Single Electron Delivery to Lewis Pairs: An Avenue to Anions by Small Molecule Activation

Article abstract of DOI:10.1021/jacs.7b05120

Single electron transfer (SET) reactions are effected by the combination of a Lewis acid (e.g., E(C₆F₅)₃ E = B or Al) with a small molecule substrate and decamethylferrocene (Cp?₂Fe). Initially, the corresponding reactions of (PhS)₂ and (PhTe)₂ were shown to give the species [Cp?₂Fe][PhSB(C₆F₅)₃] 1 and [Cp?₂Fe][(μ-PhS)(Al(C₆F₅)₃)₂] 2 and [Cp?₂Fe][(μ-PhTe)(Al(C₆F₅)₃)₂] 3, respectively. Analogous reactions with di-tert-butyl peroxide yielded [Cp?₂Fe][(μ-HO)(B(C₆F₅)₃)₂] 4 with isobutene while with benzoyl peroxide afforded [Cp?₂Fe][PhC(O)OE(C₆F₅)₃] (E = B 5, Al 6). Evidence for a radical pathway was provided by the reaction of Ph₃SnH and p-quinone afforded [Cp?₂Fe][HB(C₆F₅)₃] 7 and [Cp?₂Fe]₂[(μ-O₂C₆H₄)(E(C₆F₅)₃)₂] (E = B 8, Al 9). In addition, the reaction of TEMPO with Lewis acid and Cp?₂Fe afforded [Cp?₂Fe][(C₅H₆Me₄NOE(C₆F₅)₃] (E = B 10, Al 11). Finally, reactions with O₂, Se, Te and S₈ gave [Cp?₂Fe]₂[((C₆F₅)₂Al(μ-O)Al(C₆F₅)₃)₂]₂ 12, [Cp?₂Fe]₂[((C₆F₅)₂Al(μ-Se)Al(C₆F₅)₃)₂]₂ 13, [Cp?₂Fe][(μ-Te)₂(Al(C₆F₅)₂)₃] 14 and [Cp?₂Fe]₂[(μ-S₇)B(C₆F₅)₃)₂] 15, respectively. The mechanisms of these SET reactions are discussed, and the ramifications are considered.

Full text of DOI:10.1021/jacs.7b05120

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Article
Single Electron Delivery to Lewis Pairs: An
Avenue to Anions by Small Molecule Activation
Liu (Leo) Liu, Levy L. Cao, Yue Shao, and Douglas W. Stephan
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b05120 • Publication Date (Web): 27 Jun 2017
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Single Electron Delivery to Lewis Pairs: An Avenue to Anions by
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Liu (Leo) Liu, Levy L. Cao, Yue Shao and Douglas W. Stephan*
Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario, M5S 3H6, Canada.
E-mail: dstephan@chem.utoronto.ca
ABSTRACT: Single electron transfer (SET) reactions are effected by the combination of a Lewis acid (e.g. E(C F ) E = B or
6
5 3
Al) with a small molecule substrate and decamethylferrocene (Cp* Fe). Initially, the corresponding reactions of (PhS)
2
2
and (PhTe) were shown to give the species [Cp* Fe][PhSB(C F ) ] 1 and [Cp* Fe][(µ-PhS)(Al(C F ) ) ] 2 and [Cp* Fe][(µ-
2
2
6
5
3
2
6
5
3
2
2
PhTe)(Al(C F ) ) ] 3, respectively. Analogous reactions with di-tert-butyl peroxide yielded [Cp* Fe][(µ-HO)(B(C F ) ) ] 4
6
5
3
2
2
6 5 3 2
with isobutene while with benzoyl peroxide afforded [Cp* Fe][PhC(O)OE(C F ) ] (E = B 5, Al 6). Evidence for a radical
2
6 5 3
pathway was provided by the reaction of Ph SnH and p-quinone afforded [Cp* Fe][HB(C F ) ] 7 and [Cp* Fe] [(µ-
3
2
6
5
3
2
2
O C H )(E(C F ) ) ] (E = B 8, Al 9). In addition, the reaction of TEMPO with Lewis acid and Cp* Fe afforded
2
6
4
6
5
3
2
2
[
Cp* Fe][(C H Me NOE(C F ) ] (E = B 10, Al 11). Finally, reactions with O , Se, Te and S gave [Cp* Fe] [((C F ) Al(µ-
2
5
6
4
6
5
3
2
8
2
2
6 5 2
O)Al(C F ) ) ] 12, [Cp* Fe] [((C F ) Al(µ-Se)Al(C F ) ) ] 13, [Cp* Fe][(µ-Te) (Al(C F ) ) ] 14 and [Cp* Fe] [(µ-S )B(C F ) ) ]
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5, respectively. The mechanisms of these SET reactions are discussed and the ramifications are considered.
14
Introduction
In 1923, Gilbert N. Lewis classified molecules that be-
have as electron-pair donors and electron-pair acceptors
the reactivity of transition metal centers, as the com-
bined ability of carbenes to act as electron donors and
acceptors effects the heterolytic cleavage of chemical
bonds.
1
as bases and acids, respectively. The combination of a
Lewis base and Lewis acid leads to the formation of a Lew-
is acid-base adduct (Figure 1). For close to a century such
adducts were viewed as thermodynamically stable species
that are generally unreactive.
This paradigm of main group reactivity was further
extended in 2006 with the report of the reversible activa-
2
tion of H by p-(Mes P)C F (B(C F ) ), (Mes = mesityl). In
2
2
6
4
6 5 2
this case, the Lewis acid-base adduct formation is inhibit-
ed by the sterically demanding substituents permitting
concerted action of the electron donor and acceptor on
the H molecule (Figure 1). Initially, this reactivity was ob-
served for a range of sterically “frustrated Lewis pairs”
FLPs). Subsequently, it has been expanded to systems
2
Figure 1. Reactivity of electron donor (ED) and electron ac-
ceptor (EA) combinations.
(
Another strategy to reactivity involves single electron
transfer (SET) processes. A variety of photo-catalytic and
transition-metal-catalyzed organic transformations have
been studied and shown to involve SET pathways. This has
where the free Lewis acid and base are accessible via dis-
sociative equilibria, allowing the combined action of nu-
cleophilic and electrophilic centers on small molecule sub-
3
-7
strates. This chemical behavior of FLP systems resembles
that of ambiphilic transition-metal complexes and has
been employed in a range of both stoichiometric and met-
1
5-17
18
led to applications in synthetic
and materials chemis-
1
9
try as well as biological sciences. However, SET processes
are seldom encountered in main group chemistry. Recent-
ly, Wang and co-workers reported the irreversible one-
electron oxidation of a main group compound, namely
triarylamine, by an equimolar portion of B(C F ) , in which
8
al-free catalytic activation of small molecules.
Other avenues to small molecule activation by main
9-11
group compounds have also been developed. In 2005,
Power and co-workers showed that the alkyne analog of
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5 3
–
1
2
the ensuing highly reactive [•B(C
quenched by reaction with the solvent. The group of
Agapie demonstrated the synthesis of dianionic
bis(borane) peroxide by the direct reduction of O by fer-
6 5 3
F ) ] was completely
germanium split H under ambient conditions. Two years
2
20
later, Bertrand demonstrated the facile cleavage of H and
2
1
3
a
NH by a singlet carbene center. Theoretical calculations
3
2
revealed the activation of these substrates is analogous to
21-22
rocenes in the presence of B(C F ) .
Additionally, there
6
5 3
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are a few examples of SET from transition-metal complex-
Page 2 of 12
(a)
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es to the strong Lewis acid, such as B(C F ) .
Chen pro-
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5 3
–
posed the formation of the transient [•Al(C F ) ] followed
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5 3
by decomposition during heating a C D Br solution of
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5
25
Al(C F ) with ferrocene at 100 °C for 3 days. We have
6
5 3
previously described the generation of highly reactive rad-
+
–
ical pairs of the form [R P•] and [•O(Al(C F ) ) ] from
3
6 5 3 2
reaction of FLPs derived from R P and Al(C F ) with
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6 5 3
26
N O. These species subsequently effected C-H bond acti-
2
vation.
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In the present work, we describe small molecule activa-
tion under mild conditions by delivery of a single electron
from decamethylferrocene (Cp* Fe) to a Lewis pair com-
2
(b)
(c)
prised of a small molecule donor and a Lewis acid of the
form E(C F ) (E = B or Al). These reactions proceed via
6
5 3
–
the transient radical anions [•E(C F ) ] loosely associated
6
5 3
with substrates yielding a series of decamethylferrocenium
salts with novel boron- or aluminum-containing anions.
