Solvent-Dependent Hemilability of (2-Diphenylphosphino)Phenol in a Ru(II) para-Cymene System

Article abstract of DOI:10.1021/acs.organomet.8b00071

The addition of Ph₂P(2-C₆H₄OH) to [(η⁶-p-cymene)RuCl(μ-Cl)]₂ led to the formation of three distinct products, depending on the experimental conditions. The previously reported [(η⁶-p-cymene)RuCl{κ²P,O-PPh₂(2-C₆H₄O)}], 1, was obtained in 90% yield using MeOH as the solvent, in the presence of a base (Et₃N). Conversely, [(η⁶-p-cymene)RuCl{κ²P,O-PPh₂(2-C₆H₄OH)}]Cl, [2]Cl, was afforded (88% yield) in MeOH without using the base. However, [(η⁶-p-cymene)RuCl₂{κP-PPh₂(2-C₆H₄OH)}], 3, was the major species in chlorinated solvents. Compounds 1, [2]Cl, and 3 were characterized by analytical and spectroscopic (IR, NMR) methods. The X-ray structures of [2]⁺ and 3 were determined, with the latter forming hydrogen bond dimeric units in the solid state. The dissolution of [2]Cl into a series of deuterated solvents, except methanol, led to rapid equilibration between [2]Cl and 3, revealing the hemilabile behavior of the phosphino-phenol ligand. According to Pulsed-Field Gradient Spin Echo (PGSE)-NMR and DFT studies, the dimeric nature of 3 persists in solution; thus, the hydrogen-bonding properties of MeOH are crucial to stabilize [2]Cl with respect to 3, with the latter being 3.4 kcal mol^-1 more stable than the former in the gas phase. Compound 1 underwent electrophilic additions by HCl, HBF₄, and MeCOCl to give, respectively, [2]Cl (the reverse process being viable with Et₃N), [2]BF₄, and the ester [(η⁶-p-cymene)RuCl₂{κP-PPh₂(2-C₆H₄OCOMe)}], 5. The reaction of 1 with AgNO₃ afforded the nitrate complex [(η⁶-p-cymene)Ru(NO₃){κ²P,O-PPh₂(2-C₆H₄O)}], 4. Compounds [2]BF₄, 4, and 5 were isolated in the solid state in good to high yields and characterized by elemental analysis and IR and NMR spectroscopy.

Full text of DOI:10.1021/acs.organomet.8b00071

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Solvent-Dependent Hemilability of (2-Diphenylphosphino)Phenol in
a Ru(II) para-Cymene System
†
,‡
†,‡
,†,‡
Stefano Zacchini,‡,§ Andrea Monti,†
Lorenzo Biancalana, Gianluca Ciancaleoni,
Fabio Marchetti,† and Guido Pampaloni*
,‡
†
Universita
̀
di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Moruzzi 13, I-56124 Pisa, Italy
CIRCC, via Celso Ulpiani 27, I-70126 Bari, Italy
§Universita
di Bologna, Dipartimento di Chimica Industriale “Toso Montanari”, Viale Risorgimento 4, I-40136 Bologna, Italy
S Supporting Information
‡
̀
*
6
ABSTRACT: The addition of Ph P(2-C H OH) to [(η -p-
2
6
4
cymene)RuCl(μ-Cl)] led to the formation of three distinct
2
products, depending on the experimental conditions. The
6
2
previously reported [(η -p-cymene)RuCl{κ P,O-PPh (2-
2
C H O)}], 1, was obtained in 90% yield using MeOH as the
6
4
6
solvent, in the presence of a base (Et N). Conversely, [(η -p-
cymene)RuCl{κ P,O-PPh (2-C H OH)}]Cl, [2]Cl, was af-
3
2
2
6
4
forded (88% yield) in MeOH without using the base.
6
However, [(η -p-cymene)RuCl {κP-PPh (2-C H OH)}], 3,
2
2
6
4
was the major species in chlorinated solvents. Compounds 1, [2]Cl, and 3 were characterized by analytical and spectroscopic
+
(
IR, NMR) methods. The X-ray structures of [2] and 3 were determined, with the latter forming hydrogen bond dimeric units
in the solid state. The dissolution of [2]Cl into a series of deuterated solvents, except methanol, led to rapid equilibration
between [2]Cl and 3, revealing the hemilabile behavior of the phosphino-phenol ligand. According to Pulsed-Field Gradient Spin
Echo (PGSE)-NMR and DFT studies, the dimeric nature of 3 persists in solution; thus, the hydrogen-bonding properties of
MeOH are crucial to stabilize [2]Cl with respect to 3, with the latter being 3.4 kcal mol− more stable than the former in the gas
1
phase. Compound 1 underwent electrophilic additions by HCl, HBF , and MeCOCl to give, respectively, [2]Cl (the reverse
4
6
process being viable with Et N), [2]BF , and the ester [(η -p-cymene)RuCl {κP-PPh (2-C H OCOMe)}], 5. The reaction of 1
3
4
2
2
6
4
6
2
with AgNO afforded the nitrate complex [(η -p-cymene)Ru(NO ){κ P,O-PPh (2-C H O)}], 4. Compounds [2]BF , 4, and 5
3
3
2
6
4
4
were isolated in the solid state in good to high yields and characterized by elemental analysis and IR and NMR spectroscopy.
INTRODUCTION
■
Hemilabile ligands play a prominent role in coordination
chemistry, since their reversible binding to one metal site i1s
crucial to the effectiveness of many metal mediated processes.
In this regard, a number of heteroditopic P,O-donors have been
2
reported to behave as hemilabile ligands, most of the examples
Figure 1. Structure of (2-diphenylphosphino)phenol.
3
being referred to phosphines containing an additional ether,
2
c−e,4
2b,5
carbonyl,
or phosphine-oxide functionality.
However,
1
1
the hemilability properties of phosphino-alcohols have been
much less developed, as a consequence of the increased acidity
of the OH unit when approaching the metal center, thus
facilitating the formation of stable metal-alkoxide derivatives via
combination in heterobimetallic compounds. It is noteworthy
2
that complexes of various metals containing the κ P,O-(2-
diphenylphosphino)phenolate ligand have been studied as
catalysts for alkene oligomerization and polymerization,
hydroformylation, and hydrogenation reactions.
8a,c,12
6
13
9a,b
deprotonation. This process is even more favorable when
In this
dealing with phosphino-phenols, due to the superior acidity of
the phenolic group. As a matter of fact, (2-
setting, examples of structurally characterized metal adducts
7
14
containing non-deprotonated (2-diphenylphosphino)phenol,
6a,15
diphenylphosphino)phenol (Figure 1), i.e., a typical phosphi-
no-phenol widely employed in coordination chemistry, is
usually found in related complexes as its conjugate base, i.e., (2-
diphenylphosphino)phenolate. The presence in the latter of
both soft (P) and hard (O) donor atoms enables firm binding
of the anion to a variety of metal centers in different oxidation
and more generally, a non-deprotonated phosphino-phenol,
are exceedingly rare. These systems may show some hemilabile
character of the P,O-ligand in solution, via reversible binding to
the metal of the hydroxyl pendant.
