Synthesis and structural analysis of Bis(2-hydroxyphenyl) phenylamine, PhN(o-C6H4OH)2: Comparison with Tris(2-hydroxyphenyl)amine N(o-C6H4OH)3

Article abstract of DOI:10.1007/s10870-005-5360-0

The molecular structures of N(o-C₆H₄OH)₃, PhN(o-C₆H₄OH)₂, and p-TolN(o-C ₆H₄OMc)₂ have been determined by X-ray diffraction, thereby indicating several stru

Full text of DOI:10.1007/s10870-005-5360-0

ꢀC
Journal of Chemical Crystallography, Vol. 35, No. 12, December 2005 ( 2005)
DOI: 10.1007/s10870-005-5360-0
Synthesis and structural analysis of Bis(2-hydroxyphenyl)
phenylamine, PhN(o-C6H4OH)2: Comparison with
Tris(2-hydroxyphenyl)amine N(o-C6H4OH)3
∗
Bryte V. Kelly,(1) Joseph M. Tanski,(1) Mary Beth Anzovino,(1) and Gerard Parkin(1)
Received March 2, 2005; accepted April 18, 2005
The molecular structures of N(o-C6H4OH)3, PhN(o-C6H4OH)2, and p-TolN(o-C6H4OMe)2
have been determined by X-ray diffraction, thereby indicating several structural differences.
For example, whereas the nitrogen in N(o-C6H4OH)3 is pyramidal with ꢀC
=
--- N--- C
348.3◦, the nitrogen atoms in PhN(o-C6H4OH)2 and p-TolN(o-C6H4OMe)2 are trigonal
planar with ꢀC
= 359.9◦ and ꢀC
= 360.0◦, respectively. The phenyl and
--- N--- C
--- N--- C
p-tolyl groups of PhN(o-C6H4OH)2 and p-TolN(o-C6H4OMe)2 lie close to the trigonal
plane, while the o-C6H4OH and o-C6H4OMe groups are almost orthogonal to this plane.
The coplanar and orthogonal orientations of the aryl groups of PhN(o-C6H4OH)2 and
p-TolN(o-C6H4OMe)2 are in marked contrast to those of the phenyl groups within Ph3N,
which exhibit dihedral angles in the range 38–52◦ and approximate D3 symmetry. The
observed structures of PhN(o-C6H4OH)2 and p-TolN(o-C6H4OMe)2 may be rationalized
in terms of maximizing delocalization of the nitrogen lone pair into the phenyl and
p-tolyl groups, while minimizing unfavorable overlap with the o-C6H4OH and o-C6H4OMe
groups due to the presence of π-donating ortho-substituents; the orthogonal orientation of
the o-C6H4OH and o-C6H4OMe groups is also one that minimizes unfavorable steric
interactions between the ortho-substituents.
KEY WORDS: Aryloxide; amine; phenol; tris(2-hydoxyphenyl)amine.
Introduction
example of a molecule that affords tris(aryloxide)
derivatives. An interesting aspect of tripodal lig-
Alkoxide (OR) and aryloxide (OAr) lig-
ands of the type [N(–L)3], where “–” represents
a spacer and L is a donor atom, is that the ni-
trogen may either coordinate to the metal or re-
main uncoordinated. A complex is termed an
“atrane” if the nitrogen coordinates and a “pro-
atrane” if there is no interaction.3 Both coordina-
tion modes have been reported for derivatives of
N(o-C6H4OH)3;2,4–9 however, despite exten-
sive structural studies on derivatives of N(o-
C6H4OH)3, the molecular structure of N(o-
C6H4OH)3 itself has not been reported. In this
paper, we report the molecular structure of the
ands feature prominently in the chemistry of the
transition and main group elements.1 While the
majority of studies have focused on monoden-
tate alkoxides and arlyoxides, multidentate vari-
ants have also found extensive use. For example,
tris(2-hydroxyphenyl)amine (also called 2,2ꢁ,2ꢁꢁ-
nitrilotriphenol), N(o-C6H4OH)3,2 is a simple
(1) Department of Chemistry, Columbia University, New York 10027.
∗To whom correspondence should be addressed; e-mail: parkin@
chem.columbia.edu.
969
ꢀ
C
1074-1542/05/1200-0969/0 2005 Springer Science+Business Media, Inc.

