Transition-metal-substituted acyl phosphanes and phosphaalkenes. 32. Transformation of an FeP=C unit of a phosphaalkene into a FeP=C-N-N=C moiety by chain extension through insertion of the 1,3-dipole (-N-N(Ar)-CH+) of sydnones

Article abstract of DOI:10.1021/om9700876

The metallophosphaalkene (η₅-C₅Me₅)(CO)₂FeP=C(NMe ₂)₂ (1) underwent reaction with sydnones 3-aryl-NNOC(O)CH (aryl = C₆H₅ (2a), 4-FC₆H₄ (2b), 4-ClC₆H₄ (2c), 4-BrC₆H₄ (2d)) to afford the novel ferriophosphaalkenes (η⁵-C₅Me₅)(CO) ₂FeP=CHN(aryl)N=C(NMe₂)₂ (3a-d). Compound 3a forms the [2 + 2] phosphetanyl cycloadduct 4a with dimethyl fumarate. The molecular structure of 3a was determined by single-crystal X-ray diffraction.

Full text of DOI:10.1021/om9700876

2958
Organometallics 1997, 16, 2958-2962
Tr a n sition -Meta l-Su bstitu ted Acyl P h osp h a n es a n d
P h osp h a a lk en es. 32.1 Tr a n sfor m a tion of a n F eP dC Un it
of a P h osp h a a lk en e in to a F eP dCsNsNdC Moiety by
Ch a in Exten sion th r ou gh In ser tion of th e 1,3-Dip ole
(-NsN(Ar )sCH+) of Syd n on es
Lothar Weber,* Matthias H. Scheffer, Eike Beckmann,
Hans-Georg Stammler, and Beate Neumann
Fakulta¨t fu¨r Chemie der Universita¨t Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany
Received February 5, 1997X
The metallophosphaalkene (η5-C5Me5)(CO)2FePdC(NMe2)2 (1) underwent reaction with
sydnones 3-aryl-NNOC(O)CH (aryl ) C6H5 (2a ), 4-FC6H4 (2b), 4-ClC6H4 (2c), 4-BrC6H4 (2d ))
to afford the novel ferriophosphaalkenes (η5-C5Me5)(CO)2FePdCHN(aryl)NdC(NMe2)2 (3a -
d ). Compound 3a forms the [2 + 2] phosphetanyl cycloadduct 4a with dimethyl fumarate.
The molecular structure of 3a was determined by single-crystal X-ray diffraction.
Sch em e 1
In tr od u ction
Mesoionic compounds2 such as 1,2,3-oxadiazolium-5-
olates (sydnones) are masked 1,3-dipoles, which smoothly
convert alkynes into pyrazole derivatives.2,3 The treat-
ment of sydnones with alkenes give rise to the forma-
tion of ∆2-pyrazolines as the result of [3 + 2] cycload-
ditions.4 Extension of this methodology to phos-
phaalkynes and suitably functionalized phosphaalkenes
provides a useful access to 1,2,4- and 1,2,3-diazaphos-
pholes5,6 (Scheme 1).
P-Metallophosphaalkenes7 function as electron-rich
heteroalkenes, which undergo [1+2] cycloadditions with
isocyanides8 and [2 + 2] cycloadditions with electron-
deficient alkenes9 and alkynes.10 The initial step in the
formation of N-metallo-1,2,3-diazaphospholes from (η5-
C5Me5)(CO)2FePdC(NMe2)2 and diazoacetates may be
considered as a [3 + 2] cycloaddition11 (Scheme 2). With
regard to the rich chemistry displayed by metallophos-
phaalkenes, we were interested in the reactivity of such
compounds toward sydnones, and here we describe the
unprecedented insertion of a 1,3-dipole into the PdC
double bond of the phosphaalkene.
Exp er im en ta l Section
All operations were performed with standard Schlenk
techniques in an oxygen-free argon atmosphere. Solvents were
X Abstract published in Advance ACS Abstracts, May 15, 1997.
(1) Part 31: Weber, L.; Kaminski, O.; Quasdorff, B.; Stammler, H.-
G.; Neumann, B. J . Organomet. Chem., in press.
(2) Review: Newton, C. G.; Ramsden, C. A. Tetrahedron 1982, 38,
2965.
