CO, isocyanide, alkene, and alkyne insertions into platinaoxetane Pt-O bonds

Article abstract of DOI:10.1021/om8005849

Platinaoxetanes Pt(COD)(C₇H₁₀O) (1) and Pt(PEt ₃)₂(C₇H₁₀O) (2) undergo insertion of CO into their Pt-O bonds to afford Pt(COD)(C(O)OC₇H₁₀) (3) and Pt(PEt₃)₂)(C(O)OC₇H₁₀) (4), respectively. Complex 4 is also available from 3 and PEt₃. Platinaoxetanes [Pt(COD)(C₇H₁₀O)Pt(COD)Cl)]⁺ (5) and Pt(COD)(C₇H₁₀OBF₃) (6), with Lewis acids bonded to the platinaoxetane ring oxygen atom, give free norbornene when treated with CO. Treatment of 3 with BF₃ · Et₂O immediately gives 6. Both types of platinaoxetanes are inert to CO₂. Treatment of 1 with tetracyanoediylene (TCNE) yields Pt(COD)-(TCNEOC ₇H₁₀) (7) by alkene insertion into me Pt-O bond, while 1 shows no reactivity with ethylene or isobutylene. Similarly 1 reacts with diethylacetylenedicarboxylate (DEAD) to give a rare alkyne M-O bond insertion product Pt(COD)(DEADOC₇H₁₀) (8) but is inert to diphenylacetylene. Reaction of 1 with isocyanide in a 1:3 molar ratio gives Pt(Bu¹NC)₂(C₇H₁₀OBu^tNC) (9), a result of COD displacement by 2 isocyanides and insertion of another isocyanide into the Pt-O bond. Complex 3 was characterized by single-crystal X-ray crystallography.

Full text of DOI:10.1021/om8005849

4810
Organometallics 2008, 27, 4810–4816
CO, Isocyanide, Alkene, and Alkyne Insertions into Platinaoxetane
Pt-O Bonds
Jianguo Wu and Paul R. Sharp*
Department of Chemistry, UniVersity of Missouri-Columbia, Columbia, Missouri 65211
ReceiVed June 24, 2008
Platinaoxetanes Pt(COD)(C7H10O) (1) and Pt(PEt3)2(C7H10O) (2) undergo insertion of CO into their
Pt-O bonds to afford Pt(COD)(C(O)OC7H10) (3) and Pt(PEt3)2)(C(O)OC7H10) (4), respectively. Complex
4 is also available from 3 and PEt3. Platinaoxetanes [Pt(COD)(C7H10O)Pt(COD)Cl)]+ (5) and
Pt(COD)(C7H10OBF3) (6), with Lewis acids bonded to the platinaoxetane ring oxygen atom, give free
norbornene when treated with CO. Treatment of 3 with BF3 · Et2O immediately gives 6. Both types of
platinaoxetanes are inert to CO2. Treatment of 1 with tetracyanoethylene (TCNE) yields Pt(COD)-
(TCNEOC7H10) (7) by alkene insertion into the Pt-O bond, while 1 shows no reactivity with ethylene
or isobutylene. Similarly 1 reacts with diethylacetylenedicarboxylate (DEAD) to give a rare alkyne M-O
bond insertion product Pt(COD)(DEADOC7H10) (8) but is inert to diphenylacetylene. Reaction of 1 with
isocyanide in a 1:3 molar ratio gives Pt(ButNC)2(C7H10OButNC) (9), a result of COD displacement by
2 isocyanides and insertion of another isocyanide into the Pt-O bond. Complex 3 was characterized by
single-crystal X-ray crystallography.
Scheme 1
Introduction
The insertion of small unsaturated molecules such as CO,
olefins, and alkynes into transition metal-carbon bonds is a
key step in a number of metal-catalyzed reactions and has
received considerable interest for a long time.1,2 Studies of
similar insertions into late transition metal alkoxide linkage are
more limited, although such reactions are also important in
catalytic and stoichiometric reactions.3-5 Both of these types
of insertion reactions are possible with 1-metalla-2-oxacyclobu-
tanes (metallaoxetanes6) as illustrated in Scheme 1. The
involvement of metallaoxetanes in alkene oxidations,7-13 ep-
oxide reactions,14-16 and other reactions17-19 necessitates an
understanding of their reaction chemistry. Metallaoxetanes also
provide the opportunity for a direct comparison of the reactivity
of M-C and M-O bonds with small molecules.
* Corresponding author. E-mail: SharpP@missouri.edu.
(1) Fundamentals of Molecular Catalysis; Kurosawa, H., Yamamoto,
A., Eds.; Elsevier: New York, 2003.
The first metallaoxetanes PtL2(C2(CN)4O) (L ) AsPh3, PPh3)
show no reactivity with CO or CO2 at room temperature.14
Ruthenaoxetane Ru(PMe3)4(OC(Me)(Ph)CH2) undergoes CO
insertion into the metal-carbon bond rather than the metal-
oxygen bond.18 In contrast, iridaoxetane Cp*Ir(PMe3)(CH2-
CMe2O) undergoes CO2 or tert-butyl isocyanide insertion into
the metal-oxygen bond,20 and [(tpa)Rh(CH2CH2O)]+ (tpa )
N,N,N-tri(2-pyridylmethyl)amine) inserts MeCN into the metal-
oxygen bond but only on protonation of the rhodaoxetane
oxygen atom.21,22 (An aza-palladaoxetane or palladaazetidine
does an intramolecular alkene Pd-C bond insertion on treatment
with CuI.23)
(2) Catalysis: An Integrated Approach to Homogeneous, Heterogeneous,
And Industrial Catalysis; Moulijn, J. A., van Leeuwen, P. W. N. M., van
Santen, R. A., Eds.; Elsevier: New York, 1993.
(3) Fulton, J. R.; Holland, A. W.; Fox, D. J.; Bergman, R. G. Acc. Chem.
Res. 2002, 35, 44–56.
(4) Fryzuk, M. D.; Montgomery, C. D. Coord. Chem. ReV. 1989, 95,
1–40.
(5) Bryndza, H. E.; W., T. Chem. ReV 1988, 88, 1163–1188.
(6) We limit the metallaoxetane classification to complexes with sp3 C
centers in the ring.
(7) Day, V. W.; Klemperer, W. G.; Lockledge, S. P.; Main, D. J. J. Am.
Chem. Soc. 1990, 112, 2031–2033.
(8) Flood, T. C.; Iimura, M.; Perotti, J. M.; Rheingold, A. L.; Concolino,
T. E. Chem. Commun. 2000, 1681, 1682.
(9) Szuromi, E.; Shan, H.; Sharp, P. R. J. Am. Chem. Soc. 2003, 124,
10522–10523.
(10) de Bruin, B.; Budzelaar, P. H. M.; Gal, A. W. Angew. Chem., Int.
Ed. 2004, 43, 4142.
