Novel insertion of ethynylbenzene derivatives bearing an electron-withdrawing substituent at the 4-position into a P-C bond and their transannular insertion between a metal atom and an //?.s0-carbon atom of the phosphine ligandf

Article abstract of DOI:10.1039/b004984k

Reactions of Cp*MCl(P-O) (M = Rh, Ir) bearing P-O coordination with ethynylbenzene derivatives having an electron-withdrawing group in the presence of a PF6 anion result in either insertion into a P-C bond or a transannular addition between a metal and an ipso-carbon of the phosphine. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b004984k

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Novel insertion of ethynylbenzene derivatives bearing an
electron-withdrawing substituent at the 4-position into a P–C
bond and their transannular insertion between a metal atom
and an ipso-carbon atom of the phosphine ligand†
Yasuhiro Yamamoto and Kenichiro Sugawara
Department of Chemistry, Faculty of Science, Miyama 2-2-1, Funabashi, Chiba,
274-8510 Japan. E-mail: yamamoto@chem.sci.toho-u.ac.jp
Received 21st June 2000, Accepted 28th July 2000
Published on the Web 14th August 2000
Reactions of Cp*MCl(P–O) (M ؍ Rh, Ir) bearing P–O
coordination with ethynylbenzene derivatives having
an electron-withdrawing group in the presence of a PF6
anion result in either insertion into a P–C bond or a
transannular addition between a metal and an ipso-carbon
of the phosphine.
were treated with [Cp*MCl(MDMPP-κ2P,O)] (1a: M = Rh;3
1b: M = Ir4) or [Cp*RhCl(BDMPP-κ2P,O)] 2a5 (BDMPP-
κ2P,O = κO-1-O-κP-2-PRPh-3-MeOC6H3) bearing
P,O
bidentate ligand derived from (2,6-dimethoxyphenyl)diphenyl-
phosphine (MDMPP) and bis(2,6-dimethoxyphenyl)phenyl-
phosphine (BDMPP) in the presence of KPF6, we found that
novel types of reaction: an insertion into a P–C bond or a trans-
annular addition between a Rh atom and an ipso-carbon atom
of the phosphine ligand, occurred readily. We report here the
reactions with ethynylbenzene derivatives bearing an electron-
withdrawing substituent such as the COOMe or NO2 group.
a
When transition metal halide complexes are allowed to react
Ϫ
Ϫ
with alkynes in the presence of anions such as PF6 , BF4 , etc.,
it is well-known that vinylidene or carbene complexes may be
formed, depending on the solvent.1 However, we have recently
reported that the unprecedented insertion of alkyne into a
metal–oxygen σ-bond can occur without the formation of
vinylidene complexes.2 On treatment of the rhodium complex
[Cp*RhCl(MDMPP-κ2P,O)] 1a (MDMPP-κ2P,O = κO-1-O-
κP-2-PPh2-3-MeOC6H3) with mono- and di-substituted alkynes
᎐
Reaction of 1a with HC᎐CC H COOMe-4 at room temper-
᎐
4
ature in the presence of KPF66 in acetone–CH2Cl2 gave two
compounds by crystallization from CH2Cl2–diethyl ether: 3a‡
and 4a‡ as confirmed from elemental analyses and FAB mass
spectroscopy (Scheme 1). X-Ray analysis revealed that 3a con-
tained a (P,O,C) tridentate ligand resulting from the head-to-
head double-insertion of alkyne into the Rh–O bond.§ Two
carbon atoms bearing the phenyl group were connected to the
Rh and O atoms. The infrared spectrum showed bands due to
methoxycarbonyl and PF6 groups at 1717 and 839 cmϪ1,
᎐
᎐
᎐
(HC᎐CPh, HC᎐CCOOR or ROOCC᎐CCOOR; R = Me, Et)
᎐
᎐
᎐
Ϫ
in the presence of the PF6 anion, single and double insertion
of alkynes into the Rh–O bond occurred to form various types
of complex, depending on the alkyne, as follows; (1) a complex
bearing five- and six-membered rings arising from a double
insertion, (2) a seven-membered metallacycle bearing a CO
ligand arising from a single insertion and an extraction of
CO from an ester and (3) a neutral complex bearing a seven-
membered ring arising from a single insertion.2
1
respectively. The H NMR spectrum in CD2Cl2 showed one
doublet at δ 1.36 due to the Cp* protons and three singlets at
δ 3.35, 3.88 and 3.95; the former is due to the methoxy group
and the others are due to the methoxycarbonyl groups.
