Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ-η5:η1 bonding indolyl and μ3-oxo groups

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Synthesis, structure, and catalytic activity of

novel trinuclear rare-earth metal amido

complexes incorporating μ–η⁵:η¹bonding

indolyl and μ₃-oxo groups†

Cite this: Dalton Trans., 2014, 43,

2521

Song Yang,^aXiancui Zhu,^aShuangliu Zhou,^aShaowu Wang,*^a,bZhijun Feng,^a

Yun Wei,^aHui Miao,^aLiping Guo,^aFenhua Wang,^aGuangchao Zhang,^aXiaoxia Gu^a

and Xiaolong Mu^a

The reactions of diﬀerent pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me₃Si)₂N]₃-

RE^III(μ-Cl)Li(THF)₃(RE = Yb, Er, Dy, Eu, Y) produced diﬀerent kinds of rare-earth metal amido complexes.

Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides

[(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃(RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75–80 °C

aﬀorded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in

μ–η⁵:η¹bonding modes and a μ₃-O group, which is believed to originate from cleavage of the THF ring

based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)

ethanamine with rare-earth metal(^III) amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃(RE = Yb, Dy) produced mono-

nuclear ytterbium and dysprosium amides having the indolyl ligand in an η¹bonding fashion. The results

indicate that substituents not only have an inﬂuence on reactivity, but also have an inﬂuence on the

bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido com-

plexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were

explored. The results indicate that these complexes display a high catalytic activity for the C–P bond for-

mation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones).

Thus, it provides a potential way to prepare α-hydroxy phosphonates.

Received 27th April 2013,

Accepted 10th October 2013

DOI: 10.1039/c3dt51107c

www.rsc.org/dalton

compounds such as olefin polymerization,²hydroamination/

cyclization,³hydrophosphination,⁴hydrophosphonylation,⁵

Introduction

The chemistry of organo rare-earth metal complexes is one of and hydrosilylation of a variety of unsaturated organic com-

the most active fields and has received continuous interest pounds,⁶or as catalysts in synthetic chemistry.⁷On the other

amongst transitional metal chemistry for their unique struc- hand, organo rare-earth metal complexes have been found to

tures and properties,¹and their potential applications as cata- exhibit a potential application in the activation of small

9

lysts in a wide range of transformations of unsaturated molecules such as CO₂, CO,^1i,8N₂and organic or inorganic

compounds.^1k,10

Recently, research on pyrrolyl and indolyl derivatives has

^aKey Laboratory of Functionalized Molecular Solids, Ministry of Education,

attracted particular attention in rare-earth metal chemistry

because they can act as versatile ligands, due to their η⁵/η¹

Anhui Laboratory of Molecule-Based Materials, Institute of Organic Chemistry,

School of Chemistry and Materials Science, Anhui Normal University, Wuhu,

bonding capability, and are anticipated to be alternatives to

Anhui 241000, P. R. China. E-mail: swwang@mail.ahnu.edu.cn;

cyclopentadienyl or indenyl ligands.^9g,11It is found that reac-

Fax: +86-553-3883517; Tel: +86-553-5910015

^bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic

tions of functionalized pyrroles with rare-earth metal amides

[(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃display diﬀerent chemistry

with findings of redox chemistry between europium amide

and pyrrolyl-functionalized secondary amines, and the de-

hydrogenation reaction between secondary amines and rare-

earth metal amides.¹²In comparison with the chemistry of

Chemistry, Shanghai 200032, P. R. China. E-mail: swwang@mail.ahnu.edu.cn

†Electronic supplementary information (ESI) available: Characterization data for

new compounds, scheme showing the preparation of ligand and complexes,

figures illustrating the structures of complexes 3a–3e, 4a and 4b. CCDC 935210–

935215, and 959910. For ESI and crystallographic data in CIF or other electronic

format see DOI: 10.1039/c3dt51107c

This journal is © The Royal Society of Chemistry 2014

Dalton Trans., 2014, 43, 2521–2533 | 2521

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rare-earth metal complexes with cyclopentadienyl/indenyl or (1) in 88% yield. Reaction of tryptamine with N-methyl-pyrro-

pyrrolyl ligands, chemistry of rare-earth metals with indolyl lyl-2-aldehyde in ethanol at room temperature gave N-((1-

ligands is far less developed.¹³Recently, we found that reac- methyl-1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine

tions of 3-t-butylimino-functionalized indole with rare-earth (3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅NH) (2) in 92% yield.

metal amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃(RE = Yb, Y) pro- These transformations are outlined in Schemes S1 and S2

duced novel rare-earth metal complexes containing an unusual (ESI†).

indolyl-1,2-dianion bonded to the metals in a novel η¹:

(μ₂–η¹:η¹) mode through imino-directed C–H bond activa-

Reactivity of the ligands with rare-earth metal(^III) amides

tion.^13bIt is also found that the reaction of [(Me₃Si)₂N]₃-

Initially,

the

novel

trinuclear

europium

complex

Ln^III(μ-Cl)Li(THF)₃with 2 equiv. of 3-(CyNHCH₂)C₈H₅NH in

toluene produced the amino-coordinate-lithium bridged bis-

(indolyl) lanthanide amides [μ–{[η¹:η¹:η¹:η¹-3-(CyNHCH₂)

Ind]₂Li}RE[N(SiMe₃)₂]₂] (Cy = cyclohexyl, Ind = indolyl).^13c

Recently, we also found that the reaction of 2-(2,6-diisopropyl-

phenylaminomethylene)indole 2-(2,6-ⁱPr₂C₆H₃NHCH₂)C₈H₅NH

with europium amide [(Me₃Si)₂N]₃Eu^III(μ-Cl)Li(THF)₃aﬀorded

a novel europium(^II) complex formulated as {[µ–η⁶:η¹:η¹-2-

(2,6-ⁱPr₂C₆H₃NvCH)C₈H₅N]Eu[2-(2,6-ⁱPr₂C₆H₃NvCH)

[(μ–η⁵:η¹):η¹:η¹-3-(2-C₄H₃NCHvNCH₂CH₂)C₈H₅N]Eu₃(μ₃-O)(μ₂-

Cl)₂(THF)₂[N-(SiMe₃)₂] (3b) was isolated from the reaction of 1

with 1 equiv. of [(Me₃Si)₂N]₃Eu^III(μ-Cl)Li(THF)₃in THF at

75 °C. X-ray and elemental analysis revealed that this novel tri-

nuclear complex contains a μ₃-O group. Then, the same reac-

tion was carried out in toluene while the other conditions

stayed the same, and again, the trinuclear europium complex

was isolated. Treatment of 1 with 1 equiv. of [(Me₃Si)₂N]₃-

RE^III(μ-Cl)Li(THF)₃in toluene at 75–80 °C also produced the

novel trinuclear rare-earth complexes [(μ–η⁵:η¹):η¹:η¹-3-(2-

C₄H₃N-CHvNCH₂CH₂)C₈H₅N]RE₃(μ₃-O)(μ₂-Cl)₂(THF)₂[N(SiMe₃)₂]

