Synthesis of the first 1,3,4λ3-dioxaphospholane complexes

Article abstract of DOI:10.1021/om0609214

The first 1,3,4λ³-dioxaphospholane complexes 4a,b were obtained by thermolysis of P-Cp*-substituted 2H-aza-phosphirene complex 1 in the presence of aldehydes 2a,b; the intermediate formation of phosphacarbonyl-ylide complexes 3a,b is proposed.

Full text of DOI:10.1021/om0609214

Organometallics 2007, 26, 245-246
245
Synthesis of the First 1,3,4λ3-Dioxaphospholane Complexes
Maren Bode, Martin Nieger, and Rainer Streubel*
Institut fu¨r Anorganische Chemie, Rheinische Friedrich-Wilhelms-UniVersita¨t Bonn,
Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany
ReceiVed October 7, 2006
Scheme 1. Dioxaphospholanes I-IVa
Summary: The first 1,3,4λ3-dioxaphospholane complexes 4a,b
were obtained by thermolysis of P-Cp*-substituted 2H-aza-
phosphirene complex 1 in the presence of aldehydes 2a,b; the
intermediate formation of phosphacarbonyl-ylide complexes 3a,b
is proposed.
a
E denotes either two ubiquitous organic substituents, a metal
Introduction
complex, an oxygen, or a lone pair.
1,3,2-Dioxaphospholanes I (Scheme 1) have attracted a great
deal of interest over the years because of their applicability as
precursors for polymeric and/or copolymeric materials,1 some
of which are fire-resistant and some biodegradable2 Conse-
quently, several valuable synthetic methods have been developed
for a wide variety of PIII and PV derivatives. In contrast,
knowledge about the synthesis and reactivity of 1,3,4-dioxa-
phospholanes II with PV centers is comparatively scarce,3 and
nothing is known about derivatives of II with a PIII center.4
Also, derivatives of 1,2,3-dioxaphospholane III are very rare5
and 1,2,4-dioxaphospholanes IV are unknown.
Scheme 2. Synthesis of 1,3,4λ3-Dioxaphospholane
Complexes 4a,b (i) and Assumed Formation via Transient
Complexes 3a,b (ii)
In principle, it might be possible to synthesize 1,3,4λ3-
dioxaphospholanes II via consecutive reactions starting from
λ3-oxaphosphiranes; unfortunately, they are unknown. Although,
λ3-oxaphosphirane complexes have been reported by Mathey
and co-workers6 and us,7 so far no investigations on their
chemistry have been reported. On the other hand, transiently
formed phosphacarbonyl-ylide complexes, which have a zwit-
terionic, 1,3-dipolar CR2dO-PR moiety, could provide ac-
cess,8 although some reactions may yield surprises.9 Here, we
report our first investigations on thermal reactions of a P-Cp*-
substituted 2H-azaphosphirene complex with aldehydes.
Experimental Results
formed regio- and diastereoselectively (Scheme 2, i) and could
be easily isolated without using column chromatography. Our
assumption on the reaction course (ii) is shown at the bottom
of Scheme 2. After transient formation of 1,3-dipole complexes
3a,b (cf. ref 9) an intermolecular [3+2] cycloaddition with
aldehydes 2a,b led to the final products 4a,b. Unfortunately,
neither 3a,b nor their cyclic isomers, the oxaphosphirane
complexes, were detected under these conditions. The observed
diastereoselectivity parallels observations made for nitrilium
phosphane-ylides (cf. ref 11b) and is, most probably, stereo-
chemically controlled. Further studies to elucidate the mecha-
nism are currently underway.
A selective reaction was observed when 2H-azaphosphirene
complex 110 was heated in toluene in the presence of an excess
of aldehydes 2a,b. Under these conditions complexes 4a,b were
* Corresponding author. Fax: (49)228-739616. Tel: (49)228-735345.
E-mail: r.streubel@uni-bonn.de.
(1) As most results are described in patents, just some selected refer-
ences: (a) Huang, X.-J.; Xu, Z.-K.; Wan, L.-S.; Wang, Z.-G.; Wang, J.-L.
Macromol. Biosci. 2005, 5, 322. (b) Fontaine, L.; Derouet, D.; Brosse, J.
C. Eur. Polym. J. 1990, 26, 865. (c) Biela, T.; Klosinski, P.; Penczek, S. J.
Polym. Sci. Part A: Polym. Chem. 1989, 27, 763. (d) Yasuda, H.; Sumitani,
M.; Nakamura, A. Macromolecules 1981, 14, 458.
