Structural and electronic properties of tris(4-trifluoromethyltetrafluorophenyl)phosphine

Article abstract of DOI:10.1016/j.jfluchem.2015.08.014

Theoretical calculations on tris(4-trifluoromethyltetrafluorophenyl)phosphine, 1, and spectroscopic studies of its complexes, trans-[PtCl₂{P(C₆F₄CF₃-4)₃}₂], 3, and trans-[RhCl(CO){P(C₆F₄CF₃-4)₃}₂], 4, indicate that it is a poorer σ donor than tris(pentafluorophenyl)phosphine. The structures of 1, 3 and 4 have been determined by single crystal X-ray diffraction, and indicate that the cone angle of 1 is the same as that of tris(pentafluorophenyl)phosphine.

Full text of DOI:10.1016/j.jfluchem.2015.08.014

Journal of Fluorine Chemistry 180 (2015) 15–20
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Structural and electronic properties of
tris(4-trifluoromethyltetrafluorophenyl)phosphine
Graham C. Saunders
School of Science, University of Waikato, Hamilton 3240, New Zealand
A R T I C L E I N F O
A B S T R A C T
Article history:
Theoretical calculations on tris(4-trifluoromethyltetrafluorophenyl)phosphine, 1, and spectroscopic
studies of its complexes, trans-[PtCl2{P(C6F4CF3-4)3}2], 3, and trans-[RhCl(CO){P(C6F4CF3-4)3}2], 4,
Received 31 July 2015
Accepted 17 August 2015
Available online 20 August 2015
indicate that it is a poorer
s donor than tris(pentafluorophenyl)phosphine. The structures of 1, 3 and 4
have been determined by single crystal X-ray diffraction, and indicate that the cone angle of 1 is the same
as that of tris(pentafluorophenyl)phosphine.
Keywords:
ß 2015 Elsevier B.V. All rights reserved.
Tris(4-trifluoromethyltetrafluorophenyl)
phosphine
Electron-withdrawing
Rhodium
Platinum
1. Introduction
originally reported (without NMR and structural data) in a patent
in 1970 [5], is higher than that of tris(pentafluorophenyl)pho-
Electron-poor phosphines are useful ligands for enhancing the
catalytic properties of a number of transition metal complexes
[1,2]. Polyfluoroaryl phosphines are particularly valuable as
electron-poor phosphines [3] because of the high electronegativity
of fluorine. The coordination properties of tris(pentafluorophe-
nyl)phosphine and less fluorinated analogues have been studied
extensively, but decreasing the basicity of these by replacement of
one or more fluorine atoms by other electron-withdrawing groups
has been little explored. As indicated by the Swann–Lupton
constants, a number of functional groups are more electron-
sphine (1.50) [6], and its lower basicity was confirmed by the value
of
n(CBO) of trans-[RhCl(CO){P(C6F4CF3-4)3}2] in chloroform
solution (2016 cmꢀ1) being 8 cmꢀ1 higher than that of trans-
[RhCl(CO){P(C6F5)3}2].
Here are reported the results of a further investigation into the
steric and electronic properties of tris(4-trifluoromethyltetrafluor-
ophenyl)phosphine, including its structure, and those of platinum
and rhodium complexes, determined by single crystal X-ray
diffraction.
withdrawing than fluorine (F 0.45,
R
ꢀ0.39), for example
2. Results and discussion
diazonium (F 1.58, R 0.33), nitro (F 0.65, R 0.13) and nitrile (F
0.51, R 0.15) [4]. These groups are however susceptible to
reactions, which precludes their use as ligand substituents in
catalysis. In contrast the trifluoromethyl group is typically
unreactive, and although it has a lower inductive effect than
2.1. Synthesis and characterization
Tris(4-trifluoromethyltetrafluorophenyl)phosphine, 1, was pre-
pared in a manner similar to that reported [5], but using
trifluoromethyltetrafluorophenylmagnesium bromide as the nu-
cleophile. The 31P NMR spectrum displays a septet of multiplets at
fluorine (F 0.38), it is
p-withdrawing (R 0.16). Consequently
substitution of fluorine by trifluoromethyl in pentafluorophenyl-
phosphines is expected to decrease the basicity of the phosphine. If
the replacement is in the para position then there is expected to be
minimal effect on the steric demands around the metal. A previous
investigation [2] indicated that the Taft
trifluoromethyltetrafluorophenyl)phosphine (1.54), which was
d
ꢀ70.9 with the magnitude of the three-bond phosphorus–
fluorine coupling being 32 Hz. These data are similar to those of
tris(pentafluorophenyl)phosphine (
NMR spectrum displays three resonances at
d
ꢀ74.0, 3JPF 36 Hz) [7]. The 19
F
s* value of tris(4-
d
= ꢀ57.7, ꢀ128.5 and
ꢀ138.6, which is consistent with the spectrum of bis{bis(4-
trifluoromethyltetrafluorophenyl)phosphino}methane (
d
ꢀ57.22,
ꢀ128.1, ꢀ138.0) [8]. Phosphine 1 was further characterized by
E-mail address: g.saunders@waikato.ac.nz.
