Attenuation of intramolecular Ru-H?H-N dihydrogen bonding in aminocyclopentadienyl ruthenium hydride complexes containing phosphite ligands

Full text of DOI:10.1021/om010966z

1898
Organometallics 2002, 21, 1898-1902
Atten u a tion of In tr a m olecu la r Ru -H‚‚‚H-N Dih yd r ogen
Bon d in g in Am in ocyclop en ta d ien yl Ru th en iu m Hyd r id e
Com p lexes Con ta in in g P h osp h ite Liga n d s
Yat Fai Lam,† Chuanqi Yin,*,§ Chi Hung Yeung,† Siu Man Ng,†
Guochen J ia,*,‡ and Chak Po Lau*,†
Department of Applied Biology & Chemical Technology, The Hong Kong Polytechnic
University, Hung Hom, Kowloon, Hong Kong, China, Department of Chemistry,
The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon,
Hong Kong, China, and Department of Pharmacology, Wuhan Institute of Chemical
Technology, Wuhan, Hubei 430074, China
Received November 7, 2001
Replacement of the dppm ligand in (η5-C5H4(CH2)2NMe2H+)Ru(dppm)H with two less
donating triphenyl phosphite ligands reduces the strength of the intramolecular Ru-H‚‚‚
H-N dihydrogen bond to such an extent that it is hardly evidenced by NMR measurements.
Unlike its dihydrogen-bonded dppm analogue, the triphenyl phosphite complex (η5-
C5H4(CH2)2NMe2H+)Ru(P(OPh)3)2H shows no catalytic activity for reduction of carbon dioxide
to formic acid.
Sch em e 1
In tr od u ction
The unconventional hydrogen bond (dihydrogen bond)
between a transition metal hydride and a hydrogen
bond donor containing an O-H or an N-H group might
be regarded as intermediates in hydride protonation to
generate a η2-H2 ligand and the reverse reaction,
heterolytic splitting of dihydrogen.1 It is also recognized
for activating the M-H bond for reactions such as H/D
exchange, proton transfer, and substitution.1 The im-
portance of dihydrogen bonding for controlling the
reactivity and stereochemistry of organometallic hydride
complexes has been well-demonstrated also.2
We have recently synthesized and characterized the
intramolecularly Ru-H‚‚‚H-N dihydrogen-bonded com-
plex (η5-C5H4(CH2)nNMe2H+)Ru(dppm)H (n ) 2 or 3) (1),
which shows rapid and reversible hydride/proton ex-
change via the intermediacy of a η2-dihydrogen tau-
tomer, [(η5-C5H4(CH2)nNMe2)Ru(dppm)(H2)]+ (2) (Scheme
1).3 Sabo-Etienne, Chaudret, and co-workers have,
however, reported that in the triphenylphosphine ana-
logue of 1 an exchange process between the hydride and
the ammonium proton does not involve proton transfer
within the dihydrogen bond.4 The Ru-H‚‚‚H-N dihy-
drogen bond in 1 is the key feature in the catalytic
hydrogenation of CO2 to formic acid. A theoretical study
of this catalytic reaction with 1 has recently been
reported.5
Continuing our studies of dihydrogen bonding in
aminocyclopentadienyl ruthenium hydride complexes
and the catalytic activity of these complexes in CO2
hydrogenation, we chose to study the influence of
decreased basicity of the metal center on the strength
of the Ru-H‚‚‚H-N dihydrogen bond and the efficiency
of CO2 hydrogenation. The basicity of the metal center
in the aminocyclopentadienyl ruthenium complex was
decreased by replacement of the dppm ligand of 1 or 3
† The Hong Kong Polytechnic University.
‡ The Hong Kong University of Science and Technology.
§ Wuhan Institute of Chemical Technology.
