Reactivity of SeOCl2 with titanium and zirconium tetrachlorides. the unexpected formation of a μ-oxo-bridged titanium(iv) derivative

Article abstract of DOI:10.1039/b004057f

The reaction of TiCl₄ with SeOCl₂ affords the μ-oxo derivative [TiCl₃(SeOCl₂)₂]₂(μ-O) through a deoxygenation reaction of SeOCl₂ to SeCl₄ whereas ZrCl₄ gives 1:1 or 1:2 adducts of formula ZrCl₄(SeOCl₂)_n, n = l, 2. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b004057f

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Reactivity of SeOCl2 with titanium and zirconium tetrachlorides.
The unexpected formation of a ꢀ-oxo-bridged titanium(IV)
derivative
Fausto Calderazzo,a Michele D’Attoma,a Fabio Marchettib and Guido Pampaloni*a
a Università di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35,
I-56126, Pisa, Italy. E-mail: pampa@dcci.unipi.it
b Università di Roma “La Sapienza”, Dipartimento di Ingegneria Chimica,
dei Materiali e delle Materie Prime e Metallurgia, Via del Castro Laurenziano 7,
Box 15 Roma 62, I-00185 Roma, Italy
Received 22nd May 2000, Accepted 21st June 2000
Published on the Web 4th July 2000
The reaction of TiCl4 with SeOCl2 affords the ꢀ-oxo
derivative [TiCl3(SeOCl2)2]2(ꢀ-O) through a deoxygenation
reaction of SeOCl2 to SeCl4 whereas ZrCl4 gives 1:1 or 1:2
adducts of formula ZrCl4(SeOCl2)n, n ؍ 1, 2.
Recently some of us reported that thionyl chloride forms
oxygen-bonded adducts with TiCl4 of formula [TiCl4(SOCl2)]2
(three modifications were isolated between 220 and 234 K)
which are unstable at room temperature.1 On the other hand,
ZrCl4 and HfCl4 give 1:1 adducts which are stable at room
temperature or higher.
As the donor number (DN) of SeOCl2, as defined by
Gutmann, was reported to be considerably higher than that
of SOCl2 (DNSOCl = 0.4; DNSeOCl = 12.2),2 it was of interest to
2
2
extend our studies to seleninyl chloride in an attempt to clarify
the nature of an insufficiently described compound of formula
TiCl4ؒ2SeOCl2 which has been reported to be yellow3,4 or
colourless.5 Moreover, a weaker chalcogen–oxygen bond is
expected for selenium with respect to sulfur,6 a parameter
which could interfere with the behaviour of a simple acid–base
adduct.
We have found that, by operating at room temperature, the
addition of a dichloromethane solution of SeOCl2 to a solution
of TiCl4 in the same solvent gives a pale yellow solid.† The
observed IR absorptions of coordinated SeOCl2 at 858 (m) and
Fig.
1
View of the molecular structure of [TiCl3(SeOCl2)2]2-
830 (s) cmϪ1 (Nujol), with wavenumber shifts (97 and 125 cmϪ1
)
(µ-O)ؒCH2Cl2, showing the weaker interactions of the selenium
atoms with their neighbouring chlorine atoms. Ellipsoids are at 30%
probability. Dichloromethane hydrogen atoms have been omitted for
clarity. Selected bond lengths (Å) and angles (Њ): Ti–Cl(1) 2.431,
Ti–Cl(2) 2.252, Ti–O(1) 1.787, Se–O 1.644(4) (av.), Se–Cl 2.145(2) (av.),
Se ؒ ؒ ؒ Cl 2.938–3.465; Ti–O(1)–TiЈ 159.9(1).
with respect to uncoordinated SeOCl2 (955 cmϪ1),7 are similar
to SnCl4ؒ2SeOCl2 (835 cmϪ1, ∆ = 120 cmϪ1)4 and SbCl5ؒSeOCl2
(757 cmϪ1, ∆ = 198 cmϪ1).8 Single crystals were grown by slowly
cooling (Ϫ30 ЊC) a saturated dichloromethane solution, and an
X-ray analysis showed‡ the compound to be a dinuclear deriv-
ative of titanium() of formula [TiCl3(SeOCl2)2]2(µ-O)ؒCH2Cl2
with an oxygen atom bridging two titanium centres, the slightly
distorted octahedral geometry at titanium being completed
by three Cl atoms and two oxygen atoms from the SeOCl2
ligand, see Fig. 1. The two TiCl3(SeOCl2)2 units connected by
the bridging oxygen are related by a two-fold axis passing
through O(1). An identical operation relates the two halves of
the lattice dichloromethane. The two titanium coordination
octahedra have staggered equatorial ligands, the Cl(2)–
Ti ؒ ؒ ؒ TiЈ–Cl(2Ј) dihedral angle being 44.3Њ. The seleninyl
ligand maintains the trigonal pyramidal geometry typical of the
different temperatures (even at Ϫ60 ЊC) and with different
Se/Ti molar ratios, [TiCl3(SeOCl2)2]2(µ-O) was the only product
observed.§ The 77Se NMR spectrum of the mother-liquor after
removal of the dinuclear titanium derivative showed a peak
at δ 395 assigned to SeCl4 (by comparison with an authentic
sample) thus suggesting that [TiCl3(SeOCl2)2]2(µ-O) was formed
by a deoxygenation reaction of SeOCl2 operated by TiCl4 as in
eqn. (1).