(2) (a) Huang, S.-W.; Wang, J.; Zhang, P.-C.; Mao, H.-Q.; Zhuo, R.-X.;
Zhuo, K.; Leong, W. Biomacromolecules 2004, 5, 306. (b) Iwasaki, Y.;
Akiyoshi, K. Macromolecules 2004, 37, 7637.
The structures of complexes 4a,b in solution and solid state
were unambiguously established by multinuclear NMR studies,
(3) (a) Novikova, Z. S.; Odinets, I. L.; Lutsenko, I. F. Zh. Obshch. Khim.
1987, 57, 706. (b) Boisdon, M.; Barrans, T. J. J. Chem. Soc., Chem.
Commun. 1988, 615.
(8) Inubushi, Y.; Tran Huy, N. H.; Ricard, L.; Mathey, F. J. Organomet.
Chem. 1997, 533, 83.
(9) Streubel, R.; Ostrowski, A.; Wilkens, H.; Ruthe, F.; Jeske, J.; Jones,
P. G. Angew. Chem. 1997, 109, 409; Angew. Chem., Int. Ed. Engl. 1997,
36, 378.
(4) A current literature search revealed no example of the free ligand
system II having a PIII center.
(5) For a bicyclic derivative, see: Edmundson, R. S. R. S.; Mitchell, E.
W. J. Chem. Soc. C 1971, 19, 3179.
(6) Bauer, S.; Marinetti, A.; Ricard, L.; Mathey, F. Angew. Chem. 1990,
102, 1188; Angew. Chem., Int. Ed. Engl. 1990, 29, 1166.
(7) Streubel, R.; Kusenberg, A.; Jeske, J.; Jones, P. G. Angew. Chem.
1994, 106, 2564; Angew. Chem., Int. Ed. Engl. 1994, 33, 2427.
(10) Streubel, R.; Rohde, U.; Jeske, J.; Ruthe, F.; Jones, P. G. Eur. J.
Inorg. Chem. 1998, 2005.
(11) (a) Streubel, R. Top. Curr. Chem. 2002, 223, 91. (b) Streubel, R.;
Wilkens, H.; Ruthe, F.; Jones, P. G. Organometallics 2006, 25, 4830.
10.1021/om0609214 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 12/08/2006

246 Organometallics, Vol. 26, No. 1, 2007
Notes
standard Schlenk techniques with conventional glassware, and
solvents were dried according to standard procedures. NMR data
were collected on a Typ Bruker DMX 300 (303 K), at 121.5 MHz
(31P), 75 MHz (13C), and 300.1 MHz (1H), using TMS and 85%
H3PO4 as standard references; J/Hz. Mass spectra were recorded
on a Kratos MS 50 spectrometer (70 eV); only m/z values are given.
Melting points were obtained on a Bu¨chi 535 capillary apparatus.
Elemental analyses were performed using a Elementar (Vario EL)
analytical gas chromatograph. The κP notation in the nomenclature
is intended to differentiate between P- and O-coordination of the
appropriate heterocycle to the metal.
Synthesis of Complexes 4a,b. Ninety-six milligrams (0.16
mmol) (a) or 147 mg (0.25 mmol) (b) of 1 and 10 equiv of the
corresponding aldehyde (a: benzaldehyde, b: o-tolylaldehyde)
dissolved in 1.2 or 1.7 mL, respectively, of toluene were stirred at
65 °C for 2 h. The solvent was evaporated and the solids were
washed with n-pentane to deliver the products as colorless solids.
