A fluorene-based diphosphinite ligand, its Ni, Pd, Pt, Fe, Co and Zn complexes and the first structurally characterized diphosphinate metal chelates

Article abstract of DOI:10.1016/j.ica.2010.06.007

The diphosphinite ligand 9,9-(Ph₂POCH₂) ₂-fluorene (1) was reacted with group 10 metal dichlorides to form chelate complexes of formula [MCl₂(1)] (MNi, 2; MPd, 3; MPt, 4) showing 8-membered metallocycles. Chlori

Full text of DOI:10.1016/j.ica.2010.06.007

Inorganica Chimica Acta 363 (2010) 4337–4345
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A fluorene-based diphosphinite ligand, its Ni, Pd, Pt, Fe, Co and Zn complexes
and the first structurally characterized diphosphinate metal chelates
1
*
Changxiu Li , Roberto Pattacini, Pierre Braunstein
Laboratoire de Chimie de Coordination, Institut de Chimie, UMR 7177 CNRS, Université de Strasbourg, 4 rue Blaise Pascal, F-67081 Strasbourg, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 13 June 2010
The diphosphinite ligand 9,9-(Ph2POCH2)2-fluorene (1) was reacted with group 10 metal dichlorides to
form chelate complexes of formula [MCl2(1)] (M@Ni, 2; M@Pd, 3; M@Pt, 4) showing 8-membered metal-
locycles. Chloride abstraction from 3 with AgOTf afforded the dinuclear complex [M(l-Cl)Pd(1)]2(OTf)2
Dedicated to Professor Achim Müller, in
recognition for his outstanding and diverse
contributions to chemistry.
(5), in which the ligand adopts a different conformation with respect of 3. In 5, the fluorene moiety
and the phenyl groups display stabilizing interactions with the anion which is located close to the metal
centre. With Fe(II), Co(II) and Zn(II) chlorides, the non-isolated intermediates [MCl2(1)] readily undergo
oxidation to [MCl2(1ox)] (M@Fe, 6; M@Co, 7; M@Zn, 8; 1ox = 9,9-(Ph2P(O)OCH2)2-fluorene) in which the
diphosphinate ligand and the metal centre form 10-membered metallocycles. Complexes 6–8 are the first
examples of structurally characterized diphosphinate metal chelates. The Zn(II) diphosphinite complex
[ZnCl2(1)] (9) could be observed by NMR spectroscopy, along with the mixed phosphinite–phosphinate,
mono-oxidized complex which is an intermediate in the formation of 8. Complex [ZnCl2(9.9-fluorene-
dimethanol)(Ph2P(O)H)] (10) was also observed as hydrolysis product of 9. The X-ray molecular struc-
tures of 2, 3, 5.2OTf, 6, 7, 8 and 10 are reported.
Keywords:
Diphosphinites
Diphosphinates
Fluorene
Anion coordination
Host–guest
Ligand conformation
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
Ligand 1 has been previously used for the formation of cationic
dinuclear Pd(II) complexes of formula [Pd(l-Cl)(1)]2(X)2 (X = BF4,
Diphosphinite ligands are generally readily available and their
metal complexes find numerous applications, mostly in homoge-
neous catalysis [1]. For example, the POCOP class of metallated li-
PF6) [5]. In the solid state, the anions were found close to the metal
centres, positioned in cavities delimitated by the aryl groups (Ph,
fluorene) of the chelating ligands. The stabilization of these cat-
ion–anions couples was improved by close HÁ Á ÁF contacts between
the aryl protons and the fluorinated anions. The flat fluorene moi-
ety was found to be orthogonal to the metal coordination planes,
giving rise, with the phenyl groups, to the aforementioned cavities.
These host–guest systems were identified in solution by means of
1H–19F HOESY NMR experiments whose results were fully consis-
tent with the intermolecular connectivities observed in the solid
state.
gands (POCOP = j3-1,3-(PR2O)2C6H3) has been much studied
recently [2], and has often been proven to be superior to the re-
lated PCP tertiary diphosphines, in terms of stability of the com-
plexes and catalytic activity [3]. The axial chiral diphosphinites
BINOP, similar to the famous BINAP diphosphines, represent an-
other important class of ligands [4].
