Activation of acetyl ligands through hydrogen bonds: A new way to platinum(II) complexes bearing protonated iminoacetyl ligands

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pubs.acs.org/Organometallics

Activation of Acetyl Ligands through Hydrogen Bonds: A New Way

to Platinum(II) Complexes Bearing Protonated Iminoacetyl Ligands

Tim Kluge,^†Martin Bette,^†Tobias Ruﬀer,^‡Clemens Bruhn,^§Christoph Wagner,^†Dieter Strohl,^†

̈

Jurgen Schmidt,^⊥and Dirk Steinborn*^,†

̈

^†Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 2, D-06120 Halle, Germany

^‡Institute of Chemistry, Chemnitz University of Technology, Straße der Nationen 62, D-09111 Chemnitz, Germany

^§Institute of Chemistry, University of Kassel, Heinrich-Plett-Straße 40, D-34132 Kassel, Germany

^⊥Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany

S

* Supporting Information

ABSTRACT: The dinuclear platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-

Cl)₂] (1) reacted with 2-pyridyl-functionalized monoximes and with

dioximes in the presence of NaOMe to yield oxime−diacetyl

platinum(II) complexes [Pt(COMe)₂(2-pyCRNOH)] (R = H, 4a;

Me, 4b; Ph, 4c) and [Pt(COMe)₂(HONCR−CRNOH)] (R/R =

Me/Me, 5a; Ph/Ph, 5b; (CH₂)₄, 5c; NH₂/NH₂, 5d), respectively. The

strong intramolecular O−H···O hydrogen bonds in these complexes

give rise to an activation of the acetyl ligands for Schiﬀ-base type

reactions, thus forming with primary amines iminoacetyl platinum

complexes [Pt(COMe)(CMeNHR′)(2-pyCRNO)] (R/R′ = H/

Bn, 6a; Me/Bn, 6b; Ph/Bn, 6c; H/CH₂CH₂Ph, 6d; H/CH₂CHCH₂,

6e; Bn = benzyl) and [{Pt(CMeNHR′)₂(ONCR−CRNO)}₂]

(R/R = Me/Me, 7a−d; Ph/Ph, 8a−d; (CH₂)₄, 9a; R′ = Bn, a; CH₂CH₂Ph, b; CH₂CHCH₂, c; CH₂CH₂OH, d). The

intramolecular N−H···O hydrogen bonds in type 6−9 complexes make clear that protonated iminoacetyl ligands (i.e.,

aminocarbene ligands) and deprotoanted oxime ligands are present. These complexes could also be obtained in reactions of

[Pt(COMe)₂(NH₂R′)₂] (3) with pyridyl-functionalized monoximes and with dioximes where type 4/5 complexes were found to

be intermediates. In solution, the bis(iminoacetyl) complexes 7−9 were found to be present as dimers (as also 8a in the solid

state) with smaller amounts of monomers. The importance of hydrogen bonds for activation of acetyl ligands was further

evidenced by synthesis of complexes [Pt(COMe)₂(2-pyCHNOMe)] (10) and [Pt(COMe)₂(HONCMe−CMeNOMe)]

(11) bearing O-methylated oxime ligands and their reactivty toward amines. The hydrogen-bond activated acetyl and iminoacetyl

ligands in type 5, 7, and 8 complexes were found to undergo in CD₃OD solutions facile H/D exchange reactions resulting in

complexes bearing C(CD₃)O/C(CD₃)NDR′ ligands. The constitution of all complexes was unambiguously conﬁrmed

analytically, spectroscopically and in part by single-crystal X-ray diﬀraction analyses. Structural and NMR parameters as well as

DFT calculations gave evidence for relatively strong intramolecular hydrogen bonds.

acyl platinum(II) complexes. Thus, the “parent” platina-β-

diketone (R = Me, 1) reacted with bidentate N^∧N donors such

as 2,2′-bipyridine to form thermally extraordinarily stable

hydrido−diacetyl platinum(IV) complexes (Scheme 1, reaction

path A).³At elevated temperatures, they were found to undergo

a reductive C−H elimination and in the presence of bases a

reductive H−Cl elimination yielding mono- and diacetyl

platinum(II) complexes, respectively (Scheme 1, B/C).^3,4

Reactions of 1 with 2-pyridyl ketoximes and aldoximes

proceeded analogously, but the thermal decomposition of the

platinum(IV) intermediate complexes resulted in the formation

both of mono- and diacetyl platinum(II) complexes bearing 2-

pyridyl ket-/aldoxime ligands (Scheme 1, D/E).⁵In an isolated

1. INTRODUCTION

Metalla-β-diketones are formally derived from enol forms of

1,3-diketones by replacing the central CH group by a metal

fragment L_xM. Thus, they can be understood as hydroxy-

carbene complexes that are stabilized by intramolecular O−H···

O hydrogen bonds. Due to its electron count (16 VE; VE =

valence electrons) and its kinetically labile coordination sphere,

the dinuclear platina-β-diketones [Pt₂{(COR)₂H}₂(μ-Cl)₂]

exhibited a unique reactivity¹that is completely diﬀerent

from Lukehart’s metalla-β-diketones²such as [Re-

{(COMe)₂H}(CO)₄], which are electronically saturated (18

VE), kinetically inert complexes. A typical reactivity of platina-

β-diketones is a ligand-induced proton shift from the O−H···O

bridges, yielding hydrido−acyl platinum(IV) complexes

[PtHCl(COR)₂L₂], which can undergo reductive C−H and/

or H−Cl elimination reactions, resulting in the formation of

Received: August 13, 2013

Published: November 26, 2013

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Scheme 1. Reactivity of the Platina-β-diketone 1 toward N^∧N Donors

case, the diacetyl platinum complex 5a, bearing a dioxime

ligand, was obtained in the reaction of the 1D-coordination

polymeric diacetyl-bridged platinum(II) complex 2 with

dimethylglyoxime (H₂dmg) (Scheme 1, F/G).⁶

2. RESULTS AND DISCUSSION

2.1. Diacetyl Platinum(II) Complexes Bearing Mon-

oxime and Dioxime Ligands. 2.1.1. Synthesis and

Spectroscopic Characterization. At −78 °C, the dinuclear

platina-β-diketone 1 was reacted in methylene chloride with 2-

pyridyl-functionalized monoximes and with dioximes followed

by the addition of a base (NaOMe in MeOH), to yield diacetyl

platinum(II) complexes bearing monoxime (4a−c) and

dioxime ligands (5a−d), respectively (Scheme 2). Instead of

The concept of ligand reactivity comprises metal-assisted

transformations in which upon coordination to a metal the

reactivity of a substrate L is changed such that a reaction can

proceed that would otherwise not take place.⁷Thus, ligands

may oﬀer an altered reactivity that allows, for example, the

synthesis of organic molecules that are not accessible in a classic

way, whereby, as the case may be, metal coordination is

Scheme 2. Synthesis of Diacetyl Platinum(II) Complexes

Bearing Monoxime and Dioxime Ligands (4a−c, 5a−d)

8

required for stabilization (e.g., NHCMe₂). Furthermore,

transformations of this type also include, for example,

hydrolysis⁹and condensation reactions,¹⁰the activation of

coordinated nitriles¹¹and isocyanides¹²toward nucleophilic or

electrophilic attack, and template syntheses to form macrocyclic

structures.¹³

Whereas condensation reactions of aldehydes and ketones

are frequently known and, in general, readily proceed, those of

acyl ligands have not been often reported yet. Thus, for

example, acyl tin compounds were found to react with primary

amines in Schiﬀ-base type reactions, yielding iminoacyl tin

complexes (e.g., [SnBu₃(CMeNBu)]¹⁴). Analogously, acyl

germanium complexes underwent with O-benzylhydroxylamine

and N,N-dimethylhydrazine proton-catalyzed condensation

reactions.¹⁵In the case of platinum, such reactions are not

known until now, but iminoacyl platinum complexes are

accessible via migratory insertion of an isonitrile into a Pt−C

bond,^16,17as also for other metals.¹⁸

Here, we report on reactions of the platina-β-diketone 1 and

of bis(amine)−diacetyl platinum complexes [Pt-

(COMe)₂(NH₂R)₂] (3) with 2-pyridyl-functionalized mon-

oximes (2-pyCRNOH), which are known for a bidentate

κN,κN′ coordination¹⁹and with dioximes (HONCR−CR

NOH). In the resulting oxime−diacetyl platinum(II) com-

plexes, the oxime ligands act as H donor and the acetyl ligands

as H acceptor for strong intramolecular O−H···O hydrogen

bonds. This gives rise to an activation of the acetyl ligands that

opens up in reactions with primary amines a new synthetic

route for iminoacetyl platinum(II) complexes.

NaOMe in MeOH, NaOH in water or NEt₃can be used as

base. The complexes were isolated in 35−75% yield. They are

stable in air over weeks. The monoxime complexes 4a−c are

orange-colored both in the solid state and in solution

(CH₂Cl₂). In methylene chloride, the dioxime complexes 5a−

d are orange-colored, whereas in the solid state, except for 5d,

they are dark blue (5a/c) and dark green (5b), likely due to

closed-shell Pt···Pt (d⁸···d⁸) interactions.^6,20The constitution of

all complexes was unambiguously identiﬁed analytically, by

NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopy, and in the case of

the monoxime complexes 4a−c also by single-crystal X-ray

diﬀraction analyses.

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Table 1. Selected NMR Spectroscopic Parameters (δ in ppm, J in Hz; in CDCl₃) of the Diacetyl Platinum(II) Complexes

a

[Pt(COMe)₂(N^∧N)] (4a−c, 5a−d, 10, 11)

δ_H(³J_Pt,H

)

δ_H(³J_Pt,H

COCH₃

)

δ_C(²J_Pt,C

)

δ_C(¹J_Pt,C

CO

)

δ_Pt

N^∧N

NOH

COCH₃

4a

4b

4c

5a

5b

5c

5d

10

11

2-pyCHNOH

15.8 (32)

15.5 (32)

15.9 (32)

14.2 (22)

14.6 (26)

14.1

2.27 (33.0)/2.53 (20.6)

2.27 (32.8)/2.52 (21.3)

2.31 (31.6)/2.58 (18.5)

2.39 (24.9)

41.6 (353.7)/44.6 (319.5)

41.7 (348.7)/44.8 (321.6)

41.6 (344.1)/44.8 (319.8)

42.9 (308.4)

229.8 (1335)/233.3 (1284)

230.6 (1334)/234.0 (1274)

231.1 (1332)/233.8 (1277)

236.8 (1324)

−3430

−3421

−3428

−3481

−3487

−3422

−3411

−3433

−3533

2-pyCMeNOH

2-pyCPhNOH

HONCMe−CMeNOH

HONCPh−CPhNOH

1,2-Cy(NOH)₂

2.55 (23.4)

42.9 (315.4)

237.0 (1325)

2.37 (25.7)

42.9 (300.7)

237.0 (1319)

b

HONC(NH₂)−C(NH₂)NOH

2-pyCHNOMe

12.5

2.30 (23.5)

43.0 (340.3)

232.7 (1342)

2.24 (26.8), 2.33 (23.4)

2.20 (33.0), 2.50 (18.5)

41.9 (399.2), 44.8 (362.5)

40.0 (362.1), 44.7 (304.3)

223.3 (1308), 228.0 (1260)

H(Me)dmg

15.6 (35)

227.6 (1381), 231.2 (1271)

a

b

For complexes 4 the NMR parameters of the acetyl ligands trans to the N_pyand the N_NOHatoms are given separated by a slash. Measured in

acetone-d₆.

Table 2. Selected NMR Spectroscopic Parameters (δ in ppm, J in Hz; in CDCl₃) of the Acetyl−Iminoacetyl Platinum(II)

Complexes [Pt(COMe)(CMeNHR′)(2-pyCRNO)] (6a−e)

δ_H(³J_Pt,H

)

δ_H(³J_Pt,H

)

δ_H(³J_Pt,H

)

δ_C(²J_Pt,C

)

δ_C(²J_Pt,C

)

δ_C(¹J_Pt,C

)

δ_C(¹J_Pt,C

)

δ_Pt

C(CH₃)

R

R′

NOH

COCH₃

NHR′

COCH₃

NHR′

COCH₃

NHR′

6a

6b

6c

6d

6e

H

Bn

15.6 (78)

16.2 (73)

15.9 (76)

15.2 (78)

15.2 (71)

2.47 (16.0)

2.46 (18.1)

2.51 (14.0)

2.42

2.20 (57.4)

2.17 (56.1)

2.17 (56.4)

2.00 (55.2)

2.16 (55.4)

44.5 (247.7)

44.7 (249.0)

44.7 (247.7)

44.5 (247.6)

44.5 (246.4)

29.3 (159.0)

29.1 (157.2)

29.2 (159.0)

28.6 (155.3)

28.8 (158.7)

236.6 (1133)

237.9

196.3 (1358)

196.5

−3384

−3391

−3389

−3391

−3385

Me

Ph

H

237.2 (1124)

236.2 (1140)

236.2 (1133)

197.4 (1337)

195.3 (1357)

196.1 (1351)

CH₂CH₂Ph

H

CH₂CHCH₂

2.47 (14.7)

Characteristic H, ¹³C, and ¹⁹⁵Pt NMR spectroscopic data of

the diacetyl platinum(II) complexes with pyridyl-functionalized

monoxime (4a−c) and dioxime ligands (5a−d) are compiled in

Table 1. The spectra conﬁrm the identities of the complexes; all

signals are found in the expected chemical shift ranges with

correct intensities in the proton NMR spectra. Upon

coordination, in the monoxime complexes 4a−c, the oxime

protons (NOH) exert a strong low-ﬁeld shift by about 6

ppm, resulting in δ_NOHvalues of 15.5−15.9 ppm (4a−c). This

is a strong indication of the formation of (intramolecular) O−

H···O hydrogen bonds because the coordinated induced shifts

(CIS) upon N coordination of an oxime (without hydrogen

bond formation) in other platinum(II) complexes are much

smaller (e.g., CIS_NOHin [Pt(C₆H₄CMeNOH-κC,κN)-

(DMSO)Cl]: 1.3 ppm²¹). The oxime protons in the dioxime

complexes 5a−c were found at 14.1−14.6 ppm, whereby for

solubility reasons and/or H/D exchange reactions the CIS

could not be determined. Nevertheless, both in complexes 4a−

c and in 5a/b the oxime protons show ³J_Pt,Hcouplings (22−32

Hz), thus showing unambiguously the N coordination.

Whereas the two acetyl ligands in the dioxime−diacetyl

complexes 5a−d are chemically equivalent, this is not the case

for the monoxime−diacetyl complexes 4a−c. With complexes

4a/b as examples, in NOESY and, additionally, in 2D NMR

experiments (HMQC, HMBC) a correlation of the acetyl

protons (δ_H= 2.53/2.52) with H⁶of the pyridine rings allowed

an assignment of the acetyl ligands trans to N_pyand N_NOH

atoms (Table 1). This assignment is in accord with the

chemical shifts of the acetyl ligands in acetyl−iminoacetyl

complexes 6a−d (vide infra, Table 2). The platinum chemical

shifts (−3411 to −3487 ppm, Table 1) of the oxime−diacetyl

complexes (4/5) are in the range of those of other diacetyl

platinum(II) complexes with nitrogen coligands.^6,23,24

1

As expected, in deuterated methanol the hydrogen-bonded

protons in the oxime complexes (4/5) are replaced by

deuterium. Unexpectedly, in the dioxime complexes 5a/b,

additionally, the methyl protons of the acetyl ligands are

exchanged by deuterium, as proven by the disappearance of the

COCH₃signals in the ¹H NMR spectra in CD₃OD and also by

2

the detection of the requisite CD₃signals in the H NMR

The diaminoglyoxime ligand (H₂dag) in complex 5d may

coordinate through the oxime N atoms or through the amino N

atoms. The CIS of the oxime and the amine protons of 3.5 and

1.5 ppm (measured in acetone for solubility reasons),

respectively, might indicate that the oxime N atoms are

coordinated to Pt and N−O−H···O hydrogen bonds are

present. Such a coordination of the H₂dag ligand was also

found in other complexes, for example in [Pt(Hdag)₂].²²

Furthermore, this is also in accord with DFT calculations of the

two possible conﬁguration isomers of 5d, where that with the

H₂dag ligand coordinated through the NH₂groups was found

to be 23.5 kcal/mol higher in standard Gibbs free energy (with

consideration of solvent eﬀects, acetone) than the one with the

ligand coordinated through the NOH groups.

spectra in CHCl₃at 2.47/2.32 ppm. At room temperature, this

H/D exchange is deﬁnitely complete after one day, with

(roughly) estimated half-lifes of about 1 (5a) and 2 h (5b). Due

to a slow decomposition of the monoxime complex 4a in

CD₃OD, no clear conclusion regarding the H/D exchange can

be drawn in this case.