(3) (a) Huisgen, R.; Grashey, R.; Gotthardt, H. Angew. Chem. 1962,
74, 29. (b) Gotthardt, H.; Reiter, F. Chem. Ber. 1979, 112, 1193, 1206.
(4) Gotthardt, H.; Reiter, F. J ustus Liebigs. Ann. Chem. 1979, 63.
(5) Ro¨sch, W.; Richter, H.; Regitz, M. Chem. Ber. 1987, 120, 1809.
(6) Review: Schmidpeter, A.; Karaghiosoff, K. In Multiple Bonds
and Low Coordination in Phosphorus Chemistry; Regitz, M., Scherer,
O. J ., Eds.; Thieme: Stuttgart, Germany, 1990; p 258.
(7) Review: Weber, L. Angew. Chem. 1996, 108, 292; Angew. Chem.
Int. Ed. Engl. 1996, 35, 271.
(8) Weber, L.; Ru¨hlicke, A.; Stammler, H.-G.; Neumann, B. Orga-
nometallics 1993, 12, 4653.
(9) Weber, L.; Kaminski, O.; Stammler, H.-G.; Neumann, B.; Ro-
manenko, V. D. Z. Naturforsch., B, 1993, 48, 1784.
(10) Weber, L.; Kaminski, O.; Stammler, H.-G.; Neumann, B.; Boese,
R. Z. Naturforsch., B 1994, 49, 1693.
dried by standard methods and was freshly distilled under
argon. Infrared spectra were recorded on a Bruker FT-IR
IFS66 spectrometer, and the 1H, 13C, and 31P NMR spectra
were recorded in C6D6 at 22 °C on Bruker AM Advance
DRX 500, Bruker AC 250, and Bruker AC 100 instruments.
Standards: SiMe4 (1H, 13C), external 85% H3PO4 (31P). El-
emental analyses were performed in the microanalytical lab-
oratory of our department. Mass spectra were obtained with
a Varian MAT-CH5-DF spectrometer. The metallophosphaalk-
ene (η5-C5Me5)(CO)2FePdC(NMe2)2 (1)9 and the sydnones
RNNOC(O)CH (R ) Ph,12 4-FC6H4,13 4-ClC6H4,14 4-BrC6H4,15
4-MeOC6H4,16 Me17 ) were prepared according to the literature.
Dimethyl fumarate was purchased commercially.
(11) Weber, L.; Kaminski, O.; Stammler, H.-G.; Neumann, B.;
Organometallics 1995, 14, 581.
(12) Earl, J . C.; Mackney, A. W. J . Chem. Soc. 1935, 899.
(13) Bellas, M.; Suschnitski, H. J . Chem. Soc. 1966, 189.
S0276-7333(97)00087-3 CCC: $14.00 © 1997 American Chemical Society

Transformation of an FePdC Unit of a Phosphaalkene
Organometallics, Vol. 16, No. 13, 1997 2959
dichloromethane to the slurry was accompanied by efferves-
cence and a color change from dark red to orange. Stirring
was continued for 24 h at 20 °C. Volatile compounds were
removed in vacuo, and the remaining red-brown powder was
extracted with 40 mL of ether. The extract was freed from
the solvent to yield 3b as a red-brown powder (1.41 g, 66%).
Attempts to crystallize the compound invariably led to decom-
position. IR (Nujol, cm-1): ν 1982 vs [ν(CO)], 1934 vs [ν(CO)],
1560 w, 1500 m, 1310 w, 1291 m, 1264 m, 1227 m, 1151 w,
1097 w, 930 w, 844 w, 642 w, 580 m. 1H NMR: δ 1.53 (s,
15H, C5Me5), 2.40 (s, 6H, NCH3), 2.67 (s, 6H, NCH3), 7.15 (m,
Sch em e 2
2
4H, aryl H), 9.14 (d, J PH ) 9.0 Hz, PdCH). 13C{1H} NMR: δ
9.36 [s, C5(CH3)5], 38.8 (s, NCH3), 39.2 (s, NCH3), 95.7 [s, C5-
(CH3)5], 114.3 s, 115.6 s, 115.8 s, 144.8 (s, aryl C), 165.8 (s,
1
C)N), 175.1 (d, J PC ) 69.2 Hz, PdC), 219.0 (s, CO). 31P{1H}
NMR: δ 204.4 s. 19F{1H} NMR: δ 97.4 s. MS/CI: m/z 514
(M+), 458 (M+ - 2CO). Anal. Calcd for C24H32FFeN4O2P
(514.36): C, 56.04; H, 6.27; N, 10.89. Found: C, 54.80; H, 5.98;
N, 10.30. Various attempts at purification were unsuccessful
due to partial decomposition to (η5-C5Me5)2Fe2(CO)4 and
unidentified components.
