Preparation of functionalized p-phenylenediamine derivatives using arene-iron chemistry

Article abstract of DOI:10.1021/jo951677l

Selective displacement of chloride from cyclopentadienyl(1,4-dichlorobenzene)iron(1+) by a series of cyclic secondary amine nucleophiles is described. This selectivity, in combination with further manipulation of the complexes, allows access to a series of unsymmetrical and/or functionalized etraalkyl-p-phenylenediamine complexes. A series of demetalated phenylenediamines were shown by CV to have redox potentials distributed over a range of 320 mV, as a consequence of remote functionality. Preliminary fluorescence studies on a series of electron acceptor-substituted phenylenediamines indicated quenching of the phenylenediamine fluorescence, attributable to rapid electron transfer.

Full text of DOI:10.1021/jo951677l

J . Org. Chem. 1996, 61, 1297-1305
1297
P r ep a r a tion of F u n ction a lized p-P h en ylen ed ia m in e Der iva tives
Usin g Ar en e-Ir on Ch em istr y
Anthony J . Pearson* and Ann M. Gelormini
Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106
Marye Anne Fox and Diana Watkins
Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1167
Received September 12, 1995X
Selective displacement of chloride from cyclopentadienyl(1,4-dichlorobenzene)iron(1+) by a series
of cyclic secondary amine nucleophiles is described. This selectivity, in combination with further
manipulation of the complexes, allows access to a series of unsymmetrical and/or functionalized
tetraalkyl-p-phenylenediamine complexes. A series of demetalated phenylenediamines were shown
by CV to have redox potentials distributed over a range of 320 mV, as a consequence of remote
functionality. Preliminary fluorescence studies on a series of electron acceptor-substituted
phenylenediamines indicated quenching of the phenylenediamine fluorescence, attributable to rapid
electron transfer.
In tr od u ction
protection/deprotection sequences which are incompat-
able with the phenylene diamine functionality. Conven-
tional syntheses for the few derivatives which have been
reported in the open literature are quite low yielding.8 A
recent report has disclosed a palladium-based cross-
coupling reaction which has been applied to the synthesis
of some simple tetraalkyl derivatives in good yields.9
We4a,b and others10 have described the use of secondary
amines as nucleophiles for arene-iron complexes.
We report herein a protocol for the use of arene-iron
chemistry in the synthesis of unsymmetrical and func-
tionalized Wurster’s Blue derivatives, our solutions to the
problems inherent in the critical decomplexation step,
and the synthesis of functionalized Wurster’s Blue de-
rivatives containing a covalently linked electron-acceptor
functionality. In this work, the FeCp moiety serves in a
three-fold capacity. Complexation of p-dichlorobenzene
to [FeCp]+ facilitates SNAr reactions, allows them to be
conducted chemoselectively, and renders the arene suf-
ficiently electron poor that neighboring functionality can
be manipulated without the risk of oxidation of the target
phenylenediamine.
Transition-metal activated nucleophilic aromatic sub-
stitution is beginning to play a role in various polymer
and materials applications.1-3 While triaryl-diether and
polyphenylene oxide derivatives that are accessible from
these complexes have been thoroughly investigated,1-4
other derivatives, such as N-substituted phenylenedi-
amines, have seen far less attention. While several well
known methods for the construction of the arene-
nitrogen bond may be found, these reactions either
proceed via a benzyne intermediate, and suffer the
attendant regiocontrol problems,5 or they require high
temperatures (Ullmann conditions) or the presence of
specific functionality on the ring (traditional SNAr reac-
tions). The alternative SRN1 pathway is complicated by
the presence of a dimethylamino substituent on the ring.6
We are interested in applying arene-iron chemistry
to the synthesis of unsymmetrical and/or functionalized
“Wurster’s Blue” derivatives. The parent N,N,N′,N′-
tetramethyl-p-phenylenediamine (TMPD) is a powerful
electron donor, and has been extensively studied.7 How-
ever, unsymmetrical or functionalized derivatives, which
might be incorporated into molecular electronic devices,
have not been widely explored. This may be because any
synthesis from p-phenylenediamine or from p-nitro-
aniline would require functional group manipulation or
Resu lts a n d Discu ssion
Syn th esis a n d Decom p lexa tion Stu d ies. The sym-
metrical p-phenylenediamine-FeCp cations 2-5 were
prepared in 80-96% yields by double nucleophilic dis-
placement reactions on the p-dichlorobenzene-FeCp
complex 1 (Scheme 1). The reaction conditions are quite
straightforward, consisting of stirring a THF solution of
1 and an excess of the appropriate nucleophile, in the
presence of K2CO3, for 12-24 h at room temperature. The
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
(1) (a) Pearson, A. J .; Gelormini, A. M. Macromolecules 1994, 27,
3675-3677. (b) Pearson, A. J .; Gelormini, A. M. J . Org. Chem. 1994,
59, 4561-4570.
(2) (a) Abd-El-Aziz, A. S.; Schreimer, D. C.; de Denus, C. R.
Organometallics 1994, 13, 374-384. (b) Abd-El-Aziz, A. S.; de Denus,
C. R. J . Chem. Soc., Chem. Commun. 1994, 663-665. (c) Abd-El-Aziz,
A. S.; Epp, K.; de Denus, C. R. Organometallics 1994, 13, 2299.
(3) (a) Dembek, A. A.; Burch, R. R.; Fiering, A. E. J . Am. Chem.
Soc. 1993, 115, 2087-2088. (b) Dembek, A. A. ; Burch, R. R. Fiering,
A. E. Macromolecules 1993, 26, 2992-2994. (c) Segal, J . A. J . Chem.
Soc., Chem. Commun. 1985, 1338-1339.
(4) (a) Pearson, A. J .; Gelormini, A. M. J . Org Chem. 1995, 60, 281-
284. (b) Pearson, A. J .; Park, J . G.; Zhu, P. Y. J . Org. Chem. 1992, 57,
3583-3589. (c) Park, J . G.; Yang, Y. S.; Chuang, Y. J . Chem. Soc.,
Chem. Commun. 1989, 1363-1364.
(5) Razzuk, A.; Biehl, E. R. J . Org. Chem. 1987, 52, 2619-2622.
(6) For examples of each of the described cases, see March, J .
Advanced Organic Chemistry, 4th ed.; Wiley: New York, 1992 and
references cited therein.
(8) For example, Nelsen, S. F.; Yunta, M. J . R. J . Phys. Org. Chem.
1994, 7, 55 describes the synthesis of compounds structurally similar
to several of our derivatives. In no case is the yield of any step higher
than 20%. A few recent patent applications have appeared (e.g. Muto,
N.; Myamoto, E.; Nakazawa, S. J pn. Kokai Tokkyo Koho J P 01,118,-
141 [89,118,1411] Chem. Abstr. 1989, 111, 184160s and Yoshikawa,
M.; Suzuki, T.; Kojima, A.; Masayuki, S. J p. Kokai Tokkyo Koho J P
01,154,571 [89,154,571] Chem. Abstr. 1990, 112, 29317a) which employ
such derivatives in thin-film photoconductive photoreceptors.
(9) Guram, A. S.; Buchwald, S. L J . Am. Chem. Soc. 1994, 116,
7901-7902.
(7) For a review, see Foster, R. Organic Charge Transfer Complexes;
Academic Press: New York, 1969.
(10) Abd-El-Aziz, A. S.; Pio´rko, A.; Lee, C. C.; Sutherland, R. G. Can.
J . Chem. 1989, 67, 1618-1623.
0022-3263/96/1961-1297$12.00/0 © 1996 American Chemical Society

1298 J . Org. Chem., Vol. 61, No. 4, 1996
Pearson et al.
Sch em e 1
initially reasoned this behavior to be the result of amine
coordination of the liberated iron.11
To circumvent this, the Boc (tert-butoxycarbonyl) pro-
tected derivative 6 was synthesized and decomplexed in
95% yield to give 10; however, attempted deprotections
were unsuccessful. Protection of 2 as its Cbz- (benzy-
loxycarbonyl) and trifluoroacetate derivatives (7, 8) or its
derivatization to the bis-terephthalamide 11 also pro-
ceeded without incident; however, once again, the de-
complexations were problematic, indicating that there
were additional complications besides iron ligation. Per-
forming the decomplexation under room lighting for
extended periods (36-48 h) afforded a partial solution
to the problem, as is evidenced in Table 1, indicating that
amine photooxidation could be a competing problem.12
The above constraints required that we select reaction
conditions that are at most mildly photolytic and which
allow us to irreversibly remove the metal from participa-
tion, once it is freed from the arene. Pyrolytic sublima-
tion is one decomplexation technique that would fit these
requirements;13 however, this method is tedious, and the
arene must be stable at the required temperatures (>200
°C). Attempts to pyrolytically sublime 2 and the bis-
terephthalamide 11 failed.