formation of the oxide, 2, by treatment of an NMR sample with
http://dx.doi.org/10.1016/j.jfluchem.2015.08.014
0022-1139/ß 2015 Elsevier B.V. All rights reserved.

16
G.C. Saunders / Journal of Fluorine Chemistry 180 (2015) 15–20
similar for the two structures. The planes defined by the aryl rings
of 1 subtend angles of 27.0, 50.9 and 64.68 with that defined by
C(11), C(21) and C(31). The analogous angles for tris(pentafluor-
ophenyl)phosphine are 33.2, 48.5 and 78.98.
Theoretical calculations indicate that, as expected, 1 is less basic
than tris(pentafluorophenyl)phosphine: the proton affinity of 1
was calculated by the B3LYP [11], wB97XD [12], M062x [13] and
M06L [13] methods using the 6ꢀ311G++(2d,2p) basis set to be
lower by 34.8, 35.1, 37.3 and 29.5 kJ molꢀ1 respectively, and lower
than that of triphenylphospine by 166.3, 162.8, 172.9 and
153.7 kJ molꢀ1
properties of
.
In order to assess the electronic and steric
experimentally, the complexes trans-
1
[PtCl2{P(C6F4CF3-4)3}2], 3, and trans-[RhCl(CO){P(C6F4CF3-4)3}2]
[2], 4, were studied.
The structures of 3 and 4 were determined by single-crystal X-
ray diffraction. Crystallographic data are given in Table 1 and
selected bond distances and angles are given in Tables 3 and 4
¯
respectively. Complex 3 crystallized in the space group P1 with
two independent molecules in the unit cell, with the platinum
atom of each molecule lying on an inversion centre. Consistent
with the structures of other compounds containing trifluoro-
methylaryl groups there is considerable disorder of the fluorine
atoms of the trifluoromethyl groups [14]. Complex 4 crystallized in
the space group P21/c.
Fig. 1. Structure of P(C6F4CF3-4)3 (1). Thermal ellipsoids are at the 50% probability
level.
Both molecules of 3 possess the expected square planar
geometry, but the two molecules of 3 differ slightly. The Pt–P
hydrogen peroxide. The 31P NMR spectrum of 2 displays a
˚
multiplet at
d
ꢀ9.0, similar to that of tris(pentafluorophenyl)pho-
and Pt–Cl distances of one molecule are ca. 0.007 A longer and
sphine oxide [9], and the 19F NMR spectrum is similar to that of 1.