Received: February 5, 2018
8
,9
10
states,
including main group elements and early late
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00071
Organometallics XXXX, XXX, XXX−XXX

Organometallics
In the framework of our investigation on (η -arene)Ru(II)-
phosphine compounds as possible anticancer agents, herein
we report on the synthesis and structural characterization of
three compounds exhibiting distinct coordination modes of (2-
diphenylphosphino)phenol(ate). The uncommon hemilabile
character of this ligand will be discussed with reference to
variable experimental conditions, with the assistance of PGSE-
NMR and DFT studies.
Article
6
C H OH)}], 3, was detected via NMR in solution upon
reaction of Ph P(2-C H OH) with [(η -p-cymene)RuCl(μ-
Cl)] in chlorinated solvents, together with minor amounts of
6
4
16
6
2 6 4
2
[2]Cl (Scheme 1c).
Compounds 1 and [2]Cl were isolated as orange-brown air-
stable solids and characterized by analytical and spectroscopic
techniques. IR, NMR, and conductivity data are given in the
Supporting Information; selected data are compiled in Table 1.
The 31P resonance of the phosphine ligand within [2]Cl was
found at ca. 45 ppm, slightly shifted with respect to 1 (50.2
ppm), whereas compound 3 displayed a signal at ca. 24 ppm; all
RESULTS AND DISCUSSION
■
6
Coordination of Ph P(4-C H OH) to [(η -p-Cymene)-
2
6 4
RuCl(μ-Cl)] . The reaction between (2-diphenylphosphino)-
these δ
P
values are considerably deshielded with respect to that
2
6
phenol and [(η -p-cymene)RuCl(μ-Cl)] resulted in the
of uncoordinated (2-diphenylphosphino)phenol (δ
P
= −27.8
≈ 20−30
2
ppm). Analogous 31P chemical shift separation (Δδ
formation of three different products, depending on the
experimental conditions (Scheme 1). The previously reported
P
ppm) between bidentate and monodentate coordination of (2-
diphenylphosphino)phenol(ate) to a given metal system can be
8
e,13,14b,17
found in the literature,
the absolute δP values
Scheme 1. Different Modes of Incorporation and Bidentate
a
depending on the chemical environment. Compound 2[Cl],
P,O Coordination
1
13
as well as 1, manifested distinct resonances for all H and
C
nuclei belonging to the p-cymene ligand and for the two
diastereotopic phenyl rings. Moving from 1 to its protonated
1
counterpart, [2]Cl, the H resonances related to the aromatic
1
8
19
protons and the 1,2-disubstituted phenyl ring experienced
1
3
1
deshielding (ΔδH = +0.2−0.3 ppm). Concerning C{ H}
spectra, the resonance belonging to the C−O atom moved
+
upfield from 177.5 (1, phenoxide) to 165.3 ppm ([2] , phenol)
while the corresponding 13C− P coupling constant ( J
31
1
=
CP
5
(
0−55 Hz) became smaller with protonation. Such trends
31
including the P data discussed above) were previously
3
14a
observed for (η -allyl)M (M = Ni, Pd) derivatives. The ionic
nature of [2]Cl in methanol was consistent with the observed
high molar conductivity, approaching that of HCl in the same
2
−1
35
solvent (140−150 S·cm ·mol ), and the Cl NMR spectrum,
displaying a signal at −30 ppm accounting for the chloride
1
6c
anion.
+
The structures of [2] and 3 were determined by X-ray
diffraction studies on single crystals of 3·CH COCH and 3·
2]Cl, the latter being a cocrystal of the two complexes. In
3
3
[
particular, 3·[2]Cl contains neutral complex 3, which shows the
same structure and bonding parameters as those found in 3·
+
−
CH COCH , and the cationic complex [2] , with Cl as
3
3
counterion. Views of the structures are shown in Figures 2 and
3, while relevant bonding parameters are reported in Table 2.
Hydrogen bonding parameters are summarized in Table 3.
a
(
a−c) Different modes of incorporation of (2-diphenylphosphino)-
6
phenol within (η -p-cymene)Ru(II) compounds. (d) Bidentate P,O
coordination of (2-diphenylphosphino)benzoic acid with release of
HCl.
+
Complexes [2] and 3 adopt a typical three-leg piano-stool
20
geometry, and the bonding parameters around the Ru(II)
6
center are similar to those previously reported for [(η -p-
6
2
6,16a−d,21
[
(η -p-cymene)RuCl{κ P,O-PPh (2-C H O)}], 1, comprising
cymene)RuCl
(κP-PR
2
)] and related compounds.
3
The
2
6
4
the P,O-chelating phosphino-phenolate ligand, can be obtained
structure of the neutral complex 3, as found in both 3·
CH COCH and 3·[2]Cl, is closely related to those of the
already reported [(η -p-cymene)RuCl
p-cymene)RuCl {κP-PPh (4-C CO
in ca. 80% yield upon addition of the organic reactant to a
3
3
6
6
22
6
suspension of [(η -p-cymene)RuCl(μ-Cl)] in MeOH in the
{κP-PPh }] and [(η -
2 3
23
2
+
presence of a base (Et N in the present work, Scheme 1a;
2
2
6
H
4
H)}]. Cation [2]
2
3
9a
6
Cs CO according to the literature procedure).
within 3·[2]Cl represents a rare example of (η -arene)Ru
2
3
2
6b,24
Performing the same reaction in the absence of a base, the
complex with a κ P,O-coordinated phosphino-alcohol;
by a
6
2
2
unprecedented cationic derivative [(η -p-cymene)RuCl{κ P,O-
different point of view, the chelating κ P,O coordination
+
+
PPh (2-C H OH)}] , [2] , featuring a P,O-chelating phosphi-
exhibited here by (2-diphenylphosphino)phenol is rather
2
6
4
1
4,25
no-phenol ligand, was isolated in 88% yield as its chloride salt,
2]Cl (Scheme 1b). For comparison, under analogous
conditions, the more Bronsted acidic (2-diphenylphosphino)-
benzoic acid coordinated as a bidentate phosphino-carboxylate
uncommon (see the Introduction).
The presence of the OH group in the structures of both [2]+
and 3 is confirmed by the occurrence of H-bonds involving the
alcohol and chloride anions/ligands within the crystals of 3·
CH COCH and 3·[2]Cl (Table 3). In particular, in the solid-
state structure of 3·CH COCH , dimers of 3 are present,
generated by 2 equivalent intermolecular H-bonds involving the
[
̈
16d
ligand, with concomitant release of HCl (Scheme 1d).
