(Carbonyl)iron-selenolates: New synthetic methods and reactions with electrophiles. Crystal structures of [(CO)6Fe2(μ-SeR)2]; R = Me3SiCH2 and p-O2NC6H4CH2, {(CO)6Fe2[μ-η2-Se,Se′-o-(SeCH2C6H4CH2Se)]}

Article abstract of DOI:10.1002/(SICI)1521-3749(199902)625:2<352::AID-ZAAC352>3.0.CO;2-E

The reactions of Fe(CO)₅ or Fe₃(CO)₁₂ with NaBEt₃H or KB[CH(CH₃)C₂H₅]₃H, respectively and treatment of the resulting carbonylates M₂Fe(CO)₄, M = Na, K with elemental selenium in appropriate ratios lead to the formation of M₂[Fe₂(CO)₆(μ-Se)₂]. Subsequent reactions with organo halides or the complex fragment cpFe(CO)₂⁺, cp = η⁵-C₅H₅ afforded the selenolato complexes [Fe₂(CO)₆(μ-SeR)₂], R = CH₂SiMe₃ (1), CH₂Ph (2), p-CH₂C₆H₄NO₂ (3), o-CH₂C₆H₄CH₂ (4) and cpFe(CO)₂⁺ (5) in moderate to good yields. A similar reaction employing Ru₃(CO)₁₂, Se and p-O₂NC₆H₄CH₂Br leads to the formation of the corresponding organic diselenide. The X-ray structures of 1, 3, 4 and 5 were determined and revealed butterfly structures of the Fe₂Se₂ cores. The substituents in 1, 3 and 5 adopt different conformations depending on their steric demand. In 4, the conformation is fixed because of the chelate effect of the ligand. The Fe-Se bond lengths lie in the range 235 to 240 pm, with corresponding Fe-Fe bond lengths of 254 to 256 pm. The ⁷⁷Se NMR data of the new complexes are discussed and compared with the corresponding data of related complexes.

Full text of DOI:10.1002/(SICI)1521-3749(199902)625:2<352::AID-ZAAC352>3.0.CO;2-E

(Carbonyl)Iron-Selenolates: New Synthetic Methods and Reactions
with Electrophiles.
Crystal Structures of [(CO)6Fe2(l-SeR)2]; R = Me3SiCH2
and p-O2NC6H4CH2, {(CO)6Fe2[l-g2-Se,Se'-o-(SeCH2C6H4CH2Se)]},
and [(CO)6Fe2(l-SeFe(CO)2cp)2]
Stefan JaÈger, Peter G. Jones, JoÈrg Laube, and Carsten ThoÈne*
Braunschweig, Institut fuÈr Anorganische und Analytische Chemie der Technischen UniversitaÈt
Received September 14th, 1998.
Dedicated to Professor Armand Blaschette on the Occasion of his 65th Birthday
Abstract. The reactions of Fe(CO)5 or Fe3(CO)12 with
NaBEt3H or KB[CH(CH3)C2H5]3H, respectively and treat-
ment of the resulting carbonylates M2Fe(CO)4, M = Na, K
with elemental selenium in appropriate ratios lead to the
structures of 1, 3, 4 and 5 were determined and revealed but-
terfly structures of the Fe2Se2 cores. The substituents in 1,
3 and 5 adopt different conformations depending on their
steric demand. In 4, the conformation is fixed because of the
chelate effect of the ligand. The Fe±Se bond lengths lie in
the range 235 to 240 pm, with corresponding Fe±Fe bond
lengths of 254 to 256 pm. The 77Se NMR data of the new
complexes are discussed and compared with the correspond-
ing data of related complexes.
formation of M2[Fe2(CO)6(l-Se)2]. Subsequent reactions
+
with organo halides or the complex fragment cpFe(CO)2
,
cp = g5-C5H5
afforded the selenolato
complexes
[Fe2(CO)6(l-SeR)2], R = CH2SiMe3 (1), CH2Ph (2), p-
+
CH2C6H4NO2 (3), o-CH2C6H4CH2 (4) and cpFe(CO)2 (5)
in moderate to good yields. A similar reaction employing
Ru3(CO)12, Se and p-O2NC6H4CH2Br leads to the forma-
tion of the corresponding organic diselenide. The X-ray
Keywords: Iron; ruthenium; selenolato complexes; crystal
structure; 77Se NMR
(Carbonyl)Eisen-Selenolate: Neue Synthesen und Reaktionen mit Elektrophilen.
