Organometallics
Article
preparation of compound [P(Ph)3Me]ClO4.32 Under an inert
atmosphere, to a solution of the corresponding phosphine in toluene
was added a stoichiometric amount of methyl iodide. After 6−8 h of
stirring at refluxing temperature, a white precipitate appeared.
Filtration of the solution allowed us to obtain the corresponding
iodide salt. To a solution of this compound in dichloromethane was
added a stoichiometric amount of silver perchlorate. After 7 h of
stirring, the solution was filtered. Finally, concentration under vacuum
and addition of hexane (5 mL) led to the precipitation of the
corresponding products [P(C6H4OMe)3Me]ClO4 and [P-
(C6H4F)3Me]ClO4, as white solids.
315 cm−1 ν(Au−Cl). MS (ESI+): calcd for C19H17AuClNaP [M +
Na]+ 531.0314; found 531.0317.
[AuCl(CH2P(C6H4F)3)] (6). Yield: 61%. Anal. Calcd for 6
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(C19H14AuClF3P): C, 40.55; H, 2.51. Found: C, 40.46; H, 2.60. H
NMR (400 MHz, 298 K, CDCl3): 7.76 (m, 6H, PC6H4F), 7.27 (m,
6H, PC6H4F), 2.10 (d, 2H, CH2). 19F NMR (377 MHz, 298 K,
CDCl3): −102.3 (m). 31P{1H} NMR (162 MHz, 298 K, CDCl3): 29.2
(s). 13C{1H} NMR (101 MHz, 298 K, CDCl3): 166.0 (dd, C-F), 135.8
(dd, CArH), 121.2 (dd, P-CAr), 117.6 (dd, CArH), −0.1 (d, CH2). FT-
IR (Nujol mull): 522 ν(Au-C), 323 cm−1 ν(Au-Cl). MS (ESI+): calcd
for C19H14AuClF3NaP [M + Na]+ 585.0031; found 585.0013.
[AuCl(CH2P(C6H4OMe)3)] (7). Yield: 64%. Anal. Calcd for 7
[P(C6H4OMe)3Me]ClO4. Yield: 95%. Anal. Calcd for [P-
(C6H4OMe)3Me]ClO4 (C22H24ClO7P): C, 56.60; H, 5.18. Found:
C, 56.22; H, 5.16. 1H NMR (400 MHz, 298 K, CDCl3): 7.52 (m, 6H,
PC6H4OCH3), 7.14 (m, 6H, PC6H4OCH3), 3.90 (s, 9H, OCH3), 2.71
(d, 3H, CH3). 31P{1H} NMR (162 MHz, 298 K, CDCl3): 18.7 (s).
FT-IR (Nujol mull): 1106, 624 cm−1 ν(ClO4). MS (ESI+): calcd for
C22H24O3P [P(C6H4OMe)3Me]+ 367.1458; found 367.1467. MS
(ESI−): calcd for ClO4 [ClO4]− 98.9480; found 98.9486.
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(C22H23AuClO3P): C, 44.13; H, 3.87. Found: C, 44.25; H, 3.96. H
NMR (400 MHz, 298 K, CDCl3): 7.63 (m, 6H, PC6H4OMe), 7.00 (m,
6H, PC6H4OMe), 3.86 (s, 9H, OCH3), 2.02 (d, 2H, CH2). 31P{1H}
NMR (162 MHz, 298 K, CDCl3): 27.8 (s). 13C{1H} NMR (101 MHz,
298 K, CDCl3): 163.4 (d, C-OCH3), 134.9 (d, CArH), 117.0 (d, P-
CAr), 115.1 (d, CArH), 55.7 (s, OCH3), 0.1 (d, CH2). FT-IR (Nujol
mull): 525 ν(Au-C), 309 cm−1 ν(Au-Cl). MS (ESI+): calcd for
C22H23AuClNaO3P [M + Na]+ 621.0631; found 621.0619.
