Bond activation in iron(II) and nickel(II) complexes of polypodal phosphanes

Article abstract of DOI:10.1515/znb-2010-0304

A pyridine-derived tetraphosphane ligand (donor set: NP₄) has been found to undergo remarkably specific C-P bond cleavage reactions, thereby producing a ligand with an NP₃ donor set. The reaction may be reversed under suitable condit

Full text of DOI:10.1515/znb-2010-0304

Bond Activation in Iron(II) and Nickel(II) Complexes of Polypodal
Phosphanes
Simon-Andreas Gentschowa, Stephan W. Kohla, Walter Bauerb, Frank W. Heinemannc,
Dennis Wiedemanna, and Andreas Grohmanna
a Technische Universita¨t Berlin, Institut fu¨r Chemie, Straße des 17. Juni 135, 10623 Berlin, Germany
b Universita¨t Erlangen-Nu¨rnberg, Department Chemie und Pharmazie, Organische Chemie,
Henkestraße 42, 91054 Erlangen, Germany
c Universita¨t Erlangen-Nu¨rnberg, Department Chemie und Pharmazie, Anorganische Chemie,
Egerlandstraße 1, 91058 Erlangen, Germany
Reprint requests to Prof. Dr. A. Grohmann. E-mail: andreas.grohmann@chem.tu-berlin.de
Z. Naturforsch. 2010, 65b, 238 – 250; received January 3, 2010
Dedicated to Professor Rolf W. Saalfrank on the occasion of his 70th birthday
A pyridine-derived tetraphosphane ligand (donor set: NP4) has been found to undergo re-
markably specific C–P bond cleavage reactions, thereby producing a ligand with an NP3 donor
set. The reaction may be reversed under suitable conditions, with regeneration of the origi-
nal NP4 ligand. In order to investigate the mechanism of this reaction, the NP3 donor ligand
C5H3N[CMe(CH2PMe2)2][CMe2(CH2PMe2)] (11) was prepared, and its iron(II) complex 4 gener-
ated from Fe(BF4)2 · 6 H2O, with methyl diethylphosphinite (7) as an additional monodentate ligand.
Ligand 11 has, in addition to the NP3 donor set, one methyl group in close contact with the iron
center, reminiscent of an agostic M···H–C interaction. Depending on the stoichiometric amount of
iron(II) salt, a side product 15 is formed, which has a diethylphosphane ligand instead of the phosphi-
nite 7 coordinated to iron(II). While attempts to deprotonate the metal-coordinated methyl group in 4
were unsuccessful, the reaction was shown to occur in an alternative complex (18), which is similar
to 4 but has a trimethylphosphane ligand instead of the phosphinite 7. The reaction of complex 15
with CO gave two different products, which were both characterized by single-crystal X-ray diffrac-
tion. One (19) is the dicarbonyl iron(II) complex of the triphosphane ligand 11, the other (3) is the
carbonyl iron(II) complex of the tetraphosphane C5H3N[CMe(CH2PMe2)2]2 (1). This suggests an
intermolecular mechanism for the C–P bond formation in question.
Key words: Bond Activation, N/P Ligands, Polypodal Ligands, Agostic Interaction, Iron, Nickel
Introduction
Fe(BF4)2 · 6 H2O and the pyridine-derived tetrapodal
tetraphosphane 1 in methanol proceeds with solvent-
induced cleavage of one C–PMe2 bond. Depending on
the reaction temperature, two different products are ob-
served: treatment of 1 with a stoichiometric amount of
the iron(II) salt in methanol at room temperature leads
to complex 2b, which has a methyl group in agostic
interaction with the iron center, while the analogous
Homogeneous catalysts are often transition metal
complexes with tertiary phosphane ligands (e. g.,
Wilkinson’s catalyst [1]). A known decomposition
reaction in such complexes is intramolecular C–H
bond activation, the best known example being or-
thometalation of a phenyl ring in arylphosphane lig-
ands [2]. The reaction proceeds by insertion of the
metal into a C–H bond of the ligand, and usually
deactivates the catalyst. A less frequently observed
type of side reaction is metal insertion into a C–P
bond of the ligand, sometimes initiated by the sol-
vent, which acts as a nucleophile [3]. We recently de-
scribed what appears to be the first solvent-induced
C–P bond cleavage in an alkylphosphane ligand [4, 5].
As outlined in Scheme 1, complex formation between
◦
procedure at −50 C forms complex 2a, which con-
tains a carbanionic methylene group. In both cases, a
monodentate phosphinite ligand Me2P(OMe), formed
from the cleaved PMe2 group and methanol, com-
pletes the coordination octahedron. While treatment
of 2b with CO does not lead to any well-defined prod-
ucts, compound 2a, under analogous conditions, re-
acts unexpectedly with reversion of the previous P–C
bond cleavage. This restores the original pentadentate
c
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
239
Scheme 1. P–C bond breaking and remaking reactions involving the pyridine-derived tetraphosphane ligand 1.
Scheme 2. Most likely products
(boxes) of the reaction of 5 with
CO, depending on whether the
reaction follows an intra- or in-
termolecular pathway.
NP4 ligand, giving complex 3. In terms of mechanism,
In order to elucidate the mechanism of this re-
the process may be intramolecular (and thereby entail action, we attempted to synthesize a “carbanionic”
breaking a P–O bond in the phosphinite ligand which complex similar to 2a, differing only in the phosphi-
is expected to be strong) or intermolecular (requir- nite ligand. Instead of methyl dimethylphosphinite, we
ing transfer of a PMe2 unit from a sacrificial second aimed to introduce a methyl diethylphosphinite lig-
molecule of the starting complex).
and (complex 4 in Scheme 2). If a tetrapodal pen-
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240
S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
tadentate phosphane ligand was to be produced from
this complex upon reaction with CO, in the same way
as shown in Scheme 1, we reasoned that for an in-
tramolecular process, the new NP4 ligand would con-
tain a diethylphosphanyl group in the place of one
of the dimethylphosphanyl groups in 1 (complex 6 in
Scheme 2) whereas, if complex 3 was detected, the
reaction would undoubtedly follow an intermolecular
pathway.
As complex 5 is not accessible along the route
that produces complex 2a, we chose to prepare
the permethylated triphosphane ligand C5H3N[CMe-
(CH2PMe2)2][CMe2(CH2PMe2)] (11), hoping to ob-
tain 4 from its complexation reaction with iron(II)
tetrafluoroborate hexahydrate in the presence of 1 eq.
methyl diethylphosphinite (7). Deprotonation of 4 was
then expected to provide access to the carbanionic lig-
and complex 5.
