Porphodimethene-zirconium: A new entry into zirconium macrocycle organometallic chemistry

Article abstract of DOI:10.1021/om990688s

The cis-dichloro-meso-hexaethylporphodimethene-zirconium(IV) complex has been functionalized to the corresponding dialkyl derivatives [R = Me, PhCH₂, Ph], 3-5, displaying a variety of migratory pathways. In the case of benzyl derivative 4, the spontaneous migration of the first benzyl to the ligand, 6, is followed by the second one, photochemically induced, thus forming a Zr-porphyrinogen complex, 7. The methyl derivative undergoes thermally induced methane elimination with the metalation of the meso ethyl chains, 8. Migration of both methyl groups has been observed in the reaction of 3 with Bu^tNC, with the preliminary formation of η²-imine, rearranging to the corresponding enamine, 9.

Full text of DOI:10.1021/om990688s

5198
Organometallics 1999, 18, 5198-5200
P or p h od im eth en e-Zir con iu m : A New En tr y in to
Zir con iu m Ma cr ocycle Or ga n om eta llic Ch em istr y
Lucia Bonomo, Gu¨lsen Toraman, Euro Solari, Rosario Scopelliti, and
Carlo Floriani*
Institut de Chimie Mine´rale et Analytique, BCH, Universite´ de Lausanne,
CH-1015 Lausanne, Switzerland
Received August 26, 1999
Sch em e 1
Summary: The cis-dichloro-meso-hexaethylporphodi-
methene-zirconium(IV) complex has been functionalized
to the corresponding dialkyl derivatives [R ) Me, PhCH2,
Ph], 3-5, displaying a variety of migratory pathways.
In the case of benzyl derivative 4, the spontaneous
migration of the first benzyl to the ligand, 6, is followed
by the second one, photochemically induced, thus form-
ing a Zr-porphyrinogen complex, 7. The methyl deriva-
tive undergoes thermally induced methane elimination
with the metalation of the meso ethyl chains, 8. Migra-
tion of both methyl groups has been observed in the
reaction of 3 with ButNC, with the preliminary forma-
tion of η2-imine, rearranging to the corresponding enam-
ine, 9.
Macrocycles have had a remarkable development
quite recently as ancillary ligands in the early transition
metallorganic chemistry.1 The metal par excellence
chosen within the context has so far been zirconium in
combination with tmtaa [tmtaa ) dibenzotetramethyl-
tetraaza[14]annulene],2 calix[4]arenes,3 azatranes,4 por-
phyrinogens,5 and porphyrins.6 A quite recent synthetic
methodology has made available the possibility of large-
scale production of the dianionic macrocycle meso-
* To whom correspondence should be addressed.
(1) For leading references on organometallic chemistry based on
macrocyclic ligands see refs 2-6.
(2) For tmtaa [dibenzotetramethyltetraaza[14]annulene], see: (a)
Mountford, P. Chem. Soc. Rev. 1998, 27, 105, and references therein.
(b) Floriani, C.; Ciurli, S.; Chiesi-Villa, A.; Guastini, C. Angew. Chem.,
Int. Ed. Engl. 1987, 26, 70. (c) Solari, E.; De Angelis, S.; Floriani, C.;
Chiesi-Villa, A.; Rizzoli, C. Inorg. Chem. 1992, 31, 96. (d) De Angelis,
S.; Solari, E.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Inorg.
Chem. 1992, 31, 2520. (e) Giannini, L.; Solari, E.; Floriani, C.; Chiesi-
Villa, A.; Rizzoli, C. Angew. Chem., Int. Ed. Engl. 1994, 33, 2204. (f)
Giannini, L.; Solari, E.; De Angelis, S.; Ward, T. R.; Floriani, C.; Chiesi-
Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1995, 117, 5801. (g) Black, D.