We recently reported the almost quantitative synthesis of the
new ligand 9,9-(Ph2POCH2)2-fluorene, by reaction of Ph2PCl with
9H-fluorene-9,9-dimethanol (Scheme 1), in the presence of NEt3
as HCl scavenger [5]. This stable compound, which shows only
moderate sensitivity towards hydrolysis, air and moisture, can be
included in the family of large bite angle phosphorus donors.
Because of the resulting steric and/or electronic influence of the
P–M–P angle, this often results in specific reactivities of the metal
complexes [6].
The dinuclear complex [Ag(PF6)(1)]2 was formed by reaction of
1 with AgPF6 and it displays a 16-membered metallocyclic struc-
ture resulting from the bridging bonding mode of 1. In its solid
state structure, the phenyl groups and the fluorene rings are dis-
posed in such a way that two large, mutually centrosymmetric cav-
ities are formed. Because of their size and favorable HÁ Á ÁF contacts
À
similar to those described above, the PF6 anions were inserted in
these cavities and interacted with the metal centres in a remark-
able F5P-(l-F) coordination mode, which is unprecedented for
the hexafluorophosphate anion (Scheme 2) [5].
In order to study the reactivity of this diphosphinite ligand 1
with other transition metals, we have reacted it with halide com-
* Corresponding author. Tel.: +33 368 851 308; fax: +33 368 851 322.
E-mail address: braunstein@unistra.fr (P. Braunstein).
On leave from: Beijing Research Institute of Chemical Industry, SINOPEC, Beijing
1
100013, China.
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.06.007

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C. Li et al. / Inorganica Chimica Acta 363 (2010) 4337–4345
2 PPh2Cl
2 NEt3
OH
HO
P
P
O
O
-2 [HNEt3]Cl
1
Scheme 1. Synthesis of the diphosphinite ligand 1.
F
F
F
P
F
F
F
P
O
Ag
P
O
O
P
Ag
F
O
P
F
Fig. 1. ORTEP of the molecular structure of complex 2 in 2ÁCH2Cl2. Displacement
F
P
F
F
parameters include 40% of the electron density.
F
Scheme 2. Ag–PF6 interactions through a remarkable F5P-(l-F) coordination mode
in [Ag(PF6)(1)]2 [5].
plexes of Fe(II), Co(II), Ni(II), Zn(II), Pd(II) and Pt(II) and report here
the results of these studies.
2. Results and discussion
The reaction of 1 with divalent metal complexes from the group
10,
namely
[NiCl2(DME)]
(DME = 1,2-dimethoxyethane),
[PdCl2(NCPh)2] and [PtCl2(NCPh)2] afforded in good yields com-
plexes [NiCl2(1)] (2), [PdCl2(1)] (3) and [PtCl2(1)] (4), respectively
(Scheme 3). The crystal structures of 2 and 3 were determined by
single crystal X-ray diffraction. Complex 4 was found to be iso-
structural with 3, and their unit cell parameters share analogous
values. ORTEP views of the molecular structure of 2 and 3 are de-
picted in Figs. 1 and 2. Selected bond distances and angles are re-
ported and compared in Table 1.
Ph2
O
O
P
O
O
Cl
Cl
PPh2
PPh2
Fig. 2. ORTEP of the molecular structure of compound 3 in 3Á2CHCl3, which is
isostructural with 4Á2CHCl3. Displacement parameters include 40% of the electron
density.
+
MCl2L2
M
-L2
P
Ph2
M = Pd, Pt; L2 = 2 PhCN
M = Ni; L2 = DME
2 M = Ni
3 M = Pd
4 M = Pt
In the molecular structure of complex 2, the metal centre is che-
lated by diphosphinite 1 and coordinated by two mutually cis ter-
minal chlorides, in a slightly distorted square planar geometry. As
expected, the structural features of 3 are analogous to those of 2,
although the M–P and M–Cl bond distances are longer, as expected,
considering the difference in ionic radii between these metals
(rPd–rNi = 0.11 Å) [7]. A slight distortion from planarity is observed
in 3, and the P1–P2–Cl2–Cl1 torsion angle of 9.35(3)° is larger than
in 2 [2.62(3)°]. The P–M–P bite angle is 104.27(4)° for 2 and
102.67(4)° for 3.
