Synthesis and coordination chemistry of meta-perfluoroalkyl-derivatised triarylphosphines

Article abstract of DOI:10.1016/S0277-5387(99)00202-8

The synthesis and coordination chemistry of the PPh_x(C₆H₄-3-C₆F₁₃) _3-x (x=0, 1, 2) ligands containing perfluoroalkyl ponytails have been investigated. A comparison of the spectroscopic data for coordination complexes containing these ligands with those for complexes containing PPh₃ or the related para-derivatised triarylphosphines indicates that these meta-derivatised ligands are slightly poorer σ-donors and that steric crowding in the [PtCl₂L₂] complexes results in the formation of the normally thermodynamically less-favourable trans-isomers. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00202-8

Polyhedron 18 (1999) 2913–2917
www.elsevier.nl/locate/poly
Synthesis and coordination chemistry of meta-perfluoroalkyl-derivatised
triarylphosphines
*
Eric G. Hope , Ray D.W. Kemmitt, Danny R. Paige, Alison M. Stuart, Dan R.W. Wood
Department of Chemistry, University of Leicester, Leicester, LE1 7RH UK
Received 17 May 1999; accepted 7 July 1999
Abstract
The synthesis and coordination chemistry of the PPhx(C6H4-3-C6F13
)
(x50, 1, 2) ligands containing perfluoroalkyl ponytails have
32x
been investigated. A comparison of the spectroscopic data for coordination complexes containing these ligands with those for complexes
containing PPh3 or the related para-derivatised triarylphosphines indicates that these meta-derivatised ligands are slightly poorer s-donors
and that steric crowding in the [PtCl2L2] complexes results in the formation of the normally thermodynamically less-favourable
trans-isomers.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Fluorous biphase; Phosphine; Platinum group metals
1. Introduction
out on a Bruker ARX250 spectrometer at 250.13, 235.34
and 101.26 MHz or on a Bruker DRX 400 spectrometer at
400.13, 376.50 and 161.98 MHz. All chemical shifts are
quoted in ppm using the high-frequency positive conven-
Following the introduction of the fluorous biphase
approach to the heterogenisation of homogeneous catalysis
[1,2], a range of ligand systems and metal complexes have
been derivatised with long perfluoroalkyl ‘ponytails’ and
their solubilities and reactivities under fluorous biphasic
conditions have been described [2–16]. Throughout this
work, phosphorus(III) ligands, in particular phosphines,
have been pre-eminent [2–12]. We have described a
general route to the synthesis of para-derivatised triaryl
phosphine ligands [8] and have recently established the
criteria for preferential perfluorocarbon solubility as well
as the electronic influence of the perfluoroalkyl sub-
stituents on the coordination chemistry of these ligands
[11]. Here, we extend this work to an analogous series of
meta-substituted ligands to establish the steric and elec-
tronic implications of introducing the perfluoroalkyl sub-
stituents in this position.
1
tion; H NMR spectra were referenced to external SiMe4,
19F NMR spectra to external CFCl3 and 31P NMR spectra
to external 85% H3PO4. Assignments of the 19F NMR
resonances were made using correlation experiments and
follow the order outlined previously [8]. The IR spectra
were recorded on a Digilab FTS40 Fourier-transform
spectrometer at 4 cm21 resolution for the complexes as
Nujol mulls held between KBr discs. Elemental analyses
were performed by Butterworth Laboratories Ltd. Mass
spectra were recorded on a Kratos Concept 1H mass
spectrometer.
The complexes, [Cp*RhCl2]2 and [RhCl(CO)2]2, were
commercial samples (Aldrich) and were used as supplied
whilst cis-[PtCl2(MeCN)2] was prepared as previously
described [17]. Dichloromethane, chloroform and
perfluoro-1,3-dimethylcyclohexane (PP3) were each dried
by refluxing over calcium hydride under dinitrogen, dis-
tilled under nitrogen and stored in closed ampoules over
molecular sieves. PP3 was also freezed/pumped/thawed
three times to remove all dissolved gases. Hexane was
dried by refluxing over potassium metal under nitrogen,
distilled and was stored similarly. Toluene and diethyl
ether were dried by refluxing over sodium metal under
nitrogen, distilled and stored similarly.
