5-Methyl-2-thienylcalcium iodide

Article abstract of DOI:10.1039/c8dt01398e

The reduction of 2-bromo- and 3-bromothiophene with calcium powder gives impure thienylcalcium complexes due to interference of various subsequent metalation and calcium-halogen exchange reactions as well as ether degradation. Therefore, calcium-iodine exchange succeeds via the reaction of trimethylsilylmethylcalcium halide with 3-iodothiophene in tetrahydrofuran at -78 °C in the presence of chloro-trimethylsilane, leading to the quantitative formation of 3-(trimethylsilyl)thiophene. The synthesis and isolation of a thienylcalcium halide, a heavy Grignard reagent with a thienyl group, is possible via the reduction of 2-iodo-5-methylthiophene with activated calcium in THF. Substitution of the thf ligands in 5-methyl-2-thienylcalcium iodide ([5-MeThien-2-Ca(thf)₄I], 1) by dissolution in tetrahydropyran (THP) leads to the thp complex of 5-methyl-2-thienylcalcium iodide ([5-MeThien-2-Ca(thp)₄I], 2). A low field shift of the calcium-bound carbon atom is characteristic of thienylcalcium complexes.

Full text of DOI:10.1039/c8dt01398e

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5-Methyl-2-thienylcalcium iodide†
Cite this: DOI: 10.1039/c8dt01398e
Alexander Koch, Sven Krieck,
Helmar Görls and Matthias Westerhausen
*
The reduction of 2-bromo- and 3-bromothiophene with calcium powder gives impure thienylcalcium
complexes due to interference of various subsequent metalation and calcium–halogen exchange reac-
tions as well as ether degradation. Therefore, calcium–iodine exchange succeeds via the reaction of tri-
methylsilylmethylcalcium halide with 3-iodothiophene in tetrahydrofuran at −78 °C in the presence of
chloro-trimethylsilane, leading to the quantitative formation of 3-(trimethylsilyl)thiophene. The synthesis
and isolation of a thienylcalcium halide, a heavy Grignard reagent with a thienyl group, is possible via the
reduction of 2-iodo-5-methylthiophene with activated calcium in THF. Substitution of the thf ligands in
Received 10th April 2018,
Accepted 24th April 2018
4
5-methyl-2-thienylcalcium iodide ([5-MeThien-2-Ca(thf) I], 1) by dissolution in tetrahydropyran (THP)
DOI: 10.1039/c8dt01398e
leads to the thp complex of 5-methyl-2-thienylcalcium iodide ([5-MeThien-2-Ca(thp)
shift of the calcium-bound carbon atom is characteristic of thienylcalcium complexes.
4
I], 2). A low field
rsc.li/dalton
Gronowitz showed a significantly higher reactivity of thio-
phene than that of furan with respect to metalation reactions.
Introduction
9
1
2
3,4
Aryllithium, -magnesium and -calcium compounds
are
A thorough reinvestigation of the lithiation of furan and
convenient organometallics for diverse reactions and represent thiophene with n-butyllithium has shown that the reaction is
1
0
valuable metalation and aryl transfer reagents. Contrary to the much more complex than that reported earlier. Depending
straightforward synthesis of these s-block metal complexes via on the reaction temperature and time, solvent, ratio of furan/
direct synthesis (Grignard reaction) or via metal–halogen thiophene to n-butyllithium and on addition of N,N,N′,N′-tetra-
exchange, the preparation of thienyllithium compounds methylethylene-1,2-diamine
(1,2-bis(dimethylamino)ethane,
proved to be challenging, not always certain and often confus- tmeda), various amounts of mono- and dilithiofuran
ing, even though the chemistry of metalated thiophene deriva- (Scheme 1, EvO) and -thiophene (EvS) have been observed.
tives has a long tradition.
