Butenynyl complexes of iron(II) containing the tripodal tetraphosphine ligand P(CH2CH2PMe2)3

Article abstract of DOI:10.1039/a902784j

The preparation and characterisation of iron(II) η³-but-1-en-3-yn-2-yl complexes [Fe(η³-RC≡C-C=CHR)L]+ [L = P(CH₂CH₂PMe₂)₃, R = Ph 1; R = Bu^t 2; R = p-HC≡CC₆H₄ 3] is reported. The phenyl substituted butenynyl complex 1 was prepared by the reaction of FeCl₂L 5, FeH(Cl)L 6 or [FeH(H₂)L]⁺ 7 with phenylacetylene in alcohol solvent. The coordinated but-1-en-3-yn-2-yl fragment is bound as a σ-vinyl/π-acetylenic ligand. In solution, complex 1 exists as a pair of equilibrating isomers (1a and 1b) which differ in the anchoring mode of the butenynyl ligand i.e. depending on whether the π-bound acetylenic group is cis or trans to the apical phosphorus of L in the octahedral coordination sphere. Assignment of the relative stereochemistry of 1a and 1b was achieved by analysis of the 2D NOESY spectrum. Exchange peaks in the NOESY spectrum also provided information on the mechanism of exchange between 1a and 1b. The crystal structure of 1 showed the solid state structure to be that of the major solution state isomer 1a (π-bound acetylenic group is cis to the apical phosphorus of L). Complex 1 catalyses the stereospecific head-to-head dimerisation of phenylacetylene to Z-1,4-diphenylbut-1-en-3-yne.

Full text of DOI:10.1039/a902784j

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Butenynyl complexes of iron(II) containing the tripodal
tetraphosphine ligand P(CH2CH2PMe2)3
Leslie D. Field,* Barbara A. Messerle,* Ronald J. Smernik, Trevor W. Hambley and
Peter Turner
School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
E-mail: L.Field@chem.usyd.edu.au
Received 8th April 1999, Accepted 16th June 1999
3
3
ϩ
᎐
The preparation and characterisation of iron() η -but-1-en-3-yn-2-yl complexes [Fe(η -RC᎐C–C᎐CHR)L]
᎐
᎐
t
᎐
[L = P(CH CH PMe ) , R = Ph 1; R = Bu 2; R = p-HC᎐CC H 3] is reported. The phenyl substituted butenynyl
᎐
2
2
2
3
6
4
complex 1 was prepared by the reaction of FeCl2L 5, FeH(Cl)L 6 or [FeH(H2)L]ϩ 7 with phenylacetylene in alcohol
solvent. The coordinated but-1-en-3-yn-2-yl fragment is bound as a σ-vinyl/π-acetylenic ligand. In solution, complex
1 exists as a pair of equilibrating isomers (1a and 1b) which differ in the anchoring mode of the butenynyl ligand
i.e. depending on whether the π-bound acetylenic group is cis or trans to the apical phosphorus of L in the octahedral
coordination sphere. Assignment of the relative stereochemistry of 1a and 1b was achieved by analysis of the 2D
NOESY spectrum. Exchange peaks in the NOESY spectrum also provided information on the mechanism of
exchange between 1a and 1b. The crystal structure of 1 showed the solid state structure to be that of the major
solution state isomer 1a (π-bound acetylenic group is cis to the apical phosphorus of L). Complex 1 catalyses
the stereospecific head-to-head dimerisation of phenylacetylene to Z-1,4-diphenylbut-1-en-3-yne.
L1]ϩ.2a–c,e Reaction of the osmium dinitrogen hydrido complex
Introduction
[OsH(N2)L1]ϩ with terminal alkynes also yields butenynyl
The reaction of metal complexes with terminal alkynes to
afford butenynyl complexes is an important C–C bond forming
complexes.2d The reaction proceeds via the vinylidene hydride
complex [OsH(C᎐CHR)L1]ϩ and one equivalent of RCH᎐CH
᎐
᎐
2
reaction. In a number of cases, the free butenyne is sub-
sequently liberated, effectively completing the catalytic cycle of
head-to-head dimerisation of the alkyne.1,2 As part of a wider
study examining the dimerisation (and oligomerisation) of
acetylenes, we have examined a range of metal complexes
where alkyne coupling occurs. Octahedral complexes contain-
ing tripodal tetradentate ligands appear particularly suited to
alkyne dimerisation since the two sites available for alkyne
coordination are constrained by the nature of the ligand to be
mutually cis, facilitating the coupling of the alkyne fragments.
Indeed, both the formation of butenynyl complexes and cat-
alytic head-to-head coupling of terminal alkynes have been
reported for complexes containing the tripodal tetraphosphine
ligands P(CH2CH2PPh2)3 (L1) 82 and P(CH2CH2CH2PMe2)3
(L2) 9.3
is produced as the reaction progresses. Butenynyl complexes of
osmium can also be prepared directly from the dichloro com-
plex OsCl2L1.2d
The reaction of the iron complexes [FeH(X)L1]ϩ (X = N2, H2)
with terminal alkynes affords σ-alkenyl complexes [Fe(HC᎐
᎐
1 ϩ
CHR)L1]ϩ and σ-alkynyl complexes [Fe(C᎐CR)L ] , but these
᎐
᎐
do not react further to give the corresponding butenynyl
complexes.7
We have recently reported8 an efficient and high-yielding
synthesis of the tetradentate ligand P(CH2CH2PMe2)3 (L) 4,
which has facilitated investigation of iron complexes contain-
ing 4.9 Here, we report the synthesis of the iron() butenynyl
3
ϩ
t
᎐
᎐
complexes, [Fe(η -RC᎐CC᎐CHR)L] [R = Ph 1, Bu 2, p-HC᎐
᎐
᎐
᎐
CC6H4 3] and their characterisation by NMR spectroscopy and
X-ray crystallography.
