C-H and C-S bond cleavage in cyclopentadienyltitanium phenoxide thiolate complexes

Article abstract of DOI:10.1021/om961093p

The thiolate complexes CpTi(OC₆H₃-2,6-i-Pr₂)(SR)Cl (R) Et, 1; t-Bu, 2; CH₂Ph, 3; Ph, 4) were prepared. Attempts to methylate 1-4 and thus obtain the potentially reactive alkyltitanium thiolate derivatives were unsuccessful. Thiolation of CpTi(OC₆H₃-2,6-i-Pr₂)-(Me)Cl (5) with 1,1-dimethylethanethiol in the presence of base afforded the species CpTi-(OC₆H₃-2,6-i-Pr₂)(Me)(SCMe₃) (6). The analogous species CpTi(OC₆H₃-2,6-i-Pr₂)(Me)(SCH₂-Me) (7) is unstable, liberating methane and yielding the dimeric product of C-H bond activation, [CpTi(OC₆H₃-2,6-i-Pr₂)(μ-SCHMe)]₂ (8). In a related thermolysis of CpTi(OC₆H₃-2,6-i-Pr₂)(SBn)₂ (9), the dimer species [CpTi(μ-S)(OC₆H₃-2,6-i-Pr₂)]₂ (10) and (PhCH₂)₂S are obtained. In contrast, thermolysis of the closely related species CpTi(OC₆H₃-2,6-i-Pr₂)-((SCH₂)₂C₆H₄) (11) and CpTi(OC₆H₃-2,6-i-Pr₂)(SCH₂Me)₂ (12) resulted in no reaction, suggesting a radical process is operative in the formation of 10. Reduction of 2 with LiPCy₂ gave (PCy₂)₂ and the S-C bond cleavage product [CpTi(OC₆H₃-2,6-i-Pr₂)(μ³-S)]₃TiCp (13). These pathways of C-H and C-S bond activation are discussed and the implications considered.

Full text of DOI:10.1021/om961093p

Organometallics 1997, 16, 2183-2188
2183
C-H a n d C-S Bon d Clea va ge in
Cyclop en ta d ien yltita n iu m P h en oxid e Th iola te
Com p lexes
Andrea V. Firth and Douglas W. Stephan*
Department of Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada N9B 3P4
Received December 26, 1996X
The thiolate complexes CpTi(OC6H3-2,6-i-Pr2)(SR)Cl (R ) Et, 1; t-Bu, 2; CH2Ph, 3; Ph, 4)
were prepared. Attempts to methylate 1-4 and thus obtain the potentially reactive
alkyltitanium thiolate derivatives were unsuccessful. Thiolation of CpTi(OC6H3-2,6-i-Pr2)-
(Me)Cl (5) with 1,1-dimethylethanethiol in the presence of base afforded the species CpTi-
(OC6H3-2,6-i-Pr2)(Me)(SCMe3) (6). The analogous species CpTi(OC6H3-2,6-i-Pr2)(Me)(SCH2-
Me) (7) is unstable, liberating methane and yielding the dimeric product of C-H bond
activation, [CpTi(OC6H3-2,6-i-Pr2)(µ-SCHMe)]2 (8). In a related thermolysis of CpTi(OC6H3-
2,6-i-Pr2)(SBn)2 (9), the dimer species [CpTi(µ-S)(OC6H3-2,6-i-Pr2)]2 (10) and (PhCH2)2S are
obtained. In contrast, thermolysis of the closely related species CpTi(OC6H3-2,6-i-Pr2)-
((SCH2)2C6H4) (11) and CpTi(OC6H3-2,6-i-Pr2)(SCH2Me)2 (12) resulted in no reaction,
suggesting a radical process is operative in the formation of 10. Reduction of 2 with LiPCy2
gave (PCy2)2 and the S-C bond cleavage product [CpTi(OC6H3-2,6-i-Pr2)(µ3-S)]3TiCp (13).
These pathways of C-H and C-S bond activation are discussed and the implications
considered.
In tr od u ction
Early-metal thiolates are a class of compounds that
have drawn attention for a number of reasons over the
years. This chemistry has been recently reviewed.1 The
long-standing interest of chemists in biological systems
containing early metals has prompted and continues to
prompt numerous studies.2 More recently, the utility
of such complexes in the synthesis of organosulfur
compounds and as precursors for metal sulfide materials
in MOCVD processes has resulted in further studies.3
In the case of titanium thiolates, the bulk of the
chemistry known to date centers around titanocene
derivatives, while much less is known about homoleptic
and monocyclopentadienyl derivatives.1 We have re-
cently reported several studies addressing various
aspects of monocyclopentadienyltitanium thiolate deriv-
atives.4-6 Synthetic routes to complexes of the form
CpTi(SR)x(L)3-x have been described and the structural
implications of the Lewis acidity of the Ti center
described.4 The utility of monocyclopentadienyltita-
nium thiolate derivatives as metalloligands for early-
late heterobimetallics has also been probed.5 Most
recently, we have described C-H bond activation in the
species CpTi(SCH2CH2CH2S)Cl. The thiametallacycle
[CpTi(SCHCH2CH2S)]2 provides a metal-mediated syn-
thetic route to a variety of organosulfur compounds.6
In this report, we describe the synthesis of related
thiolate derivatives of monocyclopentadienyltitanium
phenoxide complexes. Alkylation, thermolysis, or re-
duction of these species is shown to induce C-H bond
activation or S-C bond cleavage, depending on the
nature of the thiolate substituents. These results are
presented and the implications considered.
