Deprotonation of μ-vinyliminium ligands in diiron complexes: A route for the synthesis of mono- and polynuclear species containing novel multidentate ligands

Article abstract of DOI:10.1021/om050095j

The deprotonation of μ-Vinyliminium ligands in diiron complexes was performed for the synthesis of mono-and polynuclear species containing novel multidentate ligands. Insertions of alkynes into the metal-carbon bond of bridging alkylidene and alkylidyne dinuclear complexes provided a synthetic pathway to the C-C bond formation in dinuclear transition-metal complexes. The reaction were carried under a nitrogen atmosphere using standard Schlenk techniques. It was observed that the resulting neutral species were not stable and rapidly evolved to give tetra-, di-, or mononuclear complexes.

Full text of DOI:10.1021/om050095j

Organometallics 2005, 24, 2297-2306
2297
Deprotonation of µ-Vinyliminium Ligands in Diiron
Complexes: A Route for the Synthesis of Mono- and
Polynuclear Species Containing Novel Multidentate
Ligands
Luigi Busetto, Fabio Marchetti, Stefano Zacchini, and Valerio Zanotti*
Dipartimento di Chimica Fisica e Inorganica, Universita` di Bologna, Viale Risorgimento 4,
40136 Bologna, Italy
Received February 10, 2005
The Câ-H hydrogen in the diiron vinyliminium complexes [Fe2{µ-η1:η3-Cγ(R′)dCâHCRd
N(Me)(R)}(µ-CO)(CO)(Cp)2][SO3CF3] (R ) Me, 1; R ) Bz, 2 (Bz ) CH2Ph); R ) Xyl, 3 (Xyl
)2,6-Me2C6H3)) is easily removed by sodium hydride; different products are consequently
formed, depending on the nature of the substituents R and R′. Thus, deprotonation of [Fe2{µ-
η1:η3-C(R′)dCHCdN(Me)(R)}(µ-CO)(CO)(Cp)2][SO3CF3] (R ) Me, R′ ) COOMe, 1a; R ) Me,
R′ ) Me, 1b; R ) Bz, R′ ) COOMe, 2a) yields the tetranuclear complexes [Fe2{µ-η1:η2-C(R′)-
CCN(Me)(R)}(µ-CO)(CO)(Cp)2]2 (R ) Me, R′ ) COOMe, 4a; R ) Me, R′ ) Me, 4b; R ) Bz,
R′ ) COOMe, 4c). Conversely, treatment with NaH of the vinyliminium complexes [Fe2{µ-
η1:η3-C(R′)dCHCdN(Me)(R)}(µ-CO)(CO)(Cp)2][SO3CF3] (R ) Me, R′ ) SiMe3, 1d; R ) Me,
R′ ) Tol, 1e; R ) Bz, R′ ) SiMe3, 2b; R ) Bz, R′ ) Tol, 2c (Tol ) 4-MeC6H4); R ) Xyl, R′ )
SiMe3, 3a; R ) Xyl, R′ ) Tol, 3b; R ) Xyl, R′ ) Ph, 3c) leads to the selective formation of
the corresponding µ-aminocarbyne alkynyl complexes [Fe2{µ-CN(Me)(R)}(µ-CO)(CO)(CtCR′)-
(Cp)2] (R ) Me, R′ ) SiMe3, 5a; R ) Me, R′ ) Tol, 5b; R ) Bz, R′ ) SiMe3, 5c; R ) Bz, R′
) Tol, 5d; R ) Xyl, R′ ) SiMe3, 5e; R ) Xyl, R′ ) Tol, 5f; R ) Xyl, R′ ) Ph, 5g). Compounds
5c,d react with methyl iodide to give the vinyliminium cations [Fe2{µ-η1:η3-C(R′)dC(Me)Cd
N(Me)(Bz)}(µ-CO)(CO)(Cp)2]+ (R′ ) SiMe3, 6a; R′ ) Tol, 6b). Finally, the reactions of [Fe2{µ-
η1:η3-C(R′)dCHCdN(Me)(R)}(µ-CO)(CO)(Cp)2][SO3CF3] (R ) Me, R′ ) Bun, 1c; R ) Xyl, R′
) Me, 3d; R ) Xyl, R′ ) COOMe, 3e; R ) Xyl, R′ ) CMe2OH, 3f) with NaH afford the
1-metalla-2-aminocyclopenta-1,3-dien-5-one species [Fe(Cp)(CO){CN(Me)(R)CHC(R′)C(O)}]
(R ) Me, R′ ) Bun, 7a; R ) Xyl, R′ ) Me, 7b; R ) Xyl, R′ ) COOMe, 7c; R ) Xyl, R′ )
CMe2OH, 7d). The molecular structures of 4a‚CH2Cl2, 4b, 5e, and 7b have been determined
by X-ray diffraction studies.
Introduction
vinyliminium complexes [Fe2{µ-η1:η3-C(R′)dC(R′′)Cd
N(Me)(R)}(µ-CO)(CO)(Cp)2][SO3CF3] (R ) Me (1), Bz (2),
Xyl (3)).3 Since the reactivity of vinyliminium ligands
has been largely unexplored,4 we have started to
investigate the reactions of 1-3 with nucleophiles. In
particular, we have found that NaBH4 adds H- at the
µ-vinyliminium ligand to form neutral derivatives,
whose nature depends on the steric hindrance of the
iminium nitrogen substituents.5 Indeed, the sterically
demanding Xyl group inhibits hydride attack at the
iminium carbon and directs the addition to the Câ
position, affording the bis-alkylidene complexes [Fe2{µ-
η1:η2-C(R′)CH2CN(Me)(Xyl)}(µ-CO)(CO)(Cp)2]. In con-
trast, with the less hindered Me or CH2Ph substituent,
Insertions of alkynes into the metal-carbon bond of
bridging alkylidene1 and alkylidyne2 dinuclear com-
plexes provide a synthetic pathway to the C-C bond
formation in dinuclear transition-metal complexes. The
alkyne (R′CCR′′) insertion reaction, extended to the
diiron µ-aminocarbynes [Fe2{µ-CN(Me)(R)}(µ-CO)(CO)-
(NCMe)(Cp)2][SO3CF3] (R ) Me, CH2Ph (Bz), 2,6-
Me2C6H3 (Xyl)), provided access to the novel bridging
* To whom correspondence should be addressed. E-mail:
valerio.zanotti@unibo.it. Tel: +39/0512093700. Fax: +39/0512093690.
(1) (a) Dyke, A. F.; Knox, S. A. R.; Naish, P. J.; Taylor, G. E. J.
Chem. Soc., Chem. Commun. 1980, 803. (b) Sumner Jr., C. E.; Collier,
J. A.; Pettit, R. Organometallics 1982, 1, 1350. (c) Colborn, R. E.; Dyke,
A. F.; Knox, S. A. R.; Macpherson, K.; Orpen, A. G. J. Organomet.
Chem. 1982, 239, C15. (d) Adams, P. Q.; Davies, D. L.; Dyke, A. F.;
Knox, S. A. R.; Mead, K. A.; Woodward. P. J. Chem. Soc., Chem.
Commun. 1983, 222. (e) Colborn, R. E.; Davies, D. L.; Dyke, A. F.; Knox,
S. A. R.; Mead, K. A.; Orpen, A. G.; Guerchais, J. E.; Roue´, J. J. Chem.
Soc., Dalton Trans. 1989, 1799. (f) Akita, M.; Hua, R.; Nakanishi, S.;
Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16, 5572. (g) Rowsell,
B. D.; McDonald, R.; Ferguson, M. J.; Cowie, M. Organometallics 2003,
22, 2944. (h) Kaneko, Y.; Suzuki, T.; Isobe, K.; Maitlis, P. M. J.
Organomet. Chem. 1998, 554, 155.
(3) Albano, V. G.; Busetto, L.; Marchetti, F.; Monari, M.; Zacchini,
S.; Zanotti, V. Organometallics 2003, 22, 1326. (b) Albano, V. G.;
Busetto, L.; Marchetti, F.; Monari, M.; Zacchini, S.; Zanotti, V. J.
Organomet. Chem. 2004, 689, 528.
(4) (a) Bernard, D. J.; Esteruelas, M. A.; Lopez, A. M.; Modrego, J.;
Puerta, M. C.; Valerga, P. Organometallics 1999, 18, 4995. (b) Gamble,
A. S.; White, P. S.; Templeton, J. L. Organometallics 1991, 10, 693.
(5) (a) Albano, V. G.; Busetto, L.; Marchetti, F.; Monari, M.; Zacchini,
S.; Zanotti, V. Organometallics 2004, 23, 3348. (b) Albano, V. G.,
Busetto, L.; Marchetti, F.; Monari, M.; Zacchini, S.; Zanotti, V. J.
Organomet. Chem. 2005, 690, 837.
(2) Casey, C. P.; Woo, L. K.; Fagan, P. J.; Palermo, R. E.; Adams, B.
R. Organometallics 1987, 6, 447.
10.1021/om050095j CCC: $30.25 © 2005 American Chemical Society
Publication on Web 04/06/2005

2298 Organometallics, Vol. 24, No. 10, 2005
Busetto et al.
Scheme 1
Scheme 2
Chart 1. Vinyliminium Complexes Investigated in
This Paper
[SO3CF3] (R ) Me, R′ ) COOMe, 1a; R ) R′ ) Me, 1b;
R ) Bz, R′ ) COOMe, 2a) react with NaH in THF
solution, affording the novel tetrairon complexes [Fe2{µ-
η1:η2-C(R′)CCN(Me)(R)}(µ-CO)(CO)(Cp)2]2 (R ) Me, R′
) COOMe, 4a; R ) R′ ) Me, 4b; R ) Bz, R′ ) COOMe,
4c) (Scheme 2).
Compounds 4a-c have been obtained in 60-70%
yield, after purification by column chromatography on
alumina, and characterized by IR and NMR spectra and
ESI-MS analyses.
The structures of 4a,b have been determined by X-ray
diffraction: the ORTEP molecular diagrams are shown
in Figures 1 and 2, whereas relevant bond lengths and
angles are reported in Tables 1 and 2, respectively.
