peri-interactions in naphthalenes, 10 [1]. In search of independent criteria for N→P bonding: Protonation studies on (8-diethylamino-naphth-1-yl)-diphenyl-phosphine

Article abstract of DOI:10.1515/znb-2003-0710

Enhancement of the basicity of the amino group in (8-dialkylamino-naphth-1-yl)-diphenylphosphines diverts protonation from the P to the N atom. Thus the cation 8-Et₂N⁺(H)-C ₁₀H₆-PPh₂ becomes available whose ¹H and ³¹P NMR spectra provide arguments against dative N→P interactions in the phosphines and their quaternary phosphonium salts. Likewise, the X-ray structure of 8-Et₂N-C₁₀H₆-PPh ₂ does not indicate such interactions.

Full text of DOI:10.1515/znb-2003-0710

peri-Interactions in Naphthalenes, 10 [1]. In Search of Independent
Criteria for N−→ P Bonding: Protonation Studies on
(8-Diethylamino-naphth-1-yl)-diphenyl-phosphine
Gu¨nter Paulus Schiemenz, Christian Na¨ther, and Simon Po¨rksen
Institut fu¨r Anorganische Chemie der Universita¨t, 24098 Kiel, Germany
Reprint requests to Prof. Dr. G. P. Schiemenz. Fax: +49 (0)431 880 1558.
E-mail: schiemenz@ac.uni-kiel.de
Z. Naturforsch. 58b, 663 – 671 (2003); received February 10, 2003
Enhancement of the basicity of the amino group in (8-dialkylamino-naphth-1-yl)-diphenyl-
phosphines diverts protonation from the P to the N atom. Thus the cation 8-Et2N+(H)-C10H6-PPh2
1
becomes available whose H and 31P NMR spectra provide arguments against dative N→P inter-
actions in the phosphines and their quaternary phosphonium salts. Likewise, the X-ray structure of
8-Et2N-C10H6-PPh2 does not indicate such interactions.
Key words: N→P Bonding, NMR Protonation Shifts, d(N···P) Distances
Introduction
tently had been expressed by the formulae 5 – 7B with
the N→P/Si symbol [4, 5, 7 – 10, 12, 13, 22 – 24]. The
claim rests exclusively on the fact that d(N···P/Si) is
smaller than the sum of the respective van der Waals
radii, Σr(vdWN,P/Si) [4 – 10, 12b, 25]. While the rigid-
ity of the C10 skeleton renders Σr(vdW) an inappro-
priate reference for peri-substituted naphthalenes [1,
2, 11, 15, 17 – 20], it has been observed that in such
silanes the criteria of steric hindrance are less pro-
nounced than in several 1,8-disubstituted naphthalenes
which lack the possibility of intersubstituent donor
/ acceptor interaction [15]. Though alternative ratio-
nalizations are at hand, the question has been raised
whether the phenomenon may reflect an attractive con-
tribution to the overall effect in which the repulsive one
dominates [15, 26].
In 8-dialkylamino-naphth-1-yl-phosphorus com-
pounds (“DAN-P”), suitably substituted phosphorus is
able to overcome the geometric resistance of the C10
skeleton and to engage in a N−P bond of conventional
length (213.2 pm in 1) [2]. Concomitantly, the peri
bonds P−C(1) and N−C(8) are inclined towards each
other (splay angle −11.5◦ in 1). The new bond is one
of four two-electron bonds emanating from the N atom
which thereby has ammonium character. The P atom
may (as in 1A) or may not be the site of a negative
charge. The N−P bond is conveniently described as a
covalent single bond whose two electrons are donated
by the N atom as a nucleophile and accepted by the
P atom as an electrophile. It is therefore adequately
called a dative bond and hence may be depicted by the
common symbol of the latter, hence as N→P, as in 1B,
Obviously, no answer can be provided solely by re-
course to d(N···P/Si). It is indispensable to search for
in analogy of the familiar representation of the amine independent criteria which respond more specifically
oxides by the formula R3N→O [3].
to dative N→P/Si bonding. The decisive feature is the
availability of the lone pair at the N atom for peri inter-
actions. Insight into its role may be expected if it could
be blocked with as little change in the steric situation
as possible and respective derivatives studied for com-
parison.
On the other hand, the structures of DAN-
phosphines 2 [1, 4 – 7], DAN-phosphonium salts 3 [6 –
11], and DAN-silanes 4 [12– 14] exhibit the criteria of
steric repulsion between the peri substituents [1, 2, 11,
15 – 20], viz. interatomic distances d(N···P/Si) = ca.
280 20 pm [1, 4 – 14] and positive splay angles [1,
In DAN-phosphines 2, the nucleophilicity of the N
2, 15, 17 – 21]. Nevertheless, it has been claimed that atom could be eliminated by the use of the lone pair for
in these compounds a dative interaction (albeit a weak a new σ-bond, hence by turning to 8-ammonio-sub-
one [4, 7, 8, 12b, 13, 22]) is operative which consis- stituted naphth-1-yl-phosphines (2 → 8). A significant
c
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Scheme 1.
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665
charge transfer from the donor D to the acceptor A is librium 5A/B ꢀ 2 would enable even small quantities
typical for dative bonds [27] and should therefore be a of 2 to be trapped by N-protonation (2 → 8b). A sim-
prominent feature of the DAN-phosphines if N→P in- ilar degree of ammonium character of the N atom in
teraction played the alleged role. More clearly than in the neutral species 5A/B and in the ammonium salt 8b
1
the formula D→A, such transfer is expressed (though would cause the protonation shift of N−C− H NMR
possibly overemphasized [28]) in the alternative for- signals to be unusually small.
mula D+−A− (e. g. 1A and R3N+−O|− rather than
Unfortunately, both N-alkylation and N-protonation
of DAN-phosphines face severe preparative difficul-
1B and R3N →O for 1 and the amine oxides, respec-
tively), hence 5A for the DAN-phosphines [29]. If 5A
were an adequate formula of the DAN-phosphines, the
latter would share an electron depletion at the N atom
with their ammonium derivatives 8. This should be re-
ties. 9a is not easily methylated [36]; peri sub-
stituents further reduce the nucleophilicity of the
Me2N group [37, 38]. On the other hand, tri-
arylphosphines exhibit a much greater nucleophilic-
ity towards alkyl halides than N,N-dimethylanilines.