(1) (a) Abdur-Rashid, K.; Lough, A. J .; Morris, R. H. Organometallics
2000, 19, 2655. (b)Abdur-Rashid, K.; Gusev, D. G.; Lough, A. J .; Morris,
R. H. Organometallics 2000, 19, 834. (c) Gru¨ndemann, S.; Ulrich, S.;
Limbach, H.-H.; Golubev, N. S.; Denisov, G. S.; Epstein, L. M.; Sabo-
Etienne, S.; Chaudret, B. Inorg. Chem. 1999, 38, 2550. (d) Caballero,
A.; J alo´n, F. A.; Manzano, B. R. Chem. Commun. 1998, 1879. (e)
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la Torre, J . R. J . Chem. Soc., Dalton Trans. 1998, 745. (f) Ayllo´n, J .
A.; Gervaux, C.; Sabo-Etienne, S.; Chaudret, B. Organometallics 1997,
16, 2000. (g) Schlaf, M.; Morris, R. H. J . Chem. Soc., Chem. Commun.
1995, 625. (h) Lee, J . C., J r.; Peris, E.; Rheingold, A. L.; Crabtree, R.
H. J . Am. Chem. Soc. 1994, 116, 11014.
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(b) Abad, M. M.; Atheaux, I.; Maisonnat, A.; Chaudret, B. Chem.
Commun. 1999, 381. (c) Aime, S.; Fe´rriz, M.; Gobetto, R.; Valls, E.
Organometallics 1999, 18, 2030. (d) Guari, Y.; Ayllon, J . A.; Sabo-
Etienne, S.; Chaudret, B. Inorg. Chem. 1998, 37, 640. (e) Aime, S.;
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10.1021/om010966z CCC: $22.00 © 2002 American Chemical Society
Publication on Web 04/03/2002

Intramolecular Ru-H‚‚‚H-N Dihydrogen Bonding
Organometallics, Vol. 21, No. 9, 2002 1899
with triphenyl phosphite. We used the less donating
phosphite because we anticipated that usage of more
donating monodentate phosphine PR3 might result in
the formation of a dihydride complex instead of the Ru-
H‚‚‚H-N dihydrogen-bonded species analogous to 1. It
is well-known that the final thermodynamic products
of protonation of ruthenium cyclopentadienyl hydride
complexes (η5-C5R5)Ru(PR3)2H containing more basic
PR3 ligands adopt the dihydride form trans-[(η5-C5R5)-
Ru(PR3)2(H)2]+,6 although the kinetic products may be
η2-dihydrogen complexes.7
to the two inequivalent phosphites at δ 144.2 and 172.9
ppm (J (PP) ) 89 Hz). The sharp AX pattern indicates
that there is no interconversion of the two phosphites
at room temperature by reversible metalation/demeta-
lation of ortho-hydrogens on the two different phos-
phites. It was known from variable-temperature 31P
NMR spectroscopic study that interconversion of the
phosphines is facile in the orthometalated iridium
complex IrH(C2Ph)(PtBu2Ph)(η2-C6H4PtBu2).10 The dou-
blet signal at δ 111.2 ppm (J (CP) ) 16.1 Hz) in the 13C
NMR spectrum of 5-OTf is diagnostic of a metalated
ortho-carbon atom Ru-C. Signals with similar chemical
shifts and P-C coupling constants also appear in the
13C NMR spectra of similar orthometalated Ru(II)
complexes.8,9a The amine group in the sidearm was
protonated. Evidence for amine protonation was pro-
Resu lts a n d Discu ssion
We intended to prepare the triphenyl phosphite
analogue of 3 (see Scheme 1) and then react the complex
with pressurized H2 to obtain (η5-C5H4(CH2)2NMe2H+)-
Ru(P(OPh)3)2H, the phosphite analogue of 1, with which
we would study the strength of its Ru-H‚‚‚H-N inter-
action. Comparisons in terms of H-bond strength and
reactivity of this complex with those of 1 could then be
made. We reacted the chloro complex (η5-C5H4(CH2)2-
NMe2)Ru(P(OPh)3)2Cl (4) with AgOTf, anticipating that
removal of the chloro ligand would create a vacant site,
which would be occupied by the amine sidearm, thus
producing the desired complex. But apparently, instead
