Nickel complexes supported by quinoline-based ligands: Synthesis, characterization and catalysis in the cross-coupling of arylzinc reagents and aryl chlorides or aryltrimethylammonium salts

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Nickel complexes supported by quinoline-based ligands: synthesis,

characterization and catalysis in the cross-coupling of arylzinc reagents and

aryl chlorides or aryltrimethylammonium salts†

Qiang Zhang, Xue-Qi Zhang and Zhong-Xia Wang*

Received 24th April 2012, Accepted 8th June 2012

DOI: 10.1039/c2dt30886j

Lithium and nickel complexes bearing quinoline-based ligands have been synthesized and characterized.

Reaction of 8-azidoquinoline with Ph₂PNHR (R = p-MeC₆H₄, Bu^t) affords N-(8-quinolyl)-

iminophosphoranes RNHP(Ph₂)vN(8-C₉H₆N) (1a, R = p-MeC₆H₄; 1b, R = Bu^t. C₉H₆N = quinolyl)).

Reaction of 1a with (DME)NiCl₂generates a nickel complex [NiCl₂{N(8-C₉H₆N)vP(Ph₂)NH-

(p-MeC₆H₄)}] (2a). Treatment of 1b with (DME)NiCl₂and following with NaH produces [NiCl{(1,2-

C₆H₄)P(Ph)(NHBu^t)vN(8-C₉H₆N)}] (4). Complex 4 was also obtained by reaction of (DME)NiCl₂with

[Li{(1,2-C₆H₄)P(Ph)(NHBu^t)vN(8-C₉H₆N)}] (5) prepared through lithiation of 1b. Reaction of

2-PyCH₂P(Ph₂)vN(8-C₉H₆N) (6, Py = pyridyl) and PhNvC(Ph)CH₂P(Ph₂)vN(8-C₉H₆N) (8),

respectively, with (DME)NiCl₂yields two ﬁve-coordinate N,N,N-chelate nickel complexes, [NiCl₂{2-

PyCH₂P(Ph₂)vN(8-C₉H₆N)}] (7) and [NiCl₂{PhNvC(Ph)CH₂P(Ph₂)vN(8-C₉H₆N)}] (9). Similar

reaction between Ph₂PCH₂P(Ph₂)vN(8-C₉H₆N) (10) and (DME)NiCl₂results in ﬁve-coordinate N,N,P-

chelate nickel complex [NiCl₂{Ph₂PCH₂P(Ph₂)vN(8-C₉H₆N)}] (11). Treatment of [(8-C₉H₆N)Nv

P(Ph₂)]₂CH₂(12) [prepared from (Ph₂P)₂CH₂and 2 equiv. of 8-azidoquinoline] with LiBuⁿand (DME)

NiCl₂successively affords [NiCl{(8-C₉H₆N)NP(Ph₂)}₂CH] (13). The new compounds were characterized

by ¹H, ¹³C and ³¹P NMR spectroscopy (for the diamagnetic compounds), IR spectroscopy (for the nickel

complexes) and elemental analysis. Complexes 2a, 4, 7, 9, 11 and 13 were also characterized by single-

crystal X-ray diffraction techniques. The nickel complexes were evaluated for the catalysis in the cross-

coupling reactions of arylzinc reagents with aryl chlorides and aryltrimethylammonium salts. Complex 7

exhibits the highest activity among the complexes in catalyzing the reactions of arylzinc reagents with

either aryl chlorides or aryltrimethylammonium bromides.

of available compounds.⁵Hence the catalytic coupling reactions

using organic chlorides as electrophiles have attracted intensive

Introduction

Transition-metal-catalyzed cross-coupling reactions, including

Kumada, Negishi, Suzuki, Stille and Hiyama reaction, are

reliable and versatile tools in modern organic synthesis.^1,2The

Negishi reaction is one of the most useful methods for construct-

ing new C–C bonds because of the ready availability and the

functional-group compatibility of the organozinc reagents.^1,3

Organic bromides and iodides are usually employed as the elec-

trophilic substrates in the cross-coupling reactions.⁴The use of

organic chlorides as electrophiles has proven more difﬁcult due

to low reactivity of the C–Cl bond. However, chlorides are more

useful substrates due to their lower cost and the wider diversity

attention in the past decade. The Negishi reaction using chlorides

as the electrophiles has also achieved important progress. For

example, Herrmann and co-workers reported the ﬁrst example of

a palladium-catalyzed Negishi coupling of an unactivated aryl

chloride in 1999.⁶Dai and Fu reported the ﬁrst general method

for palladium-catalyzed Negishi cross-coupling of aryl chlorides

in 2001.^5aMilne and Buchwald found an extremely active palla-

dium catalyst for the coupling reaction of aryl chlorides.⁷Organ

and co-workers found that NHC-coordinated palladium com-

plexes (Pd-PEPPSI) can catalyze aryl–aryl and alkyl–alkyl

coupling of organozinc reagents and chlorides.⁸However,

inexpensive nickel-based catalysts are less successful for the

coupling reaction of unactivated chlorides with organozinc

reagents although a few examples have been reported.^9–11Devel-

opment of highly active and widely applicable nickel catalysts

for the cross-coupling of chloride substrates is still of

signiﬁcance.

CAS Key Laboratory of Soft Matter Chemistry and Department of

Chemistry, University of Science and Technology of China, Hefei, Anhui

230026, People’s Republic of China. E-mail: zxwang@ustc.edu.cn;

Fax: +86 551 3601592; Tel: +86 551 3603043

†Electronic supplementary information (ESI) available: ESR and UV

spectra of complexes 2a, 7, 9, 11 and 13. CCDC reference numbers

878348–878353. For ESI and crystallographic data in CIF or other elec-

tronic format see DOI: 10.1039/c2dt30886j

On the other hand, nitrogen-containing compounds such as

alkyl- and arylamines are potential electrophiles in catalytic

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cross-couplings because these compounds are widely available

in the natural world and in industry. The amino groups in aryl-

amines are also important activating and directing groups which

can lead to selective functionalization of aromatic rings.

However, cross-coupling reactions through C–N bond cleavage

of arylamines are scarce. In 2007 Kakiuchi and co-workers

reported a ruthenium-catalyzed Suzuki coupling through C–N

bond cleavage of anilines, but a carbonyl group at the ortho

position of the amino group is indispensable.¹²Several examples

using aryltrimethylammonium salts as electrophilic substrates

have been reported. Wenkert and co-workers carried out the

nickel-catalyzed reaction of aryltrimethylammonium iodides

with Grignard reagents in the early stage of cross-coupling

studies. However, this method suffers from a limited substrate

scope and low product yields.¹³Recently, Reeves et al. devel-

oped the coupling using aryltrimethylammonium triﬂates as the

electrophiles and (Ph₃P)₂PdCl₂as the catalyst.¹⁴In 2003, Blakey

and MacMillan carried out the Suzuki coupling of aryltrimethyl-

ammonium triﬂates with Ni(cod)₂/IMes as a catalyst.¹⁵Our

group performed the coupling of aryltrimethylammonium

iodides and aryl or alkylzinc chlorides catalyzed by

(Cy₃P)₂NiCl₂, and more recently, by pincer nickel complexes.¹⁶

We intended to design new catalysts for improving the cataly-

sis in the activation of C–Cl and C–N bonds. To achieve the

aim, the choice of ligands is crucial because the properties of the

complexes strongly rely on supporting ligands besides the metal

itself. Our studies have shown that pincer nickel complexes (e.g.

I–IV in Chart 1) are active in catalyzing cross-coupling of aryl-

zinc reagents with aryl chlorides or aryltrimethylammonium

salts.^11a,b,16bIn complexes II and III, the N-heterocyclic carbene

and the iminophosphoranyl nitrogen atom are strong electron-

donor groups. Replacement of the carbene part with a weaker

electron-donor group will tune the electron property of the

central metal and make the side-arm coordinate group dis-

sociation from the central metal easier, which will possibly

change the catalytic behavior of these complexes. The quinolyl

group seems a logical choice due to the modest electron-donor

ability of its nitrogen atom. Quinoline-based complexes of tran-

sition metals also show good catalytic activity in C–C bond for-

mation reactions.¹⁷We also hoped to improve catalysis of

complex IV in the cross-coupling of aryltrimethylammonium

salts with arylzinc reagents through modiﬁcation of the ligand

by replacing the imino group in complex IV using an imino-

phosphoranyl group. Iminophosphoranes essentially behave as

strong π and σ donor ligands and do not exhibit π accepting

capacity in contrast to imines.¹⁸These properties of imino-

phosphoranes in the ancillary ligands will provide different elec-

tronic environments at the metal center and hence regulate the

catalytic properties of the complexes. Based on the ideas, we

designed new ligands which involve quinolyl and imino-

phosphoranyl motifs, synthesized and characterized a series of

nickel complexes bearing these ligands, and evaluated the cata-

lysis of the nickel complexes in the reactions of aryl chlorides or

aryltrimethylammonium salts with arylzinc chlorides. Here we

report the results.

