2-Diphenylphosphino-2′-hydroxybiphenyl-based P-ligands and their platinum(II) complexes

Article abstract of DOI:10.1016/j.jorganchem.2006.08.080

2-Diphenylphosphino-2′-hydroxybiphenyl (2), become readily available via a ring opening reaction of a dibenzo[c.e][1,2]oxaphosphorine, was utilized as P-ligand in complexation with dichlorodibenzonitrile platinum to give a Cl₂Pt2₂ co

Full text of DOI:10.1016/j.jorganchem.2006.08.080

Journal of Organometallic Chemistry 691 (2006) 5038–5044
www.elsevier.com/locate/jorganchem
2-Diphenylphosphino-20-hydroxybiphenyl-based P-ligands and
their platinum(II) complexes
a,
a
b
*
´
´
Gyo¨rgy Keglevich , Andrea Kerenyi , Helga Szelke ,
c,d
e
´
´
Krisztina Ludanyi , Tamas Kortvelyesi
¨
a
Department of Organic Chemical Technology, Budapest University of Technology and Economics, 1521 Budapest, Hungary
b
Research Group of the Hungarian Academy of Sciences at the Department of Organic Chemical Technology,
Budapest University of Technology and Economics, 1521 Budapest, Hungary
c
Semmelweis University, Faculty of Pharmacy, Department of Pharmaceutics, 1092 Budapest, Hungary
d
Hungarian Academy of Sciences, Chemical Research Center, 1525 Budapest, Hungary
e
Department of Physical Chemistry, University of Szeged, 6701 Szeged, Hungary
Received 6 July 2006; received in revised form 23 August 2006; accepted 23 August 2006
Available online 1 September 2006
Abstract
2-Diphenylphosphino-20-hydroxybiphenyl (2), become readily available via a ring opening reaction of a dibenzo[c.e][1,2]oxaphosph-
orine, was utilized as P-ligand in complexation with dichlorodibenzonitrile platinum to give a Cl2Pt22 complex (4) with trans geometry.
The O-benzyl derivative (5) could not be involved in complexation. A bidentate P-ligand (7) obtained by the interaction of hydroxy-
diphenylphosphinobiphenyl 2 with chloro-dibenzo[c.e][1,2]oxaphosphorine (1) formed an 8-ring transition metal complex (Cl2Pt7 = 9)
in reaction with PtCl2(PhCN)2. Under the conditions of chromatography, separation of the diastereomers of 7 was not possible due
to a partial isomerisation by rotation around the biphenyl axis of the molecule that is justified by the average barrier height of
6.0 kcal/mol.
The stereostructure of P-ligands 2 and 7, as well as platinum complexes 4 and 9 was evaluated by B3LYP quantum chemical
calculations.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Mono and bidentate P-ligands; Transition metal complex; Stereospecific coupling; Stereostructure; Quantum chemical calculations
1. Introduction
including chiral derivatives have been introduced [5–7]. A
hydroxyaryl-aryloxydibenzooxaphosphorine along with
its rhodium(I) complex has also been described [8]. In the
course of the preparation of phenyl-dibenzo[c.e][1,2]oxa-
phosphorine from the corresponding P-chloro species and
phenylmagnesium bromide, a ring opening side-reaction
resulting in 2-diphenylphosphino-20-hydroxybiphenyl was
observed [5]. We decided to make use of this reaction in
order to synthesize biaryl-related P-ligands and their
complexes.
These days, a great variety of P-ligands is known, from
among the P-heterocyclic derivatives form a special group
[1]. These may be components in transition metal com-
plexes that, in turn, are potential catalysts [1]. Hence,
driven by green chemistry, the development of new mono-
dental and bidental P-ligands and their complexes remains
a challenge for organic chemists. The family of dib-
enzo[c.e][1,2]oxaphosphorines with a P(III) function repre-
sents a typical class [2–4]. Recently, P-aryl-, P-alkoxy- and
P-amino derivatives, as well as their platinum complexes
2. Results and discussion
*
After an optimisation, it was found that using 2.5 equiv.