G.; Swenson, D. C.; J ordan, R. F. Organometallics 1995, 14, 3539. (h)
Blake, A. J .; Mountford, P.; Nikonov, G. I.; Swallow, D. Chem.
Commun. 1996, 1835. (i) Schumann, H. Inorg. Chem. 1996, 35, 1808.
(j) Nikonov, G. I.; Blake, A. J .; Mountford, P. Inorg. Chem. 1997, 36,
1107. (k) Black, D. G.; J ordan, R. F.; Rogers, R. D. Inorg. Chem. 1997,
36, 103. (l) Martin, A.; Uhrhammer, R.; Gardner, T. G.; J ordan, R. F.
Organometallics 1998, 17, 382.
(3) For calix[4]arenes, see: (a) Floriani, C. Chem. Eur. J . 1999, 5,
19. (b) Giannini, L.; Caselli, A.; Solari, E.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C.; Re, N.; Sgamellotti, A. J . Am. Chem. Soc. 1997, 119,
9198 and 9709. (c) Caselli, A.; Giannini, L.; Solari, E.; Floriani, C.;
Re, N.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1997, 16, 5457.
(d) Zanotti-Gerosa, A.; Solari, E.; Giannini, L.; Floriani, C.; Chiesi-
Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1998, 120, 437. (e) Giannini,
L.; Solari, E.; Floriani, C.; Chiesi-Villa, C.; Rizzoli, C. J . Am. Chem.
Soc. 1998, 120, 823. (f) Giannini, L.; Solari, E.; Dovesi, S.; Floriani,
C.; Re, N.; Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1999, 121,
2784. (g) Giannini, L.; Guillemot, G.; Solari, S.; Floriani, C.; Re, N.;
Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1999, 121, 2797. (h)
Giannini, L.; Dovesi, S.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. Angew. Chem., Int. Ed. 1999, 38, 807. (i) Castellano, B.; Solari, E.;
Floriani, C.; Re, N.; Chiesi-Villa, A.; Rizzoli, C. Chem. Eur. J . 1999, 5,
722.
hexaethylporphodimethene (see Scheme 1),7 which paves
the way from porphyrinogen to porphyrin and combines
some of the features of both skeletons.
This is a preliminary report on the organic chemistry
of zirconium based on the porphodimethene ligand, with
the purpose of emphasizing (i) the synthesis of Zr-C
functionalities, (ii) the migration of an alkyl group from
the metal either to the macrocyclic ligand or to an
incoming substrate, and (iii) the intramolecular meta-
lation of aliphatic C-H bonds.
(4) (a) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9. (b) Verkade, J . G.
Coord. Chem. Rev. 1994, 137, 233. (c) Duan, Z.; Verkade, J . G. Inorg.
Chem. 1995, 34, 5477, 4311, 1576. (d) Neuner, B.; Schrock, R. R.
Organometallics 1996, 15, 5. (e) Schrock, R. R.; Cummins, C. C.;
Wilhelm, T.; Lin, S.; Reid, S. M.; Kol, M.; Davis, W. M. Organometallics
1996, 15, 1470. (f) Freundlich, J . S.; Schrock, R. R.; Davis, W. M.
Organometallics 1996, 15, 2777. (g) Nomura, K.; Schrock, R. R.; Davis,
W. M. Inorg. Chem. 1996, 35, 3695. (h) Freundlich, J . S.; Schrock R.
R.; Davis, W. M. J . Am. Chem. Soc. 1996, 118, 3643. (i) Memmler, H.;
Walsh, K.; Gade, L. H.; Lauher, J . W. Inorg. Chem. 1995, 34, 4062. (j)
Findeis, B.; Schubart, M.; Gade, L. H.; Mo¨ller, F.; Scowen, I.; McPartlin,
M. M. J . Chem. Soc., Dalton Trans. 1996, 125. (k) Aspinall, H. C.;
Tillotsen, M. R. Inorg. Chem. 1996, 35, 2163.
