Inorganic Chemistry
Article
spectrometer with a liquid nitrogen finger dewar at −195 °C
(microwave frequency, 9.255 GHz; microwave power, 6 mW; scan
time, 240 s; time constant, 0.03 s; field modulation amplitude, 1 mT;
g = 2.05 and 2.01).
70%. 1H NMR (400 MHz, CDCl3) δ 6.99 (s, 8H), 6.94 (s, 1H), 2.29
(s, 24H). Compound (j’): Bis(4-methoxy-2-methylphenyl)-
formamidine (0.5 g, 1.76 mmol), NaHMDS (0.35 g, 1.93 mmol),
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Cu(MeCN)4PF6 (0.66 g, 1.76 mmol). Yield: 0.84 g, 69%. H NMR
General Synthesis of Formamidine Ligands (c) and (f)−(m).
Mesityl aniline (1.0 g, 7.40 mmol), triethyl orthoformate (0.55g, 3.7
mmol), and acetic acid (3−5 drops) were mixed in a 25 mL round-
bottom flask. The flask was fitted with a condenser and a receiving
flask and heated at 140 °C for 1 h, condensing MeOH. After that, the
temperature was raised to 170 °C, and the mixture was heated for
another 2 h. The reaction mixture was then allowed to reach room
temperature. The resulting off-white hard solid was mixed with Et2O
and ground with a glass rod until a fine powder was produced. The
white powder was collected by filtration and washed with several
portions of Et2O and vacuum-dried. Yield: 0.85 g, 82%. Other
derivatives were prepared using the same procedure with the
appropriate aniline in place of mesityl aniline.
(400 MHz, CDCl3) δ 7.53 (s, 2H), 6.85 (d, J = 8.4 Hz, 4H), 6.69 (d, J
= 3.0 Hz, 4H), 6.66−6.61 (m, 4H), 3.75 (s, 12H), 2.39 (s, 12H), 0.28
(s, residual HMDS). Compound (k’): Bis(6-methoxy-2-
methylphenyl)formamidine (0.5 g, 1.76 mmol), NaHMDS (0.35 g,
1.93 mmol), Cu(MeCN)4PF6 (0.66 g, 1.76 mmol). Yield: 0.79 g, 65%.
1H NMR (400 MHz, CDCl3) δ 7.43 (s, 2H), 6.88 (t, J = 8.0 Hz, 4H),
6.75 (d, J = 7.5 Hz, 4H), 6.69 (d, J = 8.0 Hz, 4H), 3.66 (s, 12H), 2.41
(s, 12H). Compound (l’): Bis(6-chloro-2-methylphenyl)formamidine
(0.5 g, 1.71 mmol), NaHMDS (0.34 g, 1.88 mmol), Cu(MeCN)4PF6
(0.64 g, 1.71 mmol). Yield: 0.86 g, 71%. 1H NMR (400 MHz, CDCl3)
δ 7.20 (d, J = 7.9 Hz, 4H), 7.18 (s, 2H), 7.06 (d, J = 7.5 Hz, 4H), 6.91
(t, J = 7.8 Hz, 4H), 2.42 (s, 12H). Compound (m’): Bis(2,6-
diisopropylphenyl)formamidine (0.5 g, 1.37 mmol), NaHMDS (0.28
g, 1.51 mmol), Cu(MeCN)4PF6 (0.51 g, 1.37 mmol). Yield: 0.86 g,
73%. 1H NMR (400 MHz, CDCl3) δ 7.09−7.02 (m, 14H), 3.61
(hept, J = 6.9 Hz, 8H), 1.26 (d, J = 6.9 Hz, 24H), 1.18 (d, J = 6.9 Hz,
24H).
Synthesis of [Cu2((diphenylphosphanyl)-N-mesitylmethan-
imine)2](PF6)2 (a’). Cu(MeCN)4(PF6) (0.5140 g, 1.38 mmol) was
dissolved in acetone (∼3 mL) and was added dropwise to a solution
of (a) (0.4570 g, 1.38 mmol) in Et2O (∼12 mL). Formation of a
yellow suspension was seen (if yellow clumps are formed, adding few
drops of acetone would break them up and make a nice solid). The
reaction mixture was stirred overnight at room temperature and
filtered to obtain the title compound as a yellow powder. It was
washed with Et2O (2 × 5 mL) and vacuum-dried. Yield: 0.6451 g,
81%. 1H NMR (400 MHz, CDCl3) δ 8.56 (d, J = 23.6 Hz, 2H), 7.68−
7.43 (m, 20H), 6.82 (s, 4H), 2.22 (s, 6H), 2.03 (s, 12H), 1.79 (s,
12H-metal coordinated MeCN). 31P{1H} NMR (400 MHz, CDCl3) δ
−3.22 (s), −145.89 (sept, PF6). Anal. cacld. for C48H50Cu2F12N4P4:
C, 49.62; H, 4.34; N, 4.82. Found: C, 50.09; H, 4.57; N, 4.72.
