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Generation Stereochemistry and Molecular Dynamics of a 1 3-Bis(phosphonio)propenide Cation.

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copper proteins, may have polymeric structures as a result of ligand flexibility: J. Whelan, B. Bosnich, Inorg. Chem. 25 (1986) 3671.
The helix can he visualized by following the chain Ag-imidazole -C,-C,CO-N-C,-C = N-Ag-imidazole- etc (Fig. 1).
3.08 8, z 1.59 8, (covalent radius Ag) + 1.02 8, (covalent radius S) +
0.40 8, (usual tolerance); radii: Manual Cambridge Crystallographic Data
a) J. M. Guss, H. C. Freeman, J. Mol. Biol. 169 (1983) 521, b) J. M. Guss,
P. R. Harrowell, M. Murata, V. A. Norris, H. C. Freeman, ;hid. 192(1986)
a) E. T. Adman, L. H. Jensen, D r . J. Chem. 21 (1981) 8; b) G. E. Norris,
B. F. Anderson, E. N . Baker, J. A m . Chem. SOC.108 (1986) 2784.
'09Ag-NMR spectrum (4.66 MHz, 10 mm tube, 0.67 g of the complex in
1.9 ml of CD,OD, room temperature) was measured directly, the shift
being relative to external AgNO, (5.9 M in D,O). Acquisition time 1.64 s,
delay time 200 s, number of scans: 1149.
Details of the synthesis and X-ray structure analysis of 1: J. F. Modder,
G. van Koten, A. L. Spek, J. Org. Chem., in press
Careful deprotonation of the dication in 3 using triethylethylidenephosphorane[' 'I as a transylidating agent [la]
leads to the 2-methyl-l,3-bis[(methyl)diphenylphosphonio]propenide monocation, which crystallizes as the iodide salt 5
in almost quantitative yield (87%). The only other product
is tetraethylphosphonium iodide. Organolithium reagents,
sodamide, or other strong bases can also be used for the
conversion of 3 into 5.
According to analytical, spectroscopic, and X-ray diffraction data, 5 is present as only one isomer with a stereochemistry as indicated in Scheme 1. Surprisingly, the reprotonation of 5 with ethereal HCI is equally stereoselective and
yields only one dication isomer in the form of the salt 6 (the
assignment in Scheme 1 is tentative). It should be noted that
the dications of 3 and 6 are regioisomers when referring to
Generation, Stereochemistry, and Molecular
Dynamics of a 1,3-Bis(phosphonio)propenide
Cation **
By Hubert Schmidbaur, * Chrislos Paschalidis,
Oliver Steigelmann, and Gerhard Miiller
Ally1 ions are the most simple resonance-stabilized 71-systems in organic chemistry. Knowledge of their structure and
molecular dynamics is of prime importance for an understanding of, e.g., allyl coordination to metals['] and reaction
pathways involving synthons with allyl-functionality.[21
Structural studies on classical metal propenide systems give
ambiguous results regarding the stereochemistry of the free
anions, since direct or indirect metal contacts cannot be excluded, either in the crystal or in the solution state[31. The
situation is not unlike the problem associated with the
stereochemistry of "free" simple carbanions (or carbenium
ions), where aggregation via the counterions Lie, Na@,KO,
MgXQ etc. (or Xo in the case of carbenium ions) is a common feat~re.1~'
In previous studies we have been able to demonstrate that
the configuration of carbanions can be determined by structural studies on phosphorus ylides, where the carbanionic
charge is compensated intramolecularly by the phosphonium centers. Cyclopropanides and cycl~butanides~~'
shown to have distinctly pyramidal carbanionic centers, and
even the simple methanides and 2-propanides are clearly
species with nonplanar ylidic functions.[61Moreover, it could
be proven that bis(phosphonio)methanediides ("carbodiphosphoranes") are highly bent."' Following the preparation of a neutral phosphoniopropenide[81we have now synthesized and structurally characterized the corresponding
bis(phosphonio)propenide cation.
1,I ,-Bis(diphenyIphosphinomethyl)ethene,l,I9] was found
to undergo facile base-catalyzed rearrangement, affording
the two stereoisomers of 2-methyl-l,3-bis(diphenylphosphino)propene (2a, b; Scheme 1). This isomerization is not
unexpected and has been observed previously in related systems.["] In contrast, 1 reacts with excess iodomethane or
diiodomethane to give 3, containing a symmetrical openchain dication, or 4, containing a cyclic 1,3-diphosphonia
dication, respectively.
