Titanocene - 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl complexes - Crystal structures and their retro reaction

Article abstract of DOI:10.1016/j.jorganchem.2004.08.035

The formation of the π-coordinated 1,4,6-tris(trimethylsilyl)hex-3-ene- 1,5-diyne-3-yl ligand at the (Ti^III) atom is a general reaction for highly methyl-substituted titanocenes. The retroreaction to 1,4- bis(trimethylsilyl)buta-1,3-diyne is induced by oxidation with PbCl₂. Paramagnetic titanocene complexes containing the unsaturated carbyl group which consists of one and half molecule of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD) are formed by the reduction of titanocene dichlorides with one molar equivalent of magnesium in the presence of 1.5 molar equivalent BSD in tetrahydrofuran (THF) for titanocene moieties Ti(η⁵-C ₅H_{5 - n}Me_n)₂ (n = 5 (1), 4 (2), and 3 (3)) and Ti{Me₂Si(η⁵-C₅Me ₄)₂} (4). The non-methylated titanocene moiety affords under identical conditions known diamagnetic bis(η⁵- cyclopentadienyl)-2,4-bis(trimethylsilylethynyl)-3,5-bis(trimethylsilyl) titanacyclopenta-2,4-diene (5) as the major product. Crystal structures of 3 and 4 show the same bonding scheme for the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5- diyne-3-yl ligand as previously found for compound 1 [P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal, Chem. Commun. (1999) 2505]. Compound 1 is stable against weak proton donors like methanol or alk-1-ynes even at 90°C, however, it undergoes retroreaction when oxidized by PbCl₂ in THF, yielding nearly quantitatively BSD and [TiCl ₂(η⁵-C₅Me₅)₂].

Full text of DOI:10.1016/j.jorganchem.2004.08.035

Journal of Organometallic Chemistry 689 (2004) 4592–4600
www.elsevier.com/locate/jorganchem
Titanocene – 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl
complexes – crystal structures and their retro reaction
a
Michal Hor a´ cˇ ek , Ivana C ´ı sa rˇ ov a´ , Ji rˇ ´ı Kubi sˇ ta , Anke Spannenberg , Kai Dallmann ,
b
a
c
c
,
c,1
a, ,1
*
Uwe Rosenthal * , Karel Mach
a
J. Heyrovsk y´ Institute of Physical Chemistry, Organometallic Catalysis, Academy of Sciences of the Czech Republic,
Dolej sˇ kova 3, 182 23 Prague 8, Czech Republic
b
Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
c
Leibniz-Institut f u¨ r Organische Katalyse an der Universit a¨ t Rostock e.V., Buchbinderstrasse 5-6, D-18055 Rostock, Germany
Received 26 April 2004; accepted 19 August 2004
Available online 25 September 2004
Abstract
Paramagnetic titanocene complexes containing the unsaturated carbyl group which consists of one and half molecule of 1,4-
bis(trimethylsilyl)buta-1,3-diyne (BSD) are formed by the reduction of titanocene dichlorides with one molar equivalent of magne-
5
sium in the presence of 1.5 molar equivalent BSD in tetrahydrofuran (THF) for titanocene moieties Ti(g -C
5 n 2
H5 ꢀ nMe ) (n = 5 (1), 4
5
(
2), and 3 (3)) and Ti{Me Si(g -C Me ) } (4). The non-methylated titanocene moiety affords under identical conditions known dia-
2 5 4 2
5
magnetic bis(g -cyclopentadienyl)-2,4-bis(trimethylsilylethynyl)-3,5-bis(trimethylsilyl)titanacyclopenta-2,4-diene (5) as the major
product. Crystal structures of 3 and 4 show the same bonding scheme for the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl ligand
as previously found for compound 1 [P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg, K. Mach, U. Rosenthal,
Chem. Commun. (1999) 2505]. Compound 1 is stable against weak proton donors like methanol or alk-1-ynes even at 90 ꢀC, how-
5
ever, it undergoes retroreaction when oxidized by PbCl
ꢁ
2
in THF, yielding nearly quantitatively BSD and [TiCl
2
(g -C
5
Me
5
)
2
].
2004 Elsevier B.V. All rights reserved.
Keywords: Titanium; Titanocene; 1,3-Butadiyne; Carbyl ligand; Bond cleavage; Electron spin resonance; X-ray crystallography
1
. Introduction
mentioned stoichiometry: when the BSD:Ti ratio equals
to 1.0 and the Mg/Ti ratio is also 1.0 a simple adduct with
one coordinated triple bond (A) is obtained [2] whereas
an excess of magnesium gives rise to tweezer complexes
1
Recently, we have reported that the paramagnetic d
5
3
complex [Ti(g -C Me ) {g -Me SiC @C(C„CSiMe )-
5
5 2
3
3
3
5
ꢀ
+
SiMe }] (1) can be obtained by the reduction of
5
[Ti(g -C H
Me ) (C„CSiMe ) ] [Mg(THF)Cl] (n =
3
5
5ꢀ n
n 2
3 2
[
TiCl (g -C Me ) ] with one molar equivalent of magne-
5, 4) (B , B ) in a process involving the scission of
1 2
2
5
5 2
sium in the presence of 1.5 equivalents of 1,4-bis(trimeth-
ylsilyl)buta-1,3-diyne (BSD) in tetrahydrofuran [1]. The
formation of 1 requires essential keeping to the above
BSD molecule [3] (Scheme 1). The non-methylated
titanocene– bis(trimethylsilyl)ethyne (BTMSE) complex
5
2
[Ti(g -C H ) (g -Me SiC„CSiMe )] reacted with 2.0
5
5 2
3
3
equivalents of BSD to give the diamagnetic titanacyclo-
pentadiene complex 5 [4], and with 0.5 equivalent of
BSD the dimeric Ti(III) titanocene-acetylide (C) [5]
(Scheme 2). Of the above mentioned products the tweezer
complex B1 was used as a catalyst for linear dimerization
*
Corresponding
420286582307.
E-mail address: mach@jh-inst.cas.cz (K. Mach).
author.
Tel.:
+420266053735;
fax:
+
1
Both highly appreciate a smooth, long-time publishing coopera-
tion with this journal.
