Trisilane-1,3-diolato complexes of Ti and Zr: Syntheses and X-ray crystal structures

Article abstract of DOI:10.1021/ic0514997

The syntheses and structures of zirconium and titanium complexes containing the novel chelating trisilane-1,3-diolate ligand [Me₂Si(R ₂SiO)₂]^2- (R = SiMe₃) (5)-H ₂ are reported. The chloride complexes [Me₂Si(R ₂SiO)₂]TiCl₂ (7a) and [Me₂Si(R ₂SiO)₂]ZrCl₂·2THF (7b) were prepared by the reaction of MCl₄ (M = Ti, Zr) with [Me₂Si(R ₂-SiO)₂]₂Ti (6a) and [Me₂Si(R ₂SiO)₂]₂Zr (6b), which are derived from the reaction of 5 with M(NEt₂)₄, respectively. In the presence of TiCl₄, complexes 6a and 7a undergo a ring-opening reaction to produce the dinuclear complex [Me₂Si(R₂SiO) ₂][TiCl₃]₂ (9). [Me₂Si(R ₂SiO)₂]TiMe₂ (10) and [Me₂Si(R ₂SiO)₂]TiBnZ₂ (11) were prepared in moderate yields from reactions of 7a with 2 equiv of MeMgBr and BnzMgCl, respectively. According to NMR spectroscopic investigations, the reaction of the dimethyltitanium complex 10 with B(C₆F₅)₃ led to full exchange of both methyl groups by C₆F₅ groups under quantitative formation of [Me₂Si(R₂SiO) ₂]Ti(C₆F₅)₂ (12) and a mixture of B(C₆F₅)_3-nMe_n, where n = 1-3. The structure of 12 is further evidenced by the preparation of an identical sample from the reaction of 7a with 2 equiv of C₆F₅MgBr. Refluxing an ether solution of 12 surprisingly gave [Me₂Si(R ₂SiO)₂]₂TiC₆F₅] ₂O (13) as a result of ether cleavage. The structures of the complexes 7a, 7b, 9, 10, and 13 were determined by X-ray crystallography, and structural discussion of the bond parameters will be given.

Full text of DOI:10.1021/ic0514997

Inorg. Chem. 2006, 45, 3203−3211
Trisilane-1,3-diolato Complexes of Ti and Zr: Syntheses and X-ray
Crystal Structures†
C. Krempner,* M. Ko1ckerling, H. Reinke, and K. Weichert
Institut fu¨r Chemie der UniVersita¨t Rostock, A.-Einstein-Strasse 3a, D-18059 Rostock, Germany
Received September 1, 2005
The syntheses and structures of zirconium and titanium complexes containing the novel chelating trisilane-1,3-
-
diolate ligand [Me2Si(R2SiO)2]2 (R
(7a) and [Me2Si(R2SiO)2]ZrCl2
)
SiMe3) (5)-H2 are reported. The chloride complexes [Me2Si(R2SiO)2]TiCl2
Ti, Zr) with [Me2Si(R2-
‚2THF (7b) were prepared by the reaction of MCl4 (M
)
SiO)2]2Ti (6a) and [Me2Si(R2SiO)2]2Zr (6b), which are derived from the reaction of 5 with M(NEt2)4, respectively. In
the presence of TiCl4, complexes 6a and 7a undergo a ring-opening reaction to produce the dinuclear complex
[Me2Si(R2SiO)2][TiCl3]2 (9). [Me2Si(R2SiO)2]TiMe2 (10) and [Me2Si(R2SiO)2]TiBnz2 (11) were prepared in moderate
yields from reactions of 7a with 2 equiv of MeMgBr and BnzMgCl, respectively. According to NMR spectroscopic
investigations, the reaction of the dimethyltitanium complex 10 with B(C6F5)3 led to full exchange of both methyl
groups by C6F5 groups under quantitative formation of [Me2Si(R2SiO)2]Ti(C6F5)2 (12) and a mixture of B(C6F5)3 nMen,
-
where n
) 1−3. The structure of 12 is further evidenced by the preparation of an identical sample from the
reaction of 7a with 2 equiv of C6F5MgBr. Refluxing an ether solution of 12 surprisingly gave [Me2Si(R2SiO)2]2TiC6F5]2O
(13) as a result of ether cleavage. The structures of the complexes 7a, 7b, 9, 10, and 13 were determined by X-ray
crystallography, and structural discussion of the bond parameters will be given.
Introduction
applications as catalysts in olefin polymerizations,4 olefin
metatheses,5 C-H activation,6 and oxidation reactions.1h,7
Silanolate ligands similar to alkoxides are capable of being
In addition to being precursors for metal oxides and
silicates in sol-gel and related processes1 and models for
silica-supported heterogeneous catalysts,2 group 4 metal
silanolates3 derived from silanediols, silanetriols, disilox-
anediols, trisiloxanediols, and related species have found
(3) Reviews: (a) Lickiss, P. D. AdV. Inorg. Chem. 1995, 42, 147. (b)
Murugavel, R.; Voigt, A.; Walawalkar, M. G.; Roesky, H. W. Chem.
ReV. 1996, 96, 2205. (c) King, L.; Sullivan, A. C. Coord. Chem. ReV.
1999, 189, 19. (d) Lorenz, V.; Fischer, A.; Giessmann, S.; Gilje, J.
W.; Gun’ko, Y.; Jacob, K.; Edelmann, F. T. Coord. Chem. ReV. 2000,
206-207, 321. (e) Marciniec, B.; Maciejewski, H. Coord. Chem. ReV.
2001, 223, 301.
(4) (a) Feher, F. J.; Walzer, F. J.; Blanski, R. L. J. Am. Chem. Soc. 1991,
113, 3618. (b) Feher, F. J.; Blanski, R. L. J. Am. Chem. Soc. 1992,
114, 5886. (c) Abbenhuis, H. C. L.; Krijnen, S.; van Santen, R. A.
Chem. Commun. 1997, 331. (d) Duchateau, R.; Abbenhuis, H. C. L.;
van Santen, R. A.; Thiele, S. K.-H.; van Tol, M. F. H. Organometallics
1998, 17, 5222.
(5) Feher, F. J.; Tajima, T. L. J. Am. Chem. Soc. 1992, 116, 2145.
(6) Bannett, J. L.; Wolczanski, P. T. J. Am. Chem. Soc. 1997, 119, 10696.
(7) (a) Buys, I. E.; Hambley, T. W.; Houlten, D. J.; Maschmeyer, T.;
Masters, F. A.; Smith, A. K. J. Mol. Catal. 1994, 86, 309. (b) Crocker,
M.; Herold, R. H. M.; Orpen, A. G. Chem. Commun. 1997, 2411. (c)
Maschmeyer, T.; Klunduk, M. C.; Martin, C. M.; Shepard, D. S.;
Thomas, J. M.; Johnson, B. F. G. Chem. Commun. 1997, 1847. (d)
Murugavel, R.; Roesky, H. W. Angew. Chem., Int. Ed. Engl. 1997,
36, 477. (e) Van Santen, R. A.; Abbenhuis, H. C. L.; Vorsten-
bosch, M. L. W. PCT Int. Appl. 1998, 31 pp. (f) Crocker, M.; Herold,
R. H. M.; Orpen, A. G.; Overgaag, M. T. A. J. Chem. Soc., Dalton
Trans. 1999, 3791. (g) Fujiwara, M.; Wessel, H.; Park, H.-S.;
Roesky, H. W. Tetrahedron 2002, 58, 239. (h) Fujiwara, M.; Wessel,
H.; Park, H. S.; Roesky, H. W. Chem. Mater. 2002, 14, 4975. (i)
Skowronska-Ptasinska, M. D.; Vorstenbosch, M. L. W.; van
Santen, R. A.; Abbenhuis, H. C. L. Angew. Chem., Int. Ed. 2002, 41,
637.
† Dedicated to Prof. M. H. Chisholm on the occasion of his 60th birthday.
* To whom correspondence should be addressed. E-mail:
clemens.krempner@uni-rostock.de. Tel: +49 (0)381 498 6385. Fax: +49
(0)381 498 6382.
(1) (a) Perego, G.; Ballussi, G.; Corno, C.; Tamarasso, M.; Buonomo, F.;
Esposito, A. New Developments in Zeolite Science and Technology.
In Studies in Surface Science and Catalysis; Murakami, Y., Iijima,
A., Word, J. W., Eds.; Elsevier: Amsterdam, The Netherlands, 1986.
