Chromium Imidate Complexes from the Metathesis-Like Reaction of Phosphinimines and Chromium(0) Fischer Carbene Complexes

Article abstract of DOI:10.1021/om034347x

The thermal reaction of phosphinimines with alkyl-substituted chromium(0) Fischer carbene complexes is reported. The process occurs through a metathesis-like reaction to yield stable chromium imidate complexes. The formation of the azametallacycle 15 from zwitterion 14 is the key to the process. The length of the phosphinimine tether, the electrophilicity of the imine moiety, and the bulkiness of the imine substituents determine whether the metathesis process occurs. Only those compounds having short or rigid tethers and electrophilic and moderately hindered imine groups react with electrophilic Fischer carbene complexes. Bulkier imines or less electrophilic carbene complexes are unable to form the key azametallacycles and either decompose or form the condensation products derived from acid-base reactivity.

Full text of DOI:10.1021/om034347x

Organometallics 2004, 23, 1851-1856
1851
Ch r om iu m Im id a te Com p lexes fr om th e Meta th esis-Lik e
Rea ction of P h osp h in im in es a n d Ch r om iu m (0) F isch er
Ca r ben e Com p lexes
Israel Ferna´ndez, Mar´ıa J ose´ Manchen˜o,* Mar Go´mez-Gallego, and
Miguel A. Sierra*,†
Departamento de Qu´ımica Orga´nica, Facultad de Qu´ımica, Universidad Complutense de
Madrid, 28040 Madrid, Spain
Tore Lejon and Lars K. Hansen‡
Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
Received December 4, 2003
The thermal reaction of phosphinimines with alkyl-substituted chromium(0) Fischer
carbene complexes is reported. The process occurs through a metathesis-like reaction to yield
stable chromium imidate complexes. The formation of the azametallacycle 15 from zwitterion
14 is the key to the process. The length of the phosphinimine tether, the electrophilicity of
the imine moiety, and the bulkiness of the imine substituents determine whether the
metathesis process occurs. Only those compounds having short or rigid tethers and
electrophilic and moderately hindered imine groups react with electrophilic Fischer carbene
complexes. Bulkier imines or less electrophilic carbene complexes are unable to form the
key azametallacycles and either decompose or form the condensation products derived from
acid-base reactivity.
Sch em e 1
In tr od u ction
The chemistry of Fischer carbene complexes has
experienced a great development in the last few years,
mainly due to their unique reactivity. Today many
efficient processes are based on these versatile synthons,
which have become very valuable building blocks in
organic synthesis.1 In this context, the reactivity of
Fischer carbene complexes with imines has been a
subject of interest, as imines have both nucleophilic and
electrophilic sites and are unsaturated, a combination
of factors that could lead to different reaction pathways.
The thermal behavior of group 6 Fischer carbene
complexes toward imines is strongly dependent on the
structure of the reagents and the reaction conditions.
Thus, the reaction of the methyl complex 1 with the
N-methyl imine of benzaldehyde gives the R,â-unsatur-
ated complex 2 as a result of a base-induced condensa-
tion between the relatively acidic compound 1 and the
imine.2 On the other hand, imino complexes 4 can be
obtained from acyloxy- and alkoxycarbene complexes 3
and N-trimethylsilyl imines.3 Additionally, heating
alkoxycarbene complexes 5 and N-tosylimines forms the
â-methoxyallylamine derivatives 64 (Scheme 1). The
reactivity of imines, enamines, and azadienes with R,â-
unsaturated group 6 carbene complexes has been thor-
oughly investigated by Barluenga’s group, which has
allowed them to describe a plethora of novel cycloaddi-
tion processes.5 Finally, the photoinduced reaction of
Fischer carbene complexes with imines to produce
† E-mail: sierraor@quim.ucm.es.
‡ To whom inquiries regarding the structural determination of
complex 10a should be addressed.
(1) Selected reviews in the chemistry and synthetic applications of
Fischer carbene complexes: (a) Do¨tz, K. H.; Fischer, H.; Hoffmann,
P.; Kreissel, F. R.; Schubert, U.; Weiss, K. Transition Metal Carbene
Complexes; Verlag Chemie: Deerfield Beach, FL, 1983. (b) Do¨tz, K.
H. Angew. Chem., Int. Ed. Engl. 1984, 23, 587. (c) Wulff, W. D. In
Comprehensive Organometallic Chemistry II; Abel, E. W., Stone, F.
G. A., Wilkinson, G., Eds.; Pergamon: New York, 1995; Vol. 12,
Chapter 5.3, p 469. (d) Hegedus, L. S. In Comprehensive Organome-
tallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon: New York, 1995; Vol. 12, Chapter 5.3, p 549. (e) Harvey,
D. F.; Sigano, D. M. Chem. Rev. 1996, 96, 271. (f) Sierra, M. A. Chem.
Rev. 2000, 100, 3591.
(3) Murray, C. K.; Warner, B. P.; Dragisich, V.; Wulff, W. D.; Rogers,
R. D. Organometallics 1990, 9, 3142.
(2) Hegedus, L. S.; McGuire, M. A.; Schultze, L. S.; Yijun, C.;
Anderson, O. P. J . Am. Chem. Soc. 1984, 106, 2680.
(4) Sangu, K.; Kagoshima, H.; Fuchibe, K.; Akiyama, T. Org. Lett.
2002, 4, 3967.
10.1021/om034347x CCC: $27.50 © 2004 American Chemical Society
Publication on Web 03/20/2004

1852 Organometallics, Vol. 23, No. 8, 2004
Ferna´ndez et al.
