2-Pyridylmetallocenes, part IV. Cycloplatination of 2-pyridyl-ferrocene, -ruthenocene and -cymantrene. Molecular structures of σ-Pt{CpM[C 5H3(2-C5H4N)]}Cl (DMSO) (M = Fe, Ru) and σ-Pt{CpFe[C5H3(2-C5H 4N)]}(acac)

Article abstract of DOI:10.1016/j.ica.2013.01.022

The 2-pyridylmetallocenes [C₅H₃R(2-C ₅H₄N)]ML_n (1a-e, ML_n = FeCp, RuCp, Mn(CO)₃, R = H, CH₃) react with cis-[PtCl ₂(DMSO)₂] to give the cycloplatinated complexes σ-Pt{L_nM[C₅H₂(2-C₅H ₄N)(R)]}Cl (DMSO) (ML_n = FeCp (R = H: 2a; R = Me: 2b), RuCp (R = H, 3a; R = Me, 3b), Mn(CO)₃ (R = H, 4)). The reaction of 1a with the chiral sulfoxide complexes cis-[PtCl₂{S(O)Me(p-C ₆H₄Me)}₂] or K[PtCl₃S(O)Me(p-C ₆H₄Me)] yields a mixture of σ-Pt{CpFe[C ₅H₂(2-C₅H₄N)(R)]}Cl[S(O)Me(p-C ₆H₄Me)] diastereomers (R_pR_S/S _pS_S)- and (R_pS_S/S_PR _S)-5. Treatment of 2a with sodium pentane-2,4-dionate ( Na(acac) ) gives the bischelate σ-Pt{CpFe[C₅H ₃(2-C₅H₄N)]}(acac) (6a). Refluxing solutions of 2a with glycine in the presence of sodium methoxide yields the amino acidato complex Pt{CpFe[C₅H₃(2-C₅H₄N)]}(gly) 6b. The molecular structures of 2a, b, 3a and 6a have been determined by X-ray diffraction. 2a, b and 3a show a trans-N, S configuration of the pyridine nitrogen and the DMSO sulfur atoms.

Full text of DOI:10.1016/j.ica.2013.01.022

Inorganica Chimica Acta 399 (2013) 193–199
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
2-Pyridylmetallocenes, part IV. Cycloplatination of 2-pyridyl-ferrocene,
-ruthenocene and –cymantrene. Molecular structures of
r
-Pt{CpM[C5H3(2-C5H4N)]}Cl (DMSO) (M = Fe, Ru) and r-Pt{CpFe[C5H3
(2-C5H4N)]}(acac)
⇑
Karlheinz Sünkel , Ramona Branzan, Stefan Weigand
Department of Chemistry, Ludwig-Maximilians-University Munich, Butenandtstr. 9, 81377 Munich, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 July 2012
Received in revised form 7 January 2013
Accepted 13 January 2013
Available online 4 February 2013
The 2-pyridylmetallocenes [C5H3R(2-C5H4N)]MLn (1a–e, MLn = FeCp, RuCp, Mn(CO)3, R = H, CH3) react
with cis-[PtCl2(DMSO)2] to give the cycloplatinated complexes -Pt{LnM[C5H2(2-C5H4N)(R)]}Cl (DMSO)
(MLn = FeCp (R = H: 2a; R = Me: 2b), RuCp (R = H, 3a; R = Me, 3b), Mn(CO)3 (R = H, 4)). The reaction of
r
1a with the chiral sulfoxide complexes cis-[PtCl2{S(O)Me(p-C6H4Me)}2] or K[PtCl3S(O)Me(p-C6H4Me)]
yields
and (RpSS/SPRS)-5. Treatment of 2a with sodium pentane-2,4-dionate (‘‘Na(acac)’’) gives the bischelate
-Pt{CpFe[C5H3(2-C5H4N)]}(acac) (6a). Refluxing solutions of 2a with glycine in the presence of sodium
a mixture of r-Pt{CpFe[C5H2(2-C5H4N)(R)]}Cl[S(O)Me(p-C6H4Me)] diastereomers (RpRS/SpSS)-
Keywords:
r
2-Pyridylmetallocenes
Cycloplatination
Crystal structures
methoxide yields the amino acidato complex Pt{CpFe[C5H3(2-C5H4N)]}(gly) 6b. The molecular structures
of 2a, b, 3a and 6a have been determined by X-ray diffraction. 2a, b and 3a show a trans-N, S configura-
tion of the pyridine nitrogen and the DMSO sulfur atoms.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
metallocenylpyridines. With the rich chemistry of arylpyridines
and their interesting physicochemical properties and their applica-
Cyclometalation reactions continue to receive considerable
attention, as well from mechanistic and preparative aspects as
from the numerous applications of the metallacycles that are pro-
duced by these reactions [1]. Known cyclometalated organometal-
lic platinum complexes are mostly based on 2-arylpyridines, and
have been tested mainly for their luminescence properties [2],
but also for their antitumour activity [3], and very recently for
interaction with amyloid-b-peptide in the context of Alzheimer’s
disease [4]. Usually it was found that the particular properties
could be tuned by variations as well in the aryl part as in the pyr-
idine part of the cyclometalating ligand. One possible modification
of the aryl moiety would be the use of a substituted metallocene,
e.g., ferrocene. There is a rather long tradition of cycloplatination
of ferrocenylamines [5] and ferrocenylimines [6]. Cycloplatinated
ferrocenylimines have been tested e.g., for their electrochemical
properties [7], or their potential utility as molecular switches [8].
