Assembly of symmetrical or unsymmetrical cyclometalated organoplatinum complexes through a bridging diphosphine ligand

Article abstract of DOI:10.1021/om100295q

The cyclometalated complexes [Pt(ppy)Ar(SMe₂)] or [Pt(bhq)Ar(SMe₂)], where ppyH = 2-phenylpyridine, bhqH = benzo[h]quinoline, and Ar = 4-tolyl or 4-anisyl, react with bis(diphenylphosphino)methane, dppm, in a 1:1 ratio to give the corresponding complexes [Pt(ppy)Ar(κ¹-dppm)] and [Pt(bhq) Ar(κ¹-dppm)], in which the dppm ligands are monodentate, or in a 2:1 ratio to give the symmetrical binuclear complexes [{Pt(ppy)Ar} ₂(μ-dppm)] and [{Pt(bhq)Ar}₂(μ-dppm)], in which the dppm ligands are bridging bidentate. Most remarkably, the reaction of [Pt(ppy)Ar(SMe₂)] with [Pt(bhq)Ar′(κ¹-dppm)] or of [Pt(bhq)Ar′(SMe₂)] with [Pt(ppy)Ar(κ¹- dppm)] occurs selectively to give the unsymmetrical bridged complexes [(ppy)ArPt(μ-dppm)PtAr′(bhq)]. An example of each structural type has been characterized crystallographically, and it is shown that some of the bhq complexes undergo supramolecular self-assembly through π-stacking.

Full text of DOI:10.1021/om100295q

Organometallics 2010, 29, 4893–4899 4893
DOI: 10.1021/om100295q
Assembly of Symmetrical or Unsymmetrical Cyclometalated
Organoplatinum Complexes through a Bridging Diphosphine Ligand†
S. Masoud Nabavizadeh,‡ Mohsen Golbon Haghighi,‡ Ahmad R. Esmaeilbeig,‡
Fatemeh Raoof,‡ Zeinab Mandegani,‡ Sirous Jamali,§ Mehdi Rashidi,‡,^, and
Richard J. Puddephatt*,^
‡Department of Chemistry, Faculty of Sciences, Shiraz University, Shiraz 71454, Iran, §Department of
Chemistry, Persian Gulf University, Bushehr 75169, Iran, and ^Department of Chemistry, The University of
Western Ontario, London, Ontario, Canada N6A 5B7. On leave from Shiraz University, Iran
Received April 12, 2010
The cyclometalated complexes [Pt(ppy)Ar(SMe2)] or [Pt(bhq)Ar(SMe2)], where ppyH = 2-phenyl-
pyridine, bhqH = benzo[h]quinoline, and Ar = 4-tolyl or 4-anisyl, react with bis(diphenylphosphino)-
methane, dppm, in a 1:1 ratio to give the corresponding complexes [Pt(ppy)Ar(κ1-dppm)] and
[Pt(bhq)Ar(κ1-dppm)], in which the dppm ligands are monodentate, or in a 2:1 ratio to give the
symmetrical binuclear complexes [{Pt(ppy)Ar}2(μ-dppm)] and [{Pt(bhq)Ar}2(μ-dppm)], in which the
dppm ligands are bridging bidentate. Most remarkably, the reaction of [Pt(ppy)Ar(SMe2)] with
[Pt(bhq)Ar0(κ1-dppm)] or of [Pt(bhq)Ar0(SMe2)] with [Pt(ppy)Ar(κ1-dppm)] occurs selectively to give
the unsymmetrical bridged complexes [(ppy)ArPt(μ-dppm)PtAr0(bhq)]. An example of each structural
type has been characterized crystallographically, and it is shown that some of the bhq complexes
undergo supramolecular self-assembly through π-stacking.
Introduction
regard, it has been shown that the chelate ring in complex A4
can be opened by reaction with a chelating diphosphine, PP =
bis(diphenylphosphino)ferrocene, to give the monodentate
2-pyridylphenylplatinum complex G.5 With only a half equiva-
lent of the diphosphine, the symmetrical bridged binuclear
complex H was formed.5 This article shows that the short bite
diphosphine ligand bis(diphenylphosphino)methane, dppm,9
does not displace the pyridine donor from complexes analogous
to A but forms only a monodentate dppm complex, and it will
The chemistry of cyclometalated organometallic compounds
is of great current interest, on the basis of applications of such
compounds in stoichiometric or catalytic organic synthesis and
in sensing and functional materials.1 As in other areas of
organometallic chemistry,2 studies of the cyclometalation of
platinum complexes have given many interesting complexes as
well as new insight into the mechanisms of the reactions.1,3-6
The cyclometalation reactions can be brought about by using
either electrophilic6 or nucleophilic3-5 platinum(II) precursor
complexes, such as those with formula [PtR2(SMe2)2] or
[Pt2R4(μ-SMe2)2].3-5,7,8 Some typical complexes formed from
2-phenylpyridine or benzo[h]quinoline are shown as A-F
in Chart 1.
(6) (a) Fernandez, S.; Fornies, J.; Gil, B.; Gomez, J.; Lalinde, E.
Dalton Trans. 2003, 822. (b) Ghedini, M.; Pugliese, T.; La Deda, M.;
Godbert, N.; Aiello, I.; Amati, M.; Belviso, S.; Lelj, F.; Accorsi, G.;
Barigelletti, F. Dalton Trans. 2008, 4303. (c) Wong-Foy, A. G.; Henling,
L. M.; Day, M.; Labinger, J. A.; Bercaw, J. E. J. Mol. Catal. 2002, 189, 3. (d)
Cave, G. W. V.; Fanizzi, F. P.; Deeth, R. J.; Errington, W.; Rourke, J. P.
Organometallics 2000, 19, 1355. (e) Crosby, S. H.; Clarkson, G. J.; Rourke,
J. P. J. Am. Chem. Soc. 2009, 131, 14142. (f) Circu, V.; Ilie, M.; Ilis, M.;
Dumitrascu, F.; Neagoe, I.; Pasculescu, S. Polyhedron 2009, 28, 3739. (g)
Rachford, A. A.; Castellano, F. N. Inorg. Chem. 2009, 48, 10865. (h) Yen,
S. K.; Young, D. J.; Huynh, H. V.; Koh, L. L.; Hor, T. S. A. Chem. Commun.
2009, 6831. (i) Rao, Y.-L.; Wang, S. Inorg. Chem. 2009, 48, 7698. (j)
Fukuda, H.; Yamada, Y.; Hashizume, D.; Takayama, T.; Watabe, M. Appl.
