Synthesis, reactivity, structural aspects, and solution dynamics of cyclopalladated compounds of N,N′,N′′-Tris(2-anisyl)guanidine

Article abstract of DOI:10.1021/om1009445

N,N′,N′′-Tris(2-anisyl)guanidine, (ArNH)₂C=NAr (Ar = 2-(MeO)C₆H₄), was cyclopalladated with Pd(OC(O)R)₂ (R = Me, CF₃) in toluene at 70 °C to afford palladacycles [Pd{κ²(C,N)-C₆H ₃(OMe)-3(NHC(NHAr)(=NAr))-2}(μ-OC(O)R)]₂ (R = Me (1a) and CF₃ (1b)) in 87% and 95% yield, respectively. Palladacycle 1a was subjected to a metathetical reaction with LiBr in aqueous ethanol at 78 °C to afford palladacycle [Pd{κ²(C,N)-C₆H ₃(OMe)-3(NHC(NHAr)(=NAr))-2}(μ-Br)]₂ (2) in 90% yield. Palladacycle 2 was subjected to a bridge-splitting reaction with Lewis bases in CH₂Cl₂ to afford the monomeric palladacycles [Pd{κ²(C,N)-C₆H₃(OMe)-3(NHC(NHAr)(=NAr))- 2}Br(L)] (L = 2,6-Me₂C₅H₃N (3a), 2,4-Me ₂C₅H₃N (3b), 3,5-Me₂C ₅H₃N (3c), XyNC (Xy = 2,6-Me₂C ₆H₃; 4a), ^tBuNC (4b), and PPh₃ (5)) in 87-95% yield. Palladacycle 2 upon reaction with 2 equiv of XyNC in CH ₂Cl₂ afforded an unanticipated palladacycle, [Pd{κ²(C,N)-C(=NXy)(C₆H₃(OMe)-4)-2(N= C(NHAr)₂)-3}Br(CNXy)] (6) in 93% yield, and the driving force for the formation of 6 was ascribed to a ring contraction followed by amine-imine tautomerization. Palladacycles 1a,b revealed a dimeric transoid in-in conformation with "open book" framework in the solid state. In solution, 1a exhibited a fluxional behavior ascribed to the six-membered "(C,N)Pd" ring inversion and partly dissociates to the pincer type and κ²-O,O′-OAc monomeric palladacycles by an anchimerically assisted acetate cleavage process as studied by variable-temperature ¹H NMR data. Palladacycles 3a,b revealed a unique trans configuration around the palladium with lutidine being placed trans to the Pd-C bond, whereas cis stereochemistry was observed between the Pd-C bond and the Lewis base in 4a (as determined by X-ray diffraction data) and 5 (as determined by ³¹P and ¹³C NMR data). The aforementioned stereochemical difference was explained by invoking relative hardness/softness of the donor atoms around the palladium center. In solution, palladacycles 3a-c exist as a mixture of two interconverting boat conformers via a planar intermediate without any bond breaking due to the six-membered "(C,N)Pd" ring inversion, whereas palladacycles 4a,b and 5 exist as a single isomer, as deduced from detailed ¹H NMR studies.

Full text of DOI:10.1021/om1009445

572 Organometallics 2011, 30, 572–583
DOI: 10.1021/om1009445
Synthesis, Reactivity, Structural Aspects, and Solution Dynamics
of Cyclopalladated Compounds of N,N0,N00-Tris(2-anisyl)guanidine
Kanniyappan Gopi and Natesan Thirupathi*
Department of Chemistry, University of Delhi, Delhi 110 007, India
Munirathinam Nethaji
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
Received September 30, 2010
N,N0,N00-Tris(2-anisyl)guanidine, (ArNH)2CdNAr (Ar = 2-(MeO)C6H4), was cyclopalladated
with Pd(OC(O)R)2 (R = Me, CF3) in toluene at 70 °C to afford palladacycles [Pd{κ2(C,N)-C6H3-
(OMe)-3(NHC(NHAr)(dNAr))-2}(μ-OC(O)R)]2 (R=Me (1a) and CF3 (1b)) in 87% and 95% yield,
respectively. Palladacycle 1a was subjected to a metathetical reaction with LiBr in aqueous ethanol at
78 °C to afford palladacycle [Pd{κ2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-2}(μ-Br)]2 (2) in
90% yield. Palladacycle 2 was subjected to a bridge-splitting reaction with Lewis bases in CH2Cl2 to
afford the monomeric palladacycles [Pd{κ2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-2}Br(L)]
(L = 2,6-Me2C5H3N (3a), 2,4-Me2C5H3N (3b), 3,5-Me2C5H3N (3c), XyNC (Xy = 2,6-Me2C6H3;
4a), tBuNC (4b), and PPh3 (5)) in 87-95% yield. Palladacycle 2 upon reaction with 2 equiv of XyNC
in CH2Cl2 afforded an unanticipated palladacycle, [Pd{κ2(C,N)-C(dNXy)(C6H3(OMe)-4)-2(NdC-
(NHAr)2)-3}Br(CNXy)] (6) in 93% yield, and the driving force for the formation of 6 was ascribed to
a ring contraction followed by amine-imine tautomerization. Palladacycles 1a,b revealed a dimeric
transoid in-in conformation with “open book” framework in the solid state. In solution, 1a exhibited
a fluxional behavior ascribed to the six-membered “(C,N)Pd” ring inversion and partly dissociates
to the pincer type and κ2-O,O0-OAc monomeric palladacycles by an anchimerically assisted
1
acetate cleavage process as studied by variable-temperature H NMR data. Palladacycles 3a,b
revealed a unique trans configuration around the palladium with lutidine being placed trans to the
Pd-C bond, whereas cis stereochemistry was observed between the Pd-C bond and the Lewis base in
4a (as determined by X-ray diffraction data) and 5 (as determined by 31P and 13C NMR data). The
aforementioned stereochemical difference was explained by invoking relative hardness/softness of
the donor atoms around the palladium center. In solution, palladacycles 3a-c exist as a mixture of
two interconverting boat conformers via a planar intermediate without any bond breaking due to the
six-membered “(C,N)Pd” ring inversion, whereas palladacycles 4a,b and 5 exist as a single isomer, as
deduced from detailed 1H NMR studies.
Introduction
their widespread use as stoichiometric reagents in organic
synthesis, precatalysts in C-C and C-heteroatom bond-
forming reactions, metallomessogens, resolving agents, and
anticancer agents is well known.2-7 The labile Pd-C bond in
[C,N ] Palladacycles are one of the popular classes of
organometallic compounds discovered as early as 1965,1 and
*To whom correspondence should be addressed. E-mail: tnat@
chemistry.du.ac.in, thirupathi_n@yahoo.com.
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pubs.acs.org/Organometallics
Published on Web 01/05/2011
2011 American Chemical Society

Article
Organometallics, Vol. 30, No. 3, 2011 573
[C,N] palladacycles permitted intriguing insertion reactions
with small molecules such as alkynes, alkenes, alkyl/aryl iso-
cyanides, and CO to afford a wide range of organopalladium
intermediates that upon depalladation were shown to afford
various nitrogen heterocycles and carbocycles.2,3b,c,j,8 [C,N] Pal-
ladacycles with ring size from four to 11 are known, and among
these, the five-membered [C,N] palladacycles are by far the most
thoroughly studied system.
Six-membered [C,N] palladacycles are less well studied
than their five-membered counterparts, and the scarcity of
the former was believed to be due to their lesser stability as
compared with the latter.9 Examples of six-membered [C,N]
palladacycles have become more common recently,8c,9c,10-13
but still remain relatively rare. Some six-membered [C,N]
palladacycles were proven as excellent precatalysts for C-C
and C-heteroatom bond-forming reactions.10f,j,m,q,r,11b,e,j,13
Moreover, the six-membered [C,N] palladacycle skeleton
was often encountered as intermediate species in stoichio-
metric3b,j,14 and catalytic15 organic transformations mediated
by palladium.
Recently, we reported a one-pot synthesis for a series
of N,N0,N00-triarylguanidines and studied their conforma-
tional features by NMR and X-ray diffraction data.16 We set
out to study the cyclopalladation reactions of N,N0,N00-tris-
(2-anisyl)guanidine, (ArNH)2CdNAr (Ar=2-(MeO)C6H4;
LH22-anisyl) with Pd(OC(O)R)2 (R = Me, CF3) to investi-
gate how the intrinsic basic and 2-anisyl substituent in the
guanidine influence the solid-state and solution structures and
the reactivity pattern of the resulting guanidine palladacycles.
From such an endeavor, guanidine palladacycles [Pd{κ2-
(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-2}(μ-X)]2 (Ar =
2-(MeO)C6H4; X=OC(O)R (R=Me (1a), CF3 (1b), and Br
(2)), [Pd{κ2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-2}Br-
(L)] (L = 2,6-Me2C5H3N (3a), 2,4-Me2C5H3N (3b), 3,5-
Me2C5H3N (3c), XyNC (4a), tBuNC (4b), and PPh3 (5)), and
[Pd{κ2(C,N)-C(dNXy)(C6H3(OMe)-4)-2(NdC(NHAr)2)-
3}Br(CNXy)] (Xy = 2,6-Me2C6H3; 6) shown in Chart 1 were
isolated, and the structures and solution dynamics of represen-
tative palladacycles were studied by X-ray diffraction data
and variable-temperature (VT) 1H NMR data. The molecular
structure of the partly cyclopalladated complex of N,N0,N00-
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574 Organometallics, Vol. 30, No. 3, 2011
Gopi et al.
