P-H bond addition to a dinuclear ruthenium imido complex: Synthesis and reactivity of an amido phosphido complex

Article abstract of DOI:10.1021/om701260y

Treatment of the imido complex [(Cp*Ru)₂(μ₂- NPh)(μ₂-CO)] (3; Cp* = η⁵-C ₅Me₅) with phenylphosphine resulted in the P-H bond addition across the Ru-N bonds to give the amido phosphido complex [(Cp*Ru)₂(μ₂-NHPh)(μ₂-PHPh) (μ₂-CO)] (4). Exposure of 4 to atmospheric carbon monoxide resulted in the formation of the phosphinidene complex [{Cp*Ru(CO)} ₂(μ₂-PPh)(μ₂-CO)] (6) and aniline. With excess phenylphosphine, compound 4 gave the bis(phosphido) phosphine complex [Cp*Ru(CO)(μ₂-PHPh)₂-Ru(PH₂Ph) Cp*] (5). Treatment of 4 with 2-propanol led to an overall hydrogenolysis of the Ru-N bonds to give the hydrido phosphido complex [(Cp*Ru) ₂(μ₂-H)(μ₂-PHPh)(μ₂-CO)] (7). Reaction of 4 with 4-tert-butylphenol resulted in a P-O bond formation yielding the hydrido aryloxyphosphido complex [(Cp*Ru)₂(μ ₂-H)(μ₂-PPh(OC₆H₄-t-Bu-p) (μ₂-CO)] (8). Crystal structures of 4, 5, and 8 are reported.

Full text of DOI:10.1021/om701260y

1780
Organometallics 2008, 27, 1780–1785
P-H Bond Addition to a Dinuclear Ruthenium Imido Complex:
Synthesis and Reactivity of an Amido Phosphido Complex
Shin Takemoto, Yu Kimura, Ken Kamikawa, and Hiroyuki Matsuzaka*
Department of Chemistry, Graduate School of Science, Osaka Prefecture UniVersity, Sakai,
Osaka 599-8531, Japan
ReceiVed December 18, 2007
Treatment of the imido complex [(Cp*Ru)2(µ2-NPh)(µ2-CO)] (3; Cp* ) η5-C5Me5) with phenylphos-
phine resulted in the P-H bond addition across the Ru-N bonds to give the amido phosphido complex
[(Cp*Ru)2(µ2-NHPh)(µ2-PHPh)(µ2-CO)] (4). Exposure of 4 to atmospheric carbon monoxide resulted in
the formation of the phosphinidene complex [{Cp*Ru(CO)}2(µ2-PPh)(µ2-CO)] (6) and aniline. With excess
phenylphosphine, compound 4 gave the bis(phosphido) phosphine complex [Cp*Ru(CO)(µ2-PHPh)2-
Ru(PH2Ph)Cp*] (5). Treatment of 4 with 2-propanol led to an overall hydrogenolysis of the Ru-N bonds
to give the hydrido phosphido complex [(Cp*Ru)2(µ2-H)(µ2-PHPh)(µ2-CO)] (7). Reaction of 4 with 4-tert-
butylphenol resulted in a P-O bond formation yielding the hydrido aryloxyphosphido complex
[(Cp*Ru)2(µ2-H)(µ2-PPh(OC6H4-t-Bu-p)(µ2-CO)] (8). Crystal structures of 4, 5, and 8 are reported.
has received considerable study recently since it would provide
insights into metal-catalyzed transformations of organophos-
phorus compounds.4,5 In case of primary phosphine activation,
the resulting PHR– ligand still has a P-H bond, whose reactivity
such as conversion into a phosphinidene ligand and addition to
alkenes and alkynes has also been the subject of numerous
studies.6,7 Three major types of reaction modes have been known
for transition metal-mediated phosphine P-H activation: (i)
oxidative addition to low-valent metal centers,4,8 (ii) addition
across metal-metal bonds,9 and (iii) protonolysis of metal-alkyl
Introduction
Phosphido-bridged di- and polynuclear transition metal
complexes have attracted intense interest as multimetallic
reagents or catalysts for organic/inganic transformations.1–3
Preparation of these complexes via the activation of P-H bonds
of primary or secondary phosphines on transition metal centers
* Corresponding author. E-mail:matuzaka@c.s.osakafu-u.ac.jp.
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10.1021/om701260y CCC: $40.75
2008 American Chemical Society
Publication on Web 03/18/2008

P-H Addition to a Dinuclear Ru-Imido Complex
Organometallics, Vol. 27, No. 8, 2008 1781
Scheme 1
Chart 1
comparison of whose chemistry with that of their nitrogen
analogues would be of interest. Herein we report a reaction of
phenylphosphine with the imido complex 3, which produces
the amido phosphido complex [(Cp*Ru)2(µ2-NHPh)(µ2-PHPh)(µ2-
CO)] (4) via P-H bond activation by the Ru-N linkage. We
also describe some reactivity of 4 including conversion into a
phosphinidene complex and an aryloxyphosphido complex via
activation of the P-H bond of the bridging phsophido ligand.
