Effect of fluorine and trifluoromethyl substitution on the donor properties and stereodynamical behaviour of triarylphosphines

Article abstract of DOI:10.1039/a903211h

A series of 2-, 3- or 4-trifluoromethyl substituted triarylphosphines and their oxide, chalcogenide and Fe(CO)₄ derivatives have been prepared and characterised spectroscopically and crystallographically. Electronic effects of CF₃ su

Full text of DOI:10.1039/a903211h

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Effect of fluorine and trifluoromethyl substitution on the donor
properties and stereodynamical behaviour of triarylphosphines
James A. S. Howell,*a Natalie Fey,a Jonathan D. Lovatt,a Paul C. Yates,a Patrick McArdle,b
Desmond Cunningham,b Einat Sadeh,c Hugo E. Gottlieb,c Zeev Goldschmidt,c
Michael B. Hursthoused and Mark E. Lightd
a Chemistry Department, Keele University, Keele, Staffordshire, UK ST5 5BG
b Chemistry Department, University College, Galway, Ireland
c Chemistry Department, Bar Ilan University, Ramat Gan 52900, Israel
d Department of Chemistry, University of Southampton, Southampton, UK SO17 1BJ
Received 22nd April 1999, Accepted 29th June 1999
A series of 2-, 3- or 4-trifluoromethyl substituted triarylphosphines and their oxide, chalcogenide and Fe(CO)4
derivatives have been prepared and characterised spectroscopically and crystallographically. Electronic effects of CF3
substitution are cumulative and felt equally in the 2, 3 or 4 position. Substitution in the 2 position substantially
hinders the complexing ability for steric reasons. Correlated P–C rotation in the 2-substituted derivatives has been
analysed by variable temperature NMR and molecular mechanics calculations.
Introduction
Results and discussion
The synthesis and study of fluorinated analogues of organic
molecules continues to be an area of intense activity. In
organometallic chemistry a related interest has been manifest in
the design of fluorinated phosphorus donor ligands. Two par-
ticular areas are worthy of recent note, namely the development
of long chain fluorinated phosphines such as P(CH2CH2-
(CF2)5CF3)3 1 and 2 for application in catalysis using fluorous
media or supercritical CO2 as solvent,1,2 and the fine tuning of
enantioselectivity in the use of diarylphosphinite ligands such
as 3 and 4 through fluoro or trifluoromethyl substitution of the
aryl ring.3 Of particular interest for 4 is the observation that
The fluorinated phosphines 7a–10a were prepared by reaction
of the appropriate aryllithium with PCl3. The mixed derivatives
11a and 12a were prepared similarly by reaction of 2-CF3-
C6H4Li with (2-CH3C6H4)PCl2 5 and (2-CH3C6H4)2PCl 6
respectively.
Stable oxides 7b, 11b, 12b and 13b are formed by all phos-
phines in the P(2-CH3C6H4)n(2-CF3C6H4)3Ϫn (n = 0–3) series. In
contrast, reaction with sulfur and selenium is restricted to the
higher alkylated members 12a and 13a. While reactions of 13a
with S and Se under standard conditions5 proceed to comple-
tion to give 13c and 13d, treatment of 12a under the same
conditions provides only mixtures of 12a with 12c and 12d
[12a:12c = 5.3:1; 12a:12d = 1:1.5, identified by integration of
31P resonances]. Only the selenide 12d has been isolated pre-
paratively, and on heating in benzene is reconverted through
selenium extrusion into the same ratio of 12a:12d. The results
surprisingly imply a greater thermodynamic stability for the sel-
enide compared to the sulfide. No adduct formation is observed
on reaction of 7a or 11a with S or Se, whereas reactions of 8a,
9a and 10a proceed to completion to give the selenides 8b, 9b
and 10b.
Complexation to Fe(CO)4 tends to mirror the selenide chem-
istry. Stable Fe(CO)4 adducts 8c, 9c, 10c, 13c and 14c are iso-
lated from the reaction of Fe2(CO)9 with compounds 8a, 9a,
10a, 13a and 14a. Reaction of 7a provides only recovered start-
ing material, while reactions using 11a and 12a are incomplete
and are best investigated under equilibrium conditions using
the exchange reaction6 (1). No substitution is observed with 7a,
such electron withdrawing groups enhance enantioselectivity in
the hydrocyanation of alkenes where reductive elimination is
viewed as the key mechanistic step, whereas for hydrogenation,
where oxidative addition is rate determining, enantioselectivity
is enhanced by electron donor substituents on the aryl ring.3a
An understanding of the consequences of fluorine for hydrogen
substitution on the donor properties and structure and stereo-
dynamics of such ligands and their metal complexes is thus
desirable.
We report here our results on the effect of fluoro and tri-
fluoromethyl substitution on the complexing properties of tri-
arylphosphines towards Fe(CO)4, together with studies on the
stereodynamics of the ortho-substituted derivatives which have
also yielded valuable information regarding the energetics of
correlated P–C rotation in both the free phosphines and their
oxide and chalcogenide derivatives.4
60 ЊC
[Fe(CO) (PhCH᎐CH )] ϩ PR
3
᎐
4
2
Toluene
[Fe(CO) (PR )] ϩ PhCH᎐CH (1)
᎐
4
3
2
whereas reactions using 11a and 12a proceed to equilibrium
with equilibrium constants of 0.06 and 0.6 respectively.
The crystal and molecular structures of the phosphines 7a
and 11a, the oxide 7b, the selenides 9b and 10b and Fe(CO)4
complexes 8c, 9c and 10c have been determined by X-ray dif-
fraction as part of this work (Fig. 1). Important structural and
geometric parameters are listed in Table 1, together with rele-
vant literature data. All Fe(CO)4 compounds exhibit structures
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which depart little from trigonal bipyramidal, with phosphines
in the axial position. Compounds 7a, 11a and 7b exhibit an
exo3 † conformation of the triaryl moiety. Examination of the
X–P–Cipso–Cα torsion angles shows that almost all 2- and
4-substituted derivatives and [Fe(CO)4(PPh3)] 15 exhibit a regu-
lar helical array of the triaryl propeller which is slightly flat-
tened by the introduction of O, Se or Fe(CO)4 into the fourth
co-ordination position. In contrast, the aryl conformations in
the 3-substituted derivatives deviate considerably from regular
helicity, containing one ring whose plane is collinear with the
P–X axis (X–P–Cipso–Cα Ϫ6 to 23Њ), one ring perpendicular to
the P–X axis (62–85Њ) and one ring at an intermediate value
(18–32Њ). Whilst (3-CH3C6H4)3PSe adopts an exo1 configur-
ation, those of 8b and 10b are exo2, in keeping with the reduced
tendency of CF3 to occupy an endo position (see below),
though energy differences between exo/endo conformations for
3-substituted compounds are clearly less than those for the 2-
spectra. Covering a range of appropriately 100 Hz in Table 2,
these J(PSe) values provide probably the most sensitive probe,
increasing with increasing electron withdrawing character of
the aryl substituent. Though this is said to reflect increasing
s-orbital participation on the phosphorus, there is no systematic
variation in the C–P–C angles from structural data (Table 1).
