C-H activation of diphenylphosphinoaryl-derivatives with dimethyltetrakis(trimethylphosphine)iron(II)

Article abstract of DOI:10.1016/j.jorganchem.2008.08.017

Fe(CH₃)₂(PMe₃)₄ reacts with 1-(diphenylphosphino)naphthalene or benzyldiphenylphosphine within 4 h at 20 °C to give the novel metallated methyl iron complexes Fe(CH₃){P(C₆H₅)₂(C₁₀H₆)}(PMe₃)₃ (1) and Fe(CH₃){(C₆H₄)CH₂P(C₆H₅)₂}(PMe₃)₃ (3), respectively, via selective activation of the C-H bond of the pre-chelating ligands. The complexes are thermally unstable releasing metal through a reductive elimination of the aromatic backbone and leading to a C,C-coupling product that is regiospecifically methylated, namely 8-methyl(diphenylphosphino)naphthalene (2). Carbonylation (1 bar, 20 °C, 1 h) of complex 1 effects monosubstitution of a trimethylphosphine ligand trans to the metallated 8-C atom to afford Fe(CH₃){P(C₆H₅)₂(C₁₀H₆)}(CO)(PMe₃)₂ (4). The remaining methyl group in the parent complex 1 reacts with trimethylsilylethyne and tert-butylethyne affording the new complexes 5 and 6 bearing an alkynyl substituent trans to the diphenylphosphino anchoring group. The complexes 1 and 3-6 are diamagnetic and possess octahedral coordination geometry. All novel complexes were fully characterized by spectroscopic methods and by X-ray diffraction.

Full text of DOI:10.1016/j.jorganchem.2008.08.017

Journal of Organometallic Chemistry 693 (2008) 3471–3478
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
C–H activation of diphenylphosphinoaryl-derivatives with dimethyltetrakis
(trimethylphosphine)iron(II)
a
a,
a
c
b
Robert Beck a,b, , Tingting Zheng , Hongjian Sun , Xiaoyan Li , Ulrich Flörke , Hans-Friedrich Klein
*
*
a School of Chemistry and Chemical Engineering, Shandong University, Shanda Nanlu 27, 250100 Jinan, PR China
b Eduard-Zintl-Institut für Anorganische und Physikalische Chemie der Technischen Universität, Darmstadt, Petersenstrasse 18, 64287 Darmstadt, Germany
c Anorganische und Analytische Chemie, Universität Paderborn, Warburger Straße 100, D-33098 Paderborn, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 July 2008
Received in revised form 12 August 2008
Accepted 14 August 2008
Available online 20 August 2008
Fe(CH3)2(PMe3)4 reacts with 1-(diphenylphosphino)naphthalene or benzyldiphenylphosphine within
4 h at 20 °C to give the novel metallated methyl iron complexes Fe(CH3){P(C6H5)2(C10H6)}(PMe3)3 (1)
and Fe(CH3){(C6H4)CH2P(C6H5)2}(PMe3)3 (3), respectively, via selective activation of the C–H bond of
the pre-chelating ligands. The complexes are thermally unstable releasing metal through a reductive
elimination of the aromatic backbone and leading to a C,C-coupling product that is regiospecifically
methylated, namely 8-methyl(diphenylphosphino)naphthalene (2). Carbonylation (1 bar, 20 °C, 1 h) of
complex 1 effects monosubstitution of a trimethylphosphine ligand trans to the metallated 8-C atom
to afford Fe(CH3){P(C6H5)2(C10H6)}(CO)(PMe3)2 (4). The remaining methyl group in the parent complex
1 reacts with trimethylsilylethyne and tert-butylethyne affording the new complexes 5 and 6 bearing
an alkynyl substituent trans to the diphenylphosphino anchoring group. The complexes 1 and 3–6
are diamagnetic and possess octahedral coordination geometry. All novel complexes were fully charac-
terized by spectroscopic methods and by X-ray diffraction.
Keywords:
C–H Activation
C,C-coupling
Iron
P ligands
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
It has been shown that many of these cyclometalation reactions
are reversible (Scheme 1). However, with a methyl group in the
C–H activation of various organic substrates and cyclometala-
tion reactions have been extensively studied for more than five
decades finding applications in industrial processes. In particular
activation of small molecules has become an important area of re-
search in homogenous catalysis. Most cyclometalation reactions
postulate a pre-coordination of heteroatoms N, P, or S when form-
ing a metallacycle. Among the oldest C–H activation processes are
those involving P-donor groups with electron-rich complexes of
the late transition metals [1].
starting complex the formation of a metallacycle is practically irre-
versible (D = donor atom, N, P or S) through elimination of
methane, because methane has never been observed to cleave a
Fe–C or Co–C bond which can occur with dihydrogen [2].
Recently we observed highly selective formations of four- (A),
five- (B) and six-membered (C) metallacycles (Scheme 2) by C–H
activation of aliphatic- and aromatic C–H bonds with methyl-co-
balt(I) in reaction with various ortho substituted diphenylphos-
phino-aryl derivatives [3].
With regard to phosphorus ligands, such as triarylphosphines
containing additional ortho alkyl- or aryl-substituents of the
phenyl rings, have been successfully used for the preparation of
cyclometallated transition metal complexes through C–H bond
cleavage, which represents the initial step for the catalytic or stoi-
chiometric functionalization of organic substrates.
On the basis of the results with cobalt, we report an extension of
our work with trimethylphosphine supported dimethyl–iron com-
plexes, the preparation and reactivity of cyclometallated aryl-func-
tionalized diphenylphosphino complexes of Fe(II) under very mild
conditions.
2. Results and discussion
Upon P-coordination of 1-diphenylphosphinonaphthalene as a
pre-chelating reactant rotational orientations of ortho C–H bonds
will be restricted, when compared with 2-diphenylphosphino-tol-
uene [4]. Nevertheless, reaction with [Fe(CH3)2(PMe3)4] proceeds
below 20 °C (Eq. (1).
* Corresponding authors. Address: School of Chemistry and Chemical Engineer-
ing, Shandong University, Shanda Nanlu 27, 250100 Jinan, PR China. Fax: +86 531
88564464 (R. Beck).
E-mail addresses: metallacycle@gmail.com (R. Beck), hjsun@sdu.edu.cn (H. Sun).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.08.017

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R. Beck et al. / Journal of Organometallic Chemistry 693 (2008) 3471–3478
C30 = 2.021(4) Å] when compared with average Fe–C bond dis-
tances. All other bond length show typical values of bond distances
and the sum of internal angles (536.8°) in the five membered ring
indicates less deviation from planarity. A multiplet arising from
multiple phosphorus couplings at d = ꢀ0.38 ppm (3H) in the 1H
NMR spectrum at 293 K is attributable to the Fe-CH3 group, and
Scheme 1. C–H activation with methyl-iron and methyl-cobalt.