(RE = Y (3a), Dy (3c), Er (3d), and Yb (3e)) (Scheme 1,

route a). These results imply that the reactions are reproduci-

ble both in THF and toluene, and can be expanded to rare-

earth metals like Y, Dy, Er and Yb. As the same results can be

obtained in toluene, this suggests that the μ₃-O group may

come from the coordinated THF of the rare-earth metal(^III)

amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃. It has been documen-

ted that lanthanide complexes with pentamethylcyclopentadi-

enyl,¹⁴Schiﬀ base,¹⁵dipyrrolide,¹⁶triamido-amine,¹⁷indenyl,¹⁸

carborane¹⁹and porphyrinogen²⁰ligands can react with THF

or oxygen-containing compounds such as epoxides to give the

μ-oxo-containing or enolate complexes. It has also been

reported that the alkyl lanthanide complexes can thermally

decompose THF to give the enolate complexes in the presence

of THF–LiCl.²¹However, the synthesis and characterization of

lanthanide complexes with both indolyl ligands and the μ-oxo

groups has not been reported.

C₈H₅N]}₂with a bridged indolyl ligand in novel µ–η⁶:η¹:η¹hap-

ticities with the reduction of europium(^III) to europium(II) and

the oxidation of amino to imino group. Reactivity studies led

to the discovery of novel bonding modes of the indolyl ligands

with europium(^II) metal.^13fThese results suggested that reac-

tions of diﬀerent functionalized indoles with rare-earth metal

amides displayed diﬀerent reactivities, and that indolyl ligands

show diﬀerent bonding modes with rare-earth metals. These

results promoted us to further study the reactivity of other

functionalized indoles with rare-earth metal(^III) amides

[(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃.

Recently, we investigated the catalytic activities of various

lanthanide amido complexes for the hydrophosphonylation of

various substituted aldehydes, aldimines and unactivated

ketones. The results showed that the lanthanide amido com-

plexes exhibited a high catalytic activity for the C–P bond for-

mation when using low catalyst loadings under mild

conditions. These results promoted us to explore the catalytic

activity of the lanthanide amido complexes with a μ₃-oxo group

for hydrophosphonylation.

In this paper, we will report the reactivity of diﬀerent pyrro-

lyl-functionalized indoles with rare-earth metal amides

[(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃(RE = Yb, Er, Dy, Eu, Y), with

the isolation and characterization of a series of novel trinuc-

lear organo rare-earth metal complexes containing both

bridged indolyl ligands and a μ₃-oxo group. The eﬀects of the

conditions and coordinated LiCl on the reactions are also

examined. The catalytic activity of these lanthanide amido

complexes with a μ₃-oxo group for the hydrophosphonylation

of various substituted aldehydes and ketones is also reported.

The complexes were characterized by elemental analysis, IR,

¹H and ¹³C NMR spectroscopy as well as X-ray analysis (Fig. 1).

Results and discussion

Ligands

The reaction of tryptamine with pyrrolyl-2-aldehyde in ethanol

at room temperature gave N-((1H-pyrrol-2-yl)methylene)-2-(1H-

indol-3-yl)ethanamine (3-(2-C₄H₃NHCHvNCH₂CH₂)-C₈H₅NH) Scheme 1 Preparation of complexes.

2522 | Dalton Trans., 2014, 43, 2521–2533

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Fig. 2 Representative molecular structures of complexes 4a and 4b.

Fig. 1 Representative molecular structure of complexes 3a–3e.

while the reaction of the N-methylated pyrrolyl-functionalized

indole with ytterbium and dysprosium amides produces

mononuclear complexes incorporating an indolyl ligand η¹

bonded with a metal.

They are very sensitive to air and moisture, but stable in an

inert atmosphere for months. They are soluble in polar sol-

vents and toluene but insoluble in hexane.

To further prove that the μ₃-O group comes from THF

through cleavage of the ring, several experiments were carried

out. The reaction of ligand 1 with 1 equiv. of [(Me₃Si)₂N]₃RE^III

Molecular structures

(by sublimation of the corresponding amide [(Me₃Si)₂N]₃- X-ray analyses revealed that complexes 3a–3e are C₂-symmetric

RE^III(μ-Cl)Li(THF)₃in vacuo) proved unsuccessful, resulting in structures consisting of three rare-earth metal ions bridged by

the full recovery of the [(Me₃Si)₂N]₃RE^IIIcrystals even when a μ₃-O atom and two dianion ligands coordinated to rare-earth

excess LiCl was added. This result implied that the μ₃-O group metals in a η¹mode through the nitrogen atom of a pyrrolyl

resulted from the cleavage of the coordinated THF in the rare- ring, in a η¹mode through the imino N atom and in μ–η⁵:η¹

earth metal(^III) amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃. Further bonding modes of the indolyl ligand. All of the rare-earth

experiments on capturing the excluded gas with Br₂/CCl₄solu- metal ions in the complexes have a distorted-octahedral

tion followed by examination by GC-HRMS showed the m/z coordination geometry.

peaks at 185.8680 and 189.8637 for C₂H₄⁷⁹Br₂and C₂H₄⁸¹Br₂

The μ-O atom, RE(2) and N atom of the N(SiMe₃)₂ligand

(Calc. 185.8680 and 189.8639 for C₂H₄⁷⁹Br₂and C₂H₄⁸¹Br₂, formed a line as the C₂symmetry axis of the structures, while

respectively, see Experimental section and ESI†) with almost the μ₃-O atom and the three rare-earth metal ions are coplanar

equal relative abundance (2.79% and 2.70%) relative to with a mean deviation (0.0670 Å for 3a, 0.0000 Å for 3b,

C₂H₄⁷⁹Br⁺(100%). The results clearly proved the presence of 0.0638 Å for 3c, 0.0638 Å for 3d and 0.0000 Å for 3e) on the

ethylene excluded from the reaction mixture. These results basis of a least-squares calculation. To the best of our knowl-

proved that the μ₃-O group resulted from the cleavage of the edge, this is the first report of trinuclear organolanthanide(^III)

THF ring with release of ethylene.

complexes containing both bridged indolyl ligands and a μ₃-

When N-((1-methyl-1H-pyrrol-2-yl)methylene)-2-(1H-indol-3- oxo group in the molecular structure.