This is borne out by the exclusive P-alkylation
of tertiary (4-dimethylamino-phenyl)-phosphines (10)
[39] and of (4-dimethylamino-naphth-1-yl)-diphenyl-
phosphine (11a) [30]. 8-Trialkylammonio-substituted
(naphth-1-yl)-phosphines 8a thus remain out of reach.
We therefore focussed our attention on selective
N-protonation of DAN-phosphines. N,N-dimethyl-
anilines are much more basic than most tertiary phos-
phines. E. g., 10a and 11a are first protonated at the
N atom [1, 40]. However, DAN-phosphines exhibit an
extraordinary P-basicicity and are protonated exclu-
sively at the P atom [1, 6]; as with the proton sponge
[41], bis-protonation of both basic centres does not
take place [1].
To achieve N-protonation, it would be essential ei-
ther to decrease the basicity of the phosphino func-
tion or to increase the basicity of the amino group.
Secondary phosphines R2PH are frequently consider-
ably weaker bases than similar tertiary phosphines R3P
[42]; hence, phosphines (DAN)(R)PH looked promis-
ing. However, 12a exhibited an unusual P-basicity and
was again protonated at the P atom [1]. It remained
to enhance the N-basicity of DAN-phosphines. This
would likewise improve the conditions for dative N→P
bonding, so that respective phosphines 2 deserve par-
ticular attention.
1
flected by similar positions of the H NMR signals of
1
the protons within the R groups at N, δ(N−C− H).
If, on the other hand, N→P interaction played no sig-
nificant role, the DAN-phosphines and their ammo-
nium derivatives should differ to a similar degree as 1-
1
dimethylamino-naphthalene(9a, δ(N−C− H) = 2.91
1
in CDCl3 [30]) and its methiodide (δ(N−C − H) =
4.12 in CF3COOH [31]) do. To be sure, aromatic ring
current effects of the C10 skeleton and of the phenyl
substituents at the P atom have a strong impact on the
signal positions [2, 15, 17, 30], but they can be as-
sumed to be roughly constant provided that the steric
changes are kept at a minimum.
In principle, quaternization of the R2N group
(2 → 8a) would serve the envisaged purpose, but
it would significantly enhance the steric congestion
within the peri space. E. g., a trimethylammonio group
would sterically resemble a tert-butyl group which is
known to cause exceptional steric hindrance [32]. N-
alkylation would therefore cause a stronger deforma-
tion of the C10 skeleton (including an increased dis-
tance d(N···P)) which might have repercussions on
1
δ(N−C− H). In addition, replacement of a bond be-
tween N and P (Pauling electronegativity 2.1 [33, 34])
in 5 by a bond between N and C (Pauling elec-
tronegativity 2.5 [33]) in 8a would be expected to
1
induce a downfield shift of N−C− H signals [35]
which has no bearing on the problem under investi-
gation.
Results and Discussion
N-Protonation would be preferable for several rea-
sons. Hydrogen and phosphorus happen to have equal
Though the phenomenon defies a straightforward
electronegativities (2.1 [33]) so that the effect of the re- explanation, it is known that N,N-dialkylanilines Ar-
placement should be kept at a minimum. Sterically, the NR1R2 have a maximum basicity for R1 = R2 = Et [43].
Me2(H)N+ group would resemble an isopropyl group It is also shown by the N,N-dialkyl-o-toluidines(2-Me-
which in a hetera-naphthalene has been shown to fit C6H4NR2, R = Et/Me: ∆pKa = 1.32 [43]). We there-
reasonably well into the peri space in a similar manner fore turned to (8-diethylamino-naphth-1-yl)-diphenyl-
as a Me2N group does in DAN-P/Si compounds [19]. phosphine (2b), which was obtained in 37% yield by
While 5A/B lacks a basic nitrogen function, an equi- lithiation of 1-diethylamino-naphthalene (9b) in the 8-
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G. P. Schiemenz et al. · peri-Interactions in Naphthalenes, 10
The C10 skeleton is almost planar, and both the
N atom and the P atom reside almost in the C10
plane (torsional angles P−C(1)−C(9)−C(8) −0.9◦,
N−C(8)−C(9)−C(1) −5.8◦). Consequently, the N···P
interatomic connecting line is also very close to the C10
plane (N···P−C(1)−C(9) +3.1◦, P···N−C(8)−C(9)
+6.4◦). On the other hand, the directions of the N−CH2
bonds imply that the lone pair at N does not point to-
wards the P atom: One of them is virtually perpendic-
ular to the C10 plane (C(13)−N−C(8)−C(9) −90.9◦),
the other one in the anticlinal sector with respect to the
C(1)···C(8) connecting line (C(11)−N−C(8)−C(9)
+145.8◦) so that the occupied orbital at N would be
estimated to reside approximately at the borderline be-
tween the synperiplanar and the synclinal sectors [46].
Of the two P−CPh bonds, one is coplanar with the C10
plane in the sterically most favourable antiperiplanar
direction (C(31)−P−C(1)−C(9) −179.7◦), the other
one not far from orthogonality in the synclinal sector
(C(21)−P−C(1)−C(9)−77.1◦) (hence, again in a ster-
ically favourable position). The lone pair at P then is lo-
cated in the synclinal sector at the opposite face of the
C10 plane so that Coulomb repulsion of the lone pairs
is minimized. The joint effects of Coulomb repulsion
and the steric requirements then account for the con-
formation of the substituents, whereas no involvement
of the N lone pair in the N···P interaction is indicated.
