Interaction of PdCl2-2-(β-diphenylphosphine)ethylpyridine complex with diols and CO: Synthesis of new alkoxycarbonyl complexes, key intermediates to cyclic carbonates

Article abstract of DOI:10.1021/om060012e

PdCl₂PN (PN = 2-(β-diphenylphosphine)ethylpyridine) was found to be effective in the promotion of the alkoxycarbonylation of diols [(1,2-hydroxyethane (HE); 1,2- and 1,3-hydroxypropane (1,2HP, 1,3HP), 1,2-, 1,3-, and 1,4-hydroxybutane (1,2HB, 1,3HB, 1,4HB)]. The relevant mono-alkoxycarbonyl complexes of the diols, of formula PdClPN(COO-R-OH), were isolated, characterized in solution, and studied for their reactivity. All complexes in the presence of different reagents release the alkoxycarbonyl group directly as cyclic carbonate or as chloroformate, which "in situ" converts into cyclic carbonate or other valuable carbonyl products. The structure of the complexes PdCl[(COO-CH₂-CH₂-CH ₂(OH)](PN) (4c) and PdCl(COO-CH₂-CH(OH)-C ₂H₅)(PN) (4d) was also derived by single-crystal X-ray diffraction.

Full text of DOI:10.1021/om060012e

2872
Organometallics 2006, 25, 2872-2879
Interaction of PdCl2-2-(â-diphenylphosphine)ethylpyridine Complex
with Diols and CO: Synthesis of New Alkoxycarbonyl Complexes,
Key Intermediates to Cyclic Carbonates
Potenzo Giannoccaro,*,† Daniele Cornacchia,† Salvatore Doronzo,† Ernesto Mesto,‡
Eugenio Quaranta,† and Michele Aresta†
Dipartimento di Chimica, UniVersita` di Bari, Via Orabona 4, Bari Italy, and
Dipartimento Geomineralogico, UniVersita` di Bari, Via Orabona 4, Bari Italy
ReceiVed January 5, 2006
PdCl2PN (PN ) 2-(â-diphenylphosphine)ethylpyridine) was found to be effective in the promotion of
the alkoxycarbonylation of diols [(1,2-hydroxyethane (HE); 1,2- and 1,3-hydroxypropane (1,2HP, 1,3HP),
1,2-, 1,3-, and 1,4-hydroxybutane (1,2HB, 1,3HB, 1,4HB)]. The relevant mono-alkoxycarbonyl complexes
of the diols, of formula PdClPN(COO-R-OH), were isolated, characterized in solution, and studied for
their reactivity. All complexes in the presence of different reagents release the alkoxycarbonyl group
directly as cyclic carbonate or as chloroformate, which “in situ” converts into cyclic carbonate or other
valuable carbonyl products. The structure of the complexes PdCl[(COO-CH2-CH2-CH2(OH)](PN) (4c)
and PdCl(COO-CH2-CH(OH)-C2H5)(PN) (4d) was also derived by single-crystal X-ray diffraction.
Scheme 1. Double-Step Pathway for Converting Alcohols
into Chloroformates or Carbonates
1. Introduction
Transition and post-transition metal compounds have suc-
cessfully been used as catalysts for the oxidative carbonylation
of alcohols to give carbonates (reaction 1),1 a process on stream
for the synthesis of DMC.2
2 ROH + CO + 1/2 O2 f CO(OR)2 + H2O
(1)
Alkoxycarbonyl complexes 1 are key intermediates that, by
further reaction with alcohol, give carbonates. We have already
shown that complexes 1 can be used for the synthesis of
chloroformates 2, and we have proposed a protocol for the
conversion, through a double-step path, without the use of
phosgene, of alcohols into either chloroformates or carbonates
3 (Scheme 1).3
Now we have found that this procedure can be applied to
the alkoxy carbonylation of diols, which can be converted into
the relevant chloroformates 5 or cyclic carbonates 6 (Scheme
2), which are precursors of polycarbonates.
Scheme 2. Conversion of Diols into Chloroformates or
Cyclic Carbonates
* To whom correspondence should be addressed. E-mail:
giannoccaro@chimica.uniba.it.
† Dipartimento di Chimica.
‡ Dipartimento Geomineralogico.
(1) (a) Kondo, K.; Sonoda, S.; Tsutsumi, T. Tetrahedron Lett. 1971 4885.
(b) Saegusa, T.; Tsuda, T.; Nishijima, K. Tetrahedron Lett. 1968, 831. (c)
Fenton, D. M.; Steinward, P. J. J. Org. Chem. 1974, 39, 701. (d) Graziani,
M.; Uguagliati, P.; Carturan, G. J. Organomet. Chem. 1971, 27, 275. (e)
Nefedov, B. K.; Sergeeva, N. S.; Eidus, Y. T. IzV. Akad. Nauk. SSSR, Ser.
Khim. 1972 1635. (f) Manov-Yuvenski, V. I.; Nefedov, B. K. Usp. Khim.
1981, 50, 889 (in Russian). (g) Temkin, O. N.; Bruk, L. G. Usp. Khim.
1983, 52, 206 (in Russian).
(2) (a) Pernotti, E.; Cipriani, G. US Pat. 3 846 468, (CA 82, 101055),
1974. (b) Romano, U.; Tesei, C.; Cipriani G.; Micucci, L. US Pat. 4 218 391,
1980. (c) Romano, U.; Tesei, C.; Massi Mauri M.; Rebora, P. Ind. Ing.
Chem., Prod. Res. DeV. 1980, 19, 396. (d) Delledonne, D.; Rivetti, F.;
Romano, U. J. Organom. Chem. 1995, 488, C15-C19.
(3) (a) Giannoccaro, P.; Ravasio, N.; Aresta, M. J. Organomet. Chem.
1993, 451, 243. (b) Giannoccaro, P.; Tommasi, I.; Aresta, M. J. Organomet.
Chem. 1994, 476, 13. (c) Aresta, M.; Giannoccaro, P.; Tommasi, I.;
Dibenedetto, A.; Manotti, A. M.; Ugozzoli, F. Organometallics 2000, 19,
3879.
Cyclic carbonates are mostly prepared by transesterification
of alkyl carbonates with diols in the presence of inorganic or
organic catalysts.4 Two five-membered cyclic carbonates have
also been synthesized by direct carbonylation of ethylene glycol
or 1-phenylethanediol,5 but no attempt has been made so far
10.1021/om060012e CCC: $33.50 © 2006 American Chemical Society
Publication on Web 04/26/2006

Alkoxycarbonyl Complexes with a Di-alcohol
Organometallics, Vol. 25, No. 11, 2006 2873
Table 1. Some IR Spectroscopic Features of
PdClPN(CO-OR-OH) Complexes
Table 2. Decomposition of Complexes with HCl and CO
Evolved
IR (cm-1
)
complex
mmol
V CO (mL)
CO (mmol)
HO-R-OH
complex 4
OH
CO
C-O-C
4b
4a
4c
4d
4f
0.31
0.24
0.26
0.24
0.24
6.7
5.0
5.5
5.1
5.2
0.30
0.22
0.24
0.23
0.23
1,2-HE
1,2-HP
1,3-HP
1,2-HB
1,3-HB
1,4-HB
a
b
c
d
e
f
3415
3391
3430
3429
3439
3443
1651
1659
1655
1661
1665
1634
1085-1068
1085-1055
1070-1031
1075-1028
1068-1023
1082-1053
Scheme 3. Possible Routes for Alkoxycarbonylation of
Mono-alcohols
for isolating or characterizing the relevant alkoxycarbonyl
complexes 4.