0
022-328X/$ - see front matter ꢁ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.08.035

M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
4593
by magnesium in the presence of 1.5 molar equivalent
of BSD in THF affords nearly quantitatively titanocene
III
Ti ) complexes (1, 2, and 3, respectively) with 1,4,6-
(
tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl carbyl ligand
L) whose C(1–2) triple bond is p-coordinated to the
titanium atom (for 1 see [1]). Fully analogous product
(
5
4
C Me ) }] upon the same treatment (Scheme 3). All
was also obtained from ansa-[TiCl {Me Si(g -
2 2
5
4 2
the complexes display a similar EI-MS fragmentation,
+
showing a low abundant molecular ion and [M ꢀ HL]
ion as a base peak. The characteristic fragments are also
+
a highly abundant ion m/z 179 [C (SiMe ) –Me] , its
4
3 2
+
low-abundant precursor m/z 194 [C (SiMe ) ] , highly
4
3 2
+
abundant m/z 73 [SiMe ] and moderately abundant
3
+
m/z 97 [C SiMe ] . The other spectroscopic data also
2
3
showed that the structure of the coordinated hex-
-ene-1,5-diyne ligand did not vary remarkably with
Scheme 1.
3
stereoelectronic changes in titanocene skeleton of 1–4. A
decreasing electron density on the metal with decreasing
number of methyl substituents on cyclopentadienyl lig-
ands in 1, 2, and 3 or a sterically more opened skeleton
of 4 did not result in noticeable changes in IR m(C„C)
of alk-1-ynes [6] and compound 5 was explored for the
synthesis of thiophene derivative, 2,4-bis(trimethylsilyle-
thynyl)-3,5-bis(trimethylsilyl)thiophene [7]; the chemical
reactivity of 1 has not been studied yet. The purpose of
this work is to establish whether analoga of compound
ꢀ
1
wavenumbers of the non-coordinated (2098–2104 cm
)
triple bonds which were accompanied by a weak satelite
1
are formed for the less methyl-substituted titanocene
5
moieties Ti(g -C H
more opened ansa-Ti{Me Si(g -C Me ) } sandwich,
Me ) (n = 4, 3, or 0) and for the
n 2
5
5 ꢀ n
ꢀ
1
5
band occuring at wavenumbers higher by 42 (2) cm
The double bond of the ligand weakly absorbs in the
.
2
5
4 2
and to establish the reactivity of compound 1 towards
weak protonic acids and oxidation by PbCl2.
ꢀ
1
range of 1548–1568 cm . The coordinated triple bonds
ꢀ
1
were found absorbing in the range 1834–1859 cm
,
however, the lowest value was found for 2 and the high-
est values for 1 and 4. The absence of an expected
decrease of m(C„C) wavenumbers with increasing num-
ber of Me groups on the cyclopentadienyl ligands as
2
. Results and discussion
The reduction of methyl-substituted titanocene
5
5
2
dichlorides [TiCl (g -C H
Me ) ] (n = 5, 4, and 3)
n 2
demonstrated e.g., in Ti(g -C H
Me ) (g -BTMSE)]
5 ꢀ n n 2
2
5
5 ꢀ n
5
Scheme 2.

4594
M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
shifted m(C„C) wavenumbers down to 1662–1598
ꢀ
1
cm [8]. A much smaller shift of m(C„C) of the coordi-
nated triple bond in 1–4 reflects the fact that the Ti(III)
atom in highly methyl-substituted titanocene moieties is
5
a
C H
weak Lewis acid only. E.g., the [TiCl(g -
Me ) ] complexes for n = 3 and 4 coordinate
n 2
5
5 ꢀ n
THF only at low temperature while for n = 5 [12a] and
5
the ansa-[Me Si(g -C Me ) TiCl] complex [12b] do not
2
5
4 2
coordinate it at all.
5
The reduction of [TiCl (g -C H ) ] under the same
2
5
5 2
stoichiometry of all components as in the above exper-
iments afforded diamagnetic compound 5 [4] as far the
main isolated product in the yield of 65%. The iden-
tity of the compound was determined by single-crystal
X-ray diffraction analysis, EI-MS and IR spectra. The
mother liquor after crystallization of 5 contained a
small amount of a paramagnetic product whose ESR
Scheme 3.
(
n = 0–5) complexes [8] precludes to correlate the
strength of coordination with electronic factors induced
by cyclopentadienyls ligands in 1–3. This is also true for
evaluation of ESR spectra whose giso values spanned a
narrow range 1.9913(3) for 1 and 1.9947(3) for 4. These
data (giso = 1.995, DH = 2.5 G, aTi = 3.2 G) could be
3
compatible with the presence of [Ti(g –Me SiC„C–
3
3
5
values, close to the values of g -allyl titanocenes [9], and
C(C„CSiMe )@CSiMe )(g -C H ) ]. The correspond-
3
3
5
5 2
narrow linewidths of the ESR single line signal (DH 1.9–
.0 G) indicate that the unpaired electron density is
ing tweezer complex, if stable, should have likely a
larger aTi coupling constant (cf. B2: giso = 1.9935(3),
DH = 2.5 G, aTi = 7.3 G [2,13]). This overwhelming
formation of 5 means that lowering of the number
of methyl substituents on the cyclopentadienyl ligands
to zero favours the double cycloaddition of BSD even
when at least 1/4 of the titanocene compound has to
be converted into another, unknown product(s).