Kristallstrukturen von [(CO)6Fe2(l-SeR)2]; R = Me3SiCH2 and p-O2NC6H4CH2,
{(CO)6Fe2[l-g2-Se,Se'-o-(SeCH2C6H4CH2Se)]} und [(CO)6Fe2(l-SeFe(CO)2cp)2]
InhaltsuÈbersicht. Die Reaktionen von Fe(CO)5 und
Fe3(CO)12 mit NaBEt3H oder KB[CH(CH3)C2H5]3H liefern
die Carbonylate M2Fe(CO)4, M = Na, K, die ihrerseits mit
elementarem Selen in geeigneten VerhaÈltnissen zu den Se-
lenolaten M2[Fe2(CO)6(l-Se)2] reagieren. Umsetzungen mit
organischen Halogeniden oder dem Komplexfragment
cpFe(CO)2+, cp = g5-C5H5 liefern die Selenolato-Komplexe
[Fe2(CO)6(l-SeR)2], R = CH2SiMe3 (1), CH2Ph (2), p-
Kristallstrukturen von 1, 3, 4 und 5 wurden bestimmt. Sie
zeigen alle eine Butterfly-Struktur am zentralen Fe2Se2
Ring. Die Substituenten in 1, 3 und 5 nehmen in AbhaÈn-
gigkeit ihres sterischen Anspruches unterschiedliche Konfor-
mationen ein. Aufgrund des Chelat-Effekts des Liganden ist
die Konformation in 4 fixiert. Die Fe±Se BindungslaÈngen
liegen im Bereich von 235 bis 240 pm mit entsprechenden
Fe±Fe BindungslaÈngen von 254 bis 256 pm. Die 77Se NMR
Spektren der neuen Komplexe werden diskutiert und mit
den entsprechenden Daten verwandter Komplexe vergli-
chen.
+
CH2C6H4NO2 (3), o-CH2C6H4CH2 (4) and cpFe(CO)2 (5)
in moderaten bis guten Ausbeuten. Eine aÈhnliche Reaktion,
ausgehend von Ru3(CO)12, Se und p-O2NC6H4CH2Br fuÈhrt
zur Bildung des entsprechenden organischen Diselenids. Die
Introduction
theses of chalcogenolato complexes are metatheses,
amine elimination processes and oxidative additions
of organic dichalcogenides to unsaturated metal frag-
The current interest in selenium- and tellurium-con-
taining complexes arises from their potential activity
in catalytic processes and their potential use as pre-
cursors for solid state materials [1]. Common syn-
ments, whereas chalcogenido complexes are accessible
2±
via reactions of soluble Zintl ions (e. g. Sen2±, Te4
)
with metal halides and carbonyls or by reacting sily-
lated chalcogenide reagents with appropriate metal
fragments.
(Carbonyl)iron chalkogenides of the type Fe2(CO)6(E2)
and Fe3(CO)9(E)2, E = S, Se, Te were first synthesized
* Dr. Carsten ThoÈne
Institut fuÈr Anorganische und Analytische Chemie
Hagenring 30
D-38106 Braunschweig
352
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0044±2313/99/625352±358 $ 17.50+.50/0
Z. anorg. allg. Chem. 1999, 625, 352±358

(Carbonyl)Iron Selenolates: New Synthetic Methods and Reactions with Electrophiles
by Hieber and Gruber in 1958 via redox reactions of
The new iron complexes are dark red air-stable
iron carbonylates with S5 or EO32±, respectively [2].
2±
crystalline materials. The molecular structures of the
disubstituted complexes [Fe2(CO)6(l-SeCH2SiMe3)2]
(1), [Fe2(CO)6(l-SeCH2Ph)2] (2) and [Fe2(CO)6(l-p-
SeCH2C6H4NO2)2] (3) in solution correspond to the
three possible geometrical isomers (Scheme 2).
Starting from the dinuclear complexes Fe2(CO)6(E2),
iron-selenolato complexes can be prepared by addi-
tion of alkynes or by reductive E±E bond cleavage
and subsequent reactions with electrophiles [3, 4].
Recently we have found that selenolato complexes
can be prepared alternatively via selenium insertion
into alkali-metal transition-metal bonds of carbony-
lates and subsequent reactions with organic electro-
philes [5]. This led to complexes of the type
[cpM(CO)3SeR], M = Mo, W and [Mn(CO)4SeR]2. In
the case of tungsten, the organometallic selenolate in-
termediates [cpW(CO)3Sen]±, n = 2, 3, 4 can be easily
oxidized to produce the corresponding selenido com-
plexes [6].
1
From the H and 77Se NMR data it can be seen
that in 1 the CH2SiMe3 groups are equivalent. This is
attributable to the geometrical isomers aa or ee.
Because of the bulky substituent, isomer ee is steri-
cally favoured and it is found also in the solid state
Here we report on the synthesis of dinuclear iron-
selenolato complexes of the type [Fe2(CO)6(l-SeR)2]
via insertion of selenium into the alkali metal-iron
bonds of the carbonylates M2Fe(CO)4, M = Na, K and
subsequent reactions with selected electrophiles. Ad-
2±
ditionally, a corresponding reaction of the Ru(CO)4
anion with selenium followed by treatment with p-
O2NC6H4CH2Br is described.