The mechanistic implications are considered.
Results and discussion
Homolytic Cleavage of E-E Bonds (E = S, Te, O)
Initial control experiments showed that the combina-
tion of Cp* Fe with E(C F ) (E = B or Al) in a molar ratio
2
6 5 3
of 1:1 in toluene led to the slow formation of decame-
+
thylferrocenium [Cp* Fe] , with less than 20 % conversion
2
2
1
after 24 h for B(C F ) and 1 h for Al(C F ) . This was con-
6
5
3
6 5 3
current with the formation of unidentified Lewis acid deg-
1
9
radation byproducts as evidenced by F NMR spectrosco-
py. These results suggest SET from Cp* Fe to strong Lewis
2
–
acid E(C F ) generating [•E(C F ) ] . These species are
6
5
3
6 5 3
known to be extremely reactive and are quenched via reac-
27-28
tion with solvent or itself at room temperature.
None-
theless, the possibility of the activation of a substrate mol-
–
ecule by transient [•E(C F ) ] or single electron delivery to
6
5 3
loosely associated Lewis pairs was probed.
Figure 2. POV-ray depiction of the anions of 1 (a), 2 (b) and
(c). C: black; F: pink; B: yellow-green; Al: turquoise; S: yel-
3
low; Te: yellow-gray; All H atoms and the decamethylferroce-
nium cations are omitted for clarity.
1
9
F NMR spectroscopy (Figures S57-S59 in the SI). Fur-
thermore, these substrates were inert to Cp* Fe over 3
days in toluene. However, the mixtures of E(C F ) (E = B
2
6
5 3
and Al), (PhS) and Cp* Fe gave rise to deep green solu-
2
2
19
tions in 24 h and 2 min, respectively (Scheme 1). F NMR
spectra were consistent with newly formed tetra-
coordinated boron and aluminum centers. Indeed, the
products 1 and 2 were isolated and fully characterized
spectroscopically and via X-ray diffraction studies (Figures
2a and b) confirming compounds 1 and 2 to be
[
Cp* Fe][PhSB(C F ) ] and [Cp* Fe][(µ-PhS)(Al(C F ) ) ],
2
6
5
3
2
6 5 3 2
respectively. In the case of 1 repeated crystallization at-
tempts yielded poor quality crystals, nonetheless prelimi-
nary X-ray studies confirmed the connectivity as the dec-
Scheme 1 Synthesis of 1-3.
amethylferrocenium salt of the known anion,
– 29
Diphenyl disulfide and diphenyl ditelluride are weakly
Lewis basic. Indeed, no adducts were formed on mixing of
[
PhSB(C F ) ] . The Al-S bond lengths were found to be
6 5 3
2.358(2) Å and 2.339(2) Å. The ditelluride (PhTe) reacted
2
E(C F ) (E = B or Al) and the substrates (PhS)2 and
6
5
3
similarly within 2 min of addition to a mixture of one
equivalent of Cp* Fe and 2 equivalents of Al(C F ) to give
(
PhTe) in toluene at room temperature as indicated by
2
2
6 5 3
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splits disulfide bond to give IN1 (21.3 kcal/mol) generating
[Cp* Fe][(µ-PhTe)(Al(C F ) ) ] 3 (Figure 2c). The Al-S-Al
2
6 5 3 2
o
–
1
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5
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angle of 143.57(7) in 2 is less acute than the Al-Te-Al angle
of 123.71(5) in 3.
[PhSAl(C
cies are intercepted by more Al(C F )
6 5 3
6
F
5
)
3
] anion and neutral radical •SPh. These spe-
o
to give final product
P-2 and IN2 (-14.4 kcal/mol), respectively. Finally, one
electron reduction to IN2 and additional Al(C F ) affords
a second equivalent of P-2 (-38.6 kcal/mol).
The electronic structures of the anions of 1 and 2, were
examined via natural bond orbital (NBO) analysis at the
M06-2X/SVP level of theory. The results demonstrated
that the boron (0.43 a.u.) and aluminum (1.63 and 1.64 a.u.)
centers are predominantly positively charged, while the
negative charges are delocalized on S (-0.05 a.u. in 1 and -
6
5 3
30-32
Born−Oppenheimer molecular dynamics (BOMD)
simulations were performed at the UB3LYP/SVP level of
theory at 300 K (Figure 3b) for this reaction. The initial
–
0
.30 a.u. in 2), F and most C atoms. The calculated Wiberg
complex of [(PhS)
2
•Al(C
6
F
5
)
3
] exists in a doublet electron-
0
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bond indices (WBIs) suggested the weak single bond char-
acters of B-S (0.88) and Al-S (0.48 and 0.51), respectively.
ic state with S-S and Al-S distances of 2.065 and 2.565 Å,
respectively. From 0 to 10 fs, constant lengthening of S-S
distance and shortening of Al-S distance are observed.
–
This is concurrent with a deformation of the [•Al(C F ) ]
6
5 3
structure giving a tetra-coordinate Al center. This for-
mation of the Al-S bond (2.260 Å) is facile affording a re-
laxed structure in approximately 10 fs at room temperature.
3
3-35
While the O centers of carbonyl compounds
ethers
or
are known to readily coordinate to strong Lewis
acids, treatment of B(C F ) with di-tert-butyl peroxide
3
6-39
6
5 3
1
1
revealed no adduct formation as evidenced by the B and
1
9
F NMR spectra (Figures S60 and S61 in the SI). Nonethe-
less, upon subsequent addition of Cp* Fe to the mixture, a
2
color change from yellow to green was observed after 1 h.
The reaction was complete after 3 h and the product 4 was
isolated as brilliant green crystals in 68 % yield (Scheme
2). X-ray crystallography confirmed the structure as
[
Cp* Fe][(µ-HO)(B(C F ) ) ] 4 (Figure 4a). This formula-
2
6 5 3 2
tion inferred the loss of isobutene, and this was confirmed
4
0
by NMR spectroscopy on the reaction mixture.
Figure 3. (a) Free energy (kcal/mol) profile for the formation
of the salt 2. (b) Example BOMD (300 K) trajectories showing
S-S bond cleavage and Al-S bond formation. Distances are
given in Å.
For a better understanding of the mechanistic pathway
leading to the homolytic cleavage of the disulfide bond,
density functional theory (DFT) calculations were per-
formed at the SMD-M06/TZVP//M06/SVP level of theory
Figure 4. POV-ray depiction of the anions of 4 (a) and 5 (b)
(for 6, see Figure S75 in the SI). C: black; F: pink; B: yellow-
green; O: red; All H atoms of benzoyl and the decamethylfer-
rocenium cations are omitted for clarity.
(
Figure 3a) for the reaction of Al(C F ) , (PhS) and Cp* Fe.
6 5 3 2 2
One electron reduction of Al(C F ) /(PhS) homolytically
6
5
3
2
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The formation of the salt 4 requires the cleavage of O-O,
C-O and C-H bonds. Two plausible pathways for this
transformation were probed by DFT calculations (Figure
of anions of the salts 5 and 6 were further confirmed by X-
ray diffraction studies as [Cp* Fe][PhC(O)OE(C F ) ] (E =
B 5, Al 6) (Figures 4b and S75). These reactions can be
1
2
3
4
5
6
7
8
9
1
1
1
1
1
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4
4
4
4
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5
5
5
5
5
5
5
5
5
5
6
2
6 5 3
5
). These data show that homolytic splitting of the O-O
formally viewed as a homolytic cleavage of peroxide bond
–
bond of di-tert-butyl peroxide by delivery of a single elec-
by a transient [•E(C F ) ] although the precise mechanis-
6
5 3
t
tron from Cp* Fe to the Lewis pair affording [ Bu-
tic picture may be more complicated. As such, these ob-
servations are analogous to the capture of a free boryl rad-
ical with 0.5 equiv of benzoyl peroxide reported by Yama-
2
–
OB(C F ) ] IN3 (-28.3 kcal/mol) is an exothermic reaction.
6
5 3
However, the subsequent extrusion of an isobutene mole-
cule via a four-membered-ring transition state TS1 (29.4
kcal/mol) is found to be very energy-demanding (57.7
kcal/mol). An alternative pathway involves homolytic
cleavage of both O-O and C-O bonds with the aid of
4
1
shita, Ohkoshi and Nozaki.
