Ylide-Substituted Phosphines with a Cyclic Ylide-Backbone: Angle Dependence of the Donor Strength

Dependence of the Donor Strength

Article

Ylide-Substituted Phosphines with a Cyclic Ylide-Backbone: Angle

Julian L ö ﬄ er, Richard M. Gauld, Kai-Stephan Feichtner, Ilja Rodstein, Jana-Alina Zur, Jens Handelmann,

Christopher Schwarz, and Viktoria H. Gessner*

Cite This: https://doi.org/10.1021/acs.organomet.1c00349

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sı Supporting Information

ABSTRACT: Ylide-substituted phosphines (YPhos) have been

shown to be highly electron-rich and eﬃcient ligands in a variety of

palladium catalyzed transformations. Here, the synthesis and

characterization of novel YPhos ligands containing a cyclic

backbone architecture are reported. The ligands are easily

synthesized from a cyclic phosphonium salt and the chlorophos-

phines Cy PCl (L1) and Cy(Flu )PCl (L2, with Flu = 9-

methylﬂuorenyl) and were characterized in both solution and solid

states. The smaller PCy -substituted ligand, L1, readily formed the

biscoordinate L1 Pd species when treated with Pd (dba) and

showed no activity in palladium-catalyzed amination reactions even

when applied as deﬁned palladium(II) η -allyl, t-Bu-indenyl, or

cinnamyl precursors. Bulkier ﬂuorenyl-substituted ligand L2 similarly was inactive, despite its ability to form the stable

monophosphine complex L2·Pd(dba). Assessment of the electronic properties by experimental and computational methods revealed

that L1 and L2 are considerably less electron-rich than previously synthesized YPhos ligands. This was shown to be the result of the

small P−C−S bond angle, which is sterically enforced due to the cyclic nature of the backbone. Density functional theory

calculations revealed that the small angle results in an increased s-character of the lone pair at the ylidic carbon atom and leads to a

polarization of the C−P bond toward the carbon atom, thus decreasing the electron density at the phosphorus atom. The results

demonstrate the tunability of the donor strength of YPhos ligands by modiﬁcation of the ligand backbone beyond simple changes of

the substitution pattern and are thus important for future ligand design, with a careful balance of many factors to be considered to

achieve catalytic activity.

INTRODUCTION

cone angle, and the buried volume. These measures facilitate

the understanding of structure activity relationships in catalysis

■

Phosphines are a privileged class of ligands ubiquitous in

homogeneous catalysis, a vital cornerstone of modern synthetic

chemistry, with applications ranging from large-scale pharma-

and build the foundation to computer-aided catalyst design.

In the past years, many research eﬀorts have focused on the

preparation of highly electron-rich phosphines due to their

beneﬁcial properties for late transition metal catalysis. For a

long time, trialkyl phosphines particularly with tertiary alkyl

substituents such as t-Bu or Ad (Ad = adamantyl) groups were

the phosphines ligands with the highest donor strength. For

example, Carrow and co-workers synthesized tri(1-adamantyl)-

−3

ceuticals to ﬁne stereo control of complex natural products.

Although extensive research eﬀorts have focused on N-

heterocyclic carbenes (NHCs) as ligand systems in the past

few decades due to their in general higher electron-donating

properties when compared with phosphines, phosphines

remain the ligand systems of choice for many applications.

This continuing popularity is due to several reasons, including

the simplicity of their synthesis, generally from commercially

available starting materials, and the wide breadth of possible

substitution patterns, which allows for the precise control of

the phosphines electronic and steric properties, enabling the

ﬁne-tuning of the phosphine properties toward a desired

purpose. Several advances in homogeneous catalysis over

phosphine, PAd , and impressively demonstrated its applic-

ability in palladium catalysis. However, other substituents at

phosphorus also have been applied in past years to further

increase the donor strength. Thus, Dielmann and co-workers

Received: June 11, 2021

previous decades have been driven by this fact.

For

systematic ligand design various metrics are used in order to

describe the electronic and steric properties of phosphine

ligands, including the Tolman electronic parameter (TEP),

XXXX The Authors. Published by

American Chemical Society

Organometallics XXXX, XXX, XXX−XXX

Organometallics

designed phosphine ligands.

Article

reported on the use of imidazolidin-2-imino substituents

(

IAPs), and Sundermeyer and co-workers on phosphazenyl

groups (PAPs) to access super basic phosphines (Figure 1).

Their donor capacity can compete with or even surpass that of

NHCs, demonstrating the electronic ﬂexibility of specially

Figure 1. Examples of highly electron-rich phosphines.

Figure 2. Synthesis of the YPhos ligands L1 and L2 with a cyclic ylide

backbone and molecular structures of the cation of 1. Ellipsoids drawn

at 50% probability level; hydrogen atoms omitted for clarity. Selected

bond lengths [Å] and angles [°]: P(1)−C(1) 1.803(2), S(1)−C(1)

1.824(2), P(1)−C(1)−S(1) 108.3(1).

Recently, our group reported on ylide-substituted phos-

phines (YPhos), which feature an ylide group directly bonded

to the phosphorus center. As a result of this ylide group and

its strong electron-donating abilities, these phosphines

exhibited strong electron-donating capabilities, with donor

capacities surpassing those of simple phosphines and NHCs.

These ligands were shown to be ideal scaﬀolds for catalytic

applications, ranging from gold-catalyzed hydroamination and

products, likely due to unwanted deprotonation of the CH

group of the isopropyl moiety. The ylide is a dark red oil at

room temperature, characterized by a high-ﬁeld-shifted signal

at δ = 50.2 ppm in the P{ H} NMR spectrum. In keeping

cyclization reactions

to palladium catalysis, such as

with the reactivity of ylide species, exposure of the solution to

air resulted in the formation of a decomposition product, in

which the phosphonium moiety is oxidized to phosphine

oxide, with the concomitant loss of the bridging carbon atom

between the sulfur and phosphorus centers (see the Supporting

Information ). Attempts to obtain the corresponding yldiide of

2 by using a second equivalent of a strong metal base were

unsuccessful, even with the use of strong bases such as NaNH₂,

KHMDS, or benzyl potassium and at elevated temperatures.

With the ylide in hand, desired ligand L1 was synthesized by

Buchwald−Hartwig aminations as well as Negishi couplings

and α-arylation reactions under mild conditions. Recently, it

has been shown that YPhos palladium catalysts are even

capable of directly coupling aryl chlorides and alkyl lithium

reagents, giving very high selectivities while supplementing the

need for any additional transmetalation reagents.

Due to the eﬃciency of YPhos ligands in catalysis, we

became interested in a more profound understanding of the

impact of the ligand architecture on the catalytic ability. In this

contribution, we showcase the development of a new class of

YPhos ligands with a cyclic ylide functionality and demonstrate

that this cyclic structure has a decisive impact on the electronic

properties.

slow addition of 0.5 equiv of Cy PCl to 2. Thereby, the ylide

acts as reagent and base, thus leading to the re-formation of the

chloride salt of 1 ([1]Cl) and ﬁnal ligand L1. Within the

synthesis pathway, formation of an α-phosphino-substituted

phosphonium salt was never observed, suggesting that its

deprotonation to L1 by ylide 2 is a fast process. After removal

of [1]Cl by ﬁltration ([1]Cl being reobtained in 82% yield),

L1 was obtained as orange solid in 79% yield. Analysis via

RESULTS AND DISCUSSION

■

Ligand and Complex Syntheses and Catalytic

Studies. In order to synthesize a cyclic YPhos ligand, we

selected easily accessible phosphonium salt 1 as the ﬁrst test

system. We initially set out to synthesize corresponding

dicyclohexylphosphine L1 in order to allow for comparison

with previously synthesized YPhos ligands. Phosphonium salt

P{ H} NMR spectroscopy showed a set of doublets at δ =

50.7 ppm for the phosphonium group and at δ = −14.9 ppm

for the phosphine moiety with a coupling constant of J

108.6 Hz. Recrystallization from hot acetonitrile furnished

crystals suitable for XRD analysis, which conﬁrmed the

connectivity of the new ligand (Figure 3).

[

1]I could be obtained in 57% yield in a one-pot reaction of 2

equiv of nBuLi and TMEDA with thiophenol, followed by the

slow addition of di-iso-propylchlorophosphine to give an ortho-

phosphino thiolate, which was subsequently cyclized via

diiodomethane addition (Figure 2). The successful formation

Next, the ability of phosphine L1 in palladium catalysis was

tested by means of Buchwald−Hartwig aminations. The

reactions were carried out using 4-bromotoluene and 4-

chlorotoluene as electrophiles and n-butylamine and N-

methylaniline as amines with 3 mol % of Pd dba and free

of [1]I could be conﬁrmed by a singlet at δ = 76.5 ppm in the

P{ H} NMR spectrum and by XRD analysis (see the

Supporting Information for further details). The structure

shows a distorted ﬁve-membered ring, with a slight deviation of

the phosphorus center out of the plane (Figure 2). Starting

from [1]I, the corresponding ylide could be isolated in near-

quantitative yields by treatment with strong, sterically

demanding metal bases such as KHMDS or KOt-Bu.

Deprotonation using such bases in THF aﬀorded ylide 2

within 1 h. Attempted deprotonation using other bases such as

nBuLi or KH resulted in the formation of a mixture of

ligand, both at room temperature and 50 °C. After a period

of 24 h, the reaction mixture was analyzed by GC analysis,

revealing no detectable conversion for any substrate combina-

tion. This contrasts the high activity of the acyclic YPhos

ligands which provided high yields in these reactions at room

15,16

temperature usually within only a couple of minutes.

