Synthesis, characterization and molecular structure of oxo and phenylimido rhenium(V) complexes of 1-phenyl-2-(diisopropylphosphino)-ethanone

Article abstract of DOI:10.1016/S0020-1693(02)01198-2

New rhenium-oxo and phenylimido complexes were synthetized and isolated by reaction of 1-phenyl-2-(diisopropylphosphino)ethanone on ReOX₃(PPh₃)₂ (X=Cl, Br, I), ReO(OEt)Cl₂(PPh₃)₂ and Re(NPh)Cl₃(PPh₃)₂ in basic media (NEt₃). In these complexes the ligand bonds mainly as monoanionic enolato chelating agent. The reactions are solvent dependent. The disubstituted ReOX(P-O)₂ compounds (1-7) adopt a 'twisted' octahedral structure with a mixture of cis-PP and trans-PP configurations in toluene, thus indicating that in this case the stability gap between the two diastereoisomers is small. In ethanol, only the 'twisted' cis-PP conformers ReOCl(P-O)₂(1) and ReO(OEt)(P-O)₂ (7) were observed. The ethoxo-oxo complex ReO(OEt)(P-O)₂ (7) resulting from the stereoselective substitution of the halide by the ethoxo group is the unique species isolated when X=Br and I. The reaction with Re(NPh)Cl₃(PPh₃)₂ was less selective and, in ethanol, excess of ligand was needed to get trans-PP-Re(NPh)Cl(P-O)₂ (8) as unique species. A mixture of (8), of the monosubstituted Re(NPh)Cl₂(PPh₃)(P-O) (9) and of Re(NPh)Cl₂(P-C=O)(P-O) (10) was observed in toluene with and without base. All these data emphasize the influence of the basicity and steric hindrance of the phosphinoenolato ligand on the rhenium complexes formation.

Full text of DOI:10.1016/S0020-1693(02)01198-2

Inorganica Chimica Acta 343 (2003) 307Á312
/
www.elsevier.com/locate/ica
Synthesis, characterization and molecular structure of oxo and
phenylimido rhenium(V) complexes of 1-phenyl-2-
(diisopropylphosphino)-ethanone
Xavier Couillens, Marie Gressier, Miche`le Dartiguenave *
´
Laboratoire de Chimie Inorganique, Universite Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex, France
Received 3 June 2002; accepted 13 July 2002
Abstract
New rhenium-oxo and phenylimido complexes were synthetized and isolated by reaction of 1-phenyl-2-(diisopropylphos-
phino)ethanone on ReOX3(PPh3)2 (XꢀCl, Br, I), ReO(OEt)Cl2(PPh3)2 and Re(NPh)Cl3(PPh3)2 in basic media (NEt3). In these
complexes the ligand bonds mainly as monoanionic enolato chelating agent. The reactions are solvent dependent. The disubstituted
ReOX(PÃO)2 compounds (1Á7) adopt a ‘twisted’ octahedral structure with a mixture of cis-PP and trans-PP configurations in
toluene, thus indicating that in this case the stability gap between the two diastereoisomers is small. In ethanol, only the ‘twisted’ cis-
PP conformers ReOCl(PÃO)2(1) and ReO(OEt)(PÃO)2 (7) were observed. The ethoxo-oxo complex ReO(OEt)(PÃO)2 (7) resulting
from the stereoselective substitution of the halide by the ethoxo group is the unique species isolated when XꢀBr and I. The reaction
with Re(NPh)Cl3(PPh3)2 was less selective and, in ethanol, excess of ligand was needed to get trans-PP-Re(NPh)Cl(PÃO)2 (8) as
unique species. A mixture of (8), of the monosubstituted Re(NPh)Cl2(PPh3)(PÃO) (9) and of Re(NPh)Cl2(PÃCÄO)(PÃO) (10) was
/
/
/
/
/
/
/
/
/
/
/
/
observed in toluene with and without base. All these data emphasize the influence of the basicity and steric hindrance of the
phosphinoenolato ligand on the rhenium complexes formation.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Synthesis; Oxo-rhenium(V) complexes; Phenylimido rhenium(V) complexes; 1-Phenyl-2-(diisopropylphosphino)-ethanone
1. Introduction
nylphosphines functionalized with nucleophilic substi-
tuents such as phenol or ketone i.e. bidentate ligands
with soft phosphorus(III) donor and hard phenolato or
Because of their chemical and structural diversity and
their good coordinative properties, functionalized phos-
phines have attracted considerable attention in strategies
aimed at developing new technetium complexes as
imaging agents in nuclear medicine. The recent avail-
ability of rhenium 188, obtained from 188W/188Re
generator boosted the use of this radioelement as
enolato groups [5Á
acterized by the OÄ
species) and PhNÄReÃ
/
12]. All the complexes were char-
ReÃO linkage (in all the Re-oxo
O one (in all the Re-phenylimido
/
/
/
/
compound). This has for consequence to stabilize
‘twisted’ octahedral complexes with either cis-PP (A)
or trans-PP (B) conformation. In both cases the enolato
ligands are located in two perpendicular planes (Scheme
1). Thus these ligands, besides having strong coordina-
tive properties, favor the formation of single isomer,
which is essential for radiopharmaceutical applications.