4
residing largely on ligand L. A low electron density at
the titanium atom was corroborated by finding of very
low aTi coupling (2.7 G) observed in compound 1 which
displayed the linewidth of 1.7 G only [1]. The ESR spec-
trum thus does not fit to the formula containing r-bond
between the titanium(III) atom and the C-3 carbon of
the C ligand (see Scheme 1) because such a structure
6
should give a lower g-value and a larger linewidth of
ESR signal (e.g., DH > 10 G for alkyl [10a,10b] or acety-
lide [10c,10d]). The ESR spectra rather suggest an g -
˚
bonded ligand as depicted in Chart 1 (values in A for
2.1. On the mechanism of formation of the 1,4,6-
tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl carbyl ligand
3
Since the reacting system is heterogeneous the mo-
lar ratios of the components do change both in time
and at the magnesium surface. Under such conditions
both the products shown in Scheme 1 as well as the
Ti–C and C–C bonds of 1 [1]). The crystallographic
bond lengths for 1 [1], 3, and 4 also corroborate the view
of the bonding electron delocalized over C1–C3 carbon
atoms of the carbyl ligand (vide infra). The electronic
absorption spectra of all the compounds display one
absorption band in the 500–600 nm region and a weaker
band close to 1000 nm. The former one falls into the
5
monomeric acetylide [Ti(III)(C„CSiMe )(g -C Me ) ]
3
5
5 2
(D) can be considered to be intermediates in the for-
mation of 1–4. Compound D, at variance with the
non-substituted acetylide C (Scheme 2), does not
dimerize because the electron-donating effect of methyl
substituents makes the titanium less electropositive.
The composition of 1–4 implies that an intermediate
with cleaved BSD combines with BSD or with a com-
pound containing uncleaved BSD or vice versa, and
the nature of the primary intermediate is therefore
the clue to the mechanism. To prove one of the possi-
III
region where titanocene(Ti ) compounds absorb [11],
the latter coincides with the band occuring in the titano-
cene–BTMSE complexes where, however, a strong back
donation interaction of Ti(II) with the triple bond
ble ways and to differentiate between acetylide groups,
5
[
equivalent of BSD. Under very mild conditions the
Ti(C„CCMe )(g -C Me ) ] [14] was reacted with one
3
5
5 2
titanocene containing the 1,4-bis(trimethylsilyl)-
6
-t-butylhex-3-ene-1,5-diyne-3-yl carbyl ligand (6) was
obtained as far the main product (Eq. (1)). Its compo-
sition and atom connectivity was proved by X-ray
crystallography [15]. The structure of 6 was solved eas-
ily, however, the diffraction data were of low quality
Chart 1.

M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
4595
due to an extensive disorder over the permethylcyclo-
pentadienyl ligands and trimethylsilyl groups. The
structure of 6 showed that the reaction pathway
through an acetylide intermediate is feasible, however,
its formation through the tweezer intermediate B
THF resulted in nearly quantitative formation of the
titanocene dichloride, and the only organic product
of the reaction was BSD. This result indicates that a
retro reaction proceeds with a high efficiency. Retro
reactions proceed generally effectively for products of
cycloaddition reactions, and in titanocene chemistry a
recent example is known. The cyclizations of pendant
alkenyl groups induced by the reduction of titanocene
dichlorides to titanocenes yielding cyclopentadienyl
ring-tethered titanacyclopentane derivatives undergo a
(
Scheme 1) cannot be excluded. Similar zircono-
5
cene(IV)-ate complex Li[Zr(C„CPh) (g -C H ) )] was
3
5
5 2
assumed by Negishi [16] as an intermediate in the reac-
5
tion of [ZrCl (g -C H ) )] with 3 equivalents of
2
5
5 2
LiC„CPh, however, Choukroun et al. [17] isolated
from such a system a Zr(II) complex and determined
retro reaction upon oxidation with PbCl to give initial
2
5
2
its crystal structure as Li[Zr(g -C H ) )(C„CPh)(g -
titanocene dichlorides with restored pendant alkenyl
groups [19].
5
5 2
PhC„CC„Ph)]. Such a complex in our (non-ionic)
case represents an intermediate complex preceding
the insertion of p-coordinated triple bond of BSD into
the Ti–C bond of the acetylide (see Eq. (1)). The inser-
tion reaction is apparently driven by a steric conges-
tion of the intermediate complex and by a decrease
of electronic energy. Reversely, stability of the above
zirconium complex compared to the corresponding Ti
intermediate in Eq. (1) is enhanced due to a higher
electropositivity and larger covalent radius of Zr and
a smaller size of non-substituted cyclopentadienyl
ligands.
2.3. Crystal structures of complexes 3 and 4
The crystal structures of compounds 3 and 4 are
very similar to the structure of 1 [1] as it is seen from
comparison of geometric parameters given in Table 1.
The view of the compounds is represented by ORTEP
drawing of molecule of 3 in Fig. 1. The bent titano-
cene moieties differ in the bite angle / whose magni-
tude is determined by the steric congestion at the
hinge position for 1 and 3 and by ansa-SiMe bridge
2
in 4. The steric hindrance of methyl groups in the
hinge position of staggered cyclopentadienyl rings of
1
makes the bite angle smaller than in 3 whose stag-
gered cyclopentadienyl rings have only hydrogen
atoms at the hinge positions (ꢁ41ꢀ versus 49.4(2)ꢀ).
The fixed eclipsed cyclopentadienyl rings due to the
ansa-SiMe bridge in 4 determine the largest bite angle
2
of 53.0(1)ꢀ. The planar 1,4,6-tris(trimethylsilyl)hex-3-
ene-1,5-diyne-3-yl ligand has virtually the same struc-
ture in all the compounds. The differences in bond
lengths and valence angles given in Table 1 are smaller
than threefold esdÕs except for the angles C14–C15–
C16 (171.8(2)ꢀ for 4, 175.3(3)ꢀ for 3 and 173.2(4)ꢀ
for 1. The p-coordinated triple bond C2–C3 is pro-
˚
longed (1.248(4)–1.251(3) A) compared to the non-
˚
coordinated one (C14–C15 1.211(5) A) and the double
˚
bond C1–C16 is longer (1.353(4)–1.362(5) A) than
ð1Þ
the free double bond (1.33 A˚ ). The C1–C2 bond
˚
1.376(3)–1.386(5) A indicates a large contribution of
sp hybridization. Similar bond lengths were found
2
3
2
.2. Reactivity of 1 toward weak protonic acids and PbCl2
Compound 1 was further investigated for their reac-
in 1,4-substituted g -butenyne ligands bonded to tran-
sition metals, e.g., Ru [20], Os [21], W [22] and Fe [23],
3
and in zirconocene-g -propargyl complexes [24].
tivity toward terminal alkynes, methanol, and PbCl2.