Values of J(PSe) correlate well with other data, and with the
Hammett σm and σp parameters.13 For the CF3 derivatives
examined, J(PSe) values appear cumulative. Thus ∆J (PSe)
(relative to SePPh3) for SeP(3,5-(CF3)2C6H3)3 is twice that of
SeP(3-CF3C6H4)3. For 4 substitution, the electron-withdrawing
power of F is approximately one half to one third that of CF3.
It is tempting to speculate that J(PSe) values may provide an
estimate of the electronic effect only of 2 substitution. On this
basis, donation by CH3 increases in the order m < p < o while
the electron withdrawing effect of the almost purely inductive
CF3 is felt almost equally at the o, m and p positions.
substituted analogues. Though the P᎐O distance in 7b and 13b
is not responsive to substitution of CH3 by electron withdraw-
It may be noted that J(PSe) values for 2-methoxy derivatives
are perhaps not as low as expected. Crystal structures of the
oxide, sulfide and selenide of [2,4,6-(MeO)3C6H2]3P15,20 have
demonstrated a possible interaction between the methoxy lone
pair and phosphorus which reduces its ability to enter into res-
onance with the aromatic ring. Crystal structures of several
metal complexes of 2-methoxy substituted triarylphosphines
also demonstrate metal co-ordination of the methoxy lone
pair.21
᎐
ing CF , both P᎐Se and P–Fe bond lengths respond to the
᎐
3
electron withdrawing nature of the aryl substituent. These
bond lengths, and other appropriate spectroscopic measures of
donor/acceptor character, are collected in Table 2 together with
relevant literature data. Generally, both P᎐Se and P–Fe bond
᎐
lengths decrease with increasing electron withdrawing character
of the aryl substituent. Increasing δ(13CO) and J(P–CO) values
are also consistent with decreasing σ-donor/π-acceptor char-
acter of the phosphine, with consequent diminution in back
donation to carbon monoxide. The data indicate that
P(OC6H5)3 and P[3,5-(CF3)2C6H3]3 are similar in their overall
electronic interactions with Fe(CO)4. DFT Calculations18 indi-
cate that this is due to a decreased σ donation for the phos-
phine, but an increased π-acceptor character for the phosphite.
The lack of reactivity of 7a thus appears purely steric in origin.
Though 13a forms a stable selenide, P(C6H2(CH3)3-2,4,6)3 does
not.19
During slow recrystallisation of compound 9c, a small
amount of disproportionation resulted in deposition of
[Fe(CO)3{P(4-CF3C6H4)3}2] 17a as
a minor component
(νCO = 1901, 1914 (sh) cmϪ1) which was also structurally char-
acterised (Fig. 2, Table 1). The phosphine ligands occupy trans
positions in a trigonal bipyramidal structure and in com-
mon with [Fe(CO)3(PPh3)2] 17b,12a,b the Fe–P bond length is
substantially shortened relative to the [Fe(CO)4L] analogue.
Compounds 17a, 17b exhibit an interesting conformational
difference in that while 17b has an almost eclipsed array of
phenyl rings (Cipso–P–PЈ–CЈipso ≤ 6Њ) with opposite chirality of
the triaryl helices, that of 17a is staggered (Cipso–P–PЈ–
CЈipso ≤ 76Њ) with the same chirality of the helices (Fig. 2). It has
been suggested12c that intermolecular arene–arene interactions
may be important in determining conformation in the solid
state. Examination of the solid state packing shows that
whereas shorter range arene–arene interactions in 17b are of a
Selenium satellites generated by the 31P77Se isotopomers
(7.6% natural abundance) are readily observed in the 31P NMR
† If a regular pyramid is constructed from the lone pair (lp), O, Se or
Fe(CO)4 as the apex and the three para ring carbons as the base, an exo
substituent will point away from the base, while an endo substituent will
point towards the base.
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Fig. 1 Molecular structures of compounds 7a, 7b, 8c, 9b, 9c, 10b, 10c and 11a.
perpendicular T-shaped type, those in 17a are almost exclus-
which has been previously observed for the 2-CH3 substituted
ively of a parallel face-to-face arrangement. It may be noted
that whereas [Ru(CO)3(PPh3)2] is conformationally identical to
17b,12d [Os(CO)3(PPh3)2] has a staggered conformation similar
to that of 17a (Cipso–P–PЈ–CЈipso = 48Њ) with the same sign of
helicity.12e
derivatives5 and in general for molecular propellers of the types
Ar3Z and Ar3ZX.22
Crystal structure determinations of various P(2-CH3C6H4)3
derivatives, including those reported herein, exhibit either
23
24
exo3 or exo2 conformations. On the assumption that only
these two isomers are populated, P–C rotational isomerism for
an Ar2ArЈPX compound via 1-, 2- and 3-ring flip mechanisms
may be represented as in Scheme 1. Eight conformers [(A)–(D)
and their enantiomeric equivalents (AЈ)–(DЈ)] are possible. For
Ar3PX derivatives, (B)–(D) and (BЈ)–(DЈ) are equivalent and the
number of conformers is reduced to four.
NMR Spectra of all 3- and 4-CF3 substituted derivatives are
temperature invariant down to Ϫ100 ЊC, implying that P–C and
P–Fe rotation and pseudorotation of the Fe(CO)4L trigonal
bipyramid remain fast on the NMR timescale. In contrast, sev-
eral of the 2-CF3 substituted complexes exhibit temperature
1
dependent H, 19F and 31P spectra which are consistent with
correlated P–C rotation and consequent exo/endo ring exchange
Molecular mechanics calculations on the phosphines repro-
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Table 2 Structural and spectroscopic data relevant to donor/acceptor character
Compound
d(P᎐Se)/Å
d(P–Fe)/Å
J(P–Se)/Hz
ν(CO)/cmϪ1
δ (13CO)
σm or σp
᎐
14
P(2-CH3OC6H4)3
720
717
710
703
726
715
733
741
14,15
P[2,6-(CH3O)2C6H3]3
2.135(3)
14
P(4-CH3OC6H4)3
Ϫ0.12
7,14
P(2-CH3C6H4)3 9,14
2.116(5)
2.109(5)
2.306(1)
2.244(1)
2047
214.6
P(3-CH3C6H4)3 14
P(4-CH3C6H4)3
Ϫ0.06
Ϫ0.14
0
14,16
P(C6H5)3
2.112
2050
2052
2052
2050
2057
2056
2065
2065
213.6
213.5
17
P(4-FC6H5)3
0.15
P(2-CH3C6H4)(2-CF3C6H4)2
P(2-CH3C6H4)28(2-CF3C6H4)
P(3-CF3C6H4)3
P(4-CF3C6H4)3
P(3,5-(CF3)2C6H4)3
P(OC6H5)3
727
766
765
802
2.094(2)
2.100(1)
2.085(1)
2.234(1)
2.245(1)
2.210(1)
212.7
212.8
210.7
211.4
0.46
0.53
The 31P NMR spectra of all the phosphines exhibit a single
31P resonance down to Ϫ100 ЊC, indicative of either an
exclusive population of exo3 or an exo2/exo3 mixture in which
interconversion remains fast on the NMR timescale. The essen-
tially identical chemical shift of H6 for the 2-CH3C6H4 (δ 6.56–
6.73) and 2-CF3C6H4 (δ 6.89–7.06) rings, which may be used as
a measure of exo2 content,5 indicates that the former explan-
ation is correct. While helix inversion (3-ring flip) of the exo3
conformer represents a hidden process for PAr3, it is required
for exchange of chemically equivalent rings in PAr2ArЈ and can
be observed experimentally in the broadening and resolution
into two of the CF3 (19F) and CH3 (1H) resonances of 11a and
12a respectively (Table 5, Fig. 3). The presence of long range
P–F coupling in the 2-CF3C6H4 phosphines 7a, 11a, 12a may be
noted, but is absent in the oxides 7b, 11b and 12b, the selenide
12d and the 3- and 4-substituted phosphines.