Fig. 1. Crystal structure of 2b with labelling and displace-
ment ellipsoids drawn at the 50% probability level.
position and subsequent reaction with chloro-diphenyl-
phosphine (cf. Scheme 1). Reaction with iodomethane
proceeded smoothly at room temperature and afforded
the quaternary phosphonium iodide 3a in quantitative
yield from which the tetraphenylborate 3b was pre-
pared.
A single crystal X-ray structure determination of
2b revealed a structure which closely resembles that
of the corresponding N,N-dimethylamino compound
2a [5]. The distance d(N···P), 280.3 pm, is ca.
30 pm longer than estimated for a DAN-phosphine
of ideal geometry [1, 2, 11, 16 – 20, 44] and slightly
longer than in 2a (270.6/272.9 pm in two independent
molecules [5]), but almost identical with d(N···P) =
278.0/279.2 pm in 12b [4] and slightly shorter than
d(N···P) = 282.0/282.8/288.5 pm in 12c [6]. The
gradual increase 2a < 12b < 2b < 12c is likely
to reflect enhanced steric hindrance, though the ad-
ditional carbon atoms of the ethyl groups in 2b re-
side outside the peri space and thus do not visibly
increase the congestion within it (see Fig. 1). The
bay angles P−C(1)−C(9) (122.5◦), C(1)−C(9)−C(8)
(125.0◦) and N−C(8)−C(9) (119.4◦) yield a splay an-
gle of +6.9◦ which is again an indication of consider-
able steric hindrance. As elsewhere, C(1)−C(9)−C(8)
is the largest and N−C(8)−C(9) the smallest angle
[17,20]. Likewise, the non-bonding interatomic dis-
tance d(C(1)···C(8)) = 255.5 pm exceeds the distance
in naphthalene of ideal geometry by 8.7 pm [2, 11, 15],
whereas the opposite peri distance d(C(4)···C(5)) =
244.3 pm is slightly compressed [45]. Compound 2b
is thus a flawless example of a 1,8-disubstituted naph-
thalene with repulsive steric interactions between the
peri-substituents where no N→P dative bond is indi-
cated.
The angle C(1)−P−C(31) (i. e. C(1) of the antiperi-
planar phenyl group), 102.9◦, is within the range of the
C−P−C angles in Ph3P (102.1– 103.6◦ [47]). Because
of d(P−C(1)) > d(N−C(8)) the angle N···P−C(1) is
smaller than 90◦, viz. 76.3◦. As a trivial geometric con-
sequence, the atoms N, P and C(31) are aligned vir-
tually linearly in the C10 plane (angle N···P−C(31)
177.1◦). This linearity would permit to describe the en-
vironment of the P atom as a distorted trigonal bipyra-
mid with N and C(31) in apical positions [48] and with
a much deformed equatorial plane in which the P lone
pair occupies one of the coordination sites [17,20,49].
However, the arrangement has nothing to do with pen-
tacoordination; it rather suffices to invalidate conclu-
sions in favour of attractive N/Te and F/Se interac-
tions in the ditelluride (8-Me2N- C10H6-Te-)2 and an
aryl-(8-fluoro-naphth-1-yl)-selenide derived from the
“T-shaped alignments” of N···Te(C(1))−Te [50] and
F···Se(C(1))−CAr [51].
NMR spectra of the isolated compounds
In the 31P NMR spectrum of 2b, the signal position
at low field (δ = +0.24 ppm) is virtually identical with
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G. P. Schiemenz et al. · peri-Interactions in Naphthalenes, 10
667
that of 2a (δ = +0.54 ppm [1,44]). δ = +24.46 ppm action. The phenomenon resembles the very large cou-
2
of 3b is unconspicuous; J(1H, 31P) = 13.5 Hz of the pling constants of peri-bound 19F and 31P for which a
P−C1H3 signal in the 1H NMR spectrum is proof that theory has been developed which assumes orbital in-
the methylation had occurred at the P centre.
teractions which, however, are not bonding [53].
In 2b and its methyl-phosphonium salts 3a,b,
the geminal protons of the N−CH2 groups are di-
astereotopic due to restricted rotation around the
N−C(8) bond [20]. Correspondingly, the N−C1H2 re-
In the 1H NMR spectrum, the sharp N−CH2−C1H3
triplet experienced a downfield shift of ∆δ = 0.32 ppm.
The N−C1H2 protons gave two ill-resolved multiplets
at 3.83 and 4.00 ppm which indicate protonation shifts
of 1.02 and 0.98 ppm, larger than in the proton sponge
(∆δ = 0.80 ppm [38a]), almost double as large as in
11a,b (∆δ = 0.56 ppm [1]) and more similar to the
quaternization shift ∆δ = 1.21 ppm of the N−C1H3
signals of 9a and its methiodide [30,31]). The posi-
1
gion of the H NMR spectrum of 2b consists of two
doublets of quartets, positioned at slightly higher field
than the N−C1H2 quartet in 9b (δ = 3.15): HA: δ =
2.85, HB: δ = 2.98, 2J(1HA, 1HB) = 13.0 Hz, 3J(1HA,B
,
C1H3) = 7.1 Hz. Upon quaternization at P, both multi-
plets are shifted to higher field: 3a: HA: δ = 2.28, HB:
δ = 2.76, 2J(1HA, 1HB) = 13.3 Hz, 3J(1HA,B, C1H3) =
7.1 Hz. This phenomenon had previously been ob-
served with 2a and its alkyl phosphonium iodides and
ascribed to a change in the ring current effect of the
phenyl groups attached to the P atom [30]. As in the
Me2N compounds, a significant counterion induced
shift (CIS) effect [52] of the BPh−4 anion is restricted to
the P−C1H3 protons (3a/b: ∆δ = 0.51 ppm), whereas
the N−C1H2 signals are not much affected (3a → 3b:
2.28/2.76 ppm → 2.21/2.70 ppm). The different sensi-
tivity demonstrates that the P atom is the centre of the
positive charge [30].
