C-C and C-N coupling reactions of an imidotitanium complex with isocyanides

Article abstract of DOI:10.1021/om0005710

Reaction of the imidotitanium complex [(k³-N₂Npy)Ti(=NtBu)(py)] (1) [N₂Npy = (2-C₅H₄N)C(Me)(CH₂NSiMe₃) ₂] with 2,6-xylylisocyanide led to double insertion of the isocy

Full text of DOI:10.1021/om0005710

4784
Organometallics 2000, 19, 4784-4794
C-C a n d C-N Cou p lin g Rea ction s of a n Im id otita n iu m
Com p lex w ith Isocya n id es
Allan Bashall,† Philip E. Collier,§ Lutz H. Gade,*,‡,| Mary McPartlin,†
Philip Mountford,*,§, Stephen M. Pugh,§ Sanja Radojevic,† Martin Schubart,‡
Ian J . Scowen,† and Dominique J . M. Tro¨sch‡
School of Applied Chemistry, The University of North London, Holloway Road,
London N7 8DB, U.K., 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, and Inorganic Chemistry Laboratory,
South Parks Road, University of Oxford, Oxford OX1 3QR, U.K.
Received J uly 3, 2000
Reaction of the imidotitanium complex [(κ3-N2Npy)Ti(dNtBu)(py)] (1) [N2Npy ) (2-
C5H4N)C(Me)(CH2NSiMe3)2] with 2,6-xylylisocyanide led to double insertion of the isocyanide
into the imidotitanium bond and yielded the four-membered titanacycle [(κ3-N2Npy)Ti-
{N(tBu)C(dN-2,6-Me2C6H3)C(dN-2,6-C6H3Me2)}] (2), which was characterized by X-ray
crystallography. While unreactive toward bulky arylisocyanides, 2 reacted with a whole series
of isocyanides R-NC [R ) Et, nBu, iPr, Cy, tBu, PhCH2, p-Tol, (R)-CH(CH3)Ph] to give the
iminoketene complexes [(κ3-N2Npy)Ti{N(tBu)C[N(2,6-Me2C6H3)]C(dCdNR)N(2,6-Me2C6H3)]-
(R ) Et, 3a ; nBu, 3b; iPr, 3c; Cy, 3d ; tBu, 3e; PhCH2, 3f; p-Tol, 3g; (R)-CH(CH3)Ph, 3h ).
Single-crystal X-ray structure analyses of 3d , 3f, and 3g were carried out, which established
the coordination of an imidoylketeneimene fragment to the metal center. The reaction of 1
with alkyl isocyanides bearing H atoms R to the NC group leads to a sequential coupling of
3 molar equiv of the isocyanide with the imido complex, yielding metal-bonded diaminodi-
hydropyrimidine derivatives [(κ3-N2Npy)Ti{N(tBu)[-CdNCH(R)N(CH2R)CHC‚NCH2R}] (R
) H, 4a ; CH3, 4b; C3H7, 4c; Ph, 4d ) and [(κ3-N2Npy)Ti{N(tBu)[-CdNCRR′N(CHRR′)CHC-]
NCHRR′}] (R,R′ ) C5H10, 5a ; CH3,CH3, 5b; Ph,CH3, 5c). An X-ray diffraction study of 4a
unambiguously established the structure of this type of organometallic complex. These
products are thought to be formed in a reaction sequence involving intermediates that are
analogous to the stable complexes 2 and 3a -h . The latter are then converted to the
N-heterocycles via a diazahexatriene generated through a 1,5-sigmatropic H-shift and the
subsequent cyclization to give the pyrimidine derivatives.
In tr od u ction
cently, the use of an appropriate set of monodentate or
multifunctional polydentate ligands has provided a
series of imidotitanium complexes that combine suf-
ficient stability with an adequate reactivity to allow the
systematic development of the reaction chemistry of the
TidNR fragment.2,3
From the early work on terminal imidotitanium
complexes one was tempted to conclude that these
compounds were either relatively unreactive if coordi-
natively saturated or, alternatively, highly reactive, low-
coordinate species of a transient nature.1-3 More re-
A strategy in which the thermal stability of an
imidotitanium complex is achieved by coordinative
saturation which, however, allows the reversible genera-
tion of a reactive low-coordinate species involves the use
of a formally dianionic diamidopyridine ligand system
(A) developed previously by us.4,5 We have shown that
the coordination of this ligand to titanium leads to stable
monomeric imido complexes such as 1.6 This compound
possesses labile pyridine and pyridyl functionalities
† University of North London.
‡ Universite´ Louis Pasteur.
| E-mail: Gade@chimie.u-strasbg.fr.
§ University of Oxford.
E-mail: Philip.Mountford@chemistry.oxford.ac.uk.
(1) Bennet, J . L.; Wolczanski, P. T. J . Am. Chem. Soc. 1997, 119,
10696. (b) Mountford, P. Chem. Commun. 1997, 2127. Lead references
for group 4 imido chemistry: 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. (c) McGrane, P. L.; J ensen, M.; Living-
house, T. J . J . Am. Chem. Soc. 1992, 114, 5459. (d) Dunn, S. C.;
Batsanov, A. S.; Mountford, P. J . Chem. Soc., Chem. Commun. 1994,
2007.
(3) Polse, J . L.; Andersen, R. A.; Bergman, R. G. J . Am. Chem. Soc.
1998, 120, 13405.
(2) Blake, A. J .; McInnes, J . M.; Mountford, P.; Nikonov, G. I.;
Swallow, D.; Watkin, D. J . J . Chem. Soc., Dalton Trans. 1999, 379.
(b) Cloke, F. G. N.; Hitchcock, P. B.; Nixon, J . F.; Wilson D. J .;
Mountford, P. Chem. Commun. 1999, 661. (c) Pugh, S. M.; Tro¨sh, 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,
submitted.
(4) 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.
(5) Gade, L. H. Chem. Commun. 2000, 173.
(6) Blake, A. J .; Collier, P. E.; Gade, L. H.; McPartlin, M.; Mountford,
P.; Schubart, M.; Scowen, I. J . Chem. Commun. 1997, 1555.
10.1021/om0005710 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 10/21/2000

C-C and C-N Coupling Reactions
Organometallics, Vol. 19, No. 23, 2000 4785
Ch a r t 1
that, under appropriate reaction conditions, may dis-
sociate to yield unsaturated and highly reactive species
hitherto generally only accessible via irreversible ther-
molyses of appropriate precursors.1a
The high polarity of the imido-metal bond in the
complexes of the titanium triad makes this structural
unit the preferred point of attack for polar unsaturated
organic substrates. Far from being an ancillary ligand,
as in much of the chemistry of the imido complexes of
the metals further to the right in the transition series,7
the imidotitanium unit may be a synthon in element-
nitrogen coupling reactions in organic synthesis. In this
paper we describe the C-N and C-C- coupling reac-
tions of the imidotitanium complex 1 with isocyanides,
along with a mechanistic study of these transformations.
They demonstrate that the patterns of reactivity that
are observed may be useful in the synthesis of N-
heterocycles. Three reports of the reaction of imido
complexes with isocyanides have been published previ-
ously.8 A part of this work has been communicated.6
Resu lts a n d Discu ssion
F igu r e 1. Molecular structure of complex 2. The principal
bond lengths and interbond angles are listed in Table 1.
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
[(K3-N2Np y)Ti{N(tBu )C(dN-2,6-Me2C6H3)C(dN-2,6-
Me2C6H3)}] (2). The reaction of the previously reported
imido titanium compound [(κ3-N2Npy)Ti(dNtBu)(py)]
(1)6 with 2,6-xylylisocyanide was carried out with the
aim of obtaining the product of a C-N coupling reaction,
a metal-bonded carbodiimide. Such a reaction has been
reported by Bergman and co-workers in their study of
the reactivity of imido-zirconium and -iridium com-
plexes toward tBuNC.8a,b The latter proved to be un-
reactive toward 1, while a whole range of isocyanides
studied in this work reacted immediately. However, no
product of single C-N coupling reaction could be
isolated with any of the substrates. The most straight-
forward reaction was that of 1 with xylylisocyanide,
which cleanly gave the product of a double insertion into
the imidotitanium bond, [(κ3-N2Npy)Ti{N(tBu)C(dN-
2,6-Me2C6H3)C(dN-2,6-Me2C6H3)}] (2) (Scheme 1).
This complex is obtained as a dark green solid that
is sparingly soluble in aromatic hydrocarbons but could
be recrystallized from thf to yield crystals suitable for
an X-ray diffraction study. Its molecular structure is
depicted in Figure 1, and the principal bond lengths and
angles are listed in Table 1.
Sch em e 1. Dou ble In ser tion of 2,6-Xylylisocya n id e
in to th e TidNR Un it of 1 to Give th e Tita n a cycle 2
Compound 2 has an interesting molecular geometry
due to the coordination of the tridentate diamidopyri-
dine ligand and the organometallic NCC fragment
which is part of a metallacycle. It may be viewed as a
highly distorted trigonal bipyramidal arrangement with
the pyridyl-N atom and the tBuN unit derived from the
imido ligand occupying the apical positions while the
amido functions and C(5) of the metallacycle are in the
equatorial plane. This results in an arrangement that
is closely related to the postulated transition state
structure in Ugi’s turnstile mechanism for the polytopal
rearrangement of pentacoordinate phosphorus com-
pounds.9
(7) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.
(8) Walsh, P. J .; Hollander, F. J .; Bergman, R. G. Organometallics
1993, 12, 3705. (b) Glueck, D. S.; Wu, J . X.; Hollander, F. J .; Bergman,
R. G. J . Am. Chem. Soc. 1991, 113, 2041. (c) Danopoulos, A. A.;
Wilkinson, G.; Sweet, T. K. N.; Hursthouse, M. B. J . Chem. Soc., Dalton
Trans. 1996, 271.
There are two main deviations from ideal trigonal
bipyramidal geometry. First the deviation from the ideal
value of 180° by the angle between the “apical” atoms,

4786 Organometallics, Vol. 19, No. 23, 2000
Ta ble 1. Selected Bon d Len gth s a n d An gles for Com p lexes 2, 3d , 3f, 3g, a n d 4a
Bashall et al.