To the best of our knowledge, the only alkoxycarbonyl
complex of a diol reported in the literature is the bipyridyl
ruthenium complex, of formula Ru(bipy)(CO)2Cl(COOCH2CH2-
OH), isolated in the course of a study on a water gas shift
process.6
We report here the first well-characterized examples of
alkoxycarbonyl complexes of palladium, obtained by direct
carbonylation of diols having from two to four carbon atoms
and the procedure for converting the alkoxycarbonyl group into
chloroformate or cyclic carbonate. The solid-state structure of
complexes 4c and 4d was also derived by X-ray diffraction
analysis.
2. Results and Discussion
2.1. Synthesis and Characterization of Complexes. By
reacting PdCl2PN [(PN ) 2-(â-diphenylphosphine)ethylpyri-
dine)] with diols [(HO-R-OH) ) 1,2-hydroxyethane (HE); 1,2-
or 1,3-hydroxypropane (1,2HP; 1,3HP); 1,2-, 1,3-, or 1,4-
hydroxybutane (1,2HB, 1,3HB, 1,4HB); diol/Pd ) 4)], in CH3-
CN, under carbon monoxide at atmospheric pressure and room
temperature, in the presence of triethylamine as base, the
alkoxycarbonyl complexes of formula PdClPN(COO-R-OH)
(4a-f) were isolated in good yields (60-80%) as white-cream
or yellow-cream microcrystalline products (reaction 2).
to their formulation, one mole of CO per mole of complex
(reaction 3 and Table 2). The gas evolved was measured using
a gas buret and identified as CO by GC analysis.
PdClPNCO-OR-OH + HCl f
PdCl2PN + CO + HO-R-OH (3)
The decomposition of complexes under acid conditions
suggests that the base NEt3 plays a double role in the reaction.
Its presence is needed for (i) shifting reaction 2 to the right by
converting the strong acid HCl into the weak acid NEt3HCl and
(ii) promoting the deprotonation of diols during the formation
of the alkoxy-carbonyl group (see Scheme 3).
NEt3
PdCl2PN + CO + HO-R-OH
8
PdClPN(COO-R-OH) + NEt3H+Cl- (2)
4
Complexes 4a-f have been fully characterized in solution
by NMR (1H, 13C, 31P) spectroscopy. In all the compounds, the
P resonance of the PN ligand is within a narrow range, between
22 and 24 ppm. In the 13C spectrum, the signal of the carboxyl
carbon atom appears in the expected region (around 175 ppm)
as a doublet because of coupling with the P atom of the chelating
ligand. The 2JC-Pd-P coupling constants range between 14.2 and
15.3 Hz and are close to the value of 10-15 Hz found for trans-
bis-phosphine-acyl and carbamoyl-Pd complexes.10 The 2JC-Pd-P
observed values suggest that complexes 4a-f have a P-Pd-
C(O)O cis arrangement. Such an arrangement has been docu-
mented for complexes 4c and 4d also in the solid state by X-ray
diffraction analysis (see later). This result leads us to the
conclusion that compounds 4c and 4d are configurationally
stable complexes, which maintain their configuration also in
solution.
All compounds are stable in the solid state and can be
manipulated in the air for long periods without any appreciable
modification. In solution, they are stable only at room temper-
ature; upon heating (T > 40 °C) they decompose, with a reaction
rate depending on the type of diol, giving metallic palladium
and carbonate (see later).
The complexes were characterized by analytical and spec-
troscopic data (IR, Table 1; NMR) and through the decomposi-
tion reactions with HCl. Molecular structures of 4c and 4d were
derived by single-crystal X-ray diffraction.
Their IR spectra in Nujol show characteristic absorptions
ascribable to the stretching of the free hydroxyl group of diol
and to the ν(CdO) and ν(C-O-C) of the alkoxycarbonyl group
(Table 1). The above values are consistent with the data found
for other alkoxycarbonyl complexes of mono-alcohols.4,7-9 All
complexes react with HCl in methanol and develop, according
(7) Vasapollo, G.; Nobile, C. F.; Sacco, A. J. Organomet. Chem. 1985,
296, 435.
(4) Grey, Roger A. (Arco Chemical Tecnology, Inc.) U.S. Patent
5091543, 1992. Clements, J. H.; Klein, H. P.; Marquis, E. T. (Huntsman
Petrochemical Corporation) PCT Int. Appl., 2003.
(5) Tamma, W. J. Org. Chem. 1986, 51, 2977.
(6) Haukka, M.; Hirva, P.; Luukkanen, S.; Kallinen, M.; Ahlgre´n, M.;
Pakkanen, T. A. Inorg. Chem. 1999, 38, 3182.
(8) Bertani, R.; Cabinato, G.; Toniolo, L.; Vasapollo, G. J. Mol. Catal.
1993, 84, 165.
(9) Dervisi, A.; Edwards, P. G.; Newman, P. D.; Tooze, R. P.; Coles, S.
J.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1999, 1113.
(10) Huang, L.; Ozawa, F.; Yamamoto, A. Organometallics 1990, 9,
2603.

2874 Organometallics, Vol. 25, No. 11, 2006
Giannoccaro et al.
Figure 1. Perspective view of 4c. Displacement ellipsoids are
drawn at the 30% level of probability. Hydrogen atoms have been
omitted for clarity.
Figure 2. Perspective view of 4d. Displacement ellipsoids are
drawn at the 30% level of probability. Hydrogen atoms have been
omitted for clarity.
The 13C spectra of compounds 4a, 4c, and 4f show a unique
set of signals for both phenyl rings of the PN ligand. These
signals are doublets because of coupling with the phosphorus
atom of the ligand. However, in complexes 4b, 4d, and 4e the
presence of a chiral center in the diol chain makes the two
phenyl rings diastereotopic and no longer equivalent. Also the
CH2P and CH2Py protons of the PN ligand are, respectively,
diastereotopic in complexes 4b, 4d, and 4e. This may account
for the different fine structure of the CH2P and CH2Py signals
in 4b, 4d, and 4e with respect to that exhibited by enantiotopic
CH2P and CH2Py protons in complexes 4a, 4c, and 4f.
Pd-N bond distances for 4d are longer than that found in the
PdCl2L2 (L2 ) o-diphenylphospino-N,N-dimethylbenzylamine)
complex14 and shorter than that observed in the same complex
when a chlorine atom is substituted with a strong trans ligand.15
3. Reaction Mechanism and Reactivity of Complexes
It has already been ascertained by us and other authors that
the alkoxy carbonylation of mono-alcohols can proceed through
two mechanisms that differ in the sequence with which the CO
and the alcohol interact with the metal center in the presence
of a base (Scheme 3, routes a and b). According to route a in
Scheme 3, the complex reacts first with the CO, giving a
carbonyl intermediate, in which Pd is pentacoordinate, which
undergoes nucleophilic attack by alcohol and evolves into the
final product through pathway 1 or 2.16 Through route b, the
reaction starts with the formation, promoted by NEt3, of an
alkoxy complex, which by insertion of CO into the metal-
alkoxy bond affords the alkoxy-carbonyl final species.17 Route
a appears to be the most probable in the case of diols. In fact,
when the PdCl2PN was allowed to interact with the diol and
NEt3 under a nitrogen atmosphere, the extraction of chloride
ion with formation of NEt3HCl was not observed. This seems
to exclude route b.
