Reactions of 1,4- and 2,3-diazadienes with titanocene and zirconocene complexes of bis(trimethylsilyl)-acetylene: Acetylene coupling or substitution including subsequent C-H activation, C-C coupling, and N-N cleavage to heterobimetallic complexes

Article abstract of DOI:10.1021/om980466e

The reaction of 1,4-diazadienes RN=CHCH=NR with the titanocene and zirconocene complexes of bis(trimethylsilyl)acetylene Cp₂M(L)(η²-Me₃SiC₂SiMe ₃) (M = Ti, without L (1); M = Zr, L = THF (2), pyridine (3)) is a general and new method to obtain 1-metalla-2,5-diazacyclopent-3-ene complexes Cp₂M(η²-1:4-RNCH=CHNR) (M = Zr, R = 2,6-ⁱPr₂C₆H₃ (4a), 4-Me-C₆H₄ (4b), Cy (4c); M = Ti, R = 2,6-ⁱPr₂C₆H₃ (5a), 4-Me-C₆H₄ (5b), Cy (5c)). In the analogous reaction with differently substituted azines RR′C=NN=CRR′ the products depend strongly on the metals used, Zr and Ti, as well as on the substituents R and R′. With R = R′ -Me and M = Ti, a substitution of the alkyne by the azine and a subsequent CH activation to the 1-titana-2,3-diazacyclopent-3-ene species 6 was observed. Using R = Ph and R′ = H the acetylene was also substituted and, by a reductive coupling of two azine molecules, the paramagnetic binuclear Ti(III) complex (Cp₂Ti)₂[μ-(η ⁴-2:3,6:7-PhHC=NNCHPhCHPhNN= CHPh) (7) was formed. With M = Zr and R = Ph and R′ = H no substitution of the acetylene was observed, but one of the C=N double bonds of the azine inserts into the Zr-C bond of the zirconacyclopropene moiety of the starting acetylene complex to yield the 1-zircona-2-azacyclopent-4-ene species 8, which is additionally stabilized by N-coordination of the second imino group as a substituent in α position to the metal. Using R = R′ = Ph, the central N-N single bond of the azine is cleaved by both of the metals and the bis(imido) complexes Cp₂M(-N=CPh₂)₂ (M = Zr (9), Ti (10)) were isolated. The central C-C bond of 7 is cleaved in a subsequent reaction with CpCo(C₂H₄)₂ and, after an activation of the N-N bond of the azine, the heterobimetallic complex (Cp₂Ti)(μ-N=CHPh)₂(CpCo) (11) was formed. In the reaction of benzaldehyde azine with CpCo(C₂H₄)₂ the isoelectronic homobimetallic bis-(alkylideneamido) complex (CpCo)(μ-N=CHPh)₂(CpCo) (12) was prepared. In reactions of 9 and 10 with CpCo(C₂H₄)₂ heterobimetallic complexes of this type analogous to complex 11 were not obtained. All new complexes have been characterized by spectroscopic methods, and additionally, 4a, 7, 8, 10, 11, and 12 were characterized by single-crystal X-ray structure analysis.

Full text of DOI:10.1021/om980466e

Organometallics 1998, 17, 4429-4437
4429
Rea ction s of 1,4- a n d 2,3-Dia za d ien es w ith Tita n ocen e
a n d Zir con ocen e Com p lexes of Bis(tr im eth ylsilyl)-
a cetylen e: Acetylen e Cou p lin g or Su bstitu tion In clu d in g
Su bsequ en t C-H Activa tion , C-C Cou p lin g, a n d N-N
Clea va ge to Heter obim eta llic Com p lexes
Thorsten Zippel, Perdita Arndt, Andreas Ohff, Anke Spannenberg,
Rhett Kempe, and Uwe Rosenthal*
Abteilung Komplexkatalyse, Institut fu¨r Organische Katalyseforschung an der Universita¨t
Rostock, Buchbinderstrasse 5-6, 18055 Rostock, Germany
Received J une 8, 1998
The reaction of 1,4-diazadienes RNdCHCHdNR with the titanocene and zirconocene
complexes of bis(trimethylsilyl)acetylene Cp2M(L)(η2-Me3SiC2SiMe3) (M ) Ti, without L (1);
M ) Zr, L ) THF (2), pyridine (3)) is a general and new method to obtain 1-metalla-2,5-
diazacyclopent-3-ene complexes Cp2M(η2-1:4-RNCHdCHNR) (M ) Zr, R ) 2,6-iPr2C6H3 (4a ),
4-Me-C6H4 (4b), Cy (4c); M ) Ti, R ) 2,6-iPr2C6H3 (5a ), 4-Me-C6H4 (5b), Cy (5c)). In the
analogous reaction with differently substituted azines RR′CdNNdCRR′ the products depend
strongly on the metals used, Zr and Ti, as well as on the substituents R and R′. With R )
R′ ) Me and M ) Ti, a substitution of the alkyne by the azine and a subsequent CH activation
to the 1-titana-2,3-diazacyclopent-3-ene species 6 was observed. Using R ) Ph and R′ ) H
the acetylene was also substituted and, by a reductive coupling of two azine molecules, the
paramagnetic binuclear Ti(III) complex (Cp2Ti)2[µ-(η4-2:3,6:7-PhHCdNNCHPhCHPhNNd
CHPh) (7) was formed. With M ) Zr and R ) Ph and R′ ) H no substitution of the acetylene
was observed, but one of the CdN double bonds of the azine inserts into the Zr-C bond of
the zirconacyclopropene moiety of the starting acetylene complex to yield the 1-zircona-2-
azacyclopent-4-ene species 8, which is additionally stabilized by N-coordination of the second
imino group as a substituent in R position to the metal. Using R ) R′ ) Ph, the central
N-N single bond of the azine is cleaved by both of the metals and the bis(imido) complexes
Cp2M(-NdCPh2)2 (M ) Zr (9), Ti (10)) were isolated. The central C-C bond of 7 is cleaved
in a subsequent reaction with CpCo(C2H4)2 and, after an activation of the N-N bond of the
azine, the heterobimetallic complex (Cp2Ti)(µ-NdCHPh)2(CpCo) (11) was formed. In the
reaction of benzaldehyde azine with CpCo(C2H4)2 the isoelectronic homobimetallic bis-
(alkylideneamido) complex (CpCo)(µ-NdCHPh)2(CpCo) (12) was prepared. In reactions of
9 and 10 with CpCo(C2H4)2 heterobimetallic complexes of this type analogous to complex 11
were not obtained. All new complexes have been characterized by spectroscopic methods,
and additionally, 4a , 7, 8, 10, 11, and 12 were characterized by single-crystal X-ray structure
analysis.
In tr od u ction
4 metallocene acetylene complexes 2a-c with acetylenes
and with substituted butadiynes as well as with ke-
tones, aldehydes, and imines we could often illustrate
unexpected results, which also lead to an interesting
chemistry.2d Reactions of titanocene and zirconocene
complexes with CdN double bonds are well-known.3 We
Reactions of organic substrates containing multiple
bonds with transition-metal complexes are of general
interest in organometallic chemistry from the theoreti-
cal and the synthetic point of view, respectively.1 In a
series of investigations concerning the reactions of group
(3) (a) J ensen, M.; Livinghouse, T. J . Am. Chem. Soc. 1989, 111,
4495. (b) Ito, H.; Taguchi, T.; Hanzawa, Y. Tetrahedron Lett. 1992,
33, 4469. (c) Coles, N.; Whitby, R. J .; Blagg, J . Synlett 1990, 271. (d)
Buchwald, S. L.; Watson, B. T.; Wannamaker, M. W.; Dewan, J . C. J .
Am. Chem. Soc. 1989, 111, 4486. (e) Grossman, R. B.; Davis, W. M.;
Buchwald, S. L. J . Am. Chem. Soc. 1991, 113, 2321. (f) Harris, M. C.
J .; Whitby, R. J .; Blagg, J . Tetrahedron Lett. 1995, 36, 4289. (g) Coles,
N.; Harris, M. C. J .; Whitby, R. J .; Blagg, J . Organometallics 1994,
13, 190. (h) Dekura, F.; Honda, T.; Mori, M. Chem. Lett. 1997, 825. (i)
Buchwald, S. L.; Wannamaker, M. W. J . Am. Chem. Soc. 1989, 111,
776. (j) Davis, J . M.; Whitby, R. J .; J axa-Chamiec, A. Tetrahedron Lett.
