Quasilinear 3d-metal(i) complexes [KM(N(Dipp)SiR3)2] (M = Cr-Co) - structural diversity, solution state behaviour and reactivity

Article abstract of DOI:10.1039/d1dt00121c

The synthesis and characterization of neutral quasilinear 3d-metal(i) complexes of chromium to cobalt of the type [KM(N(Dipp)SiMe₃)₂] (Dipp = 2,6-di-iso-propylphenyl) are reported. In solid state these metal(i) complexes either occur as isolated molecules (Co) or are part of a potassium ion linked 1D-coordination polymer (Cr-Fe). In solution the potassium cation is either ligated within the ligand sphere of the metal silylamide or is separated from the complex depending on the solvent. For iron, we showcase that it is possible to use sodium or lithium metal for the reduction of the metal(ii) precursor. However, in these cases the resulting iron(i) complexes can only be isolated upon cation separation using an appropriate crown-ether. Further, the neutral metal(i) complexes are used to introduce NBu₄⁺as an organic cation in the case of cobalt and iron. The impact of the intramolecular cation complexation was further demonstrated upon reaction with diphenyl acetylene which leads to bond formation processes and redox disproportionation instead of η²-alkyne complex formation.

Full text of DOI:10.1039/d1dt00121c

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Quasilinear 3d-metal(I) complexes [KM(N(Dipp)SiR ) ]
3
2
(
M = Cr–Co) – structural diversity, solution state
Cite this: Dalton Trans., 2021, 50,
890
4
behaviour and reactivity†
a
a
b
b
Ruth Weller, Igor Müller, Carine Duhayon,
Sylviane Sabo-Etienne,
b
a
Sébastien Bontemps
and C. Gunnar Werncke
*
The synthesis and characterization of neutral quasilinear 3d-metal(I) complexes of chromium to cobalt of
the type [KM(N(Dipp)SiMe ] (Dipp = 2,6-di-iso-propylphenyl) are reported. In solid state these metal(I)
3 2
)
complexes either occur as isolated molecules (Co) or are part of a potassium ion linked 1D-coordination
polymer (Cr–Fe). In solution the potassium cation is either ligated within the ligand sphere of the metal
silylamide or is separated from the complex depending on the solvent. For iron, we showcase that it is
possible to use sodium or lithium metal for the reduction of the metal(II) precursor. However, in these
cases the resulting iron(I) complexes can only be isolated upon cation separation using an appropriate
+
Received 13th January 2021,
Accepted 2nd March 2021
crown-ether. Further, the neutral metal(I) complexes are used to introduce NBu4 as an organic cation in
the case of cobalt and iron. The impact of the intramolecular cation complexation was further demon-
strated upon reaction with diphenyl acetylene which leads to bond formation processes and redox dispro-
DOI: 10.1039/d1dt00121c
2
rsc.li/dalton
portionation instead of η -alkyne complex formation.
higher than the expected spin-only values, due to unquenched
orbital momentum, as well as a strong magnetic anisotropy,
Complexes with two-coordinate, open-shell 3d-metal(I) ions, attributed to their (near) linear ligand arrangement.
Introduction
4
,13–15
known for chromium to nickel, are a young and rare class of Further, linear metal(I) complexes are shown to mediate intri-
1
,2–11
compounds in coordination chemistry.
They combine an guing bond activation processes like cleavage of H , P–aryl,
2
7
,9,10,16
uncommon coordination motif with an unusual oxidation and C–F bonds or trimerisation of alkynes.
The number
state. The isolation of such compounds relies mostly on the of homoleptic, linear metal(I) complexes bearing anionic
use of sterically encumbering and/or electronically stabilizing ligands is very limited, and restricted to silylmethanides and
ligands, such as bulky amides or N-heterocyclic carbenes. silylamides. For silylamides this gave so far few examples of
Thereby intramolecular dispersion forces are generally complex salts of the type [K{18c6}][M(N(Dipp)SiR ) ] (Cr – Cu;
3
2
thought to be crucial for their kinetic stabilisation of two-coor- 18c6 = 18-crown-6; Dipp = 2,6-di-iso-propylphenyl) or [K{m}][M
1
1,12
2,3,6,8,11
dinate metal ions.
Given the labile nature of two-coordi- (N(SiMe
3
)
2
)
2
] (Cr, Fe, Co; m = 18c6 or crypt.222).
Their
nate metal(I) complexes, the physical properties, as well as synthesis is achieved by reacting a two-coordinate metal(II) pre-
their reactivity concerning small molecules and various sub- cursor with potassium graphite in the presence of a cryptand
strates is only partially explored. Reports concerning their or crown-ether. The latter is generally thought to be needed to
respective behaviour indicate a high potential, e.g. remarkable sequestrate the cation, and by that to prevent decomposition
2
,4
single molecule magnetic properties. These stem from the of the homoleptic complex anion, which was demonstrated in
−
2
fact that these compounds can exhibit magnetic moments case of [Fe(N(SiMe
3 2 2
) ) ] . A notable exception was reported by
Tilley and co-workers in the case of the nickel(I) complex [KNi
5
(
N(Dipp)SiMe ) ], for which the monovalent state is compar-
3 2
ably stable. Here the potassium ion is ligated within the ligand
sphere (Fig. 1), leading to an overall neutral compound.
Given the fundamental interest of expanding the coordi-
nation chemistry of two-coordinate 3d-metal ions we wanted to
elucidate the synthesis of monovalent compounds of the type
a
Department of Chemistry, Philipps-University Marburg, Hans-Meerwein-Straße 4,
5
,6
D-35032 Marburg, Germany. E-mail: gunnar.werncke@chemie.uni-marburg.de
b
CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne,
3
1077 Toulouse and Université de Toulouse, UPS, INPT, 31077 Toulouse, France
1
†
Electronic supplementary information (ESI) available: H-NMR-, UV/Vis
spectra, crystallographic details. CCDC 2010651, 2010659, 2010661–2010666,
011200, 2011213, 2011333, 2011409, 2011410 and 2047637–2047641. For ESI
[
KM(L) ] of the earlier 3d-transition metals. The presence of an
2
2
unmasked alkali metal cation in the vicinity of a 3d-metal is pro-
spective of distinct reactivity due to synergistic effects, as shown
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
d1dt00121c
4890 | Dalton Trans., 2021, 50, 4890–4903
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Scheme 1 Synthesis of solvent and cryptand free [KM(L)
1–4) (Dipp = 2,6-di-iso-propylphenyl).
2
] (M = Cr–Co)
(
plexes, also revealing how the alkali metal ion is extracted in
donor solvents. First studies on the reactivity of [KM(L) ] com-
2
Fig. 1 Known anionic or neutral quasilinear open-shell 3d-metal(I) plexes towards diphenyl acetylene hint to the consequences of
silylamides.
the lack of persistent cation separation.
for example for low-coordinate alkali metal ferrates or manga-
nates, may labilise the 3d-metal–amide bond or can be used
for introduction of further functionalities or other cations.
Results and discussion
17
Synthesis and structure of [KM(L) ] complexes
2
1
i
Herein we report the isolation of quasilinear complexes of The quasilinear metal(II) complexes [M(L) ] (L = N(Dipp)Si Pr
2
3
1
i
2
5
2
the type [KM(L) ] (L = N(Dipp)Si Pr (Cr); L = N(Dipp)SiMe
3
(Cr, due to reported instability of the SiMe derivative); L =
2
3
3
(
Mn – Co)), with intra- or intermolecular complexation of the N(Dipp)SiMe (Mn – Co)) were reacted with 1.1 equivalent KC
3
8
potassium cation, leading to unusual coordination polymers in toluene at room temperature (Scheme 1) leading to an
bearing open-shell, two-coordinate metal(I) ions. For iron we instantaneous change of colour in each case (Cr: dark red →
showcase the first use of lithium or sodium metal as reductants, red; Mn: colourless → dark violet; Fe: red → greenish brown;
whereas respective compounds are unstable and have to be Co: red violet → green). Crystalline material was obtained from
stabilized by masking of the alkali metal cation. In due course a diffusion of n-pentane into a toluene solution of each com-
1
2
large structural variety of the ligand arrangement within the pound at −40 °C giving green [KCr(L ) ], 1, violet [KMn(L ) ],
2
2
2
2
quasilinear silyl amide complexes can be observed that depends 2, red brown [KFe(L ) ], 3, and green [K(toluene)Co(L ) ], 4.
2
2
on interligand as well as cation⋯anion interactions. We provide X-Ray diffraction analysis of compounds revealed for com-
insights into the solution state dependence of the [KM(L) ] com- pounds 1–3 a polymeric structure (Fig. 2), where formally [M
2
Fig. 2 Sections of the crystal structure of 1 (top left), 2 (top right), 3 (bottom left) and 4 (bottom right). H atoms are omitted for clarity. For com-
pounds 1–3 the amide unit of neighbouring complex molecules is shown.
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L)
Dalton Transactions
(
2
]− anions are linked via potassium cations, which are situ- a torsion angle of 60(2)°, the rings are standing more or less
ated between the aryl rings of two neighbouring molecules. trans to each other in 2 (161.68(14)°) and 3 (123.65(15)°).