Sch em e 2
Sch em e 3
aldehyde in CH2Cl2 at room temperature (Scheme 2).
Heating equimolecular amounts of pentacarbonyl-
(ethoxymethylcarbene)chromium(0) (9) and imine 8a in
a mixture of hexane and benzene (1:1) yielded a new
chromium complex lacking the carbene carbon (Scheme
3). The 13C NMR spectrum of this complex exhibited
three signals at 227.2, 227.0, and 219.0 ppm attributable
to a [(CO)4Cr] moiety, together with a signal at 166.3
â-lactams has also been studied in depth. This reaction
involves the reversible formation of chromium ketene
complexes able to react with ketenophiles to yield
ketene-derived products by either inter- or intramolecu-
lar reactions.6 This type of process has been widely
applied in synthesis1d,6 and has been of longstanding
mechanistic interest.7
The reaction of Fischer carbene complexes with phos-
phines is a well-known process that leads to new
carbene complexes formed by ligand exchange of the
coordination sphere of the metal.8 During our studies
directed at discovering novel processes in the chemistry
of group 6 metal carbenes,7b,c the synthesis of chromium-
(0) carbene complexes having phosphinimine ligands
was needed. Our results indicate that, instead of the
expected CO-phosphine interchange, a new thermal
process, the formation of imidate species coordinated to
chromium, was observed. We report here a detailed
study of the scope and limitations of this new type of
reaction.
1
ppm that may correspond to a CdN bond. The H NMR
analysis showed the presence of a methyl group (δ 2.44
(s)) and an ethoxy group (δ 1.33 (t) and 4.05 (q)) linked
to an sp2 carbon. A single crystal of this compound was
submitted to X-ray diffraction analysis, and its structure
was unambiguously established as the cyclic phosphi-
noimidate (CO)4Cr complex 10a (Figure 1).9 The reac-
Resu lts a n d Discu ssion
Imines 8 were prepared in quantitative yields from
diphenylphosphino amines 7 and the corresponding
(5) For reactions of Fischer carbene complexes with R,â-unsaturated
imines, see: (a) Danks, T. N.; Velo-Rego, D. Tetrahedron Lett. 1994,
35, 9443. (b) Barluenga, J .; Toma´s, M.; Ballesteros, A.; Santamar´ıa,
J .; Lo´pez-Ort´ız, F. J . Chem. Soc., Chem. Commun. 1994, 321. (c)
Barluenga, J .; Toma´s, M.; Lo´pez-Pelegr´ın, J . A.; Rubio, E. J . Chem.
Soc., Chem. Commun. 1995, 665. (d) Barluenga, J .; Toma´s, M.; Rubio,
E.; Lo´pez-Pelegr´ın, J . A.; Garc´ıa-Granda, S.; Pertierra, P. J . Am. Chem.
Soc. 1996, 118, 695. (e) Barluenga, J .; Toma´s, M.; Ballesteros, A.;
Santamar´ıa, J .; Carbajo, R. J .; Lo´pez-Ort´ız, F.; Garc´ıa-Granda, S.;
Pertierra, P. Chem. Eur. J . 1996, 2, 88. (f) Barluenga, J .; Toma´s, M.;
Ballesteros, A.; Sua´rez-Sobrino, A. J . Org. Chem. 1997, 62, 9299. (g)
Barluenga, J .; Toma´s, M.; Rubio, E.; Lo´pez-Pelegr´ın, J . A.; Garc´ıa-
Granda, S.; Priede, M. P. J . Am. Chem. Soc. 1999, 121, 3065 and
references therein. For other reactions, see: (h) Kagoshima, H.;
Akiyama, T. J . Am. Chem. Soc. 2000, 122, 11741. (i) Kagoshima, H.;
Okamura, T.; Akiyama, T. J . Am. Chem. Soc. 2001, 123, 7182.
(6) For reviews in the photochemistry of group 6 metal carbene
complexes, see: (a) Hegedus, L. S. Tetrahedron 1997, 53, 4105. (b)
Schwindt, M. A.; Miller, J . R.; Hegedus, L. S. J . Organomet. Chem.
1991, 413, 143.
F igu r e 1. ORTEP drawing of complex 10a . Hydrogens
atoms have been omitted for clarity.
tion of complex 9 with imines 8b,c under the same
conditions as those above produced the analogous
complexes 10b,c in 60% and 16% yields, respectively.
In this latter case, together with complex 10c, a new
carbene complex was formed in 6% yield. This compound
was identified as pentacarbonyl(ethoxystyrylcarbene)-
chromium(0), by comparison of its spectroscopic data
with those obtained from an authentic sample.10 In all
(9) The structure of 10a was elucidated by X-ray crystallography.
Crystal data: Mr ) 573.51, monoclinic, space group C2/c, a ) 33.327-
(7) (a) Hegedus, L. S.; de Weck, G.; D’Andrea, S. J . Am. Chem. Soc.
1988, 110, 2122. (b) Arrieta, A.; Coss´ıo, F. P.; Ferna´ndez, I.; Go´mez-
Gallego, M.; Lecea, B.; Manchen˜o, M. J .; Sierra, M. A. J . Am. Chem.
Soc. 2000, 122, 11509. (c) Sierra, M. A.; Ferna´ndez, I.; Manchen˜o, M.
J .; Go´mez-Gallego, M.; Torres, M. R.; Coss´ıo, F. P.; Arrieta, A.; Lecea,
B.; Poveda, A.; J ime´nez-Barbero, J . J . Am. Chem. Soc. 2003, 125, 9572.