2
a broad multiplet at d = 0.42 ppm indicates a collapse of the J(P,H)
coupling by reversible trimethylphosphine dissociation, whereas
the aromatic hydrogen atoms (16H) resonate in the typical area
of 6.45–7.83 ppm.
Cyclometallated iron complexes through C–H activation
brought about with a diphenylphosphino group are very rare and
only a few compounds have been identified by NMR spectra [6].
There is only one X-ray structure of a related complex known from
literature which shows a cyclometallated phenyl(methyl)naph-
thylphosphine ferracycle with supporting cyclopentadienyl ligands
which has not yet been fully characterized [7]. The broadening of
signals in the NMR spectra of 1 (iron(II) in an octahedral coordina-
tion) when the sample is slightly warmed (40 °C), can be attributed
to a partial reductive elimination in polar solvents, which leads to
the new C,C-coupling product 2 and releasing a Fe(0) fragment and
elemental iron (Eq. (1)). Concentrated ether solutions at 4 °C afford
colourless crystals of 2 which were suitable for X-ray diffraction
(Fig. 2).
Scheme 2. Four-, five- and six-membered cobaltacycles.
PMe3
CH3
Fe(CH3)2(PMe3)4
Fe
- CH4, - PMe3
P
PMe3
PMe3
P
The X-ray structure confirms what the NMR spectra indicated:
formation of a newly assembled phosphine ligand which had al-
ready been prepared in a multistep reaction [8].
Ph
Ph
Ph
Ph
1
Most characteristic is the shift of the phosphorus nucleus in
31P{1H} NMR at 0.8 ppm as singlet and the introduced CH3-group
in 8-position of the naphthalene ring which appears in 1H NMR
5
ΔT
reductive elimination
- Fe(PMe3)3
as a doublet (3.12 ppm, JP,H = 4.2 Hz) resonance indicating a cou-
ð1Þ
pling with the phosphorus nucleus also observed in the 13C{1H}
4
NMR at d = 27.5 ppm as doublet with JP,C = 32.2 Hz. The C–C dis-
tances and the C–P bond lengths (1.8379–1.8526 Å) are in the
range reported for other arylphosphines. Ligand 2 shows a typical
propeller-type conformation of two phenyl rings and a naphthyl
CH3
P
Ph
Ph
2
Red-orange crystals of 1, melting with decomposition above
127 °C, were obtained from pentane solutions when cooling down
to ꢀ27 °C. In the 31P{1H} NMR spectrum, the observed coordination
chemical shift of d = 75 ppm is only compatible with the PPh2-
group (d = 66.9 ppm) as part of a five-membered ferracycle [5].
This configuration is confirmed in the molecular structure of 1.
The iron atom is centered in an octahedron with a meridional
arrangement of the trimethylphosphine ligands. The PPh2-anchor-
ing group and the methyl group (C32) are in trans configuration
and the metallated carbon (C30) with the naphthyl-backbone
and the P-anchoring group, forming a C30–Fe1–P4 bite angle of
83.99(12)°. The naphthyl backbone describes a slightly twisted
conformation. If we define the naphthyl system as a plane, then
the P4 donor atom of the PPh2 anchoring group lies with 0.305 Å
above this plane and the iron center Fe1 with 0.229 Å under this
plane. It appears as a result of steric repulsion, originated by the
spatial requirement of the phenylsubstituents, forcing a bending
of the two trans disposed trimethylphosphine ligands [P2–Fe1–
P3 = 159.84(5)°], towards the less space requiring methyl group
C1. Similar distortions were previously observed from us with re-
lated cobalt complexes [3].
Fig. 1. Molecular structure of 1. Selected distances [Å] and angles [°]: Fe1–C30
2.021(4), Fe1–C32 2.114(4), Fe1–P4 2.2192(11), Fe1–P2 2.2539(13), Fe1–P1
2.2629(13), Fe1–P3 2.3028 (11); C30–Fe1–P4 83.99(12), C30–Fe1–P1 173.24(13),
P2–Fe1–P1 92.78(5), P4–Fe1–P3 93.54(4), P4–Fe1–P1 101.28(5), P2–Fe1–P3
159.84(5), P1–Fe1–P3 103.29(5), C32–Fe1–P2 90.62(13), C32–Fe1–P3 79.92(13),
C32–Fe1–P1 81.73(12), C30–Fe1–C32 93.48(16).
The Fe–C(sp3) bond is very long [Fe–C32 = 2.114(4) Å], while
the metallated carbon distance Fe–C(sp2) is shortened [Fe1–

R. Beck et al. / Journal of Organometallic Chemistry 693 (2008) 3471–3478
3473
C3
C11
C12
C13
C9
C4
C2
C8
C10
C5
C21
C10
C7
C6
C1
C14
C9
C11
C26
C17
P1
C12
C22
C18
P2
C16
C23
C13
C19
C23
C15
C20
P1
C22
P3
C14
Fe01
C15
C1
C21
C24
C25
C3
C2
C7
C16
C20
C4
C19
C8
C6
C5
C18
C27
C28
P4
C17
Fig. 2. Molecular structure of 2. Selected distances [Å] and angles [°]: P1–C1
1.8379(18), P1–C7 1.8403(18), P1–C13 1.8526(18), C15–C23 1.508(3), C14–C13
1.448(2), C14–C15 1.442(2), C13–C22 1.377(2), C14–C19 1.432(2), C15–C16
1.378(3); C1–P1–C7 101.66(8), C1–P1–C13 103.06(8), C7–P1–C13 100.01(8), C14–
C15–C23 125.04(18).
C29
Fig. 3. Molecular structure of 3. Selected distances [Å] and angles [°]: Fe01–C3
2.080(5), Fe01–C8 2.113(6), Fe01–P1 2.229(4), Fe01–P2 2.261(10), Fe01–P3
2.251(4), Fe01–P4 2.251(8), C1–C2 1.498(5), C2–C3 1.413(4); C3–Fe01–P1
80.30(7), C3–Fe01–P3 177.89(6), P1–Fe01–P2 99.62(3), P3–Fe01–P2 90.65(3), P4–
Fe01–P2 164.00(3), P1–Fe01–P4 95.40(3), C8–Fe01–P2 82.65(8), C8–Fe01–P4
81.48(8).
ring bonded to the phosphorus atom, which can be also found in
various tris-(aryl) substituted phosphine ligands in solid state [9].