yl)ethanamine (2-(3-C₈H₅NHCH₂CH₂NvCH)C₄H₃NCH₃) (2)

Compounds 3a, 3c and 3d are isomorphous and thus iso-

instead of 1 was treated with [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃structural, sharing the same cell symmetry with space group

(RE^III= Yb³⁺, Dy³⁺) in toluene, new hetero-nuclear bimetallic P2₁/n. Compounds 3b and 3e are isostructural with space

complexes (η¹:η¹-[η¹-3-(2-(N-CH₃)C₄H₃N–CHvNCH₂CH₂)C₈H₅N]- groups Pbcn and C₂/c respectively. The RE–μ-O distances are

Li[μ–η²:η¹-3-(2-(N-CH₃)C₄H₃NCHvN–CH₂CH₂)C₈H₅N])- 2.091(3), 2.269(3), and 2.111(3) Å in 3a; 2.0676(12), 2.261(5),

RE[N(SiMe₃)₂]₂(RE^III= Yb (4a), Dy (4b)) were isolated respect- and 2.0676(12) Å in 3b; 2.123(3), 2.281(3), and 2.097(3) Å in 3c;

ively (Scheme 1, path b). The representative molecular struc- 2.105(3), 2.267(3), and 2.080(3) Å in 3d; 2.0742(10), 2.231(4),

ture of 4 is shown in Fig. 2. No μ₃-O group was found in these and 2.0742(10) Å in 3e respectively. The RE–Cl distances are

complexes, indicating no THF ring cleavage in the reactions. 2.7836(12) and 2.7153(13) Å in 3a; 2.7560(14) and 2.6559(15) Å

These results suggest that the ligands play a key role in the in 3b; 2.7895(12) and 2.7274(12) Å in 3c; 2.7722(13) and 2.6960

reactivities of pyrrolyl-functionalized indoles with rare-earth (13) Å in 3d; and 2.7342(12) and 2.6755(13) in 3e respectively.

metal amides [(Me₃Si)₂N]₃RE^III(μ-Cl)Li(THF)₃, with reactions of The variation in the RE–μ-O and RE–Cl distances in com-

the unprotected pyrrolyl-functionalized indole with rare-earth pounds 3a–3e can be accounted for steric eﬀects by taking into

metal amides aﬀording novel trinuclear rare-earth metal com- consideration the change in the ionic radii of the RE(^III) ions

plexes incorporating an η⁵:η¹-indolyl ligand and a μ-O group, in going from Y³⁺to Yb^{3+ 22}

.

In complex 3a, the Y–μ-O distances

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Table 1 Selected bond lengths (Å) and angles (°) for complexes 3a–3e, 4a–4b

3a

3b

3c

Y(1)–O(1)

Y(1)–Cl(1)

Y(2)–O(1)

Y(2)–Cl(2)

Y(2)–Cl(1)

Y(3)–O(1)

2.091(3)

2.7954(12)

2.269(3)

2.6990(12)

2.7316(13)

2.111(3)

Eu(1)–O(1)

Eu(1)–Cl(1)

Eu(2)–O(1)

Eu(2)–Cl(1)

2.0676(12)

2.7560(14)

2.261(5)

Dy(1)–O(1)

Dy(1)–Cl(1)

Dy(2)–O(1)

Dy(2)–Cl(1)

Dy(2)–Cl(2)

Dy(3)–O(1)

2.123(3)

2.7801(11)

2.281(3)

2.7084(11)

2.7463(12)

2.097(3)

2.6559(15)

Y(3)–Cl(2)

2.7717(11)

77.29(3)

78.98(3)

149.87(14)

104.64(11)

105.13(11)

Dy(3)–Cl(2)

2.7989(12)

79.31(3)

77.50(3)

149.55(15)

105.32(12)

104.81(12)

Y(2)–Cl(1)–Y(1)

Y(2)–Cl(2)–Y(3)

Y(1)–O(1)–Y(3)

Y(1)–O(1)–Y(2)

Y(3)–O(1)–Y(2)

Eu(2)–Cl(1)–Eu(1)

Eu(1)#1–O(1)–Eu(1)

Eu(1)–O(1)–Eu(2)

77.58(4)

153.9(3)

103.07(14)

Dy(2)–Cl(1)–Dy(1)

Dy(2)–Cl(2)–Dy(3)

Dy(3)–O(1)–Dy(1)

Dy(1)–O(1)–Dy(2)

Dy(3)–O(1)–Dy(2)

3d

3e

4a and 4b

4a

4b

Er(1)–O(1)

Er(1)–Cl(1)

Er(2)–O(1)

Er(2)–Cl(1)

Er(2)–Cl(2)

Er(3)–O(1)

2.105(3)

2.7625(12)

2.267(3)

2.6788(13)

2.7132(14)

2.080(3)

Yb(1)–O(1)

Yb(1)–Cl(1)

Yb(2)–O(1)

Yb(2)–Cl(1)

2.0742(10)

2.7342(12)

2.231(4)

RE–N(1)

RE–N(4)

RE–N(7)

RE–N(8)

Li–N(2)

Li–N(5)

2.247(3)

2.339(7)

2.291(7)

2.245(6)

2.259(7)

2.027(19)

1.999(19)

2.268(3)

2.202(3)

2.207(3)

2.005(9)

2.024(8)

2.6755(13)

Er(3)–Cl(2)

2.7819(13)

78.98(3)

77.31(4)

150.84(16)

104.60(13)

104.23(13)

N(1)–RE–N(4)

N(7)–RE–N(8)

N(7)–RE–N(1)

N(7)–RE–N(4)

N(8)–RE–N(1)

N(8)–RE–N(4)

87.53(13)

85.3(3)

Er(2)–Cl(1)–Er(1)

Er(2)–Cl(2)–Er(3)

Er(3)–O(1)–Er(1)

Er(1)–O(1)–Er(2)

Er(3)–O(1)–Er(2)

Yb(2)–Cl(1)–Yb(1)

Yb(1)#1–O(1)–Yb(1)

Yb(1)–O(1)–Yb(2)

77.37(3)

153.1(2)

103.45(11)

120.82(11)

114.30(12)

108.10(12)

108.95(12)

112.25(11)

122.3(3)

115.9(2)

106.5(3)

108.1(3)

112.8(3)

Table 2 Selected bond lengths (Å) between RE(1) and the nitrogen

heterocyclic ring of the indolyl for complexes 3a–3e

of 2.091(3) Å for Y(1)–μ-O, and 2.111(3) Å for Y(3)–μ-O are

nearly equal, but the Y(2)–μ-O distance of 2.269(3) Å is slightly

longer, while the coordination number of Y(1) and Y(3) are

eight but the coordination number of Y(2) is six. Similar

results could be found in complexes 3b–3e.