10.1021/om990688s CCC: $18.00 © 1999 American Chemical Society
Publication on Web 11/11/1999

Communications
Organometallics, Vol. 18, No. 25, 1999 5199
Complex 2, which represents the entry into the
zirconium-porphodimethene organometallic chemistry,
has been synthesized according to Scheme 1.8 The cis
arrangement of the two chloride atoms is particularly
appropriate for the metal functionalization, as was the
case for a variety of other macrocyclic ancillary ligands
such as tmtaa,2 calix[4]arenes,3b and porphyrins.6 The
cis arrangement of the two chloride atoms is the
consequence of the saddle shape conformation of the
ligand having two sp3 and two sp2 meso-carbons and
with the metal 0.932(2) Å out of the N4 plane.9 Particu-
larly significant are the Zr‚‚‚CH2 short contacts with two
meso-ethyl groups, thus suggesting a structural inter-
mediate in the metal-assisted aliphatic C-H activation
(see below). The alkylation of 2 led to the bis-alkyl
derivatives, two of them, 310 and 5, being isolated and
characterized, while 4, which might not be isolated, led
to the migration of one benzyl group to the monosub-
stituted meso-position,11 thus forming the trianionic
porphomethene ligand7 in complex 6.12 The structure
of 6 (Figure 1)13 shows the η1:η1:η1:η5 bonding mode of
F igu r e 1. View of compound 6 (hydrogens omitted for
clarity). Selected bond lengths (Å) and angles (deg): Zr1-
η5(Pyr), 2.219(4); Zr1-N2, 2.257(7); Zr1-N3, 2.290(6); Zr1-
N4, 2.188(7); Zr1-C40, 2.312(8); Zr1-O1, 2.453(5); C41-
C40-Zr1, 129.8(6). η5(Pyr) indicates the centroid.
(5) For metal-porphyrinogen: (a) Floriani, C. Pure Appl. Chem.
1996, 68, 1. (b) J acoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. J . Am. Chem. Soc. 1995, 117, 2805. (c) Isoz, S.; Floriani, C.; Schenk,
K.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1996, 15, 337. (d)
J acoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Am.
Chem. Soc. 1995, 117, 2793. (e) De Angelis, S.; Solari, E.; Floriani, C.;
Chiesi-Villa, A.; Rizzoli, C. Angew. Chem., Int. Ed. Engl. 1995, 34, 1092.
(f) J acoby, D.; Isoz, S.; Floriani, C.; Schenk, K.; Chiesi-Villa, A.; Rizzoli,
C. Organometallics 1995, 14, 4816. (g) Solari, G.; Solari, E.; Floriani,
C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1997, 16, 508. (h)
J acoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Am.
Chem. Soc. 1995, 117, 2793.
(6) For porphyrins, see: (a) Brand, H.; Arnold, J . Angew. Chem.,
Int. Ed. Engl. 1994, 33, 95. (b) Brand, H.; Arnold, J . Organometallics
1993, 12, 3655. (c) Kim, H.-J .; Whang, D.; Kim, K.; Do, Y. Inorg. Chem.
1993, 32, 360. (d) Arnold, J .; J ohnson, S. E.; Knobler, C. B.; Hawthorne,
M. F. J . Am. Chem. Soc. 1992, 114, 3996. (e) Brand, H.; Arnold, J . J .
Am. Chem. Soc. 1992, 114, 2266. (f) Brand, H.; Arnold, J . Coord. Chem.
Rev. 1995, 140, 137. (g) Aida, T.; Inoue, S. Acc. Chem. Res. 1996, 29,
39. (h) Kim, H.-J .; J ung, S.; J eon, Y.-M.; Whang, D.; Kim, K. Chem.
Commun. 1999, 1033. (i) Ryu, S.; Whang, D.; Kim, H.-J .; Kim, K.;
Yoshida, M.; Hashimoto, K.; Tatsumi, K. Inorg. Chem. 1997, 36, 4607.
