Stereoselective addition of diphenylphosphine to substituted diphenylethynes: Synthetic, NMR and X-ray crystallographic studies

Article abstract of DOI:10.1039/a707210d

The base-catalysed addition of diphenylphosphine to the substituted diphenylethynes RC≡CR′ (R = Ph, R′ = Ph, o-tolyl, m-tolyl or 2-biphenyl; R = m-tolyl, R′ = o-tolyl or m-tolyl) yielded Ph₂PC(R)=CHR′ and/or Ph₂PCH(R)CH(R′)PPh₂. Proton, ¹³C, ¹³P and two-dimensional rotating frame Overhauser enhancement ¹H NMR spectra have been used to determine the stereochemical pathways of the reactions and the stereochemistry of the products. In general the more hindered alkynes undergo monoaddition ultimately to yield phosphinoalkenes with the Ph₂P attached to the carbon bearing the least bulky substituent and cis to the olefinic proton, while for the less hindered alkynes the trans isomer is formed initially and this then reacts further to give mesolerythro-diphosphinoalkanes. Bis(o-tolyl)ethyne does not react with Ph₂PH under the same conditions. Crystal structures were determined for E- and Z-Ph₂P(Ph)C=CHPh and show distortions of interbond angles consistent with the pattern of strain implied by the foregoing reactions. The sulfides of the phosphinoalkenes and the Mo(CO)₄ complexes of the diphosphinoalkanes were also prepared and their ¹H, ¹³C and ³¹P NMR spectra recorded. In several cases the pattern of ¹³CO NMR signals for the complexes was used unambiguously to determine the stereochemistry of the parent diphosphines.

Full text of DOI:10.1039/a707210d

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Stereoselective addition of diphenylphosphine to substituted
diphenylethynes: synthetic, NMR and X-ray crystallographic studies
Jonathan L. Bookham,*,a Darren M. Smithies,a Anna Wright,a Mark Thornton-Pettb and
William McFarlanec
a Department of Chemical and Life Sciences, University of Northumbria at Newcastle,
Newcastle upon Tyne, UK NE1 8ST
b School of Chemistry, University of Leeds, Leeds, UK LS2 9JT
c Department of Chemistry, University of Newcastle upon Tyne, Newcastle upon Tyne,
UK NE1 7RU
᎐
The base-catalysed addition of diphenylphosphine to the substituted diphenylethynes RC᎐CRЈ (R = Ph,
᎐
RЈ = Ph, o-tolyl, m-tolyl or 2-biphenyl; R = m-tolyl, RЈ = o-tolyl or m-tolyl) yielded Ph PC(R)᎐CHRЈ and/or
᎐
2
Ph2PCH(R)CH(RЈ)PPh2. Proton, 13C, 13P and two-dimensional rotating frame Overhauser enhancement 1H
NMR spectra have been used to determine the stereochemical pathways of the reactions and the stereochemistry
of the products. In general the more hindered alkynes undergo monoaddition ultimately to yield
phosphinoalkenes with the Ph2P attached to the carbon bearing the least bulky substituent and cis to the olefinic
proton, while for the less hindered alkynes the trans isomer is formed initially and this then reacts further to give
meso/erythro-diphosphinoalkanes. Bis(o-tolyl)ethyne does not react with Ph2PH under the same conditions.
Crystal structures were determined for E- and Z-Ph P(Ph)C᎐CHPh and show distortions of interbond angles
᎐
2
consistent with the pattern of strain implied by the foregoing reactions. The sulfides of the phosphinoalkenes and
the Mo(CO)4 complexes of the diphosphinoalkanes were also prepared and their 1H, 13C and 31P NMR spectra
recorded. In several cases the pattern of 13CO NMR signals for the complexes was used unambiguously to
determine the stereochemistry of the parent diphosphines.
Base-catalysed anti-Markovnikov additions of diphenylphos-
C
C
phine to substrates with activated carbon–carbon multiple
bonds are of interest because they can lead to a wide range of
bi- and poly-dentate phosphines with versatile co-ordinative
behaviour.1–6 Recently we have shown that these reactions
may provide a potential route to chiral 1,2-diphosphino-
alkanes which find wide application in metal-mediated
asymmetric synthesis. An example is the reaction of diphenyl-
ethyne with 2 equivalents of diphenylphosphine which affords
Ph2PH
Ph2PH
Ph2P
Ph2P
Ph
H
Ph
H
Ph
Ph
Ph2PH
C
C
C
C
HC CH
Ph
Ph
Ph2P
PPh2
1
2
3
the 1,2-diphosphine meso-Ph2PCH(Ph)CH(Ph)PPh2
3 as
Scheme 1
the major and E-Ph PC(Ph)᎐CHPh 1 as a minor product
᎐
2
(Scheme 1).7
OH–
RCH2PPh3+Cl–
+
R′CHO
RCH CHR′
Conclusions from this study were that (i) the first step ini-
tially yields a mixture of the intermediate isomeric alkenes E-
Br2
and Z-Ph PC(Ph)᎐CHPh 1 and 2 (i.e. C-phenyl groups cis and
᎐
2
trans respectively), (ii) only the Z isomer 2 reacts further and
gives the diphosphine 3, (iii) the E isomer 1 is formed both
directly from the parent alkyne and also by isomerisation of its
Z isomer under the reaction conditions used, and (iv) the E
isomer 1 is inert to further addition under the reaction condi-
tions (and also at elevated temperatures) and remains as a by-
product of the reaction.
R
R′
HC CH
Br Br
KOH
RC CR′
Scheme 2 R, RЈ = Aryl
Results and Discussion
We have now prepared ranges of substituted and heterobis-
(aromatic) diarylalkynes in order both to study further the
efficiency and stereoselectivity of such addition reactions of
phosphines and to provide a route to new and unusual chiral
diphosphines and their derivatives. In this paper we report the
synthesis of a series of symmetrical and unsymmetrical methyl-
and phenyl-substituted diphenylalkynes and their subsequent
base-catalysed addition reactions with diphenylphosphine. We
also report the results of comprehensive one- and two-
dimensional NMR studies on the products of these reactions
and on their sulfide and Mo(CO)4 derivatives, together with the
molecular structures of 1 and 2 determined by single-crystal
X-ray diffraction.
