Bisguanidines with biphenyl, binaphthyl, and bipyridyl cores: Proton-sponge properties and coordination chemistry

FULL PAPER

DOI: 10.1002/chem.201204294

Bisguanidines with Biphenyl, Binaphthyl, and Bipyridyl Cores:

Proton-Sponge Properties and Coordination Chemistry

Astrid Maronna, Olaf Hꢀbner, Markus Enders, Elisabeth Kaifer, and

[

a]

Hans-Jçrg Himmel*

Dedicated to Professor Werner Uhl on the occasion of his 60th birthday

Abstract: Herein, we report on the syn-

case of the bipyridyl systems, coordina-

tion occurs exclusively at the pyridine

N atoms, as opposed to protonation.

The spin-density distribution and the

magnetism were evaluated for a series

the aid of paramagnetic NMR spectro-

thesis, protonation, and coordination

chemistry of chelating guanidine li-

gands with biphenyl, binaphthyl, and

bipyridyl backbones. The ligands are

shown to be proton sponges, and this

protonation was studied experimentally

and by using quantum-chemical calcu-

lations. Group 10 metal (Ni, Pd, and

Pt) complexes with different metal/

ligand ratios were synthesized. In the

scopic studies in alliance with quan-

tum-chemical calculations and magnet-

ic (SQUID) measurements. Through

direct delocalization from the singly oc-

cupied molecular orbitals (SOMOs), a

significant amount of spin density is

placed on the guanidinyl groups, and

spin polarization also transports spin

density onto the aromatic backbone.

II

of paramagnetic Ni complexes with

Keywords: guanidine

·

nickel

·

NMR spectroscopy · palladium ·

platinum

Introduction

Charge-density studies have shown the guanidine–metal

bond to be composed of s and p contributions, which ex-

press themselves by significant elongation of the imino (N=

Chelating guanidine and guanidinate ligands have found

manifold applications in the fields of coordination chemistry

[7]

C) bond length upon coordination.

The modular synthesis of guanidines allows tuning of

[

1]

and material science. For example, bicyclic guanidinates

have been used in dinuclear transition-metal complexes with

[8]

their properties and their use as versatile ligands. Some

special organic compounds that feature two guanidinyl

groups in proximity have been identified as organosuperbas-

[

2]

a multiple bond between two highly oxidized metal atoms

[

1g,3]

and in catalysis.

Acyclic guanidinates with sterically de-

[

9–11]

manding organic groups have served as substituents in di-

es and proton sponges;

an example is 1,8-bis(tetrame-

I

[4]

[12]

meric Mg compounds. Neutral hybrid–guanidine ligands

have also been applied in catalytic reactions, such as lactide

thylguanidinyl)naphthalene. Such compounds have a vari-

ety of applications in organic synthesis. Moreover, there is

some evidence that frustrated Lewis pairs of a guanidine

[9]

[

5]

polymerization. Tripodal guanidine ligands have been used

to obtain the first structurally characterized end-on bonded

Cu–superoxo complex, which exhibits a rich chemistry.

proton sponge and B ACHTUNGTRENN(NUG C F ) add H under ambient condi-

6 5 3 2

[6]

[13]

tions.

Recently, we developed guanidinyl-functionalized aromat-

ic compounds (GFAs) as a new class of organic electron

[

a] Dr. A. Maronna, Dr. O. Hꢀbner, Prof. Dr. M. Enders, Dr. E. Kaifer,

Prof. Dr. H.-J. Himmel

Anorganisch-Chemisches Institut

Ruprecht-Karls-Universitꢁt Heidelberg

Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)

Fax : (+49)6221-545707

donor. Two examples, namely 1,2,4,5-tetrakis(tetramethyl-

[12,14]

guanidinyl)benzene (ttmgb)

methylguanidinyl)naphthalene (ttmgn),

and 1,4,5,8-tetrakis(tetra-

[15,16]

are shown in

Scheme 1. These compounds feature guanidinyl groups in

E-mail: hans-jorg.himmel@aci.uni-heidelberg.de

Supporting information for this article is available on the WWW

under http://dx.doi.org/10.1002/chem.201204294. It contains the mo-

lecular structure of [(1H)PtCl

3

]; comparison between the calculated

and experimental observed chemical shifts of the NMR spectra of

[

NiCl

NiBr

2

(2)], [NiBr

(2)], [Ni(5)

2

(2)], [NiCl

2

(3)], and [NiBr

2

(3)]; magnetic curves of

2

3

2

]Cl and [Ni(6)

3

2

]Cl ; calculated structures of the

1

3

1

protonated ligands and their hypothetical isomers; C– H-coupled

and HETCOR NMR spectra of [NiCl (2)], [NiBr (2)], [NiCl (3)],

and [NiBr (3)]; Curie plots from the VT-NMR spectroscopic experi-

ments; NMR spectra at different temperatures for [{PdCl

2

Scheme 1. Two examples of GFA compounds (i.e., ttmgb and ttmgn),

which illustrate the general structure of this new class of redox-active

ligand, and bisguanidine btmgb.

3

AHCTUNGERTNNUNG( h -

3

3 5 2 3 5 2

C H )} (5)] and [{PdCl ACHTUNGTRENUNG( h -C H )} (6)].

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para positions to each other. The superbasic, redox and

2)], and [PtCl₂ AHCTUNGTRENNUN(G C H ) ACHUTNGTREUNNGN

2 4

previous work.

[

7,29–31]

ligand properties of GFAs could interplay or compete with

[17]

each other, and the chosen reaction conditions (especially,

of course, the solvent polarity) could favor one reaction

channel over the other. Two-electron oxidation leads to the

formation of a dication, which could best be described as

two bisguanidinyl–allyl cations connected by two CꢀC single

pyridine backbone, had not yet been reported. The bipyri-

dine (bpy) ligand and derivatives have found a variety of ap-

[32–34]

plications in coordination chemistry

and were even

[35]

praised as “the most widely used ligands”. Generally, the

2

bpy ligand binds in an N,N’-k fashion with both pyridine N

[18]

bonds.

radical monocationic, or dicationic ligand.

parison, most of the commonly used redox-active ligands

In metal complexes, ttmgb was either a neutral,

atoms bound to the metal center. In the case of ligands 5

and 6, the guanidinyl groups compete for the metal center

by bonding with the pyridine N atoms.

[14,19–22]

For com-

[23]

(

e.g., o-quinone or a-diimine ligands) are neutral–anionic.

The observation of temperature-dependent electrical con-

ductivity in the coordination polymer {[(CuI)₂-

(ttmgb)](I ) } (in line with a classical semiconductor) was

By using quantum-chemical calculations, 1 was identified

[36]

as a proton sponge and superbase. Herein, protonation is

thoroughly studied for ligands 1–6 by employing experimen-

tal studies and quantum-chemical calculations (considering

several tautomeric forms).

[24]

2 n

ACHTUNGTRENNUNG

3

interpreted as a proof of principle for the possibility of

metal–ligand charge flow, which is typical for “noninnocent”

[25]

ligand behaviour.

As reference systems, we studied complexes of bisguani-

dines, such as 1,2-bis(tetramethylguanidinyl)benzene

Results and Discussion

[26]

(

btmgb; Scheme 1), with two guanidinyl groups in ortho

Ligand synthesis: Compounds 5 and 6 were synthesized ac-

cording to Scheme 4 by reaction between 3,3’-diamino-2,2’-

bipyridine and the “Vilsmeier salts” 2-chloro-1,1’,3,3’-tet-

[7,25–28]

positions to each other.

An analysis of the paramagnet-

[37]

II

ic Ni complex [NiCl₂

Scheme 2) by using experimen-

tal charge-density studies and

variable-temperature (VT)

A

H

U

G

E

N

(btmgb)]

ramethylformamidinium chloride or 2-chloro-1,3-dimethyle-

(

NMR spectroscopy in alliance

with quantum-chemical calcula-

tions at various levels points to

significant spin-density delocali-

Scheme 2. Lewis structure of

[

2

NiCl ACHTUNGTRENNUNG( btmgb)].

zation onto the guanidinyl groups and also, to some extent,

[7,26]

onto the aromatic core.

Herein, we analyze the properties of Group 10 complexes

of the six ligands shown in Scheme 3. Ligands 1–4 and some

aspects of their coordination chemistry (i.e., complexes

1

[

NiCl (1)], [NiBr (1)], [PtCl AHCTUNGTRENNNUG( C H ) ACHTNUGRTUNNNE(G k -1)], [PtCl ACHTUNGTRENUNN(G C H ) AHCUTRENTGNUN(G k -

2 2 2 2 4 2 2 4

Scheme 4. Synthesis of the 5 and 6.

thyleneformamidinium chloride (for 5 and 6, respectively).

The “Vilsmeier salts” were freshly prepared from the corre-

sponding urea compounds and oxalyl chloride. Crystals of 5

were obtained from a mixture of toluene/n-hexane and crys-

tals of 6 from dichloromethane. Figure 1 displays the molec-

ular structures of the two new ligands as derived from a

XRD study. The bond lengths within the guanidinyl groups

point to intact N=C double bonds of equal length (i.e.,

1

.302(3)/1.301(3) and 1.3001(10)/1.2955(14) ꢃ in 5 and 6, re-

spectively). The dihedral angle between the two ring planes

measures 121.63 and 56.908 in 5 and 6, respectively.

In general, cyclic aromatic hydrocarbons without extend-

ed conjugated aromatic systems (i.e., benzene, toluene)

[38]

Scheme 3. The bisguanidine ligands relevant to this study.

show only little fluorescence intensity. The new ligands 5

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

Ligand 5 gave only poor emission efficiency with a fluores-

cence quantum yield of F <0.01. Fluorescence of ligand 6

F

was more effective and a quantum yield of F =0.05 was de-

F

termined.

Protonation: As already mentioned, ligand 1 was classified

as a proton sponge and superbase on the basis of quantum-

[36]

chemical calculations. In this study, we verified this classi-

fication by protonation experiments and extended the stud-

ies to the other ligands. Monoprotonation of the guanidine

ligands was achieved by reaction with NH PF . Structurally

4

6

characterized compounds were obtained with ligands 1, 2, 4,

and 6 (Figures 2 and 3).

Figure 1. a,b) Molecular structures of ligands 5 and 6. Thermal ellipsoids

are drawn at the 50% probability level. Selected bond lengths [ꢃ] and

angles [8] for 5: N1–C1 1.400(3), N1–C11 1.302(3), N2–C11 1.392(3), N3–

C11 1.368(3), N4–C5 1.343(3), N5–C6 1.349(3), N6–C10 1.388(3), N6–C16

Figure 2. Fraction of the structures of the salts a) [1H]PF

and c) [4H]PF (anion not shown). Thermal ellipsoids are drawn at the

0% probability level. Selected bond lengths [ꢃ] for [1H]PF : N1–C1

.4129(19), N1–C13 1.3118(19), N2–C13 1.364(2), N3–C13 1.375(2), N4–

6 6

, b) [2H]PF ,

1

.301(3), N7–C16 1.387(3), N8–C16 1.368(3), C1–C5 1.409(3), C5–C6

.500(3), C6–C10 1.422(3); C1-N1-C11 119.6(2), N2-C11-N3 115.31(19),

6

5

1

6

C10-N6-C16 123.48(19), N7-C16-N8 115.1(2). Selected bond lengths [ꢃ]

and angles [8] for 6: N1–C1 1.3889(14), N1–C11 1.3001(13), N2–C11

C12 1.4231(19), N4–C18 1.3503(19), N5–C18 1.3391(19), N6–C18

.3315(19), N4–H 0.869(2), N1···H 2.020(2), N1···N1’ 2.761(3). Selected

bond lengths [ꢃ] for [2H]PF : N1–C1 1.430(3), N1–C13 1.323(3), N2–C13

.334(3), N3–C13 1.348(3), N4–C12 1.419(3), N4–C18 1.298(3), N5–C18

.369(3), N6–C18 1.379(3), N1–H 0.803(2), N4···H 2.085(4), N1···N4

.763(3). Selected bond lengths [ꢃ] for [4H]PF : N1–C1 1.429(2), N1–

1

.3797(15), N3–C11 1.3812(14), N4–C10 1.3972(15), N4–C16 1.2955(14),

N5–C16 1.3786(15), N6–C16 1.3821(15), N7–C5 1.3448(14), N8–C6

.3483(14), C1–C5 1.4166(15), C5–C6 1.4980(15), C6–C10 1.4140(15); C1-

1

6

1

2

N1-C11 123.11(10), N2-C11-N3 108.51(9), C10-N4-C16 121.67(10), N6-

C16-N5 108.38(9). c) Absorption and flurorescence spectrum (excited at

l=327 nm) of 5 in CH CN.

3

6

C21 1.336(2), N2–C21 1.341(2), N3–C21 1.334(2), N4–C11 1.412(2), N4–

C26 1.297(2), N5–C26 1.384(2), N6–C26 1.371(2), C1–C10 1.380(2), C10–

C20 1.500(2), C11–C20 1.380(2), N1–H 0.846(2), N4···H 2.055(2), N1···N4

2

.780(2).

and 6 are fluorescent like some other bipyridine compounds,

for example, 6,6’-diamino-2,2’-bipyridine (see Figure 1c and

the Supporting Information), whereas the related ligand

Table 1 compares some structural details. Protonation of

3

,3’-diamino-2,2’-bipyridine (DABPy) and ligands 1–4 with

ligand 6 occurs, similar to the situation for 2 and 4, at the

guanidinyl group, and not at the pyridine N atom (Figure 3).

In the case of 3,3’-diamino-2,2’-bipyridine, the pyridine N

[39]

homocyclic backbones are not luminescent. The absorp-

tion spectrum of 5 features bands at l=228 and 279 nm, the

latter with a shoulder toward low energies (ca. l=315 nm).

The emission spectrum exhibits a maximum of intensity at

l=451 nm. The absorption spectrum of 6 is quite similar

with bands at l=228 and 280 nm and a shoulder near l=

[33]

atoms are protonated, thus reflecting the lower basicity of

+

amines relative to guanidines. The protons in 1H , 2H ,

+

4H , and 6H are captured in an intramolecular NꢀH···N

asymmetrical bridge, as previously postulated for the cation

+

[36]

3

13 nm. The emission signal of 6 is centered at l=426 nm.

1H on the basis of DFT calculations. Protonation leads

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J. Himmel et al.

Table 1. Structural XRD parameters (bond lengths [ꢃ] and dihedral angle [8] between the two aromatic ring planes) for 1, 2, 4, and 6 and changes upon

protonation.

+

[a]

+

+[a]

+[b]

1

1H

2

2H

4

4H

6

6H

d

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(C=N)dp

(C=N)ip

(CꢀN)dp

1.290(1)

1.295(1)

1.402(1)

1.403(1)

1.389(1)/

1.350(2)//1.350(2)

1.312(2)//1.313(2)

1.423(2)//1.425(2)

1.413(2)//1.411(2)

1.339(2)/1.332(2)//

1.335(2)/1.333(2)

1.364(2)/1.375(2)//

1.359(2)/1.381(2)

2.761(3)//2.749(1)

0.870(3)//0.839(3)

2.020(3)//2.024(4)

142//144

1.289(2)

1.285(2)

1.403(2)

1.413(2)

1.384(2)/

1.387(2)

1.387(2)/

1.385(2)

4.657(1)

–

1.323(3)

1.298(3)

1.430(3)

1.419(3)

1.334(3)/

1.348(3)

1.369(3)/

1.379(3)

2.763(3)

0.806(2)

2.082(3)

142

1.275(2)

1.296(2)

1.399(2)

1.395(2)

1.390(2)/

1.382(2)

1.369(2)/

1.385(2)

3.347(5)

–

1.336(2)//1.339(2)

1.297(2)//1.299(2)

1.429(2)//1.430(3)

1.412(2)//1.413(2)

1.341(2)/1.334(2)//

1.337(2)/1.329(2)

1.384(2)/1.371(2)//

1.380(2)/1.376(2)

2.780(2)//2.773(5)

0.846(2)//0.807(1)

2.055(3)//2.141(4)

143//135

1.300(1)

1.296(1)

1.389(1)

1.397(1)

1.380(2)/

1.381(1)

1.379(2)/

1.382(2)

3.114(4)

–

1.323(3)

–

A

C

H

T

U

N

G

T

R

E

N

U

N

G

A

C

H

T

U

N

G

T

R

E

N

U

N

G

1.412(3)

–

1.365(3)/

1.343(3)

–

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(CꢀN)ip

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(CꢀN)dp1/dp2

1

.378(1)

1.375(1)/

.385(1)

d

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(CꢀN)ip1/ip2

1

d

b

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(N···N)

(NꢀH)

(N···H)

(N···HꢀN)

4.663(2)

–

2.734(3)

0.917(5)

2.037(3)

131

A

C

H

T

U

N

G

T

R

E

N

U

N

G

A

C

H

T

U

N

G

T

R

E

N

U

N

G

–

A

C

H

T

U

N

G

T

R

E

N

U

N

G

dihedral angle

126.1

ꢀ58.4//ꢀ60.5

126.6

ꢀ58.5

ꢀ110.2

ꢀ67.3//ꢀ63.0

ꢀ59.5

ꢀ57.9

+

[

a] Two different molecules in the unit cell. [b] The hydrogen positions at the imino N atoms in 6H are occupied by half of an atom; therefore, the

XRD structural data are averaged values.

nidino)naphthalene and 1,8-bis(dimethylethyleneguanidino)-

[10b,11a]

naphthalene (in CD CN and CD Cl ), respectively.

