condition where the L : M ratio is 1 : 1. This is a unique
behavior relative to other type II ligands.
A mixture of 3 (3.7 g, 19 mmol) in HBr (15 ml, 48%) and
concentrated H2SO4 (2.4 ml) was refluxed (4 h) at 130 ЊC. The
mixture was cooled, slowly neutralized with KOH solution
(0–5 ЊC, pH = 7–7.5), filtered and the solid recovered was
washed with Et2O (4 × 20 ml). The aqueous filtrate was
also extracted with Et2O (4 × 30 ml) and the combined Et2O
solution was dried over Na2SO4. The dried solution was
vacuum evaporated leaving 4-ethyl-2,6-bis(bromomethyl)-
The multistep syntheses described here for 6-Et and 6-Oct
provide a useful pathway to 4-pyridyl substituted derivatives of
ligand type II. The 6-Oct derivative has good solubility in aro-
matic hydrocarbons and modest solubility in aliphatic hydro-
carbons. Hence, it is feasible to study the LLE properties of a
family of ligands against [Ph2P(O)CH2]2C5H3NO when 6 is
present in 2 : 1 L : M ratios or higher. The structural studies
suggest that the 4-substitution will not drastically affect
extractant binding. Liquid–liquid extraction and ligand bind-
ing thermodynamic studies are planned in the near future in
support of these studies.
1
pyridine 4 as an orange oil (4.5 g, 81%); H NMR (CDCl3):
δ 1.24 (t, J = 7.6 Hz), 2.64 (q, J = 7.6 Hz), 4.50, 7.21;
13C{1H}NMR (CDCl3): J 13.8, 27.7, 33.4, 122.2, 155.1,
156.2.
A solution of Ph(EtO)(H)P(O) (3.54 g, 20.8 mmol) in an
Et2O (8 ml)–C6H6 (15 ml) mixture was added dropwise to
PhMgBr (14.0 ml, 3 M solution in Et2O, 42.0 mmol). The tem-
perature of the mixture rose and the rate of addition was
adjusted in order to control the reflux. When the addition was
complete, THF (20 ml) was added and the mixture was refluxed
(65 ЊC, 1.5 h). The mixture was cooled and 4 (3.0 g, 10.2 mmol)
in THF (20 ml) was added. This mixture was refluxed (65 ЊC,
4 h) and then allowed to stand at 20 ЊC (12 h). A saturated
aqueous solution of NH4Cl (30 ml) and CH2Cl2 (40 ml) was
added to the reaction mixture. This combination was agitated in
a separatory funnel, and the phases were separated. The aque-
ous phase (pH = 7–8) was washed with CH2Cl2 (2 × 30 ml) and
the combined organic phases dried over Na2SO4. The solvent
was removed by vacuum evaporation and the residue was puri-
fied by column chromotography (silica, CHCl3–MeOH 100 :
2.5). The product, 4-ethyl-2,6-bis[(diphenylphosphino)methyl]-
pyridine P, PЈ-dioxide 5-Et was isolated as a white solid (4.1 g,
75%), mp 72–74 ЊC. IR (KBr, cmϪ1) νPO 1192; 31P NMR
Experimental
The organic reagents employed in the synthetic schemes were
purchased from Aldrich Chemical Co. and used as received
unless noted otherwise. Organic solvents were obtained from
VWR, and they were dried by standard procedures. The lan-
thanide nitrate salts were purchased from Ventron. Infrared
spectra were recorded on a Mattson 2020 FTIR and NMR
spectra were obtained from Bruker FX-250 and JEOL GSX-
400 spectrometers using Me4Si (1H, 13C) and 85% H3PO4 (31P)
as external shift standards. All downfield shifts from the refer-
ence are designated as ϩ δ. The mass spectra were obtained at
the Midwest Center for Mass Spectrometry, University of
Nebraska. Elemental analyses were acquired from Galbraith
Laboratories.
Ligand synthesis
1
(CDCl3): δ 30.9; H NMR (CDCl3): δ 0.91 (t, JPH = 7.6 Hz,
The ligands 6-Et and 6-Oct were prepared in a similar fashion
and full details are provided for 6-Et. Variances for 6-Oct are
summarized in the ESI along with the five step synthesis for
compound 1 starting with diethyl oxalate.
3H), 2.32 (q, J = 7.6 Hz, 2H), 3.71 (d, JPH = 14.6 Hz, 4H),
6.84 (1H), 7.33–7.42 (12H), 7.61–7.69 (8H); 13C{1H} NMR
(CDCl3): δ 13.9, 27.2, 40.4 (d, JPC = 65.0 Hz), 122.6, 128.3
(d, JCP = 12.0 Hz), 131.1 (d, JCP = 9.6 Hz) 131.6, 132.5 (d,
JCP = 100.4 Hz), 151.8 (d, JCP = 7.0 Hz), 153.7.
Sodium hydride (60% in mineral oil, 19.2 g, 0.48 mol)
was washed under a dry nitrogen atmosphere with diethyl ether
(3 × 40 ml), vacuum dried and then added to dimethylform-
amide (DMF) (800 ml). To this suspension, CH3I (82 g, 0.58
mol) and 1 (16.2 g, 0.074 mol) were added with stirring at 0 ЊC.
