Photochemical incorporation of N-benzylidene(phenyl)amine into the complex [{Ti(η5-C5Me5)(η-O)}3(μ3-CH)] as a model of the titanium oxide surface

Article abstract of DOI:10.1039/a905129e

The photochemical incorporation of PhCH=NPh to the metal oxide model [{TiCp*(μ-O)}₃(μ3_-CH)] (Cp* = η⁵C₅Me₅) occurs by breaking of the C=N imine bond and formation of μ-imido and σ-alkenyl groups on the [Ti₃O₃] core; the crystal structure of the obtained product, [{TiCp*(μ-O)}₃(μ-NPh)(CH=CHPh)], was determined by X-ray diffraction.

Full text of DOI:10.1039/a905129e

Photochemical incorporation of N-benzylidene(phenyl)amine into the complex
5
[{Ti(h -C5Me5)(h-O)}3(m3-CH)] as a model of the titanium oxide surface†
Pilar Go´mez-Sal, Avelino Mart´ın, Miguel Mena,* Mar´ıa del Carmen Morales and Cristina Santamar´ıa
Departamento de Qu´ımica Inorga´nica, Universidad de Alcala´, E-28871 Alcala´ de Henares, Madrid, Spain.
E-mail: mmena@inorg.alcala.es
Received (in Basel, Switzerland) 25th June 1999, Accepted 9th August 1999
The photochemical incorporation of PhCHNNPh to the
[{TiCp*Me}3(m-O)3] (av. 2.09 Å),4b [{Ti4Cp*4Me2}(m-O)5]
(2.11 Å),4c [{TiCp*(m-O)}3(m3-CMe)] (av. 2.11 Å),4d
[{TiCp*(m-O)}3(CH2CHNCHMe)3] (av. 2.13 Å)4e or Ti–C(sp2)
in alkenyl biscyclopentadienyl derivatives.5 Within the styryl
group, the C(41)–C(42) bond length [1.320(12) Å] is within the
range for a CNC double bond.6
5
metal oxide model [{TiCp*(m-O)}3(m3-CH)] (Cp* = h -
C5Me5) occurs by breaking of the CNN imine bond and
formation of m-imido and s-alkenyl groups on the [Ti3O3]
core; the crystal structure of the obtained product,
[{TiCp*(m-O)}3(m-NPh)(CHNCHPh)], was determined by X-
ray diffraction.
On the opposite side of the molecule, the Ti(1), Ti(3), N(13)
and O(13) atoms form a distorted square (see Fig. 1), almost
perpendicular to the Ti(1)–Ti(2)–Ti(3) and phenyl [C(51)–
C(56)] planes. The N(13) atom shows a planar environment
with Ti–N distances of 1.957(6) and 1.948(6) Å, close to the
value of 1.91 Å (av.) found in [TiCp*(NMe2)3]7 and also to that
of 1.939 Å reported in the cubane structure [{Ti4Cp*4}(m3-
N)4].8 The average Ti–O bond distance (1.84 Å)9 and Ti–ring
centroid distance (2.06 Å) are comparable to those in the
literature for the titanium organometallic oxides [{TiCp*(m-
O)}3X3] (X = Me,4b Cl,10 Br11).
Ti3O3(m3-CR) systems are surface models suitable for examina-
tion of both the cooperative interaction between metal centres
maintained in close proximity and the chemistry of alkylidyne
groups on a metallic oxide support. Recently we have described
that the reactions under mild conditions of carbon monoxide
and isocyanides with [{TiCp*(m-O)}3(m3-CR)] complexes pro-
ceed via insertion into the m3-alkylidyne units.1 However, the
incorporation of ketones follows other pathways and the
experimental data support the insertion of carbonyl groups,
R2CNO, into the Ti–H bond of the in situ formed [{TiCp*(m-
O)}3(m-CNCH2)(H)] intermediate to give alkoxide–vinylidene
derivatives [{TiCp*(m-O)}3(m-CNCH2)(OCHR2)].2 Here, we
present the preliminary result observed from the photochemical
treatment of the trinuclear titanium derivative [TiCp*(m-
O)}3(m3-CH)] 13 with N-benzylidene(phenyl)amine.
A reasonable proposal for this reaction (Scheme 2) involves
imine insertion into one of the three titanium–carbon(alk-
When a solution of 1 and PhCHNNPh in hexane was
irradiated for 45 h the alkenylimido complex [{TiCp*(m-
O)}3(CHNCHPh)(m-NPh)] 2 (Scheme 1) was obtained in good
1
yield.‡ The H NMR spectrum of compound 2 shows two
signals in a 2+1 ratio for the Cp* ligands in accord with Cs
symmetry in solution, and supports the presence of a trans-
styryl group (3JHH 18.3 Hz).‡ This ligand is s-bonded to the
titanium atom in accord with the observation in the 13C NMR
spectrum of a doublet of doublets at d 190.4 (1J 126.0, 2J 2.5 Hz)
and a doublet of multiplets at d 140.2 (1J 154.4 Hz)
corresponding to Ca and Cb resonances, respectively. A band of
medium intensity at 1581 cm21 in the IR spectrum is assigned
to the alkenyl carbon–carbon double bond.
Scheme 1
An X-ray diffraction study of 2 reveals (Fig. 1)§ a trans-
alkenyl group on one titanium atom and a phenyl imido moiety
bridging the other two titanium atoms in a syn–syn disposi-
tion.
The styrene environment is planar with a Ti(2)–C(41) bond
length of 2.127(9) Å, similar to those observed for Ti–C(sp3)
bonds in alkyl titanium complexes [TiCp*Me3] (av. 2.10 Å),4a
5
Fig. 1 Molecular structure of [{Ti(h -C5Me5)(m-O)}3(CHNCHPh)(m-NPh)]
2. Selected lengths (Å) and angles (°): Ti–Cp* 2.06(av.), Ti–O 1.84(5)(av.),
Ti(2)–C(41) 2.127(9), C(41)–C(42) 1.32(1), Ti(1)–N(13) 1.957(6), Ti(3)–
N(13) 1.948(6); O(12)–Ti(1)–O(13) 102.4(2), O(12)–Ti(1)–N(13)
101.4(2), O(13)–Ti(1)–N(13) 84.8(2), O(12)–Ti(2)–O(23) 106.6(2), O(12)–
Ti(2)–C(41) 105.4(3), O(23)–Ti(2)–C(41) 100.2(3); O(13)–Ti(3)–O(23)
100.7(2), O(13)–Ti(3)–N(13) 84.5(2), O(23)–Ti(3)–N(13) 102.5(3), Ti(1)–
N(13)–Ti(3) 88.7(3), Ti(2)–O(12)–Ti(1) 122.7(3), Ti(1)–O(13)–Ti(3)
95.6(2), Ti(2)–O(23)–Ti(3) 123.7(3). Cp* is the centroid of the C5Me5
ring.
†
Dedicated to Alexander von Humboldt on the occasion of his
commemorative year 1999.
Chem. Commun., 1999, 1839–1840
1839

