(i6-Arene)ruthenium(n) complexes containing enantiomerically pure (-aminoalkyl)phosphines or a (p-aminoalkyl) phosphinite: Synthesis, stereochemical and kinetic studies

Article abstract of DOI:10.1039/b003514i

Thechiral P-N* ligands [(S)-2-(dimethyIamino)-3-phenylpropyl]diphenylphosphine, (S)-phephos, 1, [(5)-2-(dimethylamino)-2-phenyIethyl]diphenylphosphine, (S)-phglyphos, 2, [(S)-2-(dimethylamino)-3-methylbutyl]-diphenylphosphine, (SJ-valphos, 3, and [(+)-(2S, 3/J)-4-(dimethylamino)-3-methyl]-2-diphenylphosphinoxy-l, 2-diphenylbutane, (+)-(25, 3)-chiraldphos, 4, reacted with [Ru(n6-arene)Cl2]2 (arene =/?-cymene, benzene or hexamethylbenzene), in dichloromethane or tetrahydrofuran solution, affording the corresponding [Ru(η6-arene)-(P-N*)C12] complexes, 5, in which the P-N* acts as a monodentate P-bonded ligand. In methanol the same reactions easily afforded the corresponding chelate complexes [Ru(η6-arene)(P-N*)Cl]Cl. Using ligands 1-3, when the arene is/j-cymene, 90:10 diastereomeric mixtures of the cationic complexes have been obtained while only one diastereomer was formed in the corresponding reactions when the arene is benzene or hexamethylbenzene. The determination of the absolute configuration of the major products as RRa, Sc diastereoisomers was made from the crystal structure and CD spectra comparison of the complex (Ru, Sc)-[Ru(n6-/7-MeC6H4Pr')-(5-phglyphos)Cl]BF4. Complexes [Ru(n6-arene)(P-N*)Cl]Cl were also obtained by adding small amounts of methanol to solutions of [Ru(η6-arene)(P-N*)Cl2] in chloroform. A kinetic study, in CDC13 solution containing variable amounts of methanol, on the chelation process in the neutral species [Ru(n6-arene)(P-N*)ClJ showed first-order behaviour of the A'obs values with the nucleophile (methanol) concentration. The pseudo-first-order rate constants are ascribed to replacement of Cl- by a molecule of methanol. A reaction mechanism is proposed. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b003514i

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(ꢀ6-Arene)ruthenium(II) complexes containing enantiomerically
pure (ꢁ-aminoalkyl)phosphines or a (ꢁ-aminoalkyl) phosphinite:
synthesis, stereochemical and kinetic studies
Carmela G. Arena,a Stefania Calamia,a Felice Faraone,*a Claudia Graiff b and
Antonio Tiripicchiob
a Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica,
Università di Messina, Salita Sperone, 31 Vill. S. Agata, I-98166 Messina, Italy.
E-mail: faraone@chem.unime.it
b Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica,
Università di Parma, Centro di Studio per la Strutturistica Diffrattometrica del CNR,
Parco Area delle Scienze 17A, I-43100 Parma, Italy
Received 3rd May 2000, Accepted 11th July 2000
Published on the Web 29th August 2000
The chiral P–N* ligands [(S)-2-(dimethylamino)-3-phenylpropyl]diphenylphosphine, (S)-phephos, 1, [(S)-2-
(dimethylamino)-2-phenylethyl]diphenylphosphine, (S)-phglyphos, 2, [(S)-2-(dimethylamino)-3-methylbutyl]-
diphenylphosphine, (S)-valphos, 3, and [(ϩ)-(2S,3R)-4-(dimethylamino)-3-methyl]-2-diphenylphosphinoxy-1,2-
diphenylbutane, (ϩ)-(2S,3R)-chiraldphos, 4, reacted with [Ru(η6-arene)Cl2]2 (arene = p-cymene, benzene or
hexamethylbenzene), in dichloromethane or tetrahydrofuran solution, affording the corresponding [Ru(η6-arene)-
(P–N*)Cl2] complexes, 5, in which the P–N* acts as a monodentate P-bonded ligand. In methanol the same
reactions easily afforded the corresponding chelate complexes [Ru(η6-arene)(P–N*)Cl]Cl. Using ligands 1–3,
when the arene is p-cymene, 90:10 diastereomeric mixtures of the cationic complexes have been obtained while
only one diastereomer was formed in the corresponding reactions when the arene is benzene or hexamethyl-
benzene. The determination of the absolute configuration of the major products as RRu,SC diastereoisomers was
made from the crystal structure and CD spectra comparison of the complex (RRu,SC)-[Ru(η6-p-MeC6H4Pri)-
(S-phglyphos)Cl]BF4. Complexes [Ru(η6-arene)(P–N*)Cl]Cl were also obtained by adding small amounts of
methanol to solutions of [Ru(η6-arene)(P–N*)Cl2] in chloroform. A kinetic study, in CDCl3 solution containing
variable amounts of methanol, on the chelation process in the neutral species [Ru(η6-arene)(P–N*)Cl2] showed
first-order behaviour of the kobs values with the nucleophile (methanol) concentration. The pseudo-first-order
rate constants are ascribed to replacement of ClϪ by a molecule of methanol. A reaction mechanism is proposed.
ligand; X = halide) are easily prepared from [Ru(η6-arene)Cl2]2
Introduction
by reaction with one equivalent of the bidentate chiral ligand;1,2
in some cases the neutral species [Ru(η6-arene)(L–L*)X2], con-
taining the L–L* as a monodentate ligand, were also isolated.7
Neutral diastereomeric η6-areneruthenium() chelate com-
plexes were also obtained, in these reactions, using chiral
chelating anions. Among the complexes of the latter group
are diastereomeric ruthenacycles.8 Diastereomeric pseudo-
tetrahedral η6-areneruthenium() complexes are often
configurationally unstable at the stereogenic metal centre and
epimerization at this centre can occur.9
Pseudo-tetrahedral transition metal complexes in which the
metal is a stereogenic centre that contain optically active
ligands are important in determining the role that the metal
plays in the stereochemical course of reactions such as ligand
substitution or migratory insertion.1 This information could be
useful for understanding the stereochemical course of homo-
geneous asymmetric reactions catalysed by transition metal
complexes.2 A literature search revealed that extensive studies
have been performed on half-sandwich η5-C5H5 complexes.
Especially relevant are the stereochemical studies performed by
Consiglio and Morandini2a on ruthenium complexes of the
type [Ru(η5-C5H5)X(prophos)] [prophos = (R)-1,2-propanediyl-
bis(diphenylphosphine)]. Analogous η6-areneruthenium com-
plexes have been studied to a lesser extent. There is renewed
interest in η6-areneruthenium() complexes owing to the great
stability of the metal–arene bond in these compounds3 and
their ability to act as effective precursors for catalytic asym-
metric hydrogenation4 and to promote the synthesis of complex
organic compounds.5 In addition, studies on the kinetics of
CH3CN–CD3CN exchange equilibria in the isoelectronic com-
plexes [Ru(η5-C5η5)(CH3CN)3]ϩ and [Ru(η6-C6η6)(CH3CN)3]2ϩ
have evidenced different pathways for these two simple substitu-
tion reactions.6
We report here the synthesis of η6-areneruthenium()
complexes of the type [Ru(η6-arene)(P–N*)Cl2] (P–N* =
[(S)-2-(dimethylamino)-3-phenylpropyl]diphenylphosphine,
(S)-phephos, 1; [(S)-2-(dimethylamino)-2-phenylethyl]diphenyl-
phosphine, (S)-phglyphos, 2; [(S)-2-(dimethylamino)-3-methyl-
butyl]diphenylphosphine, (S)-valphos, 3; or (ϩ)-(2S,3R)-
4-(dimethylamino)-3-methyl-2-diphenylphosphinoxy-1,2-di-
phenylbutane, (ϩ)-(2S,3R)-chiraldphos, 4), in which the P–N*
ligand is monodentate P-bonded (see Chart 1). The ring closure
processes affording the diastereomeric ionic complexes [Ru(η6-
arene)(P–N*)Cl]Cl are studied. On the basis of kinetic data the
ClϪ replacement can be considered as a bimolecular solvolytic
process due to the attack of methanol at co-ordinated chloride.
