Aminophosphanes with bulky amino groups: Molecular structure, coupling constants 1J(31P, 15N) and 2J(31P, 29Si), and isotope-induced chemical shifts 1Δ14/15N(31</

Article abstract of DOI:10.1002/hc.10084

The preferred conformation of aminophosphanes with bulky amino groups (1-20) was determined by NMR spectroscopy in solution, in two cases in the solid state (11,17) and in one case (11) by X-ray crystallography. Trimethylsilylaminodiphenylphosphanes Ph

Full text of DOI:10.1002/hc.10084

Heteroatom Chemistry
Volume 13, Number 7, 2002
Aminophosphanes with Bulky Amino Groups:
Molecular Structure, Coupling Constants
1 31 15
2 31 29
J( P, N) and J( P, Si),
and Isotope-Induced Chemical
1 14/15 31
Shifts ꢀ N( P)
Bernd Wrackmeyer,1 Christian Ko¨hler,1 Wolfgang Milius,1
Jean Michel Grevy,2,3 Zureima Garcı´a-Herna´ndez,2
and Rosalinda Contreras2
1Laboratorium fu¨ r Anorganische Chemie, Universita¨t Bayreuth, D-95440 Bayreuth, Germany
2Departamento de Quı´mica, Centro de Investigacio´n y de Estudios Avanzados del IPN,
A.P. 14-740, 07000 Me˙xico, D.F., Mexico
3Universidad Auto´noma del Estado de Morelos, Centro de Investigaciones Quı´micas,
Av. Universidad No. 1001, Col. Chamilpa, Cuernavaca Morelos, 62000 Me˙xico
Received 21 February 2002; revised 29 April 2002
R = Bz, Rꢀ = Ph (16), R = Rꢀ = Ph (17), R = Rꢀ = Me3Si
ABSTRACT: The preferred conformation of amino-
(18)), 3-tert-butyl-2-chloro-1,3,2-oxazaphospholane
phosphanes with bulky amino groups (1–20) was
determined by NMR spectroscopy in solution, in
(19), and benzyl(tert-butyl)aminodichlorophosphane
1
(20) were studied by H, 13C, 15N, 29Si, and 31P NMR
two cases in the solid state (11,17) and in one case
spectroscopy. In all cases, the more bulky substituent
(11) by X-ray crystallography. Trimethylsilylaminodi-
at the nitrogen atom prefers the syn-position with
phenylphosphanes Ph2PN(R)SiMe3 (R = Bu (1), Ph
respect to the assumed orientation of the phosphorus
(2), 2-pyridyl (3), 2-pyrimidyl (4), Me3Si (5)), amino-
lone pair of electrons. Many of the derivatives studied
(chloro)phenylphosphanes Ph(Cl)PNRRꢀ (R = Bz,
adopt this preferred conformation even at room
t
Rꢀ = Me (6), R = Bz, Rꢀ = Bu (7), R = Et, Rꢀ = Ph (8)),
temperature. Numerous signs of coupling constants
amino(chloro)tert-butylphosphanes
tBu(Cl)PNRRꢀ
2
2
1 J(31P, 15N), J(31P, 13C), and J(31P, 29Si) were deter-
mined. Low temperature NMR spectra were measured
for derivatives for which rotation about the P N bond
at room temperature is fast, showing the presence
of two rotamers at low temperature. The respective
conformation of these rotamers could be assigned by
13C, 15N, and 31P NMR spectroscopy. Isotope-induced
i
t
(R = Rꢀ = Pr (9), R = Me, Rꢀ = Bu (10), R = Bz,
t
t
Rꢀ = Bu (11), R = H, Rꢀ = Bu (12), R = Et, Rꢀ = Ph
i
(13), R = Pr, Rꢀ = Ph (14), R = Bu, Rꢀ = Ph (15),
Correspondence to: Bernd Wrackmeyer; e-mail: b.wrack@uni-
bayreuth.de.
Contract grant sponsor: CONACYT.
Contract grant number: 34714-E.
Contract grant sponsor: Cinvestav.
1
chemical shifts ꢀ15/14N(31P) were determined for all
compounds at natural abundance of 15N by using
Hahn-echo extended polarization transfer experi-
ments. The molecular structure of 11 in the solid state
Contract grant sponsor: Deutsche Forschungsgemeinschaft.
Contract grant sponsor: Fonds der Chemischen Industrie.
2002 Wiley Periodicals, Inc.
c
ꢁ
667

668 Wrackmeyer et al.
reveals pyramidal surroundings of the nitrogen atom
and mutual trans-positions of the tert-butyl groups
ꢁ
C
at phosphorus and nitrogen. 2002 Wiley Periodicals,
Inc. Heteroatom Chem 13:667–676, 2002; Published on-
line in Wiley InterScience (www.interscience.wiley.com).
DOI 10.1002/hc.10084
INTRODUCTION
Aminophosphanes with bulky amino groups are of
interest in the synthesis of compounds which re-
quire kinetic stabilization [1–4]. With regard to the
structure of aminophosphanes, the bulkiness of the
amino group may enforce a preferred conformation
of the aminophosphane, which otherwise would be
less populated. If one or two trimethylsilyl groups
are linked to the nitrogen atom, important elec-
tronic properties of the amino group are affected
[5,6]. Effects exerted by the bulky amino groups
should be reflected by NMR parameters. Very few
systematic studies on such aminophosphanes have
been reported. Trimethylsilylaminophosphanes have
been studied focusing on 1H, 13C, 29Si, 31P NMR
data and on coupling constants 2 J(31P, 29Si) [7],
and a second report has dealt with similar topics
together with 15N NMR parameters and isotope-
SCHEME 1 Aminophosphanes studied.
a colorless oil from the reaction of PCl3 in hexane
with N-tert-butyl ethanolamine, tBuNH-CH2CH2-
OH, in the presence of 2 equiv of triethylamine.