1992, 33, 5655. (k) Honda, T.; Satoh, S.; Mori, M. Organometallics
1995, 14, 1548. (l) Honda, T.; Mori, M. J . Org. Chem. 1996, 61, 1196.
(m) Honda, T.; Mori, M. Organometallics 1996, 15, 5464.
(1) Reviews: Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke,
R. G. Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987.
(2) (a) Burlakov. V. V.; Polyakov, A. V.; Yanovsky, A. I.; Struchkov,
Y. T.; Shur, V. B.; Vol’pin, M. E.; Rosenthal, U.; Go¨rls, H. J . Organomet.
Chem. 1994, 476, 197. (b) Rosenthal, U.; Ohff, A.; Michalik, M.; Go¨rls,
H.; Burlakov, V. V.; Shur, V. B. Angew. Chem., Int. Ed. Engl. 1993,
32, 1193. (c) Rosenthal, U.; Ohff, A.; Baumann, W.; Tillack, A.; Go¨rls,
H.; Burlakov, V. V.; Shur, V. B. Z. Anorg. Allg. Chem. 1995, 621, 77.
(d) Ohff, A.; Pulst, S.; Lefeber, C.; Peulecke, N.; Arndt, P.; Burlakov,
V. V.; Rosenthal, U. Synlett 1996, 111 and references therein. (e) Ohff,
A.; Zippel, T.; Arndt, P.; Spannenberg, A.; Kempe, R.; Rosenthal, U.
Organometallics 1998, 17, 1649.
S0276-7333(98)00466-X CCC: $15.00 © 1998 American Chemical Society
Publication on Web 09/12/1998

4430 Organometallics, Vol. 17, No. 20, 1998
Zippel et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta of 4a , 7, 8, 10, 11, a n d 12
4a 10
7
8
11
12
cryst color, habit
cryst system
space group
lattice constants
a (Å)
yellow-orange, prism brown-black, prism yellow, prism dark red, prism red-brown, prism brown, prism
monoclinic
monoclinic
orthorhombic orthorhombic
monoclinic
orthorhombic
P21/c
Pn
P212121
P212121
Pc
Pca21
13.789(3)
15.397(3)
15.188(3)
12.007(2)
15.337(2)
22.660(4)
7.900(2)
14.012(3)
28.718(6)
13.698(3)
13.784(3)
15.102(3)
17.962(4)
15.293(3)
8.796(2)
21.602(4)
10.129(2)
9.660(2)
b (Å)
c (Å)
R (deg)
â (deg)
102.70 (3)
103.99 (2)
98.35(3)
γ (deg)
Z
4
4
4
4
4
4
cell vol (Å3)
3145.7(11)
1.263
293 (2)
0.375
4049.1(11)
1.267
293(2)
0.432
1.85-24.34
10793
5982
3178.9(12)
1.254
293(2)
0.443
2.03-24.36
9477
4859
3501
334
2851.5(10)
1.254
293(2)
0.327
2.00-24.31
8593
4593
3038
352
2390.6(9)
1.418
293(2)
1.047
1.76-24.33
7014
3759
2633
596
2113.7(7)
1.434
293(2)
1.580
1.89-24.22
6010
3224
2761
261
density (g cm-3
temp (K)
)
µ(Mo KR) (mm-1
θ range (deg)
)
1.91-24.34
no. of rflns (measd) 9267
no. of rflns (indep)
no. of rflns (obsd)
no. of params
5035
3746
352
3181
973
R1 (I > 2σ(I))
wR2 (all data)
0.036
0.095
0.048
0.126
0.041
0.108
0.037
0.075
0.062
0.173
0.027
0.073
at calculated positions. All other non-hydrogen atoms were
refined anisotropically. Cell constants and other experimental
details were collected and recorded in Table 1. XP (SIEMENS
Analytical X-ray Instruments, Inc.) was used for structure
representations.
have studied reactions of bis(trimethylsilyl)acetylene
titanocene and zirconocene complexes with isolated Cd
N double-bond-containing compounds, e.g. for aldimines,
ketimines,4a oxazoles, isoxazoles, thiazoles,4b and sil-
oximes.4c In addition, lactams (keto-amine hydroxy-
P r epar ation of Com plexes. Cp2Zr [η2-1:4-(2,6-iP r C6H3N-
CHdCHN-2,6-iP r C6H3)] (4a ). To a solution of 480 mg (1.02
mmol) of Cp2Zr(Py)(η2-Me3SiC2SiMe3) (3) in 10 mL of THF was
added a solution of 385 mg (1.02 mmol) of glyoxalbis[(2,6-
diisopropylphenyl)imine] in 10 mL of THF, and the mixture
was stirred at room temperature for 5.5 h. The color changed
from green to red-orange within this time. After the solvent
was removed in vacuo, the oily residue was redissolved in Et2O
and the solution filtered. The red filtrate was then dried in
vacuo and the obtained yellow foam was crystallized from
n-pentane at -40 °C. After 4 days the mother liquor was
decanted, and the yellow-orange crystals were washed with
cold n-pentane and dried in vacuo. Yield: 285 mg (47%).
Mp: 127-129 °C. MS: m/ z 597 (M+), 532 (M - Cp+), 221
(Cp2Zr+). 1H NMR (benzene-d6, 297 K): δ 1.22, 1.29, 1.31, 1.34
4e
imine tautomerization)4d and 2-vinylpyridine,
con-
taining special CdN double bonds, were investigated.
Herein we offer a full report on reactions of zirconocene
and titanocene complexes of bis(trimethylsilyl)acetylene
with 1,4- and 2,3-diazadienes under substitution or
coupling of the acetylene as well as subsequent C-H
activation, C-C coupling, N-N cleavage, and prepara-
tion of “early-late” heterobimetallic complexes.2e
Exp er im en ta l P a r t
Gen er a l Con sid er a tion s. All operations were carried out
under an inert atmosphere (argon) using standard Schlenk
techniques. Solvents were freshly distilled from sodium
tetraethylaluminate under argon prior to use. Deuterated
solvents were treated with sodium or sodium tetraethylalu-
minate, distilled, and stored under argon. The following
spectrometers were used: NMR, Bruker ARX 400 at 9.4 T
(chemical shifts are given in δ (ppm) referenced to the signals
of the solvents used: benzene-d6, δH 7.16, δC ) 128.0; toluene-
d8, δH ) 2.03, δC ) 20.4; THF-d8, δH ) 1.73, δC ) 25.2); IR,
Nicolet Magna 550 (Nujol mulls using KBr plates); MS, AMD
402. Melting points were measured in sealed capillaries on a
Bu¨chi 535 apparatus. Elemental analyses were carried out
on a Leco CHNS-932 elemental analyzer.
X-r a y Cr ysta llogr a p h ic Stu d y of Com p lexes 4a , 7, 8,
10, 11, a n d 12. Data were collected with a STOE-IPDS
diffractometer using graphite-monochromated Mo KR radia-
tion. The structures were solved by direct methods (SHELXS-
86)5 and refined by full-matrix least-squares techniques
against F2 (SHELXL-93).6 The hydrogen atoms were included
3
i
(d, J HH ) 6.7 Hz, 4 × 6H, Me), 3.05, (m, 2H, CH, Pr), 3.92
i
(septet, 2H, CH, Pr), 5.54 (s, 2H, CHdCH), 5.77, 5.83 (s, 2 ×
5H, Cp), 7.11-7.21 (m, 6H, Ar). 13C{1H} NMR (benzene-d6,
297 K): δ 24.2, 24.8, 26.5, 27.0, 27.1, 27.7 (4 × Me, 2 × CH,
iPr), 106.7, 110.0 (Cp), 114.3 (CdC), 124.1, 124.7, 124.9 (C3-
5, Ar), 142.2, 145.7 (C2, C6, Ar), 148.4 (C1, Ar). Anal. Calcd
for C36H46N2Zr (597.99): C, 72.31; H, 7.75; N, 4.68. Found:
C, 72.32; H, 7.59; N, 4.75.