2.1.2. Structural Characterization. From the complexes

[Pt(COMe)₂(2-pyCRNOH)] (R = H, 4a; Me, 4b; Ph, 4c)

single crystals suitable for X-ray diﬀraction measurements could

be grown. The complexes were found to crystallize in isolated

molecules. The asymmetric unit of crystals of complex 4a

contains two symmetry-independent molecules that are

structurally similar. The molecular structures of the complexes

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4a−c are shown in Figures 1−3; selected structural data are

given in the respective ﬁgure captions.

Figure 3. Molecular structure of [Pt(COMe)₂(2-pyCPhNOH)]

(4c, displacement ellipsoids at 30% probability). Selected distances

(Å) and angles (deg): Pt−C1 1.974(6), Pt−C3 1.980(6), Pt−N1

2.104(5), Pt−N2 2.121(5), C1−O1 1.201(7), C3−O2 1.240(8), N1−

O3 1.364(6), C1−Pt−N1 170.8(2), C3−Pt−N2 170.2(2), O3···O2

2.540(7), O3−H 0.77, O2···H 1.81, O3−H···O2 160.

Figure 1. Molecular structure of one of the two symmetry-

independent molecules of [Pt(COMe)₂(2-pyCHNOH)] (4a,

displacement ellipsoids at 30% probability). Selected distances (Å)

and angles (deg); the values for the two symmetry-independent

molecules are given separated by a slash: Pt−C1 1.984(4)/1.991(4),

Pt−C3 1.977(3)/1.986(4), Pt−N1 2.105(3)/2.116(3), Pt−N2

2.130(3)/2.148(3), C1−O1 1.227(5)/1.215(5), C3−O2 1.242(5)/

1.232(5), N1−O3 1.361(3)/1.360(4), C1−Pt−N1 172.6(1)/

173.4(1), C3−Pt−N2 170.8(1)/170.5(1), O3···O2 2.548(4)/

2.541(4).

upper quartile 1.385/1.408 Å; n = 27, n = number of

observations²⁸), as also supported by DFT calculations, see

Section 2.4.2. Furthermore, the formation of hydrogen bonds

gives rise to a signiﬁcant elongation of the C3O2 bonds

(1.232(5)−1.242(5) Å) compared to the C1O1 bond

lengths of the acetyl ligands that are not involved in hydrogen

bonds (1.201(7)−1.227(5) Å); see also Section 2.4.2. The Pt−

C bond lengths (1.974(6)−1.991(4) Å) are within the range of

platinum(II) complexes with acyl ligands trans to N donor

ligands (Pt−C: median 1.997; lower/upper quartile 1.981/

2.010 Å; n = 31²⁸).

In crystals of 4a and 4b, intermolecular interactions were

found: In 4b the pyridine rings are π stacked²⁹with a centroid−

centroid distance of 3.467(2) Å and an angle between the

centroid−centroid vector and the normal to the plane of 13.8°.

Furthermore, in crystals of 4a and 4b the ﬁve-membered

PtNCCN rings are stacked with centroid−centroid distances

between 3.457(2) and 3.592(2) Å and angles between the

centroid−centroid vectors and the normals to the planes

between 12.2° and 17.8°. In no case were closed shell Pt···Pt

(d⁸···d⁸) interactions observed.²⁰

2.2. Acetyl−Iminoacetyl Platinum(II) Complexes Bear-

ing Monoxime Ligands. 2.2.1. Synthesis and Spectroscopic

Characterization. Previous investigations showed that the

amine ligands in complexes [Pt(COMe)₂(NH₂R′)₂] (3a−c)

are only weakly coordinated, and, thus, they are easily subject to

ligand substitution reactions.^23,24Unexpectedly, the bis-

(amine)−diacetyl platinum complexes 3a−c were found to

react with pyridyl-functionalized monoximes not only under

ligand substitution but, additionally, under conversion of one of

the two acetyl ligands into a protonated iminoacetyl ligand

(Pt−CMeO → Pt−CMeNHR′), thus yielding complexes

of the type [Pt(COMe)(CMeNHR′)(2-pyCRNO)] (6a−

e, Scheme 3, reaction path A). These complexes were isolated

in moderate to good yields (35−80%). The yellow complexes

were fully characterized analytically, by NMR (¹H, ¹³C, ¹⁹⁵Pt)

and IR spectroscopy, and by single-crystal X-ray diﬀraction

analyses (6a, 6b·H₂O, 6e).

Figure 2. Molecular structure of [Pt(COMe)₂(2-pyCMeNOH)]

(4b, displacement ellipsoids at 30% probability). Selected distances

(Å) and angles (deg): Pt−C1 1.980(3), Pt−C3 1.978(4), Pt−N1

2.104(3), Pt−N2 2.116(3), C1−O1 1.214(5), C3−O2 1.237(5), N1−

O3 1.368(4), C1−Pt−N1 171.1(1), C3−Pt−N2 168.9(1), O3···O2

2.542(4), O3−H 0.84, O2···H 1.72, O3−H···O2 167.

In the three complexes, the platinum centers are square-

planar coordinated (sum of angles around Pt: 360.0/360.1°,²⁵

4a; 360.5°, 4b; 359.9°, 4c) by two nitrogen atoms of the

bidentate 2-pyridyl oxime ligand and by two carbon atoms of

the acetyl ligands in mutual cis position. As mostly found in

acetyl platinum complexes,^4,6,23,24one of the two acetyl ligands

is nearly perpendicular to the complex plane (interplanar angle:

86.7/86.1°, 4a; 82.0°, 4b; 85.9°, 4c). In contrast, unusually, the

other acetyl ligand lies in the complex plane (2.7/0.6°, 4a;

16.0°, 4b; 1.9°, 4c), which is forced by the formation of an

intramolecular O−H···O hydrogen bond to the oxime group

(graph set:²⁶S(6)). The O3···O2 distances (2.548(4)/2.541(4)

Å, 4a; 2.542(4) Å, 4b; 2.540(7) Å, 4c) and O3−H···O2 angles

(167°, 4b; 160°, 4c; in 4b/c the H atoms were located in the

electron density map) are an indication for moderate to strong

hydrogen bonds.²⁷In addition, the N1−O3 bonds (1.360(4)−

1.368(4) Å) are shorter than those in oxime platinum(II)

complexes without hydrogen bonds (median 1.393; lower/

To prove whether the previously described type 4 complexes

(obtained from reactions of the platina-β-diketone 1 with 2-

pyCRNOH/NaOMe) are intermediates in the formation of

the iminoacetyl complexes 6, the complexes 4a−c were reacted

with primary amines (Scheme 3, B). In all cases the iminoacetyl

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to about 50% in 1 h), which points to an H/D exchange, but

additionally, a decomposition of the complex took place.

2.2.2. Structural Characterization and DFT Calculations.

The structures of the complexes [Pt(COMe)(CMeNHR′)-

(2-pyCRNO)] (R/R′ = H/Bn, 6a; Me/Bn, 6b·H₂O; H/

CH₂CHCH₂, 6e), obtained by X-ray diﬀraction measure-

ments, are shown in Figure 4−6. Selected structural parameters

Scheme 3. Synthetic Routes to Acetyl−Iminoacetyl

Platinum(II) Complexes Bearing Monoxime Ligands (6a−e)

complexes 6a−e were obtained in 30 to 75% yields, which

points out that also in reactions according to path A (Scheme

3) type 4 complexes were formed ﬁrst followed by a Schiﬀ-base

type reaction yielding complexes 6. In contrast to type B

reactions described above, complex 4a showed no reactivity

against the less basic aniline and adenine.

Figure 4. Molecular structure of [Pt(COMe)(CMeNHBn)(2-

pyCHNO)] (6a, displacement ellipsoids at 30% probability).

Selected distances (Å) and angles (deg): Pt−C1 1.992(4), Pt−C3

2.007(4), Pt−N1 2.137(3), Pt−N2 2.105(3), C1−O1 1.223(5), C3−

N3 1.298(6), N1−O2 1.328(4), C1−Pt−N1 172.0(1), C3−Pt−N2

174.3(1), N3···O2 2.636(5), N3−H 0.83, O2···H 1.84, N3−H···O2

162.

1

Selected H, ¹³C, and ¹⁹⁵Pt NMR spectroscopic data of the

acetyl−iminoacetyl platinum(II) complexes 6a−e are given in

Table 2. The chemical shifts and coupling constants as well as

the signal intensities in the ¹H NMR spectra are fully consistent

with the constitution of the complexes given in Scheme 3. The

presence of strong intramolecular N−H···O hydrogen bonds is

veriﬁed by low-ﬁeld-shifted broad signals (15.2−16.2 ppm) in

the proton NMR spectra. COSY experiments with complexes

6a, 6d, and 6e as examples exhibited a coupling of the

hydrogen-bonded proton to the NCH₂group (δ_H= 3.68−

4.81), thus pointing to the presence of a deprotonated oxime

ligand and a protonated iminoacetyl ligand, which is further

supported by single-crystal X-ray diﬀraction analyses and by

are given in the respective ﬁgure captions. The platinum atoms

are square-planar coordinated (sum of angles around Pt:

360.0°, 6a; 360.3°, 6b; 360.2°, 6e) by the bidentate 2-pyridyl-

functionalized oxime ligand as well as one acetyl and one

iminoacetyl ligand (conﬁguration index: SP-4-3). The oxime

and the iminoacetyl ligands form intramolecular N3−H···O2

3

DFT calculations (vide infra). The relatively large J_Pt,H

coupling constants (71−78 Hz) (compared with those in

type 4 complexes at 32 Hz) might also be attributed to this fact.

Furthermore, two-dimensional NMR experiments (HMBC)

showing a correlation between these NCH₂protons and the

iminoacetyl C atoms allowed distinguishing between these C

atoms (195.3−197.4 ppm) and those of the acetyl ligands

(236.2−237.9 ppm). In the same way, the methyl C atoms were

assigned to the iminoacetyl and acetyl ligands (Table 2). In all

cases the signals of the acetyl ligands are more low-ﬁeld shifted

3

than those of the iminoacetyl ligands. Furthermore, the J_Pt,H

coupling constants (55.2−57.4 Hz vs 14.0−18.1 Hz) of the

methyl protons of the iminoacetyl ligands proved to be much

higher than those of the acetyl ligands. The same holds for the

¹J_Pt,Ccoupling constants (1337−1358 Hz vs 1124−1140 Hz).

2

On the other hand, J_Pt,Ccouplings showed the opposite

Figure 5. Structure of [Pt(COMe)(CMeNHBn)(2-pyCMe

NO)]·H₂O in crystals of 6b·H₂O (displacement ellipsoids at 30%

probability). Selected distances (Å) and angles (deg): Pt−C1

1.994(4), Pt−C3 2.000(4), Pt−N1 2.120(3), Pt−N2 2.082(3), C1−

O1 1.212(6), C3−N3 1.294(5), N1−O2 1.327(4), C1−Pt−N1

170.3(2), C3−Pt−N2 173.6(2), N3···O2 2.646(5), N3−H 0.83,

O2···H 1.86, N3−H···O2 157, O3···O2 2.786(5), O3−H 0.90, O2···H

1.89, O3−H···O2 175, O3···O1′ 2.817(7), O3−H 0.84, O1′···H 1.99,

O3−H···O1′ 169.

(155.3−159.0 Hz vs 246.4−249.0 Hz). The platinum shifts δ_Pt

(−3384 to −3391 ppm) are similar to those of the diacetyl

platinum(II) complexes 4 and are in a range typical for organo

platinum(II) complexes.^6,23,24

As exempliﬁed by complex 6a, in deuterated methanol an

immediate H/D exchange of the hydrogen-bonded proton was

observed, as expected. Furthermore, the intensity of the signal

of the iminoacetyl protons (C(CH₃)NDBn) decreased (up

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(1.360(4)−1.368(4) Å) and in platinum(II) complexes with

(neutral) oxime ligands that are not involved in hydrogen

bonds (median 1.393 Å; lower/upper quartile 1.385/1.408 Å; n

= 27²⁸). Both the elongation at the H donor site (N−H) and

the shortening at the H acceptor site (N−O) were also

observed in DFT calculations (see Section 2.4.2).

Other structural parameters are similar to those of complexes

4a−c. Within the 3σ criterion, the Pt−C bonds of the acetyl

(1.992(4)−2.01(1) Å) and the protonated iminoacetyl ligands

(2.000(4)−2.03(1) Å) are of the same length. Furthermore, as

expected, the acetyl ligands lie nearly perpendicular to the

complex planes (interplanar angles: 82.9°, 6a; 84.8°, 6b; 85.9°,

6e).

Crystals of 6a and 6e consist of molecules without unusual

intermolecular interactions. In crystals of 6b·H₂O the water

molecules act as H donors in intermolecular O−H···O

hydrogen bonds (graph set:²⁶C²₂(8)). H acceptors are, on

one side, O2 atoms of the deprotonated oxime ligands (O3···

O2 2.786(5) Å, O3−H···O2 175°) and, on the other, O1′

atoms of the acetyl ligands (O3···O1′ 2.817(7) Å, O3−H···O1′

169°); see Figure 5.

To further conﬁrm the connectivity of the intramolecular

(asymmetric) hydrogen bonds (N−H···O vs O−H···N) in type

6 complexes [Pt(COMe)(CMeNHR′)(2-pyCRNO)],

high-level DFT calculations (details see Experimental Section)

were performed with a type 6 complex, but for reduction of

computational expense associated with substituents R/R′ =

Me/Me (6f*³¹). Despite the diﬀerent substituents R/R′, the

calculated and experimentally found (6a, 6b, 6e) values of bond

lengths and angles are in a good agreement, especially the

parameters of the hydrogen bonds. In accordance with the

experimental ﬁndings, the thermodynamically stable conﬁg-

uration of 6f*, both in the gas phase and with consideration of

solvent eﬀects (CH₂Cl₂), is that with an intramolecular N−H···

O hydrogen bond. We failed to localize an equilibrium

structure having the opposite connectivity (O−H···N). Relaxed

potential energy surface scans (with consideration of solvent

eﬀects) indicate that this structure is about 7.2 kcal/mol higher

in energy than the equilibrium structure discussed above; for

details see the Supporting Information.

Figure 6. Molecular structure of [Pt(COMe)(CMeNHCH₂CH

CH₂)(2-pyCHNO)] (6e, displacement ellipsoids at 30% proba-

bility). Selected distances (Å) and angles (deg): Pt−C1 2.01(1), Pt−

C3 2.03(1), Pt−N1 2.131(8), Pt−N2 2.122(9), C1−O1 1.20(1), C3−

N3 1.31(1), N1−O2 1.31(1), C1−Pt−N1 171.4(4), C3−Pt−N2

173.8(4), N3···O2 2.65(1).

hydrogen bonds. In complexes 6a and 6b, the hydrogen-

bonded protons could be located in the electron density maps,

showing asymmetrical hydrogen bonds. Thus, protonated

iminoacetyl ligands (i.e., aminocarbene ligands) and deproto-

nated oxime ligands are present, which is in accordance with

NMR measurements and DFT calculations.

Due to the intramolecular N3−H···O2 hydrogen bonds

(graph set:²⁶S(6)) the protonated iminoacetyl ligands lie

nearly in the complex plane (interplanar angles: 6.6°, 6a; 20.2°,

6b; 11.1°, 6e). The N3···O2 distances (2.636(5) Å, 6a;

2.646(5) Å, 6b; 2.65(1) Å, 6e) indicate moderate hydrogen

bonds.²⁷The C3N3 bond lengths (1.294(5)−1.31(1) Å) are

at the lower end of the range of other platinum(II) complexes

bearing protonated iminoacyl ligands in which the NH protons

are not involved in hydrogen bonds (1.31(1)−1.346(5) Å; n =

6^17,30), but longer than those in platinum complexes bearing

(nonprotonated) iminoacyl ligands (median 1.276 Å; lower/

upper quartile 1.261/1.288 Å; n = 14²⁸). Furthermore, the

deprotonation of the oxime ligands gives rise to a strong

shortening of the N1−O2 bonds (1.31(1)−1.328(4) Å) in

comparison to the respective bonds both in type 4 complexes

Scheme 4. Synthetic Routes to Dinuclear (7−9) and Mononuclear (7′−9′) Bis(iminoacetyl) Platinum(II) Complexes Bearing

a

Dioxime Ligands

a

The assignment of the signal sets (S1/S2) of the dinuclear complexes may be reversed (see text).