(8) Fischer, E. O.; Fischer, H. Chem. Ber. 1974, 107, 657.
(9) Å, b ) 9.3291(14) Å, c ) 19.595(8) Å, V ) 5856(3) Å3, Z ) 8, Dz
)
1.301 Mg m-3, Μï ΚR radiation (λ ) 0.710 69 Å), µ ) 0.484 mm-1
,
R ) 0.0131, Rw ) 0.1434, 5135 reflections, 355 refined parameters,
refinement on F2. The data were collected with an Enraf-Nonius CAD-4
difractometer (T ) 298(2) K). The structure and the refinement of the
crystal structure were done with the SHELXL97 program.
(10) Aumann, R.; Heinen, H. Chem. Ber. 1987, 120, 537.

Chromium Imidate Complexes
Organometallics, Vol. 23, No. 8, 2004 1853
Sch em e 4
cases, the imidate complexes 10 were obtained as single
isomers and their structures were established by com-
parison with the spectroscopic data of 10a .
intermediate 13 in the first step. Nucleophilic attack of
the imine moiety on the electrophilic carbene carbon
may lead to zwitterion 14, which evolves to azametal-
lacycle 15 by attack of the nucleophilic chromium center
at the iminium moiety. Finally, breakage of the metal-
lacyclic intermediate 15 should form the new carbene
complex 16, which evolves by extrusion of the arylcar-
bene moiety to compounds 10.11 This step may be
induced by the metal-imidate coordination. Overall, the
evolution of phosphinimines 8 to complexed imidates 10
can be considered a metathesis-like reaction (Scheme
6).
To evaluate the role of the electrophilicity of the
CdN double bond in the formation of the imidate
complexes, the reactions of complex 9 with imines 8d -f
having electron-withdrawing or electron-donating groups
in the aromatic ring were tested next. The results are
compiled in Scheme 4. The most electrophilic imine, 8d ,
yielded complex 10b in 54% yield. Imine 8e behaves in
a similar way, affording complex 10b in 46% yield, but
the less electrophilic imine 8f rendered a complex
reaction mixture where pentacarbonyl[ethoxy(p-meth-
oxystyryl)carbene]chromium(0) was the only product
that could be isolated (Scheme 4).
Sch em e 6
The reactivity of ethoxyphenyl chromium carbene
complex 11 with imine 8a was tested next. This time,
the imino complex 12a was the sole identifiable reaction
product and was obtained as a syn/anti mixture of
isomers across the double bond. The isomers were
separated by column chromatography on silica gel, and
their structures were established on the basis of NOE
measurements. A similar behavior was found when
complex 9 was treated with the bulky ferrocenylimine
8g, yielding a syn/anti mixture of ferrocenylimino
complexes 12b as reaction products. As in the case of
12a , the isomers were separated by chromatography
and their structures established on the basis of NOE
measurements (Scheme 5).
The effect of the length of the tether on the yields of
imidate complexes 10 (60% for imine 8b and 16% for
imine 8c) and that of the rigidity (53% yield for imine
8a and only 16% for imine 8c) supports the hypothesis
that the coordination of the phosphine ligand should
precede the metallacycle formation. Otherwise, the
reactivity of imines 8a -c should be comparable. As the
formation of metallacycle 15 requires the attack of the
chromium nucleus at the CdN bond, poorly electrophilic
imines inhibit this reaction step, leading to decomposi-
tion products together with compounds derived from the
normal acid-base reactivity reported earlier by Hege-
dus.2 Other factors disfavoring the formation of this key
intermediate 15 are bulky substituents on the imine (as
in 8g) or the choice of a less reactive Fischer carbene
complex, such as 11.
Sch em e 5
Clear trends emerge from the data above: the forma-
tion of chromium(0) imidate complexes 10 from the alkyl
Fischer carbene complex 9 is favored with electrophilic
phosphinimines 8, while a less electrophilic carbene
complex such as 11 or a bulky substituent at the imine
carbon (as in 8g) leads exclusively to products 12, in
which the carbene and one of the CO ligands have been
interchanged by the phosphinimine moiety. Considering
all the experimental observations, the formation of
imidate complexes 10 could be explained by a stepwise
mechanism, which is illustrated in Scheme 6. The
thermal CO-phosphine ligand exchange should form
(11) The detection of mixtures of cis- and trans-stilbenes in the
reaction of acyloxy- and alkoxycarbene complexes and N-trimethylsilyl
imines has been reported by Wulff.3 We have carried out the reactions
of complex 9 and imines 8b,d with the goal of isolating the expected
products of evolution of the corresponding intermediates 16. Direct
observation of stilbenes was hampered due to the presence of the
diphenylphosphine moiety, which masked the aromatic region of the
NMR spectra of the crude reaction mixtures. Chromatography led to
pure imidate complex 10b, together with mixtures of unidentified
products. The sequence irradiation-light oxidation was used also in
these reactions, leading to total decomposition of complex 10b together
with very complex reaction mixtures.

1854 Organometallics, Vol. 23, No. 8, 2004
Ferna´ndez et al.
phosphomolybdic acid solution in 95% EtOH were used to
develop the plates.
