Cyclophosphazene hydrazides as scaffolds for multi-ferrocenyl assemblies: Synthesis, structure, and electrochemistry

Article abstract of DOI:10.1021/om020760d

Reactions of N-methylhydrazine with chlorocyclophosphazenes, N₃P₃Cl₃ (1), N₃P₃(OPh)Cl₅ (2),gem-N₃P₃Ph₂Cl₄ (3), spiro-N₃P₃(O

Full text of DOI:10.1021/om020760d

976
Organometallics 2003, 22, 976-986
Cyclop h osp h a zen e Hyd r a zid es a s Sca ffold s for
Mu lti-F er r ocen yl Assem blies: Syn th esis, Str u ctu r e, a n d
Electr och em istr y
Vadapalli Chandrasekhar,*,† Gurusamy Thangavelu Senthil Andavan,†
Selvarajan Nagendran,† Venkatasubbaiah Krishnan,†
Ramachandran Azhakar,† and Raymond J . Butcher‡
Department of Chemistry, Indian Institute of Technology, Kanpur-208 016, India, and
Department of Chemistry, Howard University, Washington, D.C. 20059
Received September 12, 2002
Reactions of N-methylhydrazine with chlorocyclophosphazenes, N3P3Cl6 (1), N3P3(OPh)-
Cl5 (2), gem-N3P3Ph2Cl4 (3), spiro-N3P3(O2C12H8)2Cl2 (4), N3P3(OPh)5Cl (5), and diphenylphos-
phinic chloride, Ph2P(O)Cl (6), proceed in a regiospecific manner to afford the products
N3P3[N(Me)NH2]6 (1a ), N3P3(OPh)[N(Me)NH2]5 (2a ), gem-N3P3Ph2[N(Me)NH2]4 (3a ), spiro-
N3P3(O2C12H8)2[N(Me)NH2]2 (4a ), N3P3(OPh)5[N(Me)NH2] (5a ), and Ph2P(O)[N(Me)NH2] (6a ).
The terminal NH2 groups in all of these compounds are reactive and have been used in the
condensation reaction involving ferrrocene-2-carboxaldehyde to afford the corresponding
hydrazones N3P3[N(Me)NdCHC5H4FeC5H5]6 (1b), N3P3(OPh)[ N(Me)NdCHC5H4FeC5H5]5
(2b), gem-N3P3Ph2[N(Me)NdCHC5H4FeC5H5]4 (3b), spiro-N3P3(O2C12H8)2[N(Me)NdCHC5H4-
FeC5H5]2 (4b), N3P3(OPh)5[N(Me)NdCHC5H4FeC5H5] (5b), and Ph2P(O)[ N(Me)NdCHC5H4-
FeC5H5] (6b). The structures of 1-6(a ,b) have been determined by the use of multinuclear
NMR, mass spectroscopy, and elemental analysis. X-ray crystal structures of 1b, 3b, 4b,
5b, and 6b have also been determined, which confirm their molecular structures. Cyclic
voltammetric experiments on the ferrocenyl derivatives 1b-6b reveal an essentially
reversible oxidation peak. Further, all of these are electrochemically quite robust and do
not decompose on oxidation.
In tr od u ction
and co-workers have utilized a benzene type core
prepared from (η5-C5H5)Fe(η6-2,3,5,6-Me4-C6H2) to graft
ferrocene moieties in the periphery.4 Alternate ap-
proaches include using ferrocenyl silylation of triallyl
benzene derivatives to prepare appropriate dendrons,
which have been used in a convergent synthesis to
assemble ferrocene dendrimers.5 Other types of synthe-
ses involving both convergent and divergent methods
are known.6 However, all of these examples involve
multistep synthesis with the final yields of the products
being low to moderate. Also X-ray crystal structures of
these multi-ferrocene compounds are not known.
In an effort to find shorter synthetic methods for the
preparation of multi-ferrocene assemblies in good yields,
we have chosen inorganic alternatives. Chlorocyclo-
phosphazenes such as N3P3Cl6 with a reactive periphery
and a robust framework provide an excellent choice for
supporting redox-active substituents because these
In recent years there is a considerable amount of
interest in the preparation of multi-metallocenyl as-
semblies in general and multi-ferrocenyl assemblies in
particular.1 This emanates from the objective of gener-
ating novel materials possessing interesting chemical,
electric, optical, and magnetic properties. Thus, such
compounds possessing electrochemically active groups
can be viewed as excellent candidates for multielectron
reservoir systems, electron-transfer mediators, redox-
active materials for the modification of electrodes, ion
sensors, or materials for electronic devices.2 Among the
various classes of compounds that have received atten-
tion, dendrimers containing a redox-active periphery of
ferrocenes have been most actively investigated.3 Astruc
† Indian Institute of Technology.
‡ Howard University.
(1) (a) Newkome, G. R.; He, E.; Moorefield, C. N. Chem. Rev. 1999,
99, 1689. (b) Nguyen, P.; Elipe, P. G.; Manners, I. Chem. Rev. 1999,
99, 1515.
(2) (a) Flanagan, J . B.; Margel, S.; Bard, A. J .; Anson, F. C. J . Am.
Chem. Soc. 1978, 100, 4248. (b) Astruc, D. New. J . Chem. 1992, 16,
305. (c) Astruc, D. Top. Curr. Chem. 1991, 160, 47. (d) Hill, H. A. U.;
Page D. J .; Walton, N. J . J . Electroanal. Chem. 1987, 217, 141. (e)
Vale´rio, C.; Fillaut, J .-L.; Ruiz, J .; Guittard, J .; Blais J .-C.; Astruc, D.
J . Am. Chem. Soc. 1997, 119, 2588.
(3) (a) Bard, A. J . Nature 1995, 374, 13. (b) Beer, P. D. Acc. Chem.
Res. 1998, 31, 71. (c) Astruc, D. Acc. Chem. Res. 2000, 33, 287. (d)
Nlate, S.; Ruiz, J .; Sartor, V.; Navarro, R.; Blais J .-C.; Astruc, D. Chem.
Eur. J . 2000, 6, 2544. (e) Takada, K.; D´ıaz, D. J .; Abrun˜a, H. D.;
Cuadrado, I.; Casado, C.; Alonso, B.; Mora´n, M.; Losada, J . J . Am.
Chem. Soc. 1997, 119, 10763.
(4) Vale´rio, C.; Alonso, E.; Ruiz, J .; Blais, J .-C.; Astruc, D. Angew.
Chem., Int. Ed. 1999, 38, 1747.
(5) Nlate, S.; Ruiz, J .; Blais J -C.; Astruc, D. Chem. Commun. 2000,
417.
(6) (a) Cuadrado, I.; Mora´n, M.; Casado, C. M.; Alonso, B.; Lobete,
F.; Garc´ıa, B.; Ibisate M.; Losada, J . Organometallics 1996, 15, 5278.
(b) Cuadrado, I.; Casado, C. M.; Alonso, B.; Mora´n, M.; Losada, J .;
Belsky, V. J . Am. Chem. Soc. 1997, 119, 7613. (c) J utzi, P.; Batz, C.;
Neumann. B.; Stammler, H.-G. Angew. Chem., Int. Ed. Engl. 1996,
35, 2118. (d) Turrin, C. O.; Chiffre, J .; Daran, J . C.; de Montauzon, D.;
Caminade, A.-M.; Manoury, E.; Balavoine G.; Majoral, J . P. Tetrahe-
dron 2001, 57, 2521. (e) Turrin, C. O.; Chiffre, J .; de Montauzon, D.;
Daran, J . C.; Caminade, A.-M.; Manoury, E.; Balavoine G.; Majoral,
J . P. Macormolecules 2000, 33, 7328.