(E)-(η5-C5Me5)(CO)2F eP dCH N(4-ClC6H 4)NdC(NMe2)2
(3c). Similarly, compound 1 (0.80 g, 2.12 mmol) and 3-(p-
chlorophenyl)sydnone 2c (0.43 g, 2.12 mmol) were reacted in
a mixture of ether (30 mL) and dichloromethane (10 mL) at
0-10 °C. After 2 h of stirring the solution was evaporated to
dryness, and the red-brown solid residue was extracted with
ether (40 mL). Filtration of the extract and removal of solvent
in vacuo yielded 3c as a red-brown powder (0.81 g, 72%). IR
(Nujol, cm-1): ν 1983 vs [ν(CO)], 1934 vs [ν(CO)], 1758 w, 1665
w, 1589 w, 1557 w, 1485 s, 1307 w, 1287 m, 1263 m, 1222 w,
1151 w, 1093 w, 817 m, 797 w, 641 w, 582 m. 1H NMR: δ
1.52 (s, 15H, C5Me5), 2.38 (s, 6H, NCH3), 2.66 (s, 6H, NCH3),
7.00-7.14 (m, 4H, aryl H), 9.16 (d, 2J PH ) 9.2 Hz, PdCH). 13C-
{1H} NMR: δ 9.34 [s, C5(CH3)5], 38.5 (s, NCH3), 39.2 (s, NCH3),
95.8 [s, C5(CH3)5], 115.6 s, 129.1 s, 144.4 (s, aryl C), 165.9 (s,
1
CdN), 174.5 (d, J PC ) 67.7 Hz, PdC), 218.8 (s, CO). 31P{1H}
P r ep a r a t ion of Com p ou n d s. (E)-(η5-C5Me5)(CO)2-
F eP dCHN(P h )NdC(NMe2)2 (3a ). A sample of solid 3-phen-
ylsydnone 2a (0.50 g, 3.06 mmol) was added to a solution of
(η5-C5Me5)(CO)2FePdC(NMe2)2 (1) in diethyl ether (40 mL).
In order to obtain a homogeneous solution, dichloromethane
(10 mL) was added at ambient temperature, whereupon an
effervescence and a color change from dark red to orange-red
was observed. After the mixture was stirred overnight, solvent
and volatiles were removed in vacuo. The remaining red-
brown powder was extracted with ether (40 mL) and filtered.
The filtrate was stored at -30 °C for 24 h to yield dark red
diamond-shaped crystals. Concentration of the mother liquor
to ca. 10 mL and repeated crystallization furnished a second
crop of 3a . Yield: 0.93 g (61%). IR (Nujol, cm-1): ν 1985 vs
[ν(CO)], 1940 s [ν(CO)], 1589 s [ν(CN)], 1551 s, 1490 s, 1422
w, 1365 s, 1305 m, 1264 m, 1218 w, 1176 w, 1151 m, 1137 w,
1105 m, 1074 w, 1063 w, 1041 w, 1027 w, 991 m, 930 m, 899
w, 874 w, 817 m, 776 w, 763 m, 746 s, 690 m, 640 m, 630 m,
578 s, 548 s, 510 m. 1H NMR: δ 1.69 (s, 15H, C5Me5), 2.59 (s,
6H, NCH3), 2.85 (s, 6H, NCH3), 6.86-7.53 (s, br, 5H, C6H5),
NMR: δ 215.4 s. MS/CI: m/z 530 (M+), 502 (M+ - CO), 474
(M+ - 2CO). Anal. Calcd for C24H32ClFeN4O2P (580.82): C,
54.30; H, 6.07; N, 10.56. Found C, 54.43; H, 6.12; N, 10.15.