Results and Discussion
The highly nucleophilic tetracarbonylferrate dianion
[Fe(CO)4]2± readily reacts with elemental grey sele-
nium in a 1 : 2 ratio to produce the selenium-centred
dianion [(CO)6Fe2(l-Se)2]2± in good yield. Treatment
of the reaction solutions with the organic electrophiles
C6H5CH2Cl, Me3SiCH2Cl, p-O2NC6H4CH2Cl and o-
C6H4(CH2Cl)2 leads to the corresponding organosele-
nolato-iron(I) complexes, whereas cpFe(CO)2Cl pro-
duces the tetranuclear iron complex [Fe2(CO)6(l-
SeFe(CO)2cp)2]. The transformations can be per-
formed as one-pot syntheses starting from Fe(CO)5 or
Fe3(CO)12 (Scheme 1). From the stoichiometry of the
selenium addition, the formation of the alkali-metal
selenides M2Se2, M = Na, K seems probable. How-
ever, the addition of the organic electrophiles does
not produce the corresponding organic diselenides,
probably because of the higher nucleophilicity of
Scheme 1 The one-pot syntheses of [Fe2(CO)6(l-SeR)2]
starting from Fe(CO)5 and Fe3(CO)12
2±
[(CO)6Fe2(l-Se)2]2± compared with the Se2 anion.
[(CO)6Fe2(l-Se)2]2± was first synthesised by Seyferth
via reductive Se±Se bond cleavage of [(CO)6Fe2(l,g1-
Se2)] with LiBEt3H solutions in THF [4 a]. This trans-
formation proceeds in nearly quantitative yield, but
the synthesis of the starting complex requires more
complicated steps, namely the reaction of [Fe(CO)4]2±
2±
with Se5 under acidic conditions or the oxidation
2±
of [Fe(CO)4]2± with SeO3 under acidic conditions;
[(CO)9Fe3(l3-Se)2] is formed first and must be trans-
formed into the binuclear iron complex by reaction
with NaOMe [2].
Scheme 2 The three geometrical isomers of [Fe2(CO)6(l-
SeR)2]
Z. anorg. allg. Chem. 1999, 625, 352±358
353

St. JaÈger et al.
(vide infra). In 2 all three possible isomers can be de-
tected. The corresponding 77Se NMR spectrum shows
three singlets with comparable intensities indicating
three conformational energy minima with low transi-
tion barriers. The p-nitrobenzyl substituted deriva-
tive 3 adopts two configurations in solution, whereas
in the bridged complex [Fe2(CO)6(l-g2-Se,Se'-o-
SeCH2C6H4CH2Se)] (4) the only possible isomer is
aa. The tetranuclear complex 5 displays three singlets
complexes with Ru2Se2 cores additional stabilizing li-
gands (e. g. phosphines, Cp) are present. Carbonylates
and the corresponding selenocarbonylates are strong
reducing agents and a more facile synthesis of seleno-
lato ruthenium carbonyl complexes is the oxidative
addition of organic diselenides to Ru3(CO)12 (e. g.
[Ru2(CO)6(l-SePh)2] from Ph2Se2 and Ru3(CO)12)
[8]. In the case of tellurium, a reduction of the Ru±Ru
bond in [Cp*RuCl2]2 on reaction with Me3SiTeR was
observed, which led to the formation of a RTeTeR
unit on the two ruthenium centers [9].
1
for the cp-rings in the H and 13C NMR spectra indi-
cating the presence of all three possible geometrical
isomers in solution. However, in the solid state only
the isomer ae is observed (vide infra).
Crystal Structures of [Fe2(CO)6(l-SeCH2SiMe3)2] (1),
[Fe2(CO)6(l-p-SeCH2C6H4NO2)2] (3),
The observed 77Se NMR chemical shifts of the new
complexes lie in the range +29 to +310 ppm. These va-
lues are comparable with those in other [Fe2(CO)6(l-
[Fe2(CO)6(l-g2-Se,Se'-o-SeCH2C6H4CH2Se)] (4)
and [Fe2(CO)6(l-SeFe(CO)2cp)2] (5)
SeR)2] complexes and strongly depend on the electron
-
The molecular structure of 1 is presented in Fig. 1.
The central Fe2Se2 moietiy displays a butterfly geome-
try with a corresponding hinge angle of 95.19(3)°.
Both Me3SiCH2 groups are attached at the selenium
atoms in the equatorial position so that the overall
structure corresponds to the geometric isomer ee.
The same isomer was found in the crystal structure
of [Fe2(CO)6(l-SeMe)2] [4 b]. The Fe±Se bond lengths
(238.25(8) to 238.81(8) pm) are comparable with
those observed in [Fe2(CO)6(l-SeMe)2] (236.5(10)
ic influences of the organic groups at the selenium
atoms and their orientations. In 1 the CH2SiMe3 pos-
sesses a strong +I-effect and therefore the 77Se signal
(d = +90.4) is shifted to high field in comparison with
the other complexes. In the benzyl complexes 2 and 3
the signals appear in the range +220 to +310 ppm. The
chemical shift of the o-xylylselenolato complex 4 at
d = +221.3 suggests that the comparable value in 2
(d = +222.6) corresponds to the aa isomer, since the
electronic influences of benzyl and xylyl groups do
not differ greatly. Following this argument, the ob-
served values for the nitrobenzyl-substituted complex
3 should correspond to the isomers ae and ee. How-
ever, in the case of 2 and 3 the observed isomers only
occur in solution and their low transition barriers do
not permit separation via column chromatographic
methods. Similar to the benzyl complex 2, the tetra-
nuclear iron complex 5 displays three singlets in the
77Se NMR spectrum with a range from +29 ppm to
+306 ppm, probably due to completely different elec-
tronic influences of the cpFe(CO)2 group compared to
the above mentioned organic substituents. Several
reports concerning 77Se NMR shifts in organic substi-
tuted [Fe2(CO)6(l-Se)2] complexes have appeared in
the literature; typical values are +40 to +70 ppm for
alkyl derivatives (e. g. d = +45.5 in [Fe2(CO)6(l-
SeMe)2] [4 b], +67.6 in [Fe2(CO)6(l-SeCH2Se)] [3 i])
and +350 to +460 ppm for the corresponding alkyne
complexes (e. g. d = +369.3 and +458.8 in
[Fe2(CO)6Se2]2(l-s-trans-C4H2) [3 f]).
