Nitrile ligands activation in dinuclear aminocarbyne complexes

Journal of Organometallic Chemistry 690 (2005) 1959–1970

www.elsevier.com/locate/jorganchem

*

Luigi Busetto, Fabio Marchetti, Stefano Zacchini, Valerio Zanotti , Eleonora Zoli

`

Dipartimento di Chimica Fisica ed Inorganica, Universita di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy

Received 2 November 2004; accepted 4 November 2004

Available online 15 December 2004

Abstract

The diiron complexes [Fe(Cp)(CO){l-g²:g²-C[N(Me)(R)]N@C(C₆H₃R⁰)C@CH(Tol)}Fe(Cp)(CO)] (R = Xyl, R⁰= H, 3a;

R = Xyl, R⁰= Br, 3b; R = Xyl, R⁰= OMe, 3c; R = Xyl, R⁰= CO₂Me, 3d; R = Xyl, R⁰= CF₃, 3e; R = Me, R⁰= H, 3f; R = Me,

R⁰= CF₃, 3g) are obtained in good yields from the reaction of [Fe₂{l-CN(Me)(R)}(l-CO)(CO)(p-NCC₆H₄R⁰)(Cp)₂]⁺(R = Xyl,

R⁰= H, 2a; R = Xyl, R⁰= Br, 2b; R = Xyl, R⁰= OMe, 2c; R = Xyl, R⁰= CO₂Me, 2d; R = Xyl, R⁰= CF₃, 2e; R = Me, R⁰= H,

2f; R = Me, R⁰= CF₃, 2g) with TolC„CLi. The formation of 3 involves addition of the acetylide at the coordinated nitrile and

C–N coupling with the bridging aminocarbyne together with orthometallation of the p-substituted aromatic ring and breaking

of the Fe–Fe bond. Complexes 3a–e which contain the N(Me)(Xyl) group exist in solution as mixtures of the E-trans and Z-trans

isomers, whereas the compounds 3f,g, which posses an exocyclic NMe₂group, exist only in the Z-cis form. The crystal structures of

Z-trans-3b, E-trans-3c, Z-trans-3e and Z-cis-3g have been determined by X-ray diﬀraction experiments.

Keywords: Nitrile; Acetylide addition; Aminocarbyne; Diiron complexes; Crystal structure

1. Introduction

We have recently investigated the reactivity of diiron

and diruthenium aminocarbyne complexes containing

nitriles, i.e., [M₂{l-CN(Me)(R)}(l-CO)(CO)(NCCR⁰)-

(Cp)₂]⁺(M = Fe, Ru; R = Xyl, Bz, Me; R⁰= Me,

CMe₃). Although acetonitrile is readily displaced, in

the above complexes, by a variety of ligands including

amines, imines, phosphines, isocyanides, cyanide, hy-

dride and halides [8], it has been found that treatment

with NaH or LiR removes a proton from the coordi-

nated MeCN, and consequently promotes its rearrange-

ment to cyanomethyl ligand [9]. Dinuclear complexes

containing trimethylacetonitrile, [M₂{l-CN(Me)(R)}(l-

CO)(CO)(NCCCMe₃)(Cp)₂]⁺[M = Fe, Ru; R = Xyl,

Me], lack of acidic a-CH. Their reactions with acetylides

proceed via LiCCR⁰addition to the nitrile aﬀording,

after protonation, the alkynyl imino complexes [M₂-

{l-CN(Me)(R)}(l-CO)(CO){N(H)@C(CMe₃)(C„CR⁰)}-

(Cp)₂]⁺[8b,10]. In the case of the diiron complexes,

the reaction can further proceed via coupling between

the azavinylidene intermediate and the bridging

Activation of nitriles by coordination to transition

metals is a very important issue in organometallic chem-

istry and plays a fundamental role in organic synthesis

[1]. Depending on the nature of the organometallic

frame, coordinated nitriles can react with both nucleo-

philes and electrophiles or display increased a-CH acid-

ity [2]. Activation towards nucleophilic addition can

result in enhancement of the reaction rate from 10⁶to

10¹⁰and occasionally to 10¹⁸[3]. Nucleophilic additions

to metal coordinated nitriles mostly involve protic

nucleophiles such as amines [4], alcohols [5] and water

[6], leading to the formation of the corresponding ami-

dines, imidoesters and amidates. Additions of carbon

nucleophiles are also known, although less common [7].

*

Corresponding author. Tel.: +39 0512093700; fax: +39

0512093690.

E-mail address: valerio.zanotti@unibo.it (V. Zanotti).

doi:10.1016/j.jorganchem.2004.11.006

1960

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

aminocarbyne resulting, upon addition of CF₃SO₃H, in

the formation of the l-allenyl-diaminocarbene complex

[Fe₂{l-g¹:g³-C(Tol)@C@C(CMe₃)N(H)CN(Me)(Xyl)}-

(l-CO)(CO)(Cp₂)]⁺[10]. The latter reaction represents

an interesting example in which the diiron amino-

carbyne frame acts as a template for the preparation

of new ligands via formation of new C–C and C–N

bonds.

With the aim of extending our knowledge on the acti-

vation of nitriles by dinuclear aminocarbyne complexes,

we have investigated the reactions of diiron amino-

carbyne complexes containing aryl nitriles, with TolC„

CLi. The results of these studies are the object of this

paper.

Me, 3d; R = Xyl, R⁰= CF₃, 3e; R = Me, R⁰= H, 3f;

R = Me, R⁰= CF₃, 3g), which are obtained in

good yields (ca. 60%) after column chromatography

(Scheme 2).

The crystal structures of 3b, 3c, 3e and 3g have been

determined by X-ray diﬀraction studies. Their molecular

structures are shown in Figs. 1–4, whereas the most rel-

evant bond lengths and bond angles are reported in

Tables 1 and 2.

Two independent molecules are present in the asym-

metric unit of 3c Æ 0.5C₅H₁₂. All the molecules 3b, 3c,

3e and 3g are composed by two ﬁve member metallacy-

cles, fused on an edge formed by a C–N bond. Both iron

atoms show a tetrahedral geometry, with two coordina-

tion sites occupied by a Cp and a CO ligand, respec-

tively. The coordination sphere of Fe(1) is completed

by a diaminocarbene and a vinyl ligand. In agreement

2. Results and discussion

˚

with this, both Fe(1)–C(13) [1.916(7)–1.926(6) A] and

˚

C(13)–N(2) [1.310(7)–1.341(7) A] show some double

bond character, whereas Fe(1)–C(15) [1.952(7)–

The nitrile complexes [Fe₂{l-CN(Me)(R)}(l-CO)-

(CO)(p-NCC₆H₄R⁰)(Cp)₂]⁺(R = 2,6-Me₂C₆H₃(Xyl),

R⁰= H, 2a; R = Xyl, R⁰= Br, 2b; R = Xyl, R⁰= OMe,

2c; R = Xyl, R⁰= CO₂Me, 2d; R = Xyl, R⁰= CF₃, 2e;

R = Me, R⁰= H, 2f; R = Me, R⁰= CF₃, 2g) can be ob-

tained in high yield by Me₃NO assisted replacement of

a CO ligand of [Fe₂{l-CN(Me)(R)}(l-CO)(CO)₂(Cp)₂]-

[SO₃CF₃] (R = Xyl, 1a; Me, 1b) in THF (Scheme 1), fol-

lowing the same procedure previously reported for the

analogous acetonitrile and trimethylacetonitrile com-

plexes [8a]. Complexes 2 have been fully characterised

by spectroscopic methods (NMR and IR) and elemental

analyses (see Section 4).

