Complexes Containing a Phenol–Platinum(II) Hydrogen Bond: Synthons for Supramolecular Self-Assembly and Precursors for Hydridoplatinum(IV) Complexes

Article abstract of DOI:10.1002/ejic.201900480

The cycloneophylplatinum(II) complexes [Pt(CH₂CMe₂C₆H₄)(κ²-NN′-2-C₅H₄NCH₂-NH-R], R = 2-C₆H₄OH, 1; R = 3-C₆H₄OH, 2; R = 4-C₆H₄OH, 3, and [Pt(CH₂CMe₂C₆H₄)(κ²-NN′-2-C₅H₄NCH=N-2-C₆H₄OH)], 4, are reported. The structures of 1 and 4 each contain an intramolecular OH··Pt hydrogen bond, while complex 3 contains an intermolecular OH··Pt hydrogen bond and forms a new type of supramolecular polymer. In contrast, the complex [PtCl₂(κ²-NN′-2-C₅H₄NCH=N-2-C₆H₄OH)], 5, forms a dimer through intermolecular OH··ClPt hydrogen bonding. Reaction of complex 4 with HCl or HBr occurs by oxidative addition to give hydridoplatinum(IV) complexes [PtHX(CH₂CMe₂C₆H₄)(κ²-NN′-2-C₅H₄NCH=N-2-C₆H₄OH)], 6, X = Cl; 7, X = Br. The sequential formation of isomers of these compounds is interpreted in terms of a proposed reaction mechanism.

Full text of DOI:10.1002/ejic.201900480

A Journal of
Accepted Article
Title: Complexes Containing a Phenol-Platinum(II) Hydrogen Bond:
Synthons for Supramolecular Self-Assembly and Precursors for
Hydridoplatinum(IV) Complexes
Authors: Ava Behnia, Mahmood Azizpoor, Paul D. Boyle, and Richard
J. Puddephatt
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201900480
Link to VoR: http://dx.doi.org/10.1002/ejic.201900480

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Complexes Containing a Phenol-Platinum(II) Hydrogen Bond: Synthons for
Supramolecular Self-Assembly and Precursors for Hydridoplatinum(IV) Complexes
Ava Behnia,[a] Mahmood Azizpoor Fard,[a] Paul D. Boyle[a] and Richard J. Puddephatt*[a]
[a]
Department of Chemistry, The University of Western Ontario, London, Canada N6A
5B7
E-mail: pudd@uwo.ca
Abstract
The cycloneophylplatinum(II) complexes [Pt(CH2CMe2C6H4)(κ2-NN’-2-C5H4NCH2-
NH-R], R = 2-C6H4OH,
[Pt(CH2CMe2C6H4)(κ2-NN’-2-C5H4NCH=N-2-C6H4OH)],
of and
each contain an intramolecular OH..Pt hydrogen bond, while complex
contains an intermolecular OH..Pt hydrogen bond and forms a new type of supramolecular
polymer. In contrast, the complex [PtCl2(κ2-NN’-2-C5H4NCH=N-2-C6H4OH)],
, forms
a dimer through intermolecular OH..ClPt hydrogen bonding. Reaction of complex
with
HCl or HBr occurs by oxidative addition to give hydridoplatinum(IV) complexes
[PtHX(CH2CMe2C6H4)(κ2-NN’-2-C5H4NCH=N-2-C6H4OH)],
, X = Cl; , X = Br. The
1
; R = 3-C6H4OH,
2
; R = 4-C6H4OH,
3
,
and
4
, are reported. The structures
1
4
3
5
4
6
7
sequential formation of isomers of these compounds is interpreted in terms of a proposed
reaction mechanism.
Introduction
In many catalytic reactions involving platinum or its complexes, the interaction of a
platinum atom with a hydroxylic solvent or reagent is critically important. It may involve
formation of a non-classical O-H..Pt hydrogen bond,[1] formation of a reactive
hydridoplatinum intermediate,[2] or a long range interaction involving another reagent
such as dioxygen.[3] In forming a non-classical O-H..Pt hydrogen bond, the electron-rich
platinum atom can be considered to act as a 2-electron donor while maintaining its
oxidation state,[1,4] while hydride formation typically occurs by oxidative addition.[2] The
intermolecular O-H..Pt hydrogen bond can also participate in self-assembly to form
polymeric complexes in the crystalline state.[1] Appended phenol substituents are known
to form intramolecular O-H..Pt(II) hydrogen bonds (Scheme 1), but these do not lead to
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
oxidative addition of the O-H bond to make hydridoplatinum(IV) complexes, and no
intermolecular equivalents are known.[1,5] Indeed there has been doubt that these
hydrogen bonds would ever be considered as structure-directing elements for extended
supramolecular arrays.[1e] One example is known in which a platinum(II) complex with
an NH..Pt hydrogen bond from an appended pyridinium group is in equilibrium with the
hydrido(pyridine)platinum(IV) complex,[6] but no OH..Pt(II) and O-Pt(IV)-H isomers
appear to be known.
Scheme 1. Pt(II)-phenol hydrogen bonds.
This article reports the synthesis and structure of three new complexes containing
phenolic OH..Pt(II) hydrogen bonds, including the first example of a supramolecular
polymer based on intermolecular OH..Pt hydrogen bonds and an estimate of the bond
strength. It also investigates the formation of hydridoplatinum(IV) complexes from the
platinum(II) precursor complexes.