The potassium ion are located at the outer (1, Cr), inner and These large differences originate likely from respective aryl–K
outer (2, Mn) or inner (3, Fe) side of the respective aryl ring. In interaction as well as inter- or intramolecular dispersion forces
case of compound 3 (Fe), the potassium ion is situated directly between an iso-propyl group and an aryl ring of a second
between two aryl rings with no apparent Fe⋯K interaction (Fe– ligand. In the cobalt complex 4, the aryl rings of both ligands
K 4.3564(3) Å), whereas in 2 (Mn) it is clearly oriented towards are facing each other (torsion angle of 1.22(23)°) which is
the transition metal (Mn–K 3.8423(5) Å). These structural fea- enforced by the potassium ion. The intramolecular K⋯arene
tures lead to a zig-zag 1D-polymer chain for 2 (Mn) and 3 (Fe), distances in 4 are with 3.1419(7) Å longer than in polymeric
and a more linear chain for 1 (Cr). This is also reflected by the 1–3 (approx. 2.8 Å), probably due to the enforced proximity of
intermolecular M–M′ distances, which gives for 1 (Cr) a Cr–Cr′ opposing iso-propyl groups. Together with literature known [M
2
−
2
distance of 12.4099(9) Å within and of 9.9095(8) Å between the (L ) ] complexes, as well as further examples presented below,
chains (Table 1). For 2 (Mn) and 3 (Fe), the situation is inverse it reveals a rotational flexibility of the amide ligands around
with shorter intra- (2: 9.8350(5) Å; 3: 8.7128(5) Å) than inter- the N–M–N axis. This structural diversity contrasts the situ-
chain M–M′ distances (2: 11.0784(5) Å; 3: 11.6773(6) Å). The ation of the divalent precursors which exhibit a (symmetry gen-
1
8
chain-like arrangement in solid state for compounds 1–3 is a erated) linear N–M–N axis with trans-oriented aryl rings only.
so far unknown feature of complexes with open-shell, two- As such, the amide ligand orientation is dictated by K-arene
coordinate transition metal ions. It contrasts the situation of and not by interligand dispersion interactions via CH ⋯arene
3
5
the related [KNi(L)
2
], where the potassium ion is ligated in an or CH
3
3
⋯CH units.
intramolecular fashion. Such a situation is observed for the
cobalt derivative 4 (Co), where a toluene molecule is complet-
ing the coordination sphere of the potassium ion (Co–K dis-
Solution state behaviour of [KM(L) ] complexes
2
1
H NMR spectroscopy. Given the observed structural varia-
tance of 3.5652(6) Å). The N–M–N bond angles within the poly- bility of compounds 1–4 in solid state and their envisioned use
meric compounds are almost linear in the case of chromium for substrate activation, we sought further insights into their
(
177.44(10)°, 1) and slightly bent in manganese (165.56(6)°, 2) behaviour in solution with respect to the potassium cation spe-
and iron (170.59(5)°, 3). For the monomeric cobalt compound ciation. Thereby it is important to note that 1–4 are highly
, the N–Co–N bond angle amounts to 178.43(8)°. The M–N soluble in toluene or Et O, contrasting the congeners with
4
2
bond lengths shorten along the series from ca. 2.07 Å (1, Cr) to 18-crown-6 masked potassium cations (only slightly soluble in
1
1
.96 Å (2, Mn) and down to 1.88 Å (4, Co).
Et O). All complexes were first examined by H NMR spec-
2
A large variety was observed for the Caryl–N–N′–C′aryl torsion troscopy in non-coordinating C D revealing their paramag-
6
6
angles (Table 1). While in 1 the opposing aryl rings twist with netic nature by strongly shifted (in comparison with their
2
Table 1 Selected structural metrics of compounds 1–9 (L = –N(Dipp)SiMe
3
)
Metal
Cr
Compound
M–N1/Å
M–N2/Å
M–M′/Å
N1–M–N2/°
Torsion angle/°
59.97(23)
Shortest, interligand C–C distance
3.719(4) (CH3(Si
a
1
2.076(2)
2.070(2)
9.9095(8)
177.44(10)
i
i
Pr3)
Pr3)⋯CHMe2(Si )
12.4099(9)
3.796(3) (Ph⋯CH3(Dipp)
.680(4) (CH3(Dipp)⋯CHMe2(Si
3.954(2) (CH3(Si Pr3)⋯CH3(Si
.536(1) (Ph⋯CH3(Dipp)
)
3
i
Pr3)
)
5
2
2.0576(14)
1.9653(16)
1.961(3)
2.0528(14)
1.9681(15)
1.954(3)
11.1564(9)
9.8350(5)
174.12(5)
165.56(6)
167.12(14)
170.59(5)
42.41(12)
161.68(14)
49.1(2)
i
i
Pr3)
)
3
)
Mn
Fe
3.979(2) (Ph⋯CH3(SiMe3)
)
a
11.0784(5)
2
8
[
K{18c6}][Mn(L )
2
]
10.8687(11)
3.867(5) (Ph⋯CH3(SiMe3)
)
4
.661(7) (CH3(SiMe3)⋯CH3(SiMe3))
3
1.9005(15)
1.9014(13)
8.7128(5)
123.65(15)
4.139(3) (CH3(Dipp)⋯CH3(SiMe3)
)
a
11.6773(6)
b
b
3·2DMAP
1.9121(3)
1.911(3)
1.9121(3)
10.7640(19)
10.5043(9)
180
16.8(3)
148.9(3)
4.469(7) (CH3(SiMe3)⋯CH3(SiMe3))
6
1.915(3)
1.903(4)
1.918(2)
175.34(13)
170.82(14)
175.27(7)
4.825(5) (Ph⋯CH3(SiMe3)
.200(10) (CH3(Dipp)⋯CH3(SiMe3)
3.804(9) (CH3(Dipp)⋯CH3(Dipp)
.136(9) (CH3(SiMe3)⋯CH3(SiMe3)
)
4
)
7
8
1.894(4)
1.915(2)
11.518(2)
7.0(4)
)
4
)
10.8837(18)
111.35(17)
4
3.604(2) (Bu N⋯Ph)
4
.089(4) (CH3(Dipp)⋯CH3(SiMe3)
)
2
3
[
K{18c6}][Fe(L )
2
]
1.9135(14)
1.8787(23)
1.9147(14)
1.8782(24)
10.625(17)
7.7857(8)
172.65(6)
178.43(8)
95.05(15)
1.22(23)
3.936(2) (CH3(Dipp)⋯SiCH
3
)
Co
4
3.416(4) (CH3(Dipp)⋯CH3(Dipp)
)
4
.391(5) (CH3(SiMe3)⋯CH3(SiMe3)
)
9
1.878(2)
1.884(2)
11.1161(7)
176.28(10)
3.93(25)
3.500(3) (Bu
4
N⋯Ph)
3
4
.497(4) (CH3(Dipp)⋯CH3(Dipp)
)
.121(4) (CH3(SiMe3)⋯CH3(SiMe3)
)
2
3
b
b
b
[
K{18c6}][Co(L )
2
]
1.8835(10)
1.8835(10)
10.5574(6)
180
180
3.951(2) (CH3(Dipp)⋯CH3(SiMe3))
a
b
M–M′ distances along the 1D chain. Generated via a crystallographic inversion centre on the metal atom.
4892 | Dalton Trans., 2021, 50, 4890–4903
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1
i
Table 2 H NMR signals of the complex anions of 1–9 with R = Pr (Cr), Me (Mn–Co) in ppm. The signal(s) belonging to the K{18c6} or NBu
4
cations
are found around their diamagnetic positions
Metal
Cr
Compound
solvent
SiR
3
CH
3
CHMe
2
m-Ph
p-Ph
1
6 6
C D
6.81
No signal attribution possible
THF-d
THF-d
8
No signal attribution possible
No signal attribution possible
No signal attribution possible
−1.65
−0.09
−3.63
−1.03
−0.49
—
5
2
3
8
Mn
Fe
C
C
6
D
D
6
/THF-d
8
6
6
−78.0/39.7
−103.1/—
−78.6/39.4
−99.8/—
−102.2/—
−102.3/—
−72.3/29.3
−86.5/17.7
−88.0/17.4
59.3
—
—
—
—
—
5.79
29.7
30.1
23.4
—
26.6
—
—
—
21.4
16.5
16.0
4.33
—
19.4
—
—
—
9.26
4.27
7.31
THF-d
8
3
6
7
8
4
·2DMAP
C
D
6 6
THF-d
THF-d
THF-d
8
8
8
Co
Toluene-d
8
3.67
13.9
14.0
THF-d
THF-d
8
9
8
expected diamagnetic signal position) and broadened proton shifted downfield by approx. 10 ppm to 13.9 ppm, signals of
signals. The paramagnetic shift comes primarily from inter- the methyl groups of the Dipp-units are shifted by around
actions of the respective proton with the metal(I) ion via 12 ppm to higher field and are found at −86.5 ppm and
through-bond (contact shift) and through-space (pseudo- 17.7 ppm, respectively (toluene-d
8
: −72.3, 29.3 ppm). The spec-
is thereby analogous to the one
were thus hampered (Table 2), e.g. for chromium (1) and obtained for the potassium ion separated complex [K
1
9
contact shift) interactions. In some cases, signal assignments trum of 4 (Co) in THF-d
8
2
7
2 8
manganese (2) only very broad signatures were detected. The {18c6}][Co(L ) ] (THF-d , Fig. S19†), speaking to the complete
proton spectra of 3 (iron, Fig. S5†) and especially 4 (cobalt, solvation of the potassium ion by THF. Thereby, the process of
Fig. 3, left) are better behaved allowing for signal assignment the extraction of the potassium ion by THF requires a large
via signal positions and integral intensities (Table 2). In 4, excess of THF as addition of up to 20 equivalents of THF to a
1
which shows rather sharp signatures, the signal belonging to toluene-d
8
solution of 4 (Co) led just to a slight shift of its H
the SiMe fragment in 4 is found at 3.67 ppm whereas the iso- proton signals. In contrast, upon Et O addition no shifting
3
2
propyl groups give rise to two signals at −72.3 and 29.3 ppm. signals were observed, even using pure Et
Looking at the solid state structure the latter two signals likely weak ability of THF and inability of Et O to fully solvate the
represents the inward and outward positioned methyl func- potassium cation. At low temperatures, the spectra of 4 in
tions of each iso-propyl group, suggesting suppression of the THF-d and toluene-d did not coincide (Fig. S20 and S22†),
2
O. This reflects the
2
8
8
free rotation of the iso-propyl groups in solution. The huge which indicated a persistent diverging potassium cation spe-
paramagnetic shift difference between these two signals is ciation between these solvents. All paramagnetic signals of 4
remarkable and likely comes from pseudo-contact interactions, (Co) follow the Curie–Weiss law (δ(T) ∼ 1/T) in THF-d
given the identical bond connection but different spacial dis- (Fig. S23†) as well as in toluene-d (Fig. S21†). Together with
8
8
2
,8
tances to the metal ion (average d(Co–C ) 4.3 Å vs. d(Co–Cout) the absence of signal splitting, this showed that, like the
in
5
.1 Å). Together with differences in line-broadening it suggests cation/anion interaction, the electronic situation and complex
that the stronger paramagnetically influenced signal at geometry remained unchanged over the examined temperature
72.3 ppm belongs to the inward oriented methyl group and range.
