Ferrous carbonyl dithiolates as precursors to FeFe, FeCo, and FeMn carbonyl dithiolates

Article abstract of DOI:10.1021/om400752a

Reported are complexes of the formula Fe(dithiolate)(CO) ₂(diphos) and their use to prepare homo- and heterobimetallic dithiolato derivatives. The starting iron dithiolates were prepared by a one-pot reaction of FeCl₂ and CO with chelating diphosphines and dithiolates, where dithiolate = S₂(CH₂)₂ ^2- (edt^2-), S₂(CH₂)₃ ^2- (pdt^2-), S₂(CH₂) ₂(C(CH₃)₂)^2- (Me₂pdt ^2-) and diphos = cis-C₂H₂(PPh₂) ₂ (dppv), C₂H₄(PPh₂)₂ (dppe), C₆H₄(PPh₂)₂ (dppbz), C ₂H₄[P(C₆H₁₁)₂] ₂ (dcpe). The incorporation of ⁵⁷Fe into such building block complexes commenced with the conversion of ⁵⁷Fe into ⁵⁷Fe₂I₄(ⁱPrOH)₄, which then was treated with K₂pdt, CO, and dppe to give ⁵⁷Fe(pdt)(CO)₂(dppe). NMR and IR analyses show that these complexes exist as mixtures of all-cis and trans-CO isomers, edt^2- favoring the former and pdt^2- the latter. Treatment of Fe(dithiolate)(CO)₂(diphos) with the Fe(0) reagent (benzylideneacetone)Fe(CO)₃ gave Fe₂(dithiolate)(CO) ₄(diphos), thereby defining a route from simple ferrous salts to models for hydrogenase active sites. Extending the building block route to heterobimetallic complexes, treatment of Fe(pdt)(CO)₂(dppe) with [(acenaphthene)Mn(CO)₃]⁺ gave [(CO)₃Mn(pdt) Fe(CO)₂(dppe)]⁺ ([3d(CO)]⁺). Reduction of [3d(CO)]⁺ with BH₄^- gave the C _s-symmetric μ-hydride (CO)₃Mn(pdt)(H)Fe(CO)(dppe) (H3d). Complex H3d is reversibly protonated by strong acids, the proposed site of protonation being sulfur. Treatment of Fe(dithiolate)(CO)₂(diphos) with CpCoI₂(CO) followed by reduction by Cp₂Co affords CpCo(dithiolate)Fe(CO)(diphos) (4), which can also be prepared from Fe(dithiolate)(CO)₂(diphos) and CpCo(CO)₂. Like the electronically related (CO)₃Fe(pdt)Fe(CO)(diphos), these complexes undergo protonation to afford the μ-hydrido complexes [CpCo(dithiolate) HFe(CO)(diphos)]⁺. Low-temperature NMR studies indicate that Co is the kinetic site of protonation.

Full text of DOI:10.1021/om400752a

Article
pubs.acs.org/Organometallics
Ferrous Carbonyl Dithiolates as Precursors to FeFe, FeCo, and FeMn
Carbonyl Dithiolates
Maria E. Carroll, Jinzhu Chen, Danielle E. Gray, James C. Lansing, Thomas B. Rauchfuss,* David Schilter,
Phillip I. Volkers, and Scott R. Wilson
Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
S
* Supporting Information
ABSTRACT: Reported are complexes of the formula Fe(dithiolate)-
(CO)2(diphos) and their use to prepare homo- and heterobimetallic dithiolato
derivatives. The starting iron dithiolates were prepared by a one-pot reaction of
FeCl2 and CO with chelating diphosphines and dithiolates, where dithiolate =
2−
2−
S2(CH2)2 (edt2−), S2(CH2)3 (pdt2−), S2(CH2)2(C(CH3)2)2− (Me2pdt2−)
and diphos = cis-C2H2(PPh2)2 (dppv), C2H4(PPh2)2 (dppe), C6H4(PPh2)2
(dppbz), C2H4[P(C6H11)2]2 (dcpe). The incorporation of 57Fe into such
building block complexes commenced with the conversion of 57Fe into
57Fe2I4(iPrOH)4, which then was treated with K2pdt, CO, and dppe to give
57Fe(pdt)(CO)2(dppe). NMR and IR analyses show that these complexes exist
as mixtures of all-cis and trans-CO isomers, edt2− favoring the former and pdt2− the latter. Treatment of Fe(dithiolate)-
(CO)2(diphos) with the Fe(0) reagent (benzylideneacetone)Fe(CO)3 gave Fe2(dithiolate)(CO)4(diphos), thereby defining a
route from simple ferrous salts to models for hydrogenase active sites. Extending the building block route to heterobimetallic
complexes, treatment of Fe(pdt)(CO)2(dppe) with [(acenaphthene)Mn(CO)3]+ gave [(CO)3Mn(pdt)Fe(CO)2(dppe)]+
−
([3d(CO)]+). Reduction of [3d(CO)]+ with BH4 gave the Cs-symmetric μ-hydride (CO)3Mn(pdt)(H)Fe(CO)(dppe)
(H3d). Complex H3d is reversibly protonated by strong acids, the proposed site of protonation being sulfur. Treatment of
Fe(dithiolate)(CO)2(diphos) with CpCoI2(CO) followed by reduction by Cp2Co affords CpCo(dithiolate)Fe(CO)(diphos)
(4), which can also be prepared from Fe(dithiolate)(CO)2(diphos) and CpCo(CO)2. Like the electronically related
(CO)3Fe(pdt)Fe(CO)(diphos), these complexes undergo protonation to afford the μ-hydrido complexes [CpCo(dithiolate)-
HFe(CO)(diphos)]+. Low-temperature NMR studies indicate that Co is the kinetic site of protonation.
4,8,11
Scheme 1. Illustrative Routes to Fe2(SR)2(CO)6
INTRODUCTION
■
Compounds of the type Fe2(SR)2(CO)6−xLx are topical
because of their relationship to the active sites of the [FeFe]-
hydrogenases (H2ases).1 The quest for a deeper understanding
of the enzyme mechanism, as well as interest in base metal H2-
processing catalysts,2 has led chemists to prepare many
examples of these dithiolates.3 Since the [NiFe]-H2ases feature
related Ni(SR)2Fe(CO)L2 centers, a new methodology
addresses both families of enzymes. This paper describes a
new route to models of these two families of enzyme active
sites.
Promising precursors to dimetallic dithiolato complexes are
monoiron complexes of the type Fe(dithiolate)(CO)2(PR3)2.