[P(C6H4F)3Me]ClO4. Yield: 92%. Anal. Calcd for [P(C6H4F)3Me]-
ClO4 (C19H15ClF3O4P): C, 52.98; H, 3.51. Found: C, 53.07; H, 3.49.
1H NMR (400 MHz, 298 K, CDCl3): 7.72 (m, 6H, PC6H4F), 7.39 (m,
General Procedure for the Catalytic Synthesis of Cyclic
Acetals. Catalysis at 100 °C during 4 h. In a two-necked round-
bottomed flask, evacuated and filled with nitrogen, were dissolved the
alkyne (1 mmol), the ethylene glycol (1 mmol), the corresponding Au
complex (0.02 mmol), and the silver salt, AgOTf (0.02 mmol), in 5
mL of toluene. The reaction was protected from light and placed at
100 °C with stirring. Aliquots of the reaction mixture (around 0.1 mL)
were periodically withdrawn from the reactor and analyzed by GC-MS.
Catalysis at 75 °C during 1 h. We performed the test in a similar
way but carrying out the reaction in ambient conditions at 75 °C.
Computational Details. All geometry optimizations were carried
out using the M06-2X hybrid functional.33 In all calculations, the
heteroatoms were treated by SDD pseudopotentials,34 including only
the valence electrons for each atom. For these atoms double-ζ basis
sets were used, augmented with d-type polarization functions.35 For H
atoms, a double-ζ basis set was used, together with a p-type
polarization function.36 The 19-valence electron SDD pseudopoten-
tial37 was employed for Au atoms, together with two f-type
polarization functions.38 Full geometry optimizations and transition
structure (TS) searches were carried out with the Gaussian 09
package.39 The possibility of different conformations was taken into
account for all structures. Frequency analyses were carried out at the
same level used in the geometry optimizations, and the nature of the
stationary points was determined in each case according to the
appropriate number of negative eigenvalues of the Hessian matrix.
Scaled frequencies were not considered. Mass-weighted intrinsic
reaction coordinate (IRC) calculations were carried out by using the
Gonzalez and Schlegel scheme40,41 in order to ensure that the TSs
indeed connected the appropriate reactants and products. Bulk solvent
effects were considered implicitly by performing single-point energy
calculations on the gas-phase optimized geometries, through the
IEFPCM polarizable continuum model42 as implemented in Gaussian
09. The internally stored parameters for toluene were used to calculate
solvation free energies (ΔGsolv). Gibbs free energies (ΔG) were used
for the discussion on the relative stabilities of the considered
structures. The Au−L bond dissociation energies and the Au−π
interaction energies were estimated using counterpoise correction for
the BSSE.43
6H, PC6H4F), 2.93 (d, 3H, CH3). 19F NMR (377 MHz, 298 K,
CDCl3): −99.1 (s). 31P{1H} NMR (162 MHz, 298 K, CDCl3): 21.4
(s). FT-IR (Nujol mull): 1100, 623 cm−1 ν(ClO4). MS (ESI+): calcd
for C19H15F3P [P(C6H4F)3Me]+ 331.0858; found 331.0865. MS
(ESI−): calcd for ClO4 [ClO4]− 98.9480; found 98.9482.
Synthesis of [Au(C6F5)(CH2P(C6H4F)3)] and [Au(C6F5)(CH2P-
(C6H4OMe)3)]. This synthesis is a modification of the preparation of
compound [Au(C6F5)(CH2PPh3)].25 In a Schlenk under an inert
atmosphere was suspended 0.412 mmol of corresponding phospho-
nium salt ([P(C6H4OMe)3Me]ClO4 or [P(C6H4F)3Me]ClO4) in 25
mL of dry diethyl ether. Then 0.412 mmol of butyllithium and 0.412
mmol of [Au(C6F5)(tht)] were added to the suspension to obtain a
colorless solution, which was filtered. Finally, concentration under
vacuum and addition of hexane (5 mL) led to the precipitation of the
corresponding products, [Au(C6F5)(CH2P(C6H4F)3)] and [Au-
(C6F5)(CH2P(C6H4OMe)3)], as white solids.
