Ferrocenyl-nitrogen donor ligands. Synthesis and characterization of rhodium(I) complexes of ferrocenylpyridine and related ligands

Journal of Organometallic Chemistry 691 (2006) 4573–4588

www.elsevier.com/locate/jorganchem

Ferrocenyl-nitrogen donor ligands. Synthesis and characterization

of rhodium(I) complexes of ferrocenylpyridine and related ligands

a

b,

*

Jaisheila Rajput , Alan T. Hutton , John R. Moss , Hong Su , Christopher Imrie

a

Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701, South Africa

Department of Chemistry, University of Port Elizabeth,¹PO Box 1600, Port Elizabeth 6000, South Africa

b

Received 10 April 2006; received in revised form 17 May 2006; accepted 17 May 2006

Available online 7 June 2006

Abstract

The preparation of a series of complexes of the types [RhCl(CO)₂(L)], [RhCl(cod)(L)] and [Rh(cod)(L)₂]ClO₄, where L is a ligand incor-

porating a ferrocenyl group and a pyridine ring is described. Complexes were characterized using NMR, IR and electronic spectroscopy.

The electrochemical behaviour of the complexes was examined using cyclic voltammetry. The X-ray structures of three of the complexes,

[RhCl(CO)₂{NC₅H₄C@NC₆H₄(g⁵-C₅H₄)Fe(g⁵-C₅H₅)}], [RhCl(cod)(3-Fcpy)] and [RhCl(cod){3-Fc(C₆H₄)py}], were determined.

Keywords: Ferrocenyl-nitrogen donor ligands; Ferrocenylpyridines; Rhodium(I); Electrochemistry

1. Introduction

Fe

Despite the extensive work on the symmetrical ferroce-

Cl

N

CO

nylphosphine [1] and unsymmetrical ferrocenyl ligands

[2], it was apparent from reviewing the literature that the

chemistry and application of symmetrical and unsymmetri-

cal ferrocenyl-nitrogen donor ligands has not been very

well developed. Miller et al. [3] described the use of 4-

ferrocenylpyridine as a ligand. It was coordinated to rhe-

nium to provide complex 1. The electrochemical properties

of the complex were compared to a series of rhenium-

ferrocenyl complexes containing ferrocenylphosphine coor-

dination complexes. The complexes were investigated to

determine whether changes in the oxidation state of the

redox ferrocenyl ligand could result in changes in the reac-

tivity of the rhenium centre, essentially without changing

the coordination sphere of rhenium. The preparation of a

platinum complex (2) of 3-ferrocenylpyridine has also been

described [4].

N

Cl

Re

Pt

CO

Fe

1

2

Of particular interest was the speciﬁc role of platinum as

a linker between the ferrocenyl groups. A single redox wave

was observed for 2 corresponding to a two-electron oxida-

tion at the platinum electrode indicating little or no com-

munication between the respective ferrocenyl groups. It

would appear that the platinum metal centre in 2 inhibits

electronic communication between the ferrocenyl groups.

Complexes 1 and 2 contain systems in which the metals

are connected through conjugated pathways and this pro-

vides an avenue for through-bond electronic communica-

tion. The signiﬁcance of a conjugated system has been

illustrated by Carr and co-workers with a comparison of

the electrochemical behaviour of complexes 3 and 4 [5].

*

Corresponding author. Tel.: +27415042823; fax: +27415042573.

E-mail address: Christopher.Imrie@nmmu.ac.za (C. Imrie).

University of Port Elizabeth has recently been incorporated into the

1

Nelson Mandela Metropolitan University, Port Elizabeth, South Africa.

doi:10.1016/j.jorganchem.2006.05.048

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J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

K[PtCl₃(C₂H₄)] provided the analogous complex to 7.

n⁺

Work has also been reported on the coordination chemistry

of ferrocenyl-4-pyridylacetylene. Nunes et al. reported on

the preparation of some ruthenium(II) complexes contain-

ing this ligand [11], whilst Santos et al. reported on the

preparation of a complex between this ligand and methyltri-

oxorhenium(VII) [12]. Ferrocenyl-nitrogen donor ligands

have also received some attention by materials chemists.

Examples include ligands incorporated into dendrimer

architectures [13], redox-active sensors [14], non-linear opti-

cal materials [15] and organometallic oligomers [16]. In a

previous publication, we reported on the synthesis and

medicinal properties of a series of ferrocenyl-nitrogen

donor coordination complexes of palladium, platinum, irid-

ium and rhodium [17]. In that paper, the emphasis was

placed on the synthesis and characterization of the palla-

dium and platinum complexes. The current paper describes

in full the chemistry and properties of the rhodium(I) com-

plexes of ferrocenylpyridine and related ligands.

R

N

Pt

R

Fe

3

4

a: R = Cl^-, n = 0

b: R = py, n= 2

The redox behaviour of the uncomplexed ferrocenyl

ligands in 3 and 4 were similar but on complexation there

was a shift of approximately +150 mV in the case of the

conjugated system of complex 3b compared to only

+30 mV in the unconjugated system of complex 4b.

Although the synthesis of the disubstituted ferrocenyl

ligand, 1,1⁰-bis(2-pyridyl)ferrocene (5), was reported many

years ago [6], it was only in more recent times that the coor-

dination chemistry of 5 has been investigated. Tani et al. [7]

described the preparation and characterization of rho-

dium(I) and silver(I) complexes of 5. Subsequently, the

platinum and palladium complexes of 5 have been pre-

pared (6 and 7) and their catalytic reactivity with regard

to carbonyl insertion reactions has been studied [8]. Inser-

tion of carbon monoxide into the palladium–methyl bond

of 6 occurred rapidly but detailed kinetic studies on the

reaction were not possible due to weak ligand–metal bind-

ing. The ligand 5 has also been shown to act as an eﬃcient

electrochemical sensor for magnesium, calcium, zinc and

cadmium ions in acetonitrile solution [9].

N

Fe

N

8

2. Results and discussion

2.1. Preparation of rhodium carbonyl complexes

N

Fe

The rhodium(I) carbonyl monosubstituted pyridyl coor-

dination complexes 9a–e in this study were prepared

through a bridge-splitting reaction of the rhodium carbonyl

dimer, dichlorotetracarbonyldirhodium. Replacement of

this dimer by the related cyclooctadiene dimer, chloro(1,5-

cyclooctadiene)rhodium(I), leads to the formation of the

analogous cyclooctadiene complexes. The carbonyl com-

plexes may also be obtained by bubbling carbon monoxide

through a solution of the cyclooctadiene complex. The labile

cyclooctadiene group is displaced by the carbonyl ligands.

N

5

Cl

Pt

N

Cl

N

Me

Cl

Fe

Pd

9a: R = H

R

9b: R = NH₂

N

Cl

OC

N

9c: R = Fc

Pt

Rh

Cl

9d: R = (C=N)-Ph

9e: R = (C=N)(C₆H₄)Fc

Cl

7

6

Neumann et al. have described the synthesis and coordi-

nation chemistry of octamethyl-1⁰,1⁰-bis(2-pyridyl)ferro-

cene (8) [10]. The reactivity of 8 with two equivalents of

Complexes 9a–e were obtained in good yield. The eﬀect

of derivatising the pyridyl ligand as well as the eﬀect of the

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4575

substituent on the electron density at the rhodium metal

2.2. Preparation of rhodium cyclooctadiene complexes

centre was reﬂected in shifts in the carbonyl stretching

frequencies in the infrared spectra. The spectra were

recorded as potassium bromide pellets. Strong bands were

obtained at 2091 and 2016 cm^ꢀ1for complex 9a and are

assigned to the carbonyl stretching frequencies of the

cis-isomer. The introduction of the amine group in 9b

results in a shift in the bands to 2076 and 2012 cm^ꢀ1whilst

substitution of a ferrocenyl group in complex 9c moves the

bands to 2086 and 2011 cm^ꢀ1. Comparison of shifts in the

carbonyl stretching frequency of 9a with 9b–9e showed a

shift to lower energy. This corresponded to an increased

electron density at the rhodium centre. A further compar-

ison can be made between the free ligand and complex in

both 9d and 9e by evaluating the imine stretching

frequency. A stretching frequency of 1595 cm^ꢀ1was

obtained for the free ligand in 9d. This shifted to

1605 cm^ꢀ1on complexation to the rhodium centre. Simi-

larly, a shift from 1623 to 1643 cm^ꢀ1was observed on com-

plexation in 9e. This was attributed to a lowering in energy

on coordination of the ligand to the rhodium metal. Minor

The rhodium cyclooctadiene dimer, chloro(1,5-cyclo-

octadiene)rhodium(I), can be readily prepared by the reac-

tion of excess cyclooctadiene and rhodium trichloride

trihydrate. This dimer is known to readily undergo a

bridge-splitting reaction on addition of an uncharged

monodentate ligand. The presence of the labile cycloocta-

diene ligand appears to promote catalytic activity by

readily dissociating as part of the catalytic cycle. Several

nitrogen donor ligands were coordinated to the rhodium

metal centre in a bridge splitting reaction of the rhodium

dimer followed by addition of the ligand (see 10a–g, 11a–b,

12a–b, 13). Changes in the proton chemical shift values

for the pyridyl groups were observed on variation of the

substituent on the pyridyl ring. For example, complex

10d showed chemical shifts at 8.76 and 7.32 ppm whilst

introduction of the phenyl substituent in 10e showed a shift

of these peaks to 8.75 and 7.57 ppm for H_aand H_b, respec-

tively. Complex 10f showed a more pronounced shift of

8.88 and 7.46 ppm for H_aand H_b. A slight shift in the

imine proton peak position from 8.44 to 8.47 ppm was

observed on complexation for complex 10f. This can also

be compared to the related carbonyl complex 9d where

an imine peak was observed at 8.81 ppm. Complex 10g

showed shifts in both sets of pyridyl ring protons to 8.60

and 7.30 ppm, respectively. The direction of shifts in peak

positions on comparison of free ligand and complex are

similar for both the carbonyl and cyclooctadiene com-

plexes. The positional shifts were overall more pronounced

in the carbonyl complexes. This may be accounted for by

considering the synergistic eﬀect of the carbonyl groups

on the metal through signiﬁcant p back-bonding interac-

tion. Complexes 10a–c, 11a–b, 12a–b and 13 include ferr-

ocenyl substituents on the pyridyl ring. Several structural

comparisons can be made between these complexes and

the eﬀect considered in terms of their impact on the rho-

dium centre. Complex 13 is unique with the nitrogen donor

atom occurring on the cyclopentadienyl ring of the

1⁰,2⁰,3⁰,4⁰,5⁰-pentamethylazaferrocene compound. The

cyclopentadienyl protons for complexes 10a–c showed sim-

ilar chemical shift values, while only 10a showed signiﬁcant

diﬀerences on comparison of the free ligand and complex.

