Rhodium vinylidene and alkyne complexes containing a pendant uracil group

Article abstract of DOI:10.1016/j.jorganchem.2009.09.020

Reaction of HC{triple bond, long}CUr (Ur = uracil) with [RhCl(PiPr₃)₂] results in the formation of the vinylidene complex [RhCl(PiPr₃)₂({double bond, long}C{double bond, long}C{H}Ur)]. In the solid state this complex forms a hydrogen bonded network which consists of complementary interactions between uracil groups on neighbouring rhodium complexes and with the methanol of crystallisation. The η²-alkyne complexes [RhCl(PiPr₃)₂(η²-PhC{triple bond, long}CUr)] and [Rh(η⁵-C₅H₅)(PiPr₃)(η²-PhC{triple bond, long}CUr)] have also been prepared. In contrast to the behaviour of [Rh(η⁵-C₅H₅)(PiPr₃)(η²-PhC{triple bond, long}CUr)], [RhCl(PiPr₃)₂(η²-PhC{triple bond, long}CUr)] shows little evidence for the formation of hydrogen bonded aggregates in solution. The difference in behaviour between the two species is rationalised on the basis of steric effects.

Full text of DOI:10.1016/j.jorganchem.2009.09.020

Journal of Organometallic Chemistry 695 (2010) 18–25
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Rhodium vinylidene and alkyne complexes containing a pendant uracil group
*
Michael J. Cowley, Jason M. Lynam , Adrian C. Whitwood
Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 July 2009
Received in revised form 4 September 2009
Accepted 10 September 2009
Available online 17 September 2009
Reaction of HC„CUr (Ur = uracil) with [RhCl(PiPr3)2] results in the formation of the vinylidene complex
[RhCl(PiPr3)2(@C@C{H}Ur)]. In the solid state this complex forms a hydrogen bonded network which
consists of complementary interactions between uracil groups on neighbouring rhodium complexes
and with the methanol of crystallisation. The
g g
2-alkyne complexes [RhCl(PiPr3)2( 2-PhC„CUr)] and
[Rh(
[Rh(
g
g
5-C5H5)(PiPr3)(
g
g
2-PhC„CUr)] have also been prepared. In contrast to the behaviour of
5-C5H5)(PiPr3)(
2-PhC„CUr)], [RhCl(PiPr3)2( 2-PhC„CUr)] shows little evidence for the formation
g
Keywords:
Rhodium
Vinylidene ligands
Alkyne ligands
Uracil
of hydrogen bonded aggregates in solution. The difference in behaviour between the two species is
rationalised on the basis of steric effects.
Ó 2009 Elsevier B.V. All rights reserved.
Self-assembly
1. Introduction
Ur)(PPh3)2]+, alkynyl [Ru(
g
5-C5H5)(ÀC„CUr)(PPh3)2] and phos-
phonio-alkenyl [Ru(
g
5-C5H5)(ÀC{H}@C{PPh3}Ur)(PPh3)2]+ ligands
The synthesis of metal complexes which contain functional
groups in their secondary coordination sphere that are capable of
engaging in hydrogen bonding is an area of considerable current
interest [1]. For example, the use of functional groups which may
engage in self-complementary hydrogen bonding has been used
to dictate the assembly of inorganic complexes in the solid state
[2]. In addition, functional groups such as amino-pyridines [3]
and modified barbituates [4] have been used to develop novel an-
ion sensors [5] and complexes containing pendant nucleobase
units have been developed as biological probes [6] and novel ther-
apeutic agents [7].
[10,11]. All of these complexes show evidence of aggregation in
solution and the solid state structures of the carbene and phospho-
nio-alkenyl complexes show a dimeric arrangement of the uracil
groups. In addition, we have prepared a gold complex containing
a uracil-substituted phosphine, viz. [AuCl(PPh2Ur)] [12]. In this
case the uracil groups form a hydrogen bonded tape structure uti-
lising both N–H and C@O functional groups of the nucleobase. The
tape structures pack in such a manner as to create a cavity of
dimensions 11.720 and 11.4547 Å which is occupied by THF mole-
cules of crystallisation.
As there are many possible applications of metal complexes
containing pendant nucelobase groups, the development of versa-
tile synthetic routes to these species is an important goal. As part of
our programme utilising substituted alkynes to achieve the facile
incorporation of uracil groups into the periphery of different me-
tal-containing compounds, the series of rhodium complexes based
on the RhCl(PR3)2 motif pioneered by Werner and co-workers were
targeted as possible supports for the nucleobase [13]. Using termi-
nal alkynes a series of complexes containing alkyne, A, alkynyl
hydride AH, and vinylidene, V, ligands have been prepared
(Fig. 1) and their mechanism of interconversion has been probed
in recent theoretical [14–16] and experimental studies [17–19].
