Synthesis and stereoselective interconversion of chiral 1-aza-3,6-diphosphacycloheptanes

Article abstract of DOI:10.1002/ejic.201101337

Cyclic seven-membered bisphosphanes, namely 1-aza-3,6- diphosphacycloheptanes 3-5 (3: 3,6-diphenyl-1-(1-phenylethyl)-1-aza-3,6- diphosphacycloheptane; 4: 1-[(1R)-1-(4′-methoxyphenyl)ethyl]-3,6-diphenyl- 1-aza-3,6-diphosphacycloheptane; 5: 3,6-diphenyl-1-[

Full text of DOI:10.1002/ejic.201101337

FULL PAPER
DOI: 10.1002/ejic.201101337
Synthesis and Stereoselective Interconversion of Chiral 1-Aza-3,6-
diphosphacycloheptanes
Elvira I. Musina,*[a] Andrey A. Karasik,[a] Anna S. Balueva,[a] Igor D. Strelnik,[a]
Tatiana I. Fesenko,[a] Alexey B. Dobrynin,[a] Tatiana P. Gerasimova,[a] Sergey A. Katsyuba,[a]
Olga N. Kataeva,[a] Peter Lönnecke,[b] Evamarie Hey-Hawkins,[b] and Oleg G. Sinyashin[a]
Keywords: Phosphanes / Phosphorus / Platinum / Heterocycles / Stereoconversion
Cyclic seven-membered bisphosphanes, namely 1-aza-3,6-
diphosphacycloheptanes 3–5 (3: 3,6-diphenyl-1-(1-phenyl-
ethyl)-1-aza-3,6-diphosphacycloheptane; 4: 1-[(1R)-1-(4Ј-
methoxyphenyl)ethyl]-3,6-diphenyl-1-aza-3,6-diphosphacy-
cloheptane; 5: 3,6-diphenyl-1-[(1R)-1-phenylpropyl]-1-aza-
3,6-diphosphacycloheptane), with chiral exocyclic substitu-
ents at the nitrogen positions have been synthesized, with
the prevailing formation of meso stereoisomers (PRPS) as ki-
{(3R,6S)-3,6-diphenyl-1-[(1R)-1-phenylpropyl]-1-aza-3,6-
diphosphacycloheptane}platinum(II) dichloride). The fast
and selective formation of the cationic complex (9) of the
meso isomer 5RSR allowed for the separation of the 5RRR and
5SSR isomers of the bisphosphane 5. In solution, selective ste-
reoconversion of the pure 3RSS, 3RSR and 4RSR isomers into a
mixture containing 3RRS, 3SSR and 4SSR stereoisomers as the
predominant products was observed. As a result, the stereo-
netically controlled products, by stereoselective condensa- conversion is accompanied by a change in not only the value
tion of 1,2-bis(phenylphosphanyl)ethane, formaldehyde and
primary optically pure amines, namely (S)-(–)-1-phenylethyl-
but also in the sign of the specific rotation, [α]2D0. The ratio of
the stereoisomers in an equilibrium mixture of 3C(S) (3RSS
/
amine, (R)-(+)-1-phenylethylamine, (R)-(+)-1-phenylpropyl- 3RRS/3SSS in a 24:48:28 ratio) is in accord with their relative
amine, (R)-(+)-1-(4Ј-methoxyphenyl)ethylamine. The meso
stereoisomers of bisphosphanes 3RSS, 3–5RSR readily form
neutral and cationic P,P-chelate complexes 6–9 with plati-
num(II) (6: cis-dichloro-(3R,6S)-3,6-diphenyl-1-[(1S)-1-phen-
energies that were calculated with the B3LYP/6-31G* basis.
Kinetic studies of the stereoconversion of bisphosphane 3C(S)
have been performed. The rate constants that were deter-
mined are indicative of a bimolecular interconversion mecha-
nism, which is supposedly the reason for the relatively low
activation energies for inversion at phosphorus. Molecular
structures were obtained, by X-ray crystal structure analysis,
for the meso 3RSS and 3RRS stereoisomers of the N-(S)-1-phen-
ylethyl]-1-aza-3,6-diphosphacycloheptaneplatinum(II);
7:
cis-dichloro-(3R,6S)-1-[(1R)-1-(4Ј-methoxyphenyl)ethyl]-3,6-
diphenyl-1-aza-3,6-diphosphacycloheptaneplatinum(II); 8:
bis{(3R,6S)-[(1R)-3,6-diphenyl-1-(1-phenylethyl)-1-aza-3,6-
diphosphacycloheptane]}platinum(II) dichloride; 9: bis-
ylethyl-substituted bisphosphanes and for 4RSR
.
ment to enable the stereochemical control of the substrate.
Most chiral bisphosphane ligands are planar chiral and/or
possess chirality due to a stereogenic carbon center. How-
ever, transition metal complexes of bisphosphanes bearing
P-stereogenic or P- and C-stereogenic centers have proved
to be excellent catalysts for asymmetric allylic substitu-
tion,[5] asymmetric hydrogenation,[5,6,7] asymmetric hydro-
formylation,[5,8] and asymmetric hydrosilylation[7,9] reac-
tions, and display high enantioselectivity.[10] Therefore, the
development of synthetic approaches to P-stereogenic bis-
phosphanes and methods for the resolution of their
enantiomers have received increasing attention. Most com-
mon synthetic approaches to P-chirogenic bisphosphanes
involve the introduction of chiral spacers between the two
phosphorus atoms,[11–16] synthesis from chiral borane-pro-
tected monophosphanes,[17–18] as well as procedures em-
ploying the enantiodifferentiated deprotonation of prochi-
ral phosphane–boranes in the presence of chiral induc-
tors.[19–21] However, these methods are usually labor inten-
sive and rather complicated to perform.
Introduction
Optically active phosphanes play a very important role
as chiral ligands in various metal catalyzed enantioselective
processes, and numerous chiral phosphanes have been re-
ported in the past three decades.[1–4] Chiral chelating
bisphosphanes are of special interest due to their high effec-
tiveness in many asymmetric catalytic reactions. The rela-
tively rigid chelate structure of their metal complexes stabi-
lizes the configuration of the metal center and provides it
with a fixed position relative to the chiral center or frag-
[a] A. E. Arbuzov Institute of Organic and Physical Chemistry,
Russian Academy of Sciences, Kazan Scientific Center,
Arbuzov str. 8, 420088 Kazan, Russian Federation
Fax: +7-8432-752-253
E-mail: elli@iopc.ru
[b] Institut für Anorganische Chemie der Universität Leipzig,
Johannisallee 29, 04103 Leipzig, Germany
E-mail: hey@rz.uni-leipzig.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201101337.
Eur. J. Inorg. Chem. 2012, 1857–1866
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E. I. Musina et al.
FULL PAPER
Mild, reversible, self-regulating and self-correcting pro-
cesses seem to be very promising approaches to the synthe-
sis of P-chirogenic bisphosphanes. The Mannich-type con-
densation that occurs in the phosphane (or bisphosphane)/
formaldehyde/amine system is one such process, and has the
advantage of variability that allows for different types of
phosphane ligands bearing a wide variety of chiral substitu-
ents on the heteroatoms to be obtained.[22] We have already
reported the synthesis of the first representatives of a new
class of seven-membered cyclic aminomethylphosphanes,
namely 1-aza-3,6-diphosphacycloheptanes, which were ob-
tained as equimolar mixtures of meso and rac diastereoiso-
mers from the condensation reaction of 1,2-bis(phenylphos-
phanyl)ethane with paraformaldehyde and primary aryl-
amines.[23] Only the rac diastereoisomers of these cyclic bis-
phosphanes have been isolated in pure forms. We have,
therefore, now employed enantiomerically pure primary
amines in the synthesis of 1-aza-3,6-diphosphacyclo-
heptanes in order to facilitate the resolution of the dia-
stereoisomers with R,R and S,S configurations at the phos-
phorus atoms, or to possibly modify the stereochemical
products of the condensation reaction. The corresponding
meso diastereoisomers (PR,PS) are also interesting as these
Scheme 1. Synthesis of 1-aza-3,6-diphosphacycloheptanes 3–5.
cyclic bisphosphanes would also be new optically active ratio of meso and rac isomers in the starting material 1,2-
chelate ligands. The study of the configurational stability of bis(phenylphosphanyl)ethane was ca. 1:1, inversion of the
the phosphorus atoms and the ability of 1-aza-3,6-di- configuration at phosphorus must take place during the
phosphacycloheptanes to undergo stereoconversion in solu- course of the condensation reaction. The meso isomer 5RSR
tion are other points of interest.
crystallized spontaneously from the reaction mixture; the
meso isomers 3RSS and 3RSR were obtained by recrystalli-
zation of the crude products from ethanol/acetone (5:1).
