Bis(enamino-Cp) Group 4 metal complex chemistry: Developing a Mannich-type carbon-carbon coupling reaction at the bent metallocene famework

Journal of Organometallic Chemistry 690 (2005) 14–32

www.elsevier.com/locate/jorganchem

Bis(enamino-Cp) Group 4 metal complex chemistry: developing a

Mannich-type carbon–carbon coupling reaction at the bent

metallocene famework

*

Stephanie Knuppel, Cun Wang, Gerald Kehr, Roland Frohlich, Gerhard Erker

¨

Organisch-Chemisches Institut der Universita¨t Mu¨nster, Corrensstrasse 40, 48149 Mu¨nster, Germany

Received 23 April 2004; accepted 2 August 2004

Available online 14 October 2004

Abstract

Treatment of 6-methyl-6-dimethylaminofulvene (2a) with methyl lithium in ether results in a deprotonation reaction to yield the

enamino-substituted lithium cyclopentadienide reagent 3a. Its reaction with zirconium tetrachloride (0.5 molar equivalents) results

in the formation of the [1-dimethylaminobutadien-1,3-diyl-bis(cyclopentadienyl)]zirconium dichloride product 4a. The unsaturated

ansa-metallocene is probably formed via a Lewis acid-catalyzed Mannich-type carbon–carbon coupling reaction of an in situ gen-

erated bis[(dimethylaminoethenyl)cyclopentadienyl]ZrCl₂intermediate. A number of related examples of this condensation reaction

at the intact Group 4 bent metallocene framework is described, using diﬀerent amino-substituents and Ti, Zr and Hf systems. Three

examples of the unsaturated ansa-metallocene systems were characterized by X-ray diﬀraction. In a few cases it was possible to iso-

late the open (enamino-Cp)₂ZrCl₂complexes. In the case of, e.g., (piperidinoethenylcyclopentadienyl)₂ZrCl₂(13c) treatment with a

catalytic quantity of the Lewis acid ZrCl₄or the Brønsted acid ½PhNMe₂H^þꢀ½BPh₄^ꢁꢀ resulted in a clean conversion to the respective

Mannich condensation product, here the ansa-metallocene complex 4c. The strongly electrophilic borane HB(C₆F₅)₂did not cata-

lyze the CC-coupling reaction under the applied reaction conditions but added cleanly to the enamino-C@C double bond of, e.g.,

13c to yield a cyclic nitrogen donor-stabilized hydroboration product (19).

Keywords: Zirconocene; ansa-Metallocene; Mannich reaction; Carbon–carbon coupling; Hydroboration; Enamines

1. Introduction

interconversion at Cp-substituents has very rarely been

described. The introduction of functional groups is usu-

ally not carried out at the metallocene stage (although

an increasing number of speciﬁc examples seems to ap-

pear in the recent literature) [2] – organic functional

groups are mostly introduced at the ligand stage and

then carried along with the Cp-anion systems in the

course of the actual bent metallocene synthesis [3,4].

Conventional CC-coupling of functional groups is

diﬃcult to achieve at the sensitive Group 4 metallocene

frameworks since the oxophilic metals titanium and

especially zirconium and hafnium possess chemical fea-

tures that are often not easily compatible with the typi-

cal reaction conditions usually applied when performing

Organic functional group chemistry at substituted g⁵-

cyclopentadienyl ligands is very well developed in the

case of many late transition metal complexes. Ferrocene

chemistry is a prominent example where equivalents of

arene substitution chemistry has very well been worked

out, and typical functional group conversions have been

described for many examples [1]. This is very diﬀerent

for Group 4 metallocene chemistry. Functional group

*

Corresponding author. fax: +49 251 83 36503.

E-mail address: erker@uni-muenster.de (G. Erker).

doi:10.1016/j.jorganchem.2004.08.021

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

15

coupling reactions e.g. of the aldol condensation family.

A short while ago we found that some such reactions

can successfully being carried out at Group 4 bent met-

allocene frameworks when care is taken that the actual

reaction conditions are adjusted to the speciﬁc features

of these Group 4 metal compounds [5,6]. We here de-

scribe some details of carrying out carbon–carbon cou-

pling reactions of the Mannich-type at suitably

substituted zirconocene or hafnocene frameworks that

are fully compatible with the typical properties of such

sensitive organometallic educts and products.

In this way, interesting series of new ansa-metalloce-

nes have become readily available. In addition, it has

turned out that this methodology, originally developed

to cope with the speciﬁc requirements of the sensitive

Group 4 bent metallocenes has even been found to be

a very useful addition to the synthetic methodology ap-

plied at the organic functional group chemistry of the

ferrocenes [7].

2. Results and discussion

Scheme 1.

For this study we have chosen enamines as the func-

tional groups at the Cp-ring systems. The enamino func-

tionalities were in all cases introduced by means of a

fulvene route. Following a general procedure described

by Hafner et al. [8] a series of 6-amino-6-methyl fulvenes

were prepared starting from the corresponding aceta-

mide precursors. O-methylation was achieved by treat-

ment with dimethylsulfate [9]. Subsequent treatment

with cyclopentadienide then gave the respective amino-

fulvenes 2a–d (see Scheme 1). The amino-fulvenes are

C–H acidic [10]. Deprotonation at the 6-methyl group

was carried out by treatment with a suitable base

(methyl lithium or LDA) to cleanly yield the enamino-

substituted cyclopentadienides 3a–d.

The reagents 3 were then reacted with zirconium tet-

rachloride in the following way: A suspension of 3a in

ether was cooled to ꢁ78 ꢁC and then solid ZrCl₄was

added. After warming, the mixture was stirred for 12 h

at room temperature. Workup including recrystalliza-

tion from diethyl ether then gave an orange crystalline

solid (56% isolated) which was not the bis(enamino-

Cp)ZrCl₂product, that might have been expected, but

the condensation product 4a [5]. Similarly, the reaction

of the enamino-Cp anion equivalents 3b and d with

ZrCl₄gave the unsaturated ansa-zirconocene dichlorides

4b and d (69% and 22% isolated). Analogous treatment

of 3a or 3b with HfCl₄gave the ansa-hafnocene dichlo-

rides 5a and 5b, respectively, and the ansa-titanocene

dichloride 6a was obtained from the reaction of the

(1-dimethylamino-ethenyl)cyclopentadienide 3a with

TiCl₄under similar conditions.

aﬀecting the backbone. This treatment of the ansa-zir-

conocene- or -hafnocene dichlorides (4, 5) with methyl

lithium gave the corresponding [Zr]Me₂and [Hf]Me₂

complexes (7, 8, see Scheme 1). Treatment of complex

4a (M = Zr, NR₂= NMe₂) with two molar equivalents

of LiNMe₂cleanly gave the bis(dimethylamido) ansa-

zirconocene complex 9a (see Scheme 1).

The ansa-metallocene complexes show very charac-

teristic NMR spectra. A typical example is the zirco-

nium complex 7a. It exhibits four ¹³C NMR signals

of the four pairs of C₅H₄methine (CH) carbon centers

at d 116.2, 116.1, 109.8 and 107.5 (corresponding ipso-

carbon resonances at d 140.1 and d 118.6). The carbon

NMR signals of the 1-(dimethylamino)-1,4-butadien-

1,3-diyl bridge occur at d 148.0 (CNMe₂), 103.7

(CH), 128.3 (C) and 107.7 (@CH₂). The corresponding

¹H NMR signals of the ansa-bridge of complex 7a

were located at d 5.32 (@CH–) and d 4.85/4.65

(@CH₂), respectively. Complex 7a features only a sin-

gle NMe₂¹H NMR resonance at d 2.58 [6H] (¹³C: d

41.4) and also only a single ZrMe₂signal (d ꢁ0.37,

s, 6H) [¹³C: d 29.1]. Thus, in solution complex 7a be-

haves as if it were C_s-symmetric (as do the other com-

plexes in this series). However, this is probably due to

a rapid conformational equilibration of a non-mirror

symmetric structure in a degenerate double-minimum

situation.

Evidence for this interpretation originates from the

results of the X-ray crystal structure analysis of three

representative examples of this class of unsaturated

C₃-bridged ansa-Group 4 metallocenes. Single crystals

suitable for the X-diﬀraction study were obtained from

The unsaturated ansa-metallocenes undergo salt

metathesis reactions at the central [M]Cl₂unit without

16

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

the complexes 4a (M = Zr), 5a (M = Hf) and 9a

(M = Zr).

The structure of compound 9a shall be discussed as a

typical example. The dienamino-bridge of 9a is planar.

It shows the typical bond alternation that is expected for

isolated: 44%). The reaction of the tert-butyl-substituted

reagent 10b with ZrCl₄gave a 1:1 mixture of the closely

related meso-11b and rac-11b isomers (48% isolated, see

Scheme 2). The analogous reactions of 10a and 10b were

also carried out with HfCl₄to yield similar mixtures of

the corresponding ansa-hafnocenes meso-12(a,b) and

rac-12(a,b).

Several of the ansa-metallocene complexes were em-

ployed as components for the generation of active

homogeneous Ziegler-Natta catalysts [12]. We had pre-

viously described some of their typical features in

ethene polymerization as well as in copolymerization

reactions. The systems meso-/rac-11a/MAO were also

employed in propene polymerization [5]. Propene

polymerization of the meso-/rac-11a/methylalumoxane

catalyst in toluene at room temperature (2 bar pro-

pene) gave a mixture of polypropylene products that

was separated by solvent extraction. The combined

pentane to heptane soluble fractions (ca. 60% of the

polymer) was close to atactic (ca. 30% mmmm) [13],

˚

such a system [C6–C7: 1.333(3) A, C6–C8: 1.464(3) A,

˚

C8–C9: 1.345(3) A, C9–N10: 1.411(3) A]. The enamino-

nitrogen center is trigonal planar [angles C9–N10–C12:

116.0(2)ꢁ, C9–N10–C11: 114.9(2)ꢁ, C11–N10–C12:

111.6(2)ꢁ]. The sum of the bonding angles at N10 amounts

to 342.5ꢁ.

Both the bent metallocene frame and the aminodien-

diyl bridge are not strained. The Zr–C(Cp) bond lengths

˚

are within a narrow range (2.514(2)–2.637(2) A), and the

bond angles at the bridge are in the normal range [C5–

C6–C8: 119.2(2)ꢁ, C6–C8–C9: 125.4(2)ꢁ, C8–C9–C13:

123.5(2)ꢁ]. This situation is achieved by an internal rota-

tion of the ansa-metallocene framework from C_s-sym-

metrical to a chiral ‘‘twist’’ conformation (see Fig. 1).

This conformation may be characterized by the angle

between the C7–C6–C8–C9–N10 plane and the ‘‘r-lig-

and plane at zirconium’’ (i.e., the N18–Zr–N21 plane)

which amounts to 45.7ꢁ.

The complexes 4a (Zr) and 5a (Hf) (NR₂= NMe₂) are

both very similar (see Fig. 2). The structures of these

complexes seem to be determined more by the rigid

framework of the ligand system than by the metal. As ex-

pected, the hafnium complex (5a) features slightly shorter

M–C(Cp) bond lengths [11] (see Fig. 2 and Table 1).

We introduced a stereochemical component into the

system by using the 3-methyl- or 3-tert-butylenamino-

Cp lithium reagents 10a and 10b, respectively, for our

synthesis. Treatment of 10a with ZrCl₄analogously as

described for the previous cases (see above) resulted in

Mannich-CC-coupling and the formation of the ansa-

metallocene dichloride complex 11a. This system was

obtained as a mixture of two diastereoisomers, meso-

11a and rac-11a in a close to 1:1 mixture (total yield

but had

a

rather high molecular weight

(M_gꢂ 420.000), whereas the remaining heptane insolu-

ble fraction showed a much higher isotacticity (ca. 70%

mmmm) [14], but had a lower molecular weight

(M_gꢂ 82.000). The overall catalyst activity amounted

to ca. 220

g

of polypropylene/mmol[cat] Æ bar

(propene) Æ h.

Since it was likely that the non-bridged bis(enamino-

Cp)MCl₂complexes (13) were the essential precursors

for the metallocene Mannich coupling reaction we tried

to prepare and isolate them. This was successful when

we treated the morpholino-ethenyl-CpLi reagent 3d with

ZrCl₄Æ 2 THF in ether at 0 ꢁC. Workup after 1 h reac-

tion time at this temperature led us isolate the (morpho-

lino-ethenyl-Cp)₂ZrCl₂product (13d) as a solid in 44%

yield. In a similar reaction the bis(piperidino-ethenyl-

Cp)ZrCl₂product (13c) was obtained and isolated as a

yellow solid (50% yield).

˚

Fig. 1. Two projections of the molecular structure of complex 9a. Selected bond lengths (A) and angles (ꢁ): C5–C6 1.476(3), C6–C7 1.333(3), C6–C8

1.464(3), C8–C9 1.345(3), C9–C13 1.478(3), C9–N10 1.411(3), N10–C11 1.458(3), N10–C12 1.453(3), Zr–N18 2.087(2), Zr–N21 2.087(2), N18–C19

1.463(3), N18–C20 1.448(3), N21–C22 1.451(3), N21–C23 1.459(3); C5–C6–C8 119.2(2), C6–C8–C9 125.4(2), C8–C9–C13 123.5(2), C8–C9–N10

123.2(2), C9–N10–C11 114.9(2), C9–N10–C12 116.0(2), C11–N10–C12 111.6(2), N18–Zr–N21 94.4(1), Zr–N18–C19 115.7(1), Zr–N18–C20 136.4(2),

C19–N18–C20 107.9(2), Zr–N21–C22 134.5(2), Zr–N21–C23 116.8(2), C22–N21–C23 108.3(2).

