Inorganic Chemistry
Article
Method B. To a stirred solution of 1 (400 mg, 0.63 mmol, 1.0
equiv) in toluene (10 mL) was added dropwise a solution of
(trimethylsilyl)methyllithium (59.8 mg, 0.63 mmol, 1.0 equiv) in
toluene (3 mL). The yellow, cloudy suspension was allowed to stir at
room temperature overnight and then filtered through a pad of Celite.
All volatiles were removed in vacuo, and the crude product was
recrystallized from n-hexane at −40 °C to yield 3a as a yellow solid
(261.5 mg, 383.5 μmol, 60%). Single crystals of 3a suitable for X-ray
crystallography were obtained as dark-yellow crystals by recrystalliza-
tion from n-hexane at −40 °C. 1H NMR (600.13 MHz, C6D6, 295 K):
δ 232.8 (s, 2H, CH(CH3)2), 121.0 (s, 2H, CHHP), 116.1 (s, 2H,
CHHP), 72.7 (s, 2H, CH(CH3)2), 46.7 (s, 2H, HCarb4/5), 30.0 (s, 6H,
CH(CH3)2), 20.2 (s, 6H, CH(CH3)2), 19.1 (s, 9H, Si(CH3)3), 4.1 (s,
2H, HCarb2/7), 1.7 (s, 18H, C(CH3)3), −11.1 (bs, 12H, CH(CH3)2).
13C NMR (150.92 MHz, C6D6, 295 K): δ 1167.0 (s, 2C, CH(CH3)2,
C16), 1101.5 (s, 2C, CCarb8a/9a), 741.5 (s, 2C), 727.0 (s, 2C), 440.5 (s,
3C, Si(CH3)3, C20), 374.7 (s, 2C, CCarb1/8), 328.1 (s, 2C, CCarb3/6),
299.2 (s, 2C), 292.4 (s, 2C), 245.4 (s, 2C, CH(CH3)2, C18), 102.9 (q,
1JCH = 125.4 Hz, 6C, C(CH3)3, C11), 45.0 (s, 2C, CH(CH3)2, C17),
Method B. A solution of 3a (40.0 mg, 58.7 μmol) in C6D6 (0.8 mL)
was filled in a NMR tube with a J. Young Teflon valve and set under an
atmosphere of hydrogen (8 bar) for 24 h. The NMR tube was shaken
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at irregular intervals, and the reaction progress was monitored via H
NMR spectroscopy. After the reaction was complete, all volatiles were
removed in vacuo, and the dark-brown residue was taken up in a little
n-pentane, filtered through Celite, concentrated, and kept at −40 °C
for 2 days to yield 4 as dark-red crystals (29.0 mg, 48.7 μmol, 83%).
Single crystals of 4 suitable for X-ray crystallography were obtained as
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dark-red crystals by recrystallization from n-pentane at −40 °C. H
NMR (600.13 MHz, C6D6, 295 K): δ 52.3 (s), 38.7 (s), 37.1 (s), 22.0
(s), 15.2 (s), 7.4 (s), 4.1 (s), 3.7 (s), 1.4 (s), −1.3 (s), −4.5 (s), −16.3
(s), −44.9 (s), −65.3 (s). μeff = 6.8 μB (Evans, C6D6, 295 K). Anal.
Calcd for C68H110Fe2N2P4: C, 68.56; H, 9.31; N, 2.35. Found: C,
69.05; H, 9.02; N, 2.13.
Synthesis of (PNP)Fe(CO)2H (5). To a solution of 4 (40 mg, 67.3
μmol) in C6D6 was added an atmosphere of CO (5 bar). The color of
the solution changed from brown to deep purple. After 30 min, all
volatiles were removed in vacuo, and the crude product was taken up
in a little n-pentane, filtered, and kept at −40 °C overnight. The dark-
brown solution was separated from the purple crystals. The solution
was evaporated to dryness to yield 5 as a dark-brown solid (23.1 mg,
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12.5 (d, JCH = 150.3 Hz, CCarb4/5), −27.0 (d, JCH = 150.3 Hz, 2C,
CCarb2/7), −46.1 (s, 2C, C(CH3)3, C10), −173.7 (s, 2C, CH2P, C12). μeff
= 4.9 μB (Evans, C6D6, 295 K). Anal. Calcd for C38H65FeNP2Si: C,
66.94; H, 9.61; N, 2.05. Found: C, 66.65; H, 9.65; N, 2.04.
