Nucleophilic attack of amides onto coordinated ethylene in platinum complexes supported by a chelating pyridyl-pyrrolide ligand: Azaplatinacyclobutane and vinylamine complexes

Article abstract of DOI:10.1021/om900569b

The platinum ethylene complexes (PyPyr)Pt(C₂H₄)Cl (1) and (PyPyr)Pt(C₂H₄)OTf (4) (PyPyr = 3,5-diphenyl-2-(2- pyridyl)pyrrolide) were treated with 1 equiv of LiN(SiMe₃) ₂, LiNⁱPr₂, and LiNH(o-xylyl) to produce the platinum complexes (PyPyr)PtH[η²-CH₂=CHN(SiMe ₃)₂] (5), (PyPyr)Pt[k²C, N-(CH ₂CH₂NⁱPr₂)] (6), and (PyPyr)Pt{k²C, N-[CH₂CH₂NH(o-xylyl)]} (7), respectively. X-ray crystallography reveals that 7 adopts a square-planar geometry at the platinum center and the azaplatinacyclobutane ring displays a puckering of the β-carbon out of planarity by 0.270 A. Thermolysis of 5 and 7 at 60 °C for 16 h releases the vinylamines (CH₂=CH) N(SiMe₃)₂ and (CH₂=CH)NH(o-xylyl), respectively. Heating 5 and 7 under 1 atm of H₂ at 60 °C releases the ethylamines EtN(SiMe₃)₂ and EtNH(o-xylyl), respectively. Addition of PⁱPr₃ to 7 produces (PyPyr)Pt(PⁱPr₃)[CH₂CH₂NH(o-xylyl)] (8) in 95% yield, while additions of 1 equiv of a Lewis base (L) to 1 result in displacement of ethylene to give (PyPyr)Pt(L)Cl (L = NEt₃ (9), NH₂Ph (10), PⁱPr₃ (11)). The amido complex (PyPyr)Pt(PⁱPr₃)[NH(o-xylyl)] (12) results from treament of 11 with LiNH(o-xylyl), and 12 does not undergo ethylene insertion into the Pt-N bond under 1 atm Of C₂H₄ at 120 °C over 3 days. Addition of 1 equiv of LiNH(o-xylyl) to (PyPyr)Pt(SMe₂)Cl (2) produces the μ-amido-bridged dimer [(PyPyr)Pt(uμ-NH(o-xylyl))]₂ (13), and treatment of 13 with 2 equiv of ⁱPr₃P produces 12. These reactivity studies are consistent with a mechanism for the formation of 5-7 involving nucleophilic attack of an amide onto coordinated olefin.

Full text of DOI:10.1021/om900569b

184 Organometallics 2010, 29, 184–192
DOI: 10.1021/om900569b
Nucleophilic Attack of Amides onto Coordinated Ethylene in Platinum
Complexes Supported by a Chelating Pyridyl-Pyrrolide Ligand:
Azaplatinacyclobutane and Vinylamine Complexes
Jennifer L. McBee and T. Don Tilley*
Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences
Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
Received July 1, 2009
The platinum ethylene complexes (PyPyr)Pt(C2H4)Cl (1) and (PyPyr)Pt(C2H4)OTf (4) (PyPyr =
3,5-diphenyl-2-(2-pyridyl)pyrrolide) were treated with 1 equiv of LiN(SiMe3)2, LiNiPr2, and LiNH-
(o-xylyl) to produce the platinum complexes (PyPyr)PtH[η2-CH2dCHN(SiMe3)2] (5),
(PyPyr)Pt[κ2C,N-(CH2CH2NiPr2)] (6), and (PyPyr)Pt{κ2C,N-[CH2CH2NH(o-xylyl)]} (7), respec-
tively. X-ray crystallography reveals that 7 adopts a square-planar geometry at the platinum center
and the azaplatinacyclobutane ring displays a puckering of the β-carbon out of planarity by
˚
0.270 A. Thermolysis of 5 and 7 at 60 ꢀC for 16 h releases the vinylamines (CH2dCH)N(SiMe3)2
and (CH2dCH)NH(o-xylyl), respectively. Heating 5 and 7 under 1 atm of H2 at 60 ꢀC releases the
ethylamines EtN(SiMe3)2 and EtNH(o-xylyl), respectively. Addition of PiPr3 to 7 produces
(PyPyr)Pt(PiPr3)[CH2CH2NH(o-xylyl)] (8) in 95% yield, while additions of 1 equiv of a Lewis base
(L) to 1 result in displacement of ethylene to give (PyPyr)Pt(L)Cl (L = NEt3 (9), NH2Ph (10), PiPr3
(11)). The amido complex (PyPyr)Pt(PiPr3)[NH(o-xylyl)] (12) results from treament of 11 with
LiNH(o-xylyl), and 12 does not undergo ethylene insertion into the Pt-N bond under 1 atm of C2H4
at 120 ꢀC over 3 days. Addition of 1 equiv of LiNH(o-xylyl) to (PyPyr)Pt(SMe2)Cl (2) produces the
μ-amido-bridged dimer [(PyPyr)Pt(μ-NH(o-xylyl))]2 (13), and treatment of 13 with 2 equiv of iPr3P
produces 12. These reactivity studies are consistent with a mechanism for the formation of 5-7
involving nucleophilic attack of an amide onto coordinated olefin.
Introduction
investigations into hydroamination reactions catalyzed by
late-transition-metal complexes;4,7-16 however, an under-
standing of the possible role of azametallacyclobutanes in
these hydroamination mechanisms has not been firmly
established.
In principle, azametallacyclobutanes can form via two
different mechanistic pathways that are commonly proposed
for late-transition-metal-catalyzed hydroaminations, which
are generalized by the two cycles of Scheme 1.17 One me-
chanism involves nucleophilic attack of an amine onto a
coordinated olefin, to generate an aminoalkyl intermediate,
which could then convert to an azametallacyclobutane
(given an available empty coordination site). This reaction
could occur with transfer of a proton to the metal or to
another base in the reaction mixture. Indeed, azaplatina-
cyclobutanes have been obtained via cationic aminoalkyl
platinum complexes. For example, the aminoalkyl platinum
A number of azametallacyclobutanes have been reported
over the past few decades, and recently they have been
postulated as intermediates in catalytic hydroaminations of
olefins by late-transition-metal catalysts.1-4 There is great
interest in catalytic transformations that lead to amine
products, since the latter have numerous commercial appli-
cations as pharmaceuticals and other fine chemicals,
detergents, and personal care products.5,6 The high
value associated with many amine products has prompted
*To whom correspondence should be addressed. E-mail: tdtilley@
berkeley.edu.
(1) Bender, C. F.; Widenhoefer, R. A. J. Am. Chem. Soc. 2005, 127,
1070–1071.
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Soc. 1988, 110, 6738–6744.
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(4) Utsunomiya, M.; Kuwano, R.; Kawatsura, M.; Hartwig, J. F.
J. Am. Chem. Soc. 2003, 125, 5608–5609.
(5) Lawrence, S. A. Amines: Synthesis, Properties, and Applications;
Cambridge University Press: Cambridge, U.K., 2004.
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(7) Utsunomiya, M.; Hartwig, J. F. J. Am. Chem. Soc. 2004, 126,
2702–2703.
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127, 12640–12646.
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(12) Fadini, L.; Togni, A. Chem. Commun. 2003, 30–31.
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Soc. 2006, 128, 1446–1447.
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r
2009 American Chemical Society
pubs.acs.org/Organometallics
Published on Web 12/10/2009

Article
Organometallics, Vol. 29, No. 1, 2010 185
Scheme 1
Chart 1
initial investigations of azaplatinacyclobutanes obtained via
reactions of (PyPyr)Pt(η2-C2H4)X (PyPyr = 3,5-diphenyl-
2-(2-pyridyl)pyrrolide; X= Cl, OTf) with lithium amides.
Reactivity studies are most consistent with a mechanism
involving direct nucleophilic attack of the amide onto the
platinum-bound olefin.
