Palladium(II)-promoted cyclization reaction of 4-hydroxybutyronitrile to 2-Iminotetrahydrofuran. X-ray structure of cis-PdCl2{N(H)=CCH2CH2CH 2O}-(PPh3)·1/2CH2Cl2

Article abstract of DOI:10.1021/om950740u

Reaction of 3-bromo-1-propanol with Et₄N(CN) in CH₂Cl₂ at room temperature gives in high yield 4-hydroxybutyronitrile, HO(CH₂)₃CN (1), which upon reaction with Na₂PdCl₄ affords [PdCl₂{N(H)=CCH₂CH₂CH₂O} ₂] (2), containing two 2-iminotetrahydrofuran ligands derived from intramolecular cyclization of 1. Substitution of one imino ligand for an entering nucleophile L leads to the complexes [PdCl₂{N(H)=CCH₂CH₂CH₂0}(L)] (L = PPh₃ (3), py (4), DMF (5)). Similarly, the reaction of 2 with 1 equiv of cis-Ph₂PCH=CHPPh₂ results in the displacement of the two iminolactone ligands and formation of [PdCl₂(Ph₂PCH=CHPPh₂)]. The ligand 1 and the complexes 2-5 were characterized by analytical and spectroscopic techniques. IR data suggest that 2 and 3 are present as a mixture of cis and trans isomers, while 4 and 5 have a trans stereochemistry. Complex 3 gave crystals of the cis form, as evidenced by an X-ray structural determination.

Full text of DOI:10.1021/om950740u

1236
Organometallics 1996, 15, 1236-1241
P a lla d iu m (II)-P r om oted Cycliza tion Rea ction of
4-Hyd r oxybu tyr on itr ile to 2-Im in otetr a h yd r ofu r a n .
X-r a y Str u ctu r e of cis-[P d Cl2{N(H)dCCH2CH2CH2O}-
(P P h 3)]‚1/2CH2Cl2
Roberta Bertani, Marta Gotti, Rino A. Michelin,* and Mirto Mozzon
Centro di Chimica e Tecnolgia dei Composti Metallorganici degli Elementi di Transizione del
CNR and Istituto di Chimica Industriale, Facolta` di Ingegneria, Universita` di Padova,
Via F. Marzolo 9, 35131 Padova, Italy
Giuliano Bandoli
Dipartimento di Scienze Farmaceutiche, Universita` di Padova,
Via F. Marzolo 5, 35131 Padova, Italy
Robert J . Angelici*
Department of Chemistry, Iowa State University, Ames, Iowa 50011
Received September 18, 1995X
Reaction of 3-bromo-1-propanol with Et4N(CN) in CH2Cl2 at room temperature gives in
high yield 4-hydroxybutyronitrile, HO(CH2)3CN (1), which upon reaction with Na2PdCl4
affords [PdCl2{N(H)dCCH2CH2CH2O}2] (2), containing two 2-iminotetrahydrofuran ligands
derived from intramolecular cyclization of 1. Substitution of one imino ligand for an entering
nucleophile L leads to the complexes [PdCl2{N(H)dCCH2CH2CH2O}(L)] (L ) PPh3 (3), py
(4), DMF (5)) . Similarly, the reaction of 2 with 1 equiv of cis-Ph2PCHdCHPPh2 results in
the displacement of the two iminolactone ligands and formation of [PdCl2(Ph2PCHdCHPPh2)].
The ligand 1 and the complexes 2-5 were characterized by analytical and spectroscopic
techniques. IR data suggest that 2 and 3 are present as a mixture of cis and trans isomers,
while 4 and 5 have a trans stereochemistry. Complex 3 gave crystals of the cis form, as
evidenced by an X-ray structural determination.
In tr od u ction
intramolecularly the metal-coordinated nitrile, thus
providing a new route to heterocyclic compounds. Hy-
droxyalkyl nitriles of the type HO(CH2)nCN having a
suitable chain length (n ) 3, 4) would likely fulfill these
requirements, since they are expected, upon coordina-
tion to late transition-metal ions, to give iminolactones
by intramolecular nucleophilic attack of the -OH
functionality on the nitrile carbon atom as illustrated
in eq 1.
Coordination of a nitrile, RCN, to an electron-
withdrawing transition-metal ion results in an en-
hanced electrophilicity of the nitrile carbon, thus mak-
ing it susceptible to nucleophilic attack. Reactions of
metal nitriles with protic nucleophiles such as water,
alcohols, and amines to generate the corresponding
amidates, imido esters, and amidines, respectively, have
been extensively reviewed.1
We have been recently concerned with the conversion
of Pt(II)-coordinated nitriles to N-heterocycles such as
2-oxazoline and 1,3-oxazine, which are formed upon
reaction of RCN ligands with HOCH2CH2Cl/base2a,b or
OCH2CH2/Cl- 2c and HOCH2CH2CH2Cl/base2d systems,
respectively. An extension of this reaction chemistry
would take advantage of the incorporation in the nitrile
alkyl chain of a nucleophilic group capable of attacking
Here we report the synthesis of 4-hydroxybutyroni-
trile, HO(CH2)3CN, and its conversion to 2-iminotet-
rahydrofuran promoted by Pd(II).
X Abstract published in Advance ACS Abstracts, December 15, 1995.