Organomet. Chem. 2009, 23, 154. (k) Zhou, G.-J.; Wang, Q.; Wong, W.-Y.;
Ma, D.; Wang, L.; Lin, Z. J. Mater. Chem. 2009, 19, 1872. (l) Chang, S.-Y.;
Cheng, Y.-M.; Chi, Y.; Lin, Y.-C.; Jiang, C.-M.; Lee, G.-H.; Chou, P.-T.
Dalton Trans. 2008, 6901. (m) Whitfield, S. R.; Sanford, M. S. Organome-
tallics 2008, 27, 1683. (n) Liu, J.; Yang, C.-J.; Cao, Q.-Y.; Xu, M.; Wang, J.;
Peng, H.-N.; Tan, W.-F.; Lu, X.-X.; Gao, X.-C. Inorg. Chim. Acta 2009, 362,
575. (o) Ghavale, N.; Wadawale, A.; Dey, S.; Jain, V. K. J. Organomet.
Chem. 2010, 695, 1237.
There is interest in assembling the cyclometalated complexes
to give dimers (D, Chart 1),6n oligomers, or polymers.1 In this
† Part of the Dietmar Seyferth Festschrift. Dedicated to Professor Dietmar
Seyferth for his pioneering research in organometallic chemistry and his
outstanding service to Organometallics.
*Corresponding author. E-mail: pudd@uwo.ca.
(1) (a) Albrecht, M. Chem. Rev. 2010, 110, 576. (b) Omae, I. Coord.
Chem. Rev. 2004, 248, 995. (c) Canty, A. J.; van Koten, G. Acc. Chem. Res.
1995, 28, 406. (d) Ryabov, A. D. Chem. Rev. 1990, 90, 403.
(2) Seyferth, D. Organometallics 2001, 20, 2.
(3) (a) Zucca, A.; Petretto, G. L.; Stoccoro, S.; Cinellu, M. A.;
Manassero, M.; Manassero, C.; Minghetti, G. Organometallics 2009,
28, 2150. (b) Fortman, G. C.; Scott, N. M.; Linden, A.; Stevens, E. D.; Dorta,
R.; Nolan, S. P. Chem. Commun. 2010, 46, 1050. (c) Anderson, C.; Crespo,
M.; Morris, J.; Tanski, J. M. J. Organomet. Chem. 2006, 691, 5635. (d)
Yagyu, T.; Ohashi, J.; Maeda, M. Organometallics 2007, 26, 2383. (e)
Calvet, T.; Crespo, M.; Font-Bardia, M.; Gomez, K.; Gonzalez, G.; Martinez,
M. Organometallics 2009, 28, 5096.
(7) Rashidi, M.; Hashemi, M.; Khorasani-Motlagh, M.; Puddephatt,
R. J. Organometallics 2000, 19, 2751.
(8) (a) Scott, J. D.; Puddephatt, R. J. Organometallics 1983, 2, 1643.
(b) Anderson, C.; Crespo, M.; Ferguson, G.; Jennings, M. C.; Puddephatt,
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Chem. 2002, 648, 302.
(9) (a) Cowie, M. Can. J. Chem. 2005, 83, 1043. (b) Puddephatt, R. J.
Chem. Soc. Rev. 1983, 99.
(4) Owen, J. S.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 2004,
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r
2010 American Chemical Society
Published on Web 06/07/2010
pubs.acs.org/Organometallics

4894 Organometallics, Vol. 29, No. 21, 2010
Nabavizadeh et al.
Chart 1
Figure 1. (a) View of the structure of complex 2a. Selected bond
˚
parameters (A and deg): Pt(1)-C(3) 2.030(8); Pt(1)-C(10)
2.052(8); Pt(1)-N(1) 2.142(7); Pt(1)-S(1) 2.358(2); C(3)-Pt(1)-
C(10) 93.4(4); C(10)-Pt(1)-N(1) 80.9(3); C(3)-Pt(1)-S(1)
91.7(3); N(1)-Pt(1)-S(1) 93.9(2). (b) Supramolecular structure
of complex 2a formed through π-stacking of the bhq groups.
Scheme 1a
Scheme 2. The Cyclometalation Reactions
a PP = bis(diphenylphosphino)ferrocene.
be shown that this property can be exploited to form not only
symmetrical complexes analogous to H (Scheme 1) but also
unsymmetrical binuclear complexes containing two different
cyclometalated groups.
solid state through π-stacking of the planar bhq groups, as
˚
shown in Figure 1b (mean interplanar separation 3.3 A).
Results and Discussion
The reaction of the dimethylsulfide complex 1 or 2 with
the ligand bis(diphenylphosphino)methane, dppm, in a 1:1
or 2:1 ratio gave either the corresponding monodentate
dppm complex 3 or 4 or the bridging dppm complex 5 or 6,
respectively, according to Scheme 3. The free phosphorus
donor of the dppm ligand in complex 3 or 4 did not displace
the nitrogen-donor from complex 3 or 4 to give a complex
analogous to G (Scheme 1).5 The complexes 5 and 6 formed
according to Scheme 3 have effective C2v symmetry in
The reaction of 2-phenylpyridine or benzo[h]quinoline with
[PtAr2(SMe2)2] gave the corresponding complexes [PtAr-
(ppy)(SMe2)] (1a, Ar = 4-MeC6H4; 1b, Ar = 4-MeOC6H4)
or [PtAr(bhq)(SMe2)] (2a, Ar = 4-MeC6H4; 2b, Ar =
4-MeOC6H4), according to Scheme 2. The formation of
the analogous methylplatinum complexes from [Pt2Me4(μ-
SMe2)2] has been reported previously.4,5
The structures of complexes 1 and 2 are readily deduced
from the 1H NMR spectra,4,5 and the structure of complex 2a
has been confirmed by X-ray structure determination
(Figure 1). The two aryl groups are mutually cis in the
square-planar structure (Figure 1a), as expected,5 and the
largest deviation from ideal geometry is the angle C(10)Pt-
(1)N(1) = 80.9(3)o, which is associated with the Pt(bhq)
chelate ring. There is loose association of the molecules in the
1
solution. Thus, the H NMR spectra contain a single reso-
nance for the CH2P2 protons of the dppm ligand, and the 31
P
and 195Pt NMR spectra each contain a single resonance. The
dppm-bridged complexes 5 and 6 could be prepared in a
single step from 1 or 2, respectively, or in two separate steps.