Another approach is to introduce stronger iron ligators
than acetonitrile to the reaction mixture, in anticipation
that this would promote decomplexation and more ef-
ficiently sequester the iron once it is removed. While the
reaction would still require photoinitiation, intense and
prolonged irradiation could be avoided. Decomplexation
of these complexes using acetylacetone14 and 1,10-
phenanthroline15 as competing ligands have been de-
scribed; however, the focus of those studies was on the
resulting metal complexes. No attention was given to
the liberated organic ligand and no attempts were made
to isolate the arene or to develop this into a useful
synthetic method. Conceptually, however, this approach
was appropriate for our complexes. Owing to the inher-
ent advantages of phenanthroline (a very strong donor
ligand, the possiblity of following the reaction spectro-
photometrically, the need to eliminate only an ionic solid
byproduct) we began our investigations there and have
optimized conditions for this decomplexation method.
In our initial approach to the phenanthroline-assisted
demetalations, the complex was stirred with an acetoni-
trile/water solution containing a modest excess of
phenanthroline‚HCl‚H2O, in the presence of room light,
for 24-36 h. The excess was used to ensure complete
capture of the iron. Although the reaction appeared to
be reaching completion by UV-vis spectrophotometry,
severe losses were incurred in attempting to separate the
excess phenanthroline. This procedure was then modi-
fied to employ phenanthroline as the limiting reagent
(2.9:1), The yields were increased, often dramatically, by
this adjustment.
purification is likewise simple; the cationic product is
precipitated by addition of ether to a concentrated
dichloromethane solution of the crude reaction mixture.
While 4 could be decomplexed using established meth-
odology1 (stirring a solution of the complex in acetonitrile,
under a sunlamp, for 2-4 h), attempts to decomplex 2
and 3 in this manner failed and starting material was
not recovered. We obtained, instead, an orange-brown
precipitate which gave positive qualitative tests for the
presence of iron and a Wurster’s Blue derivative (red
coloration on addition to aqueous phenanthroline and
blue coloration of a solution in 10% HCl). Very little free
phenylenediamine remained in the acetonitrile solution.
If the precipitate was treated with aqueous base and then
neutralized, iron hydroxide precipitated; however, this
procedure also resulted in substantial oxidation of the
amine. The desired product was obtained only in low
yield and was accompanied by several impurities. We
In this manner, we were able to prepare a series of
protected or functionalized p-phenylenedipiperazines and
(11) Bertoncello, K.; Fallon, G. D.; Hodgkin, J . D.; Murray, K. S.
Inorg. Chem. 1988, 27, 4750-4758.
(12) For example, see Albrecht, A. C. J . Am. Chem. Soc. 1960, 82,
3813-1816.
(13) For an example, see Sutherland, R. G.; Piorko, A.; Gill, U. S.;
Lee, C. C. J . Heterocycl. Chem. 1982, 19, 801-803.
(14) Razuvaev, G. A.; Domrachev, G. A.; Suvorova, O. N.; Abaku-
mova, L. G. J . Organomet. Chem. 1971, 32, 113-120.
(15) (a) McNair, A. M.; Schrenk, J . L.; Mann, K. R. Inorg. Chem.
1984, 23, 2633-2640. (b) Brown, R. A.; Fernando, S. I. S.; Roberts, R.
M. G. J . Chem. Soc., Perkin Trans. 1 1994, 197-201.

Preparation of p-Phenylenediamine Derivatives
J . Org. Chem., Vol. 61, No. 4, 1996 1299
Ta ble 1. Com p a r ison of Yield s fr om P h otolytic a n d P h en a n th r olin e-Assisted Decom p lexa tion Meth od s
decomplexation
product
phenanthroline-assisted
decomplexation, %
hν-assisted
decomplexation, %
decomplexation
under room light, %
complex
2
3
4
17
15
9
0 (separation problem)
67
25 (separation problem)
5-10
0
66
5
6
7
8
11
25
26
27
28
29
30
37
16
10
12
13
14
31
32
33
34
35
36
38
51
Not attempted
94
39
75
42
82
78
72
95
24
trace, deprotection
20
39
52
30
81
77 (over two steps)
53
Sch em e 2
related molecules, (Scheme 2); however, the free diamine
17 remained elusive. While evidence for decomplexation
was obtained, it was not possible to separate the [Fe-
(Phen)3]2+ from the liberated diamine. Attempts to
deprotect the benzyloxycarbonyl derivative were unsuc-
cessful, presumably due to catalyst poisoning by the
diamine. The trifluoroacetate derivative was not ob-
tained in good yield and was therefore not pursued
further. Attempted decomplexation using imidazole as
a competing ligand was again accompanied by a separa-
tion problem. We were, however, able to recover the
imidazole nearly quantitatively after the decomplexation.
This led us to speculate that increasing the basicity of
the reaction mixture causes precipitation of iron hydrox-
ide and drives the reaction to completion. Decomplex-
ation of 2 in dilute, aqueous ammonia, under room
lighting, followed by extraction of the product into
chloroform, provided a pathway to 17 in yields of ca. 75%.
This method is potentially more straightforward in terms
of purification than the phenanthroline-assisted decom-
plexation and would be adequate as long as no hydro-
lytically unstable functionality is present. For example,
treatment of the model compound 18 under identical
conditions resulted in complete ester hydrolysis.
Syn th esis of Don or -Accep tor System s. The pos-
sibility of obtaining unsymmetrically substituted arenes
by sequential, chemoselective SNAr reactions on dichlo-
robenzene FeCp cations is well precedented.1,2,4 We have
applied this methodology to the preparation of the
unsymmetrical phenylenediamine complexes 23 and 24.
Unfortunately, we were not able to obtain acceptable
selectivity with piperazine as the first nucleophile. We
obtained almost complete selectivity, however, by using
nearly stoichiometric amounts of either N-methylpipera-
zine or piperidine as the first nucleophile. The morpho-
line adducts 19 and 22 have been described previously.1b
Following a second substitution with piperazine as the
nucleophile, we were in possession of three electronically
differentiated tetraalkyl-p-phenylenediamine complexes
22-24, each with the secondary piperazine nitrogen as
a point for further functionalization. Treatment of these
complexes with the acid chloride of mono-methyl tereph-
thalate gave the corresponding amides 25-27, each with
a potential electron acceptor incorporated into the struc-
ture (Scheme 3). Complex 24 was also allowed to react
with the acid chlorides of 2-naphthoic acid and an-
thraquinone-2-carboxylic acid to give compounds 28 and
29. The amidations proceeded in 80-97% yields.
h, K2CO3), to give 30 and then 36 in 77% overall yield
(Scheme 4). Complex 30 was isolated in 66% yield;
however, its synthesis is accompanied by some decom-
We were also able to use 24 in a conventional SNAr
reaction, with p-nitrofluorobenzene (refluxing glyme, 24

1300 J . Org. Chem., Vol. 61, No. 4, 1996
Pearson et al.
Sch em e 3a
a
Reagents and conditions: (a) amine nucleophile, K2CO3, THF, 12-24 h, rt; (b) piperazine, K2CO3, THF, 12 h, rt; (c) monomethyl
terephthalate, oxalyl chloride, pyridine, CH2Cl2, rt; (d) 20 or 22, product of c, K2CO3, CH2Cl2, rt. (e) 21, prodcut of c, Et3N, CH2Cl2 rt; (f)
phenanthroline ‚HCl‚H2O, MeCN-H2O, room light, 24 h, rt.
plexation. Therefore, in order to maximize the yield of
36, the crude product mixture was usually taken forward
to the decomplexation step. Surprisingly, attempts to
prepare 30 directly from 21 and the commercially avail-
able 4-(4-nitrophenyl)piperazine were unsucessful. Even
under relatively forcing conditions (5 equiv of amine, K2-
CO3, refluxing THF, 20 h) we observed only partial (ca.
20%) conversion.
signals for the coresponding atoms of any metalated
compounds.