10.1021/om020760d CCC: $25.00 © 2003 American Chemical Society
Publication on Web 02/05/2003

Cyclophosphazene Hydrazides
Organometallics, Vol. 22, No. 5, 2003 977
gift from the Vikram Sarabhai Space Research Centre, Thiru-
vananthapuram, India. N3P3Cl6 (Aldrich) was recrystallized
from n-hexane before use. Ferrocene carboxaldehyde,12 N3P3-
[N(Me)NH2]6 (1a ),13 N3P3(OPh)Cl5 (2),14 gem-N3P3Ph2Cl4 (3),15
spiro-N3P3(O2C12H8)2Cl2 (4),16 N3P3(OPh)5Cl (5),17 and Ph2P-
(O)[N(Me)NH2] (6a )18 were prepared according to literature
procedures.
rings are multifunctional and are stable to redox
processes. A second advantage of using cyclophos-
phazenes as supports for multi-ferrocene assemblies is
that in most instances the chemistry of these ring
systems can be readily extended to the polymeric
analogues.7 However, directly using N3P3Cl6 for building
fully substituted ferrocenyl-containing compounds has
not met with success. Previous efforts at introducing the
metallocenyl substituent on the cyclophosphazene ring
have involved the reaction of the corresponding lithium
salts with fluoro- or chlorocyclophosphazenes.8 In both
instances the reactions are complex, and although
interesting products have been isolated, fully substi-
tuted derivatives have not been obtained. Recently Allen
and co-workers have reported the reactions of N-
(ferrocenylmethyl)-N-methyl amine, 1-ferrocenyl-2-pro-
panol, 2-ferrocenylethanol, or ferrocenylmethanol with
N3P3Cl6.9,10 In the reactions of N-(ferrocenylmethyl)-N-
methyl amine substitution of only three chlorines has
been achieved with the yields of the bis- and tris-
substituted products being very low.9 In the reactions
with ferrocenyl methanol degraded products were ob-
served, while products up to bis substitution were
observed in reactions with ferrocenyl ethanol.10 Togni
and co-workers have reported a convergent methodology
for preparing phosphine-containing chiral ferrocene-
substituted cyclotetraphosphazenes.11 However, this
compound has not been characterized by X-ray crystal-
lography and its electrochemical behavior also has not
been reported.
We report an alternate and a more convenient syn-
thetic strategy of using cyclophosphazenes as scaffolds
for supporting ferrocenes. Our method consists of first
converting chlorocyclotriphosphazenes (1-5) to the cor-
responding cyclotriphosphazene hydrazides which con-
tain reactive -NH2 groups (1a -5a ). As a model for the
multifunctional cyclophosphazenes we have utilized the
monofunctional acyclic phosphorus hydrazide Ph2P(O)-
[N(Me)NH2] (6a ). These hydrazides are amenable to
further reaction with ferrocene carboxaldehyde to afford
the corresponding hydrazones (1b-6b). This strategy
allowed us to even synthesize a cyclophosphazene (1b)
containing six ferrocene units. The ferrocenyl deriva-
tives 1b-6b are electrochemically robust. All of these
compounds have been characterized by various spec-
troscopic techniques. Further, compounds 1b, 3b, 4b,
5b, and 6b have also been characterized by X-ray
crystallography. These aspects are discussed in the
following account.
In str u m en ta tion . Infrared spectra were recorded in Nujol
mull or as KBr pellets on a FT-IR Bruker-Vector model.
Electronic spectra were recorded on a Perkin-Elmer-Lambda
20 UV-vis spectrometer and on a Shimadzu UV-160 spec-
trometer using dichloromethane as the solvent. Cyclic volta-
mmetric experiments were carried out on a EG&G Princeton
Applied Research model 273A polarographic analyzer utilizing
a three-electrode configuration of a platinum working elec-
trode, a commercially available saturated calomel electrode
(SCE) as the reference electrode, and a platinum mesh
electrode. Half-wave potentials were measured as the average
of the cathodic and anodic peak potentials. The voltammo-
grams were recorded in dichloromethane containing 0.1 M
tetrabutylammonium hexafluorophosphate as the supporting
electrolyte and the potential was scanned from -1.5 to +1.5
V at various scan rates. The data obtained from the optical
spectra and the cyclic voltammetric experiments were analyzed
by the Origin Professional 6.0 program. Elemental analyses
of the compounds were obtained from Thermoquest CE instru-
ments CHNS-O, EA/110 model. FAB mass spectra were
recorded on a J EOL SX 102/DA-6000 mass spectrometer/data
system using argon/xenon (6 kV, 10 mA) as the FAB gas. The
accelerating voltage was 10 kV, and the spectra were recorded
at room temperature. EI mass spectra were obtained on a
1
J EOL D-300 spectrometer. The 31P{1H}, 13C{1H}, and H NMR
spectra were recorded in CDCl3 solutions on a J EOL J NM
LAMBDA 400 model spectrometer. Chemical shifts are re-
ported in ppm with respect to TMS (internal reference) for 13C
and 1H chemical shifts and 85% H3PO4 (external reference)
for the 31P chemical shifts.
X-r a y Str u ctu r e Deter m in a tion of 1b, 3b, 4b, 5b, a n d
6b. The crystal data for 1b, 3b, and 4b are given in Table 1
and for 5b and 6b in Table 2, respectively. X-ray quality
crystals for compound 1b were obtained by a slow evaporation
of a 1:1 dichloromethane and benzene solution of it, and those
of 3b were obtained by a slow evaporation of a solution of it
in ethyl acetate and hexane (30:70). In the case of 4b, 5b, and
6b suitable crystals were obtained by vapor diffusing n-hexane
into their chloroform solutions at room temperature. X-ray
diffraction data for 3b and 6b were collected using an Enraf
Nonius FR590 CAD-4 diffractometer. The structures were
solved using WINGX 1.64.03a, a collective crystallographic
package.19 All the hydrogen atoms were included in idealized
positions, and a riding model was used. The data for the
compounds 1b and 4b were collected on a Siemens P4S
diffractometer. All structures were solved by direct methods
(SHELXS-97) and refined by full-matrix least-squares methods
Exp er im en ta l Section
(12) Sato, M.; Kono, H.; Shiga, M.; Motoyama, I.; Hata, K. Bull.
Chem. Soc. J pn. 1968, 41, 252.
(13) Galliot, C.; Caminade, A.-M.; Dahan, F.; Majoral, J . P. Angew.
Chem., Int. Ed. Engl. 1993, 32, 1477.
(14) Dell, B.; Fitzsimmons, B. W.; Shaw, R. A. J . Chem. Soc. 1965,
4070.
(15) McBee, E. T.; Okuhara, K.; Morton, C. J . Inorg. Chem. 1966,
5, 450.
(16) Carriedo, G. A.; Fernander-Catuxo, L.; Garcia Alonso, F. J .;
Gomex-Elipe, P.; Gonzealez, P. A. Macromolecules 1996, 29, 5320.
(17) Selvaraj, I. I.; Reddy, D.; Chandrasekhar, V.; Chandrasekar,
T. K. Heterocycles 1991, 32, 703.
Rea gen ts a n d Gen er a l P r oced u r es. All operations have
been carried out in an inert atmosphere of nitrogen or argon.
The solvents and general chemicals were purified and dried
according to standard procedures. Ph2P(O)Cl (6) (Lancaster,
U.K.), 2,2′-dihydroxybiphenyl (Fluka), and ferrocene (Aldrich)
were used as obtained. N-Methylhydrazine was obtained as a
(7) Saraceno, R. A.; Riding, G. H.; Allcock H. R.; Ewing, A. G. J .