These compounds should be obtainable from complexes of the
form FeX2(CO)2(PR3)2,12−14 which in turn are accessed by
mild carbonylation of ferrous halides in the presence of
phosphine ligands. Ferrous bis(thiolato) complexes appear
especially amenable to carbonylation15,16 (eq 1). Routes to
ferrous dithiolato carbonyls have been established in the case of
Fe(edt)(CO)2(PMe3)2 (edt2− = ethanedithiolate)17 and related
complexes containing bidentate phosphine ligands (Scheme
2).18 The benzenedithiolates Fe(S2C6H2X2)(CO)2(PMe3)2 (X
= H, Cl) are formed from diiron dithiolato precursors,19 which
undergo cleavage upon treatment with PMe3. With regard to
structure, complexes of the type FeX2(CO)2(chel) exist in
Traditionally, compounds of the type Fe2(SR)2(CO)6−xLx
are prepared by ligand (L) substitution of hexacarbonyls
Fe2(SR)2(CO)6,4 which in turn are obtained by treating
5
Fe3(CO)12 with thiols. Complementarily, Fe2(S2)(CO)6 is an
ideal precursor to diiron complexes6 of more elaborate
organosulfur ligands.7 Diiron dithiolato carbonyls can also be
prepared from more oxidized iron sources, as exemplified by
the reductive carbonylation of ferrous halides in the presence of
dithiolates (Scheme 1).8 The method, which proceeds in at
least modest yields, is suited for generating 57Fe-labeled
derivatives, which are of interest for nuclear resonance
vibrational spectroscopy (NRVS)9 and Mossbauer measure-
Received: July 28, 2013
̈
ments.10
© XXXX American Chemical Society
A
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possible for an octahedral complex of type M(chel)(chel′)L2.
The complex FeCl2(CO)2(dppe)13 was observed spectroscopi-
cally as an intermediate in the preparation of 1d. Although
yields ranged from 10 to 50%, the necessary reagents are readily
available. A complementary route to 1d involving the reaction
of Fe(CO)3(dppe) and pdtH2 did not proceed.
2FeSO + 2CO + 2RSNa + chel
4
→ Fe(SR)2(CO)2(chel) + Na2SO
4
(chel = dppe, en, phen, bipy)
(1)
Scheme 2. Synthetic Routes to Fe(dithiolate)(CO)2L2
Spectroscopic measurements on the new compounds
indicate the presence of two isomers, with the 31P{1H} NMR
spectra exhibiting three signals: a singlet corresponding to the
symmetrical isomer and a pair of doublets corresponding to the
unsymmetrical isomer (Table 1). For 1,2-ethanedithiolate
(edt2−) complexes 1a,b, the unsymmetrical isomer is the
major species, whereas the symmetrical isomers predominate
for complexes of 1,3-propanedithiolate (pdt2−) and 2-dimethyl-
1,3-propanedithiolate (Me2pdt2−), 1c−f. (Table 1, Scheme 3).
The IR spectra of the edt2− complexes 1a,b exhibit two or three
bands in the νCO region. The pair of bands at ∼2000 and 1960
cm−1 is assigned to the unsymmetrical isomer, and one band at
1970 cm−1 is assigned to the symmetrical trans-dicarbonyl
isomer. The complex Fe(pdt)(CO)2(dcpe) (1f) was also
prepared. As with the other pdt2− complexes, it exists as a
mixture of symmetrical and unsymmetrical isomers. Relative to
the dppe analogue 1b, the νCO bands for 1f are shifted by 20
cm−1 to lower energy. Unlike complexes 1a−g, Fe(edt)-
(CO)2(PMe3)2 is present in solution as a single isomer with
mutually trans PMe3 ligands.17 The IR spectrum of solid 1d
indicates that the trans isomer dominates, which is also the
predominant isomer in THF solution.
various isomeric forms.13,20 Fe(SPh)2(CO)2(dppe) crystallizes
as the all-cis isomer.15 Complexes of formula
FeX2(CO)2(PR3)2, in which all the ligands are monodentate,
exist as both the cis,cis,trans and all-trans isomers, depending
on the phosphine ligand.21
Ferrous carbonyl thiolates have been examined as metal-
loligands, analogous to the use of metal dithiolates to prepare
diverse dithiolato-bridged dimetallic complexes.22 Thiolates
retain significant basicity even when bound to a metal, as
evidenced by the formation of adducts of Fe-
(SPh)2(CO)2(dppe) with HgCl2.15 Similarly, the bis(chelate)
complex Fe(pdt)(CO)2(dppe) is a useful precursor to
bimetallic species, including Ni−Fe dithiolates (eq 2).23
Fe(pdt)(CO)2(dppe) + NiCl2(dppe)
→ [(dppe)(CO)FeCl(pdt)Ni(dppe)]Cl
(2)
Diffraction-quality crystals of 1a and 1c were obtained, and
the molecular structures were determined by X-ray crystallog-
raphy (Figures 1 and 2). In both cases, the major solution
isomer crystallized.
Presented here is a general route to monoiron precursors.
Reactions of these monoiron precursors with iron, manganese,
and cobalt carbonyl complexes afford the respective FeFe,
MnFe, and CoFe complexes. In the course of this work, one of
the authors (J.C.) published some of these results without the
knowledge of the other authors.24 The new compounds and
new synthetic routes demonstrate the broad scope for first-row
analogues of the active sites of the [FeFe]- and [NiFe]-H2ases.
Starting from 57Fe2I4(iPrOH)4, which can be derived from
metallic 57Fe, the isotopically labeled complex 57Fe(pdt)-
(CO)2(dppe) (571d) was prepared (eqs 3 and 4). Character-
257Fe + 2I2 + 4iPrOH → 57Fe2I4(iPrOH)4
(3)
RESULTS
■
57Fe2I4(iPrOH)4 + 2dppe + 2K2pdt + 4CO →
Ferrous Dithiolato Carbonyls. New diphosphine-sub-
stituted ferrous carbonyl dithiolates were prepared by carbon-
ylation of a slurry of anhydrous FeCl2 and the diphosphine
ligand, followed by the addition of the sodium dithiolate
(Scheme 3). The reaction affords a mixture of the two isomers
257Fe(pdt)(CO)2(dppe) + 4KI + 4iPrOH
57
(4)
1d
ization of cis/trans-571d included the observation of 57Fe−31P
coupling in the 31P{1H} NMR spectrum (1JPFe = 35 and 38 Hz
for cis and trans isomers, respectively, Figure 3).25
Scheme 3. Main Route to Fe(dithiolate)(CO)2(diphosphine)
Diiron Dithiolato Carbonyl Complexes via Compro-
portionation. A comproportionation reaction was applied to
the synthesis of unsymmetrically disubstituted subferrous diiron
dithiolates (eq 5; xdt = edt, pdt; diphos = diphosphine; bda =
Fe(xdt)(CO)2(diphos) + (bda)Fe(CO)3
→ Fe2(xdt)(CO)4(diphos) + bda + CO
(5)
benzylideneacetone). Thus, the reaction 1a + (bda)Fe(CO)3
gave the known complex Fe2(edt)(CO)4(dppv) (2a).26 The
reaction occurred over the course of several hours at room
temperature, giving 83% isolated yield. The complex Fe2(pdt)-
(CO)4(dppe) (2d) was prepared analogously in about 60%
yield. This species can be obtained in modest yields under very
specific conditions by substitution of Fe2(pdt)(CO)6.27,28 The
B
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Article
a
Table 1. Spectroscopic Data for Ferrous Carbonyl Complexes
isomer ratio unsym:sym
31P{1H} NMR (δ) unsym
JP−P
(Hz)
31P{1H} NMR (δ) sym
complex
(20 °C)
νCO (cm−1) (THF)
isomer
isomer
Fe(edt)(CO)2(dppv) (1a)
2:1
2013 (s), 1978 (s), 1960 (s)
89.4 (d)
59.9 (d)
78.3 (d)
48.1 (d)
87.3 (d)
60.4 (d)
78.0 (d)
51.2 (d)
78.5 (d)
68.2 (d)
79.19 (d)
55.8 (d)
78.3 (d)
52.6 (d)
21.1
21.1
29.1
29.1
22.0
22.1
30.9
30.6
38.6
39.3
32.9
32.9
30.5
30.8
87.7 (s)
77.5 (s)
81.2 (s)
73.7 (s)
80.8 (s)
81.34 (s)
73.8 (s)
Fe(edt)(CO)2(dppe) (1b)
Fe(pdt)(CO)2(dppv) (1c)
Fe(pdt)(CO)2(dppe) (1d)
Fe(pdt)(CO)2(dppbz) (1e)
Fe(pdt)(CO)2(dcpe) (1f)
Fe(Me2pdt)(CO)2(dppe) (1g)
3:1
1:4
2:3
1:7
1:2
1:3
2009 (s), 1973 (s), 1959 (s)
2010 (m), 1975 (s)
2004 (m), 1969 (s), 1958 (sh)
2012 (m), 1970 (s)
1990 (m), 1940 (s)
2006 (m), 1969 (s)
a
IR spectra are reported for THF, wherein signals are better resolved. 31P{1H} NMR spectra were recorded in CD2Cl2 solution, but isomer ratios
were similar in THF solution.