2
3d
3f
3g
4a
(a) Lengths (Å)
2.294(3)
1.908(3)
1.896(3)
2.050(3)
Ti-N(1)
2.195(9)
1.899(9)
1.900(8)
2.024(8)
2.346(5)
1.906(4)
1.900(4)
2.058(4)
1.983(4)
2.287(6)
1.901(5)
1.885(5)
2.049(5)
2.013(5)
2.282(2)
1.937(2)
1.890(2)
2.035(2)
1.964(2
Ti-N(2)
Ti-N(3)
Ti-N(4)
Ti-N(5)
2.012(3)
Ti-C(5)
2.249(11)
1.36(1)
1.26(1)
1.57(1)
1.27(1)
N(4)-C(4)
N(5)-C(5)
C(4)-C(5)
C(4)-N(6)
C(5)-C(6)
N(2)-C(2)
N(3)-C(3)
C(6)-N(7)
N(5)-C(51)
N(6)-C(7)
N(6)-C(61)
N(7)-C(71)
N(7)-C(7)
1.380(5)
1.422(5)
1.481(5)
1.295(5)
1.325(5)
1.481(5)
1.483(5)
1.226(5)
1.442(5)
1.372(7)
1.426(7)
1.480(7)
1.302(7)
1.316(8)
1.464(7)
1.472(7)
1.222(7)
1.447(5)
1.371(8)
1.415(8)
1.480(9)
1.294(8)
1.331(9)
1.486(7)
1.478(7)
1.224(8)
1.451(6)
1.379(3)
1.393(4)
1.485(4)
1.298(4)
1.350(4)
1.474(3)
1.476(3)
1.414(4)
1.462(4)
1.457(4)
1.45(1)
1.48(1)
1.397(9)
1.40(1)
1.407(5)
1.490(5)
1.397(5)
1.471(7)
1.413(6)
1.424(8)
1.450(5)
(b) Angles (deg)
77.8(1)
89.6(1)
166.6(1)
90.6(1)
106.2(1)
101.4(1)
137.0(1)
103.3(1)
115.1(1)
80.9(1)
112.4(2)
115.4(2)
116.7(3)
113.2(3)
N(1)-Ti-N(2)
82.2(4)
90.1(4)
158.6(4)
97.1(4)
107.7(4)
102.8(4)
133.6(4)
107.7(4)
118.7(4)
64.2(4)
110.7(6)
112.2(7)
104.9(6)
80.1(2)
86.0(2)
172.0(2)
93.6(2)
108.5(2)
99.9(2)
131.0(2)
101.5(2)
119.6(2)
80.3(2)
113.7(3)
113.9(3)
117.0(4)
115.2(3)
78.1(2)
89.4(2)
167.8(2)
91.5(2)
79.48(9)
85.64(9)
163.96(9)
88.81(9)
108.5(1)
98.64(9)
131.9(1)
109.9(1)
117.0(1)
80.60(9)
111.3(2)
115.7(2)
112.2(2)
114.5(2)
N(1)-Ti-N(3)
N(1)-Ti-N(4)
N(1)-Ti-N(5)/C(5)
N(2)-Ti-N(3)
107.8(2)
101.0(2)
135.3(2)
102.3(2)
115.6(2)
80.6(2)
112.1(4)
113.9(4)
116.6(4)
113.6(4)
N(2)-Ti-N(4)
N(2)-Ti-N(5)/C(5)
N(3)-Ti-N(4)
N(3)-Ti-N(5)/C(5)
N(4)-Ti-N(5)/C(5)
Ti-N(2)-C(2)
Ti-N(3)-C(3)
Ti-N(4)-C(4)
Ti-N(5)-C(5)
Ti-C(5)-C(4)
88.7(6)
Ti-N(5)-C(51)
Ti-C(5)-N(5)
134.3(3)
132.0(3)
134.2(4)
128.3(2)
153.0(8)
114.9(9)
118.3(1)
126.3(9)
117.6(9)
N(2)-C(2)-C(1)
N(3)-C(3)-C(1)
N(4)-C(4)-N(6)
N(5)-C(5)-C(4)
N(5)-C(5)-C(6)
C(4)-C(5)-C(6)
C(5)-C(6)-N(7)
N(6)-C(6)-N(7)
C(4)-N(6)-C(61)
C(4)-N(6)-C(7)
C(6)-N(7)-C(71)
115.9(3)
117.1(3)
123.4(4)
116.5(3)
120.9(4)
122.1(4)
170.3(4)
117.1(4)
117.8(4)
124.7(5)
115.5(5)
120.8(5)
123.5(5)
170.8(6)
116.4(5)
119.3(6)
123.4(6)
116.0(6)
121.0(6)
122.7(7)
168.9(7)
117.5(2)
116.5(2)
125.9(3)
114.3(2)
127.5(3)
117.6(3)
120.7(3)
116.8((3)
126.5(9)
124.2(4)
121.0(4)
125.2(5)
120.7(5)
124.5(6)
124.1(6)
112.6(6)
112.1(3)
N(1)-Ti-N(4) 158.6(4)°, is dictated by the steric strain
of the azatitanacyclobutane ring, which enforces a N(4)-
Ti-C(5) angle of 64.2(4)°. Second, the coordination at
titanium deviates markedly from the anticipated Cs
symmetry, with the “equatorial” angles N(2)-Ti-C(5)
and N(3)-Ti-C(5) having values of 133.6(4)° and
118.7(4)°, respectively. The steric reasons for this large
angular distortion can be seen by reference to Figure
1b, which shows a view of the molecule perpendicular
to the N(2)-Ti-N(3) plane; an ortho hydrogen atom of
the pyridyl ring is very close to the xylyl group,
H(15)‚‚‚C(51) 2.47 Å (sum of van der Waals radii 2.95
Å). It appears that the repulsion between these atoms
not only causes the enlargement of N(2)-Ti-C(5) angle
but forces the pyridyl ring from a vertical orientation
by 12.6°.
The NMR spectroscopic data of 2 are very similar to
those obtained for other complexes containing the
diamidopyridine ligand. However, the signal of the H6-
proton in the pyridyl ring is observed at 7.41 ppm and
thus at remarkably high field. The corresponding reso-
nance in all other previously characterized compounds
has been observed between δ 8.4 and 9.5 (the corre-
sponding signal for the free amine is observed at 8.45
ppm).4-6 This high-field shift is thought to be due to the
location of the proton within the anisotropy cone of one
of the xylyl groups. This interpretation is consistent
with the very close contacts between the H6 proton of
the pyridyl [H(15)] and the xylyl group discussed above.
To our knowledge, compound 2 represents only the
second example of a structurally characterized azatitana-
cyclobutane. We recently reported the reaction product
of methylallene with the imidototanium complex 1
giving the metallacycle I, depicted in Figure 2.10 The
(9) Ugi, I.; Marquarding, D.; Klusacek, H.; Gokel, G.; Gillespie, P.
Angew. Chem. 1970, 82, 741. (b) Ugi, I.; Marquarding, D.; Klusacek,
H.; Gillespie, P.; Ramirez, F. Acc. Chem. Res. 1971, 4, 288. See also:
Wang, P.; Agrafiotis, D. K.; Streitwieser, A.; v. R. Schleyer, P. J . Chem.
Soc., Chem. Commun. 1990, 201, and references therein.
(10) Bashall, A.; Collier, P. E.; Gade, L. H.; McPartlin, M.; Mount-
ford, P.; Tro¨sch, D. J . M. Chem. Commun. 1998, 2555.

C-C and C-N Coupling Reactions
Organometallics, Vol. 19, No. 23, 2000 4787
Sch em e 2. Rea ction of 2 w ith Isocya n id es to Give th e Im id oylk eten eim in e Com p lexes 3a -h
Ta ble 2. Ch a r a cter istic Sp ectr oscop ic Da ta of th e
Im id oyl Im in ok eten e Com p lexes
IR ν(iminoketene),
13C NMR CâdCRdN,
compound
cm-1
ppm
3a
3b
3c
3d
3e
3f
1976
1969
1973
1967
1967
1982
1954
1963
102.3, 193.1
101.7, 193.6
102.8, 190.3
104.0, 187.1
102.6, 197.2
103.4, 189.7
105.0, 200.4
104.8, 193.6
3g
3h
Reaction of 2 with a whole series of isocyanides R-NC
[R ) Et, nBu, iPr, Cy, tBu, PhCH2, p-Tol, (R)-CH(CH3)-
Ph] led to the selective conversion to the complexes 3a -
h , which contain an imidoylketimine unit coordinated
to the metal center and are the products of a triple
isocyanide coupling reaction (Scheme 2).
F igu r e 2. Comparison of the metric parameters of the
four-membered metallacycle in 2 with the titanacycles in
I-III reported in the literature; tripod ) ligand A.
Whereas compounds 3a , 3b, 3f, and 3g are generated
instantaneously at ambient temperature, the complete
conversion to 3c, 3d , and 3h takes ca. 30 min, and the
reaction with tBuNC requires 24 h for completion. The
most characteristic spectroscopic featutes of 3a -h are
the infrared band of the keteneimine unit that is
observed between 1964 and 1982 cm-1 and the 13C NMR
chemical shifts of the same fragment, which are given
in Table 2. The imine band that would be expected in
the range between 1540 and 1615 cm-1 is obscured by
the absorptions of the pyridyl unit. The proximity of one
of the xylyl rings and the pyridyl ring again leads to a
significant high-field shift of the resonance attributable
to the H6 proton of the pyridyl unit, which is observed
below 7.15 ppm in all cases.
The unusual combination of polar unsaturated func-
tional groups in the organometallic fragment obtained
by imido-isocyanide coupling made it desirable to
obtain detailed structural data for this type of complex.
Single crystals of compounds 3a , 3d , 3f, and 3g were
obtained, and single-crystal X-ray structure analyses of
all four complexes were carried out. Although the basic
features of its molecular structure are established, due
to the poor quality of the data obtained for 3a , a
discussion of the structural parameters of this com-
pound is not given. The molecular structures of 3d , 3f,
and 3g are shown in Figure 3, and the principal bond
lengths and angles are listed in Table 1.
only other structures reported in the literature that are
related to this system are the azatinanacyclobutenes
[Cp*2Ti{κ-C,N-Nd(tBu)-C(dCH2)}] (II) and [(CpTiCl)2-
(µ-N2C2Xyl2)] (III).11,12
It is instructive to compare the bond lengths in the
metallacycles of 2 and I-III. The Ti-N distances vary
between 1.904(3) Å in I and 2.024(8) Å in 2 and do not
seem to be strongly affected by the substituent (or
absence of a substituent) at the nitrogen atom. The
Ti-C distance of 2.249(11) Å in 2 is the greatest in all
the structures compared in Figure 2, which may be a
consequence of interligand repulsion between the xylyl
group and the pyridyl unit of the tripodal ancillary
ligand.