Results and Discussion
Synthesis of (PyPyr)Pt(olefin)X (X = Cl, OTf) and
(PyPyr)Pt(η3-allyl) Complexes. The syntheses of the plati-
num complexes (PyPyr)Pt(C2H4)Cl (1) and (PyPyr)Pt-
(SMe2)Cl (2) (Chart 1) have been previously described.20
Addition of (PyPyr)Li (either generated in situ or produced
as an isolated solid) to a THF solution of 0.5 equiv of
[(C2H4)PtCl2]2 produced 1 as a yellow powder in 80%
yield. Similarly for complex 2, treatment of 0.5 equiv of
[(SMe2)PtCl2]2 in THF with (PyPyr)Li gave (PyPyr)Pt-
(SMe2)Cl (2) as a yellow solid in 92% yield.
complex [(tmeda)Pt(CH2CH2NHMe2)Cl][ClO4], generated
by the addition of NHMe2 to [(tmeda)Pt(CH2CH2)Cl]-
[ClO4], is converted to the cationic azaplatinacyclobutane
{(tmeda)Pt[κ2C,N-(CH2CH2NMe2)]}[ClO4] upon treatment
with aqueous KOH.18 A second pathway to an azaplatina-
cyclobutane involves insertion of an alkene into a metal-
nitrogen bond (Scheme 1). An example of this reactivity is
provided by the iridium complex Ir(PEt3)3(NHPh)(H)Cl,
which reacts with norbornene to give the azairidacylobutane
insertion product Ir(PEt3)2[κ2C,N-(C7H10NHPh)](H)Cl.2
Also, the platinum amido complex trans-PtCl2(PPh3)[NH-
(CH2Ph)(CH2CPh2CH2CHdCH2)] converts to an azaplati-
nacyclobutane at 40 ꢀC,1 and {κ3-[2,6-(Ph2PCH2)2C6H3]}-
Pt[NH(C6H4Me-p)] reacts with 1 equiv of acrylonitrile in
benzene-d6 to generate the anilidoalkyl complex {κ3-[2,6-
(Ph2PCH2)2C6H3]}Pt[CH(CN)CH2NH(C6H4Me-p)].3 Un-
fortunately, it has not been established whether these reac-
tions proceed via olefin insertion into the Pt-N bond or by
an initial ligand exchange to give an olefin coordination
complex that then undergoes nucleophilic attack. However,
the rhodium complex (PEt3)3Rh[NH(p-tolyl)] transfers its
amido group to alkenes, to produce imines by migratory
insertion of olefin into the rhodium-amide bond to initially
produce an aminoalkyl intermediate.19 In a catalytic hydro-
amination cycle, an azametallacyclobutane intermediate
could possess a reactive metal-carbon bond (due to ring
strain), which might readily undergo transformations
(e.g., via protonation) to give the amine product.
A platinum allyl complex supported by PyPyr was also
synthesized. Addition of in situ generated (PyPyr)Li to
0.5 equiv of [(η3-CH2CMeCH2)PtCl]2 in toluene produced
(PyPyr)Pt(η3-CH2CMeCH2) (3) as a yellow-orange powder
1
in 70% yield (eq 1). The H NMR spectrum of 3 possesses
four different resonances for the platinum allyl methylene
protons at 1.98, 2.12, 2.76, and 2.83 ppm, as expected for the
structure given in eq 1. The 13C NMR spectrum has two
resonances for the allyl methylene carbons at 44.5 and 37.9
ppm. A 2D 1H, 13C{1H} HMQC spectrum reveals a correla-
1
tion between resonances in the H NMR spectrum at 2.12
and 2.83 ppm and a resonance in the 13C NMR spectrum at
44.5 ppm. Similarly, a correlation with the resonances in the
1H NMR spectrum at 1.98 and 2.76 ppm is found with a
resonance at 37.9 ppm in the 13C NMR spectrum. A 2D
NOESY NMR spectrum further reveals that the methylene
unit with the two 1H NMR resonances at 1.98 and 2.76 ppm
is cis to the pyrrolide donor, while the methylene unit with
resonances at 2.12 and 2.83 ppm is cis to the pyridyl donor.
For investigations of the formation of azametallacyclobu-
tane complexes, and their structural and chemical properties,
neutral platinum complexes of the type (LX0)Pt(olefin)X
(LX0 = an anionic, chelating ligand) appear to be good
starting points. In a manner analogous to that shown in
Scheme 1, reaction of such complexes with an amide reagent
could lead to an azaplatinacyclobutane by nucleophilic
attack of the amide onto the bound olefin, followed by salt
elimination. Alternatively, an initial ligand exchange could
give an olefin amido complex, which might undergo migra-
tory insertion to give the same product. This report describes
The platinum ethylene triflate complex (PyPyr)Pt-
(C2H4)OTf (4; OTf = O3SCF3) was also prepared. A salt
metathesis reaction involving 1 equiv of AgOTf and 1 equiv
of 1 in methylene chloride produced 4 as a yellow-orange
1
powder in 80% yield (eq 2). The H NMR spectrum of 4
has two resonances for the ethylene protons at 4.31 and 3.65
ppm. A 2D NOESY NMR spectrum of 4 revealed that the
ethylene ligand is cis to the pyridyl group, as in complex 1.
(18) Lorusso, G.; Barone, C. R.; Di Masi, N. G.; Pacifico, C.;
Maresca, L.; Natile, G. Eur. J. Inorg. Chem. 2007, 2144–2150.
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(20) McBee, J. L.; Tilley, T. D. Organometallics 2009, 28, 3947–3952.

186 Organometallics, Vol. 29, No. 1, 2010
McBee and Tilley
The 19F NMR spectrum of 4 possesses a resonance at
-76.22 ppm for the triflate ligand coordinated to the plati-
num center, and the 13C NMR spectrum of 4 displays a
resonance at 74.3 ppm for the ethylene ligand.
been isolated.34-36 For example, the diiminate complex
[{(o-Me2-p-tBu-C6H2)NC(Me)}2CH]Pt(H)(CH2CHtBu) poss-
1
esses a H NMR resonance for the hydride ligand at -21.5
ppm (JPtH = 1185 Hz), which is comparable to the value
associated with 5 (-20.68 ppm).36
Reactivity of LiNR2 toward (PyPyr)Pt(C2H4)X (X = Cl,
OTf) and (PyPyr)Pt(η3-allyl) Complexes. Addition of 1 equiv
of LiN(SiMe3)2 to 1 in THF gave the platinum vinylamine
hydride complex (PyPyr)PtH[CH2dCHN(SiMe3)2] (5) as a
In a similar manner, a solution of 1 in THF was treated
with 1 equiv of LiNiPr2 to produce the azaplatinacyclobu-
tane complex (PyPyr)Pt[κ2C,N-(CH2CH2NiPr2)] (6) as a
yellow powder in 92% yield (eq 4). The 1H NMR spectrum
of 6 does not contain an upfield resonance associated with a
platinum hydride but exhibits two resonances at 1.11 and
4.16 ppm, each integrating to two protons. These resonances
are consistent with those reported for the azaplatinacyclo-
butane complex {(tmeda)Pt[κ2C,N-(CH2CH2NMe2)]}-
1
yellow-brown powder in 85% yield (eq 3). The H NMR
=
spectrum of5 hasan upfield resonanceat-20.68ppm(JPtH
1404 Hz) associated with the platinum hydride. Furthermore,
three resonances for the vinyl group are observed at 5.63, 3.68,
and 2.67 ppm (each with broad Pt satellites), and 2D NOESY
NMR spectroscopy revealed that the vinylamine ligand is cis
to the pyridyl group. A 1H, 29Si{1H} HMBC NMR spectrum
revealed a 29Si{1H} NMR resonance at 8.5 ppm for the SiMe3
groups, and the 13C NMR spectrum of 5 contains resonances
for the olefinic carbons at 105.1 (CHN) and 39.5 ppm (CH2).
Complex 5 may result from β-hydrogen elimination from an
azaplatinacyclobutane (following dissociation of the amino
group to generate an open coordination site) and is of interest
in that few platinum olefin hydride complexes have
been isolated, due to the ease with which they undergo
migratory insertion.21 Note that some of the known platinum
olefin hydride complexes may be better described as β-agostic
alkyl complexes.22-25 Many of the platinum olefin hydride
complexes are stabilized by attachment of the olefin to an
ancillary ligand,26,27 are cationic,22,23,28-31 or adopt a pseudo-
six-coordinate Pt(II) environment.32,33 Only one type of
neutral, four-coordinate platinum olefin hydride complex
1
[ClO4], which possesses H NMR resonances at 1.49 and
4.46 ppm for the CH2 groups in the ring.18 A 2D NOESY
NMR spectrum of 6 revealed that the amino group of the
ring is cis to the pyrrolide ring. The 13C NMR spectrum of 6
possesses two resonances for the methylene carbons at 60.4
and -28.7 ppm, with the latter resonance associated with the
carbon bound to platinum. This is also consistent with
{(tmeda)Pt[κ2C,N-(CH2CH2NMe2)]}[ClO4], which pos-
sesses two 13C NMR resonances at 67.4 and -29.2 ppm.
Currently it is not entirely clear why these reactions lead to
different types of products (5 vs 6), but it is possible that
steric pressure provided by the bulky -N(SiMe3)2 group
promotes β-H elimination.
supported by
a chelating nitrogen-based ligand has
(21) Chatt, J.; Coffey, R. S.; Gough, A.; Thompson, D. T. J. Chem.
Soc. A 1968, 190–194.