In complex 3e, the Yb(1)–O(1) distances of 2.0742(10), 2.231(4),

and 2.0742(10) Å are comparable to those found in [{η⁵:η⁵-

(CH₂)₂(C₉H₆)₂}Yb(μ-Cl)(μ₃-O)Yb(Cl)N(SiMe₃)₂Li-(THF)₄]₂(2.126(8),

2.107(9) and 2.200(9) Å)¹⁸and those found in [η⁵:η⁵-

(CH₃)₂Si(C₉H₆)₂Yb]₂(μ-Cl)(μ-O)Li(THF)₂(2.070(5) and 2.063(5) Å).¹⁸

The axis, along with the rare-earth metal to the centroid

vectors of the five-membered nitrogen heterocyclic ring of the

indolyl in complexes 3a–3e, are nearly perpendicular to the

five-membered heterocyclic ring planes (θ = 7.6° for 3a; θ =

9.1° for 3b; θ = 7.5° for 3c; θ = 7.9° for 3d and θ = 10.1° for 3e,

respectively), indicative of an η⁵bonding pattern.

3a

3b

3c

3d

3e

RE(1)–N(3)

RE(1)–C(8)

RE(1)–C(9)

RE(1)–C(10)

RE(1)–C(15)

RE(1)–Ind^a

2.646(4)

2.660(4)

2.817(5)

2.919(5)

2.816(5)

2.772(5)

2.631(4)

2.610(5)

2.775(6)

2.933(6)

2.842(5)

2.758(6)

2.682(4)

2.668(5)

2.814(5)

2.938(5)

2.847(4)

2.790(5)

2.669(4)

2.647(5)

2.796(5)

2.930(5)

2.844(5)

2.777(5)

2.656(4)

2.613(6)

2.793(6)

2.963(6)

2.906(6)

2.786(6)

^aRE(1)–Ind means the average bond distances between the rare-earth

metal ion and the five-membered heterocyclic ring of the indolyl

ligand.

the ligand. The Er(1)–Ind of 2.777(5) Å in 3d is slightly longer

than Er(1)–Pyr of 2.732(8) Å in {(μ–η⁵:η¹):η¹-2-[(2,6-ⁱPr₂C₆H₃)-

12b

NCH₂]C₄H₃N]ErN-(SiMe₃)₂}₂

and 2.706(5) Å calculated from

The bond lengths of the rare-earth metal ions and atoms of

the five-membered heterocyclic ring of the indolyl in com-

plexes 3a–3e are listed in Table 1, and the average distances

between the rare-earth metal ions with the five-membered

heterocyclic ring of the indolyl group are also provided in

Table 2. The average distances RE(1)–Ind of 3a (2.772(5) Å), 3b

(2.758(6) Å), 3c (2.790(5) Å), 3d (2.777(5) Å) and 3e (2.786(6) Å)

are in agreement with the trend of the lanthanide contraction.

The Yb(1)–Ind of 2.786(6) Å in 3e is comparable to Yb–C(av.)

in [η⁵:η⁵-(CH₂)₂(C₉H₅SiMe₃)₂]Yb(THF)₂(2.784(9) Å),¹⁸but

longer than Yb–C(av.) in [{η⁵:η⁵-(CH₂)₂(C₉H₆)₂}Yb(μ-Cl)(μ₃-O)-

Yb(Cl)–N(SiMe₃)₂Li(THF)₄]₂(2.691(17) Å)¹⁸and [η⁵:η⁵-(CH₃)₂Si-

(C₉H₆)₂Yb]₂(μ-Cl)(μ-O)Li(THF)₂(2.657(10) Å).¹⁸These deviations

are probably due to the diﬀerent steric eﬀects resulting from

the selected bond lengths in {[(μ–η⁵:η¹):η¹-2-[(2,4,6-Me₃C₆H₂)-

NCH₂]C₄H₃N]ErN-(SiMe₃)₂}₂.^11jThe Y(1)–Ind of 2.772(5) Å in

3a is also slightly longer than Y(1)–Pyr of 2.723(4) Å in

{(μ–η⁵:η¹):η¹-2-[(2,4,6-Me₃C₆H₂)NCH₂]C₄H₃N]Y-N(SiMe₃)₂}₂.^11j

The above diﬀerences are probably due to the restraint of the

μ-oxo group to the molecular structure resulting in diﬀerent

steric eﬀects.

Catalytic activities of complexes 3a–3e on the

hydrophosphonylation of aldehydes

When complexes 3a–3e were used as catalysts for the hydro-

phosphonylation reaction of aldehydes, high catalytic activity

and compatibility with a wide range of substrates under

2524 | Dalton Trans., 2014, 43, 2521–2533

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Table 3 Hydrophosphonylation of benzaldehyde with diethyl

phosphite^a

Table 4 Hydrophosphonylation of aldehydes with diethyl phosphite

catalyzed by complex 3e^a

Entry

Cat.

Loading (mol%)

Solvent

Yield^b(%)

Entry

1

R

Product

Yield^b(%)

99

1

2

3

4

5

6

7

8

9

Complex 3e

None

Complex 3a

Complex 3b

Complex 3c

Complex 3d

1

Toluene

Solvent-free

99

98

68

99

0

98

99

5a

0.5

0.1

0.05

0.1

2

3

4

5b

5c

5d

99

98

0.1

10

^aBenzaldehyde and diethyl phosphite (1 : 1 equiv.), room temperature,

solvent (2 mL) or solvent-free. ^bIsolated yields.

5

6

5e

5f

97

environmentally benign solvent-free conditions was observed.

The results are listed in Table 3.

From the table (entry 1), the product of the hydrophospho-

nylation of benzaldehyde could be produced in 99% yield in

toluene at room temperature within 10 min in the presence of

a catalyst loading of 1 mol% of complex 3e. The decrease of

the catalyst loading from 1 mol% to 0.5 mol% and to 0.1 mol%

did not aﬀect the outputs of the catalytic reactions (entries

1–3), but further decreasing the catalyst loading to 0.05 mol%

led to a low product yield (entries 4). When the reaction was

carried out under solvent-free conditions, a high output of the

product was observed (99% yield, entry 5). However, when the

reaction was carried out in the absence of a catalyst under

the same conditions, no product was obtained (entry 6). Thus, the

reaction conditions of 0.1 mol% of the rare-earth metal com-

plexes at room temperature for 10 min under solvent-free con-

ditions were selected for the following studies. Examinations

of the catalytic activity of 3a–3d under the selected conditions

also provided high isolated yields of the products. These

results indicate that the ionic radii of the rare-earth metals

have less influence on the catalytic activity of these catalysts

(entries 7–10).