Exp er im en ta l Section
Gen er a l Da ta . All preparations were done under an
atmosphere of dry, O2-free N2 employing either Schlenk line
techniques or a Vacuum Atmospheres inert atmosphere glove-
box. Solvents were reagent grade, distilled from the appropri-
ate drying agents under N2, and degassed by the freeze-thaw
method at least three times prior to use. All organic reagents
were purified by conventional methods. 1H and 13C{1H} NMR
spectra were recorded on a Bruker AC-300 operating at 300
and 75 MHz, respectively. Trace amounts of protonated
solvents were used as references, and chemical shifts are
reported relative to SiMe4. 31P{1H} NMR spectra were re-
corded on a Bruker AC-200 operating at 81 MHz and are
referenced to 85% H3PO4. Combustion analyses were per-
formed by Galbraith Laboratories Inc. (Knoxville, TN) or
Schwarzkopf Laboratories (Woodside, NY). CpTiCl3, CpTi-
(OC6H3-2,6-i-Pr2)Cl2, and CpTiMeCl2 were prepared via lit-
erature methods.7-9
X Abstract published in Advance ACS Abstracts, April 15, 1997.
(1) Stephan, D. W.; Nadasdi, T. T. Coord. Chem. Rev. 1996, 147,
147.
(2) (a) Steifel, E. I. Prog. Inorg. Chem. 1977, 22, 1. (b) Robson, R.
L.; Eady, E. E.; Richardson, T. H.; Miller, R. W.; Hawkins, M.; Postgate,
J . R. Nature 1986, 322, 388. (c) Hales, B. J .; Case, E. E.; Morningstar,
J . E.; Dzeda, M. F.; Mauterer, L. A. Biochemistry 1986, 25, 7251. (d)
Kustin, K.; Macara, I. G. Comments Inorg. Chem. 1982, 2, 1.
(3) Bochmann, M.; Hawkins, I.; Wilson, L. M. J . Chem. Soc., Chem.
Commun. 1988, 344.
(4) Nadasdi, T. T.; Huang, Y.; Stephan, D. W. Inorg. Chem. 1993,
32, 347.
(5) Nadasdi, T. T.; Stephan, D. W. Inorg. Chem. 1994, 33, 1532.
(6) (a) Huang, Y.; Nadasdi, T. T.; Stephan, D. W. J . Am. Chem. Soc.
1994, 116, 5483. (b) Huang, Y.; Etkin, N.; Heyn, R. R.; Nadasdi, T. T.;
Stephan, D. W. Organometallics 1996, 15, 2320.
Syn th esis of Cp Ti(OC6H3-2,6-i-Pr2)(SR)Cl (R ) Et, 1; t-Bu,
2; CH2Ph, 3; Ph, 4). These compounds were prepared in a
(7) Erskine, G. J .; Hurst, G. J . B.; Weinberg, E. L.; Hunter, B. K.;
McCowan, J . D. J . Organomet. Chem. 1984, 267, 265.
S0276-7333(96)01093-X CCC: $14.00 © 1997 American Chemical Society

2184 Organometallics, Vol. 16, No. 10, 1997
Firth and Stephan
similar manner, and thus only one representative preparation
is described. To CpTi(OC6H3-2,6-i-Pr2)Cl2 (50 mg, 0.13 mmol)
dissolved in benzene were added ethanethiol (9.5 µL, 0.13
mmol) and NEt3 (20 µL, 0.14 mmol). The reaction mixture
was stirred for 8 h and filtered, and then the solvent was
removed. Red/orange crystals of 1 were obtained from a
hexane solution in 64% yield.
1: 1H NMR (C6D6, 25 °C) δ 1.17 (d, 6H, |J H-H| ) 7 Hz), 1.24
(d, 6H, |J H-H| ) 7 Hz), 1.30 (dd, 3H, |J H-H| ) 7 Hz), 3.45 (sept,
2H, |J H-H| ) 7 Hz), 3.94 (dq, 2H, |J H-H| ) 7 Hz), 6.09 (s, 5H),
7.01 (m, 3H); 13C{1H} NMR (C6D6, 25 °C) δ 17.1, 23.6, 23.8,
26.3, 35.5, 116.9, 123.4, 123.5, 138.1, 162.3. Anal. Calcd for
3.70 (dq, 2H, |J H-H| ) 13.0, 7 Hz), 3.80 (dq, |J H-H| ) 13, 7 Hz),
5.98 (s, 5H), 6.9-7.1 (m, 3H).
Syn th esis of [Cp Ti(OC6H3-2,6-i-P r 2)(µ-SCHMe)]2 (8). To
CpTiCl2Me (91 mg, 0.46 mmol) suspended in pentane were
added ethanethiol (34 µL, 0.46 mmol), NEt3 (66 µL, 0.47 mmol),
and Li(OC6H3-2,6-i-Pr2) (84 mg, 0.46 mmol). The mixture was
stirred for 12 h and then filtered. The solvent was removed
and the residue extracted into benzene and heated overnight
at 70 °C. During this time, gas evolution was observed,
concurrent with the darkening to orange-brown. On cooling,
brown crystals of 8 were deposited in 14% yield: 1H NMR
(C7D8, 230 K) δ 0.38 (d, 3H, |J H-H| ) 7 Hz), 0.75 (d, 3H, |J H-H
|
) 7 Hz), 1.23 (d, 3H, |J H-H| ) 7 Hz), 1.33 (d, 3H, |J H-H| ) 7
Hz), 2.27 (d, 3H, |J H-H| ) 7 Hz), 2.67 (sept, 1H, |J H-H| ) 7
Hz), 3.74 (sept, 1H, |J H-H| ) 7 Hz), 4.28 (q, 1H, |J H-H| ) 7
Hz), 5.92 (s, 5H), 6.7-6.9 (m, 3H); 13C{1H} NMR (C7D8, 230
K) δ 20.4, 25.3, 25.5, 26.0, 27.5, 29.0, 99.5, 114.7, 121.9, 122.9,
124.6, 137.2, 137.7, 162.2. Anal. Calcd for C38H52O2S2Ti2: C,
65.13; H, 7.48. Found: C, 65.00; H, 7.25.
C
19H27ClOSTi: C, 58.99; H, 7.04. Found: C, 58.79; H, 6.90.
2: yield 59%; 1H NMR (C6D6, 25 °C) δ 1.20 (d, 3H, |J H-H| )
7 Hz), 1.23 (d, 3H, |J H-H| ) 7 Hz), 1.70 (s, 9H), 3.53 (sept, 2H,
|J H-H| ) 7 Hz), 6.14 (s, 5H), 7.00-7.14 (m, br, 3H); 13C{1H}
NMR (C6D6, 25 °C) δ 23.8, 24.2, 26.0, 33.9, 52.9, 117.5, 123.5,
123.6, 138.4, 162.3. Anal. Calcd for C21H31ClOSTi: C, 60.79;
H, 7.53. Found: C, 60.59; H, 7.46.
