C-N coupling reactions of allenes and methylacetylenes with an imidotitanium complex

Article abstract of DOI:10.1021/om010253g

Reaction of the imidotitanium complexes [(N₂Npy-κ³N)Ti(-NtBu)(py)] (1) and [(N₂Npy-κN)Ti(=NtBu)] (1a) (N₂Npy = (2-C₅H₄N)C(Me)CH₂NSiMe₃)₂ ) with 2-butyne and 1-phenyl-propyne led to C-N coupling with the imido ligand and yielded the four-membered titanaazetidines [(N₂Npy-κ³N)Ti{N(tBu)C(CHCH₃) CH₂}] (2) and [(N₂Npy-κ³N)Ti{N(tBu)C-(CHC₆H₅ )CH₂}] (3), respectively. The same reaction products were obtained in 2 + 2 cycloaddition reactions of 1 and 1a with 1,2-butadiene and phenylallene. The four-membered metallacycle with an exocyclic C=C double bond was established by X-ray diffraction studies of both compounds. A mechanism to explain the observed products from both types of reactions is proposed. Whereas the reactions of 1 with CO₂, tBuNCO, and PhNCO were highly unspecific and did not lead to an isolable product, the conversion with the sterically encumbered isocyanate 2,6-iPr₂C₆H₃NCO yielded the product of 2 + 2 cycloaddition to the Ti=N bond, namely [(N₂Npy-κ³N)Ti{N(tBu)C(N-2,6-C₆ H₃iPr₂)O}(py)] (4), the structure of which was elucidated by NMR spectroscopy.

Full text of DOI:10.1021/om010253g

3308
Organometallics 2001, 20, 3308-3313
C-N Cou p lin g Rea ction s of Allen es a n d
Meth yla cetylen es w ith a n Im id otita n iu m Com p lex
Dominique J . M. Tro¨sch,† Philip E. Collier,‡ Alan Bashall,§ Lutz H. Gade,*,†
Mary McPartlin,§ Philip Mountford,*,‡ and Sanja Radojevic§
Laboratoire de Chimie Organome´tallique et de Catalyse (CNRS UMR 7513), Institut Le Bel,
Universite´ Louis Pasteur, Strasbourg, 4, rue Blaise Pascal, 67070 Strasbourg Cedex, France,
School of Applied Chemistry, The University of North London, Holloway Road,
London N7 8DB, U.K., and Inorganic Chemistry Laboratory, University of Oxford,
South Parks Road, Oxford OX1 3QR, U.K.
Received March 27, 2001
Reaction of the imidotitanium complexes [(N2Npy-κ3N)Ti(dNtBu)(py)] (1) and [(N2Npy-
κ3N)Ti(dNtBu)] (1a ) (N2Npy ) (2-C5H4N)C(Me)(CH2NSiMe3)2) with 2-butyne and 1-phenyl-
propyne led to C-N coupling with the imido ligand and yielded the four-membered
titanaazetidines [(N2Npy-κ3N)Ti{N(tBu)C(CHCH3)CH2}] (2) and [(N2Npy-κ3N)Ti{N(tBu)C-
(CHC6H5)CH2}] (3), respectively. The same reaction products were obtained in 2 + 2
cycloaddition reactions of 1 and 1a with 1,2-butadiene and phenylallene. The four-membered
metallacycle with an exocyclic CdC double bond was established by X-ray diffraction studies
of both compounds. A mechanism to explain the observed products from both types of
reactions is proposed. Whereas the reactions of 1 with CO2, tBuNCO, and PhNCO were
highly unspecific and did not lead to an isolable product, the conversion with the sterically
encumbered isocyanate 2,6-iPr2C6H3NCO yielded the product of 2 + 2 cycloaddition to the
TidN bond, namely [(N2Npy-κ3N)Ti{N(tBu)C(N-2,6-C6H3iPr2)O}(py)] (4), the structure of
which was elucidated by NMR spectroscopy.
In tr od u ction
of the MdNR linkages themselves with examples rang-
ing from the activation of C-H bonds to cycloaddition
reactions with unsaturated C-C or C-X bonds.11-13
In a systematic study we have shown that the
coordination to titanium of the diamidopyridine ligand
system developed previously by us14,15 leads to stable
monomeric imidotitanium complexes such as 1 (Chart
1).16,17 The tert-butylimido compound 1 possesses labile
Imido ligands (NR where R typically is an organic
group) generally behave as ancillary or supporting
groups in the chemistry of high-valent metal complexes
of the group 5-group 7 transition metals.1-3 However,
recent investigations4-10 of the chemistry of group 4
imides has uncovered a variety of novel transformations
* Authors to whom correspondence should be addressed.
E-mail: L.H.G., Gade@chimie.u-strasbg.fr; P.M., Philip.Mountford@
chemistry.oxford.ac.uk.
(9) (a) Dunn, S. C.; Batsanov, A. S.; Mountford, P. J . Chem. Soc.,
Chem. Commun. 1994, 2007. (b) Blake, A. J .; Collier, P.; Dunn, S. C.;
Li, W.-S.; Mountford, P.; Shishkin, O. V. J . Chem. Soc., Dalton Trans.
1997, 1549. (c) Collier, P. E.; Dunn, S. C.; Mountford, P.; Shishkin, O.
V.; Swallow, D. J . Chem. Soc., Dalton Trans. 1995, 3743.
(10) Lewkebandra, T. S.; Sheridan, P. H.; Heeg, M. J .; Rheingold,
A. L.; Winter, C. H. Inorg. Chem. 1994, 33, 5879.
(11) (a) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J . Am.