of sidearm coordination, proximal generation of a vacant
coordination site at the cationic ruthenium center
induced cyclometalation of one of the triphenyl phos-
phite ligands and produced the orthometalated complex
[(η5-C5H4(CH2)2NMe2H+)Ru(P(OPh)3)(η2-P(OPh)2OC6H4)]-
OTf- (5-OTf) (eq 1). Formation of 5-OTf is not too
1
vided by the H NMR spectrum of 5-OTf; it showed the
protons of the two N-methyl groups, which are diaste-
reotopic, as two doublets at δ 2.60 (J (HH) ) 4.4 Hz) and
2.70 (J (HH) ) 4.3 Hz) ppm. The doublets were down-
field-shifted from the N-methyl proton signal of the free
ligand C5H5(CH2)2NMe2 (δ 2.27 ppm). Similar downfield
shifts of the N-methyl protons have been observed in 1
and its chloro analogue (η5-C5H4(CH2)nNMe2H+)Ru-
(dppm)Cl,3 as well as molybdenum11 and rhodium12
complexes containing similar ligands. Protonation of the
amine group in 5-OTf was also supported by observa-
tion of the broad signal of N-H at δ 8.20 ppm. Although
5-OTf is well-characterized by NMR spectroscopy, it is
difficult to obtain good elemental analysis results, due
to difficulty in completely removing the silver salts from
the complex, which is a sticky semisolid. We attempted
to purify 5-OTf by column chromatography using
neutral alumina, but the product collected was the
deprotonated form of 5-OTf, i.e., (η5-C5H4(CH2)2NMe2)-
Ru(P(OPh)3)(η2-P(OPh)2OC6H4) (6). The 31P{1H} NMR
spectrum of 6 is similar to that of 5-OTf, showing two
doublets at δ 144.3 (J (PP) ) 99.9 Hz) and 170.9 (J (PP)
) 99.9 Hz) ppm. The 13C NMR spectrum of 6, similar
to that of 5-OTf, also contains a doublet in the downfield
region at δ 111.1 ppm (J (CP) ) 16.0 Hz), due to Ru-C.
1
However, the H NMR spectrum of 6, shows, instead of
a pair of downfield-shifted doublets for the N-methyl
protons, a relatively upfield singlet, which integrates
to 6 hydrogens, at δ 2.03 ppm. No N-H signal is
observable in the downfield region. Acidification of 6
with HBF4‚OEt2 gives pure [(η5-C5H4(CH2)2NMe2H+)-
Ru(P(OPh)3)(η2-P(OPh)2OC6H4)]BF4 (5-BF 4), whose
-
surprising, since it is known that the unsubstituted Cp
complex (η5-C5H5)Ru(PPh3)(P(OPh)3)Cl reacts with Ag-
OTf in the presence of piperidine at room temperature
to give the orthometalated complex (η5-C5H5)(PPh3)(η2-
P(OPh)2OC6H4).8 Orthometalated Cp ruthenium and
osmium complexes are well-documented.8,9 Complex
5-OTf was characterized by NMR spectroscopy. The 31P-
{1H} NMR spectrum showed two doublets corresponding
NMR spectroscopic data are identical to those of 5-OTf.
Complex 6 can also be prepared by refluxing 4 with
sodium methoxide in methanol. Similar orthometalation
has been achieved for (η5-C5H5)Ru(P(OPh)3)2Cl by re-
fluxing the complex with methoxide ion in methanol.9a
However, the complexes (η5-C5H5)Ru(PPh3)2Cl and (η5-
C5H5)Ru(PPh3)(P(OPh)3)Cl cannot be orthometalated
under the same experimental conditions.8
Study of reactivity of 5-BF 4 and 6 toward pressurized
dihydrogen gave interesting results. Complex 5-BF 4
reacted, as expected, with H2 (10 atm) in chlorobenzene
(6) (a) J essop, P. G.; Morris, R. H. Coord. Chem. Rev. 1992, 121,
155. (b) Heinekey, D. M.; Oldham, W. J ., J r. Chem. Rev. 1993, 93, 913.
(7) Chinn, M. S.; Heinekey, D. M. J . Am. Chem. Soc. 1990, 112, 5166.
(8) J oslin, F. L.; Mague, J . T.; Roundhill, D. M. Organometallics
1991, 10, 521.
(9) (a) Bruce, M. I.; Humphrey, M. G.; Swincer, A. G.; Wallis, R. C.