7

8

5g

5h

99

9

5i

5j

97

98

97

10

11

5k

12

13

5l

98

96

5m

^aReaction conditions: aldehyde (10.0 mmol) and diethyl phosphite

(10.0 mmol) for 10 min, catalyst 3e (0.1 mol%), solvent-free, room

temperature. ^bIsolated yields.

As all the complexes exhibited similar catalytic activity, so

the ytterbium complex 3e was selected as the catalyst for the

following studies of the electronic and steric eﬀects of the sub- eﬀects of aldehydes have little influence on the outputs of the

strates and the scope of the hydrophosphonylation reaction of reaction (entries 5–13). For example, when the more sterically

aldehydes. Under the optimized reaction conditions, a variety hindered aldehydes such as 2,2-dimethyl-propionaldehyde or

of aromatic and aliphatic aldehydes were evaluated and the the less bulky propionaldehyde were employed in the reac-

results are presented in Table 4.

tions, the outputs of the reaction still remained at 96%–98%

As shown in Table 4, a wide range of substituted aromatic yields (entries 9–13). A heteroaromatic aldehyde, such as

aldehydes and aliphatic aldehydes are suitable for the catalytic furan-2-carbaldehyde, was also used as the substrate under

addition of diethyl phosphite. The substituents on the phenyl optimal reaction conditions to form the product 5h in an excel-

ring of aldehydes could be either electron-donating groups, lent yield (Table 4, entry 8). These results further suggest that

such as CH₃O-, or electron-withdrawing groups, such as –Cl these lanthanide complexes containing a μ₃-O group exhibited

and –NO₂, and excellent yields (97–99%) of the products can a high catalytic activity for the C–P bond formation similar

be isolated (entries 2–7). The results also show that the steric to those lanthanide complexes which were supported by

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aminocoordinate-lithium bridged bis(indolyl) ligands,^13cbut

Table 6 Hydrophosphonylation of ketones with diethyl phosphite cata-

lyzed by complex 3e^a

higher than the previous lanthanide amides [(Me₃Si)₂N]₃-

23

La(μ-Cl)Li(THF)₃

and {(μ–η⁵:η¹):η¹-2-[(2,6-Me₂C₆H₃)NCH₂]-

(C₄H₃N)SmN(SiMe₃)₂}₂.^5b

Catalytic activities of complexes 3a–3e on the

hydrophosphonylation of ketones

Entry

1

Ketones

Time (h)

1

Product

Yield^b(%)

79

To further investigate the scope of the catalysts for the hydro-

phosphonylation reaction, we tried to explore the application

of the above complexes in the catalytic reaction of dialkyl phos-

phate to the unactivated ketones. The ytterbium complex 3e

was used as a catalyst for selecting the optimized reaction con-

ditions for the addition of diethyl phosphite to acetophenone,

and the results are summarized in Table 5.

From Table 5, we can see that the catalysts displayed a good

catalytic activity of the hydrophosphonylation of acetophenone

under similar conditions as that used for the hydrophosphonyl-

ation of aldehydes except the acetophenone and diethyl phos-

phite ratio was 1 : 1.2. Examination of the catalytic activity of

other lanthanide amides on the hydrophosphonylation of

ketones also showed that similar yields of the product were

obtained in the presence of diﬀerent catalysts, indicating that

the ionic radii of the lanthanide metals have little influence on

the catalytic activity of the hydrophosphonylation of

acetophenone.

The substrate scope of the catalytic hydrophosphonylation

of ketones was then investigated using the ytterbium complex

3e as a catalyst at room temperature under solvent-free con-

ditions, and the results are presented in Table 6. It was found

that the electronic nature of the substituents on the aryl

groups had some eﬀect on the reactivity of the hydrophospho-

nylation of ketones. Electron-withdrawing substituents such as

–NO₂, –CF₃and –Cl on the phenyl ring favor the yields of pro-

ducts 6b–6d (Table 6, entries 2–4), while the electron-donating

substituents such as CH₃– on the phenyl ring will disfavor the

yields of products 6e and 6f (Table 6, entries 5 and 6), after a

longer reaction time. The steric hindrance of the substrates

6a

2

3

4

1

6b

6c

6d

83

80

83

5

6

5

3

6e

6f

33

71

7

0.5

6g

82

^aReaction conditions: ketone (10.0 mmol), diethyl phosphite

(12.0 mmol), catalyst 3e (0.1 mol%), solvent-free, room temperature.

^bIsolated yields.

also had a significant eﬀect on the activity of the hydrophos-

phonylation of ketones; for example, the addition of diethyl

phosphite to 4′-methylacetophenone gave the product 6f in

71% yield in 3 h (Table 6, entry 6), whereas the addition of

diethyl phosphite to 2′-methylacetophenone gave the product

in only 33% yield even after 5 h (Table 6, entry 5). It should be

noted that the catalyst 3e also worked well for aliphatic

ketones, aﬀording the corresponding α-hydroxy phosphonate

in a moderate yield (Table 6, entry 7).

Table 5 Hydrophosphonylation of acetophenone with diethyl phosphite^a

Entry

Cat.

Loading (mol%)

Solvent

Yield^b(%)

1

2

3

4

5

6

7

8

9

Complex 3e

Complex 3a

Complex 3b

Complex 3c

Complex 3d

1

THF

Toluene

Solvent-free

79

77

34

76

79

78

79

77

78

0.5

0.1

0.05

0.1

Experimental section

Materials and methods

All syntheses and manipulations of air- and moisture-sensitive

materials were performed under dry argon and an oxygen-free

atmosphere using standard Schlenk techniques or in a glove-

box. Hexane, toluene and THF were refluxed and distilled over

sodium benzophenone ketyl under argon prior to use. Other

10

^aAcetophenone and diethyl phosphite (1 : 1.2 equiv.), room

temperature, solvent (2 mL) or solvent-free. ^bIsolated yields.