(22) Shiotsuki, M.; White, P. S.; Brookhart, M.; Templeton,
J. L. J. Am. Chem. Soc. 2007, 129, 4058–4067.
(23) Johnson, J. A.; Sames, D. J. Am. Chem. Soc. 2000, 122, 6321–
6322.
(24) Carr, N.; Mole, L.; Orpen, A. G.; Spencer, J. L. J. Chem. Soc.,
Dalton Trans. 1992, 2653–2662.
(25) Spencer, J. L.; Mhinzi, G. S. J. Chem. Soc., Dalton Trans. 1995,
3819–3824.
(26) Fekl, U.; Goldberg, K. I. J. Am. Chem. Soc. 2002, 124, 6804–
6805.
(27) Kloek, S. M.; Goldberg, K. I. J. Am. Chem. Soc. 2007, 129, 3460–
3461.
(28) Mole, L.; Spencer, J. L.; Carr, N.; Orpen, A. G. Organometallics
Addition of 1 equiv of LiNH(o-xylyl) to a THF solution
of 1 gave (PyPyr)Pt{κ2C,N-[CH2CH2NH(o-xylyl)]} (7) as a
yellow powder in 82% yield (eq 4). As with 6, the 1H NMR
spectrum of 7 does not have an upfield resonance for a
hydride ligand; rather, four proton resonances at 5.43,
3.90, 3.25, and 1.48 ppm are observed for the two methy-
lene groups of the azaplatinacyclobutane ring. The pre-
sence of four distinct resonances is attributed to the
unsymmetrical substitution of the nitrogen atom in
the chelate ring. The 13C NMR spectrum possesses reso-
nances for the methylene carbons at 67.9 and -23.1 ppm,
with the latter resonance associated with the carbon bound
to the platinum. A 2D NOESY NMR spectrum of 7
revealed that the platinum-bound methylene group is cis
to the pyridyl ring.
1991, 10, 49–52.
(29) Kostelansky, C. N.; MacDonald, M. G.; White, P. S.; Templeton,
J. L. Organometallics 2006, 25, 2993–2998.
(30) Reinartz, S.;Baik, M.-H.;White, P.S.;Brookhart,M.;Templeton,
J. L. Inorg. Chem. 2001, 40, 4726–4732.
(31) Holtcamp, M. W.; Henling, L. M.; Day, M. W.; Labinger, J. A.;
Bercaw, J. E. Inorg. Chim. Acta 1998, 270, 467–478.
(32) De Felice, V.; Ferrara, M. L.; Panunzi, A.; Ruffo, F. J. Organo-
met. Chem. 1992, 439, C49–C51.
(33) Albano, V. G.; Castellari, C.; Ferrara, M. L.; Panunzi, A.; Ruffo,
F. J. Organomet. Chem. 1994, 469, 237–244.
(34) West, N. M.; White, P. S.; Templeton, J. L. Organometallics
2008, 27, 5252–5262.
(35) West, N. M.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc.
2007, 129, 12372–12373.
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Article
Organometallics, Vol. 29, No. 1, 2010 187
Heating a solution of 5 in C6D6 resulted in no conversion
to the azaplatinacyclobutane; instead, PyPyrH and
(CH2dCH)N(SiMe3)2 were produced in g95% yield after
16 h at 60 ꢀC (by 1H NMR spectroscopy and GCMS).37 This
thermolytic conversion was unaffected by the addition of
1 equiv of aniline. However, heating a benzene solution of
5 in the presence of 1 equiv of HSiEt3 resulted in formation of
(CH2dCH)N(SiMe3)2 and the platinum(IV) complex
(PyPyr)Pt(H)2(SiEt3)20 in g95% yield after 16 h at 60 ꢀC.
Furthermore, thermolysis of 5 under 1 atm of H2 in C6D6
produced 1 equiv of EtN(SiMe3)2 after 16 h at 60 ꢀC (by 1H
NMR spectroscopy and GCMS).38
Heating a solution of 7 in C6D6 gave no observable
conversion to the platinum vinylamine hydride; instead,
PyPyrH and (CH2dCH)NH(o-xylyl) were produced in
1
g95% yield after 16 h at 80 ꢀC (by H NMR spectroscopy
Figure 1. ORTEP diagram of the molecular structure of 7.
Hydrogen atoms and the pentane molecule are omitted for clarity.
and GCMS). The formation of (CH2dCH)NH(o-xylyl)
suggests that β-elimination from 7 occurs. The addition of
1 equiv of aniline to the reaction mixture did not lead to an
isolable platinum complex, and after 16 h at 60 ꢀC, PyPyrH
and (CH2dCH)NH(o-xylyl) were observed (g95% yield by
1H NMR spectroscopy and GCMS).39 As with 5, addition of
1 equiv of HSiEt3 to 7 in C6H6, followed by heating to 60 ꢀC
for 16 h, gave (CH2dCH)NH(o-xylyl) and (PyPyr)Pt-
(H)2(SiEt3) in g95% yield. Under 1 atm of H2 in C6H6, the
thermolysis of 7 gave a mixture of (CH2dCH)NH(o-xylyl)
and EtNH(o-xylyl) in a 1:1 ratio and 1 equiv of PyPyrH after
16 h at 60 ꢀC. Treatment of 10 mol % of 7 with aniline and
1 atm of C2H4 in benzene-d6 led to no hydroamination
products after 3 days at 80 ꢀC and only (CH2dCH)NH-
(o-xylyl) was observed (10% yield by 1H NMR spectroscopy
and GCMS).
˚
Bond lengths (A) and angles (deg): Pt1-N1 = 2.102(8), Pt1-N2 =
1.989(8), Pt1-N3 = 2.079(8), Pt1-C8 = 2.055(9), C8-C9 =
1.51(1), N3-C9 = 1.53(1); —N1-Pt1-N2 = 77.9(3), —N1-
Pt1-C8 = 176.6(4), —N1-Pt1-N3 = 109.9(3), —N2-Pt1-
N3 = 171.4(3), —N2-Pt1-C8 = 102.4(4), —N3-Pt1-C8 =
69.6(4), —Pt1-N3-C9 = 93.0(6), —N3-C9-C8 = 101.1(8),
—Pt1-C8-C9 = 94.7(6).
X-ray-quality crystals of 7 were obtained by vapor diffu-
sion of pentane into a THF solution of 7. The solid-state
structure contains one molecule of 7 and one molecule of
pentane in the asymmetric unit (Figure 1). The plati-
num-nitrogen distances associated with the PyPyr ligand,
˚
2.102(8) and 1.989(8) A, and the N1-Pt1-N2 bond angle of
Addition of 1 equiv of PiPr3 to a benzene solution of 7 gave
(PyPyr)Pt(PiPr3)[CH2CH2NH(o-xylyl)] (8) as a yellow pow-
1
der in 95% yield (eq 5). The H NMR spectrum for 8 has
77.9(3)ꢀ are consistent with related values for (PyPyr)Pt-
˚
(SMe2)Cl (Pt-N = 2.045(3), 2.000(3) A and N1-Pt-N2 =
79.4(1)ꢀ).20 The C-C bond distance of 1.51(1) A in the
˚
azaplatinacyclobutane ring is consistent with a single bond.
Bond angles in the azaplatinacyclobutane ring range from
69.6(4)ꢀ (N-Pt-C) to 101.1(8)ꢀ (N-C-C), and a distortion
from planarity may be described by a displacement of the
resonances at 3.09 and 1.60 ppm for the methylene groups,
with the latter resonance associated with the methylene
group bound to platinum. The 13C NMR spectrum contains
resonances at 52.0 and 0.7 ppm, with the latter resonance
corresponding to the carbon bound to platinum. A 2D
NOESY NMR spectrum confirms that the PiPr3 ligand is
cis to the pyridyl group. Interestingly, a benzene-d6 solution
of 8 did not undergo loss of amine or β-elimination to
generate a platinum hydride complex after 4 days in ben-
˚
β-carbon, C9, by 0.270 A from the least-squares plane
defined by the Pt; N, and C8 atoms. The phenyl substituent
on the pyrrolide ligand and the o-xylyl substituent of the amido
nitrogen atom appear to be oriented in order to facilitate a
π-stacking interaction between these two moieties, resulting in
˚
1
inter-ring C-C distances of 3.5-3.9 A.
zene-d6 at 25 ꢀC (by H NMR spectroscopy). For compar-
ison, the complex {(tmeda)Pt[CH2CH(CH3)NHEt2]Cl}-
Addition of 1 equiv of LiN(SiMe3)2 to a benzene-d6
solution of (PyPyr)Pt(η3-CH2CMeCH2) (3) gave no change
at 25 ꢀC over 1 h, and heating the solution to 80 ꢀC for 16 h
1
[ClO4] possesses a H NMR resonance for the platinum-
bound methylene group at 1.59 ppm and 13C NMR
resonances for the carbon atoms of the PtCH2CH moiety at
62.6 and 1.0 ppm (the latter resonance corresponds to the
carbon bound directly to platinum).18 Thermolysis of 8 at
80 ꢀC for 4 h gave (CH2dCH)NH(o-xylyl), PyPyrH,
PiPr3, and (PyPyr)Pt(PiPr3)(H)20 (in a 1.16:1:1:0.16 ratio by
1H NMR spectroscopy), confirming that β-elimination from
8 occurs. The platinum hydride complex (PyPyr)Pt-
(PiPr3)(H) has previously been synthesized by addition of 1
equiv of PiPr3 to a benzene solution of (PyPyr)Pt(H)2-
(SiEt3).20 For comparison, addition of 1 equiv of PiPr3 to a
1
also resulted in no reaction (by H NMR spectroscopy).