The reactivity of 1-(diphenylphosphino)-8-methyl-naphthalene
(2) was investigated with Fe(CH3)2(PMe3)4 under same reaction
conditions as for complex 1. We observed similar as for 2-diph-
enylphosphinotoluene and triphenylphosphine, no indication of
an ortho metalation or sp3-CH activation, that might produce four-
or five-membered metallacycles, as previously shown by us with
methyl cobalt complex [Co(CH3)(PMe3)4]. Both complexes
[Co(CH3)(PMe3)4] and [Fe(CH3)2(PMe3)4] have the same set of trim-
ethylphosphine ligands, except for the iron complex which carries
an additional, labile methyl group in cis configuration of octahedral
coordination. It appears that in a competition of cyclometalation
versus reductive elimination, [Fe(CH3)2(PMe3)4] releases ethane,
when reacting with triphenylphosphine with a non optimum fit
bite angle [Co: four-membered metallacycle = 71.5°] [3], when
compared with the observed five membered metallacycle (1:
83.99(12°)).
From a steric point of view both pre-chelating ligands are sim-
ilar, moreover 2-diphenylphosphinotoluene contains three alkylic
C–H bonds for activation, when compared with one aromatic C–
H bond in 8-diphenylphosphinonaphthalene. Secondly, aliphatic
C–H bonds are weaker with (96–102 kcal/mol) than aromatic C–
H bonds with (110 kcal/mol), but it is a common observation that
the stronger aromatic C–H bond is activated in preference of the
weaker aliphatic C–H bond due to higher energy of the metal–car-
bon(aryl) bond strength formed in the product complex [1]. This
might explain why we don’t observe C–H activation of the methyl
substituent in 2-diphenylphosphinotoluene.
All volatile materials were removed in vacuum as soon as pre-
cipitation of the orange product 3 started. Extraction of the
remaining solid with diethyl ether at 20 °C and cooling down the
red-brown solution gave short orange rods in only moderate yield.
Complex 3 is air-stable for some minutes but under argon decom-
poses above 52 °C.
The 31P{1H} NMR spectrum contains a singlet at (d = 72.3 ppm)
with a large coordination shift (84 ppm) as compared to benzyldi-
phenylphosphine, indicating incorporation of the PPh2 group in a
five-membered metallacycle. Two sets of signals of anisochronic
trimethylphosphine arise at 17.6 ppm and 10.0 ppm with a ratio
of 2:1 consistent with a meridional arrangement. Slow decomposi-
tion in solution of 3 is observed in the 31P{1H} NMR, accompanied
by line broadening and suppressing of the P,P-couplings when
compared with the thermodynamic more stable mono carbonyl
complex 4. The most striking feature in the 13C{1H} NMR of 3 is a
singlet resonance for the metallated aryl carbon at 178.1 ppm
which is close to that for the related complex 1 (178.5 ppm).
The expected configuration is confirmed in the molecular struc-
ture of 3 (Fig. 3). All bond lengths in 3 are similar to those in the
naphthyl derivative 1 (Fig. 1). In particular, the distances [Fe01–
C3 = 2.080(5) Å and Fe01–C8 = 2.113(6) Å] fall in the range re-
ported for Fe–C(sp3) and Fe–C(sp2) bonds (1.97–2.09 Å) [10,19].
Only Kubas reported a dimethyl–iron complex which contains
Fe–C distances at 2.15 Å and 2.18 Å [20]. The approximation of
octahedral geometry is less ideal than in 1, and the sum of the
internal angles in the five-membered ring (528.1°) is smaller than
expected for planarity (540°) while this sum in 1 is 536.8°. The dis-
tortion of the five-membered metallacycle is a result of the meth-
ylene bridge in the ligand which causes angular strain and
therefore directly influences the thermal stability (dec. > 52 °C)
when compared with complex 1 (>123 °C dec.) with a better fit
of its rigid naphthyl backbone.
However, when formally inserting a methylene bridge in the
pre-chelating phosphine, i.e. using benzyldiphenylphosphine, a
cyclometalation is observed to arrive at the same ring size but with
reversed ring positions as compared with 2-diphenylphosphinotol-
uene. After combining the reactants at ꢀ70 °C the mixture turned
from red to red brown within 4 h (Eq. (2).
Similar cyclometalation reactions by C–H activation in ortho po-
sition of benzyldiphenylphosphines have been previously de-
scribed with Au [11], Ni [12], Co [13], Pt [14], and Pd [15].
Products with related pincer type ligands incorporating two ben-
zylic phosphine anchoring groups have been shown in other labo-
ratories to attain higher thermal stabilities [16].
ð2Þ

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R. Beck et al. / Journal of Organometallic Chemistry 693 (2008) 3471–3478
the color instantly changes to yellow and an evolution of gas com-
mences (Eq. (4)).
3. Reaction with carbon monoxide
Carbonylated methyliron compounds, [Fe(CH3)2(CO)2(PMe3)2]
or [Fe(CH3)I(CO)2(PMe3)2] [17], are unreactive towards diphe-
nyl(2-substituted phenyl)phosphines under similar conditions
and fail to undergo cyclometalation involving a C–H activation of
the prescribed type. However, CO ligands are smoothly introduced
into metallacyclic product complexes. In solution under 1 bar of CO
at 20 °C, 1 is smoothly transformed into the monocarbonyl com-
plex 4 (Eq. (3).
ð4Þ
Under mild conditions the acidic tert-butylethyne and trimeth-
ylsilylacetylene smoothly substitute the methyl group from the
parent complex 1, affording orange yellow cubic crystals (from
pentane at 4 °C). The lustrous yellow orange crystals of 5 and 6
have narrow melting ranges (5: 92–95 °C; 6: 102–105 °C) and melt
without decomposition. In solution both complexes are thermally
more stable than complex 1. Heating solutions of 5 and 6 does
not induce reductive C,C-coupling reactions, but bis(alkinyl)tetra-
kis(trimethylphosphine)iron(II) complexes were identified as
byproducts. Related bis(alkinyl)iron(II) complexes are described
in the literature with supporting bis(dimethylphosphino)-ethane
ligands [21].