Aust. J . Chem. 1984, 37, 1747. (b) Wanandi, P. W.; Tilley, T. D.
Organometallics 1997, 16, 4299. (c) Esteruelas, M. A.; Gutie´rrez-
Puebla, E.; Lo´pez, A. M.; On˜ate, E.; Tolosa, J . I. Organometallics 2000,
19, 275. (d) Baya, M.; Crochet, P.; Esteruelas, M. A.; On˜ate, E.
Organometallics 2001, 20, 240.
(10) Cooper, A. C.; Huffman, J . C.; Caulton, K. G. Organometallics
1997, 16, 1974.
(11) (a) Wang, T.-F.; Lee, T.-Y.; Chou, J .-W.; Ong, C.-W. J . Orga-
nomet. Chem. 1992, 423, 31. (b) Wang, T.-F.; Wen, Y.-S. J . Organomet.
Chem. 1992, 439, 155.
(12) Philippopoulos, A.; Hadjiliadis, N.; Hart, C. E.; Donnadieu, B.;
McGowan, P. C.; Poilblanc, R. Inorg. Chem. 1997, 36, 1842.

1900 Organometallics, Vol. 21, No. 9, 2002
Lam et al.
and 248 K). The similarity of the T1(min) values of the
hydride ligands of 7 and 8 lends further support to the
notion that intramolecular dihydrogen-bonding interac-
tion in the former is minimal. It is obviously true that
the less donating triphenyl phosphite ligands lower the
basicity of the metal center in 7, which in turn decreases
the hydridicity of the hydride ligand to such an extent
that the Ru-H‚‚‚H-N dihydrogen bond is no longer
stable. The M-H‚‚‚H-X dihydrogen bond is a hydride-
proton interaction, and its bond strength can be modu-
lated by tuning the nucleophilicity of M-H and/or the
electrophilicity of H-X.1b,14 Epstein, Berke, and co-
workers have reported that the strengths of the dihy-
drogen bonds in the tungsten hydride-alcohol com-
plexes W(CO)2(NO)(L)2H‚‚‚HOR increase with the donor
abilities of the ligand L (PPh3 < P(OiPr)3 < PEt3
<
PMe3).13
Unlike the dppm analogue 1, 7 is stable toward H2
loss even after refluxing in THF or heating at 90 °C in
chlorobenzene for 2 days. This is not unexpected since
lack of Ru-H‚‚‚H-N dihydrogen bonding in 7 precludes
the possibility of eliminating H2 via the intermediacy
of a η2-H2 species.
at room temperature to yield our target complex [(η5-
C5H4(CH2)2NMe2H+)Ru(P(OPh)3)2H]BF4- (7) (eq 2). Un-
der identical experimental conditions, 6 is, however,
inert to H2. We expect 6, in analogy with 5-BF 4, to react
with H2, forming the deprotonated form of 7, i.e., (η5-
C5H4(CH2)2NMe2)Ru(P(OPh)3)2H (8). It was later found
that 8 could be obtained by deprotonation of 7 with
aqueous KOH in THF.
To learn more about the reaction of 5-BF 4 with H2,
we reacted [(η5-C5H4(CH2)2NMe2D+)Ru(P(OPh)3)(η2-
P(OPh)2OC6H4)]BF4- (5D-BF 4), the deuterated form of
5-BF 4 in which the amine sidearm was deuterated, with
H2 and studied the distribution of deuterium in the
1
In the H NMR spectrum of 7, the hydride signal is a
sharp triplet (J (HP) ) 26.0 Hz) at δ -11.83 ppm.
Similar to its precursor 5-BF 4, complex 7 shows a
downfield-shifted signal (δ 2.61 ppm) for its N-methyl
protons, but the signal is a singlet rather than a pair of
doublets as observed for the N-methyl protons of 5-BF 4.
The N-H of 7, which does not split the N-methyl signal,
appears as a broad peak at δ 8.47 ppm. The 31P{1H}
NMR spectrum of 7 shows a singlet at δ 149.7 ppm,
indicating that the two phosphorus atoms are equiva-
lent. Several attempts to obtain single crystals of 7 for
X-ray structural determination have not been success-
ful; in fact, this complex, and other phosphite complexes
reported in this work, are sticky solids: they all resist
single-crystal formation.
