Early-transition-metal ketenimine complexes: Synthesis, reactivity, and structure of ketenimine-containing titanocene and zirconocene complexes

Article abstract of DOI:10.1021/om970568p

Reaction of Cp₂M(PMe₃)₂ complexes (M = Ti, Zr; Cp = η⁵-C₅H₅) with the N-(p-tolyl)-diphenylketenimine Ph′N=C=CPh₂ (Ph′ = p-MeC₆H₄) in a 1:1 molar ratio affords the ketenimine-containing metallocene derivatives Cp₂M(η²-(C,N)-Ph′N=C=CPh₂)(PMe ₃) (M = Ti (1); Zr (2)). The ketenimine ligand reacts in the same way with the Cp*₂M species (Cp* = η⁵-C₅Me₅) generated from the reduction of the corresponding Cp*₂MCl₂ complexes with Li^tBu (1:2 molar ratio) to give the related complexes Cp*₂M(η²-(C,N)-Ph′N=C=CPh₂) (M = Ti (3); Zr (4)). The molecular structure of 3 shows a titanium atom bonded to two η⁵-cyclopentadienyl rings and a η² -(C,N)-bonded ketenimine ligand. Reaction of Cp*₂Ti with the ketenimine ligand in a 1:2 molar ratio gives 1,1,5,5-tetraphenyl-3-(p-tolyl)-2-(p-toluidino)-3-aza-1,4-pentadiene, which probably results from the coupling, followed by hydrolysis, of two ketenimine molecules coordinated to one titanocene moiety. Protonation of 3 with Et₃NHCl or H₂O (1:1 molar ratio) affords the intermediate species Cp*₂Ti(X)(η²-(C,N)-Ph′N=C(H)-CPh ₂) (X - Cl (5); OH (6)), which on hydrolysis evolves to give the enamine Ph′N(H)-CH=CPh₂ as the final product. Finally, 3 reacts reversibly with H₂ to give the hydride enamidate complex Cp*₂Ti(H)(η¹-Ph′N-CH-CPh₂) (7). The structures of the different compounds have been determined by IR and NMR spectroscopic methods.

Full text of DOI:10.1021/om970568p

Organometallics 1997, 16, 5283-5288
5283
Ea r ly-Tr a n sition -Meta l Keten im in e Com p lexes:
Syn th esis, Rea ctivity, a n d Str u ctu r e of
Keten im in e-Con ta in in g Tita n ocen e a n d Zir con ocen e
Com p lexes
Rosa Fandos,*,† Maurizio Lanfranchi,§ Antonio Otero,*,‡
Mar´ıa Angela Pellinghelli,§ M. J ose´ Ruiz,† and J an H. Teuben*,
Departamento de Quı´mica Inorga´nica, Orga´nica y Bioquı´mica, Facultad de Quı´micas,
Universidad de Castilla-La Mancha, Campus de Toledo, c/ S. Lucas, 6, 45001 Toledo, Spain,
and Campus de Ciudad Real, 13071 Ciudad Real, Spain, Centro di Studio per la
Structturistica Diffractometrica del CNR, Dipartimento di Chimica Generale ed Inorga´nica,
Chimica Anal´ıtica, Chimica Fisica, Universita´ degli Studi di Parma, Vialle delle Science 78,
I-43100 Parma, Italy, and Chemistry Department, Groningen University, Nijenborgh 4,
NL- 9747 AG Groningen, The Netherlands
Received J uly 7, 1997X
Reaction of Cp2M(PMe3)2 complexes (M ) Ti, Zr; Cp ) η5-C5H5) with the N-(p-tolyl)-
diphenylketenimine Ph′NdCdCPh2 (Ph′ ) p-MeC6H4) in a 1:1 molar ratio affords the
ketenimine-containing metallocene derivatives Cp2M(η2-(C,N)-Ph′NdCdCPh2)(PMe3) (M )
Ti (1); Zr (2)). The ketenimine ligand reacts in the same way with the “Cp*2M” species (Cp*
) η5-C5Me5) generated from the reduction of the corresponding Cp*2MCl2 complexes with
LitBu (1:2 molar ratio) to give the related complexes Cp*2M(η2-(C,N)-Ph′NdCdCPh2) (M )
Ti (3); Zr (4)). The molecular structure of 3 shows a titanium atom bonded to two
η5-cyclopentadienyl rings and a η2 -(C,N)-bonded ketenimine ligand. Reaction of “Cp*2Ti”
with the ketenimine ligand in a 1:2 molar ratio gives 1,1,5,5-tetraphenyl-3-(p-tolyl)-2-(p-
toluidino)-3-aza-1,4-pentadiene, which probably results from the coupling, followed by
hydrolysis, of two ketenimine molecules coordinated to one titanocene moiety. Protonation
of 3 with Et3NHCl or H2O (1:1 molar ratio) affords the intermediate species Cp*2Ti(X)(η2-
(C,N)-Ph′N--C(H)--CPh2) (X ) Cl (5); OH (6)), which on hydrolysis evolves to give the
enamine Ph′N(H)sCHdCPh2 as the final product. Finally, 3 reacts reversibly with H2 to
give the hydride enamidate complex Cp*2Ti(H)(η1-Ph′NsCHdCPh2) (7). The structures of
the different compounds have been determined by IR and NMR spectroscopic methods.
