Insertion of isocyanides across the Pd-C bond in alkyl or aryl palladium(II) complexes bearing mixed nitrogen-sulfur and nitrogen-phosphorus ancillary ligands. The mechanism of reaction

Article abstract of DOI:10.1021/om700555a

An exhaustive study dealing with the kinetic and mechanistic behavior of alkyl- and arylpalladium complexes bearing pyridyl-thioethers (NS-R) and quinoline-phosphines (NP) as ancillary ligands when reacting with 2,6-dimethyl isocyanide (DIC) and tosylmethyl isocyanide (TosMIC) was undertaken. In these reactions some differently substituted isocyanides insert into the palladium-carbon bond of alkyl and aryl complexes bearing mixed (NS or NP) ligands. The reactions were carried out under equimolecular conditions since such a restrictive approach allows the determination of the rate constants related to the isocyanide insertion attack. Reactions carried out under nonstoichiometric conditions were also taken into account and the reaction products characterized. Usually the formation of an inserted bis-substituted isocyanide halide derivative of palladium(II) was observed. In a particular case the formation of an imidoyl dimer was detected. The structures of the monoinserted [Pd(NSt-Bu)(C(Tol)=NR²)I] (NSt-Bu = 2-(tert- butylthiomethyl)pyridine) and of the dimer [Pd(CNR²)(C(=NR ²)Me)Cl]₂ (R² = 2,6-Me₂C ₆H₃) were reported.

Full text of DOI:10.1021/om700555a

5590
Organometallics 2007, 26, 5590-5601
Insertion of Isocyanides across the Pd-C Bond in Alkyl or Aryl
Palladium(II) Complexes Bearing Mixed Nitrogen-Sulfur and
Nitrogen-Phosphorus Ancillary Ligands. The Mechanism of
Reaction
Luciano Canovese,*,# Fabiano Visentin,# Claudio Santo,# Carlo Levi,# and
Alessandro Dolmella§
Dipartimento di Chimica, UniVersita` Ca’ Foscari, Calle Larga S. Marta 2137, 30123 Venezia, Italy, and
Dipartimento di Scienze Farmaceutiche, UniVersita` di PadoVa, Via F. Marzolo 5, 35131 PadoVa, Italy
ReceiVed June 7, 2007
An exhaustive study dealing with the kinetic and mechanistic behavior of alkyl- and arylpalladium
complexes bearing pyridyl-thioethers (NS-R) and quinoline-phosphines (NP) as ancillary ligands when
reacting with 2,6-dimethyl isocyanide (DIC) and tosylmethyl isocyanide (TosMIC) was undertaken. In
these reactions some differently substituted isocyanides insert into the palladium-carbon bond of alkyl
and aryl complexes bearing mixed (NS or NP) ligands. The reactions were carried out under equimolecular
conditions since such a restrictive approach allows the determination of the rate constants related to the
isocyanide insertion attack. Reactions carried out under nonstoichiometric conditions were also taken
into account and the reaction products characterized. Usually the formation of an inserted bis-substituted
isocyanide halide derivative of palladium(II) was observed. In a particular case the formation of an imidoyl
dimer was detected. The structures of the monoinserted [Pd(NSt-Bu)(C(Tol)dNR2)I] (NSt-Bu ) 2-(tert-
butylthiomethyl)pyridine) and of the dimer [Pd(CNR2)(C(dNR2)Me)Cl]2 (R2 ) 2,6-Me2C6H3) were
reported.
to give copolymers as the result of the catalytic alternate
insertion,9 were studied from both theoretical and experimental
points of view.6 On the contrary, the isoelectronic isocyanides
CNR were scarcely investigated despite their steric and elec-
tronic properties, which can be easily modulated by taking
advantage of the nature of the substituent R.10 To the best of
our knowledge, only two detailed mechanistic studies dealing
with insertion in palladium complexes bearing bidentate nitrogen
or phosphine ligands have appeared so far in the literature.7b,11
Thus, our propensity to kinetic investigation and curiosity toward
interesting synthetic applications led us to undertake an exhaus-
tive study of the kinetic and mechanistic behavior of alkyl- and
arylpalladium complexes bearing pyridyl-thioethers (NS-R)
and quinoline-phosphines (NP) as ancillary ligands when
reacting with 2,6-dimethyl isocyanide (DIC) and tosylmethyl
isocyanide (TosMIC). As a matter of fact, the palladium alkyl
derivatives with pyridyl-thioether ligands often display an
Introduction
The insertion reactions of unsaturated molecules across
palladium-carbon bonds represent an extensively studied topic
owing to its importance in a remarkable number of metal-
mediated organic syntheses.1,2
Alkynes,3 alkenes,4 allenes,5 carbon monoxide,6 and isocya-
nides7 are the most widely studied unsaturated molecules when
reacting with alkyl-,5 aryl-,7 and acyl-palladium complexes.7a,8
In particular, the reactivity characteristics of carbon monoxide,
which, among other properties, reacts in association with alkenes
* Corresponding author. E-mail: cano@unive.it.
# Universita` Ca’ Foscari.
§ Universita` di Padova.
(1) Heck, R. F. In Palladium Reagents in Organic Synthesis; Academic
Press: New York, 1985.
(2) Tsuji, J. In Palladium Reagents and Catalysts; John Wiley: Chich-
ester, U.K., 1995.
(3) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.; Santo, C.;
Dolmella, A. Organometallics 2005, 24, 3297, and references therein (for
structural comparison entry codes PAQPED, PAQPIH).
(4) Delis, J. G. P.; Aubel, P. G.; Vrieze, K.; van Leeuwen, P. W. N. M.;
Veldman, N.; Speck, A. L. Organometallics 1997, 16, 4150.
(5) (a) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.; Santo, C.;
Bandoli, G.; Maini, L. Organometallics 2003, 22, 3230, and references
therein. (b) Groen, J. H.; Delis, J. G. P.; van Leeuwen, P. W. N. M.; Vrieze,
K. Organometallics 1997, 16, 68. (c) Delis, J. G. P.; Aubel, P. G.; Vrieze,
K.; van Leeuwen, P. W. N. M.; Veldman, N.; Speck, A. L. Organometallics
1997, 16, 2948.
(6) (a) Wojcicki, A. A. AdV. Organomet. Chem. 1973, 11, 87. (b)
Kulhman, E. J.;. Alexander, J. J. J. Coord. Chem. ReV. 1980, 33, 195. (c)
Backer, T. M.; Alexander, J. J.; Krause Bauer J. A.; Nauss, J. L.; Wireko,
F. C Organometallics 1999, 18, 663 (d) Haore, J. L.; Cavell, K. J.; Hecker,
R.; Skelton, B. W.; White, A. H. J. Chem. Soc., Dalton Trans. 1996, 2197.
(e) Koga, N.; Morokuma, K. In Theoretical Aspects of Homogeneous
Catalysis; van Leeuwen, P. W. N. M., Morokuma, K., van Lenthe, J. H.,
Eds.; Kluwer: Dordrecht, The Netherlands, 1995. (f) Calhorda, H. J.; Brown,
J. M.; Cooley, N. A. Organometallics 1991, 10, 1431. (g) Margl, P.; Ziegler,
T. J. Am. Chem. Soc. 1996, 118, 7337.
(7) (a) Veya, P.; Floriani, C. Organometallics 1993, 12, 4899. (b) Delis,
J. G. P.; Aubel, P. G.; Vrieze, K.; van Leeuwen, P. W. N. M.; Veldman,
N.; Speck, A. L.; van Neer, F. J. R. Organometallics 1997, 16, 2948. (c)
Owen, G. R.; Vilar, R.; White, A. J. P.; Williams, D. J. Organometallics
2002, 21, 4799. (d) Vicente, J.; Abad, J-A.; Martinez-Viviente, E.; Jones,
P. G. Organometallics 2002, 21, 4454, and references therein.
(8) (a) Canovese, L.; Visentin, F.; Chessa, G.; Santo, C.; Uguagliati, P.;
Bandoli, G. J. Organomet. Chem. 2002, 650, 43, and references therein
(for structural comparison entry code HUGGAR). (b) Delis, J. G. P.; Aubel,
P. G.; van Leeuwen, P. W. N. M.; Vrieze, K.; Veldman, N.; Speck, A. L.
J. Chem. Soc., Chem. Commun. 1995, 2233.
(9) (a) Drent, E.; van Broekhoven, J. A. M.; Doyle, M. J. J. Organomet.
Chem. 1991, 417, 235. (b) Sen, A.; Jiang, Z. Macromolecules 1993, 26,
911. (c) Brookhart, M.; Wagner, M. I. J. Am. Chem. Soc. 1994, 116, 3641.
(d) van Asselt, R.; Gielens, E. E. C. G.; Ru¨lke, R. E.; Vrieze, K.; Elsevier,
C. J. J. Am. Chem. Soc. 1994, 116, 977. (e) Markies, B. A.; Kruis, D.;
Rietveld, M. H. P.; Verkerk, K. A.; Boersma, J.; Koijman, H.; Lakin, M.
T.; Speck, A. L.; van Koten, G. J. Am. Chem. Soc. 1995, 117, 5263. (f)
Rix, F. C.; Brookhart, M.; White, P. S. J. Am. Chem. Soc. 1996, 118, 4746.
10.1021/om700555a CCC: $37.00 © 2007 American Chemical Society
Publication on Web 10/06/2007

Insertion of Isocyanides across the Pd-C Bond
Organometallics, Vol. 26, No. 23, 2007 5591
Scheme 1
enhanced reactivity toward insertion reactions,12 and moreover
no investigations were hitherto carried out on alkyl- or arylpal-
ladium complexes bearing mixed ancillary ligands. The present
study attempts to determine the reaction rates and elucidate the
intimate mechanism involved when some differently substituted
isocyanides insert into the palladium-carbon bond of alkyl and
aryl complexes bearing mixed (NS or NP) ligands. We also
aimed at characterizing the compounds produced when a
stoichiometric amount or an excess of reacting isocyanide is
used. The complexes, the isocyanides involved, and the number-
ing scheme are reported in Scheme 1.
higher than nitrogen, and the ensuing trans structure is
maintained also in the vinyl and butadienyl derivatives, which
represent the products of the insertion of activated alkynes across
the palladium-carbon bond.3
At present, as can be deduced from the NMR and IR spectra,
all the complexes in Scheme 1 display only one isomer in
solution. On the basis of our experience and knowledge of these
systems and on the basis of the resolved structure reported in
this paper (Vide post), we suggest that only the trans isomer of
the starting complex is present in any studied case (the trans
influence of phosphorus being considerably higher than that of
nitrogen) and that the insertion reactions proceed with retention
of configuration.
Results and Discussion
Insertion Reactions. Preliminary studies carried out by
means of NMR technique in CDCl3 confirm that the insertion
of isocyanide into the Pd-C bond when performed under
stoichiometric conditions proceeds according to the reaction
reported in Scheme 1.
As can be deduced from the NMR data reported in the
Experimental Section, a general rearrangement of the spectra
can be observed upon addition of the isocyanide CNR2 to a
solution of the starting complex [Pd(NS-R)(R′)X] or [Pd-
(DPPQ)(R′)X]. For instance, in the case of the reaction of the
complex [Pd(DPPQ)(Me)Cl] the addition of DIC isocyanide
induces the upfield shift of the Qui-H2 signal (from 10.02 to
9.97 ppm), the downfield shift of the Pd-CH3 signal (from 0.91
General Considerations. As we have already shown, the
structure of the methylpalladium derivatives with mixed biden-
tate nitrogen-sulfur ligands is determined by the mutual trans
influence exerted between the alkyl group and the coordinating
atoms of the ancillary ligand. Thus, only the geometric isomer
with the methyl group lying trans to nitrogen (hereafter trans)
was observed. As a matter of fact, sulfur exerts a trans influence
(10) Crociani, B. In Reactions of Coordinated Ligands; Plenum: New
York, Vol. 1, 1982; p 553, and references therein.
(11) Kayaki, Y.; Shimizu, I.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1997,
70, 917.
(12) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.; Bandoli, G.
Organometallics 2000, 19, 1461.

