An improved synthetic method for diphenyl-1-pyrenylphosphine and the properties and structure of its borane adduct

Article abstract of DOI:10.1080/10426500490463529

An efficient synthetic method for diphenyl-1-pyrenylphosphine, DPPP, has been developed involving a low temperature Li-Br exchange reaction using the commercially available 1-bromopyrene. An estimate of the donor ability of this phosphine has been obtaine

Full text of DOI:10.1080/10426500490463529

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AN IMPROVED SYNTHETIC METHOD FOR DIPHENYL-1-
PYRENYLPHOSPHINE AND THE PROPERTIES AND
STRUCTURE OF ITS BORANE ADDUCT
Derek T. Craft a , Sarah M. Arcella a , Susan M. McDowell a , Bruce N. Storhoff a , Abigail E.
Gay b , Michael A. Deibel b , Paul J. Ogren b & Phillip E. Fanwick c
a Ball State University , Muncie, Indiana, USA
b Earlham College , Richmond, Indiana, USA
c Purdue University , West Lafayette, Indiana, USA
Published online: 16 Aug 2010.
To cite this article: Derek T. Craft , Sarah M. Arcella , Susan M. McDowell , Bruce N. Storhoff , Abigail E. Gay , Michael A.
Deibel , Paul J. Ogren & Phillip E. Fanwick (2004) AN IMPROVED SYNTHETIC METHOD FOR DIPHENYL-1-PYRENYLPHOSPHINE AND
THE PROPERTIES AND STRUCTURE OF ITS BORANE ADDUCT, Phosphorus, Sulfur, and Silicon and the Related Elements, 179:7,
1365-1371, DOI: 10.1080/10426500490463529
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Phosphorus, Sulfur, and Silicon, 179:1365–1371, 2004
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Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490463529
AN IMPROVED SYNTHETIC METHOD
FOR DIPHENYL-1-PYRENYLPHOSPHINE
AND THE PROPERTIES AND STRUCTURE
OF ITS BORANE ADDUCT
Derek T. Craft,a Sarah M. Arcella,a Susan M. McDowell,a
Bruce N. Storhoff,a Abigail E. Gay,b Michael A. Deibel,b
Paul J. Ogren,b and Phillip E. Fanwickc
Ball State University, Muncie, Indiana, USA;a Earlham College,
Richmond, Indiana, USA;b and Purdue University,
West Lafayette, Indiana, USAc
(Received October 15, 2003; accepted November 20, 2003)
An efficient synthetic method for diphenyl-1-pyrenylphosphine, DPPP,
has been developed involving a low temperature Li-Br exchange reac-
tion using the commercially available 1-bromopyrene. An estimate of
the donor ability of this phosphine has been obtained by measuring the
A1υ(CO) band of the Ni(CO)3L complex which was found to be 0.4 wave
numbers lower than that from the PPh3 complex indicating that DPPP
is a slightly better donor than PPh3. The BH3 adduct of DPPP has been
prepared and, as the situation for the oxide of DPPP, this adduct is fluo-
rescent. It is estimated that the fluorescence intensity is about half that
of DPPPO. An x-ray structure of this adduct has been obtained, and the
bond lengths and angles appear to be in expected ranges.
Keywords: Borane; diphenyl-1-pyrenylphosphine; DPPP; structure
Detection of lipid oxidation and the presence of oxidizing agents in lipids
has attracted considerable recent attention in view of the direct con-
nections with aging, diseases such as atherosclerosis and food quality.1
One of the fluorometric reagents used to detect the presence of oxidiz-
ing agents in lipids is diphenyl-1-pyrenylphosphine, DPPP (Figure 1)
which is a commercially available product.2−9 DPPP is not fluorescent
Thanks is given to the donors of the Petroleum Research Fund, administered by the
American Chemical Society, along with the Ball State University Faculty Grants Program
and Honors College for support of this research. Funding for the fluorescence system came
from a Howard Hughes Medical Institute grant.
Address correspondence to Bruce N. Storhoff, Department of Chemistry, Ball State
University, Muncie, IN 47306-0445, USA. E-mail: bstorhof@bsu.edu
1365

1366
D. T. Craft et al.
FIGURE 1 Diphenyl-1-pyrenylphosphine.
but the oxide, DPPPO, is, so it provides a method for such detection
especially when used in conjunction with HPLC methods.
Recently it came to our attention that an efficient and well described
synthetic method for DPPP had yet to be published,∗ and that no x-ray
structural data for this compound or its derivatives had been reported.
As a result, we developed a synthetic method that provides the phos-
phine in high yield, and we prepared a BH3 derivative that provided
x-ray quality crystals. Herein we report the results from that study.
EXPERIMENTAL
Reagents and Materials
Methyl diphenylphosphinite, 1-bromopyrene, 2.5 M n-butyllithium and
1.0 M borane-tetrahydrofuran complex were purchased from Aldrich
Chemical Co. Ni(CO)4 was purchased from Strem Chemicals, Inc. Ultra
low water tetrahydrofuran, THF, was purchased from J. T. Baker. The
oxide of DPPP, DPPPO, was prepared as previously described.8
Methods and Instruments
Reactions and purifications were carried out under a blanket of argon.
IR and NMR spectra were recorded on Perkin Elmer Spectrum 1000
and JEOL Eclipse instruments, respectively. The 11B and 31P NMR
spectra were recorded in CDCl3, and they are referenced to BF3OEt2
and H3PO4, respectively. The IR instrument was calibrated with solu-
tions of Ni(CO)3PPh3 for which the A1 υ(CO) stretching band has been
reported to be 2068.9 cm−1 10
Elemental analyses were carried out by
.
Midwest Microlab Ltd., Indianapolis, IN. Fluorescence spectra were
recorded on an instrument built at Earlham College. The x-ray analy-
sis was carried out on a Nonius KappaCCD at the Purdue Chemistry
Crystallography Center, Purdue University, West Lafayette, IN.
∗The method described in Akasaka et al.9 involves reacting PPh−2 with 1-bromopyrene
providing a 13.6% yield. There is also mention of grignard-based reaction in reference 8.