Chem. Soc. 1988, 110, 8731. (b) Bennet, J . L.; Wolczanski, P. T. J .
Am. Chem. Soc. 1997, 119, 10696.
† Universite´ Louis Pasteur.
‡ University of Oxford.
§ University of North London.
(1) (a) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds;
Wiley-Interscience: New York, 1988. (b) Chisholm, M. H.; Rothwell,
I. P. In Comprehensive Coordination Chemistry; Wilkinson, G., Gillard,
R. D., McCleverty, J . A., Eds.; Pergamon Press: Oxford, U.K., 1987;
Vol. 2.
(2) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.
(3) For applications of imido complexes in olefin polymerization
catalysis see: (a) Coles, M. P.; Dalby, C. I.; Gibson, V. C.; Clegg, W.;
Elsegood, M. R. J . J . Chem. Soc., Chem. Commun. 1995, 1709. (b)
Chan, M. C. W.; Chew, K. C.; Dalby, C. I.; Gibson, V. C.; Kohlmann,
A.; Little, I. R.; Reed, W. Chem. Commun. 1998, 1673. For applications
of imido complexes in ring opening metathesis polymerization see: (c)
Schrock, R. R. Acc. Chem. Res. 1990, 23, 158. (d) Gibson, V. C. Adv.
Mater. 1994, 6, 37.
(12) (a) Meyer, K. E.; Walsh, P. J .; Bergman, R. G. J . Am. Chem.
Soc. 1994, 116, 2669. (b) Meyer, K. E.; Walsh, P. J .; Bergman, R. G. J .
Am. Chem. Soc. 1995, 117, 974.
(13) (a) Cloke, F. G. N.; Hitchcock, P. B.; Nixon, J . F.; Wilson, D. J .;
Mountford, P. Chem. Commun. 1999, 661. (b) Thorman, J . L.; Guzei,
I. A.; Young, V. G.; Woo, L. K. Inorg. Chem. 2000, 39, 2344. (c)
Thorman, J . L.; Woo, L. K. Inorg. Chem. 2000, 39, 1301. (d) Zuckerman,
R. L.; Krska, S. W.; Bergman, R. G. J . Organomet. Chem. 1999, 591,
2. (e) Zuckerman, R. L.; Bergman, R. G. Organometallics 2000, 19,
4795. (f) Harlan, C. J .; Tunge, J . A.; Bridgewater, B. M.; Norton, J . R.
Organometallics 2000, 19, 2365.
(14) (a) Friedrich, S.; Gade, L. H.; Edwards, A. J .; McPartlin, M. J .
Chem. Soc., Dalton Trans. 1993, 2861. (b) Friedrich, S.; Schubart, M.;
Gade, L. H.; Scowen, I. J .; Edwards, A. J .; McPartlin, M. Chem. Ber.
1997, 120, 11751. (c) Galka, C. H.; Tro¨sch, D. J . M.; Schubart, M.; Gade,
L. H.; Radojevic, S.; Scowen, I. J .; McPartlin, M. Eur. J . Inorg. Chem.
2000, 2577.
(4) Mountford, P. Chem. Commun. 1997, 2127.
(5) (a) Hill, J . E.; Profilet, R. D.; Fanwick, P. E.; Rothwell, I. P.
Angew. Chem., Int. Ed. Engl. 1990, 29, 664. (b) Roesky, H. W.; Voelker,
H.; Witt, M.; Noltemeyer, M. Angew. Chem., Int. Ed. Engl. 1990, 29,
669.
(6) (a) Walsh, P. J .; Hollander, F. J .; Bergman, R. G. J . Am. Chem.
Soc. 1988, 110, 8729. (b) Glueck, D. S.; Wu, J . X.; Hollander, F. J .;
Bergman, R. G. J . Am. Chem. Soc. 1991, 113, 2041. (c) Walsh, P. J .;
Hollander, F. J .; Bergman, R. G. Organometallics 1993, 12, 3705.
(7) Cummins, C. C.; Schaller, C. P.; Van Duyne, G. D.; Wolczanski,
P. T.; Chan, A. W. E.; Hoffmann, R. J . Am. Chem. Soc. 1991, 113, 2985.
(8) McGrane, P. L.; J ensen, M.; Livinghouse, T. J . J . Am. Chem.
Soc. 1992, 114, 5459.
(15) Gade, L. H. Chem. Commun. 2000, 173.
(16) Blake, A. J .; Collier, P. E.; Gade, L. H.; McPartlin, M.;
Mountford, P.; Schubart, M.; Scowen, I. J . Chem. Commun. 1997, 1555.
(17) For a review of imido complexes with diamido donor ligands
see: Gade, L. H.; Mountford, P. Coord. Chem. Rev., in press.
10.1021/om010253g CCC: $20.00 © 2001 American Chemical Society
Publication on Web 06/26/2001

C-N Coupling Reactions with an Imidotitanium Complex
Organometallics, Vol. 20, No. 15, 2001 3309
Ch a r t 1
Neither of the reaction products 2 and 3 contain the
auxiliary pyridine ligand present in the starting mate-
rial, and the 1H and 13C NMR spectra indicate a
transformation of a methyl group of the acetylene
substrate. Thus, new singlet resonances for a metal-
bound CH2 group were observed (δ(1H/13C): 2, 1.77/62.4;
3, 2.03/63.6) as well as signals for an olefinic CH unit
(δ(1H/13C): 2, 4.76 (quartet)/86.7; 3, 5.86 (singlet)/96.4).
