Chemistry of homoleptic phenylethynyl complexes of lanthanides

Article abstract of DOI:10.1134/S1070363215080198

Methods to prepare homoleptic phenylethynyl complexes of lanthanides, the products properties and possible applications in organoelement synthesis of polyfunctional compounds are discussed.

Full text of DOI:10.1134/S1070363215080198

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 8, pp. 1910–1919. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © S.F. Zhiltsov, O.N. Druzhkova, N.A. Pimanova, V.M. Makarov, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85, No. 8,
pp. 1355–1364.
Chemistry of Homoleptic Phenylethynyl Complexes
of Lanthanides
S. F. Zhiltsov, O. N. Druzhkova, N. A. Pimanova, and V. M. Makarov
Kozma Minin Nizhny Novgorod State Pedagogical University, ul. Ulyanova 1, Nizhny Novgorod, 603950 Russia
e-mail: chemical@mininuniver.ru
Received April 9, 2015
Abstract—Methods to prepare homoleptic phenylethynyl complexes of lanthanides, the products properties
and possible applications in organoelement synthesis of polyfunctional compounds are discussed.
Keywords: homoleptic complex, phenylethynyl, lanthanide, complex, polyfunctional compound, synthesis,
catalytic activity
DOI: 10.1134/S1070363215080198
Homoleptic phenylethynyl compounds of lantha-
nides (PhC≡C)2Ln and (PhC≡C)3Ln (Ln standing for a
lanthanide) are notable for the presence of the reactive
metal–carbon bond and the unsaturated ligand, the
latter acting as the second active center of the
molecule; hence, such compounds are bifunctional
reagents suitable for various organoelement syntheses.
Even though certain representatives of this class have
been known for long [1], their wide application has
been limited by the absence of the convenient
preparation methods.
action of tris[bis(trimethylsilyl)amides] of lanthanides
with phenylacetylene at the molar ratio of 1 : 3 at room
temperature in toluene or hexane [Eq. (3)] [4].
[(Me3Si)2N]3Ln + 3PhC≡CH
→ (PhC≡C)3Ln + 3(Me3Si)2NH,
(3)
Ln = Pr, Sm, Eu, Gd, Tb, Er, Yb.
Phenylethynyl derivatives of lanthanides(III) were
isolated with yields of 70–95% and identified by
means of elemental analysis and IR spectroscopy. The
products were dark-colored pyrophoric amorphous
compounds decomposing upon heating above 200°С,
soluble in 1,2-dimethoxyethane, tetrahydrofuran, and
benzene, readily hydrolysable to give phenylacetylene
and Ln(OH)3. IR spectra of the prepared (PhC≡C)3Ln
were similar to that of tri(phenylethynyl)scandium [5].
This work summarizes the preparation methods of
the phenylethynyl compounds of lanthanides(II, III);
their properties and application in the synthesis of
polyfunctional organic and organoelement derivatives
are discussed.
Phenylethynyl derivatives of lanthanides(II) have
been described for samarium, europium, and ytter-
bium. They have been prepared for the first time via
transmetalation of organomercury compounds [Eq. (1)]
[2, 3] and the acid-base interaction of phenylacetylene
with bis(pentafluorophenyl)- or bis(tert-butylethynyl)-
ytterbium [Eq. (3)] [2].
A drawback of the described synthesis of the
homoleptic lanthanide compounds was a labor
intensive stage of preparation of the starting silylamide
derivatives. In detail, it consisted of four stages:
preparation of butyllithium, its interaction with
hexamethyldisilazane
to
form
lithium
bis
(trimethylsilyl)amide, reaction of the latter with
anhydrous lanthanide chloride, and the intermediate
product reaction with phenylacetylene.
(PhC≡C)2Hg + Ln → (PhC≡C)2Ln + Hg ,
(1)
Ln = Eu, Yb;
R2Yb + PhC≡CH → (PhC≡C)2Yb + 2RH,
R = С6F5, t-С4H9C≡C.
(2)
Reactions of lanthanides iodides LnI2 and LnI3 with
phenylethynylsodium in THF [Eqs. (4), (5)] is a more
convenient and universal method to prepare the
phenylethynyl derivatives of lanthanides(II, III) [6].
