Reaction of ketones with the organotitanium oxide [{TiCp*(μ-O)}3(μ3-CMe)] via the hydride-vinylidene [{TiCp*(μ-O)}3(μ-C=CH2)(H)] intermediate

Article abstract of DOI:10.1039/a709194j

Thermal and/or photochemical treatment of [{TiCp*(μ-O)}₃(μ₃-CMe)] 1 (Cp* = η⁵-C₅Me₅) with organic ketones affords the new oxo derivatives [{TiCp*(μ-O)}₃(μ-C=CH₂)(OCHRR′)](R = R′

Full text of DOI:10.1039/a709194j

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Reaction of ketones with the organotitanium oxide [{TiCp*(m-O)}3(m3-CMe)]
via the hydride–vinylidene [{TiCp*(m-O)}3(m-CNCH2)(H)] intermediate‡
Mikhail Galakhov, Miguel Mena*† and Cristina Santamar´ıa
Departamento de Qu´ımica Inorga´nica de la Universidad de Alcala´, E-22871 Alcala´ de Henares, Madrid, Spain
R
H
Thermal and/or photochemical treatment of [{TiCp*(m-
H
H
5
Me
C
C
O
O)}3(m3-CMe)] 1 (Cp* · h -C5Me5) with organic ketones
R′
C
affords the new oxo derivatives [{TiCp*(m-O)}3(m-
CNCH2)(OCHRRA)] (R = RA = Me 2, Ph 3; R = Ph, RA = Me
4, Et 5); these reactions take place by insertion of the ketones
CO group into the Ti–H bond of the in situ formed
[{TiCp*(m-O)}3(m-CCH2)(H)] intermediate.
heat or hn
RCOR′
C
[Ti]
[Ti]
[Ti]
[Ti]
[Ti]
O
O
[Ti]
O
O
O
O
1
R = R′ = Me 2, Ph 3
R = Ph; R′ = Me 4, Et 5
[Ti] = Ti(η5-C5Me5)
We have reported the unprecedented oxotitanium complexes,
[{TiCp*(m-O)}3(m3-CR)] (R = H, Me),1 possessing a m3-
alkylidyne sp3-carbon similar to that found for the early-
transition-metal clusters [M3(m3-CRA)(OR)9] (M = Mo, W)2
and in contrast with the sp-hybridized alkylidyne carbon of the
species as [Co3(m3-CR)(CO)9].3 The chemistry of these
m3-alkylidynetrimetal clusters have been extensively explor-
ed.3a,4 Meanwhile, to our knowledge, the [{CrCp(m-Cl)}3(m3-
CH)],5 [{TiCp*(m-O)}3(m3-CR)]1 and [{TiCp*}4(m3-CH)4]6
complexes are the only reported examples of m3-alkylidyne
units supported on trinuclear cores without metal–metal bonds
and their reactivity is, as yet, practically unknown.7 This
chemistry might be of great current interest, imitating the
behaviour of the alkylidyne groups attached to metal or metal
oxide surfaces and establishing a clear connection between
organometallic and solid surface systems.8 Here, we report the
surprising reactivity of diverse ketones and the m3-ethylidyne
group on an organotitanium oxide.
Scheme 1
the presence of the characteristic signals for m-vinylidene,
alkoxide and Cp* ligands.
The 13C NMR spectra of 2–5 reveal triplets at dav 317.5 (2J 5
Hz) attributed to the Ca resonance of the bridging vinylidene
fragment >CaNCbH2, which are very similar to those found for
other known vinylidene complexes.11 The terminal moiety
(NCbH2) of this fragment appear, in both H and 13C NMR
1
spectra, in the typical range for organic alkenes. The NMR
spectra also display the clear presence of the OCHRRA signals
whose chemical shifts and multiplicity depend on the nature of
the ketone substituents (Table 1) and the values of 1JCH ≈ 142
Hz are according to the proximity of the oxygen atom.
Additionally, the NMR spectra of 4 and 5 show signals for three
different Cp* ligands in 1 :1:1 ratio and AB spin systems for
the vinylidene protons due to the chiral carbon atoms of the
alkoxy groups.