5592 Organometallics, Vol. 26, No. 23, 2007
CanoVese et al.
Scheme 2
to 1.83 ppm), and the appearance of the signal at 1.87 ppm
attributable to the protons of the methyl substituents of the
aromatic ring of DIC isocyanide. The 31P{H} NMR spectrum
displays the upfield shift of the coordinated phosphorus from
39.9 to 22.2 ppm, and the 13C-1H HMBC NMR spectrum
displays the coupling between the imino carbon C(CH3)dN
(179.1 ppm) and the C(CH3)dN protons. Furthermore the IR
spectrum of the inserted complex displays a strong band at 1622
cm-1 attributable to the νCdN stretching.
The [Pd(NS-R)(R′)X] derivatives behave similarly if an
excess of free ligand is added ([NS-R]:[Pd(NS-R)(R′)X] )
3:1) in order to counteract the displacement of the ligand itself
caused by the isocyanide acting as entering rather than inserting
nucleophile. Under these experimental conditions the insertion
reaction is easily followed by NMR technique, as can be
deduced in the case of the reaction between the complex [Pd-
(NSt-Bu)(Tolyl)I] and the tosMIC isocyanide. The signal
attributable to the Py-H6 proton undergoes an upfield shift from
9.69 to 9.42 ppm. The Pd-C6H4CH3 singlet slightly shifts
downfield from 2.25 to 2.32 ppm, and the appearance of a
couple of doublets at 5.66 and 5.44 ppm, attributable to the
methylene protons of the inserted tosMIC fragment, is also
noticed. The 13C{H} NMR and the 13C-1H HMBC NMR
Figure 1. Molecular structure of the complex [Pd(NSt-Bu)-
(C(Tol)dNC6H3Me2)I]. Hydrogen atoms are not shown for clarity.
Thermal ellipsoids are at the 40% probability level.
pyridyl-thioether ligand induced by the remarkable trans
influence of the carboimine group and the subsequent recoor-
dination, as was observed by other authors.5c Moreover,
fluxional rearrangements via associative processes promoted by
the sulfur lone pair could also be operative.14 However, a
detailed study on these conformational aspects is outside the
scope of this paper, and a specific investigation on these
problems will be carried out in the future.
At variance with the pyridyl-thioether derivatives, the
complexes bearing the flat DPPQ do not obviously give rise to
any rotamer.
spectra together with the IR spectrum (νCdN ) 1594 cm-1
)
confirm the insertion. As a matter of fact, the 13C-1H HMBC
NMR spectrum displays the coupling among the imino-carbon
C(C6H3CH3)dN and both the CH2SO2 and Hb′ (tolyl group)
protons. These observations can be generalized for any other
studied case, as can be deduced from the data in the Experi-
mental Section, where the main NMR and IR features for all
the complexes involved in this study are reported in detail.
Fluxional Rearrangement in Solution. The inserted com-
plexes bearing the pyridyl-thioether ligands at RT give rise to
a rapid rearrangement in solution due to (a) sulfur absolute
configuration inversion, (b) free rotation around the Pd-C bond,
and (c) free rotation around the dN-C bond. It is well-known
that the absolute configuration inversion of the coordinated
sulfur is a low-energy phenomenon;13 thus at low temperature
it is possible to “freeze” this otherwise rapid rearrangement.3
A further decrease of temperature can also “freeze” the Pd-C
rotation (Scheme 2). In this case a couple of rotamers could
turn up. Moreover when DIC isocyanide is used as inserting
nucleophile, the “freezing” of free rotation of the dN-C bond
makes the two methyl ortho substituents of phenyl group
distinguishable.
X-ray Crystal Structure. The ORTEP15 representation of
the neutral complex [Pd(NSt-Bu)(C(Tol)dNC6H3Me2)I], to-
gether with the pertinent labeling scheme is shown in Figure 1.
The square-planar environment about Pd shows some tetrahedral
distortion; the S-Pd-N “bite” angle is 82.7(2)°, the I-Pd-
C(11) angle is 93.4(3)°, and the dihedral angle between the
triangles S-Pd-N(1) and I-Pd-C(11) is 11.0° (ideal value
0°). The atoms Pd, S, N(1), I, and C(11) deviate from the main
coordination plane by -0.03, -0.16, +0.14, -0.12, and +0.14
Å, respectively. Nevertheless, the sum of the angles about Pd
is quite close to 360° (360.7°). The configuration about the
double bond of the imino ligand is Z (that is, the xylyl and
p-tolyl moieties of the ligand are trans disposed).
The findings of the present investigation have been compared
with those stored in the Cambridge Crystallographic Database
(CCD).16 The present compound is structurally similar to the
only known complex with the same donor set around Pd ([PdC-
(t-Bu/Me)dC(Me/t-Bu)C6H4-2-CH2S-t-Bu(C5H5N)I]; 7c in the
ref 17; code ZAFDAL).
In particular, the Pd-N bond (2.231(8) Å) is rather long,
being the second longest reported so far after 2.240 Å in [PdC-
(t-Bu/Me)dC(Me/t-Bu)C6H4-2-CH2S-t-Bu(C5H5N)I]. Likewise,
the relatively long Pd-S (2.306(3) Å) and the relatively short
Pd-C (2.005(9) Å) distances also agree with reported data and
can be explained in terms of the trans influence. In fact, the
pyridine ligand and the sulfur atom are faced by a negatively
charged σ-bonded C ligand and by an iodide, respectively. The
1
The low-temperature (223 K) H NMR spectrum in CD2Cl2
(see Figure 1SI in Supporting Information) of the complex [Pd-
(NS-Me)(C(Me)dNR2)Cl] (R2 ) 2,6-Me2C6H3) witnesses the
formation of a couple of differently populated endo and exo
rotamers.
On the basis of the structural determination (Vide infra) we
suggest that the exo rotamer probably represents the most
abundant species.
(14) Canovese, L.; Lucchini, V.; Santo, C.; Visentin, F.; Zambon, A. J.
Organomet. Chem. 2002, 642, 58.
(15) Johnson, C. K. ORTEP, Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN, 1976.
However, we are aware that these rearrangements might also
be promoted by ring opening at the pyridine nitrogen of the
(13) (a) Abel, E. W.; Evans, D. G.; Koe, J. R.; Sik, V.; Hursthome, M.
B.; Bates, P. A. J. Chem. Soc., Dalton Trans. 1989, 2315. (b) Abel, E. W.;
Dormer, J. C.; Ellis, K. J.; Hursthome, M. B.; Mazid, M. A. J. Chem. Soc.,
Dalton Trans. 1991, 107.
(16) Allen, F. H. Acta Crystallogr. 2002, B58, 380-388; Cambridge
Structural Database (Version 5.27 of November 2005 + 3 updates).
(17) Spencer, J.; Pfeffer, M.; Kyritsakas, N.; Fischer, J. Organometallics
1995, 14, 2214 (entry codes ZAFCUE, ZAFDEP, ZAFDAL).

Insertion of Isocyanides across the Pd-C Bond
Organometallics, Vol. 26, No. 23, 2007 5593
KCL ) [[Pd(NS-Me)(CNR2)(Me)]+][Cl-]/[[Pd(NS-Me)
(Me)Cl]][CNR2] ≈ 3.5 × 10-3 (1)
KL ) [[Pd(CNR2)2(Me)Cl]][NS-Me]/[[Pd(NS-Me)
(Me)Cl]][CNR2]2 ≈ 500 (2)
Owing to the nucleophilicity of isocyanides, the KCL value
sounds very small compared with KL. However, it is well-known
that unsolvated chloride in aprotic solvents acts as a very strong
nucleophile.20
trans influence of these bases and the distortion induced by the
bulky iodide ligand lead to long Pd-N/Pd-S and short Pd-C
bonds. The Pd-I bond (2.642(1) Å) is longer than the
corresponding one in [PdC(t-Bu/Me)dC(Me/t-Bu)C6H4-2-CH2S-
t-Bu(C5H5N)I] (2.632 Å); the latter is also the mean value for
the Pd-I distance in more than 300 Pd complexes in the CCD.
As for nonbonding interactions, an examination of the packing
diagram does not reveal any significant contact.
Mechanistic Study
Determination of Equilibrium Constants. If an equimolar
amount of DIC is added at low temperature (223 K) to a CD2-
Cl2 solution of [Pd(NS-Me)(Me)Cl] ([Pd]0 ≈ 2 × 10-2 mol
dm-3), the ensuing 1H NMR spectrum displays the simultaneous
presence of three species, the concentrations of which do not
change with time. At different temperatures (240, 255 K), the
mutual concentrations of the different species change, but again,
no formation of the inserted product [Pd(NS-Me)(C(Me)d
NC6H3Me2)Cl] is noticed.18 Apparently, the three species are
in a mutual equilibrium. Such a situation however evolves into
the inserted complex [Pd(NS-Me)(C(Me)dNC6H3Me2)Cl] on
increasing the temperature to 298 K. On the basis of a detailed
analysis of the NMR spectra and of some chemical deductions
(Vide post), we suggest the following equilibrium network:
Kinetic Measurements. Addition under spectrophotometric
conditions of an equivalent of isocyanide to a CH2Cl2 solution
of [Pd(NS-R)(R′)X] ([Pd]0 ) 2 × 10-4 mol dm-3) at RT (298
K) leads to the formation of the inserted complex [Pd(NS-R)-
(C(R′)dNR2)X] as unique product. Apparently, the reaction
mixture produces only one species, and this fact can be
considered a further proof that a fast equilibrium among
reactants is operative. Moreover the rate of reaction is strongly
influenced by the addition of variable aliquots of the appropriate
NS-R ligand and/ or chloride (TEBACl, triethylbutyl am-
monium chloride).
In particular, addition of free ligand enhances the rate of
reaction; conversely addition of Cl- induces a decrease in rate.
It is apparent that increasing the amount of added ligand leads
to a suppression of the equilibrium (2), and the attainment of
the asymptotic rate would coincide with the complete suppres-
sion of the equilibrium. This condition is easily reached when
the free ligand is 10 times the concentration of the starting
complex itself, this result being compatible with the value of
the calculated equilibrium constant. (Under these conditions the
concentration of the starting complex is almost coincident with
[Pd]0 since the extent of reaction is about 0.01 × [Pd]0.21)
Therefore, the overall mechanism of isocyanide insertion can
be described by Scheme 3 (the meaning of the symbols A, C,
C′, and D will be specified further on).
[Pd(NS-Me)(Me)Cl] + CNR2 S
[Pd(NS-Me)(CNR2)(Me)]+ + Cl-
KCl (1)
KL (2)
[Pd(NS-Me)(Me)Cl] + 2 CNR2 S
[Pd(CNR2)2(Me)Cl ] +NS-Me
R2 ) 2,6-Me2C6H3
As a matter of fact, the 223 K 1H NMR spectrum in CD2Cl2
of the reaction mixture displays an easily recognizable series
of signal. The doublet at 8.51 ppm, the singlet at 3.74 ppm,
and the singlet at 1.99 ppm are attributable to H6 of the pyridine
ring, to -CH2-S, and to -S-CH3 protons, respectively, of
the uncoordinated NS-Me ligand. The unreacted starting
complex displays the Py-H6 at 9.05 ppm, the -CH2-S AB
system at 4.27 ppm, the -S-CH3 signal at 2.40 ppm, and the
Pd-CH3 at 0.67 ppm. The presence of uncoordinated ligand
and the absence of any appreciable decomposition suggest
the formation of the complex [Pd(CNR2)2(Me)Cl], which is
characterized by the singlet at 0.96 ppm ascribable to Pd-CH3
and by the singlet at 2.45 ppm related to C6H3(CH3)2 protons.
A further substrate that we identify as the [Pd(NS-Me)(CNR2)-
(Me)]+ complex is detected in solution with its relevant
signals, namely, the doublet at 8.66 ppm (Py-H6), the signal
at 4.50 ppm (-CH2-S), that at 2.13 ppm (-S-CH3), and
eventually the broad singlet at 1.00 ppm ascribable to Pd-CH3
protons. The identification of the nature of the complexes [Pd-
(CNR2)2(Me)Cl ] and [Pd(NS-Me)(CNR2)(Me)]+ is also based
on their reactivity as will be described later. From the calculated
concentrations of all the species present in solution an ap-
proximate value of equilibrium constants KCl and KL can be
estimated. The linear regression of ln K vs 1/T according to
van’t Hoff’s equation allows a coarse determination of the
equilibrium constants at 298 K. The ensuing values are19
The rate law for the reaction in Scheme 3 is
-d[S]/dt ) [S][CNR2](KClki +
k2[Cl-])/(KCl[CNR2] + [Cl-]) (3)
where
[S] ) [[Pd(NS-Me)(Me)Cl]] + [[Pd(NS-Me)(CNR2)
(Me)]+] ) [A] + [C]
In the presence of a strong excess of Cl- the rate law (3)
becomes
-d[S]/dt ) k2[S][CNR2]
(4)
This expression is easily handled, and thus information on the
direct attack of an equimolar amount of isocyanide (second-
order condition) on the starting complex can be obtained. It is
worth noting that the addition of TEBACl slows down the
reaction rate, suggesting that the dechlorinated substrate is
(19) Owing to the very large errors affecting the determination of the
concentrations, standard errors of the van’t Hoff regression are not reported.
Therefore, the equilibrium constant values must be considered as rough
estimates of their order of magnitude.
(20) Annibale, G.; Canovese, L.; Cattalini, L.; Marangoni, G.; Michelon,
G.; Tobe, M. L. Inorg. Chem. 1981, 20, 2428.
(21) The NSMe species represents the less strongly bonded ligand among
all the ligands used in this work. Therefore, its added concentration would
represent the limiting concentration also in the case of NSt-Bu (DPPQ and
DPPQMe are not displaced by isocyanide).
(18) At higher temperature (255 K) traces of the insertion product are
observed; however the estimated concentration of the latter is less than 5%
of the concentration of the starting complex.