The kinetic control of the asymmetric induction in the
formation of the chelate complexes [Ru(η6-arene)(P–N*)Cl]Cl
is discussed. The crystal structure of [Ru(η6-p-MeC6H4Pri)(S-
Diastereomeric η6-areneruthenium() chelate complexes of
the type [Ru(η6-arene)(L–L*)X]ϩ (L–L* = chiral chelating
DOI: 10.1039/b003514i
J. Chem. Soc., Dalton Trans., 2000, 3149–3157
This journal is © The Royal Society of Chemistry 2000
3149

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C6H6)(1–3)Cl2] complexes. (S)-phephos (0.111 g, 0.320 mmol)
was added to a suspension of [Ru(η6-C6H6)Cl2]2 (0.080 g, 0.16
mmol) in dichloromethane (30 mL). The reaction mixture was
then stirred for approximately 2 h at room temperature until no
brown solid remained. The resulting red-orange solution was
reduced to ca. 5 mL and by addition of hexane (30 mL) an
orange powder precipitated. It was separated by filtration,
washed with hexane (3 × 5 mL) and dried. Yield 80%. Calc. for
C29H32Cl2NPRu: C, 58.29; H, 5.4; Cl, 11.87; N, 2.34. Found: C,
58.31, H, 5.45; Cl, 11.90; 5.45%.
Chart 1
[Ru(ꢀ6-C6Me6)(S-phephos)Cl2] 5c. The following procedure
for the preparation of 5c is typical and was used for all [Ru(η6-
C6Me6)(1–3)Cl2] complexes. [Ru(η6-C6Me6)Cl2]2 (0.096 g, 0.144
mmol) was dissolved in 20 mL of chloroform and a solution of
(S)-phephos (0.100 g, 0.288 mmol) in the same solvent (5 mL)
was added. The resulting orange solution was stirred at room
temperature for 30 min then, the solvent was reduced to ca.
5 mL and by addition of hexane (40 mL) an orange powder was
obtained. It was separated by filtration, washed with hexane
(4 × 5 mL) and dried. Yield: 88%. Calc. for C35H44Cl2NPRu: C,
61.67; H, 6.51; Cl, 10.40; N, 2.05. Found: C, 61.52, H, 6.40; Cl,
10.60; N, 2.01.
phephos)Cl2], 5a, is also reported. In order to assign the abso-
lute configuration of the diastereomer formed as the only or
major product in the ring closure process, the structure of
[Ru(η6-p-MeC6H4Pri)(S-phglyphos)Cl]BF4 was determined by
X-ray methods.
Experimental
An established method was used to prepare the compound
[Ru(η6-C6Me6)Cl2]2.10 (ϩ)-(2S,3R)-chiraldphos, 4, was prepared
starting from the corresponding chiral aminoalcohol by a
previously described procedure.11 All other reagents were pur-
chased and used as supplied. Solvents were dried by standard
procedures. All experiments were performed under an atmos-
phere of purified nitrogen. IR spectra were obtained as Nujol
mulls on KBr plates using a Perkin-Elmer FTIR 1720 spec-
[Ru(ꢀ6-p-MeC6H4Pri)(S-phglyphos)Cl2]
6a.
Red-orange
powder. Yield: 83%. Calc. for C32H38Cl2NPRu: C, 60.09; H,
5.99; Cl, 11.09; N, 2.19. Found: C, 60.20; H, 6.05; Cl, 11.21; N,
2.15%.
trometer, H and 31P-{1H} NMR spectra on a Bruker AMX
1
[Ru(ꢀ6-C6H6)(S-phglyphos)Cl2] 6b. Orange powder. Yield
78%. Calc. for C28H30Cl2NPRu: C, 57.64; H, 5.18; Cl, 11.15; N,
2.40. Found: C, 57.75, H, 5.19; Cl, 12.18; N, 2.38%.
R300. 1H NMR spectra were referenced to internal tetra-
methylsilane and 31P-{1H} spectra to external 85% H3PO4; posi-
tive chemical shifts for all nuclei are to higher frequency. NMR
data for complexes 5–13 are reported in Tables 1 and 2. Circular
dichroism (CD) spectra were recorded on a JASCO J-500
spectrophotometer. Elemental analyses were performed by
Redox s.n.c., Cologno Monzese, Milano.
[Ru(ꢀ6-C6Me6)(S-phglyphos)Cl2] 6c. Orange powder. Yield
86%. Calc. for C34H42Cl2NPRu: C, 61.16; H, 6.34; Cl, 10.62; N,
2.10. Found: C, 61.30, H, 6.40; Cl, 10.79; N, 2.06%.
[Ru(ꢀ6-p-MeC6H4Pri)(S-valphos)Cl2] 7a. Red-orange powder.
Yield 88%. Calc. for C29H40Cl2NPRu: C, 57.52; H, 6.66; Cl,
11.71; N, 2.31. Found: C, 57.59, H, 6.68; Cl, 11.69; N, 2.29%.
Preparations
[ꢁ-(Dimethylamino)alkyl]diphenylphosphines 1–3. The pro-
cedure previously reported was modified.12 The procedure for
the preparation of (S)-phephos 1 is typical. Triphenylphos-
phine (2.29 g, 8.75 mmol) was slowly added to a stirred solution
of sodium (0.443 g, 18.8 mmol) in liquid ammonia (70 mL) at
Ϫ78 ЊC. An immediate reaction took place and the solution
became deep orange. After about 2 h, (S)-2-(dimethylamino)-3-
phenylpropyl chloride hydrochloride (2.05 g, 8.75 mmol) was
added at Ϫ 78 ЊC. The resulting mixture was stirred for 12 h.
During this time the ammonia evaporated and a white solid was
obtained. It was extracted 3 times with a total of 30 mL of
hexane. Removal of the hexane left a white solid in 50% yield.
The compound (S)-phglyphos 2, white solid, 20% yield, and (S)-
valphos 3, colorless syrup, 95% yield, were obtained similarly.
[Ru(ꢀ6-C6H6)(S-valphos)Cl2] 7b. Orange powder. Yield: 79%.
Calc. for C25H32Cl2NPRu: C, 54.65; H, 5.87; Cl, 12.90; N, 2.55.
Found: C, 54.80, H, 5.96; Cl, 12.69; N, 2.50%.
[Ru(ꢀ6-C6Me6)(S-valphos)Cl2] 7c. Orange powder. Yield:
86%. Calc. for C31H44Cl2NPRu: C, 58.76; H, 7.00; Cl, 11.19; N,
2.21. Found: C, 58.90, H, 7.10; Cl, 11.10; N, 2.18%.
[Ru(ꢀ6-p-MeC6H4Pri)(chiraldphos)Cl2] 8a. A solution of
chiraldphos (0.153 g, 0.326 mmol) in tetrahydrofuran (10 mL)
was added to a stirred solution of [Ru(η6-p-MeC6H4Pri)Cl2]2
(0.100 g, 0.163 mmol) in the same solvent (25 mL). During the
addition the orange solution changed to a deep red. After 10
min the reaction mixture was concentrated to ca. 5 mL and by
slow addition of hexane (30 mL) a red-orange microcrystalline
powder precipitated. It was separated by filtration, washed with
cold toluene (3 mL) and dried. Yield 75%. Calc. for C48H40-
Cl2NOPRu: C, 63.64; H, 6.25; Cl, 9.12; N, 1.81. Found: C,
63.79, H, 6.30; Cl, 9.19; N, 1.79%.
[Ru(ꢀ6-p-MeC6H4Pri)(S-phephos)Cl2] 5a. The following pro-
cedure for the preparation of 5a is typical and was used for all
[Ru(η6-p-MeC6H4Pr)(1–3)Cl2] complexes. A solution of 0.113 g
(0.326 mmol) of (S)-phephos in dichloromethane (10 mL)
was added to a stirred solution of [Ru(η6-p-MeC6H4Pri)Cl2]2
(0.100 g, 0.163 mmol) in the same solvent (25 mL). During
the addition the orange solution changed to a deep red. After
15 min the reaction mixture was concentrated to ca. 5 mL and
by slow addition of hexane (30 mL) a red-orange microcrystal-
line powder precipitated. It was separated by filtration, washed
with hexane (3 × 5 mL) and dried. Yield 85%. Calc. for C33H40-
Cl2NPRu: C, 60.64; H, 6.17; Cl, 10.85; N, 2.14. Found: C, 60.78,
H, 6.26; Cl, 11.02; N, 2.18%.