Am. Chem. Soc. 1998, 110, 7254.
(8) Allcock, H. R.; Desorcie, J .; Riding, G. H. Polyhedron 1987, 6,
164.
(9) Myer, C. N.; Allen, C. W. Inorg. Chem. 2002, 41, 60.
(10) Nataro, C.; Myer, C. N.; Cleaver, W. M.; Allen, C. W. J .
Organomet. Chem. 2001, 637-639, 284.
(11) Schneider, R.; Ko¨llner, C.; Weber I.; Togni, A. Chem. Commun.
1999, 2415.
(18) Majoral, J . P.; Kraemer, R.; Navech, J .; Mathis, F. Tetrahedron
1976, 32, 2633.
(19) (a) Farrugia, L. J . WinGX, Version 1.64.03a; An Integrated
System of Windows Programs for the Solution, Refinement and
Analysis of Single-Crystal X-Ray Diffraction Data; Department of
Chemistry, University of Glasgow, 1997-2002. (b) Farrugia, L. J . J .
Appl. Crystallogr. 1999, 32, 837.

978 Organometallics, Vol. 22, No. 5, 2003
Chandrasekhar et al.
Ta ble 1. Cr ysta l a n d Str u ctu r e Refin em en t Da ta for Com p ou n d s 1b, 3b, a n d 4b
parameter
empirical formula
1b
3b
C60H62Fe4N11P3
1253.52
293(2)
0.71069
triclinic
P1h
4b
C
1798
293(2)
0.71069
monoclinic
C2/c
79H88Cl3Fe6N15OP3
C49H43Cl3Fe2N7O4P3
1104.86
fw
temperature, K
wavelength, Å
cryst syst
space group
unit cell dimens
293(2)
0.71073
triclinic
P1h
a ) 24.028(14), Å R ) 90.000(9)° a ) 13.006(5) Å, R ) 112.821(5)° a ) 11.222(16) Å, R ) 101.260(10)°
b )16.329(8) Å, â ) 113.04(14)° b ) 13.888(5) Å, â ) 95.174(5)°
c ) 22.363(5) Å, γ ) 90.000(13)° c ) 17.159(5) Å, γ ) 92.084(5)°
b ) 14.214(2) Å, â ) 108.595(12)°
c ) 17.108(5) Å, γ ) 101.877(13)°
2429.0(6), 2
1.511
0.914
volume, Å3, Z
density(calcd), Mg/m3
abs coeff, mm-1
F(000)
8074(8), 4
1.479
2836.5(17), 2
1.468
1.263
1.138
3708
1296
1132
cryst size, mm
θ range for data collection, deg 2.49 to 25.00
limiting indices
0.32 × 0.47 × 0.43
0.40 × 0.32 × 0.28
0.06 × 0.42 × 0.29
1.61 to 22.48
2.14 to 25.00
0 e h e 23, -19 e k e 0,
-26 e l e 24
6865
0 e h e 13, -14 e k e 14,
-18 e l e 18
7760
-13 e h e 0, -15 e k e 16,
-19 e l e 20
8924
no. of reflns collected
no. of ind reflns
completeness to θ
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and
hole, e Å-3
6687 (Rint ) 0.1346)
7369 (Rint ) 0.0398)
8471 (Rint ) 0.0360)
93.9
99.8
98.9
full-matrix least-squares on F2
6687/0/438
full-matrix least-squares of F2
7369/ 0/ 707
full-matrix least-squares on F2
8471/0/659
1.004
0.923
1.048
R1 ) 0.0938, wR2 ) 0.2104
R1 ) 0.2309, wR2 ) 0.2849
0.753 and -0.528
R1 ) 0.0507, wR2 ) 0.1259
R1 ) 0.1498, wR2 ) 0.1755
0.343 and -0.388
R1 ) 0.0610, wR2 ) 0.1284
R1 ) 0.1569, wR2 ) 0.1870
0.508 and -0.491
Ta ble 2. Cr ysta l a n d Str u ctu r e Refin em en t Da ta for Com p ou n d s 5b a n d 6b
parameter 5b 6b
empirical formula 42H38FeN5O5P3
C
C24H23FeN2OP
442.26
fw
841.53
temperature, K
wavelength, Å
cryst syst
space group
unit cell dimens
93(2)
293(2)
0.71069
0.71073
monoclinic
P2(1)/c
a ) 10.9501(12) Å, R ) 90.000 °
b ) 16.4398(18) Å, â ) 92.249(2)°
c ) 21.431(12) Å, γ ) 90.000°
3854.9(7), 4
1.450
0.569
1744
monoclinic
P21/c
a ) 11.911 (5) Å, R ) 90.000(9)°
b ) 8.250(18) Å, â ) 96.388(14)°
c ) 21.789(5) Å, γ ) 90.000(13)°
2127.8(16), 4
1.381
0.801
920
volume, Å3, Z
density(calcd), Mg/m3
abs coeff, mm-1
F(000)
cryst size, mm
θ range for data collection, deg
limiting indices
0.50 × 0.60 × 0.60
0.40 × 0.38 × 0.22
1.90 to 24.88
1.72 to 22.45
-12 e h e 12, -19 e k e 19,
-25 e l e 25
22 256
-5 e h e 12, -8 e k e 1,
-23 e l e 23
2999
no. of reflns collected
no. of ind reflns
completeness to θ
refinement method
6651 (Rint ) 0.0737)
2746 (Rint ) 0.0085)
99.4%
99.3%
full-matrix least-squares on F2
6651/0/544
full-matrix least-squares on F2
2746/0/354
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
R indices (all data)
1.031
1.147
R1 ) 0.0461, wR2 ) 0.1219
R1 ) 0.0584, wR2 ) 0.1310
0.721 and -0.688
R1 ) 0.0470, wR2 ) 0.1244
R1 ) 0.0637, wR2 ) 0.1453
0.531 and -0.514
largest diff peak and hole, e Å-3
against F2 (SHELXL-97).20 Hydrogen atoms were fixed at
calculated positions, and their positions were refined by a
riding model. Non-hydrogen atoms were refined with aniso-
tropic displacement parameters.
Syn th esis of Cyclop h osp h a zen e Hyd r a zid es. N3P 3-
(OP h )[N(Me)NH2]5 (2a ). To a stirred solution of N-methyl-
hydrazine (1.79 g, 39.0 mmol) in chloroform (30 mL) at 0 °C
was added dropwise a solution of N3P3Cl5(OPh) (1.05 g, 2.6
mmol) taken in choloroform (30 mL). After the addition was
complete the reaction mixture was allowed to come to room
temperature and was further stirred for a period of 36 h. At
this stage the reaction was stopped and the reaction mixture
was filtered to remove N-methylhydrazine hydrochloride.
Removal of solvent from the filtrate in vacuo afforded a waxy
solid. This was chromatographed over a basic alumina column
using methanol-ethyl acetate (10:90) as the eluant to afford
1
pure 2a as a waxy solid. Yield: 0.92 g, 78.3%. H NMR: 2.41,
3
2.75, 2.93 (d, 15H, N(CH3), J (1H-31P) ) 10.5, 10.7, and 11.5
Hz, respectively); 3.07 (s, 10H, -NH2), 7.26-7.53 (m, 5H,
aromatic). 31P NMR: 29.3 (d, P(N(Me)-)2), 22.3 (t, P(N(Me)-
)(OPh)), 2J (P-N-P) ) 40.4 Hz. FAB-MS: 453 (M+). Anal.