The a-H and b-H in 10a showed upﬁeld shifts relative to

1

diﬀerences in the chemical shifts of the H NMR between

the free ligand and coordinated complex were observed

mainly on the a-proton adjacent to the nitrogen-donor

atom on the pyridyl ring. Shifts in the position of the imine

bond proton in 9d and 9e were also observed on compari-

son of the free ligand with complex, with downﬁeld shifts

of 8.44 to 8.81 and 8.54 to 8.57 ppm, respectively. Compar-

1

ing the cyclopentadienyl H NMR chemical shifts of the

ferrocenyl groups of 9c and 9e as well as relative to the free

respective ligands, assisted in the evaluation of the eﬀect of

the spacer group. Furthermore, the eﬀect of coordinating

the rhodium metal could be determined on comparison

of the NMR spectra of the free ligand and complex

(Fig. 1).

On comparing the shifts due to the complex with that of

the free ligand, no signiﬁcant diﬀerences could be estab-

lished between these speciﬁc chemical shifts in 9e. It would

appear that the long-range conjugative eﬀect between the

rhodium centre and the ferrocenyl group was reduced by

the presence of the spacer, despite a conjugated system of

bonds between the two. This proposal is lent some validity

when comparing the diﬀerences between the free ligand and

complex for 9c.

N

OC

N

Rh

Fe

Rh

Fe

Cl

9c

9e

-H:4.76; -H:4.56; Cp: 4.08 [9c]

-H:4.68; -H:4.36; Cp: 4.06 [9e]

-H:4.82; -H:4.6 ; Cp: 4.08 (ligand)

-H:4.68; -H:4.36; Cp: 4.06 (ligand)

Fig. 1. Comparison of ¹H NMR chemical shifts (ppm) for the ferrocenyl substituents in 9c and 9e.

4576

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

the free ligand, indicating shielding of these protons on

coordination of the rhodium metal, similar to the related

carbonyl complex, 9c. The comparable chemical shifts for

the free ligand and complex for both 10b and 10c indicated

a reduced conjugative eﬀect between the ferrocenyl group

and rhodium metal due to the presence of the spacer

groups. The protons in complex 13, contrary to those

in complex 10a, showed signiﬁcant downﬁeld shifts on

complexation of the rhodium metal centre. This indicated

deshielding of these protons. The complex was paramag-

netic and broad signals were obtained for it in the ¹H

NMR.

complex by displacement of the solvent from the rhodium

coordination sphere.

14a: R = H

R

14b: R = Ph

14c: R = (C=N)-Ph

14d: R = Fc

N

ClO₄

Rh

14e: R = (C₆H₄)Fc

14f: R = (C=N)(C₆H₄)Fc

R

H_b

A variation on the preparation of complex 14a

included preparation of the complex with a hexaﬂuoro-

phosphate counter-ion. The synthesis of the complex

[Rh(cod)L₂]PF₆involved the addition of excess pyridine

to the rhodium dimer in ethanol, followed by addition

of a concentrated aqueous solution of ammonium hexa-

ﬂuorophosphate. The product was obtained as a precipi-

tate that was collected by vacuum ﬁltration. The

preparation of further complexes with this counter-ion

was not carried out as the complex [Rh(cod)L₂]PF₆

showed similar properties to that of complex 14a. The

cationic complexes were obtained in good yield through

concentration of the reaction mixture followed by addi-

tion of solvents such as diethyl ether or pentane to precip-

itate the product.

10a: R = Fc

H_a

R

10b: R = (C₆H₄)Fc

10c: R = (C=N)(C₆H₄)Fc

10d: R = H

N

H_b

Rh

H_a

Cl

10e: R = Ph

10f: R = (C=N)-Ph

10g: R = (C=C)(C₆H₄)-OC₈H₁₇

N

11a: R = Fc

R

Rh

11b: R = (C₆H₄)Fc

Cl

R

2.4. Preparation of 1,1⁰-bis(pyridyl)ferrocene ligand

complexes

N

12a: R = Fc

Rh

12b: R = (C₆H₄)Fc

Cl

The rhodium complexes described so far have been pre-

pared using monosubstituted ferrocenyl nitrogen donor

ligands. For comparative purposes, a selection of 1,1⁰-

disubstituted ferrocenylpyridines were prepared and com-

plexed to rhodium using similar synthetic routes to those

already described. The preparation of complexes 15a–b

has been reported using this synthetic route. Complex

15b was prepared using the same synthetic route as

described in the literature except that ethanol was used

as solvent since some decomposition was observed in ace-

tone. A downﬁeld shift was observed for the ferrocenyl

protons of complex 15b on complexation to the rhodium,

in contrast to complex 15a, where no diﬀerence was

observed. The negligible change in chemical shifts for the

ferrocenyl group for complex 15a was in line with those

observed with the monosubstituted complex 12a. The

downﬁeld shifts observed in the ferrocenyl protons for

complex 15b were contrary to the upﬁeld shifts observed

for the monosubstituted neutral complex 10a and cationic

complex 14d. Assuming that the eﬀect of coordination to

rhodium is felt through the conjugative system of bonds,

it would appear that the eﬀect diﬀers in the disubstituted

complexes.

N

13

Rh

Fe

Cl

2.3. Preparation of cationic rhodium complexes

[Rh(cod)L₂]ClO₄

The cationic rhodium complexes examined in this study

contain two pyridyl ligands and in the case of ferrocenyl

ligands, constitute the preparation of a trimetallic complex.

The cationic rhodium(I) complexes 14a–f were prepared

using the general synthetic route described in Scheme 1. Sil-

ver perchlorate was added to a solution of the rhodium

dimer in acetone, yielding a solvated complex of general

formula [Rh(cod)(Me₂CO)_x]ClO₄. The addition of a nitro-

gen-donor ligand to this complex produced a cationic

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4577

Cl

acetone

+

AgClO₄

[Rh(cod)(Me₂CO)_x]ClO₄

+

AgCl

Rh

Cl

N

Fe

N

Rh

ClO₄

14f

Scheme 1. Preparation of cationic rhodium complexes.

bond axis was obtained for each of the molecules. The pyr-

idyl and phenyl rings were conﬁrmed as delocalized.

The spectroscopic data and crystal structure analysis of

the complex 9e suggests that despite the existence of a con-

jugated network between the respective metals, the

extended spacer group between the metals results in a

diminished interaction. In both molecules the cyclopenta-

dienyl ferrocene rings are planar. The rings show a mar-

ginal tilt towards each other with angles of 0.73ꢁ (0.27)

and 1.93ꢁ (0.29) for the molecules. The cyclopentadienyl

rings are not completely eclipsed in the ferrocenyl group

but are rotated away from each other by an angle of 7.8ꢁ

and 3.0ꢁ in each of the molecules. This degree of rotation

has been related to monosubstitution of the ferrocenyl

group and to the nature of the substituent. The phenyl ring

showed a 26.7ꢁ rotation relative to the plane of the adjacent

cyclopentadienyl ring of the ferrocenyl group. The mole-

cules are packed in a tail-to-tail arrangement in the unit

cell.

N

ClO₄

Fe

Rh

N

15a

N

Rh

Fe

ClO₄

15b

The crystal structure of complex 11a was obtained from

single crystals grown from a mixture of dichloromethane

and pentane (Fig. 3). The complex was observed to crystal-

2.5. X-ray crystal structure analysis

ꢀ

lize in the triclinic space group P1. Details of crystal and

The molecular structure for complex 9e with atom num-

bering scheme is shown in Fig. 2. Complex 9e crystallized

with two molecules in an asymmetric unit (see Table 2

for details of crystal and reﬁnement data). The molecules

have no obvious intermolecular coordination between

them. Selected bond lengths and angles for 9e are listed

in Table 1 and were found to compare favourably with lit-

erature-cited bond lengths and angles for similar com-

plexes. The coordination geometry around the rhodium is

square planar. The dihedral angle between the plane of

the pyridyl ring and the rhodium square plane was

obtained as 136.3ꢁ(3) and 140.1ꢁ(2) for each of the mole-

cules, similar to the observed angle of 141ꢁ in complex

9a. The trans geometry of the imine bond and its double

bond character were conﬁrmed by X-ray crystallography.

A torsion angle of 178.0ꢁ(3) and 177.3ꢁ(3) along the imine

structure reﬁnement data are summarized in Table 3. The

coordination geometry around the rhodium metal in com-

plex 11a is square planar. A torsion angle of 129ꢁ was

obtained between the pyridyl ring and the adjacent cyclo-

pentadienyl ring. The cyclopentadienyl rings are planar

with a tilt angle of 1.6ꢁ. The rings are not completely

eclipsed, having a rotation angle of 5.6ꢁ. The Rh–N bond

˚

length is 2.109 A, which is in accordance with observed

bond lengths of similar complexes reported in the litera-

ture. The crystal structure of 11b was also obtained using

single crystals grown in a mixture of dichloromethane

and pentane (Fig. 4). The complex was observed to crystal-

ꢀ

lize in the triclinic space group P1. Least squares reﬁnement

of the structure gave a ﬁnal R factor of 0.0289. Details of

crystal and structure reﬁnement data are summarized in

4578

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

Fig. 2. Molecular structure of complex 9e showing the atom numbering scheme.

Table 1

Table 2

˚

Selected bond lengths (A) and angles (ꢁ) for the two molecules in the

asymmetric unit of 9e

Crystal and structure reﬁnement data for complex 9e

Compound

9e

Molecule 1

Molecule 2

Empirical formula

Formula weight

Crystal size (mm)

Temperature (K)

Crystal system

C₂₄H₁₈ClFeN₂O₂Rh

560.61

0.25 · 0.09 · 0.07

173(2)

Monoclinic

P2₁/c

Rh(1)–Cl(1)

Rh(1)–N(1)

Rh(1)–C(1)

Rh(1)–C(2)

O(1)–C(1)

O(2)–C(2)

N(2)–C(9)

N(2)–C(8)

C(7)–C(8)

N(1)–C(5)

C(5)–C(6)

C(6)–C(7)

C(9)–C(12)

C(12)–C(13)

C(13)–C(14)

C(14)–C(15)

2.357(1)

2.108(4)

1.852(5)

1.857(6)

1.133(6)

1.111(6)

1.415(6)

1.265(6)

1.467(6)

1.333(4)

1.374(5)

1.388(5)

1.386(5)

1.377(5)

1.395(5)

1.478(5)

Rh(2)–Cl(2)

Rh(2)–N(5)

Rh(2)–C(28)

Rh(2)–C(29)

O(3)–C(28)

O(4)–C(29)

N(38)–C(39)

C(37)–N(38)

C(34)–C(37)

N(5)–C(32)

C(32)–C(33)

C(33)–C(34)

C(39)–C(42)

C(42)–C(43)

C(43)–C(44)

C(44)–C(45)

2.353(1)

2.115(4)

1.862(6)

1.850(5)

1.098(6)

1.128(6)

1.416(6)

1.271(6)

1.478(6)

1.345(4)

1.367(5)

1.387(5)

1.395(5)

1.371(5)

1.387(5)

1.474(5)

Space group

Unit cell dimensions

˚

a (A)

14.480(1)

18.790(1)

17.116(1)

90

111.507(1)

90

4332.7(5)

1.579

˚

b (A)

˚

c (A)

a (ꢁ)

b (ꢁ)

c (ꢁ)

3

˚

Volume (A )

l (Mo Ka) (mm^ꢀ1

)

Z

8

Reﬂections collected/unique

Goodness-of-ﬁt on F²

Final R indices [I > 2sigma(I)]

R indices (all data)

23441/9672 [R_int= 0.0513]

1.008

R₁= 0.0430, wR₂= 0.0725

R₁= 0.1013, wR₂= 0.0857

Cl(1)–Rh(1)–N(1)

N(1)–Rh(1)–C(1)

C(1)–Rh(1)–C(2)

Cl(1)–Rh(1)–C(2)

Cl(1)–Rh(1)–C(1)

90.20(8)

176.22(14)

89.09(16)

179.14(13)

90.62(11)

Cl(2)–Rh(2)–N(5)

N(5)–Rh(2)–C(29)

C(28)–Rh(2)–C(29)

Cl(2)–Rh(2)–C(29)

Cl(2)–Rh(2)–C(28)

91.22(8)

177.96(15)

88.67(16)

90.20(11)

176.53(13)

Table 3 with selected bond lengths and angles for 11a and

11b listed in Table 4.

