Acetylide-bridged organometallic oligomers via the photochemical metathesis of methyl-iron(II) complexes

Article abstract of DOI:10.1021/ja011105k

The acetylido methyl iron(II) complexes, cis/trans-[Fe(dmpe)₂(C≡R)(CH₃)] (1) and trans-[Fe(depe)₂(C≡CR)(CH₃)] (2) (dmpe = 1,2-dimethylphoshinoethane; depe = 1,2-diethylphosphinoethane), were synthesized by transmetalation from the corresponding alkyl halide complexes. Acetylido methyl iron(II) complexes were also formed by transmetalation from the chloride complexes, trans-[Fe(dmpe)₂(C≡CR)(Cl)] or trans-[Fe(depe)₂(C≡CR)(Cl)]. The structure of trans-[Fe(dmpe)₂(C≡CC₆H₅) (CH₃)] (1a) was determined by single-crystal X-ray diffraction. The methyl acetylido iron complexes, [Fe(dmpe)₂(C≡CR)-(CH₃)] (1), are thermally stable in the presence of acetylenes; however, under UV irradiation, methane is lost with the formation of a metal bisacetylide. Photochemical metathesis of cis- or trans-[Fe(dmpe)₂(CH₃)(C≡CR)] (R = C₆H₅ (1a), 4-C₆H₄OCH₃ (1b)) with terminal acetylenes was used to selectively synthesize unsymmetrically substituted iron(II) bisacetylide complexes of the type trans-[Fe(dmpe)₂(C≡CR)(C≡CR′)] [R = Ph, R′ = Ph (6a), 4-CH₃OC₆H₄ (6b), ^tBu (6c), Si(CH₃)₃ (6d), (CH₂)₄C≡CH (6e); R = 4-CH₃OC₆H₄, R′ = 4-CH₃OC₆H₄, (6g), ^tBu (6h), (CH₂)₄C≡CH (6i), adamantyl (6j)]. The structure of the unsymmetrical iron(II) bisacetylide complex trans-[Fe(dmpe)₂(C≡CC₆H₅) (C≡CC₆H₄OCH₃)] (6b) was determined by single-crystal X-ray diffraction. The photochemical metathesis of the bis-acetylene, 1,7-octadiyne, with trans-[Fe(dmpe)₂(CH₃)(C≡CPh)] (1a), was utilized to synthesize the bridged binuclear species trans,trans-[(C₆H₅C≡C)Fe(dmpe)₂ (μ-C≡C(CH₂)₄C≡C)Fe(dmpe)₂ (C≡CC₆H₅)] (11). The trinuclear species trans,trans,trans-[(C₆H₅C≡C)Fe(dmpe)₂ (μ-C≡C(CH₂)₄C≡C)Fe(dmpe)₂ (μ-C≡C(CH₂)₄C≡C)Fe(dmpe)₂ (C≡CC₆H₅)] (12) was synthesized by the photochemical reaction of Fe(dmpe)₂(C≡CPh)(C≡C(CH₂)₄ C≡-CH) (6e) with Fe(dmpe)₂(CH₃)₂. Extended irradiation of the bisacetylide complexes with phenylacetylene resulted in insertion of the terminal alkyne into one of the metal acetylide bonds to give acetylide butenyne complexes. The structure of the acetylide butenyne complex, trans-[Fe(dmpe)₂(C≡CC₆H₄ OCH₃)(η¹-C(C₆H₅)=CH (C≡CC₆H₄OCH₃))] (9a) was determined by single-crystal X-ray diffraction.

Full text of DOI:10.1021/ja011105k

Published on Web 03/16/2002
Acetylide-Bridged Organometallic Oligomers via the
Photochemical Metathesis of Methyl-Iron(II) Complexes
Leslie D. Field,*,† Anthony J. Turnbull, and Peter Turner
Contribution from the School of Chemistry, The UniVersity of Sydney, Sydney, Australia, 2006
Received May 1, 2001
Abstract: The acetylido methyl iron(II) complexes, cis/trans-[Fe(dmpe)2(CtCR)(CH3)] (1) and trans-[Fe-
(depe)2(CtCR)(CH3)] (2) (dmpe ) 1,2-dimethylphoshinoethane; depe ) 1,2-diethylphosphinoethane), were
synthesized by transmetalation from the corresponding alkyl halide complexes. Acetylido methyl iron(II)
complexes were also formed by transmetalation from the chloride complexes, trans-[Fe(dmpe)2(CtCR)-
(Cl)] or trans-[Fe(depe)2(CtCR)(Cl)]. The structure of trans-[Fe(dmpe)2(CtCC6H5)(CH3)] (1a) was
determined by single-crystal X-ray diffraction. The methyl acetylido iron complexes, [Fe(dmpe)2(CtCR)-
(CH3)] (1), are thermally stable in the presence of acetylenes; however, under UV irradiation, methane is
lost with the formation of a metal bisacetylide. Photochemical metathesis of cis- or trans-[Fe(dmpe)2(CH3)-
(CtCR)] (R ) C6H5 (1a), 4-C6H4OCH3 (1b)) with terminal acetylenes was used to selectively synthesize
unsymmetrically substituted iron(II) bisacetylide complexes of the type trans-[Fe(dmpe)2(CtCR)(CtCR′)]
[R ) Ph, R′ ) Ph (6a), 4-CH3OC6H4 (6b), tBu (6c), Si(CH3)3 (6d), (CH2)4CtCH (6e); R ) 4-CH3OC6H4, R′
) 4-CH3OC6H4, (6g), tBu (6h), (CH2)4CtCH (6i), adamantyl (6j)]. The structure of the unsymmetrical iron(II)
bisacetylide complex trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b) was determined by single-crystal
X-ray diffraction. The photochemical metathesis of the bis-acetylene, 1,7-octadiyne, with trans-[Fe(dmpe)2-
(CH3)(CtCPh)] (1a), was utilized to synthesize the bridged binuclear species trans,trans-[(C6H5CtC)Fe-
(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2(CtCC6H5)] (11). The trinuclear species trans,trans,trans-[(C6H5CtC)-
Fe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2(CtCC6H5)] (12) was synthesized
by the photochemical reaction of Fe(dmpe)2(CtCPh)(CtC(CH2)4CtCH) (6e) with Fe(dmpe)2(CH3)2.
Extended irradiation of the bisacetylide complexes with phenylacetylene resulted in insertion of the terminal
alkyne into one of the metal acetylide bonds to give acetylide butenyne complexes. The structure of the
acetylide butenyne complex, trans-[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9a) was
determined by single-crystal X-ray diffraction.
Introduction
to provide a mechanism for electronic communication between
the metal centers.
Oligomeric and polymeric rigid-rod metal acetylides have
become an important target class of organometallic compounds.
The metal acetylide fragment possesses a π bonding system
that facilitates electronic communication between the conjugated
organic ligand and the metal and the resulting bridged poly-
nuclear organometallic compounds have applications in the
fields of nonlinear optics,1,2 liquid crystals,3-6 and semiconduct-
ing materials.6-9 There has been considerable recent interest in
linking metals using conjugated polyacetylenic bridging units,
The synthesis of acetylenic polymeric materials containing
transition metals has mainly centered on the polycondensation
reactions of bifunctional organic monomer units with bifunc-
tional metal complexes. Typically, this approach has resulted
in uncontrolled condensation often yielding high molecular
weight polymeric material. The condensation reactions have
generally relied either upon the coupling of acetylenic sites
tethered to metal atoms10 or on acetylenic substitution or
coupling reactions at the metal centers.11
The demand for compounds with well-defined molecular
weight requires careful stepwise syntheses, where each monomer
unit is introduced in a controlled stepwise fashion to one
terminus (or both termini) of a growing polymer. This in turn
requires a suitable suite of synthetic methods for selectively
forming the metal-acetylide bond.
† School of Chemistry, The University of Sydney, Sydney, Australia,
2006.
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3692
J. AM. CHEM. SOC. 2002, 124, 3692-3702
10.1021/ja011105k CCC: $22.00 © 2002 American Chemical Society

Acetylide-Bridged Organometallic Oligomer
A R T I C L E S
Scheme 1
Scheme 2
The simple reaction of metal dihydride complexes, cis-
[M(H)2(dmpe)2] (M ) Fe, Ru) with mixtures of terminal alkynes
has been explored as a route to unsymmetrical (and symmetrical)
metal bisacetylide complexes.12,13 The unsymmetrical reaction
products can be purified from the product mixture by chroma-
tography or fractional recrystallization; however, this approach
is not atom efficient and selectivity for the mixed acetylenic
substrates is generally poor. Furthermore, the synthetic method
becomes impracticable when oligomeric or polymeric systems
are required.9
Unsymmetrically substituted ruthenium bisacetylide com-
plexes have been synthesized by dehydrohalogenation of
vinylidene ruthenium(II) complexes in the presence of a second
terminal acetylene.14 Unsymmetrical ruthenium bisacetylides
have also been synthesized from acetylido ammonium ruthe-
nium(II) complexes in the presence of a second terminal
acetylene.15
In this paper we report the photochemical metathesis of
acetylido alkyl iron(II) complexes in the presence of terminal
acetylenes to form metal bisacetylides (Scheme 1). To our
knowledge, the light-induced metathesis of metal alkyls to form
metal acetylides has not previously been reported and represents
a new approach to forming the metal-carbon bond. The
photochemical metathesis reaction was exploited to selectively
synthesize a number of unsymmetrically substituted iron(II)
bisacetylide compounds.
alkyl metathesis reactions and there is evidence for reductive-
elimination oxidative-addition or protonation-substitution or
σ-bond metathesis mechanisms.23,24,27,29,30 The metathesis reac-
tion of rhodium(I) methyl complexes with alkynes has been
reported31 to form the corresponding rhodium acetylide com-
plexes. A similar thermal metathesis reaction of uranium dialkyl
complexes with acetylenes has also been reported32 to give the
corresponding uranylbisacetylide complexes.
