Imidazolyl-phenyl (IMP) anions: A modular structure for tuning solubility and coordinating ability

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Hicks, W. Sabbers and G. E. Dobereiner, Dalton Trans., 2019, DOI: 10.1039/C9DT03511G.

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14 March 2017

Pages 3073-3412

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PAPER

Imidazolyl-Phenyl (IMP) Anions: A Modular Structure for Tuning

Solubility and Coordinating Ability†

Derek I. Wozniak, Andrew J. Hicks, William A. Sabbers, and Graham E. Dobereiner*

Received 00th January 20xx,

Accepted 00th January 20xx

The effect of counteranion upon a cation’s solution-phase reactivity depends on a subtle interplay of weak interactions.

Although these effects are widely appreciated in synthesis and catalysis, probing and controlling anion-cation interactions

remains a significant challenge. Here we report the synthesis, characterisation and reactivity of the IMP anions, a family of

anions with a coordinating ability that can be tuned for a given application. The anions are robust, compatible with both

strongly basic and acidic media, suitable for isolation of unstable organometallic species, and effective as counteranions for

homogeneous catalysis. IMP anions are prepared in two steps: deprotonation of substituted 2-phenylimidazoles with NaH,

followed by addition of 2 equiv. B(C₆F₅)₃. The anions prepared feature a range of functionality, including nitro, ester, amide,

amine and alcohol groups. Based on the spectroscopic properties of [Pd(IPr)(C(O)C₉H₆N)] [IMP-R], the coordinating ability of

DOI: 10.1039/x0xx00000x

[IMP-R]⁻ranges between BF₄⁻and BAr^{F −}, depending on the polarity of the R group. Gold complexes of type [L-Au-L’][IMP-R]

4

have been isolated and characterised, resulting in the first X-ray structure of a (²-diphenylacetylene)Au complex.

[(tBuXPhos)Au(MeCN)][IMP-R] catalyses [2+2] cyclisation of alkenes and alkynes, as well as the hydroalkoxylation of alkynes.

−

Unlike SbF₆⁻and BArF₄, the [IMP-H]⁻and [IMP-CF₃]⁻salts are sufficiently soluble to efficiently promote cyclisations in toluene

with [(tBuXPhos)Au(MeCN)]⁺.

Although “superweak” anions, such as the charge-diffuse

halogenated tetraarylborate BAr^{F − 15-18}

have been widely

,

Introduction

4

adopted in catalysis, some catalytic reactions actually

demonstrate superior activity and selectivity in the presence of

more tightly-coordinating anions.^19-25In gold(I) catalysis, basic

Weakly-coordinating anions (WCAs; Fig. 1)^1-4enable isolation of

highly electrophilic species^5-7and play essential roles in

homogeneous catalysis.^8-10Anions compete with solvent,

ancillary ligands, substrate, and potentially product, for inner-

sphere binding to a cationic metal centre’s coordination sites.

The most weakly-binding anions therefore permit cations to

interact with substrate with minimal competition from anion.¹¹

Highly lipophilic anions also solubilise catalysts in weakly-

binding solvents, permitting catalysis in media that minimizes

competitive coordination of solvent to binding sites.^{11, 12}Weak

anion coordination is often beneficial for catalytic rates,

although coordination can also protect catalytic intermediates

against deactivation.^{13, 14}These inner-sphere phenomena are

discrete from ion-pair aggregation or outer-sphere interactions

with substrate-coordinated complexes, which can further

attenuate the behaviour of catalytic intermediates and

influence barriers to product. The complex nature of the

equilibria that depend on inner-sphere anion binding,

combined with the weak and unpredictable nature of outer-

sphere interactions, makes it very difficult to determine an ideal

anion for a given organometallic application without extensive

empirical exploration.

counteranions are thought to participate in cooperative

24, 26-31

reactions with cationic intermediates.^19-21,

Toste and

coworkers^{32, 33}have pioneered a chiral counteranion strategy

for Au(I) catalysis, where chiral anions associated through ion-

pairing and/or hydrogen bonding engage substrate during a

stereoselectivity-determining step. Zuccaccia, Belanzoni and

coworkers^19-21and Zhdanko and Maier²⁴have explored anion

effects in Au-catalysed alkyne hydroalkoxylation, finding OTs⁻

and OTf⁻promote nucleophilic attack by hydrogen bonding with

the alcohol nucleophile; more weakly-coordinating anions

−

(SbF₆) are inferior hydrogen bond acceptors and are far less

effective. At the other extreme, more strongly coordinating and

basic anions (OAc⁻, TFA⁻) bind too well to Au for facile substrate

binding, and can further deactivate catalyst by formation of Au-

OR. Here a balance in basicity is key to achieving the highest

catalytic rates.

Because anions can play various roles in catalysis,^34-36

extensive screening may be needed before an effective

counteranion and solvent is identified. Stability of anion and

compatibility with cation are other important considerations.³⁷

Just like ligands, various physical properties of anions –

solubility, basicity, hydrogen bonding/proton affinity, metal

affinity – can influence reaction outcomes, but unlike the

myriad variants of highly modular phosphorus and carbene

Department of Chemistry, Temple University, Philadelphia, PA 19122, United

States. E-mail: dob@temple.edu

† Electronic supplementary information (ESI) available: NMR and IR spectra. CCDC

1919818-1919840. For ESI and crystallographic data in CIF or other electronic

format see DOI: 10.1039/x0xx00000x

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DOI: 10.1039/C9DT03511G

Fig 1 Selected examples of modular weakly-coordinating anionic scaffolds.

ligand classes employed by organometallics chemists, most metal-ligand connectivity with a pendant weakly-coordinating

catalytic explorations rely on a small collection of “traditional” anionic element,^50-56can yield valuable insights into

−

anions (e.g., ClO₄, BF₄, and PF₆). These anions are, in general, counteranion effects.

less charge-diffuse and more coordinating^38,than modern

Surprisingly, tuneable weakly-coordinating anions that

39

WCAs such as borates, aluminates, and halogenated or engage metals with weak, transient dative bonds have not been

40-43

alkylated carboranes;^1-3,

they are also, in general, more used widely to study and control anion effects in organometallic

structurally heterogeneous than modern WCAs and vary catalysis. Select modern WCA anion scaffolds that could be used

dramatically in physical properties from one another. for fine-tuning of anion effects are highlighted in Fig. 1. These

A systematic approach to tuning anion coordinating ability scaffolds combine stability in acidic and basic media with

would be useful in empirical optimisation of catalytic expansive synthetic versatility. One class, the tetraarylborates,

conditions, especially in cases where anion functionality show variable coordinating ability depending on the extent of

facilitates

a

key step. More broadly, controlling the halogenation on the aromatic rings. The 6-arene coordination³

−

hydrophobicity of counteranions permits “fine-tuning” in the common for BPh₄can be reduced with partial fluorination

rational design for synthetic routes, including construction of (BAr^{F −});-coordination of the perfluorinated arenes of B(C₆F₅)₄

−

4

ionic liquids and soft (polymer) materials.⁴⁴Another potential has not yet been observed crystallographically.²Similarly, a

use is in exploring the structure/activity relationships within a wide variety of closo-carboranes and dodecaboranes with

mechanistic study. Computational approaches to considering diverse coordinating ability and solubility properties can be

ion-pairing effects have led to important insights,⁴⁵and formed via reaction at either the carbon vertex or boron

− 43

examination of solid-phase data provides a comparison of vertices of CHB₁₁H₁₁

.

Carboranes of type [CHB₁₁R₅X₆]⁻(R=H,

weakly-coordinating character.⁴⁶However, pinpointing the role Me, X; X=F, Cl, Br, I) have a balance of high thermal stability,

of anions in solution-phase reactions remains challenging good solubility⁵⁷and tuneable coordinating ability⁵⁸that has

because weak anion/cation solution interactions are difficult to been useful for stabilizing extremely electrophilic species.⁵

measure. Several NMR techniques are available for More recent efforts exploring applications beyond the

quantification if key resonances can be observed in situ.^{11, 47-49}conventional WCA contexts showcase the synthetic breadth of

Granular adjustments to anion coordinating ability could reveal carboranes.^{41, 42}Finally, aluminates can be modified through

potential roles of counteranion during catalysis, offering a modifying the alkoxy, aryloxy or anilide substituents.⁵⁹For

broader understanding of underlying mechanisms. Employing example, While [Al(OC(CF₃)₃)₄]⁻is very weakly coordinating and

Zwitterionic complexes, featuring ligands that combine robust

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stable to protonolysis,⁶⁰biphenolic aluminates such as CH₂NMe₂] show Na⁺coordinating to the heteroatomic (O, N)

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“altebate”⁶¹are highly lipophilic yet unstable in protic media.⁶²anion functionality; Na[IMP-CH₂OH] further shows a 2.659(7) Å

DOI: 10.1039/C9DT03511G

The present work describes the synthesis and properties of O–H···O hydrogen bond between -CH₂OH and cocrystallised THF

a “bridged WCA”²platform. Prior examples of this class include (Fig. 3). Na[BIMP] demonstrates Na⁺coordination to mutually

63-65

Bochmann’s [(F₅C₆)₃B-LB-B(C₆F₅)₃]⁻

(LB = CN, NH₂, etc.), ortho-fluorines on one C₆F₅ring, while [IMP-(CF₃)₂]⁻exhibits no

Ingo-Krossing’s [((F₃C)₃CO)₃Al(-F)Al(OC(CF₃)₃)₃]⁻, and Piers’ contacts with Na⁺. On the whole, X-ray analysis shows the

66

chelating diborane^67,

(Fig. 1). These anions are Lewis negative charge of [IMP-R]⁻to be highly diffuse, such that

68

acid/base adducts where two large lipophilic Lewis acids are coordination of para-substituents to Na⁺mimics the behaviour

bound to a single monoanionic ligand, forming an even larger of neutral organic molecules.

and more charge-diffuse structure.²The parent of our anion

a

Table 1 IMP anions prepared via reaction of sodium imidazolates and B(C₆F₅)₃

family,³⁴the weakly-coordinating phenylimidazole-based anion

([IMP-H]⁻, Fig. 1) is itself a derivative of the superweak [imid]⁻

bridged WCA prepared by LaPointe, Klosin, Babb and co-

70

workers^69,

and part of a broader class of borane-adduct

bridged WCAs.^{63-65, 71-73}

The IMP anion family we report is simple to synthesise, air-

and moisture-stable, and features an array of installed

functionalities. [IMP-R]⁻anions have been paired with

[Pd(IPr)(C(O)C₉H₆N)]⁺(1) to assess donor abilities³⁴via NMR, IR,

DFT, and percent buried volume. Preliminary examination of

counteranion effects have been explored in Au-catalysed

intermolecular [2+2] cyclisation of phenylacetylene with α-

methyl styrene as well as the Au-catalysed alkoxylation of 3-

hexyne with two different nucleophiles. We find that the choice

of installed anion functionality affects the coordinating ability of

the IMP anions as well as their solubility, and therefore serves

as a means to control the structure and reactivity of

organometallic cations.

Anion

[IMP-CF₃]

-Ar

Yield

62%

74%

62%

56%

41%

46%

77%

4-(trifluoromethyl)phenyl

3,5-bis(trifluoromethyl)phenyl

4-nitrophenyl

4-(methoxycarbonyl)phenyl

4-(dimethylcarbamoyl)phenyl

4-(di-n-butylcarbamoyl)phenyl

4-(piperidine-1-carbonyl)phenyl

[IMP-(CF₃)₂]

[IMP-NO₂]

[IMP-CO₂Me]

[IMP-DMA]

[IMP-DBA]

[IMP-pipA]

^aSee electronic supplementary Information (ESI) for synthetic procedures.

B(C₆F₅)₃

N

CF₃

Ar =

Ar

B(C₆F₅)₃

CF₃

[IMP-(CF₃)₂]

Results

N

[IMP-CF₃]

Synthesis and Characterisation of Na[IMP-R] Salts.

Deprotonation of substituted 2-phenylimidazoles or 2-

phenylbenzimidazole with NaH followed by addition of B(C₆F₅)₃

at –35 C yields the sodium salts of [IMP-R]⁻(Table 1).

Benzimidazole-based [BIMP]⁻was prepared similarly (Fig. 2). In

our hands Li imidazolates were incompatible with B(C₆F₅)₃and

formed other products, but once prepared, [IMP-R]⁻are stable

to Li⁺including in strongly basic and reducing conditions. For

example, lithium aluminium hydride reduction of Na[IMP-

CO₂Me] and Na[IMP-DMA] affords the benzyl alcohol- and

benzyl amine-substituted anions [IMP-CH₂OH] and [IMP-

CH₂NMe₂] (Fig. 2).

O

NO₂

OMe

[IMP-NO₂]

O

[IMP-CO₂Me]

O

N

N(ⁿBu)₂

NMe₂

[IMP-DMA]

[IMP-DBA]

[IMP-pipA]

B(C₆F₅)₃

N

The salts are indefinitely air- and moisture-stable, and in our

N

hands less hygroscopic than NaBAr^F. Recrystallisation of anions

Ph

4

N

from dichloromethane/tetrahydrofuran/pentane results in

Na(THF)_x[IMP-R]. Like the parent [imid]⁻anion (Fig. 1),⁶⁹the

bond distances of the anion’s phenylimidazolato core are

essentially the same as those of the parent imidazoles. For

example, bond parameters of 4-(1H-imidazol-2-yl)-N,N-

dimethylbenzamide are nearly identical to Na[IMP-DMA]; 2-

(3,5-bis(trifluoromethyl)phenyl)-1H-imidazole and Na[IMP-(CF-

₃)₂] also have similar bond lengths and angles (see structure

reports for each in the ESI). In the obtained structures of

Na[IMP-CO₂Me] (Fig. 3), Na[IMP-DMA], Na[IMP-DBA], and

Na[IMP-pipA], Na⁺coordinates to the anion C═O, with Na–O

bonds ranging 2.25 – 2.32 Å. Na[IMP-CH₂OH] and Na[IMP-

N

OH

B(C₆F₅)₃

[BIMP]

B(C₆F₅)₃

[IMP-CH₂OH]

B(C₆F₅)₃

N

NMe₂

B(C₆F₅)₃

[IMP-CH₂NMe₂]

Fig. 2 Structures of anions prepared.

