Spectral and structural studies of platinum group metal complexes of 3-(di-2-pyridylaminomethyl)benzamide and formation of mutual intermolecular hydrogen bonding in some complexes

Article abstract of DOI:10.1002/zaac.201100501

The new ligand, 3-(di-2-pyridylaminomethyl)benzamide, L, which carries two different coordination sites, i.e. the primary amide moiety on one side and a di-2-pyridylamine unit as a strong chelating group on the other side is synthesized. Reaction of chlor

Full text of DOI:10.1002/zaac.201100501

ARTICLE
DOI: 10.1002/zaac.201100501
Spectral and Structural Studies of Platinum Group Metal Complexes of
3-(Di-2-Pyridylaminomethyl)Benzamide and Formation of Mutual
Intermolecular Hydrogen Bonding in Some Complexes
Sairem Gloria,[a] Peng Wang,[b] and Kollipara Mohan Rao*[a]
Keywords: Arene; Pentamethylcyclopentadienyl; Ruthenium; Rhodium; Iridium
Abstract. The new ligand, 3-(di-2-pyridylaminomethyl)benzamide, L, lation [(η6-arene)Ru(L)Cl]BF4 [arene = C6H6 (1), C10H14 (2), C6Me6
which carries two different coordination sites, i.e. the primary amide (3)] and [Cp*M(L)Cl]BF4 [M = Rh (4); Ir (5)]. All these complexes
moiety on one side and a di-2-pyridylamine unit as a strong chelating
group on the other side is synthesized. Reaction of chloro-bridged di-
are characterized by micro analyses, IR, and 1H NMR spectroscopic
analyses and finally by single crystal XRD study of some representa-
mers viz., [(η6-arene)Ru(μ-Cl)Cl]2 and [Cp*M(μ-Cl)Cl]2 with two tive complexes. Complexes 3 and 5 show mutual intermolecular hydro-
equivalents of the ligand L in methanol followed by the addition of gen bonding by amide–amide interactions.
NH4BF4 results the formation of mononuclear complexes of the formu-
have a free torsion angle about their hydrogen bond it leads to
the formation of a range of possible structures with no obvious
Di-2-pyridylamine-based ligands are employed in different
predictability and certainty.[18]
1 Introduction
fields of chemistry e. g. metal coordination, supramolecular
Herein, we are reporting the synthesis of a new ligand de-
chemistry,[1–5] as well as the synthesis of new luminescent ma-
rived from di-2-pyridylamine with an appended benzamide
terials.[6–8] Recently, Romain et al. reported the importance of
substituent and five new complexes bearing this newly synthe-
catalytic activity of di-2-pyridylamine ruthenium(II) com-
sized ligand. For the complexes bearing a symmetrical co-li-
plexes in the transfer of hydrogenation of aromatic ketones in
gand viz., hexamethylbenzene and the pentamethylcyclopen-
water.[9] Complexes of CuII,[10] as well as PdII and PtII[11,12]
tadienyl, a mutual hydrogen bonding network at the amide
with polydipyridylamines were investigated for use in bio-
moiety could be observed, whereas this form of bonding is
logical applications. Earlier, monomeric complexes bearing di-
absent in the p-cymene ruthenium complex. The synthesis of
2-pyridylamine and dimeric complexes with 1,2-bis(di-2-pyr-
the ligand used in this study is shown below (Scheme 1).
idylamino methyl)benzene were reported in our labora-
tory.[13,14] However, complexes containing a di-2-pyridylamine
unit with an amide group at the meta-position have not yet
been reported. We were interested to synthesize the ligand 3-
(di-2-pyridylaminomethyl)benzonitrile and to employ it in the
synthesis of heterobimetallic complexes. But because the ni-
trile group tends to hydrolyze, we ended up in obtaining an
amide product. Among the many possible functional groups
such as carboxylic acids and alcohols that can be used for the
design of hydrogen-bonded networks, amides, in particular pri-
mary amides, have been the subject of extensive studies due to
the self-complementary nature of its hydrogen-bonded donors/
acceptors, but also because of the abundance of amide moieties
in biological systems.[15–17] Since simple amides are known to
* Prof. Dr. K. M. Rao
Fax: +91-364-2550076
E-Mail: mohanrao59@gmail.com
[a] Department of Chemistry
North Eastern Hill University
Shillong 793 022, India
[b] Department of Chemistry
McMaster University
Scheme 1. Schematic diagram for the synthesis of 3-(di-2-pyridylami-
nomethyl)benzamide.
1280 Main Street West
Hamilton, Ontario L8S 4M1, Canada
634
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 638, (3-4), 634–640

Platinum Group Metal Complexes of 3-(Di-2-pyridylaminomethyl)benzamide
2 Results and Discussion
2.1 Ligand Synthesis and Characterization
The ligand 3-(di-2-pyridylaminomethyl)benzamide was syn-
thesized by adopting Steel’s procedure.[19] With respect to the
starting precursors employed for the preparation of the ligand,
we expected to get 3-(di-2-pyridylaminomethyl)benzonitrile;
but because of hydrolysis of the nitrile end we obtained the
amide product as 3-(di-2-pyridylaminomethyl)benzamide.