Figure 1. Structure of the unsymmetrical isomer of Fe(edt)-
(CO)2(dppv) (1a). Thermal ellipsoids are set at the 50% probability
level. Hydrogen atoms are omitted for clarity. Key distances (Å) and
angles (deg): Fe1−C1, 1.777(3); Fe1−C2, 1.790(3); Fe1−P2,
2.2304(8); Fe1−P1, 2.2648(7); Fe1−S1, 2.3313(8); Fe1−S2,
2.3471(7); C1−Fe1−C2, 93.60(12); C1−Fe1−P2, 94.43(8); C2−
Fe1−P2, 95.80(9); C1−Fe1−P1, 95.90(8); C2−Fe1−P1, 170.41(9);
P2−Fe1−P1, 84.80(3); C1−Fe1−S1, 85.78(8); C2−Fe1−S1,
89.16(9); P2−Fe1−S1, 175.01(3); P1−Fe1−S1, 90.23(3); C1−
Fe1−S2, 174.68(8); C2−Fe1−S2, 85.05(9); P2−Fe1−S2, 90.80(3);
P1−Fe1−S2, 85.32(3); S1−Fe1−S2, 89.07(3).
Figure 2. Structure of the symmetrical isomer of Fe(pdt)(CO)2(dppv)
(1c). Thermal ellipsoids are set at the 50% probability level. Hydrogen
atoms are omitted for clarity. Key distances (Å) and angles (deg):
Fe1−C1, 1.808(2); Fe1−C2, 1.799(2); Fe1−P2, 2.2204(1); Fe1−P1,
2.214(1); Fe1−S1, 2.3441(6); Fe1−S2, 2.3462(6); C1−Fe1−C2,
169.3(1); C1−Fe1−P2, 91.10(7); C2−Fe1−P2, 95.25(7); C1−Fe1−
P1, 93.85(7); C2−Fe1−P1, 91.80(7); P2−Fe1−P1, 86.76(2); C1−
Fe1−S1, 87.82(7); C2−Fe1−S1, 82.97(7); P2−Fe1−S1, 177.54(2);
P1−Fe1−S1, 91.58(2); C1−Fe1−S2, 83.20(7); C2−Fe1−S2,
91.74(6); P2−Fe1−S2, 89.50(2); P1−Fe1−S2, 175.07(2); S1−Fe1−
S2, 92.25(2).
low yields result from complications arising from the flexibility
of the dppe ligand, which allows other intra- and intermolecular
processes (Scheme 4).27,28
The reaction of the dcpe complex 1f with (bda)Fe(CO)3
afforded Fe2(pdt)(CO)4(dcpe) (2f) in 81% yield. As with the
analogous dppe complex 2d, 2f exists in solution as a 3:1
mixture of apical−basal and dibasal isomers. The reaction of
Fe2(pdt)(CO)6 and dcpe gives only a low yield of 2f,
highlighting the advantage of the building block method.
When, however, Fe(pdt)(CO)2(PMe3)2 was treated with
(bda)Fe(CO)3, the product is the known complex Fe(pdt)-
(CO)4(PMe3)2,29 where the phosphine ligands are bound to
different iron centers.
(doublets at δ 48 and 76) and a symmetrical species (singlet at
δ 58). In these species the diphosphine ligands occupy apical−
basal and dibasal sites on the Fe centers (Scheme 5). The initial
isomer ratio matches that of the starting iron complex. The
unsymmetrical isomer was found to convert to the symmetrical
isomer over the course of 24 h (Figure 4). Comparably slow
isomerism is observed in related diiron(II) dithiolates.31
Analogous complexes featuring different dithiolate and
diphosphine ligands were also examined. Reaction of
[(acenaphthene)Mn(CO)3]BF4 with the ethanedithiolate 1b
afforded a mixture of isomers even after extended time for
equilibration. The result is not surprising, since edt2− vs pdt2−
affects the isomer ratio in 1b and 1d. The complexes
[(CO)3Mn(pdt)Fe(CO)2(dppbz)]BF4, [(CO)3Mn(pdt)Fe-
(CO)2(dcpe)]BF4, and [(CO)3Mn(Me2pdt)Fe(CO)2(dppe)]-
Synthesis of MnIFeII Complexes. The salt [(CO)3Mn-
(pdt)Fe(CO)2(dppe)]BF4 ([3d(CO)]BF4) forms upon treat-
ment of 1d with [(acenaphthene)Mn(CO)3]BF4, a well-known
source of Mn(CO)3 (Scheme 5).30 When monitored by
+
31P{1H} NMR spectroscopy, the reaction was found to produce
two isomeric MnFe compounds: an unsymmetrical species
C
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slightly closer to Fe (1.62(2) Å) than to MnH (1.75(2) Å). The
d6d6 36e-complex (H3d is 34e-) FeMn(μ-SPh)3(CO)6 has been
described.32 The cyclic voltammogram of H3d consists of a
reversible oxidation event at 0.125 V vs Fc+/0, characterized by
the linear dependence of ip on (scan rate)1/2 (Supporting
Information).
