Activation of a 1,10-phenanthroline ligand on a rhenium tricarbonyl complex

Article abstract of DOI:10.1039/b412447b

The reactions of complex [Re(PPh₂)(CO)₃(phen)] with either methyl acrylate or methyl propiolate afford products in which the phen ligand has been activated.

Full text of DOI:10.1039/b412447b

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Activation of a 1,10-phenanthroline ligand on a rhenium tricarbonyl
complex{
Luciano Cuesta,a Eva Hevia,a Dolores Morales,a Julio Pe´rez,*a V´ıctor Riera,a Elena Rodr´ıgueza and
Daniel Miguelb
Received (in Cambridge, UK) 12th August 2004, Accepted 27th September 2004
First published as an Advance Article on the web 22nd November 2004
DOI: 10.1039/b412447b
acetylenic substrates to afford products resulting from addition to
the N-adjacent carbon of phen.
The reactions of complex [Re(PPh2)(CO)3(phen)] with either
methyl acrylate or methyl propiolate afford products in which
the phen ligand has been activated.
The phosphido complex 1 was found to react with methyl
acrylate and with methyl propiolate, affording the new compounds
2 and 3, respectively, as the single products (see Scheme 2).17,18
These products could be isolated in high yield and characterized
both in solution by IR and NMR (1H, 13C and 31P) spectroscopies
and in solid state by single-crystal X-ray diffraction. The IR
spectra indicated the persistence of fac-Re(CO)3 moieties in 2 and
3, thus ruling out intramolecular attack on one of the carbonyl
ligands, as have been found in the reactions of hydroxo and amido
complexes with DMAD (see above) and in previous studies of the
reactivity of iron, molybdenum and tungsten phosphido com-
plexes. The observation of coupling to phosphorus in the signals of
the carbonyl ligands in the 13C NMR spectra strongly suggests
2,29-Bipyridine (bipy), 1,10-phenanthroline (phen) and their
substituted analogues form robust metal complexes that have
played important roles in several areas of chemistry.1–3
Coordinated bipy and phen are so inert that the nucleophilic
attack of hydroxide anion on a N-adjacent carbon, proposed to
explain the anomalous behaviour of some bipy or phen
complexes,4 is discussed in textbooks5 and continues to attract
interest while remaining controversial.6,7
We have recently found that complexes [MoY(g3-
allyl)(CO)2(N–N)] and [ReY(CO)3(N–N)] (Y 5 alkoxo, hydroxo
or amido; N–N 5 bipy or phen) react with dimethylacetylene
dicarboxylate (DMAD).8–11 The results are consistent with initial
attack by the Y ligand at one of the acetylenic carbon atoms and
addition of the putative resulting vinyl carbanion to either the
metal (for M–OR complexes with displacement of oxygen) or a
CO ligand (hydroxo or amido complexes). These results are
depicted in Scheme 1.
1
that the Re–P bond also remains intact. The H NMR spectra
revealed the desymmetrization of the phenanthroline ligand. These
features are consistent with the solid-state structures, showed in
Figs. 1 (compound 2) and 2 (compound 3).{
The molecules of 2 and 3 are distorted octahedra consisting of
fac-Re(CO)3 moieties bonded to the asymmetric PNN9 donor set
of a new tridentate ligand in which the C2 unit from the olefin or
acetylene links the phosphorus atom to the C2 atom of the phen
backbone thus creating a six-membered metallacycle. The loss of
aromaticity in the phen ring attacked resulted in its distortion from
planarity. The phosphorus is bonded to the non-substituted atom
of the olefin or acetylene, a fact consistent with the mechanistic
proposal (in line with our previous studies on the reactivity of
alkoxo, hydroxo and amido complexes) shown in Scheme 3, since
the nucleophilic phosphido group would attack the more
electrophilic carbon of the organic substrate. The bonding scheme
depicted for the attacked phen ring of the product in Scheme 3 is
substantiated by the comparison of the intraligand distances in 1
We also reported the synthesis and highly nucleophilic character
of the phosphido complex [Re(PPh2)(CO)3(phen)] (1).12 Studies of
the reactivity of terminal phosphido complexes are scarce.13–16
Here we report that 1 reacts with electron-poor olefinic or
˚
(in A, numbering scheme as for 2 and 3: N(1)–C(11) 1.327(11),
C(11)–C(12) 1.387(15), C(12)–C(13) 1.354(17)) with those found in
2 and 3 (see captions of Figs. 1 and 2).