These results demonstrate that the conversion from A to AH and
V occurs in a unimolecular fashion and the formation of the vinyl-
idene complexes is essentially irreversible. The use of internal al-
kynes such as PhC„CPh prohibits the formation of alkynyl
We have previously demonstrated that the incorporation of
pendant uracil groups into metal complexes may be employed to
direct self assembly in the solid state and solution [8]. For example,
reaction of [RuCl(
kyne HC„CUr in the presence of a suitable halide scavenger results
in the formation of [Ru(
5-C5H5)(@C@C{H}Ur)(PPh3)2]+. This reac-
g
5-C5H5)(PPh3)2] with the uracil-substituted al-
g
tion is highly selective and we reasoned that the soft metal–sub-
strate reacts selectively with the C„C functionality of the alkyne
rather than the hard N and O donor atoms of the uracil. By virtue
of hydrogen bonds between the uracil groups, [Ru(g5
-
C5H5)(@C@C{H}Ur)(PPh3)2]+ self-assembles in the solid state to
give hexagonal arrays containing six ruthenium cations [9]. This
vinylidene complex acts as a precursor to a range of uracil-substi-
tuted complexes containing carbene [Ru(g
5-C5H5)(@C{OMe}CH2-
hydride and vinylidene complexes and the resulting
p-alkyne spe-
* Corresponding author. Tel.: +44 1904432534.
E-mail address: jml12@york.ac.uk (J.M. Lynam).
cies [RhCl(PiPr3)2(
g
2-PhC„CPh)] may prepared which, on reaction
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.09.020

M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
19
are typical for vinylidene ligands supported by the RhClL2 motif
[13b,18]. In addition, a series of resonances for the uracil substitu-
ent were observed in the 1H NMR spectrum notably resonances for
the two N–H protons of the uracil group were observed at d = 10.16
and 9.56 as well as a peak for the C–H(5) proton at d 7.06 (d,
3JHH = 5.2 Hz): a series of resonances for this group were also ob-
served in the 13C{1H} NMR spectrum.
Recrystallisation of 3 from methanol at À20 °C resulted in the
formation of crystals of the complex suitable for study by single
crystal X-ray diffraction. The resulting structural determination
demonstrated that 3 crystallised as a MeOH solvate in the ortho-
rhombic space group Pbca: an ORTEP diagram of the asymmetric unit
of 3ÁMeOH is shown in Fig. 2. Complex 3 adopts a square planar
geometry with mutually trans phosphine ligands. The bond lengths
and angles within the vinylidene ligands are typical with short
Rh(1)–C(1) (1.791(3) Å) and C(1)–C(2) (1.319(4) Å) distances and
an essentially linear vinylidene geometry (Rh(1)–C(1)–C(2)
179.5(3)°). The uracil and hydrogen atom attached to the vinyli-
dene ligand lie in a plane which is perpendicular to the square
plane containing the rhodium. Indeed, the structural metrics
Fig. 1. Structures of rhodium alkyne (A), alkynyl hydride (AH) and vinylidene (V)
complexes.
with NaCp, may be converted into the corresponding half sandwich
complexes [RhCl(g g
5-C5H5)(PiPr3)( 2-PhC„CPh)] [20].
We now report the reaction of the uracil-substituted alkynes
HC„CUr and PhC„CUr with the RhCl(PR3)2-system to give vinyli-
dene
[RhCl(PiPr3)2(
shown to react with NaC5H5 to afford [RhCl(
[RhCl(PiPr3)2(@C@C{H}Ur)]
and
alkyne
complexes
g
2-PhC„CUr)], respectively. The latter was also
g
5-C5H5)(PiPr3)(g2
-
PhC„CUr)].
2. Results and discussion
and topology of
3 are essentially identical to [RhCl(PiPr3)2-
(@C@C{H}Me)] reported by Werner [13b]. The bond lengths and
angles within the uracil group are also typical: H(1) and H(2A)
were located in the electron difference map and refined as part
of the structural solution.
The synthetic routes employed to prepare all of the complexes
reported in this study are shown in Scheme 1. The compounds
were characterised principally by multinuclear NMR spectroscopy,
IR spectroscopy and mass spectrometry: the structure of
[RhCl(PiPr3)2(@C@C{H}Ur)] was also determined by single crystal
X-ray diffraction.
As is the case in all the uracil-containing complexes we have
prepared to date, the solid state structure of 3 exhibits a series of
intermolecular hydrogen bonding interactions. The uracil groups
on neighbouring molecules of 3 engage in a complementary hydro-
gen bonding interaction between C@O(2) and N(2)–H(2A) (N(2)–
H(2A)Á Á ÁO(2) 2.786(3) Å), Fig. 3a. This type of hydrogen bonding
interaction between uracil groups has been observed as part of a
larger construct in the case of AuCl(PPh2Ur) [12]. In organometallic
complexes, dimeric arrays based on complementary hydrogen
bonds between C@O(4) and N(2)–H(2a) have been observed in sev-
eral cases, although in these instances the complexes are cationic
with the anion being involved in hydrogen bonding to N–H(1)
[9–11]. In the case of complex 3, each uracil group is involved in
hydrogen bonding to two molecules of MeOH:N–H(1) acts as a
hydrogen bond donor to the oxygen atom, O(3), of the MeOH
(N(1)–H(1)Á Á ÁO(3) 2.732(3) Å), whereas C@O(4) acts as hydrogen
bond acceptor with the hydroxyl proton of a second methanol mol-
ecule (O(3)–H(3)Á Á ÁO(1) 2.730(3) Å).