Treatment of [{TiCp*(m-O)}3(m3-CMe)] 1 with 1 equiv. of
RCORA (R = RA = Me, Ph; R = Ph, RA = Me, Et) in toluene
or hexane, heating at temperatures between 100 and 120 °C or
irradiating with a sunlamp for several days, leads to the
formation (46–77% yield) of blue–violet complexes charac-
terised as [{TiCp*(m-O)}3(m-CCH2)(OCHRRA)] (R = RA = Me
2, Ph 3; R = Ph, RA = Me 4, Et 5 (Scheme 1).§
A plausible pathway for these reactions involves initial
b-hydrogen elimination in the m3-ethylidyne ligand to generate
the intermediate [{TiCp*(m-O)}3(m-CCH2)(H)]. Similar con-
version of m3-alkylidyne complexes to vinylidenes has been
found for many trinuclear clusters11a and may be responsible of
the H/D exchange reactions in ethylidynes on metal surfaces.8a,c
Interestingly, we have also observed that the complex 1
incorporate deuterium in the m3-ethylidyne group when a C6D6
solution of 1 is heated above 200 °C,¶ and this H/D exchange is
easy to explain if we assume the participation of the above
mentioned hydride intermediate.12 Finally the insertion of the
ketones into the Ti–H bond of [{TiCp*(m-O)}3(m-CCH2)(H)]
takes place (Scheme 2).13
The IR spectra of these complexes show a weak band at 1580
(2) and 1598 cm21 (3, 4, 5) assigned to the n(CNC) of the
m-vinylidene moiety, as in the case of the bimetallic systems
[Ru2(CO)3Cp2(m-CNCH2)] (1586 cm21 9
)
and [ClNi(m-
dppm)2(m-CNCH2)NiCl] (1580 cm21).10 The NMR spectra
(Table 1) are consistent with the proposed structure and reveal
Table 1 Selected NMR data (d, J/Hz) for complexes [{TiCp*(m-O)}3(m-CCH2)(OCHRRA)] (R = RA = Me 2, Ph 3; R = Ph, RA = Me 4, Et 5)a
1H
13C
Assignment
2
3
4
5
2
3
4
5
C5Me5
2.11 (s, 15 H) 2.03 (s, 15 H) 2.07 (s, 15 H), 2.05 (s, 15 H), 11.7, 11.4
1.99 (s, 30 H) 1.97 (s, 30 H) 2.03 (s, 15 H), 2.04 (s, 15 H),
1.97 (s, 15 H) 1.97 (s, 15 H)
11.9, 11.7
11.6, 11.7,
11.9
11.6, 11.7,
11.8
C5Me5
120.4, 122.3
120.7, 123.1
120.6, 122.6
125.7
120.5, 122.6,
126.0
m-CNCH2
m-CNCH2
–OCHRRA
6.04 (s, 2 H)
5.78 (s, 2 H)
6.80 (s, 1 H)
5.93av (2 H,
5.97av (2 H,
120.9 (t, 1J
154.9)
122.0 (t, 1J
155.6)
121.6 (t, 1J
155.4)
121.1 (t, 1J
154.8)
2J 4.5)
2J 4.8)
317.3 (t, 2J
5.2)
317.2 (t, 2J
5.7)
317.5 (t, 2J
4.8)
79.5 (dm, 1J
144.2)
318.0 (t, 2J
4.9)
85.5 (dm, 1J
140.2)
4.80 (spt,
1 H, 3J 6.0)
5.78 (q, 1 H,
3J 6.6)
5.46 (dd, 1 H, 74.9 (dm, 1J
85.3 (dm, 1J
141.4)
3J 4.5, 8.4)
140.9)
a Recorded on Varian Unity 300 or 500 Plus in C6D6 at 20 °C.
Chem. Commun., 1998
691

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Full NMR and analytical data for the new compounds 2–5 can be
acquired as supplementary material upon request from the authors.