Acetylido Methyl Complexes of Iron. Acetylido methyl
complexes [Fe(dmpe)2(CtCR)(CH3)] (1) and [Fe(depe)2(CtCR)-
(CH3)] (2) were synthesized by reaction of the corresponding
chloro methyl complexes, [Fe(dmpe)2(CH3)(Cl)] (3) and [Fe-
(depe)2(CH3)(Cl)] (4), with magnesium bisacetylides. Alterna-
tively, the acetylido methyl complexes could be synthesized by
the reaction of chloro acetylido complexes [Fe(dmpe)2(CtCR)-
(Cl)] (5) or [Fe(depe)2(CtCR)(Cl)] (6) with dimethylmagne-
sium (Scheme 2). The rate of chloride substitution by the
reaction of the methyl Grignard reagent with the acetylido chloro
iron(II) complexes was slow (ca. 2 days) compared with the
rate of chloride substitution by acetylido Grignard on the chloro
methyl iron(II) complexes (ca. 10-45 min). The acetylido
methyl complexes were obtained as stable, air-sensitive crystal-
line solids.
Results and Discussion
Thermal metathesis reactions involving transition metal
alkyl complexes have been reported previously and have
involved substrates including boranes,16 silanes and phos-
phines,17 alcohols,18,19 dihydrogen,19,20 acids,21,22 and terminal
acetylenes.20,21,23-28 There are various mechanisms for metal-
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J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002 3693

A R T I C L E S
Field et al.
Scheme 3
When syntheses were performed at room temperature, the
acetylido methyl complexes were obtained as mixtures of cis
and trans isomers. The complex [Fe(dmpe)2(CtCPh)(CH3)] (1a)
could be obtained cleanly as the trans isomer if the synthesis
was completed at low temperature (-78 °C). The cis and trans
isomers of [Fe(dmpe)2(CtCPh)(CH3)] do not interconvert
readily at room temperature; however, at 100 °C, a toluene
solution enriched in the trans isomer (trans:cis ) 90:10) was
obtained after 18 h. When a mixture of the cis and trans isomers
was irradiated with UV light, the trans isomer formed exclu-
sively within 10 min. These results suggest that the cis and trans
isomers are kinetically relatively stable and that the isomeriza-
tion of the cis isomer to the more stable trans isomer can be
induced thermally or photochemically. The mechanism of
isomerization probably involves the reversible loss of one end
of a bidentate phosphine donor leading to an intermediate
5-coordinate species where there is less hindrance to structural
reorganization (Scheme 3).
Figure 1. An ORTEP33 depiction of trans-[Fe(dmpe)2(CtCC6H5)(CH3)]
(1a) with atom displacement ellipsoids shown at the 20% level.
31P{1H} NMR of trans-[Fe(dmpe)2(CtCPh)(CH3)] (1a) and
trans-[Fe(depe)2(CtCPh)(CH3)] (2a) shows singlets at δ 72.2
and 80.6 ppm, respectively. 31P{1H} NMR of cis-[Fe(dmpe)2-
(CtCPh)(CH3)] (1a) exhibits four coupled 8-line multiplets at
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
trans-[Fe(dmpe)2(CtCC6H5)(CH3)] (1a)
bond
length (Å)
bonds
angle (deg)
Fe(1)-C(1)
Fe(1)-C(2)
Fe(1)-P(1)
Fe(1)-P(3)
C(2)-C(3)
2.144(3)
1.923(3)
2.1965(9)
2.2083(9)
1.214(5)
C(1)-Fe(1)-C(2)
C(2)-Fe(1)-P(1)
P(1)-Fe(1)-P(2)
P(1)-Fe(1)-P(4)
P(1)-Fe(1)-P(3)
179.26(15)
90.65(10)
86.47(4)
93.61(4)
178.52(4)
1
δ 55.3, 62.0, 71.0, and 75.0 ppm. The H NMR of trans-[Fe-
(dmpe)2(CtCPh)(CH3)] (1a) exhibits a distinct pentet for the
iron bound CH3 group at δ -1.79 ppm (3JP-H ) 7.3 Hz) and
the isomeric cis-[Fe(dmpe)2(CtCPh)(CH3)] (1a) exhibits the
methyl resonance as a multiplet (an apparent quartet) at δ -0.47
ppm. The corresponding methyl resonance for trans-[Fe(depe)2-
(CtCPh)(CH3)] (2a) occurs at δ -1.60 ppm (3JP-H ) 6.6 Hz).
In 13C NMR, the CH3-Fe resonances of the trans isomers of 1
and 2 occur at approximately -20 ppm and exhibit a well-
resolved 31P coupling of 16-18 Hz. For the cis complexes, [Fe-
(dmpe)2(CtCPh)(CH3)] (1a) and [Fe(dmpe)2(CtCC6H4OCH3)-
(CH3)] (1b), the CH3-Fe resonances appear at δ -8.7 and -7.5
ppm, respectively.
Table 2. Comparison of Bond Lengths (Å) for trans-Acetylido
Iron(II) Complexes
complex
M−P
M−Ct
CtC
ref
trans-Fe(dmpe)2-
(CtCPh)CH3 (1a) 2.2035(10)
trans-Fe(dmpe)2-
(CtCPh)Cl (5a)
2.1965(9)
1.923(3) 1.214(5) this work
1.880(5) 1.216(8) 34
2.216(2)
2.216(2)
2.213(2)
2.217(2)
2.191(3)
2.180(5)
trans-Fe(dmpe)2-
(CtCPh)2 (6a)
1.925(6) 1.209(9) 35, 36
Structural Characterization of trans-[Fe(dmpe)2-
(CtCC6H5)(CH3)] (1a). The crystal structure of trans-[Fe-
(dmpe)2(CtCC6H5)(CH3)] (1a) was determined by single-
crystal X-ray diffraction from a suitable crystal grown by slow
evaporation of toluene. An ORTEP33 depiction of the structure
of 1a is provided in Figure 1, and selected bond lengths and
angles are listed in Table 1.
A comparison of the significant bond lengths in 1a with other
acetylido iron(II) complexes is given in Table 2. No significant
changes in iron-phosphorus bond lengths were observed
between 1a and those in the related acetylido chloro iron(II)
[Fe(dmpe)2(CtCPh)(Cl)] (5a)34 and bisacetylido iron(II) [Fe-
(dmpe)2(CtCPh)2] (6a)35,36 complexes. The 1a and 5a triple
bond lengths are the same (within error limits), suggesting that
the chloride π interaction does not involve significant mixing
with the acetylide π* orbitals. The relatively short metal-
acetylide bond in 5a presumably results from the trans influence
of the chloride and reflects the weak σ donor capacity of the
halide. The methyl ligand of 1a acts only as a σ orbital donor
to the iron center and therefore does not greatly influence the
metal acetylide π-bond.
(34) Field, L. D.; George, A. V.; Hambley, T. W. Inorg. Chem. 1990, 29, 4565-
4569.
(33) (a) Johnson, C. K. ORTEPII, Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, Tennessee, 1976. (b) Hall, S. R.; du Boulay, D.
J.; Olthof-Hazekamp, R., Eds. Xtal3.6 System, 1999; University of Western
Australia.
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Organometallics 1991, 10, 3842-3848.
9
3694 J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002

Acetylide-Bridged Organometallic Oligomer
A R T I C L E S
Scheme 4
Scheme 5
Metathesis Reactions of Acetylido Methyl Complexes.
Heating a toluene solution of trans-[Fe(dmpe)2(CtCC6H5)-
(CH3)] (1a) in the presence of an excess of a terminal acetylene
produced no detectable reaction. However, UV irradiation of
benzene or thf solutions of trans-[Fe(dmpe)2(CtCR)(CH3)]
(R ) C6H5 (1a), 4-C6H4OCH3 (1b)) in the presence of an excess
of a terminal acetylene selectively afforded the bisacetylido-
iron(II) complexes trans-[Fe(dmpe)2(CtCR)(CtCR′)] [R )
Ph, R′ ) 4-C6H4OCH3 (6b), tBu (6c), Si(CH3)3 (6d), 7-octynyl
Scheme 6
t
(6e); R ) 4-C6H4OCH3, R′ ) 4-C6H4OCH3 (6g), Bu (6h),
5-hexynyl (6i), adamantyl (6j)] (Scheme 4) with the elimination
of methane.
The unsymmetrical iron(II) bisacetylides were isolated by
removal of solvent and excess acetylene in Vacuo. The
complexes were soluble in most organic solvents and were
purified by recrystallization from hexane or pentane at -78 °C.
The unsymmetrical bisacetylidoiron(II) complexes, trans-[Fe-
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b)
bond
length (Å)
bonds
angle (deg)
Fe(1)-P(1)
Fe(1)-P(2)
Fe(1)-C(1)
C(1)-C(2)
C(2)-C(3)
2.1924(16)
2.2021(16)
1.924(6)
1.198(7)
1.435(8)
C(1)-Fe(1)-C(1)
P(1)-Fe(1)-P(1)
P(1)-Fe(1)-P(2)
C(1)-Fe(1)-P(1)
Fe(1)-C(1)-C(2)
180.00
180.00
85.75(7)
92.32(16)
177.7(5)
t
(dmpe)2(CtCC6H5)(CtCR′)] (R′ ) Bu (6c), Si(CH3)3 (6d),
5-hexynyl (6e)), were microanalytically pure as isolated. Desilyl-
ation of 6d by treatment with potassium fluoride afforded trans-
[Fe(dmpe)2(CtCC6H5)(CtCH)] (6f).
During the irradiation of cis- and trans-[Fe(dmpe)2(CtCC6H5)-
(CH3)] (1a) with terminal acetylenes, no intermediate complexes
were detected by 31P or 1H NMR. Methane was detected in the
reaction headspace by GC and this suggests a σ bond metathesis
mechanism that is probably initiated by the photochemical loss
of one end of the bidentate phosphine donor to open a free
coordination site for the acetylene (Scheme 5).