Cp 2Zr [η2-1:4-(4-Me-C6H4NCHdCHN-4-MeC6H4)] (4b). A
solution of 200 mg (862 µmol) of glyoxalbis(p-tolylimine) in 10
mL of THF was added to 400 mg (862 µmol) of Cp2Zr(THF)-
(η2-Me3SiC2SiMe3) (2) in 10 mL of THF, and the mixture was
stirred at room temperature for 4 h. The solvent was removed
in vacuo, and the remaining oil was dissolved in the minimum
volume of Et2O. After addition of 15 mL of n-pentane, the
claret-colored solution was passed through a frit. Cooling to
-40 °C for 7 days induced the formation of orange-red needles,
which were separated from the mother liquor, washed with
cold n-hexane, and dried in vacuo. Yield: 295 mg (75%) of
4b. Mp: 85-87 °C dec. MS: m/ z 457 (M+), 392 (M - Cp+),
221 (Cp2Zr+). IR (Nujol mull): 1569, 1606 cm-1 (νCdN). 1H
NMR (THF-d8, 220 K): δ 2.29 (s, 6H, Me), 5.81 (s, 2H, CHd
CH), 5.88, 6.14 (s, 2 × 5H, Cp), 6.77 (d, J ) 8.3 Hz, 4H, Ar),
7.05 (d, J ) 8.3 Hz, 4H, Ar). 1H NMR (THF-d8, 297 K): δ
2.29 (br s, 6H, Me), 5.80 (br s, 2H, CHdCH), 5.98 (br s, 10H,
Cp), 6.57, 7.03 (d, 2 × 4H, J ) 8.3 Hz, Ar).13C{1H} NMR (THF-
d8, 220 K): δ 20.8 (Me), 105.3, 109.3 (Cp), 113.0 (CdC), 121.0,
(4) (a) Lefeber, C.; Arndt, P.; Tillack, A.; Baumann, W.; Kempe, R.;
Burlakov, V. V.; Rosenthal, U. Organometallics 1995, 14, 3090. (b)
Arndt, P.; Lefeber, C.; Kempe, R.; Rosenthal, U. Chem. Ber. 1996, 129,
207. (c) Tillack, A.; Arndt, P.; Spannenberg, A.; Kempe, R.; Rosenthal,
U. Z. Anorg. Allg. Chem. 1998, 624, 737. (d) Arndt, P.; Lefeber, C.;
Kempe, R.; Tillack, A.; Rosenthal, U. Chem. Ber. 1996, 129, 1281. (e)
Thomas, D.; Baumann, W.; Spannenberg, A.; Kempe, R.; Rosenthal,
U. Organometallics 1998, 17, 2096.
(5) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(6) Sheldrick, G. M. SHELXL-93; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1993.

Reactions of Cp2Ti and Cp2Zr Complexes
Organometallics, Vol. 17, No. 20, 1998 4431
129.8 (C2/6, C3/5, Ar), 130.5 (C4, Ar), 151.4 (C1, Ar). Anal.
Calcd for C26H26N2Zr (457.73): C, 68.23; H, 5.73; N, 6.12.
Found: C, 68.13; H, 6.09; N, 5.56.
dark green. The solvent was evaporated in vacuo, and the
residue was crystallized at -78 °C from n-hexane. After 5
days the solution afforded dark green crystals, which were
washed with n-hexane and dried in vacuo. Yield: 520 mg
(88%) of 5c. Mp: 106 °C dec. MS: m/ z 398 (M+), 333 (M -
Cp+), 178 (Cp2Ti+). IR (Nujol mull): 1491 cm-1 (νCdN). 1H
NMR (benzene-d6, 297 K): δ 0.95-1.06 (m, 2H, CH2, Cy),
1.13-1.32 (m, 8H, CH2, Cy), 1.53-1.57 (m, 2H, CH2, Cy), 1.67-
1.73 (m, 8H, Cy), 3.20 (tt, J HH′ ) 11.3 Hz, J HH ) 3.37 Hz,
2H, CH, Cy), 5.50 (s, 10H, Cp); 6.16 (br, 2H, CHdCH). 1H
NMR (THF-d8, 220 K): δ 1.19-1.45 (m, 10H, CH2, Cy), 1.60-
1.85 (m, 10H, CH2, Cy), 2.95 (m, 2H, CH, Cy), 5.40 (s, 2H, CHd
CH), 5.50, 5.87 (s, 2 × 5H, Cp). 13C{1H} NMR (benzene-d6,
297 K): δ 26.4, 26.8, 35.9 (CH2, Cy), 66.2 (CH, Cy), 104.7 (Cp),
121.1 (CdC). 13C{1H} NMR (THF-d8, 220 K): δ 26.8, 26.9,
27.4, 37.2, 38.0 (CH2, Cy), 66.2 (CH, Cy), 101.8, 108.1 (Cp),
110.8 (CdC). Anal. Calcd for C24H34N2Ti (398.43): C, 72.35;
H, 8.60; N, 7.03. Found: C, 72.57; H, 8.62; N, 7.02.
Cp 2Zr [η2-1:4-(CyNCHdCHNCy)] (4c). A solution of 200
mg (908 µmol) of glyoxalbis(cyclohexylimine) in 10 mL of THF
was added to 430 mg (913 µmol) of Cp2Zr(Py)(η2-Me3SiC2SiMe3)
(3) in 15 mL of THF via syringe, and the mixture was stirred
at 60 °C for 5 h. After 15 min the color of the solution changed
from violet to dark green. The solvent was removed in vacuo,
and the resulting oil was washed with cold n-hexane. The
residue was crystallized from n-pentane at -40 °C. After 3
days the solution afforded bright, orange crystals, which were
isolated by filtration, washed with n-hexane, and dried in
vacuo. Yield: 274 mg (68%) of 4c. Mp: 108-110 °C dec. MS:
m/ z 440 (M+), 330 (M - CyNC+), 221 (Cp2Zr+). IR (Nujol
mull): 1786, 1679 cm-1 (νCdN). 1H NMR (benzene-d6, 297 K):
δ 1.00-1.40 (m, 12H, CH2, Cy), 1.58-1.89 (m, 8H, CH2, Cy),
2.95-3.03 (m, 2H, CH, Cy), 5.32 (br s, 2H, CHdCH), 5.45, 5.85
(br s, 2 × 5H, Cp). 13C{1H} NMR (benzene-d6, 297 K): δ 19.7,
30.6, 31.6 (CH2, Cy), 61.6 (CH, Cy), 101.7, 107.7 (br s, Cp),
110.3 (CdC). Anal. Calcd for C24H34N2Zr (441.47): C, 65.25;
H, 7.76; N, 6.34. Found: C, 65.07; H, 7.92; N, 6.12.
3
3
Cp 2Ti[N(CHMe2)NdC(Me)CH2] (6). To a solution of 275
mg (789 µmol) of Cp2Ti(η2-Me3SiC2SiMe3) (1) in 15 mL of THF
was added 105 µL (793 µmol) of acetone azine. As the
yellowish brown reaction mixture was stirred at 60 °C for 15
h, the color changed to dark green within 15 min. After
removal of the solvent in vacuo, dissolution of the residue in
a THF/n-hexane mixture, filtration, and repeated removal of
the solvent, the turquoise complex 6 was dried in vacuo.
Yield: 153 mg (67%) of 6. MS: m/ z 290 (M+). IR (Nujol
mull): 1603 cm-1 (νCdN). 1H NMR (toluene-d8, 330 K): δ 1.12
(d, 6H, Me), 1.36 (s, 2H, CH2), 2.24 (s, 3H, Me), 3.82 (septet,
1H, CH), 5.21 (s, 10H, Cp). 1H NMR (toluene-d8, 297 K): δ
Cp 2Ti[η2-1:4-(2,6-iP r C6H3NCHdCHN-2,6-iP r C6H3)] (5a ).
A 360 mg (0.96 mmol) amount of glyoxalbis[(2,6-diisoprop-
ylphenyl)imine] in 10 mL of THF was added to a yellowish
brown solution of 330 mg (0.95 mmol) of Cp2Ti(η2-Me3SiC2-
SiMe3) (1) in 10 mL of THF. The color changed to dark brown
within 20 min. After the mixture was stirred at 20 °C for 2.5
h, the solvent was removed in vacuo and the residue crystal-
lized from n-hexane. After 1 week at -40 °C the solution
afforded brown crystals, which were separated from the
mother liquid, washed with cold n-hexane, and dried in vacuo.