2 TiCl4 ϩ 5 SeOCl2 → [TiCl3(SeOCl2)2]2(µ-O) ϩ SeCl4 (1)
10
free molecule.9 As observed in SnCl4ؒ2SeOCl2 and SbCl5ؒ
SeOCl2,11 additional inter- and intra-molecular interactions
between the selenium and chlorine atoms are observed, selen-
ium achieving 3 ϩ 3 coordination as shown in Fig. 1. Although
the bond distances between the selenium atoms and their three
nearest neighbours range from 1.639 to 2.154 Å, three longer
distances (dashed lines in Fig. 1) are observed between
2.938 and 3.465 Å, the greatest value representing the CH2Cl2
chlorine atoms–selenium separation. Although the reaction
between TiCl4 and SeOCl2 has been repeated several times, at
At variance with titanium tetrachloride, ZrCl4 reacts with
SeOCl2 in dichloromethane without formation of SeCl4; as a
matter of fact, 1:1 or 1:2 adducts are obtained depending on
the molar ratio of the reagents, see eqn. (2) and (3).¶ No 1:2
ZrCl4 ϩ SeOCl2 → ZrCl4(SeOCl2)
(2)
ZrCl4 ϩ 2 SeOCl2 → ZrCl4(SeOCl2)2
(3)
DOI: 10.1039/b004057f
J. Chem. Soc., Dalton Trans., 2000, 2497–2498
2497
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collected, 2538 independent reflections [Rint = 0.0213], 128 variables,
adduct of ZrCl4 with SOCl2 has been found, again in agreement
R1 = 0.0409, wR2 = 0.0823. CCDC reference number 186/2044. See
http://www.rsc.org/suppdata/dt/b0/b004057f/ for crystallographic files
in .cif format.
with the reported DN’s (DNSOCl < DNSeOCl ).
2
2
The derivatives of titanium() and zirconium(),
[TiCl3(SeOCl2)2]2(µ-O) and ZrCl4(SeOCl2)2 promptly react with
excess SOCl2 || with formation of TiCl4 and [SeCl3]2[ZrCl6],12
respectively, see eqn. (4) and (5), formation of SO2 being the
§ When a Se/Ti molar ratio of 1:1 was used, the solution contained the
corresponding amount of unreacted TiCl4.
¶ (a) SeOCl2/ZrCl4 molar ratio = 1:1. Preparation of ZrCl4(SeOCl2)ؒ
0.5CH2Cl2. A solution of SeOCl2 (0.37 ml, 5.4 mmol) in CH2Cl2
(70 ml) was added dropwise at room temperature to a suspension of
ZrCl2 (1.25 g, 5.4 mmol) in CH2Cl2 (100 ml). After 12 h stirring at room
temperature, the colourless solid was filtered off and dried in vacuo
at room temperature affording 1.195 g (50% yield) of ZrCl4(SeOCl2)ؒ
0.5CH2Cl2 as a colourless solid exceedingly sensitive to moisture.
Found: Cl (inorganic, after treatment of the sample with a boiling
aqueous solution of KOH), 48.0; Zr, 21.9%. Calcd. for C0.5HCl7OSeZr
requires: Cl, 48.2; Zr, 20.7%. IR (Nujol) ν(cmϪ1): 1263 (w), 871 (s),
802 (m), 765 (m), 723 (m), 669 (w). (b) SeOCl2/ZrCl4 molar ratio = 2:1.
Preparation of ZrCl4(SeOCl2)2. A solution of SeOCl2 (0.69 ml, 10.1
mmol) in CH2Cl2 (70 ml) was added dropwise at room temperature to a
suspension of ZrCl4 (1.07 g, 4.6 mmol) in CH2Cl2 (100 ml). After 12 h
stirring at room temperature, the volume of the orange solution was
reduced to 20 ml and the colourless solid was filtered off and dried
in vacuo at room temperature affording 1.275 g (46% yield) of ZrCl4-
(SeOCl2)2ؒ0.5CH2Cl2 as a colourless solid exceedingly sensitive to
moisture. Found: Cl (inorganic, after treatment of the sample with a
boiling aqueous solution of KOH), 46.8; Zr, 15.1%. Calcd. for
C0.5HCl9O2Se2Zr: Cl, 46.7; Zr, 15.0%. IR (Nujol) ν(cmϪ1): 1262 (w),
858 (s, br), 722 (m, br).
[TiCl3(SeOCl2)2]2(µ-O) ϩ 5 SOCl2 →
2 TiCl4 ϩ 4 SeCl4 ϩ 5 SO2 (4)
ZrCl4(SeOCl2)2 ϩ 2 SOCl2 → [SeCl3]2[ZrCl6] ϩ 2 SO2 (5)
driving force of the reaction. Noteworthy is the fact that TiCl4
does not react with SeCl4 under the same experimental condi-
tions used for zirconium.