F(000) = 836. l = 0.71073 Å, m(Mo-Ka) = 0.544 mm21. The data were
collected on an Enraf Nonius CAD4 diffractometer. Intensity measurements
were performed by w–q scans in the range 6 < 2q < 44° at 19 °C on a
crystal of dimensions 0.45 3 0.40 3 0.38 mm. Of the 5916 measured
reflections, 5577 were independent; largest minimum and maximum in the
final difference Fourier synthesis: 20.415 and 1.422 e Å23, R1 = 0.077 and
wR2 = 0.251 [for 4025 reflections with F > 4s(F)]. The structure was
solved by direct methods (SHELXS-97) and refined by least-squares against
F2 (SHELXL-97). CCDC 182/1374. See http://www.rsc.org/suppdata/cc/
1999/1839/ for crystallographic data in .cif format.
Scheme 2
1 R. Andre´s, M. Galakhov, M. P. Go´mez-Sal, A. Mart´ın, M. Mena and C.
Santamar´ıa, Chem. Eur. J., 1998, 4, 1206.
2 M. Galakhov, M. Mena and C. Santamar´ıa, Chem. Commun., 1998,
691.
3 R. Andre´s, M. Galakhov, A. Mart´ın, M. Mena and C. Santamar´ıa,
J. Chem. Soc., Chem. Commun., 1995, 551; R. Andre´s, Thesis Doctoral,
Universidad de Alcala´, Madrid, 1995.
4 (a) R. Blom, K. Rypdal, M. Mena, P. Royo and R. Serrano,
J. Organomet. Chem., 1990, 391, 47; (b) S. G. Blanco, M. P. Go´mez-
Sal, S. M. Carreras, M. Mena, P. Royo and R. Serrano, J. Chem. Soc.,
Chem. Commun., 1986, 1572; (c) P. Go´mez-Sal, A. Mart´ın, M. Mena
and C. Ye´lamos, Inorg. Chem., 1996, 35, 242; (d) R. Andre´s, M.
Galakhov, A. Mart´ın, M. Mena and C. Santamar´ıa, Organometallics,
1994, 13, 2159; (e) R. Andre´s, M. Galakhov, M. P. Go´mez-Sal, A.
Mart´ın, M. Mena and C. Santamar´ıa, J. Organomet. Chem., 1996, 526,
135.
5 G. S. Herrmann, H. G. Alt and U. Thewalt, J. Organomet. Chem., 1990,
393, 83; R. Beckhaus, I. Strauss and T. Wagner, J. Organomet. Chem.,
1994, 464, 155; R. Beckhaus, J. Sang, J. Oster and T. Wagner,
J. Organomet. Chem., 1994, 484, 179; R. Beckhaus, J. Sang, T. Wagner
and B. Ganter, Organometallics, 1996, 15, 1176; J. J. Eisch, A. M.
Piotrowski, S. K. Brownstein, E. J. Gabe and F. L. Lee, J. Am. Chem.
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Allg. Chem., 1998, 624, 277.
6 J. March, Advanced Organic Chemistry. Reactions, Mechanism, and
Structure, John Wiley & Sons, Inc., New York, 1985.
7 A. Mart´ın, M. Mena, C. Ye´lamos, R. Serrano and P. R. Raithby,
J. Organomet. Chem., 1991, 467, 79.
8 P. Go´mez-Sal, A. Mart´ın, M. Mena and C. Ye´lamos, J. Chem. Soc.,
Chem. Commun., 1995, 2185.
9 Although all the Ti–O distances are similar, the Ti–O–Ti angles present
very different values if they form the distorted square (95.6°) or the rest
of the core (123°).
10 T. Carofiglio, C. Floriani, A. Sgamellotti, M. Rosi, A. Chiesi-Villa and
