Synthesis, structure, reactivity, and electrochemical study of a (2,2′-biphosphinine)(η 5-pentamethylcyclo-pentadienyl)chlororuthenium(II) complex

Article abstract of DOI:10.1021/om960063j

[RuCp*(η⁴-C₆H₁₀)Cl] (Cp* = C₅Me₅; 1) reacts with the tmbp ligand (2; tmbp = 4,4′,5,5′-tetramethyl-2,2′-biphosphinine) in THF to afford the [RuCp*(tmbp)Cl] complex 3, which has also been characterized by a single-crystal X-ray diffraction study. Complex 3 crystallizes with one THF molecule. The environment about the Ru atom corresponds to that of a classical three-legged piano-stool structure. Reaction of 3 with LiBr and KCN in CH₂Cl₂/ MeOH afforded [RuCp*(tmbp)Br] (4) and [RuCp*(tmbp)CN] (5), respectively. 3 also reacts in CH₂C1₂, in the presence of NH₄PF₆, with various monodentate ligands to produce a series of stable cationic complexes of the type [RuCp*(tmbp) (L)]⁺[PF₆]^- (L = acetonitrile (6), pyridine (7), trimethyl phosphite (8), triphenylphosphine (9), 2-bromo-4,5-dimethylphosphinine (10), tert-butyl isocyanide (11), cis-cyclooctene (12), norbornene (13)). All complexes were obtained in good yields and have been characterized by a combination of elemental analyses and spectroscopic methods (IR and ³¹P, ¹H, and ¹³C NMR). The redox chemistry of 3 has been investigated by cyclic voltammetry in MeCN. Complex 3 is reversibly oxidized in [RuCp*^III(tmbp)Cl] at +0.49 V (vs SCE). The first irreversible monoelectronic reduction wave, which occurs at -1.82 V vs SCE, indicates the formation of the [Ru^ICp*(tmbp)] complex with the loss of Cl^-. The second reversible reduction wave at -2.24 V was assigned to the formation of the anionic [Ru⁰Cp*(tmbp)]^- complex, which is stable within the time scale of the cyclic voltammetry.

Full text of DOI:10.1021/om960063j

Organometallics 1996, 15, 3267-3274
3267
Syn th esis, Str u ctu r e, Rea ctivity, a n d Electr och em ica l
Stu d y of a (2,2′-Bip h osp h in in e)(η5-p en ta m eth ylcyclo-
p en ta d ien yl)ch lor or u th en iu m (II) Com p lex
Pascal Le Floch, Stephane Mansuy, Louis Ricard, and Franc¸ois Mathey*
Laboratoire “he´te´roe´le´ments et Coordination”, URA CNRS 1499, DCPH, Ecole Polytechnique,
91128 Palaiseau Cedex, France
Anny J utand and Christian Amatore*
De´partement de Chimie, URA CNRS 1679, Ecole Normale Supe´rieure, 24 rue Lhomond,
75231 Paris Cedex 05, France
Received J anuary 31, 1996X
[RuCp*(η4-C6H10)Cl] (Cp* ) C5Me5; 1) reacts with the tmbp ligand (2; tmbp ) 4,4′,5,5′-
tetramethyl-2,2′-biphosphinine) in THF to afford the [RuCp*(tmbp)Cl] complex 3, which has
also been characterized by a single-crystal X-ray diffraction study. Complex 3 crystallizes
with one THF molecule. The environment about the Ru atom corresponds to that of a
classical three-legged piano-stool structure. Reaction of 3 with LiBr and KCN in CH2Cl2/
MeOH afforded [RuCp*(tmbp)Br] (4) and [RuCp*(tmbp)CN] (5), respectively. 3 also reacts
in CH2Cl2, in the presence of NH4PF6, with various monodentate ligands to produce a series
of stable cationic complexes of the type [RuCp*(tmbp) (L)]+[PF6]- (L ) acetonitrile (6),
pyridine (7), trimethyl phosphite (8), triphenylphosphine (9), 2-bromo-4,5-dimethylphosphi-
nine (10), tert-butyl isocyanide (11), cis-cyclooctene (12), norbornene (13)). All complexes
were obtained in good yields and have been characterized by a combination of elemental
analyses and spectroscopic methods (IR and 31P, 1H, and 13C NMR). The redox chemistry of
3 has been investigated by cyclic voltammetry in MeCN. Complex 3 is reversibly oxidized
in [RuCp*III(tmbp)Cl] at +0.49 V (vs SCE). The first irreversible monoelectronic reduction
wave, which occurs at -1.82 V vs SCE, indicates the formation of the [RuICp*(tmbp)] complex
with the loss of Cl-. The second reversible reduction wave at -2.24 V was assigned to the
formation of the anionic [Ru0Cp*(tmbp)]- complex, which is stable within the time scale of
the cyclic voltammetry.
In tr od u ction
ligand is disrupted and the phosphinine nucleus be-
haves as a genuine cyclophosphahexatriene with a
highly reactive PdC double bond. The following ex-
ample of a Pt(II) complex is highly illustrative. In the
presence of traces of water, a selective addition of water
to the PdC6 double bond of the phosphinine ring trans
to the less electron donating ligand is observed4 (eq 2).
It is now well-established that the field of interest
of 2,2′-biphosphinines in coordination chemistry will
be markedly different from that of classical tertiary
diphosphines and 2,2′-bipyridines.1 Due to a suitable
balance between their poor σ-donor and their strong
π-accepting power, they act as powerful chelate li-
gands for the stabilization of electron-excessive metal
centers. Recently, we demonstrated that point in the
case of an electrochemically reduced (tmbp)2 Ni0
complex2a (tmbp ) 4,4′,5,5′-tetramethyl-2,2′-biphosphi-
nine)3 (eq 1).
This reactivity is not specific to biphosphinines, and
similar reactions have also been observed by Venanzi’s
On the other hand, their coordination chemistry
toward metallic centers having a positive oxidation state
(essentially +2) still remains unclear and from a previ-
ous report it appears that, in some cases, complexes are
less stable. Upon complexation, the aromaticity of the
(2) (a) Le Floch, P.; Ricard, L.; Mathey, F.; J utand, A.; Amatore, C.
Inorg. Chem. 1995, 34, 5070. (b) Several homoleptic complexes of
zerovalent metals having the parent phosphinine C5H5P as a ligand
have been synthesized; see: Elschenbroich, C.; Nowotny, M.; Behrendt,
A.; Massa, W.; Wocaldo, S. Angew. Chem., Int. Ed. Engl. 1992, 31, 1343.
Elschenbroich, C.; Nowotny, M.; Kroker, J .; Behrendt, A.; Massa, W.;
Wocaldo, S. J . Organomet. Chem. 1993, 459, 157. Elschenbroich, C.;
Nowotny, M.; Behrendt, A.; Harms, K.; Wocaldo, S.; Pebler, J . J . Am.
Chem. Soc. 1994, 116, 6217.
X Abstract published in Advance ACS Abstracts, J une 15, 1996.
(1) Mathey, F.; Le Floch, P. Chem. Ber., in press.
