Selective formation of one or two C-C bonds promoted by carbanion addition to [Fe2(cp)2(CO)2(μ-CO)(μ-CSMe)]+

Article abstract of DOI:10.1021/om9609168

The reactions of [Fe₂(cp)₂(CO)₂(μ-CO)(μ-CSMe)]CF ₃SO₃ (1; cp = η-C₅H₅) with a variety of carbon nucleophiles result in C-C bond formation at different sites of the molecule, (allyl)-MgCl (allyl = C₃H₅) undergoes cp addition to form [Fe₂(cp)(η⁴-C₅H₅-allyl)(CO) ₂(μ-CO)(μ-CSMe)] (₂) and the alkylidene complex [Fe₂(cp)(η-C₅H₄-allyl) (CO)₂(μ-CO){μ-C(SMe)H}] (3), derived from cp to μ-C hydrogen migration. Li₂Cu(CN)R₂ adds at the μ-C atom to yield [Fe₂(cp)₂(CO)₂(μ-CO){μ-C(SMe)R}] (R = Ph, 4; R = Me, 8), [FeFe(cp)₂(CO)(μ-CO){μ-C(SMe)R}] (R = Ph, 5; R = Me, 9), and [Fe₂(cp)₂(CO)(μ-CO){μ-C(ηl²-Ph)Ph}] (6) or the vinylidene derivative [Fe₂(cp)₂(CO)(μ-CO)(μ-C=CH₂)] (10) in the case of phenyl or methyl organocuprate reagents, respectively. The latter complexes are the result of C-SMe bond breaking occurring, through different reaction paths, in 4 and 8. Likewise, the formation of [Fe₂-(cp)₂(CO)(μ-CO){μ-C=C(CN)₂}] (11) from 1 and NaCH(CN)₂ occurs via a direct addition at the μ-C carbon followed by HSMe elimination. The nucleophilic attack at the terminal CO in 1 is achieved with LiC≡CPh, which forms two new C-C bonds in the alkylidene complex [FeFe(cp)₂(CO)(μ-CO){μ-C(SMe)C(O)CCPh}] (12) after C(O)CCPh migration from Fe to the bridging carbene carbon. The analogous [FeFe(cp)₂(CO)(μ-CO)(μ-C(SMe)C(O)(2-th)}] (13; 2-th = 2-C₄H₃S) and [Fe₂(cp)(η⁴-C₅H₅-(2-th)(CO) ₂(μ-CO)(μ-CSMe)] (14) are obtained from 1 and Lith via addition at the CO and cp groups, respectively. The relevance of these reactions is discussed in terms of selective C-C bond formation that, if it occurs at the cp or CO terminal ligands, favors the hydrogen migration (e.g. formation of 3) or the carbyne-carbonyl migratory coupling (e.g. formation of 12 and 13), respectively. The X-ray structures of [Fe₂-(cp)₂(CO)(μ-CO){μ-C(η²-Ph)Ph}] (6) and [FeFe(cp)₂(CO)(μ-CO){μ-C(SMe)C(O)(2-th)}] (13) have revealed the peculiarity of the Ph and SMe group coordination to the iron. Their structural features are discussed in comparison with those of analogous complexes.

Full text of DOI:10.1021/om9609168

1224
Organometallics 1997, 16, 1224-1232
Selective F or m a tion of On e or Tw o C-C Bon d s
P r om oted by Ca r ba n ion Ad d ition to
[F e2(cp )2(CO)2(µ-CO)(µ-CSMe)]+
Silvia Bordoni,† Luigi Busetto,*,† Chiara Camiletti,† Valerio Zanotti,†
Vincenzo G. Albano,*,‡ Magda Monari,‡ and Fabio Prestopino‡
Dipartimento di Chimica Fisica ed Inorganica, Universita` di Bologna, Viale Risorgimento 4,
I-40136 Bologna, Italy, and Dipartimento di Chimica “G. Ciamician”, Universita` di Bologna,
Via Selmi 2, I-40126 Bologna, Italy
Received October 29, 1996X
The reactions of [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]CF3SO3 (1; cp ) η-C5H5) with a variety of
carbon nucleophiles result in CsC bond formation at different sites of the molecule. (allyl)-
MgCl (allyl ) C3H5) undergoes cp addition to form [Fe2(cp)(η4-C5H5-allyl)(CO)2(µ-CO)(µ-
CSMe)] (2) and the alkylidene complex [Fe2(cp)(η-C5H4-allyl) (CO)2(µ-CO){µ-C(SMe)H}] (3),
derived from cp to µ-C hydrogen migration. Li2Cu(CN)R2 adds at the µ-C atom to yield
[Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)R}] (R ) Ph, 4; R ) Me, 8), [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)R}]
(R ) Ph, 5; R ) Me, 9), and [Fe2(cp)2(CO)(µ-CO){µ-C(η2-Ph)Ph}] (6) or the vinylidene
derivative [Fe2(cp)2(CO)(µ-CO)(µ-CdCH2)] (10) in the case of phenyl or methyl organocuprate
reagents, respectively. The latter complexes are the result of CsSMe bond breaking
occurring, through different reaction paths, in 4 and 8. Likewise, the formation of [Fe2-
(cp)2(CO)(µ-CO){µ-CdC(CN)2}] (11) from 1 and NaCH(CN)2 occurs via a direct addition at
the µ-C carbon followed by HSMe elimination. The nucleophilic attack at the terminal CO
in 1 is achieved with LiCtCPh, which forms two new CsC bonds in the alkylidene complex
[FeFe(cp)2(CO)(µ-CO){µ-C(SMe)C(O)CCPh}] (12) after C(O)CCPh migration from Fe to the
bridging carbene carbon. The analogous [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)C(O)(2-th)}] (13;
2-th ) 2-C4H3S) and [Fe2(cp)(η4-C5H5-(2-th)(CO)2(µ-CO)(µ-CSMe)] (14) are obtained from 1
and Lith via addition at the CO and cp groups, respectively. The relevance of these reactions
is discussed in terms of selective CsC bond formation that, if it occurs at the cp or CO
terminal ligands, favors the hydrogen migration (e.g. formation of 3) or the carbyne-carbonyl
migratory coupling (e.g. formation of 12 and 13), respectively. The X-ray structures of [Fe2-
(cp)2(CO)(µ-CO){µ-C(η2-Ph)Ph}] (6) and [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)C(O)(2-th)}] (13) have
revealed the peculiarity of the Ph and SMe group coordination to the iron. Their structural
features are discussed in comparison with those of analogous complexes.
In tr od u ction
(CO)2(µ-CO)(µ-CR)]+.3 In contrast, the thiocarbyne
analogue [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]CF3SO3 (1)4 ex-
hibits an extensive chemistry toward nucleophiles5 but
undergoes only a few reactions generating new CsC
bonds. These include the nucleophilic addition of CN-
at the µ-C carbon of 1 to form the corresponding
µ-carbene derivative [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)-
CN}]6 and the carbonyl-thiocarbyne coupling promoted
Dinuclear or polynuclear transition-metal complexes
containing bridging hydrocarbon ligands have been
extensively studied as models of intermediates postu-
lated in several important metal-catalyzed processes.1
In particular, the study of reactions leading to the
formation of CsC bonds in dinuclear compounds may
result in a better understanding of surface-catalyzed
hydrocarbon chain growth (Fischer-Tropsch reactions).2
A number of reactions of carbon-carbon bond formation
have recently been described. They are based upon the
strong electrophilic character of the bridging carbyne
ligand in diiron cationic complexes of the type [Fe2(cp)2-
by LiHBEt3, which affords [FeFe(cp)2(CO)(µ-CO){µ-
C(CHO)SMe}].7 In addition to these reactions, which
form a CsC bond at the µ-C carbyne carbon, we have
(3) (a) Casey, C. P.; Crocker, M.; Vosejpka, P. C.; Fagan, P. J .;
Marder, S. R.; Gohodes, M. A. Organometallics 1988, 7, 670. (b) Casey,
C. P.; Marder, S. R.; Fagan, P. J . J . Am. Chem. Soc. 1983, 105, 7197.
(c) Casey, C. P.; Meszaros, M. W.; Fagan, P. J .; Bly, R. K.; Marder, S.
R.; Austin, E. A. J . Am. Chem. Soc. 1986, 118, 4043. (d) Casey, C. P.;
Vosejpka, P. C.; Crocker, M. J . Organomet. Chem. 1990, 394, 339.