Yield: 400 mg (75%). Mp: 145-147 °C. MS: m/ z 554 (M+),
489 (M - Cp+), 333 (C26H36N2 - iPr+), 178 (Cp2Ti+). 1H NMR
(THF-d8, 230 K): δ 1.08, 1.14, 1.30, 1.36 (d, 4 × 3H, Me), 2.80,
3
1.14 (d, J HH ) 6.3 Hz, 6H, Me), 1.36 (br, 2H, CH2), 2.28 (s,
3H, Me), 3.82 (septet, 3J HH ) 6.3 Hz, 1H, CHMe2), 5.17 (s,
10H, Cp). 1H NMR (toluene-d8, 220 K): δ 0.65 (s, 1H, CH2),
1.23, 1.36 (br, 2 × 3H, Me), 2.16 (s, 1H, CH2), 2.35 (s, 3H, Me),
3.73 (br, 1H, CHMe2), 5.06, 5.21 (s, 2 × 5H, Cp), 13C{1H} NMR
(toluene-d8, 297 K): δ 24.5, 25.7 (Me), 55.9 (CH2), 60.2 (CH),
105.2 (Cp), 151.7 (CdN). 13C{1H} NMR (toluene-d8, 220 K):
δ 24.0, 25.0, 25.9 (Me), 55.0 (CH2), 59.8 (CH), 102.7, 107.3 (Cp),
151.8 (CdN). Anal. Calcd for C16H22N2Ti (290.24): C, 66.21;
H, 7.64; N, 9.65. Found: C, 66.35; H, 7.58; N, 9.70.
i
3.75 (septet, 2 × 1H, CH, Pr), 5.68, 5.76 (s, 2 × 5H, Cp), 6.29
(s, 2H, CHdCH), 7.06-7.17 (m, 6H, CH, Ar). 1H NMR
(benzene-d6, 297 K): δ 1.18, 1.34 (d, 2 × 12H, Me), 3.4 (br s,
2H, CH, iPr), 5.65 (br s, 10H, Cp), 6.21 (s, 2H, CHdCH), 7.12-
7.18 (m, 6H, Ar). 13C{1H} NMR (THF-d8, 230 K): δ 23.4, 23.8,
i
25.7, 26.4, 27.9, 28.4 (4 × Me, 2 × CH, Pr), 106.0, 111.3 (br,
Cp), 124.3, 124.7, 125.7, 125.8 (C3-C5, Ar, 1 × CdC), 142.1,
(C p 2 T i )2 [µ-(η4 -2:3,6:7-P h H C dN N C H P h C H P h N N d
CHP h ) (7). To a solution of 550 mg (1.58 mmol) of Cp2Ti(η2-
Me3SiC2SiMe3) (1) in 10 mL of toluene was added a solution
of 330 mg (1.58 mmol) of trans,trans-benzaldehyde azine in
10 mL of toluene, and the mixture was stirred at 60 °C for 20
h. The color of the solution changed from yellowish brown to
dark brown within 15 min. The solvent was removed in vacuo,
and the residue was dissolved in 2 mL of THF. After addition
of 15 mL of cold n-hexane (-78 °C), the crude product
precipitated, which was washed with a further 10 mL of
n-hexane and dried in vacuo. Yield: 530 mg (87%). The brown
powder was redissolved in a THF/n-hexane (1:3) solution at
60 °C and filtered. The filtrate was then allowed to crystallize
at -78 °C. The obtained brown crystals were washed with
cold n-hexane and dried in vacuo. Yield: 485 mg (80%) of 7.
Mp: 192 °C dec. MS: m/z 387 (M/2+). IR (Nujol mull): 1594,
1576 cm-1 (νCdN). NMR: no spectra, since complex 7 is
paramagnetic. Anal. Calcd for C48H44N4Ti2 (772.67): C, 74.62;
H, 5.74; N, 7.25. Found: C, 74.71; H, 5.87; N, 7.28.
146.6 (C2/6, Ar), 151.6 (C1, Ar). 13C{1H} NMR (benzene-d6,
i
297 K): δ 23.7 (Me), 27.1 (br, CH, Pr), 27.7 (Me), 108.3 (br,
Cp), 124.3, 124.4, 125.8 (C3-5, Ar), 144.2 (br, C2/6, Ar), 151.0
(C1, Ar). Anal. Calcd for C36H46N2Ti (554.65): C, 77.96; H,
8.36; N, 5.05. Found: C, 77.68; H, 8.66; N, 5.13.
Cp2Ti[η2-1:4-(4-Me-C6H4NCHdCHN-4-MeC6H4)] (5b). To
a solution of 430 mg (1.23 mmol) of Cp2Ti(η2-Me3SiC2SiMe3)
(1) in 10 mL of THF was added 290 mg (1.23 mmol) of
glyoxalbis(p-tolylimine) in 10 mL of THF. As the red-brown
reaction mixture was stirred at room temperature for 4.5 h,
the color changed to dark brown. The solvent was removed
under reduced pressure, affording a brown oil. The oil was
dissolved in a minimum amount of Et2O and then covered by
n-pentane. A brown product crystallized, which was separated
from the mother liquid, washed with cold n-pentane, and dried
in vacuo. Yield: 240 mg (58%) of 5b. Mp: 144-146 °C dec.
MS: m/ z 414 (M+), 349 (M - Cp+), 178 (Cp2Ti+). IR (Nujol
mull): 1608 cm-1 (νCdN). 1H NMR (benzene-d6, 297 K): δ 2.26
(s, 6H, Me), 5.60 (br s, 10H, Cp), 6.29 (s, 2H, CHdCH), 6.70
(d, J ) 8.0 Hz, 4H, CH, Ar), 7.04 (d, J ) 7.7 Hz, 4H, CH, Ar).
13C{1H} NMR (benzene-d6, 297 K): δ 20.8 (Me), 107.0 (Cp),
121.7 (CdC), 123.9, 129.4 (C2/6, C3/5, Ar), 132.0 (C4, Ar); 152.5
(C1, Ar). Anal. Calcd for C26H26N2Ti (414.39): C, 75.36; H,
6.32; N, 6.76. Found: C, 75.19; H, 6.39; N, 3.83.
Cp 2Zr [C(SiMe3)dC(SiMe3)CHP h NNdCHP h ] (8). A so-
lution of 195 mg (936 µmol) of trans,trans-benzaldehyde azine
in 5 mL of THF was added to a stirred solution of 435 mg (938
µmol) of Cp2Zr(THF)(η2-Me3SiC2SiMe3) (2) in 15 mL of THF.
After 15 h at 20 °C the solvent and eliminated bis(trimethyl-
silyl)acetylene were removed from the green solution in vacuo.
The residue was redissolved in Et2O, filtered and dried in
vacuo to yield 255 mg (44%) of analytically pure 8. Alterna-
tively, crystallization of the crude material from 15 mL of
Cp 2Ti[η2-1:4-(CyNCHdCHNCy)] (5c). To a solution of
520 mg (1.49 mmol) of Cp2Ti(η2-Me3SiC2SiMe3) (1) in 20 mL
of toluene was added 330 mg (1.50 mmol) of crystalline
glyoxalbis(cyclohexylimine). As the yellowish brown reaction
mixture was stirred for 20 h at 100 °C, the color changed to

4432 Organometallics, Vol. 17, No. 20, 1998
Zippel et al.
n-pentane at -40 °C yielded the pure crystalline orange
complex 8 in 41% yield. Mp: 102-103 °C dec. MS: m/z 209
((PhCHdN)2+), 171 ((Me3SiC)2+). IR (Nujol mull): 1543 cm-1
(νCdN). 1H NMR (benzene-d6, 297 K): δ 0.18, 0.51 (s, 2 ×
9H, SiMe3), 5.42 (br, 1H, CH), 5.72, 5.87 (s, 2 × 5H, Cp), 7.05
(m, 2H, Ph), 7.21 (m, 4H, Ph), 7.36 (s, 1H, NdCH), 7.42 (m,
4H, Ph). 13C{1H} NMR (benzene-d6, 297 K): δ 3.7, 6.0 (SiMe3),
91.6 (CH), 109.2, 109.9 (Cp), 124.2, 124.5, 126.9, 127.6, 128.5,
129.1, 129.6 (C2-6, Ph, 1 × CH), 136.5, 141.1 (C1, Ph), 167.6
(Câ-SiMe3), 218.7 (CR-SiMe3). Anal. Calcd for C32H40N2Si2Zr
(600.07): C, 64.05; H, 6.72; N, 4.67. Found: C, 64.54; H, 6.74;
N, 4.77.