(E)-(η5-C5Me5)(CO)2F eP dCH N(4-Br C6H 4)NdC(NMe2)2
(3d ). Analogously, equimolar amounts of 1 (1.76 g, 4.65 mmol)
and 3-(p-bromophenyl)sydnone 2d (1.20 g, 4.65 mmol) were
reacted in a mixture of ether (40 mL) and dichloromethane
(10 mL) in the temperature range of 0-10 °C. Workup as
described above afforded 1.79 g (67%) of 3d as a red-brown
powder. IR (Nujol, cm-1): ν 1983 vs [ν(CO)], 1934 vs [ν(CO)],
1583 w, 1481 m, 1262 w, 1148 m, 1073 w, 1031 m, 973 w, 815
m, 801 w, 642 w, 582 m. 1H NMR: δ 1.53 (s, 15H, C5Me5),
2.39 (s, 6H, NCH3), 2.67 (s, 6H, NCH3), 7.10-7.44 (m, 4H, aryl
2
H), 9.14 (d, J PH ) 9.4 Hz, PdCH). 13C{1H} NMR: δ 9.30 [s,
C5(CH3)5], 38.5 (s, NCH3), 39.2 (s, NCH3), 95.8 [s, C5(CH3)5],
116.2 s, 131.9 s, 144.8 (s, aryl C), 165.9 (s, CdN), 174.5 (d,
1J PC ) 68.3 Hz, PdC), 218.8 (s, CO). 31P{1H} NMR: δ 216.7
s. MS/CI: m/z ) 576 (M+ + H), 548 (M+ + H - CO), 520 (M+
+ H - 2CO). Anal. Calcd for C24H32BrFeN4O2P (575.27): C,
50.11; H, 5.61; N, 9.74. Found C, 49.35; H, 5.63; N, 9.22.
Various attempts at purification were unsuccessful due to
partial decomposition.
2
9.41 (d, J PH ) 8.8 Hz, PCH). 13C{1H} NMR: δ 10.1 [s, C5-
(CH3)5], 39.4 (s, NCH3), 40.0 (s, NCH3), 94.6 [s, C5(CH3)5], 115.6
s, 121.1 s, 129.9 s, 146.9 (s, phenyl C), 166.6 (s, CdN), 176.0
(d, 1J PC ) 69.2 Hz, PdC), 219.7 (s, CO). 31P{1H} NMR: δ 204.9
s. MS/CI: m/z ) 496 (M+), 440 (M+ - 2CO), 397 (M+ - 2CO
- MeNdCH2). Anal. Calcd for C24H33FeN4O2P (496.36): C,
58.07; H, 6.70; N, 11.29. Found: C, 57.95; H, 6.88; N, 11.19.
(E)-(η5-C5Me 5)(CO)2F eP dCH N(4-F C6H 4)NdC(NMe 2)2
(3b). A sample of solid 3-(fluorophenyl)sydnone 2b (0.74 g,
4.15 mmol) was added to a chilled solution (0 °C) of 1 (1.57 g,
4.15 mmol) in 50 mL of ether. The addition of 10 mL of
R ea ct ion
of
E -(η5-C5Me5)(CO)2F eP dCH N(P h )Nd
C(NMe2)2 (3a ) w ith Dim eth yl F u m a r a te. A solution of 0.25
g (1.73 mmol) of dimethyl fumarate in 10 mL of ether was
added over 30 min to the chilled solution (-30 °C) of 0.86 g
(1.73 mmol) of 3a in 50 mL of ether. After it was warmed to
ambient temperature, the orange solution was stirred for 24
h. Filtration was followed by evaporation of the filtrate to
dryness. The solid residue was dissolved in 25 mL of ether
and stored at 5 °C for 24 h to yield 0.69 g (63%) of orange
crystalline 4a . IR (Nujol, cm-1): ν 1997 vs [ν(CO)], 1939 vs
[ν(CO)], 1723 vs [ν(CO)ester], 1595 m, 1579 m, 1560 m, 1506 m,
1484 w, 1435 w, 1351 w, 1313 w, 1263 w, 1209 m, 1157 w,
1120 w, 1065 w, 1035 w, 993 w, 953 w, 918 w, 754 w, 699 w,
(14) Baker, W.; Ollis, W. D.; Poole, V. D. J . Chem. Soc. 1949,
307.
(15) Eade, R. A.; Earl, J . C. J . Chem. Soc. 1948, 2307.