The metathesis with aliphatic terminal acetylenes proceeded
cleanly and relatively rapidly. Although the reactions proceed
when stoichiometric amounts of the starting materials are used,
in practice the reaction is significantly faster if the reacting
acetylene is present in excess. With aromatic acetylenes, some
photochemical decomposition of the acetylene occurred and this
darkened the reaction solutions and prevented efficient irradia-
tion as the reaction progressed. The photochemical reaction of
[Fe(dmpe)2(CH3)(CtCC6H4OCH3)] (1b) with phenylacetylene
resulted in the unsymmetrical bisacetylidoiron(II) complex trans-
[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b) formed in suf-
ficient quantities to be isolated before significant darkening of
the reaction solution resulted. The complex was isolated and
characterized structurally and spectroscopically.
structure of 6b is provided in Figure 2, and selected bond lengths
and angles are listed in Table 3.
Comparison of the bond lengths with the corresponding
symmetrical bisacetylidoiron(II) complexes trans-[Fe(dmpe)2-
(CtCC6H5)2] (6a)35 and trans-[Fe(dmpe)2(CtCC6H4OCH3)2]
(6g)37 with the unsymmetrical bisacetylidoiron(II) complex (6b)
shows no major differences in the core bond lengths (Table 4).
Photochemical Reactions of Bisacetylide Complexes. Ex-
tended UV irradiation of the bisacetylide complexes in the
presence of an excess of a terminal aromatic acetylene resulted
in the insertion of the terminal alkyne into the metal acetylide
bond to give a butenynyl complex of the type trans-[Fe(dmpe)2-
(CtCR)(C(Ph)dCH(CtCR))] (8) (Scheme 6).
UV irradiation of the bisacetylide complexes with aromatic
alkynes also resulted in exchange of acetylide ligands with the
free alkyne. UV irradiation of the bisacetylide complex trans-
[Fe(dmpe)2(CtCC6H4OCH3)2] (6g) with 20 equiv of phenyl-
acetylene over 16 h resulted in a mixture of all three possible
bisacetylide complexes, trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4-
OCH3)] (6b) (14%), trans-[Fe(dmpe)2(CtCPh)2] (6a) (9%),
and trans-[Fe(dmpe)2(CtCC6H4OCH3)2] (6g) (16%), and all
four possible acetylide butenynyl complexes, trans-[Fe(dmpe)2-
A single crystal of trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4-
OCH3)] (6b) suitable for X-ray diffraction analysis was grown
by slow evaporation from thf. An ORTEP depiction of the
(37) Pike, S. R. Ph.D. Thesis, 1997, The University of Sydney.
9
J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002 3695

A R T I C L E S
Field et al.
Table 4. Comparison of Bisacetylidoiron(II) Complex Bond Lengths (Å)
trans-bisacetylide complex
Fe−P
Fe−Ct
CtC
tC−C
ref
[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b)
2.1924(16)
2.2021(16)
2.191(3)
2.180(5)
2.2055(9)
2.1999(9)
1.924(6)
1.198(7)
1.435(8)
this work
[Fe(dmpe)2(CtCC6H5)2] (6a)
1.925(6)
1.926(3)
1.209(9)
1.207(4)
1.438(9)
1.437(4)
35
37
[Fe(dmpe)2(CtCC6H4OCH3)2] (6g)
Scheme 7
Table 5. Selected Bond Lengths (Å) and Angles (deg) for trans-
[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtCC6H4OCH3))]
(9a)
bond
length (Å)
bond
angle (deg)
Fe(1)-C(18)
Fe(1)-C(4)
C(18)-C(19)
Fe(1)-P(1)
C(1)-C(2)
1.937(2)
2.067(2)
1.222(3)
2.2332(11)
1.203(3)
C(18)-Fe(1)-C(4)
C(3)-C(4)-Fe(1)
C(19)-C(18)-Fe(1)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
178.30(8)
126.00(16)
177.73(19)
124.9(2)
110.08(18)
9d were characterized by 31P NMR with singlet resonances at
δ 65.9 and 65.8 ppm, respectively.
The photochemical insertion and exchange reactions can be
rationalized by a reaction scheme analogous to Scheme 5 where
photochemical loss of one end of the bidentate bisphosphine
provides a free coordination site for binding a free acetylene
prior to coupling or exchange (Scheme 7). The Z/E isomerization
of the coordinated butenyne could be metal assisted; however,
the photochemical isomerization of phenyl-substituted alkenes
is well-known.
Figure 2. An ORTEP33 depiction of trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4-
OCH3)] (6b) with atom displacement ellipsoids shown at the 20% level.
The molecule resides on a pseudo-crystallographic inversion center, and
the crystal structure has axial ligand disorder about the inversion site, with
the methoxy and C(6) hydrogen sites having refined occupancies of 0.5.
(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9a)
(19%),
trans-[Fe(dmpe)2(CtCC6H5)(η1-C(C6H5)dCH-
(CtCC6H5))] (9b) (14%), trans-[Fe(dmpe)2(CtCC6H4OCH3)-
(η1-C(C6H5)dCH(CtCC6H5))] (9c) (8%), and trans-[Fe-
(dmpe)2(CtCC6H5)(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9d)
(8%). The complex trans-[Fe(dmpe)2(CtCC6H4OCH3)(η1-
C(C6H5)dCH(CtCC6H4OCH3))] (9a) was initially formed in
the reaction mixture and isolated as an orange air-sensitive solid.
Butenyne complexes are well-known as rearrangement products
derived from iron bisacetylides.38 An authentic sample of trans-
[Fe(dmpe)2(CtCC6H5)(η1-C(C6H5)dCH(CtCC6H5))] (9b) was
synthesized independently by irradiation of phenylacetylene with
trans-[Fe(dmpe)2(CtCPh)2] (6a). The insertion products 9c and
A single crystal of trans-[Fe(dmpe)2(CtCC6H4OCH3)-
(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9a) suitable for X-ray
diffraction analysis was grown by slow evaporation from thf.
An ORTEP33 depiction of the 9a crystal structure is provided
in Figure 3, and selected bond lengths and angles are listed in
Table 5.
The 31P{1H} NMR spectrum of trans-[Fe(dmpe)2(CtCC6H4-
OCH3)(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9a) exhibited a
singlet resonance at δ 66.4 ppm, 2.7 ppm upfield of the
1
corresponding bisacetylide complex (6g). The H NMR spec-
trum of the complex exhibits a singlet resonance at 5.56 ppm
due to the alkenyl proton and this shows no resolvable 31P
coupling. 13C{1H} NMR of the complex exhibited two pentets
(38) Field, L. D.; George, A. V.; Purches, G. R.; Slip, I. H. M. Organometallics
1992, 11, 3019.
9
3696 J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002

Acetylide-Bridged Organometallic Oligomer
A R T I C L E S
Scheme 8
10a, 10b, and 10c, were observed by 31P NMR as singlets at δ
77.1, 77.7, and 78.4 ppm, respectively. The symmetrical
bisacetylide complexes were identified by comparison with
authentic samples produced by an alternative synthetic route.
The same mixture of iron bis-acetylides was formed when trans-
[Fe(depe)2(CH3)(CtCPh)] (2a) was heated at 65 °C with a
benzene solution of tert-butylacetylene.
Formation of Binuclear Complexes. The bridged dinuclear
complex trans,trans-[C6H5CtCFe(dmpe)2(µ-CtC(CH2)4CtC)-
Fe(dmpe)2CtCC6H5] (11) was formed by irradiation of thf or
benzene solutions of [Fe(dmpe)2(CtCPh)(CH3)] (1a) with 0.5
equiv of 1,7-octadiyne (Scheme 8).
The progress of the reaction was monitored clearly by 31P
NMR. The first addition of one terminus of the difunctional
acetylene to [Fe(dmpe)2(CtCPh)(CH3)] (1a) was characterized
by the appearance of a singlet resonance at δ 72.2 ppm for
the mixed bisacetylidoiron(II) monomer trans-[Fe(dmpe)2-
(CtCPh)(CtC(CH2)4CtCH)] (6e). The subsequent addition
of trans-[Fe(dmpe)2(CtCPh)(CH3)] (1a) to 6e resulted in the
formation of the binuclear complex 11 that was observed by
31P NMR as a singlet at δ 68.03 ppm. The dinuclear complex
was isolated as a microanalytically pure yellow powder with
spectral properties entirely consistent with the formulation
trans,trans-[C6H5CtCFe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2-
CtCC6H5] (11).
Figure 3. An ORTEP33 depiction of trans-[Fe(dmpe)2(CtCC6H4OCH3)-
(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9a) with atom displacement ellipsoids
shown at the 20% level.
Formation of a Trinuclear Complex. The trinuclear com-
plex trans,trans,trans-[PhCtCFe(dmpe)2(µ-CtC(CH2)4CtC)-
Fe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2CtCPh] (12) was
synthesized by extended irradiation of a thf solution of trans-
[Fe(CH3)2(dmpe)2] (13) with 2 equiv of trans-[C6H5CtCFe-
(dmpe)2CtC(CH2)4CtCH] (6e) (Scheme 9). The reaction was
followed by 31P NMR in thf solution. The singlet resonances
at δ 76.6 and 69.4 ppm due to trans-[Fe(dmpe)2(CH3)2] (13)
and trans-[C6H5CtCFe(dmpe)2CtC(CH2)4CtCH] (6e) dis-
appeared slowly with the formation of two resonances at δ
69.8 and 72.8 ppm assigned to the intermediate dinuclear
complex, trans,trans-[C6H5CtCFe(dmpe)2(µ-CtC(CH2)4CtC)-
Fe(dmpe)2CH3)] (14). The resonances of 14 subsequently
decreased as the resonances of the product (12) appeared at δ
69.1 and 69.9 ppm in a ratio of 2:1, respectively. The tri-
nuclear complex was isolated as a microanalytically pure beige
powder with spectral data entirely consistent with the formula
trans,trans,trans-[PhCtCFe(dmpe)2(µ-CtC(CH2)4CtC)-
Fe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2CtCPh] (12).