All commercially available compounds were used without
further purification. 2-(Diphenylphosphino)benzylamine was
prepared according to literature methods.14
Gen er a l P r oced u r e for th e Syn th esis of P h osp h in -
im in es 8a -g. A solution of 2-(diphenylphosphino)ethylamine,
3-(diphenylphosphino)propylamine, or 2-(diphenyphosphino)-
benzylamine and the corresponding benzaldehyde in stoichio-
metric amounts and a large excess of MgSO4 in dry CH2Cl2
were stirred at room temperature for 24 h. The mixture was
filtered, and the solvent was removed under reduced pressure
to yield the corresponding imines.
Finally, to check the effect of the metal in the starting
carbene on the reaction mechanism, imine 8a was
treated with pentacarbonyl(ethoxymethylcarbene)tung-
sten(0) under the same conditions used for complex 9.
In this case, the expected imidate was not formed and
the reaction yielded a complex mixture of products from
which only pentacarbonyl(ethoxystyrylcarbene)tungsten-
(0) could be isolated. This result may be explained by
the lower electrophilicity of the carbene carbon in
tungsten Fischer carbene complexes, compared to their
chromium analogues, which is further diminished in
this case by the electron-donating effect of the phosphine
ligand.
In summary, a new thermal reaction of imines with
chromium Fischer carbene complexes has been studied.
Stable chromium imidate complexes are obtained in a
metathesis-like process.12,13 The formation of azamet-
allacycles 15 from zwitterions 14 is the key to the
reaction. The length of the phosphinimine tether, the
electrophilicity of the CdN bond, and the bulkiness of
the imine substituents determine whether the meta-
thesis-like process occurs. Only those compounds having
short or rigid tethers or electrophilic and moderately
hindered CdN groups react with electrophilic carbene
complexes. Otherwise, bulkier imines or less electro-
philic carbene complexes are unable to form the key
azametallacycles and either decompose or form the
condensation products derived from acid-base reactiv-
ity.
Im in e 8a . Following the general procedure, from 570 mg
(1.96 mmol) of 2-(diphenylphosphino)benzylamine (7a ), 208 mg
(1.96 mmol) of benzaldehyde, 1.77 g (14.7 mmol) of MgSO4,
and 30 mL of dry Et2O was obtained 742 mg (quantitative
1
yield) of the imine 8a as a pale pink oil. H NMR (300 MHz,
CDCl3): δ 4.97 (s, 2H), 6.82 (m, 2H), 7.18-7.51 (m, 18H), 8.16
(s, 1H). 13C NMR (50 MHz, CDCl3): δ 63.0 (d, J C-P ) 22.7 Hz),
127.1, 128.1, 128.4 (d, J C-P ) 3.5 Hz), 128.6 (d, J C-P ) 2.8 Hz),
129.0, 130.5, 132.0 (d, J C-P ) 9.6 Hz), 133.4, 133.9 (d, J C-P
19.9 Hz), 136.3 (d, J C-P ) 20.2 Hz), 136.4, 143.9 (d, J C-P ) 24.1
Hz), 162.3. IR (CCl4): ν 3057, 2926, 2854, 1647, 1435 cm-1
)
.
Anal. Calcd for C26H22NP: C, 82.30; H, 5.84; N, 3.69. Found:
C, 82.51; H, 5.69; N, 3.84.
Im in e 8b. Following the general procedure, from 500 mg
(2.18 mmol) of 2-(diphenylphosphino)ethylamine (7b), 213 mg
(2.18 mmol) of benzaldehyde, 1.97 g (16.4 mmol) of MgSO4,
and 35 mL of dry CH2Cl2 was obtained 692 mg (quantitative
yield) of the imine 8b as a pale yellow solid. 1H NMR (300
MHz, CDCl3): δ 2.41 (m, 2H), 3.06 (m, 2H), 7.24-7.40 (m,
13H), 7.58 (m, 2H), 8.15 (s, 1H). 13C NMR (75.5 MHz, CDCl3):
δ 29.8 (d, J C-P ) 12.7 Hz), 58.4 (d, J C-P ) 21.1 Hz), 128.0, 128.5,
128.5 (d, J C-P ) 8.0 Hz), 128.7, 130.6, 132.7 (d, J C-P ) 18.8
Hz), 136.0, 138.3 (d, J C-P ) 12.4 Hz), 161.3. IR (CCl4): ν 3057,
2841, 1643, 1433 cm-1. Anal. Calcd for C21H20NP: C, 79.47;
H, 6.35; N, 4.41. Found: C, 79.62; H, 6.21; N, 4.65.
Im in e 8c. Following the general procedure, from 323 mg
(1.33 mmol) of 2-(diphenylphosphino)propylamine (7c), 141 mg
(1.33 mmol) of benzaldehyde, 1.20 g (9.96 mmol) of MgSO4,
and 25 mL of dry CH2Cl2 was obtained, after vacuum distil-
lation, 410 mg (93%) of the imine 8c as an orange solid. 1H
NMR (300 MHz, CDCl3): δ 1,81 (m, 2H), 2.05 (m, 2H), 3.67
(td, 2H, J ) 6.7 Hz, J H-P ) 0.9 Hz), 7.23-7.37 (m, 13H), 7.63
(m, 2H), 8.19 (s, 1H). 13C NMR (50 MHz, CDCl3): δ 25.6 (d,
Exp er im en ta l Section
Gen er a l P r oced u r es. 1H NMR and 13C NMR spectra were
recorded at 22 °C on Bruker Avance 300 (300.1 and 75.4 MHz)
or Bruker 200-AC (200.1 and 50 MHz) spectrometers. Chemi-
cal shifts are given in ppm relative to TMS (1H, 0.0 ppm) and
CDCl3 (13C, 77.0 ppm). IR spectra were taken on a Perkin-
Elmer 781 spectrometer. Flame-dried glassware and standard
Schlenk techniques were used for moisture-sensitive reactions.
