Probing the effect of the ligand X on the properties and catalytic activity of the complexes RuHX(diamine)(PPh3)2 (X = OPh, 4-SC 6H4OCH3, OPPh2, OP(OEt)2, CCPh, NCCHCN, CH(COOMe)2; diamine = 2,3-Diamino-2,3-dimethylbutane, (R,R)-1,2-Diaminocyclohexane)

Article abstract of DOI:10.1021/om060661q

The reactivity of the ruthenium-amido bond in RuH(NH₂CMe ₂CMe₂NH)(PPh₃)₂ (1) toward weak acids HX and the influence of the X group on the catalytic activity of the resulting complex are explored here. Complex 1 reacts with the weak acids HX (X = OPh, 4-SC₆H₄OMe, OPPh₂, OP(OEt)₂, CCPh, NCCHCN, CH(COOMe)₂) to form complexes of the type RuHX(tmen)(PPh₃)₂ (tmen = 2,3-diamino-2,3-dimethylbutane). The complexes with X = PhOH...OPh, 4-SC₆H₄OMe, OP(OEt)₂, CCPh, CH-(COOMe)₂ have been characterized by X-ray crystallography. The X group is situated trans to the hydride in all cases and is bonded to ruthenium via the donor atoms O, S, P, C, and O, respectively. The phenol in the phenoxide adduct RuH(PhOH...OPh)(tmen)(PPh ₃)₂ bridges via hydrogen bonds between the alkoxide oxygen and an amino hydrogen to form a six-membered RuO...HO...HN ring. One carbonyl oxygen of the malonate bonds to the Ru, while the other accepts a hydrogen bond from an amino hydrogen. The analogous complexes RuHX(dach)(PPh₃)₂ (dach = (R,R)-1,2-diaminocyclohexane) were synthesized by the reaction of RuHCl(dach)(PPh₃)₂ (2) with an equimolar amount of potassium tert-butoxide and HX. For all of the complexes the Ru-H vibrational frequency and the ¹H NMR chemical shift of Ru-H correlate with the electronegativity of the trans atom X. The amido complex 1 and the complexes with X = CH(COOMe)₂ and OPh are active catalysts for the Michael addition of dimethyl malonate to 2-cyclohexen-1-one. RuH(NCCHCN)(tmen)(PPh₃)₂ reacts with the Michael acceptor 2-cyclohexen-1-one to give RuH(NCC(C₆H ₉O)CN)(tmen)(PPh₃)₂, a trapped Michael adduct that has been characterized by X-ray crystallography. On the basis of these observations a catalytic cycle for the Michael addition reactions is proposed that involves the addition of the C-H bond of the Michael donor to the Ru-N bond followed by attack on the Michael acceptor and elimination of the Michael adduct, possibly by a 1,3-proton migration as observed for the malononitrile adduct. Only the complexes with X = H, CCPh are catalysts or precatalysts for the hydrogenation of neat acetophenone to 1-phenylethanol in the absence of added base under 10 atm of H₂ at 20°C. Evidence is provided that the phenylacetylide complexes are precatalysts that are converted to the active trans-dihydride catalysts (X = H).

Full text of DOI:10.1021/om060661q

Organometallics 2006, 25, 5477-5486
5477
Probing the Effect of the Ligand X on the Properties and Catalytic
Activity of the Complexes RuHX(diamine)(PPh3)2 (X ) OPh,
4-SC6H4OCH3, OPPh2, OP(OEt)2, CCPh, NCCHCN, CH(COOMe)2;
diamine ) 2,3-Diamino-2,3-dimethylbutane,
(R,R)-1,2-Diaminocyclohexane)
Sean E. Clapham, Rongwei Guo, Marco Zimmer-De Iuliis, Nailyn Rasool, Alan Lough, and
Robert H. Morris*
Department of Chemistry, UniVersity of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6,
Canada
ReceiVed July 21, 2006
The reactivity of the ruthenium-amido bond in RuH(NH2CMe2CMe2NH)(PPh3)2 (1) toward weak
acids HX and the influence of the X group on the catalytic activity of the resulting complex are explored
here. Complex 1 reacts with the weak acids HX (X ) OPh, 4-SC6H4OMe, OPPh2, OP(OEt)2, CCPh,
NCCHCN, CH(COOMe)2) to form complexes of the type RuHX(tmen)(PPh3)2 (tmen ) 2,3-diamino-
2,3-dimethylbutane). The complexes with X ) PhOH···OPh, 4-SC6H4OMe, OP(OEt)2, CCPh, CH-
(COOMe)2 have been characterized by X-ray crystallography. The X group is situated trans to the hydride
in all cases and is bonded to ruthenium via the donor atoms O, S, P, C, and O, respectively. The phenol
in the phenoxide adduct RuH(PhOH···OPh)(tmen)(PPh3)2 bridges via hydrogen bonds between the alkoxide
oxygen and an amino hydrogen to form a six-membered RuO‚‚‚HO‚‚‚HN ring. One carbonyl oxygen of
the malonate bonds to the Ru, while the other accepts a hydrogen bond from an amino hydrogen. The
analogous complexes RuHX(dach)(PPh3)2 (dach ) (R,R)-1,2-diaminocyclohexane) were synthesized by
the reaction of RuHCl(dach)(PPh3)2 (2) with an equimolar amount of potassium tert-butoxide and HX.
1
For all of the complexes the Ru-H vibrational frequency and the H NMR chemical shift of Ru-H
correlate with the electronegativity of the trans atom X. The amido complex 1 and the complexes with
X ) CH(COOMe)2 and OPh are active catalysts for the Michael addition of dimethyl malonate to
2-cyclohexen-1-one. RuH(NCCHCN)(tmen)(PPh3)2 reacts with the Michael acceptor 2-cyclohexen-1-
one to give RuH(NCC(C6H9O)CN)(tmen)(PPh3)2, a trapped Michael adduct that has been characterized
by X-ray crystallography. On the basis of these observations a catalytic cycle for the Michael addition
reactions is proposed that involves the addition of the C-H bond of the Michael donor to the Ru-N
bond followed by attack on the Michael acceptor and elimination of the Michael adduct, possibly by a
1,3-proton migration as observed for the malononitrile adduct. Only the complexes with X ) H, CCPh
are catalysts or precatalysts for the hydrogenation of neat acetophenone to 1-phenylethanol in the absence
of added base under 10 atm of H2 at 20 °C. Evidence is provided that the phenylacetylide complexes are
precatalysts that are converted to the active trans-dihydride catalysts (X ) H).
splits heterolytically across the ruthenium-amido bond to form
the trans-dihydrido diamino complex trans-RuH2(tmen)(PPh3)2.
Complex 1 reacts reversibly with other weak acids, including
Introduction
Late-transition-metal amido complexes are of interest as
catalysts for polar bond transfer hydrogenation and H2
hydrogenation1-3 and as intermediates in catalytic hydroami-
nation and other C-N bond-forming reactions such as arylamine
synthesis.4 The amido hydrido complex RuH(NH2CMe2CMe2-
NH)(PPh3)2 (1)3 is a catalyst for the H2 hydrogenation of ketones
to alcohols. Metal- and nitrogen-based reactivity are key to the
catalyst’s activity. In the catalytic cycle, dihydrogen, a very weak
acid (pKRTHF(H2/H-) > 44,5 pKaMeCN(H2/H-) ) 76/1.37 ) 556),
DMSO
acetophenone (pKa
) 24.7),7 to give the enolate complex
t
RuH(OCPhdCH2)(tmen)(PPh3)2 and with the alcohols BuOH
and iPrOH (pKaDMSO ) 30-32) to give the alkoxide complexes
RuH(OR)(tmen)(PPh3)2.3 It reacts irreversibly with formic acid
DMSO
(pKa
≈ 11) to give the formate complex RuH(OCHdO)-
(tmen)(PPh3)2.3 These are reactions of a 16-electron complex
with a dative8 amido group.
Another class of ruthenium complexes with dative amido
bonds that show metal-ligand bifunctional reactivity are the
* To whom correspondence should be addressed. E-mail: rmorris@
chem.utoronto.ca.
(1) Haack, K. J.; Hashiguchi, S.; Fujii, A.; Ikariya, T.; Noyori, R. Angew.
Chem., Int. Ed. Engl. 1997, 36, 285-288.
(2) Ikariya, T.; Murata, K.; Noyori, R. Org. Biomol. Chem. 2006, 4, 393-
(5) Abdur-Rashid, K.; Fong, T. P.; Greaves, B.; Gusev, D. G.; Hinman,
J. G.; Landau, S. E.; Morris, R. H. J. Am. Chem. Soc. 2000, 122, 9155-
9171.
(6) Raebiger, J. W.; Miedaner, A.; Curtis, C. J.; Miller, S. M.; Anderson,
O. P.; DuBois, D. L. J. Am. Chem. Soc. 2004, 126, 5502-5514.
(7) Bordwell, F. B. Acc. Chem. Res. 1988, 21, 456-463.
(8) Fulton, J. R.; Holland, A. W.; Fox, D. J.; Bergman, R. G. Acc. Chem.
Res. 2002, 35, 44-56.
406.
(3) 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.
(4) Hartwig, J. F. Acc. Chem. Res. 1998, 31, 852-860.
10.1021/om060661q CCC: $33.50 © 2006 American Chemical Society
Publication on Web 09/27/2006

5478 Organometallics, Vol. 25, No. 22, 2006
Clapham et al.