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Table 3. Selected NMR (δ in ppm, J in Hz; in CDCl₃/CD₂Cl₂) Spectroscopic Parameters of the Complexes [{Pt(CMe

NHR′)₂(N^∧N)}₂] (N^∧N = dmg, 7a−d; dpg, 8a−c; 1,2-Cy(NO)₂, 9a)

a

δ_H(³J_Pt,H

)

δ_H(³J_Pt,H

)

δ_C(²J_Pt,C

)

δ_C(¹J_Pt,C

)

δ_Pt

R′

NH S2/S1

C(CH₃)NHR′ S1/S2

7a

7b

7c

7d

8a

8b

8c

8d

9a

Bn

13.6 (107)/17.4 (62)

12.5 (105)/17.0 (61)

1.39 (44.3)/2.91 (35.1)

1.42 (43.4)/2.77 (36.1)

1.91(45.0)/2.82 (36.1)

29.6 (118)/35.5 (56)

28.6/35.3

195.4 (1098)/222.8 (1178)

194.4/222.6

−3534

−3539

−3552

−3521

−3515

−3507

CH₂CH₂Ph

CH₂CHCH₂

CH₂CH₂OH

Bn

12.8/17.0

29.8/35.2

e

195.1/221.8

b

c

d

2.11(44.0)/2.69 (36.8)

199.7/225.2

12.5 (110)/17.3 (69)

11.9 (111)/16.9 (73)

1.38 (43.6)/2.72 (35.5)

1.39 (43.6)/2.63 (33.6)

1.89 (43.6)/2.69 (34.1)

29.5/35.2

28.5/34.7

196.8/223.4 (1271)

194.5/221.9

CH₂CH₂Ph

CH₂CHCH₂

CH₂CH₂OH

Bn

12.1/17.1

29.5 (108)/34.5 (58)

e

195.3 (1088)/222.6 (1208)

c

d

e

2.21 (44.6) 2.76 (36.9)

1.42 (45.6)/2.93 (36.2)

13.7 (120)/17.3

29.7/35.7

195.6/222.8

a

b

c

Due to poor solubility Pt,C couplings could not be observed in all cases. For solubility reasons measured in CD₃OD. NH signals were not

d

e

observed due to H/D exchange. Due to H/D exchange, CH₃signals could only be observed in freshly prepared solutions. CD₃and C(CD₃)ND

signals could not be observed due to bad signal-to-noise ratio.

2.3. Bis(iminoacetyl) Platinum(II) Complexes Bearing

Dioxime Ligands. 2.3.1. Synthesis and Spectroscopic

Characterization of the Dinuclear Complexes. The bis-

(amine)−diacetyl platinum(II) complexes 3a−c were re-

actedanalogously to the synthesis of the platinum complexes

6a−e, bearing 2-pyridyl-functionalized monoxime ligands

with dioximes, yielding dinuclear bis(iminoacetyl) platinum(II)

complexes of the type [{Pt(CMeNHR′)₂(ONCR−CR

NO)}₂] (R/R = Me/Me, 7a−d, Ph/Ph, 8a−d, (CH₂)₄, 9a)

(Scheme 4, reaction path A). Although two equivalents of

primary amines NH₂R′ were set free in the initial ligand

substitution reaction, to facilitate the subsequent formation of

two protonated iminoacetyl ligands (Pt−CMeO → Pt−

CMeNHR′), the addition of about two further equivalents of

NH₂R′ is advantageous. The complexes 7−9 were isolated as

yellow powders and microcrystalline substances, respectively, in

moderate to good yields (35−90%) and fully characterized

analytically, by NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopy, as

well as by single-crystal X-ray diﬀraction analysis (8a·2CH₂Cl₂).

In solution monomer−dimer equilibria were established

(Scheme 4, C); see Section 2.3.3.

Reactions of the dioxime−diacetyl complexes 5a−c

(obtained from reactions of the platina-β-diketone 1 with

HONCR−CRNOH/NaOMe) with four equivalents of a

primary amine NH₂R′ resulted also in the formation of the

bis(iminoacetyl) complexes 7−9 (Scheme 4, B), thus indicating

that type 5 complexes are intermediates in reaction A.

Furthermore, reaction path B is superior to A because the

requisite bis(amine)−diacetyl complexes 3 do not have to be

synthesized as precursor complex. Moreover, complexes 7d/8d

are only accessible via route B because the precursor complex 3

bearing two ethanolamine ligands could not be synthesized.

Notably, the synthesis of bis(iminoacetyl) platinum(II)

complexes bearing diaminoglyoxime ligands (HONC-

(NH₂)−C(NH₂)NOH) failed in both routes A and B: Via

route A only complex 5d was obtained and, moreover, 5d was

found not to react with primary amines (route B).

which ones to set S2 (Scheme 4). With the assumption that the

intramolecular N−H···O hydrogen bond is stronger than the

hydrogen bonds bridging the mononuclear platinum units, we

tentatively assigned the more low-ﬁeld-shifted signals (δ_H

=

16.9−17.4) to the protons of the intramolecular H bonds (S1)

and the other ones (δ_H= 11.9−13.7) to the bridging H bonds

(S2). Nevertheless, this assumption remains to be speculative.

The ³J_Pt,Hcoupling constants for the hydrogen-bonded protons

at higher ﬁelds are much greater (105−120 Hz) than the

couplings of the signals at lower ﬁelds (61−73 Hz). On the

basis of the assignment of the N−H···O protons, the 2D NMR

experiments made clear that all other signals of the iminoacetyl

ligand assigned to the signal set S1 are more high-ﬁeld shifted

than those of signal set S2. The ³J_Pt,Hcouplings (Pt−C−C−H)

of signal set S2 are slightly smaller than those of S1 (33.6−36.9

Hz vs 43.4−45.6 Hz). As expected, in dinuclear complexes 7a,

8a, and 9a the NCH₂protons show an AB system (as also for

complexes 7b−d and 8b/c, but with additional couplings to

other protons) with typical geminal H,H couplings (13.1−15.2

Hz). At lower temperature (−30 °C), an additional splitting

could be observed due to coupling to the NH protons, which

was further conﬁrmed (7a/8a) by COSY experiments.

As shown exemplarily for 7a/8a, as for the diacetyl−dioxime

complexes 5a/b, in deuterated methanol, additionally to a fast

H/D exchange of the hydrogen-bonded protons, an H/D

exchange of the protons of the methyl group of the iminoacetyl

ligand (CH₃→ CD₃) took place. For this H/D exchange a half-

life of about one hour was estimated.

2.3.2. Structure of [{Pt(CMeNHBn)₂(ONCPh−CPh

NO)}₂] (8a). From CH₂Cl₂/diethyl ether solutions of [{Pt-

(CMeNHBn)₂(ONCPh−CPhNO)}₂] (8a) single crys-

tals of 8a·2CH₂Cl₂suitable for X-ray measurements were

obtained. No unusual interactions between the platinum

complex 8a and solvate molecules were observed. The

dinuclear complex 8a exhibits crystallographically imposed

inversion symmetry, and its molecular structure is shown in

Figure 7 with selected structural parameters given in the ﬁgure

caption. The platinum centers are square-planar coordinated

(sum of angles around Pt: 360.3°) each by a doubly

deprotonated bidentate diphenylglyoxime ligand and by two

protonated iminoacetyl ligands (the hydrogen-bonded protons

could be located in the electron density map). The terminal

protonated iminoacetyl ligands are involved in intramolecular,

moderate N3−H···O2 hydrogen bonds (N3··O2 2.547(6) Å;

N3−H··O2 166°; graph set:²⁶S(6)). Due to this, the planes of

Characteristic NMR spectroscopic data of the dinuclear

1

complexes 7−9 are shown in Table 3. In H and ¹³C NMR

spectra two sets of signals (S1, S2) were found both for the

iminoacetyl ligands and for the dioxime ligands (Scheme 4).

This gives proof for a dinuclear structure in solution having (on

the NMR time scale) inversion symmetry. Two-dimensional

NMR experiments (COSY, HMQC, HMBC) made clear which

H and C atoms of the iminoacetyl ligands belong to set S1 and

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of the mononuclear complexes present in solution, not all

NMR parameters could be obtained. In general, the ¹H and ¹³

C

signals of the monomeric complexes lie in between the

corresponding signals of the sets S1 and S2 of the dinuclear

complexes. In complexes 7c/d, 8d, and 9a smaller signals

indicate a content of monomer of <5%, but due to signal

overlapping, they could not be unambiguously identiﬁed.

As exempliﬁed with complex 8a, an EXSY (exchange

spectroscopy) spectrum showed cross-peaks between the

C(CH₃)NHBn signals of the monomer and the dimer,

thus giving proof of a monomer−dimer equilibrium.

Furthermore, the portion of the monomeric complexes

increases in CDCl₃solution at higher temperatures (27 °C,

25% of the monomer 8′a; 50 °C, 36%) and by dilution (10, 25,

40% of the monomer 8′a at a concentration of about 30, 7, 2

mg/mL). In addition, the portion of the monomer is

dependent on the substitution pattern of the imine (R′) and

the dioxime (R) with the tendency that less bulky groups give

rise to smaller monomer concentrations (Table 4).

High-resolution ESI mass spectra in methylene chloride of

complexes 7a/8a−d showed peaks of the mono- and dinuclear

complexes as well as, additionally, smaller amounts of a

trinuclear structure that was likely formed due to the ionization

process. Moreover, in CD₃OD solution, the ESI mass spectrum

of complex 7a showed an H/D exchange both of the hydrogen-

bonded protons and of the CH₃protons of the iminoacetyl

ligands.

2.4. Investigations on the Inﬂuence of the Hydrogen

Bond on Activation of Acetyl Ligands. 2.4.1. Synthesis

and Characterization of Diacetyl Platinum Complexes

Bearing O-Methylated Oxime Ligands. To clarify that

activation of acetyl ligands for a Schiﬀ-base reaction has the

origin in the hydrogen bonds, O-methylated oxime ligands were

taken into account. Thus, the methylated monoxime 2-pyCH

NOMe as well as the mono- and dimethylated dioximes

H(Me)dmg and Me₂dmg, respectively, were reacted with the

platina-β-diketone 1 in an alkaline medium (NaOMe).

Reactions with 2-pyCHNOMe and H(Me)dmg resulted in

the formation of orange-colored diacetyl platinum(II) com-

plexes 10 and 11 in good yields (80/60%, Scheme 5, A/B). On

the other hand, the doubly O-methylated dioxime Me₂dmg did

not react with the platina-β-diketone 1 in the presence of

NaOMe; instead, 1 reacted with NaOMe, yielding the 1D-

coordination polymer [{Pt(COMe)₂}_n] (2), as known,⁶

whereby Me₂dmg remained unchanged (Scheme 5, C). The

reason might be that the doubly methylated dioxime, which is

incapable of forming any hydrogen bond, is too weakly

coordinated to form the desired complex.

Figure 7. Structure of [{Pt(CMeNHBn)₂(HONCPh−CPh

NO)}₂] (8a) in crystals of 8a·2CH₂Cl₂(displacement ellipsoids at

30% probability). H atoms except those of the hydrogen bonds are

omitted for clarity. Selected distances (Å) and angles (deg): Pt−C1

2.002(5), Pt−C3 1.985(4), Pt−N1 2.075(4), Pt−N2 2.066(3), C1−

N3 1.298(6), C3−N4 1.289(6), N1−O1 1.311(5), N2−O2 1.338(5),

C1−Pt−N1 173.1(2), C3−Pt−N2 169.0(2), N3···O2 2.547(6), N3−

H 1.07, O2···H 1.49, N3−H···O2 166, N4···O1′ 2.666(6), N4−H

1.02, O1′···H 1.66, N4−H···O1′ 169.

these iminoacetyl ligands lie in the complex planes (interplanar

angle 15.2°), quite analogously to complexes 6. The other

protonated iminoacetyl ligands form intermolecular N4−H···

O1′ hydrogen bonds (graph set:²⁶R₂²(12)), thus yielding the

dinuclear structure. These hydrogen bonds are weaker (N4···

O1′ 2.666(6) Å; N4−H··O1′ 169°) than the intramolecular

ones. Furthermore, these iminoacetyl ligands are rotated out of

the complex plane by 73.5°.

Within the 3σ criterion the two CN bonds (1.298(6)/

1.289(6) Å) of the iminoacetyl ligands are not diﬀerent. The

N−O bond length of the deprotonated oxime group that is

involved in the intramolecular hydrogen bond is longer than

that which forms the intermolecular hydrogen bond (1.338(5)

vs 1.311(5) Å) and similarly shortened as in complexes 6. All

other structural features are as expected for a platinum(II)

complex bearing organyl ligands trans to N donor ligands.

2.3.3. Monomer−Dimer Equilibria in Bis(iminoacetyl)

Platinum(II) Complexes. In most of the complexes 7−9,

NMR spectra measured in deuterated chloroform showed,

additionally to the signals of the dinuclear complexes, smaller

signals, which have to be assigned to the respective

mononuclear complexes 7′−9′ (Scheme 4, C). Characteristic

NMR parameters of the mononuclear complexes 7′a/b and

8′a−c are given in Table 4, whereby, depending on the portion

Table 4. Portion of Mononuclear Complexes [Pt(CMeNHR′)₂(N^∧N)] (N^∧N = dmg, 7′a,b; dpg, 8′a−c) in CDCl₃along with

Selected NMR (δ in ppm, J in Hz) Spectroscopic Parameters

δ_H(³J_Pt,H

)

δ_C

δ_Pt

a

R′

C(CH₃)NHR′

7′a

7′b

8′a

8′b

5

Bn

2.24 (40.0)

1.95 (39.9)

2.26 (39.8)

1.92 (41.8)

2.34 (41.5)

31.2

30.7

31.3

30.6

30.8

194.9

200.0

207.1

202.5

203.1

15

10

25

5

CH₂CH₂Ph

Bn

CH₂CH₂Ph

CH₂CHCH₂

−3435

−3439

b

8′c

a

Portion of the mononuclear complex at 27 °C (in %, related to total amount of Pt) at a concentration of about 25−35 mg/mL. From the values

b

given equilibrium constants (c(7/8) ⇌ 2c(7′/8′)) between 10⁻²and 10⁻⁴mol/L were estimated. In CD₂Cl₂.

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Scheme 5. Synthesis of Diacetyl Platinum(II) Complexes Bearing Methylated Monoxime (10) and Dioxime Ligands (11) and

Their Reactivity toward Primary and Secondary Amines (H(Me)dmg = HONCMe−CMeNOMe; Me₂dmg = MeON

CMe−CMeNOMe)

As already described in ref 24, complex 11, bearing the

H(Me)dmg ligand, was found to react with primary and

secondary amines, yielding bis(amine)−diacetyl platinum(II)

complexes 3 and 12 (Scheme 5, D). Here, we found that

complex 10, bearing the methylated oxime ligand 2-pyCH

NOMe, reacts in an analogous way. In contrast to the

respective oxime complexes 4a and 5a (cf. Schemes 3/4)

Schiﬀ-base reactions with formation of iminoacetyl platinum

complexes were not observed.

The identities of complexes 10 and 11 were conﬁrmed

analytically, by NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopy, as

well as by single-crystal X-ray diﬀraction measurement (11). As

shown in Table 1, the NMR spectroscopic parameters of

complexes 10 and 11 are close to those of the complexes

bearing the corresponding non-methylated monoxime and

dioxime ligand, 4a and 5a, respectively. In complex 11 the

proton of the O−H···O hydrogen bond is more low-ﬁeld

shifted (by 1.4 ppm) than that in 5a.

planar coordinated (sum of angles around Pt: 360.0°) by the

monomethylated dioxime ligand in a κ²N,N′ coordination

mode and two acetyl ligands in mutal cis position. The oxime

group acts as H donor and the CO group of an acetyl ligand

as H acceptor, thus forming an intramolecular O3−H···O2

hydrogen bond (graph set:²⁶S(6)). Due to that, this acetyl

ligand is forced into the complex plane (interplanar angle:

1.8°), whereas the other one lies perpendicular to the complex

plane (89.6°), as usual. The O3···O2 distance of 2.54(1) Å is in

the same range as in complexes 4 (2.540(7)−2.548(4) Å). Due

to the hydrogen bond, the C3−Pt−N1 angle is smaller

(94.9(3)°) than the other one (C1−Pt−N2 103.7(3)°). In

addition, the N1−O3 bond (1.380(8) Å) is slightly shorter than

the N2−O4 bond of the methylated oxime group (1.404(8) Å).