(11) Cinellu, M. A.; Minghetti, G.; Cocco, F.; Stoccoro, S.; A.; Zucca;
Manassero, M. Angew. Chem., Int. Ed. 2005, 44, 6892–6895.
(12) Keith, J. A.; Nielsen, R. J.; Oxgaard, J.; Goddard, W. A. J. Am.
Chem. Soc. 2007, 129, 12342–12343.
(16) Calhorda, M. J.; Galvao, A. M.; Unaleroglu, C.; Zlota, A. A.;
Frolow, F.; Milstein, D. Organometallics 1993, 12, 3316–3325.
(17) Hartwig, J. F.; Bergman, R. G.; Andersen, R. A. J. Am. Chem.
Soc. 1990, 112, 3234–3236.
(13) Khusnutdinova, J. R.; Newman, L. L.; Zavalij, P. Y.; Lam, Y. F.;
Vedernikov, A. N. J. Am. Chem. Soc. 2008, 130, 2174–2175.
(14) Schlodder, R.; Ibers, J. A.; Lenarda, M.; Grazianilb, M. J. Am.
Chem. Soc. 1974, 96, 6893–6900.
(15) Lenarda, M.; Pahor, N. B.; Calligaris, M.; Graziani, M.; Randaccio,
L. J. Chem. Soc., Dalton Trans. 1978, 279, 282.
(18) Hartwig, J. F.; Bergman, R. G.; Andersen, R. A. Organometallics
1991, 10, 3344–3362.
(19) Bazan, G. C.; Schrock, R. R.; O’Regan, M. B. Organometallics
1991, 10, 1062–1067.
(20) Klein, D., P.; Hayes, J. C.; Bergman, R. G. J. Am. Chem. Soc.
1988, 110, 3704–3707.
10.1021/om8005849 CCC: $40.75
2008 American Chemical Society
Publication on Web 08/27/2008

Insertions into Platinaoxetane Pt-O Bonds
Organometallics, Vol. 27, No. 18, 2008 4811
Scheme 2
carbon atom, C2, is found at 85.7 ppm with JPt-C ) 44 Hz.
The 195Pt NMR resonance for 3 (-3820 in C6D6) is at a lower
frequency than for 1 (-2891 ppm in C6D6).
Crystals of 3 suitable for an X-ray diffraction study were
obtained from toluene/hexane at -30 °C, and analysis of the
data confirmed the proposed structure. A drawing of 3 is given
in Figure 1. Crystallographic data are summarized in Table 2.
Selected bond distances and bond angles are given in Table 3.
As suggested by the 1H and 13C NMR data, the four olefinic
Pt-C distances, Pt1-C9, Pt1-C10, Pt1-C13, and Pt1-C14,
are nearly identical, indicative of a similar trans-influence for
the two carbon centers, C1 and C8, trans to the COD ligand.
The Pt-C8 distance of 2.005(7) Å for the inserted CO carbon
is slightly shorter than that of Pt-C1 (2.063(8) Å), consistent
with the smaller radius of an sp2-hybridized center. The O1-C8
bond distance of 1.215(9) Å is typical for a carbon-oxygen
double bond. The C1-Pt-C8 angle of 82.1(3)° is much bigger
than the corresponding angle in known platinaoxtanes
(∼70°),9,14,15,24,25 indicating that the distortion of the square-
planar Pt(II) geometry is much reduced. This may be attributed
to the four-membered to five-membered ring expansion resulting
from CO insertion. Similarly, the angles C2-C1-Pt and
C1-C2-O2 (110.3(5)° and 112.9(6)°, respectively) have
opened considerably from the corresponding angles (∼93° and
∼101°) in the platinaoxetanes. Similar angles are also present
in Pt(IV) platinaoxetanes.13
Recently a family of platinaoxetanes has been synthesized
and characterized by our group.9,24,25 While unusual reversible
alkene extrusion involving C-O bond cleavage was discov-
ered,25 we also began to explore insertion chemistry of the
platinaoxetanes. Herein we report that the unsaturated molecules
CO, tert-butyl isocyanide, and activated alkene and alkynes
insert exclusively into the Pt-O bond of the platinaoxetanes.
Results
Carbon monoxide addition to a benzene solution of 1 at room
temperature for 3 h leads to the complete loss of the most
downfield H NMR signal for 1 (broad singlet at 6.62 ppm),
and a new doublet appears at 4.03 ppm. Evaporation of the
solvent affords the white product Pt(COD)(C(O)OC7H10) (3)
in 93% isolated yield (Scheme 2).
Structurally characterized five-membered metallalactones
similar to 3 are relatively rare.26-34 The most closely related is
the platinalactone Pt(PPh3)2(C(O)OCMe2C(CH2)) obtained by
carbonylation of the alkyne complex Pt(PPh3)2(HOCMe2-
CCH).35,36 This complex has a Pt-C(sp2) bond in the ring rather
than a Pt-C(sp3) bond as in 3. Nonetheless, the structures of
the platinalactone rings are quite similar.
1
The infrared absorption for the inserted CO is observed at
1644 cm-1, indicative of the presence of a C-O double bond.
Table 1 gives selected NMR data and atom-numbering schemes.
1H NMR spectra of 3 in C6D6 exhibit resonances for all 10
protons. Unlike precursor 1, which shows only two widely
spaced olefinic COD peaks, four distinct olefinic COD reso-
nances without 195Pt satellites are observed at 5.52, 5.33, 4.97,
and 4.79 ppm for 3. A doublet at 4.03 ppm with JH-H ) 6.3
Hz is assigned to the proton adjacent to the oxygen atom (H2).
A doublet of doublets at 2.80 ppm with JPt-H ) 105 Hz is
assigned to the Pt-bonded CH (H1). A doublet at 2.66 ppm is
assigned to H6, the bridgehead hydrogen atom adjacent to the
Pt-bonded carbon atom. A broad singlet at 2.10 ppm with
weaker coupling to 195Pt (32 Hz) is assigned to H3, the
bridgehead hydrogen atom adjacent to the oxygen-bonded
carbon atom. 13C NMR spectra show the expected 16-carbon
resonances. A resonance at 180.5 ppm is assigned to the inserted
CO. In contrast to precursor 1, the chemical shifts for the four
olefinic COD carbon atoms are very close at 109.0, 108.4, 107.7,
and 106.8 ppm and are flanked by 195Pt satellites with similar
JPt-C (∼50 Hz), indicating similar electron-donating groups
trans to the COD ligand. This and the similarity of the olefinic
COD proton resonances are consistent with CO insertion into
the Pt-O bond of 1. A 13C peak at 60.4 ppm shows a large
13C-195Pt coupling of 853 Hz and is assigned to the Pt-bonded
norbornene carbon atom C1. The oxygen-bonded norbornene
Phosphine-substituted platinaoxetane 2 also reacts with carbon
monoxide (Scheme 2). Addition of CO to a benzene solution
of 2 at room temperature gives the white insertion product
Pt(PEt3)2)(C(O)OC7H10) (4) in 90% isolated yield. Complex 4
is also available from 3 by COD ligand displacement via
addition of 2 molar equiv of PEt3 (Scheme 2). Evidence that
insertion has taken place into the Pt-O bond rather than the
Pt-C bond of 2 is provided by NMR spectroscopy and by the
formation of 4 from 3.