All compounds are sensitive to moisture, can
be kept for a prolonged time under an inert at-
mosphere, and are readily soluble in benzene,
toluene or dichloromethane, and chloroform. Slow
decomposition takes place in chloroform.
Molecular Structure of Benzyl(tert-butyl)amino-
tert-butyl(chloro)phosphane (11)
1
induced chemical shifts ꢀ14/15N(31P), with empha-
The molecular structure of 11 is shown in Fig. 1
together with selected structural data given in the
sis on (Me3Si)2N-PMe2 and derivatives [8]. Re-
1
cently we determined ꢀ14/15N(31P) values and 15N
NMR parameters for a series of aminodiphenyl-
phosphanes [9]. The present work covers similar
aspects of some analogous N-trimethylsilyl deriva-
tives 1–5. Amino(phenyl)chlorophosphanes 6–8,
amino(tert-butyl)chlorophosphanes 9–18, a hetero-
cyclic amino(chloro)phosphane 19, and an amino-
dichlorophosphane 20 were studied in order to
show the general relevance of the NMR data. In the
case of 11, an X-ray structural analysis was carried
out, and solid state 13C and 31P MAS spectra were
measured to compare the main structural features
in the solid and liquid state (see Scheme 1).
RESULTS AND DISCUSSION
Synthesis of the Aminophosphanes
Compounds 1–5 were prepared by the reaction of
the respective freshly prepared N-lithiotrimethyl-
silylamine with Ph2PCl [10,11]. The same types
FIGURE 1 ORTEP view of the molecular structure of 11
(50% probability level). Selected bond lengths (pm) and
angles (degrees): P N 168.9(2), P Cl 216.46(11), P C(12)
189.0(3), N C(1) 148.7(3), N C(8) 154.4(3), C(1) C(2)
153.6(3), C(8) C(9) 153.4(4), C(12) C(13) 154.0(4);
N P Cl 103.92(8), Cl P C(12) 97.94(9), P N C(1)
120.98(16), P N C(8) 114.8(2), C(1) N C(8) 115.14(18),
N C(1) C(2) 115.8(2); dihedral angles: C(8)NPC(12) 157.2,
C(1)PNC(12) 57.4, C(8)PNCl 99.3, C(1)NPCl 46.1.
t
of reaction, using PhPCl2, BuPCl2, or PCl3 and 1
equiv of the respective lithium amide, afforded the
chlorophosphanes 6–18 and 20 either as colorless
oils or as colorless solids. The heterocyclic com-
pound 19 was obtained in moderate yield (35%) as

Aminophosphanes with Bulky Amino Groups 669
legend [12]. To the best of our knowledge, this is
the first example of a molecular structure of an
aminophosphane bearing a chloro function and an
alkyl group at the phosphorus atom. The P N bond
(168.8(2) pm) is significantly elongated when com-
pared with that in F2P NMe2(162.8 pm [13]), and
topes using Hahn-echo extended (HEED) NMR ex-
periments [15], based on polarization transfer [16]
from 1H to 31P.
Conformation of the Aminophosphanes
t
it is only slightly shorter than that in Bu2P NEt2
Typical of the conformation with syn and anti ori-
entation of the N C bond with respect to the as-
sumed orientation of the lone pair of electrons at
the phosphorus atom, the sign of 2 J(31P, N, 13C) is
positive and the magnitude of the coupling constant
is large (syn) or the coupling constant is small and
of either (frequently negative) sign [17,18]. This is
true for most of the phosphanes studied, even at
room temperature, and points clearly towards hin-
dered rotation about the P N bond and the presence
of a preferred conformation. In the case of the N-
silylaminophosphanes 1–4, the magnitude of 2 J(31P,
N, 29Si) is large and the sign is negative [7,8] (re-
duced coupling constant 2 K(31P, N, 29Si) > 0 because
of γ(29Si) < 0), which indicates that the N Si bond is
in the syn position and the N C bond in the anti po-
sition. Because of the presence of an N-trimethylsilyl
group in 2, 3, and presumably also in 4 a coplanar
arrangement of the amino group and the respective
aromatic ring (phenyl, 2-pyridyl, and 2-pyrimidyl) is
energetically unfavorable, and, therefore, (pp)π in-
teractions between the amino-nitrogen atom and the
pyridine ring will not be efficient, as indicated by the
nitrogen and carbon NMR data shown in Scheme 2
(note the reduced shielding of the pyridine nitrogen
and the 13C(3) nuclei in 3).
(169.1 pm [14]). Other noteworthy features of the
molecular structure of 11 are the gauche conforma-
tion with a maximum distance between the two tert-
butyl groups (torsion angle C(12)PNC(8) 156.9◦) and
the nonplanar, i.e. pyramidal surroundings of the ni-
trogen atom (sum of bond angles at nitrogen 351.1◦).
The latter is remarkable since the surroundings of
t
the nitrogen atom in Bu2P NEt2 are close to trigo-
nal planar (sum of bond angles 358.5◦ [14]). The par-
ticular conformation of 11 in the solid state means
that the N C(tBu) bond is almost exactly syn and the
N C(Bz) bond is almost exactly anti with respect to
the assumed orientation of the lone pair of electrons
at the phosphorus atom.
