Branching the electron-reservoir complex [Fe(η5-C 5H5)(η6-C6Me6)] [PF6] onto large dendrimers: "click", amide, and ionic bonds

DOI: 10.1021/ic100797x

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Inorganic Chemistry p. 6085 - 6101 (2010)

Update date:2022-08-04

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Authors:

Djeda, Rodrigue

Ornelas, Catia

Ruiz, Jaime

Astruc, Didier

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Article abstract of DOI:10.1021/ic100797x

Several strategies have been used to functionalize 1,3,5-trisubstituted arene-cored dendrimers with the organometallic electron-reservoir moiety [Fe(η⁵-C₅H₅)(η⁶-C ₆Me₆)]⁺, 1, to provide dendritic multielectron reservoirs. They all start from the carboxylic acid [Fe(η⁵-C ₅H₄COOH)(η⁶-C₆Me ₆)][PF₆], 2, or its acyl chloride derivative [Fe(η⁵-C₅H₄COCl)(η⁶-C ₆Me₆)][PF₆], 3. For this purpose, a series of new polyamine dendrimers from G₀ to G₂ with 1→ 3 C connectivity of the branching to the core have been synthesized. Amide, "click" and ionic ammonium carboxylate linkage successfully provided G₀, G₁, and G₂ metallodendrimers with 9, 27, and 81 cationic terminal organoiron groups respectively. Further construction of large metallodendrimers up to G₇ with approximately 14 000 organoiron termini was only possible by combining amide, "click", and tether lengthening strategies to avoid steric bulk at the dendrimer periphery. Reduction of the 18-electron Fe^II metallodendrimers, exemplified by a G₄-DAB-64-Fe^II complex, was achieved exergonically using the parent electron-reservoir complex [Fe(η⁵-C₅H ₅)(η⁶-C₆Me₆)], 1a, at ?30 °C in MeCN, which allowed further reduction of 64 equiv of C₆₀ to C₆₀^·? using the 19-electron Fe^I metallodendrimer.

Full text of DOI:10.1021/ic100797x

Inorg. Chem. 2010, 49, 6085–6101 6085

DOI: 10.1021/ic100797x

Branching the Electron-Reservoir Complex [Fe(η⁵-C₅H₅)(η⁶-C₆Me₆)][PF₆] onto

Large Dendrimers: “Click”, Amide, and Ionic Bonds

ꢀ

Rodrigue Djeda, Catia Ornelas, Jaime Ruiz, and Didier Astruc*

ꢀ

Institut des Sciences Moleculaires, UMR CNRS N°5255, Universite Bordeaux 1, 33405 Talence Cedex, France

Received April 23, 2010

Several strategies have been used to functionalize 1,3,5-trisubstituted arene-cored dendrimers with the organometallic

electron-reservoir moiety [Fe(η⁵-C₅H₅)(η⁶-C₆Me₆)]^þ, 1, to provide dendritic multielectron reservoirs. They all start

from the carboxylic acid [Fe(η⁵-C₅H₄COOH)(η⁶-C₆Me₆)][PF₆], 2, or its acyl chloride derivative [Fe(η⁵-C₅H₄COCl)-

(η⁶-C₆Me₆)][PF₆], 3. For this purpose, a series of new polyamine dendrimers from G₀to G₂with 1f 3 C connectivity of

the branching to the core have been synthesized. Amide, “click” and ionic ammonium carboxylate linkage successfully

provided G₀, G₁, and G₂metallodendrimers with 9, 27, and 81 cationic terminal organoiron groups respectively. Further

construction of large metallodendrimers up to G₇with approximately 14 000 organoiron termini was only possible by

combining amide, “click”, and tether lengthening strategies to avoid steric bulk at the dendrimer periphery. Reduction of

the 18-electron Fe^IImetallodendrimers, exemplified by a G₄-DAB-64-Fe^IIcomplex, was achieved exergonically using

the parent electron-reservoir complex [Fe(η⁵-C₅H₅)(η⁶-C₆Me₆)], 1a, at -30 °C in MeCN, which allowed further

reduction of 64 equiv of C₆₀to C₆₀^•-using the 19-electron Fe^Imetallodendrimer.

Introduction

redox scale,^2,3but some of them stand at very negative or very

positive potentials. The reduced form of the former category

serve as electron-reservoir systems (strong reductants),

whereas the oxidized form of the later category serve as

reservoirs of electron holes (strong oxidants).²The mixed-

sandwich complexes [Fe(η⁵-C₅H₅)(η⁶-C₆Me₆)]^nþ, (1 for n =

1, 1a for n = 0), have the property to serve as either electron

reservoirs for the redox couple involving n = 1/0⁹or

reservoirs of electron holes for n = 2/1.¹⁰Indeed, the family

of 18-electron complexes [Fe(η⁵-C₅H₅)(η⁶-arene)]^þis very

large because of the reactivity of the coordinated arene that is

activated by the cationic 12-electron group CpFe^þ.¹¹A key

Transition-metal sandwich complexes, the prototype of

which is ferrocene, are well-known for their ability to contain

flexible numbers of valence electrons on the metal center,

unlike the other families of organometallic complexes.^1,2This

property is particularly marked for the late first-row transi-

tion-metal sandwich complexes because of the stereoelectro-

nic properties of the delocalized π-cyclic ring ligands.^1,2As

a result, these complexes have rich redox properties that

find applications as stoichiometric redox reagents,³redox

catalysts,⁴electron-transfer-chain catalysts,⁵redox sensors,⁶

electrochemical references,⁷and anticancer drugs.⁸The var-

ious redox potentials of these compounds span over the entire

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*To whom correspondence should be addressed. E-mail: d.astruc@

ism.u-bordeaux1.fr.

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2010 American Chemical Society

Published on Web 06/02/2010

pubs.acs.org/IC

6086 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

property of this series of complexes was found in the electron-

reservoir properties of the 19-electron neutral Fe^Icomplexes

[Fe(η⁵-C₅H₅)(η⁶-arene)] that are only useful if the arene

ligand is peralkylated, in particular with hexamethyl-

benzene.¹²A carboxylic acid derivative of [Fe(η⁵-C₅H₅)(η⁶-

C₆Me₆)] could be obtained upon carrying out ligand ex-

change of the unsubstituted cyclopentadienyl ring of ferro-

cenecarboxylic acid by hexamethylbenzene in the presence of

CO₂and aluminum chloride. The resulting complex [Fe(η⁵-

C₅H₄-COOH)(η⁶-C₆Me₆)][PF₆], 2, allowed further functio-

nalization of the stable electron-reservoir complexes through

reaction of its acyl chloride derivative [Fe(η⁵-C₅H₄COCl)(η⁶-

C₆Me₆)][PF₆], 3 with amines, alcohols, and thiols.¹³

Metallodendrimers have a very rich chemistry that has

been largely reviewed.^14,15Our group have been interested in

studying the redox properties of different types of metallo-

dendrimers, including giant ferrocenyl¹⁶and cobaltocenyl¹⁷

dendrimers. However, our efforts to attach the [Fe(η⁵-

C₅H₅)(η⁶-C₆Me₆)][PF₆] complex to the periphery of dendri-

mers have been marred by insolubility problems, as shown in

a previous communication.¹⁸Branching of iron-sandwich

complexes in which the arene ligand was not fully permethy-

lated was also reported to be easier, but without hope to form

stable Fe^Icomplexes.¹⁹The inclusion of [Fe(η⁵-C₅H₅)-

(η⁶-C₆Me₆)]^þinto dendrimers was a high synthetic chall-

enge because of the combination of the positive charge and

large bulk and rigidity of the arene in the mixed-sandwich

complex.

We now report several synthetic strategies used to attach

[Fe(η⁵-C₅H₄R)(η⁶-C₆Me₆)]^þmoieties onto periphery of the

dendrimers. New amino-terminated dendrimers were syn-

thesized and used to provide amide links and ionic bond-

ing, upon reactions with the organometallic acyl chloride 3

and carboxylic acid 2 respectively with up to 81 termini.

Tether lengthening of polyallyl dendrimers to form long-

arm azido-terminated dendrimers allowed the synthesis of

giant metallodendrimers by “click” chemistry with pro-

pargylated organoiron groups. Only the later bond-length-

ening route allows avoiding the bulk problems for these

metallodendrimer syntheses above the second genera-

tion (G₂), up to G₇with a theoretical number of 19683

termini.

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Results and Discussion

1. Synthesis of the Dendrimer Series. Our synthetic

strategy to build our series of dendrimers follows the

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(CH₃)₂CH₂Cl and the Karstedt catalyst, regioselectively

gives the nona-chloromethyl(dimethyl)silyl derivative, 5.

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Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6087

Scheme 1. Synthesis of the Nona-Allyl Core 4, Phenoltriallyl Dendron 6, and G₁-27-allyl 7

Scheme 2. Construction of the Series of Allyl Dendrimers^a

^aThe syntheses of the G_n-3^nþ2-allyl (n = 0-7) dendrimers follows the iteration reactions shown in Scheme 1: hydrosilylation reaction and Williamson

reaction using the phenoltriallyl dendron.²³

dendron 6,²²afforded the first-generation (G₁) dendrimer

containing 27 allyl termini, 7 (Scheme 1).²³

Repetition of the sequence of reactions (iteration)

involving hydrosilylation of the allyl dendrimers followed

by coupling with the phenoltriallyl dendron 6, until G₉,

afforded the series of giant pentane-soluble allyl-termi-

nated dendrimers (Scheme 2).²³

2. Functionalization of the Organic Dendrimers with the

Organoiron Cation [Fe(η⁵-C₅H₅)(η⁶-C₆Me₆)]^þ. 2.1. New

Dendritic Amines and Branching the Organoiron Cation with

Amide and Ionic Linkage, up to 81 Termini. 2.1.1. Synthe-

sis of New Polyamine Dendrimers. Amine-terminated den-

drimers were synthesized from the chloromethyl-terminated

dendrimers in two steps: (i) nucleophilic substitution of the

terminal chloride by azide using NaN₃, affording the poly-

azide dendrimers;²⁴(ii) reduction of the azide termini using

either PPh₃/H₂O or LiAlH₄. Both reductants give quantita-

tive yields, but the use of LiAlH₄is preferred to avoid the

difficult separation of the amine dendrimers from PPh₃

and O=PPh₃(this later species resulting from reduction of

the azide groups with PPh₃/H₂O). This synthesis was carried

out for G_n-3^nþ2-NH₂(n = 0-2), providing polyamine

dendrimers that contain respectively 9 (G₀-9-NH₂, 14), 27

(G₁-27-NH₂, 15), and 81 (G₂-81-NH₂, 16) terminal pri-

mary amine groups (Chart 1). The nona-amine 14 is soluble

in water, unlike 15 and 16, and the three polyamine den-

drimers are soluble in ether, dichloromethane, and chloro-

form.

Polyamine dendrimers have important applications as

largely known with poly(amidoamine) (PAMAM), poly-

(propylene imine) (PPI), and melanine dendrimers.^14a-d,25

2.1.2. Attachment of the Complex [Fe(η⁵-C₅H₄CO₂H)-

(η⁶-C₆Me₆)][PF₆] to Amine Dendrimers through Covalent

Amide Linkages. It was found that the reaction between

the acid derivative 2 and amine groups gave optimal

yields when the acyl chloride derivative 3 ([Fe(η⁵-C₅H₄-

COCl)(η⁶-C₆Me₆)][PF₆]) was freshly prepared by reflux-

ing 2 overnight in thionyl chloride, and then added to a

dichloromethane solution of the amine compound in

presence of triethylamine.^13,18Reactions of propylamine

(17) and the polyamine dendrimers 14 and 15 with the acyl

chloride 3 yielded the monomeric compound [Fe(η⁵-

C₅H₄CONHPr)(η⁶-C₆Me₆)][PF₆], 18 and the dendritic

complexes G₀-9-[Fe(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)]-

[PF₆], 19, and G₁-27-[Fe(η⁵-C₅H₄CONH-dendr)(η⁶-

C₆Me₆)][PF₆], 20 as orange powders (eq 1 and Chart 2).

The dendritic complexes are soluble in dichloromethane,

acetonitrile, and dimethylformamide, but not in ether nor

water.

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(25) (a) Tomalia, D. A.; Baker, H.; Dewald, J.; Hall, M.; Kallos, G.;

Martin, S.; Roeck, J.; Ryder, J.; Smith, P. Polym. J. 1985, 17, 117–132. (b)

de Brabander-van den Berg, E. M. M.; Meijer, E. W. Angew. Chem., Int. Ed.

Engl. 1993, 32, 1308–1312. (c) Chen, H. T.; Neerman, M. F.; Parrish, A. R.;

Simanek, E. E. J. Am. Chem. Soc. 2004, 126, 10044–10048.

6088 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

Chart 1. Three Generations G₀-G₂of Amine-Terminated Dendrimers

For comparison, we also carried out the reaction bet-

ween the commercially available diaminobutane (DAB)

dendrimer G₄-DAB-64-NH₂, 21, and 3 in MeCN/CH₂Cl₂

(2:1) in the presence of triethylamine, yielding the den-

dritic complex G₄-DAB-64-[(η⁵-C₅H₄CONH-dendr)(η⁶-

C₆Me₆)][PF₆], 22, as an orange powder with similar

solubility properties.

and polyamine dendrimers has also been studied. Ferro-

cenecarboxylic acid 27 was mixed with propylamine

stoichiometrically in tetrahydrofuran (THF), which al-

lowed precipitation of an orange solid, 28. The same

reaction was carried out with the three dendritic amines

G₀-9-NH₂, G₁-27-NH₂, and G₂-81-NH₂also resulting in

the formation of the polyammonium carboxylates 29, 30,

and 31 as orange powders (Chart 3). These compounds

were soluble only in acetone and slightly so in methanol.

They were characterized by IR (in KBr) and H NMR

spectroscopy (rapidly recorded spectra in CD₃COCD₃).

Table 1 shows the comparative NMR and IR data for

the carboxylic acid 2, the carboxylate sodium salt [Fe(η⁵-

C₅H₄CO₂^-Na^þ)(η⁶-C₆Me₆)][PF₆], 2a, the carboxylate

propylammonium salt [Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁶-

C₆Me₆)][PF₆], 23, and the dendritic ammonium salts

[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 24-26.