970
Kelly, Tanski, Anzovino, and Parkin
Fig. 1. Molecular structure o◦f N(o-C6H4OH)3 (20% ellipsoids). Selected
˚
---
---
bond lengths (A) and angles ( ): N C(11), 1.441(2); N C(21), 1.432(2);
---
--- ---
N
--- ---
N C(31),
N
C(31), 1.430(2); C(11)
C(21), 117.0(1); C(11)
--- ---
N C(31), 116.82(9).
114.52(9); C(21)
tris(phenol) compound N(o-C6H4OH)3 as de-
termined by X-ray diffraction and compare it
with that of the analogous bis(phenol) derivative
PhN(o-C6H4OH)2.
the magnitude of the displacement of the planes
of the phenoxy groups out of the plane defined
by the three ipso carbon atoms, however, varies
Results and discussion
Structural characterization of N(o-C6H4OH)3
2a
The molecular structure of N(o-C6H4OH)3
has been determined by single crystal X-ray
diffraction studies on crystals obtained from ace-
tone, as illustrated in Figs. 1 and 2, from which
there are several noteworthy features. Firstly, it
is pertinent to note that N(o-C6H4OH)3 partici-
pates in an extensive hydrogen bonding network,
as illustrated in Fig. 2. Specifically, two of the
OH groups serve as hydrogen bond donors to
the oxygen of an acetone molecule [dO···O = 2.67
˚
and 2.93 A], while the other OH serves as a hy-
drogen bond donor toward the hydroxyl group
of another N(o-C6H4OH)3 molecule [dO···O
=
˚
2.76 A], thereby forming an infinite strand of
[N(o-C6H4OH)3(OCMe2)] units. With respect to
the structure of the individual N(o-C6H4OH)3
moiety, the three o-C6H4OH groups are arranged
in a trigonal pyramid about the nitrogen with
an approximate C3 propeller-like configuration;
Fig. 2. A portion of the hydrogen bonding network of
[N(o-C6H4OH)3·(OCMe2)]. Hydrogen bonding distances:
˚
˚
d(O1···O1S) = 2.93 A, d(O3···O1S) = 2.67 A, and
ꢁꢁ
˚
d(O3···O2 ) = 2.76 A.

Synthesis and structural analysis
971
Table 1. Structural Comparison of Some Ar3N Derivatives
ꢀC
(◦)a
Dihedral range (◦)b
CCDC#
Reference
--- N--- C
N(C6Cl5)3
N[C6H3(o-OMe)2]3
N(C6H5)3
N(C6H4-p-CHO)(p-Tol)2
N(C6H4-p-Br)(C6H3-o-Br-p-Me)2
N(o-C6H4OMe)3
N(o-C6H4OH)3
PhN(o-C6H4OH)2
p-TolN(o-C6H4OMe)2
360.0
360.0
358.9
359.9
355.2
352.8
348.3
359.9
360.0
50–55
61–62
38–52
28–56
27–57
40–47
36–66
2–89
CLPHAM
YEVVIE
ZZZJLQ01
QUTPIE
QUTPOK
JAPCIM01
Hayes et al.11
Stoudt et al.12
Sobolev et al.14
Xue et al.13
Xue et al.13
Mu¨ller and Bu¨rgi10
This work
This work
4–83
This work
aꢀC
= 328.5◦ and 360◦ for idealized “tetrahedral” and trigonal planar geometries, respectively.
--- N--- C
bAngle between the plane of the aromatic group and the plane of the three ipso carbon atoms.
over the substantial range of 36–66◦. The extent
of pyramidalization at nitrogen may be readily
Synthesis and structural characterization of
ArN(o-C6H4OR)2 (Ar = Ph, p-Tol; R = H, Me)
--- ---
gauged by consideration of the C N C bond an-
gles [114.5(1)◦, 116.8(1)◦, and 117.0(1)◦] which
By analogy to the extensive chemistry
that has been developed with the tris(phenol)
compound N(o-C6H4OH)3, the closely related
bis(phenol) PhN(o-C6H4OH)2 also has consid-
erable potential for applications in coordination
chemistry. In this regard, much attention has
been given to bis(aryloxide) ligands in which the
two aryloxide moieties are directly connected,17
or joined by a linker, such as CH2 or S.18–20
Since the chemistry of the system may be mod-
ified profoundly by the nature of the linker,21
we are interested in exploring the application
of bis(aryloxide) ligands with different bridges,
such as nitrogen. As such, the synthesis of the
bis(phenol) PhN(o-C6H4OH)2 was viewed to be
a worthwhile objective.22,23
PhN(o-C6H4OH)2 may be readily obtained
by a sequence which is analogous to that used
for the synthesis of N(o-C6H4OH)3.2 Specifi-
cally, PhN(o-C6H4OH)2 is synthesized by a two-
step sequence involving (i) a copper-catalyzed
Ullmann-type condensation of PhNH2 with 1,2-
C6H4(OMe)I to give PhN(o-C6H4OMe)2, fol-
lowed by (ii) ether cleavage using AlCl3
(Scheme 1).
total 348.3◦, a value that is approximately mid-
--- ---
way between those for “tetrahedral” (C N C =
109.5◦ and ꢀC
= 328.5◦) and trigonal pla-
---N---C
◦
nar (C N C = 120.0 and ꢀC
= 360.0◦)
--- ---
---N---C
geometries.
The degree of pyramidalization of N(o-
C6H4OH)3 is compared with those of other NAr3
molecules in Table 1, including the methoxy
derivative, N(o-C6H4OMe)3.10 As expected, the
extent of pyramidalization for N(o-C6H4OH)3
[ꢀC
= 348.3◦] is comparable to that
---N---C
of the methoxy derivative N(o-C6H4OMe)3
[ꢀC
= 352.8◦], but distinctly greater
---N---C
than that of the protonated derivative [HN(o-
C6H4OH)3]+ [ꢀC
= 340.5◦]. Of the
---N---C
compounds listed in Table 1, N(o-C6H4OH)3
exhibits the smallest ꢀC
value (348.3◦),
---N---C
thereby indicating that it has the greatest
degree of pyramidalization. Indeed, planar
geometries are common for NAr3 derivatives,
as illustrated by N(C6H5)3 and N(C6Cl5)3,
with ꢀC
values of 358.9◦ and 360.0◦,
---N---C
respectively; it should, however, be noted that
the planarity of the triarylamines N(C6H5)3 and
N(C6Cl5)3 is in marked contrast to the distinctly
nonplanar structures of trialkylamines, e.g. Me3N
The molecular structure of PhN(o-
C6H4OH)2 has been determined by single
crystal X-ray diffraction (Figs. 3 and 4) which
indicates the presence of both intramolecular and
[ꢀC
= 332.1◦] and Pri N [ꢀC
=
---N---C
---N---C
3
348.6◦].15,16