NMR Spectroscopic Results
Selected NMR data of the compounds studied are
listed in Tables 1 (1–5), 2 (6–8), 3 (9–18), and 4 (19,
20). The assignment of all NMR data was straightfor-
ward, routine 1D and 2D methods being used. The
particular structural attraction of the phosphanes
studied is the question of their conformation in so-
lution and in the solid state, and in which way this
property is reflected by NMR parameters. Further-
more, all phosphanes studied here possess only one
P N bond, which makes them suitable candidates
for the determination of isotope induced chemical
In the case of 5, the 29Si NMR spectrum at low
temperature reveals a large and a small value of
2 J(31P, N, 29Si), which correspond to the mean value
at room temperature only if the signs are opposite.
1
shifts ꢀ14/15N(31P) at natural abundance of the iso-
a
TABLE 1 Selected NMR Data of Trimethylsilylaminodiphenylphosphanes, Ph2P N(R) SiMe3 (1–5), in C6D6 at (23 1)◦C
ꢀ
No.
δ
31P
δ
15N
δ
13C(P)
δ
13C(NR)
δ
29Si(N)
1ꢀ14/15N( 31P)
1
2
3
49.2
52.2
42.9
−349.2 [+65.6]
−322.1 [70.6]
−305.9 [+71.1]
−86.1 [0.7]
140.9 [−17.9]
139.9 [−17.9]
138.0 [−22.6]
48.2 [−5.5]
145.6 [ 8.2]
159.3 [ 6.9]
11.1 [−31.8]b
11.5 [−31.6]
11.5 [−30.0]
−35.1
−46.0
−46.8
4
46.3
−289.5 [+73.7]
−125.5 [<0.5]
[+21.8]d
139.1 [19.0]
164.1 [5.8]
12.7 [−27.9]
−46.5
4Se
5
59.0c
50.2
[+90.7]d
17.1 [5.7]
−32.5
−34.9
−351.4 [+65.8]
140.8 [−24.6]
4.2 [6.1]
10.3 [−6.9]e,f
aCoupling constants J(31P, 13C), J(31P, 15N), and J(31P, 29Si) are given in brackets ( 0.1 Hz). Isotope-induced chemical shifts 1ꢀ14/15N(31P) are
given in ppb ( 1 or less), and a negative sign denotes that the resonance signal of the heavy isotopomer is shifted to lower frequency.
b1J(29Si,15N) = 15.1 Hz.
c1J(31P, 77Se) = 778.2 Hz.
dData measured from 31P NMR spectra.
e1J(29Si,15N) = 7.9 Hz.
f Coalescence temperature in 29Si NMR spectra: −20◦C; energy of activation about the P N bond: ꢀG∗ = 53.3 2 kJ/mol. At −40◦C, the 29Si
NMR spectrum shows two doublets at δ29Si 12.4 [10.0] and 9.05 [24.7].

670 Wrackmeyer et al.
The sign of 1 J(31P, 15N) can be assumed as posi-
tive (1 K(31P, 15N) < 0 because γ(15N) < 0) for all the
phosphanes studied. This was checked by a series of
appropriate 2D HETCOR experiments (mainly cor-
relations of the type 13C/1H and 15N/1H) for some rep-
resentative examples (1, 7, 12, 19, 20) in the same
way as has been shown for other aminophosphanes
[8,9,19,20]. The lone pair of electrons at the phos-
phorus atom is mainly responsible for the negative
contributions to 1 K(31P, 15N) [21].
In some cases, for less bulky amino groups,
the 15N NMR spectra were also measured at low
temperature, in order to find out whether different
conformations have a significant influence on the
magnitude of 1 J(31P, 15N). As expected, the room tem-
perature 15N NMR spectra of 6, 13, 15, and 16 show
a doublet corresponding to the mean value of 1 J(31P,
15N), whereas the low temperature 15N NMR spectra
show two doublets, proving the presence of two ro-
tamers in solution (see Fig. 2). This is also evident
from two 31P NMR signals at low temperature. The
similar magnitude of the 1 J(31P, 15N) values for each
pair of rotamers (Tables 2 and 3) indicates that this
parameter is not very sensitive to the conformation:
This again proves that both the sign and range of
SCHEME 2 Proposed preferred conformation of 3. Com-
parison of 15N and 13C NMR data of 3 with related 2-
aminopyridine derivatives [9,36].
It is important to use 29Si NMR to study the dynamic
behavior of 5, since the hindered rotation about the
P N bond (ꢀG∗ (253 K) = 53.3 2 kJ/mol) is not
readily apparent from 1H and 13C NMR spectra: The
1
expected H and 13C NMR signals for nonequiva-
lent NSiMe3 groups are not resolved. If the groups
at the nitrogen atom become less bulky, rotation
about the P N bond becomes fast on the NMR time
scale. For example, in the case of 17, the low tem-
perature 13C NMR spectrum is required to show the
presence of two different N Ph groups, in agree-
ment with the solid-state 13C MAS spectrum. Since
the δ31P and δ13C NMR data for the solid state and
for the solution of 17 at −65◦C are rather similar,
it can be assumed that the solid-state structure is re-
tained in solution at low temperature. The same situ-
ation applies for solid-state and solution-state NMR
data of 11 (even at room temperature), where the
solid-state structure was determined by X-ray analy-
sis (vide supra). The activation energies ꢀG∗ for ro-
tation about the P N bond are in a small range for
those aminophosphanes which do not give separate
signals of the conformers at room temperature (at
coalescence: ꢀG∗ = 49.7 (6, see Ref. [18a] for simi-
lar phosphanes), 48.3 (13), 46.6 (15), 41.7 (16), 42.0
(17) all 2 kJ/mol). In all cases studied here, the con-
formation with the more bulky group at the nitrogen
atom in the syn-position with respect to the assumed
orientation of the phosphorus lone pair of electrons
is preferred.