Corresponding author. Tel.: +36 1 4631111/5883; fax: +36 1 4633648.
of the Grignard reagent, chloro-dibenzo[c.e][1,2]oxa-
E-mail address: keglevich@mail.bme.hu (G. Keglevich).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.08.080

G. Keglevich et al. / Journal of Organometallic Chemistry 691 (2006) 5038–5044
5039
LANL2DZ calculations. The perspective views are shown
in Figs. 1 and 2, respectively. It was found that in the case
of ligand 2, there may be a stabilizing H-bond between the
proton of the phenolic hydroxy function and the phospho-
rus atom of the PPh2 group. In complex 4, an intramolec-
ular interaction between one of the two phenolic hydroxy
groups and a suitable chlorine atom bond to the central
platinum atom was substantiated. The Hꢀ ꢀ ꢀP and Hꢀ ꢀ ꢀCl
distances in the above complexes (2 and 4) were found to
5
2
4
3
6
1
1., 26 ˚C, 20 h
2.5 eq. PhMgBr
THF
..
..
Cl
P
PPh2
2.,
H2O
O
OH
7
12
11
8
9
10
2
1
Scheme 1.
˚
be 3.082 and 2.186 A, respectively. Nevertheless, the H-
bond in 2 did not prevent the complexation of the phos-
1
phosphorine 1 was efficiently transformed at 26 °C to 2-
diphenylphosphino-20-hydroxybiphenyl 2 (Scheme 1). The
yield of 90% seemed to be competitive with that of other
procedure [9]. The biaryl P-ligand (2) was protected against
oxidation as its borane complex (3) from which the phos-
phine (2) was regenerated by a standard procedure apply-
ing diethylamine [10] (Scheme 2). The interaction of
phorus atom. An NMR study including record of the H
NMR spectrum of 4 on a 250 and 500 MHz spectrometer
suggested that the phenolic hydroxy lines at dH 5.30 and
5.57 are not the consequences of a coupling, but are distinct
signals due to some kind of asymmetry of the molecule that
may be explained with the intramolecular interaction at
only one side of the complex mentioned above. At the 3-
21G* basis set, relative stability of 4 and the symmetric ver-
sion with two H-bonds cannot be established reliably due
to the overestimation of the H-bond energy.
biaryldiphenylphosphine
2 with dichlorodibenzonitrile
platinum in a molar ratio 2:1, at benzene reflux afforded
complex 4 exhibiting the P-ligands, on the basis of the ste-
reospecific J
coupling [5,11] of 2621 Hz, in trans dis-
Then, the ortho-arylphenol P-ligand was modified by
benzylation. The benzylether (5) obtained was identified as
its P-oxide (6) due to its high sensitivity towards air (Scheme
2). It was a surprising experience that the diphenylphosphin-
ophenylphenol ether (5) could not be involved in complexa-
tion with PtCl2(PhCN)2 that may be, on one hand, due to
steric hindrance caused by the benzyl substituent (Fig. 3).
195Pt–31P
position (Scheme 2). It is noteworthy that the similar
reaction of P-substituted dibenzo[c.e][1,2]oxaphosphorines
led to the formation of the corresponding cis complexes [7].
The stereostructure of P-ligand 2 was evaluated by
B3LYP/3-21G* calculations, while that of platinum com-
plex was 4 determined by B3LYP/3-21G* and B3LYP/
26 ˚C, 4 h
Me2S⋅BH3
CH2Cl2
5
4
3
6
1
BH3
2
↑
PPh2
OH
60 ˚C, 2 h
HNEt2
CHCl3
7
12
11
8
9
10
3
5
2
4
3
6
1
78 ˚C , 1.5 h
PtCl2(NCPh)2
Ph
Cl
P
Cl
PhH
HO
Ph
Pt
2
Ph
OH
7
P
12
11
8
9
Ph
10
4
56 ˚C, 3 h
BnBr
K2CO3
5
5
2
4
3
6
1
0 ˚C, 1 h
H2O2
CH2Cl2
4
3
6
1
O
2
..