The preparation and characterisation of a number of
butenynyl complexes containing bi- and tetra-dentate phos-
phine ligands have been reported. Iron() dihydrogen hydrido
complexes containing the bidentate phosphines 1,2-bis-
(dimethylphosphino)ethane (dmpe) and 1,2-bis(diethylphos-
phino)ethane (depe) react with terminal alkynes to form
bis(acetylide) complexes in good yield.4 The bis(acetylide)
complexes are protonated to initially form metal vinylidene
complexes which rearrange and couple to form complexes con-
taining coordinated butenynes. For some bis(acetylide) com-
plexes, methanol employed as a reaction solvent is sufficiently
acidic to carry out the protonation, in others, a stronger acid
(e.g. trifluoroacetic acid) is required.5 The dichloro complex
FeCl2(dmpe)2 also reacts with phenylacetylene in the presence
of hexafluorophosphate to give the corresponding butenynyl
complex.6
Results and discussion
Preparation of butenynyl complexes
3
᎐
The iron() diphenylbutenynyl complex [Fe(η -PhC᎐C–C᎐
᎐
᎐
CHPh)L]ϩ 1 was prepared by the reaction of phenylacetylene
with the dichloro complex 5, the chloro hydrido complex 6 or
the dihydrogen hydrido complex 7 in alcohol solvent (Scheme
1). In the reactions of phenylacetylene with 6 and 7, styrene was
observed as a by-product.
+
Ph
P
Fe
P
P
C
PhC
CH
Y
X
P
P
C
Fe
P
ROH
P
C
Reaction of the ruthenium dihydrogen hydrido complex
[RuH(H2)L1]ϩ with terminal alkynes proceeds via two isolable
C
P
X=Cl, Y=Cl 5
X=H, Y=Cl 6
X=H, Y=H2
intermediates, the σ-alkenyl complex [Ru(CH᎐CHR)L1]ϩ and
Ph
H
᎐
1 ϩ
7
᎐
1
the σ-alkynyl complex [Ru(C᎐CR)L ] , to eventually give the
corresponding butenynyl complex [Ru(η -RC᎐C–C᎐CHR)-
᎐
3
᎐
Scheme 1
᎐
᎐
J. Chem. Soc., Dalton Trans., 1999, 2557–2562
2557

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H2a
of the resonances of the minor species at 300 K is due to
H2a
H2
PT
H2
PT
MeB
MeA
MeB
MeA
exchange between the two products at this temperature. The
two species were identified (vide infra) as the isomeric com-
plexes 1a and 1b which differ in the orientation of the butenynyl
ligand with respect to the rest of the molecule. For convenience,
the exchanging mixture of isomeric butenynyl complexes 1a
and 1b is referred to as 1.
H1a
H1a
Ph1
H1
PU
H1
PU
H
H
MeC
Fe
MeC
Fe
PC
PC
H
H
H
H
PT
PT
(a)
Ph2
+
+
1a
1a
Ph1
C
H
P
P
Ph2'
(b)
C
C
P
P
C
Fig. 1 Schematic representation of cross peaks observed between L
and butenynyl ligands in the NOESY spectrum of the major diphenyl-
phenylbutenynyl isomer 1a. (a) Cross peaks between the vinylic proton
and MeA, backbone protons H1 and H2, and between the ortho protons
of Ph2 and MeA indicate that Ph2 lies near to the central phosphorus PC;
(b) cross peaks between the ortho proton of Ph1 and MeA, MeB and
MeC, indicate that Ph1 lies near the terminal phosphorus PU.
Fe
Fe
C
P
C
P
C
C
P
P
Ph2
H
Ph1'
1a
1b
Reaction of the chloro hydrido complex FeH(Cl)L 6 with
tert-butylacetylene afforded the corresponding butenynyl com-
plex 2. In contrast to 1, only one set of resonances was observed
in the 233 K 31P NMR spectrum of 2. This may be due to
the absence of appreciable quantities of the minor product
corresponding to 1b, or fast exchange between isomers even
at this temperature. Reaction of the chloro hydrido complex
FeH(Cl)L 6 with 1,4-diethynylbenzene also afforded the cor-
responding butenynyl complexes 3a and 3b. The 31P NMR
spectrum of 3a,b at both 300 and 233 K were similar to those
of the phenylbutenynyl complexes, with two products observed
at 233 K in the ratio of approximately 8:1. The 31P NMR spec-
tra of 3 and 1 are almost identical and the major and minor
isomers of 3 would therefore correspond to those of the phenyl-
butenynyl complex.
H2a
H2
PT
MeB
MeA
H1a
Ph2
H1
PU
H
MeC
Fe
PT
PC
H
Ph1
1b
Fig. 2 Schematic representation of cross peaks observed between L
and butenynyl ligands in the NOESY spectrum of the minor diphenyl-
butenynyl isomer 1b. Cross peaks between the vinylic proton and MeC,
indicate that Ph2 lies near the terminal phosphorus PU. Cross peaks
between the ortho protons on Ph1 and the ligand backbone protons H1
and H2, and also MeA indicate that Ph1 lies near to the central phos-
phorus PC.
Assignment of stereochemistry in butenynyl complexes
Isomeric butenynyl complexes have been observed for the
ruthenium and osmium systems with L. In these cases no
exchange is apparent in the 300 K 31P NMR spectrum. As
discussed by Bianchini et al.,2b octahedral complexes of L offer
two different sites for the unsymmetrical bidentate butenynyl
ligand and hence two isomers are possible, with the triple bond
trans to either PC or trans to PU. There is also the possibility of
E/Z isomers about the butenynyl double bond, resulting in a
total of four possible isomers (I–IV). A trans stereochemistry
Reaction of phenylacetylene with 6 and 7 was rapid and no
intermediates were detected (by 31P NMR) in either case.