Calcd for C11H30N13OP3: C, 29.14; H, 6.67; N, 40.16. Found:
C, 28.95; H, 6.39; N, 39.93.
gem -N3P 3P h 2[N(Me)NH2]4 (3a ). The preparation of 3a was
done in the same manner as that of 2a . The quantities of the
reactants involved are gem-N3P3Cl4Ph2 (3) (5.00 g, 11.6 mmol)
and N-methylhydrazine (4.81 g, 105.0 mmol). A solid obtained
at the end of workup was dissolved in hot benzene (75 mL)
and was allowed to cool to 25 °C. To this n-hexane (120 mL)
(20) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Analysis (release 97-2); University of Go¨ttingen: Go¨ttingen, Germany,
1998.

Cyclophosphazene Hydrazides
Organometallics, Vol. 22, No. 5, 2003 979
was added and the solution was kept at 5 °C to obtain a white
solid. Yield: 4.33 g, 79.5%. Mp: 112 °C. H NMR: 2.80 (d, 12
Ch a r t 1
1
H, -N(CH3); 3J (1H-31P) ) 10.8 Hz), 3.57 (s, 8H, -NH2), 7.35-
7.86 (m, 10 H, aromatic). 31P NMR: 28.1 (d, P(N(Me)-)2), 20.2
(t, P(Ph)2), 2J (P-N-P) ) 17.8 Hz. EI-MS: 469 (M+). Anal.
Calcd for C16H30N11P3: C, 40.94; H, 6.44; N, 32.82. Found: C,
40.83; H, 6.34; N, 32.76.
N3P 3(O2C12H8)2[N(Me)NH2]2 (4a ). The preparation of 4a
was done in the same manner as that of 2a except that there
was no need for a chromatographic separation. The quantities
involved were N3P3Cl2(O2C12H8)2 (4) (6.00 g, 10. 4 mmol) and
N-methylhydrazine (2.40 g, 52.1 mmol). A solid obtained at
the end of workup was dissolved in hot acetonitrile (125 mL)
and kept at 5 °C to afford a crystalline product (6.19 g, 88.8%).
Mp: 276 °C. 1H NMR: 2.98 (d, 6H, -N(CH3); 3J (1H-31P) )
11.0 Hz), 3.07 (s, 4H, -NH2), 7.26-7.53 (m, 16 H, aromatic).
31P NMR: 29.3 (t, P(N(Me)-)2), 26.6 (d, P(O2C12H8)2), 2J (P-
N-P) ) 58.2 Hz. FAB-MS: 548 (M+ - N(Me)NH2). Anal. Calcd
for C26H26N7O4P3: C, 52.62; H, 4.42; N, 16.52. Found: C, 52.31;
H, 4.42; N, 16.44.
N3P 3(OP h )5[N(Me)NH2] (5a ). To a stirred solution of
N-methylhydrazine (0.77 g, 16.6 mmol) in chloroform (60 mL)
at 0 °C was added dropwise a solution of N3P3Cl(OPh)5 (4.24
g, 6.67 mmol) taken in choloroform (60 mL). After the addition
was complete the reaction mixture was allowed to come to
room temperature and was further stirred for a period of 12
h. At this stage the reaction was stopped and filtered to remove
the hydrochloride of N-methylhydrazine. Removal of the
volatiles from the filtrate in vacuo afforded an oil, which was
chromatographed over a basic alumina column (eluant: ethyl
acetate-n-hexane, 12:88) to afford pure 5a as a yellow oil (1.02
1
3
g, 80%). H NMR: 2.54 (d, 3H, -N(CH3); J (1H-31P) ) 11. 5
Hz), 3. 07 (s, 2H, -NH2), 6.91-7.27 (m, 25H, aromatic).
31P NMR: 20.7 (t, P(OPh)(N(Me)-)), 9.4 (d, P(OPh)2),
2J (P-N-P) ) 71.2 Hz. FAB-MS: 646 (M+). Anal. Calcd for
C
31H30N5O5P3: C, 57. 68; H, 4.68; N, 10.85. Found: C, 57.02;
) 57.7 Hz. FAB-MS: 1434 (M+). Anal. Calcd for C66H70N13
OP3Fe5: C, 55.30; H, 4.92; N, 12.70. Found: C, 54.66; H, 4.41;
N, 12.37.
-
H, 4.36; N, 10.29.
Con d en sa tion of th e Hyd r a zid es w ith F er r ocen e Ca r -
boxa ld eh yd e. N3P 3[N(Me)NdCHC5H4F eC5H5]6 (1b). To a
solution of 1a (0.41 g, 1.00 mmol) in methanol (60 mL) was
added dropwise over a period of 30 min a solution of ferrocene-
2-carboxaldehyde (1.35 g, 6.31 mmol) in methanol (60 mL).
The reaction mixture was stirred at 25 °C for 12 h. Removal
of the solvent in vacuo afforded a solid. This was purified over
a basic alumina column. Elution with ethyl acetate-n-hexane
(5:95) removed the unreacted ferrocene-2-carboxaldehyde. Pure
1b was obtained by elution with ethyl acetate-n-hexane (40:
60). Yield: 1.22 g, 77%. Mp: 104 °C. UV-visible (CH2Cl2): λmax
(ꢀ), 442 nm (30 845 mol-1 cm-1). 1H NMR: 3.30 (d, 18H,
-N(CH3); 3J (1H-31P) ) 8.6 Hz), 4.03 (s, 30H, ferrocene), 4.22
(s, 12H, ferrocene), 4.79 (s, 12H, ferrocene), 7.36 (s, 6H, imino).
31P NMR: 16.9 (s). FAB-MS: 1581 (M+). Anal. Calcd for
N3P 3P h 2[N(Me)NdCHC5H4F eC5H5]4 (3b). Compound 3b
was prepared by adopting a procedure analogous to that used
for preparing 1b. The quantities of the reactants and product
are 3a (0.47 g, 1.0 mmol); ferrocene-2-caboxaldehyde (0.90 g,
4.20 mmol). Yield: 0.99 g, 79%. Mp: 114 °C. UV-visible (CH2-
1
Cl2): λmax (ꢀ), 448 nm (19 795 mol-1 cm-1). H NMR: 3.18 (d,
12H, -N(CH3); 3J (1H-31P) ) 8.8 Hz), 4.07 (s, 20H, ferrocene),
4.20 (s, 8H, ferrocene), 4.54 (s, 8H, ferrocene), 7.34 (s, 4H,
imino), 7.35-8.01 (m, 10H, aromatic). 31P NMR (CDCl3): 15.1
2
(d, P(N(Me)-)2), 20.2 (t, PPh2), J (P-N-P) ) 24.2 Hz. FAB-
MS: 1253 (M+). Anal. Calcd for C60H62N11P3Fe4: C, 57.49; H,
4.99; N, 12.29. Found: C, 57.12; H, 4.89; N, 12.16.
N3P 3(O2C12H8)2[N(Me)NdCHC5H4FeC5H5]2 (4b). This com-
pound was prepared in the same manner as described for 1b
except that one of the reactants, 4a , was taken in dichlo-
romethane (50 mL), while ferrocene-2-carboxaldehyde was
taken in ethanol. The quantities of the reactants are 4a (2.38
g, 4.00 mmol) and ferrocene-2-carboxaldehyde (1.75 g, 8.2
mmol). The product 4b precipitates from the reaction medium
and is purified by washing with ethanol (2 × 25 mL) (6.19 g,
88.8%). Mp: 260 °C. UV-visible (CH2Cl2): λmax (ꢀ) 449 nm
C
72H78N15P3Fe6: C, 54.68; H, 4.97; N, 13.29. Found: C, 53.81;
H, 4.67; N, 13.07.
