Thermal reactions of 2-hydroxymethylpyridine (HMP) with [
Hydroxymethylpyridines are valuable intermediates and have promising application, for example, in the synthesis of pharmaceuticals and agrochemicals, such as mefloquine hydrochloride and pineprofen [
Molybdenum complexes also catalyze nitrogen fixation in plants by some microorganisms [
Recently we have reported the reactions of [Mo(CO)6] and [Ru3(CO)12] with 1-(2-pyridylazo)-2-naphthol (PAN) [
2
[Mo(CO)6] and [Ru3(CO)12], HMP, and PPh3 were supplied by Fluka. All chemicals were of analytical reagent grade and were used without purification. All solvents were purified by distillation prior to their use.
Infrared measurements (KBr pellets) were carried out on a Unicam-Mattson 1000 FT-IR spectrometer. Electronic absorption spectra were measured on a Unicam UV2-300 spectrometer. Nuclear magnetic resonance measurements (1H NMR) were performed on a Spectrospin-Bruker AC 200 MHz spectrometer. Samples were dissolved in deuterated dimethylsulphoxide (DMSO) using tetramethylsilane (TMS) as internal reference. Magnetic measurements of the complexes in the solid state (Gouy method) were recorded on a Sherwood magnetic susceptibility balance. Elemental analyses for carbon, hydrogen, and nitrogen (CHN) were performed on a Perkin-Elmer 2400 CHN elemental analyzer. Mass spectrometry measurements of the solid complexes (70 eV, EI) were carried out on a Finnigan MAT SSQ 7000 spectrometer. Thermogravimetric (TG) analyses were carried out under nitrogen atmosphere with a heating rate of
Elemental analysis and mass spectrometry data for the complexes.
Complex | C% Found (Calcd.) | H% Found (Calcd.) | N% Found (Calcd.) | Mass spectrometry | ||
Molecular formula | Chemical formula | Molecular weight | ||||
Mo2O6(HMP)2 | [Mo2(C12H14O8N2)] | 28.2 (28.5) | 2.6 (2.8) | 5.7 (5.5) | 506.14 | 507 [P+] |
W2O6(HMP)2 | [W2O6(HMP)2] | 21.5 (21.2) | 1.9 (2.1) | 4.3 (4.1) | 681.96 | 682 [P+] |
Ru(CO)3(HMP) | [Ru(C9H7O4N)] | 36.5 (36.8) | 2.2 (2.4) | 4.6 (4.8) | 294.23 | 239 [P–2CO]+ |
Ru(CO)2(HMP)(PPh3) | [Ru(C26H22O3NP)] | 58.8 (59.1) | 4.0 (4.2) | 2.9 (2.7) | 528.47 | 501 [P–CO]+ |
[Mo(CO)6] (0.10 g, 0.38 mmol) and HMP (0.04 g, 0.38 mmol) were mixed in tetrahydrofuran (THF) (
Similar procedure was employed as used for the preparation of [Mo2O6(HMP)2] complex (reaction period: 10 hours; fine brown crystals; yield 80%).
[Ru3(CO)12] (0.032 g, 0.05 mmol), and HMP (0.016 g, 0.15 mmol) were mixed in THF (ca. 30 cm3) and heated to reflux in air for 5 hours. After complete reaction, a brown solid was collected by filtration. The solid was washed several times with hot petroleum ether (60–80) and then recrystallized from hot ethanol giving fine brown crystals (yield 80%).
A mixture of [Ru3(CO)12] (0.032 g, 0.05 mmol), HMP (0.016 g, 0.15 mmol) and PPh3 (0.04 g, 0.15 mmol) in THF (ca. 30 cm3) was heated to reflux in air for 4 hours. A reddish-brown solid was obtained, separated by filtration and then recrystallized from hot ethanol to give brownish crystals (yield 60%).
Interaction of [M(CO)6], M = Mo and W, with 2-hydroxymethylpyridine (HMP) in THF in air gave the oxo complexes [Mo2O6(HMP)2],
Important IR data for HMP and its molybdenum, tungsten, and ruthenium complexes.
Compound | IR data | |||||||
HMP | 3249 (s) | — | 1597 (s) | 1438 (s) | 1364 (m) | 1222 (m) | 633 (m) | — |
PPh3 | — | — | — | — | — | — | — | 1430 (m) |
— | — | — | — | — | — | — | 745 (s) | |
— | — | — | — | — | — | — | 694 (s) | |
— | — | — | — | — | — | — | 493 (s) | |
3445 (s) | — | 1609 (s) | 1478 (m) | 1401 (m) | 1288 (m) | 651 (m) | — | |
3424 (s) | — | 1613 (s) | 1441 (m) | 1400 (m) | 1286 (m) | 655 (m) | — | |
3423 (s) | 2040 (m) | 1650 (m) | 1458 (m) | 1432 (m) | 1282 (m) | 672 (m) | — | |
1969 (s) | ||||||||
1923 (s) | ||||||||
3422 (s) | 1972 (s) | 1651 (s) | 1433 (m) | 1478 (m) | 1186 (m) | 695 (s) | 748 (m) | |
1896 (s) | 722 (m) | |||||||
— | 517 (s) |
1H NMR data of HMP and its molybdenum, tungsten, and ruthenium complexes.