972
Kelly, Tanski, Anzovino, and Parkin
becomes effectively trigonal planar in PhN(o-
--- ---
C6H4OH)2. Thus, the sum of the C N C bond
angles for PhN(o-C6H4OH)2 is close to 360◦
for both of the crystallographically independent
molecules: i.e. ꢀC
= 359.9◦ for N(1)
---N---C
and ꢀC
= 359.8◦ for N(2). Secondly, in
---N---C
contrast to N(o-C6H4OH)3 where the aromatic
rings are twisted in the range 36–66◦ relative
to the plane defined by the three ipso carbon
atoms, the aromatic rings in PhN(o-C6H4OH)2
span the much greater range of 7–89◦ and 2–85◦
for the two independent molecules. Furthermore,
for each of the independent molecules, it is
the phenyl group that lies close to the trigonal
plane, with the two phenoxy groups being almost
orthogonal.
While it is sterically unfavorable for all three
aromatic groups to lie in the trigonal plane, it
is worthwhile to consider why it is the phenoxy
groups and not the phenyl group that rotate out
of the plane. Thus, factors that contribute to caus-
ing the phenoxy groups to rotate out of the plane
include:
1. The hydroxy groups are larger than a hy-
drogen atom and steric congestion is re-
lieved when the ring with the larger sub-
stituent rings rotate out of the trigonal
plane.
Scheme 1.
2. Delocalization of the nitrogen lone pair
into the phenyl ring is more favored than
delocalization into the o-C6H4OH ring be-
cause the π-donating OH groups destabi-
lize a resonance structure that localizes a
negative charge on the ortho carbon atom
(Fig. 5).
3. A hydrogen bonding interaction between
the two phenolic groups (Fig. 3) becomes
feasible when the phenoxy groups ro-
tate out of the plane, and thereby sta-
bilizes the structure. However, evidence
that the hydrogen bonding interaction is
not a dominant factor is provided by the
fact that a closely related ether derivative
p-TolN(o-C6H4OMe)2 (Fig. 6) exhibits
a very similar orthogonal orientation
intermolecular hydrogen bonding interactions,
resulting in a dimeric structure that exhibits a
---
“square” array of four O H· · ·O hydrogen bonds
(Fig. 4). For each of the independent dimeric
units, the intermolecular O· · ·O separation
˚
˚
(2.72 A and 2.76 A) is slightly shorter than the
corresponding intramolecular O· · ·O separation
˚
˚
(2.84 A and 2.81 A). More interesting than the
nature of the hydrogen bonding interactions,
however, is the manner in which the replacement
of a single OH group in N(o-C6H4OH)3 by
a hydrogen atom influences the structure of
the molecule. Significantly, there are several
noteworthy modifications. Firstly, as illustrated
by comparison of Figs. 1 and 3, the nitrogen atom