3: yield 83%; 1H NMR (C6D6, 25 °C) δ 1.19 (d, 6H, |J H-H| )
7 Hz), 1.26 (d, 6H, |J H-H| ) 7 Hz), 3.49 (sept, 2H, |J H-H| ) 7
Hz), 5.12 (d, 1H, |J H-H| ) 13 Hz), 5.26 (d, 1H, |J H-H| ) 13 Hz),
6.08 (s, 5H), 7.0-7.30 (m, br, 8H); 13C{1H} NMR (C6D6, 25 °C)
δ 23.7, 24.0, 26.4, 44.9, 117.1, 123.5, 123.6, 126.8, 128.1, 128.8,
138.2, 141.0, 162.4. Anal. Calcd for C24H28ClOSTi: C, 64.36;
H, 6.30. Found: C, 64.19; H, 6.15.
4: yield 79%; 1H NMR (C6D6, 25 °C) δ 1.09 (d, 6H, |J H-H| )
7 Hz), 1.15 (d, 6H, |J H-H| ) 7 Hz), 3.37 (sept, 2H, |J H-H| ) 7
Hz), 6.11 (s, 5H), 6.8-7.2 (m, 7H), 7.8 (d, 1H, |J H-H| ) 7 Hz);
13C{1H} NMR (C6D6, 25 °C) δ 23.5, 24.1, 26.3, 117.9, 123.4,
123.5, 126.6, 128.7, 131.8, 138.4, 142.7, 162.7. Anal. Calcd
for C23H26ClOSTi: C, 63.67; H, 6.04. Found: C, 63.39; H, 6.00.
Syn th esis of Cp Ti(OC6H3-2,6-i-P r 2)(Me)Cl (5). (i) To a
solution of CpTiCl2Me (90 mg, 0.45 mmol) in benzene was
added Li(OC6H3-2,6-i-Pr2 ) (85 mg, 0.45 mmol). The reaction
was stirred for 1 h at 25 °C and then filtered. The benzene
was removed, and a yellow solid was crystallized from hexane.
(ii) An alternative synthesis of 5 is achieved via the reaction
of CpTi(OC6H3-2,6-i-Pr2)Cl2 (200 mg, 0.51 mmol) with ZnMe2
(140 mL of a 2 M solution in toluene, 0.70 mmol) in THF (0.5
mL). The mixture was stirred at 25 °C overnight and the
solvent removed. The residue was extracted into hexane and
filtered, and then the solvent was removed to give 132 mg of
the yellow solid 5 (80%): 1H NMR (C6D6, 25 °C) δ 1.17 (d, 6H,
|J H-H| ) 7 Hz), 1.23 (d, 6H, |J H-H| ) 7 Hz), 1.48 (s, 3H), 3.28
(sept, 2H, |J H-H| ) 7 Hz), 5.93 (s, 5H), 6.8-6.95 (m, br, 3H);
13C{1H} NMR (C6D6, 25 °C) δ 23.4, 23.5, 26.9, 61.6, 116.2,
123.3, 123.4, 137.9, 162.1. Anal. Calcd for C18H25ClOTi: C,
63.45; H, 7.40. Found: C, 63.25; H, 7.19.
Syn th esis of Cp Ti(OC6H3-2,6-i-P r 2)(Me)(S-t-Bu ) (6), To
CpTiCl2Me (91 mg, 0.46 mmol) in hexane was added NEt3 (70.4
µL, 0.46 mmol), followed by 57.0 µL (0.46 mmol) of HS-t-Bu.
After the solution was stirred for a few minutes 92.5 mg, (0.50
mmol) of LiOC6H3-2,6-i-Pr2 was added. This mixture was
allowed to stir a few minutes and then filtered. A red solid
was isolated after a few days in 53% yield: 1H NMR (C6D6, 25
°C) δ 1.07 (s, 3H), 1.20 (d, 6H, |J H-H| ) 7 Hz), 1.21 (d, 6H,
|J H-H| ) 7 Hz), 1.68 (s, 9H), 3.44 (sept, 2H, |J H-H| ) 7 Hz),
6.00 (s, 5H), 6.9-7.1 (m, 3H); 13C{1H} NMR (C6D8, 25 °C) δ
23.5, 23.8, 26.6, 35.3, 50.0, 52.3, 114.6, 123.5, 138.1, 161.4.
Anal. Calcd for C22H34OSTi: C, 66.99; H, 8.69. Found: C,
66.59; H, 8.65.
Syn th esis of Cp Ti(OC6H3-2,6-i-P r 2)(SBn )2 (9), Cp Ti-
(OC6H3-2,6-i-P r 2)((SCH2)2C6H4) (11), a n d Cp Ti(OC6H3-2,6-
i-P r 2)(SEt)2 (12). These compounds were prepared in a
similar manner, and thus only one representative preparation
is described. To a solution of CpTi(OC6H3-2,6-i-Pr2)Cl2 (50 mg,
0.13 mmol) in pentane were added benzyl mercaptan (30.1 µL,
0.26 mmol) and NEt3 (30 mg, 0.30 mmol). The solution was
stirred at 25 °C for 30 min and then filtered, and the solvent
was removed under vacuum, affording 9 in 54% yield.
9: 1H NMR (C6D6, 25 °C) δ 1.23 (d, 12H, |J H-H| ) 7 Hz),
3.62 (sept, 2H, |J H-H| ) 7 Hz), 4.74 (s, 4H), 6.07 (s, 5H), 7.0-
7.3 (m, 13H); 13C{1H} NMR (C6D6, 25 °C) δ 24.0, 26.4, 43.4,
115.2, 123.4, 123.5, 126.7, 128.4, 128.7, 138.1, 141.9, 161.8.