Reaction of 5 with phenylacetylene was significantly slower,
and a number of (uncharacterised) intermediate complexes
were visible if the course of the reaction was followed by
31P NMR. The addition of an ethanol solution of sodium
tetraphenylborate to an ethanol solution of 1 resulted in the
immediate precipitation of the red tetraphenylborate salt of 1.
The tetrafluoroborate salt of 1 was also prepared by the
+
+
R
H
P
Fe
P
P
R
C4
C1
P
P
C3
Ϫ
C2
R
addition of sodium tetrafluoroborate, however, the BF4 salt
Fe
C2
C3
C4
P
P
was more soluble in methanol and ethanol, resulting in
incomplete precipitation. Both the tetrafluoroborate and
tetraphenylborate salts of 1 were soluble in acetone.
C1
R
P
H
The 31P NMR spectrum of 1 (BPh4Ϫ salt in acetone) at room
temperature contains sharp resonances at δ 171.9 (t, PC), 64.4
(t, PU) and 49.5 (dd, PT). For the purposes of identifying the
phosphorus nuclei of the coordinated ligand L, mutually trans
terminal phosphorus nuclei were labelled PT, the central phos-
phorus from which the three arms radiate was labelled PC and
the remaining terminal phosphorus was labelled PU (see Figs. 1
and 2 for a labelled diagram). In complex 1, no spin–spin
coupling was detected between the terminal phosphines, PT and
PU, in contrast with most complexes of L which have been
characterised.9 A smaller set of broadened resonances arising
from a second, minor product, was observed at δ 165.4 (PC),
78.9 (PU) and 54.1 (PT). At 233 K both species gave rise to sharp
resonances in the 31P NMR spectrum. The major species gave
rise to signals at δ 171.7 (t, PC), 65.1 (t, PU) and 50.5 (dd, PT);
the minor species gave rise to resonances at δ 164.8 (dt, PC), 79.3
(dt, PU) and 55.4 (dd, PT). The coupling constant between PT
and PU for the minor species was also small (12.9 Hz). The ratio
of major to minor species was ca. 11:1 at 233 K. The broadness
I
II
+
+
R
R
H
P
Fe
P
P
Fe
P
C4
C1
C3
P
P
C2
H
C2
C3
C4
P
P
C1
R
R
IV
III
about the double bond of the ruthenium2b and osmium2d
complexes of L was assigned (structures I and II) on the basis
of the size of the long range coupling constant 3JC(2)–H(C4)
.
18
The relative stereochemistry of the butenynyl ligand with
respect to L and the stereochemistry about the double bond
for 1a and 1b was determined using 2D NMR COSY and
2558
J. Chem. Soc., Dalton Trans., 1999, 2557–2562

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NOESY experiments. These spectra were recorded on the
1
tetrafluoroborate salt (to avoid complication of H spectra by
resonances of the tetraphenylborate counter ion). Both the
major and the minor isomers exhibited strong cross peaks
between the vinylic proton and the relevant (see below) protons
of L in the NOESY spectrum and were hence assigned a Z
configuration about the butenyne double bond. The major
isomer 1a was found to have structure I whilst the minor isomer
1b was assigned structure II.
In complex 1a, strong NOESY cross peaks from the ortho
protons on Ph1 to MeA, MeB and MeC indicated that the triple
bond was trans to PC. Cross peaks from the olefinic proton, to
MeA, H1 and H2 and from the ortho protons on Ph2 to MeA
confirmed this assignment (Fig. 1). The expected cross peak
from the vinylic proton H to the ortho proton of Ph2 was
obscured by the stronger cross peak between the ortho and meta
protons on Ph2 (δ 7.57 (Ph2 Hmeta), 7.56 (Ph2 Hortho)).
The stereochemistry of the minor isomer 1b was also
determined from the NOESY spectrum and a full spectral
assignment of the 1H NMR spectrum of 1b was achieved
1
despite the large excess of 1a. The H resonances of L were
assigned using the same methodology as was used for other
octahedral complexes of L.9 A strong NOESY cross peak
between the resonance of the vinylic proton and MeC indicated
that the double bond is located trans to PC. This stereo-
chemistry was confirmed by the presence of strong NOESY
cross peaks between the resonances of the ortho protons on Ph1
and H1 and H2 on the backbone of the PP3 ligand (Fig. 2).
Exchange between isomers 1a and 1b
Exchange processes on a timescale similar to the mixing time of
the NOESY experiment (usually 1–10 s) give rise to exchange
cross peaks in the NOESY spectrum. These cross peaks are
easily differentiated from the ‘real’ NOESY cross peaks in small
molecules as they are characteristically of opposite sign. The
NOESY spectrum of the diphenylbutenynyl complexes 1a and
1b acquired at 303 K contains exchange peaks as well as the
expected NOESY cross peaks.
Fig. 3 Aromatic region of the NOESY spectrum (600 MHz, 303 K,
3
ϩ
᎐
acetone-d6) of [Fe(η -PhC᎐C–C᎐CHPh)L] 1 (BPh4 salt). Negative
᎐
᎐
cross peaks are represented by dashed contours, positive peaks (due to
exchange) are represented as solid contours.
