Neutral trichlorooxorhenium(V) complexes containing new heterofunctionalized phosphane ligands of the type PN2 and PNO

Article abstract of DOI:10.1002/1099-0682(200007)2000:7<1523::AID-EJIC1523>3.0.CO;2-2

The new heterofunctionalized phosphane [(1R,2R)-N-(2-aminocyclohexyl)]- 2-(diphenylphosphanyl)benzamide (L¹), N(2-aminoethyl)-2- (diphenylphosphanyl)benzamide (L²) and 2-(diphenylphosphanyl)-N-(2- hydroxyethyl)benzamide (L³) were synthesized by reaction of N-[2- (diphenylphosphanyl)benzoyloxy]succinimide (3) in dichloromethane with (1R,2R)(-)-diaminocyclohexane, ethylenediamine and ethanolamine, respectively. Reactions of [Re(O)Cl₄]^- with L¹, L² and L³, at a 1:1 metal/ligand molar ratio gave neutral trichlorooxorhenium(V) complexes of the type [Re(O)Cl₃[κ²-L}] [L = L¹ (4), L² (5), L³ (6)]. The characterization of the compounds involved IR, ¹H- and ³¹P-NMR spectroscopy, and X-ray crystallographic analysis for L¹, 5 and 6. The Re atom: is six-coordinate in complexes 4-6, with an oxo ligand, three chloride ligands and a neutral bidentate heterofunctionalized phosphane ligand.

Full text of DOI:10.1002/1099-0682(200007)2000:7<1523::AID-EJIC1523>3.0.CO;2-2

FULL PAPER
Neutral Trichlorooxorhenium(V) Complexes Containing New
Heterofunctionalized Phosphane Ligands of the Type PN2 and PNO
[a]
[a]
[a]
ˆ
˜
Joao D. G. Correia, Angela Domingos, and Isabel Santos*
Keywords: Rhenium / P ligands / Chelates / Radiopharmaceuticals
The new heterofunctionalized phosphane [(1R,2R)-N-(2-ami-
and L3, at a 1:1 metal/ligand molar ratio gave neutral trichlo-
nocyclohexyl)]-2-(diphenylphosphanyl)benzamide (L1), N- rooxorhenium(V) complexes of the type [Re(O)Cl3{κ2-L}] [L =
(2-aminoethyl)-2-(diphenylphosphanyl)benzamide (L2) and
2-(diphenylphosphanyl)-N-(2-hydroxyethyl)benzamide (L3)
were synthesized by reaction of N-[2-(diphenylphosphanyl)-
benzoyloxy]succinimide (3) in dichloromethane with (1R,2R)-
L1 (4), L2 (5), L3 (6)]. The characterization of the compounds
1
involved IR, H- and 31P-NMR spectroscopy, and X-ray crys-
tallographic analysis for L1, 5 and 6. The Re atom is six-
coordinate in complexes 4−6, with an oxo ligand, three
(−)-diaminocyclohexane,
ethylenediamine
and
eth- chloride ligands and a neutral bidentate heterofunctionalized
anolamine, respectively. Reactions of [Re(O)Cl4]− with L1, L2
phosphane ligand.
Introduction
adducts where the ligands coordinate to the metal centre in
a bidentate and neutral fashion.
The continuous demand for more sensitive and specific
probes for targeting diseased organs or physiological func-
tions in Nuclear Medicine, both in the diagnostic or thera-
peutic field, has led to an increasing interest in the develop-
ment of receptor-binding radiopharmaceuticals.[1] Due to
its physico-chemical properties and widespread availability,
99mTc is still the most used radionuclide for diagnosis, and
both 186Re and 188Re appear as interesting radionuclides for
the development of radiopharmaceuticals with therapeutic
potential.[2] For the metal centre in the oxidation state (V)
and an [MϭO]3ϩ core, the use of a bifunctional tetradent-
ate or a tridentate ligand, and a bifunctional unidentate col-
igand ([3ϩ1] approach) are among the most popular strat-
egies for the design and preparation of new, more specific
radiopharmaceuticals.[3] Due to its σ-donor and π-acceptor
properties, phosphanes are known to stabilize complexes of
rhenium and technetium with the metal centre in different
oxidation states.[4,5] A number of heterofunctionalized pho-
sphane-containing ligands have previously been described
and used to stabilize the core [MϭO]3ϩ (M ϭ Re, Tc).[6Ϫ8]
Results and Discussion
Synthesis and Characterization of the Ligands
The heterofunctionalized phosphane ligands L1, L2 and
L3 were synthesized as depicted in Scheme 1. The activation
of 2-(diphenylphosphanyl)benzoic acid with N-hydroxysuc-
cinimide was achieved in good yield (94%) by a slight modi-
fication of a reported method.[11] Reaction of N-[2-(di-
phenylphosphanyl)benzoyloxy]succinimide (3) in CH2Cl2 at
room temperature with (1R,2R)-(Ϫ)-diaminocyclohexane,
ethylenediamine and ethanolamine afforded, after appropri-
ate workup, L1 (89%), L2 (74%) and L3 (87%), respectively.