Anal. Calcd for C31H36OS2Ti: C, 69.38; H, 6.76. Found: C,
69.19; H, 6.65.
11: yield 24%; 1H NMR (C6D6, 25 °C) δ 1.25 (d, 12H, |J H-H
|
) 7 Hz), 3.65 (sept, 2H, |J H-H| ) 7 Hz), 4.62 (d, 2H, |J H-H| )
14 Hz), 4.93 (d, 2H, |J H-H| ) 14 Hz), 5.93 (s, 5H), 6.9-7.1 (m,
br, 7H); 13C{1H} NMR (C6D6, 25 °C) δ 23.9, 26.2, 37.7, 114.0,
122.9, 123.4, 128.3, 128.8, 136.2, 138.4, 142.11, 164.4. Anal.
Calcd for C25H30OS2Ti: C, 65.48; H, 6.59. Found: C, 65.29;
H, 6.42.
12: yield 58%; 1H NMR (C6D6, 25 °C) δ 1.23 (d, 12H, |J H-H
|
) 7 Hz), 1.32 (t, 6H, |J H-H| ) 7 Hz), 3.57 (q, 4H, |J H-H| ) 7
Hz), 3.61 (sept, 2H, |J H-H| ) 7 Hz), 6.07 (s, 5H), 7.0-7.1 (m,
3H); 13C{1H} NMR (C6D6, 25 °C) δ 18.5, 24.0, 26.1, 33.3, 114.9,
123.1, 123.5, 138.2, 161.5. Anal. Calcd for C21H32OS2Ti: C,
61.14; H, 7.82. Found: C, 60.99; H, 7.75.
Syn th esis of [Cp Ti(µ-S)( OC6H3-2,6-i-P r 2)]2 (10). To a
suspension of CpTiCl2( OC6H3-2,6-i-Pr2) (150 mg, 0.39 mmol)
in hexane were added benzyl mercaptan, (95.6 mg, 0.77 mmol)
and NEt3 (80 mg, 0.8 mmol). The mixture was stirred
overnight at 25 °C and then filtered. The solvent was removed
and the solid redissolved in toluene. This mixture was heated
at 80 °C overnight. Dark red crystals of 10 were deposited
from toluene at -4 °C after 12 h in 49.6% yield: 1H NMR
(C6D6, 25 °C) δ 1.39 (d, 12H, |J H-H| ) 7 Hz), 3.40 (sept, 2H,
|J H-H| ) 7 Hz), 6.3 (s, 5H), 7.0-7.22 (m, 3H); 13C{1H} NMR
(C6D6, 25 °C) δ 23.8, 27.0, 115.8, 122.1, 123.5, 137.4, 163.8.
Anal. Calcd for C34H44O2S2Ti2: C, 63.35; H, 6.88. Found: C,
63.09; H, 6.65.
Syn th esis of [Cp Ti(OC6H3-2,6-i-P r 2)(µ3-S)]3TiCp (13).
To a suspension of 2 (150 mg, 0.36 mmol) in benzene (2 mL)
was added LiPCy2 (68 mg, 0.36 mmol). The mixture im-
mediately became dark green-black and was stirred overnight
at 25 °C and then filtered. Upon standing for 7 days, dark
crystals of 13 were deposited in 58% yield. EPR (C7H8) g 1.990.
Anal. Calcd for C56H71O3S3Ti4: C, 62.28; H, 6.63. Found: C,
62.09; H, 6.60.
Gen er a tion of Cp Ti(OC6H3-2,6-i-P r 2)(Me)(SEt) (7). The
procedure for the generation of 7 was analogous to that
employed for 6. The instability of 7 precluded isolation and
complete characterization: 1H NMR (C6D6, 25 °C) δ 1.04 (s,
3H), 1.22 (d, 6H, |J H-H| ) 7 Hz), 1.25 (d, 6H, |J H-H| ) 7 Hz),
1.30 (dd, 3H, |J H-H| ) 7 Hz), 3.40 (sept, 2H, |J H-H| ) 7 Hz),
X-r a y Da ta Collection a n d Red u ction . X-ray quality
crystals of 4 and 8-13 were obtained directly from the
preparations as described above. The crystals were manipu-
lated and mounted in capillaries in a glovebox, thus maintain-
ing a dry, O2-free environment for each crystal. Diffraction
(8) Fussing, I. M. M.; Pletcher, D.; Whitby, R. J . J . Organomet.
Chem. 1994, 470, 109.
(9) Erskine, G. J .; Hurst, G. J . B.; Weinberg, E. L.; Hunter, B. K.;
McCowan, J . D. J . Organomet. Chem. 1984, 267, 265.

C-H and C-S Bond Activation in Titanium Thiolates
Ta ble 1. Cr ysta llogr a p h ic P a r a m eter sa
10
C23H27OTiSCl C38H52O2S2Ti2 C31H36OTiS2 C34H44O2Ti2S2 C25H30OTiS2 C21H32OS2Ti C56H71Ti4S4O3
Organometallics, Vol. 16, No. 10, 1997 2185
4
8
9
11
12
13
formula
formula weight
a, Å
b, Å
c, Å
434.88
700.75
536.64
10.945(8)
14.84(1)
9.745(7)
106.39(8)
91.46(6)
75.00(7)
1464(2)
P-1
1.22
2
4.55
32.0
5150
4.5-50
2585
316
0.87-1.00
5.0
644.64
457.52
10.636(3)
11.814(3)
9.985(3)
96.95(3)
97.27(2)
102.50(2)
1200.7(6)
P-1
1.26
2
5.43
32.0
2540
4.5-45
1478
197
0.85-1.00
5.9
412.50
13.064(7)
17.716(6)
10.665(7)
94.70(4)
99.60(5)
106.75(3)
2308(2)
P-1
1.19
2
5.58
32.0
8147
4.5-50
2506
281
0.69-1.00
9.0
1112.02
10.4161(1)
14.1133(4)
21.8288(6)
107.385(1)
95.458(1)
91.287(1)
3044.1(1)
P-1
1.21
2
6.80
na
6246
4.5-42.0
2776
315
0.99-1.00
8.0
10.918(7)
12.89(2)
16.46(1)
11.129(3)
16.560(4)
20.415(3)
12.649(6)
16.75(1)
16.076(4)
R, deg
â, deg
92.82(8)
99.72(3)
91.59(4)
γ, deg
V, Å3
2314(3)
P21/n
1.25
4
5.8
8.0
2601
4.5-45
594
3708(1)
P21/n
1.25
4
5.74
3403(3)
P21/c
1.26
4
6.19
space group
d(calc), g cm-1
Z
µ, cm-1
scan speed, deg/min
no. of data collected
2θ/index ranges, deg
16.0
16.0
6796
4.5-50
2047
287
0.83-1.00
6.5
6217
4.5-50
1986
251
0.87-1.00
7.4
2
2
no. of data Fo > 3σ(Fo
)
no. of variables
transmission factors
R, %b
94
0.81-1.00
9.3
9.7
Rw, %c
5.5
3.8
5.8
5.1
7.1
9.0
goodness of fit
1.93
1.58
1.51
1.95
1.96
2.40
2.22
a
All data collected at 24 °C with Mo KR radiation (λ ) 0.710 69 Å), a scan range of 1.0 above KR1 and 1.0 below KR1, with a background
to scan ratio of 0.5. R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw ) [∑w(|Fo| - |Fc|)2/∑|Fo| ]0.5
.