Results and Discussion
Synthesis of Amido Phosphido Complex 4. Treatment of
the imido complex 3 with 0.9 equiv of phenylphosphine in THF
at -80 °C produced the amido phosphido complex 4 (Scheme
1). 1H NMR analysis of the reaction mixture showed that
complex 4 was formed in ∼80% yield. Use of 1 equiv of
phenylphosphine resulted in significant contamination with
byproducts including the bis(phosphido) phosphine complex
[Cp*Ru(CO)(µ2-PHPh)2Ru(PH2Ph)Cp*] (5; vide infra). Treat-
ment of 3 with phenylphosphine-d2 (PhPD2, 90% d) in THF
resulted in the formation of [(Cp*Ru)2(µ2-NDPh)(µ2-PDPh)(µ2-
CO)] (4-d2; 90% d for PhPD and 80% d for PhND), showing
that almost all of the N-H and P-H hydrogen atoms in 4 result
from phenylphosphine. The contamination of 10% H on the
nitrogen center in 4-d2 in the above deuterium-labeling experi-
ment might be due to participation of adventitious water in
deuteron transfer step. Complex 4 was isolated in 33% yield as
dark green crystals after recrystallization from hexanes and
characterized by both spectroscopic and crystallographic tech-
niques. The 1H NMR spectrum of 4 exhibits one Cp* resonance
and -hydride bonds.5,10 Metal-element multiple bonds have
recently been recognized as a versatile class of functional groups
capable of cleaving a variety of E-H bonds (E ) H, C, N, O,
S, etc.).11 However, this type of protocol has rarely been
implemented for the activation of P-H bonds.11i Work in our
laboratories has focused on the chemistry of dinuclear late
transition metal complexes with heteroatom bridging ligands
such as amido, imido, aryloxo, and dithiolato ligands.12,13
Specifically, we have recently reported the formation of the
diruthenium bridging imido complex [(Cp*Ru)2(µ2-NPh)(µ2-
CO)] (3) from the reaction of the coordinatively unsaturated
amido complex [Cp*Ru(µ2-NHPh)]2 (1) with carbon monoxide
(Scheme 1).13 The reaction initially produces a thermally un-
stable yet spectroscopically identifiable µ2-CO adduct [(Cp*-
Ru)2(µ2-NHPh)2(µ2-CO)] (2). The intermediate spontaneously
eliminates 1 equiv of aniline to produce the imido complex 3,
which can be described as a hybrid of two resonance structures
with a Ru-N multiple bond (Chart 1). As an extension of these
studies, we sought to examine possible routes to the corre-
sponding phosphido and phosphinidene diruthenium systems,
4
as a doublet (δ 1.62 ppm, JPH ) 1.4 Hz), indicating a
symmetrical dinuclear structure with one bridging phosphido
ligand. Resonances attributable to the P-H and N-H protons
are observed at δ 1.74 (d, 1JPH ) 320 Hz) and 0.82 (d, 3JPH
)
(10) (a) Shaver, M. P.; Fryzuk, M. D. Organometallics 2005, 24, 1419–
1427. (b) Ohki, Y.; Suzuki, H. Angew. Chem., Int. Ed. 2000, 39, 3120–
3122.
12 Hz) ppm, respectively. In its 13C{1H} NMR spectrum, a
resonance due to the µ2-carbonyl carbon was observed at 256.8
ppm as a doublet (2JPC ) 8.6 Hz). The structure of 4 deduced
by single-crystal X-ray diffraction is shown in Figure 1. Because
of a site disorder between the NPh and PPh groups, the solved
structure possesses a crystallographic mirror plane that contains
the ruthenium atoms and the bridging CO ligand. Thus, the
nitrogen and phosphorus atoms are treated as duplicate atoms
in the same position with equal Uij values and 50% occupancy
for each. Although this prevents us from discussing bond lengths
and angles around these atoms, the overall atom connectivity
within the structure as well as the equatorial orientation of the
two phenyl substituents have been unequivocally established.
The ruthenium atoms are separated 2.6857(7) Å from each other,
a distance consistent with a metal-metal bonding interaction.
We had expected that 4 might eliminate aniline to produce
the phosphinidene complex [(Cp*Ru)2(µ2-CO)(µ2-PPh)], as the
bis(amido) complex 2 does to give the imido complex 3.13
However, compound 4 is stable in solution at room temperature
and showed no sign of spontaneous aniline elimination. In the
case of the bis(amido)-to-imido conversion, the electron-
deficiency on the ruthenium centers caused by the loss of aniline
is compensated by the formation of π-bonds between the imido
(11) (a) Hoyt, H. M.; Bergman, R. G. Angew. Chem., Int. Ed. 2007, 46,
5580–5582. (b) Bailey, B. C.; Fan, H.; Huffman, J. C.; Baik, M.-H.;
Mindiola, D. J. J. Am. Chem. Soc. 2007, 129, 8781–8793. (c) Hazari, N.;
Mountford, P. Acc. Chem. Res. 2005, 38, 839–849, and references cited
therein. (d) Duncan, A. P.; Bergman, R. G. Chem. Rec. 2002, 2, 431–445.
(e) Schaller, C. P.; Cummins, C. C.; Wolczanski, P. T. J. Am. Chem. Soc.