Radical Traps
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Attempts to trap the transient radicals by reaction with
11
19
–
26
Ph
spectroscopy suggest weak coordination of B(C F )
6 5 3
the tin-hydride (Figures S65 and S66 in the SI), addition
3
SnH were also undertaken. While B and F NMR
B(C F ) to afford a transient [•O(B(C F ) ) ]
and tert-
6
5
3
6 5 3 2
4
0
with
butyl radical (IN4, 18.5 kcal/mol). Subsequent abstrac-
tion of a H atom from tert-butyl radical by [•O(B(C F ) ) ]
42
–
6
5 3 2
of Cp* Fe with stirring at room temperature for 12 h gave a
–
2
would yield isobutene and [(µ-HO)(B(C F ) ) ] (P-4, -42.3
6
5 3 2
suspension containing dark gray and green powders. The
dark gray powder showed sparingly solubility in common
organic solvents, precluding its formulation. However,
product 7 was isolated as a green powder in 60 % yield.
kcal/mol).
1
1
The B NMR spectrum of 7 showed a doublet at -25.3 ppm
1
(
43
JB-H
=
90.0 Hz).
The formulation of
7
as
[
Cp* Fe][HB(C F ) ] was further confirmed by X-ray dif-
2
6 5 3
1
19
fraction studies (Figure S75 in the SI). The Sn NMR
spectrum of the crude reaction mixture were consistent
with the formation of Ph SnSnPh (-138.5 ppm ).
4
4
3
3
Scheme 2. Synthesis of 4-6.
Scheme 3 Synthesis of 7.
Quinones are also well known reagents for trapping of
41, 45-47
radicals.
As control reactions, independent solutions
of E(C F ) (E = B and Al) were mixed separately to an
6
5 3
equivalent of p-benzoquinone (p-O C H ) and monitored
2
6
4
1
9
by F NMR spectroscopy. The formations of classical Lew-
is adducts were observed (Figures S67-S69 in the SI). In
addition, there was no reaction observed for the mixture
of Cp* Fe and p-O C H after 48 h. Gratifyingly, the reac-
2
2
6
4
tions of E(C F ) , p-O C H (E = B and Al) with Cp* Fe pro-
6
5
3
2
6
4
2
ceeded cleanly within 1 min, providing the ensuing prod-
ucts 8 and 9, respectively (Scheme 4). The formulation of
8
and 9 as [Cp* Fe] [(µ-O C H )(E(C F ) ) ] was confirmed
2
2
2
6
4
6 5 3 2
X-ray diffraction studies (Figure 6a and S75). The B-O and
Al-O bond lengths are 1.471(5) and 1.715(6) Å, respectively.
Figure 5. Free energy (kcal/mol) profile for the formation
of the salt 4.
The corresponding combination of benzoyl peroxide
with E(C F ) (E = B or Al) led to a mixture of what are
6
5 3
presumed to be weak adducts (Figures S62-S64 in the SI).
However slow addition of benzoyl peroxide to a mixture of
E(C F ) (E = B and Al) and Cp* Fe selectively afforded
Scheme 4. Synthesis of 8-11.
6
5
3
2
products 5 and 6, respectively (Scheme 2). The formations
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Al(C F ) /O in chlorobenzene with Cp* Fe immediately
6
5
3
2
2
1
9
1
2
3
4
5
6
7
8
9
gave a deep green solution. Although the F NMR spectra
displayed a complex mixture, after work-up salts 12 and
[
Cp* Fe][Al(C F ) ] were isolated (Scheme 5). X-ray dif-
2 6 5 4
fraction studies revealed the formulation of 12 as
[
Cp* Fe] [((C F ) Al(µ-O)Al(C F ) ) ] (Figure 7a). This
2
2
6
5
2
6 5 3 2 2
confirms the cleavage of the O-O bond affording the unu-
sual dianionic species 12 with an Al O core. The geometry
2
2
of Al O core is planar, featuring the average Al-O bond
2
2
lengths of 1.828 (5) Å, while the exocyclic O-Al(C F ) dis-
6
5 3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
tances averaged 1.813 (5) Å. The central Al-O bond lengths
are longer than that (1.760 (1) and 1.763 (1) Å) observed in a
5
2
neutral Al O core. The Al-Al separation was found to be
2
2
2.656(3) Å. NBO analysis revealed that the central Al at-
oms (1.95 and 1.95 a.u.) carried the most positive charges,
while the O atoms (-1.41 and -1.42 a.u.) and F atoms are
negatively charged, consistent with the ionic nature of the
central Al-O core.
Figure 6. POV-ray depiction of the anions of 8 (a), 10 (b) and
1 (c). C: black; F: pink; B: yellow-green; O: red; Cl: green; Al:
turquoise; N: blue. All H atoms and the decamethylferroceni-
um cations are omitted for clarity.
1
A computational study of this reaction demonstrates the
coordination of triplet O with Al(C F ) is an endothermic
2 6 5 3
process (20.4 kcal/mol), leading to the formation of IN5.
The subsequent reduction of IN5 by Cp* Fe affords a rela-
2
While Cp* Fe does not react with TEMPO, B(C F ) is
2
6 5 3
4
8
tively stable dianionic bis(alane) peroxide IN6 (-47.9
kcal/mol). The O-O bond length is computed to be 1.515 Å.
Both O atoms interact with Al centers to form a four-
membered ring with Al-O bond lengths of 1.788 and 2.163
Å. IN6 could serve as a •C F radical donor. The dimeriza-
known to form an adduct (Figure S70 in the SI). In a sim-
ilar fashion, Al(C F ) also forms a neutral radical adduct
6
5 3
1
9
within seconds as supported by F NMR spectroscopic
data (Figure S71). DFT calculations reveal that the spin
density of the radical adducts TEMPO-E(C F ) (E = B and
6
5
6
5 3
tion of •C F would give decafluorobiphenyl. However,
6
5
Al) is predominantly distributed over the N [62.6 % and
1.6 %] and O [31.5 % and 31.6 %] centers, respectively. The
experimentally, treatment of decafluorobiphenyl with
Al(C F ) /Cp* Fe slowly provided a complex mixture in 48
6
6
5
3
2
small WBIs of E-O (0.47, E = B and 0.29, E = Al) suggest
weak dative bonds between E and O. The singly occupied
molecular orbitals (SOMOs) are mainly localized at the
TEMPO fragments, with minor contributions from the p
orbitals of E centers (Figure S76 in the SI). This allows
h. Thus, trapping of •C F with Al(C F ) /Cp* Fe is likely to
6
5
6
5
3
2
give the observed byproduct [Cp* Fe][Al(C F ) ] (-57.1
2
6 5 4
kcal/mol). Finally, IN7 (-34.1 kcal/mol) is formed with the
O-O distance of 2.545 Å, which then combines with
Al(C F ) to yield P-12 (129.3 kcal/mol). It is important to
6
5 3
these species to accept one electron from Cp* Fe prompt-
2
note that the release of •C F radicals results in the cleav-
6
5
ing formation of the products 10 and 11 (Scheme 4). The
nature of these products was unambiguously confirmed by
X-ray crystallography to be [Cp* Fe][(C H Me NOE(C F ) ]
age of O-O bond, reminiscent of the splitting of dioxygen
53-54
by some transition-metal complexes.
2
5
6
4
6 5 3
Elemental selenium was also shown to react with
(
E = B 10, Al 11, Figures 6b and c). The X-ray diffraction
study of 10 revealed a drastic lengthening of the O-N bond
1.461 (4) Å) compared to that of the adduct of B(C F )
5 3
Al(C F ) and Cp* Fe to form a salt 13 (Scheme 5) and
6
5
3
2
[
Cp* Fe][Al(C F ) ], as well as some unidentified byprod-
(
2 6 5 4
6
ucts. The product, [Cp* Fe] [((C F ) Al(µ-Se)Al(C F ) ) ]
with TEMPO (1.311 (2) Å). In addition, the B-O bond of
.493 (5) Å in anion of 10 is significantly shorter than that
2
2
6
5
2
6 5 3 2 2
1
3 (Figure 7b) features a dianionic Al Se core analogous to
1
2 2
that observed in 12. The central Al Se ring is nearly
reported for the neutral adduct (1.594 (3) Å).
2
2
square (Al-Se: 2.418 (2), 2.428 (2) Å; Se-Al-Se: 92.70 (2)°;
Al-Se-Al: 87.29 (8)°. The Al-Al distance was found to be
Reactions with Elemental O , Se, Te and S8
2
Alkylaluminum(III) compounds are known to react with
3
.344 (2) Å, which is much longer than that (2.656 (3) Å) of
O normally gives aluminum alkoxides or alkylperoxides
2
12. Two exocyclic Al(C F ) units are located in the trans-
6
5 3
49-51
via insertion reaction into the Al-alkyl bond.
