Selective formation of heteroligated Pt(II) complexes with bidentate phosphine-thioether (P, S) and phosphine-selenoether (P, Se) ligands via the halide-induced ligand rearrangement reaction

Article abstract of DOI:10.1021/ic901991w

Bidentate phosphine-selenoether (P, Se) ligands were synthesized, and their heteroligated Pt(II) complexes were made and studied. The unique P, S/P, Se ligand coordination to Pt(II) can be realized via the halide-induced ligand rearrangement reaction. In all cases, the exclusive formation of semi-open heteroligated complexes was achieved as shown by ³¹P and ⁷⁷Se NMR spectroscopy and from single crystal X-ray diffraction studies. This is the first example of the use of ⁷⁷Se NMR spectroscopy to characterize these types of structures through direct observation of the weak-link interaction with the metal center. Heteroligated structure formation is believed to be driven by the relative electrondonating ability of the substituent groups on the seleno or thioether moieties. This effect is studied by comparing the structures of corresponding P, SMe and P, SeMe complexes bearing a hemilabile P, SCH₂CF₃ group, which is less sterically demanding than P, SPh but is similar in terms of electron withdrawing ability.

Full text of DOI:10.1021/ic901991w

Inorg. Chem. 2010, 49, 1577–1586 1577
DOI: 10.1021/ic901991w
Selective Formation of Heteroligated Pt(II) Complexes with Bidentate
Phosphine-Thioether (P,S) and Phosphine-Selenoether (P,Se) Ligands
via the Halide-Induced Ligand Rearrangement Reaction
Alexander M. Spokoyny, Mari S. Rosen, Pirmin A. Ulmann, Charlotte Stern, and Chad A. Mirkin*
Department of Chemistry and the International Institute for Nanotechnology, Northwestern University,
2145 Sheridan Road, Evanston, Illinois 60208
Received October 7, 2009
Bidentate phosphine-selenoether (P,Se) ligands were synthesized, and their heteroligated Pt(II) complexes were
made and studied. The unique “P,S/P,Se” ligand coordination to Pt(II) can be realized via the halide-induced ligand
rearrangement reaction. In all cases, the exclusive formation of semi-open heteroligated complexes was achieved as
shown by 31P and 77Se NMR spectroscopy and from single crystal X-ray diffraction studies. This is the first example of
the use of 77Se NMR spectroscopy to characterize these types of structures through direct observation of the weak-link
interaction with the metal center. Heteroligated structure formation is believed to be driven by the relative electron-
donating ability of the substituent groups on the seleno or thioether moieties. This effect is studied by comparing the
structures of corresponding “P,SMe” and “P,SeMe” complexes bearing a hemilabile “P,SCH2CF3” group, which is less
sterically demanding than “P,SPh” but is similar in terms of electron withdrawing ability.
Introduction
Researchers frequently target rigid structures with well-
defined cavity sizes and shapes; however, structurally flexible
complexes are often desired, especially when one wants to
mimic the properties of a biological system.4 The weak-link
approach (WLA) is unique among these three synthetic
strategies in that it produces species that can be dynamically
interconverted between structurally rigid and flexible states
via small-molecule coordination chemistry.5 This property
makes the WLA particularly attractive for the preparation of
sophisticated allosteric structures that can be up- or down-
regulated via the interaction of small molecules with regula-
tory sites strategically located within the complex.6
The most general and utilized strategies for synthesiz-
ing supramolecular complexes include the directional bond-
ing,1 symmetry interaction,2 and weak-link approaches.3
*To whom correspondence should be addressed. E-mail: chadnano@
northwestern.edu. Fax: (1) 847-467-5123.
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C. P.; Mahoney, W.; Osifchin, R. G.; Reifenberger, R. Science 1996, 272, 1323–
1325. (c) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. Rev. 2000, 100, 853–907.
(d) Seidel, S. R.; Stang, P. J. Acc. Chem. Res. 2002, 35, 972–983. (e) W€urthner, F.;
You, C.-C.; Saha-Moller, C. Chem. Soc. Rev. 2004, 33, 133–146. (f) Piermattei,
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M.; Reinhoudt, D. N. Angew. Chem. 2006, 118, 7705–7708. (g) Lee, S. J.; Lin,
W. Acc. Chem. Res. 2008, 41, 521–537. (h) Spokoyny, A. M.; Kim, D.; Sumrein,
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Yamauchi, Y.; Fujita, M. Chem. Soc. Rev. 2009, 38, 1714–1725. (j) Lu, Z.;
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Raymond, K. N. J. Am. Chem. Soc. 2008, 130, 11423–11429. (f) Stoddart, J. F.
Chem. Soc. Rev. 2009, 38, 1521–1529. (g) Faiz, J. A.; Heitz, V.; Sauvage, J.-P.
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Nitschke, J. R. Science 2009, 324, 1697–1699. (i) Li, Q.; Zhang, W.; Miljanic,
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The WLA relies on the use of hemilabile ligands and
metal ions to rapidly assemble supramolecular structures
in which the ligands chelate via both strong and weak binders
€
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Kay, E. R.; Leigh, D. A.; Zerbetto, F. Angew. Chem., Int. Ed. 2006, 46, 72–191.
(5) (a) Gianneschi, N. C.; Bertin, P. A.; Nguyen, S. T.; Mirkin, C. A.;
Zakharov, L. N.; Rheingold, A. L. J. Am. Chem. Soc. 2003, 125, 10508–
10509. (b) Gianneschi, N. C.; Cho, S. H.; Nguyen, S. T.; Mirkin, C. A. Angew.
Chem., Int. Ed. 2004, 43, 5503–5507. (c) Gianneschi, N. C.; Nguyen, S. T.;
Mirkin, C. A. J. Am. Chem. Soc. 2005, 127, 1644–1645. (d) Oliveri, C. G.;
Gianneschi, N. C.; Nguyen, S. T.; Mirkin, C. A.; Stern, C. L.; Wawrzak, Z.; Pink,
M. J. Am. Chem. Soc. 2006, 128, 16286–16296. (e) Masar, M. S., III;
Gianneschi, N. C.; Oliveri, C. G.; Stern, C. L.; Nguyen, S. T.; Mirkin, C. A. J.
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Res. 2005, 38, 825–837.
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129, 10074–10075. (b) Kuwabara, J.; Yoon, H.-J.; Mirkin, C. A.; DiPasquale, A.
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r
2010 American Chemical Society
Published on Web 01/22/2010
pubs.acs.org/IC

1578 Inorganic Chemistry, Vol. 49, No. 4, 2010
Spokoyny et al.
Scheme 1. WLA Is a Versatile Method for Constructing a Variety of Supramolecular Complexesa
a Depending on the metal and the specific set of ligands, one can exclusively access species like (a) macrocycles, (b) tweezers, and (c) triple-decker
complexes. The formation of heteroligated structures is dictated by the relative electron-donating differences between the chalcogens (X and Y, where X
is a stronger binder than Y) and the presence of a halide ancillary ligand (L), which constitutes the basis of halide induced ligand rearrangement (HILR).
In all cases, one can reversibly abstract L and access the corresponding condensed species.
(Scheme 1).7,8 Structures realized thus far include tweezers,9a
macrocycles,9b,d,g triple-decker complexes,9f and triangular
prisms.9c The weak binders can be selectively and reversibly
displaced with small molecules, thus inducing a dramatic
shape and size change in the chemically active pockets in
these complexes.8
Bidentate phosphine-ether (P,O) ligands with Rh(I) were
the first ligand-metal combinations studied in the context of
the WLA.7,8 Since then, the WLA has been studied with a
wide variety of ligands and metals, including Ru(II), Pd(II),
Ir(I), and Cu(I).9 This synthetic tool box has allowed re-
searchers to construct allosteric enzyme mimics,5e multime-
tallic complexes with catalytic properties that resemble
important biological systems like PCR,5f and enantiomeri-
cally pure structures with the ability to selectively recognize
and sequester one enantiomer in a racemic mixture.5d
Subsequent to the initial development of the WLA, we
discovered a new reaction involving d8 transition metals
that allows one to easily prepare heteroligated structures
(Scheme 1b and c).10 In Rh(I) systems, this reaction works
well with phosphine-ether (P,O) and phosphine-thioether (P,S)
ligands to form exclusively A-Rh(I)-B mixed ligand structures.