The 31P spectra of the oxides 7b, 11b and 12b are all resolved
into two unequally populated resonances at low temperature
(Fig. 4). The major and minor resonances are assigned to exo3
and exo2 respectively. In agreement, for example, the 19F spec-
trum of 7b exhibits a single large resonance assignable to
equivalent CF3 groups of exo3 together with three minor reson-
ances due to the non-equivalent CF3 groups of the exo2 isomer.
For the mixed derivatives 11b and 12b, a population of only one
of the three possible exo2 conformers is observed. Line shape
analyses, shown only for 7b, provide barriers for the 2-ring flip
exo2/exo3 exchange process. For the mixed CF3/CH3 oxides 11b
and 12b, line shape analysis of the higher temperature 19F and
1H spectra respectively (Fig. 5) also provides barriers for the
higher energy 3-ring flip process. Two points of interest may be
noted. (i) Relative to 13b, all CF3-substituted oxides exhibit a
reduced population of the exo2 isomer. In all cases, however,
the exo2 population increases substantially with increasing
temperature, with the sensitivity to temperature becoming
more pronounced with increasing degree of CF3 substitution.
In particular, the large linewidths in the 31P spectra of 7b in
the 193–213 K range are impossible to simulate without the
approximate five- to ten-fold decrease in Keq. (ii) Barriers for
the 2-ring flip process in the oxides and 3-ring flip process in the
phosphines increase slightly (ca. 5%) with increasing degree of
CF3 substitution. The influence of increasing CF3 substitution
on the increasing barrier to 3-ring flip in the oxides is much
more substantial (ca. 12%), consistent with a more demanding
oxygen–CF3 as opposed to lone pair–CF3 interaction in the
presumed intermediate (IV).
Fig. 2 (a) Molecular structure of [Fe(CO)3{P(4-CF3(C6H4)3}2]. (b)
View down P–P axis of [Fe(CO)3L2] [L = PPh3 or P(4-CF3C6H4)3]
(only ipso carbon of aryl ring shown).
duce well the observed exo3 geometry as the energy minimum in
all cases. The minimised geometries of the exo2 conformers are
also consistent with observed exo2 structures, particularly the
approximate collinearity of the plane of the endo ring with the
lp–P axis. The exo2 isomers lie between 2.0 and 4.3 kcal higher
in energy than exo3 (Table 3), with the energy difference becom-
ing more pronounced with increasing CF3 substitution. For the
mixed derivatives, conformers with endo 2-CF3C6H4 rings are
less stable than those with endo 2-CH3C6H4. Relative barriers
for the various ring flip processes may be screened by molecular
mechanics calculations of the energies of idealised transition
states for the 1-ring (I, II), 2-ring (III) and 3-ring (IV, V) flip
processes (Table 4). For the phosphines, the calculations show
clearly that the 2-ring flip (interconverting exo2 and exo3) is the
process of lowest energy, followed by the 3-ring flip (helix
interconversion in the exo3). Intermediates I, II and V lie at
much higher energies, and indeed are not required to rationalise
the variable temperature NMR spectra of the phosphines or
phosphine oxides.
In contrast to compounds 11b and 12b, the single room
temperature 19F resonance of the selenide 12d is resolved into
four unequal resonances at low temperatures, consistent with
population of the four possible conformers exo3 and exo2a–c
.
Satisfactory simulation of the spectrum (Fig. 6) can be accom-
plished only by assigning the least abundant resonance C to
exo3 and assuming that this represents a unique pivot for
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strongly negative rather than neutral entropy of activation (Fig.
7). The results imply a different mechanism for the higher
energy ring exchange process in 12d. Indeed, preliminary
molecular mechanics calculations show that, whereas for the
phosphine 12a and phosphine oxide 12b relative magnitudes
of the barriers are in the order 2-ring < 3-ring Ӷ 1-ring, for the
sulfide or selenide the ordering changes to 2-ring < 1-ring < 3-
ring, and that C ←→ CЈ exchange via a 1-ring flip mechanism
provides the pathway of lowest energy for helix inversion (and
thus exchange of chemically equivalent aryl rings).
Conclusion
The electronic effect of CF3 substitution on complexation
properties of triarylphosphines is cumulative and essentially
independent of position; sterically, 2-CF3 substitution dramatic-
ally reduces complexing ability towards transition metal frag-
ments. Rotational mobility about phosphorus–aryl bonds in
XP(aryl)3 compounds is substantially reduced in the 2-substi-
tuted derivatives. While exo2/exo3 exchange invariably occurs by
a 2-ring flip mechanism, the mechanism for helix inversion
changes from 3-ring flip for small substituents (X = lp or O) to
1-ring flip for larger substituents (X = Se).
Experimental
CAUTION: explosions have been reported in the preparation of
Grignard and lithium reagents from fluoro- and trifluoro-
methyl-arenes, probably associated with elimination of LiF
from solid reagents formed by solvent evaporation.25,26 Reac-
tions using [Fe2(CO)9] generate toxic, volatile Fe(CO)5 as a
by-product. Care should be taken to trap this material when
evaporating solutions.