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35.5 μmol, 53%). H NMR (600.13 MHz, C6D6, 295 K): δ 8.35 (d,
Synthesis of (PNP)FeMe (3b). To a stirred solution of 1 (200.0
mg, 0.32 mmol, 1.0 equiv) in THF (10 mL) was added methyllithium
(12.6 mg, 0.57 mmol, 1.8 equiv). The yellow suspension stirred at
room temperature for 24 h. The solvent was removed in vacuo, and
the residue was taken up in n-pentane and filtered through a pad of
Celite. The reaction mixture was concentrated in vacuo and kept at
−40 °C overnight to yield 3b as yellow crystals (146 mg, 0.24 mmol,
4JHP = 1.5 Hz, 2H, HCarb2/7), 7.33 (s, 2H, HCarb4/5), 3.40−3.36 (m, 2H,
CHHP), 3.28−3.23 (m, 2H, CHHP), 2.10−1.97 (m, 4H, CH(CH3)2),
1.57 (s, 18H, C(CH3)3), 1.06 (dd, 3JHH = 16.2 Hz, 3JHP = 7.0 Hz, 6H,
CH(CH3)2), 1.02 (dd, 3JHH = 16.2 Hz, 3JHP = 7.0 Hz, 6H, CH(CH3)2),
3
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0.83 (dd, JHH = 14.7 Hz, JHP = 7.0 Hz, 6H, CH(CH3)2), 0.81 (dd,
3JHH = 14.7 Hz, 3JHP = 7.0 Hz, 6H, CH(CH3)2), −6.32 (t, JHP = 53.0
2
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75%). H NMR (600.13 MHz, C6D6, 295 K): δ 89.6 (bs, 2H), 66.2
Hz, 1H, FeH). 13C{1H} NMR (150.92 MHz, C6D6, 295 K): δ 217.3 (t,
2JCP = 26.3 Hz, CO), 211.7 (t, 2JCO = 9.6 Hz, CO), 147.9 (vt, JCP = 4.2
(bs, 2H), 43.0 (s, 2H, HCarb), 33.9 (bs, 4H), 4.9 (bs, 24H), 2.9 (s, 2H,
HCarb), 1.3 (s, 18H, C(CH3)2). 13C NMR (150.92 MHz, C6D6, 295 K):
δ 949.9 (s, 2C), 706.7 (bs, 2C), 357.2 (s, 2C), 309.8 (s, 2C), 306.0 (bs,
Hz, CCarb8a/9a), 137.9 (s, CCarb3/6), 128.3 (s, CCarb1/8), 124.0 (vt, JCP
=
4.4 Hz, CCarb2/7), 118.1 (s, CCarb4a/4b), 115.1 (s, CH, CCarb4/5), 34.5 (s,
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4C), 97.3 (q, JCH = 126.0 Hz, C(CH3)3, C11), 17.4 (d, JCH = 152.0
Hz, CCarb), −8.4 (d, 1JCH = 152.0 Hz, CCarb), −41.2 (s, 2C), −70.3 (bs,
2C). μeff = 4.9 μB (Evans, C6D6, 295 K). Anal. Calcd for C35H57FeNP2:
C, 68.96; H, 9.42; N, 2.30. Found: C, 68.93; H, 9.70; N, 2.26.
Synthesis of (PNP)FeBn (3c). To a stirred solution of 1 (200.0
mg, 0.32 mmol, 1.0 equiv) in THF (10 mL) was added dropwise a
solution of Bn2Mg(THF)2 (132.6, 0.38 mmol, 1.2 equiv) in THF (2
mL). The yellow solution was stirred at room temperature for 3 h. The
solvent was removed in vacuo, and the residue was taken up in n-
hexane and filtered through a pad of Celite. The reaction mixture was
concentrated in vacuo and kept at −40 °C overnight to yield 3c as
dark-yellow crystals (0.1571 mg, 0.23 mmol, 72%). Single crystals of
3c suitable for X-ray crystallography were obtained as dark-yellow
crystals by recrystallization from n-pentane at −40 °C. 1H NMR
(600.13 MHz, C6D6, 295 K): δ 240.3 (s, 2H), 119.8 (s, 2H), 72.8 (s,
2H), 64.2 (s, 2H), 43.8 (s, 2H), 40.1 (s, 2H), 28.8 (s, 6H, CH(CH3)2),
24.4 (s, 6H, CH(CH3)2), 3.6 (s, 2H), 1.0 (s, 18H), −6.0 (s, 6H,
CH(CH3)2), −15.0 (s, 6H, CH(CH3)2), −38.3 (s, 2H) −73.1 (s, 1H,
Hp‑Ph). 13C NMR (150.92 MHz, C6D6, 295 K): δ 1062.5 (s, 2C),
1026.7 (s, 2C), 854.5 (s, 2C), 756.6 (s, 2C), 721.8 (s, 2C), 638.2 (s,
2C), 394.7 (s, 2C), 369.1 (s, 2C), 334.4 (s, 2C), 302.1 (s, 2C), 252.7
(s, 2C), 99.8 (q, 1JCH = 125.2 Hz, 2C), 69.2 (t, 1JCH = 149.4 Hz, 2C),
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C(CH3)3), 32.5 (s, C(CH3)3), 26.7 (t, JCP = 10.5 Hz, CH(CH3)2),
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26.5 (t, JCP = 15.3 Hz, CH(CH3)2), 25.9 (t, JCP = 10.5 Hz, CH2P),
18.3 (s, CH(CH3)2), 18.2 (s, CH(CH3)2), 17.6 (s, CH(CH3)2), 17.3
(s, CH(CH3)2). 31P{1H} NMR (242.92 MHz, C6D6, 295 K): δ 62.6
(s). IR (cm−1): 1936 (CO), 1859 (CO). Anal. Calcd for
C36H55FeNO2P2: C, 66.36; H, 8.51; N, 2.15. Found: C, 66.25; H,
8.38; N, 2.20. Occasionally isolated samples contained 6 as an
impurity.