In this work, we report on the characterization of the
oxo and imido complexes resulting from the reaction of
radiotherapeutic anti cancer agent [1Á4]. As a conse-
quence, development of suitable rhenium complexes
remains an important goal.
In the recent past, many studies on Re(V) complexes
have been devoted on ligand exchange reactions between
ReOCl3(PPh3)2, Re(NPh)Cl3(PPh3)2 and various diphe-
/
i
the 1-phenyl-2-(diisopropylphosphino)ethanone Pr2P-
CH2C(Ä
/
O)Ph on ReOX3(PPh3)2 and Re(NPh)Cl3-
* Corresponding author. Tel.: ꢁ
556118
E-mail address: dartigue@chimie.ups-tlse.fr (M. Dartiguenave).
/
33-5-61 556121; fax: ꢁ33-5-61
/
(PPh3)2 and compare the data with those obtained
with the related diphenylphosphinoketone, the main
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 1 9 8 - 2

308
X. Couillens et al. / Inorganica Chimica Acta 343 (2003) 307Á312
/
(found) for C28H40ClO3P2Re: C, 47.48 (47.37); H, 5.69
(5.34)%. IR (KBr, cmꢂ1): 974 (n(ReÄ
O)); 1543 (n(CÄ
CÃO). MS DCI/NH3 m/z (%): 726 (37) [Mꢁ
NH4]ꢁ;
709 (100) [Mꢁ
/
/
/
/
/
H]ꢁ; 690 (21) [Mꢂ
/
HClꢁ
NH4]ꢁ; 673 (5)
/
[Mꢂ
1.02 (dd, JHP
/
HClꢁ
/
H]ꢁ. 1H NMR (CDCl3, 400.13 MHz; ppm):
3
3
ꢀ
/
16, JHH
ꢀ7 Hz, 3H, CH3); 1.13 (dd,
/
3JHP
3JHH
Hz, 3H, CH3); 1.43 (dd, JHP
ꢀ
ꢀ
/
17, JHH
ꢀ/7 Hz, 3H, CH3); 1.17 (dd, JHP
ꢀ16,
/
3
3
3
3
Scheme 1.
/
7 Hz, 3H, CH3); 1.33 (dd, JHP
ꢀ
/
14, JHH
7 Hz, 3H,
7 Hz, 3H, CH3); 1.62
7 Hz, 3H, CH3); 1.64 (dd,
ꢀ7
/
3
3
ꢀ
ꢀ
/
16, JHH
ꢀ
/
3
3
differences between these two ligands being the steric
hindrance (Â1568 for the 1-phenyl-2-(diisopropylpho-
sphino)ethanone compared to Â1368 for the 1-phenyl-
2-(diphenylphosphino)ethanone [13]) and the basicity
(pKaꢀ
2.73 for PPh3 and 9.30 for PiPr3) of the
CH3); 1.51 (dd, JHP
3
(dd, JHP
ꢀ
/
13, JHH
/
3
16.5, JHH
/
ꢀ
/
ꢀ
/
3
2
3JHP
12, 3JHH
ꢀ
/
15, JHH
ꢀ
/
7 Hz, 3H, CH3); 2.24 (dhep, JHP
Hz, 1H, CH ÃCH3); 2.36 (oct,
Hz, 1H, CH ÃCH3); 2.68 (dhep,
7 Hz, 1H, CH ÃCH3); 3.25 (dhep,
7 Hz, 1H, CH ÃCH3); 5.51 (d,
5.0 Hz, 1H, CH); 5.77 (d, JHP 5.0 Hz, 1H,
8.13 (m, 10H, aromatics).
ꢀ
/
/
ꢀ
/7
/
2JHPꢀ3
/
JHH
ꢀ
/
7
/
/
2JHP
2JHP
2JHP
ꢀ
ꢀ
ꢀ
/
9, JHH
ꢀ
/
/
3
phosphines [14]. It is of interest also to compare these
results to those obtained with the related phosphino-
3
/
12, JHH
ꢀ
/
/
2
phenol R2PC6H4OH (RꢀiPr and Ph) where the steric
/
/
ꢀ
/
hindrance of the phosphine played the major role.
CH); 7.11Á
/
2.2.2. Synthesis of trans-PP-ReOCl(PÃ
/
O)2 (2)
2. Experimental
Same method as above for 1. The solution remaining
after filtration of 1 at r.t. was concentrated in vacuo.
The residue was dissolved in Et2O (10 ml). Addition of
C5H12 gave 2 as a pure microcrystalline green solid
which was filtrated and dried in vacuo (yield: 21%).