N3P 3(OP h )[N(Me)NdCHC5H4F eC5H5]5 (2b). Compound
2b was prepared by adopting a similar protocol as used for
1b except that ethanol was used as the solvent. The quantities
of the reactants are 2a (0.45 g, 1.00 mmol); ferrocene-2-
carboxaldehyde (1.12 g, 5.25 mmol). The workup of the reaction
afforded a solid. This was purified over a basic alumina
column. After eluting unreacted ferrocene-2-carboxaldehyde
using a mixture of ethyl acetate-n-hexane (5:95) the pure
fraction of 2b was eluted with ethyl acetate-n-hexane (40:
60). The total amount of 2b obtained was 1.05 g, 73.2%. Mp:
89 °C. UV-visible (CH2Cl2): λmax (ꢀ), 444 nm (30 575 mol-1
cm-1). 1H NMR: 3.09, 3.26, and 3.27 (d, 15H, -N(CH3); 3J (1H-
31P) ) 8.8, 8.5, and 8.8 Hz, respectively); 4.00 (s, 25H,
ferrocene), 4.36 (s, 10H, ferrocene), 4.52 (s, 10H, ferrocene),
7.16 (s, 5H, imino), 7.18-7.36 (m, 5H, aromatic). 31P NMR:
17.5 (d, P(N(Me)-)2), 13.8 (t, P(OPh)(N(Me)-)), 2J (P-N-P)
1
3
(11 995 mol-1 cm-1). H NMR: 3.29 (d, 6H, -N(CH3); J (1H-
31P) ) 8.8 Hz), 4.07 (s, 10H, ferrocene), 4.22 (s, 4H, ferrocene),
4.57 (s, 4H, ferrocene), 7.28-7.53 (m, 8H, aromatic and imino).
31P NMR: 18.8 (t, P(N(Me)-)2), 26.2 (d, P(O2C12H8)2), 2J (P-
N-P) ) 71.2 Hz. FAB-MS: 985 (M+). Anal. Calcd for
C
48H42N7O4P3Fe2: C, 58.50; H, 4.30; N, 9.95. Found: C, 57.97;
H, 4.11; N, 9.49.
N3P 3(OP h )5[N(Me)NdCHC5H4F eC5H5] (5b). To a solution
of 5a (1.29 g, 2.0 mmol) in methanol (35 mL) was added
dropwise ferrocene-2-carboxaldehyde (0.45 g, 2.1 mmol) in
methanol (40 mL) at 25 °C and stirred for 8 h. Removal of

980 Organometallics, Vol. 22, No. 5, 2003
Chandrasekhar et al.
Sch em e 1
solvent from the reaction mixture in vacuo afforded an oil. This
was chromatographed over a basic alumina column. Ethyl
acetate-n-hexane (5:95) was used to elute unreacted ferrocene-
2-carboxaldehyde, while elution with ethyl acetate-hexane
(25:75) afforded the title compound in a pure state. This was
recrystallized from a mixture of dichloromethane and n-hexane
(1:2) at 5 °C to afford a shiny crystalline compound (1.35 g,
80%). Mp: 94 °C. UV-visible (CH2Cl2): λmax (ꢀ), 448 nm (4770
mol-1 cm-1). 1H NMR: 2.54 (d, 3H, -N(CH3); 3J (1H-31P) ) 9.5
Hz), 3.91 (s, 5H, ferrocene), 4.07 (s, 2H, ferrocene), 4.10 (s,
2H, ferrocene), 7.12 (s, 1H, imino), 6.85-7.08 (m, 25 H,
aromatic). 31P NMR: 14.1 (t, P(OPh)(N(Me)-)2), 9.1 (d, P(OPh)2),
2J (P-N-P) ) 76.0 Hz. FAB-MS: 841 (M+). Anal. Calcd for
ing from six reactive chlorines to one as the starting
materials (Chart 1). As a model for these compounds,
the acyclic phosphorus derivative Ph2P(O)Cl (6) was
chosen. These were reacted with N-methylhydrazine to
afford the corresponding hydrazides 1a -6a (Scheme 1,
Chart 2). In all of these reactions N-methylhydrazine
was also used to scavenge the liberated hydrogen
chloride, obviating the need for an additional base. All
of these reactions are regiospecific; the N-methyl end
of the difunctional reagent reacts with the phosphorus
compound, leading to products containing reactive
terminal -NH2 groups (Scheme 1, Chart 2). Another
notable feature of these reactions is the complete
absence of cross-linked products and the isolation of the
products 1a -6a in excellent yields. Condensation of the
hydrazides 1a -6a with stoichiometric amounts of fer-
rocene carboxaldehyde occurs at room temperature to
afford the corresponding hydrazones 1b-6b in quanti-
tative yields (Schemes 2 and 3, Chart 2). Thus by the
use of a mild reaction pathway involving the extrusion
of water as the byproduct we have assembled cyclophos-
phazenes supporting from six ferrocenes to one.
C
42H38N5O5P3Fe: C, 59.94; H, 4.55; N, 8.32. Found: C, 59.38;
H, 4.39; N, 8.11.
P h 2P (O)[N(Me)NdCHC5H4F eC5H5] (6b). This was pre-
pared by a procedure analogous to that used for 1b. The
quantities of the reactants are 6a (0.98 g, 4.00 mmol);
ferrocene-2-carboxaldehyde (0.90 g, 4.2 mmol). Pure 6b was
obtained by elution with ethyl acetate-n-hexane, 30:70.
Yield: 1.5 g, 84.9%. Mp: 142 °C. UV-visible (CH2Cl2):
λ
max(ꢀ): 448 nm (4675 mol-1 cm-1). 1H NMR: 3.20 (d, 3H,
-N(CH3); J (1H-31P) ) 7.2 Hz), 4.02 (s, 5H, ferrocene), 4.21
(s, 2H, ferrocene), 4.37 (s, 2H, ferrocene), 7.38 (s, 1H, imino),
7.44-7.85 (m, 10H, phenyl). 31P NMR: 31.1 (s). FAB-MS: 442
(M+). Anal. Calcd for C24H23N2OPFe: C, 65.18; H, 5.24; N, 6.33.
Found: C, 65.01; H, 5.17; N, 6.11.
3
The compounds 1a -6a and 1b-6b show prominent
parent ion peaks in their mass spectra. The proton NMR
spectra of these compounds are characterized by a
doublet for the N-CH3 protons. The compounds 2a and
2b show three resonances for the N-CH3 resonances.
The second-order effect of virtual coupling is seen for
N-CH3 resonance arising out of the dP[N(CH3)NH2]2
Resu lts a n d Discu ssion
Syn th etic a n d Sp ectr oscop ic Asp ects. We have
chosen various chlorocyclophosphazenes (1-5) contain-

Cyclophosphazene Hydrazides
Organometallics, Vol. 22, No. 5, 2003 981
Ch a r t 2
Sch em e 2
group (1a -3a , 5a ) and the dP(N(CH3)NdCHC5H4-
FeC5H5)2 group (1b-3b, 5b). The N-CH3 resonance for
all the compounds (1a -6a ) moves downfield upon
conversion to the corresponding hydrazones (1b-6b);
simultaneously the 3J *(P-H) value decreases (Table 3).
