Synthesis and use of borane and platinum(II) complexes of 3-diphenylphosphino-1-phenylphospholane (LuPhos)

Article abstract of DOI:10.1002/hc.20741

3-Diphenylphosphinoyl-1-phenylphospholane 1-oxide (2) obtained by the Michael addition of diphenylphosphine oxide to the double-bond of 1-phenyl-2-phospholene 1-oxide (1) was subjected to double deoxygenation to afford the corresponding bisphosphine (3, LuPhos) that was converted to bis(phosphine borane) 4 and to cis chelate platinum(II) complex 6. A mixed phosphine oxide-phosphine borane 5 was also prepared. Stereostructures of the bidentate P-ligand 3 and the ring platinum(II) complex (6) were evaluated by quantum chemical calculations. Complex 6 used as a catalyst showed modest activity, but unusual regioselectivity in the hydroformylation of styrene and its 4-substituted analogues.

Full text of DOI:10.1002/hc.20741

Heteroatom Chemistry
Volume 22, Number 6, 2011
Synthesis and Use of Borane and Platinum(II)
Complexes of 3-Diphenylphosphino-1-
phenylphospholane (LuPhos)
K. Michał Pietrusiewicz,1 Anna Flis,1 Vikto´ria Ujj,2 Tama´s
Ko¨rtve´lyesi,3 La´szlo´ Drahos,4 Pe´ter Pongra´cz,5 La´szlo´ Kolla´r,5
and Gyo¨rgy Keglevich6
1Department of Organic Chemistry, Faculty of Chemistry, Marie Curie-Sklodowska University,
20614 Lublin, Poland
2Research Group of the Hungarian Academy of Sciences at the Department of Organic Chemistry
and Technology, Budapest University of Technology and Economics, 1521 Budapest, Hungary
3Department of Physical Chemistry and Material Science, University of Szeged,
6701 Szeged, Hungary
4Hungarian Academy of Sciences, Chemical Research Center, 1525 Budapest, Hungary
5Department of Inorganic Chemistry, University of Pe´cs, H-7624 Pe´cs, Hungary
6Department of Organic Chemistry and Technology, Budapest University of Technology
and Economics, 1521 Budapest, Hungary
Received 17 March 2011
showed modest activity, but unusual regioselec-
ABSTRACT: 3-Diphenylphosphinoyl-1-phenylphos-
tivity in the hydroformylation of styrene and its
pholane 1-oxide (2) obtained by the Michael addi-
ꢀ
C
4-substituted analogues. 2011 Wiley Periodicals, Inc.
tion of diphenylphosphine oxide to the double-bond
Heteroatom Chem 22:730–736, 2011; View this article on-
of 1-phenyl-2-phospholene 1-oxide (1) was subjected
line at wileyonlinelibrary.com. DOI 10.1002/hc.20741
to double deoxygenation to afford the correspond-
ing bisphosphine (3, LuPhos) that was converted
to bis(phosphine borane) 4 and to cis chelate plat-
inum(II) complex 6. A mixed phosphine oxide–
phosphine borane 5 was also prepared. Stereostruc-
tures of the bidentate P-ligand 3 and the ring
platinum(II) complex (6) were evaluated by quantum
chemical calculations. Complex 6 used as a catalyst
INTRODUCTION
Platinum(II) complexes incorporating P(III)-ligands
are important catalysts in homogeneous catalytic
transformations [1–4].
Complexes including heterocyclic P-ligands
form
a representative group [5]. Heterocyclic
P-ligands occurring in Pt(II) complexes, comprise,
among others [6–8], arylphospholes [9,10], phos-
pholenes [11], phospholanes [11,12], phosphinine
(phosphorine) derivatives [11,12], phosphep-
anes [12], as well as 9-phosphabicyclononanes
Correspondence to: G. Keglevich; e-mail: gkeglevich@mail
.bme.hu.
Contract grant sponsor: Hungarian Scientific and Research
Fund.
Contract grant number: OTKA K83118.
c
ꢀ
2011 Wiley Periodicals, Inc.
730

Synthesis and Use of Borane and Platinum(II) Complexes of 3-Diphenylphosphino-1-phenylphospholane (LuPhos) 731
BH3
(Phobanes) [13] and 6-phospha-2,4,8-trioxaadaman-
tanes [14].