¶ In the 1H NMR spectra we have detected the presence of m3-CCH2D
and m3-CCHD2 isotopomers.
CH3
C
H
CH3-nDn
C
C
C
H
C6D6
heat or hn
H
[Ti]
[Ti]
[Ti]
[Ti]
[Ti]
[Ti]
O
[Ti]
[Ti]
O
O
O
[Ti]
O
O
O
1 (a) R. Andre´s, M. Galakhov, A. Mart´ın, M. Mena and C. Santamar´ıa,
Organometallics, 1994, 13, 2159; (b) R. Andre´s, M. Galakhov,
A. Mart´ın, M. Mena and C. Santamar´ıa, J. Chem. Soc., Chem. Commun.,
1995, 551; (c) R. Andre´s, Doctoral Thesis, Universidad de Alcala´,
Madrid, 1995.
O
O
[Ti] = Ti(η5-C5Me5)
RCOR′
H
H
R
H
C
O
2 M. H. Chisholm, D. L. Clark, J. Hampden-Smith and D. H. Hoffman,
Angew. Chem., Int. Ed. Engl., 1989, 28, 432.
R′
C
C
O
3 (a) D. Seyferth, Adv. Organomet. Chem., 1976, 14, 97; (b)
B. E. R. Schilling and R. Hoffman, J. Am. Chem. Soc., 1979, 101, 3456;
(c) P. T. Chesky and B. M. Hall, Inorg. Chem., 1981, 20, 4419.
4 R. D. W. Kemmitt and D. R. Russell, in Comprehensive Organometallic
Chemistry, ed. G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon,
Oxford, UK, 1982, vol. 5, p. 162; (b) M. I. Bruce, ibid, vol. 4, p. 843; (c)
J. B. Keister, in Encyclopedia of Inorganic Chemistry, ed. R. B. King,
Wiley, Chichester, UK, 1994, p. 3348; (d) M. Akita, in Comprehensive
Organometallic Chemistry II, ed. G. Wilkinson, F. G. A. Stone and E.
W. Abel, Pergamon, Oxford, UK 1995, vol. 7, p. 259; (e) A. K. Smith,
ibid, vol. 7, p. 747; (f) C. E. Barnes, ibid, vol. 8, p. 419; (g) Y. Chi and
D.-K. Hwang, ibid, vol. 10, p. 85 (see also references therein).
5 D. S. Richeson, S.-W. Hsu, N. H. Fredd, G. V. Duyne and
K. H. Theopold, J. Am. Chem. Soc., 1986, 108, 8273.
[Ti]
[Ti]
[Ti]
O
O
Scheme 2
Thus the incorporation of the ketones onto the organometallic
titanium oxide [{TiCp*(m-O)}3(m3-CMe)] can be best inter-
preted in terms of an insertion process of the carbonyl groups
into a Ti–H bond of the hydride–vinylidene species [{TiCp*(m-
O)}3(m-CCH2)(H)]. Further studies are required in order to
determine the behaviour of other carbonyl derivatives and
unsaturated molecules against these m3-alkylidyne complexes.
We wish to thank the DGICYT (project PB93-0476) and the
Universidad de Alcala´ for financial support of this research. C.
Santamar´ıa also thanks the MEC for a Predoctoral Fellow-
ship.
6 R. Andre´s, P. Go´mez-Sal, E. de Jesu´s, A. Mart´ın, M. Mena and
C. Ye´lamos, Angew. Chem., Int. Ed. Engl., 1997, 36, 115.
7 We have communicated some aspects about the reactivity of the
[{TiCp*(m-O)}3(m3-CR)] derivatives: see ref. 1(b), R. Andre´s, M.
Galakhov, M. P. Go´mez-Sal, A. Mart´ın, M. Mena and C. Santamar´ıa,
XIth FECHEM Conference on Organometallic Chemistry, Parma, Italy,
1995, p. 172; XIIth FECHEM Conference on Organometallic Chem-
istry, Prague, Czech Republic, 1997, PB118.