In complex 4e the resonance of the methyne proton has been
unequivocally located by means of homonuclear decoupling
experiments. The observed value at 3.63 ppm is too high field
to support the formation of the regioisomer Cl(PN)Pd-C(O)-
OCH(CH3)CH2CH2OH11 and is consistent with the reported
formulation of 4e as Cl(PN)Pd-C(O)OCH2CH2CH(OH)CH3.
Analogous considerations lead us to characterize the complex
and 4b and 4d as 1-OH regioisomers. In the case of 4d, this is
also supported by X-ray analysis, which shows that the diol is
bonded to the CO through the primary alcoholic group.
The molecular structures, with the atom-labeling scheme
adopted, are shown in Figures 1 and 2. As expected for
tetracoordinated Pd(II) complexes, Pd[PPh2C2H4Py]Cl[COO-
CH2-CH2-CH2-OH] (4c) and Pd[PPh2C2H4Py]Cl[COO-CH2-
CH(OH)-C2H5] (4d) display a square planar coordination with
Cl and P atoms in trans position to each other. The compounds
exhibit a slight distortion from exact planarity at the metal
center. The pyridine ligand shows an arrangement with an angle
of 53.32° and 43.13° with respect to the coordination plane for
the complexes 4c and 4d, respectively, while the O-CdO group
is almost perpendicular with respect to coordination plane for
both the molecules (dihedral angle between the Cl1P1N120C10
and O11C10O10 planes is 88.71° and 83.67° for 4c and 4d,
respectively). The Pd-C(sp2) bond distance values for both
studied complexes indicate a back π-bonding character from
the metal to the ligand for the Pd-C(O) bond in the complex,
as the sum of covalent radii of Pd(II) and the sp2 carbon is
2.05 Å.3c,12 The Pd-Cl, Pd-P, and Pd-N bond distances are
similar to that observed in the analogous PPh3 complexes.13 The
Compounds 4a-f, similarly to the alkoxy-carbonyl complexes
having an alkoxy group coming from a mono-alcohol,3 react,
under nitrogen atmosphere, at room temperature with dry CuCl2
or an halogen (Cl2, I2), to form the relevant chloroformate and
regenerating the initial Pd complex, which can be recovered
and reused (reactions 4 and 5 and Scheme 2).
(14) Takenaka, A.; Sasada, Y.; Yamamoto, K.; Tsuji, J. Bull Chem. Soc.
Jpn. 1977, 50, 3177.
(15) De Graaf, W.; Harder, S.; Boesma, J.; van Koten, G. J. Organomet.
Chem. 1988, 358, 545.
(16) Clark, H. C, Dixon, K. R; Jacobs, W. J. J. Am. Chem. Soc. 1969,
91, 1346. Byrd J. E.; Halpern J. J. Am. Chem. Soc. 1971, 93, 1634, and
references therein. Giannocaro, P.; Nobile, C. F. Inorg. Chim. Acta 1990,
175, 133-139.
(17) Ruiz, J.; Martinez, M. T.; Florenciano, F.; Rodriguez, V.; Lopez,
G. Inorg. Chem. 2003, 42, 3650-3661. MacGregor, S. A.; Neave, G. W.
Organometallics 2003, 22, 4547-4556. Tam, W. J. Org. Chem. 1986, 51,
2977-2981. Bennett, M. A.; Yoshida, T. J. Am. Chem. Soc. 1978, 100,
1750-1759. Michelin, R. H.; Napoli, M.; Ros, R. J. Organomet. Chem.
1979, 175, 238-255. Reese, W. M.; Atwood, J. D. Organometallics 1985,
4, 402-406. Bryndza, H. E. Organometallics 1986, 4, 1686.
(11) In 1,3-butandiol dimethylmethacrylate the methyne proton resonance
was found at 5.11, while the OCH2 signal was observed at 4.22 ppm.
(12) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D.
G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1979, S1-S83.
(13) McCridle, R. A.;. McAlles, J.; Zang, E.; Ferguson, G. Acta
Crystallogr. 2000, C56, e132-133.

Alkoxycarbonyl Complexes with a Di-alcohol
Organometallics, Vol. 25, No. 11, 2006 2875
Scheme 4. Hydrolysis of Chloroformate
PdClPNCO-OR-OH + 2CuCl2 f
PdCl2PN + ClCO-OR-OH + 2 CuCl (4)
PdClPNCO-OR-OH + X2 f
PdClXPN + XCO-OR-OH (5)
(X2 ) Cl2, I2)
Reactions 4 and 5 were carried out by adding to the
suspension of the complex in CH3CN a CH3CN solution
containing dry CuCl2 (Cu/Pd ) 2) or the halogen (X2/Pd ) 1).
Chloroformates are formed in very high yields only if CuCl2
and the reaction solvent are strictly anhydrous. Some amount
of CO2, which increases with increasing the water content, is
also obtained. It is quite probable that CO2 is formed by
hydrolysis of the chloroformate, which evolves first to hydroxy-
carbonate and then decomposes to CO2 and alcohol (Scheme
4).
It is possible to convert directly the alkoxycarbonyl group of
complexes 4a-f into cyclic carbonate, avoiding the chlorofor-
mate formation, by adding NEt3 to the reaction mixture. Thus,
the base is responsible for cyclization of chloroformate to cyclic
carbonate 6. It is very likely that the cyclization to carbonate
occurs by intramolecular nucleophilic attack of the oxo group,
coming from interaction between the base and the free OH of
the alkoxycarbonyl ligand, on the carboxyl carbon. In this way,
five- (6a, 6b, 6d), six- (6c, 6e), and seven- (6f) membered cyclic
carbonates (Figure 3) are synthesized by evolution of chloro-
formates coming respectively from the relevant complexes. The
conversion of chloroformate to carbonates was monitored
following the change of IR spectrum of the reaction solution.
Solutions containing chloroformates display a medium-intensity
band in the range 1778-1780 cm-1 due to the ν(CdO) of
ClCO-O-R-OH. Addition of NEt3 causes the shift of the CO
stretching upon cyclic carbonate formation. The new absorptions
Figure 3. Five-, six-, and seven-membered carbonates.
