A new highly active diphosphane-palladium(II) complex as a catalyst precursor for the heck reaction

Article abstract of DOI:10.1002/1099-0682(200111)2001:11<2907::AID-EJIC2907>3.0.CO;2-7

The new diphosphane ligand cis-1,3-bis[(diphenylphosphanyl)methyl]cyclohexane (4) has been prepared and has allowed the synthesis of the palladium complex cis-[Pd(4)(CO₂CF₃)₂] (6). To obtain cis complexation of the diphosp

Full text of DOI:10.1002/1099-0682(200111)2001:11<2907::AID-EJIC2907>3.0.CO;2-7

FULL PAPER
A New Highly Active Diphosphane-Palladium(II) Complex as a Catalyst
Precursor for the Heck Reaction
Sven Sjövall,[a] Maria H. Johansson,[a] and Carlaxel Andersson*[a]
Keywords: Palladium / Phosphanes / Catalysis / Heck reaction
The new diphosphane ligand cis-1,3-bis[(diphenylphosphan-
structure that has been verified by an X-ray structure deter-
yl)methyl]cyclohexane (4) has been prepared and has al- mination. This complex efficiently catalyses the vinylation of
lowed the synthesis of the palladium complex cis-
[Pd(4)(CO2CF3)2] (6). To obtain cis complexation of the di-
iodo- and bromobenzenes in high yields. For the best reac-
tion, with methyl acrylate and iodobenzene, a yield of Ͼ98%
phosphane in 6 the cyclohexane skeleton adopts a chair con- was obtained with an average turnover frequency of 11 760
formation with a diaxial orientation of the substituents, a
h−1 and a turnover number of 1 176 000.
Introduction
ring carbons from sp2 to sp3, the different electronic proper-
ties of ligand 4 relative to 4Ј should modify the reactivity
of the resulting complex. However, when we first investig-
ated the coordination chemistry of ligand 4 we found a tot-
ally different coordination mode, as evidenced by X-ray
crystallography, from the analogous aromatic diphosphane.
We also describe some preliminary results on the catalytic
vinylation of aryl halides by the PdII complex synthesised
herein.
Novel or improved homogeneous catalytic reactivities are
continuously being achieved with a large variety of organo-
metallic complexes. The main method of controlling and
directing the reactivity of a metal in such a compound is
by modifying the steric and/or electronic properties of the
coordinated ligands.[1] The effect of using different ‘‘fine-
tuned’’ ligands in catalysis is perhaps best illustrated by the
widely studied Heck reaction,[2] the generation of sp2Ϫsp2
carbonϪcarbon bonds by palladium-catalysed arylation of
olefins with aryl halides.[3] In order to increase the catalyst
efficiency in this potentially industrially important reaction
a great deal of efforts have been made recently and this has
led to the development of improved palladium catalysts in
terms of both stability and activity.[4Ϫ10] A variety of differ-
ent ligands have been investigated for these high-performing
catalysts, such as sterically hindered, highly basic phos-
phanes,[4] carbenes,[5] cyclometallated phosphanes,[6] phos-
phites,[7] mono- and bis-chelating diphosphanes[8] and im-
ines,[9] as well as more traditional Heck coupling catalysts
Results and Discussion
Ligand Synthesis
combined with additives such as [PPh4]Cl or PtBu3.[10]
A
Based on the fact that the sterically demanding substitu-
ents of cis-1,3-cyclohexanedicarboxylic acid (1) prefer an
equatorial orientation,[12] we have chosen 1 as the starting
material for the preparation of cis-1,3-bis[(diphenylphos-
phanyl)methyl]cyclohexane (4) following the procedure de-
picted in Scheme 1. In the initial step, 1 was reduced with
an excess of BH3 in THF yielding cis-1,3-bis(hydroxyme-
thyl)cyclohexane (2). A good leaving group was introduced
in 2 by treating it with a stoichiometric amount of trifluoro-
methanesulfonic anhydride in the presence of a base, giving
cis-1,3-bis[(trifluoromethylsulfonyloxy)methyl]cyclohexane
(3). This colourless oil undergoes decomposition within
hours, even when it is stored below Ϫ18 °C, and was there-
fore used immediately after isolation. The reaction of 3 with
2 equiv. of LiPPh2 in THF furnished phosphane 4. An
NMR spectroscopic analysis showed the phosphane to be
essentially pure and, because of its high air-sensitivity, it
was used without further purification. However, sulfuriz-
key feature of several of these systems is the stabilisation of
the active catalyst by either ligand chelation or steric shield-
ing of the transition metal centre. This confers a high ther-
mal stability on the catalyst allowing long reaction times
and high reaction temperatures without noticeable catalyst
deactivation. Intrigued by the delicate ligand effects in the
Heck reaction we have initiated a general program aimed
at the development and catalytic investigation of bidentate
phosphane ligands that can potentially cyclometallate at an
sp3 carbon.
