Aminodiphenylphosphanes: Isotope-induced chemical shifts 1Δ14/15N(31P), coupling constants 1J(31P,15N), and chemical shifts δ15N and δ31P

Article abstract of DOI:10.1002/hc.1083

A series of aminodiphenylphosphanes 1 [Ph₂P-N(H)tBu (a), -NEt₂ (b), -NiPr₂ (c)], 2 [Ph₂P-NHPh (a), -NH-2-pyridine (b), -NH-3-pyridine (c), -NH-4-pyridine (d), NH-pyrimidine (e), NH-2,6-Me₂-C₆

Full text of DOI:10.1002/hc.1083

Heteroatom Chemistry
Volume 12, Number 6, 2001
Aminodiphenylphosphanes: Isotope-Induced
1 14/15 31
Chemical Shifts 1
N( P), Coupling
1 31 15
31
Constants J( P, N), and Chemical Shifts
15
N and P
Rosalinda Contreras,1 Jean Michel Grevy,1,2 Zureima
Garc´ıa-Herna´ndez,1 Marisol Gu¨izado-Rodriguez,1
and Bernd Wrackmeyer1,3
1Departamento de Quimica, Centro de Investigacion y de Estudios Avanzados del IPN,
A.P. 14-740, Mexico D.F. 07000 Me´xico
2Universidad Auto´noma del Estado de Morelos, Centro de Investigaciones Quı´micas,
Av. Universidad No. 1001, Col. Chamilpa. Cuernavaca Morelos, 62000 Me´xico
3Laboratorium fu¨ r Anorganische Chemie, Universita¨t Bayreuth,
D-95440 Bayreuth, Germany
Received 22 January 2001; revised 9 April 2001
phorus atom. The X-ray structural analysis of 2b is re-
ABSTRACT: A series of aminodiphenylphosphanes 1
[Ph2P-N(H)tBu (a), -NEt2 (b), -NiPr2 (c)], 2 [Ph2P-
NHPh (a), -NH-2-pyridine (b), -NH-3-pyridine (c),
-NH-4-pyridine (d), NH-pyrimidine (e), NH-2,6-Me2-
C6H3 (f), NH-3-Me-2-pyridine (g)], 3 [Ph2P-N(Me)Ph
(a), -NPh2 (b)], and N-pyrrolyldiphenylphosphane 4
(Ph2P-NC4H4) was prepared and studied by NMR (1H,
13C, 31P, 15N NMR) spectroscopy. The isotope-induced
chemical shifts 1114/15N(31P) were determined at natural
abundance of 15N by using HEED INEPT experiments.
A dependence of 1114/15N(31P) on the substituents at ni-
trogen was found (alkyl < H < aryl; increasingly neg-
ative values). The magnitude and sign of the coupling
constants 1J(31P,15N) (positive sign) are dominated by
the presence of the lone pair of electrons at the phos-
ported, showing the presence of dimers owing to inter-
C
molecular hydrogen bridges in the solid state. 2001
John Wiley & Sons, Inc. Heteroatom Chem 12:542–550,
2001
INTRODUCTION
Aminophosphanes have been in the center of various
1
NMR studies, and there is a wealth of H, 13C, and
31P NMR data available [1–4]. More recently, many of
these studies were complemented by 15N NMR mea-
surements in order to provide 15N and 1 J(31P,15N)
data [4,5]. 15N chemical shifts are useful for assess-
ing the nature of the PN bond, and they respond to
the substituents at the nitrogen atoms. In the case
of numerous representative aminophosphanes, the
positive sign of the 1 J(31P,15N) values [the reduced
coupling constants 1 K(31P,15N) are negative owing
to (15N) < 0] having been firmly established [6,7].
In contrast, a further NMR parameter, the isotope-
induced chemical shift 1114/15N(31P) has received
Correspondence to: Rosalinda Contreras.
Contract Grant Sponsor: CONACYT.
Contract Grant Number: E 26341.
Contract Grant Sponsor: Cinvestav.
Contract Grant Sponsor: Deutsche Forschungsgemeinschaft.
Contract Grant Sponsor: Fonds der Chemischen Industrie.
2001 John Wiley & Sons, Inc.
c
542

Aminodiphenylphosphanes 543
SCHEME 1 Numbering of aminodiphenylphosphanes stud-
ied.