Their diastereomeric purities were unambiguously con-
firmed by 31P and 1H NMR spectroscopy. Fractions en-
riched with one of the diastereoisomers with identical con-
Results and Discussion
Syntheses
figurations at the phosphorus atoms, namely 3RRS or 3SSR
,
Reaction of rac/meso-1,2-bis(phenylphosphanyl)ethane were obtained from the filtrates after isolation of the meso
(1)[24] with paraformaldehyde at 100–110 °C smoothly led isomers 3RSS or 3RSR. Attempts to obtain fractions enriched
to the formation of rac/meso-1,2-bis[(hydroxymethyl)phen- with the third diastereoisomer (3SSS or 3RRR) were unsuc-
ylphosphanyl]ethane (2), which was used without ad- cessful. In the case of compound 5, fractional crystalli-
ditional purification. Condensation reaction of 2 with pri- zation did not give the pure diastereoisomers; only mixtures
mary amines with chiral substituents, namely (S)-(–)-1- enriched with one of the isomers were obtained: the ratios
phenylethylamine, (R)-(+)-1-phenylethylamine, (R)-(+)-1-
5RSR:5RRR:5SSR in the first, second and third fractions were
(4Ј-methoxyphenyl)-ethylamine and (R)-(+)-1-phenylprop- 75:25:0, 22:61:17 and 23:26:51, respectively. However, these
ylamine, in ethanol, gave 1-aza-3,6-diphosphacycloheptanes different fractions allowed for the signals in their 31P and
3–5 as air-stable crystalline solids that are soluble in benz- 1H NMR spectra to be assigned to the corresponding iso-
ene, chloroform, acetone and DMF (Scheme 1).
mers.
The 31P NMR spectra of the reaction mixtures of 3–5
The 31P NMR spectra of the meso isomers of 3–5 showed
showed three sets of signals indicating the presence of three two doublets for the nonequivalent phosphorus atoms in
diastereoisomers: the meso isomers PRPSCS(R) (3RSS, 3– the range δP = –33 to –34 ppm with coupling constants 3JPP
5
RSR) and two different isomers with identical configura- of 51–53 Hz. The coupling constants are larger than those
tions at phosphorus, namely PSPSCS(R) (3SSS, 3–5SSR) and reported for acyclic bisphosphanylethanes (35–45 Hz)[25]
PRPRCS(R) (3RRS, 3–5RRR). The presence of three stereoiso- and indicate strong interactions between the two phos-
mers is caused by the additional C-chiral substituents at the phorus atoms in the compounds, possibly due to their
nitrogen positions.
eclipsed position in the P–CH2CH2–P fragment. This non-
In contrast to the previously described 1-aza-3,6-diphos- equivalence was observed only when the samples were dis-
phacycloheptanes with aryl substituents on the nitrogen solved in selected solvents (in DMF for 3RSS, 3RSR, 4RSR
,
atoms,[23] a high prevalence of the meso isomers was ob- and in CDCl3 for 5RSR) whereas in spectra recorded with
served for 3–5 [80–90% for 3C(S), 3C(R) and 4; 60% for 5], the samples in other solvents these signals coalesced into
which indicates the stereoselectivity of the reactions. As the slightly broadened singlets. All methylene protons of the P-
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Chiral 1-Aza-3,6-diphosphacycloheptanes
CH2-N fragments are nonequivalent and were observed as
1
four groups of signals in the H NMR spectra of the meso
isomers of 3–5.
The 31P spectra of the two isomers 3RRS and 3SSS as well
as 3–5SSR and 3–5RRR showed singlets for the heterocycles
that are present in these compounds at slightly higher field
relative to the signals in the spectra of 3RSS or 3–5RSR (δP
1
= –34 to –35 ppm). In the H NMR spectra, the methylene
protons of the P–CH2–N fragments are observed as two
multiplets that correspond to the axial and equatorial pro-
tons.
The configurations of the meso isomers 3RSS and 4RSR
were also proved by X-ray structure analysis (Figures 1 and
2).
Figure 2. Molecular structure of 4RSR
.
atoms are in pyramidal environments (sum of bond angles:
342.27° for 3RSS, 342.22° for 4RSR) with the exocyclic sub-
stituents in the axial positions. To the best of our knowl-
edge, up to now stable chair conformations have only been
described for cycloheptanes with rigid benzo groups or un-
saturated ethene-1,2-diyl fragments linking the phosphorus
atoms.[26]
It should be noted that quantum chemical optimization
of the structure of 3RSS, with a starting geometry deter-
mined by XRD analysis, within the DFT framework, pro-
duces two energetically favored typical twist-chair conform-
ers (Figure 3, A and C), while the chair conformation corre-
sponds to the saddle point of the potential energy surface
Figure 1. Molecular structure of 3RSS
.
The seven-membered rings in 3RSS and 4RSR exhibit un-
usual chair conformations with almost planar P–C–C–P
fragments [the torsion angles P(3)–C(4)–C(5)–P(6) in 3RSS
and 4RSR are –2.1 and 8.0°, respectively (Table 1)] with the
P–C bonds in eclipsed positions. Both phenyl substituents
on the phosphorus atoms are pseudo-equatorial and the
electron lone pairs of the phosphorus atoms are in axial
positions. The P(3)···P(6) distances are short (3.120 and
3.118 Å for 3RSS and 4RSR, respectively) in comparison with
P···P distances within known rac isomers of 1-aza-3,6-di-
Figure 3. B3LYP/6-31G* calculated stable conformations of 3RSS
,
their conformational energies (ΔE, kcal/mol) relative to the elec-
tronic energy of the most stable conformation (C), and computed
phosphacycloheptanes (3.599–3.985 Å).[23] The nitrogen values of the P–C–C–P torsion angles (°).
Table 1. Selected bond lengths [Å], contact distances [Å] and angles [°] in 3RSS, 3RRS and 4RSR and computational results for 3RSS and
3RRS
.
3RSS
XRD
3RRS
XRD
4RSR
XRD
B3LYP[a]
B3LYP[b]
B3LYP
P(3)–C(2)
P(3)–C(4)
P(6)–C(5)
P(6)–C(7)
N(1)–C(2)
N(1)–C(7)
C(4)–C(5)
P(3)···P(6)
C(2)–N(1)–C(7)
C(2)–N(1)–C(8)
C(7)–N(1)–C(8)
P(3)–C(4)–C(5)–P(6)
1.877(9)
1.84(1)
1.839(9)
1.858(9)
1.44(1)
1.45(1)
1.54(1)
3.120(5)
114.0(6)
116.7(7)
111.2(6)
–2.1(9)
1.929
1.900
1.881
1.917
1.454
1.452
1.538
3.516
114.1
117.2
114.9
–53.1
1.928
1.886
1.885
1.924
1.449
1.458
1.546
3.304
113.9
117.8
113.8
32.3
1.857(3)
1.856(3)
1.851(3)
1.877(3)
1.477(3)
1.455(3)
1.518(4)
3.574(2)
113.9(2)
110.0(2)
113.8(2)
–72.0(3)
1.893
1.886
1.885
1.918
1.466
1.462
1.538
3.628
113.8
110.16
112.8
–67.3
1.895(2)
1.847(3)
1.849(3)
1.891(2)
1.445(3)
1.456(3)
1.530(3)
3.118(2)
112.8(2)
111.9(2)
117.4(2)
8.0(3)
[a] Computational results for conformer B (Figure 3). [b] Computational results for conformer A (Figure 3).
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E. I. Musina et al.
FULL PAPER
(Figure 3, B). The rather small relative energy of B suggests Platinum(II) Complexes of 1-Aza-3,6-
that even the weak influence of the crystal packing could diphosphacycloheptanes
easily transform the twist-chair conformers A and C into
the chair conformer B that was observed in the X-ray dif-
fraction analysis of 3RSS
Reactions of 3RSS, 3RSR and 4RSR with dichloro(1,5-cy-
clooctadiene)platinum(II) in CH2Cl2 in different stoichio-
metric ratios gave either neutral (6, 7) or cationic (8) com-
plexes (Scheme 2).
.
Single crystals of 3RRS were obtained from the filtrate
after isolation of 3RSS [recrystallization of crude 3C(S) from
ethanol/acetone (5:1)]. The X-ray structure analysis unam-
biguously established the configurations of 3RRS in the solid
state (Figure 4, Table 1), as well as the typical twist-chair
conformation of the seven-membered ring.
The 31P NMR spectra of 6 and 7 showed two peaks (27.8
and 27.9 ppm, 26.5 and 26.6 ppm, respectively) with cou-
1
pling constants JPtP in the range of 3219–3230 Hz, which
is typical for cis-chelate P,P complexes of cyclic aminometh-
ylphosphanes of PtCl2. The 31P NMR spectrum of 8
showed only one peak at δ = 26.3 ppm; the coupling con-
1
stant JPtP = 2384 Hz is typical for complexes with a trans
arrangement of the phosphane ligands. The downfield shifts
of the signals for complexes 6–8 in comparison with the
signals of the free ligands (Δδ = 59–61 ppm) is indicative of
the formation of five-membered metallacycles.[23] The sig-
nals of the protons of the P–CH2–N fragments were ob-
served as complex multiplets and a broad doublets in the
1H NMR spectra of 6–8. Elemental analysis and NMR
spectroscopic data shows that 6 and 7 are neutral chelate
complexes with a ligand-to-metal ratio of 1:1, while 8 is a
cationic chelate complex (ratio 2:1) (Scheme 2).