AgOTf
-AgCl
O
O
Ph2P
Pd
1/2
PPh2
(OTf)2
Cl
Pd
O
O
P
P
Cl
Ph2
Ph2
5⋅2OTf
Scheme 3.
The 31P{1H} NMR spectra of 3 and 4 show typical values for Pd
and Pt phosphinite complexes, with singlets at 125.4 and

C. Li et al. / Inorganica Chimica Acta 363 (2010) 4337–4345
4339
Table 1
2.890(4) Å], which bridges the Pd atoms through two sulfonate
oxygens. Indeed, the aB parameter (93.9(1)° for Pd1 and 94.7(1)°
for Pd2), defined as the mean value of the L–PdÁ Á ÁO angles (L = P
or Cl) is fully consistent with an oxygen atom donating electron
Comparison between selected bond distances (Å) and angles (°) in compounds
2ÁCH2Cl2 (M@Ni), 3Á2CHCl3 (M@Pd) and 5Á2OTfÁ2CHCl3 (M@Pd).
2ÁCH2Cl2
3Á2CHCl3
5Á2OTfÁ2CHCl3
density into the empty
P
orbital of the metal from the aforemen-
M–P1
Pd2–P3
M–P2
Pd2–P4
M–Cl1
Pd2–Cl1
M–Cl2
Pd2–Cl2
P1–O1
P3–O3
2.1727(9)
2.237(1)
2.245(1)
2.239(1)
2.251(1)
2.252(1)
2.398(1)
2.400(1)
2.4055(1)
2.4335(1)
1.593(4)
1.601(3)
1.604(3)
1.600(3)
90.31(4)
91.18(4)
84.23(4)
83.58(4)
1.92(5)
z
tioned distances [10]. These represent the shortest interactions re-
ported between a non-coordinating, bridging triflate and Pd(II)
centres. Indeed, the closest separations between two triflate oxy-
gen atoms and two tetracoordinated Pd(II) centres found in the
CCDC database [11] is 3.073 and 3.234 Å for a trinuclear species
[12]. The shortest Pd(II)Á Á ÁO separation between a non-coordinat-
ing triflate and a Pd(II) centre is 2.796 Å [13].
The conformation of the diphosphinite ligand in 5Á2OTf differs
from that in its mononuclear precursor 3. Simplified structural dia-
grams of 3 and 5 are compared in Fig. 4.
Ligand 1 changes conformation on going from 3 to 5Á2OTf. In 3,
the C–O bonds are oriented in almost orthogonal directions, point-
ing below and above the P, P, Cl, Cl plane. In 5, probably con-
strained by the dramatically decreased bite angle [102.67(4)° in
3, 90.31(4)° and 91.18(4)° in 5], the two C–O bonds are almost par-
allel to each other [angle between the lines defined by C1–O1 and
C2–O2 in 5: 9.9(3)° vs. 79.4(2)° in 3]. Consequently, the fluorene
group is almost perfectly orthogonal to the metal coordination
plane [angles between the mean planes defined by P1, P2, Pd1,
Cl1, Cl2 and the atoms forming the fluorene groups: 62.80(5)° for
3 and 89.37(5)° for 5Á2OTf]. In turn, this allows the triflate in the
5ÁOTf moiety to interact with the fluorene ring and the metal cen-
tre in a host–guest arrangement, through HÁ Á ÁO contacts between
the sulfonate oxygen atoms and some of the fluorene protons, as
shown in Fig. 5.
