Use of an iodide-modified merrifield resin in the synthesis of ruthenium hydride complexes. the structure of RuHI((R)-binap)(PPh3)

Article abstract of DOI:10.1021/om700360r

Transition metal complexes that function as catalysts or precatalysts are sometimes synthesized by the displacement of phosphine ligands from precursor complexes. A common problem in the synthesis is the separation of the desired complex from the phosphine contaminants that have similar solubility properties. This is the case in the synthesis of the coordinatively unsaturated ruthenium complexes RuHX((R)-binap)(PPh₃) (X = Cl, 2; X = I, 3) from RuHCl(PPh₃)₃ (1). The new iodo ruthenium complex RuHI((R)-binap)(PPh₃) (3) is prepared in good yield and purity by treatment of the chloro derivative 2, which is contaminated with triphenylphosphine, triphenylphosphine oxide, binap, binap monoxide, and binap dioxide, with an iodide-modified Merrifield resin. The resin was prepared following a modification of a procedure described by Lipshutz and Blomgren. The structure determination of 3 by single-crystal X-ray diffraction is reported. Complex 3 reacts with the alkoxides KOCR₂-2-py (R = Me, potassium dimethyl-2-pyridylmethoxide; R = Ph, potassium diphenyl-2-pyridylmethoxide) to produce the coordinatively unsaturated hydrido alkoxide complexes RuH(OCR ₂-2-py)((R)-binap) (R = Me 4, R = Ph 5). Complexes 4 and 5 are poor catalysts for asymmetric hydrogenation and are not catalysts for Michael addition reactions at room temperature, conditions where certain ruthenium complexes with diamine and phosphine ligands are known to be very active. The modified resin is demonstrated to be an effective phosphine scavenger in the synthesis of the known complex irons-RuH(I)(dppe)₂ (6) and the new complex trans-RuH(I)(dppb)₂ (7).

Full text of DOI:10.1021/om700360r

Organometallics 2008, 27, 503–508
503
Articles
Use of an Iodide-Modified Merrifield Resin in the Synthesis of
Ruthenium Hydride Complexes. The Structure of
RuHI((R)-binap)(PPh3)
Xiaoxi Zhao, Nina Ivanova, Alen Hadzovic, Marco Zimmer-De Iuliis, Alan J. Lough, and
Robert H. Morris*
DaVenport Laboratory, Department of Chemistry, UniVersity of Toronto, 80 St George Street,
Toronto, Ontario M5S 3H6, Canada
ReceiVed April 12, 2007
Transition metal complexes that function as catalysts or precatalysts are sometimes synthesized by the
displacement of phosphine ligands from precursor complexes. A common problem in the synthesis is the
separation of the desired complex from the phosphine contaminants that have similar solubility properties.
This is the case in the synthesis of the coordinatively unsaturated ruthenium complexes RuHX((R)-
binap)(PPh3) (X ) Cl, 2; X ) I, 3) from RuHCl(PPh3)3 (1). The new iodo ruthenium complex RuHI((R)-
binap)(PPh3) (3) is prepared in good yield and purity by treatment of the chloro derivative 2, which is
contaminated with triphenylphosphine, triphenylphosphine oxide, binap, binap monoxide, and binap
dioxide, with an iodide-modified Merrifield resin. The resin was prepared following a modification of a
procedure described by Lipshutz and Blomgren. The structure determination of 3 by single-crystal X-ray
diffraction is reported. Complex 3 reacts with the alkoxides KOCR2-2-py (R ) Me, potassium dimethyl-
2-pyridylmethoxide; R ) Ph, potassium diphenyl-2-pyridylmethoxide) to produce the coordinatively
unsaturated hydrido alkoxide complexes RuH(OCR2-2-py)((R)-binap) (R ) Me 4, R ) Ph 5). Complexes
4 and 5 are poor catalysts for asymmetric hydrogenation and are not catalysts for Michael addition reactions
at room temperature, conditions where certain ruthenium complexes with diamine and phosphine ligands
are known to be very active. The modified resin is demonstrated to be an effective phosphine scavenger
in the synthesis of the known complex trans-RuH(I)(dppe)2 (6) and the new complex trans-RuH(I)(dppb)2
(7).
Most of these sponge reagents are oxidizing or reactive toward
transition metal hydride complexes such as the 16-electron
complex RuHCl(binap)(PPh3), binap ) (R)- or (S)-2,2′-bis-
(diphenylphosphino)-1,1′-binaphthyl (2).12,13 This latter complex
is prepared by the reaction of RuHCl(PPh3)3 (1) with binap,
but is very difficult to separate from excess binap and PPh3,
released as the byproduct (eq 1).
Introduction
The synthesis of a transition metal complex with phosphine
ligands is often complicated by the separation of the product
from phosphine in solution when their solubilities are similar
and the complex cannot survive conventional chromatography.