Figure 1. Molecular structure of 4a in the crystal (thermal ellip-
soids at 50% probability level). H atoms (except H1 and H2) are
omitted for clarity. Selected bond lengths [Å] and angles [deg]:
P1-W1 2.497(1), P1-C1 1.899(2), P1-O2 1.645(2), P1-C3
1.877(2), C1-O1 1.423(3), O1-C2 1.416(3), C2-O2 1.447(3);
C1-P1-O2 88.9(1), P1-C1-O1 102.7(1), C1-O1-C2 107.5-
(2), O2-C2-O1 108.2(2), P1-O2-C2 114.4(1), C1-P1-O2-
C2 6.3(2).14
Selected data for 4a. Mp: 168 °C. Yield: 47 mg (42%). 1H NMR
3
(C6D6): 0.87 (s, 3H, Cp*-CH3), 1.18 (d, J(P,H) ) 10.4 Hz, 3H,
Cp*(C1)-CH3), 1.51 (dd, J(H,H) ) 5.5 Hz, J(H,H) ) 0.9 Hz, 3H,
Cp*-CH3), 1.57 (dd, J(H,H) ) 3.7 Hz, J(H,H) ) 0.9 Hz, 3H, Cp*-
CH3), 1.83 (s, 3H, Cp*-CH3), 5.64 (d, J(P,H) ) 13.6 Hz, 1H, PCH),
5.71 (s, 1H, POCH), 7.06-7.24 (mc, 6H, Ph), 7.67 (dmc, J(H,H)
) 6.5 Hz, 2H, Ph), 7.79 (br d, J(H,H) ) 7.5 Hz, 2H, Ph). 13C{1H}
NMR (C6D6): 9.8 (d, J(P,C) ) 1.0 Hz, Cp*-CH3), 10.2 (d, J(P,C)
) 1.9 Hz, Cp*-CH3), 10.4 (d, J(P,C) ) 1.3 Hz, Cp*-CH3), 11.5 (s,
Cp*-CH3), 13.4 (d, J(P,C) ) 5.5 Hz, Cp*(C1)-CH3), 65.0 (d, 1J(P,C)
) 5.5 Hz, Cp*(C1)), 94.5 (s, PCO), 102.7 (d, J(P,C) ) 9.4 Hz,
OCO), 125.1 (s, Ph), 125.8 (d, J(P,C) ) 2.9 Hz, Ph), 127.2 (d,
J(P,C) ) 2.6 Hz, Ph), 127.3 (s, Ph), 127.6 (d, J(P,C) ) 2.3 Hz,
Ph), 128.3 (s, Ph), 132.5 (d, J(P,C) ) 2.3 Hz, Ph), 134.3 (d, J(P,C)
) 10.3 Hz, Cp*), 134.7 (d, J(P,C) ) 2.3 Hz, Ph), 137.9 (s, Cp*),
141.2 (d, J(P,C) ) 5.2 Hz, Cp*), 141.7 (d, J(P,C) ) 9.1 Hz, Cp*),
195.2 (dSat, 2J(P,C) ) 7.4 Hz, 1J(W,C) ) 125.4 Hz, cis-CO), 196.5
mass spectrometry, and elemental analyses and, in addition,
complex 4a by single-crystal X-ray diffraction analysis.
The 31P{1H} NMR parameters of the new compounds are of
special interest, as they show resonances around 138 ppm (4a:
138.6 (1J(W,P) ) 284.8 Hz) and 4b: 137.4 (1J(W,P) ) 282.3
Hz)), which is significantly highfield-shifted in comparison to
known 1,3,2-oxaphospholane complexes, which resonate be-
tween 170 and 195 ppm and also have significantly higher phos-
phorus-tungsten coupling constant magnitudes.9 The two hetero-
cyclic ring carbon atoms of 4a,b display resonances at 94.5 (s,
PCO) and 102.7 ((2+3)J(P,C) ) 9.4 Hz, OCO) (4a) and 92.1 (d,
J(P,C) ) 6.1 Hz, PCO) and 99.5 ((2+3)J(P,C) ) 8.7 Hz, OCO)
(4b), thus confirming the different carbon environments; this
assignment was made tentatively. It should be noted that small
coupling constants have been observed previously for endocyclic
phosphorus-carbon bonds in heterocyclic PIII complexes.12
The structure of 4a (Figure 1) shows the nonplanar 1,3,4-
dioxaphospholane ring as a central unit having the two phenyl
groups and the Cp* in a cis position; O1 is 0.57 Å out of the
best plane (C1-P1-O2-C2 torsion angle 6.3° and folding
angle with C2-O1-C1 138°). Noteworthy is also that the two
P-C distances (P1-C1 1.899(2) Å, P1-C3 1.877(2) Å) are at
the upper boundary for P-Csp3 single bonds.13
2
(d, J(P,C) ) 30.1 Hz, trans-CO) ppm. MS (EI, 70 eV): m/z )
2
702 [M+, 9]. 197.9 (d, J(P,C) ) 33.5 Hz, trans-CO) ppm. MS
(EI, 70 eV): m/z ) 588 [M+, 28]. Anal. Calc: C 40.84, H 3.60.
Found: C 41.39, H 3.80.
Selected data for 4b. Mp: 198 °C (dec). Yield: 68 mg (37%).