Synthesis and structural analysis
973
Fig. 3. Structures of the two independent molecules of PhN(o-C6H4OH)2 (20% ellipsoids). Selected bond
◦
˚
---
---
---
---
lengths (A) and angles ( ): N(1) C(11), 1.432(2); N(1) C(21), 1.433(2); N(1) C(31), 1.409(2); N(2) C(41),
--- --- --- --- --- ---
1.434(2); N(2) C(51), 1.434(2); N(2) C(61), 1.404(2); C(11) N(1) C(21), 118.4(1); C(11) N(1) C(31),
--- --- --- --- --- ---
119.8(1); C(21) N(1) C(31), 121.7(1); C(41) N(2) C(51), 118.4(1); C(41) N(2) C(61), 120.3(1);
˚
---
---
---
---
C(51) N(2) C(61), 121.1(1). Dihedral angles (A) between C11 C21 C31 plane and aromatic rings:
˚
---
---
---
---
---
C11 C16 89.2, C21 C26 68.0, C31 C36 7.0. Dihedral angles (A) between C41 C51 C61 plane and
---
---
---
aromatic rings: C41 C46 80.4, C51 C56 85.3, C61 C66 1.8.
of the (o-C6H4OMe) groups, with the ex-
Evidence that delocalization of the nitrogen
lone pair into the aryl ring provides a significant
contribution to the bonding is provided by the
ception that the methoxy groups adopt
a “trans” disposition such that p-
TolN(o-C6H4OMe)2 exhibits C2 symme-
try whereas PhN(o-C6H4OH)2 exhibits
approximate Cs symmetry.
---
---
fact that the Ph N and p-Tol N bond lengths in
PhN(o-C6H4OH)2 and p-TolN(o-C6H4OMe)2 are
---
consistently shorter than the N C6H4OR bond
Fig. 4. Hydrogen bonding network for the two independent molecules of PhN(o-C6H4OH)2.

974
Kelly, Tanski, Anzovino, and Parkin
Fig. 5. Resonance structures which illustrate that delocaliza-
tion of the nitrogen lone pair into the phenyl ring is more
favored than that into the C6H4OR ring because the negative
charge on the ortho carbon is destabilized by a π-interaction
with the oxygen lone pair.
Fig. 6. Molecular structure of p-TolN(o-C6H4OMe)2 (20%
◦
˚
ellipsoids). Selected bond lengths (A) and angles ( ):
--- --- --- ---
C(11), 1.433(2); N C(21), 1.391(3); C(11) N C(21),
N
ꢁ
--- ---
---
121.1(1); C(11)
˚
N
C(11 ), 117.8(2). Dihedral angles
ꢁ ---
(A) between C11 C11 C21 plane and aromatic rings:
lengths, as summarized in Table 2. Furthermore,
ꢁ
---
---
C11 C16, 82.6; C21 C22 , 3.8.
---
---
the Ph N and p-Tol N bond lengths are also
---
shorter than the N C6H4OH bond length in N(o-
C6H4OH)3.
HOMO would be destabilized if the ortho sub-
stituent were to be a π-donor (cf. Fig. 5) and
thus it is electronically more favored for the C6H5
group, rather than the o-C6H4OH group, to reside
in the trigonal plane.
Additional support that there is a definite
preference for the phenyl rather than aryloxy
group to reside in the trigonal plane is provided
by geometry optimization calculations on PhN(o-
C6H4OH)2. Thus, as illustrated in Fig. 7 and
Table 3, the geometry optimized structure of
PhN(o-C6H4OH)2 corresponds closely to the ex-
perimental structure in terms of (i) the planarity of
the nitrogen center (ꢀC
orientation of the phenyl and phenoxy groups, (iii)
the hydrogen bonding interaction between the two
---
hydroxy groups, and (iv) the shorter Ph N bond
For further comparison, geometry optimiza-
tion calculations on N(o-C6H4OH)3 (Fig. 9) are
also in accord with the experimental observations
with the geometry at nitrogen being nonplanar
= 358.9◦), (ii) the
with ꢀC
= 350.8◦ (compared to the ex-
---N---C
---N---C
perimental value of 348.3◦) and a propeller-like
configuration of the o-C6H4OH groups .24
To determine the magnitude of the prefer-
ence for the phenyl group to reside in the trigonal
plane, a geometry optimization was performed in
which the phenyl group is constrained to be per-
pendicular to the plane of the three ipso carbon
atoms (Fig. 7). The energy of this conformation
is 8.0 kcal mol−1 higher than that of the fully op-
˚
---
length (1.415 A) than N C6H4OH bond lengths
˚
(1.433 A).
The calculations also provide evidence for
delocalization of the nitrogen lone pair into the
aryl ring, as illustrated by the bonding and anti-
bonding molecular orbitals involving the nitrogen
p-orbital shown in Fig. 8. Of these orbitals, the
antibonding combination is the HOMO of the
molecule and has a significant contribution on
the ortho carbon atoms of the phenyl ring. The
---
timized structure; furthermore, the N Ph bond
˚
length of the perpendicular structure (1.443 A) is
greater than that of the fully optimized structure
˚
(1.415 A).