Dioumaev et al. overcame this problem in synthesizing tri-
methylphosphine ruthenium complexes by using BPh3 to remove
a PMe3 contaminant as the less soluble borane-phosphine
adduct.1 They provide a useful list of “phosphine sponge”
reagents mentioned in the literature, which are used in syntheses
or to promote phosphine dissociation in catalysis. These
reagents, along with more recent examples, include MeI,2–4
boranes,1,5,6 sulfur,3 CS2,7 ONMe3,8 cuprous halides,9–11 and a
variety of metal complexes.1
RuHC1(PPh3)3 + binap f
1
RuHC1(PPh3)(binap) + 2PPh3 (1)
2
Complex 1 has been used to prepare a variety of RuHCl(bi-
nap)(L-NH2) complexes where L-NH2 are enantiopure bidentate
(7) Uson, R.; Fornies, J.; Uson, M. A. Synth. React. Inorg. Met.-Org.
Chem. Ber. 1984, 14, 355–367.
* Corresponding author. E-mail: rmorris@chem.utoronto.ca.
(1) Dioumaev, V. K.; Plössl, K.; Carroll, P. J.; Berry, D. H. Organo-
metallics 2000, 19, 3374–3378.
(8) Klabunde, U.; Ittel, S. D. J. Mol. Catal. 1987, 41, 123–134.
(9) Farina, V.; Kapadia, S.; Krishnan, B.; Wang, C.; Liebeskind, L. S.
J. Org. Chem. 1994, 59, 5905–5911.
(2) Lazarowych, N. J.; Morris, R. H. Can. J. Chem. 1990, 68, 558–
564.
(10) Dias, E. L.; Nguyen, S. T.; Grubbs, R. H. J. Am. Chem. Soc. 1997,
119, 3887–3897.
(3) Brumbaugh, J. S.; Whittle, R. R.; Parvez, M.; Sen, A. Organome-
tallics 1990, 9, 1735–1747.
(11) Amoroso, D.; Fogg, D. E. Macromolecules 2000, 33, 2815–2818.
(12) Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. Organometallics
2001, 20, 1047–1049.
(4) Richter, F.; Vahrenkamp, H. Chem. Ber. 1982, 115, 3243–3256.
(5) Luck, R.; Morris, R. H. Inorg. Chem. 1984, 23, 1489–1491.
(6) Wang, C.; Friedrich, S.; Younkin, T. R.; Li, R. T.; Grubbs, R. H.;
Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149–3151.
(13) Abdur-Rashid, K.; Faatz, M.; Lough, A. J.; Morris, R. H. J. Am.
Chem. Soc. 2001, 123, 7473–7474.
10.1021/om700360r CCC: $40.75
2008 American Chemical Society
Publication on Web 01/23/2008

504 Organometallics, Vol. 27, No. 4, 2008
Zhao et al.
1
and 161.8 MHz for 31P. The H and 13C{1H} resonances of the
partially deuterated solvents were used as the internal reference,
but the chemical shifts are reported with respect to TMS. All 31P
chemical shifts are reported relative to 85% H3PO4 as an external
reference. The infrared spectrum was recorded on a Spectrum One
FT-IR spectrometer (Perkin-Elmer). Elemental analysis was done
on a sample handled under Ar in the Department of Chemistry,
University of Toronto. Merrifield resin (4.3 mmol/g Cl loading;
2% cross-linked with divinylbenzene; 200–400 mesh particle size)
was purchased from Fluka. RuHCl(PPh3)3 was prepared according
to the literature procedure.28
ligands such as diamines12–14 and ꢀ-aminophosphines (eq
2).15–17 These are precatalysts for the asymmetric hydrogenation
of the polar bonds of ketones and imines where the amino group
plays a crucial role in the outer-sphere H+/H- transfer from a
ruthenium hydridoamine H-RuN-H grouping to the polar
bond.18
2 + L-NH2 f RuHC1(L-NH2)(binap) + PPh3 (2)
The amine complexes of eq 2 are usually less soluble than
PPh3 and can be separated and purified in acceptable yields.