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Fig. 4 Crystal structures of inner-sphere 1[IMP-NO₂] (top) and 1[IMP-CO₂Me] (bottom)

complexes. C₆F₅rings and diisopropylphenyl substituents shown in wireframe; solvent

hidden for clarity. Ellipsoids shown at 50% probability.

The lipophilicity of the B(C₆F₅)₃groups is apparently

insufficient to impart dichloromethane (DCM) solubility to

O

C

O

NaX

X

C

IPr

Cl

IPr

Pd

DCM

- NaCl

or

X

N

1[IMP-CF₃]

1[IMP-(CF₃)₂]

1Cl

1[IMP-NO₂]

1[IMP-CO₂Me]

complexes of the more basic [IMP-R]⁻variants. Upon adding 1Cl

to amide-containing Na[IMP-DMA], Na[IMP-DBA], or Na[IMP-

pipA] in DCM, bright yellow solids rapidly precipitated, likely O-

bound inner-sphere complexes akin to 1[IMP-CO₂Me]. The

strength of amide binding may outcompete weakly-

coordinating DCM and prevent dissolution. However, the yellow

solids dissolve upon addition of more coordinating solvents.

When recrystallised from DCM/pentane in the presence of

O

C

N

O

N

IPr



Pd

N

1

Fig. 3 Thermal ellipsoid plots of Na[IMP-CO₂Me] (top) and Na[IMP-CH₂OH] (bottom).

Ellipsoids shown at 50% probability. THF and C₆F₅rings shown as wireframe for clarity.

O–H···O hydrogen bond drawn with dashed line.

Assessment of [IMP-R] Coordinating Ability. Pairing of

[IMP-R]⁻with the [Pd(IPr)(C(O)C₉H₆N)] cation (1) allowed us to

use several metrics previously reported by our group³⁴to assess

qualitative differences in donor ability in both solid and solution

states in the context of Pd chemistry. With more tightly-binding

−

anions (e.g., BF₄, OTf⁻, ClO₄), complexes of 1 crystallise with

counteranion bound in the primary coordination sphere; if the

−

anion is sufficiently weakly-coordinating (SbF₆, BAr^{F −}), IPr

4

isopropyl groups instead will form agostic interactions to

occupy the vacant site (Scheme 1).

Scheme 1 Synthesis of 1[IMP-R] complexes.

Addition of Na[IMP-R] salts to a solution of 1Cl followed by

recrystallisation

from

dichloromethane/pentane

or

toluene/pentane resulted in X-ray quality crystals. Inner-sphere

coordination was observed for 1[IMP-NO₂] and 1[IMP-CO₂Me]

(Fig. 4). Both anions are bound to 1 via oxygen atoms, owing to

the polarity of the nitro (N–O) and ester (C–O) bonds. 1[IMP-

CF₃] and 1[IMP-(CF₃)₂] instead crystallise as outer-sphere ion

pairs like the previously reported 1[IMP-H].³⁴

4 |Dalton Trans., 2019, 10, 1-8

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Solution-state IR spectroscopy also offers valuable

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information about the coordination en^Dv^Oir^Io^:n¹⁰m^.1e⁰³n⁹t^/Co⁹f^DTth⁰³e⁵¹P^1Gd

centre; the Pd-acyl C═O stretch shifts to lower energy when a

donor is bound to the coordination site trans to the acyl.³⁴

Complexes of 1 exhibited nearly identical C═O stretches in

solution, consistent with weakly-associated ion pairs (Table 2).

In contrast, solid-state IR suggests [IMP-R] anions range in

coordinating ability. At one extreme, [IMP-CF₃]⁻is nearly as

weakly coordinating as BAr^{F −}; meanwhile the more tightly-

4

coordinating anions [IMP-DMA]⁻and [IMP-pipA]⁻provide as

nearly as much electron density as BF₄. While larger in volume

than all of the traditional anions in Fig. 1, IMP anions are not

symmetrical, and their steric profile depends upon coordination

mode. Percent buried volume (%V_bur) calculations carried out

on X-ray structures of 1[IMP-NO₂] and 1[IMP-CO₂Me] using the

SambVca2 program⁷⁴indicate both [IMP-NO₂]⁻and [IMP-

CO₂Me]⁻have a %V_burbelow the previously-determined

threshold for binding to 1 (< ~ 20%).³⁴The methyl ester group

imparts slightly more steric demand than the nitro group. [IMP-

NO₂]⁻%V_bur(16.9%) is actually smaller than ClO₄⁻(17.3%) when

bound to 1. Based on these calculations, the sterically

demanding B(C₆F₅)₃groups appear to offer only modest steric

demand around the imidazolyl phenyl substituent.

Coordination in the solid-state is mostly dependent on the

donating character of the para-phenyl group.

Fig. 5 Crystal structure of [1(MeCN)][IMP-pipA]. Ellipsoids shown at 50% probability; C₆F₅

rings and diisopropylphenyl substituents shown in wireframe.

MeCN ion pairs can be cleanly isolated with MeCN bound in the

fourth coordination site (for example, [1(MeCN)][IMP-pipA],

Fig. 5). Solubility also complicated isolation of 1[IMP-CH₂OH]

and 1[IMP-CH₂NMe₂], and in these cases the compounds could

not be sufficiently purified for characterisation.

Beyond insights from solid-state structures, 1 is a useful

probe of coordinating ability of anions in solution. When

dissolved in DCM, anions weakly bound to 1 depart the primary

coordination sphere, forming ion pairs. The IPr isopropyl

methine chemical shift in ¹H NMR (CD₂Cl₂, 298 K) correlates with

the coordinating ability of the anion: the farther upfield the

shift, the less interaction there is between cation and anion.³⁴

Based on this benchmark, soluble 1[IMP-R] compounds all fully

dissociate in CD₂Cl₂; the cation/anion interactions of 1[IMP-

NO₂] and 1[IMP-CO₂Me] observed in the solid state are

apparently disrupted by DCM (Table 2). Since complexes 1[IMP-

R] of the amide-functionalised anions are insoluble in CD₂Cl₂

they cannot be directly compared. Instead, 1[IMP-DMA] was

[IMP-R] anions in Au catalysis. To assess the stability and

compatibility of [IMP-R]⁻in organometallic reactions, we

prepared [AuL_n][IMP-R] complexes and compared activity to

catalysts featuring traditional anions. [tBuXPhosAu(MeCN)]⁺(2)

shows counteranion-dependent activity in the [2+2] cyclisation

of -methyl styrene and phenylacetylene; Echavarren and

coworkers^75-78found 2[BAr^F] and 2[SbF₆]^{77, 78}to provide higher

4

−

yields than more-coordinating anions (BF₄, PF₆, NTf₂, OTf⁻).⁷⁷

Addition of Na[IMP-R] to tBuXPhosAuCl in a 1:1 mixture of

DCM/MeCN generated the analogous 2[IMP-R] complexes.

When performed in CD₂Cl₂(1 mol%, RT) the [2+2] cyclisation of

-methyl styrene and phenylacetylene was compatible with

[IMP-CF₃]⁻, [IMP-NO₂]⁻, and [IMP-CO₂Me]⁻anions as well as the

dissolved in DMSO-d₆and compared to 1[BAr^F]. Although

4

DMSO was expected to coordinate in both cases to form

identical Pd environments, chemical shifts of Pd IPr and

acylquinoline ligands differed substantially, suggesting [IMP-

DMA]⁻retains some cation association − even in tightly

coordinating DMSO.

phenylbenzimidazole-based anion [BIMP]⁻(Table 3). 2[BAr^F],

4

2[BIMP] and 2[SbF₆] showed slightly better yields and reaction

rates than the 2[IMP-R] complexes (Fig. 6). Moving to toluene

presents a solubility challenge for conventional gold salts; even

with the lipophilic tBuXPhos ligand, 2[SbF₆] is completely

Table 2 ¹H NMR Methine Chemical Shifts, Pd-Acyl C═O Frequencies, and %V_burof

complexes of 1

ν_C═O

,

ν_C═O,

insoluble, while 2[BAr^F] is only slightly soluble. In contrast,

Anion

δ (ppm)

%V_bur

4

ATR-IR^a

1776

1770

1757

1759

1755

1737

1729

1695

1689

1684

DCM^a

1760

1761

1760

1761

1760

1761

several of the IMP-R complexes dissolve in toluene, including

2[IMP-H], 2[IMP-CF₃], 2[IMP-NO₂] and 2[BIMP]. 2[IMP-CO₂Me]

is completely insoluble. 2[IMP-H] and 2[IMP-CF₃] provide good

yields and rates in cyclisations run in toluene-d₈(Fig. 7), while

the more tightly-coordinating [IMP-NO₂]⁻shows decreased

reactivity, and [IMP-CO₂Me]⁻fails entirely. Meanwhile the

34

BAr^F

2.75

2.74

2.75

2.76

-

4

IMP-CF₃

IMP-H³⁴

34

PF₆

IMP-(CF₃)₂

IMP-NO₂

16.9

18.7

-

poorly-soluble 2[BAr^F] provides inconsistent conversions in

IMP-CO₂Me

IMP-DMA

IMP-pipA

4

b

-

toluene.

b

-

34

BF₄

2.89

3.12

1760

1695

14.2

17.3

34

ClO₄

^aAll frequencies in cm^-1. ^bComplexes are insoluble in DCM.

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Table 3 Activity of complexes 2[X] in [2+2] cyclisations

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Ph

2[X] (1 mol%)

Ph

CD₂Cl₂or C₇D₈

18h, RT

Ph

2[X] =

Ph

L

Au NCMe

X

ⁱPr

L =

2[IMP-H]

2[SbF₆]

2[BAr^F

Fig. 8 Au complexes 3-4.

2[IMP-CF₃]

2[IMP-NO₂]

2[IMP-CO₂Me]

2[BIMP]

]

4

P(^tBu)₂

that the variable coordinating ability of [IMP-R]⁻anions would

allow for an exploration of the accelerating effect observed by

Zuccaccia, Belanzoni and coworkers^19-21and Zhdanko and

Maier.²⁴

ⁱPr

% Yield in CD₂Cl₂at

% Yield in toluene-d₈at

Anion

18h^a

46

47

46

52

53

64

54

18h^a

47

37

0

35

23

-

Among the complexes prepared were series 3. The X-ray

structures of 3[IMP-H] and 3[IMP-CF₃] are, to our knowledge,

the first of Au complexes of diphenylacetylene. These

compounds proved to be thermally unstable, decomposing at

−35 C over the course of several days. In the solid-state

structure of 3[IMP-H] the C-C≡C alkyne bond angle is

significantly distorted from linearity (~162; Fig. 9). Because of

their rapid decomposition at cryogenic conditions we did not

consider complexes 3 further in catalytic experiments. Complex

4 was stable at room temperature but in our hands solutions

became bright purple during attempts at hydroalkoxylation of

3-hexyne with methanol, suggesting the formation of gold

nanoparticles; the complexes were also significantly less

efficient than (IPr)Au(OTs).²³

IMP-H

IMP-CF₃

IMP-NO₂

IMP-CO₂Me

BIMP

BAr^F

4

SbF₆

^aAll yields are average of at least two trials.

0.12

0.1

IMP-H

0.08

0.06

0.04

0.02

0

IMP-CF3

IMP-NO2

IMP-CO2Me

BIMP

BArF4

SbF6

0

500

1000

Time (minutes)

Fig. 6 Reaction profile of [2+2] cyclisation in dichloromethane catalysed by 2[X].

0.12

0.1

IMP-H

0.08

IMP-CF3

0.06

IMP-NO2

IMP-CO2Me

Fig. 9 Thermal ellipsoid plot of 3[IMP-H]. Ellipsoids shown at 50% probability; hydrogens

hidden for clarity; diisopropylphenyl and C₆F₅substituents shown in wireframe.

0.04

0.02

0

BIMP

BArF4

In contrast, complexes 2 were much more stable and did not

generate purple solutions in the hydroalkoxylation of 3-hexyne

with methanol (Fig. 10). In all cases only the ketal product was

observed, consistent with general acid-catalysed conversion of

the intermediate vinyl ether.⁷⁹The 2[IMP-R] complexes

0

500

1000

Time (minutes)

Fig. 7 Reaction profile of [2+2] cyclisation in toluene catalysed by 2[X]; error bars show

standard deviation of three runs.

performed comparably to 2[BAr^F], suggesting [IMP-R]⁻is

4

compatible with the acidic conditions generated in situ. We

note that the tBuXPhos catalysts react more slowly than the

corresponding IPr complexes reported by Zuccachia and

coworkers.²³

A second series of Au complexes (Fig. 8) was prepared for

the gold-catalysed hydroalkoxylation of 3-hexyne, a reaction

where basic counteranions have been proposed to play active

roles in catalytic mechanisms (vide supra). Empirical evidence

reported by Zuccaccia and co-workers shows that anion identity

has a marked effect on catalytic activity, even in the presence

of a coordinating solvent such as methanol.^20-22,25We believed

6 |Dalton Trans., 2019, 10, 1-8

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DOI: 10.1039/C9DT03511G

100

80

IMP-H

IMP-CF3

IMP-NO2

IMP-CO2Me

BIMP

60

Anion

IMP-H

% Conversion (18 h)

TON (18 h)

40

73

77

66

80

88

70

292

308

264

320

352

280

BArF4

IMP-CF₃

IMP-CO₂Me

IMP-NO₂

20

SbF6

OTs

0

BAr^F

4

0

1000

Time (minutes)

2000

3000

SbF₆

OTs

Fig. 10 Conversions, Turnover Numbers (TONs), and reaction profile of hydroalkoxylation of 3-hexyne with methanol catalysed by 2[X].

60

50

40

30

IMP-H

IMP-CF3

IMP-NO2

IMP-CO2Me

BIMP

Anion

IMP-H

IMP-CF3

IMP-CO2Me

IMP-NO2

BArF4

% Conversion (18 h)

TON (18 h)

29

26

27

19

28

7

58

52

38

56

14

20

10

0

BArF4

SbF6

OTs

SbF6

OTs

0

1000

Time (minutes)

2000

3000

Fig. 11 Conversions, Turnover Numbers (TONs), and reaction profile of hydroalkoxylation of 3-hexyne with triethyleneglycol monomethyl ether catalysed by 2[X].