Results and discussion

Synthesis and characterization of ligands and complexes

Synthesis of ligands 1a, 1b and complexes 2a–5 are summarized

in Scheme 1. Reaction of 8-azidoquinoline with Ph₂PNHR (R =

p-MeC₆H₄, Bu^t) produces N-(8-quinolyl)iminophosphoranes

RNHP(Ph₂)vN(8-C₉H₆N) (1a, R = p-MeC₆H₄; 1b, R = Bu^t).

Reaction of 1a with (DME)NiCl₂gives a N,N-chelate nickel

complex [NiCl₂{N(8-C₉H₆N)vP(Ph₂)NH(p-MeC₆H₄)}] (2a).

Treatment of 1b with (DME)NiCl₂and following with NaH

forms [NiCl{(1,2-C₆H₄)P(Ph)(NHBu^t)vN(8-C₉H₆N)}] (4),

Chart 1

Scheme 1 Synthesis of compounds 1a–5.

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rather than N,N,N-chelate nickel complex 3. The ﬁrst step of the

reaction should give a N,N-chelate nickel complex 2b. Treatment

of 2b with NaH leads to deprotonation of one of the phenyl

groups attached on the phosphorus atom of complex 2b and for-

mation of a C–Ni bond. Construction of the Ni–NvP–N four-

membered ring in 3 through deprotonation of the NH to be

difﬁcult and instead, a deprotonation process on the phenyl

group proceeded. Complex 4 was also obtained by reaction of

1b with LiBuⁿand then treatment with (DME)NiCl₂. In this

reaction LiBuⁿabstracts a proton from the phenyl group rather

than NH group attached on the phosphorus atom, forming N,N,

C-chelate lithium complex [Li{(1,2-C₆H₄)P(Ph)(NHBu^t)v

N-(8-C₉H₆N)}] (5). Attempts to transform 2a into 3 or a ana-

logue of 4 by treatment with NaH were unsuccessful, the reac-

tion leading to an unidentiﬁed mixture. Both 1a and 1b are

crystalline solids and gave satisfactory elemental analytical

close to that of Ni–N2 in [NiBr₂{(o-PrⁱOC₆H₄)NvC(SiMe₃)-

CH₂(2-Py)}] [1.993(3) Å].²⁰The P1–N2 distance of 1.601(3) Å

is a little longer than a P–N double bond which is about 1.57 Å,

and the P1–N3 distance of 1.641(4) Å is between a formal P–N

single (1.77 Å) and double bond.²¹

Complex 4 is a deep red diamagnetic crystalline solid which

1

was characterized by elemental analysis, H, ¹³C and ³¹P NMR

and IR spectroscopy. Both ¹H NMR and IR spectra show the pres-

ence of an NH group. For example, its ¹H NMR spectrum exhibits

a NH signal at δ 3.19 ppm as a doublet. The IR spectrum displays

the NH absorption at 3198 cm⁻¹. The structure was further

conﬁrmed by single-crystal X-ray diffraction (Fig. 2). In the

complex the central nickel atom is surrounded by the quinolyl

nitrogen atom (N1), the iminophosphoranyl nitrogen atom (N2),

the carbon atom (C11) of the phenylene and a chlorine atom,

having a distorted square-planar coordination geometry. The phos-

phorus atom is also approximately coplanar with the plane consti-

tuted by N1N2C11Cl1Ni1 atoms. Both N1–Ni–C11 and N2–Ni–

Cl1 are approximately linear, the bond angles being 171.69(14)

and 176.69(9)°, respectively. The amido nitrogen atom is sp²

hybridized, the sum of the angles around N2 being 359.99°. The

Ni–N1 distance of 1.961(3) Å is shorter than those of Ni–N1 in

complex 2a and Ni–N(Py) in the complex [Ni(Cl){2-{(CN(Me)-

(CH)₂–N)C₆H₄NvP(Ph₂)CH₂Py}]⁺I⁻[1.984(4) Å],^11bbut

within a normal range. The Ni–N2 distance of 1.891(2) Å is

very close to the corresponding bond in an amido pincer

nickel complex [Ni-(Cl){N{CH(Ph)P(Ph₂)vO}C₆H₄(PPh₂)-2}]

[1.893(5) Å].²²The Ni–C11 distance of 1.885(3) Å is compar-

able to the C–Ni bond lengths in arylnickel complexes.²³The

P1–N2 distance of 1.608(3) Å is a little longer than a typical

P–N double bond (1.57 Å), while the P1–N3 distance of

1.631(2) Å is between a formal P–N single and double bond.²¹

1

results. Their structures were also conﬁrmed by H, ¹³C and ³¹P

NMR spectroscopy. Complex 2b was not isolated and was

directly applied for further reactions.

Complex 2a is a paramagnetic crystalline solid which gave

satisfactory elemental analysis. Its IR spectrum displays a NH

absorption at 3222 cm⁻¹. Single-crystal X-ray diffraction (Fig. 1)

shows that the quinolyl nitrogen atom (N1) and the imino-

phosphoranyl nitrogen atom (N2) of the ligand coordinate to the

central nickel atom, while the amino nitrogen atom (N3) is

coordination-free. The four-coordinated nickel atom has a dis-

torted tetrahedral coordination geometry and is coplanar with the

N1C5C6N2 plane. The Ni–N1 distance of 1.981(4) Å is slightly

longer than the corresponding value in P,N(quinolyl)-chelate

nickel complex Ni[8-{Ph(Me)P}C₉H₆N]^2,19but comparable

to that of Ni–N1 in [NiBr₂{(o-PrⁱOC₆H₄)NvC(SiMe₃)CH₂-

(2-Py)}] [1.986(3) Å]. The Ni–N2 distance of 1.996(3) Å are

Fig. 2 ORTEP drawing of complex 4 (30% probability; THF molecule

is omitted). Selected bond lengths (Å) and angles (°): Ni(1)–N(1) 1.961(3),

Ni(1)–N(2) 1.891(2), Ni(1)–C(11) 1.885(3), Ni(1)–Cl(1) 2.1695(11),

N(2)–P(1) 1.608(3), N(3)–P(1) 1.631(2), N(3)–C(22) 1.486(4), P(1)–

C(10) 1.765(3), N(2)–C(2) 1.390(4); C(11)–Ni(1)–N(2) 88.18(13),

C(11)–Ni(1)–N(1) 171.69(14), N(2)–Ni(1)–N(1) 83.51(12), C(11)–

Ni(1)–Cl(1) 94.96(11), N(2)–Ni(1)–Cl(1) 176.69(9), N(1)–Ni(1)–Cl(1)

93.34(9), C(1)–N(1)–Ni(1) 112.1(2), C(2)–N(2)–P(1) 125.8(2), C(2)–

N(2)–Ni(1) 114.4(2), P(1)–N(2)–Ni(1) 119.79(14), C(10)–C(11)–Ni(1)

117.8(3), N(2)–P(1)–N(3) 120.52(13).

Fig. 1 ORTEP drawing of complex 2a (30% probability; CH₂Cl₂mol-

ecule is omitted). Selected bond lengths (Å) and angles (°): Ni(1)–N(1)

1.981(4), Ni(1)–N(2) 1.996(3), Ni(1)–Cl(1) 2.2154(14), Ni(1)–Cl(2)

2.2294(15), P(1)–N(2) 1.601(3), P(1)–N(3) 1.641(4), N(1)–C(5)

1.383(5), N(2)–C(6) 1.413(5); N(1)–Ni(1)–N(2) 83.30(15), N(1)–Ni(1)–

Cl(1) 111.67(12), N(2)–Ni(1)–Cl(1) 115.24(10), N(1)–Ni(1)–Cl(2)

105.39(11), N(2)–Ni(1)–Cl(2) 117.89(11), Cl(1)–Ni(1)–Cl(2) 117.23(6),

C(5)–N(1)–Ni(1) 113.1(3), C(6)–N(2)–Ni(1) 111.4(3), N(2)–P(1)–N(3)

113.87(19).

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Complex 5 is a yellow crystalline solid and was characterized

by elemental analysis and multinucelar NMR spectroscopy.