2.1. Synthesis and structure of [RhCl(PiPr3)2(@C@C{H}Ur)], 3
Reaction of HC„CUr, 1, with [RhCl(PiPr3)2], 2, (prepared in situ
from the reaction of [Rh(coe)2(l-Cl)]2and excess PiPr3, coe = cyclo-
octene), in THF solution resulted in an immediate colour change
from dark violet to bright orange: over the course of 30 min a final
colour change to violet/dark green was observed. After 16 h, the
reaction mixture was subjected to a work-up procedure to afford
a blue/green precipitate of [RhCl(PiPr3)2(@C@C{H}Ur)], 3. The pres-
ence of the vinylidene ligand in 3 was confirmed by resonances in
1
the 13C{1H} NMR spectrum at
d
295.50 (dt, JCRh = 58.3 Hz,
2JCP = 15.8 Hz) and 99.71 (dt, JCRh = 15.9 Hz, JCP = 6.3 Hz) for the
2
2
a
- and b-carbons, respectively. A triplet resonance was observed
4
at d 1.30 (t, JHP = 3.0 Hz) in the 1H NMR spectrum for the proton
attached to the b-carbon of the vinylidene ligand. These resonances
Scheme 1. (i) + Excess PiPr3; (ii) + 1, THF; (iii) + PhC„CUr, THF; and (iv) + NaCp.

20
M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
sional array of uracil and methanol groups is present. The uracil
groups are present in two distinct planes (Fig. 3b): in each plane ura-
cil groups are present that are engaged in complementary hydrogen
bonding. The angle between the planes is ca. 64° and uracil groups in
the respective planes are bridged by the methanol of crystallisation
which acts as a both a hydrogen bond donor and acceptor to two dif-
ferent uracil groups. One important facet of this structure is that
both of the uracil hydrogen bond donor and both acceptor groups
are employed in the creation of the network. This ensures that the
maximum number of hydrogen bonding interactions are present,
which is consistent with our results which show that, within the
confines of steric hindrance, this is tends to be the case.
2.2. Synthesis and solution state behaviour of [RhCl(PiPr3)2(g2
PhC„CUr)], 4
-
Reaction of in situ-prepared 2 with PhC„CUr in THF solution re-
sulted in the formation of [RhCl(PiPr3)2(
2-PhC„CUr)], 4, in good
yield. This method is analogous to that employed by Werner for
the formation of [RhCl(PiPr3)2(
2-PhC„CPh)] [20], although this
g
Fig. 2. ORTEP representation of 3ÁMeOH, thermal ellipsoids shown at the 50%
probability level and selected hydrogen atoms omitted for clarity. Selected bond
lengths (Å) and angles (°): C(1)–Rh(1) 1.791(3), P(1)–Rh(1) 2.3598(7), P(2)–Rh(1)
2.3624(7), Cl(1)–Rh(1) 2.3735(7) C(1)–C(2) 1.319(4), C(2)–C(3) 1.464(4),C(3)–C(5)
1.350(4), C(3)–C(4) 1.464(4), C(4)–O(1) 1.221(3),C(4)–N(2) 1.382(3), C(5)–N(1)
1.375(3), C(6)–O(2) 1.234(3) C(6)–N(1) 1.352(3), C(6)–N(2) 1.376(4), N(1)–H(1)
0.9030, N(2)–H(2A) 0.8890. C(1)–Rh(1)–P(1) 89.94(8), C(1)–Rh(1)–P(2) 90.00(8),
P(1)–Rh(1)–P(2) 178.93(3), C(1)–Rh(1)–Cl(1) 177.43(9), P(1)–Rh(1)–Cl(1) 89.45(2),
P(2)–Rh(1)–Cl(1) 90.57(2), C(1)–C(2)–C(3) 124.4(3), C(5)–C(3)–C(4) 117.4(2), C(5)–
C(3)–C(2) 124.8(2), C(4)–C(3)–C(2) 117.8(2), O(1)–C(4)–N(2) 120.2(2), O(1)–C(4)–
C(3) 124.9(3), N(2)–C(4)–C(3) 114.9(2), C(3)–C(5)–N(1) 123.3(2), O(2)–C(6)–N(1)
122.4(3), O(2)–C(6)–N(2) 122.5(2), N(1)–C(6)–N(2) 115.1(2), C(6)–N(2)–H(2A)
112.9, C(4)–N(2)–H(2A) 120.1.
g
latter case the reaction was performed in pentane – which is pre-
cluded in this instance due to the insolubility of PhC„CUr in this
solvent. The 1H NMR spectrum of 4 recorded in d8-THF solution
exhibited the expected series of resonances. Notably, the N–H res-
onances of the uracil group were observed at d 10.33 (d, br,
3JHH = 5.43 Hz, NH(1)) and 10.31 (s, br, NH(3)): the assignment of
these resonances was confirmed with the aid of a 1H–1H COSY
experiment which demonstrated that the peak at d 10.33 was cou-
pled to the proton in the 5-position of the uracil group (d 8.44, d,
3JHH = 5.43 Hz). The presence of the
g
2-alkyne ligand was con-
firmed by resonances in the 13C{1H} NMR spectrum at d 81.07
1
2
1
(dt, JCRh = 14.8 Hz, JCP = 2.4 Hz) and 68.76 (dt, JCRh = 16.2 Hz,
2JCP = 2.3 Hz). As in the case of complex 3, the NMR data for 4 clo-
sely match those observed for the aryl-substituted analogues indi-
cating that the incorporation of the uracil group does not
significantly alter either the structure of the complex or the nature
of the bonding between the organic ligand and the metal.