5594 Organometallics, Vol. 26, No. 23, 2007
CanoVese et al.
Scheme 3
Scheme 4
somewhat more reactive than the chlorinated one. No informa-
tion can be however obtained about the monomolecular insertion
rate ki since the numerical analysis of eq 3 is rather complicated
([Cl-] is a function of time) even if an approximate value for
KCl is available.22 The higher reactivity of the substrate [Pd-
(NS-Me)(CNR2)(Me)]+ compared with [Pd(NS-Me)(Me)Cl)]
can be traced back to its cis structure allowing the facile
migration of the methyl group.23 An indirect confirmation of
the proposed mechanism is given by the reactivity behavior of
the iodo and DPPQ derivatives. The rates of the reaction of the
iodo derivatives are independent of added iodide, while the rates
of DPPQ complexes are not affected by the addition of free
DPPQ ligand in solution; the reaction rates of complexes
containing DPPQ and iodide are independent of both ligand
and iodide added. It is well-known that chloride is easily
displaced by iodide in Pd(II) planar tetracoordinated substrates,
the Cl-/ I- exchange equilibrium constant being 3/4 orders of
magnitude in favor of iodide.24 Apparently, iodide is not
displaced by isocyanide; therefore no equilibria like equilibrium
(1) is operative in the case of iodide derivatives. The DPPQ
ligand is not displaced either; thus in neither of these cases do
equilibria like equilibrium (2) exist. In Table 1 the kinetic data
obtained in the presence and in the absence of added ligand or
halide for all the studied substrates are reported.
In an attempt at unifying the overall reactivity, we propose
an intimate mechanism based on the theory of nucleophilic
substitutions on planar tetracoordinated complexes. On the basis
of such a theory the entering nucleophile simply replaces the
leaving group occupying its position. The key intermediate is a
trigonal bipyramid in which the entering, the leaving, and the
group trans to the leaving group itself occupy the equatorial
plane. Scheme 4 suggests the possible paths, which take into
account all the possible species involved.
As can be seen in Scheme 4, only the intermediates B and E
can be obtained from the isocyanide attack to the starting
complex [Pd(NS-R)(R′)Cl]. B gives rise to the inserted product
D via the cationic cis complex C when Cl- is the leaving group
Table 1. Second-Order Rate Constant k2 (mol-1 dm3 s-1) for
the Insertion of the Isocyanides DIC and TosMIC across the
Pd-C Bond of Complexes [Pd(L-L′)(R′)X]
complexes
DIC
TosMIC
1
2
[Pd(NS-Me)(Me)Cl] + 10 equiv ligand 250 ( 4
too fast
too fast
[Pd(NS-Me)(Me)Cl] +
65 ( 1
10 equiv ligand + 10 equiv Cl-
[Pd (NS-Me)(Me)I] + 10equiv ligand
[Pd (NS-Me)(Me)I] +
3
4
20 ( 1
19 ( 2
880 ( 72
866 ( 56
10 equiv ligand + 10 equiv I-
[Pd(NSt-Bu)(Me)Cl] + 10 equiv ligand
[Pd(NSt-Bu)(Me)Cl] +
5
6
100 ( 1
56.0 ( 0.2 too fast
too fast
10 equiv ligand + 10 equiv Cl-
[Pd(NSt-Bu)(Me) I] + 10 equiv ligand
[Pd(NSt-Bu)(Me) I] +
7
8
18 ( 1
18 ( 3
821 ( 51
815 ( 55
10 equiv ligand + 10 equiv I-
[Pd(NS-Me)(Tolyl)I] +
9
433 ( 20
439 ( 26
48 ( 1
1220 ( 85
1205 ( 90
540 ( 30
550 ( 38
10 equiv ligand
(22) (a) Strictly speaking, eq 3 turns into eq 4 at very high chloride
concentration according to the limit: lim (KClki + k2[Cl-])/(KCl[CNR2] +
[Cl-]) ) k2 for [Cl-] f ∞. In practice, the amount of added chloride was
the concentration at which the rate of reaction levels off to an asymptotic
value (k2). This value is reached even at 3-4 times the concentration of
the starting complex [Pd(NSMe)(Me)Cl]. We however decided to add a
10-fold excess in all cases studied in order to ensure the constancy of
chloride concentration with time. Moreover, under this condition the extent
of reaction for the chloride displacement equilibrium (KCl) is virtually zero,
equilibrium (1) being completely shifted to the left. (b) Analogously to
those calculated in the presence of an excess of halide, approximate k2 values
were determined in the absence of added chloride by numerical regression
of the absorbance vs time data according to the second-order treatment.
Such values are purely indicative since the treatment is obviously inadequate
owing to the complexity of the overall reaction mechanism. Nevertheless,
the comparison among rates is warranted by the fairly satisfactory fit
obtained.
10 [Pd(NS-Me)(Tolyl)I] +
10 equiv ligand + 10 equiv I-
11 [Pd(NSt-Bu)(Tolyl)I] +
10 equiv ligand
12 [Pd(NSt-Bu)(Tolyl)I] +
10 equiv ligand + 10 equiv I-
13 [Pd(DPPQ)(Me)Cl]
50 ( 3
1.0 ( 0.1
0.4 ( 0.1
253 ( 3
236 ( 2
3. 2 ( 0.5
1.2 ( 0.1
1130 ( 20
1118 ( 20
14 [Pd(DPPQ)(Me)Cl] + 10 equiv Cl-
15 [Pd(DPPQ-Me)(Me)Cl]
16 [Pd(DPPQ-Me)(Me)Cl] +
10 equiv Cl-
17 [Pd(DPPQ)(Me)I]
4.5 ( 0.5
4.4 ( 0.7
202 ( 1
200 ( 4
116 ( 1
120 ( 5
150 ( 3
155 ( 7
18 [Pd(DPPQ)(Me)I] + 10 equiv I-
19 [Pd(DPPQ)(Tolyl)I]
20 [Pd(DPPQ)(Tolyl)I] + 10 equiv I-
(23) Canovese, L.; Visentin, F.; Chessa, G.; Santo, C.; Uguagliati, P.
Inorg. Chim. Acta 2003, 346, 158.
(24) Tobe, M. L.; Burgess, J. In Inorganic Reactions Mechanisms;
Addison Wesley: New York, 1999.
(path 2). In particular, the reaction sequence B f C f C′ f P
involves intramolecular insertion of isocyanide (C f C′) to give
the cationic coordinatively unsatured intermediate C′, which

Insertion of Isocyanides across the Pd-C Bond
Organometallics, Vol. 26, No. 23, 2007 5595
Scheme 5
rapidly reacts with chloride to yield the final neutral product.
Addition of TEBACl clearly suppresses the formation of C. In
path 1 the leaving group R′ gives rise to complex D via direct
migration.
correlated and represent different aspects of the same chemical
behavior, as Scheme 5 shows.
The rigid DPPQ molecule hampers the formation of inter-
mediate I, thereby lowering the reactivity of the complex itself
(a similar decrease in reactivity was already noticed with DPPQ
derivatives when other insertion reactions were studied).3
Moreover intermediate II is probably less stabilized than
intermediate I due to the mutual trans influence exerted by the
phosphine and isocyanide in the ensuing cationic species. Thus,
the k2 path becomes predominant even though the ki path is not
impossible (see entries 15 and 16). The enhanced reactivity of
DPPQMe derivatives derives from the distortion induced by the
methyl substituent in position 2 of the quinoline ring, which
somehow makes the formation of the pentacoordinate interme-
diates easier.8a,17d
Reaction in the Presence of Isocyanide in Excess. Com-
plexes Bearing Isocyanide as Substituent and Inserted
Moiety. At variance with the DPPQ derivatives, which give
rise to isocyanide polyinsertion, the NS-Me complexes react
with an excess of isocyanide in CHCl3 at RT according to the
following reaction:
The formation of the species L is obtained from both the
intermediates B and E passing through the species H, I and F,
G, respectively. As a matter of fact, the leaving group in B
could be represented by Cl- or by the thioetheric sulfur.
Analogous considerations can be made when the reaction
proceeds via the species E. According to the nucleophilic
substitution theory, intermediates G and I would produce cis-
[Pd(CNR2)2(R′)Cl] (not reported in Scheme 4), which however
quickly isomerizes to the more stable trans form L.
The following remarks are in order.
(a) The limiting reaction rate is always reached upon addition
of the labile ligands (NS-R) and/or halide (Cl-). Addition of
iodide and/or DPPQ ligand does not affect the overall reactivity.
(b) The isocyanide TosMIC is almost always more reactive
than the DIC one. This fact can be traced back to the associative
nature of the nucleophilic attack, which is strongly influenced
by the steric requirement of the species involved coupled with
the reduced charge density on the isocyanide carbon,10 which
favors the internal migration of the methyl (or tolyl) group (path
1). However the influence of the steric requirement of the
sulfur substituent R, which is probably away from the crowded
intermediate, is not so important (entries 2, 6 and 4, 8 in Table
1).
(c) Thanks to its higher basicity and the consequent stronger
Pd-C bond, methyl is less efficient than tolyl as a migrating
group (entries 10, 4 and 12, 8).
(d) When path 1 is imposed by halide and ligand addition,
the nature of the halide is not very important since the halide
itself is out of the mechanistic context (Scheme 5) and its
influence is limited to a slight difference in the charge density
on the metal induced by the different basicity of the halides
(entries 2, 4 and 6, 8).
(e) The importance of the steric hindrance on the starting
complex arises when t-Bu and tolyl groups are both present. In
this case a decrease in the absolute and relative reactivity is
observed (entries 12 and 8 compared with 10 and 4).
A detailed analysis of the reactivity of the complexes studied
must take into account the comparison among NS-R and DPPQ
derivatives. The reactivity of phosphine-quinoline substrates
is in general (i) not influenced by free ligand addition; (ii) lower
than that of their pyridyl-thioether counterparts (entry 16 will
be dealt with further on); and (iii) scarcely influenced by addition
of free halide.
The obtained complexes are stable with the exception of the
complex [Pd(CNR2)2(C(Tolyl)dNR2)I] (R2) CH2Tosyl), which
undergoes fast decomposition. The presence of one single
symmetric isomer in solution suggests that the trans bis-
substituted isocyanide derivative is obtained. For instance, when
DIC is reacted with [Pd(NS-Me)(Me)Cl], only a singlet (12H)
ascribable to (CH3)2C6H3 protons at 2.41 ppm is detected. The
singlets at 2.69 ppm (3H) and at 2.12 ppm (6H) ascribable to
(CH3)-CdN and CdN-C6H3(CH3)2 protons, respectively,
confirm the formation of one single isomer. The IR spectrum
displays one strong band at 2173 cm-1 (νCtN of the coordinated
isocyanide) and another strong band at 1658 cm-1 (νCtN inserted
isocyanide).
Dimeric Imidoyl Complex. When a 2-fold stoichiometric
excess of DIC isocyanide is added to a solution of palladium
complexes bearing labile ligands [Pd(LL)(Me)Cl] (LL ) NS-
R, COD), the reaction mixture yields the dimeric imidoyl
derivative [Pd(CNR2)(C(dNR2)Me)Cl]2. Crystals suitable for
X-ray diffractometric structural determination were grown and
As for point (i), owing to the efficiency of the phosphine as
ligand, addition of free DPPQ does not modify the reactivity
of the corresponding complexes since DPPQ is not displaced
by the entering isocyanide. As for points (ii) and (iii), they are

