Synthesis and Crystal Structures of P-Halogeno(imino)methylenephosphoranes X-P(=NtBu3C6H2)=C(SiMe3)2 (X = Cl, Br, I)

Article abstract of DOI:10.1002/(SICI)1099-0682(199801)1998:1<83::AID-EJIC83>3.0.CO;2-K

The iminophosphane (Me₃Si)₃C-P=N-MeS* (1) reacts with iodine to form the imino(inethylene)phosphorane I-P(=N-Mes*)=C(SiMe₃)₂ (2). Upon subsequent treatment with AgCl, the corresponding chloro derivative 3 is obtained. Chlorine/bromine exchange in 3 with bromotrimethylsilane affords the bromo analogue 4. The structures of 2, 3 and 4 were confirmed by X-ray crystal structure analysis; each of the compounds features a trigonal-planar phosphorus atom.

Full text of DOI:10.1002/(SICI)1099-0682(199801)1998:1<83::AID-EJIC83>3.0.CO;2-K

FULL PAPER
Synthesis and Crystal Structures of P-Halogeno(imino)methylene-
phosphoranes X؊P(؍NtBu3C6H2)؍C(SiMe3)2 (X ؍ Cl, Br, I)
Alexander Ruban, Martin Nieger, and Edgar Niecke*
Anorganisch-Chemisches Institut der Universität Bonn,
Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
Fax: (internat.) ϩ49(0)228/735357
Received July 28, 1997
Keywords: Phosphorus ylides / Bis(ylene)phosphoranes / Halogenophosphoranes / X-ray structure analysis
The iminophosphane (Me3Si)3CϪP=NϪMes* (1) reacts with
Chlorine/bromine exchange in 3 with bromotrimethylsilane
iodine to form the imino(methylene)phosphorane IϪP- affords the bromo analogue 4. The structures of 2, 3 and 4
(=NϪMes*)=C(SiMe3)2 (2). Upon subsequent treatment with
AgCl, the corresponding chloro derivative 3 is obtained.
were confirmed by X-ray crystal structure analysis; each of
the compounds features a trigonal-planar phosphorus atom.
Introduction
Scheme 1
The discovery of the first stable compound containing a
trigonal-planar phosphorus(V) center in 1974[1] represents
a landmark in organophosphorus chemistry. It opened the
door to a rapid development of the chemistry of such com-
pounds and structurally related derivatives[2 . Among these,
bis(imino)-[3a] and bis(methylene)phosphoranes[3b] have at-
tracted considerable attention, not only because they are
valuable building blocks in organophosphorus and or-
ganometallic chemistry[4], but also because they are suitable
precursors for monomeric metaphosphate analogues[5] and
have found application in the catalysis of olefin polymeri-
zation[6]. In contrast, information concerning imino(meth-
ylene)phosphoranes, which feature both PϪN- and PϪC-
pπ bonds, is comparatively sparse[3c]. Herein, we report on
the synthesis and crystal structure analysis of the first P-
halogeno(imino)methylenephosphoranes.
nuclei on going from the iodo derivative 2 to the chloro
analogue 3 [31P: δ ϭ 53.3 (2) < 65.2 (4) < 72.5 (3)] is a
Results and Discussion
characteristic feature of tetracoordinated PV compounds[9]
.
Treatment of the iminophosphane (Me3Si)3CϪPϭ
The 13C-NMR signals of the methylene carbon atoms,
NϪMes* (1)[7], with iodine in THF at Ϫ40°C cleanly af- which are observed at lower fields than in “classical” meth-
forded the P-iodo(imino)methylenephosphorane 2. Further ylenephosphoranes, show the inverse trend. A stronger car-
reaction with AgCl in CH2Cl2 at 25°C resulted in I/Cl ex- bon shielding is found on going from compound 2 to 4 to
change of 2, yielding the chloro derivative 3. Subsequent 3, i.e. on increasing the electronegativities of the substitu-
reaction of 3 with Me3SiBr led smoothly to the bromo de- ents [13C: δ ϭ 68.0 (2) > 58.2 (4) > 51.7 (3)]. At the same
rivative 4. By crystallization from small volumes of n-hex- time, a significant increase in the magnitude of 1J(C,P) from
ane, compounds 2Ϫ4 were isolated as highly air- and moist- 34.1 Hz (2) through 50.6 Hz (4) to 65.3 Hz (3) is observed.