3
3
Furthermore, the neutral adduct with a κP-monodentate
3 3
6
phosphine ligand, i.e., [(η -p-cymene)RuCl {κP-PPh (2-
2
2
B
DOI: 10.1021/acs.organomet.8b00071
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Table 1. Selected IR, NMR, and Conductivity Data for PPh (2-C H OH) and Ru Compounds 1, [2]X (X = Cl, BF ), and 3−5
2
6
4
4
b
IR
NMR
coord.
mode
1H(Ru-CH) δ
13
C(C−O) δ
13
C(C−P) J
1
31P δ
(ppm)
CP
compound
υ
̃
(cm−1)a
(ppm)
(ppm)
(Hz)
c
Λm (S·cm ·mol−1)d
2
PPh (2-C H OH)
ν(OH): 3518w, 3232m-br
159.4
177.5
n.d.
55
−27.8
2
6
4
5
.84, 5.59, 5.36, 4.81
2 (CH Cl )
2
2
1
κ2P,O
(5.64, 5.40, 5.08,
50.7
e
34 (MeOH)
4
.74)
[
[
2]Cl
κ2P,O(H) ν(OH): 3500−3400w-br
6.08, 5.81, 5.64, 5.13
6.05, 5.80, 5.63, 5.12
5.48, 4.85
165.3
166.1
51
51
44.6
45.0
23.9
53.6
154 (MeOH)
25 (CH Cl )
ν(OH): 3500−3450w-br
κ2P,O(H)
2
2
2]BF4
ν(BF ): 1056s-br
86 (MeOH)
4
3
4
κP
3
6
ν(NO
84m
): 1471m, 1262s,
5.68, 5.53,
3
(CH Cl )
2
2
κ2P,O
3
178.1
55
41
9
5.04 (×2)
91 (MeOH)
Ar
ν(CO): 1764s, 1750s.
769 (CH Cl )
151.4 (C −O)
168.2 (CO2)
5
κP
5.22, 4.97
21.8
1
2
2
a
b
Solid-state IR data, unless otherwise specified. Compounds 3−5 and PPh (2-C H OH) in CDCl solutions; 1 and [2]X (X = Cl, BF ) in CD OD
2
6
4
3
4
3
c
d
−3
−1
solutions, except where otherwise noted. Related to the 1,2-disubstituted aryl ring (C12 on Charts 1−5). Measured on ca. 1 × 10 mol·L
solutions. CDCl solution.
e
3
Table 2. Selected Bond Distances (Å) and Angles (deg) for 3
and [2]+
a
b
[2]+
b
3
3
6
Ru(1)−(η -p-cymene)
2.21(2)
2.22(5)
2.21(5)
av
Ru(1)−P(1)
Ru(1)−Cl(1)
Ru(1)−Cl(2)
2.365(2)
2.405(2)
2.414(2)
2.361(7)
2.414(6)
2.403(6)
2.313(7)
2.399(6)
Ru(1)−O(1)
P(1)−C(11)
P(1)−C(17)
P(1)−C(23)
2.071(17)
1.82(2)
1.84(3)
1.83(3)
1.36(3)
1.844(8)
1.846(8)
1.832(8)
1.375(10)
85.10(7)
1.85(2)
1.85(2)
1.81(2)
1.37(3)
89.3(2)
C(12)−O(1)
Cl(1)−Ru(1)−Cl(2)
Cl(1)−Ru(1)−O(1)
Cl(1)−Ru(1)−P(1)
Cl(2)−Ru(1)−P(1)
O(1)−Ru(1)−P(1)
Ru(1)−P(1)−C(11)
P(1)−C(11)−C(12)
C(11)−C(12)−O(1)
C(12)−O(1)−Ru(1)
84.7(5)
87.6(2)
88.72(8)
87.37(7)
88.9(2)
88.1(2)
80.4(5)
Figure 2. View of the structure of 3. Displacement ellipsoids are at the
0% probability level. H atoms, except H(1), have been omitted for
clarity.
3
113.7(3)
119.8(6)
117.1(7)
111.7(8)
125.4(18)
118(2)
100.3(8)
114.5(17)
119(2)
121.4(15)
a
b
As found in 3·CH COCH . As found in 3·[2]Cl.
3
3
+
Table 3. Hydrogen Bonds for [2] and 3: Distances (Å) and
Angles (deg)
a
b
[2]+
b
3
3
O(1)−H(1)
H(1)···Cl(2)
O(1)···Cl(2)
O(1)−H(1)···Cl(2)
0.84
2.19
0.83
1.89, 2.72
2.71(2), 3.49(4) 2.62(3), 3.22(4)
172.7, 157.2 161(11), 137(15)
0.84(2)
1.81(2), 2.55(12)
3.017(6)
167.3
a
As found in 3·CH COCH . Symmetry transformations used to
3
3
b
generate equivalent atom Cl(2)#1: −x, −y + 1, −z + 1. As found in 3·
[
2]Cl. Cl(2) is disordered over two positions.
+
Figure 3. View of the structure of the cation [2] with the chloride
anion Cl(2) as found in 3·[2]Cl. Displacement ellipsoids are at the
OH groups and Cl(2) ligands of the two symmetry related (by
an inversion center) molecules (Figure 4). Conversely, in the
solid-state structure of 3·[2]Cl, both the OH groups of 3 and
3
0% probability level. H atoms, except H(1), have been omitted for
+
+
clarity. Since the cation [2] cocrystallizes with 3, [2] has been
relabeled in Figure 3 respect to the corresponding cif file, in order to
+
+
[2] form H-bonds with the same chloride anion (Figure 5).
facilitate the comparison between [2] and 3. The O(1)−H(1)···Cl(2)
Equilibrium between [2]Cl and 3 in Solution: PGSE-
NMR and DFT Studies. It is apparent from the previous
section that the solvent plays a key role in the interaction
H-bond between the cation and anion is represented as a dashed line.
C
DOI: 10.1021/acs.organomet.8b00071
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
27
CD OD and CD OD:D O 4:1 v/v, where only [2]Cl was
3
3
2
present (Scheme 2a/b). Compound 3 was the major species
detected in (CD ) CO (0.75 molar fraction), CDCl (0.70),
3
2
3
CD Cl2 (0.65), and CD CN (0.40). A third species was
2
3
identified in CD CN, featured by a chiral Ru atom and a
3
monodentate phosphine ligand (δP = 28.3 ppm), being
6
presumably the CD CN monosolvate complex [(η -p-cymene)-
3
+
+
RuCl{κP-PPh (2-C H OH)}(MeCN)] ([3-MeCN] ; Scheme
2
6
4
2
c). Acetonitrile displacement of the coordinated oxygen donor
2
belonging to κ P,O-(2-diphenylphosphino)phenol was previ-
ously observed in [Rh(CO)(PPh ){κ P,O-Ph P(2-
C H OH)}] .