In an effort to better understand the effect of [IMP-R] anions

upon catalysis, alkoxylation of 3-hexyne was attempted using

the more nucleophilic triethyleneglycol monomethyl ether (Fig.

Discussion

11). Consistent with previous findings of Zuccaccia and

D’Amora,²¹lower turnover numbers are observed than seen

with methanol, despite the stronger nucleophilicity. SbF₆

Thanks to the charge-diffuse B(C₆F₅)₃groups flanking both sides

of the imidazole ring, the imidazolyl phenyl groups installed on

the [IMP-R]⁻anion scaffold retain most of the characteristics of

the parent phenylimidazole molecules. The IMP anion series

therefore exhibits a range of properties that can be tuned by

the para-phenyl functionality. Based on the spectroscopy of

series 1 the most weakly-coordinating is [IMP-CF₃]⁻, which

−

performed slightly better than [IMP-R]⁻when using methanol as

a nucleophile, but with the more challenging triethyleneglycol

monomethyl ether, the rates were nearly identical, with the

exception of the poorly-performing [IMP-NO₂]⁻anion.

(tBuXPhos)Au(OTs) performed worse than other weakly-

coordinating anions tested, in contrast to the beneficial effect

of OTs⁻seen by Zuccaccia and co-workers for the [(IPr)Au(3-

hexyne)]⁺series of catalysts. The differences in anion influences

between IPr and tBuXPhosAu complexes illustrate the complex

interplay of factors – involving both ligand and counterion – that

determines the efficiency of gold catalysts.²³

mimics the coordinating ability of BAr^{F −}and performs similarly

4

when employed in catalytic reactions of 2. One advantage of

[IMP-H]⁻and [IMP-CF₃]⁻is their extreme lipophilicity, as seen

by the solubility of 2[IMP-CF₃]⁻and 2[IMP-H]⁻in toluene. The

sheer size and inert nature of several lipophilic [IMP-R]⁻anions

also permitted the isolation of previously-unknown

diphenylacetylene complexes 3. Like other classes of

“superweak” anions, the IMP anions will likely be useful in

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applications where extremely large, inert counteranions can

provide stability against decomposition.

Conclusions

View Article Online

DOI: 10.1039/C9DT03511G

Weakly- to moderately-coordinating [IMP-R] anions have been

prepared by forming B(C₆F₅)₃adducts of substituted

phenylimidazolates. The coordinating ability of the anions

depends on the substituent present on the phenyl ring, with

more Lewis-basic functionalities resulting in stronger

coordination to transition metal cations. The anions are

compatible with gold catalysis, including cyclisation and alkyne

functionalisation reactions. Complexes of lipophilic IMP anions

2[IMP-H] and 2[IMP-CF₃] perform particularly well in a very low

dielectric medium (toluene). We envision that the IMP anion

family will enable a rational tuning of anion coordinating ability

and solubility – similar to steric and electronic tuning of ligands

– thus allowing for enhanced control over catalytic reactions.

Anions [IMP-NO₂]⁻and [IMP-CO₂Me]⁻feature polar

functional groups on the para position of the imdazolyl phenyl

scaffold, enabling inner-sphere binding to transition metals in

the solid-state. Based on solid-state IR measurements on 1[IMP-

R], [IMP-NO₂]⁻and [IMP-CO₂Me]⁻are between PF₆⁻and BF₄⁻in

coordinating ability. In solution, Pd complexes 1[IMP-NO₂] and

1[IMP-CO₂Me] appear to be fully dissociated ion pairs in CD₂Cl₂.

In Au catalysis in CD₂Cl₂, 2[IMP-CO₂Me] is superior to 2[IMP-

NO₂], and approximately as active as the more weakly-

coordinating [IMP-CF₃]⁻and [IMP-H]⁻.

The amide-functionalised [IMP-DMA]⁻and [IMP-pipA]⁻

anions are nearly as coordinating as BF₄⁻according to the solid-

state IR spectra of complexes 1. But unlike 1[BF₄], 1[IMP-DMA]

and 1[IMP-pipA] are insoluble in DCM. The solubility of 1[IMP-

DMA] in DMSO, and the apparent association of anion and

cation in this extremely polar solvent, suggests the amide-based

anions would have utility in homogeneous catalysis where very

strong coordination is needed. Meanwhile, alcohol and amine-

functionalised [IMP-CH₂OH]⁻and [IMP-CH₂NMe₂]⁻present

difficult solubility challenges, precluding a full comparison of

physical properties in organometallic venues. Nonetheless,

their isolation confirms that a wide range of functional groups

are compatible with the IMP scaffold.

Experimental section

General Methods. Unless otherwise specified, all

manipulations were performed under a dry N₂atmosphere

using standard Schlenk techniques or a Vacuum Atmospheres

inert atmosphere glovebox. Analytical data were obtained from

the CENTC Elemental Analysis Facility at the University of

Rochester, funded by NSF CHE-0650456. NMR spectra were

collected on Bruker Avance III 500 and 400 MHz instruments. ¹H

NMR chemical shifts (δ, ppm) are referenced to residual

protiosolvent resonances and ¹³C NMR chemical shifts are

referenced to the deuterated solvent peak.^{80 19}F

(fluorobenzene) and ³¹P (phosphoric acid) NMR chemical shifts

were referenced to external standards. IR spectra were

collected on a Thermo Scientific Nicolet iS5 FT-IR benchtop

spectrometer with either an iD5 diamond ATR or iD1

IMP anions have proven robust and compatible with Au(I)

catalysis. In the [2+2] cycloaddition reaction between alkynes

and alkenes, Echavarren and coworkers⁷⁷find the rate

increased with “bulkiness and softness” of the anion, BAr^{F −}

>

4

SbF₆> BF₄. The sterically large and lipophilic [IMP-H]⁻and

−

[IMP-CF₃]⁻surprisingly perform somewhat worse than BAr^{F −}

4

and SbF₆⁻in CD₂Cl₂(although better in toluene due to enhanced

solubility). Echavarren proposes the counteranion influences

rate-determining ligand exchange to form [LAu(alkyne)]⁺, a

species in equilibrium with [LAu(MeCN)]⁺and an inactive digold

complex. Assuming this step is rate-limiting for all

counteranions examined, differences in rate may arise from

other factors besides the softness of the anion. It is possible that

all IMP-R anions are sufficiently “soft” to stabilise [LAu(alkyne)]⁺

and other forces drive the equilibrium. In considering anion

“softness” of the IMP scaffold, the conventional measures (size,

charge diffusivity) are perhaps less critical than localised

parameters (charge, steric environment) for different regions of

these extremely large anions. Future work in our group will

consider how to best evaluate the coordinating ability and

basicity of unsymmetrical anions.

Catalysts 2[IMP-R] are moderately effective in alkyne

hydroalkoxylation, but for the R groups investigated here (H,

CF₃, CO₂Me, NO₂) the substituent has only a negligible effect on

activity. The ligand dependence of the anion effect has been

observed previously²⁰and underscores the importance of

screening both anion and ligand influences during development

of Au(I) catalytic methods. Ongoing work in our laboratories is

exploring the use of anions featuring more basic groups in the

preparation of Au complexes, since hydrogen bond acceptors

are known to facilitate nucleophilic attack⁷⁹and accelerate Au

reactions where protodeauration is a turnover-limiting step.³¹

transmission

accessory.

Dichloromethane

(DCM),

tetrahydrofuran (THF), pentane, acetonitrile, and toluene were

purified using a commercial solvent purification system. All

deuterated NMR solvents (Cambridge Isotope Laboratories)

were dried over activated 4 Å molecular sieves for 48 h before

use.

Tris(pentafluorophenyl)borane

(B(C₆F₅)₃,

Boulder

Scientific) was purified via sublimation (100 mtorr, 90 °C) prior

to use. Chloro(dimethyl sulfide) gold (I) was purchased from

Strem Chemicals. All benzonitriles, aminoacetaldehyde diethyl

acetal, and tBuXPhos were purchased from Oakwood

Chemicals. Sodium hydride and 2-phenylbenzimidazole were

purchased

from

Sigma

Aldrich.

2-(4-

(trifluoromethyl)phenyl)imidazole, 2-(4-nitrophenyl)imidazole,

and methyl 4-(imidazol-2-yl)benzoate were prepared as

reported by Zhichkin and coworkers.⁸¹Sodium tetrakis(3,5-

bistrifuloromethyl)phenylborate (NaBAr^F) was prepared using

4

the procedure of Yakelis and Bergman.¹⁶[Pd(μ-Cl)(C(O)-

C₉H₆N)]₂was prepared as reported by Pregosin and

coworkers.⁸²1Cl was prepared as previously reported by our

group.³⁴(^tBuXPhos)AuCl and [(^tBuXPhos)Au(NCMe)][BAr^F]

4

were prepared using the procedures reported by Echavarren.⁷⁸

(IPr)AuCl was synthesised using the procedure reported by

Nolan and coworkers.⁸³4-(1H-imidazol-2-yl)benzoic acid was

synthesised according to the procedure of Hagedorn et al.⁸⁴4-

8 |Dalton Trans., 2019, 10, 1-8

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Paper

(1H-imidazol-2-yl)benzoyl chloride was synthesised according 158.55, -159.72, -159.77, -159.82, -164.44, -164.49, -166.55 ¹¹

B

View Article Online

DOI: 10.1039/C9DT03511G

to the procedure of Webber et al.⁸⁵

NMR (161 MHz, CD₂Cl₂) δ -8.07.

Sodium 2-(4-(trifluoromethyl)phenyl)imidazolide. In an

Sodium 2-(4-(CO₂Me)phenyl)imidazolide. In an inert

inert atmosphere glovebox, a 16 mL vial was charged with 133 atmosphere glovebox, a 16 mL vial was charged with 202 mg

mg (0.625 mmol) 2-(4-(trifluoromethyl)phenyl)imidazole and 10 (1.00 mmol) 2-(4-(CO₂Me)phenyl)imidazole and 15 mL THF and

mL THF and cooled to -35 °C. The suspension was then stirred, cooled to -35 °C. The suspension was then stirred, and 24 mg

and 15 mg (0.625 mmol) sodium hydride was added. The (1.00 mmol) sodium hydride was added. The suspension was

suspension was stirred for 20 hours and dried in vacuo. Yield stirred for 76 hours and dried in vacuo. Yield 99% ¹H NMR (500

99% ¹H NMR (500 MHz, DMSO-d₆) δ 8.05 (d, ³J = 7.9 Hz, 2H, aryl), MHz, DMSO-d₆) δ 7.97 (d, ³J = 8.6 Hz, 2H, aryl), 7.74 (d, ³J = 8.6

7.48 (d, ³J = 8.1 Hz, 2H, aryl), 6.84 (s, 2H, imidazolyl).

Hz, 2H, aryl), 6.82 (s, 2H, imidazolyl), 3.79 (s, 3H C(O)CH₃).

Na[IMP-CO₂Me]. In an inert atmosphere glovebox, a 16 mL

Na[IMP-CF₃]. In an inert atmosphere glovebox, a 16 mL vial

was charged with 140 mg (0.598 mmol) sodium 2-(4- vial was charged with 112 mg (0.50 mmol) sodium 2-(4-

(trifluoromethyl)phenyl)imidazolide and 8 mL toluene and (CO₂Me)phenyl)imidazolide and 8 mL toluene and cooled to -35

cooled to -35 °C. This solution was stirred, and 613 mg (1.197 °C. This solution was stirred, and 512 mg (1.00 mmol)

mmol) tris(pentafluorophenyl) borane was added and stirred tris(pentafluorophenyl) borane was added and stirred for 26

for 23 hours while coming to RT. The vial was removed from the hours. The vial was removed from the glovebox and 75 mL

glovebox and 75 mL pentane was added to precipitate the pentane was added to precipitate the desired product as a

desired product as a white solid. The solid was filtered, washed white solid. The solid was filtered, washed with pentane, and

with pentane, and dried in vacuo. Purification via slow diffusion dried in vacuo. Purification via slow diffusion of pentane into

of pentane into methylene chloride/THF yielded X-ray quality methylene chloride/THF yielded X-ray quality crystals of the

crystals of the product as the Na(THF)₄salt. Yield 62%. Anal. product as the Na(THF)₄salt. Yield 56%. Anal. Calc. for

Calc. for NaC₄₆N₂F₃₃B₂H₆·1.75C₄H₈O·0.25 CH₂Cl₂C, 45.50 %, H, NaC₄₇N₂O₂F₃₀B₂H₉·1C₄H₈O C, 46.40 %, H, 1.30 %, N, 2.12 %,

1

1.47 %, N, 1.99 %, found C, 45.214 %, H, 1.829 %, N, 1.894%. ¹H found C, 46.214 %, H, 1.574 %, N, 2.056%. H NMR (500 MHz,

3

4

NMR (500 MHz, CD₂Cl₂) δ 7.20 (s, 2H, imidazolyl), 7.02 (d, J = CD₂Cl₂) δ 7.32 (d, J = 8.8 Hz, 2H, aryl), 7.23 (d, J = 3.7 Hz, 2H,

8.4 Hz, 2H, aryl), 6.58 (d, J = 7.6 Hz, 2H, aryl). ¹³C NMR (126 aryl), 6.51 (d, ³J = 7.7 Hz, 2H, imidazolyl), 3.89 (s, 3H, C(O)CH₃).

3

MHz, CD₂Cl₂) δ 149.45, 147.87, 147.52, 132.62, 131.05, 130.79, ¹³C NMR (126 MHz, CD₂Cl₂) δ 169.39, 149.62, 147.54, 138.67,

129.89, 127.13, 125.32, 125.02, 124.09. ¹⁹F NMR (471 MHz, 137.80, 136.04, 134.64, 129.92, 129.19, 128.05, 125.38.¹⁹F NMR

CD₂Cl₂) δ -63.95, -126.72, -133.16, -158.80, -160.16, -164.61, - (471 MHz, CD₂Cl₂) δ -125.87, -133.25, -158.70, -160.61, -164.58,

166.90. ¹¹B NMR (161 MHz, CD₂Cl₂) δ -8.24. Unit cell (XRD) -167.08.¹¹B NMR (161 MHz, CD₂Cl₂) δ -8.12. Unit cell (XRD)

monoclinic P, a = 13.103(3) Å, b = 27.136(5) Å, c = 16.187(3) 372 triclinic, a = 12.2126(18) Å, b = 16.759(2) Å, c = 17.209(3) Å, α =

Å, β = 92.560(3)°.