In tr od u ction
p-BrC6H4, p-MeC6H4) and [Cp′2Nb(η2-(C,N)-PhNdCd
CPhR)(L)]+ (L ) nitriles or isonitriles), prepared using
this method, has been described.5 The results obtained
encouraged us to try to prepare analogous ketenimine
complexes of group 4 metallocenes, with the aim of
further studying their reactivity. In order to explore
this chemistry, it was decided to study the reactivity of
Ti(II) and Zr(II) complexes Cp2M(PM3)2 and Cp*2M (Cp
) η5-C5H5; Cp* ) η5-C5Me5) toward the free N-(p-tolyl)-
diphenylketenimine which had already been succesfully
employed in the synthesis of the niobocene complexes.
This paper will focus on the synthesis and structural
details of new titanium and zirconium ketenimine
complexes Cp2M(η2-(C,N)-Ph′NdCdCPh2)(PMe3) and
Cp*2M(η2-(C,N)-Ph′NdCdCPh2) and some of their trans-
formations.
Ketenes, ketenimines, and related heterocumulenes
are very reactive organic molecules whose organic
chemistry is now well defined. Several reviews on
aspects of their synthesis and reactivity are available.1
In particular, ketenimine complexes of transition metals
have proven to be useful in new synthetic approaches
to carbocyclic and four-, five-, and six-membered N-
heterocyclic rings.2 Ketenimine complexes have been
commonly prepared by C-C coupling reactions, for
example by reacting carbene or carbyne3 complexes with
isocyanides, but only in a few cases have they been
prepared directly by coordination of free ketenimines.4
A family of neutral and cationic ketenimine niobocene
complexes Cp′2Nb(X)(η2-(C,N)-R′NdCdCPhR) (Cp′ ) η5-
C5H4SiMe3; X ) Cl, Br; R ) Me, Et, Ph; R′ ) C6H5,
† Universidad de Castilla-La Mancha, Campus de Toledo.
‡ Universidad de Castilla-La Mancha, Campus de Ciudad Real.
§ Universita´ degli Studi di Parma.
Resu lts a n d Discu ssion
Groningen University.
Complexes Cp2M(PMe3)2 (M ) Ti, Zr) reacted with 1
equiv of N-(p-tolyl)diphenylketenimine (Ph′NdCdCPh2,
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) (a) Patai, S. The Chemistry of Ketenes, Allenes and Related
Compounds; Wiley: New York, 1980. (b) Ulrich, H. Cycloaddition
Reactions of Heterocumulenes; Academic Press: New York, 1967.
(2) Aumann, R. Angew. Chem., Int. Ed. Engl. 1988, 27, 1456.
(3) (a) Aumann, R.; Fischer, E. O. Chem. Ber. 1968, 101, 954. (b)
Kreiter, C. G.; Aumann, R. Chem. Ber. 1978, 11, 1223. (c) Aumann,
R.; Heinen, H.; Kru¨ger, C.; Tsay, Y.-H. Chem Ber. 1986, 119, 3141. (d)
Fischer, E. O.; Schambeck, W.; Kreissl, F. R. J . Organomet. Chem.
1979, 169, C-27. (e) Fischer, E. O.; Schambeck, W. J . Organomet. Chem.
1980, 201, 311.
(4) (a) Sielisch, T.; Behrens, U. J . Organomet. Chem. 1986, 310, 179.
(b) Sielisch, T.; Behrens, U. J . Organomet. Chem. 1987, 322, 203.
(5) (a) Antin˜olo, A.; Fajardo, M.; Lo´pez-Mardomingo, C.; Otero, A.;
Mourad, Y.; Mugnier, Y.; Sanz-Aparicio, J .; Fonseca, I.; Florencio, F.
Organometallics 1990, 9, 2919. (b) Antin˜olo, A.; Fajardo, M.; Gil-Sanz,
R.; Lo´pez-Mardomingo, C.; Otero, A.; Atmani, A.; Kubicki, M. M.; El
Krami, S.; Mugnier, Y.; Mourad, Y. Organometallics 1994, 13, 1200.
S0276-7333(97)00568-2 CCC: $14.00 © 1997 American Chemical Society

5284 Organometallics, Vol. 16, No. 24, 1997
Fandos et al.
Sch em e 1
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 3a
Ph′ ) p-MeC6H4) to give the ketenimine-containing
metallocene complexes 1 and 2 (Scheme 1), which were
isolated as very air-sensitive pure crystalline solids after
appropriate workup (see Experimental Section).