Results and Discussion
The ligands used in this work are shown in Scheme 2. They contain a pyridyl group
and an amine (L1
platinum(II). They also contain an appended phenol group that can be placed in the
ortho
meta or para position and which, when deprotonated, can act as a third donor.[7]
Dimethylplatinum(II) complexes with these ligands are electron-rich and are very easily
oxidized; they have not been structurally characterized.[8]
Cationic
– L3) or imine group (L4) that allow the ligands to chelate to
,
monomethylplatinum(II) complexes, such as [PtMe(SMe2)(L1)]Cl, are also known and
they form supramolecular polymers through OH..Cl and NH..Cl hydrogen bonding, and
do not contain OH..Pt hydrogen bonds.[9] The new electron-rich cycloneophylplatinum(II)
complexes
1
–
4
were prepared by reaction of the precursor complex
[Pt2(CH2CMe2C6H4)2(μ-SMe2)2][10] with the corresponding ligands L1
– L4, with
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
displacement of the weakly bound dimethylsulfide ligands (Scheme 2).
complexes were characterized spectroscopically and complexes and were shown to
contain OH..Pt hydrogen bonds by X-ray structure determinations.
The new
1
,
2
3
Scheme 2. The ligands and their cycloneophylplatinum(II) complexes.
The structures of the 2-hydroxyphenyl derivatives
1 and 4 are shown in Figure 1. In
each case, the platinum(II) center is square planar with the aryl and pyridyl groups
mutually trans. This stereochemistry is expected because it avoids unfavorable steric
interactions between the roughly co-planar aryl and pyridyl groups.[10] However, the
main feature of interest is the presence of an OH..Pt hydrogen bond in each complex.
The structural data for complex
refine the OH hydrogen atom position. The parameters O(1)-H(1A) 0.84(5) Å,
Pt(1)..H(1A) 2.37(3) Å, O(1)-H(1A)..Pt(1) 162(2)o, are similar to those for complex
(Scheme 2, O-H 0.91(4) Å, Pt..H 2.10(4) Å, O-H..Pt 162(4)o], clearly showing the
presence of the OH..Pt bond.[5] The Pt..O distance in [Pt(1)..O(1) 3.23(1) Å] is slightly
higher than in
[Pt(1)..O(1) 3.175(1) Å], perhaps indicating a slightly weaker OH..Pt
hydrogen bond; the difference probably arises from geometrical constraints of the imine
group in
1 were of high quality and it was possible to locate and
A
4
1
4
.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Figure 1. Structures of complexes (a) 4 and (b) 1, showing 30% probability ellipsoids. (a)
Pt(1)C(1) 2.035(5), Pt(1)C(6) 1.995(5), Pt(1)N(1) 2.110(4), Pt(1)N(2) 2.125(4), Pt(1)..O(1)
3.23(1) Å; C(1)Pt(1)C(6) 80.2(2), N(1)Pt(1)N(2) 77.3(1)o. (b) Pt(1)C(13) 1.9954(11),
Pt(1)C(20) 2.0228(12), Pt(1)N(1) 2.1056(10), Pt(1)N(2) 2.2075(11), Pt(1)..O(1) 3.175(1),
Pt(1)..H(1) 2.37 Å; C(13)Pt(1)C(20) 81.38(5), N(1)Pt(1)N(2) 78.04(4)o.
The structure of complex
3
is shown in Figure 2. The stereochemistry at platinum(II)
, with the aryl and pyridyl groups mutually trans. In this
is similar to that found in and
1
4
case, formation of an intramolecular OH..Pt bond is impossible but an intermolecular
bond is formed instead. The short Pt..O contact of 3.14(1) Å clearly represents the OH..Pt
bond; the distance is somewhat shorter than in
1 and 4. The hydrogen atom was located
and the associated distance Pt..H = 2.28(8) Å and angle Pt..H-O = 155(7)o are similar to
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
the values found for complex
1
. Propagation of this motif gives a supramolecular
polymeric structure, with chains running parallel to the x-axis. The molecule is chiral at
the amine nitrogen atom, so each individual polymer chain is isotactic. The space group
is not chiral and so there are equal numbers of chains with RRR and SSS chirality. The
complex with an electron-rich metal center and a ligand with an appended 4-
hydroxyphenyl group is particularly well suited for making one-dimensional
supramolecular polymers, and it should be possible to prepare many other examples.
Figure 2. The structure of complex 3, showing 30% probability ellipsoids. Selected bond
parameters: Pt(1)C(1) 2.036(6), Pt(1)C(6) 1.985(6), Pt(1)N(1) 2.205(5), Pt(1)N(2)
2.097(5), Pt(1A)..O(1) 3.14(1) Å; C(1)Pt(1)C(6) 80.7(2), N(1)Pt(1)N(2) 79.6(2)o.
Symmetry equivalent atoms: x, y, z; x-1, y, z.
In order to compare the above structures with that of a more typical inorganic
platinum(II) complex, we have prepared the dichloroplatinum(II) derivative [PtCl2(L4)],
5
(Scheme 3). Complex 5 is a sparingly soluble yellow solid, prepared either by ligand
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
displacement from [PtCl2(SMe2)2] or by cleavage of the cycloneophylplatinum group
from complex by excess HCl. The structure of complex is shown in Figure 3. There
4
5
is no OH..Pt hydrogen bond but there is a long CH..Pt interaction (Pt..H 2.66 Å, C-H..Pt
157o) which could indicate a weak hydrogen bond.[1] Two square planar units are
connected to form a supramolecular dimer by OH..Cl hydrogen bonding, with
O(1)..Cl(1A) = Cl(1)..O(1A) = 3.187(2) Å. In this case, it seems that the chloride ligand is
a better hydrogen bond acceptor than the platinum(II) center, which is less electron-rich
than in the cycloneophyl complexes.
Scheme 3. Synthesis of complex 5.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Figure 3. Structure of complex
5
, showing 30% probability ellipsoids: above a solvated
molecule; below, a supramolecular dimer. Selected bond parameters: Pt(1)N(1)
2.0098(15), Pt(1)N(2) 2.0142(15), Pt(1)Cl(1) 2.2874(6), Pt(1)Cl(2) 2.3014(6),
O(1)..Cl(1A) 3.187; N(1)Pt(1)N(2) 80.08(6), Cl(1)Pt(1)Cl(2) 89.456(16)o. Symmetry
equivalent atoms: x, y, z; 1-x, 1-y, 2-z.