To understand the origin of the inactivity of L1, we set out

to examine its steric and electronic properties. Reaction of the

new ligand with (tht)AuCl allowed us to obtain the

Organometallics XXXX, XXX, XXX−XXX

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Article

Figure 3. (A) Molecular structures of L1 and L1·AuCl; ellipsoids are

drawn at a 50% probability level. Hydrogen atoms are omitted for

clarity. Selected bond lengths [Å] and angles [°]: L1: P1−C1

.7077(12), S1−C1 1.7920(12), C1−P2 1.7746(12), P1−C1−S1

11.44(6), P1−C1−P2 124.43(7). L1·AuCl: P1−C1 1.717(2), S1−

Figure 4. (Top) Molecular structure of L1 Pd; ellipsoids are drawn at

C1 1.793(1), C1−P2 1.754(2), P2−Au1 2.248(1), Au1−Cl1

a 50% probability level. Hydrogen atoms are omitted for clarity.

Selected bond lengths [Å] and angles [°]: P(1)−C(1) 1.706(3),

S(1)−C(1) 1.796(3), C(1)−P(2) 1.766(3), P(1)−Pd(1) 2.300(1),

Pd(1)−H(11) 2.44(3), P(1)−C(1)−S(1) 110.9(1), P(1)−C(1)−

P(2) 126.4(1), P(2)−Pd(1)−H(11) 88.59(2). (Bottom left)

.303(1), P1−C1−S1 112.7(1), P1−C1−P2 130.0(1). (B) Steric

map of L1 derived from L1·AuCl using the SambVca 2.0 (P−M

distance of 2.28 Å including H atoms).

corresponding gold complex in 73% yield, which was fully

characterized by various analytical methods, including XRD

analysis (see the Experimental Section for full details). The

obtained molecular structure of L1·AuCl shows a slight

shortening of the C1−P2 bond [1.754(2) Å] upon

coordination of the metal [1.775(1) Å in L1], as expected.

The P1−C1−P2 angle increases from 124.43(7) to 130.0(1)°,

thus reducing steric repulsion between the iPr groups and the

gold center (Figure 3). From this structure, the buried volume

Contour-line diagram of the Laplacian distribution of L1 Pd. Solid

lines indicate charge depletions [∇ ρ(r) > 0]; dashed lines indicate

charge concentrations [∇ ρ(r) < 0]. (Bottom right) Section of the

molecular structure of L1 Pd.

between the two phosphine atoms, with the P(2)−Pd(1) bond

of 2.300(1) Å being shorter than the one found for the acyclic

keYPhos ligand, Cy PC(Me)PCy , featuring a PCy moiety

(2.332(6) Å). Also of interest is the observation of a short

Pd(1)−H(11) distance of only 2.47(3) Å between the

palladium and the hydrogen atom of an iPr group. Thus, the

palladium center adopts a pseudo-square-planar geometry. The

bonding nature of the Pd−H interaction was also conﬁrmed by

DFT calculations. QT/AIM studies showed the presence of a

bond critical point between the Pd and H atoms, suggesting

the presence of a stabilizing interaction. Such interactions have

been previously observed with the keYPhos ligand; however, in

the latter case a slightly larger distance of 2.52(3) Å was

was calculated using SambVca. The obtained buried volume

of 42.5% is lower than that of other acyclic YPhos ligands with

PCy or PPh moieties, which usually showed volumes of

13−15

approximately 50%.

Furthermore, the steric map of L1

shows areas of steric bulk only on one side of the of the ligand,

namely, the phosphonium moiety. The cyclohexyl groups are

unable to reach toward the metal center. This observation

suggests, that L1 might be too small to eﬃciently stabilize the

monoligated LPd species and instead leads to the formation of

15a,16

the corresponding bisphosphine complex L Pd, which have

observed.

16,19

been shown to be inactive in catalysis.

As previously shown via mechanistic studies, monoligated

PdL species are the active catalysts in a plethora of palladium-

catalyzed reactions involving bulky monophosphines, while in

To prove this hypothesis, we attempted the isolation of

palladium complexes with L1. Reaction of L1 with Pd (dba)

resulted in instantaneous formation of a new species, detected

via P{ H} NMR spectroscopy. The NMR spectrum showed a

contrast the PdL species are often considered as catalytically

16,19

inactive.

To prevent the formation of PdL₂deﬁned

set of two doublets at δ = 53.6 and 13.1 ppm. The reaction

precatalysts featuring a ligand to metal ratio of 1:1 have been

designed to facilitate the formation of catalytically active Pd

reached full conversion within 10 min, and the resulting

bisphosphine ligated complex could be isolated in high yields

of 81%. Crystallization from pentane and THF conﬁrmed the

species and inhibit the formation of PdL₂. Prominent

examples of such monophosphine systems include η -allyl, t-

formation of the L Pd species (Figure 4). While the formation

Bu-indenyl, and cinnamyl complexes.

In this vein,

of such complexes was found to be hampered with the acyclic

precatalysts of L1 based on the η -allyl, cinnamyl, and t-Bu-

indenyl complexes were synthesized (Scheme 1) by mixing of

the free ligand and the dimeric palladium precursors in pentane

giving the three desired complexes (Pd 1, Pd 1, and Pd 1)

YPhos ligands reported earlier, L1 readily forms the

bisphosphine species because of its low steric bulk. In the

molecular structure, the palladium lies on the inversion center

cin

ind

Organometallics XXXX, XXX, XXX−XXX

Organometallics

formed through substitution of the allyl group from the Pd −

Article

allyl precursor together with [Pd(allyl)Cl₂]⁻as counterion.

Formation of this species is very slow, with only small

quantities formed after several days in solution, thus excluding

that this decomposition reaction is the reason for the catalytic

activity of L1.

Scheme 1. Synthesis of the Palladium Complexes with L1

and L2

We then assessed the electronic properties of the

dicyclohexyl ligand by measurement of the CO stretching

vibration in [L1·Rh(acac)(CO)]. Correlation with stretching

frequencies in LNi(CO) complexes yielded a TEP of 2057.1

−

cm . This value is surprisingly high compared with other

YPhos ligands, which usually featured high donor strengths

similar to carbenes. For example, the acyclic YPhos ligands

keYPhos with a PCy moiety and a methyl group in the ylide

−1

backbone exhibited a TEP value of 2050.1 cm . The high

TEP value of L1 was further conﬁrmed by DFT calculations.

To this end, the minimum of the molecular electrostatic

potential (MESP) at the phosphorus atom was calculated and

correlated with the TEP, a method previously described by

in good yields directly from solution. In all three cases, NMR

spectroscopic analysis shows one set of doublets with similar

shifts in the P{ H} NMR spectrum, with the resonances for

Suresh and Koga. This method yielded a TEPESP of 2057.1

−

cm , thus corroborating with the experimentally obtained

value.

the phosphonium moiety appearing at approximately δ = 56

ppm and for the phosphine moiety between δ = 20.3 and 27.0

To understand whether the catalytic inactivity of the

palladium complexes of L1 is due to the low steric demand

or the weak donor strength, we accessed an analogues ligand to

L1 with a bulkier phosphine moiety containing a 9-

methylﬂuorenyl substituent. The ﬂuorenyl group was expected

to further expand toward the coordination sphere of the metal

ppm. Structural analysis was carried out on Pd 1 and Pd 1,

cin

ind

with both showing shortened carbon−phosphorus bonds

1.7563(3) and 1.720(2) Å] and larger P(1)−C(1)−P(2)

[

angles [130.0(2) and 130.1(1)°] compared to the free ligand.

The isolated palladium complexes were not only applied in

BHA but also showed no activity under the reaction conditions

mentioned above.

and thus impede the formation of the detrimental L Pd

species. New ligand L2 was synthesized from in situ formed

ylide 2 and CIPCyFlu, which was made from 9-methylﬂuorene

We also attempted to crystallize the Pd−allyl complex;

however, we were instead only able to obtain a decomposition

product (Figure 5), in which a second phosphonium moiety is

(

Flu H, see the Supporting Information) by deprotonation

with nBuLi and slow addition to a solution of cyclo-

hexyldichlorophosphine at −60 °C. Similar to L1, slow

addition of 0.5 equiv of the chlorophosphine to 2 directly

gave way to ﬁnal ligand L2, which was obtained as a yellow

solid in 65% yield after puriﬁcation. L2 is characterized by a set

of doublets at δ = 52.0 and 12.2 ppm with a coupling constant

of J_p_p= 119.5 Hz in the P{ H} NMR spectrum.

Recrystallizing from hot acetonitrile furnished single crystals

of L2 suitable for single-crystal XRD analysis (Figure 6). The

Figure 6. Molecular structure of L2. Selected bond lengths [Å] and

angles [°]: P1−C1 1.713(1), S1−C1 1.794(1), C1−P2 1.761(1), P2−

C20 1.927(1), P1−C1−S1 109.5(1), P1−C1−P2 124.5(1).

Figure 5. (Top) Molecular structures of (left) Pd 1 and (right)

cin

Pd_i_n_d2 with ellipsoids drawn at a 50% probability level. Hydrogen

atoms are omitted for clarity. Selected bond lengths [Å] and angles

ligand adopts the desired conformation, whereby the ﬂuorenyl

substituent is directed toward the coordination site of the

phosphine. Thus, L2 appears to be bulkier than L1. The P1−

C20 bond length, which is that between the ﬂuorenyl and the

phosphine, amounts to 1.927(1) Å and is thus relatively long

when compared to typical bonds between phosphorus and an

alkyl group (e.g., P2−C14 1.847(1) Å). In contrast, the P1−

[

°]: Pd 1: P1−C1 1.715(3), S1−C1 1.791(3), C1−P2 1.756(3),

cin

P2−Pd1 2.306(1), Pd1−Cl1 2.365(1), P1−C1−S1 111.1(1), P1−

C1−P2 130.0(2). Pd 1: P1−C1 1.720(2), S1−C1 1.796(2), C1−P2

ind

.756(2), P2−Pd1 2.283(1), Pd1−Cl1 2.376(1), P1−C1−S1

10.4(1), P1−C1−P2 130.1(1). (Bottom) Molecular structure of

decomposition product of Pd 1.

