The synthesis of (η5-cyclopentadienyl)titanium(IV) alkoxides by alcoholysis of the Ti-π-ligand bond in permethyl η3:η4-allyldiene-(η5- cyclopentadienyl)titanium(II)

Article abstract of DOI:10.1016/S1387-7003(03)00151-5

The η³:η⁴-allyldiene-(η⁵- cyclopentadienyl)titanium(II) complex [Ti(η⁵-C₅Me₅){η³: η⁴-C₅Me₃(CH₂)₂}] (1) reacts with three mo

Full text of DOI:10.1016/S1387-7003(03)00151-5

Inorganic Chemistry Communications 6 (2003) 974–977
www.elsevier.com/locate/inoche
The synthesis of (g5-cyclopentadienyl)titanium(IV) alkoxides
by alcoholysis of the Ti–p-ligand bond in permethyl
g3:g4-allyldiene-(g5-cyclopentadienyl)titanium(II)
a
Karel Mach , Jirı Kubista , Libor Trojan , Ivana Cısarova , Petr Stepnicka
a
b
b
b,
*
ꢀ
ꢀꢁ
ꢀ
ꢁ ꢀ ꢁ
ꢀ
ꢀ
a
J. Heyrovskyꢁ Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejꢀskova 3, 182 23 Prague 8, Czech Republic
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
b
Abstract
The g3:g4-allyldiene-(g5-cyclopentadienyl)titanium(II) complex [Ti(g5-C5Me5){g3:g4-C5Me3(CH2)2}] (1) reacts with three
molar equivalents of substituted propargylic alcohols FcCBCCMe2(OH) (2a) and PhCBCCH2OH (2b) at elevated temperature to
give (g5-pentamethylcyclopentadienyl)titanium(IV) alkoxides [Ti(g5-C5Me5)(FcCBCCMe2O-jO)3] (3a) and [Ti(g5-C5Me5)
(PhCBCCH2O-jO)3] (3b), respectively. The crystal structure of 3a has been determined by single-crystal X-ray diffraction.
Ó 2003 Elsevier Science B.V. All rights reserved.
Keywords: Titanium; Cyclopentadienyl; Ferrocene; Alkyne; Alkoxide; X-ray crystallography
1. Introduction
2. Results and discussion
Electron-poor cyclopentadienyltitanium compounds
willingly react with polar molecules. Except for a simple
coordination of a Lewis donor onto the titanium atom
that produces a more stable adduct, the primary reac-
tions are frequently followed by molecular rearrange-
ments, oxidative addition, insertion and C–H activation
processes, Ti–p-ring bond cleavage and also by consec-
utive addition reactions [1]. Recently [2], we have
reported about the insertion of alkynylketones RCB
CC(O)Me, where R ¼ Fc (ferrocenyl) and SiMe3, into
Ti–C bond in g5-pentamethylcyclopentadienyl-(g3:g4-
trimethylallyldiene)titanium(II) (1) [3]. In this contri-
bution, we describe alcoholysis of 1 with substituted
propargylalcohols FcCBCCMe2(OH) (2a) and PhCB
CCH2OH (2b), which affords (g5-pentamethylcyclo-
pentadienyl)titanium(IV) alkynylalkoxides [Ti(g5-C5Me5)
(FcCBCCMe2O-jO)3] (3a) and [Ti(g5-C5Me5) (PhCB
CCH2O-jO)3] (3b), respectively, and the crystal struc-
ture of 3b.
The reaction of 1 with alcohol 2a proceeds reasonably
well only at elevated temperatures. As revealed by NMR
analysis of crude reaction mixtures obtained at various
1:2a molar ratios, the educts react in 1:3 molar ratio to
give 3a (Scheme 1), while a possible excess of either
educt remains unreacted. Thus, the reaction can be
formulated as:
1 þ 3 2a ! ½Tiðg5-C5Me5ÞðFcCBCCMe2O-jOÞ ꢀ ð3aÞ
3
þ C5Me5H
and rationalized as a protonolysis of both Ti–CH2
bonds in 1 with two molecules of 2a followed by a
cleavage of the Ti–g5-C5Me5 bond with the third alco-
hol equivalent to afford 3a. A reaction of 1 with three
equivalents of 2a furnished alkoxide 3a in 65% isolated
as a dark yellow orange crystalline solid, which was
characterized by spectral methods and X-ray crystal-
lography.