Chart 1. Coordination Mode of the X Ligand in the
η6-arene complexes Ru(arene)((S,S)-NHCHPhCHPhNTs).1 These
are catalysts for the asymmetric transfer hydrogenation of
ketones and imines9 and the Michael addition of malonates and
â-keto esters to R,â-unsaturated ketones10,11 and nitroalkenes.12
In these reactions the C-H bond of the Michael donor is
proposed to add across the Ru-amido bond, and in one case a
carbon-bonded malonate complex, Ru[CH(CO2CH3)2][(R,R)-
Tsdpen](η6-mesitylene), was structurally characterized.10 Reac-
tion of the η6-cymene complex with an acidic alcohol produces
the unstable alkoxide complexes Ru(cymene)(OCH2CF3)(((S,S)-
NHCHPhCHPhNTs).13 We show here that complex 1 and some
of its derivatives are also catalysts for the Michael addition
reaction, although they operate via an oxygen-bonded malonate
route. In addition, a Michael adduct has been trapped at the
metal in one case.
Complex trans-RuHX(diamine)(PPh3)2 Arranged by the
Group in the Periodic Table of the Atom Attached to
DMSO
Ruthenium and the pKa
Values of the Weak Acid HX
Used To Generate the Complex According to Eq 1 or 2
Fryzuk and co-workers14,15 and Caulton and co-workers16
have observed HX addition reactions, including intramolecular
C-H addition across the Ru-amido bond in pincer ligand
complexes of the type Ru(N(SiMe2CH2PPh2)2)(PPh3)Cl and
Ru(N(SiMe2CH2PtBu2)2)OTf. There is also much recent chem-
istry concerning nondative amido complexes in 18-electron
ruthenium complexes where the nitrogen is the site of reactivity,
serving as a very strong base.8,17-21 For example, the 18-electron
ruthenium amido complex RuH(NH2)(dmpe)220 reacts with weak
acids with a range of pKa values: methanol (29.0 in DMSO),
water (31.2 in DMSO), phenol (18 in DMSO), aniline (30.6 in
DMSO), dihydrogen (>44 in THF5), phenylacetonitrile (22.3
in DMSO), fluorene (22.9 in THF), phenylacetylene (28.7 in
DMSO), and triphenylmethane (31.5 in THF). These reactions
are thought to proceed via protonation at nitrogen without
coordination to the metal to produce an ion pair.
amine)25 and RuH(BH4)(diamine)(diphosphinite)26 allow the
successive enantioselective Michael addition reactions of ma-
lonates with enones followed by enantioselective hydrogenation.
Ruthenium-amido chemistry is suspected to be key to this
reactivity.
An objective of the current work is to determine the influence
of the X group trans to hydride in the complexes RuHX-
(diamine)(PPh3)2 on catalytic activity toward H2 hydrogenation
of ketones and Michael addition reactions. It is known that X
) H is an active catalyst, while X ) Cl is inactive for the
hydrogenation reaction in the absence of added base.3,22,23
Similarly, in the related RuHX(diamine)(diphosphine) com-
plexes X ) H,3 BH424 are catalysts in the absence of base, while
X ) Cl is inactive. The complexes RuH(BH4)(binap)(phosphine-
Results and Discussion
Preparation. The complexes RuHX(tmen)(PPh3)2 are syn-
thesized by reacting 1 with the appropriate weak acid in toluene
under argon, as shown in eq 1, where HX is HOCHO,3 HOPh,
CH2(COOMe)2, 4-HSC6H4OMe, NCCH2CN, OPHPh2, OPH-
3
(OEt)2, H2 or HCCPh.
(9) Noyori, R.; Hashiguchi, S. Acc. Chem. Res. 1997, 30, 97-102.
(10) Watanabe, M.; Murata, K.; Ikariya, T. J. Am. Chem. Soc. 2003,
125, 7508-7509.
(11) Wang, H.; Watanabe, M.; Ikariya, T. Tetrahedron Lett. 2005, 46,
963-966.
A variety of weak acids with a range of pKaDMSO(HX) values
was employed to produce a range of structures with O, S, N, P,
H, and C donor atoms, as listed in Chart 1. The weak acids
aniline (pKaDMSO ) 30.6), triphenylmethane (pKa ) 31.5), and
triethoxysilane as reagents in eq 1 gave no reaction.
In the reaction of eq 1, the red solution of 1 in toluene quickly
becomes yellow upon addition of the weak acid. The charac-
teristically yellow products are precipitated with the addition
of hexanes. Solutions were found to be very air sensitive, readily
turning black upon exposure to air. Solid samples are less air
sensitive, gradually darkening within minutes to hours.
The modes of coordination of the X ligands shown in Chart
1 were determined by a combination of NMR, IR, and X-ray
crystallographic studies, as described below.
(12) Watanabe, M.; Ikagawa, A.; Wang, H.; Murata, K.; Ikariya, T. J.
Am. Chem. Soc. 2004, 126, 11148-11149.
(13) Koike, T.; Ikariya, T. Organometallics 2005, 24, 724-730.
(14) Fryzuk, M. D.; Montgomery, C. D.; Rettig, S. J. Organometallics
1991, 10, 467-473.
(15) Fryzuk, M. D.; Montgomery, C. D. Coord. Chem. ReV. 1989, 95,
1-40.
(16) Walstrom, A.; Pink, M.; Tsvetkov, N. P.; Fan, H. J.; Ingleson, M.;
Caulton, K. G. J. Am. Chem. Soc. 2005, 127, 16780-16781.
(17) Rais, D.; Bergman, R. G. Chem. Eur. J. 2004, 10, 3970-3978.
(18) Conner, D.; Jayaprakash, K. N.; Wells, M. B.; Manzer, S.; Gunnoe,
T. B.; Boyle, P. D. Inorg. Chem. 2003, 42, 4759-4772.
(19) Fox, D. J.; Bergman, R. G. Organometallics 2004, 23, 1656-1670.
(20) Fulton, J. R.; Sklenak, S.; Bouwkamp, M. W.; Bergman, R. G. J.
Am. Chem. Soc. 2002, 124, 4722-4737.
(21) Zhang, J.; Gunnoe, T. B.; Petersen, J. L. Inorg. Chem. 2005, 44,
2895-2907.
(22) Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. Organometallics
2000, 19, 2655-2657.
(23) Abbel, R.; Abdur-Rashid, K.; Faatz, M.; Hadzovic, A.; Lough, A.
J.; Morris, R. H. J. Am. Chem. Soc. 2005, 127, 1870-1882.
(24) Sandoval, C. A.; Ohkuma, T.; Mun˜iz, K.; Noyori, R. J. Am. Chem.
Soc. 2003, 125, 13490-13503.
(25) Guo, R.; Morris, R. H.; Song, D. J. Am. Chem. Soc. 2005, 127,
516-517.
(26) Guo, R.; Elpelt, C.; Chen, X.; Song, D.; Morris, R. H. Org. Lett.
2005, 7, 1757-1759.

RuHX(diamine)(PPh3)2
Organometallics, Vol. 25, No. 22, 2006 5479
1-one in toluene to give RuH(NCC(C6H9O)CN)(tmen)(PPh3)2
according to eq 3. This is an unusual case where the Michael
Figure 1. (a) Transition-state structure for dihydrogen splitting at
RuH(NHCH2CH2NH2)(PH3)2.3 (b) Possible transition-state structure
for H-X bond splitting.
The mechanism of the H-X addition reactions (eq 1) may
be similar to that observed for complex 1 with dihydrogen,3
where a weakly interacting η2-dihydrogen ligand on ruthenium
is deprotonated by the amido nitrogen (Figure 1a). In a similar
fashion the H-X bonds could be activated and cleaved
heterolytically (Figure 1b). If the metal has a coordination site
as in complex 1, then a weak interaction of HX with Ru would
increase the acidity of HX. With HX coordinated, the amido
nitrogen can no longer act as a π-donor to ruthenium and thus
becomes more basic. This metal-ligand bifunctional effect
allows the cleavage of unactivated bonds. An alternative
mechanism involving the addition of weak acids to ruthenium-
(0) by oxidative addition, a mechanism known for 50 years,27,28
is much less likely. For example, the complex RuH2{P(CH2-
CH2PPh2)3} is thought to add phenylacetylene to give RuH-
(CCPh){P(CH2CH2PPh2)3} by a reductive elimination/oxidative
addition route.29 The reductive elimination of one end of the
tmen ligand to give a transient ruthenium(0) intermediate, Ru-
(PPh3)2(tmen), has not been observed.
adduct is trapped on the metal. Usually the adduct falls off in
the reaction of coordinated anions derived from nitriles with
electrophiles.30 However, Hayashi and co-workers have ob-
served, by use of NMR, a Michael adduct intermediate in the
asymmetric 1,4-addition of organoboronic acids to enones
catalyzed by [Rh(binap)(OH)]2.31 In addition, Michael adducts
are retained in the metal complex resulting from the addition
of Michael acceptors to η2-arene complexes, a powerful method
for regio- and stereospecific C-C bond formation.32-34
X-ray Crystallography. Complexes containing the tmen
ligand crystallized much more readily than those containing the
dach ligand. Seven pseudo-octahedral tmen-containing com-
plexes, those with X ) OCHO,3 PhOH‚‚‚OPh, 4-SC6H4OMe,
PO(OEt)2, CCPh, OC(OMe)CHCOOMe, NCC(C6H9O)CN),
have been characterized by X-ray crystallography (Figures 2-7;
all but the ipso phenyl carbons of the PPh3 ligands have been
removed for clarity). The structure of the distorted square
pyramid defined by the fragment RuHN2P2 to which the X
ligand is attached varies only slightly from complex to complex.