PPh2
PPh2
OBn
MeC( O)Me
OBn
7
7
12
11
8
9
12
11
8
9
10
10
5
6
Scheme 2.

5040
G. Keglevich et al. / Journal of Organometallic Chemistry 691 (2006) 5038–5044
˚
Fig. 1. Perspective view of 2 with bond lengths (A), bond angles (°) and
torsion angles (°) obtained at the B3LYP/3-21G* level of theory. C(1)–P:
1.850, C(2)–C(7): 1.497, C(8)–O: 1.382, P–C(10): 1.844, P–C(100): 1.841,
C(10)–P–C(100): 101.24, C(7)–C(8)–O(H): 122.44, C(1)–C(2)–C(7): 121.21,
C(2)–C(7)–C(8): 118.96, C(1)–C(2)–C(7)–C(8): ꢂ74.05, C(7)–C(2)–C(1)–P:
ꢂ1.78, C(2)–C(1)–P–C(10): 170.38, C(2)–C(1)–P–C(20): ꢂ85.82, O–C(8)–
C(7)–C(2): 2.66.
˚
Fig. 3. Perspective view of 5 with bond lengths (A), bond angles (°) and
torsion angles (°) obtained at the B3LYP/3-21G* level of theory. P–C(1):
1.850, C(2)–C(7): 1.495, C(8)–O: 1.397, O–C(CH2): 1.469, C(10)–P: 1.846,
C(100)–P: 1.844, C(1)–C(2)–C(7): 122.36, C(2)–C(7)–C(8): 120.13, C(7)–
C(8)–O: 116.18, C(8)–O–C(CH2): 117.88, C(1)–C(2)–C(7)–C(8): 113.48,
C(2)–C(7)–C(8)–O: ꢂ3.66, C(7)–C(8)–O–C(CH2): 156.49, C(10)–P–C(1)–
C(2): 169.82, C(100)–P–C(1)–C(2): ꢂ86.98.
As molecular mechanics (PCMODEL/MMX) calculations sug-
gested, benzyl substitution results in a structure with possi-
ble clashes with the other parts of the molecules. On the
other hand, it is also possible that only some conformations
may enable the formation of the complex. As an analogy,
2-(anisylphenylphosphino)-20-methoxy-1,10-binaphthyl has
been described that was obtained from the correspond-
ing phosphine oxide by deoxygenation using phenylsilane.
It is worthy of mention that after a reduction over 3 days
at 80 °C, partial epimerisation of the P-centrum occurred
[12].
As an interesting modification, the ortho-arylphenol (2)
was reacted with chloro-dibenzo[c.e][1,2]oxaphosphorin
(1) to afford a novel bidental P-ligand (7) that was obtained
as a 64–36% mixture of two diastereomers (Scheme 3). The
phosphine–phosphonite (7) was fully characterized as its
dioxide (8) obtained by oxidation with 30% hydrogen per-
oxide (Scheme 3). Attempts on the separation of the two
diastereomers by column chromatography failed, even an
enrichment of the major component was not possible. In
all cases, the ꢁ64–36% mixture of isomers was regenerated.
This experience suggests that the diastereomers of 7 are not
stable enough at room temperature to be separated that
˚
Fig. 2. Perspective view of 4 with bond lengths (A), bond angles (°) and
torsion angles (°) obtained at the B3LYP/3-21G* and B3LYP/LANL2DZ
leve0l of theory. Pt–P(1): 2.399, Pt–P(2): 2.384, P(1)–C(1): 1.842, P(1)–
C(1 ): 1.835, P(1)–C(100): 1.835, P(2)–C(1*): 1.844, P(2)–C(10*): 1.826, P(2)–
C(100*): 1.846, C(2)–C(7): 1.500, C(2*)–C(7*): 1.495, Pt–P(1)–C(1): 113.04,
Pt–P(1)–C(10): 123.42, C(1)–P(1)–C(10): 101.39, C(1)–P(1)–C(100): 104.23,
C(1*)–P(2)–C(10*): 102.39, C(1*)–P(2)–C(100*): 105.74, C(1)–C(2)–C(7):
124.47, C(1*)–C(2*)–C(7*): 124.97, C(1)–C(2)–C(7)–C(8): ꢂ102.51,
C(1*)–C(2*)–C(7*)–C(8*): ꢂ105.55, Oꢀ ꢀ ꢀCl: 3.096, O–Hꢀ ꢀ ꢀCl: 149.63,
C(8)–O–Hꢀ ꢀ ꢀCl: 103.84, C(2)–C(1)–P(1)–Pt: 60.74, C(2*)–C(1*)–P(2)–Pt:
ꢂ51.45. * : Numbering of the second P-ligand in the complex.