Merck silica gel (230-400 mesh) was used as the stationary
phase for purification of crude reaction mixtures by flash
column chromatography. Identification of products was made
by TLC (Kieselgel 60F-254). UV light (λ 254 nm) and 5%
J C ) 11.7 Hz), 27.3 (d, J C-P ) 16.3 Hz), 64.2 (d, J C-P ) 13.1
-P
(12) The examples of chromium imidate tetracarbonyl phosphine
complexes are scarce. See: (a) Raubenheimer, H. G.; Kruger, G. J .;
Vijoen, H. W.; Hendrik, W.; Lotz, S. J . Organomet. Chem. 1986, 314,
281. The synthesis of imidate thioether chelates can be found in: (b)
Raubenheimer, H. G.; Kruger, G. J .; Vijoen, H. W. J . Organomet. Chem.
1986, 319, 361. For earlier examples of the formation of chromium(0)
imidate pentacarbonyl complexes, among other different products in
the reaction of chromium(0) pentacarbonyl alkoxycarbene complexes
and hydroxylamine, see: (c) Fischer, E. O.; Aumann, R. Chem. Ber.
1968, 101, 963. Dimethylhydrazine: (d) Raubenheimer, H. G.; Lotz,
S.; Kruger, G. J .; Gafner, G. J . Organomet. Chem. 1979, 173, C1.
(13) The formation of metal-free imidates from group 6 metal
carbene and different reagents is well-known. From aziridines: (a)
Hegedus, L. S.; Kramer, A.; Yijun, C. Organometallics 1985, 4, 1747.
(b) Curtis, M. D.; Hay, M. S.; Butler, W. M.; Kampt, J . Organometallics
1992, 11, 2884. From azobenzene: (c) Arndtsen, B. A.; Sleiman, H. F.;
Chang, A. K.; McElwee-White, L. J . Am. Chem. Soc. 1991, 113, 4871.
(d) Sleiman, H. F.; Mercer, S.; McElwee-White, L. J . Am. Chem. Soc.
1989, 111, 8007. (e) Hegedus, L. S.; Lundmark, B. J . Am. Chem. Soc.
1989, 111, 9194. (f) Hegedus, L. S.; Kramer, A. Organometallics 1984,
3, 1263. (g) Sleiman, H. F.; McElwee-White, L. J . Am. Chem. Soc. 1988,
110, 8700. (h) Maxey, C. T.; Sleiman, H. F.; Massey, S. T.; McElwee-
White, L. J . Am. Chem. Soc. 1992, 114, 5153. From imines and
O-acylchromium(0) carbene complexes: see ref 3. From nitrosoben-
zene: (i) Herndon, J . W.; McMullen, L. A. J . Organomet. Chem. 1989,
368, 83. (j) Pilato, R. S.; Williams, G. D.; Geoffroy, G. L.; Rheingold,
A. L. Inorg. Chem. 1988, 27, 3665. From sulfilimines: (k) Alcaide, B.;
Casarrubios, L.; Dom´ınguez, G.; Sierra, M. A. J . Org. Chem. 1993, 58,
3886. (l) Alcaide, B.; Dom´ınguez, G.; Plumet, J .; Sierra, M. A.
Organometallics 1991, 10, 11.
Hz), 128.0, 128.4 (d, J C-P ) 8.9 Hz), 128.4, 128.5, 130.5, 132.7
(d, J C-P ) 18.4 Hz), 136.2, 138.6 (d, J C-P ) 13.1 Hz), 161.2. IR
(CCl4): ν 3059, 2926, 2852, 1708, 1647, 1435 cm-1. Anal. Calcd
for C22H22NP: C, 79.74; H, 6.69; N, 4.23. Found: C, 79.55; H,
6.84; N, 4.50.
Im in e 8d . Following the general procedure, from 248 mg
(1.08 mmol) of 2-(diphenylphosphino)ethylamine (7b), 163 mg
(1.08 mmol) of p-nitrobenzaldehyde, 977 mg (8.11 mmol) of
MgSO4, and 18 mL of dry CH2Cl2 were obtained 391 mg
(quantitative yield) of the imine 8d as an orange solid. 1H NMR
(300 MHz, CDCl3): δ 2.39 (m, 2H), 3.70 (m, 2H), 7.19-7.37
(m, 10H), 7.65 (d, 2H, J ) 8.8 Hz), 8.07 (d, 2H, J ) 8.8 Hz),
8.14 (s, 1H). 13C NMR (75.5 MHz, CDCl3): δ 29.4 (d, J C-P
13.1 Hz), 58.5 (d, J C-P ) 20.3 Hz), 123.5, 128.2 (d, J C-P ) 6.9
Hz), 128.4, 128.5, 132.6 (d, J C-P ) 18.7 Hz), 138.0 (d, J C-P
)
)
12.4 Hz), 141.3, 148.7, 158.8. IR (CCl4): ν 3057, 2922, 2850,
1647, 1603, 1525, 1435, 1344 cm-1. Anal. Calcd for C21H19N2-
O2P: C, 69.61; H, 5.29; N, 7.73. Found: C, 69.84; H, 5.14; N,
7.94.
Im in e 8e. Following the general procedure, from 150 mg
(0.65 mmol) of 2-(diphenylphosphino)ethylamine (7b), 92 mg
(14) Brunner, A.; Ku¨hnle, F. N. M.; Seebach, D. Helv. Chem. Acta
1996, 79, 319.