Since powdered anhydrous sodium hydroxide and potassium
hydroxide in DMSO can be used to convert nitriles to
amides,[20] this conversion is unambiguous. The conversion of
nitrile to amide is confirmed by the disappearance of the nitrile
Scheme 2. Syntheses of [(η6-arene)Ru(L)Cl]BF4 and [Cp*M(L)Cl]BF4
complexes.
band at around 2236 cm–1, which is present in 3-bromometh-
ylbenzonitrile and the appearance of strong amide I and amide
II bands at 1646 and 1593 cm–1, respectively, in the infrared
spectrum. The presence of two strong bands at 3390 and
3197 cm–1, respectively, supports the formation of a primary
amide and these bands arise from the symmetrical and asym-
metrical stretching of the N–H group. The IR spectrum of the
ligand also exhibits sharp bands ca. 1474 and 1381 cm–1 corre-
sponding to the stretching frequencies of C=C and C=N bonds
of the aromatic rings.
firmed from the single crystal XRD analyses of some of the
representative complexes and these are discussed below ac-
cordingly.
2.2.1 IR Spectroscopic Studies
The IR spectra of the complexes display the symmetric and
asymmetric N–H stretching frequency ca.3400 and 3200 cm–1,
in which the range remain unaltered when compared with that
of the free ligand. This indicates that the amide moiety does
not compete strongly with the coordinating site for the binding
of central metal atom.[21] This may be due to the fact that
the formation of four membered chelate rings around it is not
favorable because of steric hindrance. Apart from these bands,
the two important bands i.e. the amide I and amide II are also
observed at around 1670 and 1600 cm–1 resulting from the –
C=O and –N–H stretching frequency, respectively. The IR
spectra of these complexes also exhibit a sharp bands due to
chelated N,N-donor bidentate ligands (ca. 1450 and 1380 cm–
1) corresponding to the stretching frequencies of C=C and C=N
bonds of the aromatic rings. Since the ligand is neutral, it
forms a monocationic complex, in which the charge is bal-
anced by the BF4 counterion and its ionic nature is thus con-
firmed from the sharp peak at around 1080 cm–1 arising from
the νB–F stretching frequency.
1
The H NMR spectrum of the ligand displays two doublet
signals at around 8.31 and 7.16 ppm and two triplet signals at
around 7.32 and 6.86 ppm for the pyridyl protons; one singlet
signal at δ = 7.82 ppm and a multiplet signal at δ = 7.52 ppm
for the phenyl protons; two broad singlet signals for each of
the two protons of the –NH2 group at δ = 6.16 and 5.68 ppm
and one singlet signal at δ = 5.53 ppm for the –CH2– protons.
The formation of the amide product is also confirmed from the
13C NMR spectrum by the presence of a resonance at
169.4 ppm, which is assigned to the carbonyl carbon of the
amide group. Although we were unable to obtain the single
crystal XRD structure of the ligand separately, its formation
1
was confirmed by IR, H NMR, and 13C NMR spectroscopic
data, and finally from the crystal structures of the complexes.
2.2 [(η6-arene)Ru(L)Cl]BF4 [arene = C6H6 (1), C10H14 (2),
C6Me6 (3)] and [Cp*M(L)Cl]BF4 [M = Rh (4), Ir (5)]
Reactions of chloro-bridged dimers, viz. [(η6-arene)Ru(μ-
Cl)Cl]2 and [Cp*M(μ-Cl)Cl]2 with two equivalents of ligand
L in methanol followed by the addition of NH4BF4 results the
formation of mononuclear complexes of the formulation [(η6-
1
2.2.2 H NMR Spectroscopic Studies
In the 1H NMR spectra of complexes 1–5, the signals of the
arene)Ru(L)Cl]BF4 and [Cp*M(L)Cl]BF4, which takes place ligands are shifted downfield as compared to those of the free
through chloro-bridge cleavage followed by the dissociation of ligand due to the change in electron density after coordination
one chloride ligand of the mentioned starting precursors as to the central metal atom. The ligand protons of complex 1
shown below (Scheme 2).