Despite repeated attempts, we have been unable to grow a crys-
tal of 4 suitable for study by single crystal X-ray diffraction. There-
fore, in order to probe any aggregation effects induced by the uracil
group a series of 1H NMR spectra of 4 were recorded at a range of
concentrations in d8-THF solution (Fig. 4a). Considering dimeric
structures alone, there are six possible interaction by which the
uracil group may become engaged in complementary N–HÁ Á ÁO@C
hydrogen bonding (Fig. 5). Hydrogen bonded dimers with struc-
tures A, B and C have been observed by low temperature NMR
experiments on substituted uracil and 1-methylthymine [21].
The experiments indicate that there is little difference in energy
between the three motifs which is supported by theoretical calcu-
lations on the self-aggregation of 1-methylthymine which indicate
only a 0.1 kcal molÀ1 difference in energy between the three forms
[22]. In addition, NMR studies performed on 1-cyclohexyluracil
have demonstrated that both C@O(2) and C@O(4) may act as
hydrogen bond acceptors [23]. Furthermore, calculations on the
hydrogen bonding between uracil and water illustrate that there
is a similar difference in energy between the binding of water to
N–H(1) or N–H(3) [22]. These data indicate that, in principle, the
formation of hydrogen bonded dimers may occur by any of the
six modes A–F in Fig. 5.
Fig. 3. (a) Hydrogen bonding interactions between 3 and MeOH. (b) Extended
hydrogen bonding motif in 3.MeOH viewed down the b-axis of the unit cell. For
clarity, the RhCl(PiPr3)2 unit is represented by purple spheres.
Our previous studies on ruthenium complexes containing pen-
dant uracil groups had demonstrated that the N–H protons of the
uracil groups were a useful probe of aggregation processes occur-
ring in solution [9–11]. By examining the changes in chemical shift
of the N–H protons of the uracil group we have obtained evidence
for all six modes being present in the various ruthenium complexes
we have studied [9–11]. In the case of complex 4 it is evident that
An extended view of the structure (Fig. 3b) demonstrates that a
series of domains are present. One series of domains contains the
non-polar regions of the rhodium complexes, whereas the others
contain the polar uracil and methanol molecules. The clustering of
polar and non-polar regions is common in structures containing
pendant uracil groups [8,12]. Within the polar domain a two dimen-

M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
21
Fig. 4. (a) NH region of the 1H NMR spectrum of 4 recorded at a range of concentrations in d8-THF solution. (b) Graph of chemical shift of N–H resonances versus
concentration.
the changes in chemical shift of the two N–H protons on increasing
the concentration are small. Indeed, between the least (6.1 mM)
and most (196.7 mM) concentrated solutions the proton for N–
and given that the changes in chemical shift for both NH protons
are similar over the concentration range studied aggregation may
be occurring by any, or indeed all, of the binding modes in Fig. 5.
H(1) exhibited
a downfield shift from d 10.30 to 10.37
2.3. Synthesis and solution state behaviour of [Rh(g -
5-C5H5)(PiPr3)(g2
PhC„CUr)], 5
(0.07 ppm): for N–H(3) the corresponding shift is from d 10.21 to
10.32 (0.11 ppm). Although the resonances for N–H(3) shows
greater changes in chemical shift at lower concentrations
(Fig. 4b) it must be emphasised that they are extremely small par-
ticularly when compared to the ruthenium complexes, albeit typi-
cally recorded in CD2Cl2 solution, where changes in chemical shift
of 1 ppm are typical even when smaller concentrations ranges are
employed. Unfortunately, the poor solubility of 5 in CH2Cl2 pre-
cluded any direct comparison of the ruthenium- and rhodium-con-
taining systems. These data therefore appear to indicate that the
extent of aggregation exhibited by 4 is limited in THF solution,
The cyclopentadienyl-containing complex [Rh(
g
2-PhC„CUr)], 5, was prepared from the reaction of a THF solu-
g
5-C5H5)(PiPr3)-
(
tion of 4 with 2 equiv. of NaC5H5 in an analogous manner to that
reported by Werner et al. [20]. After stirring for 10 h the solvent
was removed in vacuo and the resulting solid washed with hexane.
Complex 5 was obtained as a yellow solid by precipitation from
THF solution of the complex with hexane and characterised by
1H and 31P{1H} NMR spectroscopy.

22
M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
Fig. 5. Possible dimeric hydrogen bonding arrangements for complexes with pendant uracil groups. [Rh] = RhCl(PiPr3)2(@C@C{H}), 3, [RhCl(PiPr3)2(
C5H5)(PiPr3)(
2-PhC„C–)], 5.
g -
2-PhC„C–)], 4, [Rh(g5
g
In contrast to 4, the NMR spectra of 5 exhibited the effects of
intermolecular hydrogen bonding. The NMR spectra of 5 recorded
in d4-methanol solution were sharp. For example, the 31P{1H}
NMR spectrum exhibited a resonance at d 72.63 (1JPRh = 203.7 Hz),
Fig. 6a. In addition, the 1H NMR spectrum confirmed the presence
of the pertinent structural features in 5. For example, a singlet res-
onance due to the cyclopentadienyl group was observed at d 5.31,
as were resonances for the two N–H groups at 8.42 and 7.90 and
fact that the uracil group will sit in a plane between two sterically
demanding PiPr3 groups inhibits aggregation. In the case of 5, one
of the PiPr3 groups has been removed and the uracil group is now
orientated away from this ligand and as such may more freely en-
gage in hydrogen bonding.