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reagents were used in their commercial form without further 2H) (–CH₂CH₂N–); 3.12 (t, J = 6.24 Hz 2H) (–CH₂–CH₂N–);

purification unless otherwise noted. [(Me₃Si)₂N]₃RE^III(μ-Cl)- ¹³C NMR (CDCl₃, ppm): δ_C151.7(–CHvN–), 135.4, 129.0,

Li(THF)₃(RE = Y, Eu, Dy, Er, Yb) were prepared according to 126.6, 121.2, 120.8, 118.1, 118.0, 114.6, 113.1, 110.3, 107.2

literature methods.²⁴Elemental analysis data were obtained on (pyrrolyl and indolyl), 61.6 (–CH₂CH₂N–), 26.4 (–CH₂CH₂N–),

a Perkin-Elmer 2400 Series II elemental analyzer for CHN 35.3 (–NCH₃). HRMS/MALDI [C₁₆H₁₇N₃+ H]⁺, Calc. for:

analysis and by the Schöniger oxygen flask combustion 252.1501. Found: 252.1495.

method for chloride ion analysis. Melting points were deter-

[(μ–η⁵:η¹):η¹:η¹-3-(2-C₄H₃NCHvNCH₂CH₂)C₈H₅N]Y₃(μ₃-O)-

mined in sealed capillaries without correction. High-resolution (μ₂-Cl)₂(THF)₂[N(SiMe₃)₂] (3a). To a toluene (10.0 mL) solution

mass spectra were obtained on an Agilent 6200 MS instrument. of 3-(2-C₄H₃NHCHvNCH₂CH₂)C₈H₅NH (0.237 g, 1.00 mmol)

¹H NMR and ¹³C NMR spectra for the analysis of compounds was added a toluene (20.0 mL) solution of [(Me₃Si)₂N]₃-

were recorded on

a

Bruker AV-300 NMR spectrometer Y^III(μ-Cl)Li(THF)₃(0.829 g, 1.00 mmol) at room temperature.

(300 MHz for ¹H; 75.0 MHz for ¹³C in C₆D₆for lanthanide After the reaction mixture was heated to 75–85 °C for 72 h, the

complexes). Chemical shifts (δ) were reported in ppm. J values color of the solution gradually changed from light brown to

are reported in Hz. IR spectra were recorded on a Shimadzu brown. The solvent was evaporated under reduced pressure.

FTIR-8400S spectrometer (KBr pellet).

The residue was extracted with n-hexane (2 × 10 mL). The

combined extractions were concentrated to about 10.0 mL.

Light brown crystals were obtained at 0 °C after several days

Synthesis of the ligands and complexes

3-(2-C₄H₃NHCHvNCH₂CH₂)C₈H₅NH (1). To a solution of (0.391 g, 35% yield). M.p. 206–208 °C (dec.). Found: C, 46.91;

tryptamine (1.60 g, 10.0 mmol) (recrystallised prior to use) in H, 5.81; N, 8.41; Cl, 6.05. Calc. for C₄₄H₆₀Cl₂N₇O₃Si₂Y₃:

ethanol (20.0 mL) was added a solution of pyrrole-2-aldehyde C, 46.82; H, 5.36; N, 8.69; Cl, 6.28%. ν_max(KBr)/cm⁻¹: 2946 w,

(0.95 g, 10.0 mmol) (recrystallised prior to use) in ethanol 2850 w, 1632 s, 1551 s, 1487 s, 1395 m, 1350 w, 1236 s, 1225 s,

(20.0 mL) at room temperature. After complete addition, the 1135 s, 1078 w, 933 s, 819 m, 714 w. δ_H(300 MHz, C₆D₆, ppm):

mixture was stirred for 48 h at room temperature. The reaction 9.66, 7.66, 7.26, 7.12, 6.83, 6.51, 6.06, 3.60, 2.50, 2.16, 1.41,

mixture was concentrated under reduced pressure to give a 0.15 (s, Si(CH₃)₃). ¹³C NMR (75 MHz, C₆D₆, ppm): δ_C135.5,

light brown residue. This material was re-dissolved in dichloro- 128.0, 127.1, 126.8, 126.4, 121.2, 120.9, 118.2, 118.1, 112.6,

methane, washed by water, dried over anhydrous Na₂SO₄and 110.2, 66.7, 26.2, 24.4, 1.4.

filtered. After the solvent was removed under reduced pressure,

the final product is obtained as a light yellow powder in ca. (μ₂-Cl)₂(THF)₂[N(SiMe₃)₂] (3b). To a THF (10.0 mL) solution of

88% yield (2.09 g). M.p. 113–115 °C (dec.). ν_max(KBr)/cm⁻¹

3-(2-C₄H₃NHCHvNCH₂CH₂)C₈H₅NH (0.237 g, 1.00 mmol) was

[(μ–η⁵:η¹):η¹:η¹-3-(2-C₄H₃NCHvNCH₂CH₂)C₈H₅N]Eu₃(μ₃-O)-

:

3350 v, 3130 s, 2615 w, 2440 w, 1660 m, 1614 m, 1487 s, 1398 added a THF (20.0 mL) solution of [(Me₃Si)₂N]₃Eu^III(μ-Cl)Li-

s, 1348 s, 1282 m, 1255 m, 945 s, 825 s, 709 m; ¹H NMR (THF)₃(0.892 g, 1.00 mmol) at room temperature. After the

(CDCl₃, ppm): δ_H8.01 (s, 1H) (–CHvN–), 7.67–6.93 (m, 5H) reaction mixture was heated to 75 °C for 72 h, the color of

(indolyl), 6.91–6.27 (m, 3H) (pyrrolyl), 3.90 (t, J = 6.80 Hz 2H) the solution was gradually changed from brown to red brown.

(–CH₂CH₂–N–), 3.13 (t, J = 6.91 Hz 2H) (–CH₂CH₂N–); ¹³C NMR The solvent was evaporated under reduced pressure. The

(CDCl₃, ppm): δ_C151.8 (–CHvN–), 135.3, 129.0, 126.5, residue was extracted with toluene (2 × 10 mL). The combined

121.5, 121.4, 120.9, 118.2, 117.9, 114.0, 112.7, 110.3, 108.7 extractions were concentrated to about 10.0 mL. The dark red

(indolyl and pyrrolyl), 60.0 (–CH₂CH₂N–), 26.1 (–CH₂CH₂N–); crystals were obtained at 0 °C for several days (0.433 g, 33%

HRMS/MALDI [C₁₅H₁₅N₃+ H]⁺, Calc. for: 238.1339. Found: yield). M.p. 205–208 °C (dec.). ν_max(KBr)/cm⁻¹: 2920 w, 2883 w,

238.1325.