1
tions of the N−C− H multiplets of N-protonated 2b
closely resemble δ(C1H3) = 3.75 and 4.01 for the
N+(H)Me2 and the N+Me3 groups, respectively, in 8-
Me3N+-C10H6N+(H)Me2 [38b]. The obvious conclu-
sion is that in the phosphine 2b, the N atom does not
bear a positive charge.
When 1H NMR spectra of 2b in the presence of 0.96
equiv. of TsOH were recorded at lower temperatures at
intervals of 10 K down to 243 K, no sharpening of the
N−C1H2 multiplets was observed. They rather merged
into one unresolved signal at δ = 4.05 (243 K), because
the highfield multiplet migrated to lower field faster
than the lowfield multiplet. At lower temperatures, the
resolution of the N−CH2−C1H3 triplet deteriorated;
the phenomenon may be caused by the freezing of ro-
tation around further single bonds (the P−C(1) bond
as a first choice) and hence the formation of diastere-
omers. The N−C1H2 absorption of a minor diastere-
omer may account for a new, non-resolved signal of
small intensity at ca. 3.82– 3.85 ppm (243– 263 K).
NMR protonation shifts
Protonation studies were performed as previously
1
described [1]. In the H- coupled 31P NMR spectrum
of 2b, addition of 0.96 equivalents of p-toluenesulfonic
acid (TsOH) caused a highfield shift of the 31P sig-
1
nal from +0.24 to −15.52 ppm. No 1J(31P, H) cou-
pling due to P-protonation was observed; the 31P reso-
When addition of CF3COOH to the 2b/0.96 equiv.
nance was recorded as one somewhat broadened signal of TsOH solution enhanced the amount of acid to 10.0
in which the 3J(31P, 1H) coupling with the four 2,6-H’s equivalents, the 1H-coupled 31P NMR spectrum ex-
of the phenyl rings and the 2-proton of the DAN group hibited two sharp signals of roughly equal intensities
was not resolved.
at −14.89 and −15.81 ppm. Again, the signal posi-
The value δ = −15.52 ppm is incompatible with a tions exclude P-protonation; in addition, ∆δ = 74 Hz
phosphonium structure, but similar to the values ob- does not qualify for a J(31P, H) coupling constant.
served in other (naphth-1-yl)-diphenyl-phosphines in No 3J(31P, 1H) couplings were visible. The signals
which no downfield R2N effect is operative [44] (e. g., may be ascribed to two diastereomers. This is corrob-
1
1
1
11a– g : δ = −11.98 to −19.6; cf. Scheme 1). On the orated by the H 200 MHz NMR spectrum: A sharp
one hand, the highfield shift of ∆δ = 15.76 ppm upon N−CH2−C1H3 triplet at 1.09 ppm (3J = 7.2 Hz) is ac-
N-protonation demonstrates the decisive role of the N companied by a less intense, equally sharp triplet, δ =
lone pair for the unusual δ values of the phosphines 1.00 (3J = 7.2 Hz). The N−C1H2 absorption consists
2a,b and 12b,c [44]. On the other hand, their signal of two multiplets which tentatively can be interpreted
positions at very low field exclude phosphorane or λ 6- as the almost perfect superposition of the lowfield mul-
phosphate structures and hence a bonding N→P inter- tiplets of both stereoisomers, centered at δ = 3.80, and
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G. P. Schiemenz et al. · peri-Interactions in Naphthalenes, 10
Table 1. Selected distances (pm), angles (◦) and torsion
a partial superposition of the highfield multiplets, that
of the major isomer being centred at δ = ca. 3.53 and
that of the minor isomer at δ = ca. 3.44. These sig-
nal positions would correspond to protonation shifts
of ∆δ = 0.82, 0.68 and 0.59 ppm, respectively, still
exceeding that of 11a,b. The decrease is likely to re-
flect a solvent effect, as ca. 90 mg of CF3COOH had
been added to 0.6 ml of CDCl3. The occurrence of
only one, but broadened 31P NMR signal in the spec-
trum of 2b + 0.96 equiv. of acid may be attributed to
an interconversion process between the stereoisomers.
Since no such isomerization is observed at high acid
concentrations, it is suggested that it proceeds via 2b,
hence, that the steric stability of 2b is enhanced by
N-protonation. Conceivably, the cancellation of inver-
sion at the N atom could play a role. Finally, hydrogen
bonding of the cation with the excess acid may also be
involved.
angles (◦) for 2b.
P···N
280.3(2) P−C1
143.8(2) N−C11
146.7(4) C11−C12
150.2(4) P−C31
182.4(2)
185.2(2)
147.1(2)
151.1(3)
184.8(2)
C8−N
N−C13
C13−C14
P−C21
C1−P−C21
C1−P−C31
C21−P−C31
C9−C1−P
101.4(1) C8−N−C11
102.9(1) C8−N−C13
99.5(1) C11−N−C13
122.5(2) N−C11−C12
119.4(2) N−C13−C14
125.0(2)
115.0(2)
106.0(2)
111.2(2)
114.5(2)
112.3(3)
C9−C8−N
C1−C9−C8
P−C1−C2−C3
P−C1−C9−C10
P−C1−C9−C8
C21−P−C1−C2
C31−P−C1−C2
C21−P−C1−C9
C31−P−C1−C9
C2−C1−C9−C8
C3−C4−C10−C5
C6−C5−C10−C4
C7−C8−C9−C1
179.4(3) N−C8−C7−C6
178.5(2) N−C8−C9−C10
−0.5(3) N−C8−C9−C1
104.4(2) C11−N−C8−C7
1.8(2) C13−N−C8−C7
−177.2(2)
175.2(2)
−5.8(3)
−37.4(3)
85.9(3)
−77.1(2) C11−N−C8−C9
−179.7(2) C13−N−C8−C9
178.1(2) C8−N−C11−C12
179.1(3) C8−N−C13−C14
179.4(3) C11−N−C13−C14
145.8(2)
−90.9(3)
−55.4(3)
175.3(3)
−59.0(4)
Conclusion
177.4(2) C13−N−C11−C12 −175.8(3)
The NMR data of 2b, its N-protonated derivative
and its quaternary phosphonium salts 3a,b indicate that
placed by 10 ml of diethyl ether. Then 1.05 ml (5.85 mmol)
of chloro-diphenylphosphine was added within 10 min by
neither in 2b nor in the quaternized compounds there means of a syringe. After stirring at room temperature for
19 h, the mixture was hydrolyzed with 10 ml of water
and 3 ml of 2 N NaOH. The phosphine was extracted
into 30 ml of toluene, the solution filtered through a col-
umn of magnesium sulfate and silica gel and evaporated.
