Acetimine and 2-methyl-2-amino-4-iminopentane complexes of palladium(II)

Article abstract of DOI:10.1021/om020434y

By reaction between the labile complex cis- [Pd(C₆F₅)₂(PhCN)₂] and aqueous ammonia-acetone solutions the palladium complexes [Pd(C₆F₅)₂L₂] [L = NH₃ (1), NHCMe₂ (2) and L₂ = NHC(Me)CH₂C(Me₂)NH₂ (3)] are obtained. The reaction product depends on the experimental conditions used. The cationic complexes [Pd(dmba)L₂]ClO₄ [L = NH₃ (5), NHCMe₂ (6) and L₂ = NH C(Me)CH₂C(Me₂)NH₂ (7)] with the N,C-chelating 2-(dimethylaminomethyl)phenyl (dmba) ligand have been obtained by treating [(dmba)Pd(μ-Cl)₂Pd-(dmba)] with AgClO₄ in aqueous ammonia-acetone solution. The mono(acetimine) complex [Pd(dmba)(PPh₃)(NHCMe₂)]ClO₄ (8) is obtained by a similar procedure starting from [Pd-(dmba)(PPh₃)Cl]. The crystal structures of 1-3 and 6 and 7 have been determined; there is extensive hydrogen bonding (N-H?F-C or N-H?OClO₃) in all the compounds.

Full text of DOI:10.1021/om020434y

4912
Organometallics 2002, 21, 4912-4918
Acetim in e a n d 2-Meth yl-2-a m in o-4-im in op en ta n e
Com p lexes of P a lla d iu m (II)
J ose´ Ruiz,* Venancio Rodr´ıguez, Natalia Cutillas, and Gregorio Lo´pez*
Departamento de Quı´mica Inorga´nica, Campus Universitario de Espinardo,
Universidad de Murcia, 30071-Murcia, Spain
J ose´ Pe´rez
Departamento de Ingenierı´a Minera, Geolo´gica y Cartogra´fica (Area de Qu´ımica Inorga´nica),
Universidad Polite´cnica de Cartagena, 30203-Cartagena, Spain
Received J une 3, 2002
By reaction between the labile complex cis-[Pd(C6F5)2(PhCN)2] and aqueous ammonia-
acetone solutions the palladium complexes [Pd(C6F5)2L2] [L ) NH3 (1), NHCMe2 (2) and L2
) NHC(Me)CH2C(Me2)NH2 (3)] are obtained. The reaction product depends on the
experimental conditions used. The cationic complexes [Pd(dmba)L2]ClO4 [L ) NH3 (5),
NHCMe2 (6) and L2 ) NH C(Me)CH2C(Me2)NH2 (7)] with the N,C-chelating 2-(dimethyl-
aminomethyl)phenyl (dmba) ligand have been obtained by treating [(dmba)Pd(µ-Cl)2Pd-
(dmba)] with AgClO4 in aqueous ammonia-acetone solution. The mono(acetimine) complex
[Pd(dmba)(PPh3)(NHCMe2)]ClO4 (8) is obtained by a similar procedure starting from [Pd-
(dmba)(PPh3)Cl]. The crystal structures of 1-3 and 6 and 7 have been determined; there is
extensive hydrogen bonding (N-H‚‚‚F-C or N-H‚‚‚OClO3) in all the compounds.
In tr od u ction
these ligands. Furthermore, no systematic method of
preparation of these complexes is found in the literature.
Chemical or electrochemical oxidation of coordinated
isopropylamine,5 redox-catalyzed condensation of an
ammine complex with acetone,6 oxidative addition of
2-bromo-2-nitrosopropane,8 oxidative addition of an
iminium salt to low-valent metal complexes,9 reduction
of coordinated acetonitrile,10 controlled-potential elec-
trochemical oxidation of coordinated 2,3-dimethyl-2,3-
diaminobutane,11 the reaction between [LAu(acac)]+-
type complexes and NH4X in acetone,12 and thermal
decomposition of [Si(CMe3)2(OEt2){N(CMe3)AlCl3}]13 are
the methods reported in the literature for the synthesis
of acetimine complexes.
The addition of ammonia to ketones would be ex-
pected to give the corresponding hemiaminal and/or
imine. However, these compounds are generally un-
stable and unsubstituted NH-ketimines spontaneously
polymerize, the stable compound being the result of
combinations and condensations of one or more mol-
ecules of the hemiaminal and/or the imine with each
other or with additional molecules of ammonia.1 In the
particular case of acetone, the formation of acetimine
(Me2CdNH) from acetone and ammonia has been
reported: low loadings of acetone and ammonia on the
medium-pore zeolite HZMS-5 over 250 °C give ace-
timine, and when the large-pore zeolite HY is used, the
ammonia adduct of acetone (2-aminopropan-2-ol) is
detected at low temperature;2 acetimine is also formed
by an NH4Cl-catalyzed reaction between acetone and
ammonia at 50 bar and 120 °C.3 However, the stable
product is the result of cyclotrimerization with the loss
of one molecule of ammonia.4 Acetimine is stable at 0
°C for short periods of time and decomposes on storage
to give 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimi-
dine (acetonine).4
The work reported in this paper shows that both
acetimine and its dimer (2-methyl-2-amino-4-iminopen-
(6) Harman, W. D.; Taube, H. Inorg. Chem. 1988, 27, 3261.
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1995, 14, 1417.
The instability of both acetimine5-13 and its amino-
imine dimer (2-methyl-2-amino-4-iminopentane)14-17
could account for the scarcity of metal complexes with
(11) Wong, K.-Y.; Che, C.-M.; Li, C.-K.; Chiu, W.-H.; Zhou, Z.-Y.;
Mak, T. C. W. J . Chem. Soc., Chem. Commun. 1992, 754.
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J ones, P. G.; Ram´ırez de Arellano, M. C. Chem. Eur. J . 2001, 7, 638.
(13) Klingebiel, W.; Noltemeyer, M.; Schmidt, H.-G.; Schmidt-Base¨,
D. Chem. Ber./ Recl. 1997, 130, 753.
(14) Rose, N. J .; Elder, M. S.; Busch, D. H. Inorg. Chem. 1967, 6,
1924.