(16) Eade, R. A.; Earl, J . C. J . Chem. Soc. 1946, 591.
(17) Hammick, D. L.; Voaden, D. J . J . Chem. Soc. 1961, 3303.

2960 Organometallics, Vol. 16, No. 13, 1997
Weber et al.
638 w, 592 w. 1H NMR (500 MHz, 300 K): δ 1.38 (s, 15H,
C5Me5), 2.60 (s, 6H, NCH3), 2.86 (s, 6H, NCH3), 3.32 (s, br,
3H, OCH3), 3.39 (s, 3H, OCH3), 3.56 (s, br, 1H, CHNPh), 4.31
[s, br, 1H, PCH(CO2Me)CH], 5.53 [s, br, 1H, PCH(CO2Me)],
6.76 (t, 3J HH ) 7.2 Hz, 1H, p-phenyl H), 7.22 (m, 2H, m-phenyl
Sch em e 3
3
H), 7.55 (d, J HH ) 7.4 Hz, o-phenyl H). 1H NMR (100 MHz,
335 K): δ 1.38 (s, 15H, C5Me5), 2.56 (s, 6H, NCH3), 2.81 (s,
6H, NCH3), 3.31 (s, 3H, OCH3), 3.38 (s, 3H, OCH3), 3.53 (dd,
2
3
3J HH ) 10.2 Hz, J PH ) 4.2 Hz, PCHN), 4.43 [dt, J HH ) 10.4
3
3
Hz, J PH ) 4.1 Hz, PCH(CO2Me)CH], 5.33 (dd, J HH ) 10.2
2
3
Hz, J PH ) 1 Hz, 1H, PCH(CO2Me)), 6.76 (t, J HH ) 7.2 Hz,
3
1H, p-phenyl H), 7.22 (m, 2H, m-phenyl H), 7.55 (d, J HH
)
7.4 Hz, o-phenyl H). 13C{1H} NMR: δ 9.0 [s, C5(CH3)5], 34.6
1
(d, J PC ) 17.3 Hz, PCHCO2Me), 39.46 [s, PCH(CO2Me)C],
39.51 (s, NCH3), 48.4 (s, br, OCH3), 51.2 (s, OCH3), 62.9 (d,
1J PC ) 11.3 Hz, PCHN), 96.5 [s, C5(CH3)5], 116.1 s, 118.3 s,
128.8 s, 152.7 s (phenyl C), 165.6 (s, NdCN2), 173.0 [s, C(O)-
OCH3], 175.0 [d, 2J PC ) 11.6 Hz, PCHC(O)OCH3], 216.1 (s, CO),
217.5 (s, CO). 31P{1H} NMR: δ 113.0 s. MS/CI: m/z 641 (M+
+ H), 612 (M+ - CO), 584 (M+ - 2CO). Anal. Calcd for C30H41
-
FeN4O6P (640.50): C, 56.26; H, 6.45; N, 8.75. Found: C, 56.30;
H, 6.40; N, 8.75.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 3a . Single
crystals of 3a were grown from diethyl ether at 5 °C. A dark
red crystal with the approximate dimensions 0.60 × 0.50 ×
0.40 mm3 was measured on a Siemens P21 diffractometer with
Mo KR radiation at 173 K. Crystal data and refinement de-
tails (refined from the diffractometer angles of 20 centered
reflections): a ) 9.020(3) Å, b ) 9.104(2) Å, c ) 16.155(4) Å,
R ) 83.73(2)°, â ) 76.42(2)°, γ ) 74.55(2)°, V ) 1241.4(6) Å3,
Z ) 2, dcalcd ) 1.328 g cm-3, µ ) 0.699 mm-1, space group P1h,
data collection of 5664 unique intensities (2Θmax ) 55°),
structure solution by direct methods and anisotropic refine-
ment with full-matrix least-squares methods on F2 for all non-
hydrogen atoms (program used Siemens SHELXTLplus
/SHELXL-93), riding groups for hydrogen atoms, 298 param-
eters, maximum residual electron density 0.3 e/Å3, R1 ) 0.029
based on 4936 reflections with (I > 2σ(I)), Rw ) 0.081 (w )
1/[σ2(Fo2) + (0.0347P)2 + 0.6085P] with P ) (Fo2 + 2Fc2) for all
data.
nance was observed at δ 8.64 (d, 2J PH ) 14.9 Hz).18 The
carbon atom of the PdC bond of the products gave rise
to doublets at δ(13C) 174.5-176.0 (1J PC ) 67.7-69.2 Hz)
in their 13C{1H} NMR spectra. In PhPdC(H)NMe2 the
methylene carbon atom was registered at δ 187.5 (d,
1J PC ) 48.0 Hz).
