N-heterocyclic silyl pincer ligands

Article abstract of DOI:10.1021/om400792j

The reaction of 1,2-C₆H₄(NHCH₂PPh ₂)₂ with chlorosilanes Cl₂SiHR (R = Ph, Cl) affords the benzosiladiazoles RHSi(NCH₂PPh₂) ₂C₆H₄ (R = Ph, 1; Cl, 2). The phenyl derivative 1 undergoes chelate-assisted Si-H activation with [RuPhCl(CO)(PPh ₃)₂] and [RhCl(PPh₃)₃] to afford the structurally characterized silyl pincer complexes [RuCl(CO)(PPh ₃){κ³-P,Si,P′-SiPh(NCH₂PPh ₂)₂C₆H₄}] (3) and [RhHCl(PPh ₃){κ³-P,Si,P′-SiPh(NCH₂PPh ₂)₂C₆H₄}] (4). The reaction of 4 with [Et₂NH₂][S₂CNEt₂] affords the complex [RhH(S₂CNEt₂){κ³-P,Si,P′- SiPh(NCH₂PPh₂)₂C₆H₄}] (5), structural data for which demonstrate a pronounced trans influence for the σ-silyl donor.

Full text of DOI:10.1021/om400792j

Article
pubs.acs.org/Organometallics
N‑Heterocyclic Silyl Pincer Ligands
Lily S. H. Dixon, Anthony F. Hill,* Arup Sinha, and Jas S. Ward
Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
S
* Supporting Information
ABSTRACT: The reaction of 1,2-C6H4(NHCH2PPh2)2 with
chlorosilanes Cl2SiHR (R = Ph, Cl) affords the benzosiladia-
zoles RHSi(NCH2PPh2)2C6H4 (R = Ph, 1; Cl, 2). The phenyl
derivative 1 undergoes chelate-assisted Si−H activation with
[RuPhCl(CO)(PPh3)2] and [RhCl(PPh3)3] to afford the
structurally characterized silyl pincer complexes [RuCl(CO)-
(PPh3){κ3-P,Si,P′-SiPh(NCH2PPh2)2C6H4}] (3) and [RhHCl-
(PPh3){κ3-P,Si,P′-SiPh(NCH2PPh2)2C6H4}] (4). The reaction
of 4 with [Et2NH2][S2CNEt2] affords the complex [RhH-
(S2CNEt2){κ3-P,Si,P′-SiPh(NCH2PPh2)2C6H4}] (5), structur-
al data for which demonstrate a pronounced trans influence for
the σ-silyl donor.
Chart 1. Representative LXL6−12 and XLX6,13,14 Silyl Pincer
Ligands
INTRODUCTION
■
Pincer ligands have enjoyed intense study in recent times1 due
in part to the stability that the meridional geometry confers on
their complexes and because of the broad scope for modular
variations in the electronic and steric features of both the axial
and equatorial donors. The vast majority of pincer scaffolds
involve classical phosphorus, nitrogen, oxygen, and carbon
donor atoms, with the inclusion of N-heterocyclic carbene
donors attracting increasing attention.2 Recently, the possibility
of incorporating highly electropositive boron as the equatorial
donor has begun to be explored,3−5 thereby drawing attention
to the question of incorporating other less conventional donor
atoms. Silicon as a donor is of particular interest in that
electropositive σ-silyl ligands are able to stabilize higher
oxidation states and through their strong trans influence help
to labilize trans ligands, both features of potential utility in
catalysis.
Stobart’s investigations of phosphine/silyl-based pincer
ligands with flexible alkyl backbones6 predated the current
focus on pincer ligands, and in the interim other more rigid
silicon pincer frameworks have been developed featuring
NSiN,7,8 PSiP,9,10 and SSiS11 LXL (five-electron, Chart 1a)
donor sets.12 Alternatively, four-electron XLX pincer ligands
have been described with SiPSi,6 SiOSi,13 and SiNSi14 donor
triads in which the (two) silicon donors occupy axial positions
(Chart 1b). The majority of these ligands share a predilection
toward adopting a facial coordination mode rather than the
meridional geometry usually associated with pincer ligands, this
being a corrollary of including sp3-tetrahedral silicon within the
metallabicycles. Indeed, Tilley has exploited this feature with
the d8-square planar complex [PtCl{κ3-N,Si,N′-SiMe(quin-
8)2}] (quin-8 = 9-quinon-8-yl), which activates dihydrogen,
thereby allowing the strained mer-platinabicycle to relax to a
facial geometry in the d6-octahedral complex [PtH2Cl{κ3-
N,Si,N′-SiMe(quin-8)2}].7 We have therefore turned our
attention to the design of silicon-based pincer ligands for
which the meridional geometry might be enforced by inclusion
of a suitably rigid backbone. To this end, we report herein the
synthesis of the first examples of N-heterocyclic σ-silyl pincer
ligands that bear a PSiP-LXL donor triad.