Moreover, the formation of the hydrogen bond gives rise to a

slight elongation of the C3O2 bond (1.25(1) Å) compared

with the C1O1 bond of the acetyl ligand that is not involved

in a hydrogen bond (1.232(9) Å). Furthermore, the other

structural parameters of complex 11 are similar to those of

complexes 4.

2.4.2. DFT Calculations on the Strength of the Hydrogen

Bonds. To get insight into the strength of hydrogen bonds in

complexes having one (4b*/11*)³¹and two (5a*) intra-

molecular O−H···O hydrogen bonds, high-level DFT calcu-

lations (for details see the Experimental Section) were

performed. The comparison of structural data of the calculated

complexes 4b* and 11* (representing structures in the gas

phase) with those obtained by X-ray diﬀraction measurements

(representing structures in crystals of 4b and 11) exhibited a

good agreement, especially of the parameters of the hydrogen

bonds (Table S4).

An X-ray diﬀraction measurement of [Pt(COMe)₂{H(Me)-

dmg}] (11) shows that crystals consist of isolated molecules

without notable intermolecular interactions. The molecular

structure of 11 is shown in Figure 8 with structural parameters

given in the ﬁgure caption. The platinum center is square-

Whereas the strength of an intermolecular hydrogen bond

X−H···Y is clearly deﬁned as the bond dissociation energy of

reaction A (Scheme 6), all three components are in the

equilibrium state. The case of an intramolecular hydrogen bond

(B) is more complicated because the equilibrium state of the

non-hydrogen-bonded structure (“open conformation”) may

not be rigorously deﬁned. Thus, for example, in acetylacetone

(13a*, Scheme 6) the reference structure for the open

conformation is 13b* and not the thermodynamically most

stable conformer 13c*. To come to a more general deﬁnition,

in ref 32 the non-hydrogen-bonded (“open”) reference

structures are obtained by rigid rotation of the X−H group

around the Z−X bond by 180° (Scheme 6, B) followed by

Figure 8. Molecular structure of [Pt(COMe)₂{H(Me)dmg}] (11,

displacement ellipsoids at 30% probability). Selected distances (Å) and

angles (deg): Pt−C1 1.990(8), Pt−C3 1.981(8), Pt−N1 2.126(6),

Pt−N2 2.175(6), C1−O1 1.232(9), C3−O2 1.25(1), N1−O3

1.380(8), N2−O4 1.404(8), C1−Pt−N1 175.5(2), C3−Pt−N2

167.6(3), O3···O2 2.54(1).

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equilibrium conformation of the pyridyl-functionalized mon-

oxime−diacetyl complex 4b*(o) is only 20.7 kcal/mol higher in

energy than the hydrogen-bonded equilibrium structure

4b*(c). Thus, 4b*(c) is 7.2 kcal/mol more stable than the

open conformation obtained by rigid O−H rotation, which can

be attributed to an increased O···O distance (3.790 versus

2.630 Å) of the oxime−acetyl O atoms and a weak C−H···O

hydrogen bond between the o-CH group of the pyridyl ring and

an O atom of an acetyl ligand (C···O 2.985 Å; see Supporting

Information). Another example is complex 5a*, in which the

opening (based on the equilibrium structures) of the ﬁrst

hydrogen bond in 5a* costs 16.6 kcal/mol and that of the

second one 23.8 kcal/mol (cf. with the strength of the

hydrogen bonds of 25.0 and 28.8 kcal/mol). In the open

equilibrium structures 5a*(co)/5a*(oo), on the one hand, the

rotation of the acetyl ligands results in a decreased steric

repulsion between the two methyl groups of the acetyl ligands

(C_Me···C_Me4.148/4.689 Å, 5a*(co)/5a*(oo); cf. with the

corresponding values in the structures obtained by rigid O−

H rotation 3.226/3.187 Å). On the other hand, the open

equilibrium structures, as for 4b*, are stabilized by increased

O···O distances (see Table 5).

It is worth mentioning that the N−O−H···OC hydrogen-

bonded structures in 4b*(c), 5a*(cc), and 11*(c) showed C

O bond lengths of 1.235−1.239 Å and N−O bond lengths of

1.350−1.356 Å. In the open (nonequilibrium) conformations

4b*(o), 5a*(co), 5a*(oo), and 11*(o) (obtained by rigid

rotation of the O−H group followed by relaxation of all bond

lengths and angles) shorter CO bonds (1.207−1.213 Å) and

elongated N−O bonds (1.363−1.371 Å) were observed, as

expected for the H acceptor site and the H donor site,

respectively, of hydrogen bonds.²⁷In accordance with these

calculated values, in crystals of 4a−c and 11 the formation of

such hydrogen bonds also gave rise to an elongation of the

respective CO bonds and a shortening of the respective N−

O bonds (see Sections 2.1.2 and 2.4.1).

Scheme 6. Strength of Inter- (A) and Intramolecular (B)

Hydrogen Bonds

a

Acetylacetone is given as an example with energies given in

parentheses (in kcal/mol) of the open conformers 13b*/13c* relative

to the hydrogen-bonded structure 13a*.³²

relaxation of all bond lengths and angles (but with ﬁxed torsion

angles). In the case of acetylacetone the energy of this open

(nonequilibrium) structure was found to be very close to that

of the open equilibrium structure 13b* (16.1 vs 15.9 kcal/mol).

Calculated energies for the oxime−diacetyl platinum

complexes under discussion are given in Table 5. On the

basis discussed above, in all complexes the open (non-

equilibrium) conformations obtained by rigid rotation of the

O−H group followed by relaxation of all bond lengths and

angles are between 25.0 and 28.8 kcal/mol higher in their

energies than those of the hydrogen-bonded structures. These

values represent the strength of the intramolecular hydrogen

bonds. The “benchmarks” for the strength of intermolecular

and intramolecular O−H···O hydrogen bonds are those in the

gaseous water dimer (5.0 kcal/mol)³³and in acetylacetone

(16.1 kcal/mol),³²respectively. Thus, the hydrogen bonds in

the oxime−diacetyl platinum(II) complexes are much stronger

than that in acetylacetone and comparable with those in

dinuclear platina-β-diketones and in Lukehart’s metalla-β-

diketones (25.7−27.2 kcal/mol).³²

2.5. Conclusions. Investigations on synthesis, character-

ization, and reactivity of diacetyl platinum(II) complexes

bearing monoxime (4a−c), dioxime (5a−d), and O-methylated

oxime ligands (10/11) exhibited that intramolecular O−H···O

hydrogen bonds can activate acetyl ligands such thatwith

On the other hand, the energies of the open equilibrium

structures of complexes 4b*, 5a*, and 11* do not represent the

strength of the hydrogen bonds. Thus, for example, the open

a

Table 5. Energies (ΔE, in kcal/mol) of Non-Hydrogen-Bonded Oxime−Diacetyl Platinum(II) Complexes Relative to the

Corresponding Hydrogen-Bonded Structures

structural

hydrogen-bonded structure (equilibrium

structure)

open conformation (equilibrium

structure)

open conformation (rotated O−H

b

type

group)

c

4b*

5a*

11*

c → o

0.0 (2.556)

20.7 (3.790)

27.9 (2.630)

cc → co

co → oo

cc→ oo

c → o

0.0 (2.582/2.583)

16.6 (4.105/2.549)

23.8 (3.511/4.037)

40.4 (3.511/4.037)

20.5 (3.755)

25.0 (2.645/2.584)

28.8 (2.662/4.118)

51.5 (2.651/2.651)

27.0 (2.624)

d

0.0 (4.105/2.549)

0.0 (2.582/2.583)

c

0.0 (2.553)

a

Equilibrium structures and those obtained by rigid rotation of the O−H group around the N−O bond by 180° with subsequent relaxation of all

b

bond lengths and angles. O···O distances (in Å) are given in parentheses. c (closed) = hydrogen-bonded structure; o (open) = open conformation.

c

d

For comparison, experimental values: O···O 2.542(4) Å, 4b; 2.54(1) Å, 11. Equilibrium structure 5a*(co) with only one hydrogen bond.

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Schiﬀ-base formationplatinum(II) complexes 6−9 bearing

protonated iminoacetyl ligands were formed, which could be

isolated and fully characterized. As distinguished from the

mononuclear diacetyl complexes 5 bearing dioxime ligands, the

corresponding bis(iminoacetyl) complexes 7−9 were found to

be present in solution in a monomer−dimer equilibrium.

Concerning the activation of acetyl ligands by hydrogen bonds

the following conclusions can be drawn:

(1) In diacetyl platinum(II) complexes the activation of an

acetyl ligand by a suﬃciently strong hydrogen bond is a

prerequisite for forming iminoacetyl complexes in a Schiﬀ-base

reaction. Thus, [Pt(COMe)₂(2,2′-bpy)] did not react with

amines to iminoacetyl complexes but yielded bis(amine)−

diacetyl platinum(II) complexes 3,²⁴as also iminoacetyl

complexes were not formed in reactions of 3 with tripodal

ligands.²³Another way to activate acyl ligands for Schiﬀ-base

type reactions proved to be the protonation as exempliﬁed with

acyl tin compounds.¹⁴The activation of acetyl ligands discussed

here should not be confused with reactions of metalla-β-

diketones (i.e., hydrogen-bridged hydroxycarbene−acyl com-

plexes) with amines, resulting in metalla-β-ketoimines, which

proceed at the hydroxycarbene ligand.^2,30

(2) Although in complex 11 one of the two acetyl ligands is

activated by an intramolecular O−H···O hydrogen bond, in

reactions with amines a Schiﬀ-base type reaction did not take

place, but a ligand exchange reaction did (Scheme 5, reaction

path D). The molecular structure of complex 11 (Figure 8) and

DFT calculations indicate that the strength of the hydrogen

bond is comparable with those in complexes 4/5. Thus, it can

be concluded that the ligand substitution is preferred because of

a too weak coordination of the mono-O-methylated dioxime

ligand in 11. In accordance with this, (i) the synthesis of the

complex [Pt(COMe)₂(Me₂dmg)] (Scheme 5, C) bearing a di-

O-methylated dioxime ligand failed and (ii) the pyridyl-

functionalized O-methyloxime ligand in complex 10 could be

easily cleaved oﬀ (Scheme 5, D).

(3) The O−H···O hydrogen bonds in complexes 4a−c and

11 are relatively strong, as shown by the distance criterion²⁷

(O···O 2.54(1)−2.548(4) Å) and by the low-ﬁeld shift of the

NOH signals (15.5−15.9 ppm). This is further supported by

DFT calculations, which showed for 4b*and 5a* hydrogen

bond strengths (25.0−28.8 kcal/mol) analogous to those both

in Lukehart’s metalla-β-diketones and in dinuclear platina-β-

diketones (25.7−27.2 kcal/mol).³²The N−H···O hydrogen

bonds in the iminoacetyl platinum complexes 6 were found to

be slightly weaker (N···O 2.636(5)−2.65(1) Å; NH δ_H= 15.2−

16.2). In these complexes, NMR data, X-ray diﬀraction

analyses, and DFT calculations give evidence for asymmetrical

hydrogen bonds in which an NH group acts as H donor and an

O atom as H acceptor. Thus, protonated iminoacetyl ligands

(i.e., aminocarbene ligands) and deprotonated oxime ligands

are present.

under basic conditions (Scheme 2) is analogous to that of

reactions of 1 with other N^∧N donors: (i) cleavage of the Pt−

Cl−Pt bridges, thus yielding mononuclear platina-β-diketones

[Pt{(COMe)₂H}(N^∧N)]⁺; (ii) H shift to Pt, thus forming

hydrido−diacetyl platinum(IV) complexes (Scheme 1, A/D);

(iii) base-induced reductive H−Cl elimination (Scheme 1,

C).^1,4

(6) The experimental ﬁndings indicate that the iminoacetyl

complexes 6−9 starting from bis(amine)−diacetyl platinum(II)

complexes 3 and the respective monoxime/dioxime are yielded

according to the following mechanism: (i) Due to the strong

trans eﬀect of the acetyl ligands, the amine ligands in complexes

3 are only weakly coordinated²⁴and were easily substituted²³

by the oxime, thus forming type 4/5 complexes. (ii) The amine

cleaved oﬀ attacks nucleophilically the C atom of the acetyl

ligand, which is activated by an intramolecular hydrogen bond,

thus forming a Pt-bound hemiaminal as intermediate, from

which the iminoacetyl complexes 6−9 were formed by cleavage

of water. Apparently, the mechanism is analogous to the

formation of “purely” organic Schiﬀ bases starting from

aldehydes or ketones.

(7) As demonstrated by the reactivity of complexes 10/11

bearing O-methylated oxime ligands (Scheme 5), the intra-

molecular O−H···O hydrogen bond is essential both to

stabilize the coordination of the oxime ligand, thus preventing

its substitution by the amine, and to activate the acetyl ligand

for a Schiﬀ-base type reaction.

(8) In dioxime platinum complexes 5, 7, and 8, a further

aspect of the activation of acetyl/iminoacetyl ligands by

intramolecular O−H···O/N−H···O hydrogen bonds is a facile

H/D exchange of the methyl protons of the activated acetyl/

iminoacetyl ligands. Analogously, organic methyl ketones are

subject to acid-catalyzed H/D exchange reactions,³⁴but,

notably, not the classical Fischer methyl(methoxy)carbene

complexes [M{C(CH₃)OMe}(CO)₅] (M = Cr, Mo, W).³⁵

The present investigations open a new pathway for the

synthesis of platinum(II) complexes bearing protonated

iminoacetyl ligands by activation of acetyl ligands through

strong intramolecular O−H···O hydrogen bonds. This is a

further instructive example how the reactivity of ligands in

metal complexes can be inﬂuenced in a targeted way.

3. EXPERIMENTAL SECTION

3.1. General Remarks. All reactions were performed in an argon

atmosphere using the standard Schlenk techniques. Solvents were

dried (Et₂O and n-pentane over Na/benzophenone; MeOH over Mg;

CHCl₃and CH₂Cl₂over CaH₂) and distilled prior to use. NMR

spectra were, unless otherwise speciﬁed, recorded at 27 °C on Varian

Gemini 200 MHz, VNMRS 400 MHz, and INOVA500 MHz NMR

spectrometers. Solvent signals (¹H, ¹³C) were used as internal

references, and H₂[PtCl₆] (δ(¹⁹⁵Pt) = 0) was used as external

reference. IR spectra were recorded on a Bruker Tensor 27

spectrometer with a Platinum ATR unit or on a Galaxy Mattson

5000 FT-IR spectrometer. Microanalyses were performed by the

University of Halle microanalytical laboratory using CHNS-932

(LECO) and Vario EL (Elementar Analysensysteme) elemental

analyzers. The positive ion high-resolution ESI mass spectra were

measured at a Bruker Apex III Fourier transform ion cyclotron

resonance (FT-ICR) mass spectrometer (Bruker Daltonics, Billerica,

MA, USA), which is equipped with an inﬁnity cell, a 7.0 T

superconducting magnet (Bruker), an RF-only hexapole ion guide,

and an external electron spray ion source. The complexes

[Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1) and [Pt(COMe)₂(NH₂R′)₂] (3a−c)

were prepared according to literature methods.^36,24The mono- and

dioximes used in this study were commercially available. 2-pyCH

(4) In complexes 4 and 11, the formation of intramolecular

O−H···O hydrogen bonds gives rise to an elongation of the

CO bond and a concomitant shortening of the N−O bonds,

as expected.²⁷The elongation of the CO bonds caused by

the H bond formation amounts to 0.015−0.039 Å, thus

showing an activation of the requisite acetyl ligand. This is in

accord with DFT calculations, in which for 4b* and 11* values

of 0.018/0.019 Å were found.

(5) The way of formation of type 4/5 complexes from

reactions of the dinuclear platina-β-diketone 1 with pyridyl-

functionalized monoximes and with dioximes, respectively,

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2

NOMe was synthesized by the reaction of the aldehyde 2-pyCHO

with O-methylhydroxylamine hydrochloride.³⁷In an analogous way,

H(Me)dmg and Me₂dmg were synthesized starting from HON

CMe−CMeO and OCMe−CMeO, respectively.