Molecules 4a,b each have two [Fe2{µ-C(R′)CCN(Me)2}-
(µ-CO)(CO)(Cp)2] (R′ ) CO2Me, 4a; R′ ) Me, 4b)
moieties, with the Fe(1)-Fe(2) and Fe(3)-Fe(4) axes
nearly orthogonal (Fe(1)-Fe(2)-Fe(3)-Fe(4) dihedral
angles -89.18(2) and -84.07(4)°, respectively). Each
the reaction with NaBH4 occurs selectively at the
iminium carbon, yielding the vinylalkylidene complexes
[Fe2{µ-η1:η3-C(R′)dCHC(H)N(Me)2}(µ-CO)(CO)(Cp)2]-
[SO3CF3] (Scheme 1).
In addition to nucleophilic additions, the reactivity
of the bridging vinyliminium ligand in 1-3 could be
further extended by the removal of the Câ-H proton.
This possibility is suggested by the deprotonation of the
vinyliminium ligand, described for the mononuclear
complex [Ru(Cp){C(dNEt2)CHdCPh2}(CO)(PPri3)][BF4],
to form the aminoallenyl derivative [Ru(Cp){C(NEt2)d
CdCPh2)}(CO)(PPri3)].4a Moreover, the Fe-CR interac-
tion in the µ-vinyliminium species 1-3 displays some
Fisher-type aminocarbene character,3 and adjacent
C-H hydrogens, in Fisher carbenes, are known to be
acidic.6
These considerations led us to determine to what
extent Câ-H is susceptible to deprotonation, with the
aim of exploring the opportunities that this would
eventually offer. Here, we present the results of these
investigations, which have been performed on a variety
of vinyliminium complexes (Chart 1), to elucidate pos-
sible steric and electronic effects due to the nature of
the substituents R and R′.
Results
Synthesis of Tetrairon Complexes. Compounds
[Fe2{µ-η1:η3-C(R′)dCHCdN(Me)(R)}(µ-CO)(CO)(Cp)2]-
(6) (a) Fischer, H.; Kreissel, F. R.; Schubert, U.; Hoffman, P.; Dotz,
K. H.; Weiss, K. In Transition Metal Carbene Complexes; VCH:
Weinheim, Germany, 1983. (b) Kreiter, C. G. Angew. Chem., Int. Ed.
Engl. 1968, 7, 390. (c) Casey, C. P.; Anderson, R. L. J. Am. Chem. Soc.
1974, 96, 1230. (d) Casey, C. P.; Brunsvold, W. R. J. Organomet. Chem.
1976, 118, 309. (e) Bernasconi, C. F. Chem. Soc. Rev. 1997, 26, 299. (f)
Plantevin, V.; Wojcicki, A. J. Organomet. Chem. 2004, 689, 2000.
Figure 1. ORTEP drawing of [Fe2{µ-C(COOMe)CCN-
(Me)2}(µ-CO)(CO)(Cp)2]2 (4a). All H atoms have been
omitted for clarity. Thermal ellipsoids are at the 30%
probability level.

Deprotonation of µ-Vinyliminium Ligands
Organometallics, Vol. 24, No. 10, 2005 2299
Table 2. Selected Bond Lengths (Å) and Angles
(deg) for 4b
Fe(1)-Fe(2)
Fe(1)-C(21)
Fe(1)-C(22)
Fe(2)-C(22)
Fe(1)-C(25)
Fe(2)-C(25)
Fe(2)-C(26)
Fe(2)-C(27)
C(21)-O(21)
C(22)-O(22)
C(25)-C(26)
C(26)-C(27)
N(1)-C(27)
N(1)-C(30)
N(1)-C(31)
C(25)-C(28)
C(26)-C(33)
2.514(7)
1.716(7)
1.964(6)
1.847(6)
1.981(5)
2.001(5)
2.456(5)
1.886(5)
1.164(7)
1.188(7)
1.473(7)
1.451(7)
1.313(7)
1.466(7)
1.462(7)
1.525(7)
1.425(7)
Fe(3)-Fe(4)
Fe(4)-C(23)
Fe(4)-C(24)
Fe(3)-C(24)
Fe(4)-C(32)
Fe(3)-C(32)
Fe(3)-C(33)
Fe(3)-C(34)
C(23)-O(23)
C(24)-O(24)
C(32)-C(33)
C(33)-C(34)
N(2)-C(34)
N(2)-C(37)
N(2)-C(38)
C(32)-C(35)
2.5132(11)
1.730(6)
1.982(6)
1.822(6)
1.989(5)
2.001(5)
2.454(5)
1.892(5)
1.150(6)
1.189(7)
1.467(7)
1.435(7)
1.313(7)
1.467(7)
1.457(7)
1.528(7)
Fe(1)-C(25)-Fe(2) 78.32(19) Fe(4)-C(32)-Fe(3) 78.08(19)
C(25)-C(26)-C(27) 101.7(4)
C(26)-C(27)-Fe(2) 93.9(3)
C(26)-C(27)-N(1) 127.8(5)
Fe(2)-C(27)-N(1) 138.2(4)
C(25)-C(26)-C(33) 125.3(5)
C(27)-C(26)-C(33) 131.7(5)
C(32)-C(33)-C(34) 101.8(4)
C(33)-C(34)-Fe(3) 94.0(3)
C(33)-C(34)-N(2) 129.2(5)
Fe(3)-C(34)-N(2) 136.6(4)
C(32)-C(33)-C(26) 124.1(4)
C(34)-C(33)-C(26) 133.1(5)
) 1.990(3) and 1.989(5) Å, Fe(3)-C(32) ) 1.999(3) and
2.001(5) Å for 4a,b, respectively), as expected for
a bridging alkylidene. Conversely, the Fe(2)-C(27)
(1.901(4) and 1.886(5) Å) and Fe(3)-C(34) (1.889(3) and
1.892(5) Å) interactions as well as N(1)-C(27) (1.305(5)
and 1.313(7) Å) and N(2)-C(34) (1.325(5) and 1.313(7)
Å) show some double-bond character, typical for a
terminal aminocarbene ligand. The two [Fe2{µ-C(R′)-
CCN(Me)2}(µ-CO)(CO)(Cp)2] units in 4a,b are joined by
the C(26)-C(33) interaction (1.408(5) and 1.425(7) Å),
which shows some double-bond character. The C(26) and
C(33) atoms adopt an almost perfect sp2 hybridization
(sum of angles 358.6(5) and 359.4(5)° for 4a and 358.7(8)
and 359.0(8)° for 4b), and the C(25)-C(26)-C(27)-
C(32)-C(33)-C(34) unit is nearly planar (mean devia-
tion from the C(25)-C(26)-C(27)-C(32)-C(33)-C(34)
least-squares plane 0.1619 and 0.1878 Å, for 4a,b,
respectively). Relative to this plane, the CpFe(2) and
CpFe(3) fragments lay on opposite sides, to minimize
steric repulsions. The sp2 hybridization of C(26) and
C(33) in the bridging bis-alkylidene ligands generates
some important differences between these ligands and
that present in [Fe2{µ-C(CO2Me)CH2CN(Me)(Xyl)}(µ-
CO)(CO)(Cp)2], where Câ has sp3 hybridization. First,
the Fe(2)-C(26) (2.477(3) and 2.456(5) Å) and Fe(3)-
C(33) (2.506(3) and 2.454(5) Å) distances in 4a,b are
significantly shorter than the corresponding distance
in [Fe2{µ-C(CO2Me)CH2CN(Me)(Xyl)}(µ-CO)(CO)(Cp)2]
(2.589(2) Å), suggesting some interactions between the
metal and Câ in the former. This fact, together with
steric repulsions between the two units, can account for
the lengthening of the C(26)-C(33) interaction com-
pared to a pure double bond. Second, both C(25)-C(26)
(1.471(5) and 1.473(7) Å), C(32)-C(33) (1.493(5) and
1.467(7) Å) and C(26)-C(27) (1.446(5) and 1.451(7) Å),
C(33)-C(34) (1.448(5) and 1.435(7) Å) interactions are
shorter than the corresponding interactions in [Fe2{µ-
C(CO2Me)CH2CN(Me)(Xyl)}(µ-CO)(CO)(Cp)2] (1.535(3)
and 1.489(3) Å, respectively), indicating also some
delocalization in the C(25)-C(26)-C(27) and C(32)-
C(33)-C(34) systems and suggesting an allylidene
contribution to the bonding. Finally, it is worth noting
Figure 2. ORTEP drawing of [Fe2{µ-C(Me)CCN(Me)2}(µ-
CO)(CO)(Cp)2]2 (4b), All H atoms have been omitted for
clarity. Thermal ellipsoids are at the 30% probability level.
Only the main image of the disordered Cp ligand bonded
to Fe(1) is reported.