(15) Gould, R. O.; Stephenson, T. A.; Thomson, M. A. J . Chem. Soc.,
Dalton Trans. 1978, 769.
(1) March, J . Advanced Organic Chemistry: Reactions, Mechanisms
and Structure, 4th ed.; J ohn Wiley & Sons: New York, 1992; p 896.
(2) Xu, T.; Zhang, J .; Haw, J . F. J . Am. Chem. Soc. 1995, 117, 3171.
(3) Verardo, G.; Giumanini, A. G.; Strazzolini, P.; Poiana, M. Synth.
Commun. 1988, 18, 1501.
(4) Findeisen, K.; Heitzer, H.; Deehnicke, K. Synthesis 1981, 702.
(5) Adcock, P. A.; Keene, F. R.; Smythe, R. S.; Snow, M. R. Inorg.
Chem. 1984, 23, 2336.
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Inorg. Chim. Acta 1993, 205, 79.
(17) Hanic, F.; Serator, M. Chem. Zvesti 1964, 18, 572.
10.1021/om020434y CCC: $22.00 © 2002 American Chemical Society
Publication on Web 10/09/2002

Synthesis of [Pd(C6F5)2L2] and [Pd(dmba)L2]ClO4 Complexes
Organometallics, Vol. 21, No. 23, 2002 4913
Sch em e 1a
Sch em e 2
a
Conditions: (a) +2NH3(aq), in Me2CO, room temperature,
10 min. (b) +20NH3(aq), in Me2CO, room temperature, 4 h.
(c) +2NH3(aq), in Me2CO, room temperature, 2 d.
tane) can be conveniently trapped by PdII from acetone-
ammonia solutions.
Resu lts a n d Discu ssion
Bis(p en ta flu or op h en yl) Com p lexes. The labile
complexes cis-[M(C6F5)2(PhCN)2] (M ) Ni, Pd) have
been used as starting materials for the preparation of
metal complexes.18,19 When cis-[Pd(C6F5)2(PhCN)2]20 is
treated with 20% aqueous ammonia in acetone, com-
plexes 1-3 are obtained in high yields, the specific
product depending on the experimental conditions given
in Scheme 1. Complexes 1-3 are all white, air-stable
solids that decompose on heating above 190 °C. Their
IR spectra show the characteristic absorptions of the
1-3 can readily be understood on the assumption that
in an acetone-ammonia mixture it works the equilib-
rium shown in Scheme 2. Depending on the experimen-
tal conditions used (Scheme 1), the predominant N-do-
nor species (NH3, NHdCMe2 or NH2C(Me)2CH2C(Me)d
NH) would be trapped by the cis-Pd(C6F2)2 fragment
with the concomitant displacement of benzonitrile. Since
the ammonia complex 1 is formed quickly (within 10
min), compound 2 is more likely derived from 1 by
ligand substitution of NH3 with NHdCMe2. So, the
unstable acetimine and its dimer are stopped by pal-
ladium on the way to the most stable product (aceto-
nine).4 Furthermore, no acetonine-palladium complex
was detected when the reaction was carried out with
longer periods of time. However, during the isolation of
complex 2 some impurity was detected in the NMR
spectra that was attributed to the presence of the mixed
complex [Pd(C6F5)2(NH3)(NHdCMe2)] (4). This was
confirmed when a 1:1 molar mixture of [Pd(C6F5)2-
(NH3)2] and [Pd(C6F5)2(NHdCMe2)2] was put into the
NMR tube containing CDCl3. After a few minutes the
1H spectrum showed that there were three palladium
species: [Pd(C6F5)2(NH3)2], [Pd(C6F5)2(NHdCMe2)2], and
[Pd(C6F5)2(NH3)(NHdCMe2)] [δ 8.3 (br, 1H, NH), 2.5 (s,
C6F5 group (1630 m, 1490 vs, 1050 s, and 950 vs cm-1 21
)
and a split band at ca. 800 cm-1 assigned to the cis-Pd-
(C6F5)2 moiety.22,23 The NH stretching modes are found
in the 3300-cm-1 region and the CdN vibrations of 2
and 3 at ca. 1660 cm-1
.
The 19F NMR spectra of 1 and 2 show the expected
three signals for two equivalent C6F5 rings with relative
1
intensities of 2Fo:1Fp:2Fm. The H NMR spectrum of 2
reveals the inequivalence of the Me groups of the imine
ligands, arising from restricted rotation around the
CdN bond at room temperature: a singlet at δ 2.38 for
the Me group cis to the hydrogen atom of the NH group
and a doublet (4J HH ) 1.8 Hz) at δ 2.07 for the trans-
Me group. The asymmetry of complex 3 due to the
presence of the amino-imine ligand is manifested in
the 19F NMR spectrum by two sets of signals arising
from one C6F5 trans to NH2 and one C6F5 trans to NH,
respectively. The assignment of the 1H resonances is
straightforward: two broad singlets at δ 9.63 and 3.63
are assigned to the NH and NH2 groups, respectively,
two singlets at δ 2.77 and 1.50 for the CH2 and the gem-
Me groups, respectively, and a doublet (4J HH ) 1.45 Hz)
at δ 2.20 for the Me group.
4
3H, cis-Me), 2,1 (d, 6H, trans-Me, J HH ) 1.2 Hz), 1.7
(br, 3H, NH3)], the integrated intensities being 1:3:5,
respectively, because only the diimine complex is com-
pletely soluble in CDCl3. The reaction leading to the
formation of complex 3 is related to the recently reported
palladium-assisted aldol condensation.24 About the for-
mation of 3, an alternative mechanism is via deproto-
nation of a methyl group in 2 under basic conditions,
followed by an intramolecular nucleophilic attack. How-
ever, when 2 was treated with aqueous [NBu4]OH in
methanol for 24 h the formation of 3 did not take place;
Compounds 2 and 3 are the first palladium(II) com-
plexes with these ligands. The synthesis of complexes
1
the H and 19F NMR spectra showed that the recovered
(18) Sa´nchez, G.; Serrano, J . L.; Momblona, F.; Ruiz, F.; Garc´ıa, J .;
Pe´rez, J .; Lo´pez, G.; Chaloner, P. A.; Hitchcock, P. B. Polyhedron 2001,
20, 571.
product consisted of unchanged 2 and traces of [NBu4]2-
[Pd2(C6F5)4(µ-OH)2].