Elemental analytical results match the expected C, H and N com-

position of complex 5. The ¹H NMR spectrum indicates the pres-

ence of an NH signal at δ 3.56 ppm as a doublet and

corresponding signals of other groups. The ¹³C and ³¹P NMR

spectra are also consistent with the structure. In addition,

elemental analysis and NMR spectra also show no coordinated

solvent in the molecule. Hence the complex may be a dimer.

Attempts to grow single crystals for X-ray diffraction analysis

were unsuccessful.

The synthesis of complexes 7 and 9 is shown in eqn (1) and

(2), respectively.

Fig. 3 ORTEP drawing of complex 7 (30% probability). Selected

bond lengths (Å) and angles (°): Ni(1)–N(1) 2.0796(19), Ni(1)–N(2)

2.0753(19), Ni(1)–N(3) 2.153(2), Ni(1)–Cl(1) 2.3403(8), Ni(1)–Cl(2)

2.3260(8), P(1)–N(2) 1.605(2), P(1)–C(22) 1.792(2), N(2)–C(6)

1.396(3), C(22)–C(23) 1.492(4); N(1)–Ni(1)–N(2) 78.82(7), N(2)–

Ni(1)–N(3) 89.51(8), N(1)–Ni(1)–N(3) 157.53(8), N(2)–Ni(1)–Cl(2)

99.48(6), N(1)–Ni(1)–Cl(2) 99.20(6), N(3)–Ni(1)–Cl(2) 101.64(6),

N(2)–Ni(1)–Cl(1) 158.76(6), N(1)–Ni(1)–Cl(1) 92.15(6), N(3)–Ni(1)–

Cl(1) 92.06(6), Cl(1)–Ni(1)–Cl(2) 100.94(3), N(2)–P(1)–C(22)

106.38(11), C(6)–N(2)–P(1) 121.58(17), C(6)–N(2)–Ni(1) 114.31(15),

P(1)–N(2)–Ni(1) 122.84(11).

ð1Þ

ð2Þ

Treatment of (DME)NiCl₂with 6 in CH₂Cl₂at room tempera-

ture generates complex 7 as yellow green crystals. Complex 9, a

red–orange crystalline solid, was prepared similarly by reaction

of (DME)NiCl₂with 8 in CH₂Cl₂. Both 7 and 9 are paramag-

netic and were characterized by elemental analysis and IR spec-

troscopy. The structures were also further conﬁrmed by single-

crystal X-ray diffraction techniques. The ORTEP drawing of

complex 7 is shown in Fig. 3, along with selected bond lengths

and angles. The central nickel atom is ﬁve-coordinate and has a

distorted square-pyramidal geometry. The Cl1N1N2N3 atoms as

the base of the square pyramid are coplanar, the torsion angle

being 0.3° with the nickel atom deviating a little from the plane.

The metal ring consisting of Ni1N2P1C22C23N3 atoms adopts

a boat-like conformation; the N2N3C23P1 atoms are approxi-

mately coplanar. The Ni–N1 distance of 2.0796(19) Å is close to

that of Ni–N2 [2.0753(19) Å], and both of them are shorter than

that of Ni–N3 which is 2.153(2) Å. These bond distances are

within the normal range for a coordinated nickel complex.²⁴It is

also noted that the Ni–N1 distance in complex 7 is longer than

the Ni–N(quinolyl) distance in complex 4. This may be caused

by different coordination numbers of the complexes. The P–N2

distance of 1.605(2) Å is almost the same as the corresponding

distance in complex 4, and is normal for a coordinated

iminophosphorane.^11b,22

Fig. 4 ORTEP drawing of complex 9 (30% probability; THF and

CH₂Cl₂molecules are omitted). Selected bond lengths (Å) and angles

(°): Ni(1)–N(1) 2.052(6), Ni(1)–N(2) 2.052(5), Ni(1)–N(3) 2.171(6),

Ni(1)–Cl(1) 2.328(2), Ni(1)–Cl(2) 2.296(2), N(2)–P(1) 1.602(6), P(1)–

C(10) 1.806(7), C(10)–C(11) 1.523(9), N(3)–C(11) 1.264(9); N(1)–

Ni(1)–Cl(1) 102.83(16), N(1)–Ni(1)–Cl(2) 94.59(19), N(2)–Ni(1)–Cl(1)

98.92(16), N(2)–Ni(1)–Cl(2) 164.76(16), N(3)–Ni(1)–Cl(1) 106.75(16),

N(3)–Ni(1)–Cl(2) 91.29(17), N(1)–Ni(1)–N(2) 80.0(2), N(1)–Ni(1)–

N(3) 149.0(2), N(2)–Ni(1)–N(3) 86.4(2), Cl(2)–Ni(1)–Cl(1) 96.18(7).

of complex 7. Thus, the central nickel atom is ﬁve-coordinate

and the coordination geometry is a very distorted square

pyramid. However, unlike that of complex 7, the base atoms of

the square pyramid in complex 9 do not lie on a plane. The bond

angle of N1NiN3 is 149.0(2)° and the bond angle of N2NiCl2 is

164.76(16)°. The bond distances of both Ni–N1 and Ni–N2

The structure of complex 9 is shown in Fig. 4, along with

selected bond lengths and angles. The structure is similar to that

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[2.052(6) Å and 2.052(5) Å, respectively] are slightly shorter

than the corresponding values in complex 7, while the Ni–N3

distance of 2.171(6) Å is a little longer than the corresponding

value in complex 7. The P–N distance is close to that in complex

7, and the C11–N3 distance of 1.264(9) Å is indicative of a C–N

double bond.

The ﬁve-coordinate nickel atom has a distorted trigonal-bipyra-

mid geometry. The N1 and N4 atoms occupy the axial positions

and arrangement of N1NiN4 atoms is close to linear [bond

angle = 170.52(14)°]. The N2N3Cl1 atoms occupy the equator-

ial positions and the N2N3Cl1Ni atoms are approximately co-

planar, the sum of the angles at nickel being 359.50°. The metal

ring consisting of P1C19P2N4Ni1N2 atoms adopts a boat-like

conformation. The P1P2N4N2 atoms are approximately co-

planar, the torsion angle being 2.2°. The Ni–N distances, of

average 2.059 Å, are comparable to the corresponding values in

complexes 7 and 9, and are within the normal range for a ﬁve-

coordinate nickel complex. The P–N distances of average

The synthesis of compounds 11–13 is summarized in

Scheme 2. Compound 10, prepared from (Ph₂P)₂CH₂and an

equimolar amount of 8-azidoquinoline, was treated with (DME)-

NiCl₂to afford complex 11. Reaction of (Ph₂P)₂CH₂with two

equiv. of 8-azidoquinoline forms bis(iminophosphoranyl)-

methane 12. Treatment of 12 with LiBuⁿand following (DME)-

NiCl₂yields complex 13. Complex 11 is paramagnetic and was

characterized by elemental analysis and IR spectroscopy. Single-

crystal X-ray diffraction analysis conﬁrms its molecular structure

and the ORTEP drawing is displayed in Fig. 5. The central

nickel atom is ﬁve-coordinate and has a distorted trigonal-bipyra-

midal geometry with the iminophosphorane nitrogen atom and

two chlorine atoms occupying the equatorial positions and the

quinolyl nitrogen atom and the phosphine atom occupying

the axial positions. The N1NiP2 angle is 162.7(4)°, showing the

atoms to be close to linear. The Cl1Cl2N2Ni atoms are coplanar,

the sum of the angles at nickel being 360.0°. Due to poor data

quality, the bond parameters are not further discussed.

Complex 13 is also a paramagnetic species and was character-

ized by elemental analysis, IR spectroscopy and single-crystal

X-ray diffraction analysis. The ORTEP drawing is displayed

in Fig. 6, along with selected bond lengths and angles.

Fig. 5 ORTEP drawing of complex 11 (30% probability).

Fig. 6 ORTEP drawing of complex 13 (30% probability; toluene mo-

lecule is omitted). Selected bond lengths (Å) and angles (°): Ni(1)–N(1)

2.068(4), Ni(1)–N(2) 2.056(3), Ni(1)–N(3) 2.056(4), Ni(1)–N(4)

2.055(3), Ni(1)–Cl(1) 2.3115(13), P(1)–N(2) 1.625(3), P(1)–C(19)

1.713(4), P(2)–N(4) 1.611(4), P(2)–C(19) 1.691(4); N(4)–Ni(1)–N(3)

79.73(15), N(4)–Ni(1)–N(2) 97.27(14), N(3)–Ni(1)–N(2) 115.41(15),

N(4)–Ni(1)–N(1) 170.52(14), N(3)–Ni(1)–N(1) 93.63(15), N(2)–Ni(1)–

N(1) 79.37(14), N(4)–Ni(1)–Cl(1) 94.73(10), N(3)–Ni(1)–Cl(1)

100.62(11) N(2)–Ni(1)–Cl(1) 143.46(12), N(1)–Ni(1)–Cl(1) 93.14(11),

P(1)–N(2)–Ni(1) 119.10(18), P(2)–N(4)–Ni(1) 121.3(2), N(2)–P(1)–

C(19) 111.23(19), N(4)–P(2)–C(19) 108.8(2), P(1)–C(19)–P(2) 126.4(3).

