˚
(
2.21 A), a bonding interaction can be unequivocally implicated
rical arrangement of the four atom transition state of the r-bond
metathesis reaction. Attempts to prove this experimentally by
further tuning of the macrocycle and to establish relationships
between the structure of the anionic azamacrocycle and its
spectator characteristics with the early transition metals are in
progress.
by the conformation of the coordinated macrocycle, with both
oxygen atoms pointing towards the metal centre. In solution
a rigid C
NMR spectroscopy. The coordination shift of the C atoms a to
the ether oxygen is 6.0–8.6 ppm. Since the application of simple
electron counting rules would render Zr(N
1
2
structure is supported by variable temperature H-
−
2
O)
2
as a 20e species,
In summary, we have prepared the first face-capping diamido
we believe that the Zr–O interaction may have predominantly
an electrostatic origin. Theoretical calculations to elucidate the
nature of this interaction are in progress.
macrocyclic complexes with Zr and Ti. Zr(N
goes a facile comproportionation reaction to Zr(N
2
O)(NEt
O)
2
)
2
under-
2
2
possibly
driven by the macrocyclic effect of the ligand. In addition we
have observed the facile metallation of the macrocyclic rim by
C–H activation a-to the amido functional group. The synthesis
of early transition metal complexes with anionic azamacrocyclic
ligands and their reactivity is the subject of work in progress.
Insight into the mechanism of formation of Zr(N
2
2
O) was
gained by monitoring the early stages of the reaction by
NMR spectroscopy.† The initial product is thought to be the
expected Zr(N
to Zr(N O) and Zr(NEt
ison to an authentic sample. Analogous reactivity was observed
by using Z(NMe Cl (thf) instead of Z(NEt Cl (thf) ; in this
case, in addition to Zr(N O) , Zr(NMe was also formed. It is
2
O)(NEt
2
)
2
, which comproportionates within 1 h
2
2
)
2 4
. The latter was identified by compar-
2
)
2
2
2
2
)
2
2
2
Acknowledgements
2
2
)
2 4
We thank Professor M. B. Hursthouse for provision of X-ray
facilities and the EPSRC for support.
possible that this reaction is driven by the macrocyclic effect of
the ligand.
Attempts to prepare a diamido macrocyclic complex of
titanium by alkanolysis of Ti(Benzyl)
4
with (NH) O at room
2
Notes and references
‡ Spectroscopic data: For Zr(N O) : d (C D ) 0.96 (6H, s, CH ), 1.94
temperature produced crystals of the complex shown in
Fig. 2.§ The molecule is a centrosymmetric dimer with amido
bridging groups. The macrocycle coordinates to the metal via
one terminal amido nitrogen and one ether oxygen, while
a metallaziridine ring is formed incorporating the carbon a
to the amido nitrogen. The observed metrical data are in
agreement with a metallaziridine formulation. To the best of our
knowledge, this is the first example in which an azamacrocycle
has been metallated on the macrocyclic rim by a transition
2
2
H
6
6
3
(6H, s, CH
.37 (2H, ddd, J 4.1, 9.8, 11.3, OCH
2H, d, J 10.2, NCH C(CH ), 3.56 (2H, d, J 12.1, NCH
.67 (2H, dd, J 5.7, 9.8, OCH CH ), 3.88 (2H, dd, J 4.9, 9.8,
OCH CH ), 4.22 (2H, ddd, J 5.3, 12.1, 14.7, OCH CH ), 4.40 (2H,
ddd, J 4.9, 11.7, 16.2, OCH CH ). d (C ) 25.85, 29.50 (CH ),
3
), 2.42 (2H, d, J 12.1, NCH
2
C(CH
CH
3
)
2
), 2.55–2.70 (6H, m),
3
2
2
), 3.41–3.51 (2H, m), 3.47
C(CH ),
(
2
3
)
2
2
3 2
)
3
2
2
2
2
2
2
7
2
2
C
6
D
6
3
38.81 (NCH C(CH ) ), 52.33, 52.74 (NCH C(CH ) ), 67.36,67.38
2
3
2
2
3 2
(OCH
data for [Ti(N
solubility in inert solvents.
O)
2
CH
2
),77.17,79.81 (OCH
2
CH
2
2 2
). For [Ti(N O)*(Benzyl)] : NMR
metal. Reaction of Me
methyl groups. C–H activation of crown thioethers coordinated
to rhodium has been reported.