The 31P NMR spectrum of 4 in C6D6 shows two doublets
flanked by 195Pt satellites. The inequivalence of the phosphine
ligands and the small P-P coupling of 9 Hz are consistent with
(26) Gladysz, J. A.; Selover, J. C.; Strouse, C. E. J. Am. Chem. Soc.
1978, 100, 6766.
(27) Bauer, C.; Guggolz, E.; Herrmann, W. A.; Kriechbaum, G.; Ziegler,
M. L. Angew. Chem., Int. Ed. 1982, 21, 212.
(28) Herrmann, W. A.; Kriechbaum, G. W.; Bauer, C.; Koumbouris,
B.; Pfisterer, H.; Guggolz, E.; Ziegler, M. L. J. Organomet. Chem. 1984,
262, 89.
(29) Selover, J. C.; Vaughn, G. D.; Strouse, C. E.; Gladysz, J. A. J. Am.
Chem. Soc. 1986, 108, 1455.
(30) Sellin, M.; Luart, D.; Salaun, J.-Y.; Laurent, P.; Toupet, L.; des
Abbayes, H. Chem. Commun. 1996, 857.
(31) Bruce, M. I.; Meier, A. C.; Skelton, B. W.; White, A. H.; Zaitseva,
N. N. Aust. J. Chem. 2001, 54, 319.
(32) Cabon, P.; Sellin, M.; Salaun, J.-Y.; Patinec, V.; des Abbayes, H.;
Kubicki, M. M. Organometallics 2002, 21, 2196.
(33) Cabon, P.; Rumin, R.; Salaun, J. Y.; Triki, S.; des Abbayes, H.
Organometallics 2005, 24, 1709.
(34) Cabon, P.; Rumin, R.; Salaun, J.-Y.; des Abbayes, H.; Triki, S.
Eur. J. Inorg. Chem. 2006, 1515.
(21) de Bruin, B.; Boerakker, M. J.; De Gelder, R.; Smits, J. M. M.;
Gal, A. W. Angew. Chem., Int. Ed. 1999, 38, 219–222.
(22) de Bruin, B.; Boerakker, M. J.; Verhagen, J. A. W.; de Gelder, R.;
Smits, J. M. M.; Gal, A. W. Chem.-Eur. J. 2000, 6, 298–312.
(23) Ney, J. E.; Wolfe, J. P. J. Am. Chem. Soc. 2006, 128, 15415–15422.
(24) Wu, J.; Sharp, P. R. Organometallics 2008, 27, 1234–1241.
(25) Szuromi, E.; Wu, J.; Sharp, P. R. J. Am. Chem. Soc. 2006, 128,
12088–12089.
(35) Empsall, H. D.; Shaw, B. L.; Stringer, A. J. J. Chem. Soc., Dalton
Trans. 1976, 185, 188.
(36) Norton, M. C.; McDonald, W. S. Acta Crystallogr., Sect. B 1976,
32, 1597–1599.

4812 Organometallics, Vol. 27, No. 18, 2008
Wu and Sharp
Table 1. Selected NMR Data and Atom-Numbering Schemea,b
δ H2
δ H1
δ C2
δ C1
δ Pt
1c
2c
3
4
7
5.99 (JPtH ) 60)
6.92 (JPtH ) 40)
4.03 (JHH ) 6.3)
4.24 (JHH ) 6.9)
4.29 (JHH ) 5.7)
3.63 (JHH ) 6.9)
4.46 (JHH ) 6.9)
0.69 (br s, JPtH ) 66)
98.7
100.1
85.7
84.6
85.7
82.8
89.5
8.8
8.2
-2908
-3883
-3820
-4564
-3895
-3937
-4337
0.77 (m, JPtH ) 40.5)
2.80 (dd, JH-H ) 6.3, 2.1, JPtH ) 105)
2.63 (dd, JH-H ) 8.1, 1.5, JPtH ) 23)
2.08 (dd, JH-H ) 5.7, 2.1, JPtH ) 106)
2.40 (dd, JH-H ) 7.8, 1.8, JPtH ) 117)
3.03 (dd, JH-H ) 6.9, 2.4, JPtH ) 75)
60.4
56.7
50.4
51.2
52.3
8
9
a Shifts in ppm, coupling constants in Hz. b In C6D6. c From ref 24.
phosphine ligands. The 13C NMR spectrum displays a resonance
for the inserted CO as a doublet of doublets at 195.0 ppm (JP-C
) 150 and 7.5 Hz) and a resonance for the Pt-bonded norbornyl
carbon atom (C1) as a doublet of doublets at 56.7 ppm (JP-C
)
77.0 and 5.3 Hz). Three other norbornene carbons (C3, C5, C7)
also exhibit coupling to the 31P nuclei of the phosphine ligands.
The signal for the oxygen-bonded carbon atom (C2) of the
norbornyl unit is found at 84.6 ppm flanked by satellites with
a small 13C-195Pt coupling of 9.8 Hz but with no 31P-13
C
coupling. 1H NMR spectra of 4 in C6D6 show all 10 norbornyl
proton peaks in addition to the resonances for the phosphine
ligands. A doublet at 4.24 ppm with JH-H ) 6.9 Hz is assigned
to H2, and a doublet of doublets with satellites (JPt-H ) 23
Hz) at 2.63 ppm is assigned to H1. Finally, a CdO stretching
absorption is observed at 1642 cm-1 in the infrared spectrum
of 4.
Figure 1. Drawing of the solid-state structure of Pt(COD)-
(C(O)OC7H10) (3).
Table 2. Crystal Data and Structure Refinement Details for 3a
In contrast to 1 and 2, addition of 1 equiv of CO to
platinaoxetane 5 in CD2Cl2 results in (COD)PtCl2 and free
norbornene (NB) (eq 1). Presumably, CO2 and the fragments
“(COD)Pt2+” and “(COD)Pt” are also formed, although the fate
of these fragments is unknown. No CO insertion product is
observed. Excess CO and 5 gives a black precipitate (assumed
to be finely divided Pt metal), free COD, norbornene, and
presumably CO2. Similarly, addition of CO to 6 in C6D6 gives
norbornene with CO2, BF3, and “(COD)Pt” as presumed
additional products (eq 1). To examine the stability of an
insertion product, 3 was treated with BF3 · Et2O (eq 2). Complex
6 was immediately produced (presumably along with CO),
indicating that the CO insertion product of 6 is unstable.
formula
fw
space group
a, Å
b, Å
c, Å
C16H22O2Pt
441.43
C2/c
20.776(2)
13.8500(14)
11.4466(12)
122.2070(10)
V, Å3
Z
2786.9(5)
8
2.104
10.065
0.0375, 0.0800
1.092
dcalc, g/cm3
µ, mm-1
R1b, wR2c
Gof
ꢀ, deg
T
-100 °C
a λ ) 0.71073 Å (Mo). b R1 ) (∑|Fo| - |Fc|)/∑Fo. c wR2 )
[(∑w(|Fo| - |Fc|)2)/∑wFo2 1/2; w ) 4Fo2/(∑Fo2)2.