Chart 1
triphenylguanidine, (PhNH)2CdNPh, is reported,17 but no other
data are presently available. The results presented in this paper
were communicated in a national conference.18
Figure 1. ORTEP representation of 1a at the 40% probability
level. Only the NH hydrogens are shown for clarity. Selected
bond distances (A) and angles (deg): N1-Pd1, 2.010(3); C21-
Pd1, 1.956(4); O1-Pd1, 2.153(3); O3-Pd1, 2.054(2); C12-N1,
1.307(4); C12-N2, 1.382(4); C12-N3, 1.350(4); C20-N3, 1.408(3);
N4-Pd2, 2.017(2); C43-Pd2, 1.967(3); O4-Pd2, 2.144(3); O2-Pd2,
2.040(2); C34-N4, 1.300(4); C34-N5, 1.372(4); C34-N6, 1.361(3);
Results and Discussion
Carboxylato-Bridged Six-Membered Guanidine Pallada-
cycles (1a,b). Metallacycles are usually prepared by a C-H
activation process.2,19 Therefore, LH22-anisyl was cyclopalla-
dated with Pd(OC(O)R)2 (R=Me, CF3) in toluene at 70 °C
for 8 h to afford 1a,b in 87% and 95% yield, respectively. The
1H NMR data of 1a,b appeared complicated, and hence
these palladacycles were structurally characterized by X-ray
diffraction data.
The molecular structure of 1a is depicted in Figure 1.
Palladacycle 1a exists as a dimer wherein two palladium
atoms are bridged by a pair of syn-syn bidentate bridging acetate
moieties. Palladacycle 1a revealed a pseudo C2 symmetry that
C42-N6, 1.393(5); Pd1 Pd2, 3.005(2); C21-Pd1-N1, 89.2(1)
3 3 3
C21-Pd1-O3, 91.1(2); N1-Pd1-O1, 92.3(1); O3-Pd1-O1,
87.1(2); N1-Pd1-O3, 177.9(9); C21-Pd1-O1, 172.0(1); N1-
C12-N3, 122.3(2); N1-C12-N2, 123.0(3); N3-C12-N2, 114.7(3);
C12-N3-C20, 124.3(3); C43-Pd2-N4, 89.9(2); C43-Pd2-O2,
90.0(3); N4-Pd2-O4, 94.3(2); O2-Pd2-O4, 85.8(2); N4-Pd2-
O2, 179.2(9); C43-Pd2-O4, 174.1(1); N4-C34-N6, 122.6(3);
N4-C34-N5, 122.7(3); N6-C34-N5, 114.6(3); C34-N6-
C42,126.2(3).
passes across the center of the Pd Pd vector to afford a transoid
3 3 3
in-in conformation with “open book” framework. The palla-
dium atom is surrounded by two oxygen atoms of the acetate,
imine nitrogen, and palladated carbon and displayed a distorted
square-planar geometry. The six-membered “(C,N)Pd” rings
exhibited a pseudo boat conformation. The Pd-N distances,
2.010(3) and 2.017(2) A, in 1a are comparable with the predicted
value of 2.01 A (based upon r(Pd(II))=1.31 A and r(N)=0.70
A)20 and that reported for the N,N0-diphenylbenzamidine-de-
rivedsix-membered[C,N] palladacycle (2.013(3) A).17 The Pd-C
distances, 1.956(4) and 1.967(3) A,in1a are comparable with that
reported for the N,N0-diphenylbenzamidine-derived six-mem-
bered [C,N] palladacycle (1.960(3) A)17 but are shorter than the
predicted value of 2.05 A,21 indicating some multiple-bond
character in the Pd-C(aryl) linkages. The Pd-O distances,
2.153(3) and 2.144(3) A, trans to the palladated carbon are longer
than those that are trans to the imine nitrogen (2.054(2) and
Chart 2
2.040(2) A) due to higher trans influence of the palladated carbon
than that of the imine nitrogen.22 The Pd Pd distance, 3.005(2)
A, in 1a is shorter than the sum of the van der Waals radii (3.26
3 3 3
A)23 but longer than the sum of the covalent radii (2.62 A)24 of
two palladium atoms, and hence the Pd Pd interaction is
3 3 3
considered as weak.
The structure and bonding of the CN3 core in 1a can be
understood from the values of ΔCN, ΔCN , and the degree of
pyramidalization (DP%) defined in Chart 2. The ΔCN value
is the difference between the endocyclic C-N single and
CdN double bond distances, whereas the ΔCN value is the
difference between the exocyclic C-N single and CdN
double bond distances, and these values are used as
a measure of the delocalization of π-electron density across
0
(17) Berry, J. F.; Cotton, F. A.; Ibragimov, S. A.; Murillo, C. A.;
Wang, X. Inorg. Chem. 2005, 44, 6129–6137.
(18) Presented at the 12th Biennial Symposium on Modern Trends in
Inorganic Chemistry (MTIC-XII), Dec 06-08, 2007 (p P-D1-019 of the
book of Abstracts), Indian Institute of Technology Madras, Chennai
600 036, India.
(19) (a) Albrecht, M. Chem. Rev. 2010, 110, 576–623. (b) Ryabov, A. D.
Chem. Rev. 1990, 90, 403–424.
(20) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; Table 7-2, p 224.
(21) Churchill, M. R.; Wasserman, H. J.; Young, G. J. Inorg. Chem.
1980, 19, 762–770.
0
(23) Bondi, A. J. Phys. Chem. 1964, 68, 441–451.
(24) Churchill, M. R. Perspect. Struct. Chem. 1970, 3, 91–164 (see,
particularly, Section X-A on pp 153-155).
(22) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335–422.

Article
Organometallics, Vol. 30, No. 3, 2011 575
1
Figure 2. VT H NMR (400 MHz, CD2Cl2) spectrum of 1a shown for OC(O)CH3 protons. For structures of A-E see Scheme 1.
b: adventitious moisture in CD2Cl2.
the -N-CdN- component of amidines.25a The DP% value
estimates the deviation of the bond angles in a three-coordinate
aminonitrogencenterfromthefull angle (normalized to 90°) and
is expressed as a percentage.25b The ΔCN 0.032(6) A value for the
coordination of the guanidine moiety through the imine
nitrogen.10m,n,12a,26-28 Two signature bands were observed
at 1579 and 1412 cm-1 for 1a and at 1676 and 1536 cm-1 for
1b, assignable to νas(OCO) and νs(OCO), respectively. The
Δν=νas(OCO) - νs(OCO)=167 and 140 cm-1 values for 1a,
b, respectively, indicate a syn-syn bidentate bridging car-
boxylate coordination mode.29
0
CN3 unit around Pd1 is significantly shorter than the ΔCN
0
0.075(6) A value, and the difference between ΔCN and ΔCN
around Pd2 is comparable within the experimental uncertainties
1
[ΔCN=0.061(5) A; ΔCN0 =0.072(6) A]. The smaller ΔCN value
Palladacycle 1a was subjected to a VT H NMR study
0
compared with ΔCN around Pd1 may be ascribed to a better
from 303 to 213 at 10 K intervals, and the stack plot obtained
for OC(O)CH3 protons is shown in Figure 2. At 293 K, six
signals were observed at δH=1.26, 1.32, 1.42, 1.48, 1.54, and
1.58 ppm, assignable to the OC(O)CH3 protons. However,
only three signals were observed, at δH=1.25, 1.42, and 1.50
ppm, at 213 K, while three remaining signals almost merged
with the baseline. This observation can be explained by
invoking a dynamic equilibria involving transoid in-in (A),
transoid in-out (B), and transoid out-out (C) conformers by
a process involving “(C,N)Pd” ring inversion, and such ring
inversion was previously invoked to explain the fluxional
behavior of the related acetato-bridged six-membered [C,N]
palladacycle12k (see Scheme 1). Conformers A and C were
anticipated to reveal one singlet, whereas conformer B was
anticipated to reveal two singlets for OC(O)CH3 protons, as
two former conformers possess a C2 symmetry whereas
the latter lacks it. Cisoid in-in, cisoid in-out, and cisoid
alignment of the lone pair on the endocyclic amino nitrogen with
the CdNπ* orbital than that on the exocyclic amino nitrogen for
a maximum n-π conjugation. Further, ΔCN and ΔCN0 values in
2-anisyl
1a are considerably smaller than that observed in LH2
(ΔCN=0.100(6) A and ΔCN =0.111(6) A),16 indicating a better
0
n-π conjugation in the former. The amino nitrogens in 1a and
LH22-anisyl are planar (DP%: 0.0). Palladacycle 1b is isostructur-
al with 1a except for a crystallographic C2 symmetry that passess
across the center of the Pd Pd vector (see Figure S1 in the SI).
3 3 3
0
The ΔCN 0.038(4) A value in 1b is slightly shorter than the ΔCN
0.059(4) A value, and the amino nitrogens are planar (DP%: 0.0).
The IR spectrum of 1a revealed a band at 3384 cm-1, and
that of 1b revealed two bands at 3408 and 3314 cm-1
assignable to the NH stretch. Palladacycles 1a,b revealed a
band at 1636 and 1624 cm-1, respectively, assignable to the CdN
stretch. The Δν=ν(CdN)complex - ν(CdN)LH22-anisyl=-19
and -31 cm-1 values for 1a,b, respectively, indicate
ꢀ
(27) Garcı
Ranninger, C.; Rodrı
1992, 11, 3013–3018.
(28) Navarro-Ranninger, C.; Lopez-Solera, I.; Alvarez-Valdes, A.;
Rodrıguez-Ramos, J. H.; Masaguer, J. R.; Garcıa-Ruano, J. L.; Solans,
X. Organometallics 1993, 12, 4104–4111.
´
a-Ruano, J. L.; Lopez-Solera, I.; Masaguer, J. R.; Navarro-
€
(25) (a) Hafelinger, G.; Kuske, F. K. H. In The Chemistry of Amidines
´
guez, J. H.; Martinez-Carrera, S. Organometallics
and Imidates; Patai, S., Rappoport, Z., Eds.; Wiley: Chichester, 1991; Vol. 2.
ꢀ
ꢁ
ꢀ
ꢀ
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(b) Maksic, Z. B.; Kovacevic, B. J. Chem. Soc., Perkin Trans. 2 1999,
2623–2629.
´
´
ꢀ
(26) Garcı
M. A.; Navarro-Ranninger, C.; Rodrı
1994, 476, 111–120.
´
a-Ruano, J. L.; Lopez-Solera, I.; Masaguer, J. R.; Monge,
´
guez, J. H. J. Organomet. Chem.