For example, an equimolar mixture of nBuLi and thiophene in
th
In the early 20 century, metalation of thiophene has been hexane at reflux temperature yields 42% of 2-monolithiothio-
studied by several groups and the products have been identi- phene and 30% of 2,5-dilithiothiophene after the addition of
fied by derivatization reactions. Schorigin metalated thiophene tmeda, n-butyllithium has been consumed quantitatively. In
1
0
with ethylsodium, intermediately prepared from sodium and addition, an equilibrium shown in Scheme 2 complicates the
5
diethylmercury. Already in 1949, Gilman and Shirley pub-
6
lished the lithiation of thiophene with n-butyllithium.
Metalation of thiophene and alkyl-substituted thiophene in
2
-position succeeds also with sodium or sodium amalgam in
7
benzene or diethyl ether. Lithiation is also possible via the co-
condensation of thiophene with lithium atoms at 77 K; the
8
products have been quenched with chloro-trimethylsilane in
order to deduce the lithiation products. Extensive studies by Scheme 1 Stepwise lithiation of thiophene with n-butyllithium in the
presence of TMEDA (E = O, S).
Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena,
Humboldtstrasse 8, D-07743 Jena, Germany. E-mail: m.we@uni-jena.de;
Fax: +49 (0) 3641-9-48132
†
Electronic supplementary information (ESI) available: NMR spectra of
{
[5-MeThien-2-Ca(thp) I] (2)} and preparative details for the calcium–iodine
4
exchange reaction. CCDC 1835240 for 2 (excluding structure factors). For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c8dt01398e
Scheme 2 Equilibrium between 2-lithiothiophene on the one side and
2,5-dilithiothiophene and thiophene on the other (E = O, S).
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preparation and isolation of pure monolithio derivatives.
Lithiation in the 3- and 4-positions has not been observed at
furan and thiophene. However, 2-methylthiophene reacts with
excess n-butyllithium to afford 2-lithio-5-methylthiophene
(
95%) and only traces of 2,3-dilithio-5-methylthiophene (3%)
Scheme 4 Synthesis of polythiophene via Halogen Dance reactions
and nickel(II)-mediated Murahashi coupling.
5
are discovered. This complex shows a monomer–dimer equili-
brium in ethereal solvents.
1
1
Already in 1948, Schick and Hartough noticed that sodium
and 2-bromo- as well as 2-iodothiophene are metalated by
sodium in the 5-position yielding 5-halo-2-thienylsodium
To limit side reactions, 2-bromo-5-methylthiophene was
used as a substrate for the synthesis of thienyllithium and
7
rather than 2-thienylsodium. The use of bromo- or iodosubsti-
-magnesium derivatives for subsequent conversions without
tuted thiophene in the reaction with lithium-based organome-
tallics leads to competing reactions of metalation, directed
metalation in vicinal position to the halogen atom and lithium–
halogen exchange. The situation is even more complicated
because intermediately formed lithiothiophenes also interfere
with the substrate as well as products, leading to new bromi-
nated thiophenes as shown exemplarily in Scheme 3 and known
the isolation of these s-block organometallics. Examples
2
0
include the transfer of the thienyl group as well as addition
21
22,23
to organic azides and C–C coupling reactions.
The metala-
tion of thiophene and 2-methylthiophene with butyllithium
yields tetrameric 2-thienyl- and 5-methyl-2-thienyllithium,
respectively. The determination of the crystal structures of their
ether adducts verifies tetranuclear complexes with central Li
4
4,25
1
2
2
as Halogen Dance. The reaction of 2,3-dibromothiophene with
lithium diisopropylamide (LDA) at −80 °C primarily yields the
metalation product 2,3-dibromo-5-lithiothiophene which reacts
with the substrate via a lithium–bromine exchange to form the
products 2,3,5-tribromothiophene and 3-bromo-2-lithiothio-
phene. Another lithium–bromine exchange converts 2,3,5-tribro-
mothiophene into 3,5-dibromo-2-lithiothiophene as depicted in
Scheme 3. Excellent reviews summarize these Halogen Dance
tetrahedra and the thienyl groups located above the Li faces.