We wondered whether alcohol ligands, such as L-OH, could
be used instead of L-NH2 to produce complexes of the type
RuHX(binap)(L-OH) and lead to active catalysts. These might
utilize a H-RuO-H motif in ketone hydrogenation. Complexes
with the HRu(C5R4OH) substructure are already known to
catalyze the outer-sphere hydrogenation of ketones.19–24 For
such an approach to succeed, it is important to remove traces
of free PPh3, which would compete with the weakly coordinating
alcohol donor for ruthenium. However the sponge reagents
mentioned seem too reactive. We therefore investigated the
approach described by Lipshutz and Blomgren,25 where PPh3
and OPPh3 can be scavenged by using an iodide-modified
Merrifield resin (chloromethylpolystyrene-divinylbenzene). This
allowed them to efficiently purify the C-C coupled products
of Pd-catalyzed Stille reactions and Ni-catalyzed Negishi,
Suzuki, and Kumada reactions. This report describes the
successful use of this purification method and the synthesis of
new hydrido alkoxo complexes of ruthenium. Other complexes
of this class have been identified as important species in the
catalytic hydrogenation of ketones.26,27
The catalytic hydrogenation experiments and the kinetic mea-
surements were performed under constant pressures of H2 gas in a
50 mL Parr high-pressure reactor. A constant temperature for these
experiments was maintained using a Fisher Scientific IsoTemp
1016D water bath. The samples were analyzed by chiral GC on a
Perkin-Elmer Autosystem XL with a Chrompack capillary column
(ChirasilDEX CB 25 m × 0.25 mm). Hydrogen was used as a
carrier gas at 5 psi in the column at 130 °C. The injector and FID
temperatures were 250 and 275 °C, respectively. The retention times
were as follows: acetophenone, 5.20 min; (R)-1-phenylethanol, 8.95
min; (S)-1-phenylethanol, 9.50 min.
Preparation of Potassium Dimethyl-2-pyridylmethoxide
(KOCMe2-2-py). Dimethyl-2-pyridylmethanol29 as well as the
corresponding lithium alkoxide30 have been described in the
literature. In this experiment, the precursor alcohol was prepared
by a modified literature method.31 A solution of 2-acetylpyridine
(10.0 g, 83 mmol) in 70 mL of THF was added to a THF solution
of methyl lithium (1.6 M, 56.2 mL, 90 mmol) and was reacted for
1 h at -95 °C (toluene/N2(l)) under Ar. After stirring overnight at
20 °C, the addition of aqueous NH4Cl solution (40.0 g NH4Cl, 100
mL of H2O) was followed by the addition of CHCl3 (200 mL) and
subsequent separation of the two layers. The solvents in the organic
phase were evaporated. Precipitation from diethyl ether/hexane
yielded a reddish-orange oil. Yield of dimethyl-2-pyridylmethanol:
4.40 g, 32 mmol (39%). Potassium hydride (0.300 g, 7.5 mmol)
was suspended in ca. 10 mL of THF and this was added dropwise
to a solution of the reddish-orange oil (1.02 g, 7.4 mmol) in ca. 10
mL of THF at –78 °C under N2. After stirring for 30 min, the solvent
was evaporated from the filtrate to yield a reddish solid, which
was redissolved in diethyl ether. The mixture was then filtered
through Celite, and the filtrate was concentrated. Addition of hexane
yielded an orange product that was isolated by filtration and dried
in vacuo. Yield of potassium dimethyl-2-pyridylmethoxide: 1.20 g
(92%). Overall yield: 36%. 1H NMR (DMSO-d6, δ): 8.66 (d, 3JHH
) 4.48 Hz, py), 8.26 (d, 3JHH ) 7.89 Hz, py), 7.85 (t, 3JHH ) 7.59
Hz, py), 7.31 (t, 3JHH ) 5.73 Hz, py), 1.64 (s, CH3). 13C{1H} NMR
(DMSO-d6, δ): 176.6, 146.6, 134.9, 119.25, 119.2 (py), 72.49
(quarternary C), 34.21 (CH3).
Experimental Section
General Information. All syntheses and manipulations except
for the preparation of iodide-modified Merrifield resin were carried
out under Ar or N2 atmosphere using conventional Schlenk line
and glovebox techniques. Dry, oxygen-free solvents were always
used. Tetrahydrofuran, diethyl ether, and hexane were distilled from
sodium benzophenone under argon. Deuterated solvents were
degassed and dried over activated molecular sieves. NMR spectra
were recorded on Mercury and Varian NMR System 400 MHz
1
spectrometers, which were 400 MHz for H, 100.4 MHz for 13C,
(14) Abdur-Rashid, K.; Clapham, S. E.; Hadzovic, A.; Harvey, J. N.;
Lough, A. J.; Morris, R. H. J. Am. Chem. Soc. 2002, 124, 15104–15118.
(15) Guo, R.; Lough, A. J.; Morris, R. H.; Song, D. Organometallics
2004, 23, 5524–5529. Addition: Organometallics, 2005, 24 (13), 3354–
3354.
(16) Abdur-Rashid, K.; Guo, R.; Lough, A. J.; Morris, R. H.; Song, D.
AdV. Syn. Catal. 2005, 347, 571–579.