(1) (a) Michelin, R. A.; Mozzon, M.; Bertani, R. Coord. Chem. Rev.
1996, 147, 299. (b) Storhoff, B. N.; Lewis, H. C. Coord. Chem. Rev.
1977, 23, 1.
(2) (a) Michelin, R. A.; Bertani, R.; Mozzon, M.; Bombieri, G.;
Benetollo, F.; Angelici, R. J . Organometallics 1991, 10, 1715. (b)
Michelin, R. A.; Bertani, R.; Mozzon, M.; Bombieri, G.; Benetollo, F.;
Angelici, R. J . J . Chem. Soc., Dalton Trans. 1993, 959. (c) Michelin,
R. A.; Mozzon, M.; Berin, P.; Bertani, R.; Benetollo, F.; Bombieri, G.;
Angelici, R. J . Organometallics 1994, 13, 1341. (d) Michelin, R. A.;
Belluco, U.; Mozzon, M.; Berin, P.; Bertani, R.; Benetollo, F.; Bombieri,
G.; Angelici, R. J . Inorg. Chim. Acta 1994, 220, 21.
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were carried out under
an N2 atmosphere. Tetrahydrofuran (THF) and diethyl ether
were distilled from sodium/benzophenone, and CH2Cl2 was
distilled from CaH2; all the other solvents were of reagent
grade and were used without further purification. IR spectra
were taken on a Perkin-Elmer 983 spectrophotometer (abbrevi-
ations: s ) strong, m ) medium, w ) weak). Proton and
0276-7333/96/2315-1236$12.00/0 © 1996 American Chemical Society

Palladium(II)-Promoted Cyclization Reaction
Organometallics, Vol. 15, No. 4, 1996 1237
carbon-13 NMR spectra were obtained on a Bruker AC-200
spectrometer. 1H NMR shifts were recorded relative to the
residual H resonances in the deuterated solvents: CDCl3, δ
[CH2(CdN)]; 15.5 (-CH2-). FAB MS (m-nitrobenzyl alco-
hol; m/ z (relative abundance %)): 489 ([(PPh3)Pd(HN-
1
CCH2CH2CH2O)Cl]+, 40%); 453 ([(PPh3)Pd(HNCCH2CH2-
7.23; CD3SOCD3, δ 2.50. The 13C{1H} NMR shifts are given
relative to the solvent resonance: CDCl3, δ 77.0; CD2Cl2, δ
53.8. 31P{1H} NMR spectra were run on a Varian FT 80-A
spectrometer; chemical shifts are referenced to external 85%
H3PO4, with downfield values taken as positive. In all the
NMR spectra J values are in Hz (abbreviations used: s )
singlet, t ) triplet, m ) multiplet, br ) broad). The fast atom
bombardment (FAB) mass spectra were obtained on a VG ZAB
2F instrument operating with a Xe atom beam energy of 8 keV
using m-nitrobenzyl alcohol as a matrix. The GC-MS analy-
ses were performed on a Carlo Erba QMD 1000 instrument
using a PS 264 capillary column (30 m × 3 µm) from 100 to
250 °C at 10 °C/min with a He flow of 1 mL/min. Elemental
analyses were performed by the Department of Analytical,
Inorganic and Organometallic Chemistry of the University of
Padova. The melting points were taken on a hot plate
apparatus and are uncorrected.
CH2O)]+, 10%); 369 ([Pd-PPh3]+, 35%); 404 ([ClPd(PPh3)H]•+
30%).
,
L ) p y (4). To a suspension of 2 (0.15 g, 0.43 mol) in CH2-
Cl2 (20 mL) an excess of pyridine (0.15 mL, 1.8 mol) was added
and the reaction mixture was stirred at room temperature
until complete dissolution of the starting complex. After 4 h
the yellow solution was concentrated under reduced pressure
to a small volume (3 mL) and treated with Et2O (20 mL). A
yellow solid formed, which was filtered off, washed with Et2O
(2 × 10 mL), and dried under vacuum. Yield: 0.11 g (78%).
Mp: 201 °C dec. Anal. Calcd for C9H12N2Cl2Pd: C, 31.66; H,
3.54; N, 8.20. Found: 32.14; H, 3.74; N, 8.64. IR (Nujol
mull): ν(NH) 3198 cm-1 (s); ν(CdN) 1679 cm-1 (s); ν(PdCl) 354
cm-1 (m). 1H NMR (δ, CDCl3): 5.70 (br, 1H, NH); 4.41 (m,
2H, OCH2); 3.33 (m, 1H, NCCH2); 2.91 (m, 1H, NCCH2); 2.24
(m, 2H, CH2).
Syn th esis of HO(CH2)3CN (1). To a solution of Et4N(CN)
(4 g, 0.026 mol) in CH2Cl2 (20 mL) was added HO(CH2)3Br
(2.5 mL, 0.027 mol) at room temperature to give a pale yellow
solution. The reaction course was followed by IR spectroscopy,
which showed the disappearance with time of the ν(CtN) band
at 2065 cm-1 due to Et4N(CN) and an increase of the corre-
sponding absorption at 2249 cm-1 due to the final product.