2. Experimental
Proton, 19F and 31P NMR spectroscopies were carried
*Corresponding author. Tel.: 144-116-252-2108; fax: 144-116-252-
3789.
E-mail address: egh1@le.ac.uk (E.G. Hope)
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00202-8
1999 Elsevier Science Ltd. All rights reserved.

2914
E.G. Hope et al. / Polyhedron 18 (1999) 2913–2917
2.1. 3-(Tridecafluorohexyl)bromobenzene 1
2.3. PPh(C6H4-3-C6F13 )2 3
A solution of C6F13I (18.78 g, 0.042 mol) in hexafluoro-
benzene (40 cm3) was added dropwise over 3 h to a stirred
mixture of 3-bromoiodobenzene (11.91 g, 0.042 mol),
copper powder (5.88 g, 0.092 mol), 2,29-bipyridine (0.46
g, 2.95 mmol), DMSO (40 cm3) and C6F6 (60 cm3) at
708C. The mixture was subsequently stirred at 708C for 72
h. After cooling, it was poured into a beaker containing
dichloromethane (100 cm3) and water (100 cm3). After
filtering, the organic layer was separated, washed with
water (3350 cm3) and dried over CaCl2 and MgSO4.
After concentration in vacuo to ca. 30 cm3, the crude
product was extracted into PP3 (3320 cm3) and the
solvent was removed in vacuo. Distillation in vacuo using
This was prepared similarly using phenyldichlorophos-
phine (1.16 g, 6.50 mmol) affording the product as a white
solid (3.4 g, 54%) (Found: C, 40.4; H, 1.5; P, 4.6;
C30H13F26P requires C, 40.1; H, 1.4; P, 3.5%); m/z (FAB)
898 ([M]1, 56%), 821 (6) and 503 (18); dP (CDCl3) 25.0
(s); dH (CDCl3) 7.2–7.6 (13H, m, C6H5 and C6H4); dF
(CDCl3) 281.2 (6F, t, 3JFF 10, CF3), 2111.2 (4F, t, 3JFF
14, CaF2), 2122.0 (4F, m, CbF2), 2122.2 (4F, m, CdF2),
2123.2 (4F, m, CeF2), 2126.7 (4F, m, CgF2).
2.4. P(C6H4-3-C6F13 )3 4
This was prepared similarly using phosphorus trichloride
(0.57 g, 4.20 mmol), affording the product as a white solid
(4.1 g, 71%) (Found: C, 35.4; H, 1.0; P, 4.4; C36H12F39P
requires C, 35.5; H, 1.0; P, 2.5%); m/z (FAB) 1216 ([M]1,
97%), 821 (51) 169 (21) and 69 (100); dP (CDCl3) 26.0
(s); dH (CDCl3) 7.2–7.8 (12H, m, C6H4); dF (CDCl3)
281.5 (9F, t, 3JFF 10, CF3), 2111.7 (6F, t, 3JFF 14, CaF2),
2122.0 (6F, m, CbF2), 2122.5 (6F, m, CdF2), 2123.4
(6F, m, CeF2), 2126.8 (6F, m, CgF2).
¨
a Kugelrohr apparatus gave the product as a colourless
liquid (bp 80–908C, 0.02 mmHg) (8.6 g, 0.018 mol, 45%)
(Found: C, 29.5; H, 0.8; C12H4BrF13 requires C, 30.3; H,
0.8%); m/z (EI) 474/6 ([M]1, 27%), 455/7 (6), 205/7
(100), 126 (37) and 69 (15): dH (CDCl3) 7.67 (1H, s,
2-C6H4), 7.65 (1H, d, 3JHH 7.9, 6-C6H4), 7.45 (1H, d, 3JHH
7.9, 4-C6H4), 7.31 (1H, t, 3JHH 7.9, 5-C6H4); dF (CDCl3)
281.3 (3F, t, 3JFF 10, CF3), 2111.2 (2F, t, 3JFF14, CaF2),
2122.0 (2F, m, CbF2), 2122.2 (2F, m, CdF2), 2123.2
(2F, m, CeF2), 2126.6 (2F, m, CgF2).