(d) Kim, H.-J .; J ung, S.; J eon, Y.-M.; Whang, D.; Kim, K. Chem.
Commun. 1997, 2201.
the tetrapyrrolic ligand and the η1 bonding mode of the
benzyl group. The migration of the second benzyl group
was photochemically induced, thus forming 7, where
zirconium is η5:η1:η5:η1 bonded5 to the meso-hexaethyl-
bisbenzylporphyrinogen tetraanion. The bonding mode
of the macrocyclic ligand in both 6 and 7 has been
1
confirmed by the H NMR spectra in solution and the
X-ray analysis in the solid state.
The chemical evolution of 3 upon heating is com-
pletely different from that of 4. The reaction produced
methane and led to the formation of Zr-C bonds with
the R-carbons of the two meso-ethyl groups, as shown
in complex 8.14 In the case of 3, we assume, as for the
structure of 2, that the close geometrical proximity
(12) Procedure for 6. (PhCH2)2Mg (29.9 mL, 0.44 M in THF, 13.0
mmol) was added to a solution of 2 (8.35 g, 13.0 mmol) in toluene (350
mL) cooled to -30 °C. The reaction mixture was stirred at room
temperature for 1 h and then was evaporated to dryness. Toluene (300
mL) was added, and the undissolved white solid, MgCl2, was filtered
off. The solution was evaporated to dryness, and the residue was
treated with n-pentane to give a pink powder, which was collected and
dried in vacuo (6.5 g, 61%). Crystals suitable for X-ray analysis were
obtained by recrystallisation in THF/Et2O. Anal. Calcd for 6, C50H60N4-
OZr: C, 72.86; H, 7.34; N, 6.80. Found: C, 72.45; H, 7.05; N, 6.34. 1H
NMR (C6D6, 400 MHz, 298 K): δ 7.28 (d, J ) 4.4 Hz, 1H, C4H2N);
7.14 (m, 4H, ArH); 7.01 (d, J ) 4.4 Hz, 1H, C4H2N overlapping with
m, 2H, ArH); 6.75 (m, 1H, ArH); 6.53 (d, J ) 4.4 Hz, 1H, C4H2N); 6.51
(d, J ) 2.93 Hz, 1H, C4H2N); 6.50 (m, 3H, ArH); 6.40 (d, J ) 2.93, 1H,
C4H2N); 6.23 (d, J ) 2.93 Hz, 1H, C4H2N); 6.22 (d, J ) 4.4 Hz, 2H,
C4H2N); 5.79 (d, J ) 2.93, 1H, C4H2N); 4.13 (d, J ) 13.2, 1H, CH2Ph);
3.17 (s broad, 4H, THF); 3.49 (d, J ) 13.2, 1H, CH2Ph); 2.70 (q, J )
7.34 Hz, 2H, CH2); 2.40 (dq, J gem ) 13.6 Hz, J vic ) 7.34 Hz, 1H, CH2);
2.18 (dq, J gem ) 13.2 Hz, J vic ) 7.34 Hz, 1H, CH2); 2.03(m, 4H, CH2);
1.95-1.7 (m, 6H, CH2); 1.23 (t, J ) 7.34 Hz, 3H, CH3 overlapping with
s broad, 4H, THF); 1.11 (t, J ) 7.34 Hz, 3H, CH3); 0.8 (t, J ) 7.34 Hz,
3H, CH3 overlapping with t, J ) 7.34 Hz, 3H, CH3); 0.75 (t, J ) 7.34
Hz, 3H, CH3); 0.68 (t, J ) 7.34 Hz, 3H, CH3).