Compound | 1H NMR data (ppm) |
---|---|
HMP | 8.47 (s, 1H, OH), 7.79–7.73, 7.50–7.47, 7.22–7.20 (m, 4H, py), 5.44 (s, 2H, CH2) |
9.99 (s, 2H, 2OH), 8.41–8.39, 8.05–7.89, 7.60–7.36 (m, 8H, 2py), 5.59 (s, 4H, 2CH2) | |
9.99 (s, 2H, 2OH), 8.71–8.44, 8.10–7.68, 7.67–6.11 (m, 8H, 2py), 4.68 (s, 4H, 2CH2) | |
8.75 (s, 1H, OH), 8.13–8.04, 7.89–7.76, 7.56–7.28 (m, 4H, py), 5.18 (s, CH2) | |
8.79 (s, 1H, OH), 7.78–7.22 (m, 19H, py & Ph), 4.53(s, 2H, CH2) |
In the far IR spectrum of
The proposed structure of [M2O6(HMP)2] [M = Mo,
Thermal reaction of a mixture of [Ru3(CO)12] and HMP produced a brown complex with a molecular formula of [Ru(CO)3(HMP)],
The proposed structure of [Ru(CO)3(HMP)],
Reaction of [Ru3(CO)12] with HMP in presence of PPh3 resulted in the formation of [Ru(CO)2(HMP)(PPh3)],
The proposed structure of [Ru(CO)2(HMP)(PPh3)],
In order to give more insight into the structure of the complexes, thermal studies on the solid complexes using TG and differential thermogravimetric (DTG) techniques were performed [
Thermal analysis data for HMP and its molybdenum, tungsten, and ruthenium complexes.
Complex | Decomposition step, K | % Weight loss | Mol. wt. | Species eliminated | % Solid residue |
---|---|---|---|---|---|
490–620 | 21.76 | 110.14 | C6H6 + O2 | 2MoO | |
620–760 | 22.15 | 112.11 | C6H8 + O2 | ||
760–900 | 11.86 | 60.03 | 2NO | ||
480–650 | 12.48 | 85.11 | C4H5 + O2 | 2WO | |
650–800 | 12.62 | 86.06 | C4H6 + O2 | ||
800–1000 | 16.29 | 111.09 | C4H3 +2NO | ||
341–500 | 19.04 | 56.02 | 2CO | RuO | |
500–734 | 41.20 | 121.22 | C7H7 +NO | ||
341–467 | 10.60 | 56.02 | 2CO | RuO | |
467–730 | 27.67 | 146.23 | C11H14 | ||
730–1200 | 39.58 | 209.17 | C13H8NP |
The TG and DTG plots of W2O6(HMP)2 [W2(C12H14O8N2)]; M. wt. = 681.96] exhibited also three decomposition steps in the temperature range 480–1000 K. The first, second, and third steps occurred in the temperature ranges (480–650), (650–800), and (800–1000) K with a net weight loss of 12.48%, 12.62% and 16.29% corresponding to the elimination of (C4H5 + O2), (C4H6 + O2), and (C4H3 + 2NO), respectively, to give finally 2WO as residual, Table
Thermal studies of the ruthenium complex, Ru(CO)3(HMP), were carried out using thermogravimetry. The TG plot of Ru(CO)3(HMP) [Ru(C9H7O4N); M. wt. = 294.23] showed two well-defined and non-overlapping steps in the 341–734 K range to give finally a solid residual of RuO, Table
The TG plot of Ru(CO)2(HMP)(PPh3) [Ru(C26H22O3NP); M. wt. = 528.47] showed three-step decomposition. The first at 341–467 K, with a net weight loss of 10.60% corresponds to elimination of 2CO [
2-Hydroxymethylpyridine is an important substance in biological and pharmaceutical fields. Reactions of molybdenum, tungsten, and ruthenium carbonyls with HMP yielded the two oxo complexes [Mo2O6(HMP)2] and [W2O6(HMP)2] and the tricarbonyl complex [Ru(CO)3(HMP)]. In presence of PPh3 the reaction gave the dicarbonyl complex [Ru(CO)2(HMP)(PPh3)].
The authors are gratefully acknowledged the generous support of SABEC Industrial Company and El-Baha University, Kingdom of Saudi Arabia.