1996, 118, 591–611. (f) Ohki, Y.; Matsuura, N.; Muramoto, T.; Kawaguchi,
H.; Tatsumi, K. J. Am. Chem. Soc. 2003, 125, 7978–7988. (g) Sweeney,
Z. K.; Polse, J. L.; Anderesen, R. A.; Bergman, R. G.; Kubinec, M. G.
J. Am. Chem. Soc. 1997, 119, 4543–4544. (h) Dobbs, D. A.; Bergman,
R. G. Organometallics 1994, 13, 4594–4605. (i) Baranger, A. M.; Bergman,
R. G. J. Am. Chem. Soc. 1994, 116, 3822–3835. (j) Michelman, R. I.; Ball,
G. E.; Bergman, R. G.; Andersen, R. A. Organometallics 1994, 13, 869–
881. (k) Freudenberger, J. H.; Schrock, R. R. Organometallics 1985, 4,
1937–1944.
(12) (a) Takemoto, S.; Ogura, S.; Yo, H.; Kamikawa, K.; Hosokoshi,
Y.; Matsuzaka, H. Inorg. Chem. 2006, 45, 4871–4873. (b) Takemoto, S.;
Morita, H.; Kamikawa, K.; Matsuzaka, H. Chem. Commun. 2006, 1328–
1330. (c) Takemoto, S.; Shimadzu, D.; Kamikawa, K.; Matsuzaka, H.;
Nomura, R. Organometallics 2006, 25, 982–988. (d) Takemoto, S.; Ogura,
S.; Kamikawa, K.; Matsuzaka, H. Inorg. Chim. Acta 2006, 359, 912–916.
(e) Takemoto, S.; Oshio, S.; Shiromoto, T.; Matsuzaka, H. Organometallics
2005, 24, 801–804. (f) Takemoto, S.; Oshio, S.; Kobayashi, T.; Matsuzaka,
H.; Hoshi, M.; Okimura, H.; Yamashita, M.; Miyasaka, H.; Ishii, T.;
Yamashita, M. Organometallics 2004, 23, 3587–3589.
(13) Takemoto, S.; Kobayashi, T.; Matsuzka, H. J. Am. Chem. Soc. 2004,
126, 10802–10803.

1782 Organometallics, Vol. 27, No. 8, 2008
Takemoto et al.
Figure 1. ORTEP drawing of 4. Ellipsoids are drawn at the 35%
probability level. All H atoms except for those on N and P atoms
are omitted. The ellipsoid labeled E(1) represents P and N atoms
modeled to occupy the same site with 50% occupancy. The at-
oms E(1) and E(1)* are symmetry related to each other.
Figure 2. ORTEP drawing of 5. Ellipsoids are drawn at the 35%
probability level. All H atoms are omitted. Selected interatomic
distances (Å) and bond angles (deg): Ru(1) · · · Ru(2) ) 3.73;
Ru(1)-P(1) ) 2.3502(9); Ru(2)-P(1) ) 2.3325(9); Ru(1)-P(2)
) 2.3453(8); Ru(2)-P(2) ) 2.3382(9); Ru(1)-P(3) ) 2.2276(10);
Ru(2)-C(1) ) 1.821(3); Ru(1)-P(1)-Ru(2) ) 105.77(3); Ru(1)-
P(2)-Ru(2))105.75(3);P(1)-Ru(1)-P(2))71.25(3);P(1)-Ru(2)-
P(2) ) 71.69(3).
Scheme 2
zation from toluene/acetonitrile. Complex 5 was also obtained
in 84% yield by treating the imido complex 3 with excess
phenylphosphine. Complex 5 was characterized by NMR
spectroscopy (1H, 13C{1H}, 31P{1H}), IR spectroscopy, elemen-
tal analysis, and single-crystal X-ray diffraction. An ORTEP
diagram is shown in Figure 2. The molecule exhibits a doubly
bridged dinuclear structure with two bridging phosphido ligands.
A phenylphosphine is bound to one ruthenium center and a
terminal CO ligand coordinates to the other ruthenium site.
These terminal ligands are trans to each other with respect to
the four-membered Ru(1)-P(1)-Ru(2)-P(2) ring. The Ru2P2
ring takes an elongated butterfly shape with acute P-Ru-P
angles (av. 71.5°), wide Ru-P-Ru angles (av. 105.8°), and a
large Ru · · · Ru separation (3.73 Å). The dihedral angle between
Ru(1)-P(1)-P(2) and Ru(2)-P(1)-P(2) planes is 21.6°.