Preparation of Potassium Diphenyl-2-pyridylmethoxide
(KOCPh2-2-py). Diphenyl-2-pyridylmethanol32,33 as well as the
corresponding lithium alkoxide30 have been described in the
literature. A THF (44 mL) solution of 2-bromopyridine (6.17 mL,
65 mmol) was slowly added to another THF (44 mL) solution of
butyl lithium (1.6 M, 43.5 mL, 70 mmol). Stirring at -95 °C
(toluene/liq. N2) for 45 min under Ar resulted in a deep red solution.
Benzophenone (12.7 g, 70 mmol) was then added, followed by
(17) Guo, R.; Morris, R. H.; Song, D. J. Am. Chem. Soc. 2005, 127,
516–517.
(18) Clapham, S. E.; Hadzovic, A.; Morris, R. H. Coord. Chem. ReV.
2004, 248, 2201–2237.
(19) Blum, Y.; Czarkie, D.; Rahamim, Y.; Shvo, Y. Organometallics
1985, 4, 1459–1461.
(20) Shvo, Y.; Czarkie, D.; Rahamim, Y.; Chodosh, D. F. J. Am. Chem.
Soc. 1986, 108, 7400–7402.
(21) Casey, C. P.; Johnson, J. B.; Singer, S. W.; Cui, Q. J. Am. Chem.
Soc. 2005, 127, 3100–3109.
(22) Casey, C. P.; Singer, S. W.; Powell, D. R.; Hayashi, R. K.; Kavana,
M. J. Am. Chem. Soc. 2001, 123, 1090–1100.
(23) Casey, C. P.; Singer, S. W.; Powell, D. R. Can. J. Chem. 2001,
79, 1002–1011.
(28) Schunn, R. A.; Wonchoba, E. R. Inorg. Synth. 1971, 13, 131–134.
(29) Backman, G. B.; Micucci, D. D. J. Am. Chem. Soc. 1948, 70, 2381–
2384.
(30) ver der Schaaf, P. A.; Boersma, J.; Smeets, W. J. J.; Spec, A. L.;
van Kohen, G. Inorg. Chem. 1993, 32, 5108.
(31) Wibaut, J. P.; De Jonge, A. P.; van der Voort, H. G. P.; Otto,
P. P. H. L. Recl. TraV. Chim. Pays-Bas. 1951, 70, 1054.
(32) Tschitschib, A. E. J. Physiol. (Paris, 1946–1992) 1907, 75, 526–
528.
(24) Casey, C. P.; Bikzhanova, G. A.; Cui, Q.; Guzei, I. A. J. Am. Chem.
Soc. 2005, 127, 14062–14071.
(25) Lipshutz, B. H.; Blomgren, P. A. Org. Lett. 2001, 3, 1869–1871.
(26) Hamilton, R. J.; Bergens, S. H. J. Am. Chem. Soc. 2006, 128,
13700–13701.
(27) Daley, C. J. A.; Bergens, S. H. J. Am. Chem. Soc. 2002, 124, 3680–
3691.
(33) Emmert, B.; Asendorf, E. Ber. Dtsch. Chem. Ges. 1939, 72B, 1188–
1194.

Synthesis of Ruthenium Hydride Complexes
Organometallics, Vol. 27, No. 4, 2008 505
another portion of THF (40 mL), yielding a deep green mixture.
After stirring overnight at room temperature, the mixture turned
blue. The subsequent addition of H2O (50 mL) gave a yellow
mixture, which was separated into two layers. The aqueous phase
was washed with CHCl3 (15 mL), and the combined extracts were
dried over MgSO4 overnight. Evaporation of the solvents then
yielded a white solid product. Yield of diphenyl-2-pyridylmethanol:
10.3 g, 62%. When the alcohol (1.00 g, 3.8 mmol) was reacted
with potassium hydride (0.153 g, 3.8 mmol) in THF (20 mL) under
N2, H2 gas evolved and a yellow solution with white precipitate
resulted. The mixture was filtered through Celite and washed
extensively with THF in order to remove residual potassium
hydride. The solvent was evaporated from the filtrate in Vacuo.
Hexane was then added to the concentrated solution in order to
precipitate the white product. The product was filtered, washed with
hexane, and dried in Vacuo. Yield: 0.906 g, 3.0 mmol (79%).
Scheme 1
of about 5% free PPh3. This complex does not withstand the
conditions used for the resin method of purification or for ESI-MS
or EI-MS characterization.
1
Preparation of RuH(OCPh2-2-py)((R)-binap) (5). The proce-
dure for synthesizing 4 was followed to react RuHI((R)-binap)(PPh3)
(120 mg, 0.11 mmol) with KOCPh2-2-py (61 mg, 0.2 mmol). Yield:
Overall yield: 49%. H NMR (DMSO-d6, δ): 8.33, 7.97 (m, py),
7.52, 7.39, 7.09–6.97 (m, phenyl, pyridyl). 13C{1H} NMR (DMSO-
d6, δ): 172.9 (py), 154.1 (Ph), 146.3 (py), 135.0 (py), 128.3 (Ph),
126.1 (Ph), 124.2 (Ph), 122.2 (py), 119.7 (py), 83.49 (quarternary
C).