(i) Alkyne synthesis
(2-Methylphenyl)phenylethyne [phenyl(o-tolyl)ethyne], (3-
methylphenyl)phenylethyne [phenyl(m-tolyl)ethyne], bis(2-meth-
ylphenyl)ethyne[bis(o-tolyl)ethyne],(2-methylphenyl)(3-methyl-
phenyl)ethyne [(m-tolyl)(o-tolyl)ethyne], and (2-biphenyl)-
phenylethyne were prepared from appropriate starting reagents
using the reaction sequence of Scheme 2. Bis(m-tolyl)ethyne
was prepared from 3-bromotoluene and 2-methylbut-3-yn-2-ol
using a modified palladium coupling method of Rossi and
co-workers.8 Bis(o-tolyl)ethyne could not be prepared by this
latter method presumably due to steric hindrance. In all cases
the final alkynes were obtained after work-up as colourless or
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818
811

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Table 1 Yields of product from the addition of diphenylphosphine to diarylethynes
᎐
Ethyne (RC᎐CRЈ)
᎐
Approx. molar
proportiona (%)
Isolated yield
(%)
R
RЈ
Product
Ph
Ph
1
27
73
85
15
26b
71b
31
9
68
3
Ph
o-Tolyl
4
9
m-Tolyl
Ph
m-Tolyl
Ph
o-Tolyl
5
>95
m-Tolyl
m-Tolyl
2-Biphenyl
10
>95
>95
40
60
—
75
11
70
6
7
57c
57c
—
o-Tolyl
o-Tolyl
No reaction
a Calculated from the integrals of the 31P NMR signals in the reaction mixtures. b Taken from ref. 7. c Compounds 6 and 7 combined.
Table 2 Analytical data (%) for the new isolated species with calcu-
lated values in parentheses
tolyl)ethene 4 and results from the addition of a single equiva-
lent of Ph2PH. The minor product was identified as the diphos-
phine 9 resulting from two successive additions. An analogous
reaction starting from (m-tolyl)(o-tolyl)ethyne yielded solely the
corresponding alkene intermediate E-1-diphenylphosphino-1-
(m-tolyl)-2-(o-tolyl)ethene 5. The isomeric identities of 4 and 5
(and all subsequent new compounds) were established by NMR
spectroscopy (see below). In neither of the preceding reactions
was there any direct evidence for the formation of significant
amounts of the corresponding Z isomer although this can
be inferred indirectly in the former case from the formation
of the diphosphine 9. The reaction of phenyl(m-tolyl)ethyne
under the same conditions led to the formation of 1,2-bis-
(diphenylphosphino)-1-phenyl-2-(m-tolyl)ethane 10 as the sole
isolable product. There was no direct evidence for the formation
of significant amounts of either of the corresponding alkene
intermediates. An analogous reaction starting from bis-
(m-tolyl)ethyne proceeded similarly to afford 1,2-bis(diphenyl-
phosphino)-1,2-bis(m-tolyl)ethane 11. The 31P NMR spectrum
of the reaction mixture showed, in addition to this main prod-
uct, a very small peak (ca. 2% of total) at δ ϩ8.8 which is
tentatively attributed to a trace of the corresponding E-alkene
on the basis of its chemical shift, although this compound was
not isolated from the mixture. Compounds 9, 10 and 11 were
confirmed as being erythro, erythro and meso respectively on the
basis of the 13C NMR spectra of their octahedral Mo(CO)4
derivatives (see below). From the reaction of (2-biphenyl)-
phenylethyne with 2 equivalents of diphenylphosphine a
mixture of the expected E-alkene 6 with, unusually, its corre-
sponding Z isomer 7 was isolated in an approximately 2:3 ratio,
as indicated by 31P NMR spectroscopy. There was no evidence
for the formation of any diphosphine in this reaction. The reac-
tion of bis(o-tolyl)ethyne with diphenylphosphine gave no isol-
able addition products under the same reaction conditions. A
31P NMR spectrum of this reaction mixture showed essentially
all phosphorus to be present either as unchanged diphenyl-
phosphine at ca. δ Ϫ41 or tetraphenyldiphosphane at ca. δ Ϫ16
together with two new peaks at δ ϩ6.5 and Ϫ5.8 (ca. 1 and 4%
relative to Ph2PH) which may be very tentatively assigned as
arising from E-1-diphenylphosphino-1,2-bis(o-tolyl)ethene 8
and meso-1,2-bis(diphenylphosphino)-1,2-bis(o-tolyl)ethane 12
respectively on the basis of their 31P chemical shifts (see discus-
sion of NMR later). When the reaction conditions included a
6 h reflux period a 31P NMR spectrum of the reaction mixture
showed only slightly greater proportions of 8 and 12 (ca. 5%
each relative to Ph2PH). Increased reaction duration at either
room or reflux temperature to as much as 168 h had little
further effect on the relative proportions of these products and
all attempts to separate them from the unchanged diphenyl-
phosphine were unsuccessful.
Compound
C
H
4
5
6
85.8 (85.7)
85.8 (85.7)
87.5 (87.3)
78.2 (79.0)
79.6 (79.2)
83.3 (83.0)
82.4 (83.0)
83.0 (83.0)
61.8 (61.6)
67.0 (66.9)
66.9 (67.2)
6.0 (6.1)
6.4 (6.4)
5.5 (5.7)
5.5 (5.7)
5.9 (5.9)
6.1 (6.1)
5.8 (6.1)
6.1 (6.3)
4.0 (4.2)
4.4 (4.4)
4.3 (4.6)
4s
5s
9
10
11
9m*
10m
11m
* Isolated as a 1:1 dichloromethane solvate to which these figures
apply.
pale yellow viscous oils which were found to be essentially pure
by gas chromatography–mass spectroscopy and used without
further purification.
R1
R2
Ph2P
C1 C2
H
R2
R1
HC CH
PPh2
Ph2P
R1
R2
H
R1
R2
H
H
H
H
H
3
9
10
1
o-Me
m-Me
m-Me
o-Me
4
5
6
8
H
m-Me
H
o-Me
o-Me
o-Me
o-Ph
o-Me
11 m-Me
12 o-Me
R2
Ph2P
C1 C2
R1
R2
R1
H
H
H
o-Ph
2
7
H
(ii) Addition reactions with Ph2PH
Table 1 summarises the outcomes of reactions of diphenyl-
phosphine with the alkynes. Microanalytical data for all isol-
ated species are shown in Table 2. Treatment of phenyl-
(o-tolyl)ethyne with 2 equivalents of diphenylphosphine in
tetrahydrofuran (thf) at room temperature in the presence of
potassium tert-butoxide led to the formation of two isolable
products in an approximately 6:1 molar ratio. The major prod-
uct was identified as E-1-diphenylphosphino-1-phenyl-2-(o-
In all the foregoing reactions 31P NMR spectroscopy of the
reaction mixtures showed a peak at approximately δ Ϫ16 aris-
ing from the by-product tetraphenyldiphosphane. We have
812
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818

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of 4–6. Following (iii) a further attack by Ph2PϪ on the more
(ii)
Ph2PH
hindered carbon of the olefin occurs with a syn orientation (vi)
to yield the erythro-diphosphine. Reaction (ii) does not occur
readily when X is of even moderate bulk, presumably for steric
reasons. Note that the erythro-diphosphine can arise only from
a syn–anti or an anti–syn mechanism and that in fact the latter
can be excluded owing to the established unreactivity of the E-
alkenes which would precede its second step.