An attempted reaction of 4 with 1 equiv of phenylphosphine
was conducted in THF at 50 °C to isolate a phosphine-free
bis(phosphido) complex. This resulted in the formation of a 1:4:6
mixture of unreacted 4, complex 5, and a compound that we
tentatively formulate as a bis(phosphido) complex [Cp*Ru(µ2-
CO)(µ2-PHPh)2RuCp*] on the basis of a triplet C5Me5 resonance
ligand and the ruthenium atoms. Furthermore, the shortening
of the Ru-N bond distances strengthens the Ru-N σ-bonding
interactions. Since several experimental and theoretical data
suggest that a P-H bond is generally more acidic than a
corresponding N-H bond,14 the greater stability of 4 as
compared to that of 2 with respect to aniline elimination could
be ascribed to the decreased tendency of phosphorus 3p orbitals
as compared to nitrogen 2p orbitals to participate in π-bonding,15
though stable compounds with M-P π-bonds within a M(µ2-
PR)M framework are known.16
Reaction of 4 with Excess Phenylphosphine. Treatment of
4 with a 5-fold excess of phenylphosphine in THF led to the
elimination of aniline and incorporation of 2 equiv of phe-
nylphosphine to give the bis(phosphido) phosphine complex
[Cp*Ru(CO)(µ2-PHPh)2Ru(PH2Ph)Cp*] (5) (Scheme 2), which
was isolated as orange crystals in 30% yield after recrystalli-
1
4
in the H NMR spectrum (δ 1.74, JPH ) 1.6 Hz; C6D6), a
singlet resonance in the 31P{1H} NMR spectrum (δ 7.38), and
a triplet µ2-CO resonance in the 13C{1H} NMR spectrum (δ
2
250.4, JPC ) 13.7 Hz). Isolation of this material was not
achieved due to its similar solubility to that of 4 and 5. Addition
of excess phenylphosphine (4 equiv) to the mixture of these
compounds led to clean conversion to 5 in 46% crystallized
yield based on 4.
Reaction of 4 with Excess Carbon Monoxide: Synthesis
of Phosphinidene Complex 6. Addition of carbon monoxide
(1 atm) to a benzene-d6 solution of 4 resulted in the loss of
aniline (detected by 1H NMR in 66% yield) and the formation
of a phosphinidene complex [{Cp*Ru(CO)}2(µ2-PPh)(µ2-CO)]
(6, 77%; Scheme 2). From a separate experiment carried out in
(14) Nam, P.-C.; Nguyen, M. T.; Chandra, A. K. J. Phys. Chem. A 2004,
108, 11362–11368, and references cited therein.
(15) Schmidt, M. W.; Truong, P. N.; Gordon, M. S. J. Am. Chem. Soc.
1987, 109, 5217–5227.
(16) Arif, A. M.; Cowley, A. H.; Norman, N. C.; Orpen, A. G.; Pakulski,
M. Organometallics 1988, 7, 309–318.

P-H Addition to a Dinuclear Ru-Imido Complex
Organometallics, Vol. 27, No. 8, 2008 1783
Scheme 3
THF solution, the phosphinidene 6 was isolated in 39% yield
as orange crystals and characterized by NMR spectroscopy (1H,
13C, and 31P), IR spectroscopy, and elemental analysis. The
existence of the phosphinidene moiety was supported by a
characteristic downfield resonance in the 31P{1H} NMR
spectrum.6b,10a,16 The observed 31P chemical shift of δ 457.2
ppm is comparable to that observed for the isoelectronic diiron
µ2-phenylphosphinidene complex cis-[{CpFe(CO)}2(µ2-PPh)(µ2-
CO)] (δ 498.2 ppm), which has been shown to have a pyramidal
phosphorus center by single-crystal X-ray diffraction.6b For
comparison, µ2-arylphosphinidene complexes with a trigonal
planar phosphorus center exhibit 31P resonances in a more
downfield region (δ 650-690 ppm).16 The IR spectrum of 6
shows two terminal CO bands at 1961 and 1926 cm-1 along
with one bridging CO band at 1757 cm-1. The 1H NMR
spectrum of 6 shows only one Cp* resonance along with signals
corresponding to one phenyl group. These data are consistent
with the phosphinidene-bridged cis dinuclear structure with a
pyramidal phosphorus center. In the absence of single-crystal
X-ray data, stereochemistry around the phosphorus atom is not
obvious but a configuration such that the phenyl substituent
points away from the Cp* groups is expected from steric reason.
Figure 3. ORTEP drawing of 8. Ellipsoids are drawn at the 35%
probability level. All H atoms except for those on Ru atoms are
omitted. Selected bond distances (Å) and angles (deg): Ru(1)-Ru(2)
) 2.6124(5); Ru(1)-P(1) ) 2.3502(9); Ru(2)-P(1) ) 2.3325(9);
Ru(1)-P(2) ) 2.3453(8); Ru(2)-P(2) ) 2.3382(9); Ru(1)-P(3)
) 2.2276(10); Ru(2)-C(1) ) 1.821(3); Ru(1)-P(1)-Ru(2) )
105.77(3); Ru(1)-P(2)-Ru(2) ) 105.75(3); P(1)-Ru(1)-P(2) )
71.25(3); P(1)-Ru(2)-P(2) ) 71.69(3).
the phosphorus and the P-H hydrogen nuclei (2JPH ) 50.1 Hz
and 3JHH ) 8.6 Hz). The P-H resonances for the cis and trans
isomers were observed at δ 5.25 ppm (d, 1JPH ) 332.7 Hz) and
δ 4.77 ppm (dd, 1JPH ) 379.1 Hz, 3JHH ) 8.6 Hz), respectively.