MHz, CDCl₃): δ 41.6 (s+d, J_Pt,C= 344.1 Hz, COCH₃), 44.8 (s+d,

²J_Pt,C= 319.8 Hz, COCH₃), 125.3 (s, C³py), 126.0 (s, C⁵py), 128.6 (s,

o-C Ph), 128.8 (s, i-C Ph), 129.0 (s, m-C Ph), 130.5 (s, p-C Ph), 139.7

(s, C⁴py), 151.5 (s+d, ²J_Pt,C= 42.4 Hz, C⁶py), 155.0 (s, C²py), 156.5

(s, CNOH), 231.1 (s+d, ¹J_Pt,C= 1332 Hz, COMe), 233.8 (s+d, ¹J_Pt,C

= 1277 Hz, COMe). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3428 (s). IR:

ν 3473(w), 3022(w), 2942(m), 1607(s), 1556(m), 1480(s), 1429(w),

1340(w), 1235(w), 1137(m), 1113(w), 1040(w), 852(w), 774(m),

679(m), 651(m), 580(w) cm⁻¹.

3.2. Synthesis of Diacetylplatinum(II) Complexes 4, 5, 10,

and 11 Bearing Oxime/Dioxime and O-Methylated Oxime

Ligands. At −78 °C, to a yellow suspension of [Pt₂{(COMe)₂H}₂(μ-

Cl)₂] (1) (188 mg, 0.3 mmol) in CH₂Cl₂(10 mL) was added under

stirring a monoxime (2-pyCRNOH, R = H, Me, Ph; 0.6 mmol), a

dioxime HONCR−CRNOH (R/R = Me/Me, H₂dmg; Ph/Ph,

H₂dpg; (CH₂)₄, 1,2-Cy(NOH)₂; NH₂/NH₂, H₂dag; 0.6 mmol), or

a O-methylated oxime (2-pyCHNOMe, H(Me)dmg; 0.6 mmol) in

CH₂Cl₂(3 mL). After about half an hour, to the orange-colored

suspension was slowly added a solution of sodium methoxide (1.1 mL,

0.6 mol/L) in methanol, resulting in an orange-colored solution. After

stirring for 3 h at room temperature, water (3 mL) was added. Then,

the phases were separated, and the aqueous phase was extracted with

CH₂Cl₂(2 × 3 mL). From the combined and dried (Na₂SO₄) organic

phases, the solvents were removed in vacuo. The residue was dissolved

in CH₂Cl₂(2 mL). Addition of diethyl ether (3 mL)/n-pentane (3

mL) resulted in precipitation of an orange (4a−c, 5d, 10, 11), dark

blue (5a/c), and dark green (5b) precipitate, which was ﬁltered oﬀ,

washed with diethyl ether (1 mL), and dried in vacuo.

5a, [Pt(COMe)₂(HONCMe−CMeNOH)]. Yield: 180 mg

(75%). Anal. Found (Calcd): C₈H₁₄N₂O₄Pt (397.29), C 24.24

(24.18), H 3.36 (3.55), N 7.01 (7.05). ¹H NMR (400 MHz,

3

CDCl₃): δ 2.16 (s, 6H, CH₃dmg), 2.39 (s+d, J_Pt,H= 24.9 Hz, 6H,

COCH₃), 14.2 (s+d, ³J_Pt,H= 22 Hz, 2H, NOH). ¹H NMR (400 MHz,

2

CD₃OD): δ 2.19 (s, 6H, CH₃dmg). H NMR (61 MHz, CHCl₃): δ

2.47 (s(br), 6D, COCD₃). ¹³C NMR (100 MHz, CDCl₃): δ 12.8 (s,

CH₃dmg), 42.9 (s+d, ²J_Pt,C= 308.4 Hz, COCH₃), 157.0 (s+d, ²J_Pt,C

=

31.2 Hz, CNOH), 236.8 (s+d, J_Pt,C= 1324 Hz, COCH₃). ¹⁹⁵Pt

NMR (107 MHz, CDCl₃): δ −3481 (s). IR: ν 3150(w), 3113(m),

3053(w), 3032(w), 2018(w), 1825(w), 1626(m), 1491(m), 1453(m),

1393(s), 1337(s), 1138(s), 1082(m), 997(w), 940(m), 822(m),

712(m), 662(m), 529(w), 488(w) cm⁻¹.

1

5b, [Pt(COMe)₂(HONCPh−CPhNOH)]. Yield: 167 mg

(55%). Anal. Found (Calcd): C₁₈H₁₈N₂O₄Pt (521.43), C 40.80

(41.46), H 3.21 (3.48), N 5.07 (5.37). HRMS (ESI) m/z found

4a, [Pt(COMe)₂(2-pyCHNOH)]. Yield: 170 mg (70%). Anal.

Found (Calcd): C₁₀H₁₂N₂O₃Pt (403.29), C 29.80 (29.78), H 2.84

(3.00), N 6.82 (6.94). ¹H NMR (400 MHz, CDCl₃): δ 2.27 (s+d, ³J_Pt,H

(calcd): for [C₁₈H₁₉N₂O₄Pt]⁺522.0992 (522.0987). H NMR (500

1

3

= 33.0 Hz, 3H, COCH₃), 2.53 (s+d, J_Pt,H= 20.6 Hz, 3H, COCH₃),

MHz, CDCl₃): δ 2.55 (s+d, J_Pt,H= 23.4 Hz, 6H, COCH₃), 7.15 (m,

7.46 (m, 1H, H⁵py), 7.56 (m, 1H, H³py), 7.96 (m, 1H, H⁴py), 8.38

(m+d(br), ³J_Pt,H= 23 Hz, 1H, H⁶py), 8.47 (s+d, ³J_Pt,H= 22.9 Hz, 1H,

4H, m-H Ph), 7.22−7.32 (m, 6H, o/p-H Ph), 14.6 (s+d(br), ³J_Pt,H= 26

Hz, 2H, NOH). ²H NMR (61 MHz, CHCl₃): δ 2.32 (s(br), 6D,

COCD₃). ¹³C NMR (50 MHz, CDCl₃): δ 42.9 (s+d, ²J_Pt,C= 315.4 Hz,

COCH₃), 128.1 (s, m-C Ph), 128.7 (s, i-C Ph), 129.4 (s, o-C Ph),

130.3 (s, p-C Ph), 157.0 (s+d, ²J_Pt,C= 26.4 Hz, CNOH), 237.0 (s+d,

²J_Pt,C= 1325 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3487

(s). IR: ν 3146(w), 3049(w), 1844(w), 1628(m), 1560(w), 1507(m),

1487(m), 1441(s), 1406(s), 1345(s), 1309(m), 1140(s), 1075(m),

1026(w), 986(m), 888(w), 774(w), 722(s), 693(m), 668(w), 490(w),

383(w) cm⁻¹.

3

1

CHNOH), 15.8 (s+d, J_Pt,H= 32 Hz, 1H, NOH). H NMR (400

3

MHz, CD₃OD): δ 2.17 (s+d, J_Pt,H= 32.7 Hz, 3H, COCH₃), 2.55 (s

+d, ³J_Pt,H= 20.5 Hz, 3H, COCH₃), 7.63 (m, 1H, H⁵py), 7.85 (m, 1H,

H³py), 8.15 (m, 1H, H⁴py), 8.27 (m, 1H, H⁶py), 8.78 (s+d, ³J_Pt,H

=

24 Hz, 1H, CHNOH). ¹³C NMR (125 MHz, CDCl₃): δ 41.6 (s+d,

²J_Pt,C= 353.7 Hz, COCH₃), 44.6 (s+d, J_Pt,C= 319.5 Hz, COCH₃),

2

124.5 (s, C³py), 126.2 (s+d, ³J_Pt,C= 19.6 Hz, C⁵py), 140.2 (s, C⁴py),

2

146.4 (s+d, J_Pt,C= 23.1 Hz, CNOH), 151.7 (s+d, J_Pt,C= 43.2 Hz,

C⁶py), 153.1 (s+d, J_Pt,C= 10.2 Hz, C²py), 229.8 (s+d, J_Pt,C= 1335

2

1

5c, [Pt(COMe)₂{1,2-Cy(NOH)₂}]. Yield: 171 mg (70%). Anal.

Found (Calcd): C₁₀H₁₆N₂O₄Pt (423.33), C 28.84 (28.37), H 3.74

(3.81), N 6.43 (6.62). HRMS (ESI) m/z found (calcd): for

[C₁₀H₁₇N₂O₄Pt]⁺424.0837 (424.0842). ¹H NMR (200 MHz,

1

Hz, COMe), 233.3 (s+d, J_Pt,C= 1284 Hz, COMe). ¹⁹⁵Pt NMR (107

MHz, CDCl₃): δ −3430 (s). IR: ν 3034(m), 2974(m), 1987(w),

1836(w), 1734(w), 1647(m), 1607(s), 1499(s), 1410(s), 1347(m),

1326(s), 1294(m), 1250(w), 1214(m), 1138(s), 1097(s), 1066(s),

1022(m), 952(m), 897(m), 874(m), 768(m), 738(w), 672(m),

635(m), 598(w), 512(m) cm⁻¹.

CDCl₃): δ 1.70 (s, 4H, H⁴/H⁵Cy), 2.37 (s+d, J_Pt,H= 25.7 Hz, 6H,

3

COCH₃), 2.64 (s, 4H, H³/H⁶Cy), 14.1 (s(br), 2H, NOH). ¹³C NMR

(100 MHz, CDCl₃): δ 20.7 (s, C⁴/C⁵Cy), 25.9 (s, C³/C⁶Cy), 42.9 (s

+d, ²J_Pt,C= 300.7 Hz, COCH₃), 157.7 (s, C¹/C²Cy), 237.0 (s+d, ¹J_Pt,C

= 1319 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3422 (s).

IR: ν 3144(m), 3046(m), 2941(m), 2865(m), 1619(m), 1476(s),

1412(s), 1339(s), 1139(s), 1078(w), 1044(w), 986(m), 943(w),

878(w), 711(w), 664(w), 380(w) cm⁻¹.

4b, [Pt(COMe)₂(2-pyCMeNOH)]. Yield: 125 mg (50%). Anal.

Found (Calcd): C₁₁H₁₄N₂O₃Pt (417.32), C 31.58 (31.66), H 3.57

(3.38), N 6.60 (6.71). ¹H NMR (400 MHz, CDCl₃): δ 2.27 (s+d, ³J_Pt,H

= 32.8 Hz, 3H, COCH₃), 2.36 (s, 3H, C(CH₃)NOH), 2.52 (s+d,

³J_Pt,H= 21.3 Hz, 3H, COCH₃), 7.46 (m, 1H, H⁵py), 7.66 (s, 1H, H³

3

py), 7.99 (m, 1H, H⁴py), 8.42 (m+d, J_Pt,H= 23.1 Hz, 1H, H⁶py),

5d, [Pt(COMe)₂{HONC(NH₂)−C(NH₂)NOH}]. Yield: 57

mg (50%). Anal. Found (Calcd): C₆H₁₂N₄O₄Pt (399.26), C 18.86

(18.05), H 3.19 (3.03), N 13.46 (14.03). ¹H NMR (200 MHz,

15.5 (s+d, ³J_Pt,H= 32 Hz, 1H, NOH). ¹H NMR (200 MHz, CD₃OD):

3

δ 2.16 (s, 3H, C(CH₃)NOH), 2.27 (s+d, J_Pt,H= 19.3 Hz, 3H,

3

COCH₃), 2.40 (s+d, J_Pt,H= 20.8 Hz, 3H, COCH₃), 7.32 (m, 1H, H⁵

acetone-d₆): δ 2.30 (s+d, J_Pt,H= 23.5 Hz, 6H, COCH₃), 6.64 (s(br),

4H, NH₂), 12.5 (s(br), 2H, NOH). ¹³C NMR (50 MHz, acetone-d₆):

δ 43.0 (s+d, ²J_Pt,C= 340.3 Hz, COCH₃), 149.2 (s, CNOH), 232.7 (s

py), 7.55 (m, 1H, H³py), 7.98 (m, 1H, H⁴py), 8.22 (m+d, ³J_Pt,H= 22

Hz, 1H, H⁶py). ¹³C NMR (50 MHz, CDCl₃): δ 11.8 (s, C(CH₃)

NOH), 41.7 (s+d, ²J_Pt,C= 348.7 Hz, COCH₃), 44.8 (s+d, ²J_Pt,C= 321.6

+d, J_Pt,C= 1342 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz, acetone-d₆): δ

1

3

Hz, COCH₃), 123.0 (s, C³py), 125.9 (s+d, J_Pt,C= 20.7 Hz, C⁵py),

−3411 (s). IR: ν 3467(m), 3354(s), 3242(m), 3183(m), 2970(w),

1708(w), 1643(s), 1543(m), 1464(s), 1430(m), 1141(m), 1048(w),

947(w), 821(w), 748(w), 634(w) cm⁻¹.

10, [Pt(COMe)₂(2-pyCHNOMe)]. Yield: 200 mg (80%). Anal.

Found (Calcd): C₁₁H₁₄N₂O₃Pt (417.32), C 31.20 (31.66), H 3.66

(3.38), N 6.57 (6.71). ¹H NMR (200 MHz, CDCl₃): δ 2.24 (s+d, ³J_Pt,H

139.9 (s, C⁴py), 151.1 (s+d, ²J_Pt,C= 42.6 Hz, C⁶py), 154.68 (s, C²py),

154.75 (s, CNOH), 230.6 (s+d, ¹J_Pt,C= 1334 Hz, COCH₃), 234.0 (s

1

+d, J_Pt,C= 1274 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ

−3421 (s). IR: ν 2966(w), 2892(w), 1612(s), 1572(m), 1510(w),

1467(m), 1446(m), 1328(w), 1269(w), 1225(m), 1188(m), 1114(m),

1051(w), 1015(w), 930(w), 761(w), 694(w), 605(w), 436(w) cm⁻¹.

4c, [Pt(COMe)₂(2-pyCPhNOH)]. Yield: 96 mg (35%). Anal.

Found (Calcd): C₁₆H₁₆N₂O₃Pt (479.39), C 39.98 (40.09), H 3.37

(3.36), N 5.59 (5.84). ¹H NMR (500 MHz, CDCl₃): δ 2.31 (s+d, ³J_Pt,H

3

= 26.8 Hz, 3H, COCH₃), 2.33 (s+d, J_Pt,H= 23.4 Hz, 3H, COCH₃),

3.88 (s, 3H, NOCH₃), 7.48 (m, 1H, H⁵py), 7.66 (m, 1H, H³py), 8.00

(m, 1H, H⁴py), 8.57 (m, 1H, H⁶py), 8.65 (s+d, ³J_Pt,H= 13.3 Hz, 1H,

CHNOCH₃). ¹³C NMR (50 MHz, CDCl₃): δ 41.9 (s+d, J_Pt,C

=

2

399.2 Hz, COCH₃), 44.8 (s+d, ²J_Pt,C= 362.5 Hz, COCH₃), 64.0 (s+d,

³J_Pt,C= 20.6 Hz, NOCH₃), 126.1 (s, C³py), 127.4 (s+d, ²J_Pt,C= 17.6

Hz, C⁵py), 139.0 (s, C⁴py), 150.9 (s+d, ²J_Pt,C= 40.5 Hz, C⁶py), 151.3

3

= 31.6 Hz, 3H, COCH₃), 2.58 (s+d, J_Pt,H= 18.5 Hz, 3H, COCH₃),

7.32 (m, 1H, H³py), 7.41 (m, 2H, o-H Ph), 7.47 (m, 1H, H⁵py), 7.54

3

(m, 3H, p/m-H Ph), 7.86 (m, 1H, H⁴py), 8.48 (m+d, J_Pt,H= 32 Hz,

1H, H⁶py), 15.9 (s+d, J_Pt,H= 32 Hz, 1H, NOH). ¹³C NMR (125

(s, C²py), 154.4 (s+d, J_Pt,C= 20.9 Hz, CNOCH₃), 223.3 (s+d,

3

2

7101

dx.doi.org/10.1021/om400812w | Organometallics 2013, 32, 7090−7106

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Article

1

3

¹J_Pt,C= 1308 Hz, COCH₃), 228.0 (s+d, J_Pt,C= 1260 Hz, COCH₃).