Alcohol 2b reacts analogously and under similar
conditions to give alkoxide [Ti(g5-C5Me5)(PhCB
CCH2O-jO)3] (3b), which was obtained as a light yellow
oil and identified by spectral methods. A similar reaction
between 1 and excess MeOH also proceeds with the
cleavage of the Ti–g5-C5Me5 bond, but yields a mixture
* Corresponding author. Tel.: +420-221-951-260; fax: +420-221-951-
253.
ꢀ
E-mail address: stepnic@natur.cuni.cz (P. Stepnicka).
ꢀ
ꢀ
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1387-7003(03)00151-5

K. Mach et al. / Inorganic Chemistry Communications 6 (2003) 974–977
975
Scheme 1.
containing several diamagnetic Ti(g5-C5Me5) methox-
ides including [Ti(g5-C5Me5)(OMe)3], which was
identified by NMR spectra of the mixture [4], and the
least hexane-soluble, paramagnetic complex [{(g5-
C5Me5)Ti(OMe)2(l-OMe)}2], which was isolated as
a brown crystalline solid and characterized by X-ray
diffraction [5].
The alcoholysis of 1 represents an alternative syn-
thetic approach to the preparation (g5-cyclopentadie-
nyl)titanium tris(alkoxides) as they were so far
synthesized usually by salt metathesis of chlorides
[TiCl3(g5-C5R51)] and [TiCl(OR2)3] with alkali metal
alkoxides and cyclopentadienides, respectively [6]. Alk-
oxides [Ti(g5-C5R51)Cl3ꢁx(OR2)x] (x ¼ 1 ꢁ 3) are of
practical importance, in combination with excess
methylalumoxane (MAO), because they provide efficient
catalysts for syndiospecific polymerization of styrene [7].
Fig. 1. A view of the molecular structure of alkoxide 3a drawn at 30%
probability level. For clarity, labels of only pivotal and its adjacent
carbon atoms in cyclopentadienyl rings are given. Full atom num-
bering is shown only for alkoxide unit 1 because the labelling scheme
adopted for alkoxide units 2 and 3 is analogous, the atom labels in
these moieties being obtained by adding 20 and 40 to the respective
atom number, respectively. All hydrogen atoms were omitted.
Table 1
a;b
ꢂ
The selected geometric parameters for 3a (A) and (°)
Alkoxide unit
1
2
3
Ti–O
Cg–Ti–O
/
1.830(2)
113.19(5)
4.4(1)
1.791(1)
119.06(5)
82.9(1)
1.830(2)
110.56(6)
77.3(1)
2.1. The crystal structure of 3b
As revealed by X-ray crystallography, complex 3a
possesses the expected three-legged piano stool structure
ꢂ
(Fig. 1, Table 1). The Ti–Cg distance is 2.075(1) A and
Fe–Cg (subst.)
Fe–Cg (unsubst.)
Cg–Fe–Cg
O–C
1.652(1)
1.652(1)
178.84(6)
1.417(3)
1.485(3)
1.192(3)
1.431(3)
109.6(2)
173.3(2)
175.9(2)
1.651(1)
1.656(1)
177.81(6)
1.423(2)
1.483(3)
1.193(3)
1.435(3)
108.6(2)
179.4(2)
176.2(2)
1.647(1)
1.655(1)
178.58(6)
1.411(2)
1.488(3)
1.197(3)
1.436(3)
111.6(2)
173.7(2)
176.4(2)
ꢂ
the titanium atom is displaced by 0.746(1) A from the
O–C–C
CBC
CBC–C(Fc)
O–C–C
plane of the three ligating oxygen atoms. The cyclo-
pentadienyl and {O1O2O3} planes are slightly tilted
from a coplanar arrangement at a dihedral angle of
9.4(1)°. This is also reflected by a variance among the
O–Ti–O and Cg–Ti–O angles.
C–CBC
CBC–C(Fc)
a Cp and Cg denote a cyclopentadienyl ring and its centroid, re-
spectively. / is the dihedral angle subtended by the Cp(Ti) and the
respective substituted Cp(Fe) cyclopentadienyl least-squares planes.
