Half-sandwich cyclopentadienyl ruthenium complexes of achiral and chiral diphosphazanes

Article abstract of DOI:10.1039/b205247d

Reaction of [CpRu(PPh₃)₂Cl] (1) {Cp = η⁵-(C₅H₅)} with X₂PN(CHMe₂)PYY′ {X = Y = Y′ = Ph (L¹); X = Y = Ph, Y′ = OC₆H₄Me-4 (L⁴); X = Y =

Full text of DOI:10.1039/b205247d

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Half-sandwich cyclopentadienyl ruthenium complexes of achiral
and chiral diphosphazanes†
Kannan Raghuraman, Setharampattu S. Krishnamurthy* and Munirathinam Nethaji
Department of Inorganic and Physical Chemistry, Indian Institute of Science,
Bangalore-560 012, India. E-mail: sskrish@ipc.iisc.ernet.in; Fax: ϩ91-80-3600683
Received 29th May 2002, Accepted 20th August 2002
First published as an Advance Article on the web 15th October 2002
Reaction of [CpRu(PPh3)2Cl] (1) {Cp = η5-(C5H5)} with X2PN(CHMe2)PYYЈ {X = Y = YЈ = Ph (L1); X = Y = Ph,
YЈ = OC6H4Me-4 (L4); X = Y = Ph, YЈ = OC6H3Me2-3,5 (L5); X = Y = Ph, YЈ = N2C3HMe2 (L6)} yields the cationic
chelatecomplexes, [CpRu(η2-(X2PN(CHMe2)PYYЈ))PPh3]Cl. Ontheotherhand, thereactionof1withX2PN(CHMe2)-
PYYЈ {X2 = YYЈ = O2C6H4(L2)} gives the complex, [CpRu(η1-L2)2PPh3]Cl. Both types of complexes are formed with
X2PN(CHMe2)PYYЈ {X = Ph, YYЈ = O2C6H4 (L3)}. The reaction of 1 with (R),(S )-(H12C20O2)PN(CHMe2)PPh2 (L7)
yields both cationic and neutral complexes, [CpRu{η2-(L7)}PPh3]Cl and [CpRu{η1-(L7)}2PPh3]Cl and [CpRu{η2-(L7)}-
Cl]. The reactions of optically pure diphosphazane, Ph2PN(*CHMePh)PPhY (Y = Ph (L8); Y = N2C3HMe2-3,5 (L9))
with 1 give the neutral and cationic ruthenium complexes, [CpRu{η2-(Ph2PN(R)PPhY)}Cl] and [CpRu{η2-(Ph2PN(R)-
PPhY)}PPh3]Cl. “Chiral-at-metal” ruthenium complexes of diphosphazanes have been synthesized with high diastereo-
selectivity.Theabsoluteconfigurationofanovelrutheniumcomplex,(SCSPRRu)-[(η5-C5H5)Ru*{η2-(Ph2PN(*CHMePh)-
P*Ph(N2C3HMe2-3,5))}Cl] possessing three chiral centers, is established by X-ray crystallography. The reactions
of [CpRu{η2-(L8)}Cl] with mono or diphosphanes in the presence of NH4PF6 yield the cationic complexes,
[CpRu{η2-(L8)}{η1-(P)}]PF6 {P = P(OMe)3, PPh3, Ph2P(CH2)nPPh2 (n = 1 or 2)}.
X = Y = Ph, YЈ = OC6H4Me-4 (L4); X = Y = Ph, YЈ =
Introduction
OC6H3Me2-3,5 (L5); X = Y = Ph, YЈ = N2C3HMe2 (L6); X = Ph,
The synthesis of half-sandwich optically active “chiral-at-
metal” ruthenium complexes has attracted considerable interest
in recent years because they can be used as probes to follow
the stereochemical course of reactions of organometallic
YYЈ = (R),(S )-O2C20H12 (L7); (S )-Ph2PN(*CHMePh)PPh2 (L8)
and Ph2PN(*CHMePh)*PPh(N2C3HMe2-3,5) (L9). In the case
of L9, the SCRP-diasteromer or a mixture of SCSp- and SCRP-
diasteromers has been used. The absolute configuration of
complexes and they have also been investigated as promising
SCRP-L9 has been established previously by X-ray crystallo-
catalysts for a variety of organic transformations.1 Active use of
graphy.4d
chirality at a metal center in enantioselective catalysis is a chal-
lenging area.2 Several ruthenium complexes with a stereogenic
Preparation of the complexes
metal center have been synthesised using Schiff-base ligands,
Reactions of 1 with achiral diphosphazanes of the type
X2PN(R)PX2 and X2PN(R)PY2. The reaction of 1 with 1 : 1
molar proportions of L1 in toluene at 110 ЊC gives the cationic
complex [CpRu{η2-(L1)}(PPh3)]Cl (2) in 90% yield. An entirely
different behavior is exhibited by the diphosphazane L2, bear-
ing the catecholato moiety at both the phosphorus ends; its
reaction with 1 yields the cationic complex, [CpRu{η1-(L2)}2-
(PPh3)]Cl (3) containing one triphenyl-phosphane and two
mono-coordinated diphosphazanes (Scheme 1). A similar type
of complex is obtained in the reaction of N-phenyl biscatechol-
ato derivative with 1 in which the sole product is [CpRu{η1-
(C6H4O2)2PN(Ph)P(O2C6H4)}2PPh3]Cl.6b The reaction of 1
with the mixed diphosphazane derivative Ph2-PN(CHMe2)-
P(O2C6H4) (L3) gives a chelate complex [CpRu{η2-(Ph2PN-
(CHMe2)P(O2C6H4)}(PPh3)]Cl (4a) akin to 2 and [CpRu-
{η1-(Ph2PN(CHMe2)P(O2C6H4)}2(PPh3)]Cl (4b) akin to 3 but
in this complex, the PPh2 phosphorus of the diphosphazane
ligand is bonded to ruthenium. Other products are also formed
in this reaction as shown by the 31P NMR spectrum of the
reaction mixture (see Experimental). Evidently the π-acceptor
nature of the phosphorus center has a pronounced effect on the
type of products formed. The presence of aryloxy substituents
at phosphorus enhances the π-acceptor capability of phos-
phorus and favours the formation of η1-coordinated complexes,
whereas the presence of aryl substituents favours chelated
(η2-coordinated) complexes.