Received: August 7, 2013
© XXXX American Chemical Society
A
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unsaturated σ-silyl complexes [Ru(SiR3)Cl(CO)(PPh3)2].17
Accordingly, the reactions of these substrates with 1 were
investigated. In contrast to simple silanes, which require heating
(benzene reflux), 1 reacted with either 3 or 4 at room
temperature. Given the steric clutter about the silicon center in
1, this increase in reactivity may be attributed to rapid initial
coordination of a phosphine arm prior to, and assisting, Si−H
activation. Over a period of 24 h, the starting complexes and 1
were consumed accompanied by the liberation of one
equivalent of triphenylphoshine and the corresponding hydro-
carbon (C6H6, PhCHCH2). The reaction did not however
provide a single product, but rather a mixture of two
noninterconverting diastereomers, 5a and 5b, the ratio of
which varied depending on the precursor (Scheme 2), allowing
RESULTS AND DISCUSSION
■
N-Heterocyclic σ-boryl pincer ligand complexes of iridium,
rhodium, and ruthenium have been described previously,3b,4
resulting from chelate-assisted B−H activation of the
diazaboroles HB(NCH2PR2)2C6H4-1,2 (R = Ph, Cy). Setting
the stage for a similar strategy, the reactions of
C6H4(NHCH2PPh2)2-1,24 with chlorosilanes RHSiCl2 (R =
Ph, Cl) in the presence of triethylamine were explored and
found to readily afford the 2,1,3-siladiazoles HSiR-
(NCH2PPh2)2C6H4 (R = Ph, 1; Cl, 2, Scheme 1). Among
Scheme 1. Synthesis of Silyl Pincer Pro-ligands
Scheme 2. Synthesis of Ruthenium Silyl Pincer Complexes
(R = Ph, CHCHPh)
the spectroscopic data for 1, the most noteworthy are (i) a
strong absorption in the infrared spectrum (KBr: 2176 cm−1)
corresponding primarily to the νSiH mode; (ii) a silicon hydride
1
1
resonance at δH = 5.52 (4JPH = 4, JSiH = 245 Hz) in the H
NMR spectrum; and (iii) a broadened resonance at δSi = −12.4
in the 29Si{1H} NMR spectrum. Similar data were obtained for
2. The characterization of 1 included a crystallographic study,
the results of which are summarized in Figure 1, confirming the
us to conclude that the isomers are not in equilibrium. The
difference in ratio resulting from different precursors (5a:5b =
1:3.2 (R = Ph), cf. 1:7.62 R = CHCHPh) presumably reflects
the relative rates of benzene compared with styrene elimination
from a fluxional intermediate. These isomers, each of which
1
involve a mer-RuP3 geometry on the basis of 31P{1H} and H
NMR data, arise from the various possible arrangements of the
three unidentate ligands Cl, CO, and PPh3 and their
relationship (syn, anti) to the silicon phenyl substituent (six
isomers are conceivable). Two of these, 5a and 5b, are related
by exchange of chloride and carbonyl ligands and cocrystal-
lized.18
Figure 1. Molecular structure of 1 (50% displacement ellipsoids).
Selected bond distances (Å) and angles (deg): N1−Si1 1.7311(13),
N2−Si1 1.7420(12), Si1−H1 1.460(17), Si1−N1−C1 129.09(10),
Si1−N2−C2 126.26(10), N2−Si1−N1 91.61(6), N2−Si1−H1
115.9(7), N1−Si1−H1 116.6(7), Σ°(N1) 359.6, ∑°(N2) 259.9.
A crystallographic analysis on one such crystal was
successfully modeled by a 5a0.7·5b0.3 composition, with the
molecular geometry of the major isomer 5a being depicted in
Figure 2.19 The crystal structure confirms that the pincer ligand
does indeed adopt the meridional geometry, although this is
accompanied by some distortions from ideality. These include
slightly pyramidalized nitrogen centers (mean ∑°(N) = 347°),
a splayed Ru1−Si1−C31 linkage (128.27(8)°), and contraction
from linearity of the trans bisaxial P1−Ru1−P2 arrangement
(152.49(2)°). These Ru−P bonds are significantly (ca. 170 esd)
shorter than that trans to the trans-influential silyl donor (Ru1−
P3 = 2.5007(6) Å). The ruthenium−silicon separation
formation of the desired pro-ligand. Both the crystal structure
and the computationally optimized (DFT-B3LYP-6-31G*)
geometry of 1 involve an essentially coplanar arrangement of
the C6H4(NC)2Si unit (mean ∑°(N) = 359.8°), presaging a
geometrically induced reluctance of σ-silyl complexes derived
from 1 to adopt facial coordination geometries.