SCHEME 2
only limited attention, although it can be determined
now for many examples at natural abundance of
15N (0.37%) using so-called HEED (Hahn-echo ex-
tended) polarization transfer experiments [8,9]. By
spective N-lithio derivatives. All phosphanes are col-
orless solids or oils, sensitive to moisture and well
soluble in most hydrocarbons.
1
using this technique, the set of data 114/15N(31P) is
already steadily increasing and shows a consider-
able range, depending on the formal oxidation state
of phosphorus, its coordination number, and on the
substituents at the phosphorus and nitrogen atoms.
In spite of the fact that many aminodiphenylphos-
phanes are known or can be readily prepared, only a
single derivative, (Ph2P)2NH 5 [10], has been stud-
Molecular Structure of
2-Pyridylaminodiphenylphosphane 2b
The crystal structure of 2e has been reported [12],
and recently, parallel to our work, the structure of
2b was also published [11]. However, details of the
structures were not discussed at all (2e) or very
briefly summarized (2b). The crystal data, reported
for 2b, crystallized from CDCl3 [11], differ from our
data (single crystals of 2b were obtained from ben-
zene solution) as far as the cell dimensions, the space
1
ied so far with respect to 114/15N(31P). Therefore,
we have prepared a series of these compounds with
alkyl, hydrogen, or aryl groups linked to nitrogen (1–
4 in Scheme 1). In all cases it proved possible to de-
1
termine the 114/15N(31P) data without 15N labeling.
group, and the angle
are concerned. Otherwise,
The pyridine derivatives were of interest because of
their potential use in coordination chemistry [11],
and these derivatives were also useful to investigate
a particular effect of the heteroaromatic system in
comparison to a phenyl group. Compound 2b was
isolated in crystalline state, and an X-ray structural
analysis [11] was carried out.
the results are very similar. The molecular struc-
ture of 2b [13] is shown in Figure 2, which reveals
that dimeric units are present in the lattice due to
intermolecular hydrogen bridging. The main struc-
tural features of 2b and 2e are similar. The sur-
roundings of the phosphorus atoms in 2b are pyra-
midal, as expected; however, the bond angles are
rather large (all >102 ). The angle C(2)N(7)P(8) =
129.6(11) at the amino nitrogen atom is wide, as a
result of bonding to two fairly bulky groups and one
hydrogen atom. The small angle (3.7 ) between the
planes N(1)C(2)C(3) and C(2)N(7)P(8) is at least in
part enforced by the intermolecular hydrogen bridg-
ing in the solid state. However, even in the absence
of these hydrogen bridges (e.g., in solution), one
expects a fairly small dihedral angle in order to allow
for efficient (pp) interactions between the amino
RESULTS AND DISCUSSION
Synthesis of the Aminodiphenylphosphanes
There are three methods (Scheme 2) that all work
well to prepare aminodiphenylphosphanes of the
type 1, 2, and 3a. N,N-diphenylaminodiphenylpho-
sphane 3b and the N-pyrrolyl derivative 4 are best
obtained from the reaction of Ph2PCl with the re-

544 Contreras et al.
FIGURE 1 In the lattice, dimeric units of 2b are formed, due to head-to-tail (P)N–H–N(py) intermolecular hydrogen
bridging as indicated. Molecular structure of 2-pyridylaminodiphenylphosphane 2b. Selected bond lengths (pm) and an-
gles ( ): P(8)N(7) 167.2(12), P(8)C(9) 184(2), P(8)C(15) 185(2), C(2)N(7) 135(2), N(1)C(2) 129(2), N(1)C(6) 128(2);
N(7)P(8)C(9) 102.6(7), N(7)P(8)C(15) 104.1(8), C(9)P(8)C(15) 102.5(7), C(2)N(7)P(8) 129.6(11), N(1)C(2)N(7) 121.4(13);
planes N(1)C(2)C(3)/C(2)N(7)P(8) 3.7, C(15)P(8)C(9)/C(2)N(7)P(8) 88.9, C(10C(9)C(14)/C(16)C(15)C(20) 80.9.
nitrogen atom and the 2-pyridyl heteroaromatic
system. Semiempirical calculations (AM1 [14]) of
monomeric 2b in the gas phase gave the bond
angle C(2)N(7)P(8) = 130.9 (in good agreement
with the experimental data; vide supra), and the di-
hedral angle N(1)C(2)N(7)P(8) = 17.7 . The calcu-
lated bond angles at the phosphorus atom are slightly
larger than those determined by X-ray analysis.