Scheme 5. Previous [9] (including compounds in brackets)
and modified synthetic route to LiPMe2 (14).
in an autoclave at 140 ◦C yielded the trialcohol
C5H3N[CMe(CH2OH)2][CMe2(CH2OH)] (8) as a col-
orless solid. The three pyridine protons show as an
ABC system in the 1H-NMR spectrum of 8 [δ =
7.66 ppm (t, 3J(H,H) = 7.9 Hz, 1 H, py-H3), 7.20 ppm
(d, 3J(H,H) = 8.0 Hz, 1 H, py-H2), 7.17 ppm (d,
3J(H,H) = 8.0 Hz, 1 H, py-H4)]. The hydroxyl groups
give rise to a broad signal at 4.14 ppm.
Results and Discussion
Whereas the preparation of 1 involves clean
tosylation of the corresponding tetraalcohol, tosy-
lation of the trialcohol does not proceed cleanly.
The required P ligands were synthesized in a first
step. Methyl diethylphosphinite (7) was prepared in
good yield (88%) from the reaction of equimolar
amounts of chlorodiethylphosphane, triethylamine and
methanol in pentane (Scheme 3).
The preparation of 11 followed the synthetic
route shown in Scheme 4. Unlike the route to
tetraphosphane 1 [4, 6, 7], the synthesis of triphos-
phane 11 starts from 2-ethyl-6-isopropyl-pyridine
(which we prepared as described by Wakatsuki
and Yamazaki [8]). Hydroxymethylation of the re-
active α-carbon atoms with aqueous formaldehyde
Attempted reactions of
8 using the combina-
tions TsCl/NaOH/THF/H2O, TsCl/KOH/THF and
TsCl/NEt3/dichloromethane gave only about 12 % of
the desired product, plus several types of unwanted
chlorides. We therefore prepared the trimesylate
C5H3N[CMe(CH2OMes)2][CMe2(CH2OMes)]
(9)
by reaction of 8 with methanesulfonyl chloride
and triethylamine in dichloromethane (yield: 9◦3 %).
9 was then treated with lithium bromide at 70 C in
DMSO to give the tribromide C5H3N[CMe(CH2Br)2]-
[CMe2(CH2Br)] (10). In the last step, 10 was
subsequently reacted with lithium dimethylphosphide
1
in diethyl ether at −78 ◦C, producing 11. The 31P{ H}-
NMR spectrum of the product shows two singlets
with a ratio of 2 : 1 at −62.06 and −61.84 ppm for
the non-equivalent P atoms of the dimethylphosphanyl
Scheme 3.
1
groups. In the H-NMR spectrum, there again is an
ABC spin system (t, d, d), due to the three pyridine
protons, and the non-equivalent ortho-carbon atoms of
the pyridine ring give rise to two signals (167.5 ppm,
1
165.8 ppm) in the 13C{ H}-NMR spectrum.
The established route to lithium dimethylphos-
phide (14) [9, 10] starts from thiophosphoryl chlo-
ride and goes through five reaction steps ending
in the conversion of dimethylphosphane with n-
butyllithium [11] (Scheme 5). We were able to
Scheme 4. Synthesis of the triphosphane 11 (stereochemical introduce a shortcut into the reaction sequence by
representation arbitrary).
converting tetramethyldiphosphane disulfide (12)
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
241
Fig. 1. Increase of side
products in the com-
plexation reaction pro-
ducing 4 as a func-
tion of the amount of
iron(II) salt employed
(1H-, 31P-NMR spec-
tra; signals due to side
products marked with
asterisks).
directly into two equivalents of dimethylphos- the amount of iron(II) salt employed. The 1H- and 31P-
phane (13) [12, 13], thereby avoiding the prepa- NMR traces summarized in Fig. 1 clearly demonstrate
ration of chlorodimethylphosphane sulfide and the correlation between the stoichiometry (amount of
chlorodimethylphosphane, and at the same time Fe(BF4)2 · 6 H2O used) and the formation of pure prod-
increasing the yield of 13 from 37 % to 83 % (based uct 4: only the desired complex 4 is formed when the
on tetramethyldiphosphane disulfide; see Scheme 5).
The subsequent complexation reaction of the
triphosphane 11 with Fe(BF4)2 · 6 H2O in the presence
of 1 eq. 7 produced complex 4. To our surprise, how-
ever, the selectivity of the reaction depends strongly on
ratio of 11 : 7 : iron(II) salt is 1 : 1 : 0.1. Most signifi-
cantly, there is a prominent and slightly broadened sig-
1
nal at high field (−3.7 ppm) in the H-NMR spec-
trum, which is characteristic of the methyl group in
close contact with the metal center. The broadening
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242
S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
Scheme 6.
Scheme 7. P–C bond break-
ing involving the triphos-
phane ligand 11 at nickel(II).
is presumably due to rotation of the methyl group, tion with 0.5 equivalents of iron salt in methanol gave
which is relatively slow on the NMR time scale. A dark-purple crystals of this side product (complex 15
doublet assignable to the phosphinite ligand is located in Scheme 6). While the crystals were of insufficient
at 3.82 ppm. The three protons on the pyridine ring quality for a full structure determination, the obtained
show up as an ABC spin system (triplet, doublet, dou- data allowed unambiguous clarification of the connec-
blet) between ca. 7.6 and 8.2 ppm, as is characteristic tivity in the complex. As deduced from the NMR spec-
for this asymmetrical molecule. The region between troscopic data, it contains the triphosphane ligand 11,
ca. 0.7 and 3.0 ppm shows the partially overlapping with one methyl group in contact with the metal. Un-
signals due to the six PMe2 groups, two methyl groups like complex 4, however, the monodentate P ligand at
and the three methylene groups. In the 31P-NMR spec- the sixth coordination site is diethylphosphane instead
trum, there is a total of four signals. The signal at about of methyl diethylphosphinite.
184 ppm is characteristic of the coordinated phosphi-
nite, and the other three signals, between ca. 10 and
50 ppm, are due to the coordinated triphosphane.