The NMR spectra were recorded using either JEOL GSX270
(1H, 270; 13C, 68; 31P, 109 MHz) or Bruker DPX300 (1H, 300;
13C, 75; 31P, 121; 19F, 282 MHz) spectrometers. Temperatures
were measured using the built in copper–constantan thermo-
couple previously calibrated with a platinum resistance therm-
ometer. Chemical shifts were measured relative to SiMe4 (1H,
13C), 85% H3PO4 (31P) and CFCl3 (19F); numbers in parentheses
after 13C chemical shifts represent J(P–C) values. Infrared spec-
tra were recorded on Perkin-Elmer 257 or Paragon 1000 spec-
trometers and calibrated with polystyrene. Line shape analyses
of NMR spectra were performed by computer simulation. For
the case of two exchanging nuclei, an in-house program based
on the equation of Sutherland27 was used. For greater numbers
of nuclei a program written by R. E. D. McClung, Department
of Chemistry, University of Alberta, Canada was adapted for
use.
Diethyl ether and tetrahydrofuran were distilled from
LiAlH4. Reactions involving lithium and magnesium reagents
were conducted under argon. Excepting the preparation of
phosphine oxides, other reactions were conducted under nitro-
gen. The phosphines (2-, (3- and (4-CF3C6H4)3P28 and [3,5-
(CF3)2C6H3]3P29 were prepared as described. The [Fe(CO)4L]
complexes of (4-FC6H5)3P,30 (2-CH3C6H4)3P,10 PPh3 and
Scheme 1
exchange between exo2 conformers. The implication, confirmed
by preliminary molecular mechanics calculations on the phos-
phines, is that direct interconversion between exo2 isomers via
1-ring flip processes does not contribute to the exchange process
in this temperature range. Barriers for the three independent
2-ring flip processes differ only slightly and the increase in
barriers for the 2-ring flip process between 12b and 12d is
comparable to that observed between OP(2-CH3C6H4)3 and
SeP(2-CH3C6H4)3 (∆∆G‡ ≈ 9 kcal molϪ1).5
The barrier for the higher temperature ring averaging process
in compound 12d may be determined from line shape analysis
of the CH3 (1H) subspectra, which in appearance are similar to
those of Fig. 5. Though, as expected, it is higher than the
barrier for 2-ring flip, it is surprisingly lower than the measured
3-ring flip barrier for oxides 11b and 12b and characterised by a
31
P(OPh)3 have previously been reported. Syntheses of 532 and
6
33 were adapted from literature procedures.
Syntheses
(a) (2-CH3C6H4)PCl2 5. A solution of the Grignard reagent
2-CH3C6H4MgBr was prepared by addition of o-bromotoluene
(47.1 g, 280 mmol) in diethyl ether (200 ml) to magnesium turn-
ings (6.81 g, 280 mmol) using 1,2-dibromoethane as initiator.
After refluxing for 1 h the solution was cooled to Ϫ60 ЊC and
(Et2N)2PCl (48.8 g, 232 mmol, δP (CDCl3) 160.6)34 in diethyl
ether (70 ml) added with stirring. After warming to room tem-
perature and stirring for a further hour, the solvent was evapor-
ated and the crude (Et2N)2P(2-CH3C6H4) (δP (CDCl3) 92.3)
was redissolved in diethyl ether (150 ml). With stirring, HCl gas
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Table 3 Molecular mechanics energies and geometries of 7a, 11a, 12a and 13a
Compound
Conformer
Energy/kcal
d(P–C)/Å
C–P–C/Њ
X–P–Cipso–Cα/Њ
P(2-CH3C6H4)2
exo3
exo2
exo3
exo2a
exo2b
exo2c
exo3
exo2a
exo2b
exo2c
exo3
exo2
0
2.3
0
1.841
1.842
1.841
1.842
1.842
1.841
1.840
1.841
1.841
1.842
1.840
1.841
102.5
103.4
102.6
104.0
103.5
103.5
102.7
103.7
104.1
104.1
102.9
104.3
43
20 (endo), 48, 55
42
21 (endo), 48, 56
21 (endo), 48, 53
26 (endo), 38, 57
41
26 (endo), 40, 53
24 (endo), 44, 56
21 (endo), 50, 53
38
P(2-CH3C6H4)2(2-CF3C6H4)
4.3
2.7
2.7
0
3.1
4.9
4.3
0
P(2-CH3C6H4)(2-CF3C6H4)2
P(2-CF3C6H4)3
4.7
25 (endo), 45, 53
Table 4 Molecular mechanics transition state energies for ring flip processes in 7a, 11a, 12a and 13a
Compound
Flip mechanism
Interconversion
Intermediate type
Energy/kcal
P(2-CH3C6H4)3
2-ring
3-ring
3-ring
1-ring
1-ring
2-ring
2-ring
2-ring
3-ring
3-ring
3-ring
1-ring
1-ring
1-ring
1-ring
2-ring
2-ring
2-ring
3-ring
3-ring
3-ring
1-ring
1-ring
1-ring
1-ring
2-ring
3-ring
3-ring
1-ring
1-ring
A ←→ BЈ
A ←→ AЈ
B ←→ BЈ
B ←→ BЈ
B ←→ BЈ
A ←→ BЈ
A ←→ CЈ
A ←→ DЈ
A ←→ AЈ
B ←→ BЈ
C/D ←→ DЈ/CЈ
B ←→ CЈ
C ←→ CЈ
D ←→ DЈ
B ←→ DЈ
A ←→ BЈ
A ←→ CЈ
A ←→ DЈ
A ←→ AЈ
B ←→ BЈ
C/D ←→ CЈ/DЈ
B ←→ CЈ
C ←→ CЈ
D ←→ DЈ
B ←→ DЈ
A ←→ BЈ
A ←→ AЈ
B ←→ BЈ
B ←→ BЈ
B ←→ BЈ
III
IV
V
3.0
8.1
19.3
12.1
29.6
4.2
3.5
3.5
8.8
25.1
19.6
35.4
13.0
30.4
13.7
4.9
I
II
III
III
III
IV
V
V
II
I
II
I
III
III
III
IV
V
V
II
I
II
I
III
IV
V
I
II
P(2-CH3C6H4)2(2-CF3C6H4)
P(2-CH3C6H4)(2-CF3C6H4)2
P(2-CF3C6H4)3
4.7
5.0
10.6
20.7
25.1
35.4
16.4
39.0
14.5
6.1
13.4
25.4
16.9
38.2
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Fig. 3 Representative experimental and simulated variable temperature NMR spectra: (a) 19F of compound 11a; (b) 1H of 12a.
was bubbled through the solution for 3 h. After filtration of the
copious precipitate of [Et2NH2]Cl and removal of solvent, the
residue was distilled (60–76 ЊC, 0.5 mmHg) to provide com-
pound 5 as a clear liquid (26.5 g, 64%). δP (CDCl3) 163.9.
δH (CDCl3) 7.20 (1 H, t, Ph), 7.3–7.5 (2 H, m, Ph), 8.01 (1 H,
t, Ph) and 2.62 [3 H, d, J(PH) 3.4 Hz, Me]. δC (CDCl3) 126.9
(2), 130.2 (11), 130.7 (3), 132.5, 137.7 (57), 140.5 (35), 19.8
(26 Hz).
vacuum, toluene (100 ml) was added and the solution filtered.