159 °C dec. MS: 456 (M+), 351 (M - NdCHPh+), 189 (Cp2-
Co+), 124 (CpCo+), 77 (Ph+), 59 (Co+). IR (Nujol mull): 1565,
1573, 1583 cm-1 (νCdN). Cs-symmetric product: 1H NMR (THF-
d8, 297 K) δ 4.71, 4.86 (s, 2 × 5H, Cp), 7.27 (m, 2H, Ph), 7.40
(t, J ) 7.6 Hz, 4H, Ph), 8.04 (m, 4H, Ph), 9.20 (s, 2H, NdCH).
C2-symmetric product: 1H NMR (THF-d8, 297 K): δ 4.82 (s,
10H, Cp), 7.23 (m, 2H, Ph), 7.36 (t, J ) 7.6 Hz, 4H, Ph), 7.89
(m, 4H, Ph), 9.30 (s, 2H, NdCH).13C{1H} NMR (THF-d8, 297
K): Cs, δ 79.7, 80.6 (Cp); C2, δ 80.2 (Cp); Cs + C2, 126.7, 126.8,
128.6 (2), 128.7 (2) (C2-6, Ph), 137.4, 137.6 (C1, Ph), 173.6,
174.1 (NdCH). Anal. Calcd for C24H22N2Co2 (456.32): C,
63.17; H, 4.86; N, 6.14. Found: C, 63.35; H, 4.87; N, 6.02.
Cp 2Zr (-NdCP h 2)2 (9). A 420 mg (1.17 mmol) amount of
benzophenone azine was added to a yellowish brown solution
of 540 mg (1.16 mmol) of Cp2Zr(THF)(η2-Me3SiC2SiMe3) (2) in
20 mL of THF. The solution was stirred at 60 °C for 14 h.
Under reduced pressure the reaction volume was decreased
to a volume of about 2 mL, and 15 mL of cold n-hexane was
added to precipitate the product. Filtering followed by wash-
ing with cold n-hexane (2 × 5 mL) and drying in vacuo yields
580 mg (86%) of 9. The red powder crystallized by diffusion
of n-pentane into a THF solution. After standing for 2 days
at room temperature red crystals separated, which were
decanted, washed with n-hexane, and dried in vacuo. Yield:
510 mg (75%). Mp: 157 °C dec. MS: m/z 581 (M+), 401 (M -
Ph2CdN+), 221 (Cp2Zr+), 180 (Ph2CdN+), 77 (Ph+). IR (Nujol
mull): 1632, 1655 cm-1 (νCdN). 1H NMR (benzene-d6, 297 K):
δ 5.77 (s, 10H, Cp), 7.17-7.24 (m, 12H, CH, Ph), 7.61-7.64
(m, 8H, CH, Ph). 13C{1H} NMR (benzene-d6, 297 K): δ 108.8
(Cp), 128.2, 128.6 (C2/6, C3/5, Ph), 128.5 (C4, Ph), 141.8 (C1,
Ph), 170.3 (CdN). Anal. Calcd for C36H30N2Zr (581.87): C,
74.31; H, 5.20; N, 4.81. Found: C, 74.28; H, 5.21; N, 4.78.
Cp 2Ti(-NdCP h 2)2 (10). An amount of 440 mg (1.22 mmol)
of benzophenone azine was added to a stirred solution of 430
mg (1.23 mmol) of Cp2Ti(η2-Me3SiC2SiMe3) (1) in 20 mL of
toluene, and the mixture was stirred at 60 °C while the
yellowish brown reaction mixture became dark brown within
5 min. After 1 day the solvent was evaporated under reduced
pressure. The residue was dissolved in n-hexane (60 °C), the
solution was filtered, and dark red crystals were obtained by
crystallization at room temperature. Yield: 580 mg (85%) of
10. Mp: 145 °C dec. MS: m/ z 538 (M+), 473 (M - Cp+), 358
(M - NdCPh2+), 77 (Ph+). IR (Nujol mull): 1622 cm-1 (νCdN).
1H NMR (benzene-d6): δ 5.57 (s, 10H, Cp), 7.17-7.22 (m, 12H,
Ph), 7.51-7.54 (m, 8H, Ph). 13C{1H} NMR (benzene-d6): δ
109.4 (Cp), 141.7 (C1, Ph), 129.1, 129.4, 129.7 (C2-6, Ph),
165.8 (CdN). Anal. Calcd for C36H30N2Ti (538.53): C, 80.29;
H, 5.61; N, 5.20. Found: C, 80.10; H, 5.60; N, 5.20.
Resu lts a n d Discu ssion
P r ep a r a tion of Com p lexes. Since the bis(trimeth-
ylsilyl)acetylene titanocene Cp2Ti(η2-Me3SiC2SiMe3) (1)2a
and zirconocene complexes Cp2Zr(L)(η2-Me3SiC2SiMe3)
(L ) THF (2),2b pyridine (3))2c are excellent starting
materials for the generation of the reactive Cp2Ti and
Cp2Zr fragments,2d the reactions with 1,4-diazadienes
RNdCHCHdNR were carried out with 1-3 as metal-
locene precursors. These complexes react via substitu-
tion of the acetylene (and, in the case of zirconium, of
ligands L) to give the corresponding 1-metalla-2,5-
diazacyclopent-3-ene (diazadiene) complexes Cp2M(η2-
1:4-RNCHdCHNR) (M ) Zr, R ) 2,6-iPr2C6H3 (4a ),
4-MeC6H4 (4b), Cy (4c); M ) Ti, R ) 2,6-iPr2C6H3 (5a ),
4-MeC6H4 (5b), Cy (5c)) (eq 1).
(1)
(Cp 2Ti)(µ-NdCHP h )2(Cp Co) (11). A solution of 40 mg
(222 µmol) of CpCo(C2H4)2 in 10 mL of THF was added to 85
mg (110 µmol) of complex 7 in 10 mL of THF. The orange-
brown solution changed to dark violet within 10 min. After 6
h the solvent was evaporated in vacuo and the residue
crystallized from THF/n-hexane at -78 °C. After 4 days the
solution afforded brown, well-formed prismatic crystals, which
were washed with n-hexane and dried in vacuo. Yield: 94 mg
(83%) of 7. Mp: 187 °C dec. MS: m/ z 510 (M+), 124 (CpCo+),
104 (NdCHPh+), 77 (Ph+). IR (Nujol mull): 1592 cm-1 (νCd
N). 1H NMR (benzene-d6, 297 K): δ 4.51 (s, 5H, Cp), 5.44 (s,
10H, Cp), 7.28-7.35 (m, 6H, m-, p-Ph), 7.77 (m, 4H, o-Ph),
10.70 (s, 2H, NdCH). 13C{1H} NMR (benzene-d6, 297 K): δ
90.2 (Co-Cp), 108.6 (Ti-Cp), 125.3, 126.2, 129.4 (C2-6, Ph),
138.5 (C1, Ph), 170.5 (CdN). Anal. Calcd for C29H27N2CoTi
(510.36): C, 68.25; H, 5.33; N, 5.49. Found: C, 67.98; H, 5.50;
N, 5.58.
(7) (a) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger,
L. M.; Latesky, S. L.; McMullen, A. K.; Steffey, B. D.; Rothwell, I. P.;
Folting, K.; Huffman, J . C. J . Am. Chem. Soc. 1987, 109, 6068. (b)
Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I. P.;
Huffman, J . C. Organometallics 1985, 4, 1896. (c) Bocarsly, J . R.;
Floriani, C.; Chiesi-Villa, C.; Guastini, C. Organometallics 1986, 5,
2380. (d) Berg, F. J .; Petersen, J . L. Organometallics 1991, 10, 1599.
(e) Berg, F. J .; Petersen, J . L. Tetrahedron 1992, 48, 4749. (f) Scholz,
J .; Dlikan, M.; Stro¨hl, D.; Dietrich, A.; Schumann, H.; Thiele, K.-H.
Chem. Ber. 1990, 123, 2279. (g) Scholz, J .; Dietrich, A.; Schumann,
H.; Thiele, K.-H. Chem. Ber. 1991 124, 1035. (h) Hadi, G. A.; Wunderle,
J .; Thiele, K.-H.; Fro¨hlich, R. Z. Kristallogr. 1994, 209, 372. (i) Goddard,
R.; Kru¨ger, C.; Hadi, G. A.; Thiele, K.-H.; Scholz, J . H. Z. Naturforsch.,
B 1994, 49, 519. (j) Herrmann, W. A.; Denk, M.; Scherer, F.; Klingan,
F.-R. J . Organomet. Chem. 1993, 444, C21. (k) Aoyagi, K.; Gantzel, P.