Table 1. Selected Bond Lengths (Å) and Angles
(deg) for 4a
Fe(1)-Fe(2)
Fe(1)-C(21)
Fe(1)-C(22)
Fe(2)-C(22)
Fe(1)-C(25)
Fe(2)-C(25)
Fe(2)-C(26)
Fe(2)-C(27)
C(21)-O(21)
C(22)-O(22)
C(25)-C(26)
C(26)-C(27)
N(1)-C(27)
N(1)-C(30)
N(1)-C(31)
C(25)-C(28)
C(28)-O(1)
C(28)-O(2)
C(29)-O(2)
C(26)-C(33)
2.5251(8)
1.753(4)
1.976(4)
1.846(4)
2.014(3)
2.031(3)
2.477(3)
1.901(4)
1.150(5)
1.191(5)
1.471(5)
1.446(5)
1.305(5)
1.460(5)
1.477(5)
1.497(5)
1.205(4)
1.351(4)
1.446(4)
1.408(5)
Fe(3)-Fe(4)
Fe(4)-C(23)
Fe(4)-C(24)
Fe(3)-C(24)
Fe(4)-C(32)
Fe(3)-C(32)
Fe(3)-C(33)
Fe(3)-C(34)
C(23)-O(23)
C(24)-O(24)
C(32)-C(33)
C(33)-C(34)
N(2)-C(34)
N(2)-C(37)
N(2)-C(38)
C(32)-C(35)
C(35)-O(3)
C(35)-O(4)
C(36)-O(4)
O(1)...C(35)
2.5299(9)
1.746(4)
1.975(4)
1.859(4)
1.990(3)
1.999(3)
2.506(3)
1.889(3)
1.155(5)
1.184(4)
1.493(5)
1.448(5)
1.325(5)
1.454(5)
1.467(5)
1.499(5)
1.211(4)
1.353(4)
1.440(4)
2.750(45)
Fe(1)-C(25)-Fe(2) 77.25(12) Fe(4)-C(32)-Fe(3) 78.74(12)
C(25)-C(26)-C(27) 100.2(3)
C(26)-C(27)-Fe(2) 94.5(2)
C(26)-C(27)-N(1) 127.0(3)
Fe(2)-C(27)-N(1) 137.9(3)
C(25)-C(26)-C(33) 130.3(3)
C(27)-C(26)-C(33) 128.1(3)
C(32)-C(33)-C(34) 99.5(3)
C(33)-C(34)-Fe(3) 96.5(2)
C(33)-C(34)-N(2) 128.6(3)
Fe(3)-C(34)-N(2) 134.6(3)
C(32)-C(33)-C(26) 129.1(3)
C(34)-C(33)-C(26) 130.8(3)
moiety contains an Fe2(µ-CO)(CO)(Cp)2 core and a
bridging µ-C(R′)CCN(Me)2 ligand. The former adopts a
cis arrangement of the Cp ligands as in the parent
compounds 1a,b. The bridging ligand resembles the bis-
alkylidene present in [Fe2{µ-C(CO2Me)CH2CN(Me)-
(Xyl)}(µ-CO)(CO)(Cp)2].5a The iron atoms show a nearly
pure σ interaction with the bridging carbon atoms in
the two moieties (Fe(1)-C(25) ) 2.014(3) and 1.981(5)
Å, Fe(2)-C(25) ) 2.031(3) and 2.001(5) Å, Fe(4)-C(32)

2300 Organometallics, Vol. 24, No. 10, 2005
Chart 2. Possible Isomers for the Complex 4c
Busetto et al.
Scheme 3
that the two moieties composing 4b are completely
identical, whereas they differ only in the orientation of
the carboxylate groups in 4a. In particular, the C(35)-
O(3)-O(4)-C(36) group in 4a is nearly coplanar with
Fe(4)-C(32)-C(33) (Fe(4)-C(32)-C(35)-O(3) dihedral
angle -15.3(5)°), whereas C(28)-O(1)-O(2)-C(29) is
almost orthogonal to the plane determined by Fe(1)-
C(25)-C(26) (Fe(1)-C(25)-C(28)-O(1) dihedral angle
90.0(4)°). This orientation of the COOMe groups allows
extra stabilization of the molecule via a weak interaction
between O(1) and C(35) (O(1)‚‚‚C(35) ) 2.750(45) Å),
which is significantly shorter than the sum of the van
der Waals radii of carbon and oxygen (i.e. 3.15 Å).
The 1H NMR spectrum of 4a, recorded at 233 K,
shows a unique set of resonances for the two Fe2
frames: thus, two Cp resonances are observed (at δ 4.84
and 4.35 ppm) and one signal is found for the COOMe
groups (at δ 4.00 ppm). The main feature in the 13C
NMR spectrum, recorded at 233 K, consists of the
typical low-field resonance attributable to the amino-
carbene carbons CR (δ 247.3 ppm). At room temperature,
the spectra show some broadening and a single reso-
nance for the four Cp ligands, indicating the occurrence
of an exchange process. The latter requires exchange
between the aminocarbene ligand and the terminally
bonded CO. Fluxionality within the Cp2Fe2(CO)2 frame
is favored by the fact that both aminocarbene and CO
can easily switch between bridging and terminal coor-
dination positions. A related fluxional behavior has been
observed in diiron aminocarbene complexes of the type
[Fe2(µ-CO)2{CH(NR2)}(CO)(Cp)2], in which exchange
between terminally bonded aminocarbene and CO ligands
resulted in the equivalence of the Cp ligands, on the
NMR time scale.7 Compound 4c behaves similarly to
4a and shows fluxionality, whereas 4b does not exhibit
any exchange process at room temperature, suggesting
that the fluxionality observed for 4a,c is related to the
presence of the COOMe groups.
Synthesis and Reactivity of σ-Coordinated Acet-
ylide Diiron Complexes. The reaction of 1d,e, 2b,c,
and 3a-c with NaH results in formation of the σ-
alkynyl complexes [Fe2{µ-CN(Me)(R)}(µ-CO)(CO)(Ct
CR′)(Cp)2] (R ) Me, R′ ) SiMe3, 5a; R ) Me, R′ ) Tol,
5b; R ) Bz, R′ ) SiMe3, 5c; R ) Bz, R′ ) Tol, 5d; R )
Xyl, R′ ) SiMe3, 5e; R ) Xyl, R′ ) Tol, 5f; R ) Xyl, R′
) Ph, 5g), in about 90% yield (Scheme 3). The molecular
structure of [Fe2{µ-CN(Me)(Xyl)}(µ-CO)(CO)(CtCSiMe3)-
(Cp)2] (5e) has been established by X-ray diffraction
analysis (Figure 3 and Table 3).
The Fe2(µ-CO)(CO)(Cp)2 core in 5e shows a cis ar-
rangement of the Cp ligands, as in the parent compound
3a. The N(1)-C(13) interaction (1.307(7) Å) falls within
the range found previously for other aminocarbyne
species,8 and it shows some significant double-bond
character, also indicating the iminium nature of the
bridging ligand. The Xyl group is on the side opposite
to CtCSiMe3, to minimize steric repulsions. A compari-
son of Fe(1)-C(12) (2.021(6) Å) and Fe(2)-C(12) (1.843-
(7) Å) shows the remarkable asymmetry of µ-CO, and
this is due to the different electronic properties of the
terminal ligands present on Fe(1) and Fe(2). In particu-
lar, µ-CO shows a longer interaction with Fe(1), which
is bonded to an acidic terminal CO, whereas Fe(2) is
bonded to a stronger σ-donor such as CtCSiMe3. The
latter adopts an almost linear geometry, in agreement
with the sp hybridizations of C(23) and C(24) (Fe(2)-
C(23)-C(24) ) 177.2(5)° and C(23)-C(24)-Si(1) )
The NMR spectra of 4c, recorded at 233 K, indicate
the presence of one isomer, although several isomeric
forms are possible, due to the different orientations that
the nonequivalent nitrogen substituents (Me and Bz)
can assume, and because of the hindered rotation
around the N-C(carbene) bond. The observed isomer
is, presumably, the Z,Z form, in which steric repulsions
between the benzyl groups are minimized (Chart 2).
(8) (a) Boss, K.; Cox, M. G.; Dowling, C.; Manning, A. R. J.
Organomet. Chem. 2000, 612, 18. (b) Albano, V. G.; Busetto, L.;
Camiletti, C.; Castellari, C.; Monari, M.; Zanotti, V. J. Chem. Soc.,
Dalton Trans. 1997, 4671. (c) Albano, V. G.; Busetto, L.; Camiletti,
C.; Monari, M.; Zanotti, V. J. Organomet. Chem. 1998, 563, 153. (d)
Albano, V. G.; Busetto, L.; Monari, M.; Zanotti, V. J. Organomet. Chem.
2000, 606, 163.
(7) Zanotti, V.; Bordoni, S.; Busetto, L.; Carlucci, L.; Palazzi, A.;
Serra, R.; Albano, V. G.; Monari, M.; Prestopino, F.; Laschi, F.; Zanello,
P. Organometallics 1995, 14, 5232.

Deprotonation of µ-Vinyliminium Ligands
Organometallics, Vol. 24, No. 10, 2005 2301
Scheme 4
Scheme 5
Figure 3. ORTEP drawing of the main image of [Fe2{µ-
CN(Me)(Xyl)}(µ-CO)(CO)(CtCSiMe3)(Cp)2] (5e). All H at-
oms have been omitted for clarity. Thermal ellipsoids are
at the 30% probability level. Only the main images of the
disordered groups are reported.
THF, followed by exchange of I- with SO3CF3-, yielded
the vinyliminium complexes [Fe2{µ-η1:η3-C(R′)dC(Me)Cd
N(Me)(Bz)}(µ-CO)(CO)(Cp)2][SO3CF3] (R′ ) SiMe3, 6a;
R′ ) Tol, 6b) (Scheme 4).
Complex 6a has been previously obtained by insertion
of MeCtCSiMe3 into the Fe-aminocarbyne bond of
[Fe2{µ-CN(Me)(Bz)}(µ-CO)(NCMe)(Cp)2][SO3CF3].5b The
spectroscopic properties of 6b are those expected for a
bridging vinyliminium diiron complex.3
Synthesis of 1-Metalla-2-aminocyclopenta-1,3-
dien-5-one Complexes. The vinyliminium complexes
1c and 3d-f react with NaH to give the corresponding
1-metalla-2-aminocyclopenta-1,3-dien-5-one complexes
7a-d, in about 70-80% yield (Scheme 5).
Table 3. Selected Bond Lengths (Å) and Angles
(deg) for 5e
Fe(1)-Fe(2)
Fe(1)-C(11)
Fe(1)-C(12)
Fe(2)-C(12)
Fe(1)-C(13)
Fe(2)-C(13)
Fe(2)-C(23)
2.5069(13)
1.757(6)
2.021(6)
1.843(7)
1.875(5)
1.824(5)
1.889(5)
C(11)-O(11)
C(12)-O(12)
N(1)-C(13)
N(1)-C(14)
N(1)-C(15)
C(23)-C(24)
C(24)Si(1)
1.140(7)
1.168(7)
1.307(7)
1.494(7)
1.462(12)
1.240(7)
1.806(6)
Fe(1)-C(13)-Fe(2)
85.3(2) C(13)-N(1)-C(14) 122.6(5)
Fe(2)-C(23)-C(24) 177.2(5) C(13)-N(1)-C(15) 121.8(8)
C(23)-C(24)-Si(1)
173.7(5) C(14)-N(1)-C(15) 115.1(8)
Complexes 7a-d have been purified by chromatog-
raphy and fully characterized by spectroscopy and
elemental analysis. Moreover, the X-ray structure of
173.7(5)°). The Fe(2)-C(23) distance (1.889(5) Å) reveals
some π interaction between the metal and the acetylide,
and this causes a slight lengthening of the C(23)-C(24)
bond (1.240(7) Å) compared to a pure CtC triple bond
(e.g. 1.18 Å in HCtCH).9
[Fe(Cp)(CO){CN(Me)(Xyl)CHC(Me)C(O)}] (7b) has been
determined: the ORTEP molecular diagram is shown
in Figure 4, and relevant bond lengths and angles are
reported in Table 4. The five atoms constituting the
1-metalla-2-aminocyclopenta-1,3-dien-5-one ring are es-
sentially coplanar (mean deviation from the Fe(1)-
C(7)-C(8)-C(9)-C(10) least-squares plane 0.0116 Å).
