Ruthenium-stabilized low-coordinate phosphorus atoms. p-cymene ligand as reactivity switch

Article abstract of DOI:10.1021/om7004854

A detailed comparative study of the structural and spectroscopic features and of the reactivity of ruthenium phosphinidene complexes (η⁶- Ar)(PCy³)Ru(PMeS*) (2a, Ar = p-cymene; 2b, Ar = benzene) has been undertaken. The structures of complexes 2a and 2b have been determined by single-crystal X-ray diffraction and display similar features. Both compounds possess identical chemical behavior toward Broensted acids such as HBF ₄: protonation of the phosphinidene ligand yields the new cationic complexes [(η⁶-Ar)(PCy₃)Ru(PHMes*)]BF ₄ (3aBF₄, Ar = p-cymene; 3bBF₄, Ar = benzene), which exhibit an unprecedented phosphenium-bearing hydrogen substituent. 3aBF₄ has been characterized using X-ray diffraction techniques. The lone pair of the phosphorus atom of the phosphinidene ligand remains also accessible to the Lewis acid BH₃: the reactions of 2a and 2b with borane give the adducts (η⁶-Ar)(PCy₃)Ru[P(BH ₃)MeS*] (4a, Ar = p-cymene; 4b, Ar = benzene). In the presence of the larger borane BPh3, no reaction occurs until water is introduced in the reaction vessel. This results in the generation of [(η₆-Ar) (PCy₃)Ru(PHMes*)]BPh₃OH (3aBPh₃OH, Ar = p-cymene; 3bBPh₃OH, Ar = benzene) presumably through protonation of 2a and 2b by the previously unknown adduct H₂O-BPh₃. Phosphinidene complexes react also with electrophilic alkylating reagents such as organic iodides provided the alkyl substituent is small. Treatment of 2a and 2b with 1 equiv of methyliodide leads to the alkylation at the phosphinidene center and yields the phosphenium complexes [(η⁶-Ar)(PCy ₃)Ru(PMeMes*)]I (5a, Ar = p-cymene; 5b, Ar = benzene). Examination of the reactivity toward electron-rich reagents such as the alkynes RCCH (R = Me₃Si, Ph) yields unexpected results: 2a instantaneously reacts to generate phosphaindane complexes 6 and 7, whereas no reaction occurs when using 2b. A detailed kinetic study provides evidence for a dissociative mechanism involving the release of the phosphine ligand in 2a and explains its specificity. The /?-cymene ligand in 2a acts as a reactivity switch due to the higher steric hindrance of this arene.

Full text of DOI:10.1021/om7004854

Organometallics 2007, 26, 5091-5101
5091
Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms.
p-Cymene Ligand as Reactivity Switch
Richard Menye-Biyogo,‡ Fabien Delpech,*,‡,§ Annie Castel,‡ Ve´ronique Pimienta,†
Heinz Gornitzka,‡ and Pierre Rivie`re‡
Laboratoire He´te´rochimie Fondamentale et Applique´e, UMR 5069, UniVersite´ Paul Sabatier, 118 Route de
Narbonne, 31062 Toulouse Cedex 09, France, and Laboratoire des Interactions Mole´culaires et Re´actiVite´
Chimique et Photochimique, UMR 5623, UniVersite´ Paul Sabatier, 118 Route de Narbonne,
31062 Toulouse Cedex 09, France
ReceiVed May 16, 2007
A detailed comparative study of the structural and spectroscopic features and of the reactivity of
ruthenium phosphinidene complexes (η6-Ar)(PCy3)Ru(PMes*) (2a, Ar ) p-cymene; 2b, Ar ) benzene)
has been undertaken. The structures of complexes 2a and 2b have been determined by single-crystal
X-ray diffraction and display similar features. Both compounds possess identical chemical behavior toward
Bro¨nsted acids such as HBF4: protonation of the phosphinidene ligand yields the new cationic complexes
[(η6-Ar)(PCy3)Ru(PHMes*)]BF4 (3aBF4, Ar ) p-cymene; 3bBF4, Ar ) benzene), which exhibit an
unprecedented phosphenium-bearing hydrogen substituent. 3aBF4 has been characterized using X-ray
diffraction techniques. The lone pair of the phosphorus atom of the phosphinidene ligand remains also
accessible to the Lewis acid BH3: the reactions of 2a and 2b with borane give the adducts (η6-Ar)-
(PCy3)Ru[P(BH3)Mes*] (4a, Ar ) p-cymene; 4b, Ar ) benzene). In the presence of the larger borane
BPh3, no reaction occurs until water is introduced in the reaction vessel. This results in the generation of
[(η6-Ar)(PCy3)Ru(PHMes*)]BPh3OH (3aBPh3OH, Ar ) p-cymene; 3bBPh3OH, Ar ) benzene)
presumably through protonation of 2a and 2b by the previously unknown adduct H2O‚BPh3. Phosphinidene
complexes react also with electrophilic alkylating reagents such as organic iodides provided the alkyl
substituent is small. Treatment of 2a and 2b with 1 equiv of methyliodide leads to the alkylation at the
phosphinidene center and yields the phosphenium complexes [(η6-Ar)(PCy3)Ru(PMeMes*)]I (5a, Ar )
p-cymene; 5b, Ar ) benzene). Examination of the reactivity toward electron-rich reagents such as the
alkynes RCCH (R ) Me3Si, Ph) yields unexpected results: 2a instantaneously reacts to generate
phosphaindane complexes 6 and 7, whereas no reaction occurs when using 2b. A detailed kinetic study
provides evidence for a dissociative mechanism involving the release of the phosphine ligand in 2a and
explains its specificity. The p-cymene ligand in 2a acts as a reactivity switch due to the higher steric
hindrance of this arene.
development of strategies for the generation of phosphinidene
in the coordination sphere of transition metals.5 Thus, several
pathways are currently available and have allowed preparation
and full characterization of phosphinidene complexes incorpo-
rating different transition metals (Ti,6 Zr,7 V,8 Ta,9 Mo,10 W,11
Re,12 Fe,13 Ru,14,15 Os,13 Co,16 Rh,16 Ir,17 Ni18). From a synthetic
Introduction
Transition metal-catalyzed carbon-heteroatom bond forma-
tion is a fundamental process in chemical synthesis.1 Among
the existing methodologies, catalyzed atom transfer plays a
pivotal role and has stimulated the tremendous development of
the chemistry of carbene, imido, and oxo complexes.2 In this
context, phosphinidene complexes have attracted considerable
attention since their existence was evidenced.3 In the last two
decades, these efforts have resulted in significant progress
exemplified by the first structural characterization of terminal
phosphinidene complexes.4 These advances have stimulated the
(4) Cowley, A. H. Acc. Chem. Res. 1997, 30, 445-451.
(5) (a) Dillon, K. B.; Mathey, F.; Nixon, J. F. Phosphorus: The Carbon
Copy; Wiley: Chichester, 1998; Chapter 3. (b) Lammertsma, K. Phosphin-
idenes. In Topics in Current Chemistry: New Aspects in Phosphorus
Chemistry III; Springer: Berlin, 2003; Vol. 229, pp 95-119. (c) Mathey,
F. Angew. Chem., Int. Ed. 2003, 42, 1578-1604.
(6) Basuli, F.; Tomaszewski, J. C.; Huffman, J. C.; Mindiola, D. J. J.
Am. Chem. Soc. 2003, 125, 10171-10172.
* Author to whom the correspondence should be addressed. E-mail:
fdelpech@insa-toulouse.fr.
(7) Hou, Z.; Breen, T. L.; Stephan, D. W. Organometallics 1993, 12,
3158-3167.
‡ Laboratoire He´te´rochimie Fondamentale et Applique´e.
† Laboratoire des Interactions Mole´culaires et Re´activite´ Chimique et
Photochimique.
(8) Basuli, F.; Bailey, B. C.; Huffman, J. C.; Baik, M.-H.; Mindiola, D.
J. J. Am. Chem. Soc. 2004, 126, 1924-1925.
§ Present address: Laboratoire de Physique et Chimie des Nano-Objets,
De´partement de Ge´nie Physique, Institut National des Sciences Applique´es,
135 Avenue de Rangueil, 31077 Toulouse Cedex 04, France.
(1) (a) Han, L. B.; Tanaka, M. Chem. Commun. 1999, 395-402. (b)
Bedford, R. B.; Cazin, C. S. J.; Holder D. Coord. Chem. ReV. 2004, 248,
2283-2321.
(9) Cummins, C. C.; Schrock, R. R.; Davis, W. M. Angew. Chem. 1993,
105, 758-761.
(10) Hitchcock, P. B.; Lappert, M. F.; Leung, W. P. J. Chem. Soc., Chem.
Commun. 1987, 1282-1283.
(11) Cowley, A. H.; Pellerin, B.; Atwood, J. L.; Bott, S. G. J. Am. Chem.
Soc. 1990, 112, 6734-6735.
(2) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley:
New York, 1989.
(3) Mathey, F. Angew. Chem., Int. Ed. Engl. 1987, 26, 275-286.
(12) Graham, T. W.; Cariou, R. P. Y.; Sa´nchez-Nieves, J.; Allen, A. E.;
Udachin, K. A.; Regragui, R.; Carty, A. J. Organometallics 2005, 24, 2023-
2026.
10.1021/om7004854 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 08/24/2007

5092 Organometallics, Vol. 26, No. 20, 2007
Menye-Biyogo et al.
standpoint, only terminal phosphinidene complexes are of major
interest since bridging phosphinidenes display little reactivity
in a µ2-, µ3-, or µ4-bridging modes except in rare cases.19
Terminal phosphinidene complexes exist in two varieties, which
display electrophilic Fisher-type or nucleophilic Schrock-type
properties and, thus, mimic their carbene analogues. A recent
computational study has shown that, in addition to the ancillary
ligands on the metal, both the charge on the complex and the
nature of the phosphinidene substituents can significantly
influence electro- or nucleophilicity.20
benzene).26 As a part of our ongoing studies of the reactivity
of phosphinidene complexes, we examined the behavior (η6-
Ar)(PCy3)Ru(PMes*) (Ar ) p-cymene, benzene) toward elec-
trophilic reagents and alkynes. Surprisingly, in the latter case,
the benzene ligand derived complex did not react, while total
consumption of (η6-p-cymene)(PCy3)Ru(PMes*) was immedi-
ately observed. To the best of our knowledge, there is no
example in the literature reporting that benzene and the
p-cymene ligand could induce such different behaviors of the
corresponding organometallic complexes. This prompted us to
investigate in depth their structural and chemical features. In
this paper, we describe (i) the full characterization of these
phosphinidene complexes and (ii) their respective reactivity
toward electrophilic and electron-rich reactants in order to
identify the exact origin of this contradictory behavior. This
comparative analysis addresses this issue, and we will show
how subtle structural changes result in dramatic enhancement
of the reactivity of such species.