1
The H NMR spectrum of 1 (303 K, 600 MHz) contained
resonances due to the two isomers 1a and 1b, although
the resonances for the minor isomer 1b were significantly
broadened by exchange. The NOESY spectrum acquired at
303 K indicated that exchange processes were occurring within
as well as between the two isomeric complexes. Each of the
isomers 1a and 1b has three methyl resonances and exchange
peaks are present between all of the methyl resonances of L
(a six site exchange). Exchange peaks were also observed within
and between the methylene resonances of L of both isomers.
In the aromatic region of the 2D NOESY spectrum acquired
at 303 K (Fig. 3), more specific exchange was observed. An
exchange peak was observed between the vinylic proton of
the major isomer and the corresponding vinylic proton in the
minor isomer. Exchange peaks were also observed between
the alkyne-bound phenyl group in the major isomer (Ph1)
and the alkyne-bound phenyl group in the minor isomer
(Ph1Ј), and between the corresponding alkene-bound phenyl
groups Ph2 and Ph2Ј (Fig. 4).
Ph1
P
Fe
P
P
Fe
P
H'
Ph2'
P
P
P
P
H
Ph2
Ph1'
1a
1b
Fig. 4 Schematic representation showing the exchange observed in the
303 K NOESY spectrum between H-o of 1a and HЈ-o of 1b, Ph1 of 1a
and Ph1Ј of 1b, and Ph2 of 1a and Ph2Ј of 1b.
+
+
+
Ph1
P
Ph
P
H
P
Ph2'
P
P
P
Fe
Fe
Fe
P
P
P
Ph
H
P
P
Ph1'
P H Ph2
The most probable mechanism for the exchange involves the
decoordination of the acetylene of the butenynyl ligand to give
complex 10 (where the butenyne is coordinated by the σ-bond
to the vinylic carbon) followed by rotation around the metal–
carbon bond and re-coordination of the alkyne to give the
other stereoisomer (Scheme 2). There is ample precedent for the
existence of η1-bound butenynyl complexes, including X-ray
crystal structures.1a,b
10
1b
1a
Scheme 2
1. The structure determination shows the solid state structure to
be the same as that determined for the major isomer 1a by 2D
NMR methods (Fig. 5). The crystal data parameters are
summarised in Table 1. Selected bond lengths and angles are
listed in Tables 2 and 3.
Comparison of the structure of 1a with that of the tri-
phenylphosphine chloro complex [FeCl(PPh3)L]BPh4 119a
shows the Fe–L fragment to be similar for both complexes,
despite the different co-ligands (Table 2). Fe–P bond lengths
3
᎐
X-Ray crystallography of [FeL(ꢀ -PhC᎐C–C᎐CHPh)]BPh 1a
᎐
᎐
4
Diffraction quality crystals were obtained by slow evaporation
of a saturated acetone solution of the tetraphenylborate salt of
J. Chem. Soc., Dalton Trans., 1999, 2557–2562
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Table 2 Comparison of selected bond lengths (Å) and angles (Њ) in
3
᎐
the FeL fragments of [Fe(η -PhC᎐C–C᎐CHPh)L]BPh4 1a and [FeCl-
᎐
᎐
(PPh3)L]BPh4 119a
+
Ph
Ph
+
PT
PT
Fe
PU
PC
PU
PPh3
Cl
Fe
PT
PC
PT
H
11
1a
1a
119a
Fe–PC
Fe–PU
Fe–PT(P1)
Fe–PT(P4)
2.140(2)
2.218(2)
2.266(2)
2.280(2)
2.202(2)
2.234(2)
2.312(2)
2.312(2)
Fig. 5 ORTEP plot (25% thermal ellipsoids, non-hydrogen atoms) of
PC–Fe–PU
87.45(8)
83.32(7)
83.58(7)
99.38(7)
93.84(7)
160.91(7)
83.85(9)
83.66(9)
83.24(9)
98.71(9)
93.40(9)
161.07(9)
3
[Fe(η -PhC᎐C–C᎐CHPh)L]ϩ 1a (BPh4 salt).
᎐
᎐
᎐
PC–Fe–PT(P1)
PC–Fe–PT(P4)
PU–Fe–PT(P1)
PU–Fe–PT(P4)
PT–Fe–PT
3
ϩ
᎐
Table 1 Crystallographic data for [Fe(η -PhC᎐C–C᎐CHPh)L] 1a
᎐
᎐
(BPh4 salt)
Empirical formula
Formula weight
C52H61BFeP4
876.61
Table 3 Comparison of bond lengths (Å) and angles (Њ) in the
Crystal system
Space group
Z
Triclinic
P1
2
3
᎐
metal–butenynyl fragments of [Fe(η -PhC᎐C–C᎐CHPh)L]BPh4 1a,
᎐
᎐
¯
3
3
[Fe(η -PhC᎐C–C᎐CHPh)(dmpe)2]BPh4 125b,c and [Ru(η -Me3SiC᎐C–
᎐
᎐
᎐
᎐
᎐
C᎐CHSiMe3)L1]BPh4 132a
᎐
Lattice Parameters:
a/Å
b/Å
c/Å
α/Њ
13.459(4)
13.517(6)
13.843(6)
76.75(4)
74.45(4)
78.76(4)
2337(2)
21.0
Ph
+
+
+
Ph
SiMe3
Ph
Ph
C1
C2
P
Fe
P
PT
PT
C1
C1
PU
PC
PU
PC
P
β/Њ
Fe
Ru
C2
C2
Ph
P
γ/Њ
C3
C4
C3
C3
C4
V/Å3
PT
PT
C4
T/ЊC
H
H
Ph
H
SiMe3
µ(Mo-Kα)/cmϪ1
4.935
1a
12
13
No. of reflections measured
Total
Unique
8595
8218
1a
125b,c
132a
Rint
0.030
0.053, 0.043
M–C1
M–C2
M–C3
C1–C2
C2–C3
C3–C4
2.176(6)
2.071(5)
1.986(5)
1.250(7)
1.380(7)
1.340(7)
2.309(8)
2.093(7)
1.985(7)
1.249(9)
1.396(10)
1.338(9)
2.485(3)
2.234(3)
2.144(3)
1.247(5)
1.392(5)
1.335(5)
Residuals: R, Rw
for 1a are slightly shorter than those of 11. The bond angles are
similar, with deviations from the octahedral angles of 90 and
180Њ brought about by the small natural bite angle of L.