Ti-C1
Ti-C2
Ti-C3
Ti-C4
Ti-C5
Ti-N1
2.431(6)
2.429(6)
2.422(7)
2.439(7)
2.416(7)
2.024(7)
Ti-C18
2.119(9)
2.124(7)
1.360(12)
1.454(13)
1.485(10)
1.334(13)
Ti-CE1
C18-C19
C19-C20
C19-C26
N1-C18
Ketenimine-containing titanocene or zirconocene com-
plexes 3 and 4 were alternatively prepared by reacting
the unsaturated moieties “Cp*2M” (prepared “in situ”
by reacting the corresponding Cp*2MCl2 species with 2
equiv of LitBu) with 1 equiv of the already-mentioned
free ketenimine (Scheme 1). These complexes were also
isolated as very air-sensitive materials, although 4 was
invariably contaminated with 5-10% of organic impuri-
ties. Interestingly, when the reaction was carried out
in the presence of an excess of PMe3, 4 was isolated as
a pure PMe3-free complex. The stabilization of the 16-
electron complexes 3 and 4, even in the presence of
PMe3, may be explained by the presence of the Cp*
ligand, which is more bulky and electron-donating than
the Cp ligand. The new families of ketenimine-contain-
ing complexes were characterized by spectroscopic
CE1-Ti-CE1′
C18-Ti-CE1′
C18-Ti-CE1
N1-Ti-CE1′
N1-Ti-CE1
N1-Ti-C18
Ti-N1-C18
Ti-N1-C11
139.6(2)
C11-N1-C18
Ti-C18-N1
N1-C18-C19
Ti-C18-C19
C18-C19-C26
C18-C19-C20
C20-C19-C26
138.2(9)
67.4(5)
106.5(3)
113.4(3)
105.9(3)
109.3(3)
37.5(3)
139.7(10)
152.8(7)
121.3(7)
124.1(9)
114.7(8)
75.1(5)
144.8(6)
a
CE1 is the centroid of the Cp* ring. Prime indicates -x, y,
1
/
- z.
2
methods. The IR spectra show a band at ca. 1500 cm-1
,
which agrees with the bathochromic shift reported for
other side-on π-bonded ketenimine complexes.2,5 On the
basis of these data, both η2-(C,N) and η2-(C,C) coordina-
tion modes are possible, and it is only through an
X-ray crystal structure determination on 3 that the
η2-(C,N) coordination mode was confirmed. A similar
structural situation has previously been found for
ketenimine niobocene complexes.5 A view of 3 is shown
in Figure 1, together with the atomic numbering
scheme. Selected bond distances and angles are given
in Table 1.
The coordination of Ti can be described as a distorted
tetrahedron with the vertices occupied by two Cp* ring
centroids and by N1 and C18 atoms from the CdN
moiety of the ketenimine ligand. The coordination
presents a crystallographic C2 symmetry, with the two-
fold axis passing through the Ti atoms and approxi-
F igu r e 1. View of 3 with the atomic numbering scheme
(30% probability ellipsoids).
mately through the CdN midpoint. The element of
symmetry generates two disordered ketenimine mol-
ecules distributed in two positions of equal occupancy

Early-Transition-Metal Ketenimine Complexes
Organometallics, Vol. 16, No. 24, 1997 5285
Sch em e 2
factor. Figure 1 shows one of the two molecules. The
ketenimine moiety is coordinated as η2-(C,N), like that
found in three parent complexes5,6 which were retrieved
from the Cambridge Structural Database System files.7
The coordinating metals in these complexes, however,
are cobalt and niobium. The bond distances and angles
of the C11sN1dC18dC19 fragment of the ketenimine
molecule (N1-C18 ) 1.33(1) Å, C18-C19 ) 1.36(1) Å,
C11-N1-C18 ) 138.2(9)°, N1-C18-C19 ) 139.7(10)°),
despite the high disorder in the Cp* ring, are in
accordance with those found in the literature;5 the
moiety is not planar and shows a torsion angle of -16-
(2)°, probably due to the steric hindrance of the sub-
stituents (Ph rings). The two bent Cp* rings form a
dihedral angle of 39.9(3)° and are bound to the Ti atom
in a symmetric conventional η5-fashion (Ti-CCp* ranges,
2.416(7)-2.439(7) Å). To the best of our knowledge, this
titanium ketenimine complex is the first to be structur-
ally characterized. The 1H NMR spectra show reso-
nances corresponding to the cyclopentadienyl, the keten-
imine, and the phosphine (for 1 and 2) ligands. The
NMR spectra of the crude products isolated before
crystallization (see Experimental Section) show the
resonances which correspond to only one isomer, the
commented η2-(C,N) ketenimine-containing isomer, and
the results indicate that the possibility that both
isomers η2-(C,N) and η2-(C,C) shoud be formed and the
η2-(C,C) isomer shoud be simply removed on the crystal-
lization process can be eliminated. Particularly signifi-
cant are the observed 13C NMR resonances of the
coordinated ketenimine, which are shifted when com-
pared to those of the free ketenimine.8 It is noteworthy
that the chemical shift of the ketenimine CR in 3 appears
at lower field than that in the free ketenimine. We are
considering the possibility of a different coordination
mode (possibly η2-(C,C)) for the ketenimine in solution.
Furthermore, both 1H and 13C NMR data for 1 and 2
indicate the presence of only one of the two possible
N-outside and N-inside isomers (Scheme 1). The N-
outside structure is proposed by NOE experiments. In
fact, irradiation of the N-(p-tolyl)ketenimine signal (2.03
and 2.09 ppm for 1 and 2, respectively) resulted in no
observable enhancement of the signal due to the PMe3
methyl groups.
drolysis, gives 1,1,5,5-tetraphenyl-3-(p-tolyl)-2-(p-tolui-
dino)-3-aza-1,4-pentadiene (Scheme 2).
Similar coupling has been observed for ketenes with
titanium9 and niobium10 organometallics. The new
organic compound was isolated as a white, air-sensitive
crystalline solid which was characterized spectroscopi-
cally.