3. Conclusions
3
the resonance for the C–H(5) group at d 8.10 (d, JHH = 7.9 Hz). In
In this manuscript we have demonstrated that the reactions of
uracil-substituted alkynes with the low valent, electron-rich rho-
dium precursor 2 exhibit few differences when compared to simple
aryl- and alkyl-substituted analogues. The crystal structure of 3
demonstrates that non-covalent interactions may play an impor-
tant role in the assembly of organometallic complexes in the solid
state. It is also evident that steric effects have an important role in
determining the modes of assembly in complexes such as this.
When the uracil group is remote from the metal (as in 3) then all
of the functional groups may be utilised in hydrogen bonding.
The same effects appear to occur in solution, in more hindered sit-
uations such as 4 aggregation appears to be very limited, whereas
in 5 more pronounced intermolecular interactions are present.
contrast recording the 31P{1H} and 1H NMR spectra in d8-THF solu-
tion resulted in an extremely broad series of resonances. For exam-
ple, the 31P{1H} NMR spectrum of 5 exhibited an extremely broad
resonance at d 73.08 (1JPRh = 211.3 Hz), Fig. 6b. The 1H NMR spec-
trum was similarly broad.
We have interpreted these data in the following manner. In
MeOH solution the uracil group is able to engage in hydrogen
bonding to the solvent, as has been demonstrated in the structure
of complex 3, MeOH is able to act as both hydrogen bond acceptor
and donor to this functional group. Therefore, little aggregation be-
tween uracil groups on different molecules is observed. In contrast,
in THF solution, the solvent is not able to participate in significant
interaction with the uracil and hence the structure in solution is
dominated by hydrogen bonding between uracil groups. As this
hydrogen bond may occur via several different modes and, in prin-
ciple, aggregates with different nuclearity may also be present,
broadening of the 31P{1H} NMR spectra occurs. We have observed
almost identical effects in the NMR spectra of the alkynyl complex
4. Experimental
4.1. General considerations
[Ru(–C„CUr)(
g
5-C5H5)(PPh3)2] [11].
All experimental procedures were performed under an atmo-
sphere of dinitrogen or argon using standard Schlenk line and
glove box techniques. Solvents were purified by distillation under
argon prior to use from appropriate drying agents (MeOH from
Mg/I2, THF and hexane from Na wire). The d8-THF used for NMR
experiments was dried over potassium metal and degassed with
three freeze-pump-thaw cycles. The compounds HC„CUr, 1 [24],
It is interesting to compare the aggregation behaviour exhibited
by 4 and 5 in THF solution. In the case of the former little evidence
for hydrogen bonding was obtained whilst the opposite is true of
the latter. As discussed above, our previous studies have indicated
that, within steric constraints, the uracil group strives to employ all
of its N–H and C@O groups in hydrogen bonding in both the solid
state and solution. Therefore, we propose that in the case of 4 the
and [Rh(l-Cl)(coe)2]2 [25] were prepared according to published

M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
23
Fig. 6. (a) 31P{1H} NMR spectrum of 5 in MeOD. (b) 31P{1H} NMR spectrum of 5 in d8-THF.
procedures, PhC„CUr was provided by Dr Benjamin Moulton and
was obtained from the Sonogashira reaction of PhC„CH with
IUr. NMR spectra were acquired on a Bruker AV 500 spectrometer
(Operating Frequencies 1H 500.13 MHz, 31P 202.47 MHz) or a Bru-
ker Avance 700 Spectrometer (Operating Frequencies 1H
700.13 MHz, 31P 283.46 MHz). Solution state NMR studies were
performed using standard d8-THF or d4-methanol solutions of 4
and 5 made to the appropriate concentrations by using serial dilu-
tion. IR spectra were acquired using a Mattson Research Series FTIR
spectrometer using solution state cells. Mass spectrometry mea-
surements were performed on Bruker MicroTOF instrument and
data for the peak at highest m/z are reported. Attempts to obtain
satisfactory combustion analyses were unsuccessful.
ing a saturated solution in methanol, filtering off the solid and stor-
ing the filtrate at À20 °C for several days. Yield 194 mg, 64%.
1H NMR: (d8-THF, 300 K) d = 10.16 (s, 1H, NH), 9.56 (s, 1H, NH),
3
7.06 (d, JHH = 5.2 Hz, 1H, uracil C5H), 2.77 (m, 6H, PCHCH3), 1.35
3
3
4
(dd, JHP = 13.7 Hz, JHH = 6.8, 36 H, PCHCH3), 1.30 (t, JHP = 3.0 Hz,
1H, Rh@C@C(H)Ur). 31P{1H} NMR: (d8-THF, 300 K) d = 42.51
(d,1JRhP = 134.2 Hz, PiPr3). 13C{1H} NMR: (d8-THF, 300 K)
1
2
d = 295.50 (dt, JCRh = 58.3 Hz, JCP = 15.8 Hz, Rh@C), 161.25 (s,
C@O), 150.20 (s, C@O), 132.72 (s, Ur C5H), 99.71 (dt, 2JCRh = 15.9 Hz,
2JCP = 6.3 Hz, Rh@C@C), 96.18 (s, Ur C1), 23.48 (vt, J = 10 Hz, PC),
19.63 (s, PCHCH3). IR: (THF) 2962 cmÀ1
,
2906 cmÀ1 (NH);
1703 cmÀ1, 1647 cmÀ1(CO); 1622 cmÀ1 (C@C). ESI mass spectrum:
(MeOH, positive mode) m/z = 559.2093 (Calc. for C24H46N2O2P2Rh
[MÀClÀ] 559.2084).
