 1 H,
CH), 3.19 (dd, 3J(H,H) = 10.5 Hz, 3J(H,H) = 6.6 Hz, 1 H, CH), 3.24
2
(m, 1 H, CH), 3.29 (m, 1 H, CH), 3.40 (d, J(H,H) = 15.4 Hz, 1 H,
NCH2P), 3.65 (m, 1 H, CH), 5.23 (bs, 2 H, o-HAr), 6.54−7.60 (m, 24
H, HAr), 8.65 (m, 1 H, HAr), 8.90 ppm (m, 1 H, HAr). 13C{1H} NMR
(C6D6, 150.92 Hz, 295 K): δ 34.6 (d, 2J(C,P) = 4.0 Hz, CH2), 34.8 (d,
2J(C,P) = 6.6 Hz, CH2), 35.4 (s, CH2), 36.5 (s, CH2), 36.5 (s, CH2),
(dd, J(P,P) = 37.5 Hz, J(P,P) = 29.3 Hz, 1 P), 32.0 (dd, J(P,P) =
2
2
2
2
2
37.4 Hz, J(P,P) = 33.2 Hz, 1 P), 54.4 ppm (dd, J(P,P) = 32.9 Hz,
2J(P,P) = 29.5 Hz, 1 P). 19Si NMR (C6D6, 79.44 Hz, 296 K, resonance
detected by 1H, 19Si-HMBC): 4.8 ppm. Anal. Calcd for
C63H64NP3RuSi: C, 71.57; H, 6.10; N, 1.32. Found: C, 71.29; H,
5.85; N, 1.33. HRMS (ESI): m/z calcd for C63H62NP3102RuSi ([M −
H2]) 1055.2908, found 1055.2919.
2
38.2 (d, J(C,P) = 3.1 Hz, CH2), 43.4 (m, CH), 45.3 (m, CH), 46.1
(m, CH), 50.6 (m, NCH2P), 50.8 (m, NCH2P), 51.4 (m, NCH2P),
55.7 (m, CH), 57.5 (m, CH), 60.0 (m, CH), 121.9 (s, CHAr), 122.2 (b,
CHAr), 123.1 (s, CHAr), 123.9 (m, CHAr), 124.5 (m, CHAr), 125.2 (m,
CHAr), 125.8 (s, CHAr), 126.2 (s, CHAr), 126.4 (m, CHAr), 126.5 (s,
CHAr), 127.1 (s, CHAr), 128.2 (m, CHAr), 128.5 (s, CHAr), 128.6 (s,
CHAr), 129.0 (s, CHAr), 129.5 (m, CHAr), 130.5 (m, CHAr), 134.1 (s,
CHAr), 139.2 (m, CHAr), 140.3 (d, J(C,P) = 4.2 Hz, CAr), 140.6 (m,
CHAr), 141.8 (d, J(C,P) = 5.0 Hz, CAr), 143.4 (d, J(C,P) = 7.1 Hz,
CAr), 152.1 (m, CAr), 152.3 (m, CAr), 153.9 (d, J(C,P) = 24.7 Hz, CAr),
178.7 (m, CAr), 185.3 ppm (m, CAr). 31P{1H} NMR (C6D6, 242.92 Hz,
Synthesis of [(N(CH2DPP)3SiPh2H2-κ3P,κ3SiH2)RuH] (7). A
solution of [Ru(C3DPPSiPh2)H2] (11.1 mg, 0.0105 mmol) in C6D6
(0.5 mL) was pressurized with H2 (10 bar) in a pressure NMR tube.
The product forms within seconds upon shaking. The reaction is
reversible, and the product is in equilibrium with the starting complex
(4% based on 31P{1H} NMR). Purging of the NMR tube with argon
leads to the back-formation of the starting complex. As the product is
1
stable only under a hydrogen atmosphere, it cannot be isolated. H
2
2
295 K): δ 29.7 (dd, J(P,P) = 29.3 Hz, J(P,P) = 19.3 Hz, 1 P), 60.1
NMR (C6D6, 600.13 MHz, 295 K): δ −7.48 (m, 3 H, hydrides), 0.98
(m, 1 H, CH2), 1.35−1.53 (m, 3 H, CH, 2 × CH2), 1.63 (m, 1 H,
CH), 1.81 (m, 1 H, CH2), 1.97 (m, 1 H, CH2), 2.02−2.38 (m, 7 H, 5
2
2
(dd, J(P,P) = 27.7 Hz, J(P,P) = 19.4 Hz, 1 P), 107.6 ppm (dd,
2J(P,P) = J(P,P) = 28.5 Hz, 1 P). Anal. Calcd for C51H52NP3Ru: C,
2
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dx.doi.org/10.1021/om400574a | Organometallics 2013, 32, 4409−4415

Organometallics
Article
× CH2, NCH2P, CH), 2.42−2.59 (m, 4 H, 2 × CH2, 2 × NCH2P),
(SFB 623, TP B6). We thank Prof. Markus Enders for expert
advice concerning the NMR T1 measurements.
2
2
2.73 (d, J(H,H) = 15.2 Hz, 1 H, NCH2P), 2.92 (d, J(H,H) = 15.0
2
Hz, 1 H, NCH2P), 3.04 (d, J(H,H) = 15.6 Hz, 1 H, NCH2P), 3.46
(m, 1 H, CH), 3.59 (m, 1 H, CH), 3.69 (m, 1 H, CH), 6.74−7.69 (m,
34 H, HAr), 7.95 (d, 3J(H,H) = 7.3 Hz, 1 H, HAr), 8.29 (d, 3J(H,H) =
7.4 Hz, 2 H, HAr), 8.52 ppm (m, 2 H, HAr). 13C{1H} NMR (C6D6,
150.92 Hz, 295 K): δ 26.6 (d, 2J(C,P) = 9.9 Hz, CH2), 29.2 (d, 2J(C,P)
= 8.6 Hz, CH2), 30.7 (d, 2J(C,P) = 17.7 Hz, CH2), 31.1 (d, 2J(C,P) =
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1
X-ray Crystal Structure Determinations. Crystal data of
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= 11.90299(5) Å, b = 19.06264(8) Å, c = 22.67018(10) Å, V =
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ASSOCIATED CONTENT
■
̈
S
* Supporting Information
Figures showing the temperature dependences of the spin−
lattice relaxation times (T1) for 4, 5, 6, and 7. Temperature-
1
dependent H NMR spectra for 6. CIF files giving crystallo-
graphic data for 6. This material is available free of charge via
the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail: lutz.gade@uni-hd.de. Fax: (+49) 6221-545609. Tel:
(+49) 6221-548443.
Notes
■
The authors declare no competing financial interest.
Gorls, H.; Mynott, R. J.; Theyssen, N.; Milstein, D.; Leitner, W.
̈
ACKNOWLEDGMENTS
We are grateful to the Landesgraduiertenforderung des Landes
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