to
239.8(9) pm),
[Fe2(CO)6{l-SeC(Ph)=C(H)Se}]
(237.92(9) to 239.01(9) pm) and other related com-
plexes [3] and in the non-substituted complex
[Fe2(CO)6(l-Se2)] (235.4(2) to 237.8(2) pm) [10]. The
Fe±Fe bond length of 255.56(9) pm is attributable to a
single bond and falls into the observed range of 251 to
258 pm in related complexes [3, 4 b]. According to the
butterfly geometry, the selenium atoms are in rela-
tively close non-bonding contact (297.4(1) pm vs.
The reaction of Ru3(CO)12 with KB[CH(CH3)C2H5]3H
in THF according to the method of Gladysz affords a
fawn-coloured suspension of K2Ru(CO)4 which reacts
readily with elemental selenium to form a red-brown
solution that presumably contains K2[Ru2(CO)6(l-
Se2)] [7]. Treatment of this solution with p-
O2NC6H4CH2Br resulted in the formation of the or-
ganic diselenide [p-O2NC6H4CH2Se]2 in good yield
accompanied by Ru3(CO)12. A reductive elimination
process from a Ru2Se2 core seems likely, since in most
Fig. 1 Molecular structure of [Fe2(CO)6(l-SeCH2SiMe3)2]
(1) (50% probability ellipsoids,
H atoms omitted for
clarity) [a]
[a]
Selected bond lengths [pm] and angles [°]: Fe1±Fe2 255.56(9), Fe1±Se1
238.25(8), Fe1±Se2 238.59(8), Fe2±Se1 238.81(8), Fe2±Se2 238.44(8),
Se1 ´ ´ ´ Se2 297.4(1), Se1±C7 196.8(4), Se2±C11 197.0(4); Se1±Fe1±Se2
77.18(3), Fe1±Se1±Fe2 64.78(2), Se1±Fe2±Se2 77.11(3), Fe1±Se2±Fe2
64.79(3), Fe1±Se1±C7 111.01(13), Fe2±Se1±C7 111.80(12), Fe1±Se2±C11
110.30(12), Fe2±Se2±C11 113.82(12).
354
Z. anorg. allg. Chem. 1999, 625, 352±358

(Carbonyl)Iron Selenolates: New Synthetic Methods and Reactions with Electrophiles
229.3(2) pm in [Fe2(CO)6(l-Se2)]). Common features
of the Fe2Se2 cores in Se-substituted complexes are
small endocyclic bond angles at the selenium atoms
(ranging from 63 to 66°) with corresponding angles at
iron atoms ranging from 74 to 83°, depending on the
substituent at the selenium atom and the chelate ef-
fect of bidental ``bis-selenolateº-ligands. In 1, the en-
docyclic angles at the selenium atoms are 64.78(3)°
(Fe1±Se1±Fe2) and 64.79(3)° (Fe1±Se2±Fe2). The cor-
responding bond angles at the iron atoms, 77.11(3)°
(Se1±Fe2±Se2) and 77.18(3)° (Se1±Fe1±Se2), lie near
the middle of the above mentioned range. Almost the
same values were found in [Fe2(CO)6(l-SeMe)2]. In
complexes with a bridging C2 unit the endocyclic an-
gles at the iron atoms become larger (e. g. 82.26(3)° in
[Fe2(CO)6(l-SeCH2CH2Se)]), whereas a bridging CH2
group causes smaller angles at iron (e. g. 74.27(2)°,
74.43(3)° in [Fe2(CO)6(l-SeCH2Se)] without affecting
the angles at the selenium atoms [3 i]. All other bond
distances and angles are unexceptional.
bonding Se±Se distance of 309.3(1) pm. Again the en-
docyclic angles at selenium are not affected, with va-
lues in the usually observed range (Fe1±Se1±Fe2:
65.03(3)°, Fe1±Se2±Fe2: 65.57(3)°). The Fe±Fe and
Fe±Se bond lengths are closely similar to those deter-
mined in 1. All other bond metricals are as expected.