S0276-7333(96)00063-5 CCC: $12.00 © 1996 American Chemical Society
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3268 Organometallics, Vol. 15, No. 15, 1996
Le Floch et al.
group during their studies on the coordination chemistry
of the 2-(2-pyridyl)-4,5-dimethylphosphinine ligand
(NIPHOS) with Pt(II) and Pd(II) cationic centers.5
More convincing results have been obtained with Ru-
(II) centers, for which two biphosphinine complexes, cis-
[Ru(tmbp)(dmso)2Cl2] and cis-[Ru(tmbp)2Cl2], have been
characterized6 by us in 1992. Nevertheless, during a
preliminary investigation of their reactivity, we found
that the stability of their cationic derivatives was
dramatically dependent on the nature of the ancillary
ligands. The first series of experiments aiming to
synthesize biphosphinine analogs of the [Ru(bpy)3]2+
dication showed us that the stability of complexes
increased with the number of bipyridine ligands. In
that way, whereas the instability of the two dications
[Ru(tmbp)3]2+[BF4]-2 and [Ru(tmbp)2(bpy)]2+[BF4]-2 pre-
and the traditional ligand exchange with (η2-olefin)2 or
[RuCp*(η4-diene)Cl] complexes.11 All these methods
were attempted with the tmbp ligand 1. Surprisingly,
the reaction of 1 with the [RuCp*Cl2]n polymer/Zn
mixture in THF at room temperature did not proceed
cleanly and the expected Cp*Ru(tmbp)Cl complex 3 was
only formed in low yields (<30%) along with other
unidentified biphosphinine complexes. The reaction of
1 with the tetrameric [RuCp*(µ3-Cl)]4 in THF at 25 °C
afforded 3 in 60% yield. Finally, the best fit was
obtained using the precursor [RuCp*(η4-DMB)Cl]10d
(DMB ) 2,3-dimethyl-1,3-butadiene), which was pre-
pared directly from the [RuCp*Cl2]n polymer by a
reductive procedure (see Experimental Section). The
substitution of the diene was performed in THF at 35
°C and gave complex 3 in 85% yield (eq 3).
vented any characterizations, the [Ru(tmbp)(bpy)2]2+
-
[BF4]- complex was found to be rather stable.7
2
The different factors which govern the stability of
complexed biphosphinines have not been totally ratio-
nalized thus far; nevertheless, it is quite clear that the
electron density available at the metal center plays a
decisive role in providing (or not) sufficient π back-
donation within the π* delocalized system of the ligand.
To confirm this hypothesis, we decided to explore the
synthesis and the chemistry of very electron-rich cat-
ionic ruthenium(II) complexes and, quite logically, we
focussed our study on the RuCp* fragment, which is
probably the best prototype. Besides the theoretical
information provided by this study, we also found that
it might be of interest to appreciate to what extent the
Lewis acidic character of this electron-rich fragment can
be modulated by a strongly π accepting chelate ligand.
Indeed, the chemistry of [RuCp*L2X] complexes has
been essentially studied so far with good σ-donor
ligands. In this paper, we report the synthesis and an
electrochemical study of the [RuCp*(tmbp)Cl] complex,
as well as some studies on its reactivity.
Complex 3 was isolated as a red-brown powder, air
stable in the solid state for long periods, soluble in CH2-
Cl2 and acetone, moderately soluble in THF and alco-
hols, and insoluble in ether and petroleum ether. In
31P NMR, the complexation induces a strong downfield
shift (δ(CDCl3) 224.60 ppm for 3 vs δ(CDCl3) 178.32 ppm
for the free ligand 1). As expected, 3 presents a good
resistance toward hydrolysis and no reaction was ob-
served at the complexed PdC double bonds upon treat-
ment with water and alcohols in dichlromethane at 30
°C for hours. Fortunately, we were able to grow crystals
of 3 by cooling a THF/pentane (1:1) solution at -20 °C.
The molecular structure of 3 has been determined by
a single-crystal X-ray diffraction study. An ORTEP
view of the molecule is presented in Figure 1. Selected
bond distances and angles are given in Table 1. The
environment about the Ru atom corresponds to that of
a classical three-legged piano-stool structure. Interest-
ing structural features of this complex are the two Ru-P
bond distances. As expected for a strong π-acceptor
ligand, these two bonds (Ru-P1 ) 2.2475(7) Å and Ru-
P12 ) 2.2375(7) Å) are clearly short when compared to
those observed for classical tertiary phosphines, which
usually are in the range 2.30-2.35 Å in [RuCp*(R3P)2L]
neutral or cationic complexes.11,12 Besides, the distance
Resu lts a n d Discu ssion
(i) Syn th esis a n d Str u ctu r e of [Ru Cp *(tm bp )Cl].
Several approaches have been devised for the synthesis
of [RuCp*L2Cl] complexes (L ) phosphorus or nitrogen
2e- donor ligands). These include the reaction of L with
8
the [RuCp*Cl2]n polymer in the presence of a reducing
agent9 or with the tetrameric [RuCp*(µ3-Cl)]4 complex10
(3) (a) Le Floch, P.; Carmichael, D.; Ricard, L.; Mathey, F. J . Am.
Chem. Soc. 1991, 113, 667. (b) Le Floch, P.; Carmichael, D.; Ricard,
L.; Mathey, F.; J utand, A.; Amatore, C. Organometallics 1992, 11, 2475.
(c) Le Floch, P.; Ricard, L.; Mathey, F. Bull. Soc. Chim. Fr. 1994, 131,
330.
(4) Carmichael, D.; Le Floch, P.; Mathey, F. Phosphorus, Sulfur
Silicon Relat. Elem. 1993, 77, 255.
(5) Schmid, B.; Venanzi, L. M.; Gerfin, T.; Gramlich, V. Mathey, F.
Inorg. Chem. 1992, 31, 5117.
(6) Carmichael, D.; Le Floch, P.; Ricard, L.; Mathey, F. Inorg. Chim.
Acta 1992, 198-200, 437.
(7) Mansuy, S.; Le Floch, P.; Mathey, F. Unpublished results.
(8) (a) Tilley, T. D.; Grubbs, R. H.; Bercaw, J . E. Organometallics
1984, 3, 274. (b) Oshima, N.; Suzuki, H.; Moro-oka, Y. Chem. Lett. 1984,
1161.
(9) Chaudret, B.; J alon, F. A. J . Chem. Soc., Chem. Commun. 1988,
711.
(10) (a) Fagan, P. J .; Ward, M. D.; Caspar, J . V.; Calabrese, J . C.;
Krusic, P. J . J . Am. Chem. Soc. 1988, 110, 2981. (b) Fagan, P. J .; Ward,
M. D.; Calabrese, J . C. J . Am. Chem. Soc. 1989, 111, 1698. (c) Koelle,
U.; Kossakowski, J . J . Organomet. Chem. 1989, 362, 383. (d)
Fagan, P. J .; Mahoney, W. S.; Calabrese, J . C.; Williams, I. D.
Organometallics 1990, 9, 1843. (e) Luo, L.; Nolan, S. P. Organometallics
1994, 13, 4781.
(11) Luo, L.; Zhu, N.; Zhu, N.-J .; Stevens, E. D.; Nolan, S. P.; Fagan,
P. J . Organometallics 1994, 13, 669.
(12) See for example: (a) Lindner, E.; Haustein, M.; Fawzi, R.;
Steimann, M.; Wegner, P. Organometallics 1994, 13, 5021. (b) Le
Lagadec, R.; Roman, E.; Toupet, L.; Mu¨ller, U.; Dixneuf, P. H.
Organometallics 1994, 13, 5030. (c) Bruce, M. I.; Humphrey, M. G.;
Patrick, J . M.; White, A. H. Aust. J . Chem. 1983, 36, 2065.