X
C
C
Y
Ph2PC(X) CHY
syn or anti
Ph2PH
syn
(i)
Ph2PH
anti
(iii)
X
H
PPh2
X
Y
C
C
C
Y
C
H
PPh2
It is apparent that relatively small steric effects have a strong
influence on the outcome of these reactions. The failure of
bis(o-tolyl)ethyne to react demonstrates the strong retarding
impact of an ortho-methyl group, presumably a consequence of
steric hindrance. This is confirmed by the behaviour of (o-
tolyl)(m-tolyl)ethyne in which only 1 equivalent of diphenyl-
phosphine adds to the triple bond under our reaction condi-
tions and the sole product is the E-alkene in which the bulky
diphenylphosphino group is bonded to C1 rather than the more
hindered C2. The same stereochemical outcome was observed
for the corresponding reaction of phenyl(o-tolyl)ethyne,
although in this case the formation of a small amount of the
diphosphine product was also observed. Conversely, the pres-
ence of a methyl group at the meta position on the parent
alkyne has little apparent effect on the rate or steric course of
the addition reaction as phenyl(m-tolyl)ethyne and bis(m-tolyl)-
ethyne undergo successive addition reactions with diphenyl-
phosphine to produce diphosphines analogous to that from
the reaction with diphenylethyne. Steric effects also appear to
influence the isomerisation of Z- to E-alkenes in the reaction
mixture. It is reasonable to suggest that this involves deproton-
ation at C2 (by Ph2PϪ and/or ButOϪ) followed by reprotonation.
The extreme bulk of the biphenyl group on C2 in 7 appears not
only to prevent further addition but also retards the isomeris-
ation sufficiently to permit the isolation of both isomeric
alkenes resulting from a single addition.
Ph2PH
syn
Ph2PH
anti
(vi)
(v)
(iv)
Ph2PH
H
C
H
C
H
X
C
Y
C
X
Y
H
Ph2PCHX CHYPPh2
Ph2P
PPh2
Ph2P
PPh2
+
+
X
C
Y
C
X
C
H
C
H
H
H
Y
Ph2P
PPh2
Ph2P
PPh2
erythro pair
threo pair
Scheme 3
found this behaviour previously in a wide range of addition and
substitution reactions involving the Ph2PϪ anion, especially in
cases where there is appreciable steric hindrance to the desired
reaction.9 This may account for the relatively low overall yields
in some of the addition reactions reported herein; nevertheless,
the relatively high solubility of tetraphenyldiphosphane
allowed the products to be isolated in the majority of cases.
None of the E-alkenes isolated from the reaction mixtures was
found to undergo further addition reactions with diphenyl-
phosphine under normal or more forcing reaction conditions
nor was there any indication of isomerisation of the Z form.
Addition reactions of diphenylphosphine and other second-
ary phosphines to alkynes have had some attention but most
recent studies centre on reactions carried out under free-radical
conditions. Early reports of ionic additions10 include the
exclusive formation of compound 2 following hydrolysis of the
products of the addition of LiPPh2 to diphenylethyne in thf.10a
In the presence of diethylamine the same reaction was reported
to yield 1 but with butylamine the main product was 2.10b The
use of NaPPh2 in place of LiPPh2 was also reported to yield 2
for several amines. The relative instability of the Z isomer 2
with respect to isomerisation to the E isomer 1 is also docu-
mented.10b Recent reports of ionic additions concentrate on
reactions of co-ordinated Ph2PH with co-ordinated phos-
phinoalkynes11 but the electronic and steric effects have little
As discussed above it is evident that the mechanism of ad-
dition is complex, but it is clear that the extent and stereo-
chemistry of addition are critically dependent on quite small
variations in reaction conditions. The inertness of the E-alkenes
to further addition compared to the reactivity of the Z-alkenes
is difficult to explain in terms of variations in electronic effects
and may be steric in origin. The crystal structures of com-
pounds 1 and 2 (see later) indicate that the immediate environ-
ment of the C᎐C double bond of 2 is less crowded than its
᎐
counterpart in 1 and, in apparent conformity, preliminary
molecular modelling studies9 based on optimised geometrical
models derived from the crystal structures suggest that in 1 any
close approach of Ph2PϪ (and indeed of Ph2PH and Ph2P ) is
ؒ
prevented by steric hindrance from the phenyl groups, whereas
this is not so in 2. These effects may account for the very differ-
ent reactivities of 1 and 2 towards phosphine addition under
the conditions used here.
The isolated vinylphosphines 1, 2, 4–7 reacted smoothly with
an atomic equivalent of elemental sulfur in various solvents
to yield their corresponding phosphine sulfides 1s, 2s, 4s–7s in
virtually quantitative yields as indicated by 31P NMR spec-
troscopy. The diphosphines 9–11 [L] reacted readily with
cis-[Mo(CO)4(pip)2] (pip = piperidine) in chloroform to give
the corresponding cis-[Mo(CO)4L] derivatives 9m–11m which
were isolated as pale yellow air-stable crystals.
relevance to this study.
᎐
Under radical conditions the addition of Ph PH to PhC᎐CR
᎐
2
(R = H or Me) yields primarily but not exclusively Z-alkene
derivatives with the Z isomer increasingly favoured after pro-
longed standing of the reaction mixture,12 an apparent contrast
to the previous case using ionic conditions. The same study also
showed the formation of by-products of the type Z-
Ph PC(R)᎐CHPPh from the reaction of RC᎐CH with Ph PH,
presumably as a result effectively of syn addition of tetra-
phenyldiphosphane, from combination of two Ph2P radicals.
᎐
᎐
2
2
2
ؒ
None of the foregoing reports gives any evidence for the forma-
tion of diphosphines resulting from two successive addition
reactions. but it is known that the alkynes with more electron-
All new isolated phosphines, phosphine sulfides and car-
bonyl complexes were obtained as air-stable solids, soluble in
chlorinated solvents such as dichloromethane or chloroform
but insoluble in alcohols such as methanol or ethanol.