The molecular structure of the xylyl-bridged deriva-
tive 4 is shown in Fig. 3. Because of the chelating li-
gand, it corresponds to the geometrical isomer aa. Be-
cause of the less pronounced bite of a C4 unit, the
butterfly angle becomes larger (111.83(5)°). As a di-
rect consequence, the non-bonding Se±Se contact is
again longer (332.6(1) pm) and the endocyclic bond
angles at iron are strongly affected (Se1±Fe1±Se2:
88.89(5)°, Se1±Fe2±Se2: 88.61(4)°). All other bond
metricals are similar to those observed in 1 and 3.
The molecular structure of the tetranuclear com-
plex 5 is presented in Fig. 4. Crystal structures with
Se-bonded metal atoms at Fe2Se2 cores are rare and
apart from one example with a bridging PtPPh3 moi-
ety [11] and one with a l4-Ru(CO)3 unit [12] only
complexes with additional Fe-containing moieties
were examined.
The molecular structure of 3 is presented in Fig. 2.
The molecule corresponds to the geometric isomer ae.
Because of the different steric demand of the p-
O2NC6H4CH2 group, the hinge angle in 3 is some-
what larger (101.56(3)°) than in 1. This is in accord-
ance with the observed values for the endocyclic an-
gles at iron (Se1±Fe1±Se2: 81.27(3)° and Se1±Fe2±Se2:
81.59(3)°) and therefore a significantly longer non-
The hinge angle of the central Fe2Se2 butterfly is
99.00(3)°. The overall structure corresponds to the
geometrical isomer ae with the endocyclic angles at
the selenium atoms 65.53(3)° (Fe2±Se1±Fe1) and
64.44(3)° (Fe1±Se2±Fe2). The corresponding angles at
Fig. 2 Molecular structure of
[Fe2(CO)6(l-p-SeCH2C6H4NO2)2] ´ CH2Cl2 (3) in the crystal
(50% probability ellipsoids, H atoms and CH2Cl2 omitted
for clarity)[a]
Fig. 3 Molecular structure of [Fe2(CO)6(l-g2-Se,Se'-o-
SeCH2C6H4CH2Se)] (4) in the crystal (50% probability
ellipsoids, H atoms omitted for clarity) [a]
[a]
[a]
Selected bond lengths [pm] and angles [°]: Fe1±Fe2 255.84(9), Fe1±Se1
Selected bond lengths [pm] and angles [°]: Fe1±Fe2 254.8(2), Fe1±Se1
238.34(8), Fe1±Se2 236.64(8), Fe2±Se1 237.60(9), Fe2±Se2 235.84(8),
Se1 ´ ´ ´ Se2 309.3(1), Se1±C7 200.0(3), Se2±C14 199.0(4); Se1±Fe1±Se2
81.27(3), Fe1±Se1±Fe2 65.03(3), Se1±Fe2±Se2 81.59(3), Fe1±Se2±Fe2
65.57(3), Fe1±Se1±C7 111.97(11), Fe2±Se1±C7 109.53(11), Fe1±Se2±C14
113.11(11), Fe2±Se2±C14 112.86(11).
237.69(13), Fe1±Se2 237.34(14), Fe2±Se1 237.13(13), Fe2±Se2 239.11(14),
Se1 ´ ´ ´ Se2 332.6(1), Se1±C7 199.1(7), Se2±C14 200.9(6); Se1±Fe1±Se2
88.89(5), Fe1±Se1±Fe2 64.90(4), Se1±Fe2±Se2 88.61(4), Fe1±Se2±Fe2
64.65(4), Fe1±Se1±C7 114.7(2), Fe2±Se1±C7 109.7(2), Fe1±Se2±C14
113.4(2), Fe2±Se2±C14 116.6(2).
Z. anorg. allg. Chem. 1999, 625, 352±358
355

St. JaÈger et al.
dure of Gladysz. 0.6 g Se (7.6 mmol) was then added to the
resulting colourless suspension. CO evolution occurred and
the Se was consumed within 15 min, affording a deep red-
brown solution. After 1 h of stirring the organic electrophile
was added (Me3SiCH2Cl, p-O2NC6H4CH2Br: excess; o-
C6H4(CH2Br)2: 0.5 g, 1.9 mmol). The work-up procedure
after 18 h of stirring comprised the removal of THF in va-
cuo, addition of CH2Cl2 to the remaining residue, removal of
the potassium halogenide via filtration over Celite and col-
umn chromatography (20 × 4 cm) on silica. The separated
products were recrystallised from ethanol [1 and 2], toluene/
hexanes (3) or hexanes (4) at ±60 °C.
Route B: The same as route A employing 0.5 g Fe3(CO)12
(1 mmol) in 30 ml THF, 6 ml NaBEt3H (6 mmol) and 0.47 g
Se (6 mmol).
Bis(l-trimethylsilylmethylselenolato)-(hexacarbonyl)di-iron(I)
1: Chromatography using hexanes as eluent afforded one
red band of 1. Route A: 0.5 g (41%, based on Fe(CO)5);
Route B: 0.48 g (52%, based on Fe3(CO)12). M. p. 41 °C, red
crystals.