We have developed a procedure to prepare phenyl-
ethynyl derivatives of lanthanides(III) via the inter-
1910

CHEMISTRY OF HOMOLEPTIC PHENYLETHYNYL COMPLEXES OF LANTHANIDES
1911
Table 1. Yields and magnetic moments of phenylethynyl complexes of lanthanides prepared via reactions (3) and (4)
Compound
Yield, %
Color
μeff, µB
а
(PhC≡C)2Sm(THF)2
(PhC≡C)2Yb(THF)
(PhC≡C)3Pr(THF)
(PhC≡C)3Nd(THF)
(PhC≡C)3Dy(THF)
(PhC≡C)3Ho(THF)b
88
85
87
89
91
90
92
Dark-brown
Dark-violet
Dark-brown
Brown
Dark-brown
Brown
0
3.52
3.67
10.19
10.28
c
(PhC≡C)3Er(THF)2
Dark-brown
a
IR spectrum, ν, cm–1: 3030 m, 2140 w, 2025 w, 1940 w, 1880 w, 1800 w, 1585 m, 1475 s, 1435 s, 1190 w, 1175 w, 1155 w, 1065 m,
1025 s, 915 m, 755 s, 690 s, 545 m, 490 m; 1040 m, 840 m (coordinated THF). b IR spectrum, ν, cm–1: 3030 m, 2160 w, 2030 w, 1940 w,
1870 w, 1800 w, 1585 m, 1780 s, 1440 s, 1190 w, 1175 w, 1155 w, 1070 m, 1025 s, 960 w, 910 m, 755 s, 690 s, 535 m, 495 m; 1035 m,
870 m (coordinated THF). c IR spectrum, ν, cm-1: 3050 m, 2170 w, 2115 w, 2045 m, 1945 w, 1880 w, 1800 w, 1590 m, 1480 s, 1195 w,
1175 w, 1155 w, 1070 m, 1035 m, 1026 s, 970 w, 910 m, 840 w, 755 s, 690 s, 610 w, 550 w, 516 m.
LnI2(THF)4 + 2PhC≡CNa
along with phenylacetylene, accompanied by the metal
oxidation state to +3.
THF
20°C
(PhC≡C)2Ln(THF)x + 2NaI,
Ln = Sm, Yb; x = 1, 2;
(4)
(5)
Organometallic compounds containing the polar
metal–carbon bonds have been widely used in organic
synthesis. They act as alkylating or arylating agents
towards carbonyl compounds and organoelement
halides. In order to prepare polyfunctional organic
compounds, we performed the reactions of phenyl-
ethynyl derivatives of the lanthanides with esters and
organoelement halides R3EX and Ph4SbX (E = C, Si,
Ge, or Sn; R = CH3 or C6H5; X = Cl, Br, or I).
LnI3(THF)3 + 3PhC≡CNa
THF
20°C
(PhC≡C)3Ln(THF)x + 3NaI,
Ln = Pr, Nd, Dy, Ho, Er; x = 1, 2.
Using of lanthanides iodides instead of the
chlorides resulted in more complete substitution of the
halogen with phenylethynyl moiety.
Reactions (6) of tris(phenylethynyl)lanthanides
with esters (ethyl acetate and methyl isobutyrate)
occurred at room temperature via the nucleophilic
addition of the ligand at the carbonyl group of the ester
to form novel polyfunctional alkoxy derivatives of
lanthanides (Table 2) [8]; the products were isolated
with yields of 80–90%.
Table 1 lists the yields and compositions of the
phenylethynyl derivatives of lanthanides in the form of
the complexes with THF incubated in vacuum during
1.5–2 h at 40–50°С to constant mass. The products
were characterized by means of elemental analysis, IR
spectroscopy, and magnetochemistry.
C
C
CPh
The prepared phenylethynyl complexes were dark
solids decomposing above 200°С, extremely sensitive
to air moisture and oxygen, readily soluble in THF and
benzene, and insoluble in hexane. The (PhC≡C)2Yb·
(THF) compound was diamagnetic, corresponding to
the +2 oxidation state of ytterbium. UV spectrum of
the (PhC≡C)2Sm(THF)2 complex solution in THF
contained the absorption bands with maximums at 345
and 415 nm, typical of Sm2+ [7]. The μeff values for
(PhC≡C)3Ln(THF)x (Table 1) corresponded to the +3
oxidation state of the lanthanides. IR spectra of the
phenylethynyl compounds of lanthanides(II, III) were
practically identical and confirmed the presence of the
PhC≡C groups and the coordinated THF molecules.
R1
C
O
R1
(
O)3Ln
(PhC C)3Ln + 3
OR2
OR2
(6)
Ln = Pr, Sm, Tb; R1 = CH3, (CH3)2CH; R2 = CH3, C2H5.
Alkoxy derivatives of the lanthanides were dark
colored compounds decomposing at 220–230°С,
unstable in air, soluble in THF, 1,2-dimethoxyethane,
and toluene. Elemental analysis data for the prepared
complexes are given in Table 2. Their IR spectra
contained the absorption bands characteristic of the
PhC≡C bonds (2140–2150 cm–1), the absorption band
of the carbonyl group (≈1720 cm–1) being absent.
The reaction of aldehydes and ketones with phenyl-
ethynyl derivatives of lanthanides(II) [9] yielded the
Hydrolysis of the phenylethynyl complexes in THF
at room temperature resulted in hydrogen formation
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ZHILTSOV et al.