However, they are all either bidentate, with PN, PO or PS
[6Ϫ8]
donor sets
or tetradentate.[9] We have synthesized new
tridentate PNO- and PN2-type ligands, with potential tri-
dentate character, with the aim of designing new radiophar-
maceuticals using the [3ϩ1] approach. Surprisingly, we ob-
served that, depending on the reaction conditions, these li-
gands are very versatile in terms of coordination mode and
charge. Indeed, they can act as neutral, mono- or dianionic
bi/tridentate chelates.[10] In this paper we report on the syn-
thesis and characterization of the new heterofunctionalized
phosphane ligands as well as on the preparation of ReV
[a]
´
Departamento de Quımica, ITN,
Scheme 1. Synthesis of the Ligands L1, L2, and L3; R ϭ N-succini-
mido; (i) dichloromethane, room temperature
´
Estrada Nacional 10, 2686-953 Sacavem Codex, Portugal
E-mail: isantos@itn1.itn.pt
Eur. J. Inorg. Chem. 2000, 1523Ϫ1529
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0707Ϫ1523 $ 17.50ϩ.50/0
1523

J. D. G. Correia, A. Domingos, I. Santos
FULL PAPER
The IR spectra of L1 and L2 exhibit ν(NH2) stretching
bands at 3220 cmϪ1 and 3320 cmϪ1, respectively, and for L3
the IR spectrum shows a strong band at 3310 cmϪ1 which is
assigned to ν(OH). In all the spectra a strong band appears
1
at 1630 cmϪ1 due to ν(CϭO). In the H-NMR spectra of
L1 a doublet appears at δ ϭ 5.71 due to the NH of the
amide group. For L2 and L3 the signals of these groups
appear as broad singlets at δ ϭ 6.23 and 6.27, respectively.
Unlike L1, where a multiplet at δ ϭ 1.89, assigned to
1
the protons of the amine group, is observed, the H-NMR
spectrum of L2 does not present any signal for this group.
For L3, no resonance signal is observed for the hydroxy
group. The 31P-NMR spectra of L1, L2, and L3 show only
one peak at δ ϭ Ϫ10.5, Ϫ9.3 and Ϫ9.9, respectively. L3
decomposed slightly in solution on standing, leading to the
corresponding phosphane oxide, as indicated by the new
31P-NMR signal which appears at δ ϭ 36.6.[12]
Single colorless crystals of L1, suitable for X-ray diffrac-
tion analysis, were obtained from a mixture of dichlorome-
thane/hexane. L1 crystallizes in the monoclinic acentric
space group P21 with three crystallographically independ-
ent molecules in the asymmetric unit. The three independ-
ent molecules are labelled similarly, being distinguished by
the first digit of the atom label.
Scheme 2. Synthesis of the complexes 4Ϫ6; (i) MeOH, room tem-
perature; (ii) dichloromethane, room temperature
Synthesis and Characterization of the Complexes
Reactions of L1, L2 and L3 with [nBu4N][Re(O)Cl4] (1)
in methanol, at a 1:1 molar ratio, at room temperature, af-
forded the new unusual neutral trichlorooxorhenium(V)
complexes 4Ϫ6 (Scheme 2). To the best of our knowledge,
several compounds containing the ‘‘Re(O)Cl3’’ moiety are
known. However, this unit is stabilized either by diphos-
phanes or by neutral monodentate ligands.[14]Ϫ[16] When a
heterofunctionalized phosphane ligand such as (2-hydroxy-
phenyl)diphenylphosphane (PO) is used, deprotonation oc-
curs with formation of the monoanionic complex
[Re(O)Cl3(PO)]Ϫ.[7c] Phosphane-containing peptides (PN2O
donor set) were studied, and deprotonation was also ob-
served. In this case, the ligands coordinate in a dianionic
and tetradentate fashion.[9b] Thus, the neutral behavior of
our ligands and the observed coordination mode are not
very common, probably as a result of the influence of the
type of substituents attached to the amide nitrogen atom.
Complex 6 was also obtained by stoichiometric reaction
Figure 1. ORTEP drawing of ligand L1 with the atom numbering
scheme; thermal ellipsoids are drawn at the 30% probability level;
˚
selected mean bond lengths [A] and angles [°]: C(1)ϪO(1) 1.231(8),
N(1)ϪC(1) 1.329(9), N(1)ϪC(10) 1.448(9), C(11)ϪN(11) 1.449(11),
C(1)ϪC(101) 1.498(10), P(1)ϪC(100) 1.848(8), P(1)ϪC(110)
1.838(9), P(1)ϪC(120) 1.837(8), av. (CϪC)cyclohex 1.51(1), av.