Coupling Constants 1 J( 31P,15N)
FIGURE 2 30.4 MHz 15N NMR spectra (1H inverse gated de-
coupled) of 15 in CD2Cl2 at room temperature (lower trace)
and at −50◦C upper trace. The two rotamers are present in
almost equal amounts. The one with the larger coupling con-
stant 1J(31P, 15N) is slightly in excess as can be seen by
comparison with the mean value of 1J(31P, 15N). The δ15N
values change slightly with temperature.
The application of polarization transfer, based on
small long-range scalar 15N 1H coupling [3 J(15N,
1H)], proved successful for measuring the 15N NMR
spectra of 1–20 at natural abundance. The 1 J(31P,
15N) data thus obtained confirm the assignment of
15N satellites in the HEED experiments (vide infra).

Aminophosphanes with Bulky Amino Groups 671
TABLE 2 Selected NMR Dataa of Amino(phenyl)chlorophosphanes, Ph(Cl)P NRRꢀ (6–8), in C6D6 at (23 1)◦C
No.
6b
7
δ
31P
δ
15N
δ
13C(P)
δ
13C(N)
1ꢀ14/15N( 31P)
139.7
134.0
134.0
−320.1 [+77.6]
−290.6 [+86.5]
−289.9 [+80.9]
139.9 [−28.9]
138.4 [−31.1]
138.7 [−30.6]
58.7 [+24.0] (R)
36.0 [<1] (Rꢀ)
−37.0
49.1 [−9.8] (R)
59.0 [+18.0] (Rꢀ)
46.1 [<1] (R)
−38.3
8
−39.5
145.2 [13.6] (Rꢀ)
aCoupling constants J(31P, 13C) and J(31P, 15N) are given in brackets ( 0.1 Hz). Isotope-induced chemical shifts 1ꢀ14/15N(31P) are given in ppb
(
1 or less), and a negative sign denotes that the resonance signal of the heavy isotopomer is shifted to lower frequency.
bNMR spectra measured at −60◦C in CD2Cl2: δ13C 34.0 [−11.4] (N Meanti), 60.2 [+38.2] (N CH2 syn) (70%), 38.9 [+33.2] (N Mesyn), 54.5
[−10.5] (N CH2 anti) (30%); δ15N −319.1 [76.7] (30%), −318.9 [78.0] (70%); δ31P 142.5 (30%), 144.4 (70%).
1 J(31P, 15N) are dominated by the presence and the
nature of the lone pair of electrons at the phosphorus
atom.
for phosphaalkenes and phosphaalkynes have been
noted [22]. In aminophosphanes containing only one
P N bond, the 31P/14N and 31P/15N isotopomers dif-
fer significantly with respect to the relaxation rate of
the 31P nuclei. In the 31P/14N isotopomer the transver-
sal relaxation time T2(31P) is governed by the mecha-
nism ascribed to the scalar relaxation of the second
kind [23] owing to unresolved 31P 14N scalar cou-
pling (14N: I = 1), and this is reflected by broadened
Isotope-Induced Chemical Shifts 1ꢀ14/15 N( 31P)
Recently isotope-induced chemical shifts in phos-
phorus compounds have attracted considerable in-
terest, in particular the fairly large 1ꢀ12/13C(31P) data
TABLE 3 Selected NMR Dataa of Amino(tert-butyl)chlorophosphanes, tBu(Cl)P NRRꢀ (9–18), in C6D6 at (23 1)◦C
No.
δ
31P
δ
15N
δ
13C(P)
δ
13C(N)
1ꢀ14/15N( 31P)
9
143.1
151.6
−296.9 [+82.6]
−309.4 (+86.3]
37.8 [−33.3]
37.5 [−34.9]
48.0 (broad) (R, Rꢀ)b
31.5 [−7.6] (R)
57.6 [+20.2] (Rꢀ)
49.8 [−7.1] (R)
59.2 [+20.2] (Rꢀ)
–
−35.7
−28.9
10
11
161.0
136.8
153.3
151.9
154.6
153.3
−297.0 [+85.9]
−289.5 [+76.4]
−297.0 [+81.9]
−287.5 [+87.3]
−298.5 [+85.1]
−298.1 [+85.7]
37.7 [−40.0]
34.5 [−22.9]
38.1 [−34.9]
37.3 [−33.8]
38.1 [−34.3]
38.3 [−34.9]
−29.5
−42.3
−39.0
−25.9
−31.4
−36.7
12c
13d
14
52.2 [+10.4] (Rꢀ)
50.2 [ 4.4] (R)
146.6 [+18.5] (Rꢀ)
58.8 [+21.8] (R)
142.7 [<1] (Rꢀ)
55.1 [+19.1] (R)
146.6 [ 2.7] (Rꢀ)
59.4 [+20.2] (R)
146.5 [ 2.7] (Rꢀ)
147.4 [ 6.0] (R, Rꢀ)
15e
16 f
17g
18h
145.8
161.5
–
37.6 [−33.2]
38.5 [−50.4]
−39.1
−28.8
−324.8
10.0 [−32,4](29Si; R)
10.0 [+5.8] (29Si; Rꢀ)
aCoupling constants J(31P, 13C), J(31P, 15N), and J(31P, 29Si) are given in brackets ( 0.1 Hz). Isotope-induced chemical shifts 1ꢀ14/15N(31P) are
given in ppb ( 1 or less), and a negative sign denotes that the resonance signal of the heavy isotopomer is shifted to lower frequency.
bRotation about the P N bond is slow on the NMR time scale. 13C NMR spectrum measured at −40◦C in CD2Cl2: δ13C 45.1 [+27.4] (N CHsyn),
49.0 [−8.4] (N CHanti).