Resu lts a n d Discu ssion
Two singlets in the range of δ 2.38-2.59 and 2.66-
2.85, each accounting for six protons, agree with two
magnetically and chemically different dimethylamino
groups. A singlet in the 13C NMR spectra at δ 165.9-
166.6 was attributed to the carbon atom of a guanidino
unit. The terminal carbonyl groups resonated at δ
218.8-219.7 ppm. The IR spectra of 3a (Nujol) featured
two intense ν(CO) bands at 1985 and 1940 cm-1. In the
haloaryl-substituted analogues 3b-d the bands of the
stretching modes of the Fe(CO)2 group appear at 1983
and 1934 cm-1. Thus, the electron-withdrawing effect
of the halophenyl substituent is only weakly mirrored
by the 13C NMR resonances and ν(CO) absorptions of
3b-d . Chemical ionization mass spectra showed that
in the products the fragment NsN(aryl)CH was incor-
porated in 1. The spectroscopic data are consonant with
ferriophosphaalkenes displaying a (C5Me5)(CO)2FePd
CHN(aryl) group and a guanidino unit.
X-r a y Str u ctu r e An a lysis of 3a . Single crystals of
3a were grown from diethyl ether at 5 °C. The results
of the structural determination are shown in Figure 1.
Positional parameters are given in the Supporting
Information, and selected bond lengths and angles for
the compound are given in Table 1. The analysis
confirms the presence of an E-configured ferriophos-
phaalkene with a distorted “piano stool” geometry
The metallophosphaalkene (η5-C5Me5)(CO)2FePd
C(NMe2)2 (1) smoothly reacted with equimolar amounts
of the sydnones 3-aryl-NNOC(O)CH (aryl ) C6H5 (2a ),
4-FC6H4 (2b), 4-ClC6H4 (2c), 4-BrC6H4 (2d )) in an ether/
dichloromethane mixture (0-10 °C) to afford the red-
brown microcrystalline ferriophosphaalkenes (E)-(η5-
C5Me5)(CO)2FePdCHN(aryl)NdC(NMe2)2 (3a-d) in good
yields (61-72%) (Scheme 3). In contrast to this, the re-
action of 1 with the more electron-rich 3-methylsydnone
or 3-(p-methoxyphenyl)sydnone led to decomposition.
Compound 3a was purified by crystallization from ether,
whereas solutions of 3b-d suffer from partial decom-
position under similar conditions. The course of the
reaction was monitored by 31P NMR spectroscopy. The
singlet for compound 1 (δ 140.0) was replaced by a
singlet at δ 204.9 -216.7 for the products, which falls
in the range of phosphaalkenes.
No intermediates such as the also conceivable bicyclic
1,3-cycloadduct A or the heterocycle B could be detected.
It is remarkable that the reaction of the metallophos-
phaalkene with the sydnones 2c and 2d came to
completion after about 3 h, whereas with 2a and 2b a
1
reaction time of 24 h was necessary. In the H NMR
spectra of 3a -d doublets at δ 9.14-9.41 (1J PH ) 8.8-
9.4 Hz) were indicative of the presence of a PdCH
function. In PhPdCH(NMe2) the corresponding reso-
(18) Becker, G.; Mundt, O. Z. Anorg. Allg. Chem. 1980, 462, 130.

Transformation of an FePdC Unit of a Phosphaalkene
Organometallics, Vol. 16, No. 13, 1997 2961
F igu r e 2.
N(1)-C(14) (1.399(2) Å) are shortened as compared to
the single bonds between N(3) and N(4) with the carbon
atoms of the methyl substituents (average 1.454 Å). The
bond length N(2)-C(20) (1.303(2) Å) agrees with a
double bond. The plane defined by the atoms C(20),
N(3), and N(4) and the above-mentioned plane with the
atoms P(1), C(13), N(1), and N(2) enclose an interplanar
angle of 103.0°. The nitrogen atoms N(1) and N(2) are
linked by a single bond (1.420(2) Å). From the torsion
angles C(11)-Fe(1)-P(1)-C(13) (48.7°) and C(12)-
Fe(1)-P(1)-C(13) (-45.6°) it is obvious that the orga-
nophosphorus ligand bisects the Fe(CO)2 angle and is
oriented trans to the η5-C5Me5 ligand (Figure 2).
It is conceivable that the formation of metallophos-
phaalkenes 3a -d was initiated by a [1,3]-dipolar cy-
cloaddition, resulting in the bicyclic species A. In
keeping with the precedents in alkyne and alkene
chemistry carbon dioxide is extruded to give heterocycle
B, which undergoes ring opening to the final products.
The formation of a stable guanidino function may be
one of the driving forces of this process. Accordingly,
no reaction was observed between (η5-C5Me5)(CO)2-
FePdC(SiMe3)2 and sydnone 2a .
The reaction of equimolar amounts of 3a and dimethyl
fumarate led to the formation of an orange crystalline
product (4a ) in 63% yield. Elemental analysis as well
as spectroscopic data revealed the compound as a [2 +
2] cycloadduct involving the PdC and CdC bonds of the
reactants. Thus, the 31P{1H} NMR resonance of 3a at
δ 204.9 was replaced by a singlet at δ 113.0. This
resonance compares well with the signal for the meta-
lated phosphorus atom in diphosphetane 5 (δ 124.5)20
and agrees with the presence of a phosphetanyl ligand
in 4a (Scheme 4).
F igu r e 1.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3a
Fe(1)-C(11)
Fe(1)-C(4)
Fe(1)-C(5)
Fe(1)-C(1)
P(1)-C(13)
O(2)-C(12)
N(1)-C(14)
N(2)-C(20)
N(3)-C(21)
N(4)-C(20)
N(4)-C(24)
1.746(2)
2.101(2)
2.113(2)
2.146(2)
1.697(2)
1.149(2)
1.399(2)
1.303(2)
1.447(3)
1.364(2)
1.457(2)
Fe(1)-C(12)
Fe(1)-C(3)
Fe(1)-C(2)
Fe(1)-P(1)
O(1)-C(11)
N(1)-C(13)
N(1)-N(2)
N(3)-C(20)
N(3)-C(22)
N(4)-C(23)
1.752(2)
2.106(2)
2.120(2)
2.2956(7)
1.147(2)
1.377(2)
1.420(2)
1.381(2)
1.456(2)
1.454(2)
C(11)-Fe(1)-C(12) 94.23(8) C(20)-N(4)-C(23) 121.5(2)
C(11)-Fe(1)-P(1)
C(12)-Fe(1)-P(1)
C(13)-P(1)-Fe(1) 109.67(6) O(1)-C(12)-Fe(1) 178.7(2)
C(13)-N(1)-C(14) 123.09(13) O(1)-C(11)-Fe(1) 178.42(14)
C(13)-N(1)-N(2)
C(14)-N(1)-N(2)
C(20)-N(2)-N(1)
89.94(6) C(20)-N(4)-C(24) 122.1(2)
87.07(6) C(23)-N(4)-C(24) 114.5(2)
117.55(12) N(1)-C(13)-P(1)
116.80(12) C(17)-C(16)-C(15) 120.9(2)
114.22(13) C(17)-C(18)-C(19) 121.4(2)
125.00(12)
C(20)-N(3)-C(21) 118.1(2)
C(20)-N(3)-C(22) 120.0(2)
C(21)-N(3)-C(22) 115.0(2)
N(2)-C(20)-N(4)
N(2)-C(20)-N(3)
N(4)-C(20)-N(3)
128.1(2)
116.7(2)
115.1(2)
(P(1)-Fe(1)-C(11) ) 89.94(6)°, P(1)-Fe(1)-C(12) )
87.07(6)°, C(11)-Fe(1)-C(12) ) 94.23(8)°). Two legs are
represented by nearly linear carbonyls. The phos-
phaalkenyl ligand is connected via an FesP single bond
(2.2956(7) Å) to the (η5-C5Me5)(CO)2Fe fragment.18 In
1 an FesP bond distance of 2.325(2) Å was observed.9
The PdC bond length of 1.697(2) Å compares well with
the corresponding bond distance in 1 (1.709(5) Å) and
falls into the typical range for amino-substituted phos-
phaalkenes (1.70-1.76 Å).19 Shorter PdC bond lengths
of 1.65-1.67 Å were observed in nonconjugated phos-
phaalkenes, which are close to the calculated value of
1.646 Å in HPdCH2.19 The atoms P(1), C(13), N(1), and
N(2) are located in a plane (average deviation 0.043 Å),
from which the iron atom Fe(1) and the carbon atom
C(20) are displaced by 0.3067 and 1.0090 Å, respectively.
The dihedral angle between the phenyl group at N(1)
and the plane defined by P(1), C(13), N(1), and N(2)
amounts to 14.8°, which points to an efficient conjuga-
tion of the lone pair at N(1) with the PdC bond and the
6-π-electron system of the aryl group. In keeping with
this, the bond lengths C(13)-N(1) (1.377(2) Å) and
Further structural information is derived from the 1H
and 13C{1H} NMR spectra of 4a . The 1H NMR spectrum
(500 MHz) at 300 K displays sharp singlets at δ 1.38
(15H), 2.60 (6H), 2.86 (6H), and 3.39 (3H) for the C5-
Me5 group, two distinct N(CH3)2 groups, and one methyl
ester function. The second methyl ester group gives rise
to a broad singlet at δ 3.32. Broad singlets at δ 3.56
(1H), 4.31 (1H), and 5.53 (1H) are due to the protons at
the four-membered heterocycle. At 335 K both ester
methyl groups are observed as sharp singlets. A doublet
3
of triplets (3J HH ) 10.4, J PH ) 4.1 Hz) at δ 4.43 is
attributed to HA, which experiences 3J HH trans couplings
3
to HB and HC, and a J PH coupling to the phosphorus
3
atom. In 5 the corresponding couplings are J HH ) 13
3
Hz and J PH ) 4.1 Hz.20
(19) Chernega, A. N.; Ruban, A. V.; Romanenko, V. D.; Markovski,
L. N.; Korkin, A. A.; Antipin, M. Yu.; Struchkov, Yu. T. Heteroat. Chem.
1991, 2, 229.
(20) Weber. L.; Frebel, M.; Boese, R. Chem. Ber. 1990, 123, 733.

2962 Organometallics, Vol. 16, No. 13, 1997
Weber et al.
Sch em e 4
nitrogen-substituted CH group. In the 1,3-diphosphe-
tane (PhPCHNMe)2 the respective proton gives rise to
2
a triplet at δ 3.69 (t, J PH ) 3.4 Hz).18
The 13C nuclei of the four-membered ring resonate at
δ 34.6 (d, 1J PC ) 17.3 Hz), 39.46 (s), and 62.9 (d, 1J PC
)
11.3 Hz). Only the carbon atoms adjacent to the
phosphorus center experience heteronuclear coupling.
For the chemically and magnetically different methyl
ester units a broad singlet at δ 48.4 and a sharp singlet
at δ 51.2 are seen, whereas a singlet at δ 173.0 and a
doublet at δ 175.0 (2J PC ) 11.6 Hz) account for the ester
carbonyls. Singlets at δ 165.6, 216.1, and 217.5 are
assigned to the three-coordinate carbon of the guanidino
group and the terminal carbonyl ligands, respectively.
The temperature dependence of the 1H NMR spec-
trum may be rationalized by the bending of the four-
membered ring about the C-C diagonal.
The doublet of doublets at δ 5.33 is due to HB and
reflects the coupling J AB ) 10.2 Hz, as well as a small
coupling to the phosphorus of 1.0 Hz. A similarly small
2J PH coupling (1.5 Hz) is encountered in the 1,2-
dihydrophosphete 6.9
3
Ack n ow led gm en t. This work was generously sup-
ported by the Deutsche Forschungsgemeinschaft, Bonn,
Germany, the Fonds der Chemischen Industrie, Frank-
furt/M., Germany, and the BASF AG, Ludwigshafen,
Germany, which are gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tal data and structure refinement details, positional and
thermal parameters, and bond distances and angles for 3a (7
pages). Ordering information is given on any current mast-
head page.
The doublet of doublets at δ 3.53 (3J HC ) 10.2,
2J PH ) 4.2 Hz) is assigned to the proton HC of the
OM9700876