Exposure
configuration of the planar Al Se ring with the average Al-
2
2
of a chlorobenzene solution of Al(C F ) to excess dry O at
6
5
3
2
Se bond length of 2.424 (2) Å. The salt 13 presented the
55-59
room temperature resulted in a light yellow solution.
first example of a dianionic Al (µ-Se) species.
2
2
1
9
However, the F NMR spectra showed no new species
formed in 2 h (Figure S72 in the SI). Upon standing in O2
atmosphere at room temperature for 36 h, Al(C F ) de-
Treatment
of
elemental
tellurium
with
o
Al(C F ) /Cp* Fe in toluene at 0 C afforded a green sus-
6
5
3
2
6
5
3
19
pension within 6 h. After careful work-up, F NMR spec-
trum suggested two sets of pentafluorophenyl resonances,
indicating the generation of two major products. Indeed,
composed slowly affording an unidentified complex mix-
ture.
In contrast to the Agapie synthesis of a dianionic
the salt 14 with the formulation of [Cp* Fe][(µ-
2
bis(borane) peroxide by the direct reduction of O by fer-
2
Te) (Al(C F ) ) ] as well as [Cp* Fe][Al(C F ) ], were isolat-
2
6
5
2
3
2
6 5 4
21
rocenes in the presence of B(C F ) , treatment of
6
5 3
ed by fractional recrystallization. Single crystal X-ray
ACS Paragon Plus Environment

Journal of the American Chemical Society
structure analysis shows the anion of 14 to be a bicy-
Page 6 of 12
O
6 5 3
Al(C F )
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(C
6
F
5
)
3
Al
O
clo[1,1,1]pentane-like core with two tricoordinated Te at-
oms and three tetracoordinated Al atoms (Figure 7c). The
average Te-Al bond length is 2.658 (5) Å. The pentafluoro-
phenyl substituents exhibit π–π stacking surround the
Al Te core. Computations predict the average charge of Al
(20.4)
IN5
(0.0)
+ 3
2Cp*
2
Fe
Al(C
6
F
5
)
3
O
2
3
2
2
2[Cp* Fe]
and Te atoms of 1.14 a.u. and -0.55 a.u., respectively.
(-47.9)
IN6
2
O
O
2.163
(C
F
)
Al
6 5 3
Al(C F )
6
5
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2 6 5 3
Cp* Fe + Al(C F )
2
C
6
F
5
6 5 4
[Al(C F ) ]
[
2
Cp* Fe]
2
6 5
C F
.760 2.545
O
Al
6 5
C F
1
1
.
C
F
Al
O
5
7
6
0
6
5
6
C F
(-34.1)
IN7
+
6 5 3
2Al(C F )
2
6 5
C F
(C
6
F
5
)
3
Al
O
Al
6 5
C F
C
6
F
5
Al
O
5
6 5 3
Al(C F )
6
C F
(-129.3)
P-12
Figure 8. Free energy (kcal/mol) profile for the formation
of the salt 12. Bond lengths are given in Å.
Scheme 5. Reactions of O , Se, Te and S with E(C F ) and
2
8
6 5 3
Cp* Fe.
2
The corresponding reaction of S , B(C F ) and Cp* Fe
Figure 7. POV-ray depiction of the anions of 12 (a), 13 (b),
8
6
5
3
2
resulted in conversion to a single boron-containing prod-
1
4 (c) and 15 (d). C: black; F: pink; Te and B: yellow-green;
1
1
O: red; Cl: green; Al: turquoise; The decamethylferroceni-
um cations are omitted for clarity.
uct as suggested by a singlet signal at -10 ppm in B NMR
1
9
spectrum and one set of signals in F NMR spectrum. Sin-
gle crystals of 15 (Figure 7d) suitable for an X-ray diffrac-
tion study were grown by slow vapor diffusion of pentane
ACS Paragon Plus Environment

Page 7 of 12
Journal of the American Chemical Society
into a saturated dichloromethane solution at -20 ° C. The-
se data revealed the formulation of 15 as [Cp* Fe] [(µ-
Chlorobenzene (C H Cl), benzene (C H ) and chloroform-
6 5 6 6
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
d (CDCl
B(C
) were degassed and dried over calcium hydride.
was purified from sublimation at 100 C followed
2
2
3
S )B(C F ) ) ]. The dianion features a bent S7 chain with
6
F
5
)
3
̊
7
6 5 3 2
the average of S-S bond lengths of 2.036 (3) Å which is
slightly shorter than that (2.050 (4) Å) of a free dianionic
by stirring with chlorodimethylsilane at room temperature
for two hour, and dried under vacuo. Decamethylferrocene
60
S7 chain. The B-S bond lengths are 1.965 (9) and 1.988 (8)
(Cp*
ride [(PhTe)
triphenyltin hydride (Ph
), TEMPO, dry O , decafluorobiphenyl, elemental
Se and S were purchased and used directly. Al(C F ) •tol
2
Fe), diphenyl disulphide [(PhS)
], di-tert-butyl peroxide, benzoyl peroxide,
SnH), p-benzoquinone (p-
2
], diphenyl ditellu-
Å, which is in the range of B-S single bond. The S chain
2
7
carried negative charge of -0.47 a.u., whereas boron atoms
3
(
0.42 and 0.42 a.u.) are positively charged. Repeated ex-
O
2
C
6
H
4
2
periments using varying equivalents of S also afforded 15
8
8
6 5 3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
suggesting that this species has both thermodynamic sta-
bility and appropriate solubility properties to permit isola-
tion.
was prepared using literature methods. Combustion anal-
yses were performed in-house employing a Flash 2000
from Thermo Instruments CHN Analyzer. Spectra were
recorded on a Bruker Avance III 400 MHz, an Agilent DD2
In general, the reactions described herein provide a
novel route to unique anion salts. These reactions can be
viewed from two perspectives. One view involves delivery
5
00 MHz, and an Agilent DD2 600 MHz spectrometer and
1
spectra were referenced to residual solvents of CD Cl ( H
=
7
2
2
1
3
1
13
5.32 ppm; C = 53.8 ppm), CDCl ( H = 7.26 ppm; C =
3
of one electron (from Cp* Fe) to the combination of a
2
1
1
19
7.0 ppm), or externally [ B: (Et O)BF (δ 0.00), F: CFCl
Lewis acid (E(C F ) ) and base (chalcogenide species). An
2 3 3
6
5 3
(
δ 0.00)]. Chemical shifts (δ) are reported in ppm and the
alternatively perspective considers these reactions of a
one-electron donor and Lewis acid with a chalcogenide
substrate molecule. In this latter view, the present results
open a new pathway to the generation of a transient frus-
trated radical pair (FRP) and a radical pathway for FLP
chemistry. Such an avenue has recently been uncovered
absolute values of the coupling constants (J) are in Hz.
UV-Vis spectra were obtained on an Agilent 8553 UV-is
spectrophotometer using Quartz cells modified with a J-
young NMR cap to assure a near-perfect seal. High-
resolution mass spectra (HRMS) were obtained on a JMS-
T100LC JOEL DART.
61
and substantiated.
Synthesis of [Cp* Fe][PhSB(C F ) ] (1) A mixture of
Conclusions
2
6 5 3
Cp* Fe (16.3 mg, 0.050 mmol), B(C F ) (26.0 mg, 0.050
2
6 5 3
The above reactivity illustrates a general and new strat-
egy to activate small molecule substrates. Delivery of a
single electron to Lewis pairs consisting of strong Lewis
acids E(C F ) (E = B and Al) and a variety of substrates,
mmol) and diphenyl disulfide (5.5 mg, 0.025 mmol) was
stirred in 3 mL DCM at room temperature for 24 h to give
a green solution. Pentane (5 mL) was added to the solu-
tion with rapid stirring. A green solid was obtained by fil-
tration and washed with pentane (1 mL). All vola-
tiles/solvents were removed in vacuo to afford the salt 1 as
a green solid (21.8 mg, 46%). Single crystals of 1 suitable
for X-ray diffraction were obtained from layering of pen-
6
5 3
including small molecules or elemental chalcogenides af-
fords access to novel anions. These reactions can be for-
mally viewed as an avenue to access the reactivity of the
–
elusive radical anions [•E(C F ) ] . The utility of this SET
6
5 3
protocol in the production of other anions, the subsequent
chemistry of these new salts and the extension of this re-
activity to catalysis are the subjects of ongoing work.