Fig. 4 Molecular structure of [Fe2(CO)6(l-SeFecp(CO)2)2]
(5) in the crystal (20% probability ellipsoids, H atoms
omitted for clarity) [a]
1H NMR (CDCl3): d = 0.15 ppm (s, 18 H, CH3), 1.78 (s, 4 H, CH2). ±
13C NMR (CDCl3): d = ±1.5 ppm (s, CH3), 14.2 (s, CH2), 209.9, 210.7 (s,
CO). ± 77Se NMR (CDCl3): d = 90.4 ppm (s). ± IR (CH2Cl2): m = 2061,
[a]
Selected bond lengths [pm] and angles [°]: Fe1±Fe2 256.26(10),
Fe1±Se1 237.09(9), Fe1±Se2 239.89(9), Fe2±Se1 236.42(8), Fe2±Se2
240.74(9), Se1 ´ ´ ´ Se2 305.99(7), Se1±Fe3 240.56(9), Se2±Fe4 244.01(8);
Se1±Fe1±Se2 79.81(3), Fe1±Se1±Fe2 65.53(3), Se1±Fe2±Se2 79.77(3),
Fe1±Se2±Fe2 64.44(3), Fe1±Se1±Fe3 126.05(3), Fe2±Se1±Fe3 122.10(3),
Fe1±Se2±Fe4 117.18(3), Fe2±Se2±Fe4 122.15(3).
2026, 1983 (CO).
±
MS (70 eV); m/z (%): 614(30) [M+], 530(53)
[M+±3 CO], 446(100) [M+±6 CO].
C14H22Fe2O6Se2Si2 (612.1): C 27.46 (calc. 27.47); H 3.62
(3.62)%.
the iron atoms are 79.81(3)° (Se1±Fe1±Se2) and
79.77(3)° (Se1±Fe2±Se2), respectively. The Fe±Se
bond lengths differ slightly and lie in the range
236.42(8) pm (Se1±Fe2) to 244.01(8) pm (Se2±Fe4).
Comparable values were found in [(CO)6Fe2Se2(l-
Fe,Fe'-Fe2Se2)Se2Fe2(CO)6]2± [13 a, b] and [(CO)9Fe3(l3-
Se)2] [14]. The observed Fe±Fe bond length of
256.26(10) pm lies in the above mentioned range of
Fe±Fe single bonds in related complexes. All other
bond distances and angles are similar to those ob-
served in 1, 3 and 4.
Bis(l-benzylselenolato)-(hexacarbonyl)di-iron(I) 2: Route A:
Chromatography using hexanes as eluent afforded four
bands with traces of orange by-products. The fifth red band
contained 0.525 g (44%, based on Fe(CO)5) of 2. Route B:
A mixture of toluene/hexanes 1 : 9 as eluent afforded a violet
and an orange band with traces of by-products. The third red
band contained 0.432 g (46%, based on Fe3(CO)12) of 2.
M. p. 85 °C (dec.), red crystals.
1H NMR ([D6] acetone): d = 3.59, 4.01, 4.03 ppm (s, R 4 H, CH2), 7.30 (m,
10 H, Ph). ± 13C NMR (CDCl3): d = 27.6 ppm (s, CH2), 32.8 (s, CH2),
126.7, 127.8, 128.5, 128.8, 129.0 (s, o-, m- und p-C6H5), 139.1, 139.2 (s,
ipso-C, C6H5), 210.4 (s, CO). ± 77Se NMR (CDCl3): d = +222.6 ppm (s),
+273.0 (s), +295.5 (s). ± IR (CH2Cl2): m = 2062, 2029, 1987 (CO). ± MS
(70 eV); m/z (%): 622(14) [M+], 538(25) [M+±3 CO], 454(72) [M+±6 CO].
Experimental Section
C20H14Fe2O6Se2 (619.9): C 38.64 (calc. 38.75), H 2.44 (2.28)%.
All manipulations were carried out under a dry nitrogen at-
mosphere using conventional Schlenk techniques. ± NMR:
Bruker AC 200 (1H 200 Mhz, 13C 50.3 Mhz, 77Se 38.2 Mhz).
The spectra were recorded using CDCl3 or [D6]acetone as
Bis(l-p-nitrobenzylselenolato)-(hexacarbonyl)di-iron(I) ´
1/2 toluene 3: The nitrobenzyl complex was prepared follow-
ing route A. The chromatographic work-up using toluene/
hexanes 7 : 3 as eluent afforded four red-brown bands with
traces of by-products. The fifth red band contained 0.684 g
(47%, based on Fe(CO)5) of 3. M. p. 117 °C, red crystals.
1
solvents. Standards: H, 13C TMS internal; 77Se Me2Se exter-
nal. ± IR: Biorad FTS 165. ± MS: Finnigan MAT 8430. Tetra-
hydrofuran (THF) was dried over sodium in nitrogen atmo-
sphere and distilled prior to use. KB[CH(CH3)C2H5]3H,
NaBEt3H, KBEt3H (1 m solutions in THF), grey Se and
Fe(CO)5 were purchased from Aldrich and used as received.
Fe3(CO)12, Ru3(CO)12 and cpFe(CO)2Cl were prepared
according to literature methods [15, 16, 17].