..
PPh2
PPh2
0
→
25 ºC
Among the bidentate heterocyclic P-ligands,
DuPhos [15], PennPhos [16], and BIPNOR [17] are
well known. In this series, only DuPhos has been
applied in platinum complexes [18–20]. 3-Diphenyl-
phosphino-1-phenyl-1,2,3,6-tetrahydrophosphinine
and its 1,2,3,4,5,6-hexahydrophosphinine derivative
were also described as novel bidentate P-ligands in
Pt(II) complexes [21–26] showing unusual regio-
selectivity as catalysts in the hydroformylation of
styrene [27].
4
3
Cl3SiH
Me2S
PhH
⋅
BH3
THF
5
2
1
2-trans
.
P
P
.
PhH
−
Ph
Ph
BH3
3-trans
4-trans
SCHEME 2 Preparation of a bis(phosphine borane) as a
protected bidentate P-ligand.
separated from the expected product 4 by column
chromatography.
In this paper, 3-diphenylphosphino-1-phenyl-
phospholane (LuPhos) [28] is converted to novel bo-
rane and Pt(II) complexes useful as protected ligands
or catalyst, respectively.
O
PPh2
4
5
3
2
1
P
Ph
BH3
5-trans
RESULTS AND DISCUSSION
3-Diphenylphosphinoyl-1-phenylphospholane oxide
Phospholane boranes 4 and 5 were identified by
31P, 13C, and 1H NMR, as well as mass spectral data.
The 31P NMR spectrum of 4 comprised two broad
signals, whereas that of 5 showed a broad signal for
the ring P and a doublet of 29.9 Hz for the exocyclic
2
was prepared by the Michael addition of
diphenylphosphine oxide to the double-bond of
1-phenyl-2-phospholene 1-oxide (1) at 26◦C in the
presence of NaOMe/MeOH in toluene (Scheme 1).
The diastereomer exhibiting the P-phenyl and the
P(O)Ph2 substituents in position trans was formed
selectively.
Bis(phosphine oxide) 2 was then subjected to
double deoxygenation by trichlorosilane in ben-
zene at 0 → 25◦C to give bidentate P-ligand LuPhos
(3). The configurations of the stereogenic centers
were preserved during the double deoxygenation.
The reaction of LuPhos (3) with two equivalents of
dimethylsulfide borane afforded bis(phosphine bo-
rane) 4 (Scheme 2).
Phosphine boranes may be regarded as precur-
sors of phosphines, because on treatment with sec-
ondary amines in an aromatic solvent at around 80◦C
they undergo deboronation [29].
It was found that without the complete exclusion
of air during the deoxygenation of bis(phosphine ox-
ide) 2 and subsequent operations, a 55:45 mixture
of bis(phosphine borane) 4 and phosphine borane–
phosphine oxide 5 was formed. Compound 5 was
1
P-function. The similar JPC couplings of ca 34 Hz
for C2 and C5 of phospholanes 4 and 5 in the 13C
NMR spectra confirmed the ring phosphine borane
moiety.
LuPhos 3 was also reacted with one equivalent
of dichlorodibenzonitrile-platinum(II) in benzene at
26◦C, to provide cis chelate complex 6 (Scheme 3).
The structure of complex 6 was confirmed by
31P and 1H NMR, as well as mass spectral data.
In the 31P NMR spectrum, the two phosphorus
atoms are coupled by a JPP of 14.1 Hz, whereas
the two P-signals revealed a JP−Pt of 3409 (P1) and
3488 (P2) Hz. It is worthy to mention that the cis
chelate structure of complex 6 is of novelty. In
some respects, analogous platinum complexes incor-
porating the 3-diphenylphosphino-1-phenyl-1,2,3,6-
tetrahydrophsophinine or the 3-diphenylphosphino-
1-phenyl-1,2,3,4,5,6-hexahydrophosphinine bidentate
P-ligands were described by the authors in previous
articles [25,26].
O
2
°
26 C
PPh2
26 °C
PtCl2(PhCN)2
Ph2P(O)H
NaOMe/MeOH
4
5
3
2
3
PPh2
4
1
3
P1
5
P
P
PhH
PhMe
PtCl2
o
o
Ph
Ph
Ph
1
2-trans
6
SCHEME 1
Preparation of a bis(phosphine oxide) by
Michael addition.