Similarly, treating 3 with 1 equiv of LiNH(o-xylyl) in
benzene-d6 gave no reaction at 25 ꢀC over 1 h or upon
heating the reaction mixture to 80 ꢀC for 16 h (by 1H
NMR spectroscopy).
Complexes 5-7 can also be synthesized by employing the
triflate (PyPyr)Pt(C2H4)OTf (4) as a precursor. For example,
addition of 1 equiv of LiN(SiMe3)2 to a THF solution of 4
quantitatively yielded 5 (by 1H NMR spectroscopy, in
C6D6). Likewise, addition of 1 equiv of LiNiPr2 to a THF
solution of 4 quantitatively generated 6, and reaction of
LiNH(o-xylyl) with 4 in THF quantitatively produced 7 (by
1H NMR spectroscopy, in C6D6).
(37) Ahlbrecht, H.; Duber, E.-O. Synthesis 1983, 1, 56–57.
(38) Bestmann, H. J.; Wolfel, G.; Mederer, K. Synthesis 1987, 9, 848–
850.
(39) McMaster, P. D.; Byrnes, E. W.; Feldman, H. S.; Takman, B. H.;
Tenthorey, P. A. J. Med. Chem. 1979, 22, 1177–1182.
Chemical Reactivity of 5 and 7. It was of interest to
investigate simple chemical transformations of 5 and 7, to
assess their possible participation in catalytic processes.

188 Organometallics, Vol. 29, No. 1, 2010
McBee and Tilley
benzene-d6 solution of 5 quantitatively generated (PyPyr)-
Pt(PiPr3)(H) (by 1H and 31P NMR spectroscopy).
Addition of Neutral Lewis Bases to (PyPyr)Pt(C2H4)Cl. It
was of interest to determine whether or not weaker nucleo-
philes, such as an amine, might attack the ethylene ligand of
1. Addition of 3 equiv of NEt3 to a benzene solution of 1 gave
Figure 2. ORTEP diagram of the molecular structure of 11.
Hydrogen atoms and the THF molecule are omitted for
clarity. Bond lengths (A) and angles (deg): Pt1-N2 = 2.048(3),
Pt1-N1 = 2.089(3), Pt1-P1 = 2.2824(9), Pt1-Cl1 = 2.306(1);
N2-Pt1-N1 = 78.0(1), N2-Pt1-P1 = 106.26(9), N1-Pt1-
P1 = 168.44(9), N2-Pt1-Cl1 = 167.85(9), N1-Pt1-Cl1 =
89.83(9), and P1-Pt1-Cl1 = 85.61(3).
1
no change at 25 ꢀC over 1 h (by H NMR spectroscopy).
˚
When the reaction mixture was heated to 60 ꢀC for 16 h,
(PyPyr)Pt(NEt3)Cl (9) was generated and this complex was
isolated as a yellow-orange powder in 80% yield (eq 6). A 2D
NOESY NMR spectrum of 9 revealed that the NEt3 ligand is
cis to the pyrrolide group, which is consistent with the
geometry at the platinum center for 2. For comparison,
note that the cationic platinum complex [(phen)Pt(C2H4)Cl]-
(ClO4) (phen = 1,10-phenanthroline) undergoes nucleophi-
lic attack at the bound ethylene ligand upon exposure to
NEt3. This reaction, involving the addition of 3 equiv of
NEt3 to a methylene chloride solution of [(phen)Pt(C2H4)-
Cl](ClO4), generated the aminoalkyl platinum complex
[(phen)Pt(C2H4NEt3)Cl]ClO4 in 90% yield after 3 h at
25 ꢀC.40
coordination to the platinum center. A 2D NOESY NMR
spectrum of 11 revealed that the PiPr3 ligand is cis to the
pyrrolide group. The X-ray crystal structure of 11 confirms
the geometry determined from NMR spectroscopy
(Figure 2). Complex 11 adopts a square-planar geometry
with a small N1-Pt1-N2 bite angle of 78.0(1)ꢀ and Pt-N
˚
bond distances of 2.048(3) and 2.089(3) A that are consistent
with those of other (PyPyr)Pt complexes.20,41,42 When the
very poor Lewis base pentafluoropyridine was added to 1 in
C6D6, no reaction was observed by 1H NMR spectroscopy,
after heating the reaction mixture to 60 ꢀC for 16 h. It is
worth noting that the substitution reactions leading to 9-11
are accompanied by a change in configuration for the com-
plex, such that chloride moves to a position trans to the
pyrrole group.
Addition of LiNR2 to (PyPyr)Pt(L)Cl Complexes (2, 9-11;
L = SMe2, NEt3, NH2Ph, iPr3P). It was of interest to obtain
platinum amido complexes of the type (PyPyr)PtNRR0(L),
to evaluate their ability to undergo olefin insertion to give
products such as 5-7. With this in mind, 1 equiv of LiNH-
(o-xylyl) was added to the amine complex 9 in THF at 25 ꢀC,
Addition of 1 equiv of PhNH2 to a benzene solution of 1
resulted in no change at 25 ꢀC over 1 h (by 1H NMR
spectroscopy), but heating the reaction mixture to 75 ꢀC
for 16 h gave (PyPyr)Pt(NH2Ph)Cl (10) as a yellow solid in
1
and this gave a mixture of products (by H NMR spectro-
scopy). Similar results were observed for the addition of
1 equiv of LiN(SiMe3)2 to a THF solution of 9, which also
produced a mixture of compounds over 16 h at 25 ꢀC.
Additions of lithium amides to 10 also gave product mix-
tures. For example, treatment of a benzene solution of 10
with 1 equiv of LiN(SiMe3)2 over 16 h at 25 ꢀC led to multiple
compounds (by 1H NMR spectroscopy).
Addition of 1 equiv of LiNH(o-xylyl) to a THF solution of
the phosphine complex 11 at 25 ꢀC gave (PyPyr)Pt(PiPr3)-
[NH(o-xylyl)] (12) in 83% yield (eq 7). The 1H NMR
spectrum of 12 contains a broad singlet at 4.85 ppm with
platinum satellites for the N-H proton of the NH(o-xylyl)
ligand. The 31P NMR spectrum of 12 contains a resonance
at 27.80 ppm (JPtP = 2426 Hz), indicating that the pho-
sphine ligand remains coordinated to the platinum
center. A 2D NOESY NMR spectrum of 12 confirms the
1
88% yield (eq 6). The H NMR spectrum of 10 contains a
resonance at 5.59 ppm exhibiting a 2JPtH coupling constant
of 40.0 Hz for the NH protons of the aniline group, which
confirms coordination of the amine to the platinum center. A
2D NOESY NMR spectrum of 10 revealed that the NH2Ph
ligand is cis to the pyrrolide group. In a similar manner, 1 was
treated with 10 equiv of PhNH2 in C6H6 under 1 atm of C2H4
and only 10 (no hydroamination) was observed after 2 days
at 80 ꢀC. Interestingly, addition of 1 equiv of aniline to a
solution of the allyl complex 3 in benzene-d6 gave neither
ligand displacement nor olefin attack after heating at
100 ꢀC for 4 days, and 3 remained unchanged (by 1H
NMR spectroscopy).
Addition of 1 equiv of PiPr3 to 1 at 25 ꢀC gave (PyPyr)Pt-
(PiPr3)Cl (11) as a yellow-brown solid in 93% yield (eq 6).
The 31P NMR spectrum of 11 possesses a resonance at
16.01 ppm with JPtP = 3718 Hz, indicative of phosphine
(41) Karshtedt, D.; McBee, J. L.; Bell, A. T.; Tilley, T. D. Organo-
metallics 2006, 25, 1801–1811.
(40) Barone, C. R.; Benedetti, M.; Vecchio, V. M.; Fanizzi, F. P.;
Maresca, L.; Natile, G. Dalton Trans. 2008, 5313–5322.
(42) Luedtke, A. T.; Goldberg, K. I. Inorg. Chem. 2007, 46, 8496–
8498.