Finally, the reactivity of 3 toward protonation and
hydrogenation processes was considered. 3 reacts with
1 equiv of Et3NHCl or H2O to give a new enamine,
N-(2,2-diphenylvinyl)-4-methylaniline and [Cp*2TiO]n
or Cp*2TiCl2 (Scheme 3). However, when the reaction
time was short, a mixture of the enamine and the
corresponding azatitanacyclobutenes 5 and 6 was iso-
lated.11
All attempts to prepare 5 or 6 as pure materials were
unsuccessful since they were always contaminated with
the enamine. In light of these results, we might suppose
that complexes 5 and 6 are formed either by initial
protonation at CR of the complexed ketenimine to give
an azatitanacyclobutene, followed by chloride or hy-
droxide trapping, or by the reverse procedure. However,
an alternative process implicating coordination of the
Et3NHCl or H2O with subsequent proton transfer can-
not be excluded. A similar behavior was previously
observed for cationic ketenimine-containing niobocene
complexes [Cp′2Nb(η2-(C,N)-PhRCCNPh(L)][X],5b al-
though in these and related neutral ketenimine-
containing niobocene complexes, [Cp′2Nb(X)(η2-(C,N)-
PhRCCNPh)],12 electrophilic attack occurred at the free
terminus of the complexed ketenimine ligand to give
stable η2-iminoacyl derivatives. Complexes 5 and 6 and
the enamine derivative, which was isolated as a pure,
air-sensitive white crystalline solid, have been spectro-
1
scopically characterized. The H NMR spectra of 5 and
6 show single resonances at 8.28 and 9.38 ppm, respec-
tively, which correspond to the CH group of the azati-
tanacyclobutene moiety. In addition, a broad resonance
at 5.85 ppm for the OH group attached to the Ti center
appears for 6. In the 13C NMR spectrum of 6, the
expected resonances for the azatitanacyclobutene moiety
were found at 108.5 (Ph2C) and 114.3 ppm (CHdN).
Complex 3 also reacts with dihydrogen (1 atm, 25 °C)
to give a hydride enamidate complex (7), which results
An interesting reaction was observed when “Cp*2Ti”
was treated with 2 equiv of ketenimine. This reaction,
which probably proceeds via the coordination of two
ketenimine molecules, followed by coupling and hy-
(9) Fachinetti, G.; Biran, C.; Floriani, C.; Chiese-Vila, A.; Guastini,
C. J . Am. Chem. Soc. 1978, 100, 1921.
(10) Fermin, M. C.; Hneihen, A. S.; Maas, J . J .; Bruno, J . W.
Organometallics 1993, 12, 1845.
(6) Strecker, B.; Horlin, G.; Schulz, M.; Werner, H. Chem. Ber. 1991,
124, 285.
(11) Azametallacyclobutenes of early transition metals are
uncommon: (a) Guram, A. S.; Swenson, D. C.; J ordan, R. F. J . Am.
Chem. Soc. 1992, 114, 8991. (b) With, J .; Horton, A. D.; Orpen, A. G.
Organometallics 1993, 12, 1493. (c) Coles, N.; Harris, M. C. J .; Whitby,
R. J .; Blagg, J . Organometallics 1994, 13, 190.
(12) Antin˜olo, A.; Fajardo, M.; Gil-Sanz, R.; Lo´pez-Mardomingo, C.;
Mart´ın-Villa, P.; Otero, A.; Kubicki, M. M.; Mugnier, Y.; El Krami, S.;
Mourad, Y. Organometallics 1993, 12, 381.
(7) Allen, F. H.; Bellard, S.; Brice, M. D.; Cartwright, B. A.;
Doubleday, A.; Higgs, H.; Hummelink, T.; Hummelink-Peters, B. G.;
Kennard, O.; Motherwell, W. Acta Crystallogr., Sect. B 1979, 35, 2331.
(8) (a) Collier, C.; Webb, G. A. Org. Magn. Reson. 1979, 12, 659. (b)
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Hartmann, W.; Utikal, H. P. Chem. Lett. 1975, 51.

5286 Organometallics, Vol. 16, No. 24, 1997
Fandos et al.
Sch em e 3
from hydrogenolysis of a Ti-C bond (Scheme 3). Com-
plex 7 was spectroscopically characterized when the
reaction was monitored by 1H NMR. However, all
attempts to isolate 7 working to preparative scale were
unsuccessful, because the green reaction solution of 7
was observed to reverse to the initial red solution of 3
on removing the H2 atmosphere, suggesting that the
reaction of the rupture of the azatitanacyclopropane
under H2 atmosphere is highly reversible. This behav-
ior is surprising and unique since analogous ketene-
containing zirconocene species described by Bercaw et
al.13 undergo nonreversible hydrogenation processes. In
addition, a solution of 7 under H2 atmosphere was easily
hydrolyzed to give the enamine N-(2,2-diphenylvinyl)-
Exp er im en ta l Section
Gen er al Con sider ation s. Ph′NdCdCPh2,14 Cp2Ti(PMe3)2,15
18
Cp2Zr(PMe3)2,16 Cp2*TiCl2,17 and Cp2*ZrCl2 were prepared
by published methods. LitBu, Cp2TiCl2, and Cp2ZrCl2 were
used as received from Aldrich.
