Diastereotopic relationship between planar and central chiralities in the formation of Ru(η3-allyl)(CO)(PPh3)(L-L′) complexes

Article abstract of DOI:10.1016/S1387-7003(03)00214-4

Hydride ruthenium complexes, RuHCl(CO)(PPh₃)₂(L-L′) 3 (L-L′ = bidentate ligand having nitrogen and oxygen) react with allenes to give Ru(η³-allyl)(CO)(PPh₃)(L-L′) complexes 5 in good yields via hydrometalation r

Full text of DOI:10.1016/S1387-7003(03)00214-4

Inorganic Chemistry Communications 6 (2003) 1140–1143
www.elsevier.com/locate/inoche
Diastereotopic relationship between planar and central chiralities
in the formation of Ru(g3-allyl)(CO)(PPh3)(L–L0) complexes
*
*
Hisahiro Sasabe, Saburo Nakanishi , Toshikazu Takata
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-83753, Japan
Received 21 February 2003; accepted 12 June 2003
Published online: 12 July 2003
Abstract
Hydride ruthenium complexes, RuHCl(CO)(PPh3)2(L–L0) 3 (L–L0 ¼ bidentate ligand having nitrogen and oxygen) react with
allenes to give Ru(g3-allyl)(CO)(PPh3)(L–L0) complexes 5 in good yields via hydrometalation reaction. The complexes 5 have planar
chirality at the g3-allyl ligand and central chirality at the Ru metal, and consist of one pair of enantiomers. Ligand substitution
reaction of Ru(g3-allyl)Cl(CO)(PPh3)2 complexes 6 with bidentate ligands (L–L0) also afford the complexes 5 which have the same
stereochemistry as those formed by the hydrometalation reaction. The planar chirality is controlled by the central chirality at the Ru
metal in both the formations of the complexes 5. The structure of 5a (L–L0 ¼ N–N bidentate ligand) was determined by the X-ray
crystal structure analysis.
Ó 2003 Published by Elsevier Science B.V.
Keywords: g3-Allyl ruthenium complex; Hydrometalation; Ligand substitution; Diastereotopic relation; Planar and central chiralities
1. Introduction
pected to be particularly effective because of the prox-
imity between the metal and the g3-allyl ligand.
Planar chiral organometallic complexes have at-
tracted much attention due to their potential as effective
asymmetric catalysts [1]. Among these planar chiral
complexes, many g3-allyl transition metal complexes of
iron [2], palladium [3] and molybdenum [4] have been
demonstrated as excellent allylation reagents in asym-
metric organic transformations. With respect to ruthe-
nium complexes, only one planar chiral g3-allyl complex
has been reported [5], although the corresponding pla-
nar chiral g5-cyclopentadienyl complexes have been
widely investigated [6]. One of the useful methods to
prepare the planar chiral g3-allyl complexes is asym-
metric coordination of allylic reagents to metals which is
induced by central chirality at the metals and also chi-
rality of the auxiliary ligands. Asymmetric induction by
a chiral center at the metal to the g3-allyl ligand is ex-
We have recently found that RuHCl(CO)(PPh3)3 re-
acted with allenes to give g3-allyl complexes Ru(g3-al-
lyl)(CO)(Cl)(PPh3)2 which further undergoes the ligand
substitution of the Cl and PPh3 ligands with bidentate
ligand (L–L0) to afford Ru(g3-allyl)(CO)(PPh3)(L–L0)
complexes. The complexes Ru(g3-allyl)(CO)(PPh3)(L–
L0) have both planar chirality at the g3-allyl ligand and
central chirality at the metal. Further, the complexes
have also been prepared by hydrometalation reaction of
RuH(CO)(PPh3)2(L–L0) with allenes. A remarkable
correlation is observed for the chirality at the metal
center and the g3-allyl ligand between these formation
reactions of Ru(g3-allyl)(CO)(PPh3)(L–L0) complexes.