We have previously employed the complexes [RuRCl(CO)-
(PPh3)2] (R = CHCHPh, 3;15 Ph, 416) for the synthesis of
N-heterocyclic σ-boryl and borane complexes of ruthenium via
chelate-assisted B−H activation3 while 4 has been shown to
react with conventional silanes, HSiR3, to afford coordinatively
B
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Scheme 3. Synthesis of Rhodium Silyl Pincer Complexes
Figure 2. Molecular structure of 5a in a crystal of 5a0.7·5b0.3 (50%
displacement ellipsoids; hydrogen atoms omitted). 5b is related to 5a
by positional disorder of chloride and carbonyl ligands. Selected bond
distances (Å) and angles (deg): Cl10−Ru1 2.475(2), N1−Si1
1.770(2), N2−Si1 1.767(2), P1−Ru1 2.3573(6), P2−Ru1 2.3998(6),
P3−Ru1 2.5007(6), Ru1−Si1 2.3723(6), Si1−N2−C2 119.27(16),
Si1−N2−C8 109.54(17), P2−Ru1−P1 152.49(2), P2−Ru1−Si1
77.44(2), P1−Ru1−Si1 77.98(2), Ru1−Si1−C31 128.27(8),
∑°(N1) = 345.1, ∑°(N2) = 348.4.
(2.3723(6) Å) is somewhat short when compared with data for
nonchelated octahedral ruthenium silyl complexes (2.41−2.48
Å),20 although similarly shortened Ru−Si bonds are observed
when electronegative silicon substituents (Cl, OEt) are
involved,21 a feature attributed, on the basis of ab initio
calculations, to the importance of M−Si π-interactions.22
The complex [RhCl(PPh3)3] (6) is an effective alkene
hydrosilyation catalyst, with the first step in such a cycle being
the oxidative addition of the Si−H bond to rhodium(I).23 It
therefore seemed that 6 would provide a suitable entry point
into rhodium complexes based on 1. A smooth reaction ensues
between 1 and 6 at room temperature to afford two isomers of
the complex [RhHCl(PPh3){κ3-P,Si,P′-SiPh(NCH2PPh2)2-
C6H4}] (7a/7b) in addition to two equivalents of liberated
PPh3, the 31P resonance for which is broadened, indicating
exchange with the coordinated phosphine on the 31P NMR
time scale (Scheme 3).
Crystals of both 7a and 7b were obtained and crystallo-
graphically analyzed (see Supporting Information). The
topologies of the molecular structures of 7a and 7b are very
similar to that of 5a with further indications that although the
meridional geometry is enforced, this is accompanied by some
strain, reflected in the modest pyramidalization at nitrogen and
bending of the phosphine chelate arms toward the sterically
unassuming hydride ligand. The Rh1−P3 (PPh3) bond length
of 2.5047(10) Å (cf. 2.3572(11), 2.3276(11) Å for the axial
donors) is somewhat long for octahedral rhodium, indicating
perhaps, as with 5a/5b, the operation of a significant trans
influence by the σ-silyl donor, implicitly manifest as a trans
effect with respect to phosphine dissociation.
dissociation/recoordination of the phosphine ligand via the
coordinatively unsaturated species “RhHCl{SiPh-
2
(NCH2PPh2)2C6H4}”, and the magnitude of the JPH
couplings15 suggests that both isomers involve cis coordination
of the hydride and PPh3 ligands (Scheme 3). It should however
be noted that this alone does not account for the syn/anti-
periplanar interchange of the Ph−Si−Rh−H positions, raising
the possibility that either reversible Si−H elimination/addition
operates or that dissociation of one pincer arm allows access to
stereochemically less constrained geometries. For 5a and 5b,
which do not interconvert, a Si−H elimination/addition
sequence is precluded. To obviate problems associated with
the separation of 7a/7b from liberated PPh3, the same isomeric
mixture was obtained in two steps via the sequential reaction of
1 with half an equivalent of [Rh2(μ-Cl)2(η4-cod)2] (cod =
cycloocta-1,5-diene) and one equivalent of PPh3.
To more definitely assess the trans influence of the silyl
donor,7,22,24 the synthesis of a chelate dithiocarbamate derivate
[RhH(S2CNEt2){SiPh(NCH2PPh2)2C6H4}] (8) was devel-
oped via the reaction of the 7a/7b isomeric mixture with
[Et2NH2][S2CNEt2] or of 1 with [Rh2(μ-Cl)2(η4-cod)2] and
[Et2NH2][S2CNEt2]. A single isomer of 8 was formed in
spectroscopically quantitative yield in each case, and both
synthetic routes presumably proceed via the 16-electron five-
coordinate species “RhHCl{SiPh(NCH2PPh2)2C6H4}”, where-
in the different steric impact of the chloride and hydride ligands
most likely accounts for the ultimately observed regiochemistry.