ð3Þ
Yellow-orange crystals of 4 were obtained from pentane which
are air-sensitive and decompose under argon above 161 °C. In the
infrared spectra a strong (mC„O) absorption is registered at
1872 cmꢀ1 and clearly indicates a terminal carbon monoxide li-
gand [18]. In the 1H NMR the loss of the cis-disposed trimethyl-
phosphine resonance indicates substitution at this position. The
31P{1H} NMR spectrum contains a triplet (d = 74.4 ppm, PPh2) and
a doublet (d = 15.9 ppm, PMe3), with couplings that suggest a
five-membered ferracycle as part of an octahedral coordination
with two trans-disposed PMe3 ligands perpendicular to the ring
plane and the (PPh2)-donor group in a cis-position. The expected
configuration is confirmed in the molecular structure of 4 (Fig. 4).
The IR spectrum of 5 contains two conspicuous new bands
which are assigned to the terminal alkinyl ligand and the deforma-
tion mode in the SiMe3-group [5:
m
= 1972 (C„C), 829 cmꢀ1 (d
SiMe3); 6:
m
= 2049 (C„C) cmꢀ1]. The 31P{1H} NMR spectra of 5
and 6 in [d6]-benzene at 298 K show a pattern of three resonances
[5: d = 4.4 ppm, 9.8 ppm, 81.5 ppm; 6: d = 5.6 ppm, 10.8 ppm,
78.5 ppm] with similar 2J(PP)-couplings (28.5 Hz and 33.5 Hz), sug-
gesting three P-donor functions in an octahedral coordination
geometry, which is only in accord with a meridional configuration.
Both solution structures of mer-5 and mer-6 were confirmed for
the crystal by an X-ray diffraction analysis (Figs. 5 and 6).
In the molecular structure of 5 (Fig. 5) the iron atom attains an
octahedral coordination by two trans PMe3 groups (P4–Fe1–
P2 = 159.59(5)°) a cis PMe3 group (P3) opposite to the metallated
carbon (C1) atom (C1–Fe1–P3 = 174.38(14)°), and the chelating
phosphorus atom (P1) trans to the alkinyl group (C„CSiMe3) with
an angle of (C32–Fe1–P1 = 172.99(16)°). Bond angles are close to
90°, with the smallest being the bite angle of the five-membered
4. Reaction with alkynes
Using alkyne reactants, the interesting question arises as
whether attack by the metal would proceed as a regioselective
addition or promote ring opening through a subsequent reductive
C,C-coupling reaction. When the reactants are combined at ꢀ70 °C,
C4
C3
C6
C5
C30
C31
C34
Si1
C2
C29
C7
C35
C10
P1
C8
C1
P4
C9
C33
C32
C25
Fe1
C36
C17
C22
C16
C21
C23
P2
C18
C19
C28
C20
C11
C15
C14
P3
C27
C24
C12
C26
C13
Fig. 4. Molecular structure of 4. Selected distances [Å] and angles [°]: Fe1–C101
1.685(5), Fe1–C130 2.163(10), Fe1–C102 2.048(11), C101–O1 1.147(12), Fe1–P11
2.228(3), Fe1–P12 2.226(3), Fe1–P13 2.204(3), C110–C111 1.388(14), C102–C111
1.442(15); C102–Fe1–P13 82.8(4), C130–Fe1–P13 177.8(3), C101–Fe1–C102
177.6(6), P13–Fe1–P11 97.32(13), P13–Fe1–P12 97.22(13), P11–Fe1–P12
161.82(14), C102–Fe1–C130 99.4(4), C130–Fe1–P12 83.2(3), C102–Fe1–C130
99.4(4), O1–C101–Fe1 179.6(15).
Fig. 5. Molecular structure of 5. Selected distances [Å] and angles [°]: Fe1–C1
2.005(5), Fe1–C32 1.921(4), Fe1–P1 2.2396(12), Fe1–P2 2.2649(14), Fe1–P3
2.2821(15), Fe1–P4 2.2986(13), C32–C33 1.210(6), C33–Si1 1.799(5); C1–Fe1–P1
83.99(12), C1–Fe1–P3 174.38(14), C1–Fe1–P2 83.89(14), P1–Fe1–P2 96.19(5), C32–
Fe1–P4 79.04(15), P1–Fe1–P3 100.11(5), C32–Fe1–P1 172.99(16), C1–Fe1–P4
79.65(13), P1–Fe1–P4 94.01(5), P2–Fe–P4 159.59(5), P3–Fe1–P4 103.75(6).

R. Beck et al. / Journal of Organometallic Chemistry 693 (2008) 3471–3478
3475
of Fe(PMe3)4 as a prevailing side reaction and other byproducts
which could not be identified. This can be also understood as an
elusive ortho-metallated intermediate, which demetalates by
reductive C,C-coupling affording the newly assembled ligand 2. Be-
sides, we should consider that C–H bond activation in aromatic
hydrocarbons is favoured over aliphatic ones due to kinetic and
thermodynamic reasons, which might explain that we do not ob-
serve C–H activation of the methyl substituent in 2-diph-
enylphosphinotoluene. Carbon monoxide smoothly substitutes
selectively one trimethylphosphine ligand trans to the PPh2-group
(in complex 4) but no insertion products are observed. The at-
tached methyl group in the cyclometallated complex 1 can be eas-
ily substituted by an acidic alkyne which increases the
thermodynamic stability of the product complexes 5 and 6.
C29
C30
C8
C35
C6
C7
C3
C31
C5
C9
C1
P4
C36
C37
C2
P1
C34
C10
C4
C33
C28
C32
C21
C20
C22
Fe1
C19
C17
C18
P3
C11
C16
C12
P2
C23
C27
C25
C13
C14
C26
C24
C15
6. Experimental
Fig. 6. Molecular structure of 6. Selected distances [Å] and angles [°]: Fe1–C1
2.024(6), Fe1–C32 1.961(6), Fe1–P1 2.2269(17), Fe1–P2 2.2657(18), Fe1–P3
2.2826(18), Fe1–P4 2.2906(17), C32–C33 1.198(9), C33–C34 1.464(9), C1–C2
1.437(8), C2–C3 1.421(9); C1–Fe1–P1 83.56(17), C1–Fe1–P3 174.41(18), P1–Fe1–
P2 96.13(6), C32–Fe–P3 82.46(19), P2–Fe1–P3 91.99(7), P1–Fe1–P3 100.25(7), C32–
Fe1–P4 79.0(2), C1–Fe1–P4 80.22(17), P1–Fe1–P4 94.30(6), P2–Fe1–P4 159.53(7),
P3–Fe1–P4 103.4(7).
General procedures and materials: Standard vacuum techniques
were used in manipulations of volatile and air-sensitive materials.