resonate in the region 8.97 to 5.52 ppm, whereas for com-
These complexes are yellow to orange in color, air stable, plexes 2 and 3 the protons of the ligand resonate in the region
non hygroscopic, readily soluble in polar solvents like meth- 8.61 to 5.43 ppm and 8.52 to 5.61 ppm, respectively. The de-
anol, dichloromethane, and acetone and sparingly soluble in tails of the assignment of the signals are shown in the Experi-
chloroform but are insoluble in low boiling non-polar solvents mental Section. Apart from these ligand signals, complexes 1
like hexane, diethyl ether, and petroleum ether. These com- and 3 exhibit singlet signals at δ = 6.15 and 1.88 ppm, which
plexes are well characterized by micro-analyses, infrared, and represent the proton signals of benzene and the hexameth-
1H NMR spectral analyses and finally the structures are con- ylbenzene ligand, respectively. The p-cymene co-ligand of
Z. Anorg. Allg. Chem. 2012, 634–640
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
635

S. Gloria, P. Wang, K. M. Rao
ARTICLE
complex 2 shows two doublet signals at δ = 5.63 and 5.47 ppm
for the aromatic protons, a septet signal at δ = 2.52 ppm for
the methine proton of the isopropyl group, a singlet signal at
δ = 2.16 ppm for the methyl group, and a doublet signal at δ
= 1.11 ppm for the methyl protons of the isopropyl group. The
ligand protons in complex 4 and 5 resonate in the region 8.73
to 5.80 ppm and 8.70 to 5.57 ppm, respectively. Apart from
these ligand signals, complexes 4 and 5 display singlet signals
at δ = 1.87 and 2.09 ppm for the pentamethylcyclopentadienyl
protons.
The protons of the amide moiety are magnetically and
chemically equivalent due to free rotation about the C–N bond
and hence display broad singlet signals at δ = 5.63, 5.55, and
5.57 ppm for complexes 1, 2, and 5 respectively. For complex
3, two broad singlet signals are observed at δ = 6.97 and
6.23 ppm due to restricted rotation about the C–N bond. But
for complex 4, the chemical shift value of the amide protons
cannot be properly assigned due to overlapping of its broad
singlet signal with the doublet signal of the phenyl group at δ
= 7.43 ppm.
Figure 1. Molecular structure of complex 2 at 45% probability level.
Hydrogen atoms and BF4 ions are omitted for clarity. Selected bond
–
lengths /Å and bond angles /°: Ru(1)–Centroid 1.680; Ru(1)–N(21)
2.118(7); Ru(1)–N(31) 2.107(6); Ru(1)–Cl 2.418(2); C(07)–N(08)
1.360(11); C(07)–O(9) 1.197(11); N(31)–Ru(1)–N(21) 84.86(12);
N(21)–Ru(1)–Cl 86.7(3); N(31)–Ru(1)–Cl 87.52(18); O(9)–C(07)–
N(08) 120.3(11); C(41)–C(06)–N(05) 112.5(8).
2.2.3 Molecular Structures and Interactions
In order to confirm the chloride bound cations, crystal struc-
ture analyses of some of the representative complexes were
carried out, which are discussed below.
H···N) with a bond length of 2.731 Å. Consequently, a 1D hy-
The X-ray quality crystals of complex 2 are grown by the drogen-bonded network is observed as shown in Figure 2,
slow diffusion of petroleum ether into dichloromethane solu- which is entirely different from the expected hydrogen bonding
tion of the complex, which later yielded as yellow block crys- mode.
tals. The crystal is found to crystallize in the monoclinic P21/
Crystals of complex 3 suitable for single crystal XRD analy-
¯
c space group. Molecular structure of complex 2 is shown in sis are grown and found to crystallize in the triclinic P1 space
Figure 1. The ruthenium cation adopts the expected and usual group. As in the case of complex 2, ruthenium cation adopts
pseudo-octahedral half sandwich “piano-stool” arrangement the “piano-stool” arrangement around the ruthenium atom as
around the Ru(1) atom with the p-cymene ligand occupying shown in Figure 3.
one face of the octahedron and the coordination of the biden-
The Ru–N(35), Ru–N(41), and Ru–Cl bond lengths are also
tate di-2-pyridylamine moiety and the chloride ion on the in agreement with the reported literatures being in the range
other. The Ru(1)–N(31), Ru(1)–N(21) and Ru(1)–Cl bond 2.0792(18), 2.0842(18), and 2.4068(18) Å, respectively. The
lengths being 2.107(6), 2.118(7), and 2.418(2) Å, respectively, metal to arene ring centroid separation is 1.699 Å, whereas the
are within the range of reported arene ruthenium complexes bite angle around N(35)–Ru–N(41) is 80.89(6)°, which are
with di-2-pyridylamine.[9,14] The “piano-stool” arrangement also consistent with the reported value of ruthenium complexes
about ruthenium atom is further reflected by small bite angle of di-2-pyridylamine.
