Co-ordinative properties of a hybrid phosphine-bipyridine ligand

Article abstract of DOI:10.1039/a702463k

6-(2-Diphenylphosphinoethyl)-2,2′-bipyridine, L, has been prepared in three steps from 6-methyl-2,2′-bipyridine: (i) metallation followed by reaction with paraformaldehyde; (ii) bromination with HBr-MeCO₂H; (iii) phosphination using Li(PPh₂). Reaction of L with [{RuCl₂(CO)₂}_n] in NEt₃-MeOH gave a mixture of trans-Cl₂-[RuCl₂L(CO)] 1 and cis-Cl₂-[RuCl₂L(CO)] 2, the L ligand displaying in both complexes a meridional tridentate binding mode. This behaviour was confirmed, in the case of 1, by an X-ray structural study. Electrochemical oxidation of 1 and 2 is reversible and occurs at E_1/2= 0.80 V and 1.04 V vs. Ag-Ag⁺ (0.01 M), respectively. The cyclic voltammogram of 1 shows one irreversible system at E_pc = -1.71 V and two reversible systems at E_1/2 = -1.86 and -1.91 V. In the presence of CO₂ the latter redox system exhibits a pronounced electrocatalytic current, resulting in the formation of carbon monoxide. Reaction of L with [{RuCl₂(CO)₂}_n] in the presence of small amounts of H⁺ afforded the monodentate L complex cis-Cl₂-trans-P,P-cis-(CO)₂-[RuCl₂L ₂(CO)₂] 3 (yield 80%). Copper(I)-induced assembly of two molecules of 3 results in the selective and quantitative formation of a 36-membered metallomacrocycle 4. This complex exhibits a quasi-reversible oxidation at E_1/2 = 0.29 V and an electrodeposition-redissolution redox system at E_pc = -0.21 and E_pa = -0.10 V due to formation of Cu⁰ on the electrode surface. Reaction of L with [{RhCl(C₂H₄)₂}₂] led to the (chloromethyl)-rhodium(III) complex [RhCl₂(CH₂Cl)L] 5 (90%). Treatment of 5 in ethanol in the presence of silver(I) resulted in the formation of [RhCl₂(CH₂OEt)L] 6 (63% yield), where the meridional arrangement of the phosphine was maintained.

Full text of DOI:10.1039/a702463k

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Co-ordinative properties of a hybrid phosphine–bipyridine ligand
Raymond Ziessel,*,a Loïc Toupet,b Sylvie Chardon-Noblat,c Alain Deronzierc and
Dominique Matt*,d
a Laboratoire de Chimie, d’Electronique et de Photonique Moléculaires,
Ecole Européenne de Chimie, Polymères, Matériaux (ECPM), Université Louis Pasteur,
1 rue Blaise Pascal, F-67008 Strasbourg Cedex, France
b Groupe Matière Condensée et Matériaux, Université de Rennes 1, Bât. 11B, Campus Beaulieu,
F-35042 Rennes Cedex, France
c Laboratoire d’Electrochimie Organique et de Photochimie Rédox,
Université Joseph Fourier Grenoble 1, BP 53, F-38041 Grenoble Cedex 9, France
d Groupe de Chimie Inorganique Moléculaire, Université Louis Pasteur, 1 rue Blaise Pascal,
F-67008 Strasbourg Cedex, France
6-(2-Diphenylphosphinoethyl)-2,2Ј-bipyridine, L, has been prepared in three steps from 6-methyl-2,2Ј-bipyridine:
(i) metallation followed by reaction with paraformaldehyde; (ii) bromination with HBr–MeCO2H;
(iii) phosphination using Li(PPh2). Reaction of L with [{RuCl2(CO)2}n] in NEt3–MeOH gave a mixture of
trans-Cl2-[RuCl2L(CO)] 1 and cis-Cl2-[RuCl2L(CO)] 2, the L ligand displaying in both complexes a meridional
tridentate binding mode. This behaviour was confirmed, in the case of 1, by an X-ray structural study.
ϩ
₁
Electrochemical oxidation of 1 and 2 is reversible and occurs at E = 0.80 V and 1.04 V vs. Ag–Ag (0.01 ),
₂
respectively. The cyclic voltammogram of 1 shows one irreversible system at Epc = Ϫ1.71 V and two reversible
₁
systems at E = Ϫ1.86 and Ϫ1.91 V. In the presence of CO2 the latter redox system exhibits a pronounced
₂
electrocatalytic current, resulting in the formation of carbon monoxide. Reaction of L with [{RuCl2(CO)2}n] in
the presence of small amounts of Hϩ afforded the monodentate L complex cis-Cl2-trans-P,P-cis-(CO)2-
[RuCl2L2(CO)2] 3 (yield 80%). Copper()-induced assembly of two molecules of 3 results in the selective and
quantitative formation of a 36-membered metallomacrocycle 4. This complex exhibits a quasi-reversible oxidation
₁
at E = 0.29 V and an electrodeposition–redissolution redox system at Epc = Ϫ0.21 and Epa = Ϫ0.10 V due to
₂
formation of Cu0 on the electrode surface. Reaction of L with [{RhCl(C2H4)2}2] led to the (chloromethyl)-
rhodium() complex [RhCl2(CH2Cl)L] 5 (90%). Treatment of 5 in ethanol in the presence of silver()
resulted in the formation of [RhCl2(CH2OEt)L] 6 (63% yield), where the meridional arrangement of the
phosphine was maintained.
The co-ordination chemistry of difunctional ligands containing
both PIII and a N-donor is currently a topic of great interest.1
One important feature of such hybrid ligands is their ability to
form non-symmetric chelate complexes. Owing to the distinct
electronic properties of the soft phosphorus and hard nitrogen
centres it might be anticipated that structures containing such
chelating ligands allow precise control of the co-ordination
sphere during a catalytic cycle, and, in particular, facilitate the
positioning and orientation of entering mono- or di-functional
substrates (trans to P or N). One may also take advantage of the
hemilabile behaviour of some P,N ligands in certain chelate
complexes, i.e. their ability to generate by labilisation of the N-
bonded fragment a free co-ordination site.2
OH
Br
PPh2
N
N
N
N
(iii )
79%
(i )
(ii )
80%
30%
N
N
N
N
L
Scheme 1 Synthesis of L. (i) LiNPri2, Ϫ78 ЊC, tetrahydrofuran (thf),
anhydrous paraformaldehyde; (ii) HBr (33%)–MeCO2H; (iii) Li(PPh2),
Ϫ78 ЊC, thf
Whereas most studies on P,N-ligands have been concerned
with phosphino-substituted pyridines, relatively little attention
has been paid to oligopyridylphosphines, notably to bipyridyl-
phosphines.3 The latter combine the co-ordination properties
of a remarkable chelator, the bipy unit, with that of a trivalent
phosphorus atom. In a preliminary account we have briefly
described the synthesis of 6-(2-diphenylphosphinoethyl)-
2,2Ј-bipyridine, L, and shown that it may display either P-
monodentate behaviour a towards transition-metal ions or act
as a bridging ligand b between two metal centres.4 Mode a was
exploited for the construction of highly organised architectures
generated by assembling bipyridine units belonging to distinct
metal complexes.
N
N
N
N
P
P
N
N
P
M
N
N
M′
M
M
a
b
c
Ph2P
L
Results and Discussion
Ligand synthesis
The P,N,N ligand L has been obtained as a white solid in three
steps from 6-methyl-2,2Ј-bipyridine5 as sketched in Scheme 1.