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

17

˚

Fig. 2. Projections of the molecular structures of complexes 4a (M = Zr, left) and 5a (M = Hf, right). Selected bond lengths (A) and angles (ꢁ) of 4a:

C5–C6 1.490(5), C6–C7 1.333(6), C6–C8 1.464(6), C8–C9 1.353(6), C9–C13 1.481(5), C9–N10 1.399(5), N10–C11 1.455(5), N10–C12 1.468(6), Zr–

Cl1 2.432(1), Zr–Cl2 2.441(1); C5–C6–C8 117.5(4), C6–C8–C9 125.1(3), C8–C9–C13 123.1(3), C8–C9–N10 122.9(3), C9–N10–C11 117.2(4), C9–

N10–C12 118.5 (3), C11–N10–C12 112.4(3), Cl1–Zr–Cl2 97.4(1); of 5a C5–C6 1.482(7), C6–C7 1.337(7), C6–C8 1.457(7), C8–C9 1.360(7), C9–C13

1.484(6), C9–N10 1.391(6), N10–C11 1.457(6), N10–C12 1.461(7), Hf–Cl1 2.410(1), Hf–Cl2 2.415(1); C5–C6–C8 117.3(4), C6–C8–C9 125.2(4), C8–

C9–C13 122.7(4), C8–C9–N10 122.7(4), C9–N10–C11 117.6(4), C9–N10–C12 118.7 (4), C11–N10–C12 112.3(4), Cl1–Hf–Cl2 96.3(1).

Table 1

A comparison of typical bonding parameters of the complexes 4a, 5a and 9a

C5–C6

C6–C7

C6–C8

C8–C9

C9–C13

C9–N10

D1–M

D2–M

4a

5a

9a

1.490(5)

1.482(7)

1.476(3)

1.333(6)

1.337(7)

1.333(3)

1.464(6)

1.457(7)

1.464(3)

1.353(6)

1.360(7)

1.345(3)

1.481(5)

1.484(6)

1.478(3)

1.399(5)

1.391(6)

1.411(3)

2.192

2.176

2.253

2.206

2.183

2.281

C5–C6–C8

C6–C8–C9

C8–C9–C13

C8–C9–N10

D1–M–D2

4a

5a

9a

117.5(4)

117.3(4)

119.2(2)

125.1(3)

125.2(4)

125.4(2)

123.1(3)

122.7(4)

123.5(2)

122.9(3)

122.7(4)

123.2(2)

128.1

128.4

123.9

(1H, 8-H), d 4.82/4.77 (2H, @CH₂)]. The morpholino-

substituted system 13d was employed in more system-

atic short series of investigations that revealed that

the Mannich condensation reaction of this (enamino-

Cp)₂ZrCl₂complex was generally catalyzed by suitable

Lewis acids or by Brønsted acids (see Scheme 3). Thus,

treatment of 13d with 30 mol% of ZrCl₄in dichloro-

methane (introduced as the bis-THF adduct) com-

pletely converted this functionalized open bent

metallocene at room temperature to the C₃-bridged

unsaturated ansa-metallocene product 4d within 24 h.

Brønsted catalysis seems even more eﬀective: when

13d was mixed with 30 mol% of [PhNMe₂H]⁺[BPh₄]^ꢁ

in CD₂Cl₂at ambient temperature, ca. 17% conversion

to 4d was found when the mixture was monitored by

¹H NMR. Control by ¹H NMR after 24 h also re-

vealed complete conversion to 4d. Under the same con-

ditions a solution of 13d in CD₂Cl₂was found

unchanged even after 7 d. The weak Lewis acid

CpZrCl₃[15] also catalyzes the 13d–4d condensation

reaction, albeit at much lower overall reaction rates.

When we treated the starting material 13d with one

molar equivalent of CpZrCl₃in dichloromethane at

room temperature, only ca. 5% conversion was

Scheme 2.

In solution, complex 13d features the NMR spectra

of a conformationally equilibrating non-bridged bent

1

metallocene. It shows two H NMR signals of the g⁵-

C₅H₄moieties at d 6.76 and d 6.03 (in d₆-benzene, each

multiplet representing 4H) and the @CH₂hydrogen

resonances at d 4.81 and d 4.15 [2H each, ¹³C signals

at d 150.3 and 95.5 (C@CH₂), d 122.2 (ipso-C), 118.8,

116.5 (C₅H₄)].

The (piperidino-ethenyl-Cp)₂ZrCl₂system (13c) fea-

tures similar NMR spectra [¹H: d 4.85/4.24; ¹³C: d

151.5/95.2 (C@CH₂) in d₆-benzene]. This complex was

treated with 3 mol% of ZrCl₄in ether for 12 h at ambi-

ent temperature to cleanly yield the Mannich conden-

sation product 4c [84% isolated, ¹H NMR: d 5.43

18

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

Scheme 3.

observed after 24 h. It required 7 d at ambient temper-

ature to eventually achieve a near to quantitative con-

version to 4d. According to the stoichiometry of the

reaction cleavage of one equivalent of the amine must

be assumed in all these cases. For the example of the

13d–4d conversion mediated by a stoichiometric quan-

tity of CpZrCl₃we actually isolated a small quantity of

the [CpZrCl₃Æ (morpholine)] adduct as a chloride-

bridged dimer (14) [16] that was identiﬁed by an

X-ray crystal structure analysis (see Fig. 3).

Our observations indicate that we here have a Man-

nich-type carbon–carbon coupling reaction [17] take

place under these conditions at the Group 4 bent met-

allocene framework. A schematic reaction course is de-

picted in Scheme 4. The reaction sequence is probably

Scheme 4.

initiated by addition of the Lewis acid catalyst to the

nucleophilic b-carbon atom of an enamino substituent

to generate a dipolar iminium-type intermediate (15a).

Alternatively, protonation of the enamine would di-

rectly give an iminium-ion intermediate (15b). The acti-

vated iminium carbon center of 15 is then

intramolecularly attacked by the adjacent enamine

nucleophile, that is attached at the other Cp-ring, to

form a new carbon–carbon linkage (16). Subsequent

amine elimination and cleavage of the metal Lewis

acid (or deprotonation, respectively) then would di-

rectly lead to the observed ansa-metallocene products

(e.g., 4) and close the catalytic cycle (see Scheme 4).

The transformations described in this article probably

represent the ﬁrst examples of eﬃciently catalyzed

aldol-type carbon–carbon coupling reactions that were

carried out in the coordination sphere of a series of

sensitive Group 4 metallocene complexes to yield the

respective unsaturated functionalized C₃-bridged ansa-

metallocene dihalide products in a simple and straight-

forward way.

Fig. 3. A view of the molecular structure of the [CpZrCl₃(morpholine)]

˚

dimer 14. Selected bond lengths (A) and angles (ꢁ): Zr–N10 2.446(2),

N10–C11 1.490(4), N10–C15 1.488(3), C11–C12 1.515(4), C12–O13

1.419(4), O13–C14 1.428(4), C14–C15 1.507(4), Zr–Cl1 2.579(1), Zr–

Cl1* 2.824(1), Zr–Cl2 2.449(1), Zr–Cl3 2.474(1); Zr–N10–C11

119.9(2), Zr–N10–C15 117.28(2), C15–N10–C11 108.0(2), N10–C11–

C12 113.2(2), C11–C12–O13 111.7(3), C12–O13–C14 108.3(2), O13–

C14–C15 111.2(3), C14–C15–N10 112.0(3), Cl1–Zr–Cl1* 72.19(2),

Cl1–Zr–Cl2 150.34(3), Cl1*–Zr–Cl2 78.66(2), Cl1–Zr–Cl3 88.20(2),

Cl1*–Cl3 78.12(2), Cl2–Zr–Cl3 91.15(3), Cl1–Zr–N10 79.76(6), Cl1*–

Zr–N10 73.35(6), Cl2–Zr–N10 86.89(6), Cl3–Zr–N10 151.24(6).

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

19

We wanted to learn more about the structural and

chemical features of the bis(enamino-Cp)zirconocenes

as a class of compounds. For that purpose we synthe-

sized the substituted (enamino-Cp)zirconium complexes

13e and 13f and investigated their structures in the solid

state. Both the ligand systems were prepared by means

of the above mentioned fulvene route. Treatment of

the [Z-(2-phenylethenyl)Cp]lithium reagent 3e with zir-

conium tetrachloride in ether gave Z-13e (52% isolated).

It is characterized by a pair of ¹H NMR C₅H₄signals at

d 6.66 and 6.10 [in d₆-benzene, ¹³C NMR signals at d

Fig. 4. A projection of the molecular structure of complex Z-13e,

showing the conformational arrangement of the pair of enamino

˚

substituents at the bent metallocene wedge. Selected bond lengths (A)

1

119.0, 117.0 and 124.3 (ipso-C)] as well as a single H

and angles (ꢁ): C5–C6 1.487(3), C6–C7 1.343(3), C7–C10 1.473(3), C6–

N 1.398(3), N–C8 1.450(3), N–C9 1.449(3), Zr–Cl 2.435(1); C5–C6–C7

119.8(2), C5–C6–N 114.0(2), C6–C7–C10 129.1(2), C6–N–C8 120.4(2),

C6–N–C9 119.3(2), C8–N–C9 114.5(2), Cl–Zr–Cl* 97.2(1).

NMR resonance of the alkenyl substituent hydrogen

(7-H) at d 6.10 [¹³C: d 113.8 (C7), d 142.9 (C6)]. Photol-

ysis of Z-13e (3 h, HPK 125, Pyrex ﬁlter) in d₆-benzene

resulted in a complete (P99%) conversion to the E-13e

isomer under photostationary conditions [18]. Complex

E-13e shows typically diﬀerent ¹H and ¹³C NMR spectra

[¹H: d 6.12, 5.87 (¹³C: d 115.9, 115.1, 128.2, C₅H₄), d

6.01 (¹³C: 116.2, C7), and d 116.1 (C6)].

Single crystals were obtained from complex Z-13e

that were suited for an X-ray crystal structure analysis.

The X-ray crystal structure analysis of Z-13e shows a

pseudotetrahedral coordination geometry of the zirco-

˚

nium center with typical parameter Zr–Cl = 2.435(1) A,

˚

Cp(centroid)–Zr = 2.207 A and angles Cp(centroid)–

Zr–Cp(centroid) = 127.9ꢁ, Cl–Zr–Cp(centroid) = 107.5ꢁ.

The complex is C₂-symmetric. The enamino substituents

are arranged close to coplanar with their adjacent Cp

rings (dihedral angles C1–C5–C6–C7 = ꢁ24.7(3)ꢁ and

C1–C5–C6–N = 160.2(2)ꢁ). The C5–C6 bond is rather

˚

long at 1.487(3) A. The C6–N bond is short (1.398(3) A)

and the length of the C6–C7 double bond was found at

˚

typical 1.343(3) A. The phenyl substituent at the terminal

Scheme 5.

enamino carbon atom C7 is rotated markedlyfrom the en-

amino plane (C6–C7–C10–C11: ꢁ38.3(4)ꢁ).

adjacent Cp rings (hC1–C5–C6–C7: 158.2(5), C1–C5–

C6–N: ꢁ19.1(7)ꢁ). The C6–C7 bond length amounts to

The overall conformation of the substituted bent met-

allocene complex [19] Z-13e is such that the bulky

–C(NMe₂)@CH–Ph substituents are both oriented to-

ward the hind lateral sector of the bent metallocene

wedge (‘‘4-oꢀclock and 8-oꢀclock positions’’) with the

phenyl rings protruding to opposite metallocene sides.

Both the –NMe₂groups point C₂-symmetrically toward

the narrow metallocene backside (see Fig. 4).

˚

1.325(8) A, the C6–N distance is 1.416(6) A (see Fig. 5).

Very electrophilic boranes have found extensive use in

organometallic chemistry and catalysis. Especially, the

C₆F₅-substituted examples have been of great value in

that sense [20,21]. In the course of this study we have

Complex 13f was prepared analogously (see

Scheme 5). The X-ray crystal structure analysis (single

crystals from dichloromethane) again shows a C₂-sym-

metric structure of this di-substituted Group 4 metallo-

cene in the solid state. However, complex 13f features a

metallocene conformation that is distinctly diﬀerent

from that of Z-13e. In 13f both bulky 1-aminoethenyl

groups are oriented toward the open front side of the

bent metallocene wedge. The torsional angle between

the C5–C6 and C5*–C6* vectors amount to ca. 20ꢁ

(compared to ca. 250ꢁ for Z-13e). The enamino substit-

uent planes in 13f are again close to coplanar with their

Fig. 5. A view of the molecular structure of complex 13f. Selected

˚

bond lengths (A) and angles (ꢁ): C5–C6 1.465(7), C6–C7 1.325(8), C6–

N 1.416(6), N–C8 1.443(7), N–C9 1.411(6), Zr–Cl 2.457(1); C5–C6–C7

121.9(5), C5–C6–N 115.9(4), C7–C6–N 122.1(5), C6–N–C8 116.9(5),

C6–N–C9 119.2(4), C8–N–C9 118.0(4), Cl–Zr–Cl* 98.8(1).

20

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

brieﬂy investigated whether the strongly electrophilic bor-

ane HB(C₆F₅)₂[22] was reacting with the enamino-substi-

tuted bent metallocene systems 13 primarily as a Lewis

acid to induce the intramolecular Mannich coupling reac-

tion or predominantly exhibit its H[B]-functionality.

Complex 13f was treated with a stoichiometric quantity

of HB(C₆F₅)₂in toluene for 12 h at room temperature.

This reaction cleanly resulted in a desamination reaction

to yield the known organometallic product (vinyl-

C₅H₄)₂ZrCl₂(17) [23] [¹H NMR: d 6.32 (1H), 6.02/5.80

(2H, –CH@CH₂)] and the corresponding aminoborane

18 (see Scheme 6).

Desamination reactions of organic enamines is com-

monly observed upon treatment with boranes. Such

reactions had been shown to proceed by means of regio-

selective hydroboration to yield a b-amino alkylborane,

which is often stable in unpolar solvent but is rapidly

cleaved to the products upon addition of e.g. methanol

[24].

We were able to show for two examples, that a

similar reaction course was followed in the case of

the organometallic enamines 13. Treatment of the

bis(piperidinoethenyl-Cp)zirconium dichloride complex

13c with two molar equivalents of HB(C₆F₅)₂in tolu-

ene at room temperature (48 h) gave the addition

product 19 (81% isolated). The borane was regioselec-

tively added to the C@C double bond of the enamino

substitutents. This created a pair of chiral centers (at

the a-carbon atoms of the substituents), and conse-

quently a mixture of two diastereoisomers, meso-19

and rac-19, was formed. From the spectra we could

not positively identify which of the components of

the 2:3 mixture was meso-19 and which was rac-19.