3
-tacn with BuLi metallated one of the
2
O)*(Benzyl)] could not be obtained due to its poor
2
8
9
§ Crystal data: For Zr(N
2
2
: C18
H
36
N
4
O
2
Zr, M = 431.73, monoclinic,
◦
a = 10.2993(18) A˚ , b = 11.2657(13) A˚ , c = 17.021(3) A˚ , b = 90.041(9) ,
U = 1973.9(5) A˚ , T = 120 K, space group P2
3
/c, Z = 4, l(Mo-Ka) =
1
−
1
˚
2
.986 mm , k = 0.71073 A, 11501 reflections measured, 4492 unique
2
(
0
R
int = 0.0355) which were used in all calculations. The final wR(F ) was
.0745 (all data) and R = 0.0339 [I > 2r(I)]. For [Ti(N
2 2
O)*(Benzyl)] :
C
1
32
H
48
N
4
O
2
Ti
2
, M = 616.54, monoclinic, a = 9.0291(5) A˚ , b =
◦
3
0.7445(6) A˚ , c = 15.7401(9) A˚ , b = 90.157(3) , U = 1526.99(15) A˚ ,
−1
T = 120 K, space group P21/c (no.14), Z = 4, l(Mo-Ka) = 2.986 mm
,
k = 0.71073 A˚ , 7564 reflections measured, 3514 unique (Rint = 0.0612)
2
which were used in all calculations. The final wR(F ) was 0.0884 (all
data) and R = 0.0541 [I > 2r(I)]. CCDC reference numbers 253241
and 253242. See http://www.rsc.org/suppdata/dt/b4/b418431a/ for
crystallographic data in CIF or other electronic format.
1
2
(a) L. H. Gade, Chem. Commun., 2000, 173–181; (b) R. Kempe,
Angew. Chem. Int. Ed., 2000, 39, 468–493.
(a) For a recent review see: V. C. Gibson and S. K. Spitzmesser, Chem.
Rev., 2003, 103, 283–316; (b) S. Doye and I. Bytschkov, Eur. J. Org.
Chem., 2003, 935–946.
Fig. 2 ORTEP representation of [Ti(N
2
O)*(Benzyl)]
2
at 50% prob-
3 (a) J. A. R. Schmidt, G. R. Giesbrecht, C. Cui and J. Arnold, Chem.
Commun., 2003, 1025–1033; (b) G. R. Giesbrecht, A. Gebauer, A.
Shirif and J. Arnold, J. Chem. Soc., Dalton Trans., 2000, 4018–4020;
(c) S. Y. Bylikin, D. A. Robson, N. A. H. Male, L. H. Rees, P.
Mountford and M. Schr o¨ der, J. Chem. Soc., Dalton Trans., 2001,
170–180.
ability ellipsoids. Hydrogen atoms are omitted for clarity. Selected
◦
bond lengths ( A˚ ) and angles ( ): Ti(1)–C(3) 2.089(3), Ti(1)–N(1)
2
2
ꢀ
.106(2), Ti(1)–N(1 ) 2.171(2), Ti(1)–N(2) 1.968(2), Ti(1)–O(1)
.1975(19), Ti(1)–C(10) 2.209(3); C(4)–C(3)–N(1) 125.5(2), C(7)–O(1)–
C(1) 115.0(2), C(2)–N(1)–C(3) 121.3(2), C(6)–N(2)–C(5) 114.0(2),
Ti(1)–C(10)–C(11) 88.30(16).
4 L. Lee, D. J. Berg and G. W. Bushnell, Organometallics, 1997, 16,
2
556–2561 and references cited therein.
5
S. Chandrasekhar and A. McAuley, J. Chem. Soc., Dalton Trans.,
992, 2967–2970.
6 S. Brenner, R. Kempe and P. Arndt, Z. Anorg. Allg. Chem., 1995,
21, 2021.
In order to clarify the mechanism of the formation of
1
[
Ti(N
with (NH)
one hour after mixing of solutions of the two reagents in C
in the glove box at room temperature is consistent with the
presence of the species Ti(N O)(Benzyl) .† On standing, this
2
O)*(Benzyl)]
2
we monitored the reaction of Ti(Benzyl)
4
1
2
O by H-NMR spectroscopy. The spectrum recorded
6
6
D
6
7
M. H. Chisholm, C. E. Hammond and J. C. Huffman, Polyhedron,
1988, 7, 2515–2520.
2
2
8 J. Arnold, V. Knapp, J. A. R. Schmidt and A. Shafir, J. Chem. Soc.,
Dalton Trans., 2002, 3273–3274.
solution converts to the observed product, which crystallises
out, and toluene. a-Metallation of dialkylamides of the early
transition metals has been observed previously, mainly with
zirconocene and Group 5 amido complexes. Relevant reactions
with titanium are rare. It may be argued that the facile activation
observed here is due to a macrocycle assisted favourable geomet-
9
A. J. Blake, A. J. Holder, T. I. Hyde, H. J. K u¨ ppers, M. Schr o¨ der, S.
Stoelzer and K. Wieghardt, Chem. Commun., 1989, 1600–1602.
1
0 (a) S. L. Buchwald, B. T. Watson, M. W. Wannamaker and J. C.
Dewan, J. Am. Chem. Soc., 1989, 111, 4486–4494; (b) W. A. Nugent
and S. J. Holmes, Organometallics, 1983, 2, 161–162; (c) P. Berno and
S. Gambarotta, Organometallics, 1995, 14, 2159–2161.
10
4
2 8
D a l t o n T r a n s . , 2 0 0 5 , 4 2 7 – 4 2 8