Cyclic Volta m m etr y. In acetonitrile, N,N,N′,N′-
tetramethyl-p-phenylenediamine exhibits a fully revers-
ible first oxidation wave at 120 mV vs SCE .16 The
latitude of nucleophile and substituent control available
by using arene-metal chemistry provides a potential
method for preparing derivatives of TMPD with attenu-
ated oxidation potentials. “Tuning devices” (inductively
electron-withdrawing or sterically demanding groups)
can be incorporated as heteroatoms in the cyclic second-
ary amine nucleophile or introduced by further reaction
at the secondary piperazine nitrogen(s) in e.g. 2, and 22-
24, or can be present on the starting dichlorobenzene
complex, such as with complex 37 (Figure 1). Several of
the compounds presented above were analyzed by CV in
acetonitrile, and the results are tabulated in Table 2. The
increase in redox potential from TMPD to 16 is presum-
ably the result of the different steric requirements for
the planarization of the system which accompanies
oxidation. We observed an additional attenuation of the
redox potential which was dependent on the inductive
electron-withdrawing ability of remote substituents,
which covered a range of 320 mV. The most dramatic
effects were seen by tuning devices incorporated in the
heterocyclic nucleophiles. As expected, only minor ad-
justments were induced by more remote functionality.
With the exception of compounds with a tertiary aliphatic
amine remote from the arene, the oxidation waves
observed were either fully or quasireversible over a range
of 0 to +1.00 V.
Phenanthroline-mediated decomplexations of these
amides were straightforward, proceeding in 70-91%
yields (this is quite comparable to yields obtained by
standard photolytic decomplexations of compounds not
presenting chelation or oxidation problems)1,12 to give the
series of donor-acceptor dyads 31-36. The workup in
each case consisted of adsorbing the reaction mixture
onto basic alumina (adding basic alumina to the reaction
mixture, removing the solvent, and drying the residue
thoroughly), placing this atop a short alumina column,
and washing the organic product through with chloro-
form. This preadsorption was necessary in order to avoid
introducing polar solvents onto the column, which causes
cochromatographing of the Fe(Phen)32+. In most cases,
the chloroform eluant was washed with 0.05 M HCl and
then water and dried, the solvent removed, and the
product recrystallized, usually from acetone. Further
chromatographic purification was usually undertaken to
obtain material suitable for sensitive physical studies
(e.g. fluorescence spectroscopy).
At ambient temperatures the proton and 13C NMR
spectra of both the complexed and free amides exhibit
severe broadening of the piperazine ring signals, presum-
ably due to slow rotation about the C-N bond as a result
of amide resonance. Partial coalescence was observed at
90 °C in CD3NO2; however, the signals were still not well
resolved. Low temperature spectroscopy in CD2Cl2 was
therefore employed to obtain the resolved spectra re-
ported herein. We were unable to obtain well-resolved
Compound 38 is interesting in that the o-methyl
substituent results in an increased oxidation potential,
presumably due to steric inhibition of resonance domi-
(16) Nelsen, S. F.; Kessel, C. R.; Brien, D. J . J . Am. Chem. Soc. 1980,
102, 702-711.

Preparation of p-Phenylenediamine Derivatives
J . Org. Chem., Vol. 61, No. 4, 1996 1301
Sch em e 4a
Ta ble 2. F ir st Oxid a tion P oten tia ls of Der iva tized
p-P h en ylen ed ia m in es (vs NHE)
symmetrical derivatives
unsymmetrical derivatives
compd
mV
compd
mV
16
17
9
15
14
13
192
246
292
299
393
443
36
34
33
35
32
38
31
272
285
291
295
343
343
377
Ta ble 3. P er cen t Qu en ch in g of th e Tr ip let Em ission of
P h en ylen ed ia m in e Un its Con ta in ed in 32 a n d 14,
F ollow ed by Stea d y-Sta te Em ission In ten sities
compound
% quenching I/Io
15
32
14
0
95
99
donor 15, the donor-acceptor dyad 32, and the acceptor-
donor-acceptor triad 14 were examined. Dyad 32 could
probe the effect of one donor on ET quenching of 15,
whereas triad 14 would provide information of the effects
of symmetrical substituents on this emission.
Steady-state emission studies were carried out in
MeTHF on compounds 14, 15, and 32. Their relative
triplet emission intensities, from steady-state measure-
ments, are collected in Table 3. Comparison of emission
intensities of the unsubstituted donor to the acceptor-
donor dyads indicates fluorescence quenching. From the
triplet energies of the donor 15 (ET ) 2.64 eV) and the
acceptor (ET ) 3.10 eV) it is clear that the acceptor is
not capable of quenching the donor T1 state. Hence we
attribute steady-state quenching in the donor-acceptor
dyads to rapid electron transfer quenching.
Con clu sion s
We have illustrated the use of arene-iron complexes
in synthesizing unsymmetrical and functionalized Wurst-
er’s blue derivatives. The presence of the metal moiety
renders the phenylenediamine sufficiently electron de-
ficient that it may be manipulated conveniently. The
decomplexations of these derivatives are not straightfor-
ward due to complications involving metal chelation and
possible photooxidation reactions of the phenylenedi-
amine. To circumvent this, we have developed a method
for the decomplexation of these derivatives, which in-
volves a combination of a mild light source and 1,10-
phenanthroline. The phenanthroline coordinates the
liberated iron, removing it from further participation in
the reaction, and we have applied this procedure to the
synthesis of a series of monomers (e.g. 9, 15) and donor-
acceptor systems. We have illustrated an attenuation
of the first oxidation wave of these compounds, as a
function of remote functionality, over a range of 350 mV,
and we are presently involved in further study of their
electronic properties.
a
Reagents and conditions: (a) ArCOOH, (ClC(O))2, py, rt; (b)
compound 22, product of a, K2CO3, CH2Cl2, rt; (c) as for Scheme
3, step f; (d) glyme, K2CO3, reflux, 24 h.
F igu r e 1.
nating over the inductive electron release of the methyl
group. Additionally, in the corresponding complex 37,
the methyl serves as a site for further functionalization.
Protons of methyl groups on arene-iron complexes show
enhanced acidity owing to the ability of the FeCp frag-
ment to stabilize the resulting carbanion, and deproto-
nation-alkylation sequences have been explored by
Sutherland17 and Astruc.17
Exp er im en ta l Section
Gen er a l. Complex 1 was prepared according to a previ-
ously published procedure.1b For general methods, see refer-
ence 12b. General procedures are given below and variations
F lu or escen ce Stu d ies. In order to establish whether
electronic interactions couple the chromophores in this
series, low temperature emission spectra of the electron
(18) (a) Moulines, F.; Gloaguen, B. Astruc, D. Angew. Chem., Int.
Ed. Engl. 1992, 31, 458-460. (b) Fillaut, J .-L.; Boese, R.; Astruc, D.
Synlett 1992, 55-56. (c) Moulines, F., Djakovitch, L.; Fillaut, J .-L.,
Astruc, D. Synlett 1992, 57-58.
(17) Sutherland, R. G.; Steele, B. R.; Demchuk, K. J .; Lee, C. C. J .
Organomet. Chem. 1979, 181, 411-424.

1302 J . Org. Chem., Vol. 61, No. 4, 1996
Pearson et al.
are noted with the spectral data for individual compounds.
Nuclear magnetic resonance spectra were recorded for solu-
tions of complexes in acetone-d6, and spectra for products of
decomplexation reactions were taken for solutions in CDCl3,
at rt or at low temperatures in CD2Cl2 unless otherwise
specified. Cyclic voltammetry studies were performed on a
BAS-100 electrochemical analyzer in CH3CN with TBAP (0.1
M) as the supporting electrolyte and a sample concentration
of 1.0 mM, using a platinum electrode. Reported oxidation
potentials are vs NHE and were calculated according to the
formula E(vs NHE) ) Eex(vs SCE) - EFc(vs SCE) + 400 mV
where EFc ) the potential of the ferrocene/ferricinium couple
taken immediately prior to the measurement of the unknown.
Emission spectra were recorded at 77 K (λ ) 300 nm) in a
MeTHF glass, using a SLM Aminco SPF 500 spectrofluorim-
eter, since room temperature measurements showed no emis-
sion. All solutions were deoxygenated by bubbling with
nitrogen and had an OD < 0.10 in a 1 cm cuvette. The
emission spectra were measured in the ratio mode (to correct
for variations in lamp intensity with time). Delayed fluores-
cence and phosphorescence spectra were recorded on a SLM
Aminco SPF 500 spectrofluorometer with a phosphoroscope
attachment that uses light baffles and a variable-speed chop-
per (0-10000 rpm). To prevent light scattering of the excita-
tion wavelength from the low-temperature dewar, a 350 nm
cut-off filter was inserted at the front end of the emission
monochromator.