90.069(3)°, β = 104.596(3)°, γ = 106.610(3)°.

Sodium 2-(4-(nitro)phenyl)imidazolide. In an inert

Sodium 2-phenylbenzimidazolide. In an inert atmosphere

atmosphere glovebox, a 16 mL vial was charged with 118 mg glovebox, a 16 mL vial was charged with 194 mg (1.00 mmol) 2-

(0.625 mmol) 2-(4-(nitro)phenyl)imidazole and 10 mL THF and phenylbenzimidazole and 10 mL THF and cooled to -35 °C. The

cooled to -35 °C. The suspension was then stirred, and 15 mg suspension was then stirred, and 24 mg (1.00 mmol) sodium

(0.625 mmol) sodium hydride was added. The suspension was hydride was added. The suspension was stirred for 76 hours and

1

stirred for 20 hours and dried in vacuo. Yield 99% ¹H NMR (500 dried in vacuo. Yield 99% H NMR (500 MHz, DMSO-d₆) δ 8.22

MHz, DMSO-d₆) δ 8.03 (s, 4H, aryl), 6.95 (s, 2H, imidazolyl).

Na [IMP-NO₂]. In an inert atmosphere glovebox, a 16 mL vial (t, ³J = 7.2 Hz, 1H, aryl), 6.75 (s, 2H, aryl).

(dd, ³J = 8.2, ⁴J = 1.2 Hz, 2H, aryl), 7.36 – 7.30 (m, 4H, aryl), 7.19

was charged with 125 mg (0.592 mmol) sodium 2-(4-

Na[BIMP]. In an inert atmosphere glovebox, a 40 mL vial was

(nitro)phenyl)imidazolide and 8 mL toluene and cooled to -35 charged with 223 mg (1.031 mmol) sodium 2-

°C. This solution was stirred, and 607 mg (1.18 mmol) phenylbenziimidazolide and 8 mL toluene and cooled to -35 °C.

tris(pentafluorophenyl) borane was added and stirred for 23 This solution was stirred, and 1055 mg (2.062 mmol)

hours while coming to RT. The vial was removed from the tris(pentafluorophenyl) borane was added and stirred for 27

glovebox and 75 mL pentane was added to precipitate the hours. The vial was removed from the glovebox and 75 mL

desired product as a light brown solid. The solid was filtered, pentane was added to precipitate the desired product as a

washed with pentane, and dried in vacuo. Purification via slow white solid. The solid was filtered, washed with pentane, and

diffusion of pentane into methylene chloride/THF yielded X-ray dried in vacuo. Purification via slow diffusion of pentane or

quality crystals of the product as the Na(THF)₄salt. Yield 62%. HMDSO into methylene chloride/THF yielded X-ray quality

Anal. Calc. for NaC₄₅N₃F₃₀B₂H₆·1.5C₄H₈O C, 45.60 %, H, 1.35 %, crystals. Yield 79%. Anal. Calc. for NaC₄₇N₂O₂F₃₀B₂H₉·2.5C₄H₈O

1

N, 3.13 %, found C, 45.418 %, H, 1.684 %, N, 3.238%. H NMR C, 49.85 %, H, 1.97 %, N, 2.13 %, found C, 49.951 %, H, 1.927 %,

3

4

(500 MHz, CD₂Cl₂) δ 7.61 (d, J = 9.1 Hz, 2H, aryl), 7.25 (d, J = N, 2.131%. Na[BIMP] appears to exhibit complex fluxional

3.5 Hz, 2H, aryl), 6.63 (d, J = 8.1 Hz, 2H, imidazolyl). ¹³C NMR behaviour due to hindered rotation, likely due to the increased

3

(126 MHz, CD₂Cl₂) δ 149.50, 147.64, 146.87, 146.31, 140.97, size of the benzimidazole core versus the imidazole core of the

138.98, 137.90, 136.51, 135.85, 131.12, 125.72, 122.16. ¹⁹F IMP anions, and this behaviour manifests itself as broad signals

1

NMR (376 MHz, CD₂Cl2) δ -126.21, -133.22, -158.44, -158.50, - in the H NMR spectrum as well as with increased number of

signals in the ¹⁹F spectrum. ¹H NMR (500 MHz, CD₂Cl₂) δ 7.53 (v

This journal is © The Royal Society of Chemistry 20xx

Dalton Trans., 2019, 10, 1-8 | 9

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3

4

3

br s, 2H, aryl), 7.33 (v br s, 2H, aryl), 6.97 (dd, J = 6.1, J = 3.2 (500 MHz, CD₂Cl₂) δ 7.24 (d, J = 4.3 Hz, 2H, aryl)_V, _ie6_w.6_A9_rtic(_ld_e,_OnJ_lin=_e

Hz, 4H, aryl), 6.81 (v br s, 1H, aryl). ¹³C NMR (126 MHz, CD₂Cl₂) 8.7 Hz, 2H, aryl), 6.42 (d, J = 5.6 Hz, 2H, imidazolyl), 3.01 (s, 3H,

δ 137.83, 130.90, 128.08, 127.86, 122.90, 116.12, 114.22. ¹⁹F CH₃), 2.89 (s, 3H, CH₃). ¹³C NMR (126 MHz, CD₂Cl₂) δ 171.72,

NMR (376 MHz, CD₂Cl2) δ -117.04, -118.92, -128.16, -129.34, - 147.56, 136.81, 130.76, 130.35, 125.23, 125.12, 39.62, 35.53.

129.86, -133.91, -135.53, -136.61, -137.97, -139.02, -159.43, - ¹⁹F NMR (471 MHz, DMSO-d₆) δ -125.42, -133.54, -158.46, -

159.87, -159.92, -159.97, -160.14, -160.20, -160.25, -160.89, - 160.17, -164.38. ¹¹B NMR (161 MHz, CD₂Cl₂) δ -8.37. Unit cell

164.00, -164.87, -166.22, -166.99, -167.46¹¹B NMR (161 MHz, (XRD) monoclinic P, a = 13.3526(11) Å, b = 30.789(2) Å, c =

CD₂Cl₂) δ -7.77. Unit cell (XRD) monoclinic P, a = 15.0906(12) Å, 16.1477(13) Å, β = 93.240(2)°.

3

DOI: 10.1039/C9DT03511G

b = 16.8592(13) Å, c = 23.0499(18) Å, β = 99.144(2)°.

Na[IMP-CH₂OH] In an inert atmosphere glovebox, a 40 mL

4-(1H-imidazol-2-yl)-N,N-dimethylbenzamide

Under vial was charged with 300 mg (0.240 mmol) Na[IMP-CO₂Me]

ambient conditions, a 100 mL round bottom flask was charged and 20 mL THF and stirred to dissolve. The clear, light yellow

with 10 mL dichloromethane and cooled to 0° C. 1.85 mL (8.45 solution was cooled to – 35 °C and 10 mg (0.263 mmol) LiAlH₄

mmol) of 2.0 M dimethylamine in THF was added, followed by was added. The reaction was stirred while coming to room

1.18 mL of triethylamine. The solution was stirred, and 822 mg temperature, and then for an additional 3 days. The vial was

(3.382 mmol) of 4-(1H-imidazol-2-yl)benzoyl chloride•HCl was removed from the glovebox and cooled to 0 °C, at which point

added, resulting in HCl gas evolution. The solution was stirred 1 mL H₂O, 5 drops 10% aqueous NaOH, and 15 mL diethyl ether

for 20 minutes in the ice bath and then allowed to stir overnight were added sequentially. The solution was stirred while coming

at room temperature. The reaction was diluted with 100 mL to room temperature and then dried over MgSO₄. The reaction

dichloromethane and extracted sequentially with 15 mL was filtered and dried in vacuo, resulting in a pure, bright white

saturated NaHCO₃, brine, and NH₄Cl. The organic layer was solid. Yield 79%. Analytically pure X-ray quality crystals were

dried over Na₂SO₄, filtered, and concentrated to dryness under obtained by layering a concentrated THF solution of the product

reduced pressure, resulting in a highly hygroscopic tan solid. with hexanes at room temperature. Anal. Calc. for NaC-

Yield 48%. Recrystallisation via slow layer diffusion of pentane ₄₆N₂B₂F₃₀OH₉·1.45 C₄H₈O C, 46.97 %, H, 1.57 %, N, 2.11 %, found

into a concentrated dichloromethane solution under N₂C, 46.690 %, H, 1.885 %, N, 2.217 %. ¹H NMR (500 MHz, CD₂Cl₂)

atmosphere resulted in x-ray quality crystals as colourless δ 7.21 (d, ³J = 4.0 Hz, 2H, aryl), 6.72 (d, ³J = 8.5 Hz, 2H, aryl), 6.41

needles. Anal. Calc. for C₁₂H₁₃N₃O•0.1C₅H₁₂•0.1 CH₂Cl₂C, 65.53 (d, ³J = 7.5 Hz, 2H, imidazolyl), 4.54 (s, 2H, Ar-CH₂-OH). ¹³C NMR

%, H, 6.28 %, N, 18.19 %, found C, 65.195 %, H, 6.544 %, N, (126 MHz, CD₂Cl₂) δ 140.66, 139.08, 130.23, 129.73, 126.51,

18.581%. ¹H NMR (500 MHz, CD₂Cl₂) δ 11.09 (s, 1H, NH), 7.82 – 125.06, 65.61. ¹⁹F NMR (471 MHz, DMSO-d₆) δ -125.42, -133.54,

7.75 (m, 2H, aryl), 7.35 (dd, J = 8.2, J = 1.5 Hz, 2H, aryl), 7.13 -158.46, -160.17, -164.38. ¹¹B NMR (161 MHz, CD₂Cl₂) δ -8.37.

(s, 2H, imdazolyl), 3.09 (s, 3H, CH₃), 2.96 (s, 3H, CH₃). ¹³C NMR Unit cell (XRD) triclinic, a = 12.7032(13) Å, b = 13.4507(13) Å, c

(126 MHz, CD₂Cl₂) δ 171.49, 146.10, 136.33, 131.91, 127.89, = 20.407(2) Å, α = 91.293(2)°, β = 91.963(2)°, γ = 107.760(2)°.

3

4

125.55, 39.75, 35.49. Unit cell (XRD) monoclinic P, a =

Na[IMP-CH₂N(Me)₂] In an inert atmosphere glovebox, a 40

15.0906(12) Å, b = 16.8592(13) Å, c = 23.0499(18) Å, β = mL vial was charged with 500 mg (0.3965 mmol) Na[IMP-DMA]

99.144(2)°. Unit cell (XRD) orthorhombic P, a = 7.9951(13) Å, b and 30 mL THF and stirred to dissolve. The clear solution was

= 14.758(2) Å, c = 21.725(4) Å.

cooled to -35 °C and 17 mg (0.4360 mmol) LiAlH₄was added.

Na[IMP-DMA] In an inert atmosphere glovebox, a 40 mL vial The reaction was stirred while coming to room temperature,

was charged with 200 mg (0.930 mmol) 4-(1H-imidazol-2-yl)- and then for an additional 3 days. The vial was removed from

N,N-dimethylbenzamide and 4 mL THF. The suspension was the glovebox and cooled to 0 °C, at which point 1 mL H₂O, 5

stirred briefly and cooled to – 35 °C. 23 mg (0.930 mmol) of NaH drops 10% aqueous NaOH, and 20 mL diethyl ether were added

was added, and the suspension was stirred while coming to sequentially. The solution was stirred while coming to room

room temperature and then for an addition 15 h. The reaction temperature, and then dried over MgSO₄. The reaction was

was dried in vacuo, yielding a beige solid. This solid was filtered and dried in vacuo, resulting in a pure, bright white

suspended in 5 mL toluene and stirred briefly before being solid. Yield 80%. Analytically pure X-ray quality crystals were

cooled to -35 °C. 952 mg (1.860 mmol) of B(C₆F₅)₃was added obtained by layering a concentrated DCM/THF solution of the

and the solution was stirred while coming to room temperature, product with hexanes at room temperature. Anal. Calc. for NaC-

and then for an additional 16 h. 30 mL of pentane was added to ₄₈N₃B₂F₃₀H₁₄·2 C₄H₈O, 0.4 C₅H₁₂C, 49.05 %, H, 2.47 %, N, 2.96 %,

1

the reaction, resulting in a large amount of white precipitate. found C, 49.03 %, H, 2.52 %, N, 2.91 %. H NMR (500 MHz,

4

3

The reaction was removed from the glovebox, poured onto an CD₂Cl₂) δ 7.25 (d, J = 2.4 Hz, 2H, aryl), 6.74 (d, J = 8.4 Hz, 2H,

additional 40 mL pentane, and the precipitate was filtered off, aryl), 6.43 (s, 2H, imidazolyl), 3.53 (s, 2H, Ar-CH₂-N), 2.47 (d, ³J =

washed with hexanes, and dried in vacuo. The solid was 9.5 Hz, 6H, N(CH₃)₂).¹³C NMR (126 MHz, CD₂Cl₂) δ 128.95, 44.38,

dissolved in THF, filtered to remove insoluble impurities, and 22.74. ¹⁹F NMR (471 MHz, CD₂Cl₂) δ -125.68, -133.30, -158.78, -

dried in vacuo. Recrystallisation via layer diffusion of hexanes 160.56, -164.60, -167.16. ¹¹B NMR (161 MHz, CD₂Cl₂) δ -8.19.

into a concentrated THF/dichloromethane solution yielded X- Unit cell (XRD) monoclinic P, a = 12.1872(17) Å, b = 19.000(3) Å,

ray quality crystals of the analytically pure sample; adventitious c = 14.971(2) Å, β = 111.618(3)°.

acetone was also present in the solid-state structure. Yield 41

4-(1H-imidazol-2-yl)-N,N-dibutylbenzamide Under ambient

%. Anal. Calc. for NaC₄₈H₁₂N₃B₂F₃₀O·1.3C₄H₈O C, 47.16 %, H, 1.67 conditions, a 100 mL round bottom flask was charged with 40