Literature methods were used in the preparation of trimethy-
lsilylethyne and tert-butylethyne [24], 1-diphenylphosphinonaph-
thalene [25], benzyldiphenyl-phosphine [26], 2-diphenylphosphi-
notoluene [27], dimethyltetrakis(trimethyl-phosphine)eisen(II)
[28]. Other chemicals were used as purchased. Infrared spectra
(4000–400 cmꢀ1), as obtained from Nujol mulls between KBr disks,
were recorded on a Nicolet 5700. 1H, 13C, and 31P NMR spectra
were recorded on a Bruker Avance 300 and on a Bruker DRX 500
spectrometer. 13C{1H} and 31P{1H} NMR resonances were obtained
with broadband proton decoupling. Elemental analyses were
carried out at Kolbe Microanalytical Laboratory, Mülheim/Ruhr
(Germany) and on an Elementar Vario EL III. Melting points were
measured in capillaries sealed under argon and are uncorrected.
chelate ring (C1–Fe1–P1 = 83.99(12)°). The sum of internal angles
is 537°, indicating considerable relaxation of the metallacycle to-
wards planarity. The Fe–P bond lengths from (2.23–2.29 Å) fall
within the range observed for other Fe(II) complexes containing
PMe3 groups [22]. The complex contains two different Fe–C bonds
with sp-and sp2 hybridization with (1.921(4) and 2.005(5) Å),
which are consistent with literature reports. When compared to
the parent complex 1 the shortened Fe–C1 bond length is due to
the electron-withdrawing influence of the alkynyl group.
6.1. Methyl[8-(diphenylphosphanyl)naphthyl-C1,P]tris(trimethyl-
From the reaction of 1 with tert-butylethyne, pentane solutions
afforded shiny orange red crystals of 6. An X-ray diffraction study
reveals that complex 6 attains a molecular structure (Fig. 6) that is
closely related with that of complex 5.
The coordination geometry (Fig. 6) shows an octahedrally sur-
rounded iron atom bearing the tert-butylethynyl substituent in
the position of the former methyl group (trans to the PPh2-group).
The bite angle C1–Fe1–P1 = 83.56(17)° almost matches that in 5
(83.99(12)°), while no influence of the bulky tert-butyl group is
recognized, when comparing the bite angle with that of the parent
phosphine)iron(II) (1)
1-(Diphenylphosphanyl)naphthalene (710 mg, 2.27 mmol) in
50 mL of THF at ꢀ70 °C was combined with FeMe2(PMe3)4
(895 mg, 2.27 mmol) in 50 mL of THF. During warm-up a gas evo-
lution was observed and the mixture turned red brown and was
kept stirring for further 4 h at 20 °C. The volatiles were removed
in vacuo and the remaining residue was extracted with three
80 mL portions of pentane. At ꢀ27 °C the solution afforded dark
red rhombic crystals of 1. Yield 1040 mg (75%); m.p. 127–129 °C.
IR (Nujol):
m .
= 1578 w (v C@C) cmꢀ1 1H NMR (500 MHz, [D8]THF,
complex
1 (83.99(8)°). The triple bonds in 6 with C32–
C33 = 1.198(9) Å and in 5 (1.210 Å) are similar with a proposed
cumulene-type coordination of a related iron-complex (1.196 Å
and 1.210 Å) but in our case with no significant deviation from lin-
earity along the axis FeCCSi, that is believed to indicate such type
of coordination [23]. The Fe–P and Fe–C distances fall in the usual
ranges of bond lengths in trimethylphosphine stabilized iron(II)
complexes.
293 K, ppm): d = ꢀ0.38 (m(br), 3H, Fe-CH3), 0.42 (m(br), 27H,
PCH3), 6.45–7.83 (m, 16H, Ar-H) ppm. 13C{1H} NMR (125 MHz,
[D8]THF, 293 K, ppm): d = ꢀ4.5 (m, Fe-CH3), 13.8 (m, PCH3), 17.7
(m, PCH3), 117.8 (s, CH), 122.6 (s, CH), 122.6 (s, CH), 125.8 (s,
CH), 127.4 (s, CH), 128.7 (s, CH), 132.3 (s, C), 133.3 (s, C), 134.0
(s, CH), 142.9 (s, CH), 178.1 (s, Fe–C) ppm. 31P{1H} NMR
2
(200 MHz, [D8]THF, 293 K, ppm): d = 7.91 (dd, JP,P = 107.3 Hz,
2
2JP,P = 73.8 Hz, 1P, PCH3), 30.5 (d, JP,P = 73.8 Hz, 2P, PCH3), 66.9
2
(d, JP,P = 107.3 Hz, 1P, PPh2) ppm. Anal. Calc. for C32H36FeP4
5. Conclusions
(610.5): C, 62.95; H, 7.60. Found: C, 62.84; H, 7.75%.
Reactions of diphenylphosphino substituted aryl compounds
with Fe(CH3)2(PMe3)4 achieve cyclometalation by C–H activation
of aromatic C–H bonds under mild conditions (ꢀ70 °C) forming no-
vel five-membered iron(II) metallacyles 1 and 3. At the present
stage of our investigation, our attempts to induce similar reactions
in the case of triphenylphosphine by an ortho metalation resulting
in four-membered metallacycles remained unsuccessful, probably
due to the fact that a reductive elimination of the two methyl
groups in the starting complex is favoured by an irreversible re-
lease of ethane. Indeed, in such cases, we do observe the formation
6.2. [1-(Diphenylphosphino)-8-methyl-naphthalene] (2)
After combining 1-(diphenylphosphino)naphthalene (710 mg,
2.27 mmol) with FeMe2(PMe3)4 (895 mg, 2.27 mmol) in 50 mL of
THF, the reaction mixture was slightly warmed to 40 °C. After
4 h, 10 ml of 2 N NH4Cl solution was added and the organic phase
separated. THF was removed in vacuo and the remaining oil resi-
due taken up in 50 ml ether which afforded white cubic crystals
of 2 when cooled to 4 °C. (274 mg, 37%); m.p. 126–128 °C. 1H

3476
R. Beck et al. / Journal of Organometallic Chemistry 693 (2008) 3471–3478
NMR (300 MHz, [d6]acetone, 293 K, ppm): d = 3.12 (d, 5JP,H = 4.2 Hz,
3H, CH3), 7.15 (ddd, JH,H = 6.4, JP,H = 5.0, JH,H = 1.5 Hz, 1H, CH),
C30H37FeOP3 (562.4): C, 64.07; H, 6.63; P, 16.52. Found: C, 63.85;
H, 7.06; P, 16.37%.