G. Keglevich et al. / Journal of Organometallic Chemistry 691 (2006) 5038–5044
5041
A somewhat larger barrier height (10.0 and 9.6 kcal/mol)
was predicted for the atrop isomers of the diphenylphosph-
ino-binaphthylphosphito-biphenyl mentioned above [14].
This energy value should allow at least a partial isomerisa-
tion by rotation around the C–C axis of the biphenyl moi-
ety. For this reason, it is more appropriate to call the
isomers under discussion ‘‘tropos’’ rather than ‘‘atropos’’
[15]. Methyl substitution in the corresponding ortho posi-
tions of the above molecules (7 and the literature molecule
[14]) prevents, however, the rotation as it was suggested by
the PM3 calculations. This is in a good agreement with the
experimental results [14].
15
12
14
13
16
11
O
PPh2
8
7
9
10
O
P
O
6a
4a
17
20
10a
18
19
22
21
O
1a
3
1
2
4
8
0 ˚C, 1 h
H2O
The interaction of bidental P-ligand
7 with di-
CH2Cl2
chlorodibenzonitrile platinum led to the formation of cyclic
platinum complex 9. Starting from the diastereomeric mix-
ture of the bidental P-ligand (7), the transition metal com-
plex (9) was also formed as isomers (62–38%). The 2JP(1)P(2)
of 15.7 Hz detected on both phosphorus atoms, as well as
15
12
14
13
16
11
26 ˚C, 5 h
Et3N
..
8
PPh2
7
9
10
PhMe
..
P
O
1
1
6a
4a
1 + 2
the J
of 5093 Hz and J
of 3400 Hz con-
195Pt–31Pð2Þ
195Pt–31Pð1Þ
17
20
10a
18
19
22
21
firmed the cis position of the P-moieties. It is recalled that
the second coupling should be around 2620 Hz (as it is in 4)
in case of a trans relationship of the ligands. Due to the low
solubility of complex 9 in the usual solvents, it was not pos-
sible to obtain 13C NMR data. The stereostructure of the
O
1a
1
2
4
3
7
80 ˚C, 1.5 h
PtCl2(NCPh)2
PhH
15
12
14
13
16
11
Cl
Ph
P
Cl
Pt
8
7
9
Ph
O
10
6a
4a
17
P
10a
18
19
22
21
20
O
1a
1
2
4
3
9
Scheme 3.
may be due to a partial isomerisation by rotation around
the biphenyl axis of 7. It is also clear that, in this particular
case, the rotation around the C–C bond in solution is
slower than the NMR time scale. A similar situation was
found for the diastereomers of 2-diphenylphosphino-
20-(100,1000-binaphthyl-200,2000-phosphito-)1,10-biphenyl
by
Nozaki et al. [13,14]. They experienced, however, that the
presence of additional ortho substituents (even methyl
groups) prevented the rotation around the C–C axis.
Analogous binaphthol derivatives, such as 2-diphe-
nylphosphino-20-(100,1000-binaphthyl-200,2000-phosphito-)1,10-
binaphthol were, of course stable species [14].
The barrier heights for the interconversion of the atrop
isomers (diastereomers) of 7 were found to be 6.9 and
5.1 kcal/mol by PM3 calculations suggesting that the rela-
tive energy of one isomer to the other one is 1.8 kcal/mol.