2.5. [RhCl2(h5-C5Me5 )hPPh2(C6H4-3-C6F13 )j] 5
The ligand (0.145 g, 0.25 mmol) and [RhCl2(h5-
C5Me5)]2 (0.77 g, 0.12 mmol) were stirred in refluxing
ethanol (60 cm3) under nitrogen for 1 h. The solvent was
removed in vacuo and the resulting reddish solid was
washed with hexane (10 cm3), yielding a fine, red/orange
powder (0.14 g, 0.16 mmol, 67%) (Found: C, 45.7; H, 3.1;
C34H29F13PCl2Rh requires C, 45.9; H, 3.3%); m/z (FAB)
853 ([M2Cl]1) and 818 ([M22Cl]1); dP (CDCl3) 30.6
2.2. PPh2(C6H4-3-C6F13 ) 2
n-Butyl-lithium (8.63 cm3, 1.6 M solution in hexane) in
diethyl ether (25 cm3) was added dropwise over 1 h to
BrC6H4-3-C6F13 (6.57 g, 0.014 mol) with stirring under
nitrogen in diethyl ether (75 cm3) at 2788C and the
reaction mixture was stirred at this temperature for a
further 1 h. Diphenylchlorophosphine (3.04 g, 0.014 mol)
in diethyl ether (25 cm3) was then added dropwise, at
2788C, to the reaction mixture over a further hour before
the reaction mixture was allowed to warm slowly to room
temperature with continuous stirring over a 12 h period.
The mixture was hydrolysed with 10% aqueous NH4Cl (50
cm3), the organic layer was collected, washed with water
(2330 cm3) and dried over MgSO4. The organic layer
was concentrated in vacuo to ca. 15 cm3 and passed
quickly through a separating funnel half-filled with
alumina using light petroleum (bp 40–608C) as eluent.
After the solvent was removed, the white solid was heated
1
(d, JRhP 144); dH (CDCl3) 7.3–8.0 (14H, m, C6H5 and
C6H4), 1.4 (15H, d, JHP 4, Cp*); dF (CDCl3) 281.7 (3F,
3
3
t, JFF 10, CF3), 2111.3 (2F, t, JFF 14, CaF2), 2122.0
(2F, m, CbF2), 2122.4 (2F, m, CdF2), 2123.3 (2F, m,
CeF2), 2126.7 (2F, m, CgF2).
2.6. [RhCl2(h5-C5Me5 )hPPh(C6H4-3-C6F13 )2 j] 6
This was prepared similarly using PPh(C6H4-3-C6F13)2
3 (0.225 g, 0.25 mmol) and the resulting red solid was
recrystallized from dichloromethane–hexane, affording a
fine, red/orange powder (0.23 g, 0.18 mmol, 78%)
(Found: C, 40.2; H, 2.4; P, 2.2; C40H28F26PCl2Rh requires
C, 39.8; H, 2.3; P, 2.6%); m/z (FAB) 1206 ([M]1), 1171
([M2Cl]1) and 1136 ([M22Cl]1); dP (CDCl3) 30.8 (d,
1JRhP 147); dH (CDCl3) 7.2–8.0 (13H, m, C6H5 and
C6H4), 1.4 (15H, d, JHP 4, Cp*); dF (CDCl3) 281.3 (6F,
¨
in a Kugelrohr apparatus (1808C, 0.05 mmHg) to remove
any remaining starting material, yielding the product as a
white solid (5.1 g, 62%) (Found: C, 49.3; H, 2.3;
C24H14F13P requires C, 49.7; H, 2.4); m/z (FAB) 580
([M]1, 100%), 503 (21); dP (CDCl3) 24.8 (s); dH
(CDCl3) 7.2–7.6 (14H, m, C6H5 and C6H4); dF (CDCl3)
281.1 (3F, t, 3JFF 10, CF3), 2111.1 (2F, t, 3JFF 14, CaF2),
2122.0 (2F, m, CbF2), 2122.2 (2F, m, CdF2), 2123.2
(2F, m, CeF2), 2126.7 (2F, m, CgF2).
3
3
t, JFF 10, CF3), 2111.6 (4F, t, JFF 14, CaF2), 2121.9
(4F, m, CbF2), 2122.1 (4F, m, CdF2), 2123.4 (4F, m,
CeF2), 2126.7 (4F, m, CgF2).