%, N, 3.10 %, found C, 46.868 %, H, 1.934 %, N, 3.284%. ¹H NMR mL dichloromethane, 925 μL (5.5 mmol) di-n-butylamine, and 3

10 |Dalton Trans., 2019, 10, 1-8

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mL of triethylamine. The solution was stirred, and 1215 mg (5 was allowed to stir for 15 hours and was then diluted with 50

View Article Online

DOI: 10.1039/C9DT03511G

mmol) of 4-(1H-imidazol-2-yl)benzoyl chloride•HCl was added, mL of dichloromethane. The reaction was extracted

resulting in HCl gas evolution and a rapid colour change from sequentially with 5 mL saturated NaHCO₃, and 5 mL brine. The

orange/yellow to brown. The reaction was allowed to stir for 20 organic layer was dried over Na₂SO₄, filtered, and concentrated

hours and was then diluted with 50 mL of dichloromethane. The to dryness under reduced pressure, resulting in light brown

reaction was extracted sequentially with 5 mL saturated solid. Yield 82%. Anal. Calc. for C₁₅H₁₇n₃O·0.1CH₂Cl₂C, 68.75 %,

NaHCO₃, and 5 mL brine. The organic layer was dried over H, 6.57 %, N, 15.93 %, found C, 68.360 %, H, 6.969 %, N,

1

Na₂SO₄, filtered, and concentrated to dryness under reduced 16.317%. H NMR (500 MHz, CD₂Cl₂) δ 11.18 (v br s, 1H, NH),

3

4

3

pressure, resulting in a viscous brown oil. The oil was triturated 7.81 – 7.75 (dd, J = 8.4, J = 1.8, 2H, aryl), 7.31 (d, J = 8.1 Hz,

with hexanes and dried again, resulting in a brown foam that 2H, aryl), 7.11 (s, 2H, imidazolyl), 3.69 (br s, 2H, N-CH₂), 3.33 (br

became a solid powder when broken up. Yield 56%. HRMS (ESI) s, 2H, N-CH₂), 1.67 (br s, 4H, N-CH₂-CH₂), 1.50 (br s, 2H, CH₂-CH₂-

1

calc. for C₁₈H₂₅N₃O ([M + H]⁺): 300.2070, found 300.2077. H CH₂). ¹³C NMR (126 MHz, CD₂Cl₂) δ 170.23, 146.21, 136.32,

NMR (500 MHz, CD₂Cl₂) δ 10.67 (s, 1H, NH), 7.78 (d, ³J = 8.0 Hz, 132.03, 127.62, 125.63, 49.15, 46.20, 43.52, 26.88, 26.05.

2H, aryl), 7.32 – 7.25 (m, 2H, aryl), 7.12 (s, 2H, imidazolyl), 3.53

– 3.44 (m, 2H, N-CH₂), 3.24 – 3.13 (m, 2H, N-CH₂), 1.65 (s, 2H, N- was charged with 255 mg (1.00 mmol) 4-((1H-imidazol-2-yl)-

CH₂-CH₂), 1.54 – 1.34 (m, 4H, N-CH₂-CH₂+ CH₂-CH₂-CH₂), 1.17 – phenyl)(piperidin-1-yl)methanone and mL THF. The

Na[IMP-pipA] In an inert atmosphere glovebox, a 20 mL vial

5

1.04 (m, 2H, CH₂-CH₂-CH₂), 0.99 (t, ³J = 7.3 Hz, 3H, CH₃), 0.77 (t, suspension was stirred briefly and cooled to – 35 °C. 24 mg (1.00

J = 6.6 Hz, 3H, CH₃).¹³C NMR (126 MHz, CD₂Cl₂) δ 171.64, 143.19, mmol) of NaH was added, and the suspension was stirred while

137.28, 131.61, 130.60, 127.24, 125.58, 49.25, 44.98, 31.13, coming to room temperature and then for an addition 18 h. The

30.04, 20.72, 20.14, 14.13, 13.80.

reaction was dried in vacuo, yielding a brown solid. This solid

Na[IMP-DBA] In an inert atmosphere glovebox, a 20 mL vial was suspended in 10 mL toluene and stirred briefly before being

was charged with 299 mg (1.00 mmol) 4-(1H-imidazol-2-yl)-N,N- cooled to -35 °C. 1024 mg (2.00 mmol) of B(C₆F₅)₃was added

dibutylbenzamide and 5 mL THF. The suspension was stirred and the solution was stirred while coming to room temperature,

briefly and cooled to – 35 °C. 24 mg (1.00 mmol) of NaH was and then for an additional 17 h. 30 mL of pentane was added to

added, and the suspension was stirred while coming to room the reaction, resulting in a large amount of white precipitate.

temperature and then for an addition 23 h. The reaction was The reaction was removed from the glovebox, poured onto an

dried in vacuo, yielding a beige solid. This solid was suspended additional 50 mL pentane, and the precipitate was filtered off,

in 8 mL toluene and stirred briefly before being cooled to -35 °C. washed with hexanes, and dried in vacuo. Yield 77%.

1024 mg (2.00 mmol) of B(C₆F₅)₃was added and the solution Recrystallisation via layer diffusion of hexanes into

a

was stirred while coming to room temperature, and then for an concentrated THF/dichloromethane solution yielded X-ray

additional 18 h. 30 mL of pentane was added to the reaction, quality crystals of the analytically pure sample. Anal. Calc. for

resulting in a large amount of white precipitate. The reaction NaC₅₁H₁₆N₃B₂F₃₀O·2 C₄H₈O C, 49.03 %, H, 2.23 %, N, 2.91 %,

1

was removed from the glovebox, poured onto an additional 50 found C, 49.338 %, H, 2.435 %, N, 3.031%. H NMR (500 MHz,

3

mL pentane, and the precipitate was filtered off, washed with CD₂Cl₂) δ 7.24 (d, J = 4.0 Hz, 2H, aryl), 6.67 (d, J = 8.4 Hz, 2H,

hexanes, and dried in vacuo. Yield 46%. Recrystallisation via aryl), 6.43 (br s, 2H, imidazolyl), 3.58 (br s, 2H, 2H, N-CH₂), 3.24

3

layer diffusion of hexanes into

a

concentrated – 3.19 (m, 2H, 2H, N-CH₂), 1.68 (p, J = 6.2, J = 5.8 Hz, 2H, N-

THF/dichloromethane solution yielded X-ray quality crystals of CH₂-CH₂), 1.61 (dt, ³J = 11.0, ³J = 5.8 Hz, 2H, N-CH₂-CH₂), 1.52 (p,

the

analytically

pure

sample.

Anal.

Calc.

for ³J = 6.2 Hz, 2H, CH₂-CH₂-CH₂). ¹⁹F NMR (471 MHz, CD₂Cl₂) δ -

NaC₅₄H₂₄N₃B₂F₃₀O·1.3C₄H₈O C, 49.41 %, H, 2.41 %, N, 2.92 %, 125.39, -133.45, -158.48, -160.12, -164.41, -166.03. ¹¹B NMR

found C, 49.652 %, H, 2.400 %, N, 3.201%. H NMR (500 MHz, (161 MHz, CD₂Cl₂) δ -8.82. ¹³C NMR (126 MHz, CD₂Cl₂) δ 170.06,

1

3

CD₂Cl₂) δ 7.23 (d, J = 5.1 Hz, 2H, aryl), 6.63 (d, J = 8.4 Hz, 2H, 147.62, 141.42, 137.13, 130.48, 125.23, 124.87, 121.80, 49.23,

aryl), 6.32 (br s, 2H, imidazolyl), 3.37 (br s, 2H, N-CH₂), 3.04 (br 43.64, 26.58, 24.45. Unit cell (XRD) triclinic, a = 14.2164(17) Å,

s, 2H, N-CH₂), 1.56 (m, 2H, N-CH₂-CH₂), 1.24 (m, 6H, N-CH₂-CH₂b = 14.4515(17) Å, c = 17.120(2) Å, α = 81.955(2)°, β =

+ CH₂-CH₂-CH₂), 0.93 (t, ³J = 7.4 Hz, 3H, CH₃), 0.73 (t, ³J = 7.3 Hz, 72.302(2)°, γ = 67.813(2)°.

3H, CH₃). ¹³C NMR (126 MHz, CD₂Cl₂) δ 171.98, 138.06, 130.98,

2-(3,5-bis(trifluoromethyl)phenyl)-1H-imidazole

This

130.02, 129.36, 128.55, 125.11, 124.30, 49.34, 45.13, 30.99, compound was synthesised using a modified version of the

29.61, 20.60, 19.79, 13.98, 13.49. ¹⁹F NMR (471 MHz, CD₂Cl₂) δ procedure reported by Zhichkin and coworkers.⁴⁰Under air, a

-125.28, -133.47, -158.45, -160.10, -164.29, -165.76. ¹¹B NMR 100 mL round bottom flask was charged with 10 mL methanol

(161 MHz, CD₂Cl₂) δ -8.40. Unit cell (XRD) monoclinic P, a = and 1.68 mL (10 mmol) 3,5-bis(trifluoromethyl)benzonitrile and

33.184(3) Å, b = 15.7566(14) Å, c = 26.172(2) Å, β = 109.217(2)°. stirred. Sodium methoxide in methanol (25%, 1 mmol) was

(4-(1H-imidazol-2-yl)phenyl)(piperidin-1-yl)methanone

added and the solution was stirred at room temperature for 2

Under ambient conditions, a 100 mL round bottom flask was h. Aminoacetaldehyde diethyl acetal (1.45 mL, 10 mmol) and

charged with 30 mL dichloromethane, 434 μL (4.4 mmol) 1.2 mL glacial acetic acid were then added, and the reaction was

piperidine, and 2.2 mL of triethylamine. The solution was heated to 50 °C for 1 h. The reaction was cooled and diluted

stirred, and 972 mg (4 mmol) of 4-(1H-imidazol-2-yl)benzoyl with 20 mL methanol, followed by addition of 5 mL 6 M HCl, and

chloride•HCl was added, resulting in HCl gas evolution and a the reaction was heated to 75 °C for 5 h. After cooling, solvent

rapid colour change from orange/yellow to brown. The reaction was removed with a rotary evaporator, and the white residue

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was taken up in 30 mL 1:1 water/diethyl ether and extracted. 139.89, 133.84, 131.36, 129.94, 129.64, 129.37, 125.27, 124.96,

View Article Online

-1

NaOH was added to the clear aqueous layer until it attained a 124.04, 123.90, 29.38, 25.11, 25.05. IR^D(^Oth^I:i¹n^0.1f⁰il³m^9/,^Cc⁹m^DT0)³:⁵¹ν¹_C^G_O

pH of 10; the white precipitate that formed was filtered and 1770; IR (CH₂Cl₂, cm^-1): ν_CO1761. Unit cell (XRD) triclinic, a =

dried in vacuo. The aqueous filtrate was allowed to stand 14.1686(15) Å, b = 18.684(2) Å, c = 19.045(2) Å, α = 114.321(4)°,

overnight, during which time X-ray quality crystals grew as large β = 98.469(4)°, γ = 107.830(4)°.

colourless needles. Yield 22%. HRMS (ESI) calc. for C₁₁H₆N₂F₆

1[IMP-NO₂] In an inert atmosphere glovebox, a 4 mL vial was

([M + H]⁺): 281.0513, found 281.0512. ¹H NMR (500 MHz, charged with 50 mg (0.079 mmol) of 1Cl and 2 mL of

DMSO-d₆) δ 13.06 (s, 1H, NH), 8.58 (s, 2H, aryl), 8.06 (s, 1H, aryl), dichloromethane and stirred to dissolve. To the bright orange

7.29 (s, 2H, aryl). ¹³C NMR (126 MHz, DMSO-d₆) δ 143.21, solution was added 107 mg (0.087 mmol) of Na[IMP-NO₂], and

133.39, 131.77, 131.51, 131.25, 130.98, 124.83, 122.66, 121.43. the solution immediately turned bright yellow. The reaction was

¹⁹F NMR (471 MHz, DMSO-d₆) δ -61.55.

allowed to stir for 16.5 h and the solution was filtered through

Na[IMP-(CF₃)₂] In an inert atmosphere glovebox, a 40 mL vial celite and layered with pentane. This resulted in the product

was charged with 280 mg (1.0 mmol) 2-(3,5- oiling out; layer diffusion of HMDSO into dichloromethane

bis(trifluoromethyl)phenyl)-1H-imidazole and 5 mL THF. The resulted in an analytically pure sample. Subsequent vapor

solution was stirred briefly and cooled to -35 °C. 24 mg (1.0 diffusion of pentane into a concentrated toluene solution

mmol) of NaH was added, and the suspension was stirred while yielded X-ray quality crystals as yellow blocks. Yield 92%. Anal

coming to room temperature and then for an addition 24 h. The Calc. for PdC₈₁N₆O₃F₃₀B₂H₄₉C, 52.52 %, H, 2.67 %, N, 4.54 %,

reaction was dried in vacuo, yielding a white solid. This solid was found C, 52.473 %, H, 2.364 %, N, 4.516 %. ¹H NMR (500 MHz,

suspended in 8 mL toluene and stirred briefly before being CD₂Cl₂) δ 8.52 (d, ³J = 8.3 Hz, 1H, quinolyl), 8.21 (d, ³J = 4.6 Hz,

cooled to -35 °C. 1024 mg (2.0 mmol) of B(C₆F₅)₃was added and 1H, quinolyl), 8.17 – 8.10 (m, 1H, quinolyl), 7.92 (dd, ³J = 7.3, ⁴J

the solution was stirred while coming to room temperature, and = 1.0 Hz, 1H, quinolyl), 7.65 – 7.52 (m, 6H, quinolyl + IPr aryl +

then for an additional 17 h. 30 mL of pentane was added to the IMP-NO₂aryl), 7.39 (d, ³J = 7.8 Hz, 4H, IPr aryl), 7.36 (s, 2H, IPr

reaction, resulting in a large amount of white precipitate. The imidazolyl), 7.24 (d, ³J = 4.0 Hz, 2H, IMP-NO₂aryl), 6.59 (d, ³J =

3

reaction was removed from the glovebox, poured onto an 7.9 Hz, 2H, IMP-NO₂imidzolyl), 2.76 (hept, J = 6.4 Hz, 4H,

3

additional 40 mL pentane, and the precipitate was filtered off, CH(CH₃)₂), 1.31 (d, J = 6.8 Hz, 12H, CH(CH₃)₂), 1.27 (d, J = 6.9

washed with hexanes, and dried in vacuo. The solid was purified Hz, 12H, CH(CH₃)₂).¹³C NMR (126 MHz, CD₂Cl₂) δ 175.12, 150.78,

via slow diffusion of hexanes into a concentrated DCM/THF 149.37, 147.45, 146.58, 139.87, 138.97, 137.94, 135.80, 135.54,

solution of the product. It should be noted that the product, 133.85, 133.73, 131.30, 130.91, 129.61, 129.36, 125.53, 125.09,

while solid, is very tacky and must be kept under somewhat 124.95, 123.87, 122.02, 29.33, 25.13, 24.97. IR (thin film, cm^-1):

anhydrous conditions. Yield 74 %. Anal. Calc. for ν_CO1737; IR (CH₂Cl₂, cm^-1): ν_CO1761. Unit cell (XRD) monoclinic

NaC₄₇H₅N₂B₂F₃₆·2C₄H₈O C, 44.93 %, H, 1.44 %, N, 1.91 %, found P, a = 18.6043(18) Å, b = 26.890(3) Å, c = 21.779(2) Å, β =

C, 45.070 %, H, 1.615 %, N, 1.986%. ¹H NMR (500 MHz, CD₂Cl₂) 101.862(2)°.