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
t h e Im in ok et en e Com p lexes [(K3-N2Np y)Ti{N-
(tBu )C[N(2,6-Me2C6H3)]C(dCdNR)N(2,6-Me2C6H3)}]
(R ) Et, 3a ; n Bu , 3b; iP r , 3c; Cy, 3d ; tBu , 3e; P h CH2,
3f; p-Tol, 3g; (R)-CH(CH3)P h , 3h ). The clean reaction
of 1 with xylylisocyanide to give complex 2 is probably
a consequence of the steric demand of the 2,6-xylyl
groups, which suppresses further reaction with excess
xylylisocyanide. Another factor may be the low solubility
of the reaction product in benzene, which leads to
immediate precipitation upon its formation. That the
metallacycle 2 is by no means an unreactive species is
apparent from its interaction with isocyanides other
than the bulky 2,6-xylylisocyanide or 2,6-diisopropyl-
phenylisocyanide.
The five-membered azatitanacyclopentane ring, with
the iminoketene [C(5)-C(6)-N(7)] and an imine [C(4)-
N(6)] group adjacent to each other, is the structural
centerpiece in the molecular structures of the three
complexes. The keteneimine unit is positioned between
the two 2,6-xylyl groups, which, most probably for steric
reasons, are oriented orthogonal to it. The reduced steric
strain imposed by the five-membered metallacycle in
(11) Beckhaus, R.; Strauss, I.; Wagner, T. Angew. Chem., Int. Ed.
Engl. 1995, 34, 688.
(12) Hessen, B.; Blenkers, J .; Teuben, J . H. Organometallics 1989,
8, 830.

4788 Organometallics, Vol. 19, No. 23, 2000
Bashall et al.
172.0(2)°; 3g, 167.8(2)°] but considerably less so than
in 2 [158.6(4)°]. The three molecular structures show
distortions from idealized Cs symmetry very similar to
those illustrated in Figure 1b for compound 2, with the
equatorial angles N(2)-Ti-N(5) in 3d , 3f, and 3g [range
131.0(2)-137(1)°] being very much larger than the
equivalent equatorial angles N(3)-Ti-N(5) [range
115.1(1)-119.6(2)°] and the pyridyl ring being tilted
from vertical relative to the T-N(2)-N(3) plane (dihe-
dral angles 3d , 77.4°; 3f, 86.3°; 3g, 77.1°). These
distortions are again attributable to repulsion between
the pyridyl hydrogen atom H(15) and the xylyl unit,
which are in very close contact [H(15)‚‚‚C(51) 3d , 2.37;
3f, 2.38; 3g, 2.36 Å]. This proton, H6 in the NMR
spectrum, is therefore expected to lie in the magnetic
anisotropy cone of the aryl ring, which is consistent with
1
the observation of the H NMR resonance at high field
as discussed above. The amido-N-Ti bond lengths as
well as the pyridyl-N-Ti bond lengths are unexcep-
tional.
Compounds 3d , 3f, and 3g are the first structurally
characterized complexes in which a iminoketene group
and an imino group have a mutual Z-configuration. Both
fragments are not located in the same plane due to steric
interactions between the iminoketene unit and the
neigboring xylyl groups. The torsion angles N(6)-C(4)-
C(5)-N(5) and C(6)-C(5)-N(5)-C(51) are 21.0° and
-19.5° (3d ), 7.8° and -7.8° (3f), and 13.8° and -13.8°
(3g).
There are two examplexs of complexes in the litera-
ture in which an imino group and an iminoketene unit
adopt an E-configuration. Gerlach and Arnold reported
the crystal structure analysis of [(Me3Si)2N}2V-
{tBuNdC(Me)C(CdCdNtBu)NtBu}] [C-C 1.345(4),
C-N 1.205(4) Å, C-C-N 171.7(3)°],13 and Rothwell
et al. synthesized [Ta(OC6H3iPr2-2,6)2Cl2{tBuNdCHC-
(CdCNtBu)NtBu)}] [C-C 1.338(6), C-N 1.206(5) Å,
C-C-N 169.3(4)°].14 The structural parameters of the
iminoketene units found in 3d , 3f, and 3g are thus very
similar: C-C 1.316(8)-1.331(9) Å, C-N 1.224(8)-
1.226(5) Å, C-C-N 168.9(7)-170.8(6)° (Table 1).
Rea ction of th e Im id otita n iu m Com p lex 2 w ith
Isocya n id es Bea r in g Tw o or Th r ee r-H yd r ogen
Atom s. The reaction of methyl isocyanide with 1
occurred spontaneously and highly selectively at ambi-
ent temperature. The conversion to a single product 4a
was complete after addition of 3 molar equiv of the
isocyanide, as was monitored by NMR spectroscopy.
Even if small quantities of the substrate were titrated
to the solution of the imido complex, at 200 K in toluene-
1
d8, no intermediates could be detected in the H NMR
spectra, which were recorded during the procedure. The
1H and 13C NMR spectra of the reaction product were
consistent with the formation of a metal-bound di-
aminodihydropyrimidine, as shown in Scheme 3.
The molecular structure of the reaction product 4a
was established by a single-crystal X-ray structure
analysis and is displayed in Figure 4, while the principal
bond lengths and interbond angles are listed in Table
1.
F igu r e 3. Molecular structure of complexes 3d (a), 3f (b),
and 3g (c). The principal bond lengths and interbond angles
of all three compounds are listed in Table 1.
comparison with the four-membered ring in 2 is re-
flected in the reduced distortion of the molecular
geometry from an idealized trigonal bipyramidal ar-
rangement. There is still a significant deviation of the
angle N(3)-Ti-N(4) from 180° [3d , 166.6(1)°; 3f,
(13) Gerlach, C. P.; Arnold, J . J . Chem. Soc., Dalton Trans. 1997,
4795.
(14) Clark, J . R.; Fanwick, P. E.; Rothwell, I. P. Organometallics
1996, 15, 3232.

C-C and C-N Coupling Reactions
Organometallics, Vol. 19, No. 23, 2000 4789
Sch em e 3. Rea ction of 1 w ith Alk ylisocya n id es to Give 4a -d Con ta in in g a Meta l-Bou n d
Dia m in id ih yd r op yr im id in e Liga n d
cascade of C-N and C-C coupling reactions yielding
the heterocyclic derivatives of 4 described above leads
to the formation of stereogenic centers located on
tertiary carbon atoms. To assess whether it was pos-
sible to obtain quaternary carbon centers in this posi-
tion, the reaction of the imido complex 1 was carried
out using the secondary alkyl isocyanides CyNC, iPrNC,
and (R)-Ph(Me)CHNC. In all three cases an immedi-
ate conversion to the titanium complexes bearing
the N-heterocycles [(κ3-N2Npy)Ti{NtBu}{η2-NCHRR′}-
[-CdNCRR′N(CHRR′)CHC-]] (R,R′ ) C5H10, 5a ; CH3,
CH3, 5b; Ph,CH3, 5c) was observed (Scheme 4).
Whereas compounds 5a and 5c are achiral, a mixture
of two diastereomers in a relative ratio of 4:1 is obtained
for 5b. This is clearly a consequence of the de novo
generation of the stereogenic center in the ring, which
is thought to occur through an intermediate containing
an sp2-carbon in this position (vide infra). The formation
F igu r e 4. Molecular structure of complex 4a . The prin-
cipal bond lengths and interbond angles are listed in Table
1.
of both diastereomers in nonequal amounts is due to
the presence of two additional R-configurated chiral
centers in the molecule which do not undergo a trans-
formation and provide the chiral environment that
favors one of the two diastereomers formed in the
reaction.
As in the molecular structures discussed in the
previous section, complex 4a contains a central five-
coordinate Ti atom with a distorted trigonal-bipyramidal
arrangement of the N-donor atoms [N(1)-Ti-N(41)
163.94(9)°]. The apical positions are occupied by the
pyridyl [Ti-N(41) 2.282(2) Å] and the tert-butyl amide
fragment N-donor atoms. The TidNtBu unit of 1 has
undergone C-N and C-C coupling (with concomitant
C-H bond migration) with three molecules of MeNC to
form a coordinated 3-methyl-5,6-diamino-2,3-dihydro-
P r op osa l of a Mech a n ism of th e Rea ction Ca s-
ca d e Lea d in g to th e Meta l-Bou n d Heter ocycles. As
mentioned above, the reaction of the imido complex 1
with alkyl isocyanides to give the N-heterocyclic frag-
ments coordinated to titanium occurs without detectable
intermediates, which implies that the first reaction step
is the rate-determining step in this conversion. This
situation pertains even if the pyridine-free imidotita-
nium complex [(κ3-N2Npy)TidNtBu] (1a )15 is employed
in these reactions.15 The first C-N coupling reaction is
therefore assumed to be the slow reaction step rather
than the displacement of pyridine. Unfortunately, the
extreme rapidity of this conversion to the cyclized
species even at low temperatures renders the system
unsuitable for a kinetic study using conventional meth-
ods. The proposed mechanism displayed in Scheme 5 is
thus based on the evidence obtained in the reactions
described above and by analogy with known reactions
of isocyanides.
1
pyrimidine derivative. In the H NMR sprectrum of 4a
the signal of the methylene protons in the heterocycle
is observed at δ 4.86, while that of the CH group appears
at 5.45 ppm.
To establish the generality of this reaction, the
analogous conversion was carried out using EtNC,
n-BuNC, and PhCH2NC, which yielded the cycliza-
tion products [(κ3-N2Npy)Ti{η2-NCH2R}[-CdNCH(R)N-
(CH2R)CHC-NtBu] (R ) CH3, 4b; C3H7, 4c; Ph, 4d )
(Scheme 3). Their formulation was established by
elemental analysis and NMR spectroscopy. While the
1
resonance patterns in the H and 13C NMR spectra are
The first step is thought to be the insertion of an
isocyanide group into the imidotitanium unit to give the
metal-bonded carbodiimide in A. Although no model
compound derived from 1 of this first postulated inter-
mediate could be characterized, the existence of such
entirely analogous to those of 4a , the presence of a chiral
center in the ring structure of the coupling product
renders the trimethylsilyl groups and the methylene
groups of the ligand diastereotopic and thus chemically
inequivalent.
Rea ction of th e Im id otita n iu m Com p lex 2 w ith
Isocya n id es Bea r in g On e r-Hyd r ogen Atom . The
(15) Collier, P. E.; Gade, L. H.; Lloyd, J .; McPartlin, M.; Mountford,
P.; Pugh, S. E.; Schubart, M.; Tro¨sch, D. J . M. Inorg. Chem. 2000, in
press.