1
25 mg, 0.024 mmol (23%). H NMR (CD2Cl2, δ): 8.59 – 6.17(m,
Ph, py), -20.36 (dd, 2JHP ) 26.74, 42.71 Hz, RuH). 13C{1H} NMR
(CD2Cl2, δ): 137.9–123.2 (binaphthyl, py), 65.83 (quarternary C).
31P{1H} NMR (CD2Cl2, δ): 90.07 (d, 2JPP ) 39.4 Hz, binap), 63.20
(d,2JPP ) 39.4 Hz, binap). The spectra also revealed the presence
of about 7% free PPh3. This complex does not tolerate the conditions
used for ESI-MS or EI-MS.
Preparation of Iodide-Modified Merrifield Resin. High-loading
4.3 mmol Cl/g Merrifield resin (1.92 g) was stirred with sodium
iodide (1.24 g) in acetone (10 mL). The resultant solid was filtered
and washed extensively with water in order to eliminate the NaCl
byproduct and any unreacted NaI. The resin was then washed with
acetone and dried in Vacuo to give 2.56 g of the product.
Preparation of RuHI((R)-binap)(PPh3) (3). RuHCl(PPh3)3 (638
mg, contains 1 equiv of free PPh3, 0.54 mmol) was reacted with
(R)-binap (430 mg, 0.69 mmol) for 16 h in refluxing THF (15 mL)
under N2. The 31P NMR spectrum recorded at this time on the
reaction mixture with an insert (C6D6/trimethyl phosphite) as an
internal reference indicated the presence of RuHCl((R)-binap)(PPh3)
as well as substantial amounts of free PPh3 and binap and minor
amounts of phosphine oxides. Iodide-modified Merrifield resin (900
mg) was added to the mixture and was left stirring overnight. The
solvent was evaporated, diethyl ether (7 mL) was added to the con-
centrated solution, and Celite was used to filter out the phosphine-
bound resin. The filtrate was concentrated to 3 mL, and hexane (4
mL) was added to precipitate the product. The red solid was filtered
out, washed with hexane, and dried in Vacuo. The 31P NMR
spectrum of the isolated product showed no evidence for the
presence of free phosphines and phosphine oxides. After the product
was isolated, dark red crystals were collected from the filtrate. Yield:
Catalytic H2-Hydrogenation. The alkoxide complex 4 or 5 (5
mg, ca. 5 µmol) and acetophenone (305 mg, 2.5 mmol) were
dissolved in 2-propanol or benzene (4 mL) and stirred under 10
atm of H2 at 22 °C. The conversion to 1-phenylethanol was
monitored by chiral gas chromatography. Complex 4 contaminated
i
with 5% PPh3 in PrOH gave only 14% conversion to 1-phenyle-
thanol (13% ee (R)) after 3 days. Complex 5 was not active in
iPrOH. Using 5 contaminated with 12% PPh3 in benzene gave 22%
conversion to 1-phenylethanol (49% ee (R)) after 23 h. With 7%
contamination by PPh3 of 5, the conversion after 23 h was only
6% (33% ee (R)).
Attempted Michael Addition Reactions. The alkoxide complex
4 or 5 (5 mg, ca. 5 µmol), dimethyl malonate (66 mg, 0.5 mmol),
and 2-cylcohexen-1-one (48 mg, 0.5 mmol) were stirred in THF
under Ar. There was no conversion after 24 h.
Preparation of trans-RuHI(dppe)2 (6). RuHCl(PPh3)3 (150 mg,
0.12 mmol contaminated with PPh3) was stirred with dppe (100
mg, 0.25 mmol added in two portions with monitoring by 31P NMR
to ensure complete conversion) in THF (10 mL) under N2 for 2 h,
during which time the color changed from purple to brownish
orange. The mixture was filtered through Celite. Iodide-modified
Merrifield resin (570 mg) was added to the filtrate, and the resulting
mixture was stirred overnight. The resin was filtered out with Celite,
and the filtrate was concentrated to approximately 1 mL, from which
a yellow precipitate formed. The product was filtered and dried in
Vacuo and shown to be spectroscopically pure. Elemental analyses
were acceptable for H and N but low for C probably due to a
1
494 mg, 83%. H NMR (CD2Cl2, δ): 8.2–6.1 (m, phenyl, binaph-
2
thyl), -22.87 (dt, JHP ) 23.54, 33.16 Hz, RuH). 13C{1H} NMR
(CD2Cl2, δ): 138.2–124.3 (binaphthyl, phenyl). 31P{1H} NMR
(CD2Cl2, δ): 81.91 (X part of ABX, 2JPP ) 20.4, 38.3 Hz, binap),
2
45.09 (B part of ABX, JPP ) 38.3, 290.7 Hz, binap), 37.65 (A
2
part of ABX, JPP ) 20.4, 290.7 Hz, PPh3). IR (CH2Cl2, cm-1):
1967 (ν(RuH)). Anal. Calcd for RuIP3C62H48: C, 66.85; H, 4.34.