᎐
᎐
withdrawing substituents MeO CC᎐CCO Me and F CC᎐CCF
᎐
᎐
2
2
3
3
can undergo double addition reactions of this sort, probably
under radical conditions, to give diphosphines in each case.13–16
The behaviour found here is summarised in Scheme 3 in which
X is assumed to be bulkier than Y. Initial nucleophilic Michael-
like attack by Ph2PϪ is on the ethynic carbon atom which carries
the least bulky substituent as in (i) (syn) or (iii) (anti). In the
case of (i) no further reaction occurs and the E isomer of the
mono(diphenylphosphino)alkene can be isolated in the cases
(iii) NMR spectroscopy
(a) Phosphinoalkenes. Proton, 13C and 31P NMR data for the
phosphinoalkenes are in Tables 3–6 and the labelling scheme for
1H and 13C NMR assignments is in Scheme 4. The 31P chemical
shifts for the new methyl-substituted derivatives are close to
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818
813

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o
o
m
Table 5 Carbon-13 NMR data for the phosphinoalkenes with methyl
p
P
H2
C1 C2
i
substituents
m
3
4
Compoundb
14
12
9
810
5
13
Parametera
4
4s
5
5s
11
6
7
δ(C1)
δ(C2)
δ(C3)
δ(C4)
δ(C5)
δ(C6)
δ(C7)
δ(C7Ј)c
δ(C8)
δ(C9)
δ(C10)
δ(C11)
δ(C12)
δ(C13)
142.6, 17.8 136.8, 74.7 142.3, 17.6 136.8, 74.1
137.7, 11.9 143.5, 13.3 137.4, 11.3 143.4, 13.5
R
R′
O
140.7, 19.8 135.9, 9.7
C3
Ph2
P1
130.3, 7.9
129.0, 0
127.7, 1.8
129.0, 0
—
131.0, 4.6
128.8, 0
128.3, 2.3
128.8, 0
—
R
O
C4
o-tolyl
m-tolyl
m-tolyl
Ph
9m
10m
11m
C1
C2
H1
R′
Ph
m-tolyl
Mo
C5
P2
H2
O
Ph2
130.3, 7.9
137.5, 4.5
130.0, 0
126.2, 0
127.9, 0
130.7, 0
137.4, 1.0
20.9, 0
131.0, 4.6
134.9, 17.4 137.3, 5.0
130.6, 8.8
131.8, 3.5
135.1, 17.9
129.7, 0
126.0, 0
129.0, 0
130.7, 0
138.4, 4.4
20.9, 0
C6
O
129.7, 0
126.0, 0
128.3, 0
130.7, 0
138.2, 1.0
20.9, 0
129.7, 0
125.9, 0
127.6, 0
130.5, 0
137.1, 1.2
20.7, 0
Scheme 4 The NMR labelling schemes. Upper: for the phosphino-
alkenes 1, 2, 4–7 and their corresponding sulfides (the system is the
same for both E and Z stereochemistries). The substitution patterns
are: 4, 4s, 14-methyl; 5, 5s, 7,14-dimethyl; 6, 6s, 7, 7s, 14-phenyl. Lower:
for the metal complexes 9m–11m
δ(C14)
δ(C14Ј
δ(Ci)
δ(Co)
δ(Cm)
δ(Cp)
)
c
136.5, 11.8 132.2, 84.3 136.3, 11.3 132.2, 84.3
135.2, 20.2 133.3, 10.1 135.0, 20.1 133.4, 10.2
129.4, 7.2
129.9, 0
129.0, 12.3 129.1, 6.3
132.1, 3.2 129.6, 0
128.9, 12.3
132.1, 2.7
Table 3 Phosphorus-31 and proton NMR data for the methyl-
substituted phosphinoalkenes
a Chemical shifts in ppm ( 0.1 ppm) relative to SiMe4 (δ 0.0). b Figures
in italics are values of nJ(31P13C) in Hz ( 0.2 Hz). c CnЈ refers to the
methyl carbon attached to position n.
Compound
Parameter
δ(31P)a
4
4s
5
5s
5.3
48.5
5.3
48.4
Table 6 Carbon-13 NMR data for the phosphinoalkenes without
methyl substituentsa
δ(H2)b
δ(H4)
δ(H5)
δ(H6)
δ(H7)
δ(H8)
δ(H10)
δ(H11)
δ(H12)
δ(H13)
δ(H14)
δ(Ho)
δ(Hm)
δ(Hp)
6.40
7.18
7.06
7.01
7.06
7.18
6.72
6.77
6.94
7.01
2.10
7.46
7.28
7.28
7.58
6.41
6.95
6.94
6.83
2.13
7.11
6.79
6.77
6.94
7.01
2.11
7.48
7.28
7.26
7.62
6.97
7.09
7.12
7.09
6.97
6.76
6.80
7.05
7.09
2.22
7.87
7.43
7.49
6.73
6.94
6.92
2.07
6.70
6.78
6.78
7.03
7.07
2.22
7.83
7.40
7.46
Compoundc
Parameterb
1
1s
2
2s
δ(C1)
142.1, 19.2 135.6, 73.8
138.6, 18.3 144.4, 13.4 145.6, 28.4 146.5, 6.4
140.6, 16.5 136.1, 8.5
192.8, 6.4
129.1, 0
127.6, 1.8
136.7, 6.4
129.9, 0
128.6, 0
127.9, 0
c
136.8, 75.2
δ(C2)
δ(C3)
c
d
d
d
d
d
d
d
d
δ(C4)/δ(C8)
δ(C5)/δ(C7)
δ(C6)
f
f
f
130.5, 8.3
c
126.9, 0
c
c
c
c
c
δ(C9)
135.4, 18.9
δ(C10)/δ(C14)
δ(C11)/δ(C13)
δ(C12)
f
f
f
a In ppm ( 0.2 ppm) to high frequency of external 85% H3PO4 (δ 0.0).
b 3J(31P1H2) = 8.4, 23.9, 7.3 and 21.2 Hz ( 0.2 Hz) for 4, 4s, 5 and 5s
respectively.
δ(Ci)
136.0, 11.9 131.7, 84.8
132.5, 83.8
δ(Co)
δ(Cm)
δ(Cp)
134.9, 19.2 133.2, 10.4 134.0, 18.3 132.4, 10.1
129.1, 6.4
129.6, 0
128.8, 12.2
132.1, 3.0
c
c
128.3, 12.4
131.2, 2.8
Table 4 Phosphorus-31 and selected proton NMR data for the
phosphinoalkenes without methyl substituents
a Compounds 6, 6s,
7
and 7s: δ(C2) [2J(31P13C)] = 137.7[10.1],
143.1[12.8], 146.2[33.0] and 146.2[6.5] respectively; other signals were
not assigned due to unfavourable signal overlaps. b Chemical shifts in
ppm ( 0.1 ppm) relative to SiMe4 (δ 0.0). c Figures in italics are values
of nJ(31P13C) in Hz ( 0.2 Hz). d Assignment uncertain/overlapping
signals [δ 143.6 (d, 3.4), 139.9 (d, 27.8), 137.4 (d, 4.3), 136.9 (d,
11.6 Hz) and 128.9–127.9 (complex overlapping signals)]. Assignment
uncertain [δ 141.7 (d, 10.5), 135.8 (d, 5.0), 130.6 (d, 1.4), 129.3 (d, 4.6),
128.7 (s), 128.5 (d, 1.0), 128.8 (s) and 127.8 (d, 1.4 Hz)]. f Assignment
uncertain [δ 130.8 (s), 130.7 (d, 1.2), 129.5 (s), 129.1 (d, 1.8), 128.7 (s)
and 128.4 (d, 2.5 Hz)].
Compound
δ(31P)a
δ(H2)
3J(31P1H2)b
1
1s
2
2s
6
6s
7
7s
8.7
48.5
6.50
7.65
7.45
7.47
6.16
7.01
7.30
7.35
9.3
23.8
24.1
37.9
7.0
23.2
25.6
39.0
Ϫ7.8
36.8
7.3
48.4
Ϫ5.5
36.4
a In ppm ( 0.2 ppm) to high frequency of external 85% H3PO4 (δ 0.0).
b In Hz ( 0.2 Hz).
studies reported here. Sulfurisation of the phosphorus causes
the H2 signal to move approximately 1.0–1.2 ppm to high fre-
quency and 3J(PH) shows an expected17 increase in magnitude
those of their unsubstituted homologues and are unremark-
able. Stereochemistries were determined by detailed analyses of
1H and 13C spectra together with two-dimensional ROESY
(rotating frame Overhauser enhancement spectroscopy) and
COSY experiments.
in conformity with unaltered stereochemistry about the C᎐C
᎐
double bond. Changes in the parameters for the P-phenyl pro-
tons are also in accord with those found in previous studies.18
In compound 4 the relative positions of the phenyl and o-
tolyl groups on the C1᎐C2 backbone were established in two-
dimensional ROESY experiments.19 These showed a strong
NOE interaction between the methyl proton resonance H14 at δ
2.10 and the olefinic proton resonance at δ 6.40 thus establishing
that the o-tolyl group is attached to C2.