The NMR spectra of the complexes
1
–
3
were unremarkable. The presence of the
1
chiral center at nitrogen leads to no symmetry and this is clearly seen in the H NMR
1
spectra. For example, in the H NMR spectrum of complex
1
, the CH2 protons of the
cycloneophyl group are non-equivalent and appeared as two sharp doublets at
δ 2.60 and
1
2.02, with geminal coupling 2J(HH) = 10 Hz. In contrast, the H NMR spectrum of
complex
4
at room temperature gave no visible resonance for these CH2 protons;
however, at -20oC the expected resonances were observed at
δ
3.38 and 2.48, with
geminal coupling 2J(HH) = 12 Hz. The coalescence temperature is 25oC and, because of
the significant chemical shift difference, the resonance is too broad to observe. The data
are interpreted according to the mechanism in Scheme 4. The hydrogen bonded ground
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
state structure
4 has no symmetry and, for the molecule to gain an effective plane of
symmetry to make the CHaHb protons equivalent, the hydrogen bond must break to allow
rotation of the 2-hydroxyphenyl group to form the hydrogen bond on the opposite side of
the square plane via the intermediate 4* (Scheme 4). The activation energy
estimated as 55 kJ mol-1 at 298K from the Eyring equation (see experimental) and could
be taken as an upper limit of the OH..Pt bond energy. The NMR spectrum of
showed
Δ
G† is
4
the presence of a minor component, suggested to be the isomer with the CH2 group trans
to pyridine, 4’, but it was never present in more than 5% abundance.
O
H
HO
N
N
N
N
Pt
Pt
Ha
Hb
H
H
4
4*
Scheme 4. Inversion of the hydrogen bond structure in complex
4.
DFT calculations (see experimental for details) give some insight into the nature of the
hydrogen bonds (Figure 4). In complex
4
, the OH hydrogen atom is directed towards the
2
platinum atom and the main interaction is with the filled dz orbital of the electron-rich
platinum(II) center (Figures 4a, 4b). In contrast, the OH hydrogen atom in complex
5 is
directed towards the adjacent chloride ligand and the main interaction is with one of the
filled pπ orbitals of the chlorine atom (Figures 4c, 4d), which are at higher energy than the
d
z2 orbital of the less electron-rich platinum(II) center. In the solid state structure, a
closer OH..Cl approach is possible and the dimer structure is formed (Figure 3). The
hydrogen bond interaction in complex
1
(Figures 4e, 4f) is similar to that in complex
4,
2
involving the dz orbital of platinum(II). In complex
3
, no intramolecular hydrogen
bonding is possible (Figures 4g, 4h). It is noteworthy that the orbital with mostly 5dz2
character lies at -6.27 eV in but at -5.74 eV in , reflecting the stabilization of this
orbital by the hydrogen bonding in
1
4
1
. All of the DFT calculations support the view that
2
the OH..Pt hydrogen bond strength depends on the energy of the filled dz orbital, which
acts as the hydrogen bond acceptor.[4,5]
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Figure 4. Calculated structures and H-bond frontier orbitals: (a), (b), complex
complex ; (e), (f), complex ; (g), (h) complex . For (b), (f), (h), the filled orbital has
mostly platinum 5dz2 character while, for (d) it has mostly Cl 3pz character.
4; (c), (d),
5
1
3
The platinum(II) complexes
hydridoplatinum(IV) isomers in solution. DFT calculations predict that the isomerization
of complex
to the platinum(IV) complex [PtH(CH2CMe2C6H4)(κ3-NN’O-2-
1 – 4 did not equilibrate with their potential
4
C5H4NCH=N-2-C6H4O)] is unfavorable by 68-83 kJ mol-1, depending on the isomer
formed, so this is not surprising. However, platinum(IV) hydride complexes were formed
by reaction of
4
with strong acids HCl or HBr and are expected to have the structure
, X = Cl; , X = Br . The
[PtHX(CH2CMe2C6H4)(κ2-NN’-2-C5H4NCH=N-2-C6H4OH)],
6
7
reagent HCl was generated in CD2Cl2 solution by reaction of Me3SiCl with water and it
1
was added to a solution of complex
4
in CD2Cl2 at -60oC and H NMR spectra were
recorded as the solution was warmed to room temperature. Four hydride complexes were
detected, as illustrated in Figure 5. At -30oC (Figure 5a), the dominant hydride resonance
1
was at δ −19.62, JPtH = 1466 Hz (isomer 6a), at 25oC (Figure 5b) the dominant hydride
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
resonance was at δ −19.51, 1JPtH = 1400 Hz (isomer 6b), and after one day at 25oC (Figure
5c) the dominant hydride resonance was at δ −19.17, 1JPtH = 1380 Hz (isomer 6c). Under
conditions where 6b was dominant, a complete 1H NMR analysis was possible. A fourth
hydride resonance was observed at δ −20.19, 1JPtH = 1484 Hz (isomer 6d, indicated by an
asterisk in Figure 5b), but it was never the major complex present. By integration against
an internal standard, the total yield of hydride complexes was determined to be essentially
quantitative at 25oC, but it was reduced to about 70% after one day and to zero after one
week, with parallel formation of complex
5 (Scheme 3). If the hydride complexes were
generated in CD2Cl2 solution as above, with isolation by evaporation of the solvent,
washing of the residue with ether to remove organosilicon compounds, drying under
vacuum and redissolving in CD2Cl2, the same hydride complexes 6a
– 6d were detected
by their hydride resonances but the product mixture contained about 80% of complex
4
1
by H NMR analysis. This indicates that HCl addition to complex
4
to give 6a
. Attempts to grow crystals from the
mixture of hydride complexes at low temperature were unsuccessful so unambiguous
assignment of the isomer structures was not possible. The reaction of complex with
HBr occurred in a similar way to give isomers of [PtHBr(CH2CMe2C6H4)(L4)], , formed
in the sequence 7a [δ −19.66, JPtH = 1453 Hz], 7b [δ −19.56, JPtH = 1395 Hz], 7c [δ
– 6d is
reversible, and that HCl loss regenerates complex
4
4
7
1
1
1
1
−19.16, JPtH = 1356 Hz], with minor isomer 7d [δ −20.06, JPtH = 1444 Hz]. The trans
influence series is imine, pyridine > Cl-, Br-, so the data are consistent with the initially
formed isomer 6a or 7a having hydride trans to halide while the later isomers 6b 6c 7b
-
,
,
,
7c have hydride trans to a nitrogen-donor ligand.[11] A hydride trans to CH2 or C6H4
would give a much lower coupling constant,[2] so only isomers with the fac-PtHC2
coordination need to be considered.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Figure 5. 1H NMR spectra (400 MHz) of complex 6 in the hydride region: a) at -30°C; b) at
25°C; c) after 24 h. at 25°C.