2

1.986(7) A] is essentially a pure Fe–C(sp ) single bond.

˚

In agreement with the vinyl nature of the latter ligand,

˚

C(15)–C(16) [1.320(8)–1.366(9) A] is an almost pure

double bond. Interestingly, the C(13)–N(1) interaction

˚

[1.384(7)–1.407(2) A] has mainly the character of a sin-

gle bond and, thus, the diaminocarbene carbon exhibits

a considerably asymmetry in the bonding with the exo-

and endo-cyclic nitrogen, probably because the latter

is involved in the coordination to Fe(2) and also because

of delocalisation involving C(14). Some p-interaction is

present also in the bond between Fe(2) and the metal-

˚

The reaction of 2 with TolC„CLi (Tol = p-MeC₆H₄)

in THF at low temperature, followed by stirring at room

temperature for 1 h aﬀords the new diiron complexes

[Fe(Cp)(CO){l-g²:g²-C[N(Me)(R)]N@C(C₆H₃R⁰)C@

CH(Tol)}Fe(Cp)(CO)] (R = Xyl, R⁰= H, 3a; R = Xyl,

R⁰= Br, 3b; R = Xyl, R⁰= OMe, 3c; R = Xyl, R⁰= CO₂

lated aromatic ring [Fe(2)–C(25) 1.926(7)–1.9447(19) A].

In spite of the fact that the molecules present similar

bond lengths and bond angles, some stereochemical dif-

ferences are to be outlined. First, the Cp rings adopt a

pseudo trans arrangement in 3b, 3c and 3e, whereas they

can be considered cis in 3g. Other diﬀerences consist in

+

Me

Fe

R

Me

Fe

R

N

C

N

C

OC

NC

R'

CO

NC

R'

OC

1)

2)

Fe

C

O

C

O

Me₃NO in THF

R

Xyl

R'

H

R = Xyl 1a

R = Me 1b

2a

2b

2c

2d

2e

2f

Xyl

Me

Br

OMe

COOMe

CF₃

H

CF₃

2g

Scheme 1.

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

1961

R

Me

+

N

Me

Fe

R

Fe

CO

N

C

N

O

C

OC

NC

R'

C

Fe

LiCCTol

C

O

R'

C

H

Tol

2a-g

R

R'

3a

3b

3c

3d

3e

3f

Xyl

Me

H

Br

OMe

COOMe

CF₃

H

CF₃

3g

Scheme 2.

C30

N2

O11

O2

C13

C12

C11

N1

Fe2

Fe1

C14

C15

C25

C16

H16

C17

C24

Br1

Fig. 1. Molecular structure of 3b (all H atoms, apart from H16, have been omitted). Displacement ellipsoids are at 30% probability level.

the conﬁguration of the exocyclic C(15)@C(16) bond,

which adopts a Z conﬁguration in 3b, 3e and 3g whereas

it is E in 3c. Therefore the compounds shown in Figs. 1–

4 should be appropriately described as Z-trans-3b,

E-trans-3c, Z-trans-3e and Z-cis-3g. The diﬀerent conﬁg-

urations of C(15)@C(16) do not aﬀect sensibly the rest

of the molecule, whereas the diﬀerent geometries of the

Cp ligands have important eﬀects on the conformation

of the two condensed metallacycles. Thus, the ring com-

prising Fe(2) is almost planar in all the four complexes

and, in fact, Fe(2), C(25), C(24), C(14) and N(1) show

a very small deviation from their mean squares plane

1962

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

˚

[1.427(8)–1.472(8) A] and C(14)–C(24) [1.435(8)–

2

˚

1.454(2) A] are sensibly shorter than a single C(sp )–

C(sp²) bond. On the basis of all these considerations,

these complexes can be also described as a 1-metalla-2-

amino-3-aza-5-alkylidencyclopenta-1,3-diene which acts

a chelating ligand on Fe(2) via the endocyclic nitrogen

and an orthometallated aromatic ring.

C30

The IR spectra of 3 show the presence of a single

band at 1915–1930 cm^ꢀ1for both the CO ligands.

The NMR spectra of 3a–e indicate the presence in

solution of two isomers in ca. 2–1:1 ratio, whereas a

single species in present in the case of 3f,g. On the basis

of the solid state structures, it is possible to assume

that the two species present in the case of 3a–e are

the E-trans and Z-trans isomers, whereas the complexes

3f,g maintain a Z-cis structure (Scheme 3). NMR mea-

surements on the crystalline materials, dissolved in

CDCl₃, conﬁrm this hypothesis and have helped on

the assignment of the NMR data to all the diﬀerent

isomers.

N2

O12

C12

Fe2

C13

N1

O11

Fe1

C11

C14

C25

C15

C24

C16

H16

C17

The Z isomers are characterized by the ¹³C vinyl res-

onance due to Fe(1)–C(15) at d 200–206 ppm, whereas it

is shifted at lower frequencies for the E isomers (d 177–

O1

1

194 ppm). Moreover, the H C(16)–H(16) proton reso-

nates always at higher frequencies for the Z isomers

than for the E isomer. Other important features in the

¹³C NMR spectra are the high frequencies resonances

due to Fe(1)@C(13) (249–269 ppm) and C(14)@N(1) (d

198–208 ppm); the former falls within the typical range

for iron diaminocarbenes. The carbon of the orthomet-

allated aromatic ring C(25) resonates at d 150–168 ppm,

whereas the exocyclic vinyl C(16)–H(16) shows a reso-

nance at d 130–144 ppm. Finally, it is noteworthy that

Fig. 2. Molecular structure of 3c (all H atoms, apart from H16, have

been omitted). Only one of the two independent molecules is

represented. Displacement ellipsoids are at 30% probability level.

˚

of 0.0225 A in Z-cis-3g and 0.0812–0.0948 A in the trans

complexes. In the case of Z-cis-3g both C(15) and

C(13) lay very close to this plane [torsion angles

C(15)–C(14)–C(24)–C(25) ꢀ179.9(7)ꢁ, C(24)–C(14)–

N(1)–C(13) 168.4(5)ꢁ], whereas they are considerably

out of the plane in Z-trans-3b, E-trans-3c and Z-

trans-3e [torsion angles C(15)–C(14)–C(24)–C(25)

ꢀ166.02(16)ꢁ to ꢀ169.6(6)ꢁ, C(24)–C(14)–N(1)–C(13)

141.3(5)–149.5(6)ꢁ]. These diﬀerences in the conforma-

tion of the two ﬁve member cycles seems to aﬀect the

C(14)–N(1) bond length, which lays on the edge shared

by the two rings and appears shorter for Z-cis-3g

1

in the H NMR spectra of 3f,g the protons of both Cp

ligands resonante at distinct but similar frequencies (d

ca. 4.5 ppm), whereas they are separate by 0.5–0.6

ppm in the complexes 3a–e which contain the Xyl group

on the diaminocarbene. NOE studies indicate that the

Cp at higher frequencies [d 4.2–4.4 ppm] is the one close

to the N(2)–Me substituent [thus bound to Fe(1)],

whereas the Xyl group shields the Fe(2)–Cp protons [d

3.7–3.8 ppm]. Similar results have been obtained on

both the isomers of 3a–e, conﬁrming that they diﬀer

only for the conﬁguration of the exocyclic

C(15)@C(16) bond, whereas they maintain the trans

arrangement of the Cp and the E conﬁguration of

C(13)–N(2).