Since the formation of such motifs is dependent on the presence
of a halide ion, this new reaction within the WLA family is
called the halide-induced ligand rearrangement (HILR).10
To evaluate the generality of the HILR, we have explored
analogous chemistry with Pd(II) and Pt(II).11 When air stabi-
lity is necessary, the use of Pt(II) provides clean access to A-
Pt(II)-B products with P,S ligands.11a,c Until now, all ligands
studied in the context of the WLA have contained either P,O;
P,S; and, to a lesser extent, P,N moieties. These ligands and
metal combinations are a rich platform for complex construc-
tion, but they offer no convenient way to probe the interaction
between the weak-binding nuclei and the metal. As the com-
plexity of the structures we synthesize grows and obtaining a
definitive structure via X-ray analysis becomes more difficult,
additional, routine characterization techniques are necessary
and represent an important advance. Therefore, we have
synthesized a series of model P,Se hemilabile ligands and their
corresponding WLA complexes. NMR-active 77Se nuclei were
used to probe the nature of the Se-metal interaction.12 These
(7) Farrell, J. R.; Mirkin, C. A.; Guzei, I. A.; Liable-Sands, L. M.;
Rheingold, A. L. Angew. Chem., Int. Ed. 1998, 37, 465–467.
(8) Farrell, J. R.; Eisenberg, A. H.; Mirkin, C. A.; Guzei, I. A.; Liable-
Sands, L. M.; Incarvito, C. D.; Rheingold, A. L.; Stern, C. L. Organome-
tallics 1999, 18, 4856–4868.
(9) (a) Eisenberg, A. H.; Dixon, F. M.; Mirkin, C. A.; Stern, C. L.;
Incarvito, C. D.; Rheingold, A. L. Organometallics 2001, 20, 2052–2058. (b)
Gianneschi, N. C.; Mirkin, C. A.; Zakharov, L. N.; Rheingold, A. L. Inorg. Chem.
2002, 41, 5326–5328. (c) Ovchinnikov, M. V.; Holliday, B. J.; Mirkin, C. A.;
Zakharov, L. N.; Rheingold, A. L. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 4927–
4931. (d) Eisenberg, A. H.; Mirkin, C. A. J. Am. Chem. Soc. 2003, 125, 2836–
2837. (e) Masar, M. S., III; Mirkin, C. A.; Stern, C. L.; Zakharov, L. V.;
Rheingold, A. L. Inorg. Chem. 2004, 43, 4693–4701. (f) Jeon, Y.-M.; Heo, J.;
Brown, A. M.; Mirkin, C. A. Organometallics 2006, 25, 2729–2732. (g) Wiester,
M. J.; Mirkin, C. A. Inorg. Chem. 2009, 48, 8054–8056.
(10) (a) Brown, A. M.; Ovchinnikov, M. V.; Stern, C. L.; Mirkin, C. A.
J. Am. Chem. Soc. 2004, 126, 14316–14317. (b) Oliveri, C. G.; Ulmann, P. A.;
Wiester, M. J.; Mirkin, C. A. Acc. Chem. Res. 2008, 41, 1618–1629. (c) Brown,
A. M.; Ovchinnikov, M. V.; Mirkin, C. A. Angew. Chem., Int. Ed. 2005, 44,
4207–4209.
(11) (a) Ulmann, P. A.; Brown, A. M.; Ovchinnikov, M. V.; Mirkin,
C. A.; DiPasquale, A. G.; Rheingold, A. L. Chem.;Eur. J. 2007, 13, 4529–
4534. (b) Ulmann, P. A.; Mirkin, C. A.; DiPasquale, A. G.; Liable-Sands, L. M.;
Rheingold, A. L. Organometallics 2009, 28, 1068–1074. (c) Ulmann, P. A.;
Braunschweig, A. B.; Lee, O.-S.; Wiester, M. J.; Schatz, C. G.; Mirkin, C. A.
Chem. Commun. 2009, 5121–5123.
(12) (a) Hope, E. G.; Levason, W. Coord. Chem. Rev. 1993, 122, 109–170.
(b) Murray, S. G.; Hartley, F. R. Chem. Rev. 1981, 81, 365–414.

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1579
Scheme 2. Syntheses of P,Se Ligands 1b and 2b and P,S Ligands 3b
and 4b
2-tetrachloroethane (TCE) to evaluate the role of solvent
effects on the synthesis and 31P{1H} NMR spectroscopy of
these compounds was performed. In 1,2-dichloroethane,
the 31P{1H} NMR spectrum of the reaction mixture exhi-
bits two resonances at δ 42.1 (d, JP-P = 13 Hz) and δ 10.8
(d, JP-P = 11 Hz), assigned to the phosphines of 5a on
chelating ligand 2b and non-chelating ligand 1b, respec-
tively. The 31P{1H} NMR spectrum of 5a in dichloro-
methane also exhibits two resonances, with a broad signal
at 10.8 ppm. Upon gradually cooling 5a to -50 °C in
CD2Cl2, this signal broadens further and a broad reso-
nance at δ 46.7 emerges, indicating the chelation of the
chalcogen in ligand 1b. To work athighertemperatures, we
studied 5a in TCE, which at room temperature exhibits a
spectrum almost identical to 5a in dichloromethane. Upon
heating this complex to 50 °C, the broad peak at 10.8 ppm
sharpens into a well-resolved doublet. The observed
changes in the NMR spectra are likely a result of a
fluxional closing process associated with ligand 1b that is
fast on the NMR time scale at higher temperatures, but
that is slow enough to induce signal broadening at lower
temperatures. This dynamic process is also affected by
solvent polarity. In favor of this argument, the HILR
confirmation experiment11a,c in dichloromethane, which
is less polar than 1,2-dichloroethane, reveals slow rearran-
gement and incomplete formation of the heteroligated
species even after 12 h. In contrast, the same experiment
in 1,2-dichloroethane results in a spontaneous rearrange-
ment within minutes. A quantitive assessment of solvent
and temperature effects on heteroligated structure forma-
tion of Pt(II) WLA complexes will be addressed in sub-
sequent work. The signal broadening in the 31P{1H} NMR
spectrum could also result from the dipole-dipole relaxa-
tionpathway provided bythe 77Se nucleus innon-chelating
ligand 1b in complex 5a. If this were indeed the case, the
restrained 77Se nucleus in chelating ligand 2b would not
contribute to the resonance broadening in the 31P NMR
spectrum of 5a via a dipole-dipole relaxation pathway.15
Consistent with these assumptions, the resonance for the P
atom farthest from the nonchelated selenoether does not
exhibit significant broadening. The phosphorus atom that
is part of chelating ligand 2b in 5a exhibits a larger P-Pt
coupling constant (JP-Pt = 3538 Hz) than the analogous
phosphorusatominnon-chelatingligand 1b(JP-Pt = 3152
Hz) because of the trans-directing nature of the SeMe
group.16 A single crystal X-ray diffraction study of 5a is
consistent with this observation: the P-Pt bond involving
the P atom trans to the bound selenoether moiety is
Scheme 3. Synthesis of the Semi-Open P,Se Complex 5a
ligands are the first of a new class of selenoether hemilabile
ligands.13 Not only do they expand the toolbox of WLA
chemistry, but they also provide important fundamental
insights into the coordination chemistry of P,Se-type ligands
with Pt(II).