Figure 4. Molecular structure of 3RRS
.
Taking into account the higher thermodynamic stability
According to the Henderickson method, based on the of chelate complexes in comparison with polymeric struc-
sequence of the signs of the torsional angles[27] the confor- tures with bridging bisphosphane ligands, we used complex
mation of the seven-membered ring in 3RRS may be de- formation for the separation of the diastereoisomers of the
scribed as twist-chair like the conformations of the pre- cyclic bisphosphane 5. A similar approach based on the dif-
viously studied rac isomers of N-aryl-1-aza-3,6-diphos- ferent complexing properties of meso and rac isomers has
phacycloheptanes.[23] The nitrogen atom is in a pyramidal been reported for the separation of the meso and rac iso-
environment (the sum of the bond angles is 337.81°), and mers of 1,3-diphosphacyclohexanes.[28] The reaction of a
the exocyclic substituent on the nitrogen atom is in an axial stereoisomeric mixture of 5 (5RSR:5RRR:5SSR = 55:30:15)
position. The phenyl groups on the phosphorus atom are with stoichiometric amounts (calculated for the formation
in pseudo-equatorial positions, and the pseudo-axial elec- of the homoleptic cationic complex) of dichloro(1,5-cyclo-
tron lone pairs of phosphorus are pointing towards oppo- octadiene)platinum(II) {[PtCl2(cod)]} in CH2Cl2 led to the
site sides of the ring.
formation of the desired complex [Pt(5RSR)2]Cl2 (9), which
Scheme 2. Synthesis of platinum complexes 6–8.
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Chiral 1-Aza-3,6-diphosphacycloheptanes
Scheme 3. Separation of the diastereomers of 5 by complex formation with [PtCl2(cod)].
is similar to 8 (Scheme 3). The 31P NMR spectrum of the 48%), with almost equal amounts of 3SSS (ca. 28%) and
reaction mixture showed one peak at δP = 26.5 ppm for 9 3RSS (ca. 24%) being present, which indicates that asym-
and two singlets for the unreacted diastereomers 5RRR and metric induction takes place over the course of the stereo-
5SSR at δP = –33.5 and –35.0 ppm.
conversion process leading to the predominant formation
Addition of ethanol to the reaction mixture resulted in of the heterocycle with only one configuration at the phos-
precipitation of unreacted 5RRR and 5SSR (61:39). Complex phorus atom. As a result, the stereoconversion is ac-
9 was isolated from the filtrate after removal of unreacted companied by a change not only in the value but also in
isomers of 5.
the sign of the specific rotation [α]2D0, which changes from
+25.6 for pure 3RSS to –5.0 for the final mixture of isomers
3RRS (ca. 48%), 3SSS (ca. 28%) and 3RSS (ca. 24%).
These results indicate that the meso isomers of 1-aza-
3,6-diphosphacycloheptanes are the kinetically controlled
products of the condensation reactions between 1,2-bis-
[(hydroxymethyl)phenylphosphanyl]ethane, formaldehyde
and enantiopure α-alkylbenzylamines, whereas the PRPRCS
and PSPSCR isomers are the thermodynamically favored
products. These stereoisomers are of interest for catalytic
systems containing stereogenic bisphosphane ligands.
Quantum chemical estimation of the composition of the
equilibrium mixture of 3RRS, 3SSS and 3RSS produced re-
sults that were very similar to those obtained by experi-
ment.
Racemisation Kinetics and Configurative
Stability
The stability of the configurations at the chiral phos-
phorus atoms is extremely important. Interconversion of
stereoisomers has been observed for the heterocycles 3RSS
3RSR and 4RSR and was studied, with the representative
compound 3RSS in deuterated benzene, by 31P NMR spec-
troscopy (Scheme 4).
,
The following fractions of the diastereomers were calcu-
lated on the basis of the B3LYP/6-31G* computed ΔG val-
ues reported in Table 2 and with the Boltzmann equation:
3
RRS (ca. 48%), 3SSS (ca. 29%), 3RSS (A, ca. 20%) and 3RSS
(B, ca. 3%). The practically perfect agreement between the
computed composition of the mixture and the experimental
data demonstrates the suitability of the DFT B3LYP/6-
31G* level for studies of the relative thermodynamic sta-
bility of the diastereomeric and rotameric forms of 3. Ab
initio Hartree–Fock (HF) computations produce qualita-
tively similar ΔG values to those obtained by DFT
(Table 2).
Scheme 4. Interconversion of the stereoisomers of 3.
After several hours (7 and 11 h for highly and lowly con-
centrated solutions, respectively) two additional signals for
It should be noted that dispersion interactions cannot be
the isomers 3SSS and 3RRS appeared at δP = –35.0 and evaluated properly by either HF or by B3LYP methods. In
–36.0 ppm, respectively, in the 31P NMR spectra of the contrast to B3LYP, the Minnesota functional M05-2X pro-
solutions. The thermodynamic equilibrium was established vides a correct description of dispersion forces. Thus, we
after 720 h at 295.5 K or after 32 h at 343 K. The isomer have tried to evaluate whether or not M05-2X produces rel-
3RRS noticeably prevailed in the equilibrium solution (ca. ative energies for the structural forms under study that are
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E. I. Musina et al.
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Table 2. Electronic energies (E), Gibbs free energies (G) for the diastereomers of 3, and their values relative to the most stable form 3RRS
(ΔE, ΔG).
Computation method
HF/6-31G*
Diastereomer
E (a.e.u.)
G (a.e.u.)
ΔE [kcal/mol]
ΔG [kcal/mol]
3RRS
3SSS
3RSS (A)
3RSS (B)
–1660.4291740
–1660.4284876
–1660.4254989
–1660.4226109
–1659.999795
–1659.999133
–1659.997015
–1659.993016
0
0
0.4
2.3
4.1
0.4
1.7
4.3
B3LYP/6-31G*
3RRS
–1668.2481509
–1668.2478568
–1668.2469941
–1668.2462763
–1667.853385
–1667.852924
–1667.852557
–1667.850607
0
0
3SSS
0.2
0.7
1.2
0.3
0.5
1.7
3RSS (A)
3RSS (B)
M05–2X/6-311++G**
3RRS
–1668.4101827
–1668.4097616
–1668.4085023
–1668.4083288
0
3SSS
0.3
1.1
1.2
3RSS (A)
3RSS (B)
different from those obtained with the B3LYP method. The formation of 16-membered rings (instead of eight-mem-
results of the M05-2X/6-311++G** single-point calculation bered rings) was observed in the condensation reaction of
of relative energies, ΔE (Table 2), are in reasonable agree- 1,3-bis(arylphosphanyl)propanes with formaldehyde and
ment with the data obtained from the B3LYP/6-31G* com- various benzylamines.[31]
putations, which suggests a rather moderate role for the dis-
persion forces in the stereoconversion process studied.
Determination of rate constants, reaction orders and ac-
tivation parameters for the inversion at phosphorus in 3C(S)
were carried out with dynamic 31P NMR spectroscopy con-
ducted with two different sample concentrations (0.0255
and 0.0750 m) and at two different temperatures (295.5 K
and 343 K). Each kinetic curve (Supporting Information)
was plotted in the form Δc vs. t (with ca. 12–14 data points).
Treatment of the data obtained by the initial rates method
(first 6 points) allowed for the calculation of rates, reaction
orders and activation energies. These kinetics parameters
are given in Table 3.
Conclusions
It has been shown that a mixture of meso and rac dia-
stereoisomers of 1,2-bis[(hydroxymethyl)phenylphosphan-
yl]ethane stereoselectively reacts with enantiopure α-substi-
tuted benzylamines to give the meso isomers (PRPS) of the
corresponding 1-aza-3,6-diphosphacycloheptanes as the
major kinetically controlled products. Separation of the di-
asteroisomers has been achieved by fractional crystalli-
zation or by selective formation, with the meso isomers, of
platinum(II) dichloride chelate complexes. In the solid state,
the meso isomers of 1-aza-3,6-diphosphacycloheptanes ex-
hibit unusual chair conformations, whereas isomers with
identical configurations at the phosphorus atoms adopt
twist-chair conformations.
Table 3. Kinetic parameters for the diastereoisomeric interconver-
sions of 3C(S)
.
Reaction direction Rate constant Rate constant Activation energy
(T = 295.5 K) (T = 343 K)
[kcal/mol]
The meso isomers of the cyclic bisphosphanes 3–5 spon-
taneously and stereoselectively convert to a mixtures of iso-
mers with PSPSCR (PRPRCS) being the prevailing form. The
stereoselectivity of this conversion is a result of the asym-
metric induction of the chiral exocyclic substituent. The
conversions proceed with relatively low activation energies
and probably do so via a series of intermolecular nucleo-
philic substitution reactions.