For the E-phosphinoalkenes 1, 4–6 δ(H2) is in the range 6.16–
6.50 with 3J(PH) in the range 7.0–9.3 Hz. The NMR parameters
determined for H2 in 1 was the basis of the original identific-
ation of the P/H cis geometry7 and this has now been confirmed
by the additional NMR experiments and X-ray diffraction
In compound 5 phenyl proton H8 showed an intense NOE
814
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818

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interaction with the methyl resonance at δ 2.13 and no discern-
ible interaction with the methyl resonance at δ 2.11. This there-
fore establishes the signals at δ 2.13 and 2.11 as arising from the
meta- and ortho-methyl substituents respectively. Furthermore,
the olefinic proton resonance H2 shows a strong NOE inter-
action with the ortho-methyl resonance at δ 2.11 and no detect-
able interaction with the meta-methyl resonance at δ 2.13 thus
confirming that the ortho-tolyl group is on C2 and the meta-
tolyl group is on C1.
The two-dimensional ROESY spectra of compounds 4s and
5s show analogous NOE interactions to those in 4 and 5
respectively confirming both the original alkene stereo-
chemistry of their parent phosphorus() species and the reten-
tion of that stereochemistry on sulfurisation. Fig. 1 shows a
relevant portion of the ROESY spectrum obtained for 5s.
7 and 8. The NMR labelling scheme for these species is in
Scheme 4. The unsymmetrical diphosphine 9 has five chem-
ically inequivalent phenyl groups and a single ortho-tolyl
group; the aromatic region of its 1H NMR spectrum was
too complex to analyse. The two backbone protons H1 and H2
3
give multiplets at δ 4.51 and 4.38 with J(HH) of 6.2 Hz. A
slight broadening of these signals possibly arises from
restricted conformational interchange. The somewhat lowered
chemical shift of the methyl group protons (δ 1.70 compared
with 2.0–2.2 for all its precursors and analogues in the syn-
thetic pathway) may be attributable to their being sterically
forced into a position above a neighbouring phenyl group
where they experience the diamagnetic shielding effect of the
ring current. This is consistent with the foregoing suggestion
of restricted conformational mobility. In 10 the inequivalent
backbone CH protons have such similar chemical shifts that
they appear as a doublet at δ 4.16. The resonance of the
methyl protons is at δ 2.01 suggesting that the steric effects
proposed for 9 are negligible here, owing to their more remote
location. The chemical shifts of the methyl and backbone
(b) Diphosphines. Selected NMR data for the diphosphine
ligands 9–11 and their complexes 9m–11m are given in Tables
Table 7 Selected phosphorus-31, carbon-13 and proton NMR data
for the diphosphines. Data for compound 3 are from ref. 7
Compoundb
Parametera
9
10
11
3
δ31P1
Ϫ 3.8
Ϫ 3.8
c
Ϫ 4.5
Ϫ 4.5
c
Ϫ 4.0
Ϫ 4.0
c
Ϫ 5.4
Ϫ 5.4
c
δ31P2
J(31P1᎐31P2)
δ(H1)
4.51, 11.8, 5.6
4.38, 7.0, 6.0
6.2
4.16c,d
4.15, [4.1]
4.15, [4.1]
4.19, [5.4]
4.19, [5.4]
δ(H2)
4.16c,d
3J(H1H2)
δ(CH3)
c
c
c
1.70
2.01
2.0
—
δ(C1)
44.2, 22.0, 18.8
50.0, 21.5, 18.8
20.0
50.0c,d
50.0c,d
21.1
50.0 [<1.0] 50.0 [<1.0]
50.0 [<1.0] 50.0 [<1.0]
δ(C2)
δ(CH3)
21.0
—
a Phosphorus-31 chemical shifts in ppm ( 0.2 ppm) to high frequency
of external 85% H3PO4 (δ 0.0); carbon-13 and proton chemical shifts in
ppm ( 0.1 ppm) relative to SiMe4 (δ 0.0). b Figures in italics are coup-
ling constants to 31P in Hz ( 0.2 Hz) where observed, figures in square
brackets are values of N(31P13C) = |J(31P1᎐13C) ϩ J(31P2᎐13C)|. c Coupling
constant data not determined due to unfavourable signal overlap and/or
molecular symmetry. d Quoted as a mean value.
Fig. 1 Part of the two-dimensional phase-sensitive 500 MHz ROESY
spectrum obtained for compound 5s. The NOE correlations are as
follows: A, H7–H6; B, H7–H8; C, H14–H2; D, H14–H13
Table 8 Selected phosphorus-31, carbon-13 and proton NMR data for the tetracarbonylmolybdenum diphosphine derivatives. Data for compound
3m are from ref. 7
Compoundb
Parametera
9m
10m
11m
68.5
68.5
3m
68.7
68.7
δ31P1
68.9c
70.5d
δ31P2
68.9c
68.0d
J(31P1᎐31P2)
e
e
f
f
δ(H1)
4.98, 37.3, 12.4
4.44, 10.5, 4.9
6.2
1.58
45.6, 16.8, 16.8
54.6, 22.8, 9.3
214.9, 8.5, 8.5
216.2, 26.2, 7.9
217.7, 26.2, 8.5
206.9, 7.0, 7.0
19.9
4.54, 15.9, 11.7
4.50, 11.7, 5.0
5.8
1.91
53.6, 18.9, 13.4
54.1, 20.8, 11.0
215.1, 9.2, 9.2
217.4, 26.2, 8.5
217.7, 26.3, 8.6
207.9, 7.0, 7.0
21.5
4.48, [9.8]
4.48, [9.8]
4.49, [8.8]
4.49, [8.8]
δ(H2)
3J(H1H2)
δ(CH3)
δ(C1)
f
f
—
1.91
53.2, [32.1]
53.2, [32.1]
214.5, 9.2, 9.2
216.9, [17.5]
216.9, [17.5]
207.3, 6.9, 6.9
20.9
54.3, [34.8]
54.3, [34.8]
215.1, 8.8, 8.8
217.4, [16.9]
217.4, [16.9]
207.9, 7.0, 7.0
—
δ(C2)
δ(C3)
δ(C4)g
δ(C5)g
δ(C6)
δ(CH3)
a Phosphorus-31 chemical shifts in ppm ( 0.2 ppm) to high frequency of external 85% H3PO4 (δ 0.0); carbon-13 and proton chemical shifts in ppm
( 0.1 and 0.01 ppm) relative to SiMe4 (δ 0.0). b Figures in italics are coupling constants to 31P in Hz ( 0.2 Hz) where observed. Figures in square
brackets are values of N(31P1H) = |J(31P1᎐1H) ϩ J(31P2᎐1H)| and N(31P13C) = |J(31P1᎐13C) ϩ J(31P2᎐13C)| for 1H and 13C resonances respectively.
c Quoted as a mean value. d Assignment uncertain. e Not observed due to line broadening. f Not available by inspection due to chemical equivalence.
g Assignment of C4 and C5 uncertain and may be interchanged.