Results and Discussions
Syntheses of Ligands. There are several existing meth-
ods in the synthetic literature for introducing a seleno-
ether moiety within a molecule.14 From these available
routes, we chose one developed by the Sharpless group
that involves the in situ reduction of diselenide precursors
(1a or 2a) and the use of the reduced product in the
subsequent nucleophilic substitution of an alkyl halide in
1-chloroethanediphenylphosphine (Scheme 2).13c This
reaction proceeds cleanly in 70-80% yield with no sig-
nificant degradation of the diphenylphosphine moiety.
Although the dimethyldiselenide precursor has an ex-
tremely pungent odor, ligands 1b and 2b, when purified,
are odorless. Importantly, the synthetic approach for 1b
and 2b should be easily adaptable to other diselenide
synthons bearing other functional groups (R in Scheme 2)
compatible with NaBH4. Ligands incorporating thio-
ether moieties, such as 3b and 4b, were synthesized as
reported previously from thioether precursors 3a and 4a
(Scheme 2).11a
Synthesis of Heteroligated Semi-Open Complexes.
Upon mixing ligands 1 (1 equiv) and 2 (1 equiv) with the
Pt(II) precursor(Pt(cod)Cl2, cod=cyclooctadiene, 1equiv)
in 1,2-dichloroethane, the heteroligated semi-open com-
plex 5a forms in quantitative yield (Scheme 3). The reac-
tion was also performed in dichloromethane and 1,1,2,
˚
elongated (∼2.28 A) relative to the bond involving the P
˚
atom trans to the chloride (∼2.23 A) (Figure 1). Electro-
spray ionization mass spectroscopy (m/z [M-Cl]þ = 907)
and elemental analysis are consistent with the proposed
composition and structure of complex 5a.
The mixed P,S/P,Se heteroligated species 6a and 7a
(Scheme 4) can be synthesized by combining two of the
ligands from the pool of 1b-4b, where one ligand features
an electron withdrawing group on the chalcogen and
the other an electron donating group, with 1 equiv of
(13) (a) Durran, S. E.; Elsegood, M. R. J.; Smith, M. B. New J. Chem.
2002, 26, 1402–1408. (b) Curran, R.; Cunningham, J. A.; Eisenberg, E. Inorg.
Chem. 1970, 9, 2749–2754. (c) Jones, R. C.; Madden, R. L.; Skelton, B. W.;
Tolhurst, V.-A.; White, A. H.; Williams, A. M.; Wilson, A. J.; Yates, B. F. Eur. J.
Inorg. Chem. 2005, 6, 1048–1055. (d) Esterhuysen, M. W.; Br€ull, R.; Rauben-
heimer, H. G.; Esterhuysen, C.; Kruger, G. J. J. Organomet. Chem. 2001, 619,
164–178. (e) Carland, M.; Abrahams, B. F.; Denny, W. A.; Murray, V.; McFayden,
W. D. CrystEngComm. 2005, 7, 701–705.
(15) (a) Multinuclear NMR; Mason, J., Ed.; Premium Press: New York, 1987.
(b) High Resolution NMR Techniques in Organic Chemistry; Claridge, T., Ed.;
Elsevier: New York, 2009.
(16) Spokoyny, A. M.; Reuter, M. G.; Stern, C. L.; Ratner, M. A.;
Seideman, T.; Mirkin, C. A. J. Am. Chem. Soc. 2009, 131, 9482–9483.
(14) (a) Mizuno, M.; Cava, P. M.; Garito, A. F. J. Org. Chem. 1976, 41,
1485–1486. (b) Klayman, D. L.; Griffin, T. S. J. Am. Chem. Soc. 1973, 95, 197–
199. (c) Sharpless, K. B.; Lauer, R. F. J. Am. Chem. Soc. 1973, 95, 2697–2699.

1580 Inorganic Chemistry, Vol. 49, No. 4, 2010
Spokoyny et al.
Figure 1. Crystal structures of the semi-open complexes 5a, 6a, and 7a drawn with 50% thermal ellipsoid probability. In all cases, hydrogens, solvent
molecules, and anions are omitted for clarity. Only one enantiomer is shown. Platinum atoms are black; sulfur, green; selenium, red; phosphorus, blue;
˚
chlorine, yellow; and carbon, gray. Selected bond lengths [A] and angles [deg]: (a) 5a: Pt1-Se1 2.462(6), Pt1-P1 2.236(1), Pt1-P2 2.285(1), Pt1-Cl1
2.362(1), P1-Pt1-P2 99.40(4), Se1-Pt1-Cl1 85.91(3), P2-Pt1-Cl1 88.62(4), P1-Pt1-Se1 86.15(3), P2-Pt1-Se1 172.63(3), P1-Pt1-Cl1 171.96(4) (b)
6a: Pt1-Se1 2.4605(3), Pt1-P1 2.2334(7), Pt1-P2 2.2750(7), Pt1-Cl1 2.3589(8), P1-Pt1-P2 99.64(3), Se1-Pt1-Cl1 85.91(2), P2-Pt1-Cl1 88.43(3),
P1-Pt1-Se1 86.09(2), P2-Pt1-Se1 172.53(2), P1-Pt1-Cl1 171.92(3) (c) 7a: Pt1-S1 2.354(1), Pt1-P1 2.2829(9), Pt1-P2 2.2377(9), Pt1-Cl1 2.3593(9),
P1-Pt1-P2 99.30(3), S1-Pt1-Cl1 86.40(3), P2-Pt1-S1 85.91(3), P1-Pt1-Cl1 88.52(3), P1-Pt1-S1 172.57(3), P2-Pt1-Cl1 172.1(3).
ligand 1b. The 77Se{1H} NMR spectrum of complex 5a
exhibits a singlet at δ 360 assigned to the Se atom of the
Scheme 4. Formation of Heteroligated Semi-Open Mixed P,Se/P,S
Pt(II) Complexes
non-chelated SePh moiety in ligand 1b and a poorly
resolved doublet of doublets (appearing as a broad doub-
let) at δ 332 for the Se atom in chelating ligand 2b
(Figure 2). In contrast, the 77Se{1H} NMR spectrum of
6a is well-resolved, revealing a doublet of doublets for the
2
Se atom (1JSe-P = 11 Hz, JSe-P = 134 Hz) with the
expected Pt satellites (JSe-Pt=49 Hz). The relatively weak
interaction between the Se and the Pt atoms results in a
smaller J-value for the Pt(II) satellites compared to other
reported systems, such as with Pt-selenide complexes.18
The signal broadening in the 77Se{1H} NMR spectrum of
complex 5a and its absence in the analogous spectrum of
complex 6a may be explained if the rate of the fluxional
closing and opening process is slower for complex 5a.
This hypothesis is supported by the observation of a
broad doublet at δ 254 in the 77Se{1H} NMR spectrum
of complex 5a at -50 °C. Indeed, this shift is consistent
with the 77Se{1H} resonance for 5a after chloride abstrac-
tion (see next section). Since we did not observe solvent-
induced sharpening of these resonances at both low and
high temperatures, the presence of the chemical shift
anisotropy (CSA) relaxation pathway (available because
of the presence of the 77Se nucleus) cannot be dismissed.