In this communication, we report the formation and
structure of the Ru(g3-allyl)(CO)(PPh3)(L–L0) com-
plexes, and discuss diastereotopic relationship between
the planar and central chiralities.
The reaction of RuHCl(CO)(PPh3)3 1 with N–N
bidentate ligand 2a in the presence of KOHgave hy-
dride ruthenium complex 3a in 83% yield as air and
moisture stable yellow solids (Scheme 1). The structure
* Corresponding authors. Tel.: +81-722-54-9295; fax: +81-722-54-
9910.
E-mail address: nakanisi@chem.osakafu-u.ac.jp (S. Nakanishi).
1387-7003/$ - see front matter Ó 2003 Published by Elsevier Science B.V.
doi:10.1016/S1387-7003(03)00214-4

H. Sasabe et al. / Inorganic Chemistry Communications 6 (2003) 1140–1143
1141
Scheme 1.
Fig. 1. Molecular structure of 5a. All hydrogen atoms are omitted for
ꢀ
clarity. Selected bond lengths (A) and angles (deg): C(1)–C(2) 1.404(5),
C(2)–C(3) 1.405(5), Ru–C(1) 2.277(3), Ru–C(2) 2.199(3), Ru–C(3)
2.209(4), Ru–C(4) 1.848(4), Ru–P 2.365(4), Ru–N(1) 2.137(3), Ru–
N(2) 2.159(3), C(1)–C(2)–C(3) 122.4(4), N(1)–Ru–C(4) 175.6(1), N(1)–
Ru–N(2) 77.1(1), N(2)–Ru–P 93.35(8).
Scheme 2.
1
of 3a was determined by the spectral charactaristics.
The complex 3b was similarly prepared, while the
complex 3c was synthesized according to the literature
procedure [7].
5a revealed that no isomerization occurs between the
diastereomers at 90 °C in C6D6.
The molecular structure of 5a is unambiguously
Hydrometalation of the complexes 3 with allenes 4
1
afforded g3-allyl ruthenium complexes 5 in good
yields, which consisted of only one pair of enantiomers
determined by X-ray crystal structure analysis, as illus-
2
trated in Fig. 1. Complex 5a has a trigonal bipyrami-
(Rallyl, SRu)-5 and (Sallyl, RRu)-5 among the four possible
1
dal structure where the anionic nitrogen and carbonyl
ligands are located at the apical position, whereas PPh3,
imine nitrogen and g3-allyl ligands are at the equatorial
positions. The phenyl group on the g3-allyl ligand is
situated away from PPh3 ligand. It should be noted that
5a possesses both planar and central chiralities.
A plausible mechanism for the formation of 5 is
shown in Scheme 3. Hydrometalation of 4 with the hy-
dride complex 3 affords r-allyl complex 7 which is then
converted to 5 via face-selective p-complexation. Path B
is disfavored probably owing to the steric replusion
between the g3-allyl and PPh3 ligands. In fact, the
complex (Rallyl, SRu)-5 and its enantiomer were pro-
duced with no formation of diastereomer (Sallyl, SRu)-5
or (Rallyl, RRu)-5.