The IR carbonyl bands of the acid complex 2 at 1702

and 1618 cm^-1are shifted to 1630 and 1580 cm^-1for the

sodium carboxylate salt 2a; likewise they are found at

1634 and 1591 cm^-1for the propylammonium as well as

for the dendritic ammonium salts, suggesting the ex-

pected protonation of the primary amino group by the

2.1.3. Ionic Binding between the Polyammonium Den-

drimers and Two Organoiron Carboxylates [Fe(η⁵-C₅H₄-

CO₂H)(η⁶-C₆Me₆)][PF₆] and [Fe(η⁵-C₅H₄CO₂H)(η⁵-

C₅H₅)]. The formation of dendritic ammonium carbox-

ylates from dendritic amines and carboxylic acid is

precedented.^14a-d,26This property was used to bind

complex 2 to the amine dendrimers through ionic bonds

(eq 2). Propylamine 17 and the polyamine dendrimers 14,

15, and 16 were mixed with [Fe(η⁵-C₅H₄CO₂H)(η⁶-

C₆Me₆)][PF₆], 2, in MeCN at room temperature under

inert atmosphere, affording respectively the monomeric

salt 23 and the dendritic polyammonium carboxylates 24,

25, and 26 (Chart 3) as orange powders that were char-

acterized by ¹H and ¹³C NMR, IR, and elemental analysis.

carboxylic acid. In H NMR, the proton signals of the

substituted cyclopentadienyl ligand of acid 2 are found at

4.97 ppm for the β proton and at 4.79 ppm for the γ

proton, and these signals are shifted to 4.73 ppm and 4.45

ppm, respectively, for the sodium carboxylate salt. The

corresponding proton signals on the propyl- and dendri-

tic ammonium salts are found at 4.73-4.77 ppm and

4.55-4.58 ppm, that is, intermediate between those of the

acid 2 and those of the sodium carboxylate 2a, probably

because of hydrogen bonding between the primary ammo-

R⁰NH₂þ R⁰⁰CO₂H f R⁰⁰CO₂-----^þNH₃R⁰ð2Þ

For comparison, the ionic binding of the neutral iron

complex ferrocenecarboxylic acid, 27, to propylamine

nium and the carboxylate group. The H signal of the

methylene group that is bound to the amino group is found

at 2.60 ppm for propylamine and 2.14 ppm for the dendri-

mers, and it is shifted downfield to 2.98 ppm for the

propylammonium and to 2.40 ppm for the polyammonium

(26) (a) Ornelas, C.; Boisselier, E.; Martinez, V.; Pianet, I.; Aranzaes,

J. R.; Astruc, D. Chem. Commun. 2007, 5093–5095. (b) Boisselier, E.; Ornelas,

C.; Pianet, I.; Aranzaes, J. R.; Astruc, D. Chem.;Eur. J. 2008, 14, 5577–5587.

Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6089

Chart 2. Metallodendrimers Synthesized through Amide Linkages According to Equation 1

dendrimers. All these IR and NMR data are in agreement

with the dendritic ammonium carboxylate formulation.

Table 2 shows the ¹H NMR and IR data for the

ferrocenecarboxylic acid 27, the carboxylate propylam-

The concept of “click chemistry” was introduced by

Sharpless and co-workers in 2001²⁷and among the

“click” reactions, the Cu(I)-catalyzed alkyne azide 1,3-

dipolar cycloaddition (CuAAC) is the most popular.²⁸

CuAAC was successfully applied in different areas of

materials chemistry,²⁹including dendrimers.³⁰In dendri-

mer chemistry, CuAAC was used for the convergent^30a

and divergent^6ksyntheses as well as in their func-

tionalization.^24,30b-30dThe continuous success of this

reaction inspired us in the development of a new synthetic

strategy to attach the iron complex 1 to giant dendrimers

that include: (i) lengthening of the allyl dendrimers tethers

using a silane with a long chain and a bromo termini,

followed by substitution of the bromide termini by azide

groups; (ii) functionalization of complex 1 with alkyne

termini; and (iii) CuAAC reaction between the giant-long

azide dendrimers with the alkyne iron complexes.

monium salt [Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁵-C₅H₅)], 28,

and the dendritic ammonium salts [Fe(η⁵-C₅H₄CO₂

dendrNH₃^þ)(η⁵-C₅H₅)], 29-31, recorded in (CD₃)₂CO.

Table 3 shows the H, ¹³C NMR and IR data for the

sodium ferrocenecarboxylate salt 27a and the carboxylate

propylammonium salt [Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁵-

C₅H₅)], 28, recorded in D₂O.

The IR carbonyl band of ferrocenecarboxylic acid, 27,

at 1657 cm^-1is shifted to 1533 cm^-1in the carboxylate

sodium salt, 27a, 1518 cm^-1for the propylammonium

salt, 28, and 1545 to 1548 cm^-1for the dendritic polyam-

monium ferrocenenecarboxylate salts 29-31. Similarly to

the ionic binding of iron complex 2, the ionic binding of

ferrocenecarboxylic acid with the polyamine dendrimers

2.2.1. Synthesis of New Polyazido Dendrimers with

Lengthened Tethers. A silane compound with a long chain

and a bromo termini, 11-bromoundecyl(dimethyl)silane,

32, was synthesized by hydrosilylation of bromo-1-un-

decene with (dimethyl)chlorosilane followed by LiAlH₄

reduction (scheme 3).

shows an upfield shift on the H NMR signals of the

cyclopentadienyl protons adjacent to the acid group from

4.80 ppm to 4.73 ppm (Table 2). ¹³C NMR spectra of the

ionic dendritic ferrocenyl derivatives could not be carried

out satisfactorily because acetone slowly reacts with them

during the time necessary for recording the ¹³C NMR

The tethers of the polyallyl dendrimers 4, 7, 10, and 13

(G₀, G₁, G₄, and G₇) with 9, 27, 729, and 19683 termini

spectra, and the solubility in CD₃OD is not sufficient. ¹³

NMR spectra could be recorded in D₂O for the sodium

and propylammonium carboxylate salts 27a respec-

tively 28. The data gathered in Tables 2 and 3 strongly

suggests the formation of the ferrocenylcarboxylate salts

of propylammonium 28 and dendritic polyammonium

29-31.

(27) Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem., Int. Ed.

2001, 40, 2004–2021.

(28) Meldal, M.; Tornoe, C. W. Chem. Rev. 2008, 108, 2952–3015.

(29) (a) Meldal, M. Macromol. Rapid Commun. 2008, 29, 1016–1051. (b)

Boisselier, E.; Diallo, A. K.; Salmon, L.; Ruiz, J.; Astruc, D. Chem. Commun. 2008,

4819–4821. (c) Durot, S.; Mobian, P.; Collin, J. P.; Sauvage, J. P. Tetrahedron 2008, 64,

8496–8503. (d) Megiatto, J. D.; Schuster, D. I. J. Am. Chem. Soc. 2008, 130, 12872–

12873.

2.2. Attachment of the Complex [Fe(η⁵-C₅H₄R)(η⁶-

C₆Me₆)][PF₆] to Giant Dendrimers up to 14 000 Termini:

Tether Lengthening and “Click” Reaction. Several at-

tempts to attach complex 1 to giant dendrimers through

amide coupling reaction have failed, mainly because of

the quick insolubilization of the high generation amine-

terminated dendrimers, with or without long tethers.

(30) (a) Wu, P.; Feldman, A. K.; Nugent, A. K.; Hawker, C. J.; Scheel, A.;

ꢀ

Voit, B.; Pyun, J.; Frechet, J. M. J.; Sharpless, K. B.; Fokin, V. V. Angew.

Chem., Int. Ed. 2004, 43, 3928–3932. (b) Joralemon, M. J.; O'Reilly, R. K.;

Matson, J. B.; Nugent, A. K.; Hawker, C. J.; Wooley, K. L. Macromolecules

2005, 38, 5436–5443. (c) Srinivasachari, S.; Fichter, K. M.; Reineke, T. M. J. Am.

Chem. Soc. 2008, 130, 4618–4627. (d) For a review on “click” dendrimers: Franc,

G.; Kakkar, A. Chem. Commun. 2008, 5267–5276.

6090 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

Chart 3. Polyammonium Carboxylates Generated by Mixing the Carboxylic Acid Complexes 2 and 27 with the Polyamine Dendrimers

respectively, were lengthened by hydrosilylation reaction

with the silane 32. The bromo group of the bromoalkyl-

terminated dendrimers was subsequently substituted

by an azido group upon nucleophilic substitution using

Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6091

Table 1. ¹H, ¹³C NMR, and IR Data of the Complexes Obtained by Mixing [Fe(η⁵-C₅H₄CO₂H)(η⁶-C₆Me₆)][PF₆], 2, with Propylamine 17 and the Amino-Terminated

Dendrimers 14-16, in CDCN

compound

¹H_β/¹³C_βδ(ppm) ¹H_γ/¹³C_γδ(ppm) ¹H/¹³C(CH₂NH₃^þ) δ(ppm) IR- CO(cm^-1) KBr

[Fe(η⁵-C₅H₄CO₂H)(η⁶-C₆Me₆)][PF₆], 2

[Fe(η⁵-C₅H₄CO₂^-Na^þ)(η⁶-C₆Me₆)][PF₆], 2a

Pr-NH₂, 17

4.97/80.7

4.73/79.1

4.79/78.2

4.45/78.4

1702; 1618

1630; 1580

2.60/43.9

2.98/

[Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 23

G₀-9-NH₂, 14

4.73/79.3

4.73/79.5

4.76/79.6

4.77/79.8

4.55/78.3

4.58/78.2

1634; 1591

2.14/29.9

2.40/27.1

2.14/30.6

2.40/27.0

2.14/30.0

2.40/27.0

G₀-9-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 24

G₁-27-NH₂, 15

G₁-27-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 25

G₂-81-NH₂, 16

G₂-81-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 26

Table 2. ¹H NMR and IR Data of the Complexes Obtained by Mixing [Fe(η⁵-C₅H₄CO₂H)(η⁵-C₅H₅)], 27, with Propylamine 17 and Amino-Terminated Dendrimers 14-16,

in (CD₃)₂CO

compound

¹H_βδ(ppm)

¹H_γδ(ppm)

¹H (CH₂NH₃^þ) δ(ppm)

IR- CO(cm^-1) KBr

1657

[Fe(η⁵-C₅H₄CO₂H)Cp], 27

Pr-NH₂, 17

4.80

4.50

2.64

3.13

2.14

2.04

2.14

2.04

2.14

3.04

[Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)Cp], 28

G₀-9-NH₂, 14

4.72

4.73

4.40

4.36

4.34

4.39

1518

1545

1548

G₀-9-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)Cp], 29

G₁-27-NH₂, 15

G₁-27-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)Cp], 30

G₂-81-NH₂, 16

G₂-81-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)Cp], 31

Table 3. ¹H, ¹³C NMR and IR Data of the Sodium Ferrocenecarboxylate Salt 27a and the Carboxylate Propylammonium Salt [Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁵-C₅H₅)], 28,

in D₂O

compound

¹H_β/¹³C_βδ(ppm)

¹H_γ/¹³C_γδ(ppm)

¹H/¹³C(CH₂NH₃^þ) δ(ppm)

IR- CO(cm^-1) KBr

1533

[Fe(η⁵-C₅H₄CO₂^-Na^þ)(η⁵-C₅H₅)], 27a

Pr-NH₂, 17

4.59/76.3

4.36/70.7

2.64/42.7

2.90/40.9

[Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁵-C₅H₅)], 28

4.61/70.73

4.37/70.01

1518

sodium azide, affording the new long-arm polyazide den-

drimers 33 (G₀-long-9-N₃), 34 (G₁-27-long-N₃), 35 (G₄-

729-long-N₃), and 36 (G₇-19683-long-N₃)₁₉₆₈₃) (Scheme 3).

2.2.2. Synthesis of the Alkyne Derivatives of Complex 1.

Two alkyne derivatives of complex 1 were obtained by

coupling reaction between freshly prepared [Fe(η⁵-C₅H₄-

COCl)(η⁶-C₆Me₆)][PF₆], 3, and propagyl amine and pro-

pargyl alcohol (following the same procedure shown on

eq 1). The new propargyl ester and propargyl amide com-

plexes [Fe(η⁵-C₅H₄CO₂CH₂CtCH)(η⁶-C₆Me₆)][PF₆], 37,

and [Fe(η⁵-C₅H₄CONHCH₂CtCH)(η⁶-C₆Me₆)][PF₆],

38, were obtained in high yields and fully characterized

(Scheme 4).

2.2.3. CuAAC Reactions between the Giant Azide Den-

drimers and Alkyne Derivatives of the Iron Complexes. The

CuAAC reaction between the iron complexes 33 and 34

with the new long-arm polyazide-terminated dendrimers

was carried out in CH₂Cl₂/H₂O (1:1), using CuSO₄/

sodium ascorbate as the Cu^Isource. The completion of

all the “click” reactions was verified by IR spectroscopy

by the disappearance of the azide band at 2097 cm^-1, and

by ¹H NMR showing the appearance of the new triazole

6092 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

Scheme 3. Synthesis of the Long-Arm Polyazide Dendrimers, Example of G₀

Scheme 4. CuAAC Reaction between the Long-Arm Azido Dendrimers and the Propargyl Iron Complexes Yielding the “Click” Metallodendrimers

protons at 7.99 ppm and the disappearance of the CH₂N₃

signal at 3.25 ppm.

compounds only became completely insoluble orange

solids after several days of storage at air conditions and

room temperature.

When using the propargyl ester iron complex 37, the

“click” reaction easily afforded the metallodendrimers 39

and 40 bearing 9 and 27 [Fe(η⁵-C₅H₄CO₂R)(η⁶-C₆Me₆)]-

[PF₆] complexes, respectively (Scheme 4 and Chart 4).