[*] Prof. Dr. H. Schmidbaur, DipLChem. C. Paschalidis,
Dipl.-Chem. 0. Steigelmann [ + ]
Dr. habil. G. Miiller [ + ]
Anorganisch-chemisches Institut der Technischen Universitat Munchen
Lichtenbergstrak 4, D-8046 Garching (FRG)
['I Rontgenstrukturanalyse
[**I This work was generously supported by the Deutsche Forschungsgemeinschaft (Leibniz-Programm), by the Fonds der Chemischen Industrie, and
by Hoechst AG, Knapsack (FRG)
Q VCH Verlagsgesellschafl mbH. 0-6940 Weinheim,1989
MePh2b@ @bPh2Me
Scheme 1, Reactions starting from the diphosphino compound 1. B
= base.
The NMR spectra of the salt 5 indicate the presence of two
slightly nonequivalent diphenylmethylphosphoniogroups in
the anion at ambient temperature in C,D,NO, or CD,CN as
solvent. Similarly, the allyl carbon atoms C1 and C3 and
their hydrogen atoms are only marginally nonequivalent, as
expected for a configuration where the onium centers reside
in synlanti ( E / Z )positions relative to the allylic system. 31Pand I3C-NMR chemical shifts are in the range typical for
ylidic bonding, where onium character can be assigned to the
phosphorus atoms (6(P) = 7.9, 7.2), while carbanionic character appears to predominate at the neighboring carbon centers, whose resonances (6(Cl/C3) = 56.7/58.5) are clearly
upfield from the olefinic region. By contrast, the resonance
of the central carbon atom (C2) has its position in the aromatic region (S(C2) = 167.6), in agreement also with the
simple MO diagram for allylic anions['31 and with previous
The magnetic nonequivalence of Pl/P2, Cl/C3, and H1/
H3 affords proof of rigidity of the anion configuration in
solution at room temperature on the NMR time scale. The
spectra are, however, temperature-dependent, and on heating a reversible collapse of pertinent signals can be detected.
From the coalescence temperatures, a free activation energy
for the rotational barrier of the allylic anion can be calculated. The result (AG* = 20.5 5 1.0 kcal/mol)[14] is in good
agreement with data obtained previously for alkali-metal
propenide solution^.^^] It should be noted that for small
0570-0833/89/1212-t700 $02.50/0
Angew. Chem. Znt. Ed. Engl. 28 (1989) No. 12
cations like Li@even greater geometrical changes are to be
expected for the anions, which would lead to a complete
change also of the molecular dynamics.114b1
Figure 1 shows the result of a single crystal structure analysis of compound 5.['" As expected the allylic moiety is
L 3P1
(t. J(PC) = 40.0 Hz, P O ) , 26.89 ( A A part of a A A X X system, N = 50.36 Hz.
CCHZP), 126.27 (t, J(PC) = 10.3 Hz, =CH,), 127.98 (t, J(PC) = 26.7 Hz,
= CC,), one set of phenyl-C resonance signals.--'H-NMR
6 = 4.8 (A,A2 part of A,A,XX system, J(PH) = 14.65 Hz, 4H. CCH,P),
5.9 (t, J(PH) = 15.26 Hz, 2H, PCH,P), 6.0 (br. s, 2H, =CH,), 7.6-8.0 (m,
20H, Ph).
5 : A suspension of 1.0 g (1.41 mmol) of the salt 3 in 100 mL of tetrahydrofuran
was cooled to -40°C and treated with a solution of 0.20g (1.41 mmol) of
Et,P=CHMe in 10 mL of the same solvent. The reaction mixture was allowed
to warm to room temperature and stirred for 1 h. The precipitate was filtered
off and recrystallized from toluene/acetonitrile (0.4 g E1,PI). The filtrate was
concentrated and the oily residue crystallized from benzeneihexane (5, 0.70 g,
87%, m.p. 174"C).--"P{'H}-NMR
(CD,CN. 25°C): 6 = 7.89, 7.18(s);
''P{'H}-NMR (C6D,N02,25°C): 6 = 6.07,5.50; coalescence temperature (at
161.83 MHz): 369 K (96"C).-13C{'H}-NMR (CD,CN, -35°C): 6 = 10.93
(d, J(PC) = 63.1 Hz, PMe), 13.13 (d, J(PC) = 62.6 Hz, PMe), 25.8 (dd,
J(PC) = 18.6, 8.3 Hz, MeC), 56.7 (dd, J(PC) = 118.6. 8.6 Hz, PCH). 58.5 (dd,
J(PC) = 106.4, 1 7 3 Hz, PCH), 167.6 (dd, J(PC) = 6.86, 5.33 Hz, CMe), two
sets of phenyl-C resonance signals.--'H-NMR (C,D,NO,, 150'C): 6 = 1.98
(s, MeC), 2.33 (d, J(PH) = 12.9 Hz, PMe), 3.51 (br. s, PCH), equivalent phenylH resonance signals.