2
3
2
+
14b
Our findings suggest that the hydrogen-
6
4
bonding properties of MeOH are crucial to stabilize the ionic
species [2]Cl; otherwise, the Cl− ion may substitute the
phenolic group to give 3, thus determining a change in the
coordination mode of the hemilabile phosphino-phenol ligand.
Additional NMR experiments and DFT calculations were
performed, aiming to rationalize the factors affecting the
equilibrium between [2]Cl and 3. On considering that 3 exists
in the solid state as a hydrogen-bonded dimer (Figure 4), the
presence of analogous adducts in solution was investigated. It
should be mentioned here that self-aggregation of both
Figure 4. View of the hydrogen-bonded dimer of 3 as found in the
crystal structure of 3·CH COCH . Displacement ellipsoids are at the
3
3
3
0% probability level. H atoms, except H(1), have been omitted for
clarity. The second molecule of the dimer is generated by an inversion
center (symmetry transformation −x, −y + 1, −z + 1).
28
29
neutral and cationic Ru(II) p-cymene complexes in solution
was previously documented. Therefore, Pulsed-Field Gradient
30
Spin Echo (PGSE) NMR measurements were performed on
mixtures of [2]Cl and 3 in CDCl , obtained by dissolution of
3
pure [2]Cl at two different total concentrations (cRu,total = 17
and 77 mM, respectively, Table 4). At the lower concentration,
Table 4. Diffusion Coefficients (1010 D , m s ), Average
2
−1
t
3
Hydrodynamic Radii (r , Å), Volumes (V , Å ), Aggregation
H
H
Numbers (N), and Concentration (C, mM) for Compounds
[
2]Cl and 3 (in Equilibrium) in CDCl3
Figure 5. View of the hydrogen-bonds involving the OH groups of 3
+
compound
Dt
rH
VH
N
C
and [2] and the chloride anion, as found in the crystal structure of 3·
a
[2]Cl. Displacement ellipsoids are at the 30% probability level. H
3
10.3
n.d.
5.08
n.d.
549
n.d.
788
792
1.31
n.d.
12
5
a
atoms, except those bonded to O atoms, have been omitted for clarity.
[2]Cl
b
3
8.91
8.89
5.73
5.74
1.89
1.89
61
16
6
b
between (2-diphenylphosphino)phenol and [(η -p-cymene)-
[2]Cl
a
RuCl(μ-Cl)] (see Scheme 1 for details). In order to shed light
Species in equilibrium in the same solution; overall Ru concentration
b
2
on this point, [2]Cl was dissolved in a series of deuterated
= 17 mM. Species in equilibrium in the same solution; overall Ru
concentration = 77 mM. n.d. = not determined.
solvents (CD OD, CD Cl , CDCl , (CD ) CO, CD CN) and
3
2
2
3
3 2
3
1
the resulting solutions (c
= 17 mM) were analyzed by H
Ru,total
and 31P NMR (see the Experimental Section and Supporting
the molar ratio between [2]Cl and 3 is 5:12, whereas at the
higher concentration it is 16:61. The hydrodynamic volume
(V ) of 3 was 549 Å at 12 mM, i.e., slightly larger than the
26
Information). A rapid equilibration (t < 15 min) between [2]
Cl and 3 took place in all the solvents with the exception of
3
H
a
Scheme 2. Behaviour of [2]X (X = Cl, BF ) in Different Solvents
4
a
+
+
cRu,total = ca. 16−17 mM. Equilibrium between [2]Cl and 3 (a), presence of [2] only (b), and formation of [3-MeCN] (c).
D
DOI: 10.1021/acs.organomet.8b00071
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
−1
Figure 6. Optimized geometries of 3 , [2]Cl, and 3 and corresponding energies (in kcal mol ) in gas phase and in different solvents. H···Cl
int
ext
hydrogen bond distances are in Å.
Scheme 3. Reactivity of 1 towards HX (X = F, Cl, BF ), NH Y (Y = Cl, HF ), CH Z (Z = COCl, I), and AgNO
3
4
4
2
3
3
corresponding van der Waals volume (418 Å ). Possible
explanations for this discrepancy may be the presence of a small
amount of dimer or the fact that in some cases the vdW volume
addition of [R N]X (R = hexyl, X = Cl; R = Me, X = F) to
4
solutions of [2]Cl in CDCl did not increase the amount of 3
3
(see the Supporting Information for details). However, in
0
31
underestimates the V of the isolated monomer (V ). At the
[2]BF (see onward) the anion is presumably weakly bound to
H
H
4
higher concentration (c
increases up to 788 Å , thus confirming the presence of a
= 77 mM; 61 mM for 3), V (3)
the −OH moiety, thus allowing the formation of hydrogen-
Ru,total
H
3
bonded dimers and leaving the hydrodynamic ratio of the
3
+
monomer−dimer equilibrium in solution. If 418 Å is taken as
monomer [2] undetermined.
0
V , then the aggregation number values, i.e., the ratio N
DFT calculations were performed in order to evaluate the
relative stability of [2]Cl and 3; DFT-optimized structures and
ΔG values are reported in Figure 6. The geometry of 3 was
optimized starting from the solid-state structure, leading to a
local energy minimum in which the proton of the phosphine
OH group points to the opposite direction with respect to
ruthenium (3 ). However, 3 is the most stable conformation
H
0
between VH and V , are 1.3 and 1.9 at the low and high
H
concentrations, respectively. The measurement of V ([2]Cl)
was not possible in the more diluted solution (cRu,total = 17 mM;
H
5
mM for [2]Cl) because of the broadness of the
corresponding signals. At a higher concentration (cRu,total = 77
mM; 16 mM for [2]Cl), it exhibited the same V value as 3, as
H
ext
ext
expected when considering that [2]Cl and 3 are in rapid
equilibrium and the PGSE NMR technique only provides
average information. It must be considered that hydrodynamic
only if a hydrogen-bonded dimer is formed (see X-ray and
PGSE NMR results). In the isolated monomer, the OH can
establish an intramolecular hydrogen bond with one of the
+
radii of [2] and 3 cannot be measured independently. In fact,
chloride ligands, 3 , leading to a conformation that is 10.0 kcal
int
E
DOI: 10.1021/acs.organomet.8b00071
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Organometallics
Article
mol− more stable than 3ext in terms of free energy in the gas
1
The reaction of AgNO (as chloride acceptor) with 1 in
3
6
phase. When the solvent is taken into account using a
methanol afforded the nitrato complex [(η -p-cymene)Ru-
32
2
conductor-like polarizable continuum model (CPCM, see
the Computational Details section), the ΔG between the two
conformers decreases to 5.0, 4.4, 4.2, and 4.1 kcal mol− in
dichloromethane, acetone, methanol, and acetonitrile, respec-
tively. For this reason, and since at the studied concentration
the monomer is the most abundant species (see Diffusion
NMR section), only 3int will be considered in the following
discussion.