(4) Quick, M. H.; Angelici, R. J . Inorg. Chem. 1981, 20, 1123.
(5) (a) Schroeder, N. C.; Funchess, R.; J acobson, R. A.; Angelici, R.
J . Organometallics 1989, 8, 521. (b) Schroeder, N. C.; Angelici, R. J .
J . Am. Chem. Soc. 1986, 108, 3688. (c) Busetto, L.; Carlucci, L.; Zanotti,
V.; Albano, V. G.; Braga, D. J . Chem. Soc., Dalton Trans. 1990, 243.
(6) Busetto, L.; Bordoni, S.; Zanotti, V.; Albano, V. G.; Braga, D.
Gazz. Chim. Ital. 1988, 118, 667.
†Dipartimento di Chimica Fisica ed Inorganica.
‡Dipartimento di Chimica “G. Ciamician”.
X Abstract published in Advance ACS Abstracts, February 15, 1997.
(1) (a) Muetterties, E. L.; Rhodin, R. N.; Band, E.; Brucker, C. F.;
Pretzer, W. R. Chem. Rev. 1979, 79, 91. (b) Roofer-Depoorter, C. K.
Chem. Rev. 1981, 81, 447. (c) Cutler, A. R.; Hanna, P. K.; Vites, J . C.
Chem. Rev. 1988, 88, 1363. (d) Maitlis, P. M.; Long, H. C.; Quyoum,
R.; Turner, M. L.; Wang, Z. Q. J . Chem. Soc., Chem. Commun. 1996,
1.
(2) (a) Herrmann, W. A. Angew. Chem., Int. Ed. Engl. 1982, 21, 117.
( b) Turner, M. L.; Long, H. C.; Shenton, A.; Byers, P. K.; Maitlis, P.
M. Chem. Eur. J . 1995, 1, 549.
S0276-7333(96)00916-8 CCC: $14.00 © 1997 American Chemical Society

Carbanion Addition to [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]+
Organometallics, Vol. 16, No. 6, 1997 1225
Sch em e 1
Sch em e 2
recently found that Grignard reagents (RMgCl) add at
one cp ring of 1, yielding the corresponding cyclopen-
tadiene (η4-C5H5R) derivative.8
In the present paper we extend our studies to the
reactions of 1 with carbon nucleophiles, including
stabilized carbanions, organocopper, and organomag-
nesium reagents. All give addition reactions leading,
however, to quite different product distributions, de-
pending on the site of 1 (cp, CO, or µ-CSMe) involved.
Unusual rearrangements, following the direct carbon-
carbon bond formation, are also observed; some of these
have been ascertained by X-ray crystallographic studies.
The structures of two of these products, namely [Fe2-
spectrum is the low-field resonance at 11.4 ppm due to
the methylidene proton.
Ad d ition a t th e µ-CSMe Liga n d . Rea ction of 1
w ith Or ga n ocop p er Rea gen ts. The reaction of 1
with Li2Cu(CN)Ph2 in thf solution at -40 °C rapidly
affords a mixture of products: [Fe2(cp)2(CO)2(µ-CO){µ-
C(SMe)Ph}] (4; 42%), [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)-
Ph}] (5; 18%), and [Fe2(cp)2(CO)(µ-CO){µ-C(η2-Ph)Ph}]
(6; 27%) (Scheme 2), which have been separated by
alumina column chromatography and obtained as air-
stable microcrystalline solids.
(cp)2(CO)(µ-CO){µ-C(η2-Ph)Ph}] and [FeFe(cp)2(CO)(µ-
CO){µ-C(SMe)C(O)(2-th)}], are discussed.
The thioalkylidene complex 4 shows in its IR spec-
trum the usual strong-weak-medium ν(CO) band
pattern (at 1986, 1947, and 1780 cm-1 in CH2Cl2
solution) observed in the analogous µ-alkylidene com-
plexes [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)X}] (X ) H, CN),5a,6
adopting a cis configuration (facing CO and cp ligands,
respectively). In accord with an idealized Cs symmetry,
compound 4 has equivalent cp groups, reflected in the
occurrence of one signal in both its 1H and 13C NMR
spectra (at 4.99 and 91.6 ppm, respectively). The
µ-alkylidene carbon in 4 displays, in its 13C NMR
spectrum, a low-field-shifted signal (193.7 ppm) within
the characteristic range of µ-CR2 ligands (140-200
ppm). Analogously to the (thiomethoxy)alkylidenes
[Fe2(cp)2(CO)2(µ-CO)(µ-C(SMe)X] (X ) H, CN), complex
4 can be easily converted (61% yield) into the cy-
anoalkylidene [Fe2(cp)2(CO)2(µ-CO){µ-C(Ph)(CN)}] (7)
by a two-step reaction consisting of: (i) S-methylation
(with MeSO3CF3) and (ii) SMe2 displacement by cyanide
(NBu4CN) addition.10 Complex 7 has been identified by
its spectroscopic data (see Experimental Section).
Resu lts
Ad d ition a t th e cp Liga n d . Rea ction s of 1 w ith
Gr ign a r d Rea gen ts. Allylmagnesium chloride reacts
with 1, as previously described1 for other Grignard
reagents RMgCl (R ) phenyl, benzyl, isopropyl), to form
the η4-cyclopentadiene complex [Fe2(cp)(η4-C5H5-allyl)-
(CO)2(µ-CO)(µ-CSMe)] (2) and the alkylidene complex
[Fe2(cp)(η-C5H4-allyl)(CO)2(µ-CO){µ-C(SMe)H}] (3)
(Scheme 1). Compound 2 is the result of direct CsC
bond formation at the cp ligand of 1; the allyl group
addition occurs at the exo side of the cp ring, as indicated
by the absence of the characteristic IR absorption of the
cyclopentadiene H-exo atom around 2750 cm-1 9
The
.
previously documented hydrogen migration from the
C5H5R group to the µ-C carbyne carbon generates 3.8
Compounds 2 and 3 have been isolated from the reaction
mixture in 7% and 74% yields, respectively, indicating
that 2 is largely converted into 3. In contrast, in the
reported reactions of 1 with RMgX (R ) Ph, Bz, iPr)2
the corresponding type 2 and 3 products have been
obtained in about 40% and 20% yields, respectively,
suggesting that the nature of the R group in the
η4-C5H5R ligand may influence the hydrogen migration
process.
The greenish-brown complex [FeFe(cp)2(CO)(µ-CO)-
{µ-C(SMe)Ph}] (5), in which the sulfur is coordinated
to one Fe atom, is obviously generated from 4 (in about
18% yield) by intramolecular CO displacement. This
The air-stable complex 3 exhibits the expected spec-
troscopic properties; the key feature in its 1H NMR
(10) (a) Albano, V. G.; Bordoni, S.; Braga, D.; Busetto, L.; Palazzi,
A.; Zanotti, V. Angew. Chem., Int. Ed. Engl. 1991, 30, 847. (b) Busetto,
L.; Cassani, M. C.; Zanotti, V.; Albano, V. G.; Braga, D. J . Organomet.
Chem. 1991, 415, 395. (c) Busetto, L.; Zanotti, V.; Bordoni, S.; Carlucci,
L.; Albano, V. G.; Braga. D. J . Chem. Soc., Dalton Trans. 1992, 1105.
(d) Busetto, L.; Carlucci, L.; Zanotti, V.; Albano, V. G.; Monari, M.
Chem. Ber. 1992, 125, 1125. (e) 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.
(7) Busetto, L.; Zanotti, V.; Norfo, L.; Palazzi, A.; Albano, V. G.;
Braga, D. Organometallics 1993, 12, 190.
(8) Albano, V. G.; Bordoni, S.; Busetto, L.; Monari, M.; Zanotti, V.
Organometallics 1995, 14, 5455.
(9) (a) Davison, A.; Green, M. L. H.; Wilkinson, G. J . Chem. Soc.
1961, 3172. (b) White, D. A. Organomet. Chem. Rev. A 1968, 3, 497.
(c) Khand, I. U.; Pauson, P. L.; Watts, W. E. J . Chem. Soc. C 1969,
2024. (d) Faller, J . W. Inorg. Chem. 1980, 19, 2857.

1226 Organometallics, Vol. 16, No. 6, 1997
Bordoni et al.