chiral bidentate ligands with mixed donor sites or chiral
diphosphanes (with chirality at the back-bone of the ligand).3
However, the synthesis of half-sandwich ruthenium complexes
of chiral diphosphazane ligands based on the P–N–P motif has
not been attempted.4,5 In continuation of our work on the
organometallic chemistry of diphosphazanes,4c,4d,5 herein we
describe the results of our investigations on the reactions of
achiral, unsymmetrically substituted P-stereogenic and optic-
ally pure diphosphazanes with [CpRu(PPh3)2Cl] (Cp = η5-C5H5)
(1) (containing a prochiral metal center) to generate “chiral-at-
metal” complexes and the isolation and absolute configuration
of a novel ruthenium complex bearing three chiral centers,
(SCSPRRu)-[CpRu*{η2-(Ph2PN(*CHMePh)*PPh(N2C3HMe2-
3,5)}Cl].
Results and discussion
The diphosphazanes used in the present study to synthesise
ruthenium complexes are: X2PN(CHMe2)PYYЈ (X = Y = YЈ =
Ph (L1); X2 = YYЈ = O2C6H4 (L2); X = Ph, YYЈ = O2C6H4 (L3);
† Organometallic chemistry of diphosphazanes. Part 15.5
Electronic supplementary information (ESI) available: the 31P{1H}
NMR (162 MHz, CDCl3) spectrum of the reaction mixture obtained by
the reaction of 1 with (SCRP)- and (SCSP)-L9. See http://www.rsc.org/
suppdata/dt/b2/b205247d/
DOI: 10.1039/b205247d
J. Chem. Soc., Dalton Trans., 2002, 4289–4295
This journal is © The Royal Society of Chemistry 2002
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Scheme 1 Synthesis of half-sandwich ruthenium complexes of diphosphazanes (2–8)
Reactions of [CpRu(PPh3)2Cl] with chiral racemic diphospha-
zanes of the type X2PN(R)PYYЈ. The reaction of a racemic
unsymmetrical diphosphazane such as L4–L6 with 1 may lead to
the formation of two diastereomeric pairs, {(RR), (SS )}-
racemic diastereomer and {(SR), (RS )}-meso diastereomer as a
result of the generation of a stereogenic center at the metal. The
ligand exchange reaction between 1 and the chiral racemic
diphosphazanes L4–L6 in boiling toluene yields the cationic
chelate complexes [CpRu*{η2-(Ph2PN(CHMe2)PPh(Y))}-
PPh3]Cl (5–7) by the replacement of only one PPh3 ligand. As
shown in Scheme 1, chelation of the unsymmetrical diphos-
phazanes L4–L6 produces a chiral center and the phosphorus
atom provides a second chiral center; one would therefore
expect the formation of two diastereomeric {(RR),(SS )}-
(racemic) and {(SR), (RS )}-(meso) pairs. In the reaction of L4
with 1 both the diastereomeric pairs (5a : 5b) are formed in the
ratio 2.3 : 1; the major diastereomeric pair 5a (racemic or meso)
has been isolated in a pure form as a yellow crystalline solid,
whereas the minor diastereomeric pair 5b (meso or racemic) is
obtained only as an oily liquid. In contrast to the above result,
the reactions of L5 and L6 with 1 give only one diastereomeric
pair of cationic ruthenium diphosphazane complexes, [CpRu-
{η2-(L5 or L6)}PPh3]Cl (L5 6 or L6 7) respectively, in good yields.
The reaction of 1 with 1 : 1 molar proportions of the racemic
diphosphazane L7, bearing the C2-chiral binapthylene dioxy
moiety, in toluene at 110 ЊC for 5 h gives the complexes 8a–8e of
which the cationic complex, [CpRu{η2-(L7)}PPh3]Cl 8a is the
major product and is isolated in a pure state; it may be either
racemic or meso diastereomer. The remaining compounds (8b–
8e) could not be isolated in a pure state but have been identified
using 31P NMR spectroscopy (see Fig. 1 for 31P–31P COSY
NMR spectrum).
Fig. 1 The 31P–31P COSY (162 MHz, CDCl3) spectrum of the reaction
mixture (after separating 8a) obtained by the reaction of 1 with L7.
Reactions of [CpRu(PPh3)2Cl] with optically pure diphospha-
zanes. The reaction of an optically pure diphosphazane L8 with
1, in sharp contrast to the N-isopropyl derivative L1, gives the
neutral complex [CpRu{η2-(L8)}Cl] (9a) and the cationic
complex [CpRu{η2-(L8)}PPh3]Cl (9b) in 70 and 5% yields
respectively.
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Scheme 2 Synthesis of half-sandwich ruthenium complexes of diphosphazanes (9–14).
The results obtained from the reactions of L4–L6 suggest that
good yields. Analogous reactions of complex 9a with diphos-
an optically pure P-stereogenic unsymmetrical diphosphazane
can be used to synthesise ruthenium complexes with a stereo-
genic metal center with a high diastereoselectivity. This possi-
bility has been realized in the reaction of the optically pure
P-stereogenic unsymmetrical diphosphazane (SCRP)-Ph2PN-
(*CHMePh)P*Ph(N2C3HMe2-3,5) (L9) with 1, which yields the
neutral chloro complex, (SCSPRRu)-[CpRu*{η2-(Ph2PN-
(*CHMePh)*PPh(N2C3HMe2-3,5)}Cl] (10a) (see below for the
X-ray structure) and the cationic complex [CpRu*{η2-(Ph2PN-
(*CHMePh)*PPh(N2C3HMe2-3,5)}PPh3]Cl (10b) in 60 and
20% yield respectively. The complex 10a can be separated from
the reaction mixture by selective crystallization. The complex
10b could not be isolated in a pure form.