Anal. Calc. (Found) for C28H40ClO3P2Re: C, 47.48
2.1. Reactants and physical measurements
All reactions were carried out under a nitrogen
atmosphere using standard Schlenk techniques. Re-
(48.33); H, 5.69 (5.80)%. IR (KBr, cmꢂ1): 969 (n(ReÄ
O)), 1537 (n(CÄCÃO)). MS DCI/NH3 m/z (%): 726 (3)
[Mꢁ HClꢁ
NH4]ꢁ; 709 (100) [MꢁH]ꢁ; 690 (3) [Mꢂ
NH4]ꢁ; 673 (11) [Mꢂ H]ꢁ. H NMR (CDCl3,
HClꢁ
400.13 MHz, ppm): 1.23 (dd, JHP
/
OX3(PPh3)2
Re(NPh)Cl3(PPh3)2 [17] and 1-phenyl-2-(diisopropyl-
phosphino)ethanone (PÃCÄO) [18] were prepared as
described in the literature. IR spectra (4000Á
400 cmꢂ1
[15],
ReO(OEt)X2(PPh3)2
[16],
/
/
/
/
/
/
/
/
1
/
)
/
/
3
3
were recorded as KBr pellets on a Vector 22 Bruker
ꢀ
/
15.5, JHH
ꢀ7 Hz,
/
1
spectrophotometer. H NMR spectra were obtained at
room temperature on Bruker AMX 400 and WM 250
3H, CH3); 1.43Á
/
1.63 (m, 21H, 7 CH3); 2.54 (dhep,
3
2JHP
2JHP
2JHP
2JHP
2JHP
ꢀ
/
11, JHH
ꢀ
/
7 Hz, 1H, CH Ã
7 Hz, 1H, CH Ã
7 Hz, 1H, CH Ã
7 Hz, 1H, CH Ã
1.3 Hz, 1H, CH); 4.94 (dd, JHP
1.4 Hz, 1H, CH); 7.13Á7.84 (m, 10H,
/
CH3); 2.77 (dhep,
CH3); 2.92 (dhep,
CH3); 3.32 (dhep,
3
instruments. The residual solvent signals (dꢀ5.20 ppm
/
ꢀ
/
11, JHH
ꢀ
ꢀ
ꢀ
/
/
3
for CD2Cl2 and 7.30 for CDCl3) were used as internal
standards and the chemical shifts are reported with
respect to Me4Si. For the 31P{1H} NMR spectra, the
AC 200, AMX 300 and ARX 400 instruments were used
ꢀ
/
11, JHH
/
/
3
ꢀ
/
11, JHH
/
/
CH3); 4.58 (dd,
4
2
ꢀ
/
3, JHP
ꢀ
/
ꢀ
/
4
5.9, JHP
aromatics).
ꢀ
/
/
and the external standard was H3PO4 (82% D2O, dꢀ0.0
/
ppm). Mass spectra were measured with a NERMAG
R10-10 spectrometer. Elemental analyses were carried
out at the Laboratoire de Controˆle de l’Ecole Nationale
Supe´rieure de Chimie de Toulouse.
2.2.3. Synthesis of trans-PP-ReOBr(PÃ
Same method as above for 1 with 0.450 g (0.40 mmol)
of ReOBr3(PPh3)2, 0.33 g (1.39 mmol) of PÃCÄO, 0.130
/
O)2 (4)
/
/
g (1.43 mmol) of NEt3 refluxed in 20 ml of C6H5CH3 for
4 h. Filtration of the solution to eliminate (HNEt3)Cl,
concentration by one-half, addition of C5H12 (20 ml)
2.2. Synthetic work
2.2.1. Synthesis of cis-PP-ReOCl(PÃ
A mixture of 0.423 g (0.51 mmol) of ReOCl3(PPh3)2,
0.24 g (1.02 mmol) of PÃCÄO and 0.102 g (1.01 mmol)
of NEt3 was refluxed in 20 ml of C6H5CH3 for 4 h.
Cooling the solution to room temperature (r.t.) pro-
duced the precipitation of (HNEt3)Cl as a white solid
that was eliminated by filtration. The resulting green
solution was concentrated to one-half. Addition of
C5H12 gave a green solid which was filtered, washed
with, C5H12 and dried in vacuo (yield: 27%). Anal. Calc.
/
O)2 (1)
and cooling to ꢂ20 8C gave a green micro crystalline
/
solid which was filtrated, washed with C5H12 and dried
under reduced pressure. Recrystallisation from
C6H5CH3/C5H12 (1/1) gave 4 as a pure complex (yield:
37%). Anal. Calc. (Found) for C28H40BrO3P2Re: C,
44.69 (45.37); H, 5.36 (5.46)%. IR (KBr, cmꢂ1): 969
/
/
(n(ReÄ
753 (100) [Mꢁ
[MꢂHBrꢁ
H]ꢁ. 1H NMR (CDCl3, 400.13 MHz, ppm):
1.25 (dd, 3JHP 15.5, 3JHH
7 Hz, 3H, CH3); 1.43Á1.66
/
O)), 1537 (n(CÄ
/
CÃ
/
O)). MS DCI/NH3 m/z (%):
/
H]ꢁ; 690 (1) [Mꢂ
/
HBrꢁ
/
NH4]ꢁ; 673 (4)
/
/
ꢀ
/
ꢀ
/
/

X. Couillens et al. / Inorganica Chimica Acta 343 (2003) 307Á
/312
309
2
3
3
3H, CH3); 1.45 (dd, JHP
3
13, JHH
(m, 21H, 7 CH3); 2.54 (dhep, JHP
ꢀ
/
11, JHH
ꢀ
/
7 Hz,
7 Hz, 1H,
7 Hz, 1H,
7 Hz, 1H,
1.2 Hz, 1H, CH);
1.3 Hz, 1H, CH); 7.11Á7.80
ꢀ
/
ꢀ
/
7 Hz, 3H, CH3);
3
1.48 (dd, JHP
3
15.5, JHH
1H, CH Ã
/
CH3); 2.82 (dhep, 2JHP
ꢀ
/
11, 3JHH
ꢀ
/
ꢀ
ꢀ
/
ꢀ7 Hz, 3H, CH3); 1.55 (dd,
/
2
3
3
15, JHH
2
7 Hz, 3H, CH3); 2.00 (dhep, JHP
CH Ã
CH Ã
CH Ã
4.99 (dd, JHP
(m, 10H, aromatics).