It appeared to be completely unreactive toward com-
mon terminal alkynes where no reaction was observed
after heating to 90 ꢀC for 10 h. After treating solid 1
in anhydrous methanol to 90 ꢀC for 24 h only traces
of a yellow-brown oil were found while compound 1
remained largely unreacted. On the other hand, the
oxidation of 1 by one equivalent of PbCl2 [18] in
2.4. Conclusions
Electronically ‘‘rich’’ methyl-substituted titanocene
5
moieties Ti(g -C H
Me ) (n = 5, 4, and 3) and
n 2
5
5 ꢀ n
4 2
5
Ti{Me Si(g -C Me ) } form Ti(III) complexes 1–4
2
5
with the 1,4,6-tris(trimethylsilyl)hex-3-ene-1,5-diyne-3-yl

4596
M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
Table 1
Selected bond lengths (A) and angles (ꢀ) for complexes 3 and 4 and 1
˚
3
4
1
Bond distances
a
Ti–Cg1
e
e
2.073(2)
2.072(2)
2.220(3)
2.294(3)
2.417(3)
1.379(4)
1.248(4)
1.353(4)
1.430(4)
1.211(4)
1.822(3)
1.893(3)
1.852(3)
2.079(1)
2.082(1)
2.222(2)
2.290(2)
2.438(2)
1.376(3)
1.251(3)
1.356(3)
1.429(3)
1.211(3)
1.826(2)
1.884(2)
1.855(2)
2.112(5)
2.105(5)
2.234(4)
2.302(4)
2.471(4)
1.386(5)
1.250(5)
1.362(5)
1.429(5)
1.211(5)
1.830(4)
1.884(4)
1.850(4)
a
Ti–Cg2
Ti–C1
Ti–C2
Ti–C3
C1–C2
C2–C3
C1–C16
C15–C16
C14–C15
Si1–C14
Si2–C16
Si3–C3
Bond angles
Cg1–Ti–Cg2
Si3–C3–C2
C1–C2–C3
e
135.4(2)
143.5(3)
149.4(3)
133.9(3)
120.6(3)
175.3(3)
179.2(3)
121.5(2)
66.1(1)
135.2(1)
142.7(2)
150.9(2)
133.1(2)
122.3(2)
171.8(2)
178.4(2)
124.4(2)
65.9(1)
139.2(2)
141.2(3)
152.0(3)
130.7(3)
122.1(3)
173.3(4)
177.3(4)
121.0(3)
65.6(1)
C2–C1–C16
C1–C16–C15
C14–C15–C16
Si1–C14–C15
Si2–C16–C1
C1–Ti–C3
Fig. 1. Molecular structure of 3 (30% probability thermal motion
ellipsoids) showing the atom numbering scheme. For clarity, the
disordered positions of carbon atoms in the trimethylsilyl group (Si2)
and all hydrogen atoms are omitted.
b
e
/
49.4(2)
25.1(2)
24.5(2)
53.0(1)
27.0(1)
26.0(1)
ꢁ41
c
w1
–
–
d
w2
a
Cg1 and Cg2 denote the centroids of the C(4–8) and C(9–13)
cyclopentadienyl rings, respectively.
3
. Experimental
b
Dihedral angle subtended by the cyclopentadienyl least-squares
planes.
c
3
.1. General comments
Dihedral angle between the least-squares plane of the C(4–8)
cyclopentadienyl ring and the least-squares plane of the Ti, C1, C2, C3
moiety.
Reductions of titanocene dichlorides by magnesium
d
in the presence of 1,4-bis(trimethylsilyl)buta-1,3-diyne
(BSD) in THF and all subsequent manipulations with
solutions of the products were performed on a vacuum
line in all-glass devices equipped with magnetically
breakable seals. A combined device equipped with a pair
of quartz cuvettes (10.0 and 1.0 mm, Hellma) and a
Spectrosil quartz tube were used for UV–near IR and
EPR measurements, respectively. Crystals for EI-MS
measurements and melting point determinations were
placed into glass capillaries and samples in KBr pellets
for infrared measurement were prepared in a glovebox
Labmaster 130 (mBraun) under purified nitrogen (con-
centrations of oxygen and water lower than 2.0 ppm).
ESR spectra were registered on an ERS-220 spectrome-
ter (Centre for Production of Scientific Instruments,
Academy of Sciences of GDR, Berlin, Germany)
equipped with a magnet controlling and data acquisition
CU1 unit (Magnettech, Berlin, Germany) in the X-band.
Dihedral angle between the least-squares plane of the C(9–13)
cyclopentadienyl ring and the least-squares plane of the Ti, C1, C2, C3
moiety.
e
Average values of disordered parameters of cyclopentadienyl
rings.
ligand (L). The non-methylated titanocene moiety
affords under identical conditions the known diamagnetic
Ti(IV) complex bis(g -cyclopentadienyl)-2,4-bis(trimeth-
ylsilylethynyl)-3,5-bis(trimethylsilyl)titanacyclopenta-
2,4-diene 5 as the major product. Compound 1 is stable
against weak proton donors like methanol or alk-1-ynes
5
even at 90 ꢀC, however, it undergoes retroreaction when
oxidized by PbCl in THF, yielding BSD and permethyl-
2
titanocene dichloride. The ease of the retro-reaction and
its high efficiency imply a relatively simple and straight-
forward reaction pathways including a scission of ligand
L and recombination of (trimethylsilyl)ethynyl radicals
to BSD. Intermediacy of Ti(III) (trimethylsilyl)ethynyl
complexes, following from the synthesis of 6 from
Ti(III)-t-butylethynyl complex and BSD corroborates
the above opinion.
2
+
g-Values were determined using an Mn (M = ꢀ1/2
I
line) standard at g = 1.9860. An STT-3 variable temper-
ature unit was used for the measurement in the range
from ꢀ140 to +20 ꢀC. UV–near IR measurements were
performed on a Varian Cary 17 D spectrometer in the
range 340–2000 nm. EI-MS spectra were obtained on

M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
4597
a VG-7070E double-focusing mass spectrometer at
0 eV. Crystalline samples in sealed capillaries were
23 ꢀC): 305 > 330(sh) > 350(sh) ꢂ 550 > 1000(sh) nm.
7
Calc. for C H Si Ti: C, 68.11; H, 9.18. Found: C,
3
3
53
3
opened and inserted into the direct inlet under argon.