The Fe(1)-C(7) (1.940(3) Å) and Fe(1)-C(10) (1.910(3)
Å) interactions are typical for a metal-acyl and a
metal-aminocarbene; the latter shows a strong π back-
bonding, whereas the former is mainly a σ interaction.
Accordingly, the C(7)-O(2) interaction (1.216(3) Å) is
an almost pure double bond, and also the aminocarbene
C(10)-N(1) interaction (1.328(3) Å) shows a partial
double-bond character. The C-C interactions present
an alternating behavior; thus, C(8)-C(9) (1.332(4) Å)
is an almost pure double bond, whereas C(7)-C(8)
(1.508(4) Å) and C(9)-C(10) (1.467(4) Å) are essentially
single bonds.
Compounds 5c-g exist in solution as mixtures of two
isomers, as usually found in complexes of the type
[Fe2{µ-CN(Me)(R)}(µ-CO)(CO)(L)(Cp)2] (L ) C(O)R,
CH2CN, CN, Cl; R ) Xyl, Bz).8 These isomers are due
to the different orientations that the nonequivalent
nitrogen substituents (Me and CH2Ph, or Me and Xyl)
can assume with respect to the µ-CN interaction, which
exhibits partial double-bond character. A characteristic
downfield 13C NMR resonance accounts for the presence
of the aminocarbyne carbon (e.g. at δ 330.5 ppm for 5a).
Finally, attempts to transform the σ-alkynyl species
5a-g into the parent vinyliminium compounds 1-3, or
into new vinylidene ligands (Fe2{dCdCH(R′)}), by
treatment with HSO3CF3 failed, resulting in extensive
decomposition. Conversely, the reaction of [Fe2{µ-
CN(Me)(Bz)}(µ-CO)(CO)(CtCR′)(Cp)2] (R′ ) SiMe3, 5c;
R′ ) Tol, 5d) with an excess of methyl iodide in refluxing
In the 13C NMR spectra of 7a-d, typical low-field
resonances have been found for the acyl carbon (e.g. at
δ 270.7 ppm for 7b) and for the aminocarbene carbon
(9) Simonetta, M.; Gavezzotti, A. In The Chemistry of the Carbon-
Carbon Triple Bond; Wiley: New York, 1978.

2302 Organometallics, Vol. 24, No. 10, 2005
Busetto et al.
Chart 4
on the coordinated ligands. Fragmentation has been
observed only in a few cases, which include the reac-
tion of [M2{µ-CN(Me)(R)}(µ-CO)(CO)2(Cp)2][SO3CF3]
(M ) Fe, Ru) with KH and acetonitrile, to form a
metallapyrrole ring,12 and acetylide addition at co-
ordinated nitrile in [Fe2{µ-CN(Me)(R)}(µ-CO)(CO)(p-
NCC6H4R′)(Cp)2]+, yielding a five-membered metalla-
cycle (1-metalla-2-amino-3-aza-5-alkylidenecyclopenta-
1,3-diene).13
Figure 4. ORTEP drawing of [Fe(Cp)(CO){CN(Me)(Xyl)-
CHC(Me)C(O)}] (7b). All H atoms, except H(9), have been
omitted for clarity. Thermal ellipsoids are at the 30%
probability level.
Table 4. Selected Bond Lengths (Å) and Angles
(deg) for 7b
Fe(1)-C(6)
Fe(1)-C(7)
Fe(1)-C(10)
C(6)-O(1)
C(7)-C(8)
C(8)-C(9)
1.727(3)
1.940(3)
1.910(3)
1.138(4)
1.508(4)
1.332(4)
C(9)-C(10)
C(7)-O(2)
C(8)-C(11)
C(10)-N(1)
N(1)-C(12)
N(1)-C(13)
1.467(4)
1.216(3)
1.501(4)
1.328(3)
1.471(3)
1.441(3)
Discussion
Reactions of the vinyliminium complexes with NaH
selectively form three different types of products, result-
ing from dimerization of the dinuclear compounds (4a-
c), fragmentation (7a-d), or alkyne deinsertion (5a-
g). Since Câ-H proton abstraction is presumably the
initial step in all of these reactions, the different
outcomes could be related to the nature of the depro-
tonated intermediates (Chart 4). The simple proton
abstraction would leave a zwitterionic intermediate
(Chart 4, I), bearing a negative charge on the Câ and a
positive charge placed on the iminium moiety. However,
proton removal, generating an highly unsaturated
organic fragment, can be accompanied by changes in the
coordination mode: the bridging ligand might assume
a bis-alkylidene coordination mode (II), in which the Câ,
no longer coordinated to the metals, displays a “carbene
character”. Other rearrangements are also possible,
leading to a bridging alkynylaminocarbene (III),14 or a
coordinated allene-1,3-diyl (IV).15
The formation of the tetranuclear complexes 4a-c
(Scheme 2) is well explained by the dimerization of type
II intermediates (Chart 4). Similar dimerizations have
been reported for the deprotonated forms of some
alkoxy- and aminocarbene complexes, which undergo
oxidative coupling to give bridging bis-carbene com-
plexes in an overall sequence described as “dehy-
drodimerization”.16 The formation of 4a-c is pre-
sumably related to the smallness of both R and R′
substituents, which do not oppose steric hindrance to
the dimerization. In agreement with this, the complexes
C(10)-Fe(1)-C(7)
Fe(1)-C(7)-C(8)
C(7)-C(8)-C(9)
82.92(12) C(8)-C(9)-C(10)
115.0(3)
113.4(2)
113.3(3)
C(9)-C(10)-Fe(1) 115.27(19)
Chart 3. E/Z Isomers for Complex 7d
CR (e.g. at 266.2 ppm for 7b). NOE investigations have
outlined that the nitrogen substituents of both 7b and
7c adopt in solution the E arrangement, in agreement
with what is observed in the solid state. Conversely,
complex 7d exists in solution as mixture of two isomeric
forms, which have been identified as E and Z, with a
prevalence of the former (Chart 3).
Examples of 1-metallacyclopent-3-ene-2,5-dione10 and
1-metallacyclopent-3-en-2-one complexes11 have been
reported in the literature. Interestingly, complex 7b
represents, to our knowledge, the first 1-metallacyclo-
penta-1,3-dien-5-one ring structurally characterized.
The formation of 7a-d is the result of an intra-
molecular rearrangement, which requires coupling of
the vinyliminium with a CO ligand and fragmentation
of the diiron assembly. It should be remarked that the
diiron frame Fe2Cp2(µ-CO) is usually very robust and
is unaffected even by strong rearrangements, occurring
(12) Busetto, L.; Camiletti, C.; Zanotti, V.; Albano, V. G.; Sabatino,
P. J. Organomet. Chem. 2000, 593, 335.
(13) Busetto, L.; Marchetti, F.; Zacchini, S.; Zanotti, V.; Zoli, E. J.
Organomet. Chem., in press.
(14) Davis, J. H.; Lukehart, C. M.; Sacksteder, L. Organometallics
1987, 6, 50.
(10) (a) Elarraoui, A.; Ros, J.; Ya´n˜ez, R.; Solans, X.; Font-Bardia,
M. J. Organomet. Chem. 2002, 642, 107. (b) Mao, T.; Zhang, Z.;
Washington, J.; Takats, J.; Jordan, R. B. Organometallics 1999, 18,
2331.
(11) (a) Kayan, A.; Gallucci, J. C.; Wojcicki, A. J. Organomet. Chem.
2001, 630, 44. (b) Huffman, M. A.; Liebeskind, L. S. Organometallics
1992, 11, 255.
(15) (a) Clarke, L. P.; Davies, J. E.; Raithby, P. R.; Shields, G. P.
Dalton 2000, 4527. (b) Akita, M.; Chung, M. C.; Terada, M.; Miyauti,
M.; Tanaka, M.; Moro-oka, Y. J. Organomet. Chem. 1998, 565, 49.
(16) (a) Rabier, A.; Lugan, N.; Mathieu, R.; Geoffroy, G. L. Organo-
metallics 1994, 13, 4676. (b) Rabier, A.; Lugan, N.; Mathieu, R. J.
Organomet. Chem. 2001, 617-618, 681. (c) Lattuada, L.; Licandro, E.;
Maiorana, S.; Molinari, H.; Papagni, A. Organometallics 1991, 10, 807.

Deprotonation of µ-Vinyliminium Ligands
Organometallics, Vol. 24, No. 10, 2005 2303
[Fe2{µ-η1:η3-C(R′)dCHCdN(Me)(Xyl)}(µ-CO)(CO)(Cp)2]-
[SO3CF3] (R′ ) Me, 3d; R′ ) COOMe, 3e), which differ
from 1a,b for the presence of the more hindered Xyl
substituent, do not dimerize upon treatment with NaH.
The deinsertion of the acetylide unit (Scheme 5),
which represents a different type of reaction path,
consequent to Câ-H proton abstraction, should be better
explained by the formation of an aminoalkylidene
intermediate of type III (Chart 4).
Scheme 6
Since the vinyliminium complexes have been obtained
by alkyne insertion into Fe-aminocarbyne, the sequence
shown in Scheme 3 can be considered the corresponding
reverse reaction, although the acetylide fragment re-
mains σ coordinated to an Fe atom.
It is not obvious why deinsertion is observed for the
reactions of 1d,e, 2b,c, and 3a-c, rather than dimer-
ization or fragmentation. This behavior is related to the
nature of the substituent at Cγ, since the sterically
demanding SiMe3 and aryl substituents are thought to
prevent the dimerization. Moreover, (trimethylsilyl)-
and arylacetylides are among the most stable σ-alkynyl
ligands, and this may also favor the formation of 5a-
g.
Interestingly, the deinsertion reaction affords σ-
alkynyl complexes, which are not otherwise available.