[Ru(ꢀ6-p-MeC6H4Pri){PhPCH2CH(CH2Ph)NHMe2}Cl2]PF6
9. NH4PF6 (0.019 g, 0.12 mmol) was added under stirring to a
solution of [Ru(η6-p-MeC6H4Pri)(S-phephos)Cl2] (0.080 g, 0.12
mmol) in dichloromethane (10 mL). After 1 h the solvent was
reduced to ca. 3 mL and by addition of hexane (20 mL) an
orange powder was obtained. It was separated by filtration,
washed with hexane (5mL) and dried. Yield: 88%. IR (KBr,
Nujol): ν(PF6) 840 cmϪ1. Calc. for C33H41Cl2F6NP2Ru: C, 49.57;
H, 5.17; Cl, 8.87; N, 1.75. Found: C, 49.51, H, 5.15; Cl, 8.89;
[Ru(ꢀ6-C6H6)(S-phephos)Cl2] 5b. The following procedure for
the preparation of 5b is typical and was used for all [Ru(η6-
3150
J. Chem. Soc., Dalton Trans., 2000, 3149–3157

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1
N, 1.74%. H NMR (CDCl3): δ 0.85 and 1.1 (2 d, 6 H, J = 7,
6.34; Cl, 10.62; N, 2.10. Found: C, 61.26, H, 6.40; Cl, 10.71; N,
CHCH3), 1.84 (s, 3 H, CH3), 2.11 (m, 1 H, CH), 2.52 (sept, 1 H,
J = 7, CHCH3), 2.65–2.85 (m, 4 H, 2CH2), 2.90 and 2.95 (s, 6 H,
NCH3), 4.86 (d, 1 H, J = 5.9, CHcy), 5.03 (d, 1 H, J = 5.9, CHcy),
5.08 (d, 1 H, J = 5.9, CHcy), 5.28 (d, 1 H, J = 5.9, CHcy), 6.99–
7.21 (m, 5 H, CHAr), 7.37–7.47 (m, 6 H, CHAr), 7.69 (t, 2 H,
J = 9 Hz, CHAr), 8.07 (m, 2 H, CHAr) and 8.35 (br s, 1 H, NHϩ).
2.12%. Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 93.8 (ohmϪ1 cm2 molϪ1).
(RRu,SC)-[Ru(ꢀ6-p-MeC6H4Pri)(S-valphos)Cl]Cl 12a. Red-
orange powder. Yield 88%. Calc. for C29H40Cl2NPRu: C, 57.52;
H, 6.66; Cl, 11.71; N, 2.31. Found: C, 57.63, H, 6.71; Cl, 11.77;
N, 2.25%. Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 92.7 (ohmϪ1 cm2
molϪ1).
31P-{1H} NMR (CDCl3):
δ 22.1 (s) and Ϫ143.8 (sept,
J(PF) = 717 Hz, PF6Ϫ). Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 90 (ohmϪ1
cm2 molϪ1).
(RRu,SC)-[Ru(ꢀ6-C6H6)(S-valphos)Cl]Cl 12b. Orange powder.
Yield 79%. Calc. for C25H32Cl2NPRu: C, 54.65; H, 5.87; Cl,
12.90; N, 2.55. Found: C, 54.76; H, 5.95; Cl, 12.70; N, 2.56%. Λ
(5 × 10Ϫ4–10Ϫ3 M, CH3OH) 99 (ohmϪ1 cm2 molϪ1).
(RRu,SC)-[Ru(ꢀ6-p-MeC6H4Pri)(S-phephos)Cl]Cl 10a. The fol-
lowing procedure for the preparation of 10a is typical and was
used for all chelate complexes. (S)-phephos (0.135 g, 0.389
mmol) was added to a stirred solution of [Ru(η6-p-MeC6-
H4Pri)Cl2]2 (0.120 g, 0.195 mmol) in CH3OH (25 mL) at room
temperature. After 1 h the solvent was removed under reduced
pressure and the residue recrystallized from CH2Cl2–hexane to
(RRu,SC)-[Ru(ꢀ6-C6Me6)(S-valphos)Cl]Cl 12c. Orange powder.
Yield 86%. Calc. for C31H44Cl2NPRu: C, 58.76; H, 7.00; Cl,
11.19; N, 2.21. Found: C, 58.88, H, 7.09; Cl, 11.09; N, 2.17%.
Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 101 (ohmϪ1 cm2 molϪ1).
give an orange powder. H and 31P-{1H} NMR spectra (see
1
Table 2) showed that the orange solid was a diastereomeric mix-
ture of 10a and 10aЈ in the ratio 90:10. From a solution of the
diastereomeric mixture left for 72 h at ambient temperature in
chloroform 10a was obtained as pure sample. Yield 70%. Calc.
for C33H40Cl2NPRu: C, 60.64; H, 6.17; Cl, 10.85; N, 2.14.
Found: C, 60.75, H, 6.19; Cl, 10.79; N, 2.16%. Λ (5 × 10Ϫ4–10Ϫ3
M, CH3OH) 91 (ohmϪ1 cm2 molϪ1).
[Ru(ꢀ6-p-MeC6H4Pri)(chiraldphos)Cl]Cl 13a and 13aЈ. Red-
orange microcrystalline solid, 60:40 diastereomeric mixture.
Yield 75%. Calc. for C48H40Cl2NOPRu: C, 63.64; H, 6.25; Cl,
9.12; N, 1.81. Found: C, 63.77, H, 6.31; Cl, 9.20; N, 1.77%.
Kinetics
The reactions were followed in CDCl3 containing variable
amounts of methanol, ethanol, 2-propanol or 2-methyl-2-
propanol by recording the decrease in intensity of the 31P-{1H}
NMR resonance of the starting material. The alcohol solvents
were purified and dried by standard methods. The kinetic runs
were performed by adding a known volume of methanol (or
of alcohol) to a solution of known concentration of [Ru-
(η6-arene)(P–N*)Cl2] in CDCl3. All the concentrations are
expressed in moles per kilogram of solvent. The kinetics was
studied under pseudo-first-order conditions with the methanol
concentration at least 20 times that of the complex. Under these
conditions, keeping constant the methanol concentration, no
variations in the rate constant were observed when the concen-
tration of the complex was varied. The kinetics are first order
with respect to the free methanol concentration and the plots of
kobs vs. [CH3OH] were linear with no significant intercepts. The
rate constants have been calculated as the means of three
kinetic runs. Activation parameters were obtained from the
Eyring equation.
(RRu,SC)-[Ru(ꢀ6-C6H6)(S-phephos)Cl]Cl 10b. Orange powder.
Yield 81%. Calc. for C29H32Cl2NPRu: C, 58.29; H, 5.4; Cl,
11.87; N, 2.34. Found: C, 58.33, H, 5.43; Cl, 11.90; N, 2.30%. Λ
(5 × 10Ϫ4–10Ϫ3 M, CH3OH) 95.4 (ohmϪ1 cm2 molϪ1).
(RRu,SC)-[Ru(ꢀ6-C6Me6)(S-phephos)Cl]Cl 10c. Orange micro-
crystalline solid. Yield: 80%. Calc. for C35H44Cl2NPRu: C,
61.67; H, 6.51; Cl, 10.48; N, 2.05. Found: C, 61.73, H, 6.58; Cl,
10.58; N, 2.07%. Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 98 (ohmϪ1 cm2
molϪ1).
(RRu,SC)-[Ru(ꢀ6-p-MeC6H4Pri)(S-phglyphos)Cl]Cl 11a. Red-
orange powder. Yield 69%. Calc. for C32H38Cl2NPRu: C, 60.09;
H, 5.99; Cl, 11.09; N, 2.19. Found: C, 60.15; H, 6.03; Cl, 11.11;
N, 2.15%. Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 94.7 (ohmϪ1 cm2
molϪ1).
(RRu,SC)-[Ru(ꢀ6-p-MeC4H4Pri)(S-phglyphos)Cl]BF4
11aЉ.
NaBF4 (0.014 g, 0.125 mmol) was added to a solution of
complex 10a (0.080 g, 0.125 mmol) in 5 mL of methanol. The
reaction mixture was stirred for 12 h, and the orange micro-
crystalline compound that precipitated filtered off and washed
with water and diethyl ether. Yield: 70%. The mother liquors
were vacuum-evaporated to dryness. The residue was dissolved
in dichloromethane and by addition of hexane an orange solid
was obtained. Yield: 15%. Both reaction products showed only
one resonance at δ 48.03 in their 31P-{1H} NMR spectra
(CDCl3). Calc. for C32H38BClF4NPRu: C, 55.63; H, 5.54; Cl,
5.13; N, 2.03. Found: C, 55.70, H, 5.59; Cl, 5.30; N, 1.99%. 1H
NMR (CDCl3): δ 1.26 and 1.30 (2 d, 6 H, J = 7, CHCH3), 1.36
(s, 3 H, CH3), 2.85 (m, 4 H, 2CH2), 2.96 and 3.11 (s, 6 H,
NCH3), 3.50 (m, 1 H, CHCH3), 4.48 (m, 1 H, CH), 5.17 (d, 1 H,
J = 6, CHcy), 5.29 (m, 1 H, CHcy), 5.97 (d, 1 H, J = 6, CHcy), 6.17
(d, 1 H, J = 6 Hz, CHcy) and 7.35–7.62 (m, 15 H, CHAr). Λ
(5 × 10Ϫ4–10Ϫ3 M, CH3OH) 97 (ohmϪ1 cm2 molϪ1).