3
24
26
Multidentate amino bases or ethers lead to structures of
lower nuclearity. Thienylmagnesium complexes are accessible via
a direct synthesis of magnesium turnings with 2-bromothio-
phene yielding [(thf)
with hexa-coordinate magnesium atoms. The structures of
-thienyllithium and -magnesium derivatives are very rare and
4 2 2
Mg(2-Thien) ] and [(dme) Mg(2-Thien)Br]
27
3
28
steric requirements are needed to stabilize such complexes.
13,14
reactions at thiophene derivatives and halobenzenes.
In another reaction 2,5-dibromo-3-hexylthiophene has been
reacted with LDA yielding intermediately 2,4-dibromo-3-hexyl-5-
lithiothiophene after a lithium–bromine exchange and a Halogen
Results and discussion
15,16
Dance reaction.
Nickel-mediated Murahashi C–C-coupling The reaction of 2-bromothiophene with activated calcium gave
low yields of thienylcalcium complexes and diverse side pro-
finally gives the corresponding polythiophene (Scheme 4).
The difficulties in preparing magnesiated thiophenes ducts besides thiophene. Thiophene can be formed via diverse
strongly depend on the number and position of the bromine mechanisms, including the metalation of 2-bromothiophene
1
7
substituents. Magnesiated thiophenes are accessible via the by thienylcalcium derivatives or via ether degradation. A
magnesium–bromine exchange at 0 °C in tetrahydrofuran. similar reaction of 3-bromothiophene with calcium powder
Thus, a regioselective magnesium–bromine exchange allows yielded 3-bromo-2-thienylcalcium complexes but again the
the synthesis of 2-bromo-3-methylthio-5-chloromagnesiothio- yields were very low. This product was formed via an insertion
phene using iPrMgCl·LiCl and 2,5-dibromo-3-(methylthio)thio- of the metal into the C–Br bond (yielding 3-thienylcalcium
1
8
phene. In a recent study Yamane et al. demonstrated that bromide) which metalated another equivalent of 3-bromothio-
magnesium bis(amides) are also able to initiate Halogen phene in the 2-position. Due to diverse side products, the iso-
1
9
Dance reactions.
lation of a pure compound failed. Therefore, the metalation of
-bromothiophene was performed with diphenylcalcium
Scheme 5) and after the addition of 18-crown-6 ether the
molecular structure of the crown ether adduct of bis(3-bromo-
3
(
4
2-thienyl)calcium was determined.
Based on our encouraging studies on calcium–halogen
2
9
exchange reactions, we reacted trimethylsilylmethylcalcium
iodide with 3-iodothiophene in tetrahydrofuran at −50 °C. The
NMR spectroscopic investigation of the resulting solution
showed several species including thiophene as well as 3-thie-
nylcalcium and 2-thienylcalcium complexes besides iodo-
methyl-trimethylsilane (Scheme 6). The calcium-bound carbon
atoms show very characteristic low field shifted resonances at
δ = 181.6 and 180.1 ppm, respectively. However, the isolation
and purification of an organocalcium complex from these
Scheme 3 Halogen Dance via lithiation and lithium–bromine exchange
reactions.
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3
,4,30
for organocalcium reagents
and that we observed thio-
phene formation during crystallization attempts, an ether with
less acidic α-hydrogen atoms was chosen. Solvent exchange led
to the formation of the tetrahydropyran (THP) complex of
5
-methyl-2-thienylcalcium iodide ([5-MeThien-2-Ca(thp) I], 2).
4
The characteristic low field shift of the calcium-bound carbon
atom of δ = 178.4 ppm verified the formation of a heavy
Grignard reagent. Recrystallization of this complex from tetra-
hydropyran gave long needles of ([5-MeThien-2-Ca(thf) I] (2)),
4
suitable for X-ray diffraction experiments.
Scheme 5 Metalation of 3-bromothiophene with diphenylcalcium and
formation of the 18-crown-6 ether complex of bis(3-bromo-2-thienyl)
calcium.