(19) Sa´nchez, G.; Momblona, F.; Sa´nchez, M.; Pe´rez, J .; Lo´pez, G.;
Casabo´, J .; Molins, E.; Miravitlles, C. Eur. J . Inorg. Chem. 1998, 1199.
(20) De Haro, C.; Garc´ıa, G.; Sa´nchez, G.; Lo´pez, G. J . Chem. Res.,
Synop. 1986, 11; J . Chem. Res., Miniprint 1986, 1128.
(21) Long, D. A.; Steel, D. Spectrochim. Acta 1963, 19, 1955.
(22) Maslowski, E. Vibrational Spectra of Organometallic Com-
pounds; Wiley: New York, 1977; p 437.
Cr ysta l Str u ctu r es of Com p lexes 1-3. The crystal
structure of complex 1 is shown in Figure 1. The
coordination around Pd is almost square planar. The
angle between the two C6F5 rings is 85.87(9)° and the
(23) Alonso, E.; Fornie´s, J .; Fortun˜o, C.; Toma´s, M. J . Chem. Soc.,
Dalton Trans. 1995, 3777.
(24) Ruiz, J .; Rodr´ıguez, V.; Cutillas, N.; Pardo, M.; Pe´rez, J .; Lo´pez,
G.; Chaloner, P. A.; Hitchcock, P. B. Organometallics 2001, 20, 1973.

4914 Organometallics, Vol. 21, No. 23, 2002
Ruiz et al.
F igu r e 1. Molecular structure of complex 1. Selected bond
lengths (Å): Pd1-N1 2.132(2), Pd1-N2 2.119(2), Pd1-C1
2.004(2), Pd1-C7 1.997(2). Hydrogen bonds (Å) and angles
(deg): N(1)‚‚‚F(6)#1 3.264(3), H(1A)‚‚‚F(6)#1 2.53(6), N(1)-
H(1A)‚‚‚F(6)#1 141(4); N(1)‚‚‚F(4)#2 3.161, H(1B)‚‚‚F(4)#2
2.38, N(1)-H(1B)‚‚‚F(4)#2 154(4); N(1)‚‚‚F(7)#3 3.200(3),
H(1C)‚‚‚F(7)#3 2.49(5), N(1)-H(1C)‚‚‚F(7)#3 148(4); N(1)‚
‚‚F(10)#4 3.010(3), H(1C)‚‚‚F(10)#4 2.62(5), N(1)-
H(1C)‚‚‚F(10)#4 112(4); N(2)‚‚‚F(1)#1 3.029(3), H(2A)‚‚‚F(1)-
#1 2.41(5), N(2)-H(2A)‚‚‚F(1)#1 139(4); N(2)‚‚‚F(2)#5
3.107(3), H(2B)‚‚‚F(2)#5 2.62(5), N(2)-H(2B)‚‚‚F(2)#5
120(4); N(2)‚‚‚F(3)#5 3.349(3), H(2B)‚‚‚F(3)#5 2.62(5), N(2)-
H(2B)‚‚‚F(3)#5
148(4);
N(2)‚‚‚F(10)#4
3.065(3),
H(2C)‚‚‚F(10)#4 2.37(6), N(2)-H(2C)‚‚‚F(10)#4 137 (4) (sym-
metry transformations used to generate equivalent
atoms: #1 - x, -y, -z; #2 -x, -y + 1, -z; #3 x, -y, z - 1/2;
1
1
1
#4 -x + /2, -y + /2, -z; #5 x + /2, y - 1/2, z).
angle between the two NH3 ligands is 91.42(9)°. The
Pd-N distances (2.119(2) and 2.132(2) Å) are longer
than those observed in the ammine palladium com-
plexes trans-[Pd(NH3)2(1-MeC)2](NO3)2 (1-MeC ) 1-me-
thylcytosine),25 [Pd(CBDA-O,O′)(NH3)2] (CBDA ) cy-
clobutane-1,1-dicarboxylate),26 and [Pd(NH3)4]2+ 27
and
,
F igu r e 2. (a) Molecular structure of complex 2. Selected
bond lengths (Å): Pd1-N1 2.082(2), Pd1-N2 2.086(2),
Pd1-C1 2.008(3), Pd1-C7 2.005(3), N1-C13 1.259(4), N2-
C16 1.268(4). (b) Hydrogen bonds (Å) and angles (deg):
N‚‚‚F 3.089-3.091, N-H‚‚‚F 151-166.
slightly shorter than that observed in [Pd(dmpe)Me-
(NH3)] (dmpe ) 1,2-bis(dimethylphosphino)ethane)
(2.139(5) Å).28 In the crystal, a rather complex three-
dimensional macromolecular network structure is ob-
served built up by extensive hydrogen bonding, which
involves the NH groups of the ammine ligands and the
o- or m-fluorine atoms of the pentafluorophenyl rings
of five neighboring molecules (see caption of Figure 1),
although some of the H‚‚‚F interactions are within the
range reported for the sum of the van der Waals radii
of H and F (2.5-2.7 Å)29 and F‚‚‚H-N contacts of 2.5 Å
and greater are very weak and caution must be exer-
cised in attributing a particular stabilizing significance
to interactions of this length and longer.30 Fluorine,
when covalently bound to carbon, does not frequently
form hydrogen bonds with conventional hydrogen bond
donors such as the O-H and N-H groups,31 and aryl
fluorines are less effective than aliphatic fluorines as
hydrogen bond acceptors.30 Intermolecular hydrogen
bonds (O-H‚‚‚F-C) in [trans-Pt{µ-CtCC(OH)Ph2}-
(C6F5)(PPh3)]2‚CH2Cl2 have been reported.32 Two of the
hydrogen bridges in complex 1, those involving the
H(1C) and H(2B) atoms (caption of Figure 1), are three-
center (bifurcated) hydrogen bonds.33 Three-center hy-
drogen bonds involving two oxygen atoms are relatively
common, whereas those involving two fluorine atoms
bound to sp2- or sp3-hybridized carbons are rare; three-
center CF‚‚‚HN intramolecular hydrogen bonding in the
2,6-bis(2,6-difluorophenyl)piperidine systems has been
observed.34
The crystal structure of complex 2 is shown in Figure
2. The coordination around Pd is almost square planar.
The N1, N2, C1, and C7 atoms form a perfect plane with
the Pd atom 0.06(1) Å above. The four ligands are plane
fragments. The angle between the two C6F5 rings is
(25) Krumm, M.; Mutikainen, I.; Lippert, B. Inorg. Chem. 1991, 30,
884.
(26) Barnham, K. J .; Djuran, M. I.; Frey, U.; Mazid, M. A.; Sadler,
P. J . J . Chem. Soc., Chem. Commun. 1994, 65.
(27) Mealli, C.; Pichierri, F.; Randaccio, L.; Zangrando, E.; Krumm,
M.; Holtenrich, D.; Lippert, B. Inorg. Chem. 1995, 34, 3418.
(28) Seligson, A. L.; Togler, W. C. J . Am. Chem. Soc. 1991, 113, 2520.
(29) Teff, D. J .; Huffman, J . C.; Caulton, K. G. Inorg. Chem. 1997,
36, 4372.
(30) Howard J . A. K.; Hoy, V. J .; O’Hagan D.; Smith, G. T.
Tetrahedron 1996, 52, 12613.
(31) Dunitz, J .; Taylor, R. Chem. Eur. J . 1997, 3, 89.
(32) Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Mart´ın, A.; Serrano,
B. J . Chem. Soc., Dalton Trans. 2001, 2926.
(33) Steiner T. Angew. Chem., Int. Ed. 2002, 41, 48.
(34) Pham, M.; Gdaniec, M.; Polonski, T. J . Org. Chem. 1998, 63,
3731.

Synthesis of [Pd(C6F5)2L2] and [Pd(dmba)L2]ClO4 Complexes
Organometallics, Vol. 21, No. 23, 2002 4915
Sch em e 3a
F igu r e 3. Molecular structure of complex 3. Selected bond
lengths (Å): Pd1-C1 2.009(5), Pd1-C7 2.010(5), Pd1-N1
2.068(4), Pd1-N2 2.100(4).
a
Conditions: (a) +2NH3(aq), in Me2CO, room temperature,
5 min. (b) +10NH3(aq), in Me2CO, room temperature, 30 min.
(c) +10NH3(aq), in Me2CO, room temperature, 24 h.
88.8(1)° and the angle between the two imines is
89.1(1)° with the two CMe2 groups toward the same side
of the coordination plane. The Pd-N distances lie within
the range reported in complexes containing the {Pd-
(C6F5)2N2} moiety (2.064-2.131 Å) such as [Pd(C6F5)2-
{NHdC(OMe)Me}2]35 and [Pd(C6F5)2(pz‚‚‚H‚‚‚pz)] (pz )
pyrazolate).36 The acetimino ligands present in complex
2 show CdN bond lengths (1.259(4) and 1.268(4) Å)
similar to those observed in [AlCl3(NHdCMe2)]
(1.282(4) Å),13 [W(PhCtCPh)3(NHdCMe2)] (1.284(7)
Å),10 and [Au(NHdCMe2)2]+ (1.285(8) and 1.271(7) Å)12
but somewhat longer than those found in [Ru(bipy)2-
(NHdCMe2)2]+ (1.159 Å).11 In the crystal, dimeric ag-
gregates are formed through four hydrogen bonds
between the NH groups of the acetimine ligands and
half the o-fluorine atoms of the pentafluorophenyl rings
as shown in Figure 2b. The coordination planes of the
two fragments are parallel to each other, forming a very
symmetrical structure.
The crystal structure of complex 3 is shown in Figure
3. Only three crystal structures of 2-methyl-2-amino-
4-iminopentane complexes are available for comparison
with that of 3 (Figure 3).15-17 The amino-imino ligand
acts in a bidentate fashion achieving a six-membered
ring. The imine C13-N1 bond is 0.23 Å shorter than
the amine C16-N2 distance and both are similar to
those found in related complexes: [Ru(PMe2Ph)2{SC-
(O)Ph}2{NHdC(Me)CH2C(Me2)NH2}]15 (1.333(26) and
1.482(26) Å), [Co(methazolamidate)(NH3){NHdC(Me)-
CH2C(Me2)NH2}2](NO3)2‚2H2O16 (1.30(3) and 1.50(2) Å),
and [Cu{NHdC(Me)CH2C(Me2)NH2}2]17 (1.30 and 1.51
Å). The Pd-N1 bond length is 0.032 Å shorter than the
Pd-N2 distance. The three N-H groups, two p-fluo-
rines, and one o-fluorine are involved in hydrogen
bonding; each molecule is surrounded by three other
molecules forming two hydrogen bonds with each one
and resulting in a sheet parallel to the ac plane.
Dm ba Com p lexes. The dmba analogues of com-
plexes 1-3 have been prepared from the precursor [Pd2-
(dmba)2(µ-Cl)2]. After precipitation of AgCl by addition
of AgClO4, the solvento complex [Pd(dmba)(Me2CO)2]-
ClO4 generated in situ reacts with the acetone-am-
monia mixture to give complexes 5-7 (Scheme 3) in 57-
72% yields. As stated above for complexes 1-3, the
reaction conditions specified in Scheme 3 are critical for
the identity of the isolated complex.
Complexes 5-7 are white, air-stable solids that
decompose on heating above 170 °C. Their acetone
solutions show conductance values corresponding to 1:1
electrolytes (ΛM in the range 130-145 S cm2 mol-1 37
)
and the IR band observed at ca. 1090 cm-1 is consistent
with the presence of free perchlorate with Td symmetry.