(29) Nakammoto, K. Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 5th ed.; Wiley: New York, 1997.

576 Organometallics, Vol. 30, No. 3, 2011
Gopi et al.
Scheme 1
Figure 3. ORTEP representation of 2 at the 40% probability
level. Hydrogen atoms except the NH hydrogens and acetone
are omitted for clarity. Selected bond distances (A) and angles
(deg): N1-Pd1, 2.038(3); C17-Pd1, 1.985(4); Br1-Pd1, 2.465(8);
Br1-Pd1, 2.590(8); C8-N1, 1.310(5); C8-N3, 1.348(5); C8-N2,
1.362(5); C16-N3, 1.417(5); Pd1 Pd1, 3.696(4); C17-Pd1-
3 3 3
N1, 86.6(1); C17-Pd1-Br1, 94.1(1); N1-Pd1-Br1, 94.6(9);
Br1-Pd1-Br1, 84.8(3); N1-Pd1-Br1, 179.3(9); C17-Pd1-Br1,
175.5(1); Pd1-Br1-Pd1, 95.2(3); N1-C8-N3, 119.9(3); N1-
C8-N2, 121.8(4); N3-C8-N2, 118.3(3);C8-N1-Pd1, 122.6(3);
C8-N3-C16, 123.2(3).
Chart 3
nitrogen of F (first signal), G (middle two signals), and H (last
signal), respectively. Thus, the adduct 1c exists as trans F in the
solid state (IR evidence) and as a mixture of trans F, cis G, and
monomeric H (1H NMR evidence) in solution. The dimer of the
type F was previously identified as an intermediate in the
formation of six-membered [C,N] palladacycles.11g,s
Bromo-Bridged Six-Membered Guanidine Palladacycle (2).
Palladacycle 1a was subjected to a metathetical reaction with
LiBr in aqueous ethanol at 78 °C to afford 2 in 90% yield.
The molecular structure of 2 is depicted in Figure 3. Pallada-
cycle 2 exists as a dimer in transoid conformation. The
palladium atom is surrounded by two bromine, an imine
nitrogen, and palladated carbon and revealed a slightly
distorted square-planar geometry. Two halves of the mole-
cule are related by an inversion symmetry. The six-mem-
bered “(C,N)Pd” ring revealed a pseudo boat conformation,
and the “[Pd(μ-Br)2Pd]” unit revealed a planar rhomboid
conformation (Pd-Br-Pd: 95.2(3)°; Br-Pd-Br: 84.8(3)°).
The Pd-C(aryl) distance, 1.985(4) A, in 2 is slightly shorter
than that known for the related six-membered [C,N] pallada-
cycle (Pd-CH2 = 2.021(7) A)11x perhaps owing to better
out-out conformations are less likely for 1a, as there will be
an unfavorable steric repulsion between two o-anisyl moieties
attached to the imino nitrogen, although such conformers
were invoked to explain the 1H NMR spectral data of some
six-membered [C,N] palladacycles.10m,11u,y,12h The o-OMe
substituent on the aryl moiety of the imine nitrogen in 1a
could have cleaved the acetate bridge intramolecularly by
anchimeric assistance30 to afford a pincer-type monomer (D)
and κ2-O,O0-OAc monomer (E). We, therefore, conclude
that palladacycle 1a exists as conformer A in the solid state
but as a mixture of conformers A-C and monomers D and E
in solution at 293 K and as a mixture of conformers A and B
at 213 K.
Intermediates of Cyclopalladation. Pd(OAc)2 was treated
with LH22-anisyl in 1:1 mol ratio in CH2Cl2 at 10 °C to afford
[(LH22-anisyl)Pd(μ-OAc)(OAc)]2 (1c) as a brown solid in 90%
yield. The IR data of 1c indicated both monodentate (Δν=
290 cm-1) and bridging bidentate (Δν=161 cm-1) coordina-
tion modes for the OAc moiety.29 The 1H NMR spectrum of
1c revealed seven signals at δH =1.37, 1.46, 1.54, 1.60, 1.86
(br), 1.98 (br), and 2.10 ppm assignable to the OC(O)CH3
protons of trans/cis-[(LH22-anisyl)Pd(μ-OAc)(OAc)]2 (F and
G) and a monomer [(LH22-anisyl)Pd(κ2-O,O0-OAc)(OAc)] (H)
(see Chart 3). Further, four singlets were observed at δH =
3.14, 3.20, 3.25, and 3.39 ppm in 1.00:0.57:0.57:0.47 ratios for
OCH3 protons of the o-anisyl moiety bound to the imine
1
back-donation in the former. The H NMR spectrum of 2
revealed three signals at δH=3.73 (s), 3.85 (s), and 4.17 (br)
ppm assignable to OCH3 protons and a typical28,31 upfield
shifted doublet at δH=6.56 ppm (JHH=8.10 MHz) assign-
able to the aryl CH proton adjacent to the palladated carbon.
Monomeric Six-Membered Guanidine Palladacycles
(3a-c, 4a,b, and 5). A suspension of 2 in CH2Cl2 was treated
with Lewis bases at ambient temperature to afford 3a-c, 4a,b,
and 5 in 87-95% yield. The 1H NMR spectra of 3a,b appeared
quite complex, and hence these palladacycles were subjected to
X-ray diffraction analyses. The molecular structures of 3a,b are
depicted in Figures 4 and 5, respectively. The palladium atom in
€
(31) (a) Bednarski, P. J.; Ehrensperger, E.; Schonenberger, H.;
Burgemeister, T. Inorg. Chem. 1991, 30, 3015–3025. (b) Selbin, J.; Gutierrez,
M. A. J. Organomet. Chem. 1981, 214, 253–259. (c) Gutierrez, M. A.;
Newkome, G. R.; Selbin, J. J. Organomet. Chem. 1980, 202, 341–350.
(30) Zanini, M. L.; Meneghetti, M. R.; Ebeling, G.; Livotto, P. R.;
Rominger, F.; Dupont, J. Inorg. Chim. Acta 2003, 350, 527–536.

Article
Organometallics, Vol. 30, No. 3, 2011 577
Figure 5. ORTEP representation of 3b at the 40% probability
level. Only the NH hydrogens are shown for clarity. Selected
bond distances (A) and angles (deg): N1-Pd1, 2.049(3); C17-
Pd1, 1.977(3); N4-Pd1, 2.160(3); Br1-Pd1, 2.446(5); C8-N1,
1.297(4); C8-N3, 1.361(4); C8-N2, 1.362(4); C16-N3, 1.413(4);
C17-Pd1-N1, 88.2(1); N1-Pd1-N4, 91.4(1); C17-Pd1-Br1,
92.9(1); N4-Pd1-Br1, 87.6(8); C17-Pd1-N4, 178.2(1); N1-
Pd1-Br1, 177.2(8); N1-C8-N3, 121.3(3); N1-C8-N2, 122.6(3);
N3-C8-N2, 116.0(3); C8-N1-Pd1, 123.0(2).
Figure 4. ORTEP representation of molecule 1 of 3a at the 40%
probability level. Two molecules were obtained in an asym-
metric unit, but only molecule 1 is shown. Only the NH hydro-
gens are shown for clarity. Selected bond distances (A) and
angles (deg): N1-Pd1, 2.060(4); C17-Pd1, 1.983(4); N4-Pd1,
2.173(4); Br1-Pd1, 2.441(6); C8-N1, 1.298(6); C8-N3,
1.365(6); C8-N2: 1.375(6); C16-N3, 1.410(6); C17-Pd1-N1,
90.0(2); N1-Pd1-N4, 89.9(1); C17-Pd1-Br1, 92.1(1); N4-
Pd1-Br1, 87.9(1); C17-Pd1-N4, 178.1(2); N1-Pd1-Br1,
176.1(1); N1-C8-N3, 121.7(4); N1-C8-N2, 123.7(5); N3-C8-
N2, 114.6(4); C8-N1-Pd1, 123.2(3); C8-N3-C16, 125.8(4).
3a,b is surrounded by an imine nitrogen, a palladated carbon, a
bromine, and the nitrogen atom of the lutidine and revealed a
slightly distorted square-planar geometry. Remarkably, lutidine
is coordinated to the palladium in trans relation with respect
to the Pd-C bond in both palladacycles. The six-membered
“(C,N)Pd” ring in 3a,b revealed a pseudo boat conformation.
The lutidine plane in 3a,b is rotated by 79.2(1)° (molecule 1),
76.9(1)° (molecule 2), and 86.9(9)°, respectively, along the
Pd-Nlutidine bond with respect to the palladium coordination
plane to avoid the unfavorable steric repulsion with the o-anisyl
ring bound to the imine nitrogen.
The molecular structure of 4a is depicted in Figure 6. The
XyNC is coordinated to the palladium atom in cis relation
with respect to the Pd-C bond as anticipated (see later). The
six-membered “(C,N)Pd” ring in 4a revealed a pseudo boat
conformation. The ΔCN value (0.026(1) A) is smaller than the
ΔCN0 value (0.038(1) A), and the amino nitrogens are planar
(DP%: 0.0).
Usually, Lewis bases such as 2,4,6-collidine and 2,6-luti-
dine lie cis to the Pd-C bond in five-membered [C,N]
palladacycles,32 although five five-membered [C,N] pallada-
cycles26,28,33,34 and two five-membered [C,N] platinacycles35
are known to contain Lewis bases trans to the M-C bond.