Attempts to synthesize the G₂analogue (81 termini), led

to characterization by IR showing the absence of the

azido band and by ¹H NMR, including the observation of

the triazole protons, indicating completion of the “click”

reaction. However, the compound became completely

3. Characterization of the Metallodendrimers. All the

metallodendrimers reported here were characterized by

¹H and ¹³C NMR, elemental analysis, UV-vis spectros-

copy, and CV. Dynamic light scattering was used to mea-

sure the size of the giant metallodendrimers 43 and 44.

3.1. UV-vis of the Metallodendrimers. As expected,

the metallodendrimers bearing the complex [Fe(η⁵-

C₅H₄COR)(η⁶-C₆Me₆)][PF₆] present an absorption band

at 411-416 nm in the UV-vis spectra. This band is

located at 416 nm for the amide derivatives, 413 nm for

the ester derivatives, and 411 nm for the carboxylate com-

plexes (Table 4). It was possible to estimate the number of

terminal organoiron groups by UV-vis spectroscopy

using the Lambert-Beer law, from the ε/ε₀ratio between

the molar extinction coefficient ε of the dendritic complex

and that of the monomer, ε₀(Table 4). The estimated

number of terminal groups are in agreement with the

expected structures up to G₄, but much lower than the

theoretical value for G₇. This result was expected because

of the large amounts of defects formed in the divergent

construction. Similar agreements and discrepancies were

insoluble in all solvents after recording the H NMR

spectrum in CD₃CN, thus, record of the ¹³C NMR spec-

trum and further characterization were not possible.

For the “click” reactions carried out with the propargyl

amide iron complex 38, four generations of metalloden-

drimers bearing theoretical numbers of 9, 27, 729, and 19

683 [Fe(η⁵-C₅H₄CO₂R)(η⁶-C₆Me₆)][PF₆] species respec-

tively (41-44) were obtained as orange powders that were

completely soluble in acetone (Scheme 4 and Chart 4).

The high solubility of these “click” metallodendrimers

allowed their characterization by ¹H and ¹³C NMR, UV-

vis spectroscopy, cyclic voltammetry (CV), and dyna-

mic light scattering (for the higher generations). These

Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6093

Chart 4. Metallodendrimers G₀and G₁Synthesized by CuAAC Reactions

observed for the ferrocenyl dendrimers, indicating that

the divergent construction is responsible for the defects

rather than the final metal-loading step. The discrepan-

cies become very large only with G₇(14000 ( 1000 ter-

minal organoiron groups for a theoretical number of

19683). In addition, G₇also presents the maximum ability

to encapsulate inorganic salt impurities.¹⁶

3.2. Dynamic Light Scattering of the Giant Metalloden-

drimers. Dynamic Light Scattering (DLS) is a very useful

technique to characterize the giant metallodendrimers

because it allows to determine the size (hydrodynamic

diameter) of the dendrimers in solution, and consequently

calculate their diffusion coefficient (D) using the Stokes-

Einstein equation: D = kT/6πηR_h, where R_his the hydro-

dynamic radius, ηis the solvent viscosity, kis the Boltzmann’s

constant, and T is the temperature. It is known that high-

generation dendrimers present globular shapes and, along

the search of their physical properties, they are often assimi-

lated to perfect spheres.^17a-dWe also used this approxima-

tion to calculate the volume and the density of the metallo-

dendrimers 43 and 44 (Table 5).

3.3. Cyclic Voltammetry. All the covalent and ionic

metallodendrimers containing the organoiron group [Fe-

(η⁵-C₅H₄COR)(η⁶-C₆Me₆)][PF₆] were studied by CV using

DMF as the solvent, [n-Bu₄][PF₆] as the supporting electro-

lyte, and decamethylferrocene as the internal reference. A

single reversible CV wave was observed, corresponding to the

cathodic reduction Fe^IIfFe^I(Figure 1 and Table 6). This CV

wave is known from several reports for the family of mono-

metallic complexes [Fe(η⁵-C₅H₅)(η⁶-arene)][PF₆].^3,4a,12,31

Table 6 gathers the data for all the compounds reported here.

The CV wave is seemingly chemically and electrochemically

reversible, but its observation was more or less marred by

adsorption, and attempts to measure the number of electrons

involved in the electron-transfer process did not work above

G₀, unlike with the ferrocenyl dendrimers (UV-vis spectros-

copy was more appropriate for this purpose for the present

family of compounds).

4. Reduction to Dendritic 19-Electron Fe^IComplexes

and Multielectron-Reservoir Properties. Although several

functional complexes of this family could be reduced to

stable Fe^I, 19-electron complexes, dendritic branching is

less favorable for the stability of these compounds. For

instance, reduction of G₀-9-[Fe(η⁵-C₅H₄CO₂dendr)(η⁶-

C₆Me₆)][PF₆], 41, by the 19-electron complex 1 led to

decomplexation of the organoiron sandwich fragment in

the dendrimer, as indicated by the finding of the decoor-

dinated arene C₆Me₆in ¹H NMR.

Attempts to reduce the dendrimer 22 using Na/Hg or

LiAlH₄in THF or dimethyl ether (DME) failed because of

the insolubility of both this dendritic 18-electron complex

and the reductant in these solvents. The only reductant that

proved to be efficient to reduce 22 was the 19-electron

complex 1a. This electron-reservoir complex 1 has a redox

potential of the Fe^II/Icouple that is 0.15 V more negative

than that of the dendritic complex 22 because of the presence

of the electron-withdrawing amido link on the cyclopenta-

dienyl group of 22. Thus, stoichiometric reduction of the

dendritic 18-electron complex 22 in MeCN using 64 equiv of

complex 1a gave the dendritic 19-electron complex 22a

(Scheme 5). The complex 22a shows the typical deep-blue-

green color of such 19-electron complexes, and it was also

characterized by electron paramagnetic resonance (EPR) at

10 K (Figure 2), showing the classic rhombic distorted

signal. The complex 22a decomposed around 0 °C.^12a,18,32

(31) (a) Dessy, R. E.; Stary, F. E.; King, R. B.; Waldrop, M. J. Am. Chem.

Soc. 1966, 88, 471–472. (b) Nesmeyanov, A. N.; Denisovitch, L. I.; Gubin, S. P.;

Vol'kenau, N. A.; Sirotkina, E. I.; Bolesova, I. N. J. Organomet. Chem. 1969, 20,

169–174. (c) Astruc, D. Electron Transfer and Radical Processes in Transition

Metal Chemistry; VCH: New York, 1995; Chapter 2.

6094 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

Table 4. UV-vis Data for the Dendritic Complexes and Estimated Number of Metalated Branches Using the Lambert-Beer Law

theoretical number

of branches

calculated number of

branches (ε/ε₀)

complex

λ (nm)

Covalent Bonds

[Fe(η⁵-C₅H₄CONHCH₂CCH)(η⁶-C₆Me₆)][PF₆], 38

416

413

729

19683

ε₀= 151

12300

4080

ε₀= 151

1340

4070

106000

2170000

ε₀= 394

3520

G₀-9-[Fe(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], 19

9 ( 1

27 ( 1

G₁-27-[Fe(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], 20

[Fe(η⁵-C₅H₄CONHCH₂CCH)(η⁶-C₆Me₆)][PF₆], 38

G₀-9-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆], 41

G₁-27-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆], 42

G₄-729-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆], 43

G₇-19683-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆], 44

[Fe(η⁵-C₅H₄CO₂CH₂CCH)(η⁶-C₆Me₆)][PF₆], 37

9 ( 1

27 ( 1

700 ( 40

14000 ( 1000

G₀-9-[Fe(η⁵-C₅H₄CO₂CH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆], 39

9 ( 1

Ionic Bonds

[Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 23

411

ε₀= 321

2700

8500

G₀-9-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 24

G₁-27-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 25

G₂-81-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 26

9 ( 1

27 ( 1

81 ( 1

25800

Table 5. Hydrodynamic Diameters of the “Clicked” Giant Metallodendrimers Obtained by DLS, and Calculated Diffusion Coefficient, Volume and Density

product^a,^b

MM (g mol^-1

)

hydrodynamic diameter^c(nm)

diffusion coefficient (m²s^-1

)

volume^d(m³)

density (kg/m³)

G₄-FE (43)

G₇-FE (44)

666 158

18 008913

26.6 ( 0.5

33.2 ( 1.7

5.37 ꢀ 10^-14

(9.9 ( 0.2) ꢀ 10^-24

110 ( 20

1560 ( 40

2.93 ꢀ 10^-14

(1.9 ( 0.4) ꢀ 10^-23

^aG₄-FE (36) = G₄-729-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆]; G₇-FE (37) = G₇-19683-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-

triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆]. ^bIt was not possible to obtain the hydrodynamic diameters of G₀and G₁dendrimers by DLS because they are below

the lower limit of the technique. ^cMeasured in acetone at 25 °C. ^dConsidering the globular shape of the dendrimer as a perfect sphere (V = (4/3)πr³).

Reduction of C₆₀at -30 °C in situ (MeCN) by 22a gave

an insoluble precipitate that was characterized as the

stable complex 45 (Chart 5) by the known EPR signal

€

(Figure 3) and its Mossbauer spectrum show-

•-33

of C₆₀

ing the characteristic doublet of the Fe^IIsandwich com-

plex (Figure 4).³⁴

Concluding Remarks

Branching the 18-electron complex [Fe(η⁵-C₅H₄COR)(η⁶-

C₆Me₆)][PF₆] onto the tether termini of large dendrimers was

planned to form redox-robust complexes that might ulti-

mately serve as molecular batteries. Various branching modes

are presented here. Previous branching via the C₆Me₆ligand

subsequent to C-H activation of this ligand by O₂in the 19-

electron complex 1a failed because of the insolubility of the

small dendritic complexes. Branching via the amino group of

the arene ligand in complexes of the type [Fe(η⁵-C₅H₅)(η⁶-

C₆H₅NHR)] would not be satisfactory because of the in-

stability of such 19-electron complexes of functional arenes

even below room temperature. Branching using the car-

boxylic acid was still the best choice given the recently repor-

ted thermal stability of various 19-electron Fe^Icomplexes of

the type [Fe^I(η⁵-C₅H₄R⁰)(η⁶-C₆Me₆)] (R⁰= carboxylate,

ester, thioester, amide) at room temperature.^13c

Figure 1. Cyclic voltammogram obtained for G₄-729-[Fe(η⁵-C₅H₄-

CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)][PF₆], 43 in DMF.

also been shown here that the bond-lengthening strategy,

already used earlier for the synthesis of giant ferrocenyl and

cobaltocenyl dendrimers,^16,17combined with the CuAAC

“click” reaction, leads to large organoiron dendrimers with

the amido linkage in [Fe(η⁵-C₅H₄CONH-dendr-)(η⁶-C₆Me₆)]-

[PF₆]. The ester linkage was also probed here, and its limit was

provided both by the insolubilization of the G₂-81-metallo-

dendrimer and by the decomplexation at ambient temperature

of the dendritic Fe^I, 19-electron complexes. This latter feature

recalls the decreased thermal stability of the Fe^I, 19-electron

complexes [Fe^I(η⁵-C₅H₅)(η⁶-C₆R₆)] when the length of the

alkyl substituents R increases.³⁵

Finally, ionic bonding by reactions between the amino-

terminated dendrimers and the carboxylic acid was achieved

here also with up to 81 organoiron groups. The ionic strategy

is limited by the solubility of the dendritic polyamine to

81 terminal branches, because the 243-amino dendrimer is

not soluble in THF, unlike the smaller amino-terminated

Thus, covalent branching via an amido linkage with the Cp

ligand has been possible in the present work for various

dendrimers up to a theoretical number of 64 groups. It has

(32) Rajasekharan, M. V.; Giezynski, S.; Ammeter, J. H.; Oswald, N.;

Hamon, J.-R.; Michaud, P.; Astruc, D. J. Am. Chem. Soc. 1982, 104, 2400–

2407; See also ref 31, Chapter 3.

(33) Hirsch, A. The Chemistry of Fullerenes; Thieme: Stutgart, 1994;

Chapter 2.

(34) Mariot, J.-P.; Michaud, P.; Lauer, S.; Astruc, D.; Trautwein, A. X.;

Varret, F. J. Phys. (Paris) 1983, 44, 1377–1385.

ꢁ

(35) Hamon, J.-R.; Hamon, P.; Boukheddaden, K.; Linares, J.; Varret,

F.; Astruc, D. Inorg. Chim. Acta 1995, 240, 105–108.

Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6095

Table 6. Redox Potentials of the Complexes Obtained by CV

complexes

E_1/2(V)^a

Ionic Complexes

G₀-9-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)]-

[PF₆], 24

-1.680

G₂-81-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)]-

[PF₆], 26

Covalent Complexes

G₀-9-[Fe(η⁵-C₅H₄CO₂CH₂-1,2,3-triazolyl-dendr-)-

(η⁶-C₆Me₆)][PF₆], 39

-1.220

G₀-9-[Fe(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], 19

G₁-27-[Fe(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], 20

G₀-9-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)-

(η⁶-C₆Me₆)][PF₆], 41

-1.360

-1.320

Figure 2. Left: Cyclovoltammogram of the dendritic 18-electron com-

plex G₄-DAB-64-[Fe^II(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)], 22 in MeCN,

scan rate 0.1 V s^-1. Supporting electrolyte: [n-Bu₄N][PF₆]. Reference:

ferrocene (Fc). Right: EPR spectrum of the dendritic 19-electron complex

G₄-DAB-64-[Fe^I(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)], 22a, generated as

shown in Scheme 5, with 3 g values and rhombic distortion that are

G₁-27-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)-

(η⁶-C₆Me₆)][PF₆], 42

-1.320

G₄-729-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)-

(η⁶-C₆Me₆)][PF₆], 43

characteristic of the Fe^ICp(η⁶-arene) family.^12a,18,32

G₇-19683-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)-

(η⁶-C₆Me₆)][PF₆], 44

64 electrons to reduce 64 C₆₀molecules to 64 C₆₀^•-at -30 °C

in acetonitrile.

^aCV recorded at 0.200 V s^-1; 20 °C. Solvent: dimethylformamide.