Lithiation of 6-methyl-2,2Ј-bipyridine with lithium diisoprop-
ylamide, at low temperature, was followed by reaction with
anhydrous paraformaldehyde. After work-up the primary
alcohol 6-(2-hydroxyethyl)-2,2Ј-bipyridine was obtained in 30%
We now report full synthetic data for the tridentate ligand L,
and for complexes of type a and b and also describe a new
bonding mode of L, namely the meridional co-ordination type
c, found in some ruthenium and rhodium complexes.
J. Chem. Soc., Dalton Trans., 1997, Pages 3777–3784
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Fig. 1 Partial view of the 1H NMR spectrum of L in CDCl3. The peak marked with an asterisk corresponds to residual CHCl3
yield. Treatment of it with HBr (33%)–MeCO2H resulted in
formation of the bromo derivative in 80% yield. Further reac-
tion with Li(PPh2) at low temperature afforded L in 79% yield.
The 1H NMR spectrum of this phosphine displays the expected
seven bipyridine H signals in the aromatic region (Fig. 1) and
an A2B2X [X = P, A = PCH2, 2J(PA) = 9 Hz] pattern for the two
methylene protons. The phosphorus signal appears at δ Ϫ14.9
in the 31P-{1H} NMR spectrum.
Cl
Ru
Cl
Cl
PPh2
CO
PPh2
Ru
N
N
+
Cl
N
N
C
O
(i )
1 (49%)
2 (43%)
N
PPh2
Ruthenium carbonyl complexes
N
For the present study [{RuCl2(CO)2}n] was used as ruthenium
precursor. Since this polymeric complex contains traces of acid
originating from its preparation,6 we decided first to use it in
association with triethylamine. Reaction of this system with n
equivalents of L gave a mixture of complexes 1 and 2 (Scheme
2), which were separated by flash chromatography.
N
(ii )
N
N
L
Ph2P
OC
OC
Cl
Cl
+ 1 + 2
Ru
Ph2P
The meridional arrangement of the P,N,N ligand in com-
plexes 1 and 2 was inferred from a combination of IR and
NMR data and confirmed in the case of 1 by an X-ray struc-
tural analysis (Fig. 2; Table 1). The ruthenium atom in 1 is in an
almost octahedral environment with the two Cl atoms occupy-
ing trans positions [Cl(1)᎐Ru᎐Cl(2) 171.98(8)Њ]. The six-
membered phosphorus-containing metallocycle adopts an
envelope shape, the folding being about the C(11)᎐C(13) axis
[dihedral angle between the C(11)᎐C(12)᎐C(13) and the
N(2)᎐Ru᎐P planes: 64Њ]. This ring appears somewhat strained
as shown by the rather large C(13)᎐C(12)᎐C(11) angle
[114.0(8)Њ]. The Ru᎐P bond length is 2.290(2) Å and the two
Ru᎐N distances differ only slightly [Ru᎐N(1) 2.122(6),
Ru᎐N(2) 2.177(6) Å]. The meridional P,N,N arrangement
imposes a tilt angle between the pyridine rings of 10Њ.
N
3 (80%)
Scheme 2 (i) [{Ru(CO)2Cl2}n] (1 equivalent), NEt3 (1 equivalent),
MeOH, room temperature (r.t.); (ii) [{Ru(CO)2Cl2}n] (0.5 equivalent),
MeOH, r.t.
31P-{1H} NMR spectrum of complex 3 displays a singlet at δ
18.2 (free phosphine δ Ϫ14.9), showing the equivalence of the
two phosphorus atoms. As expected for a trans arrangement of
the phosphine ligands, the PCH2 groups appear as a virtual
1
Reaction of L with [{RuCl2(CO)2}n] (L:Ru ratio 2n:n) in
methanol, at room temperature, in the absence of triethylamine
resulted mainly in formation of the colourless complex 3 (80%
yield), with small amounts of 1 and 2. It is likely that during the
formation of 3 transient protonation of the bipyridine moiety
occurs and hence favours P-monodentate co-ordination. The
triplet in the CH2(bipy)-decoupled H NMR spectrum.8 The
cis-(CO)2, cis-Cl2 stereochemical arrangement in complex 3 was
deduced from the presence of two ν(C᎐O) absorption bands
᎐
(2052 and 1988 cmϪ1) and two strong ν(Ru᎐Cl) stretching vibra-
tions (299 and 285 cmϪ1) in the IR spectrum.9 The trans-P2-cis-
(CO)2-cis-Cl2 stereochemistry was confirmed by a single-crystal
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J. Chem. Soc., Dalton Trans., 1997, Pages 3777–3784

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X-ray diffraction study (Fig. 3) which has been previously
reported.4
respect to their electrochemical properties. It was found that
electrochemical reduction of trans-dichloro stereoisomers
exclusively leads to a polymeric film of generic formula [{Ru-
(bipy)(CO)2}n] which displays outstanding catalytic activity in
the electrochemical reduction of carbon dioxide.10,11 The form-
ation of such organometallic polymers results from addition of
two electrons to [RuIICl2(bipy)(CO)2] and subsequent loss of two
chloride ligands. Electropolymerisation proceeds via transient
formation of di- and tetra-meric complexes. Structural param-
eters such as the relative positions of the leaving groups play a
crucial role in this process; interestingly, electroreduction of the
cis-Cl2 stereoisomers did not lead to polymer formation, but
afforded dimers.12 Extension of this electropolymerisation
technique to other ruthenium carbonyl complexes is an import-
ant question.13 The availability of complexes 1 and 2 afforded
a good opportunity to study whether polymer formation still
occurs when phosphine donors are present in the co-ordination
sphere of the ruthenium centre.
It is interesting that the tridentate behaviour of the P,N,N
ligand in complexes 1 and 2 induces a high-field shift of the 31
P
NMR resonances with respect to the phosphorus signal of the
P-monodentate complex 3 (δ 47.6 1, 35.9 2, 18.2 3).
Electrochemical properties of complexes 1 and 2
Ruthenium complexes of the type [RuIICl2(bipy)(CO)2]
(bipy = 2,2Ј-bipyridine) have recently been investigated with
Table 1 Selected bond lengths (Å) and angles (Њ) for complex 1
Ru᎐P
2.290(2)
2.383(2)
2.407(2)
2.122(6)
2.177(6)
P᎐C(13)
P᎐C(14)
P᎐C(20)
Ru᎐C(1)
C(1)᎐O
1.802(9)
1.831(8)
1.846(7)
1.820(8)
1.144(8)
Ru᎐Cl(1)
Ru᎐Cl(2)
Ru᎐N(1)
Ru᎐N(2)
The electrochemical behaviour of complex 1 (10Ϫ3 ) in
MeCN containing NBu4ClO4 (0.1 ) is illustrated by the cyclic
voltammogram shown in Fig. 4. In the positive region [curve
(a)] the complex is oxidised reversibly by a one-electron process
Cl(1)᎐Ru᎐Cl(2)
P᎐Ru᎐N(1)
N(2)᎐Ru᎐C(1)
P᎐Ru᎐Cl(1)
P᎐Ru᎐Cl(2)
171.98(8)
171.8(2)
172.8(3)
93.63(7)
90.85(8)
Ru᎐P᎐C(13)
Ru᎐P᎐C(14)
Ru᎐P᎐C(20)
P᎐C(13)᎐C(12)
C(13)᎐C(12)᎐C(11)
106.6(3)
119.8(3)
121.3(2)
110.0(6)
114.0(8)
into the corresponding ruthenium() species [RuIIICl2L(CO)]ϩ
13
{E = 0.80 V, compare E = 1.45 V for trans-Cl2-[RuIICl2-
₁
₁
₂
₂
(bipy)(CO)2]}. Exhaustive oxidation at 1.00 V with subsequent
reduction at 0.60 V regenerated quantitatively the initial com-
plex. This result shows that [RuIIICl2L(CO)]ϩ is stable, unlike
[RuIIICl2(bipy)(CO)2]ϩ which readily undergoes substitution of
one chloride and one CO under similar conditions.14 The visible
absorption spectrum of [RuIIICl2L(CO)]ϩ displays absorption
bands at 614 (ε = 1300) and 474 nm (ε = 1200 Ϫ1 cmϪ1) while
that of the initial complex lies at 400 nm (ε = 1000 Ϫ1 cmϪ1).
