Inorganic Chemistry
Article
NCH′eq), −0.10 (3H, br s, pyCH′N), −0.64 (3H, br s, NCH′ax), −0.93
(3H, br s, NCHeq), −4.79 (3H, br s, NCHax). UV [H2O; λmax, nm (ε,
M−1 cm−1)]: 274 (14000). τ(H2O) = 1.26 ms, τ(D2O) = 1.54 ms,
ϕem(H2O) = 9%, and tR = 6.81 min.
The following complexes were prepared in an analogous manner
and were isolated as colorless solids (unless stated), which gave single
peaks on HPLC analysis (λexc 275 nm) with a retention time of 6.80
( 0.05) min. 31P NMR relaxation rate data for each lanthanide
complex are reported in Table 4.
under argon. The resulting solution was decanted from the white
ammonium salt precipitate and the solvent removed under reduced
pressure. Purification of the yellow oil by column chromatography on
silica (CH2Cl2/0−1.6% CH3OH in 0.1% increments) gave a colorless
oil (700 mg, 29%). 1H NMR (CDCl3, 11.7 T, 295 K, δ): 7.75 (1H, dd,
3J = 7.0 Hz, 3JH−P = 10 Hz, H5), 7.59 (1H, td, 3J = 7.0 Hz, 4JH−P = 4.8
Hz, H4), 7.16 (1H, d, 3J = 7.0 Hz, H3), 3.86 (2H, dqd, 2J = 80 Hz, 3J =
7.0 Hz, H3, JH−P = 4.5 Hz, H7), 2.50 (3H, s, H1), 1.66 (3H, d, 2JH−P
=
3
15 Hz, H9), 1.61 (3H, t, J = 7.0 Hz, H8). 13C NMR (CDCl3, 296 K,
150.8 MHz, δ): 159.4 (d, 3JC−P = 20 Hz, C2), 153.7 (d, 1JC−P = 158 Hz,
[CeL1]: pale-yellow solid (12.2 mg, 77%). Anal. Calcd for
C42H42N6O6P3Ce·3.5H2O: C, 49.3; H, 4.79; N, 8.21. Found: C,
49.1; H, 5.05; N, 8.01. ESMS+: m/z 960.3 [M (140Ce) + H]+. 31P
NMR (CD3OD, 9.4 T, 295 K, δ): +27.8. UV [H2O; λmax, nm (ε, M−1
cm−1)]: 275 (14500), 340 (120). [PrL1] (13.3 mg, 84%). ESMS+: m/z
961.3 [M (141Pr) + H]+. 31P NMR (CD3OD, 9.4 T, 295 K, δ): +31.3.
[NdL1] (12.7 mg, 80%). ESMS+: m/z 964.2 [M (144Nd) + H]+. 31P
NMR (CD3OD, 9.4 T, 295 K, δ): +21.0. [SmL1] (12.5 mg, 78%).
ESMS+: m/z 972.2 [M (152Sm) + H]+. 31P NMR (CD3OD, 9.4 T, 295
K, δ): +31.4. τ(H2O) = 0.03 ms, τ(D2O) = 0.04 ms, and ϕem(H2O) =
0.7%. [GdL1] (13.0 mg, 81%). ESMS+: m/z 976.2 [M (156Gd) + H]+.
r1p (20 MHz, 298 K, 10%MeOH in H2O): 0.58 mM−1 s−1. [TbL1]
(12.6 mg, 78%). ESMS+: m/z 979.2 [M (159Tb) + H]+. 31P NMR
(CD3OD, 9.4 T, 295 K, δ): −35.7. τ(H2O) = 1.63 ms, τ(D2O) = 1.84
ms, and ϕem(H2O) = 50%. [DyL1] (13.0 mg, 80%). ESMS+: m/z 984.2
[M (164Dy) + H]+. 31P NMR (CD3OD, 9.4 T, 295 K, δ): −13.9.
τ(H2O) = 0.04 ms, τ(D2O) = 0.045 ms, and ϕem(H2O) = 2.9%.
[HoL1] (12.7 mg, 78%). ESMS+: m/z 985.3 [M (165Ho) + H]+. 31P
NMR (CD3OD, 9.4 T, 295 K, δ): −24.6. [ErL1] (14.3 mg, 88%).
ESMS+: m/z 988.2 [M (168Er) + H]+. 31P NMR (CD3OD, 9.4 T, 295
K, δ): −10.5. [TmL1] (12.9 mg, 79%). ESMS+: m/z 989.3 [M (169Tm)
+ H]+. 31P NMR (CD3OD, 9.4 T, 295 K, δ): +8.4.
C6), 136.0 (d, JC−P = 10 Hz, C4), 125.6 (d, JC−P = 3 Hz, C3), 124.6
3
2
(d, 4JC−P = 22 Hz, C5), 60.8 (d, 2JC−P = 6 Hz, C7), 24.5 (C1), 16.3 (C8)
13.3 (d, JC−P = 103 Hz, H9). 31P NMR (CDCl3, 9.4 T, 295 K, δ):
1
+41.2. HRMS+: m/z 200.0858 [M + H]+ (C9H14O2NP requires m/z
200.0862). Rf = 0.25 (silica, CH2Cl2/5% MeOH).
Ethyl Methyl(6-methyl-1-oxopyridin-2-yl)phosphinate (5).
To a stirred solution of ethyl (6-methylpyridin-2-yl)(methyl)-
phosphinate (600 mg, 3.0 mmol) in CHCl3 (15 mL) was added
MCPBA (1.04 g, 6.0 mmol). The resulting solution was stirred at 65
°C for 16 h under argon. The reaction was monitored by TLC [silica;
CH2Cl2/5% CH3OH; Rf(product) = 0.19; Rf(reactant) = 0.25] and the
solvent removed under reduced pressure to give a yellow oil. CH2Cl2
(10 mL) was added and the solution decanted from the white
precipitate. CH2Cl2 was removed under reduced pressure and the
resultant oil purified by column chromatography on silica (CH2Cl2/
0−3.2% CH3OH in 0.2% increments) to give a pale-yellow oil (360
mg, 56%). 1H NMR (CDCl3, 11.7 T, 295 K, δ): 7.90 (1H, dd, 3J = 7.0
Hz, 3JH−P = 10 Hz, H3), 7.40 (1H, d, 3J = 7.0 Hz, H5), 7.26 (1H, td, 3J
= 7.0 Hz, 4JH−P = 4.8 Hz, H4), 4.03 (2H, dqd, 2J = 80 Hz, 3J = 7.0 Hz,
3JH−P = 4.5 Hz, CH2O), 3.05 (1H, br s, OH), 2.50 (3H, s, CH2OH),
2
3
1.96 (3H, d, JH−P = 15 Hz, PMe), 1.28 (3H, t, J = 7.0 Hz, Me). 13C
[YbL1] (13.6 mg, 83%). Anal. Calcd for C42H42N6O6P3Yb·3.5H2O:
C, 47.8; H, 4.64; N, 7.96. Found: C, 47.6; H, 4.47; N, 8.14. ESMS+: m/
z 994.2 [M (174Yb) + H]+. 31P NMR (CD3OD, 9.4 T, 295 K, δ):
+17.7. 13C NMR (CD3OD, 296 K, 150.8 MHz, δ): 164.0 (br s, py C6),
NMR (CDCl3, 296 K, 150.8 MHz, δ): 149.7 (d, JC−P = 20 Hz, C6),
3
142.6 (d, JC−P = 158 Hz, C2), 130.4 (d, JC−P = 3 Hz, C5), 124.5 (d,
1
2
4JC−P = 22 Hz, C3), 124.5 (d, 3JC−P = 10 Hz, C4), 61.7 (d, 2JC−P = 6 Hz,
CH2O), 17.5 (pyMe), 16.3 (CMe), 11.7 (d, 1JC−P = 103 Hz, PMe). 31
P
1
163.5 (d, pyC2, J = 155 Hz), 143.9 (s, pyC4), 129.0 (s, pyC3), 128.1
NMR (CDCl3, δ): +34.3. HRMS+: m/z 238.0607 [M + Na]+
(C9H14O3NPNa requires m/z 238.0609). Rf = 0.19 (silica, CH2Cl2/
5% MeOH).
(s, pyC5), 127.1 (br s, PhC2), 126.6 (d, PhC1, 1J = 150 Hz), 126.3 (br
s, PhC4), 124.0 (s, PhC3), 71.2 (s, NCH2py), 46.8 (s, CH2N), 36.3 (br
1
s, CH2N). H NMR (CD3OD, 16.5 T, 298 K, δ): 20.4 (1H, br s,
Ethyl [6-(Hydroxymethyl)pyridine-2-yl](methyl)phosphinate
(6). Ethyl methyl(6-methyl-1-oxopyridin-2-yl)phosphinate (360 mg,
1.67 mmol) was dissolved in CHCl3 (10 mL), and (CF3CO)2O (8.0
mL, 56 mmol) was added. The mixture was stirred at 60 °C and the
formation of the trifluoroacetate ester of the title compound
monitored by LC−MS. After 3 h, the solution was cooled to 22 °C
and the solvent removed under reduced pressure. The residue was
dissolved in EtOH (10 mL) and the solution stirred at 60 °C for 3 h.
The solvent was removed under reduced pressure to give the crude
alcohol, which was purified by column chromatography (silica,
CH2Cl2/0−2.5% CH3OH in 0.25% increments) to give a colorless
oil (220 mg, 60%). 1H NMR (CDCl3, 11.7 T, 295 K, δ): 7.91 (1H, dd,
3J = 7.0 Hz, 3JH−P = 10 Hz, H3), 7.80 (1H, td, 3J = 7.0 Hz, 4JH−P = 4.8
pyCHN), 10.8 (9H, PhH2 + pyH5), 10.4 (3H, s, pyH4), 6.80 (3H, br s,
NCH′eq), 5.50 (3H, s, PhH4), 4.16 (6H, s, PhH3), 0.01 (6H, br s,
pyCH′N + pyH3), −2.95 (3H, br s, NCH′ax), −4.73 (3H, br s,
NCHeq), −12.9 (3H, br s, NCHax).