o
1
tane with a saturated DCM solution at -15 C. H NMR (400
MHz, CD Cl , 298 K,): δ 7.89 (bs, 2H, o-C H ), 7.29 (bs, 3H,
2
2
6
5
+
13
1
p-C H and m-C H ), -33.98 (bs, Cp* Fe ). C{ H} NMR (126
6
5
6
5
2
1
MHz, CD Cl , 298 K): δ 147.6 (dm, J = 241 Hz, o-C F ),
2
2
C-F
6 5
Experimental Section
General Considerations: All manipulations were per-
1
1
139.4 (dm, J = 249 Hz, p-C F ), 136.7 (dm, J = 251 Hz,
C-F
6
5
C-F
m-C F ), 135.7 (s, SC), 128.9 (s, o-C H ), 128.1 (s, m-C H ),
6
5
6
5
6
5
1
9
formed under an atmosphere of dry, oxygen-free N by
2
125.2 (s, p-C H ) 120.9 (bs, BC). F NMR (377 MHz, CDCl ,
6 5 3
means of standard Schlenk or glovebox techniques
298 K): δ -120.9 (br, 12F, o-C F ), -155.5 (br, 6F, p-C F ), -
6
5
6 5
1
9
1
(
MBraun LABmaster SP dry box and Innovation Technol-
163.8 (br, 12F, m-C F ). F{ H} NMR (377 MHz, CD Cl , 298
6
5
2
2
ogy glovebox both equipped with a -35 °C freezer). Tolu-
ene, pentane, and dichloromethane (DCM) were collected
from a Grubbs-type column system manufactured by In-
novative Technology. These solvents, along with fluoro-
K): δ -131.7 (bs, 6F, o-C F ), -162.7 (bs, 3F, p-C F ), -167.4
6
5
6 5
1
1
(
(
bs, 6F, m-C F ). B NMR (128 MHz, CD Cl , 298K): -9.9
6 5 2 2
-
s). HRMS (DART) calcd. for [C H BF S] 620.9966, found
24 5 15
6
20.9973. Elemental analysis for C H BF FeS: calcd.: C
44 35 15
benzene (C H F) chlorobenzene (C H Cl) and 1,2-
6
5
6
5
55.78, H 3.72, found: C 55.70, H 3.68.
dichlorobenzene (1,2-C H Cl ), were dried over 4 Å molec-
6
4
2
Synthesis of [Cp* Fe][(µ-PhS)(Al(C F ) ) ] (2) A mixture
6 5 3 2
2
ular sieves. Molecular sieves, type 4 Å (pellets, 3.2 mm
diameter) purchased from Sigma Aldrich were activated
prior to usage by iteratively heating with 1050 W Haier
microwave for 5 minutes and cooling under vacuo. The
process was repeated until no further moisture was re-
leased upon heating. Dichloromethane-d (CD Cl ), bro-
of Cp* Fe (16.3 mg, 0.050 mmol), Al(C F ) •tol (62.0 mg,
2
6 5 3
0
.10 mmol) and diphenyl disulfide (5.5 mg, 0.025 mmol)
was stirred in 2 mL toluene at room temperature. After 2
min, the green solid product starts to be precipitated. Pen-
tane (5 mL) was added into the solution with rapid stir-
ring. The green solid was obtained by filtration and
washed with pentane (1 mL). All volatiles/solvents were
removed in vacuo to afford the salt 2 as a green solid (67.1
2
2
2
mobenzene-d (C D Br) purchased from Cambridge Iso-
5
6
5
tope Laboratories, were degassed and stored over 4 Å mo-
lecular sieves in the glovebox for at least 8 h prior to use.
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 12
mg, 90 %). Single crystals of 2 suitable for X-ray diffraction
were obtained from layering of pentane with a saturated
1 h, pentane (5 mL) was added into the solution with rapid
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
stirring. The green solid was obtained by filtration and
washed with pentane (1 mL). All volatiles/solvents were
removed in vacuo to afford the salt 5 as a green solid (31.7
mg, 66%). Single crystals of 5 suitable for X-ray diffraction
were obtained from layering of pentane with a saturated
o
1
DCM solution at -15 C. H NMR (400 MHz, CDCl , 298 K):
3
δ 7.18 (bs, 2H, o-C H ), 7.09 (bs, 1H, m-C H ), 6.95 (bs, 2H,
6
5
6
5
+
13
1
p-C H ), -36.82 (bs, Cp* Fe ). C{ H} NMR (126 MHz,
6
5
2
CDCl , 298 K, Al-bonded C could not be observed): δ 149.5
3
1
1
o
1
(
dm, J = 237 Hz, o-C F ), 141.0 (dm, J = 237 Hz, p-
C F ), 136.3 (dm, J = 250 Hz, m-C F ), 137.4 (s, SC), 128.0
s, o-C H ), 127.8 (s, m-C H ), 114.9 (s, p-C H ). F NMR
377 MHz, CDCl , 298 K): δ -120.9 (br, 12F, o-C F ), -155.5
DCM solution at -15 C. H NMR (400 MHz, CD Cl , 298
2 2
C-F
6
5
C-F
1
K): δ 8.12 (bs, 2H, o-C H ), 7.52 (bs, 3H, p-C H and m-
6 5 6 5
6
5
C-F
6
5
1
9
+
13
1
(
(
(
C H ), -33.75 (bs, Cp* Fe ). C{ H} NMR (126 MHz, CD Cl ,
6 5 2 2 2
6
5
6
5
6
5
298 K, B-bonded C could not be observed): δ 167.8 (C=O),
3
6 5
27
1
1
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
br, 6F, p-C F ), -163.8 (br, 12F, m-C F ). Al NMR (104
148.3 (dm, J = 249 Hz, o-C F ), 137.0 (dm, J = 255 Hz,
C-F 6 5 C-F
6
5
6
5
1
MHz, CDCl3, 298K): blank. Elemental analysis for
C H Al F FeS: calcd.: C 49.92, H 2.36, found: C 49.97, H
p-C F ), 136.3 (dm, J = 246 Hz, m-C F ), 131.4 (s, p-C H ),
6 5 C-F 6 5 6 5
129.9 (s, CC(O)O), 128.6 (s, o-C H ), 128.2(s, m-C H ).
62
35
2
30
6
5
6
5
1
9
1
3
2.42.
F{ H} NMR (377 MHz, CD Cl , 298 K): δ -135.0 (d, J
=
2
2
3
C-F
2
0.7 Hz, 6F, o-C F ), -163.4 (t, J = 19.5 Hz, 3F, p-C F ), -
6 5 C-F 6 5
Synthesis of [Cp* Fe][(
µ
-PhTe)(Al(C F ) ) ] (3) A mix-
2
6 5 3 2
11
1
167.6 (m, 6F, m-C F ). B{ H} NMR (128 MHz, CD Cl , 298
K): δ -4.7 (bs). HRMS (DART) calcd. for [C H BF O ]
6
5
2
2
ture of Cp* Fe (16.3 mg, 0.050 mmol), Al(C F ) •tol (62.0
2
6
5
3
-
25
5
15
2
mg, 0.10 mmol) and diphenyl ditelluride (10.3 mg, 0.025
mmol) was stirred in 2 mL toluene at room temperature.
After 2 min, the green solid product starts to be precipi-
tated. Pentane (5 mL) was added into the solution with
rapid stirring. The green solid was obtained by filtration
and washed with pentane (1 mL). All volatiles/solvents
were removed in vacuo to afford the salt 3 as a green solid
633.0143, found 633.0137. Elemental analysis for
C H BF FeO : calcd.: C 56.34, H 3.68, found: C 56.70, H
4
5
35
15
2
3.80.
Synthesis of [Cp*
of Cp* Fe (16.3 mg, 0.050 mmol) and Al(C
0.050 mmol) was stirred in 3 mL C Cl. Benzoyl peroxide
Fe][PhC(O)OAl(C F )
] (6) A mixture
F ) •tol (31.0 mg,
6 5 3
2
6 5 3
2
H
5
6
(
62.8 mg, 79 %). Single crystals of 3 suitable for X-ray dif-
(6.1 mg, 0.025 mmol) was added slowly into solution. After
2 min, pentane (5 mL) was added into the solution with
rapid stirring. The green solid was obtained by filtration
and washed with pentane (1 mL). All volatiles/solvents
were removed in vacuo to afford the salt 6 as a green solid
(37.1 mg, 76%). Single crystals of 6 suitable for X-ray dif-
fraction were obtained from layering of pentane with a
o
1
saturated C H F solution at -15 C. H NMR (400 MHz,
6
5
CD Cl , 298 K): δ 7.82 (d, 2H, J= 6.2 Hz, o-C H ), 7.25 (m,
2
2
6
5
+
1
H, m-C H ), 7.19 (m, 2H, p-C H ), -25.35 (bs, Cp* Fe ).