Compare [CpFe(η⁶-C₆Me₆][PF₆], 1, that has an E_1/2value of -1.425 V vs

Cp₂*Fe in DMF.^4a,12a,12b

Experimental Section

General Data. For general data including solvents, appara-

tuses, compounds, reactions, spectroscopies and CV, see the

Supporting Information. G_nindicates the generation number n.

The mononuclear complexes [Fe(η⁵-C₅H₄CO₂H)(η⁶-C₆Me₆)]-

[PF₆], 2, and [Fe(η⁵-C₅H₄COCl)(η⁶-C₆Me₆)][PF₆], 3, were syn-

thesized according to ref 13c.

Scheme 5. Reduction Fe^IIf Fe^Iin the Dendrimer G₄-DAB-64-[Fe-

(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], 22 Using Complex 1a and Produ-

cing the Dendritic 19-Electron Complex G₄-DAB-64-[Fe^I(η⁵-C₅H₄-

CONH-dendr-)(η⁶-C₆Me₆)], 22a

General Synthesis of Amine Dendrimers. A suspension of

LiAlH₄(1.5 equiv per branch) in 20 mL of THF cooled at

0 °C under nitrogen, was added dropwise to a solution of azido-

terminated dendrimer in 10 mL of THF, that was also cooled at

0 °C under nitrogen. The reaction mixture was stirred for 6 h at

0-8 °C under nitrogen. After slow, cautious addition of H₂O

(9 equiv per branch), the gray mixture was stirred at 0 °C for

20 min and filtered over a pad of Celite under nitrogen. The

solvent was removed, yielding a colorless solid.

G₀-9-NH₂, 14. The nona-amine dendrimer 14 was synthesized

from G₀-9-N₃(0.100 g, 0.066 mmol), LiAlH₄(0.034 g, 0.89

mmol) and H₂O (0.096 mL, 5.34 mmol) using the general

procedure for the synthesis of amino dendrimers. The product

was obtained as a white solid (0.068 g, 81% yield). H NMR

(CD₃CN, 200 MHz), δ_ppm: 7.07 (s, 3H, CH core), 2.13 (s, 18H,

SiCH₂NH₂), 1.70 (m, 18H, C_qCH₂CH₂CH₂Si), 1.47 (s, 18H,

SiCH₂NH₂), 1.16 (m, 18H, C_qCH₂CH₂CH₂Si), 0.55 (m, 18H,

C_qCH₂CH₂CH₂Si), 0.00 (s, 54H, Si(CH₃)₂CH₂NH₂). ¹³C NMR

(CD₃CN, 50 MHz), δ_ppm: 145.7 (C_qof arom. core), 121.6 (CH of

arom. core), 43.7 (C_qCH₂CH₂CH₂Si), 41.9 (C_qCH₂CH₂CH₂Si),

29.9 (Si(CH₃)₂CH₂NH₂), 17.8 (C_qCH₂CH₂CH₂Si), 14.4 (C_q-

CH₂CH₂CH₂Si), -5.0 (Si(CH₃)₂CH₂NH₂). Anal. Calcd for

C₆₃H₁₄₇Si₉N₉: C 58.90, H 11.45; found: C 57.97, H 11.37.

G₁-27-NH₂, 15. The 27-arm amine dendrimer 15 was synthe-

sized from G₁-27-N₃(0.31 g, 0.049 mmol), LiAlH₄(0.075 g, 1.97

mmol), and H₂O (0.02 mL, 2.82 mmol) using the general

procedure for the synthesis of amine dendrimers. The product

was obtained as a colorless solid (0.214 g, 79% yield). ¹H NMR

(CDCl₃, 200 MHz), δ_ppm: 7.22 (d, 18H, arom.), 6.86 (d, 18H,

arom.), 7.07 (s, 3H, CH core), 3.54 (s, 18H, SiCH₂O), 2.14 (s,

54H, SiCH₂NH₂), 1.62 (m, 72H, C_qCH₂CH₂CH₂Si), 1.13 (m,

72H, C_qCH₂CH₂CH₂Si), 0.50 (m, 72H, C_qCH₂CH₂CH₂Si),

0.01 (s, 216H, Si(CH₃)₂CH₂NH₂). ¹³C NMR (CDCl₃, 50 MHz),

dendrimers. It is probable that quadruple-ion aggregates are

present in these ionic bonds, involving both PF₆and

carboxylate anions and both iron-centered and ammonium

cations.

The strategy involving combination of bond-lengthening

and “click” reaction turned out to be the most valuable one,

as in the metallocene series. Indeed, it was the only one that

could lead to large organoiron dendrimers of this type. All of

the strategies are limited to G₁or G₂except when the den-

dritic tethers are lengthened as for the syntheses of large

ferrocenyl and cobaltocenyl metallodendrimers. In this case,

amido “click” dendrimers could be synthesized up to G₇with

14 000 ( 1 000 cationic organoiron termini.

Exergonic reduction of the 18-electron Fe^IImetalloden-

drimers to 19-electron Fe^Imetallodendrimers at low tem-

perature is only possible, for solubility reasons, using the

classic electron-reservoir complex [Fe^I(η⁵-C₅H₅)(η⁶-C₆Me₆)],

1a, as shown with the reduction of the 18-electron metallo-

dendrimer G₄-DAB-64-[Fe^II(η⁵-C₅H₄CONH-dendr)(η⁶-C₆-

Me₆)], 22, in MeCN. The dendritic 19-electron complex 22a

generated in this way serves as a reservoir of approximately

_ppm: 159.3 (arom. OC_q), 139.7 (arom. C_q), 127.4 and 113.7

(arom. CH of dendron), 60.4 (SiCH₂O), 43.3 (C_qCH₂CH₂-

CH₂Si), 42.4 (C_qCH₂CH₂CH₂Si), 30.6 (Si(CH₃)₂CH₂NH₂),

18.0 (C_qCH₂CH₂CH₂Si), 14.9 (C_qCH₂CH₂CH₂Si), -4.2 (Si-

(CH₃)₂CH₂NH₂). Anal. Calcd for C₉₆₃H₁₉₄₇N₈₁O₃₆Si₁₁₇: C

61.78, H 10.67; found: C 60.92, H 10.65.

6096 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

Chart 5. Dendr-64-NHCOCpFe(C₆Me₆)^64þ, 64 C₆₀^•-, 45, Resulting from the Reaction of 22a with C₆₀in MeCN/Toluene at -30°C

G₂-81-NH₂, 16. The 81-arm amine dendrimer 16 was synthe-

sized from G₂-81-N₃(0.100 g, 0.004 mmol), LiAlH₄(0.018 g,

0.47 mmol), and H₂O (0.050 mL, 2.82 mmol) using the general

procedure for the synthesis of amino-dendrimers. The product

was obtained as a colorless solid (0.051 g, 63% yield). ¹H NMR

(CDCl₃, 200 MHz), δ_ppm: 7.15 (d, 72H, arom.), 6.86 (d, 72H,

arom.), 7.07 (s, 3H, CH core), 3.53 (s, 72H, SiCH₂O), 2.14 (s,

162H, SiCH₂NH₂), 1.63 (m, 234H, C_qCH₂CH₂CH₂Si), 1.10 (m,

234H, C_qCH₂CH₂CH₂Si), 0.50 (s, 234H, C_qCH₂CH₂CH₂Si),

0.00 (s, 702H, Si(CH₃)₂CH₂NH₂). ¹³C NMR (CDCl₃, 50 MHz),

G₀-9-[Fe(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)][PF₆], 19. The

metallodendrimer 19 was synthesized from 14 (0.50 g; 0.039

mmol), 2 (0.248 g; 0.526 mmol), SOCl₂(40 mL), and triethyla-

mine (0.354 g, 3.50 mmol) using the general procedure for the

synthesis of the metallocene amido dendrimers G_n-(3^nþ2)-[Fe-

(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], (n=0, 2). The product was

obtained as a dark orange solid (0.150 g, 71% yield). ¹H NMR

(CD₃CN, 200 MHz), δ_ppm: 7.02 (s, 3H, CH core), 6.74 (s, 9H,

CpCONHCH₂Si), 4.90 (s, 18H, Cp), 4.68 (s, 18H, Cp), 2.93 (s,

18H, CpCONHCH₂Si), 2.42 (s, 162H, CH₃Ar), 1.66 (m, 18H,

C_qCH₂CH₂CH₂Si), 1.14 (m, 18H, C_qCH₂CH₂CH₂Si), 0.57 (m,

δ_ppm: 159.0 (arom. OC_q), 139.2 (arom. C_q), 127.2 and 113.4

(arom. CH of dendron), 60.1 (SiCH₂O), 42.9 (C_qCH₂CH₂-

CH₂Si), 42.1 (C_qCH₂CH₂CH₂Si), 30.2 (Si(CH₃)₂CH₂NH₂),

17.7 (C_qCH₂CH₂CH₂Si), 14.6 (C_qCH₂CH₂CH₂Si), -4.3 (Si-

(CH₃)₂CH₂NH₂). Anal. Calcd for C₉₆₃H₁₉₄₇N₈₁O₃₆Si₁₁₇: C

62.50, H 10.53; found: C 62.19, H 10.27.

18H, C_qCH₂CH₂CH₂Si), 0.04 (s, 54H, Si(CH₃)₂CH₂NH₂). ¹³

NMR (CD₃CN, 50 MHz), δ_ppm: 162.1 (C_q=O), 145.7 (C_qof

arom. core), 126.9 (CH of arom. core), 99.2 (Cq of C₆Me₆), 84.2

(Cq of Cp), 79.6 and 75.7 (CH of Cp), 43.6 (C_qCH₂CH₂CH₂Si),

41.5 (C_qCH₂CH₂CH₂Si), 29.4 (Si(CH₃)₂CH₂NH₂), 17.5

(C_qCH₂CH₂CH₂Si), 16.0 (CH3Ar), 14.7 (C_qCH₂CH₂CH₂Si),

-4.4 (Si(CH₃)₂CH₂NH₂). Anal. Calcd for C₂₂₅H₃₃₆N₉O_9-

General Synthesis of Metallocene Amido Dendrimers G_n-

(3^nþ2)-[Fe(η⁵-C₅H₄CONH-)(η⁶-C₆Me₆)][PF₆], (n=0-2). A sus-

pension of 2 was heated in refluxing SOCl₂(40 mL) for 16 h,

and a homogeneous red solution was obtained. SOCl₂was re-

moved using a trap-to-trap system under nitrogen atmosphere,

and [Fe(η⁵-C₅H₄COCl)(η⁶-C₆Me₆)][PF₆], 3, was obtained as a

red powder.^13cThen, the complex 3 (1.5 equiv per branch) was

dissolved in dry dichloromethane and slowly added to a di-

chloromethane solution of amino dendrimer and triethylamine

(10 equiv per branch). The mixture was stirred under nitrogen

atmosphere for 12 h at room temperature. The solvent was re-

moved under vacuum, and the solid residue was dissolved in

dichloromethane and washed with an aqueous solution of

K₂CO₃, then with an aqueous solution of HPF₆. The organic

solution was dried over sodium sulfate, filtered, and removed

under vacuum. The product was precipitated with dichloro-

methane/ether. The product was obtained as an orange powder.

Si₉P₉F₅₄: C 55.52, H 6.90; found: C 54.23, H 6.91. IR ν_c=o

1653 cm^-1

G₁-27-[Fe(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)][PF₆], 20. The

complex 20 was synthesized from 15 (0.50 g, 0.009 mmol),

2 (0.171 g, 0.362 mmol), SOCl₂(40 mL), and triethylamine

(0.244 g, 2.413 mmol) using the general procedure for the

synthesis of the amido metallodendrimers G_n-(3^nþ2)-[Fe(η⁵-

C₅H₄CONH-dendr)(η⁶-C₆Me₆)][PF₆], (n =0, 2). The product

was obtained as a dark orange solid (0.090 g, 58% yield). H

NMR (CD₃CN, 200 MHz), δ_ppm: 7.20 and 6.86 (d, 36H, arom.),

6.71 (s, 27H, SiCH₂NHCO), 4.90 (s, 54H, Cp), 4.67 (s, 18H, Cp),

3.57 (s, 18H, SiCH₂O), 2.90 (d, 54H, CpCONHCH₂Si), 2.40

(s, 486H, CH₃Ar), 1.66 (m, 72H, C_qCH₂CH₂CH₂Si), 1.18 (m,

72H, C_qCH₂CH₂CH₂Si), 0.59 (m, 72H, C_qCH₂CH₂CH₂Si),

0.05 (s, 216H, Si(CH₃)₂CH₂NH₂). ¹³C NMR (CD₃CN, 50 MHz),

Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6097

and 2 (0.200 g, 0.423 mmol) using the above general procedure

for the synthesis of [Fe(η⁵-C₅H₄CO₂^-NH₃^þPr)(η⁶-C₆Me₆)]-

[PF₆] and G_n-(3^nþ2)-[Fe(η⁵-C₅H₄CO₂^-NH₃^þdendr)(η⁶-C₆Me₆)]-

[PF₆]. The product 23 was obtained as an orange powder (0.221 g;

99% yield). ¹H NMR (CD₃CN, 200 MHz), δ_ppm: 4.73 and 4.55 (s,

4H, Cp), 2.97 (t, 2H, ^þNH₃CH₂CH₂CH₃), 2.44 (s, 18H, C₆Me₆),

1.78 (m, 2H, ^þNH₃CH₂CH₂CH₃), 1.06 (t, 2H, ^þNH₃CH₂CH₂-

CH₃). ¹³C NMR (CD₃CN, 50 MHz), δ_ppm: 168.1 (CdO), 98.6

(C₆Me₆), 88.3 (Cq of Cp), 79.3 and 78.3 (CH of Cp), 16.0 (CH₃of

C₆Me₆). Anal. Calcd for C₂₁H₃₂NO₂FePF₆: C 47.45, H 6.02;

found: C 46.62, H 5.80

G₀-9-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 24. The

complex 24 was synthesized from 14 (0.025 g, 0.020 mmol) and 2

(0.083 g, 0.175 mmol) using the above general procedure for

the synthesis of G_n-(3^nþ2)-[Fe(η⁵-C₅H₄CO₂^-NH₃^þdendr)(η⁶-C₆-

Me₆)][PF₆]. The product was obtained as an orange powder (0.106

g, 99% yield). ¹H NMR (CD₃CN, 200 MHz), δ_ppm: 6.95 (s, 3H,

CH core), 4.73 and 4.58 (s, 36H, Cp), 2.42 (m, 162H of C₆Me₆and

18H of SiCH₂NH₃^þ), 1.60 (s, 18H, C_qCH₂CH₂CH₂Si), 1.08 (s,

18H, C_qCH₂CH₂CH₂Si), 0.65 (s, 18H, C_qCH₂CH₂CH₂Si), 0.15

(s, 54H, Si(CH₃)₂CH₂NH₃^þ). ¹³C NMR (CD₃CN, 50 MHz),

Figure 3. EPR spectrum of 45 in frozen MeCN at 10 K displaying the

C60^•-signal.³²

δ_ppm: 167.9 (CdO), 145.5 (C_qof arom. core), 121.5 (CH of arom.

core), 98.7, (Cq of C₆Me₆), 87.4 (Cq of Cp), 79.5 and 78.2 (CH of

Cp), 43.6 (C_qCH₂CH₂CH₂Si), 41.5 (C_qCH₂CH₂CH₂Si), 27.1

(Si(CH₃)₂CH₂NH₃^þ), 17.5 (C_qCH₂CH₂CH₂Si), 15.9 (CH₃of

C₆Me₆), 14.3 (C_qCH₂CH₂CH₂Si), -4.5 (Si(CH₃)₂CH₂NH₃^þ).