Apparently, when the amount of iron(II) salt is in-
creased, the reaction proceeds, at least in part, with
reduction of the phosphinite to a phosphane. Inter-
The more the amount of iron(II) salt used in the re- estingly, this reduction is not confined to iron(II) as
action is increased, the more we observe the formation the central metal, as a control experiment showed it
of an unexpected side product, with diagnostic signals to occur also when reacting the triphosphane 11 with
1
both in the H- and 31P-NMR spectra (Fig. 1; signals phosphinite 7 and nickel(II) tetrafluoroborate hexahy-
labeled with an asterisk). This product is expected to drate in methanol (Scheme 7). Isothermal diffusion
be very similar to the desired product 4, because it ap- of diethyl ether into a solution of the crude reaction
parently also contains a methyl group in the vicinity product in DMSO gave orange single crystals. Pre-
of the metal center (a second signal of growing inten- liminary X-ray data established the connectivity and
1
sity appears in the H-NMR spectrum at high field), allowed identification of the product 16 and, sepa-
and it apparently also contains the ligand 11 (there is rately, 17. Two details about this reaction merit par-
a second set of three signals in the 31P-NMR spectrum ticular mention.
between 10 to 50 ppm, whose intensity increases as the
proportion of iron salt is increased in the reaction). Fi-
nally, the reaction of equimolar amounts of 11, 7 and
iron salt seems to give more than one side product,
and both the 1H-NMR and the 31P-NMR spectra show
broadened signals.
Firstly, the reaction converts methyl diethylphos-
phinite to diethylphosphane, which is coordinated to
nickel(II). We are at this stage unable to offer an ex-
planation as to how this reduction proceeds. Simi-
lar reactions in the literature use metal hydrides [14]
or Birch conditions (Li solvated in NH3) [15]. It
Isothermal diffusion of diethyl ether into a solu- could be speculated that in our case insertion of the
tion of the product mixture obtained from the reac- metal center into a C–H bond of the phosphane lig-
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
243
˚
Table 1. Bond lengths (A) and angles (deg) in the nickel(II)
dication of 17 (standard deviations in parentheses).
Ni1–O1
Ni1–O2
2.044(4)
2.066(3)
O1–Ni1–O1
O1–Ni1–O2
O2–Ni1–O2
91.0(2), 91.0(2), 91.0(2)
86.5(2), 90.5(2), 177.1(2)
92.1(2), 92.1(2), 92.1(2)
Fig. 2. Molecular structure of the dicationic nickel(II) com-
plex in 17 in the crystal (only heteroatoms labeled for
clarity).
Scheme 8.
Despite varied efforts, deprotonation of complex 4
to give complex 5 could not be achieved, owing to
lability of the phosphinite ligand towards bases, as
monitored by NMR spectroscopy: the addition of base
causes the signals assigned to the phosphinite group
to disappear almost instantaneously, and the reaction
leads to undefined products. We therefore decided to
synthesize a complex similar to 4 but with a monoden-
tate phosphane ligand which we expected to be inert
towards base. We sought to determine whether such a
complex, with a methyl group in close (agostic) inter-
action with the metal atom, could be deprotonated at
all. The reaction of equimolar amounts of triphosphane
ligand 11, iron(II) salt and trimethylphosphane as co-
ligand in methanol gave pure complex 18 in 86 % yield
(Scheme 8).
and could produce a metal hydride, which could then
transfer H− to the phosphorus atom, to yield di-
ethylphosphane. This process would, however, require
oxidative addition at nickel(II), which appears un-
likely, as the hydride ligand is not expected to toler-
ate high nickel oxidation states. Secondly, the conver-
sion entails another C–P bond breaking event, as 16
is a square-planar nickel(II) complex in which the
newly formed NP2 ligand C5H3N[CMe2(CH2PMe2)]2
(“py(PMe2)2”) occupies three coordination sites, and
newly formed diethylphosphane the fourth. This ac-
tivation is most probably initiated by solvate wa-
ter of the nickel(II) precursor. In a parallel exper-
iment in methanol, isothermal diffusion of diethyl
ether into a solution of the crude reaction product
gave green-yellow single crystals. The X-ray struc-
ture analysis has revealed a nickel(II) complex of oc-
tahedral symmetry (17), whose structure is shown in
Fig. 2. Apparently, water (or hydroxide) cleaves a
PMe2 group to produce dimethylphosphinous acid,
Me2P(OH), six equivalents of which coordinate, in
the form of the more stable dimethylphosphane ox-
ide tautomer, to a nickel(II) center. All phosphorus-
bonded H atoms were located as electron density resid-
uals in difference Fourier maps at meaningful dis-
tances and angles relative to their respective P carrier
atoms.
1
Its H-NMR spectrum (Fig. 3) resembles the spec-
trum of 4. The pyridine protons give rise to an ABC
system (triplet, doublet, doublet) between ca. 7.6 and
8.2 ppm (see enlargement at left). The signal of the
agostic methyl group is located at −3.48 ppm. The
enlargement at right shows six doublets for the three
inequivalent PMe2 groups (each having a pair of di-
astereotopic Me groups), the doublet for the PMe3
group and the proton signals for the methyl and methy-
lene groups. The integrated intensities of all signals are
as expected.
The 31P-NMR spectrum (Fig. 4) shows four signals.
Table 1 gives a selection of bond lengths and The signal at ca. 15 ppm belongs to the coordinated
angles. The crystal system is trigonal (space group PMe3 ligand, and the other three signals belong to the
P31c, Z = 2). All Ni–O distances are in the expected three PMe2 groups of the triphosphane ligand. For a
˚
range, with values between 2.04 and 2.07 A [16]. more precise interpretation of the signals we simulated
The coordination geometry at nickel(II) is quite reg- the experimental spectrum. As shown in Fig. 4, agree-
ular.
ment is excellent.
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
Fig. 3. 1H-NMR spectrum ([D4]methanol]) of complex 18.
Table 2. Coupling constants (in Hz) in the 31P-NMR spec-
sired product. However, all attempts at its purification
failed, and complex 18 was thus unavailable for the in-
tended mechanistic study.
trum of 18.
Chemical shifts
(ppm)
P2
P3
P4
P1
As an alternative, we reacted complex 15 with ex-
cess CO, reasoning that reduction of CO (to give
formaldehyde) could transform, by dehydrogenation,
complex 15 into a more reactive species. The reaction,
which was performed in EtOH in an autoclave at 65 ◦C
over 4 h with a CO pressure of 10 bar, produced a yel-
low solid. Isothermal diffusion of diethyl ether into a
solution of the solid in acetonitrile and methanol gave
two kinds of single crystals (orange-yellow and yel-
low), which were suitable for analysis by single-crystal
X-ray diffraction. The crystals represent complexes 19
and 3 (Scheme 9).
P2
P3
P4
P1
45.98 (a)
23.40 (b)
15.07 (c)
14.34 (d)
–
–
–
–
–
–
–
–
–
–
−58.22 (ab)
−69.82 (ac) +39.33 (bc)
−65.17 (ad) −78.55 (bd) +37.29 (cd)
The extracted coupling constants (in Hz) with their
relative signs are listed in Table 2. The true signs are
unknown.