Scheme 2 Synthesis of compounds 11–13.

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1.618 Å show that the P–N bond has a bond order signiﬁcantly

greater than unity.²¹The P–C19 distances of average 1.702 Å are

in between that of a formal single (1.83 Å) and double (1.57 Å)

bonds.²¹

reactions require only 0.5 mol% catalyst loadings. Each of reac-

tions of p-MeC₆H₄ZnCl with the phenyl chlorides bearing

p-benzoyl, p-ethoxyformyl and p-aminoformyl groups gives

almost quantitative cross-coupling product in 2 or 3 h, whereas

(2-chlorophenyl)(phenyl)methanone displays lower reactivity

due to steric hindrance of the o-benzoyl group; its reaction with

p-MeC₆H₄ZnCl requires a period of 24 h to reach completion,

giving the cross-coupling product in 91% yield. Reaction of

o-MeC₆H₄ZnCl with p-ClC₆H₄C(O)Ph, p-ClC₆H₄COOEt, and

p-ClC₆H₄C(O)NEt₂gives comparable results to those of

p-MeC₆H₄ZnCl. The electron-rich arylzinc reagents including

p-MeOC₆H₄ZnCl, p-Me₂NC₆H₄ZnCl and 2-furylzinc chloride

also displayed excellent reactivity in the catalytic reaction. Their

reactions with p-ClC₆H₄C(O)Ph and p-ClC₆H₄COOEt lead to

excellent results. Reactions of electron-deﬁcient arylzinc reagent,

p-CF₃C₆H₄ZnCl, with p-ClC₆H₄C(O)Ph and p-ClC₆H₄COOEt,

respectively, under the same conditions as those mentioned

above also afford the corresponding products in high yields, but

longer reaction time is necessary. It should be indicated that the

reactions using p-MeOC₆H₄ZnCl and p-CF₃C₆H₄ZnCl as the

nucleophiles require 2.5 equiv. of zinc reagents due to homo-

coupling of the arylzinc reagents (Table 2).

Complex 7 catalyzes the cross-coupling of heteroaryl chlo-

rides and arylzinc chlorides under the same conditions as indi-

cated above and the screened results are listed in Table 3.

Reaction of p-MeC₆H₄ZnCl with either 2-chloropyridine or

2-chloro-4-methylquinoline gives almost quantitative yield in 6 h

(entries 1 and 2, Table 3). o-MeC₆H₄ZnCl shows a little lower

reactivity. Its reaction with 2-chloropyridine requires a longer

reaction time and gives the desired product in 84% yield while

reaction of o-MeC₆H₄ZnCl with 2-chloro-4-methylquinoline

requires 1 mol% catalyst loading and 24 h reaction time (entries

3 and 4, Table 3). Reactions of p-CF₃C₆H₄ZnCl as an electron-

deﬁcient nucleophile with 2-chloropyridine and 2-chloro-

4-methylquinoline, respectively, result in good product yields in

Catalytic studies of the nickel complexes

(1) Cross-coupling of aryl chlorides with arylzinc reagents.

In our previous studies of the cross-coupling of organozinc

reagents using an amido pincer nickel as the catalyst a

1 : 1 mixture of THF and NMP was found to be the most

suitable solvent.¹¹Hence we ﬁrst examined the catalysis of

complexes 2a, 4, 7, 9, 11 and 13 towards the cross-coupling of

p-MeOC₆H₄Cl with p-MeC₆H₄ZnCl in a 1 : 1 mixture of THF

and NMP. The results showed that the yields are 7 > 4, 11 > 9,

2a > 13 (entries 1–6, Table 1). The low catalytic activity of

complex 13 may result from a overcrowded coordination

environment which prevents interaction between the central

nickel atom and the reaction substrates. However, the activity

difference of the other complexes seems to arise from electronic

effects. Complexes 7 and 9 have very similar skeleton structures.

The stronger electron donor ability of pyridyl group than imino

group results in higher catalytic activity of the former. The Ph₂P

group is also a stronger electron donor group than the imino

group, and hence complex 11 is more active than complex 9. In

complex 4 the phenyl anion binds and transfers its electrons to

the central metal ion and hence leads to an increase of electron

density of the nickel. Indeed, complex 4 exhibits good catalytic

activity. Bidentate coordinated complexes seem to be less effec-

tive than tridentate coordinated complexes for this series of

studied complexes.

We also tested the reaction in THF or NMP (entries 7 and 8,

Table 1) and the results showed that both of these solvents are

less effective than a 1 : 1 mixture of THF and NMP. It was also

noted that the 7-catalyzed cross-coupling can be further

improved by increasing the catalyst loadings, 2 mol% of 7

leading to 80% product yield and 4 mol% of 7 giving 91%

product yield (entries 9 and 10, Table 1).

Table 2 Complex 7-catalyzed cross-coupling of aryl chlorides with

arylzinc chlorides^a

With the optimized reaction conditions, we tested reactions

between functionalized phenyl chlorides and various arylzinc

chlorides catalyzed by 7. Because the functional groups are elec-

tron-withdrawing ones which activate the C–Cl bonds, the

Entry

R

Ar

t/h

Yield^b(%)

Table 1 Evaluation of complexes 2a, 4, 7, 9, 11 and 13 in catalytic

cross-coupling of p-MeOC₆H₄Cl with p-MeC₆H₄ZnCl^a

1

2

3

4

5

6

p-PhC(O)

p-COOEt

p-C(O)NEt₂

o-PhC(O)

p-PhC(O)

p-C(O)NEt₂

p-COOEt

p-PhC(O)

p-COOEt

p-PhC(O)

p-MeC₆H₄

o-MeC₆H₄

p-CH₃OC₆H₄

p-Me₂NC₆H₄

2-Furyl

2

3

24

4

9

4

3

5

1.5

99

96

99

91

98

99

95

96

94

99

92

90

Entry

Cat. (mol%)

Solvent

Yield^b(%)

1

2

3

4

5

6

7

8

9

2a (1)

4 (1)

7 (1)

9 (1)

11 (1)

13 (1)

7 (1)

7 (2)

7 (4)

NMP–THF (1 : 1)

THF

NMP

NMP–THF (1 : 1)

36

50

76

38

50

Trace

69

71

80

7

8^c

9

10

11^c

12^c

p-CF₃C₆H₄

12

9

^aUnless otherwise stated reactions were performed with 0.5 mmol aryl

chlorides and 0.75 mmol arylzinc chlorides according to the conditions

indicated by the above equation. ^bIsolated product yield. ^c2.5 equiv. of

arylzinc reagents were employed, NMP–THF = 1.5 : 2.5.

10

91

^aReactions were performed with 0.5 mmol p-MeOC₆H₄Cl and

0.75 mmol p-MeC₆H₄ZnCl at 80 °C for 12 h. ^bIsolated product yield.

10458 | Dalton Trans., 2012, 41, 10453–10464

This journal is © The Royal Society of Chemistry 2012

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Table 3 Complex 7-catalyzed cross-coupling of heteroaryl chlorides

Table 4 Screening of catalysts, counterions and solvents^a

with arylzinc chlorides^a

Entry

Catalyst

X

Solvent

Yield^b(%)

Entry

1

Aryl chloride

Ar

t/h

Yield^b(%)

99

1

2

3

4

5

6

7

8

2a

4

7

I

THF–NMP (1 : 1)

THF

33

50

85

56

p-MeC₆H₄

6

9

11

13

7

60

Trace

92^c

98

95

65

75

11

80

84

2

p-MeC₆H₄

6

99

Br

Cl

BF₄

OTf

Br

9

10

11

12

13

14

3

14

15

14

15

14

15

14

15

14

15

o-MeC₆H₄

p-CF₃C₆H₄

p-CH₃OC₆H₄

p-Me₂NC₆H₄

2-Furyl

24

12

84

99

84

90

99

95

99

92

87

96

NMP

Tol.-NMP (1 : 1)

4^c

5^d

6^d

7^d

8^d

9

7

^aThe reactions were carried out with 0.5 mmol PhNMe₃⁺X⁻and

0.75 mmol p-MeOC₆H₄ZnCl according to the conditions indicated by

the above equation unless otherwise stated. ^bIsolated product yields.