In

3

2

the case of the diprotonation of 1,4,5,8-tetrakis(tetramethyl-

guanidino)naphthalene, d=14.45ppm in CD CN was report-

3

[15]

ed. Upon protonation, the fluorescence intensity of both

bipyridine ligands 5 and 6 decreased significantly. Further-

more, a shift of the intensity maximum to l_m_a_x=431 and

4

37 nm for 5 and 6, respectively, was observed.

The structures of the protonated ligands were also ana-

lyzed by quantum-chemical calculations. In addition to the

minima found in the XRD analysis, hypothetical structures

were calculated in which the two guanidinyl groups point to

opposite sides, thus prohibiting bridging hydrogen atoms

6

Figure 3. Fraction of the structures of the salt [6H]PF . Thermal ellipsoids

are drawn at the 50% probability level. Selected bond lengths [ꢃ] and

bond angles [8] for [6H]PF : N1–C1 1.412(3), N1–C6 1.323(3), N2–C6

.365(3), N3–C6 1.343(3), C1–C5 1.397(3), C5–C5’ 1.500(5), N1–H

.917(5), N1···N1’ 2.734(3).

6

1

0

(

see Scheme 6 as example). In the corresponding hypotheti-

cal structures of 3 and 4, an opposite orientation of the gua-

+

Scheme 6. The two minima found for 1H (R=R’=Me) and 2H (R=

Me, R’=CH

ꢀ) in quantum-chemical calculations.

Scheme 5. Labeling in the protonated ligands.

2

in all cases to a significant decrease of the N···N separation

nidinyl groups cannot be realized due to the rotation around

(

imino N atoms) by up to 0.6 ꢃ (see Scheme 5 and Table 1).

the central CꢀC bond. Instead, conformational changes

Moreover, the (C=N)_d_pbond length is considerably elongat-

ed on protonation. This elongation can be rationalized by

the presence of resonance structures that lead to delocaliza-

tion of the positive charge within the guanidinyl unit.

within the guanidinyl groups also lead to minima without

hydrogen bridges. As expected, the calculated Gibbs free

energies are higher than for structures without hydrogen

bridges. Quantum-chemical (DFT) calculations were also

Where measurable, the proton in the NH···H bridge gives

employed to compare the proton affinities of the guanidine

1

[40]

rise to a signal at low field in the H NMR spectrum (d=

ligands in CH CN.

3

+

1

0.56 and 10.44 ppm for 1H and 2H , respectively, in

Two empirical formula introduced by Maksi c´ and co-

[41]

CD Cl ). This low-field shift directly signals that the hydro-

workers for the protonation of nitrogen atoms in different

2

+

gen bridges are also present in solution. For comparison, d=

4.28 and 14.22 ppm were reported for the proton in the

NH···H bridge of the proton sponges 1,8-bis(tetramethylgua-

moieties were used to estimate the pK AHCTUNGTERNNUNG( BH ) values in

S

[42]

+

1

CH CN (Table 2). The pK AHCTUNGTRENNG(U BH ) value correlated nicely

3 S

with the strength of the hydrogen bridge. In line with previ-

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

+

Table 2. Estimated pK

nated ligand) in CH

S

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(BH ) values and absolute proton affinities (of the unproto- of 1.66 and 1.70 ꢃ in 5H and 6H , respectively) to

3

CN, calculated NH···N separations, and relative DG8 values (in

the gas phase at 298 K and 1 bar) in the two tautomeric forms of the protonated li-

be most the stable in the gas phase. Conversion into

H (a) and 6H (a) is endergonic by

1 kJmol , respectively. Possibly, the change in the

steric demand of the two guanidinyl groups is one

of the factors that favors protonation at the pyri-

dine nitrogen atom in the gas phase. In general,

p conjugation of the peripheral amino groups is less

effective in dimethylethylene guanidines due to the

+

5

2

7

and

gands 1–4.

ꢀ

1

+

[a]

+

1

H (a)/1H (b)

2H (a)/2H (b)

3H (a)

4H (a)/4H (b)

+

pK

s

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(BH )

25.4/21.7

1.84/4.29

292.9/285.4

ꢀ53.5

22.2/19.7

1.84/4.05

286.6/281.3

ꢀ34.8

21.5

2.98

285.1

–

21.4/19.1

1.92/4.59

284.9/280.3

ꢀ31.4

NH···N [ꢃ]

PA [kJmol

DG8 [kJmol

ꢀ

1 [b]

]

ꢀ

1 [c]

]

+

[

a] No XRD analysis was accomplished for 3H (a). [b] Values of PA refer to the un-

protonated bisguanidine. [c] Gibbs free energy change for conversion of the form b imposed pyramidalization of the amino nitrogen

into a.

atom by the geometry of the imidazoline ring, thus

lowering the pK ACHTUNGTERNNUN(G BH ) values obtained.

S

+

[10b,11a]

Therefore, the resonance stabilization is decreased

and the repulsion between the two sterically demanding

guanidine moieties becomes more dominant. We did not

trace the NꢀH proton in our H NMR spectroscopic experi-

[

18]

ous results, compounds with tetramethylguanidinyl groups

+

exhibit larger pK_S ACHTUNGTRENNUNG( BH ) values than those with the cyclic

guanidinyl groups.

In the case of ligands 5 and 6, four monoprotonated cati-

onic species 5H

1

ments, but the equivalence of both guanidinyl groups in the

NMR spectra argues against form d and in favor of either

form a or c. Of course, if flipping of the proton from one to

the other pyridinyl nitrogen atom in form d is fast on the

NMR timescale, the guanidinyl groups would also appear to

be equivalent. Furthermore, fast exchange processes would

cause forms b and d also to be equivalent. Hence, the seem-

+

ACHTUNGTRENNUNG( a–d) and 6H ACHTNUGTRENNUNG( a–d) were considered

(

Scheme 7). Protonation can take place at the nitrogen atom

ing discrepancy between theory and experiment (crystals of

+

6

H (a) were obtained) can be attributed to the solvent

+

effect of acetonitrile because the pK ACHTUNGTERNNGN(U BH ) and absolute

S

proton affinity (PA) values correlate quite well, whereas the

DG88 values are based on calculations in the gas phase.

Group 10 complexes: In line with the soft character of the

guanidine ligands, Group 10 metals in relatively low oxida-

tion states (+II) should form stable complexes with ligands

Scheme 7. Possible tautomeric forms of the protonated ligands 5 and 6.

1

–6. The following discussion is restricted to experiments for

of a guanidinyl (a,b) or pyridine moiety (c,d), and the intra-

molecular hydrogen bridge can face towards an imino (a,d)

or pyridine (b,c) nitrogen atom.

which a complete characterization of the reaction product

was achieved. The metal/ligand ratios in the isolated prod-

ucts were invariant upon changes in the equivalents of

ligand added to the reaction mixture. The stoichiometric

ratios were later adjusted to the observed product metal/

ligand ratio (given in the Experimental Section) to optimize

the yield with respect to both reactants.

+

The XRD analysis of 5H indicates that form a (with a

NꢀH···N distance of 1.93 ꢃ) is favored over all the other

tautomers, in line with the results of our quantum-chemical

calculations on basicity in acetonitrile. Therein, the nitrogen

atoms of the guanidinyl groups are the stronger bases in the

Reaction of [NiCl₂

ACHTUNGTRNENUNG( dme)] (dme=dimethoxymethane)

molecules, and generally intramolecular hydrogen bridges

with 5 furnished complex [Ni(5) ]Cl with octahedral coordi-

3

2

+

II

toward the guanidinyl group lead to higher pK

A

H

U

G

R

N

U

G

nation of the Ni atom as the only product. No other prod-

uct was obtained in experiments in which less than three

equivalents of 5 were used. Yellow crystals of this com-

S

(

Table 3).

On the contrary, our calculations predicted tautomer d

with the shortest NꢀH···N bridges (with a NꢀH···N distance

pound were grown by slow diffusion of Et O into a solution

2

of CH Cl (see Figure 4 for a visualization of the

2

structure). Interestingly, the ligand exclusively coor-

dinates through the pyridine nitrogen atoms to the

metal center. All six guanidinyl groups remain un-

coordinated, although these groups are preferred in

the case of protonation. The six NiꢀN bond lengths

+

Table 3. Estimated pK

ed ligand) in CH

most stable tautomer in the gas phase at 298 K and 1 bar) of the protonated ligands

s

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(BH ) values and absolute proton affinities (of the unprotonat-

3

CN, calculated NH···N separations, and DG8 values (relative to the

+

for the tautomers a–d of 5H and 6H .

+

5

H

6H

a

b

c

d

a

b

c

d

cover the range from 2.064(4) to 2.108(3) ꢃ (for

+

NiꢀN7 and NiꢀN15, respectively). The coordina-

pK

s

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(BH )

23.4

1.93

18.9

3.57

13.6

2.08

20.8

1.66

19.9

1.91

16.6

1.71

14.4

2.63

19.5

1.70

NH···N [ꢃ]

PA [kJmol

DG8 [kJmol

tional mode can be compared with that reported

ꢀ

1

]

289.0 283.9 274.7 283.8

14 48

281.8 280.0 276.2 281.0

21 16 32

II

for the triflate salts of the tris-chelate Co , Ni , and

ꢀ

1

]

7

0

II

Zn complexes of the ligand 3,3’-diamino-2,2’-bipyr-

Chem. Eur. J. 2013, 00, 0 – 0

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

5

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ÞÞ

These are not the final page numbers!

J. Himmel et al.

2

+

Figure 4. Visualisation of the dication [Ni(5)

3

]

3 2

in the salt [Ni(5) ]Cl .

Thermal ellipsoids are drawn at the 50% probability level. Selected bond

lengths [pm] and bond angles [8]: Ni–N7 2.064(4), Ni–N8 2.079(4), Ni–

N15 2.108(3), Ni–N16 2.094(4), Ni–N23 2.093(4), Ni–N24 2.083(3), N1–

C1 1.389(5), N1–C11 1.291(6), N4–C10 1.372(6), N4–C16 1.322(6), N9–

C21 1.385(6), N9–C31 1.311(6), N12–C30 1.387(5), N12–C36 1.309(6),

N17–C41 1.366(5), N17–C51 1.317(6), N20–C50 1.388(6), N20–C56

1

7

.308(5); N7-Ni-N8 79.28(14), N15-Ni-N16 78.54(14), N23-Ni-N24

9.12(13).

Figure 5. Molecular structures of the dinuclear complexes a) [{PdCl-

A

H

U

G

R

N

U

G

3 5 2 3 5 2

H )} (5)] and b) [{PdCl ACHTGRUNTNEUNG( C H )} (6)]. Thermal ellipsoids are drawn at

[37]

idine (DABPy). In this case, the amino groups are, like

A

H

U

G

R

N

3

H

5

2

the guanidinyl groups in [Ni(5) ]Cl , not involved in the co-

2.3962(15), Pd1–C11 2.124(5), Pd1–C12 2.106(7), Pd1–C13 2.117(5), N1–

C1 1.385(6), N1–C6 1.320(6), N2–C6 1.363(6), N3–C6 1.357(6), N4–C2

3

2

ordinative bond. The reaction of [NiCl ACHTUNGTERNN(UNG dme)] with 6 instead

2

1

.353(5), C1–C2 1.406(6), C2–C2’ 1.505(8); N4-Pd1-Cl1 92.66(11). Select-

ed bond lengths [8] and bond angles [8] for [{PdCl(C )} (6)]: Pd1···Pd2

.279(27), Pd1–N7 2.130(2), Pd1–Cl1 2.3857(9), Pd1–C21 2.132(3), Pd1–

of 5 appears to proceed similarly. Unfortunately, a structural

analysis was not possible. The ligand/metal ratio in the prod-

uct complex could not be changed by decreasing the equiva-

lents of ligand applied in the reaction, thus arguing for a

thermodynamic reaction control. In preliminary experi-

ments, we tried to use [Ni(5) ]Cl as a ligand for the con-

A

H

U

G

R

N

3

H

5

2

3

C22 2.119(3), Pd1–C23 2.1003(17), Pd2–N8 2.134(2), Pd2–Cl2 2.3841(8),

Pd2–C24 2.1098(17), Pd2–C25 2.1337(17), Pd2–C26 2.1053(17), N1–C1

1

.392(3), N1–C11 1.296(3), N2–C11 1.387(4), N3–C11 1.366(4), N4–C10

.381(3), N4–C16 1.312(3), N5–C16 1.373(4), N6–C16 1.372(4), N7–C5

.360(3), N8–C6 1.358(3), C5–C6 1.481(3); N7-Pd1-Cl1 93.40(7), N8-Pd2-

3

2

struction of tetranuclear complexes. However, the reaction

between [Ni(5) ]Cl and an excess amount of [NiCl (dme)]

Cl2 91.73(7).

AHCTUNGTRENNUNG

3

2

led to an instable purple crude product, the NMR spectra

analysis of which provided additional peaks outside the dia-

magnetic region. Hence, the coordination of at least one Ni

ing Information for comparison of the experimental and cal-

culated structural parameters).

II

atom by the guanidinyl groups is presumed. Unfortunately,

further investigation and isolation of a clean product has

been so far impossible due to decomposition of the raw

Such a type of coordination is so far unprecedented for

related ligands, including 3,3’-diamino-2,2’-bipyridine li-

[37]

gands, which exclusively act as bidentate ligands. General-

II

2

product.

Reaction of 5 or 6 with [{PdCl

ly, bpy ligands bind to the Pd center in a N,N’-k fashion.

3

A

H

U

G

R

N

U

G

For example, the reaction between the allyl complex

3

5

2

3

pletely different products, namely, the dinuclear complexes

[{PdCl(h -C H Me)} ] and bpy afforded the salt [Pd(h -

3 4 2

3

2

[43]

[{PdCl

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C H )} (5)] and [{PdCl

A

H

U

G

R

N

U

(h -C H )} (6)]. The ligand/

C H Me) ACHTUNRTEGNNUN(G bpy)]Cl with N,N’-k -coordinated bpy ligands.

3 4

3

5

2

3

5

2

II

3

metal ratio in the Pd product complexes could not be

changed by increasing the equivalents of the ligand applied

The PdꢀN bond lengths in the salt [Pd(h -C H Me)

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(bpy)]-

3

4

AHCTUNGTREG(NNUN CF SO ) were determined to be 2.089(2) and 2.085(3) ꢃ

3

2

in the reaction. Crystals were obtained by diffusion of Et O

and are slightly shorter than the PdꢀN bond lengths of

2

3

into a solution of CH Cl (the molecular structures are dis-

2.118(4) and 2.130(2)/2.134(2) ꢃ in [{PdCl

A

H

U

G

R

N

U

G

2

3

5

2

3

played in Figure 5). Again, coordination exclusively occurs

through the pyridine nitrogen atoms. However, the ligands

are now bound to two rather than one metal atom. The Pd

atoms are clearly separated (Pd···Pd=3.394(2) and

and [{PdCl ACHTUNTGNERNUG( h -C H )} (6)], respectively. Most likely steric

3 5 2

constraints imposed by the two guanidinyl groups in the 3

and 3’ positions are responsible for the unusual coordina-

tion.

The dynamic behavior of the allyl ligands was studied in

VT-NMR spectroscopic experiments. At room temperature,

only one signal for the syn-proton and one for the anti-

proton resonances of the allyl group and one resonance

3

3.279(3) ꢃ in [{PdCl

A

H

U

T

E

N

(h -C H )} (5)] and [{PdCl

A

H

U

G

R

N

U

G

3

5

2

C H )} (6)], respectively), but oriented with their occupied

3

5

2

d_z

2

orbitals toward each other. The molecular structures

were also confirmed by DFT calculations (see the Support-

&

6

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

ꢀ

1 [31]

very low overall averaged TOF of 9 h . Under the same

II

conditions, a previously reported Pd catalyst with a pincer

CNC bis-carbene ligand presented by Peris et al. yielded

trans-stilbene in a yield of >85% after 4 hours of reaction

ꢀ

1

[47]

Scheme 8. Typical dynamic process in the Pd–allyl complexes observed

by VT-NMR spectroscopic analysis.

with a TOF of 500 h in the first 30 minutes.

The reaction of 1, 2, and 4 with the Zeise dimer [{PtCl-

AHCTUNGTREGUN(NN C H )} ] were already shown to lead to the complexes

2

4

2

1

signal of the central allyl proton can be detected due to fast

fluxional processes (Scheme 8). By lowering the tempera-

ture, signal splitting was observed. Splitting of the central

[PtCl AHCTUNGRETNNUNG( C H ) ACHTNUTGNERUNG( k -1)], [PtCl CHTUNGRNETUN(G C H ) ACHTUGNETRNUNG( k -2)], and [PtCl ACHTUNGTRENNUNG( C H )-

₂A

(k -4)]. These complexes, in which only one guanidinyl

group is bound to the metal center, were shown to catalyze

2 2 4 2 4 2 2 4

1

AHCTUNGTRENNUNG

[30,31]

allyl proton resonance occurred between 20 and 108C in

the hydrosilylation of olefins. A structural characteriza-

tion of [PtCl ACTHNGUTRENNUG( C H ) ACTHGTNUERNN(UG k -4)] has not yet been possible, but

2 2 4

crystals suitable for a single-crystal X-ray diffraction analysis

were obtained (the experimental structure is shown in

Figure 6).