Sch em e 3
Sch em e 4
The most significant difference from the corresponding
reaction with Li2Cu(CN)Ph2 is represented by the
presence of 10 among the reaction products. Interest-
ingly, the formation of 10 seems dependent on the
nature of the organocopper reagent. Indeed, when 1 is
treated with a large excess of the “low-order” cuprate
LiCu(CN)Me (MeLi/CuCN ) 1:1) the vinylidene deriva-
tive 10 is the most abundant product (73% yield). The
spectroscopic characterization of 8 and 9 (Experimental
Section) has been straightforward because of the anal-
ogy with 4 and 5, respectively. The nature of 10 has
been ascertained by comparing its spectroscopic proper-
ties with those reported.14 In particular our method
exclusively yields cis-10, which is also the only isomer
obtained by deprotonation of [Fe2(cp)2(CO)2(µ-CO)(µ-
CCH3)]+.14b
Rea ction of 1 w ith Na CH(CN)2. Treatment of 1
with NaCH(CN)2 (Scheme 4) affords the known bridging
vinylidene complex [Fe2(cp)2(CO)2(µ-CO){µ-CdC(CN)2}]
(11) in 53% yield. Unlike most of the related diiron
bridging vinylidenes,15 compound 11 consists of a mix-
ture of the cis and trans isomers, which have been
separated by column chromatography. Their spectro-
scopic properties are in agreement with those previously
reported for the same isomers obtained in low yield
(overall 3%) from [Fe(cp)(CO)2]- and Cl2CdC(CN)2.16 In
addition, the 13C NMR spectra show the bridging-
vinylidene carbon signal in the usual range15 (334.9 and
336.5 ppm for cis-11 and trans-11, respectively) al-
though shifted to low field compared to 10 (276.7 and
279.2 ppm) because of the presence of the CN groups.
Ad d ition a t th e CO Liga n d . Rea ction of 1 w ith
LiCtCP h . Treatment of 1 with LiCtCPh in thf at -20
process occurs spontaneously at room temperature in
chlorinated solvents. In fact, over a 12-14 h period,
about 50% of 4 has been converted into 5, as shown by
NMR spectroscopy. The characterization of 5 is straight-
forward, since a number of strictly related dinuclear
complexes containing the doubly coordinated µ-C(SMe)X
(X ) CN,6,12 SR,11 H12 ) ligands have previously been
described. In their 1H NMR spectra, the SMe reso-
nances appear to be high-field-shifted compared to the
corresponding uncoordinated SMe groups. Accordingly,
the SMe signal in 5 is observed at 1.25 ppm, whereas
the corresponding resonance in 4 occurs at 2.01 ppm.
The ν(CO) band pattern of 5 consists of one terminal
and one bridging carbonyl stretching at 1942 and 1759
cm-1 (CH2Cl2 solution).
The third derivative, isolated in about 27% yield from
the reaction of 1 with Li2Cu(CN)Ph2, is [Fe2(cp)2(CO)-
(µ-CO){µ-C(η2-Ph)Ph}] (6). Its nature has been eluci-
dated by an X-ray diffraction study (Figure 1). In this
molecule the bridging diphenylalkylidene ligand is
further coordinated to one Fe atom through a double
bond of one phenyl ring (see next section). The spec-
troscopic properties of complex 6 closely resemble those
of the analogous ruthenium compound [Ru2(cp)2(CO)-
(µ-CO){µ-C(η2-Ph)Ph}] obtained from [Ru2(cp)2(CO)(µ-
CO){µ-C(O)C2Ph2}].13 The resonance at 1.50 ppm ob-
1
served in the H NMR spectrum of 6 has been readily
attributed to the proton of the C6H5 ring involved in the
“olefinic bond”. The resulting inequivalence of the cp
groups gives rise to two unusually high-field shifted
signals at 4.40 and 3.94 ppm, whereas the µ-alkylidene
carbon resonance in the 13C NMR spectrum at 184.3
ppm falls in the range expected for this class of
complexes.
°C gives the alkylidene complex [FeFe(cp)2(CO)(µ-CO)-
{µ-C(SMe)C(O)CCPh}] (12), which has been isolated by
column chromatography in about 50% yield (Scheme 5).
The IR spectrum of the moderately air stable 12, in CH2-
Cl2 solution, shows terminal and bridging carbonyl
absorptions (at 1956 and 1784 cm-1) and bands at-
tributable to ν(CtC) and ν{C(dO)R} at 2187 and 1573
cm-1, respectively. The NMR spectra exhibit non-
equivalent C5H5 signals at 4.79, 4.75 (1H) and 85.7, 84.2
Treatment of 1 with Li2Cu(CN)Me2 in thf at -40 °C
results in a mixture of products: [Fe2(cp)2(CO)2(µ-CO)-
{µ-C(SMe)Me}] (8; 64%), [FeFe(cp)2(CO)(µ-CO){µ-C(S-
Me)Me}] (9; 12%), and the bridging vinylidene complex
[Fe2(cp)2(CO)2(µ-CO)(µ-CdCH2)] (10; 17%) (Scheme 3).
(14) (a) Dawkins, G. M.; Green, M.; J effery, J . C.; Sambale, C.; Stone,
F. G. A. J . Chem. Soc., Dalton Trans. 1983, 499. (b) Kao. S. C.; Lu, P.
P. Y.; Pettit, R. Organometallics 1982, 1, 911.
(15) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Amouri, H. E.;
Gruselle, M.; Chem. Rev. 1996, 96, 1077.
(16) (a) King, R. B.; Saran, M. S. J . Am. Chem. Soc. 1973, 95, 1811.
(b) Kirchner, R. M.; Ibers, J . A. J . Organomet. Chem. 1974, 82, 243.
(11) Matachek, J . R.; Angelici, R. J . Inorg. Chem. 1986, 25, 2877.
(12) Albano, V. G.; Bordoni, S.; Busetto, L.; Camiletti, C.; Monari,
M.; Prestopino, F.; Zanotti, V. J . Chem. Soc., Dalton Trans., in press.
(13) Davies, D. L.; Knox, S. A. R.; Morris, M. J .; Woodward, P. J .
Chem. Soc., Dalton Trans. 1984, 2293.

Carbanion Addition to [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]+
Organometallics, Vol. 16, No. 6, 1997 1227
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [F e2(cp )2(CO)(µ-CO){µ-C(η2-P h )P h }] (6)
Fe(1)-Fe(2)
Fe(1)-C(1)
Fe(1)-C(2)
Fe(1)-C(3)
Fe(2)-C(1)
Fe(2)-C(2)
Fe(1)-C(cp)av
Fe(2)-C(cp)av
Fe(2)-C(21)
Fe(2)-C(22)
2.525(2
1.972(5)
1.968(5)
1.742(6)
1.976(5)
1.872(6)
2.123
2.095
2.124(4)
2.232(6)
C(1)-C(11)
C(1)-C(21)
C(2)-O(2)
1.505(5)
1.520(6)
1.169(7)
1.153(7)
1.356(8)
1.496(7)
1.439(9)
1.372(11)
1.435(12)
1.309(10)
C(3)-O(3)
C(21)-C(22)
C(21)-C(26)
C(22)-C(23)
C(23)-C(24)
C(24)-C(25)
C(25)-C(26)
C(3)-Fe(1)-C(2)
C(3)-Fe(1)-C(1)
C(2)-Fe(1)-C(1)
C(3)-Fe(1)-C(35)
C(3)-Fe(1)-Fe(2)
C(2)-Fe(1)-Fe(2)
C(1)-Fe(1)-Fe(2)
C(2)-Fe(2)-C(1)
C(2)-Fe(2)-C(21)
C(1)-Fe(2)-C(21)
C(2)-Fe(2)-C(22)
C(1)-Fe(2)-C(22)
C(21)-Fe(2)-C(22)
C(2)-Fe(2)-Fe(1)
C(1)-Fe(2)-Fe(1)
C(21)-Fe(2)-Fe(1)
C(22)-Fe(2)-Fe(1)
C(11)-C(1)-C(21)
C(11)-C(1)-Fe(1)
C(21)-C(1)-Fe(1)
90.6(2) C(11)-C(1)-Fe(2)
90.4(2) C(21)-C(1)-Fe(2)
93.7(2) Fe(1)-C(1)-Fe(2)
87.3(2) Fe(2)-C(2)-Fe(1)
106.3(2) C(12)-C(11)-C(1)
47.3(2) C(16)-C(11)-C(1)
137.1(3)
73.5(2)
79.5(2)
82.2(2)
123.2(3)
116.8(3)
F igu r e 1. ORTEP drawing of [Fe2(cp)2(CO)(µ-CO){µ-C(η2-
Ph)Ph}] (6) showing the η2 coordination of one phenyl ring.