b
2
experiments for 4 and 8-12 were performed on a Rigaku AFC6
diffractometer equipped with graphite-monochromatized Mo
KR radiation. The initial orientation matrix was obtained from
20 machine-centered reflections selected by an automated peak
search routine. These data were used to determine the crystal
systems. Automated Laue system check routines around each
axis were consistent with the crystal system. Ultimately, 25
reflections (20° < 2θ < 25°) were used to obtain the final lattice
parameters and the orientation matrices. Crystal data are
summarized in Table 1. The observed extinction coefficients
were consistent with the space groups in each case. The data
sets were collected in three shells (4.5°< 2θ < 45-50.0°), and
three standard reflections were recorded every 197 reflections.
Fixed scan rates were employed. Up to four repetitive scans
of each reflection at the respective scan rates were averaged
to ensure meaningful statistics. The number of scans of each
reflection was determined by the intensity. The intensities
of the standards showed no statistically significant change over
the duration of the data collections. The data were processed
using the TEXSAN crystal solution package operating on a
SGI Challenger mainframe with remote X-terminals. The
the TEXSAN package. Hydrogen atom positions were calcu-
lated and allowed to ride on the carbon to which they are
bonded, assuming a C-H bond length of 0.95 Å. Hydrogen
atom temperature factors were fixed at 1.10 times the isotropic
temperature factor of the carbon atom to which they are
bonded. The hydrogen atom contributions were calculated but
not refined. The final values of R, Rw, and the goodness of fit
in the final cycles of the refinements are given in Table 1. The
locations of the largest peaks in the final difference Fourier
map calculation as well as the magnitude of the residual
electron densities in each case were of no chemical significance.
Positional parameters, hydrogen atom parameters, thermal
parameters, and bond distances and angles have been depos-
ited as Supporting Information.
Resu lts a n d Discu ssion
The incorporation of titanium-alkyl and titanium-
thiolate bonds into a single complex offers one avenue
to initiate C-H or S-C bond cleavage reactions. To
that end, we have prepared the series of complexes
CpTi(OC6H3-2,6-i-Pr2)(SR)Cl (R ) Et, 1; t-Bu, 2; Bn, 3;
Ph, 4) via thiolate substitution reactions on CpTi-
(OC6H3-2,6-i-Pr2)Cl2. Complexes 1-4 were character-
ized via NMR spectroscopy, and the structure of 4 was
confirmed crystallographically (Figure 1). Attempts to
replace the remaining chloride ligand with a methyl
group, thus generating the desired alkyltitanium thi-
olate derivatives, were unsuccessful. Reactions of 1-4
with MeLi led to a mixture of uncharacterized products.
Attempts to alkylate with AlMe3 or ZnMe2 resulted in
thiolate and/or alkoxide abstraction, together with a
mixture of Ti products including CpTiCl2Me, CpTi-
(OC6H3-2,6-i-Pr2)Cl2, and CpTi(OC6H3-2,6-i-Pr2)MeCl.
An alternative synthetic approach involved the initial
preparation of the species CpTi(OC6H3-2,6-i-Pr2)(Me)-
Cl (5) via reaction of CpTi(OC6H3-2,6-i-Pr2)Cl2 with
ZnMe2 or via reaction of CpTiMeCl2 with Li(OC6H3-2,6-
i-Pr2). Reaction of 5 with 1,1-dimethylethanethiol in the
presence of base afforded the species CpTi(OC6H3-2,6-
i-Pr2)(Me)(SCMe3) (6) in 53% isolated yield. The for-
mulation of this species was confirmed by NMR data.
This species was thermally robust, exhibiting no C-H
or S-C bond activation upon heating to 80 °C for 12 h.
In an analogous preparation, the species CpTi(OC6H3-
2
2
reflections with Fo > 3σFo were used in the refinements. In
the case of 13, X-ray data were collected on a Siemens SMART
system CCD diffractometer and processed employing the
SHELXS software package.
Str u ctu r e Solu tion a n d Refin em en t. Non-hydrogen
atomic scattering factors were taken from the literature
tabulations.10,11 The Ti atom positions were determined using
direct methods employing either the SHELX-86 or Mithril
direct methods routines. The remaining non-hydrogen atoms
were located from successive difference Fourier map calcula-
tions. The refinements were carried out by using full-matrix
least-squares techniques on F, minimizing the function ω(|Fo|
- |Fc|)2, where the weight ω is defined as 4Fo2/2σ(Fo2) and Fo
and Fc are the observed and calculated structure factor
amplitudes. In the final cycles of each refinement, the number
of non-hydrogen atoms assigned anisotropic temperature
factors was determined so as to maintain a reasonable data:
variable ratio. The remaining atoms were assigned isotropic
temperature factors. Empirical absorption corrections were
applied to the data sets based on either ψ-scan data or a
DIFABS calculation and employing the software resident in
(10) (a) Cromer, D. T.; Mann, J . B. Acta Crystallogr. Sect. A: Cryst.