cSolid-state 13C and 31P MAS spectra: δ13C 51.0, 142.3 (N CH2Ph), 60.0, 30.6 (N tBu), 39.1, 27.3 (P tBu); δ31P 167.1.
dNMR spectra measured at −60◦C in CD2Cl2: δ13C 41.7 [−7.1] (N CH2 anti), 146.4 [+23.4] (N Phsyn) (50%), 55.6 [+39.8] (N CH2 syn), 144.2
[−13.6] (N Phanti) (50%); δ15N −298.6 [75.7] (50%), −298.9 [91.9] (50%); δ31P 157.1 (50%), 152.8 (50%).
eNMR spectra measured at −60◦C in CD2Cl2: δ13C 47.8 [broad] (CH2 anti), 147.2 [+25.6] (N Phsyn) (55%), 60.4 [+40.3] (N CH2 syn), 144.9
[−12.7] (N Phanti) (45%); δ15N −296.5 [80.4] (45%), −298.0 [87.3] (55%); δ31P 157.7 (45%), 152.9 (55%).
f NMR spectra measured at −60◦C in CD2Cl2: δ13C 50.3 [broad] (N CH2 anti), 146.9 [+22.9] (N Phsyn) (50%), 64.7 [+43.1] (N CH2 syn), 144.4
[−13.1] (N Phanti) (50%); δ15N −302.7 [78.3] (50%), −298.8 [84.2] (50%); δ31P 161.1 (50%), 156.3 (50%).
gNMR spectra measured at −65◦C in CD2Cl2: δ13C 149.3 [+23.4] (N Phsyn), 144.5 [−8.2] (N Phanti); solid-state 13C and 31P MAS spectra:
δ13C 150.3, 145.3 (N Ph), 38.2, 27.0 (P tBu); δ31P 157.0.
hData from Ref. [8].

672 Wrackmeyer et al.
31P NMR signals. Such interactions are absent in the
phosphorus oxidation state from P(III) to P(V) as
1
1
in 4 and 4Se the values ꢀ14/15N(31P) become less
31P/15N isotopomer (15N: I = ) and, therefore, the
2
induced 31P magnetization of this isotopomer de-
cays more slowly, giving rise to sharper signals. The
negative as observed previously for other exam-
ples [8,20a,25]. Although the isotope-induced chem-
ical shifts 1ꢀ14/15N(31P) must be regarded mainly
as a consequence of electron-mediated effects [26]
(unlike effects arising from 1/2H substitution), in
the cases studied here and in similar phosphorus-
nitrogen compounds, a straightforward correlation
1
15N satellites because of J(31P, 15N) can be readily
detected (in spite of the low natural abundance of
15N: 0.37%), since the 31P NMR signal of the 31P/14N
isotopomer is suppressed to a large extent [15] (see
Fig. 3). These experiments are carried out most con-
veniently by extension of polarization transfer pulse
sequences such as INEPT [16]. They allow us to mea-
1
with changes in the coupling constants J(31P, 15N),
also an electron-mediated quantity, is not obvious.
1
This is in contrast to the situation for ꢀ12/13C(29Si)
1
sure J(31P, 15N) and at the same time the isotope-
1
[27] or ꢀ12/13C(119Sn) [28] where such correlations
induced chemical shifts 1ꢀ14/15N(31P) with high preci-
sion at natural abundance of 15N [8,9,15,24]. Because
of the high NMR sensitivity of the 31P nucleus, this
information is available even after some minutes, in
general within less than 1 h of instrument time, even
for moderately concentrated samples (10–20 mg in
0.6 ml of solvent).
exist. Since the magnitude of the coupling constants
1 J(31P, 15N) depends in a complex way on the nature
of the phosphorus lone pair, crude correlations with
the 1ꢀ14/15N(31P) may just indicate different phospho-
rus coordination numbers and oxidation states.
1
The smallest (negative) values ꢀ14/15N(31P) are
EXPERIMENTAL
found for compounds with two Me3Si groups at
the nitrogen atom, followed by the combinations
alkyl/Me3Si and alkyl/alkyl. The presence of N-aryl
groups gives rise to larger negative values. The in-
fluence of substituents at the phosphorus atom is
rather small. Thus, the 1ꢀ14/15N(31P) value for 20
is somewhat more negative than that for the cor-
responding compounds 7 and 11. By changing the
All synthetic work and the handling of samples were
carried out under an inert atmosphere (N2 or Ar), us-
ing carefully dried glassware and dry solvents. Phos-
t
phorus halides (Ph2PCl, PhPCl2, BuPCl2, PCl3), all
amines, chlorotrimethylsilane, and BuLi (1.6 M in
hexane) were commercially available. The amines
were dried according to established procedures, and
FIGURE 3 121.5 MHz 31P HEED NMR experiments (based on refocused INEPT with 1H decoupling) shown for the (A)
compounds 12 in C6D6 (3%) and (B) 5 in C6D6 (25%), both samples in 5-mm tubes. Conditions for A: 320 transients; acquisition
time 3 s; Hahn-echo delay 0.1 s; repetition delay 10 s. Conditions for B: 32 transients; acquisition time 4 s; Hahn-echo delay
0.6 s; repetition delay 5 s. In the case of 12, the 14N quadrupolar relaxation rate is rather slow, giving rise to a markedly broad
31P NMR signal (upper trace of A), which is readily suppressed completely by a short Hahn-echo delay (0.1 s). In the case of 5,
the 14N quadrupolar relaxation rate is fast and therefore, the 31P NMR signal of the 31P/14N isotopomer is much less broadened
when compared with 12. As a consequence, a much longer Hahn-echo delay (0.6 s) is required in order to suppress at least
partly the signal of the 31P/14N isotopomer.