/
CH3); 2.96 (dhep, JHP
ꢀ
/
11, JHH
ꢀ
ꢀ
/
3JHP
7.5, JHH
ꢀ
/
/
ꢀ
/
2
3
3
2
/
CH3); 3.48 (dhep, JHP
ꢀ
/
11, JHH
/
ꢀ
/
7 Hz, 1H, CH Ã
7 Hz, 1H, CH Ã
7 Hz, 1H, CH ÃCH3); 2.88 (dhep, JHP
7 Hz, 1H, CH Ã
/CH3); 2.12 (dhep, JHP
ꢀ
/
3
11.5, JHH
2
/
CH3); 4.60 (dd, 2JHP
ꢀ
ꢀ
/
3, 4JHP
ꢀ
/
ꢀ
/
/CH3); 2.77 (dhep, JHP
ꢀ
/
2
4
3
9.5, JHH
2
ꢀ
/
6, JHP
/
/
ꢀ
/
/
ꢀ
/
3
12.5, JHH
2
ꢀ
/
/CH3); 4.90 (d, JHP
ꢀ2.2
/
2
Hz, 1H, CH); 5.19 (d, JHP
ꢀ4.7 Hz, 1H, CH); 5.35
/
2
(ABH3P, JAB
3
10.8, JAH
4
6.9, JAP
2.2.4. Synthesis of cis-PP-ReOI(PÃ
ReOI3(PPh3)2 (0.366 g, 0.33 mmol), PÃ
1.06 mmol), NEt3 (0.109 g, 1.08 mmol) were refluxed in
20 ml of C6H5CH3 for 4 h. Concentration of the
solution in vacuo gave a green solid which dissolved in
Et2O. After elimination of (HNEt3)Cl by filtration, the
green solution was concentrated to one-half and cooled
to ꢂ20 8C until precipitation of 5 as a green micro-
crystalline compound (yield: 13%). Anal. Calc. (Found)
for C28H40IO3P2Re: C, 42.05 (44.73); H, 5.04 (5.20)%.
/
O)2 (5)
CÄ
ꢀ
/
ꢀ
/
ꢀ
ꢀ
/
2.0 Hz, 1H,
2
OCH2); 5.43 (ABH3P, JBA
3
10.8, JBH
4
6.9, JBP
/
/
O (0.25 g,
ꢀ
/
/
ꢀ
/
1
3.8 Hz, H, OCH2); 7.10Á8.10 (m, 10H, aromatics).
/
2.2.6. Synthesis of trans-PP-Re(NPh)Cl(PÃ
Re(NPh)Cl3(PPh3)2 (0.269 g, 0.30 mmol), PÃ
(0.28 g, 1.19 mmol) and NEt3 (0.124 g, 1.22 mmol) were
refluxed in 20 ml of EtOH for 4 h. The resulting green
solution was evaporated to dryness giving a green solid.
This solid was redissolved in 20 ml of ether to eliminate
(HNEt3)Cl. The resulting green solution was concen-
/
O)2 (8)
CÄ
/
/
O
/
IR (KBr, cmꢂ1): 964 (n(ReÄ
/
O)), 1543(n(CÄ
DCI/NH3 m/z (%): 818 (4) [Mꢁ
NH4]ꢁ; 801 (100) [Mꢁ
H]ꢁ; 673 (10) [Mꢂ NH4]ꢁ. 1H NMR (CDCl3,
HIꢁ
400.13 MHz; ppm): 0.96 (dd, JHP
/
CÃ
/
O)). MS
/
/
trated to one half then cooled to ꢂ20 8C for 1 day
/
/
/
giving a green microcrystalline solid. (Yield: 20%). Anal.
