Square Planar Coordination of Silver in a η4-Cyclobutadiene-(η5-C5H5)ReBr2 Complex Framework

Article abstract of DOI:10.1002/zaac.201800266

Halide addition and abstraction experiments with the cationic rhenacyclopentatriene [(η⁵-C₅H₅){ReC₄(SBn)₄}Br]BF₄ and the side-on cyclobutadiene complexes [(η⁵-C₅H₅)(η⁴-C₄Ph₄)ReX₂] (X = Br, I), respectively, are described. Reversible interconversion of both coordination modes of the metal bonded C₄R₄ moiety depending on the presence or absence of the second bromide ligand is demonstrated for the sulfide derivative. However, formation of the [(η⁵-C₅H₅)(ReC₄Ph₄)X]⁺ congener by halide abstraction at [(η⁵-C₅H₅)(η⁴-C₄Ph₄)ReX₂] turned out to be impossible. Instead, formation of silver halide complexes with the halide bridging rhenium and silver under retention of the metalorganic scaffold are observed. Governed by the phenyl substituent framework a square-planar coordination environment about the Ag cation is adopted for X = Br. Changing X = Br by X = I led to the formation of a heptanuclear complex with di- and three-coordinate silver ions.

Full text of DOI:10.1002/zaac.201800266

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201800266
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Square Planar Coordination of Silver in a η4-Cyclobutadiene-(η5-
C5H5)ReBr2 Complex Framework
Steffen Kleinschmidt,[a] Alexander Hinz,[b] Alexander Villinger,[a] and Wolfram W. Seidel*[a]
Dedicated to Professor Werner Uhl on the Occasion of his 65th Birthday
Abstract. Halide addition and abstraction experiments with the
cationic rhenacyclopentatriene [(η5-C5H5){ReC4(SBn)4}Br]BF4 and
[(η5-C5H5)(η4-C4Ph4)ReX2] turned out to be impossible. Instead, for-
mation of silver halide complexes with the halide bridging rhenium
the side-on cyclobutadiene complexes [(η5-C5H5)(η4-C4Ph4)ReX2] and silver under retention of the metalorganic scaffold are observed.
(X = Br, I), respectively, are described. Reversible interconversion Governed by the phenyl substituent framework a square-planar coordi-
of both coordination modes of the metal bonded C4R4 moiety nation environment about the Ag cation is adopted for X = Br. Chang-
depending on the presence or absence of the second bromide ligand
is demonstrated for the sulfide derivative. However, formation
of the [(η5-C5H5)(ReC4Ph4)X]+ congener by halide abstraction at
ing X = Br by X = I led to the formation of a heptanuclear complex
with di- and three-coordinate silver ions.
folded five-membered ring structure to allow a remote do-
nation of the distal double bond.[6] The lack of a corresponding
reactivity with C-based alkynes pointed to a stronger C/C cou-
pling tendency of S-substituted alkynes.
Introduction
The oligomerization of alkynes aided by transition metal
complexes constitutes a classical approach for the synthesis of
aromatic ring systems like benzenes or pyridines.[1] Mechan-
istic conceptions almost always include the formation of inter-
mediate metallacyclopentadienes.[2] In this conjunction, the
formation and interconvertion of alternatively connected prod-
ucts by combination of two alkynes and a central metal atom
are of interest either as bypasses like η4-cyclobutadiene[3] and
η3-allenylcarbene[4,5] complexes or as potential intermediates
like folded metallacyclopentatrienes.[6,7]
In preceding studies we found that the ReIII complex
[(η5-C5H5)Re(CO)2Br2] reacted at elevated temperature with
bis(benzylsulfanyl)acetylene to yield the rhenaallenylcarbene
complex 3 by 1,2 shift of one benzylsulfanyl substituent
(Scheme 1).[5] In contrast, Green at al. reported the formation
of the η4-cyclobutadiene complex 4a under related conditions
by applying diphenylacetylene (tolane).[8] In addition, the dif-
ferent coupling behavior of regular C- and specific S-substi-
tuted alkynes were supported by bromide abstraction at ambi-
ent temperature. Addition of a Ag+ salt to the side-on alkyne
complex [(η5-C5H5)Re{η2-C2(SBn)2}Br2] (2a) in the presence
of an additional equivalent of alkyne provided the cationic
rhenacyclopentatriene complex 5+, which adopts a remarkable
Scheme 1. Alkyne C/C coupling reactions at the [(C5H5)ReBr2] frag-
ment.