(CϪC)Phenyl 1.37(2); N(1)ϪC(1)ϪO(1) 123.3(7), O(1)ϪC(1)Ϫ
C(101) 120.7(7), N(1)ϪC(1)ϪC(101) 116.1(7), C(10)ϪN(1)ϪC(1)
124.5(6)
Figure 1 shows an ORTEP view of one molecule with the
atom numbering scheme as well as selected bond lengths of L3 with [Re(O)Cl3(PPh3)2] (2) in CH2Cl2. After evapora-
and angles. Within two standard deviations the three molec- tion of the solvent, complexes 4 and 5 were obtained as
ules can be considered chemically equivalent, presenting light blue and pale green solids, respectively. Complex 6,
similar molecular dimensions. The packing of the molecules unlike 4 and 5, precipitated from its reaction mixture and,
forms a network of hydrogen bonds involving the amide upon appropriate workup, was obtained as a dark green
NϪH group and the carbonyl oxygen atoms. The shortest solid in an almost quantitative yield. Complexes 4Ϫ6 are
˚
intermolecular distances are 2.887 A for O(1) and N(2Ј) (x, stable towards air and moisture and almost insoluble in
˚
y, Ϫ1 ϩ z), 2.862 A for O(2) and N(3Ј) (1 Ϫ x, Ϫ0.5 ϩ y, most organic solvents and water. Complexes 5 and 6 are
˚
1 Ϫ z) and 2.858 A for O(3) and N(1Ј) (2Ϫx, y ϩ 0.5, moderately soluble in acetonitrile, whereas 4 is insoluble in
˚
Ϫz) (the average N O contact distance is 2.929 A for the this solvent. Complex 4 is moderately soluble in tetrahy-
hydrogen bonds ‘‘CϭO HϪN’’).[13] The cyclohexane ring drofuran and dimethyl sulfoxide but tends to decompose in
shows the usual chain conformation.
these solvents. The characterization of 4Ϫ6 has been done
1524
Eur. J. Inorg. Chem. 2000, 1523Ϫ1529

Trichlorooxorhenium(V) Complexes Containing New Phosphane Ligands
FULL PAPER
1
by elemental analysis, IR, H- and 31P-NMR spectroscopy,
As mentioned above, complex 4 decomposed in
and by X-ray crystallographic analysis in the case of 5 and (CD3)2SO yielding partially the oxidised form of the ligand.
1
6.
However, in the phenyl and amide region of the H-NMR
The IR spectra of complexes 4؊6 exhibit ReϭO stretch- spectrum, we could easily identify some resonance signals
ing vibrations at 1000 cmϪ1. These values are in the normal that correspond to the remaining adduct 4. In fact, we ob-
range as those found for monooxorhenium complexes serve signals at δ ϭ 11.16 (1 H, d, NH), 8.71 (1 H, t, aro-
(945Ϫ1067 cmϪ1).[17] The CϭO stretching vibration of the matic), 8.11 (1 H, s, br., aromatic) and 7.19 (1 H, m, aro-
carbonyl group appears at 1570, 1590 and 1590 cmϪ1 for 4, matic). The pattern, the chemical shifts and type of splitting
5 and 6, respectively. These values are lower in energy (by compare very well with what is observed in the spectrum of
ca. 40Ϫ60 cmϪ1) relative to the corresponding free ligands, complex 5, in the same solvent. The region of the cyclo-
confirming the coordination of the carbonyl group to the hexyl protons is quite complicated and the assignment of
metal centre. In addition, all the complexes display IR ab- the resonance signals of 4 is not possible.
sorptions typical of ν(ReϪCl) at 320 cmϪ1 and at 315 cmϪ1
;
Crystal Structures of Complexes 5 and 6
and absorptions of coordinated phosphane ligands, in par-
ticular two strong absorption bands at 750 cmϪ1 and at 697
The X-ray crystallographic analysis on a poor-quality
crystal of 5 did not provide an adequate data set for an
accurate determination of the structure of this complex. It
was not possible to refine the structure with acceptable R
values (R1 ϭ 0.0925, wR2 ϭ 0.1946) and with sufficient
accuracy. However, it was possible to unambiguously define
the connectivities of the atoms around the Re atom (Fig-
ure 2), and to confirm that the molecular structure of com-
plex 5 is analogous to that of 6.
cmϪ1
, associated with CϪH and CϪC out-of-plane
bending vibrations in monosubstituted benzene rings.[18]
Due to the low solubility of all complexes their NMR
spectra were run either in CD3CN or in (CD3)2SO. The 31P-
NMR spectra of 5 and 6 in CD3CN show only one reson-
ance signal, which appears at δ ϭ Ϫ15.4 and Ϫ16.5, re-
spectively. These resonance signals are shifted slightly up-
field in (CD3)2SO, and appear at δ ϭ Ϫ18.1 for both com-
plexes. When compared with those of the free ligands, the
resonance signals found for 5 and 6 are shifted upfield (ca.
6 ppm). For complex 4, it was only possible to run the 31P-
NMR spectrum in (CD3)2SO and, in this solvent, the initial
blue solution turned green within seconds. Two resonance
signals are observed in the spectrum at δ ϭ Ϫ17.2 and 32.9.
The resonance signal at δ ϭ Ϫ17.2 compares well with the
value of δ ϭ Ϫ18.1 found for complexes 5 and 6 in the
same solvent, and led us to assign the signal to adduct 4.