In this paper we report the synthesis of the stereospecific
diphosphane cis-1,3-(Ph2PCH2)2C6H10 (4), which is the
fully aliphatic analogue to the well-known tridentate PCP
ligand 1,3-(Ph2PCH2)2C6H4 (4Ј).[11] Thus, by changing the
[a]
Inorganic Chemistry, Centre for Chemistry and Chemical
Engineering, Lund University,
P.O. Box 124, 221 00 Lund, Sweden
Eur. J. Inorg. Chem. 2001, 2907Ϫ2912
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/1111Ϫ2907 $ 17.50ϩ.50/0
2907

S. Sjövall, M. H. Johansson, C. Andersson
FULL PAPER
ation of the phosphane, by treating it with an excess of ele- with 1 equiv. of 4 in THF, yielding 6 as air-stable crystals
mentary sulfur, results in the air-stable compound cis-1,3- in reasonable yield (Scheme 2).
bis[(diphenylphosphane sulfide)methyl]cyclohexane (5),
The integral sum in the 1H NMR spectrum of 6 suggests
which was fully characterised including elemental analysis. no displacement of hydrogen from ligand 4. In addition,
Clean removal of the sulfur atoms in 5 with Raney-Nickel one of the protons in the cyclohexane ring is substantially
or trichlorosilane,[13] was unsuccessful and sulfurization shifted downfield to δ ϭ 4.46, implying a through-space
therefore does not provide a simple route to analytically interaction with the metal centre. The 31P{1H} NMR spec-
pure 4.
trum displays a singlet, which is consistent with a mirror-
plane symmetry of 6, and the position at δ ϭ 16.5 is in
accordance with other Pd cis-diphosphane complexes.[15] In
the 13C{1H} NMR spectrum, the C2 signal occurs as a trip-
let in the normal aliphatic region (δ ϭ 28.6, 3JPC ϭ 6.6 Hz).
Hence, the NMR spectroscopic data is consistent with the
structure shown in Scheme 2, i.e. the ligand binds to the
metal centre in a cis-diphosphane fashion with a diaxial
arrangement of the substituents on the cyclohexane ring.
This energetically more demanding conformation of the
cyclohexane ring, relative to the diequatorial counterpart,
was not expected.[12] Moreover, the coordination mode of 4
also deviates substantially from the fully aromatic analogue
1,3-bis[(diphenylphosphanyl)methyl]benzene, which coord-
inates as a tridentate PCP ligand in a trans-configura-
tion.[11] The reason for the reluctance of ligand 4 to activate
a CϪH bond, even though the spacing between its phos-
phorous atoms is sufficiently large for trans-coordination
when diequatorially oriented, must be due to an improper
arrangement of its CϪH bonds with respect to the palla-
dium metal centre.
Scheme 1
The 13C{1H} NMR spectra of compounds 2Ϫ5 imply Cs
An X-ray crystallographic investigation has confirmed
the structure of 6. Yellow blocks were obtained upon crys-
tallisation by layering Et2O onto a THF solution of 6. A
perspective view of the molecular structure is shown in Fig-
ure 1 including selected bond lengths and angles.
symmetry and thus confirm the cis arrangement of the
functional groups in the 1,3-positions of the cyclohexane
ring. Hence, the respective cyclohexane skeletons give rise
to four sets of signals: those of the chemically equivalent
methine groups and three chemically different sets of
methylene groups. Furthermore, the triflate substituents in
3 cause a significant downfield shift (to δ ϭ 81.2) for the α-
methylene group, which is in accordance with its good leav-
ing group capacity.