Organometallics XXXX, XXX, XXX−XXX

Organometallics

an internal standard. The reaction plot (Figure 8 ) shows that

Article

C1−P2 bond angle of 124.5(1)° is similar to that in L1 and

thus seems to be unaﬀected by the increased bulk of the

ﬂuorenyl group.

the reaction of stoichiometric quantities of L2 with Pd (dba)

via P{ H} NMR spectroscopy using triphenylphosphine as

To gain further insights into the steric properties of L2 we

attempted the synthesis of the gold chloride complex in order

to determine the buried volume, %V . Reaction with

bur

(

tht)AuCl resulted in the formation of a new species, as

detected by NMR spectroscopic studies. We were able to

observe a set of doublets in the ³¹P{ H} NMR spectrum at δ

58.4 and 44.7 ppm, with a coupling constant of J = 57.4

Hz. However, due to rapid decomposition in solution, isolation

of this species was not possible. Thus, we right away focused

on the synthesis of palladium complexes with L2. The reaction

of L2 with Pd (dba) gave way to two species. The ﬁrst of

these was identiﬁed as bisphosphine complex L2 Pd, which

showed the characteristic coupling pattern with a set of two

doublets at δ = 52.0 and 38.8 ppm in the P{ H} NMR

spectrum, similar to L1 Pd. Unambiguous identiﬁcation came

from XRD analysis (Figure 7 ). Unfortunately, disorder within

Figure 8. Schematic showing the formation of L2Pd(dba) and L2 Pd

complexes from free ligand L2 and Pd (dba) as monitored by

P( H) NMR spectroscopy with Ph3PO as internal standard.

the beginning of the reaction is characterized by the rapid

formation of L2·Pd(dba). Within the ﬁrst 30 min, the rate of

formation slows considerably, while simultaneously there is an

increase in the formation of L2 Pd and a decrease in the

concentration of free ligand. Within 3 h, an equilibrium state is

reached. Throughout the course of the reaction, L2 Pd is

observed to slowly precipitate. These observations suggest that

the combination of free ligand and L2·Pd(dba) leads to the

formation of PdL . Nonetheless, a signiﬁcant amount of the

proposed active catalyst L2·Pd(dba) remains available for

entering the catalytic cycle.

Analogous to L1, we also synthesized palladium precatalysts

Pd 2, Pd 2, and Pd 2, which were obtained as pure solids

cin

ind

in yields of 66−76% (Scheme 1). Analysis by P{ H} NMR

spectroscopy showed two sets of doublets in the case of all

complexes; all three had similar chemical shift and coupling

constant values. These two sets of signals are probably due to

the formation of diastereomers connected with the stereo-

Figure 7. Molecular structure of L2 Pd with ellipsoids drawn at 50%

probability level. Hydrogen atoms are omitted for clarity.

the structure prevented a detailed discussion of bond lengths

and angles, but the molecular connectivity is unambiguous. Of

note is the change in conformation of the ﬂuorenyl group

when compared to the free ligand. Presumably, this change is

instrumental to allow two ligands to coordinate to the Pd(0)

center.

center at phosphorus and were also seen in the H and

NMR spectra. In the molecular structures of Pd 2 and Pd 2,

however, only one isomer was observed (Figure 9). In contrast

ind

to the structure of L2 Pd, the ﬂuorenyl groups in the Pd(II)

complexes remained in the desired orientation pointing toward

the metal center. Nonetheless, one ﬂuorenyl group seems not

to be suﬃcient to fully shield one site of the metal, especially in

As a consequence of the increased bulk of the ﬂuorenyl

group relative to the Cy group and the required conforma-

comparison to biaryl phosphine ligands. This can be seen

tional changes to form L2 Pd, the diphosphine complex was

from the steric map of 2 constructed based on the molecular

not formed selectively from the reaction with Pd (dba) . The

structure of Pd 2. Whereas the map clearly reﬂects the

second species showed a pair of doublets at δ = 55.2 and 29.0

ppm, with the former being in the region expected for the

phosphonium moiety and the latter in the region previously

increased steric bulk of L2 compared to L1 exerted from both

the ylide and ﬂuorenyl substituents, the steric demand remains

moderate.

observed for PCy moiety of the LPd(dba) complex with an

Applications of L2 in Buchwald−Hartwig aminations

analogous to those described above remained unsuccessful

independently of whether the active species was formed from

L2 and Pd (dba) or one of the isolated precatalysts. Since the

acyclic YPhos ligands. Thus, this species presumably is L2·

Pd(dba), which we would expect to be a catalytically

competent species according to previous studies by our as

16,19

well as other groups.

reaction monitoring of L2 and Pd (dba) has revealed that in

2 3

To further understanding how the ligand forms the two

contrast to L1 at least some active catalyst [L2·Pd(dba)]

should be present, we reasoned that the donor strength of L2

complexes, L2·Pd(dba) and L2 Pd, we endeavored to follow

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Table 1. Calculated TEP Values of YPhos Ligands with

Cyclic Ylide Backbones and Comparable Acyclic YPhos

Ligands Previously Reported

Z (cyclic

YPhos)

MESP

[eV]

TEP

[cm

acyclic YPhos

ligand

TEP

−1

ESP

]

exp

]

−

[cm

SO₂

NMe

SiMe₂

CMe₂

−54.15914

−54.14821

−54.14466

−54.15479

−54.15951

−54.16339

2057.1

2060.3

2061.3

2058.4

2057.0

2055.9

Y_SPCy₂

2055.1

Y_S_iPCy₂

2048.8

2050.1

Y_M_ePCy₂

electronic structure of the ligands by natural bond orbital

NBO) analyses (Table 2). These NBO studies reinforced our

(

Figure 9. (Top) Molecular structures of (left) Pd 2 and (right)

assumption by showing signiﬁcant changes in the character of

the P−C bond. Thus, the orbital of the ylidic carbon atom

involved in the P−C bond to the phosphine moiety of L1 and

L2 features a higher s-character in comparison to what would

Pd_i_n_d2. Selected bond lengths [Å] and angles [°]: Pd 2: P1−C1

.724(2), S1−C1 1.780(3), C1−P2 1.754(2), P2−C20 1.935(2),

P2−Pd1 2.349(1), Pd1−Cl1 2.389(1), P1−C1−S1 110.3(1), P1−

C1−P2 129.9(1). Pd 2: P1−C1 1.730(2), S1−C1 1.769(2), C1−P2

ind

be expected for an ideal sp -hybridized carbon center (values

.763(2), P2−C20 1.955(2), P2−Pd1 2.319(1), Pd1−Cl1 2.373(1),

P1−C1−S1 110.8(1), P1−C1−P2 131.1(1). (Bottom) Steric map of

of 39.4 vs 33.3%). This increased s-character is due to the small

P−C−S angle of 111.4° which is enforced by the geometric

restraints of the ring structure and results in a higher p-

character in the corresponding bonds. For comparison reason,

the electron-rich, acyclic keYPhos and joYPhos ligands were

also investigated. As expected, keyPhos showed a much lower

2 derived from the complex Pd 2 using SambVca 2.0 (P−M

Cycl

distance of 2.28 Å including H-atoms).

would be too low to eﬃciently enable oxidative addition under

the reaction conditions. Measurement of the CO stretching

frequency in the in situ formed [L2·Rh(acac)(CO)] complex

s-character in the P−C bond due to the larger P−C−C angle

−

yielded a TEP of 2059.4 cm . Surprisingly, this value is even

higher than that of L1, suggesting that L2 is an even weaker

donor ligand. The high value was again conﬁrmed by

calculation of the minimum of the electrostatic potential

of 117.2°, and joYPhos, which is most electron-rich donor in

this series, features the largest angle of 123.0° and thus displays

the lowest s-character within the orbital with only 30.8%. As a

result of this high s-character within the bonding orbital of L1,

the C−P bond is much more polarized toward the carbon

atom, thus explaining why the cyclic ylide in L1 and L2

donates less electron density toward the phosphine. This

explanation is also in agreement with the observation that

keYPhos and joYPhos are much more electron-rich, with these

species having a lower s-character and hence a less polarized

C−P bond. This observation impressively demonstrates that

the angle between the phosphonium moiety, the ylidic carbon

atom, and Z substituent has a signiﬁcant inﬂuence on the

overall donor ability of the ligand system. It is noteworthy that

studies on the angle dependency of metal ligand interactions

have been reported before, particularly focusing on the impact

of the angle at the donor site (i.e., the C−P−C angles) on the

−

(

MESP) at the phosphorus (TEP_E_S_P= 2059.8 cm ). As both

ligands display extraordinarily high TEP values and both

feature the cyclic ylide moiety, we concluded that the cyclic

ylide itself does not behave as a strongly electron-donating

substituent.

Impact of the Cyclic Backbone on the Donor

Properties. Two possible reasons can be theorized for the

low electron-donating properties of the cyclic ylide: (i) the

anion-stabilizing eﬀects of the sulfur bound to the ylidic carbon

or (ii) the cyclic nature of the ylide. To probe these theories

further, a series of phosphines with similar cyclic ylide

backbones but diﬀering substituents Z in the backbone were

investigated via DFT calculations and compared with related

previously synthesized acyclic YPhos ligands featuring similar

backbones. The MESP at the phosphine was determined, and

the corresponding TEP calculated. The results are summarized

in Table 1. As clearly shown by the obtained results, all cyclic

phosphines examined exhibit high TEP values independent of

the Z substituent. In contrast, the related acyclic analogues

feature much lower TEP values. This observation impressively

demonstrates that the presence of the sulfur atom does not

play the decisive role in the observed electronic properties, but

instead it is the cyclic nature of the ylide, that exerts the biggest

inﬂuence on the electron-donating abilities.

donor properties.

To obtain a quantitative estimation of the impact of the

cyclic structure on the donor properties, cyclic ligand L3 with

Z = SO₂was calculated and compared to its acyclic

counterpart Y PCy . Similar to the observations mentioned

above, the acyclic ligand features a much larger P−C−S angle,

resulting in a higher p-character on the σ(C) orbital and

therefore in a higher bond polarization toward the phosphorus

atom and a lower TEP value.