Surprisingly, despite the considerable attention fueled by the
analogy with carbene, direct involvement of phosphinidene in
catalytic processes has been demonstrated in only two cases.21
Similarly, studies concerning the synthetic potential of phos-
phinidene complexes are still very rare except in the case of
the transient in situ generated complex (CO)5W(PPh). The
phosphorus atom exhibits electrophilic properties, and the
numerous examples of addition to olefinic and acetylenic
systems have been reviewed recently.22 In contrast, little of the
chemical behavior of nucleophilic phosphinidene complexes has
been explored, the most documented one being Cp2(PMe3)Zr-
(PMes*) (Mes* ) 2,4,6-tri-tert-butylphenyl). The characteristic
reactions are 1,2-additions with protic reagents, [2+2] cycload-
ditions with alkynes leading to phosphametallacycles,4,23,24 and
the phospha-Wittig reaction with carbonyl compounds.4,9,24
Comparatively, group 9 metal phosphinidene complexes of
general formula Cp*(PPh3)M(PMes*) (M ) Co, Rh, Ir) exhibit
poor reactivity, reacting only with organic iodides. DFT
calculations showed that the lower nucleophilicity of the
phosphorus atom accounts largely for such a discrepancy with
the reactivity of the related zirconium complexes.16 Additionally,
in the latter case, the facile dissociation of the PMe3 ligand also
appears crucial for explaining its unique reactivity.25
Results and Discussion
Synthesis, Spectroscopic, and Structural Characteriza-
tions. The ruthenium-complexed terminal phosphinidenes were
synthesized using the base-induced dehydrohalogenation-
ligation sequence described by Lammerstma et al.17 The reaction
of (η6-Ar)(PH2Mes*)RuCl2 (1a, Ar ) p-cymene; 1b, Ar )
benzene) with 2 equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) in the presence of PCy3 afforded (η6-Ar)(PCy3)Ru-
(PMes*) (2a, Ar ) p-cymene; 2b, Ar ) benzene) as water-
stable green crystals in high yields. Their 31P, 13C, and 1H NMR
spectra display nearly identical signals (Scheme 1). The high-
field 31P NMR resonances (δ 813 for 2a and δ 819 for 2b) for
the phosphorus atom of the phosphinidene ligand are in the
typical region for terminal phosphinidene complexes.5 The slight
shielding of this chemical shift in 2a is also observed for the
PCy3 resonance (δ 35 for 2a and δ 38 for 2b). This minor
difference can be attributed to the slight donating effect of
p-cymene, compared to that of the benzene ligand. A similar
trend is observed for (η6-Ar)(PPh3)Ru(PMes*).15,27 The η6-Ar
ligand and the Mes* moiety are in free rotation in complexes 2
since no decoalescence is observed for the aryl or the methyl
We have recently reported the synthesis and the first structural
evidence for monomeric metaphosphonate by taking advantage
of the high reactivity of the phosphinidene complex (η6-p-
cymene)(PCy3)Ru(PMes*) (p-cymene ) 4-methylisopropyl-
(13) Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. Organometallics
2003, 22, 3927-3932.
(14) Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. Organometallics
2001, 20, 2657-2659.
1
protons in the H NMR spectra, even at low temperature.
X-ray diffraction analyses of both complexes were then
conducted. The solid-state structures of 2a and 2b are shown
in Figure 1 and reveal very similar features. The environment
of the ruthenium atom is congested, and the X-ray structure
shows a long Ru-PCy3 bond (2.386(4) Å for 2a and 2.389(7)
Å for 2b) and a short Ru-PMes* one (2.205(3) Å for 2a and
2.237(7) Å for 2b). The short Ru-PMes* distances together
with the acute angles Cy3P-Ru-PMes* (85.98(14)° for 2a and
86.7(3)° for 2b) and Ru-P-Cipso(Mes*) (110.5(4)° for 2a and
107.6(8)° for 2b) are characteristic for terminal bent phosphin-
idene complexes. Concerning these angles, the difference
between 2a and 2b can be rationalized in terms of steric
repulsion between the arene ligand and Mes* substituent.
However, these variations are minor and both structures very
much resemble that of (η6-p-cymene)(PPh3)Os(PMes*) and (η6-
benzene)(PPh3)Ru(PMes*).15
(15) Termaten, A. T.; Nijbacker, T.; Schakel, M.; Lutz, M.; Spek, A.
L.; Lammertsma, K. Chem. Eur. J. 2003, 9, 2200-2208.
(16) Termaten, A. T.; Aktas, H.; Schakel, M.; Ehlers, A. W.; Lutz, M.;
Spek, A. L.; Lammertsma, K. Organometallics 2003, 22, 1827-1835.
(17) Termaten, A. T.; Nijbaker, T.; Schakel, M.; Lutz, M.; Spek, A. L.;
Lammertsma, K. Organometallics 2002, 21, 3196-3202.
(18) Melenkivitz, R.; Mindiola, D. J.; Hillhouse, G. L. J. Am. Chem.
Soc. 2002, 125, 3846-3847.
(19) (a) Garcia, M. E.; Riera, V.; Ruiz, M. A.; Saez, D.; Vaissermann,
J.; Jeffery, J. C. J. Am. Chem. Soc. 2002, 124, 14304-14305. (b) Alvarez,
C. M.; Alvarez, M. A.; Garcia, M. E.; Gonzalez, R.; Ruiz, M. A.; Hamidov,
H.; Jeffery, J. C. Organometallics 2005, 24, 5503-5505. (c) Graham, T.
W.; Udachin, K. A.; Carty, A. J. Chem. Commun. 2005, 4441-4443.
(20) Ehlers, A. W.; Baerends, E. J.; Lammertsma, K. J. Am. Chem. Soc.
2002, 124, 2831-2838.
(21) (a) Fermin, M. C.; Stephan, D. J. Am. Chem. Soc. 1995, 117, 12645-
12646. (b) Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha, H.;
Huffman, J. C.; Wu, G.; Mindiola, D. J. J. Am. Chem. Soc. 2006, 128,
13575-13585.
Since the physical properties provide no clear evidence to
rationalize the different behavior between 2a and 2b, a detailed
reactivity study was undertaken in order to gain some insight.
(22) (a) Mathey, F; Tran Huy, N. H.; Marinetti, A. HelV. Chim. Acta
2001, 84, 2938-2957. (b) Lammertsma, K.; Vlaar M. J. M. Eur. J. Org.
Chem. 2002, 1127-1138.
(23) Waterman, R.; Hillhouse, G. L. J. Am. Chem. Soc. 2003, 125,
13350-13351.
(26) Menye Biyogo, R.; Delpech, F.; Castel, A.; Riviere, P.; Gornitzka,
H. Angew. Chem., Int. Ed. 2003, 42, 5610-5612.
(27) Menye-Biyogo, R. Terminal Phosphinidene Ruthenium Com-
plexes: Synthesis and Reactivity. Ph.D. dissertation, University Paul
Sabatier, Toulouse, France, November 2005.
(24) Shah, S.; Protasiewicz, J. D. Coord. Chem. ReV. 2000, 210, 181-
201.
(25) Goumans, T. P.; Ehlers, A. W.; Lammertsma, K. J. Organomet.
Chem. 2005, 690, 5517-5524.

Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms
Organometallics, Vol. 26, No. 20, 2007 5093
Figure 1. Molecular structure of complexes 2a and 2b (50% probability level for the thermal ellipsoids). All H atoms have been omitted
for clarity. Selected metrical parameters (Å) and angles (deg): For 2a: Ru1-P1 2.205(3); Ru-P2 2.386(4); P1-C11 1.843(14); Ru1-
centroid(arene) 1.766; P1-Ru1-P2 85.98(14); Ru1-P1-C11 110.5(4). For 2b: Ru1-P1 2.237(7); Ru1-P2 2.389(7); P1-C1 1.91(2);
Ru1-centroid(arene) 1.778; P1-Ru1-P2 86.7(3); Ru1-P1-C1 107.6(8).
Scheme 1
Reactivity Studies. The philicity of terminal phosphinidene
complexes has been shown to depend essentially on the
electronic properties of the ligands.20 The electron-rich fragment
(η6-Ar)(PCy3)Ru is expected to induce a significant electronic
density flow from the transition metal on the phosphinidene
phosphorus and, thus, to enhance nucleophilicity of the phos-
phinidene ligand. Consistently, the nucleophilicity of the
phosphorus atom in 2 is illustrated by its reactivity toward
electrophilic reagents.
Reactions with Electrophiles. First, we examined the
reactivity of 2 toward Bro¨nsted acids (Scheme 1). Protonation
of the phosphinidene atom is readily achieved. However,
according to the nucleophilicity of the anion, different complexes
are obtained. Reaction with HCl results in the instantaneous
formation of (η6-Ar)(PCy3)RuCl2 (1) with the release of PH2-
Mes*. Treatment of a solution 2 with the acid HBF4 incorporat-
ing the non-nucleophilic anion BF4 leads to a rapid color
change from dark green to purple with formation of the new
cationic complexes [(η6-Ar)(PCy3)Ru(PHMes*)]BF4 (3aBF4, Ar
) p-cymene; 3bBF4, Ar ) benzene) in high yields (Scheme
1).
-
The discrepancy between the reactivity of 2 with HCl and
HBF4 is reminiscent of the somewhat related imido complex
(PMe3)2ReMe3(NPh): reaction with HBF4 led to protonation,
while in the case of CH3COOH a unidentate coordination mode
was characterized for acetate.28 These results can be attributed
to the relative nucleophilicity of the anions: The presence of
3BF4 is evident from their 31P NMR spectra, which exhibit a

5094 Organometallics, Vol. 26, No. 20, 2007
Menye-Biyogo et al.
signal assigned to the phosphenium ligand PHMes* at δ 174
(1J(P, H) ) 336 Hz, 2J(P, P) ) 84 Hz) for 3aBF4 and at δ 191
2
(1J(P, H) ) 343 Hz, J(P, P) ) 84 Hz) for 3bBF4. Of interest
is that these 31P chemical shifts are lower than the values
typically found (200-320 ppm) for phosphenium resonances
presumably because of the strong donating properties of the
ruthenium fragment.29 The 1H NMR spectra display a resonance
at δ 8.86 for 3aBF4 and δ 9.00 for 3bBF4 characteristic of the
acidic proton of the PHMes* moiety, suggesting the presence
of a non-negligeable partial positive charge on the phosphorus
atom. Other signals are slightly shifted downfield from the
corresponding resonances of 2. Interestingly, to the best of our
knowledge, 3aBF4 and 3bBF4 are the first P-H-functionalized
cationic phosphenium complexes. Despite renewed interest in
the phosphenium group as a strong π-acidic ligand in the context
of the preparation of electrophilic late transition metal catalysts,30
the range of phosphenium ligands in cationic complexes remains
indeed confined quasi-exclusively to diamino, aminoalkoxy, or
dialkoxy phosphenium moieties.29 Stabilization of hydrogen-
substituted phosphenium and more generally phosphenium
ligands bearing weakly π- and σ-donating substituents (for
instance aryl or alkyl) represents a true synthetic challenge.
[(CO)4Fe{P(Fc)2}]AlCl4 (Fc ) ferrocenyl) is the only example
for which no N- or O-based substituent (i.e., strongly π-donating
and σ-withdrawing fragments) is borne by the two-coordinate
phosphorus cation.31 However, it could not be characterized
using X-ray diffraction techniques. In this case, delocalization
on the ferrocenyl susbtituent is invoked to allow stabilization.
Concerning 3BF4, the unprecedented stabilization of a phos-
phenium ligand bearing a hydrogen substituent can be assigned
to the powerful electron-rich nature of the fragment (η6-Ar)-
(PCy3)Ru. The decisive factor is, indeed, the π-basicity of the
transition metal fragment.29 Computational studies support that
stabilization results predominantly from transition metal π-back-
donation and as a minor component from π-donation from a
phosphorus substituent.29
Figure 2. Molecular structure of complex 3aBF4‚C7H8 (50%
probability level for the thermal ellipsoids). All H atoms, the anion,
and the solvent molecule (toluene) have been omitted for clarity.
Selected metrical parameters (Å) and angles (deg): Ru1-P1
2.173(9); Ru1-P2 2.394(8); P1-C11 1.79(3); Ru1-centroid(arene)
1.743; P1-Ru1-P2 91.0(3); Ru1-P1-C11 133.2(10).
in the somewhat related phosphido complex (η5-Cp′)(PMe3)2-
Mo(PHMes*) (Cp′ ) C5EtMe4, Mo-P-C(Mes*) ) 133.0(3)°).32
The lone pair of the phosphorus atom of the phosphinidene
ligand remains also accessible to electrophilic alkylating reagents
and Lewis acids. Treatment of 2 with an excess of BH3‚SMe2
gives the expected adducts (η6-Ar)(PCy3)Ru[P(BH3)Mes*] (4a,
Ar ) p-cymene; 4b, Ar ) benzene) (Scheme 1), which were
characterized spectroscopically. These borane adducts decom-
posed on attempted recrystallization, and satisfactory elemental
analysis could not be obtained. Although no 11B-31P coupling
is observed, the 31P NMR spectrum shows some line broadening
and the PMes* chemical shift changes significantly on com-
plexation (from 813 to 506 ppm for 4a and from 819 to 521
ppm for 4b). For comparison, on formation of the adduct PH2-
Mes*‚BH3, the 31P NMR signal moves from δ -130 to -62.27
Additionally, the 11B NMR spectra display resonances in the
expected range for a tetracoordinated boron atom (at δ 18.3 for
4a and 4b), consistent with a rehybridization at boron.