6 5 6 5 2
13
1
C{ H} NMR (126 MHz, CD Cl , 298 K, Al-bonded C could
2
2
1
not be observed): δ 150.2 (dm, J = 238 Hz, o-C F ), 141.4
dm, J = 257 Hz, p-C F ), 137.0 (dm, J = 255 Hz, m-
fraction were obtained from layering of pentane with a
C-F
6 5
1
1
1
(
saturated C
(400 MHz, CD
(bs, 3H, p-C
NMR (126 MHz, CD
observed): δ 169.6 (C=O), 150.4 (dm, JC-F = 231 Hz, o-C
6
H
5
Cl solution at room temperature. H NMR
C-F
6
5
C-F
C F ), 138.0 (s, o-C H ), 130.0 (s, p-C H ), 128.5 (s, m-C H ),
2
Cl
and m-C
Cl , 298 K, Al-bonded C could not be
2
, 298 K): δ 8.35 (bs, 2H, o-C H ), 7.70
6
5
6
5
6
5
6
5
6
5
19
+
13
1
1
25.6 (s, TeC). F NMR (377 MHz, CD Cl , 298 K): δ -120.2
6
H
5
H ), -36.75 (bs, Cp* Fe ). C{ H}
6 5 2
2
2
(
bs, 12F, o-C F ), -150.9 (bs, 6F, p-C F ), -160.5 (bs, 12F, m-
2
2
6
5
6 5
1
C F ). Elemental analysis for C H Al F FeTe: calcd.: C
6
F
5
),
), 136.9 (dm, JC-F = 252 Hz,
m-C F ), 135.2 (s, p-C H ), 131.9 (s, o-C H ), 130.6 (s,
6
5
62 35
2 30
1
1
4
6.91, H 2.22, found: C 47.17, H 2.32.
141.1 (dm, JC-F = 245 Hz, p-C F
6 5
6
5
6
5
6
5
Synthesis of [Cp* Fe][(
of di-tert-butyl peroxide (3.7 mg, 0.025 mmol), B(C F )
µ
-HO)(B(C F ) ) ] (4) A mixture
2
6
5
3
2
19
1
CC(O)O), 128.5 (s, m-C H ). F{ H} NMR (377 MHz,
6
5
6
5 3
CD Cl , 298 K): δ -123.3 (bs, 6F, o-C F ), -158.3 (bs, 3F, p-
2
2
6 5
(
52.0 mg, 0.10 mmol) and Cp* Fe (16.3 mg, 0.050 mmol)
2
27
C F ), -164.6 (bs, 6F, m-C F ). Al NMR (104 MHz, CD Cl ,
6
5
6
5
2
2
was stirred in 3 mL C H Cl for 3 h. The colour of the solu-
6
5
298 K):
δ
108.9 (bs). Elemental analysis for
tion changed to green. The volatiles were removed in vac-
uo. The resulting green solid was washed with a mixture of
pentane (2 mL) and C H Cl (0.5 mL), and dried in vacuo to
C H AlF FeO : calcd.: C 55.40, H 3.62, found: C 55.51, H
4
5
35
15
2
3
.78.
6
5
Synthesis of [Cp* Fe][HB(C F ) ] (7) A mixture of Cp* Fe
give the salt 4 as green powder (54.3 mg, 87 %). Single
crystals of 4 suitable for X-ray diffraction were obtained
from layering of pentane with a saturated C H Cl solution
2
6
5
3
2
(
16.3 mg, 0.050 mmol), Ph SnH (17.6 mg, 0.050 mmol) and
3
B(C F ) (26.0 mg, 0.050 mmol) was stirred in 3 mL DCM.
6
5 3
6
5
1
After 12 h, pentane (5 mL) was added into the solution
with rapid stirring. The green solid was obtained by filtra-
tion and washed with pentane (1 mL). All vola-
tiles/solvents were removed in vacuo to afford the salt 7 as
a green solid (25.2 mg, 60 %). Single crystals of 7 suitable
for X-ray diffraction were obtained from layering of pen-
at room temperature. H NMR (400 MHz, CDCl , 298 K): δ
3
+
13
1
6
.78 (bs, 1H, OH), -37.77 (bs, Cp* Fe ). C{ H} NMR (126
2
1
MHz, CD Cl , 298 K): δ 148.1 (dm, J = 240 Hz, o-C F ),
2
2
C-F
6 5
1
1
1
39.8 (dm, J = 251 Hz, p-C F ), 137.1 (dm, J = 256 Hz,
C-F 6 5 C-F
1
9
1
m-C F ), 120.4 (bs, BC). F{ H} NMR (377 MHz, CD Cl ,
6
5
2
2
2
98 K): δ -120.8 (d, J = 19.7 Hz, 12F, o-C F ), -160.4 (bs, 6F,
6 5
1
1
1
tane with a saturated DCM solution at room temperature.
p-C F ), -165.8 (bs, 12F, m-C F ). B{ H} NMR (128 MHz,
6
5
6 5
119
The generation of Ph SnSnPh3 was confirmed by Sn
CD Cl , 298 K) δ -2.7 (bs). HRMS (ESI) calcd. for
3
2
2
1
-
NMR spectroscopy (-138.5 ppm in CD Cl ). H NMR (400
[
C HB F O] 1040.9734, found 1040.9742.
2
2
3
6
2 30
1
MHz, CD Cl , 298 K): δ 3.72 (q, J = 88.5 Hz, 1H, HB), -
2
2
B-H
Synthesis of [Cp* Fe][PhC(O)OB(C F ) ] (5) A mixture
2
6
5
3
+
13
1
3
6.67 (bs, Cp* Fe ). C{ H} NMR (126 MHz, CD Cl , 298 K):
2 2 2
of Cp* Fe (16.3 mg, 0.050 mmol) and B(C F ) (26.0 mg,
2
6
5
3
1
1
δ 148.7 (dm, J = 226 Hz, o-C F ), 138.6 (dm, J = 241 Hz,
p-C F ), 131.1 (dm, J = 249 Hz, m-C F ), 125.8 (bs, BC).
C-F
6
5
C-F
0
.050 mmol) was stirred in 3 mL DCM. Benzoyl peroxide
1
6
5
C-F
6 5
(
6.1 mg, 0.025 mmol) was added slowly into solution. After
ACS Paragon Plus Environment

Page 9 of 12
Journal of the American Chemical Society
1
9
1
1
F{ H} NMR (377 MHz, CDCl , 298 K): δ -134.2 (bs, 6F, o- 237 Hz, o-C F ), 138.7 (dm, J = 247 Hz, p-C F ), 136.7
3
6
5
C-F
6 5
3
1
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
C F ), -164.8 (t, J = 18.9 Hz, 3H, p-C F ), -167.9 (m, 6F,
m-C F ). B NMR (128 MHz, CD Cl , 298 K): δ -25.3 (d, J
=
(dm, J = 248 Hz, m-C F ), 124.6 (bs, BC), 68.3 (s, N-C),
C-F 6 5
6
5
C-F
6
5
1
1
1
19
1
36.6 (s, CH ), 35.3 (s, CH ), 19.1 (bs, CH ). . F{ H} NMR
2 2 3
6
5
2
2
B-H
-
1
90.0 Hz). HRMS (DART) calcd. for [C HBF ] 512.9932,
(377 MHz, CD Cl , 298 K): δ -136.0 (d, J = 18.6 Hz, 6F, o-
2 2 C-F
1
8
15
1
found 512.9939. Elemental analysis for C H BF Fe: calcd.:
C F ), -163.2 (t, J = 18.0 Hz, 3F, p-C F ), -167.1 (bs, 12F, m-
6 5 C-F 6 5
3
8
31
15
1
1
C 54.38, H 3.72, found: C 54.00, H 3.68.
Synthesis of [Cp* Fe] [( -O C H )(B(C F ) ) ] (8) A mix-
ture of Cp* Fe (16.3 mg, 0.050 mmol), p-O C H (2.7 mg,
0
stirred in 3 mL DCM in the dark. After 1 min, pentane (5
mL) was added into the solution with rapid stirring. The
green solid was obtained by filtration and washed with
pentane (1 mL). All volatiles/solvents were removed in
vacuo to afford the salt 8 as a green solid (39.3 mg, 88 %).