In further investigations we got interested in a potential con-
nectivity switching by halide addition or abstraction and the
possibility to isolate the mutually missing connectivity product
(Scheme 1). In this contribution we report the generation of a
benzylsulfanyl-substituted η4-cyclobutadiene complex by Br–
addition to cationic 5+. On the contrary, a reverse halide ab-
straction at phenyl-substituted η4-cyclobutadiene complex 4a
and its iodide congener turned out to be inadequate. Reactions
with Ag+ salts resulted in halide bridged polynuclear com-
plexes, which were identified by single crystal XRD.
* Prof. Dr. W. W. Seidel
E-Mail: wolfram.seidel@uni-rostock.de
[a] Institut für Chemie
Universität Rostock
Albert-Einstein-Str. 3a
18059 Rostock, Germany
[b] Karlsruhe Institute of Technology
Engesserstr. 15
76131 Karlsruhe, Germany
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201800266 or from the au-
thor.
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Results and Discussion
The outcome of the reaction of [(η5-C5H5)Re(CO)2X2],
(X = Br, I), with tolane or the related sulfide derivative
C2(SBn)2 can partially be controlled by stoichiometry and re-
action time. The alkyne complexes 1a,[9] 2a[5] (Scheme 1), and
[(η5-C5H5)Re{C2(SBn)2)I2] (2b) are the main products, if the
alkynes were applied in moderate excess with short reaction
times. Herein, the iodido derivative 2b was isolated and fully
characterized. The 13C NMR signal for the Re bonded alkyne
C atoms was detected at δ = 205.9 ppm.
Extension of the reaction time and increase of the alkyne
excess forced to the addition of a second alkyne equivalent
but resulting in a different connectivity. For the sulfur-based
derivative 2a formation of the allenylcarbene complex 3 as C4
building block was observed.[5] In contrast, the η4-cyclobuta-
diene complex 4a was prepared from [(η5-C5H5)Re(CO)2Br2]
and an excess of tolane in boiling toluene according to Dossett
et al.[8] The respective iodido derivative 4b proved accessible
by the same procedure using [(η5-C5H5)Re(CO2)I2]. The local
C4 symmetry in 4b is reflected by the observation of one signal
for the cyclobutadiene C atoms at Re at δ = 81.6 ppm.
The molecular structures of both complexes were deter-
mined by single crystal XRD (Figure 1). Overall, alkyne com-
plex 2b resembles the known bromide congener. The alkyne
is roughly oriented parallel to one Re–I bond leading to two
different Re–I bond lengths (Δ = 0.06 Å), whereas the
Re–C1/C2 bonds are almost equal. Accordingly, the observa-
tion of one 13C NMR resonance points to fast alkyne rotation
in solution. Interestingly, the C5H5 ring adopts a distinctively
asymmetric position with Re–C bond lengths ranging from
Re1–C17 at 2.182(7) to Re1–C20 at 2.408(6) Å. On the con-
trary, the C5H5 side-on bonding is rather symmetric in complex
4b coming within the limits of Re1–C32 2.241(7) Å to Re1–
C29 2.294(7) Å. In addition, the C–C bonds within the coordi-
nated cyclobutadiene are virtually identical at an average of
1.4785 Å. However, the Re1–C2 bond at 2.296(7) Å is signifi-
cantly longer (resembling those of Re-C5H5) than the other
three Re–C bonds at an average of 2.185(7) Å, reflecting the
broken symmetry of the cyclobutadiene coordination in 4b.