In summary, we have presented evidence of two reactions
resulting in the activation of a phenanthroline ligand under very
mild conditions, a transformation without precedents in the
Scheme 1
{ Electronic supplementary information (ESI) available: General experi-
mental details and atom-labeling scheme for phen9. See http://
www.rsc.org/suppdata/cc/b4/b412447b/
*japm@fq.uniovi.es
Scheme 2
116 | Chem. Commun., 2005, 116–117
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257.
˚
Fig. 1 Thermal ellipsoid (30%) plot of 2. Selected bond lengths (A):
N(1)–C(11) 1.452(11), C(11)–C(12) 1.540(14), C(12)–C(13) 1.307(14).
12 E. Hevia, J. Pe´rez, V. Riera and D. Miguel, Organometallics, 2002, 21,
1966.
13 (a) U. Segerer, S. Blaurock, J. Sieler and E. Hey-Hawkins,
Organometallics, 1999, 18, 2838; (b) U. Segerer, J. Sieler and E. Hey-
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14 M. T. Ashby and J. H. Enemark, Organometallic, 1987, 6, 1323.
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Chem., 1991, 407, 247.
16 H. Adams, N. A. Bailey, P. Blenkiron and M. J. Morris, J. Chem. Soc.,
Dalton Trans., 2000, 3074.
17 Synthesis of 2: Methyl acrylate (11 mL, 0.13 mmol) was added to a
solution of 1 (0.081 g, 0.13 mmol) in THF (10 mL). The colour of the
solution immediately changed from blue to red. The solution was stirred
for 20 h, in vacuo concentration and precipitation with hexane afforded
a red microcrystalline solid. Slow evaporation of a concentrated solution
of 2 in diethyl ether–CH2Cl2 afforded crystals of good quality for an
X-ray determination. Yield: 0.079 g, 84%. Anal. Calc. for
C31H24N2O5PRe: C, 51.59; H, 3.35; N, 3.88. Found: C, 51.42; H,
3.52; N, 3.93%. IR (THF): 2014, 1920, 1892 (nCO). 1H NMR (C6D6): d
8.15 [m, 1H], 7.53 [m, 1H], 7.01–6.94 [m, 6H], 6.76–6.65 [m, 3H], 6.56
[m, 1H], 6.41 [m, 3H], 6.12 [dd (8.54, 5.13), 1H], 6.03 [d (7.97), 1H], 5.30
[m, 2H], 3.84 [m, 1H], 3.33 [s, 3H, Me], 2.97 [m, 1H], 2.78 [m, 1H].
13C{1H} NMR (C6D6): d 198.9 [t (9.44), ReCO], 191.9 [d (74.79)
ReCO], 172.9 [d (12.84 Hz), CO2Me] 155.4, [s, phen9], 148.2, 146.7,
136.7, 135.9, 135.4, 134.2, 132.5, 131.7, 127.0, 125.8, 121.9 [phen9 and
Ph], 115.6, 107.3 [s, C3, C4 phen9], 68.4 [s, C5 phen9], 52.1 [s, CO2CH3],
49.3 [s, PCH2C(H)CO2Me], 32.9 [d (27.95 Hz), PCH2]. 31P{1H} NMR
(C6D6): d 20.86.