The 31P{1H} NMR spectrum showed a doublet at δ 35.84
(JRhP = 157.8 Hz).
When ethynylbenzene derivatives bearing an electron-
withdrawing substituent at the 4-position of the phenyl group
The infrared spectrum of 4a showed three characteristic
bands at 3285, 1717 and 1605 cmϪ1 due to the OH, carbonyl
† Electronic supplementary information (ESI) available: spectroscopic
data for complexes 3–5. See http://www.rsc.org/suppdata/dt/b0/
b004984k/
1
groups and C–C double bond, respectively. In the H NMR
spectrum a broad resonance due to a hydroxyl proton, which
᎐
Scheme 1 Reactions of 1 and 2 with HC᎐CC6H4RЈ-4 (R = 2,6-(MeO)2C6H3, RЈ = COOMe or NO2).
᎐
2896
J. Chem. Soc., Dalton Trans., 2000, 2896–2897
This journal is © The Royal Society of Chemistry 2000
DOI: 10.1039/b004984k

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occurred on treatment with 1b in acetone–CH2Cl2 to give 3b and
4b (Scheme 1).‡ The fact that a similar reaction in MeOH gave
exclusively 3a as the only isolated complex confirmed that the
chlorine atom in 4 originated from dichloromethane.
Complex 2a containing the bulky phosphine BDMPP
᎐
was treated with HC᎐CC H R-4, (R = COOMe or NO ) in
᎐
6
4
2
acetone–CH2Cl2 in the presence of KPF6 at room temperature
(Scheme 1) to yield complexes 5ac (yellow, R = COOMe) and
5ad (brown, R = NO2) as confirmed from elemental analyses
and FAB mass spectroscopy.‡ X-Ray analysis of 5ad revealed
that the structure consists of five- and six-membered rings
derived from a transannular insertion of alkyne between the Rh
atom and the ipso-carbon atom of the phosphine ligand,
accompanying the subsequent transformation of the Rh–O
σ-bond to a Rh←O coordination (Fig. 2).|| The change of this
bonding mode caused an elongation of ca. 0.06 Å in the Rh–O
bond length.
The IR spectrum showed bands due to methoxycarbonyl and
ketone groups at 1715 and 1630 cmϪ1 for 5ac and due to a
1
ketone group at 1628 cmϪ1 for 5ad, respectively. The H NMR
spectrum showed three methoxy groups at δ 2.97 (s), 3.06 (bs)
and 3.49 (bs) and one methoxycarbonyl group at δ 3.84 (s) for
5ac and three methoxy groups at δ 2.99 (s), 3.08 (bs) and 3.52
(bs) for 5ad, respectively. A remarkable feature is that the
31P{1H} NMR doublets show large downfield shifts (ca. δ 140).
Further mechanistic studies are now in progress.
Fig. 1 Molecular structure of 3a. Selected bond lengths (Å) and
angles (Њ): Rh(1)–P(1) 2.341(5), Rh(1)–Cl(1) 2.428(5), Rh(1)–Cl(2)
2.411(5); P(1)–C(23) 1.83(2), C(23)–C(24) 1.32(2); P(1)–Rh(1)–Cl(1)
87.1(2), P(1)–Rh(1)–Cl(2) 85.0(2), Cl(1)–Rh(1)–Cl(2) 93.4(2), P(1)–
C(23)–C(24) 135(1), C(23)–C(24)–C(25) 117(1).
Acknowledgements
We thank Professor Shigetoshi Takahashi and Dr Fumie Takei
for measurements of FAB mass spectroscopy. This work was
partially supported by a Grant-in-Aid for Scientific Research
from the Ministry of Education of Japan.
Notes and references
‡ Elemental analyses of all new complexes prepared here are in good
agreement with the calculated values. Elementary analyses and spectro-
scopic data are enclosed in the electronic supplementary information.†
§ Crystal data for 3a: C49H47O6P2F6Rh, M = 1010.8, monoclinic, space
group P21/a (no. 14), a = 15.534(3) Å, b = 19.986(3) Å, c = 15.757(3) Å,
β = 103.70(1)Њ, V = 4752(1) Å3, Z = 4, D = 1.413 g cmϪ3, µ = 4.96 cmϪ1
(MoKα), F(000) = 2072, T = 298 K. Data were collected on a Rigaku
AFC5S difractometer. The structure was solved by Patterson methods,
and non-hydrogen atoms were refined anisotropically using full-matrix
least-squares based on F2 to give R1 = 0.064 for 3298 reflections and
Rw = 0.198 for 8328 reflections.