Aminophosphanes with Bulky Amino Groups 673
TABLE 4 Selected NMR Dataa of 3-tert-Butyl-2-chloro-1,3,2-oxazaphospholane 19 and Benzyl(tert-Butyl)aminodichlorophos-
phane 20 in C6D6 at (23 1)◦C
No.
δ
31P
δ
15N
δ
13C(N)
1ꢀ14/15N( 31P)
−33.2
19
155.1
−274.8 [+78.1]
−277.0 [+100.4]
53.3 [6.5] (NCH2)
41.9 [8.2] (NC)
70.5 [8.2] (OCH2)
48.6 [−6.5] (NCH2)
60.2 [+24.0] (NC)
20
177.7
−37.4
aCoupling constants J(31P, 13C), J(31P, 15N), and J(31P, 29Si) are given in brackets ( 0.1 Hz). Isotope-induced chemical shifts 1ꢀ14/15N(31P) are
given in ppb ( 1 or less), and a negative sign denotes that the resonance signal of the heavy isotopomer is shifted to lower frequency.
freshly distilled before use. N-Silylated amines were
prepared according to reported procedures [29]. The
preparation of some of the compounds by using
slightly different routes has been reported previously
(1 [11a,b], 2 [11c], 5 [10], 6 [17d,30], 8 [30], 9 [10c],
12 [31], 17 [32], 18 [10c], and 19 [33]). The selenide
4Se was prepared only on NMR scale from 4 and
an excess of selenium. Progress of all reactions was
monitored by NMR spectroscopy.
Synthesis of the N-trimethylsilyl-
aminodiphenylphosphanes 1–5.
General Procedures
Trimethylsilyl(butyl)aminodiphenylphosphane 1.
A solution of butylaminodiphenylphosphane [34]
(2.03 g, 7.9 mmol) in hexane (50 ml) was cooled to
n
−78◦C, and a solution of BuLi in hexane (4.9 ml,
1.6 M) was slowly added. The stirred reaction
mixture was warmed to room temperature, and
then cooled again to −78◦C. Chlorotrimethylsilane
(0.86 g, 7.9 mmol) was slowly added under vigor-
ous stirring. This mixture was warmed to room tem-
perature and kept stirring for 0.5 h. Insoluble mate-
rial was filtered off, and the solvent was removed in
vacuo; product 1 was left as a yellow oil (2.52 g, 97%).
1H NMR (300 MHz; C6D6): δ1H = 7.50–7.05 (m, 10H,
PPh2), 3.36, 1.37, 1.23, 0.88 (m, m, m, t, 9H, N Bu),
0.45 [1.4] (d, 9H, N SiMe3).
NMR spectra were recorded from samples in
C6D6 at (23 1)◦C (if not stated otherwise), using
Bruker DPX 300, AC 300, DRX 500, JEOL 270,
and JEOL 400 instruments, equipped with multin-
uclear broad band probeheads. Chemical shifts are
given with respect to solvent signals [δ1H (C6D5H)
= 7.15; δ13C (C6D6) = 128.0, 53.8 (CD2Cl2)] and
external references for δ31P (H3PO4 (aq)) = 0 with
ꢁ(31P) = 40.480747 MHz; δ15N (MeNO2, neat) = 0
1
with ꢁ(15N) = 10.136767 MHz; 15N{ H} NMR spec-
tra were measured by the refocused INEPT pulse
sequence [16], based either on 1 J(15N, 1H) for
Trimethylsilyl(phenyl)aminodiphenylphosphane 2.
A suspension of freshly prepared N-lithio-trimethyl-
silylaniline (8 mmol) in hexane (50 ml) was cooled
to −78◦C and diphenylphosphorus chloride (0.86 g,
7.9 mmol) was slowly added. This mixture was
warmed to room temperature and kept stirring for
0.5 h. Insoluble material was filtered off, and the
solvent was removed in vacuo; the product 2 (1.97 g,
93%) was obtained as a colorless liquid.
1
the amino nitrogen or 2 J(15N, H) ≈ 10 Hz for the
pyridine-nitrogen or directly by using inverse gated
1H decoupling. 31P NMR spectra for measuring
1
isotope-induced chemical shifts ꢀ14/15N(31P) were
recorded by the INEPT–HEED pulse sequence [15],
and polarization transfer was based on a coupling
constant 3 J(31P, 1Hortho) = 10 Hz for phenylphospho-
rus derivatives and 3 J(31P, 1H) = 14.5 Hz for tert-
butylphosphorus compounds, using Hahn-echo de-
lays between 0.05 s and 1.5 s, depending on the
width of the 31P NMR signal of the 31P/14N iso-
topomer (see Fig. 3). Solid-state 13C (75.5 MHz)
and 31P (121.5 MHz) MAS NMR spectra (conven-
tional Hartmann–Hahn cross-polarization (CP) con-
ditions) were measured from samples packed into
air-tight inserts fitting into 5 mm ZrO2 rotors, using
a Bruker MSL 300 spectrometer.
1H NMR (400 MHz): δ = 7.49–6.67 (m, 15H,
N Ph, PPh2), 0.33 [1.8] (d, 9H, N SiMe3); 13C NMR
(67.9 MHz): δ [J(31P, 13C)] = 145.5 [7.8], 124.6, 130.2,
128.2 (N Ph C1,2,6,3,5,4), 139.7 [17.6], 133.3 [20.7],
127.9 [6.2], 128.5 (Ph Ci, Co, Cm, Cp), 1.4 [8.3]
(N SiMe3).
Compounds 3, 4 (similar compounds have been
reported [35]), and 5 were prepared in the same way
as 2 after N-lithiation of the respective amines.