Complexation
Our initial studies revealed that the choice of palladium
precursor was of importance, since attempts to synthesise a
monomeric palladium complex using a dihalide precursor
failed. Hence, when [PdCl2(NCPh)2] was stirred overnight
with 1 equiv. of 4 in CH2Cl2 a yellow insoluble material
was isolated in high yield. Shaw and co-workers have earlier
described similar results, which they explained with the
formation of a large-ring polynuclear palladium com-
pound.[14] Instead, the preparation of a monomeric palla-
dium complex was achieved by reacting [Pd(CO2CF3)2]
Figure 1. Perspective view (DIAMOND) of 6 (thermal ellipsoids at
˚
30% probability); bond lengths (A) and angles (deg) with estimated
standard deviations: PdϪO1 2.086(2), PdϪO3 2.074(2), PdϪP1
2.261(1), PdϪP2 2.252(1), O1ϪPdϪO3 83.36(10), P1ϪPdϪP2
93.81(4), P1ϪPdϪO1 93.36(8), P1ϪPdϪO3 173.83(7)
Scheme 2
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Eur. J. Inorg. Chem. 2001, 2907Ϫ2912

A New Diphosphane-Palladium(II) Complex as a Catalyst Precursor
FULL PAPER
Complex 6 exhibits a cis square-planar geometry. The taining catalyst in a high-yielding Heck reaction.[19] The
congested conformation of the cyclohexane ring causes the screening of different bases (Na2CO3, NaOAc, lutidine,
chelate to distort the complex slightly away from an ideal NBu3 and DABCO) revealed that 6 performs best with
geometry by widening the P1ϪPdϪP2 angle [93.81(4)°]. NBu3 as base. Of the polar solvents tested, N-methylpyrrol-
Small deviations in the bond lengths, for example for idone (NMP) was found to be superior in terms of reaction
˚
˚
PdϪP1 [2.261(1) A] and PdϪP2 [2.252(1) A], illustrate the rate (entry 1), relative to N,N-dimethylformamide or N,N-
pseudo-symmetric property of 6. The diaxial disposition of dimethylacetamide, when using the same reaction condi-
the substituents on the cyclohexane ring causes the ring to tions. The reaction can also be carried out in semi-polar
lie well above the plane of the complex (Figure 2). Note the and non-polar solvents, although at lower rates. However,
correlation of the position of the equatorial hydrogen as far as we are aware, the TONs in dioxane (333 000, entry
1
on C2 (Figure 2) and its downfield shift in the H NMR 5) and mesitylene (320 000, entry 6) are unsurpassed.[20]
spectrum of 6 (vide supra). The strained cyclohexane ring The catalyst system is sensitive and to ensure high catalytic
adopts the chair conformation, where the endocyclic bond activity the efficient exclusion of air was necessary, as well
angles deviate substantially from free cyclohexane as the use of pure solvents and starting materials. Complex
(111.5°).[16]
6 is thermally stable up to at least 140 °C, presumably due
to the stabilising chelate effect, but the reactions were rou-
tinely performed at 120 °C for comparative purposes.[8a] To
further verify the thermal stability of the complex we inten-
tionally left some reactions for prolonged times: some reac-
tion times could probably be reduced, and in no case was
any noticeable formation of palladium metal observed. The
catalyst remains highly active after the reaction is com-
pleted, and upon addition of more substrates the catalytic
reaction resumes at essentially the same rate using the reac-
tion conditions described (Table 1, entry 1).
