Access to alkynylpalladium(IV) and -platinum(IV) species, including triorgano(diphosphine)metal(IV) complexes and the structural study of an alkynyl(pincer)platinum(IV) complex, Pt(O2CArF) I(C≡CSiMe3)(NCN) (ArF

Article abstract of DOI:10.1021/om0601495

New classes of alkynylplatinum(IV) complexes are described, and the first examples of alkynylpalladium(IV) complexes have been detected, including a triorganopalladium(IV) diphosphine complex. Alkynyliodine(III) triflate reagents IPh(C≡CR²)(OTf

Full text of DOI:10.1021/om0601495

3996
Organometallics 2006, 25, 3996-4001
Access to Alkynylpalladium(IV) and -Platinum(IV) Species,
Including Triorgano(diphosphine)metal(IV) Complexes and the
Structural Study of an Alkynyl(pincer)platinum(IV) Complex,
Pt(O2CArF)I(CtCSiMe3)(NCN) (ArF ) 4-CF3C6H4, NCN )
[2,6-(dimethylaminomethyl)phenyl-N,C,N]-)
Allan J. Canty,*,† Thomas Rodemann,† Brian W. Skelton,‡ and Allan H. White‡
School of Chemistry, UniVersity of Tasmania, Hobart, Tasmania 7001, Australia, and Chemistry M313,
UniVersity of Western Australia, Crawley, WA 6009, Australia
ReceiVed February 16, 2006
New classes of alkynylplatinum(IV) complexes are described, and the first examples of alkynylpal-
ladium(IV) complexes have been detected, including a triorganopalladium(IV) diphosphine complex.
Alkynyliodine(III) triflate reagents IPh(CtCR2)(OTf) (R2 ) SiMe3, Ph) are able to transfer alkynyl groups
to diorganoplatinum(II) and “pincer” complexes Pt(O2CAr)(NCN) (NCN ) [2,6-(dimethylaminomethyl)-
phenyl-N,C,N]-, Ar ) Ph, 4-trifluoromethylphenyl (ArF)); on addition of iodide ion, complexes with
new alkynylplatinum(IV) kernels may be isolated: PtIMe2(CtCR2)(bpy) (1, 2, 3a) (bpy ) 2,2′-bipyridine),
PtI(C4H8)(CtCSiMe3)(bpy) (4a), PtIPh2(CtCSiMe3)(But2bpy) (5a), and PtI(O2CAr)(CtCR2)(NCN) [Ar
) Ph (14, 15), ArF (16, 17)]. For the reagent PtMe2(dmpe) [dmpe ) 1,2-bis(dimethylphosphino)ethane],
the unstable complexes PtIMe2(CtCR2)(dmpe) (6a, 8a) are detected prior to reductive elimination of
ethane and isolation of PtI(CtCR2)(dmpe) (7, 9). Isomerism is exhibited by the octahedral fac-PtIVR2-
(CtCR2) complexes, where complexes 1 and 2 form as a mixture of complexes with the alkynyl group
opposite the bidentate ligand and cis to the iodo ligand (1a-6a, 8a), and cis to the bidentate ligand and
trans to the iodo ligand (1b, 2b), complexes 3a-5a, 6a, and 8a having R groups mutually cis. An X-ray
structural analysis for 16 shows distorted octahedral geometry about the metal with the iodo ligand trans
to the carbon donor of the mer-pincer ligand. Studies of the reactivity of related palladium(II) substrates
at low temperature allow detection of the pincer complex Pd(O2CPh)(OTf)(CtCSiMe3)(NCN) (19) and
PdIMe2(CtCSiMe3)(dmpe) (18) as a model for frequently proposed “PdIVXR3P2” species in catalytic
and stoichiometric reactions.
{CH2(CH2PPh2)2-P,P′}PtII(µ-CtC-X-CtC-C,C)2Pt{CH2(CH2-
PPh2)2-P,P′} (X ) 3,3′′,4,4′′-tetrabutyl-2,2′:5′,2′′-terthiophene).4b
The limited exploration of (η1-alkynyl)platinum(IV) chemistry5,6
includes a single phosphine complex,6a,7a and reported synthetic
Introduction
The possible intermediacy of (η1-alkynyl)palladium(IV) spe-
cies has been discussed for several catalytic processes,1,2 but
there are no reports of the detection of any type of (η1-alkynyl)-
palladium(IV) species, and similarly, there are numerous
proposals for the intermediacy of to date undetected “PdIVRnP2”
(n ) 1,3a 2,3b,c 3;2c,3d-g P ) phosphine donor) species. For the
closely related congener platinum, (η1-alkynyl)platinum(IV)
species have been proposed as intermediates in the high-
temperature activation of Pt(CtCR)2(1,5-cyclooctadiene) pre-
catalysts for hydrosilation reactions,4a and via oxidatively
induced reductive elimination, for the synthesis of the macro-
(3) (a) Krause, J.; Haack, K.-J.; Po¨rschke, K.-R.; Gabor, B.; Goddard,
R.; Pluta, C.; Seevogel, K. J. Am. Chem. Soc. 1996, 118, 804. (b) Milstein,
D.; Stille, J. K. J. Am. Chem. Soc. 1979, 101, 4992. (c) Nakazawa, H.;
Matsuoka, Y.; Nakagawa, I.; Miyoshi, K. Organometallics 1992, 11, 1385.
(d) Trost, B. M. Acc. Chem. Res. 1990, 23, 34. (e) Kamigata, N.; Satoh,
M.; Yoshida, M. J. Organomet. Chem. 1991, 401, C26. (f) Albrecht, K.;
Reiser, O.; Weber, M.; Knieriem, B.; de Meijere, A. Tetrahedron 1994,
50, 383. (g) Catellani, M.; Motti, E.; Faccini, F.; Ferraccioli, R. Pure Appl.
Chem. 2005, 77, 1243.
(4) (a) Jagadeesh, M. N.; Thiel, W.; Ko¨hler, J.; Fehn, A. Organometallics
2002, 21, 2076. (b) Fuhrmann, G.; Debaerdemaeker, T.; Ba¨uerle, P. Chem.
Commun. 2003, 948.
(5) (a) Long, N. J.; Williams, C. K. Angew. Chem., Int. Ed. 2003, 42,
2586. (b) Belluco, U.; Bertani, R.; Michelin, R. A.; Mozzon, M. J.
Organomet. Chem. 2000, 600, 37.
(6) (a) Geisenberger, J.; Nagel, U.; Sebald, A.; Beck, W. Chem. Ber.