Scheme 5. Decomposition of Pd Complexes upon Heating
mono-alcohol carbonylation to linear carbonates proceeds
similarly. The first series of alkoxycarbonyl complexes of diols,
PdClPN(COO-R-OH), with the free OH group of the diols
bonded to either terminal or internal carbon, have been
synthesized and fully characterized. All complexes in the
presence of proper promoters release the alkoxycarbonyl group
as chloroformate, which may evolve to cyclic carbonate most
likely by intramolecular nucleophilic attack of the free OH on
the carboxyl carbon. Unlike alkoxycarbonyl of mono-alcohols,
which require an oxidant (CuCl2, Cl2, I2, Br2) as promoter for
converting the alkoxycarbonyl group into the carbonate, com-
plexes with diols are able to give cyclic carbonates also by
simple heating of their solution in the presence of a coordinating
ligand (PPh3). Under these conditions, however, the process
cannot be carried out catalytically, as the palladium is released
as Pd(0) (Scheme 5), which is not able to form alkoxy-
carbonylate diols. In contrast, the use of CuCl2 or of a halogen,
which reacts with the alkoxycarbonyl complex and releases
palladium as Pd(II), re-forms the initial complex, PdCl2PN
(Scheme 2), producing a catalytic carbonylation of diols.
are formed at 1807(s)-1776 (m), 1799(s), and 1800(s) cm-1
,
respectively, for the five-membered cyclic carbonates (6a, 6b,
6d); at 1751 and 1748 cm-1 for the six-membered carbonates
(6c, 6e); and at 1757 cm-1 for the seven-membered carbonate
6f. Carbonates were also identified by GC-MS. Molecular ions
were observed for all compounds 6a-f (see Experimental
Section).
Alkoxycarbonyl complexes are stable only in the solid state.
In CH3CN they decompose upon heating (T > 40 °C), giving
metallic Pd and variable amounts of cyclic carbonate. Probably,
upon heating, complexes undergo reductive elimination, giving
chloroformate1d and the Pd(0) complex Pd(PN), which decom-
pose respectively into carbonate and palladium black and free
ligand (Scheme 5).
Support for this reaction course is derived from the observa-
tion that it is possible to convert quantitatively the alkoxycar-
bonyl group into cyclic carbonate by heating a CH3CN solution
of the alkoxycarbonyl complex in the presence of PPh3 and NEt3
(reaction 5). The presence of triphenylphosphine stabilizes the
Pd0 complex as Pd(PN)(PPh3)2 or as Pd(PPh3)4, in the presence
of a large excess of PPh3.
5. Experimental Section
All preparations, reactions, and manipulations were carried out
under the proper gas (dinitrogen or carbon monoxide) using standard
vacuum-line techniques. Solvents and reactants (diols, NEt3, CuCl2,
I2) were Aldrich products and were used without further purification.
The PN ligand and the relevant Pd complex, PdCl2(PN), were
synthesized according to the literature.18 IR spectra were recorded
on a Shimadzu IR-Prestige-21 spectrophotometer. GC separations
and analyses of samples, both in solution and in gas phase, were
PdClPNCOO-R-OH + 4 PPh3 + NEt3 f
Pd(PPh3)4 + 6a-f + NEt3‚HCl + PN (5)
4. Conclusion
We have demonstrated for the first time that the carbonylation
of diols to cyclic carbonates, under palladium catalysis, proceeds
through the formation of alkoxycarbonyl intermediates, and
(18) Uhlig, E.; Keiser, Z. Anorg. Chem. 1974, 406, 1.

2876 Organometallics, Vol. 25, No. 11, 2006
Giannoccaro et al.
Table 3. Experimental Data for the X-ray Diffraction
Studies
Table 4. Selected Geometrical Parameters (Å, deg) of
Complex 4c
4c
4d
Pd1-C10
Pd1-N120
Pd1-P1
1.964 (19)
2.134(7)
2.237(4)
2.364(4)
1.809(9)
C10-O11
C10-O10
P1-C15
1.31(2)
1.21(2)
1.840(15)
1.806(9)
formula
C23H25O3PdPClN
C24H27O3PdPClN
dimension mm
shape, color
cryst syst
space group
cell params at 295 K
a, Å
0.200 ×.0140 × 0.025 0.280 × 0.200 × 0.020
Pd1-Cl1
P1-C100
P1-C110
plate, light yellow
monoclinic
P21/n
plate, light yellow
triclinic
P1h
Cl1-Pd1-P1
N120-Pd1-P1
N120-Pd1-C10
176.79(19)
89.29(31)
175.30(80)
Cl1-Pd1-N120
Cl1-Pd1-C10
92.32(33)
88.32(53)
8.9999 (3)
19.5797 (8)
13.1775 (4)
90
93.117 (2)
90
2321.1 (6)
2363 reflns
4
11.0551 (14)
12.4848 (17)
19.6466 (24)
103.269 (8)
97.059 (8)
89.976 (9)
2918.4 (4)
4362 reflns
4
b, Å
c, Å
Table 5. Selected Geometrical Parameters (Å, deg) of
Complex 4d
R, deg
â, deg
Pd1-C10
Pd1-N120
Pd1-P1
Pd1-Cl1
P1-C100
1.910(29)
2.172(9)
2.268(8)
2.353(10)
1.783(13)
C10-O11
C10-O10
P1-C15
1.401(19)
1.202(20)
1.850(29)
1.794(11)
γ, deg
V, Å3
cell params from
Z
P1-C110
D
calcl, g cm-3
1.533
1.396
radiation
F(000)
mol wt
scan type
scan speed, deg/min
2θ range, deg
index ranges
Mo KR
Mo KR
Cl1-Pd1-P1
176.8(4)
90.32(29)
178.20(40)
Cl1-Pd1-N120
Cl1-Pd1-C10
92.62(39)
88.83(33)
1088
1120.0
N120-Pd1-P1
N120-Pd1-C10
536.284
æ, ω
e0.167
2-25
-10 e h e10
-23 e k e 23
-15 e l e 15
42 456
550.331
æ, ω
e0.167
by direct methods and successive difference Fourier synthesis using
the SIR2002 program.21 Structure refinements were carried out in
space group P21/n and in P1h, respectively, for 4c and 4d, with the
CRYSTAL program.22 All non-H atoms in the crystal structure were
refined anisotropically, while H atoms were added at calculated
positions (aromatic H, C-H ) 0.93 Å, Uiso ) 1.2Uiso of the parent
carbon; CH2 hydrogens, C-H ) 0.97 Å, Uiso ) 1.2Uiso of the parent
carbon; O-H hydrogens, C-H ) 0.82 Å, Uiso ) 1.5Uiso of the
parent oxygen) and were refined isotropically.
X-ray data collection of 4d evidences the presence of some peak
broadening. In addition residuals (about 1 e/Å3) in Fourier difference
maps in the structure refinement are found, suggesting the presence
of disordered solvent (ethyl ether) in the unit cell. This consideration
is supported by the occurrence of large voids (V ) 272 Å3) in the
crystal lattice. To take care of the contribution of disordered solvent,
the data reflections were processed by means of the SQUEEZE
program.23
5.1. Synthesis of Complexes. Synthesis of PdCl(PN) (COO-
CH2-CH2-OH) (4a). To a suspension of PdCl2(PN) (0.400 g, 0.85
mmol) in CH3CN (10 mL) were added, under nitrogen atmosphere,
1,2-hydroxyethane (190 µL, 3.41 mmol; HE/Pd ) 4) and NEt3 (1
mL). Nitrogen was pumped off and carbon monoxide was admitted
(0.1 Mpa). The mixture was allowed to react under stirring at room
temperature for ca. 4 h. Upon reaction, the yellow initial PdCl2-
(PN) complex dissolves, giving an orange solution, from which a
yellow-cream product begins to precipitate. The CO uptake at this
time (8-10 mL, 0.36-0.44 mmol) indicates that the reaction
progress is only about 50%. The mixture was concentrated to one-
half its volume, diethyl ether (5 mL) was added, and the mixture
was allowed to react with CO for a further 12 h at room temperature.