E.G. Hope et al. / Polyhedron 18 (1999) 2813–2917
2915
3
3
2.7. [RhCl2(h5-C5Me5 )hP(C6H4-3-C6F13 )3 j] 7
(18F, t, JFF 10, CF3), 2111.8 (12F, t, JFF 14, CaF2),
2121.2 (12F, m, CbF2), 2121.8 (12F, m, CdF2), 2122.8
(12F, m, CeF2), 2126.1 (12F, m, CgF2).
This was prepared similarly using P(C6H4-3-C6F13)3 4
(0.304 g, 0.25 mmol) and the resulting red solid was
recrystallized from dichloromethane–hexane, affording a
fine, red/orange powder (0.30 g, 0.20 mmol, 83%)
(Found: C, 36.4; H, 1.8; P, 3.3; C46H27F39PCl2Rh requires
C, 36.2; H, 1.8; P, 2.0%); m/z (FAB) 1489 ([M2Cl]1)
and 1454 ([M22Cl]1); dP (CDCl3) 30.6 (d, 1JRhP 147); dH
(CDCl3) 7.4–7.9 (12H, m, C6H43), 1.4 (15H, d, JHP 4,
Cp*); dF (CDCl3) 281.5 (9F, t, JFF 10, CF3), 2111.5
2.11. cis- and trans-[PtCl2 hPPh2(C6H4-3-C6F13 )j2 ] 11
The ligand (0.377 g, 0.65 mmol) and cis-
[PtCl2(MeCN)2] (0.105 g, 0.30 mmol) were stirred for 2 h
in refluxing, dry, dichloromethane (60 cm3) under nitro-
gen. The solvent was removed in vacuo and the resulting
off-white solid was washed with light petroleum (bp 40–
608C) (10 cm3). Recrystallization from dichloromethane–
hexane resulted in a fine, white powder (0.31 g, 0.22
mmol, 73%) (Found: C, 39.1; H, 2.0; C48H28F26P2ClPt
requires C, 40.4; H, 2.0%); m/z (FAB) 1391 ([M2Cl]1)
3
(6F, t, JFF 14, CaF2), 2122.1 (6F, m, CbF2), 2122.3
(6F, m, CdF2), 2123.5 (6F, m, CeF2), 2126.8 (6F, m,
CgF2).
and 1356 ([M22Cl]1); dP (CDCl3) 21.2 (s, JPtP 2646,
1
2.8. trans-[RhCl(CO)hPPh2(C6H4-3-C6F13 )j2 ] 8
trans), 15.3 (s, 1JPtP3633, cis); dH (CDCl3) 7.2–7.8 (28H,
3
m, C6H5 and C6H4); dF (CDCl3) 281.4 (6F, t, JFF 10,
The ligand (0.273 g, 0.47 mmol) and [RhCl(CO)2]2
(0.044 g, 0.11 mmol) were stirred for 2 h in refluxing dry
dichloromethane (60 cm3) under nitrogen. The solvent was
removed in vacuo and the resulting yellow solid was
washed with light petroleum (bp 40–608C) (10 cm3),
yielding a fine yellow powder (0.42 g, 0.16 mmol, 73%)
(Found: C, 45.0; H, 2.1; P, 5.6; C49H28F26P2ClORh
requires C, 44.3; H, 2.1; P, 4.7%); m/z (FAB) 1298
CF3), 2111.8 (4F, t, 3JFF 14, C2a), 2121.8 (4F, m, CbF2),
2122.3 (4F, m, CdF2), 2123.2 (4F, m, CeF2), 2126.6
(4F, m, CgF2); IR (Nujol) y(M2Cl) 350(trans), 303, 328
(cis).
2.12. cis- and trans-[PtCl2 hPPh(C6H4-3-C6F13 )2 j2 ] 12
([M2CO]1)
and
1263
([M2CO–Cl]1);
dP
This was prepared similarly using PPh(C6H4-3-C6F13)2
3 (0.583 g, 0.65 mmol), yielding the product as a white
powder (0.33 g, 0.16 mmol, 53%) (Found: C, 34.2; H, 1.3;
C60H26F52P2ClPt requires C, 35.0; H, 1.3%); m/z (FAB)
2062 ([M]1) and 2027 ([M2Cl]1); dP (CDCl3) 21.8 (s,
1
(CDCl3)(233K) 29.7 (d, JRhP 128); dH (CDCl3) 7.2–7.9
(28H, m, C6H5 and C6H4); dF (CDCl3) 281.3 (6F, t, 3JFF
10, CF3), 2111.4 (4F, t, 3JFF 14, CaF2), 2121.8 (4F, m,
CbF2), 2122.4 (4F, m, CdF2), 2123.2 (4F, m, CeF2),
2126.6 (4F, m, CgF2).