of di-2-pyridylamine moiety N(31)–Ru(1)–N(21) is
84.86(12)°. The metal to arene ring centroid distance is intermolecular hydrogen bonding network resulting in the for-
1.680 Å, which is consistent with the reported value.[9,14]
mation of 2D sheet like arrangement consisting of various di-
The single crystal structure of complex 3 shows mutual
Due to the presence of this amide moiety, we are expecting meric units. The oxygen atom and one hydrogen atom of the
a R2 (8) and R2 (8) motif through hydrogen bonding in this amide moiety of one monomeric unit forms intermolecular hy-
2
4
complex. But such types of interactions are not observed; in- drogen bonding with nitrogen atom (2.911 Å) and oxygen
stead, a type of weak interactions involving the amide moiety atom (2.128 Å) of another amide moiety of the other mono-
is observed. The oxygen atom of the carbonyl group acts as meric unit and vice versa adopting an R2 (8) like motif. Apart
2
an acceptor and is connected to the arene system through one from these one of the hydrogen atoms of the pyridyl moiety
of the aromatic hydrogen atoms of the p-cymene co-ligand of one monomeric unit form weak hydrogen bonding interac-
forming hydrogen bonding (C–H···O) with a bond length of tions with the oxygen atom and carbon atom of the amide moi-
2.358 Å. Apart from this, one of the hydrogen atoms of the – ety of the neighboring monomeric unit giving rise to a 2D
NH2 moiety forms a weak interaction with the chlorine atom sheet like arrangement as shown in Figure 4.
(N–H···Cl) having the bond length of 2.732 Å, whereas the
Single crystals of complex 5 are grown in order to establish
nitrogen of the same forms a weak interaction with one of the the structure of [Cp*M(L)Cl]+. The representative complex of
protons of the methyl group of the p-cymene co-ligand (C– the formulation [Cp*M(L)Cl]+ is found to crystallize in the
636
www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 634–640

Platinum Group Metal Complexes of 3-(Di-2-pyridylaminomethyl)benzamide
Figure 2. Hydrogen bonding interactions in complex 2 giving rise to a 1D structure.
around N(31)–Ir(1)–N(21) is 81.6(2)°. These values are consis-
tent with the reported values.[14]
Figure 3. Molecular structure of complex 3 at 45% probability level.
–
Hydrogen atoms and BF4 ionsare omitted for clarity. Selected bond
lengths /Å and bond angles /°: Ru(1)–Centroid 1.680; Ru(1)–N(21)
2.118(7); Ru(1)–N(31) 2.107(6); Ru(1)–Cl 2.418(2); C(07)–N(08)
1.360(11); C(07)–O(9) 1.197(11); N(31)–Ru(1)–N(21) 84.86(12);
N(21)–Ru(1)–Cl 86.7(3); N(31)–Ru(1)–Cl 87.52(18); O(9)–C(07)–
N(08) 120.3(11); C(41)–C(06)–N(05) 112.5(8).
Figure 5. Molecular structure of complex 5 at 45% probability level.
Hydrogen atoms and BF4 ions are omitted for clarity. Selected bond
–
lengths /Å and bond angles /°: Ir(1)–Centroid 1.783; Ir(1)–N(21)
2.087(5); Ir(1)–N(31) 2.087(5); Ir(1)–Cl(1) 2.397(2); N(54)–C(53)
1.356(9); O(55)–C(53) 1.236(8); N(31)–Ir(1)–N(21) 81. 6(12); N(21)–
Ir(1)–Cl(1) 86.06(17); N(31)–Ir(1)–Cl(1) 87.50(16); O(55)–C(53)–
N(54) 120.4(8); N(51)–C(52)–C(41) 116.2(6).
As in the case of complex 3, the molecular structure of com-
plex 5 shows mutual intermolecular hydrogen bonding re-
sulting in the formation of dimeric unit adopting R2 (8) motif.
2
The chlorine atom of one monomeric unit exhibits weak inter-
actions with one of the hydrogens of the methyl group of the
pentamethylcyclopentadienyl ring and methylene group,
respectively. Apart from these interactions, the amide end of
the same unit exhibit mutual intermolecular hydrogen bonding
with the amide end of another monomeric unit, which already
form weak interactions with another monomeric unit through
the chlorine atom giving rise to a 2D sheet-like arrangements
as shown in Figure 6.
These entire complexes exhibit inter ionic interactions of C–
H···F contacts are detected, but these are most probably caused
by crystal packing effects and should not affect bond lengths
and angles in the molecules.
Figure 4. Formation of the 2D sheet like arrangement in complex 3.
¯
triclinic P1 space group and is shown in Figure 5. The Ir(1)–
N(31), Ir(1)–N(21) and Ir(1)–Cl(1) bond lengths are also in
agreement with the reported literatures being in the range
2.087(5), 2.087(5), and 2.397(2) Å, respectively, as reported
for the “piano-stool” arrangement complexes of iridium with
3 Conclusions
A new di-2-pyridylamine derived ligand, 3-(di-2-pyridyl-
di-2-pyridylamine. The metal to pentamethylcyclopentadienyl aminomethyl)benzamide, bearing two different interaction
ring centroid separation is 1.783 Å, whereas the bite angle sites viz., a primary amide and a di-2-pyridylamine unit cap-
Z. Anorg. Allg. Chem. 2012, 634–640
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
637

S. Gloria, P. Wang, K. M. Rao
ARTICLE
(complex 5) were grown as yellow blocks, orange bars, and yellow
plates, respectively. The intensity data for the complexes were col-
lected with a STOE IPDS II diffractometer with Mo-Kα radiation in
the whole reciprocal sphere. A numerical absorption correction was
based on the crystal shape that was originally derived from the optical
face indexing but was later optimized against equivalent reflections
using the STOE X-shape software.[22] Structures were refined with
full-matrix least-squares on F2 using SHELXL-97.[23] All non-hydro-
gen atoms were refined anisotropically. The hydrogen atoms were lo-
cated from the difference Fourier maps and refined. Structural illustra-
tions were drawn with ORTEP-3[24] for Windows. The ORTEP presen-
tations of the representative complexes are shown in Figure 1, Fig-
ure 3, and Figure 5. Crystallographic data collection parameters are
presented in Table 1.