After this period the color of the solution turned to pale yellow
and the suspension product increased. The product was filtered,
washed twice with a cold mixture of Et2O-CH3CN (4:1; 6 mL),
to dissolve impurities of triethylammonium chloride, and dried in
vacuo (0.310 g, yield 69%). The mother liquor was kept overnight
at -10 °C to afford a second fraction of product, with NEt3‚HCl
as an impurity. The salt impurities were dissolved as above, and
further pure product was obtained (0.050 g, total yield 80%).
2-21
-10 e h e11
-12 e k e 12
-19 e l e 19
63 390
no. of reflns measd
no. of unique data
no. of params
R1
3965
7040
130
143
0.039a
0.059a
wR2
0.043b
0.064c
no. of obsd reflns
criterion for
observationsd
904
Fo > 3σ(Fo)
1162
Fo > 5σ(Fo)
goodness of fit on F2 0.961
1.085
0.702, -0.665
peak, hole in final
diff Fourier map
0.275, -0.415
2
2
4
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc )2/∑wFo ]1/2 with
w ) 1/σ(Fo)2. c w1/2 ) [w′ × (1 - ((Fo - Fc)/6(F - Fc)estimated)2)2]1/2, where
w′1/2 ) [1.0/[A[0] × t[0]′(x) + A[1] × t[1]′(X) + ... + A[NP - 1] × t[NP
- 1]′(x)]]1/2. A[i] are the coefficients of a Chebyshev series in t[i]′(x), with
x ) Fc/Fc(max).25 d Goodness-of-fit ) [∑w(Fo2 - Fc )2/(n - p)]1/2, where
2
n is the number of reflections and p the number of parameters.
performed using a Varian Chromopack CP3800 GC connected to
a Varian Star chromatographic workstation. A CP Sil 8 CB 30 m,
0.53 i.d. capillary column, connected to a FID detector, was used
for solution analysis, whereas a 2 m, i.d. 2.0 mm, Restek’s
Shincarbon ST packed column connected to a TCD detector was
used for separating gaseous samples (CO, CO2). MS spectra were
recorded on a Shimadzu GC/MS QP5050A using an HP-5 MS 30
m column.
NMR spectra were run on a Bruker AM 500 instrument. 1H and
13C chemical shifts are in ppm versus TMS and were referenced to
the solvent peak. 31P resonances are reported in ppm and were
calibrated with respect to 85% H3PO4.
Single crystals, suitable for X-ray analysis, of complexes 4c and
4d were mounted on a glass rods without protection from air.
Collection of X-ray diffraction data was performed by a Bruker
AXS X8APEX system equipped with a four-circle Kappa goni-
ometer and a 4K CCD detector. Relevant crystal data and
experimental parameters for the studied complex are summarized
in Table 3, while selected bond and angles are reported in Tables
4 and 5. All data were collected at ambient temperature using a
combination of φ-ω scans and Mo KR radiation (λ ) 0.71073
Å). Cell refinement and data reduction were performed with the
SAINT19 and SADABS programs.20 The structures were resolved
(21) Burla, M. C.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.;
Giacovazzo, C.; Polidori, G.; Spagna, R. Sir2002: a new Direct Methods
program for automatic solution and refinement of crystal structures. J. Appl.
Crystallogr. 2003, 36, 1103.
(22) Watkin, D. J. CRYSTALS, a programmable program. In Crystal-
lographic Computing 6-A Window on Modern Crystallography (H. D.
Flack, L. Parkanyl, and K. Simon, Eds.); Oxford Science Publications:
Oxford, UK, 1992.
(19) Siemens SMART, SAINT (version 4.0); Siemens Analytical X-ray
Instrument Inc.: Madison, WI, 1996.
(20) Sheldrik, G. M. SADABS; University of Go¨ttingen: Germany, 1996.
(23) v. d. Sluis, P.; Speck, A. L. Acta Crystallogr. 1990, A46, 194-
201.

Alkoxycarbonyl Complexes with a Di-alcohol
Organometallics, Vol. 25, No. 11, 2006 2877
Anal. Calcd for C22H23ClNO3PPd: Pd, 20.34; Cl, 6.78; P, 5.92.
Found: Pd, 20.25; Cl, 6.71; P, 5.88. 1H NMR (CD2Cl2, 500 MHz,
293 K): δ 2.43 (m, 2H, CH2(PN)), 2.61 (br unresolved tr, 1H, OH),
3.37 (dm, 2H, CH2(PN), J ) 28.3 Hz), 3.44 (br unresolved m, 2H,
CH2OH), 3.81 (pseudo-tr, 2H, OCH2, J ) 4.7 Hz), 7.24-7.33 (m,
2H, Hâ,Py atoms), 7.42-7.54 (m, 6H, HPh), 7.70-7.80 (m, 5H,
Hγ,Py and HPh), 9.26 (partially resolved dd, 1H, HR′,Py, J ) 5.4
and 1.2 Hz). 13C NMR (CD2Cl2, 125 MHz, 293 K): δ 61.40 (CH2-
OH), 67.46 (OCH2), 176.69 (d, C(O)O, JCP ) 15.3 Hz); 25.23 (d,
CH2P, JCP ) 30.5 Hz), 35.06 (d, CH2Py, JCP ) 4.8 Hz), 123.46
and 125.06 (C â,Py atoms), 139.56 (Cγ,Py), 153.02 (CR′,Py) and
159.64 (d, CR,Py, JCP ) 2.9 Hz); 129.11 (d, Cmeta,Ph, JCP ) 10.5
and 124.95 (C â,Py atoms), 139.46 (Cγ,Py), 153.03 (C R′,Py) and
159.54 (d, CR,Py, JCP ) 2.9 Hz); 129.06 (d, Cmeta,Ph, JCP ) 11.9
Hz), 131.46 (d, Cpara,Ph, JCP ) 2.3 Hz), 131.71 (d, Cipso,Ph, JCP
)
51.5 Hz), 133.30 (d, Cortho,Ph, JCP ) 11.1 Hz). 31P{1H} NMR (CD2-
Cl2, 202 MHz, 293 K): δ 24.38.
Synthesis of PdCl(COO-CH2-CH(OH)-CH2-CH3)(PN) (4d).
PdCl2(PN) (0.500 g, 1.07 mmol), CH3CN (12 mL), 1,2-hydrox-
ybutane (382 µL, 4.26 mmol; 1,2HB/Pd ) 4), and NEt3 (1.25 mL)
were allowed to react with CO under the conditions described
above, until the initial Pd complex dissolved (about 2 h). The
resulting orange solution was concentrated to ca. 5 mL and after
addition of Et2O (10 mL) was allowed to react with CO for a further
36 h. Then the mixture was cooled at -10 °C for 5 days to give
compound 4d as white crystals with NEt3‚HCl as an impurity. The
complex was purified by washing with a mixture of Et2O-CH3-
CN (4:1) and dried (0.330 g, yield 56%). More product was isolated
by concentration and cooling of the mother liquor.
Hz), 131.54 (d, Cipso,Ph, JCP ) 51.5 Hz), 131.57 (d, Cpara,Ph, JCP
)
1.9 Hz), 133.34 (d, Cortho,Ph, JCP ) 12.4 Hz). 31P{1H} NMR (CD2-
Cl2, 202 MHz, 293 K): δ 24.47.