1JPtP 2696, trans), 15.8 (s, JPtP3602, cis); dH (CDCl3)
1
7.2–7.8 (26H, m, C6H5 and C6H4); dF (CDCl3) 281.4
3
3
(12F, t, JFF 10, CF3), 2111.8 (8F, t, JFF 14, CaF2),
2121.8 (8F, m, CbF2), 2122.3 (8F, m, CdF2), 2123.2
(8F, m, CeF2), 2126.6 (8F, m, CgF2); IR (Nujol) y(M2
Cl) 351(trans), 303, 323 (cis).
2.9. trans-[RhCl(CO)hPPh(C6H4-3-C6F13 )2 j2 ] 9
This was prepared similarly using PPh(C6H4-3-C6F13)2
3 (0.422 g, 0.47 mmol), yielding the product as a yellow
powder (0.30 g, 0.15 mmol, 69%) (Found: C, 37.6; H, 1.4;
P, 3.6; C61H26F52P2ClORh requires C, 37.3; H, 1.3; P,
3.2%); m/z (FAB) 1934 ([M2CO]1) and 1899 ([M2
2.13. trans-[PtCl2 hP(C6H4-3-C6F13 )3 j2 ] 13
1
CO–Cl]1); dP (CDCl3) 29.9 (d, JRhP 129); dH (CDCl3)
This was prepared similarly using P(C6H4-3-C6F13)3 4
(0.790 g, 0.65 mmol), yielding the product as a white
powder (0.62 g, 0.23 mmol, 78%) (Found: C, 31.8; H, 1.0;
C72H24F78P2ClPt requires C, 32.0; H, 0.9%); m/z (FAB)
7.3–7.8 (26H, m, C6H5 and C6H4); dF (CDCl3) 281.3
3
3
(12F, t, JFF 11, CF3), 2111.5 (8F, t, JFF 14, CaF2),
2121.9 (8F, m, CbF2), 2122.2 (8F, m, CdF2), 2123.3
(8F, m, CeF2), 2126.7 (8F, m, CgF2).
2663 ([M2Cl]1); dP (C6H5CF3) 21.8 (s, JPtP 2723,
1
trans); IR (Nujol) y(M2Cl) 351.
2.10. trans-[RhCl(CO)hP(C6H4-3-C6F13 )3 j2 ] 10
2.14. [RhClhP(C6H4-3-C6F13 )3 j3 ] 14
This was prepared similarly using P(C6H4-3-C6F13)3 4
(0.571 g, 0.47 mmol), yielding the product as a yellow
powder (0.45 g, 0.17 mmol, 78%) (Found: C, 33.8; H, 1.0;
P, 2.5; C73H24F78P2ClORh requires C, 33.7; H, 0.9; P,
2.4%); m/z (FAB) 2570 ([M2CO]1) and 2535 ([M2
To the ligand (0.16 mmol), dissolved in dry, degassed,
perfluoro-1,3-dimethylcyclohexane (1 cm3) in a Schlenk
flask, was added, by syringe, [RhCl(C2H4)2]2 (0.010 g,
0.027 mmol) dissolved in dry, degassed, CH2Cl2 (1 cm3)
under nitrogen. The resulting mixture was stirred vigorous-
ly for 2 min, after which time, all of the colour associated
1
CO–Cl]1); dP (d6-acetone) 31.8 (d, JRhP 132); dH (d6-
acetone) 7.7–8.2 (24H, m, C6H4); dF (d6-acetone) 281.2

2916
E.G. Hope et al. / Polyhedron 18 (1999) 2913–2917
Table 1
with the rhodium had transferred to the lower, fluorous,
phase. A sample was removed by syringe and the NMR
spectrum was recorded in PP3 in a Young’s NMR tube. dP
37.5 (2P, dd, 1JRhP 142, 2JPP 38, Ptrans-P), 49.0 (1P, dt, 1JRhP
189, 2JPP 38, Ptrans-Cl).