According to our published protocol[6] purple rhenacyclo-
pentatriene complex 5-BF4 (Scheme 1) was synthesized from
the green alkyne complex [(η5-C5H5)Re{η2-C2(SBn)2}Br2] by
addition of AgBF4 in the presence of bis(benzylsulfanyl)-
acetylene. Attempts to complement this specific coupling
product with the iodido derivative starting with alkyne com-
plex 2b failed. Addition of AgBF4 under identical conditions
led to a dissimilar reaction progress, which is apparent by the
missing color change despite AgI precipitation. From the intri-
cate reaction mixture (according to 1H NMR spectroscopy)
complex 7-BF4 could be crystallized in small quantity and
characterized by single crystal XRD (Figure S1, Supporting
Information). The connectivity of complex 7+ could be derived
showing sulfide coordination besides the unaffected side-on
bonded alkyne (Scheme 2). Obviously, the sulfide is formed
Figure 1. Molecular structures of 2b in the crystal (top) and of 4b in
the crystal 4b·CH2Cl2 (bottom); thermal ellipsoids set at 50% prob-
ability; solvent and hydrogen atoms are omitted for clarity. Selected
bond lengths /Å and angles /°: 2b: Re1–C1 1.967(6), Re1–C2 1.971(6),
Re1–I1 2.7581(6), Re1–I2 2.6980(5), C1–C2 1.369(11), Re1–
C5H5(centroid) 1.9280, I1–Re1–I2 86.228(18); 4b: Re1–C1 2.184(7),
Re1–C2 2.296(7), Re1–C3 2.191(7), Re1–C4 2.180(7), C1–C2
1.474(9), C2–C3 1.482(9), C3–C4 1.480(9), C4–C1 1.479(9), Re1–
C29 2.294(7), Re1–C30 2.278(7), Re1–C31 2.268(7), Re1–C32
2.241(7), Re1–C33 2.294(7), Re1–C5H5(centroid) 1.9121, Re1–I1
2.7475(6), Re1–I2 2.7699(6), I1–Re1–I2 82.828(17).
ortho position over the alkyne. This coupling product could
not be further investigated.
Scheme 2. C4 connectivity switch and side-reaction with BnS deriva-
tives.
The treatment of rhenacyclopentatriene complex 5-BF4 with
a stoichiometric amount of [NBu4]Br in CH2Cl2 led to a new
neutral complex species 6 (Scheme 2). The identity of 6 as
dibromido complex was confirmed by mass spectrometry at
1
by an intramolecular addition of the aromatic CH bond in 974.92521 for the Na-6+ ion. The typical H NMR signals for
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the diastereotopic methylene protons of 5+ between 3.9 and
4.9 ppm merge into a single methylene signal at δ = 4.06 ppm
reflecting the equivalence of all four CH2 groups (Figure 2).
The signal for the C5H5 group is shifted about 1 ppm highfield
to 5.43 ppm. The 13C resonance of the metal bonded C atoms
of the cyclobutadiene ring is detected at δ = 86.2 ppm, which
is in accordance with the expected range for η4-cyclobutadiene
complexes. The macroscopic reversibility of this rearrange-
ment was proven NMR spectroscopically by detection of 5+
after addition of AgBF4 to complex 6. However, this reverse
step was accompanied by side reactions (see Figure S2, Sup-
porting Information).
Scheme 3. Formation of halogenido complexes with 4a/4b.
Figure 3. Molecular structure of 8+ in the crystal 8-BF4·4.83CHCl3;
thermal ellipsoids set at 50% probability; solvent and hydrogen atoms
are omitted for clarity. Selected bond lengths /Å and angles /°: Ag1–
Br1 2.6814(5), Ag1–Br2 2.8610(6), Re1–Br1 2.5565(7), Re1–Br2
2.5603(5), Br1–Ag1–Br2 74.573(16), Br1–Ag1–Br2* 105.426(16).