A number of η3-butenynyl complexes have been reported
in the literature, including X-ray structures of complexes of
tungsten,19 iron,5b,c ruthenium2a,20 and osmium.21 The most
relevant structures to compare with that of 1a are the iron()
η3-1,4-diphenylbutenynyl complex 12,5b,c containing two dmpe
ligands, and the ruthenium() η3-1,4-bis(trimethylsilyl)-
butenynyl complex 132a containing the tripodal tetradentate
phosphine L1 8 (Table 3). The structures of 1a and 12 are very
similar. The Fe–C1 bond is slightly longer in 12, as is the C2–C3
bond. The C1–C2–C3 bond angle is smaller in 1a than in 12.
The ruthenium butenynyl complex 13 exhibits the same
regio- and stereo-chemistry as 1a, with the alkyne trans to the
central phosphorus and the metal trans to the non-hydrogen
substituent on the double bond. The metal–butenynyl bonds
are longer for 13, as would be expected for the larger
second-row metal. Bond lengths in the butenynyl fragment in 13
are similar to those of 1a and 12, however, 13 has a smaller
R–C1–C2 bond angle and a larger C1–C2–C3 bond angle.
R–C1–C2
C1–C2–C3
C2–C3–C4
150.7(7)
144.4(6)
136.7(5)
152.9(7)
149.1(7)
132.5(7)
142.0(3)
154.0(3)
133.5(3)
slow formation of 1,4-diphenylbut-3-en-1-yne, which was
identified by GC–MS and by H NMR. Only the Z isomer2c
1
was formed in the reaction and the butenynyl complex 1a was
the only iron complex detected by 31P NMR during the course
of the reaction. The reaction rate for this reaction at 80 ЊC was
approximately one turnover per day (from the 1H NMR
spectrum). This turnover rate is slow compared with other
systems, and the reaction was not further investigated.
Conclusions
3
ϩ
᎐
The iron() butenynyl complexes [Fe(η -RC᎐C–C᎐CHR)L]
(R = Ph 1; R = Bu 2; R = p-HC᎐CC H 3) have been prepared.
᎐
᎐
t
᎐
᎐
6
4
Complex 1 exists as a pair of isomers (1a and 1b) which differ
in the stereochemistry of binding of the butenynyl ligand.
Assignment of the relative stereochemistry of 1a and 1b was
achieved by analysis of the 2D NOESY spectrum. The stereo-
isomers 1a and 1b are in equilibrium and exchange peaks in
the NOESY spectrum provided information on the mechanism
of exchange. A crystal structure of 1a showed the solid state
Catalytic dimerisation of phenylacetylene
A number of transition metal complexes are catalysts for the
head-to-head dimerisation of terminal alkynes to 1,4-disub-
stituted butenynes,1,2 including the ruthenium complex 13.
Reaction of 1 with an excess of phenylacetylene results in the
2560
J. Chem. Soc., Dalton Trans., 1999, 2557–2562

View Article Online
3
ϩ
᎐
structure to be that of the major solution state isomer. Com-
plex 1 catalyses the stereospecific head-to-head dimerisation of
phenylacetylene to Z-1,4-diphenylbut-1-en-3-yne.
(20 ml) and dried in vacuo to yield [Fe(η -PhC᎐C–C᎐CHPh)L]
᎐ ᎐
1 (BPh4 salt) (72 mg, 94%), mp 242–244 ЊC.
The tetrafluoroborate salt of 1 was also prepared in an
analogous way using sodium tetrafluoroborate in the place of
sodium tetraphenylborate. MS (ϩ CI, CH4) m/z (>150): 558
(M ϩ 1, 14), 557 (M, 36), 388 (10), 363 (30), 233 (14), 206 (17),
205 (95), 165 (100). IR νmax (Nujol): 1578w, 1592w.
Experimental
All synthetic manipulations involving air sensitive materials
were carried out under an inert atmosphere of argon in an
argon filled dry box or under a nitrogen atmosphere using
standard Schlenk techniques. THF, benzene and hexane were
dried over sodium before distillation from sodium and benzo-
phenone under nitrogen. Ethanol and methanol were distilled
from magnesium under nitrogen. The iron() dichloride com-
plex FeCl2L 5,9a the iron() chloro hydrido complex FeH(Cl)L
69a and the iron() dihydrogen hydrido complex [FeH(H2)L]ϩ
Major isomer 1a. 31P-{1H} NMR (BF4 salt, 162 MHz,
2
acetone-d6, 300 K): δ 171.9 (t, 1P, PC, JP(C)–P(T) = 26.2), 49.5
(dd, 2P, PT, 2JP(T)–P(U) = 34.8 Hz), 64.4 (t, 1P, PU). 31P-{1H} NMR
(BF4 salt, 162 MHz, acetone-d6, 233 K): δ 171.7 (t, 1P, PC,
2JP(C)–P(T) = 25.8), 50.5 (dd, 2P, PT, JP(T)–P(U) = 35.3 Hz), 65.1 (t,
2
1P, PU).