Table 2. Yields and elemental analysis data for polyfunctional lanthanides alcoholates
Found, %
Yield,
Calculated, %
Compound
Formula
%
С
Н
Ln
С
Н
Ln
[CH3(C2H5O)C(C≡CPh)O)]3Pr
[CH3(C2H5O)C(C≡CPh)O)]3Tb
[(CH3)2CH(CH3O)C(C≡CPh)O)]3Pr
[(CH3)2CH(CH3O)C(C≡CPh)O)]3Sm
89
87
81
84
61.54
60.01
62.75
62.01
5.67
5.62
6.12
6.10
20.08 С36H39O6Pr
21.30 С36H39O6Tb
19.10 С39H45O6Pr
61.02
59.50
62.40
5.51
5.37
6.00
5.93
19.91
21.90
18.80
19.80
19.98 С39H45O6Sm 61.63
Table 3. Products of reactions of bis(phenylethynyl)ytterbium (PhC≡C)2Yb(THF) with organoelement halides R3ECl in the
1 : 2
Reaction products, mol per 1 mol of (PhC≡C)2Yb(THF)
Exp. no.
R3ECl (mol)
PhC≡CER3 PhC≡CYbCl(THF)2
YbCl2(THF)4
Ph6C2
PhC≡CH
1
2
3
4
Ph3CCl (0.0042)
(CH3)3SiCl (0.0036)
Ph3GeCl (0.0029)
Ph3SnCl (0.0020)
–
0.67
0.20
0.73
0.40
0.12
0.67
0.17
0.39
0.95
0.71
1.73
1.36
1.35
–
–
–
–
–
–
alkoxides, further hydrolyzed into the alcohols. The
hydrolysis was accompanied by oxidation of the
lanthanides atoms and formation of the Ln(OH)3
hydroxide, and the evolving hydrogen favored the
ketones transformation into the pinacones.
(PhC≡C)2Yb(THF) prepared via the reaction (4)
reacted with triphenylmethyl, trimethylsilicon, triphenyl-
germanium, and triphenyltin chlorides at the molar
ratio of 1 : 2 in THF at room temperature. The reagents
mixing was accompanied by the solution discoloration
and precipitate formation. Products of the reactions (7)
and (8) are given in Table 3.
Bis(phenylethynyl)ytterbium(II) tetrahydrofuranate
THF
(7)
(8)
R3EC
CYbCl(THF)2,
(PhC C)2Yb(THF) + R3ECl
CPh + PhC
THF
(PhC CYbCl(THF)2 +R3ECl
R3EC CPh + YbCl2(THF)4,
E = Si, Ge, Sn; R = CH3, C6H5.
The organolanthanide compound was capable of
the sequential substitution of the phenylethynyl ligand
with chlorine atoms. However, the nature of the
interaction with triphenylmethyl chloride was sub-
stantially different from that of the similar reactions
with R3ECl (E = Si, Ge, or Sn), the latter yielding the
non-symmetrical derivatives of silicon, germanium, or
tin R3EC≡CPh as the major products (Table 3, exp. 2–4).
The R3EC≡CPh compounds were identified by
means of elemental analysis and IR spectroscopy.
The interaction of bis(phenylethynyl)ytterbium
with triphenylmethyl chloride occurred quantitatively
to form phenylacetylene and 1-(diphenylmethylidene)-
4-triphenylmethyl-2,5-cyclohexadiene (Ph6C2) being in
the equilibrium (9) with triphenylmethyl radicals.
CPh3
Ph2C
Ph3C + Ph2C
(9)
H
H
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CHEMISTRY OF HOMOLEPTIC PHENYLETHYNYL COMPLEXES OF LANTHANIDES
1913
Triphenylmethyl radicals were identified by means
of EPR with the hyperfine interaction constants with
the protons of аНо = 0.255, аНм = 0.111, аНп = 0.278 mT;
g = 2.0027. Those parameters coincided with the
reference data [11].
The experimental data suggested that the interac-
tion of bis(phenylethynyl)ytterbium with triphenyl-
methyl chloride occurred via the radical-heterolytic
mechanism [12]. The stepwise dealkynylation involved
the one electron transfer stages [Eq. (10)].
THF
CPh
CPh3
(PhC C)2Yb + Ph3CCl
CYb
Cl
C
PhC
Ph3CCl
THF
Ph3C +
CYbCl(THF)2
PhC C + PhC
YbCl2(THF)4 + PhC
C + Ph3C
(10)
Phenylethynyl and triphenylmethyl radicals did not
recombine to form phenyl(tripenylmethyl)acetylene.