2.1458(9)
2.1923(9)
2.1948(9)
1.626(2)
1.624(2)
104.27(4)
91.87(4)
2.62(3)
2.238(1)
2.361(1)
2.357(1)
1.607(3)
1.616(3)
102.67(4)
91.74(4)
9.35(3)
P2–O2
P4–O4
P1–M–P2
P3–Pd2–P4
Cl1–M–Cl2
Cl1–Pd2–Cl2
P1–P2–Cl1–Cl2
P3–P4–Cl1–Cl2
0.48(5)
96.1 ppm, respectively, flanked in the case of 4 with 195Pt satellites
and the 1J(31P,195Pt) coupling constant of 4149 Hz is consistent
with the presence of chloride ligands in trans position to the P do-
nors [8].
In CD2Cl2 solution, complex 2 was found to be paramagnetic.
The 31P{1H} NMR signal was not detected in saturated solutions,
while the 1H spectra display temperature-dependent isotropic
shifts typical of a square planar – tetrahedral equilibrium [9] (see
ESI). Consistently, the nuclei less affected by the paramagnetic me-
tal centre of the tetrahedral isomer are those of the fluorene ring,
which (vide infra), are relatively far from it.
Of the contacts displayed in Fig. 5, the shortest HÁ Á ÁO and HÁ Á ÁF
separations are 2.633(4) Å (O5Á Á ÁH2B) and 2.487(5) Å (H14Á Á ÁF3),
respectively. Other contacts, not shown for clarity, involve the phe-
nyl groups and the triflate oxygens [shortest HÁ Á ÁO separation:
2.418(4) Å for H39Á Á ÁO5]. This is clearly in favor of a combined
Reaction of 3 with one equivalent AgOTf resulted in abstraction
of one of the chloride ligands and precipitation of AgCl and affor-
ded the dinuclear complex [Pd(
l
-Cl)(1)]2(OTf)2 (5Á2OTf, OTf = tri-
fluoromethanesulfonate). Its crystal structure was determined by
single crystal X-ray diffraction and an ORTEP of the structure of
5ÁOTf in 5Á2OTfÁ2CHCl3 is depicted in Fig. 3. The cation shares
strong similarities with that of [Pd(
l
-Cl)(1)]2(BF4)2 (5Á2BF4) [5].
Each metal centre in cationic 5 is chelated by ligand 1. Two
chloride ligands symmetrically bridge the Pd atoms (see Table 1)
which are separated by 3.5081(6) Å. The geometry around the me-
tal centres is slightly distorted from planarity, the distance of the
metal centre to the mean plane defined by the surrounding donor
atoms being 0.1617(4) Å for Pd1 and 0.1952(4) Å for Pd2. This
pyramidal distortion, directed towards the anion, suggests the
occurrence of OÁ Á ÁPd interactions with one of the two triflate an-
ions [Pd1Á Á ÁO5 and Pd2Á Á ÁO7 separations: 2.966(4) Å and
Fig. 4. Structural diagram of: (a) complex 3 and (b) the analogous fragment in
dinuclear 5 (phenyls omitted for clarity).
Fig. 5. Structural diagram of the cationic 5ÁOTf moiety, emphasizing the network of
HÁ Á ÁO and HÁ Á ÁF contacts between the fluorene group and one of the two triflate
anions. The HÁ Á ÁO and HÁ Á ÁF contacts are depicted with red dashed lines, and the
PdÁ Á ÁO contacts with blue dashed lines. Phenyls omitted for clarity.
Fig. 3. ORTEP of the molecular structure of 5ÁOTf in 5Á2OTfÁ2CHCl3. Displacement
parameters include 40% of the electron density.

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Fig. 6. van der Waals plots of 5Á2BF4 (a and b) and 5Á2OTf (c and d). The two anions closest to the metal centres are shown. In figures a and d, the orientation is similar to that
in Fig. 5, while in figures b and c, the opposite side with respect to the palladium coordination planes is shown.
influence of the fluorene and phenyl protons on the host–guest an-
ion stabilization.
troscopy. The methylene protons of 5Á2OTf give rise to a broad sin-
glet at 298 K in the 1H NMR spectrum, similarly to what has been
observed for 5Á2BF4 [5]. In the latter case, the 1H NMR spectrum
contained four broad signals at 220 K (Fig. 7).
This, together with the observation of two different conforma-
tions in the solid-state for the cation in 5Á2PF6 (a in Scheme 4)
and in 5Á2OTf (b), suggests the equilibrium shown in Scheme 4.