¹⁹⁵Pt NMR (107 MHz, CD₃OD): δ −3433 (s). IR: ν 3049(w),

2973(w), 2905(w), 1606(s), 1589(s), 1574(s), 1474(w), 1418(w),

1328 (m), 1302(w), 1090 (s), 1036(s), 928(s), 898(m), 756(s),

681(m), 644(m), 536(s) 515(s), 332(s) cm⁻¹.

249.0 Hz, COCH₃), 49.8 (s+d, J_Pt,C= 57 Hz, NHCH₂Ph), 120.1 (s,

C³py), 122.5 (s+d, ³J_Pt,C= 28 Hz, C⁵py), 127.3 (s, o-C Ph), 127.7 (s,

p-C Ph), 128.9 (s, m-C Ph), 134.5 (s, i-C Ph), 139.4 (s, C⁴py), 150.0

(s+d, ²J_Pt,C= 44 Hz, C⁶py), 153.0 (s, CNO), 158.0 (s, C²py), 196.5

(s, C(CH₃)NHBn), 237.9 (s, COCH₃). ¹⁹⁵Pt NMR (107 MHz,

CDCl₃): δ −3391 (s). IR: ν 3067(w), 3027(w), 2973(w), 2896(w),

1602(s), 1571(w), 1549(m), 1474(m), 1378(w), 1331(w), 1165(m),

1097(m), 1077(m), 916(m), 775(s), 760(m), 694(s), 632(w),

598(m), 501(m), 448(s), 388(s) cm⁻¹.

11, [Pt(COMe)₂(HONCMe−CMeNOMe)]. Yield: 145 mg

(60%). Anal. Found (Calcd): C₉H₁₆N₂O₄Pt (411.31), C 26.08

(26.27), H 4.10 (3.92), N 6.30 (6.81). ¹H NMR (400 MHz,

3

CDCl₃): δ 2.15 (s, 3H, CH₃dmg), 2.20 (s+d, J_Pt,H= 33.0 Hz, 3H,

3

6c, [Pt(COMe)(CMeNHBn)(2-pyCPhNO)]. Yield route A/

COCH₃), 2.25 (s, 3H, CH₃dmg), 2.50 (s+d, J_Pt,H= 18.5 Hz, 3H,

COCH₃), 3.80 (s, 3H, NOCH₃), 15.6 (s+d, ³J_Pt,H= 35 Hz, 1H, NOH).

¹³C NMR (100 MHz, CDCl₃): δ 13.0 (s, CH₃dmg), 14.2 (s, CH₃

dmg), 40.0 (s+d, ²J_Pt,C= 362.1 Hz, COCH₃), 44.7 (s+d, ²J_Pt,C= 304.3

B: 25/34 mg (45/30%). Anal. Found (Calcd): C₂₃H₂₃N₃O₂Pt

1

(568.52), C 48.21 (48.59), H 3.75 (4.08), N 7.03 (7.39). H NMR

3

(400 MHz, CDCl₃): δ 2.17 (s+d, J_Pt,H= 56.4 Hz, 3H, C(CH₃)

3

NHBn), 2.51 (s+d, J_Pt,H= 14.0 Hz, 3H, COCH₃), 4.73 (m, 2H,

Hz, COCH₃), 63.2 (s+d, J_Pt,C= 18 Hz, NOCH₃), 153.1 (s, C

NHCH₂Ph), 7.03 (m, 1H, H³py), 7.13 (m, 1H, H⁵py), 7.22−7.49 (m,

NOH), 167.7 (s, CNOMe), 227.6 (s+d, ¹J_Pt,C= 1381 Hz, COCH₃),

10H, o/m/p-H Ph), 7.67 (m, 1H, H⁴py), 8.29 (m+d, J_Pt,H= 27 Hz,

3

231.2 (s+d, J_Pt,C= 1271 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz,

1

1H, H⁶py), 15.9 (s+d, ³J_Pt,H= 76 Hz, 1H, NH). ¹³C NMR (125 MHz,

CDCl₃): δ −3533 (s). IR: ν 2960(m), 2922(m), 2861(w), 1672(s),

1542(w), 1500(s), 1468(m), 1410(s), 1372(w), 1336(m), 1307(w),

1261(w), 1131(m), 1094(s), 1061(m), 993(m), 941(m), 821(m)

cm⁻¹.

CDCl₃): δ 29.2 (s+d, ²J_Pt,C= 159.0 Hz, C(CH₃)NHBn), 44.7 (s+d,

²J_Pt,C= 247.7 Hz, COCH₃), 49.6 (s+d, J_Pt,C= 56.6 Hz, NHCH₂Ph),

3

121.8 (s, C⁵py), 122.4 (s, C³py), 127.0−129,4 (5 H s, o/m/p-C Ph),

132.2 (s, i-C Ph), 135.0 (s, i-C Ph), 139.1 (s, C⁴py), 150.5 (s+d, ²J_Pt,C

3.3. Synthesis of Iminoacetyl Platinum(II) Complexes 6−9

with Oxime Ligands. Route A. Dissolving the complex [Pt-

(COMe)₂(NH₂R′)₂] (R′ = Bn, 3a; CH₂CH₂Ph, 3b; CH₂CHCH₂,

3c; 0.1 mmol) and a monoxime 2-pyCRNOH (R = H, Me, Ph; 0.1

mmol) or a dioxime HONCR−CRNOH (R/R = Me/Me, Ph/

Ph, (CH₂)₄; 0.1 mmol) in CH₂Cl₂(4 mL) resulted in the case of the

monoximes in an orange-colored solution within 10 min. In the case of

the dioximes, the solution became red; an addition of the respective

amine NH₂R′ (0.2 mmol) proved to be advantageous and resulted in a

yellow solution. After two hours’ stirring, the volume of the solution

was reduced in vacuo up to about 1 mL. Addition of diethyl ether (2

mL) resulted in precipitation of the products, which were ﬁltered oﬀ,

washed with diethyl ether (2 × 1 mL), and dried in vacuo. To isolate

6c, n-pentane (2 mL) was used instead of diethyl ether.

Route B. To a solution of oxime−diacetyl platinum complexes

[Pt(COMe)₂(2-pyCRNOH)] (4a−c, 0.2 mmol) and [Pt-

(COMe)₂(HONCR−CRNOH)] (5a−c, 0.1 mmol), respectively,

in CH₂Cl₂(5 mL) was added a primary amine NH₂R′ (R′ = Bn,

CH₂CH₂Ph, CH₂CHCH₂, CH₂CH₂OH; 0.4 mmol). After 2 h of

stirring the orange (monoxime) or yellow-colored (dioxime) solution

was worked up as described for route A.

= 46.8 Hz, C⁶py), 155.6 (s, C²py), 158.9 (s+d, J_Pt,C= 41.9 Hz, C

2

1

NO), 197.4 (s+d, J_Pt,C= 1337 Hz, C(CH₃)NHBn), 237.2 (s+d,

¹J_Pt,C= 1124 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3389

(s). IR: ν 3429(w), 3027(w), 2940(w), 2897(w), 1652(w), 1604(s),

1536(m), 1492(w), 1456(s), 1441(m), 1427(s), 1349(m), 1330(w),

1262(m), 1216(s), 1142(w), 1092(w), 975(w), 777(w), 743(w),

706(m), 606(w), 457(m) cm⁻¹.

6d, [Pt(COMe)(CMeNHCH₂CH₂Ph)(2-pyCHNO)]. Yield

route A/B: 20/61 mg (40/60%). Anal. Found (Calcd): C₁₈H₂₁N₃O₂Pt

1

(506.46), C 42.64 (42.68), H 4.01 (4.18), N 8.09 (8.30). H NMR

3

(500 MHz, CDCl₃): δ 2.00 (s+d, J_Pt,H= 55.2 Hz, 3H, C(CH₃)

3

NHCH₂), 2.42 (s(br), 3H, COCH₃), 3.10 (t, J_H,H= 7.7 Hz, 2H,

CH₂Ph), 3.68 (m, 2H, NHCH₂), 7.11 (m, 1H, H⁵py), 7.20−7.31 (m,

6H, o/m/p-H Ph, H³py), 7.77 (m, 1H, H⁴py), 8.18 (m, 1H, H⁶py),

8.22 (s, 1H, CHNO), 15.2 (s+d, ³J_Pt,H= 78 Hz, 1H, NH). ¹³C NMR

2

(125 MHz, CDCl₃): δ 28.6 (s+d, J_Pt₂_,C= 155.3 Hz, C(CH₃)

NHCH₂), 34.5 (s, CH₂Ph), 44.5 (s+d, J_Pt,C= 247.6 Hz, COCH₃),

48.1 (s+d, J_Pt,C= 59.7 Hz, NHCH₂), 120.5 (s, C³py), 122.4 (s, C⁵

3

py), 126.8 (s, p-C Ph), 128.7 (s, o-C Ph), 128.7 (s, m-C Ph), 137.7 (s,

i-C Ph), 139.5 (s, C⁴py), 145.7 (s+d, ²J_Pt,C= 38.6 Hz, CNO), 150.5

(s+d, J_Pt,C= 23.6 Hz, C⁶py), 157.5 (s, C²py), 195.3 (s+d, J_Pt,C

=

2

1

6a, [Pt(COMe)(CMeNHBn)(2-pyCHNO)]. Yield route A/

B: 40/59 mg (80/60%). Anal. Found (Calcd): C₁₇H₁₉N₃O₂Pt

(492.43), C 41.11 (41.46), H 3.90 (3.89), N 8.11 (8.53). HRMS

(ESI) m/z found (calcd): for [C₁₇H₂₁N₃O₂Pt]⁺493.1191 (493.1198).

1357 Hz, C(CH₃)NHCH₂), 236.2 (s+d, ¹J_Pt,C= 1140 Hz, COCH₃).

¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3391 (s). IR: ν 3029(w),

2933(w), 1604(s), 1537(m), 1477(m), 1428(m), 1338(m), 1232(w),

1152(m), 1126(m), 1089(m), 1025(w), 908(w), 765(m), 676(m),

570(w), 430(w) cm⁻¹.

¹H NMR (200 MHz, CDCl₃): δ 2.20 (s+d, J_Pt,H= 57.4 Hz, 3H,

3

C(CH₃)NHBn), 2.47 (s+d, ³J_Pt,H= 16.0 Hz, 3H, COCH₃), 4.81 (m,

2H, NHCH₂Ph), 7.10 (m, 1H, H⁵py), 7.25−7.38 (m, 6H, o/m/p-H

Ph, H³py), 7.76 (m, 1H, H⁴py), 8.18 (m, 2H, H⁶py, CHNO), 15.6

6e, [Pt(COMe)(CMeNHCH₂CHCH₂)(2-pyCHNO)].

Yield route A/B: 15/67 mg (35/75%). Anal. Found (Calcd):

C₁₃H₁₇N₃O₂Pt (442.37), C 35.40 (35.29), H 3.70 (3.88), N 9.29

(s+d(br), J_Pt,H= 78 Hz, 1H, NH). ¹³C NMR (100 MHz, CDCl₃): δ

3

1

3

2

(9.50). H NMR (400 MHz, CDCl₃): δ 2.16 (s+d, J_Pt,H= 55.4 Hz,

29.3 (s+d, J_Pt,C= 159.0 Hz, C(CH₃)NHBn), 44.5 (s+d, J_Pt,C

=

3

247.7 Hz, COCH₃), 50.3 (s+d, ³J_Pt,C= 61.3 Hz, NHCH₂Ph), 120.5 (s,

C⁵py), 122.3 (s, C³py), 127.6 (s, o-C Ph), 128.0 (s, p-C Ph), 129.0 (s,

3H, C(CH₃)NHCH₂), 2.47 (s+d, J_Pt,H= 14.7 Hz, 3H, COCH₃),

4.09 (m, 2H, NHCH₂), 5.09 (m, 1H, CHCH₂), 5.29 (d(br), ³J_H,H

=

3

m-C Ph), 134.6 (s, i-C Ph), 139.6 (s, C⁴py), 145.6 (s+d, J_Pt,C= 41.6

2

5.7 Hz, 1H, CHCH₂), 5.93 (d(br), J_H,H= 12.5 Hz, 1H, CH

CH₂), 7.08 (m, 1H, H⁵py), 7.23 (m, 1H, H³py), 7.74 (m, 1H, H⁴py),

Hz, CNO), 150.3 (s+d, J_Pt,C= 46.8 Hz, C⁶py), 157.7 (s, C²py),

2

8.15 (m, 2H, CHNO, H⁶py), 15.2 (s+d, J_Pt,H= 71 Hz, 1H, NH).

3

1

196.3 (s+d, J_Pt,C= 1358 Hz, C(CH₃)NHBn), 236.6 (s+d, J_Pt,C

=

¹³C NMR (125 MHz, CDCl₃): δ 28.8 (s+d, J_Pt,C= 158.7 Hz,

2

1133 Hz, COCH₃). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3384 (s). IR:

ν 3463 (m), 1612(s), 1478(s), 1432(w), 1336(m), 1238(w), 1149(m),

1096(m), 836(w), 768(m), 702(w), 677(w), 568(w) cm⁻¹.

C(CH₃)NHCH₂), 44.5 (s+d, ²J_Pt,C= 246.4 Hz, COCH₃), 48.6 (s+d,

³J_Pt,C= 56.8 Hz, NHCH₂), 118.6 (s, CHCH₂), 120.5 (s, C³py),

122.3 (s, J_Pt,C= 23.6 Hz, C⁵py), 130.3 (s, CHCH₂), 139.6 (s, C⁴

3

6b·H₂O, [Pt(COMe)(CMeNHBn)(2-pyCMeNO)]·H₂O.

Yield route A/B: 21/38 mg (40/35%). Anal. Found (Calcd):

C₁₈H₂₁N₃O₂Pt·H₂O (524.47), C 41.74 (41.22), H 4.37 (4.42), N

py), 145.6 (s+d, ²J_Pt,C= 43.7 Hz, CHNO), 150.4 (s+d, ²J_Pt,C= 47.2

Hz, C⁶py), 157.5 (s, C²py), 196.1 (s+d, J_Pt,C= 1351 Hz, C(CH₃)

1

3

NHCH₂), 236.2 (s+d, J_Pt,C= 1133 Hz, COCH₃). ¹⁹⁵Pt NMR (107

1

7.93 (8.01). H NMR (400 MHz, CDCl₃): δ 2.17 (s+d, J_Pt,H= 56.1

Hz, 3H, C(CH₃)NHBn), 2.23 (s, 3H, C(CH₃)NO), 2.46 (s+d,

³J_Pt,H= 18.1 Hz, 3H, COCH₃), 4.73 (m, 2H, NHCH₂Ph), 7.13 (m,

1H, H⁵py), 7.26−7.38 (m, 6H, o/m/p-H Ph, H³py), 7.81 (m, 1H, H⁴

MHz, CDCl₃): δ −3385 (s). IR: ν 3059(w), 3031(m), 2954(w),

2890(w), 1613(s), 1540(w), 1480(s), 1453(w), 1412(w), 1331(m),

1230(w), 1150(m), 1128(m), 1096(m), 999(w), 928(w), 780(m),

675(m), 570(w), 503(w), 429(w) cm⁻¹.

py), 8.24 (m+d, ³J_Pt,H= 15 Hz, 1H, H⁶py), 16.2 (s+d, J_Pt,H= 73 Hz,

3

1H, NH). ¹³C NMR (100 MHz, CDCl₃): δ 11.1 (s, C(CH₃)NO),

7a, [{Pt(CMeNHBn)₂(ONCMe−CMeNO)}₂]. Yield route

2

3

29.1 (s+d, J_Pt,C= 157.2 Hz, C(CH₃)NHBn), 44.7 (s+d, J_Pt,C

=

A/B: 51/39 mg (90/65%). Anal. Found (Calcd): C₄₄H₅₆N₈O₄Pt₂

7102

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Organometallics

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(1151.12), C 46.10 (45.91), H 4.75 (4.90), N 9.58 (9.73). HRMS

(ESI) m/z found (calcd): for [C₂₂H₂₉N₄O₂Pt]⁺576.1926 (576.1933);

[C₄₄H₅₇N₈O₄Pt₂]⁺1151.3727 (1151.3792); [C₆₆H₈₅N₁₂O₆Pt₃]⁺

1726.5552 (1726.5653); [C₂₂H₂₀D₉N₄O₂Pt]⁺585.2488 (585.2498);

(m(br), 4H, NHCH₂, S1), 4.16 (m(br), 2H, NHCH₂, S2), 4.87

(m(br), 2H, NHCH₂, S2), 5.04−5.35 (m, 8H, CH₂), 5.74−5.95 (m,

4H, CHCH₂), 12.8 (s, 2H, NH, S2), 17.0 (s, 2H, NH, S1). ¹³C

NMR (125 MHz, CDCl₃): δ 11.7 (s, CH₃dmg), 12.6 (s, CH₃dmg),

29.8 (s(br), C(CH₃)NHCH₂, S1), 35.2 (s(br), C(CH₃)NHCH₂,

S2), 48.4 (s, NHCH₂, S1), 57.1 (s, NHCH₂, S2), 118.36 (s, CH₂),

118.42 (s, CH₂), 130.9 (s, CHCH₂), 131.0 (s, CHCH₂), 155.1

(s, CNO), 158.1 (s, CNO), 195.1 (s, C(CH₃)NHCH₂, S1),

221.8 (s, C(CH₃)NHCH₂, S2). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ

−3539 (s). IR: ν 3196(w), 3091(m), 3003(w), 2912(w), 2861(w),

1735(m), 1605(m), 1550(s), 1422(m), 1363(m), 1216(s), 1086(m),

1011(m), 938(w), 745(m), 552(w), 496(w), 405(w) cm⁻¹.

