Synthesis and characterization of cyclopentadienyl titanium(aryloxide)sulfide complexes

Article abstract of DOI:10.1021/ic001139d

We have been interested in the fundamental nature of the reactivity of early metal-sulfur bonds for some time. A variety of group four metal sulfide derivatives are known, including mono and dimetallic compounds such as (η⁵-C₅H5)₂TiS₅, 1,5-((η⁵-C₅H₅)₂Ti) ₂S₆, and 1,4-((η⁵-C₅H₅)₂Ti) ₂S₄⁵, as well as the higher nuclearity aggregates [(η⁵-C₅H₅)TiS]₄, (η⁵C₅H₅)₅ Ti₅S₆, Zr₃S₃(t-BuS)₂(BH₄)₄ (THF)₂, Zr₆S₆(t-BuS)₄ (BH₄)₈-(THF)₂, Zr₃S(S-t-Bu)₁₀, ((η⁵-C₅H₅)Ti)₄ (μ³-S)₃ (μ²-S)(μ²-SEt)₂, ((η⁵-C₅H₅)Ti)₆ (μ³-S)₄(μ³-O)₄, and [(η⁵-C₅H₅)Ti (OC₆H₃-2,6-i-Pr₂) (μ³-S)]₃Ti(η⁵- C₅H₅). In contrast, group four complexes containing terminal-sulfido ligands are much less common, being limited to [Ti(S)Cl₄], (η⁵-C₅Me₅)₂M(S)py (M = Ti, Zr, Hf), [(η⁵-C₅H₅)Ti(μ-S)(S)]₂, and (PhC(NSiMe₃)₂))₂Ti(S)py. In our own work, we have been exploring the effects of bulky aryloxide ligands in Ti-sulfide chemistry. We have previously reported dimetallic sulfide bridged complexes of the form [(η⁵-C₅H₅)Ti (OC₆H₃-2,6-i-Pr₂)(μ-S)]₂ and [(η⁵-C₅H₅)Ti (OC₆H₃-2,6-i-Pr₂)]₂ (μ-S)(μ-S₂). In the present work, we probe several strategies in quest of titanium-terminal-sulfide complexes.

Full text of DOI:10.1021/ic001139d

3824
Inorg. Chem. 2001, 40, 3824-3826
Notes
Experimental Section
Synthesis and Characterization of
Cyclopentadienyl Titanium(Aryloxide)Sulfide
Complexes
General Data. All preparations were done under an atmosphere of
dry, O2-free N2, employing both Schlenk line techniques and inert
atmosphere gloveboxes. Solvents were purified using a Grubb’s type
column system. All organic reagents were purified by conventional
1
methods. H and13C{1H} NMR spectra were recorded in C6D6 on a
Eva Witt and Douglas W. Stephan*
Bruker Avance-300 and -500, operating at 300 and 500 MHz,
respectively. Trace amounts of protonated solvents were used as
references, and chemical shifts are reported relative to SiMe4. Guelph
Chemical Laboratories Inc. of Guelph, Ontario performed combustion
analyses. Li2S was purchased from the Aldrich Chemical Co. The
complexes (η5-C5H5)Ti(OR)Cl2 (R ) C6H3-2,6-Me2 1; C6H3-i-Pr2 2)
and (η5-C5Me5)Ti(OR)Cl2 (R ) C6H3-2,6-Me2 3, C6H3-i-Pr2 4, C6H3-
2,6-t-Bu2 5) were prepared as described in the literature.17,21
School of Physical Sciences, Chemistry and Biochemistry,
University of Windsor, Windsor, ON Canada N9B 3P4
ReceiVed October 16, 2000
We have been interested in the fundamental nature of the
reactivity of early metal-sulfur bonds for some time.1,2
A
Synthesis [(η5-C5H5)Ti(OC6H3-2,6-Me2)(µ-S)]2 6, [(η5-C5Me5)Ti-
(OC6H3-2,6-Me2)(µ-S)]2 7. These compounds were prepared in a