The molecular structure and numbering scheme of
5-MeThien-2-Ca(thp) I] (2) is depicted in Fig. 1. The crystal struc-
ture contains 2% of [(thp) CaI ] and furthermore, THP molecules
[
4
4
2
are intercalated between the calcium complexes with an occu-
pation factor of 0.75 without short Ca–O contacts. Consequently,
the composition of the studied single crystal sums up to
{
[5-MeThien-2-Ca(thp)4I]0.98·[(thp) CaI2]0.02·0.75THP}. The anions
4
are in trans position to each other (I1–Ca1–C1 177.95(13)°) to
minimize electrostatic repulsion. The Ca1–C1 and Ca1–I1
bond lengths of 257.2(5) and 316.34(8) pm, respectively, lie in
the expected ranges as also found for arylcalcium iodides. The
Ca1–O distances between 237.7(3) and 239.2(3) pm show that
Scheme 6 Reactions of 3-iodothiophene with trimethylsilylmethyl- negligible steric strain is induced by the 5-methyl-2-thienyl
calcium iodide in tetrahydrofuran yielding diverse products depending ligand. Due to the hindrance induced by the C2-bound hydro-
on metalation and calcium–iodine exchange pathways.
solutions failed. In order to verify the initial product,
3
−
-iodothiophene and chloro-trimethylsilane were dissolved at
78 °C in tetrahydrofuran and trimethylsilylmethylcalcium
iodide was added. Due to the fact that the calcium–iodine
exchange is much faster than the metathesis reaction with
chloro-trimethylsilane, the thienylcalcium complex reacted
with ClSiMe , quantitatively yielding 3-(trimethylsilyl)thio-
3
phene and iodomethyl-trimethylsilane.
To limit the diversity of products during the direct synthesis
of thienylcalcium compounds, the 5-position was blocked by a
methyl group. Hence, the preparation and isolation of a thie-
nylcalcium halide (a heavy Grignard reagent with a thienyl
group) succeeded via the reaction of activated calcium with
2
-iodo-5-methylthiophene (2-I-5-MeThien) in tetrahydrofuran
at 0 °C (Scheme 7). Titration of an aliquot of the reaction solu-
tion gave a yield of 60% of the thf adduct of 5-methyl-2-thienyl-
calcium iodide ([5-MeThien-2-Ca(thf) I], 1). Furthermore,
4
calcium diiodide was formed via Wurtz-type coupling reac-
tions. Due to the fact that ether degradation is quite common
Fig. 1 Molecular structure and numbering scheme of [5-MeThien-2-Ca
thp) I] (2). Intercalated THP, superimposed [(thp) CaI ], and hydrogen
(
4
4
2
atoms are omitted for clarity reasons. Selected bond lengths (pm):
Ca1–C1 257.2(5), Ca1–I1 316.34(8), Ca1–O1 237.7(3), Ca1–O2 239.2(3),
Ca1–O3 237.7(3), Ca1–O4 238.6(3), S1–C1 172.4(5), S1–C4 173.8(4),
C1–C2 135.8(7), C2–C3 142.4(6), C3–C4 135.1(6), C4–C5 151.1(6); bond
angles (°.): I1–Ca1–C1 177.95(13), C1–Ca1–O1 92.90(14), C1–Ca1–O2
9
8
0.35(14), C1–Ca1–O3 89.70(14), C1–Ca1–O4 92.82(14), O1–Ca1–O2
3.36(10), O1–Ca1–O3 175.79(11), O1–Ca1–O4 91.69(10), O2–Ca1–O3
Scheme 7 Direct synthesis of 5-methyl-2-thienylcalcium iodide as
93.32(10), O2–Ca1–O4 174.25(10), O3–Ca1–O4 91.49(10), I1–Ca1–O1
89.15(7), I1–Ca1–O2 89.71(7), I1–Ca1–O3 88.25(7), O1–Ca1–O4
87.30(7).
4
tetrahydrofuran ([5-MeThien-2-Ca(thf) I], 1) and tetrahydropyran
adducts ([5-MeThien-2-Ca(thp) I], 2).