We further evaluated the angle-dependency of the donor

strength by computationally increasing the angle at the ylidic

carbon atom on the example of the acyclic YPhos ligand,

keYPhos and monitoring the impact on the electronic structure

To further understand the impact of the cyclic geometry on

the electronic properties of the YPhos ligands, we analyzed the

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Calculated TEP from MESP.

Article

Table 2. Results of the NBO Analysis of YPhos Ligands, Observed P−C−Z Angles, and Their Measured TEP Values

ligand

α-P−C−Z angle [deg]

σ(C) s-character

σ(C) p-character

bond polarization % P

bond polarization % C

TEP [cm⁻¹]

111.44

117.17

122.98

111.14

121.50

39.4%

33.5%

30.8%

38.2%

36.5%

60.5%

66.4%

69.1%

61.8%

63.5%

34.8%

36.5%

41.2%

33.6%

34.9%

65.2%

63.5%

58.8%

66.3%

65.1%

2057.1

2050.1

2049.3

2061.3

2057.0

keYPhos

joYPhos

Y_SPCy₂

(

Figure 10). Increasing the Cy P−C−C angle from 90 to

L₂Pd species. Formation of this bisphosphine complex can be

hampered by the bulkier ﬂuorenyl substituent in L2, but this

still does not allow for any catalytic activity. Experimental

determination of the donor strength revealed a remarkably

decreased donor capacity of L1 and L2 compared with

previously reported YPhos ligands featuring acyclic ylide

substituents. Computational studies showed that the decreased

donor strength results from the cyclic backbone. The tight P−

C−S bond angle in the cyclic ylide increases the s-character of

the bonding orbital of the ylidic carbon atom in the C−P

bond, thus resulting in a strong polarization of the C−P bond

toward the carbon and hence in a decreased electron density at

the phosphorus atom. Overall, these results demonstrate a

marked angle-dependency of the donor strength of ylide-

substituted phosphines, which may be used as further tool in

the design of new YPhos ligands in the future.

20 ° resulted in an increase of s-character in the respective

EXPERIMENTAL SECTION

■

General Procedures. All experiments unless otherwise stated

were performed under a dry, oxygen-free argon atmosphere using

standard Schlenk techniques. Solvents involved were dried with an

MBraun solvent-puriﬁcation system (SPS 800) or with standard

methods and stored under an argon atmosphere over 3 or 4 Å

Figure 10. Calculated MESP values at the lone pair at the

phosphorus, p-character of σ(C), and polarization of the C−PCy

bond toward the P atom depending on the P−C−C angle in the

keYPhos ligand.

molecular sieves. H, C{ H}, and P{ H} NMR spectra were

recorded on an Avance III 400 spectrometer from Bruker at 25 °C.

Chemical shifts are given in ppm regarding the δ scale and are

referenced to the residual protons of the deuterated solvent. All spin−

spin coupling constants are given in Hz. Multiplicities are indicated

with the following abbreviations: s = singlet, d = doublet, t = triplet, q

= quartet, dt = doublet of triplets, and so on. The assignment of

signals was supported by HSQC, HMBC, APT, and COSY

experiments. Elemental analyses were performed by Manuela Winter

and Dr. Harish Parala on an Elementar vario MICRO-cube from

Elementar. All chemicals were obtained from commercial sources and

used without further puriﬁcation. Dicyclohexylchlorophosphine and

bonds and hence in an increase of p-character of σ(C) in the

P−C bond to the phosphine moiety. This simultaneously leads

to a lower bond polarization toward the carbon atom and

hence to a lower (more negative) MESP value. Overall, the

widening of the P−C−C-angle in keYPhos by 30° leads to a

−

decrease of the TEP value by 1.4 cm . This change is similar

to the expected change when replacing one n-butyl group (χ =

−

.4 cm ) such as in P(n-Bu) by a tert-butyl substituent (χ = 0

3 i

−

cm ).

25,26

CONCLUSION

In summary, we have reported on the synthesis and

characterization of two novel YPhos ligands with a cyclic

(tht)AuCl were made according to literature methods.

Synthesis of [1]I.

■

ylide and a PCy (L1) and P(Cy)(Flu ) substituent (L2,

Flu

= 9-methylﬂuorenyl), respectively. The unexpected

complete inactivity of various palladium complexes of these

ligands in Buchwald−Hartwig aminations led us to a detailed

investigation of the spatial and electronic properties of the

novel phosphines. Analysis from a spatial viewpoint revealed

that the cyclic ylide oﬀers very little steric protection toward

the metal center in complexes with L1, thus leading to the

facile formation of the corresponding catalytically inactive

In a ﬂ ask ﬁ tted with an addition funnel, 60 mL (99.8 mmol) of a 1.66

M n BuLi solution in hexane was added to 50 mL of cyclohexane. An

additional 30 mL of cyclohexane and 15 mL (11.6 g, 99.8 mmol) of

TMEDA were added afterward slowly, followed by a further 20 mL of

cyclohexane. The solution was cooled to 0 °C and 4.66 mL (5 g, 45.4

Organometallics XXXX, XXX, XXX−XXX

Organometallics

mmol) of thiophenol dissolved in 10 mL of cyclohexane was added

Article

slowly. The solution was stirred for 30 min at 0 °C, warmed to room

temperature, and stirred overnight. A colorless solid precipitated that

was subsequently ﬁ ltered o ﬀ and washed with three 30 mL portions of

hexane. The solid was dried in vacuo (10.0 g, 44.8 mmol). The

dilithiated product was dissolved in 100 mL of THF and cooled to

obtained in 79% yield (2.54 mmol, 1.1 g). H NMR (400 MHz, THF-

d ): δ [ppm] = 1.12 (d, 3H, J = 7.12 Hz, iPr CH ), 1.16 (d, 3H, J =

7.12 Hz, iPr CH ), 1.21 (d, 3H, J = 7.12 Hz, iPr CH ), 1.25 (d, 3H,

J = 7.12 Hz, iPr CH ), 1.20−1.35 (m, 10H, PCy H

), 1.70−1.85

2+3+4

(m, 2H, PCy H

), 1.92 (m, 2H, PCy H ), 2.49 (dp, 2H, J =

2+3+4

2 1

7.12, 7.12, 7.12, 7.12 Hz, J = 10.1 Hz, iPr CH(CH ) ), 7.03 (m,

1H, CH Pos. 4), 7.20 (m, 1H, CH Pos. 2), 7.29 (m, 1H, CH Pos. 1),

7.48 (m, 1H, CH Pos. 3). C{ H} NMR (100.6 MHz, THF-d ): δ

[ppm] = 5.7 (dd, J = 34.7, 105.32 Hz, PCS), 16.75 (dd, J = 1.99

Hz, iPr CH ), 17.8 (d, J = 2.22 Hz, iPr CH ), 28.0 (s, CH PCy

C₃_/₄), 28.7 (m, CH₂PCy₂C₃_/₄), 30.3 (d,

CH(CH ) ), 31.5 (m, CH PCy C ), 32.8 (d, J = 18.7 Hz, CH₂

PCy C ), 36.6 (dd, J = 4.8 Hz, J = 9.43, CH PCy C ), 118.4 (d,

3 2

−80 °C. Next, 7.15 mL (6.84 g, 44.8 mmol) of diisopropylchlor-

ophosphine was slowly added via an addition funnel at −80 °C over a

period of 1 h. The solution was stirred and allowed to warm to room

temperature overnight. The solvent was removed, and the remaining

solid was dried in vacuo (15 g, 38.4 mmol). The obtained solid was

dissolved in 200 mL of diethyl ether and 3.09 mL (10.2 g, 38.4 mmol)

of diiodomethane was added slowly before being left to stir overnight.

The solvent was removed, and the residue redissolved in 50 mL of

DCM. The undissolved salts were ﬁ ltered o ﬀ . The solvent was

removed, and the remaining solid was suspended in 50 mL of THF,

ﬁ ltered, and washed (2 × 20 mL) with THF. The colorless solid was

dried in vacuo . Phosphonium salt [1 ]I could be obtained as a colorless

= 49.36 Hz, iPr

3/4

J_C_P= 91.0 Hz, C Pos. 6), 122.8 (d, J = 9.2, CH Pos. 3), 123.8 (d,

³J = 6.9, CH Pos. 2/4), 129.5 (d, J = 1.3 Hz, CH Pos. 2/4), 129.9

(

d, J = 2.6 Hz, CH Pos. 1), 155.7 (dd, J = 18.9 Hz, C Pos. 5).

CP CP

P{ H} NMR (162.1 MHz, THF-d ): δ [ppm] = −14.9 (d, J

08.6 Hz, PCy ), 50.67 (d, J = 108.6 Hz, PCS). IR (ATR) [cm ]:

917 (s), 2851 (m), 1439 (m), 1108 (s), 1048 (m), 874 (m), 849

(w), 711 (m), 690 (s), 653 (m), 538 (w), 471 (m), 450 (w). CHNS

for C H P S: Calcd: C: 69.09, H: 9.28, S: 7.38. Measured: C: 68.89,

−1

solid (9.4 g, 25.7 mmol, 56.5% yield). H NMR (400 MHz, DCM-

d ): δ [ppm] = 1.33 (d, 3H, J = 7.15 Hz, i Pr C H ), 1.38 (d, 3H, J =

.15 Hz, i Pr C H ), 1.41 (d, 3H, J = 7.12 Hz, i Pr C H ), 1.46 (d, 3H,

40 2

J = 7.12 Hz, i Pr C H ), 3.61 (ds, 2H, J = 7.15, 7.15, 7.12, 7.12 Hz,

H: 9.14, S: 7.38. Melting point: 93.7 °C.