The trimethylphosphane ligand does confer suffi-
cient stability on complex 18 with respect to the re-
action with base, and H-NMR data indicate the de-
1
protonation of the methyl group to proceed as desired:
The signal of the agostic methyl group can be made
19 is the product of replacement of the agostic
disappear almost completely, while two new doublets methyl group and of the diethylphosphane ligand by
appear at 0.20 and 0.54 ppm, characteristic of the com- two equivalents of CO (Fig. 5). Complex 3, which con-
plex in which a carbanionic methylene group is coordi- tains the original tetraphosphane ligand 1, should only
nated directly to the iron(II) center [4]. The 31P-NMR be accessible by an intermolecular reaction, in which
spectrum also shows the signals expected for the de- the fourth PMe2 group is provided by a second equiv-
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
245
Fig. 4. Comparison of the experimental and simulated 31P-NMR spectra of 18.
Scheme 9. Two of the
products of the reaction
of 15 with excess CO,
as ascertained by single-
crystal X-ray analysis.
alent of complex. The NP3Pꢀ ligand that would be pro- 176.44(16)◦, Fe1–C20–O1 178.5(4)◦) and P2–Fe1–
duced in an intramolecular reaction, containing one C21–O2 (P2–Fe1–C21 173.53(13)◦, Fe1–C21–O2
PEt2 group, has not been found. Future work aims to 178.6(4)◦) are essentially linear. The iron-phosphorus
elucidate the exact mechanism of this reaction, and will and iron-nitrogen distances in this dicarbonyl complex
entail careful determination of yields in all cases.
Table 3 lists selected bond lengths and angles in 19.
The coordination geometry at iron(II) is distorted oc-
are generally longer than in other complexes of lig-
and 11, as formed by C–P bond cleavage [4, 5].
The crystal structure of complex 3 is equivalent to
tahedral. One of the two carbonyl ligands is trans to that of the monocarbonyl complex obtained by the re-
the nitrogen atom of the pyridine ring, and the other is action of 2a with CO, published in 2006 [4]. The co-
trans to P2, thereby giving a cis-dicarbonyliron moiety. ordination geometry at iron(II) is a severely distorted
Due to phosphorus being a better donor than nitrogen, octahedron, as expressed by the values of the nitrogen-
the bond Fe1–C21 is longer than the bond Fe1–C20. iron-phosphorus angles, which alternate between 80◦
The two arrangements N1–Fe–C20–O1 (N1–Fe–C20 and 100◦. The pyridine-iron-carbonyl fragment (N1–
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
˚
Table 3. Bond lengths (A) and angles (deg) in the dication of
Experimental Section
Materials and instrumentation
19 · 0.5 MeCN (standard deviations in parentheses).
Fe1–N1
Fe1–P2
Fe1–C20
N1–Fe1–C20
Fe1–C20–O1
P1–Fe1–P3
P2–Fe1–C21
2.166(3)
2.267(2)
1.752(4)
176.4(2)
178.5(4)
173.29(4)
173.5(2)
Fe1–P1
Fe1–P3
Fe1–C21
N1–Fe1–C21
Fe1–C21–O2
P2–Fe1–C20
2.300(2)
2.255(2)
1.812(4)
88.5(2)
178.6(4)
90.6(2)
Unless noted otherwise, all reactions were carried out at
r. t. in dried solvents under dry dinitrogen using standard
Schlenk techniques. Fe(BF4)2 · 6 H2O and Ni(BF4)2 · 6 H2O
were purchased from Aldrich and used without further pu-
rification. Carbon monoxide (99.997 %) was purchased from
Air Liquide.
IR spectra of solids were measured as KBr disks and
assigned on the basis of literature data [17]. Spectroscopic
data were obtained with the following instruments: IR spec-
troscopy: Nicolet Magna System 750; mass spectrometry:
Varian 311 A and Spektrospin CMS FT-ICR; NMR spec-
troscopy: Bruker ARX 200 and Bruker ARX 400. Signs of
1
coupling constants in the H, 13C and 31P spectra were not
determined. The superscripts for NMR assignments follow
the numbering scheme adopted for the X-ray crystal struc-
ture of 19 · 0.5 MeCN. Elemental analyses were carried out
with a Thermo Finnigan, Flash EA, 1112 Series analyzer.
[Fe(1)CO](BF ) (3)
4 2
A suspension of 15 (125 mg, 0.181 mmol) in ethanol
(8 mL) was reacted during 4 h with CO (10 bar) in an auto-
clave at 65 ◦C. The color of the solid changed from purple to
yellow. The autoclave was allowed to cool to room tempera-
ture, opened, and the suspension transferred into an empty
flask. The ethanol was then removed by syringe. The remain-
ing yellow powder was washed with diethyl ether (2×3 mL)
and dried in vacuo. Isothermal diffusion of diethyl ether into
a solution of the material in methanol gave a small crop of
single crystals of 3.
Fig. 5. Molecular structure of the dication in 19 · 0.5 MeCN
in the crystal.
Fe1–C22 177.55(8)◦, Fe1–C22–O1 177.5(2)◦) in this
monocarbonyl complex is again linear. The Fe–P and
the Fe–N distances are in good agreement with other
iron(II) complexes of 1 [5].
Conclusion
[Fe(11)(CH )(Et POMe)](BF ) (4)
3
2
4 2
The mechanism underlying the formation of the
tetraphosphane ligand 1 in the reaction of 2a with CO
remains elusive, owing to the lability of complex 5
towards base. The deprotonation of a methyl group
forced into close proximity to the metal is possible,
however, as shown for complex 18, gives a product
with a direct Fe–C bond. The synthesis of the phos-
phinite complex 4 is accompanied by reduction of the
phosphinite ligand to a phosphane ligand. This side
reaction becomes more prominent as the amount of
iron(II) salt is increased. Its product is complex 15,
which has a diethylphosphane ligand coordinated to
iron(II), in addition to the triphosphane 11. The re-
action of complex 15 with CO gave the dicarbonyl
iron(II) complex 19 and the monocarbonyl complex 3
as well-defined products. The formation of the latter
suggests an intermolecular reaction mechanism for the
generation of the tetraphosphane ligand.