In favor of the presence of the CSA pathway, the signals
in the 77Se{1H} NMR spectra of 5a and 7a are broad, and
the Pt satellites are not resolved.19
the Pt(II) precursor. Four different heteroligated com-
plexes can be synthesized in this manner (the P,SMe/P,
SPh complex was synthesized in a previous report).11a
Interestingly, in the solid state, 5a-7a are isostructural,
having nearly identical orientations of major functional
units, the same space group (P1), and the same unit cell
parameters. Each unit cell of the heteroligated species
comprises a racemic mixture of enantiomers crystallized
in a 1:1 ratio (see Supporting Information). P-Pt bond
distances (Table 1), for which P is both trans to the Cl and
trans to the chalcoether, are statistically identical in all
˚
structures. Comparison between the Pt-Se (2.46 A) and
˚
Pt-S (2.35 A) bond distances reveal similar Pt-chalcogen
interactions when atomic radii are taken into account (Se,
(18) Some examples of characterized Pt-Se interactions: (a) Barnes, J. C.;
Hunter, G.; Lown, M. W. J. Chem. Soc., Dalton Trans. 1977, 5, 458–460. (b)
Abel, E. W.; Bhargava, S. K.; Orrell, K. G.; Zik, V.; Williams, B. L. Polyhedron
1982, 1, 289–298. (c) Gulliver, D. J.; Hope, E. G.; Levason, W. J. Chem. Soc.,
Dalton Trans. 1985, 6, 1265–1269. (d) Chadha, R. K.; Chehayber, J. M.; Drake,
J. E. Inorg. Chem. 1986, 25, 611–615. (e) Hope, E. G.; Levason, W.; Webster, M.
J. Chem. Soc., Dalton Trans. 1986, 5, 1003–1009. (f) Chiffey, A. F.; Evans, J.;
Levason, W.; Webster, M. J. Chem. Soc., Dalton Trans. 1994, 19, 2835–2840.
(g) Levason, W.; Orchard, S. D.; Reid, G. Inorg. Chem. 2000, 39, 3853–3859. (h)
17
˚
˚
1.16 A; S, 1.02 A).
77Se Characterization. 77Se nuclei (Spin = 1/2) are use-
ful for NMR spectroscopy because of their relatively
high natural abundance (7.63%) and large chemical shift
range.15 The Se atoms in ligands 1b and 2b exhi-
bit doublets at δ 334 (JSe-P=11 Hz) and δ 125 (JSe-P
=
11 Hz), respectively. Upon metalation to form 5a, 6a, and
7a, the 77Se{1H} NMR spectra reveal that the Se atoms in
both the non-chelating ligand 1b and the chelating ligand
2b exhibit a downfield chemical shift. For the chelating
ligand 2b, the resonance for the Se atom shifts downfield
by ∼210 ppm, whereas a modest ∼30 ppm shift is
observed for the analogous Se atom in non-chelating
€
ꢀ
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Dumfort, A.; Kopacka, H.; Ongania, K.-H.; Br€uggeller, P. Dalton Trans. 2003,
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A.; Belaj, F. Eur. J. Chem. 2004, 22, 4510–4520. (k) Levason, W.; Manning, J.
M.; Pawelzyk, P.; Reid, G. Eur. J. Inorg. Chem. 2006, 21, 4380–4390. (l) Aucott,
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838–843.

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1581
Table 1. Selected Bond Lengths and 31P{1H} Chemical Shifts for Heteroligated Complexes 5a-7a in 1,2-Dichloroethane-d4
31
P
31
{1H} (ppm)
P
{1H} (ppm)
nonchelate
˚
˚
˚
compound
Pt-P (A)
Pt-P (A)
Pt-Cl (A)
chelate
5a
6a
7a
2.236(1)
2.233(1)
2.237(1)
2.285(1)
2.275(1)
2.283(1)
2.362(1)
2.358(1)
2.359(1)
42.1
42.2
43.1
10.8
8.1
11.5
the analogous semi-open species as a result of the chalco-
gen coordinating to the Pt center (Scheme 5).20 In the
same spectra, the phosphorus resonances for the P,XMe
moieties are shifted downfield by only approximately 3
ppm, consistent with a significantly smaller electronic
change at the site.
The limited solubility of the closed species 5b-7b
precluded us from obtaining high-quality 77Se NMR
spectra of them. Nevertheless, in the 77Se{1H} NMR
spectrum of the closed complex 6b, we observe a doublet
of doublets (JSe-P = 97 Hz) at δ 268 ppm, approximately
64 ppm upfield relative to the analogous resonance in
the 77Se{1H} NMR spectrum of the semi-open species 6a.
A doublet in the 77Se{1H} NMR spectrum is observed for
5b at the same chemical shift, δ 268 ppm; however, JSe-P
could not be determined because of signal broadening. In
both 5b and 6b, this upfield shift is consistent with
redistribution of electron density on the Se atom after
chloride abstraction from 5a and 6a. Since the chelation
of the SePh moiety in 5b and the SPh moiety in 6b adds
electron density to the Pt(II) centers, the need for electron
donation from the SeMe moiety is diminished. This, for
example, in 5b, results in a significant bond shortening
Figure 2. 77Se{1H} NMR spectra of semi-open complexes taken in
dichloromethane-d2.
Scheme 5. Reversible Conversion of Semi-Open Complexes to the
Closed Form
˚
(0.02 A) between the selenium and the carbon atoms in
the SeMe moiety and a corresponding bond elongation
˚
(0.02 A) between the selenium and the carbon atoms in
the SePh group. Species 6b and 7b were also character-
ized by single crystal X-ray diffraction (Figure 3). As
with the semi-open species, their closed analogues are
isostructural with each unit cell consisting of a 1:1 ratio
of enantiomers. In all cases, the geometry around the
Pt(II) center is nearly square planar, with the phos-
phorus atoms in the two chelates coordinating in a cis
fashion, consistent with the P,S/P,S complexes reported
earlier.11a,c In the 77Se{1H} NMR spectrum of complex
7b, the peak corresponding to the Se atom in the SePh
moiety (ca. δ 342) is significantly broadened. As postu-
lated in the discussion of the 77Se NMR spectra of
complexes 5a and 7a above, the broadening is due to
the presence of the chemical shift anisotropy relaxation
pathway provided by the 77Se nucleus. Consequently,
cooling complex 7b to -50 °C does not sharpen the
peaks in the 77Se NMR spectrum, and no information on
the coupling constant between the P and Pt nuclei in the
complex could be obtained. In the 31P{1H} NMR spectra
of the closed species, the presence of a large number of
invertomers (at -50 °C) provides further complications.
Unfortunately, since the closed species were not suffi-
ciently soluble at temperatures below -50 °C, it was not
possible to clearly observe and assign resonances for the
frozen conformations.18c
Closed Complexes. Semi-open complexes can be con-
verted to the corresponding closed species via chloride
abstraction (Scheme 5). Initially, AgBF4 was used as a
chloride abstraction agent, but it led to a mixture of
products when used in slight excess, possibly because of
ligand and complex oxidation. A cleaner conversion was
accomplished with a 30-fold total excess of NaBF4. In a
typical procedure, a semi-open complex is stirred for a
day with NaBF4 at room temperature in dichloroethane,
followed by filtration and recrystallization of the product
in ether. Solution-phase 31P{1H} NMR spectroscopy of
the reaction mixtures showed almost quantitative con-
version to the fully closed complexes 5b-7b (Scheme 5).
Upon addition of 2 equiv of NMe4Cl to any of the closed
species, they revert back to the semi-open state as ob-
served by 31P{1H} NMR spectroscopy.
Sterics versus Electronics. There are several possible
explanations for the selective formation of the hetero-
ligated species. In all cases, we observe that these species
The phosphorus atoms in the P,YPh moieties in the closed
complexes 5b-7b exhibit a downfield shift of approxi-
mately 34 ppm in the 31P{1H} NMR spectra compared to
(20) Garrou, P. E. Chem. Rev. 1981, 81, 229–266.

1582 Inorganic Chemistry, Vol. 49, No. 4, 2010
Spokoyny et al.