3

1

[

{PdCl

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C H )} (6)] and between 0 and ꢀ108C in [{PdCl-

3

5

2

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C H )} (5)]. The coalescence temperature for the termi-

3

5

2

nal allyl proton resonances was similar for both complexes

(

0 and ꢀ208C; see the Supporting Information for selected

spectra).

The geometry of the complexes motivates oxidation ex-

[

44]

periments, which should lead to a direct PdꢀPd bond.

However, first test experiments with disulfides as oxidation

reagents were unsuccessful (see the Experimental Section).

Even at elevated temperatures, no reaction was monitored,

thus indicating a high complex stability. Furthermore, ex-

periments were carried out to synthesize a cationic hydride

complex with a Pd···H···Pd bridge. By using triethylsilane

as a hydride donor, protonation and dissociation of the allyl

group was observed accompanied by decomposition of the

dinuclear complexes.

[45]

In additional experiments, we tested the performance of

1

3

^Fⁱ^g^u^r^e⁶^.^M^o^l^e^c^u^l^a^r^s^t^r^u^c^t^u^r^e^o^f^[^P^t^C^l2

A

H

U

T

E

N

G

A

H

U

G

E

U

G

the two Pd complexes [{PdCl

A

H

U

G

R

N

U

G

A

T

N

T

E

N

(h -

2

4

3

5

2

are drawn at the 50% probability level. Selected bond lengths [ꢃ] and

bond angles [8]: Pt1–Cl1 2.3083(19), Pt1–Cl2 2.290(2), Pt1–N1 2.088(6),

Pt1–C31 2.135(7), Pt1–C32 2.137(8), N1–C1 1.428(9), N1–C21 1.342(9),

N2–C21 1.336(9), N3–C21 1.341(9), N4–C11 1.385(9), N4–C26 1.292(9),

N5–C26 1.370(9), N6–C26 1.400(9), C1–C10 1.366(9), C10–C20 1.492(10),

C11–C20 1.411(10); Cl1-Pt1-Cl2 177.30(8); C31-Pt-C32 38.0(3), N1-Pt1-

C31 163.6(3), N1-Pt1-C32 158.4(3).

C H )} (6)] in the Heck reaction outlined in Scheme 9. Li

3

5

2

Scheme 9. The performed Heck reaction.

et al. introduced [Pd

A

H

U

G

R

N

(tmg) ]Cl (tmg=tetramethylguanidine,

After coordination, ligand 1 still seems to be a strong ni-

trogen base. If the complexation reactions between ligand 1

4

2

HNC(NMe ) ) as an especially efficient and air-stable cata-

ACHTUNGTRENNUNG

2

[46]

II

lyst for Heck reactions in 2005. Table 4 contains informa-

tion about the yield of trans-stilbene, in relation to the reac-

tion time, achieved in our experiments with 5 and 6 as cata-

lysts. Both compounds show satisfying catalytic activity, with

a turnover frequency (TOF) in the first few minutes of ap-

and Pd or Pt precursors are carried in NMR tubes in air,

small amounts of the zwitterions [PdCl₃(1H)] and [PtCl -

(1H)] crystallized (see the Supporting Information and

AHCTUNGTRENNUNG

3

AHCTUNGTRENNUNG

ref. [30]). In these cases, protonation and coordination oc-

curred at the same time, and the proton is stabilized by an

NꢀH···Cl interaction. In other cases, protonation leads to

ꢀ

1

3

proximately 630 and 900 h for [{PdCl ACHTUNGTRNEU(GN h -C H )} (5)] and

3 5 2

3

[47]

[

{PdCl

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C H )} (6)], respectively.

The catalysis with

destruction of the coordinative bond.

3

5

2

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C H )} (6)] gives a higher yield of trans-stilbene

Subsequently 5 and 6 were treated with the Zeise dimer

3

5

2

(

91%). For comparison, [PdCl

A

H

U

G

R

N

U

G

[{PtCl ACHTUNGRTNNEG(U C H )} ]. The products turned out to be the mononu-

2 2 4 2

2

bene in >95% yield after 5 hours of reaction, but with a

clear complexes [PtCl (5)] and [PtCl (6)] (Figure 7). In both

2 2

[

a]

Table 4. Comparison of yield for the Heck reaction of PhI with styrene to form trans-stilbene.

[b]

[c]

Cat.

t [min]

Selectivity

5

10

20

30

40

55

70

85

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

[{PdCl

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C

3

H

5

)}

2

(5)]

(6)]

20, 631

26, 898

37, 663

40, 773

56, 579

60, 658

68, 508

75, 617

74, 438

82, 544

76, 336

88, 443

77, 269

89, 358

81, 234

91, 304

14:1

12:1

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

[{PdCl ACHTUNGTRENNUNG( h -C

5

[

a] The reactions were carried out in DMF at reflux (under Ar with 0.1 mol% catalyst and NaOAc as the base). [b] Reported as: yield [%], TOF [mol of

product/(mol of Pdꢄh)]. Yield was determined by GC-MS based on moles of product versus moles of iodobenzene. [c] Selectivity of trans-stilbene and

1

,1-diphenylethylene was determined by H NMR spectroscopic analysis after 4.5 h.

Chem. Eur. J. 2013, 00, 0 – 0

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

7

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J. Himmel et al.

Figure 7. Molecular structures of the complexes a) [PtCl

b) [PtCl (6)]. Thermal ellipsoids are drawn at the 50% probability level.

Selected bond lengths [ꢃ] and bond angles [8] for [PtCl (5)]: Pt–Cl1

.3100(9), Pt–Cl1’ 2.3099(9), Pt–N4 2.023(2), N1–C1 1.386(3), N1–C6

.327(3), N2–C6 1.364(4), N3–C6 1.369(3), N4–C5 1.371(4), C5–C5’

.476(5); Cl1-Pt-Cl1’ 88.84(5), N4-Pt-N4’ 80.62(13), C1-N1-C6 122.0(2).

2

(5)] and

2

Scheme 10. Group 10 metal complexes of ligands 5 and 6.

2

1

in the chlorido complexes. A remarkable detail of the struc-

tures is the large X-Ni-X angles; for example, the Br-Ni-Br

Selected bond lengths [ꢃ] and bond angles [8] for [PtCl

2

(6)]: Pt–Cl1

2

1

8

.2981(10), Pt–Cl2 2.2990(10), Pt–N7 2.009(3), Pt–N8 2.015(3), N1–C1

angle in [NiBr (3)] measures 141.33(2)8. Although the po-

2

.375(4), N1–C11 1.312(5), N2–C11 1.381(5), N3–C11 1.362(5), N4–C10

.370(5), N4–C16 1.307(5), N5–C16 1.356(6), N6–C16 1.374(5), N7–C5

.375(4), N8–C6 1.373(5), C5–C6 1.466(5); Cl1-Pt-Cl2 88.08(4), N7-Pt-N8

0.55(12), C1-N1-C11 122.9(3), C10-N4-C16 124.6(3).

tential-energy curve for changing this angle is flat, electronic

rather than packing effects might be responsible for these

[19]

high values. Complex [NiCl (3)] is depicted in Figure 9a

2

from another perspective, thus showing the twist imposed

on the conformation of the metal complex as a consequence

of the chiral center. The guanidinyl groups “transmit the

chiral information” from the asymmetric center to the sub-

strate binding site, thus leading to a situation similar to that

in complexes with the 2,2’-bis(diphenylphosphino)-1,1’-bi-

naphthyl (BINAP) ligand, which is one of the most common

II

2

complexes the Pt atom is coordinated in a k -N,N’-mode by

the two bipyridine nitrogen atoms. The unit cell contains

two slightly different molecules. The PtꢀN bond lengths

measure 2.023(2) and 2.009(3)/2.015(3) ꢃ in [PtCl (5)] and

PtCl (6)], respectively. The dihedral angle between the two

pyridine ring planes measures 32.83/29.72 and 18.14/19.748

in [PtCl (5)] and [PtCl (6)], respectively. The results of the

2

[

2

[48]

ligands used in enantioselective catalysis.

2

coordination-chemistry experiments with ligand 5 and 6 are

summarized in Scheme 10.

Paramagnetic NMR spectroscopy: A key goal of this study

was the analysis of the spin-density distribution in paramag-

II

The reluctance of the guanidinyl groups in 5 and 6 to par-

ticipate in the direct coordinative link contrasts with the co-

ordination chemistry of the related ligands 1–4. Previously,

netic Ni complexes. To this end, the Ni complexes

[NiX (2)], [NiX (3)] (X=Cl and Br), [Ni(5) ]Cl , and

2

3

2

[Ni(6) ]Cl were studied in solution by using paramagnetic

3

2

II

we reported on the synthesis and characterization of the Ni

NMR spectroscopy in combination with quantum-chemical

calculations. These studies provide information about possi-

ble spin-density delocalization from the Ni centers onto the

ligand. Moreover, dynamic processes in the complexes were

analyzed by VT-NMR spectroscopic studies. In accordance

[7,26]

complexes [NiX (1)] (X=Cl or Br).

Figures 8 and 9

show the structures of the four newly synthesized Ni com-

2

II

plexes [NiX (2)] and [NiX (3)], the latter being the first

2

structurally authenticated complexes of the binaphthyl sys-

tems. These complexes were synthesized by a ligand-substi-

II

with other previously studied Ni –halide complexes that fea-

[7]

II

tution reaction between the free ligands and [NiX

A

H

U

G

R

N

U

G

ture bisguanidines as chelating ligands, the tetrahedral Ni

2

II

Unfortunately, the syntheses of the corresponding Ni com-

plexes of ligand 4 were not successful because the initially

formed purple complexes were not stable in solution and de-

composed.

complexes gave rise to well-resolved NMR spectra. The

signal assignment is based on the analysis of the chemical

shifts and the line shape as a function of the temperature,

1

3

1

C– H correlation data, and comparison with DFT calculat-

ed spin-density distributions.

2

All four complexes feature N,N’-k -bonded ligands. The

NiꢀN bond lengths are slightly shorter in the bromido than

&

8

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Chem. Eur. J. 0000, 00, 0 – 0

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

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3

/10

5/8

tons (H , H ), which undergo a low-field shift, could be

1

distinguished by using H– H COSY experiments.

Only one signal for the methyl protons and two for the

CH groups of the guanidinyl moiety can be observed at

2

room temperature because of fluxional processes. However,

splitting of the broad central signal of the methyl protons is

visible in both complexes at ꢀ408C (200 MHz, CD Cl ). All

2

the signals sharpened at ꢀ808C to two discrete peaks with a

broader one at d=45.34 and 22.59 ppm with line widths of

Dn₁_/₂=170 and 225 Hz (methyl groups I) and a sharp one at

d=8.98 and 7.39 ppm with line widths of Dn₁_/₂=30 and

4

8 Hz (methyl groups II) of the complexes X=Cl and Br,

I

respectively. The ratio of the different line widths Dn₁

/

/2

II

Dn₁_/₂of the two methyl groups at ꢀ808C can be used to de-

termine whether Fermi-contact or dipol interactions mainly

[49,50]

causes the line broadening.

If the latter is dominant, the

ꢀ

6

line width ratio should equal the ratio of the r values. If

one assumes the value r (the distance between the paramag-

netic center and the C nucleus of the observed methyl

group) to be the value from the experimental XRD data,

one obtains a ratio r (methyl groups I)/r (methyl groups

II) of 13.6:1 and 12.9:1 for X=Cl and Br, respectively.

Hence, it is poorly consistent with the average ratio of

ꢀ

6

ꢀ6

I

II

Dn₁_/₂/Dn₁_/₂=5.7:1 and 4.7:1 for [NiCl (2)] and [NiBr (2)],

2

respectively. If the Fermi-contact interaction is dominant,

the ratio of the squared temperature-dependent paramag-

netic shift Dd between ꢀ80 and 208C should agree with

Figure 8. Molecular structures of the two complexes a) [NiCl

b) [NiBr (2)]. Selected bond lengths [ꢃ] and angles [8] for [NiCl

2

(2)] and

(2)]: Ni–

I

II

Dn /Dn

.

1/2

2

1

/2

I

2

II 2

Cl1 2.2557(14), Ni–Cl2 2.2488(15), Ni–N1 2.027(4), Ni–N4 2.017(4), N1–

C1 1.444(6), N1–C13 1.328(6), N2–C13 1.361(6), N3–C13 1.364(6), N4–

C12 1.426(6), N4–C18 1.323(6), N5–C18 1.361(6), N6–C18 1.365(6), C1–

C6 1.389(7), C6–C7 1.490(7), C7–C12 1.388(7); Cl1-Ni-Cl2 119.81(6); N1-

Ni-N4 99.31(15), C1-N1-C13 116.6(4), C12-N4-C18 117.6(4). Selected

The ratio amounts to (Dd ) /

ACHTUNGTRENNUNG( Dd ) =7.3 and 5.7 and,

therefore, it is in better agreement with the average ratio of

I

II

Dn₁_/₂/Dn₁_/₂. We conclude that the Fermi-contact interaction

has the dominant effect on the relaxation processes and line

bond lengths [ꢃ] and angles [8] for [NiBr

2

(2)]: Ni–Br1 2.3939(9), Ni–Br2

broadening. Splitting of the two CH resonance signals into

2

1

.4192(7), Ni–N1 1.984(2), Ni–N4 1.988(2), N1–C1 1.443(3), N1–C13

four occurs at similar temperature in complex [NiCl (2)]. By

2

.323(3), N2–C13 1.360(3), N3–C13 1.357(4), N4–C12 1.433(3), N4–C18

.319(3), N5–C18 1.373(3), N6–C18 1.355(3), C1–C6 1.394(4), C6–C7

.490(4), C7–C12 1.403(4); Br1-Ni-Br2 136.12(3), N1-Ni-N4 102.50(9),

using the Eyring equation, the Gibbs free activation energy

°

of the fluxional process was estimated to DG =(44ꢁ

ꢀ1

C1-N1-C13 117.2(2), C12-N4-C18 116.9(2).

2) kJmol with an averaged reaction rate of 580 s at a co-

alescence temperature of (ꢀ45ꢁ5)8C for both signals.

Upon cooling down, the CH groups in [NiBr (2)] differ in

2

The signals of the Ni complexes with ligand 2 were of rel-

atively narrow line widths (Figure 10); therefore, integration

allowed the separation of the signals into aromatic, methyl,

and ethylene protons (see Table S1 in the Supporting Infor-

their fluxional behavior. The coalescence temperature is at

(ꢀ65ꢁ5)8C for the low-field-shifted signal pair and at

(ꢀ35ꢁ5)8C for the other pair. The reaction rates of 206

ꢀ

1

and 1150 s , respectively, can be extracted from the temper-

°

mation). On account of the C symmetry, a total of four sig-

ature that leads to a Gibbs free activation energy of DG =

2

ꢀ

1

nals for the aromatic protons is expected. The assignment of

the aromatic protons was realized by considering typical fea-

tures of the electron–nucleus interactions in paramagnetic

(43ꢁ2) kJmol . Figure 10 displays the H NMR spectra re-

corded at 200 MHz for these two complexes at room tem-

1

3

perature and ꢀ808C. Assignment of the C NMR resonance

[49]

compounds. It was assumed that the signals at d=ꢀ17.71

and ꢀ17.16 ppm for the chlorido and bromido complexes,

respectively, correspond to the aromatic proton closest to

signals was accomplished through 2D heteronuclear chemi-

1

3

cal-shift correlation (HETCOR) experiments and C NMR

spectroscopic data without broadband H decoupling. The

1

2

/11

the paramagnetic center (H ). Due to spin polarization,

the sign of the Fermi-contact interaction alternates with the

number of bonds between the paramagnetic center and the

observed proton. Therefore, the second signal with a nega-

tive contact shift at d=ꢀ11.48 and ꢀ12.14 ppm for the

chlorido and bromido complexes, respectively, and was as-

latter analysis provides three singlet signals for the quater-

13

nary C atoms and four doublets for the aromatic C NMR

nuclei. In neither of the experiments, resonance signals or

heteronuclear J coupling of the CH and CH group can be

2

3

[51]

observed.

1

Integration of the signals in the H NMR spectrum of

4/9

signed to H . The remaining two signals of aromatic pro-

[NiX (3)] complexes returned the expected 3:1 ratio for

2

Chem. Eur. J. 2013, 00, 0 – 0

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&

9

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J. Himmel et al.

methyl and aromatic protons,

with an overall number of

3

6 protons (see Table S2 in the

Supporting Information). The

assignment of the signals can be

accomplished in a similar way

as for [NiCl (2)] and [NiBr (2)],

2

again under the assumption of

the leading role of the Fermi-

contact interaction. A high-field

shift, or rather negative contact

shift, of the resonance signal

can be observed if an even

number of bonds separates the

nuclei in the aromatic ring

system from the paramagnetic

2

/12

center, for example, H

C

or

(see Table 5 and Fig-

ure 11).

Relative to the complexes of

ligand 2, [NiCl (3)], and

1

/11

2

[

NiBr (3)] are rigid on the

2

Figure 9. Molecular structures of a) [NiCl

probability level. Selected bond lengths [ꢃ] and bond angles [8] for [NiCl

2

1

2

(3)] and b) [NiBr

2

(3)]. Thermal ellipsoids are drawn at the 50%

(3)]: Ni–Cl1 2.2632(12), Ni–Cl3

.2495(13), Ni–N1 2.020(3), Ni–N4 1.990(3), N1–C1 1.427(5), N1–C21 1.337(5), N2–C21 1.353(5), N3–C21

NMR timescale and four dis-

tinct methyl resonances are visi-

2

.363(6), N4–C11 1.427(5), N4–C26 1.335(5), N5–C26 1.369(5), N6–C26 1.340(5), C1–C10 1.379(6), C10–C20 ble at room temperature in the

.509(6), C11–C20 1.389(6); Cl1-Ni-Cl3 130.30(5), N1-Ni-N4 103.64(13), C1-N1-C21 119.1(3), C11-N4-C26

20.6(3). Selected bond lengths [ꢃ] and bond angles [8] for [NiBr (3)]: Ni–Br1 2.4100(4), Ni–N1 1.9770(18),

1

13

H and the C NMR spectra.