The 13C{1H,31P} NMR spectrum of 12 shows 6 acetylenic
resonances at δ 110.4, 110.8, 111.7, 112.0, 115.4, and 141.2
ppm. All of the iron-bound carbons showed 31P-13C coupling
when spectra were recorded without 31P decoupling. The R and
(at 206 ppm, J ) 18 Hz and at 135 ppm, J ) 29 Hz) which
collapse to singlets upon 31P decoupling and these corresponded
to the two metal bound carbons of the alkenyl and acetylide
ligands, respectively. The noncoordinated alkynyl carbons were
observed at 88 and 93 ppm.
Reaction of trans-[Fe(depe)2(CH3)(CtCPh)] (2a). In com-
parison to iron complexes containing dmpe ligands, complexes
with bulkier bidentate phosphines are significantly more labile
and exhibit a greater tendency to reversibly lose a phosphine.39-41
UV irradiation of trans-[Fe(depe)2(CH3)(CtCPh)] (2a) in the
presence of 10 equiv of tert-butylacetylene rapidly afforded a
mixture of three bisacetylidoiron(II) complexes, trans-[Fe-
(depe)2(CtCC6H5)2] (10a), trans-[Fe(depe)2(CtCC6H5)-
(CtCtBu)] (10b), and trans-[Fe(depe)2(CtCtBu)2] (10c), in
relative yields of approximately 3%, 61%, and 36%, respec-
tively. No other phosphorus-containing species were observed
and this reflects the lability of the phosphine donors which both
promotes methyl group metathesis and also leads to alkyne
scrambling. The three possible bisacetylidoiron(II) complexes,
(39) Baker, M. V.; Field, L. D.; Hambley, T. W. Inorg. Chem. 1988, 27, 2872.
(40) Field, L. D.; Thomas, I. P. Inorg. Chem. 1996, 35, 2546.
(41) Field, L. D.; Thomas, I. P.; Turner, P.; Hambley, T. W. Aust. J. Chem.
2000, 53, 541.
9
J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002 3697

A R T I C L E S
Field et al.
Scheme 9
ended needles and gastight syringes for transferring solvents and
solutions.
All NMR spectra were recorded on a Bruker DRX 400 spectrometer
fitted with a multinuclear probe tuned to 100.61, 400.13, and 162.00
MHz for 13C, 1H, and 31P spectra, respectively. All NMR spectra were
recorded at 300 K unless otherwise stated. Chemical shifts (δ) are
reported in ppm. 13C and 1H NMR spectra were referenced to residual
solvent resonances while 31P NMR spectra were referenced to external,
neat trimethyl phosphite taken to be 140.85 ppm at 300 K. Air-sensitive
samples for NMR spectroscopy were prepared in a nitrogen-filled box
and sealed with airtight septa or prepared with a resealable NMR tube
fitted with a concentric Teflon valve. Infrared spectra were recorded
on a Perkin-Elmer 1600 Series FTIR. Electrospray mass spectra of
organometallic compounds were recorded on a Finnigan LCQ mass
spectrometer by direct infusion of a methanol or thf solution of the
complexes into the source. UV irradiation of metal complexes was
achieved by using an Oriel 300-W high-pressure mercury vapor lamp
with the incident beam directed through a water-filled jacket to filter
infrared radiation.
All solvents used with air-sensitive compounds (benzene, toluene,
hexane, pentane, thf, and ether) were either degassed with three to five
freeze-pump-thaw cycles or distilled under nitrogen from sodium
benzophenone ketyl.
Phenylacetylene, trimethylsilylacetylene, 1,7-octadiyne, and tert-
butylacetylene were obtained from Aldrich and degassed prior to use.
The bisphosphines dmpe and depe were obtained from Strem and used
as supplied. A solution of dimethylmagnesium (0.5 M, thf) was
synthesized following the reported procedure by Lu¨hder et al.42 Trans-
[Fe(dmpe)2Cl2] and trans-[Fe(depe)2Cl2] were synthesized following
literature methods.43 Details of procedures for the synthesis of bis-
(phenylethynyl)magnesium, bis(4-methoxyphenylethynyl)magnesium,
trans-[Fe(dmpe)2(CH3)Cl] (3), and trans-[Fe(depe)2(CH3)Cl] (4) are
included in the Supporting Information.
â carbon nuclei of the acetylide ligands experience a downfield
chemical shift on coordination to the iron center similar to that
of the symmetrical iron(II) bisacetylide complexes.
Mass Spectroscopy of Unsymmetrical Iron(II) Bisacetylide
Complexes. Electrospray mass spectra of methanol solutions
of unsymmetrical iron(II) bisacetylide complexes typically show
strong molecular ions of the protonated cationic complexes. The
spectra show fragmentation by sequential loss of the acetylenic
ligands with retention of the dmpe ligands at the iron center.
The dimeric complex (11) was observed in the mass spectrum
as the protonated molecular cation at m/z 1019 amu and the
diprotonated dication at M/z 510 amu. The trimeric complex
(12) exhibited a protonated molecular ion at M/z 1479 and a
diprotonated molecular dication at M/z 740 amu.
[Fe(dmpe)2(CH3)(CtCC6H4OCH3)] (1b) from trans-[Fe(dmpe)2Cl-
(CtCC6H4OCH3)] (5b). An excess of dimethylmagnesium (7.7 mL,
ca. 1.4 M) in thf was added to a solution of trans-[Fe(dmpe)2Cl-
(CtCC6H4OCH3)] (5b) (830 mg, 1.60 mmol) in thf (10 mL). The color
of the solution changed from orange to yellow over 2 days with the
formation of the product. The solvent was removed and the crude
product was extracted into hexane (2 × 100 mL). The product was
recrystallized from hexane to afford a mixture of trans- and cis-[Fe-
(dmpe)2(CH3)(CtCC6H4OCH3)] (1b) (770 mg, 95%) as a yellow
crystalline solid. Mp 195 °C dec. The complexes were characterized
spectroscopically as a mixture of cis and trans isomers (cis:trans ≈
65:35). λmax(thf; log ꢀ) 352 (4.32), 252 (4.66).
Conclusions
Methyl iron(II) complexes undergo photochemically induced
σ bond metathesis with terminal alkynes to give iron acetylides.
The mechanism of the reaction probably involves partial
dissociation of one of the bidentate phosphine donors to give a
free coordination site for metal-acetylene binding prior to
metathesis.
The photochemical metathesis scheme provides a new method
of forming the metal-acetylide bond in a clean and controlled
fashion and was used to synthesize a range of unsymmetrically
substituted iron bisacetylides. With appropriate bisacetylenes
(or trisacetylenes) as substrates, this approach provides access
to acetylide-bridged dinuclear, trinuclear, and more highly
condensed organometallic oligomers.
2
cis-1b. 31P{1H} NMR (benzene-d6): δ 57.21 (ddd, JP1P2 ) 19 Hz,
2
2
2JP1P3 ) 19 Hz, JP1P4 ) 28 Hz, 1P, P1), 63.93 (ddd, JP2P3 ) 40 Hz,
2JP2P4 ) 38 Hz, 1P, P2), 72.87 (ddd, JP3P4 ) 148 Hz, 1P, P3), 76.76
2
(ddd, 1P, P4). H{31P} NMR (benzene-d6): δ -0.47 (s, 3H, FeCH3),
1
0.78 (s, 3H, PCH3), 0.82 (s, 3H, PCH3), 0.88 (s, 3H, PCH3), 0.94 (s,
3H, PCH3), 1.17 (s, 3H, PCH3), 1.39 (s, 3H, PCH3), 1.53 (s, 3H, PCH3),
1.64 (s, 3H, PCH3), 1.30-1.60 (m, 8H, PCH2), 3.33 (s, 3H, OCH3),
1
6.81 (m, 2H, ArH), 7.24 (m, 2H, ArH). H NMR highfield (benzene-
d6): δ -0.47 (apparent quartet, splitting ) 8.8 Hz, 3H, FeCH3).
13C{1H,31P} NMR (benzene-d6): δ -7.5 (Fe-CH3), 12.8 (PCH3), 15.3
(PCH3), 17.0 (PCH3), 18.0 (PCH3), 20.7 (2 × PCH3), 21.2 (PCH3),
21.8 (PCH3), 28.3 (PCH2), 29.8 (PCH2), 31.0 (PCH2), 34.9 (PCH2),
56.4 (CH3O), 113.0 (CtC), 115.1 (ArCH), 125.4 (ArC), 132.3 (ArCH),
141.9 (Fe-C), 156.9 (ArC-O). M/z (%): 502 (92, M+), 487 (27), 356
(17), 151 (100).
Iron bisacetylides react slowly with aryl acetylenes under UV
irradiation to give acetylido butenynyl products which arise from
acetylene insertion into the metal alkyne bond.
trans-1b. Vmax (Nujol) 2037 cm-1 (Vcc). 31P{1H} NMR (benzene-
1
d6): δ 74.1. H{31P} NMR (benzene-d6): δ -1.81 (s, 3H, FeCH3),
Experimental Section
1.05 (s, 12H, PCH3), 1.48 (s, 12H, PCH3), 1.41 (m, 8H, PCH2), 3.33
General. All syntheses and manipulations involving air-sensitive
compounds were performed under a nitrogen atmosphere with a
nitrogen-filled glovebox or by using Schlenk apparatus with double-
(42) Lu¨hder, K.; Nehls, D.; Madeja, K. J. Prakt. Chem. 1983, 325, 1027.