The P-Ru-P angles vary between 96 and 100° and the diamine
bite angles between 73 and 76°.
The complex RuH(OPh)(tmen)(PPh3)2 crystallizes when an
extra 1 equiv of phenol is present in solution (Figure 2a). This
phenol is hydrogen-bonded in a six-membered Ru-O‚‚‚H-
O(Ph)‚‚‚H-N- ring in the resulting pseudo-octahedral complex
(Figure 2b). The ruthenium-oxygen bond length of 2.364(2) Å
is much longer than previously observed Ru-alkoxide distances
(e.g. 2.239(2) Å in trans-RuH(4-O-C6H4Me)(PMe2CH2CH2P-
Me2)2)35 and longer than the Ru-O distance of 2.29 Å in the re-
lated formate complex RuH(OCHO)(tmen)(PPh3)2.3 The complex
has considerable [RuH(diamine)(PPh3)2]+[PhO‚‚‚HOPh]- ion pair
character, with a weakly interacting biphenoxide ligand analo-
gous to a bifluoride ligand, as in [RuH(PMe2CH2CH2P-
Me2)2]+[FHF]- with Ru-F ) 2.284(5) Å.36,37 The hydrogen-
bonded ring structure is related to those of the alcohol-assisted
splitting of dihydrogen on ruthenium catalysts, as proposed by
Ito et al.,38 Sandoval et al.,24 Casey et al.,39 and Hedberg et
The yellow complexes RuHX(dach)(PPh3)2 containing the
diamine (R,R)-1,2-diaminocyclohexane are synthesized in a
metathesis route by reacting RuHX(dach)(PPh3)2 (2) with potas-
sium tert-butoxide and the appropriate weak acid in THF under
nitrogen (eq 2). This route gives significantly improved yields
relative to a two-step procedure where a solution of the unstable
red hydrido amido complex RuH(NHC6H10NH2)(PPh3)223 is first
generated by reaction of 2 with base and then reacted with the
weak acid HX. The structures of the complexes all have X trans
to hydride except for the phenoxide complex, where cis isomers
are also observed in minor amounts (see below).
A short-lived red color due to the amido intermediate is ob-
served when adding the reactants together with stirring. The
dach-containing complexes are more soluble than the tmen com-
plexes and are readily soluble in THF. The sensitivity of these
complexes to air was found to be similar to that for the tmen
analogues.
(30) Murahashi, S.-I.; Naota, T.; Taki, H.; Mizuno, M.; Takaya, H.;
Komiya, S.; Mizuho, Y.; Oyasato, N.; Hiraoka, M.; Hirano, M.; Fukuoka,
A. J. Am. Chem. Soc. 1995, 117, 12436-12451.
(31) Hayashi, T.; Takahashi, M.; Takaya, Y.; Ogasawara, M. J. Am.
Chem. Soc. 2002, 124, 5052-5058.
(32) Ding, F.; Harman, W. D. J. Am. Chem. Soc. 2004, 126, 13752-
13756.
(33) Ding, F.; Valahovic, M. T.; Keane, J. M.; Anstey, M. R.; Sabat,
M.; Trindle, C. O.; Harman, W. D. J. Org. Chem. 2004, 69, 2257-2267.
(34) Harman, W. D. Chem. ReV. 1997, 97, 1953-1978.
(35) Burn, M. J.; Fickes, M. G.; Hollander, F. J.; Bergman, R. G.
Organometallics 1995, 14, 137-150.
An additional complex was prepared by the Michael addition
reaction of RuH(NCCHCN)(tmen)(PPh3)2 with 2-cyclohexen-
(36) Whittlesey, M. K.; Perutz, R. N.; Greener, B.; Moore, M. H. Chem.
Commun. 1997, 187-188.
(27) Chatt, J.; Davidson, J. M. J. Chem. Soc. 1965, 843-855.
(28) Ittel, S. D.; Tolman, C. A.; English, A. D.; Jesson, J. P. J. Am.
Chem. Soc. 1978, 100, 7577-7585.
(29) Bianchini, C.; Frediani, P.; Masi, D.; Peruzzini, M.; Zanobini, F.
Organometallics 1994, 13, 4616-4632.
(37) Jasim, N. A.; Perutz, R. N.; Foxon, S. P.; Walton, P. H. Dalton
Trans. 2001, 1676-1685.
(38) Ito, M.; Hirakawa, M.; Murata, K.; Ikariya, T. Organometallics 2001,
20, 379-381.

5480 Organometallics, Vol. 25, No. 22, 2006
Clapham et al.
Figure 3. Molecular structure of RuH(4-SC6H4OCH3)(tmen)-
(PPh3)2. Selected bond distances (Å) and angles (deg): Ru(1)-
H(1RU) ) 1.57(3), Ru(1)-N(1) ) 2.181(2) Ru(1)-N(2) )
2.205(2), Ru(1)-P(1) ) 2.2695(8), Ru(1)-P(2) ) 2.2715(9), Ru-
(1)-S(1) ) 2.5274(9); N(1)-Ru(1)-N(2) ) 73.54(9), N(1)-Ru-
(1)-P(1) ) 92.05(7), N(2)-Ru(1)-P(1) ) 165.54(7) N(1)-
Ru(1)-P(2) ) 163.66(7), N(2)-Ru(1)-P(2) ) 94.46(7), P(1)-
Ru(1)-P(2) ) 99.46(3), N(1)-Ru(1)-S(1) ) 84.12(7), N(2)-
Ru(1)-S(1) ) 88.24(7), P(1)-Ru(1)-S(1) ) 91.41(3), P(2)-
Ru(1)-S(1) ) 106.99(3).
Figure 2. (a) Molecular structure of RuH(OPh)(tmen)(PPh3)2‚
HOPh. Selected bond distances (Å) and angles (deg): Ru(1)-O(1)
) 2.364(2), Ru(1)-H(1RU) ) 1.53(3), Ru(1)-N(1) ) 2.177(2),
Ru(1)-N(2) ) 2.179(2), Ru(1)-P(2) ) 2.2690(7), Ru(1)-P(1) )
2.2697(8); H(1RU)-Ru(1)-N(1) ) 88(1), N(1)-Ru(1)-N(2) )
75.20(9), N(1)-Ru(1)-P(2) ) 163.57(7), N(2)-Ru(1)-P(2) )
92.01(7), N(1)-Ru(1)-P(1) ) 93.13(7), N(2)-Ru(1)-P(1) )
167.31(7), P(2)-Ru(1)-P(1) ) 98.49(3), N(1)-Ru(1)-O(1) )
83.83(8), N(2)-Ru(1)-O(1) ) 80.87(9), P(2)-Ru(1)-O(1) )
104.62(5), P(1)-Ru(1)-O(1) ) 103.14(6). (b) The six-membered
ring. (c) Related ring structures proposed for the alcohol-assisted
splitting of dihydrogen.
al.,40 where the phenoxide ligand takes the place of the hydride
(Figure 2c).
The molecular structure of the thiolate complex RuH(4-
SC6H4OMe)(tmen)(PPh3)2 shows a pseudo-octahedral structure
with the thiolato ligand trans to hydride (Figure 3). The Ru-S
distance of 2.5274(9) Å is similar to the 2.526(1) Å Ru-S
distance in the complex trans-RuH(SPh)(PPh2CH2CH2PPh2)2,
with thiolate trans to hydride.41
The crystal structure of RuH(OP(OEt)2)(tmen)(PPh3)2 has an
intramolecular electrostatic interaction between O(3) on diethyl
phosphonate and H(2A) on a nitrogen of the tmen ligand, as
indicated by the short distance of 2.1 Å (Figure 4). The
O3‚‚‚H2A-N(2) angle is ∼139°. There are no other structurally
characterized ruthenium phosphonate complexes for comparison.
However, there is an iron phosphonate complex, Fe(CO)2(HN-
N-C)(PO(OMe)2), that has a similar intramolecular NH‚‚‚OP
hydrogen bond with H‚‚‚O ) 2.3 Å.42
Figure 4. Molecular structure of RuH(OP(OEt)2)(tmen)(PPh3)2.
Selected bond distances (Å) and angles (deg): Ru(1)-H(1RU) )
1.63(3), Ru(1)-N(1) ) 2.166(2), Ru(1)-N(2) ) 2.181(2), Ru(1)-
P(1) ) 2.2772(5) Ru(1)-P(2) ) 2.2872(5), Ru(1)-P(3) ) 2.3486-
(5); H(1RU)-Ru(1)-N(1) ) 82.0(9), H(1RU)-Ru(1)-N(2) )
91.6(9), N(1)-Ru(1)-N(2) ) 75.19(7), H(1RU)-Ru(1)-P(1) )
86.4(9), N(1)-Ru(1)-P(1) ) 163.52(5), N(2)-Ru(1)-P(1) )
93.50(5), H(1RU)-Ru(1)-P(2) ) 85.0(9), N(1)-Ru(1)-P(2) )
92.27(5), N(2)-Ru(1)-P(2) ) 167.37(5), P(1)-Ru(1)-P(2) )
98.42(2), H(1RU)-Ru(1)-P(3) ) 171.7(9), N(1)-Ru(1)-P(3) )
90.03(6), N(2)-Ru(1)-P(3) ) 83.79(5), P(1)-Ru(1)-P(3) )
100.79(2), P(2)-Ru(1)-P(3) ) 97.98(2).