3
3
4
7.23–7.29 (m, 6H, CH), 7.31–7.32 (m, 1H, CH), 7.34–7.38 (m, 6H,
3
3
CH), 7.73 (d, JH,H = 7.8 Hz, 1H, CH), 7.82 (dd, JH,H = 8.1,
6.5. Trimethylsilylethynyl[8-(diphenylphosphanyl)naphthyl-
4JH,H = 1.4 Hz, 1H, CH) ppm. 13C{1H} NMR (125 MHz, [d6]acetone,
293 K, ppm): d = 27.5 (d, JP,C = 32.2 Hz, CH3), 125.1 (s, CH), 125.9
C1,P]tris(trimethylphosphine)iron(II) (5)
4
2
(s, CH), 126.6 (d, JP,C = 16.3 Hz, C), 128.5 (s, CH), 129.2 (d,
Trimethylsilylethyne (140 mg, 1.42 mmol) in 50 mL of THF
were combined at ꢀ70 °C with a sample of 1 (870 mg, 1.42 mmol)
in 50 mL of THF effecting a change of color from red to orange.
After warm-up the mixture was kept stirring at 20 °C for 16 h,
and then the volatiles were removed in vacuo to give orange solid.
This was dissolved in 50 mL of pentane and crystallized at ꢀ20 °C
to give yellow crystals which were suitable for X-ray diffraction.
Yield 404 mg (41%); m.p. 103–105 °C (dec.). IR (Nujol):
2JP,C = 16.5 Hz, CH), 131.3 (s, CH), 131.9 (s, CH), 132.2 (m, CH),
1
1
134.6 (d, JP,C = 20.4 Hz, CH), 135.2 (d, JP,C = 29.3 Hz, C), 135.8 (s,
2
CH), 136.1 (s, C), 136.4 (s, C), 139.1 (d, JP,C = 14.0 Hz, C) ppm.
31P{1H} NMR (200 MHz, [d6]acetone, 293 K, ppm): d = 0.8 (s, 1P)
ppm. Anal. Calc. for C23H29P (326.4): C, 84.64; H, 5.87. Found: C,
83.95; H, 6.22%.
6.3. Methyl[2-(diphenylphosphanyl)benzyl-
C,P]tris(trimethylphosphine)iron(II) (3)
m
= 1972 cmꢀ1 vs (
946 vs (
1 PCH3), 829 s (d SiMe3) cmꢀ1. 1H NMR (300 MHz, [d6]ben-
m C„C), 1587 m (m C@C), 1534 m (m FeC@C),
q
zene, 293 K, ppm): d = 0.50 (s, 9H, SiMe3), 0.63 (t’,
2
Benzyldiphenylphosphine (679 mg, 2.45 mmol) in 50 mL of
THF were combined at ꢀ70 °C with FeMe2(PMe3)4 (963 mg,
2.45 mmol) in 50 mL of diethyl ether effecting a change of color
from brown to orange red. After warm-up the mixture was kept
stirring at 20 °C for 4 h, and then the volatiles were removed in
vacuo to give a light orange red solid. This was dissolved in
50 mL of diethyl ether and crystallized at 4 °C to give orange
red sticks which were suitable for X-ray diffraction. Yield
|2JP,H + 4JP,H| = 7.8 Hz, 18H, PCH3), 1.48 (d, JP,H = 3.7 Hz, 9H, PCH3),
6.87–6.91 (m, 6H, Ar-H), 6.94 (m, 1H, Ar-H), 7.22 (m, 1H, Ar-H),
7.36 (m, 4H, Ar-H), 7.72 (m, 2H, Ar-H), 9.11 (m, 2H, Ar-H) ppm.
13C{1H} NMR (75.5 MHz, [d6]benzene, 293 K, ppm): d = 1.5 (s,
SiCH3), 15.1 (m, PCH3), 18.1–18.5 (m, PCH3), 115.6 (s, CH), 117.3
(s, Fe-C„C), 120.6 (s, CH), 125.4 (m, CH), 125.6 (s, CH), 126.2 (s,
1
CH), 127.0 (s, CH), 127.3 (s, CH), 133.5 (d, JP,C = 18.2 Hz, C), 132.1
2
(s, CH), 138.5 (s, Fe-C„C), 141.8 (d, JP,C = 11.9 Hz, C), 147.1 (s, C),
323 mg (23%); m.p. 50 °C (dec.). IR (Nujol):
m
= 1584 w (
m
C@C),
193.4 (m, Fe-C) ppm. 31P{1H} NMR (121.5 MHz, [d6]benzene,
2
1565 w (
m
FeC@C) cmꢀ1, 945 vs (q1 PCH3) cmꢀ1
.
1H NMR
293 K, ppm): d = 4.4 (d, JP,P = 28.5 Hz, 1P, PCH3), 9.8 (dd,
2
2
(500 MHz, [D8]THF, 293 K, ppm): d = ꢀ0.46 (s(br), 3H, Fe-CH3),
0.45 (s(br), 18H, PCH3), 0.65 (s(br), 9H, PCH3), 1.82 (m, 2H,
PCH2), 6.53–7.60 (m, 14H, Ar-H) ppm. 13C{1H} NMR (125 MHz,
[D8]THF, 293 K, ppm): d = 4.1 (m, Fe-CH3), 14.2 (m, PCH3), 18.5
2JP,P = 28.5 Hz, JP,P = 33.5 Hz, 2P, PCH3), 81.5 (d, JP,P = 33.5 Hz, 1P,
PPh2) ppm. Anal. Calc. for C36H52FeP4Si (692.6): C, 62.43; H, 7.57.
Found: C, 62.01; H, 8.11%.
1
(m, PCH3), 49.8 (d, JP,C = 26.9 Hz, PCH2), 119.7 (s, CH), 121.5 (s,
6.6. tert-Butylethynyl[8-(diphenylphosphanyl)naphthyl-
CH), 121.9 (s, CH), 127.3 (m, CH), 127.5 (s, CH), 132.9 (d,
2JP,C = 12.8 Hz, CH), 142.1 (s, C), 143.7 (s, C), 144.9 (s, CH), 180.5
(s, FeC) ppm. 31P{1H} NMR (200 MHz, [D8]THF, 293 K, ppm):
d = 10.0 (s(br), 1P, PCH3), 17.6 (s(br), 2P, PCH3), 72.3 (s(br), 1P,
PPh2) ppm. Anal. Calc. for C29H46FeP4 ꢁ 0.5C5H12 (610.46): C,
61.97; H, 8.59; P, 20.29. Found: C, 61.80; H, 8.67; P, 20.60%.