Article
Organometallics, Vol. 29, No. 1, 2010 189
i
geometry shown in eq 7, with the Pr3P ligand cis to the
pyridyl moiety.
Scheme 2
Addition of 1 atm of C2H4 to a benzene-d6 solution of 12 in
a J. Young tube did not result in reaction over 15 min at
25 ꢀC, and heating this reaction mixture to 120 ꢀC for 3 days
did not give an observable olefin insertion (no reaction with
12 was detected by 1H and 31P NMR spectroscopy). In
principle, this lack of reactivity could originate from the
inability of ethylene to coordinate to the platinum center. To
evaluate the lability of the PiPr3 ligand in complex 12, a
benzene solution of the complex was treated with PMe3
(10 equiv) at 25 ꢀC. This resulted in rapid formation
(e5 min) of an intractable mixture of Pt complexes and
1 equiv of free PiPr3 (by 1H and 31P NMR spectroscopy).
Treatment of a THF solution of 2 with 1 equiv of LiNH-
(o-xylyl) at 25 ꢀC gave [(PyPyr)Pt{μ-NH[o-xylyl)]}2 (13) as a
yellow-brown solid in 73% yield (eq 8). The 1H NMR
spectrum of 13 contains a broad singlet at 3.34 ppm with
platinum satellites for the N-H protons of the NH(o-xylyl)
ligand. A 2D NOESY NMR spectrum of 13 exhibits a
correlation of the NH(o-xylyl) group with both the pyridyl
and pyrrolide rings of the ligand, indicating that the NH-
(o-xylyl) moiety is cis to both. This can be explained by the
proposed dimeric structure shown in eq 8. Similarly, addition
of 1 equiv of LiN(SiMe3)2 to a benzene solution of 2 gave
multiple compounds, as observed by 1H NMR spectroscopy.
Heating the reaction mixture to 75 ꢀC for 4 h did not lead to
convergence of the products to a single compound.
t
[(tBu2bpy)Pt(μ-NHSO2C6H4 Bu)]2[B(C6F5)4]2 was observed
to be inert toward norbornene under similar conditions.43
Concluding Remarks
The mechanism of the formation of azaplatinacyclobutanes
from reaction of (PyPyr)Pt(C2H4)X with lithium amides is
proposed to proceed via nucleophilic attack of the amide onto a
coordinated ethylene ligand, on the basis of reactivity studies in
this system (Scheme 2, bottom pathway). This step is consistent
with proposed mechanisms for hydroamination that involve
nucleophilic attack of a neutral amine onto a coordinated
olefin. However, note that the latter transformation would
require a coordinated olefin that is more electrophilic than the
ones described here. The rapid formation of the vinylamine
hydride complex 5 is relevant to the proposed mechanisms for
palladium-catalyzed oxidative amination of alkenes.44,45 These
catalytic reactions have been described as proceeding by initial
olefin coordination to the palladium center followed by nu-
cleophilic attack of an amine onto the coordinated olefin to
give a palladium aminoalkyl intermediate. Deprotonation
(either by added base or excess amine) followed by reductive
elimination releases the vinylamine and produces a palladium
hydride complex. To complete the catalytic cycle, this hydride
is then oxidized to the species that binds olefin. Thus, further
explorations of β-eliminations of the type that gives rise to 5
could aid in the development of oxidative amination reactions.
Experimental Section
General Procedures. All experiments were conducted under
nitrogen using standard Schlenk techniques or in a Vacuum
Atmospheres drybox. Nondeuterated solvents were distilled
under N2 from appropriate drying agents and stored in PTFE-
valved flasks. Deuterated solvents (Cambridge Isotopes) were
vacuum-transferred from appropriate drying agents. All amines
and AgOTf were purchased from Aldrich and dried over
appropriate drying agents. Ethylene was obtained from Praxair
and was used as received. [(C2H4)PtCl2]2 and PiPr3 were
purchased from Strem and used without further purification.
The compounds (PyPyr)Pt(C2H4)Cl (1),20 (PyPyr)Pt(SMe2)-
Cl (2),20 (PyPyr)Pt(H)2SiEt3,20 (PyPyr)Pt(PiPr3)H,20 PyPyrH,46
The reactivity of 13 was briefly examined. Addition of
2 equiv of PiPr3 to a THF solution of 13, followed by stirring
for 2 h, produced 12 in moderate yield (53% after re-
crystallization). In contrast, addition of 1 atm of C2H4 to a
benzene solution of 13 at 25 ꢀC did not result in reaction,
even after heating to 80 ꢀC for 4 days (by 1H NMR spectro-
scopy). In addition, no reaction was observed between 13
and 2 equiv of norbornene in benzene over 3 days at 120 ꢀC.
For comparison, the μ-amido-bridged platinum complex
(43) McBee, J. L.; Bell, A. T.; Tilley, T. D. J. Am. Chem. Soc. 2008,
130, 16562–16571.
(44) Kotov, V.; Scarborough, C. C.; Stahl, S. S. Inorg. Chem. 2007,
46, 1910–1923.
(45) Timokhin, V. I.; Stahl, S. S. J. Am. Chem. Soc. 2005, 127, 17888–
17893.
(46) Klappa, J. J.; Rich, A. E.; McNeill, K. Org. Lett. 2002, 4, 435–
437.
(47) Mann, B. E.; Shaw, B. L.; Shaw, G. J. Chem. Soc. A 1971, 3536–
3544.

190 Organometallics, Vol. 29, No. 1, 2010
McBee and Tilley
[(η3-CH2CMeCH2)PtCl]2,47 LiN(SiMe3)2,48 LiNH(o-xylyl),49
structural assignment is somewhat tentative. The low value for
carbon may result from conversion of triflate to a volatile
fluorocarbon during the combustion process.
50
and LiNiPr2 were synthesized according to literature proce-
dures. Silanes were purchased from Gelest or Aldrich and were
used without further purification.
(PyPyr)PtH[CH2dCHN(SiMe3)2] (5). To a 5 mL solution of
(PyPyr)Pt(C2H4)Cl (0.111 g, 0.200 mmol) in THF was added
LiN(SiMe3)2 (0.0334 g, 0.200 mmol). The reaction mixture was
stirred for 1 h, and then the volatile compounds were removed in
vacuo. The resulting brown solid was dissolved in 5 mL of C6H6,
the solution was passed through Celite, and the volatile materi-
als were removed under reduced pressure. The resulting solid
was dissolved in 1 mL of THF, and pentane was allowed to
vapor diffuse into the solution. A yellow-brown solid was then
isolated in 85% yield (0.133 g, 0.175 mmol). 1H NMR (C6D6):
δ 8.00 (d, JHH = 8.0 Hz, 2H, ArH), 7.54 (d, JHH = 7.5 Hz, 2H,
ArH), 7.43 (d, JHH = 8.5 Hz, 1H, ArH), 7.34 (t, JHH = 8.0 Hz,
2H, ArH), 7.26 (ov m, 4H, ArH, PyH), 6.95 (d, JHH = 6.0 Hz,
1H, PyH), 6.73 (s, 1H, PyrH), 6.63 (vt, JHH = 9.0 Hz, 1H, PyH),
6.11 (vt, JHH = 7.5 Hz, 1H, PyH), 5.63 (dd, JHH = 7.5, 16.5 Hz,
br Pt satellites, 1H, CHN), 3.68 (dd, JHH = 3.0, 16.5 Hz, br
Pt satellites, 1H, CH2), 2.67 (dd, JHH = 3.0, 16.5 Hz, br Pt
satellites, 1H, CH2), 0.15 (s, JSiH = 60.0 Hz, 18H, SiCH3),
-20.68 (s, JPtH = 1404 Hz, 1H, PtH). 13C{1H} NMR: δ 157.8
(Py), 146.7 (Py), 142.5 (Py), 138.7 (Py), 138.6 (Pyr), 137.5 (Pyr),
136.3 (Pyr), 131.4 (Pyr), 129.8 (Ar), 129.7 (Ar), 128.5 (Ar), 127.0
(Ar), 125.9 (Ar), 123.8 (Ar), 118.3 (Py), 117.7 (Py), 113.5 (Pyr),
105.1 (CHN), 39.5 (CH2), 1.62(CH3). 1H, 29Si{1H} HMBC
NMR: δ 8.53. Anal. Calcd for C29H37N3Pt: C, 51.31; H, 5.49;
N, 6.19. Found: C, 51.02; H, 5.15; N, 5.91.
Analytical Methods. 1H, 29Si{1H}, 31P{1H}, and 13C{1H}
NMR spectra were recorded using Bruker AVB 400, AV-500,
and DRX 500 spectrometers equipped with a 5 mm BB probe.