4
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Table 1 Comparison of the bond lengths of metal-bound 2-thienyl groups in selected lithium and magnesium derivatives with values of the
calcium reagent 2 (pm)
a
b
Compound
Pos.
S–C1
S–C4
C1–C2
C2–C3
C3–C4
Ref.
[
[
[
[
[
[
[
[
Li(2-Thien)]
Li(5-Me-2-Thien)]
(thf) Li(2-Thien)]
(dme)Li(2-Thien)]
(pmdeta)Li(2-Thien)]
(thf) Mg(2-Thien)
(dme) Mg(2-Thien)Br]
(thp) Ca(5-Me-2-Thien)I] (2)
4
br
br
br
br
t
t
t
173.8(2)
174.8(7)
173.0(2)
172.4(3)
172.5(2)
169.5(5)
172.8(6)
172.4(5)
171.9(2)
172.5(8)
172.4(4)
172.9(2)
172.2(2)
170.5(7)
173.4(8)
173.8(4)
138.8(3)
139.3(10)
137.8(4)
136.4(5)
136.5(5)
135.4(8)
137.6(8)
135.8(7)
141.9(3)
143.1(10)
142.4(7)
140.8(4)
139.9(6)
146.9(8)
141.9(9)
142.4(6)
134.8(3)
135.9(11)
136.4(5)
135.4(3)
134.8(3)
132.9(9)
133.3(10)
135.1(6)
24
25
24
24
24
27
27
Here
4
2
2
4
4
2
]
2
4
t
a
Abbreviations: 2-Thien = 2-thienyl, 5-Me-2-Thien = 5-methyl-2-thienyl, dme = 1,2-dimethoxyethane, pmdeta = N,N,N′,N″,N″-pentamethyldiethyl-
b
enetriamine, thf = tetrahydrofuran, thp = tetrahydropyran. br bridging position, t terminally bound thienyl group.
gen atom, the Ca1–C1–C2 (130.3(3)°) and Ca1–C1–S1 single crystal. The molecular structure of the thp adduct of
(
122.9(3)°) bond angles differ by 7.4°.
As shown in Table 1, the bond lengths of selected 2-thienyl- the iodide and thienyl ligand in contrast to the Grignard
lithium and -magnesium complexes are compared with the reagent [(dme) Mg(2-Thien)Br]. Structural parameters with
5-methyl-2-thienylcalcium iodide shows a trans arrangement of
2
values of the calcium congener 2. Regardless of the s-block respect to Ca–C, Ca–I and Ca–O bond lengths are comparable
metal rather similar bond lengths are observed. The hexa- to those of arylcalcium iodides. The influence of methyl sub-
coordinate magnesium derivative [(dme)
shows a cis-arrangement of the anionic ligands whereas the the bonding parameters of the 2-thienyl group are negligible.
bis(2-thienyl)magnesium complex [(thf) Mg(2-Thien) ] crystal- In accordance with arylcalcium complexes, the calcium-bound
2
Mg(2-Thien)Br] stitution and nature of the s-block metal (size, hardness) on
4
2
2
7
lizes as the trans-isomer as also observed for 2. The bond carbon atom of the 2-thienyl group shows a strongly low field-
lengths within the 2-thienyl groups of 2 and of the Grignard shifted resonance.
2
reagent [(dme) Mg(2-Thien)Br] are very similar but slightly
shorter S–C bonds are observed for the bis(2-thienyl)
magnesium complex. The influence of the methyl group in the Experimental
5
-position (at C4) on the structural data is negligible.