˚

[1.331(7) A] compared to Z-trans-3b, E-trans-3c and

˚

Z-trans-3e [1.355(8)–1.373(7) A]. Moreover, in all the

complexes the C(14)–N(1) interaction is longer than a

pure C@N double bond and N(1) shows some pyrami-

dalisation [sum angles 352.5(8)–356.1(8)ꢁ in Z-trans-3b,

E-trans-3c and Z-trans-3e; 358.9(8)ꢁ in Z-cis-3g]. The

The mechanism for the formation of 3 from 2 seems

to be quite complex and presumably proceeds through

several steps. Attempts to isolate or identify intermedi-

ate species failed. However, on the basis of previous

considerations on the analogous reactions of [M₂{l-

˚

Fe(2)–N(1) interaction [2.028(5)–2.0395(15)

A

in

˚

Z-trans-3b, E-trans-3c and Z-trans-3e; 2.011(5) A in

Z-cis-3g] is also slightly longer than expected for a coor-

˚

dinated imine, e.g. 1.964(3) A in [Fe₂{l-CN(Me)-

(Xyl)}(l-CO)(CO){N(H)C(C„CTol)CMe₃}(Cp)₂]⁺[10].

Delocalisation eﬀects seem to have only a minor contri-

bution to the lengthening of C(14)–N(1), even though

they should be considered. Thus, both C(14)–C(15)

CN(Me)(R)}(l-CO)(CO)(NCCMe₃)(Cp)₂]⁺

[M = Fe,

Ru; R = Xyl, Bz, Me] [8b,10] with R⁰C„CLi, it appears

reasonable that the reaction occurs via nucleophilic at-

tack of TolC„CLi on the nitrile carbon of 2, generating

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

1963

C30

N2

O12

C12

C13

O11

C11

Fe2

C25

N1

Fe1

C14

C15

C16

C24

C17

H16

F2

C39

F1

F3

Fig. 3. Molecular structure of 3e (all H atoms, apart from H16, have been omitted). Displacement ellipsoids are at 30% probability level.

C31

C30

N2

O12

Fe2

O11

C11

C12

C13

N1

Fe1

C25

C14

C15

C24

F3

C17

H16

C16

C32

F2

F1

Fig. 4. Molecular structure of 3g (all H atoms, apart from H16, have been omitted). Displacement ellipsoids are at 30% probability level.

1964

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

Table 1

Selected bond lengths (A) for complexes 3b, 3c, 3e and 3g

˚

3b

3c

3e

3g

Molecule 1^a

Molecule 2^a

Fe(1)–C(11)

Fe(2)–C(12)

Fe(1)–C(13)

Fe(1)–C(15)

Fe(2)–N(1)

Fe(2)–C(25)

C(11)–O(11)

C(12)–O(12)

C(13)–N(1)

C(13)–N(2)

C(14)–N(1)

C(14)–C(15)

C(14)–C(24)

C(15)–C(16)

C(16)–C(17)

C(24)–C(25)

a

1.712(8)

1.718(9)

1.917(7)

1.977(7)

2.031(5)

1.926(7)

1.171(9)

1.157(9)

1.398(8)

1.334(8)

1.355(8)

1.439(8)

1.446(9)

1.329(9)

1.463(9)

1.407(9)

1.704(9)

1.707(7)

1.916(7)

1.952(7)

2.038(5)

1.933(6)

1.163(9)

1.175(8)

1.396(7)

1.341(7)

1.366(7)

1.427(8)

1.436(8)

1.348(8)

1.455(9)

1.394(8)

1.704(8)

1.725(8)

1.926(6)

1.986(7)

2.028(5)

1.935(6)

1.162(7)

1.149(8)

1.384(7)

1.345(7)

1.373(7)

1.431(8)

1.435(8)

1.320(8)

1.462(9)

1.405(8)

1.7423(19)

1.753(2)

1.9167(18)

1.9858(19)

2.0395(15)

1.9447(19)

1.158(2)

1.156(2)

1.407(2)

1.338(2)

1.355(2)

1.446(2)

1.454(2)

1.344(3)

1.470(2)

1.416(2)

1.693(7)

1.727(8)

1.923(6)

1.957(7)

2.011(5)

1.929(6)

1.179(8)

1.149(9)

1.405(7)

1.310(7)

1.331(7)

1.472(8)

1.442(9)

1.366(9)

1.459(8)

1.410(8)

Two independent molecules are present in the unite cell.

Table 2

Selected bond angles (ꢁ) for complexes 3b, 3c, 3e and 3g

3b

3c

3e

3g

Molecule 1^a

Molecule 2^a

C(13)–Fe(1)–C(15)

Fe(1)–C(13)–N(1)

C(13)–N(1)–C(14)

N(1)–C(14)–C(15)

C(14)–C(15)–Fe(1)

N(1)–Fe(2)–C(25)

Fe(2)–C(25)–C(24)

C(25)–C(24)–C(14)

C(24)–C(14)–N(1)

C(14)–N(1)–Fe(2)

C(14)–C(15)–C(16)

Fe(1)–C(15)–C(16)

C(15)–C(16)–C(17)

N(1)–C(13)–N(2)

Fe(1)–C(13)–N(2)

a

79.4(3)

111.8(5)

108.1(5)

117.1(6)

99.2(4)

79.1(3)

112.6(4)

106.7(5)

116.9(5)

99.8(4)

79.3(2)

111.0(4)

106.8(5)

116.8(5)

95.3(4)

79.30(7)

111.96(12)

107.45(14)

117.68(15)

98.66(11)

81.47(7)

78.9(2)

112.6(4)

109.2(5)

117.0(5)

103.8(4)

81.8(2)

81.3(2)

81.9(2)

81.6(2)

115.6(5)

111.8(6)

116.6(6)

111.8(4)

121.2(6)

139.4(5)

129.6(7)

120.5(6)

127.7(5)

113.3(4)

115.2(5)

114.8(5)

110.9(4)

124.8(6)

135.4(5)

126.7(6)

119.1(6)

128.2(5)

113.9(4)

114.3(5)

114.9(5)

111.9(4)

132.5(6)

132.1(5)

130.8(6)

120.1(5)

128.8(4)

114.07(13)

113.61(15)

115.27(15)

112.71(11)

121.47(16)

139.76(14)

128.74(16)

120.15(15)

127.82(13)

114.3(5)

114.2(6)

114.8(5)

114.5(4)

116.4(6)

139.5(5)

129.8(6)

118.1(5)

129.3(4)

Two independent molecules are present in the unite cell.

a g¹-azavinylidene intermediate of the type [Fe₂-

{l-CN(Me)(R)}(l-CO)(CO){N@C(p-NCC₆H₄R⁰)(C„

CR⁰)}(Cp)₂]. Then, the azavynilidene ligand is supposed

to migrate and couple with the bridging aminocarbyne.