This led to the formulation of the reaction products as
depicted in Scheme 1. The same reaction products were
obtained in similar yields under virtually identical
reaction conditions from the pyridine-free imido complex
1a , which indicates that the auxiliary pyridine ligand
does not play a direct role in the conversion of the
methylacetylenes. As with all previously studied trans-
formations of 1,17 the dissociation of the pyridine
molecule appears to be the first step. This is supported
by the observation that addition of 3-5 equiv of pyridine
to a mixture of 1 and the methylacetylenes inhibits the
reaction to the extent that virtually no conversion to
the metallacycles is observed, even after 3 weeks at 80
°C. In contrast to the methylacetylenes, the homologues
containing longer chain alkyl units attached to the CtC
triple bonds were found to be unreactive toward 1 or
1a . Surprisingly, in none of these reactions was the
direct addition of the acetylenic triple bond to the
TidNtBu linkage observed, in contrast to the situation
found for the reaction of other terminal imides with
acetylenes.2 This is especially surprising, since certain
phosphaalkynes (RCP) and azaalkynes (RCN) readily
undergo 2 + 2 cycloaddition reactions with the TidNtBu
bond in 1.25b
Rea ction of 1 a n d 1a w ith Allen es. Compounds 2
and 3 are related to 2 + 2 cycloaddition products
reported by Bergman and co-workers for the reaction
of certain zirconocene imides with the CdC double
bonds of alkenes20 and allenes.21 In particular, the
reaction of a chiral imidozirconium derivative with
racemic chiral allenes occurred stereoselectively and
allowed a kinetic resolution of the racemate.21 In these
cases the reaction of an allene with the imido complex
led to a metallaazetidine with an exocyclic double bond,
as in complexes 2 and 3. Both compounds may thus be
viewed as formally derived from an analogous reaction
of 1 or 1a with 1,2-butadiene or phenylallene, respec-
tively. In fact, heating the imidotitanium complexes
with these allenes at 60 °C over a period of 14 days led
to their complete and selective conversion to compounds
2 and 3 (Scheme 2), as established by comparison of the
spectroscopic and analytical data of both products with
the corresponding products derived from the methyl-
acetylenes.
pyridine and pyridyl functionalities that, under ap-
propriate reaction conditions, may dissociate to yield
imido species of a type hitherto only accessible via
irreversible thermolysis of suitable precursors.7,11 In
fact, sublimation of the pyridine adduct 1 under high
vacuum quantitatively leads to the 14-valence-electron,
four-coordinate complex 1a in which the metal center
is already fairly exposed.18 The facile accessibility and
stability of 1 and 1a has allowed us to undertake a
systematic investigation into their reactivity, in par-
ticular C-N coupling with unsaturated hydrocarbons
or substrates containing polar functional groups.
In this paper we report the reactivity of complexes 1
and 1a toward methylacetylenes, allenes, and hetero-
allenes.19
Resu lts a n d Discu ssion
R ea ct ion of 1 a n d 1a w it h Met h yla cet ylen es.
Heating compound 1 dissolved in neat 2-butyne or
1-phenylpropyne at 80 °C for 14 days in a sealed tube
led to its complete conversion to the novel complexes
[(N2Npy-κ3N)Ti{N(tBu)C(CHCH3)CH2}] (2) and [(N2-
Npy-κ3N)Ti{N(tBu)C(CHC6H5)CH2}] (3) (Scheme 1),
Sch em e 1. Rea ction of Com p lexes 1 a n d 1a w ith
Meth yla cetylen es To Give th e Meta lla cycles
2 a n d 3
In contrast to the reaction of allenes with Bergman’s
zirconocene imido complex,21 the conversion of com-
pounds 1 to the products 2 and 3 is a slow reaction and
is irreversible. The irreversible nature was established
by a (null) crossover experiment of 2 with a large excess
of phenylallene. Thus, heating the two compounds at
80 °C for over 14 days did not lead to any detectible
generation of 3 or to the concomitant liberation of 1,2-
butadiene. Furthermore, in all the reactions leading to
respectively, which were isolated by direct crystalliza-
tion from the reaction mixture (yields: 2, 73%; 3, 70%).
(18) Blake, A. J .; Collier, P. E.; Gade, L. H.; Lloyd, J .; Mountford,
P.; Pugh, S. M.; Schubart, M.; Skinner, M. E. G.; Tro¨sch, D. J . M. Inorg.
Chem. 2001, 40, 870.
(19) Bashall, A.; Collier, P. E.; Gade, L. H.; McPartlin, M.; Mount-
ford, P.; Tro¨sch, D. J . M. Chem. Commun. 1998, 2555.
(20) Polse, J . L.; Andersen, R. A.; Bergman, R. G. J . Am. Chem. Soc.
1998, 120, 13405.
(21) Sweeney, Z. K.; Salsman, J . L.; Andersen, R. A.; Bergman, R.
G. Angew. Chem., Int. Ed. 2000, 39, 2339.

3310 Organometallics, Vol. 20, No. 15, 2001
Tro¨sch et al.
Sch em e 2. Rea ction of Com p lexes 1 a n d 1a w ith
Allen es To Give th e Meta lla cyclic Tita n iu m
Com p lexes 2 a n d 3
2 and 3 there was no detectible isomerization of the free
methylacetylenes to the corresponding free allenes or
vice versa. If such an acetylene-to-allene isomerization
takes place, it presumably must therefore occur within
the coordination sphere of the complex. It is thus
probable that both reaction pathways involve the same
intermediate, i.e., a metal π-bound allene complex, and
that the 2 + 2 cycloaddition is the slow reaction step in
the sequence of transformations leading to 2 and 3. A
mechanistic pathway which takes these observations
into account is depicted in Scheme 3.