2.6. Electrochemical study of rhodium complexes

We have investigated the electrochemical behaviour of

selected complexes and our results are summarized in Table

5. Cyclic voltammetry of the complexes in acetonitrile (con-

taining 0.1 M tetra-n-butylammonium perchlorate) at a

platinum disk electrode shows, for all the ferrocenyl-con-

taining compounds, the typical reversible redox waves

expected for the Fc/Fc⁺couple. In Table 5 the half-wave

potential, E_1/2(Fc), and the corresponding anodic E_pa(Fc)

and cathodic E_pc(Fc) peak potentials are listed, while

Fig. 5 displays the reversible redox waves for the ferrocenyl

groups in complexes 11b and 10b compared with ferrocene

itself. Shifts in the half-wave potential of this wave can be

related to the substituents on the ferrocenyl group and to

the presence of coordinated rhodium(I). In some of the

Fig. 3. Molecular structure of complex 11a showing the atom numbering

scheme.

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4579

Table 3

Crystal and structure reﬁnement data for compounds 11a and 11b

Table 4

Selected bond lengths (A) and angles (ꢁ) for complexes 11a and 11b

˚

11a

11b

11a

11b

Empirical formula

Formula weight

Crystal size (mm)

Temperature (K)

Crystal system

C₂₃H₂₅ClFeNRh

509.65

0.30 · 0.07 · 0.04

298(2)

C₂₉H₂₉ClFeNRh

585.74

0.12 · 0.10 · 0.03

298(2)

Rh(1)–Cl(1)

Rh(1)–N(1)

Rh(1)–C(1)

Rh(1)–C(2)

Rh(1)–C(5)

Rh(1)–C(6)

N(1)–C(9)

C(9)–C(10)

N(1)–C(13)

C(13)–C(12)

C(12)–C(11)

C(11)–C(10)

C(10)–C(14)

C(2)–Rh(1)–C(1)

N(1)–Rh(1)–Cl(1)

C(2)–Rh(1)–Cl(1)

C(9)–N(1)–Rh(1)

2.3585(10)

2.109(2)

2.130(3)

2.124(3)

2.104(3)

1.340(3)

1.380(3)

1.343(3)

1.366(4)

1.373(4)

1.387(4)

1.481(4)

37.84(12)

88.26(6)

90.19(9)

119.70(17)

Rh(1)–Cl(1)

Rh(1)–N(1)

Rh(1)–C(1)

Rh(1)–C(2)

Rh(1)–C(5)

Rh(1)–C(6)

N(1)–C(13)

C(13)–C(12)

N(1)–C(9)

C(9)–C(10)

C(11)–C(10)

C(12)–C(11)

C(12)–C(14)

C(14)–C(19)

C(14)–C(15)

C(19)–C(18)

C(15)–C(16)

C(18)–C(17)

C(16)–C(17)

C(17)–C(20)

C(2)–Rh(1)–C(1)

N(1)–Rh(1)–Cl(1)

C(2)–Rh(1)–Cl(1)

C(9)–N(1)–Rh(1)

2.3719(11)

2.1031(9)

2.118(3)

2.109(3)

2.131(2)

2.138(2)

1.340(3)

1.389(3)

1.343(3)

1.376(3)

1.371(4)

1.397(3)

1.482(3)

1.390(3)

1.385(3)

1.381(3)

1.375(4)

1.389(3)

1.384(4)

1.474(3)

38.48(11)

86.88(6)

158.17(8)

122.98(16)

Triclinic

ꢀ

Space group

Unit cell dimensions

P1

˚

a (A)

6.946(1)

9.999(2)

14.789(3)

91.38(3)

99.30(3)

97.11(3)

1004.8(4)

1.683

7.003(1)

˚

b (A)

10.026(2)

17.609(4)

78.60(3)

80.79(3)

85.92(3)

1195.5(4)

1.427

2

34055/5459

[R_int= 0.0465]

1.025

R₁= 0.0289,

wR₂= 0.0657

R₁= 0.0405,

wR₂= 0.0698

˚

b (A)

a (ꢁ)

b (ꢁ)

c (ꢁ)

3

˚

Volume (A )

l (Mo Ka) (mm^ꢀ1

)

Z

2

Reﬂections

collected/unique

Goodness-of-ﬁt on F²

Final R indices

[I > 2sigma(I)]

R indices (all data)

8208/4397

[R_int= 0.0315]

1.019

R₁= 0.0308,

wR₂= 0.0568

R₁= 0.0586,

wR₂= 0.0627

2-substituted ligands. Interspersing a phenylene group

between the Fc and py moieties decreases the interaction

markedly. The inductive eﬀect of the rhodium metal centre

on the ease of oxidation of the ferrocenyl group was dem-

onstrated by the decreasing half-wave potentials observed

on comparison of complexes 10a, 11a and 12a. This trend

is further observed in the related complexes 10b, 11b and

12b with phenylene spacer groups. The eﬀect of the spacer

groups is clearly demonstrated on comparison of com-

plexes 10a, 10b and 10c, where a gradual decrease in E_1/2

value is observed. Changes in the spectator ligands do

not appear to play a signiﬁcant role in electronic interac-

tions as complexes 9e and 10c displayed similar E_1/2values.

The single reversible peak obtained for the cyclic voltam-

mogram of complex 14d indicated that no electronic

communication occurs between the two ferrocenyl groups

in this complex, though there is evidence of very limited

electronic coupling between the rhodium metal centre

and ferrocenyl groups.

Fig. 4. Molecular structure of complex 11b showing the atom numbering

scheme.

complexes an irreversible anodic peak was observed at

more positive potential than the ferrocenyl peak, and this

often broad peak was ascribed to the irreversible oxidation

of the rhodium(I) metal centre, E_pa(Rh). No reduction of

the rhodium(I) metal centre was observed, even scanning

cathodically down to ꢀ1.5 V.

2.7. Electronic spectroscopy of rhodium complexes

A comparison of the wavelengths of the major bands

together with extinction coeﬃcients for a selection of the

rhodium complexes in dichloromethane is given in Table

6. Bands due to transitions in the ferrocenyl and pyridyl

groups were observed, as well as a rhodium ! ligand p^*

metal-to-ligand charge transfer band in the range 350–

550 nm (depending on the speciﬁc ligand). The lowest

energy Fe d–d transitions of the free ferrocenyl-pyridine

ligands (around 450 nm) are not signiﬁcantly shifted in

wavelength upon coordination to a rhodium centre, and

Comparing the half-wave potentials of the free ligands

with those of the Fc/Fc⁺couples in the corresponding

binuclear complexes, it is apparent that only in the case

of 10a, where L = 4-Fcpy, is there evidence of signiﬁcant

electronic interaction between the Rh and Fc centres, the

eﬀect falling oﬀ rapidly in going from the 4- to the 3- and

4580

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

Table 5

Electrochemical data for selected rhodium(I) complexes in acetonitrile^a

Complex number

Complex type

Ligand

E_pa(Rh) (mV)

E_pa(Fc) (mV)

E_pc(Fc) (mV)

E_1/2(Fc) (mV)

E_1/2(L) (mV)

Ferrocene

[RhCl(cod)]₂

RhCl(cod)L

–

py

–

+120

–

+31

–

+76

–

+446

+529

10d

10a

11a

12a

10b

11b

12b

10f

10c

9e

4-Fcpy

3-Fcpy

2-Fcpy

4-Fc(C₆H₄)py

3-Fc(C₆H₄)py

2-Fc(C₆H₄)py

Ph(NC)py

Fc(C₆H₄)NCpy

4-Fcpy

–

+377

+223

+192

+194

+165

–

+161

+145

+270

+240

+148

+118

+125

+96

+89

–

+91

+82

+179

+309

+186

+155

+160

+130

+127

–

+126

+114

+224

+206

+168

+154

+134

+132

+126

–

+113

+206

+612

–

+632

+616

–

RhCl(CO)₂L

[Rh(cod)L₂]ClO₄

14d

a

–

Measured in CH₃CN containing 0.1 M [ⁿBu₄N][ClO₄] at a scan rate of 100 mV s^ꢀ1and referenced to Ag/Ag⁺.

the complexes were analysed successfully by X-ray crystal-

lography. Selected compounds were also analysed by cyclic

voltammetry and electronic spectroscopy; results from

these methods provided information on electronic commu-

nication between the metals or lack of it in the complexes.

Compounds described here should oﬀer potential catalytic

activity and studies in this regard are currently in progress.

[FcH]

[11b]

[10b]

4

0

-4

-8

-12

4. Experimental

4.1. Puriﬁcation and characterization of the materials

500

300

100

-100

-300

-500

All manipulations, unless otherwise stated were carried

out under an inert atmosphere of nitrogen using standard

Schlenk techniques. Glass syringes were stored at 60 ꢁC

and all other glassware thoroughly dried at 210 ꢁC for at

least four hours prior to use. Melting points were deter-

mined on a Koﬂer hotstage microscope (Reichart Therm-

ovar). Microanalyses were obtained on a Carlo Erba EA

1108 elemental analyser. Fast atomic bombardment

(FAB) and high resolution (EI) mass spectra were recorded

on a VG-70SEQ mass spectrometer at the mass spectrom-

etry unit, Cape Technikon. In all cases the isotopic distri-

bution was checked against the theoretical distribution.