that the pseudo-contact and contact shifts have opposing With these results for 4 (Co) in mind, the solvent dependen-
−
1
signs. The meta-positioned protons of the aromatic systems cies of the H NMR signals were also examined for complexes
are shifted downfield to 21.4 ppm, whereas the impact of the 1 (Cr), 2 (Mn) and 3 (Fe). For all three compounds similar the
paramagnetic centre to the para-positioned ones (9.26 ppm) spectra in toluene-d
8
or C
6
D
6
(also in Et
. The latter are thereby identi-
again strongly broadened due to the proximity of the cobalt(I) cal to the H NMR spectra of the [K{18c6}][M(L) ] complexes
2
O for 3) differed sig-
are weaker. The signal of the methine protons (5.79 ppm) are nificantly from those in THF-d
8
1
2
1
1
ion. Given the well-behaved H NMR spectrum of 4 (Co), we (Table 2), whereas [K{18c6}][Cr(L )
2
], 5, had to be synthesized
3
,6,8
1
conducted further experiments to get qualitative insights into first.
the speciation in solution, especially with respect to the compounds that in non/weakly-coordinating solvents the K
location of the potassium ion (within the complex or as separ- cation is likely connected to the complex anion, presumably
ated cation). The switch to the coordinating solvent THF-d residing between the aryl rings as in the solid state structure of
impacted significantly the signal positions in comparison to 4, whereas in THF it is present as a solvent-separated counter-
the non-coordinating solvent toluene-d (Fig. 3, right). The ion.
highest impact of changing the solvent was detected for the UV/Vis spectroscopy. Given the observed H NMR spectro-
methine protons, which are now found at 29.7 ppm (Δδ = scopic features of compounds 1–4, a variable-temperature UV/
6 ppm). While the signal of the trimethylsilyl protons is Vis spectroscopic analysis was conducted. In case of the chro-
Overall, H NMR spectroscopy showed for the [KML
2
]
+
8
8
1
2
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1
#
8 8
Fig. 3 H NMR spectrum (500.1 MHz, 300 K) of 4 in toluene-d (left (A), * solvent, n-pentane) and THF-d (right (B), ^ impurities).
mium compound 1, a UV/Vis spectrum recorded in THF
−
1
showed three absorption bands at 286 nm (ε > 7930 L mol
−
1
−1
−1
cm ), 343 nm (ε = 4440 L mol cm ) and 426 nm (ε = 3320 L
mol cm ). These bands can be ascribed to ligand to metal
−
1
−1
3
,12
charge transfer (LMCT) transitions (Table 3),
and mimic
those of 5 (Cr). When switching to toluene or Et O only one
2
absorption maximum was observed for 1 (Cr) (toluene:
−
1
−1
4
31 nm, ε ≈ 5210 L mol cm ; Et O: 435 nm, ε ≈ 6940 L
2
−
1
−1
mol cm ), speaking for a similar electronic situation for 1
in these two solvents. Cooling the respective solutions to
−
110 °C had no significant effect. For 2 (Mn) examinations
were restricted to diethyl ether, due to decomposition in
toluene and THF under these dilute conditions. Two absorp- 22 °C.
Fig. 4 UV/Vis spectrum (290–700 nm) of 3 in different solvents at
−1
−1
tion maxima at 448 nm (ε ≈ 1610 L mol cm ) and 565 nm
−
1
−1
(
[
2
7
ε ≈ 2410 L mol cm ) were observed that superpose those of
2
8
K{18c6}][MnL ]. For complex 3 (Fe) maxima at 421 nm (ε =
2
whose positions are akin to the ones found for [K{18c6}][Fe
120 L mol− cm ), 610 nm (ε = 160 L mol cm ) and
1
−1
−1
−1
3
2 2
(L ) ]. The latter two maxima are tentatively assigned to d–d
−
1
−1
3
,12
73 nm (ε = 120 L mol cm ) were observed in THF (Fig. 4),
transitions.
When switching to toluene as solvent, both
2
2
Table 3 UV/Vis absorption maxima of 1–9 and [K{18c6}][M(L )
2
] (M = Fe, Co, L = –N(Dipp)SiMe
3
); 280–900 nm, (RT)
1
Metal
Cr
Compounds
Solvent
λ(ε)/nm(L mol− cm−1
)
1
Toluene
THF
431 (5210)
286 (>7930), 343 (4440), 426 (3320)
435 (6940)
288 (7710), 338 (3880), 421 (2160)
448 (1610), 565 (2410), 849 (2650)
368 (3380), 432 (3490), 602 (140)
421 (2120), 610 (160), 773 (120)
442 (1540), 601 (100)
Et
THF
Et
2
O
5
2
3
Mn
Fe
2
O
Toluene
THF
Et O
2
3
6
7
8
·2DMAP
Toluene
THF
THF
THF
THF
360 (3230), 434 (3190), 607 (130)
422 (1990), 771 (170)
420 (5020), 613 (320), 771 (260)
364 (1660), 420 (1900)
2
2
3
[
K{18c6}][FeL
]
428 (4000), 626 (100)
Co
4
Toluene
THF
385 (3080)
336 (2800), 385 (2300)
Et
THF
THF
2
O
393 (3560)
340 (4770), 390 (4120)
337 (2380), 391 (2030), 629 (100)
9
2
2
a 3
[
K{18c6}][CoL
]
a
UV/Vis spectrum was recorded but no absorption coefficients were given in the original report.
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−
1
cm−1) and highly challenging as small amounts of donor solvents such as
LMCT bands at 368 nm (ε ≈ 3380 L mol
4
−1
−1
32 nm (ε ≈ 3490 L mol
absorption maxima. Cooling these solutions down to compounds 1–4 even in n-pentane, indicative of solvent coordi-
110 °C had no considerable effect on the position of the nation. Upon rigorous drying of respective solutions, the
cm ) appear as two distinct Et O or THF lead to a very high solubility of the respective
2
−
transitions. The UV/Vis spectrum of 3 (Fe) in Et O resembled donor solvents could be removed as these complexes were
2
the one in THF with a LMCT band at 442 nm (ε ≈ 1540 L again insoluble in n-pentane. Nonetheless, in due course we
−
1
−1
mol cm ) and a d–d transition at 601 nm (ε ≈ 100 L could identify for iron the highly soluble diethyl ether adduct
−
1
cm−1). Upon cooling this solution to −110 °C the 3·Et O (Fe) using X-ray diffraction analysis (Fig. 5, left). As the
mol
reversible disappearance of the LMCT band could be crystal data suffers from some flaws, its general features are
observed, whose origin is yet unclear. only shortly discussed. In 3·Et O (Fe) the potassium cation is
The UV/Vis spectrum of 4 (Co) in toluene exhibited one coordinated in an intramolecular fashion by the two aryl rings,
2
2
−
1
−1
2
5
LMCT band at 385 nm (ε ≈ 3080 L mol cm ) which splits at as observed for 4 (Co) and [KNiL
2
]. It thus shows how the
polymeric form is transformed to a monomer in solution. A
and 410 nm (ε ≈ 3850 L mol cm ). Measurements in THF diethyl ether molecule completes the coordination sphere of
−
1
−1
−
110 °C into two bands at 387 nm (ε ≈ 3910 L mol cm )
−
1
−1
−
1
showed two absorption bands at 336 nm (ε ≈ 2800 L mol
the potassium ion. As a result of the intramolecular potassium
cm ) and 385 nm (ε ≈ 2300 L mol−1 cm ) at room tempera- cation fixation the N–Fe–N bond axis is nearly linear with a
−
1
−1
ture, which is comparable to the UV/Vis spectrum of [K negligible C –N–N′–C′ torsion angle. Given the difficulties in
Ar
Ar
3
{
18c6}][Co(L
2
)
2
]. A UV/Vis spectrum of 4 (Co) in diethyl ether the crystallization progresses, which we attributed to the vola-
O in conjunction with the high solu-
d–d transitions (ε < 100 L mol cm ) above 600 nm. Cooling bility of 3·Et O (Fe), we used DMAP as an exemplary donor
showed a broad band at 393 nm with additional low-intensity tility of the employed Et
2
−
1
−1
2
a solution of 4 (Co) in THF or Et
2
O had no considerable effect ligand. This gave the stable adduct 3·2DMAP (Fe) (Fig. 5,
onto its UV/Vis spectroscopic properties. Overall the UV/Vis middle) as green crystals in yields up to 75%. Similar to 3·Et
2
O
spectroscopic examinations showed markedly different spectra (Fe), the potassium cation is located between the two aryl rings
for complexes 1 (Cr), 3 (Fe) and 4 (Co) for either THF or in an intramolecular fashion and is further coordinated by two
toluene solutions. Thereby the spectra in THF coincided with DMAP molecules. Looking at the UV/Vis spectrum of
1
those of cation separated complexes mimicking the H NMR 3·2DMAP, two distinct LMCT bands at 360 nm (ε ≈ 3230 L
−
1
−1
−1
−1
spectroscopic results. In Et O the UV/Vis spectroscopic situ- mol cm ) and 434 nm (ε ≈ 3190 L mol cm ) are present.
2
ation is ambiguous. Whereas for 1 and 4 the respective spectra This mimics the behaviour of pure 3 in toluene, corroborating
resembled those in toluene, implicating that the potassium for the latter a persistent intramolecular potassium cation
ion is also not separated from the complex anion, for the iron complexation. For chromium, the monomeric complex 1·3THF
complex 3 the spectroscopic features in Et O are similar to (Cr) was obtained as revealed by X-ray diffraction analysis. In
2
those in THF. As this is not in line with the NMR spectroscopic 1·3THF (Cr) the potassium cation resides on the external side
observations, it speaks for an additional solvent effect, such as of one of the aryl rings of the silylamide ligand set with three
solvent coordination.
tetrahydrofuran molecules completing its coordination sphere.
Together with 3·Et O (Fe) and 3·2DMAP (Fe), 1·3THF (Cr) thus
gives insight on how the potassium cation is extracted out of
2
Structural effects of donor solvents on [KM(L) ] complexes
2
1
Having observed the H NMR and UV/Vis spectroscopic the aryl pocket of the [KM(L)
2
] complexes upon addition of
changes for complexes 1–4 when going from non-coordinating donor solvents. Remarkably, no coordination of donor solvent
to coordinating solvents, we were interested if this could be molecules to the 3d-metal ion takes place, which is observed
2
0
somewhat retraced on a structural level. This turned out to be for their divalent counterparts.
2
Fig. 5 Sections of the crystal structure of 3·Et O (left), 3·2DMAP (middle) and 1·3THF (right). H atoms are omitted for clarity. In case of 1·3THF dis-
orders found for one THF molecule as well as for two iso-propyl groups are not depicted.