There is indication that the nucleophilic amino-

nitrogen atoms in the complexes 19 were coordinated

to their electrophilic borane neighbors, to form a ‘‘azab-

oretidine’’ moiety. Such C₂BN-four membered ring

structures had previously been characterized by X-ray

diﬀraction in remotely related functionalized zircono-

cene systems [25]. The internal adduct formation in the

systems 19 is strongly indicated by their typical ¹¹B

NMR resonance (d 2.76) and the occurrence of diaster-

eomeric C₆F₅pairs of substituents (¹⁹F NMR: d ꢁ162.4/

ꢁ162.3 (m-), ꢁ156.2/ꢁ154.7 (p-), ꢁ128.3/ꢁ127.3 (o-F);

the ¹¹B and ¹⁹F NMR resonances were not diﬀerentiated

for the rac- and meso-19 isomers). The small separation

Scheme 7.

of the m-F and p-F resonances is an additional indica-

tion of the presence of four-coordinated boron in the

complexes 19 (see Scheme 7).

The azaboretidine structure in 19 makes the a- and

b-carbon atoms of the piperidine ring diastereotopic.

This is observed for each of the isomers [19A: d 56.9

(C8), 47.7 (C12); 19B: d 56.9 (C8), 47.4 (C12), d 22.1

(C9), 21.7 (C11), d 21.2 (C10)]. The reaction of the

morpholino-ethenyl-substituted metallocene 13d with

HB(C₆F₅)₂takes a similar course. A rac-/meso-mixture

of the addition products 20 (20A/20B = 3:4) is formed

(isolated in a combined yield of 65%). The complexes

20 again exhibit the typical spectroscopic features of

the internal four-membered amine/borane adducts

[¹¹B NMR: d 2.52; ¹⁹F NMR: d ꢁ162.1/ꢁ160.5, d

ꢁ154.7/ꢁ151.3; d ꢁ127.7/ꢁ122.9]. Again, typical dia-

stereotopic splitting of the a- and b-carbon (and hydro-

gen) NMR resonances of the six-membered heterocycle

is observed [¹³C NMR, 20A: d 68.2 (C9)/62.1 (C10), d

55.6 (C8)/48.9 (C11); 20B: d 67.7 (C9)/61.8 (C10), d

55.6 (C8)/50.3 (C11)]. The complexes 19 and 20 are sta-

ble in toluene solution, but they are rapidly cleaved

when dissolved in, e.g., chloroform to yield 17 and

the respective aminoborane products.

3. Some conclusions

Our study shows that a well deﬁned and selective

functional group chemistry can be devised and carried

out even at the frameworks of sensitive Group 4 bent

metallocene complexes when the overall reaction condi-

tions are adjusted to take account of the speciﬁc features

of such organometallic systems. We have shown that

even reactions out of the greater family of the aldol-type

condensation reactions – here the Mannich reaction –

can be carried out successfully at the titanocene, zir-

conocene, and hafnocene frameworks under easily

adjustable conditions. This has opened up a useful entry

to the synthesis of a variety of novel ansa-metallocene

systems.

Moreover, this type of an intramolecular Mannich-

type coupling is so easy to perform that is has even been

found very useful in preparative ferrocene chemistry, a

synthetic area where a great variety of functional group

Scheme 6.

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

21

to N-acetylpiperidine (1c, 21.2 g, 167 mmol). The mix-

ture was then stirred for 2 h at 70 ꢁC. This solution was

added at ꢁ20 ꢁC to a THF solution of 12.0 g (167

mmol) of lithium cyclopentadienide at such a rate that

the internal temperature of the reaction mixture did not

rise above ꢁ5 ꢁC. After 12 h stirring the mixture was

evaporated in vacuo to dryness and the residue taken

up in 200 ml of ether. The formed lithium methylsulfate

was removed by ﬁltration and the solvent removed

from the ﬁltrate in vacuo to yield 9.23 g (32%) of 2c

of single crystal quality, m.p. 83 ꢁC. HRMS, calcd.

for C₁₂H₁₇N: 175.13609, found 175.13666. ¹H NMR

(benzene-d₆, 200.13 MHz): d = 6.87–6.83 (m, 1H, Cp–

H), 6.81–6.77 (m, 1H, Cp–H), 6.75–6.72 (m, 1H, Cp–

H), 6.67–6.64 (m, 1H, Cp–H), 3.15–3.10 (m, 4H,

8-H), 1.89 (s, 3H, 7-H), 1.13–1.05 (m, 6H, 9-H/10-H)

ppm. ¹³C NMR (benzene-d₆, 50.32 MHz): d = 156.1

(C-6), 123.4, 121.6, 120.6, 119.7, 116.9 (C-1/C-2/C-3/

C-4 and C-5), 51.33 (C-8), 26.3 (C-9), 24.3 (C-10),

Scheme 8.

interconversion has been established. However, our met-

allocene Mannich coupling protocol has been found to

be a very useful entry to the synthesis of a number of

[3] ferrocenophane systems that were converted to opti-

cally active chelate ligands for asymmetric catalysis (see

Scheme 8) [7,26].

4. Experimental

Reactions with organometallic compounds were car-

ried out under argon using Schlenk-type glassware or in

a glovebox. Solvents were dried and distilled under ar-

gon prior to use. For additional general information

including a compilation of instruments used for physi-

~

20.5 (C-7) ppm. IR (KBr): m ¼ 3082 ðmÞ, 3057 (m),

2935 (s), 2921 (s), 1550 (vs), 1441 (s), 1371 (s),

1351(vs), 1265 (s), 1049 (s), 1022 (s), 975 (s), 895 (s),

734 (s), 646 (s) cm^ꢁ1

.

cal and spectroscopic characterization, see Huerla¨nder

¨

4.2. X-ray crystal structure analysis of the fulvene 2c

Formula C₁₂H₁₇N, M = 175.27, yellow crystal

et al. [2a] and [2c]. Most fulvenes used in this study

were prepared analogously to literature procedures.

[27] The borane HB(C₆F₅)₂was prepared as described

by Piers and co-workers [22]. Polymerization reactions

and polymer characterization was carried out analo-

gously as previously described [5,14e]. A preliminary

communication about some of this work was published

a while ago [5]. Most NMR assignments made in the

course of this study were secured by series of 2D

NMR measurements, and in some cases also by NOE

NMR experiments [28].

Data sets were collected with Enraf-Nonius CAD4,

Nonius MACH3, and KappaCCD diﬀractometers, the

later one equipped with a rotating anode generator

Nonius FR591. Programs used: data collection

EXPRESS (Nonius B.V., 1994) and COLLECT (Nonius

B.V., 1998), data reduction ^MOLEN(K. Fair, Enraf-

Nonius B.V., 1990) and ^DENZO-SMN(Z. Otwinowski,

W. Minor, Meth. Enzymol. 276 (1997) 307), absorption

correction for CCD data ^SORTAV(R.H. Blessing, Acta

Crystallogr. A51 (1995) 33; R.H. Blessing, J. Appl.

˚

3

0.45 · 0.25 · 0.25 mm, a = 7.854(1) A, b = 10.032(2) A,

˚

c = 13.245(3) A, b = 99.76(2)ꢁ, V = 1028.5(3) A ,

q

_calc= 1.132 g cm^ꢁ3, l = 4.91 cm^ꢁ1, empirical absorp-

tion correction via w scan data (0.809 6 T 6 0.887),

Z = 4, monoclinic, space group P2₁/c (No. 14),

˚

k = 1.54178 A, T = 223 K, x/2h scans, 1936 reﬂections

collected (+h, ꢁk, l), [(sinh)/k] = 0.62 A^ꢁ1, 1800 inde-

˚

pendent (R_int= 0.019) and 1365 observed reﬂections

[I P 2r(I)], 120 reﬁned parameters, R = 0.037,

wR²= 0.100, maximum residual electron density 0.14

(ꢁ0.10) e A^ꢁ3, hydrogens calculated and reﬁned as rid-

˚

ing atoms (see Fig. 6).

Crystallogr. 30 (1997) 421), structure solution ^SHELXS

-

97 (G.M. Sheldrick, Acta Crystallogr. A46 (1990) 467),

structure reﬁnement ^SHELXL-97 (G.M. Sheldrick, Uni-

versita¨t Go¨ttingen, 1997), graphics ^SCHAKAL(E. Keller,

Universita¨t Freiburg, 1997).

Fig. 6. Molecular structure of the fulvene 2c. Selected bond lengths

˚

4.1. Synthesis of 6-methyl-6-N-piperidino-fulvene (2c)

(A) and angles (ꢁ): C5–C6 1.396(2), C6–C7 1.506(2), C6–N 1.341(2),

N–C8 1.467(2), N–C12 1.465(2); C5–C6–C7 119.3(1), C5–C6–N

124.5(1), C7–C6–N 116.2(1), C6–N–C8 124.7(1), C6–N–C12

123.9(1), C8–N–C12 111.3(1).

At 50 ꢁC freshly distilled dimethylsulfate (15.8 ml,

21.0 g, 167 mmol) was added dropwise with stirring

22

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

4.3. X-ray crystal structure analysis of 6-methyl-6-N-

methylanilino-fulvene 2f

tuted lithium cyclopentadienide reagent

amorphous solid in good yield.

3 as an

The fulvene 2f was prepared as described in the litera-

ture. Single crystals were obtainedfrom dichloromethane.

Formula C₁₄H₁₅N, M = 197.27, yellow crystal

4.4.1. Lithium(dimethylaminoethenyl)cyclopentadienide

(3a)

Reaction of 6.0 g (44 mmol) of the fulvene 2a with

27.7 ml (44 mmol) of a 1.6 M ethereal MeLi solution

gave 5.6 g (89%) of 3a. ¹H NMR (benzene-d₆:tetra-

hydrofuran-d₈8:1, 200.13 MHz): d = 6.28–6.25 (m,

2H, Cp–H), 6.07–6.04 (m, 2H, Cp–H), 4.33 (d, 1H, 7-

˚

3

0.30 · 0.20 · 0.10 mm, a = 8.740(1) A, b = 18.268(2) A,

˚

c = 7.256(3) A, b = 103.14(2) A, V = 1128.2(4) A ,

q

_calc= 1.161 g cm^ꢁ3, l = 0.67 cm^ꢁ1, no absorption cor-

rection (0.980 6 T 6 0.993), Z = 4, monoclinic, space

2

group P2₁/c (No. 14), k = 0.71073 A, T = 223 K, x/2h

H, J_{7 -H}= 1 Hz), 3.91 (d, 1H, 7⁰-H, J_7-H= 1 Hz),

2.77 (s, 6H, 8-H) ppm. ¹³C NMR (benzene-d₆:tetra-

hydrofuran-d₈8:1, 50.32 MHz): d = 157.6 (C-6), 119.1

(C-5), 104.6 (C-2/C-3), 103.7 (C-1/C-4), 81.6 (C-7),

42.2 (C-8) ppm.

˚

0

scans, 2070 reﬂections collected (h, +k, +l), [(sinh)/k]

= 0.62A^ꢁ1, 1910 independent (R_int= 0.055) and 846 ob-

˚

served reﬂections [I P 2r(I)], 138 reﬁned parameters,

R = 0.049, wR²= 0.101, maximum residual electron

density 0.17 (ꢁ0.20) e A^ꢁ3, hydrogens calculated and re-

˚

ﬁned as riding atoms (see Fig. 7).

4.4.2. Lithium (N-pyrrolidinoethenyl)cyclopentadienide

(3b)

4.4. Preparation of the lithium(dialkylaminoethe-

nyl)cyclopentadienide reagents 3. General procedure

The reaction of 5.0 g (31 mmol) of 6-methyl-6-pyrrol-

idinylfulvene (2b) with 19.5 ml (31 mmol) of a 1.6 M

methyl lithium solution in ether gave 5.1 g (98%) of

3b. ¹H NMR (benzene-d₆:tetrahydrofuran-d₈8:1,

A suspension of ca. 40 mmol of the respective 6-

dialkylamino-6-alkylfulvene (2) in 80 ml of THF was

cooled to ꢁ78 ꢁC. A solution of ca. 40 mmol of

methyl lithium in ether was added dropwise with stir-

ring. Methane was evolved. The mixture was slowly

warmed to room temperature and stirred for a total

of 12 h. Solvent was removed from the clear solution

in vacuo. The residue was solidiﬁed by treatment with

pentane for 2 h. The solid was allowed to precipitate

and the pentane phase decanted oﬀ. The remaining so-

lid was dried in vacuo to yield the respective substi-

200.13 MHz): d = 6.23–6.20 (m, 2H, Cp–H), 6.02–5.99

2

(m, 2H, Cp–H), 4.04 (d, 1H, 7-H, J_{7 -H}= 1 Hz), 3.73

0

2

(d, 1H, 7⁰-H, J_7-H= 1 Hz), 3.53–3.47 (m, 4H, 8-H),

1.68–1.58 (m, 4H, 9-H) ppm. ¹³C NMR (benzene-

d₆:tetrahydrofuran-d₈8:1, 50.32 MHz): d = 154.3 (C-

6), 119.6 (C-5), 104.6, 103.3 (C–Cp), 77.8 (C-7), 49.9

(C-8), 25.3 (C-9) ppm.

4.4.3.

(3c)

Lithium(N-piperidinoethenyl)cyclopentadienide

The reaction of 6.0 g (34 mmol) of the fulvene 2c with

21.3 ml (34 mmol) of a 1.6 M ethereal methyl lithium

1

solution gave 6.0 g (97%) of 3c. H NMR (benzene-

d₆:tetrahydrofuran-d₈8:1, 200.13 MHz): d = 6.26–6.23

(m, 2H, Cp–H), 6.04–5.93 (m, 2H, Cp–H), 4.36 (s, 1H,

7-H), 3.93 (s, 1H, 7⁰-H), 3.08 (m, 4H, 8-H), 1.62–1.52

(m, 4H, 9-H), 1.47–1.41 (m, 2H, 10-H) ppm. ¹³C

NMR (benzene-d₆:tetrahydrofuran-d₈8:1, 50.32

MHz): d = 158.4 (C-6), 119.5 (C-5), 104.2 (C-2/C-3),

103.9 (C-1/C-4), 81.8 (C-7), 51.9 (C-8), 27.1 (C-9), 25.6

(C-10) ppm.