Gen er a l P r oced u r es for Dou ble SNAr Rea ction s. Com-
plex 2 was stirred with the amine (10 mmol of amine/mmol of
2) in the presence of K2CO3 (5 mmol/mmol 2) in THF (25 mL/
mmol 2) at rt for 12 h. The reaction mixture was filtered, and
the solid was washed with acetonitrile until the washings were
no longer orange. The combined filtrate and washings were
concentrated in vacuo, redissolved in a minimum of CH2Cl2,
and added dropwise to approximately a ten-fold excess of ether.
The precipitate was isolated by suction filtration and dried in
vacuo. If the initial precipitate was an oil, the suspension was
chilled overnight, the solvent was decanted, and the oil was
redissolved and reprecipitated. This procedure was repeated
until a solid was obtained.
[1,4-Bis[4-(b en zyloxyca r b on yl)p ip er a zin o]b en zen e]-
(cyclop en ta d ien yl)ir on Hexa flu or op h osp h a te (7). Com-
plex 2 (513 mg, 1.0 mmol) was stirred with benzyl chlorofor-
mate (425 mg, 357 µL, 2.5 mmol) and K2CO3 (690 mg, 5.0
mmol) in CH2Cl2 (25 mL) for 2 h at rt. Water (1.0 mL) was
added, and the mixture was stirred for an additional 0.5 h.
The mixture was diluted to 50 mL with CH2Cl2, filtered
through Celite, and washed through with additional CH2Cl2.
The combined filtrate and washings were washed with 50%
saturated aqueous NH4PF6 (10 mL), 0.1 M NaOH (2 × 10 mL),
and water (10 mL). The organic layer was dried over MgSO4,
concentrated to ca. 10 mL, and added dropwise to 100 mL
ether. The precipitate was isolated by suction filtration, rinsed
with ether (10 mL), and dried in vacuo to give 6 in 88% yield
(686 mg). 1H NMR δ 7.43-7.36 (10 H, m), 5.90 (4H, s), 5.17
(4H, s), 5.10 (5H, s), 3.67 (8H, t, J ) 6.0 Hz), 3.45 (8H, t, J )
6.0 Hz). 13C NMR δ 155.5, 137.8, 129.1, 128.8, 122.0, 74.2,
67.1, 47.3, 43.5. Two quaternary carbons were not detected.
[1,4-B is [4-(t r iflu o r o a c e t y l)p ip e r a zin o ]b e n ze n e ]-
(cyclop en ta d ien yl)ir on Hexa flu or op h osp h a te (8). Com-
pound 2 (205 mg, 0.4 mmol) was stirred with trifluoroacetic
anhydride (336 mg, 226 µL, 1.6 mmol) and pyridine (1.0 mmol,
79 mg, 81 µL) in CH2Cl2 (10 mL) for 4 h at rt. The solution
was diluted to 30 mL, washed with saturated NaHCO3 (10 mL)
and water (2 × 10 mL), dried over MgSO4, and isolated as
usual in 80% yield (226 mg). IR (film) 2957-2830 (weak),
1697, 1521, 840 cm-1 1H NMR (δ) 5.99 (4H, s), 5.16 (5H, s),
.
3.87 (8H, t, J ) 5.0 Hz), 3.65 (8H, t, J ) 5.0 Hz). 13C NMR (δ)
121.6, 75.0, 67.4, 47.1, 46.8, 45.3, 42.9.
[1-Ch lor o-4-p ip er id in ob en zen e](cyclop en t a d ien yl)-
ir on Hexa flu or op h osp h a te (21). Complex 1 (6.20 g, 15.0
mmol) was stirred with K2CO3 (2.07 g, 15.0 mmol) in THF (100
mL). To this suspension was added piperidine (1.70 g, 20.0
mmol), and the reaction was allowed to stir at room temp for
20 h. An additional 272 mg piperidine and 220 mg K2CO3 were
then added, and the mixture was stirred an additional 12 h.
The mixture was filtered and the solid washed thououghly with
CH2Cl2. The combined washings and filtrate were concen-
trated in vacuo to approximately 20 mL and were added
dropwise to ether (200 mL). The precipitate was isolated by
suction filtration, washed with ether, and dried in vacuo to
give the product in 97% yield (6.72 g). 1H NMR (δ) 6.60 (2H,
d, J ) 7.2 Hz), 6.13 (2H, d, J ) 7.2 Hz), 5.22 (5H, s), 3.59 (4H,
t, J ) 5.6 Hz), 1.79 (6H, br m). 13C NMR (δ) 127.7, 102.3,
86.7, 78.1, 66.6, 48.2, 25.7, 24.0.
(1,4-Dip ip e r a zin ob e n ze n e )(cyclop e n t a d ie n yl)ir on
Hexa flu or op h osp h a te (2). Two reprecipitations were usu-
ally necessary to remove residual piperazine. Yield: 86%. IR
(KBr pellet) 3345, 3124, 2959-2843, 1569, 1517 cm-1
.
1H
NMR δ 5.76 (4H, s), 5.06 (1H, s), 3.31 (8H, t, J ) 4.9 Hz), 2.97
[1-C h lo r o -4-(4-m e t h y lp ip e r a zin o )b e n ze n e ](c y c lo -
p en ta d ien yl)ir on Hexa flu or op h osp h a te (20). The proce-
dure was as for 21 except that 2 equiv of the amine was used
(8H, t, J ) 4.9 Hz). 13C NMR δ 123.2, 74.2, 66.3, 48.5, 46.1.
[1,4-Bis(4-m e t h ylp ip e r a zin o)b e n ze n e ](cyclop e n t a -
d ien yl)ir on Hexa flu or op h osp h a te (3). Yield: 96%. IR
1
initially and a second portion was not added. Yield: 95%. H
(KBr pellet) 3345, 2959-2843, 1569, 1517 cm-1
.
1H NMR δ
NMR (δ) 6.45 (2H, d, J ) 6.9 Hz), 6.01 (2H, d J ) 6.9 Hz),
5.13 (5H, s), 3.40 (2H, t, J ) 5.1 Hz); 2.49 (4H, t, J ) 5.1 Hz);
2.27 (3H, s). 13C NMR (δ) 126.3, 102.9, 86.8, 78.2, 68.1, 54.4,
46.9, 45.5.
5.84 (4H, s), 5.14 (5H, s), 3.44 (8H, t, J ) 5.1 Hz), 2.59 (8H, t,
J ) 5.1 Hz), 2.35 (6H, s). 13C NMR (δ) 122.6, 74.4, 66.6, 55.0,
47.6, 46.2.
[1,4-B i s [4-(2-h y d r o x y e t h y l)p i p e r a z i n o ]b e n z e n e -
[1-(4-Meth ylp ip er a zin o)-4-p ip er a zin oben zen e](cyclo-
p en ta d ien yl)ir on Hexa flu or op h osp h a te (23). Complex 18
(800 mg, 1.7 mmol) was stirred with piperazine (577 mg, 6.7
mmol) and K2CO3 (464 mg, 3.4 mmol) in THF (20 mL) for 12
h at rt. The resulting orange solution was filtered, and the
solid was washed with MeCN until it was no longer orange.
The combined filtrate and washings were concentrated to
approximately 10 mL and added dropwise to 150 mL of ether.
The resulting precipitate was isolated by suction filtration and
dried in vacuo to give the product in 87% yield (799 mg). IR
(film) 3325-3195, 3121, 2948-2804, 1565, 1520, 840 cm-1. 1H
NMR (δ) 5.76 (4H, s), 5.06 (5H, s), 3.37 (4H, t, J ) 5.1 Hz),
3.30 (3H, t, J ) 5.2 Hz), 2.96 (4H, t, J ) 5.2 Hz), 2.53 (4H, t,
J ) 5.1 Hz), 2.29 (3H, s). 13C NMR (δ) 123.3, 122.5, 74.3, 66.6,
66.2, 55.0, 48.5, 47.6, 46.7, 46.1.
(cyclop en t a d ien yl)ir on
H exa flu or op h osp h a t e
(4).
Yield: 80%. IR (film) 3380-3210, 2943-2824, 1520, 842 cm-1
.