15N resonance signals were extremely sharp (h1/2
0.1 Hz), indicating the absence of equilibria due
to intermolecular association by hydrogen bonding.
Furthermore, the NMR data of the amino-pyridine
derivatives prove the absence of prototropic equilib-
ria, in agreement with previous 1H, 13C, 15N, and 31
P
NMR studies of related (either two isopropyl groups
at phosphorus or the phosphorus atom is linked to
two oxygen atoms) 2-pyridylaminophosphanes [15].
The positive sign 1 J(31P,15N) [reduced coupling
NMR Spectroscopic Results
2
constant 1 K(31P,15N) < 0; K(A,X) = 4 J(A,X) ( (A)
The 15N and 31P NMR data of 1–5 are given in
Table 1, including coupling constants J(31P,15N) and
isotope induced chemical shifts 1114/15N(31P). 13C
NMR data are given in Table 2, and 1H NMR
data are listed in the Experimental section. The as-
signment of all NMR signals was straightforward.
The compounds are strictly monomeric in solution.
With the exception of 2d, all 15N NMR spectra
of the aminopyridines could be measured, and the
(X) h) ] has already been experimentally estab-
1
lished for 5 [10], in agreement with literature data
[6,7], and, in this work, also for Ph2PNHtBu (1a). In
the latter case, selective heteronuclear 1H 31P} double
resonance experiments served for the comparison of
1 K(31P,15N) (<0) and 1 K(15N,1H) (>0 [16]; 1 J(15N,1H)
=
77.0 Hz). In this experiment 15N is the passive
spin, and since (15N) < 0, it is advisable to use
the notation of reduced coupling constants. The 2D

Aminodiphenylphosphanes 545
interactions when compared with the aniline
derivative. This is in agreement with the results of
previous NMR studies on aminopyridines [19,20].
The 15N data appear to be more sensitive than 13C
data to changes in (pp) interactions as a result of
geometric constraints. Thus, the 13C(pyridine) data
of 2g suggest that (pp) bonding of the ring to the
exocyclic nitrogen is hardly reduced as compared
with 2b, whereas the shift of the 15N resonance
of the amino nitrogen atom to lower frequencies
(>20 ppm) and that of the pyridine nitrogen atom
to higher frequencies (>20 ppm) clearly indicate
reduced (pp) interactions. This is also in agreement
with the results of AM1 calculations [14] for 2g,
which give a dihedral angle N(1)C(2)NP = 66.4
(calculated for 2b: 17.7 ; 2e: 8 and 172 ). Another
indication of potential (pp) interactions is the
magnitude of the coupling constants 3 J(31P,13Car),
which is substantial if a planar arrangement of the
amino group and the aromatic ring is favorable
and is close to zero (see 2g) if this arrangement is
unfavorable owing to steric hindrance. Both 15N
3
and the J(31P,13Cpyr) values appear to be more reli-
able with regard to evaluation of the (pp) bonding
interactions than the changes in the 13C data.
A major contribution to the line widths of the
31P resonance signals arises from scalar relaxation
of the second kind owing to partially relaxed scalar
31P–14N coupling. Since this contribution is absent in
the case of the 31P–15N isotopomers, the 15N satellites
FIGURE 2 Contour plot of the 2D 15N/1H HETCOR exper-
iment for 1a (in C6D6 at 25 C; result of 64 scans and 32
experiments, with zero filling and Gaussian enhancement in
both dimensions; 45 minutes of spectrometer time) showing
1
owing to J(31P,15N) are sharp signals, and their 31P
a positive tilt for the cross peaks which arise from 31P–15
N
magnetization should decay more slowly than that
of the respective 31P–14N isotopomer. Therefore, an
appropriate delay ( 50 to 200 ms) in the Hahn-echo
extension of the polarization transfer pulse sequence
(INEPT-HEED) leads to reduced intensity of the
parent 31P signal, leaving the 15N satellites almost
unaffected; and by this allows for straightforward
identification of the 15N satellites as well as for
fairly accurate ( 1 ppb or better) determination
and 31P–1H(NH) coupling, indicating that the reduced cou-
pling constants 1K( 31P, 15N) (<0) and 2K( 31P, 1 H(NH)) (<0)
have identical signs.