(43) Chatt, J.; Hayter, R. G. J. Chem. Soc. 1961, 5507-5511.
9
3698 J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002

Acetylide-Bridged Organometallic Oligomer
A R T I C L E S
(s, 3H, OCH3), 6.77 (m, 2H, ArH), 7.44 (m, 2H, ArH). 13C{1H,31P}
NMR (benzene-d6): δ -19.1 (FeCH3), 13.5 (PCH3), 17.2 (PCH3), 32.1
(PCH2), 56.4 (CH3O), 114.8 (ArCH), 114.9 (CtC), 126.2 (ArC-C),
131.72 (ArCH), 139.8 (FeC), 156.5 (ArC). C22H42FeOP4: Calculated:
C 52.57, H 8.43. Found: C 52.9, H 8.7.
to give trans-[Fe(depe)2(CH3)(CtCC6H5)] (2a) as an orange crystalline
solid (580 mg, 35%). Mp: 152-153 °C. Vmax (benzene, NaCl cell) 2031
cm-1 (Vcc). 31P{1H} NMR (benzene-d6): δ 80.6. 1H{31P} NMR
(benzene-d6): δ -1.60 (s, 3H, FeCH3), 1.12 (t, 12H, CH2CH3), 1.27
(t, 12H, CH2CH3), 1.55-1.65 (m, 8H, PCHHCHHP, (CH)HCH3)),
1.80-1.95 (m, 12H, 2 × (CH)HCH3, PCHHCHHP), 2.64 (m, 4H,
(CH)HCH3), 7.01 (m, 1H, ArH), 7.27 (m, 2H, ArH), 7.44 (m, 2H,
ArH). 13C{1H,31P} NMR (benzene-d6): δ -20.4 (FeCH3), 10.7
(CH2CH3), 10.8 (CH2CH3), 19.9 (PCH2CH2), 22.1 (PCH2CH3), 23.0
(PCH2CH3), 118 (ArC), 123 (ArCH), 131 (2 × ArCH), 133 (FeCtC),
147 (FeCtC). M/z (%): 584 (4). C29H56FeP4 requires C 59.56, H 9.66.
Found: C 59.4, H 9.5.
[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) from trans-[Fe(dmpe)2(CH3)-
Cl] (3). A solution of di(phenylethynyl)magnesium (0.75 g, 3.3 mmol)
in thf (50 mL) was added dropwise with stirring at room temperature
to trans-[Fe(dmpe)2(CH3)Cl] (3) (2.45 g, 6.01 mmol) in thf (100 mL).
The color of the solution changed from deep red to orange over 3 h.
The solvent was removed in Vacuo and the residue extracted into toluene
(2 × 50 mL). The solvent was removed and the yellow solid was
extracted into hot hexane (3 × 50 mL). Slow removal of solvent in
Vacuo led to the formation of a yellow powdery solid of 65.5% cis-1a
and 34.5% trans-1a (2.20 g, 78%). The cis isomer was more soluble
in toluene than the trans isomer and could be isolated by subsequent
crystallization from toluene and filtration at -78 °C. The solvent
was removed from the filtrate and the residue recrystallized from
pentane to give cis-[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) as pale yellow
needles.
Isomerization of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H4OCH3)]
(1b). An NMR tube containing trans/cis-[Fe(dmpe)2(CH3)(CtCC6H4-
OCH3)] (1b) (cis:trans ≈ 65:35) in benzene-d6 was irradiated with a
mercury vapor lamp for 5 min. By 31P NMR, all of the cis isomer was
consumed with a corresponding increase in the amount of the trans
isomer. There was no net loss of phosphine complex.
Reactions of Acetylido Methyl Iron(II) Complexes with Terminal
Acetylenes: trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b). A
thf solution (0.5 mL) of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H4OCH3)]
(1b) (25 mg, 50 µmol) and phenylacetylene (10 µL, 91 µmol) was
irradiated for 20 h until all starting material was consumed. The solvent
was removed and the residue washed with methanol (2 × 0.5 mL)
to give trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b) as a solid
yellow powder (24 mg, 83%). Vmax (KBr disk) 2041 cm-1 (Vcc). 31P{1H}
cis-1a. λmax(thf; log ꢀ): 370 (4.15), 260 (4.42), 254 (4.52), 248 (4.52),
216 (4.67). Vmax (benzene, NaCl cell) 2051 cm-1 (Vcc). 31P{1H} NMR
(benzene-d6): δ 55.3 (ddd, 2JP1P2 ) 19 Hz, 2JP1P3 ) 19 Hz, 2JP1P4 ) 27
2
2
Hz, 1P, P1), 62.0 (ddd, JP2P3 ) 39 Hz, JP2P4 ) 36 Hz, 1P, P2), 71.0
(ddd, JP3P4 ) 145 Hz, 1P, P3), 75.0 (ddd, 1P, P4). H{31P} NMR
(benzene-d6): δ -0.51 (s, 3H, FeCH3), 0.77 (s, 3H, PCH3), 0.81 (s,
3H, PCH3), 0.86 (s, 3H, PCH3), 0.92 (s, 3H, PCH3), 1.15 (s, 3H, PCH3),
1.25-1.55 (m, 8H, PCH2), 1.37 (s, 3H, PCH3), 1.50 (s, 3H, PCH3),
1.61 (s, 3H, PCH3), 6.95, 7.17, 7.49 (m, 5H, ArH). 13C{1H,31P} NMR
(thf-d8): δ -8.73 (FeCH3), 11.7 (PCH3), 13.3 (PCH3), 14.6 (PCH3),
17.4 (PCH3), 20.0 (PCH3), 20.1 (PCH3), 20.5 (PCH3), 21.3 (PCH3),
28.1 (PCH2), 29.6 (PCH2), 34.5 (PCH2), 34.6 (PCH2), 113.5 (ArC),
122.0 (ArCH), 128.0 (ArCH), 130.5 (ArCH), 132.7 (FeCtC), 147.6
(FeCtC). M/z (%): 472 (65, M+), 356 (12), 167 (100), 151 (95).
trans-1a. Vmax (benzene, NaCl cell) 2038 cm-1 (Vcc). 31P{1H} NMR
2
1
1
NMR (benzene-d6): δ 69.1. H{31P} NMR (benzene-d6): δ 1.64 (s,
12H, PCH3), 1.65 (s, 12H, PCH3), 1.75 (s, 8H, PCH2), 3.57 (s, 3H,
CH3O), 7.03 (m, 2H, ArH), 7.17 (m, 1H, ArH), 7.39 (m, 2H, ArH),
7.47 (m, 2H, ArH), 7.58 (m, 2H, ArH). 13C{1H,31P} NMR (benzene-
d6): δ 16.8 (2 × PCH3), 31.6 (PCH2), 55.6 (CH3O), 114.8 (ArCH),
115.2 (CtC), 116.2 (CtC), 123.5 (ArCH), 125.3 (CtCC), 129.3
(ArCH), 131.1 (ArCH), 131.9 (ArCH), 132.3 (CtCC), 133.3 (FeC),
139.1 (FeC), 157.1 (ArCOCH3). M/z (%): 588 (M + 1, 100), 356 (68).
trans-[Fe(dmpe)2(CtCC6H5)(CtCtBu)] (6c). A benzene solution
(10 mL) of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) (120 mg, 0.25
mmol) and 8.5 equiv of tert-butylacetylene (260 µL, 2.12 mmol) was
irradiated for 18 h until all starting material was consumed by 31P NMR.
The solvent was removed and the yellow powder extracted into pentane
(4 × 5.0 mL) and filtered. The solvent was removed from the filtrate
to give a pale yellow powdery solid that was recrystallized from ethanol
(20 mL) to give trans-[Fe(dmpe)2(CtCC6H5)(CtCtBu)] (6c) as a pale
yellow crystalline solid (116 mg, 85%). Mp: 297 °C dec. Vmax (benzene,
NaCl cell) 2046 cm-1 (Vcc). 31P{1H} NMR (benzene-d6): δ 68.9.
1H{31P} NMR (benzene-d6): δ 1.25 (s, 9H, tBu), 1.38 (s, 12H, PCH3),
1.40 (s, 12H, PCH3), 1.52 (bs, 8H, PCH2), 6.92, 7.13, 7.30 (m, 5H,
ArH). 13C{1H,31P} NMR (benzene-d6): δ 16.7 (PCH3), 17.0 (PCH3),
31.5 (C(CH3)3, 31.6 (PCH2), 34.3 (C(CH3)3, 109.1 (Fe-CtCtBu),
115.9 (ArC), 121.4 (Fe-CtCtBu), 123.3 (ArCH), 129.1 (ArCH), 131.1
(ArCH), 132.5 (Fe-CtCPh), 140.9 (Fe-CtCPh). M/z (E.S.) (%): 539
(M + 1)+ (76), 437 (100), 356 (85). C26H46FeP4 requires C 57.97, H
8.62. Found: C 58.3, H 8.9.
1
3
(benzene-d6): δ 72.2. H{31P} NMR (benzene-d6): δ -1.79 (p, JPH
) 7.3 Hz, 3H, FeCH3), 1.06 (s, 12H, PCH3), 1.38 (m, 4H, PCH2),
1.48 (s, 12H, PCH3), 1.57 (m, 4H, PCH2), 6.94 (m, 1H, ArH), 7.16
(m, 2H, ArH), 7.3 (m, 2H, ArH). 13C{1H,31P} NMR (thf-d8): δ -20.0
(FeCH3), 13.5 (PCH3), 17.8 (PCH3), 31.2 (PCH2), 115.7 (ArC), 121.6
(ArCH), 128.0 (ArCH), 130.2 (ArCH), 132.4 (FeCtC), 145.4 (FeCtC).
C21H40FeP4 requires: C 53.37, H 8.54. Found: C 53.6, H 8.4.