In the cathodic area the voltammogram exhibits a first
irreversible system (Epc = Ϫ1.71 V) followed by two quasi-
₁
reversible ones (E = Ϫ1.86 and Ϫ1.91 V) [Fig. 4, curve (b)].
₂
In contrast to the observations made for trans-Cl2-[RuCl2-
(bipy)(CO)2],9 controlled-potential electrolysis of complex
1 at Ϫ1.70 V did not produce any polymeric electroactive
film on the working electrode. Indeed, after one electron per
molecule of complex was consumed a pale yellow solution was
obtained, characterised by a broad absorption between 340 and
500 nm. Similar results were obtained using NMe4BF4 (0.05 
in acetonitrile) as supporting electrolyte. After the one-electron
electrolysis was complete the solvent was evaporated and the
residue extracted with dichloromethane. The solution IR spec-
trum showed a unique absorption band in the carbonyl region
(at 1927 cmϪ1). Mass spectroscopy [desorption chemical ionis-
ation (DCI) electron-capture mode] unambiguously revealed
the presence of an intense peak corresponding to [RuICl(L)-
(CO)(MeCN)] (m/z 574). This complex was likely formed
according to following two-step mechanism in equations (1)
and (2).
Fig. 2 A MolView7 drawing of complex 1
[RuIICl2L(CO)] ϩ eϪ → [RuIICl2(L Ϫ)(CO)] (1)
᝽
[RuIICl2(L Ϫ)(CO)] ϩ MeCN →
᝽
[RuICl(L)(CO)(MeCN)] ϩ ClϪ (2)
The cyclic voltammogram of a solution containing the
electrochemically generated complex [RuICl(L)(CO)(MeCN)]
₁
exhibits the two successive reversible systems at E = Ϫ1.86 and
₂
Ϫ1.91 V described above. Exhaustive electrolysis carried out
at Ϫ1.85 V, in MeCN containing NBu4ClO4 (0.1 ), consumes
one electron per molecule and produces a deep green solution
(λmax 386, 520, 580 and 750 nm), suggesting12 the formation
of a dimeric complex according to the process described in
equations (3)–(5).
[RuICl(L)(CO)(MeCN)] ϩ eϪ →
[RuICl(L Ϫ)(CO)(MeCN)] (3)
Fig. 3 A MolView7 drawing of complex 3
᝽
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[RuIIICl2L(CO)]ϩ is observed at a more anodic potential
₁
₁
(E = 1.04 V) than that of the trans-Cl2 isomer 1 (E = 0.80 V).
₂
₂
In summary, this electrochemical study reveals that during
the two electron-reduction process of complex 1 a ruthenium(0)
dimer is formed, thus contrasting with the behaviour of trans-
Cl2-[RuCl2(bipy)(CO)2] which leads to formation of
a
ruthenium(0) polymeric species. This difference possibly arises
from the steric bulk of the phosphino fragment preventing
polymerisation of the reduced species. This interpretation must
however be regarded with care since isomerisation of the elec-
trochemically generated species [RuICl(L)(CO)(MeCN)] (or its
reduced form) might occur and hence result in formation of a
species with cis-located leaving groups, a stereochemical
arrangement not favourable for polymerisation.12
Mixed ruthenium(II)–copper(I) complex
Complex 3 possesses two free bipyridine subunits located at the
two ends. Clearly, the large separation between these two free
binding sites and the rigidity of the P᎐Ru᎐P spacer disfavours
complexation of both bipyridines around an additional single
metal centre. The co-ordinative properties of this ditopic
metallo-synthon were investigated towards the Cuϩ cation.
Stoichiometric mixing of complex 3 with [Cu(MeCN)4]-
15
ClO4
yielded quantitatively the deep red complex 4
(λmax = 442 nm, ε = 14 300 Ϫ1 cmϪ1). The positive-ion FAB
mass spectrum of the resulting complex gave an intense peak at
m/z 2158.9 [M Ϫ ClO4] with the expected isotopomer distribu-
tions and no significant peaks at higher mass. The self-
assembled complex 4 is best described as a 36-membered
Ru2Cu2P4N8 metallomacrocycle as confirmed by a crystal struc-
ture determination (Scheme 3 and Fig. 5).4
Fig. 4 Cyclic voltammograms at a vitreous carbon electrode (19.6
mm2), in a MeCN solution containing NBu4ClO4 (0.1 ) and complex 1
(1 m), ν = 100 mV sϪ1. Initial solution (a) between Ϫ0.65 and ϩ1.00 V,
(b) between Ϫ0.70 and Ϫ2.20 V, (c) solution after exhaustive reduction
at Ϫ1.70 V, under Ar and (d) under CO2
The IR (νCO 2050 and 1987 cmϪ1), far-IR [ν(Ru᎐Cl) 304 and
280 cmϪ1], and NMR spectroscopic data are similar to those
observed for precursor 3, in full accord with the fact that the
trans-P,P-cis-(CO)2-cis-Cl2 stereochemistry around the Ru is
maintained in the tetrametallic complex 4. A remarkable fea-
ture of this reaction is that no polymer formation was observed.
Furthermore, it is noteworthy that the copper-controlled
assembly of bipyridine units results selectively in a non-helical
arrangement (d). Similar observations were recently made with
purely organic bis(bipyridine) compounds and steric effects
have been postulated to play a major role in the formation of
the side-by-side non-helical isomer (d).16
[RuICl(L Ϫ)(CO)(MeCN)]
᝽
[Ru0L(CO)(MeCN)] ϩ ClϪ (4)
[Ru0L(CO)(MeCN)]
¹[{Ru0L(CO)(MeCN)}2]
(5)
¯
²
After quantitative formation of the dimeric species, the cyclic
voltammogram [Fig. 4, curve (c)] only shows the second revers-
₁
ible system (E = Ϫ1.91 V) which corresponds to the reduction
₂
of the dimer. In view of the quasi-reversibility of the system at
Ϫ1.86 V in the initial voltammogram, it is likely that dimer
formation occurs slowly on the experimental time-scale.
The cyclic voltammogram under CO2 of the ruthenium()
complex obtained at Ϫ1.70 V vs. Ag–Agϩ (0.01 ) is shown in
Fig. 4, curve (d). The first reduction (dimer formation, at Ϫ1.86
V) remains unaffected, while the second reduction peak, at
Epc = Ϫ1.97 V, shows a strong enhancement of the cathodic
current. This is a clear indication that the first reduction of the
resulting dimer leads to an electrocatalyst for the reduction of
CO2. A GC analysis after an electrocatalysis at Ϫ1.85 V in
MeCN–NBu4ClO4 (0.1 )–water (10% v/v) revealed the forma-
tion of carbon monoxide (faradic yield 14%). However, molecu-
lar hydrogen was formed as main product as a consequence of
the strong cathodic potential. Note that during the reduction
no formate was detected. Obviously, the high cathodic potential
of the system [E ≈ Ϫ1.80 V, Fig. 4, curve (d)] makes this
ruthenium dimer less attractive for electrocatalytic production
of CO from CO2 than the polymeric [{Ru0(bipy)(CO)2}n] film
(100% faradic yield at Ϫ1.2 V vs. saturated calomel electrode,
SCE, in water).10,11
Electrochemical properties of complexes 3 and 4
Complex 3 exhibits a unique irreversible redox process located
at a large cathodic potential (Epc = Ϫ2.14 V). Exhaustive elec-
trolysis carried out at Ϫ2.20 V involves two electrons per mol of
complex and leads to decomposition of the reduced species.