3RSS Ǟ 3SSS (k1)
3SSS Ǟ 3RSS (k–1)
3RSS Ǟ 3RRS (k2)
3RRS Ǟ 3RSS (k–2)
0.0038
0.0031
0.0031
0.0013
0.578
0.572
0.267
0.154
21.3
22.1
18.9
20.2
The inversion barriers for the phosphorus atoms of 1-
aza-3,6-diphosphacycloheptane 3C(S) (Table 3) are about
20 kcal/mol, which are noticeably lower than the typical
values reported for tertiary phosphanes (30–38 kcal/
mol).[29,30] The high rates of inversion for bisphosphanes 3–
5 can be explained by the mechanism of this process. The
value of the reaction order of ca. 1.5 indicates that at least
one of the limiting steps in the isomerization mechanism
is a bimolecular process. Since the simple inversion of the
pyramidal configuration at phosphorus and the reversible
rupture of a P–C bond are monomolecular processes, it is
reasonable to assume that the stereoconversion of 1-aza-
3,6-diphosphacycloheptanes proceeds via a series of inter-
molecular nucleophilic substitution reactions with the par-
ticipation of the phosphorus atoms, perhaps through the
Experimental Section
General: All synthetic and spectroscopic manipulations involving
1,2-bis(phenylphosphanyl)ethane and 1,2-bis[(hydroxymethyl)-
phenylphosphanyl]ethane were carried out in an inert atmosphere.
NMR spectra were recorded on a MSL-400 instrument (Bruker)
and CXP-100 with the following standards: 31P NMR (161 MHz
1
and 36.47 MHz), external 85% H3PO4; H NMR (400 MHz), in-
ternal solvent; 13C NMR (100.6 MHz), internal solvent. The atom
numbering schemes are shown in Scheme 1. Gas liquid chromatog-
raphy mass spectra were obtained on a DFS Thermo Electron Cor-
poration spectrometer (electron energy: 70 eV, ion source tempera-
intermediate formation of 14-membered heterocycles. The ture: 280 °C, DS-5MS column). Melting points were determined
1862 Eur. J. Inorg. Chem. 2012, 1857–1866
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chiral 1-Aza-3,6-diphosphacycloheptanes
with a Boetius apparatus. Specific rotations were determined on a
Perkin–Elmer Model 341 polarimeter operating at 589 nm. Circu-
lar dichroism (CD) spectra were recorded on a Jasco-500A spectro-
polarimeter.
(391.43): calcd. C 73.66, H 6.91, N 3.58, P 15.86; found C 73.14,
H 6.78, N 3.85, P 15.32.
3,6-Diphenyl-1-[(1R)-1-phenylethyl]-1-aza-3,6-diphosphacyclo-
heptane [3C(R)]: A solution of 2 (1.24 g, 4.0 mmol) and (R)-(+)-α-
methylbenzylamine (0.50 g, 4.1 mmol) in ethanol (15 mL) was
stirred at ambient temperature for 10 min. The precipitate that
formed was isolated by filtration, washed with ethanol and dried
at 0.1 Torr for 2–4 h; yield of 3: 0.82 g (52%); m.p. 124–126 °C.
Recrystallization of crude 3C(R) from acetone/ethanol (1:5) gave the
meso isomer 3RSR; m.p. 128–130 °C. [α]2D0 = –25.6 (c = 0.01 in
1,2-Bis(phenylphosphanyl)ethane (1)[23,24] was obtained from 1,2-
bis(diphenylphosphanyl)ethane (dppe), and 1,2-bis[(hydroxymeth-
yl)phenylphosphanyl]ethane (2) was obtained by heating 1 in the
presence of paraformaldehyde.[23] [PtCl2(cod)] (cod = 1,5-cyclooc-
tadiene) was prepared according to a method reported in the litera-
ture.[32]
1
C6H6). H NMR (400 MHz, CDCl3, TMS): δ = 7.19–7.50 (m, 15
3
H, C6–13-H, Ar), 4.47 [q, J(H,H) = 6.5 Hz, 1 H, C5-H], 3.68 [ddd,
3,6-Diphenyl-1-[(1S)-1-phenylethyl]-1-aza-3,6-diphosphacyclo-
heptane [3C(S)]: A solution of 2 (1.37 g, 4.47 mmol) in ethanol
(15 mL) and (S)-(–)-α-methylbenzylamine (0.54 g, 4.46 mmol) was
stirred at ambient temperature for 15 min. The precipitate that
formed was isolated by filtration, washed with ethanol and dried
at 0.1 Torr for 2–4 h; yield 1.00 g (58 %); m.p. 126–130 °C.
Recrystallization of crude 3C(S) from acetone/ethanol (1:5) gave the
meso isomer 3RSS: m.p. 128–131 °C; [α]2D0 = +25.6 (c = 0.01, in
2J(H,H) = 14.3 Hz, J = 4.4 Hz, J = 4.8 Hz, 1 H, C2-H], 3.37 [ddd,
2
4
2J(H,H) = 14.3 Hz, J(P,H) ≈ J(H,H) ≈ 2.1 Hz, 1 H, C2-H], 3.09–
3.20 (m, 2 H, C2-H), 2.30–2.50 (m, 4 H, C4-H), 1.49 [d, J(H,H) =
3
6.5 Hz, 3 H, C5-H] ppm. 1H NMR (400 MHz, [D7]DMF): δ =
7.23–7.57 (m, 15 H, C6–13-H), 4.48 [q, J(H,H) = 6.5 Hz, 1 H, C5-
3
H], 3.62 [dd, 3J(H,H) = 14.0 Hz, 2J(P,H) = 9.2 Hz, 1 H, C2-H],
3.51 [dd, 2J(H,H) = 14.3 Hz, 2J(P,H) = 5.1 Hz, 1 H, C2-H], 3.26
[dd, 2J(H,H) = 14.3 Hz, 2J(P,H) = 5.5 Hz, 1 H, C2-H], 3.06 [dd,
1
C6H6). H NMR (400 MHz, CDCl3, TMS): δ = 7.20–7.45 (m, 15
H, C6–13-H), 4.48 [q, 3J(H,H) = 6.8 Hz, 1 H, C5-H], 3.68 [ddd,
2
2J(H,H) = 14.0 Hz, J(P,H) = 8.5 Hz, 1 H, C2-H], 2.32–2.50 (m, 4
2
4
2J(H,H) = 14.2 Hz, J(P,H) ≈ J(H,H) ≈ 4.0 Hz, 1 H, C2-H], 3.37
[dd, 2J(H,H) = 14.2 Hz, 2J(P,H) = 2.9 Hz, 1 H, C2-H], 3.09–3.19
(m, 2 H, C2-H), 2.30–2.50 (m, 4 H, C4-H), 1.49 [d, 3J(H,H) =
H, C4-H), 1.47 [d, 3J(H,H) = 6.5 Hz, 3 H, C14-H] ppm. 31P{1H}
NMR (161 MHz, CDCl3, TMS): δ = –34.2 ppm. 31P{1H}
(161 MHz, C6D6, TMS): δ = –34.3 ppm. 31P{1H} (161 MHz
[D7]DMF): δ = –32.9 [d, 3J(P,P) = 53.0 Hz], –33.6 [d, 3J(P,P) =
53.0 Hz] ppm. EI-MS (70 eV): m/z (%) = 391.3 (1.0) [M+].
C24H27NP2 (391.43): calcd. C 73.66, H 6.91, N 3.58, P 15.86; found
C 73.99, H 6.99, N 3.42, P 15.12.