A solution of Fe(BF4)2 · 6 H2O (36 mg, 0.106 mmol) in
methanol (3 mL) was added dropwise to a solution of 11
(394 mg, 1.06 mmol) and 7 (0.191 mL, 1.06 mmol, 10 eq.) in
methanol (4 mL), giving a purple solution. The mixture was
stirred for 30 min, then diethyl ether (10 mL) was added,
and a purple powder precipitated. The powder was filtered
off and washed with methanol (3 × 1 mL). It was dried
in vacuo yielding purple microcrystals (35 mg, 0.05 mmol,
1
46 %). – H NMR (200 MHz, [D4]methanol, r. t.): δ = 8.18
(t, 3J(H,H) = 8.0 Hz, 1 H, py-H3), 7.90 (d, 3J(H,H) = 8.6 Hz,
3
1 H, py-H2), 7.68 (d, J(H,H) = 8.0 Hz, 1 H, py-H4), 3.82
(m, 3 H, POCH3), 2.68, 2.34 (m/m, 2 H, CH27), 2.61, 2.24
(m/m, 2 H, CH28), 2.48, 2.18 (m/m, 2 H, CH210), 2.46 – 2.13
(br, 4 H, 2× PCH2), 1.99 (m, 3 H, PCH316), 1.88 (m, 3 H,
PCH317), 1.86 (s, 3 H, CH39), 1.68 (s, 3 H, CH311), 1.48 (m,
3 H, PCH318), 1.37 (m, 3 H, PCH319), 1.29 (t, 2J(H,H) =
5.5 Hz, 6 H, 2× PCH2CH3), 0.84 (m, 3 H, PCH314),
0.73 (m, 3 H, PCH315), −3.71 (s, 3 H, CH313) ppm. –
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
247
1
31P{ H} NMR (161.97 MHz, [D4]methanol, r. t.): δ =
C
C
10), 69.38 (s, 2 C, C7,8), 45.97 (s, 1 C, C6), 42.01 (s, 1 C,
184.69 (m, PEt2OMe), 46.37 (m, P2), 25.59 (m, P3), 13.59
12), 24.95 (s, 2 C, C11,13), 19.89 (s, 1 C, C9) ppm. – IR
(m, P1) ppm. – 13C NMR (100.64 MHz, [D4]methanol, r. t.): (KBr): ν = 3299vs (OH), 2961vs, 2873vs, 1577vs, 1461vs,
δ = 170.64 (s, py-C5), 169.13 (s, py-C1), 142.74 (s, py-C3), 1042vs, 1027vs, 756s cm−1. – EI-MS (70 eV): m/z (%) = 239
124.41 (s, py-C4), 123.96 (s, py-C2), 55.99 (m, POCH3), (100) [M]+. – C13H21NO3 (239.31): calcd. C 65.25, H 8.84,
44.91 (s, CCH36), 44.52 (s, CCH312), 43.46 (m, CH210), N 5.75; found C 64.97, H 8.80, N 5.67.
38.49 (m, CH27), 35.76 (m, CH28), 32.28 (m, PCH2), 31.45
˜
(m, PCH2), 28.32 (m, CH39), 27.26 (m, CH311), 25.36 (m,
C H N[CMe(CH OMes) ][CMe (CH OMes)] (9)
5
3
2
2
2
2
CH313), 23.27 (m, PCH318), 18.40 (m, PCH319), 16.57 (m,
PCH31174), 16.29 (m, PCH315 ), 15.03 (m, PCH316), 14.75 (m,
A solution of methanesulfonyl chloride (12.8 mL,
0.166 mol) in dichloromethane (50 mL) was added drop-
wise to a solution of 8 (11.0 g, 0.046 mol) and triethylamine
(29.2 mL, 0.207 mol) in dichloromethane (200 mL) at −2 ◦C.
The mixture was allowed to warm to r. t. and stirred for 1 h.
After washing with HCl (1 N, 50 mL), water (50 mL), sat-
urated aqueous Na2CO3 (50 mL), brine (50 mL), and again
water (50 mL), the dichloromethane phase was separated and
˜
PCH3 ), 9.02 (m, PCH2CH3) ppm. – IR (KBr): ν = 2974s,
2931s, 1575s, 1464s, 1309s, 1057vs (BF4−), 1030s, 939s,
913s, 762s cm−1. – C24H49B2F8FeNOP4 (721.00): calcd.
C 39.98, H 6.85, N 1.94; found C 40.18, H 6.46, N 2.04.
Methyl diethylphosphinite (7)
A solution of chlorodiethylphosphane (2.00 g, 0.016 mol) dried over Na2SO4. The solvent was removed under reduced
in pentane (15 mL) was added to a solution of triethylamine pressure, and the residue dried in vacuo to give a light-yellow
(2.32 mL, 0.016 mol) and methanol (0.66 mL, 0.016 mol) in oil (20.3 g, 93 %). – 1H NMR (200 MHz, [D1]chloroform,
pentane (10 mL) over 45 min at 0 ◦C. The resulting triethyl- r. t.): δ = 7.70 (t, 3J(H,H) = 8.0 Hz, 1 H, H3), 7.27 (d,
ammonium chloride was filtered off, and the solvent was re- 3J(H,H) = 7.9 Hz, 1 H, H2), 7.21 (d, 3J(H,H) = 7.9 Hz, 1 H,
moved from the filtrate by distillation. The crude product can H4), 4.63 – 4.52 (dd, AB, 2J(H,H) = 8.8 Hz, 4 H, H7,8), 4.47
◦
be purified by distillation (b. p.: 124 – 126 C, 1013 mbar). (s, 2 H, H10), 2.96 (s, 6 H, SO2-CH3), 2.86 (s, 3 H, SO2-
1
The product is a colorless liquid (1.66 g, 88 %). – H NMR CH3), 1.50 (s, 3 H, H9), 1.41 (s, 6 H, H11,13) ppm. – 13C
(200 MHz, [D1]chloroform, r. t.): δ = 3.45 (d, 3J(P,H) = NMR (50.32 MHz, [D1]chloroform, r. t.): δ = 163.36 (s, 1 C,
14.7 Hz, 3 H, OCH3), 1.50 (m, 4 H, CH2), 1.03 (m, 6 H, C1), 158.42 (s, 1 C, C5), 137.56 (s, 1 C, C3), 119.13 (s, 1 C,
CH3) ppm. – 31P NMR (161.97 MHz, [D1]chloroform, r. t.): C2), 118.86 (s, 1 C, C4), 77.64 (s, 1 C, C10), 72.74 (s, 2 C,
δ = 140.88 (s, PMe2) ppm.
C
7,8), 45.14 (s, 1 C, C6), 41.35 (s, 1 C, C12), 36.84 (s, 2 C,
SO2CH3), 36.74 (s, 1 C, SO2CH3), 24.57 (s, 2 C, C11,13),
9
˜
19.16 (s, 1 C, C ) ppm. – IR (KBr): ν = 3029vs, 2976vs,
C H N[CMe(CH OH) ][CMe (CH OH)] (8)
5
3
2
2
2
2
2941vs, 1578vs, 1352vs, 1172vs, 958vs, 528vs cm−1. – EI-
MS (70 eV): m/z (%) = 394 (100) [M–SO2CH3]+.