1983, 116, 911. (b) Janzen, M. C.; Jenkins, H. A.; Jennings, M. C.; Rendina,
L. M.; Puddephatt, R. J. J. Chem. Soc., Dalton Trans. 1999, 1713. (c) Janzen,
M. C.; Jenkins, H. A.; Jennings, M. C.; Rendina, L. M.; Puddephatt, R. J.
Organometallics 2002, 21, 1257. (d) James, S. L.; Younus, M.; Raithby,
P. R.; Lewis, J. J. Organomet. Chem. 1997, 543, 233.
(7) (a) 4-Nitrophenyl azide reacts with trans-Pt(CtCPh)2(PEt3)2 to
eliminate dinitrogen and form a complex containing a 2-tetrazene-1,4-diyl
group, Pt(CtCPh)2({N(4-NO2C6H4)NdN-N(4-NO2C6H4)-N,N′}(PEt3)2.6a
(b) (MeO2C)CtC(CO2Me) reacts with PtMe2{SnMe2C(CO2Me)CdC(CO2-
Me)Se-Sn,Se}(But2bpy) [But2bpy ) 4,4′-bis(tert-butyl)-2,2′-bipyridine] to
form a complex containing methyl, alkenyl, and alkynyl groups, PtMe2-
{C(CO2Me)dCH(CO2Me)}{CtC(CO2Me)}(But2bpy).6b,c
cycle CtC-X-CtC-CtC-X-CtC on addition of iodine to
* To whom correspondence should be addressed. E-mail: Allan.Canty@
utas.edu.au. Fax: (61-3) 6226-2858.
† University of Tasmania.
‡ University of Western Australia.
(1) Gevorgyan, V. In Handbook of Organopalladium Chemistry for
Organic Synthesis; Negishi, E.-I., Ed.; Wiley: New York, 2002; Vol. 1,
Chapter IV.5, p 1463.
(2) (a) Trost, B. M.; Chan, C.; Ruhter, G. J. Am. Chem. Soc. 1987, 109,
3486. (b) Alper, H.; Saldana-Maldonado, M. Organometallics 1989, 8, 1124.
(c) Catellani, M.; Marmiroli, B.; Fagnola, M. C.; Acquotti, D. J. Organomet.
Chem. 1996, 507, 157. (d) Herrmann, W. A.; Reisinger, C.-P.; O¨ fele, K.;
Brossmer, C.; Beller, M.; Fischer, H. J. Mol. Catal. A 1996, 108, 51. (e)
Naka, A.; Okada, T.; Ishikawa, M. J. Organomet. Chem. 1996, 521, 163.
(f) Trost, B. M.; Sorum, M. T.; Chan, C.; Harms, A. E.; Ru¨hter, G. J. Am.
Chem. Soc. 1997, 119, 698.
10.1021/om0601495 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 07/04/2006

Alkynylpalladium(IV) and -Platinum(IV) Species
Organometallics, Vol. 25, No. 16, 2006 3997
temperature unless indicated otherwise. 13C NMR spectra at 75.4
MHz, 31P NMR at 121.4 MHz (H3PO4 external standard), and
COSY, HMQC, and HMBC spectra were recorded on a Varian
Mercury Plus 300 MHz spectrometer. COSY NMR was used to
assign all H NMR spectra, and H chemical shifts are given in
ppm relative to SiMe4. Microanalyses and LSMIS were performed
by the Central Science Laboratory, University of Tasmania. GC-
MS analyses were performed using an HP 5890 gas chromatograph
equipped with an HP5790 MSD and a 25 m × 0.32 mm HP1
column (0.52 µm film thickness, He at 10 psi).
routes that could be more widely applicable for the synthesis
of Pt(IV) species are confined to the oxidation of PtII(CtCTol-
4)2(Me2bpy) by iodine to form PtIVI2(CtCTol-4)2(Me2bpy).6d
For “pincer” complexes, access to Pt(IV) species has also been
elusive.5 Thus, the alkynylplatinum(II) bond in alkynyl{C6H3(CH2-
NMe2)2-2,6-N,C,N′}platinum(II) complexes is not stable to
halogen-containing oxidants,8a and cyclic voltammetry studies
for this class of Pt(II) complex,8a,b and related complexes,9 reveal
irreversible oxidation processes.
1
1
In a search for routes to new classes of alkynylmetal(IV) (M
) Pd, Pt) species, we have noted that alkynyl groups, formally
as [CtCR]+, are transferred from iodine(III) reagents IPh(Ct
CR)(O3SCF3) to rhodium(I) and iridium(I) complexes to form
d6 (η1-alkynyl)metal(III) complexes with release of iodoben-
zene.10 We report here the application of alkynyliodine(III)
reagents for the generation of detectable but unstable (η1-
alkynyl)dimethylpalladium(IV) and -platinum(IV) complexes of
bidentate bis(dimethylphosphino)ethane (dmpe), the isolation
Synthesis of Pt(O2CArF)(NCN). Silver 4-trifluoromethylben-
zoate (0.009 g, 0.039 mmol) was added to a solution of PtCl(NCN)
(0.016 g, 0.038 mmol) in acetone (5 mL). The suspension was
stirred for 15 h in the absence of light, then filtered through Celite.
The solvent was removed under a vacuum to give the product as a
1
colorless solid (18 mg, 95%). H NMR (acetone-d6) (300 MHz):
δ 8.27 (d, 3J ) 7.6 Hz, 2H, H2,6), 7.71 (d, 3J ) 7.6 Hz, 2H, H3,5),
3
3
6.93 (dd, J ) 6.3, 8.4 Hz, 1H, H4-NCN), 6.80 (d, J ) 7.7 Hz,
3
4
2H, H3,5-NCN), 4.10 (s, JPt-H ) 47.6 Hz, H, NCH2), 3.04 (s,
of alkynylplatinum(IV) complexes including moieties PtIVR1 -
2
3JPt-H ) 36.9 Hz, 12H, NCH3).
(CtCR2) (R1 ) Me, Ph) and PtIV(CtCR2)(NCN) ([NCN]- )
[2,6-(dimethylaminomethyl)phenyl-N,C,N]-), and the detection
of an unstable Pd(IV) pincer complex. Preliminary communica-
tions of part of this work have appeared.11
Synthesis of Diorgano(alkynyl)platinum(IV) Complexes 1-5a.
General Synthesis. The iodine(III) reagent (0.051 mmol) was added
to a stirred solution of the Pt(II) reagent (0.051 mmol) in acetone
under argon. Stirring was continued for 2 h (2 days for complex
6). Sodium iodide (9.0 mg, 0.060 mmol) in acetone (1 mL) was
added, and the solution stirred for a further 2 h. For complexes 1,
3a, and 4a the solvent was removed under a vacuum and the residue
dissolved in the minimum amount of acetone; diethyl ether (5 mL)
was added and the precipitated yellow product (1) collected by
filtration. For the But2bpy complexes 2, 5a, and 6, the solvent was
removed under a vacuum and the residue dissolved in the minimum
amount of diethyl ether; the addition of pentane (5 mL) allowed
the isolation of solid products by filtration.