The molecular structure of 8 is depicted in Figure 3, which in
addition to reproducing the geometric features observed for the
“M{SiPh(NCH2PPh2)2C6H4}” (M = Ru, Rh) units of 5a/5b
and 7a also offers the internally standardized opportunity for
The two isomers are in dynamic equilibrium with very little
difference in relative energy, as indicated by 1H NMR
integration of the hydride signals (CDCl3: K298 = 1.5; C6D6:
K298 = 2.7). The two isomers most likely interconvert via
C
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microanalytical service of the Australian National University. Data for
X-ray crystallography were collected with a Nonius Kappa CCD
diffractometer. The compounds [Ru(CHCHPh)Cl(CO)(PPh3)2],15
[Ru(Ph)Cl(CO)(PPh3)2],16 [RhCl(PPh3)3],25 and [Rh2(μ-Cl)2(η4-
COD)2]26 were prepared according to published procedures. The salt
[H2NEt2][S2CNEt2] was prepared from diethylamine and carbon
disulfide in diethyl ether. Other reagents were used as received from
commercial suppliers.
The compound C6H4(NHCH2PPh2)2-1,2 was prepared via minor
modifications of the method described by Yamashita:4 A stirred
suspension of paraformaldehyde (3.90 g, 0.130 mol) in diphenylphos-
phine (24.2 g, 0.130 mol) was heated to 100 °C until all the
paraformaldehyde had dissolved (40 min). The solution was left to
cool to 25 °C before being dissolved in dichloromethane (150 mL)
and transferred to a solution of o-phenylenediamine (7.03 g, 0.065
mol). The resultant solution was covered with aluminum foil and
stirred for 2 days. After the solvent was removed in vacuo, diethyl ether
(100 mL) was added to the crude, yellow solid. Stirring for 5 min
afforded a white precipitate, which was isolated by filtration. Yield:
24.15 g (0.048 mol, 74%). NMR (C6D6, 25 °C) 1H: δH 3.27 (s br, 2 H,
Figure 3. Molecular structure of 8 in a crystal (50% displacement
ellipsoids; hydrogen atoms and solvate omitted). Selected bond
distances (Å) and angles (deg): N1−Si1 1.7664(13), N2−Si1
1.7658(13), P1−Rh1 2.2885(4), P2−Rh1 2.2991(4), Rh1−S1
2.4387(4), Rh1−S2 2.4940(4), Rh1−Si1 2.2796(4), Rh1−H1 1.532,
P2−Rh1−P1 156.077(15), P2−Rh1−Si1 78.678(15), P1−Rh1−Si1
80.574(15), N1−Si1−N2 93.46(6), N1−Si1−Rh1 109.79(5), N2−
Si1−Rh1 108.20(5), N1−Si1−C31 107.45(7), N2−Si1−C31
110.40(7), Rh1−Si1−C31 123.41(5), ∑°(N1) = 344.9, ∑°(N2) =
344.3°.
2
NH), 3.51 (d, 4 H, NCH2, JHP = 4), 6.68, 6.93 (dd × 2, 2 H × 2,
C6H4, 3JHH = 6, 4JHH = 4 Hz), 7.02−7.04 (m, 12 H, C6H5), 7.33−7.39
(m, 8 H, C6H4). 31P{1H}: δP −17.9 (s). These data were consistent
with those previously published.4
Synthesis of PhHSi(NCH2PPh2)2C6H4 (1). Triethylamine (3.00
mL, 21.0 mmol) was added to
a stirred solution of
C6H4(NHCH2PPh2)2 (5.00 g, 9.90 mmol) in THF (100 mL).
Dichlorophenylsilane (1.50 mL, 10.2 mmol) was added dropwise to
the stirred solution. The resultant suspension was stirred for 4 days,
then stored at 4 °C for 2 h. The supernatant was isolated by cannula
filtration, and volatiles were removed in vacuo, leaving a sticky solid.
This was extracted with benzene, and the residual precipitate was
removed by cannula filtration. The benzene was removed in vacuo;
then trituration of the solid in diethyl ether (50 mL) yielded a white
precipitate, which was isolated by cannula filtration. Yield: 5.31 g (8.72
mmol, 88%). NMR (C6D6, 25 °C) 1H: δH = 3.85 (dd, 2 H, PCHaHbN,
comparing the relative trans influences of the hydride and σ-
silyl donors within the same complex. The Rh1−S2 bond
length (2. 2.4940(4) Å) trans to silicon is significantly (138
esd) longer than that trans to the hydride ligand (Rh1−S1 =
2.4387(4) Å), indicating that the σ-silyl donor exerts a
remarkably strong trans influence, even relative to the hydride
ligand.
In conclusion, a straightforward synthetic route to N-
heterocyclic silyl pincer pro-ligands has been demonstrated.
These pro-ligands readily install the tridentate silyl pincer
ligand via facile Si−H bond activation. Although the rigid NHSi
framework reinforces the meridional coordination geometry,
there are attendant geometric distortions associated with
including an sp3-hybridized silyl group as the equatorial
donor group. Furthermore, the ligand appears prone to
forming isomeric mixtures when coordinated to octahedral
centers bearing disparate ligands. Each of these issues would be
obviated in the case of N-heterocyclic silylene pincer ligands, a
challenge we are currently addressing.