4790 Organometallics, Vol. 19, No. 23, 2000
Sch em e 4. Rea ction of 1 w ith Secon d a r y Alk yl Isocya n id es to Give 5a -c
Bashall et al.
Sch em e 5. Mech a n istic P r op osa l for th e Ca sca d e of C-N a n d C-C Cou p lin g Rea ction s of 1 w ith
Isocya n id es Givin g 4a -d a n d 5a -c
species has been established by Bergman and co-
workers in their study on the reactivity of zirconium
and iridium imides toward isocyanides.8a,b A rapid
successive step is therefore thought to be a second
insertion of an isocyanide to give four-membered titana-
cycle B. This proposed intermediate is structurally
analogous to complex 2 discussed earlier in this study.
The facile conversion of 2 to give the iminoketene
derivatives 3a -h leads us to consider a similar trans-
formation in the reaction cascade presented in Scheme
5 (giving D). This reaction might occur via a short-lived
carbene intermediate, C, for which we were unable to
obtain direct evidence. However, in view of the well-
established chemistry of Arduengo’s carbenes16 as well
as the known reaction of carbenes and carbenoids with
isocyanides to give iminoketenes,17 this appears to us
to be a reasonable assumption.
ring closure to give the N-heterocyclic structure in 4a -d
and 5a -c. The intermediate E, in which one of the
tetrahedral R-carbon centers of an isocyanide is pla-
narized, also explains the observation of a mixture of
diastereomers in the reaction of 1 with Ph(CH3)CHNC
to give 5c. The latter rearrangement of in situ generated
imidoylketimines to dihydropyrimidines is a known
conversion that may be used in the synthesis of certain
dihydropyrimidine derivatives.18
The cascade of reactions discussed here is an example
of the complicated but selective conversions that iso-
cyanides may undergo with early transition metal
amides. A notable example from the literature of an
imide-isocyanide coupling sequence leading to a metal-
bonded N-heterocyclic system was reported by Wilkin-
son and co-workers, who studied the reactivity of
transient [Cp*CrdN(2,6-iPr2C6H3)] toward isocyanides
resulting in a coordinated amino-functionalized dihydro-
quinoline.8c
The isolation of compounds 3a -h was probably
achieved due to the absence of an N-bonded R-CH unit
at the imino group. In the presence of a hydrogen atom
in this position, a sigmatropic H-shift occurs generating
a metal-bound 1,5-diazahexatriene E, which undergoes
Con clu sion s
The imidotitanium complex 1 undergoes single or
multiple coupling reactions with isocyanides. It has been
possible to structurally characterize the principle types
of products obtained in these reactions. The most
interesting conversion is certainly the reaction cascade
leading to metal-bound diamino dihydropyrimidines and
(16) Arduengo, A. J ., III; Bock, H.; Chen, H.; Dixon, D. A.; Green,
J . C.; Herrmann, W. A.; J ones, N. L.; Wagner, M.; West, R. J . Am.
Chem. Soc. 1994, 116, 6641, and references therein.
(17) Krow, G. R. Angew. Chem., Int. Ed. Engl. 1971, 10, 435. (b)
Flowers, W. T.; Haszeldine, R. N.; Owen, C. R.; Thomas, A. J . Chem.
Soc., Chem. Commun. 1974, 134. (c) Ciganek, E. J . Org. Chem. 1970,
35, 862. (d) Boyer, J . H.; Beverung, W. J . Chem. Soc., Chem. Commun.
1969, 1377. (e) Green, J . A.; Singer, L. A. Tetrahedron Lett. 1969, 5093.
(f) Obata, N.; Takizawa, T. Tetrahedron Lett. 1969, 3403.
(18) Goerdeler, J .; Lindner, C.; Zander, F. Chem. Ber. 1981, 114,
536.

C-C and C-N Coupling Reactions
Organometallics, Vol. 19, No. 23, 2000 4791
in 5 mL of benzene and 1.2 molar equiv of the respective
isocyanide was added to the stirred suspension. The reaction
was monitored by 1H NMR spectroscopy, and the mixture was
worked up after complete conversion was observed (EtNC,
nBuNC 5 min, iPrNC 30 min, CyNC, BzNC, C6H5CH(CH3)-
NC 45 min, p-TolNC tBuNC overnight). The solvent and excess
isocyanide were removed in vacuo; subsequently, the residue
was triturated with 2-4 mL of pentane and centrifuged for
10 min at 2000 rpm. The solid thus obtained was isolated and
dried in vacuo. Compounds 3a -h are brown powders that can
be recrystallized from toluene at -35 °C. Crystals could also
be obtained from the solutions in pentane at -35 °C.
their homologs in the absence of any byproducts. This
not only provides an alternative to established syntheses
of this class of N-heterocycles18 but offers the op-
portunity of further functionalizations of the organic
product. Work toward this aim is currently under way.
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.19
[(K3-N2Np y)Ti[N(tBu )CN(2,6-Me2C6H 3)]C(dCdNE t )N-
(2,6-Me2C6H3)]}] (3a ). Yield: 71%; mp 46 °C. Anal. Calcd for
C
40H61N7Si2Ti [744.02]: C, 64.57; H, 8.26; N, 13.18. Found:
C, 64.80; H, 7.90; N, 12.12. IR (Nujol): 1976 s, 1599 w, 1552
vs, 1463 vs, 1373 m, 1272 m, 1245 s, 1202 m, 1140 w, 1089 w,
1034 s, 1011 w, 930 m, 910 m, 894 w, 863 vs, 832 s, 785 m,
1
676 w, 599 w cm-1. H NMR (400 MHz, C6D6, 295 K): δ 0.19
3
[Si(CH3)3], 0.54 (t, J HH ) 7.2 Hz, 3 H, CH2CH3), 1.02 (s, 3 H,
CCH3), 2.17 [s, 9 H, C(CH3)3], 2.35 [s, 6 H, 2,6-C6H3(CH3)2],
2.64 [s, 6 H, 2,6-C6H3(CH3)2], 2.64 (q, 2 H, CH2CH3), 3.11 (d,
2J HH ) 12.9 Hz, 2 H, CHHN), 4.03 (d, 2 H, CHHN), 6.20 (m, 1
H), 6.72 - 6.95 (m, b, 7 H), 7.12 (s, 1 H). {1H}13C NMR (100.6
MHz, C6D6, 295 K): δ 1.0 [Si(CH3)3], 14.9 (CH3), 19.9 [2,6-
C6H3(CH3)2], 21.2 [2,6-C6H3(CH3)2], 24.2 (CCH3), 31.8 [C(CH3)3],
48.3 (CCH3), 49.0 (CH2CH3), 51.2 [C(CH3)3], 64.8 (CH2N), 102.3
(CdCdN), 120.0, 120.4, 121.4, 125.2, 136.0, 138.0, 147.2, 151.4,
151.6, 159.0, 161.5, 193.1 (CdCdN). {1H}29Si NMR (39.8 MHz,
C6D6, 295 K): δ 4.0.
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.
Elemental analyses were carried out in the microanalytical
laboratory of the chemistry department at the University of
Wu¨rzburg. The imidotitanium complex [(κ3-N2Npy)Ti(dNtBu)-
(py)] (1) was prepared as previously reported by us.6 The
isocyanides were prepared according to synthetic procedures
reported in the literature.20 All other chemicals used as
starting materials were obtained commercially and used
without further purification.
(1) P r ep a r a tion of [(K3-N2Np y)Ti[N(tBu )C(dN-2,6-
Me2C6H3)C(dN-2,6-Me2C6H3)] (2). A suspension of compound
1 (1.00 g ) 1.98 mmol) and 2,6-C6H3(CH3)2NC (550 mg ) 4.19
mmol) in benzene (5 mL) was stirred for 10 min and then
centrifuged for 15 min at 2000 rpm. The liquid phase was
separated from the residue, which was resuspended in 3-4
mL of benzene and centrifuged. The solvent was then sepa-
rated from the residue, which was dried in vacuo. Compound
2 is a dark brown microcrystalline powder that can be
recrystallized from thf. Yield: 75%; mp 24 °C. Anal. Calcd for
[(K3-N2Np y)Ti[N(tBu )CN(2,6-Me2C6H3)]C(dCdNn Bu )N-
(2,6-Me2C6H3)]}] (3b). Yield: 298 mg (63%); mp 46 °C. Anal.
Calcd for C40H61N7Si2Ti [772.08]: C, 65.34; H, 8.49; N, 12.70.
Found: C, 65.39; H, 8.49; N, 12.61. IR (Nujol): 1969 s, 1599
w, 1556 s, 1459 vs, 1373 m, 1264 w, 1245 m, 1198 w, 1085 w,
1034 w, 937 w, 918 m, 887 m, 855 s, 836 m, 789 m, 766 vw,
1
750 vw, 599 w cm-1. H NMR (200.13 MHz, C6D6, 295 K): δ
3
0.2 [Si(CH3)3], 0.74 [t, J HH ) 6.1 Hz, 3 H, (CH2)3CH3], 0.86-
0.98 [m, b, 4 H, CH2(CH2)2CH3], 1.02 (s, 3 H, CCH3), 2.16 [s,
9 H, C(CH3)3], 2.36 [s, 6 H, 2,6-C6H3(CH3)2], 2.60-2.67 (m, Cd
2
CdN-CH2), 2.64 [s, 2,6-C6H3(CH3)2], 3.11 (d, J HH ) 12.8 Hz,
2 H, CHHN), 4.03 (d, 2 H, CHHN), 6.20 (m, 1 H, H3), 6.76-
6.93 (m, b, 8 H, aromatic CH). {1H}13C NMR (100.6 MHz, C6D6,
295 K): δ 1.08 [Si(CH3)3], 19.9 [2,6-C6H3(CH3)2], 20.5 [CH3],
21.2 [2,6-C6H3(CH3)2], 24.2 (CCH3), 31.9 [C(CH3)3], 32.3 (CH2),
48.3 (CCH3), 54.0 (CdNCH2), 62.0 (C(CH3)3), 64.9 (CH2N),
101.7 (CdCdN), 120.0, 120.3, 121.4, 134.2, 136.0, 147.2, 151.5,
151.6, 159.0, 161.5, 193.6 (CdCdN). {1H}29Si NMR (39.8 MHz,
C6D6, 295 K): δ 4.0.