Single crystals of 8 suitable for X-ray diffraction were ob-
tained from layering of pentane with a saturated DCM
C F ). B NMR (128 MHz, CD Cl , 298 K): δ -3.9 (s). HRMS
6 5 2 2
-
(
DART) calcd. for [C27H BF NO] 668.1242, found
18 15
µ
2
2
2
6
4
6 5 3 2
6
68.1244. Elemental analysis for C H BF FeNO: calcd.: C
37 48 15
2
2
6
4
5
0.82, H 5.53, N 1.60, found: C 51.00, H 5.77, N 1.68.
Synthesis of [Cp* Fe][(C Me NOAl(C ] (11) A mix-
ture of Cp* Fe (16.3 mg, 0.050 mmol), TEMPO (7.8 mg,
0.050 mmol) and Al(C •tol (31.0 mg, 0.050 mmol) was
.025 mmol) and B(C F ) (26.0 mg, 0.050 mmol) was
6 5 3
H
5
F )
6 5 3
2
6
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
F )
6 5 3
stirred in 3 mL DCM. After 1 min, pentane (5 mL) was
added into the solution with rapid stirring. The green solid
was obtained by filtration and washed with pentane (1
mL). All volatiles/solvents were removed in vacuo to afford
the salt 11 as a green solid (45.5 mg, 90 %). Single crystals
of 11 suitable for X-ray diffraction were obtained from lay-
1
solution at room temperature. H NMR (400 MHz, CD Cl ,
2
2
2
+
13
1
98 K): δ 6.81 (bs, 4H, C H ), -36.48 (bs, Cp* Fe ). C{ H}
6 4 2
NMR (126 MHz, CD Cl , 298 K): δ 152.6 (s, OC), 148.6 (dm,
ering of pentane with a saturated 1,2-C
6
H
4
Cl
2
solution at
, 298 K): δ
), 0.98
), -35.56 (bs). C{ H} NMR (126 MHz, CD Cl
298 K, Al-bonded C could not be observed): δ 150.0 (dm,
2
2
1
1
1
JC-F = 239 Hz, o-C F ), 139.2 (dm, J = 250 Hz, p-C F ),
room temperature. H NMR (400 MHz, CD
1.72 (m, 2H, CH ), 1.50 (m, 4H, CH
(s, 6H, CH
2
Cl
2
6
5
C-F
6 5
1
1
35.5 (dm, J = 250 Hz, m-C F ), 125.4 (bs, BC), 118.3 (s,
C H ). F{ H} NMR (377 MHz, CDCl , 298 K): δ -134.0 (bs,
2
), 1.31 (s, 6H, CH
2 3
C-F
6 5
19
1
13
1
,
2
6
4
3
3
2
1
2F, o-C F ), -163.6 (bs, 6F, p-C F ), -167.9 (bs, 12F, m-C F ).
6 5 6 5 6 5
11
1
1
B NMR (128 MHz, CD Cl , 298 K): δ -3.2 (bs). Elemental
J
C-F = 230 Hz, o-C
6
F
5
), 140.2 (dm, JC-F = 245 Hz, p-C
136.6 (dm, JC-F = 255 Hz, m-C ), 59.0 (s, N-C), 40.5 (s,
CH ), 34.1 (s, CH ), 19.0 (s, CH ), 18.1 (s, CH
377 MHz, CDCl , 298 K): δ -121.2 (bs, 12F, o-C F ), -160.1
F ),
6 5
2
2
1
analysis for C H B F Fe O : calcd.: C 55.19, H 3.61, found:
F
6 5
8
2
64
2
30
2
2
19
1
C 55.61, H 3.79.
Synthesis of [Cp* Fe] [(
2
2
3
). F{ H} NMR
3
(
(
3
6 5
µ
-O C H )(Al(C F ) ) ] (9) A mix-
2
2
2 6 4 6 5 3 2
27
m, 6F, p-C F ), -165.5 (bs, 12F, m-C F ). Al NMR (104
6
5
6 5
ture of Cp* Fe (16.3 mg, 0.050 mmol), p-O C H (2.7 mg,
2
2
6
4
MHz, CD Cl , 298 K): δ 106.8. Elemental analysis for
2
2
0
.025 mmol) and Al(C F ) •tol (31.0 mg, 0.050 mmol) was
6 5 3
C47H48NAlF15FeO: calcd.: C 55.85, H 4.79, N 1.39, found:
C 56.30, H 4.91, N 1.40.
stirred in 3 mL DCM in the dark. After 1 min, pentane (5
mL) was added into the solution with rapid stirring. The
green solid was obtained by filtration and washed with
pentane (1 mL). All volatiles/solvents were removed in
vacuo to afford the salt 9 as a green solid (81.7 mg, 90 %).
Single crystals of 9 suitable for X-ray diffraction were ob-
tained from layering of pentane with a saturated DCM
Synthesis of [Cp*
and [Cp* Fe][Al(C
into a chlorobenzene solution (1.5 mL) of Cp*
0.025 mmol) and Al(C •tol (31.0 mg, 0.050 mmol). Im-
Fe]
[((C
F
)
Al(
(excess, 4 atm) was added
Fe (8.2 mg,
µ-O)Al(C F ) ) ] (12)
2
2
6
5
2
6 5 3 2 2
F
5
) ] Dry O
4
2
6
2
2
F )
6 5 3
mediately, the colour of the solution changed to be light
green. Pentane (5 mL) was added into the solution with
rapid stirring. The green solid was obtained by filtration
and washed with pentane (1 mL). All volatiles/solvents
were removed in vacuo to afford a mixture. Single crystals
of 12 suitable for X-ray diffraction were obtained from slow
diffusion of pentane into a saturated C H Cl solution at
6 5
room temperature overnight (4 mg, 13 %). After collection
of the crystals of 12, the resulting solution was layered with
o
1
solution at -15 C. H NMR (400 MHz, CD Cl , 298 K): δ
2
2
+
13
1
7
.39 (bs, 4H, C H ), -37.21 (bs, Cp* Fe ). C{ H} NMR (126
6 4 2
MHz, CD Cl , 298 K, Al-bonded C could not be observed):
2
2
1
δ 151.9 (s, OC), 150.5 (dm, J = 238 Hz, o-C F ), 141.3 (dm,
C-F
6 5
1
1
JC-F = 249 Hz, p-C F ), 137.2 (dm, J = 254 Hz, m-C F ),
6
5
C-F
1
6 5
1
9
1
28.7 (s, C H ), 119.1 (s, C H ). F{ H} NMR (377 MHz,
6
4
6
4
CDCl , 298 K): δ -122.6 (bs, 12F, o-C F ), -158.4 (bs, 6F, p-
3
6 5
27
C F ), -164.6 (bs, 12F, m-C F ). Al NMR (104 MHz, CD Cl ,
6
5
6
5
2
2
2
98 K): δ 101.7. Elemental analysis for C H Al F Fe O :
pentane to give [Cp* Fe][Al(C F ) ] as green crystals (7.6
2 6 5 4
8
2
64
2
30
2
2
calcd.: C 54.20, H 3.55, found: C 54.41, H 3.69.
Synthesis of [Cp* Fe][(C H Me NOB(C F ) ] (10) A mix-
mg, 30 %). The NMR data of the salt 12 have not been col-
lected since the crystals of 12 grown out in some green oily
byproducts that could not be completely removed. The
2
5
6
4
6 5 3
ture of Cp* Fe (16.3 mg, 0.050 mmol), TEMPO (7.8 mg,
2
1
salt [Cp* Fe][Al(C F ) ]: H NMR (400 MHz, CD Cl , 298
2
6
5
4
2
2
0
.050 mmol) and B(C F ) (26.0 mg, 0.050 mmol) was
6 5 3
+
13
1
K): δ -36.43 (bs, Cp* Fe ). C{ H} NMR (126 MHz, CD Cl ,
2
2
2
stirred in 3 mL toluene. After 1 min, pentane (5 mL) was
added into the solution with rapid stirring. The green solid
was obtained by filtration and washed with pentane (1
mL). All volatiles/solvents were removed in vacuo to afford
the salt 10 as a green solid (39.3 mg, 90 %). Single crystals
of 10 suitable for X-ray diffraction were obtained from lay-
ering of pentane with a saturated DCM solution at room
2
98 K, Al-bonded C could not be observed): δ 150.2 (dm,
1
1
JC-F = 232 Hz, o-C F ), 140.8 (dm, J = 245 Hz, p-C F ),
6
5
C-F
1
6 5
1
19
1
36.8 (dm, J = 252 Hz, m-C F . F{ H} NMR (377 MHz,
C-F 6 5
3
CDCl , 298 K): δ -122.9 (bs, 8F, o-C F ), -158.5 (t, J = 17.8
3
6
5
C-F
27
Hz, 4F, p-C F ), -164.8 (bs, 8F, m-C F ). Al NMR (104
6
5
6 5
MHz, CD Cl , 298 K): δ 114.6. HRMS (DART) calcd. for
2
2
-
1
[C AlF ] 694.9496, found 694.9499. Elemental analysis
24 20
temperature. H NMR (400 MHz, CD Cl , 298 K): δ 1.54
2
2
+
for C H AlF Fe: calcd.: C 45.30, H 3.35, found: C 45.11, H
34 30 20
3.60.