Several ferrocene derivatives have been shown to have antitumour
activity [9], and among them a cycloplatinated ferrocenylamine
[10]. However, there seem to be no reports on cycloplatinated
tions in mind, we decided it would be worthwhile to study the
cycloplatination of some 2-pyridyl-metallocenes.
2. Experimental
All reactions were performed under argon, using standard
Schlenk techniques. cis-[PtCl2(DMSO)2], cis-[PtCl2{S(O)Me(p-
C6H4Me)}2] and K[PtCl3S(O)Me(p-C6H4Me)] were prepared as de-
scribed in the literature [11]. The 2-pyridylmetallocenes 1a–e were
prepared as recently described by us [12]. Solvents (analytical
grade) were saturated with argon.
NMR: JEOL ECP-270 and ECX-400, all NMR spectra (except for
6b) were recorded in CD2Cl2 and were referenced to the signal of
residual CHDCl2 d (1H) = 5.300 ppm, or CD2Cl2 d(13C) = 53.8 ppm;
DMSO-d6 was used for 6b: reference was set to d(1H) = 2.49 ppm
and d(13C) = 39.5 ppm.
MS: Finnigan MAT 90 and JEOL Mstation 700.
UV/Vis: Ocean Optics USB 2000. Concentration: 1.0 mg in
10.0 mL CH2Cl2.
The elemental analyses were performed at the microanalytical
laboratory at the chemistry department of Ludwig-Maximilians
University, Munich.
⇑
Corresponding author. Tel.: +49 89 2180 77773.
E-mail address: suenk@cup.uni-muenchen.de (K. Sünkel).
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.01.022

194
K. Sünkel et al. / Inorganica Chimica Acta 399 (2013) 193–199
2.1. General procedure for the preparation of chlorido[2-(2-pyridinyl-
‘‘JHH’’ = 0.8, 8.0 Hz; JPtH = 8 Hz, H3), 7.07 (‘‘dt’’, ‘‘JHH’’ = 1.4, 5.8 Hz;
H5), 5.08 (‘‘d’’, ‘‘JHH’’ = 2.2 Hz; JPtH ꢀ 8 Hz, H9), 4.73 (‘‘d’’,
‘‘JHH’’ = 2.2 Hz; JPtH = 11 Hz, H10), 4.41 (s, Cp), 3.52/3.45 (2 s,
JPtH = 25 Hz/26 Hz, SCH3), 2.32 (s, CH3). 13C NMR (100 MHz):
d = 167.1 (C2), 150.3 (JPtC ꢀ 14 Hz, C6), 139.8 (C4), 120.2 (JPtC = 31 -
Hz, C5), 118.6 (JPtC = 33 Hz, C3), 92.3 (C7), 85.0 (JPtC = 41 Hz, C11),
83.9 (C8), 75.4 (JPtC = 44 Hz, C10), 73.8 (JPtC = 95 Hz, C9), 72.4
(Cp), 47.9/46.9 (JPtC = 70 Hz/66 Hz, SCH3), 15.8 (CH3).
jN)metallocenyl-jC]dimethylsulfoxide-platinum(II),
r-Pt{LM[C5H3(2-C5H4N)]}Cl(DMSO) 2–4
The whole synthesis of 4 has to be performed in the dark. The 2-
pyridylmetallocene (0.25 mmol) and cis-[PtCl2(DMSO)2] (0.11 g,
0.25 mmol) were suspended in toluene (50 mL) and treated with
a
solution of NaOAcÁ3H2O (0.068 g, 0.50 mmol) in methanol
(1.0 mL). The mixture was refluxed (4 h for 2a,b and 3b, 6 h for
3a and 5 h for 4), and then the solvent completely removed in va-
cuo. The remaining solid was taken up in a small amount of CH2Cl2
and then chromatographed on silica gel. 2a and 3a were eluted
with a CH2Cl2/EtOAc mixture (8:1 for 2a and 3a, 3:1 for 2b, 5:1
for 3b, 4:1 for 4). After evaporation of the solvents the products
were recrystallized from CH2Cl2/hexane. Yields: 2a: 0.14 g
(0.24 mmol, 98%); 2b: 0.13 g (0.22 mmol, 93%); 3a: 0.13 g
(0.21 mmol, 82%); 3b: 0.15 g (0.24 mmol, 95%), 4: 0.15 g
(0.23 mmol, 93%).
4: Anal. Calc. for C15H13ClMnNO4PtS: C, 30.60; H, 2.23; N, 2.38;
S, 5.45. Found: C, 31.79; H, 2.43; N, 2.37; S, 5.37%. MS (DEI+): m/
z = 589.1 (M+, 22%), 505.1 (M+À3CO, 100%), 427.1 (M+-
À3COÀDMSO, 23%). 1H NMR (400 MHz), d = 9.36 (‘‘d‘‘, ‘‘JHH’’ = 5.8 -
Hz; JPtH = 34 Hz, H6), 7.87 (‘‘t‘‘, ‘‘JHH’’ = 6.9 Hz; H4), 7.37 (‘‘d‘‘,
‘‘JHH’’ = 7.7 Hz; H3), 7.25 (‘‘t‘‘, ‘‘JHH’’ = 6.0 Hz; H5), 5.20 (s, br, H9),
5.15 (s, br, H11), 4.99 (‘‘t’’, ‘‘JHH’’ = 2.8 Hz; H10), 3.59/3.56 (2 s,
JPtH = 24 Hz/24 Hz, SCH3). 13C NMR (100 MHz): d = 226.2 (CO),
161.2 (C2), 150.5 (JPtC = 17 Hz, C6), 141.1 (C4), 122.4 (JPtC = 28 Hz,
C5), 118.8 (JPtC = 29 Hz, C3), 105.2 (JPtC = 57 Hz, C7), 99.1 (C8),
85.4 (JPtC = 48 Hz, C10), 84.1 (JPtC = 86 Hz, C9), 78.8 (JPtC = 50 Hz,
C11), 47.0/46.8 (JPtC = 63 Hz/64 Hz, SCH3). 195Pt NMR (CD2Cl2):
d = À3673 ppm.