After it was stirred for 22 h, the reaction mixture was taken
to dryness under reduced pressure and the solid residue was
washed five times (5 × 20 mL) with an Et2O/CH2Cl2 (4:1 v/v)
mixture to remove Et4NBr. The washes were combined, and
after filtration, the solution was taken to dryness to give an
oily residue. Yield: 8.04 g (79%). IR (liquid film): ν(CtN)
2249 cm-1 (s); ν(OH) 3441 cm-1 (s). 1H NMR (δ, CDCl3): 3.43
[t, 3J HH 5.90, 2H, CH2OH]; 2.26 [t, 3J HH 7.03, 2H, CH2CN]; 1.61
(m, 2H, CH2); 3.59 (s-br, 1H, OH). 13C{1H-undecoupled} NMR
L ) DMF (5). A suspension of 2 (0.2 g, 0.57 mmol) in DMF
(20 mL) was stirred at room temperature. After 48 h a light
yellow solution was obtained. Workup as for 4 gave 5. Yield:
0.16 g (83%). Mp: 222 °C dec. Anal. Calcd for C7H14N2O2-
Cl2Pd: C, 25.06; H, 4.21; N, 8.35. Found: C, 25.12; H, 4.12;
N, 7.93. IR (Nujol mull): ν(NH) 3212 cm-1 (s); ν(CdN) 1684
cm-1 (s); ν(PdCl) 354 cm-1 (m). 1H NMR (δ, CDCl3): 5.70 (br,
1H, NH); 4.55 (m, 2H, OCH2); 3.29 (m, 1H, NCCH2); 2.75 (m,
1H, NCCH2); 2.21 (m, 2H, CH2).
Rea ction of 2 w ith cis-1,2-Bis(d ip h en ylp h osp h in o)-
eth ylen e. A suspension of 2 (0.1 g, 0.28 mmol) in CH2Cl2 (20
3
mL) was treated with cis-Ph2PCHdCHPPh2 (0.114 g, 0.28
mmol) at room temperature. The slow dissolution of the
starting compound 2 was accompanied by the formation of a
white precipitate, which, after 20 h, was filtered off, washed
with Et2O, and dried under vacuum. It was identified as
1
2
(δ, CDCl3): 119.55 (m, CN); 59.26 [tt, J CH 142.9, J CH 3.67,
CH2OH]; 27.38 [t, 1J CH 130.34, -CH2-); 13.045 [t, 1J CH 135.92,
CH2CN].
[PdCl2(Ph2PCHdCHPPh2)] by comparison with a sample
independently prepared.4 Yield: 0.155 g (96%). IR (Nujol
mull): ν(PdCl) 286 (m), 309 (s) cm-1
CDCl3): 48.36 ppm (s, J PtP 3682).
.
31P{1H} NMR (δ,
1
Syn th esis of [P d Cl2{N(H)dCCH2CH2CH2O}2] (2). To a
stirred suspension of PdCl2 (0.22 g, 1.00 mmol) in H2O (40 mL)
at room temperature was added an excess of NaCl (0.15 g, 2.6
mmol) to give, after 2 h, a clear yellow-brown solution, which
was then treated with an excess of 1 (0.3 mL, d ) 1.0473 g/cm3,
4.0 mmol). After the mixture was stirred at room temperature
for 3 days, a brown precipitate formed, which was filtered off,
washed with H2O (3 × 3 mL) and Et2O (5 × 3 mL), and dried
under vacuum. Yield: 0.26 g (75%). Mp: 208-211 °C dec.
Anal. Calcd for C8H14N2O2Cl2Pd: C, 26.7; H, 4.0; N, 8.0.
Found: C, 25.22; H, 3.87; N, 8.03. IR (Nujol mull): ν(NH)
3213 cm-1 (vs); ν(CdN) 1684 cm-1 (s); ν(PdCl) 353 (m), 300,
The mother liquors were taken to dryness to give an oily
residue. IR (liquid film): ν(NH) 3385 cm-1; ν(CdN) 1662 cm-1
.
1H NMR (δ, CDCl3): 3.52 (m, 2H, OCH2); 2.77 (m, 2H, NCCH2);
1.85 (m, 2H, CH2). A CH2Cl2 solution of the oil was analyzed
by GC-MS. Only one compound, apart from the solvent, was
present with the retention time 6.03 min: m/ z 86 (MH+,
relative intensity 40%); 56 ([MH - H2CO]+, 35%); 42 ([CH2-
CH2CH2]+, 98%); 28 ([CH2CH2]+, 100%).
Sin gle-Cr yst a l X-r a y Diffr a ct ion An a lysis of cis-3.
Crystals suitable for X-ray data collection were obtained from
a mixed solvent (CH2Cl2/Et2O); eventually a small crystal was
directly transferred, with mother liquor, to a glass capillary
and then mounted on the diffractometer. All crystallographic
measurements were carried out at 294 K on a Nicolet Siemens
R3m/V diffractometer, using graphite-monochromated Mo KR
radiation (λ ) 0.710 73 Å). The unit-cell parameters and their
associated estimated standard deviations were obtained from
a least-squares fit of the setting angles of 50 reflections in the
range 18 > 2θ > 26° (see Table 1 for crystal data). Although
the data collection was fast, a significant decrease (up to 30%)
in intensity was observed by two standard reflections mea-
sured after each 100 reflections throughout collection (4 days).
A correction for crystal decay was applied to the measured
counts, but an empirical absorption correction based on the
azimuthal ψ-scan method was impossible to apply. The
structure was determined via the standard heavy-atom method
and Fourier difference technique, and it was refined by full-
matrix least squares using the SHELXTL-Plus program
system.5 All non-hydrogen atoms were refined with anisotro-
and 281 (w-m) cm-1
.
1H NMR (δ, CD3SOCD3): 7.5-8.3 (br,
NH); 4.04 (m, 2H, OCH2); 3.15 [m, 1H, CH2(CdN)]; 2.71 [m,
1H, CH2(CdN)]; 2.23 (m, 2H, -CH2-).
Syn th esis of [P d Cl2{N(H)dCCH2CH2CH2O}(L). L )
P P h 3 (3). To a suspension of 2 (0.12 g, 0.322 mmol) in CH2-
Cl2 (20 mL) was added PPh3 (0.08 g, 0.320 mmol), and the
reaction mixture was stirred at room temperature until
complete dissolution of the starting complex. After 1 h a
yellow-brown solution was obtained, which was concentrated
under reduced pressure to a small volume (3 mL). Then, upon
addition of Et2O (30 mL), a yellow solid formed, which was
filtered off, washed with Et2O (2 × 10 mL), and dried under
vacuum. Yield: 0.16 g (94%). Mp: 260 °C dec. Anal. Calcd
for C22H22NOPCl2Pd: C, 50.35; H, 4.23; N, 2.67. Found: C,
49.85; H, 4.13; N, 2.58. IR (Nujol mull): ν(NH) 3156 cm-1 (s);
ν(CdN) 1676 cm-1 (s); ν(PdCl) 337, 292, and 262 cm-1 (m). 1H
3
NMR (δ, CDCl3): 6.53 (br, 1H, NH); 4.29 (t, J HH 7.05, 2H,
3
OCH2); 3.17 [t, J HH 7.03, 2H, CH2(CdN)]; 2.17 (m, 2H,
(3) Chow, K. K.; Levanson, W.; McAuliffe, C. A. J . Chem. Soc.,
Dalton Trans. 1976, 1429.
(4) Booth, G.: Chatt, J . Chem. Soc. A 1966, 634.
-CH2-). 31P{1H} NMR (δ, CDCl3): 28.03 (s) and 25.56 (s).
13C{1H} NMR (δ, CD2Cl2): 179.1 (CdN); 66.0 (OCH2); 23.8

1238 Organometallics, Vol. 15, No. 4, 1996
Bertani et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta for
appear as a multiplet at 1.61 ppm. The OH proton
resonates at 3.59 ppm, giving rise to a broad signal. In
the 13C NMR spectrum the nitrile carbon appears at
119.55 ppm.
cis-[P d Cl2{N(H)dCCH2CH2CH2O}(P P h 3)] (cis-3)
formula
fw
C22H22Cl2NOPPd‚1/2CH2Cl2
567.1
The reaction of Na2PdCl4, obtained in situ on treat-
ment of an aqueous suspension of PdCl2 with NaCl,8
with a slight excess of 1 at room temperature affords a
poorly soluble brown product, which was identified as
compound 2 (eq 3) on the basis of analytical and 1H
NMR data. The formation of 2 can be explained by
cryst syst
space group
a
b
triclinic
P1h
9.113(2) Å
16.110(4) Å
18.192(4) Å
109.21(2)°
91.78(2)°
c
R
â
γ
93.34(2)°
V
2517(1) Å3
4
Z
diffractometer
T
Siemens R3m/V
21 °C
λ
0.7107 Å
µ
11.3 cm-1
1.499 g cm-3
4674 (up to 2θ ) 45°)
F(calcd)
no. of observns (Fo g 4σ(Fo))
anisotropy for non-H atoms
initial coordination of the nitrile moiety to the Pd(II)
center, which activates the nitrile carbon toward in-
tramolecular nucleophilic attack of the dangling -OH
group; proton transfer to the imino nitrogen atom then
gives the observed product 2. The intermediate Pd(II)-
R
0.069
weighting scheme
Rw
w-1 ) σ(F) + 0.0041F2
0.081
pic thermal parameters, except for the carbon and chlorine
atoms of the disordered CH2Cl2 molecule, which were refined
isotropically. The solvent molecule was disordered essentially
1
nitrile complex could not be detected by IR or H NMR
spectroscopy. The IR spectrum of 2 shows strong
absorptions at 3197 cm-1 and at 1681 cm-1 due to NsH
and CdN stretching bands, respectively. Three absorp-
tions in the PdsCl region (350-280 cm-1) suggest the
presence of a mixture of trans (one band) and cis (two
bands) isomers, with the absorption at higher wave-
over two positions with site occupation factors of /3 and 1/3.
2
No attempts were made to locate the hydrogen atoms. The
deterioration of the crystal during the data collection and
probably the inadequate description of the disorder of the CH2-
Cl2 molecule explain the relatively high R value; however, the
model establishes the binding/stereochemistry around the
metal atom. The final atomic fractional coordinates are
reported in Table 2, while selected bond distances and angles
are given in Table 3.