Calc. (Found) for C34H45ClNO2P2Re: C, 52.13 (52.36);
H, 5.75 (5.87); N, 1.79 (1.69)%. IR (KBr, cmꢂ1): 1537
3
3
ꢀ
/
16, JHH
7 Hz, 3H, CH3);
7 Hz, 3H, CH3); 1.32 (dd,
ꢀ
/
7 Hz,
3
3
3H, CH3); 1.11 (dd, JHP
3
1.19 (dd, JHP
ꢀ
ꢀ
/
17, JHH
ꢀ
/
3
16, JHH
ꢀ
/
/
(n(CÄ
H]ꢁ; 748 (7) [Mꢂ
300.13 MHz; ppm): 0.96 (dd, JHP
/
CÃ
/
O)). MS DCI/NH3 m/z (%): 784 (100) [Mꢁ
/
3
14, JHH
3
3JHP
ꢀ
/
ꢀ
/
7 Hz, 3H, CH3); 1.44 (dd, JHP
ꢀ16,
/
/
HClꢁ
H]ꢁ. 1H NMR (CDCl3,
/
3JHH
Hz, 3H, CH3); 1.62 (dd, JHP
ꢀ
/
7 Hz, 3H, CH3); 1.51 (dd, JHP
ꢀ
/
13, JHH
7 Hz, 3H,
7 Hz, 3H, CH3); 2.20
7 Hz, 1H, CH ÃCH3); 2.39
7 Hz, 1H, CH ÃCH3); 2.68 (oct,
7 Hz, 1H, CH Ã
CH3); 3.54 (dhep, 2JHP
CH3); 4.38 (d, 2JHP
5.7 Hz,
5.7 Hz, 1H, CH); 7.11Á8.15
ꢀ7
/
3
3
3
3
15.5, JHH
ꢀ
/
ꢀ
/
7
3
3
ꢀ
/
16.5, JHH
ꢀ
/
Hz, 3H, CH3); 1.18Á1.49 (m, 18H, 6 CH3); 1.60 (dd,
/
3
3
CH3); 1.64 (dd, JHP
ꢀ
/
15, JHH
12, JHH
JHH
ꢀ
/
3JHP
ꢀ
/
15.5, 3JHH
ꢀ
/
7 Hz, 3H, CH3); 2.45 (dhep, 2JHP
ꢀ
/
2
(dhep, JHP
3
ꢀ
/
ꢀ
/
/
3
2
CH3); 2.86 (dhep, JHP
11, JHH
ꢀ
/
7 Hz, 1H, CH Ã
/
ꢀ
/
10,
10,
10,
2
(oct, JHPꢀ3
/
ꢀ
/
/
3JHH
3JHH
3JHH
ꢀ
ꢀ
ꢀ
/
7 Hz, 1H, CH Ã
7 Hz, 1H, CH Ã
7 Hz, 1H, CH Ã
1.2 Hz, 1H, CH); 4.85 (dd, JHP
1.3 Hz, 1H, CH); 7.15Á7.87 (m, 15H, aromatics).
/
CH3); 3.32 (dhep, JHP
CH3); 3.68 (dhep, JHP
CH3); 4.61 (dd, JHP
ꢀ
/
2
2JHPꢀ3
12, 3JHH
/
JHH
ꢀ
/
/
ꢀ
/
2
/
/
ꢀ
/
ꢀ
/
7 Hz, 1H, CH Ã
1H, CH); 5.65 (d, JHP
/
ꢀ
/
2
/
/
ꢀ2.2,
/
2
ꢀ
/
/
4JHP
ꢀ
/
ꢀ
/
3.9, JHP
ꢀ
/
2
4
(m, 10H, aromatics).
/
2.2.5. Synthesis of cis-PP-ReO(OEt)(PÃ
/
O)2 (7)
ReO(OEt)Cl2(PPh3)2 (0.241 g, 0.29 mmol), PÃ
/
CÄ
/
O
2.2.7. Synthesis of trans-PP-Re(NPh)Cl2(PÃ
C(ÄO)Ph) (10)
Re(NPh)Cl3(PPh3)2 (0.192 g, 0.21 mmol), PÃ
(0.20 g, 0.85 mmol) and NEt3 (0.086 g, 0.86 mmol) were
refluxed in 20 ml of C6H5CH3 for 4 h. The resulting
green solution was concentrated to one-half. Addition of
/
O)(PÃ
/
(0.27 g, 1.14 mmol) and NEt3 (0.116 g, 1.15 mmol) were
refluxed in 20 ml of EtOH for 1 h. The resulting brown
solution was evaporated under reduced pressure until
precipitation of a brown solid. Filtration then dissolu-
tion of the solid in 20 ml of Et2O precipitated
(HNEt3)Cl as a white solid which was eliminated. The
remaining solution was evaporated under reduced
pressure giving a brown solid that was recrystallized
/
/
CÄ
/
O
C5H12 (20 ml) and cooling to ꢂ20 8C for 12 h produced
/
a green microcrystalline solid (yield: 30%). Anal. Calc.
(Found) for C34H46Cl2NO2P2Re: C, 49.81 (49.49); H,
5.65 (5.91); N, 1.71 (1.88). IR (KBr, cmꢂ1): 1668 (n(CÄ
from MeCN (10 ml) at ꢂ
Anal. Calc. (Found) for C30H45O4P2Re: C, 50.19
(50.77); H, 6.27 (6.15)%. IR (KBr, cmꢂ1): 956 (n(ReÄ
O)); 1534, 1550 (n(CÄCÃO)). MS DCI/NH3 m/z (%):
719 (10) [Mꢁ EtOHꢁ
H]ꢁ; 690 (100) [Mꢂ NH4]ꢁ; 673
(20) [MꢂEtOHꢁ
H]ꢁ. 1H NMR (CDCl3, 400.13 MHz;
ppm): 1.07 (dd, 3JHH 7, 3JHP
2.5 Hz, 3H, CH3); 1.11
3.5 Hz, 3H, CH3); 1.18 (dd,
/
20 8C for 1 day. (Yield: 32%.)