These two initial steps accounts for the formation of the

C(14)–C(15) and C(13)–N(1) bond, observed in 3. Fur-

ther rearrangements must then take place in order to ex-

plain the formation of the ﬁnal product 3. A reasonable

sequence of intermediate species involved in this process

can be hardly traced out, in the absence of further evi-

dences. However some considerations can be drown:

the sequence must include an orthometallation reaction,

which, to the best of our knowledge, has never been

described in the case of diiron complexes bridged by car-

byne or carbene ligands. In general, the orthometalla-

tion reaction has been known for a long time [11], and

compounds that contain an orthometallated ligand con-

tinue to be of interest for the generation of catalysts [12],

compounds with interesting material properties [13], and

antitumor agents [14]. A second consideration concern

the fragmentation of the diiron frame Fe₂Cp₂(l-CO)

which usually appears very robust and is unaﬀected even

by strong rearrangements, occurring on the coordinated

ligands [8–10,15]. Breaking of the Fe–Fe bond has been

previously observed only in the reaction of [M₂{l-

CN(Me)(R)}(l-CO)(CO)₂(Cp)₂][SO₃CF₃] (M = Fe, Ru)

with KH and acetonitrile, to form a metallapyrrole ring

[16].

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

1965

Xyl

C

Xyl

C

Me

N

Fe

CO

Fe

CO

N

O

C

Fe

C

R'

C

H

Tol

H

Z-trans-3a-e

E-trans-3a-e

Me

C

CO

Fe

Me

N

O

C

Fe

C

R'

C

H

Tol

Z-cis-3f-g

Scheme 3.

3. Conclusions

appropriate drying agents. Infrared spectra were re-

corded on a Perkin–Elmer Spectrum 2000 FT-IR spec-

trophotometer and elemental analyses were performed

on a ThermoQuest Flash 1112 Series EA Instrument.

All NMR measurements were performed on Varian

Gemini 300 and Varian Mercury Plus 400 instruments.

The chemical shifts were referenced to internal TMS

for ¹H and ¹³C, and to external CCl₃F for ¹⁹F. The spec-

The results obtained demonstrate very well the capa-

bility of diiron aminocarbyne complexes of activating

coordinated nitriles with respect to the addition of ace-

tilydes. Nucleophilic attack at the coordinated nitrile is

accompanied by coupling with the bridging amin-

icarbyne ligand, resulting in C–N bond formation.

Further rearrangements take place depending on the

nature of the nitrile ligand, and diﬀerent products are

correspondingly formed (Scheme 4). Complexes contain-

ing the trimethylacetonitrile ligand aﬀord the allene-

amminocarbene compound [10], whereas aryl-nitriles,

causes the fragmentation of the Fe–Fe bond.

In all of the cases, it is to be outlined the role of the

two adjacent metal centres in promoting intramolecular

couplings of coordinated ligands, and building-up or-

ganic fragments. The metal atoms also provide stabiliza-

tion to these species, through a variety of coordination

modes.

1

tra were fully assigned via H,¹³C correlation measured

using gs-HSQC and gs-HMBC experiments [17]. Mono-

dimensional NOE measurements were recorded using

the DPFGSE-NOE sequence [18]. All chemicals were

used as received from Aldrich Co., except [Fe₂{l-

CN(Me)(R)}(l-CO)(CO)₂(Cp)₂][SO₃CF₃] (R = Xyl, 1a;

Me, 1b) [19] which were prepared by published methods.

TolC„CLi was prepared just before use from the reac-

tion of TolC„CH with BuⁿLi in THF at ꢀ50 ꢁC (molar

ratio 1.2:1).

4.2. Synthesis of [Fe₂{l-CN(Me)(R)}(l-CO)(CO)-

(p-NCC₆H₄R⁰)(Cp)₂] (R = Xyl, R⁰= H, 2a; R = Xyl,

R⁰= Br, 2b; R = Xyl, R⁰= OMe, 2c; R = Xyl,

R⁰= CO₂Me, 2d; R = Xyl, R⁰= CF₃, 2e; R = Me,

R⁰= H, 2f; R = Me, R⁰= CF₃, 2g)

4. Experimental

4.1. General

p-R⁰C₆H₄CN (0.700 mmol) and Me₃NO (52.5 mg,

0.700 mmol) were added to a solution of 1 (0.350 mmol)

in THF (10 ml), and the solution stirred at room temper-

ature for 3 h. The solvent was, then, removed in vacuo

All reactions were carried out routinely under nitro-

gen using standard Schlenk techniques. Solvents were

distilled immediately before use under nitrogen from

1966

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

+

R

Me

Fe

N

C

OC

NCR'

+

LiCCTol

Fe

C

O

R' = Aryl

R' = CMe₃

R

C

CMe₃

+

H

Me

N

C

R

N

Fe

C

CO

N

C

N

Tol

C

O

C

Me

Fe

C

O

R''

C

H

Tol

Scheme 4.

and the residue washed with Et₂O (2 · 10 ml) and petro-

leum ether (2 · 10 ml). The product was, therefore, fur-

ther puriﬁed by ﬁltration through celite using CH₂Cl₂as

solvent.

(l-C), 264.6 (l-CO), 211.3 (CO), 148.4 (C-ipso Xyl),

134.0–128.2 (CH arom + C–Me Xyl + C–Br), 118.3

(CN), 109.2 (C–CN), 89.4, 87.4 (Cp), 55.5 (NMe),

19.0, 17.8 (Me₂C₆H₃); Isomer b: d 338.1 (l-C), 263.9

(l-CO), 211.9 (CO), 148.3 (C-ipso Xyl), 134.0–128.2

(CH arom + C–Me Xyl + C–Br), 119.5 (CN), 109.1

(C–CN), 88.5, 88.2 (Cp), 54.4 (NMe), 18.8, 17.4

(Me₂C₆H₃).

2a: Yield: 231.5 mg (95%). Anal. Calc. for

C₃₀H₂₇F₃Fe₂N₂O₅S: C, 51.75; H, 3.91; N, 4.02. Found:

C, 51.54; H, 4.11, N, 4.21%. IR (in CH₂Cl₂, 293 K):

m(CO) 1985 (vs), 1823 (s); m(CN) 1587 (m), 1519 (m).

¹H NMR (CDCl₃, 293 K) Isomer a: d 7.41–7.04 (m,

8H, arom), 5.00, 4.22 (s, 10H, Cp), 4.35 (s, 3H, NMe),

2.51, 1.85 (s, 6H, Me₂C₆H₃); Isomer b: d 7.41–7.04 (m,

8H, arom), 5.10, 4.31 (s, 10H, Cp), 4.61 (s, 3H, NMe),

2.51, 1.85 (s, 6H, Me₂C₆H₃). Isomer ratio a:b = 3:1.

¹³C NMR (CDCl₃, 293 K) Isomer a: d 336.8 (l-C),

264.2 (l-CO), 210.6 (CO), 147.8 (C-ipso Xyl), 133.6,

133.2 (C–Me Xyl), 132.6–128.8 (CH arom), 118.6

(CN), 109.8 (C-ipso Ph), 88.8, 86.6 (Cp), 53.3 (NMe),

18.4, 17.3 (Me₂C₆H₃); Isomer b: d 337.2 (l-C), 263.4

(l-CO), 211.2 (CO), 147.7 (C-ipso Xyl), 133.5, 132.9

(C–Me Xyl), 132.6–128.8 (CH arom), 118.5 (CN),

109.7 (C-ipso Ph), 88.0, 87.5 (Cp), 53.7 (NMe), 18.2,

16.9 (Me₂C₆H₃).

2c: Yield: 228.8 mg (90%). Anal. Calc. for

C₃₁H₂₉F₃Fe₂N₂O₆S: C, 51.27; H, 4.02; N, 3.86. Found:

C, 51.52; H, 3.79, N, 4.08%. IR (in CH₂Cl₂, 293 K):

(CO) 1986 (vs), 1821 (s); m(CN) 1603 (m), 1509 (ms).

¹H NMR (CDCl₃, 293 K) Isomer a: d 7.50–6.77 (m,

7H, arom), 5.11, 4.33 (s, 10H, Cp), 4.44 (s, 3H, NMe),

3.73 (s, 3H, OMe), 2.65, 1.98 (s, 6H, Me₂C₆H₃); Isomer

b: d 7.50–6.77 (m, 7H, arom), 5.02, 4.47 (s, 10H, Cp),

4.74 (s, 3H, NMe), 3.72 (s, 3H, OMe), 2.64, 1.99 (s,

6H, Me₂C₆H₃). Isomer ratio a:b = 1.4:1. ¹³C NMR

(CDCl₃, 293 K) Isomer a: d 337.8 (l-C), 265.1 (l-CO),

211.3 (CO), 164.0 (C–OMe), 148.4 (C-ipso Xyl), 134.3,

115.4 (CH NCC₆H₄OMe), 133.8, 132.9 (C–Me Xyl),

130.2, 129.4, 129.3 (CH Xyl), 119.5 (CN), 101.7 (C–

CN), 89.3, 87.1 (Cp), 55.9 (OMe), 55.3 (NMe), 19.0,

17.9 (Me₂C₆H₃); Isomer b: d 338.7 (l-C), 264.3 (l-

CO), 211.9 (CO), 163.9 (C–OMe), 148.3 (C-ipso Xyl),

134.6, 115.3 (CH NCC₆H₄OMe), 133.5, 132.4 (C–Me

Xyl), 130.3, 129.3, 129.2 (CH Xyl), 122.7 (CN), 101.6

(C–CN), 88.4, 87.9 (Cp), 56.0 (OMe), 54.2 (NMe),

18.8, 17.4 (Me₂C₆H₃).

2b: Yield: 249.6 mg (92%). Anal. Calc. for

C₃₀H₂₆BrF₃Fe₂N₂O₅S: C, 46.48; H, 3.38; N, 3.61.

Found: C, 46.12; H, 3.01, N, 3.89%. IR (in CH₂Cl₂,

293 K): m(CO) 1986 (vs), 1822 (s); m(CN) 1587 (m),

1

1519 (m). H NMR (CDCl₃, 293 K) Isomer a: d 7.58–

7.08 (m, 7H, arom), 5.13, 4.36 (s, 10H, Cp), 4.44 (s,

3H, NMe), 2.64, 1.96 (s, 6H, Me₂C₆H₃); Isomer b: d

7.58–7.08 (m, 7H, arom), 5.06, 4.48 (s, 10H, Cp), 4.73

(s, 3H, NMe), 2.63, 1.98 (s, 6H, Me₂C₆H₃). Isomer ratio

a:b = 2:1. ¹³C NMR (CDCl₃, 293 K) Isomer a: d 337.4

2d: Yield: 232.3 mg (88%). Anal. Calc. for

C₃₂H₂₉F₃Fe₂N₂O₇S: C, 50.96; H, 3.88; N, 3.71. Found:

C, 51.13; H, 3.52, N, 3.44%. IR (in CH₂Cl₂, 293 K):

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

1967

(CO) 1985 (vs), 1822 (s); m(COOMe) 1730 (s); m(CN)

1519 (m). H NMR (CDCl₃, 293 K) Isomer a: d 7.91–

4.3. Synthesis of [Fe(Cp)(CO){l-g²:g²-C[N(Me)-

(R)]N@C(C₆H₃R⁰)C@CH(Tol)}Fe(Cp)(CO)]

1

7.03 (m, 7H, arom), 5.14, 4.38 (s, 10H, Cp), 4.44 (s,

3H, NMe), 3.80 (s, 3H, COOMe), 2.63, 1.95 (s, 6H,

Me₂C₆H₃); Isomer b: d 7.91–7.03 (m, 7H, arom), 5.08,

4.48 (s, 10H, Cp), 4.74 (s, 3H, NMe), 3.79 (s, 3H,

COOMe), 2.63, 1.97 (s, 6H, Me₂C₆H₃). Isomer ratio

a:b = 1.4:1. ¹³C NMR (CDCl₃, 293 K) Isomer a: d

337.2 (l-C), 264.3 (l-CO), 211.3 (CO), 165.1 (COOMe),

148.4 (C-ipso Xyl), 134.6 (C–COOMe), 133.7, 132.8 (C–

Me Xyl), 132.4–129.2 (CH arom), 118.2 (CN), 114.2 (C-

CN), 89.5, 87.4 (Cp), 55.5 (NMe), 52.9 (COOMe), 19.0,

17.8 (Me₂C₆H₃); Isomer b: d 337.9 (l-C), 263.6 (l-CO),

211.9 (CO), 165.2 (COOMe), 148.3 (C-ipso Xyl), 134.4

(C-COOMe), 133.4, 132.7 (C–Me Xyl), 132.4–129.2

(CH arom), 118.2 (CN), 114.1 (C–CN), 88.6, 88.3

(Cp), 54.4 (NMe), 52.9 (COOMe), 18.7, 17.4

(Me₂C₆H₃).

(R = Xyl, R⁰= H, 3a; R = Xyl, R⁰= Br, 3b; R = Xyl,

R⁰= OMe, 3c; R = Xyl, R⁰= CO₂Me, 3d; R = Xyl,

R⁰= CF₃, 3e; R = Me, R⁰= H, 3f; R = Me, R⁰= CF₃,

3g)

A solution of TolCCLi (1.45 mmol) was prepared by

addition at ꢀ50 ꢁC of BuⁿLi (0.580 ml, 2.5 M in hexane,

1.45 mmol) to TolCCH (0.200 ml, 1.58 mmol) dissolved

in THF (5 ml), and the mixture stirred at room temper-

ature for 1 h. This solution was, then, added at ꢀ50 ꢁC

to 2 (0.720 mmol) dissolved in THF (10 ml), and the

mixture stirred at room temperature for 1 h. The result-

ing red solution was, therefore, ﬁltered through Al₂O₃in

order to remove the excess of TolCCLi, and the solvent

removed from the ﬁltrated under reduced pressure. The

residue was, then, dissolved in CH₂Cl₂(3 ml) and chro-

matographed through Al₂O₃_ꢀ. The ﬁnal product was ob-

tained as a red fraction using CH₂Cl₂as eluent.

