Journal of the American Chemical Society
Article
at 80 °C. The solution was cooled to room temperature, diluted with
65 mL of diethyl ether, cooled to 0 °C, and quenched by the
successive dropwise addition of 3.8 mL of 10% NaOH solution and
11.4 mL of water. The colorless precipitate was vacuum filtered
through Celite, and the filter cake was washed with diethyl ether (3 ×
20 mL). The combined filtrate was concentrated to give a pale yellow
oil. This resulting yellow oil was purified by column chromatography
(silica gel, 100% ethyl acetate, Rf = 0.38), yielding a pale oil (4.6 g, 87%
EPR spectrum, X-band (ν = 9.186 GHz) spectrometer in acetone at 70
K: g∥ = 2.270, g⊥ = 2.043, A∥ = 172 G.
[(DB-OMe)CuII(OClO3)CH3COCH3)](ClO4), 1H,OMe. Single crystals of
a [(DB-OMe)CuII(CH3COCH3)]2+, 1H,OMe complex were obtained by
vapor diffusion of diethyl ether into a solution of the copper complex
in acetone. Elemental analysis (C36H39Cl2CuN5O10), calculated: C
(51.71), H (4.70), N (8.38); found: C (51.68), H (4.86), N (8.37).
ESI-MS: m/z = 578.5, corresponding to [(DB-OMe)CuI]+ in acetone
at room temperature. EPR spectrum, X-band (ν = 9.186 GHz)
spectrometer in acetone at 77 K: g∥ = 2.277, g⊥ = 2.049, A∥ = 175G.
[(DB-Cl-OMe)CuII(CH3COCH3)](ClO4)2, 1Cl,OMe. Elemental analysis
(C36H38Cl3CuN5O10), calculated: C (49.66), H (4.40), N (8.04);
found: C (49.35), H (4.45), N (7.79). ESI-MS: m/z = 612.5,
corresponding to [(DB-Cl-OMe)CuI]+ in acetone at room temper-
ature. EPR spectrum, X-band (ν = 9.186 GHz) spectrometer in
acetone at 70 K: g∥ = 2.272, g⊥ = 2.044, A∥ = 176 G.
1
yield). H NMR (400 MHz, CDCl3): δ 7.40−7.23 (m, 5H).
Partially Deuterated Dibenzyl Amine-d2. Deuterated benzaldehyde
(4.2 g, 48.58 mmol) and benzylamine (4.2 g 58.808 mmol) were
placed in 70 mL of EtOH in a 250 mL round-bottom flask, and then
the mixture solution was stirred for 4 h under Ar to form an imine
intermediate (Scheme 3). This intermediate imine can then be isolated
and reduced with a suitable reducing agent, deuterated sodium
borohydride. Deuterated sodium borohydride, 98 atom % D (Aldrich,
NaBD4; 3.3 g, 78.84 mmol), was slowly added to the solution and
stirred for 30 min at room temperature. To quench excess NaBD4, 20
mL of MeOH was slowly added at 0 °C, and then all solvents were
removed by rotary evaporation. The resulting crude product was
dissolved in 100 mL of CH2Cl2 and washed two times with a saturated
Na2CO3 solution. After drying over anhydrous MgSO4, the solution
was filtered and removed by rotary evaporation. The resulting yellow
oil was purified by column chromatography (silica gel, 20% ethyl
acetate with hexane, Rf = 0.67) yielding a pale oil (7.5 g, 96% yield).
1H NMR (400 MHz, CDCl3): δ 7.40−7.23 (m, 10H), 3.80 (s, 2H).
ESI-MS, m/z: 200.1 (L + H+) in MeOH at room temperature.
Fully Deuterated Dibenzyl Amine-d4. Deuterated benzaldehyde
(5.2 g, 47.634 mmol) and deuterated benzylamine (6.3 g, 58.808
mmol) were placed in 70 mL of EtOH in a 250 mL round-bottom
flask, and then the mixture solution was stirred for 4 h under Ar.
Deuterated sodium borohydride, 98 atom % D (Aldrich, NaBD4; 2 g,
47.78 mmol), was slowly added to the solution at 0 °C. To quench
excess NaBD4, 20 mL of MeOH was added, and then all solvents were
removed by using reduced pressure. The resulting crude product was
dissolved in 100 mL of CH2Cl2 and washed two times with a saturated
Na2CO3 solution. After drying over anhydrous MgSO4, the solution
was filtered and removed by rotary evaporation. The resulting yellow
oil was purified by column chromatography (silica gel, 20% ethyl
acetate with hexane, Rf = 0.67), yielding a pale oil (7.5 g, 97% yield).
1H NMR (400 MHz, CDCl3): δ 7.35−7.26 (m, 10H), 2.18 (s, 1H).
[(d2-LH,H)CuII(H2O)](ClO4)2. ESI-MS: m/z = 550.5, corresponding to
[d2-(LH,H)CuI]+ in acetone at room temperature (Figure S2). EPR
spectrum, X-band (ν = 9.186 GHz) spectrometer in acetone at 70 K:
g∥ = 2.270, g⊥ = 2.043, A∥ = 175 G (Figure S3).