Diphenyl-1-Pyrenylphosphine and its Borane Adduct
1367
DPPP
1-Bromopyrene (4.92 g, 1.75 × 10−2 mol) was dissolved in 250 ml of THF
and cooled in an ethyl acetate/liquid nitrogen bath. n-Butyllithium
(7.0 ml, 1.8 × 10−2 mol) was added via syringe over a period of 15 min
resulting in the formation of a yellow precipitate. The mixture was
stirred an additional 20 min at this temperature and then methyl
diphenylphosphinite (3.5 ml, 1.8 × 10−2mol) in 5 ml of THF was added
over a period of 15 min resulting in a solution. The mixture was stirred
and cooled for an additional 15 min and then the cold bath was re-
moved. During the course of the next hour the solution turned very
dark, but it slowly changed to a tan color as it neared room tempera-
ture. After reaching room temperature 1 ml of triethylamine and 5 ml
of 20% aqueous ammonium chloride were added, and the bulk of the
solvent was then removed with a rotary evaporator. The resulting solid
was dissolved in 75 ml of dichloromethane and extracted with 2 × 50 ml
of water. The nonaqueous phase was collected and the solvent removed
providing 6.31 g (93%) of yellow product with physical and spectro-
scopic properties that matched those reported.8 31P{H} NMR (CDCl3):
δ − 13.2.
DPPP·BH3
Borane-tetrahydrofuran complex (5.2 ml 5.2 × 10−3 mol) was added
dropwise to DPPP (2.00 g, 5.18 × 10−3 mol) in 20 ml of THF that was
cooled in an ice bath. After the addition, the solution was warmed to
room temperature and stirred for an additional 30 min. The solvent was
removed and the sample dried under vacuum providing 2.07 g (100%)
of yellow solid. A 1.72 g sample of this yellow solid was crystallized
from ca. 2 ml each of THF and hexane providing, after cooling slowly to
−10◦C, 0.93 g of yellow crystals. Anal. Calcd for C28H22BP: C, 84.02%,
H, 5.54%. Found: C, 84.36%, H, 5.65%. IR (KBr) 2384.6 (s), 2349.7 (sh).
11B{H} NMR (CDCl3) δ −35.3 (br). m.p. = 207.5–209.0◦.
Ni(CO)3 L IR Studies
The Ni(CO)3L IR studies were carried out in situ in dichloromethane
as previously described.10,11
Single-Crystal X-Ray Diffraction Study of DPPP·BH3
A colorless plate with approximate dimensions of 0.4 × 0.4 × 0.3 mm
was mounted on a glass fiber in a random orientation and cooled to

1368
D. T. Craft et al.
TABLE I Crystallographic Data
for DPPPBH3
Formula
Space group
C28H22BP
P1 (No. 2)
¯
Cell dimens at 150 K
❛
a, A
9.2385 (10)
10.6120 (10)
12.4365 (13)
66.657 (5)
74.617 (5)
78.902 (5)
1074.09 (19)
2
❛
b, A
❛
c, A
α,deg
β,deg
γ,deg
❛
V, A3
Z, molecules/cell
ρcalc, g cm−3
Unique data
R
1.238
4991
0.047
Rw
0.107
Goodness of fit
1.054
150 K. Preliminary and final data collection were performed with Mo
❛
Kα radiation, λ = 0.71073 A, on a Nonius KappaCCD. Lorentz and po-
larization corrections were applied to the data. Hydrogen atoms were
constrained and included in the refinement. Crystal and collection pa-
rameter data are presented in Table I. The data have been deposited
with the Cambridge Crystallographic Data Center.
Fluorescence Spectra
Fluorescence spectra of DPPPO and DPPPBH3 were obtained on so-
lutions prepared by dissolving 3.0 mg of each compound in 10.0 ml of
dichloromethane. The entrance and exit slits were set at 10 nm and
5 nm, respectively.
RESULTS AND DISCUSSION
DPPP has been obtained in excellent yield by way of the reaction se-
quence shown in Scheme 1. The method uses commercially available
materials, and it can be carried out in a single flask in about an hour.
The crude product is about 95% pure as indicated by NMR. For ex-
ample, the 31P spectrum displays, in addition to the DPPP signal at
δ − 13.1, small peaks at δ − 15.1, +22.0 and +33.4 which are in the
ranges expected for Ph2PBu, hydrolyzed Ph2POMe, and oxidized DPPP.
As described previously,9 the DPPP can be purified by chromatography,