2

This time, the carbon atoms of

the methyl groups give rise to

N1–C1 1.424(3), N1–C11 1.343(3), N2–C11 1.356(3), N3–C11 1.343(3), C10–C10’ 1.513(5); Br1-Ni-Br1’

1

41.33(2), N1-Ni-N1’ 103.22(11), C1-N1-C11 117.62(18).

1

Figure 10. H NMR spectra of [NiCl

2

(2)] and [NiBr

2

(2)] (200 MHz, CD

2

Cl

2

). The area in gray contains the signals from traces of uncoordinated ligand

“

L”.

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10

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

1

13

1

Figure 11. H NMR spectrum at 600 MHz (top) and C{ H} NMR spectrum at 150 MHz (bottom) of [NiCl

from the solvent and traces of the uncoordinated ligand, respectively.

2 2 2

(3)] (228C; CD Cl ). # and * denote signals

1

3

Table 5. C NMR chemical shifts

2

d [ppm] for [NiX (3)] at 228C

1

13

NMR spectra of the complexes. In the H and C spectra,

both complexes display the resonances of the guanidinyl

moiety in the diamagnetic region (see Table S3 in the Sup-

porting Information), and cross peaks in the heteronuclear

correlation (HETCOR) NMR experiments are visible. As

the through-space and through-bond-length between the

paramagnetic center and these nuclei are quite large, the

spectroscopic behavior of these complexes is comparable to

those of the diamagnetic complexes of 5 and 6. In fact, the

(

2 2

150 MHz, CD Cl ).

X=Cl

X=Br

X=Cl

X=Br

1

2

3

4

5

6

7

8

/11

/12

/13

/14

/15

/16

/17

/18

9/19

10/20

Imin

a

C

ꢀ86.2

347.9

84.2

222.9

72.7

184.8

79.3

173.5

ꢀ112.1

349.7

83.8

223.0

71.0

185.7

77.5

173.2

C

Me

112.7

326.8

657.1

315.7

97.3

2.2

112.3

327.9

685.7

281.1

88.7

2.2

ꢀ2.7

1

temperature-dependent paramagnetic shift in the H NMR

spectra of these signals was not experimentally observed

upon cooling. On the other hand, the aromatic part of the

c

b,d

1.0

1

compounds gave no well-resolved signals in the H NMR

spectrum. Only one signal at d=56.41 and 56.72 ppm arises

for [Ni(5) ]Cl and [Ni(6) ]Cl , respectively, thus showing a

3

2

3

2

1

3

1

quartets in 1D C– H coupled spectra. Figure 11 displays

temperature-dependent paramagnetic shift and significant

line broadening because of the proximity to the paramagnet-

1

13

1

the H and C{ H} NMR spectra recorded at 600 and

50 MHz, respectively, of [NiCl (3)] at room temperature

1

ic center. Hence, two of three H NMR signals of the bipyri-

2

(

see the Supporting Information for the Curie plot of the

dine moiety could not be detected due to fast relaxation

1

II

VT H NMR resonances of both the Ni complexes).

that comes from the proximity to the Ni center. In the

1

13

The H NMR chemical shifts of the bromido derivative

C NMR spectrum of [Ni(5) ]Cl and [Ni(6) ]Cl , two peaks

3

2

3

2

[

NiBr (2)] differ considerably from the shifts of [NiCl (2)]

of the aromatic ring at d=641.97/193.98 and 642.00/

2

(

see Figure 10 and Figure S35 in the Supporting Informa-

187.24 ppm, respectively, were observed. One-dimensional

C– H-coupled NMR spectroscopic data provided broad

1

3

1

tion), whereas such differences for complexes of ligand 3

are less pronounced (see Figure S36 in the Supporting Infor-

singlets for the two signals. The singlets can be caused by

either the quaternary or the tertiary carbon atoms of the bi-

pyridine ring that suffer fast relaxation processes; therefore,

possible multiplet splitting cannot be resolved.

mation). The CH group oriented toward the Ni center in

3

[

NiCl (2)] showed a chemical shift of dꢂ45 ppm at low tem-

2

peratures, whereas the corresponding shift in [NiBr (2)] is

2

only d= +15 ppm. These differences are due to differing

pseudocontact shifts. The size of the pseudocontact shift

contribution is proportional to the magnetic anisotropy Dc,

Comparison between experimentally determined and calcu-

lated paramagnetic shifts: The observed chemical shift of a

paramagnetic compound is the sum of diamagnetic (or orbi-

tal d_o_r_b) and paramagnetic (or hyperfine d_H_F_,_T) contributions.

If the Fermi-contact term dominates the hyperfine shift,

contributions caused by dipolar interactions are negligible,

hence the observed chemical shift can be approximated as

given in Equation (1).

ꢀ

3

to r (r=distance between Ni centre and observed nu-

cleus), and to the relative orientation of the Ni···H

[49,50]

vector.

The Ni···CH₃distances as extracted from the

solid-state molecular structures are very similar for both

complexes (~3.2 ꢃ) so that the observed NMR effects are a

hint of the differing size of the magnetic anisotropies in

these complexes.

The different coordination mode of the bisguanidine li-

gands in [Ni(5) ]Cl and [Ni(6) ]Cl is also reflected in the

^d^¼^dorb ^þ^dHF;T ^ꢂ^dorb ^þ^dcon

ð1Þ

3

2

3

2

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www.chemeurj.org

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11

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J. Himmel et al.

1

The Fermi-contact term d_c_o_nis directly proportional to the

residual spin density 1_a_bat the respective nucleus. Spin den-

sities can be estimated from DFT calculations and the

In general, correlation of the H NMR spectroscopic data

is worse (see the Supporting Information), but still satisfac-

tory and confirms the previous assignment. Furthermore,

the results of the spin-density calculations and calculated

chemical shift afforded the differentiation and assignment of

Fermi-contact term d

Equation (2).

can be calculated by following

con

[

50,52,53]

a

c

the methyl groups Me and Me of the complexes [NiCl (3)]

and [NiBr (3)] (Table 5). Assignment of Me and Me was

ambiguous as their chemical-shift values are very similar in

both experiment and calculation. The correlation data be-

tween the experimental and calculated chemical shift of the

C and H NMR spectra of compounds [NiCl (2)] and

NiBr (2)] are displayed in the Supporting Information.

As in the C NMR correlation data of the complexes

NiCl (3)] and [NiBr (3)] described above, the calculation

and experimental results are consistent, apart from the

nuclei close to the metal center. Due to the smaller chemi-

cal-shift range of the H NMR spectra from the Ni com-

plexes in this investigation, the contributions from the pseu-

docontact shift become more visible in the correlations be-

tween the experimental and calculated shifts by using Equa-

tions (1) and (2).

The spin-density distribution from quantum-chemical cal-

culations is plotted in Figure 13 for both [NiCl (2)] and

NiCl (3)]. In agreement with the NMR spectroscopic re-

2

B

b

d

m m g ðS þ 1Þ

0

2

ð2Þ

^dcon

¼

1_a_b

9

k

T

Herein, m denotes the permeability of a vacuum (4pꢄ

0

ꢀ

7

ꢀ1

ꢀ7

ꢀ1

10

NA ), m the Bohr magneton (9.274015ꢄ10 JT ), g

13

1

B

2

the free-electron g factor (g=2.0023), S the total spin, k the

[

2

ꢀ

23

ꢀ1

Boltzmann constant (1.380658ꢄ10 JK ), and T the abso-

13

lute temperature (in Kelvin). The first factor in Equation (2)

[

2

is described by physical constants, thus amounting to m

m g /9k=m=23.5ꢄ10 ppmK a.u. . In the constant m, the

B

0

2

6

ꢀ1

conversion factor from the SI unit into atomic units (a =

1

0

ꢀ

12

5

2.9177ꢄ10 m) and into ppm was taken into account. The

experimentally observed chemical shift d_e_x_pcan be com-

pared with the calculated chemical shift d_c_a_l_c_dobtained by

using Equations (1) and (2). The orbital terms d_o_r_bused to

determine the d_c_a_l_c_dvalues are taken from the protonated

+

bisguanidine ligands 2H and 3H as diamagnetic reference

2

systems.

[

2

Figure 12 displays the correlation between the experimen-

tal and the calculated chemical shift of the C NMR spectra

sults, it can be seen that the guanidinyl groups (mainly N=

C) host a significant amount of the spin density through

direct delocalization from the singly occupied molecular or-

bitals (SOMOs), whereas the aromatic backbone experien-

ces spin density through spin polarization.

1

3

of compounds [NiCl (3)] (see the Supporting Information

2

for [NiBr (3)]). An excellent correlation is obtained for

2

Figure 12. Comparison between the calculated dcalcd and experimentally

1

3

observed chemical shifts dexp of the C NMR spectroscopic data of

NiCl (3)]. (The optimization and spin-density calculations were carried

out by using the Turbomole program package with the B3LYP functional

and def2-TZVPP basis set.)

[

2

Figure 13. Spin-density distribution in [NiCl

(right) from quantum-chemical calculations.

2 2

(2)] (left) and [NiCl (3)]

most of the signals and to a lower extent for the signals of

SQUID magnetometric experiments: Superconducting

quantum interference device (SQUID) measurements were

carried out for the four complexes [NiBr (2)], [NiBr (3)],

Imin

10/20

a

C

, C , and Me , respectively. The deviations derive

from additional contributions to the hyperfine shift, mainly

metal- and ligand-centered pseudocontact shifts. Such con-

tributions become important for atoms close to the unpaired

spin density, combined with the anisotropy of the magnetic

susceptibility of the molecule. It would not be possible to

2

[Ni(5) ]Cl , and [Ni(6) ]Cl (see ref. [7] for [NiX (1)]). The

3

2

3

2

magnetic curves obtained from these measurements for

[NiBr (3)] are shown in Figure 14 (c=c =c_p_a_r_a; see the

2

M

Supporting Information for [NiBr (2)]). The diamagnetic

2

1

0/20

a

distinguish between the close signals C

and Me from

contribution of the constituent atoms to molar susceptibility

has already been subtracted from the data by using Pascal

constants [Eq. (3)].

only the calculations. However, unambiguous assignment

1

3

ensues from the coupling pattern in the C NMR spectra.

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12

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

h

i

D

kBT

D

kBT

2

B

2

expðꢀ ^Þ^þ²D 1 ꢀ expðꢀ

Þ

2

N m g

A

c_M¼ ₃

þ TIP

ð5Þ

D

^kB^ð^T^ꢀ^VCW^Þ

1 þ 2 expðꢀ

Þ

kBT

The resulting values for the fit parameters g, D, TIP, and

V_C_Ware listed in Table 6 for all four compounds. The values

of the axial zero-field splitting parameter D are in good

II

agreement with other studies on Ni complexes, in which

II

the D values for tetrahedral Ni complexes are larger than

those commonly encountered for distorted octahedral com-

[55,56]

plexes.

Figure 14. The temperature dependence of the inverse magnetic suscepti-

ꢀ

1

2

bility (c-TIP) and cT (see inset in the upper left corner) of [NiBr (3)]

measured in an applied field of B=1 T. The solid lines follow a fit to the

data according to Equations (3) and (5).

Table 6. The calculated effective magnetic moments m_e_f_fand the corre-

sponding cT values obtained by linear regression of the inverse suscepti-

bility data (c(T)ꢀTIP)^ꢀ

1 [a]

.

sﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ

A

H

U

G

R

N

[NiBr

2

(2)]

A

H

U

G

R

N

[NiBr

2

(3)] [Ni(5)

3

]Cl

2

3 2

[Ni(6) ]Cl

2

B

pﬃﬃﬃﬃﬃﬃ

3

N m

A

k

N m

A

2

m_e_f_f

¼

cT with c ¼

g SðS þ 1Þ

ð3Þ

m

eff/m

B

3.49

1.52

2.43

9.3

0.56

ꢀ0.29

3.24

1.31

2.29

14.3

0.70

3.10

1.20

2.19

2.6

0.81

0.08

3.45

1.48

2.43

1.8

1.26

ꢀ0.33

2

B

3kT

ꢀ3

ꢀ1

cT [cm mol K]

G

D [cm

TIP [10 cm mol

ꢀ

1

]

A linear temperature dependence of the Curie–Weiss plot

ꢀ

3

ꢀ1

]

ꢀ1

(

c-TIP) is observed above 20 K, and linear regression by

following Equation (3) yields an effective magnetic moment

^o^f^meff ⁼³^.²⁴^aⁿ^d³^.⁴⁹^mB for [NiBr (3)] and [NiBr (2)], re-

V

CW [K]

ꢀ0.01

[

a] The fit parameters g, D, TIP, and VCW were obtained by a fit to the

2

cT(T) data according to Equation (5). All the samples were measured in

spectively, thereby confirming the triplet ground state of the

a magnetic field of 1 T.

complexes. The large deviation of the m_e_f_fvalue from the

spin-only value (S=1, m_e_f_f=2.83 m ) is due to significant or-

B

II

bital angular momentum contributions, as expected for Ni

ions in a tetrahedral environment with a T ground state.

Conclusion

3

[54]

1

The curves derived for the octahedral complexes [Ni(5) ]Cl₂

A variety of superbasic bisguanidines with biphenyl, bi-

naphthyl, and bipyridine cores was synthesized and their

chemical properties have been studied. By using a combina-

tion of experimental results and quantum-chemical calcula-

tions, these compounds have been identified as proton

3

and [Ni(6) ]Cl are shown in the Supporting Information.

3

2

Owing to partial quenching of the orbital angular momen-

tum in an octahedral environment, the m_e_f_fvalue of 3.10 m is

B

closer to the spin-only value and less than in the tetrahedral

complexes, thus confirming again the expected triplet

ground state. Linear regression of the magnetic data of

ꢀ

sponges. Intramolecular N H···N hydrogen bonding was

verified by employing structural and spectroscopic data and

DFT calculations on several tautomeric forms. The bisguani-

dines were applied as ligands in Group 10 metal complexes.

Complexes of different nuclearity were obtained, thus high-

lighting the structural diversity that could be obtained with

these ligands. The observed metal/ligand ratios in the prod-

uct complexes were independent of the equivalents of

ligand used in the complexation reaction. Bisguanidines

with bipyridine cores were found to coordinate through

their ring nitrogen atoms. In contrast, protonation occurs at

the guanidinyl groups. Preliminary catalytic experiments

were carried out and showed satisfying catalytic activity of

the Pd complexes in Heck reactions. The spin-density distri-

[

3

Ni(6) ]Cl renders an effective magnetic moment of m =

3

2

e

f

II

.45 m , which is unusually high for octahedral Ni com-

B

plexes. Hence, structural analysis is essential to prove the

geometry of the complex and possible distortions that might

be responsible for the unusual m_e_f_fvalue. Deviation from the

Curie law behavior at low temperatures in the curves can be

attributed to zero-field splitting.

To model the data in the complete temperature range, an

equation for the molar susceptibility was derived on the

basis of the Hamiltonian in Equation (4).

1

3

m g

m₀

2

z

2

B

H ¼ DðD ꢀ S Þ þ

ðB SÞ

ð4Þ

0

II

bution and magnetism of a series of paramagnetic Ni com-

plexes was analyzed by using paramagnetic NMR spectro-

scopy in alliance with quantum-chemical calculations and

magnetic (SQUID) measurements. The guanidinyl groups

(mainly N=C) host a significant amount of the spin density

through direct delocalization from the SOMOs, whereas the

aromatic backbone experiences spin density through spin

polarization. The complexes provide valuable reference sys-

The molar susceptibility could be estimated by using

[55,7]

Equation (5),

in which N_Ais the Avogadro constant, k_B

is the Boltzmann constant, D is the axial zero-field splitting

parameter, V_C_Wis the Curie–Weiss temperature (applied to

take possible intermolecular interactions into account), and

TIP is the temperature-independent paramagnetism.

Chem. Eur. J. 2013, 00, 0 – 0

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

13

&

ÞÞ

These are not the final page numbers!

J. Himmel et al.

tems for studies on redox-active guanidinyl-functionalized

aromatic compounds, for which the delocalization of spin

density leads to interesting electronic situations.

5: Oxalyl chloride (9.1 mL, 107.5 mmol, 20 equiv) was added dropwise to

a solution of N,N,N’,N’-tetramethylurea (2.5 mL, 21.5 mmol, 4 equiv) dis-

solved at room temperature in CHCl (20 mL). The reaction mixture was

3

stirred under reflux for 17 h. After removal of the solvent in vacuo, the

remaining solid 2-chloro-1,1’,3,3’-tetramethylformamidinium chloride was

washed with Et

2

O (2ꢄ15 mL). This white solid was dissolved in CH

2

Cl

2

(

15 mL) and added to a solution of 3,3’-diamino-2,2’-bipyridine (1.0 g,

5

.4 mmol, 1 equiv) and triethylamine (6 mL, 43 mmol, 8 equiv) in CH

2

Cl

2

Experimental Section

(30 mL) at 253 K. The mixture was stirred at 253 K for a further 30 min

and then allowed to warm to room temperature. After 2 h of stirring at

room temperature, the reaction mixture was extracted with 10% aq.