It was shown that preferences of cis or trans isomers in square-
planar palladium and platinum complexes depend upon a
Figure 6. ORTEP representation of 4a at the 40% probability
level. Hydrogen atoms except the NH hydrogens and CH2Cl2
are omitted for clarity. Selected bond distances (A) and angles
(deg): N1-Pd1, 2.037(6); C17-Pd1, 1.986(1); Br1-Pd1, 2.496(2);
C23-Pd1, 1.901(9); C8-N1, 1.299(1); C8-N3, 1.325(1); C16-N3,
1.397(1); C23-N4, 1.132(1); C24-N4, 1.395(1); C17-Pd1-N1,
86.8(3);C23-Pd1-Br1, 86.5(3); N1-Pd1-Br1, 94.7(2);C23-Pd1-
C17, 91.9(4); C23-Pd1-N1, 178.3(4); C17-Pd1-Br1, 175.7(3);
N1-C8-N3, 120.6(7); N1-C8-N2, 122.4(8); N3-C8-N2,
116.9(7); N4-C23-Pd1, 177.4(9); C8-N1-Pd1, 121.6(6);
C8-N3-C16, 123.3(7); C23-N4-C24, 173.9(1).
combination of factors such as steric, antisymbiosis, π-back-
bonding, electrostatics, packing forces, and solvation.36 The
absence or presence of noncovalent interactions in conjunc-
tion with steric effects34a,35a and relative hardness/softness of
the substituents around the palladium and its antisymbiotic
behavior37 were invoked to explain the trans configuration of
neutral and a cationic five-membered [C,N] metallacycles, re-
spectively. The trans configuration around the palladium atom
in two neutral five-membered [C,N] palladacycles26,28 and a
(32) (a) Calmuschi, B.; Alesi, M.; Englert, U. Dalton Trans. 2004,
1852–1857. (b) Ryabov, A. D.; Kazankov, G. M.; Yatsimirsky, A. K.;
Kuz'mina, L. G.; Burtseva, O. Y.; Dvortsova, N. V.; Polyakov, V. A. Inorg.
Chem. 1992, 31, 3083–3090.
(33) Xu, C.; Gong, J.-F.; Zhang, Y.-H.; Zhu, Y.; Wu, Y.-J. Aust. J.
Chem. 2007, 60, 190–195.
(34) (a) Calmuschi-Cula, B.; Kalf, I.; Wang, R.; Englert, U. Organo-
metallics 2005, 24, 5491–5493. (b) Pfeffer, M.; Sutter-Beydoun, N.;
De Cian, A.; Fischer, J. J. Organomet. Chem. 1993, 453, 139–146.
(35) (a) Ryabov, A. D.; Kuz’lmina, L. G.; Polyakov, V. A.; Kazankov,
G. M.; Ryabova, E. S.; Pfeffer, M.; van Eldik, R. J. Chem. Soc., Dalton
Trans. 1995, 999–1006. (b) Yen, S. K.; Young, D. J.; Huynh, H. V.; Koh,
L. L.; Andy Hor, T. S. Chem. Commun. 2009, 6831–6833.
(36) Harvey, J. N.; Heslop, K. M.; Orpen, A. G.; Pringle, P. G. Chem.
Commun. 2003, 278–279.

578 Organometallics, Vol. 30, No. 3, 2011
Gopi et al.
cationic six-membered [C,N] palladacycle38 may be explained by
considering relative hardness/softness of the donor atoms
around the palladium center.
Scheme 2
The guanidine moiety in 3a,b is basic by virtue of a planar
CN3 unit, and the imine nitrogen in these palladacycles is
harder than the palladated carbon. Hence, harder lutidine
(with respect to Br) lies trans to the softer Pd-C (with respect
to the imine nitrogen) due to antisymbiosis.39 A hypothetical
cis analogue of 3a,b would be unstable according to anti-
symbiosis, as soft Br is placed trans to the soft palladated
carbon. In 4a and 5, XyNC and PPh3 are placed cis to the
Pd-C bond, as these Lewis bases are softer than Br (see
later). Further, PPh3 is bulkier than 2,6-lutidine, 2,4-lutidine,
and XyNC. We, therefore, believe that relative hardness/
softness of the substituents around the palladium atom
dictates the trans configuration in 3a,b and the cis config-
uration in 4a and 5.
Table 1. Population of r, β, and Planar Conformers of 3a As a
The IR spectra of palladacycles 3a-c, 4a,b, and 5 revealed
signature band(s) for the NH and CdN moieties. Pallada-
Function of Concentration Measured by 1H NMR Dataa
cycles 4a,b revealed additional bands at 2187 and 2206 cm-1
,
conc (μM)
respectively, assignable to ν(CtN) stretch, and these values
are comparable with that reported for the related six-mem-
bered [C,N] palladacycles10i,12b but higher than that known
for uncoordinated XyNC (2131 and 2109 cm-1) and tBuNC
(2125 and 2134 cm-1).40
7.5
14.9
22.4
29.8
37.3
44.8
52.2
population
(R:β:planar)
0.08:
0.13:
0.19:
0.25:
0.27:
0.27:
0.38:
1.00:
0.42
1.00:
0.26
1.00:
0.25
1.00:
0.18
1.00:
0.17
1.00:
0.19
1.00:
0.15
The 1H NMR spectrum of 3a at 194.1 μM concentration in
CDCl3 revealed three isomers in ca. 1.75:1.00:0.17 ratios.
a The signals of OCH3 protons at δH = 3.55 (β), 4.09 (R), and 4.18
(planar) ppm at 7.5 μM concentation were used to calculate the
population of conformers. The values of δH may vary slightly depending
on the sample concentration.
1
Two isomers revealed an identical H NMR pattern and
somewhat close resonances: two signals at δH = 2.86 (br),
3.42 (br) (isomer 1); 2.83 (s), 3.24 (s) (isomer 2) ppm for the
CH3 protons of 2,6-lutidine; three singlets at δH=3.76, 3.87,
4.08 (isomer 1); 3.54, 3.78, 3.82 (isomer 2) ppm for the OCH3
protons of the guanidine moiety. The third isomer revealed a
singlet at δH=2.52 ppm for the CH3 protons of 2,6-lutidine
and three singlets at δH = 3.74, 3.83, and 4.16 ppm for the
OCH3 protons of the guanidine moiety. The anisochronicity
of o-CH3 protons and chemical shift separation of these
protons in isomer 1 (Δδ=0.56 ppm) and isomer 2 (Δδ=0.41
ppm) clearly indicated a pseudo boat conformation for the
six-membered “(C,N)Pd” ring in solution, as observed in the
solid state. The anisochronicity of the o-CH3 protons of 2,6-
lutidine- and 2,4,6-collidine-coordinated six-membered [C,N]
palladacycles at ambient temperature11u and at -50 °C,12g respec-
tively, was considered an indication of a boat conformation for
the six-membered “(C,N)Pd” ring. Hence, we assign R and β
notations for isomers 1 and 2, respectively. The o-OMe sub-
stituent on the aryl moiety bound to the imine nitrogen is pointing
upwardintheRisomer as observed in the solid state but pointing
downward in the β isomer. The isochronicity of the o-CH3
protons of 2,6-lutidine of the third isomer indicated a planar
conformation for the six-membered “(C,N)Pd” ring. Thus, the
1H NMR pattern of 3a suggests two boat conformers (R and β)
interconverting via a planar conformer by six-membered “(C,
N)Pd” ring inversion without any bond breaking, as illustrated
in Scheme 2.
Palladacycle 3a revealed concentration-dependent ratios
of R, β, and planar conformers, as investigated by 1H NMR
data (see Table 1). The population of the R conformer
increases and that of the planar conformer decreases,
although not smoothly relative to the β conformer upon
increasing the sample concentration (see also Figure S2 in the
SI). The environment around the molecule in solution at
higher concentration perhaps resembles that present in the
solid state, explaining the observed trend. VT 1H NMR data
of a freshly prepared solution of 3a (500 MHz, CD2Cl2)
indicate three conformers at 303 K, but the population of the
R conformer increases, the planar conformer decreases re-
lative to the β conformer upon decreasing the temperature,
and this trend suggests that the “(C,N)Pd” ring inversion
is quenched in the low-temperature limit (see Figure S3 in
the SI).
1
1
The room-temperature H NMR data of 3b and VT H
NMR data (500 MHz, CD2Cl2; see Figure S4 in the SI) of 3c
clearly indicated the presence of three isomers in solution, as
identified from the signals of the CH3 and o-OCH3 protons
of the former and the o-OCH3 protons of the latter. It is to
be noted that 3b exists as an R conformer in the solid state
(see above). The CH3 protons of 3,5-lutidine in all three
conformers of 3c are located far away from the center of the
boat and are thus isochronous even at 213 K. In solution,
pyridine-coordinated six-membered [C,N] palladacycles ex-
hibited fluxional behavior due to an equilibrium between
two boat conformers through inversion of the six-membered
ꢀ
(37) Falvello, L. R.; Fernandez, S.; Navarro, R.; Pascual, I.; Urriolabeitia,
E. P. Dalton Trans. 1997, 763–771.
(38) Bosque, R.; Granell, J.; Sales, J.; Font-Bardı
J. Organomet. Chem. 1993, 453, 147–154.
(39) Pearson, R. G. Inorg. Chem. 1973, 12, 712–713.
´
a, M.; Solans, X.
1
“(C,N)Pd” ring.12g,h,k The H NMR spectral identification
of the three conformers of 3a-c in solution is unprecedented,
although the planar intermediate was invoked to explain
the fluxional behavior of the related six-membered [C,N]
palladacycle.12g
ꢀ
(40) (a) Fornies, J.; Sicilia, V.; Larraz, C.; Camerano, J. A.; Martı
´
n,
A.; Casas, J. M.; Tsipis, A. C. Organometallics 2010, 29, 1396–1405.
ꢀ
ꢀ
(b) Vicente, J.; Arcas, A.; Julia-Hernandez, F.; Bautista, D.; Jones, P. G.
Organometallics 2010, 29, 3066–3076.

Article
Organometallics, Vol. 30, No. 3, 2011 579
Scheme 3
Figure 7. ORTEP representation of 6 at the 40% probability
level. Only NH hydrogens are shown for clarity. Selected bond
distances (A) and angles (deg): N1-Pd1, 2.112(2); C23-Pd1,
2.009(3); Br1-Pd1, 2.585(4) C32-Pd1, 1.939(3); C1-N1, 1.336(4);
C1-N2, 1.346(4); C1-N3, 1.355(4); C16-N1, 1.418(4); C23-
N4, 1.268(4); C32-N5, 1.152(4); C23-Pd1-N1, 80.7(1); C32-
Pd1-Br1, 84.8(1); C32-Pd1-C23, 95.1(1); N1-Pd1-Br1,
99.3(7);C32-Pd1-N1, 175.6(1); C23-Pd1-Br1, 178.3(9); N1-
C1-N2, 117.5(3); N1-C1-N3, 126.0(3); N2-C1-N3, 116.5(3);
N5-C32-Pd1, 171.1(3); C16-N1-Pd1, 108.5(2); C23-N4-
C24, 127.3(3); C32-N5-C33, 172.9(4).