2
product. A combination of 1H and H NMR spectroscopic
studies clearly indicated that all the deuterium atoms
had been transferred to the triphenyl phosphite ligand,
and the Ru-H and N-H groups were deuterium-free
(eq 3).
The sharpness of the hydride signal of 7 indicates that
the H‚‚‚H interaction between the hydride ligand and
N-H on the pendant amine arm is very weak, if it exists
at all. On the contrary, complex 1, the dppm analogue
of 7, which shows a broad hydride signal, exhibits a
strong Ru-H‚‚‚H-N dihydrogen-bonding interaction,
and the two hydrogen atoms undergo rapid exchange
via the intermediacy of a η2-dihydrogen species (Scheme
1).3 Broadening of the hydride signal of WH(CO)2(NO)-
(PMe3)2 was observed in the presence of acidic alcohol,
due to the formation of an intermolecular M-H‚‚‚H-
OR dihydrogen bond.13 Significant broadening of the
hydride signals of both cis and trans isomers of RuH2-
(dppm)2 were also observed upon addition of excess
phenol.1f Lack of Ru-H‚‚‚H-N dihydrogen-bonding
interaction in 7 was also supported by the fact that
practically no NOE was detected between Ru-H and
N-H. Variable-temperature T1 measurements for the
hydride ligand of 7 yielded a T1(min) of 890 ms (at 400
MHz and 290 K); this value is very similar to that of
the hydride ligand of 8 (T1(min) ) 900 ms at 400 MHz
The result of the labeling experiment is in consonance
with the proposed reaction mechanism depicted in
Scheme 2. It is noteworthy that the crucial step of the
hydrogenolysis of 5-BF 4 with H2 seems to be the
protonation of the ortho-carbon in Ru-C by the rela-
tively weak alkylammonium acid sidearm; this step
might be triggered or induced by the incoming H2. It is
(14) (a) Chu, H. S.; Xu, Z.; Ng, S. M.; Lau, C. P.; Lin, Z. Eur. J .
Inorg. Chem. 2000, 993. (b) Buil, M. L.; Esteruelas, M. A.; On˜ate, E.;
Ruiz, N. Organometallics 1998, 17, 3346. (c) Peris, E.; Lee, J . C., J r.;
Rambo, J . R.; Eisenstein, O.; Crabtree, R. H. J . Am. Chem. Soc. 1995,
117, 3485.
(13) Shubina, E. S.; Belkova, N. V.; Krylov, A. N.; Vorontsov, E. V.;
Epstein, L. M.; Gusev, D. G.; Niedermann, M.; Berke, H. J . Am. Chem.
Soc. 1996, 118, 1105.

Intramolecular Ru-H‚‚‚H-N Dihydrogen Bonding
Organometallics, Vol. 21, No. 9, 2002 1901
Sch em e 2
therefore not surprising to find that 6, which is devoid
of an ammonium proton, is unreactive toward H2.
Protonation of the ortho-carbon of the orthometalated
complex by weak acid had been demonstrated by the
reaction of the iridium complex IrH(CtCPh)(PPhtBu2)-
(η2-C6H4PtBu2) with the weak carbon acid PhCtCH to
form IrH(CtCPh)2(PPhtBu2)2; the protonation mecha-
nism, which was established with the aid of a deuterium
isotope study, does not, however, involve direct delivery
of the acidic acetylenenic hydrogen to the ortho-carbon.