Figure 6. Formation of the 2D sheet like arrangement in complex 5.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-853730 (2), CCDC-853731 (3), and CCDC-853732
(5) (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk),
able of forming six membered chelate ring were synthesized.
Despite our efforts to prepare dimeric complexes by changing
the metal to ligand ratio, changing the solvent and the reaction
conditions, only monomeric complexes were obtained. Inter-
molecular hydrogen bonding resulting in the formation of
R2 (8) type motif, in which the two monomeric units are con-
2
nected by a six-membered pseudo ring formed by the amide
moieties of each monomer unit are observed in complexes 3
and 5. This may be attributed to the symmetrical nature of the
co-ligand i.e., hexamethylbenzene and pentamethylcyclopen-
tadienyl co-ligand are more symmetrical as compared to the p-
cymene co-ligand. But the exact reason for exhibiting this type
of mutual interaction only in hexamethylbenzene and penta-
methylcyclopentadienyl could not be established. Since we are
unable to obtain good quality single crystal for complex 1, we
cannot establish the exact mode of bonding in it. But, owing
to its similarity with hexamethylbenzene, we would like to
conclude that there is possibility of such kind of mutual inter-
molecular hydrogen bonding mode in it. Although hydrogen-
4.3 Synthesis of the Ligand
Di-2-pyridylamine (0.314 g, 1.83 mmol) and potassium hydroxide
(0.377 g, 6.73 mmol) were given in a round-bottomed flask (50 mL).
To the mixture, DMSO (25 mL) was added and left stirring until the
potassium hydroxide flakes dissolved and a clear yellow solution was
obtained.
Afterwards,
3-bromomethylbenzonitrile
(0.300 g,
1.53 mmol) was added and further stirred for overnight to ensure that
the reaction was complete. The clear yellow solution was poured into
crushed ice (200 g) and left to stand for some time during which a
pale yellow precipitate was obtained. The precipitate was filtered,
dried, and recrystallized from methanol to yield the pale yellow micro-
crystalline product. Yield: 0.270 g (58%); Melting Point: 80 °C; Ele-
mental Anal. C18H16N4O: calcd. C 71.04; H 5.30; N 18.41%; found
C 70.95; H 5.22; N 18.16%. IR (KBr): ν˜ = 3390 (νN–H (asymmetric));
3197 (νN–H (symmetric)); 1646 (νC=O, amide I); 1593 (νN–H, amide II);
1474–1381 (νC=C, νC=N (aromatic)) cm–1. 1H NMR (CDCl3, 400 MHz,
25 °C): δ = 8.31 (d, J = 3.6 Hz, 2 H, H1 and H5); 7.82 (s, 1 H, H12);
7.63 (d, J = 7.6 Hz, 2 H, H4 and H8); 7.52 (m, J = 8.4 Hz, 1.2 Hz, 2
H, H10 and H11); 7.32 (t, J = 7.6 Hz, 2 H, H2 and H6); 7.16 (d, J =
8.4 Hz, 1 H, H9); 6.86 (t, J = 6.8 Hz, 2 H, H3 and H7); 6.16 (s (broad),
1 H, H15); 5.68 (s (broad), 1 H, H16); 5.53 (s, 2 H, H13 and H14) ppm.
13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ = 169.4 (1C, C=O); 156.1
(2C, dipyridyl); 147.5 (2C, dipyridyl); 138.9 (1C, phenyl); 138.2 (2C,
dipyridyl); 130.816 (1C, phenyl); 128.7 (1C, phenyl); 126.5 (1C,
phenyl); 126.3 (2C, phenyl); 117.7 (2C, dipyridyl); 114.9 (2C, dipyr-
idyl); 51.5 (1C, –CH2–) ppm.
bonded network based on the R2 (8) type recognition pattern
2
is observed in complexes 3 and 5, this does not further connect
to form the 2D network R2 (8) type motif.
4
4 Experimental Section
4.1 General Remarks
Infrared spectra were recorded with a Perkin–Elmer Model 983 spec-
trophotometer with the sample prepared as KBr pellets. The NMR
spectra were obtained with a Bruker Avance II 400 spectrometer in
CDCl3, [D3]acetonitrile and [D6]acetone depending on the solubility
of the complexes. Elemental Analyses of the complexes was performed
with a Perkin–Elmer 2400 CHN/S analyser. Di-2-pyridylamine and 3-
bromomethylbenzonitrile were purchased from Aldrich and used as
received. The ligand 3-(di-2-pyridylaminomethyl)benzamide (L) is re-
ported for the first time and the precursor complexes were prepared
following the literature procedures.