The reaction of a diastereomeric mixture of diphosphazanes
(SCRP)- and (SCSP)-Ph2PN(*CHMePh) P*Ph(N2C3HMe2-3,5)
(L9) with [CpRu(PPh3)2Cl] (Scheme 2) gives three diastereo-
meric neutral chloro complexes [CpRu*{η2-(Ph2PN-
(*CHMePh)*PPh(N2C3HMe2-3,5)}Cl] (10a, 10c and 10d) and
two cationic complexes, [CpRu*{η2-(Ph2PN(*CHMePh)*PPh-
(N2C3HMe2-3,5)}PPh3]Cl (10b and 10e). The formation of
these complexes is identified only by the 31P NMR spectrum
of the reaction mixture (see supplementary material†) and
except for 10a, the other compounds could not be isolated (see
below for the 31P NMR data and the assignment of the
configurations).
phanoalkanes (dppm or dppe) yield cationic complexes of the
type [CpRu{η2-(L8)}{η1-(Ph2P(CH2)n(PPh2)}]Cl (n = 1 (13) or
n = 2 (14)). The diphosphane complexes of 13 and 14 contain an
uncoordinated phosphorus center and these “chiral metallo-
ligands” would prove useful synthons for chiral homo- and
heterometallic clusters.
NMR spectroscopic data
The structures of ruthenium () diphosphazane complexes
1
2–14 have been deduced from H and 31P NMR spectroscopic
data. The 31P NMR data are given in Table 1. The structure of
10a has been determined by single crystal diffraction studies
(see below). The 31P NMR spectrum of the η1-coordinated
cationic ruthenium complex 3 displays two quartets centred at
171.2 and 141.0 ppm and a triplet at 51.6 ppm. The spectrum is
of the A2X2M type instead of the expected AAЈXXЈM pattern.
Further investigations are required to ascertain whether any
dynamic process is occuring in this system. The resonances cen-
tered at 171.2 ppm can be assigned to the coordinated phos-
phorus centers while the resonances at 141.0 ppm arise from the
uncoordinated phosphorus centers as the latter chemical shift is
close to that of the free ligand (149.9 ppm). The phosphorus
resonance arising from the triphenylphosphane is centered
at 51.6 ppm. The 31P{1H} NMR spectra of chelated cationic
ruthenium complexes 5–7 display an AMX pattern and the
chemical shifts lie considerably downfield compared to those of
the free ligand. The 31P NMR spectrum of the reaction mixture
of 1 with L4 shows two AMX patterns corresponding to 5a and
5b; the diastereomeric composition of 5a and 5b (2.3 : 1) was
Reactivity of 9a. The neutral ruthenium complex of chiral
diphosphazane 9a reacts with monophosphanes, such as PPh3
or P(OMe)3 in the presence of NH4PF6 in dichloromethane to
yield the yellow cationic complexes 11 and 12 respectively in
J. Chem. Soc., Dalton Trans., 2002, 4289–4295
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Table 1 The 31P NMR data of half-sandwich ruthenium complexes of diphosphazanes (2–14)
Compound
δ(PA) (ppm)
δ(PM) (ppm)
δ(PX) (ppm)
JAM/Hz
JAX/Hz
JMX/Hz
2
80.3a
171.2c
169.6c
150.2d
128.4e
119.3e
123.1e
130.5e
129.6f
150.5f
132.3f
130.8f
167.0f
87.7a
–
45.2b
51.6b
45.0b
48.6b
43.6b
47.2b
43.7b
51.9b
46.3b
51.5b
67.6a
71.3a
45.0a
80.9a
44.2b
87.2
–
–
–
–
95.0
85.0
93.0
61.0
86.0
–
–
–
–
–
89.0
–
60.0
–
35.0
–
–
–
–
–
–
31.0
32.4
30.0
39.0
29.1
–
–
–
–
–
34.0
–
38.0
–
3
141.0d
121.0a
123.0a
89.5a
77.3a
86.3a
118.4a
74.3a
119.7a
–
4a
4b
–
5a
40.0
49.0
40.0
49.0
53.5
–
104.0
103.0
–
108.8
34.0
107.0
46.0
114.0
108.0
42.0
55.0
34.0
–
5b
6
7
8a
8b
8c
8d
–
–
8e
9a
9b
86.6a
82.9a
–
10a
10b
10c
10d
10e
11g
12g
13g i
14g i
99.3e
125.0e
98.7e
118.3a
–
52.4b
80.7a
82.5a
50.0b
147.9h
45.2b
Ϫ23.7j
Ϫ13.2k
90.6e
–
–
–
127.0e
88.2a
116.8a
87.9a
84.2a
84.4a
84.9a
65.0
89.0
89.0
98.5
97.9
38.0
55.0
34.0
–
87.9a
87.7a
87.9a
–
–
a PPh2. b PPh3. c P(O2C6H4) coordinated. d P(O2C6H4) uncoordinated. e PPhY. f P(O2C20H12). g PF6 resonates in the range Ϫ143.0 to Ϫ144.0, septet,
1JPF = 712–715 Hz. h P(OMe)3. i AMRX system. j Uncoordinated PPh2, PPh2-coord (PR) of dppm, resonates at 37.0 (ddd 2JMR = 36.0, 2JAR = 29.0 Hz,
2JRX = 22.5 Hz). k Uncoordinated PPh2, PPh2-coord (PR) of dppe resonates at 38.0 (ddd, 2JMR = 36.3, 2JAR = 29.4 Hz, 2JRX = 34.3 Hz).
determined from the relative integrated intensities of the two
signals for the Cp (Cp = η5-C5H5) protons at 4.26 (for 5a) and
4.41 ppm (for 5b) in their 1H NMR spectra.
Based on the chemical shifts, these resonances can be
tentatively assigned to the neutral chloro compound, [CpRu-
{η1-((H12C20O2)PN(CHMe2)PPh2)}2Cl] (8e) which contains
two monocoordinated diphosphazanes. The coordinated
[P(O2C20H12)] phosphorus resonates at 167.0 ppm and the
uncoordinated PPh2 phosphorus resonates at 45.0 ppm. The
latter chemical shift lies closer to the chemical shift of PPh2 in
the free ligand (28.3 ppm). The 31P{1H} NMR data for com-
plexes 8a–8e are listed in Table 1.
The 1H NMR spectrum of complex 8a shows a sharp singlet
at 4.60 ppm for C5H5 protons. The methyl protons of the iso-
propyl group show two different resonances (0.73 and 0.67
ppm), as they are diastereotopic. The 31P{1H} NMR spectrum
of complex 8a shows an AMX pattern. The 31P{1H} NMR
spectrum of the mother liquor after removing complex 8a
shows the presence of four other complexes (8b–8e) (Scheme 1).