ure-sensitive, red (2), light-yellow (3), or orange (4) crystals An inverse electronegativity effect on both 31P- and 13C-
(Scheme 1).
chemical shifts was also observed for substitution at the
The P-halogeno(imino)methylenephosphoranes 2؊4 methylene carbon atom in imino(methylene)phosphoranes
have been characterized on the basis of their elemental and was attributed to a polarization effect[10]. Similar
1
1
analyses and H-, 13C-, 31P-NMR and mass-spectrometric trends in the δ31P, δ13C and J(C,P) values were observed
data. Furthermore, the solid-state structures of compounds in
2؊4 have been determined by X-ray crystallography.
the
corresponding
P-halogenobis(methylene)-
phosphoranes[3a] and P-halogenobis(imino)phosphoranes
The 31P-NMR chemical shifts of compounds 2؊4 are ob- (δ31P)[11]. As compared to compounds 2؊4, the 31P nuclei
served at relatively low field values, which is typical for bis- in the former are less shielded by 30 to 65 ppm, while those
(ylene)phosphoranes[8]. The deshielding of the phosphorus in the latter appear more shielded by 30 to 70 ppm com-
Eur. J. Inorg. Chem. 1998, 83Ϫ85
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
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83

A. Ruban, M. Nieger, E. Niecke
FULL PAPER
pared to the corresponding nuclei in the imino(methyl- anes[11], but are longer than those in bis(methylene)phos-
ene)phosphoranes. Furthermore, a detailed experimental phoranes[14]. The PϪN [151.8(3)Ϫ153.1(4) pm] and PϪC
and quantum-chemical study on the influence of phos- [162.4(4)Ϫ164.2(4) pm] distances, as well as the central
phorus substituents on 15N-NMR shifts in bis(imino)phos- CϪPϪN valence angles [129.2(2)Ϫ130.5(2)°] represent typi-
phoranes led to the conclusion that the substituent effects cal structural features common to both bis(imino)- and bis-
were transmitted by both inductive and mesomeric interac- (methylene)phosphoranes[3a][3b]. The other bond lengths
tions, and revealed a correlation between increased shield- and angles show no peculiarities.
ing and higher ylidic character of the ylene bond[12]
.
Regarding the potential synthetic utility of these halo-
geno(imino)methylenephosphoranes, one can expect them
to undergo nucleophilic displacement reactions as well as
thermally induced β eliminations of silyl halide. Both of
these strategies are currently under investigation.
Table 1. Representative NMR data of P-halogenobis(ylidene)phos-
phoranes XϪP(ϭA)ϭB
δ31P
δ13C(PϭC) 1JPC [Hz]
This work was supported by the Deutsche Forschungsgemein-
schaft and the Fonds der Chemischen Industrie.
X ϭ Cl; A ϭ B ϭ N
X ϭ Br; A ϭ B ϭ N
X ϭ I; A ϭ B ϭ N
X ϭ Cl; A ϭ N; B ϭ C
X ϭ Br; A ϭ N; B ϭ C
X ϭ I; A ϭ N; B ϭ C
X ϭ Cl; A ϭ B ϭ C
X ϭ Br; A ϭ B ϭ C
X ϭ I; A ϭ B ϭ C
Ϫ18.5
Ϫ30.2
Ϫ42.9
72.5
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
65.3
50.6
34.1
38.6
30.8
23.5
51.7
Experimental Section
65.2
58.2
All experiments were carried out with the exclusion of air and
moisture under argon. Solvents were purified and dried according
to standard methods. Compound 1 was prepared according to a
literature procedure[7]. Ϫ NMR: Bruker AMX 300 (31P: 121.5
MHz, external standard 85% H3PO4; 1H: 300.1 MHz, external
standard TMS; 13C: 75.5 MHz, external standard TMS). Ϫ MS:
Kratos Instruments Concept 1 H, Kratos Instruments MS 50, VG
Instruments VG 12-250. Ϫ Elemental analyses: Analytisches La-
boratorium Pascher. Ϫ Melting points were determined in sealed
glass capillaries and are uncorrected.