All reactions and product manipulations were carried out
under an inert atmosphere (nitrogen) using standard Schlenk
and drybox techniques. Solvents were freshly distilled from
appropriate drying agents and degassed before use. Elemental
analyses were performed with a Perkin Elmer 2400 microana-
lyzer. NMR spectra were recorded on a Varian Unity FT-300
instrument. Trace amounts of protonated solvents were used
as references, and chemical shifts are reported in ppm relative
to SiM4. IR spectra were recorded as Nujol mulls between CsI
plates (in the region 4000-200 cm-1) on a Perkin Elmer PE
833 spectrophotometer.
1
4-methylaniline. The H NMR spectrum of 7 exhibits
Cp2Ti(η2-(C,N)-P h ′NdCdCP h 2)(P Me3) (1). Ph′NdCdCPh2
(340 mg, 1.20 mmol) was added to a solution of Cp2Ti(PMe3)2
(350 mg, 1.20 mmol) in 25 mL of THF, and this mixture was
stirred at room temperature overnight. The solvent and the
liberated PMe3 were removed under vacuum, and the resulting
oily brown solid was washed with pentane to give a brown-
reddish solid. The crude solid was crystallized by dissolving
in THF and placing a layer of pentane above it in a Schlenk
tube, and deep red crystals were obtained (89%).
a broad resonance at 5.50 ppm for the hydride ligand,
as well as a resonance at 4.97 ppm for the CH-N proton.
Different types of unsaturated molecules, such as alk-
enes, alkynes, aldehydes, ketones, and nitriles, did not
react with 1, 2, 3, or 4 under various experimental
conditions, and the reactions with bulky isonitriles, such
as 2,6-dimethylphenyl and tert-butylisonitrile, gave
intractable mixtures of products.
IR (Nujol mull): ν(NdCdC) 1543 cm-1 1H NMR (C6D6): δ
.
0.59 (s, 9H, PMe3), 2.03 (s, 3H, p-MeC6H4), 5.44 (s, 10H, C5H5),
6.07 (psd, 2H, J HH ) 8.10 Hz), 6.62 (psd, 2H, J HH ) 8.10 Hz),
6.80-7.52 (mc, 10H) (phenyl groups). 13C{1H} NMR (THF-
d8): δ 20.8 (p-MeC6H4), 24.7 (PMe3, J PC ) 2.4 Hz), 107.5 (C5H5),
128.0 (CPh2), 146.9 (CdN), 120.7, 120.8, 123.5, 123.6, 124.4,
124.5, 127.6, 127.7, 127.8, 127.9, 128.7, 128.8, 132.1, 132.2 (C
phenyl groups), 128.9, 129.6, 130.6, 144.9 (Cipso of phenyl
groups). Anal. Calcd for C34H36NPTi: C, 75.97; H, 6.75; N,
2.61. Found: C, 75.85; H, 6.31; N, 2.50.
Con clu d in g Rem a r k s
This study has revealed that ketenimine-containing
group 4 metallocenes can be prepared by reacting
Ti(II) and Zr(II) species with the appropriate free
ketenimine. Cp-ring-containing metallocenes are sta-
bilized in the presence of a PMe3 ligand, while the
corresponding Cp*-containing complexes are isolated as
the 16-electron species Cp*2M(η2-(C,N)-Ph′NdCdCPh2).
C-C coupling of two ketenimine molecules to the
titanium coordination sphere has also been observed,
and the reactivity of the coordinated ketenimine in the
complex Cp*2Ti(η2-(C,N)-Ph′NdCdCPh2) toward H+
and H2 was also considered. We believe that the results
reported offer a significant advance in the chemistry of
cumulene containing early transition metallocenes, and
work in this field is ongoing.
Cp 2Zr (η2-(C,N)-P h ′NdCdCP h 2)(P Me3) (2). This com-
pound was obtained as a red-orange crystalline solid (57%)
following the same procedure as described for 1. It was
(14) Bestmann, H. J .; Lienert, J .; Mott, L. Liebigs Ann. Chem. 1968,
718, 24.
(15) Kool, L. B.; Rausch, M. D.; Alt, H. G.; Herberhold, M.; Thewalt,
U.; Wolf, B. Angew. Chem., Int. Ed. Engl. 1985, 24, 394.
(16) Rausch, M. D.; Att, H. E.; Herberhold, M.; Thewalt, U. J .
Organomet. Chem. 1987, 320, 37.
(17) McKenzie, T. C.; Sanner, R. D.; Bercaw, J . E. J . Organomet.
Chem. 1975, 102, 475.
(18) Manriquez, J . M.; McAlister, D. R.; Rosenberg, E.; Shiller, A.
M.; Williamson, K. L.; Chan, S. I.; Bercaw, J . E. J . Am. Chem. Soc.
1978, 100, 3078.
(13) Moore, E. J .; Straus, D. A.; Armantrout, J .; Santarsiero, B. D.;
Grubbs, R. H.; Bercaw, J . E. J . Am. Chem. Soc. 1983, 105, 2068.