Phenylethynyl radicals interacted with THF to be
converted into phenylacetylene, and the stable tri-
phenylmethyl radicals gave the recombination product.
temperature occurred slower than in the case of the
similar ytterbium(II) compound. The major products of
those reactions were phenylacetylenides R3EC≡CPh
(E = Si, Ge, or Sn; R = CH3 or C6H5) and the hardly
separable mixtures of lanthanide halides (PhC≡C)2LnX·
(THF)n, PhC≡CLnX2(THF)n, and LnX3(THF)3 (Ln =
Pr or Dy; X = Cl or I). They were isolated from the
reaction mixtures after 3 days (room temperature) with
high yields (Table 4). In the cases of the reactions with
triphenylgermanium and triphenyltin chlorides,
hexaphenyldigermanium and hexaphenylditin were
formed in 5–10% yield. Likely, the heterolytic
exchange via reactions (7) and (8) were accompanied
by side generation of triphenylgermyl and triphenyl-
stannyl radicals, similar to the reaction (10), followed
by their recombination. The reaction products were
identified using the elemental analysis (С, Н, Hlg, and
metal) and IR spectroscopy data.
In contrast to bis(phenylethynyl)ytterbium, the
similar compounds of lanthanides(III) prepared via the
reaction (5) almost did not interact with triphenyl-
methyl chloride at room temperature. Tris(phenyl-
ethynyl)praseodymium and -dysprosium (PhC≡C)3Ln·
(THF) interacted with Ph3CCl (the molar ratio of 1 : 3)
in THF at 50°С within 3.5 h to form (with respect to
1 mol of the starting lanthanide compound) 1.42 or
0.82 mol of 1-diphenylmethylidene-4-triphenylmethyl-
2,5-cyclohexadiene along with 0.97 mol of phenyl-
ethynylpraseodymium dichloride or 0.98 mol of bis-
(phenylethynyl)dysprosium chloride, respectively. The
reactions were accompanied by substitution of one or
two of the phenylethynyl groups. Phenylacetylene was
detected in the oligomer form rather than as monomer
in the reaction products. IR spectrum of the compound
isolated from the reaction mixture corresponded to that
of poly(phenylacetylene) prepared via polymerization
of phenylacetylene in toluene in the presence of MoCl5
as catalyst [13]; IR spectrum, ν, cm–1: 3040 m, 3070 m
(СН); 1600 s (С=Сarom); 1500 s, 1450 s (С=С); 750 s
(СН); 700 s (СНarom).
From the data in Table 4 it followed that the yield
of the cross-coupling product R3EC≡CPh depended on
the nature of the heteroatom E. In the case of the
organosilicon halides, the product yield was higher
than that in the cases of germanium and tin compounds
(cf. exp. 1, 4, 5 and 2, 3, 6, 7). The reaction occurred
under mild conditions without any catalyst.
Bis(phenylethynyl)ytterbium (PhC≡C)2Yb(THF)2
readily reacted with tetraphenylantimony halides (in
the molar ratio of 1:2) in THF at room temperature to
form triphenylantimony, benzene, phenylacetylene,
phenylethynylytterbium halide PhC≡CYbX(THF)4,
and YbX2(THF)4 [14]. The high yields of benzene and
phenylacetylene pointed at the participation of phenyl
and phenylethynyl radicals in the reaction (11),
occurring via the one electron transfer mechanism.
Hence, phenylethynyl complexes of ytterbium,
praseodymium, and dysprosium interacted with tri-
phenylmethyl chloride via the same mechanism
involving generation of the free radicals.
Reactions of the phenylethynyl derivatives of
praseodymium(III) and dysprosium(III) with silicon,
germanium, and tin alkyl(aryl)halides in THF at room
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1914
ZHILTSOV et al.
Table 4. Yields of major products of reactions of organic derivatives of praseodymium(III) and dysprosium(III) with organic
halides of the IVA group elements
Yield, mola
Exp. no.
Reaction (reactants ratio)
R3EC≡CPh mixture of lanthanide halides (yield with respect to Ln)
1
2
3
4
5
6
7
(PhC≡C)3Pr(THF) + (CH3)3SiI (1 : 3)
(PhC≡C)3Pr(THF) + Ph3GeCl (1 : 3)
(PhC≡C)3Pr(THF) + Ph3SnCl (1 : 3)
(PhC≡C)3Dy(THF) + (CH3)3SiCl (1 : 3)
(PhC≡C)3Dy(THF) + (CH3)3SiI (1 : 3)
(PhC≡C)3Dy(THF) + Ph3GeCl (1 : 3)
(PhC≡C)3Dy(THF) + Ph3SnCl (1 : 3)
2.54
1.05
1.54
2.43
2.41
1.45
1.93
0.92
0.92
0.92
0.85
0.84
0.84
0.80
a With respect to 1 mol of the lanthanide organic compound.
THF
CPh(THF)2
C YbC
(PhC C)2Yb(THF)2 + Ph4SbX
PhC
Ph4Sb
X
PhC CYbX(THF)4 + [PhC
Ph3Sb + PhC
C + Ph4Sb ]
X = Cl, Br, I.