The 31P{1H} NMR spectra of 1a and 1b as well as 6a
and 6b are single lines. The others show an AX2 or A2X
type of first-order spectra. The 31P{1H} NMR data show
some interesting trends. First, reaction of the chloro
derivatives (P-Cl) to afford the hydrazides {P[N(CH3)-
NH2]} results in the chemical shift of the corresponding
phosphorus center to move downfield. Conversion of the
latter to the hydrazone {P(N(CH3)NdCHC5H4FeC5H5)}
reverses the change in chemical shift and moves it
upfield. This is illustrated in the conversion of N3P3Cl6
(+19.5 ppm) to N3P3[N(Me)NH2]6 (+29.4 ppm) and N3P3-
[N(Me)NdCHC5H4FeC5H5]6 (+16.9 ppm).
The optical absorption spectra of 1b-6b recorded
under similar concentration conditions reveal the pres-
ence of an absorption band centered in the range 448-
458 nm (Figure 1). Earlier studies by Gray and co-
workers21 and more recent work by Thomas et al.22

982 Organometallics, Vol. 22, No. 5, 2003
Chandrasekhar et al.
Sch em e 3
Ta ble 3. 1H a n d 31P NMR Da ta for th e Com p ou n d s 1a -6a a n d 1b-6b
1H 31Pa
(P-N-CH3) 3J *(P-H)b P[N(Me)R]2 P[{N(Me)R}R1]2 P(R2R3)2
compound
N3P3[N(Me)NH2]6 (1a )
N3P3[N(Me)NdCHC5H4FeC5H5]6 (1b)
N3P3(OPh)[N(Me)NH2]5 (2a )
δ
Hz
δ
δ
δ
2J (P-N-P)
2.80
3.30
2.93
2.75
2.41
3.27
3.26
3.09
2.80
3.18
2.98
3.29
11.2
8.6
11.5
10.7
10.5
8.8
8.5
8.8
10.8
8.8
11.0
8.8
29.4
16.9
29.3
22.3c
13.8c
40.4
57.7
N3P3(OPh)[N(Me)NdCH- C5H4FeC5H5]5 (2b)
17.5
gem-N3P3Ph2[N(Me)NH2]4 (3a )
28.1
15.1
29.3
18.8
20.2d
20.2d
26.6e
26.2e
17.8
24.2
58.2
71.2
gem-N3P3Ph2[N(Me)NdCH- C5H4FeC5H5]4 (3b)
gem-N3P3(O2C12H8)2[N(Me)NH2]2 (4a )
gem-N3P3(O2C12H8)2[N(Me)NdCH C5H4-
FeC5H5]2 (4b)
N3P3(OPh)5[N(Me)NH2] (5a )
N3P3(OPh)5[N(Me)NdCH- C5H4FeC5H5] (5b)
Ph2P(O)[N(Me)NH2] (6a )
2.54
2.65
2.79
3.20
11.5
9.5
10.4
7.2
20.7c
14.1c
32.3g
31.1g
9.4f
9.1f
71.2
76.0
Ph2P(O)[N(Me)NdCH C5H4FeC5H5] (6b)
a
The phosphorus chemical shifts of the corresponding chloro derivatives are as follows: N3P3Cl6, 19.5 ppm; N3P3(OPh)Cl5: δPCl2,
22.5; δP(OPh)(Cl), 12.3; gem-N3P3Ph2Cl4: δPCl2, 18.3; N3P3(O2C12H8)2Cl2: δPCl2, 19.6; N3P3(OPh)5Cl: δP(OPh)Cl, 22.2; Ph2P(O)Cl, 44.9
b
c
ppm. This value represents the apparent coupling constant in view of “virtual coupling” found in many of these compounds
R1
)
d
g
OPh. R2 ) R3 ) Ph. e R2 ) R3 ) 2,2′-biphenoxy. f R2 ) R3 ) OPh. Single phosphorus
allow this absorption to be assigned as arising due to a
d-d transition. The increase in the number of ferrocenyl
arms leads to a linear increase in the ꢀ values. Thus 1b
shows the highest ꢀ value of 30 845 mol-1 cm-1, while
5b and 6b with only one ferrocenyl arms show low ꢀ
values (4770 and 4675 mol-1 cm-1, respectively).
X-r a y Cr ysta l Str u ctu r es of 1b a n d 3b-6b. The
DIAMOND23 diagram of 1b is given in Figure 2. The
ORTEP diagrams of 3b-6b are given in Figures 3-7.
Selected metric parameters for these compounds are
given in Tables 4 and 5.
The X-ray crystal structure of the hexaferrocenyl
derivative 1b (Figure 2) reveals that the cyclotriphos-
phazene ring is perfectly planar. The molecular struc-
ture of 1b represents the first structural characteriza-
tion of a completely substituted cyclophosphazene
containing ferrocenyl arms. The six ferrocenyl pendant
groups are arranged in a symmetric manner about the
cyclophosphazene ring; each side of the ring contains
three ferrocenyl pendant groups. The overall arrange-
ment is an approximate cyclic array of the ferrocenyl
groups about the cyclophosphazene framework. The
average endocyclic P-N bond length within compound
1b is 1.579 Å, while the average N-P-N and P-N-P
(21) Sohn, Y. S.; Hendrickson, D. A.; Gray, H. B. J . Am. Chem. Soc.
1971, 93, 3603.
(22) (a) Thomas, K. R. J .; Lin, J . T.; Wen, Y. S. Organometallics
2000, 19, 1008. (b) Thomas, K. R. J .; Lin, J . T.; Lin, K. J . Organome-
tallics 1999, 18, 5285.
(23) Brandenburg, K. Diamond, Version 2.1c; Crystal Impact GbR,
1996-1999.

Cyclophosphazene Hydrazides
Organometallics, Vol. 22, No. 5, 2003 983
F igu r e 1. UV-visible spectra for the ferrocenyl deriva-
tives (1b-6b) recorded using 2 × 10-5 M dichloromethane
solution.
F igu r e 3. (a) ORTEP diagram of tetraferrocenyl assembly
3b. The thermal ellipsoids are drawn at the 50% probability
level. (b) Cyclophosphazene ring of 3b.
N3 moves away in the opposite direction by 0.20 Å. The
P-N distances flanking the P(Ph)2 unit are nearly
similar: P1-N1, 1.612(7) Å, and P1-N3, 1.599(8) Å.
The average value of the other four P-N bond distances
is 1.579 Å, which is similar to what was observed for
1b. The average values of the ring N-P-N and P-N-P
bond angles are 117.4° and 118.5°, respectively. The
exocyclic P-N bond distance is slightly longer (av 1.741
Å).
The crystal structure of the diferrocenyl derivative 4b
(Figure 4) shows that the six-membered cyclophos-
phazene ring is only very slightly nonplanar. Thus, the
maximum deviation from the mean plane of the ring is
observed for P1 (0.10 Å). The P-N bond distances
within the ring are nonequivalent, as expected for
compounds of the type gem-N3P3X2Y4. Three types of
bond distances are observed. The long bond distances
of 1.589(5) and 1.592(5) Å are observed for P1-N1 and
P1-N3, respectively, while the short bond distances of
1.557(5) and 1.565(5) Å are found for P2-N1 and P3-
N3. These trends are consistent with bond length
variations in substituted cyclophosphazenes.24 The bond
angle at P1 is the smallest at 115.5°, while at P2 and
P3 they enlarge to 118.0° and 119.1°, respectively. In
contrast, the bond angles at nitrogen are larger. The
F igu r e 2. (a) DIAMOND picture of hexaferrocenyl as-
sembly 1b. Methyl groups on the imino carbon atoms are
omitted for clarity. (b) Cyclophosphazene ring of 1b.
bond angles are 118.6° and 121.2°, respectively. The
average exocyclic P-N bond length is 1.665 Å, while the
average exocyclic N-P-N bond angle is 106.8°. These
values are analogous to those observed for other hexa-
kisaminocyclophosphazenes.24 The metric parameters
related to the ferrocenyl moiety in 1b and 3b-6b are
unexceptional (Supporting Information).