(b) Notari, B. Stud. Surf. Sci. Catal. 1988, 37, 413. (c) Terry, K. W.;
Tilley, T. D. Chem. Mater. 1991, 3, 1001. (d) Winkhofer, N.; Voigt,
A.; Dorn, H.; Roesky, H. W.; Steiner, A.; Stalke, D.; Reller, A. Angew.
Chem. 1994, 106, 1414. (e) Voigt, A.; Murugavel, R.; Chandrasekhar,
V.; Winkhofer, N.; Roesky, H. W.; Schmidt, H.-G.; Uson, I.
Organometallics 1996, 15, 1610. (f) Voigt, A.; Murugavel, R.;
Montero, M. L.; Wessel, H.; Liu, F.-Q.; Roesky, H. W.; Uson, I.;
Albers, T.; Parisini, E. Angew. Chem., Int. Ed. Engl. 1997, 36, 1001.
(g) Lugmair, C. G.; Tilley, T. D. Inorg. Chem. 1998, 37, 764. (h)
Coles, M. P.; Lugmair, C. G.; Terry, K. W.; Tilley, T. D. Chem. Mater.
2000, 12, 122. (i) Kriesel, J. W.; Tilley, T. D. Chem. Mater. 2000,
12, 1171. (j) Kriesel, J. W.; Sander, M. S.; Tilley, T. D. AdV. Mater.
(Weinheim, Germany) 2001, 13, 331. (k) Jarupatrakorn, J.; Tilley, T.
D. J. Am. Chem. Soc. 2002, 124, 8380. (l) Jones, A. C. Brit. U.K.
Pat. Appl. 2004, 26 pp.
(2) Reviews: (a) Duchateau, R. Chem. ReV. 2002, 102, 3525. (b)
Abbenhuis, H. C. L. Chem. Eur. J. 2000, 6, 25.
10.1021/ic0514997 CCC: $33.50
Published on Web 03/16/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 8, 2006 3203

Krempner et al.
σ and π donors,8 which, important for catalytic processes,
enable electronic stabilization of oxophilic metal ions in
relatively high oxidation states. For example, a dinuclear
zirconium complex derived from the reaction of Zr(Bnz)4
with (c-C6H11)7Si7O9(OH)3, an incompletely condensed poly-
hedral oligosilsesquioxane, provides after treatment with
B(C6F5)3 a highly active olefin polymerization catalyst
system.9
In this context, cp-free mononuclear cyclic complexes of
group 4 metals containing bidentate silanediolates of the
general formula [Y(R2SiO)2]2-, where Y ) O, (R2SiO2)n,
(R2Si)n, or (CH2)n, might be interesting catalyst candidates
because they may be considered as analogues to ansa-
metallocenes10 or cp-containing half-sandwich complexes of
“constraint geometry”,11 which form highly active Ziegler-
Natta catalysts with boranes or methylaluminoxane.
Particularly, the coordination chemistry of R,ω-silox-
anediolates, [O(Ph2SiO)n]2- (n ) 1-3), is well established
and documented in a recent review paper by King and
Sullivan,3c and a number of different neutral or negatively
charged spirocyclic silanolate complexes have been re-
ported.12 However, constrained five- and six-membered
monocyclic silanediolates of group 4 metals are rare. Apart
from only a handful of titanium- and zirconium-containing
five-membered ring compounds developed in our labora-
tory,13 six-membered cyclic complexes, [Y(R2SiO)2]MX2,
where X is a reactive group such as halides amide, or alkyl
are unknown in the literature.14
and zirconium complexes of the general formula [Me2Si-
(R2SiO)2]MX2, where X ) Cl, Me, Bnz, and C6F5.
Experimental Section
General Procedure. All manipulations of air- and/or moisture-
sensitive compounds were carried out under an atmosphere of argon
using standard Schlenk and glovebox techniques. Tetrahydrofuran
(THF), diethyl ether, n-heptane, and n-pentane were distilled under
argon from alkali metals prior to use. CH2Cl2 was distilled from
CaH2 and stored over molecular sieves. Benzene-d6 was dried over
activated molecular sieves and stored in the glovebox. The
36
oligosilane 316 and B(C6F5)3 were prepared as previously de-
scribed. NMR: Bruker AC 250, Bruker ARX 300, Bruker ARX
500. IR: Nicolet 205 FT-IR. MS: Intectra AMD 402, chemical
ionization with isobutane as the reactant gas.
2,4-Dihydroxy-1,1,1,3,3,5,5,5-octamethyl-2,4-bis(trimethylsi-
lyl)pentasilane (5). Freshly distilled trifluoromethanesulfonic acid
(TfOH; 10.5 mL, 0.12 mol) was added at -40 °C to a stirred
solution of 3 (31.4 g, 0.056 mol) in CH2Cl2 (250 mL), and the
mixture was allowed to warm to room temperature within 2 h. After
the solvent was changed from CH2Cl2 to diethyl ether, an aqueous
solution of NH4COONH2 (120 mL, 1 M) was added, and stirring
was continued for 30 min. The organic phase was separated and
dried over MgSO4, and the solvent was evaporated. Drying under
vacuum afforded 24.3 g (98%) of the title compound, which was
kept in a freezer. An analytically pure sample was obtained. Mp:
117-119 °C. 1H NMR (C6D6, 250 MHz): δ 1.57 (s, br, OH, 2 H),
0.43 (s, Si(CH3)2, 6 H), 0.29 (s, Si(CH3)3, 36 H). 13C NMR (C6D6,
62.9 MHz): δ -0.2 (Si(CH3)3), -1.5 (Si(CH3)2). 29Si NMR INEPT
(C6D6, 79.5 MHz): δ 7.5 (SiO), -15.3 (Si(CH3)3), -35.6 (Si(CH3)2).
MS (70 eV): m/z (%) 439 (3) [M+], 422 (2) [M+ - OH], 367 (19)
[M+ - Si(CH3)3] 349 (57) [M+ - OH - Si(CH3)3]. Anal. Calcd
for C14H44O2Si7 (441.10): C, 38.12; H, 10.05. Found: C, 37.01;
H, 9.67.
Therefore, our initial efforts have been directed toward
developing new monocyclic complexes containing dianionic
trisilane-1,3-diolates. Herein we describe the synthesis of the
novel ligand [Me2Si(R2SiO)2]H2, and among others we report
on the preparation and X-ray structures of a series of titanium
{SiMe2[(Me3Si)2SiO]2}2Ti (6a). Ti(NEt2)4 (2.15 mL, 5.95 mmol)
was added to a stirred solution of 5 (5 g, 11.34 mmol) in n-heptane
(70 mL) at room temperature. The reaction mixture was refluxed
for 2 h, and all volatiles were removed under vacuum. An
analytically pure sample of 6a was obtained by crystallization from
(8) Chisholm, M. H. Inorg. Chem. 1992, 4, 273.
(9) Duchateau, R.; Abbenhuis, H. C. L.; van Santen, R. A.; Meetsma, A.;
Thiele, S. K.-H.; van Tol, M. F. H. Organometallics 1998, 17, 5663.
(10) Reviews: (a) Brintzinger, H.-H.; Mu¨lhaupt, R.; Fischer, D.; Rieger,
B.; Waymouth, R. M. Angew. Chem. 1995, 107, 1255; Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1143. (b) Erker, G. Acc. Chem. Res. 2001,
34, 309. (c) Green, J. C. Chem. Soc. ReV. 1998, 27, 263. (d) Alt, H.
G.; Samuel, E. Chem. Soc. ReV. 1998, 27, 323. (e) Shapiro, P. J. Coord.
Chem. ReV. 2002, 231, 67. (f) Gromada, J.; Carpentier, J.-F.; Mortreux,
A. Coord. Chem. ReV. 2004, 248, 397.
(11) Reviews: (a) McKnight, A. L.; Waymouth, R. M. Chem. ReV. 1998,
98, 2587. (b) Okuda, J.; Eberle, T. Half-Sandwich Complexes as
Metallocene Analogues. In MetallocenessSynthesis, ReactiVity, Ap-
plications; Togni, A., Haltermann, A. L., Eds.; Wiley-VCH: Wein-
heim, Germany, 1998; Vol. 1, p 415.
(12) (a) Hossain, M. A.; Hursthouse, M. B. Inorg. Chim. Acta 1980, 44,
L259. (b) Hossain, M. A.; Hursthouse, M. B.; Mazid, M. A.; Sullivan,
A. C. J. Chem. Soc., Chem. Commun. 1988, 1305. (c) Hossain, M.
A.; Hursthouse, M. B.; Ibrahim, A.; Mazid, M.; Sullivan, A. C. J.