Synthesis of PdCl(PN)(COO-CH2-CH(OH)-CH3) (4b). PdCl2-
(PN) (0.300 g, 0.64 mmol), CH3CN (8 mL), 1,2-hydroxypropane
(190 µL, 2.59 mmol; HP/Pd ) 4), and NEt3 (1 mL) were charged
in a glass reactor and allowed to react under stirring with carbon
monoxide at atmospheric pressure and room temperature until the
initial yellow Pd complex dissolved. The resulting orange solution
was concentrated to one-half its volume, and after the addition of
diethyl ether (8 mL) it was kept under stirring to react with CO for
a further 24 h in order to drive the reaction to completion. The
reactor was cooled at -10 °C for 12 h, and the precipitated yellow-
cream alkoxy-carbonyl complex was filtered off, washed with a
cold mixture of Et2O-CH3CN (4:1), and dried (0.260 g, yield 60%).
More product was isolated by concentration and cooling of the
mother liquor.
Anal. Calcd for C24H27ClNO3PPd: Pd, 19.31; Cl, 6.43; P, 5.61.
1
Found: Pd, 19.27; Cl, 6.47; P, 5.58. H NMR (CDCl3, 500 MHz,
293 K): δ 0.80 (t, 3H, CH3, J ) 7.5 Hz) 1.20-1.34 (m, 2H CH2),
2.37 (m, 2H, CH2(PN)), 2.70 (br, 1H, OH), 3.31 (dm, 2H, CH2(PN)
,
J ) 28.1 Hz), 3.46-3.56 and 3.86 (two multiplets, 2H and 1H
respectively, diastereotopic OCH2 and CH), 7.18-7.28 (m, 2H, Hâ,-
Py and Hâ′,Py), 7.37-7.48 (m, 6H, HPh), 7.67-7.76 (m, 5H, Hγ,-
Py and HPh), 9.32 (br dd, 1H, HR′,Py, J ≈ 5.5 and 1.5 Hz). 13C
NMR (CDCl3, 125 MHz, 293 K): δ 9.80 (CH3), 25.62 (CH2), 70.79
and 70.10 (OCH2 and CH), 175.96 (d, C(O)O, JCP ) 15.3 Hz);
24.93 (d, CH2P, JCP ) 29.6 Hz), 34.55 (d, CH2Py, JCP ) 4.8 Hz),
123.22 and 124.52 (Câ,Py atoms), 139.04 (Cγ,Py), 153.11 (CR′,Py)
Anal. Calcd for C23H25ClNO3PPd: Pd, 19.81; Cl, 6.60; P, 5.77.
and 158.99 (d, CR,Py, JCP ) 2.9 Hz); 128.82 (d, Cmeta,Ph, JCP
11.4 Hz), 130.87 (d, Cipso,Ph, JCP ) 51.5 Hz) and 131.11 (d, Cipso,Ph
)
,
1
Found: Pd, 19.79; Cl, 6.55; P, 5.73. H NMR (CDCl3, 500 MHz,
293 K): δ 0.93 (d, 3H, CH3, J ) 6.5 Hz), 2.38 (m, 2H CH2(PN)),
2.60 (br, OH), 3.33 (dm, 2H, CH2(PN), J ) 28.1 Hz), 3.47 and 3.74-
3.81 (two multiplets, 1H and 2H, respectively, diastereotopic OCH2
and CH), 7.18-7.28 (m, Hâ,Py and Hâ′,Py), 7.36-7.50 (m, HPh),
JCP ) 51.5 Hz), 131.27 (d, br, Cpara,Ph), 132.96 (t, Cortho,Ph, JCP
12.4 Hz). 31P{1H} NMR (CDCl3, 202 MHz, 293 K): δ 22.19.
)
Synthesis of PdCl(PN)(COO-CH2-CH2-CH(OH)-CH3 (4e).
PdCl2(PN) (0.600 g, 1.28 mmol), CH3CN (15 mL), 1,3 hydrox-
ybutane (460 µL, 5.13 mmol; 1,3-HB/Pd ) 4), and NEt3 (1.5 mL)
were allowed to react with CO under the conditions described
above, until the initial Pd complex dissolved (about 3 h). The
resulting orange solution was concentrated to one-half of its volume.
The suspension was separated by filtration and purified by washing
as described above, whereas the filtered solution, after addition of
Et2O (5 mL), was left at -10 °C for 5 days. White crystals of 4e,
with a slight impurity of ammonium salt, were obtained, which
were purified by washing with a cold mixture of Et2O-CH3CN
(5:1) and dried (0.371 g total, yield 53%). More product was
obtained as described above.
7.68-7.76 (m, Hγ,Py and HPh), 9.30 (br dd, HR′,Py, J ≈ 5 Hz). 13
C
NMR (CDCl3, 125 MHz, 293 K): δ 18.07 (CH3), 65.61 and 71.35
(OCH2 and CH), 176.12 (d, C(O)O, JCP ) 15.3 Hz); 24.94 (d, CH2P,
JCP ) 29.6 Hz), 34.62 (d, CH2Py, JCP ) 4.8 Hz), 123.23 and 124.56
(Câ,Py atoms), 139.08 (Cγ,Py), 153.06 (C R′,Py) and 159.00 (d,
CR,Py, JCP ) 2.9 Hz); 128.82 (d, Cmeta,Ph, JCP ) 10.5 Hz) and 128.84
(d, Cmeta,Ph, JCP ) 10.5 Hz), 130.91 (d, Cipso,Ph, JCP ) 52.4 Hz) and
131.04 (d, Cipso,Ph, JCP ) 51.5 Hz), 131.27 (d, br, Cpara,Ph, JCP ) 2.9
Hz) and 131.30 (d, partially overlapped, Cpara,Ph), 132.94 (d, Cortho,Ph
JCP ) 12.4 Hz) and 132.96 (d, Cortho,Ph, JCP ) 11.4 Hz). 31P{1H}
NMR (CDCl3, 202 MHz, 293 K): δ 22.34.
,
Synthesis of PdCl(PN)(COO-CH2-CH2-CH2(OH) (4c). PdCl2-
(PN) (0.600 g, 1.28 mmol), CH3CN (12 mL), 1,3-hydroxypropane
(372 µL, 5.13 mmol; HP/Pd ) 4), and NEt3 (1.5 mL) were reacted
with CO for 4 h, as described above. The volume of the resulting
orange solution was reduced by concentration to about 5 mL and
after addition of diethyl ether (10 mL) was allowed to react with
CO for a further 12 h. Successive cooling of the reaction mixture
to -10 °C gave compound 4c as white-cream crystals, which were
filtered off, washed with Et2O-CH3CN (4:1), and dried (0.547 g,
yield 79%).