5596 Organometallics, Vol. 26, No. 23, 2007
CanoVese et al.
Pd-C and Pd-N distances vary from 1.976 to 2.042 Å and
from 1.989 to 2.085 Å, respectively.
The 2,6-dimethylphenyl moieties of the isocyanide and of
the ethylimino ligands make dihedral angles of 77.2° and 38.0°,
respectively, with the main coordination plane. The same
residues make dihedral angles of 34.3° and 60.4°, respectively,
with the best mean plane of the 1,4-dipalladated ring. Finally,
the two rings make an angle of 88.7° with each other. The 2,6-
dimethylphenyl moiety belonging to the ethylimino donor seems
to assume this position in order to minimize the reciprocal steric
clashes of its own methyl groups with the methyl group bound
to C(1) and with the chloride ligand. A molecular mechanics
calculation made by driving the Pd-N(1)-C(3)-C(4) dihedral
angle in a range of 40° centered on the solid-state value
(-100.4°) indicates that the conformation found in the crystal
is in fact the energetically most favorable.29 As for nonbonding
interactions, despite the presence of the solvation chloroform
molecule, the examination of the packing diagram does not
reveal any significant contact.
Figure 2. Molecular structure of complex [Pd(CNR2)(C(dNR2)-
Me)Cl]2 (R2 ) C6H3Me2). Hydrogen atoms are not shown for
clarity. Thermal ellipsoids are at the 40% probability level.
As already stated, the formation of the dimer [Pd(CNR2)-
(C(dNR2)Me)Cl]2 was observed only when the DIC isocyanide
is reacted with palladium methyl derivatives bearing labile
ligands. When a 2-fold excess of tosMIC isocyanide is added
to a solution of [Pd(LL)(Me)X] (LL ) NS-R, COD), the
formation of an equimolecular mixture of the complexes [Pd-
(LL)(C(dNR2)Me)X] and [Pd(CNR2)2(C(dNR2)Me)X] (R2 )
CH2SO2C6H4Me) is observed, and similar behavior is also
observed when the reacting complexes contain the tolyl group
instead of the methyl one even when the DIC isocyanide is used.
The extent of the Pd-N bond length (2.088 Å) might probably
be invoked in order to explain the peculiar reactivity leading to
the dimeric species. The basicity of the imidoyl nitrogen is
considerably weakened by the withdrawing capability of the
tosyl group, and the formation of a dative ligand between the
electron-poor nitrogen and the palladium in this case is not
allowed. When palladium(II) tolyl derivatives were used as
starting complexes, no formation of dimeric species was
observed either. Again, steric hindrance between bulky vicinal
groups will disfavor the formation of a weak Pd-N bond.
As for the fluxional rearrangement of the dimeric complex
[Pd(CNR2)(C(dNR2)Me)Cl]2 (R2 ) Me2C6H3), it is noteworthy
that the RT 1H NMR spectrum of the dimer displays two
distinguishable singlets ascribable to the -2,6(CH3)2C6H3
methyl groups of the DIC isocyanide (2.40, 2.36 ppm).
Apparently the DIC moiety is not allowed to rotate around the
separated from the mother solution, and the resulting structure
is reported in Figure 2.
The ORTEP25 representation of the neutral complex 2 ([Pd-
(CNR2)(C(dNR2)Me)Cl]2; R2 ) C6H3Me2), together with the
pertinent labeling scheme, is shown in Figure 2, which also
shows the solvation chloroform molecule. The molecule is a
dimer, in which each Pd atom is coordinated by a chloride ion,
by the 2,6-dimethylphenyl isocyanide, and by the 1-(2,6-
dimethylphenylimino)ethyl moiety. The latter acts as a bidentate
bridging ligand, bonding one Pd center by means of the neutral
imine nitrogen and the other one by means of the negatively
charged σ-bonded ethyl carbon. This arrangement originates a
six-membered, 1,4-dipalladated ring.
Similar cyclic dimers of palladium have already been
reported, and in fact a search in the Cambridge Crystallographic
Database (CCD)16 returns about 90 structures, but only in about
20 cases is the bridge made of C or N atoms. To the best of our
knowledge, this is the first evidence of the 1-(2,6-dimethylphe-
nylimino)ethyl synthon behaving as bridging. In the majority
of already known examples, as well as in complex 2, the six-
membered ring assumes a twist-boat arrangement. In the present
case, the two Pd atoms are at the “stern” and “prow” positions,
1.06 Å above the mean plane defined by the remaining four
atoms, which are coplanar within 0.03 Å. Compared with known
structures, the six-membered ring puckering in 2 resembles those
found in the CCD entries PZALPD10, KAMQUK, and WER-
JAF.26
(27) (a) Onitsuka, K.; Segawa, M.; Takahashi, S. Organometallics 1998,
17, 4335 (entry code JAQKAN). (b) Braunstein, P.; Durand, J.; Knorr, M.;
Strohmann, C. Chem. Commun. 2001, 211 (entry code WOXGAR). (c)
Onitsuka, K.; Yamamoto, M.; Suzuki, S.; Takahashi, S. Organometallics
2002, 21, 581 (entry code LOWVAU). (d) Owen, G. R.; Vilar, R.; White,
A. J. P.; Williams, D. J. Organometallics 2003, 22, 4511 (entry codes
UMEDOF, UMEDUL). (e) Knorr, M.; Jourdain, I.; Braunstein, P.;
Strohmann, C.; Tiripicchio, A.; Ugozzoli, F. Dalton Trans. 2006, 5248 (entry
code MESZOA).
(28) (a) Yamamoto, Y.; Tanase, T.; Yanai, T.; Asano, T.; Kobayashi,
K. J. Organomet. Chem. 1993, 456, 287 (entry code LAYPUW). (b) Delis,
J. G. P.; Aubel, P. G.; Vrieze, K.; van Leeuwen, P. W. N. M.; Veldman,
N.; Spek, A. L. Organometallics 1997, 16, 4150 (entry code NOHCUI).
(c) Bianchini, C.; Lee, H.-M.; Mantovani, G.; Meli, A.; Oberhauser, W.
New J. Chem. 2002, 26, 387 (entry code XISQIZ). (d) Owen, G. R.; Vilar,
R.; White, A. J. P.; Williams, D. J. Organometallics 2003, 22, 3025 (entry
code OKAYUU). (e) Lai, Y.-C.; Chen, H.-Y.; Hung, W.-C.; Lin, C.-C.;
Hong, F.-E. Tetrahedron 2005, 61, 9484 (entry code GATBOT). (f) Hsueh,
M.-L.; Su, S.-Y.; Lin, C.-C. Acta Crystallogr., Sect. E 2006, 62, m1784
(entry code DELRIW). (g) Zhang, W.; Sun, W.-H.; Wu, B.; Zhang, S.;
Ma, H.; Li, Y.; Chen, J.; Hao, P. J. Organomet. Chem. 2006, 691, 4759
(entry codes NESHOJ, NESJAX).
The Pd-C (ethyliminophenyl, 1.984(6) Å), Pd-C (isocya-
nide, 1.953(6) Å), Pd-N (2.088(4) Å), and Pd-Cl (2.389(2)
Å) distances about Pd agree with known data. In particular, the
Pd-Cl distance is close to the reported mean value (2.329 Å)
in the CCD;26 the same can be said about the Pd-C distance
of the isocyanide ligand (mean 1.969 Å). With respect to the
bonds involving the bridging ligand, CCD searches for Pd
complexes showing σ-bonded C5c,7c,8b,27 or N-bonded5c,7c,8b,27,28
ethyliminophenyl donors returned few entries, in which the
(25) (a) ORTEP-3 for Windows, Version 1.08; University of Glasgow,
2005. (b) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(26) (a) Henslee, G. W.; Oliver, J. D. J. Cryst. Mol. Struct. 1977, 7, 137
(entry code PZALPD10). (b) Bacchi, A.; Carcelli, M.; Pelagatti, P.; Pelizzi,
C.; Pelizzi, G.; Salati, C.; Sgarabotto, P. Inorg. Chim. Acta 1999, 295, 171
(entry code KAMQUK). (c) Wu, W.-S.; Chen, J.; Dai, J.-C.; Lin, J.-M.;
Lan, X.-R.; Huang, T.-T. Huaxue Xuebao (Chin.) (Acta Chim. Sinica) 2005,
63, 1967 (entry code WERJAF).
(29) Spartan ’06 for Windows Version 1.1.0; Wavefunction, Inc.: Irvine,
CA, 2006.

Insertion of Isocyanides across the Pd-C Bond
Organometallics, Vol. 26, No. 23, 2007 5597
Scheme 6
induced by the pyridine substituent makes these substrates very
reactive. Unfortunately their very high reaction rates and intrinsic
instability due to ligand lability disfavor a detailed study with
strong nucleophiles like isocyanates.
• The TosMIC isocyanide is more reactive than DIC due to
its reduced steric hindrance at carbon and its enhanced elec-
trophilicity.
• The reaction is scarcely influenced by the nature of the
halide. However, when chloride derivatives are used, an excess
of Cl- is added to the reaction mixture in order to suppress the
displacement of Cl- by the added isocyanide.
• Analogously, an excess of NS-R ligand is added in order
to suppress its displacement by isocyanide.
• DPPQ-Me derivatives are more reactive than the DPPQ
ones due to the distortion induced by the methyl group in
position 2 of the quinoline ring in the ground state of the starting
complexes.
• On the basis of these pieces of information, a general
scheme involving the intimate mechanism was proposed.
• The reaction of methyl or aryl palladium(II) derivatives with
a stoichiometric excess of isocyanide was carried out, and the
reaction conditions yielding monomeric or dimeric species were
carefully investigated.
N-C6H3(CH3)2 bond since it is severely hampered by the mutual
steric hindrance exerted between substituents in the crowded
dimeric structure. In this respect the NOESY spectrum of the
dimer [Pd(CNR2)(C(dNR2)Me)Cl]2 (R2 ) C6H3Me2) clearly
displays the spatial correlation between the methyl fragment
belonging to the coordinated and that of the inserted isocyanide.
Thus, only the signal of the methyl protons of the inserted
isocyanide at 2.40 ppm is directly related to the signal of the
methyl protons of the coordinated one at 2.52 ppm, while the
signal at 2.36 ppm does not display any spatial correlation (see
Figure 2SI in Supporting Information).
Similar imidoyl complexes were prepared by some research
groups following approaches that take advantage of a coordi-
native vacancy induced by aryl migration on the Pd-CNR
ligand usually promoted by heating the solution mixture
containing trans-[Pd(CNR)2(Ar)X], by means of chloro bridge
cleavage in dimeric species containing the imidoyl fragment
induced by ligand attack,30 by insertion of isocyanide across
the Pd-C ligand in palladacyclo complexes,31 or by the reaction
of the isocyanide complex with aziridines with subsequent
deprotonation of bis-carbene species.32 Interestingly, we have
synthesized the complex [Pd(CNR2)(C(dNR2)Me)Cl]2 under
very mild conditions, and on the basis of our mechanistic
observation, we advance the hypothesis that the reaction path
to the dimeric species might be summarized by Scheme 6.
Experimental Section
Solvents and Reagents. THF and toluene were dried and purified
on metallic Na and distilled immediately before use. CH2Cl2 and
CH3CN were dried on CaH2 and distilled before use. Acetone was
refluxed and distilled on molecular sieves (3 Å). All other chemicals
were commercially available grade products unless otherwise stated.
IR, NMR, and UV-Vis Measurements. The IR and H, 13C-
1
{lH}, and 31P{lH} NMR spectra were recorded on a Perkin-Elmer
Spectrum One spectrophotometer and on a Bruker 300 Avance
spectrometer, respectively. The proton and carbon assignments were
performed by 1H-13C -HMQC and -HMBC experiments. UV-vis
spectra were taken on a Perkin-Elmer Lambda 40 spectrophotometer
equipped with a Perkin-Elmer PTP6 (Peltier temperature program-
mer) apparatus.
Preliminary Studies and Kinetic Measurements. All the
insertion reactions were preliminarily analyzed by 1H NMR
technique by dissolving the complex under study in 0.6 mL of
CDCl3 ([complex]0 ≈ 3 × 10-2 mol dm-3). An appropriate aliquot
of isocyanide was added ([isocyanide]0 ≈ (3-9) × 10-2 mol dm-3),
and the reaction was followed to completion by monitoring the
signals for the disappearance of the starting complex and the
simultaneous appearance of the monoinserted or the inserted-
substituted species.
A UV-vis preliminary investigation was also performed with
the aim of determining a suitable wavelength. To this purpose, 3
mL of freshly distilled CHCl3 solution of the complex under study
([complex]0 ≈ 2 × 10-4 mol dm-3) and in the case of NS-R
derivatives also in the presence of an excess of free ligand ([NS-
R]0 ≈ 2 × 10-3 mol dm-3) was placed in a thermostated (25 °C)
cell compartment of the UV-vis spectrophotometer, and microali-
quots of a concentrated solution of the isocyanide ([isocyanide]0
≈ 2 × 10-4 mol dm-3) were added. The absorbance change was
monitored in the 245-500 nm wavelength interval.
Conclusions
The reactivity of several palladium alkyl and aryl substrates
bearing pyridyl-thioethers and phosphine-quinolines as ancil-
lary ligands toward two differently substituted isocyanides was
investigated. From this study we gathered the following pieces
of information.
• Pyridyl-thioether and phosphine-quinoline complexes in
the presence of a stoichimetric amount of isocyanide give only
the monoinserted derivative analogously to dinitrogen substrates.5c
This peculiar behavior is unusual since with phosphine deriva-
tives polyinsertion is usually observed.11
• Pyridyl-thioether subtrates are more reactive than their
phosphine and dinitrogen analogues.5c,11 It is noteworthy that
pyridyl-thioether ligands impart to their alkyl derivatives the
highest reactivity that has been hitherto observed in insertion
reactions. The reactivity of the DPPQ-Me derivatives reported
in this paper should be compared with that of alkyl (or aryl)
complexes with pyridyl-thioethers bearing a substituent at the
pyridine ring R′′NS-R (R′′ ) Me, Cl) as ligands. The distortion
X-ray Analysis. Well-formed crystals of complexes 1 ([Pd(NSt-
Bu)(C(Tol)dNC6H3Me2)I]) and 2 ([Pd(CNR2)(C(dNR2)Me)Cl]2),
suitable for X-ray work, were placed on the top of a glass capillary
and transferred to either a Philips PW-1100 (FEBO System, 1) or
a Nonius MACH3 system (2). The latter was generously made
available by colleagues at the Department of Environmental
Sciences of SUN, Caserta, Italy.
(30) (a) Uson, R.; Fornie´s, J.; Espinet, P.; Lalinde, E. J. Organomet.
Chem. 1988, 349, 269. (b) Uson, R.; Fornie´s, J.; Espinet, P.; Pueyo, L.;
Lalinde, E. J. Organomet. Chem. 1986, 299, 251, and references therein.
(31) Dupont, J.; Pfeffer, M.; Daran, J. C.; Jeannin, Y. Organometallics
1987, 6, 899, and references therein.
(32) Bertani, R.; Mozzon, M.; Michelin, R. A.; Benetollo, F; Bombieri,
G.; Castilho, T. J.; Pombeiro, A. J. L. Inorg. Chim. Acta 1991, 189, 175.
The X-ray diffraction data were collected by the ω-2θ technique
at 298(2) K, using graphite-monochromated Mo KR radiation (λ