The acid−base behavior of H3d was investigated. Upon
treatment of H3d with [H(Et2O)2]BArF , the νCO bands shifted
4
by 20−50 cm−1 to higher energy. Protonation of H3d was
anticipated to give H2 or a dihydrogen complex (see
[(H2)Mn(CO)3(dppe)]+).33 Treatment of the acidified reac-
tion mixture with Et3N gave back H3d (Figure 6). The
reversible protonation of H3 is proposed to occur at sulfur.
Similar S-protonations have been proposed for related charge-
neutral diiron dithiolate complexes.34 In contrast to the
behavior of H3d, the closely related complex [(μ-H)Fe2(pdt)-
Figure 3. 31P{1H} NMR spectrum of a mixture of the two isomers of
57Fe(pdt)(CO)2(dppe) (CD2Cl2 solution). Expanded regions show
the additional coupling to 57Fe.
(CO)4(dppv)]+ is unreactive toward [H(Et2O)2]BArF , illus-
4
trating the effect of charge on the basicity of the thiolate S
centers.
BF4 form in a manner analogous to that for [3(CO)]BF4, and
their spectroscopic data were similar.
31P{1H} and 1H NMR (hydride region) resonances for H3d
were broadened upon protonation of this complex (Supporting
Information). In the presence of 2 equiv of acid, a pair of
doublets appears at 79.6 and 78.5 in the 31P{1H} NMR
spectrum, assigned to the nonequivalent phosphorus centers in
[H3dH]+.
Synthesis of MnIFeII Hydride. Reaction of [3d(CO)]BF4
with [Bu4N]BH4 results in loss of one CO ligand and formation
of the neutral hydride complex (CO)3Mn(pdt)(μ-H)Fe(CO)-
(dppe) (H3d) (eq 6). The 1H NMR spectrum of H3d consists
Reduction of MnIFeII Complexes. The electrochemical
behavior of [3d(CO)]BF4 was investigated by cyclic
voltammetry. At −1.0 V, an irreversible reduction is observed,
followed by a reversible event centered at −1.3 V. Consistent
with its being reductive decarbonylation, the irreversible event
at −1.0 V diminishes upon further electrochemical cycling (i.e.,
as decarbonylation proceeds to completion) but is less
irreversible at low temperatures. To probe this irreversible
chemical process, a solution of [3d(CO)]BF4 was treated with
1 equiv of cobaltocene, producing a new species characterized
by νCO 1997 and 1902 cm−1. In view of the electrochemical and
chemical reduction results, the initial reduction is proposed to
induce decarbonylation, generating (CO)3Mn(pdt)Fe(CO)-
(dppe) ([3d(CO)]0). Analytically pure [3d(CO)]0 was
obtained once it was determined that its stability was greater
in THF than in CH2Cl2 solution. Cyclic voltammetry of this
salt exhibits the quasi-reversible couple at −1.3 V.
of a triplet at δ −12.3, indicating coupling to two equivalent
phosphorus centers. The 31P{1H} NMR spectrum exhibits a
singlet at δ 80.8, which confirms that the two phosphorus
centers are equivalent, both occupying basal positions.
The structure of H3d was confirmed by X-ray crystallog-
raphy, and the details are consistent with the NMR data (Figure
5). The phosphorus centers on the dppe ligand both occupy
basal positions. The bridging hydrido ligand, whose location
was identified on the difference map, refined to a position
Scheme 4. Routes to Fe2(pdt)(CO)4(dppe) and Related Complexes
D
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Scheme 5. Synthesis of [(CO)3Mn(pdt)Fe(CO)2(dppe)]BF4 from Isomers of 1d
Figure 4. 31P{1H} NMR spectra of a CD2Cl2 solution of (a)
Fe(pdt)(CO)2(dppe) (triangle, unsym isomer; circle, sym isomer),
Figure 6. IR spectra in CH2Cl2 of (a) (CO)3Mn(pdt)(μ-H)Fe(CO)-
(b) the same solution 30 min after addition of [(acenaphthene)Mn-
(CO)3]BF4 (diamond, unsym isomer; star, sym isomer), and (c) the
same solution after 12 h.
(dppe) and this solution (b) after addition of 1 equiv of
H(Et2O)2BArF , (c) after addition of 0.5 equiv of Et3N, and (d)
4
after addition of 1 equiv total of Et3N.
more reliable route to the same compounds involved the
reactions of the ferrous dithiolates with CpCoI2(CO) followed
by reduction. For example, 1d and CpCoI2(CO) react rapidly
to give an isomeric mixture of the intermediate [CpCoI(pdt)-
Fe(CO)(dppe)]+ (νCO 1952 cm−1). When this reaction is
monitored by 31P{1H} NMR spectroscopy, two isomeric Co−
Fe complexes are observed. Akin to the MnFe systems, the
31P{1H} NMR spectrum showed that one isomer is unsym-
metrical (doublets at δ 47 and 90) and the second isomer is
characterized by a singlet at δ 59. In these isomers the
phosphine ligands occupy apical−basal and dibasal sites,
respectively. Reduction of [CpCoI(pdt)Fe(CO)(dppe)]+ with
2 equiv of Cp2Co gave 4d in good yield (eqs 7 and 8).
Figure 5. Structure of (CO)3Mn(pdt)(μ-H)Fe(CO)(dppe) (H3d)
with thermal ellipsoids drawn at the 50% probability level. Selected
distances (Å): Fe1−Mn1, 2.6433(4); Fe1−C27, 1.753(2); Fe1−P1,
2.2139(5); Fe1−P2, 2.2086(5); Fe1−S1, 2.2759(5); Fe1−S2,
2.2648(5); Fe1−H1, 1.62(2); Mn1−C31, 1.789(2); Mn1−C32,
1.813(2); Mn1−C33, 1.799(2); Mn1−S1, 2.3361(6); Mn1−S2,
2.3042(5); Mn1−H1, 1.75(2).
CpCoI2(CO) + Fe(pdt)(CO)2(dppe)
→ [CpCoI(pdt)Fe(CO)(dppe)]I + 2CO
(7)
[CpCoI(pdt)Fe(CO)(dppe)]I + 2Cp2Co
→ CpCo(pdt)Fe(CO)(dppe) + 2Cp2CoI
Cobalt−Iron Dithiolates. Treatment of the ferrous
dithiolato carbonyls with CpCo(CO)2 in refluxing toluene or
THF gave complexes of the type CpCo(pdt)Fe(CO)(dppx)
(4a,d). The yields for these preparations were inconsistent,
however, varying from 50% to almost nothing. A related but
(8)
4d
These CoFe complexes are analogues of Fe2(S2CnH2n)-
(CO)4(dppx), in which CpCo replaces the Fe(CO)3 center.
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Like the corresponding diiron complexes, 4d oxidizes
reversibly, at a potential (−0.6 V vs Fc+/0) between those for
Fe2(pdt)(CO)2(dppv)2 (−0.19 V) and Fe2(pdt)(CO)4(dppv)
(−0.94 V).26,35 Crystallographic and spectroscopic character-
ization of the ethanedithiolate 4a proved mutually consistent
(Figure 7). The complex can be described as a pair of five-
Figure 8. 31P{1H} NMR spectra of a CD2Cl2 solution of 4d and 1
equiv of [H(OEt2)2]BArF . The solution was prepared at −85 °C and
4
then warmed to the indicated temperatures.