C
37H56N6Si2Ti [688.94]: C, 64.51; H, 8.19; N, 12.20. Found:
C, 63.62; H, 7.97; N, 12.09. IR (Nujol): 1599 m, 1580 m, 1572
s, 1521 vw, 1463 s, 1377 m, 1295 w, 1243 m, 1204 m, 1186 w,
1186 w, 1085 w, 1031 m, 945 vw, 918 w, 867 s, 832 m, 789 w,
1
772 w, 754 w, 727 vw, 645 vw, 602 vw cm-1. H NMR (200.13
[(K3-N2Np y)Ti[N(tBu )CN(2,6-Me2C6H3)]C(dCdNiP r )N-
(2,6-Me2C6H3)]}] (3c). Yield: 77%; mp 52 °C. Anal. Calcd for
MHz, C6D6, 295 K): δ 0.08 [s, 18 H, Si(CH3)3], 0.90 (s, 3 H,
CCH3), 2.02 [s, 9 H, C(CH3)3], 2.09 [s, 6 H, 2,6-C6H3(CH3)2],
C
41H63N7Si2Ti [758.05]: C, 64.96; H, 8.38; N, 12.93. Found:
2
2.64 [s, 6 H, 2,6-C6H3(CH3)2], 3.02 (d, J HH ) 13.0 Hz, 2 H,
C, 61.56; H, 8.15; N, 12.07. IR (Nujol, NaCl): 1982 s, 1965 w,
1601 vw, 1559 s, 1461 vs, 1377 s, 1299 vw, 1260 s, 1245 s,
1203 w, 1166 w, 1090 s, 1033 s, 943 w, 916 w, 891 w, 862 s,
CHHN), 3.63 (d, CHHN), 6.14 (m, 1 H, H3), 6.62 (m, 1 H, H5),
3
6.62 (m, 1 H, Lig.-CH), 6.73 [d, br, J HH ) 10 Hz, 4 H, 2H
H3,5 of 2,6-C6H3(CH3)2], 6.94 [t, br, 2 H, 2H H4 of 2,6-C6H3-
(CH3)2], 7.19 (m, 1 H, Lig.-CH) 7.41 (m, 1 H, H6). {1H}13C NMR
(100.6 MHz, C6D6, 295 K): δ 0.0 [Si(CH3)3], 19.2 [2,6-C6H3-
(CH3)2], 20.0 [2,6-C6H3(CH3)2], 22.9 (CCH3), 30.0 [C(CH3)3], 48.0
(CCH3), 58.9 [C(CH3)3], 63.4 (CH2N), 118.9 (CH), 119.6 (CH),
120.9 (C3), 121.7 (C5), 126.9 (CH), 127.7 (CH), 128.4 (C), 128.7
(C), 138.3 (C4), 147.2 (C6), 151.6 (C), 151.8 (C), 152.3 (C), 158.5
(C2), 212.5 (C). {1H}29Si NMR (39.8 MHz, C6D6, 295 K): δ 2.97.
(2) Gen er al P r ocedu r e for th e Syn th esis of [(K3-N2Npy)-
Ti{N(tBu )C[N(2,6-Me2C6H3)]C(dCdNR)N(2,6-Me2C6H3)] (R
) Et, 3a ; n Bu , 3b; iP r , 3c; Cy, 3d ; tBu , 3e; P h CH2, 3f; p-Tol,
3g; (R)-CH(CH3)P h , 3h ). Complex 2 (200 mg) was suspended
sh, 836 s, 807 s cm-1 1H NMR (400 MHz, C6D6, 295 K): δ
.
0.19 [s, 18 H, Si(CH3)3], 0.59 [d, 3J HH ) 3.2 Hz, 6 H, CH(CH3)2],
1.03 (s, 3 H, CCH3), 2.15 (s, 9H, tBu), 2.34, 2.63 [2H s, 2H 6
2
H, 2,6-C6H3(CH3)2], 2.92 [sep, 1 H, CH(CH3)2], 3.12 (d, J HH
)
12.8 Hz, 2 H, CHHN), 4.02 (d, 2 H, CHHN) 6.20 (m, 1 H, H5),
6.75-7.12 (m, 9 H, aromatic CH). {1H}13C NMR (100.6 MHz,
C6D6, 295 K): δ 1.0 [s, 18 H, Si(CH3)3], 14.2 [C(CH3)3], 19.9
[2,6-C6H3(CH3)2], 21.2 [2,6-C6H3(CH3)2], 22.6 [CH(CH3)2], 24.2
(CCH3), 48.2 (CCH3), 54.9 [CH(CH3)2], 61.2 [C(CH3)2], 64.7
(CH2N), 103.4 (C)CdN), 119.9, 120.2, 121.2, 125.1, 128.7 (CH),
136.3 (C), 137.8 (C4), 147.2 (C6), 151.1, 151.2, 158.8, 161.5 (C),
189.7 (CdCdN). {1H}29Si NMR (39.8 MHz, C6D6, 295 K): δ
3.65.
(19) Hellmann, K. W.; Gade, L. H. Verfahrenstechnik 1997, 31 (5),
[(K3-N2Np y)Ti[N(tBu )CN(2,6-Me2C6H 3)]C(dCdNCy)N-
(2,6-Me2C6H3)]}] (3d ). Yield: 75%; mp 110 °C. Anal. Calcd
70.
(20) Ugi, I.; Meyr, R. Org. Synth. 1961, 41, 300. (b) Ugi, I.; Meyr, R.
Org. Synth. 1961, 41, 1060.
for
C44H67N7Si2Ti [806.09]: C, 66.30; H, 8.35; N, 12.30.

4792 Organometallics, Vol. 19, No. 23, 2000
Bashall et al.
Found: C, 65.79; H, 8.44; N, 11.23. IR (Nujol): 1973 s, 1601
vw, 1551 s, 1462 vs 1377 s, 1250 s, 1233 w, 1191 w, 1167 vw,
1089 w, 1061 vw, 1035 s, 935 vw, 914 vw, 902 vw, 892 vw,
862 s, 836 w, 811 vw, 811 vw, 785 vw, 776 vw, 758 vw, 605 s
cm-1. 1H NMR (200 MHz, C6D6, 295 K): δ 0.20 (s, 18 H, SiMe3),
0.8-1.6 (m, br, 10 H, 5H CH2), 1.02 (s, 3 H, CCH3), 2.10 (s, 9
H, tBu), 2.37 [s, 6 H, 2,6-C6H3(CH3)2], 2.59 (m, 1 H, N-CH),
150.6, 151.5 [2H C1 of 2,6-C6H3(CH3)2], 159.5 [2,6-C6H3-
(CH3)2NC], 161.3 (C2), 200.4 (CdCdN) ppm. {1H}29Si NMR
(39.8 MHz, C6D6, 295 K): δ 3.8.
[(K3-N2Np y)Ti[N(t Bu )CN(2,6-Me 2C6H 3)]C(dCdNCH -
{CH3}P h )-N(2,6-Me2C6H3)]}] (3h ). Yield: 305 mg (73%); mp
50 °C. Anal. Calcd for C46H65N7Si2Ti [820.12]: C, 67.37; H,
7.99; N, 11.96. Found: C, 66.63; H, 7.90; N, 11.40. IR (Nujol):
1963 s, 1490 w, 1445 vs, 1350 s, 1278 m, 1188 w, 1145 vs,
1110 w, 1095 m, 1083 m, 1063 w, 1038 vw, 985 m, 960 m, 944
m, 929 s, 846 m, 820 m, 790 w, 754 vs, 732 s, 678 m, 660 m,
2
2.65 [s, 6 H, 2,6-C6H3(CH3)2], 3.12 (d, J HH ) 12.9 Hz, 2 H,
CHHN), 4.02 (d, 2 H, CHHN), 6.21 (m, 1 H, H5), 6.60-6.95
(m, 8 H, aromatic CH), 7.19 (1 H, CH). {1H}13C NMR (50.3
MHz, C6D6, 295 K): δ 1.0 [Si(CH3)3], 19.9 (CH2), 21.3 (CH2),
22.7 (CH3), 24.2 (CCH3), 25.3 (CH2), 26.1 (CH3), 33.2 [C(CH3)3],
48.2 (CCH3), 61.2 [C(CH3)3], 62.1 (N-CH), 64.8 (CH2N), 102.8
(CdCdN), 119.9 (CH), 120.0 (CH), 121.2 (CH), 125.2 (CH);
128.5 (CH), 128.7 (CH), 136.3 (C), 137.9 (CH), 147.2 (C6), 151.2
(C), 151.3 (C), 158.9 (C), 161.6 (C), 190.3 (CdCdN). {1H}29Si
NMR (39.8 MHz, C6D6, 295 K): δ 3.9.
595 w, 505 w cm-1
0.14 [s, 9 H, Si(CH3)3], 0.24 [s, 9 H, Si(CH3)3], 0.95 (d, J HH
.
1H NMR (200.13 MHz, C6D6, 295 K): δ
3
)
6.7 Hz, 3 H, CHCH3), 1.02 (s, 3 H, CCH3), 2.16 [s, 9 H,
C(CH3)3], 2.31 [s, 3 H, 2,6-C6H3(CH3)(CH3)], 2.33 [s, 3 H, 2,6-
C6H3(CH3)(CH3)], 2.60 [s, 3 H, 2,6-C6H3(CH3)(CH3)], 2.66 [s, 3
H, 2,6-C6H3(CH3)(CH3)], 3.05 (d, 2J HH ) 12.8 Hz, CHHN), 3.17
(d, CHHN), 3.92-4.07 (m, 3 H, CHCH3, CHHN and CHHN),
6.20 (m, 1 H, H3), 6.72-7.14 (m, 13 H, aromatic protons).
{1H}13C NMR (MHz, C6D6, 295 K): δ 0.8 [Si(CH3)3], 1.1 [Si-
(CH3)3], 19.9 [2,6-C6H3(CH3)(CH3)], 20.1 [2,6-C6H3(CH3)(CH3)],
21.2 [2,6-C6H3(CH3)(CH3)], 21.6 [2,6-C6H3(CH3)(CH3)], 23.7
(CHCH3), 24.3 (CCH3), 31.9 [C(CH3)3], 48.4 (CCH3), 61.4
[C(CH3)3], 62.6 (CHCH3), 64.8 (CH2N), 64.9 (CH2N), 104.8
(CdCdN), 120.1, 120.3 (2H CH), 121.4 (C3), 125.3, 125.6, 127.1,
129.8 (je CH), 135.7, 136.8 (2H C), 138.1 (CH), 145.0 (C), 147.3
(CH), 150.9, 151.2, 158.7, 161.5 (4H C), 193.6 (CdCdN).
{1H}29Si NMR (39.8 MHz, C6D6, 295 K): δ 3.9, 4.2.