5598 Organometallics, Vol. 26, No. 23, 2007
CanoVese et al.
) 0.71073 Å (1) and λ ) 0.70930 (2)) and corrected for Lorentz
and polarization effects (1, 2) and for absorption factors (1). In the
case of 2, the absorption correction was not applied since psi-scans
proved that absorption was negligible (transmission between 0.75
and 0.78), probably due to the “cuboid” shape of the specimen.
For both complexes, the unit cell parameters were determined by
least-squares refinement of the setting angles of 25 well-centered
high-angle reflections. Data analysis and cell refinement for 2 were
carried out using the programs maXus33 and SIR 92.34 Crystal
stability was periodically checked by monitoring the intensities of
two standard reflections.
(dd, 1H, J ) 1.5, 8.3 Hz, Qui-H4), 7.95 (d, 1H, J ) 7.9 Hz, Qui-
H3), 7.66-7.40 (m, 13H aromatic protons), 3.31 (s, 3H, quin-CH3),
0.97 (d, 3H, J ) 2.9 Hz, CH3-Pd). 31P{1H} NMR (CDCl3, 298 K,
δ(ppm)): 39.3. Anal. Calcd for C23H21ClNPPd: C 57.04, H 4.37,
N 2.89. Found: C 56.95, H 4.41, N 2.73.
Synthesis of the Complex [Pd(DPPQ)(Me)I]. The title complex
was obtained by heterogeneous metathesis of Cl- with I- (NaI)
under inert atmosphere at RT in CH2Cl2 according to established
procedures.23 Yield: 84% (yellow-orange microcrystals). 1H NMR
(CDCl3, 298 K, δ(ppm)): 10.41 (dd, 1H, J ) 1.6, 4.8 Hz, Qui-
H2), 8.40 (d, 1H, J ) 8.3 Hz, Qui-H4), 8.08 (d, 1H, J ) 8.1 Hz,
Qui-H5), 7.97 (m, 1H, Qui-H7), 7.66 (m, 6H), 7.50 (m, 6H), 1.12
(d, 3H, J ) 2.6 Hz, CH3-Pd). 31P{H} NMR (CDCl3, 298 K, δ-
(ppm)): 35.3. Anal. Calcd for C22H19INPPd: C 47.04, H 3.41, N
2.49. Found: C 46.96, H 3.32, N 2.57.
Synthesis of the Complex [Pd(NS-Me)(tolyl)I]. To 0.1431 g
(1.03 m.mol) of NS-Me ligand dissolved in 16 mL of anhydrous
toluene was added 0.150 g (0.34 mmol) of the complex [Pd(tmeda)-
(tolyl)I] (tmeda ) tetramethylethylenediamine)40 under inert at-
mosphere (Ar). The resulting yellow suspension was stirred at RT
for 4 h and dried under reduced pressure. The solid residue was
dissolved in CH2Cl2 (10 mL), treated with activated charcoal, and
filtered on a Celite filter. Reduction of the resulting volume under
reduced pressure and addition of diethyl ether yielded 0.1262 g
(0.272 mmol) of the complex as a pink-yellow powder. Yield: 80%.
1H NMR (CDCl3, 298 K, δ(ppm)): 9.65 (d, 1H, J ) 5.4 Hz, Py-
H6), 7.82 (td, 1H, J ) 7.7 Hz, J ) 1.7 Hz, H4pyr), 7.47 (d, 1H, J )
7.8 Hz, H3pyr), 7.38 (m, 1H, H5pyr), 7.17 (2H, d, J ) 8.0 Hz, Hb′),
6.85 (d, 2H, J ) 8.0 Hz, Hc’), 4.48 (bs, 1H, pyr-CH2-S), 4.18 (bs,-
1H, pyr-CH2-S), 2.26 (s, 3H, CH3C6H4-Pd,), 2.25 (s, 3H, S-CH3).
Anal. Calcd for C14H16INPdS: C 36.26, H 3.48, N 3.02. Found:
C 36.39, H 3.52, N 2.96.
The structures of both complexes were solved by means of the
direct methods and refined by standard full-matrix least-squares
2
based on Fo . The structure solution and refinement were performed
by means of the computer programs SHELXTL NT35 and SHELXL-
9736 using scattering factors incorporated in SHELXL-97. In the
last cycles of refinement, all the non-H atoms were allowed to
vibrate anisotropically, whereas the H atoms were included in ideal
positions and refined as a “riding model”. In both structures, the
Uiso values of hydrogen atoms were set at 1.2 times Ueq of the
appropriate carrier atom. Crystallographic data and refinement
parameters for 1 and 2 are reported in the Supporting information
in Tables 1SI and 2SI; no anomalous feature was detected. Tables
3SI and 4SI list relevant bond distances and angles for 1 and 2,
respectively.
Synthesis of the Ligands. The synthesis of the ligands 2-methyl-
thiomethylpyridyne (NS-Me), 2-tert-buylthiomethylpyridine (NSt-
Bu),37 8-diphenylphosphanyl-2-methylquinoline (DPPQ-Me),3 and
8-diphenylphosphanylquinoline (DPPQ)38 was carried out according
to published procedures.
Synthesis of the Complexes [Pd(NS-R)(Me)X]. The synthesis
of the title complexes [Pd(NS-R)(Me)X] (R ) Me, Et, i-Pr, t-Bu;
X ) Cl, I) was carried out according to published procedures.8a,23
The following complexes were prepared under conditions
analogous to those of [Pd(NS-Me)(tolyl)I] using the appropriate
ligand.
Synthesis of the Complex [Pd(DPPQ)(Me)Cl]. To 0.1317 g
(0.42 mmol) of DPPQ ligand dissolved in 16 mL of anhydrous
toluene was added 0.100 g (0.38 mmol) of the complex [Pd(COD)-
(Me)Cl]39 under inert atmosphere (Ar). The resulting whitish
suspension was stirred at RT for 4 h and dried under reduced
pressure. The solid residue was dissolved in CH2Cl2 (10 mL), treated
with activated charcoal, and filtered on a Celite filter. Reduction
of the resulting volume under reduced pressure and addition of
diethyl ether yielded 0.1615 g (0.342 mmol) of the complex as a
[Pd(NSt-Bu)(tolyl)I]. Yield: 81%, pink-yellow powder. 1H
NMR (CDCl3, 298 K, δ(ppm)): 9.69 (d, 1H, J ) 5.4 Hz, Py-H6),
7.79 (td, 1H, J ) 7.7 Hz, J ) 1.7 Hz, H4pyr), 7.45 (d, 1H, J ) 7.8
Hz, H3pyr), 7.33 (m, 1H, H5pyr), 7.21 (d, 2H, J ) 8.1 Hz, Hb′), 6.82
(d, 2H, J ) 7.6 Hz, Hc′), 4.36 (bs, 2H, pyr-CH2-S), 2.25 (s, 3H,
CH3 C6H4-Pd), 1.21 (s, 9H, S-C(CH3)3). Anal. Calcd for C17H22-
INPdS: C 40.37, H 4.38, N 2.77. Found: C 40.41, H 4.32, N 2.89.
[Pd(DPPQ)(tolyl)I]. Yield: 81%, pink-yellow powder. 1H NMR
(CDCl3, 298 K, δ(ppm)): 10.53 (dd, 1H, Qui-H2), 8.44 (d, 1H, J
) 8.2 Hz, Qui-H4), 8.09 (d, 1H, J ) 8.1 Hz, Qui-H5), 7.92 (m, 1H,
Qui-H6), 7.68 (m, 2H, Qui-H3, Qui-H7), 7.41 (m, 10H, P(C6H5)2),
6.92 (d, 2H, J ) 6.7 Hz, Hb′), 6.64 (d, 2H, J ) 7.7 Hz, Hc′), 2.16
(s, 3H, CH3 C6H4-Pd). 31P{1H} NMR (CDCl3, 298 K, δ(ppm)):
27.4. Anal. Calcd for C28H23INPPd: C 52.73, H 3.63, N 2.20.
Found: C 52.84, H 3.77, N 2.15.
1
white powder. Yield: 90%. H NMR (CDCl3, 298 K, δ(ppm)):
10.02 (dd, 1H, J ) 1.6 Hz, J ) 4.8 Hz, Qui-H2), 8.40 (d, 1H, J )
8.3 Hz, Qui-H4), 8.08 (d, 1H, J ) 8.1 Hz, Qui-H5), 7.98 (m, 1H,
Qui-H7), 7.68 (m, 6H), 7.47 (m, 6H), 0.91 (d, 3H, J ) 2.6 Hz,
CH3-Pd). 31P{1H} NMR (CDCl3, 298 K, δ(ppm)): 39.9. Anal.
Calcd for C22H19ClNPPd: C 56.19, H 4.07, N 2.98. Found: C
56.12, H 4.14, N 3.03.
Synthesis of the Complex [Pd(DPPQ-Me)(Me)Cl]. The title
complex was prepared under conditions analogous to those used
for the former substrate using DPPQ-Me as ligand. Yield: 85%
Synthesis of the Inserted Complexes. DIC Derivatives.
Synthesis of the Complex [Pd(NS-Me)(C(dNR2)Me)Cl], R2 )
2,6-Me2C6H3. To 0.100 g (0.34 mmol) of [Pd(NS-Me)(Me)Cl]
and 0.0947 g of NS-Me dissolved in 9 mL of anhydrous CH2Cl2
was added dropwise 0.0446 g (0.34 mmol) of DIC in 2 mL of CH2-
Cl2 under inert atmosphere (Ar). The resulting yellow solution was
stirred for 1 h and finally dried under reduced pressure. Diethyl
ether was added to the residue, and the ensuing suspension was
filtered off, washed twice with small aliquots of diethyl ether to
remove the ligand in excess and eventually with pentane, and dried
under vacuum at RT; 0.117 g of yellow microcrystals were obtained
(yield 81%). 1H NMR (CDCl3, 298 K, δ(ppm)): 9.13 (d, 1H, J )
4.6 Hz, Py-H6), 7.77 (td, 1H, J ) 7.5 Hz, J ) 1.7 Hz, H4pyr), 7.36
(m, 2H, H3pyr, H5pyr), 6.97 (d, 2H, J ) 7.3 Hz, Hc), 6.85 (t, 1H, J
) 7.4 Hz, Hd), 4.12-3.82 (bd, 2H, pyr-CH2-S), 2.55 (s, 3H,
1
(whitish microcrystals). H NMR (CDCl3, 298 K, δ(ppm)): 8.15
(33) Mackay, S.; Gilmore, C. J.; Edwards, C.; Stewart, N.; Shankland,
K. maXus, computer program for the solution and refinement of crystal
structures; Nonius: The Nederlands, MacScience: Japan, and the Univeristy
of Glasgow, 1999.
(34) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Gagliardi, A.; Burla,
M. C.; Polidori, G.; Cavalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(35) Sheldrick, G. M. SHELXTL NT, Version 5.10; Bruker AXS Inc.:
Madison, WI, 1999.
(36) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Germany, 1997.
(37) Canovese, L.; Visentin, F.; Uguagliati, P.; Chessa, G.; Pesce, A. J.
Organomet. Chem. 1998, 566, 61.
(38) Wehman, P.; van Donge, H. M. A.; Hagos, A.; Kamer, P. C. J.;
van Leeuwen, P. W. N. M. J. Organomet. Chem. 1997, 535, 183.
(39) Rudler-Chavin, M.; Rudler, H. J. Organomet. Chem. 1977, 134,
15.
(40) Alsters, P. L.; Boersma, J.; van Koten, G. Organometallics 1993,
12, 1629.