The structure of 1 was determined by a single-crystal X-ray
diffraction study (Fig. 1). Crystallographic data are given in Table 1
and selected bond distances and angles are given in Table 2. The
geometry around the phosphorus atom is similar to that in the
structure of tris(pentafluorophenyl)phosphine [10]. The P–C bond
distances of the two structures are identical within experimental
error, and the C–P–C angles (two of ca. 1058 and one of ca. 1008) are
shorter respectively than that of the other, and the respective P–
Pt–Cl angles differ by ca. 1.48. The Pt–P and Pt–Cl distances of both
molecules are identical within experimental error to those of trans-
˚
[PtCl2{P(C6F5)3}2] (2.280(2) and 2.304(2) A respectively) [15]. The
two phosphine ligands adopt a staggered conformation, and the
Pt–P–C angles of both molecules of 3 are similar, ca. 105, 116 and
1198, and consistent with those of trans-[PtCl2{P(C6F5)3}2]
(106.4(2), 114.5(2) and 119.5(2)8). The crystal structure of 3 also
Table 1
Crystallographic data for tris(4-trifluoromethyltetrafluorophenyl)phosphine (1), trans-[PtCl2{P(C6F4CF3-4)3] (3) and trans-[RhCl(CO){P(C6F4CF3-4)3}2] (4).a
Formula
C21F21
P
C42Cl2F42P2Ptꢁ½H2O
C43ClF42OP2Rh
Formula weight
Crystal system
Space group
682.18
1639.36
Triclinic
¯
P1
1530.73
Monoclinic
P21/c
Triclinic
¯
P1
˚
a (A)
10.1342(8)
10.7145(8)
11.5130(9)
78.596(4)
67.250(4)
77.709(4)
1117.16(15)
2
12.4453(5)
13.0090(5)
17.7257(10)
105.709(3)
95.664(3)
112.285(2)
2490.1(2)
2
12.30075(14)
24.5392(3)
15.9060(3)
–
˚
b (A)
˚
c (A)
a
b
g
(8)
(8)
(8)
95.1371(13)
–
3
˚
V (A )
Z
4781.96(11)
4
T (K)
Dc (g cmꢀ3
89(2)
89(2)
100(2)
)
2.028
2.186
2.126
Radiation
˚
Mo K
Mo K
Cu K
a
a
a
l
(A)
0.71073
0.71073
1.54184
Crystal size (mm)
(mmꢀ1
range (8)
0.52 ꢂ 0.50 ꢂ 0.40
0.18 ꢂ 0.13 ꢂ 0.11
0.08 ꢂ 0.07 ꢂ 0.03
m
u
)
0.310
3.184
5.971
1.93 ! 32.67
1.80 ! 27.94
3.32 ! 73.80
Total reflections
29337
59534
46138
Unique reflections (Rint
)
7384 (0.0537)
11,856 (0.0430)
9531 (0.0721)
Observed reflections [I > 2
Parameters
s(I)]
5648
9535
7230
401
863
811
Final R indices
R1 0.0580
R1 0.0315
R1 0.0392
[I > 2s(I)]
wR2 0.1599
wR2 0.0780
wR2 0.0853
R indices (all data)
R1 0.0771
R1 0.0447
R1 0.0638
wR2 0.1769
wR2 0.0855
wR2 0.0947
Weighting scheme
w = 1/[s2(Fo2) + {0.0822
(Fo2 + 2Fc2)/3}2 + 1.3687(Fo2 + 2Fc2)/3]
0.825, ꢀ0.580
1.050
w = 1/[s2(Fo2) +{0.0360
(Fo2 + 2Fc2)/3}2 + 8.1523(Fo2 + 2Fc2)/3]
2.797, ꢀ1.488
1.032
w = 1/[s2(Fo2) + {0.0318
(Fo2 + 2Fc2)/3}2 + 5.1809(Fo2 + 2Fc2)/3]
0.900, ꢀ0.793
1.072
ꢀ3
˚
Max., min. Dr (eA
)
Goodness of fit on F2
a
Estimated standard deviations are given in parentheses.

G.C. Saunders / Journal of Fluorine Chemistry 180 (2015) 15–20
17
Table 2
Selected bond distances (A) and angles (8) for tris(4-trifluoromethyltetrafluorophenyl)phosphine, (1).
a
˚
P–C(11)
1.830 (2)
1.833 (2)
1.336 (3)
1.315 (10)
105.30 (9)
100.49 (9)
116.62 (16)
89.34 (14)
128.80 (17)
116.13 (18)
116.71 (15)
ꢀ7.8 (2)
P–C(21)
1.841 (2)
1.385 (3)
1.511 (3)
P–C(31)
Mean C–C (C6)
Mean C–CF3
Mean C–F (C6)
Mean C–F (CF3)
C(11)–P–C(21)
C(21)–P–C(31)
P–C(11)–C(16)
P–C(21)–C(22)
C(11)–P–C(31)
P–C(11)–C(12)
C(12)–C(11)–C(16)
104.47 (9)
126.91 (16)
115.3 (2)
P–C(21)–C(26)
114.94 (15)
127.40 (15)
115.76 (18)
167.8 (2)
C(22)–C(21)–C(26)
P–C(31)–C(36)
P–C(31)–C(32)
C(32)–C(31)–C(36)
C(11)–P–C(21)–C(26)
C(11)–P–C(31)–C(36)
C(21)–P–C(11)–C(16)
C(21)–P–C(31)–C(36)
C(31)–P–C(11)–C(16)
C(31)–P–C(21)–C(26)
C(11)–P–C(21)–C(22)
C(11)–P–C(31)–C(32)
C(21)–P–C(11)–C(12)
C(21)–P–C(31)–C(32)
C(31)–P–C(11)–C(12)
C(31)–P–C(21)–C(22)
81.7 (2)
ꢀ102.6 (2)
ꢀ67.1 (2)
126.1 (2)
ꢀ27.2 (2)
20.7 (2)
148.4 (2)
ꢀ172.5 (2)
ꢀ83.9 (2)
100.5 (2)
a
Estimated standard deviations are given in parentheses.