The cyclic voltammogram obtained after this exhaustive reduc-
tion showed the typical reversible one-electron reduction signal
₁
of free L (E = Ϫ2.54 V).
₂
In the mixed Ru2Cu2 complex 4 the CuII/I redox system
₁
appears as quasi-reversible (E = 0.29 V), while a typical
₂
electrodeposition–redissolution peak system due to copper(0)
formation at the working electrode surface is obtained
(Epc = Ϫ0.21 V, Epa = Ϫ0.10 V).17
Rhodium complexes
Since L is suitable for meridional co-ordination, we surmised
that it would also display tridentate behaviour in square-planar
complexes. We therefore investigated its co-ordinative proper-
ties towards rhodium().
The cis-Cl2 isomer 2 presents essentially the same electro-
chemical behaviour as that of complex 1, involving similar
redox processes. The formation of the corresponding
[RuICl(L)(CO)(MeCN)] complex occurs at Ϫ1.83 V, while the
quasi-reversible dimerisation lies at E = Ϫ1.78 V and the result-
ing dimer is reversibly reduced at E = Ϫ1.94 V. On the other
Treatment of [{RhCl(C2H4)2}2] with 2 equivalents of L in
dichloromethane resulted in the formation of a pale yellow,
sparingly soluble species (yield 90%) which was characterised
1
by elemental analysis, mass spectrometry, 31P and H NMR
₁
₂
spectroscopies. Its 31P NMR spectrum displays a doublet at δ
28.3 [J(RhP) = 123 Hz]. The 1H NMR spectrum exhibits signals
₁
₂
hand, the reversible one-electron oxidation of 2 leading to
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0.5 equivalent [{RhCl(C2H4)2}2]
(i )
2+
–
2 ClO4
Et
Ph2P
Ph2P
O
Cl
CH2
CH2
OC
OC
Cl
Cl
OC
OC
Cl
Cl
(i )
PPh2
Ru
Ru
Ph2P
Ru
Ph2P
PPh2
Cl
92%
PPh2
N
N
(ii )
Cl
Cl
Rh
CO
CO
Rh
Cl
N
N
Cl
Cl
PPh2
5 90%
6 63%
3
Scheme 4 (i) L (1 equivalent), CH2Cl2; (ii) AgO3SCF3 (1 equivalent),
EtOH
4
N
Cu+
≡
≡
P
Ru
P
N
Scheme 3 (i) [Cu(MeCN)4]ClO4, MeCN–CH2Cl2 (1 : 1), r.t.
non-helical
P
Ru
P
d
P
Ru
P
helical
P
Ru
e
P
NMR spectrum. The FAB mass spectrum shows an intense
peak at m/z 565.1 (intensity 100%) corresponding to the
[RhCl(CH2OEt)L]ϩ cation (expected isotopic profile) and a
fragment of mass 506.1 (intensity 40%) due to the loss of the
‘CH2OEt’ ligand. Although the monocrystals obtained for 6
were of poor quality,† X-ray diffraction data clearly confirmed
the proposed meridional arrangement of the tridentate ligand
and the cis dichloro configuration.
Fig. 5 A MolView7 drawing of complex 4
Conclusion
In this study three co-ordination modes were found for the tri-
dentate L ligand. An example of monodentate behaviour was
found in cis-Cl2-cis-(CO)2-trans-P,P-[RuCl2(CO)2L2] 3, a com-
plex where the RuP2 fragment plays the role of a rigid spacer
between two well separated bipyridine units. The whole com-
plex 3 can be regarded as a multisite metallo-synthon suitable
for the preparation of highly organised architectures. This is
illustrated by the 36-membered metallomacrocycle 4 in which
the L ligand behaves as a non-symmetric linker between a
ruthenium() and a copper() centre. Tridentate-meridional co-
ordination was observed in the chlororuthenium() carbonyl
complexes 1 and 2 and in the rhodium() species 5 and 6. In
contrast to trans-Cl2-[RuCl2(bipy)(CO)2], the electrochemical
reduction of the ruthenium() complex 1 does not generate a
polymer, but a dimeric species, suggesting that the bulky phos-
phine controls the transformation of the species obtained after
a two-electron reduction. The electrogenerated dimer is active
towards the reduction of carbon dioxide to carbon monoxide,
but at much lower cathodic potential than for the above-
mentioned polymer.
characteristic of the PCH2CH2 moiety [two complex multiplets
(2 H:2 H), at δ 3.5 and 2.8] and a well resolved ABXY spin
system (δA 4.1 and δB 3.7, X = P, Y = Rh, intensity 1 : 1), con-
sistent with a metal-bound CH2R group. The formation of a
chloromethyl complex was confirmed by the FAB mass spec-
trum which shows an intense peak at m/z 555.0 (intensity 100%,
expected isotopic profile), corresponding to a [RhCl(CH2Cl)L]ϩ
cation. A fragmentation peak (at m/z 506.0, intensity 35%) cor-
responding to the loss of a ‘CH2Cl’ fragment was also detected.
These results are consistent with the formula drawn for complex
5 (Scheme 4).
It is likely that reaction between ligand L and the rhodium()
ethylene complex generates the electron-rich [RhICl(L)]
intermediate which in turn undergoes facile oxidative addition
of methylene chloride affording the rhodium() complex 5.
Dichloromethane activation by rhodium() phosphine com-
plexes has previously been observed.18
Nucleophilic substitution at the chloromethyl fragment in
complex 5 by EtOH was achieved using AgO3SCF3 and
afforded the highly soluble yellow complex 6 (Scheme 4). It is
noteworthy that no reaction occurs with ethanol in the absence
of silver salt. The phosphorus resonance of complex 6 appears
The electron-rich rhodium() intermediate obtained by treat-
ing the P,N,N ligand with [{RhCl(C2H4)2}2] results in activation
of dichloromethane under ambient conditions. Chemical trans-
formation of the co-ordinated ‘CH2Cl’ fragment maintains the
1
at δ 27.7 [J(RhP) = 132 Hz] (cf. δ 28.3 for 4). The H NMR
spectrum exhibits signals corresponding to an ethyl group, two
multiplets for the PCH2CH2 spacer and an ABX pattern
(X = Rh) for the Rh᎐CH2OEt hydrogens. The co-ordinated
methylene resonates at δ 72.0 [J(CRh) = 17 Hz] in the 13C-{1H}
† Crystal data: orthorhombic, space group Pbca, a = 11.915(6),
b = 14.55(2), c = 29.77(2) Å.
J. Chem. Soc., Dalton Trans., 1997, Pages 3777–3784
3781

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meridional P,N,N co-ordination of the ligand, emphasising its
potential role as an ancillary ligand for further stereocontrolled
reactions.
Electrochemical instrumentation and procedures
Acetonitrile (Rathburn, HPLC grade) was used as received.