The 1H NMR spectrum of 4a,band 5indicated incorporation
t
of one XyNC, BuNC, and PPh3, respectively per “(C,N)Pd”
unit and further revealed the presence of only one conformer
in solution in each case. Palladacycle 4b is believed to possess
a cis configuration as analogously observed in 4a. The 31P
NMR spectrum of 5 revealed a singlet at δP=36.00 ppm, and
this value falls within the 32-41 ppm range reported for
the known cis-configured six-membered [C,N] palladacyc-
les.8c,10d,e,h,n,u,w,11a,b,g-i,k,l,o,q,s,t,z,12a Further, the 13C NMR
spectral pattern for the carbon nuclei of PPh3 and Pd-C-
(aryl) in 5 matched well with the known cis-configured six-
membered [C,N] palladacycles.8c,10e,n,11b,g,i,s
Insertion Reaction. The insertion reaction of [C,N] palla-
dacycles with isocyanides was shown to afford ring-ex-
panded [C,N] palladacycles.10i,41 Therefore, palladacycle 2
was treated with XyNC in 1:2 ratio with a view to probe the
lability of the Pd-C bond, and this reaction afforded
palladacycle 6 in 93% yield instead of the anticipated
seven-membered [C,N] palladacycle [Pd{κ2(C,N)-C(dNXy)-
(C6H3(OMe)-4)-2(NHC(NHAr)(dNAr))-3}Br(CNXy)] (Ar=
2-(MeO)C6H4, Xy = 2,6-Me2C6H3) (I). The palladacycle I
is envisaged as one of the intermediates in the formation
of 6 and possibly undergoes ring contraction to afford
another intermediate (J) that subsequently undergoes amine-
imine tautomerization to afford 6 as depicted in Scheme 3.
Amine-imine tautomerization was invoked to explain the
formation of a few organopalladium12b,42 and organolant-
hanide43 complexes. A species such as J was proposed as one
of the intermediates in the insertion of CO into an aryl
carbon-palladium bond of the amidine-derived six-mem-
bered [C,N] palladacycle.14a
surrounded by an imine nitrogen, a ring carbon, a carbon
atom of XyNC, and Br and exhibited a slightly distorted square-
planar environment. The N4-C23 distance, 1.268(4) A, is
shorter than the N1-C1 distance, 1.336(4) A, and the greater
length of the latter may be ascribed to n-π conjugation
involving the lone pair of electrons on the amino nitrogen
with the CdN π* orbital of the guanidine unit. The five-
membered “(C,N)Pd” ring revealed an envelope conformation
with N1, C16, C17, and C23 atoms forming a plane and the
palladium atom lying above the mean plane at 0.7334(2) A.
The five-membered “(C,N)Pd” ring in palladacycle 7 revealed a
planar conformation (see Chart 444), and the conformational
difference between 6 and 7 may be ascribed to the unfavorable
steric repulsion between the C(NHAr)2 and OMe moieties on
the palladated ring in the former.
The IR spectrum of 6 revealed two bands at 3284 and
3184 cm-1 assignable to the ν(NH) stretch. In addition, three
signature bands were observed at 2180, 1629, and 1609 cm-1
assignable to ν(CtN), ν(CdNXy), and ν(CdN) stretches,
respectively. The 1H NMR spectrum of 6 revealed incorpora-
tion of two XyNC per palladium. The 13C NMR spectrum of
6 revealed two signals at δC=18.7 and 19.5 ppm assignable
to the CH3 carbon of the XyNC moiety and two signals at
δC=55.3 and 55.6 ppm assignable to the OCH3 carbon of the
guanidine moiety. Further, two characteristic signals were
observed at δC = 151.7 and 178.2 ppm assignable to Pd-
CtN and Pd-CdN carbon nuclei, respectively, and these
δC values are comparable with those reported for 7 [δC 152.2
(CtN); 175.0 (CdN)].44
The molecular structure of 6 is depicted in Figure 7. The
XyNC is coordinated to the palladium atom in cis orienta-
tion with respect to the Pd-C bond. The palladium atom is
€
(41) (a) Vicente, J.; Saura-Llamas, I.; Grunwald, C.; Alcaraz, C.;
Jones, P. G.; Bautista, D. Organometallics 2002, 21, 3587–3595.
(b) Yamamoto, Y.; Yamazaki, H. Inorg. Chim. Acta 1980, 41, 229–232.
(c) Ma, J.-F.; Kojima, Y.; Yamamoto, Y. J. Organomet. Chem. 2000, 616,
149–156. (d) O'Sullivan, R. D.; Parkins, A. W. J. Chem. Soc., Chem.
Commun. 1984, 1165–1166. (e) Zografidis, A.; Polborn, K.; Beck, W.;
Markies, B. A.; van Koten, G. Z. Naturforsch., B: Chem. Sci. 1994, 49,
1494–1498.
Concluding Remarks
2-anisyl
LH2 was cyclopalladated with Pd(OC(O)R)2 (R =
Me, CF3) under facile reaction conditions to afford dimeric
palladacycles 1a,b in high yield. The solid-state structures of
(42) Wu, K.-M.; Huang, C.-A.; Peng, K.-F.; Chen, C.-T. Tetrahedron
ꢀ
2005, 61, 9679–9687.
(44) Vicente, J.; Abad, J.-A.; Frankland, A. D.; Lopez-Serrano, J.;
(43) Zhang, J.; Cai, R.; Weng, L.; Zhou, X. Organometallics 2004, 23,
3303–3308.
Ramirez de Arellano, M. C.; Jones, P. G. Organometallics 2002, 21,
272–282.

580 Organometallics, Vol. 30, No. 3, 2011
Gopi et al.
Chart 4
for 8 h and then cooled. During the course of the reaction,
palladacycle 1a deposited as a yellow residue. The residue was
filtered, washed with toluene (10 mL), and dried under vacuum.
Crystals suitable for X-ray diffraction data were grown from a
toluene/CH2Cl2 mixture over a period of several hours. Yield:
210 mg, 0.194 mmol, 87%. Dec pt (DSC): 226.9 °C. Anal. Calcd
for C48H50N6O10Pd2 (1083.80): C, 53.20; H, 4.65; N, 7.75. Found:
C, 53.21; H, 4.69; N, 7.74. IR (KBr, cm-1): ν(NH) 3384; ν(CdN)
1636; νas(OCO) 1579, νs(OCO) 1412. 1H NMR (300 MHz,
CDCl3): δ 1.26, 1.37, 1.46, 1.53, 1.59, 1.61 (s, 6 H, CH3), 3.14,
3.21, 3.27, 3.41, 3.66, 3.74, 3.76, 3.80, 3.82, 3.91, 3.92, 3.94 (s, 18 H,
OCH3), 5.94, 6.06, 6.17 (t, JHH=8.81 Hz), 6.26 (d, JHH=7.66 Hz),
6.39 (br m), 6.62 (d, JHH=8.01 Hz), 6.72-7.22 (m), 7.36, 7.42,
7.59 (t, JHH=7.85 Hz), 7.78, 8.06 (ArH and NH protons). Solid-
state CP-MAS 13C NMR (75.5 MHz): δ 22.06, 25.55 (CH3),
52.76, 53.65, 55.08, 56.59, 56.93 (OCH3), 102.36, 104.75, 108.33,
110.59, 112.56, 114.65, 118.59, 119.97, 122.10, 123.56, 124.24,
125.84, 127.34, 128.97, 129.96, 130.25, 131.32, 132.50, 133.23,
135.14, 142.91, 143.97, 146.49 (br), 153.46, 154.21, 155.07, 156.05
(ArC and CdN), 177.01, 177.55 (OCO). Note: only 5 and 27
carbon resonances were observed for OCH3 and ArC carbons,
respectively, rather than the expected 6 and 36 resonances, pre-
sumably due to overlapping peaks. TOF-MS ESþ, m/z (relative
intensity %), [ion]: 1026 (100), [M - OAc]þ; 523 (81), [(C,N)Pd
þ K]þ; 482 (45), [(C,N)Pd]þ; 376 (77), [LH22-anisyl - H]þ.
1a,b and solution dynamics of 1a were studied by X-ray
diffraction data and VT 1H NMR studies, respectively. The
salt metathesis reaction of 1a with LiBr in aqueous ethanol
afforded dimeric palladacycle 2 in high yield. Palladacycle 2
was subjected to a bridge-splitting reaction with various
Lewis bases in CH2Cl2 to afford monomeric, rare trans-
configured palladacycles 3a,b or cis-configured pallada-
cycles 4a and 5 depending on the relative hardness/softness
of the Lewis bases. The stereochemical outcome of the
bridge-splitting reaction indicates that 3a,b are kinetic pro-
ducts, whereas 4a and 5 are thermodynamic products. The
six-membered “(C,N)Pd” ring in guanidine palladacycles
revealed a pseudo boat conformation with a significant n-π
conjugation involving the lone pair on the amino nitrogen
with the CdN π* orbital of the guanidine unit. Palladacycle
2 upon insertion reaction with 2 equiv of XyNC afforded a
novel ring-contracted five-membered [C,N] palladacycle (6)
in high yield, and the driving force for the formation of 6 was
ascribed to the ring contraction followed by amine-imine
tautomerization.