C + C6H5
(11)
Recombination of the radicals pair did not occur,
since it gave the unstable compound. The metal-
centered radical was stabilized via elimination of
hydride in THF at 20–50°С in the absence of any
catalyst. The reaction occurred in several stages
depending on the molar ratio of the reactants. The
vinyl tin-containing lanthanide derivative (mono
adduct) was formed at the 1 : 3 ratio [Eq. (14)]. Further
addition of 3 mol of Ph3SnH to the mono adduct or the
reaction with triphenyltin hydride at the 1 : 6 ratio gave
rise to the products of complete addition (bis adducts
A) [Eq. (15)].
phenyl
radical
to
form
triphenylantimony.
Phenylethynylytterbium halide was partially subject to
further dealkynylation to form the ytterbium halide
YbX2(THF)4.
The reactions of organic lanthanides compounds
with organoelement halides R3EХ and Ph4SbX (E = Si,
Ge, or Sn; X = Cl, Br, or I) gave the non-symmetric
organoelement compounds R3EC≡CPh and the mixed
organolanthanide compounds PhC≡CYbX(THF)n,
PhC≡CPrХ2(THF)4, and (PhC≡C)2DyХ(THF)4 with
high yields; the products properties are given in Table 5.
THF
(PhC≡C)3Ln + 3Ph3SnH
[PhCH=C(Ph3Sn)–]3Ln, (14)
(PhC≡C)3Ln + 6Ph3SnH → [PhCH2–C(Ph3Sn)2–]3Ln, (15)
A
Ln = Pr, Tb.
The organotin hydrides R3SnH were readily added
at the organoelement monoacetylenides R'3EC≡CН
(E = Si, Ge, or Sn) to form the organobielement
ethylene derivatives [Eq. (12)] at the equimolar ratio of
the reagents [16]. Triphenyltin hydride reacting with
phenylacetylene at the 2 : 1 ratio gave predominantly
2,2-bis(triphenylstannyl)-1-phenylethane [Eq. (13)] [17].
The structure of the bis adduct could not be con-
firmed; the formation of the isomer [Ph(Ph3Sn)CHCH·
(SnPh3)]3Ln could not be excluded. The bis adduct A
structure could not be determined via analysis of its
hydrolysis products as well. Apparently, the organotin
derivatives formed via the hydrolysis were subject to
splitting in the alkaline medium [18] to yield
hexaphenylditin and the non-identified compounds.
The lanthanide hydroxide yield was quantitative.
R3SnH + R' EC≡CH → R3Sn–CH=CH–ER' , (12)
3
3
PhC≡CH + 2Ph3SnH → PhCH2–CH(SnPh3)2. (13)
The vinyl derivatives of the lanthanides were
isolated with yield of 85–90%; they were dark-colored
Phenylethynyllanthanides were subject to hydro-
stannylation upon the interaction with triphenyltin
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CHEMISTRY OF HOMOLEPTIC PHENYLETHYNYL COMPLEXES OF LANTHANIDES
1915
Table 5. Melting points and elemental analysis data for polyfunctional organoelement compounds
mp
(decomp.),
°С
Found, %
Calculated, %
Compound
Appearance
Formula
11H14Si
С
Н
Hlg
–
Ln
–
С
Н
Hlg Ln
82а
75.36 7.90
75.86
8.05
–
–
С
(CH3)3SiC≡CPh
Yellow oily liquid
(6 mmHg)
[15]
–
–
–
–
С26H20Ge
С26H20Sn
74.13
69.23
4.94
4.44
–
–
–
–
Ph3GeC≡CPhb
White crystals
Colorless crystals
Yellow amorphous
compound
Light-brown
compound
Red-brown
compound
Light-brown
compound
84
62
288
74.10 5.04
69.53 4.39
42.44 4.47
Ph3SnC≡CPhc
d
7.08 37.60 С
42.34 4.63 7.83 38.15
12.46 26.95
PhC≡CYbCl(THF)2
16H21ClO2Yb
С24H37BrO4Yb
С24H37IO4Yb
С24H37Cl2O4Pr
С32H42ClO4Dy
11.08 24.18
18.25 24.23
11.18 23.33
4.93 23.10
PhC≡CYbBr(THF)4
PhC≡CYbI(THF)4
PhC≡CPrCl2(THF)4
188
250
160
240
18.43 25.11
11.81 23.46
(PhC≡C)2DyCl(THF)4 Brown compound
5.16 23.62
a
b
Boiling point. IR spectrum, ν, cm–1: 3040 s, 2165 s (C≡C), 1480 s, 1425 m, 1085 s, 1065 w, 1020 w, 995 m, 730 s, 690 s, 460 s
(Ph3Ge). c IR spectrum, ν, cm–1: 2125 s (C≡C), 1460 s, 1410 s, 1060 s, 1010 s, 985 s, 715 s, 685 s, 440 s (Ph3Sn). d IR spectrum, ν, cm–1:
2200 m (C≡C), 2050 m (C≡C), 1880 w, 1790 w, 1445 s, 1380 s, 1300 s, 1070 m, 1025 s, 995 s, 730 m, 670 s, 490 m; 1040 m, 840 m
(coordinated THF).
powders, decomposing in the evacuated capillary
without melting above 190°С, unstable in air, readily
soluble in THF and 1,2-dimethoxyethane, and prac-
tically insoluble in hexane.