The residual oil (1.715 g) was dissolved in 20 ml of boil-
ing ethanol. Upon cooling, 824 mg (37%) of yellow crys-
is a significant charge transfer from the N to the P atom
(and vice versa). The data thus provide an independent
argument for the conclusion reached in a recent NMR
investigation of 12a that in DAN-P compounds inter-
atomic distances d(N···P) of ca. 280 pm (much shorter
than the sum of the van der Waals radii of N and P)
occur which are not the consequence of dative N→P
interactions [1]. The conservative formulae 2 and 3
are entirely satisfactory representations of DAN-phos-
phines and DAN-phosphonium salts whereas alterna-
tive formulae such as 5A,B and 6A,B are misleading.
We therefore discourage the use of such formulae.
◦
tals separated. M. p. 119 – 121 C. – 1H NMR (200 MHz,
CDCl3): δ = 0.70 (t, 3J(H, H) = 7.1 Hz, 6H, C−C1H3),
2.85 (dq, 2J(HA, HB) = 13.0 Hz, 3J(H, H) = 7.1 Hz, 2H,
1
2
3
N−C− HA), 2.98 (dq, J(HA, HB) = 13.0 Hz, J(H, H) =
7.1 Hz, 2H, N−C− HB), 6.88 – 7.79 (m, 16H, arom. pro-
1
tons). – 13C{ H} NMR (50.3 MHz, CDCl3): δ = 9.62 (d,
1
6J(H, P) = 1.7 Hz, C− CH3), 46.92 (d, 5J(H, P) = 9.0 Hz,
13
N− CH2), 20 signals from 121.4 to 148.6 ppm. – 31P{ H}
NMR (81.0 MHz, CDCl3): δ = +0.24. – MS (EI, 70 eV):
m/z = 384 (M+1, 28%), 383 (M, 100%), 355 (M+1 − Et,
23%), 354 (M − Et, 84%), 338 (M − NEt2, 23%), 306 (M
− Ph, 40%), 278 (M − Ph − C2H4, 69%). − C26H26NP
(383.5): calcd. N 3.65, P 8.08; found N 3.81, P 8.13.
13
1
Experimental Section
The NMR spectra were recorded as described previously
[1]. Elemental analyses were performed by Mikroanalyti-
sches Labor Pascher, Remagen, Germany.
(8-Diethylamino-naphth-1-yl)-diphenyl-phosphine (2b):
(8-Diethylamino-naphth-1-yl)-methyl-diphenyl-phospho-
A commercial 1.6 M solution of n-butyllithium in n-hexane nium iodide (3a) and tetraphenylborate (3b): Crystals of 3a
(10.0 ml) was added to 1-diethylamino-naphthalene (3.208 g, began to separate from a solution of 386 mg (1.01 mmol) of
16.1 mmol, prepared from 1-amino-naphthalene and di- 2b and 0.5 ml (8 mmol) of iodomethane in 4 ml of toluene
ethyl sulfate; b.p. 181 – 184 ◦C/20 torr) in anhydrous di- within 3 min. After 30 d 527 mg (100%) of colorless 3a
◦
ethyl ether (5 ml). Within 27 d, the solution turned red. was collected. M. p. 303 – 304 C. – 1H NMR (300 MHz,
Upon stirring for 30 min, yellow crystals of 8-diethylamino- CD2Cl2): δ = 0.65 (t, 3J(H, H) = 7.2 Hz, 6H, C−C1H3),
naphth-1-yl lithium separated. After additional 6 d (with- 2.28 (dq, 2J(HA, HB) = 13.2 Hz, 3J(H, H) = 7.1 Hz, 2H,
1
2
3
out stirring) the liquid was removed with a syringe and re- N−C− HA), 2.76 (dq, J(HA, HB) = 13.4 Hz, J(H, H) =
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669
1
2
7.2 Hz, 2H, N−C− HB), 3.12 (d, J(P, H) = 13.3 Hz, 3H, (IPDS), Mo-Kα (λ = 0.71073 A), 200 K, 10871 measured
˚
P−C1H3), 7.41 – 8.26 (m, 16 H, arom. H).
reflections in the range of 3◦ ≤ 2θ ≤ 54◦, 4315 indepen-
dent reflections used for refinement, Rint = 0.0544). Structure
solution was performed using SHELXS-86, structure refine-
ment against F2 using SHELXL-93. 271 refined parameters,
R1 for 3923 reflections with I ≥ 2σ(I) = 0.0373, wR2 for all
4315 independent reflections = 0.0974, GoF 1.032, residual
340 mg (94%) of colorless 3b precipitated from a solu-
tion of 263 mg (0.50 mmol) 3a in 20 ml of methanol upon
addition of 228 mg (0.67 mmol) of sodium tetraphenylborate
dissolved in 10 ml of methanol and subsequent addition of
10 ml of water. Recrystallization from ethanol/acetone/water
(45/15/10 ml) afforded 302 mg. M. p. 186 – 187 ◦C. –
1H NMR (300 MHz, CD2Cl2): δ = 0.62 (t, 3J(H, H) =
7.1 Hz, 6H, C−C1H3), 2.21 (dq, 2J(HA, HB) = 13.5 Hz,
electron density: 0.20 / −0.23 A−3. All non-hydrogen atoms
˚
were refined using anisotropic displacement parameters. The
C−H hydrogen atoms were positioned with idealized geom-
etry and refined with fixed isotropic displacement parame-
ters using the riding model. The absolute structure was deter-
mined and is in agreement with the selected setting (Flack-x-
parameter: 0.01 (8)).