]
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 3
Pt1-C8
Pt1-C1
O1-C8
O2-C8
O2-C2
2.005(7)
2.063(8)
1.215(9)
1.354(9)
1.450(9)
Pt1-C9
Pt1-C10
Pt1-C13
Pt1-C14
C2-C1
2.262(7)
2.303(7)
2.259(7)
2.275(6)
1.542(10)
C8-Pt1-C1
C8-O2-C2
O1-C8-O2
O1-C8-Pt1
82.1(3)
O2-C8-Pt1
O2-C2-C1
C2-C1-Pt1
O2-C2-C3
117.0(5)
112.9(6)
110.3(5)
109.9(6)
116.8(6)
116.1(6)
126.7(6)
the cis-phosphine geometry at the Pt centers. The upfield doublet
at 5.49 ppm shows JP-Pt ) 1985 Hz, only ca. 130 Hz greater
than the downfield doublet at 18.57 ppm (JP-Pt ) 1856 Hz).
The disappearance of the P atom signal with the large Pt-P
coupling constant trans to the weakly donating oxygen atom in
2 and the small Pt-P coupling constants for both P atoms in 4
suggest that both P atoms are trans to more or less equally
donating carbon atoms in 4 and that the CO has inserted into
the Pt-O bond of 2. The 195Pt NMR spectrum of 4 in C6D6
shows a triplet at -4564 ppm with JP-Pt ) 1959 Hz, further
confirming coupling between the Pt center and two similar
Platinaoxetanes 1 and 5 are stable toward CO2. When a
solution of 1 or 5 is exposed to 1 atm of CO2 at room
temperature for 48 h, no evidence for CO2 insertion or any other
1
reaction is observed by H NMR spectroscopy. Since 1 also

Insertions into Platinaoxetane Pt-O Bonds
Organometallics, Vol. 27, No. 18, 2008 4813
Scheme 3
Scheme 5
Scheme 4
replaced by a new doublet at 3.63 ppm similar to the oxygen-
bonded CH (H2) peaks in insertion products 3, 4, 7, and 8,
indicating that insertion into the Pt-O bond has again occurred.
The COD olefinic protons trans to the norbornene carbon atom
(C1) appear at 5.76 and 5.53 ppm with no satellites. Although
not equivalent, the remaining COD olefinic protons are found
as a single multiplet at 4.62 ppm with satellites (JPt-H ) 46
Hz). The 195Pt NMR resonance of 8 in C6D6 is found at -3937
ppm.
shows no reactivity with ethylene, isobutylene, and norbornene,
we turned our attention to more electrophilic reagents. Treatment
of 1 with 1 equiv of tetracyanoethylene (TCNE) in C6D6 at room
temperature gives insertion product Pt(COD)(TCNEOC7H10) (7)
Treatment of 1 with 3 equiv of tert-butyl isocyanide leads to
the immediate formation of a new, pale brown product and free
COD. After removal of COD, the product is isolated in 89%
yield and characterized as (ButNC)2Pt(C7H10OButNC) (9)
(Scheme 5), the product of isocyanide substitution at the metal
center and isocyanide insertion into the metal-oxygen bond.
The infrared absorption for coordinated ButNC is observed at
2714 cm-1 and for inserted ButNC at 1573 cm-1. The 13C NMR
spectrum exhibits a resonance at 54.9 ppm with JPt-C ) 57.4
Hz for the inserted ButNC and one at 180.8 ppm for the
coordinated ButNC. The oxygen-bonded norbornylene carbon
(C2) is observed at 89.5 ppm. Similar to other insertion products,
the H2 resonance is observed as a doublet at 4.46 ppm and the
H1 resonance as a doublet of doublets at 3.03 ppm with JPt-H
≈ 75 Hz in the 1H NMR spectrum. The 195Pt NMR resonance
of 9 in C6D6 is found at -4337.
1
(Scheme 3). The H NMR spectrum of 7 displays a doublet at
4.29 ppm with JH-H ) 5.7 Hz, which is similar to the H2 peak
in the spectrum of 3 (doublet at 4.03 with JH-H ) 6.3 Hz) and
4 (doublet at 4.24 ppm with JH-H ) 6.9 Hz), suggesting TCNE
insertion into the Pt-O bond. The Pt-bonded CH (H1) appears
as a doublet of doublets with satellites at 2.08 ppm due to
coupling to H3 and H6 and 195Pt (JPt-H ) 106 Hz). Two
doublets at 2.19 and 2.66 ppm are assigned to H3 and H6,
respectively. Four nonoverlapping COD olefinic protons are
observed at 5.52, 5.33, 4.97, and 4.79 ppm with satellites. The
Ct N stretching absorption is observed at 2224 cm-1 in the
infrared spectrum, and resonances at 116.2, 114.7, 113.2, and
112.5 ppm in the 13C NMR spectrum are assigned to CN units.
The Pt-bonded norbornene carbon atom (C1) and oxygen-
bonded norbornene carbon (C2) are found at 50.4 and 85.7 ppm,
respectively. The two ethylene carbon atoms of TCNE are found
at 69.6 ppm (oxygen-bonded, C8) and 26.8 ppm (Pt-bonded,
C9). The resonances (113.1, 112.6, 102.1, 101.2) are assigned
to the four COD olefinic carbon atoms. The 195Pt NMR
resonance for 7 (-3895 ppm in C6D6) is ∼100 ppm to lower
frequency than that for 1 (-2891 ppm in C6D6) and is similar
to that for 3 (-3820 ppm in C6D6).
Reducing the amount of added tert-butyl isocyanide to 2
molar equiv and monitoring the reaction by 1H NMR spectros-
copy in C6D6 shows the formation of free COD and a new
complex. The new complex shows a doublet with satellites at
6.91 ppm with JH-H ) 5.1 Hz and JPt-H ) 49.2 Hz, typical for
the oxygen-bonded carbon proton (H2) of norbornyl platinaox-
etanes. Two equal intensity singlets at 0.86 and 0.64 ppm are
assigned to coordinated ButNC. This and the integration ratio
of the doublet and two singlets of 1:9:9 reasonably identify the
new product as the platinaoxetane (ButNC)2Pt(C7H10O) (10)
(Scheme 5). Attempts to isolate 10 were unsuccessful. Vacuum
removal of the volatiles for the reaction mixture left a white
Complex 7 is not stable in solution. When a solution of 7 in
C6D6 solution is kept overnight at room temperature, a black
precipitate forms and trace amounts of COD and free norbornene
1
are detected by H NMR spectroscopy. The amount of these
decomposition products increases with time.
Although 1 shows no reactivity with an equamolar amount
of PhCt CPh even at 75 °C for 4 h (toluene), there is a reaction
with the activated alkyne diethylacetylenedicarboxylate (DEAD).