All the preparative work was carried out in a dry Ar atmosphere by

using standard Schlenk techniques. All the solvents were dried prior to

their use. Ligands 1–4 were prepared as described previously.

HCl, the aqueous solution was washed with CH

added, and the solution was extracted with toluene. The combined tol-

uene phases were dried over K CO , and the solvent was removed in

2 2

Cl , 25% aq. KOH was

[

27,28]

The

starting compound for the synthesis of 5 and 6, 3,3’-diamino-2,2’-bipyri-

2

3

[

35]

vacuo. The remaining brown oil was washed with n-hexane and dried

under reduced pressure for 48 h. A solid could not be obtained, so the oil

was washed with hot n-hexane and after desiccation in vacuo a pale

brown oil remained, which crystallized almost quantitatively. The color-

less crystals were washed with n-hexane to obtain 5 (1.12 g, 54%) as a

dine, was prepared according to a reported procedure. The dinuclear

complexes di-m-chlorodichlorobis(ethylene)diplatinum(II) [{PtCl(C )-

(m-Cl)} ], the allylpalladium chloride dimer [{PdCl ], and the

Ni starting compounds [NiCl (dme)] and [NiBr (dme)] were purchased

A

H

U

G

R

N

U

G

A

H

U

G

R

N

U

G

2 4

H

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

2

3 5 2

ACHTUNGTRENUN(NG h -C H )}

II

2

A

H

U

G

R

N

U

G

2

ACHTUNGTRENNUNG

from ABCR. Oxalyl chloride, tetramethylurea, dimethylethyleneurea,

and n-hexane were used as delivered from Aldrich. Acetonitrile and

chloroform were delivered by Acros. Other solvents were dried by means

of standard methods before distillation. The NMR spectra were meas-

ured on Bruker Avance DPX 200, Bruker Avance II 400, or Bruker

white powder. Crystals suitable for X-ray diffraction were obtained by re-

1

crystallization from toluene/n-hexane. H NMR (399.89 MHz, CD

2

Cl

2

,

3

4

3

2

8

95.0 K): d=8.06 (dd, J=8.06, J=1.52 Hz, 2H; H4/H7), 7.05 (dd, J=

.04, 4.56 Hz, 2H; H3/H8), 6.89 (dd, J=8.02, J=1.50 Hz, 2H; H2/9),

2.58 ppm (s, 24H; CH ); C NMR (100.56 MHz, CD Cl , 296.1 K): d=

3 2 2

59.31 (2C; C11/C16), 151.59 (2C; C ), 146.98 (2C; C ), 140.25 (2C; C4/

C7), 129.10 (2C; C2/C9), 122.66 (2C; C3/C8), 39.58 ppm (8C; CH ); IR

CsI): n˜ =3035 (w), 2997 (w), 2940 (m), 2873 (m), 2813 (w), 1594 (br),

3

4

1

3

1

3

13

1

Avance III 600 NMR spectrometers. Paramagnetic C NMR and C– H

correlation spectra were recorded at 150 MHz by means of a cryogenical-

ly cooled direct detection probe (Cryo-QNP probe). Elemental analyses

were carried out at the Microanalytical Laboratory of the University of

Heidelberg. A Cary 5000 spectrophotometer was used to record UV/Vis

spectra. Fluorescence spectra were recorded at a Varian Cary-Eclipse flu-

q

1

3

(

1

559 (m), 1504 (s), 1462 (m), 1432 (s), 1408 (m), 1337 (s), 1275 (w), 1236

(

9

(

m), 1194 (w), 1144 (s), 1111 (w), 1070 (m), 1059 (m), 1018 (s), 959 (w),

22 (m), 872 (w), 849 (w), 810 (s), 787 (m), 764 (s), 743 (m), 707 (m), 684

w), 641 (w), 618 (s), 586 (m), 565 (w), 520 (m), 494 (w), 454 (m),

orescence spectrometer. Fluorescence quantum yields F

pounds were determined by using the comparative method of Williams

F

of the com-

ꢀ

1

[

57]

3

430 cm (w); UV/Vis (CH CN): l (e)=315 (sh, 5401), 279 (10539), 228

(sh, 10274 mol dm cm ) nm; fluorescence spectrum (excited at l=

3

et al. and with 9,10-diphenylanthracene with the known value of F

F

=

ꢀ

1

3

ꢀ1

[

58]

0

.90 in cyclohexane for calibration. IR spectra of CsI discs containing

+ +

30 nm): lmax =451 nm; MS (ESI ): m/z (%): 383.26677 (100) [M+H] ;

the compounds were recorded on a BioRad Merlin Excalibur FT3000

spectrometer. An EG&G Princeton 273 apparatus was used for the cyclic

voltammetry (CV) measurements.

elemental analysis (%) calcd for C20

9.29; found: C 62.82, H 7.86, N 29.00.

Crystal data for C20 : M

space group P1, a=7.729(2), b=10.409(2), c=13.085(3) ꢃ, a=85.52(3),

b=88.52(3), g=83.38(3)8, V=1042.3(4) ꢃ , Z=2, 1

H

30

N

8

(382.51): C 62.80, H 7.91, N

2

3

H

30

N

8

r

=382.51, 0.30ꢄ0.25ꢄ0.25 mm , triclinic,

3

,3’-Diamino-2,2’-bipyridine: Synthesis of the diamino precursor was per-

formed according to the experimental procedure described by Rice

¯

3

ꢀ3

[

37]

calcd

=1.219 Mgm ,

et al.

acetic anhydride (250 mL, 2.64 mol), and the solution was stirred for

8 h. The excess acetic anhydride and acetic acid were removed in vacuo

2-Chloro-3-aminopyridine (27.2 g, 0.212 mol) was dissolved in

MoKa radiation (graphite-monochromated, l=0.71073 ꢃ), T=100 K,

range =2.42–27.508; reflections measured=8199, independent=4609,

int =0.0717; final R indices [I>2s(I)]: R =0.0670, wR =0.1794.

q

4

R

1

2

at 708C. The remaining yellow oil was slowly cooled to 48C to produce

an off-white solid. Recrystallization from toluene gave 3-acetylamino-2-

chloropyridine (25.0 g, 69%) as white crystals. Activation of Cu for the

Ullman coupling was achieved by sonication of a suspension of Cu

powder (11.1 g, 0.175 mol) in DMF (20 mL) at 658C for 2 h. A solution

of 3-acetylamino-2-chloropyridine (7.44 g, 43.6 mmol) in DMF (15 mL)

was heated up to 1308C, and the activated Cu slurry was added to the

solution. Completion of the coupling was followed by TLC analysis

6: 2-Chloro-1,3-dimethylethyleneformamidinium chloride was prepared

by adding oxalyl chloride (8.2 mL, 96.9 mmol, 20 equiv) at room temper-

ature to a solution of 1,3-dimethylethyleneurea (2.1 mL, 19.5 mmol,

4.0 equiv) dissolved in CHCl

under reflux for 18 h. After evaporating the solvent, the remaining solid

was washed with Et O (2ꢄ10 mL). The synthesized Vilsmeier salt was

dissolved in CH CN (40 mL) at 253 K and added at this temperature to a

solution of 3,3’-diamino-2,2’-bipyridine (0.91 g, 4.9 mmol, 1 equiv) and

triethylamine (5.4 mL, 38.7 mmol, 8 equiv) in CH CN (20 mL). The reac-

3

(25 mL). The reaction mixture was stirred

2

3

(

2

SiO , ethyl acetate) which showed the absence of the starting material

after 3 h. The reaction mixture was allowed to cool before quenching

with water (12 mL). The solution was collected by filtration, and the re-

sulting ocher filter cake was washed with water (100 mL), ammonium hy-

droxide (100 mL), and again with water (100 mL). Under reduced pres-

sure, the filter cake was dried fully. A brown solid was extracted with di-

chloromethane (4ꢄ120 mL), and the solvent was removed in vacuo to

give crude 3,3’-diacetylamino-2,2’-bipyridine. Without further purifica-

tion, the solid was dissolved in concentrated HCl (25 mL), and the mix-

ture was stirred under reflux for 1 h. After cooling the mixture on ice,

concentrated ammonium hydroxide was added slowly to the mixture, and

a yellow solid precipitated. The crude product was collected by filtration,

dried under reduced pressure, and recrystallized from acetic anhydride to

yield 3,3’-diamino-2,2’-bipyridine (1.7 g, 42%) as yellow crystals.

3

tion mixture was allowed to warm to room temperature for 48 h. The sol-

vent was removed in vacuo, the residue was extracted with 10% aq. HCl,

25% aq. KOH was added to the aqueous phase, and the solution was ex-

tracted with Et O. The combined organic phases were dried over K CO ,

2 2 3

and the solvent was removed in vacuo. The residue was washed with n-

hexane to yield 6 (1.22 g, 66%) as a white powder. Crystals suitable for

X-ray diffraction were obtained by evaporation of the solution of 6 dis-

1

solved in CD

2

Cl

2

.

H NMR (399.89 MHz, CD

2

Cl

2

, 294.8 K): d=8.07 (t,

),

3 2 2

); C NMR (100.56 MHz, CD Cl , 296.1 K): d=

J=3.06 Hz, 2H; CH), 7.05 (d, J=3.04 Hz, 4H; CH), 3.15 (s, 8H; CH

2

1

3

2.57 ppm (s, 12H; CH

156.13 (2C; C11/C16), 152.35 (2C; C ), 145.53 (2C; C ), 140.23 (2C;

CH), 129.16 (2C; CH), 122.22 (2C; CH), 48.76 (4C; CH ), 35.47 ppm

(4C; CH ); IR (CsI): n˜ =3048 (w), 2937 (m), 2864 (m), 2822 (w), 1625/

q

2

1

3

4

H NMR (399.89 MHz, CD

2

Cl

2

,

295.0 K): d=7.96 (d, J=3.72, J=

3

1

3

2

(

1

.28 Hz 2H; CH), 7.95 (m, 4H; CH), 6.40 ppm (s, 4H; NH

2

, 296.2 K): d=144.43 (2C; C ), 140.69 (2C; C ),

35.60 (2C; CH), 123.96 (2C; CH), 123.24 ppm (2C; CH); elemental

2

); C NMR

1611 (br), 1564 (m), 1553 (m), 1492 (m), 1472 (w), 1443 (m), 1434 (m),

1411 (m), 1394 (s), 1284/1277 (s), 1236 (s), 1203 (m), 1167 (w), 1136 (w),

1123 (w), 1100 (w), 1073 (m), 1039/1031 (s), 992 (w), 971 (m), 913 (w),

880 (w), 848 (w), 806 (s), 760 (m), 745 (m), 706 (m), 665 (w), 619 (m),

q

100.56 MHz, CD

2

Cl

10 4

analysis (%) calcd for C10H N (186.21): C 64.50, H 5.41, N 30.09; found:

ꢀ1

C 64.37, H 5.46, N 29.86.

3

593 (s), 568 (w), 513 (m), 459 (w), 420 cm (w); UV/Vis (CH CN): l

&

14

&

www.chemeurj.org

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 0000, 00, 0 – 0

ÝÝ

These are not the final page numbers!

Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

ꢀ

1

3

ꢀ1

(

e)=313 (sh, 5290), 280 (9362), 228 nm (sh, 7729 mol dm cm ); fluo-

ture was stirred at room temperature for an additional 3 h. After removal

of the solvent in vacuo, the remaining solid was washed with n-hexane

+

rescence spectrum (excited at l=355 nm): lmax =426 nm; MS (FAB ):

m/z (%): 379.2333 (100) [M+H] ; elemental analysis (%) calcd for

+

(5 mL) to yield [4H]PF (20.9 mg, 87%) as a white powder. Upon recrys-

6

C

20

H

26

N

8

(378.47): C 63.47, H 6.92, N 29.61; found: C 63.29, H 6.84, N

tallization from CH Cl /n-hexane, colorless crystals suitable for X-ray

2

1

2

9.54.

Crystal data for C20

space group P2

00.17(3)8, V=1907.5(7) ꢃ , Z=4, 1calcd =1.318 Mgm , MoKa radiation

graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.13–32.068;

reflections measured=12547, independent=6587, Rint =0.0422; final R

indices [I>2s(I)]: R =0.0479, wR =0.1310.

[1H]PF : Compound 1 (17.8 mg, 0.047 mmol) was dissolved in CH

1.1 mL) and the reaction mixture was stirred for 5 min. NH

7.95 mg, 0.049 mmol) was added to the solution, and the reaction mix-

analysis were obtained. H NMR (399.89 MHz, CD Cl , 295.1 K): d=7.99

2

3

(d, J=8.76 Hz, 2H; CH), 7.95 (d, J=8.20 Hz, 2H; CH), 7.48 (d, J=

.72 Hz, 2H; CH), 7.43 (t, J=7.50 Hz, 2H; CH), 7.25 (t, J=7.64 Hz,

2H; CH), 7.07 (d, J=8.52 Hz, 2H; CH), 3.41 (m, 4H; CH ), 3.21 (m,

2

), 2.66 ppm (s, 12H; CH ); C NMR (100.56 MHz, CD Cl ,

2 3 2 2

95.1 K): d=156.71 (2C; C ), 138.76 (2C; C ), 133.15 (2C; C ), 131.48

(2C; C ), 129.86 (2C; CH), 128.78 (2C; CH), 127.44 (2C; C ), 127.19

H

26

N

8

, M

r

=378.47, 0.40ꢄ0.40ꢄ0.35 mm , monoclinic,

3

8

1

/n, a=9.975(2), b=16.136(3), c=12.040(2) ꢃ, b=

3

ꢀ3

1

(

1

3

4

2

H; CH

q

1

2

(

2C; CH), 126.16 (2C; CH), 125.56 (2C; CH), 124.83 (2C; CH), 48.82

4C; CH ), 34.96 ppm (4C; CH ); elemental analysis (%) calcd for

·0.1CH Cl

3.32; found: C 57.34, H 5.49, N 13.22.

P·CH Cl : M

orthorhombic, space group P2

A

C

H

T

U

N

G

T

R

E

N

U

N

G

6

3

CN

PF

2

3

(

4

6

[

4H]PF

6

2

(C30.1

H

33.2Cl0.2

F

6

N

6

P; 631.08):

C

57.29, H 5.30,

N

1

ture was stirred at room temperature for an additional 3 h. After removal

of the solvent in vacuo, the remaining solid was washed with n-hexane

3

Crystal data for C30

H

33

F

6

N

6

2

r

=707.52, 0.40ꢄ0.30ꢄ0.30 mm ,

(

5 mL) to yield [1H]PF

6

(21.1 mg, 86%) as a white powder. Upon recrys-

1

2

1

2

1

,

a=14.099(3), b=15.617(3), c=

3

ꢀ3

tallization from CD Cl

analysis were obtained. H NMR (399.89 MHz, CD

2

/n-hexane, colorless crystals suitable for X-ray

29.628(6) ꢃ, V=6524(2) ꢃ , Z=8, 1calcd =1.441 Mgm , MoKa radiation

(graphite monochromated, l=0.71073 ꢃ), T=100 K, qrange =1.89–33.178;

reflections measured=48480, independent=24776, Rint =0.0450; final R

1

2

Cl

2

, 295.1 K): d=

1

0.56 (s, 1H; NH), 7.39 (m, 2H; CH), 7.30 (m, 2H; CH), 7.23 (m, 2H;

1

3

CH), 6.76 (s, 2H; CH), 2.76 ppm (s, 24H; CH

CD

3

); C NMR (100.56 MHz,

1 2

indices [I>2s(I)]: R =0.0447, wR =0.1063.

q

2

Cl

2

, 295.1 K): d=161.08 (2C; C ), 143.40 (2C; C ), 134.73 (2C; C ),

[5H]PF : Compound 5 (17.4 mg, 0.045 mmol) was dissolved in CH CN

6

3

1

31.63 (2C; CH), 129.38 (2C; CH), 124.87 (2C; CH), 40.14 ppm (8C;

4 6

(1.1 mL), and the reaction mixture was stirred for 5 min. NH PF

(7.6 mg, 0.047 mmol) was added to the solution, and the reaction mixture

was stirred at room temperature for an additional 3 h. After removal of

CH

.32, N 15.96; found: C 49.84, H 6.50, N 15.87.

Crystal data for C22

clinic, space group P2

b=110.55(3)8, V=5131(2) ꢃ , Z=8, 1calcd =1.363 Mgm , MoKa radiation

graphite monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.42–27.588;

reflections measured=43022, independent=11800, Rint =0.0473; final R

indices [I>2s(I)]: R =0.0424, wR =0.1191.