4.4.4. Lithium(N-morpholinoethenyl)cyclopentadienide

(3d)

The reaction of 6.9 g (42 mmol) of the aminofulvene

2d with 24.0 ml (42 mmol) of a 1.75 M methyl lithium

1

solution in diethyl ether yielded 7.1 g (92%) of 3d. H

NMR (benzene-d₆:tetrahydrofuran-d₈8:1, 200.13

MHz): d = 6.14–6.12 (m, 2H, Cp–H), 5.96–5.92 (m,

˚

Fig. 7. Molecular structure of the fulvene 2f. Selected bond lengths (A)

2

0

2H, Cp–H), 4.23 (d, J_{7 -H}= 1 Hz, 1H, 7-H), 3.79 (d,

and angles (ꢁ): C5–C6 1.393(4), C6–C7 1.513(4), C6–N 1.342(4), N–C8

1.458(3), N–C9 1.444(4); C5–C6–C7 119.6(3), C5–C6–N 125.2(3), C7–

C6–N 115.1(3), C6–N–C8 123.9(3), C6–N–C9 120.6(3), C8–N–C9

115.2(2).

²J_7-H= 1 Hz, 1H, 7⁰-H), 3.64–3.60 (m, 4H, 9-H), 3.0–

2.96 (m, 4H, 8-H) ppm. ¹³C NMR (benzene-d₆:tetra-

hydrofuran-d₈8:1, 50.32 MHz): d = 153.9 (C-6), 121.2

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

23

(C-5), 104.3, 104.0 (C–Cp), 81.4 (C-7), 67.6 (C-9), 51.5

(C-8) ppm.

(99%) of 10b. ¹H NMR (benzene-d₆:tetrahydrofuran-

d₈8:1, 200.13 MHz): d = 6.12–6.09 (m, 2H, Cp–H),

5.90–5.87 (m, 1H, Cp–H), 4.37 (s, 1H, 7-H), 3.97 (ps,

1H, 7⁰-H), 2.77 (s, 6H, 8-H), 1.47 (s, 9H, 10-H) ppm.

¹³C NMR (benzene-d₆:tetrahydrofuran-d₈8:1, 50.32

MHz): d = 158.7 (C-6), 131.4 (C-2), 116.8 (C-5), 102.7,

101.0, 100.6 (C-1/C-3/C-4), 80.3 (C-7), 42.4 (C-8), 33.8

(C-10), 31.7 (C-9) ppm.

4.4.5. Lithium(Z-1-dimethylamino-2-phenylethenyl)cy-

clopentadienide (3e)

The reaction of 3.0 g (14 mmol) of 6-benzyl-6-dimeth-

ylaminofulvene (2e) with 8.9 ml (14 mmol) of a 1.6 M

methyl lithium solution in diethyl ether yielded 2.6 g

(84%) of 3e (Z:E-ratio, 10:1). ¹H NMR (benzene-

d₆:tetrahydrofuran-d₈8:1, 200.13 MHz) (Z): d = 7.18–

7.12 (m, 5H, 9-H/10-H/11-H), 6.25–6.22 (m, 2H,

Cp–H), 6.05–6.03 (m, 2H, Cp–H), 5.64 (s, 1H, 7-H),

2.79 (s, 6H, 12-H) ppm. ¹H NMR (benzene-d₆:tetra-

hydrofuran-d₈8:1, 200.13 MHz) (E): d = 6.91–6.88 (m,

5H, 9-H/10-H/11-H), 6.04–6.02 (m, 2H, Cp–H), 6.00–

5.98 (m, 2H, Cp–H), 5.46 (s, 1H, 7-H), 2.69 (s, 6H, 12-

H) ppm. ¹³C NMR (benzene-d₆:tetrahydrofuran-d₈

8:1, 200.13 MHz) (Z): d = 152.5 (C-6), 142.7 (C-8),

127.9, 127.8, 122.1 (C-9/C-10/C-11), 120.0 (C-5), 106.7,

104.8 (C-1/C-2/C-3/C-4), 100.4 (C-7), 43.3 (C-12) ppm.

4.5. Preparation of the bis[(1-dialkylaminoethenyl)cyclo-

pentadienyl]zirconium dichloride complexes. General

procedure

Solid zirconium tetrachloride (ca. 4 mmol) was added

to a suspension of the respective lithium(1-dialkylami-

noethenyl)cyclopentadienide (ca. 8 mmol) in ca. 100

ml of ether at 0 ꢁC. The mixture was stirred for 1 h at

0 ꢁC. The precipitate was removed by ﬁltration through

Cellite and washed with dichloromethane (2 · 15 ml).

Solvent was removed from the combined ﬁltrates and

the residue washed with 30 ml of pentane. The metallo-

cene complexes were usually obtained as orange colored

solids.

4.4.6. Lithium(N-methylanilinoethenyl)cyclopentadienide

(3f)

The reaction of 7.0 g (36 mmol) of the fulvene 2f with

22.2 ml (36 mmol) of a 1.6 M ethereal methyl lithium

solution gave 7.1 g (98%) of 3f. ¹H NMR (benzene-

d₆:tetrahydrofuran-d₈8:1, 200.13 MHz): d = 7.05–6.87

(m, 3H, 10-H/11-H), 6.58–6.51 (m, 2H, 9-H), 6.01–5.98

(m, 2H, Cp–H), 5.88–5.81 (m 2H, Cp–H), 5.03 (ps,

1H, 7-H), 4.48 (ps, 1H, 7⁰-H), 3.14 (s, 3H, 8-H) ppm.

¹³C NMR (tetrahydrofuran-d₈, 50.32 MHz): d = 154.1

(C-6), 151.4 (C-9), 128.82 (C–Ph), 117.5 (C-5), 116.6

(C–Ph), 115.5 (C–Ph), 104.9, 104.7 (C–Cp), 95.3 (C-7),

40.2 (C-8) ppm.

4.5.1. Bis[(1-pyrrolidinoethenyl)cyclopentadienyl]zirco-

nium dichloride (13b)

The reaction of 1.32 g (7.92 mmol) of 3b with 923 mg

ZrCl₄(3.96 mmol) in 100 ml of ether at 0 ꢁC yielded 1.07

g (56%) of complex 13b. This product turned out to be

so unstable that it was only characterized spectroscopi-

cally. ¹H NMR (chloroform-d₁, 200.13 MHz):

d = 6.68–6.66 (m, 2H, Cp–H), 6.19–6.16 (m, 2H, Cp–

H), 4.29 (s, 1H, 7-H), 4.07 (s, 1H, 7-H⁰), 3.14–3.07 (m,

4H, 8-H), 2.03–1.88 (m, 4H, 9-H) ppm. IR (KBr):

~

m ¼ 3072 ðwÞ, 2963 (m), 2868 (m), 1551 (vs), 1393 (s),

1380 (s), 1335 (vs), 1058 (m), 807 (m), 731 (s) cm^ꢁ1

.

4.4.7. Lithium[1-(dimethylaminoethenyl)-3-methyl]cy-

clopentadienide (10a)

4.5.2. Bis[(1-piperidinoethenyl)cyclopentadienyl]zirconi-

um dichloride (13c)

The reaction of 8.0 g (54 mmol) of 2-methyl-6-me-

thyl-6-dimethylaminofulvene with 33.5 ml (54 mmol)

of a 1.6 M methyl lithium solution in ether gave 7.9 g

(95%) of 10a. ¹H NMR (benzene-d₆:tetrahydrofuran-

d₈8:1, 200.13 MHz): d = 6.15–6.10 (m, 1H, Cp–H),

6.08–6.06 (m, 1H, Cp–H), 5.95–5.84 (m, 1H, Cp–H),

4.25 (s, 1H, 7-H), 3.82 (ps, 1H, 7⁰-H), 2.77 (s, 6H,

8-H), 2.37 (s, 3H, 9-H) ppm. ¹³C NMR (benzene-

d₆:tetrahydrofuran-d₈8:1, 50.32 MHz): d = 158.2

(C-6), 117.8 (C-2), 114.2 (C-5), 104.9, 104.0, 103.5

(C-1/C-3/C-4), 80.6 (C-7), 42.2 (C-8), 15.6 (C-9) ppm.

The reaction of 1.50 g (8.28 mmol) of 3c with 841 mg

ZrCl₄(4.14 mmol) in 80 ml of ether at 0 ꢁC gave 1.06 g

(50%) of complex 13c, m.p. 120 ꢁC. Anal. Calc. for

C₂₄H₃₂N₂ZrCl₂(M = 510.65): C, 56.45; H, 6.52; N,

1

5.49. Found: C, 56.42; H, 6.68; N, 5.38%. H NMR

(chloroform-d₁, 200.13 MHz): d = 6.72 (m, 2H, Cp–

H), 6.14 (m, 2H, Cp–H), 4.59 (s, 1H, 7-H), 4.33 (s,

1H, 7-H⁰), 2.88–2.83 (m, 4H, 8-H), 1.72 (m, 6H, 9-H/

10-H) ppm. ¹³C NMR (benzene-d₆, 50.32 MHz):

d = 151.3 (C-6), 120.9, 118.7, 116.6 (C-1/C-2/C-3/C-4/

C-5), 95.2 (C-7), 51.3 (C-8), 26.5 (C-9), 24.6 (C-10)

~

ppm. IR (KBr): m ¼ 3098 ðwÞ, 2937 (vs), 2846 (s),

4.4.8. Lithium[1-(dimethylaminoethenyl)-3-tert-butyl]-

cyclopentadienide (10b)

The reaction of 5.0 g (26 mmol) of 2-tert-butyl-6-me-

thyl-6-dimethylaminofulvene with 16.4 ml (26 mmol) of

a 1.6 M ethereal methyl lithium solution yielded 5.2 g

2801 (s), 1594 (vs), 1550 (s), 1377 (s), 1273 (s), 1113(s),

1032 (s), 975 (s), 820 (vs), 807 (vs) cm^ꢁ1. UV/Vis

(CH₂Cl₂):

(e = 27,226).

k_max= 232 nm (e = 40,465), 350 nm

24

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

4.5.3. Bis[(1-morpholinoethenyl)cyclopentadienyl]zirco-

nium dichloride (13d)

tively isomerized to E-13e. ¹H NMR (benzene-d₆, 200.13

MHz) (E): d = 7.08–6.75 (m, 5H, 9-H/10-H/11-H), 6.12

(m, 2H, Cp–H), 6.01 (s, 1H, 7-H), 5.87 (m, 2H, Cp–

H), 2.44 (s, 6H, 12-H) ppm. ¹³C NMR (benzene-d₆,

200.13 MHz) (E): d = 145.6 (C-6), 138.7 (C-8), 129.8,

128.6, 126.6 (C-9/C-10/C-11), 128.2 (C-5), 116.2 (C-7),

115.9, 115.1 (C-1/C-2/C-3/C-4), 44.0 (C-12) ppm.

The reaction of 3.54 g (13.80 mmol) of 3d with 2.61 g

(6.90 mmol) of ZrCl₄Æ 2 THF in 80 ml of ether at 0 ꢁC

gave 1.56 g (44%) of complex 13d, m.p. 93 ꢁC. Anal.

Calc. for C₂₂H₂₈N₂O₂ZrCl₂(M = 514.60): C, 51.35; H,

1

5.48; N, 5.44. Found: C, 51.93; H, 6.54; N, 3.51%. H

NMR (benzene-d₆, 200.13 MHz): d = 6.76 (m, 2H,

Cp–H), 6.03 (m, 2H, Cp–H), 4.81 (ps, 1H, 7-H), 4.15

(ps, 1H, 7-H⁰), 3.54 (bm, 4H, 9-H), 2.44 (bm, 4H, 8-H)

ppm. ¹³C NMR (benzene-d₆, 50.32 MHz): d = 150.3

(C-6), 122.2 (C-5), 118.8, 116.5 (C–Cp), 95.5 (C-7),

4.5.4.1. Bis[(N-methylanilinoethenyl)cyclopentadienyl]zir-

conium dichloride 13f. The reaction of 2.60 g (12.79

mmol) of 3f with 1.30 g (6.39 mmol) of ZrCl₄in

100 ml of ether at 0 ꢁC yielded 1.85 g (52%) of complex

13f, m.p. 112 ꢁC. Anal. Calc. for C₂₈H₂₈N₂ZrCl₂

(M = 554.67): C, 60.63; H, 5.09; N, 5.05. Found: C,

60.73; H, 5.47; N, 4.43%. ¹H NMR (chloroform-d₁,

200.13 MHz): d = 7.22–7.19 (m, 3H, 11-H/12-H), 7.15

(m, 2H, 10-H), 6.42 (m, 2H, Cp–H), 6.08 (m, 2H, Cp–

H), 5.08 (s, 1H, 7-H), 4.75 (s, 1H, 7-H⁰), 3.22 (s, 3H,

8-H) ppm. ¹³C NMR (chloroform-d₁, 50.32 MHz):

d = 148.6 (C-6), 146.1 (C-9), 128.9, 121.8, 121.1 (C-10/

C-11/C-12), 124.0 (C-5), 118.4, 114.9 (C-1/C-2/ C-3/C-

4), 101.1 (C-7), 41.8 (C-8) ppm. IR (KBr):

~m ¼ 3083 ðmÞ, 3095 (m), 3965 (m), 2941 (m), 2880

(m), 1615 (m), 1596 (vs), 1553 (s), 1496 (vs), 1376 (s),

1363 (s), 1349 (s), 1292 (s), 1132 (s), 1119 (m), 1096

~

67.0 (C-9), 50.6 (C-8) ppm. IR (KBr): m ¼ 3094 ðmÞ,

2963 (s), 2845 (s), 2829 (s), 1600 (s), 1553 (s), 1263

.

(vs), 1120 (vs), 986 (s), 865 (s), 820 (vs) cm^ꢁ1

4.5.3.1. Bis[Z-(1-dimethylamino-2-phenylethenyl)cyclo-

pentadienyl]zirconium dichloride (Z-13e). The reac-

tion of 900 mg (4.14 mmol) of 3e with 483 mg (2.07

mmol) of ZrCl₄in 80 ml of ether at 0 ꢁC gave 753 mg

(62%) of the product Z-13e, m.p. 70 ꢁC (decomp.). Anal.