Attempts to generate the alkynyl complexes 5 by simple
replacement of the labile nitrile ligand in [Fe2{µ-
CN(Me)(R)}(µ-CO)(CO)(NCR′)(Cp)2][SO3CF3] (R′ ) Me,
aryl) with LiCtCR′′ have been unsuccessful. In fact,
acetylides cause the deprotonation of the coordinated
acetonitrile and subsequent rearrangement to cyano-
methyl.17 Even when the nitriles do not contain acidic
protons (e.g. NCCMe3, arylnitriles) the reactions with
acetylides proceed via nucleophilic addition at the nitrile
ligands, instead of producing its replacement.13,18
Complexes 5a-g are interesting compounds for sev-
eral reasons. They contain a σ-coordinated alkynyl
ligand,19 whereas, in binuclear complexes, alkynyl
ligands are more commonly found in bridging posi-
tions.20 Moreover, metal-alkynyl complexes represent
an area of growing interest21 for potential applications
in nonlinear optics,22 as luminescent materials,23 and
as molecular devices.24
electronic factors related to the nature of the substitu-
ents R and R′ in the parent complexes 1c and 3d-f
seem to produce the observed fragmentation rather than
dimerization or deinsertion. The process is presumably
initiated by removal of the acidic Câ-Η. However, since
the stoichiometry of the reaction requires loss of [CpFe]+
rather than H+, we cannot exclude the possibility that
the initial step consists of one-electron reduction. To
investigate this point, compounds 1c and 3d-f have
been treated with different bases, including NEt3,
sodium naphthalenide (NaNaph), and KOH, under
conditions similar to those used in the reactions with
NaH. Investigations were not conclusive, because both
NaNaph and KOH reacted, leading to the formation of
the corresponding metallacyclopentenone complexes 7
in lower, but still comparable, yields with respect to
those obtained with NaH, whereas NEt3 failed to
produce any transformation.
Moreover, the reaction with NaH has been carried out
on the Câ-deuterated vinyliminium complex [Fe2{µ-η1:
η3-C(Bun)dC(D)CdN(Me)2}(µ-CO)(CO)(Cp)2][SO3CF3]
(1f). The reaction affords the metallacyclic ring 7a, with
loss of deuterium at Câ (Scheme 6).
This result is in agreement with the hypothesis that
removal of the Câ-H proton in the vinyliminium
complexes 1c is the initial step of the process; however,
it is not conclusive evidence, because the Câ-H in 7a is
expected to be acidic as well, and deuterium-hydrogen
exchange could take place on the metallacycle 7, during
the workup.
Conclusions
The third type of rearrangement observed, as a
consequence of the treatment with NaH, consists of the
fragmentation of the dinuclear precursor with formation
of the metallacyclic complexes 7a-d. Again, steric and
The Câ-H hydrogen in the vinyliminium complexes
[Fe2{µ-η1:η3-Cγ(R′)dCâHCRdN(Me)(R)}(µ-CO)(CO)(Cp)2]-
[SO3CF3] (1-3) is efficiently removed by NaH. The
resulting neutral species are not stable and rapidly
evolve to give tetra-, di-, or mononuclear complexes,
depending on the properties of the substituents R and
R′ on the ligand. The formation of tetrairon species is
limited to R ) Me, CH2Ph and to the presence of
relatively small R′ groups (COOMe, Me) at Cγ. When
the steric demand of R and/or R′ increases, the Fe-Fe
bond can be broken, resulting in mononuclear 1-metalla-
2-aminocyclopenta-1,3-dien-5-one compounds. Finally,
in the presence of substituents R′ ) SiMe3, Ph, Tol,
which can generate stable σ-alkynyl ligands (-CtCR′),
the reaction provides cleavage of the CR-Câ bond,
independent of the nature of R, affording diiron amino-
carbyne complexes having a terminal alkynyl ligand.
These reactions are very selective and do not form
mixtures of products.
(17) Albano, V. G.; Busetto, L.; Marchetti, F.; Monari, M.; Zanotti,
V. J. Organomet. Chem. 2002, 649, 64.
(18) Albano, V. G.; Bordoni, S.; Busetto, L.; Marchetti, F.; Monari,
M.; Zanotti, V. J. Organomet. Chem. 2003, 684, 37.
(19) Hurst, S. K.; Ren, T. J. Organomet. Chem. 2003, 670, 188.
(20) (a) Lang, H.; George, D. S. A.; Rheinwald, G. Coord. Chem. Rev.
2000, 206-207, 101. (b) Nast, R. Coord. Chem. Rev. 1982, 47, 89. (c)
Cherkas, A. A.; Randall, L. H.; Taylor, N. J.; Mott, G. N.; Yule, J. E.;
Guinamant, J. L.; Carty, A. J. Organometallics 1990, 9, 1677. (d)
Darren, S. A.; McDonald, R.; Cowie, M. Organometallics 1998, 17, 2553.
(e) Hogarth, G.; Redmond, S. P. J. Organomet Chem. 1997, 534, 221.
(f) Smith, W. F.; Yule, J.; Taylor, N. J.; Paik, H. N.; Carty, A. J. Inorg.
Chem. 1977, 16, 1593.
(21) Long, N. J.; Williams, C. K.; Angew. Chem., Int. Ed. 2003, 42,
2586.
(22) (a) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc,
M. Adv. Organomet. Chem. 1998, 42, 291. (b) Whittall, I. R.; McDonagh,
A. M.; Humphrey, M. G.; Samoc, M. Adv. Organomet. Chem. 1999,
43, 349.
(23) Yam V. W. W. Acc. Chem. Res. 2002, 35, 555.
(24) (a) Ziessel, R.; Hissler, M.; El-Ghayoury, A.; Harriman, A.
Coord. Chem. Rev. 1998, 180, 1251. (b) Paul, F.; Lapinte, C. Coord.
Chem. Rev. 1998, 178-180, 431.
The results reported here, compared with previous
findings on the reactions with NaBH4,5 evidence that

2304 Organometallics, Vol. 24, No. 10, 2005
Busetto et al.
described for 1c, by reacting [Fe2{µ-CN(Me)2}(µ-CO)(CO)-
(NCMe)(Cp)2][SO3CF3] with DCtCBun. The latter was pre-
pared treating HCtCBun, in THF solution at -40 °C, with
an equimolar amount of BunLi, followed by treatment with
D2O. Yield: 88%. Color: green. Anal. Calcd for C22H27F3Fe2-
NO5S: C, 45.08; H, 4.64; N, 2.39. Found: C, 45.11; H, 4.61;
N, 2.35. IR (CH2Cl2): ν(CO) 1990 (vs), 1805 (s), ν(CRN) 1682
the reaction products strongly depend on the nature of
the hydride reagent: NaH acts exclusively as a base,
whereas the nucleophile NaBH4 provides H- addition.
Moreover, these results indicate that the bridging
vinyliminium ligand can generate new and reactive
organic fragments, which are stabilized through coor-
dination to the metal centers, yielding a variety of new
and interesting mono- and polymetallic species. Exploi-
tation of the acidic character of Câ-H in µ-vinyliminium
ligands, for generating new C-C and C-heteroatom
bonds, is currently under investigation and will be the
matter of future reports.
1
(m) cm-1. H NMR (CDCl3): δ 5.23, 5.07 (s, 10 H, Cp); 4.18,
3.75 (m, 2 H, CγCH2); 3.87, 3.29 (s, 6 H, NMe); 2.05, 1.87 (m,
2 H, CγCH2CH2); 1.69 (m, 2 H, CγCH2CH2CH2); 1.11 (t, 3 H,
3JHH ) 7.32 Hz, CγCH2CH2CH2CH3).
Synthesis of [Fe2{µ-η1:η3-Cγ(CMe2OH)dCâHCRdN(Me)-
(Xyl)}(µ-CO)(CO)(Cp)2] [SO3CF3] (3f). A solution of the
complex [Fe2{µ-CN(Me)(Xyl)}(µ-CO)(CO)(NCMe)(Cp)2][SO3-
CF3] (210 mg, 0.331 mmol), in CH2Cl2, was treated with HCt
CC(Me)2OH (0.041 mL, 0.42 mmol). The mixture was stirred
at boiling temperature for 4 h and then filtered on a Celite
pad. Removal of the solvent gave a residue that was washed
with diethyl ether (2 × 20 mL). Crystallization from a CH2Cl2
solution, layered with diethyl ether, afforded brown crystals
of 3f. Yield: 191 mg, 85%. Anal. Calcd for C28H30F3Fe2NO6S:
C, 49.65; H, 4.46; N, 2.07. Found: C, 49.82; H, 4.38; N, 2.13.
Experimental Section
General Data. All reactions were routinely carried out
under a nitrogen atmosphere, using standard Schlenk tech-
niques. Unless otherwise stated, solvents were distilled im-
mediately before use under nitrogen from appropriate drying
agents. Chromatography separations were carried out on
columns of deactivated alumina (4% w/w water). Glassware
was oven-dried before use. Infrared spectra were recorded on
a Perkin-Elmer Spectrum 2000 FT-IR spectrophotometer, and
elemental analyses were performed on a ThermoQuest Flash
1112 Series EA instrument. ESI MS spectra were recorded
on a Waters Micromass ZQ 4000 with samples dissolved in
CH3CN. All NMR measurements were performed on Varian
Gemini 300 and Mercury Plus 400 instruments. The chemical
shifts for 1H and 13C were referenced to internal TMS. The
IR (CH2Cl2): ν(CO) 1998 (vs), 1806 (s), ν(CRN) 1632 (m) cm-1
.