As expected, both the electronic properties of the reacting
olefin and steric hindrance are decisive factors for the effici-
ency of the catalyst: methyl acrylate gave a higher average
reaction rate than styrene or n-butyl acrylate regardless of
the aryl halide employed. However, the TONs for the aryl-
ation of n-butyl acrylate (495 000, entry 3) and styrene (490
000, entry 4) with iodobenzene are again among the highest
reported.[6a] Complex 6 was also capable of catalysing the
vinylation of relatively unreactive bromobenzenes in excel-
lent yields (entry 7Ϫ10). Here it is also evident that an elec-
tron-withdrawing group on the aryl ring increases the reac-
tion rate. Unfortunately, 6 is not able to convert the rela-
tively cheaper aryl chlorides to any degree, although the
effect of adding expensive promoters like [NBu4][Br] was
not tested.[21]
Figure 2. A plot showing the chair conformation of the cyclohex-
ane skeleton in 6 including the hydrogens on C2; bond angles (deg)
with estimated standard deviations: C1ϪC2ϪC3 115.2 (3),
C2ϪC3ϪC4 109.0(3), C3ϪC4ϪC5 113.3(3), C4ϪC5ϪC6 112.2(4),
C5ϪC6ϪC1 ϭ 112.9(3), C6ϪC1ϪC2 108.8 (3)
Catalysis
As mentioned in the introduction, some chelating diphos-
phane-palladium(II) complexes are high-performing pre-
catalysts for the vinylation of aryl halides (Scheme 3), as
recently communicated by Shaw et al.[8a]
The trend of reactivity for iodo-, bromo- and chlorobenz-
enes indicates that an oxidative addition of the aryl halide
to the catalyst is involved in the rate-determining step for
the Heck reaction. Whether this mechanism involves a PdII/
PdIV catalytic cycle, as previously suggested for other palla-
dium-diphosphane catalysts,[8a] or not, is unclear for the
Scheme 3
Until then, the prevailing belief was that diphosphanes moment. However, the greater efficiency of the eight-mem-
were unsuitable ligands in Heck catalysis.[17] Intrigued by bered chelate complex 6 in catalysing the Heck reaction,
this observation we decided to investigate complex 6 as a compared to the previously reported four- to seven-mem-
precatalyst for the same reaction.
bered ones,[8a] suggests that chelate-opening is involved in
As shown in Table 1, complex 6 is indeed very active in the catalytic cycle. A similar striking chelate effect on cata-
the arylation of a variety of olefins with aryl iodides and lytic activity has been reoported by Milstein and co-
bromides. The reaction of methyl acrylate with iodobenzene workers.[4b]
is by far the most active system in the present study where
In summary, ligand 4 coordinates as a normal cis-diphos-
a TON of 1.2 ϫ 106 was achieved (TOF up to 1.2 ϫ 104, phane, which is opposed to its fully aromatic analogue. This
Table 1, entry 2). This TON is the highest observed so far is made possible by the diaxial orientation of the substitu-
for a chelating palladium-diphosphane catalyst,[18] and also ents in the cyclohexane skeleton. An investigation of the
among the highest reported overall for a phosphane-con- catalytic activity of the resulting diphosphane-palladium
Eur. J. Inorg. Chem. 2001, 2907Ϫ2912
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S. Sjövall, M. H. Johansson, C. Andersson
FULL PAPER
Table 1. Selected results of the Heck reaction with complex 6; experiments conducted with 1.2 equivalents of Bu3N in NMP except
where noted
No.
Olefin
ArX
6
time/temp
(h)/(°C)
TON[c]
Yield
(%)[d]
TOF
(mmol)[a]
(mmol)[b]
(mmol) ϫ 10Ϫ5
(hϪ1 [e]
)
1
2
3
mac (6)
mac (24)
bac (10)
sty (10)
mac (10)
mac (10)
mac (10)
bac (10)
mac (10)
bac (10)
PhI (9)
6
2
2
2
3
3
3
3
4
4
9/120
100 000
1176 000
495 000
490 000
333 000
320 000
333 000
333 000
235 000
207 500
100
98
11 111
11 760
8 840
9 075
9 250
3 370
10 410
8 125
2 975
2 310
PhI (36)
PhI (15)
PhI (15)
PhI (15)
PhI (15)
4-bba (15)
4-bba (15)
PhBr (15)
PhBr (15)
100/120
56/120
54/120
36/120
95/120
32/120
41/120
79/140
90/140
99
4
98[f]
99
5[g]
6[h]
7
95
99
99
94
8
9
10
83
[a]
[b]
[c]
mac ϭ methyl acrylate, bac ϭ n-butyl acrylate, sty ϭ styrene. Ϫ
4-bba ϭ 4-bromobenzaldehyde. Ϫ TON ϭ Turnover number
(mol product/mol catalyst). Ϫ [d] GC yield using 2-methylnaphthalene as internal standard. Ϫ [e] TOF ϭ Turnover frequency (mol product/
mol catalyst ϫ time). Ϫ trans-stilbene/cis-stilbene ϭ 9. Ϫ Dioxane as solvent. Ϫ Mesitylene as solvent.