1
numbers corresponding to the trans species.9 The H
NMR spectrum shows complex multiplets for the -CH2
ring protons, as also found in other C- or N-coordinated
ring systems such as cis-[MCl2{CN(R)CH2CH2NH}(L)]
(M ) Pd, Pt; R ) alkyl, aryl; L ) tertiary phos-
phine, isocyanide)10 and cis- and trans-[PtCl2-
Resu lts a n d Discu ssion
4-Hydroxybutyronitrile (1) was readily prepared via
a substitution reaction between 1 equiv of Et4N(CN) and
HO(CH2)3Br in CH2Cl2 at room temperature (eq 2). The
{NdC(R)OCH2CH2CH2}2].2d The chemical shift assign-
ments were made by comparison with those of Pt(II)-
coordinated N-oxazoline complexes.2b,c,11
Substitution of one imino ligand in 2 by an entering
nucleophile L leads to complexes 3-5 (eq 4). The
reaction occurs in the homogeneous phase under mild
conditions; workup of the reaction mixture gave 1 in ca.
80% yield as the only reaction product. This method
proved to be more efficient than that previously reported
involving heating EtOH/H2O solutions of KCN and
3-chloro-1-propanol.6 Compound 1 is thermally stable,
and we had no spectroscopic evidence for spontaneous
ring closure, as previously reported.7 The hydroxyal-
kanenitrile 1 was characterized by spectroscopic data.
Characteristic IR (liquid film) features are the CtN and
OsH stretching absorptions, which appear as strong
presence of the free iminolactone in solution was
confirmed by GC-MS analysis of the reaction mixtures.
As for 2, compound 3 was likely formed as a mixture of
cis and trans isomers (although crystals of 3 were
obtained only for the cis form, see the molecular
structure below), as indicated by the presence of three
bands in the Pd-Cl region; this is also supported by
1
bands at 2249 and 3441 cm-1, respectively. In the H
NMR spectrum the CH2OH and CH2CN protons appear
as triplets at 3.43 and 2.26 ppm, respectively, by
coupling with the adjacent methylene protons, which
(8) Maitlis, P. M.; Espinet, P.; Russell, M. J . H. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Eds.;
Pergamon Press: Oxford, U.K., 1982, Vol. 6, Chapter 30.1, p 233.
(9) Nakamoto, K. Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4th ed.; Wiley: New York, 1986; pp 324-
326.
(5) Sheldrick, G. M. SHELXTL-PLUS: Structure Determination
Software Programs; Siemens Analytical X-ray Instruments Inc.,
Madison, WI, 1990.
(6) (a) Nohira, H.; Nishikawa, Y.; Furuya, Y.; Mukaiyama, T. Bull.
Chem. Soc. J pn. 1965, 38, 897. (b) Aksnes, G.; Prue, J . E. J . Chem.
Soc. 1959, 103.
(10) Bertani, R.; Mozzon, M.; Michelin, R. A. Inorg. Chem. 1988,
27, 2809.
(7) Matsui, H.; Ishimoto, S. Tetrahedron Lett. 1966, 17, 1827.
(11) Roger, R.; Neilson, D. G. Chem. Rev. 1961, 61, 179.

Palladium(II)-Promoted Cyclization Reaction
Organometallics, Vol. 15, No. 4, 1996 1239
Ta ble 2. Atom ic Coor d in a tes (×104) a n d Equ iva len t Isotr op ic Disp la cem en t Coefficien ts (Å2 × 103) of cis-3
c
c
x
y
z
Ueq
x
y
z
Ueq
Pd(1)
616(1)
2076(4)
126(4)
-813(4)
3132(10)
813(12)
1892(15)
4143(18)
3543(19)
1966(16)
-278(15)
-923(19)
-507(21)
561(23)
3561(1)
4698(2)
2853(2)
2494(2)
3976(6)
4261(7)
4356(8)
4151(12)
4882(12)
4875(9)
1376(8)
728(9)
4199(1)
3953(2)
2883(2)
4420(2)
5627(5)
5353(6)
5843(8)
6312(11)
6929(9)
6689(7)
4014(7)
4287(9)
4024(10)
3487(12)
3201(12)
3492(10)
5447(8)
5843(10)
6633(11)
7031(13)
6642(11)
5869(9)
4102(7)
3714(8)
3534(10)
3744(11)
4148(9)
4292(7)
798(1)
39(1)
52(1)
62(1)
44(1)
58(4)
45(4)
47(5)
78(8)
75(7)
53(5)
46(5)
67(6)
75(7)
90(9)
83(8)
61(6)
59(6)
80(8)
99(10)
130(14)
106(11)
71(7)
49(5)
59(6)
74(7)
75(8)
66(7)
52(5)
39(1)
52(1)
60(1)
P(1B)
4802(4)
8333(10)
6014(12)
7017(13)