Infrared spectra were recorded on a Perkin Elmer Paragon

1000 FT-IR spectrometer, with solid samples prepared as

potassium bromide disks and solution samples in sodium

chloride solution cells. NMR spectra were recorded

on either a Varian Unity-400 (¹H: 400 MHz; ¹³C:

100.6 MHz) or Varian Mercury-300 (¹H: 300 MHz; ¹³C:

75.5 MHz) spectrometer at ambient temperatures. ¹H

NMR spectra were referenced internally using residual pro-

tons in the deuterated solvent (CDCl₃: d 7.27; C₆D₆: d 7.24,

CD₃OD: d 5.84, CD₃COCD₃: d 2.09) and values reported

relative to tetramethylsilane (d 0.00). ¹³C NMR spectra

were similarly referenced internally to the solvent reso-

nance (CDCl₃: d 77.0; C₆D₆: d 128.1, CD₃OD: d 49.1,

CD₃COCD₃: d 30.60 and 205.87) with values reported

relative to tetramethylsilane (d 0.0). UV–Vis spectra were

recorded on a Hewlett Packard 8452A diode array spectro-

photometer in dichloromethane. Cyclic voltammograms

Potential (mV)

Fig. 5. Overlay of cyclic voltammograms for ferrocene and complexes 10b

and 11b.

from this point of view the inﬂuence of the Rh^Icentre on

ferrocene is weak or non-existent, the largest eﬀect (a bath-

ochromic shift of 12 and 28 nm upon complexation) being

noted for 10a and 14d, respectively. This is in accordance

with the results obtained by cyclic voltammetry. Interesting

comparisons can be made between the mono- and bis-

ligand complexes 10a or 10b and 14d. In each of these

cases, a shift in the transitions to a longer wavelength

and larger extinction coeﬃcient was found on incorpora-

tion of an additional ligand.

The highly conjugated complexes 10f, 10c, 14f and 9e in

Table 6 all show relatively large extinction coeﬃcients for

each of the transitions. A comparison of complexes 10c

and 9e showed a variation in the middle band, with complex

9e exhibiting a more intense transition and increased extinc-

tion coeﬃcient with a bathochromic shift relative to complex

10c. This band also became more intense for complex 14f.

3. Conclusion

In this paper, a series of new multinuclear complexes

consisting of ferrocenyl-nitrogen donor ligands coordi-

nated to rhodium were successfully prepared and charac-

terized using an array of analytical techniques. Three of

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4581

Table 6

Electronic spectral bands and extinction coeﬃcients for selected rhodium complexes

Complex number

Wavelength/nm [Extinction coeﬃcient/mol^ꢀ1dm³cm^ꢀ1

]

10d

–

366 [1634]

298 [4210]

N

Rh

Cl

11a

450 [593]

358 [2474]

308 [4344]

N

Rh

Cl

Fe

10a

466 [1811]

482 [2760]

360 [5670]

370 [4880]

308 [14712]

314 [17249]

N

Rh

Fe

Cl

14d

Fe

N

ClO₄

Rh

N

Fe

11b

452 [1050]

362 [4333]

322 [5076]

N

Fe

Rh

Cl

10b

14e

460 [1755]

472 [4887]

376 [6095]

318 [8122]

N

Rh

Fe

Cl

384 [10080]

314 [16192]

Fe

N

ClO₄

Rh

N

Fe

10f

10c

–

354 [11644]

336 [12405]

N

Rh

Cl

488 [1998]

358 [9459]

298 [9701]

N

Cl

Fe

(continued on next page)

4582

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

Table 6 (continued)

Complex number

14f

Wavelength/nm [Extinction coeﬃcient/mol^ꢀ1dm³cm^ꢀ1

]

504 [7895]

364 [14296]

302 [13328]

Fe

N

Rh

ClO₄

9e

500 [3621]

374 [13318]

300 [9518]

N

OC

N

Rh

Fe

Cl

were obtained on a BAS 100W electrochemical analyser

with a one compartment three-electrode system consisting

of a Ag/AgNO₃(0.01 M) reference electrode, platinum

wire auxiliary electrode and platinum disc working elec-

trode. Samples (1–2 mM) were prepared and run under

argon at ambient temperature, in anhydrous acetonitrile

with tetrabutylammonium perchlorate (0.1 M) as back-

ground electrolyte. The scan rate used was 100 mV s^ꢀ1

and the system gave ferrocene E_1/2= +76 mV. The plati-

num disc working electrode was polished between runs.

X-ray diﬀraction data were collected at 173 K or 298 K

using Nonius Kappa CCD with 1.5 kW graphite-mono-

chromated Mo radiation. The strategy for data collection

was evaluated using ^COLLECT[18]. Several sets of data were

collected with both a 199ꢁ phi scan and omega scans to col-

lect cusp data. The data were scaled and reduced as well as

treated for absorption by a semi-empirical method using

DENZO-SMN [19]. Unit cell dimensions were reﬁned on all

data. The structure was solved and reﬁned using ^SHELX97

[20,21]. Molecular graphics were generated using ORTEP-III

[22], PLATON [23] and X-SEED [24], a graphical interface

for the ^SHELXprogram. For the most part, reaction solvents

were puriﬁed, dried and distilled prior to use according to

the literature methods. Less commonly used reagents and

solvents such as N,N-dimethylformamide, pyridine and tri-

ethylamine were puriﬁed and dried, followed by storage

under nitrogen in dry glass storage vessels equipped with

Teﬂon valve stopcocks. Chromatography solvents were of

analytical grade and used without puriﬁcation, with the

exception of dichloromethane and hexane which were of

chemically pure grade and distilled in air prior to use. n-

Butyllithium (1.6 M in hexanes), Superhydride^ꢂ(1.0 M in

tetrahydrofuran) and N,N,N⁰,N⁰-tetramethylethylenedi-

amine was purchased from Sigma–Aldrich and transferred

under nitrogen into a glass storage vessel with Teﬂon stop-

cock. All other commercial reagents were used as obtained

without further puriﬁcation. The following known com-

pounds were prepared and fully characterized by us as part

of this work. 4-Pyridylimine-4⁰-phenylferrocene [15c], 4-

pyridylvinyl-4⁰-phenylferrocene [14c], 4-ferrocenylpyridine

[3], 3-ferrocenylpyridine [4], 2-ferrocenylpyridine [25], 4-

ferrocenylphenyl-3⁰-pyridine [17], 4-ferrocenylphenyl-2⁰-

pyridine [17], 1,1⁰-bis(2-pyridyl)ferrocene [6b,8], 1,1⁰-bis-

(4-pyridyl)ferrocene [17], ferrocenyldiphenylphosphine

[26], dichlorotetracarbonyldirhodium [27], dicarbonyl-

chloro(pyridine)rhodium

[28],

bis(carbonyl)chloro(4-

aminopyridine)dicarbonylchlororhodium [29], chloro(1,

5-cyclooctadiene)rhodium(I) dimer [30], chloro(1,5-cyclo-

octadiene)(pyridine)rhodium [31], (1,5-cyclooctadiene)-

bis(pyridine)rhodium hexaﬂuorophosphate [32] and (1,

5-cyclooctadiene)bis(pyridine)rhodium perchlorate [32]. 1⁰,

2⁰,3⁰,4⁰,5⁰-Pentamethylazaferrocene was prepared accord-

ing to the method of Fu [33] and obtained courtesy of

Dr. P. Beagley, Organometallic Research Group, University

of Cape Town. Rhodium was obtained as the chloride salt on

loan from Johnson–Matthey and ferrocene was obtained

commercially from Sigma–Aldrich. Thin-layer chromatog-

raphy was performed on aluminium-backed silica gel or alu-

minium oxide 60F₂₅₄plates in a variety of solvent systems

using the ascending technique. Plates were analysed under

ultraviolet light. Column chromatography was conducted

either on silica gel 60, particle size 0.063–0.200 mm (70–230

mesh ASTM) or neutral alumina, particle size 0.063–

0.200 mm (70–230 mesh ASTM). Columns were generally

prepared with 1:100 ratio product to chromatographic

material.

4.2. Rhodium carbonyl complexes

4.2.1. Dicarbonylchloro(4-phenylimine-4⁰-pyridine)rhodium

(9d)

4-Phenylimine-4⁰-pyridine (56.2 mg, 0.31 mmol) was

added slowly to a solution of the rhodium dimer, dic-

hlorotetracarbonyldirhodium (60.7 mg, 0.15 mmol) in

dichloromethane (10 mL). The reaction mixture was stirred

under nitrogen for 20 min and then concentrated in vacuo.

Pentane was added to precipitate the product. The product

was collected by vacuum ﬁltration as a yellow crystalline

solid (74.0 mg, 63%); IR (KBr, cm^ꢀ1): 3040, 2088 (CO),

2013 (CO), 1605 (C@N). ¹H NMR (300 MHz; CD₃COCD₃):

d 8.96 (2H, dd, J = 6.8 Hz, C₅H₄N), 8.81 (1H, s, N@CH),

8.16 (2H, dd, J = 6.8 Hz, C₅H₄N), 7.51–7.44 (2H, tt,

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4583

J = 15.1 Hz, C₆H₅), 7.41 (2H, d, J = 1.5 Hz, C₆H₅), 7.35

(1H, t, J = 10.6 Hz, C₆H₅). ¹³C NMR (75 MHz, CDCl₃): d

158.42 (N@C), 154.78 (C₅H₄N), 130.93 (C₆H₅), 129.20

(C₅H₄N), 125.57 (C₆H₅), 122.94 (C₆H₅).

(159.0 mg, 0.32 mmol) in dichloromethane (10 mL). The

reaction mixture was stirred for a further 31 min. The reac-

tion mixture was then concentrated in vacuo and diethyl

ether added to precipitate the product. The product was col-

lected via vacuum ﬁltration as bright yellow crystals

(206.7 mg, 80%). Anal. Calc. for C₁₉H₂₁ClNRh: C, 56.8%;

H, 5.3; N, 3.5; M⁺401.74272. Found: C, 56.73%; H, 5.15;

N, 3.46; M⁺401.04176. IR (KBr, cm^ꢀ1): 2990, 2931,

2880, 2825, 2367, 2324, 1772, 1674, 1607, 1541, 1471,

1429, 1413, 1333, 1215, 1068, 993, 961, 848, 765, 733, 690,

4.2.2. Dicarbonylchloro(4-pyridylimine-4⁰-phenylferrocene)-

rhodium (9e)

4-Pyridylimine-4⁰-phenylferrocene (120.1 mg, 0.33 mmol)

was added to a solution of dichlorotetracarbonyldirhodium

(79.9 mg, 0.16 mmol) in dichloromethane (20 mL) and fur-

ther stirred for 25 min. The reaction mixture was concen-

trated in vacuo and hexane was added to precipitate the

product. The product was collected by vacuum ﬁltration

as small maroon-red rod-shaped crystals (56.0 mg, 61%);

m.p. 165–175 ꢁC. Anal. Calc. for C₂₄H₁₈ClFeN₂O₂Rh: C,

51.4%; H, 3.2; N, 5.0; M⁺560. Found: C, 51.2%; H, 3.1;

N, 4.8; M⁺560.0. IR (KBr, cm^ꢀ1): 3054, 2359, 2080, 2003,

1684, 1643, 1589, 1427, 1326, 1280, 1106, 1014, 846, 823,

1

626, 565, 486, 480. H NMR (300 MHz, CDCl₃): d 8.75

(2H, dd, J = 6.6 Hz, C₅H₄N), 7.57 (2H, d, J = 5.6 Hz,

C₅H₄N), 7.48 (5H, m, C₆H₅), 4.19 (4H, br s, cod-CH),

2.51 (4H, m, cod-CH₂), 1.84 (4H, d, J = 8.0 Hz, cod-

CH₂). ¹³C NMR (75 MHz; solvent CDCl₃): d 151.03

(C₅H₅N), 149.63 (C₅H₅N), 136.59 (C₆H₅), 129.86 (C₆H₅),

129.29 (C₆H₅), 126.97 (C₆H₅), 122.46 (C₅H₅N), 80.05

(cod), 30.88 (cod); FABMS (m/z): 401 (M⁺, 13%), 366

(MꢀCl, 100), 346 (3), 310 (4), 258 (Mꢀcod, 9), 211 (42),

181 (11), 156 (38), 136 (8), 103 (Rh, 5) and 77 (5).