Chromium Imidate Complexes
Organometallics, Vol. 23, No. 8, 2004 1855
(0.96 mmol) of p-chlorobenzaldehyde, 591 mg (4.9 mmol) of
7.38 (m, 6H), 7.55-7.63 (m, 4H). 13C NMR (75.5 MHz,
MgSO4, and 11 mL of dry CH2Cl2 was obtained 230 mg
CDCl3): δ 14.7, 20.7, 29.0 (d, J C-P ) 16.8 Hz), 48.2 (d, J C-P )
1
(quantitative yield) of imine 8e as a pale yellow oil. H NMR
9.4 Hz), 65.8, 128.5 (d, J C-P ) 9.1 Hz), 129.6 (d, J C-P ) 0.7
Hz), 131.5 (d, J C-P ) 11.1 Hz), 136.7 (d, J C-P ) 34.7 Hz), 165.8
(300 MHz, CDCl3): δ 2.36 (m, 2H), 3.62 (m, 2H), 7.18-7.67
(m, 14H), 8.02 (s, 1H). 13C NMR (75.5 MHz, CDCl3): δ 29.6
(d, J C-P ) 2.3 Hz), 219.2 (d, J C-P ) 14.3 Hz), 227.8 (d, J C-P
)
(d, J C-P ) 12.5 Hz), 58.3 (d, J C-P ) 20.8 Hz), 128.3 (d, J C-P
)
2.0 Hz), 229.1 (d, J C-P ) 14.7 Hz). IR (KBr): ν 2004, 1871,
1834, 1624 cm-1. Anal. Calcd for C22H22CrNO5P: C, 57.02; H,
4.79; N, 3.02. Found: C, 56.87; H, 4.90; N, 3.21.
6.8 Hz), 128.5, 128.6, 129.1, 132.6 (d, J C-P ) 18.8 Hz), 134.4,
136.4, 138.2 (d, J C-P ) 12.4 Hz), 159.8. IR (CCl4): ν 3057, 2925,
2852, 1645, 1489, 1458 cm-1. Anal. Calcd for C21H19ClNP: C,
71.69; H, 5.44, N, 3.98; Found: C, 71.84; H, 5.51; N, 4.12.
Im in e 8f. Following the general procedure, from 250 mg
(1.09 mmol) of 2-(diphenylphosphino)ethylamine (7b), 149 mg
(1.09 mmol) of anisaldehyde, 985 mg (8.2 mmol) of MgSO4,
and 18 mL of dry CH2Cl2 was obtained 379 mg (quantitative
yield) of the imine 8f as a pale yellow solid. 1H NMR (300 MHz,
CDCl3): δ 2.81 (m, 2H), 3.82 (s, 3H), 3.91 (m, 2H), 6.90-7.76
(m, 14H), 8.10 (s, 1H). 13C NMR (50.0 MHz, CDCl3): δ 29.9
(d, J C-P ) 12.8 Hz), 55.3, 58.1 (d, J C-P ) 20.2 Hz), 113.9, 128.3,
128.5 (d, J C-P ) 4.3 Hz), 128.7, 129.8, 132.7 (d, J C-P ) 18.8
Hz), 138.3 (d, J C-P ) 12.4 Hz), 160.5, 161.7. IR (CCl4): ν 3057,
(b) F r om Im in e 8d . Following the general procedure, from
137 mg (0.52 mmol) of complex 9 and 188 mg (0.52 mmol) of
imine 8d in 9 mL of hexane-benzene (1:1), complex 10b (131
mg, 54%) was obtained as an orange solid.
(c) F r om Im in e 8e. Following the general procedure, from
173 mg (0.65 mmol) of complex 9 and 230 mg (0.65 mmol) of
imine 8e in 12 mL of hexane-benzene (1:1), complex 10b (139
mg, 46%) was obtained after purification by flash column
chromatography on silica gel.
Com p lex 10c. Following the general procedure, from 526
mg (1.99 mmol) of complex 9 and 660 mg (1.99 mmol) of imine
8c in 30 mL of hexane-benzene (1:1), complex 10c (148 mg,
16%) was obtained as an orange solid together with 40 mg (6%)
of pentacarbonyl(ethoxystyrylcarbene)chromium(0).10 1H NMR
(300 MHz, CDCl3): δ 1.30 (t, 3H, J ) 7.0 Hz), 1.50 (m, 2H),
2.29 (m, 2H), 2.43 (s,3H), 3.33 (m, 2H), 4.01 (q, 2H, J ) 7.0
Hz), 7.31-7.45 (m, 10H). 13C NMR (75.5 MHz, CDCl3): δ 14.4,
23.6, 23.6, 29.6 (d, J C-P ) 20.2 Hz), 40.4 (d, J C-P ) 14.7 Hz),
65.9, 128.4 (d, J C-P ) 8.6 Hz), 129.6 (d, J C-P ) 1.8 Hz), 131.7
(d, J C-P ) 10.4 Hz), 136.9 (d, J C-P ) 31.9 Hz), 167.2, 221.3 (d,
J C-P ) 14.7 Hz), 225.6 (d, J C-P ) 5.5 Hz), 230.8 (d, J C-P ) 12.9
2918, 2837, 1647, 1433, 1250 cm-1. Anal. Calcd for C22H22
-
NOP: C, 76.06; H, 6.38; N, 4.03. Found: C, 76.26; H, 6.47; N,
3.94.