1643 s, 1557 s, 1478 s, 1389 m, 1355 w, 1238 s, 1226 s, 1133 s,

3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅NH (2). To a solu- 1067 w, 930 s, 823 m, 734 w. Found: C, 42.92; H, 5.42;

tion of tryptamine (1.60 g, 10.0 mmol) (recrystallised prior to N, 7.35; Cl, 4.86. Calc. for C₄₄H₆₀Cl₂N₇O₃Si₂Eu₃·C₆H₁₄:

use) in ethanol (20.0 mL) was added a solution of N-methyl- C, 42.77; H, 5.31; N, 6.98; Cl, 5.05%.

pyrrole-2-aldehyde (1.09 g, 10.0 mmol) (recrystallised prior to

The same complex can also be isolated by running the

use) in ethanol (20.0 mL) at room temperature. After complete same reaction in toluene while keeping the other conditions

addition, the mixture was stirred for another 36 h at room constant.

temperature. The reaction mixture was concentrated under

[(μ–η⁵:η¹):η¹:η¹-3-(2-C₄H₃NCHvNCH₂CH₂)C₈H₅N]Dy₃(μ₃-O)-

reduced pressure to give a light brown residue. This material (μ₂-Cl)₂(THF)₂[N(SiMe₃)₂] (3c). This compound was isolated

was re-dissolved in dichloromethane, washed by water, dried as light yellow crystals in 33% yield by treatment of

over anhydrous Na₂SO₄and filtered. After the solvent was [(Me₃Si)₂N]₃Dy^III(μ-Cl)Li(THF)₃(0.902 g, 1.00 mmol) with

removed under reduced pressure, the final product is obtained 3-(2-C₄H₃NHCHvNCH₂CH₂)C₈H₅NH (0.237 g, 1.00 mmol)

as a light yellow powder in ca. 92% yield (2.30 g). M.p. 92 °C following procedures similar to those used for the preparation

(dec.). ν_max(KBr)/cm⁻¹: 3516 s, 3439 s, 3350 v, 3130 s, 2957 v, of 3a. M.p. 211–213 °C (dec.). ν_max(KBr)/cm⁻¹: 2941 w, 2855 w,

2923 s, 2875 v, 2850 s, 1635 m, 1604 m, 1493 s, 1398 s, 1338 w, 1623 s, 1555 s, 1483 s, 1392 m, 1345 w, 1235 s, 1143 s, 1073 w,

745 w, 709 m; ¹H NMR (CDCl₃, ppm): δ_H8.07 (s, 1H) 936 s, 817 m, 718 w. Found: C, 40.62; H, 5.40; N, 6.78; Cl, 4.63.

(–CHvN–), 8.03 (s, 1H) (–NH from indolyl), 7.69–6.13 (m, 8H) Calc. for C₄₄H₆₀Cl₂N₇O₃Si₂Dy₃·0.5C₆H₁₄: C, 40.53; H, 4.85;

(indolyl and pyrrolyl), 3.90 (s, 3H) (–NCH₃), 3.85 (t, J = 6.24 Hz N, 7.04; Cl, 4.89%. The relatively low carbon and hydrogen

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analysis data may be due to the part loss of C₆H₁₄upon Determination of the excluded ethylene

heating.

To a toluene solution of 3-(2-C₄H₃NHCHvNCH₂CH₂)C₈H₅NH

was added a toluene solution of [(Me₃Si)₂N]₃Y^III(μ-Cl)Li(THF)₃

at room temperature as described above. After the reaction

mixture was heated to 78 °C, argon was inputted into the

Schlenk flask to exclude the gas, which was absorbed by the

Br₂–CCl₄solution. After careful concentration under reduced

pressure, the solution was probed by GC-MS (TOF with EI⁺).

The MS data shows the m/z peaks at 185.8680 and 189.8637 for

[(μ–η⁵:η¹):η¹:η¹-3-(2-C₄H₃NCHvNCH₂CH₂)C₈H₅N]Er₃(μ₃-O)-

(μ₂-Cl)₂(THF)₂[N(SiMe₃)₂] (3d). This compound was isolated

as pink crystals in 36% yield by treatment of [(Me₃Si)₂N]₃Er^III-

(μ-Cl)Li(THF)₃(0.904 g, 1.00 mmol) with 3-(2-C₄H₃NHCHv

NCH₂CH₂)C₈H₅NH (0.237 g, 1.00 mmol) following procedures

similar to those used for the preparation of 3a. M.p. 207–209 °C

(dec.). ν_max(KBr)/cm⁻¹: 2954 w, 2875 w, 1615 s, 1535 s, 1463 s,

1362 m, 1238 m, 1126 s, 1026 w, 928 s, 817 m, 718 w. Found:

C, 38.21; H, 4.49; N, 7.27; Cl, 5.53. Calc. for C₄₄H₆₀Cl₂N₇O₃-

Si₂Er₃: C, 38.75; H, 4.43; N, 7.19; Cl, 5.20%.

C₂H₄⁷⁹Br₂and C₂H₄⁸¹Br₂(Calc. 185.8680 and 189.8639 for

C₂H₄⁷⁹Br₂and C₂H₄⁸¹Br₂, respectively, see Experimental

section and ESI†) with almost equal relative abundance (2.79%

and 2.70%) relative to C₂H₄⁷⁹Br⁺(100%). The isotopic peak of

the molecular ion (187.8668, C₂H₄⁷⁹Br⁸¹Br⁺, Calc. 187.8659)

can also be found in the spectra with a relative abundance of

5.60% relative to C₂H₄⁷⁹Br⁺(100%), twice the relative abun-

dance of C₂H₄⁷⁹Br₂and C₂H₄⁸¹Br₂. The results and data are

available in the ESI† for this article.

+

[(μ–η⁵:η¹):η¹:η¹-3-(2-C₄H₃NCHvNCH₂CH₂)C₈H₅N]Yb₃(μ₃-O)-

(μ₂-Cl)₂(THF)₂[N(SiMe₃)₂] (3e). This compound was isolated as

orange crystals in 39% yield by treatment of [(Me₃Si)₂N]₃-

Yb^III(μ-Cl)Li(THF)₃(0.913 g, 1.00 mmol) with 3-(2-C₄H₃NHCHv

NCH₂CH₂)C₈H₅NH (0.237 g, 1.00 mmol) following proce-

dures similar to those used for the preparation of 3a.

M.p. 208–210 °C (dec.). ν_max(KBr)/cm⁻¹: 2951 w, 2866 w,

1633 s, 1520 s, 1493 m, 1375 m, 1210 s, 1117 s, 1023 m,

927 s, 826 m. Found: C, 38.04; H, 4.05; N, 6.87; Cl, 4.95.

Calc. for C₄₄H₆₀Cl₂N₇O₃Si₂Yb₃: C, 38.26; H, 4.38; N, 7.10;

Cl, 5.13%.