F igu r e 1. Molecular structure of [(N2Npy-κ3N)Ti{N(tBu)C-
(CHMe)CH2}] (2).
H atom transfer to an acetylene C atom leads to the
re-formation of the imido unit and a π-bonded allene
ligand (B). These fragments couple in the third and final
step to give the four-membered azatitanacycle present
in 2 and 3. Alternatively, intermediate A may also be
directly converted to the metallacycle. Note that since
the reversible addition of alkynes to MdNR or MdO
bonds is established, we cannot rule out the reversible
formation of an azatitanacyclobutene intermediate prior
to C-H bond migration.6c In addition, we cannot
discount an alternative mechanism in which initial
deprotonation of the Me group of a coordinated alkyne
by an amido nitrogen occurs. This would give an amido-
imido-diamido intermediate analogous to A. This then
could, in turn, collapse to the imido-allene intermediate
B and subsequently form 2/3.
Sch em e 3. P r op osed Mech a n ism for th e
F or m a tion of 2 a n d 3
X-r a y Diffr a ction Stu d ies of 2 a n d 3. Unambigu-
ous evidence for the molecular structures of 2 and 3 was
obtained from a single-crystal X-ray structure analysis
of both compounds, which are observed to have the very
similar structures depicted in Figure 1(for 2) and Figure
2(for 3). Both compounds have molecular structures of
virtual Cs symmetry. Considerable disorder of the
methyl groups in 3 led to poor diffraction by the crystals
and consequently to relatively high esd’s on the param-
eters. However, the main features are well-established,
and the mean bond lengths and angles for 3 are in most
cases equal within experimental error to those observed
for 2, with which they are compared in Table 1; the
lengths for compound 2 will be used in the discussion.
The coordination geometry of both molecules is distorted
trigonal bipyramidal. The two amido functions N(1) and
N(2) of the tripodal ligand as well as the alkyl C atom
In the first reaction step (formation of intermediate
A) the CH3 group of the methylacetylene adds across
the TidNR bond, generating an R(H)N amido ligand
and a Ti-alkyl unit. Prior coordination of the alkyne
to Ti could render the alkyne Me group C-H atoms
more acidic and amenable to deprotonation (activation)
by the tert-butylimido group. We note that C-H bond
activation reactions of transiently generated imido
compounds have been studied extensively by Wolczanski
and others in recent years.11 In a proposed second step
C(5) occupy the equatorial sites (mean Ti(1)-Nam
)
1.896(5) Å, Ti(1)-C(5) ) 2.149(7) Å), while the pyridyl
N atom (Ti(1)-N(3) ) 2.232(6) Å) and the amido N atom
(Ti(1)-N(4) ) 1.949(6) Å) derived from the imido ligand
form the axial set. The angle between the axial bonds,
N(3)-Ti(1)-N(4) ) 154.3(2)°, is distorted from the ideal

C-N Coupling Reactions with an Imidotitanium Complex
Organometallics, Vol. 20, No. 15, 2001 3311
characterized, namely [Ti(η5-C5Me5)2{OC(dCH2)CH2}],22
[Mo(NtBu)2Cl{OC(dCHPPh3)CPh2}],23 and [Ru(PMe3)4-
{OC(dCHtBu)CH2}].24 Interestingly, the last two com-
plexes have a Z configuration for the exocyclic CdC
bond, whereas the configuration in the zirconaazetidines
referred to above as well as compounds 2 and 3 is E.
Rea ction of 1 w ith Heter oa llen es. We previously
established an extensive reaction chemistry of com-
pounds 1 and 1a toward isocyanides and, thus, sub-
strates possessing polar multiple bonds, giving products
of multiple C-N and C-C coupling.25 In view of the
reactivity of allenes toward the titanium imido com-
plexes, we reacted compound 1 with heteroallenes.2,26
While upon exposure of 1 to stoichiometric amounts of
CO2, tBuNCO, and PhNCO immediate conversion of the
starting material was observed, all reactions were
highly unspecific and did not lead to an isolable product.
Only upon reaction with the sterically encumbered
isocyanate 2,6-C6H3iPr2NCO did we observe a selective
conversion to the product of 2 + 2 cycloaddition with
the TidN bond, [(N2Npy-κ3N)Ti{N(tBu)C(N-2,6-C6H3-
iPr2)O}(py)] (4) (Scheme 4).
Sch em e 4. Cycloa d d ition of 2,6-Diisop r op ylp h en yl
Isocya n a te To Give Com p ou n d 4
F igu r e 2. Molecular structure of [(N2Npy-κ3N)Ti{N(tBu)C-
(CHPh)CH2}] (3).