An upfield shift (about 7.6 ppm) relative to the resonance
signal of the free ligand [Ϫ9.6 ppm in (CD3)2SO], is ob-
served for the resonance signal of 4. This also compares
well with the shift found for complexes 5 and 6. The reson-
ance at δ ϭ 32.9 is assigned to the phosphane oxide of the
ligand.[12] This result confirms that (CH3)2SO is able to ox-
idise aromatic tertiary phosphanes coordinated to oxoRe
complexes by oxygen transfer, as previously reported.[19] In
order to confirm the presence of phosphane oxide signals in
this region of the spectrum, L1 was oxidized with hydrogen
peroxide in a parallel experiment. The 31P-NMR spectrum
of the resulting product in (CD3)2SO reveals only one res-
Figure 2. ORTEP drawing of complex 5 with the atom numbering
scheme; thermal ellipsoids are drawn at the 30% probability level
Compound 5 crystallized from boiling acetonitrile as
¯
onance signal at δ ϭ 32.0.
dark green crystals in the triclinic space group P1 with cell
1
˚
˚
The H-NMR spectra of 5 and 6 present three sets of parameters a ϭ 9.840(2) A, b ϭ 12.000(3) A, c ϭ 13.604(3)
˚
multiplets assigned to the protons of the aromatic rings. A, α ϭ 66.12(2)°, β ϭ86.01(2)°, γ ϭ 68.30(1)°, V ϭ
Two of the multiplets integrate for one proton each and the 1358.7(5) A , Z ϭ 2, Dc ϭ 1.788 gcmϪ3. Besides a disor-
3
˚
third for twelve protons. The chemical shifts are comparable dered acetonitrile molecule of solvent in the lattice, a resid-
Ϫ3
˚
in both complexes and the protons are slightly deshielded ual peak of electron density of the order of 18 eA was
with respect to those of the free L2 and L3. The remaining found which refined properly as a chloride ion. The chloride
signals observed in the spectra are due to the amide and to ion is hydrogen-bonded to the two nitrogen atoms of the
˚
the ethylene protons of the coordinated heterofunctional- molecule: to the amide N(1) atom [N(1) Cl(4) 3.073 A] and
˚
ized phosphane ligands. In both complexes the amide pro- to the amine N(2) atom [N(2) Cl(4) 3.273 A]. The molecu-
ton signal is significantly shifted downfield relative to those lar structure of 6 as well as selected bond lengths and angles
of the free ligands and this is certainly due to the more are shown in Figure 3.
acidic character of this proton after the coordination of L2
and L3 to the rhenium atom through the carbonyl group.
The overall geometry around the six-coordinate rhenium
atom is described as an highly distorted octahedron, as can
Eur. J. Inorg. Chem. 2000, 1523Ϫ1529
1525

J. D. G. Correia, A. Domingos, I. Santos
FULL PAPER
˚
[av. 2.494(3) A] and in [Re(O)(PN)2Cl] [av. 2.450(5)
[7c,6b,15]
˚
A].
˚
The ReϪCl bond length [av. ReϪCl, 2.366(5) A] com-
pares well with that found in [Re(O)Cl3(PO)]Ϫ [av. 2.380(3)
V
˚
A], but is shorter than in the Re complex containing two
[6b,7c]
˚
PN phosphane ligands [Re(O)(PN)2Cl] [2.422(6) A].
The shorter ReϪP and ReϪCl bond lengths in complex
6, relative to the corresponding bond lengths in the com-
plexes mentioned above, are most likely due to steric fac-
tors, chelating mode of the ligands and nature of the atoms
involved in the coordination with the rhenium centre. The
trans-ReϪO(2) (oxygen atom of the carbonyl group of the
˚
ligand) distance [2.133(10)A] compares well with the value
˚
found in [Re(O)Cl3(PPh3)(DMF)] [2.133(4)A] for the bond
between the oxygen atom of DMF and the metal centre.[16a]
This bond length is considerably longer than that between
the amide oxygen atom of MAG1 (mercaptoacetyl glycine)
and the rhenium atom in the complex [Re(O)(MAG1Et)2]
Figure 3. ORTEP drawing of complex 6 with the atom numbering
[2.051(5)A].[16b] This difference is probably due to the differ-
˚
scheme; thermal ellipsoids are drawn at the 30% probability level;
˚
selected mean bond lengths [A] and angles [°]: ReϪO(1) 1.659(10),
ent nature of the donor atoms of the ligands involved in the
ReϪCl(3) 2.355(4), ReϪP 2.425(5), C(2)ϪO(2) 1.26(2), N(1)ϪC(2) coordination sphere of the metal centre.
ReϪO(2) 2.133(10), ReϪCl(1) 2.367(5), ReϪCl(2) 2.377(4),
1.28(2), N(1)ϪC(1) 1.46(2), av. PϪC 1.82(2); O(1)ϪReϪO(2)
The severe problem of disorder in the terminal
167.2(5), O(1)ϪReϪCl(1) 97.6(4), O(1)ϪReϪCl(2) 107.5(4),
O(1)ϪReϪCl(3) 95.5(4), O(1)ϪReϪP 93.1(4), Cl(1)ϪReϪCl(3)
166.1(2), Cl(2)ϪReϪCl(3) 85.9(2), Cl(1)ϪReϪP 89.0(2),
Cl(2)ϪReϪP 159.3(2), O(2)ϪReϪCl(1) 85.3(4), Cl(3)ϪReϪP
94.9(2), ReϪO(2)ϪC(2) 141.0(13), O(2)ϪC(2)ϪN(1) 121(2),
O(2)ϪReϪP 74.5(3), C(2)ϪN(1)ϪC(1) 124.1(14), N(1)ϪC(2)Ϫ
C(111) 118(2)
C(3)ϪO(3)H atoms prevents any discussion or comparison
of bond lengths within the group, as can be seen by the
large standard deviations. Nevertheless, we can say that
there is no short intermolecular interaction involving the
O(3) atom. An intermolecular interaction involving
˚
Cl(2) N(1) atoms (distance of 3.272 A) is observed in the
be seen by the bond angles around the Re atom. With the packing of the molecules in the crystalline state.