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A Ruthenium(II) 2,2′-Biphosphinine Complex
Organometallics, Vol. 15, No. 15, 1996 3269
(ii) Rea ctivity of [(tm bp )Ru Cp *Cl] (3). In order
to appreciate the influence of the biphosphinine ligand
on the chemistry of the RuCp*Cl fragment, it seemed
worthwhile to explore in a first step the reactivity of
the Ru-Cl bond in 3 with regard to substitution
reactions. Owing to the good stability of 3 in alcohols,
we first investigated the metathesis of this bond with
KBr and KCN. These two reactions proceeded in a CH2-
Cl2/MeOH mixture at room temperature and gave
complexes 4 (X ) Br) and 5 (X ) CN) in good yields (eq
4). As we previously noted for 3, no side reactions
F igu r e 1. ORTEP drawing of one molecule of 3. Ellipsoids
are scaled to enclose 50% of the electron density. The
crystallographic labeling is arbitrary and different from the
numbering used for assignment of the 13C spectra.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 3a
Bond Lengths
Ru-Cl
Ru-P1
P1-C2
C2-C3
C3-C4
C4-C5
C5-C6
C6-P1
C6-C7
2.4538(7)
2.2475(7)
1.712(3)
1.408(4)
1.386(5)
1.392(4)
1.391(4)
1.740(3)
1.466(4)
Ru-Ct
1.852(3)
2.2375(7)
1.707(3)
1.397(4)
1.402(4)
1.400(4)
1.393(4)
1.730(3)
Ru-P12
P12-C11
C11-C10
C10-C9
C9-C8
(addition of MeOH) were observed at the complexed
PdC bonds of 4 and 5 during the reaction, thus
confirming their stability.
C8-C7
C7-P12
We also investigated the substitution of the Ru-Cl
bond with various monodentate ligands such as aceto-
nitrile, pyridine, phosphines (PPh3 and P(OMe)3), 2-bro-
mo-4,5-dimethylphosphinine, tert-butyl isocyanide, and
olefins (cis-cyclooctene and norbornene). All these reac-
tions were conducted in CH2Cl2 at room temperature
in the presence of NH4PF6 to facilitate the displacement
of the chlorine ligand. As does their precursor 3,
complexes 6-13, which were isolated in moderate to
good yields, show a good stability in solution and are
not moisture sensitive. All these results are sum-
marized in eq 5.
Bond Angles
78.45(3)
131.0
123.4(2)
123.0(3)
123.0(3)
125.4(3)
121.1(2)
104.1(1)
P1-Ru-P12
P1-Ru-Ct
P1-C2-C3
C2-C3-C4
C3-C4-C5
C4-C5-C6
C5-C6-P1
C6-P1-C2
Cl-Ru-Ct
120.1
130.5
P12-Ru-Ct
Cl-Ru-P1
Cl-Ru-P12
P1-C6-C7
Ru-P1-C6
Ru-P1-C2
C7-P12-C11
93.88(3)
89.77 (3)
113.1(2)
117.3(1)
138.7(1)
104.7(1)
a
Ct ) centroid of the Cp* ligand.
from the ruthenium atom to the Cp* plane (1.852(3) Å)
and the Ru-Cl bond length (2.4538(7) Å) appear quite
normal.12
Some additional interesting information is provided
by the intramolecular bond length and angle values
within the biphosphinine ligand. From these, it appears
that no dearomatization takes place in each ring, as
demonstrated, for example, by the good homogeneity of
the C-C double-bond lengths (between 1.386(5) and
1.408(4) Å; see Table 1). Additionally, as we previously
noted,2a the opening of the intracyclic CPC angle,
which can be correlated with the electron-accepting
character of the metallic fragment, is another important
piece of data which finely reflects the loss of aromaticity
in a complexed phosphinine. In complex 3 this value
(average of C2-P1-C6 and C7-P12-C11 104.4°) is
almost identical with that observed in the [Cr(tmbp)-
(CO)4] complex (104.3°),3a which is highly stable. For
comparison, in the less stable cis-[Ru(tmbp)(dmso)2Cl2]
complex,6 the opening of the CPC angle is 106.08°.
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3270 Organometallics, Vol. 15, No. 15, 1996
Le Floch et al.
F igu r e 2. Cyclic voltammetry of 3 (2 mM) in MeCN containing n-Bu4NBF4 (0.3 M) at a stationary gold-disk microelectrode
(0.5 mm diameter) and 20 °C. Scan rate: (a) 0.5 V s-1; (b) 2 V s-1; (c) 10 V s-1
.
Complexes 6-13, which have been isolated as crys-
talline solids, readily soluble in CH2Cl2, were succesfully
characterized by 31P, 1H, and 13C NMR spectroscopy and
elemental analysis in most cases. Additionally, complex
11 was also identified by IR spectroscopy (ν(NC) in CCl4
2143 cm-1),13 since the quaternary carbon of the iso-
cyanide ligand could not be detected in the 13C NMR
spectrum. For complexes 12 and 13, the η2 coordination
of the olefin is evidenced in 13C NMR by the strong shift
toward high field observed for the two olefinic carbon
atoms (δ (CD2Cl2) in ppm 74.80 in 12 and 67.95 in 13,
compared to 130.2 and 135.8 in the free ligands,
respectively).
Cl] complex (E1/2 ) 0.07 V vs SCE in CH2Cl2),15 thus
confirming that the ruthenium center is more electron
deficient in 3.
In view of the good ability of the biphosphinine ligand
to accept and delocalize electron density, we focused our
study on the electrochemical reduction of 3 to find out
whether low-valent ruthenium complexes could be vi-
able or not.
The cyclic voltammogram exhibited two reduction
peaks with different magnitudes (Figure 2a). The first
irreversible peak was observed at Ep ) -1.82 V vs
R1
SCE. The second one, of smaller magnitude, was
reversible and was observed at Ep ) -2.24 V.
A
R1
The formation of these two complexes is of particular
interest when we refer to the work on the very electron
rich [RuCp*(bpy)]+ fragment published by Balavoine et
al.14 During their investigation, they found that the
presence of the strong σ-donor bipyridine ligand strongly
disfavored the coordination of electron-rich olefins at the
Ru center, whereas complexes with olefins bearing
electron-withdrawing groups were found to be stable.
In contrast, with the [RuCp*(tmbp)]+ unit, whereas
complexes 12 and 13 were easily formed, derivatives
with methyl acrylate and diethyl maleate were too labile
to be isolated. This difference in the reactivty of the
two complexes, which cannot be rationalized in terms
of steric demand since the two ligands have nearly the
same geometry, nicely illustrates the increase of the
Lewis acidic character of the metal induced by the
coordination of the biphosphinine.
determination of the absolute number of electrons
involved in the first reduction peak16 at long time (0.2
s) revealed that two electrons were involved in the first
electrochemical process.
Increasing the scan rate resulted in a decay of the
first reduction peak current while the second one
increased (Figure 2b). At high scan rate (above 10 V
s-1), the magnitudes of the two peaks were found to
almost be similar (Figure 2c), indicating that the same
numbers of electrons were involved in the two successive
electrochemical processes. The first reduction peak
remained irreversible in the range of scan rate inves-
tigated here. Plotting the variation of the reduction
peak current of R1 as a function of the scan rate showed
that the initial two-electron transfer (taking place at
long time) evolved toward a one-electron transfer at
short time.17 Therefore, at high scan rate, two one-
electron transfers were observed that are consistent
with the mechanism given in eqs 7 and 8.
(iii) Electr och em ica l Stu d y of [Ru Cp *(tm bp )Cl]
(3). The cyclic voltammetry of 3 (2 mM) in MeCN
containing n-Bu4NBF4 (0.3 M) was performed at a
stationary gold-disk electrode with a scan rate of 0.2 V
s-1. First, to complete our comparison between biphos-
phinine and bipyridine complexes, we investigated the
oxidation of 3. A reversible oxidation peak, which is
assigned to the formation of the RuIII complex, was
observed at Ep ) +0.49 V vs SCE (eq 6).