Im in e 8g. Following the general procedure, from 178 mg
(0.78 mmol) of 2-(diphenylphosphino)ethylamine (7b), 167 mg
(0.78 mmol) of ferrocenecarbaldehyde, 701 mg (5.8 mmol) of
MgSO4, and 15 mL of dry CH2Cl2 was obtained 331 mg
(quantitative yield) of the imine 8g as an orange solid. 1H NMR
(300 MHz, CDCl3): δ 2.34 (m, 2H), 3.48 (m, 2H), 4.08 (s, 5H),
4.27 (s, 2H), 4.46 (s, 2H), 7.24-7.70 (m, 10H), 8.00 (s, 1H). 13
C
Hz). IR (CCl4): ν 2008, 1925, 1890 cm-1. Anal. Calcd for C23
24CrNO5P: C, 57.86; H, 5.07; N, 2.93. Found: C, 57.62; H,
5.18; N, 3.09.
-
NMR (75.5 MHz, CDCl3): δ 29.9 (d, J C-P ) 12.6 Hz), 58.6 (d,
J C-P ) 21.2 Hz), 68.4, 69.0, 70.3, 80.3, 128.4 (d, J C-P ) 6.7 Hz),
132.7 (d, J C-P ) 18.6 Hz), 138.4 (d, J C-P ) 12.5 Hz), 161.4. IR
H
Com p lex 12a . Following the general procedure, from 344
mg (1.05 mmol) of complex 1116 and 300 mg (0.48 mmol) of
imine 8a in 20 mL of hexane-benzene (1:1) and after chro-
matography on silica gel, 71 mg (12%) of anti-12a and 65 mg
(11%) of syn-12a were obtained as orange solids. Complex 12a
(anti isomer): 1H NMR (300 MHz, CDCl3) δ 4.60 (s, 2H), 6.74
(m, 1H), 6.88 (m, 2H), 7.09-7.41 (m, 16H), 9.05 (s, 1H); 13C
NMR (75.5 MHz, CDCl3) δ 62.6 (d, J C-P ) 9.7 Hz), 127.3, 128.5
(d, J C-P ) 9.1 Hz), 128.8, 129.0 (d, J C-P ) 4.5 Hz), 129.8, 130.1,
130.3, 130.7, 131.1, 132.7, 133.0 (d, J C-P ) 11.3 Hz), 134.5 (d,
J C-P ) 36.0 Hz), 141.5 (d, J C-P ) 17.5 Hz), 172.4 (d, J C-P ) 4.2
Hz), 219.6 (d, J C-P ) 12.8 Hz), 225.9, 227.3 (d, J C-P ) 13.9 Hz);
(CCl4): ν 3057, 2923, 2852, 1645 cm-1. Anal. Calcd for C25H24
-
FeNP: C, 70.60; H, 5.69, N, 3.29. Found: C, 70.41; H, 5.81;
N, 3.08.
Gen er a l P r oced u r e for th e Syn th esis of P h osp h in e
Im id a te Com p lexes 10. A solution of the metal carbene
complex and the corresponding phosphinimine in degassed
hexane-benzene (1:1) was heated at reflux for 9 h (unless
otherwise specified). The solvents were removed under reduced
pressure, and the residue was submitted to flash column
chromatography (SiO2, hexane-AcOEt) under an argon at-
mosphere to give pure compounds.
IR (KBr) ν 2006, 1882, 1846 cm-1. Anal. Calcd for C30H22
-
Com p lex 10a . Following the general procedure, from 517
mg (1.96 mmol) of complex 915 and 742 mg (1.96 mmol) of imine
8a in 30 mL of hexane-benzene (1:1) was obtained after
purification by flash column chromatography 549 mg (53%)
CrNO4P: C, 66.30; H, 4.08; N, 2.58. Found: C, 66.51; H, 4.21;
N, 2.71. Complex 12a (syn isomer): 1H NMR (300 MHz, CDCl3)
δ 4.80 (d, 2H, J ) 2.3 Hz), 6.93 (m, 1H), 7.21-7.42 (m, 18H),
1
8.80 (s, 1H); 13C NMR (75.5 MHz, CDCl3) δ 76.3 (d, J C-P
)
of complex 10a as a yellow solid. H NMR (300 MHz, CDCl3):
δ 1.33 (t, 3H, J ) 7.0 Hz), 2.44 (s, 3H), 4.05 (q, 2H, J ) 7.0
Hz), 4.36 (d, 2H, J ) 3.3 Hz), 6.89 (t, 1H, J ) 1.1 Hz), 7.22-
7.41 (m, 13H). 13C NMR (75.5 MHz, CDCl3): δ 14.9, 20.0, 58.4
(d, J C-P ) 13.9 Hz), 66.0, 128.3 (d, J C-P ) 9.1 Hz), 128.5, 129.6,
130.1, 130.5 (d, J C-P ) 7.5 Hz), 132.8, 132.9 (d, J C-P ) 11.0
Hz), 134.9 (d, J C-P ) 35.7 Hz), 143.2 (d, J C-P ) 17.5 Hz), 166.3,
219.0 (d, J C-P ) 12.3 Hz), 227.0 (d, J C-P ) 1.9 Hz), 227.2 (d,
J C-P ) 14.7 Hz). IR (KBr): ν 2009, 1900, 1886, 1852 cm-1. Anal.
Calcd for C27H24CrNO5P: C, 61.72; H, 4.60, N, 2.67. Found:
C, 61.95; H, 4.48; N, 2.49.
P h osp h in e Im id a te Com p lex 10b. Compound 10b was
obtained by reaction of Fischer carbene complex 9 with imines
8b,d ,e as specified below.