diastereomers (Scheme 2, Table 1). HNMR signals of
the allylic protons of 5 showed that the two enantiomers
were formed. VT-1HNMR observation of the complex
1
Selected data. For 3a: m.p. 203–205 °C (dec.), IR (KBr) 1997 (Ru–
H), 1908 (CO), 1561 (C@N) cmÀ1 1HNMR (270 MHz, CDCl 3) d
,
7.38–7.08 (m, 32H, N@CH, pyrrole and Ar), 6.78–6.71 (m, 5H, Ar),
6.53 (d, 1H, JHH ¼ 3:6 Hz, pyrrole), 6.12 (d, 1H, JHH ¼ 3:6 H z,
pyrrole), )10.83 (t, 1H, JPH ¼ 19:6 Hz, Ru–H), 31P{1H} NMR (200
MHz, CDCl3) d 45.4 (s) ppm. For 5a: m.p. 199–202 °C (dec.), IR
(NaCl) 1932 (CO), 1567 (C@N) cmÀ1 1HNMR (270 MHz, C 6D6) d
,
7.64–6.81 (m, 25H, N@CHand Ar), 6.40–6.38 (m, 1H, Ar), 6.14 (br s,
1H, Ar), 6.14–6.11 (m, 2H, Ar), 5.81–5.70 (m, 1H, @CH), 3.40 (dd, 1H,
JPH ¼ 6:6, JHH ¼ 11:9 H z,@CH), 2.98 (d, 1H, JHH ¼ 6:9 H z,@CH),
1.83 (d, 1H, JHH ¼ 11:5 H z,@CH), 31P{1H} NMR (200 MHz, CDCl3)
d 44.6 (s) ppm; for 5e: m.p. 172–174 °C (dec.), IR (NaCl) 1929 (CO),
Ligand substitution reaction of Ru(g3-allyl)(CO)(Cl)
(PPh3)2 complex 6 with bidentate ligand 2 was carried
out (Scheme 4, Table 2).
Complex 6a was synthesized from hydrometalation
of the complex 1 with phenylallene 4a in 90% yield [8].
1584, 1516, 1434, 1399 cmÀ1 1HNMR (270 MHz, C 6D6) d 7.39–6.48
,
(m, 20H, Ar), 5.34 (m, 1H, @CH), 4.49 (s, 1H, acac-H), 3.24 (dd, 1H,
JPH ¼ 7:0, JHH ¼ 11:9 H z,@CH), 2.30 (d, 1H, J ¼ 7:0 H z,@CH), 1.44
(d, 1H, J ¼ 11:2 H z,@CH), 1.08 (s, 3H, CH3), 0.89 (s, 3H, CH3) ppm,
Anal. found (calcd) for C33H31O3PRu Á 0.5H2O: C, 64.14 (64.28); H,
5.20 (5.23). For 9: m.p. 143–145 °C (dec.), IR (KBr) 1985 (Ru–H),
1908 (CO), 1577 (N@C) cmÀ1 1HNMR (270 MHz, CDCl 3) d 7.45–
,
2
7.24 (m, 30H, Ar and N@CH), 7.12–6.99 (m, 3H, Ar), 6.68 (m, 1H,
pyrrole), 6.59 (m, 1H, pyrrole), 6.38 (m, 1H, pyrrole), 5.95–5.90 (m,
3H, Ar), 3.59 (q, 1H, JHH ¼ 6:6 Hz, CHMePh), 1.12 (d, 3H, JHH ¼ 6:6
Hz, CH3), )11.12 (t, 1H, JPH ¼ 18:0 Hz, Ru–H) ppm. For 10: m.p.
Crystallographic data for 5a: C39H33ON2RuP, F :W : ¼ 677:75,
ꢀ
ꢀ
triclinic, P-1(# 2), a ¼ 9:5995ð4Þ A, b ¼ 10:5294ð4Þ A, c ¼ 16:0483ð9Þ
ꢀ
A, a ¼ 80:340ð2Þ°, b ¼ 83:113ð2Þ°, c ¼ 83:313ð1Þ°, V ¼ 1589:7ð1Þ 3,
Z ¼ 2, Dcalc ¼ 1.416 g/cm3. The intensity data were collected at 23 °C
on a Rigaku RAXIS imaging plate area detector with graphite
monochromated Mo-Ka radiation. The 14,249 independent reflections
were measured over a 2h range of 6.0–55.0°. All non-hydrogen atoms
were refined anisotropically. Full matrix least-squares refinement using
6260 reflections converged to final agreement factors R1½I > 3rðIÞꢀ ¼
0:040, wR2½I > 3rðIÞꢀ ¼ 0:089 with GOF ¼ 1.02. The structure was
solved by direct methods using SIR92 and refined by full-matrix least
squares on F. Drawings were generated using ORTEP-III (Burnett &
Jhonson, 1996).