It involves the incoming acetylene triggering the reduc-
tive elimination of the preexisting Ir-C and Ir-H
bonds.10
As expected, the 1H NMR spectrum of 8 shows a
relatively upfield singlet signal for its nonprotonated
amine group (δ 2.29 ppm), and no N-H signal is
observable in the downfield region. The two equivalent
phosphite ligands of 8 appear as a singlet at δ 143.7
ppm in the 31P{1H} NMR spectrum.
fluxional pathways are present, one of which leads to a
thermodynamically more stable species that contains a
dihydrogen bond between the hydride and the am-
monium proton. However, the complex does not lose H2
in solution at room temperature.4 We have here dem-
onstrated that in (η5-C5H4(CH2)2NMe2H+)Ru(P(OPh)3)2H
(7), which contains the less donating phosphite ligands,
the stable conformation of the complex in solution is one
in which no Ru-H‚‚‚H-N dihydrogen-bonding interac-
tion is present between the hydride and the ammonium
proton. We attribute the lack of interaction to reduced
hydridicity of the hydride ligand in 7. In summary, this
work, together with our previous one and that of Sabo-
Etienne, Chaudret, and co-workers, provides a fairly
complete picture of intramolecular M-H‚‚‚H-N dihy-
drogen-bonding interactions in aminocyclopentadienyl
ruthenium hydride complexes.
Exp er im en ta l Section
Since complex 1, the dppm analogue of 7, is believed
to play a crucial role in catalytic reduction of CO2 to
formic acid, we are thus interested in studying the
catalytic activity of 7 (or its precursor 5-BF 4) in CO2
hydrogenation. No catalytic activity was, however,
found. Lack of activity in 7 is attributable to low
hydridicity of the hydride ligand. In 7, although the
protonated amine sidearm, like that of 1, can H-bond
with one of the oxygen atoms of an incoming CO2
molecule, thus enhancing the electrophilicity at the
carbon, the hydride ligand is unfortunately not hydridic
enough to allow its abstraction by the electrophilic
carbon center.
All reactions were performed under an atmosphere of dry
nitrogen using standard Schlenk techniques. All chemicals
were obtained from Aldrich except dicyclopentadiene and
deuterated NMR solvents, which were purchased from BDH
15
and Armar, respectively. The ligands C5H5(CH2)2NMe2 and
the complexes RuCl2(PPh3)3 and (η5-C5H4(CH2)2NMe2)Ru-
16
(PPh3)2Cl3 were prepared according to published procedures.
Solvents were distilled under a dry nitrogen atmosphere with
appropriate drying agents (solvent/drying agent): ethanol/
Mg-I2, tetrahydrofuran/Na-benzophenone, toluene/Na-ben-
zophenone, hexane/Na, diethyl ether/CaH2, chlorobenzene/
P2O5. High-purity hydrogen gas was supplied by Hong Kong
Oxygen.
Proton NMR spectra were obtained from a Bruker DPX 400
spectrometer. Chemical shifts were reported relative to re-
sidual protons of the deuterated solvents. 31P and 13C NMR
spectra were recorded on a Bruker DPX 400 spectrometer at
161.7 and 100.6 MHz, respectively; 31P chemical shifts were
externally referenced to 85% H3PO4 in D2O, while 13C chemical
shifts were internally referenced to the residual peaks of
deuterated solvents. Relaxation time T1 measurements were
carried out at 400 MHz by the inversion-recovery method
using the standard 180°-τ-90° pulse sequence. High-pressure
Su m m a r y
Our previous work has demonstrated that the amino-
cyclopentadienyl-chelated complex [(η:5η1-C5H4(CH2)n-
NMe2)Ru(dppm)]+ (3) reacts with pressurized H2 to give
(η5-C5H4(CH2)nNMe2H+)Ru(dppm)H (1), in which the
Ru-H forms a Ru-H‚‚‚H-N dihydrogen bond with the
ammonium proton of the sidearm; the latter loses H2
slowly at room temperature and reverts to the former.3
In the case of (η5-C5H4(CH2)2NMe2H+)Ru(PPh3)2H,
whereas no Ru-H‚‚‚H-N dihydrogen bond is present
in the solid state, it is likely that in solution several
(15) Rees, W. S., J r.; Dippel, K. A. Org. Prep. Proced. Int. 1992, 24,
527.
(16) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth.
1970, 12, 237.