8 (a) G. A. Somorjai, Introduction to Surface Chemistry and Catalysis,
Wiley, New York, 1994, p. 400; (b) B. C. Gates, Catalytic Chemistry,
Wiley, New York, 1992, (c) F. Zaera, Chem. Rev., 1995, 95, 2651; (d)
B. E. Bent, Chem. Rev., 1996, 96, 1361; (d) H. H. Kung, Transition
Metal Oxides: Surface Chemistry and Catalysis, Elsevier Science Publ.,
Amsterdam, The Netherlands, 1989; (e) M. A. Barteau, Chem. Rev.,
1996, 96, 1413; (f) P. M. Maitlis, H. C. R. Long Quyoum, M. L. Turner
and Z.-Q. Wang, Chem. Commun., 1996, 1.
9 J. Evans and G. S. McNulty, J. Chem. Soc., Dalton Trans., 1983,
639.
10 X. L. R. Fontaine, S. J. Higgins, B. L. Shaw, M. Thornton-Pett and
W. Yichang, J. Chem. Soc., Dalton Trans., 1987, 1501.
Notes and References
† E-mail: mmena@inorg.alcala.es
‡ Dedicated to Professor Pascual Royo on the occasion of his 60th
birthday.
§ Preparations: 2: a solution of 1 (0.50 g, 0.80 mmol) and acetone (0.06 ml,
2.40 mmol) in toluene (50 ml) were transferred by cannula to a Carius tube
(volume 100 ml), cooled to 278 °C, and flame-sealed. This tube was heated
at 100 °C for 12 h to obtain a blue–violet lather (0.42 g, 77%). EI mass
spectrum: m/z 624 (M+ 2 MeCOMe, 9%), 613 (M+ 2 MeCHMe 2 C2H2,
25%). 3: this derivative was obtained analogously to 2 from 0.80 g (1.28
mmol) of 1 and 0.23 g (1.28 mmol) of benzophenone heating at 125 °C for
24 h to obtain a blue–violet crystalline solid (0.73 g, 71%). EI mass
spectrum: m/z 624 (M+ 2 PhCOPh, 6%), 613 (M+ 2 PhCHPh 2 C2H2,
28%). 4: acetophenone (0.16 ml, 1.33 mmol) diluted in 15 ml of hexane was
added to a solution of 1 (0.80 g, 1.28 mmol) in hexane (100 ml). The
reaction mixture was irradiated at room temp. for 45 h with a sunlamp. The
solution was concentrated and a crystalline blue solid was obtained at room
temp. (0.50 g, 52%). EI mass spectrum: m/z 624 (M+ 2 PhCOMe, < 1%),
613 (M+ 2 PhCHMe 2 C2H2, 3%). 5: the preparation of this complex is
similar to 4 from 0.80 g (1.28 mmol) of 1 and 0.17 ml (1.33 mmol) of ethyl
phenyl ketone irradiating for 68 h with a sunlamp; 0.44 g (46%) of a blue
solid was obtained. EI mass spectrum: m/z 624 (M+ 2 PhCOEt, 5%), 613
(M+ 2 PhCHEt 2 C2H2, < 1%).
11 (a) M. I. Bruce, Chem. Rev., 1991, 91, 197; (b) R. Beckhaus, Angew.
Chem., Int. Ed. Engl., 1997, 36, 686.
12 Comparable deuterium incorporation in the b position of an alkyl
complex (Cp*2ScCH2CH2CH2CH3) via
a hydride intermediate
(Cp*2ScH) has been reported: B. J. Burger, M. E. Thompson,
W. D. Cotter and J. E. Bercaw, J. Am. Chem. Soc., 1990, 112, 1566.
13 In an analogous manner, it is known that Cp*2TiEt reacts with Me2CNO
through a Cp*2TiH intermediate to give the product of migratory
insertion into the Ti–H bond: G. A. Luinstra, J. Vogelzang and
J. H. Teuben, Organometallics, 1992, 11, 2273.
Received in Basel, Switzerland, 23rd December 1997; 7/09194J
692
Chem. Commun., 1998