4.4 General Procedure for the Preparation of [(η6-arene)
Ru(L)Cl]BF4 [arene = C6H6 (1), C10H14 (2), C6Me6 (3)]
and [Cp*M(L)Cl]BF4 [M = Rh (4), Ir (5)]
A
mixture of 3-(di-2-pyridylaminomethyl)benzamide (0.050 g,
0.164 mmol) and [(η6-arene)Ru(μ-Cl)Cl]2 (0.082 mmol) for com-
plexes 1–3 or [Cp*M(μ-Cl)Cl]2 (0.082 mmol) for complexes 4 and 5
were stirred in methanol (25 mL) until a clear yellow solution was
obtained. Afterwards, two equivalents of NH4BF4 were added and con-
tinued to stir for another 10 h to ensure that the reaction was complete.
4.2 X-ray Single Crystal Diffraction and Structure
Refinement
X-ray quality crystals from dichloromethane/petroleum ether (complex
2), dichloromethane/acetone/hexane (complex 3) and acetone/hexane The yellow solution was evaporated under reduced pressure to yield
638 www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 634–640

Platinum Group Metal Complexes of 3-(Di-2-pyridylaminomethyl)benzamide
Table 1. Crystal data and structure refinement for complexes 2, 3, and 5.
2
3
5
Chemical formula
Formula weight
C28H30BClF4N4ORu
661.89
C30H34BClF4N4ORu
689.94
C28H31BClF4IrN4O
754.05
Crystal system
Space group
monoclinic
P21/c
triclinic
P1
triclinic
P1
¯
¯
Crystal color and shape
yellow block
0.21ϫ0.18ϫ0.15
12.757(3)
orange bar
0.26ϫ0.14ϫ0.12
8.2081(16)
12.550(3)
yellow plate
0.31ϫ0.24ϫ0.14
7.9714(16)
12.399(3)
Crystal size /mm3
a /Å
b /Å
17.307(4)
c /Å
14.346(3)
15.356(6)
15.688(3)
α /°
90.00
66.56(2)
111.33(3)
β /°
115.32(3)
85.28(4)
93.12(3)
γ /°
90.00
2862.9(10)
4
84.63(3)
1443.2(7)
2
91.32(3)
1440.7(5)
2
V /Å3
Z
T /K
293(2)
1.536
0.696
293(2)
1.588
0.694
293(2)
1.738
4.802
Dc /g·cm–3
μ /mm–1
θ range for data collection /°
Unique reflections
Rint
1.77 to 29.28.
22519
0.2048
R1 = 0.0599, wR2 = 0.0650
R1 = 0.2710, wR2 = 0.0988
0.657
1.45 to 26.62
17041
0.1521
R1 = 0.0569, wR2 = 0.0849
R1 = 0.1187, wR2 = 0.0988
0.830
1.77 to 29.14
20515
0.1042
R1 = 0.0434, wR2 = 0.0524
R1 = 0.1334, wR2 = 0.0654
0.623
Final R indices [I Ͼ 2σ(I)]a)
R indices (all data)
Goodness-of-fit
Max, min Δρ /e·Å–3
0.696, –0.570
0.658, –0.683
1.159, –1.155
2
2
2 2
2
2
2
a) Structures were refined on Fo : wR2 = [Σ[w(Fo –Fc ) ]/Σw(Fo2)2]1/2, where w–1 = [Σ(Fo )+(aP)2+bP] and P = [max(Fo , 0)+2Fc ]/3.
the yellow residue, which was extracted with dichloromethane. The
dichloromethane solution of the complex was finally layered with di-
ethyl ether and left for one day to yield the yellow microcrystalline
complexes.
ile, 400 MHz, 25 °C): δ = 8.52 (dd, J = 5.6 Hz, 2 H, H1 and H5); 7.90
(d, J = 7.6 Hz, 2 H, H4 and H8); 7.85 (t, J = 8.0 Hz, 1 H, H10); 7.74
(s, 1 H, H12); 7.52 (t, J = 6.8 Hz, 2 H, H2 and H6); 7.46 (d, J = 8.0 Hz,
1 H, H9); 7.32 (t, J = 6.8 Hz, 2 H, H3 and H7); 7.19 (d, J = 8.4 Hz, 1
H, H11); 6.97 [s (broad), 1 H, H15]; 6.23 [s (broad), 1 H, H16]; 5.61
(s, 2 H, H13 and H14); 1.88 (s, 18 H, C6Me6) ppm.
Complex
1:
Yield
0.061 g
(50%);
Elemental
Anal.