The NH stretching modes for the three complexes are
found in the 3300-3150-cm-1 range, and a band at 1650
cm-1 in the IR spectra of 5 and 6 is assigned to the
ν(CN) mode.
The 1H NMR spectra of complexes 5-7 show the
presence of the dmba ligand and the observation of the
NCH2 and NMe2 proton signals as singlets suggests that
the inversion of the configuration at the PdCCCN
chelate ring is faster than the NMR time scale at room
temperature.35 The assignments given in the Experi-
mental Section for complex 7 were supported by the
pertinent heteronuclear (1H-13C) COSY technique. The
asymmetry of complexes 5 and 6 derived from the
presence of the dmba ligand is manifested in the 1H
NMR spectra and two sets of signals are observed for
the L (NH3 or NHCMe2) ligand: one L trans to C and
1
one L trans to N. On the other hand, the H resonances
from the L ligands are found at lower field than in the
corresponding complexes
1 and 2 containing the
Pd(C6F5)2 moiety while a negligible variation is found
1
on comparing the H spectra of 3 and 7.
The acetimine complex 8 (Scheme 4) was prepared
by a similar procedure starting from [Pd(dmba)(PPh3)-
Cl] in acetone. After elimination of the chloride ligand
(35) Ruiz, J .; Cutillas, N.; Rodr´ıguez, V.; Sampedro, J .; Lo´pez, G.;
Chaloner, P. A.; Hitchcock, P. B. J . Chem. Soc., Dalton Trans. 1999,
2939.
(36) Lo´pez, G.; Ruiz, J .; Vicente, C.; Mart´ı, J . M.; Garc´ıa, G.;
Chaloner, P. A.; Hitchcock, P. B.; Harrison, R. M. Organometallics
1992, 11, 1417.
(37) Geary, W. J . Coord. Chem. Rev. 1971, 7, 81.

4916 Organometallics, Vol. 21, No. 23, 2002
Ruiz et al.
F igu r e 5. Molecular structure of complex 7. Selected bond
lengths (Å): Pd1-C1 1.975(4), Pd1-N1 2.088(3), Pd1-N2
2.133(3), Pd1-N3 2.058(3).
F igu r e 4. Molecular structure of complex 6. Selected bond
lengths (Å): Pd1-C1 1.989(3), Pd1-N1 2.079(2), Pd1-N2
2.143(2), Pd1-N3 2.018(2).
1.275(4) Å) similar to those observed in complex 2. In
the crystal, the perchlorate anion is bridging two
complex cations through N-H‚‚‚O bonds (3.260(4) and
2.989(4) Å) forming a lineal chain. Hydrogen bonds
between triflate anions and the NH groups of acetimine
ligands in [Au(NHCMe2)2](CF3SO3) have been reported
(N‚‚‚O 2.89-2.91 Å, N‚‚‚H-O 158-167°).12
Sch em e 4
The crystal structure of complex 7 is shown in Figure
5. The 2-methyl-2-amino-4-iminopentane group acts as
a chelate ligand. The coordination around Pd is almost
square planar. The structural parameters of the dmba
ligand are similar to those found in the diimino complex
6 and other Pd(dmba) complexes.35,38 The Pd-N(2)
(imine) distance (2.133(3) Å) trans to the carbon atom
is longer than the Pd-N(3) (amine) (2.058(3) Å) distance
due to higher trans influence of the C. As expected, the
imine C(10)-N(2) bond (1.236(5) Å) is shorter than the
amine C(12)-N(3) distance (1.503(5) Å). In the crystal,
the perclorate anion is bridging two complex cations
through N-H‚‚‚O bonds involving the NH2 groups to
give a lineal chain.
with AgClO4 followed by addition of 32% aqueous NH3
(Pd:NH3 molar ratio ) 1:1; 1 h of stirring at room
temperature) complex 8 was obtained in 62% yield. The
complex behaves as a 1:1 electrolyte (ΛM ) 132 S cm2
mol-1 37
in acetone and the IR spectrum showed bands
)
at 3250 (ν NH), 1660 (ν CN), and 1060 (ν ClO4) cm-1
The H NMR spectrum is consistent with the proposed
structure and the 31P resonance is observed at δ 43.5
as a singlet.
.
1
Con clu sion s
The first palladium complexes containing acetimine
and its dimer (2-methyl-2-amino-4-iminopentane) have
been prepared by using a labile palladium complex and
aqueous acetone-ammonia solutions. Acetimine and its
dimer are unstable products and the procedure de-
scribed herein appears to be a systematic approach to
the synthesis of these types of complexes. Depending
on the experimental conditions used (ammonia concen-
tration and reaction time) the ammine, acetimine, or
2-methyl-2-amino-4-iminopentane complex is isolated.
The X-ray diffraction study of the compounds reveals
that extensive C-F‚‚‚H-N or O‚‚‚H-N interactions are
present in the solids.
Cr ysta l Str u ctu r es of Com p lexes 6 a n d 7. A
drawing of the cationic complex of 6 is shown in Figure
4. The palladium atom is located in a slightly distorted
square-planar environment, surrounded by the C and
N atoms of the cyclometalated dmba ligand and the N
atoms of two imino ligands. The cyclometalated ring is
puckered with the nitrogen atom significantly out of the
plane defined by the palladium and carbon atoms, a
feature that is quite commonly observed in cyclometa-
lated dmba complexes. The Pd-C(1) (dmba) and
Pd-N(1) (dmba) distances are similar to those found
in other Pd(dmba) complexes.35,38
The Pd-N(2) (acetimino) distance (2.143 Å) trans to
the carbon atom is longer than the Pd-N(3) (acetimino)
distance (2.018 Å), due to higher trans influence of the
C atom than that of the N atom (dmba, sp3). Both
acetimine ligands show CdN bond lengths (1.271(4) and
Exp er im en ta l Section
In str u m en ta l Mea su r em en ts. C, H, and N analyses were
performed with a Carlo Erba model EA 1108 microanalyzer.