Reaction of 4 with 4-tert-Butylphenol: Synthesis of
Aryloxyphosphido Complex 8. Treatment of 4 with excess
4-tert-butylphenol in THF resulted in the formation of the
hydrido aryloxyphosphido complex [(Cp*Ru)2(µ2-H)(µ2-PPh-
(OC6H4-t-Bu-p)(µ2-CO)) (8; Scheme 3), which was isolated in
62% yield as dark red crystals and has been structurally
characterized. The existence of a hydrido ligand in this complex
Reaction of 4 with 2-Propanol: Synthesis of Hydrido
Phosphido Complexes cis-7 and trans-7. Heating a mixture
of 4 and 2-propanol (10 equiv) in C6D6 at 60 °C resulted in the
formation of a µ-hydrido µ-phosphido complex [(Cp*Ru)2(µ2-
H)(µ2-PHPh)(µ2-CO)] (7) as a 1:2 mixture of cis and trans
stereoisomers (Scheme 3).17 Herein the cis and trans denote the
relative orientations of the P-H hydrogen and the hydrido ligand
with respect to the Ru2P ring. Aniline (56%) and acetone (69%)
1
was confirmed by H NMR spectroscopy, which revealed a
doublet resonance at -20.85 ppm (2JPH ) 51.4 Hz). The
31P{1H} NMR spectrum of 8 exhibited a resonance at δ 240.4
ppm, which is more downfield as compared to the 31P NMR
shifts of cis- and trans-7. An ORTEP drawing for 8 is shown
in Figure 3. The hydrido ligand was located by Fourier syntheses
and refined with isotropic thermal parameters. The aryloxy group
exists on the phosphorus center and is trans to the hydrido
ligand. The short Ru-Ru distance (2.6124(5) Å) is consistent
with a Ru-Ru bond expected from the EAN rule.
1
were detected by H NMR analysis. Thus, the reaction is an
overall transfer hydrogenolysis of the Ru-NHPh bonds with
2-propanol as a hydrogen donor. A preparative scale experiment
was carried out in 2-propanol suspension. Filtration of the
reaction mixture afforded 7 in 62% yield as an analytically pure
red crystalline solid. The isolated solid was a 5:4 mixture of
cis-7 and trans-7 as judged by 1H NMR spectroscopy. The 1H
NMR spectrum of 7 exhibits hydride signals of the cis and trans
isomers at δ -19.58 and -20.28 ppm, respectively. The former
was observed as a doublet (2JPH ) 50.1 Hz) whereas the latter
appeared as a doublet of doublets due to coupling with both
When 4 was treated with excess ArOD (Ar ) p-tert-
butylphenyl), no deuterium was incorporated into the product
8. Treatment of [(Cp*Ru)2(µ2-CO)(µ2-PDPh)(NDPh)] (4-d2)
with ArOH also afforded 8 without incorporation of any
deuterium, showing that neither the phosphido P-H nor the
amido N-H in 4 is the source of the hydrido ligand in 8. We
also confirmed that deuterium is not introduced into 8 when
the reaction of 4 and ArOH is carried out in THF-d8, eliminating
the possibility of the solvent acting as a source of the hydrido
ligand. At present neither the origin of the hydrido nor the
mechanism of the reaction is uncertain, though the overall
(17) We use the half arrow representation of the bridging hydrido
complexes introduced in the following articles: (a) Baik, M.-H.; Freisner,
R. A.; Parkin, G. Polyhedron 2004, 23, 2879. (b) Parkin, G. In Compre-
hensiVe Organometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P.,
Eds.; Elsevier: Oxford, UK, 2007; Vol. 1,Chapter. 1.01.2.4.

1784 Organometallics, Vol. 27, No. 8, 2008
Takemoto et al.
Table 1. Crystallographic Data for 4, 5, and 8
4
5
8
formula
M
C33H42NOPRu2
701.79
C39H49OP3Ru2
828.83
C37H49O2PRu2
758.87
T/K
296
296
296
size (mm3)
cryst system
space group
Z
0.60 × 0.60 × 0.30
orthorhombic
Pnnm
0.60 × 0.50 × 0.30
orthorhombic
P212121
4
0.50 × 0.30 × 0.30
orthorhombic
P212121
4
4
a (Å)
b (Å)
13.066(5)
15.120(4)
16.021(5)
3164.9(18)
1.473
1.030
27298
3748
1.032
9.3624(14)
19.378(4)
21.286(4)
3861.8(13)
1.426
0.934
37693
8819
1.039
10.610(3)
15.178(5)
21.350(5)
3438.3(16)
1.466
0.955
32603
7839
1.036
c (Å)
V (Å3)
Dcalcd (g/cm3)
µ (mm-1
)
no. of reflns collected
no. of unique reflns
GOF on F2
R1 [I > 2σ(I)]a
wR2 (all data)b
0.0293
0.0802
0.0280
0.0725
0.0253
0.0609
2
2 2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑(w(Fo - Fc ) /∑w(Fo2)2]1/2
.
stored over activated molecular sieves. 1H and 31P{1H} NMR
spectra were recorded on a JEOL ECP500 spectrometer at the field
strength of 500.16 (1H) and 202.48 MHz (31P). 13C{1H} NMR
spectra were obtained on a Varian VNMR400 spectrometer at the
field strength of 100.55 MHz. Infrared spectra were obtained with
a JASCO FT-IR 4100 spectrometer. Elemental analyses were
performed on a Perkin-Elmer 2400 Series II CHNS/O analyzer.