4

δ 7.61 (s, 1H, aryl), 7.27 (d, J = 3.5 Hz, 2H, aryl), 6.98 (s, 2H,

1[IMP-CO₂Me] In an inert atmosphere glovebox, a 4 mL vial

imidazolyl).¹³C NMR (126 MHz, CD₂Cl₂) δ 149.45, 147.45, was charged with 61 mg (0.095 mmol) of 1Cl and 2 mL of

145.68, 131.35, 131.13, 129.58,125.73, 123.92, 123.01, 121.75, dichloromethane and stirred to dissolve. To the bright orange

108.53¹⁹F NMR (376 MHz, CD₂Cl₂) δ -64.66, -126.24, -133.41, - solution was added 100 mg (0.048 mmol) of Na[IMP-CO₂Me],

158.44, -159.51, -164.37, -166.81.¹¹B NMR (161 MHz, CD₂Cl₂) δ and the solution immediately turned bright yellow. The reaction

-8.22. Unit cell (XRD) monoclinic P, a = 15.937(3) Å, b = 25.254(4) was allowed to stir for 0.5 h and the solution was filtered

Å, c = 18.608(3) Å, β = 106.941(3)°.

through celite, layered with pentane. Recrystallisation under air

1[IMP-CF₃] In an inert atmosphere glovebox, a 4 mL vial was via vapor diffusion of hexanes into a concentrated methylene

charged with 30 mg (0.048 mmol) of 1Cl, and 2 mL of chloride solution afforded X-ray quality crystals. Yield 81%. Anal

dichloromethane and stirred to dissolve. To the bright orange Calc. for PdC₈₄N₅O₃F₃₀B₂H₅₁·1.5C₄H₈O C, 54.36 %, H, 3.13 %, N,

1

solution was added 60 mg (0.048 mmol) of Na[IMP-CF₃], and the 3.56 %, found C, 54.694 %, H, 3.139 %, N, 3.636. H NMR (500

solution immediately turned bright yellow. The reaction was MHz, CD₂Cl₂) δ 8.50 (d, ³J = 8.2 Hz, 1H, quinolyl), 8.23 (d, ³J = 4.6

allowed to stir for 2.5 h and the solution was filtered through Hz, 1H, quinolyl), 8.12 (d, ³J = 8.1 Hz, 1H, quinolyl), 7.91 (dd, ³J =

celite, layered with pentane, and stored at -35 °C to afford X-ray 7.3, ⁴J = 1.1 Hz, 1H, quinolyl), 7.65 – 7.58 (m, 2H, quinolyl), 7.56

quality crystals as yellow needles. Yield 81%. Anal Calc. for (m, J = 7.8 Hz, 3H, quinolyl + IPr aryl), 7.39 (d, ³J = 7.8 Hz, 4H, IPr

PdC₈₃N₅OF₃₀B₂H₄₉·CH₂Cl₂C, 51.18 %, H, 2.56 %, N, 3.55 %, found aryl), 7.37 – 7.35 (s + d, ³J = 8.9 Hz, 2H + 2H, IPr imidazolyl + IMP-

C, 51.119 %, H, 2.720 %, N, 3.488 %. ¹H NMR (500 MHz, CD₂Cl₂) CO₂Me aryl), 7.20 (d, ⁴J = 3.7 Hz, 2H, IMP-CO₂Me aryl), 6.44 (d,

3

δ 8.52 (d, J = 8.1 Hz, 1H, quinolyl), 8.22 (d, J = 4.8 Hz, 1H, ³J = 7.6 Hz, 2H, IMP-CO₂Me imidazolyl), 3.81 (s, 3H, C(O)CH₃),

quinolyl), 8.13 (d, ³J = 8.1 Hz, 1H, quinolyl), 7.92 (d, ³J = 7.3 Hz, 2.76 (hept, J = 6.6 Hz, 4H, CH(CH₃)₂), 1.31 (d, J = 6.8 Hz, 12H,

1H, quinolyl), 7.66 – 7.60 (m, 2H, quinolyl), 7.57 (t, J = 7.8 Hz, CH(CH₃)₂), 1.27 (d, J = 6.8 Hz, 12H, CH(CH₃)₂). ¹³C NMR (126

3

2H, IPr aryl), 7.43 – 7.34 (m, 6H, IPr aryl + imidazolyl), 7.20 (s, MHz, CD₂Cl₂) δ 166.42, 150.90, 149.33, 148.25, 146.60, 139.83,

3

2H, IMP-CF₃imidazolyl), 7.00 (d, J = 8.5 Hz, 2H, IMP-CF₃aryl), 133.82, 133.28, 131.32, 129.90, 129.59, 129.49, 129.33, 128.19,

6.58 (d, ³J = 7.6 Hz, 2H, IMP-CF₃aryl), 2.74 (hept, ³J = 6.5 Hz, 4H, 125.09, 123.90, 52.57, 35.01, 34.52, 29.33, 25.63, 25.06, 23.06,

3

CH(CH₃)₂), 1.32 (d, J = 6.8 Hz, 12H, CH(CH₃)₂), 1.27 (d, J = 6.9 11.60. IR (thin film, cm^-1): ν_CO1729; IR (CH₂Cl₂, cm^-1): ν_CO1761.

Hz, 12H, CH(CH₃)₂).¹³C NMR (126 MHz, CD₂Cl₂) δ 147.80, 146.61,

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Unit cell (XRD) monoclinic P, a = 22.722(2) Å, b = 18.9379(19) Å, J = 9.8 Hz, 6H), 2.16 (s, 3H, MeCN CH₃), 1.17 (dd, _V³_iJ_ew=_A1_rt1_ic._le9_O, _n³J_lin=_e

c = 22.844(2) Å, β = 105.759(2)°.

6.8 Hz, 24H, CH(CH₃)₂).¹³C NMR (126 M^DH^Oz^I,^{: 1}C⁰D^.1₂⁰C³l⁹₂^/)^Cδ^9D1^T07³6⁵.¹7¹6^G,

1[IMP-(CF₃)₂] In an inert atmosphere glovebox, a 4 mL vial 170.67, 150.28, 149.52, 146.61, 139.85, 135.35, 133.34, 132.31,

was charged with 50 mg (0.0786 mmol) of 1Cl and 1 mL of 130.82, 129.39, 127.40, 126.44, 125.11, 124.82, 128.28, 34.53,

dichloromethane and stirred to dissolve. To the bright orange 28.89, 26.11, 23.57, 22.75. IR (thin film, cm^-1): ν_C=O1755 cm^-1, IR

solution was added 110 mg (0.0.0825 mmol) of Na[IMP-(CF₃)₂], (CH₂Cl₂, cm^-1): ν_C=O1761 cm^-1.

and the solution immediately turned bright yellow. The reaction

1[IMP-pipA] In an inert atmosphere glovebox, a 4 mL vial

was allowed to stir for 16 h and the solution was filtered was charged with 50 mg (0.0786 mmol) of 1Cl and 1 mL of

through celite, layered with pentane, and stored at -35°C to dichloromethane and stirred to dissolve. To the bright orange

afford X-ray quality crystals as yellow blocks. Yield 93%. Anal. solution was added 108 mg (0.0.0825 mmol) of Na[IMP-pipA],

Calc. for PdC₈₄N₅OF₃₆B₂H₄₈· 0.9 CH₂Cl₂C, 50.19 %, H, 2.47 %, N, and the solution immediately turned bright yellow. After less

3.45 %, found C, 50.238 %, H, 2.502 %, N, 3.360 %. ¹H NMR (500 than a minute of stirring, a large amount of pale-yellow

MHz, CD₂Cl₂) δ 8.51 (dd, ³J = 8.4, ⁴J = 1.1 Hz, 1H, quinolyl), 8.22 precipitate was observed. The reaction was allowed to stir for

3

(d, J = 4.4 Hz, 1H, quinolyl), 8.12 (dd, J = 8.1, ⁴J = 1.0 Hz, 1H, 16 h and the solution was filtered through a frit. The pale yellow

quinolyl), 7.90 (dd, ³J = 7.3, ⁴J = 1.1 Hz, 1H, quinolyl), 7.63 – 7.53 solid and yellow filtrate were each dried in vacuo; NMR of each

(m, 5H, quinolyl + IPr aryl + IMP-(CF₃)₂aryl), 7.38 (d, ³J = 7.8 Hz, revealed that the solid was the desired product. Yield 79%.

4H, IPr aryl), 7.35 (s, 2H, IPr imidazolyl), 7.25 (d, ³J = 3.8 Hz, 2H, Recrystallisation

of

the

solid

from

IMP-(CF₃)₂aryl), 6.97 (s, 2H, IMP-(CF₃)₂imidazolyl), 2.74 (hept, dichloromethane/acetonitrile/hexanes yielded X-ray quality

3

³J = 6.7 Hz, 4H), 1.31 (d, J = 6.8 Hz, 12H), 1.26 (d, J = 6.9 Hz, crystals of the MeCN adduct. Anal. Calc. for PdC₉₀N₇O₂F₃₀B₂H₆₃·

12H). ¹³C NMR (126 MHz, CD₂Cl₂) δ 174.83, 150.89, 149.38, 1.45 C₆H₁₄1.35 CH₂Cl₂C, 54.05 %, H, 3.86 %, N, 4.43 %, found

146.60, 145.65, 139.89, 133.83, 133.75, 131.34, 131.18, 131.05, C, 54.472 %, H, 3.392 %, N, 3.949 %. H NMR of MeCN adduct

1

130.00, 129.63, 129.36, 125.70, 125.65, 125.10, 124.95, 123.93, (500 MHz, CD₂Cl₂) δ 8.54 (br s, 1H, quinolyl), 8.52 – 8.48 (m, 1H,

123.90, 122.91, 121.76, 29.36, 25.12, 25.03. Solid state IR 1755 quinolyl), 8.04 (dd, ³J = 8.1, ⁴J = 1.1 Hz, 1H, quinolyl), 7.88 (dd, ³J

cm^-1, soln. state 1761 cm^-1. Unit cell (XRD) triclinic, a = 13.652(5) = 7.3,⁴J = 1.2 Hz, 1H, quinolyl), 7.65 – 7.57 (m, 2H, quinolyl), 7.44

3

Å, b = 16.550(6) Å, c = 20.994(8) Å, α = 112.393(7)°, β = (t, J = 7.8 Hz, 2H, IPr aryl), 7.32 – 7.27 (m, 6H, IPr aryl + IPr

91.470(7)°, γ = 101.814(7)°.

imidazolyl), 7.18 (d, ³J = 3.2 Hz, 2H, IMP-pipA aryl), 6.73 (d, ³J =

1[IMP-DMA] In an inert atmosphere glovebox, a 4 mL vial 8.7 Hz, 2H, IMP-pipA aryl), 6.34 (br s, 2H, IMP-pipA imidazolyl),

was charged with 50 mg (0.0786 mmol) of 1Cl and 1 mL of 3.43 (br s, 2H, N-CH₂), 3.09 (br s, 2H, N-CH₂), 3.02 (hept, ³J = 7.0

dichloromethane and stirred to dissolve. To the bright orange Hz, 4H, CH(CH₃)₂), 2.16 (s, 3H, MeCN CH₃), 1.52 (s, 2H, N-CH₂-

solution was added 104 mg (0.0.0825 mmol) of Na[IMP-DMA], CH₂), 1.34 (s, 4H, N-CH₂-CH₂+ , CH₂-CH₂-CH₂), 1.19 (d, ³J = 6.7 Hz,

and the solution immediately turned bright yellow. After less 12H, CH(CH₃)₂), 1.16 (d, ³J = 6.8 Hz, 12H, CH(CH₃)₂).¹³C NMR (126

than a minute of stirring, a large amount of pale-yellow MHz, CD₂Cl₂) δ 176.78, 169.37, 150.36, 149.55, 148.44, 141.22,

precipitate was observed. The reaction was allowed to stir for 139.93, 137.19, 135.40, 132.27, 130.80, 130.10, 129.79, 129.40,

16 h and the solution was filtered through a frit. The pale yellow 129.32, 128.54, 127.33, 126.12, 125.13, 124.82, 123.16, 35.02,

solid and yellow filtrate were each dried in vacuo; NMR of each 34.53, 29.45, 28.88, 26.15, 25.64, 24.68, 23.51, 22.75, 20.82,

revealed that the solid was the desired product. Yield 85%. 3.51. IR (thin film, cm^-1): ν_C=O1755 cm^-1, IR (CH₂Cl₂, cm^-1): ν_C=O

Recrystallisation

of

the

solid

from 1761 cm^-1. Unit cell (MeCN adduct) (XRD) triclinic, a = 15.857(3)

dichloromethane/acetonitrile/hexanes yielded X-ray quality Å, b = 19.087(4) Å, c = 19.142(4) Å, α = 115.371(3)°, β =

crystals of the MeCN adduct. Anal. Calc. for PdC₈₇N₇O₂F₃₀B₂H₅₉· 106.919(3)°, γ = 99.963(4)°.