(13) Crystal data for 6: C50H60N4OZr, M ) 824.24, monoclinic, space
group P21/n, a ) 18.880(2) Å, b ) 11.940(2) Å, c ) 19.253(2) Å, â )
103.259(11)°, V ) 4224.6(11) Å3, Z ) 4, Fcalcd ) 1.296 g/mL, F(000) )
1744, λ(Mo KR) ) 0.71073 Å, µ(Mo KR) ) 0.302 mm-1; crystal
dimensions 0.24 × 0.16 × 0.10. Diffraction data were collected on a
KUMA CCD at 143 K. The structure was solved with direct methods
and refined using full-matrix least-squares on F2 with all non-H atoms
anisotropically defined. For 3071 observed reflections [I > 2σ(I)] and
505 parameters, the conventional R is 0.0819 (wR2 ) 0.2340 for 6996
independent reflections). Atomic coordinates, bond lengths and angles,
and thermal parameters have been deposited at the Cambridge
Crystallographic Data Centre, University Chemical Laboratory, Lens-
field Road, Cambridge CB2 1EW (England). See the Supporting
Information for more details.
(7) Benech, J .-M.; Bonomo, L.; Solari, E.; Scopelliti, R.; Floriani, C.
Angew. Chem., Int. Ed. 1999, 38, 1957, and references therein.
(8) Procedure for 2. Solid ZrCl4‚THF2 (5.57 g, 14.8 mmol) was added
to a solution of 1 (9.41 g, 14.8 mmol) in toluene (600 mL) under argon
atmosphere. The resulting solution was stirred at room temperature
for 1 day. The undissolved white solid, LiCl, was filtered off, and the
solution was evaporated to dryness. The residue was triturated with
n-pentane to give a red powder (6.8 g, 72%), which was collected and
dried in vacuo. Crystals suitable for X-ray analysis were obtained by
recrystallization in THF. Anal. Calcd for 2, C32H38N4Cl2: C, 59.98; H,
5.98; N, 8.74. Found: C, 59.73; H, 6.16; N, 8.45. 1H NMR (C6D6, 200
MHz, 298 K): δ 7.07 (d, J ) 4.4 Hz, 4H, C4H2N); 6.26 (d, J ) 4.4 Hz,
4H, C4H2N); 2.66 (q, J ) 7.32 Hz, 4H, CH2); 2.43 (q, J ) 7.32 Hz, 4H,
CH2); 1.92 (q, J ) 7.32 Hz, 4H, CH2); 1.15 (t, J ) 7.32 Hz, 6H, CH3);
0.90 (t, J ) 7.32 Hz, 12H, CH3).
(9) Unpublished results.
(10) Procedure for 3. MeLi (42.9 mL, 1.51 M in Et2O, 64.8 mmol)
was added dropwise to a solution of 2 (20.82 g, 32.4 mmol) in toluene
(600 mL) cooled to -30 °C. The resulting dark orange solution was
warmed to room temperature, and the undissolved white solid, LiCl,
was filtered off. The solution was evaporated to dryness, and n-pentane
was added to give a brown powder (13.6 g, 70%), which was collected
and dried in vacuo. Anal. Calcd for C34H44N4Zr: C, 68.06; H, 7.39; N,
9.34. Found: C, 68.51; H, 6.89; N, 9.73. 1H NMR (C6D6, 400 MHz, 298
K, ppm): δ 7.14 (d, J ) 4.4 Hz, 4H, C4H2N); 6.44 (d, J ) 4.4 Hz, 4H,
C4H2N); 2.73 (q, J ) 7.3 Hz, 4H, CH2); 2.27 (q, J ) 7.3 Hz, 4H, CH2);
2.03 (q, J ) 7.3 Hz, 4H, CH2); 1.18 (t, J ) 7.3 Hz, 6H, CH3); 0.94 (t, J
) 7.3 Hz, 6H, CH3); 0.9 (s, 6H, CH3); 0.88 (t, J ) 7.3 Hz, 6H, CH3).
(11) Migration of the alkyl group from the metal to an electron-
deficient imino group is known both for tmtaa (see ref 2) and for Schiff-
base complexes: (a) Floriani, C.; Solari, E.; Corazza, F.; Chiesi-Villa,
A.; Guastini, C. Angew. Chem., Int. Ed. Engl. 1989, 28, 64. (b) Solari,
E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Chem. Soc., Dalton Trans.