axial direction being defined along the ReϭO bond, three
equatorial positions are occupied by the chloride ions,
whereas the fourth equatorial position is occupied by the
phosphorous atom of the ligand. The equatorial plane devi-
ates from planarity (atomic deviations from Ϫ0.091 to
0.087 A), and the Re atom is displaced 0.34 A towards the have been synthesised and fully characterized. No depro-
multiply bonded oxygen. The bidentate chelate forms a tonation of these ligands occurs under mild conditions
non-planar six-membered ring through the phosphorus and when they react with [nBu4N][Re(O)Cl4]. The new com-
the carbonyl oxygen atoms bonded to the metal centre. The plexes formed are the neutral trichlorooxorhenium(V) ad-
oxygen atom of the carbonyl group coordinates to the axial ducts [Re(O)Cl3{κ2-L}], which are rare examples of oxo
Concluding Remarks
New tridentate heterofunctionalized phosphane ligands
˚
˚
position trans to ReϭO [O(1)ϪReϪO(2), 167.2(5)°].
complexes stabilized by neutral heterofunctionalized phos-
As far as we are aware, this is the first structural charac- phane ligands. The rhenium atom is six-coordinate in an
terization of an ReV neutral adduct complex of the type octahedral configuration with the oxo function trans to the
[Re(O)Cl3(κ2-L)]. For comparison, we have complexes with oxygen atom of the carbonyl group and with the phosphor-
neutral monodentate ligands or with monoanionic bident- ous atom in the equatorial position.
˚
ate ligands. The ReϪO(1) bond length [1.659(10) A] in 6
compares well with the values found in [Re(O)Cl3-
[15]
˚
(Ph3PO)(PPh3)]
[1.669(4)A],
[Re(O)Cl3(PPh3)-
Experimental Section
[16]
˚
(DMF)] [1.664(4) A], and in the anionic monooxorheni-
um(V) compound [Re(O)Cl3(PO)]Ϫ [1.669(6) A; PO ϭ (2-
˚
General Procedures: All chemicals were of reagent grade. Ethylene-
diamine and ethanolamine were purchased from Aldrich and dis-
tilled prior to use. (1R,2R)-(Ϫ)-diaminocyclohexane was purchased
from Aldrich and was used as received. The reactions were per-
formed in air unless otherwise indicated. 2-(Diphenylphosphanyl)-
benzoic acid and the complexes [nBu4N][Re(O)Cl4] (1) and [Re-
(O)Cl3(PPh3)2] (2) were prepared as reported in the literature.[20Ϫ22]
1H- and 31P-NMR spectra were recorded with a Varian Unity 300-
MHz spectrometer; 1H chemical shifts were referenced with the re-
sidual solvent resonance relative to tetramethylsilane and the 31P
hydroxyphenyl)diphenylphosphane].[7c] This distance in 6 is
slightly shorter than the corresponding values 1.692(7) and
1.69(1) A found in [Re(O)(PN)2(OEt)] and in the ortho-
˚
rhombic form of [Re(O)(PN)2Cl] [PN ϭ (2-aminophenyl)di-
phenylphosphane], respectively.[6b]
˚
The ReϪP bond length [2.425(5) A] compared well with
the value found in the anionic monooxorhenium(V) com-
pound [Re(O)Cl3(PO)]Ϫ [2.422(2) A] but is shorter than in
˚
˚
[Re(O)Cl3(Ph3PO)(PPh3)] [2.506(2) A], [Re(O)(PN)2(OEt)] chemical shifts were measured with an external H3PO4 solution
1526
Eur. J. Inorg. Chem. 2000, 1523Ϫ1529

Trichlorooxorhenium(V) Complexes Containing New Phosphane Ligands
(85%) as a reference. Chemical shifts are given in ppm. The NMR 2-(Diphenylphosphanyl)-N-(2-hydroxyethyl)benzamide (L3): N-[2-
FULL PAPER
samples were prepared in CDCl3, CD3CN or (CD3)2SO. Infrared
spectra were recorded in the range 4000Ϫ200 cmϪ1 with a
PerkinϪElmer 577 spectrometer using KBr pellets. Elemental ana-
lyses were performed with a PerkinϪElmer automatic analyser.