1H-{31P} NMR spectrum (600 MHz, acetone-d6, 303 K): δ
1.95, 2.56 (2 × m, 2 × 2H, –PCCH2CHHPT–), 2.61, 2.86 (2 × m,
2 × 2H, –PCCHHCH2PT–), 2.27 (m, 2H, –PCCH2CH2PU–),
2.10 (m, 2H, –PCCH2CH2PU–), 0.92, 1.29 [2 × s, 2 × 6H,
2 × P (CH )], 1.85 [s, 6H, P (CH ) ], 7.51 (s, 1H, C᎐CH),
7.84 (d, 2H, CCPhortho), 7.70 (d, 2H, CCPhmeta), 7.62 (t, 1H,
CCPhpara), 7.99 (d, 2H, C᎐CHPh ), 7.57 (d, 2H, C᎐CH-
1
69c were prepared using previously reported methods. H, 13C
and 31P NMR spectra were recorded on Bruker AMX400 or
AMX600 spectrometers at the temperatures quoted. 1H and 13
C
᎐
T
3
U
3 2
chemical shifts were internally referenced to residual solvent
resonances. 31P spectra were referenced to external neat tri-
methyl phosphite at δ 140.85. IR spectra were recorded on a
Perkin-Elmer 1600 series FTIR. Mass spectra were recorded
on a Finnigan MAT TSQ-46 (San Jose, CA, USA) spectrometer
equipped with a desorption probe, with a source temperature of
140 ЊC and an electron energy of 100 eV. Chemical ionisation
(CI) was used, with methane (>99.999%) as the ionisation gas.
Elemental analyses were carried out at the Joint Elemental
Analysis Facility, The University of Sydney. Melting points
were recorded on a Gallenkamp heating stage and are
uncorrected.
᎐
᎐
ortho
Phmeta), 7.39 (t, 1H, C᎐CHPhpara).
᎐
1H-{31P} NMR (BF4 salt, 600 MHz, acetone-d6, 240 K): δ
1.91, 2.51 (2 × m, 2 × 2H, –PCCH2CHHPT–), 2.57, 2.84 (2 × m,
2 × 2H, –PCCHHCH2PT–), 2.24 (m, 2H, –PCCH2CH2PU–),
2.05 (m, 2H, –PCCH2CH2PU–), 0.87, 1.26 [2 × s, 2 × 6H,
2 × P (CH )], 1.81 [s, 6H, P (CH ) ], 7.56 (s, 1H, C᎐CH), 7.84
(d, 2H, CCPhortho), 7.69 (d, 2H, CCPhmeta), 7.61 (t, 1H, CC-
Phpara), 7.99 (d, 2H, C᎐CHPh ), 7.56 (d, 2H, C᎐CHPhmeta),
᎐
T
3
U
3 2
᎐
᎐
ortho
7.37 (t, 1H, C᎐CHPhpara).
᎐
13C-{1H} NMR (chloride salt, 101 MHz, methanol-d4,
1
300 K) δ 10.0 [t, –PT(CH3), JP(T)–C = 11.4], 19.0 [t, –PT(CH3),
1JP(T)–C = 7.6], 21.2 [d, –PU(CH3)2, JP(U)–C = 22.9], 26.3 (dt,
1
–PTCH2CH2PC–, 1JP(C)–C = 21.6, 2JP(T)–C = 7.6), 32.9 (dt, –PTCH2-
Crystal structure determination
1
2
CH2PC–, JP(T)–C = 16.5, JP(C)–C = 13.4), 29.1 (dd, –PUCH2CH2-
PC–, JP(C)–C = 24.2, JP(U)–C = 15.9), 34.2 (dd, –PUCH2CH2PC–,
JP(U)–C = 29.2, JP(C)–C = 11.4), 42.6 (m, PhC᎐C–, JP–C < 2.5),
122.1 (dd, PhC᎐C–, JP(C)–C = 10.1, JP(U)–C = 7.0), 165.4 (ddt,
Fe-C᎐CHPh, JP(C)–C = 10.2, JP(U)–C = 10.2, JP(T)–C = 16.5), 134.2
(d, Fe-C᎐CHPh, J = 1.3), 131.3 (s, –C᎐CPhortho), 130.5 (s,
–C᎐CPh ), 129.6 (s, –C᎐CPh ), 126.7 (s, –C᎐CHPhortho),
130.3 (s, –C᎐CHPh ), 128.0 (s, –C᎐CHPhpara), 133.0 (d, Phipso
The crystallographic data for 1a (BPh4 salt) are summarised
in Table 1. A red–orange crystal of 1a having approximate
dimensions of 0.42 × 0.32 × 0.07 mm was mounted on an
Enraf-Nonius CAD4 diffractometer employing graphite
monochromated Mo-Kα radiation. Triclinic cell constants were
obtained from a least-squares refinement against the setting
angles of 25 reflections in the range 16 < 2θ < 27Њ. Diffraction
data were collected at a temperature of 21 1 ЊC using ω–θ
scans to a maximum 2θ value of 50Њ. The intensities of three
representative reflections measured every hour did not change
significantly during the course of the data collection. The
data were corrected for Lorentz, polarisation and absorption
(analytical) effects.
1
2
1
2
᎐
᎐
᎐
᎐
᎐
᎐
᎐
᎐
P–C
᎐
᎐
᎐
᎐
᎐
meta
para
,
᎐
᎐
meta
JP–C = 2.5), 139.1 (apparent q, Phipso, JP–C = 1.9 Hz).
Minor isomer 1b. 31P-{1H} NMR (BF4 salt, 162 MHz,
acetone-d6, 300 K): δ 165.4 (br, 1P, PC), 54.1 (dd, 2P, PT,
2JP(C)–P(T) = 30.5, 2JP(T)–P(U) = 39.1 Hz), 78.9 (br, 1P, PU).