[f]
[g]
[h]
using 3-nitrobenzyl alcohol as matrix and CsI as calibrant. Gas
complex 6 has shown it to be by far the most active chelat-
ing diphosphane-PdII catalyst reported for the Heck reac-
tion, and it shows an exceedingly high catalytic activity in-
cluding reactions of non-activated aryl bromides. Huge
TONs are also found in semi-polar or non-polar solvents,
and 6 should be placed amongst the most active phos-
phane-containing catalysts overall for vinylation of aryl hal-
ides. We believe that the catalytic cycle is assisted by a lab-
ile chelate.
chromatographic analyses were performed on a Varian 3300 instru-
ment equipped with a 12-m BP-10 fused silica capillary column
(0.22 ID). Elemental analyses were performed by MikroKemi AB,
Uppsala, Sweden.
Except for the workup of reaction mixtures, all Heck reactions were
carried out under argon. Stock solutions of catalyst were used due
to low concentrations. These were freshly prepared under anaerobic
conditions for each reaction and used only once. The solvents, aryl
halides and bases were distilled when possible and used immedi-
ately. The olefin substrates were carefully deoxygenated by at least
three freeze-pump-thaw cycles.
Experimental Section
General Procedure for the Heck Reactions: The solvent (10 mL),
aryl halide, base, olefin, 2-methylnaphthalene (internal standard)
and a magnet were placed in a Schlenk tube with a screw cap. Three
freeze-pump-thaw cycles were performed before the addition of an
appropriate volume of the catalyst stock solution. The Schlenk tube
was sealed and placed in a pre-heated, temperature-controlled oil-
bath. The mixture was stirred vigorously for the desired time.
Workup was achieved by pouring the cooled reaction mixture into
an excess of 5% HCl (aq) and extracting with CH2Cl2 or Et2O. The
combined organic phases were neutralised with 10% NaHCO3 (aq)
and dried with MgSO4. After removal of the solvent the products
All experiments with metal complexes and phosphane ligands were
carried out under an atmosphere of argon or nitrogen in a Braun
glovebox equipped with an inert gas purifier, or by using standard
Schlenk and vacuum-line techniques. All non-deuterated solvents,
reagent grade or better, were freshly distilled under a nitrogen at-
mosphere: Et2O, THF, toluene, n-hexane, and n-pentane from so-
dium/benzophenone ketyl; CH2Cl2 and CHCl3 from CaH2. Deuter-
ated solvents were used as received. Commercially available re-
agents was purchased from Aldrich and used without purification.
The cis-1,3-cyclohexanedicarboxylic acid (1) was isolated from the
commercially available cis,trans mixture according to a literature
procedure.[22] The lithium phosphide LiPPh2 was prepared by the
drop-wise addition of nBuLi to an equimolar amount of PPh2Cl
below Ϫ60 °C, allowed to age for 2 h at room temperature, and
thereafter used in situ for further reaction.