1

759, 740, 704, 491, 414. H NMR (300 MHz, CDCl₃): d

8.81 (2H, d, J = 6.6 Hz, C₅H₄N), 8.57 (1H, s, N@CH),

7.93 (2H, d, J = 6.5 Hz, C₅H₄N), 7.54 (2H, d, J = 8.5 Hz,

C₆H₄), 7.27 (2H, d, J = 8.3 Hz, C₆H₄), 4.68 (2H, t,

J = 1.8 Hz, C₅H₄), 4.36 (2H, t, J = 1.8 Hz, C₅H₄), 4.06

(5H, s, C₅H₅). ¹³C NMR (75 MHz, CDCl₃): d 153.18

(N@C), 152.89 (C₅H₄N), 147.13 (C₆H₄), 145.97 (C₆H₄),

140.34 (C₅H₄N), 126.78 (C₅H₄N), 123.75 (C₆H₄), 121.65

(C₆H₄), 84.01 (C₅H₄), 69.71 (C₅H₅), 69.44 (C₅H₄), 66.54

(C₅H₄). FABMS (m/z): 560 (M⁺, 8%), 525 (MꢀCl, 5), 496

(MꢀCO, 2), 469 (MꢀCO, 2), 367 (MꢀRh, 50), 366

(Mꢀligand, 90), 287 (Mꢀpy, 10).

4.3.2. (1,5-Cyclooctadiene)bis(4-phenylpyridine)rhodium

perchlorate (14b)

A white precipitate was observed to form immediately

on addition of silver perchlorate (66.8 mg, 0.32 mmol) to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(79.7 mg, 0.16 mmol) in acetone (20 mL). 4-Phenylpyridine

(100.1 mg, 0.64 mmol) was then added slowly to the super-

natant, which was stirred at room temperature for a further

20 min. The reaction mixture was then concentrated and

diethyl ether added to precipitate the product. The product

was collected by vacuum ﬁltration as a light yellow powder

(117.2 mg, 59%); Anal. Calc. for C₃₀H₃₀ClN₂O₄Rh: C,

58.0%; H, 4.9; N, 4.5; M⁺521.5. Found: C, 57.85%; H,

4.92; N, 4.12; M⁺521.2. IR (KBr, cm^ꢀ1): 3056, 2872,

2818, 2370, 2324, 1616, 1575, 1544, 1516, 1483, 1418,

1398, 1221, 1095, 841, 766, 733, 696, 623, 565, 481, 437.

¹H NMR (400 MHz, CDCl₃): d 8.88 (4H, d, J = 5.9 Hz,

C₅H₄N), 7.62–7.53 (10H, m, C₆H₅), 7.46 (4H, d,

J = 5.8 Hz, C₅H₄N), 4.14 (4H, br s, cod-CH), 2.69 (4H,

m, cod-CH₂), 1.99 (4H, d, J = 10.3 Hz, cod-CH₂). ¹³C

4.2.3. Dicarbonylchloro(4-ferrocenylpyridine)rhodium (9c)

4-Ferrocenylpyridine (94.9 mg, 0.36 mmol) was added

to a light yellow solution of dichlorotetracarbonyldirho-

dium (70.6 mg, 0.18 mmol) in anhydrous pentane

(10 mL). A red suspension was observed almost immedi-

ately with the supernatant turning to a much lighter,

almost clear colour. The product was isolated via vacuum

ﬁltration as red micro-crystals (113.8 mg, 69%); m.p. 128–

130 ꢁC. Anal. Calc. for C₁₇H₁₃ClFeNO₂Rh: C, 44.6%; H,

2.7; N, 3.1; M 458.9. Found: C, 44.4%; H, 2.6; N, 3.0;

M⁺458.7. IR (KBr, cm^ꢀ1): 3020, 2086 (CO), 2011 (CO),

NMR (101 MHz, CD₃COCD₃):

d 153.85 (C₅H₅N),

1

1615, 1522, 1435, 1382, 1107, 1034, 833, 482. H NMR

136.02 (C₅H₅N), 130.43 (C₅H₅N), 129.77 (C₆H₅), 129.58

(C₆H₅), 127.58 (C₆H₅), 127.28 (C₆H₅), 123.54 (C₅H₅N),

85.15 (cod), 30.54 (cod). FABMS (m/z): 521 (M⁺, 10%),

465 (3), 413 (M⁺ꢀcod, 11), 398 (6), 366 (90), 258 (29),

218 (7), 211 (37), 156 (100), 136 (17), 89 (19).

(300 MHz, CDCl₃): d 8.49 (2H, dd, J = 6.7 Hz, C₅H₄N),

7.39 (2H, dd, J = 6.7 Hz, C₅H₄N), 4.76 (2H, t, C₅H₄),

4.56 (2H, t, C₅H₄), 4.08 (5H, s, C₅H₅). ¹³C NMR

(75 MHz, CDCl₃): d 151.65 (C₅H₄N), 121.66 (C₅H₄N),

71.68 (C₅H₄), 70.36 (C₅H₅), 67.45 (C₅H₄); FABMS (m/z):

459 (M⁺, 8%), 424 (MꢀCl, 8), 389 (4), 367 (Mꢀ2CO, 3),

312 (34), 265 (ligand, 100), 235 (1), 200 (1).

4.3.3. Chloro(1,5-cyclooctadiene)(4-phenylimine-4⁰-

pyridine)rhodium (10f)

4-Phenylimine-4⁰-pyridine (52.4 mg, 0.29 mmol) was

added to a solution of chloro(1,5-cyclooctadiene)rho-

dium(I) dimer (70.6 mg, 0.14 mmol) in dichloromethane

(10 mL). The reaction mixture was stirred for a further

28 min. The reaction mixture was then concentrated in

vacuo and diethyl ether added to precipitate the product.

The product was collected via vacuum ﬁltration as ﬁne

4.3. Rhodium cyclooctadiene complexes

4.3.1. Chloro(1,5-cyclooctadiene)(4-phenylpyridine)-

rhodium (10e)

4-Phenylpyridine (100.8 mg, 0.64 mmol) was added to a

solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

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J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

yellow crystals (85.3 mg, 83%). Anal. Calc. for

C₂₀H₂₂ClN₂Rh: C, 44.6%; H, 2.7; N, 7.4. Found: C,

44.56%; H, 2.69; N, 7.26. IR (KBr, cm^ꢀ1) 3049, 2948,

2873, 2359, 1651, 1608, 1574, 1485, 1191, 1166, 1075,

1480, 1426, 1392, 1371, 1106, 1004, 977, 950, 841, 814,

807, 672, 638, 543, 495, 481, 434. ¹H NMR (300 MHz,

CDCl₃): d 8.84 (2H, d, J = 5.9 Hz, C₅H₄N), 8.48 (1H, s,

N@CH), 7.77 (2H, dd, J = 5.9 Hz, C₅H₄N), 7.51 (2H, dd,

J = 6.7 Hz, C₆H₄), 7.22 (2H, d, J = 8.5 Hz, C₆H₄), 4.66

(2H, t, J = 1.8 Hz, C₅H₄), 4.35 (2H, t, J = 1.8 Hz, C₅H₄),

4.19 (4H, br s, cod-CH), 4.03 (5H, s, C₅H₅), 2.52–2.48

(4H, m, cod-CH₂), 1.85 (4H, d, J = 8.6 Hz, cod-CH₂). ¹³C

NMR (300 MHz, CDCl₃): d 156.02 (N@C), 151.10

(C₅H₄N), 126.83 (C₅H₄N), 124.13 (C₆H₄), 121.55 (C₆H₄),

69.75 (C₅H₅), 69.40 (C₅H₄), 66.58 (C₅H₄), 30.62 (cod).

FABMS (m/z): 612 (M⁺, 1%), 532 (2), 519 (3), 382 (5),

366 (ligand, 100), 305 (26), 289 (41), 277 (41), 229 (9), 176

(27), 89 (22).

1

1055, 961, 818, 668, 481, 459, 406. H NMR (300 MHz,

CDCl₃): d 8.89 (2H, dd, C₅H₄N), 8.47 (1H, s, N@CH),

7.88 (2H, d, J = 6.2 Hz, C₅H₄N), 7.44 (2H, t, C₆H₅), 7.34

(2H, d, J = 7.2 Hz, C₆H₅), 7.26 (1H, t, C₆H₅), 4.21 (4H,

br s, cod-CH), 2.54–2.48 (4H, m, cod-CH₂), 1.82 (4H, d,

J = 8.3 Hz, cod-CH₂). ¹³C NMR (75 MHz, CDCl₃): d

156.85 (N@C), 154.28 (C₅H₄N), 151.89 (C₅H₄N), 144.51

(C₆H₅), 129.38 (C₅H₄N), 127.65 (C₆H₅), 124.24 (C₆H₅),

122.06 (C₆H₅), 85.42 (cod), 30.55 (cod).

4.3.4. (1,5-Cyclooctadiene)bis(4-phenylimine-4⁰-pyridine)-

rhodium perchlorate (14c)

4.3.6. (1,5-Cyclooctadiene)bis(4-pyridylimine-4⁰-

phenylferrocene)rhodium perchlorate (14f)

A white precipitate was observed to form immediately

on addition of silver perchlorate (58.9 mg, 0.28 mmol) to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(70.6 mg, 0.14 mmol) in acetone (15 mL). 4-Phenylimine-

4⁰-pyridine (103.5 mg, 0.57 mmol) was then added slowly

to the supernatant, which was stirred at room temperature

for a further 20 min. The reaction mixture was then con-

centrated and diethyl ether added to precipitate the prod-

uct. The product was collected by vacuum ﬁltration as a

yellow powder (110.9 mg, 59%); m.p. 199 ꢁC dec. Anal.