1
6.8 Hz, 3 H, C14-H] ppm. H NMR (400 MHz, C6D6, TMS): δ =
3
7.19–7.48 (m, 15 H, C6–13-H), 4.61 [q, J(H,H) = 6.8 Hz, 1 H, C5-
H], 3.66 [m, 2J(P,H) = 4.4 Hz, 1 H, C2-H], 3.32 [m, 2J(P,H) =
4.4 Hz, 1 H, C2-H], 3.24 [dd, 2J(H,H) = 15.1 Hz, 2J(P,H) = 4.0 Hz,
1 H, C2-H], 3.04 [dd, 2J(H,H) = 15.1 Hz, 2J(P,H) = 4.0 Hz, 1 H,
After one week, a CDCl3 solution that initially contained pure 3RSR
had converted into a mixture of 3RSR, 3RRR and 3SSR in a 27:28:45
3
C2-H], 2.04–2.21 (m, 4 H, C4-H), 1.43 [d, J(H,H) = 6.4 Hz, 3 H,
C14-H] ppm. 13C{1H} NMR (100.6 MHz, CDCl3, TMS): δ =
1
ratio. H NMR (400 MHz, CDCl3, TMS): δ = 7.19–7.49 (m, 15 H
1
1
144.64 (s, C10), 138.9 [d, J(P,C) = 46 Hz, C6], 131.72 [d, J(C,H)
= 161.5 Hz, C11], 131.24 [d, 1J(C,H) = 159.5 Hz, C7], 128.33 [d,
1J(C,H) = 165.4 Hz, C8,12], 127.8 [d, 1J(C,H) = 162.4 Hz, C13],
3
+ 15 H + 15 H, C6–13-H, 3RSR + 3RRR + 3SSR), 4.47 [q, J(H,H) =
6.7 Hz, 1 H, C5-H, 3RSR], 3.99 [q, 3J(H,H) = 6.6 Hz, 1 H, C5-H,
3
3
SSR], 3.93 [q, J(H,H) = 6.6 Hz, 1 H, C5-H, 3RRR], 3.64–3.79 (m,
127.6 [d, J(C,H) = 159.5 Hz, C9], 61.80 [tm, J(C,H) = 131.9 Hz,
1
1
1 H+2 H+ 2 H, C2-H, 3RSR + 3RRR + 3SSR), 3.37 [br.d, J(H,H) ≈
2
1J(P,C) = 13.0 Hz, C2], 58.39 [dt, 1J(C,H) = 127.0 Hz, 3J(P,C) =
14 Hz, 1 H, C2-H, 3RSR], 3.34 [br.d, J(H,H) = 14.2 Hz, 2 H+ 2 H,
2
9.0 Hz, C5], 57.38 [tm, J(C,H) = 132.9 Hz, J(P,C) = 9.3 Hz, C2],
27.40 [dt, 1J(C,H) = 122.1 Hz, 1J(P,C) = 11.8 Hz, C4], 20.80 [q,
1J(C,H) = 126 Hz, C14] ppm. 31P{1H} NMR (36.5 MHz, CDCl3,
TMS): δ = –33.2 ppm. 31P{1H} (161 MHz, C6D6, TMS): δ =
1
1
C2-H, 3RRR + 3SSR], 3.10–3.19 (m, 2 H, C2-H, 3RSR), 2.30–2.50 (m,
4 H + 2 H+ 2 H, C4-H, 3RSR + 3RRR + 3SSR), 2.21–2.27 (m, 2 H
+ 2 H, C4-H, 3RRR + 3SSR), 1.49 [d, J(H,H) = 6.7 Hz, 3 H, C14-
3
H, 3RSR], 1.45 [d, 3J(H,H) = 6.6 Hz, 3 H, C14-H, 3RRR], 1.41 [d,
3J(H,H) = 6.6 Hz, 3 H, C14-H, 3SSR] ppm. 31P{1H} NMR
(161 MHz, CDCl3, TMS): δ = –34.1 (3RSR), –34.5 (3RRR), –35.2
(3SSR) ppm.
–34.3 ppm. 31P{1H} (161 MHz, [D7]DMF): δ = –33.9 [d, J(P,P) =
3
52.6 Hz], –34.5 [d, 3J(P,P) = 52.6 Hz] ppm. EI-MS (70 eV): m/z (%)
= 391 (0.9) [M+], 363 (0.8) [M+ – C2H4], 335 (0.20) [M+ – C4H8],
314 (0.2) [M+ – Ph], 286 (7.2) [M+ – PhC2 H4 ], 258 (3.4)
[C16H21PN+], 216 (3.1) [C13H16PN+], 178 (7.6), [C10H13PN+], 133
(4.5) [C9H11N+], 132 (0.8) [C9H10N+], 105 (100.0) [PhC2H4+], 91
(10.7) [PhCH2+], 77 (25.2) [Ph+]. C24H27NP2 (391.43): calcd. C
73.66, H 6.91, N 3.58, P 15.86; found C 73.57, H 6.87, N 3.65, P
15.75.
1-[(1R)-1-(4Ј-Methoxyphenyl)ethyl]-3,6-diphenyl-1-aza-3,6-diphos-
phacycloheptane (4): A solution of 2 (1.42 g, 4.6 mmol) and (R)-
(+)-α-methyl-p-methoxybenzylamine (0.69 g, 4.6 mmol) in ethanol
(15 mL) was stirred at 60 °C for 30 min. After the solution was
cooled to ambient temperature the precipitate of 4RSR that formed
was isolated by filtration, washed with ethanol and dried at
The precipitate that formed from the filtrate was a mixture of 0.1 Torr for 2–4 h; yield of 4: 1.21 g (62%); m.p. 108–110 °C; [α]2D0
1
3
RSS:3SSS:3RRS in a 29:14:57 ratio. 1H NMR (400 MHz, C6D6, = –19.9 (c = 0.01 in C6H6). H NMR (400 MHz, CDCl3, TMS): δ
TMS): δ = 6.96–7.51 (m, 15 H + 15 H + 15 H, C6–13-H, 3RSS
+
= 7.24–7.53 [m, J(H,H) = 8.5 Hz, 10 H + 2 H, C6–9,11-H], 6.88 [d,
3J(H,H) = 8.5 Hz, 2 H, C12-H], 4.45 [q, 3J(H,H) = 6.5 Hz, 1 H,
3
3
RRS + 3SSS), 4.61 [q, 3J(H,H) = 6.4 Hz, 1 H, C5-H, 3RSS], 4.04 [q,
3J(H,H) = 6.4 Hz, 1 H, C5-H, 3RRS], 3.96 [q, J(H,H) = 6.4 Hz, 1 C5-H], 3.82 (s, 3 H, C15-H), 3.68 [ddd, 2J(H,H) = 14.7 Hz, J =
H, C5-H, 3SSS], 3.80 [br.d, 2J(H,H) ≈ 14 Hz, 2 H + 2 H, C2-H, 4.1 Hz, J = 5.1 Hz, 1 H, C2-H], 3.39 [dd, 2J(H,H) = 14.7 Hz,
3
3RRS + 3SSS], 3.64–3.69 (m, 1 H, C2-H, 3RSS), 3.46 [br.d, J(H,H) 2J(P,H) = 4.1 Hz, 1 H, C2-H], 3.21 [br.d, J(H,H) = 14.0 Hz, 1 H,
2
2
≈ 14 Hz, 2 H + 2 H, C2-H, 3RRS + 3SSS], 3.32 (m, 1 H, C2-H, 3RSS),
C2-H], 3.09 [dd, J(H,H) = 14.0 Hz, J(P,H) = 2.9 Hz, 2 H, C2-H],
2
2
3.24 [br.d, J(H,H) ≈ 15 Hz, 1 H, C2-H, 3RSS], 3.05 [br.d, J(H,H) 2.29–2.48 (m, 4 H, C4-H), 1.48 [d, J(H,H) = 6.5 Hz, 3 H, C14-H]
2
2
3
≈ 15 Hz, 1 H, C2-H, 3RSS], 2.06–2.21 (m, 4 H + 4 H + 4 H, C4-H,
ppm. 31P{1H} NMR (161 MHz, CDCl3): δ = –32.0 ppm. 31P{1H}
3
3
RSS + 3RRS + 3SSS), 1.43 [d, J(H,H) = 6.4 Hz, 3 H, C14-H, 3RSS], NMR (161 MHz, [D7]DMF): δ = –32.0 [d, 3J(P,P) = 52.7 Hz],
1.37 [d, 3J(H,H) = 6.4 Hz, 3 H, C14-H, 3SSS], 1.25 [d, 3J(H,H) =
6.4 Hz, 3 H, C14-H, 3RRS] ppm. 31P{1H} NMR (161 MHz, C6D6,
TMS): δ = –34.0 (3RSS), –34.9 (3SSS), –36.0 (3RRS) ppm. C24H27NP2
–32.3 [d, J(P,P) = 52.7 Hz] ppm. C25H29NOP2 (421.46): calcd. C
3
71.26, H 6.89, N 3.33, P 14.73; found C 70.97, H 6.57, N 3.15, P
14.80.