2
2
2
2JPH = 30, JHaHb = 14), 3.86 (dd, 2 H, PCHbHaN, JPH = 37, JHaHb
=
14), 5.52 (t, 1 H, SiH, 4JPH = 4, 1JHSi = 245 Hz), 6.85−7.53 (m, 29 H,
C6H5 and C6H4). 31P{1H}: δP = −22.0. 13C{1H}: δC = 45.9 (d, NCH2,
1JCP = 8), 108.8 [d, C2,5(C6H4), JCP = 2 Hz), 118.7 [C3,4(C6H4)],
4
128.5−138.3 (m, C6H5). 29Si{1H}: δSi = −12.4 (s br). IR (KBr): νSiH
=
2176 cm−1. ESI-MS (positive ion): m/z = 532 [M − Ph]+, 331.4 [M −
Ph + CH2PPh2]+, 319.4 [M − Ph − NCH2PPh2]+, 133.1 [M − Cl −
NCH2PPh2 − PPh2]+. Anal. Found: C, 75.20; H, 5.77; N, 4.42. Calcd
for C38H34N2P2Si: C, 74.98; H, 5.63; N, 4.60. NB: The obtention of an
analytically pure sample required multiple tedious recrystallizations to
remove traces (2−3%) of the corresponding dioxide (δP −18.03,
C6D6). For practical purposes, the crude material is suitable for further
use because the solubility of the dioxide differs more markedly from
that of the derived complexes and is easily removed during workup.
Crystals suitable for X-ray crystallography were obtained by
recrystallization from diethyl ether. Crystal data for 1: C38H34N2P2Si,
M = 608.72, T = 200(2) K, triclinic, P1 (No. 2), a = 10.5915(3) Å, b
̅
w
EXPERIMENTAL SECTION
■
= 13.0298(3) Å, c = 13.0621(3) Å, α = 71.6251(16)°, β =
78.7715(16)°, γ = 68.7673(14)°, V = 1587.97(7) Å3, Z = 2, Dcalcd
=
General Considerations. All manipulations of air-sensitive
compounds were carried out under a dry and oxygen-free argon
atmosphere using standard Schlenk and vacuum line techniques, with
dry and degassed solvents. NMR spectra were recorded at 25 °C on
Varian Mercury 300 (1H at 300.1 MHz, 31P at 121.5 MHz) and Varian
Inova 300 (1H at 299.9 MHz, 13C at 75.42 MHz, 31P at 121.4 MHz,
1.273 Mg m−3, μ(Mo Kα) = 0.21 mm−1, colorless prism, 0.45 × 0.18 ×
0.14 mm, 48 779 measured reflections with 2θmax = 60.1°, 9282
independent reflections, 9282 absorption corrected data used in F2
refinement, 524 parameters, 250 restraints, R = 0.044, Rw = 0.109 for
6994 reflections with I > 2σ(I). (CCDC 898193).
29Si at 59.6 MHz) spectrometers. The chemical shifts (δ) for H and
1
Synthesis of HClSi(NCH2PPh2)2C6H4 (2). Triethylamine (3.00
13C spectra are given in ppm relative to residual signals of the solvent,
29Si relative to an internal SiMe4 reference, and 31P relative to an
external H3PO4 reference. Low- and high-resolution mass spectra were
obtained on a ZAB-SEQ4F spectrometer by positive ion ESI
techniques using an acetonitrile matrix by the mass spectrometry
service of the Australian National University. Assignments were made
relative to M, where M is the molecular cation. Assignments were
verified by simulation of isotopic composition both for low- and high-
resolution levels. Elemental microanalysis was performed by the
mL, 21.0 mmol) was added to
a stirred solution of
C6H4(NHCH2PPh2)2 (5.00 g, 9.90 mmol) in THF (100 mL).
Trichlorosilane (1.00 mL, 9.90 mmol) was added dropwise to the
stirred solution. The resultant suspension was stirred for 1 h, then
stored at 4 °C for 2 h. The supernatant was isolated by cannula
filtration, and volatiles were removed in vacuo, leaving a sticky solid.