Calc. for C₃₂H₃₂ClN₄O₄Rh: C, 56.5%; H, 4.8; N, 8.3; M⁺

575.53486. Found: C, 55.98%; H, 4.63; N, 8.06; M⁺

575.1682. IR (KBr, cm^ꢀ1) 3583, 2339, 1770, 1738, 1622,

1610, 1109, 1086, 833, 552, 445. ¹H NMR (300 MHz,

CDCl₃): d 9.01 (4H, d, J = 5.6 Hz, C₅H₄N), 8.39 (2H, s,

N@CH), 7.86 (4H, d, J = 5.5 Hz, C₅H₄N), 7.40 (4H, t,

J = 7.3 Hz, C₆H₅), 7.28 (2H, t, J = 7.3 Hz, C₆H₅), 7.19

(4H, d, J = 8.0 Hz, C₆H₅), 4.15 (4H, br s, cod-CH), 2.71

(4H, m, cod-CH₂), 2.00 (4H, d, J = 8.8 Hz, cod-CH₂).

¹³C NMR (75 MHz; CDCl₃): d 158.21 (N@C), 151.12

(C₅H₄N), 150.89 (C₅H₄N), 143.15 (C₆H₅), 129.35

(C₅H₄N), 127.74 (C₆H₅), 124.24 (C₆H₅), 121.06 (C₆H₅),

85.42 (cod), 30.55 (cod). FABMS (m/z): 575 (M⁺, 10%),

546 (4), 532 (2), 492 (2), 471 (4), 439 (4), 409 (5), 393

(100), 364 (4), 350 (8), 284 (8), 211 (47), 183 (37), 136

(12), 89 (17), 80 (17).

A white precipitate was observed to form immediately

on addition of silver perchlorate (22.6 mg, 0.11 mmol) to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(26.9 mg, 0.05 mmol) in acetone (10 mL). 4-Pyridylimine-

4⁰-phenylferrocene (80.0 mg, 0.22 mmol) was then added

slowly to the supernatant, which was stirred at room tem-

perature for a further 30 min. The reaction mixture was

then concentrated and diethyl ether added to precipitate

the product. The product was collected by vacuum ﬁltra-

tion as a ﬁne dark maroon-red powder (92.8 mg, 81%);

m.p. 265–268 ꢁC dec. Anal. Calc. for C₅₂H₄₈Fe₂N₄Rh-

ClO₄: C, 66.2%; H, 5.1; N, 5.9; M⁺943.2. Found: C,

65.97%; H, 5.12; N, 5.78; M⁺943.2. IR (KBr, cm^ꢀ1):

3076, 3063, 2363, 2322, 2295, 1738, 1684, 1616, 1575,

1541, 1514, 1487, 1432, 1398, 1120, 1100, 1086, 1065,

998, 963, 889, 841, 821, 760, 726, 678, 617, 549, 501, 481,

434. ¹H NMR (400 MHz, CDCl₃): d 8.99 (4H, br s,

C₅H₄N), 8.47 (2H, s, N@CH), 7.87 (4H, d, J = 4.4 Hz,

C₅H₄N), 7.49 (4H, d, J = 8.4 Hz, C₆H₄), 7.19 (4H, d,

J = 8.1 Hz, C₆H₄), 4.67 (4H, br s, C₅H₄), 4.36 (4H, br s,

C₅H₄), 4.16 (4H, br s, cod-CH), 4.05 (10H, s, C₅H₅),

2.81–2.66 (4H, m, cod-CH₂), 2.02 (4H, d, J = 8.8 Hz,

cod-CH₂). ¹³C NMR (101 MHz, CDCl₃):

d 153.95

(N@C), 129.84 (C₅H₄N), 126.94 (C₅H₄N), 124.25 (C₆H₄),

121.66 (C₆H₄), 80.24 (cod), 69.95 (C₅H₅), 69.58 (C₅H₄),

66.75 (C₅H₄), 30.71 (cod). FABMS (m/z): 943 (M⁺, 4%),

577 (Mꢀligand, 93), 366 (ligand, 100).

4.3.5. Chloro(1,5-cyclooctadiene)(4-pyridylimine-4⁰-

phenylferrocene)rhodium (10c)

4-Pyridylimine-4⁰-phenylferrocene (109.0 mg, 0.29 mmol)

was added to a solution of chloro(1,5-cyclooctadiene)rho-

dium(I) dimer (73.4 mg, 0.15 mmol) in dichloromethane

(10 mL). The reaction mixture was stirred for a further

34 min. The reaction mixture was then concentrated in

vacuo and hexane added to precipitate the product. The

product was collected via vacuum ﬁltration as red crystal-

line ﬂakes (134.1 mg, 75%); m.p. 200–202 ꢁC. Anal. Calc.

for C₃₀H₃₀ClFeN₂Rh: C, 58.8%; H, 4.9; N, 4.6; M⁺

612.79361. Found: C, 58.29%; H, 4.59; N, 4.40; M⁺

612.05019. IR (KBr, cm^ꢀ1): 3056, 2954, 2879, 2356, 2329,

2295, 1745, 1731, 1684, 1616, 1609, 1575, 1541, 1514,

4.3.7. Chloro(1,5-cyclooctadiene)(4-ferrocenylpyridine)-

rhodium (10a)

4-Ferrocenylpyridine (74.6 mg, 0.28 mmol) was added

to a solution of chloro(1,5-cyclooctadiene)rhodium(I)

dimer (69.8 mg, 0.14 mmol) in dichloromethane (10 mL).

The reaction mixture was stirred for a further 15 min.

The reaction mixture was then concentrated in vacuo and

pentane added to precipitate the product. The product

was collected via vacuum ﬁltration as an orange solid

(111.7 mg, 78%); m.p. 167–169 ꢁC. Anal. Calc. for

C₂₃H₂₅ClFeNRh: C, 54.2%; H, 4.0; N, 2.7; M⁺509.0.

Found: C, 54.2%; H, 4.6; N, 2.7; M⁺509.0. IR (KBr,

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4585

cm^ꢀ1): 3069, 2872, 2832, 2358, 2331, 1739, 1670, 1615,

1568, 1544, 1516, 1475, 1436, 1398, 1338, 1286, 1106,

1031, 963, 825, 809, 674, 503. ¹H NMR (300 MHz; CDCl₃):

d 8.51 (2H, dd, J = 6.7 Hz, C₅H₄N), 7.27 (2H, dd,

J = 7.3 Hz, C₅H₄N), 4.69 (2H, t, C₅H₄), 4.47 (2H, t,

C₅H₄), 4.19 (4H, br s, cod-CH), 4.04 (5H, s, C₅H₅), 2.53–

2.49 (4H, m, cod-CH₂), 1.84 (4H, d, J = 8.1 Hz, cod-

CH₂). ¹³C NMR (75 MHz, CDCl₃): d 150.28 (C₅H₄N),

121.19 (C₅H₄N), 79.28 (cod-CH), 70.98 (C₅H₄), 70.14

(C₅H₅), 67.15 (C₅H₄), 30.90 (cod-CH₂). FABMS (m/z):

509 (M⁺, 3%), 312 (32), 265 (58), 167 (17), 89 (44).

(4H, br s, cod-CH), 4.08 (5H, s, C₅H₅), 2.51 (4H, m, cod-

CH₂), 1.85 (4H, d, J = 8.0 Hz, cod-CH₂). ¹³C NMR

(101 MHz, CDCl₃): d 148.41 (C₅H₄N), 147.52 (C₅H₄N),

133.89 (C₅H₄N), 124.01 (C₅H₄N), 80.00 (cod), 69.91

(C₅H₄), 69.81 (C₅H₅), 66.70 (C₅H₄), 30.82 (cod). FABMS

(m/z): 509 (M⁺, 3%), 474 (MꢀCl, 41), 365 (M-cod, 4),

350 (6), 310 (18), 263 (ligand, 100), 211 (Mꢀligand, 18),

154 (6), 136 (6).

4.3.10. Chloro(1,5-cyclooctadiene)(2-ferrocenylpyridine)-

rhodium (12a)

2-Ferrocenylpyridine (45.0 mg, 0.17 mmol) was added to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(42.2 mg, 0.08 mmol) in dichloromethane (10 mL). The

reaction mixture was stirred for a further 25 min. The reac-

tion mixture was then concentrated in vacuo and pentane

added to precipitate the product. The product was collected

via vacuum ﬁltration as an orange-brown powder (26.6 mg,

31%); m.p. 123–125 ꢁC. Anal. Calc. for C₂₃H₂₅ClFeNRh:

C, 54.2%; H, 4.9; N, 2.7; M⁺509. Found: C, 54.48%; H,

4.72; N, 2.48; M⁺509. IR (KBr, cm^ꢀ1) 3616, 3584, 2830,

2349, 1798, 1703, 1634, 1615, 1598, 1495, 1422, 1386,

4.3.8. (1,5-Cyclooctadiene)bis(4-ferrocenylpyridine)-

rhodium perchlorate (14d)

A white precipitate was observed to form immediately

on addition of silver perchlorate (43.8 mg, 0.20 mmol) to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(50.4 mg, 0.10 mmol) in acetone (15 mL). 4-Ferrocenyl-

pyridine (106.1 mg, 0.40 mmol) was then added slowly to

the supernatant, which was stirred at room temperature

for a further 21 min. The reaction mixture was then con-

centrated and diethyl ether added to precipitate the prod-

uct. The product was collected by vacuum ﬁltration as

small red-brown crystalline ﬂakes (162.2 mg, 96%); m.p.

225 ꢁC dec. Anal. Calc. for C₃₈H₃₈Fe₂N₂RhClO₄: C,

54.5%; H, 4.6; N, 3.3; M⁺737.0. Found: C, 54.2%; H,

4.6; N, 3.1; M⁺737.1. IR (KBr, cm^ꢀ1): 3069, 2349, 2322,

1684, 1616, 1608, 1575, 1544, 1516, 1429, 1397, 1340,

1217, 1122, 832, 686, 677, 622, 538, 481, 472, 418. ¹H

NMR (300 MHz, CDCl₃): d 8.60 (4H, d, J = 6.2 Hz,

C₅H₄N), 7.36 (4H, d, J = 6.4 Hz, C₅H₄N), 4.68 (4H, br s,

C₅H₄), 4.45 (4H, br s, C₅H₄), 4.12 (4H, br s, cod-CH),

3.98 (10H, s, C₅H₅), 2.75–2.68 (4H, m, cod-CH₂), 1.98

(4H, d, J = 8.8 Hz, cod-CH₂). ¹³C NMR (75 MHz,

CDCl₃): d 151.78 (C₅H₄N), 122.55 (C₅H₄N), 77.82 (cod-

CH), 70.52 (C₅H₅), 70.04 (C₅H₄), 67.36 (C₅H₄), 30.62

(cod-CH₂). FABMS (m/z): 737 (M⁺, 10%), 476 (30), 312

(19), 265 (97), 155 (67), 137 (56), 89 (20).