0.65 CH₂Cl₂C, 52.97 %, H, 3.06 %, N, 4.93 %, found C, 53.23 %,

2[IMP-H]. In an inert atmosphere glovebox, a 4 mL vial was

H, 3.12 %, N, 4.65 %. ¹H NMR (500 MHz, DMSO-d6) δ 9.60 (dd, charged with 61 mg (0.094 mmol) (^tBuXPhos)AuCl and 2 mL of

³J = 5.0, ⁴J = 1.5 Hz, 1H, quinolyl), 8.69 (dd, ³J = 8.3, ⁴J = 1.4 Hz, 1:1 methylene chloride:MeCN and stirred to dissolve. 123 mg

1H, quinolyl), 8.20 (dd, ³J = 8.0, ⁴J = 1.2 Hz, 1H, quinolyl), 7.81 – (0.1036 mmol) Na[(BCF)₂(imid)] was added to the vial and the

7.73 (m, 4H, quinolyl + IPr aryl), 7.71 – 7.66 (m, 1H, quinolyl), solution was stirred for 21 h. The solution was then dried in

7.39 (t, ³J = 7.7 Hz, 2H, IPr aryl), 7.30 – 7.21 (m, 6H, IPr aryl + IPr vacuo, dissolved in 2 mL of methylene chloride, filtered through

3

imidazolyl IMP-DMA aryl), 6.89 (d, J = 8.5 Hz, 2H, IMP-DMA celite, layered with pentane, and stored at -35°C. The product

aryl), 6.26 (s, 2H, IMP-DMA imidazolyl), 3.40 – 3.33 (m, 2H, crystallised as a colourless solid, yield 68%. Anal. Calc. for

CH(CH₃)₂), 3.10 (hept, ³J = 5.9 Hz, 2H, CH(CH₃)₂), 2.90 (s, 3H, N- AuPC₇₆N₃F₃₀B₂H₅₅•1.7 CH₂Cl₂C, 47.27 %, H, 2.98 %, N, 2.13 %,

1

CH₃), 2.78 (s, 3H, N-CH₃), 1.32 (d, ³J = 6.6 Hz, 6H, CH(CH₃)₂), 1.19 found C, 47.670 %, H, 2.571 %, N, 2.012. H NMR (500 MHz,

(d, ³J = 6.9 Hz, 6H, CH(CH₃)₂), 0.99 (dd, ³J = 14.1, ³J = 6.7 Hz, 12H, CD₂Cl₂) δ 7.89 (td, ³J = 9.0, ³J = 8.4, ⁴J = 1.6 Hz, 1H, P-aryl), 7.67 –

CH(CH₃)₂).¹H NMR of MeCN adduct (500 MHz, CD₂Cl₂) δ 8.52 – 7.57 (m, 2H, P-aryl), 7.36 – 7.30 (m, 1H, P-aryl), 7.16 (br s, 4H, P-

8.46 (m, 2H, quinolyl), 8.04 (dd, ³J = 8.1,⁴J = 1.1 Hz, 1H, quinolyl), aryl + IMP-H aryl), 7.04 (tt, ³J = 7.5, ⁴J =1.1 Hz, 1H, IMP-H

7.87 (dd, ³J = 7.3, ⁴J = 1.2 Hz, 1H, quinolyl), 7.64 – 7.57 (m, 2H, imidazolyl), 6.71 (t, ³J = 8.0 Hz, 2H, IMP-H aryl), 6.39 – 6.31 (m,

quinolyl), 7.44 (t, ³J = 7.8 Hz, 2H, IPr aryl), 7.32 – 7.27 (m, 6H, IPr 2H, IMP-H imidazolyl), 2.95 (hept, ³J = 7.0 Hz, 1H, Ar-CH(CH₃)₂),

3

aryl + IPr imidazolyl), 7.19 (d, J = 3.5 Hz, 2H, IMP-DMA aryl), 2.33 (hept + s, ³J = 6.7 Hz, 5H, Ar-CH(CH₃)₂+ MeCN CH₃), 1.42 (d,

3

6.77 (d, J = 8.7 Hz, 2H, IMP-DMA aryl), 6.36 (s, 2H, IMP-DMA ³J = 16.3 Hz, 18H, P-C(CH₃)₃), 1.33 (d, ³J = 6.9 Hz, 6H, Ar-

imidazolyl), 3.02 (dt, ³J = 13.2, ³J = 6.4 Hz, 4H, CH(CH₃)₂), 2.79 (d, CH(CH₃)₂), 1.26 (d, ³J = 6.8 Hz, 6H, Ar-CH(CH₃)₂), 0.93 (d, J = 6.6

Dalton Trans., 2019, 10, 1-8 | 13

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Dalton Transactions

Page 14 of 17

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Dalton Transactions

Hz, 6H, Ar-CH(CH₃)₂). ¹³C NMR (126 MHz, CD₂Cl₂) δ 150.20, AuPC₇₈N₃F₃₀B₂O₂H₅₄C, 49.63 %, H, 3.04 %, N, 2.23 %, found C,

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149.57, 147.78, 135.25, 134.57, 131.98, 129.15, 128.86, 128.67, 49.614 %, H, 3.077 %, N, 2.089%. ¹H NM^DR^O(^I5^:0¹⁰0^.1M⁰³H^9/z^C,⁹C^DD^T₂⁰C³⁵l₂¹)^1Gδ

127.98, 124.69, 124.65, 122.28, 39.15, 38.93, 34.44, 31.38, 7.92 – 7.86 (m, 1H, P-aryl), 7.61 (dddd, ³J = 15.0, ³J = 7.4, ³J = 5.4,

3

31.34, 31.31, 26.15, 23.22. ³¹P NMR (203 MHz, CD₂Cl₂) δ 58.32. ⁴J = 3.7 Hz, 2H, P-aryl), 7.38 – 7.31 (d + m, J = 9.08, 2H + 1H,

3

2[IMP-CF₃]. In an inert atmosphere glovebox, a 4 mL vial was IMP-CO₂Me aryl + P-aryl), 7.20 (d, J = 3.6 Hz, 2H, IMP-CO₂Me

charged with 47 mg (0.0696 mmol) (^tBuXPhos)AuCl and 2 mL of aryl), 7.16 (s, 2H, P-aryl), 6.44 (s, 2H, IMP-CO₂Me imidazolyl),

1:1 methylene chloride:MeCN and stirred to dissolve. 100 mg 3.84 (s, 3H, IMP-CO₂CH₃), 2.94 (hept, ³J = 7.0 Hz, 1H, Ar-

3

(0.104 mmol) Na[IMP-CF₃] was added to the vial and the CH(CH₃)₂), 2.33 (hept + s, J = 6.3 Hz, 2H+ 3H, Ar-CH(CH₃)₂+

3

solution was stirred for 17 h. The solution was then dried in MeCN CH₃), 1.42 (d, J = 16.3 Hz, 18H, P-C(CH₃)₃), 1.33 (d, J =

3

vacuo, dissolved in 2 mL of methylene chloride, filtered through 6.9 Hz, 6H, Ar-CH(CH₃)₂), 1.26 (d, J = 6.8 Hz, 6H, Ar-CH(CH₃)₂),

celite, layered with HMDSO, and stored at -35°C. The product 0.93 (d, ³J = 6.6 Hz, 6H, Ar-CH(CH₃)₂). ¹³C NMR (126 MHz, CD₂Cl₂)

crystallised as a colourless solid, yield 67%. Anal. Calc. for δ 147.77, 135.24, 131.98, 128.15, 122.28, 52.61, 39.15, 34.44,

AuPC₇₇N₃F₃₃B₂H₅₄·1.5 CH₂Cl₂C, 46.56 %, H, 2.84 %, N, 2.07 %, 31.33, 26.14, 24.33, 23.22. ³¹P NMR (203 MHz, CD₂Cl₂) δ 58.32.

found C, 46.000 %, H, 2.723 %, N, 2.320%. ¹H NMR (500 MHz, Unit cell (XRD) monoclinic P, a = 11.4352(19) Å, b = 20.494(3) Å,

CD₂Cl₂) δ 7.89 (td, ³J = 8.9, ³J = 8.4, ⁴J = 1.5 Hz, 1H, P-aryl), 7.66 – c = 17.462(3) Å, β = 98.794(4)°.

7.57 (m, 2H, P-aryl), 7.33 (ddd, ³J = 7.3, ³J = 4.9, ⁴J = 1.8 Hz, 1H,

2[BIMP]. In an inert atmosphere glovebox, a 4 mL vial was

P-aryl), 7.20 (s, 2H, IMP-CF₃aryl), 7.17 (s, 2H, P-aryl), 7.01 (d, ³J charged with 61 mg (0.094 mmol) (^tBuXPhos)AuCl and 2 mL of

3

= 8.4 Hz, 2H, IMP-CF₃aryl), 6.58 (d, J = 7.7 Hz, 2H, IMP-CF₃1:1 methylene chloride:MeCN and stirred to dissolve. 129 mg

imidazolyl), 2.95 (hept, ³J = 6.7 Hz, 1H, Ar-CH(CH₃)₂), 2.32 (hept (0.1036 mmol) Na[BIMP] was added to the vial and the solution

+ s, ³J = 6.7 Hz, 5H, Ar-CH(CH₃)₂+ MeCN CH₃), 1.42 (d, ³J = 16.3 was stirred for 24 h. The solution was then dried in vacuo,

3

Hz, 18H, P-C(CH₃)₃), 1.33 (d, J = 6.9 Hz, 6H, Ar-CH(CH₃)₂), 1.26 dissolved in 2 mL of methylene chloride, filtered through celite,

3

(d, J = 6.8 Hz, 6H, Ar-CH(CH₃)₂), 0.93 (d, J = 6.6 Hz, 6H, Ar- layered with pentane, and stored at -35°C. The product

CH(CH₃)₂). ¹³C NMR (126 MHz, CD₂Cl₂) δ 147.80, 135.27, 131.99, crystallised as a colourless solid, yield 83%. Anal Calc. for

129.93, 127.99, 125.28, 122.29, 39.17, 38.95, 34.45, 31.40, AuPC₈₀N₃F₃₀B₂H₅₉·0.5CH₂Cl₂C, 50.24 %, H, 3.14 %, N, 2.18 %,

31.35, 26.15, 24.34, 23.24.³¹P NMR (202 MHz, CD₂Cl₂) δ 58.48. found C, 50.528 %, H, 2.965 %, N, 2.154. H NMR (500 MHz,

1

Unit cell (XRD) monoclinic P, a = 11.2277(11) Å, b = 21.034(2) Å, CD₂Cl₂) δ 7.92 – 7.87 (m, 1H, P-aryl), 7.67 – 7.57 (m, 2H, P-aryl),

c = 17.1640(18) Å, β = 98.416(2)°.

7.53 (br s, 2H, BIMP aryl), 7.33 (ddd, ³J = 7.3, ³J = 3.4, ⁴J = 1.6 Hz,

2[IMP-NO₂]. In an inert atmosphere glovebox, a 4 mL vial 4H, BIMP aryl), 7.17 (s, 2H, P-aryl), 6.96 (m, 2H, P-aryl + BIMP

3

was charged with 61 mg (0.094 mmol) (^tBuXPhos)AuCl and 2 mL aryl), 6.80 (br s, 1H, BIMP aryl), 2.94 (hept, J = 7.2 Hz, 1H, Ar-

3

of 1:1 methylene chloride:MeCN and stirred to dissolve. 128 mg CH(CH₃)₂), 2.40 – 2.19 (hept + s, J = 6.3 Hz, 5H, Ar-CH(CH₃)₂+

3

(0.104 mmol) Na[IMP-NO₂] was added to the vial and the MeCN CH₃), 1.42 (d, J = 16.3 Hz, 18H, P-C(CH₃)₃), 1.33 (d, J =

3

solution was stirred for 18 h. The solution was then dried in 6.9 Hz, 6H, Ar-CH(CH₃)₂), 1.26 (d, J = 6.8 Hz, 6H, Ar-CH(CH₃)₂),

vacuo, dissolved in 2 mL of methylene chloride, filtered through 0.93 (d, ³J = 6.6 Hz, 6H, Ar-CH(CH₃)₂). ¹³C NMR (126 MHz, CD₂Cl₂)

celite, layered with pentane, and stored at -35°C. The product δ 180.71, 150.23, 147.81, 137.88, 135.22, 134.59, 132.02,

crystallised as a colourless solid, yield 69%. Anal. Calc. for 127.93, 122.90, 122.30, 116.13, 39.18, 38.95, 31.36, 26.16,

AuPC₇₆N₄F₃₀B₂H₅₄O₂•0.85CH₂Cl₂, 47.41 %, H, 2.88 %, N, 2.88 %, 24.34, 23.24. ³¹P NMR (202 MHz, CD₂Cl₂) δ 58.48. Unit cell (XRD)

found C, 47.851 %, H, 2.437 %, N, 3.010 %. ¹H NMR (500 MHz, monoclinic P, a = 11.2277(11) Å, b = 21.034(2) Å, c = 17.1640(18)

CD₂Cl₂) δ 7.92 – 7.86 (m, 1H, P-aryl), 7.66 – 7.56 (m + d, ³J = 9.3, Å, β = 98.416(2)°. Unit cell (XRD) triclinic, a = 15.447(3) Å, b =

2H + 2H, P-aryl + IMP-NO₂aryl), 7.33 (ddd, ³J = 7.3, ³J = 4.9, ⁴J = 17.053(3) Å, c = 18.040(3) Å, α = 67.410(3)°, β = 82.920(4)°, γ =

3

1.5 Hz, 1H, P-aryl), 7.24 (d, J = 3.7 Hz, 2H, IMP-NO₂aryl), 7.16 84.125(4)°.

(s, 2H, P-aryl), 6.60 (d, ³J = 8.0 Hz, 2H, IMP-NO₂imidazolyl), 2.95

3[IMP-H]. In an inert atmosphere glovebox, a 4 mL vial was

3

(hept, J = 7.0 Hz, 1H, Ar-CH(CH₃)₂), 2.33 (hept + s, J = 6.7 Hz, charged with 26 mg (0.0425 mmol) IPrAuCl, 60 mg (0.319 mmol)

3H + 2H, Ar-CH(CH₃)₂+ MeCN CH₃), 1.44 (s, 9H, P-C(CH₃)₃), 1.40 diphenylacetylene, and 60 mg (0.04675 mmol) Li[IMP-H].