These complexes could not be isolated in a pure form owing to
difficulties in their separation. Nevertheless, the presence of
these complexes is confirmed from the 31P–31P COSY spectrum,
which is illustrated in Fig. 1. From the spectrum, we can infer
that phosphorus nuclei represented by 8.1A (150.5 ppm) shows
coupling with phosphorus nuclei marked 8.1M (119.7 ppm) and
8.1X (51.5 ppm); 8.1M and 8.1X are mutually coupled with
each other. Based on the chemical shifts, the structure can be
assigned as [CpRu*{η1-((Ph2PN(CHMe2)P(O2C20H12))}2 PPh3]-
Cl (8b), which is formed in very low yield. The resonances
centered at 150.5 ppm can be assigned to uncoordinated
P(O2C20H12) phosphorus as the chemical shift lies close to that
of the free ligand (148.3 ppm) and the resonances centered at
119.7 ppm is assigned to PPh2 phosphorus coordinated to
ruthenium. The PPh3 phosphorus resonates at 51.5 ppm. The
formation of the neutral chloro complexes 8c and 8d (racemic
and meso) can also be inferred from the COSY spectrum. The
31P NMR spectra of these complexes would display an AX
pattern owing to non-equivalence of the two phosphorous
nuclei. The phosphorus nucleus represented by 8.2A (d, 132.3
ppm) shows a cross peak with the phosphorus nucleus repre-
sented by 8.2X (d, 67.6 ppm) (2JAX = 104 Hz); these resonances
can be assigned to the neutral complex [CpRu{η2-(Ph2PN-
(CHMe2)P(O2C20H12)}Cl] 8c (racemic or meso), which is the
major isomer formed. The other diastereomer (minor) [CpRu-
{η2-(Ph2PN(CHMe2)P(O2C20H12)} Cl] (8d) is also identified by
the cross peak observed between the phosphorus nucleus
marked 8.3A (d, 130.8 ppm) with the phosphorus nucleus
represented by 8.3X (d, 71.3 ppm) (2JAX = 103 Hz). The COSY
spectrum also shows a cross peak between the phosphorus
nuclei marked 8.4A (m, 167.0 ppm) and 8.4X (m, 45.0 ppm).
The 31P NMR spectra of complexes 9a and 10a display an
AX pattern where as, the complexes 9b and 10b display an
AMX pattern. The neutral chloro complexes (10a, 10c and 10d)
display an AX pattern and the cationic complexes (10b and 10e)
show an AMX pattern. The chloro complex 10a is formed by
the complexation of (SR)-diastereomer of the diphosphazane
to [CpRu] fragment and the complexes 10c and 10d are formed
from the complexation of (SS )-diastereomer to [CpRu] frag-
ment. The configuration of complexes 10c and 10d can be either
SCRPRRu or SCRPSRu. The absolute configuration at the phos-
phorus is likely to be ‘R’ in the complexes 10c and 10d as it is
formed from the (SS )-diastereomer of the diphosphazane. The
cationic complex 10e is obtained from the complexation of
(SS )-diastereomer of the diphosphazane. The absolute con-
figuration of cationic complex 10e may be either SCRPRRu or
SCRPSRu. Attempts to isolate the complexes other than complex
10a were unsuccessful.
The “chiral metalloligands” (13 and 14) possess four non-
equivalent phosphorus nuclei and as a result, an AMRX type
31P{1H} spectrum is observed in each case. The spectra show a
doublet of doublets for the phosphorus nuclei of the chelated
diphosphazane (PA and PM). The PR resonance (coordinated
phosphorus of phosphinoalkane) is observed as a doublet
of doublet of doublets (ddd); the dangling phosphorus (PX)
resonates as a doublet owing to coupling with the coordinated
phosphorus of the diphosphane.
Absolute configuration of 10a
The molecular structure and absolute configuration of the
complex 10a have been confirmed by single crystal X-ray dif-
fraction (Fig. 2). Selected bond lengths and bond angles of
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Table 2 Selected bond distances (Å) and bond angles (Њ) in 10a
selectivity. The diasteromer formation is profoundly affected
by varying the steric bulk at the substituent(s) of the chiral
P-atom. The substituent at nitrogen also plays an important
role; diphosphazanes bearing CHMe2 group at nitrogen favor
the formation of the cationic complexes of the type [CpRu-
{η2-(X2PN(CHMe2)PYYЈ)}PPh3]Cl whereas a diphosphazane
bearing *CHMePh group as substituent at the nitrogen
favors neutral chloro complexes of the type [CpRu{η2-(X2PN-
(*CHMePh)PYYЈ)}Cl].
Bond distances
Bond angles
Ru(1)–Cl(1)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–C(1)
Ru(1)–C(2)
Ru(1)–C(3)
Ru(1)–C(4)
Ru(1)–C(5)
P(1)–N(1)
P(1)–C(24)
P(1)–N(3)
P(2)–N(3)
2.420(3)
2.246(4)
2.281(3)
2.20(2)
2.17(2)
2.17(2)
2.24(2)
2.21(2)
1.75(1)
1.81(1)
1.67(1)
1.71(9)
P(1)–Ru–P(2)
Cl(1)–Ru–P(2)
Cl(1)–Ru–P(1)
Ru–P(1)–N(3)
Ru–P(1)–C(24)
Ru–P(1)–N(1)
N(1)–P(1)–N(3)
P(1)–N(1)–C(31)
P(1)–N(1)–N(2)
P(1)–N(3)–P(2)
Ru–P(1)–P(2)
N(1)–P(1)–P(2)
69.3(1)
96.8(2)
100.2(1)
97.0(4)
130.9(5)
115.6(3)
106.0(5)
128.7(1)
119.4(8)
99.2(5)
Experimental
56.0(1)
122.5(3)
Reactions were carried out under an atmosphere of argon
by using conventional Schlenk techniques. Solvents were puri-
fied according to standard procedures. The starting materials
[CpRu(PPh3)2Cl],8 Ph2PN(CHMe2)PPh2,9 (H4C6O2)PN(CH-
Me2)P(O2C6H4),10 (H4C6O2)PN(CHMe2)PPh2,10 Ph2PN(*CH-
MePh)PPh2,4d Ph2P(*CHMePh)P*Ph(N2C3HMe2-3,5),4d and
Ph2PN(CHMe2)PPhY (Y
= OC6H4Me-4, OC6H3Me2-3,5,
N2C3HMe2-3,5)11 were prepared as reported in the literature.