Crystal structure determination of complexes 5a and 11aЉ
The intensity data of complex 5a were collected at room tem-
perature (293(2) K) on a Philips PW 1100 single-crystal dif-
fractometer using graphite-monochromated Mo-Kα radiation
(λ = 0.71073 Å) and the θ–2θ scan technique. A correction for
absorption was made [maximum and minimum value for the
transmission coefficient 1.0000 and 0.7519].13 The intensity data
of 11aЉ were collected at room temperature (293(2) K) on a
Bruker AMX SMART 1000 single-crystal diffractometer using
graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å)
equipped with area detector. The SMART 1000 package was
used for data reduction and absorption correction. Crystallo-
graphic and experimental details are summarized in Table 3.
Both structures were solved by Patterson and Fourier
methods and refined by full-matrix least-squares procedures
2
(based on Fo ) with anisotropic thermal parameters in the last
cycles of refinement for all the non-hydrogen atoms. The hydro-
gen atoms were introduced into geometrically calculated posi-
tions and refined riding on the corresponding carbon atoms.
All calculations were carried out on the DIGITAL Alpha-
Station 255 computers of the “Centro di Studio per la
Strutturistica Diffrattometrica” del Consiglio Nazionale delle
Ricerche, Parma, using the SHELX 97 systems of crystallo-
graphic computer programs.14,15
(RRu,SC)-[Ru(ꢀ6-C6H6)(S-phglyphos)Cl]Cl 11b. Red-orange
powder. Yield: 78%. Calc. for C28H30Cl2NPRu: C, 57.64; H,
5.18; Cl, 12.15; N, 2.40. Found: C, 57.71, H, 5.21; Cl, 12.27; N,
2.35%. Λ (5 × 10Ϫ4–10Ϫ3 M, CH3OH) 96 (ohmϪ1 cm2 molϪ1).
(RRu,SC)-[Ru(ꢀ6-C6Me6)(S-phglyphos)Cl]Cl 11c. Orange
powder. Yield 86%. Calc. for C34H42Cl2NPRu: C, 61.16; H,
J. Chem. Soc., Dalton Trans., 2000, 3149–3157
3151

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Table 1 1H and 31P-{1H} NMR data for the complexes [Ru(η6-arene) (P–N*)Cl2]a
1Hc
Complex
31P-{1H}b
21.1 (s)
η6-arene
P–N*
1.89 (s, 6 H, NCH3), 2.09 (m, 1 H, CH), 2.67–2.90 (m, 4 H,
5a
0.67/0.87 (2d, 6 H, J 6.9/6.9, CHCH3), 1.81 (s, 3 H, CH3),
2.49 (sept, 1 H, J 6.9, CHCH3), 4.88 (d, 1 H, J 5.9, CH), CH2), 6.97 (d, 2 H, J 7, CHAr), 7.21 (m, 3 H, CHAr), 7.37 (m,
5.05 (br s, 2 H, CH), 5.26 (d, 1 H, J 5.9, CH)
2 H, CHAr), 7.47 (m, 4 H, CHAr), 7.69 (t, 2 H, J 9 CHAr),
8.07 (m, 2 H, CHAr
)
5b
5c
6a
6b
6c
7a
22.2 (s)
23.0 (s)
21.5 (s)
22.3 (s)
23.2 (s)
22.6 (s)
5.24 (br s, 6 H, CH)
1.87 (s, 6 H, NCH3), 2.14 (m, 1 H, CH), 2.58–2.70 (m, 4 H,
CH2), 6.94 (d, 2 H, J 7, CHAr), 7.14 (m, 3 H, CHAr), 7.30–
7.51 (m, 6 H, CHAr), 7.65 (t, 2 H, J 9 CHAr), 7.96 (m, 2 H,
CHAr
)
1.67 (s, 18 H, CH3)
1.88 (s, 6 H, NCH3), 2.15 (m, 1 H, CH), 2.51–2.80 (m, 4 H,
CH2), 6.87 (d, 2 H, J 7, CHAr), 6.96–7.20 (m, 4 H, CHAr),
7.39 (m, 4 H, CHAr), 7.66 (m, 1 H, CHAr), 7.86 (t, 2 H, J 9
CHAr), 8.09 (m, 2 H, CHAr
)
0.75/0.83 (2d, 6 H, J 6.6/6.7, CHCH3), 1.81 (s, 3 H, CH3),
2.51 (sept, 1 H, J 6.8, CHCH3), 4.96 (d, 1 H, J 6, CH), 5.07
(d, 1 H, J 6, CH), 5.1 (d, 1 H, J 6, CH), 5.23 (d, 1 H, J 6,
CH)
1.78 (s, 6 H, NCH3), 3.17 (m, 1 H, CH), 3.25 (br m, 2 H,
CH2), 6.74 (d, 2 H, J 7, CHAr), 6.96 (m, 3 H, CHAr), 7.15–
7.25 (m, 6 H, CHAr), 7.69 (t, 2 H, J 9, CHAr), 7.96 (m, 2 H,
CHAr
)
5.26 (s, 6 H, CH)
1.79 (s, 6 H, NCH3), 3.15 (m, 1 H, CH), 3.26 (br m, 2 H,
CH2), 6.73 (d, 2 H, J 7, CHAr), 6.95 (m, 3 H, CHAr), 7.14–
7.23 (m, 6 H, CHAr), 7.71 (t, 2 H, J 9, CHAr), 7.98 (m, 2 H,
CHAr
)
1.69 (s, 18 H, CH)
1.78 (s, 6 H, NCH3), 3.18 (m, 1 H, CH), 3.25 (br m, 2 H,
CH2), 6.76 (d, 2 H, J 7, CHAr), 6.95 (m, 3 H, CHAr), 7.15–
7.24 (m, 6 H, CHAr), 7.70 (t, 2 H, J 9, CHAr), 7.98 (m, 2 H,
CHAr
)
0.78/0.88 (2d, 6 H, J 6.9/6.9, CHCH3), 1.79 (s, 3 H, CH3),
2.49 (sept, 1 H, J 6.9, CHCH3), 4.90 (d, 1 H, J 6, CH), 5.08
0.61/0.63 (2d, 6 H, J 7/7, CHCH3), 1.54 (m, 1 H, CHCH3),
1.85 (s, 6 H, NCH3), 2.20 (m, 2 H, CH2), 2.72 (m, 1 H, CH),
(d, 1 H, J 6, CH), 5.12 (d, 1 H, J 6, CH), 5.18 (d, 1 H, J 6, 7.34–7.54 (m, 6 H, CHAr), 7.92–8.11 (m, 4 H, CHAr
)
CH)
5.3 (s, 6 H, CH)
7b
7c
8a
23.1 (s)
24.3 (s)
133.8 (s)
0.61/0.63 (2d, 6 H, J 7/7, CHCH3), 1.55 (m, 1 H, CHCH3),
1.87 (s, 6 H, NCH3), 2.19 (m, 2 H, CH2), 2.75 (m, 1 H, CH),
7.32–7.56 (m, 6 H, CHAr), 7.98–8.14 (m, 4 H, CHAr
0.61/0.63 (2d, 6 H, J 7/7, CHCH3), 1.54 (m, 1 H, CHCH3),
1.84 (s, 6 H, NCH3), 2.20 (m, 2 H, CH2), 2.74 (m, 1 H, CH),
)
1.67 (s, 18 H, CH3)
7.39–7.44 (m, 6 H, CHAr), 8.02–8.11 (m, 4 H, CHAr
)
0.87 (m, 6 H, CHCH3), 1.87 (s, 3 H, CH3), 2.39 (m, 1 H, C 1.30 (d, 3 H, J 7.2, CHCH3), 2.04 (s, 6 H, NCH3), 2.89 (m,
HCH3), 4.85 (d, 1 H, J 5.5, CH), 5.21 (br s, 2 H, CH), 5.28 3 H, CH, CH2), 3.8 (m, 2 H, CH2) 2.74 (m, 1 H, CH), 6.8 (m,
(d, 1 H, J 5.5, CH)
8 H, CHAr), 7.25–7.80 (m, 12 H, CHAr)
a δ values with J in Hz; solvent = CDCl3. b H3PO4 as external standard. c SiMe4 is the standard.
CCDC reference number 186/2086.
See http://www.rsc.org/suppdata/dt/b0/b003514i/ for crystal-
lographic files in .cif format.
analysis, IR and 1H and 31P{-1H} NMR spectroscopy; the
crystal structure of compound 5a was fully established by X-ray
analysis.