Subsequent trituration in diethyl ether (50 mL) yielded a pale yellow
precipitate, which was isolated by cannula filtration. Yield: 3.87 g (6.80
mmol, 69%). NMR (C6D6, 25 °C) 1H: δH = 3.90 (d br, 4 H, NCH2),
D
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4
1
1
2
5.58 (t, 1 H, SiH, JPH = 4, JHSi = 336), 6.83, 6.95 (dd × 2, 2 H × 2,
CH2PPh2, JPRh = 113, JPP = 22 Hz). 13C{1H}: δC = 57.7−61.7 (m,
NCH2, 7a/b), 112.2 (s, C2,5(C6H4), 7a), 114.2 (s, C2,5(C6H4), 7b),
119.1 (s, C3,4(C6H4), 7a), 121.0 (s, C3,4(C6H4), 7b), 126.9−149.5 (m,
C6H5, 7a/b).1 IR (KBr): νRhH = 2027 s, 2051, 1966, 1894, 1821br × 4
(7a/b) cm−1. ESI-MS (positive ion): m/z = 973.7 [M − Cl]+, 711.4
[M − Cl − PPh3]+. Accurate Mass: Found 973.1935 [M − Cl]+. Calcd
for C56H49N2P3103RhSi: 973.1933. Anal. Found: C, 61.69; H, 4.91; N,
3.32. Calcd for C56H49ClN2P3RhSi: C, 66.64; H, 4.89; N, 2.78. While
there is a large discrepancy between the calculated and experimental
elemental analysis, the experimental data are consistent with 7 − PPh3
Calcd: C, 61.09, H, 4.59, N, 3.75. As the PPh3 ligand is known to be
labile, it is possible that in the process of thoroughly washing the
sample to be analyzed all PPh3 was abstracted. Crystals of 7a suitable
for X-ray crystallography were obtained by slow diffusion of diethyl
ether into a saturated solution of a mixture of 7a and 7b in chloroform.
C6H4, JHH = 6, JHH = 4), 6.97−7.38 (m, 20 H, C6H5, Hz). 31P{1H}:
3
4
δP −22.7. 13C{1H}: δC = 44.8 (d, NCH2, JCP = 9 Hz), 109.8 [d,
1
C2,5(C6H4), JCP), 119.5 [C3,4(C6H4)], 128.6−138.6 (m, C6H5). δSi
=
4
−25.7. IR (KBr): νSiH = 2246 cm−1. ESI-MS (positive ion): m/z = 532
[M − Ph]+, 319.5 [M − Cl − NCH2PPh2]+, 133.1 [M − Cl −
NCH2PPh2 − PPh2)]+. Anal. Found: C, 67.44; H, 5.28; N, 5.07. Calcd.
for C32H29ClN2P2Si: C, 67.78; H, 5.15; N, 4.94.
Synthesis of [RuCl(CO)(PPh3){SiPh(NCH2PPh2)2C6H4}] (5).
[Ru(CHCHPh)Cl(CO)(PPh3)2] (0.36 g, 0.46 mmol) and 1 (0.30
g, 0.50 mmol) were dissolved in THF (40 mL). The resultant solution
was stirred for 24 h. The solvent was removed in vacuo, and the
remaining solid was suspended in diethyl ether (30 mL). Ultrasonic
trituration of this suspension yielded a yellow precipitate. The reaction
flask was stored at 4 °C for 2 h before the solid was isolated by cannula
filtration. Yield: 0.37 g (0.36 mmol, 78%). NMR (C6D6, 25 °C, major
Crystal data for 7a (RhH anti to SiPh): C56H49ClN2P3RhSi, Mw
1009.38, triclinic, P1 (No. 2) a = 11.4602(4) Å, b = 13.8696(6) Å, c =
=
1
2
isomer) H: major isomer: δH = 4.36 (d, 2 H, PCHaHbN, JHaHb
=
̅
18.1), 4.56 (dtv, 2 H, PCHaHbN, JHbHa = 12.0, JHP = 9.0 Hz), minor
2
15.3944(8) Å, α = 84.636(2)°, β = 77.551(2)°, γ = 82.766(3)°, V =
2364.80(18) Å3, Z = 2, Dcalcd = 1.417 Mg m−3, μ(Mo Kα) = 0.59
mm−1, T = 200(2) K, yellow block, 0.13 × 0.10 × 0.08 mm, F2
refinement, R = 0.049, Rw = 0.123 for 6856 reflections (I > 2σ(I), θmax.
= 25.2°), 578 parameters, CCDC 898191. Crystals of 7b·(C6H6)0.5
suitable for X-ray crystallography were obtained by slow diffusion of
pentane into a saturated solution of a mixture of 7a and 7b in benzene.
Crystal data for 7b·(C6H6)0.5 (RhH syn to SiPh): C59H52ClN2P3RhSi,
isomer: δH = 4.02 (dtv, 2 H, PCHaHbN, JHaHb = 12.0, JHP = 3 Hz),
2
2
4.31 (d, 2 H, PCHaHbN, JHbHa = 12 Hz), both isomers: δH = 6.40−
7.90 (m, 44 H). 31P{1H}: major isomer: δP = 12.22 (t, 1P, 2JP−P = 17.0
Hz) 52.1 (d, 2P, 2JP−P = 17 Hz), minor isomer: δP = 15.17 (t, 1P, 2JP−P
= 16.4 Hz), 54.73 (d, 2P, JP−P = 17 Hz). 29Si{1H} (HMBC): major
2
isomer: δSi = 103.5 (2,3JPSi = 66 Hz). 13C{1H}: major isomer: δC = 59.0
(tv, NCH2PPh2, JC−P = 17 Hz), 112.9 (s, o-phenylene C, 4JC−P = 2 Hz),
119.8 (s, m-phenylene C), 128.8−138.2 (m, phenyl C), 203.7 (s, Ru-
CO). IR (KBr): νCO = 1937 cm−1. ESI-MS (positive ion): m/z =
1001.5 [M − Cl]+, 736.6 [M − (Cl + PPh3)]+, 133.1 [M − (Cl,
NCH2PPh2, PPh2]+. Accurate Mass: Found 1001.1953 [M − Cl]+.