The C, H, N analyses were performed on a Heraeus CHN-O
rapid elemental analyzer. Nuclear magnetic resonance spectra
were recorded using a Bruker ACF-200 or a Bruker AMX-400
spectrometer with (CH3)4Si as an internal standard for 1H
NMR measurements and 85% H3PO4 as an external standard
for 31P{1H} NMR measurements. Chemical shifts downfield
from the standard were assigned positive values. Where neces-
sary, the spectra were simulated using WINDAISY program
supplied by Bruker. The X-ray diffraction data were collected
using an Enraf-Nonius CAD4 diffractometer (Mo-Kα
radiation) with a graphite monochromator.
Preparations
Synthesis of 2. A mixture of 1 (0.100 g, 1.37 × 10Ϫ4 mol) and
L1 (0.058 g, 1.37 × 10Ϫ4 mol) was dissolved in 20 mL of toluene.
The reaction mixture was heated under reflux for 5 h and cooled
to room temperature. A pale yellow solid was deposited during
the course of the reaction. The solid was filtered off and washed
with petrol. Recrystallisation of the crude product from
CH2Cl2/petrol (1 : 3) mixture yielded 2 as a crystalline solid.
Yield: 0.110 g (90%), mp 193–195 ЊC. 1H NMR (CDCl3, ppm):
7.54–6.96 (m, aryl protons), 4.38 (s, C5H5), 4.10 (m, CH–Pri),
Fig. 2 Crystal structure of 10a. The hydrogen atoms have been
omitted for clarity.
complex 10a are given in Table 2. The diphosphazane ligand is
coordinated to ruthenium in a chelating mode utilizing its two-
phosphorus donor sites. The pyrazolyl nitrogen is not involved
in coordination to the metal. The ruthenium atom is in an octa-
hedral environment and it is bound to the cyclopentadienyl ring
(formally three fac positions), to the two phosphorus atoms of
the diphosphazane ligand and to a chloride ion. The coordin-
ation geometry of the complex is that of a three legged “piano-
stool” with a slight distortion because of the small bite angle
of the diphosphazane ligand (P1–Ru–P2 angle is 69.3(1)Њ).
The stereogenic carbon center derived from the “chiral-pool”
(α-methyl benzylamine) was known to be S and this provided
an independent check for correctness of the assignment of the
absolute configuration. Considering complex 10a as a pseudo-
tetrahedral core with η5-Cp occupying one coordination site
and using modified Cahn–Ingold–Prelog rules7 with the prior-
ity series η5-Cp > Cl > PPh(N2C3HMe2-3,5) for ruthenium and
Ru > N(*CHMePh) > N2C3HMe2 >Ph for phosphorus, the
absolute configuration is assigned as SCSPRRu. The change of
configuration of the chiral phosphorus atom from R in the lig-
and to S in the metal complex arises because the ruthenium
atom in the complex, which is given the higher preference in
assigning the configuration, occupies the position of the lone
pair at the chiral phosphorus atom of the ligand. The geo-
metrical arrangement of the substituents around the chiral
phosphorus center in the free ligand does not change after
complexation.
3
0.93 (d, JHH = 7.0 Hz, CH3–Pri). C, H, N analyses for C50Cl-
H47NP3Ru, found (calculated) (%): 67.10 (67.37), 5.17 (5.31),
1.60 (1.57).
Synthesis of 3. A mixture of 1 (0.100 g, 1.37 × 10Ϫ4 mol)
and L2 (0.046 g, 1.37 × 10Ϫ4 mol) was dissolved in 20 mL of
toluene. The reaction mixture was heated under reflux for 5 h
and cooled to room temperature. Concentration of the reaction
mixture to ∼10 mL followed by addition of petrol (10 mL)
resulted in the precipitation of a pale yellow solid. The solid
was recrystallised from toluene/petrol (1 : 1) mixture to obtain a
1
pure product. Yield: 0.125 g (80%), mp 182–183 ЊC. H NMR
(CDCl3, ppm): 7.51–6.64 (m, aryl protons), 4.84 (s, C5H5),
3
2.90 (m, CH–Pri), 0.87 (d, JHH = 7.1 Hz, CH3–Pri), 0.68 (d,
3JHH = 7.0 Hz, CH3–Pri). C, H, N analyses for C53ClH50-
N208P5Ru, found (calculated) (%): 56.95 (56.11), 4.83 (4.44),
1.50 (2.47).
The reaction of 1 with L3. A mixture of [CpRu(PPh3)2Cl]
(0.1 g, 1.37 × 10Ϫ4 mol) and (C6H4O2)PN(CHMe2)PPh2
(0.053 g, 1.37 × 10Ϫ4 mol) was dissolved in 20 mL of toluene.
The reaction mixture was heated under reflux for 3 h and cooled
to room temperature. The 31P{1H} NMR spectrum of the reac-
tion mixture indicated the formation of several products, of
which 4a and 4b could be readily identified. Concentration of
the reaction mixture to ∼10 mL followed by addition of petrol
(10 mL) precipitated a pale yellow solid. The solid was filtered
Conclusions
We have shown here that P-chiral unsymmetrical diphospha-
zanes can be used to synthesize ruthenium complexes with a
stereogenic metal center with a high degree of diastereo-
J. Chem. Soc., Dalton Trans., 2002, 4289–4295
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View Article Online
and recrystallized from CH2Cl2/petrol (1 : 3). It was identified as
4a, admixed with 4b. Efforts to isolate pure 4a and 4b were
unsuccessful.
tration of the filtrate to 5 mL and addition of 5 mL of petrol
gave complex 9a as cherry red crystals.
[CpRu{η2-((S)-Ph2PN(*CHMePh)PPh2)}Cl] 9a. Yield:
0.067 g (70%), mp 185–187 ЊC. 1H NMR (CDCl3, ppm): 8.11–
6.75 (m, aryl protons), 4.45 (m, CH–*CHMePh), 4.04 (s, C5H5),
0.68 (d, 3JHH = 7.0 Hz, CH3–*CHMePh). C, H, N analyses for
C37ClH34NP2Ru, found (calculated) (%): 64.05 (64.29), 5.23
(4.95), 1.92 (2.02).