The Ti–O distances slightly differ for the three alk-
oxide units, but compare well to those in analogous
phenoxides [Ti(g5-C5H5)(OC6H3-2,6-iPr2)3] (1.79(2),
b
ꢂ
Further data: Ti–Cg 2.075(1) A; O(1)–Ti–O(2) 102.50(6)°, O(1)–Ti–
5
ꢂ
1.80(2), 1.80(2) A [8]) and [Ti(g -C5Me5)(OC6H-2,3,5,6-
O(3) 105.34(7)°, O(2)–Ti–O(3) 104.96(7)°.
ꢂ
F4)3] (1.826(3), 1.830(3) and 1.867(3) A [9]). This vari-
ation of the Ti–O bond lengths as well as differences in
the geometries of the alkoxide moieties (see Table 1) can
most likely be attributed to a steric crowding between
the bulky cyclopentadienyl and the alkoxide ligands.
The three ferrocenyl units adopt different orientations
towards the Ti(g5-C5Me5) unit (see dihedral angles / in
Table 1 and the dihedral angles between the substituted
ferrocene cyclopentadienyls: 84.5(1)°, 81.0(1)°, and
36.0(1)° for the pairs of alkoxide moieties 1–2, 1–3, and
2–3, respectively).
3. Experimental
3.1. General comments
The synthesis of alcohols 2 was carried out under
argon; their subsequent reactions with 1 were performed
on a high vacuum line using sealed all-glass devices
equipped with breakable seals. Diethyl ether and

976
K. Mach et al. / Inorganic Chemistry Communications 6 (2003) 974–977
acetone were dried over sodium metal and potassium
carbonate, respectively, and distilled under argon. Tol-
uene and hexane were dried by refluxing with LiAlH4
and stored as solutions of dimeric titanocene [(l-g5:g5-
C5H4C5H4){Ti(l-H)(g5-C5H5)}2] [10] on the vacuum
line. Complex 1 was prepared by thermolysis of
[Ti(g5-C5Me5)2(g2-Me3SiCBCSiMe3)] [11].
Samples for EI MS measurements, X-ray diffraction
analysis and melting point determinations were inserted
into glass capillaries (Lindenmann glass capillaries for
X-ray analyses) under purified nitrogen in a Labmaster
130 glovebox (mBraun) and sealed. KBr pellets were
prepared and placed into an air-protecting cuvette in the
glovebox. 1H (399.95 MHz) and 13C (100.58 MHz)
NMR spectra were recorded on a Varian UNITY Inova
400 spectrometer in C6D6 solutions at 25 °C. Chemical
shifts (d/ppm) are given relative to the solvent signal (dH
7.15, dC 128.0). EI MS spectra were recorded at 70 eV
on a VG-7070E mass spectrometer.
5 min at 0 °C, paraformaldehyde (3.0 g, 0.10 mol) was
added and stirring was continued overnight at room
temperature. Then, the reaction mixture was quenched
by saturated aqueous NH4Cl and stirring for 1 h. The
organic phase was separated, washed with saturated
aqueous NH4Cl, dried over MgSO4 and evaporated to
give a viscous oily residue which was distilled under
vacuum (89–91 °C at 0.7 Torr) to afford 2b as a col-
ourless viscous liquid (5.18 g, 78%). Prior to the reaction
with 1, alcohol 2b was degassed and distributed into
ampoules with breakable seals by distillation under
vacuum.
NMR (CDCl3): dH 3.47 (br s, 1 H, OH), 4.30 (s, 2 H,
CH2), 6.93–7.45 (m, 5 H, Ph); dC 51.2 (CH2), 85.6, 88.5
(CBC), 123.4( Cipso Ph), 128.4, 128.5, 131.9 (CH Ph).
GC-MS, m=z (relative abundance): 132 (98, MþÅ), 131
(100), 115 (46, [M–OH]þ), 103 (33, [M–CHO]þ), 77 (62,
þ
ꢁ1
~
C6H5 ), 51 (23). IR (neat): m/cm mOH 3335 br s; mCH
3082 w, 3060 w, 2918 w, 2865 w; mCBC 2238 br w; 1598
m, 1490 s, 1442 m, 1359 br m, 1257 m, 1032 composite s,
953 s, 756 s, 691 s.