² J = 10.57 Hz, i Pr C H (CH ) ), 4.30 (d, 2H, J = 9.45 Hz, PC H S),

Synthesis of L1·AuCl. A Schlenk tube was charged with L1 (200

mg, 459 μmol, 1 equiv), (tht)AuCl (147 mg, 459 μmol, 1 equiv), and

4 mL of THF, and the mixture was stirred overnight. The solvent was

removed in vacuo, and the residue dissolved in 2 mL of DCM. The

solution was layered with 20 mL of pentane and left for 1 day. A

yellow solid precipitated. The solution was then cooled to −30 °C for

2 more days. The solid was ﬁltered oﬀ and washed (2 × 5 mL) with

pentane. 224 mg (336 μmol, 73%) of the yellow crystalline solid was

obtained. Slow diﬀusion of pentane into a solution of L1·AuCl in

C D allowed crystals suitable for single-crystal XRD to be obtained.

.43 (m, 1H, C H Pos. 4), 7.49 (m, 1H, C H Pos. 2), 7.68 (m, 1H, C H

Pos. 1), 7.89 (m, 1H, C H Pos. 3). C{ H} NMR (100.6 MHz, DCM-

d ): δ [ppm] = 16.2 (d, J = 15.2 Hz, i Pr C H ), 16.3 (d, J = 15.2

Hz, i Pr C H ), 17.5 (d, J = 42.7 Hz, P C H S), 23.9 (d, J = 40.4,

i Pr C H(CH ) ), 113.2 (d, J = 85.6, C Pos. 6), 124.8 (d, J = 9.2

Hz, C H Pos. 2/4), 126.9 (d, J = 10.3 Hz, C H Pos. 2/4), 132.4 (d,

J _C _P = 10.6 Hz, C H Pos. 1), 136.1 (d, J = 2.6 Hz, C H Pos. 3), 150.3

d, J = 16.9 Hz, C H Pos. 5). P{ H} NMR (162.1 MHz, DCM-

−

d ): δ [ppm] = 76.5 (s, P CS). IR (ATR) [cm ]: 3051 (w), 2979 (w),

859 (m), 1574 (s), 1452 (s), 1427 (s), 1271 (m), 1140 (s), 1116

m), 1036 (w), 884 (m), 783 (s), 145 (m), 676 (s), 632 (m), 482 (s),

61 (s), 450 (s), 430 (m). CHNS for C H IPS: Calcd: C: 42.63, H:

H NMR (400 MHz, CD Cl ): δ [ppm] = 1.14−1.34 (4 ×rd, 12 H,

J_P_H= 7.0 Hz, iPr CH ), 1.14−1.34 (m, 6H, PCy CH ), 1.34−1.57

(m, 6H, PCy CH ), 1.63−1.71 (m, 2H, PCy CH ), 1.77−1.88 (m,

.50, S: 8.75. Measured: C: 42.57, H: 5.38, S: 8.43. Melting point:

H, PCy CH ), 1.95−2.06 (m, 4H, PCy CH ), 2.15 (tdd, 2H, J

60.1 °C.

2.1 Hz, J = 7.0, 3.3 Hz), 3.13 (dp, 2H, J = 8.9 Hz, J = 7.1, 7.1,

Synthesis of 2. In a Schlenk tube, 2.50 g (6.83 mmol) of

.0, 7.0, iPr CH), 7.12−7.18 (m, 1H, Pos. 4), 7.30−7.39 (m, 2H, Pos.

phosphonium salt [1]I and 930.0 mg (8.29 mmol) of KOt-Bu were

suspended in 15 mL of THF. The suspension immediately turned

orange. The suspension was stirred for 2 h at room temperature

before removal of the solvent under reduced pressure, with the

residue redissolved in 10 mL of pentane and stirred for 15 min. The

solution was ﬁltered, and the white residue was washed (2 × 5 mL)

with pentane. The solvent of the combined solutions was removed

and 1.55 g (6.47 mmol, 95%) of ylide 2 was obtained as a dark red

+ Pos. 3), 7.46−7.51 (m, 1H, Pos. 1). C{ H} NMR (101 MHz,

CD Cl ): δ [ppm] = 0.8 (dd, J = 103.9, 66.1 Hz, PCS), 17.0 (dd,

^JCP = 42.6 Hz, J = 2.0 Hz, iPr CH ), 26.6 (d, J = 1.7 Hz, PCy

CH ), 27.1−27.5 (m, PCy CH ), 29.2 (d, J = 48.9 Hz, iPr CH),

0.3 (d, J = 1.9 Hz, PCy CH ), 32.0 (d, J = 2.8 Hz, PCy CH ),

2 2 2 2

7.7 (dd, J = 41.5 Hz, J = 1.8 Hz, PCy CH), 118.2 (dd, J =

2.7 Hz, J = 6.7 Hz, C Pos. 6), 122.9 (d, J = 7.1 Hz, CH Pos. 2),

23.7 (d, J = 9.6 Hz, CH Pos. 4), 129.6 (d, J = 10.1 Hz, CH

Pos. 1), 130.8 (d, J = 2.2 Hz, CH Pos. 3), 151.5 (dd, J = 15.8 Hz,

J = 5.1 Hz, C Pos. 5). P{ H} NMR (162.1 MHz, CD Cl ): δ [ppm]

2 2

= 27.1 (d, J = 51.8 Hz, PCy ), 57.2 (d, J = 50.5 Hz, PCS). IR

(ATR) [cm ]: 2919 (m), 1444 (m), 1110 (m), 1066 (s), 897 (m),

741 (s), 711 (s), 687 (m), 667 (m), 636 (w), 520 (m), 445 (m), 408

m). CHNS for C H AuClP S: Calcd: C: 45.02, H: 6.04, S: 4.81.

liquid. H NMR (400 MHz, C D ): δ [ppm] = 0.76 (d, 3H, J = 7.06

Hz, iPr CH ), 0.79 (d, 3H, J = 6.76 Hz, iPr CH ), 0.83 (d, 3H, J =

.76 Hz, iPr CH ), 0.86 (d, 3H, J = 7.11 Hz, iPr CH ), 1.42 (d, 1H,

^JHP = 23.0 Hz, PCHS), 1.81 (dq, 1H, J = 7.12, 7.12, 7.12 Hz, J

−1

4.2 Hz, iPr CH(CH ) ), 6.83 (m, 1H, CH Pos. 4), 6.94 (m, 1H, CH

3 2

Pos. 2), 7.14(m, 1H, CH Pos. 1), 7.40 (m, 1H, CH Pos. 3). C{ H}

(

25 40 2

NMR (100.6 MHz, C D ): δ [ppm] = −3.4 (d, J = 103.0 Hz,

Measured: C: 44.79, H: 6.10, S: 4.43. Melting point: 207.3 °C

PCHS), 16.5 (dd, J = 154.2 Hz, J = 2.42 Hz, iPr CH ), 29.1 (d,

(decomposition).

^JCP = 48.6, iPr CH(CH ) ), 115.2 (d, J = 94.8, C Pos. 6), 121.4 (d,

Synthesis of L1 Pd. A Schlenk tube charged with L1 (200 mg, 460

μmol, 1 equiv), Pd dba (155 mg, 230 μmol, 1 equiv), and 4 mL of

⁴J = 9.6 Hz, CH Pos. 4), 124.2 (d, J = 7.48 Hz, CH Pos. 2), 127.8

(

d, J = 2.35 Hz, CH Pos. 3), 129.2 (d, J = 9.84 Hz, CH Pos. 1),

53.6 (d, J = 21.4 Hz, CH Pos. 5). P{ H} NMR (162.1 MHz,

THF was stirred at room temperature for 1 h. The solution was

subsequently ﬁltered, over-laid with 10 mL of pentane, and left for 3

days. A yellow solid precipitated from the solution. The solid was

ﬁltered oﬀ and washed (2 × 5 mL) with THF; 181 mg (185 μmol,

81%) of the yellow solid was obtained. Slow diﬀusion of pentane into

a solution of L1 Pd in C D allowed for crystals suitable for single-

C D ): δ [ppm] = 50.2 (s, PCS).

Synthesis of L1. First, 1.55 g (6.47 mmol) of ylide 2 was dissolved

in 15 mL of THF and cooled to 0 °C. To this, 0.79 mL (865.8 mg,

.56 mmol) of PCy Cl was slowly added over 10 min. Upon addition

of the chlorophosphine, the phosphonium salt precipitated as a

colorless solid. It was stirred for 2 h at room temperature and ﬁltered,

and the solid was washed with (2 × 5 mL) THF. The solvent was

removed under reduced pressure, and the red-orange residue was

suspended in 5 mL of acetonitrile and stirred for 15 h. Overnight, an

orange solid precipitated that was ﬁltered oﬀ, washed (2 × 5 mL) with

acetonitrile, and dried in vacuo. Ylide-substituted phosphine L1 was

crystal XRD to be obtained. H NMR (400 MHz, THF-d ): δ [ppm]

= 1.12 (dd, 6H, J = 7.16, 16.71 Hz, iPr CH ), 1.41 (dd, 6H, J = 7.16,

16.71 Hz, iPr CH ), 1.3−1.5 (m, 6H, PCy2 H₁₊₂₊₃₊₄), 1.76 (m, 2H,

PCy2 H

PCy H

), 1.8−2.0 (m, 8 H, PCy H

), 2.1−2.4 (m, 6H,

+2+3+4

2+3+4

), 3.72 (dp, 2H, J = 7.05, 7.05, 7.05, 7.05 Hz, J = 10.1

2+3+4

Hz, iPr CH(CH ) ), 6.72 (m, 1H, CH Pos. 4), 6.88 (m, 1H, CH Pos.

2), 6.92 (m, 1H, CH Pos. 1), 7.02 (m, 1H, CH Pos. 3). C{ H}

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

NMR: Not possible due to poor solubility of the pure compound in

Ph), 153.5 (dd, ²J_C_P= 15.3 Hz, J = 3.1 Hz, Pos. 5). P NMR (162

deuterated solvent. P{ H} NMR (162.1 MHz, THF-d ): δ [ppm] =

MHz, THF-d ) δ = 24.8 (d, J = 61.3 Hz, PCy ), 55.53 (d, J

−1

3.11 (dd, J = 44.9, 34.2 Hz PCy ), 50.7 (dd, J = 45.0, 34.2 Hz,

PCS). IR (ATR) [cm ]: 2914 (m), 2843 (m), 1441 (m), 1257 (w),

60.9 Hz, PCS). IR (ATR) [cm ]: 2918 (m), 1442 (m), 1107 (m),

1059 (s), 872 (m), 741 (s), 688 (s), 657 (w), 513 (w), 458 (m), 411

(m). CHNS for C H ClP PdS: Calcd: C: 58.87, H: 7.12, S: 4.62.