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+
Sodium, lithium and NBu
4
as counter ions
The synthesis of homoleptic quasilinear metal(I) silylamides
was so far exclusively approached using potassium graphite as
the reductant. In view of the different solid state structures of
the neutral compounds we wanted to introduce lithium and Scheme 3 Introduction of the organic cation NBu4 in [NBu ][M(L ) ]
sodium as reductants for such complexes, as these smaller
+
2
4
2
2
(
M = Fe (8), Co (9), L = N(Dipp)SiMe
3
).
ions might enforce a different solid or solution state behav-
iour. To probe this possibility we chose the iron derivative as a
2
1
representative. Treatment of [Fe(L )
2
] with lithium or sodium netic H NMR spectra in THF-d
8
for both 6 and 7 resembled
]. Similar to the extraction of the
rapid (Na) colour change from orange/red to brownish green alkali metal ion by crown-ethers, we also wanted to use the
2
1
2
(
5% Na dispersed in NaCl) led to a slow (Li), respectively those of [K{18c6}][Fe(L )
2
(
Scheme 2). Attempts to obtain the presumed neutral reaction [KM(L)
2
] complexes to introduce an organic cation (Scheme 3).
2
products [AFe(L ) ] (A = Li, Na) led to their decomposition. This was already shown in case of the related nickel complex
2
2
This was evidenced by a colour change of the reaction solu- [KNi(L )
tions overnight at −40 °C or upon evaporation of the solvent (L )
and was additionally verified via the subsequent recrystalliza-
2
] as well as in the case of chromium [K{dme}
4
][Cr
].
The reaction of 2 (Mn) with NBu Br or PPh Br led to disco-
4 4
1
5,6
2
tion of the metal(II) precursor. The initial formation of [AFe louring of the reaction mixture as well as to precipitation of
2
1
(
L ) ] could be proven via H NMR spectroscopy when perform- small amounts of a black solid on the stirring bar. This indi-
2
ing the reduction in THF-d . Adding either 12-crown-4 (for cated an insufficient stability of the cation in the presence of
8
2
2 −
lithium) or 18-crown-6 (for sodium) to a solution of [AFe(L )
led, after work-up, to the isolation of the respective ion-separ- −2.5 V vs. Fc/Fc ). The reaction of 3 (Fe) and 4 (Co) with
ated products [Li{12c4} ][Fe(L ) ], 6, and [Na{18c6}(Et O)][Fe NBu
2
]
the highly reducing manganese(I) complex [MnL
2
]
(Ered ≈
+
8
2
Br led, after work-up, to the isolation of the corres-
ponding compounds [NBu ][Fe(L ) ], 8, and [NBu ][Co(L ) ], 9
4 2 4 2
2
2
2
4
2
2
2
(
L )
2
], 7, as shown in Fig. 6.
Structural analysis via X-ray diffraction on suitable crystals (Scheme 3). X-Ray diffraction analysis revealed that the
showed most notably different orientations of the amide exchange of the cation has no significant influence on the M–
2
−
ligands within the [Fe(L )
functions are pointing in the opposite direction (torsion angle However, larger differences in the torsion angles were notable.
48.9(3)°), whereas in 7 (Fe), they are in an eclipsed position Whereas the ligand set of 9 (Co) remains in an eclipsed confor-
2
] complex anion. In 6 (Fe), the aryl N bond lengths and the N–M–N angles in the anion (Table 1).
1
(
torsion angle 7.0(4)°). As expected, the UV/Vis and paramag- mation with a torsion angle of 3.93(25)°, a rotation around the
N–M–N axis took place in 8 (Fe), resulting in a staggered con-
formation (111.35(17)°). Both features can be attributed to
interactions of the aryl rings with one of the methyl groups of
+
the NBu
4
cation, whose distances are in part even shorter
than intramolecular CH ⋯aryl/CH ⋯CH distances (Table 1).
3
3
3
It implicates that intramolecular dispersion forces, thought as
essential for the stability of two-coordinated complexes, are
here of lesser importance. The impact of attracting intra-
molecular dispersion interactions is further discussed to influ-
2
2
12,22
Scheme 2 Reduction of [Fe(L )
sodium (7), respectively.
2
] (L = N(Dipp)SiMe
3
) with lithium (6) or ence M–N distances.
However, the cobalt complexes 4
2
(KCo), 9 (NBu Co) and [K{18c6}][Co(L ) ], for example, exhibit
4
2
Fig. 6 Sections of the crystal structure of 7 (left), 8 (middle) and 9 (right). H atoms and a disorder of the 18-crown-6 fragment of 7 are omitted for
clarity. For 8 and 9 the shortest CH –arene interactions are depicted (dashed line).
3
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virtually identical Co–N distances, despite bearing drastically metal(I) silylamides [M(N(SiMe
3
)
2
)
2
]− towards alkynes, that
2
differing ligand orientations and interactions in solid state.
yielded predominantly side-on alkyne complexes ([M(η -RCCR)
−
(
N(SiMe
tionation processes in case of manganese. In this context the
N(Dipp)SiMe ligand set was already probed for manganese
3 2 2
) ) ] ) but also some bond reduction and dispropor-
2
4
Magnetic properties in solution
–
3
Having understood the speciation of the complexes 1–4 in
solution, we were briefly interested if the intramolecular pot-
2
yielding relatively stable complexes of the type [Mn(η -RCCR)
2
24
(
L )
2
] (R = Et, Ph). As such we pursued first the isolation of
assium ion complexation of the [KML ] complexes has a dis-
2
2
the iron and cobalt derivatives. Reaction of [K{18c6}][Fe(L ) ]
2
cernible impact onto the solution state magnetic properties in
comparison with to their cation separated counterparts. Using
Evans method (Table 4) the effective magnetic moments of 1
with PhCCPh led to the quantitative formation of the side-on
2
2
alkyne complex [K{18c6}][Fe(L )
2
(η -PhCCPh)], 10 (Scheme 4).
2
The same reaction with [K{18c6}][Co(L ) ] yielded in an initial
2
(Cr) and 2 (Mn) in C
6 6 B
D were determined to be 5.17μ (μS.
color change to red brown, but only the employed cobalt(I) pre-
cursor was isolated upon crystallisation. This is not surprising
as weak and reversible binding of alkynes to cobalt silylamides
was already observed in case of sterically less demanding [Co
O.(S=5/2) = 5.92μ
B
) and 4.68μ
B
(μS.O.(S=2) = 4.82μ
B
). These are
I
lower than the expected spin-only values (Cr : μ
=
S.O.(S=5/2)
I
5
.92μ
B B
, Mn : μS.O.(S=2) = 4.92μ ) but are in the range of other
linear chromium(I) and manganese(I) complexes (e.g. [K
−
24
1
2
6,8
(N(SiMe
only the starting materials. In contrast, when 3 (Fe) was treated
with PhCCPh in Et O, crystallization yielded the mixed arene/
alkyne iron complex [K(D)(Fe(C Ph )(PhCCPh)], 11·D, (D =
3 2 2
) ) ] . Treating 4 (KCo) with PhCCPh afforded also
{
dme} ][Cr(L ) ]: 5.2μ , K{18c6}[Mn(L ) ]: 4.98). Higher than
4 2 B 2
spin-only values were measured for complexes 3 (Fe) (μeff
=
2
5
.31μ
B
, μS.O.(S=3/2) = 3.87μ
B
), 3·2DMAP (Fe) (μeff = 4.89μ
B
), and 4
6
6
(
Co) (μeff = 4.50μ , μ
= 2.83μ ) which is expected for
B
S.O.(S=1)
B
none, Et O) (Fig. 7, second left, ESI†) as well as inseparable
2
linear
contributions.
complexes
with
unquenched
orbital
1
3,14,23
free hexaphenylbenzene (HPB). Following the reaction of 3 (Fe)
When switching to THF-d
8
a slight drop
1
in C
6
D
6
by H NMR spectroscopy showed the rapid consump-
in the respective magnetic susceptibilities was observed for 1
4.92μ ), 3 (4.34μ ) and 4 (3.93μ ). The values in THF are com-
tion of PhCCPh and formation of minor amounts of free HPB.
1·D corresponds to the known iron compound [K{18c6}][Fe
(
B
B
B
1
parable to those found for the respective cation separated com-
plexes (5–9), stressing that the complex anion is more or less
unaffected by a separated counter ion in solution. Within the
limits of the Evans method this indicates a beneficial factor of
intramolecular potassium ion complexation, either by block-
ing of the free amide rotation or fixation of a near-linear N–
Fe–N axis which would overall enhance orbital contributions.
2
(
HPB)(η -PhCCPh)], obtained by reaction of the iron(–I)
2
5
synthon [K{18c6}][Fe(C H ) ] with PhCCPh, as well as the
1
0
8 2
Reactivity of [KM(L) ] complexes towards diphenylacetylene
2
Lastly, we conducted first experiments concerning the impact
of the intramolecular potassium ion complexation on the reac-
tivity of the metal(I) complexes for manganese to cobalt given
the identical ligand set. For that we chose diphenyl acetylene
(PhCCPh) as a probe, given our recent examination of anionic
2
Table 4 Solution state magnetic susceptibilities of complexes 1–9 (L
N(Dipp)SiMe ) in THF-d and C
spin-only values are given for the high-spin case
=
3
8
6 6
D via the Evans method. Theoretical
μ
B
eff [μ ] in
Metal
Compound
Cation
K
B 8 6 6
μeff [μ ] in THF-d C D
Cr [μS.O.
=
1
5
2
4.92
5.17
Insoluble
4.68
5.92μ
B
]
K{18c6} 4.21
Partial
decomposition
Mn [μS.O.
=
K
B
4.90μ ]
8
[
(
K{18c6}][Mn K{18c6} 4.98
L ) ]
2
Insoluble
2
Fe [μS.O.
=
3
K
K
4.34
—
4.85
4.89
3.87μ
B
]
3·2DMAP
(
DMAP)
2
6
7
8
4
9
Na{18c6} 4.74
Li{12c4}
NBu
K
NBu
Insoluble
Insoluble
Insoluble
4.18
2
4.24
4.30
3.93
3.58
4
2
Co [μS.O.
=
Scheme 4 Reactivity of [K{m}][M(L )
2
] of manganese and iron (m =
2.83μ
B
]
4
Insoluble
none or 18c6) towards PhCCPh (HPB = C Ph ).