[CpRu{η2-(C6H4O2)PN(CHMe2)PPh2)}(PPh3)]Cl (4a).
1
Yield: 0.046 (40%), mp 203 ЊC (decomp.). H NMR (CDCl3,
ppm): 7.83–6.75 (m, aryl protons), 4.76 (s, C5H5), 2.86 (m,
3
3
CH–Pri), 0.71 (d, JHH = 6.8 Hz, CH3–Pri), 0.78 (d, JHH = 7.0
Hz, CH3–Pri). 31P NMR (CDCl3, ppm): 169.6 (t, P(O2C6H4)),
120 (br, PPh2), 45.0 (t, PPh3).
[CpRu{η2-((S)-Ph2PN(*CHMePh)PPh2)}(PPh3)]Cl 9b.
Yield: 0.006 g (5%), mp 142 ЊC (melts with decomposition). 1H
NMR (CDCl3, ppm): 7.57–6.62 (m, aryl protons), 4.34 (s,
C5H5), 4.83 (m, CH–*CHMePh), 1.14 (d, 3JHH = 7.0 Hz, CH3–
*CHMePh). C, H, N analyses for C55ClH49NP3Ru, found
(calculated) (%): 65.05 (65.29), 5.20 (5.18), 1.52 (1.47).
[CpRu{η1-{Ph2PN(CHMe2)P(O2C6H4)}2(PPh3)]Cl (4b).
31P NMR (CDCl3, ppm) (AAЈXXЈY) 150.2 (dd, AAЈ,
P(O2C6H4) uncoordinated), 123.0 (dd, XXЈ, PPh2 coordinated),
48.6 (dd, PPh3).
Synthesis of 5–7. A mixture of 1 (0.100 g, 1.37 × 10Ϫ4 mol)
and L4–L6 (0.063 g for Y = OC6H4Me-4, 0.065 g for Y =
OC6H3Me2-3,5, 0.061 g for Y = N2C3HMe2-3,5, 1.37 × 10Ϫ4
mol) was dissolved in 30 mL of toluene and the solution was
heated under reflux for 5 h. Concentration of the reaction mix-
ture to ∼10 mL followed by addition of 10 mL of petrol led to
the precipitation of a pale yellow solid. The solid was recrystal-
lized from toluene/petrol (1 : 2) to obtain the pure complexes.
[CpRu*{η2-(Ph2PN(CHMe2)PPh(OC6H4Me-4))}-
Synthesis of 10. A mixture of 1 (0.100 g, 1.37 × 10Ϫ4 mol) and
L9 (0.069 g, 1.37 × 10Ϫ4 mol) was dissolved in 30 mL of toluene.
The reaction mixture was heated under reflux for 5 h and cooled
to room temperature. The 31P NMR spectrum indicated that the
product was a mixture of complexes 10a and 10b. Concen-
tration of the reaction mixture to 10 mL followed by slow
addition of petrol gave complex 10a as dark red crystals. The
complex 10b could not be isolated in a pure form.
1
(PPh3)]Cl 5a. Yield: 0.076 g (60%), mp 208 ЊC. H NMR
(SCSPRRu)-[CpRu{η2-(Ph2PN(*CHMePh)*PPh(N2C3-
HMe2-3,5))}Cl] 10a. Yield: 0.067 g (60%), mp 205 ЊC (melts
(CDCl3, ppm): 7.62–6.87 (m, aryl protons), 4.26 (s, C5H5), 3.80
3
1
(m, CH–Pri), 2.35 (s, Me–C6H4Me-4), 1.36 (d, JHH = 7.0 Hz,
with decomposition). H NMR (CDCl3, ppm): 8.11–6.01 (m,
3
CH3–Pri), 0.88 (d, JHH = 7.0 Hz, CH3–Pri). C, H, N analyses
aryl protons), 5.40 (m, CH–*CHMePh), 4.23 (s, C5H5), 2.45
(s, Me–N2C3HMe2-3,5), 2.04 (s, Me–N2C3HMe2-3,5), 1.57 (d,
3JHH = 7.0 Hz, CH3–*CHMePh). C, H, N analyses for C36-
ClH36N3P2Ru, found (calculated) (%): 61.15 (60.97), 5.30 (5.12),
6.01 (5.92).
for C51ClH49NOP3Ru, found (calculated) (%): 65.58 (66.48),
5.43 (5.38), 1.49 (1.52).
[CpRu*{η2-(Ph2PN(CHMe2)PPh(OC6H3Me2-3,5))}-
(PPh3)]Cl 6. Yield: 0.096 g (75%), mp 197 ЊC. 1H NMR
(CDCl3, ppm): 7.82–6.64 (m, aryl protons), 4.24 (s, C5H5),
3.80 (m, CH–Pri), 2.74 (s, Me–OC6H3Me2-3,5), 2.42 (s,
The reaction of 1 with (SS )- and (SR)-L9. Reaction of
[CpRu(PPh3)2Cl] (0.100 g, 1.37 × 10Ϫ4 mol) with a diastereo-
meric mixture of the diphosphazane, (SS )- and (SR)-Ph2PN-
(*CHMePh)P*Ph(N2C3HMe2-3,5) (∼0.07 g, ∼1.400 × 10Ϫ4 mol)
in boiling toluene for 5 h gave a mixture of compounds 10a–10e
as shown by 31P NMR spectrum of the reaction mixture.
Attempts to separate the complexes in a pure form were
unsuccessful.
3
Me–OC6H3Me2-3,5), 1.39(d, JHH = 7.0 Hz, CH3–Pri), 0.88(d,
3JHH = 7.0 Hz, CH3–Pri). C, H, N analyses for C52ClH51NO-
P3Ru, found (calculated) (%): 66.63 (66.76), 5.36 (5.49), 1.44
(1.49).