[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) from trans-[Fe(dmpe)2Cl-
(CtCC6H5)] (5a). An excess of dimethylmagnesium in thf (0.25 mL,
ca. 0.9 M) was added to a thf solution (1.5 mL) of trans-[Fe(dmpe)2Cl-
(CtCC6H5)] (5a) (15 mg, 29 µmol) and stirred for 3 days at room
temperature. During this time, the color of the solution changed from
orange to pale yellow. The solvent was removed and the residue
extracted into benzene (2 × 1.0 mL) and the solvent removed. The
yellow residue of trans-[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) possessed
identical spectroscopic properties to that prepared previously.
Thermal Isomerization of cis-[Fe(dmpe)2(CH3)(CtCC6H5)] (cis-
1a) to trans-[Fe(dmpe)2(CH3)(CtCC6H5)] (trans-1a). An NMR tube
containing a benzene solution of 34.5% trans-1a and 65.5% cis-1a was
heated at 90 °C for 18 h in darkness. The resulting solution was
examined by 31P NMR and found to contain 90% trans-1a isomer and
10% cis-1a isomer with no net loss of 31P signal.
trans-[Fe(depe)2(CH3)(CtCC6H5)] (2a). A freshly prepared solution
of di(phenylethynyl)magnesium in thf (3.50 mmol) was added dropwise
to a solution of trans-[Fe(depe)2Cl(CH3)] (4) (1.50 g, 2.89 mmol) in
thf at -78 °C. The deep red color of the solution faded as the solution
was warmed to room temperature forming a yellow orange solution.
The solvent was removed in Vacuo and the yellow residue extracted
into hexane (3 × 20 mL). The solvent was removed in Vacuo and the
residue dissolved in toluene and passed through a bed of neutral alumina
at -78 °C under nitrogen. The solvent was slowly removed in Vacuo
trans-[Fe(dmpe)2(CtCC6H5)(CtCSi(CH3)3)] (6d). A solution
of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) (150 mg, 0.32 mmol)
and 10 equiv of trimethylsilylacetylene (0.45 mL, 3.18 mmol) in
thf (50 mL) was irradiated for 60 h until all starting material was
consumed. The solvent was removed and the yellow solid was
extracted into pentane and filtered and the solvent removed in
Vacuo. The yellow solid was recrystallized from hexane at -78 °C
to give trans-[Fe(dmpe)2(CtCC6H5)(CtCSi(CH3)3)] (6d) as a pale
yellow powdery solid (115 mg, 65%). Mp: 297 °C dec. Vmax (benzene,
NaCl cell) 2050 cm-1 (VCtC). 31P{1H} NMR (benzene-d6): δ 67.4.
1H{31P} NMR (benzene-d6): δ 0.26 (s, 9H, SiCH3), 1.35 (s, 12H,
PCH3), 1.40 (s, 12H, PCH3), 1.49 (m, 8H, PCH2), 6.92, 7.12, 7.27
(m, 5H, ArH). 13C{1H,31P} NMR (benzene-d6): δ 3.10 (SiCH3),
16.5 (PCH3), 16.8 (PCH3), 31.4 (PCH2), 116.0 (Fe-CtC), 118.9
9
J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002 3699

A R T I C L E S
Field et al.
3
(Fe-CtC), 123.5 (ArCH), 129.0 (ArCH), 131.1 (ArCH), 132.2
(ArC), 138.8 (Fe-CtCPh), 165.6 (Fe-CtCSi). M/z (%): 554 (M+)
(100), 453 (92), 356 (91). C25H46FeP4Si requires C 54.14, H 8.37.
Found: C 54.1, H 8.1.
8H, PCH2), 1.59 (m, 2H, CH2CH2CtCFe), 1.78 (t, JHH ) 2.7 Hz,
1H, CtCH), 2.04 (m, 2H, CH2CtCH), 2.28 (m, 2H, CH2CtCFe),
3.32 (s, 3H, OCH3), 6.76 (m, AA′XX′, 2H, ArH), 7.22 (m, AA′XX′,
2H, ArH). 13C{1H,31P} NMR (benzene-d6): δ 17.1 (2 × PCH3), 19.2
(CH2), 23.1 (CH2), 29.3 (CH2), 31.8 (PCH2), 32.0 (CH2), 55.7 (CH3O),
69.3 (CtCH), 85.6 (CtCH), 110.8 (FeC), 113.0 (FeCtC), 114.8
(FeCtCPh), 114.9 (ArCH), 125.7 (ArC), 131.9 (ArCH), 135.2 (FeC),
157.0 (CH3OCAr). M/z (E.S.) (%) 593 (100) (M + 1)+.
trans-[Fe(dmpe)2(CtCC6H5)(CtC(CH2)4CtCH)] (6e). A solution
of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H5)] (1a) (300 mg, 0.64 mmol)
and 12 equiv of 1,7-octadiyne (0.84 mL) in thf (50 mL) was irradiated
for 80 h until all starting material was consumed. The solvent was
removed and the yellow solid was recrystallized from hexane at -78
°C to give trans-[Fe(dmpe)2(CtCC6H5)(CtC(CH2)4CtCH)] (6e) as
a pale yellow solid (346 mg, 97%). Mp: 154-155 °C. Vmax (benzene,
trans-[Fe(dmpe)2(CtCC6H4OCH3)(CtC-adamantyl)] (6j). A so-
lution of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H4OCH3)] (1b) (15 mg, 30
µmol) and 12 equiv of 1-adamantylacetylene (57 mg) in toluene-d8
was irradiated for 4 h until all starting material was consumed. The
solvent was removed and the residue washed with methanol (0.5 mL)
to give trans-[Fe(dmpe)2(CtCC6H4OCH3)(CtCC10H15)] (6j) as a
yellow powdery solid (15 mg, 80%). The complex was characterized
spectroscopically. Vmax (KBr disk) 2050 cm-1 (Vcc). 31P{1H} NMR
NaCl cell) 2047 (VFeCtC), 2115 (VCtCH), 3305 (VtC-H) cm-1
.
31P{1H}
1
NMR (benzene-d6): δ 69.4. H{31P} NMR (benzene-d6): δ 1.36 (s,
12H, PCH3), 1.39 (s, 12H, PCH3), 1.50 (m, 2H, CH2), 1.52 (m, 8H,
3
PCH2), 1.60 (m, 2H, CH2), 1.78 (t, JHH ) 2.7 Hz, 1H, CtCH), 2.03
(dt, 3JHH ) 7.0 Hz, 4JHH ) 2.7 Hz, 2H, CH2CtCH), 2.27 (t, JHH ) 6.7
Hz, 2H, CH2CtCFe), 6.92, 7.13, 7.30 (m, 5H, ArH). 13C{1H,31P} NMR
(thf-d8): δ 16.3 (2 × PCH3), 18.4 (CH2), 22.3 (CH2), 28.9 (CH2), 31.4
(PCH2), 31.5 (CH2), 69.0 (CtCH), 84.7 (CtCH), 110.5 (Fe-
CtCCH2), 112.3 (Fe-CtCCH2), 115.3 (Fe-CtCPh), 122.2 (ArCH),
128.0 (ArCH), 130.3 (ArCH), 132.0 (ArC), 140.7 (Fe-CtCPh). M/z
(E.S.) (%): 563 (M + 1)+ (100), 457 (56), 356 (50). C28H46FeP4
requires C 59.77, H 8.25. Found: C 59.9, H 8.3.
(benzene-d6): δ 68.8. H{31P} NMR (benzene-d6): δ 1.44 (s, 12H,
1
PCH3), 1.47 (s, 12H, PCH3), 1.58 (s, 8H, PCH2), 1.67 (bs, 6H,
adamantyl-CH2), 1.86 (bs, 6H, adamantyl-CH2), 1.91 (bs, 3H, ada-
mantyl-CH), 3.32 (s, 3H, OCH3), 6.77 (m, AA′XX′, 2H, ArH), 7.24
(m, AA′XX′, 2H, ArH). 13C{1H,31P} NMR (benzene-d6): δ 16.8
(PCH3), 17.1 (PCH3), 30.2 (adamantyl-CH), 31.8 (PCH2), 33.1 (ada-
mantyl-C), 38.2 (adamantyl-CH2), 47.3 (adamantyl-CH2), 55.7 (CH3O),
109.8 (FeCtC-adamantyl), 114.7 (FeCtCPh), 114.9 (ArCH), 122.7
(adamantyl-CtC), 125.7 (ArC), 131.9 (ArCH), 135.5 (FeCtCPh),
160.0 (CH3OCAr). M/z (E.S.) (%): 647 (35) (M + 1)+, 356 (100).
trans,trans-[C6H5CtCFe(dmpe)2(µ-CtC(CH2)4CtC)Fe-
(dmpe)2CtCC6H5] (11). A solution containing trans/cis-[Fe(dmpe)2-
(CH3)(CtCC6H5)] (1a) (94 mg, 199 µmol) and trans-[Fe(dmpe)2-
(CtCC6H5)(CtC(CH2)4CtCH)] (6e) (112 mg, 199 µmol) in thf (10
mL) was irradiated for 100 h until all starting material was consumed.
The solvent was removed and the yellow solid was recrystallized from
benzene to give trans,trans-[C6H5CtCFe(dmpe)2(µ-CtC(CH2)4CtC)-
Fe(dmpe)2CtCC6H5] (11) as a pale yellow powdery solid (199 mg,
98%). Mp: 340 °C dec. Vmax (thf, NaCl cell) 2046 cm-1 (VCtC). 31P{1H}
NMR (thf-d8): δ 68.03. 1H{31P} NMR (thf-d8): δ 1.29-1.32 (m, 4H,
CH2CH2CtC), 1.48 (s, 24H, PCH3), 1.50 (s, 24H, PCH3), 1.73 (bs,
trans-[Fe(dmpe)2(CtCC6H5)(CtCH)] (6f). Two equivalents (10
mg) of potassium fluoride was added to a solution of trans-[Fe(dmpe)2-
(CtCC6H5)(CtCSi(CH3)3)] (6d) (45 mg, 81 µmol) in methanol (3.0
mL). The solution was refluxed for 1 h until the color of the reaction
mixture was green. The solvent was removed and the green residue
was extracted into hexane and filtered and the solvent removed in Vacuo.