6
6
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Fig. 7 Sections of the crystal structures of 10–13 (from left to right). H atoms and the K{18c6} unit of 10 are omitted for clarity.
2
24
manganese analogue [K{18c6}][Mn(HPB)(η -PhCCPh)]. The tion stoichiometry as well as reaction temperature failed so far,
latter was observed during the reaction of the manganese(I) in part by the ubiquitous presence of the complete trimerisa-
−
complex [Mn(N(SiMe
3
)
2
)
2
]
with PhCCPh under redox dispro- tion product HPB. When the reaction mixture of 2 (KMn) with
portionation and ligand redistribution. For 3 (Fe) a similar PhCCPh in Et O was layered after several minutes with 18c6 in
2
mechanism is plausible, whereas 3 acts as reductant as well as Et O and stored at −35 °C, to promote crystallisation via cation
2
2
2
source of an iron atom under formal release of KL and [Fe separation, only the known η -alkyne complex K{18c6}[Mn
2
2
2
24
(
L ) ].
(L ) (η -PhCCPh)] can be isolated, showing that the for-
2
2
Treatment of 2 (KMn) in toluene with PhCCPh resulted also mation of 12 and 13 is a slower process.
in the trimerisation product HPB. Remarkably, small amounts
of crystals of the dimeric complexes 12 and 13 (Fig. 7, right,
ESI†) were obtained that give insights into this manganese
mediated trimerisation process. In 12 two manganese ions are
Conclusions
bridged by two PhCCPh units, which are oriented orthogonal The syntheses and characterization of neutral quasilinear,
1
towards the Mn–Mn axis. The distance between the manga- homoleptic 3d-metal(I) silylamides of the type [KM(L) ] (L =
2
i
2
nese atoms are with 2.434(2) Å rather short and comparable to N(Dipp)Si Pr (Cr); L = N(Dipp)SiMe3 (Mn – Co)) via the
3
II
II
26
a ketimide linked Mn /Mn dimer. Similar to 11·D, the for- reduction of the respective quasilinear metal(II) silylamide
mation of 12 is probably the result of formal redox dispropor- with KC in non-coordinating solvents were presented. X-Ray
8
tionation of the employed 2 (Mn). Compound 12 is in close diffraction analysis shows that the alkali metal ion is coordi-
resemblance to a recently reported dinuclear iron complex nating to the aryl rings in either an intramolecular (Co) or
2
2
2
(
[(L )Fe(μ-η -PhCCPh)
2
Fe(L )], which was observed upon react- intermolecular intermolecular fashion (Cr, Mn, Fe). For the
2
ing [Fe(IDipp)(L )] (IDipp = 1,3-bis(2,6-di-iso-propylphenyl) latter this results in the presence of unprecedented 1D-coordi-
imidazolin-2-ylidene) with PhCCPh. It exhibits significantly nation polymers of linear, open-shell metal(I) complexes.
less distorted alkyne ligands (C–C 1.349(7) Å, C–C–Cphenyl Detailed H NMR spectroscopic examinations of the complexes
2
7
1
bond angle of 133.3(4)°) which speaks to
a stronger in solution showed that, in non-coordinating solvents, the
π-backbonding into the π*-orbitals of the alkyne within 12. In cation remains in the vicinity of the complex anion whereas,
the other dimeric complex 13 two manganese atoms (Mn–Mn in good donor solvents like THF, these compounds exist as an
2
.5665(11) Å) are linked via a C6-chain, stemming from incom- ion pair. When using lithium or sodium as reductants the
2
plete alkyne trimerisation. Judging from the bond lengths, the respective iron complexes [AFe(L ) ] (A = Li, Na) could be gen-
2
carbon fragment is best described as two allyl units linked via erated, which were isolated by sequestrating the alkali metal.
2
8–30
a C–C single bond giving it a formal dianionic charge.
The Starting off the formally neutral metal(I) silylamides, the alkali
coordination sphere of each manganese ion, that lacks any metals could also be exchanged by an organic cation in case of
silylamide ligation, is completed by an alkyne ligand, which iron and cobalt. Upon comparison of the structural metrics of
experiences only a moderate C–C bond elongation (1.267(7) Å all obtained and literature reported [M(L)2]− complexes, it is
and 1.287(8) Å). The presence of two potassium ions, each shown that the two amide ligands can virtually exhibit any
being located in a pocket composed of two aryl rings of the C6 orientation towards each other (cis, trans or orthogonal). This
fragment as well as one of an alkyne, leads to a formal oxi- is dependent on the presence of not only intra- but also inter-
0
dation state of Mn for both manganese ions. The formation molecular interactions in solid states and has no considerable
of the trimerised C6 fragment in 13 is remarkable as it poses a effect on the metal–amide bond length. It indicates that intra-
snapshot in the final step of alkyne trimerisation. molecular dispersion forces are an important, but not an
Metallacycloheptatriene-like intermediates in alkyne trimerisa- essential factor for the stabilization of homoleptic, two-coordi-
2
8–31
tion were so far only observed for mononuclear complexes,
nate metal(I) amides. First reactivity studies of the neutral com-
2
7
2
whereas bimetallic derivatives were only postulated. Any pounds [KM(L ) ] (M = Mn –Co) towards diphenyl acetylene
2
attempts of isolating pure 12 or 13 via adjustment of the reac- showed distinct differences with respect to their cation separ-
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ated counterparts K{18c6}[M(L )
the formation of η -alkyne complexes, the neutral complexes Crystals, suitable for X-ray diffraction analysis, were obtained
serve as coordination sites as well as reductants. This leads from a concentrated toluene solution of 1 at −40 °C. H NMR
Paper
2
2
]. Whereas the latter prefer 391 mg (0.52 mmol, 74%), Et
2
O: 447 mg (0.59 mmol, 86%).
2
1
ultimately to substrate trimerisation whereas unusual inter- (500.1 MHz, C
6
D
6
, 300 K, ppm): δ = 22 (bs, w = 1900 Hz), 15
1
2
mediates could be structurally characterized. It thus shows (bs, w = 1300 Hz), 12 (bs, w
1
1
= 310 Hz), 7 (bs, 18 H, w = 2100
1
2
2
2
that the intramolecular potassium ion complexation labilises Hz, Si(CH(CH
3
)
2
)
3
), 4.0 (s, w
1
= 42 Hz), 3.6 (s, w = 32 Hz), 2.4
1
2
2
the metal amide bond and give rise to distinct reactivities The (s, w = 20 Hz), 0.29 (s, w
1
1
= 22 Hz), −16 (bs, w = 200 Hz) ppm.
1
2
2
2
further use of neutral metal(I) silylamides as precatalysts as (300.2 MHz, THF-d , 300 K, ppm): δ = 16 (bs, w = 920 Hz), 12
1
8
2
well as a detailed inspection of their magnetic properties is (bs, w
currently explored in our lab.
1
= 810 Hz), 2.65 (s, w = 17.3 Hz). Elemental analysis:
1
2
2
42 2 2
C H76CrKN Si
(756.35 g mol− ): calcd: N 3.70, C 66.70, H
0.13; found: N 3.84, C 66.36, H 10.05%. IR (ATR, cm ): ˜ν =
941 (m), 2861 (m), 1576 (w), 1456 (m), 1407 (s), 1313 (m),
244 (s), 1140 (w), 1101 (w), 992 (w), 925 (s), 878 (m), 804 (w),
1
−
1
1
2
1
Experimental section
Materials and methods
767 (s), 719 (w), 640 (s), 554 (w), 525 (w), 487 (w), 418 (m).
EVANS (500.1 MHz, 300 K, C + 1% TMS): μeff = 5.17μ
O. = 5.92μ . (500.1 MHz, 300 K, C + 1% TMS): μeff = 4.92μ
μS.O. = 5.92μB.
KMn(N(Dipp)SiMe
SiMe ], 2 could be obtained as dark violet solid. Yield:
toluene: 5 mg (0.009 mmol, 5%), Et O: 30 mg (0.051 mmol,
6
D
6
B
; μS.
B
6
D
6
B
;
All manipulations were carried out in a glovebox under a dry
argon atmosphere, unless indicated otherwise. Used solvents
were dried by continuous distillation over sodium metal for
several days, degassed via three freeze–pump–thaw cycles and
stored over molecular sieves 4 Å. Deuterated solvents were
used as received, degassed via three freeze-pump cycles and
[
3 2
) ] (2). Using 100 mg of [Mn(N(Dipp)
3 2
)
2
28%). Crystals, suitable for X-ray diffraction analysis, were
obtained from a n-pentane layered solution of 2 in toluene at
1
stored over molecular sieves 4 Å. The H NMR spectra were
recorded on a Bruker AV 500, a Bruker HD 500 or a Bruker HD
1
−
=
35 °C. H NMR (500.1 MHz, C D , 300 K, ppm): δ = 16 (bs, w
1
2
6
6
1400 Hz), 12 (bs, w
1
= 630 Hz), 2.11 (s, w
1
= 8.09 Hz), 2.01 (s,
2
2
3
00 NMR spectrometer (Bruker Corporation, Billerica, USA).
w
1
= 14.3 Hz), 1.4 (bs, w
1
= 450 Hz), 1.21 (s, w = 8.17 Hz), 0.99
1
2
2
2
Chemical shifts are reported in ppm relative to the residual
proton signals of the solvent (for H). w1/2 is the line width of
(
s, w
1
= 18.0 Hz), 0.41 (s, w
1
= 15.4 Hz), 0.11 (s, w = 11.0 Hz),
1
1
2
2
2
−
7.3 (bs, w = 1400 Hz). (500.1 MHz, THF-d , 300 K, ppm): δ =
1
8
2
a signal at half its maximum intensity. Integrals of the broad
signals ligand set were obtained directly or by peak fitting (in
case of overlapping signals) using the MestreNova software
package (Mestrelab, Santiago de Compostela, Spain). IR
measurements were conducted on a Bruker Alpha ATR-IR
spectrometer (Bruker Corporation, Billerica, USA). The UV/VIS
measurement were recorded on an AnalytikJena Specord S600
using WinASPECT software. Elemental analysis were per-
formed by the “in-house” service of the Chemistry Department
of the Philipps University Marburg, Germany using a CHN(S)
analyser vario MICRO Cube (Elementar Analysensysteme
GmbH, Langenselbold, Germany). Dispersed sodium (5% Na/
15 (bs, w
1
= 2100 Hz), 11.0 (bs, w
Hz), 3.9 (s, w
1
2
= 470 Hz), 6.10 (s, w
1
= 55.3
= 14.8 Hz), 2.29 (s, w = 6.31
2
2
2
1
2
= 56 Hz), 2.89 (s, w
1
1
2
Hz), 0.20 (bs, w
8
1
= 220 Hz), −0.06 (s, w
1
= 34 Hz), −13 (bs, w =
2 2
1
2
2
2
(590.96 g mol−1):
60 Hz). Elemental analysis C30
H52MnKN Si
calcd: N 4.74, C 60.97, H 8.87; found: N 5.00, C 61.30, H
−1
8
.65%. IR (ATR, cm ): ˜ν = 2953 (m), 2867 (w), 1577 (vw), 1459
(
w), 1416 (s), 1380 (w), 1359 (w), 1313 (m), 1237 (vs), 1190 (s),
1
7
105 (w), 1052 (w), 1039 (w), 958 (w), 916 (s), 879 (w), 824 (vs),
84 (vs), 741 (m), 666 (m), 619 (w), 571 (w), 534(m), 431 (m).