Complexes
complexes but these were not sufficiently stable to allow characterization. For example,
reaction of complex
in CD2Cl2 with HCl gave isomers of [PtHCl(CH2CMe2C6H4)(κ2
1 – 3 also reacted with HCl to give mixtures of hydridoplatinum(IV)
1
-
NN’-2-C5H4NCH2-NH-2-C6H4OH)],
8
.
Five hydride resonances were observed [δ
1
1
−19.63, JPtH = 1340 Hz; -19.90; -20.37, JPtH = 1687 Hz; -20.91; -21.13] but 195Pt
couplings were only resolved for the two most intense peaks. Complete loss of these
peaks occurred in a few hours at room temperature. Because the hydridoplatinum(IV)
complexes from ligands L1
– L3 are chiral at both the amine and platinum(IV) centers,
more isomers are possible than with L4, and the low thermal stability hinders more
complete characterization.
The sequential formation of isomers from the reaction of complex
4 with HCl or HBr
is unusual and some DFT calculations were carried out on potential products in order to
gain further insight (Scheme 5, Figure 6). There are six potential geometrical isomers of
complex
6 having the preferred fac-PtHC2 coordination, labeled P1 – P6 in Scheme 5 and
Figure 6. They are all expected to have intramolecular OH..Cl hydrogen bonds (Figure 6),
though these are not shown in Scheme 5, for clarity. Their energies with respect to
complex
4
+ HCl lie in the range -80 to -100 kJ mol-1, so the oxidative addition is
is expected to
favorable (Figure 6). In terms of mechanism, the protonation of complex
4
form the 5-coordinate cationic square pyramidal intermediate I1 and then chloride
coordination at the vacant site would give product isomer P1. Isomerization of P1 is
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
likely to involve chloride dissociation to regenerate intermediate I1, followed by
rearrangement and recoordination of chloride. The isomerization of the 16-electron
platinum(IV) intermediates is thought to occur by migration of an equatorial group to the
vacant axial site while the axial group moves to the vacated equatorial site, by way of a
pinched trigonal bipyramidal intermediate.[10,12] In this mechanism, I1 can rearrange to I2
or I3 and chloride coordination can then give P2 or P3. Similarly, intermediates I2 and
I3 can isomerize back to I1 or go on to form I4 and I5 respectively, and chloride
coordination can then give products P4 and P5. Finally, isomerization of I4 or I5 can
give I6 and this can give P6. Of course, I6 and then P6 might also be formed by direct
reaction of HCl with the minor isomer of complex
4 (4’).
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
HO
HO
HO
-
X
N
N
N
N
N
N
+
Pt
X
Pt
+
Pt
-
H
H
- X
H
I4
P4
I6
-
-
X
- X
HO
HO
X
-
HO
X
N
X
N
+
Pt
N
-
Pt
- X
Pt
H
H
H
N
N
N
I2
P2
P6
HO
HO
O
-
H
H
H
X
HX
N
N
N
N
-
Pt
Pt
-
Pt
+
- X
- X
N
N
X
4
I1
P1
HO
HO
X
-
HO
X
N
N
H
N
H
X
+
N
Pt
Pt
-
- X
Pt
H
N
N
P6
I3
P3
-
-
- X
X
HO
-
HO
X
X
HO
N
N
H
N
N
H
+
Pt
-
N
Pt
+
Pt
- X
N
H
I6
P5
I5
Scheme 5. The six potential isomers P1
–
P6 by oxidative addition of HX to complex
I6
4,
and their likely formation through intermediates I1
–
.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Figure 6. Calculated structures for the potential isomers of [PtHCl(CH2CMe2C6H4)(κ2
-
NN’-2-C5H4NCH=N-2-C6H4OH)],
6
. Relative energies with respect to
4
+ HCl are: P1
,
P6 -80; P2
,
P3 -89, P5 -90, P4 -100 kJ mol-1.
The final challenge is to correlate the four observed structures 6a
7d (X = Br) with four of the six possible structures P1
–
6d (X = Cl) or 7a
–
–
P6 of [PtHX(CH2CMe2C6H4)(κ2
-
NN’-2-C5H4NCH=N-2-C6H4OH)] (Scheme 6). Precedents for trans oxidative addition
of HX, as a result of kinetic control (Scheme 5), predict that the first formed isomer from
4
should be P1, and the NMR data fully support the assignment of this structure to the
first formed isomer 6a or 7a [2]
.
According to Scheme 5, the first product of isomerization
should have structure P2 or P3 and so the observed complex 6b or 7b is expected to have
one of these two structures. Isomers P2 and P3 are calculated to have the same energy so
the calculations do not aid the assignment, and the assignment of 6b, 7b to have structure
P2 is therefore tentative. The isomer P4 is calculated to be most stable so the more stable
observed isomer 6c or 7c is likely to have this structure. Finally, complex 6d or 7d is
proposed to have the structure P6. Complex 6d, 7d appears to be formed primarily by
direct reaction of complex 4’ with HX. It might also be formed by isomerization of P4
(Scheme 5), though this reaction is calculated to be unfavorable.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Scheme 6.