1H NMR (CDCl3): δ 8.07-6.73 (m, 3 H, Me2C6H3); 5.44, 5.29,
5.22, 4.68 (s, 10 H, Cp); 4.95 (s, 1 H, CâH); 4.15 (s, 3 H, NMe);
2.40, 2.20, 1.92, 1.73 (s, 6 H, Me2C6H3); 1.51 (s, 6 H, CMe2OH);
E:Z ratio 5:1. 13C NMR (CDCl3): δ 255.6 (µ-CO); 231.1 (CR);
210.3 (CO); 209.6 (Cγ); 144.5 (ipso-Me2C6H3); 139.7, 136.6,
132.9, 131.0, 129.3 (Me2C6H3); 90.8, 89.5, 88.3, 87.0 (Cp); 70.0
(CMe2OH); 48.7 (Câ); 45.8 (NMe); 32.0, 31.4 (CMe2OH); 17.6,
17.0 (Me2C6H3).
spectra were fully assigned via DEPT experiments and 1H, 13
C
Synthesis of [Fe2{µ-η1:η2Cγ(R′)CâCRN(Me)(R)}(µ-CO)-
(CO)(Cp)2]2 (R ) Me, R′ ) COOMe, 4a; R ) Me, R′ ) Me,
4b; R ) CH2Ph, R′ ) COOMe, 4c). Compound 1a (148 mg,
0.252 mmol), in THF solution (10 mL), was treated with NaH
(35 mg, 1.46 mmol). The mixture was stirred for 20 min and
then filtered on an alumina pad. Removal of the solvent and
chromatography of the residue on an alumina column, with a
mixture of CH2Cl2 and THF (4:1) as eluent, afforded a dark
gray band, which was collected. Crystallization at -20 °C from
CH2Cl2 solution layered with petroleum ether (bp 40-60° C)
gave crystals of 4a. Yield: 66 mg, 60%. Anal. Calcd for C38H38-
Fe4N2O8: C, 52.22; H, 4.38; N, 3.20. Found: C, 52.26; H, 4.41;
N, 3.20. IR (CH2Cl2): ν(CO) 1939 (s), 1751 (vs), 1741 (vs), 1688
(w), 1659 (w), ν(CRN) 1568 (w), 1541 (w) cm-1. 1H NMR (CDCl3,
233 K): δ 4.84, 4.35 (s, 20 H, Cp); 4.00 (s, 6 H, CO2Me); 3.32,
2.26 (s, 12 H, NMe). 13C NMR (CDCl3, 233K): δ 278.4 (µ-CO);
247.3 (CR); 216.0 (CO); 181.8 (CO2Me); 151.4 (Cγ); 87.4, 87.3
(Cp); 71.6 (Câ); 51.5 (CO2Me); 47.1, 43.1 (NMe). ESI-MS
(ES+): m/z 874 [M+, 11%], 437 [M/2+, 100%], 409 [M/2+ - CO,
68%].
correlations measured using gs-HSQC and gs-HMBC experi-
ments.25 Unless otherwise specified, NMR spectra were re-
corded at 298 K; NMR signals due to a second isomeric form
(where it has been possible to detect and/or resolve them) are
italicized. NOE measurements were recorded using the
DPFGSE-NOE sequence.26 All the reagents were commercial
products (Aldrich) of the highest purity available and were
used as received. [Fe2(CO)4(Cp)2] was purchased from Strem
and used as received. The compounds [Fe2{µ-CN(Me)(R)}(µ-
CO)(CO)(NCMe)(Cp)2][SO3CF3]8d (R ) Me, Xyl) and [Fe2{µ-η1:
η3-C(R′)dCHCdN(Me)(R)}(µ-CO)(CO)(Cp)2][SO3CF3] (1a,b,d,e;
2a-c; 3a-e) were prepared as described in the literature.3
Synthesis of [Fe2{µ-η1:η3-Cγ(Bun)dCâHCRdN(Me)2}(µ-
CO)(CO)(Cp)2][SO3CF3] (1c) and [Fe2{µ-η1:η3-Cγ(Bun)d
CâDCRdN(Me)2}(µ-CO)(CO)(Cp)2][SO3CF3] (1f). HCtCBun
(0.068 mL, 0.59 mmol) was added to a solution of [Fe2{µ-
CN(Me)2}(µ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (250 mg, 0.471
mmol), in THF (20 mL). The mixture was stirred at boiling
temperature for 60 min, and then the solvent was removed
under reduced pressure and the residue chromatographed on
an alumina column. Elution with MeOH afforded a green
band, which was collected and evaporated to dryness. Crystal-
lization from a CH2Cl2 solution, layered with diethyl ether,
gave crystals of 1c. Yield: 248 mg, 90%. Anal. Calcd for
C22H26F3Fe2NO5S: C, 45.15; H, 4.48; N, 2.39. Found: C, 44.99;
H, 4.52; N, 2.29. IR (CH2Cl2): ν(CO) 1990 (vs), 1805 (s), ν(CRN)
Complexes 4b,c were prepared by following the same
procedure described for the synthesis of 4a, by reacting NaH
with 1b and 2a, respectively. Crystals of 4b suitable for X-ray
analysis were collected by a dichloromethane solution layered
with n-pentane, at -20 °C.
4b. Yield: 70%. Color: blue-grey. Anal. Calcd for C36H38-
Fe4N2O4: C, 55.01; H, 4.87; N, 3.56. Found: C, 55.07; H, 4.92;
N, 3.63. IR (CH2Cl2): ν(CO) 1921 (s), 1740 (s-sh), 1728 (vs),
1
1682 (m) cm-1. H NMR (CDCl3): δ 5.16, 4.99 (s, 10 H, Cp);
4.52 (s, 1 H, CâH); 4.14, 3.74 (m, 2 H, CγCH2); 3.83, 3.25 (s, 6
H, NMe); 2.05, 1.86 (m, 2 H, CγCH2CH2); 1.67 (m, 2 H, CγCH2-
1
ν(CRN) 1603 (w), 1558 (wm) cm-1. H NMR (CDCl3): δ 4.84,
3
CH2CH2); 1.10 (t, 3 H, JHH ) 7.32 Hz, CγCH2CH2CH2CH3).
4.48 (s, 20 H, Cp); 3.71, 3.48 (s, 12 H, NMe); 1.85 (s, 6 H, CγMe).
13C NMR (CDCl3): δ 272.0 (µ-CO); 262.4 (CR); 221.9 (CO); 172.6
(Cγ); 86.8, 84.7 (Cp); 79.2 (Câ); 51.4, 42.8 (NMe); 13.2 (CγMe).
4c. Yield: 68%. Color: dark gray. Anal. Calcd for C50H46-
Fe4N2O8: C, 58.52; H, 4.52; N, 2.73. Found: C, 58.43; H, 4.60;
N, 2.77. IR (CH2Cl2): ν(CO) 1939 (s), 1752 (vs), 1742 (vs), 1687
(w), 1659 (w), ν(CRN) 1568 (w), 1537 (w) cm-1. 1H NMR (CDCl3,
233 K): δ 7.45-6.91 (m, 10 H, Ph); 4.87, 4.40 (s, 20 H, Cp);
13C NMR (CDCl3): δ 257.0 (µ-CO); 225.6 (CR); 212.8 (Cγ); 209.6
(CO); 89.6, 87.3 (Cp); 54.7 (CγCH2); 51.3 (Câ); 50.9, 44.7 (NMe);
37.7 (CγCH2CH2); 22.8 (CγCH2CH2CH2); 14.1 (CγCH2CH2-
CH2CH3).
Complex [Fe2{µ-η1:η3-Cγ(Bun)dCâDCRdN(Me)2}(µ-CO)(CO)-
(Cp)2][SO3CF3] (1f) was synthesized by the same procedure
(25) Wilker, W.; Leibfritz, D.; Kerssebaum, R.; Beimel, W. Magn.
Reson. Chem. 1993, 31, 287.
(26) Stott, K.; Stonehouse, J.; Keeler, J.; Hwang, T. L.; Shaka, A. J.
J. Am. Chem. Soc. 1995, 117, 4199.
2
4.81, 4.52 (d, 4 H, JHH ) 13.7 Hz, CH2Ph); 4.03 (s, 6 H,
CO2Me); 2.07 (s, 6 H, NMe). 13C NMR (CDCl3, 233 K): δ 278.6
(µ-CO); 246.8 (CR); 216.1 (CO); 181.7 (CO2Me); 151.4 (Cγ);

Deprotonation of µ-Vinyliminium Ligands
Organometallics, Vol. 24, No. 10, 2005 2305
135.2-127.8 (Ph); 87.7, 87.3 (Cp); 70.8 (Câ); 63.3 (CH2Ph); 51.4
(CO2Me); 39.8 (NMe). ESI-MS (ES+): m/z 1026 [M+, 7%], 513
[M/2+, 100%], 485 [M/2+ - CO, 37%].
C6H4Me); isomer ratio 3:2. 13C NMR (C6D5CD3) δ 334.1, 333.7
(µ-C); 260.9, 260.6 (µ-CO); 213.7, 213.2 (CO); 157.4-124.4
(C6H4Me and Ph); 119.2, 119.1, 107.3, 106.8 (CtC); 87.6, 86.0,
85.8, 82.2 (Cp); 69.4, 68.8 (CH2Ph); 48.1, 47.3 (NMe); 21.1
(C6H4Me).
5f. Yield: 90%. Color: ochre yellow. Anal. Calcd for C31H29-
Fe2NO2: C, 66.58; H, 5.23; N, 2.50. Found: C, 66.48; H, 5.21;
N, 2.55. IR (CH2Cl2): ν(CtC) 2087 (m), ν(CO) 1971 (vs), 1792
(s), ν(CN) 1505 (w) cm-1. 1H NMR (C6D5CD3): δ 7.17-6.79 (m,
7 H, C6H4Me and Me2C6H3); 4.60, 4.53, 4.32, 3.98 (s, 10 H,
Cp); 4.08, 4.05 (s, 3 H, NMe); 2.28, 2.12 (s, 6 H, Me2C6H3); 2.22
(s, 3 H, C6H4Me); isomer ratio 7:1. 13C NMR (C6D5CD3): δ 338.5
(µ-C); 259.3 (µ-CO); 214.2 (CO); 158.1-124.0 (C6H4Me and
Me2C6H3); 120.1, 106.2 (CtC); 87.8, 86.7, 86.1, 82.2 (Cp); 51.3
(NMe); 21.2 (C6H4Me); 18.3, 17.8 (Me2C6H3). ESI-MS (ES+):
m/z 559 [M+].
5g. Yield: 87%. Color: ochre yellow. Anal. Calcd for C30H27-
Fe2NO2: C, 66.09; H, 4.99; N, 2.57. Found: C, 66.00; H, 5.05;
N, 2.56. IR (CH2Cl2): ν(CtC) 2086 (m), ν(CO) 1971 (vs), 1792
(s), ν(CN) 1504 (w) cm-1. 1H NMR (C6D5CD3): δ 7.57-6.72 (m,
8 H, Ph and Me2C6H3); 4.56, 4.54, 4.31, 3.95 (s, 10 H, Cp); 4.07,
4.04 (s, 3 H, NMe); 2.24, 2.19 (s, 6 H, Me2C6H3); isomer ratio
9:1. 13C NMR (C6D5CD3): δ 338.3 (µ-C); 260.0 (µ-CO); 214.4
(CO); 161.7-125.0 (Ph and Me2C6H3); 117.8, 106.2 (CtC); 87.6,
85.4 (Cp); 52.1 (NMe); 18.4, 17.7 (Me2C6H3).