[(Cp*Ru)2(µ2-NHPh)(µ2-PHPh)(µ2-CO)] (4). Imido complex
3 (123 mg, 0.208 mmol) was dissolved in THF (10 mL) and the
solution was cooled to -80 °C. The solution was stirred and
phenylphosphine (21 µL, 0.187 mmol) was added to the solution,
which caused a color change of the solution from dark orange to
dark green. The solution was allowed to warm slowly to room
temperature and stirred overnight. The solvent was removed in
vacuo and the residue was extracted with hexanes (20 mL).
Concentration of the extract and cooling to -30 °C gave 4 as dark
green plates. Yield 48 mg, 33%. Anal. Calcd for C33H42NOPRu2:
reaction is an addition of ArOH to a hypothetical phosphinidene
diruthenium fragment, “(Cp*Ru)2(µ2-CO)(µ2-PPh)”.
Conclusions
The imido complex [(Cp*Ru)2(µ2-NPh)(µ2-CO)] (3) has been
shown to cleave the P-H bond of phenylphosphine to give the
amido phosphido complex [(Cp*Ru)2(µ2-NHPh)(µ2-PHPh)(µ2-
CO)] (4). This reaction represents a rare example of P-H bond
activation across a metal–ligand multiple bond. Complex 4
further reacts with 2 equiv of phenylphosphine to give the
bis(phosphido) phosphine complex [Cp*Ru(CO)(µ2-PHPh)2-
Ru(PH2Ph)Cp*](5).Incontrasttotheamidoanalogue[(Cp*Ru)2(µ2-
NHPh)2(µ2-CO)] (2), the amido phosphido complex 4 is
persistent toward thermal elimination of aniline. Nevertheless,
interaction of 4 with carbon monoxide induces release of aniline
and affords a new bridging phosphinidene complex [{Cp*Ru-
(CO)}2(µ2-PPh)(µ2-CO)] (6) for which spectroscopic data and
electron counting suggest pyramidal configuration at the phos-
phorus center. Complex 4 has also been shown to react with
2-propanol and 4-tert-butylphenol via elimination of aniline. In
the case of 2-propanol the reaction is an overall transfer
hydrogenolysis of the Ru-N bonds, yielding a hydrido phos-
phido complex [(Cp*Ru)2(µ2-H)(µ2-PHPh)(µ2-CO)] (7), whereas
the reaction with 4-tert-butylphenol results in the formation of
a hydrido aryloxyphosphido complex [(Cp*Ru)2(µ2-H)(µ2-
PPh(OC6H4-t-Bu-p)(µ2-CO))] (8) via P-O bond formation and
P-H bond cleavage.
1
C, 56.48; H, 6.03; N, 2.00. Found: C, 56.14; H, 6.37; N, 2.36. H
NMR (C6D6): δ 7.30 (m, 2H, Ph), 7.15-6.95 (m, 5H, Ph), 6.79
1
(m, 1H, Ph), 6.67 (t, 1H, Ph), 6.20 (m, 1H, Ph), 1.74 (d, JPH
)
)
4
3
320 Hz, PH), 1.62 (d, JPH ) 1.4 Hz, 30H, Cp*), 0.82 (d, JPH
12 Hz, NH). 13C{1H} NMR (C6D6): δ 256.8 (d, JPC ) 8.6 Hz,
µ2-CO), 160.6 (d, J ) 8.6 Hz, Ph), 140.6 (d, J ) 43 Hz, Ph), 132.5
(d, J ) 9.8 Hz, Ph), 132.2 (s, Ph), 129.1 (s, Ph), 127.8 (d, J ) 12
Hz, Ph), 127.2 (s, Ph), 126.5 (s, Ph), 123.1 (s, Ph), 121.1 (s, Ph),
118.8 (s, Ph), 92.0 (s, C5Me5), 9.4 (s, C5Me5). 31P{1H} NMR
(C6D6): δ 19.4 (s). IR (KBr): 3063 (w), 3052 (w), 2978 (m), 2953
(m), 2909 (s), 2251 (m), 1931 (m), 1761 (vs), 1591 (s), 1578 (s),
1482 (s), 1376 (s), 1240 (s), 1026 (s), 897 (m), 753 (m), 737 (m),
2
690 (s), 575 (s), 539 (m), 510 (s) cm-1
.
[Cp*Ru(CO)(µ2-PHPh)2Ru(PH2Ph)Cp*] (5). From 3: To a
solution of 3 (34 mg, 0.057 mmol) in THF (5 mL) was added
phenylphosphine (32 µL, 0.285 mmol, 5.0 equiv) at -80 °C. The
solution was allowed to warm slowly to room temperature and
stirred overnight. The volatiles were removed in vacuo and the
residue was recrystallized from toluene/acetonitrile (1 mL/7 mL)
to give 5 as yellow plates. Yield 40 mg, 84%. From 4: To a solution
of 4 (59 mg, 0.084 mmol) in THF (10 mL) was added phenylphos-
phine (46 µL, 0.42 mmol) at -80 °C. The solution was allowed to
warm slowly to room temperature and stirred overnight. The
volatiles were removed in vacuo and the residue was recrystallized
from toluene/acetonitrile (2 mL/10 mL) to give 5 as yellow plates.