Reaction occurs (∼20 h) slowly in CH2Cl2 or C6D6 at room
temperature to give the Pt-O insertion product Pt(COD)-
(DEADOC7H10) (8) (Scheme 4), isolated as a pale yellow solid
in 85% yield. The presence of the DEAD ligand is confirmed
by IR absorption bands at 1707 cm-1 (carboxylate) and 1435
cm-1 (CdC), 13C NMR carbonyl (174.4, 164.1 ppm) and
olefinic (143.7, 141.4 ppm) resonances, and ethyl group
resonances in the 1H and 13C NMR spectra. The H1 resonance
is found as a doublet of doublets with satellites in the 1H NMR
1
residue, which when redissolved in C6D6, gave an H NMR
spectrum that showed the disappearance of the above peaks.
Discussion
Our observation of CO insertion into the Pt-O bonds of 1
and 2 is consistent with known chemistry of related systems.
CO insertion into the Pt-O bond of platinum(II) alkoxides has
been reported, and when both a Pt-O and a Pt-C bond are
present, insertion into the Pt-O bond is exclusively observed.37-41
DFT computational studies on the model complexes Pt-
(Me)(OMe)(PH3)2 and Pt(Me)(OMe)(H2PCH2CH2PH2) show
that for a CO migratory insertion pathway there is both a
thermodynamic and a kinetic preference for reaction at the Pt-O
1
spectrum. The large H-195Pt coupling constant of ∼117 Hz
suggests that the Pt-C1 bond is retained. The oxygen-bonded
CH (H2) resonance at 6.62 ppm for starting complex 1 is

4814 Organometallics, Vol. 27, No. 18, 2008
Wu and Sharp
The reaction of 1 with ButNC follows a somewhat different
course from that of CO. It is likely that the insertion follows a
similar mechanism to that of CO, but evidently the strong
bonding ability of ButNC results first in displacement of COD
and then follows the insertion into the Pt-O bond. This
sequence is evident from the observation of the ButNC-ligated
platinaoxetane 10 (Scheme 5). There is only one other report
of isocyanide insertion into a metallaoxetane.20
Scheme 6
Despite its strained ring, the alkene reaction chemistry of 1
is comparable to that reported for acyclic analogues. Tetrafluo-
roethylene inserts into the Pt-O bond of Pt(dppe)(Me)(OMe)
to give Pt(dppe)(Me)(CF2CF2OMe).39,46 Dimethyl maleate
undergoes syn addition to the Pt-OH bond of cis-Pt(PPh3)2-
(OH)(Me) to afford cis-Pt(PPh3)2(Me)(CH(CO2Me)CH(OH)-
(CO2Me)).47,48 No reactivity is observed with simple alkenes.
Apparently, alkene insertion into Pt-O bonds is limited to those
alkenes bearing strongly electron-withdrawing groups (F, CN,
CO2Me). What can be considered an exception to this was
recently reported for the complex Pt(dpms)(OH)(C2H4) (dpms
) di(2-pyridyl)methanesulfonate).13 Although the coordinated
ethylene does not insert into the Pt-OH bond, cyclooctene and
norbornene displace the ethylene and add to the Pt-OH bond,
giving protonated platinaoxetanes. Similarly, the formation of
platinacycle 5 from the [Pt4(COD)4(O)2Cl2]2+ and norbornene
can be considered an insertion, but the mechanism of this
reaction is not obvious and is currently under investigation.9
The reaction of 1 with diethylacetylenedicarboxylate (DEAD)
appears to be the first example of simple alkyne insertion into
a Pt-O bond. Alkyne insertions into M-O bonds are rare, with
examples for Rh,49 Ir,49,50 and Mn, Re, and Mo.51 Such reactions
could be important in alkyne hydration catalyzed by Pt and other
metals.52 Complex 1 shows no reactivity with diphenylacetylene,
indicating that like in alkene insertion activation of the alkyne
with electron-withdrawing groups is required. Even with DEAD
the reaction rate is much slower than the alkene insertions.
rather than the Pt-C bond.42,43 The stronger C-O bond formed
in the carbonyl-alkoxide product compared to the C-C bond
of the alternative acyl species is a key driving force. These
preferences evidently remain in effect for 1 and 2.
An alternative to migratory insertion, suggested by data for
Ir(I) alkoxo complexes, involves displacement of RO- by CO,
followed by nucleophilic attack of RO- on the coordinated
CO.44,45 While migratory insertion is supported by the above-
mentioned DFT studies and by data for Pt(dppe)(Me)(OMe),40
the ring strain in 1 and 2 could shift the reaction in the direction
of the anion displacement mechanism. While we have no data
to support or refute this possibility for CO insertion, we do find
that the alkyne insertion rate of 2 changes very little from
benzene to methylene chloride. A large increase would be
expected if formation of ionic species was involved in this
insertion, although transient coordination of a trace Lewis acid
to the platinaoxetane oxygen atom could moderate this effect.
The CO reactions of platinaoxetanes 5 and 6 (eq 1) contrast
sharply with those of 1 and 2, indicating that coordination of a
Lewis acid (E ) Pt(COD)Cl+ or BF3) to the platinaoxetane
oxygen atom greatly affects reactivity. Two possible pathways
for norbornene (NB) formation in these reactions are illustrated
in Scheme 6. The first goes through intermediate A by
norbornene extrusion and coordination of CO, probably cata-
lyzed by traces of a Lewis acid. A similar process is involved
in the alkene exchange of 5 and 6, where the norbornene unit
of 5 and 6 is replaced with another alkene.25 Intermediate A
would then go on to products by coupling of the coordinated
CO with the OE group. The second pathway, through platina-
lactone intermediate B, is based on the observed CO insertions
of 1 and 2 to give platinalactones 3 and 4. BF3 addition to 3
should also form B (E ) BF3), ultimately yielding the same
products as the reaction of 6 with CO. The second pathway is
eliminated by the outcome of the reaction of 3 with BF3. This
reaction should produce intermediate B, which would eliminate
CO2, giving the same products as the reaction of 6 with CO.
Instead, CO elimination and formation of 6 are observed.
Complex 6 then slowly reacts with the liberated CO via A.
Conclusions
As with the acyclic counterparts, insertion reactions of the
platinaoxetanes 1 and 2 occur exclusively at the Pt-O bond.
Although we have no mechanistic information on the reactions,
they probably occur by migratory insertion as is thought for
the acyclic complexes. While CO and ButNC insert readily,
alkenes and alkynes insert only if they are activated with
electron-withdrawing groups, indicating that ring strain in the
platinaoxetanes does little to activate the complexes. Coordina-
tion of a Lewis acid to the platinaoxetane ring oxygen atom
dramatically alters reactivity such that C-O bond cleavage
dominates and insertion products are not observed.