Insertion of Isocyanides across the Pd-C Bond
Organometallics, Vol. 26, No. 23, 2007 5599
7.73 (td, 1H, J ) 7.7 Hz, J ) 1.7 Hz, H4pyr), 7.33 (m, 2H, H3
C(CH3)dNR2), 2.34 (s, 6H, (C6H3-(CH3)2)), 1.73 (s, 3H, S-CH3).
13C{1H} NMR (CDCl3, 298 K, δ(ppm)): 176.4 (C(CH3)dNR2),
154.4 (C2pyr), 150.8 (C6pyr), 148. 2 (Cb), 138.3 (C4pyr), 128.0 (Ca),
127.8 (Cc), 123.72 (C3pyr), 123.3 (C5pyr), 122.5 (Cd), 45.1 (pyrCH2S),
31.8 (C(CH3)dNR2), 20.9 (S-CH3), 19.1 (C6H3-(CH3)2). IR (KBr,
cm-1): 1656 νCdN. Anal. Calcd for C17H21ClN2PdS: C 47.78, H
4.95, N 6.56. Found: C 47.81, H 4.91, N 6.45.
,
pyr
H5pyr), 7.15 (d, 2H, J ) 8.0 Hz, Hc′), 7.00 (d, 2H, J ) 7.4 Hz, Hc),
6.89 (t, 1H, J ) 7.4 Hz, Hd), 3.98 (bs, 2H, pyrCH2-S), 2.40 (s, 3H,
C(C6H4CH3)dNR2), 2.36 (s, 6H, (C6H3-(CH3)2)), 1.79 (s, 3H,
S-CH3). 13C{1H} NMR (CDCl3, 298 K, δ(ppm)): 170.5 (C(C6H4-
CH3)NR2), 154.9 (C2pyr), 153.6 (C6pyr), 148.4 (Cb), 141.2 (Ca′), 138.6
(Cd′), 138.1 (C4pyr), 129.3 (Cb′), 128.2 (Cc′), 128.2 (Ca), 127.8 (Cc),
124.1 (C3pyr), 123.4 (C5pyr), 122.5 (Cd), 44.4 (pyrCH2S), 21.3
(C(C6H4CH3)dNR2), 20.5 (S-CH3), 20.45 (C6H3-(CH3)2). IR (KBr,
cm-1): 1624 νCdN. Anal. Calcd for C23H25IN2PdS: C 46.44, H
4.24, N 4.71. Found: C 46.53, H 4.13, N 4.69.
The following complexes were prepared under conditions
analogous to those of [Pd(NS-Me)(C(dNR2)Me)Cl] (R2 ) 2,6-
Me2C6H3) using the appropriate isocyanide and starting complex.
[Pd(NS-Me)(C(dNR2)Me)I], R2 ) 2,6-Me2C6H3. Yield: 83%,
[Pd(NSt-Bu)(C(dNR2)tolyl)I], R2 ) 2,6-Me2C6H3. Yield: 90%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.48
1
(d, 1H, J ) 4.6 Hz, Py-H6), 7.76 (td, 1H, J ) 7.5 Hz, J ) 1.7 Hz,
H4pyr), 7.35 (m, 2H, H3pyr, H5pyr), 6.96 (d, 2H, J ) 7.3 Hz, Hc),
6.83 (t, 1H, J ) 7.4 Hz, Hd), 4.17 (bs, 2H, pyr-CH2-S), 2.45 (s,
3H, C(CH3)dNR2), 2.28 (s, 6H, (C6H3-(CH3)2)), 2.06 (s, 3H,
S-CH3). IR (KBr, cm-1): 1618 ν(CdN). Anal. Calcd for C17H21IN2-
PdS: C 39.36, H 4.08, N 5.40. Found: C 39.45, H 3.99, N 5.29.
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.57
(d, 1H, J ) 4.4 Hz, Py-H6), 8.24 (d, 2H, J ) 7.9 Hz, Hb′), 7.70 (td,
1H, J ) 7.7 Hz, J ) 1.7 Hz, H4pyr), 7.27 (m, 2H, H3pyr, H5pyr), 7.14
(d, 2H, J ) 8.0 Hz, Hc′), 6.97 (d, 2H, J ) 7.4 Hz, Hc), 6.88 (t, 1H,
J ) 7.2 Hz, Hd), 3.75 (bs, 2H, pyr-CH2-S), 2.43 (s, 3H, C(PhCH3)d
NR2), 2.36 (s, 6H, (C6H3-(CH3)2)), 1.06 (s, 9H, S-C(CH3)3). 13C-
{1H} NMR (CDCl3, 298 K, δ(ppm)): 169.8 (C(C6H4CH3)dNR2),
156.7 (C2pyr), 152.9 (C6pyr), 148.1 (Cb), 141.2 (Ca′), 139.0 (Cd′), 138.2
(C4pyr), 131.2 (Cb′), 127.9 (Cc′), 127.5 (Ca), 127.6 (Cc), 123.8 (C3pyr),
122.2 (C5pyr), 121.8 (Cd), 50.2 ((CH3)3C), 40.9 (pyr-CH2S), 30.3
(S-C(CH3)3), 21.3 (C(C6H4CH3)dNR2), 21.1 (C6H3-(CH3)2). IR
(KBr, cm-1): 1608 νCdN. Anal. Calcd for C26H31IN2PdS: C 49.03,
H 4.91, N 4.40. Found: C 48.97, H 4.98, N 4.42.
[Pd(NSt-Bu)(C(dNR2)Me)Cl], R2 ) 2,6-Me2C6H3.Yield: 88%,
1
pale yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.13 (d,
1H, J ) 4.8 Hz, Py-H6), 7.74 (t, 1H, J ) 7.7 Hz, H4pyr), 7.31 (m,
2H, H3pyr, H5pyr), 6.95 (d, 2H, J ) 7.1 Hz, Hc), 6.86 (m, 1H, Hd),
3.77 (bs, 2H, pyr-CH2-S)), 2.53 (s, 3H, C(CH3)dNR), 2.34 (bs,
6H, (C6H3-(CH3)2)), 1.30 (s, 9H, S-C(CH3)3). 13C{1H} NMR
(CDCl3, 298 K, δ(ppm)): 177.0 (C(CH3)dNR2), 156.3 (C2pyr),
150.1 (C6pyr), 148.1 (Cb), 138.4 (C4pyr), 128.7 (Ca), 127.7 (Cc), 123.5
(C3pyr), 122.2 (C5pyr), 121.6 (Cd), 50.3 (S-C(CH3)3), 40.8 (pyr-CH2S),
31.9 (C(CH3)dNR2), 30.5 (S-C(CH3)3), 19.6 (C6H3-(CH3)2). IR
(KBr, cm-1): 1635 νCdN. Anal. Calcd for C20H27ClN2PdS: C 51.18,
H 5.80, N 5.97. Found: C 51.07, H 5.93, N 6.03.
[Pd(DPPQ)(C(dNR2)Me)Cl], R2 ) 2,6-Me2C6H3. Yield: 88%,
pale yellow powder. 1H NMR (CDCl3, 298 K, δ(ppm)): 9.97 (dd,
1H, J ) 1.6 Hz, 4.8 Hz, Qui-H2), 8.39 (d, 1H, J ) 8.3 Hz, Qui-
H4), 8.06 (d, 1H, J ) 8.1 Hz, Qui-H5), 7.88 (m, 5H, Qui-H6,
P(C6H2)2), 7.68 (m, 2H, Qui-H7 H3), 7.46 (m, 6H, P(C6H2)2), 6.87
,
(d, 2H, J ) 7.4 Hz, Hc), 6.75 (t, 1H, J ) 7.3 Hz, Hd), 1.87 (s, 6H,
(C6H3-(CH3)2)), 1.83 (d, 3H, J ) 1.9 Hz, C(CH3)dNR2). 13C{1H}
NMR (CDCl3, 298 K, δ(ppm)): 178.9 (d, JCP ) 11.5 Hz, C(CH3)d
NR2), 153.6 (C2quin), 149.9 (C9quin), 149.7 (C10quin), 149.5 (Cb), 138.4
(C4quin), 136.4 (C6quin), 134.5 (d, J ) 43.9 Hz, C8quin), 134.0 (CP(Ph)),
131.5 (d, JCP )2.2 Hz, C5quin,), 131.2 (CP(Ph)), 129.2 (CP(Ph)), 129.0
(CP(Ph)), 127.4 (d, J ) 7.1 Hz, C7quin), 127.3 (Cc), 123.0 (C3quin),
121.5 (Cd), 28.3 (d, JCP ) 11.0 Hz, C(CH3)dNR2), 18.5 (C6H3-
(CH3)2). 31P{1H} NMR (CDCl3, 298 K, δ(ppm)): 22. 3. IR (KBr,
cm-1): 1624 νCdN. Anal. Calcd for C31H28ClN2PPd: C 61.91, H
4.69, N 4.66. Found: C 62.02, H 4.81, N 4.54.
[Pd(NSt-Bu)(C(dNR2)Me)I], R2 ) 2,6-Me2C6H3. Yield: 84%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.52
(d, 1H, J ) 4.8 Hz, Py-H6), 7.73 (t, 1H, J ) 7.7 Hz, H4pyr), 7.31
(m, 2H, H3pyr, H5pyr), 6.95 (d, 2H, J ) 7.1 Hz, Hc), 6.84 (m, 1H,
Hd), 4.04 (s, 2H, pyr-CH2-S)), 2.46 (s, 3H, C(CH3)dNR2), 2.32 (s,
6H, (C6H3-(CH3)2)), 1.32 (s, 9H, S-C(CH3)3). IR (KBr, cm-1): 1633
νCdN. Anal. Calcd for C20H27IN2PdS: C 42.83, H 4.85, N 4.99.
Found: C 42.71, H 4.91, N 4.86.
[Pd(NS-Et)(C(dNR2)Me)Cl], R2 ) 2,6-Me2C6H3. Yield: 86%,
pale yellow powder. 1H NMR (CDCl3, 298 K, δ(ppm)): 9.12 (dd,
1H, J ) 5.6 Hz, 1.8 Hz, Py-H6), 7.75 (td, 1H, J ) 7.7 Hz, J ) 1.6
Hz, H4pyr), 7.33 (m, 2H, H3pyr, H5pyr), 6.97 (d, 2H, J ) 7.4 Hz, Hc),
6.86 (t, 1H, J ) 7.3 Hz, Hd), 3.94 (bm, 2H, pyr-CH2-S), 2.54 (s,
3H, C(CH3)dNR2), 2.32 (s, 6H, (C6H3-(CH3)2)), 2.10 (m, 2H,
S-CH2CH3), 1.12 (t, 3H, J ) 7.3 Hz, S-CH2CH3). 13C{1H} NMR
(CDCl3, 298 K, δ(ppm)): 176.7 (C(CH3)dNR2), 154.9 (C2pyr),
150.6 (C6pyr), 148.4 (Cb), 138.3 (C4pyr), 127.9 (Ca), 127.6 (Cc), 123.6
(C3pyr), 122.9 (C5pyr), 122.4 (Cd), 42.2 (pyrCH2S), 31.8 (C(CH3)d
NR2), 31.4 (S-CH2CH3), 19.4 (C6H3-(CH3)2), 13.8 (S-CH2CH3). IR
(KBr, cm-1): 1642 νCdN. Anal. Calcd for C18H23ClN2PdS: C 48.99,
H 5.25, N 6.35. Found: C 49.13, H 5.11, N 6.41.
[Pd(DPPQ-Me)(C(dNR2)Me)Cl], R2
)
2,6-Me2C6H3.
1
Yield: 86%, pale yellow powder. H NMR (CDCl3, 298 K, δ-
(ppm)): 8.12 (d, 1H, J ) 8.4 Hz, Qui-H4), 7.92 (d, 1H, J ) 7.7
Hz, Qui-H3), 7.79-7.38 (m, 13H, aromatic protons), 6.88 (m 3H,
dN-C6H3(CH3)2), 3.26 (s, 3H, quin-CH3), 1.95 (s, 6H, dN-C6H3-
(CH3)2), 1.88 (d, 3H, dN-CH3, J ) 1.8 Hz). 31P{1H} NMR (CDCl3,
298 K, δ(ppm)): 21.5. IR (KBr, cm-1): 1630 νCdN. Anal. Calcd
for C32H30ClN2PPd: C 62.45, H 4.91, N 4.55. Found: C 62.51, H
4.87, N 4.49.
[Pd(DPPQ)(C(dNR2)Me)I], R2 ) 2,6-Me2C6H3. Yield: 93%,
1
[Pd(NSi-Pr)(C(dNR2)Me)Cl], R2 ) 2,6-Me2C6H3. Yield: 85%,
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 10.36
(d, 1H, J ) 4.8 Hz, Qui-H2), 8.37 (d, 1H, J ) 8.3 Hz, Qui-H4),
8.06 (d, 1H, J ) 8.1 Hz, Qui-H5), 7.88 (m, 5H), 7.64 (m, 2H),
7.48 (m, 6H), 6.85 (d, 2H, J ) 7.4 Hz, Hc), 6.74 (t, 1H, J ) 7.3
Hz, Hd), 1.87 (s, 6H, (C6H3-(CH3)2)), 1.86 (d, 3H, J ) 1.9 Hz,
C(CH3)dNR2). 31P{1H} NMR (CDCl3, 298 K, δ(ppm)): 16.6. IR
(KBr, cm-1): 1622 νCdN. Anal. Calcd for C31H28IN2PPd: C 53.74,
H 4.07, N 4.04. Found: C 53.81, H 4.11, N 3.93.
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.11
(d, 1H, J ) 5.3 Hz, Py-H6), 7.74 (td, 1H, J ) 7.7 Hz, J ) 1.6 Hz,
H4pyr), 7.33 (m, 2H, H3pyr, H5pyr), 6.96 (d, 2H, J ) 7.1 Hz, Hc),
6.86 (t, 1H, J ) 7.4 Hz, Hd), 3.73 (bs, 2H, pyr-CH2-S), 2.69 (m,
1H, S-CH(CH3)2), 2.52 (s, 3H, C(CH3)dNR2), 2.33 (bs, 6H, (C6H3-
(CH3)2), 1.30 (bs, 6H, S-CH(CH3)2). 13C{1H} NMR (CDCl3, 298
K, δ(ppm)): 176.8 (C(CH3)NR2), 155.6 (C2pyr), 150.5 (C6pyr), 148.4
(Cb), 138.3 (C4pyr), 127.5 (Ca), 127.5 (Cc), 123.6 (C3pyr), 122.2
(C5pyr), 122.2 (Cd), 40.9 (pyrCH2S), 31.7 (C(CH3)dNR2), 29.6 (S-
CH(CH3)2), 22.3 (S-CH(CH3)2), 19.5 (C6H3-(CH3)2). IR (KBr,
cm-1): 1616 νCdN. Anal. Calcd for C19H25ClN2PdS: C 50.12, H
5.53, N 6.15. Found: C 50.21, H 5.61, N 6.02.
[Pd(DPPQ)(C(dNR2)tolyl)I], R2 ) 2,6-Me2C6H3. Yield: 88%,
orange-yellow powder. 1H NMR (CD2Cl2, 298 K, δ(ppm)): 10.42
(dd, 1H, J ) 1.6 Hz, J ) 5.0 Hz, Qui-H2), 8.42 (d, 1H, J ) 8.2
Hz, Qui-H4), 8.05 (d, 1H, J ) 8.0 Hz, Qui-H5), 7.81 (m,1H, Qui-
H6), 7.68 (m, 7H, Qui-H3, Qui-H7 HP(Ph2), 7.45 (m, 2H), 7.30 (m,
,
[Pd(NS-Me)(C(dNR2)tolyl)I], R2 ) 2,6-Me2C6H3. Yield:
3H), 7.03 (d, 2H, J ) 8.1 Hz), 6.78 (d, 2H, 7.5 Hz), 6.69 (m, 1H),
6.59 (d, 2H, J ) 8.2 Hz), 2.16 (s, 3H, C(C6H4CH3)dNR2), 1.93 (s,
6H, (C6H3-(CH3)2). 31P{1H} NMR (CDCl3, 298 K, δ(ppm)): 21.6.
1
91%, orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)):
9.50 (d, 1H, J ) 5.4 Hz, Py-H6), 8.02 (d, 2H, J ) 8.0 Hz, Hb′),