The multinuclear organometallic complexes were
formed via the interaction of the phenylethynyl
derivatives of the lanthanides with phenylethynyl-
copper in THF at room temperature [Eqs. (16), (17)] as
well. Yield of the phenylethynyl cuprate complexes of
lanthanides(II, III) was close to quantitative (81–97%).
The bis adducts were isolated with yields of 86–
90%; they were light-colored compounds, decomposing
without melting above 215°С, readily soluble in THF
and 1,2-dimethoxyethane and poorly soluble in hexane.
(PhC≡C)2Ln + PhC≡CСu
THF
[(PhC≡C)3Cu][Ln(THF)2],
Ln = Yb, Sm.
(16)
(17)
The products of the phenylethynyllanthanides hyd-
rostannylation were identified by means of elemental
analysis (Table 6) and IR spectroscopy. In particular,
the IR spectra of the products contained the absorption
bands typical of the Ph3Sn group (3050, 1420, 1070,
730, 695, and 450 cm–1). IR spectra of the mono
adducts contained the absorption band assigned to the
vinyl С=С bond at 1620 cm–1. Formation of the bis
adducts was confirmed by the absence of the bands of
the С≡С, С=С (vinyl), and Sn–H (1800–1875 cm–1)
stretching in the IR spectra.
2(PhC≡C)3Ln + 3PhC≡CСu
THF
[(PhC≡C)3Cu]3[Ln2(THF)6],
Ln = Pr, Er.
Chemistry of those complexes has been discussed
in [12].
The phenylethynyl derivatives of praseodymium,
samarium, europium, erbium, and ytterbium revealed
the catalytic activity towards the low-temperature
polymerization of methyl methacrylate. The monomer
conversion was of 80% after 1 day incubation of the
reaction mixture containing methyl methacrylate and
3.1 wt% of tris(phenylethynyl)praseodymium in a
sealed ampoule at room temperature. The activity of
Hence, the phenylethynyl derivatives of the
lanthanides were highly reactive in the interactions via
the metal–carbon bond as well as at the ethynyl ligand,
the latter being hydrostannilated to form the
multinuclear organometallic compounds containing the
lanthanide and tin atoms.
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1916
ZHILTSOV et al.
Table 6. Elemental analysis data for the products of hydrostannylation
Found, %
Calculated, %
Compound
Formula
С
Н
Ln
С
Н
Ln
[PhCH=C(SnPh3)]3Pr
[PhCH=C(SnPh3)]3Tb
[PhCH2C(SnPh3)2]3Pr
[PhCH2C(SnPh3)2]3Tb
62.10
61.05
63.10
62.03
4.38
4.54
4.60
4.73
9.05
9.79
4.93
5.69
C78H63PrSn3
C78H63Sn3Tb
62.57
61.82
62.17
61.73
4.21
4.16
4.36
4.36
9.42
10.50
5.53
C132H111PrSn6
132H111Sn6Tb
C
6.20
the lanthanide derivatives towards polymerization was
revealed for the monomers prone of the radical and the
anionic initiation (methyl methacrylate and acrylo-
nitrile). The co-polymerization of acrylonitrile and
methyl methacrylate in the presence of (PhC≡C)3Pr as
catalyst yielded the polymer enriched by acrylonitrile,
pointing at the anionic mechanism of initiation. The
lanthanides derivatives acted as both a catalyst and a
co-monomer (owing to the presence of the phenyl-
ethynyl group), leading to formation of a cross-linked
polymer enriched with lanthanide; the so formed
polymer was insoluble in acetone. Incorporation of the
lanthanide in the polymer resulted in its biological
activity and the X-ray protective properties (Table 7).
under argon atmosphere in the form of Vaseline oil
suspension. Magnetochemical tests were performed as
described in [19]. EPR spectrum of paramagnetic
triphenylmethyl radical was detected using a Bruker
ER-2000-SRC instrument.
Content of the lanthanide in the organolanthanide
compounds was determined prior to the experiments.
Since the reactions were performed in THF, its
elimination from the coordination sphere of the used
derivatives was not necessary.
Praseodymium tris[2-methoxy-4-phenylbut-3-
yn-2-olate]. 0.80 g of (PhC≡C)3Pr was dissolved in
15 mL of degassed anhydrous ethyl acetate, and the
formed bright orange-brown solution was incubated
during 2 h at room temperature. The excess of the ester
was removed via re-condensation in vacuum, and the
reaction product was extracted with toluene to remove
the unreacted (PhC≡C)3Pr. Toluene was removed via
re-condensation, the residue was washed three times
with hot hexane and dried in vacuum. Yield 1.08 g
(89%), decomp. > 230°С. Other alkoxides of
praseodymium, terbium, and samarium were prepared
similarly (Table 2).