Variation of n(CO)a in trans-[RhCl(CO)L2] with the number and position
of perfluoroalkyl groups
L
meta-substitution
(x53)
para-substitution
(x54)
b
PPh3
1965
1980
1984
1992
1965
1982
1983
1993
PPh2(C6H4-x-C6F13
PPh(C6H4-x-C6F13
P(C6H4-x-C6F13
)
)
2.15. [RhClhP(C6H4-3-CF3 )3 j3 ] 15
2
)
3
a n(CO)/cm21. Recorded as Nujol mulls unless otherwise stated.
This was prepared similarly using dry, degassed, CDCl3
as the solvent throughout. dP 37.3 (2P, dd, 1JRhP 142, 2JPP
38, Ptrans-P), 50.5 (1P, dt, 1JRhP 188, 2JPP 38, Ptrans-Cl).
b In CH2Cl2 solution. Data taken from ref. [21].
NMR spectroscopic data are also insensitive to the number
of perfluoroalkyl substituents and their positions on the
aryl rings. Interestingly, as seen for trans-
[RhCl(CO)hPPh2(C6H4-4-C6F13)j2], the 31P NMR spec-
trum for trans-[RhCl(CO)hPPh2(C6H4-3-C6F13)j2] 8 is a
broad singlet at room temperature, which only resolves
into the expected rhodium coupled doublet at 233 K,
suggesting that both of these complexes are fluxional at
room temperature. In marked contrast to the NMR spectro-
scopic data, y(CO) shows a variation with the number of
perfluoroalkyl substituents, but is insensitive to the posi-
tion of the perfluoroalkyl group on the aryl rings (Table 1),
indicating that, in this series, meta- and para-substitution
reduce the s-donor properties of these phosphine ligands
by a similar amount. Only trans-[RhCl(CO)hP(C6H4-3-
C6F13)3j2] 10 is preferentially soluble in perfluorocarbon
solvents.
The reactions of the free phosphines with cis-
[PtCl2(MeCN)2] (affording 11–13) offered the first indica-
tion of the steric influence of the meta-substituents in these
ligands. Previously, we have shown that, although exclu-
sively cis-[PtCl2L2] complexes are obtained from the
reaction of the mono- and bis-derivatised para-substituted
ligands hPPh2(C6H4-4-C6F13) and PPh(C6H4-4-C6F13)2j
with [PtCl2(MeCN)2j, an inseparable mixture of cis- and
trans-isomers was obtained in the same reaction with
P(C6H4-4-C6F13)3 [11]. In this work, complexes
[PtCl2hPPh2(C6H4-3-C6F13) 2] 11 and [PtCl2hPPh(C6H4-
3-C6F13)2j2] 12 were obtained as mixtures of cis- and
trans-isomers, whilst complex 13 is exclusively trans-
3. Results and discussion
The syntheses of the meta-derivatised triaryl phosphines
2–4 with one, two and three perfluoroalkyl substituents
respectively, via 3-bromo-perfluorohexylbenzene, (Scheme
1) is essentially the same as the route used to prepare the
analogous para-derivatised compounds. The ligands were
formed in 54–70% yields as air-stable, white solids. The
spectroscopic data (Experimental) are entirely consistent
with the formulations, in particular, each gave a single
resonance in the 31Ph1Hj NMR spectrum (at ca. d 25)
typical for triarylphosphines. Only the tris-derivatised
phosphine is preferentially soluble in perfluorocarbon
solvents.
We have previously shown [11], for the para-derivatised
triarylphosphine ligands, that the introduction of the per-
fluoroalkyl group does not restrict the type of reactivity
shown by these ligands, and we observe comparable
effects for the meta-derivatised ligands, i.e. facile displace-
ment of weakly coordinated ligands and cleavage of
halide-bridged dinuclear metal complexes. On reaction
with [Cp*RhCl2]2, the mononuclear [Cp*RhCl2L] (5–7)
are formed as air-stable orange solids, which are not
soluble in perfluorocarbon solvents. For these complexes,
1JRhP is insensitive to both the number of perfluoroalkyl
substituents and the position of the perfluoroalkyl groups
on the aryl rings.