9311(18)
8588(21)
6986(16)
5649(14)
5159(18)
5780(19)
6837(19)
7347(18)
6717(15)
4511(14)
3137(17)
2962(21)
4143(23)
5522(21)
5721(17)
2935(14)
2191(16)
678(15)
7515(2)
6137(7)
5776(7)
5718(7)
5968(12)
5244(12)
5211(9)
8632(8)
9308(9)
10149(9)
10351(10)
9697(10)
8829(8)
7437(8)
7262(10)
7190(12)
7282(10)
7456(10)
7544(9)
7493(8)
6707(9)
6618(10)
7361(11)
8150(10)
8232(9)
1422(6)
554(6)
624(2)
-587(5)
-376(6)
-833(7)
-1240(10)
-1880(10)
-1676(8)
1083(8)
828(9)
1155(9)
1737(10)
1997(10)
1657(8)
-393(7)
-774(8)
-1536(10)
-1962(9)
-1590(9)
-804(9)
953(7)
40(1)
61(4)
47(4)
39(4)
74(7)
87(8)
57(6)
47(5)
66(6)
69(7)
69(7)
67(6)
50(5)
43(5)
59(6)
78(8)
73(7)
68(7)
61(6)
43(5)
54(6)
55(6)
68(7)
67(7)
55(6)
105(2)
102(2)
78(7)
78(3)
127(6)
193(33)
Cl(1A)
Cl(2A)
P(1A)
O(1B)
N(1B)
C(1B)
C(2B)
C(3B)
C(4B)
C(5B)
C(6B)
C(7B)
C(8B)
C(9B)
C(10B)
C(11B)
C(12B)
C(13B)
C(14B)
C(15B)
C(16B)
C(17B)
C(18B)
C(19B)
C(20B)
C(21B)
C(22B)
Cl(1)a
O(1A)
N(1A)
C(1A)
C(2A)
C(3A)
C(4A)
C(5A)
C(6A)
C(7A)
C(8A)
C(9A)
C(10A)
C(11A)
C(12A)
C(13A)
C(14A)
C(15A)
C(16A)
C(17A)
C(18A)
C(19A)
C(20A)
C(21A)
C(22A)
Pd(2)
-125(10)
-334(10)
277(9)
1205(18)
800(15)
-917(18)
378(21)
1165(9)
2637(8)
2515(10)
2640(12)
2890(12)
3026(14)
2901(10)
2538(9)
1783(10)
1862(11)
2657(13)
3429(12)
3341(9)
6408(1)
5244(2)
7014(2)
326(29)
-890(41)
-2133(30)
-2142(21)
-2700(15)
-3612(15)
-5037(17)
-5629(17)
-4711(16)
-3319(16)
5998(1)
769(8)
859(8)
-14(17)
729(17)
2193(15)
266(9)
1960(9)
1174(10)
1374(9)
1284(8)
338(5)
1190(5)
1069(16)
4496(8)
3615(13)
3717(55)
Cl(2)a
C(23)a
Cl(1′)b
Cl(2′)b
C(23′)b
292(27)
967(18)
8449(9)
9594(15)
8776(62)
5881(14)
4973(22)
4830(101)
Cl(1B)
Cl(2B)
7252(4)
5706(4)
1000(2)
2116(2)
a
b
Site occupancy 2/3. Site occupancy 1/3. c Equivalent isotropic U, defined as one-third of the trace of the orthogonalized Uij tensor.
Ta ble 3. Selected Bon d Len gth s (Å) a n d
the presence of two resonances of the PPh3 ligand in
the 31P NMR spectrum. On the other hand, complexes
An gles (d eg) for cis-3
4 and 5 show only one Pd-Cl band at ca. 350 cm-1
,
molecule A
molecule B
indicating a trans geometry. Other IR and 1H NMR
data (see Experimental Section) are similar to those
described for 2. The higher solubility of complexes 3-5
compared to that of 2 allowed us to grow crystals of 3
suitable for X-ray analysis, which showed that 3 con-
sisted of only the cis isomer (see below).
Pd-Cl(1)
Pd-Cl(2)
Pd-P(1)
2.371(4)
2.304(3)
2.245(4)
2.026(9)
1.27(2)
1.32(2)
1.46(2)
1.48(2)
1.49(2)
1.49(2)
1.81(1)
2.374(4)
2.302(3)
2.246(4)
2.042(10)
1.24(2)
1.33(1)
1.47(2)
1.46(2)
1.52(2)
1.48(2)
1.82(1)
Pd-N(7)
N(1)-C(1)
C(1)-O(1)
O(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(1)
Pd-C(mean)
Similarly, the reaction of 2 with 1 equiv of cis-1,2-
bis(diphenylphosphino)ethylene results in the complete
displacement of the two iminolactone ligands, as shown
in eq 5.
Cl(1)-Pd-Cl(2)
Cl(1)-Pd-P(1)
Cl(1)-Pd-N(1)
Cl(2)-Pd-P(1)
Cl(2)-Pd-N(1)
P(1)-Pd-N(1)
Pd-N(1)-C(1)
N(1)-C(1)-O(1)
C(1)-O(1)-C(2)
O(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(1)
C(4)-C(1)-O(1)
C(4)-C(1)-N(1)
91.1(1)
178.6(1)
89.1(3)
88.3(1)
172.8(3)
91.3(3)
129.7(9)
121(1)
109(1)
105(1)
106(1)
103(1)
112(1)
127(1)
90.7(1)
179.2(1)
88.9(3)
88.5(1)
172.7(3)
91.8(3)
130.8(8)
121(1)
110(1)
107(1)
105(1)
104(1)
111(1)
128(1)
X-r a y Str u ctu r e An a lysis of cis-3. The molecular
structure of cis-[PdCl2{N(H)dCCH2CH2CH2O}(PPh3)]
(cis-3) is shown in Figure 1, together with the atom
labeling.12 The crystal contains two crystallographically
independent, monomeric, neutral and well-separated
moieties (A and B) and a disordered CH2Cl2 molecule.