Decomposition temperatures were determined with a Mettler
TG-50 thermobalance at a heating rate of 5 °C min-1 and the
solid samples under nitrogen flow (100 mL min-1). Molar
(38) Falvello, L. R.; Ferna´ndez, S.; Navarro, R.; Urriolabeitia, E. P.
Inorg. Chem. 1996, 35, 3064.

Synthesis of [Pd(C6F5)2L2] and [Pd(dmba)L2]ClO4 Complexes
Organometallics, Vol. 21, No. 23, 2002 4917
conductivities were measured in acetone solution (c ≈ 5 × 10-4
mol L-1) with a Crison 525 conductimeter. The NMR spectra
were recorded on a Bruker AC 200E or Varian Unity 300
spectrometer, using SiMe4 and CFCl3 as the standard, respec-
tively. Infrared spectra were recorded on a Perkin-Elmer 1430
spectrophotometer with Nujol mulls between polyethylene
sheets. Mass spectra (positive-ion FAB) were recorded on a
V.G. AutoSpecE spectrometer and measured with 3-nitro-
benzyl alcohol as the dispersing matrix; isotope 106Pd (27.3%)
was chosen for peak assignments.
NH3(aq); 0.724 mmol) was then added. The solution was stirred
at room temperature for 5 min, the solvent was removed under
vacuum, and the residue was extracted with diethyl ether and
dried in the air. Yield 72%. Anal. Calcd for C9H18ClN3O4Pd:
C, 28.9; H, 4.9; N, 11.2. Found: C, 29.1; H, 4.9; N, 11.0. Mp:
178 °C dec. ΛM: 145 S cm2 mol-1. IR (Nujol, cm-1): 3358, 3288
ν(NH). 1H NMR at 25 °C (acetone-d6): δ 7.05-6.89 (m, 4H,
C6H4), 4.03 (s, 2H, NCH2), 3.2 (br, 3H, NH3), 3.0 (s, 6H, NMe2),
2.59 (br, 3H, NH3). Positive-ion FAB mass spectrum: m/z 297
(M - ClO4 + 23)+, 257 (M - ClO4 - NH3)+, 240 (M - ClO4 -
2NH3)+.
Mater ials. The starting complexes cis-[Pd (C6F5)2(NCPh)2],20
[Pd2(o-C6H4CH2NMe2)2(µ-Cl)2],39 and [(o-C6H4CH2NMe2)PdCl-
(PPh3)]40 were prepared as described elsewhere.
P r ep a r a t ion of Com p lex [P d (o-C6H 4CH 2NMe2)(NH -
CMe2)2]ClO4 (6). AgClO4 (112.7 mg, 0.543 mmol) was added
to an acetone (15 mL) solution of [(o-C6H4CH2NMe2)2Pd2(µ-
Cl)2] (150 mg, 0.272 mmol). After the resulting suspension was
stirred at room temperature in the darkness for 30 min, it was
filtered through Celite with 7 mL of acetone, and NH3 (338
µL of 32% NH3(aq); 5.6 mmol) was then added. The solution
was stirred at room temperature for 30 min, the solvent was
removed under vacuum, and the residue was extracted with
dichloromethane and filtered. The resulting solution was
concentrated under vacuum and water was added to give a
white precipitate that was filtered off and air-dried. The solid
was crystallized from dichloromethane-toluene. Yield: 57%.
Anal. Calcd for C15H26ClN3O4Pd: C, 39.7; H, 5.8; N, 9.3.
Found: C, 39.4; H, 5.9; N, 9.1. Mp: 171 °C dec. ΛM: 140 S
cm2 mol-1. IR (Nujol, cm-1): 3265 ν(NH), 1660 ν(CN), 1086
P r ep a r a tion of Com p lex cis-[P d (C6F 5)2(NH3)2] (1). To
a solution of [Pd(C6F5)2(NCPh)2] (100 mg, 0.155 mmol) in
acetone (15 mL) was added 20% aqueous NH3 (42.9 µL, 0.464
mmol). The resulting solution was stirred at room temperature
for 10 min, and the solvent was then evaporated to dryness.
The residue was then treated with 1:3 CHCl3-hexane and the
suspension was filtered off to separate the white solid 1, which
was washed with CHCl3 and air-dried. Yield: 60 mg, 81%.
Anal. Calcd for C12H6N2F10Pd: C, 30.37; H, 1.27; N, 5.90.
Found: C, 30.77; H, 1.20; N, 5.85. Mp: 189 °C dec. IR (Nujol,
cm-1): v(NH), 3388, 3304; v(Pd-C6F5) 798, 786. 1H NMR (300
MHz, 298 K, CDCl3): δ(SiMe4) 1.86 (br, 3H, NH3). 19F NMR
(282.4 MHz, 298 K, CDCl3): δ(CFCl3) -117.7 (m, 4Fo), -160.6
(t, 2Fp, J mp ) 19.8 Hz), -163.5 (m, 4Fm).
P r ep a r a tion of Com p lex cis-[P d (C6F 5)2(NHCMe2)2] (2).
To a solution of (C6F5)2Pd(NCPh)2 (100 mg, 0.155 mmol) in
acetone (15 mL) was added 20% aqueous NH3 (286.2 µL, 3.093
mmol). The resulting solution was stirred at room temperature
for 4 h, and the solvent was then evaporated to dryness.
Addition of 1:5 Et2O-hexane to the residue, followed by
vigorous stirring, rendered a white suspension, from which a
white solid was collected by filtration and air-dried. Complex
2 was recrystallized from CH2Cl2-toluene-hexane. Yield: 65
mg, 76%. Anal. Calcd for C18H14N2F10Pd: C, 38.97; H, 2.54;
N, 5.05. Found: C, 38.56; H, 2.55; N, 5.16. Mp: 196 °C dec.