[(K3-N2Np y)Ti[N(tBu )CN(2,6-Me2C6H3)]C(dCdNtBu )N-
(2,6-Me2C6H3)]}] (3e). Yield: 77%; mp 100 °C. Anal. Calcd
for
C42H65N7Si2Ti [772.08]: C, 65.39; H, 8.49; N, 12.70.
Found: C, 65.79; H, 8.52; N, 12.06. IR (Nujol): 1967 w, 1601
vw, 1553 w, 1458 vs, 1377 s, 1246 w, 1200 vw, 1088 vw, 1033
w, 941 vw, 920 vw, 890 vw, 859 w, 837 vw, 805 vw, 785 vw,
756 vw, 723 vw cm-1 1H NMR (400 MHz, C6D6, 295 K): δ
.
0.19 [Si(CH3)3], 0.66 [s, 9 H, CdCdNC(CH3)3], 1.04 (s, 3 H,
CCH3), 2.13 (s, 9 H, NtBu), 2.35, 2.62 [2,6-C6H3(CH3)2], 3.12
2
(d, J HH ) 12.6 Hz, 2 H, CHHN), 4.01 (d, 2 H, CHHN), 6.22
(H5), 6.67-7.13 (m, 9 H, aromatic CH). {1H}13C NMR (50.3
MHz, C6D6, 295 K): δ 0.9 [Si(CH3)3], 20.0 [2,6-C6H3(CH3)2],
21.3 [2,6-C6H3(CH3)2], 24.2 (CCH3), 29.5 [dCdNC(CH3)3], 32.0
[NC(CH3)3], 48.3 (CCH3), 60.0 [C(CH3)3], 61.2 [C(CH3)3], 64.7
(CH2N), 104.0 (CdCdN), 119.9, 120.0, 121.1, 125.1, 128.1,
128.9 (CH), 136.4 (C), 137.8 (CH), 147.3 (C6), 150.6, 150.8,
158.3, 161.6 (C), 187.1 (CdCdN). {1H}29Si NMR (39.8 MHz,
C6D6, 295 K): δ 3.9.
(3) Gen er a l P r oced u r e for th e Syn th esis of Dih yd r o-
p yr im id in e Com p ou n d s [(K3-N2Np y)Ti{NtBu }{η2-NR }-
[-CdNCH(R)NRCHC-]] (4a -d ). Meth od a . The imido
complex 1 (200 mg, 0.396 mmol) was suspended in the
isocyanide with which it was to be reacted and stirred for 15
min. The solvent was then removed in vacuo and the residue
triturated with 3-5 mL of cold pentane (0 °C). After storing
overnight at -35 °C, the solvent was decanted and the residue
dried in vacuo.
Meth od b. To a solution of 1 (200 mg, 0.396 mmol) in 5 mL
of benzene or toluene was added 3 or more equivalents of
isocyanide. The reaction mixtures turned from yellow to dark
brown. After stirring for the appropriate amount of time
(EtNC, nBuNC, iPrNC: 5-10 min; CyNC, BzNC, C6H5CH-
(CH3)NC: 30 min) the solvent, pyridine, and excess isocyanide
were removed in vacuo, and the residue was triturated with
pentane. After storing at -35 °C overnight, the solvent was
decanted from the solid precipitate, which was dried in vacuo.
[ ( K3 -N 2 N p y ) T i [ N ( t B u ) C N ( 2 ,6 -M e 2 C 6 H 3 ) ] C ( dC d
NCH2P h )N(2,6-Me2C6H3)]}] (3f). Yield: 76%; mp 44 °C. Anal.
Calcd for C44H67N7Si2Ti [798.11]: C, 67.05; H, 7.88; N, 12.16.
Found: C, 65.69; H, 7.81; N, 11.81. IR (Nujol): 1957 s, 1600w,
1553 s, 1460 vs, 1263 s, 1247 s, 1197 w, 1093 w, 1047 w, 1030
m, 913 w, 887 w, 860 m, 833 m, 810 w cm-1 1H NMR (200
.
MHz, C6D6, 295 K): δ 0.18 [s, 18 H, Si(CH3)3], 1.03 (s, 3 H,
CCH3), 2.15 (s, 9 H, NtBu), 2.29 [s, 6 H, 2,6-C6H3(CH3)2], 2.64
[s, 6 H, 2,6-C6H3(CH3)2], 3.10 (d, 2J HH ) 12.8 Hz, 2 H, CHHN),
3.80 (s, 2 H, CH2C6H5), 4.02 (d, 2 H, CHHN), 6.18 (m, 1 H,
H5), 6.72-7.15 (m, 14 H, aromatic CH). {1H}13C NMR (50.3
MHz, C6D6, 295 K): δ 1.0 [Si(CH3)3], 19.7 [2,6-C6H3(CH3)2],
21.0 [2,6-C6H3(CH3)2], 24.1 (CCH3), 31.7 [C(CH3)3], 48.3 (CCH3),
57.6 (CH2C6H5), 61.2 (C(CH3), 64.8 (CH2N), 102.6 (CdCdN),
120.0, 120.4, 121.3, 125.2, 126.6, 128.0, 128.2, 128.3, 128.8
(CH), 135.6 (C), 138.0 (CH), 138.9 (C), 147.0 (CH), 151.2, 151.3,
158.7, 161.3 (C), 197.2 (CdCdN). {1H}29Si NMR (39.8 MHz,
C6D6, 295 K): δ 3.8.
[(K3-N2Npy)Ti{NtBu }{η2-NMe}(-CdNCH2NCH3CHdC-)]
(4a ). Yield: 78%. Anal. Calcd for C25H45N7Si2Ti [547.73]: C,
54.82; H, 8.28; N, 17.90. Found: C, 54.85; H, 8.21; N, 17.96.
IR (benzene): 2940 m, 2870 m, 2840 m, 2810 m, 2770 w, 1625
w, 1595 m, 1575 m, 1530 m, 1465 m, 1428 m, 1358 m, 1240
m, 1142 m, 1054 m, 1040 m, 908 m, 855 m, 774 m, 744 m, 702
m cm-1. 1H NMR (200.13 MHz, C6D6, 295 K): δ -0.05 [s, NSi-
(CH3)3], 1.03 (s, CCH3), 2.06 [s, C(CH3)3], 2.48 (s, TiNCH3), 3.04
[(K3-N2Npy)Ti[N(tBu )CN(2,6-Me2C6H3)]C(dCdNp-Tol)N-
(2,6-Me2C6H3)]}] (3g). Yield: 75%; mp 46 °C. Anal. Calcd for
2
(d, J HH ) 12.9 Hz, CHHNSi), 3.25 (s, NCH3), 3.91 (d,
CHHNSi), 4.86 (s, CH2), 5.45 (s, CH), 6.54 (ddd, H5), 6.84 (ddd,
C
45H63N7Si2Ti [806.09]: C, 67.05; H, 7.88; N, 12.16. Found:
3
3
4
H3, J HH ) 7.9 Hz), 7.05 (dt, H,4 J HH ) 7.6 Hz, J HH ) 1.8
Hz), 8.44 (ddd, H,6 3J HH) 5.5 Hz, 4J HH) 1.5 Hz). {1H}13C NMR
(C6D6, 295 K): δ -0.5 [NSi(CH3)2], 22.9 (CCH3), 30.1 [C(CH3)3],
40.6, 40.7 (NCH3 and TiNCH3), 48.3 (CCH3), 58.7 [C(CH3)3],
64.0 (CH2NSi), 70.3 (CH2-ring), 117.2 (C4N2-CH), 120.6 (C3),
121.3 (C5), 129.3 (C4N2), 134.9 (C4N2), 138.1 (q-C), 146.9 (C6),
160.6 (C2), 162.8 (C4N2-CdN).
C, 66.29; H, 7.82; N, 11.02. IR (Nujol): 1954 vw, 1552 w, 1458
vs, 1377 s, 1277 w, 1255 w, 1204 vw, 1090 vw, 1032 w, 940
1
vw, 916 vw, 860 w, 835 vw, 722 vw cm-1. H NMR (200 MHz,
C6D6, 295 K): δ 0.24 [s, 18 H, Si(CH3)3], 1.02 (s, 3 H, C6H4-
CH3), 1.96, (s, 3 H, CCH3), 2.21 (s, 9 H, tBu), 2.40 (s, 6, 2,6-
C6H3(CH3)2), 2.66 (s, 6 H, 2,6-C6H3(CH3)2), 3.12 (d, 2J HH ) 12.8
Hz, 2 H, CHHN), 4.04 (d, 2 H, CHHN), 6.17 (m,1 H, H5), 6.57-
6.95 (m, 13 H, aromatic protons). {1H}13C NMR (50.3 MHz,
C6D6, 295 K): δ 1.1 [Si(CH3)3], 19.9 [2,6-C6H3(CH3)2], 21.0
(C6H4-CH3), 21.2 [2,6-C6H3(CH3)2], 24.1 (CCH3), 31.6 [NC-
(CH3)3], 48.3 (CCH3), 61.3 [NC(CH3)3], 64.9 (CH2N), 105.0
(CdCdN), 120.0, 121.3, 121.4 [2H C4 of 2,6-C6H3(CH3)2; C3],
124.2 [C2,6 of p-Tol], 125.3 (C5), 128.3, 128.6, 128.7, 128.8 [2H
C3,5 of 2,6-C6H3(CH3)2; C,4 C3,5 of p-Tol], 135.5, 135.8 [2H C2,6
of 2,6-C6H3(CH3)2], 138.1 (C4), 141.0 (C1 of p-Tol), 147.1 (C6),
[(K3-N 2N p y )T i{N t B u }{η-N E t }[-C dN C H C H 3N (C H 2-
CH3)dC-]] (4b). Yield: 76%; mp 16 °C (dec). Anal. Calcd for
C28H53N7Si2Ti [591.83]: C, 56.83; H, 9.03; N, 16.57. Found:
C, 54.64; H, 8.53; N, 15.64. IR (Nujol, KBr): 1461 s, 1377 s,
1245 w, 1091 w, 1920 w, 832 w, 803 w cm-1 1H NMR (400
.