/
O)), 1542(n(CÄ
/
CÃ
/
O)). MS DCI/NH3 m/z (%): 820 (44)
/
[Mꢁ
/
H]ꢁ; 784 (100) [Mꢂ
400.13 MHz, ppm): 1.13 (dd, JHP
/
HClꢁ
/
H]ꢁ. 1H NMR (CDCl3,
3
3
16.5, JHH
/
/
ꢀ
/
ꢀ7 Hz,
/
3
3
/
/
/
6H, 2 CH3); 1.26 (dd, JHP
3
CH3); 1.29 (dd, JHP
ꢀ
/
16, JHH
ꢀ
/
7 Hz, 6H, 2
7 Hz, 6H, 2 CH3);
7 Hz, 6H, 2 CH3); 3.25 (oct,
1.3 Hz, 1H, CH ÃCH3); 3.29
1.3 Hz, 2H, 2 CH ÃCH3);
1.3 Hz, 1H, CH Ã
9 Hz, 2H, CH2 ÃP); 5.04 (dd,
3
/
/
ꢀ
/
14.5, JHH
ꢀ
/
ꢀ
/
ꢀ
/
1.39 (dd, 3JHP
ꢀ
/
14, 3JHH
ꢀ
/
3
3
4
7, JHP
(dd, JHH
ꢀ
/
7, JHP
ꢀ
/
2JHPꢀ3
/
JHH
ꢀ
/
ꢀ
/
/
3
3
2
4
3JHP
ꢀ
/16, JHH
ꢀ
/
7 Hz, 3H, CH3); 1.22 (dd, JHP
ꢀ
/
(oct, JHPꢀ3
/
JHH
ꢀ
/
7, JHP
ꢀ
/
/
3
14.5, JHH
3
7 Hz, 3H, CH3); 1.27 (t, JHH
2
4
ꢀ
/
ꢀ/7 Hz,
3.34 (oct, JHPꢀ3
CH3); 4.26 (d, JHP
/
JHH
ꢀ
/
7, JHP
ꢀ
/
/
3
CH3); 1.37 (dd, JHP
3
16, JHH
2
3H, OÃCH2Ã
/
/
ꢀ
/
ꢀ
/
7 Hz,
ꢀ
/
/

310
X. Couillens et al. / Inorganica Chimica Acta 343 (2003) 307Á312
/
2JHP
aromatics).
ꢀ
/
4.1, 4JHP
ꢀ
/
1.6 Hz, 1H, CH); 7.22Á/8.01 (m, 15H,
Table 1
31P{1H} NMR and IR data for the complexes 1
/
10
Á
a
Compound
31P{1H} (CDCl3)
n(ReÄO)
cmꢂ1
2
3. Results and discussion
cis-PP-ReOCl(PÃO)2 (1)
23.3 (d, JPPꢀ10 Hz)
974
969
2
37.4, (d, JPPꢀ10 Hz)
2
trans-PP-ReOCl(PÃO)2 (2) 43.1 (d, JPPꢀ194 Hz)
2
3.1. Re(V) oxo complexes
47.1 (d, JPPꢀ194 Hz)
b
2
cis-PP-ReOBr(PÃO)2 (3)
21.8 (d, JPPꢀ9 Hz)
2
37.8 (d, JPPꢀ9 Hz)
Treating ReOX3(PPh3)2 (XꢀCl, Br, I) and Re-
O(OEt)Cl2(PPh3)2 with 2 equiv. of Pr2PCH2C(ꢀO)Ph
in presence of 2 equiv. of NEt3 as base, under reflux,
produced quantitatively the diamagnetic pseudo-octahe-
/
2
i
trans-PP-ReOBr(PÃO)2 (4) 42.1 (d, JPPꢀ194 Hz)
969
964
/
2
47.2 (d, JPPꢀ194 Hz)
2
cis-PP-ReOI(PÃO)2 (5)
trans-PP-ReOI(PÃO)2 (6)
21.7 (d, JPPꢀ6 Hz)
2
37.6 (d, JPPꢀ6 Hz)
b
2
dral complexes ReOX(PÃ
XꢀOEt). Thus as expected the ligand reacts in its enol
form, as an uninegative bidentate chelate (Scheme 2).
/
O)2 (Xꢀ
/
Cl, Xꢀ
/
Br, XꢀI,
/
40.7 (d, JPPꢀ192 Hz)
2
48.2 (d, JPPꢀ192 Hz)
/
2
cis-PP-ReO(OEt)(PÃO)2 (7) 22.1 (d, JPPꢀ8.5 Hz)
956
2
30.6 (d, JPPꢀ8.5 Hz)
Analysis of the clear green solutions obtained after
refluxing for 4 h the mixture of reactants containing
2
trans-PP-Re(NPh)-
Cl(PÃO)2 (8)
trans-PP-Re(NPh)Cl2-
33.5 (d, JPPꢀ213 Hz)
2
39.4 (d, JPPꢀ213 Hz)
Cl, Br, I) in toluene by 31P NMR
2
ReOX3(PPh3)2 (Xꢀ
/
ꢂ6.7 (d, JPPꢀ253 Hz)
b
2
(PPh3)(PÃO) (9)
trans-PP-Re(NPh)Cl2-
33.8 (d, JPPꢀ253 Hz)
showed the singlet at about ꢂ
two AX and AB spin systems with JPP coupling
constants characteristic of the ‘twisted’ cis-PP and
/
5 ppm of free PPh3 and
2
2
11.9 (dd, JPPꢀ234 Hz)
31.9 (dd, JPPꢀ234 Hz)
2
(PÃCÄO)(PÃO) (10)
a
trans-PP pseudo octahedral complexes ReOX(PÃ
(Table 1, Scheme 3).