Early-Transition-Metal Ketenimine Complexes
Organometallics, Vol. 16, No. 24, 1997 5287
alternatively prepared by the following method: 1.7 mL of Lin-
Bu (1.6 M in hexane) was added to a solution of Cp2ZrCl2 (470
mg, 1.30 mmol) in 25 mL of THF at -78 °C. The reaction
mixture was stirred and warmed to room temperature for 15
min, and to the resulting solution was added PMe3 (3.90 mmol)
at -78 °C. Finally, the ketenimine (370 mg, 1.30 mmol) was
added to the reaction mixture, which was then stirred for 1 h
at room temperature. The solvent and the excess of PMe3 were
removed under vacuum, and the resulting oily reddish solid
was washed with pentane to give a red-orange solid, which
was crystallized following the method described for 1 (54%).
reaction mixture, which was then stirred for 1 h. The solvent
was then removed, and the resulting red oil was extracted (×3)
with toluene. A white oily solid was obtained by evaporation
of the solvent, which was washed with pentane to afford a
white solid (21%).
IR (Nujol mull): 3397 cm-1 (m, νN-H). 1H NMR (C6D6): δ
1.89 (s, 3H, p-MeC6H4), 2.00 (s, 3H, p-MeC6H4), 4.48 (s, 1H,
NH), 5.93 (s, 1H, CdCH), 6.30 (2H), 6.60 (2H), 6.70-7.30 (mc,
24H) (phenyl groups). 13C{1H} NMR (C6D6): δ 20.5, 20.5 (p-
MeC6H4), 115.5, 119.3 (Ph2C), 125.5, 126.3, 127.2, 127.2, 127.5,
127.5, 127.8, 128.1, 128.3, 128.5, 128.6, 128.7, 128.8, 129.1,
129.3, 129.5, 129.7, 130.1, 130.2, 130.3, 130.4, 130.5, 131.2,
131.3, 131.4, 131.5, 131.7, 131.8, 131.9, 132.0 (C phenyl and
vinyl groups), 129.9, 129.9, 139.9, 140.5, 141.1, 142.1, 143.9,
144.2 (Cipso of phenyl groups). Anal. Calcd for C42H36N2: C,
88.69; H.6.38; N, 4.92. Found: C, 89.48; H. 6.74; N, 4.59.
Rea ction s of 3 w ith Et3NHCl or H2O. To a mixture of 3
(330 mg, 0.55 mmol) and Et3NHCl (70mg, 0.55 mmol) was
added 10 mL of THF. The solution was stirred overnight, and
then the solvent was removed in vacuo, and the resulting
residue was extracted with pentane (2 × 10 mL). The solution
was concentrated to 2 mL, and after cooling to -30 °C a white
solid of N-(2,2-diphenylvinyl)-4-methylaniline was obtained
(46%). A similar procedure with H2O was used.
IR (Nujol mull): ν(NdCdC) 1500 cm-1 1H NMR (C6D6): δ
.
0.53 (d, 9H, J PH ) 6.41 Hz, PMe3), 2.09 (s, 3H, p-MeC6H4), 5.59
(s, 10H, C5H5), 6.17 (psd, 2H, J HH ) 8.10 Hz), 6.60 (psd, 2H,
J HH ) 8.10 Hz), 7.05-7.84 (mc, 10H) (phenyl groups). 13C-
{1H} NMR (C6D6): δ 14.9 (PMe3, J PC ) 16Hz), 20.9 (p-MeC6H4),
105.6 (C5H5), 105.7 (CPh2), 170.3 (CdN), 120.2, 120.3, 123.3,
123.4, 124.0, 124.1, 127.4, 127.5, 127.8, 127.8, 127.9, 128.0,
132.6, 132.7 (C phenyl groups), 129.9, 144.9, 147.8, 153.4 (Cipso
of phenyl groups). Anal. Calcd for C34H36NPZr: C, 70.30; H,
6.25; N, 2.41. Found: C, 70.15; H, 6.15; N, 2.37.
Cp *2Ti(η2-(C,N)-P h ′NdCdCP h 2) (3). To a suspension of
Cp2TiCl2 (580 mg, 1.50 mmol) in 25 mL of THF was added
LitBu (1.7mL, 3.00 mmol, 1.7 M in hexane). After 25 min of
stirring at room temperature, the reaction mixture was cooled
to -78 °C, and the ketenimine (420 mg, 1.50 mmol) was added.
The solution was stirred and slowly warmed to room temper-
ature for 10 min. The solvent was then removed, and the
resulting red oily solid was crystallized as deep red crystals
by dissolving in THF and placing a layer of pentane above it
in a Schlenk tube (54%).
IR (Nujol mull): 3413 cm-1 (m, νN-H). 1H NMR (C6D6): δ
2.06 (s, 3H, p-MeC6H4), 5.91 (1H, NH), 6.20 (2H), 6.80 (2H),
7.02-7.29 (mc, 11H) (phenyl and vinyl groups). 13C{1H} NMR
(C6D6): δ 20.5 (p-MeC6H4), 117.4 (Ph2C), 114.3, 115.0, 125.6,
125.7, 125.9, 126.7, 127.1, 127.5, 128.6, 129.0, 129.5, 130.1,
130.3, 130.6, 130.8 (C phenyl and vinyl groups), 129.2, 139.4,
140.7, 142.5 (Cipso phenyl groups). Anal. Calcd for C21H19N:
C, 88.38; H, 6.71; N, 4.91. Found: C, 87.68; H, 6.75; N, 4.77.