After removal of solvent, the residue was distilled (120–130 ЊC,
0.01 mmHg) to yield compound 6 as a colourless liquid which
solidified to a white solid (8.1 g, 54%). δP (CDCl3) 74.3.
δH (CDCl3) 7.1–7.5 (4 H, m, Ph) and 2.45 [3 H, d, J(PH) 2.4 Hz,
Me]. δC (CDCl3) 126.4, 130.3 (4), 130.4, 131.5 (4), 135.6 (35),
141.5 (31), 20.6 (24 Hz).
(c) (2-CH3C6H4)(2-CF3C6H4)2P 11a. Butyllithium (23.1 ml of
a 1.6 M solution in hexane, 64.6 mmol) was added dropwise
over 30 min to a stirred solution of o-BrC6H4CF3 (3.6 g, 60.4
mmol) in diethyl ether (25 ml) at Ϫ10 ЊC. After stirring for 30
min, (2-CH3C6H4)2PCl2 (5.0 g, 25.9 mmol) dissolved in diethyl
ether (15 ml) was added slowly over 1 h. After warming to room
temperature and stirring for 6 h the reaction was hydrolysed
with degassed saturated NH4Cl solution (5 ml). The organic
layer was separated, washed with water and dried over MgSO4.
Removal of solvent followed by recrystallisation from ethanol
gave compound 11a as white crystals (4.1 g, 38%); 12a was
prepared similarly using (2-CH3C6H4)2PCl.
(b) (2-CH3C6H4)2PCl 6. A solution of the Grignard reagent
2-CH3C6H4MgCl was prepared by the slow addition of o-chloro-
toluene (17.8 g, 140 mmol) in tetrahydrofuran (15 ml) to
magnesium turnings (3.6 g, 150 mmol) suspended in tetra-
hydrofuran (10 ml). After initiation, the reaction was controlled
by further addition of tetrahydrofuran (20–30 ml). [The use of
1,2-dibromoethane as initiator results in contamination of the
product with (2-CH3C6H4)2PBr.] After refluxing for 6 h the
solution was cooled, transferred under argon to a pressure
equalised dropping funnel and added to a solution of PCl3 (8.2
g, 60 mmol) in tetrahydrofuran (12 ml) cooled to Ϫ78 ЊC. After
warming to room temperature the reaction was stirred over-
night and then refluxed for 1 h. After removal of solvent under
Spectroscopic data for phosphines are given below, together
with analytical data for new compounds. The 13C NMR
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Fig. 5 Representative experimental and simulated NMR spectra:
(a) 19F of 11b, (b) 1H of 12b.
Fig. 4 Representative experimental and simulated 31P NMR spectra:
(a) compound 11b at 164 K, (b) 12b at 163 K and (c) 7b.
spectra of 13a, 13b were assigned unambiguously by COSY
and HeteroCOSY techniques; assignments of 2-CH3C6H4
resonances for the mixed derivatives are based on this. Assign-
ments for fluoro and trifluoromethyl rings are based on 13C –19F
coupling constants and published substituent effects for PPh2,
CF3 and F.35
Compound 7a: mp 172–174 ЊC; δH (CDCl3) 6.89 (1 H, m),
7.35–7.55 (2 H, m) and 7.75 (1 H, m); δP (CDCl3) Ϫ17.6 [decet,
J(PF) 55 Hz]; δF (CDCl3) Ϫ57.9 (d); δC (CDCl3) 134.8 (31) [dq,
J(CF) 2, C1], 134.3 (27) [m, J(CF) 31, C2], 127.0 (6) [m, J(CF)
6, C3], 129.3 (s, C4), 131.6 (s, C5), 136.0 (s, C6) and 124.1 [q,
J(CF) 275 Hz, CF3].
Fig. 6 Representative experimental and simulated variable temper-
ature 19F NMR spectra of compound 12b.
Compound 8a: oil; δH (CDCl3) 7.39 (1 H, t), 7.48 (1 H, t),
7.56 (1 H, d) and 7.63 (1 H, d); δP (CDCl3) Ϫ4.30; δF (CDCl3)
Ϫ63.3; δC (CDCl3) 137.0 (14) (d, C1), 130.3 (25) [dq, J(CF) 4,
C2], 131.3 (8) [qd, J(CF) 33, C3], 126.2 [q, J(CF) 4, C4], 129.4
(5) (d, C5), 136.7 (16) [dq, J(CF) 2, C6] and 123.8 [q, J(CF)
273 Hz, CF3].
Compound 9a: mp 72–74 ЊC; δH (CDCl3) 7.39 (2H, t) and
7.60 (2H, d); δP (CDCl3) Ϫ5.30; δF (CDCl3) Ϫ63.4; δC (CDCl3)
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(3) (d, C4), 131.0 (13) (d, C5), 135.1 (11) (d, C6) and 123.4 (3)
[qd, J(CF) 275 Hz, CF3].
Compound 11b: mp 192–195 ЊC (Found: C, 59.0; H, 3.37.
C21H15F6OP requires C, 58.9; H, 3.53%); δH (CDCl3) 6.79 (1 H,
dd), 7.10–7.65 (7 H, m), 7.73 (2 H, t) and 7.93 (2 H, dd);
δP (CDCl3) 35.8; δF (CDCl3) Ϫ57.1 and Ϫ57.3 (br); δC (CDCl3)
(2-CH3C6H4) 130.6 (110) (d, C1), 143.7 (8) (d, C2), 133.3 (13)
(d, C3), 132.2 (s, C4), 125.1 (14) (d, C5), 132.1 (10) (d, C6) and
22.0 (4) (d, CH3); (2-CF3C6H4) 128.3 (8) [m, J(CF) 6, C3], 131.9
(3) (d, C4), 131.1 (br, C5), 134.9 (10) (d, C6) and 123.4 (3) [qd,
J(CF) 277 Hz, CF3] (C1 and C2 are not seen and presumably
broadened in the baseline).
Compound 12b: mp 186–188 ЊC (Found: C, 67.6; H, 4.91.
C21H18F3OP requires C, 67.4; H, 4.85%); δH (CDCl3) 6.89
(2 H, dd), 7.13 (2 H, t), 7.3–7.6 (6 H, m), 7.70 (1 H, t) and 7.93
(1 H, dd); δP (CDCl3) 37.9; δF (CDCl3) Ϫ57.1; δC (CDCl3)
(2-CH3C6H4) 130.7 (106) (d, C1), 143.6 (8) (d, C2), 132.9 (13)
(d, C3), 132.0 (s, C4), 125.2 (13) (d, C5), 132.0 (13) (d, C6) and
21.9 (5) (d, CH3); (2-CF3C6H4) 131.9 (92) (d, C1), 133.8 (5) [qd,
J(CF) 33, C2], 128.0 (8) [m, J(CF) 6, C3], 131.8 (3) (d, C4),
131.3 (12) (d, C5), 135.0 (11) (d, C6) and 123.4 (3) [qd, J(CF)
276 Hz, CF3].
Compound 13b: δH (CDCl3) 7.10 [H6, J(PH) 14.3], 7.15 [H5,
J(PH) 2.5], 7.42 [H4, J(PH) 1.6], 7.31 [H2, J(PH) 4.0 Hz] and
2.44 (CH3); δP (CDCl3) 37.5; δC (CDCl3) 130.5 (102) (d, C1),
143.5 (8) (d, C2), 132.0 (11) (d, C3), 131.4 (3) (d, C4), 125.5 (13)
(d, C5), 132.9 (13) (d, C6) and 22.0 (5) (d, CH3).