Proposed structures of complexes [PtHCl(CH2CMe2C6H4)(κ2-NN’-2-
C5H4NCH=N-2-C6H4OH)], 6a
– 6d (X = Cl), 7a – 7d (X = Br).
Conclusions
New examples of phenol based OH..Pt hydrogen bonds are established in the structures
of
1
,
3
and , and DFT calculations support the view that a high energy platinum 5dz2
4
orbital is most important in promoting such bonds.[4,5] The ligands used in this work are
easily modified and so are expected to yield further examples. For example, the phenol
acidity could be modified by introducing appropriate substituents and this could be used
to tailor the strength of the unconventional hydrogen bonds. The demonstration in the
structure of complex
supramolecular polymer is particularly significant. The oxidative addition of acids HX
(X = Cl or Br) to complex occurs in an unexpected way to give sequential formation of
3 that the hydrogen bonds can support formation of a
4
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
isomeric hydridoplatinum(IV) complexes, and a mechanism to account for this unusual
behavior is proposed.[2]
Experimental
IR spectra were recorded by using a Perkin Elmer UATR TWO FTIR spectrometer.
NMR spectra were recorded using a Varian Inova 600 MHz spectrometer. Complete
1
1
assignments of each compound were aided by the use of H−1H gCOSY, H−13C HSQC,
and 1H−13C HMBC experiments and are reported using the labeling scheme in Scheme 7.
The activation energy for the inversion of the hydrogen bond in complex
4 was estimated
1
from the variable temperature H NMR spectra by using the Eyring equation.[13] The
complex [Pt2(CH2CMe2C6H4)2(μ-SMe2)2] and ligands L1
– L4 were synthesized
according to the literature procedures.[7,10a] MALDI-TOF mass spectra were collected
using an AB Sciex 5800 TOF/TOF mass spectrometer using pyrene or anthracene as the
matrix in a 20:1 matrix:substrate molar ratio. Single-crystal X-ray diffraction
measurements were made using a Bruker APEX-II CCD diffractometer with graphite-
monochromated Mo Kα (λ = 0.71073 Å) radiation. Single crystals of the complexes were
immersed in paraffin oil and mounted on MiteGen micromounts. The structures were
solved using dual space methods and refined by the full-matrix least-squares procedure of
SHELXL. Crystallographic data are given in the crystallographic information files. The
DFT calculations were carried out (gas phase only) using the B1LYP functional with
double-zeta basis set and first-order scalar relativistic corrections, as implemented in
ADF-2017.[14]
4
4
3
3
2
OH 6'
5
6
5
OH
5'
5'
6
2
H
6'
4'
3'
4'
3'
1
N
1
N
1'
1'
7a
2a
7a
2a
2'
2'
Pt
Pt
9
9
3a
4a
N
N
7' 3a
7'
8
8
7
7
4a
6a
6a
5a
5a
Scheme 7. NMR labelling scheme.
[Pt(CH2CMe2C6H4)(L1)], 1.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
To a stirred solution of [Pt2(CH2CMe2C6H4)2(μ-SMe2)2], (0.196 g, 0.252 mmol) in dry CH2Cl2
(15 mL) was added 2-C5H4N-CH2-NH-2-C6H4OH, L1 (0.100 g, 0.504 mmol). An immediate
color change from yellow to brown was observed. The reaction mixture was stirred for 2.5 h., the
solvent was evaporated under vacuum, and the residue was washed with dry hexane (3 × 2 mL)
and dry ether (3 × 2 mL), to give complex 1 as a brown solid (0.172 g, 0.325 mmol, 65%). NMR
in CD2Cl2 (25°C): δ(1H, 600 MHz) 8.46 (d, 1H, J = 5 Hz, H6a), 7.85 (dd, 1H, J = 8 Hz, 5 Hz,
H4a), 7.25 (d, 1H, J = 8 Hz, H3a), 7.19 (t, 1H, J = 8 Hz, H5a, 1H), 7.02 (t, 1H, J = 8 Hz, H5),
6.81 (d, 1H, J = 8 Hz, H6’), 6.77 (t, 1H, J = 8 Hz, H5’, 1H), 6.70-6.72 (m, 2H, H4, H6), 6.49 (d,
1H, J = 8 Hz, H3), 6.35 (br dd, 1H, J = 12 Hz, 6 Hz, NH), 6.32 (d, 1H, J = 8 Hz, H3’), 6.20 (t,
1H, J = 8 Hz, H4’), 4.40 (dd, 1H, J = 16 Hz, 6 Hz, H7a, 1H), 4.13 (dd, 1H, J = 16 Hz, 12 Hz,
H7a’), 2.60 (d, 1H, J = 10 Hz, H8), 2.02 (d, 1H, J = 10 Hz, H8’), 1.37 (s, 3H, H7), 1.23 (s, 3H,
H7’). δ(13C, 151 MHz) 168.66 (C2’), 160.72 (C2a), 150.47 (C2), 147.97 (C6a), 140.38 (C1’),
137.19 (C4a), 134.37 (C3’), 133.46 (C1), 127.71 (C5), 125.07 (C3), 124.19 (C5a), 123.61 (C4’),
123.43 (C5’), 121.93 (C6’), 121.41 (C3a), 120.06 (C4), 118.91 (C6), 60.67 (C7a), 46.77 (C9),
36.51 (C7), 32.36 (C8), 30.26 (C7’). MALDI MS (anthracene matrix): calcd m/z 525.14 [M]●+,
obsd m/z 525.14. IR: ν(O-H) 2951 cm-1. Single crystals suitable for X-ray crystallographic
analysis were grown by the slow diffusion of hexane into a dichloromethane solution at -30°C
under N2.
[Pt(CH2CMe2C6H4)(L2)], 2.