Experimental Section
General Procedures. Experiments were performed under a
dinitrogen atmosphere in a Vacuum Atmosphere Corporation
drybox. Solvents were dried by standard techniques and stored under
(37) Bennett, M. A.; Yoshida, T. J. Am. Chem. Soc. 1978, 100, 1750–
1759.
(38) Michelin, R. A.; Napoli, M.; Ros, R. J. Organomet. Chem. 1979,
175, 239–255.
(39) Bryndza, H. E.; Calabrese, J. C.; Wreford, S. S. Organometallics
1984, 3, 1603–1604.
(40) Bryndza, H. E. Organometallics 1985, 4, 1686–1687.
(41) Bryndza, H. E.; Kretchmar, S. A.; Tulip, T. H. J. Chem. Soc., Chem.
Commun. 1985, 977–978.
(42) Macgregor, S. A.; Neave, G. W. Organometallics 2003, 22, 4547–
4556.
(43) Macgregor, S. A.; Neave, G. W. Organometallics 2004, 23, 891–
899.
(44) Randall, S. L.; Thompson, J. S.; Buttrey, L. A.; Ziller, J. W.;
Churchill, M. R.; Atwood, J. D. Organometallics 1991, 10, 683–688.
(45) Randall, S. L.; Miller, C. A.; See, R. F.; Churchill, M. R.; Janik,
T. S.; Lake, C. H.; Atwood, J. D. Organometallics 1994, 13, 5088–5095.
(46) Bryndza, H. E. Organometallics 1985, 4, 406–408.
(47) Bennett, M. A.; Jin, H.; Li, S. H.; Rendina, L. M.; Willis, A. C.
J. Am. Chem. Soc. 1995, 117, 8335–8340.
(48) Bennett, M. A.; Jin, H.; Li, S.; Rendina, L. M.; Willis, A. C. J. Am.
Chem. Soc. 1996, 118, 6528–6528.
(49) Yamamoto, Y.; Sugawara, K.; Han, X.-H. J. Chem. Soc., Dalton
Trans. 2002, 195–211.
(50) Woerpel, K. A.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115,
7888.
(51) Hevia, E.; Perez, J.; Riera, L.; Riera, V.; Miguel, D. Organometallics
2002, 21, 1750–1752.
(52) Review: Hintermann, L.; Labonne, A. Synthesis 2007, 1121–1150.

Insertions into Platinaoxetane Pt-O Bonds
Organometallics, Vol. 27, No. 18, 2008 4815
dinitrogen over 4 Å molecular sieves or sodium metal. Unless
otherwise specified, all reagents were purchased from commercial
suppliers and used without further purification. Complexes 1, 2, 5,
and 6 were synthesized by literature procedures.9,24,25 NMR spectra
were recorded on Bruker AMX-250, -300, or -500 spectrometers
at ambient probe temperatures. NMR data are given in ppm relative
to TMS (referenced to protio solvent signals) for 1H and 13C spectra
or relative to external standards for 195Pt (K2PtCl4/D2O, -1624
ppm), 31P (H3PO4, 0 ppm), and 19F (CFCl3, 0 ppm). IR samples
were prepared by evaporation of a CH2Cl2 solution onto a NaCl
plate. Elemental analyses (inert atmosphere) were provided by
Desert Analytics, Inc.
precipitate a yellow solid. The supernatant was carefully decanted
off the solid, which was dried and extracted with 1 mL of C6H6.
Evaporation of the C6H6 gave product 7. Yield: 7.6 mg, 72%.
Attempts to purify 7 by recrystallization resulted in decomposition,
and an analytically pure sample could not be obtained (3 attempts).
Anal. Calcd (found) for C21H22N4OPt: C, 46.58 (26.90, 42.70,
36.07); H, 4.10 (2.30, 4.90, 3.55). IR (cm-1): 2224 (νCN). 1H NMR
(300 MHz, C6D6): 5.39 (m with satellites, JPt-H ) 37 Hz, 1H, COD
CH’s), 5.00 (m with satellites, JPt-H ) 67 Hz, 1H, COD CH), 4.46
(m with satellites, JPt-H ≈ 48 Hz, 1H, COD CH), 4.37 (m, 1H,
COD CH) 4.29 (d, JH-H ) 5.7 Hz, 1H, CH-2), 2.19 (d, JH-H ) 4.5
Hz, 1H, CH-3), 2.08 (dd with satellites, JH-H ) 5.7 Hz, JH-H
)
Pt(COD)(C(O)OC7H10) (3). CO (0.63 mL, 0.028 mmol) was
injected into an agitated 0.5 mL C6D6 solution of 1 (8.0 mg, 0.019
mmol) in a screw-cap 5 mm NMR tube. After 3 h, 0.5 mL of hexane
was added. A trace amount of precipitate was removed by filtration.
Evaporation of the filtrate gave white product 3. Colorless single
crystals for the X-ray analysis were grown from toluene/hexane at
-30 °C. Yield: 7.9 mg, 93%. Anal. Calcd (found) for C16H22O2Pt:
C, 43.53 (43.25); H, 5.02 (5.20). IR (cm-1): 1664 (νCO). 1H NMR
(300 MHz, C6D6): 5.52 (m, 1H, COD CH), 5.33 (m, 1H, COD
CH), 4.97 (m, 1H, COD CH), 4.79 (m, 1H, COD CH), 4.03 (d,
JH-H ) 6.3 Hz, 1H, CH-2), 2.80 (dd, JH-H ) 6.3 Hz, JH-H ) 2.1
Hz, JPt-H ) 105 Hz, 1H, CH-1), 2.66 (d, JH-H ) 3.9 Hz, 1H, CH-
6), 2.10 (br, s, JPt-H ) 32 Hz, 1H, CH-3), 1.71 (m, 1H, CHH-7),
1.69 (m, overlapping with CHH-7, 8H, COD CH2), 1.42 (m, 1H,
CHH-4), 1.39 (m, 1H, CHH-5′), 0.98 (m, 1H, CHH-5′), 0.95 (br,
s, 1H, CHH-4′), 0.92 (br, s, 1H, CHH-7′). 13C{1H} NMR (75 MHz,
C6D6): 180.5 (CO), 109.0 (JPt-C ) 45.3 Hz, COD CH), 108.4 (JPt-C
) 54.3 Hz, COD CH), 107.7 (JPt-C ) 45.3 Hz, COD CH), 106.8
(JPt-C ) 51.3 Hz, COD CH), 85.7 (JPt-C ) 43.8 Hz, C-2), 60.4
(JPt-C ) 852.8 Hz, C-1), 43.9 (JPt-C ) 17.4 Hz, C-3), 42.2 (C-6),
35.6 (JPt-C ) 17.4 Hz, C-7), 31.3 (JPt-C ) 68.7 Hz, C-5), 29.9,
28.7, 28.6 and 27.5 (COD CH2), 24.2 (C-4). 195Pt NMR (64 MHz,
C6D6): -3820.