For example, reaction of 1a with 3a gave complex 5a
(Scheme 3).

Article
Organometallics, Vol. 29, No. 21, 2010 4895
Scheme 3
The structures of the monodentate dppm complexes 3b
and 4a have been determined and are shown in Figure 2. The
key dimensions and conformations within the molecular
structures are similar. For example, the nonbonding dis-
˚
tances Pt(1) P(2) are 4.23 and 4.25 A in 3b and 4a, respec-
3 3 3
tively. Although Pt-P bonds are usually favored over Pt-N
bonds for the soft platinum(II) metal center,5 the extra
stability of the five-membered chelate ring of the metalla-
cycle, compared to the four-membered ring formed by
chelating dppm,9 evidently favors the observed structures 3
and 4. The tendency of dppm to act as a bridging or mono-
dentate ligand is well established, and a few complexes with
monodentate dppm ligands, or the oxidized form dppmO,
have been structurally characterized.9,10 In contrast to the
case with complex 2a (Figure 1), the bhq groups in complex
4a do not take part in intermolecular π-stacking.
The stepwise formation of complexes 5 and 6 from the
monodentate dppm complexes (Scheme 3) suggested that it
might be possible to prepare unsymmetrical binuclear com-
plexes. Complexes 7 and 8, with two different aryl groups,
4-tolyl and 4-anisyl, were successfully prepared according to
Scheme 4. Complex 7 could be prepared either by reaction of
1a with 3b or by reaction of 1b with 3a and contained no
detectable impurity of the possible symmetrical complex 5a
or 5b as determined by the 31P NMR spectrum.
Figure 2. Views of the structures of (a) complex 3b and (b)
˚
complex 4a. Selected bond parameters (A and deg): 3b: Pt(1)-
C(1) 2.008(3); Pt(1)-C(32) 2.042(3); Pt(1)-N(1) 2.127(3); Pt(1)-
P(1) 2.3118(8); C(1)-Pt(1)-C(32) 89.3(1); C(32)-Pt(1)-N(1)
79.9(1); C(1)-Pt(1)-P(1) 91.87(8); N(1)-Pt(1)-P(1) 98.98(7);
4a: Pt(1)-C(39) 2.003(2); Pt(1)-C(7) 2.038(2); Pt(1)-N(1)
2.139(2); Pt(1)-P(1) 2.3095(6); C(39)-Pt(1)-C(7) 90.12(9);
C(39)-Pt(1)-P(1) 92.29(7); C(7)-Pt(1)-N(1) 80.37(8); N(1)-
Pt(1)-P(1) 97.24(5).
Scheme 4
Finally, unsymmetrical binuclear complexes 9 containing
two different cyclometalated groups could be prepared
selectively according to Scheme 5. These complexes could
contain the same (9a, 9b) or different (9c, 9d) aryl groups.
(10) (a) Martinez, J.; Adrio, L. A.; Antelo, J. M.; Ortigueira, J. M.;
Pereira, T.; Fernandez, J. J.; Fernandez, A.; Vila, J. M. J. Organomet.
Chem. 2006, 691, 2721. (b) Bruce, M. I.; Skelton, B. W.; White, A. H.;
Zaitseva, N. N. J. Organomet. Chem. 2006, 650, 141. (c) Leoni, P.; Pasquali,
M.; Pieri, G.; Englert, U. J. Organomet. Chem. 1996, 514, 243. (d)
Boettcher, H.-C.; Krug, A.; Hartung, H. Polyhedron 1995, 14, 901. (e)
Benson, J. W.; Keiter, R. L.; Keiter, E. A.; Rheingold, A. L.; Yap, G. P. A.;
Mainz, V. V. Organometallics 1998, 17, 4275. (f) Barral, M. C.; Jimeneza-
Paricio, R.; Royer, E. C.; Saucedo, M. J.; Urbanos, F. A.; Gutierrez-Puebla,
E.; Ruiz-Valero, C. Inorg. Chim. Acta 1993, 209, 105. (g) Blake, A. J.;
Fotheringham, J. D.; Stephenson, T. A. Acta Crystallogr. C 1992, 48, 1485.
(h) Frew, A. A.; Hill, R. H.; Manojlovic-Muir, Lj.; Muir, K. W.; Puddephatt,
R. J.; Thomson, M. A. J. Chem. Soc., Chem. Commun. 1982, 198. (i)
Brown, M. P.; Fisher, J. R.; Manojlovic-Muir, Lj.; Muir, K. W.; Puddephatt,
R. J.; Thomson, M. A.; Seddon, K. R. J. Chem. Soc., Chem. Commun.
1979, 931.
Again there are two routes to each complex. For example,
complex 9c could be prepared either from 1a and 4b or from
2b and 3a (Scheme 5).
The structure of complex 9a is shown in Figure 3. It can be
seen that the dppm ligand adopts an anti conformation such

4896 Organometallics, Vol. 29, No. 21, 2010
Nabavizadeh et al.
Figure 3. View of the structure of complex 9a. Selected bond
˚
parameters (A and deg): Pt(1)-C(1) 2.042(7); Pt(1)-C(8)
2.058(7); Pt(1)-N(1) 2.151(6); Pt(1)-P(1) 2.3191(19) ; Pt(2)-
C(57) 2.039(7); Pt(2)-C(56) 2.046(7); Pt(2)-N(2) 2.149(6);
Pt(2)-P(2) 2.309(2); C(1)-Pt(1)-C(8) 88.8(3); C(8)-Pt(1)-
N(1) 79.3(3); C(1)-Pt(1)-P(1) 93.9(2); N(1)-Pt(1)-P(1)
97.3(2); C(57)-Pt(2)-C(56) 88.8(3); C(56)-Pt(2)-N(2)
79.5(3); C(57)-Pt(2)-P(2) 88.6(2); N(2)-Pt(2)-P(2) 103.5(2).