1992, 367. (c) Solari, E.; Maltese, C.; Latronico, M.; Floriani, C.; Chiesi-
Villa, A.; Rizzoli, C. J . Chem. Soc., Dalton Trans. 1998, 2395.

5200 Organometallics, Vol. 18, No. 25, 1999
Communications
functionalization of the meso aliphatic chain of the
porphodimethene skeleton, due to the easy demetala-
tion, upon hydrolysis, of complexes of this type.5h An
additional interest in complex 8 comes from its potential
use in the intermolecular C-H bond activation of
hydrocarbons, as already reported for the Zr-porphy-
rinogen complexes.5a,b The Zr-Me functionality in 3 has
been engaged in other migration processes, exemplified
by its reaction with ButNC,15 which has some unusual
peculiarities. The reaction led to the migration of both
methyls to the isocyanide functionality and the inter-
mediate formation of η2-C,N imine2f,3c (see complex A
in Scheme 1), which underwent a C-H (Me) deproto-
nation followed by a hydrogen transfer to one of the
meso-positions. On the basis of the structural param-
eters, the deprotonated imine behaves more as an
N-methylated enamine than as an azaallyl ligand (see
complex 9 in Scheme 116 and Figure 217), while the
resulting porphomethene macrocycle displays an η1:η1:
η1:η1 bonding mode proven by the X-ray structure of 9
and the NMR spectra in solution.
F igu r e 2. View of compound 9 (hydrogens omitted for
clarity). Selected bond lengths (Å): Zr1-Ν1, 2.152(4); Zr1-
N2, 2.194(4); Zr1-N3, 2.217(4); Zr1-N4, 2.152(4); Zr1-
N5, 2.095(4); Zr1‚‚‚C33, 2.624(5); Zr1‚‚‚C34, 2.721(5); Zr1-
η3(N5, C33, C34), 2.280(4); N5-C33, 1.387(6); C33-C34,
1.363(7). η3(N5, C33, C34) indicates the centroid.
Ack n ow led gm en t. We thank the Fonds National
Suisse de la Recherche Scientifique (Bern, Switzerland,
Grant No. 20-53336.98) and Action COST D9 (European
Program for Scientific Research, OFES No. C98.008) for
financial support.
between the methyl group and the CH2 from two meso-
ethyl groups is crucial for the concerted elimination of
CH4 and the consequent metalation of the lateral ethyl
chains. Unlike in the case of zirconium-porphyrinogen
chemistry,5b the metalation of the aliphatic chain is
regiochemically selective; not only is the reaction oc-
curring only at the R-carbon but also it produces a single
stereoisomer. The absence of Zr‚‚‚CH2 (meso-ethyl)
interactions prevented by the sterically more demanding
benzyl subtituents in 4 opens the pathway of the
nucleophilic attack by the benzylic carbanions to the
meso-positions of the porphodimethene skeleton. The
characterization of 8 included a quite preliminary X-ray
analysis.9 The synthetic relevance of 8 has to be
emphasized; it can be used as an intermediate in the
Su p p or tin g In for m a tion Ava ila ble: ORTEP drawings
and tables giving crystal data and details of the structure
determination, atomic coordinates, bond distances and angles,
and anisotropic thermal parameters for 6 and 9. This material
is available free of charge via the Internet at htpp://pubs.acs.org.
OM990688S
(15) Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059.
(16) Procedure for 9. A solution of ButNC (0.71 g, 8.5 mmol) in
benzene (60 mL) was added dropwise to a dark orange solution of 3
(5.1 g, 8.5 mmol) in benzene (90 mL) cooled to -30 °C. The resulting
dark violet solution was stirred at room temperature for 1 day and
then evaporated to dryness. The residue was triturated with n-pentane
to give a red powder (4.5 g, 77%), which was collected and dried in
vacuo. Anal. Calcd for 9, C39H53N5Zr: C, 68.57; H, 7.82; N, 10.25.