53.3
68.0
136.8
122.5
84.7
83.3
91.3
102.9
The constitutions of compounds 2؊4 were further cor-
roborated by single-crystal X-ray diffraction studies. The
phosphorus and carbon atoms of the imino(methylene)
moieties exhibit the expected trigonal-planar geometries
(Figure 1). The atoms of the CSi2 and PϪNϪCipso moieties
are almost coplanar (dihedral angle 4.4Ϫ5.6°), while the
aryl substituent is approximately orthogonal to the central
π-bond system (angle between the plane PϪNϪCipso and
the aryl plane: 88.8Ϫ91.7°). The PϪN double bond adopts
a (Z) configuration, as is observed in P-halogeno(imino)-
phosphanes[13]. The PϪhalogen distances [3: 206.9(2), 4:
223.1(1), 2: 242.9(1) pm] are shortened in comparison with
the corresponding bond lengths in bis(imino)phosphor-
Iodo[(2,4,6-tri-tert-butylphenyl)imino][bis(trimethylsilyl)-
methylene]phosphorane (2): To a solution of iminophosphane 1
(2.61 g, 5 mmol) in 20 ml of THF, an equimolar amount of iodine,
dissolved in 20 ml of THF, was added at Ϫ40°C. The reaction
mixture was then allowed to warm to room temp. under stirring.
The solvent and all volatile components were removed in vacuo and
the remaining residue was taken up in 30 ml of n-hexane. Storage of
the resulting solution at 0°C led to the deposition of 2 in the form
of red crystals, which were found to be suitable for X-ray structural
analysis. Ϫ Yield 2.57 g (89.3%), m.p. 111Ϫ113°C. Ϫ 31P NMR
1
(C6D6): δ ϭ 53.3. Ϫ H NMR (C6D6): δ ϭ 0.57 (s, 18 H, SiMe3),
Figure 1. Crystal structure of the imino(methylene)phosphorane
5
1.47 (s, 9 H, p-tBu), 1.72 (s, 18 H, o-tBu), 7.61 (d, JHP ϭ 5.8 Hz,
3[a]
3
2 H, C6H2). Ϫ 13C NMR (C6D6): δ ϭ 5.0 (d, JPC ϭ 5.8 Hz,
5
SiMe3), 32.1 (d, JPC ϭ 4.2 Hz, p-CCH3 ), 32.9 (d, JPC ϭ 2.7 Hz,
4
o-CCH3), 35.3 (d, JPC ϭ 4.4 Hz, p-CCH3), 37.2 (d, JPC ϭ 4.7 Hz,
1
4
o-CCH3), 68.0 (d, JPC ϭ 34.3 Hz, PϭC), 123.0 (d, JPC ϭ 11.8
3
5
Hz, m-Ar), 143.7 (d, JPC ϭ 19.1 Hz, o-Ar), 145.7 (d, JPC ϭ 14.1
2
Hz, p-Ar), 145.8 (d, JPC ϭ 24.1 Hz, ipso-Ar). Ϫ MS (70 eV); m/z
(%): 574 (49) [Mϩ], 290 (100) [tBu3C6H2NPϩ]. Ϫ C25H47INPSi2
(594.7): calcd. C 52.15, H 8.22; found C 52.28, H 8.26.
Chloro[(2,4,6-tri-tert-butylphenyl)imino][bis(trimethylsilyl)-
methylene]phosphorane (3): To a solution of imino(methylene)phos-
phorane 2 (1.44 g, 2.5 mmol) in 10 ml of CH2Cl2, AgCl (0.39 g,
2.7 mmol) was added at room temp. and the suspension was stirred
for 12 h. The solvent and the volatiles were then removed in vacuo
and the remaining residue was taken up in 20 ml of n-hexane. The
insoluble silver salt (AgI) was separated by filtration. Storage of
the filtrate at 0°C resulted in the deposition of 3 in the form of
yellow crystals. Ϫ Yield: 1.05 g (86.7%), m.p. 81Ϫ82°C. Ϫ 31P
NMR (C6D6): δ ϭ 72.5. Ϫ 1H NMR (C6D6): δ ϭ 0.40 (s, 9 H,
[a]
Selected bond lengths [pm] and bond angles [°]: 3: P(1)ϪCl(1)
206.9(2), P(1)ϪN(1) 152.7(4), P(1)ϪC(1) 162.4(4), N(1)ϪC(8)
142.6(5); Cl(1)ϪP(1)ϪN(1) 113.1(1), Cl(1)ϪP(1)ϪC(1) 116.3(2),
N(1)ϪP(1)ϪC(1) 130.5(2), P(1)ϪN(1)ϪC(8) 127.0(3).