similar fashion. To a solution of 2 (100 mg, 0.28 mmol) in THF was
added Li2S (25 mg, 0.55 mmol). Upon stirring overnight, the solution
became brown. The THF was removed in vacuo, and the product was
extracted into benzene, filtered, and the solvent removed to give a brown
precipitate. 6. Yield: 50%. 1H NMR δ: 2.33 (s, 6H, Me), 6.23 (s, 5H,
(η5-C5H5)), 6.85 (m, 1H, p-Ar), 7.03 (d, 2H, m-Ar). Anal. Calcd for
C13H14STiO: C, 58.66; H: 5.30. Found: C, 58.21; H: 5.07. 7. Yield:
variety of group four metal sulfide derivatives are known,3
including mono and dimetallic compounds such as (η5-C5-
5
H5)2TiS5,4 1,5-((η5-C5H5)2Ti)2S6, and 1,4-((η5-C5H5)2Ti)2S4 , as
well as the higher nuclearity aggregates [(η5-C5H5)TiS]4,6 (η5-
C5H5)5Ti5S6,77 Zr3S3(t-BuS)2(BH4)4(THF)2, Zr6S6(t-BuS)4(BH4)8-
(THF)2,8,9 Zr3S(S-t-Bu)10,10 ((η5-C5H5)Ti)4(µ3-S)3(µ2-S)(µ2-
SEt)2, ((η5-C5H5)Ti)6(µ3-S)4(µ3-O)4, and [(η5-C5H5)Ti(OC6H3-
2,6-i-Pr2)(µ3-S)]3Ti(η5-C5H5).11 In contrast, group four complexes
containing terminal-sulfido ligands are much less common,
being limited to [Ti(S)Cl4],2-12 (η5-C5Me5)2M(S)py (M ) Ti,
Zr, Hf),13,14 [(η5-C5H5)Ti(µ-S)(S)]2,2-15 and (PhC(NSiMe3)2))2-
Ti(S)py.16 In our own work, we have been exploring the effects
of bulky aryloxide ligands in Ti-sulfide chemistry.17-20 We
have previously reported dimetallic sulfide bridged complexes
of the form [(η5-C5H5)Ti(OC6H3-2,6-i-Pr2)(µ-S)]2 and [(η5-
C5H5)Ti(OC6H3-2,6-i-Pr2)]2(µ-S)(µ-S2).18 In the present work,
we probe several strategies in quest of titanium-terminal-sulfide
complexes.
1
45%. H NMR δ: 1.90 (s, 3H, Me), 1.92 (s, 3H, Me), 2.38 (s, 15H,
(η5-C5Me5)), 6.67 (tr, 1H, p-Ar), 7.04 (d, 2H, m-Ar). Anal. Calcd for
C18H24STiO: C, 64.28; H: 7.19. Found: C, 64.11; H, 7.01.
Synthesis of (η5-C5Me5)Ti(S)(OR)‚LiCl‚2,2′-bipy, R ) (C6H3-2,6-
Me2) 8, (C6H3-2,6-i-Pr2) 9. A solution of 4 (0.50 g, 1.16 mmol), Li2S
(0.10 g, 2.18 mmol), and 2,2′-bipyridine (0.181 g, 1.16 mmol) in THF
(5 mL) was allowed to stir for 2 days. The solvent was removed and
the residue extracted into benzene; the solution was filtered and allowed
to stand. Light-brown X-ray quality crystals of 9 were deposited in
91% yield. 8. 1H NMR δ: 1.91 (s, 3H, Me), 1.93 (s, 3H, Me), 2.40 (s,
15H, (η5-C5Me5)), 6.01 (br, 2H, bipy), 6.60 (m, 2H, bipy), 6.90 (m,
3H, Ar), 7.40 (m, 2H, bipy), 8.90 (m, 2H, bipy). Anal. Calcd for C28H32-
ClLiN2STiO: C, 62.92; H, 5.99; N, 5.24; Found: C, 62.71; H, 5.84;
* To whom communication should be addressed.
(1) Stephan, D. W. Coord. Chem. ReV. 1989, 95, 41.
(2) Nadasdi, T. T.; Stephan, D. W. Coord. Chem. ReV. 1996, 147, 147.
(3) Draganjac, M.; Rauchfuss, T. B. Angew. Chem., Int. Ed. Engl. 1985,
24, 742.
(4) Muller, E. G.; Petersen, J. L.; Dahl, L. F. J. Organomet. Chem. 1976,
111, 91.