Experimental Section
The reagents MMe2(bpy) (M ) Pd,12 Pt13), M(C4H8)(bpy) (M
) Pd,14 Pt15), PtR2(But2bpy) (R ) Me,16 Ph17), MMe2(dmpe) (M
) Pd,18 Pt19), MCl(NCN) (M ) Pd, Pt),20 M(O2CPh)(NCN) (M )
Pd, Pt),21 and IPh(CtCR2)(O3SCF3) (R2 ) SiMe3, Ph)22 were
prepared as described; the new complex Pt(O2CArF)(NCN) was
prepared by a method similar to that reported for Pt(O2CPh)-
(NCN).21 1H NMR spectra were recorded on a Varian Unity Innova
400 MHz wide bore instrument at 399.7 MHz or on a Varian
Mercury Plus 300 MHz spectrometer at 299.9 MHz, at room
PtIMe2(CtCSiMe3)(bpy) (1). Yield: 90%. Anal. Found: C,
33.44; H, 3.74; N, 4.78. Calcd for C17H23N2IPtSi: C, 33.72; H,
1
3.83; N, 4.63. H NMR (acetone-d6) (400 MHz): cis-isomer (1a)
(8) (a) Back, S.; Gossage, R. A.; Lutz, M.; del Rio, I.; Spek, A. L.; Lang,
H.; van Koten, G. Organometallics 2000, 19, 3296. (b) Back, S.; Lutz, M.;
Spek, A. L.; Lang, G.; van Koten, G. J. Organomet. Chem. 2001, 620,
227. (c) Hoogervorst, W. J.; Elsevier: C. J.; Lutz, M.; Spek, A. L.
Organometallics 2001, 20, 4437.
(9) Lu, W.; Mi, B.-X.; Chan, M. C. W.; Hui, Z.; Che, C.-M.; Zhu, N.;
Lee, S.-T. J. Am. Chem. Soc. 2004, 126, 4958. (b) Wong, K. M.-C.; Tang,
W.-S.; Chu, B. W.-K.; Zhu, N.; Yam, V. W.-W. Organometallics 2004,
23, 3459.
(10) (a) Stang, P. J.; Crittell, C. M. Organometallics 1990, 9, 3191. (b)
Stang, P. J.; Tykwinski, R. J. Am. Chem. Soc. 1992, 114, 4411. (c)
Tykwinski, R. R.; Stang, P. J. Organometallics 1994, 13, 3203. (d)
Bykowski, D.; McDonald, R.; Tykwinski, R. R. ARKIVOC 2003 (vi), 21.
(11) (a) Canty, A. J.; Rodemann, T. Inorg. Chem. Commun. 2003, 6,
1382. (b) Canty, A. J.; Rodemann, T.; Skelton, B. W.; White, A. H. Inorg.
Chem. Commun. 2005, 8, 55.
(12) Byers, P. K.; Canty, A. J. Organometallics 1990, 9, 210.
(13) Kuyper, J.; van der Laan, R.; Jeanneaus, F.; Vrieze, K. Transition
Met. Chem. 1976, 1, 199.
(14) (a) Diversi, P.; Ingrosso, G.; Lucherini, A.; Murtas, S. J. Chem.
Soc., Dalton Trans. 1980, 1633. (b) Diversi, P.; Ingrosso, G.; Lucherini,
A. Inorg. Synth. 1993, 22, 167.
(15) Rashidi, M.; Esmaeilbeig, A. R.; Shahabadi, N.; Tangestaninejad,
S.; Puddephatt, R. J. J. Organomet. Chem. 1998, 568, 53.
(16) Ong, C. M.; Jennings, M. C.; Puddephatt, R. J. Can. J. Chem. 2003,
81, 1.
(17) Achar, S.; Scott, J. D.; Vittal, J. J.; Puddephatt, R. J. Organometallics
1993, 12, 4592.
(18) de Graaf, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten,
G. Organometallics 1989, 8, 2907.
δ 9.51 (m, 1H, H6-bpy), 8.87 (m, 1H, H6-bpy), 8.25 (m, 2H, H3-
2
bpy), 8.10 (m, 2H, H4-bpy), 7.67 (m, 2H, H5-bpy), 1.76 (s, JHPt
2
) 61.2 Hz, 3H, PtMe), 1.08 (s, JHPt ) 68.8 Hz, 3H, PtMe), 0.20
(s, 9H, SiMe3); trans-isomer (1b) δ 8.93 (m, 2H, H6-bpy), 8.30
(m, 2H, H3-bpy), 8.13 (m, 2H, H4-bpy), 7.67 (m, 2H, H5-bpy),
2.39 (s, 2JHPt ) 73.2 Hz, 6H, PtMe), 0.20 (s, 9H, SiMe3). IR (KBr
disk): ν(CtC) 2076 cm-1
.
PtIMe2(CtCSiMe3)(But2bpy) (2). Yield: 85%. Anal. Found:
C, 41.63; H, 5.33; N, 3.70. Calcd for C25H39N2IPtSi: C, 41.84; H,
1
5.48; N, 3.90. H NMR (acetone-d6) (300 MHz): cis-isomer (2a)
δ 9.40 (m, 1H, H6-bpy), 8.89 (m, 1H, H6-bpy), 8.74 (m, 1H, H3-
2
2
bpy), 1.71 (s, JHPt ) 68.0 Hz, 3H, PtMe), 1.01 (s, JHPt ) 69.3
Hz, 3H, PtMe); trans-isomer (2b) 8.85 (m, 2H, H6-bpy), 2.35 (s,
2JHPt ) 72.4 Hz, 3H, PtMe); 2a and 2b δ 8.41 (m, 1H, H3-bpy),
7.88 (m, 2H, H5-bpy), 1.49 (s, 3H, But), 1.48 (s, 9H, But), 0.15 (s,
9H, SiMe3). IR (KBr disk): ν(CtC) 2075 cm-1
.
cis-PtIMe2(CtCPh)(bpy) (3a). Yield: 89%. Anal. Found: C,
39.21; H, 3.18; N, 4.42. Calcd for C20H19N2IPt: C, 39.42; H, 3.14;
1
N, 4.60. H NMR (acetone-d6) (400 MHz): δ 9.59 (m, 1H, H6-
bpy), 9.04 (m, 1H, H6-bpy), 8.93 (m, 2H, H3-bpy), 8.41 (m, 2H,
3
H4-bpy), 7.95 (m, 2H, H5-bpy), 7.40 (d, J ) 8.4 Hz, 2H, H2,6-
3
Ph), 7.27 (‘t’, 2H, H3,5-Ph), 7.15 (t, J ) 7.4 Hz, 1H, H4-Ph),
1.85 (s, 2JHPt ) 67.6 Hz, 3H, PtMe), 1.12 (s, 2JHPt ) 69.2 Hz, 3H,
PtMe). IR (KBr disk): ν(CtC) 2145 cm-1
.