2a: Anal. Calc. for C17H18ClFeNOPtS: C, 35.77; H, 3.18; N, 2.45;
Fe, 9.78; S, 5.62. Found: C, 36.02; H, 3.28; N, 2.51; Fe, 9.39; S,
5.70%. MS (DEI+): m/z = 570.9 (M+), 537.1 (M+ÀCl), 493.1
(M+ÀDMSO), 456.2 (M+ÀClÀ DMSO). 1H NMR (270 MHz), d = 9.30
(‘‘ddd’’, ‘‘JHH’’ = 0.9, 1.5, 5.9 Hz; JPtH = 36 Hz, H6), 7.74 (‘‘dt’’,
‘‘JHH’’ = 1.8, 8.0 Hz; H4), 7.32 (‘‘ddd’’, ‘‘JHH’’ = 0.9, 1.5, 8.0 Hz;
JPtH = 9 Hz, H3), 7.08 (‘‘ddd’’, ‘‘JHH’’ = 1.5, 5.9, 7.4 Hz; H5), 5.01
(‘‘dd’’, ‘‘JHH’’ = 1.2, 2.4 Hz; JPtH = 8 Hz, H9), 4.66 (‘‘dd’’, ‘‘JHH’’ = 0.9,
2.7 Hz; H11), 4.50 (‘‘t’’, ‘‘JHH’’ = 2.4 Hz; JPtH = 13 Hz, H10), 4.06 (s,
Cp), 3.64/3.59 (2 s, JPtH = 25 Hz/24 Hz, SCH3). 13C NMR
(100 MHz): d = 167.8 (C2), 150.0 (JPtC = 19 Hz, C6), 139.8 (C4),
120.1 (JPtC = 30 Hz, C5), 118.2 (JPtC = 31 Hz, C3), 88.2 (JPtC = 62 Hz,
C7), 83.8 (JPtC = 1130 Hz, C8), 74.2 (JPtC = 94 Hz, C9), 70.4 (Cp),
70.0 (JPtC = 46 Hz, C10), 65.0 (JPtC = 44 Hz, C11), 47.7/47.3 (JPtC = 66 -
Hz/71 Hz, SCH3). 195Pt NMR (CD2Cl2): d = À3797 ppm.
2.2. Chlorido[2-(2-pyridinyl-
j
N)ferrocenyl-
jC]methyl-p-tolyl-
sulfoxide-platinum(II),
r-Pt{CpFe[C5H3(2-C5H4N)]}Cl[S(O)Me(p-
C6H4Me)], 5
A solution of 1a (0.066 g, 0.25 mmol) and (a) K[PtCl3S(O)Me(p-
C6H4Me)] (0.12 g, 0.25 mmol) or (b) cis-[PtCl2{S(O)Me(p-
C6H4Me)}2] (0.14 g, 0.25 mmol) in toluene (50 mL) is treated with
a solution of NaOAcÁ3H2O (0.068 g, 0.50 mmol) in 1 mL MeOH.
After refluxing for 24 h the solvent is evaporated in vacuo. The
red residue is taken up in a minimum amount of CH2Cl2 and chro-
matographed on silicagel using a 4:1 mixture of CH2Cl2/EtOAc as
eluent. 5 Elutes first and yields after evaporation a red solid (a:
0.080 g, 0.13 mmol, 50%; b: 0.11 g, 0.17 mmol, 68%).
2b: MS (DEI+) m/z: 628.8 (C20H27FeNO2PtS2+), 584.8 (M+, 75%),
506.8 (M+ÀDMSO, 100%), 468.9 ([M + H]+ÀClÀDMSO, 42%). 1H
NMR (400 MHz): d = 9.36 (‘‘d’’, ‘‘JHH’’ = 5.8 Hz; JPtH = 36 Hz, H6),
7.73 (‘‘dt’’, ‘‘JHH’’ = 1.7, 7.7 Hz; H4), 7.53 (‘‘d’’, ‘‘JHH’’ = 7.4 Hz; H3),
7.09 (‘‘dt’’, ‘‘JHH’’ = 1.1, 6.7 HZ; H5), 4.89 (‘‘d’’, ‘‘JHH’’ = 2.5 Hz; H9),
4.42 (‘‘d’’, ‘‘JHH’’ = 2.2 Hz; H10), 3.99 (s, Cp), 3.59/3.54 (2 s, JPtH = 24 -
Hz/25 Hz, SCH3), 2.32 (s, HMe). 13C NMR (100 MHz): d = 168.4
(JPtC = 65 Hz, C2), 150.5 (JPtC = 15 Hz, C6), 139.6 (C4), 120.0
(JPtC = 30 Hz, C5), 118.7 (JPtC = 33 Hz, C3), 86.3 (JPtC = 70 Hz, C7),
84.3 (JPtC = 1130 Hz, C8), 82.3 (JPtC = 44 Hz, C11), 73.3 (JPtC = 42 Hz,
C10), 72.1 (JPtC = 89 Hz, C9), 71.0 (Cp), 47.7/47.5 (JPtC = 65 Hz/71 Hz,
SCH3), 15.4 (CMe).