MHz, C6D6, 295 K): δ -0.51 [s, 9 H, Si(CH3)3], -0.1 [s, 9 H,
Si(CH3)3], 1.15 (t, 3J HH ) 7.1 Hz, 3 H, CH3, N3′-CH2CH3), 1.17

C-C and C-N Coupling Reactions
Organometallics, Vol. 19, No. 23, 2000 4793
(s, b, 3 H, CCH3), 1.30 (t, J vic ) 6.9 Hz, 3 H, Ti-N-CH2CH3),
C39H59N7Si2Ti [730.00]: C, 64.17; H, 8.15; N, 13.43. Found:
C, 63.98; H, 8.09; N, 13.25. IR (Nujol, KBr): 1629 vw, 1590
vw, 1570 vw, 1511 vw, 1460 s, 1375 s, 1247 vw, 1169 vw, 1113
3
1.64 (d, J HH ) 6.1 Hz, 3 H, CHCH3), 1.94 (s, 3 H, CH3), 2.90
2
(q, 2 H, N3′-CH2CH3), 3.15 (d, J HH ) 12.6 Hz, CHHN), 3.21
1
(d, CHHN), 3.74 (q, 1 H, Ti-N-CHHCH3), 3.80 (q, 1 H, Ti-
N-CHHCH3), 3.88 (d, 1 H, CHHN), 3.94 (d, 1 H, CHHN), 5.06
vw, 837 w, 743 vww, 719 vw cm-1. H NMR (200 MHz, C6D6,
295 K): δ 0.27 (s, 18 H [Si(CH3)3], 0.75 [d, 3J HH ) 6.3 Hz, 6 H,
TiNCH(CH3)2], 1.06 [d, J vic ) 6.6 Hz, 6 H, N3′CH(CH3)2], 1.17
(CCH3), 1.74 [s, 6 H, C2′(CH3)2], 2.10 [s, 9 H, C(CH3)3], 3.16
[sep, 1 H, TiNCH(CH3)2], 3.38 [sep, 1 H, NH3′CH(CH3)2], 3.96
(d, 2J HH ) 13.1 Hz, CHHN), 4.16 (d, 2 H, CHHN), 5.39 (s, 1 H,
H4′, 6.69 (m, 1 H, H3), 7.07 (m, 1 H, H5), 7.19 (m, 1 H, H4),
8.50 (m, 1 H, H6). {1H}13C NMR (50.3 MHz, C6D6, 295 K): δ
0.8 [Si(CH3)3], 23.8 [TiNCH(CH3)2], 28.5 (CCH3), 28.4 [N3′CH-
(CH3)2], 29.8 [C(CH3)2], 31.4 [C(CH3)3], 47.4 [TiNCH(CH3)2],
52.2 [N3′CH(CH3)2], 55.9 (CCH3), 58.8 [C(CH3)3], 64.1 (CH2N),
72.9 (C2′), 111.3 (C4′), 119.9 (C5′), 121.1, 123.6 (C3, C5), 122.1
(C5′), 135.8 C,6 150.4 (C4), 159.1, 164.4 (C2, C6′). {1H}29Si NMR
(39.8 MHz, C6D6, 295 K): δ 1.2.
5
2′ 4′
3 4
(dq, J H
) 0.9 Hz, 1 H, H2′), 5.42 (d, 1 H, H4′), 7.0 (d, J H
5 4 5 6
H
H
) 8.0 Hz, 1 H, H3), 7.10 (dd, J H
) 7.6 Hz, J H
) 5.4 Hz,
-H
6 3
H
1 H, H5), 7.22 (ddd, J H
) 1.7 Hz, 1 H, H4), 8.66 (ddd, J H
4
6
H
H
) 1.1 Hz, 1 H, H6). {1H}13C NMR (100.6 MHz, C6D6, 295 K):
δ -0.2 [Si(CH3)3], -0.1 [Si(CH3)3], 14.6 (CH2CH3), 17.0
(CH2CH3), 21.5 (CH2CH3), 23.5 (CCH3), 30.3 (C(CH3)3), 46.7
(CH2CH3), 47.8 (CH2CH3), 48.9 (CCH3), 58.9 (C(CH3)3), 64.1
(CH2N), 64.3 (CH2N), 70.7 (C2′), 114.6 (C4′), 121.0 (C3), 121.4
(C5), 130.8 (C5′), 138.2 (C6), 161.2 (C2), 161.6 (C6′). {1H}29Si
NMR (50.3 MHz, C6D6, 295 K): δ 0.17, 1.19.
[(K3-N2Npy)Ti{NtBu }{η-Nn Bu }[-CdNCH(C3H7)N(C4H7)-
CHdC-]] (4c). Yield: 67%; mp 35 °C. Anal. Calcd for
C34H65N7Si2Ti [675.99]: C, 60.41; H, 9.69; N, 14.50. Found:
C, 60.95; H, 9.22; N, 14.04. IR (Nujol): 1629 vw, 1594 vw, 1460
s, 1375 s, 1258 w, 1243 w, 1097 w, 1018 w, 833 w, 798 w, 719
w cm-1. 1H NMR (200 MHz, C6D6, 295 K): δ -0.01 [Si(CH3)3],
0.07 [Si(CH3)3], 0.88 (t, J ) 7.3 Hz, 3 H, CH3), 0.94 (t, J ) 7.3
Hz, 3 H, CH3), 1.08 (s, b, 3 H, CCH3), 1.13 (t, J ) 7.3 Hz, 3 H,
CH3), 1.18-1.45 (m, b, 6 H, 3 H CH2CH3), 1.5-2.2 (m, b, 6 H,
[(K3-N 2N p y )T i{N t B u }{η-N C (Me )P h }[-C dN C (C H 3)-
(C6H5)N(-R-CH(Me)P h )CHdC-] (5b). Anal. Calcd for
C46H65N7Si2Ti [820.12]: C, 67.37; H, 7.99; N, 11.96. Found:
C, 66.95; H, 8.02; N, 11.89. Yield: 62%; mp 23 °C. IR (Nujol):
1629 w, 1515 w, 1495 w, 1460 w, 1377 w, 1243 w, 916 w, 833
1
w, 758 w, 718 w, 665 w cm-1. H NMR (200 MHz, C6D6, 295
K): δ 0.12 [s, 9 H, Si(CH3)3], 0.37 [s, 9 H, Si(CH3)3], 1.10
(CCH3), 1.16 [d, b, 3J HH ) 5.8 Hz, 6 H, 2 H CH(CH3)2], 1.77 (s,
3 H CH2), 2.00 [s, 9 H, C(CH3)3], 2.95 (m, 1 H, N3′CHHCH2-
2
3 H, C2′CH3), 1.89 [s, 9 H, C(CH3)3], 3.80 (d, J HH ) 11.0 Hz, 1
2
CH2CH3), 2.99 (m, 1 H, N3′CHHCH2CH2CH3), 3.09 (d, J HH
)
H, CHHN), 3.82 (d, 1 H, CHHN), 3.88 (d, 2J HH ) 12.6 Hz, 1 H,
CHHN), 4.02 (CHHN), 4.22 (q, TiNCHCH3), 4.65 (q, N3′CHCH3),
5.54 (s, 1 H, H4′), 6.88-7.35 (m, b, aromatic CH), 7.87-7.91
(m, 2 H, aromatic CH), 8.39 (H6) (major product). {1H}13C NMR
(50.3 MHz, C6D6, 295 K): δ 1.1 [Si(CH3)3], 1.9 [Si(CH3)3], 21.4
(CH3), 23.8 (CCH3), 25.9 (CH3), 28.0 (CH3), 34.6 [C(CH3)3], 52.2
(CCH3), 56.3 [NCHCH3C6H5], 59.3 [C(CH3)3], 61.7 [N3′CH-
(CH3)(C6H5)], 64.6 (CH2N), 64.7 (CH2N), 77.8 (C2′), 116.7 (C4′),
121.3, 121.4, 126.4, 126.5, 126.8, 127.1, 127.4, 127.7, 127.8,
128.5, 136.7, 148.6 (CH), 121.6, 147.1, 147.8, 150.3 (C), 157.9,
163.1 (C2, C6′) (major product). {1H}29Si NMR (39.8 MHz, C6D6,
295 K): δ 1.41 [Si(CH3)3], 2.06 [Si(CH3)3].
12.6 Hz, CHHN), 3.22 (dd, 1 H, CHHN), 3.65 (m, b, 1 H,
C2′HCHHCH2CH3), 3.81 (m, b, 1 H, C2′HCHHCH2CH3), 3.88
2
(d, J HH ) 12.6 Hz, CHHN), 3.95 (d, 1 H, CHHN), 4.98 (dt,
4J H
) 1.2 Hz, J HH ) 5.9 Hz, 1 H, H2′), 5.54 (d, 1 H, H4′),
2′ 4′
3
H
6.60 (m 1 H, H3), 6.95-7.14 (m, 2 H, H,4 H5), 8.70 (m, 1 H,
H6). {1H}13C NMR (50.3 MHz, C6D6, 295 K): δ -0.1 [Si(CH3)3],
1.4 [Si(CH3)3], 14.3 (CH3), 14.5 (CH3), 14.9 (CH3), 19.9 (CH2),
20. (CH2), 21.5 (CH2), 23.4 (CCH3), 30.1 [C(CH3)3], 49.0 (CCH3),
53.7 (CH2), 54.4 (CH2), 59.0 [C(CH3)3], 64.0 (CH2N), 64.2
(CH2N), 74.9 (C2′), 115.0 (C4′), 120.7 (C3), 121.1 (C5), 131.1 (C5′),
137.8 (C6), 146.9 (C4), 161.2, 161.4 (C2, C6′). {1H}29Si NMR (39.8
MHz, C6D6, 295 K): δ 1.5.
[(K3-N2Np y)Ti{Nt Bu }{η-NCy}[-CdNC(C5H 10)N(Cy)-
[(K3-N2Np y)Ti{Nt Bu }{η-NCH 2P h }[-CdNCH (C6h 5)N-
CHdC-]] (5c). Yield: 66%; mp 18 °C. Anal. Calcd for
C40H71N7Si2Ti [754.10]: C, 63.71; H, 9.49; N, 13.00. Found:
C, 64.65; H, 9.12; N, 12.62. IR (Nujol, KBr): 1458 s, 1375 s,
(CH2P h )CHdC-]] (4d ). Yield: 56%; mp 24 °C (dec). Anal.
Calcd for C43H59N7Si2Ti [778.93]: C, 66.38; H, 7.64; N, 12.60.