Figure 3. Crystal structures of semi-open complexes 5b, 6b, and 7b drawn with 50% thermal ellipsoid probability. In all cases, only one isomer in the unit
cell is shown; hydrogens, solvent molecules, and anions are omitted for clarity. Platinum atoms are black, sulfur, green; selenium, red; phosphorus, blue; and
˚
carbon, gray. Selected bond lengths [A] and angles [deg]: (a) 5b: Pt1-Se1 2.4715(6), Pt1-P1 2.2725(9), Pt1-P2 2.268(1), Pt1-Se2 2.4549(4), P1-Pt1-P2
100.22(4), Se1-Pt1-Se2 88.43(2), P2-Pt1-Se2 85.67(3), P1-Pt1-Se1 86.28(3), P2-Pt1-Se1 168.71(3), P1-Pt1-Se2 173.32(3) (b) 6b: Pt1-Se1 2.472(7),
Pt1-S1 2.365(2), Pt1-P1 2.263(2), Pt1-P2 2.281(2), P1-Pt1-P2 97.98(6), Se1-Pt1-S1 90.02(4), P2-Pt1-S1 88.28(6), P1-Pt1-Se1 85.56(4),
P2-Pt1-Se1 175.64(5), P1-Pt1-S1 174.31(6) (c) 7b: Pt1-Se1 2.475(1), Pt1-P1 2.268(2), Pt1-P2 2.273(3), Pt1-S1 2.352(2), P1-Pt1-P2 98.87(8),
Se1-Pt1-S1 89.71(6), P2-Pt1-S1 85.54(8), P1-Pt1-Se1 86.46(6), P2-Pt1-Se1 170.85(7), P1-Pt1-S1 174.06(8).
Scheme 6. Summary of the Reactions for the Synthesis of Hetero-
ligated Complexesa
Figure 4. Crystal structures of semi-open complexes 9 (a) and 10 (b)
drawn with 50% thermal ellipsoid probability. In all cases, hydrogens,
solvent molecules, and anions are omitted for clarity. Platinum atoms are
black, sulfur, green; selenium, red; phosphorus, dark blue; carbon, gray;
˚
and fluorine, light blue. Selected bond lengths [A] and angles [deg]: (a) 9:
Pt1-S1 2.340(2), Pt1-P1 2.243(2), Pt1-P2 2.277(2), Pt1-Cl4 2.346(2),
P1-Pt1-P2 101.19(6), S1-Pt1-Cl4 84.64(6), P2-Pt1-Cl4 86.93(6),
P1-Pt1-S1 87.12(6), P2-Pt1-S1 171.41(6), P1-Pt1-Cl4 170.97(6)
(b) 10: Pt1-Se1 2.461(5), Pt1-P1 2.228(1), Pt1-P2 2.284(1), Pt1-Cl1
2.360(1), P1-Pt1-P2 98.91(5), Se1-Pt1-Cl1 86.41(4), P2-Pt1-Cl1
88.03(5), P1-Pt1-Se1 86.68(4), P2-Pt1-Se1 174.20(4), P1-Pt1-Cl1
173.00(5).
Scheme 7. Synthesis of P,SCH2CF3 Ligand 8b and the Corresponding
Heteroligated Pt(II) Complexes with Ligands 2b and 4b
a The synthesis involves the addition of two different ligands from a
pool of 1b-4b to 1 equiv of the Pt precursor, Pt(cod)Cl2.
form quantitatively only if the functional groups on the
chalcogen (S or Se) in the ligand pair we introduce have
significantly different electron donating abilities. Indeed,
the reactions involving 1b and 3b or 2b and 4b and the
Pt(II) precursor do not result in the formation of one
semi-open species, but instead result in the formation of
mixtures (Scheme 6).
For the combination of ligands 1b and 3b, the inability
to form a single complex can be explained either by the
weak chelating ability of these ligands or by steric rea-
sons. Steric repulsion between the two phenyl groups
could potentially explain the instability of the XPh/YPh
species, leading to the formation of the heteroligated
complex when the much smaller chalcogen-Me-contain-
ing ligand is introduced to this system. To address
whether the formation of the heteroligated Me/Ph species
is dictated by steric interactions or by differences in the
electronic properties of the ligands, we have synthesized
the P,SCH2CF3 ligand 8b from the thiol derivative 8a
(Scheme 7).
This ligand was intended to be less sterically demanding
than the P,SPh ligand, but still electron withdrawing, to
elucidate the driving force of this reaction. When ligand

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1583
8b was reacted with either 2b or 4b and the Pt precursor, we
observed quantitative formation of the semi-open hetero-
ligated species 9 and 10, respectively, as confirmed by 31P-
{1H} NMR spectroscopy and single crystal X-ray crystal
diffraction studies. One can probe the Pt-SeMe interaction in
complex 10 via 77Se{1H} NMR spectroscopy. This analy-
sis reveals a doublet of doublets at 336.5 (1JSe-P=11 Hz,
2JSe-P=129 Hz), similar to what is observed in case of 5a. A
small downfield shift of 3 ppm is observed via 19F{1H}
NMR for both complexes 9 and 10 relative to the
chemical shift of the Se atom in ligand 8b, which is
consistent with the slight change in the electronic en-
vironment at the CF3 moiety. Analysis of the single-
crystal X-ray diffraction data for complexes 9 and 10
(Figure 4) is consistent with the observations made
from the 77Se{1H} NMR spectra. The near square-
planar geometries on Pt(II) of 9 an 10, bond angles,
and lengths are in good correlation with the analogous
properties observed in 5a-7a. It is therefore reason-
able to propose that a difference in electron donating
ability between the two ligands is crucial in the formation
of Pt(II) heteroligated complexes. Additional mechanistic
studies examining this process in a quantitative manner
will be reported in subsequent work.
A comparison can be made between selenoether co-
ordination behavior and the behavior of the thioether
analogues. While the O,R and S,R chemistries differ
significantly, 31P{1H} and 77Se{1H} NMR spectro-
scopic analyses and solid-state crystal structures of Se,
R-containing complexes show no significant differences
in the Pt-chalcogen interaction from the case of S,R-
containing complexes. In both seleno- and thioether
coordination chemistries, the strength of the hetero-
atom-metal interaction is mainly dictated by the elec-
tron donating or withdrawing nature of its substituent.
Additionally, the study of WLA systems benefits from
the presence of the selenoether moiety: 77Se NMR
spectroscopy provides a convenient probe of the inter-
action between the weak-link moiety and the Pt center.
Given that selenoether and thioether coordination che-
mistries are very similar for Pt(II), information ob-
tained from 77Se NMR spectroscopy of selenoether-
containing WLA complexes can be extended to their
thioether analogues.
techniques under an inert nitrogen atmosphere. The syntheses
of Pt(II) complexes and all manipulations were done under
ambient conditions. All solvents were purchased as anhydrous
grade from Sigma-Aldrich and used as received. Deuterated
solvents were purchased from Cambridge Isotope Labora-
tories and used as received. All other chemicals were used as
received from Aldrich Chemical Co. or prepared according to
literature procedures.11a,c All NMR spectra were recorded on
a Bruker Avance 400 MHz. 1H and 13C{1H} NMR spectra
were referenced to residual proton and carbon resonances in
the deuterated solvents. 31P{1H} and 77Se{1H} NMR spectra
were referenced to H3PO4 and Me2Se standards, respectively.
19F{1H} NMR spectra were referenced to an external CFCl3
(in CDCl3) standard. Electrospray ionization (ESI) mass
spectra were recorded on a Micromass Quatro II triple quad-
rupole mass spectrometer; high-resolution APPI (atmos-
pheric pressure ion) on an Agilent 6210 LC-TOF with Agilent
1200 HPLC induction mass-spec system instrument. Elemen-
tal analyses were performed by Quantitative Technologies,
Whitehouse, NJ.