The product was recrystallized from hexane at -78 °C to give trans-
[Fe(dmpe)2(CtCH)(CtCC6H5)] (6f) as a pale yellow powdery solid
(24 mg, 62%). Vmax (benzene, NaCl cell) 2050 (VCC), 3233 (VCH) cm-1
.
31P{1H} NMR (benzene-d6): δ 68.9. H{31P} NMR (benzene-d6): δ
1.38 (s, 12H, PCH3), 1.44 (s, 12H, PCH3), 1.47-1.57 (bs, 8H, PCH2),
1.66 (p, 4JPH ) 3.1 Hz, Fe-CtC-H), 6.93, 7.14, 7.30 (m, 5H, ArH).
13C{1H,31P} NMR (thf-d8): δ 15.8 (PCH3), 16.0 (PCH3), 30.7 (PCH2),
98.2 (CH), 98.3 (CH), 115.2 (CtCPh), 122.7 (ArCH), 126.7 (Fe-
CtC), 130.3 (ArCH), 131.5 (ArC), 138.9 (Fe-CtC). Selected
13C{1H} NMR (thf-d8): δ 126.7 (p, 2JPC ) 25.9 Hz, Fe-CtC), 138.9
1
3
16H, PCH2), 2.00 (t, JHH ) 6.0 Hz, 4H, CH2CtC), 6.73, 6.88, 6.93
(m, 10H, ArH). 13C{1H,31P} NMR (thf-d8): δ 16.4 (PCH3), 16.5
(PCH3), 23.0 (CH2), 31.5 (PCH2), 32.5 (CH2), 110.6 (Fe-CtCCH2),
111.6 (Fe-CtCCH2), 115.4 (Fe-CtCPh), 122.3 (ArCH), 128.2
(ArCH), 130.5 (ArCH), 132.2 (ArC), 141.1 (Fe-CtCPh). M/z (E.S.)
(%): 1019 (M + 1)+ (22), 457 (43), 356 (100). C48H82Fe2P8 requires
C 56.57, H 8.12. Found: C 56.0, H 8.1.
2
(p, JPC ) 26.4 Hz, Fe-CtC). M/z (E.S.) (%): 483 (M + 1)+ (95),
457 (25), 381 (25), 356 (100).
trans-[Fe(dmpe)2(CtCC6H4OCH3)(CtCtBu)] (6h). A toluene
solution (0.5 mL) of trans/cis-[Fe(dmpe)2 (CH3)(CtCC6H4OCH3)] (1b)
(34 mg, 68 µmol) and 12 equiv of tert-butylacetylene (100 µL) was
irradiated for 4 h until all starting material was consumed. The solvent
was removed to give trans-[Fe(dmpe)2(CtCtBu)(CtCC6H4OCH3)]
(6h) as a yellow powdery solid (36 mg, 95%). The complex was
characterized spectroscopically. Vmax (thf, NaCl cell) 2051 cm-1 (Vcc).
Alternatively, a solution of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H5)]
(1a) (30 mg, 0.064 mmol) and 0.5 equiv of 1,7-octadiyne (3.4 µL) in
thf (0.5 mL) was irradiated for 60 h with monitoring by 31P NMR until
the reaction was complete. The solvent was removed from the mixture
and the yellow solid was recrystallized from benzene to give trans,trans-
[C6H5CtCFe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2CtCC6H5] (11) as
a pale yellow powdery solid (31 mg, 95%) with identical spectroscopic
properties to that prepared by the method above.
1
31P{1H} NMR (benzene-d6): δ 68.9. H{31P} NMR (benzene-d6): δ
1.28 (s, 9H, C(CH3)3), 1.43 (s, 12H, PCH3), 1.46 (s, 12H, PCH3), 1.58
(m, 8H, PCH2), 3.35 (s, 3H, OCH3), 6.8 (m, 2H, ArH), 7.26 (m, 2H,
ArH). 13C{1H,31P} NMR (benzene-d6): δ 16.8 (PCH3), 17.1 (PCH3),
31.0 (C(CH3)3, 31.7 (PCH2), 34.3 (C(CH3)3), 55.7 (OCH3), 109.4
(FeCtCtBu), 114.8 (FeCtCPh), 114.9 (ArCH), 121.4 (FeCtCtBu),
125.7 (ArCCtC), 131.9 (ArCH), 135.4 (FeCtCPh), 157.0 (Ar-
COCH3). M/z (%): 569 (M + 1)+.
trans,trans,trans-[PhCtCFe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2-
(µ-CtC(CH2)4CtC)-Fe(dmpe)2CtCPh] (12). A thf solution contain-
ing a mixture of cis/trans-[Fe(dmpe)2(CH3)2] (20 mg, 52 µmol) and
trans-[Fe(dmpe)2(CtCC6H5)(CtC(CH2)4CtCH)] (6e) (56 mg, 100
µmol) was irradiated for 40 h. The reaction was monitored by 31P NMR
until all of complex 6e was consumed. The solvent was removed and
the residue was washed with pentane (3 × 1 mL) then hexane (3 × 1
mL). The crude product was recrystallized from benzene/ethanol to
give a beige powder of trans,trans,trans-[PhCtCFe(dmpe)2(µ-
CtC(CH2)4CtC)Fe(dmpe)2(µ-CtC(CH2)4CtC)Fe(dmpe)2CtCPh] (12)
trans-[Fe(dmpe)2(CtCC6H4OCH3)(CtC(CH2)4CtCH)] (6i). A
solution of trans/cis-[Fe(dmpe)2(CH3)(CtCC6H4OCH3)] (1b) (32 mg,
64 µmol) and 12 equiv of 1,7-octadiyne (100 µL) in benzene-d6 was
irradiated for 4 h until all starting material was consumed. The solvent
was removed and the residue washed with cold pentane (0.5 mL) to
give trans-[Fe(dmpe)2(CtCC6H4OCH3)(CtC(CH2)4CtCH)] (6i) as a
yellow powdery solid (34 mg, 89%). The complex was characterized
spectroscopically. Vmax (KBr disk) 2049 cm-1 (Vcc). 31P{1H} NMR
(61 mg, 79%). Vmax (thf, NaCl cell) 2046 cm-1 (s, νCtC), 2066 (w,
1
ν
CtC). 31P{1H} NMR (thf-d8): δ 69.1 (s, 8P), 69.9 (s, 4P). H{31P}
1
(benzene-d6): δ 69.5. H{31P} NMR (benzene-d6): δ 1.39 (s, 12H,
NMR (benzene-d6): δ 1.41 (s, 24H, PCH3), 1.42 (s, 24H, PCH3), 1.47
(s, 24H, PCH3), 1.55 (bs, 16H, PCH2), 1.63 (bs, 8H, PCH2), 2.35-
PCH3), 1.42 (s, 12H, PCH3), 1.49 (m, 2H, CH2CH2CtCH), 1.55 (s,
9
3700 J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002

Acetylide-Bridged Organometallic Oligomer
A R T I C L E S
Table 6. Crystallographic Data for
trans-[Fe(dmpe)2(CtCC6H5)(CH3)] (1a),
trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b), and trans-
[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtCC6H4OCH3))]
(9a)
2.40 (m, 8H, CtC-CH2), 6.92 (m, 2H, ArH), 7.12 (m, 4H, ArH),
7.31 (m, 4H, ArH), other CH2 resonances masked by dmpe resonances.
13C{1H,31P} NMR (thf-d8): δ 16.4 (PCH3), 16.5 (PCH3), 16.6 (PCH3),
22.9 (CH2), 23.0 (CH2), 31.5 (8 × PCH2), 31.6 (4 × PCH2), 32.5 (CH2),
32.6 (CH2), 110.4, 110.8 (2 × Fe-CtCCH2), 111.7, 112.0 (2 × Fe-
CtCCH2) 115.4 (2 × Fe-CtC-Ph), 122.3 (ArCH), 128.1 (ArCH),
130.5 (ArCH), 132.2 (ArC), 141.2 (2 × Fe-CtC-Ph). M/z (E.S.)
(%): 1479 (M + 1)+ (18), 740 (M + 2)2+ (12), 457 (90), 356 (100).
C68H122Fe3P12 requires C 55.19, H 8.32. Found: C 55.8, H 8.1.
Acetylide Butenynyl Iron(II) Complexes: trans-[Fe(dmpe)2-
(CtCC6H5)(η1-C(C6H5)dCH(CtCC6H5))] (9b). A benzene solution
of trans-[Fe(dmpe)2(CtCC6H5)2] (6a) (24 mg, 43 µmol) and phenyl-
acetylene (288 µL, 2.6 mmol, 60 equiv) was irradiated with a high-
pressure mercury vapor lamp for 20 h. The reaction was followed by
31P NMR until all starting material was consumed. The solution
darkened from yellow to brown during the course of the irradiation.