1b: Palladacycle 1b was synthesized from Pd(TFA)2 (50 mg,
2-anisyl
0.15 mmol) and LH2
(57 mg, 0.15 mmol) in tolu
ene (12 mL) following the procedure previously described for
1a. Crystals suitable for X-ray diffraction data were grown from
CHCl3 at ambient temperature over a period of two days. Yield:
85 mg, 0.07 mmol, 95%. Mp (DSC): 239.58 °C. Anal. Calcd for
Pd2C48H44N6O10F6 (1191.74): C, 48.38; H, 3.72; N, 7.05. Found:
C, 48.38; H, 3.60; N, 6.93. IR (KBr, cm-1): ν(NH) 3408, 3314;
ν(CdN) 1624; νas(OCO) 1676, νs(OCO) 1536; ν(CF3) 1146, 1201.
1H NMR (300 MHz, CDCl3): δ 3.13, 3.23, 3.30, 3.49, 3.64, 3.76,
3.80, 3.88, 3.92, 4.04 (br m, 18 H, OCH3), 6.22 (d, JHH=6.71 Hz,
2 H), 6.37, 6.60 (br, 2 H), 6.73-6.93 (br m, 9 H), 7.05-7.09(brm,8H),
7.48, 7.50, 7.55 (br m, 3 H), 7.89, 8.04 (br, 2 H) (ArH and NH).
19F NMR (282.4 MHz, CDCl3):δ-74.33, -74.39, -74.56, -74.62.
MS ESIþ, m/z (relative intensity %) [ion]: 1220 (11) [M þ Na]þ;
1079 (75) [M - TFA]þ; 992 (14) [M - 2TFA]þ; 523 (40) [(C,
N)Pd þ K]þ; 376 (100) [LH22-anisyl - H]þ.
Experimental Section
All manipulations were performed using standard Schlenk
line technique under a nitrogen atmosphere unless stated other-
wise. All reagents were purchased from commercial vendors and
weighed and handled in air. LH22-anisyl was prepared following
the reported procedure.16 Solvents were purified by standard
methods.45 Melting points for 1a,b and 4a were determined on a
PerkinElmer Thermal Analysis DSC instrument. The IR spec-
tral data were obtained using KBr pellets on a Shimadzu IR435
spectrometer. 1H, 13C, 31P, and 19F NMR spectra were recorded
on a Bruker Avance 300 NMR spectrometer operating at field
strengths of 300, 75.5, 121.5, and 282.4 MHz, respectively.
Chemical shifts were referenced to tetramethylsilane (TMS) or
residual solvent signal (1H and 13C), 85% H3PO4 (external
standard, 31P), and CFCl3 (external standard, 19F). The 13C, 31P,
and 19F NMR spectra are proton decoupled. VT 1H NMR spectra
of 1a was obtained on a Bruker AMX-400 spectrometer operat-
2-anisyl
Synthesis of [(LH22-anisyl)Pd(μ-OAc)(OAc)]2 (1c). LH2
(83 mg, 0.22 mmol) and Pd(OAc)2 (50 mg, 0.22 mmol) were
dissolved in CH2Cl2 (15 mL) in a 25 mL RB flask in air. The
brown solution was stirred at 10 °C for two days, and the
reaction mixture was set aside at the same temperature for 2
days to afford 1c as a brown residue. Yield: 121 mg, 0.100 mmol,
90%. Anal. Calcd for C52H58N6O14Pd2 (1203.90): C, 51.88; H,
4.86; N, 6.98. Found: C, 51.98; H, 4.79; N, 7.36. IR (KBr, cm-1):
ν(NH) 3398; ν(CdN) 1628; νas(μ-OAc) 1572; νas(OAc) 1540;
νs(μ-OAc) 1411; νs(OAc) 1250. 1H NMR (300 MHz, CDCl3): δ
1.37, 1.46, 1.54, 1.60, 1.86 (br), 1.98 (br), 2.10 (10 ꢀ 3H, CH3),
3.14, 3.20, 3.25, 3.39 (each s, 5 ꢀ 3H, OCH3), 3.67, 3.74, 3.75,
3.77, 3.82, 3.91, 3.92, 3.95 (each s, 5 ꢀ 6H, OCH3), 5.95, 6.08,
6.16 (t, JHH=7.80 Hz), 6.26 (d, JHH=7.80 Hz), 6.40 (br), 6.63
ing at a field strength of 400 MHz. The solid-state CP-MAS 13
C
NMR spectra of 1a and 3a were recorded on a Bruker DSX-300
spectrometer operating at a field strength of 75.5 MHz, and
the chemical shifts were referenced with respect to TMS. The
electrospray ionization mass spectra (ESI-MS) were obtained
from a Thermo Finnigan LCQ 6000 advantage max ion trap mass
spectrometer using CH2Cl2 as carrier solvent. Time of flight mass
(TOF-MS) spectra were obtained on a JEOL MS Route using
electrospray positive ion mode. Elemental analyses were carried
out on an Elementar Analysen Systeme GmbH VarioEL V3.00.
Synthesis of [Pd{K2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-
2}(μ-OC(O)R)]2 (Ar=2-(MeO)C6H4; R=Me (1a), CF3 (1b)).
1a: Pd(OAc)2 (100 mg, 0.445 mmol) and LH2
0.445 mmol) were dispersed in toluene (15 mL) in a 25 mL
Schlenk flask, and the starting materials dissolved upon heating
to 70 °C. The reaction mixture was stirred at the same temperature
(d, JHH=6.90 Hz), 6.72-7.24 (m), 7.29, 7.35, 7.43, 7.58 (t, JHH
=
6.90 Hz), 7.78, 8.05 (ArH and NH). The aforementioned reac-
tion carried out at 35 °C afforded an inseparable mixture of
cyclopalladated 1a and 1c as identified by 1H NMR data.
Synthesis of [Pd{K2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-
2}(μ-Br)]2 (Ar = 2-(MeO)C6H4) (2). Palladacycle 1a (500 mg,
0.461 mmol) was dispersed in dry ethanol (180 mL) in a 250 mL
RB flask. To the aforementioned heterogeneous mixture was
slowly added 20 mL of aqueous LiBr solution (200 mg, 2.306
mmol), and the contents in the RB flask were stirred at 78 °C for
8 h and cooled. The volatiles from the reaction mixture were
removed under vacuum to leave a yellow residue and water. The
residue was extracted with CH2Cl2 (3 ꢀ 150 mL) and washed
with distilled water (3 ꢀ 20 mL). The extract was dried over
2-anisyl
(166 mg,
(45) Armarego, W. L. F.; Chai, C. L. L. Purification of Laboratory
Chemicals, 5th ed.; Butterworth-Heinemann; Elsevier Science: USA, 2002.

Article
Organometallics, Vol. 30, No. 3, 2011 581
anhydrous MgSO4 and concentrated under vacuum to afford a
yellow residue. The residue was further purified by crystal-
lization from CH2Cl2 at ambient temperature over a period of
several hours to afford 2 as colorless crystals. Crystals suitable
for X-ray diffraction study were grown from acetone at ambient
temperature over a period of several hours. Yield: 540 mg, 0.417
(d, JHH=6.90 Hz, 2 H), 7.72 (br, 2 H), 7.82 (d, JHH=7.50 Hz, 2
H), 7.92 (s, 2 H), 8.01 (s, 1 H), 8.39, 8.52 (each br, 2 H) (ArH and
NH). MS ESIþ, m/z (relative intensity %), [ion]: 589 (14), [M -
Br-]þ; 523 (47), [(C,N)Pd]þ; 376 (100) [LH2
- H]þ. The
2-anisyl
sample was crystallized from a CH2Cl2/toluene mixture at ambient
temperature to afford 3b as colorless crystals.
3c: Yield: 310 mg, 0.463 mmol, 87%. Anal. Calcd for C29H31-
N4O3PdBr (669.91): C, 52.00; H, 4.66; N, 8.36. Found: C, 51.69;
H, 4.69; N, 8.04. IR (KBr, cm-1): ν(NH) 3397; ν(CdN) 1618. 1H
NMR (300 MHz, CDCl3): R:β conformers=ca. 1:1; δ 2.10 (br, 6
H, CH3), 2.20 (s, 6 H, CH3), 3.55 (br, 3 H, OCH3), 3.77, 3.79,
3.84, 3.86, 4.10 (each s, 5 ꢀ 3 H, OCH3), 5.91 (d, JHH=6.60 Hz, 1
H), 6.35 (br, 1 H), 6.58-6.68 (br m, 3 H), 6.82 (t, JHH=7.80 Hz,
2 H), 6.89-6.99 (m, 9 H), 7.08 (t, JHH=7.05 Hz, 3 H), 7.17 (t,
mmol, 90%. Anal. Calcd for C44H44N6O6Pd2Br2 2CH2Cl2
3
(1295.40): C, 42.65; H, 3.73; N, 6.49. Found: C, 42.69; H,
3.77; N, 6.38. IR (KBr, cm-1): ν(NH) 3392, 3318; ν(CdN)
1619. 1H NMR (300 MHz, CDCl3): δ 3.73, 3.85 (each s, 2 ꢀ 6
H, OCH3), 4.17 (br, 6 H, OCH3), 6.56 (d, JHH=8.10 Hz, 2 H,
ArH), 6.67 (br, 2 H, NH), 6.73 (t, JHH=7.95 Hz, 2 H, ArH), 6.93
(t, JHH=8.25 Hz, 2 H, ArH), 7.00-7.11 (br, 8 H, ArH), 7.28 (br,
2 H, ArH), 7.35-7.53 (br, 6 H, ArH), 7.91 (br, 2 H, NH). The
13C NMR spectrum for 2 was not recorded owing to its poor
solubility in common deuterated solvents. MS ESIþ, m/z
(relative intensity %), [ion]: 1045 (44), [M - Br]þ; 992.20 (14),
[M- 2Br]þ;523(32),[(C,N)Pdþ K]þ;376(100),[LH22-anisyl - H]þ.