Single crystals of 3aBF4 were grown from a toluene solution
at -25 °C. The molecular representation is depicted in Figure
2 and confirmed the formulation deduced from NMR consid-
eration. To date, a very limited number of phosphenium
complexes have been structurally characterized.29
Replacing BH3 by BPh3 leads to interesting results. In a first
stage, no reaction is observed, the size of the borane BPh3
disfavoring presumably its coordination. However, in the
presence of water, the color of the solution changes to purple.
Similarly to what was observed in the previously reported
X-ray diffraction molecular structures, the M-P(phosphenium)
bond is substantially shorter (2.173(9) Å) than the M-P dative
bond (2.394(8) Å).29a This result is consistent with double-bond
character as evidenced with the similar ruthenium-phosphin-
idene distance found in 2a. However, all structurally character-
ized cationic phosphenium complexes involve an amino or
alkoxy substituent on the phosphorus atom, and thus, this
prevents further relevant comparison. The metrical parameters
of the fragment (η6-Ar)(PCy3)Ru of 3aBF4 are very similar to
those of 2a and 2b, but the protonation of the phosphinidene
ligand results in noteworthy modifications of the P-Ru-P and
Ru-P-C(Mes*) angles, which increase significantly (91.0(3)°
and 132.2(10)°). The latter value compares well to that observed
1
In the H, 31P, and 13C NMR spectra, very similar resonances
to those of 3BF4 were observed and assigned to [(η6-Ar)-
(PCy3)Ru(PHMes*)]BPh3OH (3BPh3OH) (Scheme 1). 11B
NMR resonances for 3aBPh3OH and 3bBPh3OH allow un-
equivocal identification of a tetracoordinated boron atom.
Studies on properties of boranes and in particular of B(C6F5)3
have focused much interest and have shown that water adducts
may be regarded as strong Bro¨nsted acid.33 The pKa for the
complex (C6F5)3B‚OH2 is estimated to be 8.4 in acetonitrile.
Such a value indicates that (C6F5)3B‚OH2 and HCl possess
comparable Bro¨nsted acidity. However, there is, to the best of
our knowledge, no report concerning direct or indirect observa-
tion of the adduct Ph3B‚OH2, which is assumed to be involved
in the formation of 3BPh3OH. Interestingly, a significant
(28) Chiu, K. W.; Wong, W. K.; Wilkinson, G. Polyhedron 1982, 1,
31-36.
(29) (a) Nakazawa, H. AdV. Organomet. Chem. 2004, 50, 108-143. (b)
Gudat, D. Eur. J. Inorg. Chem. 1998, 1087-1094.
(30) (a) Hardman, N. J.; Abrams, M. B.; Pribisko, M. A.; Gilbert, T.
M.; Martin, R. L.; Kubas, G. J.; Baker, R. T. Angew. Chem., Int. Ed. 2004,
43, 1955-1958. (b) Spinney, H. A.; Yap, G. P. A.; Korobkov, I.; DiLabio,
G.; Richeson, D. S. Organometallics 2006, 25, 3541-3543.
(31) Baxter, S. G.; Collins, R. L.; Cowley, A. H.; Sena, S. F. J. Am.
Chem. Soc. 1981, 103, 714-715.
1
difference is observed for the H, 31P, and 13C NMR arene
signals of 3aBPh3OH (and 3bBPh3OH) compared to those of
3aBF4 (and 3bBF4). This result suggests some sort of ion-
(32) Hey-Hawkins, E.; Fromm, K. Polyhedron 1995, 14, 2825-2834.
(33) Bergquist, C.; Bridgewater, B. M.; Harlan, C. J.; Norton, J. R.;
Friesner, R. A.; Parkin, G. J. Am. Chem. Soc. 2000, 122, 10581-10590.

Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms
Organometallics, Vol. 26, No. 20, 2007 5095
pairing interactions involving anion and η6-Ar ligands. However,
the exact origin of these phenomena remains to be clarified.
The reactivity of 2a and 2b toward electrophilic alkylating
reagents such as organic iodides was also examined. Treatment
of 2 with 1 equiv of methyliodide leads to the alkylation at the
phosphinidene center and yields the phosphenium complexes
[(η6-Ar)(PCy3)Ru(PMeMes*)]I (5a, Ar ) p-cymene; 5b, Ar )
benzene), which can be isolated as purple solids (Scheme 1).
This structural formulation is based on the 1H, 13C, and 31P NMR
spectra. The 31P NMR spectra display doublets of quadruplets
at δ 240 (2JPH ) 9.7 Hz; 2JPP ) 82.1 Hz) and 248 (2JPH ) 10.2
Hz; 2JPP ) 76.3 Hz) for the phosphenium ligand P(Me)(Mes*)
in 5a and 5b, respectively. Accordingly, in the 1H NMR spectra,
7 signals corresponding to two nonequivalent t-Bu groups, four
Me groups, and a new CH2 moiety indicate unambiguously the
formation of a coordinated vinylphosphine fragment.35 Ad-
ditionally, the presence of vinylic proton signals at δ ∼2.4 and
3.4 coupled with a phosphorus nucleus clearly shows the
formation of a coordinated vinylphosphine fragment. These
assignments are in agreement with those of an analogous
complex that has been recently fully characterized and showed
similar NMR resonances.15 Furthermore, 6 and 7 have been
prepared separately using the method described by Lammerstma
et al., that is, by reacting (η6-p-cymene)(PH2Mes*)RuCl2 with
2 equiv of DBU in the presence of the corresponding alkyne.15
Of interest to note is that the addition of these unsymmetrical
alkynes occurs regioselectively with the larger substituent R′′
located trans to the phosphorus atom. Only one regioisomer is
observed by 1H NMR spectroscopy since the spectrum displays
one set of resonances for Ph (or for SiMe3). Oxidation of 6
allowed formation and crystallization of the oxidized version
of the vinylphosphaindane ligand. Despite the poor quality of
these crystals, connectivity of atoms was unambiguously
established and evidenced the trans geometry of the phosphavi-
nyl derivative.36
2
the methyl signals appear as doublets (2.13 ppm, JPH ) 9.7
2
Hz for 5a and 2.21 ppm, JPH ) 10.2 Hz for 5b) arising from
the coupling with the phosphorus nucleus. In addition, the NMR
data of 5 compare well to those of complexes 3 and are
consistent with the formation of cationic complexes with a
phosphenium ligand.
However, interestingly the p-cymene ligand in 5a no longer
1
exhibits fluxional behavior anymore, as evidenced by the H
NMR spectrum, which shows for the aryl protons of the
p-cymene ligand three resonances in a 2:1:1 ratio, the last two
being significantly shifted upfield relative to those of 3a+. Such
a behavior had been previously observed in the related meta-
phosphonate complex (η6-p-cymene)(PCy3)Ru((η2-OPOMes*)26
and for half-sandwich complexes exposed to the magnetic
anisotropy cone of the phenyl substituent (known as the “â-
phenyl effect”).34 Consistently, the proximity between p-cymene
and Mes* moieties results also in restricted rotation about the
P-C(Mes*) bond, as evidenced by the presence of two Mes*
aryl signals in addition to two o-Me resonances. This result is
attributed to the higher steric congestion around the ruthenium
atom in 2a compared to that in 2b. This prompted us to study
the reactivity of 2 with the larger alkyl reagent isopropyliodide.
However, no reaction was observed, confirming that if there is
a difference in terms of steric hindrance; both complexes remain
highly encumbered, preventing in this case the electrophilic
attack.
This result is consistent with the trend observed for the
reaction of zirconocene imido37 or phosphinidene complexes38
with alkynes. The regioselectivity has been rationalized in terms
of steric repulsion between the substituent of the phosphinidene
(or imido) group and the ones of the alkyne.
In marked contrast, no reaction occurs with 2b. Additionally,
the high reactivity of 2a is in total contradiction with the lack
of reactivity of the previously reported group 8 and 9 series
compounds.15,16 Such a difference between the chemical be-
havior of 2a and 2b was very surprising, since neither the
spectroscopic properties, structural characteristics, nor the
preliminary reactivity studies give any insight of potentially
different reactivity. This prompted us to study the details of
the reaction. The phosphinidene ligand exhibits nucleophilic
properties, and thus, the first step is thought to be the
coordination of alkyne at the ruthenium center in order to allow
the reaction to proceed. The second step of this anticipated
mechanism (formation of a metallacycle) is analogous to that
described in the case of a related zirconium complex,39 then
followed by an intramolecular C-H insertion of the P atom
and subsequent H transfer to yield 6 or 7 (Scheme 2).
Evidently, the key step for the understanding of the specificity
of our system is the generation of the complex (η6-p-cymene)-
(η2-HCtCR′′)Ru(PMes*), which has, thus, focused our interest.
In the two limiting cases, complexation of alkyne could occur
according to an associative or a dissociative mechanism. In the
latter case, phosphine dissociation to generate a 16-electron
intermediate, (η6-p-cymene)Ru(PMes*), is an appealing hy-
pothesis for synthetic outcomes since it would provide an entry
to the chemistry of an unsaturated phosphinidene species related
to the valuable Cp2(PMe3)Zr(PMes*) complex. Involvement of
(η6-Ar)Ru(PMes*) has also been proposed to account for the
formation of several complexes connected to phosphinidene
Reactions with Alkynes: Mechanistic Studies. Despite the
electron-rich nature of the ruthenium fragment and the nucleo-
philicity of the phosphinidene ligand, 2a reacts instantaneously
with alkynes (Me3SiCtCH and PhCtCH) to afford the
allylphosphaindane complexes 6 and 7 (eq 1).
(35) Aitken, R. A.; Clasper, P. N.; Wilson, N. J. Tetrahedron Lett. 1999,
40, 5271-5274.
(36) Because a single crystal was of low quality, the details of the
structural parameters could not be discussed, but the regiochemistry of the
olefin moiety was determined to be the E-configuration.
(37) Baranger, A. M.; Walsh, P. J.; Bergman, R. G. J. Am. Chem. Soc.
1993, 120, 2753-2763.
The formation of 6 and 7 and the release of PCy3 are evident
1
from the NMR data. In the H and 13C NMR spectra of 6 and
(38) Breen, T. L.; Stephan, D. W. Organometallics 1996, 15, 5729-
5737.
(34) Brunner, H.; Zwack, T.; Zabel, M.; Beck, W.; Bo¨hm, A. Organo-
metallics 2003, 22, 1741-1750.
(39) Breen, T. L.; Stephan, D. W. J. Am. Chem. Soc. 1996, 118, 4204-
4205.

5096 Organometallics, Vol. 26, No. 20, 2007
Menye-Biyogo et al.
Scheme 2
Figure 3. Plot of [2a] versus time at different concentrations of
PPh3 (0 1 equiv, O 2 equiv, b 3 equiv). Solid line: best fit obtained
for the three curves simultaneously using the dissociative model.