Received: June 22, 1989 [Z 3410 IEI
German version: Angew. Chem. 101 (1989) 1739
Fig. I . Structure of the cation of 5 in the crystal (ORTEP, probability ellipsoids
50%; only the hydrogen atoms at C1/C3 are shown.) Selected bond distances
C1-C2 1.393(5), C2-C3 1.389(5), C2-C4 lS ll(5); Pl-C1
[A] and angles
1.725(4), P2-C3 1.725(3); Pl-C5 1.800(4), P2-C6 1.805(4); P1-ClO 1.800(3)
Pl-C20 1.814(3),P2-C30 1.799(3),P2-C40 1.802(3).Cl-C2-C3 124.8(3),Cl-C2C4 120.4(3), C3-C2-C4 114.8(3); P1-Cl-CZ 128.4(3), P2-C3-C2 125.9(3). Maximum deviation from the best plane through Pl,P2,Cl,C2,C3,C4 is 0.09 8, for
C1. Iodide contacts are > 3.8 A.
planar, with the phosphorus substituents in E/Z-positions.
The central carbon atom C2 is in a trigonal planar configuration with the methyl carbon at a normal aliphatic distance
(C2-C4 = 1.51 l(5) .$) and two equidistant olefinic carbon
atoms at C1 -C2 = 1.393(5) and C2-C3 = 1.389(5)A.
Ylidic bonding is obvious from the distances PIC1 = 1.725(4) and P2-C3 = 1.725(3) .$, when compard
with the lengths of the other phosphorus-carbon bonds
serving as "internal reference", and the lengths of the corresponding bonds of the precursor 1.C''
The iodide counteranion has no discrete cation contact in
the crystal. In the absence of any prominent crystal packing
effects, the propenide structure determined here can thus be
taken as the unperturbed configuration of an (onium-stabilized) allylic anion. A comparison of the results with the
numerous theoretical calculations on ally1 systems that are
now available will be dealt with in a future full paper.['61
The 'H-, "C- and '-'P-NMR spectra were recorded at 270.05, 67.80 and
161.83 MHz. 2a, b: A solution of 2.0 g (4.7 mmol) of 1 in 50 mL of tetrahydrofuran was treated with 10 g (0.91 mmol) of tBuOK and heated under reflux for
12 h. After removal of all volatile components by evaporation there remained
a mixture of the two isomers as a colorless, viscous oil (1.9 g, 94%).-''P(-'H)NMR (CDCI,): 2 a : 6 = -13.5, -30.7 (AB, 4J(PP) = 5.7Hz): 2b):
6 = -17.1, -27.2 (AB, 4J(PP) = 2.8 Hz).--"C{'H]-NMR
(CDCI,): 2a:
6 = 26.6(dd,J(PC) = Hz,CH,), 36.0(dd,J(PC) = 24.94, 16.14 Hz,
CH,), 151.7 (dd, J(PC) = 25.9, 7.8 Hz, =CP), 138.4(A part o f a AXX'system,
N = 17.6 Hz. = C C , ) ;Z b : 6 = 20.9 (dd, J(PC) = 24.9. 8.3 Hz, CH,). 42.2 (dd,
J(PC) = 16.1, 6.3 Hz, CH,), 150.1 (dd, J(PC) = 26.4, 6.85 Hz, =CP), 138.2
(A part of a AXX' system, N = 15.16 Hz, CC,). 3: see Ref. 191
4: A mixture of 2.0 g (4.7 mmol) of 1 and 0.38 mL (1.26 g, 4.7 mmol) of CH,I,
in 50 mL of CH,CI, was heated under reflux for 2 d. The precipitate was filtered
off, washed. and dried in a vacuum (1.8 g, 56%), m.p. 215°C (dec.). '-'P{*H}NMR (ID,] DMSO): 6 = 13.2(s).-I3C{'H}-NMR (IDS] DMSO): 6 = 13.27
Angew. Chem. Inr. Ed. Engl. 28 (1989) N o . 12
CAS Registry numbers:
1, 120658-80-2; 2a, 123775-75-7; 2b. 123775-76-8; 3, 120883-37-6;4, 12377577-9; 5, 123775-78-0; 6, 123775-79-1; CHJ,. 75-1 1-6; Et,P=CHMe. 1784785-7.