^c1 equiv. of LiBr was added.

0.5

1

2

10

11

12

2-Furyl

^aUnless otherwise stated reactions were performed with 0.5 mmol aryl

chlorides and 0.75 mmol arylzinc reagents according to the conditions

indicated by the above equation. ^bIsolated product yield. ^c1 mol% cat.

was employed. ^d2.5 equiv. of arylzinc chlorides were employed,

NMP–THF = 1.5 : 2.5.

reactive electrophile in comparison with the electrophiles with

I⁻, Cl⁻, BF₄⁻and OTf⁻as the counterions. Chloride has a close

reactivity to the bromide and the BF₄salt is the least reactive

(entries 8–11, Table 4). This may result from interaction of the

central metal with the anions during the catalytic cycle. Thus,

the halogen anions may enter the catalytic process through

coordination to the central nickel which stabilizes the central

metal and tunes the electron density distributions around the

central metal. Weakly coordinating OTf⁻and non-coordinating

anion BF₄⁻do not provide or provide less stabilizing and tuning

actions.²⁵We also examined other solvents and found that each

of THF, NMP and the 1 : 1 mixture of toluene and NMP is less

effective than the 1 : 1 mixture of THF and NMP (entries 12–14,

Table 4).

12 h although the yields are a little lower than those

using p-MeC₆H₄ZnCl as a nucleophile (entries 5 and 6,

Table 3). Electron-rich nucleophiles such as p-MeOC₆H₄ZnCl,

p-Me₂NC₆H₄ZnCl and 2-furylzinc chloride are highly reactive.

Their reactions with either 2-chloropyridine or 2-chloro-

4-methylquinoline afford the corresponding cross-coupling pro-

ducts in excellent yields in 0.5–2 h (entries 7–12, Table 3).

In the reactions using heteroaryl chlorides as the electrophiles

2.5 equiv. of p-MeOC₆H₄ZnCl or p-CF₃C₆H₄ZnCl were

employed, which is the same situation as those of reactions

employing substituted phenyl chlorides as the electrophilic

substrates.

Next we tested the 7-catalyzed reaction of activated, unacti-

vated and deactivated aryltrimethylammonium bromides with

arylzincs under the optimized conditions and the results are pres-

ented in Table 5. Besides p-MeOC₆H₄ZnCl listed in Table 4,

both p-MeC₆H₄ZnCl and p-Me₂NC₆H₄ZnCl also react smoothly

+

(2) Cross-coupling of aryltrimethylammonium salts with

arylzinc chlorides. Encouraged by the good results in the reac-

tion of arylzincs with aryl or heteroaryl chlorides catalyzed by

the complexes mentioned above, we further tested catalysis of

the complexes in the reaction of aryltrimethylammonium

salts with arylzinc reagents. The catalytic activity of the com-

with PhNMe₃Br⁻in the presence of 1 mol% 7, giving cross-

coupling products in 90 and 98% yields, respectively (entries 1

and 2, Table 5). However, reaction of o-MeC₆H₄ZnCl with

+

PhNMe₃Br⁻leads to low product yield (entry 3, Table 5). This

is ascribed to a steric hindrance effect of the ortho-methyl group

+

of o-MeC₆H₄ZnCl. p-MeOC₆H₄NMe₃Br⁻shows lower reactivity

+

plexes was ﬁrst evaluated using reaction of PhNMe₃I with

compared with PhNMe₃Br⁻. Its reaction with p-MeC₆H₄ZnCl

+ −

p-MeOC₆H₄ZnCl in a 1 : 1 mixture of NMP and THF and the

results are listed in Table 4 (entries 1–6). Complex 7 gave the

highest product yield compared with 2a, 4, 9, 11 and 13.

However, surprisingly, 1 equiv. of LiBr additive results in higher

product yield when catalyzed with 7 under the same conditions

(entry 7, Table 4). This experimental fact impelled us to examine

the counterion effect. The results show that bromide is the most

in the presence of 2 mol% of 7 generates the desired product in

81% yield. Increasing the catalyst loading to 4 mol% results in

96% product yield (entries 4 and 5, Table 5). Reaction of the

electron-rich nucleophile, p-Me₂NC₆H₄ZnCl, with p-MeOC₆-

+

H₄NMe₃Br⁻gives an excellent yield when 3 mol% of complex

7 is employed, while reaction of the electron-deﬁcient nucleo-

+

phile, p-CF₃C₆H₄ZnCl with p-MeOC₆H₄NMe₃Br⁻requires

This journal is © The Royal Society of Chemistry 2012

Dalton Trans., 2012, 41, 10453–10464 | 10459

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Table 5 Complex 7-catalyzed cross-coupling of aryltrimethyl-

electrophilic or nucleophilic substrates for the cross-coupling.

The catalysts can also be applied to the cross-coupling of acti-

vated, unactivated and deactivated aryltrimethylammonium salts

with substituted arylzinc chlorides and 2-furylzinc chloride. The

higher activity of complex 7 than the other complexes is ascribed

to stronger electron donor ability of the ligand, whereas the low

activity of complex 13 may be due to a crowded coordination

environment.

ammonium bromides with arylzinc chlorides^a

Entry

R

Ar

Cat. 7 (mol%)

Yield^b(%)

1

2

3

4

5

6

7

8

H

p-MeC₆H₄

p-Me₂NC₆H₄

o-MeC₆H₄

p-MeC₆H₄

p-Me₂NC₆H₄

p-CF₃C₆H₄

2-Furyl

p-MeC₆H₄

p-Me₂NC₆H₄

p-MeOC₆H₄

p-CF₃C₆H₄

o-MeC₆H₄

2-Furyl

1

2

4

3

5

3

2

1

3

4

1

4

3

90

98

46

81

96

98

83

65

80

87

98

88

47

48

97

Experimental

MeO

COOEt

All experiments were performed under nitrogen using standard

Schlenk and vacuum-line techniques. Solvents were distilled

under nitrogen over sodium (toluene), sodium–benzophenone

(benzene, THF, Et₂O and n-hexane), or CaH₂(CH₂Cl₂) and

degassed prior to use. NMP was dried with activated molecular

sieves, distilled under reduced pressure and degassed. CDCl₃

and C₆D₆were purchased from Cambridge Isotope Laboratories,

Inc., degassed and stored over activated molecular sieves

(CDCl₃) or Na/K alloy (C₆D₆). DMSO-d⁶was purchased from

ARMAR Chemicals and used as received. LiBuⁿ, Ph₂PCl,

(Ph₂P)₂CH₂, p-EtO₂CC₆H₄NMe₂, MeOTf and Me₃O⁺BF₄⁻were

purchased from Acros Organics and used as received.

9

10

11

12

13

14

15

^aThe reactions were carried out with 0.5 mmol ArNMe₃⁺X⁻and

0.75 mmol ArZnCl according to the conditions indicated by the above

equation. ^bIsolated product yields.

PhNMe₃Cl⁻and PhNMe₃Br⁻were purchased from TCI and

used as received. PhNMe₂was purchased from China National

Medicines Corporation Ltd. and puriﬁed by distillation under

reduced pressure prior to use. RNHPPh₂(R = p-MeC₆H₄, Bu^t),²⁶

8-azidoquinoline,²⁷p-MeOC₆H₄NMe₂,²⁸aryltrimethylammo-

nium salts,^16aand ligands 6,²⁹8,²⁹and 10²⁷were prepared

according to the literature. ArZnCl were prepared in situ through

reaction of ZnCl₂with the corresponding aryllithium

(p-MeC₆H₄Li,³⁰o-MeC₆H₄Li,³⁰p-Me₂NC₆H₄Li,³¹p-CF₃C₆-

H₄Li,³²p-MeOC₆H₄Li³³and 2-furyllithium³⁴). All other chemi-

cals were obtained from commercial vendors and used as

received. NMR spectra were recorded on a Bruker av300

spectrometer at ambient temperature. The chemical shifts of

¹H and ¹³C{¹H} NMR spectra are referenced to internal solvent

resonances or TMS, and the ³¹P{¹H} NMR spectra are refer-

enced to external 85% H₃PO₄. Infrared spectra were recorded on

a Bruker VECTOR-22 spectrometer. Elemental analyses were

performed by the Analytical Center of University of Science and

Technology of China.