geometry about the rhodium atom and an eclipsed conformation
of the two phosphine ligands. The two Rh–P distances are identical
within experimental error. The Rh–Cl, Rh–C and C–O distances and
P(1)–Rh–P(2), P–Rh–Cl, P–Rh–C(1) and Rh–C(1)–O angles are
identical within experimental error to those of trans-
[RhCl(CO){P(C6F5)3}2]. The Cl–Rh–C(1) angle is ca. 58 larger for 1.
The aryl rings of one phosphine ligand subtends angles of 68.9, 72.7
and 76.38 with the plane defined by Cl(1), P(1), P(2) and O(1), while
those of the other subtend angles of 50.6, 69.1 and 83.18.
The phosphine ligands of 3 and trans-[PtCl2{P(C6F5)3}2] are
related by inversion at the platinum atom, those of trans-
[RhCl(CO){P(C6F5)3}2] are close to being related by reflection in
the plane of Rh, Cl and C(1) and perpendicular to Rh–P(1) and Rh–
P(2), and those of 4 are related approximately by a C2 rotation
about Cl–Rh–C(1)–O. DFT calculations reveal that there are minima
for optimized geometries of 3 and 4 with conformations possessing
approximately i,
conformations are of equal energy and 6 kJ molꢀ1 more stable than
the v conformation. The calculated i symmetric conformation and
sv and C2 symmetry. For 3 the i and C2 symmetric
s
the experimentally determined structure possesses one P–C bond
syn to each Pt–Cl bond. For 4 the C2 symmetric conformation is the
lowest energy conformation; 14 kJ molꢀ1 and 30 kJ molꢀ1 more
Fig. 2. Structure of trans-[PtCl2{P(C6F4CF3-4)3}2]] (3). Thermal ellipsoids are at the
50% probability level.
stable than the i and
s symmetric conformations respectively. The
calculated C2 symmetric conformation is very similar to the
experimentally determined structure of 4, possessing two P–C
bonds syn to the carbonyl ligand (Fig. 3).
contains water; one molecule disordered over two sites with 50%
occupancy. It is noteworthy that these sites are bounded by
˚
fluorine atoms, the shortest OꢁꢁꢁF distance being ca. 3.35 A, which is
The cone angle of 1 was calculated to be 1738 from the
structures of 3 and 4. This is significantly lower than the value of
1848 reported by Tolman [18], but identical to that calculated from
the structure of trans-[PtCl2{P(C6F5)3}2] [15]. Discrepancies be-
tween Tolman’s values for bulky phosphines and those calculated
˚
0.35 A longer than the sum of the van der Waals radii [16], to a
fluorine atom of a trifluoromethyl group (Fig. 2).
The structure of
4
is similar to that of trans-
[RhCl(CO){P(C6F5)3}2] [17], with approximately square planar
Table 3
a
˚
Selected bond distances (A) and angles (8) for trans-[PtCl2{P(C6F4CF3-4)3}2] (3).
Pt(1)–P(1)
2.2728 (9)
2.3099 (9)
1.828 (4)
1.836 (4)
1.829 (4)
85.45 (3)
105.53 (12)
119.05 (12)
116.76 (13)
ꢀ2.6 (2)
Pt(2)–P(2)
2.2789 (9)
2.3031 (9)
1.826 (4)
1.826 (4)
1.821 (4)
84.05 (3)
119.01 (13)
115.57 (12)
104.50 (12)
ꢀ6.3 (2)
Pt(1)–Cl(1)
Pt(2)–Cl(2)
P(1)–C(1)
P(2)–C(31)
P(1)–C(11)
P(2)–C(41)
P(1)–C(21)
P(2)–C(51)
P(1)–Pt(1)–Cl(1)
Pt(1)–P(1)–C(1)
Pt(1)–P(1)–C(11)
Pt(1)–P(1)–C(21)
Cl(1)–Pt(1)–P(1)–C(11)
C(1)–P(1)ꢁ ꢁ ꢁP(1)0–C(11)0
C(1)–P(1)ꢁ ꢁ ꢁP(1)0–C(21)0
C(11)–P(1)ꢁ ꢁ ꢁP(1)0–C(21)0
P(2)–Pt(2)–Cl(2)
Pt(2)–P(2)–C(31)
Pt(2)–P(2)–C(41)
Pt(2)–P(2)–C(51)
Cl(2)–Pt(2)–P(2)–C(41)
C(31)–P(2)ꢁ ꢁ ꢁP(2)0–C(41)0
C(31)–P(2)ꢁ ꢁ ꢁP(2)0–C(51)0
C(41)–P(2)ꢁ ꢁ ꢁP(2)0–C(51)0
59.2 (2)
60.4 (2)
ꢀ60.3 (2)
60.5 (2)
ꢀ59.4 (2)
60.3 (2)
a
Estimated standard deviations are given in parentheses.