The spectra are represented by the peaks of relative
abundance higher than 6% and by important peaks of
lower intensity. IR spectra were recorded in an air-
protecting cuvette on a Nicolet Avatar FT IR spectro-
67.97; H, 9.09%.
Compound 3 was obtained as brown crystals in yield
0.59 g (1.06 mmol, 53%); m.p. 103 ꢀC. EI-MS (direct in-
+
.
let, 120 ꢀC; m/z (%)): 554 (4), 553 (M ; 6), 480
+
([M ꢀ SiMe ] ; 1), 277 (11), 263 (17), 262 (56), 261
3
ꢀ
1
+
meter in the range of 400–4000 cm
.
([M ꢀ HC (SiMe ) ] ; 100), 260 (21), 259 (14), 190 (6),
6
3 3
+
1
79 ([C (SiMe ) –Me] ; 15), 155 (7), 154 (6), 73
ꢀ1
([SiMe ] ; 51). IR (KBr, cm ): 3067 (vw), 2947 (s),
3
4 3 2
+
3
.2. Chemicals
2893 (s), 2854 (m), 2720 (vw), 2143 (vw), 2102 (s),
Solvents THF, hexane, and toluene were dried
by refluxing over LiAlH and stored as solutions of
1840 (s), 1560 (w), 1478 (w), 1444 (m), 1398 (w), 1372
(m), 1302 (vw), 1242 (vs), 1442 (s), 1096 (m), 1020 (m),
1007 (s), 933 (vw), 834 (vs,b), 793 (sh), 772 (s), 751 (s),
690 (m), 634 (s), 618 (m), 525 (w), 475 (vw), 452 (w).
ESR (hexane): g = 1.9945(3), DH = 2.7 G. UV–NIR
(hexane, 23 ꢀC): 305 ꢁ 330 > 350(sh) ꢂ 510(sh) > 1000
4
5
5
5
dimeric
titanocene
C H )} ] [25] on a vacuum line. Magnesium turnings
[(l-g :g -C H )(l-H) {Ti(g -
10 8 2
5
5
2
(
(
Aldrich, purum for Grignard reactions) and BSD
Aldrich) were used as obtained. Titanocene dichlo-
5
rides TiCl (g -C H
{
literature procedures.
Me ) (n = 5–3) [26] and TiCl -
n 2
nm. Calc. for C H Si Ti: C, 67.22; H, 8.92. Found:
31 49 3
2
5
5
5 ꢀ n
2
Me Si(g -C Me ) } [27] were obtained by the
C, 67.09; H, 9.00%.
Compound 4 was obtained in yield 0.99 g (1.55
mmol, 78%). ansa-Me Si(C Me ) Ti[C (SiMe ) ]; m.p.
2
5
4 2
2
5
4 2
6
3 3
3
.3. Preparation of complexes 1–4
212 ꢀC. EI-MS (temp. 170 ꢀC; m/z relative abundance
.+
%)): 638 (5), 637 (M ; 8), 347 (18), 346 (42), 345
(
+
All the complexes 1–4 were prepared by the general
([M ꢀ HC (SiMe ) ] ; 100), 344 (14), 343 (10), 330 (5),
6
3 3
+
+
179 ([Me SiC SiMe ] ; 5), 73 ([SiMe ] ; 2). IR (KBr,
procedure using 2.0 mmol of the respective titanocene
dichloride, 2 mmol of magnesium and 3.0 mmol of BSD
in 15 ml of THF as reported for 1 in preliminary commu-
nication [1]. The mixture was stirred at 40 ꢀC until all the
magnesium disappeared; the reaction time depended on
the length of induction period which was irreproducible
even when using the same reagents. The procedure to
3 4 2 3
ꢀ
1
cm ): 2955 (vs), 2899 (s), 2870 (m), 2146 (vw), 2104
(s), 1859 (m), 1568 (vw), 1452 (w), 1406 (vw), 1377
(w), 1350 (vw), 1316 (w), 1248 (vs), 1140 (m), 1008
(m), 841 (vs,b), 758 (s), 674 (m), 638 (m), 623 (vw),
526 (vw), 469 (m). EPR (toluene, 23 ꢀC): g = 1.9947(3),
DH = 4.0 G; (toluene, ꢀ140 ꢀC): g = 2.002, g = 1,993,
i
^
5
obtain 2: [TiCl (g -C HMe ) ] (0.722 g, 2.0 mmol),
g
av
= 1.996. UV–NIR (hexane, 23 ꢀC): 350(sh) ꢂ
35 57 4
2
5
4 2
BSD 0.583 g, 3.0 mmol), and magnesium (0.0486 g, 2.0
mmol) were weighed into an ampoule equipped with a
Teflon-coated magnetic stirrer and two breakable seals
on a vacuum line, and after evacuation, 20 ml of THF
was distilled in. The mixture was stirred at 40 ꢀC until
all metallic magnesium disappeared (after 21 h). The final
dirty green solution was evaporated in vacuum and the
residue was extracted by 20 ml of hexane. The solution
was concentrated to ca. 5 ml and cooled to ꢀ18 ꢀC for sev-
eral days for crystallization. Dark green crystals were sep-
arated, washed with a cooled hexane and dried in vacuum.
Yield of 2: 0.79 g (1.36 mmol, 68%). 2; m.p. 151 ꢀC. MS
600(sh) > 970(sh). Calc. for C H Si Ti: C, 65.88; H,
9.00. Found: C, 65.79; H, 8.94%.
Spectroscopic data for 1: m.p. 206 ꢀC. EI-MS (direct
+
.
inlet, 160 ꢀC; m/z (%)): 609 (M ; 6), 320 (10), 319 (30),
+
318 (88), 317 ([M ꢀ HC (SiMe ) ] ; 100), 316 (27), 315
6
3 3
+
(14), 313 (7), 292 ([HC (SiMe ) ] ; 16), 278 (9), 277
6
3 3
+
([HC (SiMe ) –Me] ; 27), 182 (8), 181 (9), 180 (10),
6
3 3
+
179 ([C (SiMe ) –Me] ; 19), 178 (7), 155 (14), 119 (8),
4
3 2
+
97 ([C SiMe ] ; 10), 83 (7), 73 ([SiMe ] ; 51). IR (KBr,
+
2
3
3
ꢀ
1
cm ): 2954 (vs), 2898 (vs), 2854 (m), 2715 (vw), 2146
(vw), 2104 (s), 1857 (s), 1547 (vw), 1493 (w), 1451 (m),
1432 (m), 1402 (w), 1377 (s), 1246 (vs), 1143 (s), 1106
(m), 1006 (s), 943 (vw), 840 (vs,b), 755 (s), 693 (m),
677 (w), 637 (s), 621 (w), 612 (vw), 526 (w), 455 (w).