This was prepared similarly from [Pt2(CH2CMe2C6H4)2(μ-SMe2)2] (0.196 g, 0.252 mmol) and 2-
C5H4N-CH2-NH-3-C6H4OH, L2 (0.100 g, 0.504 mmol). Yield: 0.198 g, 0.376 mmol, 75%.
NMR in (CD3)2CO at 25°C: δ(1H, 600 MHz) 8.81 (d, 1H, J = 6 Hz, H6a), 8.07 (t, 1H, J = 7 Hz,
H4a), 7.63 (d, 1H, J = 7 Hz, H3a), 7.45 (dd, 1H, J = 6 Hz, 7 Hz, H5a), 7.06-7.01 (m, 2H, H6,
H3’), 6.68-6.71 (m, 2H, H5, H2), 6.64-6.60 (m, 2H, H4’, H6’), 6.54 (t, 1H, J = 7 Hz, H4), 6.50
(t, 1H, J = 7 Hz, H5’, 1H), 4.75 (dd, 1H, J = 16 Hz, 6 Hz, H7a), 4.50 (dd, 1H, J = 16 Hz, 5 Hz,
2
H7a’), 2.42 (d, 1H, J = 9 Hz, JPtH = 104 Hz, H8), 2.19 (d, 1H, J = 9 Hz, 2JPtH = 100 Hz H8’),
1.21 (s, 3H, H7), 1.20 (s, 3H, H7’). δ(13C, 151 MHz) 167.89 (C2’), 162.58 (C6a), 157.63 (C3),
150.31 (C4a), 148.15 (C2a), 143.44 (C1’), 136.84 (C2a), 135.13 (C6), 129.56 (C3’), 124.19
(C5a), 122.41 (C5’ or C1), 121.41 (C6’), 120.94 (C4’), 112.72 (C5 or C2), 112.04 (C4), 109.04
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
(C5 or C2), 59.56 (C7a), 46.74 (C9), 33.87 (C7), 32.78 (C7’), 27.37 (C8). MALDI MS
(anthracene matrix): calcd m/z 525.14 [M]●+, obsd m/z 525.14. IR: ν(O-H) 2920 cm-1.
[Pt(CH2CMe2C6H4)(L3)], 3.
This was prepared similarly from [Pt2(CH2CMe2C6H4)2(μ-SMe2)2] (0.196 g, 0.252 mmol) and 2-
C5H4N-CH2-NH-4-C6H4OH, L3 (0.100 g, 0.504 mmol). Yield: 0.187 g, 0.356 mmol, 71%.
NMR in (CD3)2CO at 25°C: δ(1H, 600 MHz) 9.03 (d, 1H, J = 6 Hz, H6a), 8.14 (t, 1H, J = 7 Hz,
H4a), 7.68 (d, 1H, J = 7 Hz, H3a), 7.53 (dd, 1H, J = 6 Hz, 7 Hz, H5a), 7.17(d, 1H, J = 7 Hz,
H6’), 7.13 (t, 1H, H4’), 7.12 (d, 2H, J = 7 Hz, H2, H6), 6.93 (t, J = 6 Hz, NH), 6.73 (d, 2H, J = 7
Hz, H3, H5), 6.71 (t, 1H, J = 7 Hz, H5’), 6.70 (d, 1H, J = 7 Hz, H3’), 4.68 (dd, 1H, J = 16 Hz, 6
Hz, H7a), 4.48 (dd, 1H, J = 16 Hz, 6 Hz, H7a’), 1.93 (d, 1H, J = 9 Hz, H8), 1.69 (d, 1H, J = 9
Hz, H8’), 1.15 (s, 3H, H7), 1.05 (s, 3H, H7’). δ(13C, 151 MHz) 161.19 (C6a), 154.62 (C2a),
148.94, 140.25, 136.62, 133.23, 124.35, 122.70 (C3, C5), 121.49 (C5a), 121.12 (C3a), 115.12
(C2, C6), 61.28 (C7a), 54.05 (C9), 33.65 (C7), 32.88 (C7’), 26.71 (C8). MALDI MS
(anthracene matrix): calcd m/z 525.14 [M]●+, obsd m/z 525.13. IR: ν(O-H) 2920 cm-1.
[Pt(CH2CMe2C6H4)(L4)], 4.
To a stirred solution of [Pt2(CH2CMe2C6H4)2(μ-SMe2)2], (0.196 g, 0.252 mmol) in ether (50 mL)
was added a solution of 2-C5H4NCH=N-2-C6H4OH, L4 (0.100 g, 0.504 mmol) in ether (20 mL).
An immediate color change from yellow to red was observed, and a red precipitate of 4 was
formed. After 3h., the product was separated by filtration, washed with hexane (30 mL) and cold
acetone (10 mL), and dried under vacuum. Yield: 0.220 g, 0.418 mmol, 83%. NMR in CD2Cl2 at
-20°C: δ(1H) 9.38 (s, 1H, 3JPtH = 27 Hz, H7a), 9.19 (d, 1H, J = 6 Hz, H6a), 8.15 (t, 1H, J = 7 Hz,
H4a), 7.94 (d, 1H, J = 7 Hz, H3a), 7.69 (dd, 1H, J = 6 Hz, 7 Hz, H5a), 7.35 (t, 1H, J = 8 Hz, H5),
7.28 (d, 1H, J = 8 Hz, H3), 7.12 (t, 1H, J = 8 Hz, H4), 6.92 (d, 1H, J = 8 Hz, H6), 6.83 (m, 2H,
H3’, H6’), 6.48 (m, 2H, H5’, H4’), 3.38 (d, 1H, J = 12 Hz, 2JPtH = 100 Hz, H8), 2.48 (d, 1H, J =
2
13
12 Hz, JPtH = 94 Hz, H8’), 1.35 (s, 3H, H7), 1.34 (s, 3H, H7’). C{1H} NMR (CD2Cl2, 151
MHz, -20°C) δ: 168.55 (C2’), 165.46 (C7a), 155.60 (C2a), 151.62 (C2), 149.65 (C6a), 141.36
(C1’), 138.07 (C4a), 137.45 (C1), 134.18 (C4’ or C5’), 129.89 (C5), 128.51 (C5a), 127.96 (C3a),
123.75 (C3’ or C6’), 123.39 (C4’ or C5’), 121.51 (C3’ or C6’), 121.06 (C3), 120.83 (C4),
117.84 (C6), 70.82 (C8), 47.38 (C9), 34.51 (C7,C7’). At room temperature, the 1H spectrum was
similar except that no resonances were observed for the CH2 protons (H8, H8’) and a single
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
resonance was observed for the CMe2 protons of the cycloneophyl group [δ 1.35 (s, 6H, H7,
H7’)]. MALDI MS (anthracene matrix): Calc. m/z 525.14 [M]●+, obsd m/z 525.14. IR: ν(O-H)
2950 cm-1. Single crystals of 4 suitable for X-ray crystallographic analysis were grown by the
slow diffusion of hexane into a dichloromethane solution at room temperature.