Dotted line: best fit using the associative model.
species.15 However, a recent computational study on the related
group 9 metals phosphinidene complexes of general formula
Cp*(PPh3)M(PMes*) (M ) Co, Rh, Ir) showed a high dissocia-
tion energy of the stabilizing phosphine ligand.16 Additionally,
an associative pathway should not be excluded since the freeing
of a coordination site may also be achieved through ligand-
induced ring slippage of η6- to η4-arene, as previously reported
for the reaction of phosphine, phosphite, or isonitrile with a
related ruthenium-naphthalene complex.40 Finally, migration of
a metal fragment off the arene centroid and more generally arene
exchange have been shown to be facilitated for arene-ML2
complexes.41
to the two proposed pathways were used to reproduce the
experimental data. When only one experiment is presented to
each model, the quality of the fitting obtained is equivalent and
does not allow a choice between the two mechanisms. This
problem was resolved by fitting simultaneously three experi-
ments involving increasing concentrations of PPh3 (1, 2, and 3
equiv). The result is in this case clearly in favor of the
dissociative pathway (Figure 3).
Preliminary studies proved that it was difficult to investigate
mechanistic details in solution since none of the putative
ruthenium intermediate could be observed by spectroscopic
means. Consequently, we undertook a detailed kinetic study on
phosphine complexation as a model for the alkyne coordination
(Scheme 3).
The parameters extracted from the fitting procedure are (i)
the dissociation rate of PCy3 (k1 ) 3.3 × 10-2 s-1) and (ii) that
of PPh3 (k-2 ) 8.5 × 10-3 mol-1‚L‚s); (iii) without further
information on the intermediate concentration the constants k-1
and k2 cannot be reached, but their ratio can (k-1/k2 ) 9). These
results show that rate constants involving PCy3 are larger than
those of PPh3: dissociation of PCy3 from (η6-p-cymene)(PCy3)-
Ru(PMes*) (2a) is faster than that of PPh3 from (η6-p-cymene)-
(PPh3)Ru(PMes*) (8), and trapping of PCy3 by the intermediate
A is also quicker than that of PPh3. This result was unanticipated
since a less electron-donating phosphine is generally expected
to be more labile.42 Addressing the relative importance of steric
and electronic factors for tertiary phosphine ligands has attracted
much recent attention due to their ubiquitous involvement in
organometallic chemistry. In order to gain insight into the
relative influence of these factors, experiments were conduced
for a series of phosphines. For this study, the kinetic curves
This approach was successfully exploited for a phosphine/
olefin substitution study on Grubbs’ ruthenium-based olefin
metathesis catalysts.42 However, the rate of exchange between
free phosphines and PCy3 is insufficient to support spin-
saturation labeling experiments as kinetic probes. Therefore, the
concentration of the exchange products was monitored with time
1
by H NMR. This substitution reaction is reversible since the
same product distribution (K) can also be established from the
reaction of (η6-p-cymene)(PPh3)Ru(PMes*) (8) with PCy3.
A numerical approach was used to treat the kinetic curves.
The two models (see Supporting Information) corresponding
Scheme 3. [a] Dissociative Pathway; [b] Associative Pathway

Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms
Organometallics, Vol. 26, No. 20, 2007 5097
Table 1. Kinetic Parameters Extracted from Phosphine Exchange Reaction
k-1/k2
coord
k1/k-2
dissos
k-2
a
entry
PR3
K
(mol-1‚L‚s)
pKa
νCOb (cm-1
)
θc (deg)
1
2
3
4
5
6
7
P(NC4H4)3
P(p-ClC6H4)3
PPh3
P(p-MeOC6H4)3
P(m-MeC6H4)3
P(o-MeC6H4)3
P(o-MeOC6H4)3
78
0.9
1.6
9.0
13.1
6.8
72.6
1.4
3.9
3.2
7.8
4.60 × 10-4
2.42 × 10-2
8.51 × 10-3
1.06 × 10-2
4.26 × 10-3
n.d.
2090.4d
2072.8
2068.9
2066.1
2067.2
2066.6
n.d.
145d
145
145
145
165
194
205f
0.85
0.44
0.24
0.86
0
1.03
2.73
4.59
3.30
3.08
∼8.8e
0
a pKa of the corresponding conjugate acid.43 b νCO: carbonyl stretching frequency in the corresponding Ni(CO)3L complex in CH2Cl2.43 c Tolman cone
angle.43 d Electronic and steric properties are discussed in ref 44. e Electronic properties of P(o-MeOC6H4)3 were found to be comparable to those of P(i-
Pr)3.45a f Reference 45b.
were treated with the dissociative model, the values of k1 and
k-1 were fixed to those obtained previously, and k2 and k-2
were provided by fitting. Rate constants of susbstitution
reactions and steric (Tolman cone angle) and electronic char-
acteristics43 are gathered in Table 1. Considering isosteric
phosphines (P(NC4H4)3,44 P(p-ClC6H4)3, PPh3, P(p-MeOC6H4)3,
entries 1 to 4), the less basic the phosphine, the more the
equilibrium is driven toward the formation of the new complexes
(η6-p-cymene)(PR3)Ru(PMes*) (K increases). On the other hand,
examination of the ratio between coordination rate constants
(k-1/k2) establishes a clear trend: the donor properties of PR3
slow down its trapping by A. As a consequence, changing the
phosphine from P(NC4H4)3 to P(p-MeOC6H4)3 leads indeed to
an approximately 15-fold decrease in the coordination rate. The
effect of electronic properties on the dissociation rate constants
(k1/k-2) looks less obvious to rationalize in the cases of the three
arylphosphines (entries 2-4) since the variations are relatively
weak. A similar observation was made by Grubbs et al. (during
the study of phosphine dissociation in ruthenium olefin me-
tathesis catalysts), who stressed the point that no linear
correlation between phosphine pKa and its dissociation rate
constant exists.42 However, it is interesting to note that in the
case of P(NC4H4)3 the dissociation is significantly disfavored
(20-fold, entry 1).
Concerning the influence of steric effects, the phosphine PCy3
in 2a exchanges only with smaller phosphines, evidencing the
dominant role of the congestion of the added phosphine. This
is in particular illustrated by the absence of reaction of 2a with
P(o-MeC6H4)3 or P(o-MeOC6H4)3,45 although their electronic
properties should promote coordination (because they are less
basic) and disfavor decoordination.46 Interestingly, this positive
influence of a large phosphine was unexpected since the
reactivity of Cp*(PR3)Rh(PMes*) has been shown to increase
by reducing the size of its stabilizing ligand PR3.16
P(NC4H4)3 led to an important stabilization of the phosphinidene
complex 12. As an illustration, only 10% of conversion of
phenylacetylene into 7 is observed when reacting 12 at 50 °C
for 3 days. The inertness of 12 is consistent with a DFT study
on group 9 transition metal phosphinidene complexes, which
stressed a significant increase of the bond dissociation energy
of the highly π-acidic carbonyl ligand compared to that of
phosphine.16 However, the dominant effect is unambiguously
steric. This result is in perfect agreement with the observation
that reaction of alkynes occurs exclusively in the presence of
the more hindered arene, which plays the role of reactivity
switch.
Conclusion
In summary, ruthenium phosphinidene complexes (η6-Ar)-
(PCy3)Ru(PMes*) that differ only in the substituent borne by
the arene ligand were prepared and showed dramatically
different chemical behavior toward alkynes: introduction of
alkyl groups on the arene ligand, i.e., changing the arene ligand
from benzene to p-cymene, allowed the reaction with alkyne
to proceed. A detailed comparative study of the structural and
spectroscopic features of both complexes did not allow the
identification of the origin of this phenomenon. Reactivity
studies of (η6-Ar)(PCy3)Ru(PMes*) with HBF4 and MeI have
afforded unprecedented cationic phosphenium complexes and
have provided a first insight for addressing this issue: in the
case of [(η6-Ar)(PCy3)Ru(PMeMes*)]I, the free rotation of the
Mes* substituent and Ar ligand was stopped only in the case
of the more crowded arene ligand, suggesting that alkyl groups
of p-cymene could be not as innocent as initially anticipated.
Careful examination of the mechanism of reaction of phosphin-
idene complexes with alkyne and in particular of the first step
(phosphine dissociation) brought evidence for the involvement
of both electronic and steric factors. We have demonstrated that
in contrast with common expectations the lability of the
phosphine increased with its donor properties. However, the
dominant factor proved to be steric, the specificity of (η6-p-
cymene)(PCy3)Ru(PMes*) being directly related to the critical
PCy3 dissociation step, which occurs only when the arene is
p-cymene. Thus, the reactivity arises from the repulsion of the
sterically demanding phosphine ligand with the alkyl groups
of the arene ligand.
Two important ligand effects in this system involve an
acceleration of the critical step of phosphine dissociation: the
donating and the hindering characteristics of the PR3 ligand. In
other words, the presence of a strongly π-acidic phosphine
(40) Bennett, M. A.; Lu, Z.; Wang, X.; Bown, M.; Hockless, D. C. R.
J. Am. Chem. Soc. 1998, 120, 10409-10415.
(41) Muetterties, E. L.; Bleeke, J. R.; Wucherer, E. J.; Albright, T. A.
Chem. ReV. 1982, 82, 499-525.
(42) Sandford, M. S.; Love, J. A.; Grubbs, R. H. J. Am. Chem. Soc.
2001, 123, 6543-6554.
Increasing steric congestion about reactive centers is a
well-known strategy for kinetic stabilization or for controlling
chemo-,47 regio-,48 or enantioselectivity.49 Nevertheless, to the
(43) Tolman, C. A. Chem. ReV. 1977, 77, 313-348. For PCy3, the pKa
of the corresponding conjugate acid is 9.7; the carbonyl stretching frequency
in the corresponding Ni(CO)3L complex in CH2Cl2 is 2056.4 cm-1, and
Tolman cone angle (θ) is 170°.
(44) Moloy, K. G.; Petersen, J. L. J. Am. Chem. Soc. 1995, 117, 7696-
7710.
(45) (a) Pruchnick, F. P.; Smolenski, P.; Wajda-Hermanowicz, K. J.
Organomet. Chem. 1998, 570, 63-69. (b) Suomalainen, P.; Laitinen, R.;
Ja¨a¨skela¨inen, S.; Haukka, M.; Pursiainen, J. T.; Pakkanen, T. A. J. Mol.
Catal. A 2002, 179, 93-100.
(46) We have checked that the two complexes (η6-p-cymene)[P(o-
MeOC6H4)3]Ru(PMes*) and (η6-p-cymene)[P(o-MeC6H4)3]Ru(PMes*) could
be prepared separately and, thus, that these phosphines are not too large to
prevent their formation.
(47) Ananikov, V. P.; Szilagyi, R.; Morokuma, K.; Musaev, D. G.
Organometallics 2005, 24, 1938-1946.

5098 Organometallics, Vol. 26, No. 20, 2007
Menye-Biyogo et al.
2
1
2JPP ) 15.3 Hz, PCy3); 812.94 (d, JPP ) 15.3 Hz, PMes*). H
best of our knowledge, it is the first evidence reporting that
such a subtle change induces a reactivity switch. This study
provides a rare example for which the “catch 22” situation of
kinetic stabilization versus reactivity4 vanishes: hindering of
the large phosphine results on one hand in the stabilization of
the metal-phosphinidene bond and, on the other hand, in the
enhancement of the elimination rate of the phosphine that
enables the coordination of reactants. The reactivity of (η6-Ar)-
(PCy3)Ru(PMes*) and of Cp2(PMe3)Zr(PMes*) arise, thus, from
the same facile dissociation of the stabilizing ligand. In the latter
case, the pronounced oxo- and halophilicity of zirconium4 has
been used elegantly to produce new sophisticated phosphorus-
based molecules from carbonyl or dichloride compounds.
Concerning (η6-Ar)(PCy3)Ru(PMes*), the functional group
tolerance of ruthenium50 could also be exploited to complement
the scope of these reactions and to open up new perspectives
for synthetic applications of these nucleophilic phosphinidene
species.