1H NMR δ 5.87 (4H, s), 5.15 (5H, s), 3.73 (4H, t, J ) 5.6 Hz),
3.48 (8H, t, J ) 5.0 Hz), 2.76 (8H, t, J ) 5.0 Hz), 2.64 (4H, t,
J ) 5.6 Hz). 13C NMR δ 122.6, 74.4, 66.6, 60.8, 59.6, 53.3,
47.8.
[1,4-Dip ip e r id in ob e n ze n e ](cyclop e n t a d ie n yl)ir on
Hexa flu or op h osp h a te (5). Yield: 83%. 1H NMR δ 5.82 (4H,
s), 5.07 (5H, s), 3.46 (8H, t, J ) 5.5 Hz), 1.79 (8H, apparent t,
J ) 4.9 Hz), 1.75 (4H, t, J ) 4.4 Hz). 13C NMR δ 123.2, 74.4,
66.1, 48.3, 26.0, 24.1.
[1,4-Bis[4-(ter t-bu tyloxycar bon yl)piper azin o]ben zen e]-
(cyclop en ta d ien yl)ir on Hexa flu or op h osp h a te (6). Com-
plex 2 (51 mg, 0.1 mmol) and di-tert-butyl dicarbonate (48 mg,
0.22 mmol) were stirred in CH2Cl2 (2 mL) for 2 h. The mixture
was filtered through a cotton plug directly into 20 mL of 1:1
ether/pentane. The solid was allowed to settle, the solvent was
decanted, and the residue was rinsed with ether (5 mL) and
vacuum dried to give 5 (70 mg) in 98% yield. IR (film) 3007-
[1-P iper azin o-4-piper idin oben zen e](cyclopen tadien yl)-
ir on Hexa flu or op h osp h a te (24). The procedure was as for
21, giving the product in 88% yield. IR (film) 3352-3325,
3118, 2942, 2855, 1567, 1519, 840 cm-1 1H NMR δ 5.74 (4H,
.
s), 5.02 (5H, s), 3.39 (4H, t, J ) 5.4 Hz), 3.30 (4H, t, J ) 4.6
Hz), 2.99 (4H, br m), 1.74-1.66 (6H, br m). 13C NMR δ 123.6,
122.8, 74.4, 66.5, 66.1, 48.5, 48.4, 46.1, 26.0, 24.1.
2962, 1691, 1518, 840 cm-1 1H NMR δ 5.96 (4H, s), 5.16 (5H,
.
s), 3.67 (8H, t, J ) 4.8 Hz), 3.50 (8H, t, J ) 4.8 Hz), 1.54 (18H,
s). 13C NMR δ 155.2, 122.3, 80.6, 74.8, 67.1, 47.4, 28.5.
Gen er a l P r oced u r e for Am id a tion s. The appropriate

Preparation of p-Phenylenediamine Derivatives
J . Org. Chem., Vol. 61, No. 4, 1996 1303
carboxylic acid was stirred with pyridine (1.1 equiv) in CH2-
Cl2 (10-15 mL/mmol of acid). A solution of oxalyl chloride
(1.0 equiv) in CH2Cl2 (5 mL/mmol) was added dropwise to the
mixture, from a pressure equalizing dropping funnel. After
stirring for 0.5 h, the solvent was removed by rotary evapora-
tion, and the residue was dried in vacuo for 1 h. The residue
was then redissolved in CH2Cl2 (10 mL/mmol) and stirred with
K2CO3 (1.0 equiv). To this was added a solution of the selected
complex in dichloromethane (5 mL/mmol, 0.5 equiv relative
to the acid), and the mixture was stirred for 2-4 h. The
mixture was diluted with 2 volumes CH2Cl2, washed with
saturated aqueous NaHCO3, 1.0 M NaOH, and water, dried
over MgSO4, and concentrated to ∼10 mL by rotary evapora-
tion. This was added dropwise to ether, and the precipitate
was collected by suction filtration and dried under vacuum.
(Cyclop en t a d ien yl)[1,4-b is[4-[4-(m et h oxyca r b on yl)-
ben zoyl]p ip er a zin o]ben zen e]ir on Hexa flu or op h osp h a te
(11). Terephthalic acid monomethyl ester (2.05 g, 11.4 mmol)
and complex 2 (1.48 g, 2.9 mmol) were used. At the conclusion
of the reaction, the mixture was diluted with 1:1 CH2Cl2/MeCN
and worked up as usual to give the product in 78% yield (1,79
g). IR (KBr pellet) 3109, 3004-2849, 1718, 1638, 1575, 1513,
dd, J ) 8.0, 1.6 Hz), 8.03, (2H, dd, J ) 5.8, 3.3 Hz), 5.89 (2H,
d, J ) 7.3 Hz), 5.84 (2H, d, J ) 7.3 Hz), 5.13 (5H, s), 4.03 (2H,
br s), 3.81 (2H, br s), 3.63 (4H, br s), 3.46 (4H, t, J ) 4.9 Hz),
1.80 (6H, br s). 13C NMR δ 183.0, 182.9, 168.5, 142.4, 135.4,
134.7, 134.5, 134.3, 133.5, 128.2, 127.8, 126.5, 123.9, 121.5,
74.7, 67.6, 66.0, 48.3, 47.4 (br), 41.9 (br), 25.9, 24.1.
Com p lex 30. Complex 24 (102 mg, 0.2 mmol), was stirred
with 4-fluoronitrobenzene (141 mg, 106 µL, 1.0 mmol) and K2-
CO3 (55 mg, 0.4 mmol) in refluxing 1,2-dimethoxyethane (1.0
mL) in an aluminum foil-wrapped flask, for 24 h. The solution
was cooled, filtered through a cotton plug, and added dropwise
to ether (20 mL). The precipitate was isolated by suction
filtration, redissolved in CH2Cl2, and reprecipitated from ether.
This precipitate was isolated by suction filtration and dried
in vacuo to give the product in 75% yield (95 mg). IR (film)
3117, 2941, 2856, 1596, 1569, 1515, 839 cm-1 1H NMR δ 8.13
.
(2H, d, J ) 9.22 Hz), 5.85 (4H, dd, J ) 15.38, 7.14 Hz), 5.06
(5H, s), 3.79 (4H, t, J ) 5.0 Hz), 3.68 (4H, t, J ) 5.0 Hz), 3.42
(4H, t, J ) 5.4 Hz), 1.74 (6H, br m). 13C NMR δ 155.4, 139.2,
126.4, 123.8, 121.6, 113.7, 74.7, 67.3, 66.1, 48.4, 46.9, 46.8, 26.0,
24.1.
Gen er a l P r oced u r e for P h en a n th r olin e-Assisted De-
com p lexa tion s. To an acetonitrile solution of the organo-
metallic complex (0.4 mmol/20 mL) was added 2.9 equiv of
1,10-phenanthroline‚HCl‚H2O. Water sufficient to dissolve the
phenanthroline was added, and the mixture was allowed to
stir in the presence of room lighting for 24 h. Basic alumina
(Brockman I) was added to the now intensely red solution. The
solvent was removed by rotary evaporation and the alumina/
residue dried in vacuo. This was placed atop a short basic
alumina column, and the amide was washed off by passing
chloroform through the column. Any remaining phenanthro-
line was then removed by washing the chloroform eluant with
0.05 M aqueous HCl and water and then drying over MgSO4.
Recrystallization from hot acetone, unless otherwise specified,
gave a product that was pure by 1H and 13C NMR, in the yield
specified.
843 cm-1 1H NMR δ 8.09 (4H, d, J ) 8.3 Hz), 7.57 (4H, d, J
.
) 8.3 Hz), 5.56 (4H, s), 4.87 (5H, s), 3.90 (6H, s) overlapping
3.88 (4H, br), 3.86-3.23 (12H, br m). 13C NMR δ 169.8, 167.1,
141.1, 132.4, 130.5, 128.2, 122.2, 75.0, 67.4, 52.9, 47.6, 47.5,
47.7, 47.2.
[1-Mor p h olin o-4-[4-[4-(m eth oxyca r bon yl)ben zoyl]p ip -
er a zin o]ben zen e] (cyclop en ta d ien yl)ir on Hexa flu or o-
p h osp h a te (25). Complex 22 (512 mg) and terephthalic acid
monomethyl ester gave 756 mg of the product (97%) as an
orange microcrystalline powder. IR (KBr pellet) 1718, 1640,
1517 cm-1 1H NMR δ 8.08 (2H, d, J ) 7.9 Hz), 7.64 (2H, d, J
.