Eur. J. Inorg. Chem. 2012, 1857–1866
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1863

E. I. Musina et al.
3,6-Diphenyl-1-[(1R)-1-phenylpropyl]-1-aza-3,6-diphosphacyclo- cis-Dichloro-(3R,6S)-1-[(1R)-1-(4Ј-methoxyphenyl)ethyl]-3,6-di-
FULL PAPER
heptane (5): A solution of 2 (1.60 g, 5.2 mmol) and (R)-(+)-α-ethyl-
benzylamine (0.71 g, 5.3 mmol) in ethanol (20 mL) was stirred at
ambient temperature for 30 min. The precipitate that formed was
isolated by filtration, washed with ethanol and dried at 0.1 Torr for
2–4 h; yield of 5: 1.4 g (67%); m.p. 108–110 °C. Recrystallization
of crude 5 from acetone/ethanol (1:5) gave the meso isomer 5RSR
in 75% purity (with 25% of 5RRR), m.p. 110–111 °C. 1H NMR
phenyl-1-aza-3,6-diphosphacycloheptaneplatinum(II) (7): A solution
of dichloro(1,5-cyclooctadiene)platinum(II) (0.08 g, 0.2 mmol) in
CH2Cl2 (5 mL) was added dropwise to a solution of 4RSR (0.09 g,
0.2 mmol) in CH2Cl2 (5 mL). The reaction mixture was stirred at
ambient temperature for 30 min. The precipitate that formed was
filtered off and washed with CH2Cl2 to give 7; yield 0.08 g (54.5%);
m.p. Ͼ 260 °C; [α]2D0 = +17 (c = 0.01 in DMSO). 1H NMR
3
3
(400 MHz, CDCl3, TMS): δ = 7.16–7.50 (m, 15 H, C6–13-H), 4.15– (400 MHz, [D6]DMSO): δ = 7.81 [dd, J(H,H) = 7.6 Hz, J(H,H)
4.19 (m, 1 H, C5-H), 3.71 [dd, 2J(H,H) = 14.0 Hz, 2J(P,H) = 9.4 Hz, = 10.5 Hz, 2 H, C8-H], 7.69 [dd, 3J(H,H) = 7.6 Hz, 3J(H,H) =
1 H, C2-H], 3.32 [dd, 2J(H,H) = 14.0 Hz, 2J(P,H) = 5.3 Hz, 1 H,
10.5 Hz, 2 H, C8-H], 7.49–7.62 (m, 6 H, C7,9-H), 7.39 [d, J(H,H)
3
2
2
C2-H], 3.19 [dd, J(H,H) = 14.0 Hz, J(P,H) = 8.9 Hz, 1 H, C2-H], = 8.8 Hz, 2 H, C11-H], 6.94 [d, 3J(H,H) = 8.8 Hz, 2 H, C12-H], 5.03
3.09 [dd, J(H,H) = 14.0 Hz, J(P,H) = 5.7 Hz, 1 H, C2-H], 2.09– [q, J(H,H) = 6.3 Hz, 1 H, C5-H], 3.63–3.87 (m, 3 H + 2 H, C15,2
-
2
2
3
2.47 (m, 1 H + 4 H, C14A,4-H), 1.67–1.79 [m, J(H,H) = 7.3 Hz, 1 H), 2.77–2.93 (m, 2 H, C2-H), 2.26–2.50 (m, 4 H, the signal for the
3
H, C14B-H], 0.75 [t, J(H,H) = 7.3 Hz, 3 H, C15-H] ppm. 31P{1H}
C4 protons is partially masked by the [D6]DMSO signal), 1.45 [d,
3
3
NMR (161 MHz, CDCl3): δ = –33.0 [d, J(P,P) = 57.2 Hz], –33.9
3J(H,H) = 6.3 Hz, 3 H, C14-H] ppm. 31P{1H} NMR (161 MHz,
[d, 3J(P,P) = 57.2 Hz] ppm. EI-MS (70 eV): m/z (%) = 405 (1.7) [D6]DMSO): δ = 26.5 [1J(Pt,P) = 3227 Hz], 26.6 [1J(Pt,P) =
[M+], 377 (1.7) [M+ – C2H4], 349 (0.33) [M+ – C4H8], 348 (0.9) 3219 Hz] ppm. C25H29Cl2NOP2Pt (687.45): calcd. C 43.67, H 4.22,
[M+ – C4H9], 286 (12.8) [M+ – PhC3H6], 258 (4.9) [C16H21PN+], Cl 10.33, N 2.04, P 9.01, Pt 28.38; found C 43.26, H 4.12, Cl 10.62,
216 (2.5) [C13H16PN+], 178 (1.6) [C10H13PN+], 133 (3.0) [C9H11N+],
132 (0.35) [C9H10N]+, 119 (60.2) [PhC3H6+], 118 (50.9) [PhC3H5+],
105 (1.5) [PhC2H4+], 91 (100.0) [PhCH2+], 77 (9.8) [Ph+]. MALDI-
MS: 406 (100.0) [M + H+], 405 (1.0). C25H29NP2 (405.46): calcd.
C 74.07, H 7.16, N 3.46, P 15.31; found C 73.97, H 6.98, N 3.39,
P 15.12.
N 1.89, P 9.15, Pt 28.58.
Bis{(3R,6S)-3,6-diphenyl-1-[(1R)-1-phenylethyl]-1-aza-3,6-diphos-
phacycloheptane}platinum(II) Dichloride (8): A solution of
dichloro(1,5-cyclooctadiene)platinum(II) (0.05 g, 0.13 mmol) in
CH2Cl2 (5 mL) was added dropwise to a solution of 3RSR (0.11 g,
0.28 mmol) in CH2Cl2 (5 mL). The reaction mixture was stirred at
ambient temperature for 30 min. The solvent was removed in
vacuo, and the residue was recrystallized from diethyl ether, filtered
off and washed with diethyl ether; yield of 8: 0.08 g (57%); m.p. Ͼ
260 °C, [α]2D0 = –7 (c = 0.01 in CH2Cl2). 1H NMR (400 MHz,
CDCl3, TMS): δ = 6.96–7.33 (m, 30 H, C6–13-H), 4.74 (br.d, J =
10.5 Hz, 2 H, C2-H), 4.24 (br.d, J = 10.5 Hz, 2 H, C2-H), 4.02 [m,
3J(H,H) = 6.7 Hz, 2 H, C5-H], 3.13–3.40 (m, 4 H, C2-H), 2.02–2.43
(m, 8 H, C4-H), 1.56 [d, 3J(H,H) = 6.7 Hz, 6 H, C14-H] ppm.
31P{1H} NMR (161 MHz, CDCl3): δ = 26.3 [1J(Pt,P) = 2384 Hz]
ppm. C48H54Cl2N2P4Pt (1048.86): calcd. C 54.96, H 5.15, Cl 6.77,
N 2.67, P 11.83; found C 54.67, H 5.34, Cl 6.62, N 2.65, P 11.92.
A precipitate obtained from the filtrate after cooling was isolated
by filtration, washed with cool ethanol and dried at 0.1 Torr for
3 h. The precipitate was a mixture of 5RSR, 5RRR and 5SSR in the
1
ratio 22:61:17. H NMR (400 MHz, CDCl3, TMS): δ = 7.18–7.51
(m, 15 H + 15 H + 15 H, C6–13-H, 5RSR + 5SSR + 5RRR), 4.15–4.19
(m, 1 H, C2-H, 5RSR), 3.68–3.77 (m, 1 H + 2 H + 2 H, C2-H, 5RSR
+ 5SSR + 5RRR, 1 H + 1 H, C5-H, 5SSR + 5RRR), 3.32–3.39 [m,
2J(H,H) = 14.0 Hz, 1 H + 2 H + 2 H, C2-H, 5RSR + 5SSR + 5RRR],
2
2
3.22 [dd, J(H,H) = 14.0 Hz, J(P,H) = 8.8 Hz, 1 H, C2-H, 5RSR],
2
2
3.11 [dd, J(H,H) = 14.2 Hz, J(P,H) = 6.0 Hz, 1 H, C2-H, 5RSR],
2.11–2.43 (m, 1 H + 4 H + 4 H + 4 H, C14A-H of 5RSR + C4-H,
5RSR + 5SSR + 5RRR), 1.97–2.08 (m, 1 H + 1 H, C14A-H, 5SSR
+
RRR), 1.70–1.80 (m, 1 H + 1 H, C14B-H, 5SSR + 5RSR), 1.62–1.67
(m, 1 H, C14B-H, 5RRR), 0.75 [t, 3J(H,H) = 7.0 Hz, 3 H, C15-H,
Bis{(3R,6S)-3,6-diphenyl-1-[(1R)-1-phenylpropyl]-1-aza-3,6-diphos-
phacycloheptane}platinum(II) Dichloride (9): A solution of
dichloro(1,5-cyclooctadiene)platinum(II) (0.07 g, 0.2 mmol) in
CH2Cl2 (10 mL) was added dropwise to a solution of 5 (0.27 g,
0.7 mmol, containing 55 % 5RSR, 30 % 5RRR and 15 % 5SSR) in
CH2Cl2 (10 mL). The reaction mixture was stirred at ambient tem-
perature for 30 min. 31P{1H} NMR spectrum of the reaction mix-
ture (36.5 MHz, CH2Cl2): δ = 26.6 [1J(Pt,P) = 2378 Hz], –33.5,
–35.0 ppm. The solvent was evaporated in vacuo and ethanol was
added to the residue. The remaining solid was filtered off and
washed with ethanol. This solid (0.10 g) was a mixture of 5RRR
(63%) and 5SSR (37%). The solvent of the filtrate was evaporated
in vacuo, giving crude 9 which was washed with diethyl ether and
dried at 0.1 Torr for 2–4 h; yield of 9: 0.13 g (45%); m.p. Ͼ 260 °C.