3
NMR (400.1 MHz): δ 1.05 (d, JHH ) 6.6 Hz, 6H, C1-CH-
(CH3)2); 1.31 (m, 12H, CcH2); 1.57 (s, 9H, Cp-C-(CH3)3); 1.74
(s, 18H, Co-C-(CH3)3); 1.76 (s, 3H, C4-CH3); 1.93 (m, 6H, CdH2);
2.11 (m, 12H, CbH2); 2.56 (m, 4H, C1-CH-(CH3)2 and CaH); 4.71
3
3
(AB, JHH ) 5.9 Hz, 2H, C3H); 4.79 (AB, JHH ) 5.9 Hz, 2H,
C2H); 7.56 (d, JHP ) 3.9 Hz, 2H, CmH). 13C{1H} NMR (100.6
4
MHz): δ 18.74 (C4-CH3); 24.42 (C1-CH-(CH3)2); 27.37 (Cd);
28.35 (d, 3JCP ) 9.2 Hz, Cc); 30.33 (Cb); 31.29 (C1-CH-(CH3)2);
31.95 (Cp-C-(CH3)3); 32.80 (Co-C-(CH3)3); 34.93 (Cp-C-
(CH3)3); 36.84 (Ca); 38.77 (Co-C-(CH3)3); 81.46 (C3); 86.07 (C2);
89.58 (C4); 103.53 (C1); 119.09 (Cm); 145.35 (Cp); 145.99 (Co);
176.52 (Ci determined using 2D NMR experiments). Anal. Calcd
for C46H76P2Ru: C, 69.75; H, 9.67. Found: C, 69.65; H, 9.47.
(η6-Benzene)(PCy3)Ru(PMes*) (2b). A similar procedure to that
described for 2a was used. (η6-Benzene)(PH2Mes*)RuCl2 (0.321
g; 0.61 mmol) and PCy3 (0.164 g; 0.59 mmol) gave 2b as a green
solid (0.187 g, 42%). Crystallization from pentane at -25 °C gave
green crystals suitable for X-ray analysis. Mp: 180 °C dec. 31P
2
NMR (81.0 MHz): δ 38.09 (d, JPP ) 7.6 Hz, PCy3); 819.06 (d,
2JPP ) 7.6 Hz, PMes*). H NMR (200.1 MHz): δ 1.31 (m, 12H,
Experimental Section
1
CcH2); 1.57 (s, 9H, Cp-C-(CH3)3); 1.69 (s, 18H, Co-C-(CH3)3);
1.83 (m, 12H, CbH2); 2.07 (m, 6H, CdH2); 2.58 (m, 3H, CaH); 4.69
(s, 6H, CHbenzene); 7.56 (s, 2H, CmH). 13C{1H} NMR (50.3 MHz):
δ 27.41 (Cd); 28.32 (d, 3JCP ) 10.2 Hz, Cc); 30.46 (Cb); 31.88 (Cp-
C-(CH3)3); 32.35 (Co-C-(CH3)3); 34.93 (Cp-C-(CH3)3); 36.26
(dd, JCP ) 19.4 Hz, JCP ) 5.5 Hz, Ca); 38.14 (Co-C-(CH3)3);
81.90 (Cbenzene); 119.69 (Cm); 145.69 (Cp); 145.95 (Co). Anal. Calcd
for C42H68P2Ru: C, 68.54; H, 9.31. Found: C, 67.89; H, 9.05.
General Considerations. All reactions were carried out under
argon atmosphere using standard Schlenk techniques. Solvents were
dried and distilled according to standard procedures and degassed
prior to use. All reagents were purchased from Aldrich and were
used without further purification. NMR spectra were recorded in
C6D6 on Bruker AC 200 or ARX 400 instruments. Infrared spectra
were recorded with a Perkin-Elmer 1600 FT spectrometer. Elemen-
tal analyses were done by the Centre de Microanalyses de l’Ecole
Nationale Supe´rieure de Chimie de Toulouse. 1H and 13C{1H} NMR
1
3
[(η6-p-Cymene)(PCy3)Ru(PHMes*)]BF4 (3aBF4). To a green
solution of 2a (0.135 g, 0.17 mmol) in toluene (5 mL) was added
0.18 mmol of HBF4 (54 wt % in Et2O). The solution turned
immediately to violet, and the mixture was stirred for 10 min at
room temperature. The volatiles were removed in Vacuo, leaving a
violet residue. Trituration with pentane afforded pure 3aBF4 as a
violet powder (0.131 g, 88%). Crystallization from toluene at -25
°C gave green crystals suitable for X-ray analysis. Mp: 117 °C.
1
assignments were confirmed by H COSY, HSQC (1H-13C), and
HMQC (1H-13C) experiments. (η6-p-Cymene)(PCy3)RuCl2, (η6-
benzene)(PCy3)RuCl2, (η6-p-cymene)(PPh3)RuCl2, (η6-p-cymene)-
[P(p-ClC6H4)3]RuCl2, (η6-p-cymene)[P(p-MeC6H4)3]RuCl2, (η6-p-
cymene)[P(p-MeOC6H4)3]RuCl2, (η6-p-cymene)[P(NC4H4)3]RuCl2,
(η6-p-cymene)[P(m-MeC6H4)3]RuCl2, and (η6-p-cymene)[P(o-
MeOC6H4)3]RuCl2 were prepared according to literature proce-
dures.51 Atom labeling used in the NMR assignments of 2-13 is
given below (for example 2a):
2
3
31P NMR (81.0 MHz): δ 45.39 (dd, JPP ) 83.9 Hz, JPH ) 18.9
Hz, PCy3); 173.94 (dd, 1JPH ) 335.7 Hz, 2JPP ) 83.9 Hz, PHMes*).
1H NMR (400.1 MHz): δ 1.07 (d, JHH ) 6.5 Hz, 6H, C1-CH-
3
(CH3)2); 1.36 (m, 12H, CcH2); 1.46 (s, 9H, Cp-C-(CH3)3); 1.51
(s, 18H, Co-C-(CH3)3); 1.76 (s, 3H, C4-CH3); 1.95 (m, 6H, CdH2);
2.25 (m, 12H, CbH2); 2.77 (m, 3H, CaH); 3.03 (m, 1H, C1-CH-
3
3
(CH3)2); 5.32 (AB, JHH ) 4.7 Hz, 2H, C3H); 5.79 (AB, JHH
)
1
4.7 Hz, 2H, C2H); 7.61 (s, 2H, CmH); 8.86 (dd, JHP ) 335.7 Hz,
3JHP ) 18.9 Hz, PHMes*). 13C{1H} NMR (100.6 MHz): δ 18.00
3
(C4-CH3); 23.74 (C1-CH-(CH3)2); 26.97 (Cd); 27.47 (d, JCP
)
9.2 Hz, Cc); 30.39 (Cb); 31.34 (Cp-C-(CH3)3); 31.51 (C1-CH-
(CH3)2); 32.70 (Co-C-(CH3)3); 33.71 (d, 1JCP ) 7.4 Hz, Ca); 35.46
(Cp-C-(CH3)3); 38.88 (Co-C-(CH3)3); 84.87 (C3); 89.45 (C2);
(η6-p-Cymene)(PCy3)Ru(PMes*) (2a). To a red slurry of (η6-
p-cymene)(PH2Mes*)RuCl2 (0.601 g; 1.03 mmol) and PCy3 (0.274
g; 0.98 mmol) in toluene (10 mL) was added DBU (0.29 mL; 1.97
mmol). The mixture was stirred for 1 h at room temperature to
afford a dark green solution. The toluene was removed in Vacuo
and the dark green solid then extracted with pentane (10 mL) and
filtered to remove DBU‚HCl. Removal of the pentane to a minimal
volume and cooling to -25 °C gave 0.780 g of a crystalline solid
in 80% yield. Mp: 168 °C dec. 31P NMR (81.0 MHz): δ 35.27 (d,
3
100.31 (C4); 113.03 (C1); 122.81 (d, JCP ) 8.3 Hz, Cm); 152.70
(Co); 153.00 (Cp); 166.03 (Ci). 19F NMR (188.3 MHz): δ -73.40
(s). 11B NMR (96.3 MHz): δ -0.12 (br s). Anal. Calcd for C46H77-
BF4P2Ru: C, 62.79; H, 8.82. Found: C, 62.31; H, 8.58.
[(η6-Benzene)(PCy3)Ru(PHMes*)]BF4 (3bBF4). A similar pro-
cedure to that described for 3aBF4 was used. 2b (0.125 g; 0.17
mmol) and HBF4 (0.18 mmol, 54 wt % in Et2O) gave 3bBF4 as a
violet solid (0.113 g, 81%). Mp: 126 °C. 31P NMR (81.0 MHz):
2
3
(48) Bouzbouz, S.; Simmons, R.; Cossy, J. Org. Lett. 2004, 6, 3465-
3467.
(49) Cornejo, A.; Fraile, J. M.; Garcia, J. I.; Gil, M. J.; Martinez-Merino,
V.; Mayoral, J. A.; Salvatella, L. Angew. Chem., Int. Ed. 2005, 44, 458-
461.
(50) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18-29.
(51) (a) Martin, M. A. J. Chem. Soc., Dalton Trans. 1974, 233-241.
(b) Bennett, M. A.; Matheson, T. W.; Robertson, T. W.; Smith, A. K.;
Tucker, P. A. Inorg. Chem. 1980, 1014-1021. (c) Zelonka, R. A.; Baird,
M. C. Can. J. Chem. 1972, 3063-3072. (d) Demonceau, A.; Stumpf, A.
W.; Saive, E.; Noels, A. F. Macromolecules 1997, 3127-3136.
δ 48.31 (dd, JPP ) 83.9 Hz, JPH ) 16.7 Hz, PCy3); 190.93 (dd,
1JPH ) 343.3 Hz, JPP ) 83.9 Hz, PHMes*). 1H NMR (300.1
2
MHz): δ 1.41 (m, 12H, CcH2); 1.44 (s, 9H, Cp-C-(CH3)3); 1.52
(s, 18H, Co-C-(CH3)3); 1.82 (m, 6H, CdH2); 2.02 (m, 12H, CbH2);
2.53 (m, 3H, CaH); 5.30 (s, 6H, CHbenzene); 7.53 (s, 2H, CmH); 9.00
1
3
(dd, JHP ) 343.3 Hz, JHP ) 16.7 Hz, 1H, PH). 13C{1H} NMR
3
(75.5 MHz): δ 26.56 (Cd); 27.25 (d, JCP ) 10.5 Hz, Cc); 30.10
(Cb); 31.41 (Cp-C-(CH3)3); 32.34 (Co-C-(CH3)3); 33.82 (d, 1JCP
) 7.2 Hz, Ca); 36.45 (Cp-C-(CH3)3); 38.27 (Co-C-(CH3)3); 87.06

Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms
Organometallics, Vol. 26, No. 20, 2007 5099
(Cbenzene); 122.27 (d, 3JCP ) 7.8 Hz, Cm); 152.39 (Co); 152.95 (Cp);
165.76 (Ci). 19F NMR (188.3 MHz): δ -71.90 (s). 11B NMR (96.3
MHz): δ -0.18 (br s). Anal. Calcd for C42H69BF4P2Ru: C, 61.23;
H, 8.44. Found: C, 60.99; H, 8.62.
[(η6-p-Cymene)(PCy3)Ru(PHMes*)]BPh3OH (3aBPh3OH). To
a green solution of 2a (0.244 g, 0.31 mmol) in toluene (10 mL)
was added 0.074 g of BPh3 (0.31 mmol). In the presence of water
(6 µL, 0.31 mmol), the solution turned slowly to violet, and the
mixture was stirred for 24 h at room temperature. The volatiles
were removed in Vacuo, leaving a violet residue. Trituration with
pentane afforded pure 3aBPh3OH as a violet powder (0.288 g,
(η6-Benzene)(PCy3)Ru[P(BH3)Mes*] (4b). A similar procedure
to that described for 4a was used. 2b (0.089 g, 0.11 mmol) and
BH3‚SMe2 (1.1 mmol, 2 M in toluene) gave 4b as an oily violet
residue (0.069 g, 83%). 31P NMR (81.0 MHz): δ 48.40 (d, 2JPP
)
2
1
68.7 Hz, PCy3); 521.06 (d, JPP ) 68.7 Hz, P(BH3)). H NMR
(200.1 MHz): δ 1.33 (m, 12H, CcH2); 1.47 (s, 9H, Cp-C-(CH3)3);
1.59 (m, 12H, CbH2); 1.71 (s, 18H, Co-C-(CH3)3); 1.99 (m, 6H,
CdH2); 2.56 (m, 3H, CaH); 4.64 (s, 6H, CHbenzene); 7.54 (s, 2H,
CmH). 13C{1H} NMR (75.5 MHz): δ 27.20 (Cd); 29.12 (br s, Cc);
29.80 (Cb); 30.22 (Cp-C-(CH3)3); 31.41 (Co-C-(CH3)3); 33.90
(br s, Ca); 37.01 (Cp-C-(CH3)3); 41.04 (Co-C-(CH3)3); 80.43
(Cbenzene); 118.26 (Cm); 144.53 (Cp); 146.05 (Co). 11B NMR (96.3
MHz): δ 18.29 (br s).