ESR (toluene): g = 1.9913(3), DH = 1.7 G, aTi = 2.7 G;
(toluene, ꢀ140 ꢀC): g = 2.002, g = 1.990, g = 1.994.
+
.
(
direct inlet, 140 ꢀC; m/z (%)): 582 (3), 581 (M ; 5), 292
+
(
14), 291 21), 290 (67), 289 ([M ꢀ HC (SiMe ) ] ; 100),
6
3 3
2
1
1
88 (21), 287 (21), 285 (11), 278 (7), 277 (21), 180 (7),
+
79 ([C (SiMe ) –Me] ; 35), 168 (8), 167 (11), 166 (10),
4
3 2
i
^
av
+
65 (6), 164 (8), 155 (11), 97 (9), 73 ([SiMe ] ; 51). IR
UV–NIR (hexane, 22 ꢀC): 305 > 330(sh) > 350(sh) ꢂ
3
ꢀ1
(
2
(
KBr, cm ): 2947 (s), 2896 (s), 2854 (m), 2140 (vw),
098 (s), 1836 (s), 1548 (w), 1480 (w), 1435 (m), 1371
m), 1328 (vw), 1242 (vs), 1140 (s), 1100 (m), 1002 (s),
600(sh) > 1000(sh) nm.
3.4. Attempted synthesis of [Ti{C (SiMe ) }(C H ) ]
6
3 3
5
5 2
9
6
42 (vw), 830 (vs,b), 748 (s), 690 (m), 637 (m), 623 (w),
15 (vw), 529 (m), 460 (w). ESR (toluene):
5
Analogously to the above procedures [TiCl (g -
2
g = 1.9935(3), DH = 2.1 G; (toluene, ꢀ140 ꢀC):
C H ) ] (0.498 g, 2.0 mmol), BSD 0.583 g, 3.0 mmol),
5
5 2
g = 2.002, g = 1.992, g = 1.995. UV–NIR (hexane,
^
and magnesium (0.0486 g, 2.0 mmol) were weighed into
i
av

4598
M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
an ampoule equipped with a Teflon-coated magnetic
stirrer and two breakable seals on a vacuum line, and
after evacuation, THF (20 ml) was distilled in. The mix-
ture was stirred at 40 ꢀC until all metallic magnesium
disappeared (after 5 h). The final brown solution was
evaporated in vacuum and the residue was extracted
by 20 ml of hexane. The solution was concentrated to
ca. 5 ml and cooled to ꢀ18 ꢀC for several days for crys-
tallization. Brown crystals were separated, washed with
a cooled hexane and dried in vacuum. This product was
diamagnetic, and the X-ray single crystal analysis
proved the compound is identical with previously de-
scribed complex [(C H ) Ti[C (SiMe ) ] (5) [3]. Yield:
3.7. Oxidation of 1 with PbCl in THF
2
Compound 1 (0.9 g, 1.5 mmol) was dissolved in THF
(15 ml), and the solution was poured onto degassed
PbCl (0.28 g, 1.0 mmol). This mixture was stirred and
2
heated to 70 ꢀC for 6 h. The green solution turned red-
dish, and black lead precipitated at the bottom. The
solution was poured away from lead, and concentrated
5
in vacuum. Brown-red [TiCl (g -C Me ) ] crystallized
2
5
5 2
out from green mother liquor. Its identity was proved
by infrared spectrum in KBr pellet and by EI-MS anal-
ysis. The mother liquor was evaporated in vacuum and
the residue was extracted by hexane. A green solution
was separated from another portion of low soluble
5
5 2
8
3 4
0
.50 g (44%). No products in addition to 5 were isolated
from this experiment. A small quantity of paramagnetic
Ti{C (SiMe ) }(C H ) ] was very probably contained
5
[TiCl (g -C Me ) ], and the hexane and all volatile
2
5
5 2
[
products were distilled into a trap cooled by liquid nitro-
gen, finally from boiling water bath. The non-volatile
residue was dissolved in a minimum of hexane and
crystallized by cooling. The crystalline material was
identified by IR and EI-MS measurements and by sin-
gle-crystal X-ray diffraction analysis to be the initial
compound 1. The distillate was evaporated at room tem-
perature to remove hexane. A white crystalline material
was weighed and then identified by GC–MS analysis
and by IR spectra to be pure BSD. Its yield was 0.268
g (1.38 mmol, 92% on PbCl2).
6
3 3
5
5 2
in the mother liquor after crystallization of 5. Its pres-
ence was indicated by ESR spectra only. ESR (hexane):
g = 1.995, DH = 2.5 G, aTi = 3.2 G; (toluene, ꢀ140 ꢀC):
g = 2.002, g = 1.994, g = 1.990, g = 1.995.
1
2
3
av
3.5. Attempted reactions of 1 with terminal alkynes
HCCR (R = t-Bu, SiMe ) or methanol
3
Solid crystalline 1 (0.1 g, 0.16 mmol) was weighed
into an ampule in a glovebox, degassed on a vacuum
line, and HC„CCMe3 or HC„CSiMe3 or MeOH
(
2.0 ml each) were added by distillation on the line.
The sealed ampoules were heated to 90 ꢀC in a water
bath for 5 h. Compound 1 was completely dissolved
in the alkynes but only partly in MeOH. The solu-
tions were dirty green colored. Then, the ampoules
were attached to the vacuum line, the alkynes or
methanol were distilled into a trap under vacuum,
the residue was dissolved in hexane, and crystallized
out by cooling. The alkynes were analyzed by GC–
MS for the presence of dimers with negative results.