Scheme 5
Figure 4. π-Stacking of the bhq groups of complex 9a to form a
supramolecular dimer. The phenyl groups of the dppm ligands
are omitted for clarity.
that the two square-planar platinum(II) centers are well sepa-
˚
rated [Pt(1) Pt(2) = 6.73 A]. The 4-tolyl groups lie roughly
3 3 3
orthogonal to the planes of the respective platinum centers
[angles between the mean tolyl and platinum planes are 84ꢀ and
85ꢀ for Pt(1) and Pt(2), respectively]. The angle between the
square planes of Pt(1) and Pt(2) is 92ꢀ, as a result of different
conformations arising from rotation about the Pt-P bonds.
This conformation allows intermolecular π-stacking of bhq
groups to form supramolecular dimers, in a similar way to that
found in complex 2a (Figure 1b), as illustrated in Figure 4.
The structures of the dppm complexes in solution were
deduced from the 1H, 31P, and 195Pt NMR spectra, and
selected 31P NMR spectra are illustrated in Figure 5. The
complex 4a is typical of the complexes with monodentate
dppm ligands. Its 31P NMR spectrum (Figure 5a) contains
Figure 5. 31P NMR spectra of selected complexes: (a) [Pt(p-Me-
C6H4)(bhq)(η1-dppm)], 4a; (b) [(p-MeC6H4)(ppy)Pt(μ-dppm)Pt-
(p-MeC6H4)(bhq)], 9a (trace impurities indicated by * are assigned
to the symmetrical complexes 5a and 6a); (c) [Pt2(p-MeC6H4)2-
(bhq)2(μ-dppm)], 6a.
two doublet resonances with coupling 2JPP = 51 Hz for the
1
coordinated [δ = 17.1, JPtP = 2082 Hz] and free [δ =
3
-28.6, JPtP = 50 Hz] phosphorus atoms. The 31P NMR
spectra of the symmetrical dppm-bridged complexes con-
tained a single resonance, illustrated for complex 6a in

Article
Organometallics, Vol. 29, No. 21, 2010 4897
Scheme 6a
prepared in high yields. For the first time, it has been possible
to assemble pairs of these units in any combination by using
dppm as the assembling agent. This short bite diphosphine
ligand acts as a monodentate ligand only in forming the
complexes [PtAr(κ2-C,N-ppy)(κ1-P-dppm)] and [PtAr(κ2-
C,N-bhq)(κ1-P-dppm)] and not [PtAr(κ1-C-ppy)(κ2-P,P0-
dppm)] and [PtAr(κ1-C-bhq)(κ2-P,P0-dppm)]. The mono-
dentate dppm ligand can then be used as a metalloligand to
bind a second platinum unit.9-13 Binuclear platinum(II)
complexes, including examples such as [Pt(4-tolyl)(κ2-C,N-
ppy)(μ-dppm)Pt(4-anisyl))(κ2-C,N-bhq)] with two different
aryl groups and two different cyclometalated groups, can be
prepared in a selective way by using this simple methodology.
a Only the core atoms of the dppm and ppy or bhq groups are shown,
for clarity.
Figure 5c [δ = 14.6, 1JPtP = 2060 Hz, 3JPtP = 52 Hz, 2JPP
21 Hz]. There are satellite spectra arising from coupling to
=
Experimental Section
195Pt, with both 1JPtP and 3JPtP couplings resolved, and the
The 1H NMR spectra were recorded by using either a Bruker
Avance DPX 250 spectrometer (in CDCl3) or a Varian Mercury
400 spectrometer (in CD2Cl2), with TMS as reference. The labels
Ho, Hm refer to the ortho and meta protons of the aryl group,
while H6 refers to the NdCH proton of the ppy or bhq group,
and H5 refers to the adjacent hydrogen. The 31P NMR spectra
were recorded either on a Bruker Avance DRX 500 spectro-
meter (in CDCl3) or on a Varian Mercury 400 spectrometer
(in CD2Cl2), with 85% H3PO4 as reference, and 195Pt NMR
spectra were recorded on a Bruker Avance DRX 500 spectro-
meter (in CDCl3), with aqueous Na2PtCl4 as reference. The
microanalyses were performed using a Thermo Finnigan Flash
EA-1112 CHNSO rapid elemental analyzer. The monomeric
precursors cis-[PtR2(SMe2)2], R = p-MeC6H4 and p-MeOC6H4,
were prepared by the literature methods.7
2
coupling JPP is resolved in these satellite spectra. The
unsymmetrical dppm-bridged complexes give similar 31P
NMR parameters to those for 6a, but two separate reso-
nances are resolved in the spectra. For example, complex 9a
1
(Figure 5b) gave peaks at δ = 15.5 [d, JPtP = 1996 Hz,
2JPP = 20 Hz, JPtP = 46 Hz, P trans to ppy] and 14.1 [d,
3
2
3
1JPtP = 2055 Hz, JPP = 20 Hz, JPtP = 56 Hz, P trans to
bhq]. Minor impurity peaks marked with an asterisk in
Figure 5b are assigned to the symmetrical compounds 5a
and 6a, which are formed by disproportionation of complex
9a. They are present in <5% abundance, indicating high
selectivity in the formation of 9a. In all complexes studied,
the phosphorus trans to ppy occurred at higher δ and with
lower 1JPtP compared to phosphorus trans to bhq.
[Pt(p-MeC6H4)(ppy)(SMe2)], 1a. To a solution of cis-[Pt(p-
MeC6H4)2(SMe2)2] (150 mg, 0.3 mmol) in acetone (30 mL) was
added 2-phenylpyridine (43 μL, 0.3 mmol), and the reaction
mixture was refluxed for 4 h. A light green solution was formed;
then the solvent was removed under reduced pressure, and the
residue was triturated with cold acetone (2 ꢀ 2 mL). The product
as a light green solid was dried under vacuum. Yield: 141 mg,
70%; mp 225 ꢀC (dec). Anal. Calcd for C20H21NPtS: C, 47.8; H,
4.2; N, 2.8. Found: C, 48.1; H, 4.3; N, 2.9. NMR in CDCl3:
δ(1H) = 2.20 [s, 6H, 3JPtH = 25 Hz, MeS]; 2.30 [s, 3H, MeC];
6.93 [d, 2H, 3JHmHo = 7.5 Hz, Hm]; 7.46 [d, 2H, 3JPtHo = 64 Hz,
1
The H NMR spectra do not indicate restricted rotation
about the P-C bonds of the dppm ligands, so there is
probably easy conformational change of the bridged com-
plexes in solution. In some square-planar platinum(II) com-
plexes bridged by dppm ligands, the syn conformation has
been observed (analogous to J or K in Scheme 6), and this
allows a metallophilic Pt Pt interaction to occur.11 The
3 3 3
preference for conformation I (Scheme 6) for complex 9a is
probably a result of the aryl groups (Ar in Scheme 6) being
roughly orthogonal to the square plane of the platinum
center. The close approach of the platinum atoms to one
another is thus prevented by steric effects involving these aryl
groups in either the C2 (staggered) or C2h (eclipsed) con-
formation, J or K, respectively.