The reaction of 1 with dimethyl malonate produced a complex
with a rare monodentate oxygen-bonded ligand (Figure 6). In
most instances this ligand acts as a bidentate ligand in metal
complexes. In this case, only one carbonyl oxygen, O(1), binds
to the metal, while the other carbonyl oxygen, O(2), is hydrogen-
bonded to one of the protons on N(1). The planar O(1)-C(7)-
C(8)-C(9)-O(2) chain and short, similar OdC (1.239(4),
1.225(4) Å) and C-C distances (1.404(5), 1.413(5) Å) signal
the presence of π delocalization. Wang et al. have reported the
observation by NMR of a ruthenium methyl acetoacetonate
complex where both oxygen- and carbon-bonded ligands are
thought to be present.11 There has been one structural charac-
terization of a carbon-bonded malonate on ruthenium in the
complex Ru[CH(CO2CH3)2][(R,R)-Tsdpen](η6-mesitylene).10
The phenylacetylido complex RuH(CCPh)(tmen)(PPh3)2 dis-
plays a similar pseudo-octahedral geometry with hydride trans
to phenylacetylide, as shown in Figure 5. The Ru-C bond at
2.071(3) Å is the same as the Ru-C distance of 2.079 Å in the
other hydrido phenylacetylido complex that has been structurally
characterized, cis-RuH(CCPh){P(CH2CH2PPh2)3}.29
(39) Casey, C. P.; Johnson, J. B.; Singer, S. W.; Cui, Q. J. Am. Chem.
Soc. 2005, 127, 3100-3109.
(40) Hedberg, C.; Ka¨llstrom, K.; Arvidsson, P. I.; Andersson, P. G.;
Brandt, P. J. Am. Chem. Soc. 2005, 127, 15083-15090.
(41) Bartucz, T. Y.; Golombek, A.; Lough, A. J.; Maltby, P. A.; Morris,
R. H.; Ramachandran, R.; Schlaf, M. Inorg. Chem. 1998, 37, 1552-1562.
(42) Fruehauf, H. W.; Seils, F.; Stam, C. H. Organometallics 1989, 8,
2338-2343.

RuHX(diamine)(PPh3)2
Organometallics, Vol. 25, No. 22, 2006 5481
Figure 7. Molecular structure of RuH(NCC(C6H9O)CN)(tmen)-
(PPh3)2. Selected bond distances (Å) and angles (deg): Ru(1)-
H(1RU) ) 1.63, Ru(1)-N(3) ) 2.137(5), Ru(1)-N(1) ) 2.190(4),
Ru(1)-N(2) ) 2.199(5), Ru(1)-P(1) ) 2.259(1), Ru(1)-P(2) )
2.267(1); N(3)-Ru(1)-N(1) ) 86.3(2), N(3)-Ru(1)-N(2) ) 86.7-
(2) N(1)-Ru(1)-N(2) ) 76.1(2), N(3)-Ru(1)-P(1) ) 92.2(1),
N(1)-Ru(1)-P(1) ) 92.7(1), N(2)-Ru(1)-P(1) ) 168.8(1),
N(3)-Ru(1)-P(2) ) 101.3(1), N(1)-Ru(1)-P(2) ) 166.4(1),
N(2)-Ru(1)-P(2) ) 93.0(1), P(1)-Ru(1)-P(2) ) 98.08(5).
Figure 5. Molecular structure of RuH(CCPh)(tmen)(PPh3)2. Se-
lected bond distances (Å) and angles (deg): Ru(1)-H(1RU) )
1.68(3), Ru(1)-C(7) ) 2.071(3), Ru(1)-N(1) ) 2.198(3), Ru(1)-
N(2) ) 2.208(3), Ru(1)-P(1) ) 2.2550(9), Ru(1)-P(2) ) 2.2599-
(9); C(7)-Ru(1)-N(1) ) 86.9(1), C(7)-Ru(1)-N(2) ) 87.1(1),
N(1)-Ru(1)-N(2) ) 74.6(1), C(7)-Ru(1)-P(1) ) 89.8(1), N(1)-
Ru(1)-P(1) ) 167.83(8), N(2)-Ru(1)-P(1) ) 93.51(8), C(7)-
Ru(1)-P(2) ) 102.4(1), N(1)-Ru(1)-P(2) ) 93.75(8), N(2)-
Ru(1)-P(2) ) 164.68(9), P(1)-Ru(1)-P(2) ) 98.40(3).
Figure 8. Exchange of groups by the ring flip of the 2,3-diamino-
2,3-dimethylbutane ligand.
1
(AX or AB spin system) and two methyl resonances in the H
NMR spectra. Due to the lack of symmetry caused by the trans-
HRuX system, four of each of these resonances might have been
expected for axial or equatorial groups syn to the X or H sides
of the molecules. The rapid flipping of the five-membered Ru-
tmen ring causes an exchange of groups and averaging of
chemical shifts of pairs of these groups that are syn to X and
syn to H, respectively (Figure 8). In the cases where the X
groups (OCHO, POPh2, PO(OEt)2, OC(OMe)CHCOOMe) form
NH‚‚‚O hydrogen bonds (or electrostatic attractions) with the
NH groups (see Chart 1 and Figures 4 and 6), there must also
be exchange between hydrogen bond partners to achieve the
averaging of the signals. The presence of these hydrogen bonds
in solution is manifested by a downfield shift by about 2 ppm
of one of the averaged NH signals (syn to the X ligand).
Figure 6. Molecular structure of RuH(CH(COOMe)2)(tmen)-
(PPh3)2. Selected bond distances (Å) and angles (deg): Ru(1)-
H(1RU) ) 1.50, Ru(1)-N(1) ) 2.154(3), Ru(1)-N(2) ) 2.180(3),
Ru(1)-P(2) ) 2.2392(9), Ru(1)-P(1) ) 2.2494(8), Ru(1)-O(1)
) 2.265(2); N(1)-Ru(1)-N(2) ) 75.6(1), N(1)-Ru(1)-P(2) )
170.26(7), N(2)-Ru(1)-P(2) ) 94.72(8), N(1)-Ru(1)-P(1) )
91.85(7), N(2)-Ru(1)-P(1) ) 163.82(8), P(2)-Ru(1)-P(1) )
97.35(3), N(1)-Ru(1)-O(1) ) 77.3(1), N(2)-Ru(1)-O(1) ) 78.9-
(1), P(2)-Ru(1)-O(1) ) 102.61(7), P(1)-Ru(1)-O(1) ) 108.70-
(7).
1
The triplet for the hydride in the H NMR spectrum is in
The Michael adduct formed in eq 3 retains a Ru-N bond, as
shown in Figure 7. The Ru(1)-N(3) bond distance of 2.137(5)
Å is similar to that of the Ru-N bond (2.16(2) Å) for the nitrile
trans to hydride in the related complex RuH(PPh3)3(NCCH2-
CO2Et)(NCCHCO2Et)30 and the Os-N bond (2.116(3) Å) to
the malononitrile anion trans to hydride in OsH(NCCHCN)-
(PPh3)2(tmen).43 The new C-C bond created in eq 3 is between
trigonal-planar C(8) and tetrahedral C(10). There is a delocalized
π system over N(3)-C(7)-C(8)-C(9)-N(4) with N-C dis-
tances of 1.170(7) and 1.149(8) Å and C-C distances of 1.389-
(8) and 1.397(9) Å.
keeping with the hydride trans to X geometry observed in the
X-ray crystal structures. The chemical shift of the hydride varies
systematically with a change in the electronegativity of the atom
of the X ligand trans to the hydride (Figure 9). A rough
correlation is observed showing an upfield hydride shift as the
electronegativity of the atom trans to the hydride increases. This
correlation provides support for the bonding modes proposed
in Chart 1 for the ambidentate ligands. As expected from the
correlation in Figure 9, the hydride peak for the dimethyl
malonate complex is found upfield at -21.8 ppm for oxygen
trans to hydride, not downfield for carbon trans to hydride. The
chemical shift of the hydride in the malononitrile anion complex
RuH(NCCHCN)(tmen)(PPh3)2 is -15.4 ppm: more consistent,
according to Figure 9, with nitrogen coordination instead of
carbon coordination. Indeed, the structure of the analogous
osmium complex shows that it is monodentate and bonded via
NMR Characterization. There are several features of the
NMR spectra of the tmen-containing complexes that are
common to all. There are only two amine proton resonances
(43) Clapham, S. E.; Morris, R. H. Organometallics 2005, 24, 479-
481.

5482 Organometallics, Vol. 25, No. 22, 2006
Clapham et al.
1
Figure 9. Correlation between hydride H NMR shifts and the
electronegativity of the atom trans to hydride in the complexes
RuHX(tmen)(PPh3)2.
nitrogen,43 and the structurally characterized Michael adduct
(Figure 7) has a similar chemical shift of -15.3 ppm.