Anal. Calcd for C24H27ClNO3PPd: Pd, 19.31; Cl, 6.43; P, 5.61;
C, 52.38; N, 2.55; H, 4.95. Found: Pd, 19.28; Cl, 6.45; P 5.56; C,
1
52.15; N, 2.93; H, 5.08. H NMR (CD2Cl2, 500 MHz, 293 K): δ
1.01 (d, 3H, CH3, J ) 6.1 Hz), 1.24-1.43 (m, 2H, diastereotopic
CH2), 2.43 (m, 3H, OH and CH2(PN)), 3.38 (dm, CH2(PN), J ) 28.0
Hz), 3.60 (dt, 1H, diastereotopic OCH2, J ) 11.1 and 5.7 Hz), 3.63
(m, 1H, CHOH, J ) 3.5 and 8.9 Hz), 3.93 (m, 1H, diasterotopic
OCH2, J ) 4.9, 8.1, and 10.8 Hz), 7.24-7.31 (m, 2H, Hâ,Py and
Hâ′,Py), 7.42-7.52 (m, 6H, HPh), 7.68-7.77 (m, 5H, Hγ,Py and
HPh), 9.23 (br dd, 1H, HR′,Py, J ) 5.7 and 1.5 Hz). The resonance
of the methyne proton has been unequivocally located by means
of homonuclear decoupling experiments. 13C NMR (CD2Cl2, 125
MHz, 293 K): δ 23.36 (CH3), 38.64 (CH2), 63.59 (OCH2), 64.94
(CHOH), 177.08 (d, C(O)O, JCP ) 15.0 Hz); 25.45 (d, CH2P, JCP
) 30.5 Hz), 35.25 (d, CH2Py, JCP ) 5.7 Hz), 123.41 and 124.97
(Câ,Py atoms), 139.48 (Cγ,Py), 153.10 (CR′,Py) and 159.60 (d, CR,-
Py, JCP ) 2.9 Hz); 129.08 (d, Cmeta,Ph, JCP ) 11.7 Hz) and 129.10
(d, partially masked, Cmeta,Ph, JCP ≈ 11 Hz), 131.44 (d, Cpara,Ph, JCP
Anal. Calcd for C23H25ClNO3PPd: Pd, 19.81; Cl, 6.60; P, 5.77;
C, 51.51; N, 2.61; H, 4.60. Found: Pd, 19.82; Cl, 6.63; P, 5.74; C,
1
51.27; N, 2.79; H, 4.59. H NMR (CD2Cl2, 500 MHz, 293 K): δ
1.48 (quint, CH2, 2H, J ) 5.9 Hz), 2.29 (br, 1H, OH), 2.44 (m,
2H, CH2(PN)), 3.39 (dm, CH2(PN), 2H, J ) 28.1 Hz), 3.44 (br tr, 2H,
J ) 5.7 Hz, CH2OH), 3.76 (tr, 2H, OCH2, J ) 5.9 Hz), 7.24-7.32
(m, 2H, Hâ,Py and Hâ′,Py), 7.42-7.52 (m, 6H, HPh), 7.70-7.77
(m, 5H, Hγ,Py and HPh), 9.25 (br d, 1H, HR′,Py, J ) 5.5 Hz). 13C
NMR (CD2Cl2, 125 MHz, 293 K): δ 32.37 (CH2), 59.52 (CH2-
OH), 63.35 (OCH2), 177.21 (d, C(O)O, JCP ) 14.2 Hz); 25.43 (d,
CH2P, JCP ) 30.5 Hz), 35.30 (d, CH2Py, JCP ) 4.8 Hz), 123.40
) 2.9 Hz) and 131.52 (d, Cpara,Ph, JCP ) 2.9 Hz), 131.67 (d, Cipso,Ph
,
JCP ) 51.5 Hz) and 131.80 (d, Cipso,Ph, JCP ) 51.5 Hz), 133.26 (d,

2878 Organometallics, Vol. 25, No. 11, 2006
Giannoccaro et al.
Cortho,Ph, JCP ) 11.8 Hz) and 133.44 (d, Corthp,Ph, JCP ) 12.1 Hz).
31P{1H} NMR (CD2Cl2, 202 MHz, 293 K): δ 24.31.
chloroformate Cl-COO(CH2)2-(OH) (5a) and two weak intensity
bands at 1807 and 1774 cm-1 ascribed to the cyclic carbonate 6a.
Addition of NEt3 caused the complete conversion of 5a to the
relevant cyclic carbonate 6a. MS (m/z): 88 (M+, 52), 58 (9), 43
(65), 29 (100).
Synthesis of PdCl(PN)(COO-CH2-CH2-CH2-CH2(OH) (4f).
PdCl2(PN) (0.600 g, 1.28 mmol), CH3CN (15 mL), 1,4-hydrox-
ybutane (454 µL, 5.12 mmol; 1,4-HB/Pd ) 4), and NEt3 (1,5 mL)
were allowed to react with CO under the conditions described above
for about 3 h. The resulting solution, after concentration to ca. 5
mL, addition of Et2O (5 mL), and further 48 h reaction with CO,
was left overnight at -10 °C to afford white 4f contaminated with
NEt3‚HCl. The mixture was separated by filtration and purified by
washing. The filtered solution, after addition of Et2O (5 mL) and
cooling at -10 °C for 5 days, produced white crystals of 4f, slightly
contaminated with ammonium salt, which was purified by washing
with Et2O-CH3CN (4:1) and dried (0.380 g total, yield 54%). More
product could be obtained as described above.
Synthesis of 4-Methyl-1,3-dioxolan-2-one (6b). Complex 4b
(0.088 g, 0.16 mmol), in CH3CN (1.5 mL), and CuCl2 (0.048 g,
0.35 mmol) were reacted, and the IR spectrum of the reaction
solution displayed a strong band at 1779 cm-1 due to the
chloroformate Cl-COO(CH2)CH-(OH)CH3 (5b). Addition of NEt3
caused the complete conversion of 5b into the relevant cyclic
carbonate 6b, as evidenced by the IR spectrum, which showed a
new band at 1751 cm-1. MS (m/z): 102 (M+, 2), 87 (10), 57 (64),
43 (73), 29 (100).
Synthesis of 4-Ethyl-1,3-dioxolan-2-one (6d). Complex 4d,
(0.106 g, 0.19 mmol), in CH3CN (1.5 mL), and CuCl2 (0.056 g,
0.41 mmol) were reacted, and the IR spectrum of the reaction
solution displayed a strong band at 1779 cm-1 due to the
chloroformate Cl-COOCH2CH(OH)CH2CH3 (5d). Addition of NEt3
caused the complete conversion of 5d into the relevant cyclic
carbonate 6d, as evidenced by the IR spectrum, which showed a
new band at 1801 cm-1. MS (m/z): 116 (M+, 1), 87 (25), 71 (2),
44 (16), 43 (100), 42 (56), 29 (30).
Anal. Calcd for C24H27ClNO3PPd: Pd, 19.31; Cl, 6.43; P, 5.61.
Found: Pd, 19.26; Cl, 6.41; P 5.57. 1H NMR (CD2Cl2, 500 MHz,
293 K): δ 1.24-1.40 (m, 4H, CH2CH2), 2.18 (br, OH), 2.44 (m,
2H, CH2(PN)), 3.39 (dm, 2H, CH2(PN), J ) 28.1 Hz), 3.45 (tr, 2H,
CH2OH, J ) 6.2 Hz,), 3.64 (tr, 2H, OCH2, J ) 6.4 Hz), 7.24-
7.31 (m, 2H, Hâ,Py and Hâ′,Py), 7.40-7.51 (m, 6H, HPh), 7.66-
7.76 (m, 5H, Hγ,Py and HPh), 9.23 (br d, 1H, HR′,Py, J ) 5.4 Hz).