Spectra were recorded at room temperature and referenced to
the residual protonated solvent for 1H or to internal tetra-
methylsilane for 29Si. 13C{1H} NMR spectra were calibrated
internally with the resonance for the solvent relative to tetra-
methylsilane. 31P{1H} NMR spectra were referenced relative to
85% H3PO4 external standard (δ 0). Coupling constants in the
1
1H NMR spectrum (JPH) were determined by 31P-filtered H
NMR spectroscopy and 1H{31P} NMR spectroscopy. Elemen-
tal analyses were performed by the College of Chemistry Micro-
analytical Laboratory at the University of California, Berkeley.
Identities and yields of organic products were confirmed by 1H
NMR spectroscopy and by GCMS relative to an internal
standard, using an Agilent Technologies 6890N GC system with
an HP-5MS column.
(PyPyr)Pt(η3-CH2CMeCH2) (3). To a 5 mL solution of
(PyPyr)H (0.269 g, 0.910 mmol) in toluene was added LiN-
(SiMe3)2 (0.148 g, 0.886 mmol). The reaction mixture was then
stirred for 30 min, and a 5 mL toluene solution of [(η3-
CH2CMeCH2)PtCl]2 (0.127 g, 0.443 mmol) was then added.
The reaction mixture was stirred for 1 h, and then it was filtered
through Celite. The solvent was removed in vacuo, and the
resulting solid was washed with 5 mL of hexanes to give a
(PyPyr)Pt[K2C,N-(CH2CH2NiPr2)] (6). To a 5 mL solution of
(PyPyr)Pt(C2H4)Cl (0.200 g, 0.360 mmol) in THF was added
LiNiPr2 (0.039 g, 0.364 mmol). The reaction mixture was stirred
for 1 h, and then the volatile material was removed in vacuo. The
resulting yellow-brown solid was dissolved in 5 mL of C6H6, and
the resulting solution was passed through Celite. The volatile
material was removed in vacuo. The isolated solid was dissolved
in 1 mL of THF, and pentane was allowed to vapor diffuse into
the solution. The yellow solid was isolated in 92% yield (0.205 g,
1
yellow-orange powder in 70% yield (0.338 g, 0.620 mmol). H
NMR (C6D6): δ 8.15 (d, JHH = 5.0 Hz, 1H, PyH), 7.83 (d,
JHH = 5.0 Hz, 2H, ArH), 7.59 (d, JHH = 5.0 Hz, 2H, ArH), 7.39
(d, JHH = 8.0 Hz, 1H, ArH), 7.24 (ov m, 4H, ArH, PyH), 6.74 (s,
1H, PyrH), 6.54 (vt, JHH = 8.0 Hz, 1H, PyH), 5.89 (d, JHH
=
5.0 Hz, 1H, PyH), 2.83 (d, JHH = 3.0 Hz, JPtH = 15.0 Hz, 1H,
CH2), 2.76 (d, JHH = 3.0 Hz, JPtH = 15.0 Hz, 2H, CH2), 2.12
(br s, JPtH = 22.5 Hz, 2H, CH2), 1.98 (d, JHH = 3.0 Hz,
1
J
PtH = 23.0 Hz, 2H, CH2), 1.72 (s, JPtH = 34.5 Hz, 3H, CH3).
0.331 mmol). H NMR (C6D6): δ 7.97 (d, JHH = 6.0 Hz, 1H,
13C{1H} NMR: δ 152.3 (Py), 138.9 (Py), 138.6 (Py), 136.8 (Pyr),
131.6 (Pyr), 129.6 (Ar), 129.4 (Ar), 128.4 (Ar), 128.7 (Ar), 126.2
(Ar), 126.1 (Ar), 123.8 (Pyr), 118.1 (Py), 117.5 (Py), 114.0 (Py),
112.9 (Pyr), 44.5 (CH2), 37.9 (CH2), 22.7 (CMe). Anal. Calcd for
C25H22N2Pt: C, 55.04; H, 4.06; N, 5.13. Found: C, 54.83; H,
4.08; N, 5.02.
PyH), 7.79 (d, JHH = 6.8 Hz, 2H, ArH), 7.63 (d, JHH = 6.8 Hz,
2H, ArH), 7.39 (t, JHH = 6.8 Hz, 1H, ArH), 7.22 (ov m, 5H, ArH,
PyH), 7.05 (t, JHH = 6.8 Hz, 1H, ArH), 6.82 (s, 1H, PyrH), 6.53
(vt, JHH = 6.4 Hz, 1H, PyH), 5.85 (vt, JHH = 6.4 Hz, 1H, PyH),
4.16 (t, JHH = 8.4 Hz, 2H, CH2CH2N), 2.19 (m, 2H, CHCH3),
1.22 (d, JHH = 6.4 Hz, 6H, CH3), 1.11 (t, JHH = 8.0 Hz, 2H,
PtCH2), 0.85 (d, JHH = 6.4 Hz, 6H, CH3). 13C{1H} NMR: δ 159.9
(Py), 148.3, (Py) 147.3 (Py), 140.2 (Pyr), 139.2 (Pyr), 135.5 (Pyr),
135.1 (Pyr), 129.6 (Ar), 129.1 (Ar), 128.2 (Ar), 127.2 (Ar), 125.8
(Ar), 125.5 (Ar), 117.9 (Py), 116.4 (Py), 115.4 (Pyr), 60.4 (CH2N),
57.6 (NCH), 22.0 (CH3), 17.2 (CH3), -28.7 (PtCH2). Anal. Calcd
for C29H33N3Pt: C, 56.30; H, 5.38; N, 6.79. Found: C, 56.62; H,
5.10; N, 6.65.
(PyPyr)Pt(C2H4)OTf (4). To a 5 mL solution of (PyPyr)Pt-
(C2H4)Cl (0.150 g, 0.180 mmol) in methylene chloride was added
AgOTf (0.046 g, 0.180 mmol). The reaction mixture was stirred
for 1 h, and then it was filtered through Celite. The solvent was
removed under reduced pressure, and the resulting solid was
washed with 5 mL of pentane to give a yellow-orange powder
in 80% yield (0.095 g, 0.144 mmol). 1H NMR (CD2Cl2): δ 7.80
(d, JHH = 7.2 Hz, 2H, ArH), 7.50 (d, JHH = 7.2 Hz, 2H, ArH),
7.35 (m, 4H, ArH), 7.10 (ov m with benzene-d6, 3H, ArH, PyH),
6.44 (ov m, 2H, PyH), 6.39 (s, 1H, PyrH), 5.88 (vt, JHH = 6.0 Hz,
1H, PyH), 4.31 (br d, JHH = 14.0 Hz, 2H, C2H4), 3.65 (br d,
(PyPyr)Pt{K2C,N-[CH2CH2NH(o-xylyl)]} (7). To a 5 mL
solution of (PyPyr)Pt(C2H4)Cl (0.100 g, 0.180 mmol) in THF
was added LiNH(o-xylyl) (0.023 g, 0.181 mmol). The reaction
mixture was stirred for 1 h, and then the volatile compounds
were removed in vacuo. The resulting golden solid was dissolved
in 5 mL of C6H6, the solution was passed through Celite, and the
volatile compounds were removed under reduced pressure. The
isolated solid was dissolved in 1 mL of THF, and pentane was
allowed to vapor diffuse into the solution. The yellow solid was
isolated in 82% yield (0.097 g, 0.148 mmol). 1H NMR (C6D6): δ
8.03 (d, JHH = 6.0 Hz, 1H, PyH), 7.62 (d, JHH = 8.0 Hz, 2H,
ArH), 7.44 (d, JHH = 8.0 Hz, 2H, ArH), 7.33 (t, JHH = 8.0 Hz,
2H, ArH), 7.15 (ov benzene-d6, 1H, PyH), 6.91 (d, JHH = 7.5
Hz, 1H, ArH), 6.75 (t, JHH = 7.5 Hz, 3H, ArH), 6.68 (s, 1H,
PyrH), 6.65 (d, JHH = 7.0 Hz, 1H, ArH), 6.56 (ov m, 3H, ArH,
PyH), 6.26 (d, JHH = 7.0 Hz, 1H, ArH), 5.86 (vt, JHH = 5.5 Hz,
1H, PyH), 5.43 (br m, 1H, CH2CH2N), 4.22 (br t, 1H, NH), 3.90
(br m, 1H, CH2CH2N), 3.25 (br m, 1H, PtCH2), 2.09 (s, 3H,
CH3), 1.48 (m, 1H, PtCH2), 1.31 (s, 3H, CH3). 13C{1H}
J
HH = 14.0 Hz, 2H, C2H4). 19F NMR: δ -76.22. 13C{1H} NMR
(C6D6): δ 157.7 (Py), 142.7 (Py), 137.6 (Py), 136.5 (Pyr),
136.3 (Pyr), 131.2 (Pyr), 129.3 (Ar), 129.2 (Ar), 128.6 (Ar),
128.2 (Ar), 128.0 (Ar), 127.7 (Ar), 127.2 (Ar), 126.3 (Ar),
118.6 (Py), 118.5 (Py), 114.7 (Pyr), 74.3 (C2H4). Anal. Calcd
for C24H19N2F3O3PtS: C, 43.18; H, 2.87; N, 4.20. Found: C,
44.42; H, 2.92; N, 4.28. The combustion analysis gave essentially
the same results after recrystallization from THF, despite the
lack of NMR signals due to impurities in this sample. Thus, this
(48) Podraza, K. F.; Bassfield, R. L. J. Org. Chem. 1988, 53, 2643–
2644.