The smaller size of the BF4À anion compared to OTfÀ allows for a
second tetrafluoroborate to approach the metal centres in 5Á2BF4
[5] and to occupy a second cavity located on the opposite side to
that depicted in Fig. 5 (see Fig. 6b). In 5Á2OTf, this cavity is partially
occupied by two chloroform molecules. van der Waals diagrams of
5ÁOTf in 5Á2OTf and of 5Á2BF4 are shown in Fig. 6.
When the reaction was carried out with AgPF6 instead of AgOTf,
compound 5Á2PF6 was obtained which, in the solid state, has two
À
PF6 anions encapsulated in centrosymmetric cavities, at variance
with the situation in 5Á2OTf where only one triflate is involved in a
host–guest system. Furthermore, the cation in 5Á2PF6 displays C2h
symmetry rather than C2v, as found in 5Á2OTf and 5Á2BF4 (a and b
in Scheme 3, respectively) [5].
These two conformations are probably both present in solution
and in rapid exchange, as suggested by multinuclear VT NMR spec-
O
O
P
P
P
Cl
Cl
Pd
Pd
O
P
O
a
O
O
P
P
P
O
Cl
Cl
Pd
Pd
O
P
b
Scheme 4. Possible conformations of the dication 5 in solution (phenyl groups
omitted for clarity).
Fig. 7. Variable-temperature 1H NMR spectra of 5Á2BF4 in CD2Cl2 (from Ref. [5]).

C. Li et al. / Inorganica Chimica Acta 363 (2010) 4337–4345
4341
Each conformation is characterized by four equivalent pairs of dia-
stereotopic protons and gives rise to two broad signals at low tem-
perature. The 31P{1H} spectrum remains unchanged in the
temperature range examined.
Thus, as expected, the oxidation proceeds stepwise, with, qualita-
tively, similar kinetics for the first and second oxidation steps.
The superimposability of the FT-IR spectra of 6–8 suggests the
isostructural character of these complexes in the solid state. This
was confirmed by single crystal X-ray diffraction, the three com-
plexes share the same molecular structure and crystal packing.
An ORTEP view of the molecular structure of 7 is shown in Fig. 8.
In the molecular structure of 6–8, the diphosphinate ligand 1ox
chelates the metal centre through the two P@O oxygen atoms
[Co1–O3 and Co1–O4 distances in 7: 1.991(4) Å and 2.000(4) Å,
respectively]. The two chlorides are terminally bound to the metal
centres, which have a distorted tetrahedral coordination geometry.
Selected bond distances and angles are compared in Table 2. Ligand
chelation results in the formation of a 10-membered metallocycle
(see Fig. 8).
2.1. Coordination properties of 1 towards FeCl2, CoCl2 and ZnCl2
Ligand 1 readily reacted with anhydrous FeCl2, CoCl2 and ZnCl2
under inert atmosphere. However, only complexes featuring the
diphosphinate ligand 1ox could be isolated after purification by
crystallization, most likely because of the sensitivity of the hypo-
thetical intermediates [MCl2(1)] towards oxidation. When this
reaction was performed under air, yellow [FeCl2(1ox)] (6), blue [Co-
Cl2(1ox)] (7) and colourless [ZnCl2(1ox)] (8) were obtained in good
yields (Scheme 5).
Interestingly, complexes 6–8 crystallize in the chiral space
group P212121. One crystallographically independent molecule is
present in the unit cell of the three compounds and the refinement
resulted in parameters consistent with a spontaneous resolution of
one of the possible conformational enantiomers.
Only few 10-membered rings formed by chelation to Fe and Co
have been reported in the literature, and they mostly involve mul-
tidentate ligands [15]. In the case of bidentate ligands, and to the
Although pure 1 does not rapidly oxidize when exposed to air or
moisture, it is known that Co(II) promotes insertion of aerobic oxy-
gen into the P–M bond, possibly via dioxygen coordination [14].