4.2. Synthesis of [RhCl(PiPr3)2(@C@{H}Ur)], 3
4.3. Synthesis of [RhCl(PiPr3)2(
g
2-PhC„CUr)], 4
[Rh(l-Cl)(coe)2]2 (250 mg, 0.35 mmol) was placed in a Schlenk
[Rh( -Cl)(coe)2]2 (250 mg, 0.35 mmol) was placed in a Schlenk
l
tube and suspended in THF. PiPr3 (0.5 mL, 2.5 mmol) was added
rapidly to the solution, whereupon the solution underwent a col-
our change from orange to dark violet. After stirring for 10 min,
2 equiv. HC„CUr (95 mg, 0.7 mmol) were added to the solution,
which turned orange immediately, turning dark green/purple after
30 min. After stirring for 16 h, the solution was filtered and the sol-
vent removed in vacuo. The oily residue was washed with hexane
(2 Â 10 mL) and then redissolved in THF (20 mL). The THF solution
was triturated with hexane to give a blue/green precipitate. The so-
lid was isolated by filtration and washed with hexane (3 Â 10 mL),
then dried under vacuum. The complex was crystallized by prepar-
tube and suspended in THF (20 mL). PiPr3 (0.5 mL, 2.5 mmol) was
added rapidly to the solution, whereupon the solution underwent
a colour change from orange to dark violet. After stirring for
10 min, 2 equiv. PhC„CUr (148 mg, 0.7 mmol) was added to the
solution, which turned orange immediately. After stirring for
16 h, the solution was filtered and the solvent removed in vacuo.
The oily residue was washed with hexane (2 Â 10 mL) and then
redissolved in THF (20 mL). The product was precipitated from
the resulting THF solution by addition of hexane and isolated by fil-
tration. The yellow solid was washed with hexane (3 Â 10 mL),
then dried under vacuum. Yield 364 mg, 77%.

24
M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
1H NMR: (d8-THF , 300 K) d = 10.33 (d, br, 3JHH = 5.43 Hz, NH(1)),
Acknowledgements
3
10.31 (s, br, NH(3)), 8.51 (d, JHH = 7.7 Hz, 2H ortho-Ph), 8.44 (d,
3
3JHH = 5.43 Hz, 1H, Ur C5H), 7.21 (t, JHH = 7.6 Hz, 2H, meta-Ph),
We thank the EPSRC and University of York (DTA studentship to
MJC) for funding and Dr Benjamin Moulton for the sample of
PhC„CUr.
3
7.11 (t, JHH = 7.3 Hz, 1H, para-Ph), 2.26 (m, 6H PCH), 1.23 (dvt,
36 H, PCH(CH3)2). 31P{1H} NMR: (d8-THF, 300 K) d = 29.13 (d,
2JPRh = 116.5 Hz, PiPr3). 13C{1H} NMR: (d8-THF, 300 K) d = 161.04
(s, C@O), 151.20 (s, C@O), 143.52 (s, Ur C5H), 133.36 (s, ortho-
Ph), 131.14 (Ph C1), 127.76 (s, meta-Ph), 126.73 (s, para-Ph),
Appendix A. Supplementary material
1
2
105.99 (Ur C1), 81.07 (dt, JCRh = 14.8 Hz, JCP = 2.4 Hz, C„C),
1
2
CCDC 734602 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.09.020.
68.76 (dt, JCRh = 16.2 Hz, JCP = 2.3 Hz, C„C), 25.07 (s. PC), 21.08
(d, JCP = 8.07 Hz, PCH(CH3)2). IR: (THF) 3056 cmÀ1, 2929 cmÀ1
2
(NH), 1881 cmÀ1
, ,
1867 cmÀ1 (C@C), 1715 cmÀ1 1690 cmÀ1
(C@O), 1662 cmÀ1 (C@C). ESI mass spectrum: (MeOH, positive
mode) m/z = 635.2403 (Calc. for C30H50N2O2P2Rh [MÀClÀ]
635.2397).
4.4. Synthesis of [Rh(
g g
5-C5H5)(PiPr3)( 2-PhC„CUr)], 5
References
[RhCl(PiPr3)2(
g
2-PhC„CUr)] (70 mg, 0.104 mmol) was dis-
[1] (a) D.B. Grotjahn, Chem. Eur. J. 11 (2005) 7146;
solved in THF (15 mL). NaCp (0.1 mL of a 2 M solution in THF,
2 equiv, 0.200 mmol) was added to the stirred solution. The orange
solution was stirred for 10 h during which time it became darker in
colour. The solvent was removed in vacuo and the solid residue was
washed with hexane (3 Â 10 mL). The orange solid remaining was
extracted with THF. The product was precipitated from the result-
ing THF solution by addition of hexane and isolated by filtration.
1H NMR: (d4-MeOH, 300 K) d = 8.42 (s, NH), 8.10 (d,
3JHH = 7.9 Hz, Ur C5H), 7.90 (s, NH), 7.45 (d, J = 7.8 Hz, 1H, Ph),
7.30–7.22 (m, 2H, Ph), 7.16 (t, J = 7.3 Hz, 1H, Ph), 6.99 (t,
(b) K. Severin, Chem. Commun. (2006) 3859.