The molecular structure of the tetraferrocenyl deriva-
tive 3b shows that the cyclophosphazene ring is slightly
nonplanar (Figure 3b).25 The atoms P1 and P2 deviate
from the mean plane by 0.17 and 0.12 Å, while the atom
(24) Chandrasekhar, V.; Thomas, K. R. J . Struct. Bond. 1993, 81,
41.
(25) PRAST in WinGX, Version 1.64.031 (release Nov. 1999): Nardel-
li, M. J . Apply. Crystallogr. 1995, 28, 659.

984 Organometallics, Vol. 22, No. 5, 2003
Chandrasekhar et al.
F igu r e 6. ORTEP diagram of monoferrocenyl derivative
6b. The thermal ellipsoids are drawn at the 50% probability
level.
F igu r e 4. (a) ORTEP diagram of diferrocenyl assembly
4b. The thermal ellipsoids are drawn at the 50% probability
level. (b) Cyclophosphazene ring of 4b
F igu r e 7. Cyclic voltammogram (solid line) of 1b at 25
mV s-1, showing a single essentially reversible oxidation
peak; the dotted line shows the differential pulse voltam-
mogram of 1b.
F igu r e 5. (a) ORTEP diagram of monoferrocenyl deriva-
tive 5b. The thermal ellipsoids are drawn at the 80%
probability level. (b) Cyclophosphazene ring of 5b.
C5H5) segment are equal (1.593(2) Å). This value is
longer than those observed in previous instances as
discussed above. The other metric parameters are
normal.
The crystal structure of 6b is an interesting example
and serves as a reference for the other ferrocenyl
compounds discussed above. This structure shows a
tetrahedral arrangement around the phosphorus. The
P-O bond distance of 1.468(3) Å is consistent with Pd
O bond distances observed in the literature.26 The latter
is sensitive to the substituents on phosphorus. Thus the
exocyclic P-O bond angles are smaller than normal
tetrahedral angles. Within the biphenyldioxy group, the
individual phenyl rings are at an angle of 44° to each
other.
The X-ray crystal structure of the monoferrocenyl
cyclophosphazene derivative 5b is shown in Figure 5.
This is the only example where the phosphorus atom
containing the ferrocenyl pendant group also has a
different substituent (OPh). Similar to 1b the N3P3 ring
in compound 5b is also perfectly planar. The ring P-N
distances flanking the P(OPh)(N(Me)NdCHC5H4-Fe-
(26) Vilkov, L. V.; Sadova, N. I.; Zilberg, I. Y. Zh. Strukt. Khim. 1967,
8, 528.

Cyclophosphazene Hydrazides
Organometallics, Vol. 22, No. 5, 2003 985
Ta ble 4. Selected Bon d Len gth s (Å) for Com p ou n d s 1b-6b
1b
3b
4b
5b
6b
P(1)-N(1)
P(2)-N(1)
P(2)-N(2)
P(1)-N(11)
P(2)-N(21)
P(2)-N(31)
N-Navg
1.569(8)
1.578(8)
1.589(6)
1.658(8)
1.663(5)
1.673(4)
1.387
P(1)-N(1)
P(1)-N(3)
P(2)-N(1)
P(2)-N(2)
P(3)-N(3)
P(3)-N(2)
P(1)-C(1)
P(1)-C(7)
P(2)-N(4)
P(2)-N(6)
P(3)-N(8)
P(3)-N(10)
N-Navg
1.612(6)
1.599(6)
1.564(6)
1.578(6)
1.584(6)
1.591(6)
1.666(6)
1.664(5)
1.687(4)
1.671(5)
1.798(5)
1.808(5)
1.367
P(1)-N(1)
P(1)-N(3)
P(2)-N(1)
P(2)-N(2)
P(3)-N(3)
P(3)-N(2)
P(1)-N(1A)
P(1)-N(1B)
P(2)-O(2)
P(2)-O(1)
P(3)-O(3)
P(3)-O(4)
N-Navg
1.589(5)
1.592(5)
1.566(5)
1.578(5)
1.557(5)
1.580(5)
1.677(6)
1.667(5)
1.591(4)
1.585(5)
1.592(5)
1.596(5)
1.392
P(1)-N(1)
P(1)-N(3)
P(2)-N(1)
P(2)-N(2)
P(3)-N(3)
P(3)-N(2)
P(1)- N(11)
P(1)- O(1a)
P(2)-O(1b)
P(2)-O(1c)
P(3)-O(1d)
P(3)-O(1e)
N(11)-N(12)
N(12)-C(2)
1.593(2)
1.592(2)
1.580(2)
1.588(2)
1.575(2)
1.578(2)
1.662(2)
1.5962(18)
1.5881(19)
1.5981(18)
1.5937(19)
1.5859(19)
1.399(3)
P(1)-O(1)
P(1)-N(1)
P(1)-C(1)
P(1)-C(7)
N(1)-N(2)
N(2)-C(14)
1.468(3)
1.680(3)
1.799(4)
1.786(4)
1.383(5)
1.276(5)
NdCavg
1.280
NdCavg
1.271
NdCavg
1.270
1.280(3)
Ta ble 5. Selected Bon d An gles (d eg) for Com p ou n d s 1b-6b
1b
3b
4b
5b
6b
N(1)*-P(1)-N(1)
N(1)-P(2)-N(2)
P(1)-N(1)-P(2)
P(2)-N(2)-P(2)*
117.8(5) N(1)-P(1)-N(3) 116.6(3) N(1)-P(1)-N(3)
118.9(5) N(1)-P(2)-N(2) 119.1(3) N(1)-P(2)-N(2)
122.1(5) N(3)-P(3)-N(2) 117.1(3) N(3)-P(3)-N(2)
119.7(7) P(2)-N(1)-P(1) 119.1(4) P(2)-N(1)-P(1)
115.5(3) N(1)-P(2)-N(2)
118.5(3) N(3)-P(3)-N(2)
119.1(3) N(3)-P(1)-N(1)
122.1(3) P(2)-N(1)-P(1)
120.2(3) P(3)-N(2)-P(2)
122.2(3) P(3)-N(3)-P(1)
117.43(12) O(1)-P(1)-N(1)
118.67(12) C(7)-P(1)-C(1)
117.79(12) O(1)-P(1)-C(1)
121.80(14) O(1)-P(1)-C(7)
121.64(13) N(1)-P(1)-C(7)
121.20(14) N(1)-P(1)-C(1)
110.01(17)
108.40(17)
110.64(17)
114.66(18)
104.66(17)
108.06(17)
N(11)-P(1)-N(11)* 108.3(3) P(2)-N(2)-P(3) 119.1(3) P(2)-N(2)-P(3)
N(31)-P(2)-N(21) 105.2(3) P(3)-N(3)-P(1) 116.6(4) P(3)-N(3)-P(1)
C(1)-P(1)-C(7) 106.1(4) N(1a)-P(1)-N(1b) 106.4(3) O(1a)-P(1)-N(11) 104.47(10) N(2)-C(14)-C(15) 120.3(4)
N(6)-P(2)-N(4) 105.2(3) O(1)-P(2)-O(2)
N(8)-P(3)-N(10) 102.9(3) O(3)-P(3)-O(4)
102.5(2) O(1b)-P(2)-O(1c) 98.42(10) N(2)-N(1)-C(13) 121.7(4)
103.0(2) O(1e)-P(2)-O(1d) 104.18(11)
Ta ble 6. Cyclic Volta m m etr ic Da ta for Com p ou n d s 1b-6b a lon g w ith Som e Mu lti-F er r ocen e Assem bliesa ,b
compound
E1/2 (V)
∆Ep (mV)
ref
N3P3[N(Me)NdCHC5H4FeC5H5]6 (1b)
N3P3(OPh)[N(Me)NdCH-C5H4FeC5H5]5 (2b)
gem-N3P3Ph2[N(Me)NdCH-C5H4FeC5H5]4 (3b)
gem-N3P3(O2C12H8)2[N(Me)NdCH-C5H4FeC5H5]2 (4b)
N3P3(OPh)5[N(Me)NdCH-C5H4FeC5H5] (5b)
Ph2P(O)[N(Me)NdCH-C5H4FeC5H5] (6b)
C5H5FeC5H4CHO
[(C5H5)FeC6{(CH)2(C5H4FeC5H5)}6]PF6
[C6{(CH2)5(Fc)}6]
[C5H5)FeC6{(CH2)C6H4OC(O)C5H4FeC5H5}6]PF6
[C6{(CH2)2C6H4OC(O)(C5H4FeC5H5)}6]
[{BuSn(O)OC(O)(C5H4FeC5H5)}6]
+0.51
+0.51
+0.51
+0.55
+0.53
+0.58
+0.87
+0.44
+0.45
+0.78
+0.88
+0.72
+0.54
+0.54
+0.52
+0.51
+0.53
+0.49
+0.51
+0.50
205
206
154
140
108
91
142
55
-
60
120
128
92
80
100
74