+

higher catalyst loading (5 mol%) and results in lower product

yield (83%) (entries 6 and 7, Table 5). 2-Furylzinc chloride also

+

reacts with p-MeOC₆H₄NMe₃Br⁻in the presence of 7, but the

reaction leads to relatively low product yield (65%) (entry 8,

Table 5). Increasing catalyst loading and lengthening the reaction

+

time can not improve the reaction. p-EtO₂CC₆H₄NMe₃Br⁻

reacts smoothly with electron-rich nucleophiles such as

p-MeC₆H₄ZnCl, p-MeOC₆H₄ZnCl and p-Me₂NC₆H₄ZnCl, and

electron-deﬁcient nucleophile p-CF₃C₆H₄ZnCl, giving corres-

ponding cross-coupling products in good to excellent yields

(entries 9–12, Table 5). However, reaction of p-EtO₂CC₆-

H₄NMe₃Br⁻with o-MeC₆H₄ZnCl affords a poor result due to

+

steric hindrance of the ortho-methyl group of o-MeC₆H₄ZnCl.

Increasing catalyst loading can not improve the yield (entries 13

and 14, Table 5). Reaction of 2-furylzinc chloride with

+

p-EtO₂CC₆H₄NMe₃Br⁻leads to an excellent result, 3 mol%

catalyst loading giving 97% product yield.

Conclusions

Syntheses

We have synthesized and characterized a series of quinoline-

based ligands and their lithium and nickel complexes. The reac-

tivity and transformation of the complexes were studied. The

catalysis of the nickel complexes toward the reactions of arylzinc

reagents with aryl chlorides and aryltrimethylammonium salts

were evaluated and the N,N,N-chelate nickel complex, [NiCl₂-

{2-PyCH₂P(Ph₂)vN(8-C₉H₆N)}] (7), was found to be the most

effective catalyst for the cross-coupling reactions. The catalytic

reaction of arylzinc chlorides with aryl chlorides require only

low catalyst loadings and tolerate a range of functional groups

such as PhC(O), COOEt, C(O)NEt₂and CF₃groups. Both

heteroaryl chlorides, including 2-chloropyridine and 2-chloro-

4-methylquinoline, and 2-furylzinc chloride are applicable as

p-MeC₆H₄NHP(Ph₂)vN(8-C₉H₆N) (1a). A three-necked ﬂask

was charged with 8-azidoquinoline (4.08 g, 24 mol) and CH₂Cl₂

(20 cm³) and to the solution was added dropwise a solution of

p-MeC₆H₄NHPPh₂(5.83 g, 20 mmol) in CH₂Cl₂(15 cm³) with

stirring. The resultant mixture was stirred for 4 h at room temp-

erature. The solution was concentrated and then hexane was

added. The resultant solution was kept at −20 °C to form

yellow–brown crystals of 1a (7.81 g, 90%). Anal. Calc. for

C₂₈H₂₄N₃P·0.2C₆H₁₄: C, 77.81; H, 5.99; N, 9.32. Found:

1

C, 78.00; H, 6.00; N, 9.37%. H NMR (CDCl₃), δ 2.16 (s, 1H,

CH₃), 6.83 (d, J = 7.8 Hz, 2H, Ar), 6.95 (d, J = 7.5 Hz, 2H, Ar),

7.19–7.29 (m, 2H, Ar), 7.37–7.53 (m, 6H, Ar), 7.54 (d, J =

6.6 Hz, 1H, Ar), 7.98–8.09 (m, 4H, Ar), 8.10 (d, J = 8.1 Hz, 1H,

10460 | Dalton Trans., 2012, 41, 10453–10464

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[Li{(1,2-C₆H₄)P(Ph)(NHBu^t)vN(8-C₉H₆N)}] (5). A solution

of 1b (0.352 g, 0.881 mmol) in THF (10 cm³) was cooled to

about −80 °C and to the solution was added dropwise a solution

of LiBuⁿ(0.36 cm³, 2.5 M in hexanes, 0.9 mmol) with stirring.

The resulting mixture was allowed to warm to room temperature

and stirred overnight. Volatiles were removed in vacuo. The

residue was dissolved in hexane and ﬁltered. The ﬁltrate was

concentrated to afford yellow crystals of 5 (0.28 g, 78%). Anal.

Calc. for C₂₅H₂₅N₃LiP: C, 74.07; H, 6.22; N, 10.37. Found: C,

74.20; H, 6.45; N, 10.11%. ¹H NMR (C₆D₆): δ 0.72 (s, 9H,

Bu^t), 3.56 (d, J = 6.3 Hz, 1H, NH), 6.29–6.33 (m, 1H, Ar),

6.64–6.79 (m, 6H, Ar), 7.22–7.32 (m, 2H, Ar), 7.64 (s, 1H, Ar),

7.72 (d, J = 7.8 Hz, 1H, Ar), 7.95 (dd, J = 7.8, 10.8 Hz, 4H,

Ar). ¹³C NMR (C₆D₆): δ 32.37, 52.97, 115.39, 120.12, 122.92,

123.29, 128.15, 129.02, 130.08 (d, J = 2.2 Hz), 132.10

(d, J = 8.3 Hz), 136.38, 144.17. ³¹P NMR (C₆D₆): δ −2.93.

Ar), 8.82 (s, 1H, Ar). ¹³C NMR (CDCl₃): δ 38.47, 114.29,

119.88, 121.29, 121.68, 127.21, 127.29, 127.37, 127.97, 129.43,

129.55, 130.70, 130.76, 130.82, 130.88, 131.93, 132.07, 135.51,

143.22, 144.43, 148.16, 149.90. ³¹P NMR (CDCl₃): δ 7.52.

Bu^tNHP(Ph₂)vN(8-C₉H₆N) (1b). A three-necked ﬂask was

charged with 8-azidoquinoline (4.08 g, 24 mol) and CH₂Cl₂

(20 cm³) and to the solution was added dropwise a solution of

Bu^tNHPPh₂(5.15 g, 20 mmol) in CH₂Cl₂(15 cm³) with stirring.

The resultant mixture was stirred for 4 h at room temperature.

The solution was concentrated and then hexane was added. The

resultant solution was kept at −20 °C to form red crystals of 1b

(7.35 g, 92%). Anal. Calc. for C₂₅H₂₆N₃P: C, 75.17; H, 6.56;

N, 10.52. Found: C, 75.33; H, 6.65; N, 10.37%. ¹H NMR

(CDCl₃): δ 1.01 (s, 9H, Bu^t), 3.71 (d, J = 5.4 Hz, 1H, NH),

7.04–7.11 (m, 2H, Ar), 7.29–7.36 (m, 6H, Ar), 7.39–7.50 (m,

2H, Ar), 7.97 (dd, J = 1.2, 8.4 Hz, 1H, Ar), 8.01–8.09 (m, 4H,

Ar), 8.17–8.22 (m, 1H, Ar). ¹³C NMR (CDCl₃): δ 32.40,

115.05, 120.19, 121.75, 122.08, 123.29, 128.06, 128.23, 128.32,

128.37, 130.14, 131.77, 131.88, 136.18, 144.51. ³¹P NMR

(CDCl₃): δ −1.51.

[NiCl₂{2-PyCH₂P(Ph₂)vN(8-C₉H₆N)}] (7). A mixture of 6

(0.839 g, 2 mmol), (DME)NiCl₂(0.44 g, 2 mmol) and CH₂Cl₂

(30 cm³) was stirred at room temperature for 5 h. The resulting

solution was ﬁltered and the ﬁltrate was concentrated to yield

yellow green crystals of complex 7 (0.89 g, 81%). Anal. Calc.

for C₂₇H₂₂N₃Cl₂NiP·0.06CH₂Cl₂: C, 58.65; H, 4.02; N, 7.58.

Found: C, 58.67; H, 4.14; N, 7.26%. IR (KBr dispersion disc):

ν (cm⁻¹) 1282s (PvN).

[NiCl₂{N(8-C₉H₆N)vP(Ph₂)NH(p-MeC₆H₄)}] (2a). A Schlenk

tube was charged with 1a (0.867 g, 2 mmol), (DME)NiCl₂

(0.44 g, 2 mmol) and THF (30 cm³) and the mixture was stirred

at room temperature for 12 h. Solvent was removed and the

residue was dissolved in CH₂Cl₂and the resulting solution was

ﬁltered. The ﬁltrate was concentrated in vacuo and a few drops

of toluene were added to generate dark brown crystals of 2a

(0.94 g, 83%). Anal. Calc. for C₂₈H₂₄N₃Cl₂NiP·0.4C₇H₈: C,

61.82; H, 4.59; N, 7.03. Found: C, 61.66; H, 4.57; N, 7.22%. IR

(KBr dispersion disc): ν (cm⁻¹) 3222s (NH), 1285vs (PvN).