O1
(13) Cotton, F. A.; Zingales, F. J . Chem. Soc. 1961, 351.
(14) Balavoine, G. G. A.; Boyer, T.; Livage, C. Organometallics 1992,
11, 456.
As expected, this value is shifted anodically with
respect to the oxidation potential of the [RuCp*(bpy)-
(15) Koelle, U.; Kossakowski, J . Inorg. Chim. Acta 1989, 164, 23.
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A Ruthenium(II) 2,2′-Biphosphinine Complex
Organometallics, Vol. 15, No. 15, 1996 3271
At low scan rate, wave R1 remained chemically
irreversible yet and the magnitude of the second peak
R2 was smaller than half the value of that of the first
one, indicating that the complex [RuICp*(tmbp)] was
involved in a chemical reaction during the time elapsed
between R1 and R2. This reaction provoked a decay of
the concentration of [RuICp*(tmbp)] in the diffusion
layer, and only the reduction of the [RuICp*(tmbp)]
which had not completely reacted was observed at R2.
This chemical reaction of [RuICp*(tmbp)], probably with
a RuII complex, affords a binuclear complex. The fact
than more than one electron was involved at long time,
in the first electrochemical step, suggests that the
binuclear complex is more easily reduced than [RuIICp*-
(tmbp)Cl]. To support the formation of this binuclear
complex, cyclic voltammetry was performed at different
scan rates on solutions of [RuIICp*(tmbp)Cl] of various
concentrations. Plotting the variation of the peak
current of R1 as a function of log(v/[RuIICp*(tmbp)Cl])
(Figure 3) resulted in a single curve, demonstrating that
the overall reaction order in ruthenium centers in the
chemical step was 2 and therefore that a reaction
between two ruthenium complexes took place with a
rate constant in the range of 104 M-1 s-1. The mecha-
nism given by eqs 9 and 10 can be tentatively proposed
to rationalize the formation of this RuII-RuI dimer and
its monoelectronic reduction.
F igu r e 3. Variation of I/C0v-1/2 (I ) reduction current of
R1; v ) scan rate; C0 ) [RuCp*(tmbp)Cl]) as a function of
log(v/C0).
efficient precursor for the synthesis of various cationic
complexes of the type [RuCp*(tmbp)L]+[PF6]-. As
expected, the strong π-accepting character of the bi-
phosphinine ligand increases the Lewis acid character
of the Ru+Cp* fragment which coordinates electron-rich
olefins, in contrast to its bipyridine counterpart. The
electrochemical behavior of complex 3 has also been
investigated. This study reveals that, upon reduction
with one electron, the Ru-Cl bond rapidly dissociates,
leading to a [RuICp*(tmbp)] complex which can be
reduced at a more negative potential to give the stable
anion [Ru0Cp*(tmbp)]-.
In conclusion, these preliminary encouraging results
demonstrate that the biphosphinine ligand might be
succesfully used to stabilize various oxidation states
with RuCp* complexes (from +3 to 0). Investigations
are underway in our laboratory to further extend this
chemistry to other electron-rich neutral and cationic
centers.
In conclusion, the irreversibilty of the first reduction
peak R1 at high scan rates, even when the bimolecular
reaction was not operating, means that a fast chemical
step takes place after the first electron transfer. This
observation is in good agreement with a fast cleavage
of the Ru-Cl bond (as proposed in eq 7) from the anion
radical complex [RuIICp*(tmbp)Cl]•- formed upon the
first electron transfer. On the other hand, the good
reversibility of the second reduction peak R2, even at
long time (at least over 2 s), demonstrates the stability
of the Cp*Ru0(tmbp) anion. Such anionic species are
not totally unprecedented. In 1990, Fagan et al. showed
that [RuCp*(η4-diene)] and [RuCp*(η2-C2H4)2]-[Li‚
DME]+ complexes could be isolated.10d
Exp er im en ta l Section
All reactions were routinely performed under an inert
atmosphere of either nitrogen or argon by using Schlenk
techniques and dry deoxygenated solvents. Dry THF, ether,
toluene, and hexane were obtained by distillation from Na/
benzophenone, dry CH2Cl2 was obtained by distillation from
P2O5, and dry MeCN and pyridine were obtained by distillation
over CaH2. Dry Celite was used for filtration. Nuclear
magnetic resonance spectra were obtained on a Bruker AC-
200 SY spectrometer operating at 200.13 MHz for 1H, 50.32
MHz for 13C, and 81.01 MHz for 31P. Chemical shifts are
expressed in parts per million downfield from external TMS
(1H and 13C) and 85% H3PO4 (31P), and coupling constants are
given in hertz. The following abreviations are used: s,
singulet; d, doublet; t, triplet; q, quadruplet; sept, septuplet;
m, multiplet; b, broad; v, virtual). Elemental analyses were
performed by the “Service d’analyse du CNRS”, at Gif-sur-
Yvette, France. [RuCp*Cl2]n was prepared according to ref 7b.
Preparation of [RuCp*(η4-C6H10)Cl] was carried out by modi-
fications of reported methods.18
Con clu sion
In this paper, we have shown that the stability of a
complexed biphosphinine on a Ru(II) center is clearly
dependent on the nature of the ancillary ligands. With
a powerful electron-releasing ligand such as C5Me5-, the
easily available chlorine complex [RuCp*(tmbp)Cl] (3)
shows a remarkable stability and can be used as an
P r ep a r a tion of [Ru Cp *(η4-C6H10)Cl] (2). Zinc powder
(6.0 g, 91.5 mmol) was added to a solution of [RuCp*Cl2]n (6.0
g, 19.55 mmol) and 2,3-dimethyl-1,3-butadiene (8.00 g, 97.60
(16) Amatore, C.; Azzabi, M.; Calas, P.; J utand, A.; Lefrou, C.; Rollin,
Y. J . Electroanal. Chem. Interfacial Electrochem. 1990, 288, 45.
(17) In Figure 3, the limit at high scan rate appears smaller than
half the value at low scan rates. This occurs because the wave R1 is
then partially controlled by the kinetics of the electron transfer, as
evidenced by its increasing half-width. See: Bard, A. J .; Faulkner, L.
R. Electrochemical Methods; Wiley: New York, 1980.
(18) (a) Masuda, K.; Nakano, K.; Fukahori, T.; Nagashima, H.; Itoh,
K. J . Organomet. Chem. 1992, 428, C21. (b) Masuda, K.; Ohkita, H.;
Kurumatani, S.; Itoh, K. Organometallics 1993, 12, 2221. (c) Bosch,
H. W.; Hund, H.-U.; Nietlispach, D.; Salzer, A. Organometallics 1992,
11, 2087.
+
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3272 Organometallics, Vol. 15, No. 15, 1996
Le Floch et al.
mmol) in 400 mL of dry toluene. The resulting solution was
then stirred at room temperature for 4 h. After the evapora-
tion of half of the solution, dry pentane (150 mL) was added
to facilitate the precipitation of ZnCl2 and the yellow solution
obtained was filtered under nitrogen. After evaporation of
solvents, complex 2 was obtained as a yellow powder which
can be used without further purification. Yield: 5.90 g (85%).
ΣJ (C-P) ) 70.70, C2 of tmbp). IR (CH2Cl2): 2112 cm-1 (CtN).
Complex 5 did not give satisfactory elemental analysis data.