Crystal structure analyses of 3a–3e, 4a and 4b

A suitable crystal of complexes 3a–3e, 4a and 4b was each

mounted in a sealed capillary. Diﬀraction was performed on a

Bruker SMART APEX II CCD area detector diﬀractometer using

graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å),

temperature 293(2) K, φ and ω scan technique. An empirical

absorption correction was applied using the SADABS

program.²⁵All structures were solved by direct methods, com-

pleted by subsequent diﬀerence Fourier syntheses, and refined

anisotropically for all non-hydrogen atoms by full-matrix least-

squares calculations based on F²using the SHELXTL program

package.²⁶The hydrogen atom coordinates were calculated

with SHELXTL by using an appropriate riding model with

varied thermal parameters. During refinement, constraints are

used for the disordered ethylene and –N(SiMe₃)₂groups. For

compounds 3a–3e and 4b, all disordered parts based on ideal

structures were restrained by using DFIX, DELU and SIMU

instructions to make the geometrical configurations and the

displacement parameters reasonable. The residual electron

densities were of no chemical significance. Selected bond

lengths and angles are compiled in Table 1, and crystal data

and details of the data collection and structure refinements

are given in Table 7.

Reactions of equal molar amounts of 1 with [(Me₃Si)₂N]₃RE

(RE = Y, Eu, Er and Yb) in the presence of equal amounts of

LiCl did not happen. Instead, the rare-earth metal amides

[(Me₃Si)₂N]₃RE were recovered upon recrystallization.

(η¹:η¹-[η¹-3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅N]Li[μ–η²:

η¹-3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅N])Yb[N(SiMe₃)₂]₂

(4a). To

a toluene (10.0 mL) solution of 3-(2-(N-CH₃)-

C₄H₃NCHvNCH₂CH₂)C₈H₅NH (0.253 g, 1.00 mmol) was

added a toluene (20.0 mL) solution of [(Me₃Si)₂N]₃Yb^III(μ-Cl)Li-

(THF)₃(0.913 g, 1.00 mmol) at room temperature, and a clear

brown solution was obtained. After the reaction mixture was

heated to 75 °C for 72 h, the color of the solution gradually

changed from light brown to brown. The solvent was evapor-

ated under reduced pressure. The residue was extracted with

n-hexane (2

concentrated to about 10.0 mL. The light brown crystals

were obtained at °C overnight (0.739 g, 74% yield).

× 10 mL). The combined extractions were

0

M.p. 196–203 °C (dec.). ν_max(KBr)/cm⁻¹: 2935 s, 2873 s, 1630 s,

1539 m, 1495 s, 1389 m, 1231 s, 1217 s, 1143 s, 1072 w, 933

w. Found: C, 52.91; H, 6.89; N, 10.93. Calc. for C₄₄H₆₇LiN₈-

Si₄Yb: C, 52.77; H, 6.84; N, 11.19%.

CCDC 935210–935215 for 3a–3e, 4a and 959910 for 4b

contain the supplementary crystallographic data for this

paper.

(η¹:η¹-[η¹-3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅N]Li[μ–η²:

η¹-3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅N])Dy[N(SiMe₃)₂]₂

(4b). This compound was isolated as colorless crystals in

78% yield by treatment of a toluene (10.0 mL) solution of

3-(2-(N-CH₃)C₄H₃NCHvNCH₂CH₂)C₈H₅NH (0.253 g, 1.00 mmol)

General experimental procedure for the hydrophosphonylation

of aldehydes

with [(Me₃Si)₂N]₃Dy^III(μ-Cl)Li(THF)₃(0.902 g, 1.00 mmol) A mixture of complex 3e (13.81 mg, 0.01 mmol) and diethyl

following procedures similar to those used for the prepa- phosphite (10 mmol) was stirred for 5 min. Benzaldehyde

ration of 4a. M.p. 193–198 °C (dec.). ν_max(KBr)/cm⁻¹: 2931 s, (10 mmol) was then added, and the resulting mixture was

2877 s, 1627 s, 1537 m, 1505 s, 1386 m, 1229 s, 1211 s, 1143 stirred under solvent-free conditions for 10 min. After 10 min,

s, 1065 w, 931 w. Found: C, 55.91; H, 7.81; N, 10.23. the temperature of the exothermic reaction returned to room

Calc. for C₄₄H₆₈LiN₈Si₄Dy·C₆H₁₄: C, 55.76; H, 7.67; N, temperature. Water was added, and the mixture was extracted

10.40%.

with ethyl acetate (3 × 10 mL). The combined organic layers

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were dried over anhydrous Na₂SO₄. After filtration, the solvent advantages of these complexes suggest the potential appli-

was evaporated under reduced pressure. Recrystallization of cations of other rare-earth metal amides in this field. Further

the crude product from hexane and diethyl ether gave the work on the reactivity of functionalized indoles with rare-earth

desired product 5a (2.42 g, 99% yield) as white crystals.

Diethyl(hydroxy(phenyl)methyl)phosphonate (5a). Melting

point (m.p.) 82–83 °C; ¹H NMR (300 MHz, CDCl₃, ppm):

δ 7.49–7.47 (d, 2H, J = 5.8 Hz, ArH), 7.30–7.28 (d, 3H, J =

8.1 Hz, ArH), 5.01 (d, J = 9.8 Hz, 1H, CH), 4.07–3.96 (m, 4H,

CH₂), 3.73 (s, 1H, OH), 1.29–1.19 (m, 6H, CH₃). ¹³C NMR

(75 MHz, CDCl₃, ppm): δ 136.8, 128.2, 128.0, 127.1 (d, J =

5.6 Hz), 70.7 (d, J = 159.7 Hz), 63.4 (d, J = 7.0 Hz), 63.0 (d,

J = 7.4 Hz), 16.3. HRMS (ESI) m/z: calcd for C₁₁H₁₇O₄P

[M + H]⁺: 245.0943; Found: 245.0945.

metal amides is now in progress.

Acknowledgements

This work is co-supported by the National Natural Science

Foundation of China, the National Basic Research Program of

China (2012CB821600), and grants from the Ministry of Edu-

cation (20103424110001) and Anhui province (11040606M36,

KJ2012A138). We are grateful to Prof. Jiping Hu and Prof.

Gaosheng Yang for their help in running the NMR spectra.

General experimental procedure for hydrophosphonylation

of ketones

A mixture of complex 3e (13.81 mg, 0.01 mmol) and diethyl

phosphite (12 mmol) was stirred for 5 min, then acetophenone

(10 mmol) was added to the mixture. The resulting mixture

was stirred at room temperature under solvent-free conditions

for 1 h. After the reaction was completed, water was added,

and the mixture was extracted with ethyl acetate (3 × 10 mL).

The combined organic layers were dried over anhydrous

Na₂SO₄, and filtered. Then the solvent was evaporated under

reduced pressure. The final products were further purified by

washing with hexane.

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Conclusions

In summary, the reactions of diﬀerent pyrrolyl-functionalized

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The catalysts are suitable for a series of organic solvents and

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Dalton Trans., 2014, 43, 2521–2533 | 2533

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Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ-η5:η1 bonding indolyl and μ3-oxo groups

DOI: 10.1039/c3dt51107c

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Full text of DOI:10.1039/c3dt51107c

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