73
82
93
78
this workc
this workc
this workc
this workc
this workc
this workc
this workc
30c
30c
31c
31c
32c
9d
C5H5FeC5H4CH2(Me)NH
N3P3Cl5[N(Me)-CH2-C5H4FeC5H5]
9d
trans-N3P3Cl4[N(Me)-CH2-C5H4FeC5H5]2
gem-N3P3Cl4[N(Me)-CH2-C5H4FeC5H5]2
trans-N3P3Cl3[N(Me)-CH2-C5H4FeC5H5]3
gem-N3P3Cl3[N(Me)-CH2-C5H4FeC5H5]3
N3P3Cl4[N(Me)-CH2-C5H4FeC5H5][O(CH2)4CMeCH2]
N3P3Cl3[N(Me)-CH2-C5H4FeC5H5]2[O(CH2)4CMeCH2]
9d
9d
9d
9d
9d
9d
Versus SCE. The Ic/Ia and the E1/2 for ferrocene (under these experimental conditions) are 1.08 and 0.51 V, respectively. c Potential
a
b
at the scan rate of 25 mV s-1
.
Potential at the scan rate of 100 mV s-1
.
d
shortest value observed is for P(O)Br3, viz., 1.41 Å. In
Ph2P(O)NMe2, a compound that is structurally related
to 6b, the P-O bond distance is 1.47 Å. In 6b the P1-
N1 distance is 1.680(4) Å and is very close to the P-N
single bond distance of 1.70 Å.27
Electr och em ica l Stu d ies. Electrochemical studies
on ferrocenyl-substituted cyclophosphazenes are quite
limited. Allcock and co-workers have investigated the
electrochemical behavior of a few compounds where the
ferrocene is directly attached to the cyclophosphazene
such as in ansa-N3P3F4(C5H4-Fe-C5H4).28 Recently
Allen and co-workers have investigated the preparation
and electrochemical behavior of some N-(ferrocenyl-
methyl)-N-methylaminocyclotriphosphazenes9 and a
ferrocenyl alcohol derivative, N3P3Cl5OCH2CH2C5H4-
FeC5H5.10
Cyclic and differential pulse voltammetric studies
have been carried out on compounds 1b-6b. The
electrochemical data for these compounds along with
some related derivatives are summarized in Table 6,
and the cyclic voltammogram of 1b recorded at 25 mV
s-1 has been shown as a representative example (Figure
7). A single essentially reversible oxidation peak is
observed for all the compounds. The observation of a
single oxidation peak for 1b-4b suggests that all the
pendant ferrocene moieties present in these compounds
have equivalent redox potentials. It has been noted
earlier that in order for a mediator to be effective in
electron-transfer process all the redox centers present
(27) Wingerter, S.; Pfeiffer, M.; Murso, A.; Lustig, C.; Stey, T.;
Chandrasekhar, V.; Stalke, D. J . Am. Chem. Soc. 2001, 123, 1381.
(28) Saraceno, R. A.; Riding, G. H.; Allcock, H. R.; Ewing, A. G. J .
Am. Chem. Soc. 1988, 110, 7259.

986 Organometallics, Vol. 22, No. 5, 2003
Chandrasekhar et al.
should be equivalent.29-32 In compounds such as 1b-
4b, although the ferrocenyl moieties present therein are
physically well separated from each other, all of them
are oxidized at the same potential. Such an equivalence
of multiple ferrocene units arranged at the periphery
of dendrimeric structures has been observed earlier.3
The E1/2 values are shifted to less positive numbers
with an increase in the number of ferrocene arms. Thus
the E1/2 value is lowest for 1b, containing six ferrocene
arms, and is the highest for 5b and 6b, containing only
one ferrocene arm. However, all the oxidation potentials
are lower than those observed for ferrocene carbox-
aldehyde (0.87 V). The electrochemical behavior of 1b-
6b is reproducible, indicating that these compounds or
their oxidized products are perfectly stable and robust.
This has been verified up to 10 continuous electrochemi-
cal cycles. Further evidence for the electrochemical
stability of 1b-6b comes from the observation that the
peak potential does not vary with scan rate (10-200 mV
s-1).
assemblies. The advantage of this method is the con-
venience it affords in terms of varying the ferrocene
units systematically from one to six. The X-ray crystal
structures of these cyclophosphazene-supported ferro-
cenyl derivatives including N3P3[N(Me)NdCH-C5H4-
FeC5H5]6 show the adaptability of the cylophsophazene
ring in supporting the ferrocene units without any steric
congestion. The cyclophosphazene ring itself undergoes
a slight puckering in some situations. The electrochemi-
cal behavior of these ferrocenyl derivatives shows that
all of them show a single reversible oxidation wave. The
observation of this even in multi-ferrocenyl derivatives
suggests the electrochemical equivalence of the fer-
rocene moieties.
Ack n ow led gm en t. We are thankful to the Council
of Scientific and Industrial Research (New Delhi) for
financial support. GTS, S.N., and V.K. also thank this
organization for the award of a Senior Research Fel-
lowship.
Con clu sion
Su p p or tin g In for m a tion Ava ila ble: Tables (S1-S25)
giving atomic coordinates and equivalent isotropic displace-
ment parameters, bond lengths and angles, anisotropic dis-
placement parameters, hydrogen coordinates, and isotropic
displacement parameters for 1b and 3b-6b. The CIF files for
all these compounds are also presented. These materials are
available free of charge via the Internet at http://pubs.acs.org.
In conclusion, cyclophosphazene hydrazides are excel-
lent synthons for the preparation of multi-ferrocenyl
(29) Myer, C. N.; Allen, C. W. Polym. Prepr. 2000, 41, 558.
(30) Fillaut, J .-L.; Lineares, J .; Astruc, D. Angew. Chem., Int. Ed.
Engl. 1994, 33, 2460.
(31) Fillaut, J .-L.; Astruc, D. Chem. Commun. 1993, 1320.
(32) Chandrasekhar, V.; Nagendran, S.; Bansal, S.; Kozee, M. A.;
Powell, D. R. Angew. Chem., Int. Ed. 2000, 39, 1833.
OM020760D