5
5
RSR], 0.72 [t, 3J(H,H) = 7.2 Hz, 3 H, C15-H, 5SSR], 0.66 [t, 3J(H,H)
= 7.4 Hz, 3 H, C15-H, 5RRR] ppm. 31P{1H} NMR (161 MHz,
3
CDCl3): δ = –33.0 [d, J(P,P) = 57.2 Hz, 5RSR], –33.5 (5RRR), –33.9
[d, J(P,P) = 57.2 Hz, 5RSR], –35.0 (5SSR) ppm.
3
After a second crystallization of 5 the filtrate was concentrated to
give a precipitate, which was filtered off, washed with ethanol and
dried at 0.1 Torr for 3 h. The precipitate was a mixture of 5RSR
RRR and 5SSR in the ratio 23:26:51. The spectroscopic data for this
sample were identical with those given above.
,
5
cis-Dichloro-(3R,6S)-3,6-diphenyl-1-[(1S)-1-phenylethyl]-1-aza-3,6-
diphosphacycloheptaneplatinum(II) (6): A solution of dichloro(1,5-
cyclooctadiene)platinum(II) (0.10 g, 0.3 mmol) in CH2Cl2 (10 mL)
was added dropwise to a solution of 3RSS (0.10 g, 0.3 mmol) in
CH2Cl2 (5 mL). The reaction mixture was stirred at ambient tem-
perature for 30 min. The precipitate that formed was filtered off
and washed with CH2Cl2 to give 6; yield 0.10 g (62.5%); m.p. Ͼ
260 °C; [α]2D0 = –21 (c = 0.02 in DMSO). 1H NMR (400 MHz,
1H NMR (400 MHz, CDCl3, TMS): δ = 6.96–7.35 (m, 30 H, C6–13
-
H), 4.22–4.33 (m, 2 H, C5-H), 3.72 [ddd, J(H,H) = 10.6 Hz, J =
4.1 Hz, J = 6.8 Hz, 2 H, C2-H], 3.16–3.37 (m, 6 H, C2-H), 1.98–
2.40 (m, 2 H + 8 H, C14A,4-H), 1.82–1.89 (m, 2 H, C14B-H), 0.77
2
3
[t, J(H,H) = 7.3 Hz, 6 H, C15-H] ppm. 31P{1H} NMR (161 MHz,
CDCl3): δ = 26.6 [1J(Pt,P) = 2378 Hz] ppm. C50H58Cl2N2P4Pt
(1076.91): calcd. C 55.76, H 5.39, Cl 6.60, N 2.60, P 11.52; found
C 55.37, H 5.34, Cl 7.00, N 2.65, P 11.02.
3
[D6]DMSO): δ = 7.20–7.45 (m, 15 H, C6–13-H), 5.12 [q, J(H,H) =
6.8 Hz, 1 H, C5-H], 3.87 (br.d, 2 H, C2-H), 3.69–3.73 (m, 2 H, C2-
H), 2.27–2.49 (m, 4 H, C4-H), 1.49 [d, 3J(H,H) = 6.8 Hz, 3 H, C14-
H] ppm. 31P{1H} NMR (161 MHz, [D6]DMSO): δ = 27.8 [1J(Pt,P)
= 3230 Hz], 27.9 [1J(Pt,P) = 3230 Hz] ppm. C24H27Cl2NP2Pt
(657.43): calcd. C 36.53, H 4.11, N 2.13, P 9.44; found C 36.32, H
3.97, N 1.98, P 9.43.
X-ray Diffraction Studies: Data for 3RSS were collected at 20 °C on
a CAD-4 Enraf–Nonius automatic diffractometer with monochro-
mated Cu-Kα radiation (ω/2θ-scans). The stability of the crystal
and that of the experimental conditions was checked every 2 h by
1864
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 1857–1866

Chiral 1-Aza-3,6-diphosphacycloheptanes
measuring three control reflections, while the orientation of the
crystal was monitored every 200 reflections by centering two stan-
dards. Decay corrections were not necessary. Corrections for Lo-
rentz and polarization effects were applied. Unit cell dimensions
were determined from twenty-five centered reflections. Data for
4RSR were recorded on a Bruker APEX-2 diffractometer with mo-
nochromated Mo-Kα radiation (φ- and ω-scans). The data for 3RRS
were collected on a Bruker SMART 1000 CCD diffractometer[33]
operating in ω-scan mode. Data reduction was performed with
SAINT[34] and an empirical absorption correction was applied with
the program SADABS.[35] The structures were solved with direct
methods and refined by with the SHELXL97[36] program. Non-
hydrogen atoms were refined anisotropically. Hydrogen atoms for
3RSS and 4RSR were placed at calculated positions and allowed to
ride on the carbon atoms to which they were attached. For 3RRS
all H atoms were located in the difference Fourier maps that were
calculated in the final stage of the structure refinement. Crystallo-
graphic data and refinement parameters for the crystal structure
determinations are presented in Table 4. All calculations were per-
formed with WinGX.[37]
t) for the initial stages of the reactions. The reaction orders were
obtained with Equation (1), where W1 and W2 are rates of forma-
tion of b and c, respectively, at two different initial concentrations
of the stereoisomer a (c0a1 and c0a2).
αb,c = lg[Wb,c(1)/Wb,c(2)]/lg(c0a1/c0a2
)
(1)
The rate constants of the direct reactions were obtained
with Equation (2).
αb,c
k1,2 = Wb,c/c0a
(2)
The rate constants for the reversed reactions were calcu-
lated on the basis of the equilibrium constants obtained
with Equations (3), (4) and (5).
Keq1 = k1/k–1 = ([cbeq]/[caeq])αb
Keq2 = k2/k–2 = ([cceq]/[caeq])αc
k–1 = k1/Keq1, and k–2 = k2/Keq2
(3)
(4)
(5)
Table 4. Crystallographic data for 3RSS, 3RRS and 4RSR
.
The equilibrium concentrations caeq, cbeq, cceq were mea-
sured experimentally. Calculations of the kinetic parameters
were performed for the isomerization reactions performed
at 295.5 and 343 K.
3RSS
3RRS
4RSR
Formula
Mn
T [K]
C24H27NP2
391.41
293
C24H27NP2
391.41
213
C25H29NOP2
421.43
150
The energies of activation were obtained with Equa-
tion (6).
λ [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
1.54184
orthorhombic
P212121
5.212(3)
18.66(2)
22.00(3)
90
90
90
2140(4)
4
5320
3386
0.233
0.01(7)
0.99
1.215
0.71073
monoclinic
P21
6.710(4)
7.766(5)
20.41(1)
90
90.91(1)
90
1063(1)
2
14299
4864
0.051
–0.01(8)
0.95
1.222
0.71073
monoclinic
P21
14.182(1)
5.1152(4)
15.434(1)
90
100.623(4)
90
1100.5(1)
2
37561
5364
0.064
–0.08(7)
0.96
E = Rln(kT2/kT1)/[(1/T1) – (1/T2)]
(6)
Computations: All quantum chemical calculations were carried out
with the Gaussian-03 suite of programs.[38] Both density functional
theory (DFT) and ab initio Hartree–Fock (HF) approaches were
used. Two DFT methods were employed in this study: the widely
used Becke’s three parameter exchange functional[39] in combina-
tion with the Lee–Yang–Parr’s correlation functional[40] (B3LYP),
and the relatively new hybrid metageneralized gradient approxi-
mation m05-2X.[41] Calculations were carried out with the standard
basis sets: 6-31G*[42,43] and 6-311++G**[44,45] (only for single point
calculations). All stationary points were characterized as minima
by analysis of the Hessian matrices. The total energies for the opti-
mized geometries were corrected for zero point vibrational energies
(ZPE) that were evaluated without scaling.
γ [°]
V [Å3]
Z
Reflections collected
Independent reflections
Rint
Flack parameter
GOF on F2
ρcalcd. [gcm–3]
μ [mm–1]
1.272
0.214
0.0393
0.0794
0.29/–0.29
1.889
0.213
R(Fo), [IϾ2σ(I)]
0.0730
0.1790
0.26/–0.32
0.0463
0.0867
0.29/–0.21
2
Rw(Fo
)
Δρ (max./min.) [eÅ–3]
Supporting Information (see footnote on the first page of this arti-
cle): Kinetic data and CD spectra.
CCDC-856264 (for 3RSS), -856265 (for 3RRS), and -856282 (for
RSR) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
4
Acknowledgments
We are grateful to Umicore AG for a generous donations of
H2PtCl6. Financial support from the Deutsche Forschungsgemein-
schaft (DFG) [436 RUS 113/986/0-1(R)], the Russian Foundation
for Basic Research (RFBR) (grant numbers 10-03-00380-a, 11-03-
12152-ofi_m), the President of the Russian Federation (support of
leading scientific schools, grant number NSh-6667.2012.3), and the
Federal Agency of Science and Innovations (state contract
02.740.11.0633) is gratefully acknowledged. We are grateful to Dr.
V. Gubskaya (A. E. Arbuzov IOPC KSC RAS) for providing an
opportunity to record CD spectra.