Figure 2. Section of 1H NMR spectra of 5-BF4 (CD2Cl2, black) and 6
(CDCl3, red).
Aiming for a related C/C coupling/decoupling reaction with
the phenyl derivative 4a, the η4-cyclobutadiene complex was
treated likewise with AgBF4 in dichloromethane. While the
expected precipitation of AgBr was missing in this case, a new longer compared with a genuine π-coordination at Ag+ (2.32–
complex [Ag(4a)2]BF4, 8-BF4 could be isolated by crystalli- 2.70 Å).[13] A related square planar arrangement about Ag+
zation (Scheme 3). Single crystal XRD uncovered a Ag+ com- was observed in [{TpRh(PPh3)(μ2-Cl2)}2Ag]BF4.[14]
plex, in which the bromide ligands of 4a act as donors leading
Two attempts were undertaken to overcome the reluctance
to a trinuclear complex with μ2-bridging bromide ions. Re- of the bromide to be abstracted from the central ReIII atom.
markably, the central Ag+ ion adopts an unusual (square) Firstly, elevated reaction temperatures in THF led indeed to
planar coordination environment, while the deviation from 90° the precipitation of 0.5 equiv. of AgBr providing a Ag-free
angles must be taken into account. Fourfold halide coordinated product 9-BF4. According to a single crystal XRD investiga-
Ag+ ions like [AgBr4]2– moieties in [AgnBrm]n– coordination tion, two central Re atoms in 9+ are bridged by one bromide
oligomers adopt a standard tetrahedral arrangement.[10] In cat- ion (Figure S3, Supporting Information). Finally the bromide
ionic 8+ two of the Ag–Br bonds at 2.6814(5) Å (Ag1–Br1) in was replaced by iodide to count on the higher lattice energy of
trans configuration are in the range of published values for AgI. In this case however, a tricationic complex 10-(BF4)3,
[AgBr2Ag] units (Figure 3), whereas the other two bonds at composed of six molecules 4b and three Ag+ ions was isolated
2.8610(6) Å (Ag1–Br2) are somewhat longer and correspond after crystallization (Figure 4). While the overall 1:2 stoichio-
with bond length of 2.885 Å in rocksalt AgBr.[11] In turn, the metry is retained, the connectivity changes by substitution of
Re–Br distances are affected only marginally by the Ag+ coor- X = Br in 8-BF4 by X = I. Two equivalent central Ag+ ions
dination. The bond lengths Re1–Br1 and Re1–Br2 in 8+ at adopt here a trigonal arrangement with one bridging iodide
2.5565(7) and 2.5603(5) Å, respectively, are only slightly ligand at each of the three coordinated complexes of 4b. Ac-
shortened compared with 2.574(4) and 2.581(4) Å in 4a.[5]
cordingly, the angle sum about Ag1 amounts to 360°, but one
The planar coordination at the central Ag+ atom is clearly angle at 149.37(2)° is substantially larger than the other two.
imposed by the phenyl substituents of the Re-coordinated cy- In addition two of such [Ag(4b)3]+ units are connected by the
clobutadiene, which are oriented rather parallel to the Ag+ co- third linearly coordinated Ag+ ion via one out of three terminal
ordination plane. The Ag–phenyl-C distances range from iodide ligands. The average of the Ag–I bond lengths for the
3.322(7) to 3.781(11) Å, which are partially shorter than the trigonal Ag1 amounts to 2.833 Å, while Ag–I at the linearly
sum of the van der Waals radii (1.9 + 1.7 Å)[12] but markedly coordinated Ag2 is shorter at 2.755 Å. The formation of such
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Ag+ complexes even with iodide rather than AgI precipitation ably concomitant with a 4e/2e donor switch of the coordinated
points to the strength of the Re–X bond (X = Br–, I–), which alkyne in case of 2a or a hapticity change in case of 4a. This
can obviously compete with Ag–X, while the η4-cyclobuta- conclusion is corroborated by the asymmetric coordination of
diene coordination is retained in all cases.
either the η4-cyclobutadiene or the η5-cyclopentadienyl ligand.