SCHEME 3 Preparation of a novel cis chelate platinum
complex.
Heteroatom Chemistry DOI 10.1002/hc

732 Pietrusiewicz et al.
The stereostructures of the Pt(II) complex 6 and
its bidentate P-ligand 3 were evaluated by B3LYP/6-
31G∗ calculations, and LANL2DZ calculations for Pt.
The best conformation of LuPhos 3 and its Pt(II)
complex 6 (Figs. 1 and 2, respectively) suggests that
the bidentate P-ligand (3) must undergo a slight ro-
tation around the C(3)-P(Ph)2 axis before complexa-
tion, which can be considered to be a rotation with a
low energetic barrier. In the stereostructure of Pt(II)
complex of LuPhos (6), there is a weak π-stacking in-
teraction between the two phenyl rings of the PPh2
inum complexes may be adequately described by
the B3LYP/6-31G∗ – LANL2DZ calculations ap-
plied. The calculated data and stereostructure
of a related platinum complex [cis-bis(ethoxy-
dibenzooxaphosphorino)PtCl2] [30] were well vali-
dated by the X-ray measurement carried out later
on a suitable single crystal of the methoxy ana-
logue [31]. Another example of validation also jus-
tified the potential of B3LYP/6-31G∗ calculations in
the elucidation of the stereostructures of P-ligands
[32,33].
Cis chelate complex 6 was tested as a cata-
lyst precursor in the hydroformylation of styrene
and its 4-substituted derivatives. A catalyst formed
in situ from 6 and two equivalents of tin(II) chlo-
ride was used under standard “oxo-conditions”
[p(CO) p(H2) = 45 bar, 100◦C]. As observed gen-
erally, in addition to the two types of regioisomers,
1-aryl-propanal (A) and 2-aryl-propanal (B), substi-
tuted ethylbenzene (C) was also formed as a hydro-
genation by-product (Eq. (1)).
˚
moiety, as suggested by the distance of 2.95 A be-
tween the Cα‘ and Cα“ atoms and by the distance
˚
of 3.55 A between the Cβ‘ and Cβ“ atoms. The Cα‘–
Cα“ and Cβ‘–Cβ“ distances were found to be 3.02 and
˚
3.52 A, respectively, by the PM6-DH2 method. There
may be a slight interaction between the Cβ–H of
one of the two Ph2P phenyl groups and the CH of
the corresponding methylene moiety of the hetero
ring. According to PM6-DH2 calculations, the best
structure has a weak T-shape π-stacking interaction.
+
+
ArCH(CHO)CH3 ArCH2CH2CHO ArCH2CH3
CO/H
2
ArCH CH2 −→
A
B
C
Ar = C6H5, 4-CH3-C6H4, 4-AcO-C6H4, 4-Cl-C6H4
(1)
Because at 50◦C the conversion of styrene was
only 3%, the further experiments were carried out
at 100◦C (Table 1). Compared to the most widely
used PtCl2(diphosphine) catalyst precursors applied
in the hydroformylation of styrene (where diphos-
phine = achiral dppp and dppp [34], chiral chi-
raphos [35] and diop analogues [36]; for further ex-
amples see [2,4]), the catalyst containing bidentate
P-ligand 3 has shown lower activity, that is, the
conversions obtained after a reaction time of 24 h
fell in the range of 18%–20% using the above sub-
strates. Chemoselectivities toward the formyl prod-
ucts were in a narrow range of 79%–85%, which
fit well the results obtained with ligands of re-
lated structure [8]. The 4-substituent has shown
a slight influence on chemoselectivity. 4-Acetoxy-
styrene provided slightly lower aldehyde selectiv-
ity than the corresponding 4-methyl- and 4-chloro-
styrene analogues (Table 1, entries 2, 3, 6, 7).
Unlike the most conventional platinum-containing
catalysts, the use of the above system led to the pre-
dominance of the branched aldehyde (A) over the
linear one (B). Styrene has shown a regioselectiv-
ity of 58% toward the branched aldehyde, which
was slightly decreased upon 4-substitution (Table 1,
entries 2 ,3, 6, 7). Under standard conditions, less
In complex 6, the distances between Cβ‘ and C2, Cβ“
and C4, as well as Cβ and C5 are 4.0, 3.47, and 3.25
˚
A, respectively. According to PM6-DH2, these data
˚
are 4.13, 3.48, and 3.81 A, respectively. One can see
that in the case under discussion, the application of
the much simpler semiempirical calculation is also
appropriate.