18
G.C. Saunders / Journal of Fluorine Chemistry 180 (2015) 15–20
(Table 5). The magnitude of 1JPtP of 3 is considerably larger than for
similarly bulky, but more electron-rich, phosphines, and about 1%
higher than that of trans-[PtCl2{P(C6F5)3}2] [7]. The magnitude of
1JPtP for phosphine ligands of the same bulk is dependent
predominantly on the Pt–P bond length and its s orbital character
[23]. Since the Pt–P bond lengths of 3 and trans-[PtCl2{P(C6F5)3}2]
1
are identical, the larger value of JPtP is indicative of the lower
1
basicity of 1 compared to P(C6F5)3. In contrast to JPtP the
1
magnitude of JRhP of trans-[RhCl(CO)(PR3)2] shows a smaller
range and no obvious correlation with electron-withdrawing
properties, as has been noted previously [22]. The value of 1JRhP for
4 is consistent with those of complexes of similar fluoroarylphop-
shines.
It has been shown that trans-[RhCl(CO)L2] complexes show a
greater range of n(CBO) than NiL(CO)3, which were used by Tolman
to determine cone angle and an electronic parameter [18], allowing
a better comparison of electronic properties [25]. The value of
n
(CBO) of 4 in the solid state, 2021 cmꢀ1, is significantly larger than
those of all other trans-[RhCl(CO)L2] complexes with similarly
bulky phosphines (Table 5). (The value of (CBO) of in
n
4
dichloromethane solution has been reported to be 2016 cmꢀ1
[2].) The larger value compared to trans-[RhCl(CO){P(C6F5)3}2] is
entirely consistent with 1 being electron-poorer than tris(penta-
fluorophenyl)phosphine.
Fig. 3. Structure of trans-[RhCl(CO){P(C6F4CF3-4)3}2] (4). Thermal ellipsoids are at
the 50% probability level.
from their structures have been noted previously [19–21].
However, the cone angle of 1 is, as expected, the same as those
of tris(pentafluorophenyl)phosphine and tris(2,6-difluorophenyl)-
The spectroscopic and theoretical data indicate that, as
expected, 1 is a poorer
s donor than other bulky phosphines,
and therefore a weaker ligand. This is confirmed by the observation
that addition of dimethyl sulphide to a solution of 3 in acetone led
to the immediate dissociation of 1, as evidenced by NMR
spectroscopy.
phosphine. The electronic properties of 1 as a ligand were
1
investigated experimentally by comparing JPtP of 3 and
n(CBO)
of 4 with those of analogous complexes of other bulky phosphines
Table 4
a
˚
Selected bond distances (A) and angles (8) for trans-[RhCl(CO){P(C6F4CF3-4)3}2] (4).