The 150×150 mm specimens of the polymeric glass
were tested for the X-ray [λ(CuKα) 0.154 nm]
absorption using a Dron-2 diffractometer in the BSV-
10S50kV-20 mA tube operation mode. The mass
absorption coefficient μ/ρ revealed the relative
reduction of the radiation intensity after passing
through a layer of the material containing 1 g of the
substance per 1 cm2. The half-absorption thickness d0.5
was equal to the thickness of the substance layer
reducing the radiation intensity by one half.
As seen from Table 7, the polymer prepared in the
presence of the phenylethynyl lanthanides derivatives
(exp. 1–4) revealed the X-ray protective properties as
compared to the reference sample prepared with
benzoyl peroxide as catalyst (exp. 5).
Trimethylsilicon phenylacetylenide. a. 0.40 g
(0.0036 mol) of (CH3)3SiCl was added to a solution of
0.67 g (0.0015 mol) of (PhC≡C)2Yb(THF) in 30 mL of
THF; the solution color was changed, and precipitate
was formed. The reaction mixture was incubated
during 1 day at room temperature. The precipitate was
filtered off and washed with THF. The precipitate was
YbCl2(THF)4; yield 0.54 g (0.0010 mol, 67.7%), the
Yb2+-to-Cl– ratio of 1 : 2. The tetrahydrofuran extracts
were combined, the volatile components were re-
condensed under vacuum in a trap cooled with liquid
nitrogen, and hexane was added to the residue. The
substance insoluble in hexane was majorly
PhC≡CYbCl(THF)2; Yield 20% (0.1 g, 0.0003 mol).
Content of ytterbium 51.23%, that of chlorine 10.84%;
the Yb2+ : Cl– molar ratio of 1 : 1.
EXPERIMENTAL
Phenylethynyl derivatives of lanthanides were
prepared as described in [4, 6]. All the experiments
were carried out in evacuated sealed ampoules using
the thoroughly dried and degassed solvents. The
reagents used were purified via the standard
procedures.
IR spectra were recorded using Perkin-Elmer-577
and FSM 1201 instruments; the samples were prepared
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CHEMISTRY OF HOMOLEPTIC PHENYLETHYNYL COMPLEXES OF LANTHANIDES
1917
Table 7. Resistance to bacteriaa and X-ray protective properties of poly(methyl methacrylate)
X-ray protection
Exp. no.
Catalyst
(PhC≡C)3Eu
с, wt %
Resistance to bacteria,b points
μ/ρ, cm2/g
d0.5, mm
1
2
3
4
5
2.1
1.5
1.5
0.9
0.8
8.73
9.14
15.71
9.38
0.70
0.70
0.40
0.70
3.44
1 (resistant)
0 (resistant)
0 (resistant)
–
(PhC≡C)3Er
(PhC≡C)3Yb
(PhC≡C)3Yb
Benzoyl peroxide
2.01
4 (non-resistant)
a
Aspergillus oryzae, Aspergillus flavus, Aspergillus niger, Aspergillus terreus, Penicillium funiculosum, Penicillium chrysogenium,
Penicillium cyclopium, Chaetomium globosum, Trichoderma viride, Paecilomyces varioti. The mark of a resistant specimen is 0–
b
2 points.
Slow evaporation of the solvent from the hexane
The filtrate was evaporated in vacuum, and hexane
was added to the residue. The products mixture
insoluble in hexane was separated off, washed, and
dried. Yield 0.41 g. Part of the mixture was used for
determination of ytterbium and chlorine content.
PhC≡CYbCl(THF)2 was isolated from the rest of the
specimen (Table 5, exp 4).
extract gave 0.46 g of Me3SiC≡CPh. Yield 1.73 mol
per 1 mol of the starting lanthanide derivative (Table 3,
exp. 2).
b. 0.76 g (0.0038 mol) of (CH3)3SiI was added to a
solution of 0.67 g (0.0013 mol) of (PhC≡C)3Pr(THF)
in 20 mL of THF. The reaction mixture was incubated
during 3 days at room temperature. THF and other
volatile components were re-condensed in vacuum.
Hexane was added to the residue. The hexane-insoluble
praseodymium iodine derivatives (PhC≡C)2PrI,
(PhC≡C)PrI2, and PrI3 were separated off, washed with
hexane, and dried. Yield 0.95 g, praseodymium
content 17.9% (total yield with respect to the
lanthanide 0.0012 mol, 92.3%).
The hexane extract was evaporated to get 0.77 g
(0.0019 mol) of Ph3GeC≡CPh, mp 84°С (Table 3,
exp. 3; Table 5, exp. 2).
b. 1.80 g (0.0053 mol) of Ph3GeCl was added to a
solution of 0.92 g (0.0018 mol) of (PhC≡C)3Pr(THF)
in 20 mL of THF. The reaction mixture was incubated
during 3 days at room temperature. THF was distilled
off in vacuum, and benzene was added to the residue.