Calc. for C₃₀H₃₂N₂ZrCl₂(M = 582.7): C, 61.84; H, 5.54;

1

N, 4.81. Found: C, 62.42; H, 5.84; N, 4.51%. H NMR

(benzene-d₆, 200.13 MHz) (Z): d = 7.13–6.95 (m, 10H,

9-H/10-H/11-H), 6.46 (m, 2H, Cp–H), 6.32 (s, 1H, 7-

H), 6.08 (m, 2H, Cp–H), 2.31 (s, 6H, 12-H) ppm. ¹³C

NMR (benzene-d₆, 200.13 MHz) (Z): d = 142.9 (C-6),

138.2 (C-8), 127.5, 126.6, 126.2 (C-9/C-10/C-11), 124.3

(C-5), 119.0, 117.0 (C-1/C-2/C-3/C-4), 113.8 (C-7), 42.3

(m), 1032(m), 880 (m), 845 (s), 752 (s) cm^ꢁ1

.

4.5.4.2. X-ray crystal structure analysis of complex

13f. Single crystals were obtained from dichlorometh-

ane. Formula C₂₈H₂₈Cl₂N₂Zr, M = 554.64, yellow-red

~

(C-12) ppm. IR (KBr): m ¼ 3107 ðwÞ, 3070 (w), 3029

˚

(w), 2920 (m), 2901 (m), 2797 (w), 1607 (s), 1562 (vs),

1510 (s), 1451 (s), 1373 (vs), 1152 (m), 1094 (s), 1036

(s), 964 (m), 905 (m), 814 (s), 723 (s) cm^ꢁ1. UV/Vis

crystal 0.40 · 0.30 · 0.10 mm, a = 29.231(4) A,

˚

b = 6.988(1) A, c = 12.599(1) A, b = 103.70(1)ꢁ,

V = 2500.3(5) A , q_calc= 1.473 g cm^ꢁ3, l = 6.73 cm^ꢁ1

,

3

˚

(CH₂Cl₂):

(e = 47,279).

k

_max= 254 nm (e = 42,808), 327 nm

empirical absorption correction via w scan data

(0.775 6 T 6 0.936), Z = 4, monoclinic, space group

˚

C2/c (No. 15), k = 0.71073 A, T = 223 K, x/2h scans,

4.5.3.2. X-ray crystal structure analysis of complex

Z-13e. Single crystals were obtained from dichloro-

methane. Formula C₃₀H₃₂Cl₂N₂Zr, M = 582.70, yellow

2667 reﬂections collected (h, +k, ꢁl), [(sinh)/k] = 0.62

^ꢁ1, 2541 independent (R_int= 0.020) and 1961 observed

˚

A

reﬂections [I P 2r(I)], 151 reﬁned parameters,

crystal 0.70 · 0.50 · 0.30 mm, a = 14.950(1) A,

R = 0.031, wR²= 0.082, maximum residual electron

˚

b = 9.954(1) A, c = 19.100(1) A, b = 94.90(1)ꢁ,

density 0.96 (ꢁ1.29) e A^ꢁ3, hydrogens calculated and re-

˚

V = 2831.9(5) A , q_calc= 1.367 g cm^ꢁ3, l = 5.97 cm^ꢁ1

,

ﬁned as riding atoms.

3

˚

empirical absorption correction via

w scan data

(0.680 6 T 6 0.841), Z = 4, monoclinic, space group

4.6. Preparation of the [dialkylaminobutadien-1,3-diyl-

4

˚

C2/c (No. 15), k = 0.71073 A, T = 223 K, x/2h scans,

bis(cyclopentadienyl)] Group

metal dichloride

5727 reﬂections collected (h, ꢁk, +l), [(sinh)/k] =

complexes. General procedure of the Mannich-type con-

densation reaction

0.62A ^ꢁ1, 2861 independent (R_int= 0.105) and 2322

˚

observed reﬂections [I P 2r(I)], 161 reﬁned parameters,

R = 0.043, wR²= 0.094, maximum residual electron

The respective lithium(dialkylaminoethenyl)cyclo-

pentadienide (3, ca. 40 mmol) was suspended in ca. 60

ml of ether at ꢁ78 ꢁC. The pure Group 4 metal tetra-

chloride (ca. 20 mmol) was added with vigorous stirring.

The mixture was slowly allowed to warm to room tem-

perature and stirred for a total of 12 h. The precipitate

was removed by ﬁltration and washed with ether, then

with dichloromethane. Solvent was removed from the

density 0.88 (ꢁ1.19) e A^ꢁ3, hydrogens calculated and

˚

reﬁned as riding atoms.

4.5.4. Photolysis of complex Z-13e. Formation of E-13e

A solution of 35 mg (60 lmol) of complex Z-13e in

benzene-d₆was irradiated for 3 h with a HPK 125 lamp

(Pyrex ﬁlter). After this time the complex was quantita-

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

25

combined ﬁltrates in vacuo to yield the respective ansa-

metallocene complex.

d = 144.2 (C-9), 138.9 (C-5), 135.1 (C-6), 120.7 (C-13),

123.2 (C-1/C-4), 123.0 (C-15/C-16), 112.9 (C-14/C-17),

111.4 (C-2/C-3), 109.3 (C-7), 99.5 (C-8), 49.4 (C-11),

~

4.6.1. [1-Dimethylaminobutadien-1,3-diyl-bis(cyclopen-

tadienyl)]zirconium dichloride (4a)

25.1 (C-12) ppm. IR (KBr): m ¼ 3086 ðmÞ, 2960 (s),

2933 (s), 2870 (m), 1605 (vs), 1550 (vs), 1396 (s),

1359(s), 1338(s), 1289 (s), 1038 (s), 841 (m), 820 (vs),

The reaction of 2.12 g (15.0 mmol) of lithium(dimeth-

ylaminoethenyl)cyclopentadienide (3a) with 1.75 g (7.5

mmol) of zirconium tetrachloride gave 1.62 g (56%) of

4a. Subsequent recrystallization of a diﬀerent sample,

that was obtained from the reaction of 5.29 g (37.5

mmol) of 3a with 4.37 g (18.7 mmol) of ZrCl₄, from

ether yielded 2.32 g (32%) of the pure crystalline com-

plex 4a, m.p. 195.1 ꢁC (decomp.). Anal. Calc. for

C₁₆H₁₇NZrCl₂(M = 385.44): C, 49.86; H, 4.45; N,

816 (vs) cm^ꢁ1

.

4.6.4. [Piperidinobutadien-1,3-diyl-bis(cyclopentadienyl)]-

zirconium dichloride (4c)

This ansa-metallocene complex was prepared in a dif-

ferent way. Bis[(piperidinoethenyl)cyclopentadienyl]zir-

conium dichloride (13c, 800 mg, 1.57 mmol) was

suspended in 60 ml of diethyl ether. Solid zirconium tet-

rachloride (10 mg, 0.043 mmol) was added and the mix-

ture stirred for 12 h at room temperature. Solvent was

then removed in vacuo and the residue taken up in 40

ml of dichloromethane. The mixture was ﬁltered and

the ﬁltrate concentrated in vacuo to a volume of 10

ml. The ansa-metallocene product 4c precipitated at

ꢁ20 ꢁC. It was collected by ﬁltration and dried in vacuo

to yield 554 mg (84%) of complex 4e as a beige-yellow

solid, m.p. 144 ꢁC. Anal. Calc. for C₁₉H₂₁NZrCl₂

(M = 425.51): C, 53.63; H, 4.97; N, 3.29. Found: C,

52.78; H, 5.83; N, 5.13%. ¹H NMR (benzene-d₆,

200.13 MHz): d = 6.52 (m, 4H, 1-H/4-H/15-H/16-H),

5.90 (m, 2H, 14-H/17-H), 5.71 (m, 2H, 2-H/3-H), 5.43

(s, 1H, 8-H), 4.82 (s, 1H, 7-H), 4.77 (s, 1H, 7-H⁰), 3.03

(m, 4H, 11-H), 1.20 (m, 6H, 12-H/18-H) ppm. ¹³C

NMR (benzene-d₆, 50.32 MHz): d = 148.2 (C-9), 139.4

(C-5), 136.8 (C-6), 125.7 (C-13), 124.1 (C-1/C-4), 123.2

(C-15/C-16), 113.3 (C-14/C-17), 110.2 (C-2/C-3), 110.3

(C-7), 105.9 (C-8), 50.8 (C-11), 26.0 (C-12), 24.5 (C-18)

1

3.63. Found: C, 49.62; H, 4.84; N, 3.52%. H NMR

(dichloromethane-d₂, 599.87 MHz, 268 K): d = 6.71

(m, 2H, 15-H/16-H), 6.69 (m, 2H, 1-H/4-H), 6.15 (m,

2H, 14-H/17-H), 6.09 (m, 2H, 2-H/3-H), 5.64 (ps, 1H,

8-H), 5.01 (ps, 1H, 7-H), 4.93 (ps, 1H, 7-H⁰), 2.59 (s,

6H, 11-H) ppm. ¹³C NMR (dichloromethane-d₂,

150.84 MHz): d = 147.5 (C-9), 139.0 (C-5), 137.1 (C-6),

125.8 (C-13), 123.8 (C-1/C-4), 123.2 (C-15/C-16), 114.0

(C-14/C-17), 110.9 (C-2/C-3), 110.2 (C-7), 104.6 (C-8),

~

41.4 (C-11) ppm. IR (KBr): m ¼ 3095 ðwÞ, 3062 (w),

2939 (w), 2926 (w), 2872 (w), 1602 (s), 1559 (m), 1348

.

(m), 1105 (m), 1038 (m), 865 (m), 830 (s), 817 (s) cm^ꢁ1

4.6.2. X-ray crystal structure analysis of complex 4a

Single crystals were obtained from a dichloromethane

solution by very slow solvent evaporation at ambient

conditions. Formula C₁₆H₁₇Cl₂NZr, M = 385.43, yellow

˚

crystal 0.50 · 0.40 · 0.15 mm, a = 10.774(1) A,

˚

b = 10.501(1) A, c = 13.930(1) A, b = 101.52(1)ꢁ,

3

V = 1544.3(2) A , q_calc= 1.658 g cm^ꢁ3, l = 10.47 cm^ꢁ1

,

scan data

˚

~

ppm. IR (KBr): m ¼ 3082 ðmÞ, 2937 (vs), 2918 (vs),

1593 (s), 1441 (s), 1259 (s), 110 (s), 1033 (s), 821 (vs),

empirical absorption correction via

w

(0.623 6 T 6 0.859), Z = 4, monoclinic, space group

809 (vs), 797 (s) cm^ꢁ1

.

˚

P2₁/n (No. 14), k = 0.71073 A, T = 223 K, x/2h scans,

3261 reﬂections collected (h, ꢁk, ꢁl), [(sinh)/k] = 0.62

4.6.5. [Morpholinobutadien-1,3-diyl-bis(cyclopentadienyl)]-

zirconium dichloride (4d)

^ꢁ1, 3132 independent (R_int= 0.013) and 2744 observed

˚

A

reﬂections [I P 2r(I)], 183 reﬁned parameters,

According to the general procedure described above

3d (3.48 g, 19.0 mmol) was reacted with 2.23 g (9.5

mmol) of ZrCl₄to yield 897 mg (22%) of complex 4d,

m.p. 184 ꢁC. Anal. Calc. for C₁₈H₁₉NOZrCl₂

(M = 427.48): C, 50.57; H, 4.48; N, 3.28. Found: C,

50.07; H, 5.44; N, 3.33%. ¹H NMR (benzene-d₆,

599.87 MHz): d = 6.55–6.48 (m, 4H, 1-H/4-H/15-H/16-

H), 5.81 (m, 2H, 14-H/17-H), 5.71 (m, 2H, 2-H/3-H),

5.33 (ps, 1H, 8-H), 4.83 (m, 1H, 7-H), 4.76 (m, 1H, 7-

H⁰), 3.33 (m, 4H, 12-H), 2.28 (m, 4H, 11-H) ppm. ¹³C

NMR (benzene-d₆, 150.84 MHz): d = 147.7 (C-9),

138.9 (C-5), 136.4 (C-6), 124.5 (C-13), 124.0 (C-1/C-4),

123.3 (C-15/C-16), 113.3 (C-14/C-17), 111.1 (C-7),

110.2 (C-2/C-3), 106.3 (C-8), 66.5 (C-12), 50.2 (C-11)

R = 0.045, wR²= 0.165, maximum residual electron

density 0.76 (ꢁ0.97) e A^ꢁ3, hydrogens calculated and re-

˚

ﬁned as riding atoms.

4.6.3. [Pyrrolidinobutadien-1,3-diyl-bis(cyclopentadienel)]-

zirconium dichloride (4b)

The reaction of 3.00 g (18.0 mmol) of 3b with 2.10 g

(9.00 mmol) ZrCl₄gave 2.55 g (69%) of complex 4b,

m.p. 100 ꢁC (decomp.). Anal. Calc. for C₁₈H₁₉NZrCl₂

(M = 411.48): C, 52.54; H, 4.65; N, 3.40. Found: C,

51.42; H, 5.77; N, 3.29%. ¹H NMR (chloroform-d₁,

200.13 MHz): d = 6.72 (m, 2H, 1-H/4-H), 6.67 (m, 2H,

15-H/16-H), 6.17 (m, 2H, 14-H/17-H), 6.07 (m, 2H, 2-

H/3-H), 5.44 (ps 1H, 8-H), 4.92 (ps, 1H, 7-H), 4.84

(ps, 1H, 7-H⁰), 3.00 (m, 4H, 11-H), 1.88 (m, 4H, 12-H)

ppm. ¹³C NMR (chloroform-d₁, 50.32 MHz):

~

ppm. IR (KBr): m ¼ 3082 ðwÞ, 2953 (w), 2859 (w),

2818 (w), 1614 (m), 1583 (m), 1261 (s), 1230 (s), 1114

.