Compound 1 was recovered unchanged in all cases
as determined by IR spectra in KBr pellets and
EI-MS analyses.
Table 2
Crystallographic data, data collection and structure refinement data
for compounds 3 and 4
Compound
3
4
Chemical formula
Molecular weight
Crystal system
Space group
T (K)
C
553.87
31
H
49Si
3
Ti
C
35 4
H57Si Ti
638.07
Triclinic
Triclinic
ꢀ
ꢀ
P1 (No. 2)
200(2)
P1 (No. 2)
150(2)
˚
a (A)
9.925(2)
11.187(2)
15.543(3)
81.80(3)
82.57(3)
89.99(3)
1693.5(6)
2
9.4550(2)
10.6780(2)
19.9090(4)
78.1740(10)
88.8910(12)
72.9500(11)
1879.11(7)
2
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
5
3
.6. Reaction of [Ti(CCCMe )(g -C Me ) ] with BSD
3
3
5
5 2
˚
V (A ),
Z
Crystal size (mm )
5
3
[
Ti(C„CCMe )(g -C Me ) ] (250 mg, 0.63 mmol)
0.5 · 0.5 · 0.4
1.086
0.375
0.5 · 0.2 · 0.1
1.128
0.377
3
5
5 2
ꢀ
3
D
calc (g cm
)
and BSD 122 mg, 0.63 mmol) were dissolved in 20 ml
of hexane at room temperature and kept at this temper-
ature overnight. The initial brown colour of the solution
turned green. After evaporation of ca. 15 ml of hexane
ꢀ
1
l (Mo Ka) (mm
F(000)
)
598
1.84–24.17
ꢀ10/10, ꢀ12/12, 0/17
690
h Range (ꢀ)
h, k, l Range
3.09–27.56
ꢀ12/12, ꢀ12/13,
ꢀ25/25
in vacuum and cooling the solution to ꢀ30 ꢀC overnight
3
Diffractions collected
Independent diffraction
Diffractions observed
Number of parameters
R, wR [I > 2r(I)]
R, wR (all data)
S
5038
5038
34658
black crystals of the adduct [Ti{g –Me SiC„
3
5
8537
6843
CC@C(C„CCMe3) SiMe }(g -C Me ) ] (6) were
3
5
5 2
3617
313
obtained. Yield: 0.357 g (0.60 mmol, 96%); m.p. 179–
380
181 ꢀC. Anal. Calc. C, 72.81; H, 9.67. Found: C,
72.26; H, 9.98%. Crystal structure of this compound suf-
0.0456, 0.1132
0.0662, 0.1194
0.978
0.0427, 0.0949
0.0601, 0.1033
1.021
fered from extensive disorder, however, atom connectiv-
ity was safely established.
˚
ꢀ3
Dqmax,min (e A
)
0.414, ꢀ0.319
0.320, ꢀ0.392

M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
4599
3
.8. X-ray crystallography
[7] V.V. Burlakov, N. Peulecke, W. Baumann, A. Spannenberg, R.
Kempe, U. Rosenthal, Collect. Czech. Chem. Commun. 62 (1997)
3
31.
Dark brown crystal fragments of 3 and 4 were in-
[
8] (a) V.V. Burlakov, A.V. Polyakov, A.I. Yanovsky, Yu.T. Struc-
hkov, V.B. Shur, M.E. VolÕpin, U. Rosenthal, H. G o¨ rls, J.
Organomet. Chem. 476 (1994) 197;
serted into a Lindemann glass capillaries and closed by
a wax under purified nitrogen in a glovebox (mBraun),
and the capillaries were then sealed by flame. Diffraction
data of 3 were collected on a STOE-IPDS diffractometer
using graphite-monochromated Mo Ka radiation, and
those of 4 on a Nonius KappaCCD diffractometer and
analyzed by HKL program package [28]. The structure
of 3 was solved by direct methods (SHELXS-86) [29]
and refined by full-matrix least-squares techniques
(b) V. Varga, K. Mach, M. Pola
´ sˇ ek, P. Sedmera, J. Hiller, U.
Thewalt, S.I. Troyanov, J. Organomet. Chem. 506 (1996) 241, and
references therein.
9] (a) K. Mach, H. Antropiusov a´ , V. Hanu sˇ , Transition Met. Chem.
[
(
London) 10 (1985) 302;
(b) K. Mach, H. Antropiusov a´ , V. Varga, V. Hanu sˇ , J. Organ-
omet. Chem. 358 (1988) 123, and references therein.
10] (a) G.A. Luinstra, L.C. ten Cate, H.J. Heeres, J.W. Pattiasina, A.
[
2
Meetsma, J.H. Teuben, Organometallics 10 (1991) 3227;
against F (SHELXL-93) [30]. The structure of 4 was
solved by direct methods (SIR-97 [31]), followed by con-
secutive Fourier syntheses and refined by full-matrix
2
least-squares on F (SHELX-97 [32]). In 3, all non-hydro-
(
b) M. Hor a´ cˇ ek, J. Hiller, U. Thewalt, M. Pol a´ sˇ ek, K. Mach,
Organometallics 16 (1997) 4185;
(c) K. Mach, R. Gyepes, M. Hor a´ cˇ ek, L. Petrusov a´ , J. Kubi sˇ ta,
Collect. Czech. Chem. Commun. 68 (2003) 1877;
(
d) M. Hor a´ cˇ ek, I. C ´ı sa rˇ ov a´ , L. Luke sˇ ov a´ , J. Kubi sˇ ta, K. Mach,
gen atoms except the carbon atoms of the disordered
group were refined anisotropically. In 4, all non-hydro-
gen atoms were refined anisotropically. In both the
structures, hydrogen atoms were placed in ideal posi-
tions and refined as riding atoms. Relevant crystallo-
graphic data are given in Table 2.
Inorg. Chem. Commun. 7 (2004) 713.
11] W.W. Lukens, M.R. Smith III, R.A. Andersen, J. Am. Chem.
Soc. 118 (1996) 1719.
[
[12] (a) K. Mach, J.B. Raynor, J. Chem. Soc., Dalton Trans. (1992) 683;
sˇ ek, P. Sedmera, U.