When X is OP(OEt)2 and OPPh2, the usual hydride triplet
pattern is split into a doublet of triplets. As expected, the trans
coupling to the phosphorus of the diethyl phosphonyl and
diphenylphosphinyl ligands is large with respect to the cis
coupling to the triphenylphosphine ligands and shows that these
X ligands are bonded to ruthenium via phosphorus.
Figure 10. PPh3 peaks in the 31P{1H} NMR spectrum at 300 MHz
of RuH(OP(OEt)2)(dach)(PPh3)2: (a) simulated; (b) experiment.
The complex RuH(NCC(C6H9O)CN)(tmen)(PPh3)2 has unique
NMR spectra compared to those of the other tmen complexes,
due to the chiral carbon C(10) (Figure 7). The phosphine ligands
are diastereotopic, and so the 31P{1H} NMR spectrum displays
an AB pattern. Although the NH peaks are masked by the
cyclohexanoyl multiplet, four distinct methyl peaks are observed
for the tmen ligand.
The chirality of the dach ligand results in more complex NMR
spectra for its complexes. The diastereotopic phosphine ligands
produce an AB pattern in the 31P{1H} NMR spectra, except in
the case of RuH(4-SC6H4OMe)(dach)(PPh3)2, where a coinci-
dental overlapping of peaks produces a singlet. The similarity
of the environments of the phosphine ligands still produces a
Figure 11. Major and minor isomers of RuH(OPh)(dach)(PPh3)2.
1
triplet pattern for the hydride peaks in the H NMR spectra.
The hydride chemical shifts for the dach complexes follow the
same electronegativity correlation found with the tmen com-
plexes in Figure 9. The phosphorus NMR spectra for the diethyl
phosphonyl (Figure 10) and diphenylphosphinyl complexes are
interesting because of the ABX patterns produced.
The NMR spectra of RuH(OPh)(dach)(PPh3)2 provide evi-
dence for one major and two minor isomers. The major hydride
resonance is a triplet at -24.4 ppm. The relative peak intensities
indicate that this pattern corresponds with an AB pattern in the
31P{1H} NMR spectrum with δA 69.0 and δB 65.9 ppm. The
similarity to the spectra of the other dach complexes suggests
that the major isomer is the usual hydride trans to X isomer.
The minor hydride patterns consist of a triplet at -13.4 ppm
and a doublet of doublets at -13.7 ppm. These peaks correspond
with two doublets at 82.0 and 67.7 ppm and two doublets at
80.0 and 67.4 ppm, respectively, in the 31P{1H} NMR. Cis
isomers of this type have been characterized for the complexes
RuH2(dach)(PPh3)2 and RuH2(en)(PPh3)2.23 The isomers that
have a hydride trans to a phosphine give a JHP coupling constant
close to 100 Hz. All JHP constants for the minor isomers of
RuH(OPh)(dach)(PPh3)2 are significantly smaller, suggesting
that the hydride is always trans to an amine ligand. The three
isomers are shown in Figure 11.
Figure 12. Correlation between the Ru-H stretching frequency
and trans-atom electronegativity.
to the hydride, much like that found for the hydride NMR shifts.
The metal hydride stretches occur between 1770 and 2100 cm-1
.
The more electronegative atoms trans to the hydride tend to
increase the stretching frequency, as shown in Figure 12.
The CN stretching wavenumber from the IR spectrum of
RuH(NCCHCN)(diamine)(PPh3)2, diamine ) tmen (2127 cm-1),
dach (2124 cm-1), was useful in determining the coordination
mode of the dicyanomethyl ligand. This ligand can coordinate
through the deprotonated carbon or through one of the nitrile
nitrogens. The CN stretches between 2120 and 2130 cm-1 are
indicative of a nitrogen-bound ligand. Carbon-bound ligands
would be expected to give a stretching wavenumber above 2200
Infrared Characterization. The ruthenium hydride stretches
found in the IR spectra of the tmen and dach complexes follow
a rough correlation with the electronegativity of the atom trans
cm-1 44,45
. The X-ray crystal structure of the analogous osmium
complex, OsH(NCCHCN)(tmen)(PPh3)2, has been reported to
have a nitrogen-bound dicyanomethyl ligand and a CN stretch

RuHX(diamine)(PPh3)2
Organometallics, Vol. 25, No. 22, 2006 5483
Table 1. Catalysts for the Michael Addition of Dimethyl
Scheme 1. Proposed Mechanisms of the Michael Addition
Reactions Catalyzed by Complex 1 and
Malonate to 2-Cyclohexen-1-one in THF at 20 °Ca
RuH(CH(COOMe)2)(tmen)(PPh3)2
[cat.], [sub], sub: time, conversn, TOF,
cat.
mM
M
cat.
h
%
h-1
1
2.5
3.1
0.23 104
0.33 108
18
18
98
100
5.7
g6.0
RuH(CH(COOMe)2)-
(tmen)(PPh3)2
RuH(OPh)(tmen)(PPh3)2 2.0
RuHCl(tmen)(PPh3)2 3.0
0.20 101
0.33 110
24
18
94
0
4.0
0.0
a A 3 mL amount of solvent was used. Abbreviations: cat., catalyst;
sub, substrate.
of 2126 cm-1 43 A similar CN stretch at 2102 cm-1 for the
.
trapped Michael adduct suggests that this coordination mode is
maintained when 2-cyclohexen-1-one is added to the dicya-
nomethyl ligand, as indicated by the X-ray crystal structure
(Figure 7).
The CO and CC stretching absorptions at 1632 and 1538 cm-1
in the spectrum of RuH(CH(COOMe)2)(tmen)(PPh3)2 are similar
to those of the acac ligand and suggest that an electron-
delocalized enolate form of the ligand is coordinated. This is
consistent with an oxygen-bonded, as opposed to carbon-bonded,
malonate ligand.
Michael Addition. The amido complex 1 and the complexes
RuH(CH(COOMe)2)(tmen)(PPh3)2 and RuH(OPh)(tmen)(PPh3)2
all catalyze the Michael addition of dimethyl malonate to
2-cyclohexen-1-one to produce 3-[bis(methoxycarbonyl)methyl]-
cyclohexanone in THF at room temperature (eq 4 and Table
1).
enone carbonyl group with an amino N-H group, but this would
need to be probed in a future, more detailed study. The adduct
complex might quickly react with more malonate and release
the Michael adduct. Alternatively, there may be a proton shift
from the Michael donor to the R-carbon of the Michael acceptor
in a fashion analogous to eq 3. Deprotonation of the amine
ligand and release of the Michael product would complete the
catalytic cycle.
The mechanism in Scheme 1 is slightly different from that
proposed by Ikariya and co-workers,10 where a malonate that
is carbon-bonded to the metal attacks an enone that is positioned
by an N(amine)-H-O(carbonyl) hydrogen bond.
The amido and malonate complexes have similar activities,
possibly suggesting that the addition of the C-H bond of
dimethyl malonate to the amido complex is a step in the catalytic
cycle. Their activity is more than 10 times that of the complexes
RuH(BH4)(S-binap)((R,R)-PPh2CHPhCCHMeNH2) (TOF 0.4
h-1 at 20 °C),25 Ru(C6Me6)(NHCHPhCHPhNTs) (TOF 0.6 h-1
at 30 °C),10 and La(OiPr)3)/S,S-linked binol (TOF 0.13 h-1 at
20 °C),46 although these other catalysts are highly enantiose-
lective in the reaction. Tetrahydrofuran was chosen as the
solvent, because it was found to be optimum for our borohydride
catalysts.25,26 The chloro complex RuHCl(tmen)(PPh3)2 and the
malononitrile complex are not catalysts under these conditions.
While the malononitrile complex can be used as a Michael
donor to 2-cyclohexen-1-one in a stoichiometric reaction (eq
3), the malonate complex may not react in this way. NMR
spectra of a mixture of RuH(CH(COOMe)2)(tmen)(PPh3)2 and
the enone in C6D6 did not provide direct evidence for a reaction.
At the moment we propose two possible mechanisms of catalysis
(Scheme 1). Starting with the amido complex 1, the Michael
donor is first deprotonated by the amido nitrogen and then
coordinated to the metal. The Michael acceptor is attacked at
its electrophilic carbon to form a ruthenium-coordinated adduct.
This attack might be promoted by hydrogen bonding of the
The complex RuH(OPh)(tmen)(PPh3)2 also catalyzes this
Michael addition reaction (Table 1). This is explained by the
fact that the phenoxide complex rapidly reacts with an equimolar
amount of dimethyl malonate to give a rapidly equilibrating
mixture of the phenoxide complex and the complex RuH(CH-
1
(COOMe)2)(tmen)(PPh3)2. The H and 31P{1H} NMR spectra
of this reaction show hydride and phosphorus peak positions
with chemical shifts that are at an average of the positions found
for the individual malonate and phenoxide complexes. A
broadening of some peaks is also observed. Under catalytic
conditions, the large excess of dimethyl malonate would result
in a large concentration of the malonate complex, which would
then catalyze the reaction.
Hydrogenation of Acetophenone. The trans-dihydride com-
plexes RuH2(diamine)(PPh3)2, diamine ) tmen,3, dach,23 are
known to be extremely active ketone hydrogenation catalysts.