As regards the ligand LuPhos (3), the distance
˚
˚
between the Cα‘ and Cα“ atoms is 2.89 A (2.93 A by
PM6-DH2), whereas that between the Cβ’ and Cβ”
˚
˚
atoms is 3.58 A (3.72 A by PM6-DH2). The two phenyl
rings are almost perpendicular to each other. The
distances between Cβ‘ and C2, Cβ“ and C4, as well
as Cβ and C5 are 3.49, 3.75, and 3.38 A, respectively
(and by PM6-DH2 are 3.40, 3.59, and 3.32 A, respec-
˚
˚
tively).
As the geometries of the best (lowest energy)
optimized structures of complex 6 and bidentate
P-ligand 3 show, the DFT and PM6-DH2 calculations
gave similar geometrical parameters (see the geome-
tries listed in Fig. 2), meaning that, in this particular
case, the use of the PM6 semiempirical method is
adequate.
On the basis of our earlier experiences, the
stereostructures and geometrical data of the plat-
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Use of Borane and Platinum(II) Complexes of 3-Diphenylphosphino-1-phenylphospholane (LuPhos) 733
FIGURE 1 Perspective view of bidentate P-ligand 3 obtained by B3LYP/6-31G∗ calculations◦(in parenthesis: the best geometry
˚
can be seen obtained by the PM6-DH2 method). Selected bond lengths (A) and angles ( ) are as follows: P–C(Ph) 1.855,
1.858 (1.878,1.879), P1–C(Ph), 1.860 (1.882), P1–C2 1.900 (1.925), C2–C3 1.547 (1.527), C3–C4 1.545 (1.542), C4–C5 1.541
(1.527), C5-P1 1.895 (1.916), P1-C2-C3 107.52 (106.05), C2-C3-C4 106.23 (111.31), C3-C4-C5 108.79 (111.89), C4-C5-P1
108.16 (104.75), P1-C2-C3-C4 38.46 (23.99), C2-C3-C4-C5–45.09 (–37.99), C3-C4-C5-P1 30.96 (31.43), Cβ(Ph)-Cα(Ph)-P1-
C2 47.48 (55.63), Cβ(Ph)-Cα(Ph)-P-C3-17.80, 72.58 (–7.52, 83.99).
FIGURE 2 Perspective view of platinum(II) complex 6 obtained by B3LYP/6-31G∗ calculations (in parenthesis: the best
◦
˚
geometry can be seen obtained by the PM6-DH2 method). Selected bond lengths (A) and angles ( ) are as follows: Pt–
Cl, 2.418, 2.401 (2.358, 2.354), Pt–P 2.303 (2.290), Pt-P1 2.282 (2.278), P–C(Ph) 1.837, 1.836 (1.845, 1.842), P1–C(Ph),
1.817 (1.831), P1–C2 1.857 (1.907), C2–C3 1.544 (1.528), C3–C4 1.561 (1.546), C4–C5 1.561 (1.536), C5–P1 1.862 (1.903),
Cl—Pt–Cl 90.72 (81.85), Cl-Pt-P1 92.98 (97.78), Cl–Pt–P 91.99 (95.88), Pt–P1–C(Ph) 104.53 (127.45), Pt—P–C(Ph) 114.04,
120.08 (110.53, 117.67), P1–C2–C3 98.34 (97.34), C2–C3–C4 106.02 (108.52), C3-C4-C5 110.25 (112.19), C4–C5–P1
104.15 (103.07), Cl–Pt–P1-C(Ph) –22.29 (–14.66), Cl–Pt–P1–C2–152.40 (–146.14), Pt–P1–C2–C3–61.13 (–65.78), P1–C2–
C3–C4–52.77 (–50.28), C2–C3–C4–C5 33.06 (40.04), C3–C4–C5–P1 3.43 (–6.64), Cβ(Ph)–Cα(Ph)–P1–Pt 61.75 (40.16),
Cβ(Ph)–Cα(Ph)–P–Pt 29.85, –4.11 (12.16, –4.39).