15N/1H HETCOR experiment (Figure 2) shows that
2 K(31P,1 H(NH)) (<0; 2 J(31P,1 H(NH) = 11.9 Hz) and
1 K(31P,15N) (<0) have the same sign (positive tilt of
the cross peaks [17]). It can be assumed that all cou-
pling constants 1 J(31P,15N) reported in this work pos-
sess a positive sign [1 K(31P, 15N) < 0], typical of the
influence of the lone pair of electrons at the phospho-
1
of the isotope-induced chemical shifts 114/15N(31P)
1
(Figure 3). The values 114/15N(31P) obtained in this
work cover a range of 20 ppb and appear to be
dependent on the type of substituent at the nitrogen
atom (see Table 1). Isotope-induced chemical shifts
can be understood to represent the combined in-
fluence of vibrational and electronic contributions,
where the latter may be more important, in part-
1
rus atom [18]. The magnitude of J(31P, 15N) (range
from 50.3 to 63.5 Hz) changes very little, consider-
ing the different types of substituents at the nitrogen
atom. This indicates that the influence of the phos-
phorus lone pair of electrons is dominating.
1
In contrast to the 1 J(31P15N) data, there is a fair-
ly large range of the 31P data (23.8 to 62.5 ppm),
and also of the 15N data ( 226.5 to 344.7 ppm),
as one would expect. The 31P data are not
markedly affected if the phenyl (2a) is replaced
by a pyridyl group (e.g., 2b–e) at nitrogen, whereas
the 15N(amino) and 15N(pyridine) values of the
aminopyridine derivatives reflect increased (pp)
icular for heavy nuclei [21]. In the case of 112/13C
(
119Sn), many data have been collected, especially
for methyltin compounds, and it was found that the
magnitude and sign of the effect can be roughly
correlated with the value of the coupling constants
1J(119Sn,13C) [22,23], indicating the importance of
the electronic contribution, which is reflected by
the electron-mediated indirect nuclear spin–spin

546 Contreras et al.
TABLE 1 Chemical Shifts 31P, 15N, Isotope-Induced Chemical Shifts 1114/15N(31P)a, and Coupling Constants 1J (31P, 15N)
( 0.1 Hz) of the compounds 1--5
Compound
31P
15Nb
1114/15N( 31P)
1J( 31P, 15N)
1a Ph2P-NH-tBu
23.8
62.5
39.2
29.4
27.8
320.9
344.7
324.8
313.2
298.4
114.4 (py)
317.6
68.0 (py)
n.m.
290.6
125.1 (pyrim.)
302.2
321.0
93.6 (py)
n.m.
n.m.
36.4
29.5
30.6
46.9
45.7
57.1
61.3
62.2
54.3
52.7
<0.5
55.7
5.9
51.4
51.4
8.1
50.3
58.7
2.0
c
1b Ph2P-NEt2
1c Ph2P-NiPr2
d
2a Ph2P-NHPh
2b Ph2P-NH-2-pyridyl
2c Ph2P-NH-3-pyridyl
30.2
48.0
2d Ph2P-NH-4-pyridyl
2e Ph2P-NH-2-pyrimidinyl
28.3
29.0
48.0
47.0
2f Ph2P-NH-2,6-Me2-C6H3
2g Ph2P-NH-2-(3-Me)-py
27.9
37.0
47.8
45.0
3a Ph2P-N(Me)Ph
3b Ph2P-NPh2 e
4 Ph2P-NC4H4
56.8
55.5
48.7
40.0
44.8
33.5
60.7
63.5
58.5
226.5
5 Ph2P-NH-PPh2f
44.2
n.m.
40.0
57.3
aIn ppb ( 1 or better); negative sign denotes a shift to lower frequency with respect to the lighter isotopomer.
bn.m. means not measured; in the cases of 2d, 3a, 3b, and experimental conditions for INEPT could not be established; data for 5 were taken
from literature, and 5 was not measured again for 15N NMR data.
c1
J(31P, 13C) = 15.2 Hz; 1112/13C(31P) = 7.0 2 ppb (the lower accuracy is due to overlap with 13C satellites arising from 2J(31PN13C) = 15.8 Hz);
measured from the satellite spectrum of the 13
C
P
15N isotopomer.