C24H22BClF4N4ORu: calcd. C 47.54; H 3.66; N 9.24%; found C
47.03; H 3.52; N 9.03%. IR (KBr): ν˜ = 3429 (νN–H (asymmetric)) 3184
(νN–H (symmetric)); 1659 (νC=O, amide I); 1600 (νN–H, amide II); 1447–
Complex
4:
Yield
0.075 g
(70%);
Elemental
Anal.
C28H31BClF4N4ORh: calcd. C 50.59; H 4.70; N 8.42%; found C
50.25; H 3.99; N 8.36%. IR (KBr): ν˜ = 3449 (νN–H (asymmetric)); 3191
(νN–H (symmetric)); 1672 (νC=O, amide I); 1600 (νN–H, amide II); 1447–
1381 (νC=C, νC=N (aromatic)); 1076 (νB–F) cm–1. 1H NMR ([D6]acetone),
400 MHz, 25 °C): δ = 8.73 (d, J = 6.0 Hz, 2 H, H1 and H5); 8.08 (t, J
= 8.8 Hz, 2 H, H2 and H6); 8.01 (d, J = 6.4 Hz, 2 H, H4 and H8); 7.66
(d, J = 8.0 Hz, 1 H, H9); 7.58 (t, J = 8.0 Hz, 2 H, H3 and H7); 7.50 (t,
J = 6.4 Hz, 1 H, H10); 7.43 (d, J = 8.8 Hz, 1 H, H11); 6.63 (s, 1 H,
H12); 5.80 (s, 2 H, H13 and H14); 1.87 (s, 15 H, Cp*) ppm.
1
1407 (νC=C, νC=N (aromatic)); 1076 (νB–F) cm–1. H NMR ([D6]acetone,
400 MHz, 25 °C): δ = 8.97 (d, J = 4.8 Hz, 2 H, H1 and H5); 8.11 (s,
1 H, H12); 8.02 (t, J = 7.6 Hz, 2 H, H2 and H6); 7.91 (d, J = 7.6 Hz,
2 H, H3 and H7); 7.85 (d, J = 7.6 Hz, 1 H, H9); 7.62 (d, J = 8.4 Hz, 1
H, H11); 7.55 (t, J = 7.6 Hz, 2 H, H3 and H7); 7.30 (t, J = 6.4 Hz, 1
H, H10); 6.15 (s, 6 H, C6H6); 5.63 (s, 2 H, H15 and H16); 5.52 (s, 2 H,
H13 and H14) ppm.
Complex
2:
Yield
0.075 g
(69%);
Elemental
Anal.
C28H30BClF4N4ORu: calcd. C 50.80; H 4.56; N 8.46%; found C
50.67; H 4.31; N 8.34%. IR (KBr): ν˜ = 3416 (νN–H (asymmetric)); 3197
(νN–H (symmetric)); 1666 (νC=O, amide I); 1600 (νN–H, amide II); 1460–
1387 (νC=C, νC=N (aromatic)); 1082 (νB–F) cm–1. 1H NMR (CDCl3,
400 MHz, 25 °C): δ = 8.61 (d, J = 5.2 Hz, 2 H, H1 and H5); 8.02 (s,
1 H, H12); 7.87 (d, J = 7.6 Hz, 2 H, H4 and H8); 7.79 (t, J = 7.2 Hz,
2 H, H2 and H6); 7.44 (d, J = 5.6 Hz, 1 H, H9); 7.38 (t, J = 7.6 Hz, 2
H, H3 and H7); 7.31 (d, J = 8.0 Hz, 1 H, H11); 7.13 (t, J = 6.8 Hz, 1
H, H10); 5.63 (d, J = 4.8 Hz, 2 H, aromatic-cymene); 5.55 (s, 2 H, H15
and H16); 5.47 (d, J = 5.2 Hz, 2 H, aromatic- cymene); 5.43 (s, 2 H,
H13 and H14); 2.52 [sept, 1 H, J = 6.8 Hz CH(CH3)2]; 2.16 (s, 3 H, -
CH3); 1.11 [d, J = 6.8 Hz, 6 H, CH(CH3)2] ppm.
Complex
5:
Yield
0.064 g
(67%);
Elemental
Anal.
C28H31BClF4N4OIr: calcd. C 44.60; H 4.14; N 7.43%; found C 44.52;
H 4.12; N 7.26%. IR (KBr): ν˜ = 3403 (νN–H (asymmetric)); 3191 (νN–H
(symmetric)); 1666 (νC=O, amide I); 1600 (νN–H, amide II); 1460–1381
(νC=C, νC=N (aromatic)); 1076 (νB–F) cm–1. 1H NMR ([D6]acetone,
400 MHz, 25 °C): δ = 8.77 (dd, J = 1.6 Hz, 4.4 Hz, 2 H, H1 and H5);
8.06–7.98 (m, J = 1.6 Hz, 7.2 Hz, 3 H, H9, H10 and H11); 7.67 (d, J =
7.6 Hz, 2 H, H4 and H8); 7.60 (t, J = 2.0 Hz, 2 H, H2 and H6); 7.47
(s, 1 H, H12); 7.43 (t, J = 4.8 Hz, 2 H, H3 and H7); 5.76 (s, 2 H, H13
and H14); 5.57 (s, 2 H, H15 and H16); 2.09 (s, 15 H, Cp*) ppm.