Figure 7. Structure of CpCo(edt)Fe(CO)(dppv) (4a) with thermal
ellipsoids drawn at the 50% probability level. Selected distances (Å):
Fe1−Co1, 2.5038(5); Fe1−C1, 1.754(3); Fe1−P1, 2.2038(5); Fe1−
S4, 2.2318(5); Co1−S1, 2.1748(6); Co−Cp centroid, 1.6727(3).
coordinate metal centers linked by a Co−Fe bond (2.5038(5)
Å). A distinctive feature of the structure is the acute angle for
the FeP2 plane relative to the FeS2 plane.
Figure 9. 1H NMR spectra of a CD2Cl2 solution of 4d and 1 equiv of
The 31P{1H} NMR spectrum of 4d established the presence
of only one isomer, even at low temperatures. Below −60 °C,
the spectrum consists of a pair of singlets with ∼4:1 intensities,
attributed to conformational isomers arising from the pdt2−
backbone. Using an internal integration standard, >90% of the
sample was verified to be in solution at −90 °C.
[H(OEt2)2]BArF . The solution was prepared at −85 °C and then
4
warmed to the indicated temperatures.
Scheme 6. Protonation of 4d and Isomerization of Resulting
Hydride Complexes
CoIIIFeII Hydrides. At room temperature, the Co−Fe
complexes protonate to give the corresponding μ-hydrido
derivatives. Protonation shifts the νCO band from 1890 to 1975
1
cm−1. The 31P{1H} and H NMR spectra indicate that the
hydride complex is Cs-symmetric. On the basis of its chemical
shift and J(31P,1H) value of 25 Hz, the hydride ligand is
bridging the Fe and Co centers.
NMR studies on the protonation at low temperatures
revealed at least two intermediates. The initial product of
protonation, formed quantitatively at −85 °C, is characterized
DISCUSSION
1
by singlets at δ −9.0 and δ 70.7 in the H and 31P{1H} NMR
■
Ferrous dicarbonyl dithiolato diphosphine complexes are
versatile precursors to dimetallic complexes, as illustrated by
their conversion to FeFe, MnFe, and CoFe dithiolate
complexes described above. The new synthesis of Fe2(pdt)-
(CO)4(dppe) avoids side reactions that hamper the installation
of flexible chelating ligands.27,28 Related complexes can be
prepared via FeX2(CO)4.14,37 The new routes are potentially
appealing because the iron complexes are derived from FeCl2.8
Conveniently available sources of 57Fe are easily converted to
the dichloride and 57Fe2I4(iPrOH)4. Although the preparations
reported herein proceed in modest yields, the precursors are
readily available and the product workup is relatively simple.
The methods lend themselves to the incorporation of 57Fe (I =
−1/2) into ferrous carbonyl building blocks, as illustrated by the
synthesis of 57Fe(pdt)(CO)2(dppe). Interest in 57Fe labeling
spectra, respectively (Figures 8 and 9). These signals are
assigned to a terminal hydride complex with the hydride ligand
on the CpCo center (Scheme 6). When the temperature is
raised to −50 °C, this terminal hydride converts to
approximately equal amounts of two species characterized by
a doublet at δ −14.7 (J = 30 Hz) and triplet at δ −15.5 (J = 25
Hz). These species correspond to the bridging hydrides with
apical−basal and dibasal phosphines. Bridging hydrides
typically exhibit a ∼25 Hz coupling to the cis phosphine,
whereas coupling to the trans phosphine is often weak or is not
observed.36 At room temperature, the unsymmetrical isomer,
labeled a,b for apical−basal, converts to the dibasal isomer.
Comparable isomerizations have been observed for diiron
complexes.
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1
Fe(edt)(CO)2(dppe) (1b). Conducted as for 1d. Yield: 50%. H
stems from the wealth of information available from, among
NMR (CD2Cl2): δ 7.87−7.27 (m, C6H5), 2.62 (s, 4H, S CH2, sym),
2.50 (s, 4H, PCH2, sym), 2.78 (d 2H PCH2, unsym), 2.16 (d 2H
PCH2, unsym), 1.22 (s, 3H, SCH2, unsym), 0.34 (s, 1H, SCH2,
unsym). IR (THF): 2009 (s), 1973 (s), 1959 (s). Anal. Calcd for
C30H28FeO2P2S2 (found): C, 59.81 (59.78); H, 4.68 (5.0).
other techniques, Mossbauer and NRVS spectroscopy.
̈
This building block approach allowed the synthesis of the
first dithiolato-bridged MnFe complexes. Related dimanganese
dithiolate complexes had been reported by Treichel.38 The
most curious property of [(CO)3Mn(pdt)Fe(CO)2(dppe)]+ is
its tendency to decarbonylate upon 1e-reduction. The resulting
complex, (CO)3Mn(pdt)Fe(CO)(dppe), is electronically re-
lated to the mixed-valence “Hox-models” [Fe2(pdt)-
(CO)6−xLx]+.39 Similarly, the hydride (CO)3Mn(pdt)HFe-
(CO)(dppe), which was characterized crystallographically, is
isoelectronic with [HFe2(pdt)(CO)4(dppe)]+.28 The MnFe
complex is sufficiently electron rich that it undergoes a mild
one-electron oxidation (∼0.1 V vs Fc+/0), whereas oxidations of
analogous diferrous hydrides occur only at very positive
potentials.40
This building block approach also allowed the synthesis of
dithiolato-bridged iron−cobalt complexes. Two complementary
routes to these CoFe complexes were devised: a direct Co(I) +
Fe(II) pathway and an less direct but more reliable route via
Co(III) + Fe(II), followed by 2e-reduction. The latter method
is modeled after the route to (CO)3Fe(pdt)Ni(dppe) from
FeI2(CO)4 + Ni(pdt)(dppe) followed by reduction.41 The
complexes CpCo(dithiolate)Fe(CO)(diphos) are electronically
related to Fe2(dithiolate)(CO)4(diphos), both being of d7d7
configuration. Like FeIFeI dithiolates, the CoIIFeI species
undergo protonation and redox reactions.
Fe(pdt)(CO)2(dppv) (1c). Conducted as for 1d, but the column
1
was eluted with 10/1 CH2Cl2/Et2O. Yield: 78%. H NMR (CD2Cl2):
δ 7.94−7.32 (m, 20H, C6H5), 2.44 (d, 4H, CH2), 1.96 (d, 2H, SCH2).
IR (CH2Cl2): 2014, 1975. Anal. Calcd for C31H28FeO2P2S2·0.7CH2Cl2
(found): C, 56.49 (56.50); H, 4.40 (4.40).