(19) Peters, R. G.; White, S.; Roddick, D. M. Organometallics 1998,
17, 4493.
(20) Grove, D. M.; van Koten, G.; Louwen, J. N.; Noltes, J. G.; Spek,
A. L.; Ubbels, H. J. C. J. Am. Chem. Soc. 1982, 104, 6609.
(21) Canty, A. J.; Denney, M. C.; van Koten, G.; Skelton, B. W.; White,
A. H. Organometallics 2004, 23, 5432.
cis-PtI(C4H8)(CtCSiMe3)(bpy) (4a). Yield: 78%. Anal.
Found: C, 36.09; H, 3.70; N, 4.60. Calcd for C19H25N2IPtSi: C,
36.14; H, 3.99; N, 4.44. 1H NMR (acetone-d6) (400 MHz): δ 9.46
(m, 1H, H6-bpy), 9.10 (m, 1H, H6-bpy), 8.82 (m, 2H, H3-bpy),
8.41 (m, 2H, H4-bpy), 7.95 (m, 2H, H5-bpy), 3.26 [m(b), 1H, CH2],
2.46 [m(b), 1H, CH2], 2.28 [m(b), 1H, CH2], 1.61 [m(b), 1H, CH2],
(22) Bachi, M. D.; Bar-Ner, N.; Crittell, C. M.; Stang, P. J.; Williamson,
B. L. J. Org. Chem. 1991, 56, 3912.

3998 Organometallics, Vol. 25, No. 16, 2006
Canty et al.
2
3
3
1.34 [m(b), 3H, CH2], 0.61 [m(b), 1H, CH2], 0.11 (s, 9H, SiMe3).
(d, J ) 14.8 Hz, JHPt ) 39.0 Hz, 2H, NCH2), 3.37 (s, JHPt
)
3
IR (KBr disk): ν(CtC) 2076 cm-1
.
41.7 Hz, 6H, NMe), 2.97 (s, JHPt ) 24.3 Hz, 6H, NMe), 0.08 (s,
9H, SiMe3).
cis-PtIPh2(CtCSiMe3)(But2bpy) (5a) (from dichloromethane/
diethyl ether). Yield: 82%. Anal. Found: C, 49.86; H, 5.14; N,
3.26. Calcd for C35H43N2IPtSi: C, 49.94; H, 5.15; N, 3.33. 1H NMR
(acetone-d6) (300 MHz): δ 9.73 (m, 1H, H6-bpy), 9.07 (m, 1H,
H6-bpy), 8.73 (d, 4J ) 2.0 Hz, 1H, H3-bpy), 8.71 (d, 4J ) 1.8 Hz,
1
Pt(O2CPh)(OTf)(CtCPh)(NCN) (11). H NMR (acetone-d6)
(300 MHz): δ 7.96 (d, 3J ) 8.1 Hz, 2H, H2,6-O2CPh), 7.62-7.38
3
[m(b), 6H], 7.28-7.20 (m, 4H), 7.18 (t, J ) 7.4 Hz, 1H, H4-
CtCPh), 4.77 (d, 2J ) 14.9 Hz, 3JHPt ) 31.2 Hz, 2H, NCH2), 4.61
2
3
3
3
4
(d, J ) 14.9 Hz, JHPt ) 39.0 Hz, 2H, NCH2), 3.37 (s, JHPt
)
1H, H3-bpy), 8.01 (dd, J ) 6.0 Hz, J ) 1.8 Hz, 1H, H5-bpy),
3
7.96 (dd, 3J ) 6.2 Hz, 4J ) 1.8 Hz, 1H, H5-bpy), 7.67 (d, 3JHPt
)
41.7 Hz, 6H, NMe), 2.97 (s, JHPt ) 24.2 Hz, 6H, NMe).
3
Pt(O2CArF)(OTf)(CtCSiMe3)(NCN) (12). 1H NMR (acetone-
45.2 Hz, J ) 8.3 Hz, 2H, H2,6-Ph), 7.00 (m, 1H, H4-Ph), 6.92
(m, 2H), 6.81 (m, 3H), 6.70 (m, 2H), 1.47 (s, 9H, But), 1.46 (s,
3
d6) (300 MHz): δ 8.06 (d, J ) 8.2 Hz, 2H, H2,6), 7.75 (m, 2H,
9H, But), 0.15 (s, 9H, SiMe3). IR (KBr disk): ν(CtC) 2079 cm-1
.
3
3
H3,5), 7.40 (t, J ) 7.5 Hz, 1H, H4-NCN), 7.24 (d, J ) 7.8 Hz,
2
3
2H, H3,5-NCN), 4.77 (d, J ) 15.1 Hz, JHPt ) 33.0 Hz, 2H,
cis-PtIMe2(CtCSiMe3)(dmpe) (6a) and PtI(CtCSiMe3)-
(dmpe) (7). Phenyl{(trimethylsilyl)ethynyl}iodonium triflate (10.0
mg, 0.022 mmol) was added to a stirred solution of PtMe2(dmpe)
(8.3 mg, 0.022 mmol) in acetone-d6 (1 mL) at -50 °C under argon.
Stirring was continued for 30 min. Sodium iodide (4.5 mg, 0.030
mmol) was added, and the solution was stirred for a further 1 h at
-50 °C. The NMR spectrum of 6a was recorded. The solution was
warmed to room temperature, and stirring was continued for 15 h.
The solvent was removed under a vacuum and the residue dissolved
in the minimum amount of dichloromethane. Pentane (5 mL) was
added and the precipitate collected by filtration. For complex 6a,
1H NMR (acetone-d6) (300 MHz): δ 2.10-1.70 (m, PCH2 and
acetone), 1.65-1.37 (m, 6H, PMe, COSY indicates two environ-
ments), 1.25-1.18 (m, 3H, PMe), 1.15-0.95 (m, 6H, PtMe), 0.94-
0.83 (m, 3H, PMe), 0.00 (s, 9H, SiMe3). 31P NMR (acetone-d6)
(121.4 MHz): δ 1.35 (1JPtP ) 1160 Hz), -2.81 (1JPtP ) 1753 Hz).
For complex 7, yield: 82%. Anal. Found: C, 22.96; H, 4.53. Calcd
2
3
NCH2), 4.62 (d, J ) 15.1 Hz, JHPt ) 37.6 Hz, 2H, NCH2), 3.37
(s, 3JHPt ) 41.9 Hz, 6H, NMe), 2.99 (s, 3JHPt ) 24.0 Hz, 6H, NMe),
0.08 (s, 9H, SiMe3).