Ta ble 1. Selected Metr ic P a r a m eter s for 2 a n d
Selected Mea n Metr ic P a r a m eter s for th e Tw o
In d ep en d en t Molecu les of 3
2
3
(a) Bond Lengths (Å)
1.890(5)
Ti(1)-N(1)
Ti(1)-N(2)
Ti(1)-N(3)
Ti(1)-N(4)
Ti(1)-C(5)
N(4)-C(4)
C(4)-C(5)
C(4)-C(6)
mean Si-N
1.895(9)
1.919(9)
2.228(9)
1.981(11)
2.153(11)
1.39(2)
1.51(2)
1.35(2)
1.743(11)
1.903(5)
2.232(6)
1.949(6)
2.149(7)
1.404 (8)
1.515(9)
1.338(9)
1.741(6)
(b) Bond Angles (deg)
110.5(3)
86.1(2)
N(1)-Ti(1)-N(2)
N(1)-Ti(1)-N(3)
N(1)-Ti(1)-N(4)
N(2)-Ti(1)-N(3)
N(2)-Ti(1)-N(4)
N(3)-Ti1(1)-N(4)
C(5)-Ti(1)-N(1)
C(5)-Ti(1)-N(2)
C(5)-Ti(1)-N(3)
C(5)-Ti(1)-N(4)
108.9(5)
84.7(5)
109.1(6)
82.6(6)
108.6(6)
157.2(5)
125.3(6)
124.5(6)
90.8(6)
107.3(3)
83.9(2)
106.3(2)
154.3(2)
121.6(3)
127.1(3)
90.9(3)
The structure of compound 4 depicted in Scheme 3 is
67.6(2)
66.4(6)
based on the H and 13C NMR spectra of the complex
1
1
and H-1H and 13C-1H correlation spectra, as well as
linear value as a consequence of the small bite of the
coordinated chelating metalla-enamine (N(4)-Ti(1)-
C(5) ) 67.6(2)°).
1H-NOE difference spectra. Coordination of the pyridine
molecule is reflected in the chemical shifts of its protons
(ortho, δ 9.35; para, 6.98; meta, 6.74) and reduces the
molecular symmetry from Cs to C1. This renders the CH2
The bond lengths and interbond angles within the
C-N-coupled organic fragment clearly support its in-
terpretation as a metalated enamine, with C(4)-C(5)
) 1.515(9) Å and C(4)-N(4) ) 1.404(8) Å implying the
presence of predominantly single bonds, and the exo-
cyclic bond C(4)-C(6) (1.338(9) Å) being consistent with
a CdC double bond. The {Ti(NtBu)C(dCHR)CH2} met-
allaazetidine fragment in 2 and 3 is the first crystallo-
graphically authenticated example of this structural
unit and is analogous to the metallacyclic structures
characterized spectroscopically from the reaction of a
zirconocene imide with allenes by the groups of Berg-
man and Anderson.21 Related oxo-metallacyclic species
(i.e., metallaoxetanes) have only recently been fully
(22) Schwartz, D. J .; Smith, M. R.; Andersen, R. A. Organometallics
1996, 15, 1446.
(23) Hartwig, J . F.; Bergman, R. G.; Andersen, R. A. Organometallics
1991, 10, 3344.
(24) Sundermeyer, J .; Weber, K.; Pritzkow, H. Angew. Chem., Int.
Ed. Engl. 1993, 32, 731.
(25) (a) Bashall, A.; Gade, L. H.; McPartlin, M.; Mountford, P.; Pugh,
S. M.; Radojevic, S.; Schubart, M.; Scowen, I. J .; Tro¨sch, D. J . M.
Organometallics 2000, 19, 4784. (b) Pugh, S. M.; Tro¨sch, D. J . M.;
Wilson, D. J .; Bashall, A.; Cloke, F. G. N.; Gade, L. H.; Hitchcock, P.
B.; McPartlin, M.; Nixon, J . F.; Mountford, P. Organometallics 2000,
19, 3205.
(26) See the following and references therein: Blake, A. J .; McInnes,
J . M.; Mountford, P.; Nikonov, G. I.; Swallow, D.; Watkin, D. J . J .
Chem. Soc., Dalton Trans. 1999, 379.

3312 Organometallics, Vol. 20, No. 15, 2001
Tro¨sch et al.
us.16,18 Phenylallene was prepared according to a synthetic
procedure reported in the literature.28 All other chemicals used
as starting materials were obtained commercially and used
without further purification.
protons in the N2Npy ligand inequivalent, giving two
AB systems at δ 3.72, 3.33 and δ 2.31, 2.21. The signals
1
of the two Me3Si groups overlap accidentally in the H
NMR spectrum (δ 0.40) but are clearly separated in the
13C NMR spectrum (δ 1.9 and 3.1). The steric demand
of the 2,6-C6H3iPr2 group is responsible for hindered
rotation around the aryl-N bond, leading to two sets
of signals for the inequvalent isopropyl groups.
Isocyanates can add MdNR bonds to give either N,N-
bound or N,O-bound ureate derivatives.2,26 The absence
of a characteristic band attributable to a CO stretch in
the region of 1620-1640 cm-1 of the infrared spectrum
of 4 indicates the presence of an N,O-bound ureate
ligand. In a series of NOE difference spectra cross
relaxation between the tBu group and the pyridyl H6
proton, and to a lesser extent the pyridine ortho protons,
suggests the structural arrangement represented in
Scheme 4.
P r ep a r a tion of [(N2Np y-K3N)Ti{N(tBu )C(CHCH3)CH2}]
(2). Meth od A. The imido complex [(N2Npy-κ3N)Ti(dNtBu)-
(py)] (1; 340 mg, 0.672 mmol), 0.5 mL of 2-butyne, and 2 mL
of benzene were placed in a 30 mL pressure tube equipped
with a Young tap and heated at 80 °C for 14 days. After the
solution thus obtained was cooled, all volatile components were
removed in vacuo and the residue washed with 5 mL of cold
pentane. The yellow solid containd 236 mg of analytically pure
[(N2Npy-κ3N)Ti{N(tBu)C(CHCH3)CH2}] (2). Yield: 73%.
Meth od B. The imido complex [(N2Npy-κ3N)Ti(dNtBu)] (2;
200 mg, 0.435 mmol) and 1 mL of 1,2-butadiene were placed
in a 30 mL pressure tube equipped with a Young tap and
heated at 60 °C for 14 days. The workup was the same as
above. Yield: 76%.