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818
815

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Fig. 2 The carbonyl region of the 13C NMR spectrum at 67.8 MHz of
complex 9m showing the two axial and two equatorial CO resonances
protons in the symmetrical diphosphine 11 are almost exactly
the same as those of 10 thus confirming the small steric
demands of methyl groups in meta positions on the C-phenyl
rings.
Co-ordination of compounds 9, 10 and 11 to molybdenum
decreases the shielding of H1 and H2 by about 0.3 ppm and in
the case of 9 also increases their chemical shift separation. This
n
is in addition to a significant divergence in J(31P1H) which
Fig. 3 An ORTEP-type21 diagram of compound 1 viewed normal to
the C(1)᎐C(2) bond vector. Ellipsoids are shown at the 40% probability
level and, in the interests of clarity, hydrogen atoms have been drawn as
circles with an arbitrary small radius
reflects the sensitivity of these parameters to small changes in
conformation and which is most dramatic in 9m.
The 13C NMR spectra of compounds 9–11 each show com-
plex overlapping signals in the aromatic region from which little
useful information can be obtained. For 9 the backbone car-
bons appear as two nearly identical double doublets at δ 44.2
and 50.0. For 10 the two corresponding signals are essentially
isochronous at δ 50.0 and for 11 are truly equivalent also at
δ 50.0. Upon co-ordination, changes in the NMR parameters
of the backbone carbons C1 and C2 parallel those of H1 and
H2 described previously.
The 13C NMR spectra in the carbonyl region of complexes
9m–11m serve unequivocally to identify the stereochemistry of
the parent ligands 9–11 since it is unreasonable to suppose that
co-ordination of phosphorus would be accompanied by inver-
sion at C1 or C2. For 11m the presence of one equatorial and
two axial resonances can arise only from a meso stereo-
chemistry of the co-ordinated ligand and hence of free 11. The
alternative (rac or ) form for the co-ordinated ligand pro-
duces only one axial resonance and we have previously shown
that for the complex of the rac or  isomer of 3 this signal
appears very close to the mean position of the two axial signals
for the meso isomer.7 The lower symmetry of 9 and 10 results in
chemical inequivalence of the two equatorial carbonyl carbons.
These signals are separated by 1.5 and 0.3 ppm for 9 and 10
respectively and this difference is consistent with the closer
proximity of the methyl group in 9. The signals for the two axial
carbonyl carbons in 9m and 10m are separated by 8.0 and 7.2
ppm respectively and are essentially similar to those for 11m
Fig. 4 ORTEP-type21 diagram of 2 viewed normal to the C(1)᎐C(2)
bond vector. Ellipsoids are shown at the 40% probability level and, in
the interests of clarity, hydrogen atoms have been drawn as circles with
an arbitrary small radius
whilst comparable bond lengths, bond angles and torsion
angles are in Table 9. Bond lengths are comparable for the two
structures with the exception of the P᎐C(1) distance which is
some 0.014 Å longer in 2. The most obvious difference in the
structure of the two isomers is the orientation of the PPh2
group relative to the ethylene bond vector.
In compound 1 the orientation of the Ph2P group leads to a
C(11)᎐C(1)᎐P᎐lp dihedral angle (lp being the phosphorus lone
pair in an idealised tetrahedral position) of 45.2Њ. Thus the
two P-phenyl groups are directed away from the phenyl group
on C(1), that is towards the remainder of the molecule and
close to the proton on C(2). In 2 a similar orientation of the
where the separation is 7.2 ppm. The relevant region of the 13
C
spectrum of 9m is shown in Fig. 2. This pattern is consistent
only with an erythro stereochemistry of the co-ordinated
ligand. In analogy with the distinction of the meso and rac
isomers above, the corresponding threo stereochemistry of 9
and 10 would be expected to give rise to nearly isochronous
signals for the two axial carbonyls at a position close to the
mean chemical shift position of the signals from the erythro
isomer. For example, in a sequence of related Mo(CO)4
derivatives of Ph2PCH(Ph)CH(R)PPh2 (R = pyridyl or pyrimi-
dyl) the axial carbonyl resonances in each complex are separ-
ated by ca. 7 and ca. 1 ppm for the erythro and threo isomers
respectively.20
PPh2 group relative to the C᎐C double bond would create
᎐
severe steric interaction with the phenyl group on C(2) which
is in the corresponding position to the proton on C(2) in 1. As
a consequence the PPh2 group in 2 adopts an orientation
where the C(11)᎐C(1)᎐P᎐lp dihedral angle is Ϫ153.4Њ. Since
this is in the opposite sense and approximately opposed to
that of 1 the P-phenyl groups are directed away from the
remainder of the molecule. One consequence of the difference
(iv) Single-crystal X-ray analysis of compounds 1 and 2
Crystals of compounds 1 and 2 suitable for single-crystal X-ray
analysis were obtained by diffusion of methanol into their
respective dichloromethane solutions. The ORTEP-type21
drawings of the molecular structures are shown in Figs. 3 and 4
816
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818

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window function was used in each dimension prior to Fourier
transformation into a 1K × 1K data matrix.
Table 9 Selected bond distances (Å), angles (Њ) and dihedral angles (Њ)
for compounds 1 and 2 with estimated standard deviations (e.s.d.s) in
parentheses
Synthesis of phenyl(o-tolyl)ethyne
1
2
(i) 1-Phenyl-2-(o-tolyl)ethene. To a rapidly stirred suspension
of benzyltriphenylphosphonium chloride (38.9 g, 0.1 mol) in
dichloromethane (150 cm3) was added o-tolualdehyde (11.0 g,
0.1 mol) and then immediately aqueous sodium hydroxide (100
cm3, 18 ). After the vigorous reaction had subsided the mix-
ture was stirred at room temperature for 0.5 h until the yellow
coloration had completely disappeared. The resultant alkene
mixture was poured into water (500 cm3) and extracted with
dichloromethane (3 × 75 cm3). The combined extracts were
washed liberally with water until free of base, dried over mag-
nesium sulfate and the dichloromethane solvent was removed
at low pressure. The crude residue was triturated with cold n-
hexane (3 × 50 cm3), the hexane extracts were filtered and the
solvent was removed at the pump to give a viscous oil contain-
ing a crude mixture of E- and Z-2-methylstilbene (16 g, 83%).