Pt(O2CArF)(OTf)(CtCPh)(NCN) (13). 1H NMR (acetone-d6)
3
(300 MHz): δ 8.14 (d, J ) 8.2 Hz, 2H, H2,6-O2CArF), 7.80-
7.73 (m, 2H, H3,5-O2CArF), 7.59-7.38 (m, 3H), 7.31-7.22 (m,
4H), 7.20 (t, 3J ) 7.5 Hz, 1H, H4-CtCPh), 4.76 (d, 2J ) 15.1 Hz,
3JHPt ) 33.2 Hz, 2H, NCH2), 4.62 (d, J ) 15.0 Hz, JHPt ) 37.6
Hz, 2H, NCH2), 3.38 (s, 3JHPt ) 41.9 Hz, 6H, NMe), 2.99 (s, 3JHPt
) 24.1 Hz, 6H, NMe).
2
3
Pt(O2CPh)I(CtCSiMe3)(NCN) (14). Yield: 93%. Anal.
Found: C, 39.28; H, 4.63; N, 3.58. Calcd for C24H33N2O2IPtSi:
C, 39.40; H, 4.55; N, 3.83. H NMR (acetone-d6) (300 MHz): δ
1
3
8.04 (d, J ) 8.2 Hz, 2H, H2,6), 7.46-7.31 [m(b), 4H, H3, H4,
3
2
H4-NCN], 7.01 (d, J ) 7.7 Hz, 2H, H3,5-NCN), 4.65 (d, J )
14.8 Hz, 3JHPt ) 33.1 Hz, 2H, NCH2), 4.40 (d, 2J ) 14.8 Hz, 3JHPt
) 35.5 Hz, 2H, NCH2), 3.41 (s, 3JHPt ) 42.1 Hz, 6H, NMe), 3.08
1
for C11H25P2IPtSi: C, 23.21; H, 4.43. H NMR (acetone-d6) (300
3
MHz): δ 2.32-1.95 (m, PCH2 and acetone), 1.28-1.15 (m, 6H,
(s, JHPt ) 26.4 Hz, 6H, NMe), 0.08 (s, 9H, SiMe3). IR (KBr
PMe), 1.10-0.94 (m, 6H, PMe), 0.05 (s, 9H, SiMe3). 31P NMR
disk): ν(CtC) 2078 cm-1
.
(acetone-d6) (121.4 MHz): δ 26.8 (1JPtP ) 2307 Hz), 26.3 (1JPtP
)
Pt(O2CPh)I(CtCPh)(NCN) (15). Yield: 82%. Anal. Found:
C, 44.23; H, 3.75; N, 3.75. Calcd for C27H29N2O2IPt: C, 44.09; H,
3.97; N, 3.81. H NMR (acetone-d6) (300 MHz): δ 8.14 (d, J )
8.1 Hz, 2H, H2,6-O2CPh), 7.51-7.24 [m(b), 8H], 7.15 (t, 3J ) 7.5
Hz, 1H, H4-CtCPh), 7.06 (d, 3J ) 7.6 Hz, 2H, H3,5-NCN), 4.68
(d, 2J ) 14.9 Hz, 3JHPt ) 32.8 Hz, 2H, NCH2), 4.44 (d, 2J ) 14.9
2225 Hz). IR (KBr disk): ν(CtC) 2039 cm-1
.
1
3
cis-PtIMe2(CtCPh)(dmpe) (8a) and PtI(CtCPh)(dmpe) (9).
The procedure was followed as for 6a and 7, using phenyl-
(phenylethynyl)iodonium triflate. For complex 8a, 1H NMR
(acetone-d6) (300 MHz): δ 7.35 (d, J ) 7.6 Hz, 2H, H2,6), 7.25
(t, J ) 7.4 Hz, 2H, H3,5), 7.12 (t, J ) 7.4 Hz, 1H, H4), 2.13-1.75
(m, PCH2 and acetone), 1.69-1.36 (m, 6H, PMe, COSY indicates
two environments), 1.28-1.19 (m, 3H, PMe), 1.23-0.91 (m, 6H,
PtMe), 1.05-0.88 (m, 3H, PMe). 31P NMR (acetone-d6) (121.4
MHz): δ 1.47 (1JPtP ) 1210 Hz), -2.08 (1JPtP ) 1594 Hz). For
complex 9, yield: 74%. Anal. Found: C, 29.18; H, 3.43. Calcd
3
3
Hz, JHPt ) 36.2 Hz, 2H, NCH2), 3.43 (s, JHPt ) 42.3 Hz, 6H,
NMe), 3.13 (s, 3JHPt ) 26.7 Hz, 6H, NMe). IR (KBr disk): ν(Ct
C) 2143 cm-1
.
Pt(O2CArF)I(CtCSiMe3)(NCN) (16). Yield: 89%. Anal.
Found: C, 37.48; H, 3.89; N, 3.48. Calcd for C25H32N2O2IF3PtSi:
1
C, 37.55; H, 4.03; N, 3.50. H NMR (acetone-d6) (300 MHz): δ
1
8.20 (d, 3J ) 8.6 Hz, 2H, H2,6), 7.71 (d, 3J ) 8.6 Hz, 2H, H3,5),
for C14H21P2IPt: C, 29.33; H, 3.69. H NMR (acetone-d6) (300
3
3
MHz): δ 7.38 (d, J ) 7.8 Hz, 2H, H2,6), 7.27 (t, J ) 7.5 Hz, 2H,
H3,5), 7.15 (t, J ) 7.4 Hz, 1H, H4), 2.27-2.04 (m, PCH2 and
7.41 (t, J ) 7.6 Hz, 1H, H4-NCN), 7.03 (d, J ) 7.7 Hz, 2H,
2
3
H3,5-NCN), 4.67 (d, J ) 14.8 Hz, JHPt ) 32.9 Hz, 2H, NCH2),
acetone), 1.33-1.19 (m, 6H, PMe), 1.18-0.99 (m, 6H, PMe). 31
P
2
3
3
4.42 (d, J ) 14.8 Hz, JHPt ) 35.2 Hz, 2H, NCH2), 3.41 (s, JHPt
NMR (acetone-d6) (121.4 MHz): δ 27.8 (1JPtP ) 2273 Hz), 26.7
3
) 42.0 Hz, 6H, NMe), 3.08 (s, JHPt ) 25.9 Hz, 6H, NMe), 0.08
(1JPtP ) 2299 Hz). IR (KBr disk): ν(CtC) 2113 cm-1
.
(s, 9H, SiMe3). IR (KBr disk): ν(CtC) 2078 cm-1
.
General Synthesis of Alkynyl(pincer)platinum(IV) Complexes
10-17. Phenyl{(trimethylsilyl)ethynyl}iodonium triflate (0.15 mmol)
was added to a stirred solution of the platinum(II) reagent (0.15
mmol) in acetone (10 mL) under argon, and stirring was continued
for another 30 min. For complexes 10 to 13 acetone-d6 was also
used as a solvent to allow NMR characterization. Sodium iodide
(0.2 mmol) was added and the solution stirred for a further 30 min.
The solvent was removed under a vacuum and the residue was
extracted with a minimum amount of dichloromethane. The
suspension was filtered and the solvent removed under a vacuum.