87%). Mp: 198 °C. 31P NMR (81.015 MHz): δ 45.15 (dd; 2JPP
)
3
1
83.9 Hz; JHP ) 19.0 Hz; PCy3); 186.32 (dd; JPH ) 341.1 Hz;
1
2JPP ) 83.9 Hz; PHMes*). H NMR (200.132 MHz): δ 1.00 (d;
[(η6-p-Cymene)(PCy3)Ru(PMeMes*)]I (5a). To a green solution
of 2a (0.658 g, 0.83 mmol) in toluene (10 mL) was added MeI
(0.052 mL, 0.83 mmol). The solution turned slowly to violet, and
the mixture was stirred for 1 h at room temperature. The volatiles
were removed in Vacuo. Trituration with pentane afforded pure 5a
as a violet powder (0.737 g, 95%). Mp: 160 °C. 31P NMR (81.0
MHz): δ 48.80 (d, 2JPP ) 82.1 Hz, PCy3); 240.38 (dq, 2JPP ) 82.1
Hz, 2JPH ) 9.7 Hz, PMeMes*). 1H NMR (200.1 MHz): δ 1.08 (d,
3JHH ) 6.7 Hz; 6H; C1-CH-(CH3)2); 1.26 (m; 12H; CcH2); 1.37
(s; 9H; Cp-C-(CH3)3); 148 (s; 18H; Co-C-(CH3)3); 1.70 (s; 3H;
C4-CH3); 1.83 (m; 6H; CdH2); 2.24 (m; 12H; CbH2); 2.74 (m; 4H;
CaH and C1-CH-(CH3)2); 4.81 (m; 4H; C2H and C3H); 6.98 (m;
9H; CbHPh and CdHPh); 7.44 (s; 2H; CmH); 7.71 (m; 6H; CcHPh);
1
3
9.00 (dd; JHP ) 341.1 Hz; JHP ) 19.0 Hz; 1H; PH). 13C{1H}
NMR (50.323 MHz): δ 18.19 (s; C4-CH3); 23.58 (s; C1-CH-
3
3
(CH3)2); 26.37 (s; Cd); 27.51 (d; JCP ) 11.1 Hz; Cc); 30.01 (s;
3JHH ) 6.9 Hz, 3H, C1-CH-CH3); 1.32 (d, JHH ) 6.9 Hz, 3H,
Cb); 30.94 (s; C1-CH-(CH3)2); 31.20 (s; Cp-C-(CH3)3); 32.64
C1-CH-CH3); 1.43 (s, 9H, Cp-C-(CH3)3); 1.46 (s, 9H, Co-C-
(CH3)3); 1.52 (s, 9H, Co-C-(CH3)3); 1.56 (s, 3H, C4-CH3); 1.86
1
(s; Co-C-(CH3)3); 34.22 (d; JCP ) 50.9 Hz; Ca); 35.28 (s; Cp-
2
C-(CH3)3); 38.70 (s; Co-C-(CH3)3); 83.76 (s; C3); 87.99 (s; C2);
(m, 12H, CcH2); 2.13 (d, JHP ) 9.7 Hz, 3H, P-CH3); 2.26 (m,
99.45 (d; 2JCP ) 3.4 Hz; C4); 112.66 (d; 2JCP ) 2.8 Hz; C1); 122.34
6H, CdH2); 2.56 (m, 12H, CbH2); 3.27 (m, 4H, CaH and C1-CH-
(CH3)2); 3.73 (s, 1H, C2H); 4.77 (s, 1H, C3H); 5.43 (s, 2H, C2H
and C3H); 7.54 (s, 1H, CmH); 7.65 (s, 1H, CmH). 13C{1H} NMR
(50.3 MHz): δ 18.60 (C4-CH3); 21.48 (C1-CH-(CH3)2); 26.31
3
(d; JCP ) 8.3 Hz; Cm); 127.25 (s; CbPh); 128.29 (s; CaPh); 131.96
(s; CdPh); 134.90 (s; CcPh); 152.40 (s; Co); 153.06 (s; Cp); 159.05
(s; Ci). 11B NMR (96.29 MHz): δ 1.43 (br s). Anal. Calcd for
C64H93BOP2Ru: C, 73.05; H, 8.91. Found: C, 73.26; H, 9.02.
3
(Cd); 27.65 (d, JCP ) 9.2 Hz, Cc); 30.25 (Cb); 30.58 (C1-CH-
[(η6-Benzene)(PCy3)Ru(PHMes*)]BPh3OH (3bBPh3OH). A
similar procedure to that described for 3aBPh3OH was used. 2b
(0.057 g, 0.08 mmol), BPh3 (0.019 g, 0.08 mmol), and H2O (2 µL,
0.08 mmol) gave 3bBPh3OH as a violet solid (0.063 g, 83%).
(CH3)2); 31.09 (Co-C-(CH3)3); 31.26 (Cp-C-(CH3)3); 32.41 (d,
1JCP ) 7.4 Hz, Ca); 34.64 (br s, P-CH3); 35.10 (Cp-C-(CH3)3);
2
39.67 (Co-C-(CH3)3); 79.54 (C3); 83.99 (C2); 100.97 (d, JCP
)
2
3
6.5 Hz, C4); 112.96 (d, JCP ) 5.6 Hz, C1); 123.56 (d, JCP ) 7.4
2
2
Mp: 167 °C. 31P NMR (81.015 MHz): δ 48.07 (d; JPP ) 83.9
Hz, Cm); 144.94 (d, JCP ) 13.9 Hz, Co); 149.36 (Cp); 152.16 (d,
2JCP ) 2.0 Hz, Co); 166.82 (Ci). Anal. Calcd for C47H79IP2Ru: C,
3
1
2
Hz; JHP ) 18.7 Hz; PCy3); 199.13 (dd; JPH ) 350.0 Hz; JPP
)
1
60.44; H, 8.53. Found: C, 59.95; H, 8.17.
83.9 Hz; PHMes*). H NMR (300.13 MHz): δ 1.27 (m; 12H;
CcH2); 1.38 (s; 9H; Cp-C-(CH3)3); 1.45 (s; 18H; Co-C-(CH3)3);
1.75 (m; 6H; CdH2); 2.21 (m; 12H; CbH2); 2.75 (m; 3H; CaH); 4.85
(s; 6H; CHbenzene); 7.02 (m; 9H; CbHPh et CdHPh); 7.42 (s; 2H; CmH);
[(η6-Benzene)(PCy3)Ru(PMeMes*)]I (5b). A similar procedure
to that described for 5a was used. 2b (0.610 g; 0.83 mmol) and
MeI (0.052 mL, 0.83 mmol) gave 5b as a violet solid (0.641 g,
1
3
2
7.94 (m; 6H; CcHPh); 8.99 (dd; JHP ) 350.0 Hz; JHP ) 18.7 Hz;
1H; PH). 13C{1H} NMR (75.468 MHz): δ 26.40 (s; Cd); 27.51 (d;
3JCP ) 11.2 Hz; Cc); 30.14 (s; Cb); 31.17 (s; Cp-C-(CH3)3); 32.45
88%). Mp: 144 °C. 31P NMR (81.0 MHz): δ 51.89 (d, JPP
)
2
2
76.3 Hz, PCy3); 248.19 (dd, JPH ) 10.2 Hz, JPP ) 76.3 Hz,
PMeMes*). 1H NMR (200.1 MHz): δ 1.36 (s, 9H, Cp-C-(CH3)3);
1
2
(s; Co-C-(CH3)3); 33.86 (d; JCP ) 48.5 Hz; Ca); 35.28 (s; Cp-
1.56 (s, 18H, Co-C-(CH3)3); 1.85 (m, 12H, CcH2); 2.21 (d, JHP
C-(CH3)3); 38.47 (s; Co-C-(CH3)3); 86.64 (s; Cbenzene); 122.51
) 10.2 Hz, 3H, P-CH3); 2.33 (m, 6H, CdH2); 3.14 (m, 12H, CbH2);
3
(d; JCP ) 8.8 Hz; Cm); 127.15 (s; CbPh); 128.28 (s; CaPh); 132.65
3.67 (m, 3H, CaH); 5.31 (s, 6H, CHbenzene); 7.51 (s, 2H, CmH). 13C-
3
(s; CdPh); 135.02 (s; CcPh); 152.32 (s; Co); 153.55 (s; Cp); 160.77
(s; Ci). 11B NMR (96.29 MHz): δ 1.52 (s). Anal. Calcd for C60H75-
BOP2Ru: C, 73.08; H, 7.67. Found: C, 73.14; H, 8.00.
{1H} NMR (50.3 MHz): δ 26.44 (Cd); 27.77 (d, JCP ) 10.2 Hz,
Cc); 30.36 (Cb); 31.11 (Cp-C-(CH3)3); 31.52 (Co-C-(CH3)3);
1
34.29 (br s, P-CH3); 34.75 (d, JCP ) 3.7 Hz, Ca); 35.17 (s, Cp-
2
(η6-p-Cymene)(PCy3)Ru[P(BH3)Mes*] (4a). To a green solution
of 2a (0.087 g, 0.11 mmol) in toluene (5 mL) was added an excess
of BH3‚SMe2 (1.1 mmol, 2 M in toluene). The solution turned
slowly to violet, and the mixture was stirred for 15 min at room
temperature. The volatiles were removed in Vacuo, and pure 4a
was obtained as an oily violet residue (0.080 g, 90%). 31P NMR
C-(CH3)3); 39.31 (s, Co-C-(CH3)3); 87.42 (d, JCP ) 3.7 Hz,
3
2
C
benzene); 123.52 (d, JCP ) 8.3 Hz, Cm); 146.12 (d, JCP ) 15.7
2
Hz, Co); 149.95 (Cp); 152.47 (d, JCP ) 2.0 Hz, Co); 166.56 (d,
1JCP ) 44.4 Hz, Ci). Anal. Calcd for C43H71IP2Ru: C, 58.83; H,
8.15. Found: C, 58.42; H, 8.07.
(η6-p-Cymene)Ru[η3-P(CHdCHSiMe3)Mes*] (6). To a green
solution of 2a (0.214 g, 0.27 mmol) in toluene (10 mL) was added
Me3SiCtCH (0.040 mL, 0.29 mmol). The solution turned to
orange, and the mixture was stirred for 1 h at room temperature.
The volatiles were removed in Vacuo. The residue was extracted
with pentane, filtered, and concentrated. Upon standing at -20 °C,
6 was obtained as a pure orange solid (0.156 g, 95%). Mp: 82 °C.
(81.0 MHz): δ 48.69 (d, 2JPP ) 68.7 Hz, PCy3); 506.27 (d, 2JPP
)
1
3
68.7 Hz, P(BH3)). H NMR (200.1 MHz): δ 1.05 (d, JHH ) 6.9
Hz, 6H, C1-CH-(CH3)2); 1.35 (m, 12H, CcH2); 1.46 (s, 9H, Cp-
C-(CH3)3); 1.54 (m, 12H, CbH2); 1.83 (s, 18H, Co-C-(CH3)3);
2.02 (s, 3H, C4-CH3); 2.16 (m, 6H, CdH2); 2.70 (m, 4H, CaH and
C1-CH-(CH3)2); 4.55 (m, 4H, C2H and C3H); 7.65 (s, 2H, CmH).