31
dFor comparison: [(C5H4)2Fe]P-NiPr2: 23.8 ( 31P), 310.6 ( 15N), 35.0 (1114/15N(31P), 1J(31P, 15N) = 64.7 Hz [29].
eFor comparison: Me2P-NC4H4: 34.4 ( 31P), 220.2 ( 15N), 48.0 (1114/15N(31P)), 1J(31P15C) = 56.1 Hz [25]; tBu2P-NC4H4: 91.6 ( 31P), 218.5
15
(
15N), 45.6 (1114/15N(31P)), 1J(31P15N) = 63.2 Hz [26]; (Me2N)2P-NC4H4: 112.9 ( 31P), 204.2 (
N
pyrrole
), 26.0 (1114/15N(31P)), 1J(31P15N)
= 58.7 Hz; [CH2N(Me)]2P-NC4H4: 104.8 ( 31P), 187.9 (
N
pyrrole
), 17.0 (1114/15N(31P)), 1J(31P15N) = 86.7 Hz [25].
15
f Ref. [10].
coupling. Another recent study on 1112/13C(29Si) val-
ues points toward a rather complex dependence of
these parameters, not only on the coupling constants
1J(29Si,13C) but also on the nature of the substituents
[24]. This is more in agreement with the present re-
sults for 1114/15N(31P) data, where there is no obvious
relationship to changes in the magnitude of the coup-
features of all the pyrrole derivatives are the same
as suggested by AM1 calculations [14], in agreement
with low-temperature NMR studies on tBu2P-NC4H4
that show that the pyrrole group is oriented paral-
lel to the assumed orientation of the lone pair of
electrons at phosphorus [26]. It appears that an in-
crease in the electronegativity of the other groups
linked to phosphorus causes a decrease in the mag-
1
ling constants J(31P,15N). Indeed, if both sign and
nitude of 114/15N(31P) (see the similar 114/15N(31P)
of the Me2P and tBu2P derivatives in contrast to the
(Me2N)2P compound, although the 1J(31P,15N) val-
ues are all in a close range). The particular influ-
ence of the nature of the lone pair of electrons at
the phosphorus atom is evident in the case of the
cyclic diazaphospholidine derivative [25], where the
1
1
magnitude of 1J(31P,15N) are mainly governed by the
influence of the lone pair of electrons at the phospho-
rus atom (vide supra), electronic effects contributing
to 1114/15N(31P) will not be well reflected by the
changes in the magnitude of coupling constants
1J(31P,15N).
1
This problem of relating 114/15N(31P) values di-
1
value of J(31P,15N) changes by 48% and the magni-
1
rectly to coupling constants J(31P,15N) can be seen
tude of 1114/15N(31P) becomes smaller by 35% with re-
spect to the noncyclic bis(dimethylamino) derivative
[25].
by comparing the data (vide infra) for various N-
pyrrolylphosphanes available from this work and
from the literature [25,26]. The principal structural
Me2P NC4H4
t Bu2P NC4H4
Ph2P NC4H4
(Me2N)2P NC4H4
[CH2N(Me)]2P NC4H4
4
33.5
58.5
1114/15 N(31P)
1J(31P, 15N)
48.0
56.1
45.6
63.2
26.0
58.7
17.0
86.7

Aminodiphenylphosphanes 547
a
TABLE 2 13C NMR Data of the Compounds 1--4
13C
13C
(NR,R)
Compound
(Ph2P: i, o, m, p)
1a Ph2P-NH-tBub
1b Ph2P-NEt2
141.1 [13.0], 131.2 [20.2],
128.1 [5.7], 128.3
141.1 [15.2], 132.4 [20.1].