: Compound 2 (19.9 mg, 0.053 mmol) was dissolved in CH

1.1 mL), and the reaction mixture was stirred for 5 min. NH

8.81 mg, 0.054 mmol) was added to the solution, and the reaction mix-

3

); elemental analysis (%) calcd for C22

H

33

F

6

N

6

P (526.50): C 50.19, H

6

3

H

33

F

6

N

6

P

:

M

r

=526.51, 0.40ꢄ0.30ꢄ0.30 mm , mono-

the solvent in vacuo, the remaining solid was washed with n-hexane

1

/n, a=24.861(5), b=8.7330(17), c=25.239(5) ꢃ,

(5 mL) to yield [5H]PF

(399.89 MHz, CD Cl

7.17 (m, 4H; H2/H3), 2.71 ppm (s, 24H; CH

6

(19.8 mg, 83%) as a yellow powder. H NMR

1

3

ꢀ3

3

2

, 295.5 K): d 8.30 (d, J=3.64 Hz, 2H; H4), 7.27–

1

3

(

3

); C NMR (100.56 MHz,

q

CD

142.13 (2C; C ), 130.63 (2C; C2), 123.93 (2C; C3), 40.06 ppm (8C; CH

elemental analysis (%) calcd for C20 P (528.48): C 45.45, H 5.91,

N 21.20; found: C 45.10, H 6.26, N 20.63.

[6H]PF . Compound 6 (59.2 mg, 0.156 mmol) was dissolved in CH

(5 mL), and the reaction mixture was stirred for 5 min. NH PF (26.7 mg,

2 2

Cl , 297.1 K): d=160.20 (2C; C ), 150.70 (2C; C ), 143.56 (2C; C4),

q

3

);

1

2

31 6 8

H F N

[

(

2H]PF

6

3

CN

PF

4

6

A

H

U

G

R

N

U

G

6

3

CN

ture was stirred at room temperature for an additional 3 h. After the ad-

dition of Et O, colorless crystals of [2H]PF (21.1 mg, 76%) were ob-

tained. H NMR (399.89 MHz, CD Cl , 295.6 K): d=10.44 (s, 1H; NH),

4

6

2

6

0.164 mmol) was added to the solution, and the reaction mixture was stir-

red at room temperature for an additional 12 h. After removal of the sol-

vent in vacuo, the remaining solid was washed with n-hexane (8 mL) to

1

2

3

7

3

CD

1

3

.40 (t, J=7.54 Hz, 2H; CH), 7.33 (d, J=7.32 Hz, 2H; CH), 7.27 (t, J=

.30 Hz, 2H; CH), 7.17 (d, J=7.84 Hz, 2H; CH), 3.50 (m, 4H; CH

.31 (m, 4H; CH

Cl , 296.7 K): d=157.00 (2C; C ), 140.58 (2C; C ), 135.62 (2C; C ),

30.74 (2C; CH), 129.10 (2C; CH), 125.80 (4C; CH), 49.05 (4C; CH ),

4.84 ppm (4C; CH ); elemental analysis (%) calcd for C22

3

2

),

yield [6H]PF (76.9 mg, 94%) as an off-white powder. Upon recrystalliza-

6

1

3

2

), 2.60 ppm (s, 12H; CH

3

); C NMR (100.56 MHz,

tion from CD Cl , colorless crystals suitable for X-ray analysis were ob-

2

q

1

2

2 2

tained. H NMR (600.13 MHz, CD Cl , 295.1 K): d 8.43 (s, 2H; H4), 7.51

3

2

(d, J=8.04 Hz, 2H; H2), 7.37 (dd, J=8.10, 4.62 Hz, 2H; H3), 3.50 (s,

1

3

H

29

F

6

N

6

P

2 3 2 2

8H; CH ), 2.69 ppm (s, 12H; CH ); C NMR (150.90 MHz, CD Cl ,

294.9 K): d=157.27 (2C; C ), 150.39 (2C; C ), 145.42 (2C; C4), 137.93

(2C; C ), 132.50 (2C; C2), 124.32 (2C; C3), 49.06 (4C; CH ), 35.17 ppm

2

q

(

522.47): C 50.57, H 5.59, N 16.09; found: C 50.33, H 5.56, N 16.07.

3

q

Crystal data for C22

H

29

F

6

N

6

P

:

M

r

=522.48, 0.30ꢄ0.30ꢄ0.20 mm , mono-

clinic, space group P2

b=93.67(3)8, V=2425.1(8) ꢃ , Z=4, 1calcd =1.431 Mgm , MoKa radia-

tion (graphite monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.20–

1

/c, a=9.7280(19), b=18.515(4), c=13.492(3) ꢃ,

(4C; CH

45.80, H 5.19, N 21.37; found: C 45.81, H 5.22, N 21.36.

3

); elemental analysis (%) calcd for C20

H

27

F

6

N

8

P (524.45): C

3

ꢀ3

3

Crystal data for C H F N P: M =524.47, 0.20ꢄ0.20ꢄ0.10 mm , ortho-

2

0

27

6

8

r

2

9.988; reflections measured=13678, independent=7031, Rint =0.0680;

final R indices [I>2s(I)]: R =0.0536, wR =0.1189.

: Compound 3 (73.0 mg, 0.152 mmol) was dissolved in CH

5 mL), and the reaction mixture was stirred for 10 min. NH

23.9 mg, 0.147 mmol) was added to the solution, and the reaction mix-

rhombic, space group Pbcn, a=7.4520(15), b=17.157(3), c=18.260(4) ꢃ,

3

ꢀ3

1

2

V=2334.6(8) ꢃ , Z=4, 1

calcd

=1.492 Mgm , Mo_K_aradiation (graphite-

[

(

3H]PF

6

3

CN

PF

monochromated, l=0.71073 ꢃ), T=100 K,

tions measured=20015, independent=2778, Rint =0.0853; final R indices

[I>2s(I)]: R =0.0570, wR =0.1345.

[Ni(5) ]Cl : [NiCl₂ A( dme)] (34.1 mg, 0.16 mmol) was dissolved in cooled

(ꢀ788C) CH Cl (3 mL) and added to solution of (183.9 mg,

qrange =2.23–27.868; reflec-

4

6

1

2

ture was stirred at room temperature for an additional 3 h. After removal

of the solvent in vacuo, the remaining solid was washed with n-hexane

CHTUNGTRENNUNG

3

2

a

5

1

(

8 mL) to yield [3H]PF

399.89 MHz, CD Cl

d, J=8.16 Hz, 2H; CH), 7.37 (t, J=7.48 Hz, 2H; CH), 7.17 (t, J=

6

(87.7 mg, 95%) as a white powder. H NMR

0.48 mmol) in CH Cl (3 mL), also cooled to ꢀ788C. After stirring for

2

3

2

, 295.1 K): d=7.97 (d, J=8.72 Hz, 2H; CH), 7.91

20 min, the mixture was allowed to warm to room temperature and stir-

red for 16 h. The reaction mixture was filtrated with a cannula, and the

solvent removed in vacuo from the filtrate. A yellow precipitate was ob-

tained and washed with toluene (6 mL) and n-hexane (15 mL) to yield

3

7

2

.68 Hz, 2H; CH), 7.07 (d, J=8.72 Hz, 2H; CH), 6.95 (d, J=8.52 Hz,

1

3

H; CH), 2.76 ppm (s, 24H; CH

3

); C NMR (100.56 MHz, CD

2

Cl

2

,

q

95.1 K): d=160.75 (2C; C ), 141.73 (2C; C ), 133.44 (2C; C ), 131.09

1

75.2 mg (89%). Crystals suitable for X-ray diffraction were obtained by

slow diffusion of EtO at room temperature into a solution of [Ni(5) ]Cl

H NMR (600.13 MHz, CDCl , 295.1 K): d=56.41 (s, CH),

); C NMR (150.90 MHz, CD Cl , 295.0 K): d=

41.97, 193.98, 41.91 ppm (24C; CH ); IR (CsI): n˜ =3003 (w), 2965 (w),

q

(

2C; C ), 130.17 (2C; CH), 128.72 (2C; CH), 126.95 (2C; CH), 126.17

2C; CH), 125.96 (2C; C ), 125.01 (2C; CH), 123.41 (2C; CH), 40.32 ppm

2

3

2

q

1

in CH

2

6

2

Cl

2

.

3

8C; CH

7.50, H 5.95, N 13.41; found: C 57.16, H 6.26, N 13.24.

[4H]PF : Compound 4 (18.4 mg, 0.039 mmol) was dissolved in CH

1.1 mL), and the reaction mixture was stirred for 5 min. NH

6.83 mg, 0.042 mmol) was added to the solution, and the reaction mix-

3

); elemental analysis (%) calcd for C30

H

37

F

6

N

6

P (626.62): C

13

.77 ppm (s, 72H; CH

3

2

5

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

6

3

CN

PF

2930 (m), 2875 (w), 2805 (w), 1698 (w), 1571 (s), 1545 (s), 1481 (m), 1453

(m), 1438 (m), 1425 (m), 1406 (m), 1388 (s), 1308 (w), 1291 (w), 1219

(m), 1144 (m), 1113 (w), 1070 (w), 1026 (s), 950 (w), 922 (w), 868 (w),

(

4

6

Chem. Eur. J. 2013, 00, 0 – 0

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

15

&

ÞÞ

These are not the final page numbers!

J. Himmel et al.

8

5

3

6

06 (m), 789 (w), 766 (m), 735 (w), 706 (w), 649 (w), 583 (w), 538 (w),

toluene (7 mL) at room temperature. Immediately, a pale-yellow sticky

precipitate was produced. The reaction mixture was treated in a sonicator

for 20 min and then stirred at room temperature for 15 h. Afterwards, the

ꢀ

1

03 (w), 444 (w), 417 cm (w); UV/Vis (CH Cl ): l (e)=387 (18646),

2 2

ꢀ1

ꢀ

1

3

+

17 (500610), 256 nm (sh, 31188 mol dm cm ); MS (ESI ): m/z (%):

2

+

02.35560 (100) [Mꢀ2Cl]

]Cl ·CH Cl

found: C 53.74, H 7.10, N 24.34.

Crystal data for [Ni(5) ]Cl ·7CH

;

elemental analysis (%) calcd for

24Ni=1362.05): C 53.79, H 6.81, N 24.68;

solvent was decanted and the remaining yellow solid was washed with n-

3

[

Ni(5)

3

2

(C61

H

92Cl

4

N

hexane (2ꢄ10 mL) to obtain [{PdCl

A

H

U

G

R

N

(h -C H )} (6)] (312.4 mg, 86%) as a

3

5

2

light yellow powder. Crystals suitable for X-ray diffraction were grown

by slow diffusion of EtO

2

at room temperature into a solution of [{PdCl-

3

2

Cl

2

:

C

67

H

104Cl16

N

24Ni,

M

r

=1871.65,

3

1

3

¯

A

H

U

G

R

N

U

G

0

1

4

.35ꢄ0.30ꢄ0.30 mm , triclinic, space group P1, a=14.440(3), b=

8.580(4), c=19.444(4) ꢃ, a=64.99(3), b=82.93(3), g=74.61(3)8, V=

3

5

2

3

8

.14 (d, J=4.62 Hz, 2H; H4/H7), 7.31–7.22 (m, 4H; H2/H3/H8/H9), 5.86

3

ꢀ3

(s, H; CH), 5.35 (s, H; CH), 4.08 (s, 2H; C H ), 3.71 (s, 2H; C H ), 3.39

557.9(16) ꢃ , Z=2, 1calcd =1.364 Mgm , MoKa radiation (graphite-mon-

range =2.18–27.518; reflections

measured=37615, independent=20628, Rint =0.0586; final R indices [I>

s(I)]: R =0.0735, wR =0.1915.

Ni(6) ]Cl : [NiCl (dme)] (39.5 mg, 0.18 mmol) was added to a solution

of 6 (155.4 mg, 0.41 mmol) in CH Cl

3

5

3

1

5

3

(

s, 8H; CH

2

), 2.73 (s, 4H; C

3 5 3

H ), 2.66 ppm (s, 12H; CH ); C NMR

ochromated, l=0.71073 ꢃ), T=100 K,

q

(

150.90 MHz, CD

3

CN, 294.9 K): d=157.39 (2C; C11/16), 149.58 (2C;

q

C ), 149.46 (2C; C ), 143.85 (2C; C4/C7), 133.71 (2C; CH), 125.47 (2C;

CH), 61.88 (4C; C21/C23/C24/C26), 49.17 (4C; CH ), 35.92 ppm (4C;

CH ); IR (CsI): n˜ =3072 (w), 2936 (m), 2852 (m), 1611 (s), 1559 (s), 1501

m), 1484 (m), 1449 (s), 1438 (s), 1414 (s), 1397 (s), 1289 (s), 1241 (m),

214 (m), 1134 (m), 1119 (w), 1077 (w), 1040 (s), 993 (w), 974 (m), 928

2

1

2

[

3

2

ACHTUNGTRENNUNG

3

2

(4 mL) at ꢀ788C. The reaction mix-

(

1

ture was allowed to warm to room temperature over 6 h. Subsequently,

the yellow suspension was filtrated with a cannula, and the solvent re-

moved in vacuo from the filtrate. A yellow precipitate was obtained,

(

w), 898 (w), 853 (w), 807 (s), 786 (w), 762 (m), 750 (m), 709 (m), 666

w), 647 (w), 609 (w), 594 (m), 578 (w), 537 (w), 513 (w), 462 (w),

which was washed with n-hexane (10 mL) to yield 164.2 mg (95%) of

ꢀ

1

438 cm (w); UV/Vis (CH

14099), 294 nm (sh, 11307 mol dm cm ); MS (HR-FAB ): m/z (%):

713.0751 (33.6), 710.0778 (55.1), 709.0770 (75.3), 708.0800 (63.6)

2 2

Cl ): l (e)=418 (6397), 381 (sh, 4618), 320

product. H NMR (600.13 MHz, CDCl

3

, 295.1 K): d=56.72 (s, CH), 4.01

), 3.80–3.30 (s, 12H; CH ), 2.67 ppm (s, 36H; CH );

C NMR (150.90 MHz, CD Cl , 294.9 K): d=642.00, 187.24, 49.11 (12C;

CH ), 37.79 (6C; CH ), 36.93 ppm (6C; CH ); IR (CsI): n˜ =2937 (w),

ꢀ

1

3

ꢀ1

+

(

s, 12H; CH

2

3

1

3

2

+

[

MꢀCl] ; elemental analysis (%) calcd for C26

1.95, H 4.87, N 15.05; found: C 41.55, H 5.15, N 14.60.

Crystal data for C26 Pd : M

oclinic, space group P2

H36Cl

2

N

8

Pd

2

(744.36): C

2

3

4

2

1

6

865 (m), 1616 (br), 1550 (m), 1502 (m), 1443 (s), 1410 (m), 1398 (m),

290 (s), 1240 (m), 1214 (m), 1174 (w), 1132 (w), 1111 (w), 1076 (w),

039 (s), 975 (m), 897 (w), 807 (m), 758 (m), 746 (m), 731 (m), 703 (m),

3

H

36Cl

2

N

8

2

r

=744.36, 0.35ꢄ0.20ꢄ0.20 mm , mon-

1

/n, a=8.0570(16), b=19.934(4), c=18.001(4) ꢃ,

ꢀ

1

3

ꢀ3

61 (w), 637 (w), 606 (w), 594 (w), 574 (w), 533 (w), 448 (w), 420 cm

b=96.69(3)8, V=2871.4(10) ꢃ , Z=4, 1calcd =1.722 Mgm , MoKa radia-

tion (graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.34–

30.008; reflections measured=19522, independent=8365, Rint =0.0327;

(

w);

UV/Vis

(CH

2

Cl

2

):

l

(e)=393

(13923),

314 nm

ꢀ

1

3

ꢀ1

+

35009 mol dm cm ); MS (HR-FAB ): m/z (%): 1229.5859 (93.7)

+

63.6) [MꢀCl] ; elemental analysis (%) calcd for [Ni(6)

3

]Cl

2

·1.7CH

2

Cl

2

final R indices [I>2s(I)]: R

1 2

=0.0342, wR =0.0960.

C

61.7

H

81.4Cl5.4

N

24Ni=1409.41): C 52.58, H 5.82, N 23.85; found: C 52.60,

A

H

U

G

R

N

U

G

ACHTUNGTRENNUNG

2

4

2

H 6.36, N 23.91.

(4 mL) was added at room temperature to a solution of 5 (101.6 mg,

0.27 mmol) in toluene (2 mL). Immediately, a yellow precipitate was

formed, and the reaction mixture was stirred for an additional 5 h. The

precipitate was collected by filtration and washed with toluene (3 mL)

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

[{PdCl

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C

3

H

5

)}

2

(5)]: [{PdCl

A

H

U

T

E

N

(h -C

3

H

5

)}

2

] (183.2 mg, 0.50 mmol) dissolved

in toluene (3 mL) was added to a solution of 5 (196.8 mg, 0.52 mmol) in

toluene (3 mL) at room temperature. Immediately, a yellow sticky precip-

itate was produced. The reaction mixture was treated at 508C in a sonica-

tor for 10 min and then stirred for 30 min at room temperature After-

wards, approximately 50% of the solvent was removed under vacuo, and

n-hexane (4 mL) was added to the remaining suspension for quantitative

and n-hexane (3ꢄ8 mL) to yield [PtCl

2

(5)] (126.9 mg, 74%) as a yellow

powder. Crystals suitable for X-ray diffraction were obtained by evapora-

1

tion of the solvent of [PtCl

(399.89 MHz, CD Cl , 295.7 K): d=9.14 (dd, J=5.40, J=1.12 Hz, 2H;

H4/H4a), 7.18 (dd, J=8.34, 5.50 Hz, 2H; H3/H3a), 6.83 (dd, J=8.40,

2 2 2

(5)] dissolved in CD Cl H NMR

3

4

2

3

precipitation of the crude product. The solvent was decanted and the res-

idue was washed with n-hexane (2ꢄ6 mL) to obtain [{PdCl

3

4

13

A

H

U

G

R

N

(h -C

3

H

5

)}

2

(5)]

J=1.12 Hz, 2H; H2/H2a), 2.82 ppm (s, 24H; CH

(100.56 MHz, CD Cl , 297.3 K): d=158.40 (2C; C6), 150.73 (2C; C ),

149.12 (2C; C ), 140.13 (2C; C4/C4a), 131.22 (2C; C2/C2a), 124.32 (2C;

3

);

C NMR

q

(

332.5 mg, 89%) as a light yellow powder. Crystals suitable for X-ray dif-

2

q

fraction were grown by slow diffusion of Et

2

O at room temperature into

3

1

195

a solution of [{PdCl

CD

.84 Hz, 2H; H4), 6.96 (d, J=8.40 Hz, 2H; H5), 5.54 (s, 2H; CH), 3.85

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C

3

H

5

)}

2

(5)] in CH

2

Cl

2

.