Tetrabutylammonium perchlorate from Fluka was recrystal-
lised from ethyl acetate and dried under vacuum at 80 ЊC for
3 d. Tetramethylammonium tetrafluoroborate from Fluka was
dried under vacuum at 80 ЊC for 3 d. Electrochemical experi-
ments were carried out using a Princeton Applied Research
potentiostat-galvanostat (model 273) equipped with a Sefram
TGM 164 X-Y recorder. Potentials are relative to the Ag–Agϩ
(0.01 ) electrode in MeCN containing NBu4ClO4 (0.1 ).
Working electrodes for cyclic voltammetry consisted of a vitre-
ous carbon disc (5 mm diameter) polished with 2 µm diamond
paste. All experiments were run in a conventional three-
electrode cell in a dry-box (Jaram) under an argon atmosphere.
Exhaustive electrolyses were carried out with a 5 cm2 platinum
electrode.
Experimental
Nuclear magnetic resonance spectra were recorded on Bruker
SY-200 or AC-200 instruments at room temperature and at
1
200.1 MHz for H, 50.3 MHz for 13C, and 81.0 MHz for 31P.
The 1H NMR chemical shifts are reported in parts per
million (ppm) relative to residual protiated solvents (δ 7.26 for
CDCl3, 2.04 for [2H6]acetone, and 1.94 for CD3CN); 13C-{1H}
NMR chemical shifts are reported relative to CDCl3 (δ 77.03),
[2H6]acetone (δ 206.00, 29.80) and CD3CN (δ 181.21, 1.32)
while 31P-{1H} NMR chemical shifts are given relative to
external 85% H3PO4. Infrared spectra were recorded with an
IFS 25 Bruker spectrometer, with the sample in the form of
anhydrous KBr pellets. Fast atomic bombardment (FAB,
positive mode) spectra were recorded on a ZAB-HF-VB-
analytical apparatus in m-nitrobenzyl alcohol matrices; Ar
atoms were used for the bombardment (8 keV; eV ≈ 1.60 ×
10Ϫ19 J). The DCI (electron-capture mode) mass spectra were
obtained on an AEI Kratos MS 50 spectrometer fitted with
an ION Tech Ltd. gun. Routine absorption spectra were
measured in acetonitrile solutions at room temperature with a
Uvikon 941 spectrophotometer, electronic absorption spectra
of electrolysed solutions on a Hewlett-Packard HP 8452A
diode-array spectrophotometer controlled by a Compaq 286
computer equipped with a Citizen 120D printer. Structural
Preparations
6-(2-Hydroxyethyl)-2,2Ј-bipyridine. A hexane solution of
LiBun, titrated at 1.51  (19.9 cm3, 0.030 mol), was added
dropwise to a solution of diisopropylamine (3.200 g, 0.032
mol) in thf (25 cm3) at Ϫ78 ЊC. After 1 h a solution of 6-
methyl-2,2Ј-bipyridine (5.106 g, 0.030 mol) in thf (25 cm3) was
added over 10 min. The solution immediately turned deep blue,
indicative of fast metallation. After 3 h anhydrous paraformal-
dehyde (1.080 g, 0.036 mol) was added as a solid and, after
stirring for 5 h at Ϫ78 ЊC, the temperature was allowed to rise
to room temperature. The solution was hydrolysed with water
(1 cm3) presaturated with NH4Cl before the solvent was
removed by rotary evaporation. The crude product was dis-
persed on alumina and purified by column chromatography,
eluting first with CH2Cl2–hexane (1 : 1) (recovering unchanged
starting product, 1.9 g) and then with 2% MeOH in CH2Cl2
affording the analytically pure required compound 2 (Rf = 0.23;
1
assignments are based on H, 13C-{1H}, 31P-{1H} NMR, IR,
and positive-ion FAB mass spectra, and elemental analysis.
All reactions were carried out under dry argon by using
Schlenk-tube and vacuum-line techniques. Solvents, including
CDCl3, were dried over suitable and freshly distilled under
argon before use. The LiBun solutions were titrated according
to ref. 19. [{RuCl2(CO)2}n] was prepared according to ref. 6.
1
1.8 g, 30%). H NMR (CDCl3): δ 8.50 (m, 1 H, H6Ј), 8.08 (m,
2 H, H3,3Ј), 7.57 (m, 2 H, H4,4Ј), 7.05 (m, 2 H, H5,5Ј), 4.74 (s br, 1
H), 3.96 (s br, 2 H, CH2O) and 2.93 [m, 2 H, CH2(bipy)]. 13C-
{1H} NMR (CDCl3): δ 159.35 (Cq), 155.48 (Cq), 154.82 (Cq),
148.73 (CH), 137.12 (CH), 136.59 (CH), 123.36 (CH), 123.21
(CH), 120.61 (CH), 118.55 (CH), 61.33 (CH2O) and 39.12
[CH2(bipy)]. Mass spectrum: m/z 200 (100%) (Found: C, 71.85;
H, 5.87; N, 13.91. Calc. for C12H12N2O: C, 71.98; H, 6.04; N,
13.99%).
Crystallography
Crystal data for complex 1. C25H21Cl2N2OPRu, M = 568.41,
gold-yellow crystals (0.12 × 0.20 × 0.25 mm), monoclinic,
space group P2/c with a = 13.215(7), b = 15.572(6),
c = 11.581(6) Å, β = 100.63(6)Њ, U = 2342(2) Å3, Z = 4,
Dc = 1.612 g cmϪ3, F(000) = 1144, µ = 9.74 cmϪ1.
A suitable crystal was obtained by slow diffusion of hexane
into a dichloromethane solution of complex 1 at room
temperature. Data were collected on an Enraf-Nonius
CAD4 diffractometer at room temperature with graphite-
monochromated Mo-Kα radiation (λ = 0.7107 Å). The cell
parameters were obtained by fitting a set of 25 high-θ reflec-
tions. The data collection [ω–2θ scan type, 2θmax = 50Њ, ranges h
0–15, k 0–18, l Ϫ13 to 13, intensity controls without appre-
ciable decay (0.2%)] gives 4481 reflections from which 2017
were independent (Rint = 0.025) with I > 3σ(I). After Lorentz-
polarisation corrections, the structure was solved by a Pat-
terson map which revealed the ruthenium atom. The remaining
non-hydrogen atoms were found after several scale-factor and
Fourier-difference calculations. After isotropic (R = 0.095)
refinement, an absorption correction (maximum 1.5344, min-
imum 0.7763) was made using DIFABS.20 After anisotropic
refinement (R = 0.065), all hydrogen atoms were found with a
Fourier-difference map (between 0.59 and 0.27 e ÅϪ3). The
whole structure was refined by full-matrix least squares on
F {x, y, z, βij for Ru, P, Cl, N, C and O atoms and x, y, x
for H atoms; 353 variables and 2017 observations; w = 1/
6-(2-Bromoethyl)-2,2Ј-bipyridine. The above alcohol (1.8 g,
9.0 mmol) was treated with HBr (33%)–MeCO2H (25 cm3) at
100 ЊC during 18 h. After cooling the reaction mixture to room
temperature, cold water (50 cm3) was added carefully and the
resultant solution neutralised with aqueous NaOH (10%) solu-
tion. The yellowish oil so obtained was extracted with CH2Cl2
(3 × 50 cm3) and the organic phases were dried over anhydrous
Na2SO4. The crude compound was purified through a flash
chromatography column packed with silica and eluted with
CH2Cl2 containing 0.2 to 0.5% MeOH (Rf = 0.63, alumina,
CH2Cl2) affording the analytically pure compound (1.9 g, 80%).