Materials and methods
All manipulations were carried out under an inert nitrogen
atmosphere using standard Schlenk techniques, if not other-
wise noted. THF and THP were dried over KOH and distilled
Conclusion
The synthesis of thienylcalcium complexes is challenging due over sodium/benzophenone under a nitrogen atmosphere
to diverse interfering side reactions such as metalation and prior to use. Deuterated solvents were dried over sodium, dis-
calcium–halogen exchange equilibria, accompanied by ether tilled, degassed, and stored under a nitrogen atmosphere over
1
13
1
degradation reactions. Calcium–halogen exchange reactions sodium. H and C{ H} NMR spectra were recorded on Bruker
between alkylcalcium halide and iodothiophene at low tem- Avance 400 and Fourier 300 spectrometers, respectively.
peratures and the reduction of bromo- and iodothiophenes Chemical shifts are reported in parts per million relative to
4
with calcium powder allow the formation of thienylcalcium SiMe as an external standard referenced to the solvent reso-
complexes. However, the isolation of pure thienylcalcium com- nances. 2-Iodo-5-methylthiophene and 3-iodothiophene were
pounds failed due to diverse subsequent reactions. Protection purchased from Sigma Aldrich. Purity was controlled by NMR
of the 5-carbon atom by a methyl group to suppress metalation spectroscopic measurements, by determination of the alka-
in this position proves to be highly advantageous. The linity of an aliquot of the reaction solution and by complexo-
reduction of 2-iodo-5-methylthiophene in tetrahydrofuran with metric titration of the Ca content with EDTA. Activation of
activated calcium allows the synthesis of a thf adduct of a calcium metal and preparation of highly reactive calcium
heavy Grignard reagent with a thienyl ligand, 5-methyl-2-thie- powder were performed via dissolution in liquid ammonia
nylcalcium iodide ([5-MeThien-2-Ca(thf)
4
3
I], 1). Due to the fact and fast removal of NH under vacuum according to a litera-
3
f
that tetrahydrofuran easily undergoes ether degradation, ture protocol.
ligand exchange and the formation of the thp complex stabil-
ize the thienyl derivative ([5-MeThien-2-Ca(thf) I] (2)), the first
4
Synthesis of ([5-MeThien-2-Ca(thp) I]·2THP, 2·2THP)
4
structurally authenticated heavy Grignard reagent with a Activated calcium (383 mg, 9.55 mmol, 1.5 equiv.) was sus-
thienyl substituent. The crystalline state also contains very pended in 20 ml of THF. The suspension was cooled to 0 °C
small amounts of calcium diiodide and intercalated tetra- and then 1.48 g of 1-iodo-5-methylthiophene (6.6 mmol,
hydropyran molecules, leading to a formula sum of {[5-MeThien- 1 equiv.) was added. The reaction mixture was shaken for 2 h
2
-Ca(thp)4I]0.98·[(thp) CaI2]0.02·0.75THP} for the investigated at 0 °C, then warmed to r.t. and shaken for additional 2 h.
4
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Thereafter, all solids were removed by filtration, yielding 13 ml
Acknowledgements
of a 0.295 M solution of ([5-MeThien-2-Ca(thf) I], 1) in THF
4
(60% yield determined by acidimetric titration). The solvent Dr Alexander Koch is grateful to the Fonds der Chemischen
was removed and the residue was dissolved in 10 ml of THP. Industrie im Verband der Chemischen Industrie (FCI/VCI,
This procedure was repeated 3 times. Finally, the white solid Frankfurt, Germany; fund 510259) and to the Graduate
was extracted with 10 ml of THP and all solids were removed Academy of the Friedrich Schiller University Jena for generous
by filtration. The solution was cooled to −40 °C, yielding Ph.D. grants. We thank Dr Mathias Köhler and Paul Schönherr
4
53 mg of 2·2THP (0.67 mmol, 10%) as long crystalline for valuable preliminary investigations. We also acknowledge
needles. The crystals were collected, but they easily lost interca- the support by the NMR service platform (http://www.nmr.uni-
lated THP during isolation and handling. Due to this fact jena.de) of the Faculty of Chemistry and Earth Sciences of the
reliable C,H,N analytical data could not be obtained.
Friedrich Schiller University Jena.