The dihydride RuH2(tmen)(PPh3)2 is generated by reacting
complex 1 with dihydrogen, while the unstable trans-dihydride
RuH2(dach)(PPh3)2 can be accessed by reaction of the precursor
RuHCl(dach)(PPh3)2 with KOtBu under dihydrogen. The only
other complexes of the X trans to hydride series that are active
for the hydrogenation of acetophenone to 1-phenylethanol
without base at 20 °C are the phenylacetylide complexes RuH-
(CCPh)(tmen)(PPh3)2 and RuH(CCPh)(dach)(PPh3)2 (eq 5 and
Table 2).
(44) Baddley, W. H.; Choudhury, P. J. Organomet. Chem. 1973, 60,
C74-C76.
(45) Bailey, N. A.; Higson, B. M.; McKenzie, E. D. Inorg. Nucl. Chem.
Lett. 1971, 7, 591-593.
The turnover frequencies of the phenylacetylide complexes
RuH(CCPh)(diamine)(PPh3)2 forthehydrogenationsinneataceto-
phenone are less than those of the corresponding complexes 1
(46) Kim, Y. S.; Matsunaga, S.; Das, J.; Sekine, A.; Ohshima, T.;
Shibasaki, M. J. Am. Chem. Soc. 2000, 122, 6506-6507.

5484 Organometallics, Vol. 25, No. 22, 2006
Clapham et al.
Table 2. Comparison of the Activity and Enantioselectivity of the Catalysts RuHX(diamine)(PPh3)2 in Neat Ketone or Benzene
Solution at 20 °C
cat.
[cat.], mM
[ketone], M
H2 pressure, atm
time, h
conversn, %
ee, %a
TOF, h-1
In Neat Acetophenone
1
5.5
1.8
14
14
9
8.6
8.6
8.6
8.6
8.6
10
3
10
10
10
1
< 8
3.3
24
100
100
2
100
100
0
62
0
0
62
>1559
>625
4
>26
>288
RuHCl(dach)(PPh3)2/base
RuH(CCPh)(tmen)(PPh3)2
RuH(CCPh)(dach)(PPh3)2
3.5
In Benzene
1
1
5
5
5
5
0
55
62
47
33
1070b
715c
0.5
RuHCl(dach)(PPh3)2/base
RuH(CCPh)(dach)(PPh3)2
1.0
1.0
1.0
0.017
0.017
0.017
0.33
1.7
21
1
3
6
0.1
0.05
a (S)-Phenylethanol. b Maximum rate ) (112 M-1 s-1)[Ru][H2].3 c Rate ) (14 M-1 s-1)[Ru][H2].23
Scheme 2. Hypothetical Cycle for the Hydrogenation of
Acetophenone Catalyzed by the Complexes
RuHX(dach)(PPh3)2 with X Trans to Ha
and the RuHCl(dach)(PPh3)2 complex when activated by KOtBu,
especially at low conversion. The enantiopure complex RuH-
(CCPh)(dach)(PPh3)2 produces 1-phenylethanol from neat ac-
etophenone in 62% ee(S), which is exactly the same optical
purity as is observed for hydrogenations using the dihydride
complex RuH2(dach)(PPh3)2 (as a mixture of isomers).23
When benzene is used as a solvent, the TOF values for the
phenylacetylide complexes are much less than those for the
dihydride precursors. For the dach complex, the ee of the
1-phenylethanol starts off at 62% but degrades over time.
A stoichiometric mixture of RuH(CCPh)(dach)(PPh3)2 and
acetophenone in benzene-d6 under Ar does not react after 3 h.
When the solution is placed under 1 atm of hydrogen and is
left for 24 h, a 27% conversion to racemic 1-phenylethanol is
observed (eq 6). Apparently the degradation of ee at these high
ruthenium concentrations is even more serious.
a The cycle has been established for X ) H.
benzene. Catalysis is proposed to occur via Scheme 2 with X
) H only. Side products in the reaction appear to catalyze the
racemization of the alcohol that is produced, thus explaining
the degradation in ee during prolonged reaction times.
Conclusions
A variety of potential catalyst precursors RuHX(diamine)-
(PPh3)2 with X trans to hydride are generated by the reaction
of weak acids HX with the amido complex RuH(NHCMe2CMe2-
NH2)(PPh3)2. Similar complexes with the dach ligand are
produced by reaction of the KOtBu/HX with RuHCl(dach)-
The mechanism of action of the phenylacetylide complexes
(X ) CCPh) does not appear to follow the cycle established
for the dihydrides (X ) H) (Scheme 2). When X ) H, the
dihydride transfers H-/H+ equivalents rapidly to the ketone to
produce the hydridoamido complex. In contrast, this step is not
observed for the phenylacetylide complexes. Even though this
carbon-donor ligand has a low electronegativity and hence a
high trans influence, it does not make the hydride trans to CCPh
hydridic enough for the transfer reaction to acetophenone under
comparable conditions.
(PPh3)2. Acids with a range of strengths can be used, but aniline
DMSO
with pKa
) 30.6 does not react. The X ligands with
hydrogen-bond acceptors, including O2CH, OPPh2, OP(OEt)2,
and CH(COOMe)2, form O‚‚‚HN hydrogen bonds with a cis
amino group. The ambidentate ligands NCCHCN and CH-
(COOMe)2 bond to ruthenium via a N or O donor, respectively,
instead of the more hindered carbon centers. The mode of
coordination is signaled by distinctive chemical shifts of the
1
hydride resonance in the H NMR spectrum and characteristic
wavenumber values for the Ru-H stretch that vary with the
electronegativity of the donor atom on X. The amido complex
RuH(NHCMe2CMe2NH2)(PPh3)2 and the related malonate and
phenoxide complexes are active catalysts or precursors to
catalysts for the Michael addition reaction. The activation of
O-H, P-H, and S-H bonds at the ruthenium-nitrogen bond
has been demonstrated and opens the possibility of new catalytic
processes involving these elements.
These results are best explained by the conversion of the
phenylacetylide complexes to the active dihydrides, which are
the actual catalysts (eq 7). This reaction must be faster in neat
RuH(CCPh)(diamine)(PPh3)2 + H2 f
RuH2(diamine)(PPh3)2 + HCCPh + unidentified products
(7)
Only the complexes with X ) H, CCPh have activity as
catalysts for acetophenone hydrogenation at room temperature.
The phenylacetylide complexes RuH(CCPh)(diamine)(PPh3)2
are likely converted to the dihydrides under the conditions of
the hydrogenation reaction, and so only the X ) H complexes,
acetophenone than in benzene solution, because the TOF values
are much larger under the former conditions (Table 2). A peak
for free phenylacetylene is observed by gas chromatography
for reactions performed both in neat acetophenone and in

RuHX(diamine)(PPh3)2
Organometallics, Vol. 25, No. 22, 2006 5485
1
(70%). H NMR (C6D6, δ): 6.8-8.0 (m, phenyl, 30 H), 4.1-4.5
(m, NH and CH2, 6 H), 1.8 (d, NH, 2 H, JHH ) 10.2 Hz), 1.2 (t,
CH3, 6 H, JHH ) 7.0 Hz), 1.0 (s, CH3, 6 H), 0.9 (s, CH3, 6 H),
-6.5 (dt, RuH, 1 H, JHP1 ) 146.1 Hz, JHP2 ) 22.3 Hz). 31P{1H}
NMR (C6D6, δ): 121.3 (t, OP(OEt)2, 1 P, JPP ) 30.4 Hz), 70.4 (d,
PPh3, 2 P). IR (Nujol, cm-1): 3347 (ν(NH)), 1853 (ν(RuH)). Anal.
Calcd for RuP3O3N2C46H57‚0.25C7H8: C, 63.51; H, 6.59; N, 3.10.
Found: C, 63.48; H, 6.43; N, 3.01.
out of all of the X complexes tested, are true ketone hydrogena-
tion catalysts.
Experimental Section
General Considerations. All preparations and manipulations
were carried out under an argon, nitrogen, or hydrogen atmosphere
using standard Schlenk, vacuum-line, and glovebox techniques. Dry,
oxygen-free solvents were always used. Hexanes, tetrahydrofuran,
and diethyl ether were dried and distilled under argon from sodium
benzophenone ketyl. Toluene was dried and distilled under
argon from molten sodium. Deuterated solvents were degassed and
dried over activated molecular sieves. NMR spectra were recorded
on a Varian Gemini 300 MHz spectrometer (300 MHz for 1H and
121.5 MHz for 31P). All 31P chemical shifts are reported relative to
RuH(CCPh)(tmen)(PPh3)2. Phenylacetylene (18 mg, 0.176
1
mmol), 1 (100 mg, 0.135 mmol). Yield: 55 mg (48%). H NMR
(C6D6, δ): 6.9-8.2 (m, phenyl, 35 H), 2.6 (d, NH, 2 H, JHH
)
10.6 Hz), 2.0 (d, NH, 2 H, JHH ) 10.6 Hz), 0.9 (s, CH3, 6 H), 0.7
(s, CH3, 6 H), -7.5 (t, RuH, 1 H, JHP ) 22.2 Hz). 31P{1H} NMR
(C6D6, δ): 73.9 (s, PPh3, 2 P). IR (Nujol, cm-1): 3347 (ν(NH)),
3323 (ν(NH)), 3285 (ν(NH)), 3264 (ν(NH)), 2053 (ν(CC)), 1778
(ν(RuH)). Anal. Calcd for RuP2N2C50H52: C, 71.16; H, 6.21; N,
3.32. Found: C, 71.21; H, 6.34; N, 3.46.
1
85% H2PO4 as an external reference. All H chemical shifts are
reported relative to TMS but referenced to partially deuterated
solvent signals. All infrared spectra were recorded on a Nicolet
550 Magna-IR spectrometer. Elemental analyses were done in the
Chemistry Department on samples handled under argon. The
complexes containing the dach ligand were spectroscopically pure
and free of potassium salts, and yet they were reproducibly analyzed
with low carbon (about 2% below the calculated values, even when
oxidants were added).