IR (Nujol, cm-1): v(NH), 3316; v(CdN), 1668; v(Pd-C6F5), 792,
782. 1H NMR (300 MHz, 298 K, CDCl3): δ(SiMe4) 8.40 (br,
1
(ClO4-). H NMR at 25 °C (CDCl3): δ 9.3 (br, 1H, NH), 9.07
(br, 1H, NH), 7.06-6.85 (m, 3H, C6H4), 6.54 (d, 1H, C6H4, J H-H
) 7.4 Hz), 3.94 (s, 2H, NCH2), 2.71 (s, 6H, NMe2), 2.42 (s, 3H,
CMe2), 2.39 (s, 3H, CMe2), 2.31 (d, 3H, CMe2, J H-H ) 1,2 Hz),
2.25 (s, 3H, CMe2). Positive-ion FAB mass spectrum: m/z 354
(M - ClO4 - 1)+, 297 (M - ClO4 - HNCMe2)+, 240 (M - ClO4
- 2HNCMe2)+.
P r ep a r a tion of Com p lex [P d (o-C6H4CH2NMe2){NHC-
(Me)CH2C(Me2)NH2}]ClO4 (7). AgClO4 (75.1 mg, 0.362 mmol)
was added to an acetone (15 mL) solution of [(o-C6H4CH2-
NMe2)2Pd2(µ-Cl)2] (100 mg, 0.181 mmol). After the resulting
suspension was stirred at room temperature in the darkness
for 30 min, it was filtered through Celite with 2 mL of acetone,
and NH3 (219 µL of 32% aqueous NH3; 3,62 mmol) was then
added. The solution was stirred at room temperature for 24
h, the solvent was removed under vacuum, and the residue
was extracted with CHCl3, filtered, and air-dried. Yield: 67%.
Anal. Calcd for C15H26ClN3O4Pd: C, 39.7; H, 5.8; N, 9.3.
Found: C, 39.8; H, 5.8; N, 9.4. Mp: 199 °C dec. ΛM: 130 S
cm2 mol-1. IR (Nujol, cm-1): 3295, 3250, 3164 ν(NH), 1655
2H; NH), 2.38 (s, 6H; cis-CH3), 2.07 (d, 6H, trans-CH3, 4J HH
)
1.8 Hz). 19F NMR (282.4 MHz, 298 K, CDCl3): δ(CFCl3) -117.7
(m, 4Fo), -162.3 (t, 2Fp, J mp ) 19.8 Hz), -164.6 (m, 4Fm).
P r ep a r a tion of Com p lex [P d (C6F 5)2{NHC(Me)CH2C-
(Me2)NH2}] (3). To a solution of (C6F5)2Pd(NCPh)2 (100 mg,
0.155 mmol) in acetone (15 mL) was added 20% aqueous NH3
(286.2 µL, 3.093 mmol). The solution was stirred at room
temperature for 2 days, and the solvent was then evaporated
to dryness. Addition of 1:5 Et2O-hexane to the residue,
followed by vigorous stirring, rendered a white suspension,
from which a white solid was collected by filtration and air-
dried. Complex 3 was recrystallized from CH2Cl2-hexane.
Yield: 62 mg, 72%. Anal. Calcd for C18H14N2F10Pd: C, 38.97;
H, 2.54; N, 5.05. Found: C, 38.72; H, 2.66; N, 4.92. Mp: 229
°C dec. IR (Nujol, cm-1): v(NH), 3342, 3320, 3290; v(CdN),
1660; v(Pd-C6F5), 792, 782. 1H NMR (300 MHz, 298 K,
CDCl3): δ(SiMe4) 9.63 (br, 1H; NH), 3.63 (br, 2H, NH2), 2.77
(s, 2H, CH2), 2.20 (d, 3H, CH3, J HH ) 1.5 Hz), 1.5 (s, 6H, gem-
CH3). 19F NMR (282.4 MHz, 298 K, CDCl3): δ(CFCl3) -114.4
(m, 2Fo), -115.0 (m, 2Fo), -164.1 (t, 1Fp, J mp ) 19.5 Hz),
-164.3 (t, 1Fp, J mp ) 19.5 Hz), -165.8 (m, 4Fm).
1
ν(CN), 1086 (ClO4-). H NMR at 25 °C (DMSO-d6): δ 9.65 (br
s, 1H, NH), 7.90 (dd, 1H, C6H4, J HH ) 6.2 Hz, J HH ) 1.6 Hz),
6.97-6.84 (m, 3H, C6H4), 3.86 (s, 2H, NCH2), 3.67 (br s, 2H,
NH2), 2.56 (s, 6H, NMe2), 2.47 (s, 2H, CCH2 of amino-imino
ligand), 2.23 (s, 3H, CMe), 1.17 (s, 6H, CMe2). Positive-ion FAB
mass spectrum: m/z 354 (M - ClO4 -1)+.
P r ep a r a t ion of Com p lex [P d (o-C6H 4CH 2NMe2)(NH -
CMe2)(P P h 3)]ClO4 (8). AgClO4 (38.5 mg, 0.186 mmol) was
added to an acetone (10 mL) solution of [(o-C6H4CH2NMe2)-
PdCl(PPh3] (100 mg, 0.186 mmol). After the resulting suspen-
sion was stirred at room temperature in the darkness for 30
min, it was filtered through Celite with 2 mL of acetone, and
NH3 (172 µL of 32% aqueous NH3; 0.186 mmol) was then
added. The solution was stirred at room temperature for 1 h,
the solvent was removed under vacuum, and the residue was
extracted with diethyl ether, filtered off, and air-dried. Yield:
62%. Anal. Calcd for C30H34ClN2O4PPd: C, 54.6; H, 5.2; N,
4.3. Found: C, 54.3; H, 5.4; N, 4.2. Mp: 197.3 °C dec. ΛM: 132
S cm2 mol-1. IR (Nujol, cm-1): ν (NH), 3250; ν(CN), 1660;
(ClO4-), 1096. 1H NMR at 25 °C (CDCl3): δ 9.40 (br s, 1H,
NH), 7.73-7.41 (m, 15 H, PPh3), 7.03 (d, 1H, C6H4, J HH ) 7.8
Hz), 6.86 (t false, 1 H, C6H4, J HH ) 6.8), 6.4 (m, 2 H, C6H4),
4.13 (s, 2 H, NCH2), 2.76 (s, 6H, NMe2), 2.01 (s, 3H, CMe2),
P r ep a r a tion of Com p lex [P d (o-C6H4CH2NMe2)(NH3)2]-
ClO4 (5). AgClO4 (75.1 mg, 0.362 mmol) was added to an
acetone (5 mL) solution of [(o-C6H4CH2NMe2)2Pd2(µ-Cl)2] (100
mg, 0.181 mmol). After the resulting suspension was stirred
at room temperature in the darkness for 30 min, it was filtered
through Celite with 2 mL of acetone, and NH3 (67 µL of 20%
(39) Cope, A. C.; Friedrich, E. C. J . Am. Chem. Soc. 1968, 90, 909.