[PtCl2(L4)], 5.
To a solution of [PtCl2(SMe2)2] (0.121 g, 0.310 mmol) in CH2Cl2 (5 mL) was added ligand L4
(0.0.061 g, 0.310 mmol). The product 5 formed as an insoluble yellow solid, which was
separated, washed with CH2Cl2 (2 × 10 mL) and pentane (2 × 10 mL) and dried under vacuum.
Yield: 0.105 g, 0.226 mmol, 77%. NMR in (CD3)2SO: δ(1H, 600 MHz) 10.09 (s, 1H, H7a), 9.49
(d, 1H, J = 5 Hz, H6a), 8.44 (t, 1H, J = 7 Hz, H4a), 8.23 (d, 1H, J = 7 Hz, H3a), 8.00 (dd, 1H, J
= 6 Hz, 7 Hz, H5), 7.20-7.24 (m, 2H, H4, H5), 6.98 (d, 1H, J = 7 Hz, H6), 6.88 (d, 1H, J = 6 Hz,
H3). δ(13C) 168.23 (C2a), 162.29 (C7a), 153.05 (C2), 151.96 (C6a), 149.04 (C5a), 140.40 (C1),
137.75 (C3a), 130.24 (C4a), 129.91 (C5), 128.90 (C4), 126.91 (C3), 128.90 (C6). Single crystals
suitable for X-ray crystallographic analysis were grown by the slow evaporation of a solution in
dichloromethane.
[PtHCl(CH2CMe2C6H4)(L4)], 6.
To a solution of complex 4 (0.040 g, 0.076 mmol) in CD2Cl2 (1 mL), in an NMR tube at -60°C,
was added HCl generated by reaction of Me3SiCl (12.5 μL, 0.099 mmol) with H2O (2 μL, 0.038
1
mmol) in CD2Cl2 (0.5 mL). H NMR spectra were recorded at -60, -30, -20, 0 and 25oC. At -
60°C, a major hydride resonance was observed at δ −19.62, 1JPtH = 1466 Hz (isomer 6a) and a
less intense resonance at δ −19.51, 1JPtH = 1400 Hz (isomer 6b). At 0°C, a third hydride
resonance was observed at δ −19.17, 1JPtH = 1380 Hz (isomer 6c), while resonances for isomers
6a and 6b decayed. All three isomers were still present at 25oC, and decomposition occurred
over a period of several days to give complex 5.
In a similar reaction, HCl was added to complex 4 in CD2Cl2 at room temperature in the presence
of 1,3,5-trimethoxybenzene as internal standard. Spectra were recorded immediately (t = 0) and
after 15 h. Yields by integration: t = 0, total hydride yield 100%, 6a 2%, 6b 80%, 6c 18%; t =
15 h., total hydride yield 72%, 6a 2%, 6b 20%, 6c 50%. NMR data for 6b in CD2Cl2: δ(1H)
9.67 (d, 1H, J = 6 Hz, H6a), 9.33 (s, 1H, 3JPtH = 21 Hz, H7a), 8.11 (t, 1H, J = 7 Hz, H4a), 7.98
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
(dd, 1H, J = 6 Hz, 7 Hz, H5a), 7.90 (d, 1H, J = 7 Hz, H3a), 7.40 (d, 1H, J = 8 Hz, H3), 7.29 (t,
1H, J = 8 Hz, H4), 7.08 (t, 1H, J = 8 Hz, H5), 7.00 (d, 1H, J = 8 Hz, H6), 6.52-6.54 (m, 4H, H3’-
H6’), 3.20 (d, 1H, J = 15 Hz, 2JPtH = 72 Hz, H8), 2.70 (d, 1H, J = 15 Hz, 2JPtH = 70 Hz, H8’),
1.53 (s, 3H, H7), 1.32 (s, 3H, H7’), -19.51 (s, 1H, 1JPtH = 1400 Hz, PtH). IR: ν(PtH) 2290 cm-1.
MALDI MS (anthracene matrix): Calcd m/z 560.10 [M-H]+, Obsd m/z 560.11; Calcd m/z 525.14
[M-HCl]+ , Obsd m/z 525.14.
[PtHBr(CH2CMe2C6H4)(L4)], 7.
This was prepared similarly by reaction of HBr, generated by reaction of Me3SiBr (13 μL, 0.099
mmol) with H2O (2 μL, 0.038 mmol), and complex 4 (0.040 g, 0.076 mmol) in CD2Cl2 (1.5 mL)
at -60°C. The formation of complex 7 was monitored by 1H NMR as the solution was warmed to
1
1
room temperature. PtH resonances: 7a [δ −19.66, JPtH = 1453 Hz], 7b [δ −19.56, JPtH = 1395
Hz], 7c [δ −19.16, 1JPtH = 1356 Hz], with minor isomer 7d [δ −20.06, 1JPtH = 1444 Hz].