The Re–C5H5 bond lengths in 11+ vary from 2.206(3) Å for
Re1–C31 to 2.389(3) Å for Re1–C33. A related hapticity
change was suggested by DFT calculations on the mechanism
of the allenylcarbene complex formation (complex 3, Fig-
ure 1).[5]
Conclusions
Comparison of the reaction behavior of diphenylacetylene
as regular carbon-based alkyne and bis(benzylsulfanyl)acetyl-
ene as heteroatom-substituted alkyne at the Re(η5-C5H5)X2
fragment revealed clear differences. Generally, the sulfur de-
rivatives are distinctively more reactive at Re. The application
of bis(benzylsulfanyl)-acetylene led to an η3-allenylcarbene
complex as well as a rhenacyclopentatriene. In addition, the
desired reversible interconversion of the rhenacyclopentatriene
to a η4-cyclobutadiene complex by halide addition/abstraction
could be proven. In contrast, C/C coupling reactions with tol-
ane led exclusively to η4-cyclobutadiene complexes, which
turned out to be very stable. Halide abstraction experiments
yielded supramolecular silver halide complexes under reten-
tion of the cyclobutadiene coordination. A remarkable square
planar Ag+ coordination was uncovered, which is imposed by
the framework of the organometallic spectator ligands. The
formation of such Ag+ complexes even with bromide or iodide
rather than AgX precipitation underscores the strength of the
Re–X bond. On the contrary, the halide abstraction is possible
in both cases in presence of an incoming phosphine, which
points to an associative substitution mechanism.
Figure 4. Molecular structure of 10+ in the crystal 10-(BF4)3·5
CH2Cl2; thermal ellipsoids set at 50% probability; solvent and
hydrogen atoms are omitted for clarity. Selected bond lengths /Å and
angles /°: Re1–I1 2.7626(4), Re1–I2 2.7675(4), Re2–I3 2.7675(5),
Re2–I4 2.7498(5), Re3–I5 2.7645(6), Re3–I6 2.7421(6), Ag1–I1
3.0967(7), Ag1–I2 2.8343(7), Ag1–I3 3.2169(8), Ag1–I4 2.8135(7),
Ag1–I5 2.8518(7), Ag2–I5 3.0698(5), Ag2–I6 2.7556(5), I2–Ag1–I4
149.37(2), I4–Ag1–I5 101.68(2), I2–Ag1–I5 108.94(2).
The latter conclusion is interesting in conjunction with the
possibility to abstract the bromide substituents in the alkyne
complex 2a as well as in cyclobutadiene complex 4a in pres-
ence of phosphines. The reaction of 2a with AgBF4 with
Ph2PMe led straightforwardly to cationic phosphine complex
11-BF4. The result of a single crystal XRD is depicted in Fig-
ure 5 together with metric parameters. The introduced phos-
phine resides in orthogonal position with respect to the ReC2
plane. In contrast to the dibromide complex 2a, the alkyne in
11+ is coordinated symmetrically exhibiting Re1–C1 at
1.956(3) Å and Re–C2 at 1.965(3) Å, which is rather similar Experimental Section
to the diiodide complex 2b. In addition, Dossett et al. reported
General Information: One- and two-dimensional NMR spectra were
a related reactivity for cyclobutadiene complex 4a with PPh3
as well as PMe3. The importance of the incoming phosphine
for the halide abstraction shed light on the type of the substitu-
tion, which follows apparently an associative mechanism prob-
recorded at 300 K with Bruker Avance 250, 300 or 500 MHz spectrom-
1
eters, respectively. In H and 13C NMR, the chemical shifts were in-
ternally referenced to the solvent residual peak and in 31P NMR H3PO4
was used as external standard. Elemental analyses were performed
with a Thermo Finnigan Flash EA 1112 Series. Mass spectrometry by
electrospray ionization (ESI) was obtained with an Agilent 6210 time-
of-flight LC/MS. The starting materials [(η5-C5H5)Re(CO)2Br2], [(η5-
C5H5)Re(CO)2I2][15] and bis(benzylsulfanyl)acetylene[16] as well as
2a,[5] 4a,[8] and 5-BF4[6] were synthesized according to literature proto-
cols.