C. Rizzoli, J. Chem. Soc., Dalton Trans., 1992, 1081.
11 S. I. Troyanov, V. Varga and K. Mach, J. Organomet. Chem., 1991, 402,
201.
ylidyne) bonds to generate the species A which was not
detected. b-Hydrogen elimination2 would then give a hydride–
enamine intermediate B while subsequent carbon–nitrogen
bond rupture, transfer of hydrogen from titanium to the b-
carbon and formation of a nitrogen–titanium bond, would afford
the s-alkenyl-m-imido complex 2. However, we can not exclude
the possibility that the conversion of A to 2 could occur directly
by a concerted pathway.
To our knowledge, this observed behaviour is comparable
only to the alkylidene/imine metathesis-like reactions reported
by Rocklage and Schrock,12 and by Cantrell and Meyer13 for
mononuclear niobium, tantalum and molybdenum alkylidene
complexes. In our case the metathesis-like process occurs on the
Ti3O3 surface with the cooperative participation of the three
metal atoms and opens new perspectives in trinuclear titanium
chemistry. Further studies of this process with other imines are
in progress and the results will be published in due course.
The authors thank the financial support from the DGES
(PB96-0672).
Notes and references
‡ Preparation of 2: N-benzylidene(phenyl)amine (0.356 g, 197 mmol) was
added to a solution of 1 (1.0 g, 164 mmol) in 60 mL of hexane. The reaction
mixture was irradiated at room temp. for 45 h with a UV lamp. The final
reddish solution was concentrated and cooled to obtain red crystals of 2.
Yield: 0.90 g (ca. 75%). Anal. Calc. for C44H57NO3Ti3, (M = 791.64): C,
66.76; H, 7.26; N, 1.77. Found: C, 67.28; H, 7.69; N, 1.72%. Selected NMR
1
data (d, J/Hz): H (500 MHz, C6D6, 25 °C, TMS): 1.95 (s, 30H, C5Me5),
3
3
2.09 (s, 15H, C5Me5), 8.04 (d, 1H, J 18.3, –CHNCHPh), 6.84 (d, 1H, J
18.3, –CHNCHPh); 13C{1H} (125 MHz, C6D6, 25 °C, TMS): 11.7, 12.20
(C5Me5), 122.6, 122.5 (C5Me5), 140.2 (dm, 1J 154.4, –CHNCHPh), 158.9,
(Cipso, m-NPh), 190.4 (dd, 1J 126.0, 2J 2.5, –CHNCHPh). IR (KBr, cm21):
n 3052w, 2913s, 1581m, 1542w, 1488w, 1440s, 1375s, 1245s, 1024m,
898s, 759w, 729s, 688s, 397s. EI mass spectrum m/z 792 (M+, 11%).
§ Single crystals of 2 were obtained by slow cooling of a hexane solution.
12 S. M. Rocklage and R. R. Schrock, J. Am. Chem. Soc., 1982, 104,
3077.
13 G. K. Cantrell and T. Y. Meyer, J. Am. Chem. Soc., 1998, 120, 8035.
¯
Crystal data for 2: C44H57NO3Ti3, M = 791.61, triclinic, space group P1,
a = 11.4865(1), b = 12.559(1), c = 16.049(1) Å, a = 87.64(1), b =
89.82(1), g = 82.87(1)°, V = 2295.3(3) Å3, Z = 2, Dc = 1.145 g cm23
;
Communication 9/05129E
1840
Chem. Commun., 1999, 1839–1840