The solvent was removed and the residue extracted with ether (3 ×
1.0 mL). The ether was removed in Vacuo and the residue washed with
pentane (3 × 1.0 mL). The residue was dissolved in benzene and filtered
and the solvent removed to give trans-[Fe(dmpe)2(CtCC6H5)(η1-
C(C6H5)dCH(CtCC6H5))] (9b) (10 mg, 35%) as an orange air-
sensitive solid. The complex was characterized spectroscopically. Vmax
compound
1a
6b
9a
empirical formula C21H40FeP4
C29H44FeOP4
588.37
monoclinic
cut prism
yellow
P21/a (no. 14)
2
9.108(2)
18.090(3)
9.526(1)
C38H52FeO2P4
720.53
triclinic
acicular
orange
formula weight
crystal system
crystal habit
crystal color
space group
Z value
472.26
monoclinic
blade
orange
P21/n (no. 14)
4
P1h (no. 2)
2
a (Å)
b (Å)
c (Å)
9.1079(6)
8.9040(6)
30.985(2)
12.767(6)
16.259(7)
9.811(4)
104.373(8)
103.391(7)
105.219(7)
1805.2(14)
-123
R (deg)
â (deg)
95.7320(10)
94.42(1)
γ (deg)
V (Å3)
2500.2(3)
21
1564.9(4)
21
1.54178 Å
5.938
1.249
1.498
T (°C)
λ (Mo KR, Å)
0.71073
0.863
1.255
0.71073
0.628
1.326
µ (Mo KR, mm-1
)
F
calcd (g cm-3
GOF (all)
)
1.160
1.023
R1(F),d wR2(F2)d
0.0544, 0.1378a 0.0658, 0.1962b 0.0375, 0.0982c
(KBr disk) 2042 (νCtC), 2164 (νCtC) cm-1 31P{1H} NMR (thf-d8): δ
.
65.3 (s). 1H{31P} NMR (thf-d8): δ 1.48 (s, 12H, PCH3), 1.57 (s, 12H,
PCH3), 1.83 (m, 8H, PCH2), 5.49 (s, 1H, CdCH), 6.64-7.07 (m, 15H,
ArH). 13C{1H,31P} NMR (thf-d8): δ 17.9 (PCH3), 20.4 (PCH3), 31.7
(PCH2), 88.8 (CtC), 94.9 (CtC), 120.7 (ArC), 121.1 (ArC), 121.2
(dCH), 124.4 (ArCH), 124.7 (ArCH), 127.1 (ArCH), 128.6 (ArCH),
128.7 (ArCH), 129.7 (ArCH), 129.8, (ArCH), 131.4 (ArCH), 132.3
(ArCH), 142.3 (FeC), 164.8 (ArC), 209.0 (FeC). M/z (E.S.) (%): 661
(100) (M + 1)+, 559 (27), 356 (27).
a w ) 1/[σ2(Fo ) + (0.0488P)2 + 2.6954P]. b w ) 1/[σ2(Fo ) +
2
2
2
(0.0700P)2]. c w ) 1/[σ2(Fo ) + (0.0476P)2 + 0.7679P] where P )
2
2
(Fo + 2Fc )/3. d R1 ) ∑||Fo| - |Fc||/∑|Fo| for Fo > 2σ(Fo); wR2 )
2
2
2
(∑w(Fo - Fc )2/∑(wFc )2)1/2 for all reflections.
AFC7R diffractometer employing graphite monochromated Cu KR
radiation from a rotating anode generator. The data processing and
calculations for 6b were undertaken with TEXSAN.45 An empirical
absorption correction determined with SADABS46 was applied to the
data obtained for 1a and 9a, and in the case of 9a this was preceded
by a Gaussian correction.44 An empirical absorption correction based
on azimuthal scans of three suitable reflections was applied to the data
for 6b. The data were corrected for Lorentz and polarization effects.
The structures were solved by direct methods using the SIR9747 (1a
and 9a) and SHELX8648 (6b) computer programs, and refined with
SHELXL-9749 using the TEXSAN graphical user interface. ORTEP33
depictions of the complex molecules with 20% atom displacement
ellipsoids are provided in Figures 1-3. The non-hydrogen atoms were
modeled with anisotropic displacement parameters and in general a
riding atoms model was used for the hydrogen atoms. The H(3)
hydrogen site in the structure of 9a was located and modeled with an
isotropic thermal parameter. The reflection intensity distribution for
6b was ambiguous; however, the systematic absences clearly indicated
the space group P21/a. Although the complex molecule 6b does not
have a center of symmetry, the molecule resides on a crystallographic
inversion center in the centrosymmetric space group P21/a. Accordingly
the structure has axial ligand disorder about the crystallographic
inversion center, and the occupancies for the methoxy sites were refined
and then fixed at 0.5. The residuals for the partial occupancy methoxy
trans-[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtCC6H4-
OCH3))] (9a). A benzene solution containing trans-[Fe(dmpe)2-
(CtCC6H4OCH3)2] (6g) (14 mg, 23 µmol) and phenylacetylene (150
µL, 1.4 mmol, 60 equiv) was irradiated with a high-pressure mercury
vapor lamp for 16 h. The reaction was followed by 31P NMR. The
solution darkened from yellow to brown during the course of the
irradiation. The solvent was removed and the residue was washed with
ether (3 × 1.0 mL) then pentane (3 × 1.0 mL). The residue was
dissolved in benzene and filtered and the solvent removed to give trans-
[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtCC6H4OCH3))] (9a)
as an orange air-sensitive solid (8 mg, 48%). Vmax (KBr disk) 2050
(νCtC), 2166 (νCtC) cm-1 31P{1H} NMR (thf-d8): δ 66.4 (s). 1H{31P}
.
NMR (thf-d8): δ 1.24 (s, 12H, PCH3), 1.36 (s, 12H, PCH3), 1.49-
1.52 (m, 8H, PCH2), 3.13 (s, 3H, CH3O), 3.30 (s, 3H, CH3O), 5.57 (s,
CdCH), 6.51, 6.72, 6.82, 7.05, 7.07, 7.08-7.19 (m, 13H, ArH).
13C{1H,31P} NMR (thf-d8): δ 19.4 (PCH3), 21.9 (PCH3), 33.2 (PCH2),
56.6 (CH3O), 56.7 (CH3O), 88.3 (CtC), 93.2 (CtC), 115.3 (ArCH),
115.6 (ArCH), 119.5 (Fe-CtC), 121.3 (dCH), 124.5 (ArCH), 125.8
(ArC), 128.7 (ArCH), 131.4 (ArC), 132.1 (ArCH), 133.4 (ArCH), 136.8
(FeCt), 158.2 (ArCO), 160.0 (ArCO), 165.0 (ArC), 205.8 (FeC). M/z
(E.S.) (%): 721 (100) (M + 1)+, 356 (55).
Crystal Structure Determination for trans-[Fe(dmpe)2(CtC-
C6H5)(CH3)] (1a), trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)]
(6b), and trans-[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH-
(CtCC6H4OCH3))] (9a). Pertinent crystallographic details for 1a, 6b,
and 9a are listed in Table 6, and further detail is provided in the
Supporting Information. Single-crystal X-ray diffraction data for 1a
and 9b were collected with a Bruker SMART 1000 CCD diffractometer
employing graphite monochromated Mo KR generated from a sealed
tube. The data integration and reduction were undertaken with SAINT
and XPREP.44 Data for 9a were collected at 150(2) K using an Oxford
Cryosystems Cryostream. Data for 6b were obtained from a Rigaku
(45) TEXSAN and TEXSAN for Windows: Single-Crystal Structure Analysis
Software Molecular Structure Corporation (1992 and 1997), MSC, 3200
Research Forest Drive, The Woodlands, TX 77381.
(46) (a) Sheldrick, G. M. SADABS; Empirical absorption correction program
for area detector data; University of Go¨ttingen: Germany, 1996. (b)
Blessing, R. H. Acta Crystallogr. 1995, A51, 33-38.
(47) Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A. J. Appl.
Crystallogr. 1993, 26, 343.
(48) Sheldrick, G. M. In Crystallographic Computing 3; Sheldrick, G. M.,
Kruger, C., Goddard, R., Eds.; Oxford University Press: Oxford, 1985;
pp 175-189.
(49) Sheldrick, G. M. SHELXL97; Program for crystal structure refinement;
University of Go¨ttingen: Germany, 1997.
(50) (a) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876-881. (b)
Bernardinelli, G.; Flack, H. D. Acta Crystallogr., Sect. A 1985, 41, 500-
511. (c) Flack, H. D.; Bernardinelli, G. Acta Crystallogr. 1999, A55, 908-
915. (d) Flack, H. D.; Bernardinelli, G. J. Appl. Crystallogr. 2000, 33,
1143-1148.
(44) Bruker SMART, SAINT, and XPREP. Area detector control and data
integration and reduction software, 1995, Bruker Analytical X-ray Instru-
ments Inc., Madison, Wisconsin.
9
J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002 3701

A R T I C L E S
Field et al.
model were significantly lower (1.2% lower for R1(F) and 3.8% lower
for wR2(F2)) than a full occupancy methoxy model. Bond angle
restraints were required for the methoxy residue of 6b. An attempt to
model the structure in the noncentrosymmetric space group P21 resulted
in poor ligand geometry requiring restraints and rigid body refinement,
presumably because of high levels of correlation and ligand disorder.
The Flack50 parameter for the P21 structure refined to 0.52(5), further
supporting the decision to adopt the centrosymmetric structure as the
best model. The methoxy residue site disorder persists in the P21 model.
Supporting Information Available: X-ray crystallographic
data files, in CIF format, for trans-[Fe(dmpe)2(CtCC6H5)(CH3)]
(1a), trans-[Fe(dmpe)2(CtCC6H5)(CtCC6H4OCH3)] (6b),
and trans-[Fe(dmpe)2(CtCC6H4OCH3)(η1-C(C6H5)dCH(CtC-
C6H4OCH3))] (9a); synthetic procedures and spectral data for
bis(phenylethynyl)magnesium, bis(4-methoxyphenylethynyl)-
magnesium, trans-[Fe(dmpe)2(CH3)Cl] (3), and trans-[Fe(depe)2-
(CH3)Cl] (4) (PDF). This material is available free of charge
via the Internet at http://pubs.acs.org.
Acknowledgment. We gratefully acknowledge financial
support from the Australian Research Council.
JA011105K
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3702 J. AM. CHEM. SOC. VOL. 124, NO. 14, 2002