The trans-PP/cis-PP ratio increased from 1/1 when
XꢀCl to 5/1 when XꢀI that is with the size of the
halide and no variation was observed with time. When
the same reaction was performed with the analog but
less hindered 1-phenyl-2-(diphenylphosphino)ketone
/
O)2
In CDCl3.
Only observed in solution.
b
/
/
before, this probably results from the increased steric
hindrance of Br and I and illustrates the competition
between Xꢂ and EtOꢂ for the sixth site of the
i
octahedron which is the equatorial one. With Pr2PÃ
/
O,
Ph2PCH2(CÄ
/
O)Ph, only the cis-PP isomer was obtained
the chloro complex is favored, which is the thermo-
dynamic product and is also obtained by using ReO-
Cl2(OEt)(PPh3)2 as the rhenium precursor. In this case,
monitoring by 31P NMR the reaction of a fourfold
excess of ligand in ethanol on ReO(OEt)Cl2(PPh3)2
showed, after 1 h, a 3/1 mixture of the ethoxo and
chloro derivatives. Heating 3 h more produced the total
whatever the solvent was [12]. This is probably due to
steric effects as was observed in square planar complexes
of the type MX2(PR3)2 (Xꢀ
/
halides and PR3ꢀtertiary
/
phosphine) where the trans/cis ratio was favored by
bulkier L and iodine over chloride [19]. However, it is
likely that electronic effects resulting from differences in
ionic radii, polarizabilities, p-donor availability and
trans-influence of iodine compared to chlorine are
significant factors but their relative importance remains
a subject to be more investigated. However, the stability
gap between the two isomers is small. Presence of the
trans isomer in toluene is not surprising since it is well
known that non polar solvent favors trans-isomerisation
while increasing solvent polarity favors cis form [20].
This is consistent with the presence of the cis-PP isomer
as the unique species when the reactions were performed
disappearance of ReO(OEt)(PÃ
of ReOCl(PÃO)2 as unique species. This is opposite to
our precedent results on the diphenylphosphinoenolato
complexes where the ethoxo derivative was the thermo-
dynamic species and, thus, emphasis the importance of
/
O)2 and the formation
/
the balance between electronic and steric effects. The
i
fact that, in ethanol, Pr2PÃ
/
O favors the chloro species
while Ph2PÃ
/O stabilizes the ethoxo one indicates that
here the electronic effect (basicity of the phosphine) is
the main factor and influences the trans coordination
(Cl is less nucleophilic than OEt).
in ethanol. When Xꢀ
cis-PP-ReOCl(PÃO)2 (1) while only cis-PP-Re-
O(OEt)(PÃO)2 (7) was obtained when XꢀBr or I. As
/Cl, the complex was identified as
/
cis-PP-ReOCl(PÃ
/
O)2 (1) and trans-PP-ReOCl(PÃ
/
O)2
/
/
(2) have been successfully isolated from toluene due to
their differences in solubility after elimination of
(HNEt3)Cl and concentration of the solution. Com-
pound 1 was precipitated first at room temperature on
addition of pentane. Compound 2 was obtained further
by adding diethylether to the precedent filtrate. Im-
provements of the syntheses have been performed as
Scheme 2.

X. Couillens et al. / Inorganica Chimica Acta 343 (2003) 307Á
/312
311
Scheme 3.
described in Section 2. Only the trans-PP-ReOBr(PÃ
/
O)2
the equatorial plane of the molecule in trans position to
a phosphorus atom (dPꢀ30.6 ppm).
/
(4) and cis-PP-ReOI(PÃ
/
O)2 (5) have been successfully
isolated as green solids. The other complexes have only
been characterized in solution by 31P{1H} NMR (Table
3.2. Re(V) imido complexes
1). ReO(OEt)(PÃ
/
O)2 was isolated when the reaction was
ruled out in ethanol. All the complexes are fairly stable
in the solid state but may be stored under controlled
atmosphere to prevent phosphine oxidation. Their
elemental analyses confirm their proposed formula.
Their stability is confirmed by their DCI/NH3 mass
The reaction of 1-phenyl-2-(diisopropylphosphi-
no)ethanone with Re(NPh)Cl3(PPh3)2 followed a similar
pattern but the reaction was not stoichiometric and led
to more species than were observed with Re-oxo
compounds.
H]ꢁ cation as the
Monitoring by 31P NMR, in refluxing toluene for 4 h,
the reaction of Re(NPh)Cl3(PPh3)2 with a twofold molar
amount of ligand without base showed formation of two
spectra which always show the [Mꢁ
major species. Their spectrochemical features are as
expected. The ReÄO stretches lie in the narrow range of
956Á
974 cmꢂ1 indicative of strong Re-oxo multiple
/
/
/
monosubstituted complexes: Re(NPh)Cl2(PPh3)(PÃ
/
O)
bond. The lowest value of 956 cmꢂ1 observed in 7
results from the increased basicity of the ethoxo ligand
compared to Cl (974 cmꢂ1 in 1).
(9) as the major species and Re(NPh)Cl2(PÃCÄO)(PÃ
/
/
/
O) (10) as the minor one indicating monosubstitution
plus phosphine exchange in the second case (Scheme 4).