(b) V. Varga, J. Hiller, R. Gyepes, M. Pola
´
Thewalt, K. Mach, J. Organomet. Chem. 538 (1997) 63.
13] (a) V. Varga, J. Hiller, M. Pol a´ sˇ ek, U. Thewalt, K. Mach, J.
Organomet. Chem. 515 (1996) 57;
[
(b) J. Hiller, V. Varga, U. Thewalt, K. Mach, Collect. Czech.
Chem. Commun. 62 (1997) 1446.
4
. Supplementary material
[
[
14] F.G. Kirchbauer, P.-M. Pellny, H. Sun, V.V. Burlakov, P. Arndt,
W. Baumann, A. Spannenberg, U. Rosenthal, Organometallics 20
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre (CCDC-
36312 for 3, CCDC-236703 for 4). These data can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge,
CB2 1EZ, UK; fax: +44 1223 336033; or deposit@
ccdc.cam.ac.uk).
(
2001) 5289.
ꢀ
˚
15] Crystal data for 6: triclinic, space group P1, a = 9.982(2) A,
2
˚
˚
b = 11.438(2) A, c = 16.197(3) A, a = 99.77(3)ꢀ, b = 92.62(3)ꢀ,
˚
3
ꢀ3
c
= 1.084 g cm , 281
c = 91.61(3)ꢀ, V = 1819.3(6) A , Z = 2, q
parameters, 5493 reflections measured, 4092 observed (I > 2r(I)),
= 0.079, wR (all data) = 0.245.
16] K. Tagaki, C.J. Rousset, E. Negishi, J. Am. Chem. Soc. 113
1991) 1440.
R
1
[
[
[
[
[
(
17] R. Choukroun, J. Zhao, C. Lorber, P. Cassoux, B. Donnadieu,
Chem. Commun. (2000) 1511.
18] G.A. Luinstra, J.H. Teuben, J. Chem. Soc., Chem. Commun.
(1990) 1470.
Acknowledgements
ˇ
19] M. Hor a´ cˇ ek, P. St eˇ pni cˇ ka, R. Gyepes, I. C ´ı sa rˇ ov a´ , I. Ti sˇ lerov a´ ,
J. Zem a´ nek, J. Kubi sˇ ta, K. Mach, Chem. Eur. J. 6 (2000) 2397.
20] (a) C. Bianchini, P. Innocenti, M. Peruzzini, A. Romerosa, F.
Zanobini, Organometallics 15 (1996) 272;
This investigation was supported by the Grant
Agency of the Czech Republic (Project No. 203/02/
0
774). The Grant Agency of the Czech Republic also
sponsored access to Cambridge Structure Database
Grant No. 203/02/0436).
(b) C. Bianchini, M. Peruzzini, F. Zanobini, P. Frediani, A.
Albinati, J. Am. Chem. Soc. 113 (1991) 5453;
(
c) G. Jia, A.L. Rheingold, D.W. Meek, Organometallics 8 (1989)
379;
(
1
(
(
d) D.C. Liles, P.F.M. Verhoeven, J. Organomet. Chem. 522
1996) 33.
References
[
21] J. Gotzig, H. Otto, H. Werner, J. Organomet. Chem. 287 (1985)
2
47.
[22] A.K. McMullen, J.P. Selegue, J.-G. Wang, Organometallics 10
(1991) 3421.
[
[
[
[
1] P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, A. Spannenberg,
K. Mach, U. Rosenthal, Chem. Commun. (1999) 2505.
2] P.-M. Pellny, F.G. Kirchbauer, V.V. Burlakov, W. Baumann, A.
Spannenberg, U. Rosenthal, J. Am. Chem. Soc. 121 (1999) 8313.
3] S.I. Troyanov, V. Varga, K. Mach, Organometallics 12 (1993)
[23] (a) M. Akita, S. Sugimoto, M. Terada, Y. Moro-oka, J.
Organomet. Chem. 447 (1993) 103;
(b) D.L. Hughes, M. Jimenez-Tenorio, G.J. Leigh, A.T. Rowley,
J. Chem. Soc., Dalton Trans. (1993) 3151.
2820.
4] V.V. Burlakov, A. Ohff, C. Lefeber, A. Tillack, W. Baumann, R.
Kempe, U. Rosenthal, Chem. Ber. 128 (1995) 967.
5] U. Rosenthal, H. G o¨ rls, J. Organomet. Chem. 439 (1992) C36.
[24] (a) P.W. Blosser, J.C. Galluci, A. Wojcicki, J. Am. Chem. Soc.
115 (1993) 2994;
[
[
(b) P.W. Blosser, J.C. Galluci, A. Wojcicki, J. Organomet. Chem.
597 (2000) 125;
(c) A. Wojcicki, Inorg. Chem. Commun. 5 (2002) 82.
ˇ
6] V. Varga, L. Petrusov a´ , J. Cejka, K. Mach, J. Organomet. Chem.
532 (1997) 251.

4600
M. Hor a´ cˇ ek et al. / Journal of Organometallic Chemistry 689 (2004) 4592–4600
[
25] H. Antropiusov a´ , A. Dosedlov a´ , V. Hanu sˇ , K. Mach, Transition
Met. Chem. (London) 6 (1981) 90.
[29] SHELXS-86: G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
[30] G.M. Sheldrick, SHELXL-93, University of G o¨ ttingen, G o¨ ttingen,
Germany, 1993.
[
26] K. Mach, V. Varga, H. Antropiusov a´ , J. Pol a´ cˇ ek, J. Organomet.
Chem. 333 (1987) 205.
[31] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano, C.
Giacovazzo, A. Guagliardi, G. Polidori, J. Appl. Crystallogr. 27
(1994) 435.
[
[
27] P. Jutzi, R. Dickbreder, Chem. Ber. 119 (1986) 1750.
28] Z. Otwinowski, W. Minor, HKL Denzo and Scalepack program
package by Nonius, BV, Delft, 1997;
[32] G.M. Sheldrick, SHELXL-97: Program for Crystal Structure
Refinement from Diffraction Data, University of G o¨ ttingen,
G o¨ ttingen, Germany, 1997.
For a reference, see Z. Otwinowski, W. Minor, Methods Enzymol.
276 (1997) 307.