Anal. Calcd for C23H44N4Si2Ti (480.7): C, 57.47; H, 9.23; N,
11.66. Found: C, 57.45; H, 9.04; N, 11.86. IR (Nujol): ν 1587
vw, 1461 vs, 1377s, 1249 w, 918 w, 840 w, 743 vw, 723 vw
In contrast to the pronounced reactivity of 1 toward
oxygen-containing heteroallenes, leading mostly to non-
specific conversions, it proved to be unreactive to the
sulfur analogues. Thus, no reaction was observed with
either CS2 or isothiocyanates.
1
cm-1. H NMR (200.1 MHz, C6D6, 295 K): δ 0.04 [s, 18 H, Si-
(CH3)3], 1.00 (s, 3 H, CCH3), 1,77 (s, 2 H, CH2), 1.81 [s, 9 H,
C(CH3)3], 2.22 [d, 4J (HH) ) 6.3 Hz, 3 H, CHCH3], 3.08 [d,
3J (HH) ) 12.3 Hz, CHHN], 3.70 (d, 2 H, CHHN), 4.76 (q, 1 H,
CHCH3), 6.51 (m, 1 H, H5), 6.80 [d, 3J (HH) ) 17.9 Hz, 1 H,
3
3
5
H3), 7.03 [td, J (H4H5) ) 7.7, J (H4H3) ) 7.9, J (H4H6) ) 1.7
Hz, 1 H, H4], 8.59 [d, 3J (HH) ) 5.4 Hz, 1 H, H6]. 13C{1H} NMR
(50.3 MHz, C6D6, 295 K): δ 0.1 [Si(CH3)3], 13.6 (CH3), 23.3
(CH3), 30.4 (CHCH3), 46.5 (CCH3), 56.4 [C(CH3)3], 62.4 (CH2),
63.5 (CH2N), 86.7 (CHCH3), 120.6 (C3), 121.7 (C5), 138.3 (C,4
140.7 (CdCHCH3), 145.7 (C6), 159.8 (C2).
Con clu sion s
The reaction of the imidotitanium complexes 1 and
1a with 2-butyne and 1-phenylpropyne has led to the
unusual transformation to the metallacycles 2 and 3,
which are equally accessible via 2 + 2 cycloaddition of
the imido compounds with the respective allenes. The
remarkable products of a C-N coupling reaction may
be viewed as dimetalated enamines, the reactivity of
which will be the subject of future investigations. In
contrast, the pronounced reactivity of the TidN double
bond toward polar unsaturated substrates has set limits
to the possibility of selective 2 + 2 cycloaddition of 1
with these types of substrates.
P r epar ation of [(N2Npy-K3N)Ti{N(tBu )C(CHC6H5)CH2}]
(3). Meth od A. The imido complex [(N2Npy-κ3N)Ti(dNtBu)-
(py)] (1; 240 mg, 0.475 mmol), 0.5 mL of 3-phenylpropyne, and
2 mL of benzene were placed in a 30 mL pressure tube
equipped with a Young tap and heated at 80 °C for 14 days.
After the solution thus obtained was cooled, all volatile
components were removed in vacuo and the residue washed
with 5 mL of cold pentane. The yellow solid containd 180 mg
of analytically pure [(N2Npy-κ3N)Ti{N(tBu)C(CHC6H5)CH2}]
(3). Yield: 70%.
Meth od B. The imido complex [(N2Npy-κ3N)Ti(dNtBu)] (2;
200 mg, 0.435 mmol) and 1 mL of phenylallene were placed
in a 30 mL pressure tube equipped with a Young tap and
heated at 60 °C for 14 days. The workup was the same as
above. Yield: 69%.
Exp er im en ta l Section
All manipulations were performed under an inert-gas
atmosphere of dried argon in standard (Schlenk) glassware
which was flame-dried with a Bunsen burner prior to use.
Solvents were dried according to standard procedures and
saturated with Ar. The deuterated solvents used for the NMR
spectroscopic measurements were degassed by three successive
“freeze-pump-thaw” cycles and dried over 4 Å molecular
sieves. Solids were separated from suspensions by centrifuga-
tion, thus avoiding filtration procedures. The centrifuge em-
ployed was a Rotina 48 (Hettich Zentrifugen, Tuttlingen,
Germany) which was equipped with a specially designed
Schlenk tube rotor.27
The 1H, 13C, and 29Si NMR spectra were recorded on a
Bruker AC 200 spectrometer equipped with a B-VT-2000
variable-temperature unit (at 200.13, 50.32, and 39.76 MHz,
respectively) with tetramethylsilane as references. Infrared
spectra were recorded on Perkin-Elmer 1420 and Bruker IRS
25 FT spectrometers.
Anal. Calcd for C28H46N4Si2Ti (542.8): C, 61.96; H, 8.54; N,
10.32. Found: C, 61.89; H, 8.59; N, 10.28. IR (Nujol): ν 1575
w, 832 w, 1459 vs, 1377 s, 1249 s, 1050 w, 902 vw, 844 m, 774
1
vw, 750 m, 719 vw, 688 vw cm-1. H NMR (200.1 MHz, C6D6,
295 K): δ -0.03 [s, 18 H, Si(CH3)3], 0.97 (s, 3 H, CCH3), 1.81
[s, 9 H, C(CH3)3], 2.03 (s, 2 H, CH2), 3.03 [d, 2J (HH) ) 12.8
Hz, 2 H, CHHN], 3.71 (d, 2 H, CHHN), 5.86 [s, 1 H, CH(C6H5)],
3
3
5
6.50 [ddd, J (H5H4) ) 7.6 Hz, J (H5H6) ) 5.6 Hz, J (H5H3) )
1.2 Hz, 1 H, H5], 6.76 [dd, J (H3H4) ) 7.9 Hz, 1 H, H3], 6.95-
3
7.06 [m, 2 H, H4 (C5H5N), H4 (C6H5)], 7.37 [m, 2 H, H3, H5
(C6H5N)], 7.79 [m, 2 H, H2, H6 (C6H5)], 8.42 [ddd, H6 (C5H4N)].