Phys., Theor. Gen. Crystallogr. 1968, A24, 324. (b) Cromer, D. T.; Mann,
J . B. Acta Crystallogr. Sect. A: Cryst. Phys., Theor. Gen. Crystallogr.
1968, A24, 390.
(11) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Knoch Press: Birmingham, England, 1974.

2186 Organometallics, Vol. 16, No. 10, 1997
Firth and Stephan
F igu r e 2. ORTEP drawing of 8; 30% thermal ellipsoids
are shown. Ti(1)-S(1), 2.441(4) Å; Ti(1)-S(2), 2.545(4) Å;
Ti(1)-O(1), 1.814(7) Å; Ti(1)-C(35), 2.14(1) Å; Ti(2)-S(1),
2.556(4) Å; Ti(2)-S(2), 2.440(4) Å; Ti(2)-O(2), 1.816(7) Å;
Ti(2)-C(37), 2.14(1) Å; S(1)-Ti(1)-S(2), 78.1(1); S(1)-
Ti(1)-O(1), 120.5(2)°; S(1)-Ti(1)-C(35), 45.0(3)°; S(2)-
Ti(1)-O(1), 94.4(2)°; S(2)-Ti(1)-C(35), 119.9(3)°; O(1)-
Ti(1)-C(35), 98.7(4)°; S(1)-Ti(2)-S(2), 77.9(1)°; S(1)-Ti(2)-
O(2), 96.8(2)°; S(1)-Ti(2)-C(37), 119.3(4)°; S(2)-Ti(2)-
O(2), 121.0(2)°; S(2)-Ti(2)-C(37), 44.6(3)°; O(2)-Ti(2)-
C(37), 98.1(4)°; Ti(1)-C(35)-S(1), 76.5(4)°; Ti(2)-C(37)-
S(2), 76.8(5)°.
F igu r e 1. ORTEP drawing of 4; 30% thermal ellipsoids
are shown. Ti(1)-Cl(1) 2.26(1), Å; Ti(1)-S(1), 2.333(8) Å;
Ti(1)-O(1), 1.80(2) Å; Cl(1)-Ti(1)-S(1), 106.8(4)°; Cl(1)-
Ti(1)-O(1), 102.5(6)°; S(1)-Ti(1)-O(1),108.5(6)°.
Sch em e 1
Mechanistically, the formation of 8 is thought to
involve intramolecular loss of methane followed by
dimerization. This is in contrast to the mechanism
proposed for the formation of [CpTi(SCHCH2CH2S)]2,
where â-hydrogen abstraction is thought to occur.6
Nonetheless, this view is consistent with the formation
and stability of 6, where the lack of hydrogen atoms â
to the Ti permits isolation. It is also noteworthy that a
concerted four-center cyclometalation process is opera-
tive in the formation of thioformaldehyde complexes of
zirconocene.12 Attempts to obtain kinetic data for the
formation of 8 were unsuccessful, as the initial forma-
tion of the intermediate 7 was not clean, the species
being apparently subject to both redistribution and
metalation reactions.
Attempts to prepare the benzenethiolate analog of 6
were unsuccessful. Reaction of 5 with benzenethiolate
results in a complex mixture of products. NMR data
suggest that the myriad of products may include the
desired substitution products in addition to a variety
of Ti complex anions. Reaction of 5 with benzyl mer-
captan and base at 25 °C also resulted in formation of
a mixture of compounds. However, in this case, the
major product was identified as CpTi(OC6H3-2,6-i-
Pr2)(SCH2Ph)2 (9). This was confirmed via independent
synthesis from CpTi(OC6H3-2,6-i-Pr2)Cl2 and 2 equiv of
thiol in the presence of base. The formulation of 9 was
also confirmed crystallographically (Figure 3).
2,6-i-Pr2)(Me)(SCH2Me) (7) was generated in solution
and observed as a transient species by H NMR spec-
1
troscopy. However, the instability of 7 precluded its
isolation. Heating the reaction mixture to 80 °C liber-
ated methane, and the resulting product 8 was crystal-
lized from solution. The NMR data and, in particular,
the observation of a methine group as evidenced by the
13C resonance at 99.1 ppm and the 1H signal at 4.28
ppm prompted the empirical formulation of this new
species 8 as CpTi(OC6H3-2,6-i-Pr2)(SCHMe). A 6%
nuclear Overhauser effect was observed between the
cyclopentadienyl ring protons and the methyl group
proton, consistent with a geometry in which both of
The inability to obtain CpTi(OC6H3-2,6-i-Pr2)(Me)-
(SCH2Ph) may arise because thiol protolysis of the Ti-
methyl bond is competitive with deprotonation of the
these groups reside on the same side of the thiametal-
lacyclopropane ring. This, together with the dimeric
nature of 8, was subsequently confirmed crystallo-
graphically (Figure 2).
(12) (a) Buchwald, S. L.; Nielsen, R. B.; Dewan, J . C. J . Am. Chem.
Soc. 1987, 109, 1590. (b) Buchwald, S. L.; Nielsen, R. B. J . Am. Chem.
Soc. 1988, 110, 3171. (c) Buchwald, S. L.; Fisher, R. A.; Davis, W. M.
Organometallics 1989, 8, 2082. (d) Fisher, R. A.; Nielsen, R. B.; Davis,
W. M.; Buchwald, S. L. J . Am. Chem. Soc. 1991, 113, 165.

C-H and C-S Bond Activation in Titanium Thiolates
Organometallics, Vol. 16, No. 10, 1997 2187
F igu r e 3. ORTEP drawing of 9; 30% thermal ellipsoids
are shown. Ti(1)-S(1), 2.318(2) Å; Ti(1)-S(2), 2.339(2) Å;
Ti(1)-O(1), 1.796(3) Å; S(1)-Ti(1)-S(2), 108.90(7)°; S(1)-
Ti(1)-O(1), 105.6(1)°; S(2)-Ti(1)-O(1), 104.2(1)°.