1
Electron impact (EI) mass spectra at 70 eV were
recorded using a VARIAN MAT CH7 instrument with
direct inlet. Mass data are given for the isotopes 1H,
12C, 14N, 28Si, 31P, and 35Cl. Melting points (uncor-
rected) were measured using a Bu¨chi 510 apparatus.
3: yield 87% (1.89 g), yellow solid. H NMR: δ
[J(31P, 1H)] = 6.42, 6.71, 6.28, 7.96 (m, m, m, 4H, pyr.-
H3,4,5,6), 7.44, 7.06 (m, 4H, m, 6H, PPh2); 0.55 [1.6] (d,
9H, N SiMe3); 13C NMR: δ [J(31P, 13C)] = 159.3 [6.9],
116.7 [4.5], 135.6, 116.2, 146.8 (pyr.-C2,3,4,5,6), 138.0

674 Wrackmeyer et al.
[22.6], 131.2 [19.6], 128.3 [4.8], 128.1 (PPh Ci, Co,
Cm, Cp), 2.5 [10.3] (N SiMe3).
3H, N Me), 1.12 [2.1] (d, 9H, N tBu), 1.04 [14.7] (d,
9H, P tBu).
4: yield 63% (1.0 g), yellow liquid. 1H NMR:
δ [J(31P, 1H)] = 7.82, 5.93 (m, 2H, m, 1H, pyr.-
H4,6,5), 7.79, 7.21 (m, 4H, m, 6H, PPh2); 0.75 [1.9]
(d, N SiMe3); 13C NMR: δ [J(31P, 13C)] = 164.1 [5.8],
156.8, 113.7, (pyr.-C2,4,6,5), 139.1 [19.0], 132.6 [21.4],
128.3 [5.7], 128.6 (PPh Ci, Co, Cm, Cp), 3.0 [10.9]
(N SiMe3).
11: m.p. 78–79◦C; yield 58%, colorless crys-
1
1
tals from pentane at −78◦C. H NMR [n J(31P, H)]:
δ = 7.3–7.1 (m, 5H, Ph), 4.57, 4.07 (m, 2H, NCH2),
1.31 [1.0] (d, 9H, N tBu), 1.07 [14.8] (d, 9H, P tBu);
EIMS: 286 (2%, M+), 252 (15%, MH+ − Cl), 210 (29%,
MH+ − Ph), 91 (100%, PhCH2+).
12: colorless liquid; decomposes during at-
1
1
5: yield 92% (1.5 g), viscous, colorless liquid.
1H NMR (400 MHz; C7D8): δ = 7.54, 7.09 (m, 4H,
m, 6H, PPh2), 0.20 (s, 18H, N (SiMe3)2); 13C NMR
(100.5 MHz): δ13C [J(31P, 13C)] = 140.8 [24.6], 130.7
[19.6], 127.8 [4.9], 127.7 (PPh Ci, Co, Cm, Cp), 4.1
[7.4] (N SiMe3).
tempted distillation. H NMR [n J(31P, H)]: δ = 2.75
[12.0] (d, broad, 1H, NH), 1.12 [1.1] (d, 9H, N tBu),
0.99 [13.4] (d, 9H, P tBu).
13: b.p. 112–113◦C (10−2 Torr); yield 51%, color-
less liquid. 1H NMR [n J(31P, 1H)]: δ = 7.2–7.0 (m, 5H,
N Ph), 3.4, 0.88 (m, t, 2H, 3H, N Et), 0.98 [14.5] (d,
9H, P tBu). C12H19ClNP (243.70) calc./found (%): C
59.1/59.3 H 7.9/8.0 N 5.75/5.8.
Synthesis of the
Amino(chloro)phenylphosphanes 6–8 and of the
Amino(chloro)tert-butylphosphanes 9–18.
General Procedures
14: b.p. 114–115◦C (10−2 Torr); yield 64%, col-
1
1
orless liquid. H NMR [n J(31P, H)]: δ = 7.2–6.9 (m,
5H, N Ph), 3.78, 0.99, 0.91 (m, d, d, 1H, 3H, 3H,
N
IPr), 0.85 [14.3] (d, 9H, P tBu); EIMS: 257 (10%,
A solution of the respective amine (21.0 mmol) in
hexane (100 ml) was cooled to −78◦C and a solu-
tion of BuLi (20 mmol) in hexane (12.5 ml, 1.6 M)
was added under vigorous stirring. The mixture was
warmed to room temperature and heated at reflux
for 3 h. Then a solution of PhPCl2 (3.6 g, 20 mmol)
M+), 222 (18%, M+ − Cl), 200 (76%, M+ − Bu), 122
(100%, M+ − Ph). C13H21ClNP (257.73) calc./found:
C 60.6/60.4 H 8.2/8.3 N 5.4/5.7.
15: b.p. 140–150◦C (10−2 Torr) partial decompo-
sition; yield 22%, colorless oil. 1H NMR [n J(31P, 1H)]:
δ = 7.3–7.1 (m, 5H, N Ph), 3.45, 1.39, 1.25, 0.85 (m,
m, m, t, 9H, N Bu), 1.00 [14.7] (d, 9H, P tBu).
16: yellowish, oily liquid; decomposes during at-
t
or BuPCl2 (3.2 g, 20 mmol) in hexane (50 ml) was
added dropwise at room temperature, and the reac-
tion mixture was kept stirring for 24 h. Insoluble ma-
terial was filtered off, hexane was removed in vacuo,
and samples of the residue were checked for purity
by NMR spectroscopy. In general the products could
be used for reactions [3,4] without further purifica-
tion. In most cases the residues were purified either
by distillation or recrystallization.