1
were analysed by H NMR spectroscopy and MS; the yields were
determined by GC. All of the products are known compounds.[23]
Preparation of cis-1,3-Bis(hydroxymethyl)cyclohexane (2): Over a
period of 1.5 h, BH3 (100 mL, 2.2 equiv. as a 1.0  THF solution)
was slowly added to an ice-cooled, stirred solution of 1 (7.75 g,
NMR spectra were recorded either on a Varian Unity 300 MHz 45.0 mmol) in 20 mL of THF. After the addition was completed
instrument (1H, 31P, 19F) or a Bruker ARX 500 MHz spectrometer the suspension was stirred at room temperature for an additional
(13C). A 13C DEPT NMR spectrum was routinely recorded for each
compound. The NMR spectroscopic measurements were per-
formed in CDCl3 unless stated otherwise. 1H and 13C NMR chem-
ical shifts are reported in ppm downfield from tetramethylsilane
but were measured relative to the residual 1H in the deuterated
2 h, and the excess hydride was thereafter carefully decomposed by
the addition of 20 mL of 2  HCl (aq). The water phase was neut-
ralised with NaOH and about 8Ϫ10 g of K2CO3 was added in or-
der to transfer the water-soluble diol to the organic phase. The
organic phase was isolated and the water phase was further ex-
solvent. 31P NMR chemical shifts are reported in ppm downfield tracted with 2 ϫ 10 mL of CHCl3; the combined organic phases
from an external 85% solution of phosphoric acid. 19F NMR chem-
ical shifts are reported in ppm downfield from an external sample
of CClF3 in CDCl3 v ϭ virtual. NMR multiplicities are abbreviated upon standing. Yield: 5.71 g (88%). Ϫ H NMR (D2O): δ ϭ 0.45
were then dried over silica. Filtration and removal of the organic
solvent resulted in a highly viscous, colourless oil which solidified
1
2
3
as follows: s ϭ singlet, d ϭ doublet, t ϭ triplet, q ϭ quadruplet,
m ϭ multiplet, br ϭ broad. Fast Atom Bombardment (FAB) mass
(q, JHH, JHH ϭ 12.0 Hz, 1 H, CHeHa), 0.71 (m, 2 H, CH2), 1.15
(m, 1 H, CHeHa), 1.39 (m, 2 H, CH), 1.62 (m, 4 H, CH2), 3.41 (d,
spectroscopic data were obtained on a JEOL SX-102 spectrometer 3JHH ϭ 6.3 Hz, 4 H, CH2OH). Ϫ 13C{1H} NMR (D2O): δ ϭ 25.1
2910
Eur. J. Inorg. Chem. 2001, 2907Ϫ2912

A New Diphosphane-Palladium(II) Complex as a Catalyst Precursor
FULL PAPER
(s, CH2CH2CH2), 29.3 (s, CHCH2CH2), 32.3 (s, CHCH2CH), 39.4 (FABϩ): m/z ϭ 544 [C32H34P2S2ϩ]. Ϫ C32H34P2S2 (544.69): calcd.
[s, (CH)2CHCH2], 67.9 (s, CH2OH). Ϫ MS (FABϩ): m/z ϭ 142
[C8H14O2ϩ]. Ϫ C8H16O2 (144.21): calcd. C 66.6, H 11.2; found C
66.5, H 11.4.
C 70.6, H 6.3, S 11.8; found C 70.4, H 6.1, S 11.6.
Reaction of 4 with [Pd(CO2CF3)2]. Formation of [Pd(4)(CO2CF3)2]
(6): Phosphane
4 (25.1 mg, 52.2 µmol) and [Pd(CO2CF3)2]
(17.4 mg, 52.2 µmol) were dissolved in 3 mL of THF. After stirring
for 3 h, 12 mL of Et2O was layered on top of the red THF solution.
After 3 days yellow air-stable crystals were harvested. Yield:
20.5 mg (48%). Ϫ 1H NMR (CD2Cl2): δ ϭ 1.89Ϫ1.54 (m region, 7
H, CH2), 2.25 (m, 4 H, CH2P), 2.81 (m, 2 H, CH), 4.46 (br. d,
2JHH ϭ 15.3 Hz, 1 H, CHeHa), 7.39 (m, 16 H, Ar), 7.82 (m, 4 H,
Ar). Ϫ 13C{1H} NMR (CD2Cl2): δ ϭ 28.3 (s, CH2CH2CH2), 28.6
Preparation of cis-1,3-Bis[(trifluoromethylsulfonyloxy)methyl]cy-
clohexane (3): A stirred suspension of 2 (1.00 g, 6.93 mmol) and
pyridine (1.15 mL, 14.2 mmol) in 15 mL of CH2Cl2 was cooled in
an ice-bath. Dropwise addition of trifluoromethanesulfonic anhyd-