Hexaphenyldigermanium was filtered off and dried.
Yield 0.13 g (12%), mp 331°С. Found, %: С 69.80; Н
5.34. C36H30Ge2. Calculated, %: С 71.17; Н 4.94.
The hexane extract was evaporated in vacuum to
isolate 0.57 g (0.0033 mol) of Me3SiC≡CPh, identical
to that prepared via procedure a. Yield 2.54 mol per
1 mol of the starting lanthanide (Table 4, exp. 1; Table 5,
exp. 1).
The benzene filtrate was evaporated in vacuum, and
the residue was extracted with hexane. The substance
insoluble in hexane was filtered off and dried in
vacuum at room temperature during 1 h. Yield 1.74 g
(92% with respect to praseodymium, Table 4, exp. 2)
of a mixture of organic derivatives of praseodymium
(13.5% of Pr and 8.05% of Cl). IR spectrum, ν, cm–1:
(PhС≡С) 2125 w (PhС≡С), 2025 m (С≡С), 1880 w,
1790 w, 1450 s, 1350 s, 1070 m, 1060 m, 1025 s, 995
s, 750 s, 730 s, 690 s, 490 m; 1040 m, 800 m
(coordinated THF).
The yield of (СН3)3SiC≡CPh in the similar
reactions of (PhC≡C)3Dy(ТГФ) with trimethylsilicon
chloride and iodide in THF was of 2.43 mol and
2.41 mol, respectively, per 1 mol of the starting
compound (Table 4, exp. 4, 5).
Triphenylgermanium phenylacetylenide. a. 1.0 g
(0.0029 mol) of Ph3GeCl was added to a solution of
0.64 g (0.0014 mol) of (PhC≡C)2Yb(THF) in 30 mL of
THF. The reaction mixture was incubated during 1 day
at room temperature. The precipitate insoluble in THF
was separated off, washed with THF, and dried to
constant mass (0.16 g). The product composition was
close to that of ytterbium(II) chloride tetrahydro-
furanate. Found, %: Cl 20.09; Yb 42.62. C8H16Cl2O2Yb.
Calculated, %: Cl 18.30; Yb 44.59.
The hexane filtrate was evaporated. 0.77 g (0.0019 mol)
of Ph3GeC≡CPh was isolated; yield 1.05 mol per
1 mol of the starting lanthanide (Table 4, exp. 2; Table 5,
exp. 2).
A similar reaction of (PhC≡C)3Dy(THF) with
Ph3GeCl yielded 1.45 mol of triphenylgermanium
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 8 2015

1918
ZHILTSOV et al.
phenylacetylenide per 1 mol of the starting lanthanide
(Table 4, exp. 6).
Reaction of (PhC≡C)3Pr with Ph3SnH was
performed similarly (Table 6, exp. 3).
Methyl methacrylate polymerization. 0.20 g
(1.5 wt %) of (PhC≡C)3Eu was added portionwise to
13.2 mL of dry degassed methyl methacrylate in the
evacuated ampoule cooled with liquid nitrogen. The
catalyst was completely dissolved upon defrosting the
mixture to 20–25°С. A brown-red non-transparent
polymer insoluble in acetone was formed within 50 h
at room temperature with conversion of 78%.
Triphenyltin phenylacetylenide. 1.55 g (0.0040 mol)
of Ph3SnCl was added to a solution of 0.68 g
(0.0013 mol) of (PhC≡C)3Pr(THF) in 20 mL of THF.
The reaction mixture was incubated during 3 days at
room temperature. THF was re-condensed in vacuum,
and hexane was added to the residue. The insoluble
products mixture was separated off, washed with
hexane, and dried in vacuum during 1 h. Yield 0.84 g
(0.0012 mol, 92% with respect to praseodymium). The
product contained 20.4% of Pr.
Polymerization of methyl methacrylate in the
presence of other lanthanide-containing catalysts were
performed similarly.
The hexane extract was evaporated. Yield 0.91 g
(0.0020 mol) of Ph3SnC≡CPh; 1.54 mol per 1 mol of
the starting lanthanide. Colorless crystalline solid, mp
62°С (Table 4, exp. 3; Table 5, exp. 3), stable in air,
well soluble in THF, benzene, and hexane.
ACKNOWLEDGMENTS
This work was financially supported by Ministry of
Education and Science of Russian Federation
(governmental task no. 4.70.2014/K).
In a similar reaction of (PhC≡C)3Dy(THF)
(0.0014 mol) with Ph3SnCl (0.0041 mol), benzene was
added to the reaction mixture after THF revomal.
Hexaphenylditin was isolated; yield 0.04 g (4 mol %),
mp 237°С. Phenylethynyltriphenyltin was isolated
from the solution; yield 1.93 mol per 1 mol of the
starting lanthanide (Table 4, exp. 7).
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