(s, 9H, P-C(CH₃)₃), 1.33 (d, ³J = 6.9 Hz, 6H, Ar-CH(CH₃)₂), 1.26 (d, Methylene chloride (2 mL) was added and the reaction

³J = 6.8 Hz, 6H, Ar-CH(CH₃)₂), 0.93 (d, J = 6.6 Hz, 6H, Ar-CH(CH₃)₂). immediately began to turn purple, likely due to formation of

¹³C NMR (126 MHz, CD₂Cl₂) δ 150.20 , 147.78, 147.39, 146.65, gold nanoparticles. The reaction was stirred for 7 minutes, at

134.58, 132.00, 130.86, 127.98, 126.00, 125.55, 125.51, 122.28, which time it was filtered through celite, layered with pentane,

122.04, 39.16, 38.93, 34.44, 31.38, 31.34, 26.14, 24.33,23.23. and placed in the freezer, resulting in the formation of

³¹P NMR (202 MHz, CD₂Cl₂) δ 58.46.

colourless X-ray quality crystals. Yield 45%. Anal. Calc. for

2[IMP-CO₂Me]. In an inert atmosphere glovebox, a 4 mL vial AuC₈₆N₄F₃₀B₂H₅₇•2 CH₂Cl₂C, 50.22 %, H, 2.92 %, N, 2.66 %,

1

was charged with 50 mg (0.0803 mmol) (^tBuXPhos)AuCl, and 2 found C, 50.397 %, H, 2.522 %, N, 2.683. H NMR (500 MHz,

mL of 1:1 methylene chloride:MeCN and stirred to dissolve. 100 CD₂Cl₂) δ 7.66 (t, ³J = 7.8 Hz, 2H, IPr aryl), 7.49 (t, ³J = 8.2 Hz, 2H,

mg (0.104 mmol) Na[IMP-CO₂Me] was added to the vial and the diphenylacetylene aryl), 7.45 (s, 2H, IPr imidazolyl), 7.36 (d, ³J =

solution was stirred for 24 h. The solution was then dried in 7.8 Hz, 4H, IPr aryl), 7.27 (t, ³J = 7.9 Hz, 4H, diphenylacetylene

4

vacuo, dissolved in 2 mL of methylene chloride, filtered through aryl), 7.17 (d, J = 2.9 Hz, 2H, IMP-H aryl), 7.06 – 7.01 (m, 1H,

celite, layered with pentane, and stored at -35°C. The product IMP-H aryl), 6.94 – 6.89 (m, 4H, diphenylacetylene aryl), 6.71 (t,

3

crystallised as a colourless solid, yield 51%. Anal. Calc. for ³J = 8.0 Hz, 2H, IMP-H aryl), 6.36 (d, J = 7.4 Hz, 2H, IMP-H

14 |Dalton Trans., 2019, 10, 1-8

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Paper

imidazolyl), 2.48 (hept, ³J = 6.9 Hz, 4H, CH(CH₃)₂), 1.24 (d, ³J = quality crystals. Yield 90%. Anal. Calc. for AuC₇₈N_Vie₄_wF₃_A₀_rB_tic₂_lH_{e O}₅₄_nliC_ne,

6.9 Hz, 12H, CH(CH₃)₂), 1.13 (d, ³J = 6.9 Hz, 12H, CH(CH₃)₂). ¹³

C

51.03 %, H, 2.96 %, N, 3.05 %, found C, 50.920 %, H, 2.809 %, N,

DOI: 10.1039/C9DT03511G

1

3

NMR (126 MHz, CD₂Cl₂) δ 146.27, 133.23, 132.37, 132.29, 2.970. H NMR (500 MHz, CD₂Cl₂) δ 7.58 (t, J = 7.8 Hz, 2H, IPr

132.06, 129.77, 129.17, 128.66, 127.40, 125.28, 125.20, 117.45, aryl), 7.44 (s, 2H, IPr imidazolyl), 7.38 (d, ³J = 7.8 Hz, 4H, IPr aryl),

89.81, 29.31, 24.67, 24.14. Unit cell (XRD) triclinic, a = 13.708(2) 7.17 (d, ⁴J = 2.8 Hz, 2H, IMP-H aryl), 7.05 – 7.01 (m, 1H, IMP-H

Å, b = 18.136(3) Å, c = 18.494(3) Å, α = 113.739(3)°, β = aryl), 6.71 (t, ³J = 8.0 Hz, 2H, IMP-H aryl), 6.36 (d, ³J = 7.2 Hz, 2H,

97.758(3)°, γ = 99.532(3)°.

IMP-H imidazolyl), 2.51 (hept, ³J = 7.0 Hz, 4H, CH(CH₃)₂), 2.25 –

3

3[IMP-CF₃]. In an inert atmosphere glovebox, a 4 mL vial was 2.18 (m, 4H, C≡C-CH₂), 1.28 (dd, ³J = 9.3, J = 6.9 Hz, 24H,

charged with 50 mg (0.08 mmol) IPrAuCl, 72 mg (0.40 mmol) CH(CH₃)₂), 0.61 (t, J = 7.5 Hz, 6H, C≡C-CH₂-CH₃). Unit cell (XRD)

diphenylacetylene, and 100 mg (0.08 mmol) Na[IMP-CF₃]. monoclinic P, a = 12.184(6) Å, b = 19.349(10) Å, c = 33.546(17)

Methylene chloride (2 mL) was added and the reaction Å, β = 96.835(9)°.

immediately began to turn purple, likely due to formation of

(^tBuXPhos)AuOTs. In an inert atmosphere glovebox, a 4 mL

gold nanoparticles. The reaction was stirred for 2 minutes, at vial was charged with 53 mg (0.081 mmol) (^tBuXPhos)AuCl and

which time it was filtered through celite, layered with pentane, 1 mL of methylene chloride and stirred to dissolve. 25 mg (0.089

and placed in the freezer, resulting in the formation of mmol) AgOTs was added to the vial and the reaction was stirred

colourless X-ray quality crystals. Yield 96%. Anal. Calc. for for 17 hours. The solution was filtered through celite and

AuC₈₇N₄F₃₃B₂H₅₆•0.5 C₅H₁₂C, 52.72 %, H, 2.82 %, N, 2.80 %, layered with pentane, but the resulting product is too soluble to

1

found C, 52.891 %, H, 2.860 %, N, 2.877. H NMR (500 MHz, recrystallise in this method. The solution was dried in vacuo,

CD₂Cl₂) δ 7.66 (t, ³J = 7.8 Hz, 2H, IPr aryl), 7.49 (t, ³J = 8.2 Hz, 2H, and was determined to be pure by NMR, yield 90%. Anal Calc.

diphenylacetylene aryl), 7.45 (s, 2H, IPr imidazolyl), 7.36 (d, ³J = for AuPC₈₀N₃F₃₀B₂H₅₉C, 54.54 %, H, 6.61 %, N, 0 %, found C,

1

7.8 Hz, 4H, IPr aryl), 7.27 (t, ³J = 7.9 Hz, 4H, diphenylacetylene 54.371 %, H, 6.391 %, N, 0.018. H NMR (500 MHz, CD₂Cl₂) δ

aryl), 7.19 (d, ⁴J = 2.6 Hz, 2H, IMP-CF₃aryl), 7.00 (d, ³J = 8.4 Hz, 7.87 (td, ³J = 8.1, ⁴J = 1.4 Hz, 1H, P-aryl), 7.64 (d, ³J = 8.1 Hz, 2H,

2H, IMP-CF₃aryl), 6.94 – 6.90 (m, 4H, diphenylacetylene aryl), OTs aryl), 7.57 – 7.48 (m, 2H, P-aryl), 7.34 – 7.30 (m, 1H, P-aryl),

6.58 (d, ³J = 7.9 Hz, 2H, IMP-CF₃imidazolyl), 2.48 (hept, ³J = 6.9 7.18 (d, ³J = 8.0 Hz, 2H, OTs aryl), 7.06 (s, 2H, P-aryl), 2.78 (hept,

Hz, 4H, CH(CH₃)₂), 1.24 (d, ³J = 6.9 Hz, 12H, CH(CH₃)₂), 1.13 (d, ³J ³J = 6.8 Hz, 1H, Ar-CH(CH₃)₂), 2.36 (s, 3H, OTs CH₃), 2.29 (hept,

= 6.9 Hz, 12H, CH(CH₃)₂).¹³C NMR (126 MHz, CD₂Cl₂) δ 146.27, ³J = 6.6 Hz, 2H, Ar-CH(CH₃)₂), 1.36 (s, 9H, P-C(CH₃)₃), 1.33 (s, 9H,

3

133.38, 132.30, 129.77, 125.20, 73.85, 29.32, 24.68, 24.17. Unit P-C(CH₃)₃), 1.24 (dd, J = 13.5, ³J = 6.9 Hz, 12H, Ar-CH(CH₃)₂),

cell (XRD) triclinic, a = 15.320(11) Å, b = 18.411(14) Å, c = 0.90 (d, ³J = 6.6 Hz, 6H, Ar-CH(CH₃)₂). ¹³C NMR (126 MHz, CD₂Cl₂)

19.587(18) Å, α = 62.891(19)°, β = 67.043(13)°, γ = 89.683(14)°. δ 150.41, 148.34, 146.51, 135.10, 134.40, 130.95, 129.06,

3[IMP-NO₂]. In an inert atmosphere glovebox, a 4 mL vial 127.02, 126.69, 121.94, 38.77, 38.54, 34.50, 31.26, 26.35, 24.07,

was charged with 50 mg (0.08 mmol) IPrAuCl, 72 mg (0.40 22.98, 21.44. ³¹P NMR (202 MHz, CD₂Cl₂) δ 57.19.

mmol) diphenylacetylene, and 99 mg (0.08 mmol) Na[IMP-NO₂].

General procedure for [2+2] cycloadditions. An 1800 μL

Methylene chloride (2 mL) was added and the reaction stock solution of 0.00169 mmol [Au][X] and 51 mg (0.3 mmol)

immediately began to turn purple, likely due to formation of of 1,3,5-trimethoxybenzene (internal standard) was prepared in

gold nanoparticles. The reaction was stirred for 2 minutes, at an inert atmosphere glovebox. 44 μL (0.338 mmol) α-

which time it was filtered through celite, layered with pentane, methylstyrene and 19 μL (0.169 mmol) phenyl acetylene were

and placed in the freezer, resulting in the formation of each added to three NMR tubes. 600 μL of catalyst stock

colourless crystals. Yield 72%. Anal. Calc. for AuC₈₆N₅F₃₀B₂H₅₆O₂solution was then added to each tube. The tubes were capped,

C, 52.17 %, H, 2.85 %, N, 3.54 %, found C, 52.389 %, H, 2.757 %, shaken, and removed from the glovebox, and spectra were

1

3

N, 3.666. H NMR (500 MHz, CD₂Cl₂) δ 7.67 (d, J = 7.9 Hz, 2H, recorded at regular intervals. Yields are calculated based on

IPr aryl), 7.58 (d, ³J = 9.1 Hz, 2H, IMP-NO₂aryl), 7.50 (t, ³J = 7.0 ratios of integrations of product versus internal standard.

Hz, 2H, diphenylacetylene aryl), 7.46 (s, 2H, IPr imidazolyl), 7.36

General procedure for alkyne hydroalkoxylations. Gold

(d, ³J

=

7.8 Hz, 4H, IPr aryl), 7.30 7.24 (m, 4H, catalyst (0.0044 mmol) and 1,3,5,-trimethoxybenzene (7 mg,

–

diphenylacetylene aryl), 7.23 (d, ³J = 4.1 Hz, 2H, IMP-NO₂aryl), 0.044 mmol) were weighed into vials in an inert atmosphere

6.94 – 6.90 (m, 4H, diphenylacetylene aryl), 6.58 (d, ³J = 8.0 Hz, glovebox, capped, and removed. To each vial was added 400 μL

2H, IMP-NO₂imidazolyl), 2.48 (hept, ³J = 7.0 Hz, 4H, CH(CH₃)₂), CD₂Cl₂, 100 μL (0.88 mmol) 3-hexyne, and 72 μL (1.76 mmol)

3

1.24 (d, J = 6.9 Hz, 12H, CH(CH₃)₂), 1.13 (d, J = 6.9 Hz, 12H, MeOH sequentially. The vials were capped and shaken, and the

CH(CH₃)₂).¹³C NMR (126 MHz, CD₂Cl₂) δ 175.07, 146.27, 132.30, solutions were transferred to NMR tubes. Spectra were

130.79, 129.77, 125.20, 121.99, 29.32, 24.68, 24.17.

recorded at regular intervals and yields were calculated based

4[IMP-H]. In an inert atmosphere glovebox, a 4 mL vial was on ratios of integrations of product versus internal standard.

charged with 50 mg (0.08 mmol) IPrAuCl, 14 μL (0.12 mmol) 3-

hexyne, and 2 mL of dichloromethane, and stirred to dissolve.

Li[IMP-H] (106 mg, 0.09 mmol) was added, and the reaction

Conflicts of interest

immediately turned purple, indicating the formation of gold

nanoparticles. The reaction was stirred for half an hour, filtered

through celite, layered with pentane, and placed in the

glovebox freezer, resulting in the formation of colourless X-ray

There are no conflicts to declare.

Dalton Trans., 2019, 10, 1-8 | 15

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28 R. M. P. Veenboer, A. Collado, S. Dupuy, T. Lebl, L. Falivene,

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This work was supported in part by the National Science

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Donors of the American Chemical Society Petroleum Research

Fund for partial support of this research. Support of the NMR

facility at Temple University by a CURE grant from the

Pennsylvania Department of Health is gratefully acknowledged.

The authors thank Boulder Scientific for a gift of B(C₆F₅)₃and

Prof. Michael J. Zdilla for assistance with X-ray crystallography.

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Article Doi

Imidazolyl-phenyl (IMP) anions: A modular structure for tuning solubility and coordinating ability

DOI: 10.1039/c9dt03511g

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