A concentrated CH₂Cl₂solution of 2a was set aside for a few

days to form single crystals used for X-ray diffraction analysis.

A dilute solution of 7 in CH₂Cl₂was set aside for a few days

to form single crystals used for X-ray diffraction analysis.

[NiCl₂{N(Ph)vC(Ph)CH₂P(Ph₂)vN(8-C₉H₆N)}] (9). A mixture

of 8 (1.18 g, 2.26 mmol), (DME)NiCl₂(0.55 g, 2.5 mmol) and

CH₂Cl₂(30 cm³) was stirred at room temperature for 12 h. The

resulting solution was ﬁltered and the ﬁltrate was concentrated to

yield red–orange crystals of complex 9 (1.12 g, 76%). Anal.

Calc. for C₃₅H₂₈N₃Cl₂NiP: C, 64.56; H, 4.33; N, 6.45. Found:

C, 64.79; H, 4.65; N, 6.40%. IR (KBr dispersion disc): ν (cm⁻¹

1280vs (PvN).

)

[NiCl{(1,2-C₆H₄)P(Ph)(NHBu^t)vN(8-C₉H₆N)}] (4). A Schlenk

tube was charged with 1b (0.799 g, 2 mmol), (DME)NiCl₂

(0.44 g, 2 mmol) and THF (30 cm³) and the mixture was stirred

at room temperature for 12 h. NaH (0.1 g, 60%, 2.5 mmol) was

added and the resulting mixture was heated at 65–70 °C (bath

temperature) for 24 h. The solution was cooled to room tempera-

ture and solvent was removed in vacuo. The residue was dis-

solved in CH₂Cl₂and the resulting solution was ﬁltered. The

ﬁltrate was concentrated in vacuo and then added hexane to form

deep red crystals of 4 (0.601 g, 61%). Anal. Calc. for

C₂₅H₂₅N₃ClNiP·0.17CH₂Cl₂: C, 59.62; H, 5.04; N, 8.29. Found:

THF was added to a solution of 9 in CH₂Cl₂which was then

set aside to form single crystals used for X-ray diffraction

analysis.

[NiCl₂{P(Ph₂)CH₂P(Ph₂)vN(8-C₉H₆N)}] (11). A mixture of

10 (1.053 g, 2 mmol), (DME)NiCl₂(0.44 g, 2 mmol) and THF

(30 cm³) was stirred at room temperature for 12 h. Volatiles were

removed in vacuo and the residue was dissolved in CH₂Cl₂. The

resulting solution was ﬁltered and the ﬁltrate was concentrated to

produce yellow–brown crystals of complex 11 (0.97 g, 74%).

Anal. Calc. for C₃₄H₂₈N₂Cl₂NiP₂: C, 62.24; H, 4.30; N, 4.27.

Found: C, 62.22; H, 4.24; N, 4.11%. IR (KBr dispersion disc):

ν (cm⁻¹) 1280s (PvN).

1

C, 59.61; H, 5.21; N, 8.05%. H NMR (CDCl₃): δ 1.36 (s, 9H,

Bu^t), 3.19 (d, J = 7.8 Hz, 1H, NH), 6.84 (d, J = 7.2 Hz, 1H, Ar),

6.99–7.21 (m, 5H, Ar), 7.39–7.59 (m, 4H, Ar), 7.88–7.98 (m,

3H, Ar), 8.15 (d, J = 8.4 Hz, 1H, Ar), 9.19 (d, J = 5.1 Hz, 1H,

Ar). ¹³C NMR (CDCl₃): δ 32.07 (d, J = 2.8 Hz), 54.61 (d, J =

1.8 Hz), 115.03, 115.12, 116.18, 122.06, 124.44, 124.60,

127.46, 128.45, 128.68, 129.65, 129.77, 130.21, 131.17 (d, J =

7.2 Hz), 133.10, 137.32, 140.65 (d, J = 13.7 Hz), 147.05,

149.56. ³¹P NMR (CDCl₃): δ 37.85. IR (KBr dispersion disc):

ν (cm⁻¹) 3198s (NH), 1286m (PvN).

A dilute solution of 11 in CH₂Cl₂was set aside for a few days

to form single crystals used for X-ray diffraction analysis.

[(8-C₉H₆N)NvP(Ph₂)]₂CH₂(12). To a stirred solution of

8-azidoquinoline (8.17 g, 48 mmol) in CH₂Cl₂(20 cm³) was

added dropwise a solution of dppm (7.69 g, 20 mmol) in

CH₂Cl₂(40 cm³) at room temperature. The mixture was stirred

for 8 h. Solvent was removed by rotary evaporation. The residual

solid was washed with Et₂O and dried in vacuo to give a yellow

orange powder of 12 (11.1 g, 83%). Anal. Calc. for C₄₃H₃₄N₄P₂:

C, 77.23; H, 5.12; N, 8.38. Found: C, 76.93; H, 5.22; N, 8.17%.

THF was added to a solution of 4 in CH₂Cl₂which was then

set aside to form single crystals used for X-ray diffraction

analysis.

Dalton Trans., 2012, 41, 10453–10464 | 10461

View Article Online

¹H NMR (CDCl₃): δ 4.83 (t, J = 13.8 Hz, 2H, CH₂), 6.84–6.98

(m, 15H, Ar), 7.10 (d, J = 6.9 Hz, 2H, Ar), 7.20 (t, J = 7.2 Hz,

2H, Ar), 7.33 (t, J = 6.5 Hz, 1H, Ar), 7.43–7.51 (m, 1H, Ar),

7.53–7.65 (m, 7H, Ar), 7.73 (d, J = 8.1 Hz, 2H, Ar), 8.05 (d,

J = 2.7 Hz, 2H, Ar). ¹³C NMR (CDCl₃): δ 20.73, 114.02,

114.16, 119.08, 123.42 (d, J = 18 Hz), 127.70, 128.63, 128.96

(d, J = 12.9 Hz), 129.50, 131.78 (d, J = 2.2 Hz), 132.01 (d,

J = 9.5 Hz), 132.33, 132.75, 136.52, 148.02. ³¹P NMR (CDCl₃):

δ 8.04.

(for complexes 2a, 4, 9, 11 and 13) or an Oxford Diffraction

Gemini S Ultra diffractometer with mirror-monochromated

Cu-Kα radiation (λ = 1.54184 Å) (for complex 7). The structures

were solved by direct methods using SHELXS-97³⁵and reﬁned

against F²by full-matrix least squares using SHELXL-97.³⁶The

disordered solvent molecule in complex 7 was removed from the

diffraction data using the SQUEEZE program. Examination of

the structure of complex 11 with PLATON showed that there is a

potential solvent-accessible void in the crystal lattice. This may

result from molecule stacking since no deﬁnitive solvent mo-

lecule could be found. The data were modiﬁed using the

SQUEEZE program. Hydrogen atoms were placed at calculated

positions. Crystal data and experimental details of the structure

determinations are listed in Table 6.

[NiCl{(8-C₉H₆N)NP(Ph₂)}₂CH] (13). To a stirred solution of

12 (1.31 g, 1.96 mmol) in THF (30 cm³) was added dropwise a

solution of LiBuⁿ(0.8 cm³, 2.5 M in hexanes, 2 mmol) at about

−80 °C. The resulting mixture was warmed to room temperature

and stirred for 4 h. This solution was then transferred into a sus-

pension of (DME)NiCl₂(0.44 g, 2 mmol) in THF (10 cm³) at

about −80 °C. The mixture was warmed to room temperature

and stirred for 12 h. Volatiles were removed in vacuo and the

residue was dissolved in CH₂Cl₂. The resulting solution was

ﬁltered and the ﬁltrate was concentrated. Hexane was added to

form red crystals of complex 13 (0.975 g, 61%). Anal. Calc. for

C₄₃H₃₃N₄ClNiP₂·0.6CH₂Cl₂: C, 64.43; H, 4.24; N, 6.89. Found:

Catalytic cross-coupling of aryl chlorides with arylzinc chlorides

A

typical procedure is exempliﬁed by the reaction of

p-CH₃OC₆H₄Cl with p-CH₃C₆H₄ZnCl using complex 7 as a cata-

lyst. Schlenk tube was charged with p-CH₃OC₆H₄Cl

(0.0713 g, 0.5 mmol), NMP (1.5 cm³) and complex 7 (0.0114 g,

0.02 mmol). To the stirred mixture solution of p-

A

C, 64.31; H, 4.31; N, 6.98%. IR (KBr dispersion disc): ν (cm⁻¹

1276s (PvN).