13C{1H} NMR (50.3 MHz, C6D6, 295 K): δ 0.0 [Si(CH3)3], 23.4
(CCH3), 30.6 [C(CH3)3], 47.5 [C(CH3)3], 56.2 (CCH3), 58.0 (CH2),
63.6 (CH2N), 96.4 [CH(C6H5)], 120.4 [C3 (C5H4N)], 121.4 [C4
(C6H5)], 122.0 [C5 (C5H4N)], 127.9 [C2, C6 (C6H5)], 128.3 [C3,
C5 (C6H5)], 138.7 [C4 (C5H4N)], 144.23 [C1 (C6H5)], 145.8 [C6
(C5H5N)], 147.7 [CdCH(C6H5)], 159.5 [C2 (C5H5N)].
Elemental analyses were carried out in the microanalytical
laboratory of the chemistry department at the University of
Wu¨rzburg or Nottingham. The imidotitanium complexes [(N2-
Npy-κ3N)Ti(dNtBu)(py)] (1) and the complexes [(N2Npy-κ3N)-
Ti(dNtBu)] (1a ) were prepared as previously reported by
Attem p ted Cr ossover Exp er im en t of [(N2Np y-K3N)Ti-
{N(tBu )C(CHCH3)CH2}] (2) w ith P h en yla llen e. [(N2Npy-
κ3N)Ti{N(tBu)C(CHCH3)CH2}] (30 mg, 0.0625 mmol) was
dissolved in C6D6 (0.5 mL) in an NMR tube, and an excess of
phenylallene (58 mg, 0.0 mmol) added to the solution. The
reaction mixture was heated at 80 °C over a period of 3 weeks,
during which time no reaction was observed.
(27) Hellmann, K. W.; Gade, L. H. Verfahrenstechnik 1997, 31(5),
70.
(28) Ruitenberg, K.; Kleijn, H.; Elsevier, C. J .; Meijer, J .; Vermeer,
P. Tetrahedron Lett. 1981, 1451.

C-N Coupling Reactions with an Imidotitanium Complex
Organometallics, Vol. 20, No. 15, 2001 3313
P r ep a r a tion of [(N2Np y-K3N)Ti{N(tBu )C(N-2,6-C6H3-
iP r 2)O}(p y)] (4). The imido complex [(N2Npy-κ3N)Ti(dNtBu)-
(py)] (1; 410 mg, 0.810 mmol) was dissolved in benzene (30
mL), and 2,6-diisopropylphenyl isocyanate was added via a
syringe (165 mg, 173 µL, 0.81 mmol). The solution was stirred
for 10 min before the volatile components were removed under
pressure. The red solid was extracted into pentane (20 mL),
and the extract was cooled to -25 °C. The product [(N2Npy-
κ3N)Ti{N(tBu)C(N-2,6-C6H3iPr2)O}(py)] (4) was isolated as a
microcystalline red powder. Yield: 387 mg (67%). Anal. Calcd
for C37H60N6OSi2Ti (692.97): C, 62.7; H, 8.5; N, 11.9. Found:
C, 60.5; H, 8.1; N, 11.5. IR (Nujol): 1600 m, 1540 m, 1348 w,
1332 w, 1288 w, 1236 m, 1212 w, 1172 m, 1103 w, 1082 w,
1070 w, 1064 w, 1039 w, 1012 w, 964 w, 952 w, 934 w, 903 w,
886 w, 858 m, 840 m, 801 w, 773 w, 755 w, 696 w, 681 w, 663
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for Com p lexes 2 a n d 3
2
3
empirical formula
fw
C
23H44N4Si2Ti
C28H46N4Si2Ti
542.77
480.70
cryst syst
space group
monoclinic
C2/c (No. 15)
orthorhombic
Pna21 (No. 33)
unit cell dimens
a/Å
b/Å
c/Å
28.721(7)
10.450(2)
18.886(4)
100.50(2)
5567(2)
8
21.060(5)
10.250(4)
30.243(12)
â/deg
V/Å3
Z
6529(4)
8
1.104
D
calcd/Mg m-3
1.147
radiation (λ/Å)
Mo KR (0.710 73)
Mo KR (0.710 69)
1
w, 634 w, 604 w, 582 w, 570 w, 545 w, 462 w, 440 w cm-1. H
µ/mm-1
0.410
0.356
NMR (300.1 MHz, C6D6, 295 K): δ 0.40 [s, 18 H, Si(CH3)3],
0.45 (d, 3 H, CHMeMe, 3J (HH) ) 6.8 Hz), 0.69 (d, 3 H,
CHMeMe, 3J (HH) ) 6.8 Hz), 0.78 (s, 3 H, CCH3), 0.82 (d, 3 H,
F(000)
2080
2336
cryst size/mm
θ range/deg
limiting hkl indices
0.38 × 0.38 × 0.22 0.45 × 0.44 × 0.44
2.08-23.00 2.10-21.00
-1 to 24, -11 to 1, -21 to 1, -1 to 10,
-20 to 20 -1 to 30
4176 4584
3
3
CHMeMe, J (HH) ) 6.9 Hz), 0.98 (d, 3 H, CHMeMe, J (HH)
3
) 6.9 Hz), 1,58 [s, 9 H, C(CH3)3], 2.21 [d, J (HH) ) 12.9 Hz,
no. of rflns collected
no. of indep rflns (Rint
max, min transmissn
no. of data/restraints/
params
CHHN], 2.31 [d, 3J (HH) ) 12.9 Hz, CHHN], 2.67 [sept, 1H,
)
3391 (0.0893)
0.799, 0.682
3391/22/271
3769 (0.1010)
0.656, 0.560
3769/54/434
3
3
CHMe2, J (HH) ) 6.8 Hz], 2.77 [sept, 1H, CHMe2, J (HH) )
6.9 Hz], 3.33 [d, 3J (HH) ) 12.9 Hz, CHHN], 3.72 [d, 3J (HH) )
12.9 Hz, CHHN], 6.69 (m, 1 H, H5), 6.74 [t, 2H, J (HH) ) 6.3
3
Hz, m-C5H5N], 6.83-6.94 (m, overlapping m-C6H3iPr2 and H3),