An autoclave (volume: 2.1 L) was charged with 2-ethyl-
6-isopropyl pyridine (50 g, 0.33 mol) and aqueous formalde-
hyde solution (37 %, stabilized with 10 % m◦ethanol, 250 mL,
3.30 mol), and the mixture heated to 140 C for 48 h. The
mixture was allowed to cool to r. t., the autoclave opened,
C H N[CMe(CH Br) ][CMe (CH Br)] (10)
5
3
2
2
2
2
Lithium bromide (5.17 g, 0.059 mol) was dried in vacuo
and water removed from the reaction mixture under reduced at 100 ◦C for 3 d and was then added to a◦solution of 9 (6.27 g,
pressure at 60 ◦C. Excess formaldehyde was removed by dry- 0.013 mol) in DMSO (150 mL) at 70 C. The mixture was
ing the yellow syrupy liquid for 24 h at 100 ◦C in vacuo. The stirred for 2 d at this temperature and was then allowed to
residue was taken up in chloroform (250 mL) and extracted cool to r. t. Water (200 mL) was added, and the milky liquid
with water (30×70 mL). The combined water extracts were stirred for another 30 min. After extraction with diethyl ether
brought to dryness under reduced pressure, and the residue (7×70 mL) the combined organic phases were washed with
◦
dried for another 48 h at 95 C in vacuo. After trituration water (3×50 mL) to remove excess DMSO. The ether phase
with diethyl ether (200 mL), the product was obtained as a was separated and dried over Na2SO4. The solvent was sub-
colorless powder, which was filtered off and dried in vacuo sequently removed under reduced pressure and the remain-
(27.7 g, 35 %). – 1H NMR (400 MHz, [D1]chloroform, r. t.): ing light-yellow oil dried in vacuo. Column chromatogra-
δ = 7.66 (t, 3J(H,H) = 7.9 Hz, 1 H, H3), 7.20 (d, 3J(H,H) = phy (SiO2, ethyl acetate/hexane 3 : 1) gave the product as
8.0 Hz, 1 H, H2), 7.17 (d, 3J(H,H) = 8.0 Hz, 1 H, H4), 4.14 a light-yellow oil (3.1 g, 56 %). – 1H NMR (200 MHz,
(br, 3 H, OH), 3.92 – 3.75 (dd, AB, 2J(H,H) = 11.2 Hz, 4 H, [D1]chloroform, r. t.): δ = 7.66 (t, 3J(H,H) = 7.9 Hz, 1 H,
H
7,8), 3.66 (s, 2 H, H10), 1.29 (s, 6 H, H11,13), 1.17 (s, 3 H, H3), 7.23 (d, 3J(H,H) = 7.9 Hz, 1 H, H2), 7.18 (d, 3J(H,H) =
2
H9) ppm. – 13C NMR (100.64 MHz, [D1]chloroform, r. t.): 7.9 Hz, 1 H, H4), 4.00 – 3.86 (dd, AB, J(H,H) = 10.0 Hz,
δ = 165.23 (s, 1 C, C1), 163.27 (s, 1 C, C5), 137.56 (s, 1 C, 4 H, H7,8), 3.80 (s, 2 H, H10), 1.63 (s, 3 H, H9), 1.49 (s, 6 H,
C3), 118.95 (s, 1 C, C2), 118.66 (s, 1 C, C4), 71.83 (s, 1 C,
H
11,13) ppm. – 13C NMR (50.32 MHz, [D1]chloroform, r. t.):
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248
S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
δ = 164.07 (s, 1 C, C1), 160.04 (s, 1 C, C5), 137.07 (s, 1 C, Dimethylphosphane (13)
C3), 118.48 (s, 1 C, C2), 118.36 (s, 1 C, C4), 46.01 (s, 2 C,
Procedure A
C
6,12), 42.10 (s, 3 C, C7,8,10), 26.63 (s, 2 C, C11,13), 23.09
9
A
solution of chlorodimethylphosphane (4.87 g,
˜
(s, 1 C, C ) ppm. – IR (KBr): ν = 2969vs, 2870m, 1576vs,
1458vs, 1423m, 1247vs, 750s cm−1. – EI-MS (70 eV): m/z
(%) = 416 (32) [M–CH3]+, 414 (98) [M–CH3]+, 412 (100)
[M–CH3]+, 410 (34) [M–CH3]+. – C13H18Br3 (428.00):
calcd. C 36.48, H 4.24, N 3.27; found C 36.53, H 4.40,
N 3.31.
◦
0.051 mmol) in diethyl ether (20 mL), cooled to 0 C, was
added to a suspension of LiAlH4 (2.3 g, 0.061 mmol, 1.2 eq.)
in diethyl ether (30 mL) at −78 ◦C. The mixture was stirred
for 2 h and subsequently allowed to warm to r. t. Product
and solvent were jointly distilled into an empty flask cooled
with liquid N2. Because of the very similar boiling points
of the solvent and the product, the product could not be
isolated, and the yield was not determined. The product was
used without further characterization in following reactions
which were calculated for 100 % yield.
C H N[CMe(CH PMe ) ][CMe (CH PMe )] (11)
5
3
2
2 2
2
2
2
A solution of 10 (4.2 g, 9.8 mmol) in diethyl ether (80 mL)
was added dropwise to a suspension of 14 (3.6 g, 34.3 mmol)
in diethyl ether at −78 ◦C over 2 h. The mixture was stirred
overnight at r. t. The solvent was removed by distillation and
the yellow residue treated with pentane (75 mL) and filtered.
The solution was then brought to dryness, giving a colorless
Procedure B
A solution of LiAlH4 (6.12 g, 0.161 mol, 2 eq.) in di-
ethyl ether (50 mL) was added to a suspension of 12 (15 g,
0.08 mol) in diethyl ether (150 mL) over 30 min. The mix-
ture was stirred overnight, with subsequent work-up as for
Procedure A.