Ϫ 2:
P(1)ϪI(1) 242.9(1), P(1)ϪN(1) 153.1(4), P(1)ϪC(1) 164.2(4), SiMe3), 0.60 (s, 9 H, SiMe3), 1.45 (s, 9 H, p-tBu), 1.73 (s, 18 H, o-
5
tBu), 7.63 (d, JPH ϭ 3.3 Hz, 2 H, C6H2). Ϫ 13C NMR (C6D6):
N(1)ϪC(8) 142.3(5), I(1)ϪP(1)ϪN(1) 112.0(2), I(1)ϪP(1)ϪC(1)
118.8(2), N(1)ϪP(1)ϪC(1) 129.2(2), P(1)ϪN(1)ϪC(8) 125.6(3). Ϫ
4: P(1)ϪBr(1) 223.1(1), P(1)ϪN(1) 151.8(3), P(1)ϪC(1) 162.7(4),
N(1)ϪC(8) 140.8(5); Br(1)ϪP(1)ϪN(1) 112.1(1), Br(1)ϪP(1)ϪC(1)
117.5(2), N(1)ϪP(1)ϪC(1) 130.4(2), P(1)ϪN(1)ϪC(8) 127.8(3).
3
3
δ ϭ 4.2 (d, JPC ϭ 7.0 Hz, SiMe3), 4.6 (d, JPC ϭ 2.0 Hz, SiMe3),
32.1 (d, JPC ϭ 3.0, p-CCH3), 32.2 (d, 5JPC ϭ 2.3 Hz, o-CCH3), 35.2
(d, JPC ϭ 3.4 Hz, p-CCH3), 36.9 (d, 4JPC ϭ 3.8 Hz, o-CCH3), 51.7
84
Eur. J. Inorg. Chem. 1998, 83Ϫ85

P-Halogeno(imino)methylenephosphoranes
FULL PAPER
1
4
(d, JPC ϭ 65.3 Hz, PϭC), 122.7 (d, JPC ϭ 8.9 Hz, m-Ar), 140.8 SHELXTL-Plus[15], SHELXL-93[16]). Non-hydrogen atoms were
(d, 2JPC ϭ 23.3 Hz, ipso-Ar), 142.9 (d, 3JPC ϭ 15.7 Hz, o-Ar), 145.0
refined anisotropically; H atoms were refined using a riding model;
5
(d, JPC ϭ 10.7 Hz, p-Ar). Ϫ MS (70 eV); m/z (%): 483 (11) [Mϩ], the tert-butyl groups were found to be disordered. Full details of
290 (100) [tBu3C6H2NPϩ]. Ϫ C25H47ClNPSi2 (484.2): calcd. C
the crystal structure determinations (except structure factors) have
been deposited with the Cambridge Crystallographic Data Centre
as supplementary publication no. CCDC-100474 (2, 3, 4). Copies
may be obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB2 1EZ, U.K. [Fax: (internat.) ϩ 44(0)1223/
336033; E-mail: deposit@ccdc.cam.ac.uk].
62.01, H 9.78; found C 62.22, H 9.84.
Bromo[(2,4,6-tri-tert-butylphenyl)imino][bis(trimethylsilyl)-
methylene]phosphorane (4): To a solution of 3 (1.21 g, 2.5 mmol)
in 10 ml of THF was added an equimolar amount of Me3SiBr and
the reaction mixture was stirred for 2 h at room temp. The solvent
and the halosilanes were then removed in vacuo and the residue
was crystallized from a small volume of n-hexane. The product was
obtained as an orange, crystalline solid. Ϫ Yield 1.16 g (87.5%),
m.p. 99Ϫ101°C. Ϫ 31P NMR (C6D6): δ ϭ 65.2. Ϫ 1H NMR
(C6D6): δ ϭ 0.40 (s, 9 H, SiMe3), 0.60 (s, 9 H, SiMe3), 1.45 (s, 9
[1] [1a]
E. Niecke, W. Flick, Angew. Chem. 1974, 86, 128; Angew.
Chem. Int. Ed. Engl. 1974, 13, 585. Ϫ [1b] O. J. Scherer, N. Kuhn,
Chem. Ber. 1974, 107, 2123. Ϫ
[1c]
S. Pohl, E. Niecke, B. Krebs,
Angew. Chem. 1975, 87, 284; Angew. Chem. Int. Ed. Engl. 1975,
14, 261.