[2] (a) A.D. Burrows, C.-W. Chan, M.M. Chowdhry, J.E. McGrady, D.M.P. Mingos,
Chem. Soc. Rev. 24 (1995) 329;
(b) D. Braga, F. Grepioni, G.R. Desiraju, Chem. Rev. 98 (1998) 1375;
(c) A.M. Beatty, Coord. Chem. Rev. 246 (2003) 131;
(d) L. Brammer, Chem. Soc. Rev. 33 (2004) 476;
(e) D. Braga, M. Polito, F. Grepioni, Cryst. Growth Des. 4 (2004) 769;
(f) M. Oh, G.B. Carpenter, D.A. Sweigart, Acc. Chem. Res. 37 (2004) 1;
(g) S.U. Son, J.A. Reingold, G.B. Carpenter, D.A. Sweigart, Chem. Commun.
(2006) 708;
(h) J.A. Reingold, S.U. Son, S.B. Kim, C.A. Dullaghan, M. Oh, C. Frake, G.B.
Carpenter, D.A. Sweigart, Dalton Trans. (2006) 2385.
[3] (a) K.J. Wallace, R. Daari, W.J. Belcher, L.O. Abouderbala, M.G. Boutelle, J.W.
Steed, J. Organometal. Chem. 666 (2003) 63;
(b) S.J. Dickson, S.C.G. Biagini, J.W. Steed, Chem. Commun. (2007) 4955.
[4] (a) J.-L. Fillaut, J. Andriès, L. Toupet, J.-P. Desvergne, Chem. Commun. (2005)
2924;
(b) J.-L. Fillaut, J. Andriès, J. Perruchon, J.-P. Desvergne, L. Toupet, L. Fadel, B.
Zouchoune, J.-Y. Saillard, Inorg. Chem. 46 (2007) 5922.
[5] P.D. Beer, P.A. Gale, Angew. Chem., Int. Ed. 40 (2001) 486.
[6] [a] D.J. Hurley, Y. Tor, J. Am. Chem. Soc. 120 (1998) 2194;
(b) S.I. Khan, A.E. Beilstein, G.D. Smith, M. Sykora, M.W. Grinstaff, Inorg. Chem.
38 (1999) 2411;
2
J = 7.0 Hz, 1H, Ph), 5.31 (d, JHRh = 9.7 Hz, C5H5), 1.85 (m, 3H,
PCH(CH3)2) 1.03 (dq, J = 21.2 Hz, 7.16 Hz, 9H, PCH(CH3)2). 31P{1H}
(d4-MeOH, 300 K) d = 72.63 (1JPRh = 203.7 Hz). IR: (THF)
1726 cmÀ1 (br, C@O). ESI mass spectrum: (MeOH, positive ion
mode) m/z = 541.1504 (Calc. for C26H35N2O2PRh [M+H+]
541.1486).
(c) S.I. Khan, A.E. Beilstein, M.W. Grinstaff, Inorg. Chem. 38 (1999) 418;
(d) S.I. Khan, A.E. Beilstein, M.T. Tierney, M. Sykora, M.W. Grinstaff, Inorg.
Chem. 38 (1999) 5999;
4.5. Details of X-ray diffraction experiment
(e) C.J. Yu, H. Wang, Y. Wan, H. Yowanto, J.C. Kim, L.H. Donilon, C.L. Tao, M.
Strong, Y. Chong, J. Org. Chem. 66 (2001) 2937;
Diffraction data were collected at 110 K on a Bruker Smart Apex
diffractometer with Mo K
a radiation (k = 0.71073 Å) using a
ˇ
ˇ
ˇ
ˇ
(f) M. Hocek Štepnicka, J. Ludvík, I. Císarová, I. Votruba, D. Reha, P. Hobza,
Chem. Eur. J. 10 (2004) 2058;
SMART CCD camera. Diffractometer control, data collection and
initial unit cell determination was performed using ‘‘SMART” [26].
Frame integration and unit cell refinement software was carried
out with ‘‘SAINT+” [27]. Absorption corrections were applied by SAD-
ABS (v2.03, SHELDRICK). Structures were solved by direct methods
using SHELXS-97 [28] and refined by full-matrix least-squares using
SHELXL-97 [29]. All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were placed using a ‘‘riding model” and in-
cluded in the refinement at calculated positions.
(g) A.R. Pike, L.C. Ryder, B.R. Horrocks, W. Clegg, B.A. Connolly, A. Houlton,
Chem. Eur. J. 11 (2005) 344;
(h) H. Song, X. Li, Y. Long, G. Schatte, H.-B. Kraatz, Dalton Trans. (2006) 4696;
ˇ
(i) M. Vrábel, M. Hocek, L. Havran, M. Fojta, I. Votruba, B. Klepetárová, R. Pohl,
L. Rulíšek, L. Zendlová, P. Hobza, I. Shih, E. Mabery, M. Rackman, Eur. J. Inorg.
Chem. (2007) 1752.
[7] (a) N. Esho, B. Davies, J. Lee, R. Dembinski, Chem. Commun. (2002) 332;
(b) M. Etheve-Quelquejeu, J.-P. Trachier, F. Rose-Munch, E. Rose, L. Naesens, E.