1
oil (2.35 g, 64 %). – H NMR (200 MHz, [D1]chloroform,
r. t.): δ = 7.55 (t, 3J(H,H) = 7.8 Hz, 1 H, py-H3), 7.14 (d,
3J(H,H) = 7.9 Hz, 1 H, py-H2), 7.10 (d, J(H,H) = 7.9 Hz,
3
1 H, py-H4), 2.23 – 1.89 (ddd, AB, 2J(H,H) = 10.7 Hz,
2J(P,H) = 3.5 Hz, 4 H, H7,8), 1.93 (d, 2J(P,H) = 3.4 Hz, 2 H,
H
10), 1.59 (s, 3 H, H9), 1.45 (s, 6 H, H11,13), 0.92 – 0.69 (3×
Lithium dimethylphosphide (14)
d, 2J(P,H) = 3.2 Hz, 18 H, 6× PCH314,15,16,17,18,19) ppm. –
31P NMR (80.95 MHz, [D1]chloroform, r. t.): δ = −60.32
(s, 1× PMe2), –60.47 (s, 2× PMe2) ppm. – 13C NMR
(50.32 MHz, [D1]chloroform, r. t.): δ = 167.47 (s, 1 C, py-
C1), 165.83 (s, 1 C, py-C5), 136.81 (s, 1 C, py-C3), 118.17 (s,
1 C, py-C2), 117.48 (s, 1 C, py-C4), 49.50 (m, 3 C, C7,8,10),
44.73 (t, 1 C, C6), 41.59 (d, 1 C, C12), 29.63 (m, 2 C, C11,13),
26.48 (m, 1 C, C7), 16.18 (m, 6 C, PCH314,15,16,17,18,19) ppm.
A solution of n-butyllithium (2.5 M solution in hexane,
65 mL, 0.161 mol) was added to a solution of 13 (9.99 g,
0.161 mmol) in diethyl ether (50 mL) at −78 ◦C during 2 h.
The mixture was allowed to warm to r. t., depositing a col-
orless solid, and was stirred for 4 d at this temperature.
The colorless solid was filtered off and washed with diethyl
ether (3 × 20 mL). It was dried in vacuo to give a colorless
powder (14.1 g, 0.134 mol, 83 %). – 1H NMR (200 MHz,
[D8]thf, r. t.): δ = 1.27 (br, 6 H, CH3) ppm. – 13C NMR
(50.32 MHz, [D8]thf, r. t.): δ = 24.12 (d, 1J(C,P) = 38.5 Hz,
2 C, CH3) ppm. – 31P NMR (80.95 MHz, [D8]thf, r. t.): δ =
−58.11 (s, PMe2) ppm.
Tetramethyldiphosphane disulfide (12)
A solution of thiophosphorylchloride (33.5 mL, 0.33 mol)
in diethyl ether (50 mL) was added dropwise to a solu-
tion of methylmagnesium bromide (1 mol, 3 eq.) in diethyl
ether (500 mL) at −5 to −2 C. The mixture was stirred
◦
[Fe(11)(CH )(Et PH)](BF ) (15)
3
2
4 2
overnight at room temperature, after which time a color-
less solid had precipitated. The suspension was mixed with
H2O (100 mL) and was then added to a solution of concen-
trated H2SO4 (10 mL) in H2O (400 mL). The mixture was
stirred for 1 h. After filtration the colorless solid was washed
with H2O (3×25 mL) and diethyl ether (3×15 mL). It was
then dried in vacuo, yielding the product as a colorless solid
(20.9 g, 0.11 mol, 67 %). – 1H NMR (200 MHz, [D8]thf,
r. t.): δ = 1.89 (dd, 2J(P,H) = 12.2 Hz, 3J(P,H) = 4.8 Hz,
12 H, CH3) ppm. – 13C NMR (100.64 MHz, [D1]chloroform,
The procedure was the same as for the preparation of 4,
except that 0.5 eq. of Fe(BF4)2 · 6 H2O was used instead
of 0.1 eq. Isothermal diffusion of diethyl ether into a solution
of the resulting purple powder gave dark-purple single
crystals which were suitable for single-crystal diffraction
analysis.
[Ni(Et PH)(py(PMe ) )](BF ) (16)
2
2 2
4 2
1
2
r. t.): δ = 16.19 (dd, J(C,P) = 60.6 Hz, J(P,C) = 29.7 Hz,
A solution of Ni(BF4)2 · 6 H2O (90 mg, 0.264 mmol) in
4 C, CH3) ppm. – 31P NMR (80.95 MHz, [D8]thf, r. t.): δ = methanol (2 mL) was added to a solution of 11 (98 mg,
˜
33.30 (s, 2× PMe2) ppm. – IR (KBr): ν = 2968s, 2898s, 0.264 mmol) and 7 (0.047 mL, 0.264 mmol) in methanol
1402vs, 1283vs, 939vs, 882vs, 733vs (P=S), 568vs cm−1. – (3 mL). The mixture was stirred for 10 min, and an orange
EI-MS (70 eV): m/z (%) = 185 (100) [M–H]+. – C4H12P2S2 powder precipitated. The solution was transferred into an-
(186.22): calcd. C 25.80, H 6.60; found C 25.44, H 6.53.
other flask by syringe, and the remaining powder was washed
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S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
249
Table 4. Selected crystallographic data for 17 and 19 · 0.5
with methanol (2 × 2 mL) and dried in vacuo to yield an
orange microcrystalline powder (16, 12 mg). An isothermal
diffusion of diethyl ether into a solution of 16 in DMSO gave
orange single crystals which could be analyzed by single-
crystal diffraction.
MeCN.
17
19 · 0.5 MeCN
C22H37.5B2F8Fe-
N1.5O2P3
677.41
Molecular formula
C12H42B2F8-
NiO6P6
700.61
0.15×0.14×0.13
yellow
Mr
Crystal size, mm3
Color
0.32×0.18×0.10
yellow
[Ni{(O)P(H)Me } ](BF ) (17)
2 6
4 2
Crystal system
Space group
trigonal
P31c (no. 159)
11.7115(2)
11.7115(2)
12.4985(3)
90
90
120
1484.61(5)
2
1.57
monoclinic
P21 (no. 4)
9.995(2)
17.367(2)
17.904(2)
90
104.155(7)
90
3013.4(5)
4
1.49
0.7
1396
150(2)
A solution of Ni(BF4)2 · 6 H2O (90 mg, 0.264 mmol) in
methanol (2 mL) was added to a solution of 11 (98 mg,
0.264 mmol) and 7 (0.047 mL, 0.264 mmol) in methanol
(3 mL). The mixture was stirred for 10 min, during which
time an orange precipitate appeared. The mother liquor was
transferred into another flask by syringe and was treated with
diethyl ether to give a yellow powder. After removing the
mother liquor by syringe, the powder was washed with di-
ethyl ether (2×2 mL) an dried in vacuo to yield complex 17
as a yellow polycrystalline material. Isothermal diffusion of
diethyl ether into a solution of 17 in methanol gave a small
amount of green-yellow single crystals which were used in
the single-crystal diffraction analysis.