H NMR (399.89 MHz,

C3/C3a), 40.08 ppm (8C; CH

3

);

2 2

Pt NMR (85.96 MHz, CD Cl ,

3

CN, 294.9 K): d=8.17 (d, J=4.72 Hz, 2H; H3), 7.30 (dd, J=8.40,

295.7 K): d=ꢀ2175 ppm; IR (CsI): n˜ =3080 (w), 3007 (w), 2929 (br),

2866 (br), 2803 (w), 1574 (s), 1535 (s), 1479 (m), 1455 (s), 1432/1423 (s),

1406 (m), 1389 (s), 1312 (w), 1295 (w), 1258 (w), 1233 (w), 1218 (m),

1143 (m), 1070 (w), 1030 (s), 969 (w), 924 (w), 899 (w), 885 (w), 806 (m),

765 (m), 737 (w), 697 (w), 660 (w), 643 (w), 585 (w), 562 (w), 521 (w),

3

4

1

3

(

1

6

s, 4H;

100.55 MHz, CD

C

3

H

5

), 2.97 (s, 4H;

CN, 296.1 K): d=159.88 (2C; C6), 150.39 (2C; C ),

50.11 (2C; C ), 144.24 (2C; C3), 132.72 (2C; C5), 126.06 (2C; C4),

1.11 (4C; C11/C13), 40.11 ppm (8C; CH ); IR (CsI): n˜ =2927 (m), 2873

3 5

C H ), 2.78 ppm (s, 24H); C NMR

q

3

q

ꢀ

1

502 (w), 467 cm (w); UV/Vis (CH

2 2

Cl ): l (e)=445 (sh, 5208), 409

3

ꢀ1

3

ꢀ1

(

1

m), 2815 (w), 1649 (w), 1578 (s), 1545 (br), 1524 (br), 1474 (m), 1462 (s),

427 (s), 1385 (s), 1286 (m), 1263 (w), 1238 (m), 1204 (m), 1142 (s), 1072

(6206), 323 (13249), 294 (sh, 9267), 251 nm (11697 mol dm cm ); MS

(ESI ): m/z (%): 648.16940 (100) [M+H] ; elemental analysis (%) calcd

+

(

3

7

3

m), 1028 (s), 996 (w), 972 (w), 948 (m), 926 (m), 907 (w), 871 (m), 807

s), 779 (m), 762 (s), 708 (w), 646 (m), 588 (m), 543 (m), 505 (w), 475

for [PtCl

17.04; found: C 37.60, H 4.86, N 16.81.

Crystal data for C20 Pt: M

2

(5)]·0.1C

7

H

8

(C20.7

H

30.8Cl

2

N

8

Pt =657.71): C 37.80, H 4.72, N

ꢀ

1

w), 430 cm (w); UV/Vis (CH

2

Cl

2

): l (e)=409 (5515), 375 (sh, 4020),

3

H

30Cl

2

N

8

r

=648.50, 0.25ꢄ0.25ꢄ0.22 mm , mono-

ꢀ

1

3

ꢀ1

+

21 (13613), 289 nm (sh, 10328 mol dm cm ); MS (ESI ): m/z (%):

clinic, space group P2/c, a=13.362(3), b=12.334(3), c=17.595(6) ꢃ, b=

+

3

+

13.11301 (3.6) [MꢀCl] , 529.20096 (100) [MꢀPdCl

2

A

H

U

G

R

N

(h -C

3

H

5

)] ,

3

ꢀ3

1

24.78(2)8, V=2381.7(11) ꢃ , Z=4, 1calcd =1.809 Mgm , MoKa radiation

graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =1.86–31.888;

reflections measured=30033, independent=8132, Rint =0.0709; final R

indices [I>2s(I)]: R =0.0333, wR =0.0777.

[PtCl (6)]: [{PtCl (C )} ] (55.0 mg, 0.09 mmol) dissolved in toluene

3 mL) was added at room temperature to a solution of 6 (70.0 mg,

.19 mmol) in toluene (4 mL). Immediately, an orange precipitate was

3

+

83.26650 (57.2) [Mꢀ

A

C

H

T

U

N

G

T

R

E

N

U

N

G

{PdCl(h -C )} ] ; elemental analysis (%) calcd

A

H

N

T

E

N

3

H

5

2

(

for C26

.64, N 14.58.

Crystal data for C26

H

40Cl

2

N

8

Pd

2

(748.40): C 41.73, H 5.39, N 14.97; found: C 41.67, H

5

1

2

3

H

40Cl

2

N

8

Pd

2

: M

r

=748.40, 0.40ꢄ0.20ꢄ0.20 mm , mon-

A

H

U

G

R

N

U

G

2

A

T

N

T

E

N

2

H

4

2

oclinic, space group C2/c, a=17.232(3), b=12.494(3), c=15.875(3) ꢃ, b=

(

0

3

ꢀ3

1

16.09(3)8, V=3069.5(11) ꢃ , Z=4, 1calcd =1.619 Mgm , MoKa radiation

graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.09–27.538;

reflections measured=27379, independent=3530, Rint =0.0971; final R

(

formed. The reaction mixture was stirred for an additional 2 h. The pre-

cipitate was collected by filtration and washed with n-hexane to yield

indices [I>2s(I)]: R

1

=0.0522, wR

2

=0.1403.

[

PtCl

2

(6)] (83.0 mg, 72%) as an orange powder. Crystals suitable for X-

(6)]

2 2 2 2

dissolved in CD Cl . H NMR (600.13 MHz, CD Cl , 295.1 K): d=9.04 (s,

3

A

C

H

T

U

N

G

T

R

E

N

U

N

G

[{PdCl

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(h -C

3

H

5

)}

2

(6)]: [PdCl

A

H

U

G

R

N

U

G

3

H

5

2

)] (180.1 mg, 0.49 mmol) dissolved

ray diffraction were obtained by evaporation of the solvent of [PtCl

2

1

in toluene (4 mL) was added to a solution of 6 (185.5 mg, 0.49 mmol) in

&

16

&

www.chemeurj.org

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 0000, 00, 0 – 0

ÝÝ

These are not the final page numbers!

Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

ꢀ

1

2

H; H4/H7), 7.28–7.21 (m, 2H; H2/H9), 7.19–7.10 (m, 2H; H3/H8), 3.40

450 cm (w); UV/Vis (CH

2

Cl

2

+

): l (e)=676 (104), 592 (151), 373 nm (sh,

1

3

ꢀ1

3

ꢀ1

+

(

s, 8H; CH

2

), 2.72 ppm (s, 12H; CH

94.9 K): d=156.38 (2C; C11/C16), 150.07 (2C; C ), 148.06 (2C; C ),

3

); C NMR (150.90 MHz, CD

2

Cl

2

,

600 mol m cm ); MS (EI ): m/z (%): 515.0843 (5.36) [MꢀBr] ;

q

+

2

1

CH

432.1596 (10.3) [Mꢀ2HBr] , 376.2328 (100) [MꢀBr

2

Ni] ; elemental anal-

39.60 (2C; C4/C7), 132.65 (2C; C2/C9), 123.71 (2C; C3/C8), 49.02 (4C;

ysis (%) calcd for C22

H

28Br

2

N

6

Ni (595.00): C 44.41, H 4.74, N 14.12;

1

95

2

), 36.11 ppm (4C; CH

3

); Pt NMR (85.96 MHz, CD

2

Cl

2

, 295.0 K):

found: C 44.15, H 4.99, N 13.90.

Crystal data for C22 Ni: M

clinic, space group P2

00.46(3)8, V=2365.9(8) ꢃ , Z=4, 1calcd =1.671 Mgm , MoKa radiation

graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.15–31.178;

reflections measured=14937, independent=7566, Rint =0.0638; final R

indices [I>2s(I)]: R =0.0408, wR =0.0845.

[NiCl ((R)-3)]: A solution of [NiCl (dme)] (120.5 mg, 0.55 mmol) in

CH Cl

(5 mL) was cooled to ꢀ788C and slowly added to a solution of

R)-3 (293.4 mg, 0.61 mmol) in CH Cl

d=ꢀ2185 ppm; IR (CsI): n˜ =3075 (w), 2934 (br), 2866 (br), 1616 (s),

3

H

28Br

2

N

6

r

=595.00, 0.15ꢄ0.10ꢄ0.10 mm , mono-

1

6

570 (m), 1560/1546 (m), 1508/1500 (m), 1458 (m), 1444 (br), 1413 (m),

400 (m), 1291 (m), 1239 (m), 1216 (m), 1159 (w), 1139 (w), 1122 (w),

079 (w), 1040 (w), 976 (w), 913 (w), 805 (m), 746 (w), 704 (w), 670 (w),

1

/c, a=11.253(2), b=10.878(2), c=19.654(4) ꢃ, b=

3

ꢀ3

1

(

ꢀ

1

53 (w), 607 (w), 592 (w), 575 (w), 547 (w), 504 cm (w); UV/Vis

Cl ): l (e)=446 (sh, 4588), 408 (5260), 321 (10361), 298 (sh, 8602),

45 nm (10310 mol dm cm ); MS (FAB ): m/z (%): 645.1329 (46.5)

(

CH

2

1

2

ꢀ

1

3

ꢀ1

+

2

A

H

U

G

R

N

U

G

2

ACHTUNGTRENNUNG

+

[

M+H] , 644.1293 (65.6) [M] , 609.1530 (100) [MꢀHCl] .

Crystal data for C20 Pt: M =644.46, 0.60ꢄ0.40ꢄ0.35 mm , mono-

clinic, space group P2 , a=11.881(2), b=15.868(3), c=12.538(3) ꢃ, b=

06.65(3)8, V=2264.7(9) ꢃ , Z=4, 1calcd =1.890 Mgm , MoKa radiation

graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.20–30.118;

reflections measured=44865, independent=13117, Rint =0.0477; final R

indices [I>2s(I)]: R =0.0227, wR =0.0620.

[NiCl (2)]: [NiCl (dme)] (84.6 mg, 0.39 mmol) dissolved in CH

5 mL) was cooled to ꢀ788C and slowly added to a solution of 2

159.9 mg, 0.43 mmol) in CH Cl

2

3

H

26Cl

2

N

8

r

(

2

(8 mL), also cooled to ꢀ788C.

1

After stirring for 1 h, the mixture was allowed to warm to room tempera-

ture over 19 h, which resulted in the solution changing from yellow to

purple. The reaction mixture was filtered with a cannula, and the solvent

removed in vacuo from the filtrate. The residue was washed with toluene

3

ꢀ3

1

(

1

2

and n-hexane to yield [NiCl

powder. Crystals suitable for X-ray diffraction were obtained by slow dif-

fusion of n-hexane into a solution of [NiCl ((R)-3)] in toluene at room

, 295.0 K): d=51.02 (s, 6H;

), 21.77 (s, 2H; H3/13), 16.11 (s, 6H; CH ), 14.30 (s, 2H; H5/15),

12.68 (s, 2H; H7/17), 9.20 (s, 6H; CH ), 4.35 (s, 2H; H8/18), 2.27 (s, 6H;

CH

), 0.34 (s, 2H; H2/12), ꢀ1.42 ppm (s, 2H; H6/16); C NMR

(150.90 MHz, CD Cl , 295.0 K): d=657.06 (2C; C21/26), 347.86 (2C; C2/

12), 326.77 (2C; C10/20), 315.66 (2C; CH ), 222.86 (2C; C4/14), 184.83

2

((R)-3)] (221.38 mg, 66%) as a purple

A

C

H

T

U

N

G

T

R

E

N

U

N

G

2

A

C

H

T

U

N

G

T

R

E

N

U

N

G

2 2

Cl

(

2

1

2

(7 mL), also cooled to ꢀ788C. After

temperature. H NMR (600.13 MHz, CD

CH

2 2

Cl

stirring for 1 h, the mixture was allowed to warm to room temperature

over 24 h. A light-green precipitate was collected by filtration, and the

solvent of the dark-blue filtrate was removed in vacuo. The residue was

3

1

3

washed with toluene and n-hexane to yield [NiCl

a purple powder. Crystals suitable for X-ray diffraction were grown by

slow diffusion of EtO at room temperature into a solution of [NiCl (2)]

H NMR (600.13 MHz, CD Cl , 295.1 K): d=19.18 (s, 2H;

H5/8), 18.61 (s, 12H; CH ), 16.30 (s, 2H; H3/10), 10.31 (s, 4H; CH ), 1.07

s, 4H; CH

), ꢀ11.48 (s, 2H; H4/9), ꢀ17.71 ppm (s, 2H; H2/11);

C NMR (150.90 MHz, CD Cl , 295.0 K): d=806.70 (2C; C13/18), 353.24

2C; C2/11), 286.43 (2C; C6/7), 258.97 (2C; C4/9), 102.21 (2C; C5/8),

2

(2)] (150.9 mg, 77%) as

2

3

2

(2C; C6/16), 173.53 (2C; C8/18), 112.65 (2C; C9/19), 97.27 (2C; CH

84.24 (2C; C3/13), 79.26 (2C; C7/17), 72.65 (2C; C5/15), 2.17 (2C; CH

0.99 (2C; CH

(w), 2934 (m), 2890 (w), 2797 (w), 1619 (m), 1551 (s), 1528 (s), 1467 (m),

1421 (s), 1411 (m), 1397 (m), 1368 (w), 1337 (w), 1242 (w), 1205 (w),

1163 (m), 1145 (w), 1065 (w), 1049 (w), 979 (w), 915 (w), 866 (w), 845

(m), 808 (w), 747 (m), 697 (w), 672 (w), 602 (w), 575 (w), 523 (w), 496

3

),

1

in CH

2

Cl

2

.

2

3

2

3

), ꢀ86.23 ppm (2C; C1/11); IR (CsI): n˜ =3051 (w), 3007

(

2

1

3

2

(

1

3

CH

(

5.83 (2C; C3/10), ꢀ239.95 ppm (2C; C1/12) ( C NMR signals of the

and CH group could not be detected); IR (CsI): n˜ =2939 (w), 2877

w), 1617 (s), 1593 (m), 1579 (m), 1558 (s), 1494 (w), 1475 (m), 1437 (w),

ꢀ

1

2

3

(w), 449 (w), 428 cm (w); UV/Vis (CH Cl ): l (e)=635 (55), 541 (112),

2 2

3

ꢀ

1

ꢀ1

+

452 (sh, 28), 426 nm (sh, 43 mol dm cm ); MS (EI ): m/z (%):

+ +

1

421 (s), 1383 (w), 1295 (s), 1221 (m), 1160 (w), 1121 (w), 1100 (w), 1038

610.1705 (2.9) [M] , 572.1961 (4.1) [MꢀHCl] , 536.2192 (15.9)

+

(

m), 1007 (w), 983 (m), 872 (w), 825 (w), 777 (w), 762 (m), 737 (w), 689

w), 652 (w), 618 (w), 590 (w), 514 (m), 494 (w), 474 (w), 454 cm (w);

[Mꢀ2HCl] , 480.3009 (100) [MꢀCl

2

Ni] ; elemental analysis (%) calcd

Ni (627.48): C59.72, H 6.23, N

ꢀ

1

for [NiCl

2

((R)-3)]·0.2 C

6

H

14, C31.2

H38.8Cl

2

N

6

UV/Vis (CH

2

Cl

2

):

l

(e)=650 (96), 556 (128), 361 nm (sh,

13.39; found: C 59.80, H 6.47, N 13.45.

Crystal data for Ni

.20 mm , monoclinic, space group P2

6.146(3) ꢃ, b=90.10(3)8, V=3592.9(12) ꢃ , Z=4, 1calcd =1.298 Mgm

ꢀ1

3

ꢀ1

+

3

56 mol m cm ); MS (FAB ): m/z (%): 506.1061 (3.8) [M] , 469.1402

C

30

H

36Cl

2

N

6

x

C

7

H

8

:

M

r

=702.390, 0.30ꢄ0.20ꢄ

+

(

30) [MꢀCl] , 376.2316 (100) [MꢀCl

2

Ni] ; elemental analysis (%) calcd

3

0

1

, a=11.065(2), b=20.111(4), c=

for C22

.54, N 15.91.

Crystal data for C22

clinic, space group P2

2.45(3)8, V=4638.1(17) ꢃ , Z=8, 1calcd =1.450 Mgm , MoKa radiation

graphite-monochromated, l=0.71073 ꢃ), T=100 K, qrange =2.27–27.518;

reflections measured=10482, independent=10481, Rint =0.0663; final R

indices [I>2s(I)]: R =0.0679, wR =0.1793.