3J(H, H) = 7.2 Hz, 2H, N−C− HA), 2.61 (d, 2J(P, H) =
1
13.5 Hz, 3H, P−C1H3), 2.70 (dq, 2J(HA, HB) = 13.3 Hz,
3J(H, H) = 7.1 Hz, 2H, N−C− HB), 6.78 – 8.25 (m, 36 H,
1
arom. H). – 13C{ H} NMR (50.3 MHz, CD2Cl2): δ = 8.99
1
(s, C− CH3), 11.58 (d, 1J(P, C) = 65.8 Hz, P− CH3),
13
13
Crystallographic data (excluding structure factors) for the
structure have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no. CCDC
206594. Copies of the data can be obtained free of charge on
application to: The Director, CCDC, 12 Union Road, Cam-
bridge CB2 5Z, UK [fax: int. code +44(1223)336-033, e-
mail: deposit@ccdc.cam.ac.uk].
46.28 (s, N− CH2), 112.54 (d, 1J(P, C) = 92.8 Hz,
13
Cipso(Ph), 26 signals from 122.1 to 141.7 ppm, 147.35 (d,
3J(P, C) = 2.2 Hz, C(8)), 164.44 (q, 1J(B, C) = 49.3 Hz,
Cipso(BPh−) − 31P{ H} NMR (81.0 MHz, CD2Cl2): δ =
1
+24.46. – 4C51H49BNP (717.7): calcd. N 1.95, P 4.31; found
N 2.04, P 4.31.
Crystal structure determination of (8-diethylamino-
naphth-1-yl)-diphenyl-phosphine (2b): C26H26NP, MG =
383.45 g/mol, transparent plate, orthorhombic, space group
Acknowledgements
Financial support by the Volkswagen Foundation (Han-
nover) (project Experimental and theoretical conformational
P212121 (no. 19), a = 8.6646 (3), b = 10.8802 (6), c = 21.972
3
(2) A, V = 9657 (2) A , T = 200 K, ρcalc = 1.230 g·cm−3, µ = analysis of organic compounds in solution) is gratefully ac-
˚
˚
0.14 mm−1, Z = 4, STOE Imaging Plate Diffraction System knowledged.
[1] 9th Communication: G. P. Schiemenz, C. Na¨ther,
S. Po¨rksen, Z. Naturforsch. 58b, 59 (2003).
[2] G. P. Schiemenz, S. Po¨rksen, C. Na¨ther, Z. Naturforsch.
55b, 841 (2000).
[3] For examples, see: A. C. Cope, E. R. Trumbull, Org.
Reactions 11, 317 (1960).
[4] M. Chauhan, C. Chuit, R. J. P. Corriu, C. Reye´, J.-P.
Declercq, A. Dubourg, J. Organomet. Chem. 510, 173
(1996).
[10] F. H. Carre´, C. Chuit, R. J. P. Corriu, W. E. Douglas,
D. M. H. Guy, C. Reye´, Eur. J. Inorg. Chem. 647
(2000).
[11] G. P. Schiemenz, S. Po¨rksen, P. M. Dominiak, K. Woz-
niak, Z. Naturforsch. 57b, 8 (2002).
[12] a) C. Brelie`re, F. Carre´, R. J. P. Corriu, M. Poirier,
G. Royo, J. Zwecker, Organometallics 8, 1831 (1989);
b) C. Brelie`re, F. Carre´, R. J. P. Corriu, G. Royo,
M. Wong Chi Man, J. Lapasset, Organometallics 13,
307 (1994).
[5] C. Chuit, R. J. P. Corriu, P. Monforte, C. Reye´, J.-P.
Declercq, A. Dubourg, J. Organomet. Chem. 511, 171 [13] C. Chuit, R. J. P. Corriu, C. Reye, in Kin-ya Akiba
(1996).
(ed.): Chemistry of Hypervalent Compounds, pp. 81 –
146, John Wiley & Sons Ltd., Chichester (1999).
[14] In 8-Me2NC10H6SiF3, d(N···Si) = 230.3 pm (aver-
age) (F. Carre´, R. J. P. Corriu, A. Kpoton, M. Poirier,
G. Royo, J. C. Young, C. Belin, J. Organomet. Chem.
470, 43 (1994)), i. e. significantly shorter than 251 pm,
is evidence that attractive forces are able to overcome
the geometric resistance of the C10 skeleton. However,
since d(N···Si) is still too long to permit a significant
covalent interaction, it is unlikely that these forces are
of dative N→Si nature (elsewhere N→Si bonds to hy-
percoordinate Si in SiF3 compounds have a length of
197 – 200 pm [13]).
[6] A. Chandrasekaran, N. V. Timosheva, R. O. Day, R. R.
Holmes, Inorg. Chem. 39, 1338 (2000).
[7] C. Chuit, C. Reye´, Eur. J. Inorg. Chem. 1847 (1998).
[8] C. Chuit, R. J. P. Corriu, P. Monforte, C. Reye´, J.-
P. Declercq, A. Dubourg, Angew. Chem. 105, 1529
(1993); Angew. Chem. Int. Ed. 32, 1430 (1993). Cf.