13C{1H} NMR (75.5 MHz): δ 19.23 (C4-CH3); 25.68 (C1-CH-
(CH3)2); 28.28 (Cd); 30.49 (br s; Cc); 30.77 (Cb); 31.09 (C1-CH-
(CH3)2); 31.45 (Cp-C-(CH3)3); 33.51 (Co-C-(CH3)3); 34.90 (Cp-
C-(CH3)3); 35.31 (br s; Ca); 40.11 (Co-C-(CH3)3); 81.01 (C3);
85.63 (C2); 89.12 (C4); 103.05 (C1); 119.25 (Cm); 144.85 (Cp);
145.51 (Co). 11B NMR (96.3 MHz): δ 18.33 (br s).
1
31P NMR (81.0 MHz): δ -2.76 (m). H NMR (400.1 MHz): δ
0.23 (s, 9H, Si(CH3)3); 1.17 (s, 3H, P-CH2-C-CH3); 1.25 (s, 3H,
P-CH2-C-CH3); 1.27 (br s, 2H, P-CH2); 1.32 (s, 9H, Cp-C-
(CH3)3); 1.36 (d, 3JHH ) 6.8 Hz, 3H, C1-CH-CH3); 1.38 (d, 3JHH
) 6.6 Hz, 3H, C1-CH-CH3); 1.79 (s, 9H, Co-C-(CH3)3); 2.10
3
(s, 3H, C4-CH3); 2.42 (d, JHH ) 7.4 Hz, 1H, P-CHdCH); 2.66

5100 Organometallics, Vol. 26, No. 20, 2007
Menye-Biyogo et al.
2
3
(dd, JHP ) 21.8 Hz, JHH ) 7.4 Hz, 1H, P-CHdCH); 3.44 (m,
(CH3)3); 1.63 (s, 18H, Co-C-(CH3)3); 1.77 (s, 3H, C4-CH3); 2.42
3
3
1H, C1-CH-(CH3)2); 4.28 (d, JHP ) 5.5 Hz, 1H, C2H); 5.01 (d,
(m, 1H, C1-CH-(CH3)2); 4.58 (AB, JHH ) 6.1 Hz, 2H, C3H);
3JHP ) 5.1 Hz, 1H, C3H); 5.09 (d, JHP ) 5.7 Hz, 1H, C2H); 5.79
3
4.61 (AB, 3JHH ) 6.1 Hz, 2H, C2H); 7.12 (br s, 9H, CbH and CdH);
7.54 (br s, 2H, CmH); 7.94 (m, 6H, CcH). 13C{1H} NMR (100.6
MHz): δ 18.94 (C4-CH3); 24.36 (C1-CH-(CH3)2); 30.79 (C1-
CH-(CH3)2); 31.95 (Cp-C-(CH3)3); 32.84 (d, 4JCP ) 6.4 Hz, Co-
C-(CH3)3); 34.91 (Cp-C-(CH3)3); 38.66 (Co-C-(CH3)3); 84.65
3
4
(d, JHP ) 5.5 Hz, 1H, C3H); 7.22 (d, JHH ) 1.8 Hz, 1H, CmH);
7.56 (dd, 4JHP ) 4.9 Hz, 4JHH ) 1.8 Hz, 1H, CmH). 13C{1H} NMR
(100.6 MHz): δ 0.34 (Si(CH3)3); 19.34 (C4-CH3); 25.83 (C1-
CH-CH3); 26.36 (C1-CH-CH3); 28.66 (P-CH2-C-CH3); 30.55
3
2
2
(d, JCP ) 9.3 Hz, P-CH2-C-CH3); 31.34 (C1-CH-(CH3)2);
(d, JCP ) 2.8 Hz, C2); 87.22 (d, JCP ) 2.8 Hz, C3); 91.47 (C4);
105.02 (C1); 119.39 (Cm); 127.73 (Cb); 129.14 (Cd); 135.30 (d, 3JCP
) 11.1 Hz, Cc); 139.64 (d, 1JCP ) 38.8 Hz, Ca); 145.67 (Cp); 145.85
(Co); 183.59 (Ci). Anal. Calcd for C46H58P2Ru: C, 71.38; H, 7.55.
Found: C, 71.48; H, 7.73.
31.51 (Cp-C-(CH3)3); 32.52 (Co-C-(CH3)3); 33.18 (P-CHd
1
CH); 34.50 (d, JCP ) 17.6 Hz, P-CH2); 35.15 (Cp-C-(CH3)3);
1
37.78 (d, JCP ) 10.2 Hz, P-CHdCH); 37.94 (Co-C-(CH3)3);
41.42 (d, 2JCP ) 6.5 Hz, Co-C-(CH3)2); 72.71 (d, 2JCP ) 9.3 Hz,
2
C2); 74.64 (C3); 81.35 (C3); 82.85 (C2); 99.02 (d, JCP ) 4.6 Hz,
(η6-p-Cymene)[P(p-ClC6H4)3]Ru(PMes*) (9). An NMR tube
was charged with 2a (0.022 g, 0.28 mmol) and P(p-ClC6H4)3 (0.010
g, 0.28 mmol) in C6D6 (0.5 mL). The tube was maintained at 45
°C and monitored by 1H NMR. Data for (η6-p-cymene)[P(p-
C4); 110.25 (C1); 118.25 (d, 3JCP ) 7.4 Hz, Cm); 121.95 (d, 3JCP
)
8.3 Hz, Cm); 126.05 (d, 1JCP ) 32.4 Hz, Ci); 153.13 (d, 4JCP ) 1.9
Hz, Cp); 153.77 (d, 2JCP ) 9.3 Hz, Co-C-(CH3)3); 159.73 (d, 2JCP
) 12.0 Hz, Co-C-(CH3)2). Anal. Calcd for C33H53PRuSi: C,
64.99; H, 8.76. Found: C, 64.78; H, 8.69.
2
ClC6H4)3]Ru(PMes*) (9). 31P NMR (81.0 MHz): δ 37.15 (d, JPP
) 45.8 Hz, P(p-ClC6H4)3); 843.17 (d, 2JPP ) 45.8 Hz, PMes*). 1H
Upon exposure to air, complex 6 is oxidized and converted into
the corresponding phosphine oxide. 31P NMR (81.0 MHz): δ 33.24
3
NMR (200.1 MHz): δ 0.86 (d, JHH ) 6.8 Hz, 6H, C1-CH-
(CH3)2); 1.51 (s, 9H, Cp-C-(CH3)3); 1.57 (s, 18H, Co-C-(CH3)3);
1.88 (s, 3H, C4-CH3); 2.32 (m, 1H, C1-CH-(CH3)2); 4.48 (AB,
2
1
(t, JHP ) 14.4 Hz). H NMR (400.1 MHz): δ 0.14 (s, 9H, Si-
(CH3)3); 1.34 (s, 9H, Cp-C-(CH3)3); 1.52 (s, 6H, P-CH2-C-
3
3JHH ) 6.4 Hz, 2H, C3H); 4.52 (AB, JHH ) 6.4 Hz, 2H, C2H);
2
CH3); 1.58 (s, 9H, Co-C-(CH3)3); 2.19 (d, JHP ) 14.4 Hz, 2H,
3
7.19 (d, JHP ) 7.4 Hz, 6H, CbH); 7.55 (s, 2H, CmH); 7.62 (br s,
P-CH2); 6.84 (dd, 3JHH ) 19.8 Hz, 2JHP ) 31.3 Hz, 1H, P-CHd
CH); 7.28-7.54 (m, 3H, CmH and P-CHdCH).
6H, CcH).
(η6-p-Cymene)[P(p-MeC6H4)3]Ru(PMes*) (10). An NMR tube
was charged with 2a (0.025 g, 0.32 mmol) and P(p-tolyl)3 (0.010
g, 0.32 mmol) in C6D6 (0.5 mL). The tube was maintained at 45
°C and monitored by 1H NMR. Data for (η6-p-cymene)[P(p-
MeC6H4)3]Ru(PMes*) (10). 31P NMR (81.0 MHz): δ 36.40 (d, 2JPP
(η6-p-Cymene)Ru[η3-P(CHdCHPh)Mes*] (7). A similar pro-
cedure to that described for 6 was used. 2a (0.412 g; 0.52 mmol)
and PhCtCH (0.059 mL, 0.54 mmol) gave 7 as a red-orange solid
(0.306 g, 96%). Mp: 192 °C. 31P NMR (81.0 MHz): δ -10.40
(m). 1H NMR (400.1 MHz): δ 1.28 (s, 3H, P-CH2-C-CH3); 1.37
(s, 3H, P-CH2-C-CH3); 1.42 (s, 9H, Cp-C-(CH3)3); 1.43 (d,
2
1
) 45.8 Hz, P(p-tolyl)3), 831.97 (d, JPP ) 45.8 Hz, PMes*). H
3
NMR (200.1 MHz): δ 0.98 (d, JHH ) 6.8 Hz, 6H, C1-CH-
3JHH ) 6.6 Hz, 3H, C1-CH-CH3); 1.44 (d, JHH ) 6.9 Hz, 3H;
3
(CH3)2); 1.56 (s, 9H, Cp-C-(CH3)3); 1.67 (s, 18H, Co-C-(CH3)3);
1.83 (s, 3H, C4-CH3); 2.10 (s, 9H, Cd-CH3); 2.57 (m, 1H, C1-
CH-(CH3)2); 4.62 (AB, 3JHH ) 6.6 Hz, 2H, C3H); 4.66 (AB, 3JHH
C1-CH-CH3); 1.46 (br s, 2H, P-CH2); 1.97 (s, 9H, Co-C-
(CH3)3); 2.14 (s, 3H, C4-CH3); 2.79 (m, 1H, C1-CH-(CH3)2);
2
3
3.03 (dd, JHP ) 15.4 Hz, JHH ) 5.4 Hz, 1H, P-CHdCH); 3.23
3
) 6.6 Hz, 2H, C2H); 7.06 (d, JHP ) 7.2 Hz, 6H, CbH); 7.55 (s,
(d, 3JHP ) 5.5 Hz, 1H, C3H); 3.26 (d, 3JHH ) 5.4 Hz, 1H, P-CHd
2H, CmH); 7.92 (br s, 6H, CcH).
3
3
CH); 4.90 (d, JHP ) 4.4 Hz, 1H, C2H); 5.21 (d, JHP ) 5.5 Hz,
3
(η6-p-Cymene)[P(p-MeOC6H4)3]Ru(PMes*) (11). An NMR
tube was charged with 2a (0.025 g, 0.32 mmol) and P(p-MeOC6H4)3
(0.011 g, 0.32 mmol) in C6D6 (0.5 mL). The tube was maintained
at 45 °C and monitored by 1H NMR. Data for (η6-p-cymene)[P(p-
MeOC6H4)3]Ru(PMes*) (11). 31P NMR (81.0 MHz): δ 34.51 (d,
1H, C3H); 5.42 (d, JHP ) 5.5 Hz, 1H, C2H); 7.24 (m, 2H, CcH);
4
7.46 (d, JHH ) 2.0 Hz, 1H, CmH); 7.48 (s, 3H, CbH and CdH);
7.86 (dd, 4JHP ) 4.9 Hz, 4JHH ) 2.0 Hz, 1H, CmH). 13C{1H} NMR
(100.6 MHz): δ 19.82 (C4-CH3); 25.55 (C1-CH-CH3); 26.09
3
(C1-CH-CH3); 29.20 (P-CH2-C-CH3); 30.37 (d, JCP ) 9.1
2
2JPP ) 45.8 Hz, P(p-MeOC6H4)3); 830.36 (d, JPP ) 45.8 Hz,
Hz, P-CH2-C-CH3); 31.44 (Cp-C-(CH3)3); 32.51 (C1-CH-
(CH3)2); 33.29 (Co-C-(CH3)3); 33.51 (P-CHdCH); 35.12 (Cp-
1
3
PMes*). H NMR (200.1 MHz): δ 0.98 (d, JHH ) 6.8 Hz, 6H,
C1-CH-(CH3)2); 1.55 (s, 9H, Cp-C-(CH3)3); 1.67 (s, 18H, Co-
C-(CH3)3); 1.84 (s, 3H, C4-CH3); 2.54 (m, 1H, C1-CH-(CH3)2);
3.30 (s, 9H, Cd-OCH3); 4.61 (AB, 3JHH ) 6.2 Hz, 2H, C3H); 4.69
(AB, 3JHH ) 6.2 Hz, 2H, C2H); 6.86 (d, 3JHP ) 7.8 Hz, 6H, CbH);
7.54 (s, 2H, CmH); 7.92 (br s, 6H, CcH).