MS (FAB+): m/z = 647.2 (M+), 611.2 (M+ÀCl), 492.2 (M+-
ÀS(O)MeTol), 457.2 (M+ÀClÀS(O)MeTol). 1H NMR (400 MHz):
d = 9.41 (m, JPtH = 36 Hz, H6, I + II), 8.14 (‘‘d‘‘, ‘‘JHH’’ = 8.5 Hz; C6H4,
a-H, I), 8.01 (‘‘d‘‘, ‘‘JHH’’ = 8.3 Hz; C6H4, a-H, II), 7.70 (m, H4, I + II),
7.46 (‘‘d‘‘, ‘‘JHH’’ = 8.3 Hz; C6H4, b-H, I), 7.33 (‘‘d‘‘, ‘‘JHH’’ = 8.3 Hz;
C6H4, b-H, II) 7.30–7.26 m, H3, I + II⁄⁄⁄, 7.10 (m, H5, I + II), 4.83/
4.63 (2Â ‘‘dd’’, ‘‘JHH’’ = 1.1, 2.2 Hz/0.8, 2.2 Hz; H9, I/II), 4.59/4.58
(m, H11, I + II), 4.40/4.38 (2Â ‘‘t’’, ‘‘JHH’’ = 2.5 Hz/2.5 Hz; H10, I/II),
4.10 (s, Cp, II), 3.67 (s, JPtH = 20 Hz, SCH3, I + II), 3.55 (s, Cp, I), 2.43/
2.40 (2 s, Tol-CH3, I/II). 13C NMR (67.9 MHz): d = 168.0 (JPtC = 65 Hz,
C2, I + II), 149.9/149.8 (JPtC = 20/20 Hz, C6, II/I), 143.6/143.5 (C6H4-
3a: Anal. Calc. for C17H18ClNOPtRuS: C, 33.15; H, 2.95; N, 2.27; S,
5.21. Found: C, 33.29; H, 3.10; N, 2.13; S, 5.39%. MS (DEI+): m/
z = 616.2 (M+), 580.3 (M+ÀCl), 537.2 (M+ÀDMSO), 502.3 (M+-
ÀClÀDMSO). 1H NMR (270 MHz), d = 9.20 (‘‘ddd’’, ‘‘JHH’’ = 0.9, 1.5,
5.9 Hz; JPtH = 36 Hz, H6), 7.67 (‘‘dt’’, ‘‘JHH’’ = 1.5, 7.4 Hz; H4), 7.28
(‘‘ddd’’, ‘‘JHH’’ = 0.9, 1.2, 8.0 Hz; JPtH = 9 Hz, H3), 7.05 (‘‘dt’’,
‘‘JHH’’ = 1.5, 5.9 Hz; H5), 5.21 (‘‘dd’’, ‘‘JHH’’ = 0.6, 2.4 Hz; JPtH = 8 Hz,
H9), 5.03 (‘‘dd’’, ‘‘JHH’’ = 0.9, 2.4 Hz; H11), 4.72 (‘‘t’’, ‘‘JHH’’ = 2.4 Hz;
JPtH = 11 Hz, H10), 4.45 (s, Cp), 3.54/3.49 (2 s, JPtH = 26 Hz/25 Hz,
SCH3). 13C NMR (67.9 MHz): d = 166.4 (JPtC = 61 Hz, C2), 149.8
(JPtC = 19 Hz, C6), 139.9 (C4), 120.3 (JPtC = 31 Hz, C5), 117.8
(JPtC = 31 Hz, C3), 93.5 (JPtC = 64 Hz, C7), 83.2 (JPtC = 1130 Hz, C8),
75.6 (JPtC = 98 Hz, C9), 72.0 (Cp), 71.4 (JPtC = 44 Hz, C10), 66.8
(JPtC = 44 Hz, C11), 47.9/47.0 (JPtC = 72 Hz/69 Hz, SCH3). 195Pt (CD2-
Cl2): d = À3755 ppm.
Ci, II/I), 142.7/142.4 (C6H4–C , II/I), 139.8 (C4, I + II), 130.2/130.1
c
(C6H4–Cb, I/II), 125.8/125.5 (C6H4-C , II/I), 120.0 (JPtC = 31 Hz, C5,
a
I + II), 118.1 (JPtC = 32 Hz, C3, I + II), 88.1 (JPtC = 57 Hz, C7, I + II),
84.7/84.0 (C8, I/II), 74.4/74.1 (JPtC = 98/94 Hz, C9), 70.8/70.3 (Cp),
70.1/70.0 (JPtC = 46/45 Hz, C10), 64.8/64.5 (JPtC = 44/43 Hz, C11),
49.3/49.2 (JPtC = 54/58 Hz, SCH3, II/I), 21.5 (Tol-CH3). Note: ‘‘I’’ corre-
sponds to the slightly preferred RpSS/SpRS diastereomer, while ‘‘II’’ repre-
sents the minor RpRS/SpSS diastereomer.
2.3. Acetylacetonato[2-(2-pyridinyl-jN)ferrocenyl-jC]-platinum(II),
r-Pt{CpFe[C5H3(2-C5H4N)]}(acac) 6a
A solution of 2a (0.23 g, 0.40 mmol) and Na(acac)ÁH2O (0.056 g,
0.40 mmol) in acetone (40 mL) was refluxed 8 h. After addition of
50 mL water the precipitated red solid was isolated by filtration,
washed with water and dried in vacuo. Recrystallization from
CH2Cl2/n-hexane yielded 5 as dark red crystals (0.18 g, 0.33 mmol,
82%).