When the above commented reactions were carried out at
shorter reaction times, a mixture of the enamine with 5 or 6
was obtained respectively.
IR (Nujol mull): ν(NdCdC) 1527 cm-1
.
1H NMR (C6D6): δ
1.73 (s, 30H, C5Me5 ), 2.03 (s, 3H, p-MeC6H4), 5.79 (psd, 2H,
J HH ) 8.50 Hz), 6.58 (psd, 2H, J HH ) 8.50 Hz), 6.92-7.56 (mc,
10H) (phenyl groups). 13C{1H}NMR (C6D6): δ 12.6 (C5Me5),
20.7 (p-MeC6H4), 102.1 (CPh2), 124.9 (C5Me5), 120.7, 120.9,
121.9, 122.0 124.6, 124.8, 125.0, 125.2, 127.9, 128.0, 128.1,
128.3, 129.0, 132.2 (C phenyl groups), 127.8, 143.5, 145.1, 146.0
Ch a r a cter iza tion of 5. 1H NMR (C6D6): δ 1.77 (s, 30H,
C5Me5), 2.02 (s, 3H, p-MeC6H4), 5.96-7.77 (mc, 14H) (phenyl
groups), 8.28 (s, 1H, dCH).
Ch a r a cter iza tion of 6. 1H NMR (C6D6): δ 1.75 (s, 30H,
C5Me5), 2.08 (s, 3H, p-MeC6H4), 5.50-5.70 (mc, 14H) (phenyl
groups), 5.85 (br, 1H, OH), 9.38 (s, 1H, dCH). 13C{1H} NMR
(C6D6): δ 12.1 (C5Me5), 20.4 (p-MeC6H4), 108.5 (Ph2C), 114.3
(CHdN), 125.7 (C5Me5), 126.7, 126.9, 127.2, 127.5, 127.7, 128.3,
128.7, 129.5, 129.8, 130.2, 130.5, 130.8, 139.2, 139.9 (C phenyl
groups), 129.2, 146.0, 148.2, 151.3 (Cipso phenyl groups).
Rea ction s of 3 w ith H2. The reaction of 3 with H2 was
monitored by NMR. Thus, when H2 was bubbled into a C6D6
solution (0.7 mL) of 3 (30 mg, 0.05 mmol), a fast color change
from red to deep green was observed which corresponds to the
formation of 7, which was spectroscopically characterized.
However, when the H2 was removed from the NMR tube
solution of 7, a change to the initial red color was observed,
and both the disappearance of 7 and the formation of 3 were
spectroscopically established. Attempts to isolate 7 to pre-
parative scale were unsuccessful because, on removing the H2
atmosphere from the green reaction solution of 7, a red solution
of the starting complex 3 was formed.
Ch a r a cter iza tion of 7. 1H NMR (C6D6): δ 1.76 (s, 30H,
C5Me5), 2.07 (s, 3H, p-MeC6H4), 4.97 (s, 1H, CH-N) 5.50 (br,
1H, Ti-H), 6.20-7.50 (mc, 14 H, phenyl groups). 13C{1H}
NMR: δ 12.4 (C5Me5), 20.8 (p-MeC6H4), 122.1 (C5Me5), 126.9
(Ph2CdC), 123.8, 123.9, 124.1, 124.3, 125.7, 125.9, 126.3, 127.0,
127.2, 127.6, 128.2, 128.4, 129.1, 130.5, 130.8 (C phenyl groups
and CH-N), 128.1, 139.6, 140.7, 142.4 (Cipso phenyl groups).
X-r a y Da ta Collection , Str u ctu r e Deter m in a tion , a n d
Refin em en t of 3. A suitable crystal was sealed in a Linde-
mann capillary under nitrogen and used for data collection.
The crystallographic data are summarized in Table 2.
Accurate unit cell parameters were determined by least-
squares refinement of the setting angles of 32 randomly
distributed and carefully centered reflections with θ in the
range 8-18°. The data collection was performed on a Philips
(Cipso of phenyl groups), 200.8 (CdN). Anal. Calcd for C41H47
TiN: C, 81.84; H, 7.87; N, 2.33. Found: C, 81.70; H, 7.60; N,
2.30.
-
Cp *2Zr (η2-(C,N)-P h ′NdCdCP h 2) (4). Meth od A. The
complex was isolated as red crystals contaminated with
unidentified impurities in a manner similar to that for 3.
Met h od B. To a suspension of Cp*2ZrCl2 (640 mg, 1.50
mmol) in 25 mL of THF was added LitBu (1.70 mL, 1.7 M in
hexane). After 15 min of stirring at room temperature, PMe3
(6.00 mmol) and ketenimine (420 mg, 1.50 mmol) were added,
and the resulting solution was stirred again for 3 h. Both the
solvent and PMe3 were then removed, and the residue was
extracted with 5 mL of toluene to give a solution from which
an oily red solid was isolated. After crystallization as 3, pure
red crystals of 4 were obtained (23%).
IR (Nujol mull): ν(NdCdC) 1547 cm-1 1H NMR (C6D6): δ
.