3
3
3JHoHm = 7.5 Hz, Ho]; 8.87 [d, 1H, JPtH6 = 19 Hz, JH6H5
=
5.5 Hz, H6 of ppy].
The following complexes were prepared similarly by using the
appropriate starting complexes [PtAr2(SMe2)2] and the related
ligand 2-phenylpyridine or benzo[h]quinoline:
The 195Pt chemical shifts for the monodentate dppm
complexes 3a-4b lie in the range δ = -2393 to -2418,
and those for the bridging dppm complexes 5a-9d in the
range δ = -2332 to -2393. In general, the chemical shifts
are more negative for the monodentate dppm complexes
and, in most cases, more negative for the bhq compared to
ppy complexes. For the binuclear complexes, the symmetri-
cal complexes 5a-6b give a single 195Pt resonance, while the
unsymmetrical complexes 7-9d give two resonances. The
195Pt chemical shifts are in the expected range for organo-
platinum(II) complexes.5,14
[Pt(p-MeOC6H4)(ppy)(SMe2)], 1b. Yield: 65%; mp 234 ꢀC
(dec). Anal. Calcd for C20H21NOPtS: C, 46.0; H, 4.0; N, 2.7.
Found: C, 45.8; H, 4.0; N, 2.3. NMR in CDCl3: δ(1H) = 2.20
3
[s, 6H, JPtH = 25 Hz, MeS]; 3.85 [s, 3H, OMe]; 6.75 [d, 2H,
=
3
3JHmHo = 7.5 Hz, Hm]; 7.46 [d, 2H, JPtHo = 64 Hz, 3JHoHm
7.5 Hz, Ho]; 8.87 [d, 1H, 3JPtH6 = 19 Hz, 3JH6H5 = 5.5 Hz, H6].
(12) The use of monodentate dppm complexes as metalloligands is
known in other contexts. (a) Adrio, L.; Antelo, J. M.; Ortigueira, J. M.;
Lata, D.; Pereira, T.; Lopez-Torres, M.; Vila, J. M. Z. Anorg. Allg.
Chem. 2007, 633, 1875. (b) Diaz, C.; Araya, E. Polyhedron 1997, 16, 1775.
(c) Liu, L.-K.; Luh, L.-S.; Wen, Y.-S.; Eke, U. B.; Mesubi, M. A. Organo-
metallics 1995, 14, 4474. (d) Hassan, F. S. M.; McEwen, D. M.; Pringle,
P. G.; Shaw, B. L. J. Chem. Soc., Dalton 1985, 1501. (e) Langrick, C. R.;
McEwen, D. M.; Pringle, P. G.; Shaw, B. L. J. Chem. Soc., Dalton Trans.
1983, 2487. (f) Pringle, P. G.; Shaw, B. L. J. Chem. Soc., Chem. Commun.
1982, 1313.
(13) (a) Romeo, R.; Scolaro, L. M.; Plutino, M. R.; Del Zotto, A.
Transition Met. Chem. 1998, 23, 789. (b) Krevor, J. V. Z.; Simonis, U.;
Richter, J. A., II. Inorg. Chem. 1992, 31, 2409. (c) Brown, M. P.; Fisher, J. R.;
Franklin, S. J.; Puddephatt, R. J.; Seddon, K. R. J. Organomet. Chem. 1978,
161, C46.
Conclusions
Several platinum(II) complexes containing both a biden-
tate cyclometalated ppy or bhq ligand and an aryl group were
(11) (a) Koo, C.-K.; Lam, B.; Leung, S.-K.; Lam, M. H.-W.; Wong,
W.-Y. J. Am. Chem. Soc. 2006, 128, 16434. (b) Koo, C.-K.; Wong, K.-L.;
Lau, K.-C.; Wong, W.-Y.; Lam, M. H.-W. Chem.;Eur. J. 2009, 15, 7689.
(14) Kennedy, J. D.; McFarlane, W.; Puddephatt, R. J.; Thompson,
P. J. J. Chem. Soc., Dalton Trans. 1976, 874.

4898 Organometallics, Vol. 29, No. 21, 2010
Nabavizadeh et al.
[Pt(p-MeC6H4)(bhq)(SMe2)], 2a. Yield: 65%; mp 217 ꢀC
(dec). Anal. Calcd for C22H21NPtS: C, 50.1; H, 4.0; N, 2.7.
Found: C, 50.1; H, 4.0; N, 2.6. NMR in CDCl3: δ(1H) = 2.29
[s, 6H, JPtH = 24 Hz, MeS]; 2.34 [s, 3H, MeC]; 6.98 [d, 2H,
3JHmHo = 7 Hz, Hm]; 7.57 [d, 2H, 3JPtHo = 63 Hz, 3JHoHm = 7 Hz,
Ho]; 9.13 [d, 1H, 3JPtH6 = 18 Hz, 3JH6H5 = 6 Hz, H6].
The following complexes were prepared similarly by using the
appropriate starting materials:
[Pt2(p-MeOC6H4)2(ppy)2(μ-dppm)], 5b. Yield: 63%; mp 241
ꢀC (dec). Anal. Calcd for C61H52N2O2P2Pt2: C, 56.4; H, 4.0; N,
3
1
2.2. Found: C, 56.4; H, 3.8; N, 2.4. NMR data in CDCl3: H
NMR δ(1H) = 3.70 [s, 6H, MeO]; 3.10 [m, 2H, CH2P2]; 6.62 [m,
2H, H5]; δ(31P) = 16.5 [br s, 1JPtP = 1970 Hz, PtP]; δ(195Pt) =
-2393 [br d, 1JPtP ≈ 1980 Hz, Pt).
[Pt(p-MeOC6H4)(bhq)(SMe2)], 2b. Yield: 76%; mp 210 ꢀC
(dec). Anal. Calcd for C22H21NOPtS: C, 48.7; H, 3.9; N, 2.6.