1H NMR (CDCl3): δ 8.64 [ddd, 1 H, H6Ј, 3J(HH) = 4.7,
4J(HH) = 1.8, 5J(HH) = 0.8], 8.43 [dm, 1 H, H3Ј, 3J(HH) = 7.9],
8.26 [dd, 1 H, H3, 3J(HH) = 7.2, 4J(HH) = 0.8], 7.75 [ddd, 1 H,
H4Ј, 3J(HH) = 7.9, 3J(HH) = 7.5, 4J(HH) = 2.9], 7.70 [t, 1 H, H4,
3
3J(H4H3) = 3J(H4H5) = 7.9], 7.24 [ddd, 1 H, H5Ј, J(HH) = 4.8,
4
3
3J(HH) = 7.6, J(HH) = 1.3], 7.14 [dd, 1 H, H5, J(HH) = 7.7,
4J(HH) = 0.9], 3.85 [t, 2 H, CH2Br, 3J(HH) = 6.9] and 3.37 [t, 2
H, CH2(bipy), J(HH) = 7.1 Hz]. 13C-{1H} NMR (CDCl3): δ
3
¹
2 2
²
2
2
σ(Fo) = [σ (I) ϩ (0.04Fo ) ] } with the resulting R = 0.039,
RЈ = 0.035 and S = 2.30 (residual ∆ρ р 0.58 e ÅϪ3). Atomic
scattering factors were from ref. 21. All calculations were per-
formed on a Digital MicroVAX 3100 computer with the
MOLEN22 package.
157.59 (Cq), 156.02 (Cq), 155.70 (Cq), 148.99 (CH), 137.16
(CH), 136.68 (CH), 123.56 (CH), 123.23 (CH), 121.02 (CH),
118.97 (CH), 41.01 (CH2Br) and 31.46 [CH2(bipy)]. Mass spec-
trum: m/z 264/262 (4) and 183 (100%) (Found: C, 54.68; H,
4.03; N, 10.57. Calc. for C12H11BrN2: C, 54.77; H, 4.21; N,
10.65%).
CCDC reference number 186/642.
3782
J. Chem. Soc., Dalton Trans., 1997, Pages 3777–3784

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Compound L. A hexane solution of LiBun, titrated at 1.51 
(2.42 cm3, 3.66 mmol), was added dropwise to a solution of
PPh2H (0.682 g, 3.66 mmol) in anhydrous thf (30 cm3) at
Ϫ78 ЊC. After 15 min the orange-red solution thus obtained
was transferred dropwise via a cannula to a solution of
6-(2-bromoethyl)-2,2Ј-bipyridine (0.964 g, 3.66 mol) in thf
(50 cm3). During addition the temperature of the solution
was maintained at Ϫ78 ЊC and the orange coloration of the
Ph2PϪ anion immediately disappeared, showing fast nucleo-
philic substitution of the bromide. Overnight the temperature
was allowed to reach room temperature before the solution was
evaporated to dryness on a vacuum line. The residue was dis-
solved in deoxygenated CH2Cl2 and the suspension filtered over
neutral alumina (LiBr elimination). The analytically pure lig-
and L was obtained by crystallisation from a CH2Cl2–hexane
solution at Ϫ30 ЊC (Rf = 0.62, alumina, CH2Cl2–hexane 9 : 1,
1.055 g, 79%). 1H NMR (CDCl3): δ 8.69 [ddd, 1 H, H6Ј,
(s, p-C of Ph), 129.36 [d, m-C of Ph, 3J(CP) 8], 125.89 (CH of
bipy), 126.03 (CH of bipy), 124.58 (CH of bipy), 120.86 (CH
of bipy), 35.26 [CH2(bipy)] and 22.12 [d, CH2P, J(CP) 27
Hz]; 31P-{1H} NMR ([2H6]acetone–acetone 1:9) δ ϩ35.9; IR
(KBr) ν /cmϪ1 2929.2m, 1951.0s (CO), 1726.1m, 1456.9m,
1263.0m and 1103.6s; far IR 299s and 286s (Ru᎐Cl); positive-
ion FAB mass spectrum: m/z 568.0 (Mϩ, expected isotopic
profile), 540.0 (M Ϫ CO), 533.1 (M Ϫ Cl), 504.1 (M Ϫ
CO Ϫ Cl Ϫ H) and 497.1 (M Ϫ 2Cl Ϫ H) (Found: C, 52.59;
H, 3.43; N, 4.67. Calc. for C25H21Cl2N2OPRu: C, 52.83; H,
3.72; N, 4.93%).
Complex 3. A solution of compound L (0.223 g, 0.65 mmol)
in MeOH (20 cm3) was added to a stirred solution of [{RuCl2-
(CO)2}n] (0.070 g, 0.307 mmol) in anhydrous MeOH (20 cm3)
at room temperature. During the course of reaction a white
precipitate was formed. After 24 h the solvent was removed by
rotary evaporation. The crude product was purified through
a chromatography column packed with silica, previously
deactivated by treatment with triethylamine (10% in di-
chloromethane), and eluted with dichloromethane; Rf = 0.65
(dichloromethane). Recrystallisation of the precipitate by slow
evaporation of a dichloromethane–hexane solution afforded
the analytically pure colourless complex 3 (0.233 g, 80%). UV/
VIS (MeCN) λmax/nm (ε/dm3 molϪ1 cmϪ1): 283 (21 200) and 224
(19 900). 1H NMR (CD2Cl2): δ 8.62 [d, 1 H, 3J(HH) = 4.7], 8.46
4
5
3J(HH) = 4.8, J(HH) = 1.0, J(HH) = 0.8], 8.51 [dm, 1 H, H3Ј,
3
3J(HH) = 7.6], 8.28 [dm, 1 H, H3, J(HH) = 7.9], 7.79 [td, 1 H,
3
4
H4Ј, J(H4ЈH5Ј) = 3J(H4ЈH3Ј) = 7.6, J(HH) = 1.3], 7.69 [t, 1 H,
3
H4, J(H4H3) = 3J(H4H5) = 7.8], 7.59–7.35 (10 H, PPh2), 7.27
(m, 1 H, H5Ј), 7.12 [d, 1 H, H5, 3J(HH) = 7.6 Hz], 3.05 (δA) and
2.69 (δB) [two multiplets of an A2B2X system, with A = PCH2,
2J(PA) = 9 Hz and B = PCH2CH2, 4 H]. 13C-{1H} NMR
(CDCl3): δ 160.88 [d, CqP, 2J(CP) = 13], 156.27 (Cq, bipy),
155.41 (Cq, bipy), 148.91 (Cq, bipy), 138.61–118.32 (aromatic C),
34.40 [d, CH2P, J(CP) = 17] and 27.67 [d, CH2(bipy),
2J(CP) = 13 Hz]. 31P-{1H} NMR (CDCl3): δ Ϫ14.9. Fourier-
transform IR (KBr pellet): ν /cmϪ1 2925m, 1571s, 1425s, 1095s,
740vs and 693vs. EI mass spectrum: m/z 384.1 (L ϩ O) (Found:
C, 78.15; H, 5.60; N, 7.51. Calc. for C24H21N2P: C, 78.24; H,
5.75; N, 7.60%).