Heteroatom Chemistry DOI 10.1002/hc

734 Pietrusiewicz et al.
TABLE 1 Hydroformylation of Styrene and Its 4-Substituted Derivatives in the Presence of In Situ Catalysts Formed from
PtCl2(3) Complex 6 and Tin(II) Chloridea
Entry
Substrate (Ar)
Temp. (◦C)
Reaction Time (h)
Conversion (%)
Rcb (%)
Rbcr (%)
1
2
3
C6H5
C6H5
50
100
100
100
100
100
100
70
24
24
24
72
24
24
3
20
20
29
48
18
18
n.d.e
80
85
95
94
66
58
58
49
55
55
52
4-CH3-C6H4
4-CH3-C6H4
4-CH3-C6H4
4-Cl-C6H4
4-AcO-C6H4
4d
5d
6
85
79
7
aReaction conditions: Pt/SnCl2/styrene = 1:2:100, p(CO) = p(H2) = 45 bar, 1 mmol of substrate, solvent: 8 mL of toluene.
bChemoselectivity towards aldehydes (A, B). [(moles of A + moles ofB)/(moles of A + moles of B + moles of C) × 100].
cRegioselectivity towards branched aldehyde (A). [moles of A/(moles of A + moles of B) × 100].
dp(CO) = 45 bar, p(H2) = 22 bar.
eNot determined.
regioselective hydroformylation was observed with
4-acetoxy-styrene (Table 1, entry 7).
a magnetically stirred mixture of 1-phenylphosphol-
2-ene 1-oxide [37] (2.0 g, 11.4 mmol) and diphenyl-
phosphine oxide (2.3 g, 11.4 mmol) dissolved in
20 mL of dry toluene. After 0.5 h of additional
stirring at room temperature, 31P NMR monitor-
ing of the reaction mixture indicated 85% conver-
sion and formation of a single adduct. The mix-
ture was then concentrated and the residue was
dissolved in 50 mL of chloroform, washed with
2 × 10 mL of water, and dried (MgSO4). After re-
moval of the solvent, the resulting solid was crystal-
lized from toluene to afford 2.6 g (61%) of diastere-
omerically pure product 2-trans as white crystals.
Mp 209–210◦C.
The change of the partial pressures, that is,
keeping p(CO) at 45 bar and decreasing p(H2)
to 22 bar, resulted in a substantial increase in
chemoselectivity and a slight decrease in the re-
gioselectivity using 4-methyl-styrene as the sub-
strate (Table 1, entries 3 and 4). After a pro-
longed reaction time (at p(CO) = 45 bar and
p(H2) = 22 bar), the regioselectivity somewhat in-
creased (Table 1, entry 5).
In conclusion, 3-diphenylphosphinoyl-1-phenyl-
phospholane 1-oxide was prepared and used in the
synthesis of a bis(phosphine borane) complex, a
mixed phosphine borane–phosphine oxide, and a cis
chelate platinum(II) complex. The stereostructures
of the bidentate P-ligand LuPhos and its ring Pt(II)
complex were evaluated by quantum chemical calcu-
lations. It is noteworthy that the PM6 and PM6-DH2
semiempirical calculations also describe the Pt(II)
complex adequately. The cis chelate ring complex
used as a catalyst showed moderate activity and the
prevalence of the branched regioisomer in the hy-
droformylation of substituted styrenes.
31P NMR (CDCl3) δ: 31.7 (d, J = 45.7), 58.8
(d, J = 45.7); 13C NMR (CDCl3) δ: 24.7 (J =
5.3, C4), 28.9 (dd, J1 = 68.7, J2 = 10.0, C2),a 29.9
(dd, J1 = 65.1, J2 = 2.5, C5),a 38.3 (dd, J1
=
72.4, J2 = 9.2, C3), 129.29 (J = 11.6, Cγ),b 129.31
(J = 11.6, Cγ‘),b 129.34 (J = 11.5, Cγ“),b 130.2 (J =
9.6, Cβ),c 131.3 (dd, J1 = 97.8, J2 = 1.4, Cα‘), 131.4
(J = 9.0, Cβ‘),c 131.6 (J = 9.0, Cβ“),c 131.8 (J = 98.4,
Cα“), 132.5 (J = 2.8, Cδ),d 132.6 (J = 2.7, Cδ‘),d 132.7
(J = 2.6, Cδ“),d 134.1 (J = 91.1, Cα), where α, β,
γ, and δ and the one and two prime symbols mean
the corresponding aromatic carbon atoms,a−d ten-
EXPERIMENTAL
1
tative assignment; H NMR (CDCl3)δ: 1.97–2.43 (m,
General (Instruments)
6H, CH2), 2.73–2.87 (m, 1H, CH), 7.43–7.82 (m, 15H,
ArH); Elemental analysis for C22H22O2P2 (%) calcd:
C 69.46, H 5.83, found: C 69.52, H 5.82.