Rh–P(1)
2.2826 (10)
2.3599 (10)
1.128 (5)
1.830 (4)
1.833 (4)
1.831 (4)
170.63 (3)
85.70 (3)
95.10 (12)
178.2 (4)
116.13 (12)
106.22 (12)
117.73 (13)
ꢀ1.2 (2)
Rh–P(2)
2.2799 (9)
1.846 (4)
1.829 (4)
1.837 (4)
1.834 (4)
Rh–Cl
Rh–C(1)
C(1)–O
P(1)–C(11)
P(1)–C(31)
P(2)–C(51)
P(1)–C(21)
P(2)–C(41)
P(2)–C(61)
P(1)–Rh–P(2)
Cl–Rh–C(1)
179.15 (13)
86.39 (3)
P(1)–Rh–Cl
P(2)–Rh–Cl
P(1)–Rh–C(1)
P(2)–Rh–C(1)
92.83 (12)
106.91 (12)
121.33 (13)
118.76 (12)
Rh–C(1)–O
Rh(1)–P(1)–C(11)
Rh(1)–P(1)–C(31)
Rh(1)–P(2)–C(51)
Rh–P(1)–C(21)
Rh(1)–P(2)–C(41)
Rh(1)–P(2)–C(61)
C(1)–Rh–P(1)–C(31)
C(11)–P(1)ꢁ ꢁ ꢁP(2)–C(41)
C(11)–P(1)ꢁ ꢁ ꢁP(2)–C(61)
C(21)–P(1)ꢁ ꢁ ꢁP(2)–C(51)
C(31)–P(1)ꢁ ꢁ ꢁP(2)–C(41)
C(31)–P(1)ꢁ ꢁ ꢁP(2)–C(61)
C(1)–Rh–P(2)–C(51)
ꢀ3.2 (2)
ꢀ130.8 (2)
ꢀ7.2 (2)
109.8 (2)
ꢀ8.2 (2)
C(11)–P(1)ꢁ ꢁ ꢁP(2)–C(51)
C(21)–P(1)ꢁ ꢁ ꢁP(2)–C(41)
C(21)–P(1)ꢁ ꢁ ꢁP(2)–C(61)
C(31)–P(1)ꢁ ꢁ ꢁP(2)–C(51)
112.1 (2)
123.6 (2)
118.4 (2)
ꢀ126.2 (2)
ꢀ4.3 (2)
a
Estimated standard deviations are given in parentheses.
Table 5
Selected spectroscopic data for complexes of 1 and related bulky phosphines.a
Phosphine (L)
Cone angle (8)b
trans-[PtCl2L2]
trans-[RhCl(CO)L2]
1JRhP (Hz)
1JPtP (Hz)
n )
(CBO) (cmꢀ1
1
184 (173)
184 (173)
184 (173)
171 (166)
160
3167
154
155
144
136
135
139
–
2021
P(C6F5)3 [22]
3145 [7]
–
2008
P(C6H3F2-2,6)3[20]
PPh(C6F5)2 [22]
P{C6H3(CF3)2-3,5}3 [7]
P{C5H2N-4-(CF3)2-3,5}3 [2]
1965
2862
2002
2798
2000
160
–
(2017)
1941 [24]
(1974) [25]
P(cyclo-C6H11
)
170
2397 [23]
2603 [21]
3
P(C6H5Me-2)3
194 (183)
–
a
IR data are for the solid state except for values in parentheses, which were obtained in solution.
b
Tolman’s values [18], with values calculated from the experimentally determined molecular structures in parentheses.

G.C. Saunders / Journal of Fluorine Chemistry 180 (2015) 15–20
19
3. Conclusion
4.3.2. trans-[PtCl2{P(C6F4CF3-4)3}2] (3)
A solution of K2PtCl4 (0.067 g, 0.16 mmol) in water (10 cm3) was
added to 1 (0.220 g, 0.322 mmol) in warm ethanol (120 cm3). A
further 20 cm3 of water was added to aid dissolution of precipitated
K2PtCl4, and the mixture was stirred vigorously with gentle
warming. A yellow solution developed and a cream precipitate
was deposited over 4 h. The solid was filtered and washed with
hexane.Yield0.161 g(61.9%). Asampleforanalysis, containinghalfa
molecule of water per molecule of complex, was recrystallized from
acetone. Anal. Calcd for C42Cl2F42P2Pt.0.5H2O: C, 30.8; H, 0.1. Found
Structural, spectroscopic and theoretical studies of tris(4-
trifluoromethyltetrafluorophenyl)phosphine, 1, trans-[PtCl2{P(C6
F4CF3-4)3}2], 3, and trans-[RhCl(CO){P(C6F4CF3-4)3}2], 4, have been
performed. The structural studies reveal that 1 exerts similar steric
effects as tris(pentafluorophenyl)phosphine. Theoretical calcula-
tions on phosphine 1, and NMR and IR spectroscopic studies of 3
and 4 confirm that 1 is less basic than tris(pentafluorophenyl)pho-
sphine.