Calcd for C57H48ClN2OP3102Ru28Si = 1001.1949. Anal. Found: C,
66.23; H, 4.75; N, 2.64. Calcd for C57H48ClN2OP3102Ru28Si C, 66.18;
H, 4.68; N, 2.71. Crystals of 5a0.7·5b0.3 suitable for X-ray
crystallography were obtained by recrystallization from chloroform
and ethanol. Crystal data for complex 5a0.7·5b0.3: C57H48ClN2OP3RuSi
Mw = 1048.44, triclinic, P1 (No. 2) a = 11.74350(10) Å, b =
̅
13.3987(2) Å, c = 17.0566(2) Å, α = 87.2376(7)°, β = 86.4154(8)°, γ
= 67.1037(6)°, V = 2466.69(5) Å3, Z = 2, Dcalcd = 1.412 Mg m−3,
μ(Mo Kα) = 0.564 mm−1, T = 200(2) K, yellow block, 0.14 × 0.14 ×
0.22 mm, F2 refinement, R = 0.0341, Rw = 0.0790 for 12 223 reflections
(I > 2σ(I), θmax = 30.0°), 813 parameters, 394 restraints, CCDC
898194.
Synthesis of [RhH(S2CNEt2){SiPh(NCH2PPh2)2C6H4}] (8).
[Rh2(μ-Cl)2(η4-cod)2] (0.050 g, 0.10 mmol) and 1 (0.130 g, 0.20
mmol) were dissolved in THF (10 mL) and stirred for 2 h. A solution
of [Et2NH2][Et2NCS2] (0.052 g, 0.23 mmol) in THF (5 mL) was
then added. The THF was removed in vacuo, and the remaining solid
was resuspended in benzene (10 mL). The suspension was frozen and
allowed to thaw, and the supernatant was isolated by cannula transfer.
The benzene was removed in vacuo, and the solid remaining was
resuspended in ether (15 mL) in air. Agitation of the suspension
resulted in precipitation of the product. The precipitate was collected
by vacuum filtration (0.095 g, 0.11 mmol, 55%). NMR (C6D6, 25 °C)
1H: δH = −15.06 (dt, 1 H, RhH, 1JRh−H = 20 Hz, 2JP−H = 12 Hz), 0.71,
M = 1034.53, T = 200 K, triclinic, P1 (No. 2), a = 11.6868(2) Å, b =
̅
w
14.0096(2) Å, c = 15.4974(3) Å, α = 80.3054(12)°, β = 75.3846(8)°, γ
= 82.5635(11)°, V = 2410.11(7) Å3, Z = 2, Dcalcd = 1.426 Mg m−3,
μ(Mo Kα) = 0.55 mm−1, yellow block, 0.25 × 0.17 × 0.10 mm, 30 709
measured reflections with 2θmax = 55.0°, 11 076 independent
reflections, 11 076 absorption corrected data used in F2 refinement,
624 parameters, 3 restraints, R = 0.038, Rw = 0.101 for 11 076
reflections I > 2σ(I) (CCDC 898190).
Synthesis of [Rh(H)Cl(PPh3){SiPh(NCH2PPh2)2C6H4}] (7). (a) A
mixture of [RhCl(PPh3)3] (0.50 g, 0.54 mmol) and 1 (0.37 g, 0.60
mmol) was dissolved in THF (70 mL). The resultant solution was
stirred for 10 min before the solvent was removed in vacuo. The
remaining solid was suspended in diethyl ether (60 mL) and triturated,
yielding a yellow precipitate. The suspension was cooled to −78 °C,
and the precipitate was isolated by cannula filtration. Yield: 0.23 g
(0.23 mmol, 42%). Ratio of 7a/7b = 1:2.7 in C6D6 but 1:1.5 in CDCl3
(1H NMR integration). (b) A mixture of [Rh2(μ-Cl)2(η4-1,5-cod)2]
(0.054 g, 0.11 mmol) and 1 (0.134 g, 0.220 mmol) were dissolved in
THF (30 mL). The resultant solution was stirred for 3 h.