Yield 21 mg, 30%. Anal. Calcd for C39H49OP3Ru2: C, 56.51; H,
5.96. Found: C, 56.30; H, 6.10. 1H NMR (C6D6): δ 7.93-7.90 (m,
6H, Ph), 7.32-7.27 (m, 6H, Ph), 7.19-7.13 (m, 3H, Ph), 6.08 (dt,
Experimental Section
All manipulations were conducted under an atmosphere of
nitrogen with standard Schlenk techniques. The imido complex 3
was prepared according to the published method.13 Phenylphosphine
was prepared by LiAlH4 reduction of PCl2Ph in diethyl ether
followed by distillation under reduced pressure.18 Other reagents
were purchased from commercial vendors and used without further
purification unless otherwise noted. Toluene, hexanes, THF, and
diethyl ether were distilled from sodium benzophenone ketyl and
degassed before use. Acetonitrile, dichloromethane, 2-propanol
(Wako), and tert-butyl alcohol (Aldrich) were purchased as
anhydrous forms and degassed before use. Deuterated solvents were
obtained from Cambridge Isotope Laboratories, Inc., degassed, and
1
3
(18) Pass, F.; Schindlbauer, H. Monatsh. Chem. 1959, 90, 148.
2H, PH2Ph, JPH ) 320 Hz, JPH ) 10 Hz), 4.25-3.12 (m, 2H,

P-H Addition to a Dinuclear Ru-Imido Complex
Organometallics, Vol. 27, No. 8, 2008 1785
2
PHPh), 1.67, 1.43 (s, 15H each, Cp*). 13C{1H} NMR (C6D6): δ
215.8 (t, 2JPC ) 11 Hz, CO), 137.8 (t, J ) 7 Hz), 134.53-134.36
(m, Ph), 131.1 (dt, J ) 36 Hz, 6 Hz, Ph), 129.7 (d, J ) 2 Hz, Ph),
128.5 (s, Ph), 127.4 (s, Ph), 127.5 (m, Ph), 93.9, 90.3 (s, C5Me5),
9.98, 9.90 (s, C5Me5). 31P{1H} NMR (C6D6): δ 10.2 (t, 2JPP ) 10
Hz), -78.0 (d, 2JPP ) 10 Hz). IR (KBr): 3054 (w), 2965 (w), 2893
(m), 2818 (w), 2267 (s), 2217 (s), 1887 (vs), 1580 (w), 1478 (m),
1431 (m), 1375 (m), 1026 (m), 930 (m), 904 (s), 794 (s), 733 (s),
693 (s), 576 (w), 557 (w), 535 (w), 522 (m), 489 (m), 437 (m)
1H, JPH ) 51.4 Hz, µ2-H). 13C{1H} NMR (C6D6): δ 266.4 (d,
2JPC ) 9 Hz, µ2-CO), 154.2 (d, J ) 4 Hz, Ar), 145.0 (s, Ar), 144.6
(d, J ) 1 Hz, Ar), 144.4 (s, Ar), 132.2 (d, J ) 13 Hz, Ar), 126.6
(s, Ar), 125.3 (s, Ar), 120.0 (d, J ) 8 Hz, Ar), 93.9 (d, J ) 1 Hz,
C5Me5), 34.2 (s, CMe3), 31.6 (CMe3), 10.1 (C5Me5). 31P{1H} NMR
(C6D6): δ 240.5 (s). IR (KBr): 2961 (m), 2904 (m), 1732 (vs), 1506
(s), 1478 (m), 1378 (m), 1221 (s), 1173 (s), 739 (m), 697 (m), 623
(m), 561 (m), 497 (m) cm-1
.
X-ray Crystallography. A single crystal of each sample was
coated with Paratone-N hydrocarbon oil and mounted on a glass
capillary. All measurements were performed on a Rigaku RAXIS
Rapid diffractometer equipped with an imaging plate detector. The
frame data were processed with use of the Rigaku PROCESS-
AUTO program,19 and the reflection data were corrected for
absorption with an ABSCOR program.20 The structures were solved
by a direct method (SHELXS 97) and refined on F2 by the full-
matrix least-squares method by using SHELX97.21 Anisotropic
refinement was applied to all non-hydrogen atoms. Crystallographic
data are summarized in Table 1. As to compound 4, the nitrogen
and phosphorus atoms (N(1) and P(1)) are site-disordered. These
atoms are modeled to have the same atomic coordinates and U
values with 50% occupancies. The hydrogen atom on N (and P)
was located by Fourier syntheses and refined with isotropic thermal
parameters. Other hydrogen atoms were placed at the calculated
positions and treated as riding models. For compound 5, all
hydrogen atoms were placed at the calculated positions and treated
as riding models. For compound 8, the hydride ligand was located
by Fourier syntheses and refined with isotropic thermal parameters.
Other hydrogen atoms were placed at the calculated positions and
treated as riding models. For all structures, the thermal ellipsoid
plots were generated with the ORTEP-3 program22 and presented
at the 35% probability level.
cm-1
.
[{Cp*Ru(CO)}2(µ2-PPh)(µ2-CO)] (6). A solution of 4 (59 mg,
0.084 mmol) in THF (10 mL) was stirred overnight under CO
atmosphere. Removal of the solvent followed by recrystallization
from toluene/acetonitrile (2 mL/5 mL) afforded 6 as red needles.