ride (2.40 mL, 14.2 mmol), diluted with 10 mL of CH2Cl2, resulted
in a yellow-tinted solution. After 30 min., the ice-bath was removed
and the solution was allowed to age for an additional hour. The
suspension was then filtered through a short plug of silica on a G3
glass frit and the plug was rinsed with additional CH2Cl2. Removal
of the organic solvent on a rotary evaporator resulted in a colour-
less oil. The compound is too unstable for microanalysis. Yield
3
(t, JPC ϭ 6.6 Hz, CHCH2CH), 33.5Ϫ33.0 (m region, CH and
1
CH2), 116.4 (q, JFC ϭ 291 Hz, CF3), 129.0 (vt, JPC ϭ 11.1 Hz,
CH), 129.7 (vt, JPC ϭ 11.1 Hz, CH), 131.9 (s, CH), 132.5 (s, CH),
132.9 (vt, JPC ϭ 10.0 Hz, CH), 133.8 (vt, JPC ϭ 11.1 Hz, CH),
2
160.8 (q, JFC ϭ 36.2 Hz, CϭO). Ϫ 31P{1H} NMR (CD2Cl2): δ ϭ
1
2
3
2.29 g (82%). Ϫ H NMR: δ ϭ 0.89 (q, JHH, JHH ϭ 12.0 Hz, 1
H, CHeHa), 1.03 (m, 2 H, CH2), 1.37 (m, 1 H, CHeHa), 1.97Ϫ1.83
16.5 (s). Ϫ 19F NMR (CD2Cl2): δ ϭ 52.8 (s). Ϫ MS (FABϩ):
m/z
ϭ Ϫ
812 [C36H34F6O4P2Pdϩ] (correct isotope pattern).
3
(m region, 6 H, CH and CH2), 4.36 (d, JHH ϭ 6.0 Hz, 4 H,
C36H34F6O4P2Pd (813.00): calcd. C 53.2, H 4.2; found C 53.2, H
4.2.
CH2OTf). Ϫ 13C{1H} NMR: δ ϭ 24.6 (s, CH2CH2CH2), 28.4 (s,
CHCH2CH2), 31.1 (s, CHCH2CH), 37.2 [s, (CH)2CHCH2], 81.2 (s,
1
CH2OTf), 119.0 (q, JFC ϭ 320 Hz, CF3). Ϫ 19F NMR: δ ϭ 51.5
X-ray Crystal Structure Determination of Complex 6:[24] Crystal
data and details of the data collection and refinement are given in
Table 2. The intensity data were collected at 293 K with a Bruker
Smart CCD system using ω scans and a rotating anode with Mo-
(s, CF3).
Preparation of cis-1,3-Bis[(diphenylphosphanyl)methyl]cyclohexane
(4): A solution of 3 (2.33 g, 5.71 mmol) in 15 mL of THF was care-
fully added to a cooled (Ϫ60 °C) and stirred deep-red solution of
LiPPh2 (2.14 g, 11.4 mmol) in 15 mL of THF. The solution was
allowed to reach room temperature over a period of 1 h, and stirred
for an additional 18 h. The orange solution was then quenched
with 5 mL of degassed water and the colourless organic phase was
isolated. The water phase was further extracted with 2 ϫ 10 mL
of Et2O and the combined organic phases were dried over silica.
Filtration and removal of the solvent resulted in a viscous, almost
colourless oil which partly solidified upon standing. NMR spectro-
scopic analysis showed the product to be essentially pure. The air-
sensitivity precluded further purification and the phosphane was
therefore not subjected to microanalysis. Yield: 2.52 g (92%). Ϫ 1H
NMR: δ ϭ 1.41Ϫ0.84 (m region, 6 H, CH2), 1.72 (m, 1 H, CH2),
[25]
˚
Kα radiation (λ ϭ 0.710 73 A).
The intensities were corrected
for Lorentz, polarisation and absorption effects with SADABS.[26]
Table 2. Crystallographic data
Complex 6
Formula
C36H34F6O4P2Pd
Yellow prism
0.19 ϫ 0.11 ϫ 0.10
Triclinic
Crystal description
Crystal size (mm)
Crystal system
Space group
¯
P1
˚
a (A)
10.950(2)
12.174(2)
15.014(3)
91.83(3)
104.93(3)
114.76(3)
1733.7(6)
2
˚
b (A)
3
1.93 (m, 2 H, CH), 2.02 (d, JHH ϭ 6.9 Hz, 4 H, CH2P), 2.24 (m,
˚
c (A)
1 H, CH2), 7.33 (m, 12 H, Ar), 7.43 (m, 8 H, Ar). Ϫ 13C{1H}
α (°)
β (°)
γ (°)
3
NMR: δ ϭ 26.0 (s, CH2CH2CH2), 34.5 (d, JPC ϭ 9.7 Hz,
2
CHCH2CH2), 35.3 [d, JPC ϭ 13.6 Hz, (CH)2CHCH2], 36.7 (d,
1JPC ϭ 13.1 Hz, CH2P), 43.5 (t, 3JPC ϭ 9.6 Hz, CHCH2CH), 128.3
(br. s, CH), 132.8 (m, CH), 133.9 (m, CH), 134.1 (m, CH), 139.4
(m, CH). Ϫ 31P{1H} NMR: δ ϭ Ϫ21.3 (s).