The residue was washed with a small amount of cold diethyl ether
to give the product. Crystals of 15 were obtained at 0 °C from a
solution of the complex in dichloromethane/diethyl ether.
Pt(O2CArF)I(CtCPh)(NCN) (17). Yield: 78%. Anal. Found:
C, 41.69; H, 3.55; N, 3.40. Calcd for C28H28N2O2IF3Pt: C, 41.85;
H, 3.51; N, 3.49. 1H NMR (acetone-d6) (300 MHz): δ 8.25 (d, 3J
) 8.3 Hz, 2H, H2,6-O2CArF), 7.74 (d, 3J ) 8.5 Hz, 2H, H3,5-O2-
CArF), 7.45-7.26 (m, 5H), 7.15 (t, 3J ) 7.4 Hz, 1H, H4-CtCPh),
7.05 (d, 3J ) 7.7 Hz, 2H, H3,5-NCN), 4.68 (d, 2J ) 15.0 Hz, 3JHPt
2
3
) 31.9 Hz, 2H, NCH2), 4.44 (d, J ) 15.0 Hz, JHPt ) 37.1 Hz,
3
3
2H, NCH2), 3.43 (s, JHPt ) 42.2 Hz, 6H, NMe), 3.09 (s, JHPt
)
25.3 Hz, 6H, NMe). IR (KBr disk): ν(CtC) 2142 cm-1
.
NMR Studies of Reactivity of Palladium(II) Complexes. cis-
PdIMe2(CtCSiMe3)(dmpe) (18). Phenyl[(trimethylsilyl)ethynyl]-
iodonium triflate (10.0 mg, 0.022 mmol) was added to a stirred
solution of PdMe2(dmpe) (6.4 mg, 0.022 mmol) in acetone-d6 (1
mL) at -50 °C under argon. Stirring was continued for 1 h. Sodium
iodide (4.5 mg, 0.030 mmol) was added, and the solution was stirred
1
Pt(O2CPh)(OTf)(CtCSiMe3)(NCN) (10). H NMR (acetone-
3
d6) (300 MHz): δ 7.85 (d, J ) 8.1 Hz, 2H, H2,6), 7.53 (m, 2H,
H4, H4-NCN), 7.41 (m, 2H, H3,5), 7.24 (d, 3J ) 8.1 Hz, 2H, H3,5-
for a further 1 h at -50 °C. H NMR (acetone-d6, -50 °C) (300
1
2
3
NCN), 4.77 (d, J ) 14.8 Hz, JHPt ) 30.4 Hz, 2H, NCH2), 4.61
MHz): δ 2.80-2.21 (m, 4H, PCH2), 2.20 (s, 3H, PdMe), 1.84 (s,

Alkynylpalladium(IV) and -Platinum(IV) Species
Organometallics, Vol. 25, No. 16, 2006 3999
10.8050(7) Å, c ) 13.6912(9) Å, R ) 85.450(1)°, â ) 70.118(1)°,
γ ) 89.947(1)°, V ) 1387.1(2) Å3, Dc (Z ) 1) ) 1.914 g cm-3
,
)
µMo ) 6.3 mm-1; specimen: 0.25 × 0.15 × 0.08 mm; Tmin/max
0.57.
Results
Reactivity Studies for Platinum(II) Substrates. The readily
prepared reagents IPh(CtCR2)(OTf) (R2 ) SiMe3, Ph)22 were
chosen as representative alkynyliodine(III) reagents, and reactiv-
ity studies were initially confined to PtMe2(bpy) as the Pt(II)
substrate. Successful isolation of Pt(IV) complexes encouraged
studies of PtPh2(But2bpy) [But2bpy ) 4,4′-bis(tert-butyl)-2,2′-
bipyridine], where the But2bpy ligand is known to enhance the
solubility of diarylplatinum(II) species,17 the platinacyclopentane
complex Pt(C4H8)(bpy), the 1,2-bis(dimethylphenylphosphino)-
ethane complex PtMe2(dmpe), and the ‘pincer’ reagents Pt(O2-
CAr)(NCN) (Ar ) Ph, ArF (4-trifluoromethylphenyl); NCN )
[2,6-(dimethylaminomethyl)phenyl-N,C,N]-). In all cases where
reactions occurred, iodobenzene as a product was detected by
1H NMR spectroscopy.
Diorgano(alkynyl)platinum(IV) complexes of nitrogen donor
ligands (1-5) were isolated in 78-90% yield from reactions
at ambient temperature (Scheme 1). The Pt(II) substrates were
reacted with phenyl(alkynyl)iodine(III) triflates, followed by
addition of iodide as a ligand known to participate in a wide
range of stable triorganoplatinum(IV) complexes. Organoplati-
num resonances moved downfield on oxidation, e.g., PtMe by
0.1-1.44 for 1-3, and H2,6-Ph by 0.22 for 5a. Isomerism was
Figure 1. Projection of a molecule of Pt(O2CArF)I(CtCSiMe3)-
(NCN) (16), showing 50% displacement ellipsoids for the non-
hydrogen atoms, hydrogen atoms having arbitrary radii of 0.1 Å.
1
readily discernible from H NMR spectra; for example, where
cis- and trans- designate the orientation of alkynyl and iodo
ligands (Scheme 1), the cis-isomers (3a, 4a, 5a) exhibit two
pyridine environments, 3a exhibits two methylplatinum environ-
ments (2JHPt ) 61.2-73.2 Hz), the platinacyclopentane complex
4a exhibits six methylene multiplets, and integrations are
consistent within isomers and between isomers for mixtures of
cis- and trans-isomers (1a, 1b; 2a, 2b). Infrared spectra of the
isolated complexes 1, 2, and 3a-5a exhibit ν(CtC) in the range
2075-2145 cm-1, similar to the range exhibited by other
isolated alkynylplatinum complexes described here (7, 9, 15-
17) (2039-2145 cm-1).
3H, PdMe), 1.53-1.26 (m, 6H, PMe, COSY indicates two
environments), 1.17-0.86 (m, 6H, PMe, COSY indicates two
environments), 0.14 (s, 9H, SiMe3. 31P NMR (acetone-d6, -50 °C)
(121.4 MHz): δ 8.2 (d, 3JP-P ) 25.2 Hz), -16.5 (d, 3JP-P ) 25.5
Hz). The complex decomposed slowly at -50 °C to give a dark
suspension with complex NMR spectra.