A. Chandrasekaran et al. [6], G. P. Schiemenz et al.
[17], note [6].
[9] F. Carre, M. Chauhan, C. Chuit, R. J. P. Corriu,
C. Reye, Phosphorus, Sulfur, Silicon Relat. Elem. 123,
181 (1997).
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670
G. P. Schiemenz et al. · peri-Interactions in Naphthalenes, 10
[15] G. P. Schiemenz, B. Schiemenz, S. Petersen, C. Wolff,
Chirality 10, 180 (1998).
alkaloids (N. J. Leonard, in: R. H. F. Manske, H. L.
Holmes (eds): The Alkaloids. Chemistry and Physi-
ology, New York, Academic Press, 1, 107 (1950), 6,
35 (1960), R. H. F. Manske, ibid. 10, 467 (1968), F. L.
[16] G. P. Schiemenz, Chem. Listy 92, 269 (1998).
[17] G. P. Schiemenz, R. Bukowski, L. Eckholtz,
B. Varnsku¨hler, Z. Naturforsch. 55b, 12 (2000).
[18] G. Dyker, M. Hagel, G. Henkel, M. Ko¨ckerling,
C. Na¨ther, S. Petersen, G. P. Schiemenz, Z. Natur-
forsch. 56b, 1109 (2001).
[19] G. P. Schiemenz, C. Na¨ther, Z. Naturforsch. 57b, 309
(2002).
[20] G. P. Schiemenz, Z. Anorg. Allg. Chem. 628, 2597
(2002).
[21] A. Karac¸ar, V. Klaukien, M. Freytag, H. Tho¨nnessen,
J. Omelanczuk, P. G. Jones, R. Bartsch, R. Schmutzler,
Z. Anorg. Allg. Chem. 627, 2589 (2001).
[22] a) C. Chuit, R. J. P. Corriu, C. Reye´, J. C. Young,
Chem. Rev. 93, 1371 (1993); b) F. Carre´, C. Chuit,
R. J. P. Corriu, A. Mehdi, C. Reye´, Inorg. Chim. Acta
250, 21 (1996). Cf. K. Tamao, M. Asahara, T. Saeki,
A. Toshimitsu, Angew. Chem. 111, 3520 (1999);
Angew. Chem. Int. Ed. 38, 3316 (1999).
[23] C. Brelie`re, R. J. P. Corriu, G. Royo, J. Zwecker,
Organometallics 8, 1834 (1989).
[24] a) M. Chauhan, C. Chuit, A. Fruchier, C. Reye´, Inorg.
Chem. 38, 1336 (1999); b) R. R. Holmes, Main Group
Chemistry News 6, 6 (1998).
ˇ
Warren, ibid. 12, 245 (1970), F. Santavy´, ibid. 12, 333
(1970), 17, 385 (1979), V. Preininger, ibid. 15, 207
(1975), J. T. Wro´bel, ibid. 26, 327 (1985)) and have
been observed in 7- formyl-1,3,5,7-tetramethyl-3-aza-
bicyclo[3.3.1]nonane (A. J. Kirby, I. V. Komarov, V. A.
Bilenko, J. E. Davies, J. M. Rawson, J. Chem. Soc.,
Chem. Commun. 2106 (2002)). For 8-dimethylamino-
1-naphthaldehyde, cf. A. J. Kirby, J. M. Percy [37].
That the symbols D→A and D+−A− are equivalent, is
borne out by the concomitant use of the D→A formu-
lae and of the nomenclature whose names correspond
to the formulae of the type D+−A−, e. g., A. Flores-
Parra, G. Cadenas-Pliego, L. M. R. Mart´ınez-Aguilera,
M. L. Garc´ıa-Nares, R. Contreras, Chem. Ber. 126, 863
(1993); H. Bu¨rger, T. Hagen, G. Pawelke, Z. Natur-
forsch. 48b, 935 (1993) (p. 937).
[30] G. P. Schiemenz, E. Papageorgiou, Phosphorus Sulfur
13, 41 (1982).
[31] D. Hellwinkel, W. Lindner, H.-J. Wilfinger, Chem. Ber.
107, 1428 (1974). We observed δ = 4.03 in CD3OD,
hence a formal quaternization shift of ∆δ = 1.12 ppm.
∆δ would include a solvent effect in either case.
[32] R. W. Franck, E. G. Leser, J. Am. Chem. Soc. 91, 1577
(1969), J. Org. Chem. 35, 3932 (1970); J. F. Blount,
F. Cozzi, J. R. Damewood, Jr., L. D. Iroff, U. Sjo¨strand,
K. Mislow, J. Am. Chem. Soc. 102, 99 (1980).
[25] F. Carre´, C. Chuit, R. J. P. Corriu, P. Monforte, N. K.
Nayyar, C. Reye´, J. Organomet. Chem. 499, 147
(1995).
[26] It should be noted that an attractive contribution is
not necessarily synonymous with a dative interaction [33] L. Pauling [28], 2nd ed., p. 64; 3rd ed., pp. 90, 93.
which implies involvement of an electron pair in a co- [34] A negative charge on the P atom as in 5A would reduce
valent bond. At interatomic distances of ca. 280 pm no
significant covalent attractive forces between N and P
would be anticipated. Cf. note [14].
the electronegativity to ca. 1.9 (Pauling [28], 2nd ed.,
p. 66).
[35] J. W. Emsley, J. Feeney, L. H. Sutcliffe, High Res-
olution Nuclear Magnetic Resonance Spectroscopy,
Vol. 2, pp. 666 – 670, Pergamon Press, Oxford (1966).
[27] G. A. Landrum, N. Goldberg, R. Hoffmann, J. Chem.
Soc., Dalton Trans. 3605 (1997).
[28] L. Pauling, The Nature of the Chemical Bond and the [36] L. Landshoff, Ber. Dtsch. Chem. Ges. 11, 638 (1878).