C1,P]tris(trimethylphosphine)iron(II) (6)
tert-Butylethyne (91 mg, 1.11 mmol) in 50 mL of pentane were
combined at ꢀ70 °C with a sample of 1 (680 mg, 1.11 mmol) in
50 mL of diethyl ether. After warm up the mixture was kept stir-
ring at 20 °C for 16 h, and then the volatiles were removed in vacuo
to give an orange solid. This was dissolved in 50 mL of diethyl
ether/pentane (1:1) and crystallized at ꢀ20 °C to give orange
rhombic crystals which were suitable for X-ray diffraction. Yield
6.4. Methyl[8-(diphenylphosphanyl)naphthyl-
C1,P]carbonylbis(trimethylphosphine)iron(II) (4)
233 mg (31%); m.p. 92–95 °C (dec.). IR (Nujol):
m = 2049 vs (m
A sample of 1 (324 mg, 1.28 mmol) in 40 mL of THF was kept
stirring under 1 bar of CO for 1 h to become a light red solution.
The volatiles were removed in vacuo and the solid residue was ex-
tracted with three 70 mL portions of pentane. Crystallization at
ꢀ27 °C afforded orange rods of 4, which were suitable for X-ray dif-
fraction. Yield 241 mg (81%); m.p. 161–164 °C (dec.). IR (Nujol):
C„C), 1590 m (m C@C), 1533 m (m FeC@C), 942 vs (q1 PCH3)
cmꢀ1
.
1H NMR (300 MHz, [d6]benzene, 293 K, ppm): d = 0.63
2
(s(br), 18H, PCH3), 1.12 (s, 9H, CMe3), 1.45 (d, JP,H = 4.1 Hz, 9H,
PCH3), 6.78 (m, 6H, Ar-H), 6.84 (m, 1H, Ar-H), 7.73 (m, 5H, Ar-H),
7.85 (m, 1H, Ar-H), 7.90 (m, 1H, Ar-H), 8.58 (m, 2H, Ar-H) ppm.
13C{1H} NMR (75.5 MHz, [d6]benzene, 293 K, ppm): d = 14.8 (m,
PCH3), 17.7 (m, PCH3), 31.7 (s, CCH3), 34.9 (s, CCH3), 110.9 (s, Fe-
C„C), 117.6 (s, CH), 120.1 (s, Fe-C„C), 122.4 (s, CH), 123.1 (d,
m
= 1872 cmꢀ1 vs (
m C„O), 1578 m (m C@C); 935 vs (q1 PCH3)
cmꢀ1
.
1H NMR (500 MHz, [D8]THF, 293 K, ppm): d = ꢀ0.82 (dt,
3JP,H = 11.0 Hz,
3JP,H = 1.2 Hz,
3H,
Fe-CH3),
0.45
(t’,
3JP,C = 6.1 Hz, CH), 125.6 (s, CH), 126.2 (d, JP,C = 7.3 Hz, CH), 126.4
3
|2JP,H + 4JP,H| = 7.1 Hz, 18H, PCH3), 7.23–7.25 (m, 3H, Ar-H), 7.29–
(s, CH), 127.2 (s, CH), 131.6 (d, JP,C = 19.2 Hz, C), 132.1 (d,
1
3
4
2
7.33 (m, 5H, Ar-H), 7.46 (td, JH,H = 8.0 Hz, JH,H = 1.3 Hz, 1H, Ar-
2JP,C = 12.0 Hz, CH), 139.8 (d, JP,C = 10.2 Hz, C), 145.3 (m, C), 189.2
3
4
H); 7.65 (dt, JH,H = 7.2 Hz, JH,H = 1.5 Hz, 1H, Ar-H), 7.97 (dt,
(m, Fe-C) ppm. 31P{1H} NMR (121.5 MHz, [d6]benzene, 293 K,
3JH,H = 6.1 Hz, JH,H = 0.9 Hz, 2H, Ar-H), 8.11–8.15 (m, 3H, Ar-H),
ppm): d = 5.6 (d, JP,P = 30.5 Hz, 1P, PCH3), 10.8 (dd, JP,P = 30.5 Hz,
4
2
2
8.32 (dt, JH,H = 7.2 Hz, JH,H = 0.9 Hz, 1H, Ar-H) ppm. 13C{1H} NMR
2JP,P = 34.1 Hz, 2P, PCH3), 78.5 (d, JP,P = 34.1 Hz, 1P, PPh2) ppm.
3
4
2
2
(125 MHz, [D8]THF, 293 K, ppm): d = ꢀ0.21 (dt, JP,C = 20.0 Hz,
Anal. Calc. for C37H52FeP4 (676.5): C, 65.69; H, 7.75. Found: C,
65.78; H, 8.50%.