C, 31.1; H < 0.3%. 13C NMR ((CD3)2CO, 100.63 MHz):
d 147.2 (ddm,
1
4. Experimental
1JCF = 262 Hz, J = 16 Hz), 144.5 (dd, JCF = 265 Hz, J = 17 Hz), 120.4
(quart, 1JCF = 275 Hz, CF3), 114.3 (m), 108.2(m). 19F NMR ((CD3)2CO,
3
4.1. Instrumentation
376.46 MHz):
d
ꢀ57.73 (18F, t, JFF 21.6 Hz, CF3), ꢀ119.95 (6F, br,
C6F4), ꢀ127.18 (6F, br, C6F4), ꢀ139.40 (12F, br, C6F4). 31P NMR
The 13C, 19F and 31P NMR spectra were recorded in CDCl3 using
Bruker DRX300 or DPX400 spectrometers. 13C (75.48 or
100.61 MHz) were referenced internally using the solvent reso-
((CD3)2CO, 100.63 MHz):
d
ꢀ25.0 (1JPtP = 3167 Hz).
4.3.3. trans-[RhCl(CO){P(C6F4CF3-4)3}2] (4)
nance to SiMe4
CFCl3 (
0) and 31P (161.97 or 121.49 MHz) externally to 85% H3PO4
0). All chemical shifts are quoted in d (ppm), using the high
(
d
0), 19F (376.46 or 282.40 MHz) externally to
Compound 1 (0.225 g, 0.33 mmol) was added to [Rh(m-
d
Cl)(CO)2]2 (0.029 g, 0.077 mmol) in dichloromethane (30 cm3)
with stirring. Effervescence was observed and a yellow solution
resulted. The solution was filtered and heptane (20 cm3) was
added. Concentration by rotary evaporation afforded small yellow
crystals. Yield 0.220 g (93.3%). Anal. Calcd for C43ClF42OP2Rh: C,
(
d
frequency positive convention, and coupling constants in Hz. All
spectra were recorded at 300 K unless indicated otherwise.
Elemental analyses were carried out by the Campbell Microana-
lytical Laboratory, The University of Otago. The IR spectrum was
33.7. Found C, 33.8%.
100.63 MHz):
n
(CBO) 2021 cmꢀ1
.
13C NMR ((CD3)2CO,
1
recorded as
a
potassium bromide disc on
a
Perkin Elmer
d
184.6 (dm, JRhC = 70 Hz, CO), 147.1 (dd,
1JCF = 254 Hz, J = 16 Hz), 144.4 (dd, JCF = 262 Hz, J = 18 Hz), 120.5
1
Spectrum100 FT-IR spectrometer.
(quart, 1JCF = 275 Hz, CF3), 113.3 (tm, J = 37 Hz), 112.2 (m). 19F NMR
3
4.2. Materials
((CD3)2CO, 376.46 MHz):
d
ꢀ57.7 (18F, t, JFF 22 Hz, CF3), ꢀ119.9
(6F, br, C6F4), ꢀ127.2 (6F, br, C6F4), ꢀ139.5 (12F, br, C6F4); (193 K):
d
3
3
The compounds phosphorus tribromide (Aldrich), 4-bromotri-
fluoromethyltetrafluorobenzene (Apollo) and K2PtCl4 (Johnson
Matthey) were used as supplied. [Rh(m-Cl)(CO)2]2 was prepared as
described [26]. Diethyl ether was dried by passage through
activated alumina.
ꢀ57.4 (9F, t, JFF 21 Hz, CF3), ꢀ57.5 (9F, t, JFF 19 Hz, CF3), ꢀ123.1
(2F, m, C6F4), ꢀ124.8 (4F, br, C6F4), ꢀ129.3 (1F, m, C6F4), ꢀ131.0 (br,
C6F4), ꢀ137.7 (br, C6F4), ꢀ138.57 (br, C6F4), ꢀ140.7 (br, C6F4),
ꢀ141.2 (1F, m, C6F4), ꢀ142.2 (1F, m, C6F4). 31P NMR ((CD3)2CO,
1
75.48 MHz): ꢀ22.7 (br); (193 K):
d
ꢀ22.9 (dm, JRhP = 154 Hz).