A view of complex 5a with the atomic numbering scheme is
shown in Fig. 1. Selected bond distances and angles are given
in Table 4. The Ru atom displays a three legged, piano-stool
type of co-ordination involving an η6-co-ordinated p-cymene
group (the six Ru–C bond distances are in the range 2.206(4)–
2.227(4) Å), two chlorine atoms (Ru–Cl 2.420(1) and 2.425(1)
Å) and a P atom from the chiral ligand (Ru–P(1) 2.369(1) Å).
The co-ordination geometry can also be described as pseudo-
tetrahedral if the centroid of the η6-ring is taken as a single
site. The chiral centre C(2) in the ligand possesses an S
configuration.
In accordance with their formulation, compounds 5–8 are
not conducting in acetone solution. NMR data are reported in
Table 1. In the 1H NMR spectra, in CDCl3 solution, the
N(CH3)2 group of the co-ordinated ligands 1–4 displays a sing-
let at δ value nearly that of the “free” ligand, indicating that the
ligand is monodentate P-bonded. The 31P-{1H} NMR spectra,
in CDCl3 solution, exhibit a singlet in the range δ 21.1–24.3 for
the complexes with the aminophosphine ligands 1–3 and at
δ 133.8, in the phosphinoxy-region, for the one with ligand 4.
An attempt to induce ring closure of the P–N* ligand in 5a by
reaction with NH4PF6, in dichloromethane solution, afforded
{[Ru(η6-p-MeC6H4Pri){Ph2PCH2CH(CH2Ph)NHMe2}Cl2]PF6,
9, by protonation of the free nitrogen atom. Compound 9 is an
orange solid, stable to air in the solid state and in solution. In
methanol solution it is a 1:1 electrolyte. The 1H and 31P-{1H},
in CDCl3 solution, are very similar to those of the starting
Results and discussion
Synthesis
The chiral P,N-ligands 1–4 (Chart 1) were prepared starting
from the corresponding chiral aminoalcohol, modifying in
some cases the procedure reported;11,12 they represent a series of
widely different steric and, for 4, electronic properties. Differ-
ently from 1–3, which form by chelation to a metal centre
five-membered ring, the aminophosphinite ligand 4 gives a
seven-membered ring; in addition the phosphorus basicity in 4 is
lower than in 1–3.
[Ru(η-arene)(P–N*)Cl2] complexes (P–N* = (S)-phephos,
arene = p-cymene, 5a, benzene, 5b, or hexamethylbenzene, 5c;
P–N* = (S)-phglyphos, arene = p-cymene, 6a, benzene, 6b, or
hexamethylbenzene, 6c; P–N* = (S)-valphos, arene = p-cymene,
7a, benzene, 7b, or hexamethylbenzene, 7c; P–N* = (2S,3R)-
chiraldphos, arene = p-cymene, 8a, benzene, 8b, or hexamethyl-
benzene, 8c) were obtained in high yield upon reaction of the
corresponding [Ru(η6-arene)Cl2]2 with 1 equivalent of the
P–N* ligand, in dichloromethane or tetrahydrofuran as solvent,
at room temperature. They are orange solids, stable to air in the
solid state and to a limited extent in benzene, toluene and
dichloromethane solution. On standing in methanol or chlorin-
ated solvents for a long time they afford green solids that do not
contain the chiral ligand. They were characterized by micro-
3152
J. Chem. Soc., Dalton Trans., 2000, 3149–3157

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Table 2 1H and 31P-{1H} NMR data for the complexes [Ru(η6-arene) (P–N*)Cl]Cla
1Hc
Complex
31P-{1H}b
49.5 (s)
η6-arene
P–N*
10a
1.28/1.33 (2d, 6 H, J 6.6/6.6, CHCH3), 1.36 (s, 3 H, CH3), 2.64–2.78 (m, 4 H, CH2), 3.2 (m, 1 H, CH), 3.27 (s, 3 H,
3.58 (sept, 1 H, J 6.7, CHCH3), 5.15 (d, 1 H, J 6, CH), 5.37 NCH3), 3.42 (s, 3 H, NCH3), 7.28–7.65 (m, 15 H, CHAr
(br s, 1 H, CH), 5.99 (d, 1 H, J 6, CH), 6.23 (d, 1 H, J 6, CH)
)
10aЈ
45.9 (s)
1.36/1.41 (2d, 6 H, J 6.6/6.6, CHCH3), 1.44 (s, 3 H, CH3), 2.72–2.86 (m, 4 H, CH2), 3.2 (m, 1 H, CH), 3.35 (s, 3 H,
3.62 (sept, 1 H, J 6.7, CHCH3), 5.23 (d, 1 H, J 6, CH), 5.44 NCH3), 3.50 (s, 3 H, NCH3), 7.38–7.72 (m, 15 H, CHAr
(br s, 1 H, CH), 6.06 (d, 1 H, J 6, CH), 6.31 (d, 1 H, J 6, CH)
)
10b
10c
11a
48.7 (s)
47.2 (s)
48.1 (s)
5.86 (br s, 6 H, CH)
2.70–2.79 (m, 4 H, CH2), 3.3 (m, 1 H, CH), 3.50 (s, 3 H,
NCH3), 3.53 (s, 3 H, NCH3), 7.28–7.75 (m, 15 H, CHAr
2.65–2.76 (m, 4 H, CH2), 2.98 (m, 1 H, CH), 3.10 (s, 3 H,
NCH3), 3.21 (s, 3 H, NCH3), 7.18–7.55 (m, 15 H, CHAr
2.80 (m, 2 H, CH2), 2.99 (s, 3 H, NCH3), 3.15 (s, 3 H,
NCH3), 4.52 (m, 1 H, CH), 7.34–7.64 (m, 15 H, CHAr
)
2.04 (s, 18 H, CH3)
)
1.29/1.32 (2d, 6 H, J 6/6, CHCH3), 1.37 (s, 3 H, CH3), 3.54
(m, 1 H, CHCH3), 5.12 (d, 1 H, J 6, CH), 5.33 (br s, 1 H,
CH), 6.09 (d, 1 H, J 6, CH), 6.24 (d, 1 H, J 6, CH)
1.38/1.40 (2d, 6 H, J 6/6, CHCH3), 1.46 (s, 3 H, CH3), 3.62
(m, 1 H, CHCH3), 5.22 (d, 1 H, J 6, CH), 5.42 (br s, 1 H,
CH), 6.18 (d, 1 H, J 6, CH), 6.33 (d, 1 H, J 6, CH)
5.80 (s, 6 H, CH)
)
11aЈ
44.3 (s)
2.90 (m, 2 H, CH2), 3.09 (s, 3 H, NCH3), 3.25 (s, 3 H,
NCH3), 4.60 (m, 1 H, CH), 7.42–7.72 (m, 15 H, CHAr
)
11b
11c
12a
48.5 (s)
46.3 (s)
48.4 (s)
2.82 (m, 2 H, CH2), 2.95 (m, 1 H, CH), 3.05 (s, 3 H, NCH3),
4.50 (m, 1 H, CH), 7.35–7.65 (m, 15 H, CHAr
2.80 (m, 2 H, CH2), 2.91 (m, 1 H, CH), 3.00 (s, 3 H, NCH3),
4.48 (m, 1 H, CH), 7.36–7.65 (m, 15 H, CHAr
)
1.96 (s, 18 H, CH)
)