) 7.9 Hz), 5.83 (4H, s), 5.11 (5H, s), 3.92 (5H, s), 3.82 (6H, br
s), 3.54 (2H, br s), 3.63 (2H, br s), 3.36 (4H, br s). 13C NMR δ
169.4, 166.6, 141.2, 132.0, 130.3, 128.3, 122.6, 122.2, 74.8, 67.5,
66.9, 66.6, 52.7, 47.7, 41.9.
[1-[4-[4-(Met h oxyca r b on yl)b en zoyl]p ip er a zin o]-4-(4-
m e t h y lp ip e r a zin o )b e n ze n e ](c y c lo p e n t a d ie n y l)ir o n
Hexa flu or op h osp h a te (26). Triethylamine replaced potas-
sium carbonate in this reaction. Complex 23 (1.94 g, 3.8 mmol)
and terephthalic acid monomethyl ester gave 2.14 g of the
product amide (80%). IR (film) 3110, 2947-2802, 1718, 1635,
1,4-Bis[4-(ben zyloxyca r bon yl)p ip er a zin o]ben zen e (12).
The chloroform solution was washed with dilute HCl until the
washings were no longer red, the organic layer was dried over
MgSO4, the solvent was removed in vacuo, and the residue
was recrystallized from hot acetone to give the product in 83%
yield. Mp (evacuated) 168-169 °C. TLC (Al2O3, CHCl3) Rf )
0.24. IR (KBr pellet) 3059-3026, 2950-2817, 1696, 1521,
1612, 1565, 1518, 840 cm-1 1H NMR δ 8.08 (2H, d, J ) 8.2
.
Hz), 7.63 (2H, d, J ) 8.2 Hz), 5.82 (2H, d, J ) 7.2 Hz), 5.79
(2H, d, J ) 7.2 Hz), 5.08 (5H, s), 3.92 (5H, s), 3.90 (2H, br s),
3.52 (2H, br s), 3.38 (4H, t, J ) 5.0 Hz), 3.11 (2H, br s), 2.54
(4H, t, J ) 5.0 Hz), 2.29 (3H, s). 13C NMR δ 169.3, 166.7, 141.2,
132.0, 130.3, 128.3, 122.8, 122.0, 74.7, 67.5, 66.6, 54.9, 52.6,
47.5, 46.1, 42.0.
1499 cm-1 1H NMR (δ) 7.15-7.09 (5H, m), 6.66 (4H, s), 4.94
.
(4H, s), 3.43 (8H, t, J ) 5.0 Hz), 2.81 (8H, t, J ) 5.0 Hz). 13C
NMR (δ) 155.2, 145.6, 136.6, 128.5, 128.1, 127.9, 118.3, 67.2,
50.4, 43.9. HRMS calcd for C30H34N4O4 514.2580. Found
514.2566.
1,4-Bis[4-(tr iflu or oacetyl)piper azin o]ben zen e (13). This
compound was recrystallized from CHCl3/hexane. Yield: 39%.
Mp 115-116 °C. TLC (Al2O3, CHCl3) Rf ) 0.16. IR (KBr
[1-[4-[4-(Meth oxyca r bon yl)ben zoyl]p ip er a zin o]-4-p ip -
er idin oben zen e](cyclopen tadien yl)ir on Hexaflu or oph os-
p h a te (27). Complex 24 (1.05 g, 2.1 mmol) and terephthalic
acid monomethyl ester (815 mg, 4.2 mmol) gave 1.38 g of 27
(88%) yield. IR (film) 3114, 3001-2858, 1716, 1635, 1520, 840
pellet) 3048-2810, 1685, 1517 cm-1 1H NMR δ 6.67 (4H, s),
.
3.60 (4H, t, J ) 5.1 Hz), 3.52 (4H, t, J ) 5.1 Hz), 2.90 (8H, t,
J ) 5.1 Hz). 13C NMR δ 144.9, 118.1, 50.2, 49.7, 45.4, 42.9.
HRMS calcd for C18H20F6N4O2 438.1490. Found 438.1494.
cm-1 1H NMR δ 8.09 (2H, d, J ) 8.2 Hz), 7.64 (2H, d, J ) 8.2
.
Hz), 5.81 (4H, dd, J ) 12.6, 7.6 Hz), 6.06 (5H, s), 3.96 (2H, br
s), 3.92 (3H, s), 3.65 (2H, br s), 3.52 (2H, br s), 3.41 (4H, t, J
) 5.6 Hz, overlapping 2H, br s), 1.71 (6H, m). 13C NMR δ
169.3, 166.6, 141.2, 132.0, 130.3, 128.3, 124.0, 121.5, 74.7, 67.6,
66.0, 52.6, 48.4, 47.6, 41.8, 25.9, 24.1.
1,4-Bis[4-[4-(m et h oxyca r b on yl)b en zoyl]p ip er a zin o]-
ben zen e (14). Yield: 75%. Mp 257-259 °C (d). TLC (SiO2,
EtOAc, Rf ) 0.20; Al2O3, CHCl3, Rf ) 0.33). IR (KBr pellet)
2828, 1725, 1630 cm-1 1H NMR δ 8.10 (4H, dm, J ) 8.3 Hz),
.
7.49 (4H, dm, J ) 8.3 Hz), 7.26 (4H, s), 3.95 (6H, s) overlapping
3.94 (4H, br), 3.53 (4H, br), 3.17 (4H, br), 3.03 (4H, br). 13C
NMR δ 169.3, 166.3, 145.5, 139.9, 131.3, 129.9, 127.1, 118.4,
52.4, 50.9, 50.5, 47.6, 42.2. HRMS calcd for C32H34N4O6
572.2635. Found 572.2586.
Com p lex 28. Complex 24 (1.80 g, 3.5 mmol) and 2-naph-
thoic acid (1.19 g, 7.0 mmol) gave 2.10 g (91%) of the
corresponding amide. IR (film) 3108-3060, 2940, 2857, 1778,
1700, 1635, 1635, 1520, 841 cm-1 1H NMR δ 8.07-7.96 (4H,
.
m), 7.65-7.59 (3H, m), 5.87 (2H, d, J ) 7.6 Hz), 5.82 (2H, d,
J ) 7.6 Hz), 5.09 (5H, s), 3.86 (4H, br s), 3.55 (4H, br s), 3.42
(4H, t, J ) 4.9 Hz), 1.75 (6H, br m). 13C NMR δ 134.7, 134.1,
133.6, 129.3, 129.0, 128.7, 128.0, 127.8, 127.6, 125.5, 124.0,
121.7, 74.7, 67.6, 66.0, 48.4, 47.8, 26.0, 24.1.
1,4-Bis(4-m eth ylp ip er a zin o)ben zen e (15). The chloro-
form solution of the compound was concentrated in vacuo and
the residue rechromatographed (flash SiO2, 10% MeOH in
CHCl3, increasing to 50% MeOH in CHCl3 after collection of
the residual phenanthroline and then to 100% MeOH. The
solvent was removed and the residue dried to give the product
in 67% yield. For fluoresence studies, the compound was
vacuum sublimed at 120 °C. Mp 165-166 °C. TLC (Al2O3,
1% MeOH/CHCl3), Rf ) 0.30. IR (KBr pellet) 2961-2687, 1516
Com p lex 29. This reaction was conducted with only 1
equiv of the acid chloride. Complex 24. (512 mg, 1.0 mmol)
and anthraquinone-2-carboxylic acid (252 mg, 1.0 mmol) gave
599 mg (80%) of the amide. IR (film) 3110, 2940-2859, 1702,
1676, 1639, 1591, 1517, 840 cm-1 1H NMR δ 8.41 (1H, d, J )
.
8.0 Hz), 8.37 (1H, s), 8.35 (2H, dd, J ) 5.8, 3.3 Hz), 8.09 (1H,
cm-1 1H NMR (δ) 6.85 (4H, s), 3.07 (8H, t, J ) 5.0 Hz), 2.53
.

1304 J . Org. Chem., Vol. 61, No. 4, 1996
Pearson et al.
(8H, t, J ) 5.0 Hz), 2.30 (6H, s). 13C NMR (δ) 145.3, 117.6,
55.2, 50.2, 46.1. HRMS calcd for C16H26N4 274.2157. Found
274.2144.
1,4-Dip ip er id in oben zen e (16). The chloroform solution
of the compound was concentrated in vacuo and the residue
rechromatographed (flash SiO2, CHCl3 Rf ) 0.7) to give the
product in 51% yield. 1H NMR δ 6.85 (4H, br s), 2.98 (8H, br
s), 1.67 (8H, quint, J ) 5.5 Hz), 1.50 (4H, s). 13C NMR δ 146.2,
118.1, 51.9, 26.1, 24.2. HRMS calcd for C16H24N2 244.1939.