Synthesis and structural analysis
975
---
Table 2. Comparison of N C Bond Lengths
N(o-C6H4OH)3
PhN(o-C6H4OH)2
p-TolN-(o-C6H4OMe)2
˚
---
d(N Ar)/A
—
1.409(2), 1.404(2)
1.391(3)
1.433(2)
˚
---
d(N C6H4OR)/A
1.441(2) 1.432(2), 1.430(2) 1.432(2), 1.433(2), 1.434(2), 1.434(2),
It is interesting to note that the geometries of
PhN(o-C6H4OH)2 and p-TolN(o-C6H4OMe)2 dif-
fer considerably from that of Ph3N which also has
an effectively trigonal planar geometry at nitro-
gen. Specifically, whereas PhN(o-C6H4OH)2 and
p-TolN(o-C6H4OMe)2 have idealized geometries
with Cs and C2 symmetry in which the Ph and
p-Tol groups lie in the trigonal plane and the o-
C6H4OH and o-C6H4OMe groups are almost or-
thogonal, the three phenyl groups of Ph3N exhibit
comparable dihedral angles (38–52◦) such that the
molecule has approximately D3 symmetry.14 The
favored structure for Ph3N is, therefore, one in
which all three phenyl groups interact partially
with the nitrogen p-orbital, even though the over-
lap is less efficient since the phenyl groups do
not lie in the trigonal plane. Thus, the structure
of Ph3N represents a compromise between elec-
tronic and steric factors, i.e. electronic factors fa-
vor a planar D3h structure that maximizes delo-
calization of the nitrogen lone pair, while steric
factors favor rotation of the phenyl groups out of
the plane.
but also demonstrate that the transition state for
---
rotation about the Ph N bond is one in which the
disposition of the three phenyl groups resemble
those of the aryl groups in PhN(o-C6H4OH)2 and
p-TolN(o-C6H4OMe)2, i.e. one in the plane and
two orthogonal to the plane (Fig. 10).25 Thus, the
introduction of ortho-OH substituents into two
of the phenyl rings of Ph3N causes the stable
geometry of the system to resemble that of the
---
transition state for rotation about the Ph N bond
of Ph3N. Furthermore, the calculations demon-
strate that the planar transition state with C2v
symmetry (4.73 kcal mol−1) and a single phenyl
group in the trigonal plane is considerably more
stable than transition states with either pyrami-
dal C3v (12.91 kcal mol−1) or trigonal planar D3h
(13.14 kcal mol−1) geometries, as illustrated in
Fig. 10.25 As such, these calculations reinforce
the above proposal that, in the absence of steric in-
teractions between ortho substituents, the phenyl
group electronically prefers to be located in the
trigonal plane.
It is also pertinent to note that the geome-
try optimized structure of PhN(p-C6H4OH)2, in
which the OH groups are in para positions, is
Previous calculations on Ph3N not only re-
produce the experimentally observed geometry,
Fig. 7. Comparison of the freely geometry optimized structure of
PhN(o-C6H4OH)2 (left) with that in which the phenyl ring is con-
strained to being orthogonal to the trigonal plane (right).