K.; Kalai, K.; Tilley, T. D. Organometallics 1996, 15, 923. (l) Scholz,
J .; Nolte, M.; Kru¨ger, C. Chem. Ber. 1993, 126, 803. (m) Hey-Hawkins,
E. Chem. Rev. 1994, 94, 1661 and references therein.
(Cp Co)(µ-NdCHP h )2(Cp Co) (12). To a solution of 210 mg
(1.17 mmol) of CpCo(C2H4)2 in 10 mL of THF was added a
solution of 120 mg (0.58 mmol) of trans,trans-benzaldehyde
azine in 10 mL of THF. After 14 h at 60 °C the solvent was
removed in vacuo and the yellowish brown residue crystallized
from n-hexane at 20 °C. Yield: 450 mg (80%) Cs + C2. Mp:

Reactions of Cp2Ti and Cp2Zr Complexes
Organometallics, Vol. 17, No. 20, 1998 4433
was formed (eq 3).
Titanium and zirconium complexes with 1,4-diaza-
dienes are well-known and were described before.7 The
substitution of an acetylene by the 1,4-diazadiene is a
new method for preparing a series of such complexes.
In most of those complexes the â-positions are substi-
tuted.7
Complexes without substituents in these positions are
very rare,7h,j and complexes 4a -c and 5a -c are new
examples of such ethanediimine (ethylenediamide)
ligands.
In the analogous reaction with azines RR′CdNNd
CRR′ the products depend strongly on the metals used,
Zr and Ti, as well as the substituents R and R′. With
R ) R′ ) Me and M ) Ti, the reaction of 1 with acetone
azine leads after substitution of the alkyne with the
azine to an unexpected activation of the methyl C-H
bond. In the resulting green complex 6 a hydrogen atom
is shifted from one methyl group to the carbon atom of
the second CdN moiety and the five-membered 1-titana-
2,3-diazacyclopent-3-ene metallacycle 6 is obtained (eq
2).
(3)
In this reaction the acetylene was also substituted by
the azine and, by a reductive coupling of two azine
molecules, 7 was formed. The reaction path shows some
similarities to the coupling of ketones R2CdO between
two titanium(II) centers in the McMurry reaction.10 This
type of reaction has been verified also for heterocarbonyl
compounds such as R2CdNR.11
In the analogous reaction with M ) Zr, no substitu-
tion of the acetylene was observed, but one of the CdN
double bonds of the azine inserts into the Zr-C bond of
the zirconacyclopropene structure of the starting acetyl-
ene complex to yield the five-membered 1-zircona-2-
azacyclopent-4-ene species 8, which is additionally
stabilized by N-coordination of the second imino group
as substituent in a position R to the metal (eq 4).
(2)
The course of the reaction of acetone azine and
titanocene with the activation of a strong sp3 C-H bond
in 6 is rather surprising in view of the ease of oxidative
addition and cleavage of the N-N bond of Ph2CdNNdC-
Ph2 to Cp2Zr(C4H6)8b and CpCo(C2H4),9 where mono-
nuclear Cp2Zr(NdCPh2)2 or dinuclear species (CpCo)-
(µ-(NdCPh2)2(CpCo) were obtained (see also below).
A completely different result compared to that for R
) R′ ) Me was obtained in the reaction of 1 with
benzaldehyde azine using R ) Ph and R′ ) H. In this
case the paramagnetic binuclear Ti(III) complex (Cp2-
Ti)2[µ-(η4-2:3,6:7-PhHCdNNCHPhCHPhNNdCHPh)] (7)
(4)
(8) (a) Collier, M. R.; Lappert, M. F.; McMeeking, J . Inorg. Nucl.
Chem. Lett. 1971, 7, 689. (b) Erker, G.; Fro¨mberg, W.; Kru¨ger, C.;
Raabe, E. J . Am. Chem. Soc. 1988, 110, 2400.
(9) Carofiglio, T.; Stella, S.; Floriani, C.; Chiesi-Villa, A.; Guastini,
C. J . Chem. Soc., Dalton Trans. 1989, 1957.
Such a coupling of acetylenes with CdN double bonds
is not unusual,3 but this is the first example found for
azines.
(10) (a) McMurry, J . E. Acc. Chem. Res. 1983, 16, 405. (b) Dang, Y.;
Geise, H. J . J . Organomet. Chem. 1991, 405, 1. (c) Eisch. J . J .; Shi, X.;
Alila, J . R.; Thiele, S. Chem. Ber. 1997, 130, 1175. (d) Chen, T. L.,
Chan, T. H.; Shaver, A. J . Organomet. Chem. 1984, 268, C1.
(11) (a) Pasquali, M.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Inorg.
Chem. 1981, 20, 349. (b) De Angelis, S.; Solari, E.; Gallo, E.; Floriani,
C.; Chiesi-Villa, A.; Rizzoli, C. Inorg. Chem. 1996, 35, 5995.
(12) J onas, K.; Deffense, E.; Habermann, D. Angew. Chem., Int. Ed.
Engl. 1983, 22, 716.
Using R ) R′ ) Ph the central N-N single bond of
the azine is cleaved by both of the metals and the bis-
(imido) complexes Cp2M(-NdCPh2)2 (M ) Zr (9),8b
) Ti (10)) were isolated (eq 5).
M

4434 Organometallics, Vol. 17, No. 20, 1998
Zippel et al.
(7)
(6)
In reactions of 9 and 10 with CpCo(C2H4)2 heterobi-
metallic complexes of the type (Cp2Ti)(µ-NdCPh2)2-
(CpCo), being analogous to complex 11, were not ob-
tained (eq 8).
Complex 9 has been prepared before by using the Cp2-
8b
Zr(C4H6) as zirconocene precursor.
12
The reaction of 7 and CpCo(C2H4)2 yields almost
quantitatively the heterobimetallic product (Cp2Ti)-µ-
(NdCHPh)2(CpCo) (11) (eq 6).
(8)
All new complexes have been characterized by spec-
troscopic methods and, for 4a , 7, 8, 10, 11, and 12, by
single-crystal X-ray analysis.
1
NMR Sp ectr oscop ic In vestiga tion s. The H and
13C NMR spectra of the complexes 4a -c as well as 5a -c
behave like those of the previously investigated com-
plexes Cp2M(η2-1:4-R1NCR2dCR2NR1) (M ) Zr, Ti; R1
) R2 ) Ph or R1 ) Ph, R2 ) Me)7f and exhibited at room
temperature only one signal for the Cp2M moiety. The
13C resonances of the internal C atoms of the complexed
heterodiene shifted to high field in a range which is
characteristic for CdC double bonds. The 1H NMR
spectra show also a great temperature dependence;
indeed at lower temperatures (225 K) the singlet of the
Cp ligands split into two signals, which were assigned
to two diastereotopic Cp units. This dynamic behavior
(in solution) of zirconocene and titanocene complexes
with 1,4-diazadienes has been discussed in detail.7f
The NMR spectra of 6 confirm the C-H activation
by signals of a CH2 group at 1.36 ppm (very broad,
(6)
The interaction of the bis(titanocene) species 7 with
an additional Co(I) center causes the activation of the
central C-C bond as well as the cleavage of the azine
N-N bonds, leading to the bridged heterobimetallic bis-
(alkylideneamido) complex 11.
In the reaction of complex 7 with CpRh(C2H4)2 by
using thermal or photochemical activation no analogous
heterobimetallic compound was observed.
1
becomes a sharp singlet at 330 K) and 55.9 ppm in H
and 13C NMR, respectively. In addition, there are two
different methyl signals at 1.14/ 2.28 ppm and 24.5/25.7
For comparison and preparation of the homobimetal-
lic bis(alkylideneamido) complex the reaction of benzal-
dehyde azine with CpCo(C2H4)2 was investigated. The
reaction product (CpCo)(µ-NdCHPh)2(CpCo) (12) (eq 7)
is analogous to the well-known complex (CpCo)(µ-Nd
CPh2)(CpCo).9
1
ppm in the ratio of 2:1. In the H NMR spectrum the
isopropyl methyl groups appear as a doublet (1.14 ppm,
3J HH ) 6.3 Hz, 6H) and, consequently, the signal of the
methine proton is a septet at 3.82 ppm (3J HH ) 6.3 Hz,
1H). Very broad methylene and cyclopentadienyl reso-
nances at ambient temperatures result from dynamic
behavior due to a folded ground-state conformation
typical for such azametallacycles.7l Indeed, at higher
temperatures (330 K) the NMR spectra of 6 suggest Cs
molecular symmetry in solution; however, decreasing
Complex 12 consists of a mixture of Cs- and C2-
symmetric products, as shown by NMR spectra. For
X-ray crystal structure analysis a single crystal of the
C2-symmetric product was used (see below).