Chem. Soc., Dalton Trans. 1989, 2347. (d) Hossain, M. A.; Hursthouse,
M. B.; Ibrahim, A.; Mazid, M.; Sullivan, A. C. J. Chem. Soc., Dalton
Trans. 1989, 2347. (e) Motevalli, M.; Shah, D.; Sullivan, A. C. J.
Chem. Soc., Dalton Trans. 1993, 2849. (f) Lazell, M.; Motevalli, M.;
Shah, S. A. A.; Simon, C. K. S.; Sullivan, A. C. J. Chem. Soc., Dalton
Trans. 1996, 1449.
(13) (a) Hoffmann, D.; Reinke, H.; Krempner, C. J. Organomet. Chem.
2002, 662, 1. (b) Hoffmann, D.; Reinke, H.; Krempner, C. In
Organosilicon Chemistry V; Auner, N., Weis, J., Eds.; VCH: Wein-
heim, Germany, 2003; p 420.
1
n-pentane at 4 °C. Yield: 3.5 g (67%). Mp: >230 °C. H NMR
(C6D6, 250 MHz): δ 0.49 (s, Si(CH3)2, 12 H), 0.36 (s, Si(CH3)3,
72 H). 13C NMR (C6D6, 62.9 MHz): δ -0.2 (Si(CH3)3), -1.5 (Si-
(CH3)2). 29Si NMR INEPT (C6D6, 79.5 MHz): δ 11.7 (SiO), -14.4
(Si(CH3)3), -35.7 (Si(CH3)2). MS (70 eV): m/z (%) 926 (75) [M+],
911 (11) [M+ - CH3], 853 (11) [M+ - Si(CH3)3]. Anal. Calcd for
C28H84O4Si14Ti (926.08): C, 36.32; H, 9.14. Found: C, 36.05; H,
9.11.
{SiMe2[(Me3Si)2SiO]2}TiCl2 (7a). Analogously to the procedure
described above, raw 6a derived from 5 (4 g) and Ti(NEt2)4 (1.72
mL, 4.76 mmol) was dissolved in n-pentane (50 mL) and cooled
to -40 °C. After a 1 M solution of TiCl4 (4.8 mL, 4.8 mmol) in
toluene was added, the orange solution was stirred for 10 min and
allowed to warm to room temperature. Crystallization of a
concentrated n-pentane solution in a freezer affords the title
compound as orange crystals. Total yield: 3.3 g (65%). Mp: 133
1
°C (dec). H NMR (C6D6, 250 MHz): δ 0.43 (s, Si(CH3)2, 6 H),
0.25 (s, Si(CH3)3, 36 H). 13C NMR (C6D6, 75.5 MHz): δ -0.3
(Si(CH3)3), -1.4 (Si(CH3)2). 29Si NMR INEPT (C6D6, 59.6 MHz):
δ 35.7 (SiO), -10.7 (Si(CH3)3), -34.2 (Si(CH3)2). MS (70 eV):
m/z (%) 556 (12) [M+], 541 (3) [M+ - CH3], 483 (2) [M+ - Si-
(CH3)3], 349 (47) [M+ - Si(CH3)3 - OTiCl2]. Anal. Calcd for
C14H42Cl2O2Si7Ti (557.87): C, 30.14; H, 7.59; Cl, 12.71. Found:
C, 29.37; H, 7.61; Cl, 12.40.
(14) Although a zirconium complex of formula [O(Me2SiO)2]ZrBnz2 has
been described to be active in the polymerization of olefins, neither
was the compound isolated in the pure state nor could it be
spectroscopically identified. Martineau, D.; Dumas, P.; Sigwalt, P.
Makromol. Chem. 1983, 184, 1397.
3204 Inorganic Chemistry, Vol. 45, No. 8, 2006

Trisilane-1,3-diolato Complexes of Ti and Zr
{SiMe2[(Me3Si)2SiO]2}TiCl2‚TMEDA (8a). N,N-Tetramethyl-
ethylenediamine (TMEDA; 45.3 mg, 0.39 mmol) was added at 0
°C to a solution of 7a (0.2 g, 0.36 mmol) in n-pentane, upon which
an orange precipitate formed. After dissolution in the heat, orange
crystals precipitated from the solution upon cooling to room
temperature and were collected, washed with n-pentane, and dried
under vacuum. Yield: 0.21 g (88%). Mp: 174 °C. 1H NMR (C6D6,
250 MHz): δ 2.53 (s, NCH3, 12 H), 1.95 (s, NCH2, 4 H), 0.64 (s,
Si(CH3)2, 6 H), 0.48 (s, Si(CH3)3, 36 H). 13C NMR (C6D6, 75.5
MHz): δ 57.5 (NCH2), 52.1 (NCH3), 1.4 (Si(CH3)3), -0.8 (Si-
(CH3)2). 29Si NMR INEPT (C6D6, 59.6 MHz): δ 18.9 (SiO), -11.6
(Si(CH3)3), -44.0 (Si(CH3)2). Anal. Calcd for C20H58Cl2O2N2Si7-
Ti (674.06): C, 35.64; H, 8.67; N, 4.16. Found: C, 35.82; H, 8.65;
N, 4.11.
Yield: 0.58 g (82%). Mp: 110 °C. 1H NMR (C6D6, 250 MHz): δ
0.58 (s, Si(CH3)2, 6 H), 0.32 (s, Si(CH3)3, 36 H). 13C NMR (C6D6,
75.5 MHz): δ 0.6 (Si(CH3)3), -2.0 (Si(CH3)2). 29Si NMR INEPT
(C6D6, 59.6 MHz): δ 69.1 (SiO), -8.6 (Si(CH3)3), -28.7 (Si(CH3)2).
MS (70 eV): m/z (%) 558 (23) [M+ - TiCl4], 543 (6) [M+
-
TiCl4 - CH3], 350 (29) [M+ - TiCl4 - OTiCl2 - Si(CH3)3], 188
(50) [TiCl4]. Anal. Calcd for C14H42Cl6O2Si7Ti2 (747.53): C, 22.49;
H, 5.66. Found: C, 22.41; H, 5.56.
{SiMe2[(Me3Si)2SiO]2}TiMe2 (10). A 3 M solution of MeMgBr
(1 mL, 3 mmol) in diethyl ether was added dropwise to a slurry of
7a (0.75 g, 1.344 mmol) in ether (10 mL) at -78 °C. The hetero-
geneous mixture was stirred for 15 min and allowed to warm
to room temperature within 30 min, after which time the solvent
was removed under vacuum. The product was extracted with
n-pentane and filtered, and the solution was concentrated. Crystal-
lization at -40 °C afforded the title compound as highly air- and
moisture-sensitive material. Because of a slow decomposition after
several weeks at room temperature, 10 was kept in a freezer (-40
°C), where it is stable for months. Yield: 0.48 g (69%). Mp: 118
{SiMe2[(Me3Si)2SiO]2}2Zr (6b). Zr(NEt2)4 (0.9 mL, 2.43 mmol)
was added to a stirred solution of 5 (2 g, 4.53 mmol) in n-heptane
(30 mL) at room temperature. The reaction mixture was refluxed
for 2 h, and all volatiles were removed under vacuum to leave raw
6b as a white solid nearly quantitatively. An analytically pure
sample can be obtained by crystallization from n-pentane at 4 °C.
1
°C (dec). H NMR (C6D6, 300 MHz): δ 0.88 (s, Ti(CH3)2, 6 H),
1
0.44 (s, Si(CH3)2, 6 H), 0.30 (s, Si(CH3)3, 36 H). 13C NMR (C6D6,
75.5 MHz): δ 49.2 (Ti(CH3)2), -0.2 (Si(CH3)3), -0.7 (Si(CH3)2).
29Si NMR INEPT (C6D6, 59.6 MHz): δ 14.7 (SiO), -13.5 (Si-
(CH3)3), -26.6 (Si(CH3)2). MS (70 eV): m/z (%) 515 (8) [M+],
Yield: 1.2 g (55%). Mp: 139 °C. H NMR (C6D6, 250 MHz): δ
0.47 (s, Si(CH3)2, 12 H), 0.33 (s, Si(CH3)3, 72 H). 13C NMR (C6D6,
62.9 MHz): δ -0.3 (Si(CH3)3), -1.1 (Si(CH3)2). 29Si NMR INEPT
(C6D6, 59.6 MHz): δ 3.4 (SiO), -14.3 (Si(CH3)3), -35.6 (Si(CH3)2).