Found: C, 48.7; H, 3.7; N, 2.6. NMR in CDCl3: δ(1H) = 2.28
[Pt2(p-MeC6H4)2(bhq)2(μ-dppm)], 6a. Yield: 63%; mp 263 ꢀC
(dec). Anal. Calcd for C65H52N2P2Pt2: C, 59.4; H, 4.0; N, 2.1.
Found: C, 59.4; H, 4.0; N, 2.2. NMR in CD2Cl2: δ(1H) = 2.23 [s,
3
[s, 6H, JPtH = 22 Hz, MeS]; 3.84 [s, 3H, MeO]; 6.82 [d, 2H,
3JHmHo = 8 Hz, Hm]; 7.56 [d, 2H, 3JPtHo = 65 Hz, 3JHoHm = 8 Hz,
Ho]; 9.13 [d, 1H, 3JPtH6 = 17 Hz, 3JH H5 = 5 Hz, H6].
2
6
6H, MeC]; 3.17 [t, 2H, JPH = 9 Hz, CH2P2]; 8.13 [dd, 2H,
5
4
1
[Pt(p-MeC6H4)(ppy)(η1-dppm)], 3a. To a solution of [Pt(p-
MeC6H4)(ppy)(SMe2)], 1a (52 mg, 0.1 mmol), in acetone (20 mL)
was added dppm (40 mg, 0.1 mmol). The mixture was stirred at
room temperature for 1 h. After removal of the solvent by
evaporation, a residue was obtained, which was washed several
times with ether and then with cold acetone and dried under
vacuum. It was isolated as a green-yellow microcrystalline pow-
der. Yield: 58 mg, 71%; mp 231-233 ꢀC (dec). Anal. Calcd for
C43H37NP2Pt: C, 62.6; H, 4.5; N, 1.7. Found: C, 62.2; H, 4.4; N,
2.1. NMR in CD2Cl2: δ(1H) = 2.13 [s, 3H, MeC]; 2.58 [dd,
2H, 2JPH = 9 and 2 Hz, 3JPtH = 19 Hz, CH2P2]; 6.52 [ddd, 1H,
3JH5H6 = 6 Hz, 3JH5H4 = 7 Hz, 4JH5H3 = 1 Hz, H5]; δ(31P) = 17.6
3JH6H = 8 Hz, JH6H4 = 2 Hz, H6]; δ(31P) = 14.6 [s, JPtP
=
2060 Hz, 3JPtP = 52 Hz, 2JPP = 21 Hz, PtP]; NMR in CDCl3:
δ(195Pt) = -2370 [br d, 1JPtP = 2055 Hz, 2Pt].
[Pt2(p-MeOC6H4)2(bhq)2(μ-dppm)], 6b. Yield: 65%; mp 216 ꢀC
(dec). Anal. Calcd for C65H52N2O2P2Pt2: C, 58.0; H, 3.9; N, 2.1.
Found: C, 58.2; H, 4.1; N, 2.2. NMR in CDCl3:δ(1H) = 3.72 [s, 6H,
MeO]; 3.20 [t, 2H, 2JPH = 8.5 Hz, CH2P2]; 8.05 [d, 3JHH = 8 Hz,
H6];δ(31P) = 14.9 [s, 1JPtP = 2046 Hz, 2JPP=20Hz, 3JPtP =70Hz,
PtP]; δ(195Pt) = -2365 [br d, 1JPtP = 2050 Hz, Pt].
[(p-MeC6H4)(ppy)Pt(μ-dppm)Pt(p-MeC6H4)(bhq)], 9a. This
complex was prepared by the two following methods:
(a) To a solution of [Pt(p-MeC6H4)(ppy)(η1-dppm)], 3a (82 mg,
0.1 mmol), in CH2Cl2 (20 mL) was added [Pt(p-MeC6H4)(bhq)-
(SMe2)], 2a (53 mg, 0.1 mmol). The mixture was stirred at room
temperature for 1 h, and then the solvent was evaporated from the
resulting solution and the residue was washed with ether and cold
acetone and dried under vacuum to give a yellow microcrystalline
powder.
[d, 1JPtP = 2015 Hz, 2JPP = 50 Hz, 1 P], δ = -28.6 [d, 3JPtP
=
48Hz, 2JPP = 50 Hz, 1 P]; 195PtNMR (inCDCl3) δ = -2395 [dd,
1JPtP = 2010 Hz, 3JPtP = 53 Hz, Pt].
The following complexes were prepared similarly by using the
appropriate starting material 1:
[Pt(p-MeOC6H4)(ppy)(η1-dppm)], 3b. Yield: 73%; mp 203 ꢀC
(dec). Anal. Calcd for C43H37NP2Pt: C, 61.4; H, 4.4; N, 1.7.
Found: C, 60.9; H, 4.5; N, 1.8. NMR in CDCl3: δ(1H) = 3.70 [s,
3H, MeO]; 2.70 [m, 2H, CH2P2]; 6.45 [m, 1H, 3JPtH = 8 Hz, H5];
δ(31P) = 19.8 [d, 1P, 1JPtP = 2000 Hz, 2JPP = 43 Hz, PtP]; -26.8
[d, 1P, 3JPtP = 34 Hz, 2JPP = 43 Hz, P]; δ(195Pt) = -2393 [dd,
1JPtP = 1995 Hz, 3JPtP = 31 Hz, Pt].