Also, the geometry of [2]Cl was optimized, comprising a
covalent Ru−O bond (2.14 Å) and a hydrogen bond between
the anion and the OH group of the cation (1.73 Å). In [2]Cl,
the hydrogen bond is shorter than in 3 , since there are no
geometrical constraints. Thus, the chloride can assume the
most favorable position.
(NO ){κ P,O-PPh (2-C H O)}], 4 (Scheme 3d and Table 1),
3
2
6
4
isolated as a yellow-brown solid in 94% yield. Conversely, the
1
former treatment of 1 with AgPF in acetone yielded the
6
6
2
solvato-complex, [(η -p-cymene)Ru{κ P,O-PPh (2-C H O)}-
(κO-Me CO)]PF . By comparison to precursor 1, the IR
2
6
4
9b
2
6
spectrum of 4 in the solid state showed additional medium to
−1
strong bands at 1471, 1262, and 984 cm . These absorptions
37
are typical of a coordinated nitrate ligand and were already
6
38
reported for other Ru(η -arene)(κO-NO ) complexes.
3
Conductivity data suggest that 4 preserves its coordination
−
sphere in CH
occurs in MeOH (Λ
Cl solution, whereas [NO ] /solvent exchange
2
2
3
2
−1
14
= 91 S·cm ·mol ). The N NMR
m
int
spectrum of 4 displayed one resonance at −3.2 ppm (Δν1/2 =
18 Hz) in methanol and −10.2 ppm (Δν1/2 = 69 Hz) in
The free energy difference between 3 and [2]Cl is 3.4 kcal
dichloromethane; the former value is comparable to that
int
−1
mol in the gas phase, the former being more stable than the
latter; nevertheless, such a value decreases in the presence of
generated by NaNO
same solvent. On going from the chlorido (1) to the nitrato
3 N
(δ = −2.7 ppm; Δν1/2 = 14 Hz) in the
−1
31
the solvent to 0.1, −0.2, −0.3, and −0.3 kcal mol , in
chloroform, dichloromethane, acetonitrile, and methanol,
respectively (Figure 6). Considering the simplicity of our
solvation model, these ΔG values can be considered within the
computational error, but from the qualitative point of view our
results justify the simultaneous presence in solution of 3 and
2]Cl.
Reactivity of 1 toward Bro
order to test the reactivity of the chelating (2-
diphenylphosphino)phenolate ligand coordinated to the (η -
complex (4), both the P resonance (δ ≈ 54 ppm for 4) and
P
1
H signals belonging to the p-cymene ligand experience low-
field shifting (CD OD or CDCl solutions).
3
3
Remarkably, compound 1 underwent straightforward addi-
tion of acetyl chloride in CH Cl at room temperature,
2
2
6
affording [(η -p-cymene)RuCl {κP-PPh (2-C H OCOMe)}],
int
2 2 6 4
3
3
[
5 (Scheme 3e). The formation of 5 entails the activation of
39
̈
nsted and Lewis Acids. In
the Ru−phenolate bond, the phenolate being converted into
its acetyl ester. Compound 5 was isolated as an orange solid in
66% yield after purification with silica chromatography and
6
p-cymene)Ru(II) unit, compound 1 was treated with a
then characterized by IR and NMR spectroscopy (CDCl ) (see
3
3
1
1
selection of Bro
̈
nsted (HX, X = F, Cl, BF ; NH Y; Y = Cl,
Table 1). A signal at 21.8 ppm was observed in the P{ H}
NMR spectrum, in agreement with the change of the
coordination mode of the phosphine ligand from bi- to
4
4
HF ) and Lewis (CH I, CH COCl) acids. The reaction with
2
3
3
AgNO as a chloride-abstracting agent was also considered
3
(
Scheme 3).
monodentate (δ = 50.7 ppm in 1). The ester moiety in 5 gave
P
rise to new 13C resonances at 168.2 and 21.0 ppm due to the
carbonyl and methyl carbons, respectively, as well as to a strong
Compound 1 easily underwent protonation by aqueous HCl
in MeOH affording [2]Cl (Scheme 3a); the process can be
IR absorption at 1769 cm− (CH
1
Cl solution). The H
1
reversed at room temperature by treatment with Et N.
2 2
3
Protonation of 1 with aqueous HBF in MeOH gave [2]BF4
spectrum of 5 showed two doublets at 5.22 and 4.98 for the
aromatic CH of the p-cymene and a single set of signals for the
two phenyl groups, due to the loss of chirality of the Ru center
(with respect to the precursor 1).
4
(Scheme 3b), which was isolated in 77% yield as an orange
solid. The main spectroscopic features of [2]BF resemble
4
those of [2]Cl (see the Supporting Information and Table 1).
−
The [BF ] anion manifested itself with a strong IR absorption
In the light of the clean addition of acetyl chloride to 1, the
reaction with another carbon electrophilic reagent, namely,
methyl iodide, was attempted (Scheme 3f). Nevertheless,
compound 1 was inert toward addition of MeI in MeOH or
acetone. This seems consistent with the fact that the reverse
reaction, i.e., demethoxylation of an ortho-phosphine-ether
coordinated to a metal chloride, may be a favorable process,
4
−1
at 1056 cm in the solid state and by signals at −154.86 and
1
9
11 19
−
10 19
−
−
157.71 ppm in the F spectrum (for B F and B F ,
4 4
respectively). In the light of the dynamics found in solution for
2]Cl, the behavior of [2]BF in a selection of deuterated
solvents was studied by H and P NMR. Unlike the chloride
[
4
1
31
salt, [2]BF was not modified in CD Cl , CDCl , (CD ) CO,
4
2
2
3
3 2
2
and CD OD (Scheme 2b), as expected upon replacement of
affording the corresponding κ P,O chelate complex and
3
34,35
8b,17a,25c,40
−
the chloride with the less coordinating [BF4] anion.
CH
3
Cl.
Accordingly, the molar conductivity of [2]BF was high in both
4
CONCLUSIONS
CH Cl and MeOH and comparable to that of NaBF in the
■
2
2
4
2
−1
31
latter solvent (Λ ≈ 90 S·cm ·mol ). The P NMR spectrum
displayed a singlet at ca. 45 ppm in all solvents except CD CN
δ = 28.3 ppm), due to the presumable formation of [(η -p-
Phosphino-phenols bearing two sites for metal binding in
suitable positions are potential hemilabile ligands. Notwith-
standing, this feature has been substantially undeveloped in
coordination chemistry heretofore. However, ruthenium(II)
arene compounds have been intensively investigated for their
catalytic and medicinal applications, and in this light, hemilabile
ligands may play important roles to activate specific synthetic
and biological pathways.
In the present manuscript, we have described the
coordination of (2-diphenylphosphino)phenol to the [(η -p-
m
3
6
(
P
cymene)RuCl{κP-PPh (2-C H OH)}(MeCN)]BF , [3-
2
6
4
4
MeCN]BF (Scheme 2c).