Thermal ellipsoids are drawn at 40% probability.
50.3(1) C(22)-C(21)-C(26) 118.7(5)
96.6(2) C(22)-C(21)-C(1)
104.5(2) C(26)-C(21)-C(1)
43.3(2) C(22)-C(21)-Fe(2)
82.1(2) C(26)-C(21)-Fe(2) 118.2(3)
73.2(2) C(1)-C(21)-Fe(2) 63.2(2)
36.2(2) C(21)-C(22)-C(23) 120.2(6)
50.5(2) C(21)-C(22)-Fe(2) 67.6(3)
50.1(1) C(23)-C(22)-Fe(2) 123.8(4)
80.9(1) C(24)-C(23)-C(22) 120.4(7)
87.7(2) C(23)-C(24)-C(25) 118.8(7)
117.3(4) C(26)-C(25)-C(24) 122.5(7)
119.0(3) C(25)-C(26)-C(21) 119.3(6)
120.1(3)
122.2(4)
116.3(4)
76.3(3)
Sch em e 5
Sch em e 6
ppm (13C). Furthermore, in the 13C NMR spectrum the
bridging ligand {C(SMe)C(O)CtCPh} gives rise to
resonances at 161.5 and 189.8 ppm, attributable to the
alkylidene and ketone carbons, respectively, and at 93.0
and 88.7 ppm due to the -CtC- moiety. In addition,
the resonance observed in the 1H NMR for the SMe
protons at 1.72 ppm is indicative of a direct SsFe
interaction.
Rea ction of 1 w ith 2-Th ien yllith iu m . Treatment
of 1 with Lith in thf at -70 °C rapidly forms a mixture
of the complexes [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)C(O)-
(2-th)}] (13; 19%) and [Fe2(cp)(C5H5-(2-th))(CO)2(µ-CO)-
(µ-CSMe)] (14; 40%) resulting from the 2-thienyl car-
banion addition at the carbonyl and cyclopentadienyl
ligands, respectively (Scheme 6). These complexes have
been separated by column chromatography and purified
by crystallization. The spectroscopic properties of 13
are similar to those of the analogous complex 12, and
its molecular structure has been determined by an X-ray
structural study (Figure 2). The IR spectrum of 14
exhibits a ν(CO) pattern consistent with two terminal
and one bridging cis-CO (1983, 1949, 1792 cm-1). A
single resonance for the cp group is observed in both
one hydrogen would migrate from the C5H5R ring to the
µ-carbyne carbon. Complex 14 does not exhibit any
hydrogen rearrangement upon standing in CH2Cl2 solu-
tion or by treatment with silica gel.
X-r a y Molecu la r Str u ctu r es of [F e2(cp )2(CO)(µ-
CO){µ-C(η2-P h )P h }] (6) a n d [F eF e(cp )2(CO)(µ-CO)-
{µ-C(SMe)C(O)(2-th )}] (13). The solid-state structure
of 6 is illustrated in Figure 1. It contains, as expected,
the Fe2(cp)2 unit with the cp ligands in a cis configura-
tion. The FesFe bond is bridged by a CO and a
diphenylcarbene ligand. A peculiarity of the molecule
is that one of the phenyl rings is η2-coordinated to Fe-
(2), taking the place of a terminal CO ligand. The
molecule is therefore asymmetric, and the crystal
contains the racemic mixture generated by the coordi-
nation of either face of the phenyl ring, depending on
which terminal CO ligand in the precursor 1 has been
eliminated.
1
the H and 13C NMR spectra. The presence of the η4-
C5H5-(2-th) moiety is confirmed by the 13C NMR spec-
trum that shows nine distinct signals due to the
diastereotopic ring carbons at 154.1, 123.6, 122.5, 121.4
(2-th) and 91.4, 87.6, 72.1, 69.2, 56.1 ppm (C5H5-(2-Th)).
As for type 2 complexes, the absence in the IR spectrum
of the C-Hexo band at about 2750 cm-1 suggests that
the nucleophilic attack at one cp ring has occurred at
the exo position.
In contrast with the results reported above on the
addition of Grignard reagents to 1, the reaction with
2-thienyllithium forms 14 but not the alkylidene com-
plex [Fe2(cp)(C5H4th)(CO)2(µ-CO)(µ-C(H)SMe)], in which
The iron-iron distance (2.525(2) Å) is in the range of
those found in this family of compounds, and the

1228 Organometallics, Vol. 16, No. 6, 1997
Bordoni et al.
bridging carbene atom (C(1)) exhibits strictly equivalent
µ-CsFe interactions (1.972, 1.976(5) Å), in spite of the
distortions introduced by the η2 coordination of one
phenyl group. The µ-CsC(phenyl) distances are sub-
stantially equivalent (C(1)sC(11), 1.505(5) Å; C(1)sC-
(21), 1.520(6) Å) and consistent with single bonds. The
phenyl carbons coordinated to Fe are asymmetrically
bonded (Fe(2)sC(21), 2.124(4) Å; Fe(2)sC(22), 2.232-
(6) Å), and the coordination generates some π-electron
localization, resulting in a cyclohexatriene type struc-
ture (mean CsC bond distances 1.35 and 1.46 Å). The
actual structure is the one that allows improved dona-
tion to the metal. In conclusion, the diphenylcarbene
ligand is η1-bonded to Fe(1) and η3-bonded to Fe(2);
however, the geometric evidence (C(1)sC(21) and
C(21)sC(22) separations 1.520(6) and 1.36(1) Å, respec-
tively) suggests a description of this nonclassical bond-
ing system as a vinylalkylidene group, i.e. the sum of
η2 and η1 bonds. Few examples of arylalkylidene
dinuclear complexes with η2 attachment of the aryl ring
to a metal are known: e.g. [Mo2(cp)2(CO)4{C(p-
MeC6H4)2}]17 and [PtW{µ-σ:η3-CH(C6H4Me-4)}(CO)2-
(PMe3)2(cp)][BF4].18 In these molecules, as opposed to
the case under discussion, the µ-CsC(ring)sC(ring)
distances exhibit substantially equal values and have
been described as allylic groups.
The nonequivalence of the iron atoms is pointed out
by a slight asymmetry of the bridging CO ligand (Fe-
(1)sC(2), 1.968(5) Å; Fe(2)sC(2), 1.872(6) Å), the shorter
distance being from the iron bearing the coordinated
phenyl. The same effect has been observed in related
molecules containing a coordinated CdC double bond,
i.e. [Fe2(cp)2(CO)(µ-CO){µ-η3(σ)-C(O)C2(CH3)[C(O)C6H5]}]
and [Fe2(cp)(cp*)(CO)(µ-CO){µ-η3(σ)-C(O)C2(CH3)[C(O)-
n-C4H9]}].19 The shortening effect can be explained by
different σ-π bonding contributions of CO and olefinic
ligands. The same kind of asymmetries for the bridging
F igu r e 2. ORTEP drawing of [FeFe(cp)2(CO)(µ-CO){µ-
C(SMe)C(O)(2-th)} (13). Thermal ellipsoids are drawn at
30% probability.
Ta ble 2. Selected Bon d Len gth s (Å) a n d
An gles (d eg) for
F eF e(cp )2(CO)(µ-CO){µ-C(SMe)C(O)(2-th )}] (13)
Fe(1)-Fe(2)
Fe(1)-C(1)
Fe(1)-C(2)
Fe(1)-S(1)
Fe(2)-C(1)
Fe(2)-C(2)
Fe(2)-C(9)
Fe(1)-C(cp)av
Fe(2)-C(cp)av
C(2)-O(2)
2.517(1)
1.904(4)
1.846(4)
2.246(1)
1.957(3)
2.046(4)
1.756(4)
2.096
C(1)-S(1)
S(1)-C(3)
C(1)-C(4)
C(4)-O(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(7)-C(8)
C(8)-S(2)
C(5)-S(2)
1.777(4)
1.813(5)
1.476(5)
1.234(4)
1.484(5)
1.503(5)
1.494(5)
1.317(7)
1.669(5)
1.702(4)
2.110
1.169(5)
1.144(5)
CO have been observed in molecules such as [FeFe(cp)2-
C(9)-O(9)
(CO)(µ-CO){µ-C(CHO)SEt}], [FeFe(cp)2(CO)(µ-CO){µ-
C(COOMe)SMe}],7 and 13 (see later), in which the S
atoms are coordinated in the place of a terminal CO
group. As the sulfur atom is a better donor than carbon
monoxide, the coincidence of shorter Fes(µ-CO) dis-
tances observed on the side of the coordinated sulfur or
phenyl groups is indicative of a more consistent π-back-
donation to the bridging carbonyl.