(2-Phenylselenoethyl)diphenylphosphine 1. Diphenyldisele-
nide (Ph2Se2, 0.6 g, 1.9 mmol) was dissolved in anhydrous
EtOH (20 mL) in a 50 mL Schlenk flask equipped with a
magnetic stir bar at room temperature. Approximately 180
mg of NaBH4 was added slowly to a reaction mixture kept
under nitrogen. After 5 min, reduction of the diselenide was
complete as indicated by the disappearance of the solution’s
yellow color. A 0.95 g portion (3.8 mmol) of 1-chloroethane-
phosphine was added to the flask, and the reaction mixture
was refluxed for 18 h. The product mixture was filtered to remove
salts while hot, and all volatiles were evaporated in vacuo. The
residual oily substance was extracted with dichloromethane and
washed with brine, followed by column chromatography on silica
eluted with 1:1 mixture of hexane/dichloromethane. Recrystalli-
zation from cold ethanol (-20 °C) afforded 1 as a white solid (1.1
g, 78%). 31P{1H} NMR (161.98 MHz, 25 °C): δ -15.3 (s);
77Se{1H} NMR (76.34 MHz, 25 °C): δ 334.3 (d, JSe-P=11 Hz);
1H NMR (400 MHz, CD2Cl2, 25 °C): δ 7.41-7.15 (m, 15H, ArH),
2.87 (m, 2H, AliphH), 2.39 (m, 2H, AliphH); 13C{1H} NMR
(100.62 MHz, CD2Cl2, 25 °C): δ 138.5 (d, JC-P=15 Hz), 133.2 (d,
JC-P = 19 Hz), 133.1 (s), 129.7 (s), 129.3 (s), 129.1 (d, JC-P
=
7 Hz), 127.4 (s), 29.6 (d, JC-P=16 Hz), 23.8 (d, JC-P = 21 Hz).
HRMS (APPI, MeOH): m/z calcd for C20H19PSe [MþH]þ:
371.0462; found: 371.0471.
(2-Methylselenoethyl)diphenylphosphine 2. Caution! Di-
methyldiselenide emits a strong garlic-like odor in extremely
low concentrations. This reaction should be handled with
proper attire in a well-ventilated laboratory.
Compound 2 was prepared using the same procedure as in 1
from 0.75 g (4 mmol) of dimethyldiselenide (Me2Se2) and 2.0 g (8
mmol) of 1-chloroethanephosphine to afford 2 as a white solid
(2.1 g, 85%). 31P{1H} NMR (161.98 MHz, CD2Cl2, 25 °C): δ -
Conclusions
The halide-induced ligand rearrangement facilitates the
synthesis of mixed-ligand systems that form as dictated by
the substituent on the chalcoether moieties. Clean formation of
the heteroligated WLA species is observed only when the ligand
pair includes a weak and a strong electron donor at the
chalcogen site. In contrast to the behavior of O,R ligands in
WLA systems, analysis of the complexes presented here indi-
cates little difference between selenoether and thioether coor-
dination chemistry with Pt(II) in both solution and the solid
state. Therefore, through analysis of the P,Se version of such
complexes by 77Se NMR spectroscopy, we can draw conclu-
sions that can be extended to the P,S analogues with Pt(II).
1
15.2 (s). H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.41-7.23
(m, 10H, ArH), 2.52 (m, 2H, AliphH), 2.38 (m, 2H, AliphH),
1.94 (br s, 3H, AliphH); 13C{1H} NMR (100.62 MHz, CD2Cl2,
25 °C): δ 138.8 (d, JC-P = 15 Hz), 133.3 (d, JC-P = 19 Hz),
129.3 (s), 129.1 (d, JC-P = 7 Hz), 29.8 (d, JC-P = 15 Hz), 21.2 (d,
J
C-P = 20 Hz), 4.5 (s); 77Se{1H} NMR (76.34 MHz, 25 °C): δ
125.1 (d, JSe-P = 11 Hz). HRMS (APPI, MeOH): m/z calcd for
C15H17PSe [MþH]þ: 309.0306; found: 309.0319.
(2-(2,2,2-Trifluoroethane)thioethyl)dipheynlphosphine 8. One
g (1.1 equiv) of KtBuO was added to 0.95 g (8.2 mmol) of 2,2,2-
trifluoroethanethiol dissolved in 10 mL of dry acetonitrile, and
the mixture was stirred for 30 min at room temperature. A 2.04 g
portion (8.2 mmol) of 1-chloroethanephosphine dissolved in 5
mL of dry acetonitrile were added to the reaction mixture that
was allowed to stir for 48 h at room temperature. All volatiles
were evaporated in vacuo, and the residue was extracted with
ether and brine. The organic extract was evaporated in vacuo
Experimental Section
General Methods/Instrument Details. All phosphine-based
ligands were prepared and stored using standard Schlenk

1584 Inorganic Chemistry, Vol. 49, No. 4, 2010
Spokoyny et al.
Table 2. Crystallographic Data
(5a CH2Cl2)
3
(6a CH2Cl2)
3
(6b)
(9 CH2Cl2)
3
formula
fw
C36H38Cl4P2PtSe2
1027.41
C36H38Cl4P2PtSSe
980.51
C39H52BF4O4P2PtSSe
1126.07
C32H35Cl4F3P2PtS2
939.55
color, habit
cryst dimens [mm]
cryst syst
colorless plate
0.500 ꢀ 0.316 ꢀ 0.030
triclinic
colorless needle
0.519 ꢀ 0.09 ꢀ 0.02
triclinic
colorless needle
0.17 ꢀ 0.06 ꢀ 0.04
monoclinic
P2(1)/c
17.1537(3)
12.7690(2)
18.0712(3)
90
94.8700(10)
90
3943.95(11)
4
1.751
colorless needle
0.56 ꢀ 0.08 ꢀ 0.03
triclinic
space group
˚
P1
P1
P1
a [A]
9.7387(11)
11.5991(13)
16.6505(18)
83.477(2)
86.362(2)
85.674(2)
1860.5(4)
2
9.7594(4)
11.4970(5)
16.6076(6)
83.721(2)
86.262(2)
85.680(2)
1843.94(13)
2
9.5260(3)
12.7111(3)
15.8835(4)
108.108(2)
90.6480(10)
100.0850(10)
1795.32(8)
2
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
3
˚
V [A ]
Z
F
calcd [g cm-3
]
1.834
1.766
1.738
˚
radiation (λ, D [A])
Mo KR (0.71073)
6.126
100(2)
Mo KR (0.71073)
5.251
100(2)
Cu KR (1.54178)
9.475
100(2)
Mo KR (0.71073)
4.449
100(2)
μ [mm-1
T [K]
F(000)
]
996
960
2068
924
min/max transmn
2θ range [deg]
reflns collected
indep reflns
Rint
refinement method
data/restraints/params
final R indices [I2> 2σ(I)]
0.1114/0.8310
1.77 to 28.75
16962
8588
0.0293
0.2507/0.9012
2.06 to 34.50
30926
0.2879/0.6917
4.32 to 67.17
26361
6805
0.0790
0.1907/0.8969
1.72 to 30.68
37308
10835
0.0884
14339
0.0471
full-matrix least-squares on F2
8588/0/407
14339/0/407
R1 = 0.0335,
wR2 = 0.0800
R1 = 0.0509,
wR2 = 0.0860
0.881
6805/0/407
10835/6/399
R1 = 0.0502,
wR2 = 0.1251
R1 = 0.0633,
wR2 = 0.1293
1.115
R1 = 0.0365,
wR2 = 0.0893
R1 = 0.0491,
wR2 = 0.0956
1.047
R1 = 0.0393,
wR2 = 0.1026
R1 = 0.0535,
wR2 = 0.1065
1.048
R indices [all data]
GOF(F2)
largest diff peak/hole [e A
-3
˚
]