[Au(C6F5)(CH2P(C6H4F)3)]. Yield: 43%. Anal. Calcd for [Au(C6F5)-
(CH2P(C6H4F)3)] (C25H14AuF8P): C, 43.25; H, 2.03. Found: C,
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43.37; H, 1.92. H NMR (400 MHz, 298 K, CDCl3): 7.80 (m, 6H,
PC6H4F), 7.27 (m, 6H, PC6H4F), 1.82 (d, 2H, CH2). 19F NMR (377
MHz, 298 K, CDCl3): −103.0 (s, 3F, C6H4F), −116.9 (dd, 2F, Fortho),
−161.3 (t, 1F, Fpara), −163.1 (m, 2F, Fmeta). 31P{1H} NMR (162 MHz,
298 K, CDCl3): 31.6 (s). FT-IR (Nujol mull): 1500, 953, 776 ν(C6F5),
526 cm−1 ν(Au−C). MS (ESI−): calcd for C25H13AuF8P [M − H]−
693.0298; found 693.0309.
[Au(C6F5)(CH2P(C6H4OMe)3)]. Yield: 52%. Anal. Calcd for [Au-
(C6F5)(CH2P(C6H4OMe)3)] (C28H23AuF5O3P): C, 46.04; H, 3.17.
1
Found: C, 45.92; H, 3.22. H NMR (400 MHz, 298 K, CDCl3): 7.65
(m, 6H, PC6H4OMe), 7.01 (m, 6H, PC6H4OMe), 3.86 (s, 9H,
OCH3), 1.77 (d, 2H, CH2). 19F NMR (377 MHz, 298 K, CDCl3):
−116.5 (dd, 2F, Forto), −161.8 (t, 1F, Fpara), −163.4 (m, 2F, Fmeta).
31P{1H} NMR (162 MHz, 298 K, CDCl3): 30.6 (s). FT-IR (Nujol
mull): 1502, 951, 803 ν(C6F5), 528 cm−1 ν(Au−C). MS (ESI+): calcd
for C28H23AuF5NaO3P [M + Na]+ 753.0863; found 753.0847.
Preparation of [AuCl(CH2PPh3)] (5), [AuCl(CH2P(C6H4F)3)] (6),
and [AuCl(CH2P(C6H4OMe)3)] (7). To a solution of [Au(C6F5)(Y)]
(0.250 mmol; Y = CH2PPh3, CH2P(C6H4F)3, CH2P(C6H4OMe)3) in
diethyl ether at −10 °C was added an excess of a solution of HCl in
diethyl ether. After 3−4 h of stirring a white precipitate appeared.
Filtration of the solution allowed obtaining the corresponding product:
5, 6, or 7.
In the case of fragment [AuPPh3]+, all the attemps to fully optimize
the model system using the DFT M06-2X functional failed. In order to
overcome this problem, we performed a (QM/MM) ONIOM44
optimization (DFT M06-2X functional/molecular mechanical (Uni-
versal Force Field, UFF)),45 followed by a single-point full DFT
calculation to obtain the energy of the fragment in the same conditions
as other calculations. This methodology was proved with the fragment
[AuPMe3]+, finding very similar results in terms of energy.
[AuCl(CH2PPh3)] (5). Yield: 61%. Anal. Calcd for 5 (C19H17AuClP):
C, 44.86; H, 3.37. Found: C, 45.01; H, 3.42. 1H NMR (400 MHz, 298
K, CDCl3): 7.77−7.55 (m, 15H, C6H5), 2.12 (d, 2H, CH2). 31P{1H}
NMR (162 MHz, 298 K, CDCl3): 30.3 (s). 13C{1H} NMR (101 MHz,
298 K, CDCl3): 133.5 (d, CArH), 133.2 (d, CArH), 129.6 (d, CArH),
125.7 (d, P-CAr), −1.2 (d, CH2). FT-IR (Nujol mull): 512 ν(Au−C),
H
Organometallics XXXX, XXX, XXX−XXX