2e: Yield: 246.1 mg (92%). Anal. Calc. for

C₃₁H₂₆F₆Fe₂N₂O₅S: C, 48.72; H, 3.43; N, 3.67. Found:

C, 48.39; H, 3.44, N, 3.80%. IR (in CH₂Cl₂, 293 K):

3a: Yield: 290.9 mg (61%). Anal. Calc. for C₃₈H₃₄Fe₂-

N₂O₂: C, 68.90; H, 5.17; N, 4.23. Found: C, 68.59; H,

5.36, N, 4.01%. IR (in CH₂Cl₂, 293 K): m(CO) 1915

1

(CO) 1985 (vs), 1822 (s); m(CN) 1520 (ms). H NMR

(CDCl₃, 293 K) Isomer a: d 7.75–7.19 (m, 7H, arom),

5.13, 4.39 (s, 10H, Cp), 4.44 (s, 3H, NMe), 2.63, 1.97

(s, 6H, Me₂C₆H₃); Isomer b: d 7.75–7.19 (m, 7H, arom),

5.08, 4.49 (s, 10H, Cp), 4.73 (s, 3H, NMe), 2.63, 1.99 (s,

6H, Me₂C₆H₃). Isomer ratio a:b = 1.2:1. ¹³C NMR

(CDCl₃, 293 K) Isomer a: d 337.2 (l-C), 264.2 (l-CO),

211.3 (CO), 148.4 (C-ipso Xyl), 135.1–126.4 (CH

1

(vs); m(CN) 1572 (w), 1508 (m). H NMR (CDCl₃, 293

K) Isomer E: d 7.77–6.69 (m, 11H, arom), 7.26 (s, 1H,

@CH), 4.24, 3.72 (s, 10H, Cp), 3.40 (s, 3H, NMe),

2.69, 2.17 (s, 6H, Me₂C₆H₃), 2.39 (s, 3H, MeC₆H₄); Iso-

mer Z: d 7.77–6.69 (m, 11H, arom), 7.61 (s, 1H, @CH),

4.39, 3.76 (s, 10H, Cp), 3.54 (s, 3H, NMe), 2.47, 2.26 (s,

6H, Me₂C₆H₃), 2.37 (s, 3H, MeC₆H₄). Isomer ratio

E:Z = 10:9.5. ¹³C NMR (CDCl₃, 293 K) Isomer E:d

253.9 (Fe@C), 223.1, 222.5 (CO), 203.4 (C@N), 189.7

(Fe–C@CH), 168.6 (Fe–CC₆H₄), 145.1 (C-ipso Tol),

144.3 (C-ipso Xyl), 136.0 (@CH), 135.3, 134.8 (C–Me

Xyl), 136.8 (C–Me Tol), 133.9 (C-ipso C₆H₄), 132.7–

122.5 (CH arom), 84.9, 82.3 (Cp), 50.2 (NMe), 21.7

(MeC₆H₄), 19.4, 19.2 (Me₂C₆H₃); Isomer Z: d 256.4

(Fe@C), 221.8, 221.5 (CO), 203.6 (C@N), 201.0 (Fe–

C@CH), 166.6 (Fe–CC₆H₄), 145.4 (C-ipso Tol), 144.5

(C-ipso Xyl), 139.3 (@CH), 135.4, 134.5 (C–Me Xyl),

137.1 (C–Me Tol), 139.8 (C-ipso C₆H₄), 132.7–122.5

(CH arom), 85.2, 82.5 (Cp), 51.0 (NMe), 22.0

(MeC₆H₄), 20.1, 19.8 (Me₂C₆H₃).

1

arom + C–Me Xyl + C–CF₃), 123.0 (q, J_CF= 273.6

Hz, C₃), 117.7 (CN), 114.0 (C–CN), 89.4, 87.5 (Cp),

55.5 (NMe), 18.9, 17.8 (Me₂C₆H₃); Isomer b: d 337.9

(l-C), 263.6 (l-CO), 211.9 (CO), 148.3 (C-ipso Xyl),

135.1–126.4 (CH arom + C–Me Xyl + C–CF₃), 123.1

1

(q, J_CF= 273.6 Hz, C₃), 117.7 (CN), 114.0 (C–CN),

88.6, 88.3 (Cp), 54.4 (NMe), 18.7, 17.4 (Me₂C₆H₃). ¹⁹F

NMR (CDCl₃, 293 K) Isomer a: d ꢀ64.04; Isomer b: d

ꢀ63.91.

2f: Yield: 180.3 mg (85%). Anal. Calc. for

C₂₃H₂₁F₃Fe₂N₂O₅S: C, 45.58; H, 3.49; N, 4.62. Found:

C, 45.64; H, 3.23, N, 4.85%. IR (in CH₂Cl₂, 293 K):

(CO) 1982 (vs), 1816 (s); m(CN) 1589 (m). ¹H NMR

(CDCl₃, 293 K): d 7.52–7.19 (m, 5H, Ph), 4.98, 4.91(s,

10H, Cp), 4.65, 4.24 (6H, s, NMe₂).

3b: Yield: 298.9 mg (56%). Anal. Calc. for

C₃₈H₃₃BrFe₂N₂O₂: C, 61.57; H, 4.49; N, 3.78. Found:

C, 61.85; H, 4.09, N, 3.85%. IR (in CH₂Cl₂, 293 K):

2g: Yield: 219.4 mg (93%). Anal. Calc. for

C₂₄H₂₀F₆Fe₂N₂O₅S: C, 42.76; H. 2.99; N, 4.16. Found:

C, 42.98; H, 2.72, N, 4.34%. IR (in CH₂Cl₂, 293 K):

1

m(CO) 1918 (vs); m(CN) 1554 (m), 1508 (m). H NMR

1

(CO) 1981 (vs), 1816 (s); m(CN) 1589 (ms). H NMR

(CDCl₃, 293 K) Isomer E: d 7.83 (s, 1H, CH o-C₆H₃Br),

7.77–6.86 (m, 9H, arom), 6.79 (s, 1H, @CH), 4.31, 3.78

(s, 10H, Cp), 3.42 (s, 3H, NMe), 2.73, 2.18 (s, 6H,

Me₂C₆H₃), 2.40 (s, 3H, MeC₆H₄); Isomer Z: d 8.00 (s,

1H, CH o-C₆H₃Br), 7.77–6.86 (m, 9H, arom), 7.61 (s,

1H, @CH), 4.44, 3.82 (s, 10H, Cp), 3.56 (s, 3H, NMe),

2.52, 2.21 (s, 6H, Me₂C₆H₃), 2.33 (s, 3H, MeC₆H₄).

Isomer ratio E:Z = 10:5.9. ¹³C NMR (CDCl₃, 293 K)

(CDCl₃, 293 K):d 8.10–7.71 (m, 4H, arom), 5.29, 5.21

(s, 10H, Cp), 4.77, 4.43 (s, 6H, NMe₂). ¹³C NMR

(CDCl₃, 293 K): d 329.3 (l-C), 266.6 (l-CO), 212.9

2

(CO), 134.8 (q, J_CF= 8.4 Hz, C–CF₃), 135.0, 134.7

3

(CH o-NCC₆H₄CF₃), 127.8, 127.6 (q, J_CF= 4.2 and

1

3.4 Hz, CH m-NCC₆H₄CF₃), 124.7 (q, J_CF= 272.3

1

Hz, C₃), 123.0 (q, J_CF= 321.8 Hz, CF₃SO^ꢀ), 118.8

(CN), 117.6 (C–CN), 90.4, 89.0 (Cp), 54.8, 54.0 (NMe₂).

3

Isomer E: d 252.9 (Fe@C), 222.8, 222.3 (CO),

1968

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

202.9 (C@N), 186.2 (Fe–C@CH), 168.4 (Fe–CC₆H₃Br),

145.9 (CH o-C₆H₃Br), 145.0–118.2 (arom), 130.1

(@CH), 84.9, 82.2 (Cp), 50.2 (NMe), 21.9 (MeC₆H₄),

19.7, 19.1 (Me₂C₆H₃); Isomer Z: d 256.8 (Fe@C),

221.7, 221.2 (CO), 205.9 (Fe–C@CH), 202.0 (C@N),

166.5 (Fe–CC₆H₃Br), 146.1 (CH o-C₆H₃Br), 145.0–

118.2 (arom), 139.8 (@CH), 85.2, 82.4 (Cp), 51.1

(NMe), 21.7 (MeC₆H₄), 20.0, 19.4 (Me₂C₆H₃).

C, 64.41; H, 4.17, N, 4.01%. IR (in CH₂Cl₂, 293 K):

(CO) 1921 (vs); m(CN) 1508 (m). ¹H NMR (CDCl₃,

293 K) Isomer E: d 8.08–6.70 (m, 10H, arom), 6.83 (s,

1H, @CH), 4.30, 3.77 (s, 10H, Cp), 3.37 (s, 3H, NMe),

2.71, 2.17 (s, 6H, Me₂C₆H₃), 2.31 (s, 3H, MeC₆H₄); Iso-

mer Z: d 8.08–6.70 (m, 10H, arom), 7.84 (s, 1H, @CH),

4.45, 3.83 (s, 10H, Cp), 3.57 (s, 3H, NMe), 2.45, 2.24 (s,

6H, Me₂C₆H₃), 2.41 (s, 3H, MeC₆H₄). Isomer ratio

E:Z = 3:2. ¹³C NMR (CDCl₃, 293 K) Isomer E: d

249.1 (Fe@C), 222.5, 222.0 (CO), 198.2 (C@N), 177.2

(Fe–C@CH), 167.8 (Fe–CC₆H₃CF₃), 148.5 (C-ipso

C₆H₃CF₃), 144.4 (C-ipso Xyl), 140.0–118.8 (arom + C₃),

130.7 (@CH), 84.8, 81.8 (Cp), 50.8 (NMe), 21.3

(MeC₆H₄), 19.3, 18.8 (Me₂C₆H₃); Isomer Z: d 255.1

(Fe@C), 221.1, 220.4 (CO), 202.5 (Fe–C@CH), 199.6

(C@N), 166.2 (Fe–CC₆H₃CF₃), 149.4 (C-ipso

C₆H₃CF₃), 144.9 (C-ipso Xyl), 140.0–118.8 (arom + C₃),

139.1 (@CH), 85.0, 82.1 (Cp), 49.5 (NMe), 21.6

(MeC₆H₄), 19.7, 19.1 (Me₂C₆H₃). ¹⁹F NMR (CDCl₃,

293 K) Isomer E: d ꢀ62.72; Isomer Z: d ꢀ62.75.

3c: Yield: 289.2 mg (58%). Anal. Calc. for C₃₉H₃₆Fe₂-

N₂O₃: C, 67.65; H, 5.24; N, 4.05. Found: C, 67.39; H,

5.47, N, 4.39%. IR (in CH₂Cl₂, 293 K): m(CO) 1915

1

(vs); m(CN) 1575 (m), 1509 (m). H NMR (CDCl₃, 293

K): Isomer E: d 7.86–6.33 (m, 9H, arom), 7.60 (s, 1H,

CH o-C₆H₃OMe), 6.71 (s, 1H, @CH), 4.28, 3.78 (s,

10H, Cp), 3.82 (s, 3H, OMe), 3.47 (s, 3H, NMe), 2.59,

2.39 (s, 6H, Me₂C₆H₃), 2.30 (s, 3H, MeC₆H₄); Isomer

Z: d 7.86–6.33 (m, 9H, arom), 7.82 (s, 1H, CH

o-C₆H₃OMe), 7.35 (s, 1H, @CH), 4.41, 3.78 (s, 10H,

Cp), 3.90 (s, 3H, OMe), 3.56 (s, 3H, NMe), 2.75, 2.16

(s, 6H, Me₂C₆H₃), 2.42 (s, 3H, MeC₆H₄). Isomer ratio

E:Z = 1:1.04. ¹³C NMR (CDCl₃, 293 K): Isomer E: d

257.0 (Fe@C), 223.3, 222.1 (CO), 208.0 (C@N), 194.3

(Fe–C@CH), 168.9 (C–OMe), 158.2 (Fe–CC₆H₃OMe),

145.4 (C-ipso Xyl), 139.8–111.4 (arom + @CH), 84.6,

82.5 (Cp), 55.3 (OMe), 50.9 (NMe), 21.4 (MeC₆H₄),

20.0, 19.7 (Me₂C₆H₃); Isomer Z: d 256.0 (Fe@C),

222.5, 222.2 (CO), 206.0 (Fe–C@CH), 203.6 (C@N),

166.9 (C–OMe), 158.4 (Fe–CC₆H₃OMe), 145.3 (C-ipso

Xyl), 139.8–111.4 (arom + @CH), 85.1, 82.3 (Cp), 55.5

(OMe), 50.2 (NMe), 21.7 (MeC₆H₄), 19.4, 19.2

(Me₂C₆H₃).

3f: Yield: 234.9 mg (57%). Anal. Calc. for C₃₁H₂₈Fe₂-

N₂O₂: C, 65.06; H, 4.93; N, 4.90. Found: C, 65.27; H,

4.69, N, 5.02%. IR (in CH₂Cl₂, 293 K): m(CO) 1926

(vs); m(CN) 1508 (m). ¹H NMR (CDCl₃, 293 K): d

8.06–6.55 (m, 8H, arom), 7.87 (s, 1H, @CH), 4.57, 4.49

(s, 10H, Cp), 3.63, 3.58 (s, 6H, NMe₂), 2.39 (s, 3H,

MeC₆H₄). ¹³C NMR (CDCl₃, 293 K): d 268.3 (Fe@C),

220.8, 218.8 (CO), 208.5 (C@N), 197.1 (Fe–C@CH),

163.8 (Fe–CC₆H₄), 144.3 (@CH), 142.9 (C-ipso C₆H₄),

141.1 (C-ipso Tol), 138.5 (C–Me Tol), 132.6–119.1

(CH arom), 84.0, 82.8 (Cp), 49.8, 42.6 (NMe₂), 21.6

(MeC₆H₄).