η2-C,CЈ-Bis(benzylsulfanyl)acetylene-η5-cyclopentadienyl-di-
iodido-rhenium(III) (1b): A mixture of [(C5H5)Re(CO)2I2] (65 mg,
0.12 mmol) and C2(SBn)2 (50 mg, 0.18 mmol) in toluene (20 mL) was
refluxed for 2 h. After cooling and removal of the solvent in vacuo
pure 1b was crystallized by vapor-diffusion of n-pentane into a solu-
tion of the crude product in dichloromethane. Yield: 41 mg (44%).
C21H19I2ReS2 (775.52): calcd. C 32.52, H 2.47, S 8.27%; found: C
Figure 5. Molecular structure of 11+ in the crystal 11-BF4·1.5C6H5F;
thermal ellipsoids set at 50% probability; solvent and hydrogen atoms
are omitted for clarity. Selected bond lengths /Å: Re1–C1 1.956(3),
Re1–C2 1.965(3), Re1–P1 2.4203(8), Re1–Br1 2.5674(4), C1–C2
1.360(4), C1–C2–S2 141.84(24), C2–C1–S1 133.22(23).
1
32.83, H 2.55, S 7.96%. H NMR (250 MHz, CDCl3): δ = 7.45–7.25
(m, 10 H, Ph-H), 5.62 (s, 5 H, C5H5), 4.78 (s, 4 H, CH2). 13C NMR
(62.9 MHz, CDCl3): δ = 205.9 (C2), 134.8 (Ph-ipso-C), 129.0, 128.6,
128.3 (Ph-C), 92.2 (C5H5), 44.3 (CH2) ppm.
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η5-Cyclopentadienyl-diiodido-η4-tetraphenylcyclobutadiene-
η2-C,CЈ-Bis(benzylsulfanyl)acetylene-η5-cyclopentadienyl-methyl-
rhenium (III) (4b): A mixture of [(C5H5)Re(CO)2I2] (220 mg,
diphenylphosphane-iodido-rhenium(III)-tetrafluoroborate (11-
0.42 mmol) and an excess of C2Ph2 (775 mg, 4.3 mmol) in toluene
BF4): A dark green solution of 2a (216 mg, 0.31 mmol) and PPh2Me
(40 mL) was refluxed for 72 h. After cooling and removal of the sol- (70 mg, 0.31 mmol) in dichloromethane (20 mL) was added to AgBF4
vent in vacuo pure 4b was crystallized by layering a dichloromethane (61 mg, 0.3 mmol) and stirred for 12 h. The precipitate was filtered off
solution of the crude product with n-pentane. Yield: 190 mg (52%). over celite. The solvent volume was reduced in vacuo and layered with
C33H25I2Re (861.57): calcd: C 46.00, H 2.92 %; found: C 46.33,
ethyl ether. Crystallization was achieved from a saturated fluorobenz-
ene solution at –30 °C. Yield: 168 mg (61 %). C34H32BBrF4PReS2
(888.64): calcd. C 45.95, H 3.63%; found: C 46.36, H 3.67%. 1H
1
H 3.19%. H NMR (250 MHz, CDCl3): δ = 7.62–7.05 (m, 20 H, Ph-
H), 5.71 (s, 5 H, C5H5). 13C NMR (62.9 MHz, CDCl3): δ = 132.6 (Ph-
ipso-C), 128.3, 127.8, 127.4 (Ph-C), 92.7 (C5H5), 81.6 (C4Ph4) ppm.