P᎐C(1)
1.8366(14)
1.837(2)
1.833(2)
1.335(2)
1.501(2)
1.475(2)
1.851(2)
1.834(2)
1.838(2)
1.338(2)
1.492(2)
1.484(2)
P᎐C(111)
P᎐C(121)
C(1)᎐C(2)
C(1)᎐C(11)
C(2)᎐C(21)
C(111)᎐P᎐C(1)
C(121)᎐P᎐C(1)
C(111)᎐P᎐C(121)
P᎐C(1)᎐C(2)
P᎐C(1)᎐C(11)
C(11)᎐C(1)᎐C(2)
C(1)᎐C(2)᎐C(21)
105.08(6)
102.09(7)
100.39(6)
123.84(10)
112.26(10)
123.84(13)
129.32(13)
104.35(7)
99.07(7)
102.78(7)
119.52(13)
120.84(11)
119.19(14)
127.9(2)
lp*᎐P᎐C(1)᎐C(11)
45.2
Ϫ153.4
lp*᎐P᎐C(1)᎐C(2)
C(12)᎐C(11)᎐C(1)᎐C(2)
C(22)᎐C(21)᎐C(2)᎐C(1)
Ϫ132.3
16.8
Ϫ65.0(2)
149.7(2)
Ϫ55.4(2)
110.9(2)
(ii) Bromination. The crude mixture was dissolved in carbon
tetrachloride (50 cm3) and heated to approximately 70 ЊC.
Bromine (15 g, 83 mmol) in carbon tetrachloride (50 cm3) was
then added slowly with stirring to the solution over a period of
0.5 h and the mixture was cooled to room temperature. Ad-
dition of methanol (100 cm3) initiated crystallisation which was
accelerated by cooling to 0 ЊC. Filtration of the white solid and
drying under vacuum yielded a crude mixture of the stereo-
isomers of 1,2-dibromo-1-phenyl-2-(o-tolyl)ethane (20 g, 70%).
* lp corresponds to the phosphorus lone pair placed in an idealised
tetrahedral co-ordination position.
between the two orientations is greater exposure of the C᎐C
᎐
bond and the proton on C(2) in 2. The different relative dis-
positions of the two C-phenyl groups within each isomer, in
conjunction with the contrasting PPh2 group orientations,
appear also to impose significantly different degrees of strain
at C(1). In 2 all three interbond angles at C(1) are within 1Њ of
the regular sp2 angle of 120Њ whereas in the more crowded
environment in 1 they are 123.8Њ for P᎐C(1)᎐C(2), 112.3Њ for
P᎐C(1)᎐C(11), and 123.8Њ for C(11)᎐C(1)᎐C(2) respectively.
Interestingly the angular distortions observed in free 1 are
somewhat different to those in the reported [Mn2(CO)9] com-
plex,22 presumably because the relative orientations of the
PPh2 group are different.
(iii) Dehydrobromination. A mixture of the crude dibromides
(20 g, 58 mmol) and potassium hydroxide (20 g, 0.36 mmol) in
dry ethanol (200 cm3) was heated under reflux for 12 h at which
point GC-MS analysis of the mixture showed almost quantita-
tive dehydrobromination of the bromides. After cooling, the
reaction mixture was poured into water (200 cm3) and the
organic components were extracted with dichloromethane
(3 × 100 cm3). The combined extracts were washed with water
and dried with magnesium sulfate and the solvents were
removed under reduced pressure to give the desired alkyne as an
oil. The crude product was distilled rapidly at low pressure to
give the product as a straw coloured viscous liquid (9 g, 80%).
Gas chromatography–mass spectrometry and NMR spec-
troscopy showed the product to be essentially pure and it was
therefore used for addition reactions without further
purification.
Phenyl(m-tolyl)ethyne and (2-biphenyl)phenylethyne were
prepared similarly from benzyltriphenylphosphonium chloride
and the appropriate aldehyde. Bis(o-tolyl)ethyne and (o-
tolyl)(m-tolyl)ethyne were also prepared in a similar manner
from (2-methylbenzyl)triphenylphosphonium chloride and the
appropriate aldehyde. Overall yields were similar in all cases to
that described above. Bis(m-tolyl)ethyne was prepared from 3-
bromotoluene and 2-methylbut-3-yn-2-ol by modification of
Rossi’s method.8
Experimental
General
Diphenylphosphine from the Strem Chemical Company was
used without further purification. All reactions and manipula-
tions involving diphenylphosphine were carried out under an
atmosphere of dry dinitrogen. Tetrahydrofuran was dried over
sodium wire, distilled, and deaerated immediately prior to
use. Tetrakis(triphenylphosphine)palladium(0) was prepared
immediately prior to use using Clouson’s method.23 Benzyl-
triphenylphosphonium chloride was prepared by standard
literature methods involving treatment of benzyl chloride
with triphenylphosphine in refluxing 1,2-dichlorobenzene. (2-
Methylbenzyl)triphenylphosphonium chloride was prepared in
a similar manner from 2-methylbenzyl chloride. Yields were
typically over 90%. Biphenyl-2-carbaldehyde was prepared
from commercially available 2-aminobiphenyl by modification
of established procedures for (i) the conversion into 2-
iodobiphenyl via a standard diazotisation procedure, and (ii)
conversion of the iodide into the aldehyde using butyllithium
and dimethylformamide.24
Addition reactions
Typical procedure. A catalytic amount of potassium tert-
butoxide (ca. 1 mmol) was added to a solution of the alkyne (10
mmol) and diphenylphosphine (20 mmol) in thf (20 cm3). The
mixture was stirred until the potassium tert-butoxide had dis-
solved, and when a permanent orange-red coloration was
apparent the solution was left to stand until 31P NMR spec-
troscopy of the mixture indicated no further reaction was
occurring (usually no more than 2 h). Addition of methanol (20
cm3) and refrigeration induced the formation of a white solid
which was filtered off, washed with methanol, and dried under
vacuum to give the major product in each case (see Table 1 for
yields). Further crops of products were obtained from the
Proton, 13C and 31P NMR spectra were obtained from
CDCl3 solutions by standard techniques using JEOL EX270
and Lambda 500 and Bruker AMX500 spectrometers. Phase-
sensitive (using the time-proportional phase incrementation
method) ROESY spectra were acquired using the sequence 90Њ–
t1–spin lock–acquire(t2) using a spin-locking field given by γB1/
2π ≈ 5000 Hz and a spin-locking (mixing) time of 100–250 ms.
Typically 32 free induction decays were acquired into 1K
data points for each of 512 values of t1 and a shifted sine-bell
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818
817

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Crystallography
Table 10 Crystal data for compounds 1 and 2a
Data were collected on a Stoe STAD14 diffractometer operat-
ing in the ω–θ scan mode using Cu-Kα radiation (λ = 1.541 84
Å) at 293 K for compound 1 and at 160 K for 2. Full details of
crystal data, data collection and structure refinement are given
in Table 10. The structures of both compounds were solved by
direct methods using SHELXS 86.25 Refinement, by full-matrix
least squares on F2 using SHELXL 97,26 was essentially the
same for both compounds. Non-hydrogen atoms were refined
with anisotropic displacement parameters. Restraints were
applied to the phenyl rings so that they remained flat and of
overall C2v symmetry. Hydrogen atoms were constrained to
idealised positions using a riding model.