Fe(pdt)(CO)2(dppbz) (1e). Under a CO atmosphere, a solution of
0.50 g of FeCl2 (3.94 mmol) in 100 mL of acetone was treated with a
solution of 1.76 g (15.0 mmol) of dppbz in 40 mL of THF. The
solution changed from pale orange to dark orange, signaling formation
of FeCl2(CO)2(dppbz). Separately, 181 μL (4.33 mmol) of
C3H6(SH)2 and 188 mg (7.88 mmol) of NaH were combined in 15
mL of THF. After 1 h, the resulting solution of Na2S2C3H6 was added
to the solution of FeCl2(CO)2(dppbz). A large amount of red
precipitate had formed after 15 h. The solution was filtered, the filtrate
was discarded, and the red solid was extracted into 50 mL of CH2Cl2.
The product was recrystallized by addition of hexanes to a
concentrated CH2Cl2 solution. Yield: 400 mg (20%). 1H NMR
(CD2Cl2): δ 7.4−7.6 (m, 24H, C6H5 and C6H4), 2.39 (s, 4H,
SCH2CH2), 1.94 (s, 2H, SCH2CH2). IR (CH2Cl2): 2012, 1970. Anal.
Calcd for C35H30FeO2P2S2·0.2CH2Cl2 (found): C, 62.03 (62.22); H,
4.5 (4.83).
Fe(pdt)(CO)2(dcpe) (1f). Conducted as for 1d, but instead of
chromatography, the product was extracted into ∼100 mL of hexanes.
The solution volume was reduced to ∼20 mL and the solution cooled
to 0 °C, resulting in the formation of dark red crystals. Yield: 430 mg
(35%). IR (CH2Cl2): 1997 (w), 1945 (s). Anal. Calcd for
C31H54FeO2P2S2·0.2CH2Cl2 (found): C, 56.98 (56.94); H, 8.34
(8.71).
EXPERIMENTAL SECTION
■
Methods used in this work have been recently described.35
Chromatography was performed using silica gel (40−63 μm, 230−
400 mesh) as the stationary phase. K2pdt,42 [(acenaphthene)Mn-
57Fe2I4(iPrOH)4. This complex was obtained as a green powder in
95% yield analogously to the published method for Fe2I4(iPrOH)4,43
i
using 57Fe as the precursor. ESI-MS: m/z 674.8 [M − PrOH − I−]+,
(CO)3]BF4,30 57Fe2I4(iPrOH)4,43 and CpCo(CO)I2 were prepared
44
364.1 [M − iPrOH − 57Fe2+ − 3I−]+. Anal. Calcd for C12H32O4I457Fe2
(found): C, 16.72 (16.16); H, 3.74 (3.44); N, 0.00 (0.00).
according to the literature methods. ESI-MS data were recorded on
dilute CH2Cl2 solutions on a Waters Micromass Quattro II
spectrometer. ATR data were collected on a PerkinElmer Spectrum
57Fe(pdt)(CO)2(dppe) (571d). A mixture of 86.2 mg (100 μmol) of
57Fe2I4(iPrOH)4 and 79.7 mg (200 μmol) of dppe in 6 mL of 1/1
iPrOH/THF was stirred under 1 atm of CO. The suspension, which
had developed a red color, was treated with 36.8 mg (200 μmol) of
K2pdt in 3 mL of iPrOH. After it was stirred for 24 h in the absence of
light, the mixture was evaporated to dryness. The dark residue was
extracted with 2 × 5 mL of CH2Cl2, and these extracts were
concentrated to ∼0.5 mL and chromatographed on a ∼5 cm column
of silica gel, with CH2Cl2 as eluent. The second band, deep red, was
collected, concentrated to ∼2 mL, and treated with 10 mL of Et2O.
Any dark solids that formed were removed by filtration, and the filtrate
was treated with 15 mL of pentane. The mixture was allowed to stand
at −28 °C for 1 h, after which the solid that formed was isolated by
filtration, washed with additional pentane, and dried briefly to afford
the title compound as a pink powder (23.6 mg, 38.2 μmol, 19%).
31P{1H} NMR (CH2Cl2): δ 76.2 (dd, 1JPFe = 35, 2JPP = 32, cis isomer),
1
100 FT-IR instrument. H NMR spectra were recorded at 500 MHz
and 31P{1H} NMR spectra at 202 MHz. Coupling constants are
reported in Hz. IR measurements, reported in cm−1, were recorded
only in the νCO region.
Illustrative Preparation: Fe(pdt)(CO)2(dppe) (1d). Under a CO
atmosphere, a solution of 1.9 g of FeCl2 (15.0 mmol) in 250 mL of
acetone was treated with a solution of 5.98 g (15.0 mmol) of dppe in
60 mL of THF. The solution changed from pale orange to green and
then to dark orange, signaling formation of FeCl2(CO)2(dppe).
Separately, 1.71 mL (17.0 mmol) of C3H6(SH)2 and 0.72 g (30.0
mmol) of NaH were combined in 50 mL of THF. After 1 h, the
resulting solution of Na2S2C3H6 was added to the solution of
FeCl2(CO)2(dppe). After being allowed to react for 16 h, the mixture
was filtered through Celite, and the solvent was evaporated from the
filtrate. The residue was extracted into 15 mL of CH2Cl2 and purified
by flash column chromatography on a 4 × 50 cm column of silica gel.
After a yellow band eluted with CH2Cl2, the red band containing the
product eluted with 5/1 CH2Cl2/Et2O. Evaporation of solvent from
1
1
2
71.8 (d, JPFe = 38, trans isomer), 49.2 (dd, JPFe = 35, JPP = 32, cis
isomer). FTIR (CH2Cl2): 2010 (cis), 1969 (overlapping cis/trans).
ESI-MS: m/z 618.2 [M + H+]+ (similar analysis for the unlabeled
complex gave m/z 617.1).
1
this band afforded 1d as a red solid. Yield: 3.34 g (36%). H NMR
Fe(Me2pdt)(CO)2(dppe) (1g). Conducted as for 1d. Yield: 1.03 g
1
(CD2Cl2): δ 7.89−7.32 (m, 20H, C6H5), 2.63 (m, 4H, PCH2), 2.50 (d,
4H, SCH2), 1.97 (m, 2H, SCH2CH2). IR (CH2Cl2): 2010, 1968. Anal.
Calcd for C31H30FeO2P2S2·0.3CH2Cl2 (found): C, 58.56 (58.24); H,
4.80 (4.7).
(40%). H NMR (CD2Cl2): δ7.4−7.8 (m, 20H, C6H5), 2.65 (dd, 4H,
P2CH2CH2), 2.23 (s, 4H, SCH2), 1.01 (s, 6H, CCH3). IR (CH2Cl2):
2006 (w), 1969 (s). Anal. Calcd for C33H34FeO2P2S2·0.2CH2Cl2
(found): C, 60.28 (60.0); H, 5.24 (5.41).
Fe(edt)(CO)2(dppv) (1a). Conducted as for 1d. Yield: 12−50%.