(s), 1021 (s), 887 (s), 824 (s), 807 (vs) cm^ꢁ1

26

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

4.6.6. [Dimethylaminobutadien-1,3-diyl-bis(cyclopenta-

dienyl)]hafnium dichloride (5a)

1361 (s), 1336 (s), 1290 (s), 1038 (m), 842 (m), 821 (s)

cm^ꢁ1

.

The reaction of the reagent 3a (1.50 g, 10.6 mmol)

with hafnium tetrachloride (1.70 g, 5.3 mmol) gave

1.48 g (59%) of complex 5a, m.p. 174 ꢁC (decomp.).

Anal. Calc. for C₁₆H₁₇NHfCl₂(M = 472.71): C, 40.65;

H, 3.62; N, 2.96. Found: C, 40.56; H, 4.14; N, 3.34%.

¹H NMR (benzene-d₆, 200.13 MHz): d = 6.44–6.38 (m,

4H, 1-H/4-H/15-H/16-H), 5.72 (m, 2H, 14-H/17-H),

5.63 (m, 2H, 2-H/3-H), 5.31 (ps, 1H, 8-H), 4.77 (m,

2H, 7-H/7-H⁰), 2.07 (m, 6H, 11-H) ppm. ¹³C NMR (ben-

zene-d₆, 50.32 MHz): d = 147.6 (C-9), 138.8 (C-5), 134.7

(C-6), 124.6 (C-13), 122.4 (C-1/C-4), 121.6 (C-15/C-16),

111.7 (C-14/C-17), 108.5 (C-2/C-3), 110.5 (C-7), 104.3

(C-8), 41.9 (C-11) ppm. IR (KBr): ~m ¼ 3097 ðwÞ, 3065

(m), 2940 (m), 2873 (m), 1604 (vs), 1395 (s), 1348 (s),

1298 (s), 1105(vs), 1038 (vs), 875 (s), 866 (s), 832 (vs),

4.7.1. [Dimethylamidobutadien-1,3-diyl-bis(cyclopentadi-

enyl)]titanium dichloride (6a)

The reaction of 1.00 g (7.00 mmol) of 3a with 673 mg

(3.55 mmol) of titanium tetrachloride (added as a solu-

tion in 20 ml of ether) yielded 203 mg (17%) complex

6a after recrystallization from diethyl ether, m.p. 129

ꢁC (decomp.). Anal. Calc. for C₁₆H₁₇TiCl₂

(M = 342.12): C, 56.17; H, 5.01; N, 4.09. Found: C,

55.37; H, 5.67; N, 5.45%. ¹H NMR (chloroform-d₁,

200.13 MHz): d = 6.96–6.90 (m, 4H, 1-H/4-H/15-H/16-

H), 6.11–6.05 (m, 4H, 2-H/3-H/14-H/17-H), 5.64 (ps,

1H, 8-H), 5.00 (ps, 1H, 7-H), 4.93 (ps, 1H, 7-H⁰), 2.63

(s, 6H, 11-H) ppm. ¹³C NMR (chloroform-d₁, 50.32

MHz): d = 147.4 (C-9), 139.2 (C-5), 134.7 (C-6), 126.8

(C-13), 129.7 (C-1/C-4), 128.8 (C15/C-16), 116.9 (C-14/

C-17), 115.1 (C-2/C-3), 110.3 (C-7), 104.7 (C-8), 41.4

820 (vs) cm^ꢁ1

.

~

(C-11) ppm. IR (KBr): m ¼ 3101 ðmÞ, 3070 (m), 2943

4.6.7. X-ray crystal structure analysis of complex 5a

Single crystals were obtained from dichloromethane

by slow evaporation of the solvent at ambient condi-

tions. Formula C₁₆H₁₇Cl₂HfN, M = 472.70, yellow crys-

(m), 2874 (m), 1605 (vs), 1569 (vs), 1363 (s), 1349 (s),

.

1110 (s), 1041 (s), 843 (s), 829 (vs) cm^ꢁ1

4.7.2. [Dimethylaminobutadien-1,3-diyl-bis(3-methylcy-

clopentadienyl)]zirconium dichloride (11a)

˚

tal 0.25 · 0.20 · 0.20 mm, a = 10.756(2) A, b = 10.458(2)

3

˚

A, c = 13.909(3) A, b = 101.71(2)ꢁ, V = 1532.0(5) A ,

The reaction of 2.00 g (12.9 mmol) of the reagent 10a

with 1.50 g (6.5 mmol) of ZrCl₄was carried out as de-

scribed in the general procedure to yield a 1:1 mixture

of the rac- and meso-isomers of 11a (isomer A and iso-

mer B). Recrystallization from diethyl ether gave 1.17

g of the isomer mixture (44% yield), m.p. 92 ꢁC (de-

comp.). Anal. Calc. for C₁₈H₂₁NZrCl₂(413.50): C,

52.29; H, 5.12; N, 3.39. Found: C, 52.41; H, 6.57; N,

3.35%. ¹H NMR (dichloromethane-d₂, 599.87 MHz,

298 K, isomer A): d = 6.43 (m, 1H, Cp–H), 6.38 (m,

1H, Cp–H), 6.33 (m, 1H, Cp–H), 6.05 (m, 1H, Cp–H),

5.85 (m, 1H, Cp–H), 5.72 (m, 1H, Cp–H), 5.60 (s, 1H,

8-H), 4.95 (m, 1H, 7-H), 4.85 (m, 1H, 7-H⁰), 2.63 (s,

6H, 11-H), 2.32 (s, 3H, 17-H), 2.30 (s, 3H, 18-H) ppm.

¹³C NMR (dichloromethane-d₂, 150.84 MHz, 298 K,

isomer A): d = 148.2 (C-9), 139.9 (C-6), 136.5 (C-5),

133.2 (C-3), 132.6 (C-15), 124.9 (C-12), 123.8, 123.5,

123.4, 114.8, 112.6, 110.6 (C-1/C-2/C-4/C-13/C-14/C-

16), 109.1 (C-7), 104.4 (C-8), 41.7 (C-11), 15.7 (C-17/

C-18) ppm. ¹H NMR (dichloromethane-d₂, 599.87

MHz, 298 K, isomer B): d = 6.39 (m, 1H, Cp–H), 6.08

(m, 1H, Cp–H), 5.97 (m, 1H, Cp–H), 5.87 (m, 1H,

Cp–H), 5.83 (m, 1H, Cp–H), 5.77 (m, 1H, Cp–H), 5.59

(ps, 1H, 8-H), 4.94 (m, 1H, 7-H), 4.84 (m, 1H, 7-H⁰),

2.62 (s, 6H, 11-H), 2.31 (s, 3H, 17-H), 2.29 (s, 3H, 18-

H) ppm. ¹³C NMR (dichloromethane-d₂, 150.84 MHz,

298 K, isomer B): d = 148.3 (C-9), 139.9 (C-6), 136.6

(C-5), 133.4 (C-2), 132.7 (C-15), 124.7 (C-12), 123.8,

115.6, 115.1, 113.6, 113.1, 112.5 (C-1/C-3/C-4/C-13/C-

14/C-16), 109.0 (C-7), 104.4 (C-8), 41.6 (C-11), 15.6

q

_calc= 2.049 g cm^ꢁ3, l = 71.46 cm^ꢁ1, empirical absorp-

tion correction via w scan data (0.268 6 T 6 0.329),

Z = 4, monoclinic, space group P2₁/n (No. 14),

˚

k = 0.71073 A, T = 223 K, x/2h scans, 3244 reﬂections

collected (h, ꢁk, ꢁl), [(sinh)/k] = 0.62 A^ꢁ1, 3116 inde-

˚

pendent (R_int= 0.052) and 2903 observed reﬂections

[I P 2r(I)], 184 reﬁned parameters, R = 0.028,

wR²= 0.087, maximum residual electron density 1.58

(ꢁ1.95) e A^ꢁ3, hydrogens calculated and reﬁned as rid-

˚

ing atoms.

4.7. [Pyrrolidinobutadien-1,3-diyl-bis(cyclopentadienyl)]

hafnium dichloride (5b)

The reaction of 3b (1.50 g, 9.0 mmol) with 1.44 g (4.5

mmol) of hafnium tetrachloride carried out according to

the general procedure described above gave 1.08 g (49%)

of complex 5b, m.p. 93 ꢁC (decomp.). Anal. Calc. for

C₁₈H₁₉NHfCl₂(M = 498.75): C, 43.35; H, 3.84; N,

1

2.81. Found: C, 44.31; H, 4.94; N, 3.04%. H NMR

(chloroform-d₁, 200.13 MHz): d = 6.61 (m, 2H, 1-H/4-

H), 6.56 (m, 2H, 15-H/16-H), 6.05 (m, 2H, 14-H/

17-H), 5.99 (m, 2H, 2-H/3-H), 5.44 (ps, 1H, 8-H),

4.87–4.84 (m, 2H, 7-H/7-H⁰), 3.03–2.91 (m, 4H, 11-H),

1.89–1.83 (m, 4H, 12-H) ppm. ¹³C NMR (chloroform-

d₁, 50.32 MHz): d = 148.7 (C-9), 133.5 (C-5), 124.2

(C-6), 122.7 (C-13) 121.6 (C-1/C-4), 121.5 (C-15/C-16),

111.1 (C-14/C-17), 109.5 (C-2/C-3), 109.7 (C-7), 99.4

(C-8), 49.4 (C-11), 25.0 (C-12) ppm. IR (KBr):

~m ¼ 3087 ðwÞ, 2956 (m), 2869 (m), 1604 (vs), 1540 (s),

~

(C-17/C-18) ppm. IR (KBr): m ¼ 3091 ðwÞ, 2960 (m),

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

27

2933 (m), 2871 (m), 2795 (m), 1630 (vs), 1563 (s), 1453

(s), 1356 (s), 1156 (m), 1081 (m), 1053 (m), 847 (s), 813

ane-d₂, 150.84 MHz, isomer A): d = 148.1 (C-9), 139.7

(C-6), 134.4 (C-5), 131.5 (C-3), 130.8 (C-15), 124.6 (C-

12), 122.4, 122.1, 121.6, 118.1, 112.0, 111.4 (C-1/C-2/

C-4/C-13/C-14/C-16), 108.5 (C-7), 104.2 (C-8), 41.2 (C-

(s), 778 (s) cm^ꢁ1

.

1

11), 15.4 (C-17), 15.1 (C-18) ppm. H NMR (dichloro-

4.7.3. [Dimethylaminobutadien-1,3-diyl-bis(3-tert-butyl-

cyclopentadienyl)]zirconium dichloride (11b)

methane-d₂, 599.87 MHz, isomer B): d = 6.30 (m, 1H,

Cp–H), 6.25 (m, 1H, Cp–H), 6.19 (m, 1H, Cp–H), 5.88

(m, 1H, Cp–H), 5.74 (m, 1H, Cp–H), 5.73 (m, 1H,

Cp–H), 5.58 (m, 1H, 8-H), 4.89 (m, 1H, 7-H), 4.83 (m,

1H, 7-H⁰), 2.59 (s, 6H, 11-H), 2.35 (s, 3H, 17-H), 2.33

(s, 3H, 18-H) ppm. ¹³C NMR (dichloromethane-d₂,

150.84 MHz, isomer B): d = 148.0 (C-9), 139.7 (C-6),

134.2 (C-5), 131.2 (C-3), 130.7 (C-15), 124.3 (C-12),

122.4, 122.2, 122.0, 118.0, 117.0, 114.8 (C-1/C-2/C-4/C-

13/C-14/C-16), 108.6 (C-7), 104.3 (C-8), 41.0 (C-11),

The reaction of 1.70 g (8.6 mmol) of 10b with 1.00 g

(4.3 mmol) of zirconium tetrachloride gave a 1:1 mixture

of the rac- and meso-isomers of the product 11b (isomer

A and isomer B), yield 1.03 g (48%) after recrystalliza-

tion from ether, m.p. 65 ꢁC (decomp.). Anal. Calc. for

C₂₄H₃₃NZrCl₂(M = 497.66): C, 57.92; H, 6.68; N,

2.81. Found: C, 57.42; H, 7.28; N, 3.65%. ¹H NMR (tol-

uene-d₈, 599.87 MHz, 298 K, isomer A): d = 6.47 (m,

1H, Cp–H), 6.44 (m, 1H, Cp–H), 6.14 (m, 1H, Cp–H),

5.90 (m, 1H, Cp–H), 5.80 (m, 1H, Cp–H), 5.75 (m,

1H, Cp–H), 5.36 (s, 1H, 8-H), 4.87 (m, 1H, 7-H), 4.73

(m, 1H, 7-H⁰), 2.19 (s, 6H, 11-H), 1.31 (s, 9H, 20-H),

1.29 (s, 9H, 18-H) ppm. ¹³C NMR (toluene-d₈, 150.84

MHz, 298 K, isomer A): d = 148.2 (C-9), 145.7 (C-15),

145.4 (C-3), 139.6 (C-6), 132.9 (C-5), 122.9 (C-12),

124.1, 122.7, 112.6, 112.0, 111.7, 109.1 (C-1/C-2/C-4/C-

13/C-14/C-16), 108.7 (C-7), 103.8 (C-8), 41.0 (C-11),

31.2 (C-20), 31.1 (C-18), 29.9 (C-17/C-19) ppm. ¹H

NMR (toluene-d₈, 599.87 MHz, 298 K, isomer B):

d = 6.35 (m, 1H, Cp–H), 6.24 (m, 1H, Cp–H), 6.22 (m,

1H, Cp–H), 6.02 (m, 1H, Cp–H), 5.87 (m, 1H, Cp–H),

5.73 (m, 1H, Cp–H), 5.38 (s, 1H, 8-H), 4.89 (m, 1H, 7-

H), 4.75 (m, 1H, 7-H⁰), 2.18 (s, 6H, 11-H), 1.32 (s, 9H,

18-H), 1.30 (s, 9H, 20-H) ppm. ¹³C NMR (toluene-d₈,

150.84 MHz, 298 K, isomer B): d = 147.9 (C-9), 145.6

(C-2), 145.3 (C-15), 139.7 (C-6), 131.8 (C-5), 122.4 (C-

12), 121.6, 119.4, 115.9, 113.7, 110.8, 110.3 (C-1/C-3/

C-4/C-13/C-14/C-16), 109.2 (C-7), 104.1 (C-8), 40.9 (C-

11), 31.1 (C-18), 31.1 (C-20), 29.8 (C-17/C-19) ppm.

~

15.7 (C-17), 15.3 (C-18) ppm. IR (KBr): m ¼ 3096 ðwÞ,

2935 (m), 2869 (m), 2795 (m), 1617 (vs), 1564 (s), 1463

(s), 1356 (s), 1147 (m), 1075 (m), 1062 (m), 862 (m),

814 (s), 774 (s) cm^ꢁ1

.

4.7.5. [Dimethylaminobutadien-1,3-diyl-bis(3-tert-butyl-

cyclopentadienyl)]hafnium dichloride (12b)

The reaction of 2.50 g (12.7 mmol) of the reagent 10b

with 2.03 g (6.3 mmol) of hafnium tetrachloride gave a

close to 1:1 mixture of the rac- and meso-isomers of

12b (isomer A and isomer B), yield after recrystallization

from diethyl ether: 400 mg (11%), m.p. 78 ꢁC (decomp.).

Anal. Calc. for C₂₄H₃₃NHfCl₂(M = 584.93): C, 49.28;

H, 5.69; N, 2.39. Found: C, 49.64; H, 5.85; N, 3.67%.

¹H NMR (dichloromethane-d₂, 599.87 MHz, isomer

A): d = 6.25 (m, 1H, Cp–H), 6.22 (m, 1H, Cp–H), 6.12

(m, 1H, Cp–H), 5.96 (m, 1H, Cp–H), 5.93 (m, 1H,

Cp–H), 5.79 (m, 1H, Cp–H), 5.55 (m, 1H, 8-H), 4.92

(m, 1H, 7-H), 4.81 (m, 1H, 7-H⁰), 2.60 (s, 6H, 11-H),

1.34 (s, 9H, 18-H), 1.31 (s, 9H, 20-H) ppm. ¹³C NMR

(dichloromethane-d₂, 150.84 MHz, isomer A):

d = 147.9 (C-9), 145.6 (C-15), 144.1 (C-3), 139.6 (C-6),

130.2 (C-5), 114.0, 113.0, 111.9, 110.6, 110.4, 106.2 (C-

1/ C-2/C-4/C-13/C-14/C-16), 109.0 (C-7), 103.5 (C-8),

41.5 (C-11), 31.2 (C-18), 31.1 (C-20), 30.8 (C-17/C-19)

~

IR (KBr): m ¼ 3109 ðwÞ, 3089 (w), 2966 (vs), 2914 (s),

2868 (s), 2790 (m), 1620 (s), 1568(s), 1471 (s), 1367

(vs), 1243 (m), 1159 (s), 1055 (s), 1016 (s), 931 (m),

808 (s) cm^ꢁ1

.

1

4.7.4. [Dimethylaminobutadien-1,3-diyl-bis(3-methylcy-

clopentadienyl)]hafnium dichloride (12a)

ppm. H NMR (dichloromethane-d₂, 599.87 MHz, iso-

mer B): d = 6.11 (m, 1H, Cp–H), 6.09 (m, 1H, Cp–H),

6.01 (m, 1H, Cp–H), 5.98 (m, 1H, Cp–H), 5.95 (m,

1H, Cp–H), 5.80–5.79 (m, 1H, Cp–H), 5.56 (m, 1H, 8-

H), 4.90 (m, 1H, 7-H), 4.80 (m, 1H, 7-H⁰), 2.59 (s, 6H,

11-H), 1.33 (s, 9H, 18-H), 1.32 (s, 9H, 20-H) ppm. ¹³C

NMR (dichloromethane-d₂, 150.84 MHz, isomer B):

d = 147.8 (C-9), 145.2 (C-15), 143.9 (C-3), 139.5 (C-6),

130.1 (C-5), 111.7, 111.6, 111.4, 111.1, 108.6, 106.3 (C-

1/ C-2/C-4/C-13/C-14/C-16), 109.1 (C-7), 103.7 (C-8),

41.4 (C-11), 31.2 (C-18), 31.0 (C-20), 30.7 (C-17/C-19)

The reaction of 2.50 g (16.1 mmol) of the reagent 10a

with 2.58 g (8.1 mmol) of hafnium tetrachloride gave a

1:1 mixture of the rac- and meso-isomers of the product

12a, yield after recrystallization from ether: 383 mg

(9.5%), m.p. 83 ꢁC (decomp.). Anal. Calc. for

C₁₈H₂₁NHfCl₂(M = 500.77): C, 43.17; H, 4.23; N,

1

2.80. Found: C, 44.58; H, 4.90; N, 3.07%. H NMR

(dichloromethane-d₂, 599.87 MHz, isomer A): d = 6.26

(m, 1H, Cp–H), 6.21 (m, 1H, Cp–H), 5.98 (m, 1H,

Cp–H), 5.93 (m, 1H, Cp–H), 5.67 (m, 1H, Cp–H), 5.60

(m, 1H, Cp–H), 5.57 (m, 1H, 8-H), 4.88 (m, 1H, 7-H),

4.84 (m, 1H, 7-H⁰), 2.62 (s, 6H, 11-H), 2.36 (s, 3H, 17-

H), 2.34 (s, 3H, 18-H) ppm. ¹³C NMR (dichlorometh-

~

ppm. IR (KBr): m ¼ 3109 ðwÞ, 3089 (w), 2979 (s), 2914

(s), 2862 (s), 2797 (m), 1620 (s), 1568 (s), 1471 (m),

1367 (s), 1250 (m), 1159 (m), 1061 (m), 1009 (m), 925

(m), 866 (m), 834 (m), 801 (m) cm^ꢁ1

.

28

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

4.8. Preparation of the [dialkylaminobutadien-1,3-diyl-

bis(cyclopentadienyl)]dimethyl Group 4 metal com-

plexes. General procedure

(s), 2950 (s), 2921 (s), 1603 (vs), 1538 (s), 1359 (s),

1331 (s), 1289 (s), 1163 (m), 1057 (s), 1036 (s), 806

(vs), 802 (vs), 798 (vs) cm^ꢁ1

.

The

respective

[dialkylaminobutadien-1,3-diyl-

4.8.3. [Morpholinobutadien-1,3-diyl-bis(cyclopentadi-

enyl)]dimethyl zirconium (7d)

bis(cyclopentadienyl)] Group 4 metal dihalide complex

(ca. 1 mmol) was dissolved in ca. 40 ml of diethyl ether

and cooled to ꢁ40 ꢁC. At this temperature a 1.6 M ethe-

real methyl lithium solution (ca. 2 mmol) was added

dropwise with stirring. The mixture was stirred for 2 h

at ꢁ40 ꢁC, then warmed to room temperature and stir-

red for additional 30 min. The lithium chloride precipi-

tate was removed by ﬁltration. The ﬁltrate was

concentrated in vacuo until a precipitate began to form.

The mixture was then cooled to ꢁ30 ꢁC and the precip-

itated product collected by ﬁltration.

The reaction of 178 mg (0.42 mmol) of 4d with methyl

lithium (0.84 mmol) in ether gave 92 mg (57%) of com-

plex 7d, m.p. 101 ꢁC (decomp.). Anal. Calc. for

C₂₀H₂₅NOZr (M = 386.65): C, 62.13; H, 6.52; N, 3.62.

1

Found: C, 62.37; H, 6.42; N, 4.05%. H NMR (chloro-

form-d₁, 200.13 MHz): d = 6.61–6.55 (m, 4H, Cp–H),

5.79–5.73 (m, 4H, Cp–H), 5.43 (ps, 1H, 8-H), 4.91 (ps,

1H, 7-H), 4.71 (ps, 1H, 7-H⁰), 3.72–3.67 (m, 4H, 12-

H), 2.83–2.79 (m, 4H, 11-H), ꢁ0.35 (s, 6H, 18-H/19-

H) ppm. ¹³C NMR (dichloromethane-d₂, 50.32 MHz):

d = 149.8 (C-9), 136.1 (C-5), 127.5 (C-6), 117.2 (C-13),

116.7, 116.6, 110.4, 108.8 (C–Cp), 107.9 (C-7), 105.7

(C-8), 67.2 (C-12), 50.5 (C-11), 29.3 (C-18/C-19) ppm.

4.8.1. [Dimethylaminobutadien-1,3-diyl-bis(cyclopentadie-

nyl)]dimethyl zirconium (7a)

~

The reaction of 515 mg of complex 4a (1.34 mmol)

with 1.67 ml of a 1.6 M solution of methyl lithium in

ether (2.68 mmol) was carried out according to the gen-

eral procedure described above. It yielded 256 mg (55%)

of the product 7a as a yellow solid, m.p. 140 ꢁC, 197 ꢁC

(decomp.). Anal. Calc. for C₁₈H₂₃NZr (M = 344.61): C,

62.74; H, 6.73; N, 4.06. Found: C, 62.28; H, 5.92; N,

4.18%. ¹H NMR (chloroform-d₁, 599.99 MHz):

d = 6.61 (m, 2H, 15-H/16-H), 6.54 (m, 2H, 1-H/4-H),

5.76 (m, 4H, 2-H/3-H/14-H/17-H), 5.32 (s, 1H, 8-H),

4.85 (t, 1H, 7-H), 4.65 (t, 1H, 7-H⁰), 2.58 (s, 6H, 11-

H), ꢁ0.37 (s, 6H, 18-H/19-H) ppm. ¹³C NMR (chloro-

form-d₁, 154.99 MHz): d = 148.0 (C-9), 140.1 (C-5 ),

128.3 (C-6), 118.6 (C-13), 116.2 (C-1/C-4), 116.1 (C-15/

C-16), 109.8 (C-14/C-17), 107.5 (C-2/C-3), 107.7 (C-7),

103.7 (C-8), 41.4 (C-11), 29.1 (C-18/C-19) ppm. IR

IR (KBr): m ¼ 3083 ðwÞ, 2951 (m), 2853 (m), 1613 (m),

1262 (s), 1114 (s), 1020 (s), 955 (s), 875 (s), 824 (vs),

.

799 (vs) cm^ꢁ1

4.8.4. [Dimethylaminobutadien-1,3-diyl-bis(cyclopentadi-

enyl)]dimethyl hafnium (8a)

The reaction of 557 mg (1.18 mmol) of 5a with methyl

lithium (2.36 mmol) in ether gave 417 mg (82%) of the

product 5a as a beige colored solid, m.p. 146 ꢁC (de-

comp.). Anal. Calc. for C₁₈H₂₃NHf (M = 431.88): C,

50.06; H, 5.37; N, 3.24. Found: C, 50.43; H, 5.06; N,

3.30%. ¹H NMR (chloroform-d₁, 200.13 MHz):

d = 6.48 (m, 2H, Cp–H), 6.42 (m, 2H, Cp–H), 5.71–

5.67 (m, 4H, Cp–H), 5.35 (s, 1H, 8-H), 4.83 (ps, 1H,

7-H), 4.69 (ps, 1H, 7-H⁰), 2.59 (s, 6H, 11-H), ꢁ0.56 (s,

6H, 18-H/19-H) ppm. ¹³C NMR (chloroform-d₁, 50.32

MHz): d = 147.9 (C-9), 140.0 (C-5), 127.4 (C-6), 120.9

(C-13), 115.4, 115.3, 109.2, 106.7 (C-1/C-2/C-3/C-4/C-

14/C-15/C-16/C-17), 108.1 (C-7), 103.5 (C-8), 41.4 (C-

11), 35.3 (C-18/C-19). IR (KBr): ~m ¼ 3086 ðmÞ, 3071

(m), 2917 (s), 2910 (s), 2862 (s), 2837 (s), 2785 (m),

1602 (vs), 1488 (s), 1392 (s), 1352 (s), 1299 (s), 1132

~

(KBr): m ¼ 3071 ðwÞ, 2909 (m), 2859 (m), 2839 (m),

1601 (vs), 1575 (s), 1391 (s), 1351 (s), 1299 (s), 1260

(vs), 1103 (vs), 1097 (vs), 1037(vs), 860 (s), 818 (vs),

812 (vs), 800 (vs) cm^ꢁ1

.

4.8.2. [Pyrrolidinobutadien-1,3-diyl-bis(cyclopentadienyl)]-

dimethylzirconium (7b)

(s), 1103 (vs), 1038 (vs), 860 (s), 822 (s), 810 (vs), 804

ꢁ1

The reaction of 627 mg (1.52 mmol) of complex 4b

with methyl lithium (3.04 mmol) in ether gave 271 mg

(48%) of complex 7b, m.p. 78 ꢁC (decomp.). Anal. Calc.

for C₂₀H₂₅NZr (M = 370.65): C, 64.81; H, 6.80; N, 3.78.

(vs) cm

.

4.8.5. [Pyrrolidinobutadien-1,3-diyl-bis(cyclopentadi-

enyl)]dimethyl hafnium (8b)

1

Found: C, 64.95; H, 6.26; N, 4.26%. H NMR (chloro-

The reaction of 472 mg (0.95 mmol) of complex 5b

with 1.90 mmol of methyl lithium in ether gave 334

mg (77%) of 8b, m.p. 67 ꢁC (decomp.). Anal. Calc. for

C₂₀H₂₅NHf (M = 457.92): C, 52.46; H, 5.50; N, 3.06.