4.3. Preparations
4.4. Theoretical calculations
4.3.1. P(C6F4CF3-4)3 (1)
Calculations were performed using Gaussian09 [27]. The
difference in proton affinity was calculated from the enthalpies
of the phosphine and phosphonium cation according to the
A dark brown solution of 4-CF3C6F4MgBr in diethyl ether
(150 cm3), prepared from CF3C6F4Br (13.5 g, 0.046 mol) and
magnesium (1.52 g, 0.0625 mol), was added under nitrogen to
phosphorus tribromide (3.4 g, 0.013 mol) in diethyl ether (50 cm3)
over 15 min. The resulting solution was left at ambient temperature
for 16 h, after which it was exposed to the atmosphere, and water
(150 cm3) added to destroy the excess of Grignard reagent. Ethyl
acetate (100 cm3) was added and the organic layer separated. The
aqueous layer was extracted with ethyl acetate (100 cm3) and the
combined organic fractions were washed with water (2 ꢂ 50 cm3),
dried over anhydrous magnesium sulphate and filtered through
5 cm of deactivated neutral alumina. The solvent was removed by
rotary evaporation to afford a viscous golden oil which deposited
colourless crystals of 1 on standing. The product was purified by
equation:
(
D
Hf(PR3) ꢀ
D
Hf([HPR3]+)) ꢀ (
D
Hf(1) ꢀ
D
Hf([1.H]+)).
Structures of 3 and 4 were calculated using the B3LYP functional
[11] and the 6ꢀ311G++(2d,2p) basis set for all atoms except for
those of platinum and rhodium for which the LANL2DZ effective
core potentials and basis set were used.
4.5. X-ray crystallography
Crystals of 1 were grown by sublimation. Crystals of 3 and 4
were grown from acetone and dichloromethane respectively. Unit
cell dimensions and reflection data for 1 and 3 were collected at the
University of Canterbury on a Bruker Nonius Apex II CCD
diffractometer. Absorption corrections to the data were made by
SADABS [28]. Unit cell dimensions and reflection data for 4 were
collected at the University of Waikato on an Agilent supernova
diffractometer. Empirical absorption corrections were made using
spherical harmonics. Crystal and refinement data for the complex
are presented in Table 1. The structures were solved by direct
methods using SHELXS-97 [29] and refined using SHELXL-97 [30]
with all atoms, except F374, F375 and F376 of 1 and the oxygen
atom of the water molecule of 3, anisotropic. The hydrogen atoms
of the water molecule of 3 were not included. There is slight
disorder of the fluorine atoms of the C17 trifluoromethyl group of
1, which was modelled with the three fluorine atoms in two sites
with occupancies of 94% (F371, F372 and F373) and 6% (F374, F375
sublimation in vacuo. Yield 5.73 g (64.6%). Anal. Calcd for C21F21P: C,
37.05. Found C, 37.0%. 13C NMR:
d
= 147.6 (ddquart, JCF = 254,
1
2JCF = 20, 3JCF = 4 Hz, Cmeta), 144.0 (dd, 1JCF = 265, 2JCF = 18 Hz, Cortho),
1
120.3 (quartet, JCF = 275 Hz, CF3), 113.7 (m), 113.0 (m). 19F NMR:
d
= ꢀ57.7 (9F, t, 3JFF = 22 Hz, CF3), ꢀ128.5 (6F), ꢀ138.6 (6F) (X, M and
N components respectively of an A[[M]2[N]2[X3]]3 spin system). 31
P
NMR:
d
= ꢀ70.9 (sept, 3JPF = 32 Hz).
A sample of 1 in CDCl3 (ca. 1 cm3) in an NMR tube was treated
with aqueous hydrogen peroxide (30%) (4 ꢂ 1 cm3) over several
days to give the oxide 2. 19F NMR:
d
= ꢀ57.8 (9F, t, 3JFF = 22 Hz, CF3),
ꢀ130.3 (6F), ꢀ136.4 (6F) (X, M and N components respectively of
an A[[M]2[N]2[X3]]3 spin system). 31P NMR:
multiplet).
d
= ꢀ9.0 (unresolved

20
G.C. Saunders / Journal of Fluorine Chemistry 180 (2015) 15–20
[6] T. Korenaga, K. Kadowaki, T. Ema, T. Sakai, J. Org. Chem. 69 (2004) 7340–
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and F376). There is considerable disorder of the fluorine atoms of
the trifluoromethyl groups of 3. For those of C17 and C27 this was
modelled with the fluorine atoms at two sites with occupancies of
71% (F17, F18 and F19) and 29% (F17A, F18A and F19A), and 66%
(F27, F28, F29) and 34% (F27A, F28A and F29A) respectively.
Attempts to treat the trifluoromethyl groups of C47 and C57
similarly gave no significant improvement. The maximum and
minimum residual electron densities are associated with the
trifluoromethyl group of C57.
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Acknowledgements
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