Synthesis of [Pd{K2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-
2}Br(L)] (Ar=2-(MeO)C6H4; L=2,6-Me2C5H3N (3a), 2,4-Me2C5-
H3N (3b), 3,5-Me2C5H3N (3c)). 3a: Palladacycle 2 (300 mg, 0.266
mmol) was dispersed in CH2Cl2 (10 mL) in a 25 mL RB flask in air
and set to stir. To the aforementioned heterogeneous solution was
slowly added 2,6-lutidine (60 mg, 0.56 mmol) that was previously
dissolved in CH2Cl2 (5 mL), and the resulting heterogeneous mixture
was stirred for 24 h at ambient temperature. During the course of the
reaction, the residue gradually dissolved and led to the formation of a
transparent pale yellow solution. The reaction mixture was concen-
trated under vacuum to ca. 5 mL and layered with toluene to afford
3a as colorless crystals. Yield: 340 mg, 0.508 mmol, 95%. Anal. Calcd
for C29H31N4O3PdBr (669.91): C, 52.00; H, 4.66; N, 8.36. Found: C,
52.03; H, 4.70; N, 8.20. IR (KBr, cm-1): ν(NH) 3401, 3378, 3316;
ν(CdN) 1622. The 1H NMR spectrum of 3a recorded at 7.50 μM
was not conclusive, as no 1H NMR signals were apparent for CH3
J
HH=7.65 Hz, 3 H), 7.36-7.44 (br m, 2 H), 7.58-8.00 (br m, 6
H), 8.42 (s, 2 H) (ArH and NH). MS ESIþ, m/z (relative intensity
%), [ion]: 591 (12), [M - Br-]þ; 523 (45), [(C,N)Pd]þ; 376 (100),
[LH22-anisyl - H]þ.
Synthesis of [Pd{K2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-
2}Br(CNR)] (Ar=2-(MeO)C6H4; R=Xy (4a), tBu (4b)). 4a: Palla-
dacycle 2 (300 mg, 0.266 mmol) and XyNC (73 mg, 0.56 mmol) were
charged into a 25 mL Schlenk flask. To the aforementioned flask was
added CH2Cl2 (15 mL) to afford a brown solution. The solution was
stirred for 12 h, concentrated under vacuum to 8 mL, and subse-
quently layered with toluene (2 mL) to afford 4a as colorless crystals
after two days. Yield: 390 mg, 0.501 mmol, 94%. Dec pt (DSC):
137.36 °C. Anal. Calcd for C31H31N4O3PdBr CH2Cl2 (778.87): C,
3
49.35; H, 4.27; N, 7.19. Found: C, 49.16; H, 4.42; N, 7.17. IR
(KBr, cm-1): ν(NH) 3393; ν(CtN) 2187; ν(CdN) 1621. 1H NMR
(300 MHz, CDCl3): δ 2.44 (s, 6 H, CH3), 3.80, 3.86, 4.09 (each s, 3 ꢀ
3H,OCH3),6.69(d,JHH=7.80Hz,1H,ArH),6.86(t,JHH=7.80 Hz,
1 H, ArH), 6.91-7.25 (m, 12 H, ArH), 7.56, 7.92 (each s, 2 H, NH).
13C NMR (75.5 MHz, CDCl3): δ 19.0 (CH3), 55.2, 55.7, 55.9
(OCH3), 106.5, 111.2, 111.3, 120.5, 121.0, 122.0, 122.3, 125.3,
126.1, 126.5, 126.8, 127.7, 128.9, 129.1, 130.0, 133.3, 135.6, 135.8
(ArC), 144.3 (br, XyNtC), 146.0, 147.5, 150.9 (ArC), 153.8 (CdN).
Note: only 21 carbon resonances were observed for ArC carbons
rather than the expected 22 resonances, presumably due to over-
lapping peaks. MS ESIþ, m/z (relative intensity %), [ion]: 613 (100),
[M - Br-]þ; 376 (45), [LH22-anisyl - H]þ.
1
protons of 2,6-lutidine of the R conformer. Hence, the H NMR
spectrum was recorded at 194.1 μM concentration. The intensities of
OCH3 protons were considered for the calculation of ratio of
1
conformers. H NMR (300 MHz, 194.1 μM, CDCl3): R:β:planar
conformers = ca. 1.75:1.00:0.17; δ 2.52 (s, 6 H, CH3; planar con-
former), 2.83 (s, 3 H, CH3; β conformer), 2.86 (br, 3 H, CH3; R
conformer), 3.24 (s, 3 H, CH3; β conformer), 3.42 (br, 3 H, CH3; R
conformer), 3.54 (s, 3 H, OCH3; β conformer), 3.74 (s, 3 H, OCH3;
planar conformer), 3.76 (s, 3 H, OCH3; R conformer), 3.78 (s, 3 H,
OCH3; β conformer), 3.82 (s, 3 H, OCH3, β conformer), 3.83 (s, 3 H,
OCH3; planar conformer), 3.87 (s, 3 H, OCH3;Rconformer), 4.08 (s,
3 H, OCH3; R conformer), 4.16 (s, 3 H, OCH3; planar conformer),
5.57 (dd, JHH=6.90; 2.10 Hz, 2 H), 6.32 (dd, JHH=8.10 Hz, 1 H),
6.50-6.61 (m, 6 H), 6.70-7.30 (m, 29 H), 7.42-7.52 (m, 4 H), 7.74
(s, 2 H), 7.78 (dd, JHH =7.20 Hz, 1 H), 7.93 (s, 2 H), 8.00 (s, 1 H)
(ArH and NH). Solid-state CP-MAS 13C NMR (75.5 MHz): δ
24.80, 26.00, 27.44 (CH3), 53.07, 55.21, 56.79 (OCH3), 105.17, 109.11,
110.42, 112.27, 118.89, 120.62, 124.81, 126.30, 127.45, 128.77, 133.12,
136.20, 139.75, 145.55, 149.00, 150.78, 157.63, 161.32 (ArC and
CdN). MS ESIþ, m/z (relative intensity %), [ion]: 523 (37), [(C,
N)Pd]þ; 376 (100), [LH22-anisyl]þ. Palladacycles 3b,c were prepared
from 2 and the corresponding lutidine in CH2Cl2 by a procedure
analogous to that described for 3a.
4b: Palladacycle 4b was prepared from 2 (300 mg, 0.266
mmol) and tBuNC (49 mg, 0.59 mmol) in CH2Cl2 by a procedure
analogous to that described for 4a. Yield: 285 mg, 0.477 mmol,
90%. Anal. Calcd for C27H31N4O3PdBr (645.89): C, 50.21; H,
4.84; N, 8.67. Found: C, 50.43; H, 4.71; N, 8.64. IR (KBr, cm-1):
ν(NH) 3382; ν(CtN) 2206; ν(CdN) 1623. 1H NMR (300 MHz,
CDCl3): δ 1.48 (s, 9 H, CH3), 3.78, 3.85, 4.06 (each s, 3 ꢀ 3 H,
OCH3), 6.67 (d, JHH=8.10 Hz, 1 H, ArH), 6.85 (t, JHH=7.80
Hz, 1 H, ArH), 6.92 (t, JHH = 7.65 Hz, 2 H, ArH), 6.97, 7.00
(each s, 2 H, ArH), 7.08 (t, JHH=7.65 Hz, 2 H, ArH), 7.13-7.21
(m, 3 H, ArH), 7.52, 7.86 (each s, 2 H, NH). 13C NMR (75.5 MHz,
CDCl3): δ 28.7 (CH3), 54.1, 54.6, 54.8 (OCH3), 56.3 (Me3CNC),
105.2, 110.1, 110.2, 119.3, 119.8, 120.8, 121.1, 124.0, 125.0, 125.4,
125.6, 127.7, 128.8 (ArC), 130.4 (br, tBuNtC), 131.4, 134.6, 144.7,
146.2, 149.7 (ArC), 152.6 (CdN). MS ESIþ, m/z (relative intensity
%), [ion]: 565 (100), [M - Br-]þ; 509 (14), [(C,N)Pd]þ; 376 (34),
[LH22-anisyl - H]þ.
Synthesis of [Pd{K2(C,N)-C6H3(OMe)-3(NHC(NHAr)(dNAr))-
2}Br(PPh3)] (Ar=2-(MeO)C6H4 (5)). Palladacycle 5 was prepared
from 2 (300 mg, 0.266 mmol) and PPh3 (154 mg, 0.586 mmol) in
CH2Cl2 (15 mL) by a procedure analogous to that described for 4a.
Yield: 400 mg, 0.485 mmol, 91%. Anal. Calcd for C40H37N3O3-
PPdBr (823.03): C, 58.23; H, 4.52; N, 5.09. Found: C, 58.27; H, 4.48;
N, 4.95. IR (KBr, cm-1):ν(NH) 3382; ν(CdN) 1617. 1HNMR(300
MHz, CDCl3): δ 3.78, 3.88, 4.06 (each s, 3 ꢀ 3 H, OCH3), 6.15 (t,
3b: Yield: 318 mg, 0.475 mmol, 89%. Anal. Calcd for PdC29-
H31N4O3Br (669.91): C, 52.00; H, 4.66; N, 8.36. Found: C,
51.97/51.93; H, 4.69/4.80; N, 8.31/8.25. IR (KBr, cm-1): ν(NH)
1
3381; ν(CdN) 1621. H NMR (300 MHz, CDCl3): R:β:planar
conformers=ca. 0.57:1.00:0.38; δ 2.19, 2.30 (each s, 6 H, CH3, β
conformer), 2.51, 2.68 (each br, 6 H, CH3, planar conformer),
3.05, 3.28 (each br, 6 H, CH3, R conformer), 3.54, 3.62 (each br, 6
H, OCH3, planar conformer), 3.78 (s, 6 H, OCH3, R conformer),
3.84 (s, 3 H, OCH3, β conformer), 3.86 (s, 6 H, OCH3, R and β
conformers), 4.10 (s, 3 H, OCH3, β conformer), 4.18 (br, 3 H,
OCH3, planar conformer), 5.75 (br, 2 H), 6.31, 6.44 (br, 3 H),
JHH=7.80 Hz, 1 H, ArH), 6.30 (t, JHH=7.05, 1 H, ArH), 6.36 (d,
JHH=7.80Hz, 1H, ArH), 6.94 (t, JHH=8.10 Hz, 4 H, ArH), 7.11(t,
J
HH=7.65 Hz, 2 H, ArH), 7.17-7.34 (m, 11 H, ArH and NH), 7.61
6.56, 6.58, 6.62 (m, 6 H), 6.82-7.00 (br m, 15 H), 7.08 (t, JHH=
7.20 Hz, 6 H), 7.16 (d, JHH=7.50 Hz, 4 H), 7.38 (br, 1 H), 7.45
(t, JHH =9.15 Hz, 6 H, ArH), 7.83 (d, JHH=6.00 Hz, 2 H, ArH).