Found 244.1942.
(3H, m), 7.74-7.69 (4H, m), 6.73 (4H, s), 3.79 (2H, t, J ) 4.9
Hz), 3.40 (2H, t, J ) 4.9 Hz), 3.02 (2H, t, J ) 4.9 Hz), 2.87
(6H, m), 1.55-1.50 (4H, m), 1.42-1.38 (2H, m). 13C NMR δ
182.4, 168.2, 147.4, 144.1, 141.2, 134.4, 134.0, 133.6, 133.6,
132.6, 127.9, 127.4, 125.7, 118.6, 118.0, 51.6, 51.2, 50.9, 47.8,
42.4, 26.0, 24.2. HRMS calcd for C30H29N3O3 479.2209.
Found 479.2209.
4-[4-(4-P iper idin oph en yl)piper azin o]n itr oben zen e (36).
Mp 201-203 °C, TLC (Al2O3, CHCl3), Rf ) 0.25. IR (KBr
pellet) 2941-2780, 1588, 1513 cm-1 1H NMR δ 8.12 (2H, dd,
.
J ) 9.6, 2.3 Hz), 6.90 (4H, m), 6.82 (2H, dd, J ) 9.6, 2.3 Hz),
3.53 (4H, t, J ) 5.1 Hz), 3.20 (4H, br s), 3.04 (4H, br s), 1.71
(4H, t, J ) 4.8 Hz), 1.52 (2H, br s). 13C NMR δ 154.8, 144.6,
138.6, 125.9, 118.4, 118.0, 112.8, 52.0, 50.1, 47.2, 25.8, 24.0.
One quaternary carbon was not detected. HRMS calcd for
C21H26N4O2 366.2055. Found 366.2069.
1,4-Dip ip er id in o-2-m eth ylben zen e (38). Column chro-
matography (SiO2, 5% MeOH in CHCl3, Rf ) 0.3), gave the
product as an off-white oil (71 mg, 53%). 1H NMR δ 6.90 (1H,
d, J ) 8.7 Hz), 6.80 (1H, d, J )2.5 Hz), 6.72 (1H, dd, J ) 8.7,
2.5 Hz). 13C NMR δ 148.1, 145.9, 133.4, 120.1, 119.5, 114.8,
53.8, 51.6, 26.7, 26.1, 24.5, 24.3, 18.0. HRMS calcd for
C17H26N2 258.2095. Found 258.2095.
1-(4-P ip er a zin op h en yl)p ip er a zin e (17). Complex 2 (102
mg, 0.2 mmol) was dissolved in MeCN and added to 10 mL of
2.5 M, deoxygenated, aqueous ammonia. The mixture was
allowed to stir, under room lighting, for 24 h, by which time a
fine black precipitate had formed. The precipitate was re-
moved by suction filtration, an additional 162 µL of concen-
trated ammonium hydroxide was added, and the mixture
allowed to stir a further 24 h. The mixture was filtered again,
basified (1 M NaOH), and extracted exhaustively with CHCl3
to give 17 in 73% yield (36 mg). 1H NMR δ 6.82 (4H, s), 3.0
(16H, m). 13C NMR δ 145.9, 117.7, 51.6, 46.3. HRMS calcd
for C14H22N4 246.1844. Found 246.1844.
1-Mor p h olin o-4-[4-[4-(m eth oxyca r bon yl)ben zoyl]p ip -
er a zin o]ben zen e (31). 72% Yield. Mp 186-187 °C. TLC
(Al2O3, CHCl3 ,Rf ) 0.31). IR (KBr pellet, cm-1) 3050-2813,
1725, 1632, 1514. 1H NMR δ 8.08, (2H, d, J ) 8.2 Hz), 7.49
(2H, d, J ) 8.2 Hz), 6.87 (4H, s), 3.92 (5H, s), 3.83 (4H, t, J )
4.8 Hz), 3.51 (2H, br s), 3.14 (2H, br s), 3.06 (4H, t, J ) 4.8
1
Hz), 2.99 (2H, br s). Low temperature H NMR (CD2Cl2, -30
°C) δ 7.92 (2H, dd, J ) 8.2, 1.8 Hz), 7.34 (2H, dd, J ) 8.2, 1.8
Hz), 6.73 (4H, s), 3.75 (3H, s, overlapping 2H, t, J ) 4.9 Hz),
3.65 (4H, t, J ) 4.6 Hz), 3.36 (2H, t, J ) 4.9 Hz), 2.98 (2H, t,
J ) 4.9 Hz), 2.87 (4H, t, J ) 4.6 Hz), 2.82 (2H, t, J ) 4.9 Hz).
13C NMR δ 169.3, 166.3, 146.1, 144.8, 139.9, 131.2, 129.9,
127.0, 118.5, 117.2, 67.0, 52.4, 51.0, 50.7, 50.2, 47.6, 42.2.
HRMS calcd for C23H27N3O4 409.2001. Found 409.1993.
1-[4-[4-(Met h oxyca r b on yl)b en zoyl]p ip er a zin o]-4-(4-
m eth ylp ip er a zin o)ben zen e (32). The acid wash must be
omitted from this workup. Chromatography (Al2O3, CH2Cl2,
Rf ) 0.20), followed by recrystallization, gave the product in
82% yield. Mp 188-189 °C. TLC (Al2O3, CHCl3), Rf ) 0.38.
IR (KBr pellet) 2963-2740, 1729, 1631, 1609, 1519 cm-1 1H
.
NMR δ 8.08 (2H, d, J ) 8.1 Hz), 7.48 (2H, d, J ) 8.1 Hz), 6.87
(4H, s), 3.91 (5H, s), 3.50 (2H, br s), 3.11 (4H, t, J ) 4.9 Hz),
2.98 (2H, br s), 2.56 (4H, t, J ) 4.9 Hz), 2.33 (3H, s). Low
temperature 1H NMR (CD2Cl2, -30 °C) δ 7.92 (2H, dd, J )
8.2, 1.9 Hz), 7.34 (2H, dd, J ) 8.2, 1.9 Hz), 6.72 (4H, s), 3.76
(3H, s, overlapping 2H, t, J ) 5.0 Hz), 3.35 (2H, t, J ) 5.0
Hz), 2.98 (2H, t, J ) 5.0 Hz), 2.92 (4H, t, J ) 4.9 Hz), 2.82
(2H, t, J ) 5.0 Hz), 2.38 (4H, t, J ) 4.9 Hz), 2.14 (3H, s). 13C
NMR δ 169.3, 166.3, 146.1, 144.6, 140.0, 131.2, 129.9, 127.1,
118.5, 117.5, 55.2, 52.3, 51.1, 50.7, 49.9, 47.7, 46.1, 42.2.
HRMS calcd for C24H30N4O3 422.2318. Found 422.2318.
1-[4-[4-(Meth oxyca r bon ylben zoyl)p ip er a zin o]-4-p ip e-
r id in oben zen e (33). Chromatography (SiO2, 2.5% MeOH/
CHCl3, Rf ) 0.25) in lieu of recrystallization gave 28 in 78%
yield. Mp 135-6 °C. TLC (Al2O3, CHCl3), Rf ) 0.40. IR (KBr
Gen er a l P r oced u r e for P h otolytic Decom p lexa tion s.
An acetonitrile solution of the complexed phenylenediamine
was stirred in the presence of a 275 W sunlamp, under argon,
for 3 h. The acetonitrile was removed by rotary evaporation
and the residue was dissolved in 0.5 M HCl. This dark blue
soultion was immediately basified and the resulting brown
precipitate removed by suction filtration and washed until
addition of a small sample to dilute HCl resulted in a yellow
(not blue) solution (no residual diamine is present). The
filtrate was evaporated to dryness by rotary evaporation, and
the residue was stirred with refluxing CHCl3 for 6 h. The
solution was cooled, filtered, and concentrated and the residue
purified by chromatography (Al2O3, CHCl3, MeOH as required).
1,4-Bis[4-(2-h ydr oxyeth yl)piper azin o]ben zen e (9). Chro-
matography (Al2O3, 2.5% MeOH/CHCl3, Rf ) 0.40) followed
by recrystallization from acetone gave 8 in 66% yield. Mp
(evacuated) 191-193 °C dec. IR (KBr pellet) 3456-3227,
pellet) 2927-2825, 1725, 1628, 1515 cm-1
.