The oxidation is quantitative and can be detected in the FT-IR spec-
tra of 6–8 by the strong P@O stretching absorption around
1190 cmÀ1. In the case of Zn(II), we were able to characterize spec-
troscopically the diphosphinite complex [ZnCl2(1)] (9), although its
sensitivity prevented the obtention of a pure sample. In addition,
the mono-oxidized phosphinite–phosphinate complex depicted
in Scheme 6 was observed as intermediate in the formation of 8.
Ph2
O
O
P
O
O
PPh2
PPh2
MCl2
+ MCl2
-L2
P
Ph2
not isolated for M = Fe, Co,
observed for Zn (9)
2 H2O
air
-Ph2P(O)H
OH
Cl
PH
O
O
O
HO
Cl
Zn
Cl
PPh2
Ph2P
O
O
M
10
Cl
6 M = Fe
7 M = Co
8 M = Zn
Fig. 8. ORTEP of the molecular structure of 7. ORTEP diagrams of the isostructural
complexes 6 and 8 are provided in the supplementary information. Displacement
parameters include 40% of the electron density.
Scheme 5.
Table 2
Comparison between selected distances (Å) and angles (°) in 6 (M@Fe), 7 (M@Co) and
8 (M@Zn).
Ph2
P
6
7
8
O
O
1/2 O2
1/2 O2
M–O3
M–O4
M–Cl1
M–Cl2
P1–O1
P2–O2
P1–O3
P2–O4
2.031(3)
1.941(5)
2.252(2)
2.247(2)
1.582(3)
1.579(3)
1.470(4)
1.437(5)
105.2(2)
125.37(7)
89.96(8)
1.991(4)
2.000(4)
2.243(2)
2.237(2)
1.575(4)
1.585(4)
1.482(3)
1.492(4)
103.5(2)
121.03(7)
89.92(6)
1.988(2)
2.004(2)
2.219(1)
2.2107(9)
1.575(2)
1.580(2)
1.491(2)
1.495(2)
101.36(9)
123.38(4)
89.84(4)
ZnCl2
O
O
O
O
Cl
Cl
P
PPh2
Ph2P
Ph2P
Ph2
PPh2
O
O
O
Zn
Zn
Cl
Cl
8
9
δ 41.2 (P = O-Zn),
δ 91.2
δ 39.6
90.9 (br, P-Zn),
O3–M–O4
Cl1–M–Cl2
V1–V2a
3J(31P, 31P) = 5.2 Hz
Scheme 6. Stepwise oxidation of 9 to form 8. 31P{1H} NMR chemical shifts (in ppm)
a
Angle between the Cl1Á Á ÁCl2 and O3Á Á ÁO4 vectors.
are reported.

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C. Li et al. / Inorganica Chimica Acta 363 (2010) 4337–4345
phosphinate ligand 1ox in 8 would give phosphinic acids instead of
R'
R'
the observed secondary phosphine oxide Ph2P(O)H [18]. Consis-
tently, 10 was obtained during an attempt to crystallize [ZnCl2(1)]
in THF, in which water has a higher solubility than in CH2Cl2, the
solvent used for the formation of 10.
O
O
R'
R
O
O
R'
R
P
P
P
P
R
R
O
O
O
O
M
a
M
Complexes 6-8
Scheme 7. Different types of chelating diphosphinate complexes.
3. Conclusion
Ligand 1 is a versatile diphosphinite that features a variable bite
angle (see complexes 3 vs. 5.2OTf) when it chelates a metal centre.
This angle largely determines the position of the fluorene group,
which can be brought orthogonal to the metal coordination plane
(bite angle ca. 90°, complex 5.2OTf). The latter conformation facil-
itates the host–guest capabilities of its complexes [Ag(I) [5], Pd(II)],
since the fluorene group, along with the phenyls, participates in
the stabilization of cation–anion pairs through multiple HÁ Á ÁF
and/or HÁ Á ÁO interactions. With Fe(II), Co(II) and Zn(II), oxidation
of the diphosphinite ligand 1 to diphosphinate 1ox occurs. Com-
plexes [MCl2(1ox)] (M = Fe(II) 6, Co(II) 7, Zn(II) 8) represent the first
structurally characterized diphosphinate metal chelates. The dia-
magnetic Zn(II) diphosphinite complex 9 could be observed and
we have shown that its oxidation to 8 proceeds stepwise, through
the intermediacy of a mono-oxidized phosphinite–phosphinate
complex.