3
˚
V (A )
Z
Dx (Mg mϪ3
)
1.557
No. of refl. used for cell parameters
7080
0.698
824
µ (mmϪ1
F(000)
)
Preparation of cis-1,3-Bis[(diphenylphosphane sulfide)methyl]cy-
clohexane (5). Sulfur (1.76 g, 6.86 mmol) was added to a solution
of 4 (827 mg, 1.72 mmol) in 15 mL of toluene and the mixture was
stirred for 16 h. The solution was decanted and removal of the
toluene resulted in a pale yellow solid. The crude compound was
loaded on a column of silica of 10 cm height. Eluting with n-hexane
removed the remaining elementary sulfur and the white solid 5 was
recovered by washing the column with CH2Cl2 and removing the
solvent under vacuum. Yield: 759 mg (81%). Ϫ 1H NMR: δ ϭ 0.74
Tmin/Tmax
θ- range
No. of collected refl
No. of unique refl.
No. of observed refl., m [I Ͼ 2σ(I)]
Parameters, n
0.745/0.920
1.4Ϫ31.7
19208
10293
7589
442
hkl range
Ϫ15Ͻ h Ͻ 16
Ϫ17 Ͻ k Ͻ 17
Ϫ21 Ͻ l Ͻ 21
0.0486
0.1264
1.035
2
3
(m, 2 H, CH2), 0.87 (q, JHH, JHH ϭ 11.6 Hz, 1 H, CHeHa), 1.12
(m, 1 H, CHeHa), 2.01Ϫ1.42 (m region, 6 H, CH and CH2), 2.32
(m, 4 H, CH2P), 7.43 (m, 12 H, Ar), 7.82 (m, 8 H, Ar). Ϫ 13C{1H}
NMR: δ ϭ 25.6 (s, CH2CH2CH2), 33.0 (br. s, CHCH2CH2), 34.0
[d, 2JPC ϭ 6.9 Hz, (CH)2CHCH2], 39.2 (d, 1JPC ϭ 55.1 Hz, CH2P),
R[a]
wR[b]
S[c]
(∆/σ) max
ρ max/min (e /A )
0.002
1.482/Ϫ0.958
Ϫ
3
˚
3
43.5 (t, JPC ϭ 10.2 Hz, CHCH2CH), 128.5 (m, CH), 130.9 (m,
[b]
[a] R ϭ Σ(|Fo| Ϫ |Fc|)/Σ|Fo|. Ϫ wR ϭ [Σw(|Fo| Ϫ |Fc|)2/Σ|Fo|2]1/2. Ϫ
CH), 131.3 (br. s, CH), 133.2 (d, JPC ϭ 28.2 Hz, CH), 134.2 (d,
[c]
JPC ϭ 28.9 Hz, CH). Ϫ 31P{1H} NMR: δ ϭ 37.1 (s). Ϫ MS
S ϭ [Σw(|Fo| Ϫ |Fc|)2/(m Ϫ n)]1/2
.
Eur. J. Inorg. Chem. 2001, 2907Ϫ2912
2911

S. Sjövall, M. H. Johansson, C. Andersson
FULL PAPER
[10b]
M T. Reetz, G. Lohmer, R. Schwickardi, Angew. Chem.
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methods and refined by a full-matrix least-squares calculation on
F2.[28] Non-H atoms were refined with anisotropic displacement
parameters. The hydrogen atoms were constrained to their parent
sites using a riding model.
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2912
Eur. J. Inorg. Chem. 2001, 2907Ϫ2912