The 31P, 13C, 1H NMR spectra were taken on a
Bruker DRX-500 spectrometer operating at 202.4,
125.7, and 500 MHz, respectively. The couplings are
given in Hz. Mass spectrometry was performed on a
ZAB-2SEQ instrument. Elemental analysis was per-
formed on a PERKIN ELMER HCN 2400 analyzer at
the Faculty of Chemistry, Maria Curie-Sklodowska
University.
3-Diphenylphosphinborano-1-
phenylphospholane 1-borane 4
The solution of 50 mg (0.13 mmol) of 1-phenyl-
3-diphenylphosphinoyl-phospholane 1-oxide (2) in
4 mL of benzene was degassed and after cool-
ing to 0◦C, 0.30 mL (3.0 mmol) of trichlorosilane
was added. The mixture was stirred at 0◦C for 3 h
and then at 25◦C for 2 h under nitrogen to af-
ford bis(phosphine) 3 that was immediately reacted
trans-3-Diphenylphosphinoyl-1-
phenylphospholane 1-oxide (2-trans)
A solution of sodium methoxide (0.61 g, 11.4 mmol)
in 4 mL of methanol was added dropwise at 26◦C to
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Use of Borane and Platinum(II) Complexes of 3-Diphenylphosphino-1-phenylphospholane (LuPhos) 735
further. 0.26 mL of 2 M dimethyl sulfide borane in
cipitated material was removed by the filtration to
afford 80 mg (87%) of 6.
tetrahydrofuran (0.52 mmol) was added and the so-
lution was stirred at 25◦C for 24 h under nitrogen.
Then the mixture was treated with 1 mL of water and
stirred for 10 min. The precipitated boric acid was
removed by filtration and the organic phase dried
(Na2SO4). Volatile components were removed under
reduced pressure and the residue so obtained was
purified by column chromatography (silica gel, 3%
methanol in chloroform) to give 28.5 mg (57%) of 4.
31P NMR (CDCl3) δ: 22.7 (P2, broad), 34.1 (P1,
broad); 13C NMR (CDCl3) δ: 26.4 (2 J = 11.1, 1 J =
35.4, C2), 28.1 (3 J = 1.9, 1 J = 33.3, C5), 28.4 (J =
4.5, C4), 36.7 (J = 34.4, C3), 127.7 (J = 54.5, Cα’),A
127.8 (J = 53.9, Cα”),A 129.07 (J = 9.8, Cγ’),B 129.11
(J = 9.9, Cγ”),B 129.15 (J = 9.6, Cγ), 130.3 (J = 45.5,
Cα), 131.1 (J = 9.1, Cβ), 131.5 (J = 2.5, Cδ), 131.72
(J = 2.1, Cδ’),C 131.74 (J = 2.0, Cδ”),C 132.5 (J = 8.9,
31P NMR (CDCl3) δ: 27.58 (JPt−P 3488, JP−P 14.1,
P2), 33.37 (JPt−P 3409, JP−P 14.1, P1); 1H NMR
(CDCl3) δ: 1.69–1.97 (m, 6H, CH2), 2.20–2.28
(m, 1H, CH), 7.43–7.61 (m, ArH, 15H). HRMS,
[M–Cl]+found 577.0508, C22H22P325Cl194Pt requires
577.0512.