˚
Fig. 4. Perspective view of 7 with bond lengths (A), bond angles (°) and
torsion angles (°) obtained at the B3LYP/3-21G* level of theory. C(6a)–
P(1): 1.821, C(6a)–C(10a): 1.415, C(10a)–C(1a): 1.481, P(1)–O(5): 1.667,
O(5)–C(4a): 1.409, P(1)–O: 1.679, O–C(18): 1.397, C(12)–C(17): 1.496,
C(11)–P(2): 1.844, P(2)–C(10): 1.843, P(2)–C(100): 1.845, O(5)–P(1)–O:
98.30, O(5)–P(1)–C(6a): 97.59, C(6a)–P(1)–O: 99.01, C(4a)–O(5)–P(1):
123.80, C(10a)–C(6a)–P(1): 122.08, P(1)–O–C(18): 123.79, C(18)–C(17)–
C(12): 120.99, C(11)–P(2)–C(10): 101.70 C(11)–P(2)–C(100): 101.41,
C(4a)–C(1a)–C(10a)–C(6a): ꢂ16.87, C(11)–C(12)–C(17)–C(18): 79.28,
C(12)–C(11)–P(2)–C(10): 85.67, C(12)–C(11)–P(2)–C(100): ꢂ170.50,
C(4a)–O(5)–P(1)–O: 60.46, C(4a)–O(5)–P(1)–C(6a): ꢂ39.87.

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G. Keglevich et al. / Journal of Organometallic Chemistry 691 (2006) 5038–5044
3. Experimental
The 31P, 11B, 13C, and 1H NMR spectra were taken on a
Bruker DRX-500 spectrometer operating at 202.4, 160.4,
125.7 and 500 MHz, respectively. Positive chemical shifts
are downfield relative to 85% H3PO4, F3B Æ OEt2 or
TMS. The couplings are given in Hertz. Mass spectrometry
was performed on a ZAB-2SEQ instrument. The starting
chloro-dibenzo[c.e][1,2]oxaphosphorine 1 was prepared as
described earlier [2].
3.1. (20-Hydroxy-biphenyl-2-yl)-diphenylphosphane 2
To 1.0 g (4.3 mmol) of chlorooxaphosphorine 1 in 10 ml
tetrahydrofuran was added dropwise 8.5 mmol of phenyl-
magnesium bromide in 10 ml tetrahydrofuran (prepared
from 1.5 g (9.8 mmol) of bromobenzene and 0.20 g (8.5 g
atom) of magnesium in 10 ml tetrahydrofuran) at 0 °C with
stirring. After addition was complete, content of the flask
was stirred at 26 °C for 20 h under nitrogen. Solvent was
evaporated and the residue taken up in the mixture of
10 ml of chloroform, 10 ml of water and 0.8 ml (4.3 mmol)
of 37% hydrochloric acid. The organic phase was dried
(Na2SO4) and concentrated to afford 1.6 g crude product.
31P NMR (CDCl3) d ꢂ12.4 (dP lit. [8] ꢂ12.3), [5].