1.26/1.32 (2d, 6 H, J 6.9/6.9, CHCH3), 1.29 (s, 3 H, CH3), 0.86/1.08 (2d, 6 H, J 7/7, CHCH3), 2.26 (m, 1 H, CHCH3),
3.21 (m, 1 H, CHCH3), 5.09 (d, 1 H, J 6, CH), 5.29 (br s, 2.60 (m, 1 H, CH), 2.77 (m, 2 H, CH2), 3.32 (s, 3 H, NCH3),
1 H, CH), 6.47 (d, 1 H, J 6, CH), 6.88 (d, 1 H, J 6, CH)
3.44 (s, 3 H, NCH3), 7.34–7.54 (m, 6 H, CHAr), 7.35–7.49
(m, 2 H, CHAr), 7.50–7.61 (m, 8 H, CHAr
)
12aЈ
12b
12c
45.1 (s)
49.1 (s)
47.5 (s)
1.35/1.41 (2d, 6 H, J 6.9/6.9, CHCH3), 1.37 (s, 3 H, CH3), 0.95/1.96 (2d, 6 H, J 7/7, CHCH3), 2.35 (m, 1 H, CHCH3),
3.29 (m, 1 H, CHCH3), 5.17 (d, 1 H, J 6, CH), 5.39 (br s, 2.68 (m, 1 H, CH), 2.85 (m, 2 H, CH2), 3.40 (s, 3 H, NCH3),
1 H, CH), 6.56 (d, 1 H, J 6, CH), 6.96 (d, 1 H, J 6, CH)
4.02 (s, 3 H, NCH3), 7.40–7.52 (m, 2 H, CHAr), 7.56–7.68
(m, 8 H, CHAr
)
5.84 (s, 6 H, CH)
0.83/1.02 (2d, 6 H, J 7/7, CHCH3), 2.24 (m, 1 H, CHCH3),
2.71 (m, 1 H, CH), 2.78 (m, 2 H, CH2), 3.21 (s, 3 H, NCH3),
3.31 (s, 3 H, NCH3), 7.34–7.54 (m, 6 H, CHAr), 7.30–
7.45 (m, 2 H, CHAr), 7.52–7.64 (m, 8 H, CHAr
)
1.94 (s, 18 H, CH3)
0.80/1.05 (2d, 6 H, J 6.0/6.0, CHCH3), 2.2 (m, 1 H,
CHCH3), 2.81 (m, 1 H, CH), 2.56 (m, 2 H, CH2), 2.76 (m,
2 H, CH2), 2.81 (m, 1 H, CH), 3.00 (s, 3 H, NCH3), 3.09 (s,
3 H, NCH3), 7.35–7.40 (m, 2 H, CHAr), 7.47–7.59 (m, 8 H,
CHAr
)
13a
108.0 (s)
109.0 (s)
0.91 (m, 6 H, CHCH3), 1.91 (s, 3 H, CH3), 2.52 (m, 1 H, 1.35 (d, 3 H, J 7.2, CHCH3), 2.78 (m, 1 H, CH), 2.90 (m,
CHCH3), 4.96(d, 1 H, J 5.5, CH), 5.32 (br s, 2 H, CH), 5.39
(d, 1 H, J 6, CH), 6.96 (d, 1 H, J 5.5, CH)
3 H, CH, CH2), 3.01 (s, 3 H, NCH3) 3.71 (m, 2 H, CH2), 6.9
(m, 8 H, CHAr), 7.27–7.82 (m, 12 H, CHAr
0.99 (m, 6 H, CHCH3), 1.98 (s, 3 H, CH3), 2.59 (m, 1 H, 1.44 (d, 3 H, J 7.2, CHCH3), 2.86 (m, 1 H, CH), 2.98 (m,
CHCH3), 5.05 (d, 1 H, J 5.5, CH), 5.40 (br s, 2 H, CH), 5.47 3 H, CH, CH2), 3.10 (s, 3 H, NCH3) 3.80 (m, 2 H, CH2), 7.0
)
13aЈ
(d, 1 H, J 6, CH), 7.06 (d, 1 H, J 5.5, CH)
(m, 8 H, CHAr), 7.30–7.88 (m, 12 H, CHAr)
a δ values with J in Hz; solvent = CDCl3. b H3PO4 as external standard. c SiMe4 is the standard.
Table 3 Crystal data of compounds 5a and 11aЉ
Formula
Formula weight
C33H40Cl2NPRu
653.60
C32H38BClF4NPRu
690.93
Crystal system
Space group
Orthorhombic
P212121
Orthorhombic
P212121
a/Å
b/Å
17.149(5)
17.903(5)
10.066(4)
3090.4(18)
4
10.886(4)
24.897(5)
11.912(4)
3222.6(17)
4
c/Å
V/Å3
Z
µ/cmϪ1
7.55
6.64
Reflections collected
Independent reflections
Obs. reflections [I > 2σ(I)]
Data/restraints/parameters
Flack index
4153
4153
3167
4153/0/354
Ϫ0.09(4)
0.0306, 0.0551
0.0519, 0.0603
0.871 and Ϫ0.430
19073
6908 [Rint = 0.0421]
6467
6908/0/380
Ϫ0.05(2)
0.0308, 0.0806
0.0338, 0.0828
0.373 and Ϫ0.928
Final R1, wR2 indices [I > 2σ(I)]
(all data)
Largest difference peak and hole/e ÅϪ3
material except for the N(CH3)2 methyl protons resonance
which is shifted to lower field (δ 2.9 and 2.95) and the presence
of a broad signal at δ 8.35 due to the NH moiety. The 31P-{1H}
NMR chemical shift is almost the same as that of 5a (∆δ 0.9
ppm) indicating that the overall structure of the compound was
not changed by protonation of the amine.
Reaction of [Ru(η6-arene)Cl2]2 with 1 equivalent of the P–N*
ligands 1–3, in methanol, at room temperature, easily afforded
J. Chem. Soc., Dalton Trans., 2000, 3149–3157
3153

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Table 4 Selected bond lengths [Å] and angles (Њ) for complex 5a
Table 5 Selected bond lengths [Å] and angles (Њ) for complex 11aЉ
Ru(1)–C(1)
Ru(1)–C(2)
Ru(1)–C(3)
Ru(1)–C(4)
Ru(1)–C(5)
Ru(1)–C(6)
Ru(1)–P(1)
Ru(1)–Cl(1)
2.211(4)
2.227(4)
2.212(4)
2.206(4)
2.157(4)
2.183(4)
2.369(1)
2.420(1)
Ru(1)–Cl(2)
P(1)–C(23)
N(1)–C(24)
N(1)–C(25)
N(1)–C(26)
C(23)–C(24)
C(24)–C(27)
C(27)–C(28)
2.425(1)
1.834(4)
1.473(5)
1.450(6)
1.461(6)
1.551(5)
1.522(5)
1.514(5)
Ru(1)–C(1)
Ru(1)–C(2)
Ru(1)–C(3)
Ru(1)–C(4)
Ru(1)–C(5)
Ru(1)–C(6)
Ru(1)–N(1)
Ru(1)–Cl(1)
2.298(3)
2.189(3)
2.183(3)
2.269(3)
2.228(3)
2.284(3)
2.243(2)
2.383(1)
Ru(1)–P(1)
P(1)–C(23)
N(1)–C(24)
N(1)–C(25)
N(1)–C(26)
C(23)–C(24)
C(24)–C(27)
2.319(1)
1.828(3)
1.511(3)
1.502(4)
1.491(4)
1.521(4)
1.520(4)
P(1)–Ru(1)–Cl(1)
P(1)–Ru(1)–Cl(2)
Cl(2)–Ru(1)–Cl(1)
C(1)–P(1)–Ru(1)
C(25)–N(1)–C(26)
C(25)–N(1)–C(24)
84.46(4)
88.15(4)
88.14(5)
112.42(14)
112.1(4)
114.4(4)
C(26)–N(1)–C(24)
C(24)–C(23)–P(1)
N(1)–C(24)–C(27)
N(1)–C(24)–C(23)
C(27)–C(24)–C(26)
112.2(4)
119.7(3)
111.4(4)
114.1(3)
110.5(4)
P(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–P(1)
C(23)–P(1)–Ru(1)
C(25)–N(1)–C(26)
C(25)–N(1)–C(24)
C(26)–N(1)–C(24)
86.68(3)
85.46(7)
81.48(7)
104.0(1)
107.1(3)
110.9(2)
109.4(2)
C(26)–N(1)–Ru(1)
C(25)–N(1)–Ru(1)
C(24)–N(1)–Ru(1)
C(24)–C(23)–P(1)
N(1)–C(24)–C(27)
N(1)–C(24)–C(23)
C(27)–C(24)–C(26)
108.8(2)
110.9(2)
109.7(2)
108.3(2)
116.9(2)
109.0(2)
110.5(4)
Fig. 1 An ORTEP16 view of the structure of complex 5a together with
the atomic numbering scheme. The ellipsoids for the atoms are drawn at
30% probability level.
Fig. 2 An ORTEP view of the structure of the cation of complex 11aЉ
Details as in Fig. 1.