Synthesis of [Fe2{µ-CN(Me)(R)}(µ-CO)(CO)(C≡CSiMe3)-
(Cp)2] (R ) Me, 5a; R ) Bz, 5c; R ) Xyl, 5e). Compound 1d
(100 mg, 0.166 mmol), was dissolved in THF (15 mL) and
treated with NaH (21 mg, 0.875 mmol). The mixture was
stirred for 30 min, and then the solvent was removed. The
residue was washed with petroleum ether (2 × 20 mL),
dissolved in CH2Cl2, and filtered on a Celite pad. Crystalliza-
tion at -20 °C from CH2Cl2 solution, layered with petroleum
ether, gave brown crystals of 5a. Yield: 70 mg, 93%. Anal.
Calcd for C20H25Fe2NO2Si: C, 53.24; H, 5.58; N, 3.10. Found:
C, 53.27; H, 5.50; N, 3.11. IR (CH2Cl2): ν(CtC) 2011 (vs), ν(CO)
1
1972 (vs), 1794 (s), ν(µ-CN) 1534 (w) cm-1. H NMR (CDCl3):
δ 4.71, 4.68 (s, 10 H, Cp); 4.16, 4.02 (s, 6 H, NMe); -0.23 (s, 9
H, SiMe3). 13C NMR (CDCl3): δ 330.5 (µ-C); 263.9 (µ-CO); 212.3
(CO); 133.6, 117.6 (CtC); 87.2, 85.7 (Cp); 52.1, 50.8 (NMe);
1.53 (SiMe3).
Complexes 5c,e were prepared by following the same
procedure described for the synthesis of 5a, by reacting NaH
with 2b and 3a, respectively. Crystals of 5e suitable for X-ray
analysis were collected from a CH2Cl2 solution layered with
petroleum ether, at -20 °C.
5c. Yield: 95%. Color: ochre yellow. Anal. Calcd for C26H29-
Fe2NO2Si: C, 59.22; H, 5.54; N, 2.66. Found: C, 59.12; H, 5.70;
N, 2.69. IR (CH2Cl2): ν(CtC) 2011 (vs), ν(CO) 1972 (vs), 1794
(s), ν(µ-CN) 1534 (w) cm-1. 1H NMR (CDCl3): δ 7.57-7.38 (m,
5 H, Ph); 6.19, 5.74, 5.55, 5.36 (d, 2 H, 2JHH ) 15 Hz, CH2Ph);
4.80, 4.77, 4.72, 4.65 (s, 10 H, Cp); 4.06, 3.91 (s, 3 H, NMe);
-0.14, -0.17 (s, 9 H, SiMe3); isomer ratio 3:2. 13C NMR
(CDCl3): δ 333.6 (µ-C); 263.6, 263.2 (µ-CO); 212.4, 212.2 (CO);
136.2-126.9 (Ph and CtC); 118.0, 117.5 (CtC); 87.6, 87.4,
86.0, 85.9 (Cp); 69.8, 69.0 (CH2Ph); 49.6, 48.1 (NMe); 1.64, 1.60
(SiMe3).
5e. Yield: 90%. Color: ochre yellow. Anal. Calcd for C27H31-
Fe2NO2Si: C, 59.91; H, 5.77; N, 2.59. Found: C, 59.94; H, 5.77;
N, 2.50. IR (CH2Cl2): ν(CtC) 2012 (vs), ν(CO) 1973 (vs), 1792
(s), ν(µ-CN) 1506 (w) cm-1. 1H NMR (CDCl3): δ 7.34-7.16 (m,
3 H, Me2C6H3); 4.81, 4.29 (s, 10 H, Cp); 4.43 (s, 3 H, NMe);
2.67, 2.26 (s, 6 H, Me2C6H3); -0.17 (s, 9 H, SiMe3). 13C NMR
(CDCl3): δ 337.2 (µ-C); 263.6 (µ-CO); 212.8 (CO); 148.4 (ipso-
Me2C6H3); 134.3, 133.2, 129.9, 128.1, 128.0 (Me2C6H3); 131.0,
118.3 (CtC); 87.6, 85.7 (Cp); 51.5 (NMe); 18.5, 17.9 (Me2C6H3);
1.5 (SiMe3).
Synthesis of [Fe2{µ- η1:η3-Cγ(R′)dCâ(Me)CRdN(Me)(Bz)}-
(µ-CO)(CO)(Cp)2][SO3CF3] (R′ ) SiMe3, 6a; R′ ) Tol, 6b).
To a THF solution (15 mL) of 5c (120 mg, 0.228 mmol) was
added MeI (0.9 mL, 14.5 mmol), and the resulting mixture was
stirred at about 50 °C for 20 min. The solution was cooled to
room temperature, and then AgCF3SO3 (88 mg, 0.344 mmol)
was added; subsequent chromatography on alumina, using a
1:1 mixture of THF and MeCN as eluent, afforded a green
band, corresponding to 6a. Yield: 68 mg, 43%. Anal. Calcd
for C28H32F3Fe2NO5SSi: C, 48.64; H, 4.67; N, 2.03. Found: C,
48.55; H, 4.62; N, 2.05. IR (CH2Cl2): ν(CO) 1982 (vs), 1815
(s), ν(CN) 1652 (m) cm-1. 1H NMR (CDCl3): δ 7.48-7.18 (m, 5
2
H, Ph); 5.77, 5.72, 4.77, 4.67 (d, JHH ) 14 Hz, 2 H, CH2Ph);
5.00, 4.99, 4.53, 4.50 (s, 10 H, Cp); 3.96, 3.16 (s, 3 H, NMe);
2.23, 2.14 (s, 3 H, CâMe); 0.70, 0.67 (s, 9 H, SiMe3); Z:E ratio
2:1. 13C NMR (CDCl3): δ 254.6, 253.1 (µ-CO); 222.3, 221.1 (CR);
208.5 (CO); 195.2 (Cγ); 132.4-128.9 (Ph); 89.0, 88.9, 88.4, 88.2
(Cp); 70.6 (Câ); 65.2, 62.3 (CH2Ph); 45.4, 43.4 (NMe); 20.6, 20.2
(CâMe); 4.1 (SiMe3).
Complex 6b was prepared by following the same procedure
described for the synthesis of 6a, by reacting 5d with MeI and
AgCF3SO3.
Synthesis of [Fe2{µ-CN(Me)(R)}(µ-CO)(CO)(CtCR′)-
(Cp)2] (R ) Me, R′) Tol, 5b; R ) Bz, R′) Tol, 5d; R ) Xyl,
R′) Tol, 5f; R ) Xyl, R′) Ph, 5g). A solution of 1e (145 mg,
0.234 mmol) in THF (15 mL) was treated with NaH (27 mg,
1.17 mmol), and the mixture was stirred for 30 min. Then,
the solvent was removed, the residue dissolved in a 1:1 mixture
of toluene and diethyl ether, and this solution filtered on a
Celite pad. Solvent removal afforded a brown powder of 5b.
Yield: 100 mg, 91%. Anal. Calcd for C24H23Fe2NO2: C, 61.44;
H, 4.94; N, 2.99. Found: C, 61.47; H, 4.95; N, 3.06. IR (THF):
6b. Yield: 66%. Color: ochre yellow. Anal. Calcd for
C32H30F3Fe2NO5S: C, 54.18; H, 4.26; N, 1.97. Found: C, 54.22;
H, 4.39; N, 1.93. IR (CH2Cl2): ν(CO) 1989 (vs), 1807 (s), ν(CN)
1655 (m) cm-1
.
1H NMR (CDCl3): δ 7.56-7.11 (m, 9 H, Ph
2
and C6H4Me); 5.74, 5.67, 5.14, 4.44 (d, 2H, JHH ) 15 Hz,
CH2Ph); 5.26, 5.25, 4.90, 4.89 (s, 10 H, Cp); 3.75, 3.03 (s, 3 H,
NMe); 2.47 (s, 3 H, C6H4Me); 1.75, 1.73 (s, 3 H, CâMe); Z:E
ratio 3:1. 13C NMR (CDCl3): δ 258.1 (µ-CO); 226.2, 225.0 (CR);
210.6, 210.0 (CO); 202.2 (Cγ); 150.8 (ipso-C6H4Me); 136.4-125.3
(Ph and C6H4Me); 91.7, 88.0, 87.9 (Cp); 66.4, 61.5 (CH2Ph);
65.6, 65.3 (Câ); 45.9, 41.9 (NMe); 21.2 (C6H4Me); 18.3, 18.1
(CâMe).
ν(CtC) 2087 (s), ν(CO) 1963 (vs), 1788 (s) cm-1 1H NMR
.
(C6D5CD3): δ 7.48, 7.34 (d, 4 H, 3JHH ) 6.3 Hz, C6H4Me); 4.55,
4.29 (s, 10 H, Cp); 4.07, 4.00 (s, 3 H, NMe); 2.22 (s, 3 H,
C6H4Me). 13C NMR (C6D5CD3): δ 331.0 (µ-C); 261.0 (µ-CO);
213.7 (CO); 156.9 (ipso-C6H4Me); 137.9, 129.0, 126.1 (C6H4Me);
120.2, 107.8 (CtC); 87.9, 85.0 (Cp); 51.4, 50.0 (NMe); 21.3
(C6H4Me).
Synthesis of [Fe(Cp)(CO){CRN(Me)(R)CâHCγ(R)C(O)}-
] (R ) Me, R′ ) Bun, 7a; R ) Xyl, R′ ) Me, 7b; R ) Xyl, R′
) COOMe, 7c; R ) Xyl, R′ ) CMe2OH, 7d). Complex 1c (200
mg, 0.342 mmol), was dissolved in THF (20 mL) and treated
with NaH (38 mg, 1.58 mmol). The resulting mixture was
stirred for 30 min and then filtered on an alumina pad.