F igu r e 5. ORTEP drawing of 11; 30% thermal ellipsoids
are shown. Ti(1)-S(1), 2.321(3) Å; Ti(1)-S(2), 2.313(3) Å;
Ti(1)-O(1), 1.793(5) Å; S(1)-Ti(1)-S(2), 102.9(1)°; S(1)-
Ti(1)-O(1), 103.7(2)°; S(2)-Ti(1)-O(1), 103.6(2)°.
F igu r e 4. ORTEP drawing of 10; 30% thermal ellipsoids
are shown. Ti(1)-Ti(2), 3.141(3) Å; Ti(1)-S(1), 2.314(4) Å;
Ti(1)-S(2), 2.302(4) Å; Ti(1)-O(1), 1.802(8) Å; Ti(2)-S(1),
2.295(4) Å; Ti(2)-S(2, 2.307(4) Å; Ti(2)-O(2), 1.819(8) Å;
S(1)-Ti(1)-S(2), 93.9(2)°; S(1)-Ti(1)-O(1), 105.3(3)°; S(2)-
Ti(1)-O(1), 105.6(3)°; S(1)-Ti(2)-S(2), 94.3(2)°; S(1)-
Ti(2)-O(2), 106.0(3)°; S(2)-Ti(2)-O(2), 104.6(3)°; Ti(1)-
S(1)-Ti(2), 85.9(2)°; Ti(1)-S(2)-Ti(2), 85.9(2)°.
thiol by base. Alternatively, it may be that redistribu-
tion of CpTi(OC6H3-2,6-i-Pr2)(Me)(SCH2Ph) to 9 and
other uncharacterized species is facile. Heating the
reaction mixture containing 9 resulted in isolation in
low yield of a new species, 10. This species exhibited
1H NMR resonances attributable to the cyclopentadienyl
and aryl oxide ligands only. X-ray crystallographic
characterization of 10 confirmed the formulation as
[CpTi(OC6H3-2,6-i-Pr2)S]2 (Figure 4). An alternative
and higher yielding synthesis of 10 was subsequently
shown from the thermolysis of pure 9. In this way, 10
is obtained cleanly and quantitatively. The organic
byproduct of this S-C bond cleavage reaction was
identified as (PhCH2)2S by spectroscopic comparison to
an authentic sample.13
The closely related species CpTi(OC6H3-2,6-i-Pr2)-
((SCH2)2C6H4) (11) and CpTi(OC6H3-2,6-i-Pr2)(SCH2-
Me)2 (12) were prepared in a manner analogous to that
employed for 9. NMR and crystallographic data (Fig-
ures 5 and 6) confirmed the formulations. Thermolysis
of 11 or 12 at 80 °C for 12-18 h resulted in no reaction.
It is also noteworthy that similar thermolysis of 3
resulted in no reaction, and, as well, no radical coupling
F igu r e 6. ORTEP drawing of 12; 30% thermal ellipsoids
are shown. Ti(1)-S(1), 2.329(5) Å; Ti(1)-S(2), 2.304(5) Å;
Ti(1)-O(1), 1.802(8) Å; Ti(2)-S(3), 2.313(5) Å; Ti(2)-S(4),
2.318(6) Å; Ti(2)-O(2), 1.809(8) Å; S(1)-Ti(1)-S(2), 107.6(2)°;
S(1)-Ti(1)-O(1), 104.7(3)°; S(2)-Ti(1)-O(1), 104.1(3)°;
S(3)-Ti(2)-S(4), 108.4(2)°; S(3)-Ti(2)-O(2), 104.4(3)°; S(4)-
Ti(2)-O(2), 103.9(3)°.
products are observed in the formation of 10, other than
the sulfide SBn2. Given that the S-C bond strengths
and nucleophilicity of ethanethiolate and benzenethi-
olate are expected to be similar, the conversion of 9 to
10 suggests a radical process within a solvated cage.
While this supposition appears consistent with the data
and chemical intuition, further mechanistic studies are
required to confirm this postulate.
The implication of a radical process prompts questions
of the role of Ti(III) in S-C bond activation. In other
work,14 we have found phosphides to be convenient and
(14) (a) Dick, D. G.; Hou, Z.; Stephan, D. W. Organometallics 1992,
11, 2378. (b) Dick, D. G.; Stephan, D. W. Organometallics 1990, 9, 1910.
(c) Ho, J .; Stephan, D. W. Inorg. Chem. 1994, 33, 4595. (d) Dick, D.
G.; Stephan, D. W. Organometallics 1991, 10, 2811. (e) Dick, D. G.;
Stephan, D. W. Can. J . Chem. 1991, 69, 1146.
(13) A sample of SBn2 was prepared via direct reaction of LiSBn
and BnCl: 1H NMR (C6D6, 25 °C) δ 3.33 (s, 4H), 7.13 (m, 10H).

2188 Organometallics, Vol. 16, No. 10, 1997
Firth and Stephan
F igu r e 8. ORTEP drawing of the TiSO core of 13; 30%
thermal ellipsoids are shown.
ligands are the legs. In these compounds, the Ti-S
distances are very similar, all falling in the range of
2.304(5)-2.333(8) Å, as is typical of compounds contain-
ing terminal titanium thiolate ligands.1 In addition, the
Ti-S-C angles in 4, 9, 11, and 12 fall within the narrow
range of 100.6(3)-106.9(2)°, consistent with minimal
π-donation from S to the Ti centers.
The structural study of 8 confirms that two CpTi(OR)
centers form titanathiacyclopropane rings (Figure 2), in
which the Ti-C bond distances are 2.14(1) Å. The
sulfur atoms bridge the two metal centers, yielding the
dimeric complex. The Ti-S distances within the thia-
titanacyclopropane ring are 2.441(4) Å. In contrast to
the species [CpTi(SCHCH2CH2S)]2, the S atoms within
the metallacycle in 8 bridge to the adjacent Ti with an
average Ti-S distance of 2.550(6) Å.6 The cyclopenta-
dienyl rings are transoid with respect to the Ti2S2 core.