(Diphenylphosphanyl)benzoyloxy]succinimide (3.30 g, 8.20 mmol),
dissolved in dichloromethane (20 mL), was added dropwise to a
solution of ethanolamine (1.08 mL, 19.60 mmol) in the same solv-
ent (45 mL). After 3 h (TLC: ethyl acetate/hexane, 50:50 ), the
white solid, which precipitated, was eliminated by filtration through
a pad of Celite and the filtrate was concentrated to dryness. The
resulting yellowish viscous oil afforded a white solid after drying
for several hours under vacuum. The compound was washed with
water and recovered by filtration. After drying, L3 was obtained in
N-[2-(Diphenylphosphanyl)benzoyloxy]succinimide (3): 2-(Diphenyl-
phosphanyl)benzoic acid (1.00 g, 3.27 mmol) and N-hydroxysuccin-
imide (0.75 g, 6.54 mmol) were dissolved in dichloromethane
(20 mL) at room temperature, and a solution of dicyclohexylcar-
bodiimide (1.35 g, 6.54 mmol) in dichloromethane was added drop-
wise. The reaction was complete after 3 h (TLC: ethyl acetate/hex-
ane, 50:50 ). The formed urea was separated by filtration through
a pad of Celite wetted with dichloromethane, and the filtrate con-
centrated to dryness. The resulting white residue was chromato-
graphed on an appropriate column of silica gel with 20Ϫ35% ethyl
acetate/hexane (gradient), to afford a white yellowish solid, which
was further recrystallized from dichloromethane/hexane to give 3
in an analytical pure form. Yield 1.24 g (94%). Ϫ 1H NMR
(CDCl3): δ ϭ 2.81 (4 H, s, CH2), 6.99 (1 H, m aromatic), 7.19Ϫ7.32
(9 H, m, aromatic), 7.45 (3 H, m, aromatic), 8.31 (1 H, m, aro-
matic). Ϫ 31P NMR(CDCl3): δ ϭ Ϫ4.4. Ϫ IR (KBr): ν˜ ϭ 1760
cmϪ1 (vs, CϭO). Ϫ C23H18NO4P 0.5CH2Cl2 (445.8): calcd. C
63.31, H 4.30, N 3.14; found C 63.77, H 4.63, N 3.23.
1
an analytical pure form. Yield 2.50 g (87%). Ϫ H NMR (CDCl3):
δ ϭ 3.39 (2 H, q, CH2), 3.59 (2 H, t, CH2), 6.27 (1 H, s, br., NH),
6.94 (1 H, m, aromatic), 7.24Ϫ7.39 (12 H, m, aromatic), 7.59 (1 H,
m, aromatic). Ϫ 31P NMR (CDCl3): δ ϭ Ϫ 9.9. Ϫ 31P NMR
(CD3CN): δ ϭ Ϫ 8.4. Ϫ IR (KBr): ν˜ ϭ 3310 cmϪ1 (m, OH), 1630
cmϪ1 (vs, CϭO). Ϫ C21H20NO2P (349.1): calcd. C 72.18, H 5.77,
N 4.01; found C 71.74, H 6.56, N 4.25.
[{(1R,2R)-N-(2-Aminocyclohexyl)}-2-(diphenylphosphanyl)benz-
amide]trichlorooxorhenium(V), [Re(O)(κ2-L1)Cl3] HCl (4): L1
(0.068 g, 0.17 mmol), dissolved in MeOH (5 mL), was added drop-
wise to a solution of 1 (0.10 mg, 0.17 mmol) in MeOH (10 mL).
The reaction turned brown immediately and within a few minutes
turned green. After 3 h at room temperature, the solution was con-
centrated to dryness giving an highly viscous oil. After washing
several times with dichloromethane, a light blue solid precipitated,
which was vacuum-dried. Yield 0.066 g (52%). Ϫ 31P NMR:
[(CD3)2SO]: δ ϭ Ϫ17.2, 32.9. Ϫ IR (KBr): ν˜ ϭ 1570 cmϪ1 (vs, Cϭ
[(1R,2R)-N-(2-Aminocyclohexyl)]-2-(diphenylphosphanyl)benzamide
(L1): N-[2-(Diphenylphosphanyl)benzoyloxy]succinimide (0.89 g,
2.20 mmol), dissolved in dichloromethane (10 mL), was added
dropwise to a solution of (1R,2R)-(Ϫ)-diaminocyclohexane (0.50 g,
4.40 mmol) in the same solvent (25 mL). The reaction was complete
after 3 h, as indicated by the TLC (ethyl acetate/hexane, 50:50).
The mixture was washed with 25 mL of water and the organic
phase was separated. The aqueous phase was extracted with dichlo-
romethane (2 ϫ 30 mL). The organic phases were collected, dried
with MgSO4, filtered and concentrated to dryness. The resulting
viscous oil was recrystallized from dichloromethane/hexane, af-
O), 1000 cmϪ1 (vs, ReϭO), 320 cmϪ1 (m, ReϪCl).
Ϫ
C25H28Cl4N2O2PRe (747.5): calcd. C 40.17, H 3.78, N 3.75; found
C 40.18, H 3.68, N 3.81.