Fig. 7 Plots of ∆G‡ against temperature for compound 12d: ᭡
complete aryl exchange process, ᭺ (C → A) interconversion, ᭹
(C → B) interconversion and ᭝ (C → D) interconversion.
140.2 (14) (d, C1), 134.0 (20) (d, C2), 125.7 (8) [m, J(CF) 3,
C3], 131.6 [q, J(CF) 33, C4] and 123.8 [q, J(CF) 272 Hz,
CF3].
Compound 10a: mp 98–100 ЊC; δH (CDCl3) 7.71 (2 H, d) and
8.50 (1 H, s); δP (CDCl3) Ϫ3.40; δF (CDCl3) Ϫ63.6; δC (CDCl3)
137.3 (18) (d, C1), 133.2 (21) (br d, C2), 132.8 (7) [qd, J(CF) 34,
C3], 124.3 (m, C4) and 122.7 [q, J(CF) 273 Hz, CF3].
Compound 11a: mp 132–134 ЊC (Found: C, 62.0; H, 3.65.
C21H15F6P requires C, 61.2; H, 3.67%); δH (CDCl3) 6.56 (1 H,
dd), 6.99 (2 H, dd), 7.05 (1 H, t), 7.15–7.50 (6 H, m), 7.75 (2 H,
m) and 2.25 [3 H, d, J(PH) 1.1 Hz, CH3]; δP (CDCl3) Ϫ21.3
[sept, J(PF) 54 Hz]; δF (CDCl3) Ϫ58.0 (d); δC (CDCl3)
(2-CH3C6H4) 134.5 (13) (d, C1), 142.0 (28) (d, C2), 130.3 (5) (d,
C3), 129.0 (s, C4), 126.2 (s, C5), 133.2 (s, C6) and 21.0 (23) (d,
CH3); (2-CF3C6H4) 135.1 (30) (d, C1), 134.6 (27) [m, J(CF) 31,
C2], 126.7 (6) [m, J(CF) 6, C3], 129.1 (s, C4), 131.6 (s, C5),
136.0 (s, C6) and 124.2 [q, J(CF) 275 Hz, CF3].
Compound 12a: mp 95–96 ЊC (Found: C, 70.2; H, 4.99.
C21H18F3P requires C, 70.4; H, 5.07%); δH (CDCl3) 6.63 (2 H,
dd), 7.06 (1 H, t), 7.15–7.30 (5 H, m), 7.40 (1 H, m), 7.76 (1 H,
dd) and 2.32 [6 H, d, J(PH) 0.9 Hz, Me]; δP (CDCl3) Ϫ24.5 [q,
J(PF) 53 Hz]; δF (CDCl3) Ϫ58.1 (d); δC (CDCl3) (2-CH3C6H4)
134.5 (12) (d, C1), 142.3 (27) (d, C2), 130.2 (5) (d, C3), 128.8
(s, C4), 126.1 (s, C5), 133.0 (s, C6) and 21.1 (22) (d, CH3);
(2-CF3C6H4) 135.6 (28) (d, C1), 135.1 (26) [m, J(CF) 30, C2],
126.4 (6) [m, J(CF) 6, C3], 128.9 (s, C4), 131.7 (s, C5), 136.4 (2)
(d, C6) and 124.3 [q, J(CF) 275 Hz, CF3].
Compound 13a: δH (CDCl3) 6.73 [H6, J(PH) 4.3], 7.05 [H5,
J(PH) 1.5], 7.24 [H4, J(PH) 1.5], 7.21 [H3, J(PH) 1.5] and 2.39
[J(PH) 1.2 Hz, Me]; δP (CDCl3) Ϫ29.1; δC (CDCl3) 134.3 (10)
(d, C1), 142.8 (26) (d, C2), 130.2 (5) (d, C3), 128.9 (s, C4), 126.3
(s, C5), 133.2 (s, C6) and 21.3 (22) (d, CH3).
Compound 14a: δH (CDCl3) 7.03 (2 H, t) and 7.18–7.28 (2 H,
m); δP (CDCl3) Ϫ8.8; δF (CDCl3) Ϫ112.4; δC (CDCl3) 132.4 (6)
[dd, J(CF) 3, C1], 135.3 (21) [dd, J(CF) 8, C2], 115.9 (8) [dd,
J(CF) 21, C3] and 163.4 [d, J(CF) 250 Hz, C4].
(e) (2-CH3C6H4)2(2-CF3C6H4)PSe 12d. A solution of (2-
CH3C6H4)(2-CF3C6H4)2P (0.3 g, 0.85 mmol) in CHCl3 (10 ml)
was refluxed with selenium powder (0.2 g, 2.56 mmol) for 3 d,
after which time 31P NMR analysis indicated an unchanging
12a:12d ratio of 2:3. The suspension was filtered through
Celite and the solvent removed. Purification by preparative
TLC (1:9 ethyl acetate–light petroleum (bp 40–60 ЊC)) followed
by recrystallisation from ethanol–light petroleum (bp 60–80 ЊC)
gave off-white crystals of compound 12d containing a 4%
impurity of 12a. Other selenides were prepared similarly. Spec-
troscopic data are given below, together with analytical data for
new compounds.
Compound 9b: mp 196–198 ЊC (decomp.) (Found: C, 46.7; H,
2.19. C21H12F9PSe requires C, 46.3; H, 2.22%); δH (CDCl3) 7.6–
7.9 (m); δP (CDCl3) 34.9 [J(77SeP) 765 Hz]; δF (CDCl3) Ϫ63.7;
δC (CDCl3) 134.9 (92) (d, C1), 133.0 (12) (d, C2), 125.8 (14) [dq,
J(CF) 4, C3], 134.0 (3) [qd, J(CF) 34, C4] and 123.3 [q, J(CF)
273 Hz, CF3].
Compound 10b: mp 147–149 ЊC (decomp.) (Found: C, 38.1;
H, 1.08. C24H9F18PSe requires C, 38.5; H, 1.21%); δH (CDCl3)
8.10 (2 H, s) and 8.15 (1 H, s); δP (CDCl3) 33.9 [J(77SeP) 802
Hz]; δF (CDCl3) Ϫ63.5; δC (CDCl3) 133.5 (80) (d, C1), 132.2 (13)
(br d, C2), 132.6 (13) [qd, J(CF) 31, C3], 120.3 (m, C4) and
122.3 [q, J(CF) 274 Hz, CF3].