4
However, protonation of 1 by weaker Bro
̈
nsted acids, such as
+
−
−
[
NH ] (as Cl or [HF ] salt) or aqueous HF in MeOH did
4 2
41
not work, leading to quantitative recovery of the starting
material 1 (Scheme 3c). Therefore, based on a simple acid−
base model in aqueous solutions with HF as a reference
6
36
Brønsted acid, the pK of 1 is expected to be lower than 3.2.
cymene)RuCl ] frame, exhibiting unusual hemilabile character
a
2
F
DOI: 10.1021/acs.organomet.8b00071
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
9
a
in a range of solvents, consisting in the competition for one
metal site between the hydroxyl pendant and one chloride
procedure. In a 25 mL Schlenk tube, PPh
2
(2-C
H
6
4
OH) (328 mg,
6
1
.18 mmol) and [(η -p-cymene)RuCl ] (334 mg, 0.545 mmol) were
suspended in MeOH (6 mL). Addition of Et N (0.20 mL, 1.43 mmol)
afforded a dark red solution which was stirred for 1 h at room
temperature. The progress of reaction was checked by TLC and
2 2
anion. The hemilability is quenched by introducing a non-
3
−
coordinating counterion ([BF ] ) or by reaction with a base,
4
31
P
resulting in a robust, bidentate binding to the metal of the
phosphino-phenolate anion. Nevertheless, the phenolate
moiety displays significant nucleophilic character, and thus
appears to be easily derivatized via Ru−O bond cleavage,
including the regeneration of the neutral phosphino-phenol
unit. It must be remarked that the occurrence of hemilability for
phosphino-phenol ligands under modulated conditions may
open new perspectives in the chemistry and applications of
Ru(II) arene compounds.
NMR, and volatiles were removed under vacuum. The residue was
dissolved in CH Cl (10 mL) and extracted with H O (3 × 20 mL).
2
2
2
The organic phase was taken to dryness under vacuum, and the
resulting solid was suspended in Et O. The blue-green Et O solution
2
2
was separated by filtration, and the resulting orange solid was washed
with Et O then dried under vacuum (40 °C). Yield: 480 mg, 80%.
2
Alternatively, the compound was purified by silica chromatography;
impurities were eluted with CH Cl and a red band containing 1 was
2
2
eluted with CH Cl :acetone 7:1 v/v.
2
2
Alternative Preparation. A solution of compound [2]Cl (50 mg,
0
.086 mmol) in MeOH (4 mL) was treated with Et N (15 μL, 0.11
3
EXPERIMENTAL SECTION
General Experimental Details. RuCl ·3H O (99.9%) was
purchased from Strem, while all the other reactants were obtained
from Alfa Aesar, Sigma-Aldrich, or TCI Europe, and were of the
highest purity available. (2-diphenylphosphino)phenol (see the next
section for the spectral characterization of the commercial compound)
mmol). The resulting dark red solution was stirred at room
temperature for 1 h and the progress of reaction checked by
NMR. Compound 1 was isolated in 90% yield following the same
workup procedure.
Compound 1 is soluble in MeOH, acetone, and chlorinated solvents
and is insoluble in Et O and hexane. Anal. Calcd for C H ClOPRu:
C, 61.37; H, 5.15. Found: C, 61.7; H, 5.2. Spectroscopic (IR/NMR)
and conductivity data are given in the Supporting Information.
■
3
1
P
3
2
2
28 28
and acetyl chloride were stored under nitrogen as received. Compound
6
[
(η -p-cymene)RuCl(μ-Cl)] was prepared according to the liter-
2
6
2
42
[(η -p-Cymene)RuCl{κ P,O-PPh (2-C H OH)}]Cl, [2]Cl (Chart 2). In
2 6 4
ature. The syntheses of 1, 2[Cl], and 3 from (2-diphenylphosphino)-
phenol were carried out under a nitrogen atmosphere using standard
Schlenk techniques and deareated solvents. The synthesis of 5 was
performed under a nitrogen atmosphere using standard Schlenk
techniques and CH Cl distilled over CaH . All other operations were
a 25 mL Schlenk tube, PPh (2-C H OH) (209 mg, 0.751 mmol) and
2
6
4
a
Chart 2. Structure of [2]Cl
2
2
2
carried out in air with common laboratory glassware. Once isolated,
the Ru compounds were air-stable in the solid state; [2]X (X = Cl,
BF ) and 5 were stored under nitrogen for precaution. Silica gel
4
(
Merck, 70−230 mesh) was used for column chromatography. NMR
spectra were recorded at 298 K on a Bruker Avance II DRX400
instrument equipped with a BBFO broadband probe. Chemical shifts
(
expressed in parts per million) are referenced to the residual solvent
43
1
13
14
19
peaks ( H, C) or to external standard ( N to CH NO , F to
CFCl3, P to 85% H PO ; Cl to 1 M NaCl in D O). Spectra were
3
2
31
35
44
a
3
4
2
Numbering refers to carbon atoms.
1
31
assigned with the assistance of H{ P}, DEPT-135 spectra and
1
1
1
13
H− H (COSY), H− C (gs-HSQC and gs-HMBC) correlation
6
45
[(η -p-cymene)RuCl ] (192 mg, 0.314 mmol) were suspended in
experiments. CDCl stabilized either with Ag foil (Carlo Erba) or
2 2
3
MeOH (6 mL). The reaction mixture was stirred at room temperature
for 1 h, affording an orange solution. The progress of reaction was
checked by TLC and 31P NMR, and volatiles were removed under
Na CO was used for NMR samples. Infrared spectra of solid samples
2
3
were recorded on a PerkinElmer Spectrum One FT-IR spectrometer,
equipped with a UATR sampling accessory. Infrared spectra of
solutions were recorded on a PerkinElmer Spectrum 100 FT-IR
vacuum. The residue was suspended in Et O and then filtered,
2
−
1
discarding the green Et O solution. The resulting orange-green/brown
spectrometer with a CaF liquid transmission cell (4000−1000 cm
2
2
4
6
solid was washed with Et O, dried under vacuum (room temperature)
range). IR spectra were processed with Spectragryph software.
2
and stored in N . Yield: 322 mg, 88%.
Carbon, hydrogen, and nitrogen analysis was performed on a Vario
2
4
7
Alternative Preparation. A solution of compound 1 (55 mg, 0.10
MICRO cube instrument (Elementar). Conductivity measurements
were carried out at 21 °C using an XS COND 8 instrument (cell
mmol) in MeOH (3 mL) was treated with HCl (0.2 mol·L− in H O;
1
2
−1
0.50 mL, 0.10 mmol). The resulting dark red solution was stirred at
room temperature for 1 h and the progress of reaction was checked by
constant = 1.0 cm ). Molar conductivity of reference 1:1 electrolytes:
−
3
−1
2
−1
NaBF , Λ (MeOH, c = 4 × 10 mol·L ) = 93 S·cm ·mol ; NaCl,
4
m
31
−3
−1
2
−1
P NMR. Therefore, [2]Cl was isolated in 85% yield following the
Λ
(MeOH, c = 3 × 10 mol·L ) = 85 S·cm ·mol ; HCl, Λ
−3 −1 2 −1
m
m
same workup procedure.