P r ep a r a tion of [Ru Cp *(tm p b)(MeCN)][P F 6] (6). A 100
mL flask was charged with 30 mL of CH2Cl2, 0.24 g (1.5 mmol)
of NH4PF6, and 2 mL of MeCN. After 5 min of stirring, 0.52
g (1 mmol) of complex 3 was added and the resulting mixture
was stirred at room temperature. After 6 h, a 31P NMR control
indicated the end of the complexation. The CH2Cl2 and the
excess MeCN were then evaporated, leaving a brown solid
which was dissolved in CH2Cl2 (30 mL). The resulting solution
was then filtered under nitrogen (elimination of NH4Cl and
excess of NH4PF6) and the solvent was removed in vacuo,
yielding a yellow solid. Complex 6 was obtained as yellow
microcrystals after standing in a CH2Cl2/ether solution at -20
°C for 1 day. Yield: 0.57 g (85%).
31P NMR (CD2Cl2): δ 215.30 (P of tmbp), -144.40 (sept,
1J (P-F) ) 710.0, PF6). 1H NMR (CD2Cl2): δ 1.94 (t, 15H,
J (H-P) ) 2.90, Me of C5Me5), 2.13 (t, 3H, 5J (H-P) ) 1.50,
Me of CH3CN), 2.47 (d, 6H, 4J (H-P) ) 5.40, Me of tmbp), 2.54
(s, 6H, Me of tmbp), 8.27 (AA′XX′, 2H, ΣJ (H-P) ) 18.70, H3
or H6 of tmbp), 8.38 (AA′XX′, 2H, ΣJ (H-P) ) 24.90, H6 or H3
of tmbp). 13C NMR (CD2Cl2): δ 4.80 (s, Me of CH3CN), 11.50
(s, Me of C5Me5), 23.10 (s, Me of tmbp), 24.70 (AXX′, vt, ΣJ (C-
P) ) 4.60, Me of tmbp), 96.20 (s, Cq of C5Me5), 125.90 (s, CN
of CH3CN), 131.30 (AXX′, ΣJ (C-P) ) 33.70, C3 of tmbp), 136.30
(AXX′, ΣJ (C-P) ) 26.00, C4 or C5 of tmbp), 141.80 (AXX′,
ΣJ (C-P) ) 20.00, C6 of tmbp), 148.10 (AXX′, ΣJ (C-P) ) 26.10,
C4 or C5 of tmbp), 155.00 (AXX′, vt, ΣJ (C-P) ) 35.00, C2 of
tmbp). Anal. Calcd for C26H34F6NP3Ru: C, 46.70; H, 5.13.
Found: C, 46.33; H, 5.36.
P r ep a r a tion of [Ru Cp *(tm p b)(P y)][P F 6] (7). A 100 mL
flask was charged with 30 mL of CH2Cl2, 0.24 g (1.5 mmol) of
NH4PF6, and 0.30 mL (3.72 mmol) of pyridine. After 5 min of
stirring, 0.52 g (1 mmol) of complex 3 was added and the
resulting mixture was stirred at 40 °C. The complexation of
pyridine was checked by 31P NMR. After 1 h, the solvent and
excess pyridine were evaporated, yielding a viscous brown
resisdue which was washed three times with dry ether (20
mL). After each washing, the solution of ether was filtered
off and the brown powder obtained was collected. Dry CH2-
Cl2 (20 mL) was then added, and the resulting solution was
quickly filtered on Celite under nitrogen. The evaporation of
CH2Cl2 yielded complex 7 as an orange solid which can be
purified by crystallization in a CH2Cl2/ether mixture at -20
°C for 1 day. Yield: 0.53 g (75%).
P r ep a r a tion of [Ru Cp *(tm p b)Cl] (3). A 300-mL flask
was charged with 4.31 g (12.20 mmol) of complex 2 and 100
mL of THF. After 5 min of stirring, 3 g (12.20 mmol) of
biphosphinine 1 was added and the resulting solution was
heated at 35 °C for 2 h. After this period, a 31P NMR control
indicated the total disappearance of 1 and the formation of
complex 3. After cooling at room temperature, THF was
evaporated and the red powder obtained was triturated with
hexane (50 mL). The insoluble solid was then collected by
filtration, washed three times with hexane (100 mL), and dried
in vacuo. Complex 3 was recovered as a red-brown solid which
can be crystallized at -20 °C in a THF/hexane (2:1) mixture.
Yield: 5.36 g (85%).
31P NMR (CDCl3): δ 224.60. 1H NMR (CDCl3): δ 1.93 (t,
4
4
15H, J (H-P) ) 2.80, Me of C5Me5), 2.39 (d, 6H, J (H-P) )
4.60, Me of tmbp), 2.46 (s, 6H, Me of tmbp), 8.12 (AA′XX′, 2H,
ΣJ (H-P) ) 17.00, H3 or H6 of tmbp), 8.26 (AA′XX′, vd, 2H,
ΣJ (H-P) ) 24.00, H6 or H3 of tmbp). 13C NMR (CDCl3): δ
11.80 (s, Me of C5Me5), 23.10 (s, Me of tmbp), 24.80 (AXX′, vt,
ΣJ (C-P) ) 4.30, Me of tmbp), 94.70 (s, Cq of C5Me5), 130.40
(AXX′, ΣJ (C-P) ) 41.60, C3 of tmbp), 132.90 (AXX′, ΣJ (C-P)
) 38.20, C4 or C5 of tmbp), 139.90 (AXX′, ΣJ (C-P) ) 17.10,
C6 of tmbp), 146.10 (AXX′, ΣJ (C-P) ) 36.50, C4 or C5 of tmbp),
157.05 (AXX′, vt, ΣJ (C-P) ) 68.70, C2 of tmbp). Anal. Calcd
for C24H31ClP2Ru: C, 55.64; H, 6.03. Found: C, 56.39; H, 6.26.
P r ep a r a tion of [Ru Cp *(tm p b)Br ] (4). A 50 mL flask was
charged with 0.1 g (0.19 mmol) of complex 3, 5 mL of CH2Cl2,
and 5 mL of MeOH. After complete dissolution, 0.165 g of LiBr
(1.90 mmol) was added and the solution was stirred at room
temperature. The metathesis was monitored by 31P NMR.
After 5 h, the solvents were evaporated and the brown oil
obtained was partially dissolved in CH2Cl2 (10 mL). The
resulting solution was then filtered on celite under nitrogen.
The evaporation of the solvent yielded complex 4 as a brown-
red solid, which was crystallized in a THF/hexane mixture (1/
1). Yield: 0.085 g (80%).
31P NMR (CDCl3): δ 222.20. 1H NMR (CDCl3): δ 1.88 (t,
4
15H, J (H-P) ) 2.70, Me of C5Me5), 2.31-2.34 (m, 12H, 4 ×
31P NMR (CDCl3): δ 217.30 (P of tmbp), -145.10 (sept,
1J (P-F) ) 712.10, PF6). 1H NMR (CDCl3): δ 1.81 (t, 15H,
4J (H-P) ) 2.80, Me of C5Me5), 2.44 (d, 6H, J (H-P) ) 5.10,
Me of tmbp), 7.98 (AA′XX′, vt, 2H, ΣJ (H-P) ) 13.50, H3 or H6
of tmbp), 8.36 (AA′XX′, vt, 2H, ΣJ (H-P) ) 20.87, H6 or H3 of
tmbp). Anal. Calcd for C24H31BrP2Ru: C, 51.24; H, 5.55.
Found: C, 51.05; H, 5.68.