3.2. Synthesis of FcCBCCMe2(OH) (2a)
A solution of ethynylferrocene (2.20 g, 10.5 mmol) in
dry diethyl ether (40 ml) was cooled to )30 °C (tem-
perature in bath) and treated with LiBu (4.6 ml 2.5 M in
hexanes, 11.5 mmol). After stirring for 30 min at )30 °C,
acetone (1.0 ml, 13.5 mmol) was slowly added to the
formed acetylide solution and stirring was continued for
another 2.5 h at room temperature. The reaction was
terminated by addition of 5% aqueous H3PO4 (10 ml),
the organic phase was separated, washed with water,
dried (MgSO4) and evaporated under reduced pressure.
The dark orange residue was purified by chromatogra-
phy on a short silica gel column using first toluene to
remove a small amount of unreacted ethynylferrocene (a
yellow band) and then diethyl ether to elute the product
(red band). Evaporation of the second fraction afforded
2a as rusty orange solid. Yield: 2.45 g, 88%.
3.4. Synthesis of [Ti(g5-C5Me5) (FcCBCCMe2O-jO)3]
(3a)
A solution of 1 in toluene (0.22 g, 0.7 mmol in 5.0 ml)
was added to a solution of 2a (0.536 g, 2.0 mmol) in the
same solvent (20 ml) and the mixture was heated to 120
°C for 8 h. All volatiles were removed under vacuum (at
max. 80 °C) and the residue was extracted with hexane.
A small amount of blue 1 was extracted at room tem-
perature, while a repeated extraction with hot hexane
and a subsequent evaporation yielded a residue which
was recrystallized from toluene to afford 3a as a dark
yellow orange crystalline solid. Yield: 0.45 g (65%).
M.p. 139 °C. NMR (C6D6): dH 1.82 (s, 18 H, CMe2),
2.36 (s, 15 H, C5Me5), 3.92 (apparent t, 6 H, C5H4), 4.14
(s, 15 H, C5H5), 4.43 (apparent t, 6 H, C5H4); dC 12.7
(C5Me5), 34.5 (CMe2), 66.8 (CBCCMe2O and Cipso
C5H4), 68.7 (CH C5H4), 70.2 (C5H5), 71.5 (CH C5H4),
75.9, 79.6, 93.8 (CBCCMe2O and Cipso C5H4), 123.4
(C5Me5). EI-MS (250 °C): m=z (relative abundance) 984
(MþÅ; 0.2), 830 (7), 829 (10), 828 (6), 695 (8), 556 (7), 502
(9), 461 (10), 460 (25), 423 (17), 422 (65), 421 (42), 420
(75), 418 (11), 319 (10), 318 (28), 317 (50), 316 (54), 315
(12), 300 (12), 268 (12), 253 (12), 252 (44), 251
([FcCBCCMe2]þ; 90), 250 (46), 242 (13), 240 (16), 237
(12), 236 (19), 212 (14), 211 (15), 210 (½FcCBCHꢀþÅ; 42),
186 (½FcHꢀþÅ; 36), 179 (12), 178 (14), 152 (18), 136 (17),
135 ([C5Me5]þ; 45), 133 (15), 129 (14), 128 (13), 121
([C5H5Fe]þ; 100), 120 (13), 119 (43), 115 (14), 107 (10),
105 (24), 95 (14), 93 (12), 91 (23), 89 (11), 83 (13), 81
(13), 79 (17), 77 (28), 71 (13), 69 (20), 67 (14), 65 (13), 58
(22), 57 (29), 56 (Feþ; 51), 55 (42). IR (KBr): m~/cmꢁ1
3096 w, 3088 w, 2975 s, 2922 m, 2854w, 2233 w, 2208
vw, 1453 br m, 1374 m, 1352 m, 1270 m, 1194 s, 1166 vs,
NMR (C6D6): dH 1.47 (s, 6 H, CMe2), 1.66 (s, 1 H,
OH), 3.88 (apparent t, 2 H, C5H4), 4.06 (s, 5 H, C5H5),
4.37 (apparent t, 2 H, C5H4); dC 31.9 (CMe2), 65.4, 65.7
(CBCCMe2O and Cipso C5H4); 68.9 (CH C5H4), 70.2
(C5H5), 71.7 (CH C5H4), 8ꢁ01.6, 91.4( CBCCMe2O and
~
Cipso C5H4). IR (KBr): m/cm 3309 br s, 3093 w, 2975 s,
2930 w, 2232 br w, 1453 w, 1386 m, 1362 m, 1273 m,
1196 s, 1165 s, 1138 vs, 1107 m, 1040 w, 1021 m, 1001 m,
967 m, 934 s, 821 vs, 650 br w, 511 m, 493 m, 482 s, 459
w. Anal. calcd. for C15H16FeO: C, 67.19%; H, 6.01%.