1

[C₄₄H₄₀D₁₇N₈O₄Pt₂]⁺1168.4805 (1168.4860). H NMR (500 MHz,

CDCl₃): δ 1.39 (s+d, ³J_Pt,H= 44.3 Hz, 6H, C(CH₃)NHBn, S1), 2.04

(s, 6H, CH₃dmg), 2.09 (s, 6H, CH₃dmg), 2.91 (s+d, ³J_Pt,H= 35.1 Hz,

6H, C(CH₃)NHBn, S2), 4.44 (d, ²J_H,H= 15.1 Hz, 2H, CH₂Ph, S1),

4.51 (d, ²J_H,H= 15.1 Hz, 2H, CH₂Ph, S1), 4.79 (d, ²J_H,H= 13.5 Hz, 2H,

CH₂Ph, S2), 5.46 (d, ²J_H,H= 13.1 Hz, 2H, CH₂Ph, S2), 7.08−7.33 (m,

3

20H, o/m/p-H Ph), 13.6 (s+d, J_Pt,H= 107 Hz, 2H, NH, S2), 17.4 (s

3

1

+d, J_Pt,H= 62 Hz, 2H, NH, S1). H NMR (400 MHz, CD₃OD): δ

2.065 (s, 6H, CH₃dmg), 2.071 (s, 6H, CH₃dmg), 5.01 (d, ²J_H,H= 14.3

Hz, 2H, NHCH₂Ph), 5.25 (d, ²J_H,H= 14.5 Hz, 2H, NHCH₂Ph), 7.28−

7d, [{Pt(CMeNHCH₂CH₂OH)₂(ONCMe−CMeNO)}₂].

Yield route B: 27 mg (55%). Anal. Found (Calcd): C₂₄H₄₈₁N₈O₈Pt₂

(966.84), C 29.31 (29.80), H 4.84 (5.01), N 11.43 (11.59). H NMR

(200 MHz, CD₃OD, immediately measured): δ 2.01 (s, 6H, CH₃

2

7.42 (m, 20H, o/m/p-H Ph). H NMR (77 MHz, CHCl₃): δ 1.37

(s(br), 6D, C(CD₃)NHBn), 2.82 (s(br), 6D, C(CD₃)NHBn).

¹³C NMR (125 MHz, CDCl₃): δ 11.7 (s, CH₃dmg), 12.7 (s, CH₃

3

dmg), 2.06 (s, 6H, CH₃dmg), 2.11 (s+d, J_Pt,H= 44.0 Hz, 6H,

3

C(CH₃)NDCH₂, S1, H/D exchange after several hours), 2.69 (s+d,

³J_Pt,H= 36.8 Hz, 6H, C(CH₃)NDCH₂, S2, H/D exchange after

several hours), 3.61 (m, 4H, NDCH₂), 3.81−3.91 (m, 8H, CH₂OD),

3.96 (m, 2H, NDCH₂), 4.17 (m, 2H, NDCH₂). ¹³C NMR (125 MHz,

CD₃OD): δ 11.6 (s, CH₃dmg), 12.8 (s, CH₃dmg), 60.2 (s, CH₂OD),

dmg), 29.6 (s+d, J_Pt,C= 118 Hz, C(CH₃)NHBn, S1), 35.5 (s+d,

3

³J_Pt,C= 56 Hz, C(CH₃)NHBn, S2), 49.8 (s+d, J_Pt,C= 50 Hz,

3

CH₂Ph, S1), 57.9 (s+d, J_Pt,C= 96 Hz, CH₂Ph, S2), 127.5−128.9 (o/

m/p-C Ph), 135.3 (s, i-C Ph), 135.4 (s, i-C Ph), 155.1 (s(br), C

NO), 195.4 (s+d, ³J_Pt,C= 1098 Hz, C(CH₃)NHBn, S1), 222.8 (s+d,

³J_Pt,C= 1178 Hz, C(CH₃)NHBn, S2). ¹⁹⁵Pt NMR (107 MHz,

CDCl₃): δ −3534 (s). IR: ν 3425(w), 3030(w), 2926(m), 2847(w),

1610(s), 1561(s), 1498(m), 1455(m), 1410(w), 1360(w), 1214(m),

1159(m), 1078(m), 1027(w), 975(w), 907(w), 741(s), 698(s),

623(w), 485(w) cm⁻¹.

3

60.4 (s, CH₂OD), 49.8 (s, NDCH₂), 57.5 (s+d, J_Pt,C= 83.3 Hz,

NDCH₂), 157.9 (s, CNO), 158.5 (s, CNO), 199.7 (s, C(CH₃)

NDCH₂, S1), 225.2 (s, C(CH₃)NDCH₂, S2). ¹⁹⁵Pt NMR (107

MHz, CD₃OD): δ −3552 (s). IR: ν 3227(w), 3118(w), 2929(m),

2848(m), 1612(m), 1552(m), 1464(m), 1344(w), 1211(s), 1077(s),

974(m), 842(w), 740(m), 497(w) cm⁻¹.

Signals of minor intensity (ca. 5%) indicate the presence of the

8a, [{Pt(CMeNHBn)₂(ONCPh−CPhNO)}₂]. Yield route

A/B: 61/33 mg (90/45%). Anal. Found (Calcd): C₆₄H₆₄N₈O₄Pt₂

(1399.40), C 54.20 (54.93), H 4.34 (4.61), N 7.90 (8.01). HRMS

(ESI) m/z found (calcd): for [C₃₂H₃₃N₄O₂Pt]⁺700.2243 (700.2257)

[C₆₄H₆₅N₈O₄Pt₂]⁺1399.4465 (1399.4419). ¹H NMR (400 MHz,

CDCl₃): δ 1.38 (s+d, ³J_Pt,H= 43.6 Hz, 6H, C(CH₃)NHBn, S1), 2.72

(s+d, ³J_Pt,H= 35.5 Hz, 6H, C(CH₃)NHBn, S2), 4.49 (d, ²J_H,H= 15.2

monomer 7′a. Here and in the following, due to low intensity and/or

1

overlapping, not all signals of the monomer could be identiﬁed. H

NMR (500 MHz, CDCl₃): δ 2.08 (s, 6H, CH₃dmg), 2.24 (s+d, ³J_Pt,H

= 40.0 Hz, 6H, C(CH₃)NHBn), 4.67 (s, 4H, NHCH₂Ph), 7.08−

7.33 (m, 10H, o/m/p-H Ph). ¹³C NMR (125 MHz, CDCl₃): δ 12.2 (s,

CH₃dmg), 31.2 (s, C(CH₃)NHBn), 50.4 (s, NHCH₂Ph), 126.7−

128.6 (o/m/p-C Ph), 135.3 (s, i-C Ph), 154.9 (s, CNO), 194.9 (s,

C(CH₃)NHBn).

2

Hz, 2H, CH₂Ph, S1), 4.56 (d, J_H,H= 15.2 Hz, 2H, CH₂Ph, S1), 4.93

2

(d, J_H,H= 13.5 Hz, 2H, CH₂Ph, S2), 5.18 (d, J_H,H= 13.5 Hz, 2H,

7b·2H₂O, [{Pt(CMeNHCH₂CH₂Ph)₂(ONCMe−CMe

NO)}₂]·2H₂O. Yield route A/B: 52/31 mg (85/50%). Anal. Found

(Calcd): C₄₈H₆₄N₈O₄Pt₂·2H₂O (1243.26), C 46.64 (46.37), H 5.58

(5.51), N 8.64 (9.01). ¹H NMR (400 MHz, CDCl₃): δ 1.42 (s+d, ³J_Pt,H

= 43.4 Hz, 6H, C(CH₃)NHCH₂, S1), 2.06 (s, 6H, CH₃dmg), 2.12

CH₂Ph, S2), 7.03−7.34 (m, 40H, o/m/p-H Ph), 12.5 (s+d, ³J_Pt,H= 110

3

1

Hz, 2H, NH, S2), 17.3 (s+d, J_Pt,H= 69 Hz, 2H, NH, S1). H NMR

(500 MHz, CD₃OD): δ 4.66 (s(br), 1H, CH₂Ph), 4.76 (s(br), 1H,

2

CH₂Ph), 5.07 (d, J_H,H= 14.4 Hz, 1H, CH₂Ph), 5.36 (d, J_H,H= 14.4

Hz, 1H, CH₂Ph), 7.07−7.47 (m, 20H, o/m/p-H Ph). ¹³C NMR (125

MHz, CDCl₃): δ 29.5 (s, C(CH₃)NHBn, S1), 35.2 (s, C(CH₃)

NHBn, S2), 49.3 (s, NHCH₂Ph, S1), 57.5 (s, NHCH₂Ph, S2), 126.7−

130.3 (o/m/p-C Ph), 132.8 (s, i-C Ph dpg), 133.2 (s, i-C Ph dpg),

135.3 (s, i-C Ph^Bn), 135.4 (s, i-C Ph^Bn), 156.5 (s, CNO), 156.6 (s,

3

(s, 6H, CH₃dmg), 2.77 (s+d, J_Pt,H= 36.1 Hz, 6H, C(CH₃)

3

NHCH₂, S2), 2.92 (m(br), 4H, CH₂Ph, S2), 3.03 (t, J_H,H= 8.0 Hz,

4H, CH₂Ph, S1), 3.53 (m(br), 4H, NHCH₂, S1), 3.86 (s(br), 2H,

NHCH₂, S2), 4.33 (s(br), 2H, NHCH₂, S2), 7.11−7.28 (m, 20H, o/

3

m/p-H Ph), 12.5 (s+d, J_Pt,H= 105 Hz, 2H, NH, S2), 17.0 (s+d, J_Pt,H

= 61 Hz, 2H, NH, S1). ¹³C NMR (125 MHz, CDCl₃): δ 11.5 (s, CH₃

dmg), 12.6 (s, CH₃dmg), 28.6 (s, C(CH₃)NHCH₂, S1), 33.8 (s,

CH₂Ph, S2), 34.9 (s, CH₂Ph, S1), 35.4 (s, C(CH₃)NHCH₂, S2),

47.7 (s, NHCH₂, S1), 56.1 (s, NHCH₂, S2), 126.6−128.6 (o/m/p-C

Ph), 138.0 (s, i-C Ph), 138.3 (s, i-C Ph), 154.9 (s, CNO), 155.3 (s,

CNO), 194.4 (s, C(CH₃)NHCH₂, S1), 222.6 (s, C(CH₃)

NHCH₂, S2). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3539 (s). IR: ν

3424(w, br), 3025(w), 2925(m), 2865(m), 1603(m), 1560(s),

1497(m), 1454(m), 1216(s), 1153(m), 1083(m), 1029(m), 975(w),

905(w), 843(w), 743(s), 700(m), 495(w), 405(w) cm⁻¹.

1

CNO), 196.8 (s, C(CH₃)NHBn, S1), 223.4 (s+d, J_Pt,C= 1271

Hz, C(CH₃)NHBn, S2). ¹³C NMR (50 MHz, CD₃OD): δ 50.8 (s,

CH₂Ph), 58.9 (s, CH₂Ph), 128.6−131.3 (o/m/p-C Ph), 133.3 (s, i-C

Ph), 134.0 (s, i-C Ph), 136.3 (s, i-C Ph), 136.4 (s, i-C Ph), 159.0 (s,

CNO), 160.0 (s, CNO), 199.8 (s, C(CH₃)NHBn), 225.3 (s,

C(CH₃)NHBn). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3521 (s). IR:

ν 3447(w), 3030(m), 2936(m), 1604(s), 1562(m), 1497(m),

1477(m), 1454(m), 1438(m), 1410(w), 1348(m), 1267(s),

1172(m), 1135(s), 1078(w), 1027(w), 922(w), 889(s), 732(s),

696(s), 626(w), 595(m) cm⁻¹.

Signals of minor intensity (ca. 10%) indicate the presence of the

monomer 8′a. ¹H NMR (400 MHz, CDCl₃): δ 2.26 (s+d, ³J_Pt,H= 39.8

Hz, 6H, C(CH₃)NHBn), 4.74 (s, 4H, CH₂Ph), 7.03−7.34 (m, 20H,

o/m/p-H Ph). ¹³C NMR (125 MHz, CDCl₃): δ 31.3 (s, C(CH₃)

NHBn), 50.2 (s, CH₂Ph), 126.7−130.3 (o/m/p-C Ph), 132.6 (s, i-C

Ph^dpg), 135.2 (s, i-C Ph^Bn), 155.1 (s, CNO), 207.1 (s, C(CH₃)

NHBn).

Signals of minor intensity (ca. 15%) indicate the presence of the

monomer 7′b. ¹H NMR (400 MHz, CDCl₃): δ 1.95 (s+d, ³J_Pt,H= 39.9

Hz, 6H, C(CH₃)NHCH₂, 2.10 (s, 6H, CH₃dmg), 3.12 (t,³J_H,H= 7.7

Hz, 4H, CH₂Ph), 3.63 (t, ³J_H,H= 7.7 Hz, 4H, NHCH₂), 7.11−7.28 (m,

10H, o/m/p-H Ph), 15.9 (s, 2H, NH). ¹³C NMR (125 MHz, CDCl₃):

δ 12.2 (s, CH₃dmg), 30.7 (s, C(CH₃)NHCH₂), 34.7 (s, CH₂Ph),

48.3 (s, NHCH₂), 126.1−128.8 (o/m/p-C Ph), 137.8 (s, i-C), 153.2 (s,

CNO), 200.0 (s, C(CH₃)NHCH₂).

8b, [{Pt(CMeNHCH₂CH₂Ph)₂(ONCPh−CPhNO)}₂].

Yield route A/B: 57/36 mg (80/50%). Anal. Found (Calcd):

C₆₈H₇₂N₈O₄Pt₂(1455.52), C 55.98 (56.11), H 4.65 (4.99), N 7.27

(7.70). HRMS (ESI) m/z found (calcd): for [C₃₄H₃₇N₄O₂Pt]⁺

7c, [{Pt(CMeNHCH₂CHCH₂)₂(ONCMe−CMe

NO)}₂]. Yield route B: 29 mg (60%). Anal. Found (Calcd):

C₂₈H₄₈N₈O₄Pt₂(950.88), C 35.41 (35.37), H 4.75 (5.09), N 11.53

728.2541 (728.2559); [C₆₈H₇₃N₈O₄Pt₂]⁺1455.5051 (1455.5045). H

1

3

1

(11.78). H NMR (500 MHz, CDCl₃): δ 1.91 (s+d, J_Pt,H= 45.0 Hz,

6H, C(CH₃)NHCH₂, S1), 1.97 (s, 6H, CH₃dmg), 2.05 (s, 6H, CH₃

3

NMR (400 MHz, CDCl₃): δ 1.39 (s+d, J_Pt,H= 43.6 Hz, 6H,

3

dmg), 2.82 (s+d, J_Pt,H= 36.1 Hz, 6H, C(CH₃)NHCH₂, S2), 4.02

C(CH₃)NHCH₂, S1), 2.63 (s+d, J_Pt,H= 33.6 Hz, 6H, C(CH₃)

7103

dx.doi.org/10.1021/om400812w | Organometallics 2013, 32, 7090−7106

Organometallics

Article

NHCH₂, S2), 2.96 (m, 4H, CH₂Ph, S2), 3.06 (m, 4H, CH₂Ph, S1),

3.61 (m, 4H, NHCH₂, S1), 3.73 (s(br), 2H, NHCH₂, S2), 4.04 (s(br),

2H, NHCH₂, S2), 7.00−7.32 (m, 40H, o/m/p-H Ph), 11.9 (s+d, ³J_Pt,H

13.7 Hz, 2H, CH₂Ph, S2), 7.08−7.36 (m, 20H, o/m/p-H Ph), 13.7 (s

+d, ³J_Pt,H= 120 Hz, 2H, NH, S2), 17.3 (s(br), 2H, NH, S1). ¹³C NMR

(125 MHz, CDCl₃): δ 22.1/22.5 (s, C^4/5Cy), 25.3/25.8 (s, C^3/6Cy),

29.7 (s, C(CH₃)NHBn, S1), 35.7 (s, C(CH₃)NHBn, S2), 49.7/

58.0 (s, NHCH₂Ph), 127.5−128.9 (o/m/p-C Ph), 135.3 (s(br), i-C

Ph), 156.0 (s(br), CNO), 195.6 (s, C(CH₃)NHBn, S1), 222.8 (s,

C(CH₃)NHBn, S2). IR: ν 3425(w), 3010(w), 2928(m), 2858(m),

1606(m), 1559(s), 1496(w), 1451(m), 1335(w), 1315(w), 1251(w),

1205(s), 1161(m), 1062(m), 969(w), 902(w), 754(m), 697(m),

584(w), 495(w), 376(w) cm⁻¹.