(5) Bollnger, C. M.; Hoots, J. E.; Rauchfuss, T. B. Organometallics 1982,
1, 223.
(6) Bottomley, F.; Keizer, P. N.; White, P. S. J. Am. Chem. Soc. 1988,
110, 141.
1
N, 5.09. 9. Yield: 96%. H NMR δ: 1.43 (d, 6H, |JHH| ) 6.8 Hz,
CH(CH3)2), 1.49 (d, 6H, |JHH| ) 6.8 Hz, CH(CH3)2), 2.39 (s, 15H,
C5Me5), 4.11 (sept, 2H, IJHH| ) 6.8 Hz, CH(CH3)2), 6.45 (dd, 2H, bipy),
6.90 (trd, 2H, bipy), 7.06 (tr, 1H, |JHH| ) 7.5 Hz, p-Ar), 7.16 (d, 2H,
m-Ar), 7.29 (d, 2H, bipy), 8.29 (d, 2H, bipy). 13C{1H}-NMR δ: 13.3
(C5Me5), 24.8 (CH(CH3)2), 25.3 (CH(CH3)2), 26.0 (CH(CH3)2), 119.8
(Ar), 120.4 (Ar), 123.7 (Bipy), 123.9 (C5Me5), 124.3 (Bipy), 137.7
(Bipy), 137.9 (o-Ar), 150.2 (Bipy), 154.0 (Bipy), 161.6 (ipso-Ar). Anal.
Calcd for C32H40ClLiN2STiO: C, 65.03; H, 6.82; N, 4.74. Found: C,
64.81; H, 6.54; N, 4.39.
(7) Bottomley, F.; Egharevba, G. O.; White, P. S. J. Am. Chem. Soc. 1985,
107, 4353.
Generation of (η5-C5Me5)Ti(S)(OC6H3-2,6-i-Pr2)(THF) (10) and
Benzo-15-crown-5‚LiCl To a 5 mL THF solution of 4 (0.200 g, 0.46
mmol) was added Li2S (0.04 g, 0.87 mmol) and benzo-15-crown-5
(0.124 g, 0.46 mmol). This was allowed to stir for 2 days. The THF
was removed in vacuo, and the residue was extracted in benzene and
filtered. The extreme sensitivity and propensity for dimerization of this
compound precluded isolation, EA, and spectroscopic characterization
(8) Coucouvanis, D.; Lester, R. K.; Kanatzidis, M. G.; Kessissoglou, D.
P. J. Am. Chem. Soc. 1985, 107, 8279.
(9) Coucouvanis, D.; Hadjikyriacou, A.; Lester, R.; Kanatzidis, M. G.
Inorg. Chem. 1994, 33, 3645.
(10) Coucouvanis, D.; Hadjikyriacou, A.; Kanatzidis, M. G. Chem. Com-
mun. 1985, 018, 1224.
(11) Firth, A. V.; Stephan, D. W. Inorg. Chem. 1997, 36, 1260.
(12) Muller, U.; Krug, V. Angew. Chem., Int. Ed. Engl. 1988, 27, 293.
(13) Sweeney, Z. K.; Polse, J. L.; Andersen, R. A.; Bergman, R. G.;
Kubinec, M. G. J. Am. Chem. Soc. 1997, 119, 4543.
(14) Howard, W.; Trnka, T. M.; Waters, M.; Parkin, G. J. Organomet.
Chem. 1997, 528, 95.
(15) Lundmark, P. J.; Kubas, G. J.; Scott, B. L. Organometallics 1996,
15, 3631.
(16) Hagadorn, J. R.; Arnold, J. Inorg. Chem. 1997, 36, 2928.
(17) Firth, A. V.; Stephan, D. W. Organometallics 1997, 16, 2183.
(18) Firth, A. V.; Stephan, D. W. Inorg. Chem. 1998, 37, 4726.
(19) Firth, A. V.; Stephan, D. W. Inorg. Chem. 1998, 37, 4732.
(20) Firth, A. V.; Witt, E.; Stephan, D. W. Organometallics 1998, 17, 3716.