1H NMR (CD2Cl2): δ 8.14−7.32 (m, 20H, C6H5), 2.53 (s, 2H, CH2),
2.46 and 2.02 (d each, 1:1 H, CH2), 2.18 and 0.21 (t each, 1:1 H, CH).
IR (CH2Cl2): 2013 (s), 1978 (s), 1960 (s). Anal. Calcd for
C30H26FeO2P2S2·0.5CH2Cl2 (found): C, 56.98 (57.35); H, 4.23
(4.17).
Fe2(edt)(CO)4(dppv) (2a) from 1a. A mixture of 1a (125 mg,
0.208 mmol) and 50 mg (0.208 mmol) of (bda)Fe(CO)3 in 20 mL of
toluene gradually darkened over the course of several hours to a deep
red solution. The reaction was monitored by IR for the disappearance
of νCO bands for (bda)Fe(CO)3 and 1a and the appearance of 2a.
After 24 h, the reaction solution was concentrated, and the crude
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product was chromatographed on silica gel in air, with toluene as
eluent. The first brown-red band was collected and dried in vacuo.
Yield: 123 mg (83%). The IR, 1H NMR, and 31P{1H} NMR spectra of
the product match reported data.26
stirred in CH2Cl2 (20 mL) at room temperature for 2 h to give a dark
brown solution with a predominant IR band at 1978 cm−1. To this
solution was added a solution of Cp2Co (68 mg, 0.36 mmol) in 20 mL
of CH2Cl2. The IR spectrum of the resulting solution revealed a
prominent band at 1890 cm−1. After the mixture was stirred for 30
min, solvent was removed, and the residue was purified by column
chromatography, initially with a 1/1 mixture of CH2Cl2 and pentane as
eluent and gradually increasing the CH2Cl2 content. After an initial
green band, the product eluted as a brown band using CH2Cl2.
Evaporation of the solution gave the brown product. Yield: 45 mg
(39%). 1H NMR (CD2Cl2, 23 °C): δ 8.30−7.12 (m, 20 H, C6H5), 4.75
(s, 2 H, PCH), 3.36 (s, 5 H, C5H5), 2.26 and 1.84 (d each, 2 H each,
SCH2). 31P{1H} NMR (CD2Cl2, 23 °C): δ 93.56 (s). IR (CH2Cl2):
1890.
CpCo(edt)Fe(CO)(dppv) from CpCo(CO)2. A mixture of 1a (200
mg, 0.34 mmol) and CpCo(CO)2 (92 μL, 0.68 mmol) was stirred in
toluene (100 mL) at reflux for 2.0 h to give a dark brown solution
containing a small amount of red-brown solid. The IR spectrum at this
stage revealed a new band at 1896 cm−1. The solution was filtered, and
the brown filtrate was evaporated. The brown residue was washed with
∼10 mL each of hexanes and Et2O. The brown residue was extracted
into ∼4 mL of CH2Cl2, and the extract was layered with 10 mL of
hexane. Dark brown crystals of 4a formed overnight. Yields were
variable. Anal. Calcd for C34H31CoFeOP2S2 (found): C, 58.63 (58.12);
H, 4.49 (4.37). IR (CH2Cl2): 1890.
Fe2(pdt)(CO)4(dppe) (2d) from 1d. An orange mixture of 1d
(250 mg, 0.40 mmol) and (bda)Fe(CO)3 (115 mg, 0.40 mmol) in 70
mL of toluene gradually darkened over the course of several hours to a
deep red solution. The reaction was monitored by IR spectroscopy.
After 24 h, the reaction solution was concentrated, and the crude
product was chromatographed on silica gel in air, with toluene as
eluent. The first brown-red band was collected. Yield: 150 mg (60%).
1
The IR, H NMR, and 31P{1H} NMR spectra of the product match
reported data.28
Fe2(pdt)(CO)4(dcpe) (2f) from 1f. A 5 mL solution of
(bda)Fe(CO)3 (48 mg, 0.17 mmol) was added to a red solution of
1f (107 mg, 0.17 mmol) in 20 mL of toluene. The solution gradually
darkened over the course of several hours to a deep red-brown
solution. The reaction was monitored by IR spectroscopy. After 24 h,
the reaction solution was concentrated, and the crude product was
chromatographed on silica gel in a glovebox, with toluene as eluent.
The first brown-red band was collected. Yield: 101 mg (81%). 31P{1H}
NMR (CD2Cl2): δ 89.27 (s), apical−basal; 74.90 (s), dibasal. IR
(CH2Cl2): 2013 (s), 1939 (br), 1882 (br).
[(CO)3Mn(pdt)Fe(CO)2(dppe)]BF4 ([3(CO)]BF4). A solution of
500 mg (1.32 mmol) of [(acenaphthene)Mn(CO)3]BF4 in 125 mL of
CH2Cl2 was treated with a solution of 810 mg (1.32 mmol) of 1b in 50
mL of CH2Cl2. The solution was stirred for 20 h and gradually became
dark brown. The IR spectrum of the solution showed bands for the
product. The solution was evaporated to dryness. The resulting brown
residue was extracted into ∼30 mL of CH2Cl2, and the extract was
filtered through a pad of Celite. The brown solution was concentrated
to ∼10 mL and then diluted with 100 mL of hexanes. Upon storage of
the solution at 0 °C, brown microcrystals formed. Yield: 1.00 g (90%).
Crystals were obtained by layering a CH2Cl2 solution with pentane. 1H
NMR (CD2Cl2): δ 7.41−7.80 (m, 20H, C6H5), 3.50 (m, 2H, PCH2),
3.28 (m, 2H, PCH2), 3.08 (m, 2H, SCH2), 2.84 (m, 3H, SCH2CH2),
2.03 (m, 1H, SCH2CH2). 31P{1H} NMR (CD2Cl2): δ 58 (s). IR
(CH2Cl2): 2053 (w), 2027 (s), 1992 (s), 1974 (s), 1905 (br). Anal.
Calcd for C34H30BF4FeMnO5P2S2 (found): C, 48.48 (48.66); H, 3.59
(3.81).
CpCo(pdt)Fe(CO)(dppv) (4c). A mixture of 1c (200 mg, 0.32
mmol) and CpCo(CO)2 (67 μL, 0.65 mmol) was stirred in toluene
(100 mL) at reflux temperature for 2.0 h to give a dark brown solution
containing a small amount of red-brown solid. The IR spectrum at this
stage revealed a new band at 1892 cm−1. The solution was filtered, and
the brown filtrate was evaporated. The brown residue was washed with
∼10 mL of hexanes and then extracted into ∼5 mL of CH2Cl2. This
extract was layered with 10 mL of hexane to yield dark brown crystals
1
of 4b upon standing overnight. H NMR (CD2Cl2, 23 °C): δ 8.17−
7.30 (m, 20 H, C6H5), 3.51 (s, 5 H, C5H5), 2.30 and 2.20 (d each, 2 H
each, SCH2), 1.87 (m, 2 H, SCH2CH2). 31P{1H} NMR (CD2Cl2, 23
°C): δ 90.17 (s). IR (CH2Cl2): 1885.