1902 Organometallics, Vol. 21, No. 9, 2002
Lam et al.
studies were carried out in a commercial 5 mm Wilmad
pressure-valved NMR tube. Elemental analyses were per-
formed by M-H-W Laboratories, Phenix, AZ.
precipitate the product. It was collected by filtration, washed
with diethyl ether (2 × 15 mL), and dried in vacuo to yield a
sticky yellowish brown solid. Yield: 0.08 g (73%). Anal. Calcd
for C45H44BNO6F4Ru: C, 57.22; H, 4.69; N, 1.48. Found: C,
(η5-C5H4(CH2)2NMe2)Ru (P (OP h )3)2Cl (4). A solution con-
taining (η5-C5H4(CH2)2NMe2)Ru(PPh3)2Cl (1.00 g, 1.12 mol) and
triphenyl phosphite (1.02 mL, 3.92 mmol) in toluene (50 mL)
was refluxed for 48 h. Upon removal of the solvent under
vacuum, 20 mL of diethyl ether was added to the residual
paste with vigorous stirring to produce a yellow powder. The
solid was then washed with hexane (2 × 20 mL) and dried in
vacuo. Yield: 0.97 g (86%). Anal. Calcd for C45H44NO6P2-
ClRu: C, 60.50; H, 4.96; N, 1.58. Found: C, 59.96; H, 5.01; N,
1.63. 1H NMR (CDCl3, 400 MHz, 20 °C): δ 1.82 (br s, 2 H,
CH2N), 2.21 (m, 2 H, C5H4CH2), 2.28 (s, 6 H, NCH3), 3.54 (br
s, 2 H of Cp ring), 3.93 (br s, 2 H of Cp ring), 6.81-7.33 (m, 30
H of P(OPh)3). 31P{1H}NMR (CDCl3, 161.7 MHz, 20 °C): δ
138.3 (s).
1
57.54; H. 4.59; N, 1.57. H NMR (CDCl3, 400 MHz, 20 °C): δ
2.39 (m, 2 H, CH2N), 2.60 (d, 3 H, J (HH) ) 4.36 Hz, NCH3),
2.70 (d, 3 H, J (HH) ) 4.30 Hz, NCH3), 2.87 (m, 2 H, C5H4CH2),
5.04 (br s, 1 H of Cp ring), 5.20 (br s, 1 H of Cp ring), 5.45 (br
s, 1 H of Cp ring), 5.66 (br s, 1 H of Cp ring), 6.95-7.38 (m, 29
H of phosphites), 8.20 (br s, 1 H, NH). 31P{1H} NMR (CDCl3,
161.7 MHz, 20 °C): δ 144.2 (d, 2J (PP) ) 89 Hz, P(OPh)3), 172.9
(d, 2J (PP) ) 89 Hz, P(OPh)2(OC6H4)). 13C{1H} NMR (CDCl3,
2
100.6 MHz, 20 °C): δ 111.2 (d, J (PC) ) 16.1 Hz, Ru-C).
[(η5-C5H4(CH2)2NMe2H+)Ru (P (OP h )3)2H]BF 4 (7). A solu-
tion of 5 (0.20 g, 0.21 mmol) in chlorobenzene (15 mL) was
stirred at room temperature under 25 atm of H2 in a stainless
steel autoclave for 16 h. The reaction was carefully vented,
and the solvent of the resulting solution was removed by
vacuum. The product was washed with 3 × 20 mL portions of
hexane and 20 mL of diethyl ether to yield a sticky pale brown
solid. Yield: 0.15 g (75%). Anal. Calcd for C45H46BNO6F4P2-
Ru: C, 57.09; H, 4.90; N, 1.48. Found: C, 57.64; H, 5.04; N,
1.53. 1H NMR (benzene-d6, 400 MHz, 20 °C): δ -11.83 (t, 1H,
2J (HP) ) 26.0 Hz, Ru-H), 2.33 (br s, 2H, CH2N), 2.61 (s, 6H,
NCH3), 2.88 (br s, 2 H C5H4CH2), 4.48 (s, 2 H of Cp ring), 5.49
(s, 2 H of Cp ring), 7.23-7.60 (m, 30 H of P(OPh)3), 8.47 (br s,
1 H NH). 31P{1H} NMR (benzene-d6, 161.7 MHz, 20 °C): δ
149.7 (s).