(
MeOH, c = 2 × 10 mol·L ) = 140 S·cm ·mol .
Synthesis and Characterization of Ruthenium Compounds.
Compound [2]Cl is soluble in MeOH and is insoluble in Et O and
2
6
2
[
(η -p-Cymene)RuCl{κ P,O-PPh (2-C H O)}], 1 (Chart 1). The title
hydrocarbons. Dissolution of [2]Cl in other solvents (e.g., acetone,
dichloromethane, THF, chloroform) caused partial conversion to 3
2
6 4
compound was prepared according to a modified literature
(vide infra). Orange-brown solutions of [2]Cl in MeOH turned to
a
green when kept for several days at room temperature with partial
degradation of the starting material; X-ray quality crystals of 3·[2]Cl
were obtained by slow evaporation of this solution. Anal. Calcd for
C H Cl OPRu: C, 57.54; H, 5.00. Found: C, 57.1; H, 5.1.
Chart 1. Structure of 1
2
8
29
2
Spectroscopic (IR/NMR) and conductivity data are given in the
Supporting Information.
6
2
[
(η -p-Cymene)RuCl{κ P,O-PPh (2-C H OH)}]BF , [2]BF (Chart 3).
2 6 4 4 4
A solution of compound 1 (103 mg, 0.188 mmol) in MeOH (4 mL)
was treated with HBF (48% w/w in H O, 50 μL, ca. 0.38 mmol), and
4
2
the resulting dark red solution was stirred at room temperature for 1 h.
The progress of reaction was checked by 31P NMR, and volatiles were
removed under vacuum. The residue was dissolved in a few milliliters
a
Numbering refers to carbon atoms.
G
DOI: 10.1021/acs.organomet.8b00071
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Organometallics
Article
a
room temperature under protection from the light for 1.5 h affording a
red-orange solution and colorless solid (AgCl). The suspension was
filtered on a small pad of Celite, and the filtrate solution was taken to
dryness under vacuum. The residue was dissolved in CH Cl , and the
Chart 3. Structure of [2]BF4
2
2
resulting solution was filtered on a small pad of Celite. The title
compound was obtained from the filtrate solution as a foamy yellow-
brown solid after volatiles were removed under vacuum (40 °C). Yield:
7
5 mg, 94%. Compound 4 is soluble in MeOH and chlorinated
solvents and insoluble in Et O and hexane. Partial degradation with
2
formation of a green soluble derivative was observed upon contact of
a
the solid with commercial BHT-stabilized Et O. Anal. Calcd for
2
Numbering refers to carbon atoms.
C H NO PRu: C, 58.53; H, 4.91; N, 2.44. Found: C, 58.2; H, 4.9; N,
28
28
4
2
.4. Spectroscopic (IR/NMR) and conductivity data are given in the
of CH Cl , then Et O was added under vigorous stirring, leading to the
precipitation of the title compound as an orange solid. The suspension
2
2
2
Supporting Information.
6
[
(η -p-cymene)RuCl {κP-PPh (2-C H OC(O)Me)}], 5 (Chart 6).
2
2
6 4
was filtered; the solid was washed with Et O, dried under vacuum
2
In a 25 mL Schlenk tube, acetyl chloride (50 μL, 0.70 mmol) was
(
room temperature), and stored under N . Yield: 92 mg, 77%.
2
Compound [2]BF is soluble in MeOH, acetone, and chlorinated
4
a
Chart 6. Structure of 5
solvents and is insoluble in Et O and hexane. Anal. Calcd for
2
C H BClF OPRu: C, 52.89; H, 4.60. Found: C, 52.4; H, 4.6.
2
8
29
4
Spectroscopic (IR/NMR) and conductivity data are given in the
Supporting Information.
6
[
(η -p-cymene)RuCl {κP-PPh (2-C H OH)}], 3 (Chart 4). In a 25
2
2
6 4
mL Schlenk tube, PPh (2-C H OH) (68 mg, 0.24 mmol) was added
2
6
4
a
Chart 4. Structure of 3
a
Numbering refers to carbon atoms.
added to a solution of compound 1 (88 mg, 0.16 mmol) in CH Cl (6
2
2
mL). The resulting red solution was stirred at room temperature for 22
h, and the progress of reaction was checked by 31P NMR. Therefore,
Et N (0.10 mL, 0.72 mmol) was added; the reaction mixture was
3
stirred for 10 min then extracted with H O (3 × 20 mL). HCl
2
a
Numbering refers to carbon atoms.
generated by excess acetyl chloride upon air exposition is detrimental
to the Ru compound. Adding NaHCO in the aqueous phase during
the extraction step is not sufficient. Volatiles were removed under
3
6
to a brick-red solution of [(η -p-cymene)RuCl ] (62 mg, 0.101
2
2
mmol) in CDCl (5 mL), and the reaction mixture was stirred at room
temperature for 1 h. H and P{ H} NMR spectra of the resulting
orange solution revealed the formation of a mixture of [2]Cl and 3 in
5:75 molar ratio; NMR data for 3 in this solution are given in the
Supporting Information. Compound 3 is sensitive to the impurities
formed in aged CDCl solutions; stabilized CDCl is required for
NMR analysis. Then volatiles were removed under vacuum, and the
resulting orange solid was washed with Et O and dried under vacuum
vacuum from the organic phase; the residue was dissolved in CH Cl
3
2
2
1
31
1
and loaded on top of a silica column (d = 1 cm, h = 5 cm). Impurities
were eluted with CH Cl2 then a red band was eluted with
2
2
CH Cl :acetone 9:1 v/v. Volatiles were removed under vacuum, and
2
2
the residue was dissolved in few mL of CH Cl . Addition of Et O (2
2 2 2
3
3
mL) followed by hexane under vigorous stirring caused the
precipitation of the title compound as an orange solid. The suspension
was filtered; the solid was washed with hexane, dried under vacuum
2
(
40 °C). The reaction was then repeated in CD Cl , with a similar
(40 °C) and stored under N . Yield: 66 mg, 66%. Compound 5 is
2
2
2
outcome. These solid materials isolated from solutions containing both
2]Cl and 3 were not characterized by CHN analysis and NMR
spectroscopy; indeed, [2]Cl and 3 have the same formula
C H Cl OPRu) and will immediately re-equilibrate when dissolved
soluble in acetone and chlorinated solvents, poorly soluble in Et O and
2
[
insoluble in hexane and H O. Anal. Calcd for C H Cl O PRu: C,
2
30 31
2
2
57.51; H, 4.99. Found: C, 57.4; H, 5.1. Spectroscopic (IR/NMR) data
are given in the Supporting Information. Compound 5 is sensitive to
the impurities formed in aged CDCl solutions; stabilized CDCl is
(
2
8
29
2
in a solvent for NMR analysis. However, X-ray quality crystals of 3·
CH COCH were collected from an acetone solution of this solid
3
3
3
3
required for NMR analysis.
layered with petroleum ether and settled aside at −20 °C.