[2]
H, p-tBu), 1.73 (s, 18 H, o-tBu), 7.62 (d, 5JPH ϭ 3.6 Hz, 2 H, C6H2).
Multiple Bonds and Low Coordination in Phosphorus Chemistry
(Eds.: M. Regitz, O. J. Scherer), Thieme, Stuttgart, 1990.
3
Ϫ
13C NMR (C6D6): δ ϭ 4.6 (s, SiMe3), 5.0 (d, JPC ϭ 5.7 Hz,
[3] [3a]
E. Niecke, D. Gudat in ref.[2], p. 392Ϫ404, and cited litera-
5
ture. Ϫ
R. Appel in ref.[2], p. 367Ϫ374, and cited literature.
SiMe3), 32.1 (d, JPC ϭ 6.1 Hz, p-CCH3), 32.5 (d, JPC ϭ 2.6 Hz,
o-CCH3), 35.2 (d, JPC ϭ 3.8 Hz, p-CCH3), 37.0 (d, JPC ϭ 3.8 Hz,
o-CCH3), 58.2 (d, JPC ϭ 50.6 Hz, PϭC), 122.8 (d, JPC ϭ 10.2
[3b]
4
[3c]
Ϫ
H. Heydt in ref.[2], p. 375Ϫ391.
[4]
[5]
[4a] R. Appel, T. Gaitzsch, F. Knoch, G. Lenz, Chem. Ber. 1996,
1
4
[4b]
119, 1977. Ϫ
E. Niecke, M. Frost, V. von der Gönna, A.
2
3
Hz, m-Ar), 142.0 (d, JPC ϭ 24.4 Hz, ipso-Ar), 143.2 (d, JPC
ϭ
Ruban, W. W. Schoeller, Angew. Chem. 1994, 106, 2170Ϫ2172;
Angew. Chem. Int. Ed. Engl. 1994, 33, 2111Ϫ2113.
17.1 Hz, o-Ar), 145.3 (d, 5JPC ϭ 12.2 Hz, p-Ar). Ϫ MS (70 eV); m/z
(%): 527 (52) [Mϩ], 290 (100) [tBu3C6H2NPϩ]. Ϫ C25H47BrNPSi2
(528.7): calcd. C 56.79, H 8.96; found C 56.98, H 9.04.
[5a] A. R. Barron, A. H. Cowley, J. Chem. Soc., Chem. Commun.
[5b]
1987, 1272. Ϫ
H. J. Metternich, E. Niecke, Angew. Chem.
1991, 103, 336Ϫ337; Angew. Chem. Int. Ed. Engl. 1991, 30,
[5c]
Crystal-Structure Analyses. Ϫ Crystal Data: 2: C25H47INPSi2,
Mr ϭ 575.7, red tablets, 0.60 ϫ 0.50 ϫ 0.35 mm; monoclinic, space
312Ϫ313. Ϫ
P. Becker, H. Brombach, G. David, M. Leuer,
H. J. Metternich, Chem. Ber. 1992, 125, 771Ϫ774.
G. Fink, V. Möhring, Stud. Surf. Sci. Catal. (Catal. Polym. Ole-
fins) 1986, 25, 231.
[6]
[7]
˚
group P21/c (No. 14), a ϭ 8.853(3), b ϭ 33.25(1), c ϭ 10.666(4) A,
β ϭ 99.75(3)°, V ϭ 3094(2) A , Z ϭ 4, Dx ϭ 1.24 Mg mϪ3, µ(Mo-
3
˚
B. Schinkels, A. Ruban, M. Nieger, E. Niecke, J. Chem. Soc.,
Chem. Commun. 1997, 293Ϫ294.