Compound 12d: mp 150–165 ЊC (decomp.) (Found: C, 56.7;
H, 4.01. C21H18F3PSe requires C, 57.7; H, 4.15%); δH (CD2Cl2)
6.90–7.75 (10 H, m), 8.96 (2 H, dd) and 2.38 (s, CH3);
δP (CD2Cl2) 37.2 [J(77SeP) 727 Hz]; δF (CD2Cl2) Ϫ53.4;
δC (CDCl3) (2-CH3C6H4) 128.4 (78) (d, C1), 142.9 (11) (d, C2),
133.1 (12) (d, C3), 131.7 (3) (d, C4), 125.2 (13) (d, C5), 132.8
(12) (d, C6) and 23.0 (5) (d, CH3); (2-CF3C6H4) 128.3 (60) [dq,
J(CF) 2, C1], 134.2 (13) [qd, J(CF) 43, C2], 128.2 (6) [m, J(CF)
6, C3], 132.0 (3) (d, C4), 132.1 (13) (d, C5), 139.7 (14) (d, C6)
and 123.0 (2) [qd, J(CF) 275 Hz, CF3].
(d) (2-CH3C6H4)(2-CF3C6H4)2PO 11b.
A solution of
m-chloroperbenzoic acid (0.16 g, 0.92 mmol) in toluene (15 ml)
was added dropwise to a stirred solution of (2-CH3C6H4)-
(2-CF3C6H4)2P (0.3 g, 0.73 mmol) in toluene (10 ml). After
monitoring to completion by TLC (12 h), the solution was
washed with 10% Na2CO3 solution (30 ml) and dried over
MgSO4. After removal of solvent, recrystallisation from
ethanol–light petroleum (bp 60–80 ЊC) gave compound 11b as
white crystals (0.25 g, 80%). Spectroscopic data on 11b and
other oxides, together with analytical data for new compounds,
are given below.
(f) [Fe(CO)4{P(3-CF3C6H4)3}] 8c. To a solution of (3-CF3-
C6H4)3P (0.4 g, 0.86 mmol) in diethyl ether (25 ml) was added
[Fe2(CO)9] (0.63 g, 1.72 mmol). After stirring for 6 h the
solution was filtered through Celite and the solvent removed
under vacuum. After purification by column chromatography
[Grade IV alumina, light petroleum (bp 40–60 ЊC)], recrystal-
lisation from light petroleum (bp 60–80 ЊC) gave compound 8c
Compound 7b: mp 252–255 ЊC; δH (CDCl3) 7.28 (1 H, dd),
7.50 (1 H, t), 7.66 (1 H, t) and 7.90 (1 H, dd); δP (CDCl3) 35.5;
δF (CDCl3) Ϫ57.0; δC (CDCl3) 131.7 (102) [dq, J(CF) 2, C1],
133.6 (5) [qd, J(CF) 33, C2], 128.3 (9) [m, J(CF) 6, C3], 132.3
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as yellow crystals (0.35 g, 64%). Other Fe(CO)4 complexes were
prepared similarly. Spectroscopic data are given below, together
with analytical data for new compounds.
structure of the [Fe(CO)4L] complex was not available. Van der
Waals radii of 2.10 and 2.46 Å were used for CH3 and CF3
respectively.40
Compound 8c: mp 79–80 ЊC (Found: C, 47.6; H, 1.84.
C25H12F9FeO4P requires C, 47.3; H, 1.91%); νmax/cmϪ1 (CO)
2051, 1983 and 1947 (hexane); δH (CDCl3) 7.6–7.9 (4 H, m);
δP (CDCl3) 79.9; δF (CDCl3) Ϫ63.5; δC (CD2Cl2) 134.5 (48) (d,
C1), 129.9 (9) [dq, J(CF) 4, C2], 131.8 (12) [qd, J(CF) 33, C3],
128.8 (6) [m, J(CF) 6, C4], 130.3 (10) (d, C5), 136.8 (10) [dq,
J(CF) 1.5, C6], 123.9 [q, J(CF) 273 Hz, CF3] and 212.7 (19) (d,
CO).
CCDC reference number 186/1546.
Molecular mechanics studies
Molecular mechanics calculations were performed using
HYPERCHEM with a parameter set designed specifically for
triarylphosphines. Full details will be published elsewhere.
Compound 9c: mp 159–161 ЊC (Found: C, 47.2; H, 1.83.
C25H12F9FeO4P requires C, 47.3; H, 1.91%); νmax/cmϪ1 (CO)
2051, 1985 and 1949 (hexane); δH (CDCl3) 7.65 (2 H, t) and 7.77
(2H, d); δP (CDCl3) 78.8; δF (CDCl3) Ϫ62.1; δC (CD2Cl2) 137.5
(46) (d, C1), 134.0 (11) (d, C2), 126.3 (11) [m, J(CF) 5, C3],
133.6 (2) [qd, J(CF) 34, C4], 123.5 [q, J(CF) 273 Hz, CF3] and
212.8 (19) (d, CO).
References
1 I. T. Horvath, G. Kiss, R. A. Cook, J. E. Bond, P. A. Stevens and
J. Rabai, J. Am. Chem. Soc., 1998, 120, 3133; M. A. Guillevec, A. M.
Arif, I. T. Horvath and J. A. Gladysz, Angew. Chem., Int. Ed. Engl.,
1997, 36, 1612.
2 S. Kainz, D. Koch, W. Baumann and W. Leitner, Angew. Chem., Int.
Ed. Engl., 1997, 36, 1628.
3 For leading references, see (a) T. V. RajanBabu, T. A. Ayers, G. A.
Halliday, K. K. You and J. C. Calabrese, J. Org. Chem., 1997, 62,
6012; K. Nozaki, N. Sakai, T. Nanno, T. Higashijima, S. Mano,
T. Horiuchi and H. Takaya, J. Am. Chem. Soc., 1997, 119, 4413;
(c) K. Nozaki, W. Li, T. Hariuchi, H. Takaya, T. Saito, A. Yoshida,
K. Matsumura, Y. Kato, T. Imai, T. Miura and H. Kumobayashi,
J. Org. Chem., 1996, 61, 7658.
4 For a preliminary communication, see J. A. S. Howell, J. D. Lovatt,
P. McArdle, D. Cunningham, E. Maimone, H. E. Gottlieb and
Z. Goldschmidt, Inorg. Chem. Commun., 1998, 1, 118.
5 J. A. S. Howell, M. G. Palin, P. C. Yates, P. McArdle, D.
Cunningham, Z. Goldschmidt, H. E. Gottlieb and D. Hezroni-
Langerman, J. Chem. Soc., Perkin Trans. 2, 1992, 1769.