Pd(O2CPh)(OTf)(CtCSiMe3)(NCN) (19). Phenyl[(trimethyl-
silyl)ethynyl]iodonium triflate (10.0 mg, 0.022 mmol) was added
to a stirred solution of Pd(O2CPh)(NCN) (9.2 mg, 0.022 mmol) in
acetone-d6 (1 mL) at -50 °C under argon. The solution was kept
at -80 °C for 1 week. 1H NMR (acetone-d6, -50 °C) (300 MHz):
The phosphine complex PtMe2(dmpe) reacted rapidly and
cleanly with the iodonium reagents, followed by sodium iodide,
to give ethane (detected by NMR) and the complexes PtI(Ct
CR2)(dmpe) [R2 ) SiMe3 (7), Ph (9)] in 82% and 74% isolated
yield, characterized by microanalysis, infrared spectroscopy, and
3
δ 7.85 (d, J ) 7.5 Hz, 2H, H2,6), 7.76-7.69 (m, 1H, H4-NCN),
3
3
7.55 (t, J ) 7.5 Hz, 1H, H4), 7.38 (d, J ) 7.5 Hz, 2H, H3,5-
NCN), 7.32 (d, 3J ) 7.5 Hz, 2H, H3,5), 5.25 (d, 2J ) 14.5 Hz, 2H,
NCH2), 4.81 (d, J ) 14.5 Hz, 2H, NCH2), 3.46 (s, 3H, NMe),
2
3.43 (s, 3H, NMe), 3.30 (s, 3H, NMe), 3.23 (s, 3H, NMe), 0.48 (s,
9H, SiMe3).
1
both H and 31P NMR. On examining these reactions at -50
°C, 1H and 31P NMR spectra revealed the formation of
intermediates cis-[PtIMe2(CtCR2)(dmpe)] (6a, 8a). Spectra of
the Pt(IV) complexes show four PMe environments and two
PtMe environments, consistent with a cis-configuration, and as
for the nitrogen donor complexes, complexes 6a and 8a exhibit
PtMe resonances in 1H NMR spectra downfield from the Pt(II)
reagent, in these cases by ∼0.8 ppm. The single 31P resonance
for PtMe2(dmpe), at 26.8 ppm, becomes two complex reso-
nances for the Pt(IV) complexes, upfield, at 1.35 and -2.81
ppm (6a) and 1.47 and -2.08 ppm (8a), exhibiting 1JPtP coupling
(1160 and 1753 Hz for 6a, 1210 and 1594 Hz for 8a). The
isolated Pt(II) complexes PtI(CtCR2)(dmpe) (7, 9) exhibit
X-ray Data Collection, Structure Determination, and Refine-
ment for Pt(O2CArF)I(CtCSiMe3)(NCN) (16). A crystal of 16
was obtained at 0 °C from a solution of the complex in dichlo-
romethane/diethyl ether. A full sphere of CCD area-detector
diffractometer data was measured (Bruker AXS instrument, 2θmax
) 75°, ω-scans, monochromatic Mo KR radiation, λ ) 0.71073 Å;
T ca. 153 K), yielding 27 502 total reflections, merging to 14 219
unique (Rint 0.037) after empirical/multiscan absorption correction
(proprietary software), 12 056 with F > 4σ(F) considered “ob-
served” and used in the full-matrix least squares refinement on F2,
refining anisotropic displacement parameter forms for the non-
hydrogen atoms, (x, y, z Uiso)H being constrained. Final residuals
on |F| at convergence were R ) 0.034, Rw [weights: (σ2(F2) +
1.2F2)-1] ) 0.073. Neutral atom complex scattering factors were
employed within the Xtal 3.7 program system.23 Pertinent results
are given in Figure 1 and Table 1. Crystal data: C25H32F3IN2O2-
PtSi, M ) 799.6, triclinic, space group P1h, a ) 10.0061(6) Å, b )
1
appropriate integration in the H NMR spectra and two PMe
environments, ν(CtC) at 2039 (7) and 2113 cm-1 (9), and 31
P
resonances are in the same region as the PtMe2(dmpe) reagent
(26.3 and 27.8 for 7, 26.7 and 27.8 ppm for 9) and exhibit 1JPtP
coupling (2307 and 2225 Hz for 7, 2273 and 2299 Hz for 9).
The pincer complexes Pt(O2CAr)(NCN) (Ar ) Ph, ArF) also
reacted readily with IPh(CtCR2)(OTf) at ambient temperature,
(23) Hall, S. R.; du Boulay, D. J.; Olthoff-Hazekamp, R.; Eds. The XTAL
3.7 System; University of Western Australia, 2001.

4000 Organometallics, Vol. 25, No. 16, 2006
Table 1. Selected Bond Distances (Å) and Angles (deg) for Pt(O2CArF)I(CtCSiMe3)(NCN) (16)
Canty et al.
Bond Distances
Pt-C(01, 1)
Pt-N(21, 61)
Pt-O(11)
Pt-I
1.951(3), 1.966(3)
2.136(3), 2.125(3)
2.090(2)
C(01)-C(02)
C(02)-Si(2)
C(10)-O(11)
C(10)-O(12)
1.205(4)
1.828(3)
1.275(4)
1.232(4)
2.7469(3)
Bond Angles
C(01)-Pt-C(1)
85.4(1)
I-Pt-O(11)
84.86(7)
172.7(3)
117.5(3), 117.4(3)
106.0(2)
106.5(2)
C(01)-Pt-N(21, 61)
C(1)-Pt-N(21, 61)
N(21)-Pt-N(61)
O(11)-Pt-C(01, 1)
I-Pt-C(01, 1)
93.5(1), 86.3(1)
81.4(1), 81.1(1)
162.50(11)
175.7(1), 98.9(1)
90.83(9), 176.09(8)
97.92(8), 99.58(8)
Pt-C(01)-C(02)
Pt-C(1)-C(2, 6)
Pt-N(21)-C(2′)
Pt-N(61)-C(6′)
Pt-O(11)-C(10)
132.8(2)
I-Pt-N(21, 61)
Scheme 1
and in view of the results reported below for palladium
chemistry, the intermediate triflate species (10-13) were
characterized by 1H NMR spectra but not isolated (Scheme 1).
The iodo complexes (14-17) were obtained in 78-93% yield
and characterized by microanalysis (CHN) and infrared spectra
(ν(CtC) 2078-2143 cm-1); complex 16 was crystallized for
carboxylate and triflate groups in the coordination sphere of
10-13 and the Pd(IV) complex 19 (see below) could not be
determined. NMR data for 14, 15, and 17 indicate that the
orientations of carboxylate and iodo groups in these complexes
are identical to those determined for 16 (Figure 1); for example,
the CH2 and NMe2 resonances for the pincer ligand are almost
identical for 14-17 (within 0.04 ppm), but the alternative
configuration (iodo cis to the pincer) would place the iodo group
much closer to the CH2 group of the pincer and more distant
from one methyl group of the NMe2 groups.
1
a structural analysis (see below). H NMR spectra of 10-17
are consistent with the configuration found for the crystal, e.g.,
two N-methyl environments (both exhibiting 3JPtH coupling 24-
42.3 Hz), indicating the presence of two inequivalent groups in
relation to the Pt(NCN) coordination plane and large 2J coupling
(14.8-15.1 Hz) for the geminal CH2 groups (3JPtH 30.4-39 Hz).