(η5-C5H4(CH2)2NMe2)Ru (P (OP h )3(P (OP h )2OC6H4) (6). A
sample of 4 (0.25 g, 0.28 mmol) was added to excess AgSO3-
CF3 in THF (20 mL), and the resulting solution was stirred at
room temperature for 2 days. The solution was filtered to
remove the silver chloride, and the solvent of the filtrate was
removed by vacuum to yield a brown oily liquid. Elution of
this oily compound through a neutral alumina column (1 cm
× 10 cm) with toluene followed by ethanol gave, after evapora-
tion of the solvents, the pure complex as a tacky yellow solid.
Yield: 0.12 g (50%). Anal. Calcd for C45H43NO6P2Ru: C, 63.08;
1
H, 5.06; N, 1.63. Found: C, 62.86; H, 5.34; N, 1.67. H NMR
(acetone-d6, 400 MHz, 20 °C): δ 1.86 (m, 2 H, CH2N), 2.03 (s,
6 H, NCH3), 2.06 (m, 2 H, C5H4CH2), 4.08 (br s, 1H of Cp ring),
4.09 (br s, 1 H of Cp ring), 4.37 (br s, 1 H of Cp ring), 4,86 (br
s, 1 H of Cp ring), 6.89-7.52 (m, 29 H of phosphites). 31P{1H}
(η5-C5H4(CH2)2NMe2)Ru (P (OP h )3)2H (8). A sample of 7
(0.15 g, 0.16 mmol) was added to a suspension of excess
powdered potassium hydroxide in ethanol (20 mL). The
mixture was stirred overnight at room temperature. It was
filtered to remove the unreacted KOH, and the solvent of the
filtrate was removed by vacuum to yield a black oily substance,
which was then extracted with 4 × 20 mL portions of hexane.
The solvent of the extract was removed, and a very sticky
brown solid was obtained. Yield: 0.09 g (65%). Anal. Calcd
for C45H45NO6P2Ru: C, 62.93; H, 5.28; N, 1.63. Found: C,
62.81; H, 5.20; N, 1.48. 1H NMR (benzene-d6, 400 MHz, 20
2
NMR (acetone-d6, 161.7 MHz, 20 °C): 144.3 (d, J (PP) ) 99.9
Hz, P(OPh)3), 170.9 (d, 2J (PP) ) 99.9 Hz, P(OPh)2(OC6H4). 13C-
{1H} NMR (acetone-d6, 100.6 MHz, 20 °C): 111.1 (d, 2J (PC) )
16.0 Hz, Ru-C).
The complex can be prepared by an alternative method: A
sample of 4 (0.12 g, 0.13 mmol) was added to a solution of
sodium methoxide (0.13 g, 2.31 mmol) in methanol (30 mL),
and the solution was allowed to reflux for 24 h. The resulting
solution was filtered, and the solvent of the filtrate was
removed by vacuum to yield a yellow oil. Elution of the oily
product through a neutral alumina column (1 cm × 10 cm)
with toluene followed by ethanol gave, upon removal of the
solvents, the pure product. Yield: 0.08 g (33%).
2
°C): δ -11.53 (t, J (HP) ) 36.0 Hz, 1H, RuH)), 2.21 (br s, 2
H, CH2N). 2.29 (br s, 8 H, C5H4CH2 and NCH3), 4.44 (s, 2 H of
Cp ring), 4.50 (s, 2 H of Cp ring), 7.10-7.63 (m, 30 H of
P(OPh)3). 31P{1H} NMR (benzene-d6, 161.7 MHz, 20 °C): δ
143.7 (s).
[(η5-C5H4(CH2)2NMe2H+)Ru (P (OP h )3(P (OP h )2OC6H4)]-
BF 4 (5-BF 4). To a sample of 6 (0.10 g, 0.12 mmol) in 15 mL of
tetrahydrofuran was added 1.2 equiv of tetrafluoroboric acid
in etheral solution (HBF4 Et2O, 54%) (19 µL, 0.14 mmol), and
the resulting solution was stirred for 1 h. It was then
concentrated to 1-2 mL, and 20 mL of hexane was added to
Ack n ow led gm en t. The authors acknowledge the
financial support from the Hong Kong Research Grant
Council (Earmarked Grant PolyU 5178/99P) and thank
Professor Zhenyang Lin for valuable discussions.
OM010966Z