(49) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc.
1988, 110, 8729–8731.
(50) Kopka, I. E.; Fataftah, Z. A.; Rathke, M. W. J. Org. Chem. 1987,
52, 448–450.

Article
Organometallics, Vol. 29, No. 1, 2010 191
NMR: δ 160.0 (Py), 149.1 (Py), 138.9 (Pyr), 137.6 (Pyr), 135.5
(Pyr), 131.5 (Py), 131.4 (Py), 130.7 (Py), 128.9 (Ar), 128.1 (Ar),
127.9 (Ar), 127.8 (Ar), 127.4 (Ar), 127.3 (Ar), 126.5 (Ar), 125.9
(Ar), 125.3 (Ar), 124.8 (Ar), 116.6 (Py), 113.7 (Pyr), 67.9
(CH2N), 20.9 (CH3), 17.1 (CH3), -23.1 (PtCH2). Anal. Calcd
for C31H29N3Pt: C, 58.30; H, 4.58; N, 6.58. Found: C, 58.73; H,
4.73; N, 6.39.
(PyPyr)Pt(PiPr3)Cl (11). To a 5 mL solution of (PyPyr)Pt-
(C2H4)Cl (0.200 g, 0.361 mmol) in benzene was added PiPr3
(0.058 g, 0.363 mmol). The reaction mixture was stirred for 1 h,
and then the solvent was removed in vacuo. The resulting solid
was washed with 5 mL of pentane to give a yellow-brown
powder in 93% yield (0.228 g, 0.332 mmol). 1H NMR (C6D6):
δ 9.36 (br s, 1H, PyH), 7.73 (d, JHH = 7.2 Hz, 2H, ArH), 7.60 (d,
(PyPyr)Pt(PiPr3)[CH2CH2NH(o-xylyl)] (8). To a 2 mL solu-
tion of (PyPyr)Pt{κ2C,N-[CH2CH2NH(o-xylyl)]} (0.025 g, 0.039
mmol) in benzene was added PiPr3 (0.007 g, 0.039 mmol). The
reaction mixture was stirred for 1 h, and then the volatile
material was removed under reduced pressure. The resulting
solid was washed with 5 mL of pentane to give a yellow powder
in 95% yield (0.030 g, 0.037 mmol). 1H NMR (C6D6): δ 8.10 (d,
JHH = 7.2 Hz, 3H, ArH, PyH), 7.63 (d, JHH = 7.6 Hz, 2H,
ArH), 7.52 (d, JHH = 8.0 Hz, 1H, ArH), 7.30-7.20 (ov m, 5H,
ArH, PyH), 7.13 (t, JHH = 7.6 Hz, 1H, ArH), 6.93 (d, JHH = 7.6
Hz, 2H, ArH), 6.80 (ov m, 2H, ArH, PyrH), 6.63 (vt, JHH = 6.0
Hz, 1H, PyH), 6.06 (vt, JHH = 6.0 Hz, 1H, PyH), 3.09 (br dd,
2H, CH2CH2Pt), 2.66 (t, JHH = 6.0 Hz, 1H, NH), 2.10 (s, 6H,
CH3), 1.60 (br dd, 2H, CH2CH2Pt), 0.95 (dd, JPH = 14.0 Hz,
J
HH = 7.2 Hz, 2H, ArH), 7.31 (d, JHH = 8.4 Hz, 2H, ArH), 7.20
(ov m, 3H, ArH), 7.10 (ov m with benzene-d6, 2H, ArH, PyH),
7.00 (t, JHH = 6.8 Hz, 1H, ArH), 6.61 (s, 1H, PyrH), 6.48 (vt,
JHH = 6.8 Hz, 1H, PyH), 6.13 (vt, JHH = 6.8 Hz, 1H, PyH),
2.20 (m, 3H, PCH), 1.07 (dd, JPH = 14.0 Hz, JHH = 7.2 Hz,
18H, PCHCH3). 31P{1H} NMR: δ 16.01 (JPtP = 3718 Hz).
13C{1H} NMR: δ 157.7 (Py), 146.4 (Py), 145.4 (Py), 138.4 (Pyr),
137.9 (Pyr), 137.5 (Py), 135.8 (Pyr), 132.6 (Pyr), 129.6 (Ar), 129.4
(Ar), 128.1 (Ar), 127.5 (Ar), 126.5 (Ar), 126.0 (Ar), 118.4 (Py),
116.8 (Py), 115.3 (Pyr), 25.3 (PCH), 22.0 (CH3). Anal. Calcd for
C30H36N2ClPPt: C, 52.52; H, 5.29; N, 4.08. Found: C, 51.65; H,
4.81; N, 4.04.
(PyPyr)Pt(PiPr3)[NH(o-xylyl)] (12). To a 5 mL solution of
(PyPyr)Pt(PiPr3)Cl (0.100 g, 0.146 mmol) in THF was added
LiNH(o-xylyl) (0.019 g, 0.146 mmol). The reaction mixture was
stirred for 1 h, and then the volatile material was removed under
reduced pressure. The resulting solid was dissolved in 5 mL of
benzene, and the reaction mixture was filtered through Celite.
The volatile material was removed in vacuo, and the resulting
solid was washed with 5 mL of pentane to give a yellow-brown
powder in 83% yield (0.093 g, 0.121 mmol). 1H NMR (C6D6): δ
9.32 (br s, 1H, PyH), 7.72 (d, JHH = 7.5 Hz, 2H, ArH), 7.51 (d,
JHH = 7.0 Hz, 2H, ArH), 7.48 (d, JHH = 7.5 Hz, 1H, ArH),
7.30-7.20 (ov m, 2H, ArH), 6.99 (q, JHH = 7.0 Hz, 2H, ArH),
JHH = 7.2 Hz, 18H, PCHCH3). 31P{1H} NMR: δ 24.74 (JPtP
=
3986 Hz). 13C{1H} NMR: δ 159.2 (Py), 148.8 (Py), 147.3 (Py),
139.0 (Pyr), 138.3, (Pyr) 135.7 (Pyr), 129.7 (Ar), 129.2 (Ar),
128.7 (Ar), 128.5 (Ar), 128.3 (Ar), 128.2 (Ar), 128.1 (Ar), 126.0
(Ar), 125.8 (Ar), 123.9 (Ar), 120.9 (Pyr), 120.6 (Py), 118.8 (Py),
116.5 (Py), 115.9 (Pyr), 52.0 (CH2N), 22.3 (JCP = 10.2 Hz,
PCH), 19.5 (CH3), 18.9 (CH3), 0.7 (PtCH2). Anal. Calcd for
C40H50N3PPt: C, 60.14; H, 6.31; N, 5.26. Found: C, 60.44; H,
6.59; N, 5.55.
(PyPyr)Pt(NEt3)Cl (9). To a 5 mL solution of (PyPyr)Pt-
(C2H4)Cl (0.025 g, 0.045 mmol) in benzene was added 3 equiv of
NEt3 (0.014 g, 0.135 mmol). The reaction mixture was then
stirred and heated to 60 ꢀC for 16 h. The reaction mixture was
cooled, and the volatile material was removed in vacuo. The
resulting solid was washed with 5 mL of pentane to give a
6.89 (ov m, 2H, ArH, PyH), 6.79 (s, 1H, PyrH), 6.70 (t, JHH
=
7.5 Hz, 1H, ArH), 6.55 (br m, 1H, ArH), 6.48 (t, JHH = 7.0 Hz,
1H, ArH), 6.25 (vt, JHH = 6.0 Hz, 1H, PyH), 6.11 (vt, JHH = 6.0
Hz, 1H, PyH), 4.85 (br s with br pt satellites, 1H, NH), 2.16 (m,
3H, PCH), 1.84 (s, 6H, CH3), 1.20 (dd, JPH = 14.0 Hz,
JHH = 7.2 Hz, 18H, PCHCH3). 31P{1H} NMR: δ 27.80 (JPtP
= 2426 Hz). 13C{1H} NMR: δ 160.7 (Py), 147.4 (Py), 146.6 (Py),
144.6 (Pyr), 142.7 (Pyr), 138.4 (Pyr), 137.6 (Py), 131.5 (Pyr),
129.9 (Ar), 129.6 (Ar), 128.5 (Ar), 128.2 (Ar), 127.6 (Ar), 127.0
(Ar), 126.0 (Ar), 125.2 (Ar), 123.9 (Ar), 121.3 (Ar), 120.4 (Ar),
118.6 (Ar), 117.1 (Py), 116.2 (Py), 111.2 (Pyr), 25.4 (PCH), 19.7
(PCHCH3), 17.1 (CCH3). Anal. Calcd for C38H46N3PPt: C,
59.21; H, 6.01; N, 5.45. Found: C, 58.87; H, 6.24; N, 5.59.