3.319/-2.060
3.057/-1.535
1.883/-1.653
4.087/-2.785
(10 CH2Cl2 H2O)
(5b CH2Cl2)
(7a CH2Cl2)
(7b)
3
3
3
3
formula
fw
C32H37Cl4F3OP2PtSSe
1004.47
C36H38B2Cl2F8P2PtSe2
1130.13
C36H38Cl4P2PtSSe
980.51
C35H36B2F8P2PtSSe
1042.37
color, habit
cryst dimens [mm]
cryst syst
colorless plate
0.28 ꢀ 0.13 ꢀ 0.02
triclinic
colorless block
0.35 ꢀ 0.26 ꢀ 0.14
monoclinic
C2/c
37.7059(6)
13.6290(2)
17.2281(3)
90
115.7880(10)
90
7971.7(2)
8
1.883
colorless needle
0.476 ꢀ 0.116 ꢀ 0.116
triclinic
colorless tabular
0.302 ꢀ 0.138 ꢀ 0.080
monoclinic
C2/c
37.375(4)
13.3976(15)
17.394(2)
90
114.810(13)
90
7905.8(17)
8
1.752
space group
˚
P1
P1
a [A]
9.86540(10)
10.06650(10)
18.4500(2)
91.6080(10)
93.8850(10)
96.5660(10)
1814.88(3)
2
9.7524(7)
11.5428(9)
16.6607(13)
84.0610(10)
86.2950(10)
85.7670(10)
1857.3(2)
2
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
3
˚
V [A ]
Z
F
calcd [g cm-3
]
1.838
1.753
˚
radiation (λ, D [A])
Mo KR (0.71073)
5.350
100(2)
Mo KR (0.71073)
5.626
100(2)
Mo KR (0.71073)
5.213
100(2)
Mo KR (0.71073)
4.673
100(2)
μ [mm-1
T [K]
F(000)
]
980
4368
960
4086
min/max transmn
2θ range [deg]
reflns collected
0.3128/0.8823
1.11 to 30.55
36443
0.2435/0.4980
1.20 to 30.02
111134
0.2693/0.5934
1.78 to 28.76
17259
0.3809/0.7016
1.63 to 28.67
36032
indep reflns
Rint
refinement method
data/restraints/params
final R indices [I2> 2σ(I)]
11034
0.0638
11614
0.0977
8626
0.0238
9602
0.0985
full-matrix least-squares on F2
11034/0/415
R1 = 0.0421,
wR2 = 0.0971
R1 = 0.0619,
wR2 = 0.1097
0.986
11614/0/479
R1 = 0.0349,
wR2 = 0.0956
R1 = 0.0597,
wR2 = 0.1062
1.067
8626/0/411
9602/0/412
R1 = 0.0317,
wR2 = 0.0800
R1 = 0.0371,
wR2 = 0.0837
1.060
R1 = 0.0646,
wR2 = 0.1460
R1 = 0.0823,
wR2 = 0.1510
1.059
R indices [all data]
GOF(F2)
largest diff peak/hole [e A
-3
˚
]
4.131/-2.579
3.243/-2.008
2.588/-1.460
2.323/-4.051
and purified via column chromatography on silica with 6:4
hexane/dichloromethane, which afforded 8 as a slightly yellow-
ish oil (2 g, 75%). 31P{1H} NMR (161.98 MHz, 25 °C): δ - 20.4
10H, ArH), 3.11 (q, 2H, AliphH), 2.74 (m, 2H, AliphH), 2.34 (m,
2H, AliphH); 13C{1H} NMR (100.62 MHz, CD2Cl2, 25 °C):
δ 134.8 (d, JC-P =14 Hz), 129.6 (d, JC-P =19 Hz), 125.9 (s),
125.6 (d, JC-P = 7 Hz), 123.1 (d, JC-F = 276 Hz), 31.6
1
(s). H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.52-7.30 (m,

Article
Inorganic Chemistry, Vol. 49, No. 4, 2010 1585
(q, JC-F=25 Hz), 26.8 (d, JC-P = 22 Hz), 25.2 (d, JC-P = 15 Hz);
19F{1H} NMR (376.46 MHz, CD2Cl2, 25 °C): δ - 70.3 (s).
HRMS (APPI): m/z calcd for C16H16PSF3 [MþH]þ: 329.0735;
found: 329.0744.
25 °C) δ -151.77 (s, 10BF4), -150.83 (s, 11BF4). MS (ESI): m/z
calcd for C35H36P2PtSeSBF4 [M-BF4]þ: 911; found: 911; Anal.
Calcd for C35H36P2SSePtB2F8: C, 42.11; H, 3.63. Found: C,
43.12; H, 3.60.
General Procedure for Formation of Heteroligated Semi-Open
Complexes. A solution of ligand A (2 or 4) (0.33 mmol) in
ClCH2CH2Cl (5 mL) was added dropwise to a solution of
[Pt(cod)Cl2] (125 mg, 0.33 mmol, 1 equiv) in dichloroethane
(5 mL) at room temperature. The solution was allowed to stir
for 5 min before ligand B (0.33 mmol) (1, 3, or 8), dissolved in
dichloroethane (5 mL), was added dropwise. After 20 min,
the solvent was reduced to about 1 mL in vacuo, and 10 mL of
diethyl ether was added, precipitating a white solid. The solid
was filtered and washed with an additional amount of ether
(5 mL) to afford the analytically pure heteroligated com-
plex (in situ 31P{1H} NMR yields = quantitative, isolated
yields >95%).
[PtCl(K2-PPh2SCH2CH2SMe)(PPh2CH2CH2SePh)]Cl (7a).
1H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.79-6.91 (m,
25ArH), 3.72-2.21 (m, 11AliphH); 31P{1H} NMR (161.98
MHz, 25 °C, DCE-d4): δ 43.1 (d, JP-P = 3517 Hz, JP-Pt
=
3517 Hz), 11.5 (d, JP-P = 15 JP-Pt = 3125 Hz); 77Se{1H} NMR
(76.34 MHz, 25 °C): δ 359.5 (bs) MS (ESI): m/z calcd
for C35H36P2PtSeSCl [M-Cl]þ: 861; found: 861; Anal. Calcd
for C35H36P2SSePtCl2: C, 46.94; H, 4.05. Found: C, 47.43;
H, 4.07.
Pt(K2-PPh2SCH2CH2SMe)(K2-PPh2CH2CH2SePh)][BF4]2
(7b). 1H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.71-6.92 (m,
25ArH), 3.25-2.43 (m, 11AliphH); 31P{1H} NMR (161.98
MHz, 25 °C, DCE-d4): δ 47.3 (d, JP-Pt = 3192 Hz), 46.9 (bs,
General Procedure for the Formation of Heteroligated Closed
Complexes. To a solution of a heteroligated semi-open
complex (0.3 mmol) in 10 mL of dichloroethane or dichlo-
romethane, about 1 g (9 mmol, 30 eq., 15 eq. per Cl-) of
NaBF4 was added, and the solution was left vigorously
stirring for 24 h. After passing the resulting mixture through
Celite and reducing the volume of solvent to about 1 mL in
vacuo, diethyl ether was used to precipitate the solid product.
This product was then filtered and washed with additional
amount of ether (ca. 10 mL) to afford the closed heteroligated
complex (in situ 31P{1H} NMR yields = quantitative, isolated
yields >95%).
J
P-Pt = 3030 Hz); 77Se{1H} NMR (76.34 MHz, 25 °C): δ 341.5
(bs); 19F{1H} NMR (376.46 MHz, 25 °C) δ -150.95 (s, 10BF4),
-151.00 (s, 11BF4). MS (ESI): m/z calcd for C35H36P2PtSeSBF4
[M-BF4]þ: 911; found: 911; Anal. Calcd for C35H36P2SSePtB2-
F8: C, 42.11; H, 3.63. Found: C, 43.52; H, 3.64.
[PtCl(K2-PPh2SCH2CH2SMe)(PPh2CH2CH2SCH2CF3)]Cl
(9). NMR (400.13 MHz, CD2Cl2, 25 °C, CD2Cl2): δ 7.79-7.92
(b, 20ArH), 3.28-2.39 (b, 13AliphH); 31P{1H} NMR (161.98
MHz, 25 °C, DCE-d4): δ 47.0 (d, JP-P = 15 Hz, JP-Pt = 3517
Hz), 9.1 (d, JP-P = 14 Hz, JP-Pt = 3186 Hz); 19F{1H} NMR
(376.46 MHz, 25 °C): δ - 66.3 (s). MS (ESI): m/z calcd for
C31H33ClF3P2S2Pt [M-Cl]þ: 818; found: 818; Anal. Calcd for
C31H33Cl2F3P2S2Pt: C, 43.47; H, 3.89. Found: C, 43.39; H, 3.82.