MS (70 eV): m/z (%) 968 (100) [M+], 953 (12) [M+ - CH3], 895
(15) [M+ - Si(CH3)3]. Anal. Calcd for C28H84O4Si14Zr (969.39):
C, 34.69; H, 8.73. Found: C, 33.88; H, 8.82.
500 (84) [M+ - CH3], 485 (22) [M+ - 2 CH3], 421 (31) [M+
-
OTi(CH3)2], 348 (66) [M+ - OTi(CH3)2 - Si(CH3)3]. Anal. Calcd
for C16H48O2Si7Ti (517.07): C, 37.16; H, 9.36. Found: C, 36.37;
H, 9.34.
{SiMe2[(Me3Si)2SiO]2}ZrCl2‚2THF (7b). Raw 6b derived from
5 (1.18 g, 2.68 mmol) and Zr(NEt2)4 (0.52 mL, 1.41 mmol) was
dissolved in THF (30 mL), cooled to -78 °C, and added to freshly
sublimed ZrCl4 (0.38 g, 1.62 mmol). After stirring was continued
for 4 h at room temperature, the solvent was removed under
vacuum, the remaining solid was refluxed in n-heptane, and the
hot suspension was filtered. After cooling to room temperature,
colorless crystals of 7b precipitated from the solution, which were
collected, washed with n-pentane, and dried under vacuum. Total
yield: 0.79 g (40%). Mp: 194 °C. 1H NMR (C6D6, 250 MHz): δ
3.96 (m, OCH2CH2, 8 H), 1.33 (m, OCH2CH2, 8 H), 0.63 (s, Si-
(CH3)2, 6 H), 0.49 (s, Si(CH3)3, 36 H). 13C NMR (C6D6, 62.9
MHz): δ 72.4 (OCH2CH2), 25.3 (OCH2CH2), 0.7 (Si(CH3)3), -0.8
(Si(CH3)2). 29Si NMR INEPT (C6D6, 59.6 MHz): δ 1.8 (SiO), -13.2
(Si(CH3)3), -50.4 (Si(CH3)2). MS (70 eV): m/z (%) 600 (22) [M+],
{SiMe2[(Me3Si)2SiO]2}TiBnz2‚THF (11). A 1.15 M solution of
BnzMgCl (1.7 mL, 1.97 mmol) in THF was added dropwise to a
slurry of 7a (0.5 g, 0.896 mmol) in ether (10 mL) at -78 °C. The
heterogeneous mixture was stirred for 15 min and allowed to warm
to room temperature within 30 min, after which time the solvent
was removed under vacuum. The product was extracted with
n-pentane and filtered, and the solution was concentrated. Crystal-
lization at -40 °C afforded the title compound 11 as red-orange
1
crystals. Yield: 0.212 g (32%). H NMR (C6D6, 500 MHz): δ
7.28-6.88 (m, C6H5, 10 H), 3.57 (m, THF-OCH2CH2, 4 H), 1.41
(m, THF-OCH2CH2, 4 H), 2.49 (s, CH2C6H5, 4 H), 0.44 (s, Si-
(CH3)2, 6 H), 0.28 (s, Si(CH3)3, 36 H). 13C NMR (C6D6, 125.8
MHz): δ 123.5, 128.7, 129.1, 143.9 (C6H5), 75.4 (THF-OCH2CH2),
67.8 (CH2(C6H5)), 25.8 (THF-OCH2CH2), -0.1 (Si(CH3)3), -0.6
(Si(CH3)2). 29Si NMR INEPT (C6D6, 99.4 MHz): δ 15.9 (SiO),
-13.0 (Si(CH3)3), -28.1 (Si(CH3)2). Anal. Calcd for C32H64O3Si7-
Ti (741.33): C, 51.85; H, 8.70. Found: C, 51.61; H, 8.65.
Reaction of 10 with B(C6F5)3 in C6D6. A J. Young NMR tube
was charged in the glovebox with 10 (30 mg, 0.058 mmol) and
B(C6F5)3 (30 mg, 0.059 mmol) and dissolved in C6D6 (0.5 mL).
The progress of the reaction was monitored by 1H NMR spectros-
copy, and complete conversion of the starting materials into
SiMe2[(Me3Si)2SiO]2Ti(C6F5)2 (12) and a mixture of the boranes
of formula MeB(C6F5)2, Me2BC6F5, and BMe3 (molar ratio 1.0:
2.4:1.7) was observed within 5 min, according to the 1H, 29Si, 11B,
and 19F NMR spectra. After ca. 6 days, a ratio of approximately
1.0:3.6:0.2 for MeB(C6F5)2, Me2BC6F5, and BMe3 was observed.
1H NMR (C6D6, 250 MHz): δ 1.35 (m, BCH3(C6F5)2), 0.98 (m,
B(CH3)2(C6F5)), 0.74 (s, br, B(CH3)3), 0.41 (s, Si(CH3)2, 6 H), 0.21
(s, Si(CH3)3, 36 H). 29Si (C6D6, 59.6 MHz): δ 34.4 (SiO), -11.7
(Si(CH3)3), -28.5 (Si(CH3)2). 11B NMR (C6D6, 160.5 MHz, external
standard B(OCH3)3): δ 67.8 (B(CH3)3), 62.2 (B(CH3)2(C6F5)), 52.7
(BCH3(C6F5)2). 19F NMR (C6D6, 235.4 MHz): δ -160.9, -149.8,
-129.3 (B(CH3)2(C6F5)), -159.8, -145.5, -128.4 (BCH3(C6F5)2),
-158.9, -146.9, -116.7 (Ti(C6F5)2).
585 (9) [M+ - CH3], 527 (9) [M+ - Si(CH3)3], 349 (88) [M+
-
Si(CH3)3 - OZrCl2]. Anal. Calcd for C14Cl2H42O2Si7Zr‚2THF
(745.42): C, 35.45; H, 7.84; Cl, 9.51. Found: C, 34.75; H, 7.90;
Cl, 9.47.
{SiMe2[(Me3Si)2SiO]2}ZrCl2‚TMEDA (8b). TMEDA (21.4 mg,
0.18 mmol) was added at 0 °C to a solution of 7b (0.13 g, 0.17
mmol) in n-heptane, upon which a white precipitate formed. After
redissolution in the heat, crystals precipitated from the solution upon
cooling to room temperature, which were collected, washed with
n-heptane, and dried under vacuum. Yield: 88 mg (73%). Mp: 181
1
°C (dec). H NMR (C6D6, 250 MHz): δ 2.36 (s, NCH3, 12 H),
1.81 (s, NCH2, 4 H), 0.63 (s, Si(CH3)2, 6 H), 0.49 (s, Si(CH3)3, 36
H). 13C NMR (C6D6, 75.5 MHz): δ 57.0 (NCH2), 50.7 (NCH3),
0.9 (Si(CH3)3), -0.6 (Si(CH3)2). 29Si NMR INEPT (C6D6, 59.6
MHz): δ 3.0 (SiO), -13.0 (Si(CH3)3), -49.9 (Si(CH3)2). Anal.
Calcd for C20H58Cl2O2N2Si7Zr (717.42): C, 33.48; H, 8.15; N, 3.90.
Found: C, 33.39; H, 8.12; N, 3.83.
{SiMe2[(Me3Si)2SiO]2}Ti2Cl6 (9). A solution of TiCl4 (1 M, 1.6
mL, 1.6 mmol) in toluene was added to 6a (0.44 g, 0.475 mmol)
at -40 °C. Crystallization from a concentrated n-pentane solution
in a freezer afforded the title compound as red-orange crystals.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3205

Krempner et al.
Scheme 1. Synthesis of the Ligand (R ) SiMe3)
Scheme 2. Syntheses of the Complexes 6-8
Reaction of 7a with C6F5MgBr. A solution of C6F5MgBr in
diethyl ether (0.98 M, 0.4 mL, 0.39 mmol) was added to 7a (0.1 g,
0.18 mmol) dissolved in diethyl ether (3 mL). After the mixture
was stirred for 1 day at room temperature, the solvent was removed
and the residue extracted twice with n-pentane. From this solution,
the solvent was removed and the solid raw material analyzed by
NMR spectroscopy. The data obtained from this sample are identical
with those of 12.