Found: C, 52.32; H, 6.71; N, 3.33%. ¹H NMR (dichloro-

methane-d₂, 200.13 MHz): d = 6.50 (m, 2H, Cp–H), 6.38

(m, 2H, Cp–H), 5.80 (m, 2H, Cp–H), 5.67 (m, 2H, Cp–

H), 5.23 (ps, 1H, 8-H), 4.75 (ps, 1H, 7-H), 4.63 (ps, 1H,

7-H⁰), 3.03–2.97 (m, 4H, 11-H), 1.87–1.81 (m, 4H, 12-

H), ꢁ0.55 (s, 6H, 18-H/19-H) ppm. ¹³C NMR (dichloro-

form-d₁, 200.13 MHz): d = 6.60 (m, 2H, Cp–H), 6.50

(m, 2H, Cp–H), 5.86 (m, 2H, Cp–H), 5.72 (m, 2H,

Cp–H), 5.19 (s, 1H, 8-H), 4.79 (ps, 1H, 7-H), 4.61 (ps,

1H, 7-H⁰), 3.02–2.96 (m, 4H, 11-H), 1.89–1.81 (m, 4H,

12-H), ꢁ0.37 (s, 6H, 18-H/19-H) ppm. ¹³C NMR (chlo-

roform-d₁, 50.32 MHz): d = 145.8 (C-9), 139.9 (C-5),

127.8, 118.7 (C-6/C-13), 115.9, 115.6, 109.3, 106.9 (C–

Cp), 107.9 (C-7), 99.3 (C-8), 49.3 (C-11), 29.1 (C-18/C-

~

19), 25.1 (C-12) ppm. IR (KBr): m ¼ 3082 ðmÞ, 2960

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

29

˚

methane-d₂, 50.32 MHz): d = 148.6 (C-9), 140.8 (C-5),

127.3, 119.4, (C-6/ C-13), 115.7, 115.2, 107.7, 107.0

(C–Cp), 109.0 (C-7), 99.3 (C-8), 49.6 (C-11), 35.2 (C-

A

^ꢁ1, 2469 independent (R_int= 0.025) and 1993 observed

reﬂections [I P 2r(I)], 139 reﬁned parameters,

R = 0.025, wR²= 0.057, maximum residual electron

˚

~

18/C-19), 25.4 (C-12) ppm. IR (KBr): m ¼ 3086 ðwÞ,

density 0.46 (ꢁ0.33) e A^ꢁ3, hydrogen at N10 from diﬀer-

3076 (w), 2957 (m), 2897 (m), 1607 (s), 1550 (m), 1394

(m), 1261 (m), 1099 (m), 1069 (m), 1029 (m), 807 (s),

ence Fourier map and reﬁned free, others calculated and

reﬁned as riding atoms.

801(s) cm^ꢁ1

.

4.8.7. Reaction of complex 13f with HB(C₆F₅)₂, forma-

tion of bis(vinylcyclopentadienyl)zirconium dichloride

(17) and the aminoborane 18

4.8.5.1. [Dimethylaminobutadien-1,3-diyl-bis(cyclopen-

tadienyl)]bis(dimethylamido)zirconium (9a). Com-

plex 4a (770 mg, 2.0 mmol) and lithium dimethylamide

(204 mg, 4.0 mmol) were combined as solids and cooled

to ꢁ78 ꢁC, then 30 ml of precooled diethyl ether was

added. The mixture was allowed to warm to room tem-

perature with stirring and then stirred over night. Sol-

vent was removed in vacuo. The residue was taken up

with 30 ml of pentane and ﬁltered. The clear ﬁltrate

was concentrated in vacuo and the product crystallized

at ꢁ30 ꢁC to yield 523 mg (65%) of 9a. Anal. Calc. for

C₂₀H₂₉N₃Zr (M = 402.22): C, 59.65; H, 7.262; N,

The zirconium complex 13f (112 mg, 202 lmol) was

dissolved in 10 ml of toluene. A solution of 140 mg

(404 lmol) of HB(C₆F₅)₂in 5 ml of toluene was added

dropwise with stirring at ambient temperature. The mix-

ture was stirred for 12 h at room temperature. Solvent

was removed in vacuo and the residue extracted with

pentane (2 · 15 ml). Bis(vinylcyclopentadienyl)ZrCl₂

(17, 175 mg, 96% yield) was recovered from the com-

bined pentane extracts. The residue from the pentane

extraction was dried in vacuo and identiﬁed as 18 (68

1

10.43. Found: C, 58.81; H, 7.52; N, 10.60%. H NMR

mg, 98% recovered). Complex 17: H NMR (benzene-

3

(benzene-d₆, 599.9 MHz): d = 6.27 (m, 2H, 14-H/15-

H), 6.23 (m, 2H, 2-H/3-H), 5.90 (m, 2H, 13-H/16-H),

5.88 (m, 2H, 1-H/4-H), 5.48 (s, 1H, 8-H), 5.09 (m, 1H,

7-H), 4.94 (m, 1H, 7-H⁰), 2.88 (s, 12H, Zr(NMe₂), 2.33

(s, 6H, C(NMe₂)). ¹³C NMR (benzene-d₆, 150.8 MHz,

298K): d = 148.9 (C-9), 141.8 (C-6), 132.1 (C-5), 124.7

(C-12), 113.4 (C-2/C-3), 113.3 (C-14/C-15), 109.0 (C-

13/C-16), 107.7 (C-7), 106.5 (C-1/C-4), 104.0 (C-8),

49.5 (C-17/C-18)/C-19/C-20), 41.4 (C-10/C-11).

d₆, 599.87 MHz): d = 6.33 (dd, 1H, 6-H, J_cis= 10.7

3

Hz, J_trans= 16.8 Hz), 6.02 (m, 2H, 2-H/3-H), 5.80 (m,

2H, 1-H/4-H), 5.29 (dd, 1H, 7-H, ²J = 1.1 Hz,

³J_trans= 16.8 Hz), 5.02 (dd, 1H, 7-H⁰, ²J = 1.1 Hz,

³J_cis= 10.7 Hz) ppm. ¹³C NMR (benzene-d₆, 150.84

MHz): d = 130.0 (C-6), 127.1 (C-5), 115.8 (C-7), 115.3

(C-2/C-3), 114.6 (C-1/C-4) ppm.

1

Compound 18: H NMR (benzene-d₆, 599.87 MHz):

d = 6.86–6.79 (m, 4H, o-, m-Ph), 6.77 (m, 1H, p-Ph), 2.72

(s, 3H, CH₃) ppm. ¹³C NMR (benzene-d₆, 150.84 MHz):

d = 147.3 (ipso-), 129.4 (m-), 127.4 (p-), 125.8 (o-Ph),

43.2 (CH₃) ppm. C₆F₅resonances not located. ¹¹B

NMR (benzene-d₆, 64.2 MHz): d = 35.4 ppm. ¹⁹F

NMR (benzene-d₆, 282.4 MHz): d = ꢁ162.8, ꢁ161.4,

ꢁ151.9, ꢁ151.0, ꢁ131.5 ppm.

4.8.5.2. X-ray crystal structure analysis of complex

9a. Single crystals from pentane at ꢁ30 ꢁC: Formula

C₂₀H₂₉N₃Zr, M = 402.68, yellow crystal 0.30 · 0.25

˚

· 0.10 mm, a = 20.818(1) A, b = 8.438(1) A, c =

21.598(1) A, V = 3794.0(5) A , q_calc= 1.410 g cm^ꢁ3

,

3

˚

l = 5.86 cm^ꢁ1, empirical absorption correction (0.844

6 T 6 0.944), Z = 8, orthorhombic, space group Pbca

4.8.8. Reaction of complex 13c with HB(C₆F₅)₂, prepa-

ration of 19A/B

˚

(No. 61), k = 0.71073 A, T = 198 K, x and u scans,

21,307 reﬂections collected (h, k, l), [(sinh)/k] = 0.66

A

Complex 13c (70 mg, 137 lmol) was dissolved in 15

ml of toluene. A solution of 95 mg (274 lmol) of

HB(C₆F₅)₂in 5 ml of toluene was added dropwise with

stirring. The mixture was stirred for 48 h at room tem-

perature. Solvent was removed in vacuo and the residue

washed with pentane (2 · 5 ml). The remaining solid was

dried in vacuo to yield 134 mg (81%) of a 2:3 mixture of

the rac- and meso-isomers of product 19 (isomers 19A

and 19B), m.p. 109 ꢁC (decomp.). Anal. Calc. for

C₄₈H₃₄N₂B₂F₂₀ZrCl₂(M = 1202.5): C, 47.94; H, 2.85;

N, 2.33. Found: C, 48.23; H, 3.69; N, 2.25%. ¹H

NMR (benzene-d₆, 599.87 MHz, isomer A): d = 6.41

(m, 1H, Cp–H), 6.09 (m, 1H, Cp–H), 5.97 (m, 1H,

Cp–H), 5.64 (m, 1H, Cp–H), 4.74 (dd, 1H, 6-H,

^ꢁ1, 4522 independent (R_int= 0.042) and 3716 observed

˚

reﬂections [I P 2r(I)], 208 reﬁned parameters,

R = 0.032, wR²= 0.079, maximum residual electron

density 0.46 (ꢁ0.62) e A^ꢁ3, hydrogens calculated and re-

˚

ﬁned as riding atoms.

4.8.6. X-ray crystal structure analysis of the

CpZrCl₃(morpholine) dimer 14

Formula C₁₈H₂₈Cl₆N₂O₂Zr₂, M = 699.56, yellow

˚

crystal 0.25 · 0.20 · 0.10 mm, a = 9.585(1) A,

˚

b = 7.105(1) A, c = 17.942(1) A, b = 91.72(1) A,

V = 1221.3(2) A , q_calc= 1.902 g cm^ꢁ3, l = 15.29 cm^ꢁ1

,

3

˚

empirical absorption correction via

w scan data

3

0

J_7-H= 6.8 Hz, J_7-H= 12.6 Hz), 2.95 (m, 2H, 8-H),

(0.701 6 T 6 0.862), Z = 2, monoclinic, space group

3

2.59 (m, 2H, 12-H), 2.34 (dd, 1H, 7-H, J_6-H= 6.8 Hz,

˚

P2₁/n (No. 14), k = 0.71073 A, T = 223 K, x/2h scans,

2

3

J_7-H= 12.6 Hz), 1.66 (t, 1H, 7-H⁰, J_6-H= ²J_7-H= 12.6

0

2546 reﬂections collected (h, ꢁk, +l), [(sinh)/k] = 0.62

30

S. Knu¨ppel et al. / Journal of Organometallic Chemistry 690 (2005) 14–32

Hz), 1.16 (m, 2H, 9-H), 0.95 (m, 2H, 10-H), 0.64 (m, 2H,

11-H) ppm. ¹³C NMR (benzene-d₆, 150.84 MHz, isomer

A): d = 129.2 (C-5), 123.9, 118.6, 114.1, 107.5 (C-1/C-2/

C-3/C-4), 69.1 (C-6), 56.9 (C-8), 47.7 (C-12), 21.6 (C-9/

C-11), 21.2 (C-10), 19.4 (br, C-7) ppm. C₆F₅resonances

not located. ¹H NMR (benzene-d₆, 599.87 MHz, isomer

B): d = 6.18 (m, 1H, Cp–H), 6.10 (m, 1H, Cp–H), 5.98

(m, 1H, Cp–H), 5.67 (m, 1H, Cp–H), 4.75 (dd, 1H, 6-

isomers): d = ꢁ162.1, ꢁ160.5, ꢁ154.7, ꢁ151.3, ꢁ127.7,

~

ꢁ122.9 ppm. IR (KBr): m ¼ 2978 ðmÞ, 2962 (s), 2874

(m), 1656 (s), 1527 (vs), 1470 (vs), 1403 (s), 1269 (vs),

.

1320 (s), 1098 (vs), 980 (vs), 814 (s), 742 (s), 696 (s) cm^ꢁ1

5. Supplementary material

3

0

H, J_7-H= 6.8 Hz, J_7-H= 12.9 Hz), 2.95 (m, 2H, 12-

Crystallographic data (excluding structure factors)

for the structures reported in this paper have been

deposited with the Cambridge Crystallographic Data

Centre as supplementary publication CCDC 236337–

236342. Copies of the data can be obtained free of

charge on application to The Director, CCDC, 12 Un-

ion Road, CambridgeCB2 1EZ, UK [fax: int. code

+44(1223)336-033, e-mail: deposit@ccdc.cam.ac.uk].

H), 2.43 (m, 2H, 8-H), 2.42 (m, 1H, 7-H), 1.69 (t, 1H,

3

7-H⁰, J_6-H= 12.9 Hz), 0.95 (m, 2H, 9-H), 0.86 (m,

2H, 10-H), 0.02 (m, 2H, 11-H) ppm. ¹³C NMR (ben-

zene-d₆, 150.84 MHz, isomer B): d = 128.8 (C-5),

120.1, 117.8, 117.4, 108.7 (C-1/C-2/C-3/C-4), 69.5 (C-

6), 56.9 (C-8), 47.4 (C-12), 22.1 (C-9), 21.7 (C-11), 21.2

(C-10), 19.4 (br, C-7) ppm. ¹¹B NMR (benzene-d₆,

64.2 MHz, both isomers): d = 2.76 ppm. ¹⁹F NMR (ben-

zene-d₆, 282.4 MHz, both isomers): d = ꢁ162.4, ꢁ162.3,

ꢁ156.2, ꢁ154.7, ꢁ128.3, ꢁ127.3 ppm. IR (KBr):

Acknowledgements

~

m ¼ 2961 ðmÞ, 2949 (m), 2866 (w), 1645 (m), 1635 (m),

1533 (m), 1517 (s), 1464(vs), 1283 (m), 1262 (m), 1099

(s), 970 (s), 817 (s) cm

Financial support from the Deutsche Forschungsge-

meinschaft and the Fonds der Chemischen Industrie is

gratefully acknowledged. C.W. thanks the NRW Grad-

ꢁ1

.

4.8.9. Reaction of complex 13d with HB(C₆F₅)₂, prep-

aration of 20A/B

uate School of Chemistry (Munster) for a stipend.

¨

Analogously as described above the reaction of com-

plex 13d (98 mg, 190 lmol) with HB(C₆F₅)₂(132 mg,

380 lmol) in a total of 20 ml of toluene gave 150 mg

(65%) of a 3:4 mixture of the rac- and meso-isomers of

product 20 (isomers 20A and 20B), m.p. 97 ꢁC (de-

comp.). Anal. Calc. for C₄₆H₃₀N₂O₂B₂F₂₀ZrCl₂

(M = 1206.4): C, 45.80; H, 2.51; N, 2.32. Found: C,

46.24; H, 2.85; N, 2.09%. ¹H NMR (benzene-d₆,

599.87 MHz, isomer A): d = 6.28 (m, 1H, Cp–H), 6.00

(m, 1H, Cp–H), 5.91 (m, 1H, Cp–H), 5.55 (m, 1H,

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Bis(enamino-Cp) Group 4 metal complex chemistry: Developing a Mannich-type carbon-carbon coupling reaction at the bent metallocene famework

DOI: 10.1016/j.jorganchem.2004.08.021

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