1.76 (s, 30H, C5Me5), 2.08 (s, 3H, p-MeC6H4), 6.62 (psd, 2H,
J HH ) 8.50 Hz), 6.76 (psd, 2H, J HH ) 8.50 Hz), 5.71-7.51 (mc,
10H) (phenyl groups). 13C{1H} NMR (C6D6): δ 11.4 (C5Me5),
20.9 (p-MeC6H4), 111.4 (CPh2), 121.2 (C5Me5), 124.0, 124.1,
124.7, 125.2, 126.9, 127.1, 127.4, 127.8, 128.1, 128.5, 130.4,
130.7, 136.0, 136.2 (C phenyl groups), 128.8, 139.2, 141.5, 147.6
(Cipso of phenyl groups), 147.8 (CdN). Anal. Calcd for C41H47
ZrN: C, 76.34; H, 7.34; N, 2.17. Found: C, 76.28; H, 7.15; N,
2.08.
Rea ction of “Cp *2Ti” w ith P h ′NdCdCP h 2 (1:2 Mola r
Ra tio). Syn th esis of 1,1,5,5-Tetr a p h en yl-3-(p-tolyl)-2-(p-
tolu id in o)-3-a za -1,4-p en ta d ien e. To a suspension of Cp*2-
TiCl2 (330 mg, 0.85 mmol) in 25 mL of THF was added LitBu
(1mL, 1.70 mmol, 1.7 M in hexane). After 20 min of stirring
at room temperature, the reaction mixture was cooled at -78
°C, and the ketenimine (480 mg, 1.70 mmol) was added. The
resulting solution was stirred and warmed to room tempera-
ture for 20 min H2O (30 µL) was added afterward to the
-

5288 Organometallics, Vol. 16, No. 24, 1997
Fandos et al.
2
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 3a
and reduced to Fo
.
The structure was solved by direct
methods (SIR9220) and refined by full-matrix least-squares on
F2 using SHELXL-93,21 first with isotropic thermal parameters
and then with anisotropic thermal parameters for all the non-
hydrogen atoms. All the hydrogen atoms were placed at their
geometric default distance calculated positions and refined
“riding” on their parent carbon atoms. Attempts to solve the
structure in the Cc space group to avoid the great disorder
were unsuccessful. All calculations were carried out on the
ENCORE 91 of the Centro di Studio per la Strutturistica
Diffrattometrica del CNR, Parma. The programs Parst22 and
ORTEP23 were also used. The final atomic coordinates are
provided in the Supporting Information.
empirical formula
fw
C41H47NTi
601.70
temperature
wavelength
cryst syst
293(2) K
0.710 73 Å
monoclinic
space group
unit cell dimensions
C2/c
a ) 14.969(5) Å
b ) 13.830(5) Å, â ) 101.78(2)°
c ) 16.703(5) Å
3385(2) Å3
volume
Z
4
density (calcd)
abs coeff
1.181 Mg/m3
0.281 mm-1
F(000)
1288
Ack n ow led gm en t. We gratefully acknowledge fi-
nancial support from the Direccio´n General de Inves-
tigacio´n Cient´ıfica y Te´cnica (Grant No. PB92-0715)
(Spain) and the Ministero dell’Universita` e della Ricerca
Scientifica e Tecnologica (MURST) and Consiglio Na-
zionale delle Ricerche (CNR) (Rome, Italy).
cryst size
θ range for data coll
index ranges
0.15 mm × 0.23 mm × 0.35 mm
3.20-27.02°
-19 e h e 18, -17 e k e 17,
0 e l e 21
no. of reflns collected
no. of independent reflns
refinement method
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
7204
3694 [R(int) ) 0.0755]
full-matrix least-squares on F2
3586/80/296
Su p p or tin g In for m a tion Ava ila ble: Tables of final
atomic coordinates for the non-hydrogen and the hydrogen
atoms, anisotropic thermal parameters, complete list of bond
distances and angles, and complete crystallographic data for
3 (7 pages). Ordering information is given on any current
masthead page.
0.952
R1 ) 0.0791, wR2 ) 0.1998
R1 ) 0.1540, wR2 ) 0.2868
0.590 and -0.620 e Å-3
0.1604, 0.0000
largest diff peak and hole
weighting scheme, a, b
a
2
GOF ) [∑[w(Fo - Fc2)2]/(n - p)]1/2. R1 ) ∑||Fo| - |Fc||/∑|Fo|.
wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]1/2. w ) 1/[σ2(Fo2) + (aP)2 + bP],
where P ) [max(Fo2,0) + 2Fc2]/3.
OM970568P
(19) Lehmann, M. S.; Larsen, F. K. Acta Crystallogr., Sect. A 1974,
30, 580.
(20) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Gualiardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(21) Sheldrick, G. M. SHELXL-93. Program for the refinement of
crystal structures; University of Go¨ttingen: Go¨ttingen, Germany, 1993.
(22) Nardelli, M. Comput. Chem. 1983, 7, 95.
(23) J ohnson, C. K. ORTEP. Report ORNL-3794, revised; Oak Ridge
National Laboratory: Oak Ridge, TN, 1965.
PW 1100 diffractometer in the θ/2θ scan mode at 293 K with
a variable scan speed of 3-9.6° min-1 and a scan width of 1.20
+ 0.34 tan θ. One standard reflection was monitored every
100 measurements, and no significant decay was noticed over
the time of data collection. The individual profiles have been
analyzed according to the method of Lehmann and Larsen.19
Intensities were corrected for Lorentz and polarization effects