Acknowledgement
Complex
3:
Yield
0.072 g
(70%);
Elemental
Anal.
C30H34BClF4N4ORu: calcd. C 52.21; H 4.96; N 8.12%; found C
52.08; H 4.94; N 8.07%. IR (KBr): ν˜ = 3403 (νN–H (asymmetric)); 3191
(νN–H (symmetric)); 1672 (νC=O, amide I); 1600 (νN–H, amide II); 1447–
1381 (νC=C, νC=N (aromatic)); 1082 (νB–F) cm–1. 1H NMR ([D3]acetonitr-
Sairem Gloria thanks UGC, New Delhi for providing financial assist-
ance in the form of University Fellowship. K. M. Rao gratefully ac-
knowledges financial support from the UGC, New Delhi, through the
Research grant No. F.No.39–793/2010 (SR).
Z. Anorg. Allg. Chem. 2012, 634–640
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
639

S. Gloria, P. Wang, K. M. Rao
ARTICLE
[12] S. Fakih, W. C. Tung, D. Eierhoff, C. Mock, B. Krebs, Z. Anorg.
Allg. Chem. 2005, 631, 1397–1402.
References
[13] G. Gupta, S. Gloria, B. Das, K. M. Rao, J. Mol. Struct. 2010,
979, 205–213.
[1] S. Demeshko, G. Leibeling, S. Dechert, F. Meyer, Dalton Trans.
2004, 3782–3787.
[2] C. Seward, W. l. Jia, R. Y. Wang, S. Wang, Inorg. Chem. 2004,
43, 978–985.
[3] P. Gamez, P. de Hoog, O. Roubeau, M. Lutz, W. L. Driessen,
A. L. Spek, J. Reedijk, Chem. Commun. 2002, 1488–1489.
[4] P. de Hoog, P. Gamez, M. Leuken, O. Roubeau, B. Krebs, J. Reed-
ijk, Inorg. Chim. Acta 2004, 357, 213–218.
[5] W. L. Jia, D. R. Bai, T. McCormick, Q. D. Liu, M. Motala, R. Y.
Wang, C. Seward, Y. Tao, S. Wang, Chem. Eur. J. 2004, 10, 994–
1006.
[6] Q. D. Liu, W. L. Jia, G. Wu, S. Wang, Organometallics 2003, 22,
3781–3791.
[7] Y. Kang, C. Seward, D. Song, S. Wang, Inorg. Chem. 2003, 42,
2789–2797.
[8] C. Seward, W. L. Jia, R. Y. Wang, G. D. Enright, S. Wang, Angew.
Chem. Int. Ed. 2004, 43, 2933–2936.
[9] C. Romain, S. Gaillard, M. K. Elmkaddem, L. Toupet, C. Fisch-
meister, C. M. Thomas, J.-L. Renaud, Organometallics 2010, 29,
1992–1995.
[14] G. Gupta, S. Gloria, B. Therrien, B. Das, K. M. Rao, J. Or-
ganomet. Chem. 2011, 696, 702–708.
[15] J. C. MacDonald, G. M. Whitesides, Chem. Rev. 1994, 71, 2383–
2420.
[16] G. R. Desiraju, Angew. Chem. Int. Ed. Engl. 1995, 34, 2311–2327.
[17] C. B. Aakeröy, B. M. T. Scott, J. Desper, New J. Chem. 2007, 31,
2044–2051.
[18] J. J. Kane, T. Nguyen, J. Xiao, F. W. Fowler, J. W. Lauher, Mol.
Cryst. Liq. Cryst. 2001, 356, 449–458.
[19] B. Antonioli, D. J. Bray, J. K. Clegg, K. Gloe, K. Gloe, O. Kata-
eva, L. F. Lindoy, J. C. McMurtrie, P. J. Steel, C. J. Sumby, M.
Wenzel, Dalton Trans. 2006, 4783–4794.
[20] W. Roberts, M. C. Whiting, J. Chem. Soc. 1965, 1290–1293.
[21] S. A. Baudron, D. S. Mendoza, M. W. Hosseini, CrystEngComm
2009, 1245–1254.
[22] Stoe & Cie X-SHAPE, Version 2.05: Program for Crystal Optimi-
zation for Numerical Absorption Correction; Stoe & Cie GmbH,
Darmatadt, Germany, 2004.
[23] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Re-
finement, University of Göttingen, Göttingen, Germany, 1997.
[24] L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565–566.
[10] T. Chao, Y. Shao, N. Gan, Q. Xu, Z. Guo, Inorg. Chem. 2004,
43, 4761–4766.
[11] C. Tu, J. Lin, Y. Shao, Z. Guo, Inorg. Chem. 2003, 42, 5795–
5797.
Received: November 16, 2011
Published Online: February 2, 2012
640
www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 634–640