Found: C, 66.62, H, 4.24. ESI-MS (m/z) of complex in methanol:
1015.2 [RuH(binap)(PPh3)(OHCH3)]+.
1
combustion problem. Yield: 65 mg, 53%. H NMR (CDCl3, δ):
Preparation of RuH(OCMe2-2-py)((R)-binap) (4). RuHI((R)-
binap)(PPh3) (170 mg, 0.16 mmol) and KOCMe2-2-py (70 mg, 0.40
mmol) were stirred in THF (15 mL) overnight under Ar. The
solution was filtered through Celite to eliminate potassium iodide.
The solution was concentrated under vacuum, and then diethyl ether
(6 mL) was added. The solution was again concentrated to 2 mL,
and hexane (3 mL) was added to precipitate the product. The
reddish-brown precipitate was filtered out, washed with hexane,
7.2–6.6 (m, phenyl), 2.48 (m, P(CH2)2), 1.72 (m, P(CH2)2), -15.86
(qnt, 2JHP ) 19.45 Hz, RuH). 31P{2H} NMR (CDCl3, δ): 61.98 (s,
dppe). These NMR data agree with those reported by Hirano et
al.34 and Gandhi et al.35
Preparation of trans-RuHI(dppb)2 (7). The procedure for the
preparation of 6 was followed. Reaction of RuHCl(PPh3)3 (135 mg,
0.09 mmol contaminated with PPh3) with dppb (75 mg, 0.18 mmol)
in THF (10 mL) yielded a yellow solution. Treatment with iodide-
modified Merrifield resin (700 mg) removed the free PPh3 and dppb
1
and dried in Vacuo. Yield: 32 mg, 0.037 mmol (24%). H NMR
(CD2Cl2, δ): 8.42–6.21 (m, Ph, py), 1.66 (s, CH3), -19.79 (dd,
2JHP ) 27.05, 42.14 Hz, RuH). 2C{1H} NMR (CD2Cl2, δ):
138.0–124.0 (binaphthyl, py), 65.86 (quarternary C), 31.79 (CH3).
31P{1H} NMR (CD2Cl2, δ): 90.45 (d, 2JPP ) 36.5 Hz, binap), 62.99
(d, 2JPP ) 36.5 Hz, binap). The spectra also revealed the presence
(34) Hirano, M.; Takenaka, A.; Mizuho, Y.; Hiraoka, M.; Komiya, S.
J. Chem. Soc., Dalton Trans. 1999, 3209–3216.
(35) Gandhi, T.; Nethaji, M.; Jagirdar, B. R. Inorg. Chem. 2003, 42,
4798–4800.

506 Organometallics, Vol. 27, No. 4, 2008
Zhao et al.
Scheme 2
Scheme 3
from the reaction mixture. The sample was spectroscopically pure
and gave acceptable elemental analyses for N and H but low in C.
Yield: 63 mg, 65%. 1H NMR (CDCl3, δ): 7.6–6.7 (m, phenyl),
A mixture produced via eq 1, which contained complex 2,
free PPh3, OPPh3, binap, and binap oxides, was treated with
iodide-modified resin (Scheme 2) for 2 h in THF and then
filtered. The iodo resin (1 g containing e 3.1 mmol/g I) was
determined to react with up to approximately 2.1 mmol of
phosphine. The 31P NMR spectrum of the filtrate showed that
the isolated product was free of phosphorus-containing con-
taminants. However complex 2 was converted quantitatively into
the new, red iodo complex, RuHI(PPh3)((R)-binap) (3), which
was recovered in 89% yield.
2
0.91 (m, P(CH2)4), 0.52 (m, P(CH2)4), -16.42 (tt, JHP ) 15.75,
23.56 Hz, RuH). 13C{1H} NMR (CDCl3, δ): 133.5–126.7 (phenyl),
30.6 (CH2), 29.6 (CH2), 21.6 (CH2), 12.9 (CH2). 31P{1H} NMR
(CDCl3, δ): 71.37 (t, 2JPP ) 31.2 Hz, dppb), 54.76 (t, 2JPP ) 31.2
Hz, dppb). ESI-MS (m/z) of complex in methanol: 955.3 [RuH(d-
ppb)2]+.
Results and Discussion
Complex 3 can also be prepared in 83% yield directly from
RuHCl(PPh3)3 (contaminated with 1 equiv of PPh3) with the
use of the resin (Scheme 3).