[CpRu*{η2-(Ph2PN(CHMe2)PPh(N2C3HMe2-3,5))}-
(PPh3)]Cl 7. Yield: 0.094 g (75%), mp 182 ЊC. 1H NMR
(CDCl3, ppm): 7.50–6.4 (m, aryl protons), 4.32 (s, C5H5), 3.70
(m, CH–Pri), 2.80 (s, Me–N2C3HMe2-3,5), 2.42 (s, Me–
N2C3HMe2-3,5), 1.12 (d, 3JHH = 7.0 Hz, CH3–Pri), 0.94 (d, 3JHH
= 7.0 Hz, CH3–Pri). C, H, N analyses for C49ClH49N3P3Ru,
found (calculated) (%): 62.84 (64.77), 5.91 (5.43), 5.12 (4.62).
Synthesis of 11 and 12. A solution of 9a (0.051 g, 7.23 × 10Ϫ5
mol) in 20 mL of CH2Cl2 was added drop-wise to a solution of
PX3 (0.019 g for PPh3, 0.008 g for P(OMe)3, 7.23 × 10Ϫ5 mol)
and NH4PF6 (0.012 g, 7.23 × 10Ϫ5mol) in CH2Cl2. The reaction
mixture was stirred for 12 h and the solvent was removed
in vacuo to obtain a crude yellow solid. The residue was washed
twice with hot petrol to remove the monophosphane and
crystallized from CH2Cl2/petrol (1 : 3) to obtain a pale-yellow
crystalline solid.
Synthesis of 8. A mixture of [CpRu(PPh3)2Cl] (0.100 g, 1.37 ×
10Ϫ4 mol) and (S ),(R)-Ph2PN(CHMe2)P(O2C20H12) (L7)
(0.076 g, 1.37 × 10Ϫ4 mol) was dissolved in 30 mL of toluene.
The reaction mixture was heated under reflux for 5 h and cooled
to room temperature. The 31P NMR spectrum of the reaction
mixture indicated that the product was a mixture of complexes
8a–8e. Concentration of the reaction mixture to 10 mL fol-
lowed by addition of petrol resulted in the precipitation of a
pale yellow powder. The solid was filtered and recrystallised
from CH2Cl2/toluene (1 : 3) mixture to obtain yellow crystals of
8a. The 31P–31P COSY spectrum of the filtrate confirmed the
presence of complexes 8b–8e.
[CpRu{η2-((S)-Ph2PN(*CHMePh)PPh2)}(PPh3)]PF6 11.
Yield: 0.054 g (70%), mp 192 ЊC (melts with decomposition).
1H NMR (CDCl3, ppm): 7.78–6.70 (m, aryl protons), 4.34
3
(s, C5H5), 4.90 (m, CH–*CHMePh), 1.14 (d, JHH = 7.0 Hz,
CH3–*CHMePh). C, H, N analyses for C55F6H49NP4Ru,
found (calculated) (%): 62.24 (62.15), 4.62 (4.65), 1.33
(1.32).
[CpRu{η2-(L7)}(PPh3)]Cl 8a. Yield: 0.080 g (60%), mp
[CpRu{η2-((S)-Ph2PN(*CHMePh)PPh2)}{P(OMe)3}]PF6
12. Yield: 0.047 g (70%), mp 130 ЊC (melts with decom-
position). 1H NMR (CDCl3, ppm): 7.90–6.70 (m, aryl protons),
4.82 (s, C5H5), 4.32 (m, CH–*CHMePh), 3.2 (d, Me–P(OMe)3,
3JPH = 22 Hz) 1.10 (d, 3JHH = 7.0 Hz, CH3–*CHMePh). C, H, N
analyses for C40F6H43NP5Ru, found (calculated) (%): 51.20
(51.95), 4.10 (4.69), 2.20 (1.51).
1
208–212 ЊC. H NMR (CDCl3, ppm): 8.15–7.11 (m, aryl pro-
tons), 4.60 (s, C5H5), 3.20 (m, CH–Pri), 0.73 (d, 3JHH = 7.0 Hz,
CH3–Pri), 0.67 (d, 3JHH = 7.0 Hz, CH3–Pri). C, H, N analyses for
C58ClH49N02P3Ru, found (calculated) (%): 69.32 (68.19), 4.64
(4.83), 1.42 (1.37).
Synthesis of 9. A mixture of 1 (0.100 g, 1.37 × 10Ϫ4 mol) and
L7 (0.065 g, 1.37 × 10Ϫ4 mol) was dissolved in 30 mL of toluene.
The reaction mixture was heated under reflux for 5 h and cooled
to room temperature. The resultant solution was concentrated
in vacuo to 15 mL and cooled to 0 ЊC for 2 h to obtain a pale
yellow crystalline solid (9b). The solid was filtered. Concen-
Synthesis of 13 and 14. These complexes were prepared by
the same procedure as described above for the complexes 11
and 12.
[CpRu{η2-((S)-Ph2PN(*CHMePh)PPh2)}{η1-(Ph2P(CH2)-
PPh2)}]PF6 13. Yield: 0.064 g (60%), mp 179 ЊC (melts with
4294
J. Chem. Soc., Dalton Trans., 2002, 4289–4295

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Table 3 Details of the X–ray data collection and refinement for com-
pound 10a
Acknowledgements
We thank the Council of Scientific and Industrial Research,
New Delhi, for a financial support and for a Research fellow-
ship (K. R.).
Empirical formula
M
Crystal color, habit
C36 H36 Cl N3 P2 Ru
709.14
Red, prism
Crystal dimensions/mm
Crystal system
Space group
0.15 × 0.1 × 0.1
Orthorhombic
P212121
References
a/Å
b/Å
13.131(2)
14.297(2)
17.2878(2)
3245.5(7)
293(2)
4
0.694
3198
1 (a) E. P. Kundig, C. M. Saudan and G. Bernardinelli, Angew. Chem.,
Int. Ed., 1999, 38, 1220; (b) C. Standfest-Hauser, C. Slugovc,
K. Mereiter, R. Schmid, K. Kirchner, L. Xiao and W. Weissen-
steiner, J. Chem. Soc., Dalton Trans., 2001, 2989; (c) V. Ritleng,
P. Bertani, M. Pfeffer, C. Sirlin and J. Hirschinger, Inorg. Chem.,
2001, 40, 5117; (d ) W. Baratta, W. A. Hermann, R. M. Kratzer and
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and P. Rigo, Organometallics, 1999, 18, 5091; ( f ) H. Brunner,
C. Valerio and M. Zabel, New J. Chem., 2000, 24, 275.
c/Å
U/Å3
Temperature/K
Z
µ/mm
Measured reflections
Independent observed reflections (Rint
Final R indices [I > 2σ(I)]
R indices (all data)
)
3198 [R(int) = 0.0000]
R1 = 0.0634, wR2 = 0.0712
R1 = 0.1787, wR2 = 0.0950
2 (a) H. Brunner, Angew. Chem., Int. Ed., 1999, 38, 1194;
(b) G. Consiglio and F. Morandini, Chem. Rev., 1987, 87, 761;
(c) H. Brunner, Adv. Organomet. Chem., 1980, 18, 151.