3d: Yield: 280.1 mg (54%). Anal. Calc. for C₄₀H₃₆Fe₂-

N₂O₄: C, 66.69; H, 5.04; N, 3.89. Found: C, 66.92; H, 5.29,

N, 3.56%. IR (in CH₂Cl₂, 293 K): m(CO) 1917 (vs);

m(COOMe) 1716 (m); m(CN) 1508 (m). ¹H NMR (CDCl₃,

293 K) Isomer E: d 8.15–6.96 (m, 9H, arom), 7.67 (s, 1H,

CH o-C₆H₃COOMe), 6.78 (s, 1H, @CH), 4.26, 3.74 (s,

10H, Cp), 3.88 (s, 3H, COOMe), 3.33 (s, 3H, NMe),

2.69, 2.14 (s, 6H, Me₂C₆H₃), 2.27 (s, 3H, MeC₆H₄); Iso-

mer Z: d 8.22 (s, 1H, CH o-C₆H₃COOMe), 8.15–6.96

(m, 9H, arom), 7.77 (s, 1H, @CH), 4.40, 3.80 (s, 10H,

Cp), 3.93 (s, 3H, COOMe), 3.53 (s, 3H, NMe), 2.44,

2.17 (s, 6H, Me₂C₆H₃), 2.37 (s, 3H, MeC₆H₄). Isomer ra-

tio E:Z = 5:3. ¹³C NMR (CDCl₃, 293 K) Isomer E: d 249.0

(Fe@C), 222.8, 222.3 (CO), 197.5 (C@N), 177.1 (Fe–

C@CH), 168.3 (COOMe), 150.2 (Fe–CC₆H₃COOMe),

144.7 (C-ipso Xyl), 143.9 (@CH), 139.7–123.3 (arom),

85.2, 82.1 (Cp), 52.2 (COOMe), 49.7 (NMe), 21.6

(MeC₆H₄), 19.6, 19.1 (Me₂C₆H₃); Isomer Z: d 255.6

(Fe@C), 221.5, 220.8 (CO), 201.9 (Fe–C@CH), 199.7

(C@N), 168.7 (COOMe), 150.9 (Fe–CC₆H₃COOMe),

144.3 (C-ipso Xyl), 144.0 (@CH), 139.7–123.3 (arom),

85.3, 82.4 (Cp), 52.4 (COOMe), 51.0 (NMe), 21.3

(MeC₆H₄), 20.0, 19.4 (Me₂C₆H₃).

3g: Yield: 295.0 mg (64%). Anal. Calc. for

C₃₂H₂₇F₃Fe₂N₂O₂: C, 60.03; H, 4.25; N, 4.38. Found:

C, 60.29; H, 4.02, N, 4.05%. IR (in CH₂Cl₂, 293 K):

1

(CO) 1930 (vs); m(CN) 1539 (w), 1507 (m). H NMR

(CDCl₃, 293 K): d 8.09 (s, 1H, @CH), 7.91–7.15 (m,

7H, arom), 4.57, 4.51 (s, 10H, Cp), 3.64, 3.58 (s, 6H,

NMe₂), 2.38 (s, 3H, MeC₆H₄). ¹³C NMR (CDCl₃, 293

K): d 269.2 (Fe@C), 220.5, 218.1 (CO), 207.5 (C@N),

197.3 (Fe–C@CH), 163.7 (Fe–CC₆H₃CF₃), 146.8

(C-ipso C₆H₃CF₃), 143.1 (CH o-C₆H₃CF₃), 139.6

(@CH), 139.8 (C-ipso Tol), 137.3 (C–Me Tol), 132.9–

118.9 (CH arom + C₃+ C–CF₃), 84.0, 82.9 (Cp), 50.1,

42.8 (NMe₂), 21.6 (MeC₆H₄). ¹⁹F NMR (CDCl₃, 293

K): d ꢀ62.70.

4.4. X-ray structural determinations

Compounds 3b, 3c Æ 0.5C₅H₁₂, 3e and 3g Æ C₅H₁₂were

crystallised from CH₂Cl₂/pentane at ꢀ20 ꢁC. Crystal

data and collection details are reported in Table 3.

The diﬀraction experiments were carried out on a Bru-

ker SMART 2000 diﬀractometer equipped with a

CCD detector using Mo Ka radiation. Data were cor-

rected for Lorentz polarization and absorption eﬀects

3e: Yield: 315.5 mg (60%). Anal. Calc. for

C₃₉H₃₃F₃Fe₂N₂O₂: C, 64.13; H, 4.55; N, 3.84. Found:

L. Busetto et al. / Journal of Organometallic Chemistry 690 (2005) 1959–1970

1969

Table 3

Crystal data and experimental details for 3b, 3c Æ 0.5C₅H₁₂, 3e and 3g Æ C₅H₁₂

Complex

3b

3c Æ 0.5C₅H₁₂

3e

3g Æ C₅H₁₂

Formula

Formula weight

T (K)

C₃₈H₃₃BrFe₂N₂O₂

741.27

293(2)

C_41.5H₄₂Fe₂N₂O₃

728.47

293(2)

C₃₉H₃₃F₃Fe₂N₂O₂

730.37

150(2)

C₃₇H₃₉F₃Fe₂N₂O₂

712.40

293(2)

˚

k (A)

0.71073

Monoclinic

P2₁/n

0.71073

Triclinic

0.71073

Monoclinic

P2₁/n

0.71073

Monoclinic

C2/c

Crystal system

Space group

ꢀ

P1

˚

a (A)

14.411(3)

16.116(3)

15.460(3)

90

9.988(2)

17.106(3)

22.806(5)

71.26(3)

88.67(3)

79.19(3)

3621.6(13)

4

14.397(3)

16.236(3)

15.189(3)

90

33.456(7)

12.717(3)

22.746(5)

90

˚

b (A)

˚

c (A)

a (ꢁ)

b (ꢁ)

c (ꢁ)

114.53(3)

90

114.50(3)

90

131.16(3)

90

7286(3)

3

˚

Cell volume (A )

3266.5(11)

4

1.507

3230.7(11)

4

1.502

Z

8

1.299

D_c(g cm^ꢀ3

l (mm^ꢀ1

F(0 0 0)

)

1.336

0.842

1524

)

2.148

1512

0.954

1504

0.844

2960

Crystal size (mm)

h limits (ꢁ)

Reﬂections collected

Independent reﬂections (R_int

Data/restraints/parameters

Goodness-on-ﬁt on F²

R₁[I > 2r(I)]

0.19 · 0.16 · 0.11

1.63–25.03

28,607

0.24 · 0.21 · 0.13

0.94–25.03

28,638

0.36 · 0.26 · 0.19

1.64–25.68

29,661

0.21 · 0.15 · 0.12

1.62–25.02

31,663

)

5773 (0.1301)

5773/0/410

0.911

12,784 (0.0809)

12,784/477/847

0.917

6134 (0.0520)

6134/0/437

1.033

6431 (0.0991)

6431/371/455

1.065

0.0658

0.1887

0.0660

0.1947

0.0355

0.0799

0.0773

0.2412

wR₂(all data)

Largest diﬀerential peak and hole (e A

ꢀ3

˚

)

0.453/ꢀ0.901

0.683/ꢀ0.399

0.538/ꢀ0.847

0.879/ꢀ0.877

(empirical absorption correction SADABS) [20]. Struc-

tures were solved by direct methods and reﬁned by

full-matrix least-squares based on all data using F²

[21]. Hydrogen atoms were ﬁxed at calculated positions

and reﬁned by a riding model. All non-hydrogen atoms

were reﬁned with anisotropic displacement parameters,

unless otherwise stated. The Cp ligands bound to

Fe(1), Fe(2) and Fe(3) in 3c Æ 0.5C₅H₁₂and the CF₃

group in 3g Æ C₅H₁₂are disordered over two positions,

whereas the C₅H₁₂molecule in 3g Æ C₅H₁₂is disordered

over four positions. Disordered atomic positions were

split and reﬁned isotropically using similar distance

and similar U restraints and one occupancy parameter

per disordered group. In the case of the C₅H₁₂molecule

in 3g Æ C₅H₁₂the sum of the occupancy parameters for

the four positions was restrained to unit. Two indepen-

dent molecules are present in the asymmetric unit of

3c Æ 0.5C₅H₁₂.

CB2 1EZ, UK (fax: +44 1233 336033; e-mail: deposit@

ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).

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