While Lipshutz and Blomgren directly added Merrifield
resin and NaI to solutions contaminated with PPh3,25 we
found it advantageous to first isolate the iodo-substituted resin
(Scheme 1). The white Merrifield resin was converted into a
yellow iodo-substituted resin by reaction with NaI in acetone.
This was then washed with water and acetone and dried in
Vacuo.
Complex 3 in CD2Cl2 has a characteristic hydride reso-
nance as a doublet of triplets at -22.87 ppm in the 1H NMR
spectrum and a diagnostic ABX pattern in the 31P{1H} NMR
spectrum. RuHI(PPh3)((R)-binap) readily crystallizes out of
THF, diethyl ether, and hexane as long as the solution
contains no impurities, and the complex is fully converted
to the iodo product. This is significant because we have not
been able to obtain crystals of the useful synthon RuHCl-
(PPh3)((R)-binap).
The structure of a red crystal 3 is shown in Figure 1. The
metal coordination geometry in 3 is distorted trigonal bipyra-
midal with P(2) and P(3) approximately axial (P(2)-Ru(1)-P(3)
156.45(4)°). The equatorial angles involving iodide (H(1RU)-Ru
(1)-I(1) 136(2)°, P(1)-Ru(1)-I(1) 141.27(3)°) are large, while
all of the P-Ru-H angles are small, falling in the range 79–83°.
This contrasts with the angles in the equatorial plane of the
related five-coordinate complexes RuHCl(PPh2NHC6H10
NHPPh2)(PPh3) (H-Ru-Cl 158.7(12)°, P-Ru-Cl 108.92
(3)°)12 and RuHCl(bpap)(PPh3) (H-Ru-Cl 168.8(8)°, P-Ru-Cl
110.54(2)°),36 where the smaller chloride ligand takes up a
position that defines a distorted square pyramid. The Ru-I bond
distance of 2.7332(4) Å is similar to the ones found in
Ru(P(CH2)6N3)3I2(OH2), 2.710(1) and 2.717(1) Å, 37 [Ru(CO)2
I(P(OiPr)2CH2CH2CH2PPhCH2CH2CH2P(OiPr)2)]I, 2.7582(7)
Figure 1. Structure of RuHI((R)-binap)(PPh3) (3). Selected bond
distances (Å) and angles (deg): I(1)-Ru(1) 2.7332(4), Ru(1)-H(1RU)
1.59(5), Ru(1)-P(1) 2.214(1), Ru(1)-P(2) 2.313(1), Ru(1)-P(3)
2.376(1); H(1RU)-Ru(1)-P(1) 83(2), H(1RU)-Ru(1)-P(2) 80(2),
P(1)-Ru(1)-P(2) 90.37(4), H(1RU)-Ru(1)-P(3) 79(2), P(1)-Ru
(1)-P(3)98.85(4),P(2)-Ru(1)-P(3)156.45(4),H(1RU)-Ru(1)-I(1)
136(2), P(1)-Ru(1)-I(1) 141.27(3), P(2)-Ru(1)-I(1) 92.08(3),
P(3)-Ru(1)-I(1) 94.04(3).
(36) Hadzovic, A.; Lough, A. J.; Morris, R. H.; Pringle, P. G.; Zambrano-
Williams, D. E. Inorg. Chim. Acta 2006, 359, 2864–2869.
(37) Smolenski, P.; Pruchnik, F. P.; Ciunik, Z.; Lis, T. Inorg. Chem.
2003, 42, 3318.

Synthesis of Ruthenium Hydride Complexes
Organometallics, Vol. 27, No. 4, 2008 507
Scheme 4
Scheme 5
Å,38 [RuI(dppp)2]PF6, 2.705(1) Å,39 and [RuI(dppe)2]PF6,
2.6856(8) Å.39
With the pure complex 3 in hand, a variety of new hydride
complexes can be prepared including the new hydrido alkoxide
complexes RuH(OCMe2-2-py)((R)-binap) (4) and RuH(OCPh2-
2-py)((R)-binap) (5) (Scheme 4).
The utility of the resin to facilitate the synthesis of ruthenium
complexes was further explored in the reactions of RuHCl
(PPh3)3 with diphosphine ligands. The diphosphines 1,2-
diphenylphosphinoethane and 1,4-diphenylphosphine butane
were used to prepare the known complex trans-RuH(I)(dppe)2
(6) and the new complex trans-RuH(I)(dppb)2 (7) from RuHCl
(PPh3)3 that was contaminated with PPh3 in excellent yield
(Scheme 5).