[PtHCl(CH2CMe2C6H5)(L1)H], 8.
This was prepared similarly by reaction of HCl, generated by reaction of Me3SiCl (12.5 μL,
0.099 mmol) with H2O (2 μL, 0.038 mmol), with complex 1 (0.040 g, 0.076 mmol) in CD2Cl2
(1.5 mL) at -60°C. NMR in CD2Cl2 at 25°C: δ(PtH) −19.63, 1JPtH = 1340 Hz; -19.90; -20.37,
1JPtH = 1687 Hz; -20.91; -21.13. IR: ν(OH) 3045 cm-1 ν(PtH) 2290 cm-1.
Acknowledgments
We thank the NSERC (Canada) for financial support.
References
[1]
Tedesco, K. Biradha, G. R. Desiraju, Organometallics 1997
Tiekink, Coord. Chem. Rev. 2017 345, 209-228. d) A. Martin, J. Chem. Educ. 1999
578-583. e) L. R. Falvello, Angew. Chem. Int. Ed. 2010 49, 10045-10047.
[2] a) R. J. Puddephatt, Coord. Chem. Rev. 2001 219-221, 157-185. b) G. Mazzone,
N. Russo, E. Sicilia, Inorg. Chem. 2011, 50, 10091-10101. c) R. Romeo, G. D’Amico,
Organometallics 2006 25, 3435-3446. d) G. S. Hill, L. M. Rendina, R. J. Puddephatt,
a) L. Brammer, Dalton Trans. 2003, 3145-3157. b) D. Braga, F. Grepioni, E.
16, 1846-1856. c) E. R. T.
76
,
,
,
,
,
,
,
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Organometallics 1995
Chem. Soc. 1995
[3] a) M. Lersch, M. Tilset, Chem. Rev. 2005
Bercaw, J. Organomet. Chem. 2015 793, 47-53. c) E. M. Prokopchuk, H. A. Jenkins, R.
J. Puddephatt, Organometallics 1999 18, 2861-2866.
[4] a) R. Sanchez-de-Armas, M. S. G. Ahlquist, Phys. Chem. Chem. Phys. 2015
812-816. b) O. Kroutil, M. Predota, Z. Chval, Inorg. Chem. 2016 55, 3252-3264.
[5] a) M. Baya, U. Belio, A. Martin, Inorg. Chem. 2013 53, 189-200. b) J. M. Casas,
L. R. Falvello, J. Fornies, A. Martin, A. J. Welch, Inorg. Chem. 1996 35, 6009-6014.
A. N. Vedernikov, K. G. Caulton, Chem. Commun. 2003, 358-359.
a) Y.-L. Wong, J.-F. Ma, F. Xue, T. C. W. Mak, D. K. P. Ng, Organometallics 1999, 18,
,
14, 4966-4968. e) S. S. Stahl, J. A. Labinger, J. E. Bercaw, J. Am.
,
117, 9371-9372.
,
105, 2471-2526. b) J. A. Labinger, J. E.
,
,
,
17,
,
,
,
[6]
[7]
5075−5079. b) Y.-L. Wong, D. K. P. Ng, H. K. Lee, Inorg. Chem. 2002, 41, 5276−5285. c) S.
Biswas, K. Mitra, B. Adhikary, C. R. Lucas, Transition Met. Chem. 2005, 30, 586−592. d) K.
Kanamori, K. Kusajima, H. Yachi, H. Suzuki, Y. Miyashita, K.-I. Okamoto, Bull. Chem. Soc.
Jpn. 2007, 80, 324−328.
[8]
a) M. E. Moustafa, P. D. Boyle, R. J. Puddephatt, Chem. Commun 2015, 51, 10334-
10336. b) M. A. Fard, A. Behnia, R. J. Puddephatt, ACS Omega 2019, 4, 257-268. c) M. A.
Fard, A. Behnia, R. J. Puddephatt, ACS Omega 2018, 3, 10267-10272.
[9]
M. A. Fard, A. Behnia, R. J. Puddephatt, Canad. J. Chem. 2019, 97, 238-243.
[10] a) M. A. Fard, A. Behnia, R. J. Puddephatt, Organometallics 2018, 37, 3368-3377. b) M.
A. Fard, A. Behnia, R. J. Puddephatt, J. Organomet. Chem. 2019, 890, 32-42. c) R. J.
Puddephatt, Canad. J. Chem. 2019, 97, in press, doi.org/10.1139/cjc-2019-0015.
[11] T. G. Appleton, H. C. Clark, L. E. Manzer, Coord. Chem. Rev. 1973
[12] a) K. A. Grice, M. L. Scheuermann, K. I. Goldberg, Topics Organomet. Chem.
2011 35, 1-27. b) R. J. Puddephatt, Angew. Chem. Int. Ed. 2002 41, 261-263. c) G. S.
Hill, R. J. Puddephatt, Organometallics 1998 17, 1478-1486.
[13] a) H. Eyring, J. Chem. Phys. 1935 , 107-115. b) J. Sandstrom, Dynamic Nuclear
, 10, 335-442.
,
,
,
,
3
Resonance Spectroscopy, Academic Press, 1983.
[14] (a) A. D. Becke, Phys. Rev. A 1988, 38, 3098-3100. (b) ADF 2017, SCM, Vrije
Universiteit, Amsterdam, The Netherlands, http://www.scm.com.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
This article is protected by copyright. All rights reserved.

10.1002/ejic.201900480
European Journal of Inorganic Chemistry
Key Topic
Platinum-Hydrogen Bonds
Graphical abstract
Graphical abstract text
Electron-rich organoplatinum complexes can form intramolecular or intermolecular
OH..Pt hydrogen bonds, but formation of hydroplatinum(IV) complexes requires a strong
acid such as HCl.
Keywords
Platinum, Hydrogen bond, Hydride ligands, Oxidative addition
This article is protected by copyright. All rights reserved.