EVANS (500 MHz, 300 K, C
.90μB.
KFe(N(Dipp)SiMe
SiMe ], 3 could be obtained as red solid. Yield: toluene:
39 mg (0.57 mmol, 90%), Et O: 343 mg (0.58 mmol, 92%).
6 6 B
D + 1% TMS): μeff = 4.68μ ; μS.O. =
4
[
3 2
) ] (3). Using 350 mg of [Fe(N(Dipp)
2
1
i
6
8
NaCl), [Fe
(
[Cr(N(Dipp)Si Pr ) ],
[Mn(N(Dipp)SiMe ) ],
3
2
3 2
3 2
)
1
4
12
N(Dipp)SiMe ) ], and [Co(N(Dipp)SiMe ) ], were prepared
3 2 3 2
3
2
according to literature procedures.
Crystals, suitable for X-ray diffraction analysis, were obtained
from a n-pentane layered solution of 3 in toluene at −35 °C.
Synthesis and characterization
Crystals of 3·Et O, suitable for X-ray diffraction analysis, were
2
1
i
2
[
KM(L)
Co)). One equivalent of [M(L)
either 10 mL toluene or diethyl ether. After adding KC (1.1 n-pentane whereas the one without is not.
2
] (L = N(Dipp)Si Pr
3
(Cr); L = N(Dipp)SiMe
] (M = Cr–Co) was dissolved in amounts of Et
3
(Mn – obtained from a n-pentane layered solution of 3 in minimal
2
2
2
O at −35 °C. The Et O adduct is soluble in
1
H
NMR
8
equiv.) the reaction mixture was stirred for several minutes at (500.1 MHz, C
6
D
6
, 300 K, ppm): δ = 60 (bs, 2 H, CH(CH ),
3 2
)
room temperature, while a change in colour was observed (Cr: 39.7 (bs, 12 H, w
1
= 620 Hz, CH(CH
3
)
2
), 23.4 (bs, 4 H, w
1
= 470
= 7.70
2
2
2
dark red → red; Mn: beige → dark violet; Fe: orange → red; Co: Hz, m-PhH), 4.3 (bs, 2 H, w
1
= 290 Hz, p-PhH), 0.15 (s, w
1
2
dark red → light green). The graphite was filtered off and all Hz), −1.7 (bs, 18 H, w2
volatiles were removed under reduced pressure. After washing = 1200 Hz, CH(CH ). (300.2 MHz, THF-d
with n-pentane and drying in vacuo, [KM(L) ] (1–4) was 29 (bs, w = 560 Hz), 28 (bs, w = 360 Hz), 12.6 (bs, w
2
1
= 1800 Hz, Si(CH
3
)
3
), −78 (bs, 12 H, w
8
1
2
3
)
2
, 300 K, ppm): δ =
1
2
1
2
1
= 240
2
obtained in yields of 28–92%.
Hz), 1.3 (bs, w
1
= 33 Hz), 0.26 (bs, w = 20 Hz), −0.1 (bs, 18 H,
1
2
2
i
[
KCr(N(Dipp)Si Pr
3
)
2
] (1). Using 500 mg of [Cr(N(Dipp)
w
1
= 1300 Hz, Si(CH
3
)
3
), −103 (bs, w
1
= 1500 Hz, CH(CH ) ).
3 2
2
2
i
−1
Si Pr ) ], 1 could be obtained as red solid. Yield: toluene: Elemental analysis C H FeKN Si (591.87 g mol ): calcd: N
3
2
30 52
2
2
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Paper
Dalton Transactions
4
.73, C 60.88, H 8.86; found: N 4.91, C 60.97, H 8.63%. IR and storing at −40 °C for several days, [K{18c6}][Cr(N(Dipp)
ATR, cm− ): ˜ν = 2947 (m), 2864 (w), 1582 (w), 1462 (w), 1417 Si Pr ) ] (5) was obtained as orange crystals in a yield of 43%.
1
i
(
(
3 2
1
8
s), 1379 (w), 1357 (w), 1317 (m), 1238 (s), 1198 (m), 1141 (w), Yield: 31 mg (0.03 mmol, 43%). H NMR (500.1 MHz, THF-d ,
1
7
102 (m), 1051 (w), 1041 (w) 978 (m), 914 (s), 877 (m), 828 (vs), 300 K, ppm): δ = 23 (bs, w
1
= 2000 Hz), 16 (bs, w = 1700 Hz),
1
2
1
2
2
87 (vs), 745 (m), 671 (m), 624 (w), 576 (w), 541 (w), 425 (m). 3.6* (s, 24 H, 18c6), 0.4 (bs, w = 2400 Hz). * Signal is overlap-
EVANS (500 MHz, 300 K, C
6
D
6
+ 1% TMS): μeff = 4.85μ
. (500 MHz, 300 K, THF-d + 1% TMS): μeff = 4.34μ
3.87μB.
2 3 2
K(DMAP) Fe(N(Dipp)SiMe ) ] (3·2DMAP). Crystals, suitable H 9.66%. IR (ATR, cm ): ˜ν = 2953 (m), 2892 (m), 2849 (m),
B
; μS.O.
=
ping with the solvent peak, why no further information can be
; μS.O. provided. Elemental analysis C54 100CrKN Si (1020.67 g
mol ): calcd: N 2.74, C 63.55, H 9.88; found: N 2.72, C 63.10,
3
.87μ
B
8
B
H
2
O
6
2
−
1
=
−
1
[
for X-ray diffraction analysis, were obtained by adding two 1584 (w), 1469 (m), 1452 (w), 1413 (m), 1373 (w), 1350 (m),
equivalents of DMAP (20.5 mg, 0.17 mmol, 2 eq.) to 50 mg of 3 1309 (w), 1283 (w), 1241 (s), 1196 (m), 1103 (vs), 1058 (w), 991
(0.08 mmol, 1 equiv.) in Et
2
O, layering the solution with (m), 965 (m), 925 (m), 878 (m), 837 (m), 800 (w), 759 (s), 738
n-pentane and keeping it at −40 °C for several days. Yield: (m), 663 (m), 635 (s), 555 (m), 530 (w), 515 (w), 461 (w), 427
1
4
9.7 mg (0.06 mmol, 75%). H NMR (500.1 MHz, C D , 300 K, (m). EVANS (500.1 MHz, 300 K, THF-d8 + 1% TMS): μeff
=
6
6
ppm): δ = 61 (bs, w2
CH ), 26.2 (bs, 4 H, w2
70 Hz, p-PhH), 1.8 (bs, w2
bs, w2 = 96 Hz), 0.23 (bs, w2
3.6 (bs, 18 H, w2 = 1700 Hz, Si(CH
300 Hz, CH(CH ) ). Elemental analysis C H FeKN Si
2
1
= 260 Hz), 39.4 (bs, 12 H, w2
1
= 600 Hz, CH 4.21μ
B
; μS.O. = 5.92μ
B
.
(
1
(
−
3
)
2
1
= 480 Hz, m-PhH), 19.4 (bs, 2 H, w
1
2
=
[Li{12c4}
2
][Fe(N(Dipp)SiMe
3
)
2
] (6). 100 mg (0.18 mmol, 1
1
= 290 Hz), 1.2 (bs, w2
= 230 Hz), −1.75 (bs, w2
), −79 (bs, 12 H, w
1
= 63 Hz), 0.98 equiv.) [Fe(N(Dipp)SiMe ) ] were dissolved in 5 mL THF. After
3 2
1
1
1
= 550 Hz), adding a piece of lithium the reaction mixture was stirred for
1
)
3
1
2
=
2 hours at room temperature. Residual lithium was filtered off
3
1
the dark red solution and the volatiles were reduced to a
3
2
44 72
6
−
1
(
591.87 g mol ): calcd: N 10.05, C 63.20, H 8.68; found: N minimum. After layering with a solution of two equiv.
0.38, C 62.83, H 8.50%. IR (ATR, cm ): ˜ν = 2949 (m), 2863 12-crown-4 in Et O and storing at −40 °C for several days, [Li
2
−
1
1
(
1
m), 1603 (s), 1534 (m), 1461 (w), 1442 (w), 1417 (s), 1387 (m), {12c4} ] [Fe(N(Dipp)SiMe ) ] (6) was obtained as green crystals
2 3 2
1
357 (w), 1318 (m), 1230 (s), 1200 (m), 1154 (w), 1139 (w), 1106 in a yield of 57%. Yield: 94 mg (0.10 mmol, 57%). H NMR
, 300 K, ppm): δ = 29.5 (bs, w = 320 Hz),
(
(
(
m), 1056 (w), 1042 (w), 992 (s), 951 (m), 928 (s), 881 (w), 834 (300.2 MHz, THF-d
vs), 801 (vs), 781 (vs), 752 (m), 669 (m), 622 (m), 527 (m), 480 27.7 (bs, w = 480 Hz), 13 (bs, w
w), 430 (m). EVANS (500 MHz, 300 K, C
.89μ ; μS.O. = 3.87μ
8
1
2
1
1
= 200 Hz), 2.77 (s, 32 H, w
1
=
=
).