31P-{1H} NMR (BF4 salt, 162 MHz, acetone-d6, 233 K):
2
2
All calculations were performed using the teXsan10 crystallo-
graphic software package. The structure was solved by direct
methods11 and expanded using Fourier techniques.12 Neutral
atom scattering factors were taken from Cromer and Waber.13
Anomalous dispersion effects were included in the structure
factor calculation,14 and the values for ∆fЈ and ∆f Љ were those
of Creagh and McAuley.15 The values for the mass attenuation
coefficients are those of Creagh and Hubbell.16 Non-hydrogen
atoms were refined anisotropically and the hydrogen atoms
were included in the full matrix least squares refinement at
calculated positions with group temperature factors. An
ORTEP17 representation of the complex is shown in Fig. 5.
CCDC reference number 186/1518.
δ 164.8 (t, 1P, PC, JP(C)–P(T) = 30.5, JP(C)–P(U) = 12.9), 55.4 (dd,
2P, PT, 2JP(T)–P(U) = 39.1 Hz), 79.3 (t, 1P, PU).
1H-{31P} NMR (BF4 salt, 600 MHz, acetone-d6, 303 K):
δ 2.00, 2.31 (2 × m, 2 × 2H, –PCCH2CHHPT–), 3.02, 3.12
(2 × m, 2 × 2H, –PCCHHCH2PT–), 2.44 (m, 2H, –PCCH2-
CH2PU–), 2.10 (m, 2H, –PCCH2CH2PU–), 0.68, 1.14 [2 × s,
2 × 6H, 2 × PT(CH3)], 2.01 [s, 6H, PU(CH3)2], 7.84 (s, 1H,
C᎐CH), 8.02 (d, 2H, CCPhortho), 7.68 (d, 2H, CCPhmeta), 7.52 (t,
᎐
1H, CCPhpara), 8.14 (d, 2H, C᎐CHPh ), 7.63 (d, 2H, C᎐CH-
᎐
᎐
ortho
Phmeta), 7.42 (t, 1H, C᎐CHPhpara).
᎐
1H-{31P} NMR (BF4 salt, 600 MHz, acetone-d6, 240 K): δ
1.97, 2.29 (2 × m, 2 × 2H, –PCCH2CHHPT–), 3.00, 3.09 (2 × m,
2 × 2H, –PCCHHCH2PT–), 2.39 (m, 2H, –PCCH2CH2PU–),
2.05 (m, 2H, –PCCH2CH2PU–), 0.64, 1.12 [2 × s, 2 × 6H,
2 × P (CH )], 2.07 [s, 6H, P (CH ) ], 7.85 (s, 1H, C᎐CH),
8.02 (d, 2H, CCPhortho), 7.68 (d, 2H, CCPhmeta), 7.52 (t, 1H,
CCPhpara), 8.14 (d, 2H, C᎐CHPh ), 7.67 (d, 2H, C᎐CH-
See http//www.rsc.org/suppdata/dt/1999/2557/ for crystallo-
graphic files in .cif format.
᎐
T
3
U
3 2
᎐
᎐
ortho
Preparations
Phmeta), 7.50 (t, 1H, C᎐CHPhpara).
᎐
3
؉
᎐
[Fe(ꢀ -PhC᎐C–C᎐CHPh)L] 1. Phenylacetylene (33 mg, 320
᎐
᎐
3
t
t
؉
᎐
µmol) was added to a stirred solution of FeH(Cl)L 6 (34 mg,
87 µmol) in methanol (10 ml), resulting in a colour change from
yellow to red. On addition of sodium tetraphenylborate (40 mg,
120 µmol) in methanol (5 ml), a red precipitate formed. The
crude product was isolated by filtration, washed with methanol
[Fe(ꢀ -Bu C᎐C–C᎐CHBu )L] 2. tert-Butylacetylene (10 mg,
᎐ ᎐
120 mmol) was added to a stirred solution of FeH(Cl)L
6 (ca. 10 mg, 26 µmol) in methanol (5 ml), resulting in a
change from yellow to dark orange. On addition of sodium
tetraphenylborate (20 mg, 60 µmol) in methanol (5 ml), an
J. Chem. Soc., Dalton Trans., 1999, 2557–2562
2561

View Article Online
Inorg. Chim. Acta, 1994, 220, 5; (d) C. Bianchini, P. Frediani,
orange precipitate formed. The crude product was isolated by
D. Masi, M. Peruzzini and F. Zanobini, Organometallics, 1994, 13,
4616; (e) C. Bianchini, Pure Appl. Chem., 1991, 63, 829.
3 L. Dahlenburg, K.-M. Frosin, S. Kerstan and D. Werner,
J. Organomet. Chem., 1991, 407, 115.
filtration, washed with methanol (10 ml) and dried in vacuo to
3
t
t
ϩ
᎐
yield [Fe(η -Bu C᎐C–C᎐CHBu )L] 2 (BPh salt).
᎐
᎐
4
31P-{1H} NMR (BPh4 salt, 162 MHz, acetone-d6, 300 K):
2
δ 174.5 (t, 1P, PC, JP(C)–P(T) = 25.3), 48.2 (dd, 2P, PT,
4 L. D. Field, A. V. George, E. Y. Malouf, I. H. M. Slip and T. W.
Hambley, Organometallics, 1991, 10, 3842.