[PtCl(K2-PPh2SCH2CH2SeMe)(PPh2CH2CH2SCH2CF3)]Cl
(10). 1H NMR (400.13 MHz, CD2Cl2, 25 °C, CD2Cl2): δ
8.00-6.89 (b, 20ArH), 3.81-2.05 (b, 13AliphH); 31P{1H}
NMR (161.98 MHz, 25 °C, DCE-d4): δ 42.4 (d, JP-P=14 Hz
Characterization Summary of 5a-b, 6a-b, 7a-b, 9, and 10. In
all cases a small residual amount of reaction solvent was
observed in the 1H NMR even after prolonged drying in vacuo.
This is consistent with presence of solvent molecules in the unit
cells of the corresponding crystal structures and elemental
analysis data, as well as with previously reported work.11a,c
[PtCl(K2-PPh2SCH2CH2SeMe)(PPh2CH2CH2SePh)]Cl (5a).
1H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.92-6.84 (m,
25ArH), 3.77-2.28 (m, 11 AliphH); 31P{1H} NMR (100.62
MHz, DCE-d4, 25 °C): δ 42.1 (d, JP-P = 12 Hz, JP-Pt = 3538
Hz), 10.8 (d, JP-P = 11 Hz, JP-Pt = 3152 Hz); 77Se{1H} NMR
(76.34 MHz, 25 °C): δ 359.7 (bs), δ 332.4 (bd, JSe-P = 131 Hz);
MS (ESI): m/z calcd for C35H36P2PtSe2Cl [M-Cl]þ: 907; found:
907; Anal. Calcd for C35H36P2Se2PtCl2: C, 44.60; H, 3.85.
Found: C, 44.38; H, 3.59.
J
P-Pt = 3536 Hz), 9.0 (d, JP-P = 14 Hz, JP-Pt = 3190 Hz);
77Se{1H} NMR (76.34 MHz, 25 °C): δ 336.5 (dd, 1JSe-P=11 Hz,
2JSe-P = 129); 19F{1H} NMR (376.46 MHz, CD2Cl2, 25 °C):
δ -70.3. MS (ESI): m/z calcd for C31H33ClF3P2SSePt [M-Cl]þ:
865; found: 865; Anal. Calcd for C31H33Cl2F3P2SSePt: C, 41.30;
H, 3.69. Found: C, 42.27; H, 3.46.
General Procedure for Conversion of Closed Complexes to
Semi-Open. A solution of Me4NCl (0.1 mmol) in methanol (5
mL) was added to a solution of closed complex (0.1 mmol) in
dichloromethane (5 mL), resulting in a pale yellow solution.
31P{1H} NMR spectroscopy after 20 min showed predomi-
nantly the semi-open complex.
[Pt(K2-PPh2SCH2CH2SeMe)(K2-PPh2CH2CH2SePh)][BF4]2
(5b). 1H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.71-6.96 (m,
25ArH), 3.47-2.14 (m, 11H, AliphH); 31P{1H} NMR (161.98
MHz, 25 °C, DCE-d4): δ 47.0 (bs, JP-Pt = 3126 Hz), 44.8 (bs,
Control Reactions Confirming the Occurrence of the HILR in
Complex Formation.11a A mixture of ligand A (2 or 4) (0.33
mmol) and B (1, 3, or 8) (0.33 mmol) in 10 mL of 1,2-dichloro-
ethane was added dropwise to a solution of the platinum precur-
sor [Pt(cod)Cl2] (125 mg, 0.33 mmol) in 5 mL of 1,2-dichlor-
oethane at room temperature. A 31P{1H} NMR spectrum
recorded after 5 min indicated the presence of only heteroligated
species.
J
P-Pt = 3362 Hz); 77Se{1H} NMR (76.34 MHz, 25 °C): δ
268.1 (d, JSe-P = 98 Hz); 19F{1H} NMR (376.46 MHz, 25 °C)
δ -150.77 (s, 10BF4), -150. 82 (s, 11BF4). MS (ESI): m/z calcd
for C35H36P2PtSe2BF4 [M-BF4]þ: 959; found: 959; Anal. Calcd
for C35H36P2PtSe2B2F8: C, 40.11; H, 3.47. Found: C, 41.93;
H, 3.35.
[PtCl(K2-PPh2SCH2CH2SeMe)(PPh2CH2CH2SPh)]Cl (6a).
1H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.91-6.90 (m,
25ArH), 3.71-2.23 (m, 11AliphH); 31P{1H} NMR (161.98
MHz, 25 °C, DCE-d4): δ 42.2 (d, JP-P =15 Hz, JP-Pt =3538
Hz), 8.1 (d, JP-P = 14 Hz, JP-Pt = 3167 Hz); 77Se{1H} NMR
X-ray Crystallography. Crystallographic data collected for
Pt(II) complexes 5a-b, 6a-b, 7a-b, 9, and 10 is summarized in
Table 2. Single crystals of semi-open complexes suitable for
crystallographic analysis were grown in an NMR tube from a
dichloromethane solution layered with diethyl ether. Closed
complexes were grown by slow evaporation (ca. 3 days) from
dichloromethane in NMR tubes. Single crystals were mounted
using oil (Infineum V8512) on a glass fiber. All measurements
were made on a CCD area detector with graphite mono-
chromated MoK\R radiation and CuK\R for 6b. Data were
collected using Bruker APEXII detector and processed using
APEX2 from Bruker. All structures were solved by direct
methods and expanded using Fourier techniques. The non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were included in idealized positions, but not refined. Their
(76.34 MHz, 25 °C): δ 338.2 (dd, JSe-P=134 and 11 Hz, JSe-Pt
=
49 Hz). MS (ESI): m/z calcd for C35H36P2PtSeSCl [M-Cl]þ:
861; found: 861; Anal. Calcd for C35H36P2SSePtCl2: C, 46.94;
H, 4.05. Found: C, 47.51; H, 3.71.
[Pt(K2-PPh2SCH2CH2SeMe)(K2-PPh2CH2CH2SPh)][BF4]2
(6b). 1H NMR (400.13 MHz, CD2Cl2, 25 °C): δ 7.78-6.91
(m, 25ArH), 3.47-2.19 (m, 11AliphH); 31P{1H} NMR (161.98
MHz, 25 °C, DCE-d4): δ 47.2 (bs, JP-Pt = 3106 Hz), 43.1
(d, JP-P=15 Hz, JP-Pt=3464 Hz); 77Se{1H} NMR (76.34 MHz,
25 °C): δ 268.0 (d, JSeP = 97 Hz); 19F{1H} NMR (376.46 MHz,

1586 Inorganic Chemistry, Vol. 49, No. 4, 2010
Spokoyny et al.
positions were constrained relative to their parent atom using
the appropriate HFIX command in SHELXL-97.
Dr. Junpei Kuwabara for helpful suggestions, and Charles
Machan for help with synthesis of 4b. A.M.S. is grateful for a
U.S. Department of Education GAANN Fellowship.
Acknowledgment. C.A.M. acknowledges NSF, ARO, and
AFOSR through the MURI program for their generous
support. We thank Michael Wiester and Dr. Yuyang Wu
(Northwestern University IMSERC) for help with NMR,
Dr. Jennifer Seymour for mass spectrometry assistance,
Supporting Information Available: Crystallographic data for
complexes 5a-b, 6a-b, 7a-b, 9, and 10 in cif file format. This
material is available free of charge via the Internet at http://
pubs.acs.org.