Kinetics: The kinetics of the isomerization of 3RSS (a) was followed
by 31P{1H} NMR (400 MHz) spectroscopy by monitoring the ratio
of signals at –34.1 ppm (a, 3RSS), –35.0 ppm (b, 3SSS) and
–36.0 ppm (c, 3RRS) in the collected spectra. These stereoisomers
of 3a–c are shown in Scheme 4. The data points (12–14 data points)
for each kinetic curve were plotted in the form of Δc vs. t. Treat-
ment of the data obtained by the initial rates method (first 6 points)
allowed for the calculation of the rates, reaction orders, and acti-
vation energies. The reaction rates for the conversion of the stereo-
isomer a and the formation of the stereoisomers b and c were ob-
tained from the slopes of the corresponding kinetic curves (Δc vs.
[1] I. Ojima, M. Kitamura, R. Noyori, in: Catalytic Asymmetric
Synthesis (Ed.: I. Ojima), Wiley-VCH, New York, 2000.
Eur. J. Inorg. Chem. 2012, 1857–1866
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1865

E. I. Musina et al.
FULL PAPER
[2]
[26] a) E. Eliel, in: Basic organic stereochemistry (Eds.: E. Eliel,
S. H. Wilen, M. P. Doyle), chapter 11, Wiley-Interscience, New
York, 2001, and references cited therein; b) Comprehensive Het-
erocyclic Chem. (Eds.: A. R. Katritzky, C. A. Ramsden, E. F. V.
Scriven, R. J. K. Taylor), Elsevier, Amsterdam, The Nether-
lands, 2008.
[27] a) J. B. Henderickson, J. Am. Chem. Soc. 1964, 86, 4854–4866;
b) J. B. Henderickson, J. Am. Chem. Soc. 1967, 89, 7036–7043.
[28] H. Schmidbaur, S. Schnatterer, Chem. Ber. 1986, 119, 2832–
2842.
E. N. Jacobsen, A. Pfaltz, H. Yamamoto, in: Comprehensive
Asymmetric Catalysis (Eds.: E. N. Jacobsen, A. Pfaltz, H. Yam-
amoto), Springer, New York, 1999.
A. Grabulosa, J. Granell, G. Muller, Coord. Chem. Rev. 2007,
251, 25–90.
P. Barbaro, C. Bianchini, G. Giambastiani, S. L. Parisel, Coord.
Chem. Rev. 2004, 248, 2131–2150.
M. Gouygou, J.-C. Daran, E. Robe, C. Ortega, C. R. Chim.
2010, 13, 1054–1062.
B. Zupancic, B. Mohar, M. Stephan, Tetrahedron Lett. 2009,
50, 7382–7384.
R. Malacea, R. Poli, E. Manoury, Coord. Chem. Rev. 2010,
254, 729–752.
A. Gual, C. Godard, S. Castillón, C. Claver, Tetrahedron:
Asymmetry 2010, 21, 1135–1146.
Z. Freixa, P. W. N. M. van Leeuwen, Coord. Chem. Rev. 2008,
252, 1755–1786.
[3]
[4]
[5]
[6]
[29] A. Bader, T. Nullmeyers, M. Pabel, G. Salem, A. C. Willis, S. B.
Wild, Inorg. Chem. 1995, 34, 384–389.
[7]
[30] R. D. Baechler, K. Mislow, J. Am. Chem. Soc. 1970, 92, 3090–
3093.
[8]
[31] R. N. Naumov, A. A. Karasik, O. G. Sinyashin, P. Lönnecke,
E. Hey-Hawkins, Dalton Trans. 2004, 357–358.
[32] D. Drew, J. R. Doyle, Inorg. Synth. 1990, 28, 346–349.
[33] SMART: Area Detector Software Package, Siemens Industrial
Automation, Inc., Madison, WI, 1993.
[34] SAINT: Area Detector Integration Software, version 6.01, Sie-
mens Industrial Automation, Inc., Madison, WI, USA, 1999.
[35] G. M. Sheldrick, SADABS: Program for Scaling and Correction
of Area Detector Data, University of Göttingen, Germany,
1997.
[36] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[37] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837–838.
[38] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pom-
elli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P.
Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D.
Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui,
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, C. Gonzalez, J. A. Pople, Gaussian 03 (revision E.01),
Gaussian, Inc., Wallingford, CT, 2004.
[9]
[10]
[11]
[12]
[13]
N. Oohara, K. Katagiri, T. Imamoto, Tetrahedron: Asymmetry
2003, 14, 2171–2175.
T. Mino, Y. Naruse, S. Kobayashi, S. Oishi, M. Sakamoto, T.
Fujita, Tetrahedron Lett. 2009, 50, 2239–2241.
E. Cesarotti, G. Abbiati, E. Rossi, P. Spalluto, I. Rimoldi, Tet-
rahedron: Asymmetry 2008, 19, 1654–1659.
K. Tani, K. Suwa, E. Tanigawa, T. Ise, T. Yamagata, Y. Tat-
suno, S. Otsuka, J. Organomet. Chem. 1989, 370, 203–221.
[14] V. F. Kuznetsov, A. J. Lough, D. G. Gusev, Chem. Commun.
2002, 20, 2432–2433.
[15] G. Fries, J. Wolf, K. Ilg, B. Walfort, D. Stalke, H. Werner, Dal-
ton Trans. 2004, 12, 1873–1881.
[16] G. Fries, J. Wolf, M. Pfeiffer, D. Stalke, H. Werner, Angew.
Chem. 2000, 112, 575–578; Angew. Chem. Int. Ed. 2000, 39,
564–566.
[17] G. Hoge, H.-P. Wu, W. S. Kissel, D. A. Pflum, D. J. Greene, J.
Bao, J. Am. Chem. Soc. 2004, 126, 5966–5967.
[18] I. D. Gridnev, N. Higashi, T. Imamoto, Organometallics 2001,
20, 4542–4553.
[19] F. Chaux, S. Frynas, H. Laureano, Ch. Salomon, G. Morata,
M.-L. Auclair, M. Stephan, R. Merdes, P. Richard, M.-J. On-
del-Eymin, J.-C. Henry, J. Bayardon, C. Darcel, S. Juger, C. R.
Chim. 2010, 13, 1213–1226.
[20] I. D. Gridnev, Y. Yamanoi, N. Higashi, H. Tsuruta, M. Yasu-
take, T. Imamoto, Adv. Synth. Catal. 2001, 343, 118–136.
[21] T. Miyazaki, M. Sugawara, H. Danjo, T. Imamoto, Tetrahedron
Lett. 2004, 45, 9341–9344.
[22] a) A. A. Karasik, I. O. Georgiev, O. G. Sinyashin, E. Hey-Haw-
kins, Polyhedron 2000, 19, 1455–1459; b) A. A. Karasik, I. O.
Georgiev, E. I. Musina, J. Heinicke, O. G. Sinyashin, Polyhe-
dron 2001, 20, 3321–3331; c) A. A. Karasik, R. N. Naumov,
O. G. Sinyashin, G. P. Belov, H. V. Novikova, P. Loennecke, E.
Hey-Hawkins, Dalton Trans. 2003, 2209–2214.
[39] A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652.
[40] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 41, 785–789.
[41] Y. Zhao, N. E. Schultz, D. G. Truhlar, J. Chem. Theory Com-
put. 2006, 2, 364–382.
[42] W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem. Phys. 1972, 56,
2257–2261.
[23] A. A. Karasik, A. A. Balueva, E. I. Moussina, R. N. Naumov, [43] P. C. Hariharan, J. A. Pople, Theor. Chim. Acta 1973, 28, 213–
A. B. Dobrynin, D. B. Krivolapov, I. A. Litvinov, O. G. Sinya-
shin, Heteroat. Chem. 2008, 9, 125–132.
[24] J. Dogan, J. B. Schulte, G. F. Swiegers, S. B. Wild, J. Org. Chem.
2000, 65, 951–957.
[25] a) M. Nieuwenhuyzen, G. C. Saunders, E. C. M. S. Smith, Or-
ganometallics 2006, 25, 996–1003; b) B. J. Anderson, D. S.
Glueck, A. G. DiPasquale, A. L. Rheingold, Organometallics
2008, 27, 4992–5001; c) D. Moiseev, B. K. James, B. O. Patrik,
T. Q. Hu, Inorg. Chem. 2006, 45, 2917–2924.
222.
[44] a) T. Clark, J. Chandrasekhar, G. W. Spitznagel, P. v. R. Schle-
yer, J. Comp. Chem. 1983, 4, 294–301; b) M. J. Frisch, J. A.
Pople, J. S. Binkley, J. Chem. Phys. 1984, 80, 3265.
[45] a) A. D. McLean, G. S. Chandler, J. Chem. Phys. 1980, 72,
5639–5648; b) R. Krishnan, J. S.Binkley, R. Seeger, J. A. Pople,
J. Chem. Phys. 1980, 72, 650–654.
Received: November 29, 2011
Published Online: February 22, 2012
1866
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 1857–1866