976
Kelly, Tanski, Anzovino, and Parkin
Table 3. Comparsion of Experimental and Geometry Optimized Structures of PhN(o-C6H4OH)2 (Average
Values Where Appropriate)
Geometry optimized with phenyl group
orthogonal to trigonal plane
Experimental Geometry optimized
˚
---
d(N Ph)/A
1.407
1.433
2.83
1.415
1.433
2.94
1.443
1.431
2.90
˚
---
d(N C6H4OH)/A
˚
d(O···O)/A
◦
ꢀC
/
359.9
359.9
360.0
--- N--- C
= 359.9◦]. While Ph3N also has an
similar to the structure of Ph3N, with none of the
aryl groups lying in the trigonal plane (Fig. 11).
This observation provides further evidence that
steric interactions and hydrogen bonding play a
role in causing the substituted rings of PhN(o-
C6H4OH)2 and p-TolN(o-C6H4OMe)2 to rotate
out of the trigonal plane, thereby allowing the Ph
and p-Tol rings to become coplanar.
[ꢀC
---N---C
effectively trigonal planar geometry, the struc-
ture differs from that of PhN(o-C6H4OH)2 with
respect to the disposition of the aryl groups.
Thus, none of the phenyl groups of Ph3N lie
in the trigonal plane, whereas the phenyl group
of PhN(o-C6H4OH)2 lies close to this plane
with the o-C6H4OH groups being almost or-
thogonal; the ether p-TolN(o-C6H4OMe)2 has a
very similar structure. The observed structures
of PhN(o-C6H4OH)2 and p-TolN(o-C6H4OMe)2
may be rationalized in terms of maximizing de-
localization of the nitrogen lone pair into the
phenyl and p-tolyl groups, while minimizing un-
favorable overlap with the o-C6H4OH and o-
C6H4OMe groups due to the presence of elec-
tron releasing ortho-substituents. In addition,
the orthogonal orientation of the o-C6H4OH
and o-C6H4OMe groups is also one that mini-
mizes unfavorable steric interactions between the
Summary
In conclusion, comparison of the structures
of N(o-C6H4OH)3 and PhN(o-C6H4OH)2 demon-
strate that replacing one of the ortho-OH groups
in N(o-C6H4OH)3 with hydrogen causes a signifi-
cant change in the geometry of the nitrogen atom.
Specifically, N(o-C6H4OH)3 exhibits a pyramidal
geometry [ꢀC
C6H4OH)2 exhibits a trigonal planar geometry
= 348.3◦] whereas PhN(o-
---N---C
Fig. 8. π Bonding and antibonding molecular orbital involving the nitrogen p-orbital
in PhN(o-C6H4OH)2.

Synthesis and structural analysis
977
Mass spectra were measured using a JEOL JMS-
HX110HF Tandem Mass Spectrometer (FAB+;
ionizing agent: m-nitrobenzylalcohol; direct
inlet). IR spectra were recorded as KBr discs on
a Nicolet Avatar 370DTGS spectrophotometer.
Synthesis of PhN(o-C6H4OMe)2
Fig. 9. Two views of the geometry optimized structure of
N(o-C6H4OH)3.
A mixture of 1,2-C6H4(OMe)I (102.5 g,
440 mmol), PhNH2 (20 mL, 220 mmol), K2CO3
powder (122 g, 880 mmol), and Raney copper
(water decanted) (25 g, 393 mmol) in nitroben-
zene (100 mL) was refluxed under a nitrogen at-
mosphere. The liberated water was removed via
a Dean–Stark trap and organic layer from the
trap was returned to the reaction mixture. After
3 h, the mixture was cooled, the solution phase
was decanted, and the residue was extracted with
hot chloroform (3 × 100 mL). The extracts were
combined with the decanted reaction mixture and
filtered through a bed of silica (ca. 8 cm diam-
eter × 4 cm depth) and the volatile components
were removed via a rotary-evaporator. The con-
centrated extract was distilled under vacuum. The
first fraction consisted of the nitrobenzene sol-
vent (ca. 74◦C, 0.06 mmHg) and was discarded.
PhN(o-C6H4OMe)2 distilled as a light orange vis-
cous liquid (160◦C, 0.06 mmHg), which solidified
upon standing for 1 day at room temperature.
The solid obtained was dissolved in a minimal
quantity of chloroform (ca. 50 mL) and then hex-
ane (ca. 150 mL) was added. Precipitation was
ortho-substituents and, in the case of the former
compound, also maximizes a hydrogen bonding
interaction.
Experimental section
General considerations
1,2-C6H4(OMe)I,
PhNH2,
p-TolNH2,
K2CO3, and Raney copper were obtained from
Aldrich, while nitrobenzene was obtained from
Fischer Scientific. 1H and 13C NMR spectra
were measured on Bruker 300wb DRX, Bruker
Avance 400 DRX, and Bruker Avance 500 DMX
spectrometers. Chemical shifts are reported in
ppm relative to SiMe4 (δ = 0) and were refer-
enced internally with respect to the protio solvent
impurity (δ = 7.16 for C6D5H) and the 13C
resonances (δ = 128.0 for C6D6) respectively.
All coupling constants are reported in hertz.
Fig. 10. Energies of various rotamers of Ph3N (data taken from reference 25).