111 C. Elschenbroich, A. Salzer: Organometaliics, VCH Verlagsgesellschaft,
Weinheim 1989, p. 28Off. Phosphoniopropenide Complexes: H. Schmidbaur, Angew. Chem. 95 (1983) 980; Angew. Chem. Inl. Ed. Engl. 22 (1983)
[2] J. March: Advanced Organic Chemistry, Wiley, New York 1985; R. H.
DeWolfe, W. G. Young in S. Patai (Ed.): The Chemistry of Alkenes, WileyInterscience, New York 1964, p. 681 ff.
[3] G. Fraenkel, W. R. Winchester, J. Am. Chem. SOC.I l l (1989) 3794 (the
most recent pertinent publication with leading references); M. Schlosser,
M. Stahle, Angew. Chem. 92 (1980) 497; Angew. Chem. Int. Ed. Engl. 19
(1980) 487; S . Bywater, D. J. Worsfold. .
Organometal. Chem. 159 (1978)
229; W. N. Setzer, P. von R. Schleyer, Adv. Organomet. Chem. 24 (1985)
141 H. Schmidbaur, U. Deschler, B. Zimmer-Gasser, D. Neugebauer, U. Schubert, Chem. Ber. 113 (1980) 902; H . Schmidbaur, U. Deschler, B. ZimmerGasser, B. Milewski-Mahrla, ibid. 14 (1981) 608; H. Schmidbaur, U.
Deschler. 5. Milewski-Mahrla, ibid. If5 (1982) 3290.
151 H. Schmidbaur, A. Schier, B. Milewski-Mahrla, U. Schubert, Chem. Ber.
115 (1982) 722; H. Schmidbaur, A. Schier, D. Neugebauer, ibrd. 116 (1983)
161 H. Schmidbaur. A. Schier, C. M. F. Frazao, G. Miiller, J. Am. Chem. Soc.
108 (1986) 976; H. Schmidbaur, C. Kriiger, J. Jeong, A. Schier. D. L.
Wilkinson, G. Muller, N . J. Chem. 13 (1989) 341 and references cited
171 U. Schubert, C. Kappenstein, B. Milewski-Mahrla, H. Schmidbaur, Chem.
Ber. 114 (1981) 3070.
[S] H. Schmidbaur, W. Malisch, D. W H. Rankin, Chem. Ber. 104 (1971) 145.
191 H. Schmidbaur, C. Paschalidis, 0.Steigelmann, G. Miiller, Chem. Ber. 122
(1989) 1851.
[lo] L. Homer, I. Ertel, H.-D. Ruprecht, 0. Belowski, Chem. Ber. 103 (1970)
Ill] H. Schmidbaur, W.Tronich, Chem. Ber. 101 (1968) 604.
[I21 H. J. Bestmann, Chem. Ber. 95 (1962) 58.
1131 F. A. Cotton: Chemical Applications oJCroup Theory, Wiley-Interscience,
New York 1963, p. 156ff.
I141 a) G. Binsch, H. Kessler, Angew. Chem. 92 (1980) 445; Angew. Chem. Int.
Ed. Engl. I9 (1980) 411; b) G. Boche, Top. Curr. Chem. 146 (1988) 7.
1151 Crystal structure data of compound 5 (C,oH311P2,M , = 580.43): monoclinic, space group P2,/n, a = 10.018(1), b = 15.522(2), c = 17.937(2)A,
fi = 101.22(1)", V = 2735.9 A3, Z = 4,
= 1.409 g cm-', p(MoK,) =
12.9 cm-I, T = -50°C. 4757 independent reflexions (Itzn,
= 0.028). with
4110 'observed' at Fo 2 4.00(F0),[(sinojn),,. = 0.595, hkl: + 11, + 18,
k21, Mo,. radiation, 3. = 0.71069 A, graphite monochromator, Syntex
P2, diffractometer]. Structure solution by Patterson methods (SHELXS86), R (R,)= 0.032 (0.036), w = l/02(Fo); (anisotropic, H constant.
SHELX-76). Ae,,,(max/min) = O S - 0 . 4 1 eiA'. Further data are available from the Fachinformationszentrum Karlsruhe, Geselischaft fur
wissenschaftlich-technische Information mbH, D-7514 EggensteinLeopoldshafen 2, on quoting the depository number CSD-54221, the
names of the authors, and the journal citation.
1161 L. Radom in E. Buncel, T. Durst (Eds.): Comprehensive Carbanion Chemistry Part C, Elsevier, Amsterdam 1987, Chap. 1.
Veriagsgesell.whaft mbH, D-4940 Weinheim, 1989
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phosphonium, molecular, propenide, generation, dynamics, bis, cation, stereochemistry
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