˚
Fig. 5. Perspective view of 9 with bond lengths (A), bond angles (°) and
torsion angles (°) obtained at the B3LYP/3-21G* and B3LYP/LANL2DZ
level of theory. P(1)–Pt: 2.247, P(2)–Pt: 2.328, C(6a)–P(1): 1.788, C(6a)–
C(10a): 1.418, C(10a)–C(1a): 1.482, P(1)–O(5): 1.628, O(5)–C(4a): 1.409,
P(1)–O: 1.639, O–C(18): 1.416, C(12)–C(17): 1.493, C(11)–P(2): 1.847,
P(2)–C(10): 1.834, P(2)–C(100): 1.826, P(1)–Pt–P(2): 102.05, O(5)–P(1)–O:
101.78, O(5)–P(1)–C(6a): 102.30, C(6a)–P(1)–O: 101.18, C(4a)–O(5)–P(1):
124.93, C(10a)–C(6a)–P(1): 120.96, P(1)–O–C(18): 122.70, C(18)–C(17)–
C(12): 118.69, C(11)–P(2)–C(10): 101.58, C(11)–P(2)–C(100): 102.80,
C(4a)–C(1a)–C(10a)–C(6a): ꢂ14.21, C(11)–C(12)–C(17)–C(18): ꢂ76.41,
C(12)–C(11)–P(2)–C(10):ꢂ58.55, C(12)–C(11)–P(2)–C(100): ꢂ167.46, C(4a)–
O(5)–P(1)–O: 74.89, C(4a)–O(5)–P(1)–C(6a): ꢂ29.48, O(5)–P(1)–Pt–P(2):
ꢂ146.88, C(6a)–P(1)–Pt–P(2): 91.97, P(1)–Pt–P(2)–C(10): ꢂ126.68, P(1)–
Pt–P(2)–C(100): 114.72.
3.2. (20-Hydroxy-biphenyl-2-yl)-diphenylphosphane
borane 3
To the 20 ml dichloromethane solution of 1.0 g
(2.8 mmol) of phosphine 2 was added 2.1 ml (4.2 mmol)
of 2 M tetrahydrofuran solution of dimethylsulfide borane
at room temperature under nitrogen and the mixture was
stirred for 24 h. Evaporation of the volatile components
gave 1.0 g (100%) of 3 as an oil. 31P NMR (CDCl3) d
20.7; 11B NMR (CDCl3) d ꢂ33.1; 13C NMR (CDCl3) d
116.3 (C9)a, 119.8 (C11)a, 127.4 (2J = 3.1, C2), 128.2
c
(J = 9.3, C3)b, 128.7 (J = 10.2, C3 and C3 ) , 128.9
0
00
1
e
b
1
0
a
00
d
( J ꢁ 30, C1 ) , 129.3 (J = 10, C5) , 129.7 ( J = 34.0, C1 ,
1
e
4
0
129.8 (C10) , 130.4 ( J = 29.8, C1 ) , 131.0 ( J = 2.2) ,
more stable isomer of the bidentate P-ligand 7, as well as
that of the deriving transition metal complex (9) was calcu-
lated by the B3LYP/3-21G* method and, in respect of the
platinum atom, also by the B3LYP/LANL2DZ method;
the perspective views are shown in Figs. 4 and 5, respec-
tively. As a not too far analogy, a cyclic palladium complex
derived on a phosphine–phosphinite bidental P-ligand was
also described [16].
To summarize our results, novel platinum complexes
based on 2-diphenylphosphino-20-hydroxybiphenyl and
on its O-dibenzo[c.e][1,2]oxaphosphorine derivative have
been introduced whose stereostructure was evaluated by
stereospecific NMR couplings and B3LYP calculations.
The situation regarding the atrop isomerism of one of the
P-ligands was clarified experimentally and by quantum
chemical calculations. Theory and practice seem to be in
agreement.
131.1 (C12)a, 131.2 (4J = 2.3)d, 131.6 (4J = 2.2)d, [133.2
c
b
00
0
(J = 9.7, C2 ) ,133.6 (J = 9.7, C2 )] , 135.6 (J = 9.2, C6) ,
142.2 (3J = 9.6, C7), 152.9 (C8)a–d; H NMR (CDCl3) d
1
0.66–1.34 (m, 3H, BH3), 6.47–6.55 (m, 2H, Ar), 6.65 (d,
J = 8.0, 1H, OH), 7.03–7.08 (m, 1H, Ar), 7.18–7.61 (m,
15H, Ar).
3.3. Bis((20-hydroxy-biphenyl-2-yl)-diphenylphosphine)-
dichloro-platinum(II) 4
To 0.15 g (0.42 mmol) of phosphine 2 in 30 ml of benzene,
0.10 g (0.21 mmol) of dichlorodibenzonitrile platinum was
added and the mixture was stirred at reflux for 1.5 h under
nitrogen. Fractional crystallisation from the benzene solu-
tion furnished 4 as a yellow powder-like material. 31P
1
NMR (CDCl3) d 16.9 (JPt–P = 2621.4); H NMR (CDCl3)
d 5.30 (s, OH), 5.57 (s, OH), d 6.51–7.84 (m, 23H, Ar).