978
Kelly, Tanski, Anzovino, and Parkin
Fig. 11. Comparison of the rotation of the aryl rings from the
trigonal planes in PhN(o-C6H4OH)2 and PhN(p-C6H4OH)2.
induced by reducing the volume of the solution
to ca. 50 mL in vacuo. The mixture was filtered
and the precipitate obtained was washed with
hexane (2 × 20 mL) and dried in vacuo to give
PhN(o-C6H4OMe)2 as a white powder (16.0 g,
24%). Mass spectrum, m/z = 305.1 (M+). IR data
(cm−1): 3061 (w), 3033 (w), 3017 (w), 3002 (w),
2958 (w), 2935 (w), 2834 (w), 1588 (m), 1496
(vs), 1459 (m), 1432 (w), 1334 (s), 1294 (m),
1270 (s), 1238 (s), 1177 (w), 1162 (w), 1114 (m),
1080 (vw), 1045 (m), 1024 (s), 917 (w), 868 (vw),
846 (vw), 796 (w), 778 (vw), 755 (s), 741 (s),
693 (m), 624 (m), 618 (w), 566 (w), 544 (vw),
499 (w), 473 (w). 1H NMR data (C6D6): 3.20 [s,
of (C6H4OMe)2], 7.10–7.13 [m, 4H of
(CH3C6H4)N(C6H4OMe)2].
Synthesis of PhN(o-C6H4OH)2
A solution of PhN(o-C6H4OMe)2 (16.0 g,
52.0 mmol) in dry toluene (100 mL) was treated
with AlCl3 (13.9 g, 105 mmol) under a nitrogen
atmosphere and refluxed for 90 min giving a
purple solution and a white precipitate. After this
period, the mixture was cooled to room temper-
ature and the precipitate was isolated. Aqueous
HCl (42 mL of 10% w/w) was added to the white
precipitate and the mixture was stirred for 30 min.
The mixture was filtered and the precipitate
obtained was washed with hexanes (3 × 20 mL)
and dried in vacuo to give PhN(o-C6H4OH)2 as a
white solid (11.6 g, 81%). Mass spectrum: m/z =
277.2 (M+). IR data (cm−1): 3390 (m), 3288 (w),
3063 (m), 3037 (w), 1591 (s), 1494 (vs), 1451
(m), 1343 (m), 1315 (s), 1281 (s), 1230 (m),
1205 (m), 1176 (m), 1161 (m), 1146 (m), 1097
(m), 1031 (m), 994 (vw), 945 (vw), 856 (w), 823
(m), 761 (s), 746 (s), 693 (m), 627 (w), 618 (m),
6H of (C6H5)N(C6H4OCH3)2], 6.62 [d, 3J
=
H---H
8, 2H of (C6H5)N(C6H4OMe)2], 6.76–6.82 [m,
1H of (C6H5) and 2H of (C6H4OMe)2], 6.88 [d,
3J
= 8, 2H of (C6H5)N(C6H4OMe)2], 6.97
H---H
[t, 3J
= 8, 2H of (C6H5)N(C6H4OMe)2], 7.08
H---H
[t, 3J
[d, J
= 8, 2H of (C6H5)N(C6H4OMe)2], 7.35
= 8, 2H of (C6H5)N(C6H4OMe)2].
H---H
H---H
3
13C NMR data (C6D6): 55.7 [q, J
= 143,
1
H---H
1
CH3], 113.3 [d, J
= 156, CH], 117.8 [d,
C---H
1J
= 160, CH], 119.5 [d, 1J
= 165, CH],
C---H
C---H
121.6 [d, 1J
= 161, CH], 126.3 [d, 1J
=
C---H
C---H
1
1
160, CH], 128.8 [d, J
[d, J
= 153, CH], 129.6
C---H
501 (m), 475 (m). H NMR data (C6D6): 5.92
1
= 158, CH], 136.3 [s, quat.], 149.1
C---H
[s, (C6H5)N(C6H4OH)2], 6.63–6.75 [m, 3H of
(C6H5) and 4H of 2(C6H4OH)], 6.86–6.91 [m,
2H of (C6H5)N(C6H4OH)2], 6.97–7.02 [m, 2H
of (C6H5)N(C6H4OH)2], 7.12–7.14 [m, 2H of
(C6H5)N(C6H4OH)2]. 13C NMR (C6D6): 115.6
[s, quat.], 156.0 [s, quat.]. p-TolN(C6H4OMe)2
was obtained in low yield by an analogous pro-
cedure. 1H NMR data (CDCl3): 2.25 [s, 3H
of (CH3C6H4)N(C6H4OCH3)2], 3.65 [s, 6H of
3
[d, 1J
= 156, CH], 117.0 [d, 1J
= 160,
(CH3C6H4)N(C6H4OCH3)2], 6.61 [d, J
=
H---H
C---H
C---H
1
8.5, 2H of (CH3C6H4)N(C6H4OMe)2], 6.88 [t,
= 7.5, 2H of (CH3C6H4)N(C6H4OMe)2],
H---H
6.91–6.94 [m, 2H of (CH3C6H4) and 2H
CH], 119.9 [d, J
= 160, CH], 122.1 [d,
C---H
3J
1J
= 162, CH], 128.4 [d, J
= 154,
1
C---H
C---H
1
CH], 129.6 [d, J
= 160, CH], 130.4 [d,
C---H