Anal. Calcd for C₂₂₅H₃₅₄N₉O₁₈Si₉Fe₉P₉F₅₄: C 48.83, H 6.40;

found: C 48.04, H 6.50.

G₁-27-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 25.

The complex 25 was synthesized from 15 (0.025 g, 0.005 mmol)

and 2 (0.057 g, 0.121 mmol) using the above general procedure

for the synthesis of G_n-(3^nþ2)-[Fe(η⁵-C₅H₄CO₂^-NH₃^þdendr)-

(η⁶-C₆Me₆)][PF₆]. The product was obtained as an orange

€

Figure 4. Mossbauer spectrum of 45 displaying the simple quadrupole

doublet characteristic of the Fe^IIcenter of the 1^þsalts.

_ppm: 162.3 (C_q=O), 158.9 (arom. C_qO), 139.0 (arom. Cq of

dendron), 131.7 and 127.2 (arom. CH of dendron), 99.3 (Cq of

C₆Me₆), 84.3 (Cq of Cp), 79.8 and 75.9 (CH of Cp), 60.2

(SiCH₂O), 42.8 (C_qCH₂CH₂CH₂Si), 41.4 (C_qCH₂CH₂CH₂Si),

29.4 (Si(CH₃)₂CH₂NH₂), 17.6 (C_qCH₂CH₂CH₂Si), 16.2 (CH₃-

Ar), 14.7 (C_qCH₂CH₂CH₂Si), -4.4 (Si(CH₃)₂CH₂NH₂). Anal.

Calcd for C₇₇₄H₁₁₆₄N₂₇O₃₆Si₃₆P₂₇F₁₆₂: C 55.52, H 6.90; found: C

powder (0.073 g, 89% yield). H NMR CD₃CN, 200 MHz),

_ppm: 7.14 (d, 18H, arom.), 6.80 (d, 18H, arom.), 4.76 and 4.58 (s,

108H, Cp), 3.48 (s, 18H, SiCH₂O), 2.41 (m, 486H of C₆Me₆and

54H of SiCH₂NH₃^þ), 1.64 (m, 72H, C_qCH₂CH₂CH₂Si), 1.12

(m, 72H, C_qCH₂CH₂CH₂Si), 0.64 (m, 72H, C_qCH₂CH₂CH₂Si),

0.14 (s, 216H, Si(CH₃)₂CH₂NH₂). ¹³C NMR (CD₃CN, 50

MHz), δ_ppm: 167.6 (CdO), 158.9 (arom. OC_q), 139.3 (arom.

C_q), 127.2 and 113.2 (arom. CH of dendron), 98.8 (Cq of

C₆Me₆), 86.1 (Cq of Cp), 79.6 and 78.2 (CH of Cp), 60.3

(SiCH₂O), 42.8 (C_qCH₂CH₂CH₂Si), 41.4 (C_qCH₂CH₂CH₂Si),

27.2 (Si(CH₃)₂CH₂NH₃^þ), 17.3 (C_qCH₂CH₂CH₂Si), 16.1 (CH₃

of C₆Me₆), 14.3 (C_qCH₂CH₂CH₂Si), -4.7 (Si(CH₃)₂CH₂NH₃^þ).

Anal. Calcdfor C₇₇₄H₁₂₁₈N₂₇O₆₃Si₃₆Fe₂₇P₂₇F₁₆₂: C50.67, H 6.64;

found: C 50.41, H 6.58.

55.38, H 6.86. IR ν_c=o: 1657 cm^-1

G₄-DAB-64-{[Fe^II(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)][PF₆]},

22. The dendrimer DAB-dendr-(NH₂)₆₄21 (0.080 g, 0.0112 mmol)

and triethylamine (0.156 mL, 1.07 mmol) were dissolved in 20 mL

of dry CH₂Cl₂. A solution of 3, (0.500 g, 1.07 mmol) in 40 mL of

CH₃CN was added dropwise to this mixture. The solution was

stirred at room temperature overnight, then the solvent was

removed under vacuum, the solid residue was washed twice with

saturated sodium carbonate solution and twice with water, dis-

solved in CH₃CN and dried over sodium sulfate. After filtration,

the volume was reduced to 5 mL, and precipitation from this

solution with 50 mL of dry CH₂Cl₂gave the dendrimer 22 as

G₂-81-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 26.

The complex 26 was synthesized from 16 (0.025 g, 0.0014 mmol)

and 2 (0.052 g, 0.110 mmol) using the above general procedure

for the synthesis of G_n-(3^nþ2)-[Fe(η⁵-C₅H₄CO₂^-NH₃^þdendr)-

(η⁶-C₆Me₆)][PF₆]. The product was obtained as an orange

a brown powder (0.101 g, 25% yield). H NMR (CD₃CN, 200

MHz), δ_ppm: 7.69 (br, 64H, NH); 4.9 (br. 128H, C₅H₄); 4.6 (br.

128H, C₅H₄) ; 3.3 (br. 124H, NHCH₂); 2.3 (br. 1152H, CH₃and

372H, CH₂HNCH₂); 1.69 and 1.49 (br. 252H, CH₂CH₂N). ¹³C

NMR (CD₃CN, 50 MHz), δ_ppm: 162.7(CdO); 99.2 (C_q, C₆Me₆);

83.6 (C_q, C₅H₄); 79.6; 75.7 (CH, C₅H₄); 51.4 (CH₂NCH₂); 38.2

(NHCH₂); 26.5 (CH₂CH₂CH₃); 15.9 (CH₃). IR (nujol, cm^-1):

3422 (ν_NH), 1649 (ν_CdO), 1532 (ν_O=CNH), 840 (PF₆). Anal. Calcd.

for C₁₅₂₈H₂₂₂₄NOFe₆₄P₆₄F₃₈₄: C 50.65, H 6.17; found: C 48.73; H

6.23. E_1/2(V vs FeCp*₂, DMF, 20 °C): -1.370 V.

powder (0.072 g; 93% yield). H NMR CD₃CN, 200 MHz),

_ppm: 7.20 (d, 72H, arom.), 6.84 (d, 72H, arom.), 4.77 and 4.58 (s,

324H, Cp), 3.51 (s, 72H, SiCH₂O), 2.43 (m, 1458 H of C₆Me₆

and 162H of SiCH₂NH₃^þ), 1.67 (m, 243H, C_qCH₂CH₂CH₂Si),

1.13 (m, 243H, C_qCH₂CH₂CH₂Si), 0.66 (m, 243H, C_qCH₂CH₂-

CH₂Si), 0.16 (s, 702H, Si(CH₃)₂CH₂NH₂). ¹³C NMR (CD₃CN,

50 MHz), δ_ppm: 167.4 (CdO), 158.9 (arom. OC_q), 139.0 (arom.

C_q), 127.2 and 113.2 (arom. CH of dendron), 98.9 (Cq of

C₆Me₆), 85.0 (Cq of Cp), 79.8 and 78.2 (CH of Cp), 60.1

(SiCH₂O), 42.9 (C_qCH₂CH₂CH₂Si), 41.5 (C_qCH₂CH₂CH₂Si),

27.0 (Si(CH₃)₂CH₂NH₃^þ), 17.2 (C_qCH₂CH₂CH₂Si), 16.1 (CH₃

of C₆Me₆), 14.1 (C_qCH₂CH₂CH₂Si), -4.5 (Si(CH₃)₂CH₂NH₃^þ).

Anal. Calcd for C₂₄₂₁H₃₈₁₀N₈₁O₁₉₈Si₁₁₇Fe₈₁P₈₁F₄₈₆: C 51.18, H

6.71; found: C 49.21, H 6.58.

General Synthesis of [Fe(η⁵-C₅H₄CO₂^-NH₃^þPr)(η⁶-C₆Me₆)]-

[PF₆], 23, and G_n-(3^nþ2)-[Fe(η⁵-C₅H₄CO₂^-NH₃^þdendr)(η⁶-C₆-

Me₆)][PF₆], (n = 0-2), 24-26. The complex 2 (1 equiv per amine

group) in 5 mL of acetonitrile was added dropwise at ambient

temperature under nitrogen to a solution of amino dendrimer in

5 mL of acetonitrile. After 5 min of agitation, the solvent was

evaporated, and an orange powder was obtained.

[Fe(η⁵-C₅H₄CO₂^-Na^þ)Cp], 27a. To a solution of NaOH

(0.087 g, 0.217 mmol) in 5 mL of EtOH, was added 27 at

ambient temperature. After stirring for 5 min, the solvent was

[Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)(η⁶-C₆Me₆)][PF₆], 23. The com-

plex 23 was synthesized from propylamine (0.025 g, 0.43 mmol)

6098 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

removed under vacuum, and the product 27a was obtained as an

orange powder (0.080 g, 98% yield). ¹H NMR (D₂O, 200 MHz),

(D₂O, 200 MHz), δ_ppm: 180 (CdO), 76.3 (Cq of Cp), 70.7 and

70.0 (CH of Cp), 69.6 (CH of Cp).

branch) were introduced into a Schlenk flask, then dry DMF

(30 mL) was added. The reaction mixture was heated at 80 °C for

12 h under magnetic stirring. After removing the solvent in

vacuo, dichloromethane was added, and the mixture was filtered

through Celite. The solvent was removed in vacuo, and the

residue was washed with methanol (2 ꢀ 10 mL) and precipitated

from a CH₂Cl₂solution by addition of MeOH. After drying

in vacuo, the azido dendrimers were obtained as colorless

products.

_ppm: 4.59 and 4.36 (s, 4H, Cp), 4.19 (s, 5H, Cp). ¹³C NMR

General Synthesis of Ferrocene Carboxylate Propylammo-

nium, 28, and Polyammoniums 29-31. The complex 27 (1 equiv

per branch or 1 equiv for propylamine) in 5 mL of THF was

added dropwise at ambient temperature to a 5 mL-THF solu-

tion of amino-dendrimer at ambient temperature under nitro-

gen. A precipitate formed, and the solvent was evaporated,

giving an orange powder.

Synthesis of (11-Bromoundecyl)dimethylsilane, 32. (i) 11-Bromo

-1-undecene (4.29 g, 18.4 mmol), dimethylchlorosilane (3.48 g,

36.8 mmol), dry ethylic ether, and 12 drops of Kartstedt cata-

lyst were successively introduced in a Schlenk flask. The reac-

tion mixture was stirred under nitrogen atmosphere at room

temperature for 16 h. The solvent and excess of dimethylchlor-

osilane were removed under vacuum, giving (11-bromoundecyl)-

chlorodimethylsilane (18.4 mmol) as a colorless oil. (ii) (11-

Bromoundecyl)chlorodimethylsilane (18.4 mmol) was dissolved

in dry ether and slowly added to a suspension of LiAlH₄(6 g) in

dry ether. The mixture was heated at 55 °C for 2 h. The solution

was cooled at 0 °C, and an aqueous solution of HCl (35%) was

added dropwise until it reached an acidic pH value. A 300 mL

portion of ether and 100 mL of water were added, and the

organic phase was extracted and dried over sodium sulfate,

filtered, and the solvent was removed under vacuum. The

product was purified by flash chromatography using silica gel

with ether as the eluent, yielding (11-bromoundecyl)dim-

[Fe(η⁵-C₅H₄CO₂^-PrNH₃^þ)Cp], 28. The complex 28 was

synthesized from propylamine (0.025 g, 0.423 mmol) and 27

(0.097 g, 0.423 mmol) using the general procedure for synthesis

of G_n-(3^nþ2)-[Fe(η⁵-C₅H₄CO₂^-NH₃^þdendr)(η⁶-C₆Me₆)][PF₆].

The product was obtained as an orange powder (0.121 g, 99%

yield). H NMR (D₂O, 200 MHz), δ_ppm: 4.60 and 4.37 (s, 4H,

Cp), 4.20 (s, 5H, Cp), 2.90 (t, 2H, ^þNH₃CH₂CH₂CH₃), 1.61 (m,

2H, ^þNH₃CH₂CH₂CH₃), 0.91 (t, 3H, ^þNH₃CH₂CH₂CH₃). ¹³

NMR (D₂O, 50 MHz) δ_ppm: 159.8 (CdO), 76.3 (Cq of Cp), 70.7

and 70.0 (CH of Cp), 69.5 (Cp), 40.9 (^þNH₃CH₂CH₂CH₃), 20.1

(^þNH₃CH₂CH₂CH₃), 9.9 (^þNH₃CH₂CH₂CH₃). Anal. Calcd

for C₁₄H₁₉NO₂Fe: C 58.13, H 6.57; found: C 57.97, H 6.53.