1
Physical data. H NMR ([D
8
]THF, 400.13 MHz): δ = 1.53 (m,
1
1
1
9H), 1.64 (m, 10H), 2.44 (br s, 3H), 3.58 (t, 19H), 6.61 (br s,
1
3
1
H), 6.78 (br s, 1H). C{ H} NMR ([D ]THF, 100.6 MHz): δ =
8
References
4.2, 23.5, 26.6, 68.1, 125.5, 132.5, 139.6, 178.4. Ca content:
calc. for ([5-MeThien-2-Ca(thp)
found: 5.7%.
4
I]·0.75THP, 2·0.75THP): 5.9%,
1 (a) B. J. Wakefield, Organolithium Methods, Academic Press,
London, 1988; (b) Lithium Chemistry: A Theoretical and
Experimental Overview, ed. A.-M. Sapse and P. v. R. Schleyer,
Wiley, New York, 1995; (c) J. Clayden, Organolithiums:
Selectivity for Synthesis, Pergamon, Amsterdam, 2002;
(d) The Chemistry of Organolithium Compounds, ed.
Z. Rappoport and I. Marek, Wiley, Chichester, 2004;
(e) Lithium Compounds in Organic Synthesis: From
Fundamentals to Applications, ed. R. Luisi and V. Capriati,
Wiley-VCH, Weinheim, 2014.
Crystal and refinement data for {[5-MeThien-2-Ca
thp) I]0.98·[(thp) CaI 0.02·0.75THP}.
M = 781.51 g mol , colorless prism, size 0.112 × 0.102 ×
(
4
4
2
1
]
34.9 6 0.98
C H64.9CaI1.02O S ,
−
3
0
1
1
1
0
.098 mm , triclinic, space group P ˉ1 , a = 11.1815(5), b =
3.9528(7), c = 15.4047(7) Å, α = 96.140(2)°, β = 111.079(2)°, γ =
3
12.909(2)°, V = 1978.53(16) Å , T = −140 °C, Z = 2, ρ
=
calcd.
.312 g cm− , µ(Mo-K
3
−1
α
) = 10.44 cm , multi-scan, transmin:
.6303, transmax: 0.7456, F(000) = 824, 21 503 reflections in
h(−14/14), k(−18/18), l(−19/19), measured in the range 2.04° ≤
Θ ≤ 27.48°, completeness Θmax = 98.2%, 8913 independent
2 (a) B. J. Wakefield, Organomagnesium Methods in Organic
Synthesis, Academic Press, London, 1995; (b) Handbook of
Grignard Reagents, ed. G. S. Silverman and P. E. Rakita,
CRC Press, Boca Raton, 1996; (c) Grignard Reagents: New
Developments, ed. H. G. Richey, Wiley, Chichester, 2000;
(d) The Chemistry of Organomagnesium Compounds, ed.
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reflections, Rint = 0.0445, 7491 reflections with F
o
> 4σ(F
o
), 402
1
2
1
parameters, 0 restraints, R
= 0.0534, wR
= 0.1035, R
=
obs
obs
all
2
0
.0717, wR = 0.1127, GOOF = 1.092, largest difference peak
all
−
3
and hole: 1.583/−0.588 e Å
.
(
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3
1–33
using multiple-scans.
The structure was solved by direct
6
3
4
methods (SHELXS ) and refined by full-matrix least squares
2
34
techniques against F
o
(SHELXL-2018/3 ). All hydrogen atoms
(
3
were located by difference Fourier synthesis and refined isotro-
pically. The crystal of 2 was a non-merohedral twin. The twin
Rev. Inorg. Chem., 2011, 31, 143–184; (f) M. Westerhausen,
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3
5
law was determined by PLATON to (−1.000/0.000/0.000)
0.980/0.087/0.913) (0.980/1.087/−0.087). The contribution of
the main component was refined to 0.862(2). Furthermore the
crystal of compound is superimposed with 2% of
(thp) CaI ]. This was included in the refinement. All non-dis-
(
4
2
[
4
2
5
6
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ordered, non-hydrogen atoms were refined anisotropically.
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6
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870–1871.
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7
8
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Conflicts of interest
There are no conflicts to declare.
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