5600 Organometallics, Vol. 26, No. 23, 2007
CanoVese et al.
IR (KBr, cm-1): 1611 νCdN. Anal. Calcd for C37H32IN2PPd: C
57.79, H 4.19, N 3.64. Found: C 57.67, H 4.23, N 3.61.
7.44 (d, 1H, J ) 7.7 Hz, H3pyr), 7.37 (m, 3H, H5pyr, Hc), 7.08 (d,
2H, J ) 7.9 Hz, Hc), 5.66 (d, 1H, J ) 14.3 Hz, CH2-SO2), 5.43 (d,
1H, J ) 14.3 Hz, CH2-SO2), 4.66 (d, 1H, J ) 16.7 Hz, pyr-CH2-S)
4.19 (d, 1H, J ) 16.7 Hz, pyr-CH2-S), 2.43 (s, 3H, SO2-C6H4CH3),
2.32 (s, 3H, C(C6H4CH3)dNR2), 1.01 (s, 9H, S-C(CH3)3). 13C{1H}
NMR (CDCl3, 298 K, δ(ppm)): 181.1 (C(C6H4CH3)dNR2), 157.3
(C2), 152.8 (C6), 144.1 (Cd′), 140.9 (Ca), 139.4(Cd), 138.6 (C4), 135.7
(Ca′), 130.0 (Cb), 129.3 (Cc′), 129.1 (Cb′), 128.2 (Cc), 124. 2 (C3),
121.9 (C5), 80.3 (CH2SO2), 50.9 (C(CH3)3), 41.0 (CH2S), 30.1 (SC-
(CH3)3), 21.6 (SO2 C6H4CH3′), 21.3 (C(C6H4CH3)dNR2). IR (KBr,
cm-1): 1594 νCdN. Anal. Calcd for C26H31IN2O2PdS2: C 44.55, H
4.46, N 4.00. Found: C 44.61, H 4.38, N 4.12.
[Pd(DPPQ)(C(dNR2)Me)Cl], R2 ) CH2tosyl. Yield: 90%,
white powder. 1H NMR (CDCl3, 298 K, δ(ppm)): 9.84 (dd, 1H, J
) 1.6 Hz, 4.8 Hz, Qui-H2), 8.44 (d, 1H, J ) 8.3 Hz, Qui-H4), 8.11
(d, 1H, J ) 8.1 Hz, Qui-H5), 7.86 (m, 1H, Qui-H6), 7.74 (m, 6H),
7.51 (m, 8H), 7.28 (m, 2H), 5.18 (d, 1H, J ) 14.7 Hz, CH2-SO2)
4.30 (d, 1H, J ) 14.7 Hz, CH2-SO2), 2.42 (s, 3H, CH3- C6H4SO2),
2.10 (bs, 3H, C(CH3)dNR2). 31P{1H} NMR (CDCl3, 298 K, δ-
(ppm)): 28.1. IR (KBr, cm-1): 1614 νCdN. Anal. Calcd for C31H28-
ClN2O2PPdS: C 55.95, H 4.24, N 4.21. Found: C 55.79, H 4.37,
N 4.15.
[Pd(DPPQ-Me)(C(dNR2)Me)Cl], R2 ) CH2tosyl. Yield: 89%,
white powder. 1H NMR (CDCl3, 298 K, δ(ppm)): 8.18 (d,1H, J )
8.5 Hz, Qui-H4), 7.97 (d, 1H, J ) 8.5 Hz, Qui-H5), 7.89 (m, 1H,
Qui-H6) 7.75-7.42 (m, 14 H, aromatic protons), 7.23 (d, 2H, J )
8.1 Hz, Hc), 5.29 (d, 1H, J ) 14.7 Hz, CH2SO2), 5.04 (d, 1H, J )
14.7 Hz, CH2SO2), 3.28 (s, 3H, quin-CH3), 2.40 (s, 3H, CH3PhSO2),
1.89, (s, 3H, C(CH3)dNR2). 31P{1H} NMR (CDCl3, 298 K,
δ(ppm)): 27.3. IR (KBr, cm-1): 1626 νCdN. Anal. Calcd for C32H30-
ClN2O2PPdS: C 56.56, H 4.45, N 4.12. Found: C 56.55, H 4.41,
N 4.23.
TosMIC Derivatives. [Pd(NS-Me)(C(dNR2)Me)Cl], R2 )
CH2tosyl. Yield: 83%, whitish powder. 1H NMR (CDCl3, 298 K,
δ(ppm)): 9.04 (d, 1H, J ) 5.0 Hz, Py-H6), 7.85 (m, 3H, Hb, H4Pyr),
7.49 (d, 1H, J ) 7.7 Hz, H3pyr), 7.43 (t, 1H, J ) 6.5 Hz, H5pyr),
7.34 (d, 2H, J ) 8.1 Hz, Hc), 5.72-5.19 (bd, 2H, CH2-SO2), 4.48-
4.11 (bs, 2H, pyr-CH2-S), 2.54 (s, 3H, CH3 C6H4SO2), 2.45 (s, 3H,
C(CH3)dNR2), 2.36 (s, 3H, S-CH3). 13C{1H} NMR (CDCl3, 298
K, δ(ppm)): 179.8 (C(CH3)dNR2), 154.9 (C2), 150.3 (C6), 144.4
(Cd), 138.8 (C4), 135.6 (Cc), 129.5 (Cb), 128.8 (Cc), 124.1 (C3),
123.2 (C5), 77.1 (CH2SO2), 45.6 (CH2S), 32.1 (C(CH3)dNR2), 22.0
(S-CH3), 21.6 (SO2 C6H4CH3). IR (KBr, cm-1): 1627 νCdN. Anal.
Calcd for C17H21ClN2O2PdS2: C 41.55, H 4.31, N 5.70. Found: C
42.44, H 4.45, N 5.61.
[Pd(NS-Me)(C(dNR2)Me)I], R2 ) CH2tosyl. Yield: 85%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.32
(d, 1H, J ) 5.0 Hz, Py-H6), 7.84 (m, 3H, Hb, H4Pyr), 7.48 (d, 1H,
J ) 7.7 Hz, H3pyr), 7.39 (t, 1H, J ) 6.5 Hz, H5pyr), 7.34 (d, 2H, J
) 8.1 Hz, Hc), 5.60 (d, 1H, J ) 13.4 Hz, CH2-SO2), 5.18 (d, 1H,
J ) 13.4 Hz, CH2-SO2), 4.35 (bs, 2H, pyr-CH2-S), 2.47 (s, 3H,
SO2-C6H4CH3), 2.44 (s, 3H, C(CH3)dNR), 2.39 (s, 3H, S-CH3).
IR (KBr, cm-1): 1624 νCdN. Anal. Calcd for C17H21IN2O2PdS2:
C 35.03, H 3.63, N 4.81. Found: C 35.16, H 3.49, N 4.71.
[Pd(NSt-Bu)(C(dNR2)Me)Cl], R2 ) CH2tosyl. Yield: 81%,
1
pale yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.03 (d,
1H, J ) 5.0 Hz, Py-H6), 7.88 (d, 2H, J ) 8.2 Hz, Hb), 7.82 (td,
1H, J ) 7.7 Hz, J ) 1.4 Hz, H4pyr), 7.45 (d, 1H, J ) 7.7 Hz, H3pyr),
7.38 (t, 1H, J ) 6.5 Hz, H5pyr), 7.32 (d, 2H, J ) 8.1 Hz,Hc), 5.42
(d, 1H, J ) 14.3 Hz, CH2-SO2) 5.32 (d, 1H, J ) 14.3 Hz, CH2-
SO2), 4.31 (m, 2H, pyr-CH2-S), 2.44 (s, 3H, SO2-C6H4CH3), 2.37
(s, 3H, C(CH3)dNR2), 1.34 (s, 9H, S-C(CH3)3). 13C{1H} NMR
(CDCl3, 298 K, δ(ppm)): 186.0 (C(CH3)dNR2), 156.3 (C2), 150.1
(C6), 144.1 (Cd), 138.8 (C4), 135.4 (Cc), 129.3 (Cb), 129.0 (Cc),
123.8 (C3), 121.7 (C5), 77.1 (CH2SO2), 51.2 SC(CH3)3, 41.0 (CH2S),
32.9 (C(CH3)dNR2), 30.3 (S(CH3)3), 21.6 (SO2 C6H4CH3). IR (KBr,
cm-1): 1625 νCdN. Anal. Calcd for C20H27ClN2O2PdS2: C 45.03,
H 5.10, N 5.25. Found: C 44.91, H 5.27, N 5.23.
[Pd(DPPQ)(C(dNR2)Me)I], R2 ) CH2tosyl. Yield: 87%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 10.18
(dd, 1H, J ) 1.6 Hz, 4.8 Hz, Qui-H2), 8.43 (d, 1H, J ) 8.3 Hz,
Qui-H4), 8.08 (d, 1H, J ) 8.1 Hz, Qui-H5), 7.89 (m, 1H, Qui-H6),
7.81-7.42 (m, 14H), 5.05 (d, 1H, J ) 15.1 Hz, CH2-SO2), 4.10
(d, 1H, J ) 15.1 Hz, CH2-SO2), 2.42 (s, 3H, SO2 C6H4CH3), 2.11
(s, 3H, C(CH3)dNR2). 31P{1H } NMR (CDCl3, 298 K, δ(ppm)):
22.2. IR (KBr, cm-1): 1619 νCdN. Anal. Calcd for C31H28IN2O2-
PPdS: C 49.19, H 3.73, N 3.70. Found: C 49.27, H 3.79, N 3.81.
[Pd(NSt-Bu)(C(dNR2)Me)I], R2 ) CH2tosyl. Yield: 82%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.28
(d, 1H, J ) 5.0 Hz, Py-H6), 7.85 (d, 2H, J ) 8.2 Hz, Hb), 7.79 (td,
1H, J ) 7.7 Hz, J ) 1.4 Hz, H4pyr), 7.45 (d, 1H, J ) 7.7 Hz, H3pyr),
7.32 (m, 3H, H5pyr, Hc), 5.29 (d, 1H, J ) 14.2 Hz, CH2-SO2), 5.18
(d, 1H, J ) 14.2 Hz, CH2-SO2), 4.32 (ABsys, 2H 4.38, 4.28, J )
16.8 Hz, pyr-CH2-S), 2.44 (s, 3H, SO2-C6H4CH3), 2.42 (s, 3H,
C(CH3)dNR2), 1.30 (s, 9H, S-C(CH3)3). IR (KBr, cm-1): 1622
[Pd(DPPQ)(C(dNR2)tolyl)I], R2 ) CH2tosyl. Yield: 90%,
1
orange-yellow powder. H NMR (CDCl2, 298 K, δ(ppm)): 10.31
(dd, 1H, J ) 1.6 Hz, J ) 5.0 Hz, Qui-H2), 8.44 (d, 1H, J ) 8.2
Hz, Qui-H4), 8.08 (d, 1H, J ) 8.0 Hz, Qui-H5), 7.78 (m, 3H, Hb′,
Qui-H7), 7.68 (m, 4H, Hb, Qui-H3, Qui-H6), 7.49 (m, 6H, HPPh2),
7.21 (m, 2H, Hc′), 7.10 (m, 4H, HPPh2), 6.78 (d, 2H, 7.5 Hz, Hc),
5.30 (d, 1H, J ) 15.4 Hz, CH2-SO2), 4.57 (d, 1H, J ) 15.4 Hz,
CH2-SO2), 2.38 (s, 3H, SO2-C6H4CH3), 2.22 (s, 3H, C(C6H4CH3)d
NR2). 13C{1H} NMR (CDCl3, 298 K, δ(ppm)): 184.1 (C(C6H4-
CH3)dNR2), 157.4 (C2quin), 150.1 (d, 19.8 Hz, C9quin), 143.7 (Cd′),
140.2 (d, 9.3 Hz, Ca), 138.9 (C4quin), 138.2 (Cd), 137.4 (C6quin), 135.8
(Ca′), 133.5 (d, 42 Hz, C8quin), 132.9, 132.8, 132.6, 132.4, 132.1
(C5quin), 131.5, 130.3, 129.7, 129.6 (Cb′, Cb), 129.5, 129.1 (Cc′),
128.6, 128.4 (d, 4.5 Hz, C7quin), 127.7 (Cc), 123.6 (C3quin), 79.6 (CH2-
SO2), 21.5 (SO2-(C6H4CH3)), 21.1 (C(C6H4CH3)dNR2). 31P{H}
NMR (CDCl3, 298 K, δ(ppm)): 22.7. IR (KBr, cm-1): 1593 νCd
N. Anal. Calcd for C37H32IN2O2PPdS: C 53.35, H 3.87, N 3.36.
Found: C 53.26, H 3.79, N 3.43.
νCdN. Anal. Calcd for C20H27IN2O2PdS2: C 38.44, H 4.36, N 4.48.
Found: C 38.51, H 4.47, N 4.47.
[Pd(NS-Me)(C(dNR2)tolyl)I], R2 ) CH2tosyl. Yield: 85%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.48
(d, 1H, J ) 5.0 Hz, Py-H6), 7.96 (d, 2H, J ) 8.1 Hz, Hb), 7.92 (d,
2H, J ) 8.1 Hz, Hb′), 7.81 (td, 1H, J ) 7.7 Hz, J ) 1.5 Hz, H4pyr),
7.43 (d, 1H, J ) 7.7 Hz, H3pyr), 7.37 (m, 3H, H5pyr, Hc′), 7.10 (d,
2H, J ) 7.9 Hz, Hc), 5.89-5.35 (bd, 2H, CH2-SO2), 4.52-407
(bs, 2H, pyr-CH2-S), 2.46 (s, 3H, C(C6H4CH3)dNR2), 2.34 (s, 3H,
SO2-C6H4CH3), 1.9 (bs, 3H, S-CH3). 13C{1H} NMR (CDCl3, 298
K, δ(ppm)): 168.0 (C(C6H4CH3)dNR2), 155.9 (C2), 153.1 (C6),
144.4 (Cd′), 139.5(Cd), 138.5 (C4), 135.9 (Ca′), 129.4 (Cc′), 128.1
(Cb′), 128.4 (Cc), 124.4 (C3), 123.4 (C5), 80.3 (CH2SO2), 44.9
(CH2S),29.6(SO2C(CH3)),21.6(SO2 C6H4CH3),21.3(C(C6H4CH3)d
NR2), 20.4 (S-CH3). IR (KBr, cm-1): 1595 νCdN. Anal. Calcd for
C23H25IN2O2PdS2: C 41.92, H 3.82, N 4.25. Found: C 41.91, H
3.89, N 4.32.
Complexes Obtained in the Presence of Isocyanide in Excess.
[Pd(CNR2)(C(dNR2)Me)Cl]2, R2 ) 2,6-Me2C6H3. To 0.070 g
(0.26 mmol) of [Pd(COD)(Me)Cl] in CH2Cl2 (10 mL) was added
0.0682 g (0.52mmol; 2 equiv) of DIC isocyanide under inert
atmosphere (Ar). The resulting yellowish suspension was stirred
for 1 h, dried under vacuum, and treated with diethyl ether (5 mL).
The pale yellow solid obtained was washed twice with small
aliquots of diethyl ether to remove the COD in excess and
[Pd(NSt-Bu)(C(dNR2)tolyl)I], R2 ) CH2tosyl. Yield: 85%,
1
orange-yellow powder. H NMR (CDCl3, 298 K, δ(ppm)): 9.42
(d, 1H, J ) 5.0 Hz, Py-H6), 8.00 (d, 2H, J ) 8.1 Hz, Hb), 7.92 (d,
2H, J ) 8.1 Hz, Hb′), 7.81 (td, 1H, J ) 7.7 Hz, J ) 1.5 Hz, H4pyr),