1
beyond NMR methods. H NMR(C6D6) δ: 1.41 (d, 6H, |JHH| ) 6.8
Hz, CH(CH3)2), 1.45 (d, 6H, |JHH| ) 6.8 Hz, CH(CH3)2), 2.36 (s, 15H,
(η5-C5Me5)), 3.16 (br, 4H, CH2), 3.40 (br, 12H, CH2), 3.56 (m, THF),
4.21 (2H, 2H, |JHH| ) 6.8 Hz, CH(CH3)2), 6.34 (dd, 2H, Ar, crown),
6.73 (dd, 2H, Ar, crown), 6.90 (tr, 1H, p-Ar), 7.20 (d, 2H, m-Ar). 13C-
{1H}-NMR(C6D6) δ: 13.8 C5Me5, 25.0 (CH(CH3)2), 26.1 (CH(CH3)2),
(21) Fussing, I. M. M.; Pletcher, D.; Whitby, R. J. Organomet. Chem. 1994,
470, 109.
10.1021/ic001139d CCC: $20.00 © 2001 American Chemical Society
Published on Web 06/14/2001

Notes
Inorganic Chemistry, Vol. 40, No. 15, 2001 3825
Table 1. Crystallographic Parameters for 9a
formula
C32H40ClLiN2OSTi
formula weight
a (Å)
b (Å)
591.01
9.589(4)
16.990(6)
19.844(9)
othorhombic
P21/c
3232.9(23)
1.341
c (Å)
cryst syst
space group
vol (Å3)
Dcalcd (g cm-1
)
Z
4
abs coeff, µ, mm-1
R (%)
0.438
0. 0645
0.1340
Rw (%)
a All data collected at 24 C with Mo KR radiation (λ ) 0.71069 Å),
Figure 1. ORTEP drawing of 9, 20% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity (bond distances in Å, bond
angles in deg). Ti(1)-O(1) 1.849(4), Ti(1)-S(1) 2.227(2), Ti(1)-
Cl(1) 2.333(2), S(1)-Li(1) 2.465(14), Cl(1)-Li(1) 2.419(13), N(1)-
Li(1) 2.00(2), N(2)-Li(1) 2.05(2), O(1)-C(11) 1.355(7) Ti(1)-Li(1)
3.064(14), O(1)-Ti(1)-S(1) 105.50(14), O(1)-Ti(1)-Cl(1) 101.6(2),
S(1)-Ti(1)-Cl(1) 98.99(9), Ti(1)-S(1)-Li(1) 81.4(3), Ti(1)-Cl(1)-
Li(1) 80.3(4), C(11)-O(1)-Ti(1) 157.1(4), N(1)-Li(1)-N(2)
81.6(5), N(1)-Li(1)-Cl(1) 118.1(8), N(2)-Li(1)-Cl(1) 129.5(7),
N(1)-Li(1)-S(1) 123.7(7), N(2)-Li(1)-S(1) 117.8(7), Cl(1)-Li(1)-
S(1) 90.5(4).
2
2
R ) Σ||Fo|-|Fc||/Σ|Fo|, Rw ) [Σ[ω(Fo -Fc2)2]/ Σ[ωFo )2]]0.5
.
26.2 (CH(CH3)2), 66.7 (CH2), 67.9 (CH2), 69.0 (CH2), 69.1 (CH2), 112.3
(Ar, crown), 121.9 (Ar, crown), 122.4 (Ar), 123.6 (Ar), 128.9 (Me5C5),
138.1 (Ar), 147.5 (Ar, crown), 163.21 (Ar).
X-ray Data Collection and Reduction. The crystal of 9 was
manipulated and mounted in capillaries in a glovebox. Diffraction
experiments were performed on a Siemens SMART System CCD
diffractometer, collecting a hemisphere of data in 1329 frames with
10 s exposure times. Crystal data are summarized in Table 1. A measure
of decay was obtained by re-collecting the first 50 frames of each data
set. The data were processed using the SAINT, SADABS (empirical
absorption correction), XPREP, and SHELXTL packages. The reflec-
Scheme 1
2
2
tions with Fo >3σFo were used in the refinements.