Yield 22 mg, 39%. Anal. Calcd for C29H35O3PRu2: C, 52.40; H,
1
5.31. Found: C, 52.01; H, 5.64. H NMR (C6D6): δ 8.00 (m, 2H,
Ph), 7.41 (t, 2H, Ph), 7.12 (t, 1H, Ph), 1.78, (s, 30H, Cp*). 13C{1H}
NMR (C6D6): δ 251.6 (s, µ2-CO), 201.9 (s, CO), 158.9 (d, 1JPC
)
2
3
72 Hz, Ph), 130.7 (d, JPC ) 12 Hz, Ph), 127.2 (d, JPC ) 11 Hz,
4
Ph), 125.6 (d, JPC ) 12 Hz, Ph), 100.3 (C5Me5), 10.4 (C5Me5).
31P{1H} NMR (C6D6): δ 457.2. IR (KBr): 3052 (w), 3033 (w),
2970 (w), 2902 (w), 1961 (vs), 1926 (s), 1757 (vs), 1460 (w), 1378
(m), 740 (m), 696 (m), 586 (m), 482 (m) cm-1
.
[(Cp*Ru)2(µ2-H)(µ2-PHPh)(µ2-CO)] (cis-7 and trans-7). Com-
plex 4 (59 mg, 0.084 mmol) was suspended in 2-propanol (5 mL)
and the mixture was heated in an oil bath at 60 °C with stirring for
12 h. The color of the mixture changed from dark green to dark
red. The mixture was allowed to settle and cool to room temper-
ature. Filtration and vacuum drying afforded 7 as a dark red
microcrystalline solid. It was obtained as a mixture of cis and trans
isomers (cis:trans ) 5:4). Yield 32 mg, 63%. Anal. Calcd for
C27H37OPRu2: C, 53.10; H, 6.11. Found: C, 53.22; H, 6.24. 1H
1
NMR (C6D6) for cis-7: δ 7.64-7.07 (m, 5H, Ph), 5.25 (d, JPH
)
2
332.7 Hz, PH), 1.75 (s, 30H, Cp*), -19.58 (d, JPH ) 50.1 Hz,
Acknowledgment. This work was supported by a Grant-
in-Aid for Scientific Research on Priority Area (No. 18033046,
“Chemistry of Coordination Space”) from the Ministry of
Education, Culture, Sports, Science and Technology, Japan.
We are also grateful to the TOYOTA Motor Corporation
for financial support.
1H, µ2-H). 31P{1H} NMR (C6D6) for cis-7: δ 50.5 (s). H NMR
1
(C6D6) for trans-7: δ 7.64-7.07 (m, 5H, Ph), 4.77 (dd, 1H, 1JPH
)
3
379.1 Hz, JHH ) 8.6 Hz, PH), 1.79 (s, 30H, Cp*), -20.28 (dd,
1H, 2JPH ) 50.1 Hz, 3JHH ) 8.6 Hz, µ2-H). 31P{1H} NMR (C6D6)
for trans-7: δ 64.3 (s). IR (KBr): 3042 (w), 2975 (w), 2903 (m),
2246 (m), 2092 (w), 1906 (w), 1737 (vs), 1579 (m), 1477 (m),
1378 (m), 1029 (m), 938 (w), 803 (w), 740 (w), 693 (w), 628 (w),
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
586 (w), 549 (w), 525 (w), 492 (w) cm-1
.
[(Cp*Ru)2(µ2-H)(µ2-PPh(OC6H4-t-Bu-p)(µ2-CO)] (8). To a
solution of 4 (214 mg, 0.305 mmol) in THF (15 mL) was added
p-tert-butylphenol (458 mg, 3.05 mmol) at -80 °C. The solution
was allowed to warm to room temperature and stirred for 12 h.
The volatile components were removed in vacuo and the residue
was extracted with toluene (10 mL). The extract was concentrated
to 1 mL and layered with acetonitrile (5 mL). After solvent diffusion
was complete, the dark red blocks of 8 were collected by filtration
and dried in vacuo. Yield 143 mg, 62%. Anal. Calcd for
OM701260Y
(19) PROCESS AUTO, Automatic Data Acquisition and Processing
Package for Imaging Plate Diffractometer; Rigaku Corporation: Tokyo,
Japan, 1998.
(20) Higashi T. ABSCOR, Empirical Absorption Correction Based on
Fourier Series Approximation; Rigaku Corporation: Tokyo, Japan, 1995.
(21) Sheldrick, G. M., SHELX97, Program for Crystal Structure
Determination; University of Göttingen: Göttingen, Germany, 1997.
(22) ORTEP-3 for Windows: Farrugia, L. J. J. Appl. Crystallogr. 1997,
30, 565.
1
C37H49O2PRu2: C, 58.56; H, 6.51. Found: C, 58.28; H, 6.63. H
NMR (C6D6): δ 8.05 (m, 2H, Ar), 7.42 (m, 2H, Ar), 7.22-7.08
(m, 5H, Ar), 1.67 (s, 30H, Cp*), 1.21 (s, 9H, t-Bu), -20.85 (d,