the corresponding chelate complexes [Ru(η6-arene)(P–N*)Cl]-
Cl. Depending on the co-ordinated η6-arene, either only one
diastereoisomer or a pair of diastereoisomers that differ in the
configuration at the ruthenium centre was formed (P–N* = (S)-
phephos, arene = p-cymene, 10a and 10aЈ; benzene, 10b; hexa-
methylbenzene, 10c; P–N* = (S)-phglyphos, arene = p-cymene,
11a and 11aЈ; benzene, 11b; or hexamethylbenzene, 11c;
P–N* = (S)-valphos, arene = p-cymene, 12a and 12aЈ; benzene,
12b; or hexamethylbenzene, 12c). Complexes 10–12 were also
obtained by adding a small amount of methanol to solutions of
[Ru(η6-arene)(P–N*)Cl2] in chloroform. Under these condi-
tions, such as in the kinetic experiments (low methanol concen-
tration), small amounts of the second diastereoisomer were
evidenced in solution by 31P-{1H} NMR spectroscopy also
when the η6-arene is benzene (arene = benzene, P–N* = (S)-
phephos, 10bЈ; (S)-phglyphos, 11bЈ; or (S)-valphos, 12bЈ). By
monitoring the reactions of [Ru(η6-arene)Cl2]2 with 1–3 in
methanol and the ring-closure reactions of [Ru(η6-arene)-
(P–N*)Cl2], in chloroform-methanol solution, by 31P-{1H}
NMR spectroscopy, it is evident that one diastereoisomer was
predominantly formed (in some cases it is the only diastereo-
isomer formed) and that their ratio is dependent on the metha-
nol concentration. Using methanol as solvent, [Ru(η6-p-
MeC6H4Pri)Cl2]2 affords 10a and 10aЈ, 11a and 11aЈ, 12a
and 12aЈ as a 90:10 diastereomeric mixture while only one
diastereomer was formed in the corresponding reactions
when the arene is benzene or hexamethylbenzene. The major
diastereoisomer is also the more stable thermodynamically; in
fact, slow conversion of the minor diastereoisomer into the
major one occurs. At the end only one diastereoisomer was
present in the solution; it was easily obtained pure and charac-
terized by microanalysis, conductivity measurements and NMR
spectroscopy. In order to assign the absolute configuration at
the Ru of the major or unique diastereomer observed in the
closure ring process, an X-ray diffraction study of [Ru(η6-p-
MeC6H4Pri)(S-phglyphos)Cl]BF4, 11aЉ, was undertaken. A
view of the cation of the complex 11aЉ with the atomic number-
ing scheme is shown in Fig. 2. Selected bond distances and
angles are given in Table 5. The structure is strictly related to
that of 5a by substituting a Cl atom with the N atom from
S-phglyphos acting as a chelating ligand. The configuration at
the Ru atom is R. The six Ru–C bond distances involving the
η6-co-ordinated p-cymene group are in the range 2.183(3)–
2.298(3) Å. The Ru–Cl(1) bond distance, 2.383(1) Å, is only
slightly shorter than those found in 5a, whereas the Ru–P bond
distance, much shorter than in 5a, 2.319(1) Å, may be
influenced by the chelation of the ligand. The five-membered
chelation ring adopts an envelope conformation with the C(24)
atom 0.691(3) Å out of the mean plane through the other four
atoms.
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J. Chem. Soc., Dalton Trans., 2000, 3149–3157

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Fig. 3 CD spectrum of complex 10b, c = 5 × 10Ϫ4 M, 20 ЊC, CH2Cl2.
∆ε is in units of dm3 molϪ1 cmϪ1
.
Scheme 1 Arene = p-cymene, C6H6 or C6Me6; R = PhCH2, Ph or
(CH3)2CH.
Fig. 4 CD spectrum of complex 11aЉ. Details as in Fig. 3.
The crystallographic determination of the absolute configur-
ation of complex 11aЉ allowed us to assign the configuration
RRuSC to the related complexes 10a–10c, 11a–11c and 12a–12c.
Consequently, diastereomers 10aЈ, 11aЈ and 12aЈ have the SRuSC
configuration.
have conducted a kinetic study of the chelation process
(Scheme 1) in CHCl3 solution containing variable amounts of
methanol. The conversion of the [Ru(η6-arene)(P–N*)Cl2]
complexes into the corresponding ionic diastereoisomers pro-
ceeds to completion in all the reactions. The kinetics of the
reaction were followed by measuring changes in the intensity
of the 31P-{1H} NMR resonance of the starting material with
time. The conversion of [Ru(η6-p-MeC6H4Pri)(S-phephos)Cl2]
into the corresponding ionic diastereoisomers was also followed
by conductivity measurements to confirm that the slow process
can be ascribed to a step affording ionic species. In a separate
experiment by UV/VIS spectroscopy we observed that an
isosbestic point at 348 nm was maintained when only one
diastereoisomer was formed. Kinetic runs were carried out at
three different concentrations of methanol (which is the nucleo-
phile) and the rate constants calculated as the means of three
kinetic runs. The kinetics were studied under pseudo-first-order
conditions and in all cases the methanol concentration was at
least 20 times that of the complex. The kinetics follow a first-
order course and the kobs values are linearly correlated [eqn. (1)]
In Figs. 3 and 4 are reported, as example, the CD spectra, in
CH2Cl2, of the diastereoisomers 10b and 11aЉ. The CD spectra
of the other major diastereomers are very similar, supporting
the conclusion that their absolute configurations in solution are
the same. Compounds 10–13 are orange solids, stable in the air;
in methanol solution they are 1:1 electrolytes. In Table 2 are
1
reported their H and 31P-{1H} NMR data, in CDCl3 solu-
tion. The pairs of diastereomers show, in their 31P-{1H} NMR
spectra, resonances at different δ values; RRuSC diastereomers
containing the ligands 1–3 exhibit a singlet at lower field (in the
range δ 48.0–49.5) than SRuSC diastereomers (about δ 45.5).
The reaction of [Ru(η6-p-MeC6H4Pri)Cl2]2 with ligand 4, in
the molar ratio 1:2, in methanol, afforded the ionic diastereo-
mers [Ru(η6-p-MeC6H4Pri)(2S,3R-chiraldphos)Cl]Cl, 13a and
13aЈ, in the molar ratio 60:40; their 31P-{1H} NMR spectra, in
CDCl3, show resonances at δ 108.03 and 109.01. In this case,
conversion of one diastereomer into the other in methanol or
ethanol does not occur.
kobs = k[CH3OH]
(1)
Steric hindrance due to ring substituents is a determining
factor for asymmetric induction. Kumada and co-workers,12
using β-aminoalkylphosphines such as 1–3 in the catalytic
cross-coupling of a racemic Grignard reagent and vinyl
bromide, found higher stereoselectivity when bulky substituents
were present on the chiral carbon atom in α position to nitro-
gen. In some cases high diastereomeric excesses have been
explained through specific intramolecular interactions that sta-
bilize one diastereomer in comparison to the other.17 For
example, the C–H ؒ ؒ ؒ π interactions such as the β-phenyl effect
can account for the relatively high configurational stability at
the metal atom of one diastereomer with respect to the other.18
The stereoselectivity of the reactions seems not to be affected
strongly by the substituents on the chiral carbon atom of 1–3
but is affected to a major extent by the nature of the co-
ordinated arene. In fact, only when the arene is p-cymene both
diastereomers were obtained.
to the nucleophile (methanol) concentration (Table 6) with no
significant intercepts (Fig. 5).
The pseudo-first-order rate constants in Table 6 can be
related to a bimolecular solvolysis and ascribed to the replace-
ment of ClϪ from the complexes [Ru(η6-arene)(P–N*)Cl2] by
a molecule of methanol. In accordance a decrease of kobs
occurred when the reaction was performed in the presence of an
excess of added chloride ion. In Table 7 are listed the rate con-
stants for the chelation process of complex 5a, on changing the
alcohol. As expected the rate of chelation is strongly dependent
on the nature of the alcohol, showing a significant decrease on
going from methanol to ButOH. Romeo and co-workers19
found the same sequence for solvolytic processes of platinum()
complexes. The electrophilicity and nucleophilicity of the sol-
vent determine the rate of Ru–Cl bond breaking. The solvent
electrophilicity is important in determining the removal of ClϪ,
while solvent nucleophilicity is important in blocking of the
vacant co-ordination site. In protic solvents, electrophilic
solvation of ClϪ through hydrogen bond formation is the factor
determining the differences in the rates observed. This was sup-
Kinetics of the chiral P,N*-ligand ring closure
In order to gain some insight into the ring-closure process we
J. Chem. Soc., Dalton Trans., 2000, 3149–3157
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Table 6 Pseudo-first-order rate constants kobs and second-order rate constants k2 for the chelation process of [Ru(η6-arene) (1–3)Cl2] complexesa
[CH3OH]b
104kobs
k2
Complex
[CH3OH]b
104kobs
k2
c
d
c
d
Complex
5a
3.2
7.26
11.3
1.46
7.26
11.3
16.9
1.46
3.2
0.47
1.03
1.63
0.236
1.02
1.57
2.48
2.80
6.74
10.95
0.49
1.09
1.71
0.207
0.978
1.62
2.49
6c
1.32
3.1
5.00
3.2
7.26
11.3
1.46
7.26
11.3
16.9
1.46
3.2
2.63
6.43
10.55
0.476
1.1
1.68
0.253
1.09
1.57
2.52
2.83
6.77
10.96
(1.43 0.03) × 10Ϫ5
(1.99 0.07) × 10Ϫ4
(1.48 0.02) × 10Ϫ5
5b
7a
7b
(1.45 0.05) × 10Ϫ5
(2.12 0.07) × 10Ϫ4
(1.50 0.02) × 10Ϫ5
5c
6a
6b
5.29
3.2
(1.46 0.06) × 10Ϫ5
(2.12 0.07) × 10Ϫ4
7c
7.26
11.3
1.30
6.97
11.2
16.9
5.29
(1.48 0.02) × 10Ϫ5
a At 298 K. b In mol dmϪ3
.
c sϪ1
.
d In dm3 molϪ1 sϪ1
.