The molecular structure of 13 is illustrated in Figure
2. The stereogeometry is comparable, in a broad sense,
to that just described for 6. The Fe2(µ-CO)(cp)2 moieties
are strictly equivalent in the two species, and the
µ-alkylidene group, µ-C{C(O)(2-th)}(SMe), in spite of the
different substituents, exhibits coordination of the sulfur
atom to the iron atom, paralleling the η2 coordination
of the phenyl group in 6. As a consequence the same
kind of asymmetry is present in the two molecules and
the bridging CO ligand is distorted (Fe(1)sC(2), 1.846-
(4) Å; Fe(2)sC(2), 2.046(4) Å), in accord with what was
discussed above. The bridging carbene atom is slightly
asymmetric (Fe(1)sC(1), 1.904(4) Å; Fe(2)sC(1), 1.957-
(3) Å), and the same rationalization applies to it. In
fact in the bis(carbene) species [Fe2(cp)2{µ-C(CN)-
C(2)-Fe(1)-C(1)
C(2)-Fe(1)-S(1)
C(1)-Fe(1)-S(1)
S(1)-Fe(1)-Fe(2)
C(9)-Fe(2)-C(1)
C(9)-Fe(2)-C(2)
C(1)-Fe(2)-C(2)
C(9)-Fe(2)-Fe(1)
C(1)-Fe(2)-Fe(1)
C(2)-Fe(2)-Fe(1)
Fe(1)-C(1)-Fe(2)
Fe(1)-C(2)-Fe(2)
O(2)-C(2)-Fe(1)
O(2)-C(2)-Fe(2)
O(9)-C(9)-Fe(2)
97.4(2)
94.0(1)
49.9(1)
80.98(4)
94.2(2)
86.1(2)
89.4(2)
107.5(2)
48.4(1)
46.3(1)
81.4(1)
80.4(2)
149.0(4)
130.2(3)
176.2(4)
C(4)-C(1)-S(1)
C(4)-C(1)-Fe(1)
S(1)-C(1)-Fe(1)
C(4)-C(1)-Fe(2)
S(1)-C(1)-Fe(2)
C(1)-S(1)-C(3)
C(1)-S(1)-Fe(1)
C(3)-S(1)-Fe(1)
O(4)-C(4)-C(1)
O(4)-C(4)-C(5)
C(1)-C(4)-C(5)
C(4)-C(5)-C(6)
C(4)-C(5)-S(2)
C(6)-C(5)-S(2)
119.8(2)
136.0(2)
75.1(1)
121.1(2)
112.1(2)
105.3(2)
55.02(1)
108.7(2)
122.2(3)
118.8(3)
118.9(3)
127.1(3)
119.3(3)
113.7(3)
SMe}2],12 in which two iron-coordinated sulfur atoms
make the iron atoms equivalent, a slight asymmetry in
the opposite sense is present; i.e., the FesC interaction
spanned by the sulfur is longer (1.952(3) vs 1.929(3) Å).
The C(O)(C4H3S) substituent is characterized by the
two dihedral angles of the planar group C(4)sC(1)sO-
(4)sC(15) with the dimetallacyclopropane ring Fe-
(1)sFe(2)sC(1) (76.8°) and thienyl ring (8.8°). These
angles, together with the bond distances around C(4)
(17) Messerle, L.; Curtis, M. D. J . Am. Chem. Soc. 1980, 102, 7791.
(18) J effery, J . C.; Laurie, J . C. V.; Moore, I.; Razay, H.; Stone, F.
G. A. J . Chem. Soc., Dalton Trans. 1984, 1563.
(19) Wong, A.; Pawlick, R. V.; Thomas, C. G.; Leon, D. R.; Liu, L.-
K. Organometallics 1991, 10, 530.

Carbanion Addition to [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]+
Organometallics, Vol. 16, No. 6, 1997 1229
(C(4)sC(1), 1.476(5) Å; C(4)sC(5), 1.484(5) Å; C(4)sO(4),
1.234(5) Å), indicate that the pz orbital of C(4) is
primarily involved in the π bond to O(4) and little
π-electron delocalization involving C(1), C(4), and the
thienyl ring is evidenced. Other acyl substituents at
the µ-carbene atom are present in [Fe2(cp)2(CO)(µ-CO)-
(µ-CHCOPh)],20 [Fe2(cp)2(CO)(µ-CO){µ-η3(σ)-C(O)C2-
(CH3)[C(O)C6H5]}], [Fe2(cp)(cp*)(CO)(µ-CO){µ-η3(σ)-C(O)-
although no direct evidence has been found. It is worth
mentioning that the additional coordination of the C6H5
ring to the Fe atom contributes to the stability of the
complex because of the entropic gain determined by the
elimination of a CO molecule. Complex 10 may arise
from [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)Me}] (8) (Scheme
3). In this case, however, deprotonation of the hydrogen
on the carbon R to the µ-C atom and CsS bond cleavage
are required steps in order to explain the formation of
the vinylidene. The fact that the acidic R-hydrogen in
the bridging C(SMe)Me ligand plays a pivotal role in
promoting the µ-vinylidene formation is further sup-
ported by the observation that reaction of 1 with NaCH-
(CN)2 directly leads to the formation of the known cis-
and trans-vinylidene complexes [Fe2(cp)2(CO)2(µ-CO)-
{µ-CdC(CN)2}] (11) in yields higher than those obtained
by the published method.16 Although no alkylidene
intermediate of the type [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)-
CH(CN)2}] has been detected, it seems obvious that the
reaction proceeds via addition of [CH(CN)2]- at the
bridging carbon atom of 1.
The addition of RMgX, NaCCPh, and Lith occurs at
the cp or CO groups of 1. Despite the different product
distributions, a common feature of these reactions is the
intramolecular rearrangement which follows the attack.
In fact, as previously reported8 and shown in Scheme
1, hydrogen migration from the C5H5R ring to µ-C must
occur in order to explain the formation of complex 3.
This rearrangement is probably favored by the net
energy gain of the aromatization and subsequent η5
coordination of the C5H5R ring. However, other factors,
including steric crowding, may be responsible for the
transformation of 2 into 3, since in the case of [Fe2(cp)-
(C5H5-(2-th))(CO)2(µ-CO)(µ-CSMe)] (14) no detectable
amount of the rearranged product has been observed.
C2(CH3)[C(O)-n-C4H9]}],19 [FeFe(cp)2(CO)(µ-CO){µ-C(SEt)-
{C(O)H}}], and [FeFe(cp)2(CO)(µ-CO){µ-C(SMe){C(O)-
OMe}}],7 and their geometries have been found com-
parable to that of 13.