Found: C, 67.22%; H, 5.81%.
3.3. Synthesis of PhCBCCH2OH (2b)
Butyl lithium (22 ml 2.5 M in hexanes, 55 mmol) was
slowly added to an ice-cooled solution of phenylethyne
(5.11 g, 50 mmol) in dry diethyl ether (50 ml). After the
resulting suspension of lithium acetylide was stirred for

K. Mach et al. / Inorganic Chemistry Communications 6 (2003) 974–977
977
1137 vs, 1027 vs, 1002 vs, 946 s, 898 m, 821 s, 781 m,
616 m, 520 m, 484 s, 470 m, 450 m, 430 m, 420 m.
diffractions, R ¼ 4:33% for all data, Rint ¼ 3:7%; resid-
ꢂꢁ3
ual electron density +0.73, )0.59 e A
.
Crystallographic data have been deposited at the
Cambridge Crystallographic Data Centre (CCDC-
206346). The data can be obtained upon request to
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (e-
mail: deposit@ccdc.cam.ac.uk).
3.5. Synthesis of [Ti(g5-C5Me5)(PhCBCCH2O-jO)3]
(3b)
A solution of 1 in toluene (0.31 g, 1.0 mmol in 7.5 ml)
was mixed with 2b (0.5 ml, 3.4mmol). The mixture was
heated in a sealed ampoule to 100 °C for 10 h where-
upon the originally blue solution turned green and, fi-
nally, clear yellow. All volatiles were distilled off under
vacuum (finally at 100 °C) and the resulting yellow oil
was distributed for the measurement of EI-MS, NMR
and IR spectra. All attempts to crystallize the compound
from a saturated hexane solution at low temperature
failed. The yield was not determined.
Acknowledgements
This research was financially supported by Grant
Agency of the Czech Republic (Grant Nos. 203/99/
M037) and is a part of a long-term Research plan of the
Faculty of Sciences, Charles University.
NMR (C6D6): dH 2.09 (s, 15 H, C5Me5), 5.21 (s, 6 H,
References
CH2), 6.91–7.54(m, 15 H, Ph); dC 11.4(C Me5), 61.8
5
(CH2), 84.7, 90.5 (CBC); 124.3 (C5Me5), 124.0 (Cipso
Ph), 128.1, 128.5, 131.9 (CH Ph). EI-MS (120 °C): m=z
[1] (a) R. Beckhaus, in: A. Togni, R.L. Halterman (Eds.), Metallocenes,
vol. 1, Wiley-VCH, Weinheim, Germany, 1998 (Chapter 4);
(b) U. Rosenthal, V.V. Burlakov, in: I. Marek (Ed.), Titanium
and Zirconium in Organic Synthesis, Wiley–VCH, Weinheim,
2002, p. 355 (Chapter 10).
(relative abundance) 576 (MþÅ
,
2), 444 ([M–
PhCBCCH2OH]þ; 2.5), 414 (4), 405 (5), 404 (15), 403
(6), 246 (6), 245 (5), 218 (6), 217 (10), 215 (8), 202 (6),
136 (17), 135 (11), 121 (24), 119 (15), 116 (17), 115
ꢀ
[2] K. Mach, J. Kubista, R. Gyepes, L. Trojan, P. Stepnicka, Inorg.
ꢀ
Chem. Commun. 6 (2003) 352.
ꢀ
ꢀ
([PhCBCCH2]þ; 100), 105 (23), 104(6), 103 (12), 102
[3] J.W. Pattiasina, C.E. Hissink, J.L. de Boer, A. Meetsma, J.H.
Teuben, A.L. Spek, J. Am. Chem. Soc. 107 (1985) 7758.