CpCo(pdt)Fe(CO)(dppe) (4d) from CpCoI2(CO). A solution of
Fe(pdt)(CO)2(dppe) (50 mg, 0.08 mmol) and CpCo(CO)I2 (31 mg,
0.08 mmol) in CH2Cl2 (20 mL) was stirred overnight. Formation of a
new product was detected by an IR band at 1952 cm−1. The reaction
solution was treated with a solution of Cp2Co (38 mg, 0.20 mmol) in
CH2Cl2 (5 mL). After the solution was stirred for 5 min, the dominant
IR band shifted to 1879 cm−1. The solution was filtered through
Celite, and the product was purified by column chromatography on
silica gel, initially with 1/1 CH2Cl2/pentane as eluent, which produced
a green band. Eluting with CH2Cl2 gave the product as a brown band,
which was evaporated to leave a brown solid. Yield: 23 mg (40%). 1H
NMR (CD2Cl2, 23 °C): δ 7.82−7.29 (m, 20 H, C6H5), 3.84 (s, 5 H,
C5H5), 2.98 (m, 2 H, PCH2), 2.58 and 2.26 (m each, 2 H each, SCH2),
2.17 and 1.89 (m each, 1 H each, PCH2), 1.47 (m, 2 H, S(CH2)2CH2).
31P{1H} NMR (CD2Cl2, 23 °C): δ 83.48 (s). IR (CH2Cl2): 1880.
CpCo(pdt)Fe(CO)(dppe) (4d) from CpCo(CO)2. A mixture of 1d
(200 mg, 0.32 mmol) and CpCo(CO)2 (67 μL, 0.65 mmol) was
stirred in toluene (100 mL) at reflux temperature for 7 h to give a dark
brown solution. The IR spectrum at this stage revealed a new band at
1883 cm−1. The solution was filtered, and the brown filtrate was
evaporated. The brown residue was washed with ∼15 mL of toluene
and then extracted into ∼4 mL of CH2Cl2. This extract was layered
with 10 mL of hexane to yield dark brown crystals of 4d upon standing
(CO)3Mn(pdt)(μ-H)Fe(CO)(dppe) (H3). A solution of 590 mg
(0.70 mmol) of [3(CO)]BF4 in 100 mL of CH2Cl2 was cooled to −78
°C and treated with a precooled solution of 257 mg (0.70 mmol) of
[Bu4N]BH4 in 60 mL of CH2Cl2 over the course of 90 min, during
which time the solution changed from brown to dark red. The reaction
progress was monitored by IR spectroscopy. The solution was warmed
to room temperature and stirred at room temperature for 15 h before
being evaporated to dryness. An extract of the red residue in ∼20 mL
of toluene was chromatographed on silica gel with a 3/1 toluene/
hexanes mixture as eluent. The product (an orange band) eluted first,
followed by a brown band. The orange band was evaporated under
vacuum, and the resulting orange residue was extracted into ∼25 mL
of toluene. This extract was filtered through Celite, concentrated to
half volume, and then diluted with 60 mL of hexanes. After storage of
the solution at 0 °C, orange crystals formed. Yield: 98 mg (20%).
Diffraction-quality crystals were grown at 0 °C by layering a toluene
1
solution with hexanes. H NMR (CD2Cl2): δ 7.38−7.84 (m, 20H,
C6H5), 2.76 (m, 4H, PCH2), 2.58 (m, 2H, SCH2), 2.41 (m, 3H,
SCH2CH2), 1.91 (m, 1H, SCH2CH2), −12.26 (t, 1H, Mn−H−Fe).
31P{1H} NMR (CD2Cl2): δ 80.80 (s). IR (CH2Cl2): 2002 (s), 1935
(br), 1905 (br). Anal. Calcd for C33H31FeMnO4P2S2 (found): C, 54.41
(54.35); H, 4.29 (4.49).
1
overnight. Yields were variable. H NMR (CD2Cl2, 23 °C): δ 7.82−
7.29 (m, 20 H, C6H5), 3.84 (s, 5 H, C5H5), 2.98 (m, 2 H, PCH2), 2.56
and 2.25 (m each, 2 H each, SCH2), 2.18 and 1.87 (m each, 1 H each,
PCH2), 1.51 (m, 2 H, CH2SCH2). 31P{1H} NMR (CD2Cl2, 23 °C): δ
85.54 (s). Anal. Calcd for C35H35CoFeOP2S2 (found): C, 59.00
(58.89); H, 4.95 (4.83). IR (CH2Cl2, cm−1): νCO 1879. Data for the
low-temperature intermediate, terminal hydride are as follows. 1H
NMR (CD2Cl2, 23 °C): δ 7.73−7.35 (m, 20 H, C6H5), 3.61 (s, 5 H,
C5H5), 2.98 (m, 2 H, PCH2), 2.56 and 2.25 (m each, 2 H each, SCH2),
2.18 and 1.87 (m each, 1 H each, PCH2), 1.51 (m, 2 H, S(CH2)2CH2).
(CO)3Mn(pdt)Fe(CO)(dppe). A solution of [4d(CO)]BF4 (71 mg,
84 μmol) in THF (10 mL) was treated with a THF solution of Cp2Co
(16 mg, 84 μmol). The solution was filtered through Celite, and then
the solvent was removed under vacuum to yield a red solid. Yield: 46
mg (75%). IR (CH2Cl2): 1997 (s), 1902 (s). Anal. Calcd for
C33H30FeMnO4P2S2 (found): C, 54.49 (54.54); H, 4.16 (4.55).
CpCo(edt)Fe(CO)(dppv) (4a) from CpCoI2(CO). A mixture of 1a
(100 mg, 0.17 mmol) and CpCo(CO)I2 (68 mg, 0.17 mmol) was
H
dx.doi.org/10.1021/om400752a | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
31P{1H} NMR (CD2Cl2, 23 °C): δ 85.54 (s). Data for the low-
temperature intermediate, apical−basal μ-hydride are as follows. H
NMR (CD2Cl2, 23 °C): δ 7.82−7.29 (m, 20 H, C6H5), 3.84 (s, 5 H,
C5H5), 2.98 (m, 2 H, PCH2), 2.56 and 2.25 (m each, 2 H each, SCH2),
2.18 and 1.87 (m each, 1 H each, PCH2), 1.51 (m, 2 H, CH2SCH2).
31P{1H} NMR (CD2Cl2, 23 °C): δ 85.54 (s).
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1
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ASSOCIATED CONTENT
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S
* Supporting Information
Figures giving 1H NMR, 31P{1H} NMR, and IR spectra for new
complexes and CIF files giving X-ray crystallographic data. This
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Corresponding Author
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Institutes of Health
(Grant GM61153). We thank Teresa Wieckowska for help with
collection of the X-ray diffraction data. Also acknowledged is
support from the International Institute for Carbon Neutral
Energy Research (WPI-I2CNER), sponsored by the World
Premier International Research Center Initiative (WPI),
MEXT, Japan.
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