2
2
2
6
D
6
+ 1% TMS): μeff
=
19.4 Hz, 12c4), 0.12 (s, 16 H, w
1800 Hz, Si(CH
KCo(N(Dipp)SiMe ) ] (4). Using 200 mg of [Co(N(Dipp) Elemental analysis C H FeLiN O Si (912.14 g mol ): calcd:
3 2 46 84 2 8 2
1
2
= 4.0 Hz), −1 (bs, 18 H, w
1
2
4
B
B
.
3
)
3
), −100 (bs, w = 1600 Hz, CH(CH )
1
3 2
2
−
1
[
SiMe
toluene: 159 mg (0.27 mmol, 74%), Et
1%). Crystals, suitable for X-ray diffraction analysis, were (w), 1482 (w), 1443 (m), 1420 (m), 1364 (m), 1351 (w), 1313 (m),
obtained from a n-pentane layered solution of 4 in toluene at 1287 (m), 1251 (s), 1194 (m), 1134 (s), 1094 (vs), 1051 (w), 1023
3 2
) ], 4 could be obtained as light green solid. Yield: N 3.07, C 60.57, H 9.28; found: N 3.38, C 60.19, H 9.09%. IR
O: 173 mg (0.29 mmol, (ATR, cm− ): ˜ν = 3035 (vw), 2950 (m), 2913 (m), 2862 (m), 1580
1
2
8
1
−
(
25 °C. H NMR (500.1 MHz, toluene-d
s, 12 H, w2 = 29.4 Hz, CH(CH ) ), 21.4 (s, 4 H, w
m-PhH), 9.26 (s, 2 H, w2
Hz, CH(CH ), 3.7 (s, 18 H, w2
H, w = 50 Hz, CH(CH ) ). (500.1 MHz, THF-d , 300 K, ppm): δ equiv.) [Fe(N(Dipp)SiMe ) ] were dissolved in 5 mL Et O. After
8
, 300 K, ppm): δ = 29.3 (s), 921 (vs), 881 (w), 827 (vs), 778 (s), 742 (m), 666 (m), 625 (w),
1
1
2
= 26 Hz, 554 (m), 429 (m). EVANS (500.1 MHz, 300 K, THF-d8 + 1%
3
2
1
= 22 Hz, p-PhH), 5.8 (bs, 4 H, w
1
= 310 TMS): μeff = 4.74μ
; μS.O. = 3.87μ
B
.
B
2
)
2
1
= 78 Hz, Si(CH
3
)
3
), −72.3 (s, 12
[Na{18c6}][Fe(N(Dipp)SiMe ) ] (7). 150 mg (0.27 mmol, 1
3 2
3
1
2
3
2
8
3 2
2
=
30 (bs, 4 H, w2
CH(CH ), 16.5 (s, 4 H, w2
10 Hz, Si(CH ) ), 4.27 (s, 2 H, w
1
= 800 Hz, CH(CH
= 43 Hz, m-PhH), 13.9 (s, 18 H, w =
2
3
)
2
), 17.7 (s, 12 H, w2
1
= 55 Hz, adding Na/NaCl (5% w/w) (0.30 mmol (Na), 1.1 equiv.) the
reaction mixture was stirred for several minutes at room temp-
= 34 Hz, p-PhH), −86.5 (s, 12 erature. The residuals were filtered off and the resulting dark
3
)
2
1
1
2
H, w
(
1
2
3
3
1
2
= 150 Hz, CH(CH
)
). Elemental analysis C30
H
52CoKN
Si
red solution was reduced in vacuo to approx. 1 ml. After layer-
O and
C 60.24, H 8.97%. IR (ATR, cm ): ˜ν = 2953 (m), 2865 (w), 1567 storing at −40 °C for several days, [Na{18c6}][Fe(N(Dipp)
w), 1453 (m), 1415 (vs), 1367 (m), 1345 (w), 1289 (w), 1232 (s), SiMe ] (7) was obtained as red-brownish crystals in a yield of
3
2
2
2
594.96 g mol− ): calcd: N 4.71, C 60.56, H 8.81; found: N 4.90, ing with a solution of one equiv. 18-crown-6 in Et
1
2
−
1
(
1
7
3 2
)
1
134 (w), 1105 (w), 1044 (w), 978 (s), 940 (m), 829 (vs), 806 (vs), 79%. Yield: 180 mg (0.21 mmol, 79%). H NMR (300.2 MHz,
79 (s), 755 (s), 740 (m), 726 (m), 649 (m), 609 (w), 428 (w). THF-d , 300 K, ppm): δ = 29.5 (bs, w = 390 Hz), 28.0 (s, w
1
2
1
2
=
8
EVANS (500.1 MHz, 300 K, C
2.83μ . (500.1 MHz, 300 K, THF-d
μS.O. = 2.83μB.
K{18c6}][Cr(N(Dipp)Si Pr
6
D
6
+ 1% TMS): μeff = 4.18μ
B
; μS.O. 380 Hz), 12.8 (bs, w
1
= 170 Hz), 3.45 (m, 4 H, Et
2
O), 1.92 (s, 24
2
=
B
8
+ 1% TMS): μeff = 3.93μ
B
;
H, 18c6), 1.17 (m, 6 H, Et
= 540 Hz, CH(CH ) ). Elemental analysis
42 2 6 2
C H76FeN NaO Si (840.08 g mol ): calcd: N 3.33, C 60.05, H
2
O), −0.5 (bs, w
1
= 540 Hz, Si(CH
3 3
) )
2
−102 (bs, w
1
3 2
2
i
−1
[
3
)
2
] (5). 50 mg (0.07 mmol, 1
i
−1
equiv.) [Cr(N(Dipp)Si Pr
3
)
2
] were dissolved in 5 mL Et O. After 9.12; found: N 3.83, C 60.06, H 9.06%. IR (ATR, cm ): ˜ν = 3052
2
adding KC (0.08 mmol, 1.1 equiv.) it was stirred for several (vw), 3035 (vw), 2950 (m), 2879 (m), 2862 (m), 1581 (w), 1456
8
minutes at room temperature. The graphite was filtered off the (m), 1419 (s), 1375 (w), 1353 (m), 1317 (m), 1294 (w), 1233 (s),
red solution and the volatiles were reduced to a minimum. 1194 (m), 1094 (vs), 1053 (m), 1039 (w), 948 (m), 920 (s), 882
After layering with a solution of one equiv. 18-crown-6 in Et O (w), 832 (vs), 781 (s), 742 (m), 666 (m), 619 (w), 576 (w), 542
2
4900 | Dalton Trans., 2021, 50, 4890–4903
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Paper
(
w), 530 (w), 431 (m). EVANS (500.1 MHz, 300 K, THF-d
8
+ 1% δ = 27.0 (bs, w
1
= 87 Hz), 4.67 (bs, w
1
= 530 Hz), 3.50 (s, 24 H,
2
2
TMS): μeff = 4.24μ ; μ = 3.87μB.
w
1
= 37 Hz, 18c6), 3.50 (bs, w
1
= 44 Hz), 0.8 (bs, w2
1
= 99 Hz),
= 42 Hz), −25.0 (bs, w =
2
B
S.O.
2
2
[
NBu
KFe(N(Dipp)SiMe
were dissolved in 2 mL THF. After stirring over night at room mol ): calcd: N 2.71, C 65.02, H 8.38; found: N 3.19, C 65.09,
4
][Fe(N(Dipp)SiMe
3
)
2
] (8). 70 mg (0.12 mmol, 1 equiv.) −3.5 (bs, w
1
2
= 330 Hz), −8.83 (bs, w
1
2
1
[
3
)
2
] and 39 mg NBu
4 2 6 2
Br (0.12 mmol, 1 equiv.) 57 Hz). Elemental analysis C42H76FeKN O Si (1034.43 g
−
1
−
1
temperature, the solvent was removed under reduced pressure. H 8.35%. IR (ATR, cm ): ˜ν = 3054 (w), 3038 (w), 3002 (w), 2953
The green solid was resolved in Et O and layered with (m), 2911 (m), 2888 (m), 2862 (m), 1816 (w), 1587 (m), 1472
2
n-pentane, before cooling to −40 °C for crystallization. After (w), 1461 (m), 1421 (s), 1376 (w), 1351 (m), 1312 (m), 1283 (w),
several days, the solution was decanted off. The remaining 1235 (s), 1191 (m), 1154 (w), 1131 (w), 1104 (vs), 1054 (m), 1040
green crystals were dried in vacuo and crystalline [NBu
4
][Fe (m), 1024 (w), 997 (w), 962 (m), 928 (s), 912 (s), 879 (m), 831
(
5
N(Dipp)SiMe ) ] (8) was obtained in a yield of 57%. Yield: (s), 777 (s), 766 (w), 760 (m), 738 (m), 695 (m), 666 (m), 640
3
2
1
4 mg (0.07 mmol, 57%). H NMR (300.2 MHz, THF-d
8
, 300 K, (w), 618 (m), 591 (w), 572 (w), 554 (w), 530 (m), 507 (w), 490
+ 1% TMS): μeff
ppm): δ = 28 (bs, w2
H, w
1
= 550 Hz), 12.7 (s, w2 = 180 Hz), 2.49 (s, 8 (w), 438 (m). EVANS (500.1 MHz, 300 K, THF-d
1
8
+
+
1
2
= 65 Hz, NBu ), 1.0 (bs, 8 H, w
1
2
= 66 Hz, NBu ), 0.57 (s, = 3.88μ ; μ
), 0.18 (m, 12 H, w2
= 3.87μB.
S.O.
4
4
B
+
+
2
8
−
1
(
H, w2
1
= 81 Hz, NBu
4
1
= 48 Hz, NBu
4
),
Reaction of [KMn(L )
(0.10 mmol, 1.0 equiv.) [Mn(N(Dipp)SiMe
(0.15 mmol, 1.5 equiv.) were dissolved in 2 mL toluene in the
795.25 g mol ): calcd: N 5.28, C 69.48, H 11.15; found: N presence or absence of small amounts of THF, respectively.
2
] (2) with diphenyl acetylene. 53 mg
36.1 (s, w2
1
= 12.4 Hz), −56.1 (bs, w2
1
= 12.4 Hz), −102 (bs, w
1
=
3
)
2
] and 21 mg KC
8
2
100 Hz, CH(CH ) ). Elemental analysis C H FeN Si
3 2 46 88 3 2
−
1
−
1
5
.43, C 69.04, H 10.76%. IR (ATR, cm ): ˜ν = 2958 (s), 2863 (s), After stirring for several minutes at room temperature, the
1
581 (w), 1482 (m), 1459 (m), 1419 (s), 1378 (w), 1356 (w), 1314 dark violet solution was filtered in a solution of diphenyl
(
9
(
+
m), 1239 (vs), 1195 (m), 1149 (w), 1102 (w), 1041 (w), 997 (w), acetylene (20 mg, 0.11 mmol, 1.1 equiv.) in the same solvent.