Synthesis of (PNP)Fe(CO)2 (6). To a solution of 4 (40 mg, 67.3
μmol) in C6D6 was added an atmosphere of 4 bar of CO. The color of
the solution changed from brown to deep purple. After 30 min, all
volatiles were removed in vacuo, and the crude product was taken up
in little n-pentane, filtered, and kept at −40 °C overnight. The dark-
brown solution was separated from the purple crystals by decantation.
The resulting deep-purple crystals were washed with cold n-pentane,
and all volatiles were removed in vacuo to yield 6 as a dark-purple solid
(2.1 mg, 3.2 μmol, 10%). Single crystals of 6 suitable for X-ray
crystallography were obtained as dark-purple crystals by recrystalliza-
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tion from n-pentane at −40 °C. H NMR (600.13 MHz, C6D6, 295
K): δ 13.5 (bs), 11.3 (bs), 1.7 (bs). μeff = 2.0 μB (Evans, C6D6, 295 K).
IR (cm−1): 2001 (CO), 1925 (CO). Anal. Calcd for C36H54FeNO2P2:
C, 66.46; H, 8.37; N, 2.15. Found: C, 66.47; H, 8.22; N, 2.31. ESR (X-
band, C6D6, 9.447856 GHz, 295 K): g = 2.036. Occasionally isolated
samples contained 5 as an impurity.
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25.3 (t, JCH = 135.2 Hz, 2C), 13.5 (d, JCH = 153.4 Hz, 2C), 13.5 (s,
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2C), 10.2 (s, 2C), −17.3 (d, JCH = 153.4 Hz, 2C), −44.8 (s, 2C),
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−215.2 (d, JCH = 153.4 Hz, 2C). μeff = 4.8 μB (Evans, C6D6, 295 K).
Anal. Calcd for C41H61FeNP2: C, 71.81; H, 8.97; N, 2.04. Found: C,
71.60; H, 9.28; N, 2.06.
General Synthetic Procedure for the Hydrogenation of
Alkenes. Complex 3b (2.0 mg, 3.28 μmol, 1.0 equiv) and the alkene
(0.328 mmol, 100 equiv) were dissolved in C6D6 (0.4 mL) and filled
in a high-pressure J. Young tube. The reaction mixture was set under a
pressure of 8 bar of H2 and shaken at irregular intervals. The reaction
was kept under hydrogen from 2 to 72 h, while the reaction progress
was monitored periodically by 1H NMR spectroscopy. The percentage
conversion values were obtained from the relative 1H NMR
integrations of the substrate and product.
Synthesis of [(PNP)Fe(μ-H)]2 (4). Method A. To a stirred solution
of 1 (20 mg, 31.7 μmol, 1.0 equiv) in toluene (1.0 mL) was added a
solution of potassium triethylborohydride (4.4 mg, 31.7 μmol, 1.0
equiv) in toluene (0.5 mL). The dark-brown reaction mixture was
allowed to stir at room temperature for 30 min. All volatiles were
removed in vacuo, and the dark-brown residue was taken up in little n-
pentane, filtered through Celite, and kept at −40 °C for 2 days to yield
4 as dark-red crystals (14.6 mg, 24.4 μmol, 77%).
G
Inorg. Chem. XXXX, XXX, XXX−XXX