1H NMR (CDCl3): 0.99 (s, 3H, Cp*-CH3), 1.32 (d, 3J(P,H) ) 10.6
Hz, 3H, Cp*(C1)-CH3), 1.71-1.75 (m, 6H, Cp*-CH3), 1.82 (s, 3H,
Cp*-CH3), 2.52 (s, 3H, Ar-CH3), 2.75 (s, 3H, Ar-CH3), 6.02 (d,
J(P,H) ) 16.4 Hz, 1H, PCH), 6.22 (d, J(P,H) ) 1.7 Hz, 1H, POCH),
7.22-7.44 (mc, 6H, Ar), 7.22-7.44 (mc, 2H, Ar) ppm. 13C{1H}
NMR (CDCl3): 9.5 (d, J(P,C) ) 1.3 Hz, Cp*-CH3), 10.4 (d, J(P,C)
) 1.9 Hz, Cp*-CH3), 11.0 (d, J(P,C) ) 1.3 Hz, Cp*-CH3), 11.3 (s,
Cp*-CH3), 13.6 (d, J(P,C) ) 5.5 Hz, Cp*(C1)-CH3), 18.0 (s, Ar-
CH3), 21.6 (s, Ar-CH3), 64.7 (d, 1J(P,C) ) 5.8 Hz, Cp*(C1)), 92.1
(d, J(P,C) ) 6.1 Hz, PCO), 99.5 (d, J(P,C) ) 8.7 Hz, OCO), 124.4
(s, Ar-CH), 124.7 (d, J(P,C) ) 1.6 Hz, Ar-CH), 124.9 (s, Ar-CH),
126.9 (d, J(P,C) ) 2.3 Hz, Ar-CH), 127.4 (d, JP,C ) 2.3 Hz, Ar-
CH), 128.6 (s, Ar-CH), 129.7 (d, JP,C ) 1.6 Hz, Ar-CH), 129.8 (s,
Ar-CH), 132.4 (d, J(P,C) ) 2.9 Hz, Ar), 132.7 (d, J(P,C) ) 3.9
Hz, Ar), 134.0 (d, J(P,C) ) 11.3 Hz, Cp*), 135.0 (d, J(P,C) ) 2.9
Hz, Ar), 136.1 (s, Ar), 138.6 (s, Cp*), 141.4 (d, JP,C ) 5.5 Hz,
Experimental Section
General Procedures. All reactions and manipulations were
carried out under an atmosphere of deoxygenated dry argon, using
(12) This phenomenon was observed in heterocycles of various ring sizes
and constitutions; for example in three-membered heterocycles: (a) P,C
heterocycles: F. P, C: Mathey, F. Chem. ReV. 1990, 90, 997. (b) P, C
heterocycles with one additional N-ring center: Streubel, R.; Jeske, J.; Jones,
P. G.; Jones, R.; Herbst-Irmer, G. R. Angew. Chem., Int. Ed. Engl. 1994,
33, 80.
(13) Allen, F. A.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. Chem. Soc., Perkin Trans. 2 1987, 1.
2
Cp*), 141.5 (d, J(P,C) ) 9.1 Hz, Cp*), 195.6 (d, J(P,C) ) 7.4
(14) Crystal structure determination of 4a, C29H27O7PW. Crystal data:
triclinic, space group P1h (no. 2), a ) 9.2701(2) Å, b ) 11.6638(3) Å, c )
13.5918(3) Å, R ) 94.216(1)°, â ) 94.884(1)°, γ ) 110.355(1)°, U )
1364.44(5) Å3, Z ) 2, T ) 123 K. Data collection: a crystal 0.40 × 0.30
× 0.20 mm was used to register 11 368 intensities (Mo KR radiation, 2θmax
559) on a Nonius KappaCCD diffractometer. A semiempirical absorption
correction was applied. Structure solution and refinement: the structure was
solved by Patterson methods (SHELXS-9715a) and refined anisotropically
(full-matrix least-squares on F2 (program SHELXL-9715b)) to wR2 ) 0.0525
(for all data), R1 ) 0.0206 (I < 2σ(I)) for 347 parameters and 5931 inde-
pendent reflections. Hydrogen atoms were included using a riding model.
(15) (a) Sheldrick, G. M. Acta Crystallogr. A 1990, 46, 467. (b) Sheldrick,
G. M. SHELXL-97; University of Go¨ttingen, 1997.
1
2
Hz, J(W,C) ) 125.8 Hz, cis-CO), 196.3 (d, J(P,C) ) 29.7 Hz,
trans-CO) ppm. MS (EI, 70 eV): m/z ) 730 [M+, 19]. Anal.
Calc: C 50.98, H 4.28. Found: C 50.46, H 4.31.
Crystallographic data of 4a have been deposited at the Cambridge
Crystallographic Data Centre under the number CCDC 615112.
Copies may be requested free of charge from the Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, England (E-mail: deposit@
ccdc.cam.ac.uk).
OM0609214