Attempted Reactions of 1 with NH Cl, NH [HF ], HF, and MeI. A
4
4
2
6
2
[
(η -p-Cymene)Ru(NO ){κ P,O-PPh (2-C H O)}], 4 (Chart 5). A
dark red solution of 1 (50 mg, 0.091 mmol) and the selected
3
2
6 4
solution of compound 1 (76 mg, 0.14 mmol) in MeOH (3 mL) was
treated with AgNO (25 mg, 0.15 mmol). The mixture was stirred at
compound (NH Cl: 34 mg, 0.64 mmol; NH [HF ]: 10 mg, 0.19
4
4
2
3
mmol; HF ca. 1 M in H O: 0.15 mL, ca. 0.15 mmol) in MeOH (5 mL)
2
was stirred at room temperature for 20 h. Aliquots were periodically
a
31
1
taken for P{ H} NMR analysis (C D capillary), revealing that
Chart 5. Structure of 4 )
6
6
protonation of Ru−P,O did not occur [δ/ppm = 51.4]. Therefore,
volatiles were removed under vacuum, and the residue was suspended
in CH Cl . The suspension was filtered over a small pad of Celite, and
2
2
volatiles were removed under vacuum from the filtrate solution. The
1
resulting orange solid was identified as pure starting material 1 by H
and 31P NMR spectroscopy (CH OD). Reactions with MeI (25 μL,
3
0
,40 mmol) in MeOH or acetone (5 mL) were carried out under
protection from the light following an analogous procedure.
Behavior of [2]X (X = Cl, BF ) in Different Solvents: NMR
4
Study. General Procedure. Compound [2]X (X = Cl, BF ; 5.0 mg)
was dissolved in the selected deuterated solvent (0.5 mL; cRu = 10 g·
4
a
Numbering refers to carbon atoms.
H
DOI: 10.1021/acs.organomet.8b00071
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Organometallics
Article
1
L− corresponding to 17 and 16 mM for [2]Cl and [2]BF4,
Ru, especially when the quality of the crystals is low. Nonetheless, the
respectively) at room temperature. The solutions were subsequently
fact that the structure and bonding parameters of 3, as found in 3·[2]
1
31
1
26
analyzed by H and P{ H} NMR spectroscopy (t < 15 min). Molar
Cl and 3·CH COCH3 are rather similar, suggests that also the
3
1
ratios of Ru compounds were calculated on H signals for analogous
structure of [2]Cl is reliable. The presence of hydrogens on the O
atoms is confirmed by the formation of hydrogen bonds with the Cl-
atoms.
CH or CH groups of the p-cymene ligand. Results are presented in
3
Scheme 2; NMR data for each solution are given in the Supporting
Information.
[
2]Cl. (CD ) CO, CD Cl , and CDCl : orange-red solutions,
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00071.
3
2
2
2
3
■
containing [2]Cl and 3 (Scheme 2a). [2]Cl/3 molar ratio = 25:75
(CD ) CO), 35:65 (CD Cl ), 30:70 (CDCl ). CD OD and CD OD/
*
S
(
3
2
2
2
3
3
3
D O 4:1 v/v: orange-green solutions; no other Ru species besides [2]
2
Cl was identified (Scheme 2b). No changes in the NMR spectra of the
CD OD/D O 4:1 v/v solution were observed after 48 h at room
3
2
temperature. CD CN: orange-yellow solution, containing a third Ru
3
IR and NMR spectra of Ru compounds 1−5 (PDF)
Computed Cartesian coordinates of all of the molecules
reported in this study (XYZ)
6
product identified as [(η -p-cymene)RuCl{κP-PPh (2-C H OH)}-
2
6
4
(
MeCN)]Cl, [3-MeCN]Cl (Scheme 2c). [2]Cl/3/[3-MeCN]Cl
molar ratio = 30:40:30.
2]BF . CD OD, (CD ) CO, CD Cl , and CDCl : orange solutions.
[
Accession Codes
4
3
3
2
2
2
3
No other Ru species beside [2]BF4 was identified (Scheme 2b).
CCDC 1817661−1817662 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
CD CN: orange solution turning to yellow within minutes, with
3
6
quantitative formation of [(η -p-cymene)RuCl{κP-PPh (2-
2
C H OH)}(MeCN)]BF , [3-MeCN]BF (Scheme 2c) and other
6
4
4
4
minor products.
Diffusion NMR Measurements. 1H diffusion NMR measure-
ments were performed by using the double-stimulated echo sequence
4
8
with longitudinal eddy current delay at 298 K without spinning. The
dependence of the resonance intensity (I) on a constant waiting time
and on a varied gradient strength G is described by the following
equation:
AUTHOR INFORMATION
Corresponding Author
E-mail: guido.pampaloni@unipi.it.
■
*
ORCID
I
I0
⎛
⎜
δ ⎞
2
G2
ln = (γδ) D
Δ −
⎟
t
Gianluca Ciancaleoni: 0000-0001-5113-2351
Stefano Zacchini: 0000-0003-0739-0518
Fabio Marchetti: 0000-0002-3683-8708
Guido Pampaloni: 0000-0002-6375-4411
⎝
3 ⎠
where I is the intensity of the observed spin echo, I is the intensity of
the spin echo in the absence of gradient, D is the self-diffusion
coefficient, Δ is the delay between the midpoints of the gradients (0.2
s), δ is the length of the gradient pulse (4 ms), and γ is the
magnetogyric ratio. The shape of the gradients was rectangular, and
their strength G was varied during the experiments.
The self-diffusion coefficient, D , was estimated by evaluating the
proportionality constant for a sample of HDO (5%) in D O (known
diffusion coefficients in the range 274−318 K) under the exact same
conditions as the samples of interest. The solvent or TMS was taken as
internal standard. The hydrodynamic volume of the species has been
calculated from the experimental value of D through the procedure
previously described.
Computational Studies. All the geometries were optimized with
ORCA 3.0.3, using the BP86 functional in conjunction with an
augmented triple-ζ quality basis set. The dispersion corrections were
taken into account using the Grimme D3-parametrized XC func-
0
t
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
The University of Pisa is gratefully acknowledged for financial
support.
t
■
2
4
9
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■
t
30b
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I
DOI: 10.1021/acs.organomet.8b00071
Organometallics XXXX, XXX, XXX−XXX

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Organometallics XXXX, XXX, XXX−XXX