{SiMe2[(Me3Si)2SiO]2(C6F5)Ti}2O (13). A solution of C6F5-
MgBr in diethyl ether (0.98 M, 1.2 mL, 1.18 mmol) was added to
7a (0.3 g, 0.54 mmol) dissolved in diethyl ether (10 mL). After
refluxing of the mixture for 2 days, the solvent was removed, the
residue was extracted twice with n-pentane, and the combined
extracts were concentrated under vacuum. Crystallization from this
solution in a freezer afforded the title compound 13 as yellow
crystals. Yield: 0.203 g (57%). Mp: 162 °C. 1H NMR (C6D6, 250
MHz): δ 0.46, 0.39 (2s, Si(CH3)2, 2 × 3 H), 0.27, 0.19 (2s, Si-
(CH3)3, 2 × 18 H). 13C NMR (C6D6, 75.5 MHz): δ 0.7, -0.4,
(Si(CH3)3), -0.9, -1.1 (Si(CH3)2). 29Si NMR INEPT (C6D6, 59.6
MHz): δ 25.7 (SiO), -12.4 (Si(CH3)3), -30.5 (Si(CH3)2). Anal.
Calcd for C40H84F10O5Si14Ti2 (1324.04): C, 36.29; H, 6.39.
Found: C, 36.01; H, 6.31.
Synthesis and Reactivity of {SiMe2[(Me3Si)2SiO]2}MCl2
(M ) Ti, Zr). A suitable entry into the chemistry of titanium
and zirconium silanolate complexes having active sites is
the use of highly reactive metal amides. Thus, the reaction
of M(NEt2)4 (M ) Ti, Zr) with 2 equiv of 5 leads to the
formation of the spirocyclic titanium and zirconium com-
plexes 6a and 6b. Without further purification, 6a and 6b
could be transformed into the corresponding titanium dichlo-
ride 7a and the THF adduct of the zirconium dichloride 7b
in good total yields after treatment with TiCl4 or ZrCl4,
respectively (Scheme 2). Both complexes are proven to be
Lewis acidic, reacting readily with TMEDA under formation
of the hexacoordinated TMEDA adducts 8a and 8b almost
quantitatively. As expected, the coordinating THF in 7b is
completely replaced by TMEDA according to the NMR
spectra.
The proposed structures of the complexes 6a,b-8a,b were
confirmed by NMR and MS data and were in full agreement
with the results of an elemental analysis. The NMR (1H, 13C,
and 19Si) spectra of all complexes are rather straightforward
and show roughly the same features as those observed for
the corresponding ligand 5. Owing to the symmetry in the
Results and Discussion
Synthesis of 5 (R ) SiMe3). A rather straightforward
strategy for the design of the aforementioned 1,3-diolate
ligands with an oligosilane backbone involves the use of
phenyl-substituted metal silanides in salt metathesis reactions.
By treatment with R,ω-dichlorosilanes, a variety of oligosi-
lanes are available, in which the phenyl groups can be
converted into hydroxy functionalities using a simple syn-
thetic protocol.
In fact, treatment of Cl2SiMe2 with Ph(Me3Si)2SiK (2),
derived from the reaction of ButOK with Ph(Me3Si)3Si
(1),13a,15 provides easy access to the diphenyloligosilane 3
in high yields.16 This compound was reacted with 2 equiv
of TfOH to yield the ditriflate 4, which was subsequently
hydrolyzed to give almost quantitatively the silanediol 5 as
an air-stable, colorless solid that can be synthesized even
on a 20-g scale (Scheme 1). The proposed structure of 5 is
in full agreement with the NMR, IR, and MS data and the
results of an elemental analysis.
1
molecules, the H and 13C NMR spectra exhibit only one
signal for the SiMe3 and SiMe2 groups, respectively, and
also the 29Si NMR spectra showed only one signal for the
SiMe3 silicon atoms.
In addition, the molecular structures of metal dichlorides
7a and 7b have been derived from X-ray diffraction data.
Suitable single crystals were grown from pentane solutions
at room temperature. The results of the X-ray analysis (Figure
1) confirm the expected shielding of the MCl2 fragments by
the trisilane-1,3-diolate ligand and the fact that in 7b two
molecules of THF are coordinated to the Zr atom (Figure
2). Thus, its coordination environment can be regarded as
distorted octahedral with the chlorides in axial positions
and the two THF molecules in equatorial positions, where-
as the geometry of titanium in 7a is distorted tetrahedral
(Figure 1). As expected, the zirconium and titanium are
bonded in a chelate fashion [O1-Zr1-O2 96.18(12)° and
O1-Ti1-O2 104.25(3)°] to both siloxide groups of the
ligand, giving nearly planar six-membered ring systems.
The Zr-O [1.924(3) and 1.917(3) Å] and Ti-O [1.7422(6)
(15) Fischer, R.; Konopa, T.; Baumgartner, J.; Marschner, C. Organome-
tallics 2004, 23, 1899.
(16) Krempner, C.; Ja¨ger-Fiedler, U.; Mamat, C.; Spannenberg, A.;
Weichert, K. New J. Chem. 2005, 29, 1581.
3206 Inorganic Chemistry, Vol. 45, No. 8, 2006

Trisilane-1,3-diolato Complexes of Ti and Zr
Scheme 3. Formation of the Dinuclear Titanium Complex 9
spectroscopy, and the isolated yields were within 80-85%
following crystallization from n-pentane. The composition
of the thermally stable but moisture-sensitive compound
corresponds well to the results of an elemental analysis.
However, the mass spectrum shows a highest peak with a
molecular weight of 558 being consistent with the formation
of 7a.
Figure 1. Molecular structure of 7a in the crystal. The thermal ellipsoids
correspond to 50% probability. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Ti1-Cl1 2.2277(3), Ti1-Cl2
2.2376(3), O2-Ti1-O1 104.25(3), O2-Ti1-Cl1 109.65(2), O1-Ti1-Cl1
108.55(3), O2-Ti1-Cl2 110.56(2), O1-Ti1-Cl2 110.05(3), Cl1-Ti1-
Cl2 113.364(15).
Therefore, unambiguous structural characterization was
accomplished by single-crystal X-ray crystallography; suit-
able crystals were grown from n-pentane solutions. The
results clearly reveal the molecule to be the expected
dinuclear complex 9, which forms a dimeric structure in the
solid state (Figure 3). The coordination geometry of the Ti
atoms can be described as distorted octahedral. The four
titanium trichloride fragments are connected to each other
by a sophisticated network of intra- and intermolecular
chlorine bridging bonds, with the intramolecular Ti-Clbridging
bonds [Ti1-Cl1 2.5496(4) Å, Ti1-Cl2 2.4051(5) Å, Ti2-
Cl1 2.5600(4) Å, and Ti2-Cl2 2.5024(5) Å] being signifi-
cantly shorter than the intermolecular Ti-Clbridging bonds
Ti2-Cl4a and Ti1-Cl1a with values of 2.7430(4) and
2.7135(4) Å, respectively. The nonbridging Ti-Cl bonds
lengths were found to be within the normal range. Similar
structural motifs with titanium chlorine bridging bonds in
thesolidstatehavebeenobservedpreviouslyfor[µ-ClTiCl2N(SiMe2-
Cl)SiMe2NH2] and [µ-ClTiCl2N(SiMe3)SiCl2NH2].18
The formation of 9 can be understood as the result of
strong interactions of TiCl4 with the oxygen atoms of the
Figure 2. Molecular structure of 7b in the crystal. The thermal ellipsoids
correspond to 50% probability. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Cl1-Zr1 2.4742(14), Cl5-
Zr1 2.4805(13), O1-Si4 1.665(3), O1-Zr1 1.924(3), O2-Si2 1.668(3),
O2-Zr1 1.917(3), O3-Zr1 2.315(3), O4-Zr1 2.307(3), Si4-O1-Zr1
147.55(18), Si2-O2-Zr1 148.57(18), O2-Si2-Si3 109.22(11), Si4-Si3-
Si2 106.84(6), O1-Si4-Si3 109.35(12), O2-Zr1-O1 96.18(12), O2-Zr1-
O4 173.06(13), O1-Zr1-O3 174.38(12), O4-Zr1-O3 83.73(13), Cl1-
Zr1-Cl5 162.66(5).
and 1.7451(7) Å] distances within the ring are similar to those
found in the closely related dinuclear eight-membered ring
17
complexes [(OBut2SiO)MCl2]2 (M ) Ti, Zr), with values
being 1.748(2) and 1.746(2) Å for Ti-O as well as 1.930-
(3) and 1.925(3) Å for the Zr-O bond. Obviously, the ring
Zr-O bond lengths are significantly shorter than the Zr-
OTHF distances [O3-Zr1 2.315(3) Å and O4-Zr1 2.307(3)
Å].