Discu ssion
The formation of CsC bonds at the diiron thiocarbyne
complex 1 has been carried out via selective addition
at all of its electrophilic sites, resulting in a number of
reaction pathways. These include ring addition (reac-
tions with RMgX, Scheme 1), CO addition (th and
phenylacetylide reagents), and nucleophilic attack at the
µ-carbyne carbon (reactions with organocopper and
NaHC(CN)2). In spite of the considerable efforts aimed
at determining the factors influencing regio- and ster-
eochemical control in the reactions of nucleophiles with
metal carbonyl complexes,21 the nature of the products
obtained from 1 and carbon nucleophiles remains largely
unpredictable. However, previous findings show that
the soft organocuprate reagents can be conveniently
utilized to form CsC bonds at the µ-alkylidyne carbon
of [Fe2(CO)2(cp)2(µ-CO)(µ-CR)]+.3d This observation sug-
gests that the alkylidyne is a softer site compared to
CO or cp. Further support for this idea comes from the
previously reported reactions of 1 with CN-, which give
selective cyanide addition at the µ-C atom. In view of
these facts, it seems plausible that under comparable
experimental conditions, Li2Cu(CN)R2 species selec-
tively attack the µ-carbyne carbon of 1, affording the
alkylidenes [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)R}] (R ) Ph,
4; R ) Me, 8) (Schemes 2 and 3). These complexes are
The alkylidene complexes [FeFe(cp)2(CO)(µ-CO){µ-
C(SMe)C(O)R}] (R ) CCPh, 12; R ) 2-Th, 13) are very
likely formed via nucleophilic attack at the terminal CO
followed by COR migration from the iron center to the
bridging carbyne carbon. This path resembles that
observed for the analogous complexes [FeFe(cp)2(CO)-
the precursors of [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)R}] (R
) Ph, 5; R ) Me, 9), generated via intramolecular CO
displacement by the S atom. The other products
observed, [Fe2(cp)2(CO)(µ-CO){µ-C(η2-Ph)Ph}] (6) and
[Fe2(cp)2(CO)(µ-CO)(µ-CCH2)] (10), are rather unex-
pected because their formation requires µ-CsSMe bond
breaking at some stage of the reaction paths. Desulfu-
rization and nucleophilic replacement of the SMe moiety
in [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)X}] (X) CN, H, Ph) is
usually achieved only by converting SMe into SMe2,
which is a better leaving group. However, since the
CsS cleavage has been observed in the reactions of 1
(µ-CO){µ-C(SMe)C(O)R}] (R ) H, OR) obtained by
treatment of 1 with HBEt3- or RO-. Indeed in the case
of the RO- addition, the alkoxycarbonyl intermediate
[Fe2(cp)2(CO)(COOR)(µ-CO)(µ-CSR)] has been isolated
and fully characterized.7 It should be noted that two
CsC bonds are generated in the reactions forming 12
and 13: the first arises from direct attack at the
coordinated CO and the second from CO µ-carbyne
coupling. The nucleophile induced carbonyl-carbyne
coupling, recognized as a possible key step in Fischer-
Tropsch chemistry, has been largely explored since the
discovery of Kreissl in 1976.22 Another example is the
carbonyl-thiocarbyne coupling reported by Angelici.23
This latter study is somewhat related to our systems,
although it involves mononuclear complexes. Notwith-
standing this, similar reactions have never been ob-
served in dinuclear systems. Therefore, 1 provides a
unique example of a complex which selectively ac-
5a
with NCO- 5c and NHR2 and proposed to occur via
nucleophilic addition at the bridging carbon atom, it is
feasible that complex 4 is the intermediate in the
formation of [Fe2(cp)2(CO)(µ-CO){µ-C(η2-Ph)Ph}] (6),
(20) Casey, P. C.; Crocker, M.; Vosejpka, P. C.; Rheingold,A. L.
Organometallics 1989, 8, 278.
(21) (a) Brown, D. A.; Burns, J . C.; Conlon, P. C.; Deignan, J . P.;
Fitzpatrick, N. J .; Glass, W. K.; O’Byrne, P. J . Organometallics 1996,
15, 3147. (b) Brougham, D. F.; Brown, D. A.; Fitzpatrick, N. J .; Glass,
W. K. Organometallics 1995, 14, 151. (c) Brown, D. A.; Fitzpatrick, N.
J .; Groarke, J . P.; Nobuaki, K.; Morokuma, K. Organometallics 1993,
12, 2521.
(22) Kreissl, F. R.; Schubert, U.; Lindner, T. L.; Huttner, G. Angew.
Chem., Int. Ed. Engl. 1976, 15, 632.
(23) Kim, H. P.; Kim, S.; J acobson, R. A.; Angelici, R. J . Organo-
metallics 1986, 5, 248.

1230 Organometallics, Vol. 16, No. 6, 1997
Bordoni et al.
yielded, by crystallization from CH2Cl2 layered with pentane
at -20 °C, [Fe2(cp)(C5H4-allyl)(CO)2(µ-CO){µ-C(SMe)H}] (3;
123 mg, 74%). Anal. Calcd for C18H18Fe2O3S: C, 55.74; H,
4.26. Found: C, 55.68; H, 4.33. IR (CH2Cl2): ν(CO) 1981 s,
complishes the one-step nucleophilically promoted trans-
formation of a coordinated CO into aldehyde, ester, or
ketone functional groups anchored at two metal centers:
1943 w, 1780 m cm-1
.
1H NMR (CDCl3): δH 11.38 (1 H, s,
µ-CH), 6.02 (m, 1 H, CHdCH2), 5.22-5.08 (m, 2 H; CHdCH2)
4.74 (s, 5 H, cp), 4.57, 4.36, 4.32 (m, 4 H, C5H4R), 3.24 (d, 2 H,
_CH2-, J H-H ) 6 Hz), 2.82 (s, 3 H, SMe).
Rea ction of 1 w ith Li2Cu (CN)P h 2 To Give 4-6. Phe-
nyllithium (1.0 mmol) was added to a stirred suspension of
CuCN (45 mg, 0.5 mmol) in thf (10 mL) at -78 °C. The
resulting Li2Cu(CN)Ph2 solution was warmed to -40 °C and
transferred by cannula into a solution of [Fe2(cp)2(CO)2(µ-
CO)(µ-CSMe)] CF3SO3 (1; 238 mg, 0.446 mmol) in thf (10 mL)
at -40°C. The mixture was warmed to room temperature,
stirred for an additional 30 min, and filtered on a Celite pad.
Evaporation of the solvent and crystallization from CH2Cl2
layered with pentane at -20 °C gave dark red crystals of [Fe2-
(cp)2(CO)2(µ-CO){µ-C(SMe)Ph}] (4; 87 mg, 42%), which were
collected from the solution. Anal. Calcd for C21H18Fe2O3S: C,
54.58; H, 3.93. Found: C, 55.01; H, 4.13. IR (CH2Cl2): ν(CO)
The intramolecular rearrangement AfB is driven by
a favorable enthalpic balance of the bonds formed (FesS
and µ-CsC(O)R) and cleaved (FesC(O)R). It should be
pointed out that the nucleophilic attack at the terminal
CO or cp ligands unbalances the electron counting on
the iron atoms. Therefore, the observed migration may
be due to the need to saturate the formal one-electron
vacancy on the Fe atom bearing the transformed cp or
CO ligands. The COsµ-C nucleophilically promoted
migratory coupling implies the same stereochemical
modification occurring in the 1fB conversion. The
1986 s, 1947 w, 1780 m cm-1
.
1H NMR (CDCl3): δH 7.51-
7.00 (m, 5 H, Ph), 4.99 (s, 10 H, cp), 2.01 (s, 3 H, SMe). 13C
NMR (CDCl3): δC 273.7 (µ-CO), 212.5 (CO), 193.7 (µ-C), 125.3,
126.6, 132.1, 164.7 (Ph), 91.6 (cp), 23.8 (SMe).
The mother liquor was evaporated under vacuum, giving a
dark red solid residue which was chromatographed on an
alumina column with a CH2Cl2-hexane mixture (1:2 v/v) as
eluent. A first red fraction was collected, evaporated to
dryness, and recrystallized from CH2Cl2 layered with pentane
at -20 °C, affording red crystals of [Fe2(cp)2(CO)(µ-CO){µ-C)-
(η2-Ph)Ph}] (6; 56 mg, 27%). Anal. Calcd for C25H20Fe2O2: C,
64.70; H, 4.34. Found: C, 64.66; H, 4.35. IR (CH2Cl2): ν(CO)
crystal structure of 13 shows that, as in [FeFe(cp)2(CO)-
1945 s, 1764 m cm-1 1H NMR (CDCl3): δH 8.45-6.70 (m, 9
.
(µ-CO){µ-C(SR)C(O)X}] (X ) OR, H),7 the migrated
C(O)th occupies a trans position with respect to the
remaining CO group, despite the mutual cis positions
of the carbonyl ligands in the precursor 1. The observed
stereochemistry is not easily explainable; however, it
may arise from the bridge-opening mechanism common
to all these diiron complexes.
H, Ph), 4.40 (s, 5 H, cp), 3.94 (s, 5 H, cp), 1.05 (m, 1 H, Ph).
13C NMR (CD2Cl2): δC 277.4 (µ-CO), 217.2 (CO), 184.3 (µ-C),
123.6, 125.4, 126.7, 128.4, 128.7, 129.2, 130.1, 130.4, 138.2,
158.9 (Ph), 84.4, 89.4 (cp). Finally, a second green fraction
was collected and evaporated under reduced pressure, giving
a solid residue of [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)Ph}] (5; 36
mg, 18%). Anal. Calcd for C20H18Fe2O2S: C, 55.34; H, 4.18.
Found: C, 55.34; H, 4.26. IR (CH2Cl2): ν(CO) 1942 s, 1759 m
cm-1
.