G₀-9-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)Cp], 29. The metalloden-

drimer 29 was synthesized from 14 (0.025 g, 0.020 mmol) and 27

(0.040 g, 0.175 mmol) using the general procedure for synthesis

of ferrocenylcarboxylate ammonium dendrimers or propylam-

monium. The product was obtained as an orange powder (0.060

g; 92% yield). ¹H NMR (CD₃CN, 200 MHz), δ_ppm: 7.10 (s, 3H,

CH core), 4.73 and 4.36 (s, 36H, Cp), 4.19 (s, 45H, Cp), 2.02 (s,

162H, SiCH₂NH₃^þ), 1.72 (s, 18H, C_qCH₂CH₂CH₂Si), 1.20 (s,

18H, C_qCH₂CH₂CH₂Si), 0.56 (s, 18H, C_qCH₂CH₂CH₂Si), 0.00

(s, 54H, Si(CH₃)₂CH₂NH₂). Anal. Calcd for C₁₆₂H₂₃₇N₉O_18-

Si₉Fe₉: C 58.01, H 7.07; found: C 57.56, H 7.05.

G₁-27-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)Cp], 30. The metallo-

dendrimer 30 was synthesized from 15 (0.025 g, 0.0013 mmol)

and 27 (0.024 g, 0.103 mmol) using the general procedure for

synthesis of ferrocenylcarboxylate ammonium dendrimers. The

product was obtained as an orange powder (0.045 g, yield: 93%).

¹H NMR (CD₃)₂CO, 200 MHz), δ_ppm: 7.21 (d, 18H, CH arom.),

6.90 (d, 18H, CH arom.), 4.73 and 4.42 (s, 108H, Cp), 4.19 (s,

135H, Cp), 3.57 (s, 18H, SiCH₂O), 2.03 (s, 54H, SiCH₂NH₃^þ),

1.71 (m, 72H, C_qCH₂CH₂CH₂Si), 1.18 (m, 72H, C_qCH₂CH₂-

CH₂Si), 0.52 (m, 72H, C_qCH₂CH₂CH₂Si), 0.00 (s, 216H, Si-

(CH₃)₂CH₂N). Anal. Calcd for C₅₈₅H₈₆₇N₂₇O₆₃Si₃₆Fe₂₇: C

59.54, H 7.35; found: C 59.53, H 7.37

G₂-81-[Fe(η⁵-C₅H₄CO₂^-dendrNH₃^þ)Cp], 31. The metallo-

dendrimer 31 was synthesized from 16 (0.027 g, 0.0014 mmol)

and 27 (0.026 g, 0.117 mmol) using the general procedure for the

synthesis of the ferrocenylcarboxylate ammonium dendrimers.

The product 22 was obtained as an orange powder (0.050 g, 94%

yield). ¹H NMR ((CD₃)₂CO, 200 MHz), δ_ppm: 7.23 (d, 72H, CH

arom.), 6.87 (d, 72H, CH arom.), 4.73 and 4.39 (s, 324H, Cp),

4.19 (s, 405H, Cp), 3.55 (s, 72H, SiCH₂O), 2.03 (s, 162H, SiCH₂-

NH₃^þ), 1.69 (m, 234H, C_qCH₂CH₂CH₂Si), 1.19 (m, 234H,

C_qCH₂CH₂CH₂Si), 0.52 (m, 234H, C_qCH₂CH₂CH₂Si), 0.00

(s, Si(CH₃)₂CH₂N). Anal. Calcd for C₁₈₅₄H₂₇₅₇N₈₁O_138-

Si₃₆Fe₈₁: C 59.93, H 7.42; found: C 59.05 H 7.77.

ethylsilane (3.20 g, 59% yield). H NMR (CDCl₃, 300 MHz),

δ_ppm: 3.31 (m, 2H, CH₂Br), 1.84 (m, 2H, CH₂CH₂Br), 1.27 (m,

16H, (CH₂)₈), 0.58 (s, 2H, CH₂Si), 0.049 (s, 6H, Si(CH₃)₂). ¹³C

NMR (CDCl₃, 62.90 MHz), δ_ppm: 34.3 (CH₂CH₂Br), 33.0

(CH₂Br), 29.9 ((CH₂)₈), 10.5 (CH₂Si), -6.7 (Si(CH₃)₂). Anal.

Calcd for C₁₃H₂₉SiBr: C 53.23, H 9.96; found: C 53.11, H 9.87.

Synthesis of G₀-long-N₃, 33. (i) Hydrosilylation of G₀-9-allyl 4

(0.050 g, 0.104 mmol) using the silane 32 (0.549 g, 1.87 mmol)

was carried out using the general procedure for the hydrosilyla-

tion reactions giving G₀-long-Br as a colorless waxy product

(0.323 g, 99% yield). ¹H NMR (CDCl₃, 300 MHz), δ_ppm: 6.93 (s,

3H, CH core), 3.40 (m, 18H, CH₂Br), 1.84 (m, 18H, CH₂CH₂-

Br), 1.57 (s, 18H, C_qCH₂CH₂CH₂Si), 1.26 (m, 144H, (CH₂)₈),

1.04 (s, 18H, C_qCH₂CH₂CH₂Si), 0.42 (s, 36H, CH₂SiCH₂),

-0.10 (s, 54H, Si(CH₃)₂). ¹³C NMR (CDCl₃, 62.90 MHz),

_ppm: 145.7 (C_qof arom. core), 121.5 (CH of arom. core), 43.9

(C_qCH₂CH₂CH₂Si), 42.2 (benzylic C_q), 33.8 (CH₂CH₂Br), 32.8

(CH₂Br), 29.5 ((CH₂)₇), 24.0 (CH₂CH₂Si), 18.0 (C_qCH₂CH₂-

CH₂Si), 16.3 (CH₂Si), 15.6 (C_qCH₂CH₂CH₂Si), -3.1 (Si-

(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62 MHz), δ_ppm: 2.11 (Si(Me)₂).

Massspectrum(MALDI-TOF;m/z), calcd. forC₁₅₃H₃₀₉Si₉Br₉Na

(MNa^þ): 3 144.04, found: 3 144.44. Anal. Calcd for C₁₅₃

₃₀₉Si₉Br₉: C 58.88, H 9.98; found: C 59.63, H 10.24. (ii) The

dendrimer 33 was synthesized from G₀-long-Br (0.120 g, 0.0385

mmol) and NaN₃(0.045 g, 0.693 mmol) using the general

procedure for the synthesis of azido dendrimers, giving 33 as a

colorless waxy product (0.106 g, 99% yield). ¹H NMR (CDCl₃,

300 MHz), δ_ppm: 6.93 (s, 3H, CH core), 3.25 (m, 18H, CH₂N₃),

1.58 (s, 36H, CH₂CH₂CH₂Si), 1.26 (m, 180H, (CH₂)₉and

CH₂CH₂CH₂Si), 0.43 (s, 36H, CH₂SiCH₂), -0.11 (s, 54H, Si-

(CH₃)₂). ¹³C NMR(CDCl₃, 62.90 MHz), δ_ppm:145.8(C_qof arom.

core), 121.5 (CH of arom. core), 51.1 (CH₂N₃), 43.8 (C_qCH₂-

CH₂CH₂Si), 42.1 (benzylic C_q), 33.2 (CH₂CH₂N₃), 29.5 ((CH₂)₇),

23.4 (CH₂CH₂Si), 17.9 (C_qCH₂CH₂CH₂Si), 16.3 (CH₂Si), 14.9

(C_qCH₂CH₂CH₂Si), -3.3 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62

MHz), δ_ppm: 2.11 (Si(Me)₂). Anal. Calcd for C₁₅₃H₃₀₉Si₉N₂₇: C

General Procedure for the Hydrosilylation Reactions. The

olefin compound, diethyl ether, the silane derivative (2 equiv

per branch) and Kartstedt catalyst (0.1%) were successively

introduced into a Schlenk flask under a nitrogen atmosphere.

The reaction solution was stirred at 25 °C for 16 h. The solvent

was removed under vacuum and the catalyst residue was

removed by flash chromatography with ether, and the solvent

was removed.

58.88, H 9.98; found: C 59.63, H 10.24. IR υ_N3: 2 097 cm^-1

Synthesis of G₁-long-N₃, 34. (i) Hydrosilylation of G₁-27-allyl

7 (0.050 g, 0.0159 mmol) with the silane 32 (0.249 g, 0.85 mmol)

was carried out using the general procedure for the hydrosilyla-

tion reactions, yielding G₁-27-long-Br as a colorless waxy

General Procedure for the Synthesis of Azido Dendrimers. The

chloromethyl-terminated dendrimers and NaN₃(2 equiv per

product (0.174 g, 98% yield). H NMR (CDCl₃, 300 MHz),

Article

_ppm: 7.14 (d, 54H, arom), 7.05 (s, 3H, CH core), 6.84 (d, 54H,

Inorganic Chemistry, Vol. 49, No. 13, 2010 6099

(C_qCH₂CH₂CH₂Si), 16.1 (CH₂Si), 15.2 (C_qCH₂CH₂CH₂Si),

-3.6 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62 MHz), δ_ppm: 2.13

(Si(Me)₂).Anal. Calcd for C₄₄₂₈₁₈H₈₄₆₂₉₁O₉₈₃₇Si₂₉₅₂₀Br₁₉₆₈₃: C

60.92, H 9.77; found: C 57.32, H 9.52. (ii) The dendrimer 35 was

synthesized from G₇-long-Br (0.050 g, 5.73. 10^-6mmol) and

NaN₃(0.015 g, 0.226 mmol) using the general procedure for the

synthesis of azido dendrimers, giving 36 as a colorless waxy

arom), 3.51 (s, 18H, CH₂O), 3.40 (m, 54H, CH₂Br), 1.85 (m,

54H, CH₂CH₂Br), 1.55 (s, 72 H, C_qCH₂CH₂CH₂Si), 1.25 (m,

144H, (CH₂)₉), 0.41 (s, 108H, CH₂SiCH₂), -0.10 (s, 54H,

Si(CH₃)₂). ¹³C NMR (CDCl₃, 62.90 MHz), δ_ppm: 158.5 (arom.

OC_q), 139.2 (arom. C_q), 126.7 and 112.9 (arom. CH of dendron),

59.7 (SiCH₂O), 42.6 (C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q),

33.3 (CH₂CH₂Br), 32.7 (CH₂Br), 29.2 ((CH₂)₇), 24.1 (CH₂CH₂-

Si), 17.8 (C_qCH₂CH₂CH₂Si), 16.2 (CH₂Si), 15.3 (C_qCH₂CH₂-

product (0.043 g, 93% yield). H NMR (CDCl₃, 300 MHz),

_ppm: 7.11 (d, arom), 6.78 (d, arom), 3.50 (s, CH₂O), 3.25 (m,

CH₂Si), -3.6 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62 MHz), δ_ppm

CH₂N₃), 1.59 (s, C_qCH₂CH₂CH₂Si), 1.25 (m, (CH₂)₉), 0.42 (s,

CH₂SiCH₂), -0.10 (s, Si(CH₃)₂). ¹³C NMR (CDCl₃, 62.90

MHz), δ_ppm: 158.5 (arom. OC_q), 138.8 (arom. C_q), 126.6 and

112.9 (arom. CH of dendron), 59.6 (SiCH₂O), 51.2 (CH₂N₃),

42.5 (C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q), 33.5 (CH₂CH₂N₃),

32.9 (CH₂N₃), 29.3 ((CH₂)₇), 24.1 (CH₂CH₂Si), 17.6

(C_qCH₂CH₂CH₂Si), 16.3 (CH₂Si), 15.3 (C_qCH₂CH₂CH₂Si),

-3.6 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62 MHz), δ_ppm: 2.12

(Si(Me)₂).

2.12 (Si(Me)₂). Anal. Calcd for C₅₅₈H₁₀₈₃O₉Si₃₆Br₂₇: C 60.35, H

9.83; found: C 59.81, H 9.80. (ii) The dendrimer 34 was

synthesized from G₁-long-Br (0.142 g, 0.0128 mmol) and

NaN₃(0.045 g, 0.693 mmol) using the general procedure for

the synthesis of the azido dendrimers, giving 34 as a colorless

waxy product (0.128 g, 99% yield). ¹H NMR (CDCl₃, 300

MHz), δ_ppm: 7.15 (d, 54H, arom), 7.05 (s, 3H, CH core), 6.84

(d, 54H, arom), 3.51 (s, 18H, CH₂O), 3.23 (m, 54H, CH₂N₃),

1.57 (s, 72 H, C_qCH₂CH₂CH₂Si), 1.26 (m, 144H, (CH₂)₉), 0.42

(s, 108H, CH₂SiCH₂), -0.10 (s, 54H, Si(CH₃)₂). ¹³C NMR

(CDCl₃, 62.90 MHz), δ_ppm: 158.4 (arom. OC_q), 139.1 (arom.

C_q), 126.7 and 112.9 (arom. CH of dendron), 59.7 (SiCH₂O),

51.1 (CH₂N₃), 42.6 (C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q), 33.3

(CH₂CH₂N₃), 32.7 (CH₂N₃), 29.3 ((CH₂)₇), 24.1 (CH₂CH₂Si),

17.8 (C_qCH₂CH₂CH₂Si), 16.2 (CH₂Si), 15.3 (C_qCH₂CH₂-

CH₂Si), -3.6 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62 MHz),

[Fe(η⁵-C₅H₄CO₂CH₂CtCH)(η⁶-C₆Me₆)][PF₆], 37. A sus-

pension of 2 (2 g, 5.75 mmol) was heated in refluxing SOCl₂

(40 mL) for 16 h, giving an homogeneous red solution of 3.

SOCl₂was removed using a trap-to-trap system under nitrogen

atmosphere, and the red powder of 3 was dissolved in dry

dichloromethane and slowly added to a dichloromethane solu-

tion of propargyl alcohol (0.644 g, 11.49 mmol) and triethyla-

mine (3 mL). The mixture was stirred under nitrogen atmo-

sphere for 2 h at room temperature. The solvent was removed

under vacuum, dissolved with dichloromethane and washed

with an aqueous solution of K₂CO₃and with an aqueous

solution of HPF₆. The organic solution was dried with sodium

sulfate, filtered, and the solvent was removed under vacuum.