Pt(PEt3)2(C(O)OC7H10) (4). CO (0.44 mL, 0.020 mmol) was
injected into an agitated 0.5 mL C6D6 solution of 2 (9.8 mg, 0.018
mmol) in a 5 mm screw-cap NMR tube. After 90 min, the solvent
was evaporated to give product 4, which was washed with cold
hexane and dried in Vacuo. The solid was dissolved in minimum
toluene, excess hexane was added, and the mixture was kept at
-40 °C for 1 day. The resulting white precipitate was collected,
washed with cold hexane, and dried in Vacuo. Yield: 9.3 mg, 90%.
Anal. Calcd (found) for C20H40O2P2Pt: C, 42.18 (42.80); H, 7.08
(7.22). IR (cm-1) 1642 (νCO). 1H NMR (300 MHz, C6D6): 4.24 (d,
JH-H ) 6.9 Hz, 1H, CH-2), 2.82 (d, JH-H ) 4.5 Hz, 1H, CH-6),
2.63 (dd with satellites, JH-H ) 6.9 Hz, JH-H ) 1.5 Hz, JPt-H ) 23
Hz, 1H, CH-1), 2.30 (br s with satellites, JPt-H ) 28 Hz, 1H, CH-
3), 1.96 (m, 1H, CHH-7), 1.89 (m, 6H, PCH2Me), 1.61 (m, 1H,
CHH-5), 1.58 (m, 1H, CHH-4′), 1.45 (m, 6H, PCH2Me), 1.22 (m,
1H, CHH-5′), 1.05 (m, 1H, CHH-4′), 1.04 (m, 1H, CHH-7′), 0.86
(m, 18H, -CH3). 13C{1H} NMR (75 MHz, C6D6): 195.0 (dd, JP-C
) 150 Hz, 7.5 Hz, CO), 84.6 (JPt-C ) 9.8 Hz, C-2), 56.7 (dd, JP-C
) 77.0 Hz, 5.3 Hz, C-1), 44.0 (JP-C ) 2 Hz, C-3), 43.1 (C-6), 35.1
(JPt-C ) 12.8 Hz, C-7), 32.3 (JP-C ) 7.5 Hz, C-5), 24.2 (C-4),
16.4 (dd with satellites, JP-C ) 27.2 Hz, 2 Hz, JPt-C ) 19.6 Hz,
PCH2CH3), 15.5 (d with satellites, JP-C ) 24.9 Hz, JPt-C ) 15.8
Hz, PCH2CH3), 8.63 (JPt-C ) 20.4, PCH2CH3), 8.10 (JPt-C ) 19.6
Hz, PCH2CH3). 31P NMR (101 MHz, C6D6): 18.57 (d with satellites,
2.1 Hz, JPt-H ) 106 Hz, 1H, CH-1), 1.66 (d, JH-H ) 2.1 Hz, 1H,
CH-6), 1.78 (m) and 1.35 (m, overlapping with CHH-7, 8H, COD
CH2), 1.40 (d, JH-H ) 9.5 Hz, 1H, CHH-7), 1.14 (m, 1H, CHH-5),
1.11 (m, 1H, CHH-4′), 0.73 (d, JH-H ) 9.0 Hz, 1H, CHH-7′), 0.81
(m, 1H, CHH-5′), 0.71 (m, 1H, CHH-4′). 13C{1H} NMR (75 MHz,
C6D6): 116.2, 114.7, 113.1 and 112.5 (CN), 113.1, 112.6, 102.1
and 101.2 (COD CH’s), 85.7 (C-2), 69.6 (C-8), 50.4 (C-1), 43.3
(C-3), 36.7 (C-6), 35.8 (C-7), 31.7 (C-5), 31.1, 29.8, 28.1, and 26.5
(COD CH2), 26.8 (C-9), 23.8 (C-4). 195Pt NMR (64 MHz, C6D6):
1
-3895. (See the Supporting Information for copies of the H and
13C NMR spectra.)
Pt(COD)(DEADOC7H10) (8). Diethylacetylenedicarboxylate
(3.1 µL, 0.019 mmol) was added to an agitated 0.5 mL C6D6
solution of 1 (7.9 mg, 0.019 mmol). The solution slowly changed
from colorless to pale yellow and then yellow. After standing the
mixture overnight, all volatiles were removed in Vacuo to give
yellow product 8, which was washed with a small amount of cold
hexane and dried in Vacuo. Yield: 9.5 mg, 85%. Anal. Calcd (found)
for C23H32 O5Pt: C, 47.24 (46.58); H, 5.53 (5.55). IR (cm-1): 1707
(νCO), 1435 (νCdC). 1H NMR (300 MHz, C6D6): 5.76 (m, 1H, COD
CH), 5.53 (m, 1H, COD CH), 4.62 (m with satellites, JPt-H ≈ 46
Hz, 2H, COD CH), 4.33 (m, 2H, CH2Me), 4.10 (m, 2H, CH2Me),
3.63 (d, JH-H ) 6.9 Hz, 1H, CH-2), 2.89 (d, JH-H ) 7.2 Hz, 1H,
CH-3), 2.40 (dd with satellites, JH-H ) 7.8 Hz, JH-H ) 1.8 Hz,
JPt-H ≈ 117 Hz, 1H, CH-1), 2.13 (m, JPt-H ≈ 36 Hz, 1H, CH-6),
2.01 (d, JH-H ) 9.0 Hz, 1H, CH-7), 1.49 (m, 1H, CHH-4), 1.43
(m, 1H, CHH-5′), 1.20 (t, JH-H ) 7.2 Hz, 6H, CH3), 1.07 (d, JH-H
) 7.2 Hz, 1H, CHH-5′), 1.03 (t, JH-H ) 7.2 Hz, 6H, CH3), 1.01
(m, overlapping with CH3 peak, 1H, CHH-4′), 0.85 (m, 1H, CHH-
7′). 13C{1H} NMR (75 MHz, C6D6): 174.4 and 164.1 (COO), 143.7
and 141.4 (CdC), 105.4, 104.5, 100.3, and 100.0 (COD CH’s),
82.8 (C-2), 60.6 and 60.2 (OCH2Me), 51.2 (C-1), 44.3 (C-3), 41.7
(C-6), 36.01 (C-7), 32.4 (C-5), 30.2, 29.7, 28.9, and 28.4 (COD
CH2), 26.3 (C-4), 14.5 and 14.4 (Me). 195Pt NMR (64 MHz, C6D6):
-3937.