Kα) ϭ 1.18 mmϪ1, T ϭ 293(2) K, F(000) ϭ 1200, number of reflec-
K. Karaghiosoff in ref.[2], p. 463Ϫ471.
[8]
[9]
tions: 7843 (7145 independent, Rint ϭ 0.025), R(F) ϭ 0.054, wR(F2
S. Berger, S. Braun, H.-W. Kalinowski, NMR Spectroscopy of
Main Group Elements, vol. III, Thieme Verlag, Stuttgart, 1993.
E. Niecke, D.-A.Wildbredt, Chem. Ber. 1980, 113, 1549Ϫ1565.
A. Ruban, M. Nieger, E. Niecke, Angew. Chem. 1993, 105,
1544Ϫ1545; Angew. Chem. Int. Ed. Engl. 1993, 32, 1419Ϫ1420.
D. Gudat, E. Niecke, A. Ruban, V. von der Gönna, Mag. Res.
Chem. 1996, 34, 799Ϫ806.
all data)
ϭ 0.153 (266 parameters, 50 restraints). Ϫ 3:
[10]
[11]
C25H47ClNPSi2, Mr ϭ 484.2, yellow blocks, 0.40 ϫ 0.30 ϫ 0.20
mm, monoclinic, space group P21/c (No. 14), a ϭ 8.902(2), b ϭ
3
˚
˚
32.825(5), c ϭ 10.516(1) A, β ϭ 98.95(1)°, V ϭ 3035.4(9) A , Z ϭ
4, Dx ϭ 1.06 Mg mϪ3, µ(Cu-Kα) ϭ 2.44 mmϪ1, T ϭ 293(2) K,
F(000) ϭ 1056, number of reflections: 4845 (4442 independent,
Rint ϭ 0.096), R(F) ϭ 0.075, wR(F2 all data) ϭ 0.232 (266 param-
eters, 62 restraints). Ϫ 4: C25H47BrNPSi2, Mr ϭ 528.7, orange
blocks, 0.80 ϫ 0.70 ϫ 0.50 mm, monoclinic, space group P21/c
[12]
[13] [13a] E. Niecke, M. Nieger, F. Reichert, Angew. Chem. 1988, 100,
[13b]
1781; Angew. Chem. Int. Ed. Engl. 1988, 27, 1715. Ϫ
V.
Romanenko, L. S. Kachkovskaja, M. I. Povolotskii, A. N. Cher-
nega, M. Yu. Antipin, Yu. T. Struchkov, L. N. Markovskii, Zh.
[13c]
Obshch. Khim. 1988, 58, 958Ϫ969. Ϫ
M. Nieger, Thesis,
˚
[13d]
(No. 14), a ϭ 8.851(2), b ϭ 32.87(1), c ϭ 10.556(4) A, β ϭ
Universität Bonn, 1989. Ϫ
E. Niecke, D. Gudat, Angew.
99.15(3)°, V ϭ 3032(2) A , Z ϭ 4, Dx ϭ 1.16 Mg mϪ3, µ(Mo-Kα) ϭ
3
˚
Chem. 1991, 103, 251Ϫ270; Angew. Chem. Int. Ed. Engl. 1991,
30, 217Ϫ237.
1.50 mmϪ1, T ϭ 293(2) K, F(000) ϭ 1128, number of reflections:
5622 (5325 independent, Rint ϭ 0.053), R(F) ϭ 0.055, wR(F2 all
data) ϭ 0.151 (266 parameters, 62 restraints). An absorption cor-
rection on the basis of Ψ scans was applied.
[14] [14a] R. Appel, A. Westerhaus, Tetrahedron Lett. 1982, 23, 2017.
[14b]
Ϫ
R. Appel, K.-H. Dunken, E. Gaitzsch, T. Gaitzsch, Z.
Chem. 1984, 24, 384Ϫ385.
[15]
[16]
G. M. Sheldrick, SHELXTL-Plus, Siemens Analytical X-ray In-
struments Inc., Madison, Wisconsin, USA, 1989.
G. M. Sheldrick, SHELXL-93, University of Göttingen, 1993.
[97177]
Structure Solution and Refinement: The structures were solved by
direct methods and refined anisotropically on F2 (program system:
Eur. J. Inorg. Chem. 1998, 83Ϫ85
85