1
1
tempted distillation. H NMR [n J(31P, H)]: δ = 7.1–
6.8 (m, 5H, Ph), 4.51 (m, 2H, NCH2), 0.94 [14.5] (d,
9H, P tBu).
17: m.p. 51–53◦C; yield 41%, colorless crystals
from pentane at −30◦C. H NMR [n J(31P, H)]: δ =
1
1
7.1–6.8 (m, 10H, NPh2), 1.04 [15.2] (d, 9H, P tBu).
6: b.p. 101–106◦C (10−2 Torr); yield 53%, colorless
1
1
oil. H NMR [n J(31P, H)]: δ = 8.0–7.5 (m, 10H, Ph,
P Ph), 4.50, 4.34 (m, m, 2H, NCH2), 2.64 [10.2] (d,
3H, NMe).
Synthesis of Benzyl(tert-butyl)amino-
dichlorophosphane 20
Phosphorus trichloride (16.5 g, 120 mmol) was dis-
solved in ether (100 ml) and added dropwise at
0◦C to a solution of benzyl(tert-butyl)amine (19.6 g,
120 mmol) and triethylamine (12.1 g, 120 mmol) in
ether (200 ml). After stirring for 24 h at room tem-
perature, insoluble material was filtered off, and the
solvent was removed in vacuo. A slightly yellowish
oily liquid was left which was identified as pure 20
7: m.p. 53–55◦C; yield 60%, colorless crystals
from pentane at −78◦C. H NMR [n J(31P, H)]: δ =
7.8–6.8 (m, 10H, Ph, P Ph), 4.52 [5.6], 4.14 [3.8] (m,
m, 2H, NCH2), 1.45 [1.5] (d, 9H, NtBu). C17H21ClNP
(305.77) calc./found (%): C 64.7/66.8 H 8.9/8.9 N
6.75/5.6
1
1
8: b.p. 110◦C (10−2 Torr); yield 43%, colorless oil.
1H NMR [n J(31P, H)]: δ = 8.0–7.3 (m, 10H, N Ph,
1
1
(yield 86%), ready for further reactions. H NMR
P Ph), 3.6, 1.13 (m, t, 2H, 3H, N Et).
1
[n J(31P, H)]: δ = 7.4–7.1 (m, 5H, Ph), 4.76 [3.8] (d,
9: b.p. 45–48◦C (10−2 Torr); yield 52%, color-
2H, NCH2), 1.44 [3.4] (d, 9H, N tBu).
less liquid. H NMR (CD2Cl2; −40◦C) [n J(31P, H)]:
δ = 3.68, 2.72, 1.17, 0.92, 0.90, 0.74 (m, m, d, d, 1H,
1H, 3H, 3H, 3H, 3H, NIPr2)1.04 [14.9] (d, 9H, P tBu).
10: b.p. 100–105◦C (10−2 Torr); yield 68%, color-
1
1
X-Ray Structural Analysis of 11 [12]
Intensity data collection was carried out on a
Siemens P4 diffractometer with Mo Kꢀ-radiation
less liquid. H NMR [n J(31P, H)]: δ = 2.46 [4.1] (d,
1
1

Aminophosphanes with Bulky Amino Groups 675
[12] Crystallographic data (excluding structure factors)
for the structure reported in this paper have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC
179988 (11). Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44 (0)1223/336033;
e-mail: deposit@ccdc.cam.ac.uk).
[13] Morris, E. D. Jr.; Nordman, C. E. Inorg Chem 1969,
8, 1673.
[14] Nifantyev, E. E.; Gratchev, M. K.; Burmistrov, S. Yu.
Phosphorus Sulfur Silicon 1992, 70, 159.
[15] Kupcˇe, E.; Wrackmeyer, B. J Magn Reson 1992, 97,
568.
[16] (a) Morris, G. A.; Freeman, R. J Am Chem Soc 1979,
101, 760; (b) Morris, G. A. J Am Chem Soc 1980, 102,
428; (c) Burum, D. P.; Ernst, R. R. J Magn Reson 1980,
39, 163.
[17] (a) Cowley, A. H.; Dewar, M. J. S.; Jackson, W. R.;
Jennings, W. B. J Am Chem Soc 1970, 92, 5206;
(b) Simonnin, M. P.; Lequan, R.-M.; Wehrli, F. J
Chem Soc, Chem Commun 1972, 1204; (c) Barlos, K.;
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Reson Chem 1991, 29, 1045; (b) Wrackmeyer, B.;
Kupcˇe, E.; Kehr, G.; Schiller, J. Magn Reson Chem
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(λ = 71.073 pm, graphite monochromator) at 173 K.
All hydrogen atoms were on calculated positions
and were refined with isotropic thermal param-
eters (1.2 times the equivalent temperature fac-
tor of the atom to which they are attached). All
non-hydrogen atoms have been refined anisotropi-
cally. Compound 11, a colourless isometrical crys-
tal of dimensions 0.35 × 0.30 × 0.30 mm, crystal-
lizes orthorhombically, space group P212121; a =
886.8(2), b = 1069.8(2), c = 1753.4(4) pm, Z = 4, µ =
0.312 mm−1; 2232 reflections collected in the range
(2–24.8)◦ in ꢁ, 2061 reflections independent, 1907
reflections assigned to be observed (I > 2σ(I)); full
matrix least squares refinement on F2 with 164 pa-
rameters, R1/wR2-values 0.0300:0.0742, no absorp-
tion correction, max/min residual electron density
0.34/−0.22 e 10−6 pm−3.
ACKNOWLEDGMENT
We thank Dr. A. Sebald for measuring the solid-state
13C and 31P MAS NMR spectra.
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