1

1105, 817, 457, 408. H NMR (400 MHz, CDCl₃): d 8.50

(1H, d, J = 4.8 Hz, C₅H₄N), 7.57 (1H, t, J = 7.7 Hz,

C₅H₄N), 7.41 (1H, d, J = 8.1 Hz, C₅H₄N), 7.06 (1H, t,

J = 4.8 Hz, C₅H₄N), 4.92 (2H, t, J = 1.8 Hz, C₅H₄), 4.39

(2H, t, J = 1.8 Hz, C₅H₄), 4.23 (4H, s, cod-CH), 4.05 (5H,

s, C₅H₅), 2.49 (4H, m, cod-CH₂), 1.74 (4H, d, J = 8.4 Hz,

cod-CH₂). ¹³C NMR (101 MHz, CDCl₃):

d 149.25

(C₅H₄N), 145.18 (C₅H₄N), 136.51 (C₅H₄N), 120.36

(C₅H₄N), 120.04 (C₅H₄N), 78.66 (cod), 69.78 (C₅H₄),

68.48 (C₅H₅), 67.16 (C₅H₄), 30.79 (cod). FABMS (m/z):

510 (M, 9%), 509 (M⁺, 1), 473 (M⁺-Cl), 365 (Mꢀcod, 13),

303 (7), 263 (2-Fcpy, 2), 185 (100), 115 (20).

4.3.11. Chloro(1,5-cyclooctadiene)(4-ferrocenylphenyl-4⁰-

pyridine)rhodium (10b)

4-Ferrocenylphenyl-4⁰-pyridine (50.0 mg, 0.15 mmol)

was added to a solution of chloro(1,5-cyclooctadiene)rho-

dium(I) dimer (36.3 mg, 0.07 mmol) in dichloromethane

(7 mL). The reaction mixture was stirred for a further

20 min. The reaction mixture was then concentrated in

vacuo and diethyl ether added to precipitate the product.

The product was collected via vacuum ﬁltration as a dark

red powder (59.9 mg, 70%); m.p. 213 ꢁC dec. Anal. Calc.

for C₂₉H₂₉ClFeNRh: C, 59.4%, H, 5.0, N, 2.4; M⁺585.

Found: C, 59.62%; H, 5.12; N, 2.48; M⁺585. IR (KBr,

cm^ꢀ1): 3069, 2356, 2322, 2295, 1682, 1616, 1593, 1569,

1544, 1516, 1489, 1432, 1398, 1338, 1283, 1222, 1106,

1079, 1032, 998, 964, 814, 719, 698, 644, 597, 502, 475,

441. ¹H NMR (300 MHz, CDCl₃): d 8.72 (2H, dd,

J = 6.6 Hz, C₅H₄N), 7.59–7.50 (6H, m, C₆H₄and

C₅H₄N), 4.68 (2H, t, J = 1.8 Hz, C₅H₄), 4.37 (2H, t,

J = 1.8 Hz, C₅H₄), 4.18 (4H, br s, cod-CH), 4.05 (5H, s,

C₅H₅), 2.54–2.49 (4H, m, cod-CH₂), 1.84 (4H, d,

J = 7.9 Hz, cod-CH₂). ¹³C NMR (75 MHz, CDCl₃): d

150.97 (C₅H₄N), 149.25 (C₅H₄N), 142.02 (C₆H₄), 133.56

4.3.9. Chloro(1,5-cyclooctadiene)(3-ferrocenylpyridine)-

rhodium (11a)

3-Ferrocenylpyridine (78.3 mg, 0.30 mmol) was added

to a solution of chloro(1,5-cyclooctadiene)rhodium(I)

dimer (73.4 mg, 0.15 mmol) in dichloromethane (15 mL).

The reaction mixture was stirred for a further 35 min.

The reaction mixture was then concentrated in vacuo and

pentane added to precipitate the product. The product

was collected via vacuum ﬁltration as golden yellow micro-

crystals (134.5 mg, 88%); m.p. 162–164 ꢁC. Anal. Calc. for

C₂₃H₂₅ClFeNRh: C, 54.2%; H, 4.9; N, 2.7; M⁺509.65806.

Found: C, 54.20%; H, 4.76; N, 2.68; M⁺509.00799. IR

(KBr, cm^ꢀ1) 3616, 3584, 2830, 2349, 1798, 1703, 1634,

1615, 1422, 1105, 814, 667, 439, 408. ¹H NMR

(400 MHz, CDCl₃): d 8.80 (1H, br s, C₅H₄N), 8.52 (1H,

dd, J = 6.6 Hz, C₅H₄N), 7.70 (1H, dt, J = 8.1 Hz,

C₅H₄N), 7.18 (1H, dd, J = 5.5 Hz, C₅H₄N), 4.66 (2H, t,

J = 1.8 Hz, C₅H₄), 4.40 (2H, t, J = 1.8 Hz, C₅H₄), 4.22

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J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

(C₆H₄), 126.92 (C₆H₄), 126.73 (C₆H₄), 121.89 (C₅H₄N),

83.65 (cod-CH), 69.73 (C₅H₅), 69.55 (C₅H₄), 66.66

(C₅H₄), 30.90 (cod-CH₂). FABMS (m/z): 585 (M⁺, 1%),

574 (23), 387 (4-Fc(C₆H₄)py, 3), 339 (3), 273 (2), 241

(24), 185 (100), 115 (10).

¹³C NMR (101 MHz, CDCl₃): d 147.45 (C₅H₄N), 147.26

(C₅H₄N), 133.25 (C₅H₄N), 125.50 (C₆H₄), 125.15 (C₆H₄),

122.77 (C₅H₄N), 82.26 (cod), 68.11 (C₅H₅), 67.74 (C₅H₄),

65.00 (C₅H₄), 29.25 (cod). FABMS (m/z): 585 (M⁺, 1%),

550 (MꢀCl, 28), 386 (21), 339 (3-Fc(C₆H₄)py, 100), 274

(6), 238 (50), 211 (17).

4.3.12. (1,5-Cyclooctadiene)bis(4-ferrocenylphenyl-4⁰-

pyridine)rhodium perchlorate (14e)

4.3.14. Chloro(1,5-cyclooctadiene)(4-ferrocenylphenyl-2⁰-

pyridine)rhodium (12b)

A white precipitate was observed to form immediately

on addition of silver perchlorate (42.0 mg, 0.20 mmol) to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(50.0 mg, 0.10 mmol) in acetone (15 mL). 4-Ferrocenylphe-

nyl-4⁰-pyridine (106.1 mg, 0.40 mmol) was then added

slowly to the supernatant, which was stirred at room tem-

perature for a further 46 min. The reaction mixture was

then concentrated and diethyl ether added to precipitate

the product. The product was collected by vacuum ﬁltra-

tion as small dark red crystals (164.6 mg, 83%); m.p.

110–112 ꢁC. Anal. Calc. for C₅₀H₄₆ClFe₂N₂O₄Rh: C,

60.7%; H, 4.7; N, 2.8; M⁺988. Found: C, 60.32%; H,

4.72; N, 2.59; M⁺988. IR (KBr, cm^ꢀ1): 3069, 2879, 2832,

2356, 2322, 2023, 1772, 1616, 1602, 1589, 1541, 1487,

1432, 1405, 1283, 1215, 1120, 1100, 1004, 889, 814, 760,

4-Ferrocenylphenyl-2⁰-pyridine (60.0 mg, 0.18 mmol)

was added to a solution of chloro(1,5-cyclooctadiene)rho-

dium(I) dimer (43.6 mg, 0.09 mmol) in dichloromethane

(10 mL). The reaction mixture was stirred for a further

31 min. The reaction mixture was then concentrated in

vacuo and diethyl ether added to precipitate the product.

The product was collected via vacuum ﬁltration as an

orange powder (42.6 mg, 40%); m.p. 90–92 ꢁC. Anal. Calc.

for C₂₉H₂₉ClFeNRh: C, 59.5%; H, 5.0; N, 2.4; M⁺585.

Found: C, 59.42%; H, 5.12; N, 2.32; M⁺585. IR (KBr,

cm^ꢀ1) 3629, 3568, 2323, 1740, 1700, 1646, 1336, 1607,

1

1474, 783, 500, 409. H NMR (400 MHz, CDCl₃): d 8.69

(1H, dd, J = 4.8 Hz, C₅H₄N), 7.93 (2H, dd, J = 8.4 Hz,

C₆H₄), 7.74 (2H, dd, J = 6.2 Hz, C₅H₄N), 7.57 (2H, dd,

J = 8.8 Hz, C₆H₄), 7.21 (1H, dd, J = 6.6 Hz, C₅H₄N),

4.74 (2H, t, J = 1.8 Hz, C₅H₄), 4.23 (2H, t, J = 2.2 Hz,

C₅H₄), 4.11 (4H, s, cod-CH), 4.05 (5H, s, C₅H₅), 2.51

(4H, m, cod-CH₂), 1.84 (4H, d, J = 8.2 Hz, cod-CH₂).

¹³C NMR (101 MHz, CDCl₃): d 149.60 (C₅H₄N), 136.58

(C₅H₄N), 126.25 (C₆H₄), 126.77 (C₆H₄), 121.70 (C₅H₄N),

120.05 (C₅H₄N), 78.67 (cod), 69.63 (C₅H₅), 69.12 (C₅H₄),

66.49 (C₅H₄), 30.79 (cod). FABMS (m/z): 585 (M⁺, 1%),

548 (MꢀCl, 3), 388 (2-Fc(C₆H₄)py, 60), 340 (60), 274

(10), 238 (3), 115 (10).

1

726, 624, 509, 481, 475, 447. H NMR (300 MHz, CDCl₃):

d 8.85 (4H, d, J = 5.0 Hz, C₅H₄N), 7.87–7.34 (12H, m,

C₆H₄and C₅H₄N), 4.80 (4H, br s, C₅H₄), 4.50 (4H, br s,

C₅H₄), 4.31 (4H, br s, cod-CH), 4.14 (10H, s, C₅H₅),

2.89–2.56 (4H, m, cod-CH₂), 2.00 (4H, d, J = 8.4 Hz,

cod-CH₂). ¹³C NMR (75 MHz, CDCl₃):

d 150.50

(C₅H₄N), 142.47 (C₅H₄N), 126.87 (C₆H₄), 126.68 (C₆H₄),

122.88 (C₅H₄N), 84.89 (cod-CH), 70.83 (C₅H₅), 70.56

(C₅H₄), 67.40 (C₅H₄), 30.62 (cod-CH₂). FABMS (m/z):

988 (M⁺, 10%), 851 (3), 639 (7), 559 (11), 474 (9), 375

(58), 338 (4-Fc(C₆H₄)py, 7), 277 (100), 258 (20), 186

(100), 115 (33).