Hydroformylation Experiments
A solution of 6.2 mg (0.01 mmol) of PtCl2(3) and 3.8
mg (0.02 mmol) of tin(II) chloride in 8 mL toluene
containing 0.115 mL (1 mmol) of styrene was trans-
ferred under argon into a 100 mL stainless steel au-
toclave. The reaction vessel was pressurized to 90
bar total pressure (CO/H2 = 1/1) and placed in an
oil bath of appropriate temperature and the mixture
was stirred with a magnetic stirrer. Samples were
taken from the mixture and the pressure was mon-
itored throughout the reaction. After cooling and
venting of the autoclave, the pale yellow solution was
removed and immediately analyzed by GC.
1
Cβ’),D 132.6 (J = 8.9, Cβ”),A−D may be reversed; H
NMR (CDCl3) δ: 3.01 (m, H, CH), 7.41–7.60 (m, 9H,
Ar), 7.61–7.82 (m, 6H, Ar); HRMS, [M + Na]f+ound
=
399.1760, C22H28B2NaP2 requires 399.1750.
The hydroformylation experiments with the sub-
stituted styrenes were carried out following the same
procedure.
3-Diphenylphosphinoyl-1-phenylphospholane
1 borane 5
In the case that the above series of reaction (2 →
3 → 4) was carried out without careful exclusion
of air, a 55%–45% mixture of 4 and 5 was obtained.
The phosphine borane–phosphine oxide (5) was sep-
arated by column chromatography (silica gel, 3%
methanol in chloroform) in 43% yield. 31P NMR
(CDCl3) δ: 30.8 (J = 29.9, P2), 35.2 (P1, broad); 13C
NMR (CDCl3) δ: 26.4 (2 J = 12.6, 1 J = 35.5, C2), 26.7
Quantum Chemical Calculations
The structures in the conformational analysis of the
ligand molecule were calculated by the semiempir-
ical quantum chemical methods PM6 [38], PM6-
DH2 (PM6 Hamiltonian with the correction for
H-bonds and dispersion interactions) [39] and im-
plemented in MOPAC2009 [40] and DFT (density
functional theory) with B3LYP/6-31G∗ functionals
implemented in Gaussian ‘03 [41]. The structure of
the Pt complex was obtained by the same methods,
but Pt was handled by LANL2DZ effective core po-
tentials. The transition state of the inversion around
the P-atom in the ring was also calculated by the
methods mentioned above. The force constants in
the minima are positive and one and only one force
constant has a negative value in the transition state.
The gradient norm of the semiempirical calculations
was less than 0.1 kcal/mol/R A. In the DFT calcula-
tions the criteria were the default. The geometries
were evaluated by MOLDEN [42].
1
(3 J = 1.2, J = 34.0, C5), 27.0 (C4), 40.5 (J = 71.2,
C3), 128.88 (J = 11.6, Cγ’),A 128.93 (J = 11.6, Cγ”),A
129.1 (J = 9.6, Cγ), 130.5 (J = 45.4, Cα), 130.9 (J =
8.9, Cβ), 131.0 (J = 8.9, Cβ’),B 131.1 (J = 8.9, Cβ”),B
A,B
131.4 (J = 2.4, Cδ), 132.2 (J = 2.8, Cδ’,Cδ”),
may
1
be reversed; H NMR (CDCl3) δ: 2.91 (m, H, CH),
7.41–7.61 (m, 9H, Ar), 7.61–7.72 (m, 2H, Ar), 7.72–
7.83 (m, 4H, Ar); HRMS, [M + Na]+found = 401.1378,
C22H25BONaP2 requires 401.1371.
The Platinum Complex of 3-Diphenylphosphino-
1-phenylphospholane (6)
57 mg (0.15 mmol) 1-phenyl-3-diphenylphosphi-
noyl-phospholane 1-oxide (2) was double deoxy-
genated using 0.35 mL (3.5 mmol) of trichlorosilane
as described above for the 2 → 3 transformation.
The solution of bis(phosphine) 3 so obtained was
reacted with 71 mg (0.15 mmol) of dichlorodiben-
zonitrile platinum(II) and the mixture was stirred at
room temperature for 24 h under nitrogen. The pre-
ACKNOWLEDGMENTS
This work is connected to the scientific program
of the “Development of quality-oriented and har-
monized R+D+I strategy and functional model at
BME” project. This project is supported by the New
Hungary Development Plan (Project ID: TAMOP-
4.2.1/B-09/1/KMR-2010-0002). TK is grateful for the
´
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