23 (s), 879 (m), 837 (s), 777 (s), 736 (m), 668 (s), 623 (m), 575 It was layered with n-pentane and allowed to crystallize at
w), 539 (w), 519 (w), 432 (s). EVANS (500.1 MHz, 300 K, THF-d8 room temperature. After several days, dark red crystals of both
1% TMS): μeff = 4.30μ ; μS.O. = 3.87μ 12 and 13, besides pale yellow crystals of hexaphenylbenzene,
NBu ][Co(N(Dipp)SiMe ] (9). 70 mg (0.12 mmol, 1 equiv.) could be obtained, which were suitable for X-ray diffraction
KCo(N(Dipp)SiMe ) ] and 39 mg NBu Br (0.12 mmol, 1 equiv.) analysis.
B
B
.
[
4
3 2
)
[
3
2
4
2
were dissolved in 2 mL THF. After stirring over night at room
temperature, the solvent was removed under reduced pressure. (0.10 mmol, 1.0 equiv.) [KFe(N(Dipp)SiMe )
Reaction of [KFe(L )
2
] (3) with diphenyl acetylene. 59 mg
] (3) and 18 mg
3 2
The green solid was resolved in Et O and layered with diphenyl acetylene (0.10 mmol, 1.0 equiv.) were dissolved in
2
n-pentane, before cooling to −40 °C for crystallization. After 2 mL diethyl ether. It was stirred for several minutes at room
several days, the solution was decanted off. The remaining temperature. The brownish solution was filtered and layered
green crystals were dried in vacuo and crystalline [NBu ][Co with n-pentane, before crystallizing at room temperature. After
4
6
2
(
4
N(Dipp)SiMe
0 mg (0.05 mmol, 42%). H NMR (300.2 MHz, THF-d
ppm): δ = 30 (bs, w2 = 800 Hz, CH(CH ) ), 17.4 (s, 12 H, w
Hz, CH(CH ), 16.0 (s, w2
10 Hz, Si(CH ), 7.31 (s, w2
3 2
) ] (9) was obtained in a yield of 42%. Yield: several days, single crystals of [K(D)Fe(η -HPB)(η -PhCCPh)]
1
8
, 300 K, (11·D) (D = none, Et
2
O) could be obtained, suitable for X-ray
1
1
2
= 64 diffraction analysis.
3
2
3
3
)
2
1
= 38 Hz, m-PhH), 14.0 (bs, 18 H, w
= 9.48 Hz, p-PhH), 3.01 (bs, 8 H, [Fe(N(Dipp)SiMe
= 120 Hz, NBu ), 0.53–1.50 (m, 28 H, NBu ), −88.0 (bs, 12 KC (0.20 mmol, 1.1 equiv.) the reaction mixture was stirred
1
=
[K{18c6}][Fe(N(Dipp)SiMe
3
)
2
]. 100 mg (0.18 mmol, 1 equiv.)
] were dissolved in 5 mL Et
2
2
w
H, w
(
3
)
3
1
3
)
2
2
O. After adding
+
+
1
2
4
4
8
1
2
= 110 Hz, CH(CH
)
). Elemental analysis C46
H
88CoN
Si
for several minutes at room temperature, while the colour
3
2
3
2
798.33 g mol− ): calcd: N 5.26, C 69.21, H 11.11; found: N changed to red. The graphite was filtered off and it was layered
1
−
1
5
.65, C 68.77, H 10.63%. IR (ATR, cm ): ˜ν = 2950 (m), 2863 with a solution of 18-crown-6 (1.1 equiv.) in Et O. After storing
2
(
m), 1581 (w), 1477 (w), 1460 (w), 1420 (m), 1375 (w), 1318 (m), at −40 °C for several days [K{18c6}][Fe(N(Dipp)SiMe
3
)
2
] was
1
245 (s), 1229 (s), 1199 (m), 1142 (w), 1103 (w), 1042 (w), 1025 obtained as orange crystals in a yield of 64%. Yield: 99 mg
1
(w), 939 (s), 838 (vs), 778 (s), 664 (m), 616 (w), 543 (w), 436 (m). (0.12 mmol, 64%). H NMR (500.1 MHz, THF-d , ppm): δ =
8
EVANS (500.1 MHz, 300 K, THF-d
O. = 2.83μ
K{18c6}][Fe(N(Dipp)SiMe ) (η -PhCCPh)] (10). 50 mg 0.11 (s, w
8
+ 1% TMS): μeff = 3.58μ
B
; μS. 29.0 (bs, w
1
= 370 Hz), 27.5 (s, w
1
= 420 Hz), 12.4 (bs, w = 157
1
2
2
2
B
.
Hz), 2.58 (bs, 24 H, w
1
2
= 40 Hz, 18c6), 1.14 (s, w = 17.0 Hz),
1
2
2
[
1
2
= 11.1 Hz), −0.7 (bs, w = 1500 Hz, Si(CH ) ), −101
= 1400 Hz, CH(CH ) ). The spectroscopic data coincide
diphenyl acetylene (0.06 mmol, 1 equiv.) were dissolved in with H NMR measurements of [K{18c6}][Fe(N(Dipp)SiMe ) ]
mL THF. After stirring for several minutes at room tempera- synthesized via literature procedure.
1
2
3
2
3 3
(
0.06 mmol, 1 equiv.) [K{18c6}][Fe(N(Dipp)SiMe
3
)
2
] and 10 mg (bs, w
1
3 2
2
1
3 2
3
2
3
ture, the solution was layered with n-pentane, before cooling to
40 °C for crystallization. After several days, the solution was [Co(N(Dipp)SiMe
decanted off. The remaining dark red crystals were dried in (0.20 mmol, 1.1 equiv.) the reaction mixture was stirred for
[K{18c6}][Co(N(Dipp)SiMe
3 2
) ]. 100 mg (0.18 mmol, 1 equiv.)
−
3
)
2
] were dissolved in 5 mL. After adding KC
8
2
vacuo and crystalline [K{18c6}] [Fe(N(Dipp)SiMe
3 2
) (η - several minutes at room temperature, while the colour
PhCCPh)] (10) was obtained in a yield of 71%. Yield: 36 mg changed to green. The graphite was filtered off and it was
1
(
0.04 mmol, 71%). H NMR (300.2 MHz, THF-d , 300 K, ppm): layered with a solution of 18-crown-6 (1.1 equiv.) in Et O. After
8
2
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3 2
storing at −40 °C for several days [K{18c6}][Co(N(Dipp)SiMe ) ]
was obtained as light green crystals in a yield of 56%. Yield:
Author contributions
1
8
7 mg (0.10 mmol, 56%). H NMR (500.1 MHz, THF-d
ppm): δ = 29 (bs, 4 H, w2 = 900 Hz, CH(CH ), 17.3 (s, 12 H, w
48 Hz, CH(CH ) ), 16.3 (s, 4 H, w = 36 Hz, m-PhH), 13.3 (s, the manuscript.
8
, 300 K, The manuscript was written through contributions of all
1
)
2
1
2
authors. All authors have given approval to the final version of
3
=
1
2
1
2
3
2
8 H, w2
1
= 210 Hz, Si(CH
3
)
3
), 4.04 (s, 2 H, w2
1
= 23 Hz, p-PhH),
= 140 Hz,
.85 (s, 24 H, w2
1
= 26 Hz, 18c6), −86.5 (s, 12 H, w2
1
1
CH(CH ) ). The spectroscopic data coincide with H NMR Conflicts of interest
3
2
measurements of [K{18c6}][Co(N(Dipp)SiMe
3
)
2
] synthesized via
3
There are no conflicts to declare.
literature procedure.
X-Ray diffraction analysis
Acknowledgements
Data for compounds 1 (CCDC 2010661), 1·3THF (CCDC
We thank the DFG (grant WE 5627/1-1 and WE 5627/4-1 for
C. G. W.), the Philipps-University Marburg, the CNRS and the
ANR (programme blanc “IRONHYC” ANR-12 for C. G. W.,
S. S.-E. and S. B.) for funding.
2
2
2
011333), 2 (CCDC 2011213), 3 (CCDC 2010659), 4 (CCDC
010663), 5 (CCDC 2011200), 6 (CCDC 2011410), 10 (CCDC
047637), 11 (CCDC 2047640), 11·Et O (CCDC 2047641) and 13
2
(CCDC 2047638)† were collected at 100 K on a Bruker Quest
D8 diffractometer (Bruker Corporation, Billerica, USA) using
an Incoatec Microfocus Source Mo-Kα radiation and equipped
with an Oxford Instrument Cooler Device (Oxford Instruments,
Abingdon, UK) and Photon 100 detector. Data for compounds
Notes and references
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3
2
·2DMAP (CCDC 2010662), 7 (CCDC 2011409) and 12 (CCDC
047639)† were collected at 100 K on a STOE IPDS2 diffract-
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{
3 2 2
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1
986). The structures have been solved using either OLEX
3
2
SHELXT V2014/1 and refined by means of least-squares pro-
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on F) with the aid of the program SHELXL-2016/6 included
in the software package WinGX version 1.63
2
2
3
3
3
4
or using
3
5
CRYSTALS. The atomic scattering factors were taken from
3
6
International Tables for X-ray crystallography. All non-hydro-
gen atoms were refined anisotropically. All hydrogen atoms
were refined by using a riding model. Disorders were found for
1
·3THF (a coordinating THF molecule and two iso-propyl
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unit) and were modelled accordingly. The structure of 9 was
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2
O some data sets are
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probably incomplete due to strategy errors, however the struc-
ture is very good (R < 3%, 20 refl/parameter, no restrains, no
disorder, low maximum/minimum residual density).
Absorption corrections were introduced by using the
3
7
MULTISCAN and X-Red programs. Drawings of molecules are
performed with the program DIAMOND (Crystal Impact, Bonn,
Germany) with 50% probability displacement ellipsoids for
non-H atoms. Additional details are given in the ESI.†
4902 | Dalton Trans., 2021, 50, 4890–4903
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Dalton Transactions
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This journal is © The Royal Society of Chemistry 2021
Dalton Trans., 2021, 50, 4890–4903 | 4903