−

109 (m), 1058 (s), 1000 (w), 887 (m), 868 (s), 851 (w), 741 (s),

12 (m), 366 (m), 543 (w), 514 (m), 471 (m), 441 (m), 406 (m).

Measured: C: 59.18, H: 7.22, S: 4.39. Melting point: 115.2 °C

CHNS for C H P PdS : Calcd: C: 61.56, H: 8.27, S: 6.57.

(decomposition).

Measured: C: 61.88, H: 7.87, S: 6.49. Melting point: 195.8 °C

Synthesis of Pd 1. First, 250 mg (0.58 mmol) of L1 and 178 mg

(

decomposition).

of [Pd( Bu-Indenyl)Cl] (33.2 m% Pd, 0.29 mmol) were suspended

Synthesis of Pd 1. 250 mg (0.58 mmol) of L1 and 108 mg of

in 10 mL of pentane and stirred for 2 h. The dark gray suspension

[

Pd(allyl)Cl] (56.4 m% Pd, 0.29 mmol) were suspended in 10 mL of

formed was ﬁltered, and the solid was washed (2 × 5 mL) with

pentane and stirred for 30 min. A yellow suspension formed, which

pentane. Complex Pd 1 was obtained as a gray solid in 84.2% yield

was ﬁltered, and the remaining solid was washed (2 × 5 mL) with

(352 mg, 0.47 mmol). By slow diﬀusion of pentane into a solution of

Pd 1 in C D , crystals suitable for single-crystal XRD could be

pentane. Complex Pd 1was obtained as a yellow solid in 74% yield

(

255 mg, 0.56 mmol). By slow diﬀusion of pentane into a solution of

obtained. H NMR (400 MHz, C D ): δ [ppm] = 0.84−0.98 (m, 4H,

Pd 1in C D crystals of a decomposition product suitable for single-

crystal XRD could be obtained. H NMR (400 MHz, C D ): δ [ppm]

iPr CH ), 1.02−1.13 (m, 6H, iPr CH ), 1.18 (m, 2H, iPr CH ), 1.22−

1.88 (m, 18H, PCy CH H

), 1.68 (s, 9H, Bu CH ), 2.21 (m,

2+3+4 3

0.88−1.10 (m, 6H, iPr CH ), 1.10−1.29 (m, 8H, iPr CH , PCy

3H, PCy CH H

), 2.42 (m, 1H, PCy CH H

), 2.60 (dqd,

2+3+4

CH H

), 1.30−1.92 (m, 13H, PCy CH H

), 2.21−2.31 (d,

2H, J = 3.17, 9.35, 9.47, 12.1 Hz, PCy CH H ), 3.55 (dp, 1H, J

2+3+4

H, J = 12.5 Hz, PCy CH H

), 2.32 (d, 2H, J = 11.2 Hz, Allyl

14.2 Hz, J = 7.2, 7.2, 7.24, 7.24 Hz, iPr CH), 4.18 (dp, 1H, J

2+3+4

CH H ), 2.38−2.53 (dt, 2H, J = 9.0, 9.0, 22.2 Hz, PCy CH

14.2 Hz, J = 7.2, 7.2, 7.24, 7.24 Hz, iPr CH), 5.43 (dd, 1H, J = 1.37,

), 2.53−2.71 (p, 2H, J = 15.1, 15.1, 17.1, 17.1 Hz, PCy CH

2.89 Hz, Ind), 6.32 (dd, 1H, J = 0.92, 2.93 Hz, CH, Ind), 6.71 (m,

1H, CH Pos. 4), 6.79 (m, 1H, CH, Ind), 6.85 (m, 1H, CH Pos. 2),

6.93 (m, 1H, CH, Ind), 7.03 (m, 2H, CH Pos 1 + Ind), 7.19 (m, 1H,

+3+4

H ), 3.47 (dd, 1H, J = 8.7, 13.8 Hz, Allyl CH H ), 5.53 (m, 1H, Allyl

CH H ), 3.6 (dp, 1H, J = 5.24, 5.24, 5.25, 5.25 Hz, J = 14.2 Hz,

iPr CH), 3.74 (dp, 1H, J = 7.04, 7.04, 7.05, 7.05 Hz, J = 14.2 Hz,

CH Pos 3), 7.47 (m, 1H, CH, Ind). C{ H} NMR (101 MHz, C D )

6 6

iPr CH), 4.52 (t, 1H, J = 7.19, 7.19 Hz, Allyl CH H ), 4.89 (ddd, 1H,

δ = 7.24 (dd, J = 106.6, 42.8 Hz, PCS), 17.9 (d, J = 1.9 Hz, iPr

J = 7.96, 13.7, 17.9 Hz, Allyl CH H ), 6.83−6.91 (m, 1H, CH Pos.

CH ), 18.1 (d, J = 2.2 Hz, iPr CH ), 18.2 (d, J = 2.1 Hz, iPr CH ),

), 6.83−6.91 (m, 1H, CH Pos. 2), 7.01−7.12 (m, 1H, CH Pos. 1),

18.6 (d, J = 2.2 Hz, iPr CH ), 26.5 (d, J = 20.5 Hz, CH PCy

3 2 2

.13−7.23 (m, 1H, CH Pos. 3). C{ H} NMR (101 MHz, C D ) δ

C₂₊₃₊₄), 27.2 (dd, J = 12.0, 4.0 Hz, CH PCy C

), 27.7 (dd, J =

2+3+4

[

ppm] = 6.01 (dd, J = 37.9, 106.5 Hz, PCS), 18.1 (d, J = 2.2 Hz,

15.0, 12.9 Hz, CH PCy C

), 29.1 (s, CH PCy C₂₊₃₊₄), 29.5 (s,

2+3+4 2 2

iPr CH ), 26.9 (s, CH PCy C

C₂₊₃₊₄), 28.1 (d, J = 12.6 Hz, CH PCy C

C₂), 30.1 (s, CH PCy C

), 27.7 (d, J = 12.1 Hz, CH PCy

Bu C(CH ) ), 29.5 (s, Bu C(CH ) ), 29.8 (d, J = 41.8 Hz, CH Ind),

2+3+4

3 3 3 3

), 30.0 (s, CH PCy

31.0 (d, J = 47.0 Hz, CH Ind), 34.6 (d, J = 4.5 Hz, Bu C(CH ) ),

3 3

41.2 (dd, J = 52.2 Hz, J = 26.6 Hz, CH PCy C ), 64.8 (d, J = 3.5

2+3+4

), 30.4(s, CH PCy C

), 30.6

+3+4

2+3+4

CP 2 1

(

d, J = 6.5 Hz, iPr CH(CH ) ), 40.4 (dd, J = 74.1 Hz, J = 26.7

Hz, CH Ind), 107.9 (d, J = 5.8 Hz, CH Ind), 117.8 (dd, J = 88.9

Hz, CH PCy C ), 50.7 (d, J = 2.3 Hz, CH allyl), 79.6 (d, J = 29.1

Hz, CH allyl), 114.3 (d, J = 4.6 Hz, CH allyl), 118.0 (dd, J = 90.0

Hz, J = 5.9 Hz, Pos. 6), 122.2 (d, J = 9.2 Hz, Pos. 4), 122.9 (d, J =

Hz, J = 5.3 Hz, C Pos. 6), 118.0(s, CH Ind), 120.5 (s, CH Ind), 121.7

(d, J = 9.1 Hz, CH Pos. 4), 122.4 (d, J = 6.6 Hz, CH Pos. 3), 124.71

(d, J = 63.4 Hz, CH Ind), 125.9 (d, J = 23.2 Hz, C Ind), 129.0 (d, J

.7 Hz, Pos. 3), 129.5 (d, J = 2.2 Hz, Pos. 2), 130.2 (d, J = 9.3 Hz,

= 2.2 Hz, CH Pos. 2), 130.4 (d, J = 9.2 Hz, CH Pos. 1), 138.7 (d, J =

Pos. 1), 152.8 (dd, J = 15.5 Hz, J = 3.1 Hz, Pos. 5). P{ H} NMR

5.4 Hz, C Ind), 140.3 (s, C Ind), 152.1 (dd, J = 14.8 Hz, J = 3.5

(

162.1 MHz, C D ): δ [ppm] = 20.3 (d, J = 60.8 Hz, PCy ), 55.5

d, J = 61.1 Hz, PCS). IR (ATR) [cm ]: 2924 (m), 2845 (w),

442 (m), 1262 (w), 1106 (m), 1064 (s), 864 (m), 742 (s), 657 (m),

59 (m), 405 (w). CHNS for C H ClP PdS: Calcd: C: 54.37, H:

.50, S: 5.18. Measured: C: 54.22, H: 7.79, S: 5.18. Melting point:

Hz, C Pos. 5). P NMR (162 MHz, C D ) δ = 27.0 (d, J = 55.8

−1

Hz, PCy ), 56.7 (d, J = 56.0 Hz, PCS). IR (ATR) [cm ]: 2926

(m), 2843 (w), 1444 (m), 1362 (w), 1275 (w), 1196 (s), 1104 (m),

1060 (s), 1046 (m), 873 (m), 743 (s), 687 (m), 628 (w), 511 (m),

461 (s), 426 (s). CHNS for C H ClP PdS: Calcd: C: 61.04, H:

7.66, S: 4.74. Measured: C: 61.27, H: 7.89, S: 4.49. Melting point:

155.3 °C (decomposition).