˚
a, A
˚
b, A
˚
c, A
α, deg
β, deg
γ, deg
˚
V, A
Z
Dc, g cm−3
µ, mm−1
F(000), e
T, K
1.1
724
150(2)
Absorption correction
Tmin/Tmax
Scan
SCALE 3 ABSPACK SADABS
0.897 / 1.000
ω
0.778 / 1.000
ϕ and ω, 2.0◦ and
30 s per frame
6.6 – 54.2
54796
[Fe(11)(CH )(PMe )](BF ) (18)
2θ range, deg
7.0 – 57.5
11098
3
3
4 2
Measured reflections
Unique reflections
Observed reflectionsa
Refined parameters
wR2 (all data)b
2354
2036
13199
10447
A solution of Fe(BF4)2 · 6 H2O (98 mg, 0.29 mmol)
in methanol (2 mL) was added dropwise to a solution
of 11 (108 mg, 0.29 mmol) and trimethylphosphane (22 mg,
0.03 mL, 0.29 mmol) in methanol (4 mL). Stirring the mix-
ture overnight produced a purple precipitate, which was fil-
tered off, washed with methanol (3 × 2 mL), and dried in
vacuo. Purple microcrystals (169 mg, 0.25 mmol, 86 %) were
obtained. – 1H NMR (400 MHz, [D4]methanol, r. t.): δ =
81
788
0.1233
0.0499
k = 0.0733 /
l = 0.5896
0.17(2)
0.997 / −0.450
0.1723
0.0613
k = 0.1322 /
l = 0
0.10(3)
1.701 / −0.501
2
R1 (obs. data)c
Weighting schemed
Abs. struct. parameter
−3
˚
ρfin (max./min.), e A
3
3
8.15 (t, J(H,H) = 7.8 Hz, 1 H, py-H3), 7.88 (d, J(H,H) =
8.5 Hz, 1 H, py-H2), 7.68 (d, 3J(H,H) = 8.1 Hz, 1 H,
py-H4), 2.69, 2.31 (m/m, 2 H, CH210), 2.42, 1.98 (m/m,
2 H, CH27), 2.27, 1.94 (m/m, 2 H, CH28), 2.01 (m, 3 H,
PCH316), 1.89 (m, 3 H, PCH317), 1.86 (s, 3 H, CH39),
1.68 (s, 3 H, CH311), 1.63 (d, 2J(P,H) = 8.8 Hz, 9 H, 3×
PCH3), 1.55 (m, 3 H, PCH318), 1.37 (m, 3 H, PCH319), 0.79
(m, 3 H, PCH314), 0.74 (m, 3 H, PCH315), –3.48 (s, 3 H,
CH313) ppm. – 31P NMR (161.97 MHz, [D4]methanol, r. t.):
δ = 45.98 (m, P2), 23.40 (m, P3), 15.07 (m, PMe3), 14.34
(m, P1) ppm. – 13C NMR (100.64 MHz, [D6]DMSO, r. t.):
δ = 168.15 (s, py-C5), 166.28 (s, py-C1), 139.75 (s, py-C3),
121.53 (s, py-C4), 121.15 (s, py-C2), 46.49 (m, CH28), 42.18
(s, 2× CCH36,12), 39.85 (m, CH27), 30.20 (m, CH210), 28.87
(s, CH39), 27.91 (s, CH313), 26.36 (s, CH311), 20.85 (m,
PCH318), 19.71 (m, 3× PCH3), 16.83 (m, PCH319), 15.99
(m, PCH31147), 15.33 (m, PCH316), 13.92 (m, PCH315), 12.87
a With Fo ≥ 4σ(F); b wR2 = [Σw(Fo −Fc2)2/Σw(Fo2)2]1/2
;
c R1 =
Σ Fo| − |Fc /Σ|Fo|; w = [σ2(Fo2) + (kP)2 + lP]−1, where P =
d
(Max(Fo2,0)+2Fc2)/3.
[Fe(11)(CO) ](BF ) (19)
2
4 2
A suspension of 15 (125 mg, 0.181 mmol) in ethanol
(8 mL) was reacted with CO (10 bar) in an autoclave at 65 ◦C
for 4 h. During this reaction the color of the solid changed
from purple to yellow. The suspension was transferred into
an empty flask and the ethanol removed by syringe. The
remaining yellow powder was washed with diethyl ether
(2 × 3 mL) and dried in vacuo. Isothermal diffusion of di-
ethyl ether into a solution of the material in acetonitrile gave
a small crop of single crystals of 19 which were used in the
single-crystal structure determination.
Crystal structure determination
˜
(m, PCH3 ) ppm. – IR (KBr): ν = 2961s, 2920s, 1602m,
1462s, 1293s, 1055vs (BF4−), 947s, 921s, 728s cm−1. –
X-Ray diffraction intensity data were collected on a
C22H45B2F8FeNP4 (676.95): calcd. C 39.03, H 6.70, N 2.07; Bruker-Nonius KappaCCD diffractometer (19 · 0.5 MeCN)
found C 39.06, H 6.65, N 2.10. and an Oxford Diffraction Xcalibur S Sapphire diffractome-
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250
S.-A. Gentschow et al. · Bond Activation in Iron(II) and Nickel(II) Complexes
ter (17). The structures were solved by Direct Methods us- crystallographic data for 17 and 19 · 0.5 MeCN are given
ing SHELXTL NT 6.10 (19 · 0.5 MeCN) and SHELXS-97 in Table 4.
(17). All non-hydrogen atoms were refined anisotropically.
CCDC 763852 (17) and CCDC 763853 (19 · 0.5 MeCN)
In 19 · 0.5 MeCN, the asymmetric unit contains two indepen- contain the supplementary crystallographic data for this pa-
dent molecules of the iron complex salt and one acetonitrile per. This data can be obtained free of charge from the
solvent molecule. Two of the four independent tetrafluoro- Cambridge Crystallographic Data Center via www.ccdc.cam.
borate counterions are disordered. In 17, the four tetrafluoro- ac.uk/data request/cif.
borate counterions per unit cell occupy special positions and
are highly disordered. They have consequently been treated
Acknowledgement
as a diffuse contribution to the overall scattering without
specific atom positions by SQUEEZE/PLATON [18]. Selected
Support by the Deutsche Forschungsgemeinschaft is
gratefully acknowledged.
[10] A. Trenkle, H. Vahrenkamp Inorg. Synth. 1982, 21,
180 – 181.
[1] J. F. Young, J. A. Osborne, F. A. Jardine, G. Wilkinson
Chem. Commun. 1965, 131 – 132.
[11] R. Uriarte, T. J. Mazanec, K. D. Tau, D. W. Meek Inorg.
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