G. Keglevich et al. / Journal of Organometallic Chemistry 691 (2006) 5038–5044
5043
FAB-MS, 902 [Mꢂ2HCl+H]+; ½M ꢂ 2HCl þ Hꢃfþound
¼
(J = 12.1, C13) , 127.6 (J = 12.3, C2 ) , 128.1 (J = 11.8,
a
c
00
c
a
b
0
902:1881, C48H37O2P2Pt requires 902.1917; Elem. Anal.,
C, 58.86; H, 3.83, C48H38Cl2O2P2Pt requires C, 59.14; H,
3.93.
C2 ) , 128.1 (J ꢁ 13, C8) , 129.3 (C1) , 130.3 (J = 9.9,
a b c 4
00
C7) , 130.5 (C20) , 130.6 (J = 9.9, C3 ) , 130.8 ( J = 2.6,
4
b
0
00
C4 , C4 ), 131.0 ( J = 1.9, C14), 131.4 (C22) , 131.6
2
c
a
0
( J = 9.6, C12), 131.9 (J = 9.2, C3 ) , 131.9 (J ꢁ 10, C16) ,
133.0 (C3)b, 133.4 (J = 11.5, C15)a, 133.8 (C9)b, 136.9
(3J = 6.8, C1a), 141.3 (3J = 8.3, C17), 146.4 (2J = 8.1, C4a),
3.4. (20-Benzyloxy-biphenyl-2-yl)-diphenylphosphine 5
To the 20 ml dichloromethane solution of 0.85 mmol of
phosphine 2 was added 20 mg (0.085 mmol) of TEBAC
and 0.15 ml (1.27 mmol) of benzyl bromide and 5% aque-
ous sodium hydroxide containing of 0.04 g (1.02 mmol)
of sodium hydroxide at room temperature under nitrogen
and the mixture was stirred for 8 h. The organic phase
was dried (Na2SO4) and concentrated to give 0.38 g of
product 5 quantitatively. 31P NMR (CDCl3) d 23.3.
Compound 5 was characterized as its oxide (6) (obtained
by oxidation using 30% aqueous H2O2 according to a stan-
dard procedure [6]): 31P NMR (CDCl3) d 27.5; 13C NMR
(CDCl3) d 110.7 (C9)a, 119.6 (C11)a, 126.3 (Cc)b, 126.7
149.7 (2J = 8.4, C18); ðM þ HÞþ ¼ 585:1339, C36H26-
found
O4P2 requires 585.1385.
3.6. [(20-Diphenylphosphino-biphenyl-2-yl)-oxi-
dibenzo[c.e][5,6]oxaphosphorine]dichloro-platinum(II) 9
To 0.12 g (0.21 mmol) of phosphine 2 in 20 ml of ben-
zene, 0.10 g (0.21 mmol) of dichlorodibenzonitrile plati-
num was added and the mixture was stirred at reflux for
1.5 h under nitrogen. Fractional crystallisation from the
benzene solution furnished 0.12 g (71%) of 9 as a white
powder-like material consisting of a 62:38 mixture of two
isomers; ðM-Cl þ HÞþfound ¼ 783þ:0782, C36H27ClO2P2Pt
requires 783.0823, ðM-HCl þ HÞfound ¼ 782:0709, C36H26-
ClO2P2Pt requires 782.0745.