[(d4-LH,H)CuII(H2O)](ClO4)2. ESI-MS: m/z = 552.5, corresponding to
[(d4-LH,H)CuI]+ in acetone at room temperature (Figure S2). EPR
spectrum, X-band (ν = 9.186 GHz) spectrometer in acetone at 70 K:
g∥ = 2.270, g⊥ = 2.043, A∥ = 172 G (Figure S3).
DFT Calculations. Calculations on the copper hydroperoxo
complex supported by LH,H were performed with the B3LYP
functional and a TZVP basis set on the Cu-OOH fragment and the
coordinating nitrogen atoms and SV on all other atoms as
implemented in Gaussian 09.14 A TZVP basis set was utilized for an
additional equivalent of H2O2 and the nitrogen atom of NEt3 (SV on
all of the other atoms). Optimizations were performed in acetone with
the polarizable continuum model on an ultrafine integration grid. Spin
contamination was accounted for as described in the Supporting
Information. Analytical frequency calculations were performed on all
stationary points, and thermal corrections to the Gibbs free energy
were determined at −90 °C. Transition states were connected to the
corresponding products and reactants by optimizing from the
transition-state geometry, slightly distorted along the computed
imaginary frequency or with an intrinsic reaction coordinate.11
Calculations on the [(TMG3tren)CuII-OOH]+ system (TMG3tren =
(1,1,1-tris[2-[N2-(1,1,3,3-tetramethylguanidino)]ethyl]amine))) were
performed as described previously15 with Gaussian 03.16
ESI-MS, m/z: 201.6 (L) in MeOH at room temperature.
DB-d2 (d2-LH,H). 1H NMR (400 MHz, CDCl3): δ 8.59 (d, 2H), 7.63
(d, 2H), 7.54 (t, 2H), 7.37−7.11 (m, H), 7.10 (t, 2H), 6.76 (d, 1H),
6.33 (d, 1H), 4.81 (s, 2H, CH2Ph), 3.90 (s, 4H, 2CH2Py), 3.70 (s, 2H,
CH2Py). ESI-MS, m/z: 510.5 (L + Na+), 488.5 (L + H+) in MeOH at
room temperature.
RESULTS AND DISCUSSION
■
Mononuclear copper(II) complexes [(LX1,X2)CuII(Y)](ClO4)2
(1X1,X2) (Y = H2O, acetone) were generated, isolated, and
purified by reacting the various ligands (Scheme 4; X = Cl, H,
DB-d4 (d4-LH,H). ESI-MS, m/z: 490.5 (L + H+) in MeOH at room
temperature.
Scheme 4
Synthesis of Copper(II) Complexes. [(DB)CuII(H2O)(OClO3)]-
(ClO4), 1H,H. The synthesis and characterization of the DB copper
complex was recently reported. DB ligand (430 mg, 0.886 mmol) was
treated with CuII(ClO4)2·6H2O (328 mg, 0.886 mmol) in acetone (20
mL) and stirred for 10 min at room temperature. The mixture
complex was precipitated as a blue solid upon the addition of diethyl
ether (120 mL). The supernatant was decanted, and the resulting
crystalline solid was washed two times with diethyl ether and dried
under reduced vacuum to afford a blue solid. The blue solid was
recrystallized twice from acetone/diethyl ether. After vacuum-drying,
the blue crystals weighed 587 mg (87% yield). Elemental analysis
(C35H39Cl2CuN5O10), calculated: C (51.01), H (4.77), N (8.50);
found: C (50.95), H (4.66), N (8.42). ESI-MS: m/z = 548.5,
corresponding to [(DB)CuI]+ in acetone at room temperature (Figure
S1). EPR spectrum, X-band (ν = 9.186 GHz) spectrometer in acetone
at 70 K: g∥ = 2.273, g⊥ = 2.048, A∥ = 173 G.
or OMe) with Cu(ClO4)2·6H2O in acetone, precipitating solid
products with Et2O, and recrystallizing.17 An X-ray crystallo-
graphically derived structural diagram for 1H,OMe is shown in
Figure 1, along with spectroscopic data.17
Cupric hydroperoxo complexes 2X1,X2 were obtained at −90
°C in acetone by reacting CuII precursors 1X1,X2 with 10 equiv
of H2O2 or X·H2O2, X = urea, (Ph3PO)2, in the presence of
Et3N (2 equiv) under Ar (Scheme 4). Under these conditions, a
bright green product, [(LH,H)CuII-OOH]+ (2H,H), forms,
[(DB-Cl)CuII(CH3COCH3)](ClO4)2, 1H,Cl. Elemental analysis
(C35H36Cl3CuN5O9), calculated: C (50.01), H (4.32), N (8.33);
found: C (50.17), H (4.52), N (8.32). ESI-MS: m/z = 582.5,
corresponding to [(DB-Cl)CuI]+ in acetone at room temperature.
C
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX