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Dalton Transactions
pre-catalyst due to its sensitivity towards light and ensuing UV- calc. for C18H16ON3 [M + H+]: 290.1288 m/z found: 290.1287 m/
induced cyclometallation. These data offer a useful roadmap z.
for further tailoring of these versatile PYA systems towards
efficient copolymerisation catalysis.
General procedure for the synthesis of pyridinium salts
The corresponding amide (2.0 mmol) was dissolved in MeCN
(15 mL) in a pressure tube. MeI (187 μL, 3.0 mmol) was added,
and the reaction mixture was stirred for 18 h at 80 °C. The
solution was cooled to room temperature and concentrated to
Experimental
All complexes were synthesised under exclusion of air using
standard Schlenk techniques under an atmosphere of dry
nitrogen unless otherwise stated. All starting materials and
reagents were obtained from commercial sources and used as
received. NMR spectra were recorded either on a Varian
500 MHz spectrometer or a Bruker spectrometer operating at
300 MHz. Chemical shifts δ are reported in ppm (J in Hz) rela-
tive to residual protic solvents. Irradiation of complexes was
carried out using a UVP “Blak-Ray” B-100AP 100 W 365 nm
lamp.
5 mL. Et2O (50 mL) was added, and the formed yellow precipi-
tate was filtered and washed with cold Et2O to yield the com-
pounds as yellow solids.
1,3-Dimethyl-2-(picolinamido)pyridin-1-ium iodide (6). 1H
NMR (300 MHz, DMSO) δ 11.63 (s, 1H, NH), 9.03 (d, J = 5.8 Hz,
1H, CHPYA), 8.84 (d, J = 4.6 Hz, 1H), CHPyr, 8.64 (d, J = 7.8 Hz,
1H, CHPYA), 8.25–8.10 (m, 2H, 2CHPyr), 8.06 (dd, J = 7.9, 6.2
Hz, 1H, CHPYA), 7.88–7.75 (m, 1H, CHPyr), 4.27 (s, 3H, N–Me),
2.40 (s, 3H, –Me) ppm.
13C NMR (75 MHz, DMSO) δ 163.44, 148.99 (CHPyr), 148.15
(CHPYA), 147.51 (), 144.78 (CHPYA), 138.52, 137.32, 128.23,
125.50, 123.25, 116.99, 44.87, 17.34 ppm. HRMS: calc. for
General procedure for the formation of amides 2 and 3
Picolinic acid (1.231 g, 10 mmol) was refluxed in SOCl2 C13H14N3ONa [M + Na]+ 228.1122 m/z found 228.1131 m/z. EA:
(10 mL, 0.14 mol) for 3 h under an N2 atmosphere. SOCl2 was anal. calc. for C13H14N3OI: %C 43.96, %H 3.97, %N 11.83,
removed under reduced pressure and the residue was dissolved found: %C 44.05, %H 3.86, %N 11.43.
in dry THF (40 mL). This solution was transferred via cannula
1-Methyl-2-(6-phenylpicolinamido)pyridin-1-ium iodide (7).
to a solution of the corresponding aminopyridine (10 mmol) 1H NMR (300 MHz, DMSO) δ 11.43 (s, 1H), 9.05 (d, J = 5.4 Hz,
in THF (50 mL), followed by NEt3 (2.5 mL, 18 mmol). The 1H), 8.72–8.63 (m, 1H), 8.55 (dd, J = 8.4, 1.0 Hz, 1H), 8.41 (dd,
mixture was refluxed for 48 h, filtered, and the solvent was J = 7.5, 1.3 Hz, 1H), 8.35 (dd, J = 8.0, 1.4 Hz, 2H), 8.27 (t, J = 7.6
removed under reduced pressure. The brown solid residue was Hz, 1H), 8.22 (dd, J = 7.6, 1.3 Hz, 1H), 8.00–7.87 (m, 1H),
purified by column chromatography (SiO2) using a gradient 7.68–7.47 (m, 3H), 4.44 (s, 3H) ppm. 13C NMR (75 MHz,
pentane ethyl acetate eluent to yield the pure products as DMSO) δ 162.63, 155.54, 147.09, 146.98, 146.49, 145.37,
white solids.
N-(3-Methylpyridin-2-yl)picolinamide
139.92, 136.92, 130.09, 129.06, 127.16, 124.92, 123.16, 122.40,
(2).
1H
NMR 121.77, 43.92 ppm. HRMS: calc. for C18H16ON3 [M]+ 290.1288
(300 MHz, CDCl3) δ 10.18 (s, 1H N–H), 8.63 (ddd, J = 4.8, 1.6, m/z found 290.1278 m/z. EA: anal. calc. for C19H15N3OI: %C
0.9 Hz, 1H), 8.36 (dd, J = 4.8, 1.3 Hz, 1H), 8.31 (dt, J = 7.9, 1.0 51.20, %H 3.63, %N 10.10, found: %C 51.20, %H 3.77, %N
Hz, 1H), 7.90 (td, J = 7.7, 1.7 Hz, 1H), 7.59 (dd, J = 7.5, 0.9 Hz, 10.02.
1H), 7.49 (ddd, J = 7.6, 4.8, 1.2 Hz, 1H), 7.11 (dd, J = 7.5, 4.8
1,3-Dimethyl-2-(6-phenylpicolinamido)pyridin-1-ium iodide
1
Hz, 1H), 2.39 (s, 3H) ppm. 13C NMR (75 MHz, CDCl3) δ 162.21, (8). H NMR (300 MHz, DMSO) δ 11.32 (s, 1H), 9.08 (d, J = 5.7
149.84, 149.54, 148.28, 146.46, 139.71, 137.68, 127.32, 126.74, Hz, 1H), 8.68 (d, J = 7.8 Hz, 1H), 8.43–8.34 (m, 3H), 8.22 (t, J =
122.80, 121.49, 77.58, 77.16, 76.74, 18.25 ppm. HRMS: calc. for 7.8 Hz, 1H), 8.17–8.06 (m, 2H), 7.62–7.49 (m, 3H), 4.33 (s, 3H),
C12H12N3O [M + H+]: 214.0977 m/z found: 214.09755 m/z.
6-Phenyl-N-(pyridin-2-yl)picolinamide (3).
1H
2.46 (s, 3H).
13C NMR (75 MHz, DMSO) δ 163.37, 155.66, 148.20, 147.32,
NMR
(300 MHz, CDCl3) δ 10.49 (s, 1H), 8.39 (d, J = 8.4 Hz, 1H), 8.31 146.19, 144.81, 139.55, 137.54, 137.03, 129.98, 128.89 (2C),
(dd, J = 4.9, 1.0 Hz, 1H), 8.15 (dd, J = 7.1, 1.6 Hz, 1H), 127.21 (2C), 125.68, 124.43, 121.65, 45.01, 17.40. HRMS: calc.
8.04–7.95 (m, 2H), 7.93–7.79 (m, 2H), 7.74–7.63 (m, 1H), for C19H18ON3 [M − I]+ 304.1444 m/z found 304.1433 m/z. EA:
7.49–7.33 (m, 3H), 7.00 (ddd, J = 7.3, 4.9, 0.9 Hz, 1H) ppm. 13C anal. calc. for C19H18N3OI: %C 52.91, %H 4.21, %N 9.74,
NMR (75 MHz, CDCl3) δ 162.80, 156.30, 151.25, 149.18, 148.27, found: %C 52.72, %H 4.15, %N 9.65.
138.54, 138.44, 137.92, 129.75, 129.02, 127.15, 123.64, 121.01,
120.03, 114.16, 77.58, 76.74 ppm. HRMS: calc. for C17H14ON3 0.514 mmol) was dissolved in a water : methanol mixture
[M + H]+: 276.1131 m/z found: 276.1124 m/z.
(2 mL, 1 : 1). This solution was filtered and a saturated metha-
[Pd(5)(Me)(MeCN)](PF6) (9). Pyridinium
5
(0.175 g,
N-(3-Methylpyridin-2-yl)-6-phenylpicolinamide (4). 1H NMR nolic solution of NH4PF6 was added dropwise, resulting in a
(300 MHz, CDCl3) δ 10.36 (s, 1H), 8.39 (dd, J = 4.8, 1.2 Hz, 1H), thick white precipitate which was collected by filtration and
8.27 (dd, J = 7.1, 1.6 Hz, 1H), 8.13–8.04 (m, 2H), 8.04–7.90 (m, washed with copious amounts of water to yield the corres-
2H), 7.63 (dd, J = 7.5, 0.9 Hz, 1H), 7.56–7.45 (m, 3H), 7.14 (dd, ponding PF6 salt of 5 as a white solid (0.164 g, 89%). This salt
J = 7.5, 4.8 Hz, 1H), 2.43 (s, 3H). 13C NMR (75 MHz, CDCl3) δ (81 mg, 0.23 mmol) and K2CO3 (0.1 g, excess) were stirred in
162.26, 156.23, 149.55, 146.35, 139.92, 138.64, 138.28, 129.75, dry CH2Cl2 (5 mL) for 20 min. Then [Pd(cod)(Me)Cl] (59 mg,
129.07, 127.52, 127.14, 123.61, 121.56, 121.23, 18.34. HRMS: 0.23 mmol) was added and the solution stirred at room temp-
6142 | Dalton Trans., 2021, 50, 6133–6145
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