6 J. A. S. Howell, D. T. Dixon and P. M. Burkinshaw, J. Chem. Soc.,
Dalton Trans., 1980, 999.
7 T. S. Cameron and B. Dahlen, J. Chem. Soc., Perkin Trans. 2, 1975,
1737.
8 D. W. Allen, L. A. March and I. W. Nowell, J. Chem. Soc., Dalton
Trans., 1984, 483.
9 T. S. Cameron, K. D. Howlett and K. Miller, Acta Crystallogr.,
Sect. B, 1978, 34, 1639.
10 J. A. S. Howell, M. G. Palin, P. C. Yates, P. McArdle, D.
Cunningham, Z. Goldschmidt, H. E. Gottlieb and D. Hezroni-
Langerman, Inorg. Chem., 1993, 32, 3493.
Compound 10c: mp 118–120 ЊC (Found: C, 40.1; H, 1.03.
C28H9F18FeO4P requires C, 40.1; H, 1.08%); νmax/cmϪ1 (CO)
2063, 1995 and 1955 (hexane); δH (CDCl3) 7.92 (2 H, d) and
8.11 (1 H, s); δP (CDCl3) 84.9; δF (CDCl3) Ϫ63.8; δC (CD2Cl2)
134.7 (46) (d, C1), 132.5 (12) (br d, C2), 132.9 (11) [qd, J(CF)
34, C3], 126.3 (m, C4), 122.3 [q, J(CF) 274 Hz, CF3] and 210.7
(18) (d, CO).
Compound 13e: νmax/cmϪ1 (CO) 2047, 1971 and 1943 (hex-
ane); δH (CDCl3) 7.05 (1 H, t), 7.16 (1 H, t), 7.35–7.50 (2 H, m);
δP (CD2Cl2) 53.0; δC (CD2Cl2) 129.8 (43) (d, C1), 143.2 (11) (d,
C2), 132.0 (s, C3, C6), 131.1 (s, C4), 125.9 (9) (d, C5), 23.9 (s,
CH3) and 214.6 (18) (d, CO).
Compound 14c: mp 167–170 ЊC; νmax/cmϪ1 (CO) 2047, 1979
and 1947 (hexane); δH (CDCl3) 7.11 (2 H, m) and 7.46 (2 H, m);
δP (CDCl3) 71.9; δF (CDCl3) Ϫ108.3; δC (CD2Cl2) 129.9 (52) [dd,
J(CF) 3, C1], 135.8 (12) [dd, J(CF) 9, C2], 116.5 (8) [dd, J(CF)
21, C3], 164.8 [d, J(CF) 256 Hz, C4] and 213.5 (19) (d, CO).
Compound 15: mp 202–204 ЊC; νmax/cmϪ1 (CO) 2043, 1971
and 1937 (hexane); δH (CDCl3) 7.38–7.50 (5 H, m); δP (CDCl3)
71.9; δC (CD2Cl2) 133.9 (50) (d, C1), 133.1 (11) (d, C2), 128.6 (6)
(d, C3), 130.9 (3) (d, C4) and 213.6 (19) (d, CO).
11 P. E. Riley and R. E. Davis, Inorg. Chem., 1980, 19, 159.
12 (a) R. Glaser, Y. H. Yoo, G. S. Chen and C. L. Barnes,
Organometallics, 1994, 13, 2578; (b) H. P. Lane, S. M. Godfrey,
C. A. McAuliffe and R. G. Pritchard, J. Chem. Soc., Dalton Trans.,
1994, 3249; (c) R. Glaser, P. E. Haney and C. L. Barnes, Inorg.
Chem., 1996, 35, 1758; (d) F. Dahan, S. Sabo and B. Chaudret, Acta
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Compound 16: mp 69–70 ЊC; νmax/cmϪ1 (CO) 2063, 1993
and 1953 (hexane); δH (CDCl3) 7.1–7.5 (m); δP (CDCl3) 175.7;
δC (CD2Cl2) 150.4 (8) (d, C1), 121.3 (4) (d, C2), 129.7 (2) (d,
C3), 125.6 (2) (d, C4) and 211.4 (22) (d, CO).
In situ infrared studies of complexation
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To a solution of [Fe(CO) (PhCH᎐CH )]36 in toluene (15.8 mg
᎐
4
2
in 25 ml, 2 × 10Ϫ3 M) under argon was added sufficient ligand
to produce a concentration of 6 × 10Ϫ3 M. The solution was
heated at 60 ЊC and aliquots removed periodically for analysis
by FTIR. The extent of reaction was measured using the
relative intensities of the a1 vibration of [Fe(CO)4L] and
16 P. G. Jones, C. Kienitz and C. Thone, Z. Kristallogr., 1994, 209,
80.
[Fe(CO) (PhCH᎐CH )] (2083 cmϪ1).
᎐
4
2
17 R. F. de Ketelaere and G. P. van der Kelen, J. Mol. Struct., 1995, 27,
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Crystallographic studies
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Crystallographic data are summarised in Table 6. Structures
were solved by direct methods37 and refined by full matrix least
squares;38a,b SHELX operations were rendered paperless using
ORTEX.39 Data were corrected for Lorentz-polarisation effects,
but not for absorption. For compound 10c two of the unit cell
angles are close to 90Њ, though the system is not monoclinic and
all attempts to solve the structure in possible monoclinic space
groups failed. For 11a the CF3 groups are disordered with the
CH3 group and were refined using C(7) 50% CF3, C(14) 75%
CF3 and C(21) 75% CF3. For 10b, 10c thermal parameters
for the fluorine atoms were large, though attempts to use a
disordered model for the CF3 groups were not successful.
Cone angles in Table 2 were calculated from crystal structures
after adjustment of the P–Fe distance to 2.28 Å or addition of
an Fe atom to the free phosphine in cases where the crystal
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20 K. R. Dunbar and S. C. Haefner, Polyhedron, 1994, 13, 727;
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50, 1276.
21 See, for examples, K. R. Dunbar, J. S. Sun, S. C. Haefner and
J. H. Matonic, Organometallics, 1994, 13, 2713; K. R. Dunbar and
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1995, 240, 527; K. R. Dunbar, S. C. Haefner and C. Bender,
J. Am. Chem. Soc., 1991, 113, 9540; L. J. Baker, R. C. Bott,
G. A. Bowmaker, P. C. Healy, B. W. Skelton, P. Schwerdtfeger and
A. H. White, J. Chem. Soc., Dalton Trans., 1995, 1341; L. J. Baker,
G. A. Bowmaker, R. D. Hart, P. J. Harvey, P. C. Healy and A. H.
White, Inorg. Chem., 1994, 33, 3925; R. B. Bedford, P. A. Chaloner
and P. B. Hitchcock, Acta Crystallogr., Sect. C, 1994, 50, 356; 1993,
49, 1461.
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