NMR (250 MHz, CDCl3): δ = 7.52–7.00 (m, 20 H, Ph-H), 5.75 (s,
MS (ESI-TOF, CH3CN): m/e = 884.949 (correct isotopic pattern, 5 H, C5H5), 4.70 (s, 4 H, CH2), 2.48 (d, J = 10.6 Hz, 3 H, CH3). 13C
2
M+Na+).
NMR (62.9 MHz, CDCl3): δ = 211.9 (C2), 133.9, 133.0 (Ph-ipso-C),
2
132.7, 132.5, 132.0 (d, JCP = 2.5 Hz), 131.8, 131.6, 131.4, 130.8,
η5-Cyclopentadienyl-dibromido-η4-tetrabenzylsulfanylcyclobuta-
diene-rhenium(III) (6): A solution of 5-BF4 (50 mg, 0.05 mmol) in
dichloromethane (15 mL) was treated with tetrabutylammonium-brom-
ide (16 mg, 0.05 mmol) and stirred for 12 h. Subsequently the solvent
was evaporated in vacuo and the product was washed three times with
3 mL methanol. Yield: 44 mg (93%) C37H33Br2ReS4 (951.93): calcd.
C 46.68, H 3.49, S 13.47%; found: C 46.83, H 3.62, S 13.22%. 1H
NMR (250 MHz, CDCl3): δ = 7.527.28 (m, 20 H, Ph-H), 5.43 (s, 5 H,
C5H5), 4.08 (s, 4 H, CH2). 13C NMR (62.9 MHz, CDCl3): δ = 136.4
(Ph-ipso-C), 129.3, 128.6, 127.9 (Ph-C), 97.8 (C5H5), 86.2 (C4Ph4),
39.2 (CH2) ppm. MS (ESI-TOF, CH3CN): m/e = 974.925 (correct iso-
topic pattern, M+Na+).
130.0, 129.8, 129.3, 129.2, 129.1, 128.9, 128.4, 124.0 (Ph-C), 95.7
1
(C5H5), 44.9 (CH2), 16.6 (d, JCP = 41.5 Hz, CH3). 31P NMR
(101 MHz, CDCl3): δ = –16.6 (PPh2Me). MS (ESI-TOF, CH3CN):
m/e = 842.069 (correct isotopic pattern, M++CH3CN), 801.041 (M+).
X-ray Structure Analyses: Crystal data and refinement parameters
for compounds 2b, 4b, 7-BF4, 9-BF4, 10-(BF4)3 and 11-BF4 are col-
lected in Tables S1 and S2 (Supporting Information). Single crystals
suitable for X-ray diffraction analysis were selected in Fomblin YR-
1800 perfluoropolyether oil (Alfa Aesar) at ambient temperature and
mounted on a glass fiber. During the measurement the samples were
cooled either to 123(2) or 173(2) K. Diffraction data were collected
with a Bruker-Nonius Apex X8 and a Bruker Kappa Apex II dif-
fractometer using graphite monochromated Mo-Kα radiation. Structure
solutions were found by direct methods (SHELXS-97 or SHELXS-
2013)[17] and were refined by full-matrix least-squares procedures on
F2 (SHELXL-2013). All non-hydrogen atoms were anisotropically re-
fined unless stated otherwise. Hydrogen atoms were included at calcu-
lated positions with fixed thermal parameters unless stated otherwise.