3
3
[d, 1 H, J(HH) = 8.0], 8.17 [d, 1 H, J(HH) = 8.0], 7.93 (m,
4 H), 7.81 [t of d, 1 H, 3J(HH) = 7.8, 4J(HH) = 1.8], 7.63 [t, 1 H,
3J(HH) = 7.8], 7.50 (m, 6 H), 7.29 (m, 1 H), 7.00 [d, 1 H,
3J(HH) = 7.6 Hz], 3.51 (m, 4 H) and 2.75 (m, 4 H). 13C-{1H}
NMR (CDCl3): δ 192.47 [d, Ru᎐CO, 2J(CP) = 11], 159.87
(Cq, phosphine), 156.33 (Cq, bipy), 155.43 (Cq, bipy), 148.95
(Cq, bipy), 137.16–118.49 (Caromatic), 31.75 [s, CH2(bipy)] and
3
Complexes 1 ϩ 2. A solution of compound L (0.210 g, 0.570
mmol) in MeOH (25 cm3) was added to a stirred solution of
[{RuCl2(CO)2}n] (0.150 g, 0.657 mmol) in anhydrous MeOH (5
cm3) adjusted to pH ca. 7 with triethylamine. During the course
of reaction at room temperature the solution turned deep yel-
low. After 2 d, the solvent was removed by rotary evaporation.
The crude product was purified through a flash chroma-
tography column packed with silica, previously deactivated by
treatment with triethylamine (10% in dichloromethane), and
eluted with dichloromethane; Rf = 0.46 for complex 1 and 0.26
for 2 (dichloromethane). Recrystallisation of the compounds
by slow evaporation of a dichloromethane–hexane solution
afforded the analytically pure gold-yellow complex 1 (0.160 g,
49%) and the analytically pure lemon-yellow complex 2 (0.140
g, 43%).
23.29 [pseudo t, CH2P, J(CP) = 14.5 and 13.2 Hz (1J and J
not assigned)]. 31P-{1H} NMR ([2H6]acetone–acetone 1 : 9):
δ ϩ18.2. Fourier-transform IR (KBr pellet): ν /cmϪ1 3054w,
2052s (νCO), 1988s (νCO), 1579m, 1431m, 1133m, 1104m, 299
[ν(Ru᎐Cl)] and 285 [ν(Ru᎐Cl)]. Positive-ion FAB mass spec-
trum: m/z 964.9 ([M ϩ H]ϩ, expected isotopic profile) (Found:
C, 62.09; H, 4.14; N, 5.73. Calc. for C50H42Cl2N4O2P2Ru: C,
62.24; H, 4.39; N, 5.81%).
Complex 4. A solution of [Cu(MeCN)4]ClO4 (0.020 g, 0.060
mmol) in anhydrous MeCN (10 cm3) was added at room tem-
perature, under argon, to a stirred solution of complex 3 (0.058
g, 0.060 mmol) in anhydrous CH2Cl2 (15 cm3). During addition
the solution turned deep red, showing fast copper() complex-
ation. After 8 h it was filtered over Celite and evaporated to
dryness. Slow evaporation of a MeCN–toluene solution of the
crude product led to the analytically pure cherry-red complex 4
(0.062 g, 92%). UV/VIS (MeCN) λmax/nm (ε/dm3 molϪ1 cmϪ1):
442 (14 300), 292 (138 000), 260 (127 000) and 213 (153 000).
31P-{1H} NMR (CD3CN): δ ϩ19.5. Positive-ion FAB mass
spectrum: m/z 2158.9 (Mϩ Ϫ ClO4, expected isotopic profile),
2057.8 ([M Ϫ 2ClO4]ϩ) and 1029.1 ([M Ϫ Cu Ϫ 2ClO4]ϩ).
Fourier-transform IR (KBr pellet): ν /cmϪ1 3063w, 2050s (νCO),
1987s (νCO), 1597m, 1567m, 1453s, 1089vs [ν(ClO4)], 773s, 304
[ν(Ru᎐Cl)] and 280 [ν(Ru᎐Cl)] (Found: C, 53.07; H, 3.52; N,
4.78. Calc. for C100H84Cl6Cu2N8O12P4Ru2: C, 53.25; H, 3.75; N,
4.97%).
1
Complex 1. H NMR (CDCl3) δ 9.48 (m, 1 H), 8.10 (m, 2
H), 7.90 (m, 2 H), 7.77 (m, 6 H), 7.52 (m, 2 H), 7.37 (m, 4 H),
3.58 (m, 2 H) and 2.93 (m, 2 H); 13C-{1H} NMR (CDCl3)
δ 162.73 (Cq), 155.22 (Cq), 153.13 (CH, bipy), 138.85 (CH,
2
bipy), 137.66 (CH, bipy), 133.00 [d, o-C of Ph, J(CP) 11],
3
130.03 (s, p-C of Ph), 128.12 [d, m-C of Ph, J(CP) 7], 126.85
(CH bipy), 126.28 (CH of bipy), 123.00 (CH of bipy), 120.90
(CH of bipy), 32.38 [CH2(bipy)] and 21.13 [d, CH2P, J(CP) 28
Hz]; 31P-{1H} NMR (acetone ϩ 10% [2H6]acetone) δ ϩ 47.6;
IR (KBr) ν /cmϪ1 3051.5w, 2956.1w, 1943s (CO), 1601.9m,
1455.8m, 1434.7m and 1103.4m; far IR 329s (Ru᎐Cl);
positive-ion FAB mass spectrum: m/z 568.0 (Mϩ, expected iso-
topic profile) and 533.1 (M Ϫ Cl) (Found: C, 52.63; H, 3.54;
N, 4.78. Calc. for C25H21Cl2N2OPRu: C, 52.83; H, 3.72; N,
4.93%).
Complex 5. A solution of [{RhCl(C2H4)2}2] (0.045 g, 0.115
mmol) in CH2Cl2 (5 cm3) was added at room temperature,
under argon, to a stirred solution of compound L (0.085 g,
0.230 mmol) in anhydrous CH2Cl2 (5 cm3). During addition the
solution turned red-green, then olive-green. After a few minutes
the flask was kept under partial vacuum and a white precipitate
began to form. After ca. 15 min the deep green coloration
disappeared and the white precipitate was collected by centri-
fugation and dissolved in CH2Cl2 (ca. 150 cm3). After filtration
Complex 2. 1H NMR (CDCl3) δ 9.37 (m, 1 H), 8.00 (m, 2 H),
7.75 (m, 2 H), 7.68 (m, 6 H), 7.45 (m, 2 H), 7.28 (m, 4 H), 3.48
(m, 2 H) and 2.85 (m, 2 H); 13C-{1H} NMR (CDCl3) δ 163.58
(Cq), 157.54 (Cq), 155.23 (CH of bipy), 140.56 (CH of bipy),
2
138.66 (CH of bipy), 129.23 [d, o-C of Ph, J(CP) 11], 129.25
J. Chem. Soc., Dalton Trans., 1997, Pages 3777–3784
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145; J. M. Brown, D. I. Hulmes and T. P. Layzell, J. Chem. Soc.,
hexane in excess was added to the resulting pale yellow solu-
tion resulting in the crystallisation of complex 5. After 2 d at
4 ЊC the precipitate was collected and dried under vacuum
affording the analytically pure white complex 5 (0.122 g, 90%);
Chem. Commun., 1993, 1673; S. D. Perera and B. L. Shaw, J. Chem.
Soc., Chem. Commun., 1994, 1201; R.-H. Uang, C.-K. Chan, S.-M.
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P. Rigo, J. Chem. Soc., Dalton Trans., 1993, 3001.