(40) Deeming, A. J .; Rothwell, I. P.; Hursthouse, M. B.; New, L. J .
Chem. Soc., Dalton Trans. 1978, 1490.

4918 Organometallics, Vol. 21, No. 23, 2002
Ta ble 1. Cr ysta l Str u ctu r e Deter m in a tion Deta ils
Ruiz et al.
1
2
3
6
7
formula
fw
C
12H6F10N2Pd
C18H14F10N2Pd
554.71
C18H14F10N2Pd
554.71
C15H26ClN3O4Pd
454.24
C15H26ClN3O4Pd
454.24
474.59
temp (K)
173(2)
173(2)
173(2)
173(2)
173(2)
cryst syst, space group
monoclinic, C2/c
triclinic, P1h
monoclinic, P21/n
triclinic, P1h
monoclinic, P21/n
cell dimens
a (Å)
b (Å)
17.3430(10)
10.4530(10)
17.1640(10)
90
104.12
90
3017.6(4)
8
2.089
9.0910(10)
9.4170(10)
12.9790(10)
110.800(10)
101.970(10)
95.440(10)
998.74(17)
2
9.6620(10)
16.7360(10)
12.5130(10)
90
106.27(1)
90
1942.4(3)
4
1.897
9.0790(10)
9.5500(10)
12.5460(10)
81.11
73.440(10)
66.150(10)
952.68(16)
2
8.7427(4)
20.7105(11)
10.4411(6)
90
92.641(4)
90
1888.52(17)
4
1.598
c (Å)
R (deg)
â (deg)
γ (deg)
cell vol (Å3)
Z
D
calc (g cm-3
)
1.845
1.583
F (000)
1824
1.340
544
1.027
1088
1.056
464
1.137
928
1.147
µ (mm-1
)
cryst size (mm3)
θ range for data
collection (deg)
index ranges
0.30 × 0.20 × 0.20
0.40 × 0.30 × 0.20
0.50 × 0.20 × 0.10
0.40 × 0.20 × 0.20
0.50 × 0.40 × 0.10
3.13 to 25.00
3.25 to 25.00
3.13 to 24.99
3.38 to 25.00
3.05 to 25.00
-20 e h e 20,
-12 e k e 12,
-20 e l e 0
5334
-10 e h e 2,
-10 e k e 10,
-15 e l e 15
4254
-11 e h e 0,
-19 e k e 3,
-14 e l e 14
4404
-9 e h e 10,
-10 e k e 11,
-14 e l e 14
6597
-10 e h e 10,
-24 e k e 3,
0 e l e 12
4023
no. of reflns collected
ind reflns
2655 [R(int) ) 0.0202] 3425 [R(int) ) 0.0109] 3408 [R(int) ) 0.0241] 3345 [R(int) ) 0.0163] 3328 [R(int) ) 0.0296]
2655/0/250
no. of data/restraints/
3425/0/288
3408/0/280
3345/0/217
3328/0/217
params
goodness-of-fit on F2
1.046
1.118
1.122
1.061
1.038
final R indices [I > 2σ(I)] R1 ) 0.0196,
R1 ) 0.0228,
wR2 ) 0.0593
R1 ) 0.0253,
wR2 ) 0.0625
0.626 and -0.667
R1 ) 0.0436,
wR2 ) 0.0882
R1 ) 0.0507,
wR2 ) 0.0904
0.894 and -0.602
R1 ) 0.0259,
wR2 ) 0.0658
R1 ) 0.0301,
wR2 ) 0.0677
0.968 and -0.638
R1 ) 0.0357,
wR2 ) 0.0953
R1 ) 0.0454,
wR2 ) 0.1000
0.739 and -0.680
wR2 ) 0.0483
R indices (all data)
R1 ) 0.0244,
wR2 ) 0.0494
0.313 and -0.639
largest diff. peak and
hole (e Å-3
)
1.65 (s, 3H, CMe2). 31P NMR: δ 43.5 (s). Positive-ion FAB mass
spectrum: m/z 559 (M - ClO4)+, 502 (M - ClO4 - HNd
CMe2)+.
X-r a y St r u ct u r e Det er m in a t ion of 1, 2, 3, 6, a n d 7.
Crystals suitable for a diffraction study were grown from CH2-
Cl2-hexane (1), CH2Cl2-toluene-hexane (2 and 6), CH2Cl2-
hexane (3), or acetone-water (7). Mo KR radiation was used
(λ ) 0.71073 Å) and the structures were solved by the
SHELXS-9741 program and refined anisotropically on F2
(program SHELXL-9741). Other details of data collection and
refinement are given in Table 1.
Ack n ow led gm en t. Financial support of this work
by the Direccio´n General de Investigacio´n del Ministerio
de Ciencia y Tecnolog´ıa (Project No. BQU2001-0979-C-
02-01), Spain, is acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinements details, atomic coordinates and equiva-
lent isotropic displacement parameters, complete bond dis-
tances and angles, and ORTEP views for compounds 1, 2, 3,
6, and 7, as well as X-ray crystallographic data (CIF format).
This material is available free of charge via the Internet at
http://pubs.acs.org.
(41) Sheldrick, G. M. SHELX-97, Programs for Crystal Structure
Analysis (Release 97-2); University of Go¨ttingen: Go¨ttingen, Germany,
1998.
OM020434Y