The two moieties are superimposable; in fact, the
weighted root-mean-square deviation, derived from the
BMFIT program,13 is only 0.043 Å, when the fitting is
performed using the coordination geometry and the five-
membered-ring atoms. Nevertheless, no bond distances
and angles differ by more than 2 standard deviations.
The palladium atom is surrounded, as expected, by a
cis square-planar Cl2PN donor set and the distances/
angles around the metal agree well with the values in
several other monomeric cis-Cl2PdPN complexes (see
Table 4). In particular, the greater trans influence of
the phosphine,14 compared to a nitrogen donor, can be
seen in the lengthening of Pd-Cl(1) by 0.069 Å relative
to Pd-Cl(2), the average being 0.085 Å for the other
(12) J ohnson, C. K. ORTEP II, Report ORNL-5138, Oak Ridge
National Laboratory: Oak Ridge, TN, 1976.
(13) Njburg, S. C. Acta Crystallogr. 1974, B30, 251.
(14) (a) Palenik, G. J .; Giordano, T. J . J . Chem. Soc., Dalton Trans.
1987, 1175. (b) Albinati, A.; Lianza, F.; Berger, H.; Pregosin, P. S.
Inorg. Chim. Acta 1992, 198-200, 771.

1240 Organometallics, Vol. 15, No. 4, 1996
Bertani et al.
F igu r e 1. ORTEP diagram of the two molecules A and B of cis-3, showing the-atom labeling scheme. Thermal ellipsoids
are drawn at the 40% probability level. The two sites of the disordered CH2Cl2 molecule are also shown.
Ta ble 4. Com p a r ison of Bon d Dista n ces (Å), An gles (d eg), a n d Tetr a h ed r a l Distor tion (∆, Å) in Neu tr a l
Mon om er ic P a lla d iu m (II) Com p lexes Con ta in in g th e cis-Cl2P d P N Cor e, w ith tw o Un id en ta te P N liga n d s
for th e F ir st Tw o Com p lexes a n d a Bid en ta te Liga n d for th e Oth er s
Pd-Cl
trans
to P
trans
to N
Cltrans to P
Pd-P
-
Cltrans to N
Pd-N
-
Cl-
P-
complex
Pd-P
Pd-N
Pd-Cl Pd-N
∆
∆
ref
2.372(4) 2.303(3) 2.245(4) 2.036(9) 179.0(1)
172.8(4) 91.0(1) 91.6(3) 0.07 (0.06 present
Cl2P d (P Ph3)[NHdCO(CH2)2CH2]
Cl2P d (P Ph3)[Me2SNR]a
work
2.374(2) 2.289(2) 2.246(2) 2.022(5) 176.0(1)
2.386(1) 2.285(1) 2.241(1) 2.134(4) 176.3(1)
2.393(1) 2.294(1) 2.229(1) 2.078(4) 164.9(1)
175.9(2) 92.2(1) 96.4(2) 0.01 (0.06
168.1(1) 88.1(1) 94.0(1) 0.07 (0.14
176.0(1) 90.8(1) 82.3(1) 0.12 (0.17
176.7(2) 91.1(1) 86.5(2) 0.03 (0.01
175.5(3) 91.3(2) 86.9(3) 0.04 (0.08
177.0(2) 94.6(7) 87.1(2) 0.01 (0.01
171.2(2) 89.6(2) 96.1(2) 0.07 (0.22
168.6(2) 91.4(2) 84.7(2) 0.04 (0.18
174.0(8) 91.4(5) 85.1(8) 0.02 (0.05
176.0(1) 91.6(1) 93.3(1) 0.05 (0.00
e
f
g
h
h
i
j
k
l
Cl2P d [PhBuP C6H4CH(Me)NMe2]
Cl2P d [Bu2P CH2-2-R]b
Cl2P d [Ph2P CH2CH2{(CH2)2SMe}NMe2] 2.370(2) 2.293(3) 2.214(2) 2.158(7) 177.9(1)
Cl2P d [Ph2P CH2CH{(CH2)3SMe}NMe2] 2.374(3) 2.289(5) 2.194(3) 2.12(1) 173.9(2)
Cl2P d [Ph2P CH2PPh2NH]
2.375(2) 2.319(2) 2.224(2) 2.021(6) 175.4(1)
2.396(4) 2.297(4) 2.205(3) 2.108(7) 164.4(1)
2.378(2) 2.277(3) 2.232(2) 2.049(6) 171.6(1)
Cl2P d [Ph2P C10H15NNMe2]
Cl2P d [Ph2P C6H2(3,6-OMe)-2-R]c
Cl2P d [(p-MeC6H4)2P R]d
2.38(1) 2.30(1) 2.18(1) 2.14(3)
177.6(4)
Cl2P d [Ph2P C6H4CH2OCH2C5H4N]
2.351(1) 2.282(2) 2.254(1) 2.044(4) 177.5(1)
m
a
b
d
R ) 2-pyrimidinyl. R ) 8-methylquinoline. c R ) isoquinoline. R ) CH2CH(i-Pr)NHCH2(p-OMeC6H4). e Davidson, J . L.; Preston,
P. N.; Spankie, S. A. R.; Douglas, G.; Muir, K. W. J . Chem. Soc., Dalton Trans. 1989, 497. f Takenaka, A.; Sasada, Y.; Yamamoto, K.,
Tsuji, J . Bull Chem. Soc. J pn. 1977, 50, 3177. Deeming, A. J .; Rothwell, I. P.; Hursthouse, M. B.; Abdul Malik, K. M. J . Chem. Soc.,
Dalton Trans. 1980, 1974. Cross, G.; Vriesema, B. K.; Boven, G.; Kellogg, R. M.; van Bolhuis, F. J . Organomet. Chem. 1989, 370, 357.