1H NMR ([D6 acetone]: d = 2.31 ppm (s, CH3, toluene) 3.73 (s, 2 H, CH2),
4.16 (s, 2 H, CH2), 7.19 (m, C6H5, toluene), 7.47 (d, 3J = 8.7 Hz, 2 H, 3,5-
O2NC6H4), 7.81 (d, 3J = 8.8 Hz, 2 H, 3,5-O2NC6H4), 8.15 (d, 3J = 8.7 Hz,
2 H, 2,6-O2NC6H4), 8.31 (d, 3J = 8.8 Hz, 2 H, 2,6-O2NC6H4). ± 13C NMR
(CDCl3): d = 16.6, 31.9 ppm (s, CH2), 21.5 (s, CH3, toluene), 124.3, 124.6,
128.3, 129.1, 129.4, 130.0 (s, o-, m- und p-O2NC6H4), 146.3, 146.5 (s, ipso-
O2NC6H4), 208.8 (s, CO). ± 77Se NMR (CDCl3): d = +274.8 ppm (s),
+309.5 (s). ± IR (CH2Cl2): 2066, 2035, 1995 (CO). ± MS (70 eV); m/z (%):
712(9) [M+], 628(18) [M+±3 CO], 544(21) [M+±6 CO].
General synthesis procedure
Route A: 0.5 ml Fe(CO)5 (3.8 mmol) in 30 ml THF was
transformed into a solution of K2Fe(CO)4 using 7.6 ml
KB[CH(CH3)C2H5]3H (7.6 mmol) according to the proce-
C20H12Fe2N2O10Se2 ´ 1/2 C6H5CH3 (756.00): C 37.46 (calc.
37.33), H 2.28 (2.13), N 3.65 (3.71)%.
356
Z. anorg. allg. Chem. 1999, 625, 352±358

(Carbonyl)Iron Selenolates: New Synthetic Methods and Reactions with Electrophiles
l-(o-Xylylselenolato)-(hexacarbonyl)di-iron (I) 4: The work-
up procedure via route A with toluene/hexanes 1 : 4 as eluent
afforded an orange band with a trace of Fe(CO)5. The second
red band contained 0.348 g of 4 (34%, based on Fe(CO)5).
Route B led to only one red mobile fraction using the same
eluent. It contained 0.12 g (15%, based on Fe3(CO)12) of 4.
M. p. 165 °C, red crystals.
C20H10Fe4O10Se2 (791.6): C 30.08 (calc. 30.35); H 1.24
(1.27)%.
[p-O2NC6H4CH2Se]2 from
K2Ru(CO)4 /2 Se/p-O2NC6H4CH2CH2Br: 0.5 g Ru3(CO)12
(0.79 mmol) were dissolved in 30 ml THF. 4.7 ml
KB[CH(CH3)C2H5]3H solution (4.7 mmol) were added via a
syringe and the mixture was refluxed for 4 hrs, during which
the orange solution was transformed into a fawn-coloured
suspension. After cooling to room temperature, 0.37 g Se
(4.7 mmol) was added with stirring. After 15 min the sele-
nium had been consumed and the colour turned to red-
brown. Addition of 1.3 g p-O2NC6H4CH2Br (6 mmol) and
stirring for additional 15 hrs afforded a deep-red solution,
which then was evaporated to dryness. KBr was removed
via addition of 20 ml CH2Cl2 and filtration over Celite. A
chromatographic work-up procedure on silica (40 × 3 cm;
CH2Cl2/acetone 2 : 3) afforded a colourless band with traces
of p-O2NC6H4CH2Br, a yellow-orange band with traces of
an unknown by-product and as the third orange band [p-
O2NC6H4CH2Se]2 as the main product of the reaction, as
spectroscopically characterised by comparison with an
authentic sample [18]. Yield: 0.695 g (1.61 mmol, 69%). The
fourth orange band contained Ru3(CO)12 as sole detectable
material.
1H NMR (CDCl3): d = 3.52 ppm (d, 2J = 11.7 Hz, CH2, HA), 3.86 (d,
2J = 11.7 Hz, CH2, HB), 7.04 (m, 4 H, C6H4). ± 13C NMR (CDCl3):
d = 25.3 ppm (s, CH2), 128.0, 129.4 (s, C6H4), 139.1 (s, ipso-C, C6H4),
207.4, 207.9 (s, CO). ± 77Se NMR (CDCl3): d = +221.3 ppm (s). ± IR
(CH2Cl2): m = 2066, 2032, 1991 (CO). ± MS (70 eV); m/z (%): 544(25)
[M+], 460(22) [M+±3 CO], 376(100) [M+±6 CO].
C14H8Fe2O6Se2 (541.8): C 31.23 (calc. 31.03), H 1.50
(1.49)%.
Synthesis of [Fe2(CO)6(l-SeFecp(CO)2)2] 5: The solution
of K2Se2Fe2(CO)6 in THF was prepared according to
route A employing 0.5 ml Fe(CO)5 (3.8 mmol), 7.6 ml
KB[CH(CH3)C2H5]3H (7.6 mmol) and 0.6 g Se (7.6 mmol).