˚
Fig. 2 Thermal ellipsoid (30%) plot of 3. Selected bond lengths (A):
N(1)–C(11) 1.469(8), C(11)–C(12) 1.522(9), C(12)–C(13) 1.321(10).
18 Synthesis of 3: Methyl propiolate (8 mL, 0.09 mmol) was added to a
solution of 1 (0.050 g, 0.08 mmol) in THF (10 mL) causing a colour
change from blue to red. The mixture was stirred for 5 min and a
microcrystalline solid was obtained by addition of hexane. The solid was
dissolved in CH2Cl2 and filtered through alumina (activation grade IV).
The solution was concentrated in vacuo, layered with hexane and stored
at 220 uC, affording purple crystals, one of which was used for the
X-ray structure determination. Yield: 0.047 g, 81%. Anal. Calc. for
C31H22N2O5PRe: C, 51.74; H, 3.08; N, 3.89. Found: C, 51.22; H, 3.02;
N, 3.94%. IR (THF): 2015, 1922, 1896 (nCO). 1H NMR (C6D6): d 8.13
[m, 1H], 7.27 [m, 1H], 7.00 [m, 4H], 6.87 [dt (8.54, 1.42), 1H], 6.72 [m,
2H], 6.60–6.57 [m, 2H], 6.47–6.42 [m, 3H], 6.25 [dd (9.68, 1.42), 1H], 6.03
[dd (8.25, 4.84), 1H], 5.09 [d (8.25) 1H], 5.51 [dd (9.68, 4.84), 1H], 3.27 [s,
3H, Me]. 13C{1H} NMR (CD2Cl2): d 198.3 [d (6.5), ReCO], 196.9 [d
(8.1), ReCO], 193.0 [d (75.09), ReCO], 167.5 [d (15.34), CO2Me], 156.7,
156.3, 147.6, 144.7, 136.6, 1 [s, phen9], 134.7, [d (12.1), C1], 132.6, [d
(11.3), C2], 131.7, [s, phen9], 129.5 [d (7.3), Ph], 129.1 [d (10.4), Ph],
128.6, [s, phen9], 127.9 [d (9.7 Hz), Ph], 127.8 [s, Ph], 127.3, 121.9, 119.8,
[s, phen9], 114.3, 107.7 [s, C3, C4 phen9], 64.7 [s, C5 phen9], 52.6 [s,
CO2CH3]. 31P{1H} NMR (C6D6): d 3.41.
Scheme 3
chemistry of carbonyl complexes.19 Studies of the reactivity of 1
with other electrophiles are under way in our laboratory.
We thank Ministerio de Ciencia y Tecnolog´ıa for support of this
work (Projects BQU2003-08649 and BQU2002-03414).
Luciano Cuesta,a Eva Hevia,a Dolores Morales,a Julio Pe´rez,*a
V´ıctor Riera,a Elena Rodr´ıgueza and Daniel Miguelb
aDepartamento de Qu´ımica Orga´nica e Inorga´nica-IUQOEM, Facultad
de Qu´ımica-CSIC, Universidad de Oviedo, 33006, Oviedo, Spain.
E-mail: japm@fq.uniovi.es; Fax: 34 98510 3446; Tel: 34 98510 3467
bDepartamento de Qu´ımica Inorga´nica, Facultad de Ciencias,
Universidad de Valladolid, 47071, Valladolid, Spain
Notes and references
19 (a) L. M. Kobriger, A. K. McMullen, P. E. Fanwick and I. P. Rothwell,
Polyhedron, 1989, 8, 77; (b) T. M. Cameron, J. C. Gordon, B. L. Scott
and W. Tumas, Chem. Commun., 2004, 1398.
{ CCDC reference numbers 246293 (2) and 246294 (3). See http://
www.rsc.org/suppdata/cc/b4/b412447b/ for crystallographic data in .cif or
other electronic format.
This journal is ß The Royal Society of Chemistry 2005
Chem. Commun., 2005, 116–117 | 117