Synthesis of trans-RuHX(tmen)(PPh3)2. All syntheses involv-
ing the addition of a weak acid, HX, to 1 were performed in
the following manner: HX and 1 were added to a flask under
argon and dissolved in toluene (1 mL). The orange solution quickly
became yellow when stirred. The solution was stirred for
30 min. Hexanes (3 mL) was added to precipitate the product. The
yellow solid was filtered, washed with hexanes, and dried under
vacuum.
RuH(NCCHCN)(tmen)(PPh3)2. Malononitrile (15 mg, 0.227
mmol) and 1 (150 mg, 0.202 mmol) were used. Yield: 151 mg
(93%). 1H NMR (C6D6, δ): 6.7-7.8 (m, phenyl, 30 H), AB pattern
2.0 (A, NH, 2 H, JAB ) 10.9 Hz) and 1.9 (B, NH, 2 H), 0.6 (s,
CH3, 6 H), 0.5 (s, CH3, 6 H), -15.4 (t, RuH, 1 H, JHP ) 25.2 Hz).
31P{1H} NMR (C6D6, δ): 70.3 (s, PPh3, 2 P). IR (Nujol, cm-1):
3318 (ν(NH)), 3221 (ν(NH)), 3155 (ν(NH)), 2127 (ν(CN)), 1953
(ν(RuH)). Anal. Calcd for RuP2N4C45H48: C, 66.90; H, 5.99; N,
6.93. Found: C, 66.40; H, 6.02; N, 6.45.
RuH(CH(COOMe)2)(tmen)(PPh3)2. Dimethyl malonate (27 mg,
0.2044 mmol) and 1 (120 mg, 0.1618 mmol) were used. Yield: 95
mg (67%). 1H NMR (C6D6, δ): 6.8-7.8 (m, phenyl, 30 H), 4.6 (s,
CH, 1 H), 4.3 (d, NH, 2 H, JHH ) 10.6 Hz), 3.5 (s, OCH3, 6 H),
2.1 (d, NH, 2 H, JHH ) 10.6 Hz), 1.0 (s, CH3, 6 H), 0.7 (s, CH3,
6 H), -21.8 (t, RuH, 1 H, JHP ) 27.1 Hz). 31P{1H} NMR (C6D6,
δ): 69.4 (s, PPh3, 2 P). IR (Nujol, cm-1): 3349 (ν(NH)), 3302
(ν(NH)), 3112 (ν(NH)), 3057 (ν(NH)), 2098 (ν(RuH)), 1682 (ν-
(CO)), 1538 (ν(CC)). Anal. Calcd for RuP2O4N2C47H50: C, 64.59;
H, 6.23; N, 3.21. Found: C, 64.0; H, 6.41; N, 3.11.
RuH(OPh)(tmen)(PPh3)2. Phenol (46 mg, 0.489 mmol) and 1
(300 mg, 0.404 mmol) were used. Crystals of quality sufficient for
X-ray crystallography were grown by slow diffusion of hexanes
into a concentrated solution of RuH(OPh)(tmen)(PPh3)2 with an
extra 1 equiv of phenol in benzene. Yield: 260 mg (77%). 1H NMR
RuH(NCC(C6H9O)CN)(tmen)(PPh3)2. 2-Cyclohexen-1-one (9
mg, 0.0936 mmol) and RuH(NCCHCN)(tmen)(PPh3)2 (32 mg,
0.396 mmol) were added to a flask under argon and dissolved in
toluene (1 mL). The yellow solution was stirred for 3 h. Hexanes
was added to precipitate the product. The yellow solid was filtered,
washed with hexanes, and dried under vacuum. Yield: 34 mg (95%).
1H NMR (C6D6, δ): 6.8-7.8 (m, phenyl, 30 H), 1.1-2.7 (m,
cyclohexanoyl, NH, 13 H), 0.64 (s, CH3, 3 H), 0.63 (s, CH3, 3 H),
(C6D6, δ): 6.6-8.2 (m, phenyl, 35 H), 3.4 (d, NH, 2 H, JHH
)
10.0 Hz), 2.0 (d, NH, 2 H, JHH ) 10.0 Hz), 0.72 (s, CH3, 6 H),
0.65 (s, CH3, 6 H), -20.2 (t, RuH, 1 H, JHP ) 27.1 Hz). 31P{1H}
NMR (C6D6, δ): 67.7 (s, PPh3, 2 P). IR (Nujol, cm-1): 3319 (ν-
(NH)), 2029 (ν(RuH)). Anal. Calcd for RuP2ON2C48H52: C, 68.96;
H, 6.27; N, 3.35. Found: C, 68.36; H, 6.18; N, 2.99.
RuH(OPh-d5)(tmen)(PPh3)2. 1H NMR (C6D6, δ): 6.0-8.5 (m,
phenyl, 30 H), 3.5 (br s, NH, 2 H), 2.0 (br s, NH, 2 H), 0.7 (s,
CH3, 12 H), -20.7 (t, RuH, 1 H, JHP ) 27.4 Hz). 31P{1H} NMR
(C6D6, δ): 67.2 (s).
RuH(4-SC6H4OCH3)(tmen)(PPh3)2. 4-Methoxybenzenethiol (24
mg, 0.171 mmol) and 1 (100 mg, 0.135 mmol) were used. Yield:
85 mg (71%). 1H NMR (C6D6, δ): 6.6-8.1 (m, phenyl, 34 H), 3.4
(s, OCH3, 3 H), 3.2 (d, NH, 2 H, JHH ) 10.3 Hz), 1.9 (d, NH, 2 H,
JHH ) 10.3 Hz), 0.7 (s, CH3, 6 H), 0.5 (s, CH3, 6 H), -13.4 (t,
RuH, 1 H, JHP ) 24.6 Hz). 31P{1H} NMR (C6D6, δ): 67.7 (s, PPh3,
2 P). IR (Nujol, cm-1): 3340 (ν(NH)), 3321 (ν(NH)), 3270 (ν-
(NH)), 3217 (ν(NH)), 1907 (ν(RuH)). Anal. Calcd for RuSP2-
ON2C49H54‚0.25C7H8: C, 67.35; H, 6.24; N, 3.10. Found: C, 67.39;
H, 6.31; N, 3.12.
0.57 (s, CH3, 3 H), 0.48 (s, CH3, 3 H), -15.3 (t, RuH, 1 H, JHP
)
24.7 Hz). 31P{1H} NMR (C6D6, δ): AB pattern, 70.6 (A, PPh3, 1
P, JAB ) 37.8 Hz), 69.7 (B, PPh3, 1 P). IR (Nujol, cm-1): 3401
(ν(NH)), 3321 (ν(NH)), 3154 (ν(NH)), 3051 (ν(NH)), 2102 (ν-
(CN)), 1959 (ν(RuH)), 1704 (ν(CO)). Anal. Calcd for RuP2-
ON4C51H56‚0.25C6H6: C, 68.28; H, 6.28; N, 6.07. Found: C, 68.38;
H, 6.16; N, 6.04.
Synthesis of trans-RuHX(dach)(PPh3)2. All of the syntheses
involving the substitution of HCl for HX in 2 were performed as
follows: HX, potassium tert-butoxide, and 2 were added to a flask
under nitrogen and dissolved in THF (1 mL). A small amount of
red-orange solution was formed when the solvent was added, but
the solution became yellow upon stirring. The yellow solution was
stirred for 15 min and then filtered through Celite. The filtrate was
reduced to dryness, the residue was stirred in 2:1 hexanes-ether
(3 mL), this mixture was filtered, and the solid was washed with
hexanes and dried under vacuum.
RuH(OPh)(dach)(PPh3)2. Phenol (19 mg, 0.202 mmol), potas-
sium tert-butoxide (20 mg, 0.178 mmol), and 2 (127 mg, 0.164
mmol) were used. Yield: 45 mg (33%). 1H NMR (C6D6, δ): 6.5-
8.1 (m, phenyl, 35 H), 0.0-3.8 (m, diamine, 14 H), -20.4 (t, RuH
major isomer, JHP ) 26.1 Hz), -13.4 (t, RuH minor isomer 1, JHP
) 27.7 Hz), -13.7 (dd, RuH minor isomer 2, JHP1 ) 33.8 Hz, JHP2
RuH(OPPh2)(tmen)(PPh3)2. Diphenylphosphine oxide (34 mg,
0.164 mmol) and 1 (122 mg, 0.168 mmol) were used. Yield: 102
mg (66%). 1H NMR (C6D6, δ): 6.6-8.3 (m, phenyl, 40 H), 5.4 (s
br, NH, 2 H), 2.0 (d, NH, 2 H, JHH ) 9.3 Hz), 0.9 (s, CH3, 6 H),
0.8 (s, CH3, 6 H), -9.0 (dt, RuH, 1 H, JHP1 ) 99.9 Hz, JHP2
)
)
24.7 Hz). 31P{1H} NMR (C6D6, δ): 80.1 (t, OPPh2, 1 P, JPP
17.5 Hz), 65.7 (d, PPh3, 2 P). IR (Nujol, cm-1): 3342 (ν(NH)),
1926 (ν(RuH)). Anal. Calcd for RuP3ON2C54H57‚2C7H8: C, 70.71;
H, 6.32; N, 2.70. Found: C, 70.01; H, 6.29; N, 2.70.