The product was precipitated from dichloromethane with ether.

The complex [(CpCO₂CH₂CtCH)(η⁶-C₆Me₆)Fe][PF₆], 37, was

δ_ppm: 2.12 (Si(Me)₂).

Synthesis of G₄-long-N₃, 35. (i) Hydrosilylation of G₄-729-

allyl 10 (0.050 g, 4.60. 10^-4mmol) using the silane 32 (0.197 g,

0.0671 mmol) was carried out using the general procedure for

the hydrosilylation reactions, giving G₄-729-long-Br as a color-

less waxy product (0.142 g, 96% yield). ¹H NMR (CDCl₃, 300

MHz), δ_ppm: 7.12 (d, arom), 6.82 (d, arom), 3.50 (s, CH₂O), 3.38

(m, CH₂Br), 1.86 (m, CH₂CH₂Br), 1.57 (s, C_qCH₂CH₂CH₂Si),

obtained as an orange powder (2.35 g, 80% yield). H NMR

(CH₃COCH₃, 250 MHz), δ_ppm: 5.23 and 5.07 (s, 4H, Cp), 5.07

1.25 (m, (CH₂)₉), 0.42 (s, CH₂SiCH₂), -0.06 (s, Si(CH₃)₂). ¹³

(s, 2H, OCH₂), 3.31 (s, 1H, CtCH), 2.54 (s, 18H, C₆Me₆). ¹³

NMR (CDCl₃, 62.90 MHz), δ_ppm: 158.4 (arom. OC_q), 139.1

(arom. C_q), 126.7 and 112.9 (arom. CH of dendron), 59.8

(SiCH₂O), 42.6 (C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q), 33.3

(CH₂CH₂Br), 32.7 (CH₂Br), 29.2 ((CH₂)₇), 24.1 (CH₂CH₂Si),

17.8 (C_qCH₂CH₂CH₂Si), 16.1 (CH₂Si), 15.2 (C_qCH₂CH₂CH₂-

Si), -3.6 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62 MHz), δ_ppm: 2.12

(Si(Me)₂). Anal. Calcd for C₁₆₃₅₃H₃₁₂₆₉O₃₆₀Si₁₀₈₉Br₇₂₉: C 60.90,

H 9.77; found: C 59.47, H 9.77. (ii) The dendrimer 34 was

synthesized from G₄-long-Br (0.050 g, 0.000155 mmol) and

NaN₃(0.015 g, 0.226 mmol) using the general procedure for

the synthesis of the azido dendrimers. The product 34 was

NMR (CH₃COCH₃, 62.50 MHz), δ_ppm: 165.9 (CdO), 100.8 (Cq

of C₆Me₆), 90.9 (Cq of Cp), 82.2 and 79.1 (CH of Cp), 81.7

(CtCH), 77.8 (CtCH), 53.8 (OCH₂), 17.2 (CH₃of C₆Me₆).

Anal. Calcd for C₂₁H₂₅O₂FePF₆: C 49.41, H 4.90; found: C

49.57, H 4.94. IR ν_c=o: 1726 cm^-1

[CpFe(η⁶-C₆Me₆)CONHCH₂CtCH][PF₆], 38. A suspension

of [CpFe(η⁶-C₆Me₆)COOH][PF₆] (0.550 g, 1.17 mmol) was

heated in refluxing SOCl₂(40 mL) for 16 h, and an homoge-

neous red solution was obtained; SOCl₂was then removed using

a trap-to-trap system under nitrogen atmosphere, and the

complex 3 was obtained as a red powder. This complex 3 was

dissolved in dry dichloromethane and slowly added to a di-

chloromethane solution of propargylamine (0.129 g, 2.34 mmol)

and triethylamine (2 mL). The mixture was stirred under nitro-

gen atmosphere for 2 h at room temperature. The solvent was

removed under vacuum, and the solid residue was dissolved in

dichloromethane and washed with an aqueous solution of

K₂CO₃, then with an aqueous solution of HPF₆. The organic

solution was dried over sodium sulfate, filtered and the solvent

removed under vacuum, then the solid product was precipitated

from a dichloromethane solution using ether. The complex 38

was obtained as an orange powder (0.470 g, 80% yield). ¹H

NMR (CH₃COCH₃, 300 MHz), δ_ppm: 8.03 (s, 1H, NH), 5.11

and 4.89 (s, 5H, Cp), 4.18 (m, 2H, NHCH₂), 2.78 (s, 1H,

CtCH), 2.45 (s, 18H, C₆Me₆). ¹³C NMR (CH₃COCH₃, 62.90

MHz), δ_ppm: 163.6 (CdO), 100.4 (C_qof C₆Me₆), 84.2 (C_qof Cp),

81.2 and 77.2 (CH of Cp), 80.5 (CtCH), 72.7 (CtCH), 48.1

(NHCH₂), 17.0 (CH₃of C₆Me₆). Anal. Calcd for C₂₁H₂₆ON-

obtained as a colorless waxy product (0.045 g, 98% yield). H

NMR (CDCl₃, 300 MHz), δ_ppm: 7.14 (d, arom), 6.84 (d, arom),

3.50 (s, CH₂O), 3.25 (m, CH₂N₃), 1.59 (s, C_qCH₂CH₂CH₂Si),

1.28 (m, (CH₂)₉), 0.42 (s, CH₂SiCH₂), -0.10 (s, Si(CH₃)₂). ¹³

NMR (CDCl₃, 62.90 MHz), δ_ppm: 158.4 (arom. OC_q), 138.9

(arom. C_q), 126.6 and 112.8 (arom. CH of dendron), 59.5

(SiCH₂O), 51.2 (CH₂N₃), 42.5 (C_qCH₂CH₂CH₂Si), 41.2

(benzylic C_q), 33.3 (CH₂CH₂N₃), 32.7 (CH₂N₃), 29.3 ((CH₂)₇),

24.1 (CH₂CH₂Si), 17.6 (C_qCH₂CH₂CH₂Si), 16.3 (CH₂Si), 15.3

(C_qCH₂CH₂CH₂Si), -3.6 (Si(CH₃)₂). ²⁹Si NMR (CDCl₃, 59.62

MHz), δ_ppm: 2.12 (Si(Me)₂).

Synthesis of G₇-long-N₃, 36. (i) Hydrosilylation of G₇-allyl 13

(0.050 g, 1.69. 10^-5mmol) with the silane 32 (0.195 g, 0.0666

mmol) was carried out using the general procedure for the

hydrosilylation reactions, giving G₇-long-Br as a colorless waxy

product (0.134 g, 91% yield). ¹H NMR (CDCl₃, 300 MHz),

δ_ppm: 7.12 (d, arom), 6.78 (d, arom), 3.50 (s, CH₂O), 3.39 (m,

CH₂Br), 1.82 (m, CH₂CH₂Br), 1.57 (s, C_qCH₂CH₂CH₂Si), 1.26

(m, (CH₂)₉), 0.41 (s, CH₂SiCH₂), -0.06 (s, Si(CH₃)₂). ¹³C NMR

(CDCl₃, 62.90 MHz), δ_ppm: 158.3 (arom. OC_q), 139.1 (arom.

C_q), 126.8 and 112.8 (arom. CH of dendron), 59.7 (SiCH₂O),

42.7 (C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q), 33.4 (CH₂CH₂-

Br), 32.7 (CH₂Br), 29.4 ((CH₂)₇), 24.1 (CH₂CH₂Si), 17.8

FePF₆: C 49.53, H 5.15; found: C 48.38, H 5.02. IR υ_CdO:1667cm^-1

General Procedure for the Synthesis by “Click” Reactions

of the Dendrimers G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-triazolyl-

dendr)(η⁶-C₆Me₆)] [PF₆], (n = 1, 2, 4, 7 ; X = O/NH). The

complexes 37 or 38 (1.5 equiv per branch) dissolved in 30 mL of

6100 Inorganic Chemistry, Vol. 49, No. 13, 2010

Djeda et al.

degassed dichloromethane was added to a solution of the azido

dendrimer in 30 mL of degassed dichloromethane, and 60 mL of

degassed water (1:1 dichloromethane/water) was added. A

solution of CuSO₄1 M (1 equiv per branch) was added at

0 °C, followed by the dropwise addition of a freshly prepared

solution of sodium ascorbate 1 M (2 equiv per branch). The

reaction mixture was allowed to stir for 24 h under nitrogen

atmosphere at room temperature. An aqueous solution of

ammonia was then added, and the mixture was allowed to stir

10 min to remove all the copper trapped inside the dendrimer.

The organic phase was washed twice with water, dried over

sodium sulfate, filtered, and the solvent was removed under

vacuum. The product was then washed with methanol to remove

the excess alkyne and precipitated from an acetonitrile solution

with methanol.

MHz), δ_ppm: 8.21 (s, 9H, NH), 7.95 (s, 9H, CH of triazole), 7.09 (s,

3H, CH core), 5.16 and 4.90 (s, 45H, Cp), 4.62 (s, 18H, NHCH₂-

triazole), 4.40 (t, 18H, triazole-CH₂CH₂), 2.43 (s, 162H, C₆Me₆), 1.87

(t, 18H, triazole-CH₂CH₂), 1.58 (s, 36H, CH₂CH₂CH₂Si), 1.32 (m,

180H, (CH₂)₉and CH₂CH₂CH₂Si), 0.51 (s, 36H, CH₂SiCH₂), -0.36

(s, 54H, Si(CH₃)₂). ¹³C NMR (CH₃COCH₃, 75.0 MHz), δ_ppm: 162.8

(CdO), 145.7 (C_qof arom. core), 143.2 (C_qof triazole), 123.0 (CH of

triazole), 121.3 (CHofarom. core), 99.4(C_qof C₆Me₆), 83.7 and 78.3

(C_qof Cp), 80.2 and 76.3 (CH of Cp), 71.7 (triazole-CH₂CH₂), 49.8

(NHCH₂-triazole), 43.7 (C_qCH₂CH₂CH₂Si), 42.0 (benzylic C_q), 34.9

(triazole-CH₂CH₂), 29.2 ((CH₂)₇), 23.8 (CH₂CH₂Si), 17.9 (C_qCH₂-

CH₂CH₂Si), 16.0 (CH₃of C₆Me₆), 14.9 (C_qCH₂CH₂CH₂Si), -3.6

(Si(CH₃)₂). ²⁹Si NMR (CH₃COCH₃, 59.62 MHz), δ_ppm: 2.13

(SiMe₂). MS (MALDI-TOF; m/z), calcd. for C₃₄₂H₅₄₃Si₉O₉N_36-

Fe₉P₈F₄₈(M^þ): 7 218.38, found: 7 215.06. Anal. Calcd for C₃₄₂H₅₄₃

G₀-9-[Fe(η⁵-C₅H₄CO₂CH₂-1,2,3-triazolyl-dendr)(η⁶-C₆Me₆)]

[PF₆], 39. The complex 39 wassynthesized from 37 (0.242g, 0.486

mmol) and G₀-9-long-N₃33 (0.1 g, 0.036 mmol) using the general

procedure for the synthesis by“click”reactions of the dendrimers

G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-triazolyl-dendr)(η⁶-C₆Me₆)]

[PF₆], (n = 1, 2, 4, 7 ; X = O/NH). The complex 39 was obtained

as an orange powder (0.232 g, yield 89%). ¹H NMR (CH₃-

COCH₃, 250 MHz), δ_ppm: 8.23 (s, 9H, CH of triazole), 7.10 (s,

3H, CH core), 5.48 (s, 18H, OCH₂-triazole), 5.16 and 5.02 (s,

36H, Cp), 4.45 (t, 18H, triazole-CH₂CH₂), 2.47 (s, 162H, C₆Me₆),

1.94 (m, 18H, triazole-CH₂CH₂), 1.72 (m, 36H, CH₂CH₂CH₂Si),

1.30 (m, 162H, (CH₂)₉), 1.21 (t, 36H, CH₂CH₂CH₂Si), 0.51 (s,

36H, CH₂SiCH₂), -0.03 (s, 54H, Si(CH3)2). ¹³C NMR (CH₃-

COCH₃, 62.5 MHz), δ_ppm: 166.3 (CdO), 146.6 (Cq of triazole),

142.5 (Cq of arom. core), 132.2 (CH of triazole), 125.9 (CH of

arom. core), 100.7 (Cq of C₆Me₆), 90.9 (Cq of Cp), 82.0 and 79.1

(CH of Cp), 69.7 (OCH₂-triazole), 59.6 (triazole-CH₂CH₂), 55.4

(triazole-CH₂CH₂), 50.8 (triazole-CH₂CH₂CH₂), 44.7 (C_qCH₂-

CH₂CH₂Si), 43.0 (benzylic C_q), 34.7 (triazole-CH₂CH₂CH₂

CH₂), 32.08 (triazole-CH₂CH₂CH₂CH₂CH₂), 27.3 and 24.8

((CH₂)₄CH₂CH₂Si), 23.8 (CH₂CH₂Si), 18.9 (C_qCH₂CH₂CH₂-

Si), 18.8 ((CH₂)₄CH₂CH₂Si), 17.1 (CH₃of C₆Me₆), 16.9 (C_qCH₂-

CH₂CH₂Si), 16.2 ((CH₂)₄CH₂CH₂Si), -2.5 (Si(CH₃)₂). Anal.

Calcd for C₃₄₂H₅₃₄O₁₈N₂₇Si₉Fe₉P₉F₅₄: C 55.73, H 7.25; found:

Si₉O₉N₃₆Fe₉P₉F₅₄: C 55.79, H 7.43; found: C 54.93, H 7.34.