Diphenyl-1-Pyrenylphosphine and its Borane Adduct
1369
SCHEME 1 Reaction scheme for DPPP.
and we found that toluene also could be used to recrystallize the
material.
Since one of our goals was to characterize the chemical properties of
the P(III) center, we elected to study the donor properties of the cen-
ter by examining the A1 υ(CO) stretching frequency of Ni(CO)3DPPP
using well established methods that involve using Ni(CO)3PPh3 as
the standard.10,11 The values obtained for the former and latter were
2068.96 and 2069.35 cm−1 respectively. Given the paucity of data to
which the DPPP data could be compared, we elected to prepare a
small amount of PhP(pyrene)2 by the method reported for DPPP with
PhP(OMe)2 in place of Ph2POMe which yielded a compound that pro-
vided a 31P signal at δ − 21.1. This molecule also provided a υ(CO)
stretching frequency at 2068.45 cm−1. These results are consistent
with the conclusion that each pyrene group, compared to a phenyl ring,
slightly increases the donor ability of the P(III) centers.
Despite many attempts with common solvents and solvent mixtures,
x-ray quality crystals of DPPP were not, however, obtained. Given the
fact that we did not find any x-ray data for DPPP, its oxide or sulfide,
we elected to prepare the borane adduct, DPPPBH3. The adduct was
obtained in excellent yield simply by mixing the phosphine with com-
mercially available 1.0 M solution of BH3 in THF. It proved to readily
crystallize, and the structure was determined as described above. An
ORTEP diagram is shown in Figure 2, and selected bond distances and
angles are presented in Table II. In regard to bond lengths, the P C
❛
lengths are in the 1.81–1.82 A range as are six of the nine reported
distances for three reported triarylphosphine-borane molecules.12,13 In
addition all the C C lengths are unremarkable and range from 1.377 to
❛
❛
1.429 A, and the P B length,1.919 A, also matches the average reported
for other triarylphosphine borane adducts.12,13 The C P C angles for
the aforementioned three adducts are from 104 to 108◦, and those for
this adduct are clearly in that range. In regard to C P B values, those
from the three reported examples range from 109.2 to 114.1◦, whereas
those from the DPPP adduct are, as shown, between 109.2 and 117◦.
Whether the latter value is out of a normal range is uncertain given
the paucity of data for related systems.14 As evident in the ORTEP
diagram, the B H bonds are “staggered” rather than “eclipsed” with

1370
D. T. Craft et al.
FIGURE 2 ORTEP diagram of DPPPBH3.
the P C bonds. The H B P C torsion angles (see Table II) average
48.1 and −72.0◦.
One approach to evaluating whether the pyrene group has a steric
impact on the overall structure is to examine the torsion angles from
the centroid of the ipso carbons through the P atom to the ipso and
neighboring carbons as described by Dunitz.15 With this approach,
❛
TABLE II Selected Bond Lengths (A) and Angles (deg)
for DPPPBH3
Bond lengths
Bond angles
P
P
P
P
B
B
B
C1
1.8165 (16)
1.8122 (15)
1.8151 (16)
1.919 (2)
C1
C1
C111
C1
C111
C121
P
P
P
H (1B)
H (1B)
H (1B)
H (1B)
H (1B)
H (1B)
P
P
C111
C121
C121
105.00 (7)
106.31 (7)
104.52 (7)
117.00 (9)
109.15 (9)
113.82 (9)
102.8 (10)
107.9 (10)
106.5 (9)
48.8
C111
C121
B
H (1B) 1.13 (2)
H (2B) 1.116 (19)
H (3B) 1.16 (2)
P
P B
P
P
B
B
B
B
B
H (1B)
H (2B)
H (3B)
B
B
B
B
B
B
P
P
P
P
P
P
C1
C111
C111
C121
C121
C1
−70.2
44.2
−72.2
51.3
−73.5

Diphenyl-1-Pyrenylphosphine and its Borane Adduct
1371
larger angles correspond to a greater clockwise rotation around the
P C bond. This evaluation of DPPPBH3 gives rise to values of 53.5◦,
48.3◦, and 32.2◦ for the C1, C121, and C111 rings, respectively, arranged
in this order so that the torsion angle from P through these carbons
is positive. These in turn provide hexagonal coordinates (XH, YH and
ZH) of 8.8◦, 12.5◦, and 44.6◦ which are entirely consistent with those of
other reported Ph3PX fragments.15
The fluorescence spectra of both BH3DPPP and DPPPO were ob-
tained on dichloromethane solutions. For both, the positions of maxi-
mum excitation and emission were 388 nm and 402 nm respectively.
The former was estimated to be about half as fluorescent as the latter.
How the fluorescence intensity depends on the nature of the DPPP X
bond has yet to be established, but it is plausible that it is related to
the strength of that bond.
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