{(PyPyr)Pt[μ-NH(o-xylyl)]}2 (13). To a 5 mL solution of
(PyPyr)Pt(SMe2)Cl (0.100 g, 0.170 mmol) in THF was added
LiNH(o-xylyl) (0.022 g, 0.170 mmol). The reaction mixture was
stirred for 1 h, and then the volatile material was removed under
reduced pressure. The resulting solid was dissolved in 5 mL of
benzene, and the mixture was filtered through Celite. The
volatile material was removed in vacuo, and the resulting solid
was washed with 5 mL of pentane to give a yellow-brown
powder. The yellow-brown solid was crystallized by vapor
diffusion of pentane into a benzene solution of 12, which led
1
yellow-orange powder in 80% yield (0.023 g, 0.036 mmol). H
NMR (C6D6): δ 9.45 (d, JHH = 6.8 Hz, 1H, PyH), 8.13 (d,
JHH = 7.0 Hz, 2H, ArH), 7.91 (d, JHH = 6.0 Hz, 1H, ArH),
7.60 (ov m, 2H, ArH), 7.10 (ov m with benzene-d6, 2H, ArH,
PyH), 6.62 (s, 1H, PyrH), 6.48 (vt, JHH = 6.0 Hz, 1H, PyH),
5.95 (vt, JHH = 6.0 Hz, 1H, PyH), 2.16 (q, JHH = 7.0 Hz, 6H,
NCH2), 0.45 (t, JHH = 7.0 Hz, 2H, NCH2CH3). 13C{1H} NMR:
δ 159.2 (Py), 147.6 (Py), 138.2 (Py), 137.5 (Pyr), 136.6 (Pyr),
136.0 (Py), 130.1 (Pyr), 129.9 (Ar), 129.7 (Ar), 129.5 (Ar), 129.1
(Ar), 128.5 (Ar), 126.9 (Ar), 126.3 (Ar), 125.7 (Ar), 116.2 (Py),
114.6 (Pyr), 45.3 (PCH) 10.7 (CH3). Anal. Calcd for
C25H25N3ClPt: C, 50.21; H, 4.21; N, 7.03. Found: C, 49.81; H,
4.23; N, 6.86.
(PyPyr)Pt(NH2Ph)Cl (10). To a 5 mL solution of (PyPyr)Pt-
(C2H4)Cl (0.150 g, 0.271 mmol) in benzene was added PhNH2
(0.025 g, 0.271 mmol). The reaction mixture was placed in a flask
and sealed. The reaction mixture was heated to 75 ꢀC for 16 h,
and then the reaction mixture was cooled and the volatile
material was removed in vacuo. The resulting solid was washed
with 5 mL of pentane to give a yellow powder in 88% yield
(0.148 g, 0.239 mmol). 1H NMR (CD2Cl2): δ 8.96 (d, JHH = 6.6
1
to an isolated yield of 73% (0.096 g, 0.124 mmol). H NMR
(C6D6): δ 8.39 (d, JHH = 7.0 Hz, 2H, PyH), 7.67 (d, JHH = 7.5
Hz, 4H, ArH), 7.62 (d, JHH = 7.0 Hz, 4H, ArH), 7.55 (br s, 6H,
ArH), 7.30-7.20 (ov m, 12H, ArH), 6.94 (d, JHH = 7.0 Hz, 2H,
Hz, 1H, PyH), 7.83 (d, JHH = 6.6 Hz, 2H, ArH), 7.66 (d, JHH
=
6.6 Hz, 2H, ArH), 7.57 (ov, 2H, ArH), 7.45 (t, JHH = 7.8 Hz, 3H,
ArH), 7.39 (t, JHH = 7.2 Hz, 1H, ArH), 7.35 (vt, JHH = 7.2 Hz,
1H, PyH), 7.30 (d, JHH = 8.4 Hz, 1H, ArH), 7.18 (vt,
JHH = 7.2 Hz, 2H, ArH), 7.13 (d, JHH = 7.2 Hz, 1H, PyH),
6.89 (d, JHH = 7.2 Hz, 2H, ArH), 6.79 (vt, JHH = 7.2 Hz, 1H,
PyH), 6.38 (s, 1H, PyrH), 5.59 (br s, JPtH = 40.0 Hz, 2H, NH2).
13C{1H} NMR: δ 158.3 (Py), 148.7 (Py), 144.2 (Pyr), 139.9 (Py),
138.0 (Pyr), 136.5 (Pyr), 136.4 (Py), 136.2 (Ar), 130.7 (Pyr), 129.5
(Ar), 129.2 (Ar), 129.1 (Ar), 129.0 (Ar), 128.5 (Ar), 128.2 (Ar),
127.8 (Ar), 126.8 (Ar), 122.6 (Ar), 117.9 (Ar), 117.3 (Py), 113.6
(Pyr). Anal. Calcd for C27H22N3ClPt: C, 52.39; H, 3.58; N, 6.79.
Found: C, 52.91; H, 3.68; N, 6.74.
PyH), 6.89 (ov m, 4H, ArH), 6.78 (s, 2H, PyrH), 6.70 (t, JHH =
7.5 Hz, 6H, ArH), 6.55 (vt, JHH = 7.0 Hz, 2H, PyH), 6.48 (d,
JHH = 7.0 Hz, 2H, ArH), 5.94 (vt, JHH = 6.0 Hz, 2H, PyH),
3.34 (br s with br pt satellites, 2H, NH), 1.84 (s, 12H, CH3).
13C{1H} NMR: δ 160.2 (Pyr), 148.8 (Py), 148.4 (Py), 144.3 (Pyr),
142.8 (Pyr), 139.1 (Pyr), 135.7 (Py), 132.0 (Py), 131.4 (Pyr), 129.7
(Ar), 129.5 (Ar), 128.6 (Ar), 128.1 (Ar), 127.5 (Ar), 127.2 (Ar),
126.1 (Ar), 125.7 (Ar), 123.9 (Ar), 121.7 (Ar), 117.8 (Py), 113.6
(Pyr), 17.1 (CCH3). Anal. Calcd for C29H25N3Pt: C, 57.04; H,
4.13; N, 6.88. Found: C, 56.78; H, 4.14; N, 6.58.
General Procedure for Monitoring Reactions of 5 and 7.
Reactions occurred in 5 mm Wilmad NMR tubes equipped

192 Organometallics, Vol. 29, No. 1, 2010
McBee and Tilley
with a J. Young Teflon-valve seal, and heating the reaction
solutions was accomplished with a temperature-controlled
oil bath. Samples were prepared in the drybox by dissolving
either 5 or 7 (0.01 mmol) and 1 equiv of amine or silane
in 1 mL of benzene-d6. Gases were condensed into the
NMR tubes on a Schlenk line. Reaction progress was
monitored by 1H NMR spectroscopy by use of an internal
standard (hexamethylbenzene, 0.01 mmol). The identities of
organic compounds, and their yields, were confirmed by
GCMS.
All non-hydrogen atoms were refined anisotropically unless
otherwise stated.
For 7, crystals were grown from vapor diffusion of pentane
into THF at 25 ꢀC.
For 11, crystals were grown from vapor diffusion of pentane
into THF at 25 ꢀC.
Acknowledgment. This work was supported by the
Director, Office of Energy Research, Office of Basic
Energy Sciences, Chemical Sciences Division, of the
U.S. Department of Energy under Contract DE-AC02-
76SF0098. We thank Dr. Rudi Nunlist for NMR spec-
troscopy assistance and Dr. Frederick Hollander and Dr.
Antonio diPasquale for X-ray crystallography assistance.
X-ray Structure Determinations. The X-ray analyses of com-
pounds 7 and 11 were carried out at the UC Berkeley CHEX-
RAY crystallographic facility. Measurements were made
on a Bruker SMART CCD area detector with graphite-
˚
monochromated Mo KR radiation (λ = 0.710 73 A). Data were
integrated by the program SAINT and analyzed for agreement
using XPREP. Empirical absorption corrections were made
using SADABS. Structures were solved by direct methods
and expanded using Fourier techniques. All calculations were
performed using the SHELXTL crystallographic package.
Supporting Information Available:
Tables and CIF files
giving complete experimental details for X-ray crystallography
and structural data for 7 and 10. This material is available free of
charge via the Internet at http://pubs.acs.org.