Silver(tetra-μ2-bromido)bis{dibromido-η5-cyclopentadienyl-η4-
tetra-phenylcyclobutadiene-rhenium (III)}]tetrafluoroborate (8-
BF4): A mixture of 4a (46 mg, 0.06 mmol) and AgBF4 (6 mg,
0.03 mmol) was solved in dichloromethane (15 mL) and stirred for
1 h. A slight precipitation was filtered off, and the solvent was
evaporated in vacuo. Crystallization of a pure sample of 8-BF4 was
achieved by slow evaporation of the solvent from a chloroform
solution. Yield: 32 mg (62 %). C66H50AgBBr4F4Re2 (1729.81):
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1850091, CCDC-1850092, CCDC-1850093, CCDC-
1850094, CCDC-1850095, and CCDC-1850096 for 2b, 4b, 7-BF4,
9-BF4, 10-(BF4)3, and 11-BF4 (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
C
66H50AgBBr4F4Re2·CHCl3: calcd. C 43.52, H 2.78 %; found: C
43.63, H 2.82 %. 1H NMR (300 MHz, CDCl3): δ = 7.58–7.15 (m,
30 H, Ph-H), 6.82–6.65 (m, 10 H, Ph-H), 5.65 (s, 10 H, C5H5) ppm.
MS (ESI-TOF, CH3CN): m/e = 1642.872 (correct isotopic pattern,
M+).
μ2-Bromido-bis{bromide-η5-cyclopentadienyl-η4-tetraphenylcyclo-
butadiene-rhenium(III)}]tetrafluoroborate (9-BF4): A mixture of
4a (115 mg, 0.15 mmol) and AgBF4 (16 mg, 0.08 mmol) was solved
in THF (20 mL) and refluxed for 2 h. Formed AgBr precipitate was
filtered off over celite, and the solvent was evaporated in vacuo.
Crystallization of a pure sample of 9-BF4 was achieved by gas phase
diffusion of n-pentane into a dichloromethane solution. Yield: 85 mg
(74%). C66H50BBr3F4Re2 (1542.03): calcd. C 51.41, H 3.27%; found:
C 51.24, H 3.38%. 1H NMR (300 MHz, CDCl3): δ = 7.64–7.10 (m,
40 H, Ph-H), 5.63 (s, 10 H, C5H5) ppm. MS (ESI-TOF, CH3CN): m/e
= 1455.054 (correct isotopic pattern, M+).
Supporting Information (see footnote on the first page of this article):
X-ray data, molecular structures of 7-BF4 and 9-BF4 as well as ad-
ditional NMR data.
Acknowledgements
The Deutsche Forschungsgemeinschaft (SE890/3–1) is greatfully
acknowledged for financial support.
Silver(bis-μ2-iodido)bis{silver(tris-μ2-iodido)tris-η5-cyclopenta-
Keywords: Alkyne ligands; Rhenium; Silver; Coordination
dienyl-η4-tetraphenylcyclobutadiene-rhenium(III)}]-tris(tetra- modes; Supramolecular chemistry
fluoroborate) {10-(BF4)3}: Complex 4b (103 mg, 0.12 mmol) was
solved in dichloromethane (20 mL) and treated with AgBF4 (23 mg,
0.12 mmol). After stirring for 12 h a slight precipitation was filtered
off, and the solvent was evaporated in vacuo. A crystalline sample of
10·(BF4)3 was obtained by layering a dichloromethane solution with
n-pentane. Yield: 50 mg (43%). C198H150Ag3B3F12I12Re6 (5753.42):
calcd. C 41.33, H 2.63 %; found: C 41.61, H 2.69 %. 1H NMR
(300 MHz, CDCl3): δ = 7.65–6.95 (m, 120 H, Ph-H), 5.65 (s, 20 H,
C5H5), 5.53 (s, 10 H, C5H5) ppm.
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Received: June 20, 2018
Published online: ᭿
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Journal of Inorganic and General Chemistry
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Zeitschrift für anorganische und allgemeine Chemie
S. Kleinschmidt, A. Hinz, A. Villinger, W. W. Seidel* ...... 1–7
Square Planar Coordination of Silver in a η4-Cyclobutadiene-
(η5-C5H5)ReBr2 Complex Framework
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