For those complexes where the H4 resonance (12, 16) and H3,5
resonance (10, 12, 14, 15, 17) are separated from other
resonances and readily assigned, they are shifted downfield by
0.47 (H4) and 0.22-0.45 ppm (H3,5). The orientation of the
Reactivity Studies for Palladium(II) Substrates. Initial low-
1
temperature H NMR studies indicated that detection of Pd-
(IV) species was feasible but difficult, so that detailed studies
were confined to IPh(CtCSiMe3)(OTf) as reagent because of
the presence of the simple trimethylsilyl NMR singlet. Reaction
1
with PdMe2(bpy) at -50 °C led to very complex H NMR

Alkynylpalladium(IV) and -Platinum(IV) Species
Organometallics, Vol. 25, No. 16, 2006 4001
Scheme 2
Structural Study of Pt(O2CArF)I(CtCSiMe3)(NCN) (16).
In the solid state 16 has distorted octahedral geometry for
platinum (Figure 1, Table 1), based on a meridionally coordi-
nated pincer group, an iodo ligand trans to the pincer carbon
donor [176.09(8)°], alkynyl and 4-trifluoromethylbenzoate
groups oriented mutually trans [175.7(1)°], and a cis-PtC2
moiety [85.4(1)°]. One molecule of 16 devoid of crystallographic
symmetry comprises the asymmetric unit. The C(01)-C(02)
distance and Pt-C(01)-C(02) angle, 1.205(4) Å and 172.7-
(3)°, are similar to those reported for square-planar Pt(II) pincer
complexes, 1.195(10) Å and 170.6(7)° in Pt(CtCR)(NCN) [R
) C6H2(CH2NMe2)-2,6, I-4]28 and 1.200(4) Å and 174.5(2)°
in the diimine pincer complex Pt(CtCSiMe3){C6H3(CHNR)2-
2,6} (R ) C6H3(Pri)2-2,6).8c The pincer ligand is nonplanar,
with quasi-2 symmetry about the Pt-C(1) bond, the pendant
C-N arrays twisting out of plane to either side of the central
aromatic ring. The aroate plane lies quasi-normal to the C(01),
O(11), N(21,61) coordination plane [C2O2/CON2 interplanar
dihedral, 89.1(1)°].
spectra that could not be interpreted; slow decomposition occurs
at this temperature to give a black suspension, and similar results
were found for Pd(CH2)4(bpy).
However, reaction with the phosphine complex PdMe2(dmpe)
proceeded cleanly at -50 °C, to give spectra readily interpret-
able as showing the presence of PdIMe2(CtCSiMe3)(dmpe)
(18) with the same configuration as 6a (Scheme 2). In a manner
similar to the Pt(IV) analogue 6a, the PdMe resonance is shifted
downfield by ∼0.4 and ∼1 ppm, forming two multiplet
resonances in 1:1 ratio, four PMe environments (multiplets) are
observed, and the single 31P resonance for PdMe2(dmpe) is
shifted upfield to form resonances at 8.2 and -16.5 ppm,
exhibiting 3JPP 25.3 Hz. The average upfield shift on formation
of the Pd(IV) complex (18) from PdMe2(dmpe), 26.0 ppm, is
almost identical to that for formation of the Pt(IV) analogue
(6a) from PtMe2(dmpe), 27.5 ppm, and also very similar to that
reported for the mono-phosphine complex [PdIVMe3(bpy)(PMe2-
Ph)][OTf] compared with [PdIIMe(bpy)(PMe2Ph)][OTf], 21.8
ppm [the Pd(IV) cation resonance occurs at -11.3 ppm].24
For the pincer system, Pd(O2CPh)(NCN) was found to react
slowly with IPh(CtCSiMe3)(OTf) at -50 °C, and to avoid
concurrent decomposition, reaction was completed at -80 °C
over 1 week. 1H NMR spectra showed the formation of
iodobenzene and, by comparison with changes observed on
formation of the Pt(IV) complexes, resonances consistent with
the presence of Pd(O2CPh)(OTf)(CtCSiMe3)(NCN) (19), i.e.,
all environments assigned and exhibiting expected integration,
Discussion
The readily accessible alkynyliodine(III) reagents provide a
facile route to new classes of alkynylplatinum(IV) complex for
nitrogen and phosphorus donor ancillary ligands, with potential
for development of a more extensive chemistry including further
studies of reductive elimination, illustrated by 6a f 7 and 8a
f 9 in Scheme 1, related to the proposed roles of alkynylplati-
num(IV) species in organic synthesis and catalysis.4
The high reactivity of alkynyliodine(III) reagents at low
temperatures has allowed the first spectroscopic detection of
alkynylpalladium(IV) complexes, including unstable species
containing a bidentate phosphine donor (18) and a pincer ligand
(19) shown in Scheme 2. Organopalladium(IV) species with a
single phosphine donor have been reported,24,26 and in a classic
study Gillie and Stille obtained kinetic data suggesting the
presence of an undetected cis-diphosphine intermediate “PdIMe3-
(PPh2Me)2” in the reaction of cis-PdMe2(PPh2Me)2 with
iodomethane.27a Complex 18 represents the first example of
spectroscopic detection of the “PdC3P2X” donor set frequently
proposed as possible intermediates in stoichiometric27 and
catalytic reactions,2c,3d-g including for proposed alkynylpalla-
dium(IV) intermediates,2d noting that the successful synthetic
route to this donor set reported here is different from these
proposals.
2
geminal CH2 resonances with J 14.5 Hz, and resonances for
the NCN protons H4 and H3,5 that are shifted downfield by
0.79 and 0.59 ppm, respectively. However, four NMe resonances
were observed in the ratio 1:1:1:1, although COSY spectra
indicated that these resonances belong to the same species;
warming the solution to detect assumed fluxional behavior was
not possible owing to decomposition, which resulted in a black
suspension and complex spectra. As noted for platinum, NMR
spectra do not allow confident prediction of the configuration
for the six donor atoms at palladium, although the structural
analysis for the Pt(IV) complex 16 and low-temperature NMR
studies showing a cis-PdR2 configuration for the diorganopal-
ladium(IV) complexes PdX2Me2(L2) (L2 ) bis(p-tolylimino)-
Supporting Information Available: Atomic parameters, bond
distances and angles, and crystallographic details for 16, a cif file
for the structure determination, and projections of the structure of
16. This material is available free of charge via the Internet at
http://pubs.acs.org.
acenaphthene, bis(phenylimino)camphane)25a and PdI2Me(Tol-
OM0601495
25b
4)(bpy)
indicate that a “cis-Pd(mer-NCN)(CtCSiMe3)”
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fragment is expected (Scheme 2). Addition of sodium iodide
to 19 at -50 °C resulted in extremely complex NMR spectra
and a brown suspension indicating general decomposition.
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