Reactions of Cp2Ti and Cp2Zr Complexes
Organometallics, Vol. 17, No. 20, 1998 4435
F igu r e 2. Molecular structure of complex 7 (two sym-
metry-independent molecules per asymmetric unit; one is
selected) shown by an ORTEP plot. The thermal ellipsoids
correspond to 30% probability. Selected bond lengths (Å)
and angles (deg): Ti1-N1, 2.057(8); Ti1-N2, 2.096(10);
Ti2-N3, 2.054(8); Ti2-N4, 2.129(9); N1-C87, 1.456(12);
N2-C69, 1.298(12); N3-C42, 1.458(12); N4-C50, 1.309-
(12); N1-N2, 1.343(11); N3-N4, 1.344(10); C42-C87,
1.586(12); C42-C43, 1.522(13); C50-C51, 1.450(15); C69-
C70, 1.455(15); C87-C88, 1.502(13). N1-Ti1-N2, 37.7(3);
N3-Ti2-N4, 37.4(3); N1-N2-C69, 127.9(9); N3-N4-C50,
129.9(9); N2-C69-C70, 121.7(7); N4-C50-C51, 122.7(12);
N2-N1-C87, 122.1(8); N4-N3-C42, 120.0(8); N1-C87-
C88, 110.6(8); N3-C42-C43, 108.7(8); N1-C87-C42, 112.1-
(7); N3-C42-C87, 111.8(7).
F igu r e 1. Molecular structure of complex 4a , shown by
an ORTEP plot. The thermal ellipsoids correspond to 30%
probability. Selected bond lengths (Å) and angles (deg):
Zr-N1, 2.134(2); Zr-N2, 2.107(2); N1-C1, 1.386(3); N1-
C3, 1.439(3); N2-C2, 1.390(3); N2-C9, 1.425(4); C1-C2,
1.358(4); C4-C15, 1.512(4); C15-C19, 1.536(4); N1-Zr-
N2, 83.63(8); C1-N1-Zr, 92.8(2); C2-N2-Zr, 92.7(2); C1-
N1-C3, 120.5(2); C2-N2-C9, 117.9(2); C1-C2-N2, 122.6-
(3); C3-C4-C15, 123.5(3); C19-C15-C20, 109.8(3).
the temperature reveals a nonplanar molecular geom-
1
etry and the H NMR spectrum at 220 K displays two
diastereotopic Cp units (5.06 (s, 5H), 5.21 ppm (s, 5H))
as well as two nonequivalent methylene protons (0.65
(broad, 1H), 2.16 (broad, 1H)). The broad signals of the
nonequivalent methylene protons did not show the
expected fine structure.
reduced diazadiene to the other (see also above). The
Zr-N amido distances of this complex of 2.100(4), 2.107-
(4) Å and 2.125(5), 2.112(4) Å are only slightly different
from those of complex 4a of 2.107(2) and 2.134(2) Å. The
CdC distance of 1.358(4) Å and the N-C distances of
1.386(3) and 1.390(3) Å are within the normal ranges
for double and single bonds.
Due to its paramagnetism, the structure of 7 was
determined by X-ray crystallography (Figure 2).
The structure analysis was mentioned before2e in a
short communication and reveals a binuclear titanium-
(III) complex resulting from a reductive C-C coupling10
which converts two azine molecules into a dianionic
bridging ligand. Each Ti(III) center is complexed by an
amido nitrogen and additionally coordinated by the
electron pair of the second imine nitrogen. The struc-
ture of the ligand chain is characterized by two C-N
double bonds and two C-N single bonds, respectively,
intact N-N single bonds, and the newly formed central
C-C single bond.
NMR spectra of the titanocene complex 10 are very
much like those of the corresponding zirconocene com-
plex 9.8 Besides the signals of the four chemically
equivalent phenyl groups, only a single Cp resonance
has been found at δ 5.77 (9), 5.57 (10) (1H NMR, 10 H)
and δ 108.8 (9), 109.4 (10) (13C NMR) and the NdC
signal was found at δ 170.3 (9), 165.8 (10) (13C NMR).
NMR spectra of 11 show the resonances correspond-
ing to the phenyl groups and two different Cp units in
1
the ratio of 2:1. In addition, the H and 13C signals of
the azine CH function appear at 10.70 ppm (s, 2H) and
170.5 ppm, respectively.
Str u ctu r a l In vestiga tion s. Complexes 4a , 7, 8, 10,
11, and 12 were investigated by an X-ray crystal
structure analysis. The ORTEP structure of complex
4a is presented in Figure 1.
The type of structure is not new, but to the best of
our knowledge, this is the first example of a zirconocene
complex with hydrogen atoms in â positions to the
metal. Titanium complexes with hydrogen atoms in â
positions to the metal have been descibed, but with
ligands being different from Cp.7 All structural data
are in good agreement with the structure of the previ-
ously described zirconocene enediamido (diazadiene)
complex Cp2Zr(η2-1:4-PhNCPhdCPhNPh).7f This five-
membered metallacyclic ring system adopts an “enve-
lope” conformation and exhibits a dynamic NMR spec-
trum indicating a rapid intramolecular migration of the
bent metallocene unit Cp2M from one “face” of the
The molecular structure of complex 8 is presented in
Figure 3.
This type of structure is new. In the five-membered
1-zircona-2-azacyclopent-4-ene 8 species the nitrogen
atoms of the NdCHPh substituents in the position R to
the zirconium atom coordinate additionally. The five-
membered-ring system is similar to that which was
found in the reaction products resulting from oxidative
coupling of imines CdN with acetylenes. On the other
side the ring opening of benzazoles and benzthiazoles
also gives similar five-membered-ring systems,4b which

4436 Organometallics, Vol. 17, No. 20, 1998
Zippel et al.
F igu r e 3. Molecular structure of complex 8, shown by an
ORTEP plot. The thermal ellipsoids correspond to 30%
probability. Selected bond lengths (Å) and angles (deg):
Zr-N1, 2.324(4); Zr-N2, 2.021(5); Zr-C29, 2.447(5); C11-
C32, 1.452(7); C17-C31, 1.520(7); C29-C30, 1.366(7);
C30-C31, 1.547(7); C23-Si1, 1.868(7); C29-Si2, 1.874(5);
C30-Si1, 1.902(5); N1-N2, 1.331(6); N1-C32, 1.289(6);
N2-C31, 1.435(6); N1-Zr-N2, 34.79(15); N2-Zr-C29,
67.5(2); Zr-C29-C30, 113.9(4); Zr-N2-C31, 136.0(3); Zr-
N1-C32, 163.2(4); C29-C30-C31, 118.2(4); C29-C30-
Si1, 130.4(4).
F igu r e 4. Molecular structure of complex 10, shown by
an ORTEP plot. The thermal ellipsoids correspond to 30%
probability. Selected bond lengths (Å) and angles (deg):
Ti-N1, 1.944(3); Ti-N2, 1.956(2); N1-C11, 1.265(3); N2-
C24, 1.263(3); C11-C12, 1.505(4); C11-C18, 1.497(4);
C24-C25,1.495(4);C24-C31,1.516(4);N1-Ti-N2,99.27(11);
Ti-N1-C11, 160.8(2);Ti-N2-C24, 161.0(2); N1-C11-
C12, 120.7(3); N2-C24-C25, 121.4(3); C12-C11-C18,
118.3(3); C25-C24-C31, 115.9(2).
compared to the corresponding Ti-N distances of 1.944(3)
and 1.956(2) Å. The NdC distances in the zirconocene
complex of 1.259(4) and 1.266(4) Å are nearly identical
with those found in the titanocene complex (1.265(3) and
1.263(3) Å). Also, the angles Zr-NdC of 173.7(2) and
164.1(2)° are larger than those found for the titanocene
complex, 160.8(2) and 161.0(2)°. The different distances
and angles might be explained by the larger zirconium
atom.