[NiBr (2)]: [NiBr (dme)] (133.5 mg, 0.43 mmol) dissolved in cooled

H

28Cl

2

N

6

Ni (506.10): C 52.21, H 5.58, N 16.61; found: C 51.68, H

3

ꢀ3

,

6

MoKa radiation (graphite-monochromated, l=0.71073 ꢃ), T=100 K,

range =2.39–29.508; reflections measured=19033, independent=18423,

int =0.0477; final R indices [I>2s(I)]: R =0.0453, wR =0.0906.

[NiBr {(R)-3}]: [NiBr (dme)] (146.2 mg, 0.47 mmol) dissolved in cooled

ꢀ788C) acetone (5 mL) was slowly added to solution of (R)-3

237.0 mg, 0.493 mmol) in acetone (4 mL) at ꢀ788C. After stirring for

h, the mixture was allowed to warm to room temperature over 21 h. A

purple precipitate was collected by filteration, and the residue was

washed with toluene (5 mL) and n-hexane (5 mL) to yield [NiBr {(R)-3}]

(254.7 mg, 77%) as a purple powder. Crystals suitable for X-ray diffrac-

tion were obtained by slow diffusion of Et into solution of

((R)-3)] in acetone at ꢀ218C. H NMR (600.13 MHz, CD Cl

295.0 K): d=37.00 (s, 6H; CH ), 21.47 (s, 2H; H3), 16.09 (s, 6H; CH ),

14.47 (s, 2H; H5), 12.66 (s, 2H; H7), 10.19 (s, 6H; CH ), 4.23 (s, 6H;

CH

), 3.53 (s, 2H; H8), ꢀ1.60 ppm (s, 4H; H2/6);

(150.90 MHz, CD Cl , 295.0 K): d=685.74 (2C; C11), 349.70 (2C; C2),

327.89 (2C; C10), 281.05 (2C; CH ), 222.95 (2C; C4), 185.67 (2C; C6),

173.19 (2C; C8), 112.30 (2C; C9), 88.71 (2C; CH ), 83.76 (2C; C3), 77.45

(2C; C7), 71.03 (2C; C5), 2.20 (2C; CH ),

), ꢀ2.70 (2C; CH

3

H

28Cl

2

N

6

Ni: M

r

=506.10, 0.23ꢄ0.20ꢄ0.18 mm , mono-

q

1

/n, a=10.663(2), b=33.090(7), c=13.157(3) ꢃ, b=

R

1

2

3

ꢀ3

9

(

A

H

U

G

R

N

2

ACHTUNGTRENNUNG

(

a

1

2

1

A

C

H

T

U

N

G

T

R

E

N

U

N

G

2

ACHTUNGTRENNUNG

(

0

ꢀ788C) acetone (2 mL) was added slowly to a solution of 2 (171.0 mg,

2

.45 mmol) in acetone (2 mL) at ꢀ788C. The mixture was allowed to

warm to room temperature over 17 h. A turquois precipitate was collect-

2

O

a

1

ed by filtration and the residue was washed with toluene (5 mL) and n-

[NiBr

2

,

hexane (5 mL) to yield [NiBr

2

(2)] (214.5 mg, 83%) as a teak powder.

CN at 48C.

, 294.9 K): d=18.50 (s, 2H; H5/8), 17.04

s, 2H; H3/10), 11.83 (s, 12H; CH ), 10.62 (s, 4H; CH ), 0.25 (s, 4H;

CH

), ꢀ12.14 (s, 2H; H4/9), ꢀ17.16 ppm (s, 2H; H2/11); C NMR

150.90 MHz, CD Cl , 295.0 K): d=810.56 (2C; C13/18), 363.31 (2C; C2/

1), 288.65 (2C; C6/7), 260.57 (2C; C4/9), 103.09 (2C; C5/8), 35.68 (2C;

3

Crystals suitable for X-ray diffraction were obtained in CH

3

1

13

H NMR (600.13 MHz, CD

2

Cl

2

3

C NMR

(

3

2

1

3

2

3

(

1

2

3

1

3

C3/10), ꢀ252.91 ppm (2C; C1/12) ( C NMR signals of the CH

groups could not be detected); IR (CsI): n˜ =2994 (w), 2886 (w), 1593

m), 1580 (s), 1558 (s), 1517 (m), 1486 (m), 1475 (m), 1421 (s), 1410 (m),

2

and CH

3

ꢀ112.11 ppm (2C; C1); IR (CsI): n˜ =3074 (w), 3056 (w), 3012 (w), 2936

(m), 2882 (m), 2792 (w), 1621 (m), 1549 (s), 1525 (s), 1466 (s), 1420 (s),

1406 (s), 1395 (s), 1368 (m), 1339 (m), 1269 (w), 1242 (m), 1217 (w), 1204

(w), 1161 (m), 1109 (w), 1064 (w), 1050 (m), 980 (m), 937 (w), 915 (m),

863 (w), 847 (s), 829 (w), 807 (m), 768 (m), 742 (s), 674 (m), 633 (w), 600

(

1

7

384 (m), 1296 (m), 1285 (m), 1244 (w), 1154 (w), 1119 (w), 1096 (w),

042 (m), 1003 (w), 983 (w), 871 (w), 827 (w), 777 (m), 763 (m), 755 (m),

35 (w), 706 (w), 655 (w), 610 (w), 590 (w), 517 (m), 494 (w), 476 (w),

ꢀ

1

(w), 574 (w), 537 (w), 523 (m), 497 (m), 449 (w), 428 cm (w); UV/Vis

Chem. Eur. J. 2013, 00, 0 – 0

ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

17

&

ÞÞ

These are not the final page numbers!

J. Himmel et al.

[

63]

[36,41]

(

1

6

C

CH

2

Cl

2

ꢀ

):

l

(e)=657 (90), 569 (168), 455 (sh, 58), 427 nm (sh,

09 program package with a B3LYP/6-311G**//HF/6-31G* model,

whereas pure DFT calculations relied on the hybrid-method B3LYP

1

3

ꢀ1

+

01 mol dm cm ); MS (FAB ): m/z (%): 698.0679 (4.0) [M] ,

+

[64]

[65]

19.1488 (59.4) [MꢀBr]

;

elemental analysis (%) calcd for

(DFT using the Becke exchange functional and Lee–Yang–Parr cor-

relation functional) with the 6-31G** basis set. Calculations on the sol-

30

H

36Br

2

N

6

Ni (699.15): C51.54, H 5.19, N 12.02; found: C 51.15, H 5.25,

N 11.87.

Crystal data for C30

onal, space group P3

vent effect with CH

namic dielectric constant of 1.806) were carried out by using the conduc-

torlike polarizable continuum model (CPCM). Optimization and spin-

density calculation of the Ni complexes were carried out by using the

Turbomole program package with a combination of the B3LYP func-

tional and the def2-TZVPP basis set.

3

CN (with static dielectric constant e=36.64 and dy-

3

H

36Br

2

N

6

Ni: M

r

=699.18, 0.20ꢄ0.20ꢄ0.15 mm , hexag-

[

66]

1

2

1

,

a=10.8855(15), c=22.384(5) ꢃ, V=

II

3

ꢀ3

2

297.0(9) ꢃ , Z=3, 1calcd =1.516 Mgm , MoKa radiation (graphite-mono-

[

67]

chromated, l=0.71073 ꢃ), T=100 K,

measured=20150, independent=3690, Rint =0.0545; final R indices [I>

qrange =2.16–27.948; reflections

[

68]

2

s(I)]: R

[PtCl (C

[PtCl

1

2

=0.0259, wR =0.0557.

1

A

C

H

T

U

N

G

T

R

E

N

U

N

G

2

A

C

H

T

U

N

G

T

R

E

N

U

N

G

2

H

4

)

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(k -4)]: Synthesis as described in ref. [18]. Crystal data for

1

2

0

2

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(C

2

H

4

)

A

C

H

T

U

N

G

T

R

E

N

U

N

G

(k -4)]·Et

2 4 2 r

O (C68H82Cl N12OPt ): M =1615.42, 0.20ꢄ0.20ꢄ

3

.17 mm , monoclinic, space group P2(1), a=15.499(3), b=10.292(2), c=

0.832(4) ꢃ, b=102.01(3)8, V=3250.2(11) ꢃ , Z=2, 1calcd =1.651 Mgm

3

ꢀ3

,

Acknowledgements

MoKa radiation (graphite-monochromated, l=0.71073 ꢃ), T=100 K,

range =2.22–32.098; reflections measured=39629, independent=22023,

int =0.0978; final R indices [I>2s(I)]: R =0.0546, wR =0.0884.

Heck reaction: NaOAc (360 mg, 4.4 mmol) and the catalyst (0.1 mol%,

q

The authors gratefully acknowledge continuous financial support by the

Deutsche Forschungsgemeinschaft (DFG).

R

1

2

ꢀ3

4

ꢄ10 mmol) were placed in a three-necked flask fitted with a reflux

[

1] a) F. T. Edelmann, Adv. Organomet. Chem. 2008 , 57 , 183–352;

b) F. T. Edelmann, Coord. Chem. Rev. 1994 , 137 , 403–481; c) J.

Barker, M. Kilner, Coord. Chem. Rev. 1994 , 133 , 219–300; d) P. J.

Bailey, S. Price, Coord. Chem. Rev. 2001 , 214 , 91–141 ; e) S. Herres-

Pawlis, Nachr. Chem. 2009 , 57 , 20–23 ; f) M. P. Coles, Dalton Trans.

006 , 985–1001; g) M. P. Coles, Chem. Commun. 2009 , 3659–3676;

h) H. E. Abdou, A. A. Mohamed, J. P. Fackler, Inorg. Chem. 2004,

3, 166–168; i) A. A. Mohamed, H. E. Abdou, A. Mayer, J. P. Fack-

condenser and dissolved in DMF (5 mL) in an Ar atmosphere. Iodoben-

zene (0.45 mL, 4 mmol) and styrene (0.64 mL, 5.6 mmol) were added to

the reaction mixture, and the reaction vessel was placed into an oil bath

preheated to 1658C. Aliquots (0.1 mL) were removed after fixed times

and added to H

5 mL) and dried over Na

GC-MS (the yields and TOF are the average of two corroborating runs).

The reaction was quenched with H O (20 mL) after 4.5 h, and the crude

product was extracted with CH Cl (2ꢄ10 mL). The organic layer was

washed with H O (5ꢄ10 mL) and dried over Na SO . The mixture was

2

O (10 mL). The organic layer was extracted with CH

2 2

Cl

2

(

2

SO . The mixture was filtered and analyzed by

4

2

ler Jr., J. Cluster Sci. 2008 , 19 , 551–559; j) H.-J. Himmel in Modeling

of Molecular Properties (Ed. P. Comba), Wiley-VCH, Weinheim,

011; k) C. Jones, Coord. Chem. Rev. 2010 , 254 , 1273–1289.

2

4

2

filtered, the solvent was removed, and the product was recrystallized

from hot n-hexane to obtain trans-stilbene and 1,1-diphenylethylene as

white crystals (see the main text for more information).

[

2] See, for example: a) F. A. Cotton, J. H. Matonic, C. A. Murillo, J.

Am. Chem. Soc. 1997 , 119 , 7889–7890 ; b) J. L. Bear, Y. Li, B. Han,

K. M. Kadish, Inorg. Chem. 1996 , 35 , 1395–1398; c) R. Clꢅrac, F. A.

Cotton, L. M. Daniels, J. P. Donahue, C. A. Murillo, D. J. Timmons,

Inorg. Chem. 2000 , 39 , 2581–2584; d) F. A. Cotton, C. A. Murillo,

X. Wang, C. C. Wilkinson, Inorg. Chim. Acta 2003, 351, 191–200.

3] B. M. Day, N. E. Mansfield, M. P. Coles, P. B. Hitchcock, Chem.

Commun. 2011 , 47 , 4995–4997.

Oxidation experiments with Ph

CD Cl (0.6 mL) was added to

20.9 mg, 0.028 mmol) in CD Cl

2

S

2

: a) Ph

2 2

S (6.1 mg, 0.028 mmol) in

3

2

a

solution of [{PdCl ACHTNUGTREUNNNG( h -C H )} (5)]

3 5 2

(

2

(0.5 mL)at ꢀ788C. The reaction mixture

1

was monitored by H NMR spectroscopic analysis as it warmed to room

[

temperature. Only the starting materials could be observed in the

1

H NMR spectra, even after 1 day at room temperature. b) Ph

.017 mmol) in CD Cl

(0.7 mL) at ꢀ788C was added to a solution of

{PtCl (5)] (9.8 mg, 0.015 mmol) in CD Cl (0.7 mL). The reaction mix-

2 2

S (3.7 mg,

4] a) S. P. Green, C. Jones, A. Stasch, Science 2007 , 318 , 1754–1757 ;

b) M. Westerhausen, Angew. Chem. 2008 , 120 , 2215–2217; Angew.

Chem. Int. Ed. 2008 , 47 , 2185–2187.

0

[

2

1

ture was monitored by H NMR spectroscopic analysis as the mixture

warmed to room temperature. Only the starting materials could be ob-

served in the H NMR spectra, even after 1 day at room temperature.

[

5] a) J. Bçrner, U. Flçrke, K. Huber, A. Dçring, D. Kuckling, S.

Herres-Pawlis, Chem. Eur. J. 2009 , 15 , 2362–2376; b) J. Bçrner, I.

dos Santos Vieira, A. Pawlis, A. Doering, D. Kuckling, S. Herres-

Pawlis, Chem. Eur. J. 2011 , 17 , 4507–4512; c) J. Bçrner, I. dos Santos

Vieira, M. D. Jones, A. Dçring, D. Kuckling, U. Flçrke, S. Herres-

Pawlis, Eur. J. Inorg. Chem. 2011 , 4441–4456 ; d) I. dos Santos

Vieira, S. Herres-Pawlis, Eur. J. Inorg. Chem. 2012 , 765–774; e) I.

dos Santos Vieira, S. Herres-Pawlis, Z. Naturforsch. B 2012, 67, 320–

1

X-ray crystallography: Suitable crystals were taken directly out of the

mother liquor, immersed in perfluorinated polyether oil, and fixed on top

of a glass capillary. Measurements were made with a Nonius-Kappa CCD

diffractometer with a low-temperature unit by using graphite-monochro-

mated MoKa radiation, with the temperature set at 100 K. The data col-

[

59]

lected were processed by using the standard Nonius software. All the

calculations were performed by using the SHELXT-PLUS software pack-

age. The structures were solved by direct methods with the SHELXS-97

3

30.

[

6] a) C. Wꢀrtele, E. Gaoutchenova, K. Harms, M. C. Holthausen, J.

Sundermeyer, S. Schindler, Angew. Chem. 2006 , 118 , 3951–3954;

Angew. Chem. Int. Ed. 2006 , 45 , 3867–3869; b) M. P. Lanci, V. V.

Smirnov, C. J. Cramer, E. V. Gauchenova, J. Sundermeyer, J. P.

Roth, J. Am. Chem. Soc. 2007 , 129 , 14697–14709; c) D. Maiti, D.-H.

Lee, K. Gaoutchenova, C. Wꢀrtele, M. C. Holthausen, A. A. N. Sar-

jeant, J. Sunderm eyer, S. Schindler, K. D. Karlin, Angew. Chem.

008 , 120 , 88–91; Angew. Chem. Int. Ed. 2008 , 47 , 82–85.

7] P. Roquette, A. Maronna, A. Peters, E. Kaifer, H.-J. Himmel, C.

Hauf, V. Herz, E.-W. Scheidt, W. Scherer, Chem. Eur. J. 2010 , 16 ,

[

60,61]

program and refined with the SHELXL-97 program.

Graphical

handing of the structural data during solution and refinement was per-

[

62]

formed with XPMA. Atomic coordinates and anisotropic thermal pa-

rameters of non-hydrogen atoms were refined by full-matrix least-squares

calculations. CCDC-912277 ([1H]PtCl

12279 (6), CCDC-912280 ([NiBr (2)]), CCDC-912281 ([Ni(5)

CCDC-912282 ([NiCl (3)]), CCDC-912283 ([NiBr (3)]), CCDC-912284

(5)]), CCDC-912286

3

), CCDC-912278 (5), CCDC-

9

2

3

2

]Cl ),

2

[

3

(

C

[PtCl

[NiCl

)}

CCDC-912291 ([6H ]PF

2

(5)]), CCDC-912285 ([{PdCl

3 5 2

ACHTUNGTRENUN(NG h -C H )}

3

2

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Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

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Received: December 3, 2012

Revised: March 12, 2013

Published online: && &&, 0000

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These are not the final page numbers!

Bisguanidines with Biaryl Backbones as Proton Sponges and Ligands

FULL PAPER

Guanidine Ligands

A. Maronna, O. Hꢀbner, M. Enders,

E. Kaifer, H.-J. Himmel* . . . &&&& — &&&&

Bisguanidines with Biphenyl,

Binaphthyl, and Bipyridyl Cores:

Proton-Sponge Properties and Coordi-

nation Chemistry

Showing some backbone: Bisguani-

dines with flexible biaryl backbones

are proton sponges and ligands in a

series of new mono- and dinuclear

Group 10 metal complexes (see pic-

ture). The spin-density distribution in

paramagnetic Ni complexes was stud-

ied by using NMR spectroscopy and

quantum-chemical calculations.

II

Chem. Eur. J. 2013, 00, 0 – 0

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Article Doi

Bisguanidines with biphenyl, binaphthyl, and bipyridyl cores: Proton-sponge properties and coordination chemistry

DOI: 10.1002/chem.201204294

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