3b: Anal. Calc. for C18H20ClNOPtRuS: C, 34.31; H, 3.20; N, 2.22; S,
5.09%; found: C, 35.84; H, 3.55; N, 2.10; S, 4.68%. MS (DEI+): m/z:
645.0 (C19H22ClNOPtRuS+), 630.4 (M+), 594.5 (M+ÀCl), 553.3 (M+-
ÀDMSO), 530.0 (M+ÀClÀCp), 515.4 (M+ÀClÀDMSO). 1H NMR
(400 MHz), d = 9.30 (‘‘ddd’’, ‘‘JHH’’ = 0.6, 1.7, 6.0 Hz; JPtH = 35 Hz,
H6), 7.70 (‘‘dt’’, ‘‘JHH’’ = 1.7, 8.0 Hz; JPtH = 26 Hz, H4), 7.49 (‘‘td’’,
Anal. Calc. for C20H19FeNO2Pt: C, 43.18; H, 3.44; N, 2.52; Fe,
10.04; Pt, 35.07. Found: C, 43.59; H, 3.66; N, 2.38; Fe, 10.47; Pt,

K. Sünkel et al. / Inorganica Chimica Acta 399 (2013) 193–199
195
31.40%. MS (FAB+): m/z = 556.0 (M+), 457.1 (M+Àacac). 1H NMR
(270 MHz), d = 8.81 (‘‘d’’, ‘‘JHH’’ = 5.9 Hz; JPtH = 44 Hz, H6), 7.65
(‘‘dt’’, ‘‘JHH’’ = 1.2, 7.7 Hz; H4), 7.23 (‘‘d‘‘ br, ‘‘JHH’’ = 8.0 Hz; H3),
6.96 (‘‘ddd‘‘, ‘‘JHH’’ = 1.2, 5.9, 7.4 Hz; H5), 5.46 (s, H14), 4.67 (‘‘d’’
br, ‘‘JHH’’ = 2.4 Hz; H11), 4.49 (‘‘d’’ br, ‘‘JHH’’ = 2.1 Hz; H9), 4.45 (‘‘t’’
br, ‘‘JHH’’ = 2.2 Hz;H10), 4.01 (s, Cp), 1.95/1.92 (2s, H12 and H16).
13C NMR (67.9 MHz): d = 185.0 (C13), 184.2 (JPtC = 32 Hz, C15),
170.2 (C2), 147.6 (C6), 137.8 (C4), 119.3 (JPtC = 36 Hz, C5), 117.9
(JPtC = 39 Hz, C3), 102.4 (JPtC = 61 Hz, C14), 89.1 (C7), 75.7 (C8),
70.6 (JPtC = 96 Hz, C9), 70.2 (C12), 68.8 (JPtC = 49 Hz, C10), 64.1
(JPtC = 49 Hz, C11), 28.4 (C12), 27.0 (JPtC = 49 Hz, C16). 195Pt NMR
(CD2Cl2): d = À4026 ppm.
(COO), 167.3 (C2), 148.9 (C6), 138.4 (C4), 120.3 (C5), 118.0 (C3),
89.0 (C7), 73.3 (C8), 71.9 (C9), 69.5 (Cp), 68.7 (C10), 63.9 (C11),
47.7 (C ).
a
2.5. X-ray structure determinations of 2a, b, 3a and 6a
Crystals of all compounds were grown from CH2Cl2/iso-hexane
or CHCl3/hexane (3a). X-ray quality crystals were mounted on glass
fibers and cooled to 173(3) K during measurement. The data were
collected on an Oxford Xcalibur3 CCD diffractometer using graph-
ite-monochromated Mo Ka radiation (k = 0.71073 Å). A multi-scan
absorption correction was applied using the ABSPACK program [13].
The structures were solved with the SIR-97 software as imple-
mented in the WINGX software package [14]. Refinement (full matrix
least square on F2) was done with SHELXL 97 [15], also as imple-
mented in WINGX. Further details can be seen in Table 1.
2.4. (
g
2-N,O-glycinato) [2-(2-pyridinyl-
-Pt{CpFe[C5H3(2-C5H4N)]}(gly) (6b)
jN)-ferrocenyl-jC]-
platinum(II),
r
A solution of 2a (0.057 g, 0.10 mmol) in CH2Cl2 (10 mL) was
treated with a mixture of glycine (0.0080 g, 0.10 mmol) and
NaOMe (0.010 g, 0.20 mmol) dissolved in MeOH (10 mL) and re-
fluxed for 24 h. Thereafter dilute HCl (30 mL) was added and the
aqueous phase extracted three times with CH2Cl2 (20 mL each).
The combined organic phases were vigorously stirred over MgSO4,
and, after filtering, evaporated to dryness in vacuo. The remaining
red solid was taken up with Et2O and chromatographed on silica
gel. The eluted ethereal phase was discarded; the desired product
was eluted with MeOH. After evaporation a red solid remained,
which contained small amounts of an unidentified impurity (visi-
ble by additional 1H NMR signals and peaks in the mass spectra)
(0.032 g, <61%).
3. Results and discussion
3.1. Synthesis
For the preparation of mononuclear cycloplatinated complexes
of the [(C^N)Pt(L)(X)] type, the sulfoxide complex cis-[PtCl2
(DMSO)2] has been reported to be the reagent of choice [5,9c,17].
Thus, when the 2-pyridyl metallocenes 1a–e were treated with this
complex in the presence of two equivalents of sodium acetate as
base, high yields of the cycloplatinated compounds 2–4 could be
obtained [16]. We tested also the reaction of 1a with K2PtCl4,
which lead to an observable reaction followed by precipitation of
a solid that was completely insoluble in all common solvents.
The manganese compound 4 turned out to be light sensitive and
also rather unstable in solution. All attempts of recrystallization,
to obtain satisfactory combustion analysis data, lead to
decomposition.