Interestingly, when 3 equiv of TiCl4 were reacted with
the spirocyclic complex 6a, a red-orange microcrystalline
material, of what was thought to be the dinuclear complex
9, could be isolated (Scheme 3). The reaction of 1 equiv of
TiCl4 with complex 7a proceeds quite similarly, yielding 9
as the main product. The reactions are quantitative by NMR
Figure 3. Molecular structure of 9 in the crystal. The thermal ellipsoids
correspond to 50% probability. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Ti1-Cl1 2.5496(4), Ti1-
Cl1a 2.7135(4), Ti1-Cl2 2.4051(5), Ti1-Cl3 2.2123(5), Ti1-Cl4 2.3273-
(5), Ti2-Cl1 2.5600(4), Ti2-Cl2 2.5024(5), Ti2-Cl4a 2.7430(4), Ti2-
Cl5 2.2263(5), Ti2-Cl6 2.2256(5).
(17) Haoudi-Mazzah, A.; Mazzah, A.; Schmidt, H. G.; Noltemeyer, M.;
Roesky, H. W. Z. Naturforsch., B: Chem. Sci. 1991, 46, 587.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3207

Krempner et al.
Scheme 4. Syntheses of the Alkyl Complexes 10 and 11
strained ring via oxo bridging bonds, which facilitate an
insertion of TiCl4 into the Ti-O bond of 7a in a selective
manner. Similar interactions of TiCl4 with spirocyclic 6a may
allow for the formation of unstable di- and trinuclear titanium
species, which might be converted rapidly into 6a and 7a
by ligand distribution reactions and further TiCl4 insertions.
The fact that both compounds 6a and 7a efficiently undergo
ring-opening reaction into derivative 9 even at low temper-
atures clearly reflects the constraint nature of these six-
membered ring complexes relative to larger ring com-
pounds.19
Alkylation Reactions of [Me2Si(R2SiO)2]MCl2. The alkyl
derivatives of the titanium dichloride 7a could be synthesized
readily via salt metathesis. The complexes 10 and 11 were
prepared by treatment with 2 equiv of MeMgBr or BnzMgCl,
respectively, in n-pentane at -40 °C (Scheme 4). Although
NMR spectroscopic investigations of the obtained reaction
mixtures indicate the desired complexes to be formed as the
main products, the isolated yields after crystallization from
concentrated n-pentane solutions at -40 °C were low to
moderate because of their high solubility in most common
organic solvents, including benzene, toluene, diethyl ether,
THF, and n-pentane. The air- and moisture-sensitive com-
plexes 10 and 11 slowly decompose at room temperature;
however, they can be stored without any decomposition for
months in a freezer. Attempts to isolate the corresponding
zirconium dialkyl derivatives in the pure state failed. In fact,
the reaction of the zirconium dichlorides 7b and 8b with
Grignard reagents at low temperatures led to thermally
unstable alkylated species that could not be separated from
byproducts arising from M-O bond scissions.
Figure 4. Molecular structure of 10 in the crystal. The thermal ellipsoids
correspond to 50% probability. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Ti1-C2 2.0787(18), Ti1-C1
2.0829(19), O2-Ti1-O1 108.19(5), O2-Ti1-C2 107.82(7), O1-Ti1-
C2 111.24(7), O2-Ti1-C1 110.62(7), O1-Ti1-C1 109.94(7), C2-Ti1-
C1 109.01(9).
(5)°. This is remarkable insofar as [Me2Ti(OCBut3)(µ-
OMe)]2,20 in which the titanium is protected by the space
demand of the tritox ligand, and [Me2Ti(OCHMeCH2Me2-
CO)]2,21 a cyclic dialkoxide that has the same ring size as
10, are dimeric in the solid state. The Ti-C(Me) distances
in 10 with 2.0787(18) Å for Ti1-C2 and 2.0829(19) Å for
Ti1-C1 were found to be slightly shorter than that of {MeTi-
[µ-(η5-C5Me4SiMe2O)]}2(µ-CH2)22 with 2.121 Å [Ti-
C(Me)], which is to our knowledge the only known complex
with a Si-O-Ti-Me bond sequence for which X-ray data
are available. Furthermore, the Ti-C(Me) bond lengths are
only marginally longer than those of the few dimethyltita-
20
nium dialkoxides of formula [Me2Ti(OCBut3)(µ-OMe)]2
with 2.063(10) Å, Me2Ti(OC6H3Ph2-2,6)223 with 2.069(2) and
2.052(2) Å, and Me2Ti[OC6H3CH2-2-(But-6-Me-4)]2 with
24
2.031 and 2.090 Å but shorter than those in [Me2Ti-
21
(OCHMeCH2Me2CO)]2 with 2.110 and 2.183 Å.
Reaction of [Me2Si(R2SiO)2]TiMe2 with B(C6F5)3. With
the dimethyltitanium complex 10 in hand, we have investi-
gated its reactivity toward the Lewis acid B(C6F5)3 that is
known to abstract alkyl groups from the metal center to form
cationic metal species active in olefin polymerization. The
reaction was performed at room temperature in a J. Young
NMR tube using benzene-d6 as the solvent, and the course
The structures of 10 and 11 were established by means of
NMR and MS data and elemental analyses. The TiMe2 group
1
in 10 was identified by a H NMR resonance at 0.88 ppm
and a 13C NMR signal appearing at 49.2 ppm. The methylene
1
groups of the benzyl ligands in complex 11 exhibit singlets
of the reaction was monitored by H NMR spectroscopy.
1
at 2.49 ppm in H NMR and at 67.8 ppm in 13C NMR.
Complex 10 reacted cleanly with B(C6F5)3 (molar ratio 1:1)
within minutes, resulting in the quantitative formation of a
new complex. However, the reaction did not yield the
expected zwitterionic complex [{Me2Si(R2SiO)2}TiMe][MeB-
(C6F5)3]; rather, the quantitative product of C6F5 group
transfer, 12, was formed together with BMe3, Me2BC6F5, and
The results of an X-ray structure analysis of the titanium
dimethyl complex 10 reveal the molecule to be monomeric
in the solid state (Figure 4). The coordination geometry of
titanium is tetrahedral with an O-Ti-O bite angle of 108.19-
(18) (a) Buheitel, R.; Milius, W.; Schnick, W. Z. Naturforsch. 1996, 51b,
1141. (b) Rannabauer, S.; Bettenhausen, R.; Schnick, W. Z. Anorg.
Allg. Chem. 2002, 628, 373.
(20) Lubben, T. V.; Wolczanski, P. T. J. Am. Chem. Soc. 1987, 109, 424.
(21) Yoshino, A.; Shuto, Y.; Iitaka, Y. Acta Crystallogr., Sect. B: Struct.
Crystallogr. Cryst. Chem. 1970, 26, 744.
(22) Buitrago, O.; Ramirez de Arellano, C.; Jimenez, G.; Cuenca, T.
Organometallics 2004, 23, 5873.
(23) Thorn, M. G.; Etheridge, Z. C.; Fanwick, P. E.; Rothwell, I. P. J.
Organomet. Chem. 1999, 591, 148.
(24) Floriani, C.; Solari, E.; Corazza, F.; Chiesi-Villa, A.; Guastini, C.
Angew. Chem., Int. Ed. Engl. 1989, 28, 64.
(19) For comparison, hexamethylcyclotrisiloxane (D3), a six-membered ring
compound, can readily be polymerized by ring-opening polymerization
using anionic or cationic initiators, while octamethylcyclotetrasiloxane
(D4), an eight-membered ring, is much less reactive toward ring-
opening reactions. See: (a) Terman, L. M.; Klapshina, L. G.; Kurskii,
Y. A.; Zislmina, S. S. Polym. Sci. USSR 1987, 29, 1330. (b) Ziemelis,
M. J.; Saam, J. C. Macromolecules 1989, 22, 2111. (c) Yu, J. M.;
Teyssle´, D.; Khalifa, R. B.; Boilleau, S. Polym. Bull. 1994, 32, 35.