RuH(OP(OEt)2)(tmen)(PPh3)2. Diethyl phosphite (67 mg, 0.485
mmol) and 1 (300 mg, 0.404 mmol) were used. Yield: 250 mg

5486 Organometallics, Vol. 25, No. 22, 2006
Clapham et al.
) 24.4 Hz). 31P{1H} NMR (C6D6, δ): major isomer, AB pattern,
69.0 (A, PPh3, JAB ) 38.9 Hz) and 65.9 (B, PPh3); minor isomer
1, 82.0 (d, JPP ) 36.5 Hz), 67.7 (d); minor isomer 2, 80.0 (d, JPP
) 37.2 Hz), 67.4 (d). IR (Nujol, cm-1): 3319 (ν(NH)), 2028 (ν-
(RuH)).
RuH(4-SC6H4OCH3)(dach)(PPh3)2. 4-Methoxybenzenethiol (30
mg, 0.214 mmol), potassium tert-butoxide (22 mg, 0.196 mmol),
and 2 (140 mg, 0.180 mmol) were used. Yield: 135 mg (85%). 1H
NMR (C6D6, δ): 6.5-8.3 (m, phenyl, 34 H), 3.3 (s, OCH3, 3 H),
0.0-2.8 (m, cyclohexyl, 14 H), -13.8 (t, RuH, 1 H, JHP ) 23.7
Hz). 31P{1H} NMR (C6D6, δ): 69.2 (s, PPh3). IR (Nujol, cm-1):
3340 (ν(NH)), 3322 (ν(NH)), 1907 (ν(RuH)).
RuH(OPPh2)(dach)(PPh3)2. Diphenylphosphine oxide (31 mg,
0.153 mmol), potassium tert-butoxide (17 mg, 0.151 mmol), and 2
(110 mg, 0.142 mmol) were used. Yield: 70 mg (52%). 1H NMR
(C6D6, δ): 6.5-8.5 (m, phenyl, 40 H), 0.0-3.3 (m, diamine, 14
H), -9.0 (dt, RuH, 1 H, JHP1 ) 98.7 Hz, JHP2 ) 23.5 Hz). 31P{1H}
NMR (C6D6, δ): ABX pattern, 80.8 (X, OPPh2, 1 P), 66.7 (A,
PPh3, 1 P, JAX ) 16.2 Hz, JAB ) 33.7 Hz), 66.1 (B, PPh3, 1 P, JBX
) 18.8 Hz). IR (Nujol, cm-1): 3328 (ν(NH)), 3271 (ν(NH)), 1877
(ν(RuH)).
were collected at 3.25 and 24 h. Analysis by GC showed 2% and
100% conversion to 1-phenylethanol, respectively.
The above procedure was used with RuH(CCPh)(dach)(PPh3)2
(7 mg, 0.00832 mmol) and acetophenone (1.008 g, 8.3895 mmol)
(S:C ) 1008:1). An aliquot was taken at 3.5 h and analyzed by
chiral GC. The chromatogram showed 100% conversion and 62%
ee.
Hydrogenation of Acetophenone in Benzene. A solution of
RuH(CCPh)(dach)(PPh3)2 was prepared in benzene with a concen-
tration of 3.33 × 10-3 M. A 1.5 mL portion of this stock solution
was diluted in 2 mL of benzene. The solution was drawn into a
syringe. A solution of acetophenone (10 mg) was prepared in
benzene (3 mL). This was drawn into a syringe. Both solutions
were injected into a reactor under 5 atm of hydrogen gas, giving a
total sample volume of 5 mL and catalyst and substrate concentra-
tions of 1.00 × 10-3 and 0.0167 M, respectively. Aliquots were
taken at 1200, 2400, 3600, 4800, 6000, and 77 100 s and analyzed
by chiral GC for conversion and ee. Conversion (%)/ee (%) values
for the above aliquots were 1/62, 1.5/57, 2/54, 2.5/52, 3/47, and
6/33, respectively.
Stoichiometric Reaction. RuH(CCPh)(dach)(PPh3)2 (10 mg,
0.0119 mmol) and acetophenone (2 mg, 0.0166 mmol) were reacted
in C6D6 in an NMR tube with a gas adaptor. After 3 h no reaction
RuH(OP(OEt)2)(dach)(PPh3)2. Diethyl phosphite (24 mg, 0.148
mmol), potassium tert-butoxide (17 mg, 0.151 mmol), and 2 (104
1
was observed by H and 31P NMR spectroscopy. The sample was
1
mg, 0.134) were used. Yield: 20 mg (17%). H NMR (C6D6, δ):
placed under 1 atm of hydrogen gas. At this point, 1-phenylethanol
was observed in the 1H NMR. The sample was left under hydrogen
for 24 h and then analyzed by GC. The chromatogram showed 27%
conversion and 1% ee.
Michael Addition. 2-Cyclohexen-1-one, dimethyl malonate, and
a catalyst were dissolved in THF (ca. 3 mL) under argon and stirred.
An aliquot was taken and exposed to oxygen to kill the catalyst.
The sample was analyzed by chiral GC to determine conversion to
the Michael product. Specific conditions and conversions are shown
in Table 1.
6.8-8.2 (m, phenyl, 30 H), 4.5 (dq, CH2, 4 H, JHP ) 3.3 Hz, JHH
) 7.0 Hz), 0.0-4.3 (m, diamine, 14 H), 1.1 (t, CH3, 6 H), -6.6
(dt, RuH, 1 H, JHP1 ) 142.5 Hz, JHP2 ) 20.8 Hz). 31P{1H} NMR
(C6D6, δ): ABX pattern, 118.8 (X, OP(OEt)2, 1 P), 71.4 (A, PPh3,
1 P, JAX ) 29.2 Hz, JAB ) 35.2 Hz), 70.7 (B, PPh3, 1 P, JBX
)
30.4 Hz). IR (Nujol, cm-1): 3337 (ν(NH)), 3279 (ν(NH)), 3232
(ν(NH)), 1791 (ν(RuH)), 1575 (ν(OP)).
RuH(CCPh)(dach)(PPh3)2. Phenylacetylene (23 mg, 0.225
mmol), potassium tert-butoxide (22 mg, 0.196), and 2 (140 mg,
0.180 mmol) were used. Yield: 40 mg (26%). 1H NMR (C6D6, δ):
6.6-8.4 (m, phenyl, 35 H), 0.0-3.4 (m, diamine, 14 H), -7.5 (t,
RuH, 1 H, JHP ) 21.6 Hz). 31P{1H} NMR (C6D6, δ): AB pattern,
74.9 (A, PPh3, 1 P, JAB ) 42.8 Hz), 74.5 (B, PPh3, 1 P). IR (Nujol,
cm-1): 3323 (ν(NH)), 2053 (ν(CC)), 1778 (ν(RuH)).
RuH(NCCHCN)(dach)(PPh3)2. Malononitrile (10 mg, 0.151
mmol), potassium tert-butoxide (17 mg, 0.151 mmol), and 2 (107
mg, 0.138 mmol) were used. Yield: 61 mg (55%). 1H NMR (C6D6,
δ): 6.7-8.1 (m, phenyl, 30 H), 0.0-3.6 (m, diamine, 14 H), -15.8
(t, RuH, 1 H, JHP ) 25.0 Hz). 31P{1H} NMR (C6D6, δ): AB pattern,
71.2 (A, PPh3, 1 P, JAB ) 38.3 Hz) and 70.4 (B, PPh3, 1 P). IR
(Nujol, cm-1): 3324 (ν(NH)), 2124 (ν(CN)), 1959 (ν(RuH)).
Reaction of RuH(OPh)(tmen)(PPh3)2 with Dimethyl Mal-
onate. RuH(OPh)(tmen)(PPh3)2 (54 mg, 0.0646 mmol) and dimethyl
malonate (12 mg, 0.09083 mmol) were dissolved in C6D6 under
1
1
argon. Equilibrium was observed by H and 31P{1H} NMR. H
NMR (C6D6, δ): 6.5-7.9 (m, phenyl), 3.4 (s br, NH), 3.2 (s,
OCH3), 2.9 (s br, NH), 1.9 (s br, NH), 0.7 (s br, CH3), -20.7 (t,
RuH, JHP ) 27.9 Hz). 31P{1H} NMR (C6D6, δ): 68.4 (s).
Acknowledgment. We thank Dr. Datong Song for his help
in acquiring some of the crystallographic data and NSERC and
the donors of the Petroleum Research Fund, administered by
the American Chemical Society, for funding.
Hydrogenation of Neat Acetophenone. Under an argon atmo-
sphere, RuH(CCPh)(tmen)(PPh3)2 (11 mg, 0.0130 mmol) was
dissolved in acetophenone (999 mg, 8.315 mmol) (S:C ) 638:1).
The solution was transferred by syringe to a reactor under hydrogen
and the reactor pressurized with 10 atm of hydrogen gas. Aliquots
Supporting Information Available: X-ray crystallographic data
as CIF files. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM060661Q