For the air-stable, yellow trans-[RhCl(CO)L2] (8–10),
prepared from [RhCl(CO)2]2 and the free ligands, the 31P
Scheme 1.

E.G. Hope et al. / Polyhedron 18 (1999) 2813–2917
2917
[PtCl2hP(C6H4-3-C6F13)3j2], as revealed by IR and 31P
4. Conclusions
NMR spectroscopic data (Experimental). The observed
thermodynamic preference, which is opposite to that
usually seen for [PtCl2(phosphine)2] complexes, can only
arise from steric congestion around the metal centres for
the cis-isomers, which increases progressively with the
number of perfluoroalkyl substituents. We note that, al-
though integration in 31P NMR is a poor quantitative tool
The introduction of perfluoroalkyl ponytails into the
meta-positions of triarylphosphine ligands is straightfor-
ward. These ligands readily coordinate to a series of
platinum group metals wherein the meta-substitution in-
duces little or no greater electronic influence than the
related para-substitution, although there is some evidence
for a greater steric influence. Only the free tris-derivatised
ligand and the complexes trans-[RhCl(CO)L2] and
[RhClL3] hL5P(C6H4-4-C6F13)3j are preferentially solu-
ble in perfluorocarbon solvents.
[18], the cis:trans ratios in [PtCl2hPPh2(C6H4-3-C6F13) ]
2
11 and [PtCl2hPPh(C6H4-3-C6F13)2j2] 12 are approxi-
mately 3:2 and 1:3, respectively. Table 2 summarises the
1JPtP coupling constant data for these and related
platinum(II) complexes. In line with the y(CO) data for
1
trans-[RhCl(CO)L2], JPtP for the cis-isomers decreases
Acknowledgements
with the number of perfluoroalkyl substituents, reflecting
the reduction in s-donor power of the phosphorus atoms
[19]. For the trans-isomers, JPtP increases with the
1
We thank the EPSRC (D.R.P. and A.M.S.), BP Chemi-
cals Ltd. (D.R.P.) and the Royal Society (E.G.H.) for
financial support.
number of perfluoroalkyl groups, an effect that is mirrored
1
in the variation of JPtP for trans-[PtCl2L2] (PBu3 ,
PPr3 ,PEt3) [20], which can be ascribed to the increased
p-acceptor ability of the phosphorus atoms on the in-
troduction of the electron-withdrawing perfluoroalkyl
substituents. This data, for the first time in our work,
also suggests a subtle variation in the influence of the
References
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1
perfluoroalkyl groups with ring position where JPtP
for cis-[PtCl2hPPh2(C6H4-3-C6F13)2] 11 and cis-
[PtCl2hPPh(C6H4-3-C6F13)2j2] 12 are less than those for
the analogous para-substituted metal complexes, indicating
a slightly greater electron-withdrawing effect for the meta-
derivatised ligands than their para-derivatised congeners.
None of the [PtCl2L2] complexes are preferentially soluble
in perfluorocarbon solvents.
Steric congestion at the metal centre does not preclude
formation of the preferentially perfluorocarbon solvent-
soluble [RhClhP(C6H4-3-C6F13)3j3] (14) for which the
NMR spectroscopic data are almost identical to those for
the analogous tris-para-substituted ligand [11] and for the
tris-meta-CF3 ligand (15) complexes.
´
´
´
´
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Table 2
31Ph1Hj NMR data for [PtCl2Cl2]a
Ligand
cis-[PtCl2L2]
D(31P)
trans-[PtCl2L2]
1JPtP
D(31P)
1JPtP
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b
PPh3
18.9
20.1
20.8
2
3676
3633
3602
2
25.4
26.0
26.8
27.8
2
2635
2646
2696
2723
2
PPh2(C6H4-3-C6F13
PPh(C6H4-3-C6F13
P(C6H4-3-C6F13
PPh2(C6H4-4-C6F13
PPh(C6H4-4-C6F13
)
)
2
)
3
)
19.6
20.0
21.5
3653
3635
3631
)
2
2
2
P(C6H4-4-C6F13
)
28.8
2719
3
a D(31P)5dmetal complex 2dfree ligand /ppm, 1JPtP /Hz.
b Data taken from Ref. [22].