Found: C, 65.43; H, 7.24; N, 11.96. IR (Nujol, KBr): 1459 s,
1
1244 w, 836 w, 747 w, 717 w cm-1. H NMR (200 MHz, C6D6,
1
1379 s, 1243 vw, 918 vw, 833 w, 741 w, 697 w cm-1. H NMR
295 K): δ 0.34 [s, 18 H, Si(CH3)3], 1.19 (s, 3 H CCH3), 1.71 [s,
(200 MHz, C6D6, 295 K): δ -0.28 [s, 9 H, Si(CH3)3], 0.08 [s, 9
2
2
9 H, C(CH3)3], 0.60-2.40 (m, CH2 of Cy), 3.98 (d, J HH ) 13.2
H, Si(CH3)3], 1.22 (s, 3 H, CH3], 2.06 [C(CH3)3], 2.94 (d, J HH
Hz, 2 H, CHHN), 4.23 (d, 2 H, CHHN), 5.57 (s, 1 H, H4′), 6.61
(m, 1 H, H3), 7.14-7.20 (m, H,4 H5), 8.49 (m, 1 H, H6). {1H}13C
NMR (MHz, C6D6, 295 K): δ 0.9 [Si(CH3)3], 22.8 (CH2), 23.7
(CH2), 25.0 (CH2), 26.8 (CH2), 27.3 (CH2), 27.9 (CCH3), 29.4
[C(CH3)3], 32.7 (CH2), 34.1 (CH2), 34.4 (CH2), 37.2 (CH2), 54.3
(CCH3), 56.0 (CH), 58.7 [C(CH3)3], 61.8 (CH), 64.1 (CH2N), 73.5
(C2′), 110.7 (C4′), 121.2 (CH), 121.9 (CH), 123.0 (C), 128.4 (C),
128.4 (CH), 135.5 (CH), 149.2 (CH), 155.3 (C), 164.5 (C2).
{1H}29Si NMR (50.3 MHz, C6D6, 295 K): δ 1.40.
X-r a y Cr ysta llogr a p h ic Stu d ies of 2, 3d , 3f, 3g, a n d 4a .
Da ta Collection for 2, 3d , 3f, 3g, a n d 4a . Crystals of 2, 3d ,
3f, 3g, and 4a 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
Bruker P4 four-circle diffractometer. Details of data collection,
refinement, and crystal data are listed in Table 3; the only
crystals of 2, 3f, and 3g that could be obtained diffracted
relatively weakly at high angle. Lorentz-polarization and
absorption corrections were applied to the data of all the
compounds.
) 12.7 Hz, 1 H, CHHN), 3.13 (d, 2 H, CHHN), 3.80 (s, b, 2 H,
Ti-N-CH2-C6H5), 3.93 (d, 2J HH ) 13.4 Hz, 1 H, CHHN), 3.99
(d, 1 H, CHHN), 4.79 (d, 2J HH ) 14.7 Hz, 1 H, N3′-CHH-C6H5),
5.03 (d, H, N3′-CHH-C6H5), 5.31 (s, 1 H, H4′), 6.08 (s, 1 H, H2′),
6.15 (m, 1 H, H3), 6.70-7.40 (m, aromatic H), 8.02 (m, 2 H,
aromatic H), 8.54 (m, 1 H, H6). {1H}13C NMR (50.3 MHz, C6D6,
295 K): δ -0.5 [Si(CH3)3], -0.2 [Si(CH3)3], 23.1 (CCH3), 48.6
(CCH3), 53.4 (CH2C6H5), 56.6 (CH2C6H5), 59.5 [C(CH3)3], 64.1
(CH2N), 64.5 (CH2N), 76.6 (C2′), 115.8 (C4′), 120.6 (CH), 121.3
(CH), 123.6 (CH), 126.4 (CH), 126.5 (CH), 126.7 (CH), 127.2
(CH), 127.8 (CH), 128.0 (CH), 128.3 (CH), 128.4 (CH), 128.5
(CH), 128.8 (CH), 129.0 (CH), 135.4 (CH), 138.3 (CH), 146.0
(C), 147.0 (CH), 148.9 (CH), 149.6 (C), 150.4 (CH), 152.5 (C),
160.4 (C), 161.7 (C), 167.2 (C2). {1H}29Si NMR (39.8 MHz, C6D6,
295 K): δ 2.4, 2.8.
(4) Gen er a l P r oced u r e for th e Syn th esis of Dih yd r o-
p yr im id in e Com p ou n d s [(K3-N2Np y)Ti{NtBu }{η2-NR }-
[-CdNC(R′)(R′′)NRCHC-]] (5a -c). Compounds 5a -c were
synthesized according to method b descibed above. The workup
and isolation was entirely analogous.
Str u ctu r e Solu tion a n d Refin em en t for 2, 3d , 3f, 3g,
a n d 4a . For compounds 2, 3d , 3f, 3g, and 4a the positions of
the titanium, silicon atoms, and some of the other non-
hydrogen atoms were located by direct methods. The remain-
[(K3-N2Np y)Ti{Nt Bu }{η-NiP r }[-CdNC(CH 3)2N(iP r )-
CHdC-]] (5a ). Yield: 73%; mp 46 °C. Anal. Calcd for

4794 Organometallics, Vol. 19, No. 23, 2000
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for 2, 3d , 3f, 3g, a n d 4a
Bashall et al.
2‚THF
3d ‚C6H6
3f‚C7H8
3g‚C6H6
4a
empirical formula
fw
cryst syst
space group
C
41H64N6OSi2Ti
C50H73N7Si2Ti
876.23
monoclinic
C2/c
C52H71N7Si2Ti
898.24
triclinic
P1h
C51H69N7Si2Ti
884.21
monoclinic
C2/c
C25H47N7Si2Ti
761.06
orthorhombic
Pna21
549.78
triclinic
P1h
unit cell dimens
a/Å
b/Å
c/Å
21.415(5)
11.914(2)
17.770(3)
90
90
90
45333.9(14)
4
1.115
20.865(5)
12.6101(13)
39.310(4)
12.684(2)
13.876(2)
17.077(2)
74.318(9)
70.41(1)
65.00(2)
2537.1(6)
2
20.955(3)
12.483(2)
39.685(5)
10.031(2)
11.469(1)
15.465(2)
94.333(8)
108.38(1)
111.976(11)
1526.4(4)
2
R/deg
â/deg
γ/deg
V/Å3
Z
102.547(11)
102.34(1)
10096(3)
8
1.153
10142(2)
8
1.158
D
calc/Mg m-3
1.176
1.196
radiation (λ/Å)
Mo KR (0.71073)
Mo KR (0.71073)
Mo KR (0.71073)
Mo KR (0.71073)
Mo KR (0.71073)
µ/mm-1
0.277
0.257
0.257
0.256
0.384
F(000)
1640
3776
964
3792
592
cryst size/mm
θ-range/deg
limiting hkl indices
0.38 × 0.52 × 0.40
1.90-21.00
-21< h < 21,
-12 < k < 12
-17 < l < 17
5053
0.46 × 0.48 × 0.46
1.90-23.00
-22 < h < 22,
-13 < k < 13
-44 < l < 43
14470
0.50 × 0.50 × 0.36
1.83-22.00
-1 < h < 12
-13 < k < 14
-17 < l < 17
6935
0.12 × 0.50 × 0.50
1.91-21.00
-1 < h < 21,
-1 < k < 12,
-40 < l <39
6481
0.48 × 0.52 × 0.60
1.42-25.00
-1 < h < 11,
-13 < k < 12,
-18 < l < 17
6353
no. of reflns collected
no. of ind reflns
Rint
4852
0.0531
7032
0.0726
5898
0.0414
5227
0.0650
5348
0.0203
max/min transmn
refinement method
0.31317/0.24979
full matrix
least-squares on F2
4852/25/491
0.30529/0.27686
full matrix
least-squares on F2
7032/0/541
0.844087/0.507447
full matrix
least-squares on F2
5898/0/526
0.780028/0.370177
full matrix
least-squares on F2
5227/31/533
0.95820/0.61107
full matrix
least-squares on F2
5348/0/316
no. of data/restraints/
params
S on F2
0.970
0.953
1.047
0.972
1.033
final R indicesa
[I > 2σ(I)]
R1 ) 0.0744,
wR2 ) 0.1486
R1 ) 0.1681,
wR2 ) 0.1843
0.0795, 0
R1 ) 0.0529,
wR2 ) 0.1077
R1 ) 0.1142,
wR2 ) 0.1329
0.0483, 0
R1 ) 0.0691
wR2 ) 0.1651
R1 ) 0.1179
wR2 ) 0.1829
0.0945, 0.6873
0.512/-0.518
R ) 0.0714,
wR ) 0.1461
R1 ) 0.1484,
wR2 ) 0.1709
0.0760, 0
R1) 0.0436
wR2 ) 0.0918
R1) 0.0723
wR2 ) 0.1079
0.0438, 0.7628
0.234/-0.245
(all data)
weights a, ba
max and min/e Å-3
0.230/-0.333
0.260/-0.236
0.316/-0.292
S ) [∑w(Fo - Fc2)2/(n - p)]2 where n ) number of reflections and p ) total number of parameters, R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2
)
a
2
[w(F - Fc2)2]/∑[w(Fo )2]2, w-1 ) [∑2(Fo)2 + (aP)2 + bP], P ) [max(Fo2,0) + 2(Fc2)]/3.
2
2
x
o
ing non-hydrogen atoms were revealed from subsequent
methyl groups. After initial refinement with isotropic displace-
ment parameters empirical absorption corrections22 were
applied to the data. All full-occupancy non-hydrogen atoms
were assigned anisotropic displacement parameters in the final
cycles of full-matrix least-squares refinement.
difference Fourier sytheses. A spherical region of residual
electron density in 2 was intepreted as a totally disordered
THF molecule in the lattice, and the individual maxima were
included as partial atoms; this explained the rather poor
diffraction by the crystals of 2. In each of the structures 3d
and 3g a molecule of benzene and in 3f one toluene was
located, and very high thermal displacement parameters for
these atoms indicated some rotational disorder which was not
resolved. Refinement was based on F2,21 in the refinement of
2 and 3g and chemically equivalent bond lengths within the
tripod ligand were constrained to be equal within an esd of
0.02 Å. Because of the shortage of data, the phenylene rings
in 2 were constrained to idealized hexagonal geometry (C-C
1.39 Å). All hydrogen atoms, apart from those of the severely
disordered THF solvent molecule in 2, were included in
calculated positions with displacement parameters set equal
to 1.2Ueq of the parent carbon atoms or 1.5Ueq for those of the
Ack n ow led gm en t. We thank the Deutsche Fors-
chungsgemeinschaft, the Engineering and Physical Sci-
ences 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, 3a , 3d , 3f, 3g, and 4a . This material is
available free of charge via the Internet at http://pubs.acs.org.
OM0005710
(21) SHELTXL (PC version 5.03); Siemens Analytical Instruments
Inc.: Madison, WI, 1994.
(22) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.