Table 7 Effect of changing the nature of the solvent on the k2 of the
chelation process of complex 5aa
b
Solvent
k2
Methanol
Ethanol
2-Propanol
2-Methyl-2-propanol
(1.43 0.03) × 10Ϫ5
(8.1 0.2) × 10Ϫ6
(3.3 0.3( × 10Ϫ6
(1.2 0.4) × 10Ϫ6
a At 298 K. b In dm3 molϪ1 sϪ1
.
Fig. 6 Correlation plot of the second-order rate constants k2 for the
chelation process of [Ru(η6-p-MeC6H4Pri)(S-phephos)Cl2] with the
hydrogen-bonding donor properties of the solvents.
Fig. 5 Plots of kobs vs. [CH3OH] for the chelation process of
complexes 5a, 5b and 5c. T = 298 K; HMB = C6Me6.
ported by the correlation of the logarithms of the rate constant
with Taft’s α scale for the solvents (Fig. 6) for the ring-closure
process in [Ru(η6-p-MeC6H4Pri)(S-phephos)Cl2]. Taft’s α scale
values20 measure the electrophilicity of the solvent, that is its
ability to hydrogen bond with the anion.
The kinetic results lead us to propose the mechanism illus-
trated in Scheme 2. The rate-determining step of the process is
solvolysis of the starting complex in methanol. This involves
formation of a cationic areneruthenium() solvento intermedi-
ate via interaction of the co-ordinated halide with methanol.
This species is chiral at the metal centre and can assume the
configurations RRuSC and SRuSC depending on the trajectory of
the chloride substitution. Very likely these diastereomeric
solvento-species are in equilibrium and in equimolar ratio since
the stereogenic carbon atom on the monodentate P-donor
ligand is remote from the co-ordination sphere of the metal.
Scheme 2 Arene = p-cymene, C6H6 or C6Me6; R = PhCH2, Ph or
(CH3)2CH.
The subsequent reaction step is fast closure of the chelate ring
by co-ordination of the nitrogen atom to the ruthenium()
centre. This reaction step determines the stereoselectivity of
the process, occurring fast only for the formation of one
diastereomer. We are not able fully to establish the factors
determining the very different rate (and therefore the different
activation energy)8a of the ring closure in the intermediate
diastereomeric solvento-species. Nevertheless the favoured
diastereomer kinetically is also the more thermodynamically
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J. Chem. Soc., Dalton Trans., 2000, 3149–3157

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H. Adams, N. A. Bailey and C. White, Organometallics, 1990, 9,
stable as previously pointed out. It is noteworthy that there are
not many clear examples of kinetic control of asymmetric
induction in the formation of optically active organometallic
compounds containing stereogenic metal centres.8a
2594 and references therein; (i) J. W. Faller, B. P. Patel, M. A.
Albrizzio and M. Curtis, Organometallics, 1999, 18, 3096; (j) D.
Carmona, C. Vega, F. J. Lahoz, S. Elipe, L. A. Oro, M. P. Lamata,
F. Viguri, R. Garcia-Correas, C. Cativiela and M. P. Lopez-Ram de
Viu, Organometallics, 1999, 18, 3364.
The low ∆H‡ and negative ∆S‡ values of 75.66 kJ molϪ1
and Ϫ48.07 J KϪ1 molϪ1 respectively, associated with the sol-
volysis for the ring-closure process on the [Ru(η6-p-MeC6-
H4Pri)(S-phephos)Cl2] substrate at three different temperatures
are consistent with an associative mode of activation of the
chloride.
3 J. W. Faller and K. J. Chase, Organometallics, 1995, 14, 1592.
4 R. Noyori and H. Takaya, Acc. Chem. Res., 1990, 23, 345; K. Wan
and M. E. Davis, Tetrahedron: Asymmetry, 1993, 4, 2461; P. Krasik
and H. Alper, Tetrahedron: Asymmetry, 1992, 3, 1283; K. Mashima,
K. H. Kusano, N. Sato, Y. Matsumura, K. Nozaki, H. Kumo-
bayashi, N. Sayo, Y. Hori, T. Ishizaki, S. Akutagawa and H. Takaya,
J. Org. Chem., 1994, 59, 3064; T. Ohta, H. Takaya, M. Kitamura,
K. Nagai and R. Noyori. J. Org. Chem., 1987, 52, 3174.
5 A. J. Pearson and K. S. Lee, J. Org. Chem., 1994, 59, 2304; A. J.
Pearson and K. S. Lee, J. Org. Chem., 1995, 60, 7153; J. W. Janetka
and D. H. Rich, J. Am. Chem. Soc., 1995, 117, 10585; J. W. Janetka
and D. H. Rich, J. Am. Chem. Soc., 1997, 119, 6488; R. Kramer,
Angew. Chem., Int. Ed. Engl., 1996, 35, 1197; A. J. Pearson,
P. L. Zhang and K. Lee, J. Org. Chem., 1996, 61, 6581.
6 W. Luginbühl, P. Zbinden, P. A. Pittet, T. Armbruster, H.-B. Bürgi,
A. E. Merbach and A. Ludi, Inorg. Chem., 1991, 30, 2350.
7 F. Hapiot, F. Agbossou and A. Mortreux, Tetrahedron: Asymmetry,
1994, 5, 515.
8 (a) S. Attar, J. H. Nelson, J. Fischer, A. DeCian, J.-P. Sutter and
M. Pfeffer, Organometallics, 1995, 14, 4559 and references therein;
(b) H. Brunner, R. Oeschey and B. Nuber, Organometallics, 1996,
15, 3616 and references therein; (c) S. K. Mandal and A. R.
Chakravarty, J. Organomet. Chem., 1991, 417, C59; (d) S. Attar,
V. J. Catalano and J. H. Nelson, Organometallics, 1996, 15,
2932; (e) N. Gul and J. H. Nelson, Organometallics, 1999, 18, 709;
( f ) H. D. Hansen, M. Kalyani and J. H. Nelson, Inorg. Chem., 1999,
38, 2150.
The correlation of Fig. 6 supports the direct interaction of
the solvent with co-ordinated chloride and rules out a mechan-
ism involving direct attack of the solvent at the metal centre
followed by departure of the chloride. Besides, such a mechan-
ism is unlikely because the starting substrate is an 18-electron
species requiring a η6–η4 change in the co-ordination of the
arene. Consiglio and Morandini2a proposed a mechanism
involving formation of a five-co-ordinated square pyramid as
intermediate in the reaction of [Ru(η5-C5η5)LLЈR] with electro-
philes EϩYϪ.
Of note is that the nature of the arene affects the rate of
solvolysis. As expected, electron-donating substituents on the
aromatic ring enhance the rate of solvolysis. For the hexa-
methylbenzene complex the rate constants are significantly
higher than for benzene and p-cymene complexes (Fig. 5). The
different basicity associated with the co-ordinated p-cymene
and benzene is not enough to discriminate the solvolysis rates
of related complexes. In accordance with the proposed mechan-
ism, the nature of the aminophoshine does not significantly
influence the rate of ring closure.
9 H. Brunner, R. Oeschey and B. Nuber, J. Organomet. Chem., 1996,
518, 47; H. Brunner, R. Oeschey and B. Nuber, Angew. Chem., Int.
Ed. Engl., 1994, 33, 866; H. Brunner, R. Oeschey and B. Nuber,
J. Chem. Soc., Dalton Trans., 1996, 1499.
10 M. A. Bennett, T. W. Matheson, G. B. Robertson, A. K. Smith and
P. A. Tucker, Inorg. Chem., 1980, 19, 1014 and references therein.
11 G Franciò, C. G. Arena, M. Panzalorto, G. Bruno and F. Faraone,
Inorg. Chim. Acta, 1998, 277, 119.
12 T. Hayashi, M. Konishi, M. Fukushima, K. Kanehira, T. Hioki and
M. Kumada, J. Org. Chem., 1983, 48, 2195.
Acknowledgements
We thank Professor Raffaello Romeo for stimulating discus-
sions and Ministero dell’Università della Ricerca Scientifica e
Tecnologica for financial support.
13 N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39, 158;
F. Ugozzoli, Comput. Chem., 1987, 11, 109.
14 G. M. Sheldrick, SHELXS 97, Program for the Solution of Crystal
Structures, Universität Göttingen, 1997.
15 G. M. Sheldrick, SHELXL 97, Program for the Refinement of
Crystal Structures, University of Göttingen, 1997.
16 C. K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge,
National Laboratory, Oak Ridge, TN, 1976.
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