3208 Inorganic Chemistry, Vol. 45, No. 8, 2006

Trisilane-1,3-diolato Complexes of Ti and Zr
Scheme 5. Formation of 12 and 13
MeB(C6F5)2 in a 1.0:1.7:2.4 ratio, as evidenced by multi-
nuclear NMR spectral data (Scheme 5). Solutions of 12 in
C6D6 are proven to be fairly stable over a prolonged period
of time, and even at higher temperature, no substantial
decomposition occurred. Similar C6F5 transfer reactions
supposed to be responsible for a chemical deactivation of
the catalyst precursor in olefin polymerizations have been
previously observed.25 The rapid C6F5 transfer observed for
complex 10 is in agreement with theoretical calculation
indicating lower activation barriers for dialkyl complexes
with stronger electron-withdrawing ligands for systems with
similar steric properties.26 The fact that both methyl groups
have been replaced smoothly by C6F5 groups is somewhat
surprising;27 however, it indicates the high electrophilicity
of the titanium center caused by the electron-withdrawing
ligand environment.
In addition, the structural interpretation has been confirmed
by the independent synthesis of 12 from the titanium
dichloride 7a and 2 equiv of C6F5MgBr in diethyl ether at
room temperature (Scheme 5). The NMR spectroscopic data
of the raw product are identical with those found for 12
derived from the reaction of 10 with B(C6F5)3. However,
besides 12, small amounts of a new species could be detected,
and with increased reaction time under reflux conditions, the
relative concentrations of both compounds continue to
change; the new species becomes the major product, whereas
the concentration of 12 decreases. The structural character-
ization of this species was accomplished by single-crystal
X-ray crystallography; suitable crystals were obtained from
n-pentane solutions in a freezer. The analysis of the X-ray
Figure 5. Molecular structure of 13 in the crystal. The thermal ellipsoids
correspond to 50% probability. Hydrogen atoms are omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Ti1-O1 1.8038(3), Ti1-C1
2.1528(16), O2-Ti1-O3 104.99(5), O2-Ti1-O1 112.62(4), O3-Ti1-
O1 111.22(4), O2-Ti1-C1 108.40(6), O3-Ti1-C1 109.66(6), O1-Ti1-
C1 109.81(4), Ti1#1-O1-Ti1 180.0.
data revealed the compound to be the oxo-bridged dinuclear
titanium trisilane-1,3-diolate complex 13 in which only one
C6F5 group is attached to each Ti atom, respectively (Figure
5).
The coordination environment of both Ti atoms is distorted
tetrahedral with an O2-Ti1-O3 bite angle of 104.99(5)°
and a C1-Ti1-O1 angle of 109.81(4)°. The conformational
arrangement of the surrounding atoms along the linear Ti1-
O1-Ti1 axis (180°) can be ascribed as anti-periplanar. The
Ti1-O1 distance with 1.8038(3) Å was found to be
considerably longer than the Ti1-O(ring) distances with
values of 1.7577(11) and 1.7601(12) Å, reflecting the steric
repulsion of both metal complex fragments to each other.
Although the Ti1-C1(C6F5) bond length with 2.1528(16)
Å is significantly longer than the Ti-C(Me) bond lengths
in 10 with 2.0787(18) Å [Ti1-C2] and 2.0829(19) Å [Ti1-
C1], it is the shortest Ti-C(C6F5) distance observed for C6F5-
substituted titanium complexes so far [for comparison, see
ref 28].
Although the mechanism of formation of the oxo-bridged
complex 13 is still unclear, it might be suggested that a
titanium-induced ether cleavage has occurred. This probably
(25) (a) Scollard, J. D.; McConville, D. H.; Rettig, S. J. Organometallics
1997, 16, 1810. (b) Fenwick, A. E.; Phomphrai, K.; Thorn, M. G.;
Vilardo, J. S.; Trefun, C. A.; Hanna, B.; Fanwick, P. E.; Rothwell, I.
P. Organometallics 2004, 23, 2146. (c) Gomez, R.; Gomez-Sal, P.;
Del Real, P. A.; Royo, P. J. Organomet. Chem. 1999, 588, 22. (d)
Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J. Am. Chem. Soc. 2000,
122, 5499. (e) Amo, V.; Andres, R.; De Jesus, E.; De la Mata, F. J.;
Flores, J. C.; Gomez, R.; Gomez-Sal, M. P.; Turner, J. F. C.
Organometallics 2005, 24, 2331.
(26) Wondimagegn, T.; Xu, Z.; Vanka, K.; Ziegler, T. Organometallics
2004, 23, 3847.
(27) (a) Guerin, F.; Stewart, J. C.; Beddie, C.; Stephan, D. W. Organo-
metallics 2000, 19, 2994. (b) Yue, N.; Hollink, E.; Guerin, F.; Stephan,
D. W. Organometallics 2001, 20, 4424.
(28) Selected Ti-C(C6F5) distances: [ArN(CH2)3NAr]Ti[CH2B(C6F5)2]-
(C6F5), 2.191(4) Å;24a (η5-C5H5)(3,5-Me2-2,6-Ph2C6HO)Ti[CH2B-
(C6F5)2](C6F5), 2.176 Å;24b [{η5-C5H4SiMe2[η1-N(2,6-Me2C6H3)]}-
Ti[CH2B(C6F5)2](C6F5), 2.204(5) Å;24c (η5-C5H5)(But2CdN)Ti[CH2B-
(C6F5)2](C6F5), 2.263(2) Å;24d (ButPdN)2Ti(C6F5)2, 2.198(3) and
2.208(3) Å;26a Cl(C6F5)Ti[exo,exo-(η5-isodiCp)]2, 2.273 Å;29 Cl(C6F5)-
Ti[endo,endo-(η5-isodiCp)]2, 2.260 Å;29 Cl(C6F5)Ti[endo,exo-(η5-
isodiCp)]2, 2.263 Å;29 (NBu4)2Ti(C6F5)5, 2.262(8), 2.257(8), 2.221(7),
2.238(7), and 2.235(6) Å.30
(29) Zaegel, F.; Gallucci, J. C.; Meunier, P.; Gautheron, B.; Bzowej, E.
I.; Paquette, L. A. Organometallics 1995, 14, 4576.
(30) Alonso, P. J.; Falvello, L. R.; Fornies, J.; Garcia-Monforte, M. A.;
Menjon, B. Angew. Chem., Int. Ed. 2004, 43, 5225.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3209

Krempner et al.
Table 1. Selected Bond Lengths [Å] and Angles [deg] for the Titanium Complexes 7a, 9, 10, and 13 (L ) [Me2Si(R2SiO)2]; R ) SiMe3)
LTiCl2 (7a)
LTiMe2 (10)
[LTiC6F5]2O (13)
L(TiCl3)2 (9)
Ti-O
1.7422(6), 1.7451(7)
1.7068(7), 1.7114(6)
2.3831(3), 2.3816(3)
104.25(3)
145.48(5), 145.97(4)
107.75(2), 107.14(2)
107.354(10)
1.7757(11), 1.7848(11)
1.6870(11), 1.6827(11)
2.3825(6), 2.3861(6)
108.19(5)
140.97(6), 144.33(7)
107.23(4), 109.22(4)
108.10(2)
1.7577(11), 1.7601(12)
1.6962(11), 1.6970(12)
2.3745(6), 2.3808(6)
104.99(5)
146.17(7), 143.25(7)
108.18(4), 107.21(4)
107.87(2)
1.7097(10), 1.7262(10)
1.7214(10), 1.7205(11)
2.3632(6), 2.3789(6)
Si-O
Si-Si
O-Ti-O
Si-O-Ti
Si-Si-O
Si-Si-Si
167.99(7), 158.27(7)
101.98(4), 106.99(4)
113.19(2)
Table 2. Crystal Data Collection and Refinement Details for Crystal Structuresa
compound
formula
mol wt
7a
7b
9
10
13
C14H42Cl2O2Si7Ti
557.91
C22H58Cl2O4Si7Zr
745.43
C14H42Cl6O2Si7Ti2
747.61
C16H48O2Si7Ti
517.07
C40H84F10O5Si14Ti2
1324.13
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
P21
9.3300(2)
17.7010(4)
9.9319(2)
90
101.221(1)
90
1608.90(6)
2
monoclinic
P21/n
10.4226(2)
22.8237(4)
17.9217(3)
90
105.524(1)
90
4107.72(13)
4
monoclinic
P21/n
12.3918(4)
16.8550(5)
18.0253(5)
90
106.144(1)
90
3616.37(19)
4
triclinic
P1h
triclinic
P1h
10.0840(3)
10.1608(3)
15.8011(5)
79.403(2)
88.393(2)
86.560(2)
1588.29(8)
2
12.7493(3)
12.7949(3)
12.9031(3)
84.047(1)
76.721(1)
62.455(1)
1816.34(7)
1
R, deg
â, deg
γ, deg
V, Å3
Z
F, g cm-3
cryst size, mm3
2θ limit, deg
µ, mm-1
data, restraints, param
final R1, wR2b
1.152
1.205
1.373
1.081
1.211
0.55 × 0.40 × 0.25
0.60 × 0.37 × 0.22
0.90 × 0.70 × 0.60
0.80 × 0.43 × 0.33
0.37 × 0.28 × 0.17
80
50
50
50
55
0.701
19735, 1, 249
0.0271, 0.0697
0.625
7225, 0, 340
0.0344, 0.0923
1.129
6340, 0, 294
0.0200, 0.0532
0.543
5466, 0, 251
0.0242, 0.06688
0.509
8233, 0, 322
0.0339, 0.0952
a All data sets were collected on a Bruker X8Apex diffractometer system with Mo KR radiation (λ ) 0.710 73 Å, at 173 K). b The value of R1 is based
on selected data with F > 4σ(F); the value of wR2 is based on all data.