128.37 [5.8], 128.36
141.1 [14.0], 132.6 [20.8],
28.0 [4.2], 128.2
51.1 [18.7], 32.1 [8.3]
44.6 [15.8], 14.6 [3.1]
47.5 [9.3], 23.7 [6.8]
c
1c Ph2P-NiPr2
2a Ph2P-NHPh
140.5 [12.5], 131.3 [20.8],
128.6 [6.8], 128.9
146.8 [17.1] (i), 116.3 [13.0] (o),
129.3 (m), 119.6 (p)
2b Ph2P-NH-2-pyridyl
2c Ph2P-NH-3-pyridyl
2d Ph2P-NH-4-pyridyl
2e Ph2P-NH-2-pyrimidinyl
2f Ph2P-NH-2,6-Me2-C6H3
2g Ph2P-NH-2-(3-Me)-py
3a Ph2P-N(Me)Ph
140.1 [11.9], 131.4 [20.8],
128.5 [6.2], 128.9
139.3 [10.2], 131.9 [20.6],
129.0 [6.5], 129.5
139.3 [11.9], 131.5 [20.8],
128.6 [6.2], 129.2
140.3 [16.6], 131.7 [21.8],
128.5 [6.2], 128.9
142.7 [15.5], 131.5 [21.5],
128.5 [5.5], 128.7
141.5 [18.5], 131.6 [21.5],
128.5 [6.2], 128.8
137.5 [16.9], 131.9 [20.0],
128.5 [6.2], 128.7
137.4 [16.9], 132.4 [21.5],
128.1 [6.2], 128.9
159.5 [22.3] (2), 108.7 [17.6] (3),
137.4 (4), 114.8 (5), 148.3 (6)
140.3 [11.6] (3), 144.7 [17.9] (2),
122.4 [17.9] (4), 124.2 (5), 140.3 (6)
150.4 (2,6), 111.1 [14.0] (3,5), 153.9
[19.2] (4)
163.6 [16.6] (2), 157.8 [2.1] (4,6),
112.2 (5)
19.2 (Me), 143.3 [15.5] (i), 130.6 (o),
128.3 (m), 122.7 (p)
16.4 (3-Me), 156.5 [11.5] (2), 117.4 [<
1.5] (3), 137.0 (4), 114.9 (5), 146.1 (6)
35.6 [9.2] (NMe), 151.6 [26.1] (i ),
117.6 [15.4] (o), 128.9 (m), 119.9 (p)
147.8 [7.7] (i), 124.3 [7.7] (o),
128.9 (m), 122.9 (p)
3b Ph2P-NPh2
4 Ph2P-NC4H4
137.4 [12.3], 132.0 [20.0],
128.6 [6.2], 129.6
125.5 [12.3] (2,5), 112.0 (3,4)
aSolutions in C6D6 (ca. 10–20%; w/v); 13C 0.1 ppm; coupling constants nJ(31P, 13C) in brackets 0.5 Hz.
bIn reasonable agreement with data from Ref. [35].
cData for the Ni Pr2 group in agreement with Ref. [31e].
It is tempting to compare the isotope-induced
using the INEPT-HEED pulse sequence in order to
chemical shifts 114/15N(31P) with 112/13C(31P) data.
It appears that these values are small and neg-
ative for triorganophosphanes and related com-
pounds [27,28], and much larger, also negative, for
3-phosphaalkynes and 3-phosphaalkenes [27]. We
obtain these parameters with 15N at natural abun-
dance. Although there is no obvious correlation of
the 1114/15N(31P) data with bond order, with the cou-
pling constants 1 J(31P,15N), or with chemical shifts
31P or 31N, the substituents at the nitrogen atom
have a significant influence on 1114/15N(31P): alkyl <
H < aryl (increasingly negative values). The presence
of the lone pair of electrons at phosphorus domi-
1
1
1
have determined 112/13C(31P) = 7.0 ppb for 1b in
order to show that small values are also typical of
aminodiphenylphosphanes. This was only possible
by observing the satellites of the 13C–31P–15N iso-
topomer, since otherwise the 13C satellites are broad
and unresolved (see Figure 3). Apparently, the trends
1
nates the magnitude and sign of J(31P,15N), and the
1
same is true for J(31P,13C), which also covers only
a small range from 10.2 to 18.5 for the compounds
1
1
1
are similar for both 114/15N(31P) and 112/13C(31P)
studied. Thus, 114/15N(31P) (this work and [9]) and
values, considering the 1114/15N(31P) values found
1112/13C(31P) values [27] show similar trends.
in this work, and the larger 114/15N(31P) values for
1
phosphazoles [9a] and of tBuP = NtBu [9e], in which
EXPERIMENTAL
the phosphorus atoms are two coordinate.