Synthesis and structural analysis
979
Table 4. Crystal, Intensity Collection and Refinement Data
N(o-C6H4OH)3·Me2CO PhN(o-C6H4OH)2
p-TolN-(o-C6H4OMe)2
Lattice
Formula
Formula weight
Space group
Orthorhombic
C21H21NO4
351.39
Pbca
14.6789(9)
11.0975(8)
22.730(2)
90
90
90
3702.7(4)
8
Triclinic
C18H15NO2
277.31
P-1
11.236(1)
11.412(1)
12.318(1)
79.169(2)
82.931(2)
69.533(2)
1450.6(3)
4
Monoclinic
C21H21NO2
319.39
C2/c
15.034(1)
14.278(1)
10.399(1)
90
130.325(1)
90
1701.8(2)
4
˚
a (A)
˚
b (A)
˚
c (A)
α (◦)
β (◦)
γ (◦)
3
˚
V (A )
Z
Temperature (K)
243
243
243
˚
Radiation (λ, A)
0.71073
1.261
0.087
0.71073
1.270
0.083
0.71073
1.247
0.080
ρ (calcd.), g cm−3
µ (Mo Kα), mm−1
m
0.9576, 0.9334
28.3
4354
0.9836, 0.9597
28.0
6167
0.9842, 0.9688
28.2
1906
θmax (◦)
No. of data
No. of parameters
R1
250
396
112
0.0403
0.1365
1.012
0.0427
0.1148
1.088
0.0463
0.1022
1.065
wR2
GOF
1J
= 160, CH], 132.5 [s, quat.], 148.2 [s,
Geometry optimization was performed with the
B3LYP28 functional employing 6-31G∗∗ basis
set.29 The energies of the optimized structures
were reevaluated by additional single-point
calculations on each optimized geometry using
the cc-pVTZ(-f) basis sets.30
C---H
quat.], 153.6 [s, quat.].
X-ray structure determinations
Crystals suitable for X-ray diffraction
were obtained by slow evaporation from solu-
tions in the following solvents: N(o-C6H4OH)3,
acetone; PhN(C6H4OH)2, benzene; and p-
TolN(C6H4OMe)2, EtOH/nitrobenzene/pentane.
X-ray diffraction data were collected on a Bruker
P4 diffractometer equipped with a SMART CCD
detector and crystal data, data collection, and re-
finement parameters are summarized in Table 4.
The structures were solved using direct methods
and standard difference map techniques, and were
refined by full-matrix least-squares procedures on
F2 with SHELXTL (Version 5.03).26
Supplementary material Supplementary crystallographic data for
this paper, namely PhN(o-C6H4OH)2 (CCDC #264850), p-To
lN-(o-C6H4OMe)2 (CCDC #264851), and N(o-C6 H4OH)3·Me2
CO (CCDC #264852), can be obtained free of charge via www.
ccdc.cam.ac.uk/data request/cif, by e-mailing data request@ccdc.
cam.ac.uk, or by contacting The Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223-
336033.
Acknowledgment
The National Science Foundation (CHE-03-
50498) is thanked for support of this research.
Computational details
References
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All calculations were carried out using
DFT as implemented in the Jaguar 4.1 suite
of ab initio quantum chemistry programs.27

980
Kelly, Tanski, Anzovino, and Parkin
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