[YL1] (15 mg, 90%). Anal. Calcd for C42H42N6O6P3Y·3H2O: C,
53.5; H, 5.10; N, 8.91. Found: C, 53.2; H, 5.28; N, 8.73. ESMS+: m/z
908.2 [M (89Y) + H]+. 31P NMR (CD3OD, 9.4 T, 295 K, δ): +23.9. 1H
NMR (CD3OD, 11.7 T, 295 K, δ): 7.90 (9H, pyH4 + PhH2), 7.58
(3H, d, pyH5, J 8.0), 7.43 (3H, br dd, pyH3), 6.68 (6H, br m, PhH3),
4.95 (3H, d, pyCHN, J 16 Hz), 4.10 (3H, d, pyCH′N), 3.62 (3H, br m,
NCHax), 2.86 (3H, br d, NCHeq), 2.65 (6H, br m, NCH′ax + NCH′eq).
Ethyl (6-Methylpyridin-2-yl)(methyl)phosphinate (4). Neat
diethyl methylphosphonite (2.00 g, 14.7 mmol) was stirred at 0 °C,
and H2O (264 μL, 14.7 mmol) was added. The mixture was allowed to
3
Hz, H4), 7.43 (1H, d, J = 7.0 Hz, H5), 4.80 (2H, s, CH2OH), 3.93
(2H, dqd, 2J = 80 Hz, 3J = 7.0 Hz, 3JH−P = 4.5 Hz, CH2O), 1.75 (3H, d,
2JH−P = 15 Hz, PMe), 1.24 (3H, t, 3J = 7.0 Hz, Me). 13C NMR
(CDCl3, 150.8 MHz, δ): 160.4 (d, 3JC−P = 20 Hz, C6), 153.1 (d, 1JC−P
= 156 Hz, C2), 136.8 (d, 3JC−P = 10 Hz, C4), 126.3 (d, 4JC−P = 22 Hz,
1
reach 22 °C over 1 h and stirred for a further 16 h. H and 31P NMR
was used to confirm the formation of ethyl methylphosphinite, which
was used in situ without further purification. The reaction mixture also
contains 1 equiv of ethanol (>95% conversion by 1H NMR). 1H NMR
(CDCl3, 11.7 T, 295 K, δ): 7.22 (1H, dq, 1JH−P = 536 Hz, 2J = 2.1 Hz,
2
2
C3), 123.0 (d, JC−P = 4 Hz, C5), 64.1 (CH2OH), 61.1 (d, JC−P = 6
Hz, CH2O), 16.4 (Me) 13.4 (d, JC−P = 103 Hz, PMe). 31P NMR
1
2
3
3
(CDCl3, δ): +40.0. HRMS+: m/z 216.0808 [M + H]+ (C9H14O3NP
requires m/z 216.0801). Rf = 0.20 (silica, CH2Cl2/7% MeOH).
(6-[Ethoxy(methyl)phosphoryl]pyridine-2-yl)methyl Metha-
nesulfonate (7). Ethyl [6-(hydroxymethyl)pyridine-2-yl](methyl)-
phosphinate (110 mg, 0.51 mmol) was dissolved in anhydrous THF (3
mL), and NEt3 (213 μL, 1.5 mmol) was added. The mixture was
stirred at 5 °C, and methanesulfonyl chloride (59 μL, 0.77 mmol) was
added. The reaction was monitored by TLC [silica; CH2Cl2/7%
CH3OH; Rf(product) = 0.45; Rf(reactant) = 0.20] and stopped after
15 min. The solvent was removed under reduced pressure and the
residue dissolved in CH2Cl2 (15 mL) and washed with aqueous brine
(saturated, 10 mL). The aqueous layer was reextracted with CH2Cl2 (3
Ph), 4.11 (2H, dqd, J = 36 Hz, J = 7.0 Hz, JH−P = 4.0 Hz, CH2O),
2
3
3
1.54 (3H, dd, JH−P = 15.0 Hz, J = 2.0 Hz, PMe), 1.23 (3H, J = 7.0
Hz, Me). 31P NMR (CDCl3, 9.4 T, 295 K, δ): +34.5. 13C NMR
2
(CDCl3, 296 K, 150.8 MHz, δ): 62.3 (d, JC−P = 7 Hz, CH2O), 16.1
(Me), 14.9 (d, 1JC−P = 95 Hz, PMe). HRMS+: m/z 109.0414 [M + H]+
(C3H10O2P requires m/z 109.0418).
To neat ethyl methylphosphinite, (1.59 g, 14.7 mmol), containing 1
equiv of ethanol, were added dry degassed (freeze−thaw cycle)
toluene (20 mL), 2-bromo-6-methylpyridine, (2.10 g, 12.3 mmol), and
triethylamine (6.0 mL, 43 mmol). Argon was bubbled through the
solution for 1 h, tetrakis(triphenylphosphine)palladium(0) (320 mg,
0.27 mmol) was added, and the mixture was stirred at 125 °C for 16 h
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dx.doi.org/10.1021/ic300147p | Inorg. Chem. 2012, 51, 8042−8056