1
Rf = 0.57 on silica using CH2Cl2–MeOH (9 : 1 v/v). H NMR
(CDCl3): δ 9.83 (m, 1 H), 8.35 (8-line m, 3 H), 8.10 (10-line m,
4 H), 7.91 [d, 3J(HH) = 7.7 Hz, 1 H], 7.78 (12-line m, 5 H), 7.41
(m, 3 H), 4.06 (4-line m, 1 H, RhCH2Cl), 3.70 (8-line m, 1 H),
3.55–3.40 (m, 2 H) and 3.00–2.82 (m, 2 H). 31P-{1H} NMR
(CDCl3): δ ϩ28.3 [d, J(PRh) = 123 Hz]. Fourier-transform IR
(KBr pellet): ν /cmϪ1 2924m, 1603s, 1444s, 1401s, 1161s, 1101s
and 777s. Positive-ion FAB mass spectrum: m/z 555.0
([M Ϫ Cl]ϩ, expected isotopic profile), 506.0 ([M Ϫ Cl Ϫ CH2-
Cl]ϩ) and 471.1 ([M Ϫ 2Cl Ϫ CH2Cl]ϩ) (Found: C, 45.87; H,
3.53; N, 3.98. Calc. for C25H23Cl3N2PRhؒCH2Cl2: C, 46.15; H,
3.72; N, 4.14%).
3 A. A. Bahsoun and R. Ziessel, Nouv. J. Chim., 1985, 9, 225;
R. Ziessel, Tetrahedron Lett., 1989, 30, 463.
4 R. Ziessel, D. Matt and L. Toupet, J. Chem. Soc., Chem. Commun.,
1995, 2033.
Complex 6. To a suspension of complex 5 (0.075 g, 0.128
mmol) in CH2Cl2–ethanol (1 : 1, 20 cm3) was added AgO3-
SCF3 (0.035 g, 0.130 mmol) as a solid under argon. After
one night of heating at 60 ЊC, the starting complex was no
longer present according to TLC. After filtration of the
insoluble silver chloride, the solution was evaporated to dry-
ness and the residue purified by flash chromatography using a
0 to 2% gradient of methanol in CH2Cl2; Rf = 0.27 on silica
using CH2Cl2–MeOH (9 : 1 v/v). Recrystallisation from a
CH2Cl2–hexane mixture afforded the analytically pure com-
5 Th. Kauffmann, J. König and A. Waltermann, Chem. Ber., 1976,
109, 3864.
6 R. Colton and R. H. Farthing, Aust. J. Chem., 1967, 20, 1283.
7 MolView, J. M. Cense, Ecole Nationale Superieure de Chimie de
Paris, 1990.
8 E. M. Hyde, J. D. Kennedy and B. L. Shaw, J. Chem. Soc., Dalton
Trans., 1977, 1571.
9 M. J. Cleare and W. P. Griffith, J. Chem. Soc. A, 1969, 372; C. F. J.
Barnard, J. A. Daniels, J. Jeffery and R. J. Mawby, J. Chem. Soc.,
Dalton Trans., 1976, 953.
10 M.-N. Collomb-Dunand-Sauthier, A. Deronzier and R. Ziessel,
J. Chem. Soc., Chem. Commun., 1994, 189.
11 M.-N. Collomb-Dunand-Sauthier, A. Deronzier and R. Ziessel,
Inorg. Chem., 1994, 33, 2961.
12 S. Chardon-Noblat, A. Deronzier, D. Zsoldos, R. Ziessel,
M. Haukka, T. A. Pakkanen and T. Venäläinen, J. Chem. Soc.,
Dalton Trans., 1996, 2581.
13 S. Chardon-Noblat, M.-N. Collomb-Dunand-Sauthier, A. Deron-
zier, R. Ziessel and D. Zsoldos, Inorg. Chem., 1994, 33, 4410.
14 M.-N. Collomb-Dunand-Sauthier, A. Deronzier and R. Ziessel,
J. Electroanal. Chem., Interfacial Electrochem., 1993, 350, 43.
15 B. J. Hathaway, D. G. Holah and J. D. Poslethwaite, J. Chem. Soc.,
1961, 3215.
16 A. Bilyk and M. M. Harding, J. Chem. Soc., Dalton Trans., 1994, 77;
A. Bilyk, M. M. Harding, P. Turner and T. W. Hambley, J. Chem.
Soc., Dalton Trans., 1994, 2783.
17 D. Zurita, C. Scheer, J.-L. Pierre and E. Saint-Aman, J. Chem. Soc.,
Dalton Trans., 1996, 4331.
18 See, for example, Y. C. Lin, J. C. Calabrese and S. S. Wreford,
J. Organomet. Chem., 1983, 105, 1679; H. Werner, L. Hofmann,
R. Feser and W. Paul, J. Organomet. Chem., 1985, 281, 317;
B. Weinberger, G. Tanguy and H. DesAbbayes, J. Organomet.
Chem., 1985, 280, C31; T. B. Marder, W. C. Fultz, J. C. Calabrese,
R. L. Harlow and D. Milstein, J. Chem. Soc., Chem. Commun., 1987,
1543.
1
plex 6 as yellow crystals (0.048 g, 63%). H NMR (CDCl3):
δ 9.38 (m, 1 H), 8.14 (3-line m, 4 H), 8.05–7.92 (8-line m,
4 H), 7.84 (3-line m, 3 H), 7.36 (m, 5 H), 4.36 (m, 1 H, RhCH2-
OEt), 4.22 (m, 1 H, RhCH2OEt), 3.11 [8-line m, 2 H, (bipy)-
CH2CH2PPh2], 2.44 [m, 4 H, (bipy)CH2CH2PPh2 ϩ OCH2CH3]
3
and 0.33 [t, 3 H, J(HH) = 7 Hz, OCH2CH3]. 13C-{1H} NMR
(CDCl3): δ 131.7, 158.3, 155.3, 148.1, 139.1–121.7 (aromatic C),
72.0 [d, J(CRh) = 17, RhCH2O], 67.4 (s, OCH2CH3), 32.10 [d,
2
J(CP) = 54], 19.50 [d, J(CP) = 31 Hz] and 14.5 (s, OCH2CH3).
31P-{1H} NMR (CDCl3): δ 27.7 [d, J(PRh) = 132 Hz]. Fourier-
transform IR (KBr pellet): ν /cmϪ1 2977s, 1646m, 1453m,
1384m, 1262m, 1089m, 1048s and 880m. Positive-ion FAB mass
spectrum: m/z 565.1 ([M Ϫ Cl]ϩ, expected isotopic profile),
506.1 ([M Ϫ Cl Ϫ CH2OCH2CH3]ϩ) and 471.1 ([M Ϫ 2Cl-
Ϫ CH2OEt]ϩ) (Found: C, 51.21; H, 4.41; N, 4.21. Calc. for
C27H28Cl2N2OPRhؒ0.5CH2Cl2: C, 51.31; H, 4.54; N, 4.35%).
Acknowledgements
We are grateful to Dr. D. Soulivong and Ms. M. Hissler for the
measurement of some NMR and IR spectra.
19 J. Suffert, J. Org. Chem., 1989, 54, 509.
20 N. G. Walker and D. Stuart, DIFABS, Acta Crystallogr., Sect. A,
1983, 39, 158.
21 International Tables for X-Ray Crystallography, D. Riedel, Boston,
MA, 1983, p. 183.
22 C. K. Fair, MOLEN, An Interactive Intelligent System for Crystal
Structure Analysis, Enraf-Nonius, Delft, 1990.
References
1 See, for example, M. Grassi, G. DeMunno, F. Nicolo and S. Lo
Schiavo, J. Chem. Soc., Dalton Trans., 1992, 2367; G. Newkome,
Chem. Rev., 1993, 93, 2067; K. Tani, M. Yabuta, S. Nakamura and
T. Yamagata, J. Chem. Soc., Dalton Trans., 1993, 2781; P. Espinet,
P. Gómez-Elipe and F. Villafañe, J. Organomet. Chem., 1993, 450,
Received 10th April 1997; Paper 7/02463K
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J. Chem. Soc., Dalton Trans., 1997, Pages 3777–3784