Synthesis of 9-Methyl-ﬂuorene (9-Me-Fluorene). Following a

slightly modiﬁed literature procedure, 4.99 g (30 mmol) of ﬂuorene

was dissolved in 60 mL of THF and cooled to −60 °C. To this was

slowly added (over a period of 15 min) 26 mL of a 1.55 M solution of

nBuLi in hexane. The solution was warmed to room temperature and

stirred for 1.5 h. The solution was cooled to −60 °C, and 2.8 mL

(6.39 mg, 45 mmol) of MeI was added slowly over 5 min. The

solution became clear and colorless and was then stirred for 15 min at

−60 °C and 2 h at room temperature. Excess MeI was quenched with

100 mL of aqueous KOH solution. The aqueous phase was separated

46.7 °C (decomposition).

Synthesis of Pd 1. First, 200 mg (0.46 mmol) of L1 and 118 mg

cin

of [Pd(Cinnamyl)Cl] (40.2 m% Pd, 0.23 mmol) were suspended in

mL of pentane and stirred for 2 h. A red suspension formed. This

was ﬁltered, and the solid was washed (2 × 5 mL) with pentane.

Complex Pd 1 was obtained as a red-orange solid in 55.2% yield

cin

(

176 mg, 0.25 mmol). By slow diﬀusion of pentane into a solution in

THF-d , crystals suitable for X-ray diﬀraction could be obtained. H

NMR (400 MHz, THF-d ): δ [ppm] = 1.07−1.85 (m, 27H, iPr CH

PCy CH H

), 1.97−2.26 (m, 5H, PCy CH H

), 2.30−

2+3+4

.52 (m, 2H, PCy CH H ), 2.69−2.77 (d, 1H, J = 11.9 Hz, cin

CH ), 3.58 (m, 1H, iPr CH), 3.71 (m, 1H, iPr CH), 3.80 (d, 1H, J =

.7 Hz, iPr CH), 5.06 (dd, 1H, J = 13.1, 9.3 Hz, cin CH), 5.83 (m,

H, cin CHPh), 7.02−7.10 (m, 1H, Pos. 4), 7.19−7.29 (m, 4H, cin

and extracted (2 × 5 mL) with Et O. The combined organic phases

were dried with MgSO , and the solvent was removed. The crude

product was ﬁltered over a short silica column with hexane as eluent.

CH Ph + Pos. 2), 7.31−7.37 (m, 1H, Pos. 1), 7.42−7.46 (m, 2H, cin

CH Ph), 7.49−7.55 (m, 1H, Pos.3). C NMR (101 MHz, THF-d ):

The product was obtained as a yellow waxlike solid in 91% yield (5.0

δ [ppm] = 7.2 (dd, J = 107.2, 39.1 Hz, PCS), 18.6 (d, J = 2.2

g, 27.4 mmol). H NMR (400 MHz, THF-d ): δ [ppm] = 1.44 (d,

Hz, iPr CH ), 18.8 (d, J = 2.0 Hz, iPr CH ), 23.4 (s, PCy CH ),

3H, J = 7.34 Hz, CH ), 3.85 (q, 1H, J = 7.30 Hz, 9HFlu), 7.26 (m,

7.6 (s, PCy CH ), 28.0−31.3 (m, PCy CH ), 32.0 (d, J = 46.4

4H, Ar), 7.42 (d, 2H, J = 7.15 Hz, Ar), 7.67 (m, 2H, Ar).

Hz, iPr CH), 40.0 (d, J = 27.2 Hz, PCy CH), 42.5 (d, J = 25.6

Synthesis of CIPCyFlu. First, 5.00 g (27.4 mmol) of 9-Me-

Fluorene was dissolved in 110 mL of THF and cooled to −60 °C.

17.7 mL of a 1.55 M solution of nBuLi in hexane was added slowly

over 15 min. The solution turned red and was stirred for 30 min at 60

°C, before being cooled and stirred for 2 h at room temperature. A

second solution of 4.2 mL (29 mmol, 5.07 g) of PCyCl in 40 mL of

THF was prepared and cooled to −60 °C. The lithiated 9-Me-

Hz, PCy CH), 48.1 (d, J = 2.6 Hz, cin CH ), 98.8 (d, J = 26.8 Hz,

cin CH), 109.6 (d, J = 5.2 Hz, cin CHPh), 118.7 (dd, J = 89.7 Hz,

J = 5.6 Hz, Pos. 6), 123.0 (d, J = 9.2 Hz, Pos. 4), 123.4 (d, J

.7 Hz, Pos.2), 127.9 (d, J = 2.4 Hz, Pos. 1), 128.7 (d, J = 3.3 Hz,

cin CH Ph), 129.1 (d, J = 2.0 Hz, cin CH Ph), 130.2 (d, J = 2.2 Hz,

cin CH Ph), 131.5 (d, J = 9.5 Hz, Pos. 3), 138.7 (d, J = 6.1 Hz, cin C

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

Fluorene solution was cooled to −60 °C and slowly added to the

chlorophosphine solution over a period of 30 min. This was then

stirred for 30 min at −60 °C and allowed to come to room

temperature overnight. The solvent was removed, and the residue was

suspended in 20 mL of hexane and ﬁltered over Celite. The solvent

was removed in vacuo, and the crude product puriﬁed by distillation

formed was ﬁltered and the solid washed (2 × 5 mL) with pentane.

Complex Pd 2 was obtained as a yellow solid in 73% yield (295 mg,

0.414 mmol). By slow diﬀusion of pentane into a solution of Pd 2 in

THF-d , crystals suitable for single-crystal XRD could be obtained.

(The obtained molecular structures and NMR data suggest two

diﬀerent conformers in solid state and solution.) P{ H} NMR

(

1 × 10⁻bar at 147 °C). Yield was not determined. H NMR (400

(162.1 MHz, THF-d ): δ [ppm] = 34.5 (d, JPP = 63.4 Hz, PCyFlu),

MHz, DCM-d ): δ [ppm] = 0.40 (m, 1H, PCy CH H

), 0.5−1.0

35.4 (d, JPP = 63.3 Hz, PCyFlu), 59.0 (d, JPP = 62.8 Hz, PCS), 59.1

2+3+4

(

m, 6H, PCy CH + CH H

), 1.2−1.4 (m, 3H, PCy CH

(d, JPP = 63.4 Hz, PCS). H NMR and C NMR could not be

evaluated due to the presence of two diﬀerent conformers in solution.

1+2+3+4

H₂₊₃₊₄), 1.48 (s, 1H, PCy CH H

), 1.86 (d, J = 13.3 Hz,

2+3+4

−1

CH ). C{ H} NMR (100.6 MHz, DCM-d ): δ [ppm] = 23.5 (d,

IR (ATR) [cm ]: 2916 (w), 1441 (m), 1105 (m), 1048 (m), 1013

J_C_P= 21.6 Hz, CH Flu), 26.1 (d, J = 1.43 Hz, CH Cy C₃₊₄), 26.7

(m), 866 (m), 739 (s), 727 (s), 687 (s), 631 (m), 571 (w), 448 (s),

25 (m). Melting point: 133.7 °C (degradation). CHNS for

(

d, J = 8.98 Hz, CH Cy C ), 26.8 (d, J = 1.37 Hz, CH Cy C₃₊₄),

CP 2 2 2

C H ClP PdS: Calcd: C: 60.59, H: 6.36, S: 4.49. Measured: C:

8.8 (d, 6.26 Hz, CH Cy H ), 30.0 (d, J = 26.5 Hz, CH Cy C ),

36 45

3+4

59.74, H: 6.20, S: 4.19

8.5 (d, J = 38.5 Hz, CH Cy C ), 53.0 (d, J = 41.1 Hz, C Flu₉).

−

Synthesis of Pd 2. First, 300 mg (0.565 mmol) of L2 and 149 mg

IR (ATR) [cm ]: 2917 (m), 2849 (s), 1474 (s), 1437 (m), 1026 (s),

63 (s), 742 (s), 729 (s), 603 (w), 565 (w), 473 (s), 453 (s), 423

w). CHNS for C H ClP: Calcd: C: 73.06, H: 6.74. Measured: C:

cin

of [Pd(cinnamyl)Cl] (40.2 m% Pd, 0.283 mmol) were suspended in

(

mL of pentane and stirred for 2 h. The orange suspension formed

was ﬁltered, and the solid was washed (2 × 5 mL) with pentane.

Complex Pd 2was obtained as an orange solid in 76% yield (340 mg,

3.05, H: 6.81. Melting point: 69.2 °C.

Synthesis of L2. First, 1g (2.73 mmol) of phosphonium salt 1 and

06 mg (2.73 mmol) of KOt-Bu were suspended in 8 mL of THF and

cin

.431 mmol). By slow diﬀusion of pentane into a solution of Pd 2 in

cin

THF-d , crystals suitable for X-ray diﬀraction could be obtained. (The

stirred for 4 h, forming a red solution. The solvent was removed in

vacuo, and the residue was redissolved in 8 mL of pentane. The

solution was subsequently ﬁltered, and the solvent was removed. The

residue was dissolved in 8 mL of THF and cooled to 0 °C. A solution

of 449 mg of ClPCyFlu (0.5 equiv, 1.37 mmol) in 1 mL of THF was

added slowly. A beige solid immediately precipitated from the

solution. The solution was stirred for 2 h at room temperature and

ﬁltered, and the solvent was removed in vacuo. The residue was

suspended in 15 mL of hot acetonitrile and stirred until dissolution.

The solution was ﬁltered while hot and allowed to slowly cool room

temperature, precipitating a yellow solid. The solution was ﬁltered,

and the remaining solid was washed (3 × 1.5 mL) with acetonitrile.

obtained molecular structures and NMR data suggest two diﬀerent

conformers in solid state and solution.) P{ H} NMR (162.1 MHz,

THF-d ): δ [ppm] = 37.3 (d, J = 62.7 Hz, PCyFlu), 39.2 (d, J

2.57 Hz, PCyFlu), 59.10 (d, J = 63.13 Hz, PCS), 59.24 (d, J

2.49 Hz, PCS). H NMR and C NMR could not be evaluated due

to the presence of two diﬀerent conformers in solution. IR (ATR)

−

[

cm ]: 2922 (w), 1443 (m), 1110 (w), 1037 (m), 869 (m), 763 (w),

28 (s), 689 (s), 653 (m), 623 (w), 511 (w), 452 (m). Melting point:

59.2 °C (degradation).