Found: C, 68.12; H, 7.35; N, 9.82. 1H NMR (C6D6, 400 MHz, 298 K,
ppm): δ 7.01 (d, J ) 4.4 Hz, 2H, C4H2N); 6.39 (d, J ) 3.4 Hz, 2H,
C4H2N); 6.32 (d, J ) 4.4 Hz, 2H, C4H2N); 6.13 (d, J ) 3.4 Hz, 2H,
C4H2N); 4.04 (s, 3H, CH3); 2.51 (m, 4H, CH2); 2.17 (q, J ) 7.34 Hz,
4H, CH2); 1.91 (m, 2H, CH2); 1.70 (m, 6H, CH2); 1.37 (s, 3H, CH3);
1.36 (t, J ) 7.34, 3H, CH3); 1.11 (t, J ) 7.34 Hz, 3H, CH3), 1.07 (t, J
) 7.34 Hz, 6H, CH3); 0.89 (s, 9H, But); 0.61 (t, J ) 7.34 Hz, 6H, CH3).
Crystal suitable for X-ray analysis were obtained from toluene/n-
hexane.
(17) Crystal data for 9. C39H53N5Zr, M ) 683.08, triclinic, space
group P1h, a ) 9.1942(8) Å, b ) 10.9092(18) Å, c ) 17.887(3) Å, R )
89.771(14)°, â ) 87.736(12)°, γ ) 71.089(13)°, V ) 1695.9(4) Å3, Z ) 2,
Dcalcd ) 1.338 g/cm3, F(000) ) 724, λ(Mo KR) ) 0.71073 Å, µ(Mo KR) )
0.360 mm-1; crystal dimensions 0.28 × 0.20 × 0.15. Diffraction data
were collected on a KUMA CCD at 143 K. The structure was solved
with direct methods and refined using full-matrix least-squares on F2
with all non-H atoms anisotropically defined. For 4681 observed
reflections [I > 2σ(I)] and 406 parameters, the conventional R is 0.0720
(wR2 ) 0.1451 for 5140 indipendent reflections).
(14) Procedure for 8. MeLi (11.4 mL, 1.82 M in Et2O, 20.8 mmol)
was added dropwise to a solution of 2 (6.9 g, 10.4 mmol) in toluene
(300 mL) at -30 °C. The resulting dark orange solution was stirred at
room temperature for 1 h. The 1H NMR showed that 2 was entirely
converted into 3. The solution was then heated at 110 °C for 2 h, and
the undissolved white solid, LiCl, was filtered off. The solution was
evaporated to dryness and the solid residue collected with n-pentane,
yielding a brown powder (3.2 g, 55%). Anal. Calcd for 8, C32H36N4Zr:
C, 67.68; H, 6.39, N, 9.86. Found: C, 68.08; H, 6.82, N, 9.55. 1H NMR
(C6D6, 400 MHz, 298 K): δ 6.45 (d, J ) 3.91 Hz, 2H, C4H2N); 6.38 (d,
J ) 3.91 Hz, 2H, C4H2N); 5.95 (d, J ) 3.91 Hz, 2H, C4H2N); 5.90 (d, J
) 3.91 Hz, 2H, C4H2N); 2.18 (m, 4H, CH2); 2.06 (q, J ) 2.85 Hz, 2H,
CH2); 1.86 (q, J ) 7.34 Hz, 4H, CH2); 1.68 (d, J ) 2.85 Hz, 6H, CH3);
1.00 (t, J ) 7.34 Hz, 6H, CH3); 1.37 (s, 3H, CH3); 0.88 (t, J ) 7.34 Hz,
3H, CH3). Crystal suitable for X-ray analysis were obtained from THF/
Et2O.