The reddish-brown products 4 and 5 are rare, reactive five-
coordinate hydrido alkoxide complexes. They are soluble in
most common solvents to give solutions that immediately
turn green upon exposure to air. A characteristic doublet of
doublets at -19.79 ppm for 4 and -20.36 ppm for 5 was
observed for the hydride in the 1H NMR spectra of the
hydrido alkoxide complexes in CD2Cl2. An AB pattern was
seen in the 31P{1H} NMR spectrum of each of 4 and 5,
indicating complete dissociation of PPh3 from the complexes.
The isolated complexes were still contaminated with 5–7%
of PPh3. An attempt at using the resin treatment failed; instead
it destroyed these very reactive hydrido alkoxide complexes.
Complexes 4 and 5 do not react with 1 atm of H2 in C6D6,
unlike the related amido complex RuH(PPh3)2-
(NHCMe2CMe2NH2), which produces a trans dihydride
diamine complex.14
While the NMR spectra of complex 6 are simple, consisting
1
of a quintet in the hydride region of the H spectrum and a
singlet in the 31P{1H} spectrum, those of complex 7 are
somewhat unexpected for a trans complex. The hydride
resonance is a triplet of triplets, while the 31P{1H} NMR
spectrum has two triplets. These spin patterns have been
observed before, for example, for the complexes
trans-[RuH(η2-H2)((R)-binap)2]+,41 trans-[RuHL((R,R)-Me-
duphos)2]+, L ) H2, N2,42 and trans-RuHCl((R,R)-diop)2.43
The steric demands of these diphosphine ligands force the
phosphorus donors of the chelate to alternate in position
above and below the equatorial plane of complex. For the
dppb ligands of 7, one set of PPh2 groups that are trans to
each other are closer to the hydride, while the other set is
closer to the iodide, thus producing the features observed in
the NMR spectra.
Complexes 4 and 5 were tested as catalysts for the hydro-
i
genation of acetophenone using H2 or PrOH as the source of
the hydrogen. No evidence for transfer hydrogenation from
iPrOH was observed in either highly phosphine-contaminated
hydrido alkoxide complexes or those with only 5–7% PPh3. The
H2 hydrogenation activity of complex 5 increased with the
amount of the PPh3 contamination. In general these alkoxide
complexes were not active catalysts compared to the amido
complexes RuH(PPh3)2(NHCMe2CMe2NH2) and RuH(binap)
(NHCMe2CMe2NH2).14 Complexes 4 and 5 were inactive as
catalysts for the Michael addition reaction of dimethyl ma-
lonate with 2-cyclohexen-1-one. In contrast, RuH(PPh3)2
(NHCMe2CMe2NH2) is an excellent catalyst under similar
conditions.40 These results imply that the alkoxide oxygen is
not basic enough to effect the heterolytic splitting of dihydrogen
or the deprotonation of dimethyl malonate, steps that are thought
to be essential to the mechanism of action of the related amido
catalysts.40
Conclusions
We have reported the use of the iodide-modified Merrifield
resin as a scavenger of byproduct in the synthesis of a useful
new complex RuHI((R)-binap)(PPh3) (3). It was also used
effectively in the synthesis of the known complex trans-
RuH(I)(dppe)2 and the new complex trans-RuH(I)(dppb)2.
Complex 3 was used to prepare the novel hydrido alkoxide
complexes RuH(OCMe2-2-py)((R)-binap) (4) and RuH(OCPh2-
2-py)((R)-binap) (5). These are poor catalysts for asymmetric
hydrogenation, transfer hydrogenation, and Michael addition
reactions, presumably because of the weak basicity of the
alkoxide in these complexes.
(38) Jaunky, P.; Schmalle, H. W.; Blacque, O.; Fox, T.; Berke, H. J.
Organomet. Chem. 2005, 690, 1429.
(41) Ogasawara, M.; Saburi, M. J. Organomet. Chem. 1994, 482, 7–
(39) Barthazy, P.; Broggini, D.; Mezzetti, A. Can. J. Chem. 2001, 79,
904.
14.
(42) Schlaf, M.; Lough, A. J.; Morris, R. H. Organometallics 1997, 16,
1253–1259.
(40) Clapham, S. E.; Guo, R.; Iuliis, M. Z.-D.; Rasool, N.; Lough, A.;
Morris, R. H. Organometallics 2006, 25, 5477–5486.
(43) James, B. R.; Wang, D. K. W. Can. J. Chem. 1980, 58, 245–250.

508 Organometallics, Vol. 27, No. 4, 2008
Zhao et al.
Supporting Information Available: X-ray crystallographic data
in CIF format for compound 3. This material is available free of
charge via the Internet at http://pubs.acs.org.
Acknowledgment. NSERC Canada is thanked for a
Discovery Grant to R.H.M. and an Undergraduate Student
Award to N.I. Xerox Research Centre of Canada is also
acknowledged for a scholarship to X.Z. Dr. C. Sui-Seng and
Dr. S. E. Clapham are thanked for assistance.
OM700360R