Structure of Molecules and Crystals, 2nd ed., Cornell
University Press, Ithaca NY, London, Oxford (1945),
p. 72; 3rd ed., p. 101 – 102, ibid. (1960); H. A. Staab,
Einfu¨hrung in die Theoretische Organische Chemie,
p. 44, Verlag Chemie, Weinheim (1959).
[37] A. J. Kirby, J. M. Percy, Tetrahedron 44, 6903 (1988).
[38] a) R. W. Alder, P. S. Bowman, W. R. S. Steele, D. R.
Winterman, J. Chem. Soc., Chem. Commun. 723
(1968); b) R. W. Alder, M. R. Bryce, N. C. Goode, J.
Chem. Soc., Perkin Trans. 2, 477 (1982).
[29] Note that 5A and 5B, 6A and 6B, 7A and 7B [39] G. P. Schiemenz, Chem. Ber. 98, 65 (1965).
are different formulae for the same species, whereas [40] G. P. Schiemenz, Tetrahedron 27, 3231 (1971).
2 and 5A/B, 3 and 6A/B, 4 and 7A/B are iso- [41] H. A. Staab, T. Saupe, Angew. Chem. 100, 895 (1988),
mers. Closely related types of isomerism have been
described, e. g., for γ-dimethylamino- butyraldehy-
des (R. McCrindle, A. J. McAlees, J. Chem. Soc.,
Chem. Commun. 61 (1983)) and a manganese-
tricarbonyl complex of 1-(3-dimethylamino-propyl)-
borabenzene (A. J. Ashe, III, J. W. Kampf, J. R. Waas,
Organometallics 16, 163 (1997); similar processes are
common among the senecio, papaveraceae and related
Angew. Chem. Int. Ed. 27, 865 (1988); R. W. Alder,
Chem. Rev. 89, 1215 (1989); cf. A. L. Llamas-Saiz,
C. Foces-Foces, J. Elguero, J. Mol. Structure 328,
297 (1994). For the reasons of the basicity of 1,8-bis-
dimethylamino-naphthalene cf. N. G. Korzhenevska,
V. I. Rybachenko, G. Schroeder, Tetrahedron Lett. 43,
6043 (2002).
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671
[42] L. Maier, Primary, Secondary, and Tertiary Phosphines,
in G. M. Kosolapoff, L. Maier (eds): Organic Phos-
phorus Compounds, Vol. 1, pp. 1 – 287 (p. 77), Wiley-
(cf. G. Klebe, J. Organomet. Chem. 332, 35 (1987);
N. Kano, A. Kikuchi, T. Kawashima, J. Chem. Soc.,
Chem. Commun. 2096 (2001)).
Interscience, New York, London, Sydney, Toronto [50] S. C. Menon, H. B. Singh, J. M. Jasinski, J. P. Jasinski,
(1972).
R. Butcher, Organometallics 15, 1707 (1996). Simi-
larly, in some 2-Me2NCH2- C6H4-Te-SP(S)R3 com-
pounds an almost T-shaped N···Te(C)−S alignment
was believed to provide evidence for N→Te inter-
actions: J. E. Drake, M. B. Hursthouse, M. Kulcsar,
M. E. Light, A. Silvestru, J. Organomet. Chem. 623,
153 (2001). In [8-Me2N- C10H6Se(Me)]2O neither
d(N···Se) < Σr(vdWN,Se) nor the “linear alignment of
N···Se···O showed the hypervalent nature of selenium
atoms” (H. Fujihara, H. Tanaka, N. Furukawa, J. Chem.
Soc., Perkin Trans. 1, 2375 (1995); angles N···Se···O
172.2◦, 173.4◦). On the other hand, d(N···Se) = 242.0,
244.7 pm, i. e. shorter than the natural peri distance, in-
dicates some sort of attractive interaction which, how-
ever, again is not necessarily of covalent nature.
[51] W. Nakanishi, S. Hayashi, A. Sakaue, G. Ono,
Y. Kawada, J. Am. Chem. Soc. 120, 3635 (1998). See
also lit. [2].
[43] N. F. Hall, M. R. Sprinkle, J. Am. Chem. Soc. 54, 3469
(1932); cf. C. A. Streuli, Anal. Chem. 31, 1652 (1959).
[44] G. P. Schiemenz, Phosphorus, Sulfur, Silicon Relat.
Elem. 163, 185 (2000).
[45] L. J. Fitzgerald, J. C. Gallucci, R. E. Gerkin, Acta Crys-
tallogr. B 47, 776 (1991).
[46] S. Kane, W. H. Hersh, J. Chem. Educ. 77, 1366 (2000).
[47] J. J. Daly, J. Chem. Soc. 3799 (1964).
[48] Note that in the formula of DAN-SiH2Ph with a dative
N/Si interaction on the front cover of the book “Sili-
con in Organic, Organometallic, and Polymer Chem-
istry” by M. A. Brook (John Wiley & Sons, New York,
Chichester, Weinheim, Brisbane, Singapore, Toronto,
2000), the N→Si bond occupies an equatorial position.
[49] H. Schumann, B. C. Wassermann, F. E. Hahn,
Organometallics 11, 2803 (1992). The fact that a
formally pentacoordinate arrangement of 4 + 1 atoms
around a central atom can be described either as [52] G. P. Schiemenz, J. Mol. Structure 16, 99 (1973).
monocapped tetrahedral or as trigonal-bipyramidal [53] F. B. Mallory, J. Am. Chem. Soc. 95, 7747 (1973).
(both distorted), is implied by Tamao’s method to [54] R. D. Jackson, S. James, A. G. Orpen, P. G. Pringle, J.
calculate % TBP character: K. Tamao, T. Hayashi,
Organomet. Chem. 458, C3 (1993); see also lit. [21].
Y. Ito, M. Shiro, Organometallics 11, 2099 (1992)
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