Thus, although SeOCl2 behaves as a stronger base than
SOCl2, the decreasing chalcogen-to-oxygen bond strength on
going from sulfur to selenium plays an important role in deter-
mining the nature of the products.
Acknowledgements
The authors wish to thank the Ministero dell’ Università e della
Ricerca Scientifica e Tecnologica (MURST, Roma), Programmi
di Ricerca di Interesse nazionale (1998–1999), for financial
support.
||SeOCl2 reacts at room temperature with SOCl2 forming SeCl4 and
SO2.13
1 F. Calderazzo, M. D’Attoma, F. Marchetti, G. Pampaloni and
S. I. Troyanov, J. Chem. Soc., Dalton Trans., 1999, 2275.
2 V. Gutmann, A. Steininger and E. Wychera, Monatsh. Chem., 1966,
97, 461; V. Gutmann, CHEMTECH, 1977, 255; V. Gutmann, The
Donor-Acceptor Approach to Molecular Interactions, Plenum Press,
New York, London, 1978.
3 R. Weber, Pogg. Ann., 1865, 125, 325, quoted in Gmelins Handbuch
der Anorganischen Chemie, “Selen” B, Gmelin Verlag GmbH,
Claustahl-Zellerfeld, 8th edn., 1949, p. 144.
4 J. C. Sheldon and S. Y. Tyree, Jr., J. Am. Chem. Soc., 1959, 81,
2290.
5 C. R. Wise, J. Am. Chem. Soc., 1923, 45, 1233.
6 CRC Handbook of Chemistry and Physics, CRC Press, Boca Raton,
FL, 77th edn., 1996–1997.
7 G. H. Westphal and F. Rosenberger, J. Mol. Spectrosc., 1980, 83,
355.
8 M. Burgard, J. P. Brunette and M. J. F. Leroy, Inorg. Chem., 1976,
15, 1225.
9 Electron diffraction structure of SeOCl2: D. Gregory, I. Hargittai
and M. Kolonits, J. Mol. Struct., 1976, 31, 261.
10 Y. Hermodsson, Acta Crystallogr., 1960, 13, 656.
11 Y. Hermodsson, Acta Chem. Scand., 1967, 21, 1313.
12 J. Beck, P. Biedenkopf, K. Müller-Buschbaum, J. Richter and
K.-J. Schlitt, Z. Anorg. Allg. Chem., 1996, 622, 292.
13 Gmelins Handbuch der Anorganischen Chemie, “Selen” B, Gmelin
Verlag GmbH, Claustahl-Zellerfeld, 8th edn., 1949, p. 141.
Notes and references
† A solution of SeOCl2 (0.44 ml, 6.4 mmol) in CH2Cl2 (70 ml) was
added dropwise at room temperature to a solution of TiCl4 (0.7 ml,
6.4 mmol) in CH2Cl2 (25 ml). The pale yellow solution was stirred
at room temperature and cooled at ca. 4 ЊC for 48 h producing a solid
which was filtered off and dried in vacuo at room temperature giving
[TiCl3(SeOCl2)2]2(µ-O)ؒCH2Cl2 (1.25 g) as a microcrystalline, moisture-
sensitive pale-yellow solid. Found: Cl (inorganic, after treatment of the
sample with a boiling aqueous solution of KOH), 46.3; Ti, 8.8%. Calcd.
for CH2Cl16O5Se4Ti2: Cl, 46.3; Ti, 8.9%. An additional crop of yellow
crystals of [TiCl3(SeOCl2)2]2(µ-O)ؒCH2Cl2 (0.103 g, 98% total yield
based on selenium), suitable for an X-ray diffraction study, formed on
cooling the mother-liquor at ca. Ϫ30 ЊC for 24 h. The same reaction
was repeated using a Se/Ti molar ratio of 2.5:1 and mixing a solution
of the reactants at ca. Ϫ60 ЊC. The immediate formation of a yellow
solid was observed which was filtered off and dried in vacuo at room
temperature affording [TiCl3(SeOCl2)2]2(µ-O) (89% yield) as a micro-
crystalline yellow powder exceedingly sensitive to moisture. Found:
Cl, 50.9; Ti, 9.9%. Calcd. for Cl14O5Se4Ti: Cl, 50.2; Ti, 9.7%. IR (Nujol)
ν(cmϪ1): 858 (m), 830 (s), 796 (s), 724 (m).
‡ Crystal data for [TiCl3(SeOCl2)2]2(µ-O)ؒCH2Cl2 (yellow): CH2-
Cl16O5Se4Ti2, M = 1072.9, monoclinic, space group P2/n (no. 13),
µ(Mo-Kα) = 7.301 mmϪ1, a = 12.753(1), b = 8.495(1), c = 13.350(1) Å,
β = 65.58(2)Њ, V = 1439.4(2), Z = 2, T = 293.2 K, 3327 reflections
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J. Chem. Soc., Dalton Trans., 2000, 2497–2498