1
2
Crystal dimensions/mm
Space group
a/Å
b/Å
0.42 × 0.28 × 0.20
P21/c
0.52 × 0.37 × 0.28
C2/c
12.2602(6)
6.0689(3)
27.289(2)
100.484(5)
1996.2(2)
4
1.21
1.248
768
0.788, 0.622
22.2502(10)
11.8137(5)
18.7963(7)
127.833(3)
3902.2(3)
8
1.28
1.277
1536
0.716, 0.556
c/Å
β/Њ
U/Å3
Z
Dc/g cmϪ3
µ/mmϪ1
F(000)
Maximum, minimum
transmission factors
θ Range/Њ
Index ranges
CCDC reference number 186/826.
See http://www.rsc.org/suppdata/dt/1998/811/ for crystallo-
graphic files in .cif format.
3.29–64.61
Ϫ14 р h р 14,
Ϫ6 р k р 6,
Ϫ31 р l р 31
6513
3297 (0.019)
2800
4.47–64.55
Ϫ26 р h р 26,
Ϫ12 р k р 13,
Ϫ21 р l р 19
4874
3036 (0.034)
2936
Acknowledgements
We thank the EPSRC and the Leverhulme Trust for support.
Reflections collected
Unique reflections, n (Rint
Reflections with
Fc2 > 2.0σ(Fc2)
T/K
)
293
1.028
0.0060(3)
0.0308
0.0873
0.0397, 0.4537
0.162, Ϫ0.150
160
1.067
0.001 44(6)
0.0334
0.0822
0.0269, 4.8144
0.321, Ϫ0.306
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Dalton Trans., 1988, 503.
6 J. L. Bookham, W. McFarlane and M. Thornton-Pett, J. Chem. Soc.,
Dalton Trans., 1992, 2353.
Goodness of fit on F2, sb
Extinction coefficient, xc
R1d
wR2e
Weighting parameters a,bf
Largest difference peak
and hole/e ÅϪ3
a Common to both structures: empirical formula C26H21P; M = 364.40;
monoclinic: absorption correction via ψ scans; 4.0 р 2θ р 130Њ: 245
¹
parameters. b s = [w(Fo2 Ϫ Fc2)2/(n Ϫ p)]². c Fc* = kFc[1 ϩ (0.001xFc2λ3/
¹
¹
sin 2θ)]Ϫ⁴. d R1 = Σ Fo| Ϫ |Fc /Σ|Fc|. e wR2 = [Σw(Fo2 Ϫ Fc2)2/Σw(Fo )2]².
2
f w = [σ2(Fo ) ϩ (aP)2 ϩ bP]Ϫ1, where P = (Fo2 ϩ 2Fc2)/3.
2
7 J. L. Bookham, W. McFarlane, M. Thornton-Pett and S. Jones,
J. Chem. Soc., Dalton Trans., 1990, 3621.
8 A. Carpita, A. Lessi and R. Rossi, Synthesis, 1984, 571.
9 J. L. Bookham and W. McFarlane, unpublished work.
10 (a) K. Issleib and K. Jasche, Chem. Ber., 1967, 100, 412; (b)
A. M. Aguiar and T. G. Archibald, Tetrahedron Lett., 1966, 45,
5541.
11 K. Maitra, V. J. Catalano and J. H. Nelson, Bull. Soc. Chim. Fr.,
1997, 134, 471; W. L. Wilson, N. W. Alcock, E. C. Alyea, S. Song
and J. H. Nelson, Bull. Soc. Chim. Fr., 1993, 130, 673; K. Maitra,
V. J. Catalano and J. H. Nelson, J. Organomet. Chem., 1997,
529, 409.
12 T. N. Mitchell and K. Heesche, J. Organomet. Chem., 1991, 409, 163.
13 M. A. Shaw and J. C. Tebby, J. Chem. Soc. C, 1970, 5.
14 W. R. Cullen and D. S. Dawson, Can. J. Chem., 1967, 45, 2887.
15 W. R. Cullen, D. S. Dawson and G. E. Styan, Can. J. Chem., 1965,
43, 3392.
16 W. R. Cullen and W. R. Leader, Can. J. Chem., 1969, 47, 2137.
17 G. A. Mavel, Annu. Rep. N.M.R. Spectrosc., 1972, 5B, 1; J. L.
Bookham, F. Conti, H. C. E. McFarlane and M. Thornton-Pett,
J. Chem. Soc., Dalton Trans., 1994, 1791.
combined methanol washings and filtrate after refrigeration.
Products were purified by recrystallisation from methanol–
dichloromethane. In the case of the reaction of (2-biphenyl)-
phenylethyne with diphenylphosphine the two isomeric
phosphinoalkene products could not be separated by fractional
crystallisation and therefore were analysed as a mixture.
Sulfurisation. Small-scale reactions were performed in CDCl3
solution by weighing stoichiometric amounts of the phosphino-
alkene and elemental sulfur directly into a 5 mm NMR tube.
Virtually quantitative yields of the corresponding phosphine
sulfides were indicated by NMR spectroscopy after agitation
for 0.5 h and the products were unambiguously characterised in
solution but not isolated. Gram-scale preparations of com-
pounds 4s and 5s were achieved by stirring stoichiometric
amounts of the phosphinoalkene and elemental sulfur (ca. 2.5
mmol) in chloroform (20 cm3) for 1 h. Addition of methanol
(20 cm3) followed by refrigeration and filtration gave in each
case analytically pure samples of the corresponding phosphine
sulfide as air-stable colourless crystals in virtually quantitative
yield. These products had identical NMR spectra to those pre-
pared directly in NMR tubes by the previous method.
18 A. Bax and D. G. Davies, J. Magn. Reson., 1985, 63, 207.
19 I. J. Colquhoun and W. McFarlane, J. Chem. Soc., Dalton Trans.,
1982, 1915.
20 J. L. Bookham, unpublished work.
21 P. McArdle, J. Appl. Crystallogr., 1995, 28, 65.
22 K. Henrick, M. McPartlin, J. A. Iggo, A. C. Kemball, M. J. Mays
and P. R. Raithby, J. Chem. Soc., Dalton Trans., 1987, 2669.
23 D. R. Clouson, Inorg. Synth., 1971, 13, 121.
24 See, for example, J. E. Parks, B. E. Wagner and R. H. Holm, Inorg.
Chem., 1971, 10, 2472.
25 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
26 G. M. Sheldrick, SHELXL 97, Program for refinement of crystal
structures, University of Göttingen, 1997.
Complexation. In a typical procedure a solution in chloro-
form (20 cm3) of the diphosphine ligand (2 mmol) and
tetracarbonylbis(piperidine)molybdenum(0) (2 mmol) was
refluxed for 0.25 h. Methanol (10 cm3) was added to the cooled
and filtered reaction mixture to induce crystallisation of a solid
which was recrystallised from methanol–dichloromethane to
give the product as pale yellow crystals (yield > 80% in each
case).
Received 6th October 1997; Paper 7/07210D
818
J. Chem. Soc., Dalton Trans., 1998, Pages 811–818