All synthetic work and the handling of samples were
carried out under an inert atmosphere (N2 or Ar),
using carefully dried glassware and dry solvents.
Diphenylphosphorus chloride, all amines, pyrrole,
BuLi (1.6 M in hexane), and 5 were commer-
cially available. Diethylamine, N-methylaniline, pyr-
role, N,N-diisopropylamine, and tert-butylamine
CONCLUSIONS
A series of aminodiphenylphosphanes has been
studied by NMR spectroscopy, mainly with respect
to isotope-induced chemical shifts 114/15N(31P) by
1

548 Contreras et al.
broadband probehead. Chemical shifts are given
1
with respect to solvent signals [ H (C6D5H) = 7.15;
13C (C6D6) = 128.0] and external references for 31P
(H3PO4
= 0 with 4(31P) = 40.480747 MHz; 15N
(aq)
(MeNO2, neat) = 0 with 4(15N) = 10.136767 MHz;
1
15N{ H} NMR spectra were measured by the refo-
cused INEPT pulse sequence [34], based either on
1J(15N,1H) for the amino nitrogen or J(15N,1H)
2
10 Hz for the pyridine nitrogen. 31P NMR spec-
tra for measuring isotope-induced chemical shifts
1114/15N(31P) were recorded by the INEPT-HEED
pulse sequence [8], and polarization transfer was
based on a coupling constant 3J(31P,1 Hortho) = 10 Hz,
using Hahn-echo delays between 50 and 200 ms,
depending on the width of the 31P NMR signal of
the 31P–14N isotopomer (smaller line widths require
longer Hahn-echo delays).
Synthesis of the Aminodiphenylphosphanes 1–3:
General Procedures
Diethylaminodiphenylphosphane 1b. A solution
of diethylamine (4.07 g; 55.7 mmol) in hexane
(100 mL) was cooled to 78 C. Then a solution of
diphenylphosphorus chloride (6.14 g, 27.8 mmol) in
hexane (20 mL) was added under vigorous stirring,
and the mixture was warmed to room temperature
and kept stirring for 12 hours. After filtration and re-
moval of the solvent, the product 1b (7.08 g; 85%)
was obtained by fractional distillation as a color-
less liquid (b.p 110 C/0.18 Torr). 1H NMR (300 MHz;
C6D6): 1H [J(31P,1 H)] = 7.50, 7.14 (m, 10H, Ph-Ho,
H
m,p), 3.01 [9.5] (d,q, 4H, NCH2), 0.85 (t, 6H, CH3).
The compounds 1a and 1c were obtained in the
same way.
Compound 1a: Yellow liquid, b.p. 50–53 /0.1
FIGURE 3 (a) Result of application of the INEPT-HEED
pulse sequence (based on J( 31P, 1 H) = 10 Hz and four hy-
drogen atoms; 16 transients; Hahn echo delay 100 ms) to
Ph2P-NiPr2 1c (in C6D6 at 25 C; the 15N satellites are marked
by asterisks; note the appearance of the multitude of broad,
badly resolved 13C satellites; area is marked by arrows).
(b) The same experiment as in part a) but for Ph2P-NH-2-py
2b (in C6D6 at 25 C; 16 transients; the Hahn echo delay
(200 ms) has to be longer since the central line is more narrow
owing to faster 14N quadrupolar relaxation as compared to
1c).
1
Torr. H NMR (300 MHz; C6D6): ␦1H [J(31P,1 H)] =
7.45, 7.12 (m, 10H, Ph-Ho, Hm,p), 2.0 [11.9] (d, 1H,
NH, 1J(15P,1 H) = 77.0 Hz), 1.18 (s, 9H, tBu).
1c: Colorless liquid, b.p.130–140 C/0.15 Torr; 1H
NMR (300 MHz; C6D6): ␦1H [J(31P,1 H)] = 7.16, 7.14
(m, 10H, Ph-Ho, Hm,p), 3.29 [10.6] (d, sept, 2H, NCH),
1.04 [d, 12H, CH3).