)

a

CH₃C₆H₄ZnCl (1.5 cm³, a 0.5 M solution in THF, 0.75 mmol)

was added by syringe. Then the reaction mixture was stirred at

80 °C (bath temperature) for 24 h. The solution was cooled to

room temperature. Water (10 cm³) and several drops of hydro-

chloric acid were successively added. The resulting mixture was

extracted with Et₂O (10 cm³× 3). The combined extract was

dried (MgSO₄) and concentrated to dryness. The residue was

puriﬁed by column chromatography (silica gel, eluted using

petroleum ether) to afford a white solid (0.0902 g, 91%).

Toluene was added to a solution of 13 in CH₂Cl₂which was

then set aside to form single crystals used for X-ray diffraction

analysis.

p-EtO₂CC₆H₄NMe₃⁺Br⁻. To

a stirred solution of ethyl

4-dimethylaminobenzoate (1.20 g, 6.2 mmol) in DMF (10 cm³)

was added dropwise an excess of methyl bromide at room temp-

erature. The resulting solution was stirred for 4 days. Solvent

was removed in vacuo. The residue was washed with Et₂O

(10 cm³× 3) and dried under vacuum to give a white solid

(1.75 g, 98%). Anal. Calc. for C₁₂H₁₈BrNO₂: C, 50.01; H,

Catalytic cross-coupling of aryltrimethylammonium salts with

arylzinc chlorides

1

6.30; N, 4.86. Found: C, 49.87; H, 6.29; N, 4.76%. H NMR

(DMSO-d⁶): δ 1.34 (t, J = 7.2 Hz, 3H, Et), 3.66 (s, 9H, NMe),

4.51 (q, J = 7.2 Hz, 2H, Et), 8.15 (s, 4H, C₆H₄). ¹³C NMR

(DMSO-d⁶): δ 14.03, 56.33, 61.33, 121.43, 130.56, 131.21,

150.48, 164.33.

A

typical procedure is exempliﬁed by the reaction of

PhNMe₃Br⁻with p-CH₃OC₆H₄ZnCl using complex 7 as a cata-

+

lyst. PhNMe₃Br⁻(0.108 g, 0.5 mmol), complex 7 (0.0057 g,

0.01 mmol) and NMP (1.5 cm³) were added to a Schlenk tube.

To the stirred mixture was added a solution of p-CH₃OC₆H₄ZnCl

(1.5 cm³, a 0.5 M solution in THF, 0.75 mmol) by syringe. The

reaction mixture was stirred at 85 °C (bath temperature) for 12 h

and then cooled to room temperature. Water (10 cm³) and several

drops of acetic acid were successively added. The resulting

mixture was extracted with Et₂O (10 cm³× 3). The extract was

dried (Na₂SO₄) and concentrated. The residue was puriﬁed by

column chromatography (silica gel, eluted using petroleum

ether) to afford a white solid (0.0903 g, 98%).

p-MeOC₆H₄NMe₃⁺Br⁻. To a stirred solution of 4-methoxy-N,

N-dimethylbenzenamine (0.52 g, 3.4 mmol) in DMF (8 cm³)

was added dropwise an excess of methyl bromide at room temp-

erature. The resulting solution was stirred for 56 h. Solvent

was removed in vacuo and the residue was washed with

Et₂O (10 cm³× 3), dried under vacuum to give a white solid

(0.77 g, 92%). Anal. Calc. for C₁₀H₁₆BrNO: C, 48.80; H,

1

6.55; N, 5.69. Found: C, 48.90; H, 6.52; N, 5.71%. H NMR

(DMSO-d⁶): δ 3.60 (s, 3H, OMe), 3.82 (s, 9H, NMe), 7.12 (d,

J = 9.6 Hz, 2H, C₆H₄), 7.91 (d, J = 9.6 Hz, 2H, C₆H₄).

¹³C NMR (DMSO-d⁶): δ 55.77, 56.57, 114.66, 121.86, 140.10,

159.59.

Acknowledgements

This research was supported by National Basic Research

Program of China (grant no. 2009CB825300) and the National

Natural Science Foundation of China (grant no. 20772119). The

authors thank Professors D.-Q. Wang and S.-M. Zhou for deter-

mining the crystal structures. We also thank Professor G.-P. Yong

for helpful discussion on crystal structures.

X-Ray crystallography

Single crystals of complexes 2a, 4, 7, 9, 11 and 13 were respect-

ively mounted in Lindemann capillaries under nitrogen. Diffrac-

tion data were collected on a Bruker Smart CCD area-detector

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

10462 | Dalton Trans., 2012, 41, 10453–10464

View Article Online

Table 6 Details of the X-ray structure determinations of complexes 2a, 4, 7, 9, 11 and 13

2a·0.5CH₂Cl₂

4·THF

7

9·CH₂Cl₂·THF

11

13·1.5C₇H₈

Empirical formula

M_r

C₂₉H₂₆Cl₄N₃NiP

648.01

C₂₉H₃₃ClN₃NiOP

564.71

C₂₇H₂₂Cl₂N₃NiP

549.06

C₄₀H₃₈Cl₄N₃NiOP

808.21

C₃₄H₂₈Cl₂N₂NiP₂

656.13

C₁₀₇H₉₀Cl₂N₈Ni₂P₄

1800.07

T/K

298(2)

291(2)

298(2)

Crystal system

Space group

a/Å

b/Å

c/Å

α/°

β/°

Monoclinic

P2₁/n

12.1681(11)

16.3886(15)

14.9929(13)

90

94.7500(10)

90

2979.6(5)

4

Triclinic

P1

Monoclinic

C2/c

34.5863(13)

11.5292(2)

19.6821(5)

90

117.126(4)

90

6985.0(3)

8

Triclinic

P1

Orthorhombic

P2₁2₁2₁

14.7449(16)

13.6940(14)

16.1341(19)

90

3257.7(6)

4

1.338

Triclinic

P1

ˉ

10.1230(10)

11.83510(12)

12.17190(13)

99.2830(10)

111.966(2)

92.9710(10)

1324.64(13)

2

11.4343(15)

11.6020(15)

17.1801(19)

76.682(2)

73.1970(10)

64.5420(10)

1955.1(4)

2

11.7609(14)

12.4767(16)

17.3590(18)

82.3720(10)

85.171(2)

79.2300(10)

2475.6(5)

2

γ/°

V/Å³

Z

D_c/g cm⁻³

1.445

1.416

1.044

1.373

1.207

F(000)

1328

1.087

592

0.922

2256

2.758

836

0.846

1352

0.883

938

0.549

μ/mm⁻¹

θ range/°

2.42–25.01

15 435

5256

1.76–25.01

7006

4591

2.87–62.76

13 149

5522

2.20–25.02

10 204

6709

2.76–25.02

15 728

5668

1.67–25.02

13 056

8566

No. reﬂns collected

No. indep. reﬂns

R_int

0.0826

0.0297

0.0354

0.0646

0.1945

0.0239

No. data/restraints/params

Goodness of ﬁt on F²

Final R indices^a[I > 2σ(I)]

5256/0/372

1.062

4591/0/359

1.022

5522/0/307

1.015

6709/0/507

1.309

5668/0/370

1.050

8566/0/632

1.001

R₁= 0.0532,

wR₂= 0.1108

R₁= 0.1066,

wR₂= 0.1249

0.398, −0.605

R₁= 0.0435,

wR₂= 0.0623

R₁= 0.0833,

wR₂= 0.0686

0.333, −0.289

R₁= 0.0378,

wR₂= 0.1095

R₁= 0.0453,

wR₂= 0.1125

0.265, −0.208

R₁= 0.0858,

wR₂= 0.1953

R₁= 0.1415,

wR₂= 0.2113

0.920, −0.751

R₁= 0.0984,

wR₂= 0.1595

R₁= 0.2389,

wR₂= 0.1844

0.641, −0.686

R₁= 0.0569,

wR₂= 0.1716

R₁= 0.0945,

wR₂= 0.1936

0.718, −0.407

R indices (all data)

Δρ_{max, min}/e Å⁻³

^aR₁= ∑kF_o| − |F_ck/∑|F_o|; wR₂= [∑w(F_o²− F_c) /∑w(F_o⁴)]^1/2

2 2

.

2004, 346, 1812; ( j) I. Sapountzis, H. Dube and P. Knochel, Adv. Synth.

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Article Doi

Nickel complexes supported by quinoline-based ligands: Synthesis, characterization and catalysis in the cross-coupling of arylzinc reagents and aryl chlorides or aryltrimethylammonium salts

DOI: 10.1039/c2dt30886j

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Article abstract of DOI:10.1039/c2dt30886j

Full text of DOI:10.1039/c2dt30886j

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