are additionally stabilized by the coordination of o-
phenylenealcoholate and -thiolate substituents. The
distances and angles in the five-membered 1-zircona-
2-azacyclopent-4-ene ring in the o-phenylenealcoholate
complex (Zr-C ) 2.426(3), Zr-N ) 2.301(3), N-C(3) )
1.287(4), C(3)-C(4) ) 1.458(4), C(4)-C(5) ) 1.373(5) Å;
N-Zr-C(5) ) 69.2(10), Zr-C(5)-C(4) ) 115.7(2), C(3)-
C(4)-C(5) ) 114.3(3)°) and o-phenylenethiolate complex
(Zr-C ) 2.405(11), Zr-N ) 2.330(8), N-C(3) ) 1.293(13),
C(3)-C(4) ) 1.477(14), C(4)-C(5) ) 1.380(15) Å; N-Zr-
C(5) ) 69.7(17), Zr-C(5)-C(4) ) 114.8(7), C(3)-C(4)-
C(5) ) 113.9(4)°) are comparable to those of 8 (Zr-C(29)
) 2.447(5), Zr-N(2) ) 2.021(5), N(2)-C(31) ) 1.435(6),
C(30)-C(31) ) 1.547(7), C(29)-C(30) ) 1.366(7) Å;
N(2)-Zr-C(29) ) 67.5(2), Zr-C(29)-C(30) ) 113.9(4),
C(29)-C(30)-C(31) ) 118.2(4)°). Whereas the part Zr-
C(29)dC(30) is very similar, the other part Zr-N(2)-
C(31) is different due to the coordination of the -Nd
CHPh group in the R-position, which gives a three-
membered-ring system. The o-XC6H4- units (X ) O,
S) form by coordination a five-membered second ring.
At 2.324(4) Å, the Zr-N(1) bond distance of the coor-
dinating -NdCHPh is typical for coordinated imines.
The structure of 11 was unambiguously determined
by an X-ray diffraction analysis (Figure 5).
The structure was mentioned before in a short
communication.2e The bond distances and angles sup-
port the nitrogen-bridged coordination with a central
four-membered Ti-N-Co-N cycle. Additionally, there
seems to be an interaction between the titanium and
the cobalt center. The average Ti-Co distance of
2.568(6) Å in the bridged complex 11 is compatible to
the Ti-Co distances of 2.565 Å in (tBuO)3Ti-Co(CO)4
13
and 2.614 Å in [(CO)9Co3CO]Ti-Co(CO)4.14 Unequal
steric demands of the different metallocene units cause
a slight bending of the bridging alkylideneamido ligands
toward the smaller CpCo moiety (average angles: Ti-
N1-C16, 148(2)°; Ti-N2-C23, 148(2)°; Co-N1-C16,
128(2)°; Co-N2-C23, 128(2)°). Although there are
bimetallic examples known containing bridging alkyl-
ideneamido ligands,15 11 represents the first heterobi-
metallic complex of its type and the facile formation
could be an easy way to synthesize complexes of various
metal combinations.
The molecular structure of complex 10 is presented
in Figure 4.
This type of structure is known from the zirconocene
complex Cp2Zr(-NdCPh2).8a A detailed bonding de-
scription for NdCPh2 complexes as organometallic
heteroallene-type Schiff base derivatives was given by
Erker et al.8b For complex 10 it is interesting to study
the influence of titanium in comparison to the zirconium
atoms. Both complexes show nearly identical structural
parameters of the NdCPh2 ligands. The Zr-N bond
distances of 2.058(2) and 2.063(2) Å are slightly longer
(13) Selent, D.; Beckhaus, R.; Pickardt, J . Organometallics 1993,
12, 2857.
(14) Schmidt, G.; Stutte, B.; Boese, R. Chem. Ber. 1978, 111, 1239.
(15) For example: (a) Evans, W. J .; Meadows, J . H.; Hunter, W. E.;
Atwood, J . L. J . Am. Chem. Soc. 1984, 106, 1291. (b) Klose, A.; Solari,
E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.; Re, N. J . Am. Chem. Soc.
1994, 116, 9123.

Reactions of Cp2Ti and Cp2Zr Complexes
Organometallics, Vol. 17, No. 20, 1998 4437
F igu r e 6. Molecular structure of complex 12 (Cs-sym-
metric product), shown by an ORTEP plot. The thermal
ellipsoids correspond to 30% probability. Selected bond
lengths (Å) and angles (deg): Co1-N1, 1.846(3); Co1-N2,
1.846(3); Co2-N1, 1.870(3); Co2-N2, 1.869(3); Co1-Co2,
2.3472(8); N1-C11, 1.271(5); N2-C18, 1.272(5); C18-C19,
1.476(5); C11-C12, 1.477(6); N1-Co1-N2, 81.87(14); N1-
Co2-N2, 80.62(13); Co1-N1-Co2, 78.36(12); Co1-N2-
Co2, 78.34(14); N1-C11-C12, 126.9(4); N2-C18-C19,
128.7(4).
F igu r e 5. Molecular structure of complex 11, shown by
an ORTEP plot. The thermal ellipsoids correspond to 30%
probability. Selected bond lengths (Å) and angles (deg):
Co-Ti, 2.569(3); Ti-N1, 1.996(10); Ti-N2, 1.975(10); Co-
N1, 1.856(10); Co-N2, 1.851(10); N1-C16, 1.31(2); N2-
C23, 1.30(2); C16-C17, 1.47(2); C23-C24, 1.53(2); N1-
Ti-N2, 91.7(4); N1-Co-N2, 100.5(4); Co-N1-Ti, 83.6(4);
Co-N2-Ti, 84.3(4); Co-N1-C16, 127.7(9); Co-N2-C23,
127.0, N1-C16-C17, 128.6(12); N2-C23-C24, 127.4(13).
Ta ble 2. Str u ctu r a l P a r a m eter s of th e Com p lexes
The structure of 12 was determined also by an X-ray
diffraction analysis (Figure 6).
(Cp Co)(µ-NdCRR′)(Cp n M)
M ) Co, n ) 1,
M ) Co, n ) 1,
M ) Ti, n ) 2,
R ) R′ ) Ph R ) Ph, R′ ) H (12) R ) Ph, R′ ) H (11)
A structure for this type of homobimetallic cobalt(II)
complex was at first established by Floriani et al. for
the complex (CpCo)(µ-NdCPh2)(CpCo).9 The structure
of complex 12 shows an interesting influence of the
substituents R and R′ on the structures of the homobi-
metallic cobalt complexes as well as the influence of the
metals in comparison to the structure of the heterobi-
metallic and isoelectronic complex 11. Some relevant
data for these complexes (CpCo)(µ-NdCRR′)(CpnM) are
listed in Table 2.
Distances (Å)
Co-M
Co-N
Co-N′
M-N
M-N′
NdC
2.335(1)
1.881(8)
1.896(7)
2.3472(8)
1.846(3)
1.869(3)
1.846(3)
1.870(3)
2.569(3)
1.851(10)
1.856(10)
1.975(10)
1.996(10)
1.31(2), 1.30(2)
1.268(10)
1.272(5), 1.271(5)
Angles (deg)
81.87(14)
78.36(12)
80.62(13)
78.34(14)
N-Co-N′
Co-N-Co′
N-M-N′
Co-N-M
79.7(3)
76.4(3)
100.5(4)
91.7(4)
83.6(4), 84.3(4)
Con clu sion
influence of metals and of the substituents of the
substrates on the obtained products, formed by unex-
pected and manifold reaction pathways, is obvious.
Further studies aimed at the scope of the bimetallic
reactions are in progress.
We have demonstrated substitution reactions of ti-
tanocene and zirconocene bis(trimethylsilyl)acetylene
complexes with 1,4-diazadienes giving enediamido com-
plexes. In the corresponding reaction with azines the
reactions depend on the different metals and substitu-
ents which were used. With titanium the substitution
of the alkyne is favored, whereas with zirconium a
coupling of one CdN double bond with the alkyne was
found. With other azines, after substitution of the
acetylene a subsequent C-H activation or a C-C
coupling is observed. “Early-late” heterobimetallics
can be obtained by reactions of azines with two metal
centers. In these reactions an N-N single bond is
cleaved and bis(alkylideneamido) complexes are formed.
The different reactions of metallocene alkyne com-
plexes with azines show a broad scope. Again the
Ack n ow led gm en t. This work was supported by the
Max-Planck-Gesellschaft and the Fonds der Chemi-
schen Industrie.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data, atomic coordinates, thermal parameters, and
bond lengths and angles and figures giving additional views
for 4b, 7, 8, 11, and 12 (37 pages). Ordering information is
given on any current masthead page.
OM980466E