6.98 (m, 1 H, p-C5H5N), 7.01 (d, 1 H, 3J (HH) 7.6 Hz,
p-C6H3iPr2), 7.04 [td, 1 H, 3J (H4H5) ) 7.7, 3J (H4H3) ) 7.9,
5J (H4H6) ) 1.7 Hz, H4], 9.35 [d, 2 H, 3J (H6H5) ) 4.3 Hz,
S on F2
0.862
0.904
final R indicesa
I > 2σ(I)
R1 ) 0.0665,
wR2 ) 0.0983
R1 ) 0.1821,
wR2 ) 0.1221
0.0219, 0.0
R1 ) 0.0980,
wR2 ) 0.2162
R1 ) 0.2633,
wR2 ) 0.2802
0.1326, 0.0
m-C5H5N], 9.66 [d, 1 H, J (HH) ) 6.4 Hz, H6]. 13C{1H} NMR
3
all data
(75.5 MHz, C6D6, 295 K): δ 1.9, 3.1 [Si(CH3)3], 22.1 (CH3C),
23.6 (CHMeMe), 23.7 (CHMeMe), 24.0 (CHMeMe), 25.1
(CHMeMe), 28.4(2 × overlapping CHMe2), 33.5 [NC(CH3)3],
49.1 [C(CH2N)2], 56.3, 64.4 (CH2N), 64.6 (NCMe3), 119.8 (C5),
122.1, 123.0 (m-C6H3iPr2), 123.3 (m-C5H5N), 136.8 (C4), 139.9
(p-C5H5N), 137.4 (ipso-C6H3iPr2), 145.7, 156.9 (o-C6H3iPr2),
151.7 (o-C5H5N), 151.8 (C6), 163.2 (C2), 167.1 (OCdN).
X-r a y Cr ysta llogr a p h ic Stu d ies of 2 a n d 3. Da ta Col-
lection for 2 a n d 3. Crystals of 2 and 3 were mounted on a
quartz fiber in Lindemann capillaries under argon and in an
inert oil. X-ray intensity data were collected with graphite-
monochromated radiation, on a Siemens P4 four-circle diffrac-
tometer. The only crystals that could be obtained of 3 diffracted
very weakly at high angle. Details of the data collection and
refinement and crystal data are listed in Table 2. Lorentz-
polarization and absorption corrections were applied to the
data of both compounds.
weights a, ba
max, min peaks in final 0.325, -0.294
0.819, -0.426
diff map/e Å-3
a
S ) [∑w(Fo2 - Fc2)2/(n - p)]2, where n ) number of reflections
and p ) total number of parameters. R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2
) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]2]1/2, where w-1 ) [σ2(Fo)2 + (aP)2 +
2
bP] and P ) [max(Fo2,0) + 2(Fc2)]/3.
displacement parameters set equal to 1.2 times the Ueq value
of the parent carbon atoms for the methylene and aromatic
carbon groups and 1.5 times the Ueq value for methyl groups.
For 2 semiempirical absorption corrections were applied using
ψ-scans.29 After initial refinement with isotropic displacement
parameters empirical absorption corrections30 were applied to
the data of 3. All full-occupancy non-hydrogen atoms were
assigned anisotropic displacement parameters in the final
cycles of full-matrix least-squares refinement.
Str u ctu r e Solu tion a n d Refin em en t for 2 a n d 3. The
positions of most of the non-hydrogen atoms were located by
direct methods.29 The remaining non-hydrogen atoms were
revealed from subsequent difference Fourier sytheses. In the
structure of 3 there were two independent molecules per
equivalent position. Relatively high displacement parameters
for the methyl groups in 3 were consistent with some rotational
disorder, and some methyl carbon atoms were resolved into
two components of ca. 50:50 occupancy. Refinement was based
on F,2,29 and chemically equivalent bond lengths within the
molecules were constrained to be equal within an esd of 0.02.
All hydrogen atoms were placed in calculated positions with
Ack n ow led gm en t. We thank the Deutsche For-
schungsgemeinschaft, the Engineering and Physical
Sciences Research Council, the Fonds der Chemischen
Industrie, the DAAD, and the British Council for
financial support.
Su p p or tin g In for m a tion Ava ila ble: Text detailing the
structure determination and tables of crystallographic data,
positional and thermal parameters, and interatomic distances
and angles for 2 and 3. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM010253G
(29) SHELTXL, PC version 5.03; Siemens Analytical Instruments
Inc., Madison, WI, 1994.
(30) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.