13C NMR (CD2Cl2, 125 MHz, 293 K): δ 25.60 (CH2), 29.53 (CH2),
62.21 (CH2OH), 66.13 (OCH2), 176.35 (d, C(O)O, JCP ) 14.6 Hz);
25.51 (d, CH2P, JCP ) 29.6 Hz), 35.31 (d, CH2Py, JCP ) 4.6 Hz),
123.33 and 124.94 (Câ,Py atoms), 139.43 (Cγ,Py), 152.93 (CR′,Py)
Synthesis of 4-Methyl-1,3-dioxan-2-one (6e). Complex 4e (0.99
g, 0.18 mmol), in CH3CN (1.5 mL), and CuCl2 (0.057 g, 0.42 mmol)
were reacted, and the IR spectrum of the reaction solution displayed
a strong band at 1778 cm-1 due to the chloroformate Cl-COO-
(CH2)2-CH(OH)CH3 (5e) and a weak intensity band at 1749 cm-1
ascribed to the cyclic carbonate 4-methyl-1,3-dioxan-2-one (6e).
Addition of NEt3 (0.3 mL) caused the complete conversion of 5e
to the relevant cyclic carbonate 6e. MS (m/z): 116 (M+, 2,5), 101
(19), 86 (100), 71 (4), 58 (40), 44 (24), 43(45), 42 (50), 29 (43).
and 159.58 (d, CR,Py, JCP ) 2.8 Hz); 129.00 (d, Cmeta,Ph, JCP
)
11.7 Hz), 131.38 (d, Cpara,Ph, JCP ) 2.9 Hz), 131.81 (d, Cipso,Ph, JCP
) 51.5 Hz), 133.29 (d, Cortho,Ph, JCP ) 11.8 Hz). 31P{1H} NMR
(CD2Cl2, 202 MHz, 293 K): δ 24.53.
5.2. Reaction of the Complexes 4a-f with HCl. In a typical
reaction the alkoxycarbonyl complex 4b (0.168 g, 0.31 mmol), in
CH3CN (3 mL), and a methanol solution of 3 M HCl (2 mL) were
separately charged into the two branches of an inverted Y-shaped
glass reactor. The reactor was connected to a gas buret, the contents
were mixed, and the CO evolved was measured at ambient
temperature and pressure (6.7 mL at 21 °C, 0.1 MPa) and analyzed
by GC. Trace amounts of CO2 were found.
Synthesis of 1,3-Dioxacycloheptan-2-one (6f). Complex 4f
(0.150 g, 0.27 mmol), in CH3CN (1.5 mL), and CuCl2 (0.080 g,
0.59 mmol) were reacted, and the IR spectrum of the reaction
solution displayed only one band in the carbonyl range at 1778
cm-1 due to the chloroformate Cl-COO(CH2)4-OH (5f). Addition
of NEt3 caused the complete conversion of 5f into the relevant cyclic
carbonate 6f, evidenced by the IR spectrum, which displayed a band
at 1757 cm-1. MS (m/z): 116 (M+, 4), 71 (6), 57 (5), 44 (22), 43
(29), 42 (100), 41 (50), 29 (23).
The decomposition of the other complexes was performed in
the same way. The weighed amounts of complexes and volume of
CO evolved are reported in Table 2.
5.3. Reaction of Alkoxycarbonyl Complexes 4a-f with
CuCl2: Synthesis of Cyclic Carbonates via Chloroformate. All
the reactions were performed in the above-described inverted
Y-shaped glass reactor.
5.4. Reaction of Alkoxycarbonyl Complexes 4a-f with I2:
Synthesis of Chloroformate. Complex 4c (0.091 g, 0.17 mmol),
in CH3CN (2 mL), and I2 (0.044 g, 0.17 mmol), in CH3CN (2,5
mL), were separately charged into the two branches of the glass
reactor. The iodine solution was added to the suspension of the
complex, which caused its solubilization and subsequently the
precipitation of a brown product. The IR spectrum of the reaction
solution displays a strong band at 1778 cm-1, due to the chloro-
formate Cl-COO(CH2)3-OH (5c), which was identified indirectly
both by the relevant cyclic carbonate 6c and by the reaction product
with aniline. Addition of aniline to a solution of 5c gave the
expected derivative carbamate PhNHCOO(CH2)3OH, which was
recognized by MS [(m/z, M+ 194, 119, 116, 115, 93(100%), 91,
65, 47)]. The mass spectrum of the reaction solution exhibits two
further signals attributable respectively to phenyl isocyanate and
1,3-hydroxypropane, deriving from thermal decomposition of
PhNHCOO(CH2)3OH.24
Synthesis of 1,3-Dioxan-2-one (6c). Complex 4c (0.096 g, 0.18
mmol), in CH3CN (1.5 mL), and 0.050 g (0.37 mmol) of dry CuCl2,
in CH3CN (3 mL), were separately charged into the two branches
of the glass reactor. The copper solution was added to the
suspension of the complex, which caused its solubilization and
subsequently the precipitation of a yellow product. The IR spectrum
of the reaction solution displays a strong band at 1778 cm-1 and a
weak band at 1751 cm-1, due respectively to chloroformate Cl-
COO(CH2)3-OH and to small amounts of cyclic carbonate 6c. NEt3
(3 mL), added to the reaction mixture, caused an immediate
conversion of the chloroformate into carbonate, as evidenced by
the IR spectrum, which showed the extinction of the band at 1778
cm-1 and the reinforcement of the one at 1751 cm-1. The carbonate
was characterized by GC-MS and quantitatively analyzed by GC
(found 0.15 mmol, 83%). MS (m/z) (relative intensity %): 102 (M+,
13), 58 (25), 57 (47), 43 (15), 29 (100%).
The reaction with other complexes was carried out in the same
manner. The relevant chloroformates were characterized as cyclic
carbonates and carbamate derivatives.
Synthesis of 1,3-Dioxolan-2-one (6a). Complex 4a (0.101 g,
0.19 mmol), in CH3CN (1.5 mL), and CuCl2 (0.057 g, 0.42 mmol)
were reacted as described above, and the IR spectrum of the reaction
solution displayed a strong band at 1778 cm-1 due to the
(24) Rivetti, F.; Romano, U.; Sassanelli, M. U.S. Patent FCS 4514339,
1985.
(25) Carruthers, B. J.; Watkin, D. J. Acta Crystallogr. 1979, A35, 698.

Alkoxycarbonyl Complexes with a Di-alcohol
Organometallics, Vol. 25, No. 11, 2006 2879
5.5. Reaction of Alkoxycarbonyl Complexes with PPh3 and
NEt3. Typical reaction: to a suspension of complex 4b (0.102 g,
0.19 mmol) in CH3CN (4 mL) were added, under nitrogen, PPh3
(0.95 mmol; PPh3/Pd ) 5) and NEt3 (0.4 mL). The mixture was
heated at 60 °C for 3 h. During this period the initial white-cream
complex dissolved, giving a yellow solution from which Pd(PPh3)4
precipitated. The IR spectrum of the reaction solution displayed a
band at 1751 cm-1, ascribed to cyclic carbonate 6b, whose
formulation was confirmed by a mass spectrum.
Acknowledgment. The authors thank the University of Bari
and MURST (Prin Cofin 2003 prot. 2003039774) for financial
support.
Supporting Information Available: X-ray crystallographic data
in CIF format for complexes 4c and 4d. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM060012E