(b) To a solution of [Pt(p-MeC6H4)(ppy)(SMe2)], 1a (50 mg,
0.1 mmol), in CH2Cl2 (20 mL) was added [Pt(p-MeC6H4)-
(bhq)(η1-dppm)], 4a (85 mg, 0.1 mmol). The mixture was
stirred at room temperature for 1 h, and then the solvent
was evaporated from the resulting solution and the residue
was washed with ether and cold acetone and dried under
vacuum to give the product as a yellow powder. Anal. Calcd
for C63H52N2P2Pt2: C, 58.7; H, 4.1; N, 2.2. Found: C, 58.1; H,
4.1; N, 2.2. NMR in CD2Cl2: δ(1H) = 2.15 [s, 6H, MeC]; 3.16
[t, 2H, 3JPH = 9 Hz, CH2P2]; 6.51 [dt, 1H, 3JH5H6 = 3JH5H4 = 6
[Pt(p-MeC6H4)(bhq)(η1-dppm)], 4a. Yield: 93%; mp 261 ꢀC
(dec). Anal. Calcd for C45H37NP2Pt: C, 63.7; H, 4.4; N, 1.6. Found:
C, 63.4; H, 4.4; N, 1.6. NMR in CD2Cl2: δ(1H) = 2.17 [s, 3H,
MeC]; 2.60 [dd, 2H, 2JPH = 9 and 1 Hz, 3JPtH = 20 Hz, CH2P2];
8.12 [dd, 1H, 3JH6H5 = 8 Hz, 4JH6H4 = 1 Hz, H6]; δ(31P) = 17.1 [d,
Hz, 4JH5H3 = 1 Hz, H5]; 8.15 [dd, 1H, 3JH6H5 = 8 Hz, 4JH6H4
=
1P, 2JPP = 51 Hz, 1JPtP = 2082 Hz, PtP); -28.6 [d, 1P, 2JPP
=
51 Hz, 3JPtP = 50 Hz, P]; NMR in CDCl3: δ(195Pt) = -2418 [br d,
1JPtP = 2080 Hz, Pt].
1 Hz, H6]; δ(31P) = 15.5 [d, 1JPtP = 1996 Hz, 2JPP = 20 Hz,
3JPtP = 46 Hz, PtP]; 14.1 [d, 1JPtP = 2055 Hz, 2JPP = 20 Hz,
3JPtP = 56 Hz, PtP].
[Pt(p-MeOC6H4)(bhq)(η1-dppm)], 4b. Yield: 75%; mp 233 ꢀC
(dec). Anal. Calcd for C45H37NOP2Pt: C, 62.5; H, 4.2; N, 1.6.
Found: C, 61.4; H, 4.3; N, 1.6. NMR in CDCl3: δ(1H) = 3.76
[s, 3H, MeO]; 2.73 [m, 2H, CH2P2]; 8.12 [d, 1H, 3JH6H5 = 8 Hz, H6];
δ(31P) = 17.3 [d, 1P, 2JPP =46Hz, 1JPtP = 2059 Hz, PtP); -27.9[d,
1P, 2JPP = 46 Hz, P]; δ(195Pt)= -2415 [br d, 1JPtP = 2065 Hz, Pt].
[Pt2(p-MeC6H4)2(ppy)2(μ-dppm)], 5a. This was prepared by
two methods:
The following complexes were prepared similarly by both
methods using the appropriate starting materials:
[(p-MeOC6H4)(ppy)Pt(μ-dppm)Pt(p-MeC6H4)(ppy)], 7. Yield:
68%; mp 234 ꢀC (dec). Anal. Calcd for C61H52N2OP2Pt2: C, 53.2;
H, 4.0; N, 2.1. Found: C, 52.4; H, 4.0; N, 2.0. NMR in CDCl3:
δ(1H) = 2.30 [s, 3H, MeC]; δ = 3.70 [s, 3H, MeO]; 3.10 [t, 2H,
3JPH = 9 Hz, CH2P2]; 6.52 [m, 2H, H5]; δ(31P) = 16.9 [d, 1JPtP
1979 Hz, 2JPP = 32 Hz, PtP]; 16.6 [d, 1JPtP = 1994 Hz, 2JPP
=
=
(a) To a solution of [Pt(p-MeC6H4)(ppy)(SMe2)], 1a (50 mg,
0.1 mmol), in acetone (20 mL) was added dppm (19 mg, 0.05
mmol). The mixture was stirred at room temperature for 1 h.
The solvent was removed and the residue was purified to a
yellow microcrystalline powder by treatment with cold acetone
and ether and dried under vacuum.
32 Hz, PtP]; δ(195Pt) = -2332 [br d, 1JPtP = 1985 Hz, Pt]; -2351
[br d, 1JPtP = 2000 Hz, Pt].
[(p-MeC6H4)(bhq)Pt(μ-dppm)Pt(p-MeOC6H4)(bhq)], 8. Yield:
82%; mp 253-255 ꢀC (dec). Anal. Calcd for C65H52N2OP2Pt2: C,
58.7; H, 3.9; N, 2.1. Found: C, 58.4; H, 3.8; N, 2.0. NMR in
CDCl3: δ(1H) = 2.32 [s, 3H, MeC]; 3.80 [s, 3H, MeO]; 3.28 [t, 2H,
(b) To a solution of [Pt(p-MeC6H4)(ppy)(η1-dppm)], 3a (82mg,
0.1 mmol), in CH2Cl2 (20 mL) was added [Pt(p-MeC6H4)(ppy)-
(SMe2)], 1a (50 mg, 0.1 mmol). The mixture was stirred at room
temperature for 5 h. The solvent was removed and the residue was
purified to a yellow microcrystalline powder by treatment with
cold acetone and ether and drying under vacuum. Yield: 87 mg,
69%; mp 236 ꢀC (dec). Anal. Calcd for C61H52N2P2Pt2: C, 57.9;
H, 4.1; N, 2.2. Found: C, 57.8; H, 4.1; N, 2.4. NMR in CDCl3:
δ(1H) = 2.25 [s, 6H, MeC]; 3.07 [m, 2H, 3JPtH = 17 Hz, CH2P2];
3JPH = 9 Hz, CH2P2]; 8.03 [d, 2H, 3JH6H5 = 8 Hz, H6]; δ(31P) =
1
15.1 [d, JPtP = 2061 Hz, 2JPP = 21 Hz, PtP]; 14.7 [d, 1JPtP
2043 Hz, 2JPP = 21 Hz, PtP]; δ (195Pt) = -2362 [br d, 1JPtP
2040 Hz, Pt]; -2374 [br d, 1JPtP ≈ 2035 Hz, Pt).
=
≈
[(p-MeOC6H4)(ppy)Pt(μ-dppm)Pt(p-MeOC6H4)(bhq)], 9b.
Yield: 60%; mp 212-216 ꢀC (dec). Anal. Calcd for C63H52N2P2Pt2:
C, 57.3; H, 4.0; N, 2.1. Found: C, 58.4; H, 4.2; N, 2.2. NMR in
CDCl3: δ(1H) = 3.70 [s, 6H, MeO]; 3.09 [t, 2H, JPH = 9 Hz,
3
CH2P2];6.38[t, 1H, 3JH5H6 =3JH5H4 =7Hz, H5];8.00[d, 3JH6H5 =
6.49 [t, 3JH5H6 = 3JH5H4 = 6 Hz, H5]; δ(31P) = 15.5 [s, 1JPtP
=
1994 Hz, 3JPtP = 47 Hz, 2JPP = 20 Hz, PtP]; δ(195Pt) = -2342
[dd, 1JPtP = 1990 Hz, 3JPtP = 47 Hz, Pt].