¶ Crystal data for 4a: C39H42O6PCl2Rh, M = 811.5, orthorhombic,
space group Pca21 (no. 29), a = 34.835(7) Å, b = 9.135(8) Å,
c = 12.305(5) Å, V = 3915(5) Å3, Z = 4, D = 1.377 g cmϪ3, µ = 6.55 cmϪ1
(MoKα), F(000) = 1672, T = 300 K. The structure was solved by Pat-
terson methods, and non-hydrogen atoms were refined anisotropically
using full-matrix least-squares based on F2 to give R1 = 0.068 for 2216
reflections and Rw = 0.203 for 3607 reflections.
Fig. 2 Molecular structure of 5ad. Selected bond lengths (Å) and
angles (Њ): Rh(1)–P(1) 2.304(2), Rh(1)–O(3) 2.106(4), Rh(1)–C(32)
2.013(6), O(3)–C(26) 1.263(7), C(25)–C(26) 1.505(8), P(1)–C(25)
1.943(6), C(25)–C(33) 1.567(8), C(32)–C(33) 1.340(8); P(1)–Rh(1)–O(3)
81.1(1), P(1)–Rh(1)–C(32) 76.3(2), O(3)–Rh(1)–C(32) 85.2(2), Rh(1)–
P(1)–C(25) 90.2(2), P(1)–C(25)–C(26) 105.1(4), C(25)–C(26)–O(3)
118.7(5), Rh(1)–O(3)–C(26) 117.9(4), Rh(1)–C(32)–C(33) 120.4(4),
C(32)–C(33)–C(25) 114.2(5), P(1)–C(25)–C(33) 96.4(4).
|| Crystal data for 5ad: C39H46NO9P2F6Rh, M = 951.6, monoclinic,
space group P21/a (no. 14), a = 15.299(7) Å, b = 14.826(7) Å,
c = 19.505(9) Å, β = 106.78(3)Њ, V = 4235(3) Å3, Z = 4, D = 1.492 g cmϪ3
,
disappeared on treatment with D2O, appeared at δ 6.74 in
addition to three characteristic methyl resonances at δ 1.41(d),
3.44(s) and 3.83(s), due to 1,2,3,4,5-pentamethylcyclopenta-
dienyl, methoxy and methoxycarbonyl groups, respectively.
There were no signs of a PF6 group in the infrared and 31P{1H}
NMR spectra, suggesting that the complex was neutral. The
structure was confirmed by X-ray analysis (Fig. 1).¶ As
expected, the molecule is neutral and the rhodium atom is
surrounded by two chlorine atoms and one phosphorus atom.
Cis-insertion of alkyne into the P–C bond has occurred,
accompanied by cleavage of a Rh–O bond. The Rh–P bond
length of 2.341(5) Å is longer than that of 1a by 0.04 Å, due to
the absence of chelation and is 0.02 Å shorter than that
(2.366(1) Å) of Cp*RhCl2(MDMPP), probably due to lower
steric demand than in the MDMPP ligand.3 A similar reaction
µ = 5.57 cmϪ1 (MoKα), F(000) = 1952, T = 298 K. The structure was
solved by Patterson methods, and non-hydrogen atoms were refined
anisotropically using full-matrix least-squares based on F2 to give
R1 = 0.065 for 4458 reflections and Rw = 0.180 for 7708 reflections.
CCDC reference number 186/2117. See http://www.rsc.org/suppdata/
dt/b0/b004984k/ for crystallographic files in .cif format.
1 (a) M. I. Bruce, Chem. Rev., 1991, 91, 197 and refs. therein; (b) M. C.
Puerta and P. Valerga, Coord. Chem. Rev., 1999, 193/195, 977 and
refs. therein.
2 Y. Yamamoto, X.-H. Han and J.-F. Ma, Angew. Chem., Int. Ed., 2000,
39, 1965; Angew. Chem., 2000, 112, 2041.
3 X.-H. Han and Y. Yamamoto, J. Organomet. Chem., 1998, 561, 157.
4 Y. Yamamoto, K. Kawasaki and S. Nishimura, J. Organomet. Chem.,
1999, 587, 49.
5 X.-H. Han and Y. Yamamoto, unpublished work.
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