G₁-27-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆-

Me₆)][PF₆], 42. The dendrimer 42 was synthesized from G₁-long-

N₃34 (0.050 g, 0.00496 mmol) and 38 (0.099 g, 0.198 mmol) using

the general procedure for the synthesis by “click” reactions of the

dendrimers G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-triazolyl-dendr)-

(η⁶-C₆Me₆)][PF₆], (n = 1, 2, 4, 7 ; X = O/NH), giving 42 as an

orange powder (0.089 g, 76% yield). ¹H NMR (CH₃COCH₃, 300

MHz), δ_ppm: 8.21(s, 27H, NH), 7.99 (s, 27H, CH oftriazole), 7.24

(d, 54H, arom), 6.89 (d, 54H, arom), 5.21 and 4.95 (s, 45H, Cp),

4.66 (s, 54H, NHCH₂-triazole), 4.24 (t, 54H, triazole-CH₂CH₂),

3.58 (s, 18H, CH₂O), 2.48 (s, 486H, C₆Me₆), 1.92(t, 54H, triazole-

CH₂CH₂), 1.70 (s, 72H, CH₂CH₂CH₂Si), 1.31 (m, 144H, (CH₂)₉),

0.52 (s, 126H, CH₂SiCH₂), -0.050 (s, 54H, Si(CH₃)₂). ¹³C NMR

(CH₃COCH₃, 75.0 MHz), δ_ppm: 162.7 (CdO), 158.9 (arom. OC_q),

144.0 (C_qof triazole), 139.1 (arom. C_q), 126.9 and 113.5 (arom.

CH of dendron), 122.9 (CH of triazole), 99.6 (C_qof C₆Me₆), 83.7

and 78.3 (C_qof Cp), 80.2 and 76.3 (CH of Cp), 71.7 (triazole-

CH₂CH₂), 59.8 (SiCH₂O), 49.6 (NHCH₂-triazole), 42.6 (C_q-

CH₂CH₂CH₂Si), 41.2 (benzylic C_q), 34.7 (triazole-CH₂CH₂),

29.2 ((CH₂)₇), 23.8 (CH₂CH₂Si), 17.9 (C_qCH₂CH₂CH₂Si), 16.0

(CH₃of C₆Me₆), 14.9 (C_qCH₂CH₂CH₂Si), -3.7 (Si(CH₃)₂). ²⁹Si

NMR (CH₃COCH₃, 59.62 MHz), δ_ppm: 2.13 (Si(Me)₂). Anal.

Calcd for C₁₁₂₅H₁₄₈₅Si₃₆O₃₆N₁₀₈Fe₂₇P₂₇F₁₆₂: C 57.42, H 6.36;

found: C 57.04, H 6.23.

C 55.12, H 7.21. IR ν_c=o: 1721 cm^-1

G₄-729-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆-

Me₆)][PF₆], 43. The dendrimer 43 was synthesized from G₄-long-

N₃, 35, (0.045 g, 1.52. 10^-4mmol) and 38 (0.083 g, 0.166 mmol)

with the general procedure for the synthesis by “click” reactions of

the dendrimers G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-triazolyl-den-

dr)(η⁶-C₆Me₆)] [PF₆], (n = 1, 2, 4, 7 ; X = O/NH), giving 43 as

an orange powder (0.061 g, 61% yield). ¹H NMR (CH₃COCH₃,

300 MHz), δ_ppm: 8.25 (s, NH), 7.98 (s, CH of triazole), 7.21 (d,

arom), 6.88 (d, arom), 5.20 and 4.93 (s, Cp), 4.64 (s, NHCH₂-

triazole), 4.42 (t, triazole-CH₂CH₂), 3.56 (s, CH₂O), 2.46 (s,

zC₆Me₆), 1.91 (t, triazole-CH₂CH₂), 1.68 (s, CH₂CH₂CH₂Si),

G₁-27-[Fe(η⁵-C₅H₄CO₂CH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)]-

[PF₆], 40. The metallodendrimer 40 was synthesized from the azido

dendrimer G₁-long-N₃34 (0.1 g, 0.01 mmol) and 37 (0.200 g, 0.402

mmol) using the general procedure for the synthesis by “click”

reactions of the dendrimers G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-tria-

zolyl-dendr)(η⁶-C₆Me₆)] [PF₆], (n = 1, 2, 4, 7 ; X = O/NH). The

complex 31 was obtained as an orange powder (0.215 g, 92% yield).

¹H NMR (CD₃CN, 200 MHz), δ_ppm: 7.99 (s, CH of triazole), 7.21

(d, arom.), 6.85 (d, arom.), 5.45 (s, OCH₂-triazole), 4.97 and 4.79 (s,

Cp), 4.41 (t, triazole-CH₂CH₂), 3.54 (s, SiCH₂O), 2.39 (s, C₆Me₆),

1.91 (t, triazole-CH₂CH₂), 1.66 (s, CH₂CH₂CH₂Si), 1.29 (m,

(CH₂)₉), 1.15 (t, CH₂CH₂CH₂Si), 0.47 (t, CH₂SiCH₂), -0.06 (s,

216H, Si(CH3)2). ¹³C NMR (CD₃CN, 50 MHz), δ_ppm: 165.5 (Cd

O), 146.0 (Cq of triazole), 137.1 (arom. C_q), 131.8 (CH of triazole),

99.9 (Cq of C₆Me₆), 90.9 (Cq of Cp), 80.7 and 78.9 (CH of Cp), 69.7

(OCH₂-triazole), 58.9 (triazole-CH₂CH₂), 42.3 (C_qCH₂CH₂-

CH₂Si), 36.9 (triazole-CH₂CH₂CH₂CH₂), 33.7 (triazole-CH₂CH₂

CH₂CH₂CH₂), 29.5 ((CH₂)₄CH₂CH₂Si), 26.4 (CH₂CH₂Si), 23.8

(C_qCH₂CH₂CH₂Si), 19.4 ((CH₂)₄CH₂CH₂Si), 18.00 (CH₃of

C₆Me₆), 16.2 (C_qCH₂CH₂CH₂Si), 15.4 ((CH₂)₄CH₂CH₂Si), -3.3

(Si(CH₃)₂). Anal. Calcd for C₁₁₂₅H₁₄₅₈O₆₃N₈₁Si₃₆Fe₂₇P₂₇F₁₆₂: C

1.29 (m, (CH₂)₉), 0.48 (s, CH₂SiCH₂), -0.067 (s, Si(CH₃)₂). ¹³

NMR (CH₃COCH₃, 75.0 MHz), δ_ppm: 162.7 (CdO), 158.8

(arom. OC_q), 144.1 (C_qof triazole), 139.1 (arom. C_q), 126.7 and

113.5 (arom. CH of dendron), 122.9 (CH of triazole), 99.4 (C_qof

C₆Me₆), 83.7 and 78.3 (C_qof Cp), 80.2 and 76.3 (CH of Cp), 71.7

(triazole-CH₂CH₂), 59.8 (SiCH₂O), 49.6 (NHCH₂-triazole), 42.6

(C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q), 34.8 (triazole-CH₂CH₂),

29.1 ((CH₂)₇), 23.8 (CH₂CH₂Si), 17.9 (C_qCH₂CH₂CH₂Si), 16.0

(CH₃of C₆Me₆), 14.9 (C_qCH₂CH₂CH₂Si), -3.7 (Si(CH₃)₂). ²⁹Si

NMR (CH₃COCH₃, 59.62 MHz), δ_ppm: 2.13 (Si(Me)₂). Anal.

Calcd for C₃₁₆₆₂H₅₀₂₂₃O₁₀₈₉Si₁₀₈₉N₂₉₁₆Fe₇₂₉P₇₂₉F₄₃₇₄: C 57.09, H

12.47; found: C 55.01, H 12.23.

G₇-19683-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-

C₆Me₆)][PF₆], 44. The dendrimer 44 was synthesized from G₇-

long-N₃, 36, (0.040 g, 5 ꢀ 10^-6mmol) and 38 (0.073 g, 0.148

mmol) with the general procedure for the synthesis by “click”

reactions of the dendrimers G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-

triazolyl-dendr)(η⁶-C₆Me₆)][PF₆], (n = 1, 2, 4, 7 ; X = O/NH),

57.36, H 6.19, found: C 56.39; H 0.5.96 IR ν_c=o: 1721 cm^-1

G₀-9-[Fe(η⁵-C₅H₄CONHCH₂-1,2,3-triazolyl-dendr-)(η⁶-C₆Me₆)]-

[PF₆], 41. The dendrimer 41 was synthesized from G₀-long-N₃33

(0.060 g, 0.0216 mmol) and 38 (0.145 g, 0.292 mmol) using the general

procedure for the synthesis by “click” reactions of the dendrimers

G_n-n-[Fe(η⁵-C₅H₄COXCH₂-1,2,3-triazolyl-dendr)(η⁶-C₆Me₆)] [PF₆],

(n = 1, 2, 4, 7 ; X = O/NH). The complex 41 was obtained as an

orange powder (0.136 g, 87% yield). H NMR (CH₃COCH₃, 300

Article

Inorganic Chemistry, Vol. 49, No. 13, 2010 6101

giving 44 as an orange powder (0.046 g, 52% yield). H NMR

(CH₃COCH₃, 300 MHz), δ_ppm: 8.17 (s, NH), 7.95 (s, CH of

triazole), 7.21 (d, arom), 6.88 (d, arom), 5.20 and 4.93 (s, Cp),

4.64 (s, NHCH₂-triazole), 4.41 (t, triazole-CH₂CH₂), 3.56 (s,

CH₂O), 2.46 (s, C₆Me₆), 1.91 (t, triazole-CH₂CH₂), 1.71 (s,

CH₂CH₂CH₂Si), 1.29 (m, (CH₂)₉), 0.51 (s, CH₂SiCH₂), -0.064

(s, Si(CH₃)₂). ¹³C NMR (CH₃COCH₃, 75.0 MHz), δ_ppm: 162.7

(CdO), 158.7 (arom. OC_q), 144.2 (C_qof triazole), 139.1 (arom.

C_q), 126.7 and 113.5 (arom. CH of dendron), 122.7 (CH of

triazole), 99.3 (C_qof C₆Me₆), 83.7 and 78.3 (C_qof Cp), 80.2 and

76.3 (CH of Cp), 71.7 (triazole-CH₂CH₂), 59.8 (SiCH₂O), 49.6

(NHCH₂-triazole), 42.5 (C_qCH₂CH₂CH₂Si), 41.2 (benzylic C_q),

34.8 (triazole-CH₂CH₂), 29.1 ((CH₂)₇), 23.8 (CH₂CH₂Si), 17.9

(C_qCH₂CH₂CH₂Si), 16.2 (CH₃of C₆Me₆), 14.9 (C_qCH₂-

CH₂CH₂Si), -3.7 (Si(CH₃)₂). ²⁹Si NMR (CH₃COCH₃, 59.62

for the following reaction. This solution was slowly added to a

CH₃CN solution (15 mL) of 22 (0.050 g, 0.0014 mmol) upon

stirring at -40 °C until the solution turned from forest-green to

blue-green (equivalence point of the titration), indicating the

formation of 22a. The solution of 22a at -40 °C was slowly

added to a 30-mL toluene solution of C₆₀(0.063 g, 0.088 mmol)

at -40 °C, which immediately provoked the formation of a

precipitate, until the blue-green color persisted in solution

(equivalence point of the titration). The solvent was removed

under vacuum, and the residue was washed twice with CH₃CN

(the yellow extracts contained 1 as verified by H NMR), and

with toluene (colorless extract). The black powder of 45 was

dried under vacuum and was kept under N₂(0.091 g, 0.00127 mmol,

91% yield). The organic solvent resulting from the washing was

removed under vacuum and 0.032 g (0.079 mmol, 80%) of 1 was

recovered. EPR spectrum of 45 at 298 K (see Figure 3): g =

MHz), δ_ppm: 2.13 (Si(Me)₂). Anal. Calcd for C₈₅₆₁₆₁H_1358049

₂₉₅₂₀Si₂₉₅₂₀N₇₈₇₃₂Fe₁₉₆₈₃P₁₉₆₈₃F₁₁₈₀₉₈: C 57.10, H 7.60; found:

C 53.61, H 7.32.

€

2.00093; ΔH=3.12 G. Mossbauer spectrum of 45 at 77 K: a simple

quadrupole doublet (QS = 1.97 mm/s; IS = 0.56 mm/s vs Fe),

characteristic of the salts of 1.^4a,12a

[Fe(η⁵-C₅H₄CO₂^-Na^þ)(η⁶-C₆Me₆)][PF₆], 2a. The complex 2

(0.150 g, 0.3178) was added at ambient temperature to a solution

of NaOH (0.013 g, 0.3178 mmol) in 5 mL of EtOH. After stirring

for 5 min, the solvent was removed under vacuum, giving 2a as

an orange powder (0.160 g; 98% yield). ¹H NMR (CD₃CN, 200

Acknowledgment. We are grateful to Prof. Franc-ois Varret

€

(University of Versailles) for the Mossbauer spectrum of 45. The

ꢁ

Ministere de l’Enseignement Superieur et de la Recherche

Scientifique de Cote d’Ivoire (Ph.D. grant to R.D.), the

ꢀ

MHz), δ_ppm: 4.73 and 4.45 (s, 4H, Cp), 2.37 (s, 18H, C₆Me₆). ¹³

~ ^

Fundac-ao para a Ciencia e a Tecnologia (FCT), Portugal (Ph.

NMR (CD₃CN, 50 MHz) δ_ppm: 168.6 (CdO), 98.5 (C₆Me₆),

89.3 (Cq of Cp), 79.1 and 78.4 (CH of Cp), 16.0 (CH₃of C₆Me₆).

Reaction between C₆₀and 22a with Formation of G₄-DAB-

64-[Fe^II(η⁵-C₅H₄CONH-dendr)(η⁶-C₆Me₆)][C₆₀^•-], 45. 1 (0.040

g, 0.099 mmol), in 10 mL of THF was stirred with 4.6 g of Na/Hg

amalgam (1%, 2 mmol) for 1 h under N₂. Then, THF was

removed under vacuum, the residue of 1 was extracted with

15 mL of pentane, and this forest-green solution of 1 was used

ꢀ

D. grant to C.O.), the Universite Bordeaux 1, the CNRS, the

IUF (D.A.) and the ANR (ANR-06-NANO-026) are gratefully

acknowledged for financial support.

Supporting Information Available: General data and ¹H and

¹³C NMR and IR spectra of new products (PDF). This material

is available free of charge via the Internet at http://pubs.acs.org.

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