[4] NMR (C6D6): dH 1.97 (s, 15 H, C5Me5), 4.10 (s, 9 H, OMe); dC
10.8 (C5Me5), 61.4(O Me), 121.6 (C5Me5). Considering the signal
intensities and similarity with the above chemical shifts, the other
component in the mixture was tentatively assigned the l-oxo
structure, [(l-O){Ti(g5-C5Me5)(OMe)2}2]. This compound may
originate from a reaction with traces of water present in methanol;
NMR (C6D6): dH 2.05 (s, 15 H, C5Me5), 4.13 (s, 6 H, OMe); dC
11.0 (C5Me5), 61.5 (OMe), 121.8 (C5Me5).
ꢁ1
~
(17), 91 (17), 89 (6), 77 (9), 40 (39). IR (neat): m/cm
3080 (w), 3055 (m), 3033 (w), 3020 (w), 2956 (m), 2909
(s), 2837 (s), 2238 (w), 1598 (m), 1489 (vs), 1442 (s), 1376
(w), 1351 (vs), 1256 (m), 1113 (vs,b), 1070 (vs,b), 1028
(s,sh), 999 (m), 958 (m), 914(w), 755 (vs), 724(w), 691
(vs), 661 (s), 619 (m), 532 (s), 494 (m).
3.6. X-ray crystallography
ꢁ
ꢀ ꢁ
[5] I. Cısarova, K. Mach, personal communication to the Cambridge
Crystallographic Data Centre. Deposition No. CCDC-206347.
[6] M. Bottrill, P.D. Gavens, J.W. Keeland, J. McMeeking, in:
G. Wilkinson, F.G.A. Stone, E.W. Abel (Eds.), Comprehensive
Organometallic Chemistry, vol. 3, Pergamon, New York, USA,
1982, p. 338 (Chapter 22.3.1.2.1).
Structure determination for 3a: C55H60Fe3O3Ti
(M ¼ 984:5); triclinic, space group P ꢁ 1 (no. 2);
T ¼ 150 K, a ¼ 9:7886ð2Þ, b ¼ 15:1418ð3Þ, c ¼ 17:2486ð2Þ
ꢂ
A; a ¼ 73:735ð1Þ°, b ¼ 89:423ð1Þ°, c ¼ 73:409ð1Þ °; V ¼
[7] (a) R. Po, N. Cardi, Prog. Polym. Sci. 21 (1996) 47;
(b) N. Tomotsu, N. Ishihara, T.H. Newman, M.T. Malanga,
J. Mol. Catal. A: Chem. 128 (1998) 167.
3
2345:23ð7Þ A , Z ¼ 2, Dc ¼ 1:39 g cmꢁ3; orange-brown
ꢂ
plate from toluene, 0.25 ꢂ 0.25 ꢂ 0.75 mm3 (measured in
Lindenmann glass capillary under nitrogen), 2hmax
¼
[8] A.V. Firth, D.W. Stephan, Inorg. Chem. 37 (1998) 4732.
[9] M.J. Sarfield, S.W. Ewart, T.L. Tremblay, A.W. Roszak,
M.C. Baird, J. Chem. Soc. Dalton Trans. (1997) 3097.
55°, data completeness 98.1%; 44 775 collected, 10 575
unique and 9221 observed [I0 > 2rðI0Þ] diffractions
(Nonius KappaCCD diffractometer, Mo-Ka radiation,
ꢁ
ꢁ
ꢀ
[10] H. Antropiusova, A. Dosedlova, V. Hanus, K. Mach, Transition
Met. Chem. (London) 6 (1981) 90.
k ¼ 0:71073 A, l(Mo-Ka) ¼ 1.117 mmꢁ1).
ꢂ
ꢁꢀ
[11] V. Varga, K. Mach, M. Polasek, P. Sedmera, J. Hiller,
The structure was solved by direct methods (SIR92,
[12]) and refined by weighted full-matrix least-squares
on F 2 (SHELXL97, [13]). All non-hydrogen atoms were
refined anisotropically; the hydrogen atoms were in-
cluded into calculated positions (riding model). 559
parameters, final R ¼ 3:48%, wR ¼ 7:93% for observed
U. Thewalt, S.I. Troyanov, J. Organomet. Chem. 506 (1996) 241.
[12] A. Altomare, M.C. Burla, M. Camalli, G. Cascarano,
C. Giacovazzo, A. Guagliardi, G. Polidori, J. Appl. Crystallogr.
27 (1994) 435.
[13] G.M. Sheldrick, SHELXL97. Program for Crystal Structure
€
Refinement from Diffraction Data, University of Gottingen,
€
Gottingen, 1997.