c
a
d
00
(J = 12.3, C3) , 127.5 (C10) , 127.6 (J = 12.4, C3 ) , 128.2
d
b
2
0
(J = 11.8, C3 ) , 128.5 (Cb) , 129.0 ( J = 4.5, C2), 129.3
a
4
d
00
(C12) , 130.7 ( J = 2.6, C4), 131.0 (J = 9.8, C2 ) , 131.2
4
e
4
e
d
00
0
0
( J = 2.5, C4 ) , 131.3 ( J = 2.5, C4 ) , 132.2 (J = 9.1, C2 ) ,
1
1
132.7 ( J = 150.3, C1), 133.0 ( J = 103.8, C1 , C1 ), 133. 0
(d, J = 9.9, C6)c, 133.0 (Cd), 134.0 (J = 12.0, C5)c, 137.5
(Ca), 143.7 (3J = 8.6, C7), 154.8 (C8),a–e tentative assign-
Compound 91: 31P NMR (DMSO) 10.4 (JPP = 15.7,
JPt–P 3399.5), 105.6 (JPP = 15.6, JPt–P 5062.6).
Compound 92: 31P NMR (DMSO) 11.3 (JPP = 17.1,
JPt–P 3414.7), 96.1 (JPP = 17.2, JPt–P 5092.7).
0
00
1
ment; H NMR (CDCl3) d 4.57 (d, J = 12.5, 1H), 4.80 (d,
J = 12.5, 1H), 6.40 (d, J = 8.0, 1H, Ar), 6.82 (t, J = 7.5,
1H, Ar) 6.99–7.73 (m, 21H, Ar); FAB-MS, 461.2 (M+H)+;
ðM þ HÞþfound ¼ 461:1631, C31H26O2P requires 461.1670.
4. Calculations
The structures of the molecules were built up and opti-
mized by PCMODEL [17] with MMX force field. The optimized
geometries of the molecules were reoptimized at the level of
ab initio quantum chemical method implemented in GAUSS-
IAN’03 [18], where B3LYP/3-21G* basis was applied for the
C, H, O and P atoms and B3LYP/LANL2DZ (LANL2DZ
effective core potential) for the Pt atom. The force matrices
were always positive definite in the minima. The barrier
height of the atrop isomerisms was calculated by the
PM3 semiempirical quantum chemical method imple-
mented in MOPAC93 [19]. The structure of the molecules
was described by MOLDEN [20].
3.5. (20-Diphenylphosphino-biphenyl-2-yl)-oxy-
dibenzo[c.e][5,6]oxaphosphorine 7
To 1.0 g (4.3 mmol) of chloro-oxaphosphorine 1 in
20 ml of toluene was added 1.5 g (4.3 mmol) biphenyl
derivative 2 and 0.60 ml (4.3 mmol) of triethylamine. Con-
tents of the flask were stirred at 26 °C for 3 h under nitro-
gen. The reaction mixture was filtrated and the filtrate
concentrated. The crude product so obtained was refined
by column chromatography (silica gel, 3% methanol in
chloroform) to give 1.1 g (72%) of product 7 as a 64:36%
mixture of two isomers. It was not possible to enrich the
proportion of the major component by repeated column
Acknowledgements
chromatography. FAB-MS, 553 (M+H)+; ðM þ HÞfþound
553:1447, C36H26O2P2 requires 553.1486.
¼
This project was supported by the Hungarian Scientific
Research Fund (OTKA, Grant No. T042479) and jointly
by the European Union and the Hungarian State
(GVOP-3.2.2.-2004-07-0006/3.0). TK is grateful for the
Hungarian Supercomputer Centre (NIIF) for the computa-
tional facility.
Compound 71: 31P NMR (CDCl3) ꢂ12.4 and 129.9.
Compound 72: 31P NMR (CDCl3) ꢂ13.1 (JPP = 10.5),
128.9 (JPP = 10.8).
The major isomer (71) of 7 was characterized as its oxide
(81) (obtained by oxidation using 30% H2O2 according to a
standard procedure [6]): 31P NMR (CDCl3) 5.9 and 27.5;
13C NMR (CDCl3) d 119.2 (J = 2.4, C4)a, 120.0 (J = 6.7,
C19)a, 121.6 (1J = 183.0, C6a), 122.6 (2J = 12.2, C10a),
123.8 (C21)b, 124.0 (J = 12.3, C10)a, 125.3 (C2)b, 126.8
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