1H NMR (CDCl3): δH 8.0-7.2 (m, 5 H, Ph), 4.66 (s, 5
Exp er im en ta l Section
H, cp), 4.35 (s, 5 H, cp), 1.25 (s, 3 H, SMe). 13C NMR (CD2-
Cl2): δC 276.1 (µ-CO), 218.3 (CO), 184.3 (µ-C), 155.4, 129.9,
129.5, 128.2 (Ph), 87.1, 83.4 (cp), 26.2 (SMe).
Gen er a l P r oced u r es. All reactions were routinely carried
out under nitrogen by standard Schlenk techniques. Solvents
were distilled immediately before use under nitrogen from
appropriate drying agents. Glassware was oven-dried before
use. Instruments employed: IR, Perkin Elmer 983-G; NMR,
Varian Gemini 300. The 1H and 13C NMR spectra were
referenced to SiMe4. The compound [Fe2(cp)2(CO)2(µ-CO)(µ-
CSMe)]SO3CF3 was synthesized according to published meth-
ods.4 Li2Cu(CN)R2 species were prepared from CuCN and the
appropriate organolithium reagent according to the litera-
ture.24
Rea ction of 1 w ith (a llyl)MgCl To Give 2 a n d 3. Freshly
prepared (allyl)MgBr (0.45 mmol) in thf solution was added
to a stirred suspension of 1 (0.21 g, 0.39 mmol) in thf (15 mL)
cooled to 0 °C with an external ice bath. The mixture, which
rapidly turned brownish green, was stirred for about 90 min,
warmed to room temperature, and then filtered on an alumina
pad. The solution was evaporated under reduced pressure,
and the residue was chromatographed on an alumina column
with a CH2Cl2-hexane mixture (1:4, v/v) as eluent. A green
fraction was collected and evaporated to dryness, yielding [Fe2-
(cp)(C5H5-allyl)(CO)2(µ-CO)(µ-CSMe)] (2; 12 mg, 7%). IR
(CH2Cl2): ν(CO) 1981 s, 1942 w, 1785 m cm-1. Further elution
with CH2Cl2-hexane (1:1, v/v) gave a red fraction which
Rea ction of 1 w ith Li2Cu (CN)Me2 To Give 8-10.
A
solution of Li2Cu(CN)Me2 prepared from dry CuCN (45 mg,
0.5 mmol) and LiMe (1.0 mmol) in thf (10 mL) at -80 °C was
added to [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]CF3SO3 (1; 285 mg,
0.534 mmol) in thf (15 mL) at -40 °C. The mixture was
warmed to room temperature, stirred for an additional 30 min,
and filtered on an alumina pad. Evaporation of the solvent
gave a dark red solid residue which was chromatographed on
an alumina column with CH2Cl2-hexane (1:3 v/v) as eluent.
A first red fraction contained [Fe2(cp)2(CO)2(µ-CO)(µ-CdCH2)]
(10; 32 mg, 17%) that was identified by comparison of its
spectroscopic properties with those reported in the literature.14
Further elution with CH2Cl2-hexane (1:1 v/v) gave a second
red fraction, which was collected, evaporated to dryness, and
recrystallized from CH2Cl2 layered with pentane, affording red
crystals of [Fe2(cp)2(CO)2(µ-CO){µ-C(SMe)Me}] (8; 137 mg,
64%). Anal. Calcd for C16H16Fe2O3S: C, 48.04; H, 4.03.
Found: C, 47.99; H, 4.05. IR (CH2Cl2): ν(CO) 1981 s, 1942
m, 1780 m cm-1 1H NMR (CDCl3): δH 4.75 (s, 10 H, cp), 3.38
.
(s, 3 H, CH3), 2.73 (s, 3 H, CH3). Finally a third green fraction
gave, after crystallization, [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)Ph}
(9; 24 mg, 12%). IR (CH2Cl2): ν(CO) 1935 s, 1757 m cm-1
.
Syn th esis of [F e2(cp )2(CO)2(µ-CO){µ-C(P h )CN}] (7). To
a solution of 4 (209 mg, 0.45 mmol) in CH2Cl2 (10 mL) were
added CH3SO3CF3 (0.08 mL, 0.71 mmol) and, after 20 min of
(24) (a) Lipshutz, B. H. in Organometallics in Synthesis; Scholsser,
M., Ed.; Wiley: New York, 1994. (b) Lipshutz, B. H.; Wilhelm, R. S.;
Kozlowski, J . A. Tetrahedron 1984, 40, 5005.

Carbanion Addition to [Fe2(cp)2(CO)2(µ-CO)(µ-CSMe)]+
Organometallics, Vol. 16, No. 6, 1997 1231
Ta ble 3. Cr ysta llogr a p h ic Da ta for Com p lexes 6 a n d 13
6
13
chem formula
fw
C25H20Fe2O2
464.11
C19H16Fe2O3S2
468.14
temp, K
wavelength, Å
cryst syst
space group
a, Å
293(2)
293(2)
0.710 69
monoclinic
P21/n (No. 14)
9.203(6)
0.710 69
orthorhombic
Pbca (No. 61)
8.135(1)
b, Å
c, Å
17.253(7)
12.465(7)
93.61(5)
15.840(6)
28.710(9)
90
â, deg
V, Å3
1975(2)
3700(2)
Z
d
4
8
calcd, Mg/m3
1.561
1.487
1.681
1.810
abs coeff, mm-1
F(000)
952
1904
cryst dimens, mm
θ range, deg
0.32 × 0.38 × 0.050
0.075 × 0.175 × 0.20
2-25
2.5-30
scan type
ω
ω
no. of rflns collected
no. of unique obsd rflns (Fo > 4σ(Fo))
goodness of fit (GOF) on F2
R1(F),a wR2(F2)b
weighting scheme
7052 ((h, (k, (l)
5373 (+h,+k,+l)
3431
1.093
3043
1.023
0.0399, 0.1090
0.0444, 0.1209
a ) 0.0612, b ) 1.8022b
a ) 0.0807, b ) 2.4994b
R1 ) Σ||Fo| - |Fc|/Σ|Fo|. wR2 ) [Σw(Fo - Fc2)2/Σw(Fo2)2]1/2, where w ) 1/[σ2(Fo2) + (aP)2 + bP] and P ) (Fo + 2Fc2)/3.
a
b
2
2
stirring, NBu4CN (193 mg, 0.72 mmol). The mixture was
stirred for an additional 30 min; then the volatile material was
removed under vacuum. The residue was chromatographed
on an alumina column (3 × 8 cm), with a CH2Cl2-hexane
mixture (1:1, v/v) as eluent. A red fraction was collected and
evaporated to dryness, and the solid residue was recrystallized
from CH2Cl2 layered with pentane at -20 °C, giving red
crystals of 7 (121 mg, 61%). Anal. Calcd for C21H15Fe2NO3:
C, 57.19; H, 3.43. Found: C, 57.26; H, 3.44. IR (CH2Cl2): ν-
yielded [FeFe(cp)2(CO)(µ-CO){µ-C(C(O)CtCPh)(SMe)}] (12;
136 mg, 50%). Anal. Calcd for C23H18Fe2O3S: C, 56.82; H,
3.73. Found: C, 56.67; H, 3.74. IR (CH2Cl2): ν(CO) 1956 s,
1784 m, 1573 w; ν(CtC) 2187 w cm-1 1H NMR (CDCl3): δH
.
7.68-7.44 (m, 5 H, Ph), 4.79 (s, 5 H, cp), 4.75 (s, 5 H, cp), 1.72
(s, 3 H, SMe). 13C NMR (CD2Cl2): δC 267.9 (µ-CO), 217.1 (CO),
189.8 {C(O)CCPh}, 161.5 (µ-C), 133.1, 131.0, 129.6, 121.6 (Ph),
85.7, 84.2 (cp), 93.0, 88.7 (CtC), 28.0 (SMe).
Rea ction of [F e2(cp )2(CO)2(µ-CO)(µ-CSMe)]CF 3SO3 (1)
w ith 2-th ien yllith iu m To Give 13 a n d 14. To a stirred
solution of 1 (200 mg, 0.37 mmol) in thf (15 mL) at -70 °C
was added a slight excess of 2-thienyllithium (0.40 mL, 0.40
mmol of a 1.0 M solution in thf). The mixture, which rapidly
turned brownish green, was stirred for 10 min, warmed to
room temperature, and then filtered on an alumina pad. The
solution was evaporated under reduced pressure and the
residue chromatographed on an alumina column with a CH2-
Cl2-petroleum ether (40-70 °C) mixture (1:3, v/v) as eluent.