13C NMR (75.5 MHz, CDCl3): δ 55.2, 55.7, 56.2 (OCH3), 105.2,

582 Organometallics, Vol. 30, No. 3, 2011
Table 2. Crystal Data and Structure Refinement for Complexes 1a, 1b, 2, and 3a
Gopi et al.
1a
1b CHCl3
3
2 Me2CdO
3
3a
formula
fw
Pd2C48H50N6O10
1083.74
293(2)
monoclinic
P21/n
0.71073
15.769(2)
15. 769(2)
19.401(2)
90.00
90.00(3)
90.00
4824.0(9)
4
1.492
2208
0.808
1.66-33.00
87 566
18 490
PdC25H23N3O5Cl3F3
715.21
293(2)
monoclinic
C2/c
0.71073
20.559(2)
13.884(1)
21.528(2)
90.00
108.011(1)
90.00
5844.2(8)
8
1.626
2864
0.968
1.80-27.50
31 794
6689
Pd2C50H56N6O8Br2
1241.63
293(2)
monoclinic
P21/c
0.71073
10.432(5)
10.795(5)
22.836(10)
90.00
96.078(7)
90.00
2557.2(19)
2
1.613
1248
2.323
1.79-27.75
21 643
6026
PdC29H31N4O3Br
669.89
293(2)
monoclinic
P21/c
0.71073
17.836(1)
15.092(1)
21.160(2)
90.00
90.654(2)
90.00
5695.3(7)
8
1.563
2704
2.091
1.66-27.50
48 676
13 305
temp (K)
cryst syst
space group
wavelength (λ)
a (A)
b (A)
c (A)
R (deg)
β (deg)
γ (deg)
volume (A3)
Z
F
F(000)
calcd (g cm-3
)
μ(Mo KR) (mm-1
θ range (deg)
)
no. of reflns coll
no. of reflns used
parameters
603
0.0453
0.1693
0.768
365
0.0396
0.1254
0.700
312
0.0445
0.1224
0.932
695
0.0616
0.1091
1.118
R1 [I > 2σ(I)]
wR2 (all reflns)
goodness of fit on F2
largest diff peak/hole (e A-3
)
1.189/-1.838
1.019/-1.058
0.801/-0.669
0.578/-0.547
3
Table 3. Crystal Data and Structure Refinement for Complexes 3b, 4a, and 6
3b
4a CH2Cl2
3
6
formula
fw
temp (K)
cryst syst
space group
a (A)
PdC29H31N4O3Br
669.89
293(2)
monoclinic
P21/n
10.4074(7)
15.092(1)
18.066(1)
90.00
95.409(1)
90.00
2824.9(3)
4
1.575
1352
2.108
PdC32H33N4O3Cl2Br
778.83
293(2)
monoclinic
P21/n
10.268(4)
14.844(7)
21.449(9)
90.00
94.897(12)
90.00
3257(2)
4
1.588
1568
1.999
PdC40H40N5O3Br
825.08
293(2)
monoclinic
P21/n
11.0241(3)
22.6339(7)
16.1571(5)
90.00
108.578(1)
90.00
3821.4(2)
4
1.434
1680
1.574
b (A)
c (A)
R (deg)
β (deg)
γ (deg)
V (A3)
Z
F
F(000)
calcd (g cm-3
)
μ (mm-1
)
θ range (deg)
1.76-28.02
23 960
6628
348
0.0471
0.1103
1.111
0.605/-0.438
2.66-30.00
22 611
9439
393
0.0746
0.2727
0.784
1.081/-1.535
1.61-29.33
49 232
10 490
458
0.0393
0.1380
1.072
0.712/-0.872
no. of reflns coll
no. of reflns used
parameters
R1 [I > 2σ(I)]
wR2 (all reflns)
goodness of fit on F2
largest diff peak/hole (e A-3
)
3
111.2, 111.8, 120.5, 121.1, 122.2, 122.3, 125.0, 126.1, 126.7, 127.4,
127.5 (d, 2JPC=10.57 Hz, o-CH, PPh3), 128.7, 129.7 (d, 4JPC=2.26
Hz, p-CH, PPh3), 132.0, 132.1, 132.5 (d, 1JPC=49.10 Hz, i-C, PPh3),
135.2 (d, 3JPC=11.32 Hz, m-CH, PPh3), 136.7 (d, 2JPC=14.34 Hz,
Pd-C), 147.1, 147.8, 151.0 (ArC), 153.9 (CdN). 31P NMR (121.5
MHz, CDCl3): δ 36.00 ppm. MS ESIþ, m/z (relative intensity %),
[ion]: 744 (100), [M - Br]þ, 376 (48) [LH22-anisyl - H]þ.
C40H40N5O3PdBr (825.11): C, 58.23; H, 4.89; N, 8.49. Found:
C, 58.04; H, 5.04; N, 8.44. IR (KBr, cm-1): ν(NH) 3284, 3184;
1
ν(CtN) 2180, ν(CdNXy) 1629; ν(CdN) 1609. H NMR (300
MHz, CDCl3): δ 2.16 (s, 2 ꢀ 3 H, CH3), 2.40 (br, 2 ꢀ 3 H, CH3),
3.55 (s, 3 H, OCH3), 3.80 (s, 2 ꢀ 3 H, OCH3), 6.51 (t, JHH=7.44
Hz, 1 H, ArH), 6.58 (d, JHH=7.91 Hz, 1 H, ArH), 6.63-6.71 (m,
7 H, ArH and NH), 6.84 (t, JHH=7.83 Hz, 4 H, ArH), 6.94 (d,
Synthesis of [Pd{K2(C,N)-C(dNXy)(C6H3(OMe)-4)-2(NdC-
(NHAr)2)-3}(Br)(CNXy)] (Ar = 2-(MeO)C6H4 (6)). Pallada-
cycle 2 (300 mg, 0.266 mmol) and XyNC (147 mg, 1.119
mmol) were charged into a 25 mL Schlenk flask. To the
aforementioned flask was added CH2Cl2 (15 mL) under nitro-
gen atmosphere, and the contents of the flask were stirred at
room temperature for 12 h to obtain a brown solution. The
solution was concentrated to ca. 8 mL and allowed to stand at
ambient temperature for several hours to afford 6 as colorless
crystals. Yield: 410 mg, 0.497 mmol, 93%. Anal. Calcd for
JHH =7.54 Hz, 2 H, ArH), 7.04-7.12 (m, 3 H, ArH and NH),
7.38 (d, JHH = 7.12 Hz, 1 H, ArH). 13C NMR (75.5 MHz,
CDCl3): δ 18.7, 19.5 (CH3), 55.3, 55.6 (OCH3), 110.5 (br), 112.7,
116.6, 120.2, 122.3 (br), 123.2, 124.5 (br), 126.5, 126.8, 127.2,
127.6, 128.6, 134.5, 140.7, 141.0, 143.7, 150.0 (ArC), 151.7
(Pd-CtN), 152.9 (Pd-NdC), 178.2 (Pd-CdN). Note: only
2 and 17 carbon resonances were observed for OCH3 and ArC
carbons, respectively, rather than the expected 3 and 26 reso-
nances, presumably due to overlapping peaks. MS ESIþ, m/z
(relative intensity %), [ion]: 744 (63), [M - Br-]þ; 654 (18),

Article
Organometallics, Vol. 30, No. 3, 2011 583
[(C,N)Pd þ K]þ; 613 (100), [(C,N)Pd]þ; 548 (18), [{(C,N)Pd þ K}
structure was solved and refined using the SHELXL-97 program.49
The palladium atom position was observed by the Patterson method,
and the non-hydrogen atoms were located by successive difference
Fourier maps and refined anisotropically. Hydrogen atoms were
fixedinidealizedpositionsandrefined in a riding model. The relevant
crystallographic data and details of the refinement for the structures
of 1a,b, 2, 3a,b, 4a, and 6 are listed in Tables 2 and 3.
2-anisyl
- Xy]þ; 507 (20), [(C,N)Pd - Xy]þ; 401 (24), [LH2
þ Na]þ.
Crystal Structure Determinations. Suitable crystals of 1a,b, 2,
3a,b, 4a, and 6 for X-ray diffraction study were carefully selected
after examination under an optical microscope and mounted on
the goniometer head with paraffin oil coating. The unit cell
parameters and intensity data were collected at room temperature
using a Bruker SMART APEX CCD diffractometer equipped with a
fine-focus Mo KRX-ray source (50 kV, 40 mA). The data acquisition
was done using SMART software, and SAINT software was used
for data reduction.46 The empirical absorption corrections were
made using the SADABS program47 and empirical method.48 The
Acknowledgment. We thank the Department of Science
and Technology, New Delhi, for financial support (SR/S1/
IC-22/2004) and for a fellowship (K.G.). We also thank
NMR Research Centre, Indian Institute of Science, Ban-
galore 560 012, for VT 1H NMR measurements.
(46) SMART and SAINT, Version 6.22a; Bruker AXS: Madison, WI,
1999.
(47) Sheldrick, G. M. SADABS, version 2, Multiscan Absorption
Supporting Information Available: Molecular structure of 1b,
VT 1H NMR stack plots for 3a and 3c, VC 1H NMR stack plot
for 3a, CIF files for 1a,b, 2, 3a,b, 4a, and 6. This material is
available free of charge via the Internet at http://pubs.acs.org.
€
€
Correction Program; University of Gottingen: Gottingen, Germany, 2001.
(48) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33–38.
(49) Sheldrick, G. M. SHELX-97, Program for the Solution of
€
€
Crystal Structures; University of Gottingen: Gottingen, Germany, 1997.