De Clercq, Organometallics 26 (2007) 5727;
(c) C.D. Sergeant, I. Ott, A. Sniady, S. Meneni, R. Gust, A.L. Rheingold, R.
Dembinski, Org. Biomol. Chem. 6 (2008) 73.
Empirical formula C25H50ClN2O3P2Rh, formula weight 626.97,
temperature 110(2) K, k = 0.71073 Å, crystal system orthorhombic,
space group Pbca, a = 9.8959(5) Å, b = 15.7711(7) Å, c =
40.0113(19) Å. V = 6244.5(5) Å3, Z = 8, Dcalc = 1.334 mg/m3, absorp-
tion coefficient 0.761 mmÀ1, F(0 0 0) = 2640, crystal size 0.16 Â
0.12 Â 0.05 mm3, theta range for data collection 1.02–28.28°, index
ranges À13 6 h 6 13, À20 6 k 6 20, À53 6 l 6 53, reflections
collected 61 314, independent reflections 7733 (Rint = 0.0650),
completeness to u 28.28° = 99.9%, absorption correction: semi-
empirical from equivalents, max and min transmission = 0.963
and 0.856, refinement method: full-matrix least-squares on F2,
data/ restraints/parameters 7733/0/323, goodness-of-fit (GOF) on
[8] J.M. Lynam, Dalton Trans. (2008) 4067.
[9] M.J. Cowley, J.M. Lynam, A.C. Whitwood, Dalton Trans. (2007) 4427.
[10] H. Hamidov, J.C. Jeffery, J.M. Lynam, Chem. Commun. (2004) 1364.
[11] M.J. Cowley, J.M. Lynam, R.S. Moneypenny, A.C. Whitwood, A.R. Wilson, Dalton
Trans., in press, doi:10.1039/B912855G.
[12] T.D. Nixon, L.D. Dingwall, J.M. Lynam, Adrian C. Whitwood, Chem. Commun.
(2009) 2890.
[13] (a) J. Wolf, H. Werner, O. Serhadli, M.L. Ziegler, Angew. Chem., Int. Ed. Engl. 22
(1983) 414;
(b) F.J.G. Alonso, A. Höhn, J. Wolf, H. Otto, H. Werner, Angew. Chem., Int. Ed.
Engl. 24 (1985) 406;
(c) H. Werner, J. Wolf, F.J.G. Alonso, M.L. Ziegler, O. Serbadli, J. Organometal.
Chem. 336 (1987) 397;
(d) H. Werner, F.J.G. Alonso, J. Otto, J. Wolf, Z. Naturforsch. B 43 (1988) 722;
(e) H. Werner, U. Brekau, Z. Naturforsch. B 44 (1989) 1439;
(f) T. Rappert, O. Nürnberg, N. Mahr, J. Wolf, H. Werner, Organometallics 11
(1992) 4156;
(g) H. Werner, T. Rappert, M. Baum, A. Stark, J. Organometal. Chem. 459 (1993)
319;
F2 1.063, final R indices [I > 2
r(I)] R1 = 0.0369, wR2 = 0.0787, R indi-
ces (all data) R1 = 0.0623, wR2 = 0.0928, largest difference in peak
and hole = 0.879 and À0.845 e ÅÀ1
.

M.J. Cowley et al. / Journal of Organometallic Chemistry 695 (2010) 18–25
25
(h) H. Werner, M. Baum, D. Schneider, B. Windmüller, Organometallics 13
(1994) 1089.
[22] J. Pranata, S.G. Wierschke, W.L. Jorgensen, J. Am. Chem. Soc. 113 (1991) 2810.
[23] H. Iwahashia, Y. Kyogoku, J. Am. Chem. Soc. 99 (1977) 7761.
[24] J.W.B. Cooke, R. Bright, M.J. Coleman, K.P. Jenkins, Org. Proc. Res. Develop. 5
(2001) 383.
[25] A. Van der Ent, A.L. Onderdelinden, Inorg. Synth. 14 (1973) 94.
[26] Smart Diffractometer Control Software (v5.625), Bruker AXS, Bruker AXS
GmbH, Karlsruhe, Germany.
[27] SAINT+ (v6.22), Bruker AXS, Bruker AXS GmbH, Karlsruhe, Germany.
[28] G.M. Sheldrick, SHELXS-97, Program for the Solution of Crystal Structures,
Universität Göttingen, 1997.
[29] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structures,
Universität Göttingen, 1997.
[14] C.H. Suresh, N. Koga, J. Theor. Comput. Chem. 4 (2005) 59.
[15] F. De Angelis, A. Sgamellotti, N. Re, Organometallics 26 (2007) 5285.
[16] B.A. Vastine, M.B. Hall, Organometallics 27 (2008) 4325.
[17] D.B. Grotjahn, X. Zeng, A.L. Coosky, J. Am. Chem. Soc. 128 (2006) 2798.
[18] D.B. Grotjahn, X. Zeng, A.L. Cooksy, W.S. Kassel, A.G. DiPasquale, L.N. Zakharov,
A.L. Rheingold, Organometallics 26 (2007) 3385.
[19] M.J. Cowley, J.M. Lynam, J.M. Slattery, Dalton Trans. (2008) 4552.
[20] H. Werner, J. Wolf, U. Schubert, K. Ackermann, J. Organometal. Chem. 243
(1983) C63.
[21] A. Dunger, H.H. Limbach, K. Weiss, Chem. Eur. J. 4 (1998) 621.