may generate oxygen-containing titanium species that rapidly
undergo condensation reactions under the formation of Ti-
O-Ti bond sequences, finally resulting in the formation of
13.
fact, the signals for the central silicon are found to be slightly
shifted to lower field upon an increase of the electronegativity
of X in the following order TiMe2 < TiBnz2 < TiOTi(C6F5)
< Ti(C6F5)2 ∼ TiCl2 < TiCl3 [14.7 (10), 15.9 (11), 25.7 (13),
34.4 (12), 35.7 (7a), and 69.1 (9) ppm].
Concerning the Electronic Situation in the Ring and
the Ligand-to-Metal σ + π Donation. The fact that M-O
distances are shorter for M-O-R groups that have M-O-C
angles approaching 180° is generally accepted to be a clue
for strong ligand-to-metal π bonding. In the case of silanolate
ligands (R ) SiR3), caution must be given because in Si-
O-Ti functionalities the silicon is capable of interacting with
the oxygen lone pairs in a manner similar to that of titanium.
Apart from these interactions, silicon is more electropositive
than carbon; thereby, the Si-O-Ti angles are generally
expected to be larger than those of C-O-Ti.
As can be seen from Table 1, upon increasing the
electronegativity of X in [Me2Si(R2SiO)2]TiX2 in the order
TiMe2 (10) < Ti(C6F5)O (13) < TiCl2 (7a) < TiCl3 (9), the
Ti-O distances are shortened, whereas the Si-O bond
lengths to some extent are elongated. In contrast, the Si-
O-Ti [141-146°], Si-Si-O [107-108°], and Si-Si-Si
[107-108°] angles are nearly unaffected by the substitution
pattern, owing to the constrained six-membered ring geom-
etry in 7a, 10, and 13. Also the Si-O distances are in a
relatively small range with an average value of 1.70 Å,
suggesting a weak influence of the group X on the Si-O
bond lengths.
Curiously, the Si-O distances are markedly longer and
the Ti-O distances are shorter than those of the closely
related cyclic complexes [O(Ph2SiO)3]TiClCp*,31 [O(Ph2-
SiO)3]2Ti,32 [(OPh2SiO)2TiClCp*]2,33 [(OBut2SiO)2TiClCp]2,33
and [(OBut2SiO)2TiBr2]2.17 Similar values have been observed
even for the linear complexes (Ph3SiO)4Ti34 and (Ph3SiO)Ti-
(Bnz)2[C5H3(SiMe3)2]35-36 with large Si-O-Ti angles of
170-180°, which are believed to be geometrically optimal
for an efficient ligand-to-metal π bonding,
The remarkably longer Si-O distances can mainly be
attributed to the specific electronic situation in [Me2Si(R2-
SiO)2]TiX2 (R ) SiMe3), in which the central silicon atoms
are surrounded by electropositive silyl groups. These electron-
donating groups clearly diminish the capability of the silicon
(31) Murugavel, R.; Shete, V. S.; Baheti, K.; Davis, P. J. Organomet. Chem.
2001, 625, 195.
(32) Hursthouse, M. B.; Hossain, M. A. Polyhedron 1980, 3, 95.
(33) Liu, F. Q.; Schmidt, H. G.; Noltemeyer, M.; Freire-Erdbruegger, C.;
Sheldrick, G. M.; Roesky, H. W. Z. Naturforsch., B: Chem. Sci. 1992,
47, 1085.
(34) Johnson, B. F. G.; Klunduk, M. C.; Martin, C. M.; Sankar, G.; Teate,
S. J.; Thomas, J. M. J. Organomet. Chem. 2000, 596, 221.
(35) Duchateau, R.; Cremer, U.; Harmsen, R. J.; Mohamud, S. I.;
Abbenhuis, H. C. L.; van Santen, R. A.; Meetsma, A.; Thiele, S. K.-
H.; van Tol, M. F. H.; Kranenburg, M. Organometallics 1999, 18,
5447.
(36) Chernega, A. N.; Graham, A. J.; Green, M. L. H.; Haggitt, J.; Lloyd,
J.; Mehnert, C. P.; Metzler, N.; Souter, J. J. Chem. Soc., Dalton Trans.
1997, 13, 2293.
In this context, 29Si NMR spectroscopy proved to be a
useful tool in studying the electronic situation of the Si-
O-TiX2 bond sequence because the chemical shift of the
central silicon is sensitive to the electronegativity of X. In
3210 Inorganic Chemistry, Vol. 45, No. 8, 2006

Trisilane-1,3-diolato Complexes of Ti and Zr
to act as a strong π acceptor for oxygen, as was mentioned
for the former complexes. The Ti-O distances, which are a
function of the electronegativity of X, were found to be fairly
short, despite the small Si-O-Ti angles enforced by the
constrained ring geometry. From these results, it seems
evident that the relatively short Ti-O distances in the new
titanium trisilane-1,3-diolates mainly arise from ionic inter-
actions rather than ligand-to-metal π bonding.
In addition, the molecular structures of 7a, 7b, 9, 10, and
13 have been determined by X-ray crystallography. The
analysis of the bond parameters within the ring reveals the
specific electronic situation of the SiO functionality caused
by the surrounding electropositive silyl substituents. A
structural comparison of the new titanium trisilane-1,3-
diolates with closely related titanium siloxanolates and
silanolates suggests the central silicon to be a relatively weak
π acceptor for oxygen. Despite the small Si-O-Ti angles
due to the constrained ring geometry, the Ti-O distances
are fairly short, suggesting ionic Ti-O interactions rather
than ligand-to-metal π bonding to be responsible.
Conclusion
The syntheses of the strained six-membered ring com-
plexes [Me2Si(R2SiO)2]2M (6a,b), [Me2Si(R2SiO)2]MCl2
(7a,b), and [Me2Si(R2SiO)2]MCl2‚TMEDA (8a,b), where R
) SiMe3 and M ) Ti (a), Zr (b), derived from the novel
bidentate trisilane-1,3-diolate ligand [Me2Si(R2SiO)2]2- (5)-
H2, have been reported. In the presence of TiCl4, 6a and 7a
rapidly undergo a selective ring-opening reaction to [Me2-
Si(R2SiO)2][TiCl3]2 (9), clearly reflecting the constrained
nature of the chelating trisilane-1,3-diolate framework.
Especially, complex 7a has proven to be synthetically useful
because it allows for the synthesis of the novel alkyl and
aryl complexes [Me2Si(R2SiO)2]TiR2, where R ) Me (10),
Bnz (11), and C6F5 (12). The reaction of complex 10 with
B(C6F5)3 led to full exchange of both methyl groups by C6F5
groups under the quantitative formation of 12, which can be
converted by ether cleavage into 13.
Acknowledgment. We gratefully acknowledge the sup-
port of our work by the Fonds der Chemischen Industrie,
and we thank Prof. H. Oehme for his generous support.
Supporting Information Available: X-ray crystallographic data
in CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org. Crystallographic data for the structural
analysis have been deposited with the Cambridge Crystallographic
Data Centre: CCDC 278426 (7a), 278427 (7b), 278428 (9), 278429
(10), and 278430 (13). These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC,
12 Union Road, Cambridge CB2 1EZ, U.K.; fax +44 1223 336033;
e-mail deposit@ccdc.cam.ac.uk).
IC0514997
Inorganic Chemistry, Vol. 45, No. 8, 2006 3211