2JP(T)–P(U) = 35.3), 60.40 (t, 1P, PU). 31P-{1H} NMR spectrum
(BPh4 salt, 162 MHz, acetone-d6, 233 K): δ 174.0 (t, 1P, PC,
5 (a) L. D. Field, A. V. George, G. R. Purches and I. H. M. Slip,
Organometallics, 1992, 11, 3019; (b) A. Hills, D. L. Hughes,
M. Jimenez-Tenorio, G. J. Leigh, C. A. McGeary, A. T. Rowley,
M. Bravo, C. E. McKenna and M.-C. McKenna, J. Chem. Soc.,
Chem. Commun., 1991, 522; (c) D. L. Hughes, M. Jimenez-Tenorio,
G. J. Leigh and A. T. Rowley, J. Chem. Soc., Dalton Trans., 1993,
3151.
6 L. D. Field, A. V. George and T. W. Hambley, Inorg. Chem., 1990,
29, 4565.
7 (a) C. Bianchini, A. Mealli, M. Peruzzini, F. Vizza and F. Zanobini,
Organometallics, 1989, 8, 2080; (b) C. Bianchini, A. Meli,
M. Peruzzini, P. Frediani, C. Bohanna, M. A. Esteruelas and L. A.
Oro, Organometallics, 1992, 11, 138.
2JP(C)–P(T) = 24.8), 49.1 (dd, 2P, PT, JP(T)–P(U) = 35.3 Hz), 61.0 (t,
2
1P, PU).
3
؉
᎐
᎐
᎐
᎐
[Fe{ꢀ -HC᎐CC H C᎐C–C᎐CH(C H )C᎐CH}L]
3. 1,4-
᎐
᎐
᎐
6
4
6
4
Diethynylbenzene (10 mg, 80 µmol) was added to a stirred
solution of FeH(Cl)L 6 (ca. 10 mg, 26 µmol) in methanol
(5 ml), resulting in a change from yellow to red. On addition of
sodium tetraphenylborate (20 mg, 60 µmol) in methanol (5 ml)
a red precipitate formed. The crude product was isolated by
filtration, washed with methanol (10 ml) and dried in vacuo
3
ϩ
᎐
᎐
᎐
to yield [Fe{η -HC᎐CC H C᎐C–C᎐CH(C H )C᎐CH)L]
3
8 N. Bampos, L. D. Field, B. A. Messerle and R. J. Smernik, Inorg.
Chem., 1993, 32, 4084.
᎐
᎐
᎐
᎐
6
4
6
4
(BPh4 salt).
Major isomer 3a. 31P-{1H} NMR (BPh4 salt, 162 MHz,
9 (a) L. D. Field, B. A. Messerle, R. J. Smernik, T. W. Hambley and
P. Turner, Inorg. Chem., 1997, 36, 2884; (b) L. D. Field, B. A.
Messerle and R. J. Smernik, Inorg. Chem., 1997, 36, 5984; (c) R. J.
Smernik, PhD Thesis, 1996, The University of Sydney.
10 teXsan: Crystal Structure Analysis Package, Molecular Structure
Corporation, The Woodlands, Texas, 1985 and 1992.
11 SHELX86: G. M. Sheldrick, in Crystallographic Computing 3, eds.
G. M. Sheldrick, C. Kruger and R. Goddard, Oxford University
Press, 1985, pp. 175–188.
12 DIRDIF94: P. T. Beurskens, G. Admiraal, G. Beurskens, W. P.
Bosman, R. de Gelder, R. Israel and J. M. M. Smits, The DIRDIF-
94 program system, Technical Report of the Crystallography
Laboratory, University of Nijmegen, 1994.
2
acetone-d6, 300 K): δ 171.0 (t, 1P, PC, JP(C)–P(T) = 26.7,
2
2JP(C)–P(U) = 4.3), 48.9 (dd, 2P, PT, JP(T)–P(U) = 35.8 Hz), 63.7 (t,
1P, PU).
31P-{1H} NMR (BPh4 salt, 162 MHz, acetone-d6, 233 K):
δ 170.5 (t, 1P, PC, 2JP(C)–P(T) = 25.3, 2JP(C)–P(U) = 4.3 ), 49.9 (dd, 2P,
PT, 2JP(T)–P(U) = 36.2 Hz), 64.2 (t, 1P, PU).
Minor isomer 3b. 31P-{1H} NMR (BPh4 salt, 162 MHz,
2
acetone-d6, 233 K): δ 163.7 (t, 1P, PC, JP(C)–P(T) = 30.5,
2JP(C)–P(U) = 12.8), 55.5 (dd, 2P, PT, 2JP(T)–P(U) = 36.2 Hz), 78.7 (t,
1P, PU).
13 D. T. Cromer and J. T. Waber, International Tables for X-ray
Crystallography, The Kynoch Press, Birmingham, 1974, vol. 4, Table
2.2A.
14 J. A. Ibers and W. C. Hamilton, Acta Crystallogr., 1964, 17, 781.
15 D. C. Creagh and W. J. McAuley, International Tables for Crys-
tallography, ed. A. J. C. Wilson, Kluwer Academic Publishers,
Boston, 1992, vol. C, Table 4.2.6.8, pp. 219–222.
16 D. C. Creagh and J. H. Hubbell, International Tables for
Crystallography, ed. A. J. C. Wilson, Kluwer Academic Publishers,
Boston, 1992, vol. C, Table 4.2.4.3, pp. 200–206.
17 C. K. Johnson, ORTEP, A Thermal Ellipsoid Plotting Program,
Report ORNL-5138, Oak Ridge National Laboratories, Oak Ridge,
TN, 1976.
Acknowledgements
We gratefully acknowledge financial support from the
Australian Research Council, the Australian Government for
an Australian Postgraduate Award (R. J. S.) and the University
of Sydney for an H. B. and F. M. Gritton Award (R. J. S.).
References
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Paper 9/02784J
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J. Chem. Soc., Dalton Trans., 1999, 2557–2562