Synthesis of Pd_i_n_d2. First, 120 mg (0.23 mmol) of L2 and 72.4 mg

of [Pd( Bu-Indenyl)Cl] (33.2 m% Pd, 0.12 mmol) were suspended

in 4 mL of pentane and stirred for 2 h. A dark brown suspension

formed, which was subsequently ﬁltered, and the solid was washed (2

Phosphine L2 was obtained as this yellow solid in 65% yield (940 g,

.8 mmol). H NMR (400 MHz, THF-d ) δ = 0.27−0.55 (m, 3H, Cy

5 mL) with pentane. Complex Pd_i_n_d2 was obtained as brown solid

in 66% yield (127 mg). By slow diﬀusion of pentane into a solution in

THF-d , crystals suitable for single-crystal XRD could be obtained.

(The obtained molecular structures and NMR data suggest two

CH H

), 0.67 (m, 3H, Cy CH H

CH ), 1.14 (m, 1H, Cy CH H

CH H ), 1.32 (dd, J = 16.1, 7.2 Hz, 3H, iPr CH ), 1.37 (s, 1H, Cy

), 0.84−1.08 (m, 9H, iPr

2+3+4

), 1.23 (m, 2H, Cy CH H

2+3+4

CH H

), 1.48 (d, J = 11.8 Hz, 3H, Flu CH HH), 1.51 (s, 1H, Cy

), 1.97 (dp, J = 10.8, 7.1 Hz, 1H, iPr CH), 2.61 (dp, J =

2+3+4

diﬀerent conformers in solid state and solution.) P{ H} NMR

2+3+4

(

162.1 MHz, THF-d ): δ [ppm] = 40.80 (d, J = 56.7 Hz, PCyFlu),

4.5 (d, J = 56.6 Hz, PCyFlu), 58.4 (d, J = 56.8 Hz, PCS), 60.3

8 PP

0.6, 7.1 Hz, 1H, iPr CH), 6.85 (m, 1H, CH Pos. 4), 6.98−7.08 (m,

H, CH Pos. 2, CH Flu), 7.10 (m, 1H, CH Pos. 1h), 7.27 (m, 1H, CH

(d, J = 56.7 Hz, PCS). H NMR and C NMR could not be

Pos. 3), 7.33−7.39 (m, 1H, CH Flu), 7.43−7.50 (m, 1H, CH Flu),

evaluated due to the presence of two diﬀerent conformers in solution.

.51 (d, J = 7.4 Hz, 1H, CH Flu), 7.75 (d, J = 7.4 Hz, 1H, CH Flu).

−

IR (ATR) [cm ]: 2916 (m), 1444 (m), 1363 (w), 1106 (m), 1025

s), 861 (m), 737 (s), 654 (m), 621 (w), 601 (w), 463 (m), 448 (m).

C{ H} NMR (100.6 MHz, DCM-d ): δ [ppm] = 9.4 (dd, J

2.8, 103.6 Hz, PCS), 16.7 (t, J = 2.51 Hz, iPr CH ), 17.6 (d, J

2.6 Hz, iPr CH ), 17.8 (dd, J = 2.32, 12.7 Hz, iPr CH ), 18.1 (t,

(

Melting point: 148.8 °C (degradation).

Computational Details. All calculations were performed without

J_C_P= 2.56 Hz, iPr CH ), 25.9 (m, CH Cy C

), 27.6 (s, CH Flu),

2+3+4

symmetry restrictions. Starting coordinates obtained with GaussView

8.6 (d, J = 7.78 Hz, CH Cy C

), 27.4 (d, J = 17.8 Hz, CH

2+3+4

.0 or directly from the crystal structure analyses for synthesized

^C^y^C²+3+4), 32.3 (d, J = 6.95 Hz, CH Cy C

), 32.7 (d, J = 22.8

2+3+4

ligands. The geometry optimization and NBO analysis were carried

out with the Gaussian16 (revision C.01) program package, and the

AIM analysis was done with the Multiwfn program version 3.6. The

Hz, CH Cy C

), 27.9 (d, J = 47.9 Hz, CH iPr), 33.9 (d, J

2+3+4

(

6.4 Hz, CH iPr), 37.3 (dd, J = 6.55, 10.4 Hz, CH Cy C ), 55.6

dd, J = 3.27 Hz, J = 30.4 Hz, CCH Flu ), 118.7 (dd, J = 90.5

CP 3 9 CP

geometry optimization and AIM analysis of the palladium complex

Hz, J = 7.24 Hz, C Pos. 6), 120.5 (d, J = 18.8 Hz, CH Flu), 123.3 (d,

32,33

was performed using density functional theory (DFT)

with the

^JCP = 9.01 Hz, CH Pos. 4), 124.0 (d, J = 6.97 Hz, CH Flu), 125.5 (d,

PBE0 functional, through the LANL2TZ(f) basis set and the

2_J= 10.5 Hz, CH Pos. 1), 126.9 (dd, J = 8.45, 1.77 Hz, CH Flu),

35−37

corresponding ECP for palladium

and the def2svp basis set for

27.4 (d, J = 4.11 Hz, CH Flu), 129.6 (d, J = 9.32 Hz, CH Pos. 3),

30.2 (d, J = 2.18 Hz, CH Pos. 2), 141.1 (d, J = 3.44 Hz, C

Flu₁₀₊₁₁), 141.3 (s, C Flu

Hz, C Pos. 5). P{ H} NMR (162.1 MHz, THF-d ): δ [ppm] = 12.2

all other atoms, in conjunction with Grimme’s D3 dispersion

39−41

correction with Becke−Johnson damping.

For the examined

), 155.8 (dd, J = 18.3 Hz, J = 1.10

ligands, geometry optimizations were performed using DFT with

12+13

42−47

B3LYP-D3/6-31+G*.

The metrical parameters of the energy-

(

d, J = 119.5 Hz, PCyFlu), 52.0 (d, J = 119.5 Hz, PCS). IR

optimized geometries are in good agreement with those determined

by X-ray diﬀraction. Harmonic vibrational frequency analyses were

performed at the same level of theory as the optimizations to

−

ATR) [cm ]: 2912 (w), 1439 (m), 1255 (w), 1103 (m), 1056 (m),

023 (m), 868 (w), 808 (w), 757 (s), 739 (s), 729 (s), 666 (w), 636

m), 571 (w), 447s, 426 (m). CHNS for C H P S: Calcd: C: 74.69,

(

determine the nature of the structure. The vibrational frequency

analysis showed no imaginary frequencies. The NBO analysis was

performed with the B3LYP functional, the LANL2TZ(f) basis set, and

the corresponding ECP for palladium and the 6-31+G* basis set for

all other atoms. The charges were ﬁt to the electrostatic potential at

points selected according to the CHelp scheme and the electrostatic

40 2

H: 7.60, S: 6.04. Measured: C: 74.23, H: 7.51, S: 5.69. Melting point:

6.2 °C (degradation).

Synthesis of Pd 2. First, 300 mg (0.565 mmol) of L2 and 106 mg

of [Pd(allyl)Cl] (56.4 m% Pd, 0.283 mmol) were suspended in 8 mL

of pentane and stirred for 2 h. After this time, the yellow suspension

Organometallics XXXX, XXX, XXX−XXX

Organometallics

The Supporting Information is available free of charge at

Article

property for the phosphorus atom of the phosphine was taken from

that ﬁt.

Notes

The authors declare the following competing ﬁnancial

interest(s): The authors have ﬁled patent WO2019030304

covering the YPhos ligands and precatalysts discussed, which is

held by UMICORE, and products will be made commercially

available.

Crystallographic Details. Data collection of all compounds was

carried out on either an Oxford SuperNova diﬀractometer (Cu

microsource) or an XtaLAB Synergy (HyPix detector). Suitable

crystals of all compounds were mounted in an inert oil (perﬂuoropoly

aklylether) and directly transferred into a cold nitrogen stream. All

crystal structure determinations were carried out at 100 K. The

structures were solved using direct methods, reﬁned using full-matrix

ACKNOWLEDGMENTS

■

50,51

least-squares techniques on F with the SHELX software package

This work was supported by RESOLV, funded by the

Deutsche Forschungsgemeinschaft (DFG, German Research

Foundation) under Germany’s Excellence Strategy - EXC-2033

and expanded using Fourier techniques. Data collection parameters

are given in Tables S1 −S4 . Crystallographic data (including structural

factors) have been deposited with the Cambridge Crystallographic

Data Cent re as supplementary publication CCDC numbers

Projektnummer 390677874 and by the European Research

089207 −2089217 .

Council (Starting Grant: YlideLigands 677749). We also thank

UMICORE AG & Co. KG for ﬁnancial support and the

donation of chemicals.

ASSOCIATED CONTENT

■

sı Supporting Information

https://pubs.acs.org/doi/10.1021/acs.organomet.1c00349.

REFERENCES

■

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PDF)

Coordinates of the energy-optimized structures (XYZ)

Accession Codes

CCDC 2089207 −2089217 contain the supplementary crys-

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AUTHOR INFORMATION

■

Corresponding Author

Viktoria H. Gessner − Chair of Inorganic Chemistry II,

Faculty of Chemistry and Biochemistry, Ruhr-Universit ä t

Bochum, 44801 Bochum, Germany; orcid.org/0000-

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001-6557-2366 ; Email: viktoria.gessner@rub.de

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Catalyzed Suzuki −Miyaura Cross-Coupling Reactions Employing

Dialkylbiaryl Phosphine Ligands. Acc. Chem. Res. 2008, 41, 1461−

Authors

Julian Löﬄer − Chair of Inorganic Chemistry II, Faculty of

Chemistry and Biochemistry, Ruhr-Universität Bochum,

4801 Bochum, Germany

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