118–122 °C, IR (NaCl) 1923 (CO), 1580 (N@C) cmÀ1 1HNMR of
,
allyl and pheylethyl groups (270 MHz, CDCl3), major product: d 5.73–
5.62 (m, 1H, CH@), 4.27 (q, 1H, JHH ¼ 6:6 Hz, CHMePh), 2.89 (d, 1H,
JHH ¼ 7:6 Hz, CH@), 2.81 (dd, 1H, JHH ¼ 6:3, JPH ¼ 12:2 Hz, CH@),
1.53–1.50 (m, 1H, CH@), 0.82 (d, 3H, JHH ¼ 6:6 Hz, CH3), minor
product: d 5.73–5.62 (m, 1H, CH@), 4.16 (q, 1H, JHH ¼ 7:3 H z,
CHMePh), 3.09 (d, 1H, JHH ¼ 7:3 Hz, CH@), 2.66 (dd, 1H, JHH ¼ 6:3,
JPH ¼ 11:9 Hz, CH@), 1.50–1.45 (m, 1H, CH@), 0.70 (d, 3H,
JHH ¼ 7:3 Hz, CH3) ppm.

1142
H. Sasabe et al. / Inorganic Chemistry Communications 6 (2003) 1140–1143
Table 1
Hydrometalation of the complexes 3 with allenes 4
Run
Complex 3
Allene 4
R
Temp/°C
Complex 5
Yield (%)a
1
2
3
4
5
3a
3a
3a
3b
3c
4a
4b
4c
4a
4a
Ph
65
65
65
40
40
5a
5b
5c
5d
5e
93
80
52
61
73
Tolyl
p-tBuC6H4
Ph
Ph
a Isolated yield.
Table 2
Ligand substitution of the complexes 6 with ligands 2
Run
Complex 6
R
Ligand 2 Complex 5 Yield (%)a
1
2
3
4
6a
6b
6a
6a
Ph 2a
Tolyl 2a
5a
5b
5d
5e
67
90
54
52
Ph
Ph
2b
2c
a Isolated yield.
Scheme 3.
Scheme 4.
Scheme 5.
The reaction of the complex 6a with N–N bidentate li-
gand 2a in the presence of K2CO3 in DMF at 100 °C
gave the complex 5a in 67% yield. The configuration of
the complex was same as that of the complex obtained
from the above hydrometalation reaction. The reaction
proceeded via selective ligand substitution which is
probably controlled by the planar chirality of the g3-
allyl ligand to give a pair of enantiomers. Reaction of
the complex 6a with the bidentate ligands 2b and acet-
ylacetone 2c also provided the corresponding g3-allyl
ruthenium complexes 5d (54%) and 5e (52%), respec-
tively.
CHCl3 at 50 °C resulted in the formation of a diaste-
reomeric mixture of g3-allyl ruthenium complex 10 in
37% yield. HNMR spectrum revealed the de of 16%.
Now, it is not clear which the major product is. There-
fore, it was found that the chirality of the auxiliary li-
gand is transfered to the planar chirality at the g3-allyl
ligand through the central chiraltiy at the Ru metal (see
Scheme 5).
1
The above results indicate the distinct correlation of
the central chirality at the metal with the planar chirality
of the g3-allyl ligand in the formation of 5. That is to
say, central chirality SRu at the metal absolutely can
control the chirality of g3-allyl ligand to Rallyl and vice
versa.
Acknowledgements
We acknowledge the financial support by Grant-in
Aid for Scientific Research from Ministry of Education,
Science, Sports and Culture of Japan (No. 10650838).
If optically active bidentate ligand (L–L0) is used,
stereocontrolled chiral Ru center is expected to be pro-
duced. Chiral hydride complex 9 was prepared from
complex 1 and opitically active N–N bidentate ligand 8.
Treatment of the complex 9 with phenylallene 4a in
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