A first greenish yellow fraction was collected and evaporated
to dryness and the residue crystallized from CH2Cl2 layered
with pentane at -20 °C, yielding [Fe2(cp)(C5H5-(2-th))(CO)2-
(µ-CO)(µ-CSMe)] (14; 69 mg, 40%). Anal. Calcd for
(CO) 2003 s, 1966 w, 1803 m, ν(CN) 2150 w cm-1
.
1H NMR
(CDCl3): δH 7.53-7.21 (m, 5 H, Ph), 5.00 (s, 10 H, cp).
Rea ction of [F e2(cp )2(CO)2(µ-CO)(µ-CSMe)]CF 3SO3 (1)
w ith Na CH(CN)2 To Give 11. A thf solution (10 mL) of
NaCH(CN)2, obtained by reacting CH2(CN)2 (46 mg, 0.70
mmol) with equimolar amounts of NaH, was transferred by
cannula into a stirred solution of 1 (320 mg, 0.60 mmol) in thf
(15 mL) at 0 °C. The mixture was warmed to room temper-
ature and stirred for 60 min. The resulting greenish brown
solution was filtered on an alumina pad; then the solvent was
removed under vacuum. The residue, redissolved in CH2Cl2,
was chromatographed on an alumina column with a CH2Cl2-
hexane mixture (1:1, v/v) as eluent. A first red fraction
containing some [Fe2(cp)2(CO)4] was discharged. The second
red-violet fraction was collected and crystallized from a CH2-
Cl2-pentane mixture, affording trans-[Fe2(cp)2(CO)2(µ-CO){µ-
CdC(CN)2}] (trans-11; 68 mg, 28%). A third orange fraction
was finally collected with CH2Cl2 as eluent; crystallization
from CH2Cl2-Et2O gave cis-[Fe2(cp)2(CO)2(µ-CO){µ-CdC-
(CN)2}] (cis-11; 61 mg; 25%). Compounds trans-11 and cis-11
were identified by comparison of their spectroscopic properties
with those reported in the literature;16 moreover, 13C NMR
data were obtained. trans-11 δC (CD2Cl2): 336.5 (µ-C), 259.8
(µ-CO), 209.2 (CO), 116.2 (CN), 98.1 {C(CN)2}, 92.1 (cp). cis-
11 δC (CD2Cl2): 334.9 (µ-C), 260.0 (µ-CO), 208.7 (CO), 116.2
(CN), 98.0 {C(CN)2}, 90.1 (cp).
C
19H16Fe2O3S2: C, 48.75; H, 3.44; S, 13.70. Found: C, 48.95;
H, 3.39; S, 13.58. IR (CH2Cl2): ν(CO) 1983 s, 1949 m, 1792 m
cm-1 1H NMR (CDCl3): δH 7.02, 6.84, 6.63 (m, 3 H, th), 4.77
.
(s, 5 H, cp), 4.89, 4.73, 4.21, 3.91 (m, 5 H, (C5H5-(2-th)), 3.16
(s, 3 H, SMe). 13C NMR (CD2Cl2): δC 256.7 (µ-CO), 221.7, 213.1
(CO), 154.1, 123.6, 122.5, 121.4 (th), 91.4, 87.6, 72.1, 69.2, 56.1
((C5H5-(2-th)), 87.0 (cp), 34.0 (SMe).
A second green fraction was then collected, affording, after
crystallization from CH2Cl2 layered with pentane at -20 °C,
green crystals of [FeFe(cp)2(CO)(µ-CO){µ-C(SMe)C(O)(2-th)}]
(13) (33 mg, 19%). Anal. Calcd for C19H16Fe2O3S2: C, 48.75;
H, 3.44; S, 13.70. Found: C, 48.95; H, 3.39; S, 13.58. IR
(thf): ν(CO) 1944 s, 1789 m, 1601 m cm-1 1H NMR (CDCl3):
.
Rea ction of [F e2(cp )2(CO)2(µ-CO)(µ-CSMe)]CF 3SO3 (1)
w ith LiCtCP h To Give 12. To a stirred solution of 1 (300
mg; 0.56 mmol) in thf (20 mL) at -20 °C was added LiCtCPh
(0.60 mmol), freshly prepared from HCtCPh and LiBu in thf
solution. The mixture, which immediately turned brown, was
stirred for 10 min and warmed to room temperature. Evapo-
ration of the solvent under reduced pressure and chromatog-
raphy of the residue on an alumina column (8 × 3 cm) with a
CH2Cl2-hexane mixture (1:1, v/v) as eluent gave a brown
fraction, which was collected and evaporated to dryness.
Crystallization from CH2Cl2 layered with pentane at -20 °C
δH 8.11, 7.67, 7.19 (m, 3 H, th), 4.75 (s, 5 H, cp), 4.47 (s, 5 H,
cp), 1.44 (s, 3 H, SMe).
Cr ysta llogr a p h y. Crystal data and details of the data
collection for complexes 6 and 13 are given in Table 3. The
diffraction experiments were carried out at room temperature
on a fully automated Enraf-Nonius CAD-4 diffractometer using
graphite-monochromated Mo KR radiation. The unit cell
parameters were determined by a least-squares fitting proce-
dure using 25 reflections. Data were corrected for Lorentz and
polarization effects. No decay correction was necessary.

1232 Organometallics, Vol. 16, No. 6, 1997
Bordoni et al.
(a ) [F e2(cp )2(CO)(µ-CO){µ-C)(η2-P h )P h }] (6). An empiri-
cal absorption correction was applied by using the azimuthal
scan method.25 The positions of the metal atoms were found
by direct methods using the SHELXS 86 program26 and all
the non-hydrogen atoms located from difference Fourier
syntheses. The cyclopentadienyl rings and the uncoordinated
phenyl ring (C(11)-C(16)) were treated as rigid groups (CsC
) 1.42, 1.39 Å, respectively) and their hydrogen atoms were
included at calculated positions (CsH ) 0.96 Å). The hydro-
gen atoms of the η2-coordinated phenyl ring were located from
difference-Fourier maps and their positional parameters were
refined. The final refinement on F2 proceeded by full-matrix
least-squares calculations (SHELXL 93)27 using anisotropic
thermal parameters for all the non-hydrogen atoms. The
cyclopentadienyl and the phenyl H atoms were assigned an
isotropic thermal parameter 1.2 times the Ueq values of the
carbon atoms to which they were attached. In the final
difference Fourier synthesis, the electron density was found
Fourier maps. The cyclopentadienyl rings were treated as
rigid groups, and their hydrogen atoms were included in
calculated positions and treated using a riding model con-
straint with fixed isotropic displacement parameters as for 6.
The hydrogen atoms of the thienyl ring and the methyl
hydrogen atoms were located in the difference Fourier map,
but calculated positions were used. The final refinement on
F2 (SHELXL 93)27 proceeded by full-matrix least-squares
calculations, thermal motion being treated anisotropically for
all non-hydrogen atoms. The cyclopentadienyl, thienyl, and
methyl H atoms were assigned isotropic thermal parameters
1.2 times those of the attached atoms and were constrained
to ride on the attached atoms. The final difference-Fourier
map showed peaks in the range -0.63 to +0.88 e Å-3
.
Ack n ow led gm en t. Financial support from MURST
(Ministero dell’Universita` e Ricerca Scientifica), the
CNR (Consiglio Nazionale delle Ricerche), and the
University of Bologna (Projects “Sintesi, Modelli e
Caratterizzazione per Materiali Funzionali” and “Mole-
cole e Aggregati Molecolari Intelligenti”) is gratefully
acknowledged.
in the range -0.36 to +0.53 e Å-3
.
(b) [F eF e(cp )2(CO)(µ-CO){µ-C(SMe)C(O)(2-th )}] (13).
No absorption correction was applied. The structure was
solved by direct methods using the SHELX86 program,26 and
all the non-hydrogen atoms were located from difference
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
crystallographic data, positional and thermal parameters, and
bond lengths and angles for 6 and 13 (16 pages). Ordering
information is given on any current masthead page.
(25) North, A. C.; Philips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.
(26) Sheldrick, G. M. SHELXS 86, Program for Crystal Structure
Solution; University of Gottingen, Gottingen, Germany, 1986.
(27) Sheldrick, G. M. SHELXL 93, Program for Crystal Structure
Refinement; University of Gottingen, Gottingen, Germany, 1993.
OM9609168