Ring strain within the thiatitanacyclopropane ring is
evidenced by C-Ti-S angles of 45.0(3)° and 44.6(3)° and
Ti-C-S angles of 76.5(4)° and 76.8(5)°, respectively. A
similar dimeric structure is seen for 10 (Figure 4), in
which two sulfur atoms bridge the Ti centers at Ti-S
distances of 2.295(4)-2.314(4) Å. In a manner similar
to that of 8, the cyclopentadienyl ligands are transoid
with respect to the Ti2S2 plane, presumably a conse-
quence of steric preference.
The molecular structure of 13 (Figure 7) is comprised
of three CpTi(OR)S fragments forming a cyclic trimeric
ring (Figure 8). The three bridging sulfur atoms are
capped by a fourth CpTi unit. The three OR ligands
are oriented on the same side of the [CpTi(OR)S]3 ring,
again presumably an accommodation which minimizes
steric congestion. The Ti-S distances about the tri-
meric ring average 2.405(7) Å, while the Ti-S distances
to the central Ti average 2.346(5) Å.
F igu r e 7. ORTEP drawing of 13; 30% thermal ellipsoids
are shown. Ti(1)-Ti(4), 3.072(5) Å; Ti(1)-S(1), 2.399(6) Å;
Ti(1)-S(3), 2.417(5) Å; Ti(1)-O(1), 1.82(1) Å; Ti(2)-Ti(4),
3.067(5) Å; Ti(2)-S(1), 2.396(6) Å; Ti(2)-S(2), 2.407(5) Å;
Ti(2)-O(2), 1.81(1) Å; Ti(3)-Ti(4), 3.075(4) Å; Ti(3)-S(2),
2.415(6) Å; Ti(3)-S(3), 2.393(6) Å; Ti(3)-O(3), 1.79(1) Å;
Ti(4)-S(1), 2.344(6) Å; Ti(4)-S(2), 2.346(6) Å; Ti(4)-S(3),
2.345(6) Å; S(1)-Ti(1)-S(3), 95.3(2)°; S(1)-Ti(1)-O(1),
102.6(4)°; S(3)-Ti(1)-O(1), 101.6(4)°; S(1)-Ti(2)-S(2),
95.4(2)°; S(1)-Ti(2)-O(2), 100.6(4)°; S(2)-Ti(2)-O(2),
102.7(4)°; S(2)-Ti(3)-S(3), 95.3(2)°; S(2)-Ti(3)-O(3),
103.2(4)°; S(3)-Ti(3)-O(3), 102.8(4)°; S(1)-Ti(4)-S(2), 98.4-
(2)°; S(1)-Ti(4)-S(3), 98.7(2)°; S(2)-Ti(4)-S(3), 98.5(2)°;
Ti(1)-S(1)-Ti(2), 131.3(2)°; Ti(1)-S(1)-Ti(4), 80.7(2)°; Ti(2)-
S(1)-Ti(4), 80.6(2)°; Ti(2)-S(2)-Ti(3), 130.7(3)°; Ti(2)-
S(2)-Ti(4), 80.4(2)°; Ti(3)-S(2)-Ti(4), 80.4(2)°; Ti(1)-S(3)-
Ti(3), 130.4(2)°; Ti(1)-S(3)-Ti(4), 80.3(2)°; Ti(3)-S(3)-
Ti(4), 80.9(2)°; Ti(1)-O(1)-C(6), 151(1)°; Ti(2)-O(2)-C(23),
157(1)°; Ti(3)-O(3)-C(40), 152(1)°.
effective reducing agents. Treatment of 2 with LiPCy2
resulted in a dramatic color change from orange to dark
green. 31P{1H} NMR spectra of the reaction mixture
revealed the formation of (PCy2)2,14 implying redox
chemistry had, indeed, occurred. The paramagnetic Ti-
containing product 13 was isolated by fractional crystal-
lization and shown crystallographically to be [(CpTi-
(OR)(µ3-S)]3TiCp (Figure 7). Related S-C bond scission/
reduction reactions in zirconium 1,1-dimethylethane-
thiolate complexes have been previously reported to
yield the complexes Zr3S3(S-t-Bu)2(BH4)4, Zr6S6(S-t-Bu)2-
(BH4)8, and Zr3S(S-t-Bu)10.15 It is interesting to contrast
the thermal stability of the titanium(IV) 1,1-dimethyl-
ethanethiolate complex 6 with the facile S-C bond
cleavage upon reduction of the metal center.
Su m m a r y
In conclusion, C-H and S-C bond activation reac-
tions of the titanium thiolate complexes described herein
provide access to novel metallacyclic and sulfide bridged
products. The potential utility of these compounds in
either the functionalization of thiols or desulfurization
of organosulfur compounds is the subject of current
study.
Str u ctu r a l Da ta
The structural studies of 4, 8-13 are similar in that
they all contain CpTi(OR) fragments. T-O-C angles
in the range of 151(1)-165.0(6)° and the Ti-O distances
of 1.793(5)-1.82(1) Å are consistent with Ti-O π-bond-
ing. In the case of compounds 4, 9, 11, and 12 (Figures
1 3, 5, and 6), the geometries of the Ti coordination
spheres are best described as distorted “three-legged
piano stools”, in which the cyclopentadienyl ligand
serves as the seat of the stool while the three other
Ack n ow led gm en t . Financial support from the
NSERC of Canada is gratefully acknowledged. Dr.
Glenn Yap of the Windsor Molecular Structure Centre
is thanked for data collection for 13.
Su p p or tin g In for m a tion Ava ila ble: Spectroscopic data
and tables of crystallographic parameters, hydrogen atom
parameters, and thermal parameters (43 pages). Ordering
information is given on any current masthead page.
(15) (a) Coucouvanis, D.; Hadjikyriacou, A.; Kanatzdis, M. G. J .
Chem. Soc., Chem. Commun. 1985, 1224. (b) Coucouvanis, D.; Lester,
R. K.; Kanatzdis, M. G.; Kessissoglou, D. P. J . Am. Chem. Soc. 1985,
107, 8279.
OM961093P