Pt(ButNC)2(C7H10OButNC) (9). ButNC (3.3 µL, 0.029 mmol)
was added to an agitated 0.5 mL C6D6 solution of 1 (4.0 mg, 0.0097
mmol). After 5 min, the volatiles were removed in Vacuo. The
resulting oily residue was redissolved in toluene, and the mixture
was evaporated to dryness and left in Vacuo for 2 h. This procedure
was repeated for two or three times until residual COD and ButNC
were eliminated and pale brown solid product 9 was obtained. Yield:
4.8 mg, 89%. Anal. Calcd (found) for C22H37N3OPt: C, 47.64
1
(47.20); H, 6.72 (7.22). IR (cm-1): 2714 (νCN), 1573 (νCdN). H
NMR (300 MHz, C6D6): 4.46 (d, JH-H ) 6.9 Hz, 1H, CH-2), 3.03
(dd with satellites, JH-H ) 6.9 Hz, JH-H ) 2.4 Hz, JPt-H ≈ 75 Hz,
1H, CH-1), 2.74 (d, JH-H ) 4.5 Hz, 1H, CH-3), 2.58 (br s with
satellites, JPt-H ≈29 Hz, 1H, CH-6), 2.24 (d, JH-H ) 9.0 Hz, 1H,
CHH-7), 1.62 (m, 1H, CHH-4), 1.54 (m, 1H, CHH-5′), 1.31 (m,
1H, CHH-5′), 1.21 (m, 1H, CHH-4′), 1.14 (m, 1H, CHH-7′), 1.83
(s, 9H, CH3), 1.06 (s, 9H, CH3), 0.79 (s, 9H, CH3). 13C{1H} NMR
(75 MHz, C6D6): 180.8 (CN), 89.5 (JPt-C ) 37.7 Hz, C-2), 54.9
(JPt-C ) 57.4 Hz, Pt-CN), 52.3 (C-1), 44.7 (C-3), 43.5 (C-6), 35.6
(C-7), 32.2 (C-5), 24.7 (C-4), 56.6 and 56.2 (CMe3), 32.0, 29.6,
and 29.5 (Me). 195Pt NMR (64 MHz, C6D6): -4337.
JP-P ) 8.8 Hz, JPt-P ) 1855 Hz), 5.49 (d with satellites, JP-P
)
8.8 Hz, JPt-P ) 1985 Hz). 195Pt NMR (64 MHz, C6D6): -4564 (t,
JPt-P1 ≈ JPt-P2 ) 1959 Hz).
Pt(COD)(TCNEOC7H10) (7). TCNE (2.5 mg, 0.020 mmol) in
minimum C6D6 was added to an agitated 0.5 mL C6D6 solution of
1 (8.1 mg, 0.020 mmol). The solution gradually changed from
colorless to yellow. After about 5 min, the solution was reduced to
half its original volume, and then excess hexane was added to

4816 Organometallics, Vol. 27, No. 18, 2008
Wu and Sharp
Attempted Isolation of Pt(ButNC)2(C7H10O) (10). ButNC (2.8
µL, 0.029 mmol) was added to an agitated 0.5 mL C6D6 solution
of 1 (5.0 mg, 0.0015 mmol). The 1H NMR spectrum of the mixture
showed, in addition to free COD at 5.57 and 2.21 ppm, peaks at
6.91 (d with satellites, JH-H ) 5.1 Hz, JPt-H ) 49.2 Hz, 1H), 3.56
(m, 1H), 2.44 (br s, 1H), 1.63 (d, JH-H ) 5.1 Hz, 2H), 1.40 (m,
1H), 0.99 (m, 4H), 0.86 (s, 9H), and 0.64 (s, 9H). The volatiles
were removed in Vacuo, the resulting oily residue was redissolved
in toluene, and the mixture was evaporated to dryness and left in
Vacuo for 2 h. This procedure was repeated two or three times until
residual COD was eliminated. A 1H NMR spectrum of the resulting
white solid in C6D6 gave a new set of peaks with the distinctive
CH peak at 6.91 ppm for 10 absent and new major peaks at 1.86,
1.64, 1.20, 1.06 1.01, 0.96, 0.89, and 0.77 ppm.
Attempted Reactions of 1. CO2. CO2 (0.71 mL, 0.013 mmol)
was injected into an agitated 0.5 mL C6D6 solution of 1 (3.3 mg,
0.0080 mmol) in a 5 mm screw-cap NMR tube. The reaction was
monitored by NMR spectroscopy, and no reaction was observed
after two days. CH2dCH2 or CH2dCMe2. A medium-walled 5
mm NMR tube was charged with a solution of 1 (3.9 mg, 0.0087
mmol) in 0.5 mL of C6D6, and then it was connected to a vacuum
line, immersed into liquid nitrogen, and evacuated. CH2dCH2 or
CH2dCMe2 gas at atmospheric pressure (5 mL, 0.22 mmol at 25
°C) was added by vacuum transfer, and then the NMR tube was
flame-sealed and allowed to warm to room temperature. The
reaction was monitored by NMR spectroscopy. No reaction was
observed after three days. PhCCPh. PhCCPh (1.8 mg, 0.010 mmol)
was added to an agitated solution of 1 (4.3 mg, 0.010 mmol) in
0.5 mL of toluene-d8. The reaction was monitored by 1H NMR
spectroscopy. No reaction was observed after two days at room
temperature and then after 4 h at 75 °C.
Reaction of 5 with CO. CO (0.26 mL, 0.012 mmol) was injected
into a solution of 5 (11 mg, 0.012 mmol) in 0.6 mL of CD2Cl2 in
a screw-cap NMR tube,. After 1.5 h the reaction was completed
and the products CODPtCl2 and free NB were identified by 1H
NMR spectroscopy. With 4 equiv of CO, the reaction was
completed in 10 min. A black precipitate, COD, and NB were
observed.
Reaction of 6 with TCNE. TCNE (1.4 mg, 0.011 mg) was added
to a solution of 6 (5.2 mg, 0.011 mmol) in 0.5 mL of CD2Cl2.
After 5 h no reaction was observed and another 3 equiv of TCNE
was added. The reaction was immediately completed, and free NB
was observed.
Reaction of 3 with BF3. BF3 · Et2O (1.3 µL, 0.011 mmol) was
added to an agitated solution of 3 (5.0 mg, 0.011 mmol) in 0.6 mL
of C6D6. 1H and 195Pt NMR spectra showed immediate formation
of 6 in nearly quantitative yield. After 15 min a precipitate appeared
on the NMR tube walls and free NB was observed. The precipitate
and free NB increase with time. After 32 h the reaction was
complete.
Acknowledgment. Support from the Chemical Sciences,
Geosciences, and Biosciences Division, Office of Basic
Energy Sciences, Offices of Science, U.S. Department of
Energy (DE-FG02-88ER13880), is gratefully acknowledged.
A grant from the National Science Foundation (9221835)
provided a portion of the funds for the purchase of the NMR
equipment. We thank Dr. C. Barnes for X-ray data collection
and analysis.
Supporting Information Available: 1H and 13C NMR spectra
for Pt(COD)(TCNEOC7H10) (7) and details of the crystal structure
determination (cif file). This material is available free of charge
via the Internet at http://pubs.acs.org.
Reaction of 6 with CO. CO (0.28 mL, 0.013 mmol) was injected
into a screw-cap NMR tube containing a solution of 6 (6.0 mg,
0.013 mmol) in 0.6 mL of C6D6. After 1.5 h a black precipitate
appeared on the NMR tube walls and free NB was observed. After
4 h about half the NB was released from 6 and after 11 h all NB
was released as determined by NMR integration.
OM8005849