Triphenylphosphine (0.054 g, 0.21 mmol) was added to the stirred
solution. After 1 h of stirring, the solvent was removed in vacuo, and
the remaining solid was triturated in diethyl ether (20 mL). The
resultant suspension was stored at 4 °C for 2 h before the yellow
precipitate was isolate by cannula filtration. A second crop of product
was isolated from the filtrate. NMR analysis (1H NMR integration)
confirmed both crops were the same isomer mixture with similar
proportions of 7a and 7b. Yield: 0.120 g (0.12 mmol, 57% yield, two
3
0.76 (2t, 2 × 3H, S2CNCH2CH3, JH−H = 7 Hz), 3.11, 3.29 (2q, 2 ×
3
2H, S2CNCH2CH3, JH−H = 7 Hz), 3.59 (dtv, 2H, Ph2PCHaHbN,
2JHa‑Hb= 13 Hz, JHa‑P = 5 Hz), 4.62 (d, 2H, Ph2PCHaHbN, 1JHa‑Hb = 13
Hz), 6.72−7.86 (m, 29H). 31P{1H}: δP = 61.9 (dd, 2 P, −CH PPh2-
2
Rh, JRhP = 115 Hz, JHP= 10 Hz). 13C{1H}: δC = 12.4 (s,
S2CNCH2CH3), 43.4 (2s, S2CNCH2CH3), 61.0 (tv, Ph2PCH2N, JC−P
= 14 Hz), 113.9 (s, o-phenylene C-H), 120.1 (s, m-phenylene C-H),
1
2
130.1−136.8 (m, phenyl C-H), 147.3 (s, S2CNEt2). IR (KBr): νRh−H
=
1963 cm−1. ESI-MS (positive ion): m/z = 860 [M]+, 335.4 [M − (Rh
+ Et2NCS2 + CH2PPh2 + Ph)]+, 133.1 [M − (Cl, NCH2PPh2, PPh2]+.
Accurate Mass: Found 860.1426 [M]+. Anal. Found: C, 61.88; H, 5.14;
N, 4.64. Calcd for C43H44N3P2RhS2Si(C3H3) C, 61.46; H, 5.27; N,
4.67. Crystals suitable for X-ray crystallography were obtained by slow
diffusion of ether into a saturated solution of 8 in benzene. Crystal data
for complex 8: C43H44N3P2RhS2Si Mw = 859.90, monoclinic, P21/n, a
= 10.0377(1) Å, b = 19.8396(2) Å, c = 21.5427(2) Å, Z = 4, Dcalcd
=
1.394 Mg m−3, μ(Mo Kα) = 0.64 mm−1, T = 200 K, colorless block,
0.35 × 0.24 × 0.23 mm, F2 refinement, R = 0.029, Rw = 0.073 for 10
766 reflections (I > 2σ(I), θmax = 30.0°), 496 parameters, CCDC
898192.
1
1
crops). 7a: NMR (C6D6, 25 °C) H: δH = −19.14 (dtd, 1 H, JRhH
=
=
2
2
2
17, JHP(pin) = 11, JHP(PPh3) = 4), 5.56 (dtv, 2 H, NCHaHbP, JHaHb
11, JHP = 7), 5.86 (d, 2 H, NCHaHbP, 2JHaHb = 11 Hz), 6.55−7.98 (m,
C6H5 and C6H4). 31P{1H}: δP = 15.1 (dt, 1 P, PPh3, 1JPRh = 77, 2JPP
=
1
2
21), 59.1 (d.d., 2 P, CH2PPh2, JPRh = 117, JPP = 21 Hz). 7b: NMR
ASSOCIATED CONTENT
(C6D6, 25 °C) 1H: δH = −17.22 (ddt, 1 H, 1JRhH = 20, 2JHP(PPh3) = 16,
■
2JH−P(pin) = 10), 4.24 (d, 2H, NCHaHbP, JHaHb = 12), 4.75 (dtv, 2 H,
2
S
* Supporting Information
Crystallographic data for 1 (CCDC 898193), 5a/5b (CCDC
898190), 7a (CCDC 898191), 7b (CCDC 898194), and 8
NCHaHbP, 2JHaHb = 12, JHP = 5 Hz), 6.55−7.98 (m, C6H4 and C6H5).
31P{1H}: δP = 16.2 (dt, 1 P, PPh3, 1JPRh = 84, 2JPP = 22), 56.0 (dd, 2 P,
E
dx.doi.org/10.1021/om400792j | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
14236. (e) Mitton, S. J.; McDonald, R.; Turculet, L. Organometallics
2009, 28, 5122−5136. (f) MacLean, D. F.; McDonald, R.; Ferguson,
M. J.; Caddell, A. J.; Turculet, L. Chem. Commun. 2008, 5146−5148.
(g) MacInnis, M. C.; MacLean, D. F.; Lundgren, R. J.; McDonald, R.;
Turculet, L. Organometallics 2007, 26, 6522−6525.
(CCDC 898192) in CIF format. This information is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: a.hill@anu.edu.au.
■
(10) (a) Korchin, E. E.; Leitus, G.; Shimon, L. J. W.; Konstantinovski,
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by the Australian Research Council
(DP110101611).
■
(11) Hill, A. F.; Neumann, H.; Wagler, J. Organometallics 2010, 29,
1026−1031.
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dx.doi.org/10.1021/om400792j | Organometallics XXXX, XXX, XXX−XXX