Removal of the solvent and chromatography of the residue on
alumina, using a 1:1 mixture of CH2Cl2 and THF as eluent,
afforded a brown band corresponding to 7a. Yield: 73 mg, 68%.
Anal. Calcd for C16H21FeNO2: C, 60.97; H, 6.72; N, 4.44.
Found: C, 61.03; H, 6.66; N, 4.48. IR (CH2Cl2): ν(CO) 1911
Complexes 5d,f,g were prepared by following the same
procedure described for the synthesis of 5b, by reacting NaH
with 2c and 3b,c, respectively.
5d. Yield: 88%. Color: ochre yellow. Anal. Calcd for C30H27-
Fe2NO2: C, 66.09; H, 4.99; N, 2.57. Found: C, 66.01; H, 4.83;
N, 2.53. IR (THF): ν(CtC) 2090 (s), ν(CO) 1970 (vs), 1805 (s)
cm-1. 1H NMR (C6D5CD3): δ 7.56-6.80 (m, 9 H, C6H4Me and
Ph); 5.48, 5.22 (d, 2JHH ) 14 Hz, CH2Ph); 4.59, 4.55, 4.54, 4.34
(s, 10 H, Cp); 3.99, 3.98 (s, 3 H, NMe); 2.22, 2.19 (s, 3 H,

2306 Organometallics, Vol. 24, No. 10, 2005
Table 5. Crystal Data and Experimental Details for 4a‚CH2Cl2, 4b, 5e, and 7b
Busetto et al.
4a‚CH2Cl2
4b
5e
7b
formula
C
39H40Cl2Fe4N2O8
C
36H38Fe4N2O4
C
27H31Fe2NO2Si
C20H21FeNO2
fw
959.03
786.08
541.32
363.23
T, K
λ, Å
cryst syst
150(2)
0.71073
monoclinic
P21/n
293(2)
0.71073
monoclinic
P21/c
293(2)
293(2)
0.71073
monoclinic
P21/c
0.71073
orthorhombic
Aba2
space group
a, Å
18.032(4)
10.346(2)
21.479(4)
105.50(3)
3861.2(13)
4
12.735(3)
27.480(6)
10.206(2)
112.80(3)
3292.8(11)
4
9.920(2)
34.927(7)
14.849(3)
90
9.3991(19)
19.964(4)
10.132(2)
109.83(3)
1788.5(6)
4
b, Å
c, Å
â, deg
cell vol, Å3
5144.6(18)
8
Z
Dc, g cm-3
1.650
1.586
1.398
1.349
µ, mm-1
1.667
1.770
1.198
0.854
F(000)
1960
1616
256
760
cryst size, mm
θ limits, deg
no. of rflns collected
no. of indep rflns
no. of data/restraints/params
goodness on fit on F2
R1 (I > 2σ(I))
wR2 (all data)
largest diff peak and hole, e Å-3
0.24 × 0.21 × 0.15
1.31-26.37
37 213
7877 (Rint ) 0.0771)
7877/0/502
1.062
0.0502
0.1416
2.190/-1.385
0.19 × 0.16 × 0.11
1.48-25.03
26 427
5811 (Rint ) 0.1083)
5811/178/417
1.054
0.0564
0.1398
0572/-0629
0.24 × 0.22 × 0.14
1.17-25.03
22 038
4551 (Rint ) 0.0769)
4551/85/297
1.050
0.0478
0.1212
0.514/-0.340
0.24 × 0.19 × 0.11
2.04-28.70
21 148
4625 (Rint ) 0.0644)
4625/0/221
0.963
0.0494
0.1452
0.350/-0.519
(vs), ν(CRN) 1625 (w sh), ν(acyl) 1599 (m) cm-1
.
1H NMR
(ipso-Me2C6H3); 145.0, 143.5 (Câ); 133.6, 133.0, 132.2, 131.8,
129.2, 129.1, 129.0, 128.9, 128.7, 128.1 (Me2C6H3); 85.4, 84.9
(Cp); 71.5, 71.1 (CMe2OH); 49.0, 44.6 (NMe); 29.8, 29.6, 28.9,
28.4 (CMe2OH); 18.3, 17.5, 17.2 (Me2C6H3).
(CDCl3): δ 7.29 (s, 1 H, CâH); 4.48 (s, 5 H, Cp); 3.71, 3.49 (s,
6 H, NMe); 2.25 (m, 2 H, CγCH2); 1.41 (m, 2 H, CγCH2CH2);
1.31 (m, 2 H, CγCH2CH2CH2); 0.89 (t, 3JHH ) 7.32 Hz, CH2CH2-
CH2CH3). 13C NMR (CDCl3) δ 272.0 (CdO); 262.3 (CR); 221.9
(CO); 177.1 (Cγ); 145.5 (Câ); 84.8 (Cp); 51.4, 42.8 (NMe); 30.3,
27.0, 22.6 (CH2); 13.9 (CH2CH2CH2CH3).
The reaction of 1f with NaH was performed by the same
procedure described for the synthesis of 7a.
Complexes 7b-d were prepared by following the same
procedure described for the synthesis of 7a, by reacting NaH
with 3d-f, respectively. Crystals of 7b suitable for X-ray
analysis were obtained by a CH2Cl2 solution layered with
n-pentane, at -20 °C.
X-ray Crystallography. Crystal data and collection details
for 4a‚CH2Cl2, 4b, 5e, and 7b are reported in Table 5. The
diffraction experiments were carried out on a Bruker SMART
2000 diffractometer equipped with a CCD detector using Mo
KR radiation. Data were corrected for Lorentz-polarization
and absorption effects (empirical absorption correction
SADABS).27 Structures were solved by direct methods and
refined by full-matrix least squares based on all data using
F2.28 Hydrogen atoms were fixed at calculated positions and
refined by a riding model. All non-hydrogen atoms were refined
with anisotropic displacement parameters, unless otherwise
stated. The crystals of 5e appeared to be racemically twinned
with a refined Flack parameter of 0.50(3).29 Disorder was found
for one Cp ligand in 4b and 5e, and the Xyl and the SiMe3
groups in 5e are disordered. Disordered atomic positions were
split and refined isotropically using similar distances and
similar U restraints and one occupancy parameter per disor-
dered group.
7b. Yield: 73%. Color: orange. Anal. Calcd for C20H21-
FeNO2: C, 66.13; H, 5.83; N, 3.86. Found: C, 66.29; H, 5.74;
N, 3.90. IR (CH2Cl2): ν(CO) 1916 (vs), ν(CRN) 1627 (m), ν(acyl)
1597 (s) cm-1 1H NMR (CDCl3): δ 7.27-7.16 (m, 3 H,
.
Me2C6H3); 6.54 (s, 1 H, CâH); 4.62 (s, 5 H, Cp); 3.82 (s, 3 H,
NMe); 2.19, 2.10 (s, 6 H, Me2C6H3); 1.70 (s, 3 H, CγMe). 13C
NMR (CDCl3): δ 270.7 (CdO); 266.2 (CR); 221.3 (CO); 173.2
(Cγ); 148.0 (Câ); 145.3 (ipso-Me2C6H3); 132.6, 132.1, 129.2,
128.8, 128.6 (Me2C6H3); 84.8 (Cp); 48.7 (NMe); 17.6, 17.4
(Me2C6H3); 13.1 (CγMe). ESI-MS (ES+): m/z 363 [M+].
Acknowledgment. We thank the Ministero
dell’Universita` e della Ricerca Scientifica e Tecnologica
(MIUR) (project: “New strategies for the control of
reactions: interactions of molecular fragments with
metallic sites in unconventional species”) and the Uni-
versity of Bologna (“Funds for Selected Research Top-
ics”) for financial support.
7c. Yield: 67%. Color: orange. Anal. Calcd for C21H21-
FeNO4: C, 61.94; H, 5.20; N, 3.44. Found: C, 62.01; H, 5.17;
N, 3.45. IR (CH2Cl2): ν(CO) 1935 (vs), 1724 (s), ν(CRN) 1624
(m), ν(acyl) 1610 (ms) cm-1 1H NMR (CDCl3): δ 7.34-7.08
.
(m, 3 H, Me2C6H3); 7.03 (s, 1 H, CâH); 4.68 (s, 5 H, Cp); 3.83
(s, 3 H, NMe); 3.69 (s, 3 H, COOMe); 2.19, 2.11 (s, 6 H,
Me2C6H3). 13C NMR (CDCl3): δ 267.5 (CR); 241.3 (CdO); 221.9
(CO); 164.2 (COOMe); 151.7 (Câ); 145.1 (ipso-Me2C6H3); 132.3,
132.7, 129.5, 129.0, 128.7 (Me2C6H3); 85.3 (Cp); 52.0 (COOMe);
49.6 (NMe); 17.6, 17.4 (Me2C6H3).
Supporting Information Available: Crystallographic
data for compounds 4a‚CH2Cl2, 4b, 5e, and 7b as CIF files.
This material is available free of charge via the Internet at
http://pubs.acs.org.
7d. Yield: 88%. Color: brown. Anal. Calcd for C22H25-
FeNO3: C, 61.94; H, 5.20; N, 3.44. Found: C, 62.00; H, 5.20;
N, 3.32. IR (CH2Cl2): ν(CO) 1926 (vs), ν(CRN) 1620 (m), ν(acyl)
OM050095J
1
1578 (ms) cm-1. H NMR (CDCl3): δ 7.42, 6.47 (s, 1 H, Câ);
7.29-7.16 (m, 3 H, Me2C6H3); 5.27, 5.13 (s, 1 H, OH); 4.64,
3.99 (s, 5 H, Cp); 3.81, 3.67 (s, 3 H, NMe); 2.39, 2.33, 2.19,
2.09 (s, 6 H, Me2C6H3); 1.44, 1.43, 1.19, 1.18 (s, 6 H, CMe2OH);
E:Z ratio 2:1. 13C NMR (CDCl3): δ 278.3, 276.8 (CdO); 265.7,
263.8 (CR); 223.8, 220.8 (CO); 177.5, 174.8 (Cγ); 149.0, 144.9
(27) Sheldrick, G. M. SADABS, program for empirical absorption
correction; University of Go¨ttingen, Go¨ttingen, Germany, 1996.
(28) Sheldrick, G. M. SHELX97, program for crystal structure
determination; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(29) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876.