1
1
C-(CH3)3); 35.67 (d, JCP ) 17.5 Hz, P-CH2); 37.13 (d, JCP
)
8.2 Hz, P-CHdCH); 37.99 (Co-C-(CH3)3); 41.73 (d, 2JCP ) 6.5
Hz, Co-C-(CH3)2); 76.68 (C2); 80.80 (d, 2JCP ) 5.3 Hz, C3); 81.50
2
2
(d, JCP ) 5.3 Hz, C3); 82.69 (C2); 98.06 (d, JCP ) 4.2 Hz, C4);
110.02 (C1); 118.25 (d, 3JCP ) 8.3 Hz, Cm); 122.11 (d, 3JCP ) 8.4
Hz, Cm); 122.98 (Cc); 125.97 (Cb); 128.31 (Cd); 152.09 (d, 2JCP
)
(η6-p-Cymene)[P(NC4H4)3]Ru(PMes*) (12). A similar proce-
dure to that described for 2a was used. (η6-p-Cymene)[P(NC4H4)3]-
RuCl2 (0.436 g; 0.72 mmol), Mes*PH2 (0.194 g; 0.70 mmol), and
2
16.2 Hz, Ca); 153.36 (Cp); 154.24 (d, JCP ) 9.6 Hz, Co-C-
2
(CH3)3); 160.46 (d, JCP ) 12.5 Hz, Co-C-(CH3)2). Anal. Calcd
for C36H49PRu: C, 70.44; H, 8.05. Found: C, 70.51; H, 8.09.
DBU (0.210 mL; 1.4 mmol) gave 12 as a green solid (0.412 g,
2
Upon exposure to air, complex 7 is oxidized and converted into
the corresponding phosphine oxide. 31P NMR (81.0 MHz): δ 32.46
(t, JHP ) 14.0 Hz). H NMR (400.1 MHz): δ 1.33 (s, 9H, Cp-
C-(CH3)3); 1.51 (s, 6H, P-CH2-C-CH3); 1.58 (s, 9H, Co-C-
(CH3)3); 2.23 (d, JHP ) 14.0 Hz, 2H, P-CH2); 6.84 (dd, JHH
20.2 Hz, JHP ) 30.8 Hz, 1H, P-CHdCH); 7.16-7.72 (m, 8H,
CmH and Ph and P-CHdCH).
80%). Mp: 131 °C. 31P NMR (81.0 MHz): δ 95.16 (d, JPP
)
15.3 Hz, P(NC4H4)3); 886.77 (d, 2JPP ) 15.3 Hz, PMes*). 1H NMR
(200.1 MHz): δ 0.83 (d, 3JHH ) 6.8 Hz, 3H, C1-CH-CH3); 1.16
(d, 3JHH ) 6.8 Hz, 3H, C1-CH-CH3); 1.30 (s, 3H, C4-CH3); 1.48
(s, 9H, Cp-C-(CH3)3); 1.56 (s, 18H, Co-C-(CH3)3); 2.64 (m,
2
1
2
3
)
2
3JHH ) 6.8 Hz, 1H, C1-CH-(CH3)2); 4.67 (AB, JHH ) 6.6 Hz,
3
3
2H, C3H); 4.79 (AB, JHH ) 6.6 Hz, 2H, C2H); 6.33 (br s, 6H,
4
(η6-p-Cymene)(PPh3)Ru(PMes*) (8). A similar procedure to that
described for 2a was used. (η6-p-Cymene)(PPh3)RuCl2 (0.102 g;
0.16 mmol), Mes*PH2 (0.042 g; 0.150 mmol), and DBU (0.041
mL; 0.29 mmol) gave 8 as a green solid (0.117 g, 94%). Mp: 120
°C dec. 31P NMR (81.0 MHz): δ 38.75 (d, 2JPP ) 45.8 Hz, PPh3);
835.36 (d, 2JPP ) 45.8 Hz, PMes*). 1H NMR (400.1 MHz): δ 0.93
CcH); 7.18 (br s, 6H, CbH); 7.54 (d, JHH ) 2.0 Hz, 2H, CmH).
13C{1H} NMR (50.3 MHz): δ 19.16 (C4-CH3); 24.12 (C1-CH-
CH3); 24.36 (C1-CH-CH3); 30.81 (C1-CH-(CH3)2); 31.53 (Cp-
C-(CH3)3); 31.82 (Co-C-(CH3)3); 34.87 (Cp-C-(CH3)3); 38.57
2
2
(Co-C-(CH3)3); 89.29 (d, JCP ) 4.6 Hz, C3); 91.56 (d, JCP
)
3
3.7 Hz, C2); 97.85 (C4); 110.69 (C1); 111.82 (d, JCP ) 5.6 Hz,
3
(d, JHH ) 6.6 Hz, 6H, C1-CH-(CH3)2); 1.54 (s, 9H, Cp-C-
Cc); 119.64 (Cm); 125.50 (d, 2JCP ) 8.3 Hz, Cb); 146.14 (Cp); 146.73

Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms
Organometallics, Vol. 26, No. 20, 2007 5101
1
(Co); 154.43 (d, JCP ) 7.4 Hz, Ci). Anal. Calcd for C40H55N3P2-
on F2.53 Very small crystals of poor quality are responsible for
insufficient reflections and the low quality of the structure analysis.
2a: C46H76P2Ru, M ) 792.08, monoclinic, P21/c, a ) 10.359(5)
Å, b ) 22.300(10) Å, c ) 19.612(8) Å, â ) 102.577(11)°, V )
4422(3) Å3, Z ) 4, T ) 193(2) K; 17 133 reflections (5318
independent, Rint ) 0.3085) were collected. Largest electron density
Ru: C, 64.84; H, 7.48. Found: C, 65.01; H, 7.52.
(η6-p-Cymene)[P(m-MeC6H4)3]Ru(PMes*) (13). A similar pro-
cedure to that described for 2a was used. (η6-p-Cymene)[P(m-
MeC6H4)3]RuCl2 (0.253 g; 0.37 mmol), Mes*PH2 (0.092 g; 0.33
mmol), and DBU (0.099 mL; 0.66 mmol) gave 13 as a green solid
(0.246 g, 92%). Mp: 137 °C. 31P NMR (81.0 MHz): δ 38.78 (d,
residue: 0.598 e Å-3, R1 (for I > 2σ(I)) ) 0.0909 and wR2 ) 0.2229
2
2JPP ) 45.8 Hz, P(m-tolyl)3); 832.77 (d, JPP ) 45.8 Hz, PMes*).
2
(all data) with R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) (∑w(Fo
-
2 2 0.5
Fc2)2/∑w(Fo ) )
1H NMR (400.1 MHz): δ 0.99 (d, JHH ) 6.8 Hz, 6H, C1-CH-
3
.
2b: C42H68P2Ru, M ) 735.97, triclinic, P1h, a ) 10.385(13) Å,
b ) 15.164(18) Å, c ) 15.641(19) Å, R ) 61.91(2)°, â ) 73.53(2)°,
γ ) 78.16(2)°, V ) 2076(4) Å3, Z ) 2, T ) 133(2) K; 5831
reflections (3286 independent, Rint ) 0.3049) were collected. Largest
electron density residue: 1.372 e Å-3, R1 (for I > 2σ(I)) ) 0.1005
and wR2 ) 0.2578 (all data).
(CH3)2); 1.55 (s, 9H, Cp-C-(CH3)3); 1.63 (s, 18H, Co-C-(CH3)3);
1.82 (s, 3H, C4-CH3); 2.15 (s, 9H, Cc-CH3); 2.59 (m, 1H, C1-
CH-(CH3)2); 4.59 (AB, 3JHH ) 6.4 Hz, 2H; C3H); 4.71 (AB, 3JHH
3
) 6.4 Hz, 2H, C2H); 6.97 (d, JHH ) 7.8 Hz, 3H, CdH); 7.10 (t,
3
3JHH ) 7.7 Hz, 3H, CeH); 7.52 (s, 2H, CmH); 7.71 (t, JHP ) 8.4
3
Hz, 3H, CfH); 7.97 (d, JHP ) 10.6 Hz, 3H, CbH). 13C{1H} NMR
3aBF4‚C7H8: C53H81BF4P2Ru, M ) 968.00, triclinic, P1h, a )
10.669(11) Å, b ) 13.778(13) Å, c ) 18.348(18) Å, R ) 90.85(2)°,
â ) 95.22(2)°, γ ) 99.50(2)°, V ) 2648(4) Å3, Z ) 2, T ) 173(2)
K; 9216 reflections (5434 independent, Rint ) 0.4753) were
collected. Largest electron density residue: 0.620 e Å-3, R1 (for I
> 2σ(I)) ) 0.1102 and wR2 ) 0.2964 (all data).
(100.6 MHz): δ 18.98 (C4-CH3); 21.68 (Cc-CH3); 24.40 (C1-
CH-CH3); 30.88 (C1-CH-(CH3)2); 31.97 (Cp-C-(CH3)3); 32.78
(Co-C-(CH3)3); 34.91 (Cp-C-(CH3)3); 38.71 (Co-C-(CH3)3);
2
2
84.62 (d, JCP ) 2.0 Hz, C3); 87.30 (d, JCP ) 2.0 Hz, C2); 91.03
3
(C4); 104.67 (C1); 119.22 (Cm); 127.60 (d, JCP ) 9.4 Hz, Ce);
129.92 (Cd); 132.10 (d, 2JCP ) 9.2 Hz, Cf); 136.34 (d, 2JCP ) 13.9
3
1
Hz, Cb); 137.04 (d, JCP ) 10.2 Hz, Cc); 139.67 (d, JCP ) 37.9
1
Hz, Ca); 145.50 (Cp); 145.85 (Co); 154.44 (d, JCP ) 6.5 Hz, Ci).
Acknowledgment. This work was supported by the “Min-
iste`re de la Jeunesse, de l’Education Nationale et de la
Recherche” and by the CNRS. R.M.B. is grateful to the
Gabonese government for a fellowship.
Anal. Calcd for C49H64P2Ru: C, 72.12; H, 7.91. Found: C, 71.98;
H, 7.83.
Kinetic Measurements for Phosphine Substitution Reactions.
NMR tubes (5 mm) were charged with appropriate amounts of
complexes and phosphines, and C6D6 was added to a total volume
of 0.5 mL. The tube was maintained at 45 °C and monitored by 1H
NMR.
X-ray Diffraction Structure Analysis. Data for all structures
presented in this paper were collected at low temperatures using
an oil-coated shock-cooled crystal on a Bruker-AXS CCD 1000
diffractometer with Mo KR radiation (λ ) 0.71073 Å). The
structures were solved by direct methods,52 and all non hydrogen
atoms were refined anisotropically using the least-squares method
Supporting Information Available: Kinetic modeling, Com-
plete crystallographic data for compounds 2a, 2b, and 3aBF4 (CIF
files). This material is available free of charge via the Internet at
http://pubs.acs.org.
OM7004854
(52) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.
(53) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; University of Go¨ttingen, 1997.