1.58 g cpFe(CO)2Cl (7.6 mmol) was added with strirring in
one portion. After 1 h stirring at ambient temperature, the
solvent was removed in vacuo. The work-up procedure was
the same as described above using CH2Cl2/hexanes as elu-
ent. After one yellow and one orange band with traces of
by-products, the third red-brown band contained 0.97 g
(64%, based on Fe(CO)5) of 5. M. p. 102 °C (dec.), red-
brown crystals.
Crystal Structure Determinations [19]: Suitable crystals were
obtained from EtOH at ±60 °C (1), by layering a CH2Cl2 so-
lution with hexanes (ambient temperature) (3), from hex-
anes at ±60 °C (4) or by cooling a saturated CH2Cl2/hexanes
solution at ±18 °C (5). They were mounted on glass fibers in
inert oil and transferred to the cold gas stream of the dif-
fractometer (1, 4, 5 Siemens P4 at ±100 °C, 3 Stoe STADI4
1H NMR ([D6]acetone): d = 5.20, 5.28, 5.35 ppm (s, R 10 H, cp). ± 13C
NMR ([D6]acetone): d = 87.35 ppm (s, cp), 87.55 (s, cp), 87.59 (s, cp),
213.08, 214.17, 214.47, 216.62 (s, CO).
±
77Se NMR (CDCl3):
d = +29.9 ppm (s), +258.7 (s), +305.3 (s). ± IR (CH2Cl2): m = 2053, 2024,
2016, 2008, 1989, 1964 (CO).
Table 1 Crystallographic data for 1, 3, 4 and 5
3
4
5
Compound
1
Empirical formula
Formula weight/g mol±1
Crystal system
Space group (No.)
a/pm
b/pm
c/pm
α/°
b/°
C14H22Fe2O6Se2Si2
612.12
monoclinic
P21/c (14)
1261.3(2)
C20H12Fe2O10N2Se2 ´ CH2Cl2
C14H8Fe2O6Se2
541.82
triclinic
P(±1) (2)
769.1(2)
992.0(3)
1251.2(3)
71.52(2)
72.54(2)
70.89(2)
834.7(4)
2.16
C20H10Fe4O10Se2
791.6
794.86
triclinic
P(±1) (2)
934.2(2)
935.6(2)
1570.0(3)
87.00(2)
82.81(2)
89.11(2)
1359.6(5)
1.94
monoclinic
C2/c (15)
1944.6(3)
1841.1(3)
1591.8(2)
1598.8(2)
1295.0(2)
114.457(10)
116.605(12)
c/°
V/pm3 × 10±6
qcalc./g cm±3
Z
2377.3(6)
1.71
4
5095.6(13)
2.06
8
2
2
F (000)/e
1208
44.07
776
39.97
520
61.25
3056
51.4
l/cm±1
Crystal Size/mm
2 hmax/°
0.4 × 0.32 × 0.32
50
0.6 × 0.2 × 0.1
50
0.32 × 0.2 × 0.04
50
0.36 × 0.24 × 0.18
50
T/°C
±100
±130
±100
±100
Measured reflections
Unique reflections
Rint
No. of parameters
No. of restraints
4866
4175
0.0311
241
42
4877
4781
0.0103
353
0
2951
2905
0.0299
217
0
7004
4444
0.0348
325
0
T
min/Tmax
0.67/0.79
0.0349
0.052
0.0143, 0
0.79
0.67/1.00
0.0306
0.0689
0.0266, 1.0656
1.06
0.58/0.98
0.0391
0.0793
0.0323, 0
0.83
0.69/0.93
0.0323
0.0449
0.0102, 0
0.78
R(F), F > 4r(F)
Rw(F2), all refl.
Weighting parameters (a, b)
S
max. D/r
< 0.001
0.47/±0.44
< 0.001
0.47/±0.48
< 0.001
0.89/±0.68
< 0.001
0.42/±0.41
qfin (max/min) (e pm±3) × 106
Z. anorg. allg. Chem. 1999, 625, 352±358
357

St. JaÈger et al.
at ±130 °C) equipped with an LT-2 low-temperature attach-
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Ê
mator) was used to collect the intensity data in the x-scan
(1, 4, 5) or in the x/h-scan mode (3). Cell constants were
refined from setting angles of 62 reflections in the 2h range
8±23° (1, 4, 5) or from ± x values of 52 reflections in the 2h
range 20±23° (3). Absorption corrections based on w-scans
were applied. The crystallographic program system used was
SHELXL-93 [20]. All structures were solved by direct meth-
ods and refined by full-matrix least-squares procedures on
F2. All non-H atoms were refined anisotropically; hydrogen
atoms were included using a riding model or as rigid
methyls. The final difference Fourier maps were featureless.
Additional crystallographic data are presented in Table 1.
Selected bond lengths and angles are listed in the Figure
captions.
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J. A. Cabeza,
D. Miguel,
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M. A. Villa, S. Garcia-Granda, J. Chem. Soc., Dalton
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Acknowledgements. This work was supported by the Fonds
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