MS (FAB+): m/z = 531.1 (M+), 457.0 (M+Àglycine). 1H NMR (in
DMSO-d6, 270 MHz): d = 8.54 (‘‘d’’, ‘‘JHH’’ = 5.3 Hz; H6), 7.87 (‘‘dt’’,
‘‘JHH’’ = 1.2, 8.0 Hz; H4), 7.47 (‘‘d’’, ‘‘JHH’’ = 8.0 Hz; H3), 7.13 (‘‘t’’,
‘‘JHH’’ = 7.6 Hz; H5), 5.97 (s, br, NH2), 4.76 (‘‘d’’, ‘‘JHH’’ = 1.8 Hz;
H11), 4.37 (‘‘t’’, ‘‘JHH’’ = 2.1 Hz; H10), 4.29 (‘‘d’’, ‘‘JHH’’ = 1.8 Hz;
H9), 3.99 (s, Cp). 13C NMR (in DMSO-d6, 67.9 MHz): d = 180.8
Table 1
Experimental parameters of the crystal structure determinations.
Compound
2a
2b
3a
6a
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
C
17H18ClFeNOPtS
C18H20ClFeNOPtSÁCH2Cl2
669.73
monoclinic
P21/a
C17H18ClNOPtRuSÁCHCl3
735.36
C20H19FeNO2Pt
1112.60
monoclinic
C2/c
570.77
monoclinic
C2/c
triclinic
ꢀ
P1
9.6637(7)
27.927(2)
12.8174(5)
90
96.645(7)
90
3476(2)
8
2.207
9.257
9.3079(5)
26.2435(11)
9.7687(5)
90
116.795(8)
90
2130.00(18)
4
2.088
9.8621(10)
10.4803(8)
11.1942(11)
100.706(7)
96.331(8)
97.819(7)
1115.33(18)
2
16.2080(5)
12.3572(4)
17.5616(5)
90
91.026(3)
90
3516.8(2)
8
2.101
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (mg/m3)
2.190
7.523
696
Absorption coefficient (mmÀ1
F(000)
)
7.726
1288
8.785
2128
2176
Crystal size (mm)
h range for data collection (°)
Index ranges
0.13 Â 0.08 Â 0.02
4.21 to 26.29
À8 6 h 6 12,
À31 6 k < 6 34,
À11 6 l 6 15
6693
0.21 Â 0.18 Â 0.14
4.15 to 26.35
À6 6 h 6 11,
À32 6 k 6 28,
À12 6 l 6 8
8652
0.25 Â 0.18 Â 0.17
4.20 to 26.24
À12 6 h 6 12,
À11 6 k 6 13,
À13 6 l 6 13
8573
0.24 Â 0.22 Â 0.16
4.25 to 26.30°
À19 6 h 6 20,
À15 6 k 6 11,
À21 6 l 6 21
13359
Reflections collected
Independent reflections (Rint
Completeness to hmax
)
3476 (0.0512)
98.5%
4322 (0.0424)
99.2%
4462 (0.0356)
98.7%
3564 (0.0378)
99.4%
Maximum and minimum transmission
Data/parameters
0.8310 and 0.5724
3476/208
0.759
0.3390 and 0.2462
4322/249
0.947
0.2783 and 0.1603
4462/246
0.943
0.2452 and 0.1294
3564/229
0.813
Goodness-of-fit on F2
R1/wR2 [I > 2
R1/wR2 (all data)
r
(I)]
0.0335/0.0501
0.0668/0.0541
1.160 and À0.922
822045
0.0375/0.0736
0.0540/0.0772
2.065 and À1.703
886293
0.0339/0.0701
0.0473/0.0726
2.327 and À1.220
822046
0.0222/0.0410
0.0347/0.0426
0.823 and À0.615
822047
Largest difference peak and hole [e ÅÀ3
CSD number
]

196
K. Sünkel et al. / Inorganica Chimica Acta 399 (2013) 193–199
16
Cl
S
H
R
O
14
Pt
6
4
6
4
15
11
N
8
N
13
9
7
2
7 2
12
cis-PtCl2(DMSO)2
10
9
5
5
O
O
8
11
ML
9
Pt
8
10
3
3
6
4
N
R
ML
7 2
6a
6b
5
+Na(acac)
11
10
3
R
H
ML
R
H
ML
2a
FeCp
O
+ glycine/ NaOMe
CpFe
CpFe
CpRu
1a
CpFe
CpFe
CpRu
CpRu
2a
H
a
H
Me 1b
Me 2b
O
H2N
H
1c
Me 1d
Pt
H
3a
Me 3b
6
8
N
7 2
9
5
CpRu
11
10
4
3
Mn(CO)3
H
1e
Mn(CO)3
H
4
FeCp
Scheme 3. Synthesis of 6a and 6b.
Scheme 1. Synthesis of 2–4.
was attributed to the ring current effect from the sulfoxide tolyl
group. Since this signal integrates ca. 54:46 with respect to the
‘‘normal’’ Cp resonance at 4.10 ppm, and approximately the same
integral ratio can be observed for several other resonances in the
1H NMR spectrum of 5, assignment of individual signals to both
diastereomers is possible. In analogy to the literature assignment
we assign the RpSS/SPRS configuration to the slightly preferred
isomer.
The use of a chiral sulfoxide ligand should lead, in principle, to
asymmetrically cycloplatinated ferrocenes [17]. The reaction of 1a
with either a diastereomeric mixture of (meso + RR/SS)-[PtCl2{-
S(O)Me(p-C6H4Me)}2] or racemic K[PtCl3{S(O)Me(p-C6H4Me)}]
yielded a diastereomeric mixture of RpRS/SpSS- and RpSS/SpRS-5
(Scheme 2) (for the assignment of diastereomers, vide infra).