Synthesis of Cu2(2-(diphenylphosphanyl)pyrrolide)2 (p’). A
solution of lithium 2-(diphenylphosphanyl)pyrrolide (p) (0.1000 g,
0.39 mmol) in THF (∼3 mL) was added dropwise to a suspension of
Cu(MeCN)4PF6 (0.1449 g, 0.39 mmol) in THF (∼6 mL). The
resulting pale orange color solution became cloudy over time. The
reaction mixture was stirred at room temperature overnight and
filtered to collect the title compound as a white solid. It was washed
with THF (2 × 2 mL) and Et2O (2 × 3 mL) and vacuum-dried. The
title compound has poor solubility in common organic solvents but
significantly dissolves in MeCN. Yield: 0.1712 g, 62%. X-ray quality
crystals were grown using a saturated solution of (p’) in MeCN at RT.
1H NMR (400 MHz, CD3CN) δ 7.39−7.25 (m, 20H), 7.06 (s, 2H),
Compound (f): 4-methoxyaniline (1.0 g, 8.12 mmol), triethyl
orthoformate (0.60 g, 4.06 mmol). Yield: 0.78 g, 75%. 1H NMR (400
MHz, CDCl3) δ 8.37 (s, 1H), 8.04 (s, 1H), 7.05−6.78 (m, 8H), 3.79
(s, 6H). Compound (g): 4-chloroaniline (1.0 g, 7.84 mmol), triethyl
orthoformate (0.58 g, 3.92 mmol). Yield: 0.84 g, 81%. 1H NMR (400
MHz, CDCl3) δ 8.17 (s, 1H), 7.31 (s, 8H), 2.84 (brs, residual H2O).
Compound (h): 2,6-dimethylaniline (1.0 g, 8.25 mmol), triethyl
orthoformate (0.61 g, 4.15 mmol). Yield: 0.82 g, 79%. 1H NMR (400
MHz, CDCl3) δ 7.30 (brs, 1H), 7.28−6.72 (m, 6H), 2.28 (s, 12H).
Calcd m/z theoretical: 252.16, 253.17, 254.17. Found: 253.1, 254.2,
255.1. Dimeric form shows up: 505.3, 506.3, 507.2. Compound (i): 4-
chloro-2,6-dimethylaniline (1.0 g, 6.43 mmol), triethyl orthoformate
(0.48 g, 3.21 mmol). Yield: 0.79 g, 77%. 1H NMR (400 MHz, CDCl3)
δ 7.31 (brs, 1H), 7.20−6.98 (m, 4H), 2.22 (d, J = 4.5 Hz, 12H).
Calcd m/z theoretical: 320.08, 321.09, 322.08. Found: 321.3, 322.3,
323.3. Compound (j): 4-methoxy-2-methylaniline (1.0 g, 7.23 mmol),
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triethyl orthoformate (0.54 g, 3.66 mmol). Yield: 0.87 g, 84%. H
NMR (400 MHz, CDCl3) δ 7.82 (brs, 1H), 6.91−7.02 (m, 2H),
6.80−6.68 (m, 4H), 3.78 (s, 6H), 2.31 (s, 6H). Calcd m/z theoretical:
284.15, 285.16, 286.16. Found: 285.3, 286.3, 287.3. Compound (k):
6-methoxy-2-methylaniline (1.0 g, 7.23 mmol), triethyl orthoformate
(0.54 g, 3.66 mmol). Yield: 0.87 g, 84%. 1H NMR (400 MHz, CDCl3)
δ 7.88 (s, 1H), 7.56 (s, 1H), 7.04−6.70 (m, 6H), 3.90−3.70 (m, 6H),
2.37−2.22 (m, 6H). Calcd m/z theoretical: 284.15, 285.16, 286.16.