(a ) F r om Im in e 8b. Following the general procedure, from
278 mg (1.05 mmol) of complex 9 and 335 mg (1.05 mmol) of
imine 8b in 20 mL of hexane-benzene (1:1), complex 10b (294
mg, 60%) was obtained as an orange solid. 1H NMR (300 MHz,
CDCl3): δ 1.26 (t, 3H, J ) 7.0 Hz), 2.25 (m, 2H), 2.45 (s, 3H),
3.53 (m, 1H), 3.61 (m, 1H), 4.03 (q, 2H, J ) 7.0 Hz), 7.32-
12.5 Hz), 128.1, 128.4, 128.5 (d, J C-P ) 9.2 Hz), 129.2 (d,
J C-P ) 3.7 Hz), 129.8, 130.4, 130.8, 130.9, 132.3, 133.0 (d,
J C-P ) 11.1 Hz), 134.4 (d, J C-P ) 36.0 Hz), 136.2, 141.9 (d,
J C-P ) 18.2 Hz), 174.5 (d, J C-P ) 2.1 Hz), 219.1 (d, J C-P ) 12.7
Hz), 224.5 (d, J C-P ) 1.8 Hz), 227.6 (d, J C-P ) 14.5 Hz); IR
(KBr) ν 2004, 1880, 1844 cm-1. Anal. Calcd for C30H22
-
CrNO4P: C, 66.30; H, 4.08; N, 2.58. Found: C, 66.44; H, 4.23;
N, 2.63.
Com p lex 12b. Following the general procedure, from 205
mg (0.78 mmol) of complex 9 and 330 mg (0.78 mmol) of imine
8g in 13 mL of hexane-benzene (1:1) and after chromatogra-
phy on silica gel, 142 mg (31%) of anti-12b and 79 mg (17%)
of syn-12b were obtained as orange solids. Complex 12b (anti
isomer): 1H NMR (300 MHz, acetone-d6) δ 2.66 (m, 2H), 3.63
(m, 1H), 3.71 (m, 1H), 4.20 (s, 5H), 4.50 (t, 2H, J ) 1.9 Hz),
4.71 (t, 2H, J ) 1.9 Hz), 7.33-7.38 (m,6H), 7.66-7.73 (m, 4H),
8.61 (s, 1H); 13C NMR (75.5 MHz, CDCl3) δ 30.7 (d, J C-P
)
16.7 Hz), 53.7 (d, J C-P ) 8.3 Hz), 69.7, 71.4, 72.2, 76.6, 128.7
(d, J C-P ) 9.1 Hz), 129.8, 131.6 (d, J C-P ) 11.6 Hz), 136.0 (d,
(15) Hegedus, L. S.; McGuire, M. A.; Schultze, L. M. Organic
Syntheses; Wiley: New York, Collect. Vol. VIII, p 217.
(16) (a) Fischer, E. O.; Maasbo¨l, A. J . Organomet. Chem. 1968, 12,
P15. (b) Aumam, R.; Fischer, E. O. Chem. Ber. 1968, 101, 954.

1856 Organometallics, Vol. 23, No. 8, 2004
Ferna´ndez et al.
J C-P ) 34.3 Hz), 168.9, 219.9 (d, J C-P ) 14.1 Hz), 227.4, 229.3
Ack n ow led gm en t. Financial support by the Span-
ish Ministerio de Ciencia y Tecnolog´ıa (Grant BQU2001-
1283) and the Comunidad Auto´noma de Madrid (Grant
07M/0043/2002) is gratefully acknowledged. I.F. thanks
the Ministerio de Eduacio´n y Ciencia (Spain) for a
predoctoral fellowship.
(d, J C-P ) 12.9 Hz); IR (KBr) ν 2002, 1877, 1830, 1608 cm-1
.
Anal. Calcd for C29H24CrFeNO4P: C, 59.10; H, 4.10; N, 2.38.
Found: C, 59.26; H, 3.95; N, 2.51. Complex 12b (syn isomer):
1H NMR (300 MHz, CDCl3) δ 2.45 (m, 2H), 3.71 (m, 1H), 3.80
(m, 1H), 4.13 (s, 5H), 4.52 (t, 2H, J ) 1.9 Hz), 5.03 (t, 2H, J )
1.9 Hz), 7.35-7.37 (m, 6H), 7.58-7.64 (m, 4H), 8.40 (s, 1H);
13C NMR (75.5 MHz, CDCl3) δ 29.6 (d, J C-P ) 16.2 Hz), 68.5
(d, J C-P ) 8.3 Hz), 69.8, 72.1, 72.2, 76.9, 128.7 (d, J C-P ) 8.8
Hz), 129.8 (d, J C-P ) 1.6 Hz), 131.5 (d, J C-P ) 11.1 Hz), 136.4
(d, J C-P ) 35.2 Hz), 171.7, 219.4 (d, J C-P ) 14.3 Hz), 227.3 (d,
J C-P ) 2.7 Hz), 229.1 (d, J C-P ) 14.3 Hz); IR (KBr) ν 2004,
1878, 1834, 1618 cm-1. Anal. Calcd for C29H24CrFeNO4P: C,
59.10; H, 4.10; N, 2.38. Found: C, 59.01; H, 3.98; N, 2.43.
Su p p or tin g In for m a tion Ava ila ble: Tables giving X-ray
characterization data for compound 10a . This material is
available free of charge via the Internet at http://pubs.acs.org.
OM034347X