(
bs, 4H, CH ), 0.98 (s, 12H, CH ), -36.74 (bs, Cp* Fe ).
2 3 2
1
3
1
1
C{ H} NMR (126 MHz, CD Cl , 298 K): δ 147.9 (dm, J =
C-F
2
2
ACS Paragon Plus Environment

Journal of the American Chemical Society
-Se)Al(C F ) ) ] (13)
241 Hz, o-C
Page 10 of 12
1
Synthesis of [Cp* Fe] [((C F ) Al(
µ
6
F
5
), 139.8 (dm, JC-F = 241 Hz, p-C
6
F
5
), 137.2 (dm,
), 120.3 (bs, BC), F{ H} NMR (377
, 298 K): δ -131.1 (bs, 12F, o-C ), -162.0 (bs, 6F,
). B NMR (128 MHz,
-10.0. Elemental analysis for
: calcd.: C 48.02, H 3.18, found: C 47.69, H
2
2
6
5
2
6 5 3 2 2
1
19
1
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
and [Cp* Fe][Al(C F ) ] A mixture of Cp* Fe (8.2 mg,
J
C-F = 246 Hz, m-C F
6 5
2
6
5
4
2
0
.025 mmol), Se (2 mg, 0.025 mmol) and Al(C F ) •tol (31.0
MHz, CDCl
3
F
6 5
6
5 3
1
1
mg, 0.050 mmol) was stirred in 3 mL C H Cl. After 12 h,
p-C F ), -166.8 (bs, 12F, m-C F
6 5 6 5
6
5
pentane (5 mL) was added into the solution with rapid
stirring. The green solid was obtained by filtration and
washed with pentane (1 mL). All volatiles/solvents were
removed in vacuo and the resulting green solid was col-
lected and fractional recrystallized to afford 13 (6.3 mg, 20
CD
2
Cl
2
,
B
298 K):
δ
C H
76
F
2
30Fe
S
60
2
7
3.10.
X-ray crystallography X-ray crystallographic data were
collected on a Bruker Apex2 X-ray diffractometer at 150±2
%
) and [Cp* Fe][Al(C F ) ] (10.7 mg, 42 %). Single crystals
2 6 5 4
K using a graphite monochromator with MoΚ(α) radiation
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
62
of 13 suitable for X-ray diffraction were obtained from slow
diffusion of pentane into a saturated C H Cl solution at
(
λ = 0.71073 Å) and the Bruker APEX-2 software package.
6
5
Suitable crystals were selected and mounted in Paratone-
N oil on a MiTeGen cryoloop, then placed in the cold (N2)
stream of the diffractometer. Unit cell parameters were
determined from consecutive scans at different orienta-
tions. The data were integrated using the SAINT software
1
room temperature. H NMR (400 MHz, CD Br, 298 K): δ -
5
+
13
1
3
3.50 (bs, Cp* Fe ). C{ H} NMR (126 MHz, CD Br, 298 K):
2 5
no signal could be observed after 10000 scans since the low
1
9
1
solubility of the salt 13. F{ H} NMR (377 MHz, CD Br, 298
5
3
63
K): δ -120.7 (bs, 12F, o-C F , Al(C F ) ), -123.4 (d, J = 19.9
6
5
6
5
3
C-F
package and a multi-scan absorption correction was ap-
plied using SADABS . All structures were solved and re-
3
64
Hz, 8F, o-C F , Al(C F ) ), -154.3 (t, J = 18.2 Hz, 4F, p-
6
5
6
5
2
C-F
C F , Al(C F ) ), -158.4 (bs, 8F, m-C F , Al(C F ) ), -162.3
6
5
6
5
2
6
5
6
5
2
fined by direct methods in the SHELXTL suite of programs
2
(
bs, 6F, p-C F , Al(C F ) ), -165.9 (bs, 12F, m-C F ,
6 5 6 5 3 6 5
Al(C F ) ). Al NMR (104 MHz, CD Br, 298 K): δ blank. As
using XS and refinement by full-matrix least-squares on F
27
65,66
6
5
3
5
using XL.
All non-hydrogen atoms were subjected to
1
9
shown in the F NMR spectrum (see SI), trace unidenti-
fied impurities exist. Efforts were made to remove the
trace unidentified impurities but failed. Thus, the ele-
mental analyses gave unsatisfying results.
anisotropic refinement and carbon-bound hydrogen atoms
were placed in calculated positions using an appropriate
riding model and coupled isotropic temperature factors
(
U (H) = 1.2U (C)).
iso eq
Synthesis of [Cp* Fe][(µ-Te) (Al(C F ) ) ] (14) A mixture
2 6 5 2 3
of Cp* Fe (8.2 mg, 0.025 mmol), Te (3.2 mg, 0.025 mmol)
2
ASSOCIATED CONTENT
2
Supporting Information.
and Al(C F ) •tol (31.0 mg, 0.050 mmol) was stirred in 3 mL
6
5 3
o
X-ray data are deposited in CCDC #1546082-1546095 and
toluene at 0 C. After 6 h, cold pentane (5 mL) was added
into the solution with rapid stirring. The green solid was
obtained by filtration and washed with cold pentane (1
mL). All volatiles/solvents were removed in vacuo and the
1
546544. NMR spectra, crystal data and computational
details (PDF) Crystallographic data for compounds 2-15
and [Cp* Fe][Al(C F ) ] (ZIP) The Supporting Information
2
6 5 4
is available free of charge via the Internet at
http://pubs.acs.org.
resulting green solid was collected and recrystallization at
o
-
15 C to afford 14 (10.0 mg, 24 %) and [Cp* Fe][Al(C F ) ]
2
6 5 4
(
12.8 mg, 50 %). Single crystals of 14 suitable for X-ray dif-
AUTHOR INFORMATION
Corresponding Author
fraction were obtained from slow diffusion of pentane into
o
1
a saturated 1,2-C H Cl solution at -15 C. H NMR (400
6
4
2
+
13
1
MHz, CD Cl , 298 K): δ -33.35 (bs, Cp* Fe ). C{ H} NMR
2
2
2
*
dstephan@chem.utoronto.ca
(
126 MHz, CD Cl , 298 K, Al-bonded C could not be ob-
2 2
1
1
served): δ 149.7 (dm, J = 231 Hz, o-C F ), 140.4 (dm, J
C-F
Author Contributions
C-F
6
5
1
19
1
=
248 Hz, p-C F ), 136.3 (dm, J = 256 Hz, m-C F ). F{ H}
The manuscript was written with contributions of all au-
thors. All authors have given approval to the final version
of the manuscript.
6
5
C-F
6 5
NMR (377 MHz, CD Cl , 298 K): δ -120.2 (bs, 12F, o-C F ), -
2
2
6 5
3
1
58.8 (t, J = 17.7 Hz, 6F, p-C F ), -162.1 (bs, 12F, m-C F ).
C-F 6 5 6 5
27
Al NMR (104 MHz, CD Cl , 298 K): δ blank. The salt 14
2
2
Funding Sources
decomposed gradually in both solution and solid state at
room temperature with the formation of black powders,
preventing performing elemental analysis.
NSERC of Canada.
ACKNOWLEDGMENT
Synthesis of the salt [Cp* Fe] [(µ-S )B(C F ) ) ] (15) A
7 6 5 3 2
2
2
D.W.S. gratefully acknowledges the financial support from
NSERC Canada and the award of Canada Research Chair.
DWS is also grateful for the award of an Einstein Fellowship
at TU Berlin.
mixture of Cp* Fe (16.3 mg, 0.050 mmol), S (12.8 mg,
2
8
0
.050 mmol) and B(C F ) (26.0 mg, 0.050 mmol) was
6 5 3
stirred in 3 mL DCM. After 12 h, pentane (5 mL) was added
into the solution with rapid stirring. The green solid was
obtained by filtration and washed with pentane (1 mL). All
volatiles/solvents were removed in vacuo to afford the salt
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