3 (a) M. Ito, M. Hirakawa, K. Mukarta and T. Ikariya,
Organometallics, 2001, 20, 379; (b) J. W. Faller, B. P. Patel,
M. A. Albrizzio and M. Curtis, Organometallics, 1999, 18, 3096;
(c) H. Brunner and M. Prommesberger, Tetrahedron: Asymmetry,
1998, 9, 3231; (d ) H. Brunner, B. Nuber and M. Prommesberger,
Tetrahedron: Asymmetry, 1998, 9, 3223; (e) H. Brunner, R. Oeschey
and B. Nuber, Organometallics, 1996, 15, 3616; ( f ) H. Brunner,
R. Oeschey and B. Nuber, J. Chem. Soc., Dalton Trans., 1996, 1499;
(g) J. W. Faller and K. J. Chase, Organometallics, 1995, 14, 1592.
4 For references on chiral diphosphazanes and their transition metal
complexes, see: (a) Y. Gimbert, F. Robert, A. Durif, M. T. Averbuch,
N. Kann and A. E. Greene, J. Org. Chem., 1999, 64, 3492;
(b) A. Badia, R. Navarro and E. P. Urriolabeitia, J. Organomet.
Chem., 1998, 554, 105; (c) R. P. K. Babu, S. S. Krishnamurthy and
M. Nethaji, Organometallics, 1995, 14, 2047; (d ) R. P. K. Babu,
S. S. Krishnamurthy and M. Nethaji, Tetrahedron: Asymmetry,
1995, 6, 427.
1
decomposition). H NMR (CDCl3, ppm): 7.90–6.20 (m, aryl
protons), 4.75 (s, C5H5), 4.34 (m, CH–*CHMePh), 2.19 (d,
CH2-dppm), 1.92 (d, CH2-dppm), 0.34 (d, 3JHH = 7.2 Hz, CH3–
*CHMePh). C, H, N analyses for C62F6H56NP5Ru, found
(calculated) (%): 63.11 (62.84), 4.81 (4.76), 1.17 (1.18).
[CpRu{η2-((S)-Ph2PN(*CHMePh)PPh2)}{η1-(Ph2-
P(CH2)2PPh2)}]PF6 14. Yield: 0.054 g (75%), mp 168 ЊC
(melts with decomposition). H NMR (CDCl3, ppm): 7.90–
6.50 (m, aryl protons), 4.69 (s, C5H5), 4.50 (m, CH–*CHMePh),
1
3
1.48 (d, CH2-dppe), 1.22 (d, CH2-dppe), 0.46 (d, JHH
=
7.2 Hz, CH3–*CHMePh). C, H, N analyses for C63F6H58-
NP5Ru, found (calculated) (%): 63.50 (63.10), 4.90 (4.87),
1.14 (1.17).
5 Part 14. M. Ganesan, S. S. Krishnamurthy and M. Nethaji,
J. Organomet. Chem., 1998, 570, 247.
X-Ray crystallography
6 For ruthenium complexes of diphosphazanes, see: (a) M. S. Bala-
krishna, R. Panda, D. C. Smith, Jr., A. Klaman and S. P. Nolan,
J. Organomet. Chem., 2000, 599, 159; (b) M. S. Balakrishna,
K. Ramaswamy and R. M. Abhyankar, J. Organomet. Chem., 1998,
560, 131; (c) J. Ellermann, C. Schelle, F. A. Knoch, M. Moll and
D. Pohl, Monatsh. Chem., 1996, 127, 783; (d ) J. Ellermann,
C. Schelle, M. Moll, F. A. Knoch and W. Z. Bauer, Z. Anorg. Allg.
Chem., 1995, 621, 789.
7 (a) T. E. Sloan, Top. Stereochem., 1981, 12, 1; (b) K. Stanley and
M. C. Baird, J. Am. Chem. Soc., 1975, 97, 6598.
8 M. I. Bruce, I. Hameister, A. G. Swincer and R. C. Wallis, Inorg.
Synth., 1982, 21, 78.
9 R. J. Cross, T. H. Green and R. J. Keat, J. Chem. Soc., Dalton Trans.,
1976, 1424.
10 R. P. K. Babu, S. S. Krishnamurthy and M. Nethaji, Heteroat.
Chem., 1991, 2, 477.
11 R. P. K. Babu, K. Aparna, S. S. Krishnamurthy and M. Nethaji,
Phosphorus, Sulfur Silicon Relat. Elem., 1995, 103, 39.
12 G. M. Sheldrick, SHELXL97, Program for the refinement of crystal
structures, University of Göttingen, Germany, 1997.
Pertinent crystallographic data for 10a are summarized in
Table 3. A suitable crystal for X-ray analysis was glued to a
glass fiber and coated with paraffin oil to protect it from
atmospheric air and moisture during data collection. Cell con-
stants were obtained by least-squares refinement of the setting
angles of 25 reflections in the range 15 < 2θ < 30Њ. The intensity
data collection was monitored for any variations by three
repeatedly measured control reflections. Lorentz, polarization
and absorption (DIFABS) corrections were applied to the
intensity data. The structure was solved by Patterson method
using SHELXS-86; least square refinements were performed by
the full-matrix method with SHELXL-97.12 All non-hydrogen
atoms were refined anisotropically and hydrogen atoms were
refined isotropically.
CCDC reference number 186808.
See http://www.rsc.org/suppdata/dt/b2/b205247d/ for crystal-
lographic data in CIF or other electronic format.
J. Chem. Soc., Dalton Trans., 2002, 4289–4295
4295