Katti, K. V.; Batchelor, R. J .; Einstein, F. W. B.; Cavell, R. G. Inorg. Chem. 1990, 29, 808. Perera, S. D.; Shaw, B. L.; Thornton-Pett,
M. J . Chem. Soc., Dalton Trans. 1992, 999. Alcock, N. W.; Brown, J . M.; Pearson, M.; Woodward, S. Tetrahedron: Asymmetry 1992, 3,
17. Albinati, A.; Lianza, F.; Berger, H.; Pregosin, P. S.; Ru¨egger, H.; Kunz, R. W. Inorg. Chem. 1993, 32, 478. Tani, K.; Yabuta, M.;
Nakamura, S.; Yamagata, T. J . Chem. Soc., Dalton Trans. 1993, 2781.
g
h
i
j
k
l
m
complexes. The Pd-N distance of 2.036(9) Å represents
the first distance determination of a Pd-N(imine) type
bond, and it lies at the end of the wide range of values
(2.02-2.16 Å) observed in the complexes (Table 4). The
complex molecules are packed according to van der
Waals interactions (Figure 2); only the N-H‚‚‚Cl con-
tacts may be unusual. Assuming a planar geometry
around N, the intermolecular NH‚‚‚Cl (at x, 1 - y, 1 -
z) separation is 2.37 Å with an N-H‚‚‚Cl angle of 179°
(N‚‚‚Cl ) 3.27 Å) in moiety A; the corresponding values
in B (2.40 Å, 172°, and 3.29 Å) pertain to the chlorine
atom at 1 - x, 1 - y, z. On the other hand, the N‚‚‚Cl
distances are just the sum of the van der Waals radii
(1.55 + 1.75 Å),15 and these may be regarded as
interactions between these atoms.
Con clu sion s
In summary, the hydroxyalkanenitrile HO(CH2)3-
CN is readily converted to the iminolactone
HNdCCH2CH2CH2O by intramolecular ring closure
promoted by Pd(II). Although this reaction chemistry
is unprecedented for transition-metal-coordinated ni-
triles, it can be related to that reported for the hydroxy-
(15) Bondi, A. J . Phys. Chem. 1964, 68, 441.

Palladium(II)-Promoted Cyclization Reaction
Organometallics, Vol. 15, No. 4, 1996 1241
(II).16c Furthermore, the synthetic procedure described
above represents a new suitable method for the prepa-
ration of the imino tetrahydrofuran HNdCCH2CH2-
CH2O, which is alternatively prepared by organic
methods via cyclization reactions of amides17 under
stronger conditions or by ring expansion of epoxides.18
Further development of the chemistry of hydroxyal-
kanenitriles HO(CH2)nCN as well as of other function-
alized nitriles is under study.
Ack n ow led gm en t. R.A.M. thanks MURST and
CNR for support. R.A.M. and R.J .A. appreciate partial
support of this project by a NATO Collaborative Re-
search Grant (No. CRG 931224).
F igu r e 2. Packing diagram of cis-3; dotted lines show the
relevant N(1)-H‚‚‚Cl(1) contacts.
Su p p or tin g In for m a tion Ava ila ble: Anisotropic thermal
parameters (Table S1), remaining bond lengths (Table S2), and
angles (Table S3), and a diagram showing the superimposition
of molecules A and B (Figure 3) (6 pages). Ordering informa-
tion is given on any current masthead page.
alkyl isocyanide HO(CH2)3NC,16a,b which is unreactive
as the free ligand or when coordinated to transition
metals in low oxidation states toward intramolecular
nucleophilic attack at the isocyanide carbon by the
hydroxyl oxygen, but it is spontaneously converted to
the oxazolidin-2-ylidene ligand when coordinated to Pd-
OM950740U
(17) Neale, R. S.; Marcus, N. L.; Shepers, R. G. J . Am. Chem. Soc.
1966, 88, 3051. Craig, P. N. J . Am. Chem. Soc. 1952, 74, 129. Fantin,
G.; Fogagnolo, M.; Medici, A.; Pedrin, P.; Gleria, M. Heterocycles 1991,
32, 1055. Boyd, G. V.; Heatherington, K. J . Chem. Soc., Perkin Trans.
1 1973, 2523. Alanise, A. I. D.; Fishwick, C. W. G.; Srantay, C., J r.,
Tetrahedron Lett. 1989, 30, 6571.
(16) (a) Bartel, K.; Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl.
1974, 13, 599. (b) Fehlhammer, W. P.; Bartel, K.; Plaia, U.; Vo¨lkel, A.;
Liu, A. T. Chem. Ber. 1985, 118, 2220. (c) Fehlhammer, W. P.; Bartel,
K.; Plaia, U.; Vo¨lkel, A.; Liu, A. T. Chem. Ber. 1985, 118, 2235.
(18) Meyers, A. I.; Yamamoto, Y.; Mihelich, E. D.; Bell, R. A. J . Org.
Chem. 1980, 45, 2792.