3

= 111 Hz, 2H, NH, S2), 16.9 (s+d, J_Pt,H= 73 Hz, 2H, NH, S1). ¹³C

NMR (100 MHz, CDCl₃): δ 28.5 (s, C(CH₃)NHCH₂, S1), 34.1 (s,

CH₂Ph, S2), 34.7 (s, C(CH₃)NHCH₂, S2), 35.0 (s, CH₂Ph, S1),

48.2 (s, NHCH₂, S1), 55.7 (s, NHCH₂, S2), 126.4−130.3 (o/m/p-C

Ph), 133.3 (s, i-C Ph), 132.8 (s, i-C Ph), 138.07 (s, i-C Bn), 138.7 (s, i-

C Bn), 156.2/156.6 (s/s, CNO), 194.5 (s, C(CH₃)NHCH₂, S1),

221.9 (s, C(CH₃)NHCH₂, S2). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ

−3515 (s). IR: ν 3026(w), 2927(w), 2852(w), 1603(m), 1556(w),

1497(m), 1439(m), 1354(m), 1263(s), 1171(w), 1132(s), 1026(w),

922(w), 887(s), 752(m), 729(s), 694(s), 623(w), 594(w) cm⁻¹.

Signals of minor intensity (ca. 25%) indicate the presence of the

monomer 8′b. ¹H NMR (400 MHz, CDCl₃): δ 1.92 (s+d, ³J_Pt,H= 41.8

Hz, 6H, C(CH₃)NHCH₂), 3.90 (s(br), 4H, CH₂Ph), 3.77 (m, 4H,

NHCH₂), 7.00−7.32 (m, 20H, H Ph), 15.7 (s(br), 2H, NH). ¹³C

NMR (100 MHz, CDCl₃): δ 30.6 (s, C(CH₃)NHCH₂), 34.9 (s,

CH₂Ph), 47.5 (s, NHCH₂), 126.4−130.3 (o/m/p-C Ph), 133.3 (s, i-C

Ph^dpg), 138.11 (s, i-C Ph^Bn), 156.2 (s, CNO), 202.5 (s, C(CH₃)

NHCH₂). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3435 (s).

3.6. Reactivity of the Platina-β-diketone 1 toward Me₂dmg.

An NMR tube was ﬁlled with a solution of bis(O-methyl)-

dimethylglyoxime (Me₂dmg; 67 mg, 0.4 mmol) in CDCl₃(0.6 mL).

1

After recording the H and ¹³C NMR spectra, [Pt₂{(COMe)₂H}₂(μ-

Cl)₂] (1) (110 mg, 0.2 mmol) was added and the spectra were

remeasured, showing only the signals of Me₂dmg and 1. Then, sodium

methoxide (27.1 mg, 0.5 mol) was added. Within 2 h, the solution

became dark and the NMR spectra showed the signals of the

coordination polymer [{Pt(COMe)₂}_n] (2)⁶and of (noncoordinated)

Me₂dmg; see Supporting Information.

8c·CH₂Cl₂, [{Pt(CMeNHCH₂CHCH₂)₂(ONCPh−CPh

NO)}₂]·CH₂Cl₂. Yield route A/B: 21/17 mg (35/30%). Anal. Found

(Calcd): C₄₈H₅₆N₈O₄Pt₂·CH₂Cl₂(1284.10), C 46.29 (45.83), H 4.62

(4.55), N 8.72 (8.73). HRMS (ESI) m/z found (calcd): for

[C₂₄H₂₉N₄O₂Pt]⁺600.1930 (600.1933); [C₄₈H₅₇N₈O₄Pt₂]⁺

1199.3770 (1199.3793). ¹H NMR (400 MHz, CD₂Cl₂): δ 1.89 (s

3.7. Reactivity of [Pt(COMe)₂(2-pyCHNOMe)] (10) with

Primary and Secondary Amines. Stirring of [Pt(COMe)₂(2-

pyCHNOMe)] (10) (50 mg, 0.1 mmol) with an amine NH₂R′

or NHR′₂(1 mL) for one hour at room temperature (NH₂R′), at −78

°C (NHMe₂), or at 0 °C (NHEt₂) resulted in a change of color (from

red to colorless). The complexes [Pt(COMe)₂L₂] (L = NH₂Bn, 3a;

NH₂CH₂CH₂Ph, 3b; NHMe₂, 12a; NHEt₂, 12b) were isolated and

characterized (¹H, ¹³C NMR spectroscopically) as described in ref 24,

where they were prepared from reactions of [Pt(COMe)₂{H(Me)-

dmg}] (11) with the respective amine. 3a: yield 35 mg (60%). 3b:

yield 39 mg (65%). 12a: yield 21 mg (50%). 12b: yield 14 mg (30%).

3.8. X-ray Crystallography. Crystals suitable for single-crystal X-

ray diﬀraction analyses were obtained by layering a methylene chloride

(1 mL) solution of the platinum complex (ca. 15 mg) with diethyl

ether (2 mL, 4a,b, 6a, 8a·2CH₂Cl₂, 11), diethyl ether/n-pentane (1

mL/1 mL, 6e), or n-pentane (2 mL, 4c) at 5 °C. Crystals of 6b·H₂O

were obtained from a methylene chloride solution. Data for X-ray

diﬀraction analyses were collected on Stoe-IPDS 2T (4a/b, 6b·H₂O,

6e), Stoe-IPDS 2 (6a), Stoe-IPDS (11), STOE-STADI-IV (4c), and

Oxford Gemini S (8a·2CH₂Cl₂) diﬀractometers using Mo Kα

radiation (λ = 0.71073 Å, graphite monochromator). A summary of

the crystallographic data, the data collection parameters, the

reﬁnement parameters, and details of the absorption corrections is

given in Tables S1−S3 in the Supporting Information. The structures

were solved with direct methods using SHELXS-97³⁸and reﬁned using

full-matrix least-squares routines against F²with SHELXL-97.³⁹All

non-hydrogen atoms were reﬁned with anisotropic displacement

parameters, and hydrogen atoms with isotropic ones. H atoms were

placed in calculated positions according to the riding model, except

those of the O−H···O/N−H···O hydrogen bonds in complexes 4b/c,

6a/b·H₂O, and 8a, which were located in the electron density map.

3.9. Computational Details. DFT calculations were carried out

with the Gaussian 09 program package⁴⁰using the hybrid functional

B3LYP.⁴¹For the main group atoms the basis sets 6-311++G(d,p)

were employed as implemented in the Gaussian program. The valence

electrons of platinum were approximated by a split valence basis set,

too; for their core orbitals an eﬀective core potential in combination

with consideration of relativistic eﬀects was used.⁴²The appropriate-

ness of the functional in combination with the basis sets and eﬀective

core potential used for reliable interpretation of structural and

energetic aspects of related platinum complexes has been demon-

strated.^32,43Unless otherwise speciﬁed, all systems were fully

optimized without any restrictions. The resulting geometries were

characterized as equilibrium structures by analysis of the force

constants of the normal vibrations. If applicable, solvent eﬀects were

considered according to Tomasis polarized continuum model⁴⁴as

implemented in Gaussian 09.

3

+d, J_Pt,H= 43.6 Hz, 6H, C(CH₃)NHCH₂, S1), 2.69 (s+d, J_Pt,H

=

34.1 Hz, 6H, C(CH₃)NHCH₂, S2), 4.04 (m, 4H, NHCH₂, S2), 4.30

(m, 2H, NHCH₂, S1), 4.39 (m, 2H, NHCH₂, S1), 5.19−5.35 (m, 8H,

CH₂), 5.82−6.07 (m, 2H, CHCH₂), 7.10−7.19 (m, 20H, o/m/p-

H Ph), 12.1 (s, 2H, NH, S2), 17.1 (s, 2H, NH, S1). ¹³C NMR (100

MHz, CD₂Cl₂): δ 29.5 (s+d, ²J_Pt,C= 108 Hz, C(CH₃)NHCH₂, S1),

2

3

34.5 (s+d, J_Pt,C= 58 Hz, C(CH₃)NHCH₂, S2), 48.1 (s+d, J_Pt,C

=

47 Hz, NHCH₂, S1), 56.6 (s+d, ³J_Pt,C= 95 Hz, NHCH₂, S2), 117.7 (s,

CH₂), 118.2 (s, CH₂), 127.2−130.2 (o/m/p-C Ph), 131.0 (s,

CHCH₂), 131.5 (s, CHCH₂), 132.8 (s, i-C Ph), 133.1 (s, i-C Ph),

1

154.5 (s, CNO), 156.0 (s, CNO), 195.3 (s+d, J_Pt,C= 1088 Hz,

1

C(CH₃)NHCH₂, S1), 222.6 (s+d, J_Pt,C= 1208 Hz, C(CH₃)

NHCH₂, S2). ¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3507 (s). IR: ν

3022(w), 2922(w), 1603(m), 1554(m), 1410(m), 1356(m), 1265(s),

1132(s), 987(w), 920(m), 887(s), 729(s), 694(s), 625(w), 594(m)

cm⁻¹.

Signals of minor intensity (ca. 5%) indicate the presence of the

1

3

monomer 8′c. H NMR (400 MHz, CD₂Cl₂): δ 2.34 (s+d, J_Pt,H

=

41.5 Hz, C(CH₃)NHCH₂). ¹³C NMR (100 MHz, CD₂Cl₂): 30.8 (s,

C(CH₃)NHCH₂), 48.9 (s, NHCH₂), 203.1 (s, C(CH₃)NHCH₂).

¹⁹⁵Pt NMR (107 MHz, CDCl₃): δ −3439 (s).

8d·2H₂O, [{Pt(CMeNHCH₂CH₂OH)₂(ONCPh−CPh

NO)}₂]·2H₂O. Yield route B: 54 mg (90%). Anal. Found (Calcd):

C₄₄H₅₆N₈O₈Pt₂·2H₂O (1251.15); C 42.09 (42.24), H 4.51 (4.83), N

8.74 (8.96). HRMS (ESI) m/z found (calcd): for [C₂₂H₂₉N₄O₄Pt]⁺

1

608.1835 (608.1831); [C₄₄H₅₇N₈O₈Pt₂]⁺1215.3563 (1215.3589). H

3

NMR (200 MHz, CD₃OD): δ 2.21 (s+d, J_Pt,H= 44.6 Hz, 6H,

C(CH₃)NHCH₂, S1, H/D exchange after several hours), 2.76 (s+d,

³J_Pt,H= 36.9 Hz, 6H, C(CH₃)NHCH₂, S2, H/D exchange after

several hours), 3.65 (m, 4H, CH₂), 3.80 (m, 4H, CH₂), 3.94 (m, 4H,

CH₂), 4.10 (m, 2H, NHCH₂), 4.26 (m, 2H, NHCH₂), 7.04−7.19 (m,

20H, o/m/p-H Ph). IR: ν 3375(w), 3234(w), 3138(w), 3057(w),

2941(w), 2868(m), 2748(w), 1622(m), 1548(m), 1475(m), 1437(w),

1404(w), 1354(w), 1236(s), 1170(m), 1120(s), 1064(s), 735(s),

692(w) 594(m) cm⁻¹.

9a, [{Pt(CMeNHBn)₂{1,2-Cy(NO)₂}}₂]. Yield route A/B:

50/18 mg (80/30%). Anal. Found (Calcd): C₄₈H₆₀N₈O₄Pt₂

1

(1203.20), C 47.77 (47.92), H 4.99 (5.03), N 9.08 (9.31). H NMR

3

(200 MHz, CDCl₃): δ 1.42 (s+d, J_Pt,H= 45.6 Hz, 6H, C(CH₃)

NHBn, S1), 1.51−1.60 (m, 8H, H^4/5Cy), 2.55−2.76 (m, 8H, H^3/6

3

Cy), 2.93 (s+d, J_Pt,H= 36.2 Hz, 6H, C(CH₃)NHBn, S2), 4.44 (d,

2

²J_H,H= 15.0 Hz, 2H, CH₂Ph, S1), 4.51 (d, J_H,H= 15.0 Hz, 2H,

CH₂Ph,S1), 4.81 (d, ²J_H,H= 13.7 Hz, 2H, CH₂Ph, S2), 5.50 (d, ²J_H,H

=

7104

dx.doi.org/10.1021/om400812w | Organometallics 2013, 32, 7090−7106

Organometallics

Article

2005, 24, 4506. (e) Rybak-Akimova, E. V.; Nazarenko, A. Y.;

Silchenko, S. S. Inorg. Chem. 1999, 38, 2974.

(11) Kukushkin, V. Y.; Pombeiro, A. J. L. Chem. Rev. 2002, 102, 1771.

(12) (a) Michelin, R. A.; Pombeiro, A. J. L.; Guedes da Silva, M. F. C.

Coord. Chem. Rev. 2001, 218, 75. (b) Pombeiro, A. J. L.; Guedes da

Silva, M. F. C.; Michelin, R. A. Coord. Chem. Rev. 2001, 218, 43.

ASSOCIATED CONTENT

■

S

* Supporting Information

CCDC 954353 (4a), CCDC 954354 (4b), CCDC 954355

(4c), CCDC 954356 (6a), CCDC 954357 (6b·H₂O), CCDC

954358 (6e), CCDC 954359 (8a·2CH₂Cl₂), and CCDC

954360 (11) contain the supplemental crystallographic data

for this paper. These data can be obtained free of charge from

the Cambridge Crystallographic Data Centre via www.ccdc.

cam.ac.uk/data_request/cif. Supplemental data related to this

article can be found free of charge via the Internet at http://

pubs.acs.org.

(13) (a) Schalley, C. A.; Vogtle, F.; Dotz, K. H. Templates in

̈

Chemistry II; Springer: Berlin, 2004. (b) Gerbeleu, N. V.; Arion, V. B.;

Burgess, J. Template Synthesis of Macrocyclic Compounds; Wiley-VCH:

Weinheim, 1999. (c) Frischmann, P. D.; MacLachlan, M. J. Chem. Soc.

Rev. 2013, 42, 871. (d) Chambron, J.-C.; Sauvage, J.-P. New J. Chem.

2013, 37, 49. (e) Edwards, P. G.; Hahn, F. E. Dalton Trans. 2011, 40,

10278. (f) Swor, C. D.; Tyler, D. R. Coord. Chem. Rev. 2011, 255,

2860. (g) Faiz, J. A.; Heitz, V.; Sauvage, J.-P. Chem. Soc. Rev. 2009, 38,

422. (h) Kleij, A. W. Chem.Eur. J. 2008, 14, 10520.

AUTHOR INFORMATION

■

Corresponding Author

*E-mail: dirk.steinborn@chemie.uni-halle.de.

Notes

(14) Ahlbrecht, H.; Baumann, V. Synthesis 1993, 981.

(15) Iserloh, U.; Curran, D. P. J. Org. Chem. 1998, 63, 4711.

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3864.

The authors declare no competing ﬁnancial interest.

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Activation of acetyl ligands through hydrogen bonds: A new way to platinum(II) complexes bearing protonated iminoacetyl ligands

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