3
Me of tmbp), 2.58 (s, 6H, Me of tmbp), 7.20 (dd, 2H, J (H-H)
3
) 5.10 and 7.90, H3,5 of C5H5N), 7.57 (t, 1H, J (H-H) ) 7.90,
P r ep a r a tion of [Ru Cp *(tm p b)CN] (5). A 100 mL flask
was successively charged with 0.30 g (0.58 mmol) of complex
3, 20 mL of CH2Cl2, and 10 mL of MeOH. After complete
dissolution, 0.11 g (1.70 mmol) of KCN was added and the
reaction mixture was stirred at room temperature. After 3 h
H4 of C5H5N), 8.15 (AA′XX′, 2H, ΣJ (H-P) ) 18.20, H3 or H6 of
tmbp), 8.55 (d, 2H, 3J (H-H) ) 5.10, H2,6 of C5H5N), 8.56
(AA′XX′, 2H, ΣJ (H-P) ) 24.80, H6 or H3 of tmbp). 13C NMR
(CD2Cl2): δ 11.30 (s, Me of C5Me5), 23.00 (s, Me of tmbp), 24.70
(AXX′, vt, J (C-P) ) 4.50, Me of tmbp), 95.80 (s, Cq of C5Me5),
126.70 (s, C3 of C5H5N), 131.20 (AXX′, ΣJ (C-P) ) 33.90, C3 of
tmbp), 136.20 (AXX′, ΣJ (C-P) ) 30.50, C4 or C5 of tmbp),
138.50 (s, C4 of C5H5N), 141.20 (AXX′, ΣJ (C-P) ) 39.70, C6 of
tmbp), 148.40 (AXX′, ΣJ (C-P) ) 25.80, C4 or C5 of tmbp),
154.90 (AXX′, vt, ΣJ (C-P) ) 70.30, C2 of tmbp), 158.80 (t,
3J (C-P) ) 4.80, C2 of C5H5N). Anal. Calcd for C29H36F6NP3-
Ru: C, 49.29; H, 5.13. Found: C, 49.57; H, 4.89.
a
31P NMR control indicated the end of the reaction. The
solvents were evaporated, and the brown residue obtained was
partially dissolved in CH2Cl2 (40 mL). After filtration of the
resulting solution on Celite under nitrogen, the CH2Cl2 was
evaporated, yielding a brown-orange solid. After crystalliza-
tion in a CH2Cl2/hexane mixture at -20 °C, complex 5 was
isolated as a dark orange solid. Yield: 0.26 g (90%).
31P NMR (CDCl3): δ 220.27. 1H NMR (CDCl3): δ 2.09 (t,
15H, 4J (H-P) ) 2.42, Me of C5Me5), 2.44 (d, 6H, J (H-P) )
5.09, Me of tmbp), 2.51 (s, 6H, Me of tmbp), 8.10 (AA′XX′, 2H,
ΣJ (H-P) ) 3.0, H3 or H6 of tmbp), 8.26 (AA′XX′, s, 2H, H6 or
H3 of tmbp). 13C NMR (CDCl3): δ 12.05 (s, Me of C5Me5), 23.15
(s, Me of tmbp), 24.94 (d, J (C-P) ) 10.50, Me of tmbp), 97.80
(s, Cq of C5Me5), 128.70 (bs, CtN), 130.91 (AXX′, ΣJ (C-P) )
31.70, C3 of tmbp), 133.64 (AXX′, ΣJ (C-P) ) 24.30, C4 or C5
of tmbp), 140.05 (AXX′, ΣJ (C-P) ) 22.60, C6 of tmbp), 146.65
(AXX′, ΣJ (C-P) ) 18.40, C4 or C5 of tmbp), 152.75 (AXX′, vt,
P r ep a r a tion of [Ru Cp *(tm p b)(P (OMe)3)][P F 6] (8).
A
100 mL flask was charged with 30 mL of CH2Cl2, 0.24 g (1.5
mmol) of NH4PF6, and 0.25 mL of trimethyl phosphite. After
5 min of stirring, 0.52 g (1 mmol) of complex 3 was added and
the resulting mixture was stirred at room temperature. After
2 h, a 31P NMR control indicated the quantitative transforma-
tion of 3 into complex 8. The solvent was then evaporated,
and the resulting brown residue was triturated with dry ether
(20 mL). After filtration of the ether phase, the brown powder
obtained was dissolved in CH2Cl2 (30 mL) and then filtered
+
+

A Ruthenium(II) 2,2′-Biphosphinine Complex
Organometallics, Vol. 15, No. 15, 1996 3273
on Celite under nitrogen. After evaporation of CH2Cl2, com-
plex 8 was obtained as a yellow powder (0.66 g) which was
crystallized in a CH2Cl2/ether (1:1) mixture at -20 °C for 1
day. Complex 8 was then collected as yellow microcrystals
after filtration and drying. Yield: 0.60 g (80%).
) 20.70, H3 or H6 of tmbp), 8.59 (AA′XX′, 2H, ΣJ (H-P) ) 22.70,
H6 or H3 of tmbp). 13C NMR (CDCl3): δ 12.10 (s, Me of C5-
Me5), 22.20 (d, J (C-P) ) 3.50, Me of C7H8PBr), 23.20 (d, J (C-
P) ) 3.90, Me of tmbp), 23.70 (d, J (C-P) ) 10.70, Me of
C7H8PBr), 25.10 (d, J (C-P) ) 10.90, Me of tmbp), 99.80 (s,
Cq of C5Me5), 131.60 (AXX′, ΣJ (C-P) ) 30.40, C3 of tmbp),
136.40 (AXX′, ΣJ (C-P) ) 25.70, C4 or C5 of tmbp), 139.10 (d,
J (C-P) ) 24.50, C2 of C7H8PBr), 142.90 (AXX′, ΣJ (C-P) )
28.20, C6 of tmbp), 144.40 (m, ΣJ (C-P) ) 11.20, C3 of C7H8-
PBr), 148.70 (AXX′, ΣJ (C-P) ) 18.50, C4 or C5 of tmbp), 148.80
(m, ΣJ (C-P) ) 22.80, C4 or C5 of C7H8PBr), 152.60 (AXX′,
ΣJ (C-P) ) 23.20, C6 of C7H8PBr), 153.30 (AXX′, vt, ΣJ (C-P)
) 74.10, C2 of tmbp). Anal. Calcd for C31H39BrF6P4Ru: C,
44.83; H, 4.73. Found: C, 44.55; H, 5.13.
31P NMR (CDCl3): δ 217.90 (d, 2J (P-P) ) 72.10, P of tmbp),
144.40 (t, 2J (P-P) ) 72.10, P of P(OMe)3), -146.15 (sept, 1J (P-
4
F) ) 713.85, PF6). 1H NMR (CDCl3): δ 2.05 (t, 15H, J (H-P)
) 2.50, Me of C5Me5), 2.48 (d, 6H, J (H-P) ) 5.50, Me of tmbp),
3
2.57 (s, 6H, Me of tmbp), 3.37 (d, 9H, J (H-P) ) 12.20, Me of
P(OMe)3), 8.24 (AA′XX′, 2H, ΣJ (H-P) ) 18.50, H3 or H6 of
tmbp), 8.35 (AA′XX′, 2H, ΣJ (H-P) ) 20.90, H6 or H3 of tmbp).
13C NMR (CD2Cl2): δ 11.40 (s, Me of C5Me5), 23.00 (s, Me of
tmbp), 24.80 (d, J (C-P) ) 6.20, Me of tmbp), 53.40 (s, Me of
P(OMe)3), 99.70 (s, Cq of C5Me5), 131.80 (AXX′, ΣJ (C-P) )
31.60, C3 of tmbp), 136.00 (AXX′, ΣJ (C-P) ) 25.80, C4 or C5
of tmbp), 141.30 (AXX′, ΣJ (C-P) ) 29.80, C6 of tmbp), 148.50
(AXX′, ΣJ (C-P) ) 18.30, C4 or C5 of tmbp), 153.30 (AXX′, vt,
ΣJ (C-P) ) 75.30, C2 of tmbp). Anal. Calcd for C27H40F6O3P4-
Ru: C, 43.14; H, 5.36. Found: C, 43.21; H, 5.35.