[N-(2-Aminoethyl)-2-(diphenylphosphanyl)benzamide]trichloro-
oxorhenium(V), [Re(O)(κ2-L2)Cl3] HCl (5): Compound 5 was pre-
pared in a similar manner to 4. L2 (0.20 g, 0.58 mmol) and 1
(0.34 g, 0.58 mmol) were allowed to react to form a light green
solid, 5. Yield 0.23 g (58%). Single crystals of poor quality for X-
ray crystallographic analysis were obtained by recrystallization of
1
fording colourless crystals of L1. Yield 0.79 g (89%). Ϫ H NMR
(CDCl3): δ ϭ 0.85 (1 H, m, cyclohexyl), 1.17 (4 H, m, cyclohexyl),
1.65 (3 H, s, br., cyclohexyl), 1.89 (2 H, m, NH2), 2.15 (1 H, m,
CHNH2), 3.60 (1 H, m, CHNH), 5.71 (1 H, d, NH), 6.92 (1 H, m,
aromatic), 7.19Ϫ7.40 (12 H, m, aromatic), 7.62 (1 H, m, aromatic).
1
5 from boiling acetonitrile. Ϫ H NMR (CD3CN): δ ϭ 2.98 (2 H,
s, br., CH2), 3.45 (2 H, s, br, CH2), 7.16 (1 H, m, aromatic),
7.52Ϫ7.80 (12 H, m, aromatic), 8.68 (1 H, t, br., aromatic), 11.48
(1 H, s, br., NH). Ϫ 1H NMR [(CD3)2SO]: δ ϭ 2.82 (2 H, m, CH2),
3.26 (2 H, m, CH2), 7.09 (1 H, m, aromatic), 7.48Ϫ7.66 (8 H, m,
aromatic), 7.84 (2 H, m, aromatic), 8.08 (2 H, s, br., aromatic), 8.54
(1 H, m, aromatic), 11.42 (1 H, s, br., NH). Ϫ 31P NMR (CD3CN):
δ ϭ Ϫ15.4. Ϫ 31P NMR [(CD3)2SO]: δ ϭ Ϫ18.1. Ϫ IR (KBr): ν˜ ϭ
1590 cmϪ1 (vs, CϭO), 1000 cmϪ1 (vs, ReϭO), 320 cmϪ1 (s,
ReϪCl). Ϫ C21H22Cl4N2O2PRe (691.9): calcd. C 36.42, H 3.20, N
4.05; found C 36.02, H 2.60, N 3.74.
Ϫ
31P NMR(CDCl3): δ ϭ Ϫ10.5. Ϫ 31P NMR [(CD3)2SO]: δ ϭ
Ϫ9.6. Ϫ IR (KBr): ν˜ ϭ 3220 cmϪ1 (m, NH2), 1630 cmϪ1 (vs, Cϭ
O). Ϫ C25H27N2OP (402.5): calcd. C 74.61, H 6.76, N, 6.96; found
C 73.75, H 6.55, N 6.89.
N-(2-Aminoethyl)-2-(diphenylphosphanyl)benzamide (L2): N-[2-(Di-
phenylphosphanyl)benzoyloxy]succinimide (0.70 g, 1.74 mmol),
dissolved in dichloromethane (10 mL), was added dropwise to a
solution of ethylenediamine (0.25 mL, 3.70 mmol) in the same solv-
ent. After 2 h (TLC: ethyl acetate/hexane, 50:50), the white precipit-
ate was removed by filtration through a pad of Celite and the fil-
Trichloro[2-(diphenylphosphanyl)-N-(2-hydroxyethyl)benzamide]-
oxorhenium(V), [Re(O)(κ2-L3)Cl3] (6). ؊ Method a: L3 (0.10 g,
0.29 mmol), dissolved in MeOH (5 mL), was added dropwise to a
trate was concentrated to dryness. The resulting yellowish viscous solution of 1 (0.17 g, 0.29 mmol) in MeOH (10 mL). The reaction
oil was dissolved in the minimum amount of ethanol and water turned dark green immediately, then violet-blue and finally bright
was added dropwise until no more white solid precipitated. The green. A dark green solid precipitated which was then isolated by
solid was recovered by filtration, washed twice with water and dried
under vacuum, yielding L2 in an analytical pure form. Yield 0.45 g
(74%). Ϫ 1H NMR (CDCl3): δ ϭ 2.68 (2 H, t, CH2), 3.30 (2 H, q,
filtration, washed 3 times with MeOH and vacuum-dried. Complex
6 was obtained in an almost quantitative yield. Ϫ Method b: A
suspension of complex 2 (0.092 g, 0.11 mmol) in dry dichlorome-
CH2), 6.23 (1 H, s, br., NH), 6.92 (1 H, m, aromatic), 7.23Ϫ7.39 thane (25 mL) was treated with L3 (0.040 g, 0.11 mmol) under an
(12 H, m, aromatic), 7.59 (1 H, m, aromatic). Ϫ 31P NMR (CDCl3):
inert atmosphere. Within a few minutes a green reaction mixture
δ ϭ Ϫ9.3. Ϫ 31P NMR (CD3CN): δ ϭ Ϫ8.6. Ϫ IR (KBr): ν˜ ϭ was obtained. After 1 h, a dark green solid started to precipitate.
3320 cmϪ1 (m, NH2), 1630 cmϪ1 (vs, CϭO). Ϫ C21H21N2OP H2O The reaction was allowed to proceed for 18 h. The solid was then
(366.4): calcd. C 68.84, H 6.33, N 7.65; found C 69.61, H 6.08,
N 8.17.
isolated by filtration and washed 3 times with dry dichloromethane.