7 Hz, H6]; δ(31P) = 15.9 [d, JPtP = 1985 Hz, JPP = 21 Hz,
1
2
3JPtP = 48 Hz, PtP]; 14.5 [d, 1JPtP = 2041 Hz, 2JPP = 21 Hz, PtP];

Article
Organometallics, Vol. 29, No. 21, 2010 4899
Table 1. Crystal Data and Structure Refinement for the Complexes
2a
3b
4a
9a
formula
fw
T/K
λ/A
cryst syst
C22H21NPtS
526.55
150(2)
0.71073
triclinic
P1
0.18 ꢀ 0.17 ꢀ 0.13
8.705(2)
10.154(2)
11.044(2)
69.73(3)
80.06(3)
88.40(3)
901.4(3)
2
C43H37NOP2Pt
840.77
150(2)
0.71073
triclinic
P1
0.03 ꢀ 0.05 ꢀ 0.06
8.9759(4)
9.9660(4)
19.4068(9)
89.980(3)
89.733(2)
88.706(2)
1735.5(1)
2
C90H74N2P4Pt2
1697.57
150(2)
0.71073
triclinic
P1
0.08 ꢀ 0.11 ꢀ 0.13
9.2470(3)
9.8227(4)
19.3364(7)
90.239(2)
90.210(2)
93.781(2)
1752.5(1)
1
C63H52N2P2Pt2
1289.19
150(2)
0.71073
triclinic
P1
0.13 ꢀ 0.07 ꢀ 0.04
11.595(2)
13.699(3)
18.152(4)
96.83(3)
108.61(3)
111.59(3)
2447(1)
2
˚
space gp
cell dimens/mm
˚
a/A
˚
b/A
˚
c/A
R/deg
β/deg
γ/deg
3
˚
V/A
Z
d(calc)/Mg m-3
1.940
7.903
1.609
4.170
1.609
4.129
1.749
5.819
μ/mm-1
data/rest/params
R1[I > 2σ(I)]
wR2[all data]
4135/0/226
0.051
0.152
7376/0/434
0.021
0.047
6199/0/442
0.016
0.044
11 232/0/622
0.046
0.162
δ(195Pt) = -2345 [br d, 1JPtP ≈ 1970 Hz, Pt]; -2360 [br d, 1JPtP
≈
(Nonius B.V., 1997-2002). The unit cell parameters were calcu-
lated and refined from the full data set. Crystal cell refinement and
data reduction were carried out using HKL2000 DENZO-SMN
(Otwinowski and Minor, 1997). The absorption corrections were
applied using HKL2000 DENZO-SMN (SCALEPACK). The
SHELXTL/PC V6.14 for Windows NT (Sheldrick, G. M., 2001)
suite of programs was used to solve the structures by direct
methods. The hydrogen atom positions were calculated geome-
trically and were included as riding on their respective carbon
atoms. Details are given in Table 1.
2020 Hz, Pt].
[(p-MeOC6H4)(bhq)Pt(μ-dppm)Pt(p-MeC6H4)(ppy)], 9c. Yield:
86%; mp 230-235 ꢀC (dec). Anal. Calcd for C63H52N2P2Pt2: C, 58.0;
H, 4.0; N, 2.1. Found: C, 57.5; H, 4.1; N, 2.0. NMR in CD2Cl2:
δ(1H) = 2.24 [s, 3H, MeC]; 3.89 [s, 3H, MeO]; 3.18 [t, 2H, 2JPH
=
8 Hz, CH2P2]; 6.50 [dt, 1H, 3JH5H6 =3JH5H4 =7 Hz, 4JH5H3 =1 Hz,
H5]; 8.16 [dd, 3JH6H5 = 8 Hz, 4JH6H4 = 1 Hz, H6]; δ(31P) = 15.7 [d,
=
1JPtP=1998 Hz, 2JPP=21 Hz, 3JPtP=40 Hz, PtP]; 14.2 [d, 1JPtP
2
3
2041 Hz, JPP = 21 Hz, JPtP = 57 Hz, PtP]; NMR in CDCl3:
δ(195Pt) = -2356 [br d, 1JPtP ≈ 2015 Hz, Pt]; -2352 [br d, 1JPtP
=
2000 Hz, Pt].
Acknowledgment. R.J.P. thanks the NSERC (Canada)
for financial support. M.R. thanks the Iran National
Science Foundation (Grant No. 87041279) for financial
support and Shiraz University for granting sabbatical
leave. We thank Dr. G. Popov for expert assistance with
the X-ray structure determinations.
[(p-MeC6H4)(bhq)Pt(μ-dppm)Pt(p-MeOC6H4)(ppy)], 9d. Yield:
79%, mp 205-209 ꢀC (dec). Anal. Calcd for C63H52N2P2Pt2: C,
58.0; H, 4.0; N, 2.1. Found: C, 57.8; H, 4.2; N, 2.0. NMR data in
CDCl3: 1H NMR: δ(1H) = 2.35 [s, 3H, MeC]; 3.80 [s, 3H, MeO];
3.24 [t, 3JPH = 9 Hz, CH2P2]; 6.47 [t, 1H, 3JH5H6 = 3JH5H4 = 6 Hz,
H5 of ppy]; 8.05 [d, 3JH6H5 = 8 Hz, H6 of bhq]; δ(31P) = 15.7 [d,
1JPtP = 1987 Hz, 2JPP =21Hz, 3JPtP = 51 Hz, PtP]; 14.6 [d, 1JPtP
=
2055 Hz, 2JPP = 21 Hz, 3JPtP = 43 Hz, PtP]; δ(195Pt) = -2340 (br
d, 1JPtP ≈ 1950 Hz, Pt]; -2367 [br d, 1JPtP ≈ 2070 Hz, Pt].
Structure Determinations. Data were collected using a Nonius
Kappa-CCD area detector diffractometer with COLLECT
Supporting Information Available: Tables of X-ray data for
the complexes in cif format This material is available free of
charge via the Internet at http://pubs.acs.org.