Found: 285.3, 286.3, 287.4. Compound (l): 2-chloro-6-methylaniline
(1.0 g, 7.06 mmol), triethyl orthoformate (0.52 g, 3.53 mmol). Yield:
0.89 g, 86%. 1H NMR (400 MHz, CDCl3) δ 7.69−6.89 (m, 6H), 6.67
(brs, 1H), 5.86 (brs, 1H), 2.60−2.15 (m, 6H). Calcd m/z theoretical:
292.05, 293.06, 294.05. Found: 293.2, 294.2, 295.2. Compound (m):
2,6-diisopropylaniline (1.0 g, 5.64 mmol), triethyl orthoformate (0.42
1
g, 2.82 mmol). Yield: 0.81 g, 79%. H NMR (400 MHz, CDCl3) δ
6.23 (dd, J = 3.4, 2.0 Hz, 2H), 6.15 (d, J = 2.2 Hz, 2H), 2.12 (s,
coordinated CH3CN). 31P{1H} NMR (400 MHz, CD3CN) δ −14.24.
Anal. calcd for C36H32Cu2N4P2·1.4MeCN: C, 61.01; H, 4.44; N, 6.95.
Found: C, 58.78; H, 4.44; N, 6.77. Repeated attempts gave consistent
low %C values, possibly due to variability in solvent coordination.
Synthesis of Cu2(dppf)3(PF6)2 (3) and Cu12(μ4-S6)(dppf)4 (4).
[Cu(dppf)(MeCN)2]PF6 (0.5418 g, 0.640 mmol) was dissolved in
DCM (8 mL), and a solution of Na2S (0.0125 g, 0.160 mmol) in
MeOH (5 mL) was added dropwise. The resulting reddish-orange
mixture was stirred overnight and filtered through a fine frit to collect
4 as a reddish solid. It was washed with Et2O (2 × 5 mL) and
vacuum-dried. Yield: 0.0642 g. 1H and 31P{1H} NMR results in
CDCl3 were similar to the reported values.33 X-ray quality crystals
were grown overnight at room temperature using a saturated solution
of 4 in CDCl3. The filtrate was added with Et2O (10 mL) to get a
shiny yellow-orange precipitate. It was collected by vacuum filtration,
and the filtrate was reduced to half followed by addition of Et2O (10
ML) to get a second crop. The two crops were combined and washed
with Et2O (2 × 5 mL) and vacuum-dried to afford 3 as a yellow-
orange powder. Yield: 0.1983 g. 1H NMR (400 MHz, CDCl3) δ
7.47−7.15 (m, 60H), 4.25 (s, 12H), 4.04 (s, 12H), 3.74 (t, THF),
1.85 (q, THF). 31P{1H} NMR (400 MHz, CDCl3) δ −10.35 (brs),
7.29−7.01 (m, 6H), 5.55 (d, J = 11.9 Hz, 1H), 3.42−3.13 (m, 4H),
1.36−1.06 (m, 24H). Calcd m/z theoretical: 364.29, 365.29, 366.29.
Found: 365.5, 366.4
General Synthesis for Dicopper Formamidinate Precursor
Complexes (c’)31 and (h’)−(m’). NaHMDS (0.36 g, 1.96 mmol) in
THF (∼2 mL) was added dropwise to a solution of N,N-
dimesitylformamidine (0.50 g, 1.78 mmol) in THF (∼ 5 mL). The
mixture was stirred for 1 h at room temperature, and Cu(MeCN)4PF6
(0.67 g, 1.78 mmol) was added as a solid. The reaction mixture was
stirred at room temperature for 3 h, and the solvent was removed
under vacuum, providing (c’) as a white precipitate. It was collected
by filtration, washed with Et2O (2 × 3 mL), and vacuum-dried. Yield:
0.45 g, 74%. Other derivatives were prepared using the same
procedure with the appropriate formamidine in place of the dimesityl
derivative.
Compound (h’): Bis(2,6-dimethylphenyl)formamidine (0.5 g, 1.98
mmol), NaHMDS (0.40 g, 2.18 mmol), Cu(MeCN)4PF6 (0.74 g,
1
1.98 mmol). Yield: 0.80 g, 64%. H NMR (400 MHz, CDCl3) δ
7.09−7.01 (m, 10H), 6.96 (s, 1.4H), 6.94 (d, J = 1.2 Hz, 2H), 6.92 (s,
0.6H), 2.41 (s, 24H). Compound (i’): Bis(4-chloro-2,6-
dimethylphenyl)formamidine (0.5 g, 1.42 mmol), NaHMDS (0.29
g, 1.57 mmol), Cu(MeCN)4PF6 (0.53 g, 1.42 mmol). Yield: 0.77 g,
I
Inorg. Chem. XXXX, XXX, XXX−XXX