P r ep a r a tion of [Ru Cp *(tm p b)(CNtBu )][P F 6] (11).
A
100 mL flask was charged with 30 mL of CH2Cl2, 0.24 g (1.5
mmol) of NH4PF6, and 0.52 g (1 mmol) of complex 3. After 5
min of stirring, 0.25 mL (1.92 mmol) of tert-butyl isocyanide
was added and the reaction mixture was stirred at room
temperature. After 30 min a control by 31P NMR indicated
the end of the reaction with quantitative formation of complex
11. The solvent was then evaporated, yielding an orange
viscous oil which was triturated and washed three times with
dry ether (20 mL). After each washing, the ether phase was
separated from the solid by filtration. Complex 11 was then
extracted with CH2Cl2 (30 mL) and filtered on Celite under
nitrogen. The evaporation of CH2Cl2 yielded 11 as a dark
green solid which can be crystallized in a CH2Cl2/ether (1:1)
mixture at -20 °C. Yield: 0.46 g (65%).
P r ep a r a tion of [Ru Cp *(tm p b)(P P h 3)][P F 6] (9). A 100
mL flask was charged with 30 mL of CH2Cl2, 0.24 g (1.5 mmol)
of NH4PF6, and 0.40 g (1.50 mmol) of triphenylphosphine. After
5 min of stirring, 0.52 g (1 mmol) of complex 3 was added and
the resulting mixture was stirred at room temperature. After
10 h, a 31P NMR control indicated the quantitative transfor-
mation of 3 into complex 9. After CH2Cl2 (20 mL) was added,
the solution was filtered under nitrogen and the solvent was
partially evaporated. Ether (30 mL) was then added to the
resulting solution (about 5 mL) to precipitate complex 9. After
filtration of the ether phase, 9 was partially dried under
vacuum and then washed with dry hexane (40 mL). After
elimination of hexane by filtration, the complex was recovered
as a yellow powder. Long yellow needles of 9 were isolated
after a crystallization with CH2Cl2/ether (1:1). Yield: 0.71 g
(80%).
31P NMR (CDCl3): δ 210.90 (P of tmbp), -146.05 (sept,
1J (P-F) ) 711.65, PF6). 1H NMR (CDCl3): δ 1.25 (s, 9H, Me
4
of C(CH3)3), 2.09 (t, 15H, J (H-P) ) 2.80, Me of C5Me5), 2.50
(d, 6H, J (H-P) ) 5.70, Me of tmbp), 2.57 (s, 6H, Me of tmbp),
8.31 (AA′XX′, 2H, ΣJ (H-P) ) 20.20, H3 or H6 of tmbp), 8.34
(AA′XX′, 2H, ΣJ (H-P) ) 23.40, H6 or H3 of tmbp). 13C NMR
(CDCl3): δ 11.70 (s, Me of C5Me5), 23.20 (s, Me of tmbp), 24.90
(d, J (C-P) ) 10.70, Me of tmbp), 31.30 (s, Me of C(CH3)3),
58.70 (s, Cq of C(CH3)3), 99.20 (s, Cq of C5Me5), 131.70 (AXX′,
ΣJ (C-P) ) 30.60, C3 of tmbp), 136.20 (AXX′, ΣJ (C-P) ) 25.60,
C4 or C5 of tmbp), 141.50 (AXX′, ΣJ (C-P) ) 24.70, C6 of tmbp),
148.30 (AXX′, ΣJ (C-P) ) 22.10, C4 or C5 of tmbp), 153.60
(AXX′, vt, ΣJ (C-P) ) 71.90, C2 of tmbp). IR (CCl4): 2143 cm-1
(CdN). Anal. Calcd for C29H40F6NP3Ru: C, 49.01; H, 5.67.
Found: C, 48.67; H, 5.78.
31P NMR (CDCl3): δ 226.20 (d, 2J (P-P) ) 51.65, P of tmbp),
2
1
46.95 (t, J (P-P) ) 51.65, P of PPh3), -143.96 (sept, J (P-F)
) 713.85, PF6). 1H NMR (CDCl3): δ 1.76 (t, 15H, J (H-P) )
4
2.50, Me of C5Me5), 2.35 (d, 6H, J (H-P) ) 5.70, Me of tmbp),
2.55 (s, 6H, Me of tmbp), 7.10-7.32 (m, 15H, C6H5), 7.79
(AA′XX′, 2H, ΣJ (H-P) ) 20.57, H3 or H6 of tmbp), 8.34
(AA′XX′, 2H, ΣJ (H-P) ) 22.97, H6 or H3 of tmbp). 13C NMR
(CD2Cl2): δ 11.65 (s, Me of C5Me5), 23.10 (s, Me of tmbp), 25.10
(AXX′, ΣJ (C-P) ) 11.0, Me of tmbp), 98.80 (s, Cq of C5Me5),
128.50-135.0 (m, C6H5 and 2 carbons of tmbp (C3 and C4 or
C5)), 140.24 (AXX′, ΣJ (C-P) ) 27.75, C6 of tmbp), 148.25
(AXX′, ΣJ (C-P) ) 20.20, C4 or C5 of tmbp), 153.20 (AXX′, vt,
ΣJ (C-P) ) 76.20, C2 of tmbp). Anal. Calcd for C42H46F6P4-
Ru: C, 56.69; H, 5.21. Found: C, 56.80; H, 5.50.
P r ep a r a tion of [Ru Cp *(tm p b)(C7H8Br P ][P F 6] (10). A
100 mL flask was charged with 30 mL of CH2Cl2, 3 mL of
methanol, 0.24 g (1.5 mmol) of NH4PF6, and 0.22 g (1.1 mmol)
of 2-bromo-4,5-dimethylphosphinine. After 5 min of stirring,
0.52 g (1 mmol) of complex 3 was added and the resulting
mixture was stirred at room temperature. After 4 h, a 31P
NMR control indicated the end of the reaction. The resulting
reaction mixture was then evaporated to dryness and the
brown viscous residue obtained was triturated and washed
three times with hexane (3 × 30 mL). The hexane phase which
contains excess 2-bromophosphinine was separated from the
solid by filtration under nitrogen. After drying, dry CH2Cl2
(20 mL) was added and the resulting solution was filtered on
Celite under nitrogen. Complex 10 was recovered as a yellow
powder after evaporation of CH2Cl2. Yield: 0.70 g (85%).
31P NMR (CDCl3): δ 208.80 (d, 2J (P-P) ) 66.80, P of tmbp),
184.40 (t, 2J (P-P) ) 66.80, P of C7H8PBr), -146.15 (sept,
1J (P-F) ) 713.85, PF6). 1H NMR (CDCl3): δ 2.08 (d, 15H,
4J (H-P) ) 2.50, Me of C5Me5), 2.17 (d, 3H, J (H-P) ) 6.40,
Me of C7H8PBr), 2.23 (s, 3H, Me of C7H8PBr), 2.45 (d, 6H, J (H-
P) ) 5.50, Me of tmbp), 2.59 (s, 6H, Me of tmbp), 7.81 (m, 2H,
ΣJ (H-P) ) 30.40, H of C7H8PBr), 8.24 (AA′XX′, 2H, ΣJ (H-P)
P r ep a r a tion of [Ru Cp *(tm p b)(η2-cis-C8H14)][P F 6] (12).
A 100 mL flask was charged with 30 mL of CH2Cl2, 0.24 g
(1.5 mmol) of NH4PF6, and 0.52 g (1 mmol) of complex 3. After
5 min of stirring, 1 mL (7.68 mmol) of cis-cyclooctene was
added and the reaction mixture was stirred at room temper-
ature. After 2 h, a control by 31P NMR indicated the end of
the complexation. The reaction mixture was then evaporated
to dryness, yielding a green powder which was washed three
times with dry hexane (20 mL) to remove traces of cyclooctene.
After each washing, the hexane phase was separated from the
solid by filtration under nitrogen. The resulting residue was
then dissolved in dry CH2Cl2 (20 mL) and filtered on Celite
under nitrogen. After evaporation of CH2Cl2, complex 12 was
recovered as a dark green powder which can be crystallized
in a CH2Cl2/ether (1:1) mixture at room temperature. Yield:
0.37 g (50%).
31P NMR (CD2Cl2): δ 232.70 (P of tmbp), -143.25 (sevt,
1J (P-F) ) 712.85, PF6). 1H NMR (CD2Cl2): δ 1.2-1.5 (m, 12H,
CH2 of C8H14), 1.76 (t, 15H, 4J (H-P) ) 2.70, Me of C5Me5),
2.42 (d, 6H, J (H-P) ) 5.00, Me of tmbp), 2.50 (s, 6H, Me of
tmbp), 3.04 (d, 2H, 3J (H-H) ) 10.10, CH of C8H14), 8.21
(AA′XX′, m, 4H, H3 and H6 of tmbp). 13C NMR (CD2Cl2): δ
10.80 (s, Me of C5Me5), 23.30 (s, Me of tmbp), 25.20 (AXX′, vt,
ΣJ (C-P) ) 5.40, Me of tmbp), 26.40, 32.80, 33.50 (s, CH2 of
C8H14), 74.80 (s, dCH of C8H14), 99.00 (s, Cq of C5Me5), 131.40
(AXX′, ΣJ (C-P) ) 48.10, C3 of tmbp), 136.60 (AXX′, ΣJ (C-P)
) 23.30, C4 or C5 of tmbp), 140.20 (AXX′, ΣJ (C-P) ) 26.50,
C6 of tmbp), 149.10 (AXX′, ΣJ (C-P) ) 13.90, C4 or C5 of tmbp),
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3274 Organometallics, Vol. 15, No. 15, 1996
Le Floch et al.
152.00 (AXX′, vt, ΣJ (C-P) ) 76.30, C2 of tmbp). Complex 12
instrument. The voltammograms were recorded with a Nicolet
3091 digital oscilloscope and the measurements performed on
the stored curves. The cyclic voltammetric measurements
were performed on 2 mM solutions of the complex. The
absolute number of electrons was determined by a combination
of chronoamperometry and cyclic voltammetry on a stationary
gold-disk ultramicroelectrode (0.25 µm), with ferrocene as
reference, according to a published procedure.16
did not give satisfactory elemental analysis data.
P r ep a r a tion of [Ru Cp *(tm p b)(η2-C7H10)][P F 6] (13). The
experimental procedure is identical with that used for the
preparation of complex 12. The reaction occurs under the
same conditions and requires 2 h of stirring at room temper-
ature. From 0.24 g (1.5 mmol) of NH4PF6, 0.52 g (1 mmol) of
complex 3, and 0.19 g (2 mmol) of norbornene, complex 13 was
isolated as a dark green solid after crystallization in a CH2-
Cl2/ether mixture (1:1) at -20 °C. Yield: 0.50 g (70%).
X-r a y Str u ctu r e Deter m in a tion for 3. Crystals of 3,
C
28H39ClOP2Ru, were grown from a THF/pentane solution of
the compound. Data were collected at -150 ( 0.5 °C on an
Enraf-Nonius CAD4 diffractometer using Mo KR radiation (λ
) 0.710 73 Å) and a graphite monochromator. The crystal
structure was solved and refined using the Enraf-Nonius
MOLEN package. The compound crystallizes in space group
P21/n (No. 14), with a ) 11.493(1) Å, b ) 14.238(1) Å, c )
31P NMR (CD2Cl2): δ 234.90 (P of tmbp), -144.35 (sept,
1J (P-F) ) 708.70, PF6). 1H NMR (CD2Cl2): δ 1.03-2.30 (m,
23H, Me of C5Me5, 2 × CH and 2 × CH2 of C7H10), 2.48 (d, 6H,
J (H-P) ) 4.90, Me of tmbp), 2.57 (bs, 6H, Me of tmbp), 2.97
(bs, 2H, CH of C7H10), 8.28 (AA′XX′, 2H, ΣJ (H-P) ) 16.70, H2
or H6 of tmbp), 8.40 (AA′XX′, 2H, ΣJ (H-P) ) 19.50, H6 or H2
of tmbp). 13C NMR (CD2Cl2): δ 10.15 (s, Me of C5Me5), 22.60
(s, Me of tmbp), 24.55 (s, Me of tmbp), 27.85 (s, CH2 of C7H10),
35.0 (s, CH of C7H10), 42.35 (s, bridging CH2 of C7H10), 67.95
(s, dCH of C7H10), 99.55 (Cq of C5Me5), 131.85 (AXX′, ΣJ (C-
P) ) 48.82, C3 of tmbp), 136.45 (AXX′, C4 or C5 of tmbp), 140.10
(AXX′, ΣJ (C-P) ) 27.46, C6), 148.55 (AXX′, ΣJ (C-P) ) 37.80,
C5 or C4), 151.20 (AXX′, vt, ΣJ (C-P) ) 76.30, C2); Anal. Calcd
for C31H41F6P3Ru: C, 51.59; H, 5.73. Found: C, 51.38; H, 5.85.
16.605(2) Å, â ) 92.56(6)°, V ) 2714.52(77) Å3, Z ) 4, dcalc
)
1.444 g/cm3, µ ) 8.0 cm-1, and F(000) ) 1224. A total of 8561
unique reflections were recorded in the range 2° e 2θ e 60.0°,
2916 of which were considered as unobserved (F2 < 3.0σ(F2)),
leaving 5644 for solution and refinement. Direct methods
yielded a solution for most atoms. The hydrogen atoms were
included as fixed contributions in the final stages of least-
squares refinement while using anisotropic temperature fac-
tors for all other atoms. A non-Poisson weighting scheme was
applied with a p factor equal to 0.08. The final agreement
factors were R ) 0.038, Rw ) 0.060, and GOF ) 1.20.
Electr och em ica l Stu d y of 3. Transient cyclic voltamme-
try was performed in a ca. 12 mL three-electrode airtight cell
connected to a Schlenk line. The working electrode consisted
of a gold disk of 0.5 or 0.125 mm diameter made from a cross
section of a gold wire (Goodfellow) sealed in glass. The
reference electrode was an SCE (Tacussel), separated from the
solution by a bridge (3 mL) filled with a 0.3 M solution of n-Bu4-
NBF4 in MeCN identical with that used in the cell. The
counter electrode was a platinum spiral of ca. 1 cm2 apparent
surface located within 5 mm of the working electrode and
facing it. A home-built potentiostat equipped with positive
feedback for ohmic-drop compensation19 was used. The po-
tential wave form signal generator was a Tacusssel GSTP4
Su p p or tin g In for m a tion Ava ila ble: Text giving details
of the X-ray structure determination for 3 and tables of
crystal data, positional parameters, bond distances and angles
for all non-hydrogen atoms, and âij values (6 pages). Ordering
information is given on any current masthead page.
OM960063J
(19) Amatore, C.; Lefrou, C.; Pflu¨ger, F. J . Electroanal. Chem.
Interfacial Electrochem. 1988, 270, 43.
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