Single crystals, suitable for X-ray crystallographic analysis, were
Eur. J. Inorg. Chem. 2000, 1523Ϫ1529
1527

J. D. G. Correia, A. Domingos, I. Santos
FULL PAPER
Table 1. Crystal data and structure refinement of L1 and 6
L1
6
Empirical formula
M
C25H27N2OP
402.46
0.70 ϫ 0.54 ϫ 0.18
monoclinic
P21
C21H20Cl3NO3PRe CH3CN
698.95
Crystal size [mm]
Crystal system
Space group
0.34 ϫ 0.12 ϫ 0.11
orthorhombic
P212121
˚
a [A]
12.808(2)
15.193(2)
18.105(3)
106.544(14)
3377.2(9)
6
8.0460(8)
˚
b [A]
10.7286(10)
˚
c [A]
30.116(3)
β [°]
3
˚
V [A ]
Z
2599.7(4)
4
293(2)
1.786
5.071
1360
T [K]
293(2)
Dc [g cmϪ3
]
1.187
µ(Mo-Kα) [mmϪ1
F(000)
]
0.140
1284
No. reflections measured
No. unique reflections
R1[b]
6386
4566
6180 (0.0325)[a]
0.0670
4311 (0.0972[a]
0.0702
)
[b]
wR2
0.1085
0.0836
[a]
[b]
Value of R(int). Ϫ The values were calculated for data with I Ͼ 2 (I) only.
obtained by recrystallization from boiling CH3CN. Yield 0.040 g
made with ORTEP II[26] and all calculations were performed with
1
(55%). Ϫ H NMR (CD3CN): δ ϭ 3.16 (2 H, m, CH2), 3.38 (2 H, a Decα 3000 computer. A summary of the crystal data and of the
t, CH2), 7.14 (1 H, m, aromatic), 7.51Ϫ7.81 (12 H, m, aromatic), refinement procedures is given in Table 1. Crystallographic data
8.03 (1 H, t, br., aromatic), 9.08 (1 H, s, br., NH). Ϫ 1H NMR (excluding structure factors) for the structures reported in this pa-
[(CD3)2SO]: δ ϭ 3.09 (2 H, m, CH2), 3.26 (2 H, m, CH2), 7.06 (1 per have been deposited with the Cambridge Crystallographic Data
H, m, aromatic), 7.46Ϫ7.88 (12 H, m, aromatic), 8.23 (1 H, m,
Centre as supplementary publication no. CCDC-137148 (L1)
aromatic), 10.92 (1 H, s, br., NH). Ϫ 31P NMR (CD3CN): δ ϭ and -137149 (6). Copies of the data can be obtained free of
Ϫ16.5. Ϫ 31P NMR: [(CD3)2SO]: δ ϭ Ϫ 18.1. Ϫ IR (KBr): ν˜ ϭ charge on application to CCDC, 12 Union Road, Cambridge
3250 cmϪ1 (w, OH), 1590 cmϪ1 (vs, CϭO), 1000 cmϪ1 (vs, ReϭO),
CB2 1EZ, UK [Fax: int. code ϩ 44-1223/336-033; E-mail:
315 cmϪ1 (s, ReϪCl). Ϫ C21H20Cl3NO3PRe (657.9): calcd. C 38.34, deposit@ccdc.cam.ac.uk].
H 3.06, N 2.13; found C 37.97, H 2.90, N 1.97.
Acknowledgments
J. D. G. C. would like to thank the Fundaca˜o para a Ciencia e
¸
Tecnologia (National Foundation for Science and Technology) for
a PRAXIS XXI postdoctoral fellowship.
X-ray Crystallographic Analysis: A colourless crystal of L1 and a
dark green crystal of 6 were fixed inside thin-walled glass capillar-
ies. Data were collected at room temperature with an
EnrafϪNonius CAD-4 diffractometer with graphite-monochroma-
tized Mo-Kα radiation, using an ω-2θ scan mode. Unit cell dimen-
sions were obtained by least-squares refinement of the setting
angles of 25 reflections with 16.6° Ͻ 2θ Ͻ 24.0° for L1, and 16.2°
Ͻ2θϽ 29.7° for 6. A summary of the crystallographic data is given
in Table 1. Data were corrected[23] for Lorentz polarization effects,
for linear decay (no decay was observed for L1, and a decay of
16.7% was observed for 6) and for absorption by empirical correc-
tions based on ψ scans. The structures were solved by Patterson
methods[24] and subsequent difference Fourier techniques and re-
fined by full-matrix least-squares procedures on F2 using
SHELXL93[25]. For 6, an acetonitrile solvent molecule of crystal-
lization was also located in the Fourier difference map. During the
isotropic refinement of 6 the terminal C(3)ϪO(3) atoms showed
rather large thermal parameters and were found to be disordered
over two different positions with 0.52 and 0.48 occupancies. All the
non-hydrogen atoms were refined with anisotropic thermal motion
parameters, with isor restraints being applied to the disordered
atoms. The contributions of the hydrogen atoms were included in
calculated positions [except that of the disordered O(3)H atom].
The absolute configuration of both crystals studied were deter-
mined by refinement of the Flack parameters, and the refined
models proved to be the correct enantiomorphs. A final Fourier
difference synthesis was featureless for L1, and revealed residual
ˆ
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