Insertion of Isocyanides across the Pd-C Bond
Organometallics, Vol. 26, No. 23, 2007 5601
eventually with pentane; 0.0883 g of complex was obtained.
Yield: 81%. H NMR (CDCl3, 298 K, δ(ppm)): 7.25 (t, 1H, J )
C(CH3)dNR2). IR (KBr, cm-1): 1656 νCdN, 2224 νC≡N. Anal.
Calcd for C28H30ClN3O6PdS3: C 45.29, H 4.07, N 5.66. Found: C
45.18, H 3.91, N 5.82.
1
7.4 Hz, Hd), 7.12 (d, 2H, J ) 7.4 Hz, Hc), 7.05 (m, 3H, Hd′′, Hc′′),
2.52 (s, 6H, (C6H3-(CH3)2 coordinate isocyanide)), 2.40 (s, 3H,
(C6H3-(CH3)2 inserted isocyanide)), 2.36 (s, 3H, (C6H3-(CH3)2
inserted isocyanide)), 2.27 (s, 3H, (C(CH3)dNR2)). 13C{1H} NMR
(CDCl3, 298 K, δ(ppm)): 212.8 (C(CH3)dNR2), 145.4 (CNR2),
136.1(Ca), 131.0 (Cb′), 130.0 (Cd), 129.1 (Cb), 128.7, 128.4 (Cc′)
128.0 (Cc), 126.2 (Cd′), 35.0 (C(CH3)dNR2), 20.3, 19.4 (C6H4-
(CH3)2 inserted), 19.1 (C6H4-(CH3)2 coord). IR (KBr, cm-1): 1563
[Pd(CNR2)2(C(dNR2)tolyl)I], R2 ) 2,6-Me2C6H3. To 0.070 g
(0.16 mmol) of [Pd(tmeda)(tolyl)I] in CH2Cl2 (10 mL) was added
0.0643 g (0.49 mmol; 3 equiv) of DIC isocyanide under inert
atmosphere (Ar). The resulting yellowish suspension was stirred
for 1 h, dried under vacuum, and treated with diethyl ether (5 mL).
The pink-yellow solid obtained was washed twice with small
aliquots of diethyl ether to remove the tmeda in excess and
eventually with pentane; 0.0908 g of complex was obtained.
Yield: 79%. 1H NMR (CDCl3, 298 K, δ(ppm)): 8.21 (d, 2H, J )
7.4 Hz, Hb′), 7.22 (m, 4H, Hc′, Hd′′), 7.06 (d, 4H, J ) 7.4 Hz, Hc′′),
6.93 (m, 3H, Hc, Hd), 2.43 (s, 3H, C(C6H4CH3)dNR2), 2.22 (s,
12H, (C6H3-(CH3)2)2), 2.14 (s, 6H, (C6H3-(CH3)2)). IR (KBr, cm-1):
1624 νCdN, 2178 νCtN. Anal. Calcd for C34H34IN3O6PdS3: C
44.87, H 3.77, N 4.62. Found: C 45.02, H 3.89, N 4.47.
ν
CdN, 2188 νC≡N. Anal. Calcd for C38H42Cl2N4Pd2: C 54.43, H
5.05, N 6.68. Found: C 54.57, H 4.98, N 6.71.
[Pd(CNR2)2(C(dNR2)Me)Cl], R2 ) 2,6-Me2C6H3. To 0.070 g
(0.26 mmol) of [Pd(COD)(Me)Cl] in CH2Cl2 (10 mL) was added
0.1023 g (0.78 mmol; 3 equiv) of DIC isocyanide under inert
atmosphere (Ar). The resulting yellowish suspension was stirred
for 1 h, dried under vacuum, and treated with diethyl ether (5 mL).
The pale yellow solid obtained was washed twice with small
aliquots of diethyl ether to remove the COD in excess and
eventually with pentane; 0.1016 g of complex was obtained.
Acknowledgment. The authors gratefully thank Prof P.
Uguagliati for helpful discussion and Dr. R. Iacovino of the
Dipartimento di Scienze Ambientali of SUN (Caserta, Italy) for
granting access to the MACH3 diffractometer and for supervis-
ing the X-ray data collection process.
1
Yield: 71%. H NMR (CDCl3, 298 K, δ(ppm)): 7.28 (t, 2H, J )
7.4 Hz, Hd′′), 7.14 (d, 4H, J ) 7.5 Hz, Hc′′), 6.89 (m, 3H, Hd, Hc),
2.69 (s, 3H, C(CH3)dNR2), 2.41(s, 12H, (C6H3-(CH3)2)2), 2.12 (s,
6H, (C6H3-(CH3)2)). IR (KBr, cm-1): 1660 νCdN, 2180 νC≡N. Anal.
Calcd for C28H30ClN3Pd: C 61.10, H 5.49, N 7.63. Found: C 61.29,
H 5.47, N 7.72.
Supporting Information Available: Crystallographic data,
refinement parameters, bond distances and angles for complex 1
and 2 are reported in Tables 1SI, 2SI, 3SI, and 4SI, respectively.
1H-NMR spectra at 223 and 298 K of complex [Pd(NS-
Me)(C(Me)dNC6H3Me2)Cl] and the NOESY spectrum of the
complex [Pd(CNC6H3Me2)(C(dNC6H3Me2)Me)Cl]2 are reported in
Figure 1SI and 2SI, respectively. This material is available free of
charge via the Internet at http://pubs.acs.org.
[Pd(CNR2)2(C(dNR2)Me)Cl], R2 ) CH2tosyl. The synthesis
of the title compound is similar to that of the previously described
species. In this case a 3-fold excess of tosMIC isocyanide was used.
1
Yield: 83%, pale yellow powder. H NMR (CDCl3, 298 K, δ-
(ppm)): 7.88 (d, 4H, J ) 8.3 Hz, Hb′′), 7.83 (d, 2H, J ) 8.2 Hz,
Hb), 7.46 (d, 4H, J ) 8.2 Hz, Hc′′), 7.39 (d, 2H, J ) 8.0 Hz, Hc),
5.07 (s, 2H, CH2SO2), 4.82 (s, 4H, (CH2SO2 C6H4CH3)2), 2.50 (s,
6H, (SO2 C6H4CH3)2), 2.47 (s, 3H, SO2-C6H4CH3), 2.33 (s, 3H,
OM700555A