2JP,C = 7.5 Hz, Fe-CH3), 15.8 (t’, |1JP,C + 3JP,C| = 24.9 Hz, PCH3), 122.5
4
(s, CH), 123.8 (d, JP,C = 5.0 Hz, CH), 125.4 (s, CH), 128.9 (d,
1JP,C = 30.1 Hz, CH), 129.2 (s, CH), 129.6 (s, C), 132.4 (d,
6.7. Crystal structure analysis
3JP,C = 10.2 Hz, CH), 132.9 (s, C), 133.3 (d, JP,C = 7.5 Hz, C), 135.4
3
4
1
(s, C), 138.3 (d, JP,C = 5.0 Hz, CH), 143.3 (d, JP,C = 31.3 Hz, CH),
Data collections were performed on a STOE IPDSII image plate
detector and on a Bruker AXS SMART APEX diffractometer using
1
1
154.6 (d, JP,C = 42.5 Hz, CH), 173.9 (s, CH), 180.4 (d, JP,C = 8.7 Hz,
Fe-C), 221.8 (t, JP,C = 17.7 Hz, Fe-CO) ppm. 31P{1H} NMR
Mo K radiation (k = 0.71019 Å). Details of the crystal structure
2
a
2
(200 MHz, [D8]THF, 293 K, ppm): d = 15.9 (d, JP,P = 28.8 Hz, 2P,
are given in Table 1. Data collection [29]: Stoe X-AREA, Bruker
SMART. Data reduction [29]: Stoe X-RED, Bruker SAINT. The struc-
2
PCH3); 74.4 (t, JP,P = 28.8 Hz, 1P, PPh2) ppm. Anal. Calc. for

R. Beck et al. / Journal of Organometallic Chemistry 693 (2008) 3471–3478
3477
Table 1
Crystal data for compounds 1–6
1
2
3
4
5
6
Empirical formula
Molecular mass
Crystal size (mm)
Crystal system
Space group
a (Å)
C32H46FeP4
647.48
C23H19
326.25
P
C29H46FeP4ꢁ0.5C5H12
610.46
0.42 ꢂ 0.21 ꢂ 0.15
Monoclinic
P21/c
18.9534(16)
10.2773(8)
18.4165(2)
90
113.997(8)
90
C30H37FeOP3
562.36
0.22 ꢂ 0.20 ꢂ 0.05
Monoclinic
P21/c
18.696(5)
9.136(3)
34.559(8)
90
106.450(12)
90
C36H52FeP4Si
692.60
0.25 ꢂ 0.25 ꢂ 0.20
Monoclinic
Cc
13.5257(11)
14.6871(13)
19.850(2)
90
109.568(3)
90
C37H52FeP4
676.52
0.35 ꢂ 0.20 ꢂ 0.17
Monoclinic
Cc
13.206(2)
15.087(3)
19.480(4)
90
108.834(7)
90
0.50 ꢂ 0.30 ꢂ 0.20
0.13 ꢂ 0.10 ꢂ 0.08
Monoclinic
P21/c
10.535(4)
15.970(6)
10.826(4)
90
106.858(6)
90
1743.1(11)
4
Triclinic
ꢀ
P1
10.0702(19)
10.1194(19)
17.705(3)
77.361(4)
81.376(4)
74.921(4)
1691.5(5)
2
b(Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
3277.3(5)
4
1.237
5661(3)
8
1.320
3715.5(6)
4
1.238
3673.4(12)
4
1.223
Z
Dcalcd. (g/cm3)
1.271
0.658
1.244
0.158
l
(Mo K
a
) (mmꢀ1
)
0.674
0.724
0.634
0.608
Temperature (K)
298(2)
273(2)
193(2)
293(2)
273(2)
273(2)
H
h
k
-Range (°)
1.18 6
H
6 26.37
2.02 6
H
6 25.05
2.32 6
H
6 26.05
1.14 6
H
6 28.08
2.12 6
H
6 24.99
2.12 6 H 6 25.00
ꢀ12 6 h 6 12
ꢀ12 6 k 6 12
ꢀ22 6 l 6 22
15246
ꢀ12 6 h 6 11
ꢀ19 6 k 6 14
ꢀ12 6 l 6 12
9052
ꢀ23 6 h 6 23
ꢀ12 6 k 6 12
ꢀ22 6 l 6 22
31421
ꢀ24 6 h 6 24
ꢀ11 6 k 6 12
ꢀ43 6 l 6 45
45735
ꢀ16 6 h 6 16
ꢀ17 6 k 6 15
ꢀ23 6 l 6 23
20334
ꢀ15 6 h 6 15
ꢀ17 6 k 6 17
ꢀ23 6 l 6 22
16879
l
No. of reflection
measured
No. of unique data
[R(int)
6906[0.1214]
3084[0.025]
6423[0.0546]
13743[0.236]
6096[0.0606]
6280[0.065]
]
Parameters
Restraints
345
0
218
0
364
7
632
0
391
2
391
20
Goodness of fit (GoF)
0.856
1.034
0.881
0.882
1.032
0.872
on F2
R1 [I P 2
wR2 (all data)
r
(I)]
0.0589
0.1489
0.0355
0.0951
0.0355
0.0803
0.1076
0.2763
0.0466
0.1148
0.0538
0.1545
[3] (a) H.-F. Klein, R. Beck, U. Flörke, H.-J. Haupt, Eur. J. Inorg. Chem. (2003) 1380;
(b) H.-F. Klein, S. Schneider, M. He, U. Flörke, H.-J. Haupt, Eur. J. Inorg. Chem.
(2000) 2295.
[4] The proximity C–H orientations of the ortho CH3-group in 2-
diphenylphosphinotoluene is not restricted and therefore the free rotation is
to believe competes with the fast reductive elimination in Fe(CH3)2(PMe3)4;
H.-F. Klein, S. Camadanli, R. Beck, U. Flörke, Chem. Commun. (2005) 381.
[5] P.E. Garrou, Chem. Rev. 81 (1981) 229.
tures were solved by direct methods using SHELXS-97 [30], and aniso-
tropic displacement parameters were applied to non-hydrogen
atoms in a full-matrix least-squares refinement based on F2 using
SHELXL-97 [30]. For 1 it was not possible to refine the heavily
disordered enclosed Et2O solvent molecule. Accordingly, the data
was treated with the SQUEEZE facility of PLATON [31], which resulted
in smooth refinement. For 4 the structure was of marginal quality
(R1 = 0.1076) and should be understood as proof of connectivity
[6] (a) G. Hata, H. Kondo, A. Miyake, J. Am. Chem. Soc. 90 (1968) 2278;
(b) S.D. Ittel, C.A. Tolman, P.J. Krusic, A.D. English, J.P. Jesson, Inorg. Chem. 17
(1978) 3432;
only. Hydrogen atoms on
C were placed at idealized posi-
(c) H. Azizian, R. H Morris, Inorg. Chem. 22 (1983) 6;
tions (C–H = 0.93 Å, 0.96 Å for methyl groups) and were allowed
to ride on the parent atom [Uiso(H) = 1.2U(C) for CH groups and
Uiso(H) = 1.5U(C) for methyl groups].
(d) T. Ikariya, A. Yamamoto, J. Organomet. Chem. 118 (1976) 65;
(e) A. Sacco, M. Aresta, J. Chem. Soc., Chem. Commun. (1968) 1223;
(f) E. Koerner von Gustorf, I. Fischler, J. Leitich, H. Dreeskamp, Angew. Chem.,
Int. Ed. Engl. 11 (1972) 1088.
[7] F.H. Carre, Cryst. Struct. Commun. 11 (1982) 1009.
[8] R. Beck, Dissertation, Technische Universität Darmstadt, 2001.
[9] (a) D. van Allen, D. Venkataraman, J. Org. Chem. 68 (2003) 4590;
(b) B.J. Dunne, A.G. Orpen, Acta Crystallogr., Sect. C 47 (1991) 345;
(c) J. Bruckmann, C. Krüger, F. Lutz, Z. Naturforsch. Teil. B 50 (1995) 351.
[10] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Watson, R. Taylor, J. Chem.
Soc., Dalton. Trans. (1989) S1.
Acknowledgments
Financial support of this work by Fonds der Chemischen Indust-
rie is gratefully acknowledged. R.B. would also like to thank the
China Postdoctoral Science Foundation and Shandong University
Postdoctoral Science Foundation for financial support.
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CCDC 681744, 681482, 681479, 681745, 681481 and 681480
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