Structure Solution and Refinement. Non-hydrogen atomic scat-
tering factors were taken from the literature tabulations.22 The non-
hydrogen atom positions were determined using direct methods and
successive difference Fourier map calculations. The refinement was
carried out by using full-matrix least squares techniques on F,
minimizing the function ω(|Fo| - |Fc|)2, where the weight ω is defined
2
2
as 4Fo /2σ(Fo ), and Fo and Fc are the observed and calculated structure
factor amplitudes. In the final cycles of refinement, all non-hydrogen
atoms were assigned anisotropic temperature factors. Carbon-bound
hydrogen atom positions were calculated (C-H: 0.95 Å) and allowed
to ride on the carbon to which they are bonded with temperature factors
fixed at 1.10 times that of the corresponding carbon atom. Hydrogen
atom contributions were calculated, but not refined. The final values
of refinement parameters are given in Table 1. Crystallographic data
have been deposited as Supporting Information.
Results and Discussion
In work analogous to our previous reports, reactions of 1 and
4 with Li2S resulted in the isolation of the dimeric complexes
[(η5-C5H5)Ti(OC6H3-2,6-Me2)(µ-S)]2 (6) and [(η5-C5Me5) Ti-
(OC6H3-2,6-Me2)(µ-S)]2 (7), respectively.18,20 In an effort to
intercept a monomeric terminal-sulfide derivative, we examined
the reaction of the sterically congested precursor 5 with Li2S.
Surprisingly, no reaction was observed, suggesting that steric
crowding inhibits the halide/sulfide metathesis. While the
reasons for this are not clear, it may be that the steric demands
of the ancillary ligands together with aggregation of lithium
sulfide in solution contribute to unforeseen steric conflicts.
A second strategy designed to intercept a terminal-sulfide
species involved reaction of 3 and 4 with Li2S in the presence
of bipyridine (Scheme 1).
(S)‚LiCl‚(2,2′-bipy) 9 (Figure 1). Sulfur and chlorine atoms
bridge the Li and Ti pseudo tetrahedral centers. The Ti-S
distance in 9 is 2.227(2) Å, which is slightly longer than the
Ti-S distances in the terminal-sulfide species: [PhC(NSiMe3)2)]2-
Ti(S)py (2.139(1) Å),16 (η5-C5Me5)2Ti(S)py (2.217(1) Å),13 Na2-
[(η5-C5H5)Ti(µ-S)(S)]2 (2.202(1) Å, 2.187(1) Å)15 and (NEt2)2-
[Ti(S)Cl4] (2.111(1) Å).12 It is, however, shorter than the Ti-S
distances typically seen in sulfido-bridged dimers. Correspond-
ingly, the Ti-Cl distance in 9 is 2.333(2) Å. Thus, species 9 is
best viewed as a LiCl adduct of a terminal-sulfide complex.
In a similar vein, the reaction of 4 with Li2S in the presence
of benzo-15-crown-5 was allowed to stir for several days in
THF/benzene solution. NMR data were consistent with a mixture
of two species formulated as (η5-C5Me5)Ti(OC6H3-2,6-i-Pr2)-
(S)(THF) (10) and benzo-15-crown-5‚LiCl. Although these data
NMR spectra of the resulting products 8 and 9, respectively,
were consistent with a 1:1:1 ratio of (η5-C5Me5), aryloxide, and
bipyridine. An X-ray crystallographic study of 9 confirmed the
formulation of these species as (η5-C5Me5)Ti(OC6H3-2,6-i-Pr2)-
(22) Cromer, D. T.; Mann, J. B. Acta Crystallogr., Sect. A 1968, A24,
390.

3826 Inorganic Chemistry, Vol. 40, No. 15, 2001
Notes
imply the generation of a terminal-sulfide complex 10, attempts
to further characterize or isolate 10 were unsuccessful. Upon
concentration of the solution, 10 was observed to dimerize
affording the known species [(η5-C5Me5)Ti(OC6H3-2,6-i-Pr2)-
(µ-S)]2.20
In conclusion, while sulfido-bridged dimers are, in general,
readily derived from cyclopentadienyl-Ti-aryloxide complexes,
related terminal-sulfide species have been isolated as LiCl
adducts. The propensity of terminal-sulfide species for dimer-
ization appears to account for their rather elusive nature.
Acknowledgment. Financial support from NSERC of Canada
is gratefully acknowledged. E.W. is grateful for the award of a
DFG Postdoctoral Fellowship.
Supporting Information Available: Crystallographic X-ray crys-
tallographic files in CIF format for the structure determination of
compound 9. This material is available free of charge via the Internet
at http://pubs.acs.org.
IC001139D