The ferrocenyl compound 2a gave after treatment with sodium
pentanedionate (Na+acacÀ) the bis-chelate complex 6a, while with
glycine in the presence of NaOMe the bis-chelate complex 6b could
be obtained (Scheme 3). 6a could be fully characterized, however,
6b was always contaminated with an unknown impurity.
The pyridine protons H3–H6 form an ABCX spin system, with
the H6 proton next to the coordinated nitrogen showing a signifi-
cant low field shift: d(H6) d(H4) > d(H3) > d(H5). As was already ob-
served earlier, d(H6) > 9.30 ppm, when a chloride ligand is in cis-
position at the coordinated Pt atom, while it is shifted to
d < 9.0 ppm, when an oxygen atom is the cis-donor atom [18]. In
all complexes with cis Pt-Cl groups this proton shows also coupling
3.2. NMR spectra
The signal assignments (numbering scheme see Scheme 1) are
based on HMQC measurements, a NOESY experiment on 3, which
showed the coupling of H3 and H11, and the 1H and 13C NMR spec-
tra of the mono-deuterated complex [D1]-2a, which contains deu-
terium at position 11.
3
to platinum, with JPtH = 34–36 Hz, while in the acetylacetonato
complex 6a a coupling constant of 44 Hz is observed. In the DMSO
complexes, for the SCH3 protons there are always two singlets with
platinum satellites to be seen. The values for JPtH of ca. 25 Hz indi-
cate that the DMSO ligand is always S-bonded.
The cyclopentadienyl protons H9–H11 form an AXY pattern,
giving apparent ‘‘dd’’, ‘‘t’’ and ‘‘dd’’ patterns for 2a, 3a and 5 (two
signal sets), which are partially unresolved in 4 and 6a,b. In the
methylated derivatives 2b and 3b the protons H9 and H10 appear
as two doublets. In some cases 195Pt satellites can be observed for
protons H9 and H10, with coupling constants JPtH of 8 Hz and 11–
13 Hz, respectively, thus 3J < 4J. The protons of the unsubstituted
cyclopentadienyl rings are observed (in CD2Cl2) as singlets at ca
4.05 0.05 ppm in the ferrocenes and 4.43 0.02 ppm in the
ruthenocenes, except for one diastereomer of 5, which shows a
substantial high field shift two d = 3.55 ppm. This was also ob-
served for the RpSS diastereomer of the cycloplatinated dimethyl-
aminomethylferrocene with the same sulfoxide ligand [17], and
In the 13C NMR spectra the most prominent feature is the large
low-field shift of the pyridine carbon C2, from d ꢀ 160 ppm in the
free metallocene ligand to 166–170 ppm in the cycloplatinated
complexes 2–6, which was also observed in the cycloplatination
of phenylpyridines [18a]. For compounds 2b, 3a and 5 platinum
2
satellites could be observed for these resonances, with JPtC = 61–
65 Hz. For the pyridine carbon C6 in all cycloplatinated complexes,
2
except for 6a,b, JPtC = 14–20 Hz, while for the quaternary cyclo-
2
pentadienyl carbon C7 the observed JPtC amounted to 57–70 Hz
and for C9 a 2JPtC of 86–98 Hz was found. The 3JPtC couplings within
the pyridine ring were 31 2 Hz for 2–5, while within the cyclo-
pentadienyl ring values of 47 3 Hz were found. In the spectra of
ß
γ
a
H3C
O
Cl
Pt
i
Cl
Pt
S
S
N
N
O
+cis-[PtCl2{S(O)Me(pTol)}2]
H3C
1a
Fe
Fe
or
+K[PtCl3S(O)Me(pTol)]
(RpRS)- 5
Scheme 2. Synthesis of 5. It is only one enantiomer of both diastereomers ahown.
(RpSS)- 5

K. Sünkel et al. / Inorganica Chimica Acta 399 (2013) 193–199
197
Table 2
Selected UV–Vis spectroscopic data: wavelengths (k in nm) and molar extinction
coefficients (
in dm2/mol) (in parentheses).
Table 3
Important bond parameters of the Pt coordination sphere.
e
Compound
2a
2b
3a
6a
Compound
k1
k2
k3
k4
Pt–C [Å]
Pt–Cl [Å]
Pt–N [Å]
Pt–S [Å]
C–Pt–N [°]
C–Pt–Cl [°]
<(cp),(py) [°]
C–Pt–S–O [°]
‘‘H6’’Á Á ÁCl [Å]
‘‘Ha’’Á Á ÁO [Å]
(PtÁ Á ÁPt)min [Å]
1.989(7)
2.409(2)
2.079(5)
2.194(2)
80.3(2)
173.9(2)
3.1(4)
1.981(7)
2.4050(17)
2.095(5)
2.2017(17)
80.5(2)
172.7(2)
4.1(4)
À14.8(3)
2.615(1)
2.342(1)
7.955
2.001(6)
2.417(2)
2.110(5)
2.205(2)
81.3(2)
173.7(2)
6.7(3)
1.967(4)
–
2.018(3)
–
81.6(2)
–
9.6(4)
–
2a
2b
3b
6a
282 (17300)
294 (14800)
343 (4280)
344 (2843)
415 (1580)
421 (990)
502 (2460)
519 (1770)
389 (1980)
505
344
8.0(3)
6.1(3)
2.672(1)
2.421(1)
3.921
2.675(1)
2.435(1)
5.857
–
–
6.125
Fig. 1. Molecular structure of 2b, 30% probability ellipsoids.