The mixture was then stirred at 23 ЊC (20 h). Water (30 ml) was
added to quench unreacted NaH, and DMF and excess CH3I
were removed by vacuum distillation at 40 ЊC. Water (130 ml)
and saturated NaHCO3 solution (40 ml) were added to the resi-
due and the mixture extracted with Et2O (3 × 100 ml). The Et2O
layers were combined, dried with anhydrous Na2SO4 and the
Et2O removed by vacuum evaporation leaving 4-bromo-2,6-
bis(methoxymethyl)pyridine 2 as a light orange oil (17.4 g,
A sample of 5-Et (2.8 g, 5.2 mmol) in CHCl3 (25 ml) was
combined with 3-chloroperoxybenzoic acid (1.3 g, 57–86%) and
the mixture stirred at 20 ЊC (18 h). The mixture was then
extracted with saturated aqueous NaHCO3 solution (50 ml), the
aqueous phase was separated (pH = 7–8), extracted with
CH2Cl2 (2 × 30 ml) and the combined organic phases dried over
Na2SO4. The solvent was then vacuum evaporated at 25 ЊC and
the residue was washed with Et2O (3 × 15 ml). The product,
6-Et, was obtained as a white solid (2.6 g, 90%) mp 180–181 ЊC.
(Found: C, 69.38; H, 6.09; N, 2.32%. C33H31NO3P2 requires C,
71.76; H, 5.80; N, 2.54%. MS: m/z 551.1779 (Mϩ); C33H31NO3P
requires 551.1761. IR(KBr) νNO 1238 cmϪ1, νPO 1194 cmϪ1 31P
.
1
95%); H NMR (CDCl3): δ 3.48, 4.54, 7.52; 13C{1H} NMR
NMR (CDCl3): δ 31.8. 1H NMR (CDCl3): δ 0.99 (t, J = 7.6 Hz,
3H), 2.38 (q, J = 7.6 Hz, 2H), 4.10 (d, JPH = 13.9 Hz, 4H), 7.32–
7.43 (12H), 7.71–7.80 (8H). 13C{1H} NMR (CDCl3): δ 14.0,
27.2, 31.5 (JPC = 67.0 Hz), 125.3, 128.5 (d, JCP = 12.2 Hz), 130.8
(d, JCP = 9.8 Hz), 131.9 (d, JCP = 2.2 Hz, 132.2 (d, JCP = 101.7
Hz), 141.8, 142.9 (d, JCP = 4.9 Hz). Solubility: soluble in CHCl3,
CH2Cl2, C6H6 (4 × 10Ϫ3M); insoluble in toluene, o-xylene,
petroleum ether (bp 60–80 ЊC).
(CDCl3): δ 58.8, 74.7 123.0 134.2 159.4.
Ethyl magnesium bromide (14.0 ml, 3.0 M in Et2O, 42 mmol)
was added dropwise (30 min) with stirring to a mixture of 2
(9.5 g, 38.6 mmol) and dichlorobis(triphenylphosphine)-
nickel() (340 mg, 0.52 mmol) in tetrahydrofuran (THF)
(160 ml) at Ϫ20 ЊC. The mixture was warmed to 25 ЊC and
maintained below 30 ЊC ( 2 h). The resulting red-brown mix-
ture was quenched with aqueous HCl (40 ml, 2 M) and the
volatiles removed by vacuum evaporation at 25 ЊC. The residue
was treated with water (100 ml) and the mixture washed with
Et2O (2 × 70 ml). The aqueous phase was then treated with
saturated aqueous NaHCO3 solution (150 ml) and this solu-
tion (pH 7–8) was extracted with Et2O (3 × 120 ml). The com-
bined Et2O solution was washed with dilute aqueous NaHCO3
(50 ml) and the ether fraction dried over Na2SO4. The Et2O
was then vacuum evaporated leaving 4-ethyl-2,6-bis (methoxy-
methyl)pyridine 3 as an orange oil (6.3 g, 84%); 1H NMR
(CDCl3): δ 1.25 (t, J = 7.6 Hz), 2.66 (q, J = 7.6 Hz), 3.47 4.55,
7.18; 13C{1H} NMR (CDCl3): δ 14.1, 28.1, 58.5, 75.3, 119.3,
154.2, 157.4.
Synthesis of complexes
A sample of Nd(NO3)3ؒ6H2O (44 mg, 0.1 mmol) was dissolved
in methanol (MeOH) (10 ml) and a sample of 6-Et (55 mg,
0.1 mmol) was added. The mixture was stirred (5 min) and then
ethyl acetate (10 ml) was added. The resulting solution was
filtered and the filtrate was allowed to evaporate slowly (7 d).
The complex was isolated as light blue crystals [Nd(6-Et)2-
(NO3)]2[Nd(NO3)5](NO3)2ؒ1.5 H2O that were suitable for
crystallographic analysis. (Found: C, 49.15; H, 3.90; N 6.18%).
C132H127N13Nd3O40.5P8 requires C, 49.18; H, 3.97: N 5.65%; IR
(KBr, cmϪ1): νNO 1155, νPO 1126.
D a l t o n T r a n s . , 2 0 0 3 , 1 5 3 – 1 5 9
157