4.3.15. [1,1⁰-Bis(2-pyridyl)ferrocene](1,5-cyclooctadiene)-

rhodium perchlorate (15a)

4.3.13. Chloro(1,5-cyclooctadiene)(4-ferrocenylphenyl-3⁰-

pyridine)rhodium (11b)

A white precipitate was observed to form immediately

on addition of silver perchlorate (48.7 mg, 0.24 mmol) to

a solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(58.0 mg, 0.12 mmol) in acetone (15 mL). 1,1⁰-Bis(2-pyr-

idyl)ferrocene (80.0 mg, 0.24 mmol) was added to the

supernatant, which was stirred at room temperature for a

further 35 min. The reaction mixture was then concen-

trated and pentane added to precipitate the product. The

product was collected by vacuum ﬁltration as small dark

red crystals (92.6 mg, 70%); m.p. 148–150 ꢁC. Anal. Calc.

for C₂₈H₂₈ClFeN₂O₄Rh: C, 59.5%; H, 5.0; N, 2.4; M⁺

551.28874. Found: C, 59.62%; H, 4.89; N, 2.21; M⁺

551.06569. IR (KBr, cm^ꢀ1) 1596, 1555, 1494, 1419, 1283,

1120, 1086, 889, 814, 780, 746, 692, 624, 522, 447, 420;

¹H NMR (400 MHz, CDCl₃): d 8.35 (2H, d, J = 5.3 Hz,

C₅H₄N), 7.67 (2H, t, J = 7.8 Hz, C₅H₄N), 7.50 (2H, dd,

J = 6.7 Hz, C₅H₄N), 7.08 (2H, dd, J = 11.6 Hz, C₅H₄N),

4.91 (4H, t, J = 1.8 Hz, C₅H₄), 4.50 (4H, s, cod-CH),

4.36 (4H, t, J = 1.8 Hz, C₅H₄), 2.81 (cod-CH₂), 2.00 (4H,

br s, cod-CH₂). ¹³C NMR (75 MHz, CDCl₃): d 156.97

(C₅H₄N), 136.51 (C₅H₄N), 131.90 (C₅H₄N), 128.39

4-Ferrocenylphenyl-3⁰-pyridine (70.0 mg, 0.21 mmol)

was added to a solution of chloro(1,5-cyclooctadiene)rho-

dium(I) dimer (50.9 mg, 0.10 mmol) in dichloromethane

(10 mL). The reaction mixture was stirred for a further

31 min. The reaction mixture was then concentrated in

vacuo and diethyl ether added to precipitate the product.

The product was collected via vacuum ﬁltration as an

orange-mustard powder (84.6 mg, 69%); m.p. 215–217 ꢁC.

Anal. Calc. for C₂₉H₂₉ClFeNRh: C, 59.5%; H, 5.0; N,

2.4; M⁺585. Found: C, 59.59%; H, 5.00; N, 2.32; M⁺

585.0. IR (KBr, cm^ꢀ1) 3689, 3671, 2832, 1612, 1395,

1104, 803, 700, 531, 442, 430, 406, 404. ¹H NMR

(400 MHz, CDCl₃): d 8.98 (1H, br s, C₅H₄N), 8.68 (1H,

dd, J = 6.6 Hz, C₅H₄N), 7.88 (1H, dt, J = 7.3 Hz,

C₅H₄N), 7.58 (2H, d, J = 8.4 Hz, C₆H₄), 7.49 (2H, d,

J = 8.4 Hz, C₆H₄), 7.37 (1H, dd, J = 5.9 Hz, C₅H₄N),

4.69 (2H, t, J = 1.8 Hz, C₅H₄), 4.37 (2H, t, J = 1.8 Hz,

C₅H₄), 4.22 (4H, br s, cod-CH), 4.07 (5H, s, C₅H₅), 2.52

(4H, m, cod-CH₂), 1.86 (4H, d, J = 8.1 Hz, cod-CH₂).

J. Rajput et al. / Journal of Organometallic Chemistry 691 (2006) 4573–4588

4587

(C₅H₄N), 120.30 (C₅H₄N), 75.21 (cod), 71.48 (C₅H₄), 68.73

(C₅H₄), 30.02 (cod). FABMS (m/z): 551 (M⁺, 14%), 443

(M⁺-cod, 17), 387 (7), 341 (Fc(2-py)₂, 11), 258 (23), 189

(19), 154 (37), 115 (58), 89 (100).

(55.8 mg, 0.11 mmol) in dichloromethane (10 mL). The

reaction mixture was stirred for a further 50 min. The reac-

tion mixture was then concentrated in vacuo and pentane

added to precipitate the product. The product was col-

lected via vacuum ﬁltration as a light yellow powder

(86.3 mg, 67%); m.p. 89–128 ꢁC (lit. 85–130 ꢁC). ¹H

NMR (400 MHz, CDCl₃): d 8.60 (2H, d, J = 6.6 Hz,

C₅H₄N), 7.45 (2H, d, J = 8.4 Hz, C₆H₄), 7.30 (2H, d,

J = 6.6 Hz, C₅H₄N), 7.26 (1H, d, J = 16.1 Hz, CH@CH),

6.90 (2H, d, J = 8.8 Hz, C₆H₄), 6.78 (1H, d, J = 16.1 Hz,

CH@CH), 4.22 (4H, br s, cod-CH), 3.98 (2H, t,

J = 6.6 Hz, OCH₂), 2.50 (4H, m, cod-CH₂), 1.83 (4H, d,

J = 7.7 Hz, cod-CH₂), 1.42 (2H, m, CH₂), 1.29 (10H, m,

CH₂· 5), 0.89 (3H, m, CH₃). ¹³C NMR (101 MHz,

CDCl₃): d 149.10 (C₅H₄N), 133.41 (C@C), 127.12 (C₆H₄),

120.42 (C@C), 119.72 (C₆H₄), 113.34 (C₅H₄N), 66.59

(cod), 30.17 (cod), 29.28 (OCH₂), 27.70 (CH₂· 5), 21.01

(CH₂), 12.43 (CH₃).

4.3.16. [1,1⁰-Bis(4-pyridyl)ferrocene](1,5-cyclooctadiene)-

rhodium perchlorate (15b)

A white precipitate was observed to form immediately on

addition of silver perchlorate (60.9 mg, 0.29 mmol) to a

solution of chloro(1,5-cyclooctadiene)rhodium(I) dimer

(72.5 mg, 0.15 mmol) in ethanol (15 mL). 1,1⁰-Bis(4-pyr-

idyl)ferrocene (100.0 mg, 0.29 mmol) was added to the

supernatant, which was stirred at room temperature for a

further 40 min. The reaction mixture was then concentrated

and pentane added to precipitate the product. The product

was collected by vacuum ﬁltration as small dark red crystals

(107.1 mg, 67%); m.p. 208–210 ꢁC dec. Anal. Calc. for

C₂₈H₂₈ClFeN₂O₄Rh: C, 59.5%; H, 5.0; N, 2.4; M⁺551.

Found: C, 59.32%; H, 4.86; N, 2.32; M⁺551. IR (KBr,

cm^ꢀ1) 3504, 3436, 3361, 2363, 1650, 1595, 1426, 1113,

5. Supplementary material

1

1086, 841, 692, 617, 543. H NMR (400 MHz, CDCl₃): d

8.52 (4H, d, J = 5.8 Hz, C₅H₄N), 7.16 (4H, d, J = 5.6 Hz,

C₅H₄N), 4.85 (4H, t, J = 1.8 Hz, C₅H₄), 4.52 (4H, t,

J = 1.8 Hz, C₅H₄), 4.39 (4H, s, cod-CH), 2.89 (4H, m,

cod-CH₂), 1.98 (4H, br s, cod-CH₂). ¹³C NMR (101 MHz,

CDCl₃): d 149.69 (C₅H₄N), 120.18 (C₅H₄N), 75.18 (cod),

72.24 (C₅H₄), 68.45 (C₅H₄), 30.21 (cod). FABMS (m/z):

551 (M⁺, 7%), 442 (1), 387 (1), 342 (Fc(4-py)₂, 3), 279

(100), 258 (3), 223 (3), 207 (5), 185 (100), 115 (10).

Crystallographic data for the structural analyses have

been deposited with the Cambridge Crystallographic Data

Centre, CCDC No. 296884 for compound 9e, CCDC

No. 296885 for compound 11a and CCDC No. 296886

for compound 11b. Copies of this information may be

obtained free of charge from The Director, CCDC, 12

Union Road, Cambridge CB2 1EC, UK (fax: +44 1223

336 033; e-mail: deposit@ccdc.cam.ac.uk or www: http://

www.ccdc.cam.ac.uk).

4.3.17. Chloro(1,5-cyclooctadiene)(1⁰,2⁰,3⁰,4⁰,5⁰-

pentamethylazaferrocene)rhodium (13)

Acknowledgments

1⁰,2⁰,3⁰,4⁰,5⁰-Pentamethylazaferrocene (70.0 mg, 0.27

mmol) was added to a solution of chloro(1,5-cyclooctadi-

ene)rhodium(I) dimer (67.1 mg, 0.14 mmol) in dichloro-

methane (10 mL). The reaction mixture was stirred for a

further 37 min. The reaction mixture was then concen-

trated in vacuo and pentane added to precipitate the prod-

uct. The product was collected via vacuum ﬁltration as an

orange powder (47.3 mg, 67%); m.p. 192–193 ꢁC. Anal.

Calc. for C₂₂H₃₁ClFeNRh: C, 52.4%; H, 6.2; N, 2.8; M⁺

504.75. Found: C, 52.12%; H, 5.98; N, 2.65; M⁺505. IR

(KBr, cm^ꢀ1) 2907, 2872, 2832, 1738, 1704, 1650, 1575,

1473, 1446, 1371, 1324, 1113, 1066, 1018, 943, 869, 814,

767, 468. ¹H NMR (400 MHz, CDCl₃): d 5.33 (2H, s,

C₄H₄N), 4.53 (2H, s, C₄H₄N), 4.16 (2H, s, cod-CH), 3.81

(2H, s, cod-CH), 2.41 (4H, s, cod-CH₂), 2.08 (15H, s,

CH₃), 1.75 (4H, s, cod-CH₂). ¹³C NMR (101 MHz,

CDCl₃): d 88.96 (C₅Me₅), 82.64 (C₄H₄N), 75.38 (cod),

74.21 (C₄H₄N), 31.04 (cod), 30.45 (cod), 11.50 (CH₃).

FABMS (m/z): 505 (M⁺, 10%), 466 (2), 402 (2), 341 (3),

290 (4), 258 (100), 244 (8). 226 (4), 207 (7).

Mr. Harold Marchand (UPE/NMMU) and Dr. Phil

Boshoﬀ (formerly of the Cape Technikon) are gratefully

acknowledged for their technical expertise. The project

was funded by the National Research Foundation (NRF)

(Pretoria), the University of Port Elizabeth (UPE) and

the University of Cape Town (UCT).

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Article Doi

Ferrocenyl-nitrogen donor ligands. Synthesis and characterization of rhodium(I) complexes of ferrocenylpyridine and related ligands

DOI: 10.1016/j.jorganchem.2006.05.048

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