Fig. 3. View of the dimer in 3a.
3.3. UV–Vis spectra
The UV–Vis spectra of compounds 2a, 2b, 3b, 6a were measured
in ca. 10À4 M CH2Cl2 solution. Up to 4 bands could be resolved (Ta-
ble 2). The bands labeled as ‘‘k1’’, ‘‘k2’’ and ‘‘k4’’ are very similar to
the bands observed in [Pt{[(C5H3)–CH = N–(CH2–CH2–OH)]Fe(C5-
H5)]}Cl(dmso),[20] and can most likely be assigned the same
way. It was also tried to obtain emission spectra of these 0.01%
solutions in CH2Cl2, using excitation wavelengths of ca. 340 nm
or 505 nm, at r.t., but no emissions could be observed.
3.4. Crystal structures
Fig. 2. Molecular structure of 6a, 30% probability ellipsoids.
All complexes except for 4 have a high tendency to crystallize.
The molecular structures of 2b and 6a are depicted in Figs. 1 and 2.
The geometry around the platinum atom is very similar in all
complexes (see Table 3), and also similar to related platinacycles
with ligands of the phenylpyridine type [2,21] or the ferrocenyli-
mine type.[7] As can be seen from the torsion angles C–Pt–S–O,
the SO-bond of the sulfoxide ligand is coplanar with the cyclopen-
tadienyl ring, the deviation increasing in the series 3a < 2a < 2b. At
the same time the distance H9Á Á ÁO decreases from 3a to 2b. This C–
HÁ Á ÁO hydrogen bond persists in solution as can be concluded from
the substantial low-field shift of the CH proton in the 1H NMR
spectra.
1
2a,b and 3a the JPtC could be observed, amounting to 1130 Hz in
all three compounds. 1JPtC values of ca. 1100 Hz have been reported
before [18b]. Thus, within the cyclopentadienyl ring a sequence of
1J >> 2J > 3J is observed, while in the pyridine ring 2J < 3J is found.
For compounds 2a, 3a, 4 and 6a it was possible to obtain 195Pt
NMR spectra, with dPt ranging from À3755 ppm (3a) to
À4026 ppm (6a). 195Pt NMR data have been reported for several
cycloplatinated complexes, including ferrocene derivatives. High-
field signals with d À 3700 to À4000 ppm (rel. H2PtCl6) have been
regarded as typical for cycloplatinated complexes [18a,19].

198
K. Sünkel et al. / Inorganica Chimica Acta 399 (2013) 193–199
instances, by deliberate choice of counterions or sterically hin-
dered cyclometallating ligands the formation of -stacks and
p
PtÁ Á ÁPt interactions could be avoided to enforce the monomer
emissions [25]. Since the pi-coordinated (Cp-M)-fragment should
make stacking of more than two platinacycles impossible we
looked at the possibility of
p-stacked dimers. The structures of
2b and 6a show no
p–p
interactions at all, and the PtÁ Á ÁPt distances
of more than 6 Å also exclude any metal–metal interactions. In the
ruthenocene structure 3a there are head-to-tail dimers with inter-
planar distances of 3.54 Å, but the PtÁ Á ÁPt distance of nearly 6 Å still
excludes any metal–metal interaction (Fig. 3). These parameters
are very similar to the ones found in the crystal structure of
[Pt(ppy)(DMSO)Cl] [21a].
In compound 2a two molecules related by the symmetry oper-
ators (x,y,z) and (1Àx, y, 3/2 À z) and having the same planar chi-
rality approach each other to a Pt–Pt distance of 3.921 Å. Although
there are also
p–p interactions between these molecules, there is
an interplanar angle of ca. 15° which reduces the overlap substan-
tially (Figs. 4 and 5).
4. Conclusion
We could prepare cycloplatinated pyridylmetallocenes in good
to excellent yields and characterize them by NMR and mass spec-
trometry. Crystal structure determinations prove the proposed
structures and also show in some cases the formation of dimers
with p–p interactions. All ferrocene compounds have dark red col-
Fig. 4. Top view of the head-to-tail dimer in the crystal of 2a.
ors, while the ruthenocene derivative is yellow. Unfortunately
none of the prepared compounds shows fluorescence neither in
the solid state nor in solution, at least at room temperature. This
might seem to be expected, since it is known that ferrocene itself
is not luminescent and ruthenocene only at low temperatures
[26], and also that ferrocene quenches triplet states of organic
compounds [27]. On one hand, this property could be used for
the construction of fluorescence switches [28], on the other hand
it could be shown that with appropriately substituted ferrocene
good fluorescent properties are obtainable [29]. This lends hope
to further synthetic efforts, towards the preparation of luminescent
pyridylmetallocenes by proper combination of metal and ring sub-
stituents. This effort seems particularly worthwhile in the light of
recent research towards promising photoactive antitumoral plati-
num complexes [30].
Acknowledgment
Support from the Department of Chemistry of the Ludwig-Max-
imilians-University Munich is gratefully acknowledged.
Appendix A. Supplementary material
The supplementary crystallographic data for this article can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary
data associated with this article can be found, in the online version,
at http://dx.doi.org/10.1016/j.ica.2013.01.022.
Fig. 5. Side view of the dimer in 2a.
Another important structural feature for the usefulness of
square-planar platinum (II) complexes as emitters in OLED applica-
tions is their ‘‘tendency . . .to aggregate in higher concentration,
resulting in quenching of emission in the solid state’’ and the
observation ‘‘that inhibition of stacking. . . is beneficial to the emit-
ting behavior’’ [22]. On the other hand, it has been claimed that
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