Increasing the L/Re ratio to 4/1 gave (10) as the
unique species. Addition of NEt3 induced deprotonation
of the ligand, but the process was not complete and a
All the complexes show the doublet of doublet
characteristic of an AX or AB pattern in their 31P{1H}
NMR spectra (Table 1), consistent with two magneti-
cally inequivalent phosphorus atoms and thus indicating
for the complexes the cis-PP configuration A or the
trans-PP configuration (B), depending on the coupling
constants values (Scheme 1). The fact that the cis
configuration is observed confirms that the electronic
effect (basicity) of the ligand is more important than its
steric hindrance. As already observed, the largest down-
field shift is obtained with the equatorial phosphorus
atom, which makes the strongest bond with the rhenium
center.
mixture of (10) and Re(NPh)Cl(PÃ
was present. (10) was isolated by addition of pentane.
However, obtainment of Re(NPh)Cl(PÃO)2 (8) as the
/O)2 (8) in a 3/1 ratio
/
unique species was possible in refluxing ethanol, by
using 4 equiv. of ligand for 4 h. Surprisingly, no ethoxo
complex formation was observed as was the case for
Ph2PCH2(CÄ
/
O)Ph where it was the only complex
isolated [12]. This probably could be attributed to the
difference in the basicity of the two ligands.
Both complexes (8) and (10) have been isolated. They
present a trans-PP configuration as indicated by their
31P NMR spectra which show AB pattern with large JPP
values (Table 1). Their elemental analyses and NMR
spectra are as expected. The differences observed in their
The proton spectra present no unexpected feature, the
signals of the four iPr substituents being located between
1 and 1.5 ppm (CH3), 2 and 3.5 ppm (CH) and those of
the Ph substituent in the 7Á9 ppm range. Two typical
/
1
IR spectra (solid state) and H NMR (solution) agree
with their formulation as a bisubstituted complex (8)
doublets in the 5 ppm range are characteristic of the two
protons of the inequivalent enolato groups. In the trans-
complexes they appear as doublet of doublet due to their
coupling with the trans-phosphorus atom. In 7 each of
the two stereotopic AB protons of the methylene group
of the ethanolato ligand exhibits an ABH3P type
spectrum as expected from the location of OEtꢂ in
with two chelating anionic PÃ
stituted complex (10) with chelating PÃ
tate PÃC(ÄO) ligands respectively. The IR spectrum of 8
shows only a broad band at 1537 cmꢂ1 characteristic of
the n(CÄCÃO) vibration of the enolic ligands while in
10, the enolato group presents its n(CÄCÃO) at 1542
/
O ligands and a bisub-
/O and moden-
/
/
/
/
/
/

312
X. Couillens et al. / Inorganica Chimica Acta 343 (2003) 307Á312
/
Scheme 4.
cmꢂ1 while the n(CÄ
/
O) of the keto group vibrates at
1668 cmꢂ1 (1672 cmꢂ1 in the free ligand). Similar
4. Supplementary material
1
differences are also observed in the H NMR spectra.
The material is available from the authors on re-
The ethylenic protons of the two enolato chelates are
present as doublet of doublet at 4.61 and 4.85 ppm
because of the coupling with the nearby and trans
phosphorus atoms. A similar patter is observed for the
enolato proton in 10, which shows the doublet of
doublet of the ethylenic proton at 5.04 ppm while the
2 equiv. methylene protons of the phosphinoketone
resonate at 4.26 ppm as a doublet because of their
coupling with the nearby phosphorus atom.
The imido Re complexes present a trans-PP twisted
octahedral structure which is the conformation the most
currently observed with this rhenium core thus indicat-
ing that the presence of the phenyl imido susbtituent
decreases significantly space in the rhenium coordina-
tion sphere.
In conclusion, new rhenium-oxo and -phenylimido
complexes have been synthetized and isolated when 1-
phenyl-2-(diisopropylphosphino)ethanone was used as
ligand. The rhenium-oxo complexes are mainly cis-PP
derivatives. The trans-PP stereoisomers were only ob-
served in toluene as mixture of cis/trans species. In
ethanol, only cis-PP isomers were obtained, cis-PP-
quest.
References
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ReOCl(PÃ
O)2 when Xꢀ
1-phenyl-2-(diphenylphosphino)ethanone
emphasis in this case the importance of the phosphine
basicity. This is different to the results obtained with
phosphinophenols where the phosphine steric hindrance
was the major factor. The reaction of 1-phenyl-2-
(diisopropylphosphino)ethanone with the rhenium imi-
/
O)2 when Xꢀ
Br, I, OEt. Comparison with the related
complexes
/
Cl and cis-PP-ReO(OEt)(PÃ
/
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topoulou, A. Terzis, E. Chiotellis, Inorg. Chem. 38 (1999)
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/
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do precursor afforded the trans-PP-Re(NPh)Cl(PÃ
/O)2
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as the unique species in ethanol while in toluene the
reaction depends on the experimental conditions. As
observed in all the complexes with phosphinophenolato
and phosphinoenolato ligands, presence of the imido
core favors the formation of the trans PP isomer. Thus,
it may be concluded that 1-phenyl-2-(diisopropylphos-
phino)ethanone in basic ethanol is a good ligand for the
synthesis of rhenium(V) complexes.
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¨
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