1H NMR δ 8.02
(2H, d, J ) 8.2 Hz), 7.41 (2H, d, J ) 8.2 Hz), 8.61 (4H, dd, J
) 19.8, 9.2 Hz), 3.85 (3H, s, overlapping 2H, br), 3.44 (2H, br
s), 3.07 (2H, br s), 2.97 (4H, t, J ) 5.5 Hz overlapping 2H, br
s), 1.61 (4H, apparent t, J ) 5.5 Hz), 1.46 (2H, apparent q, J
1
) 5.5 Hz). Low temperature H NMR (CD2Cl2, -30 °C) δ 7.92
(2H, dd, J ) 8.2, 1.7 Hz), 7.34 (2H, dd, J ) 8.2, 1.7 Hz), 6.72
(4H, s), 3.76 (3H, s, overlapping 2H, t, J ) 4.9 Hz), 3.36 (2H,
t, J ) 4.9 Hz), 2.97 (2H, t, J ) 4.9 Hz), 2.85 (4H, t, J ) 5.4 Hz
overlapping 2H, t, J ) 4.9 Hz), 1.51 (4 H, apparent quint, J )
5.4 Hz), 1.36 (2H, apparent quint, J ) 5.4 Hz). 13C NMR δ
169.3, 166.3, 147.1, 144.3, 139.9, 131.2, 129.8, 127.0, 118.4,
118.1, 52.3, 51.7, 51.1, 50.7, 47.7, 42.2, 25.9, 24.1. HRMS calcd
for C24H29N3O3 407.2209. Found 407.2214.
2949-2730, 1513 cm-1 1H NMR δ 6.86 (4H, s), 3.63 (4H, t, J
.
) 5.3 Hz), 3.09 (8H, t, J ) 4.9 Hz), 2.65 (8H, t, J ) 5.3 Hz),
2.58 (4H, t, J ) 5.3 Hz), 2.00 (2H, br s). 13C NMR δ 145.3,
117.7, 59.3, 57.7, 52.9, 50.3. HRMS calcd for C18H30N4O4
334.2369. Found 334.2369.
1,4-Bis[4-(ter t-bu toxycar bon yl)piper azin o]ben zen e (10).
As there was no complexation of iron by this compound, a
traditional workup was possible. Following irradiation, the
acetonitrile was removed by rotary evaporation, and the
residue was chromatographed directly (SiO2, 5% MeOH/CHCl3,
Rf ) 0.4), to give the product in 95% yield. Mp 193-194 °C.
Na p h th oa te Der iva tive 34. Yield: 72%. Mp (evacuated)
163-165 °C. TLC (Al2O3, CHCl3), Rf ) 0.16. IR (KBr pellet)
3053-2808, 1623, 1609, 1515 cm-1 1H NMR δ 7.92-7.83 (4H,
.
m), 7.55-7.48 (3H, m), 6.89 (2H, d, J ) 0.4 Hz), 6.88 (2H, d,
J ) 0.4 Hz), 3.96 (2H, br s), 3.59 (2H, br s), 3.10 (4H, br s)
overlapping 3.03 (4H, t, J ) 5.4 Hz), 1.69 (4H, quint, J ) 5.6
Hz), 1.52 (2H, m). 13C NMR δ 170.4, 147.2, 144.4, 133.7, 133.0,
132.7, 128.4, 127.8, 127.1, 127.0, 126.7, 124.3, 118.4, 118.1,
50.9, 47.9, 42.4, 26.0, 24.2. HRMS calcd for C26H29N3O
399.2310. Found 399.2310.
IR (KBr pellet) 2977-2760, 1701, 1608, 1517 cm-1 1H NMR
.
δ 6.85 (4H, s), 3.53, (8H, t, J ) 4.9 Hz), 2.98 (8H, t, J ) 4.9
Hz), 1.43 (18H, s). 13C NMR δ 118.2, 79.8, 50.5, 28.4. Two
quaternary carbons were not detected. HRMS calcd for
C24H38N4O4 446.2893. Found 446.2897.
[(η5-Cyclop en t a d ien yl)(η6-2,5-d ich lor ot olu en e)]ir on -
(II) Hexa flu or op h osp h a te (39). Ferrocene (3.0 g,), AlCl3 (6.0
g), and aluminum powder (400 mg) were combined under
argon. To this was added freshly distilled 2,5-dichlorotoluene
(20 mL), n-heptane (20 mL), and water (100 µL). The reaction
mixture was purged of oxygen by a stream of argon and then
stirred at 85 °C for 12 h. The mixture was cooled to room
temperature, ice-water (50 mL) was added cautiously, and
An th r a qu in on e Am id e Der via tive 35. Yield: 80%. Mp
222-224 °C dec. TLC (Al2O3, CHCl3), Rf ) 0.13. IR (KBr
pellet) 3073-2808, 1675, 1630, 1595, 1517 cm-1 1H NMR δ
.
8.39-8.27 (4H, m), 7.87-7.80 (3H, m), 6.88 (4H, s), 3.96 (2H,
br s), 3.55 (2H, br s), 3.15 (2H, br s), 3.03 (2H, br s) overlapping
4H, t, J ) 5.2 Hz), 1.69 (4H, m), 1.53 (2H, apparent q, J ) 5.2
1
Hz). Low temperature H NMR (CD2Cl2, -40 °C) δ 8.23-8.16

Preparation of p-Phenylenediamine Derivatives
J . Org. Chem., Vol. 61, No. 4, 1996 1305
the mixture was stirred for 10 min. The aqueous layer was
of monodisplacement (275 mg, 75%). 1H NMR δ 6.02 (1H, d,
J ) 2.3 Hz), 5.87 (1H, dd, J ) 7.2, 2.3 Hz), 5.79 (1H, d, J )
7.2 Hz), 4.97 (5H, s), 3.50 (4H, t, J ) 4.9 Hz), 3.10 (4H, m),
2.64 (3H, s), 1.93-1.67 (12H, m). 13C NMR δ 125.0, 121.6,
116.5, 76.1, 70.4, 70.4, 70.0, 64.3, 53.1, 48.2, 26.8, 26.0, 24.7,
24.1, 19.4.
separated, filtered, and washed with ether (3 × 30 mL).
A
saturated aqueous solution of NH4PF6 was added to the
aqueous layer until precipitation ceased. The resulting com-
bination of yellow solid and mother liquor was extracted into
CH2Cl2 (3 × 30 mL), dried over MgSO4, and concentrated to
<20 mL. This was added dropwise to ether (200 mL), and the
resulting yellow precipitate was isolated by suction filtration
and dried under high vacuum to give 1.8 g (26%) shown by
NMR to consist of a ca. 15:1 mixture of 39 and [η6-(cyclopen-
tadienyl)-η5-(3-chlorotoluene)]iron(II) hexafluorophosphate. 1H
NMR δ 7.16 (1H, d, J ) 1.7 Hz), 7.05 (1H, d, J ) 6.6 Hz), 6.98
(1H, dd, J ) 6.6, 1.7 Hz), 5.44 (5H, s), 2.82 (3H, s). 13C NMR
δ 107.6, 106.8, 103.6, 90.3, 88.9, 88.1, 82.4, 19.5.
Ack n ow led gm en t. This work was supported by the
NSF (DMR-22227). We would like to thank Professor
Fred L. Urbach and Mr. Shawn M. Swavey for as-
sistance with the CV studies and Mr. J oel Zlotnick for
the preparation of compound 18.
Su p p or tin g In for m a tion Ava ila ble: Proton and 13C
NMR spectra are available for all new compounds (77 pages).
This material is contained in libraries on microfiche, im-
mediately follows this article in the microfilm version of the
journal, and may be ordered from the ACS; see any current
masthead page for ordering information.
1,4-Dip ip er a zin o-2-m eth ylben zen e(cyclop en ta d ien yl)-
ir on Hexa flu or op h osp h a te (37). [(η5-Cyclopentadienyl)-(η6-
2,5-dichlorotoluene)]iron(II) hexafluorophosphate (300 mg, 0.7
mmol), piperidine (595 mg, 692 µL, 7.0 mmol), and K2CO3 (483
mg, 3.5 mmol) were stirred in refluxing THF (10 mL) for 72 h
in an aluminum foil-wrapped flask. The workup was as for
1
2-5, to give a 9:1 mixture, by H NMR, of 37 and the product
J O951677L