Anilinodiphenylphosphane 2a. A solution of N-
trimethylsilylaniline (1.0 g; 6.06 mmol) in benzene
(50 mL) was cooled to 0 C. Diphenylphosphorus
chloride (1.34 g; 6.06 mmol), dissolved in benzene
(10 mL) was added under vigorous stirring. The
mixture was warmed to room temperature and
stirred continuously for 12 hours. The solvent and
chlorotrimethylsilane were removed at low pressure,
and the product 2a was obtained as a viscous yellow
were dried according to established procedures and
freshly distilled before use. N-Silylated amines were
prepared according to reported procedures [30]. The
preparation of the compounds 1a,b,c [31], 2a [30c],
2b [11,32], 2e [12], 3b [31a], and 4 [33] has been re-
ported previously. Progress of all reactions was mon-
itored by NMR spectroscopy.
1
NMR spectra were recorded using a Bruker
DPX 300 instrument, equipped with a multinuclear
liquid. H NMR (300 MHz; C6D6): 1H [J(31P,1 H)] =
4.18 [7.7] (d, 1H, NH, 1J(15N,1H = 83.2 Hz) 6.91–7.4

Aminodiphenylphosphanes 549
NMR (300 MHz; C6D6): 1H = 6.98, 7.02, 6.81 (m,
(m, 15H, PPh, NPh). The compounds 2b, 2c, 2d and
2e were prepared in the same way as 2a.
10H, NPh-Ho, Hm, Hp) 7.47, 7.16 (m, 10H, PPh-Ho,
Compound 2b: Pale yellow solid (yield 85%); 1H
NMR (300 MHz; C6D6): 1H [J(31P,1 H)] = 5.60 [8.4]
(s, 1H, NH), 7.09, 6.94, 6.27, 7.79 (m, 4H, pyr-H3,4,5,6),
7.45, 7.00 (m, 10H, Ph-Ho, Hm,p).
H
m, p ).
Crystal Structure Analysis of 2b [13]. C17H15N2P,
colorless, rectangular crystal (mounted on
capillary) of dimensions 0.364 0.168 0.168
mm, crystallizes monoclinically, space group
Ia; a = 1433.2(3), b = 828.2(2), c = 2476.5(5) pm,
a
Compound 2c: White solid (yield 87%), 1H NMR
(300 MHz; C6D6): 1H [J(31P,1 H)] = 6.32 [7.3] (d, 1H,
NH); 8.53, 6.76, 7.46, 7.92 (m, 4H, pyr.-H2,4,5,6), 7.54,
7.18 (m, 10H, Ph-Ho, Hm,p).
1
= 96.79(3) ; Z = 8, = 0.179 mm ; F(000) 1168;
Compound 2d: White solid (yield 90%); 1H NMR
(300 MHz; C6D6): 1H [J(31P,1 H)] = 5.75 [7.7] (s, 1H,
NH), 8.20, 6.75 (m, 4H, pyr.-H2,6,3,5), 7.36, 7.04 (m,
10H, PPh-Ho, Hm,p).
radiation Mo K with = 71.073 pm; scan type
ω/22 ; temperature 183 K; 5721 reflections collected
in the range 5.2 to 51.94 in 22 (index ranges
17
h
17, 0
k
10, 30
l
30), 5721 re-
In the case of 2e, the reaction mixture was
warmed and stirred for 7 days, and 2e was isolated as
a white solid (yield 80%); 1H NMR (300 MHz; C6D6):
1H [J(31P,1 H)] = 7.74, 5.85 (m, 3H, pyr.-H4,6,5), 7.46,
7.00 (m, 10H, PPh-Ho, Hm,p).
flections independent, 1994 reflections assigned to
be observed (F > 4 (F)); solution and refinement
(SHELXS-93) with direct methods (hydrogen atoms:
riding model, fixed isotropic U); full=matrix least
squares on F2; refinement with 369 parameters;
R1/wR2 values 0.0452/0.1054; max./min. residual
6
3
N-Methylanilino-diphenylphosphane 3a. A mix-
ture of N-methylaniline (1.2 g; 11.1 mmol) and
triethylamine (2.47 g; 11.2 mmol) was dissolved in
electron density 0.223/ 0.221 e 10 pm .
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hexane (150 mL) and cooled to
50 C.
Diphenylphosphorus chloride (2.47 g; 11.2 mmol)
was added under vigorous stirring. The mixture
was warmed to room temperature and kept stirring
for 2 hours. Then, insoluble material was filtered
off, the solvent was removed in vacuo, and 3a was
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1
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1
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1
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