4. Experimental
Fig. 9. ORTEP of the molecular structure of 10. Displacement parameters include
40% of the electron density. Only the H atoms bound to heteroatoms are depicted.
Selected distances (Å) and angles (°): Zn1–O1 2.032(2), Zn1–O3 1.970(2), Zn1–Cl1
2.236(1), Zn1–Cl2 2.177(1), O1–C1 1.441(3), O2–C3 1.431(3), O3–P1 1.510(2); O3–
Zn1–O1 101.39(9), Cl2–Zn1–Cl1 120.10(5).
4.1. General information
All solvents were dried and freshly distilled under nitrogen
prior to use using common techniques. All manipulations were car-
ried out using Schlenk techniques. 1H (300 MHz), 13C{1H}
(75 MHz), 31P{1H} NMR (121 MHz) spectra were recorded on a Bru-
ker AC300 instrument. FT-IR spectra were recorded on a Thermo-
Electron 6700 spectrometer with ATR techniques (key to infrared
absorption intensities: vs, very strong; s, strong; m, medium; w,
weak). Elemental analyses were performed by the ‘‘Service de
Microanalyses”, Université de Strasbourg. Ligand 1, complex
[PdCl2(1)] (3) [5], [NiCl2(DME)] [19] and [PtCl2(NCPh)]2 [20] were
prepared according to published procedures. Anhydrous FeCl2
and ZnCl2 were obtained by treating the hydrated salts in refluxing
thionyl chloride and anhydrous blue CoCl2 by heating the hydrated
salt under vaccum.
best of our knowledge, only one example was reported for Zn [16],
while no example is available for Fe and Co. In addition, complexes
6–8 appear to be the first examples of structurally characterized
chelating diphosphinate metal complexes. In the few diphosphi-
nate metal complexes reported in the literature [17], the alkoxy
group, differently from the cases reported herein, is not comprised
in the chelating ring but instead is terminally bound to phosphorus
[See (a) in Scheme 7].
The bulky fluorene group probably hinders the formation of
conceivable coordination polymers or, more generally, of a bridg-
ing coordination mode for ligand 1.
A hydrolysis product of the Zn(II) complex has been obtained as
colourless crystals and its structure, determined by X-ray diffrac-
tion (10, Fig. 9), established its nature as [ZnCl2(9,9-fluorene-
dimethanol){Ph2P(O)H}] (10).
4.2. Synthesis of complex [NiCl2(1)] (2)
In the structure of 10, the Zn(II) centre is coordinated by 9,9-flu-
orene-dimethanol through the oxygen of one of the alcohol func-
tions, by a O-bound diphenylphosphine oxide ligand and by two
terminal chlorides. The coordination geometry is distorted tetrahe-
dral. The non-coordinated alcohol function is involved in an intra-
molecular hydrogen bond with one of the terminal chlorides, in
such a way that a 8-membered pseudo-chelate ring is formed.
The coordinated alcohol group interacts, intermolecularly, with a
neighbouring molecule of 10 through hydrogen bonding with O2.
In solution, the CH2 groups of compound 10 give rise to two,
well separated sets of 13C{1H} NMR signals and to two AB spin sys-
tems in the 1H NMR spectrum. This suggests that if an exchange
occurs between O1 and O2, it is slow on the NMR time scale.
Compound 10 likely stems from the hydrolysis of the diphosph-
inite intermediate [ZnCl2(1)] (Scheme 5), by cleavage of the two O–
P bonds and formation of two molecules of Ph2P(O)H (one is found
coordinated in 10) and the corresponding alcohol. Hydrolysis of the
Solid
[NiCl2(DME)]
(DME = dimethoxyethane)
solution of ligand
(0.110 g,
1 (0.298 g,
0.50 mmol) was added to
a
0.50 mmol) in CH2Cl2 (50 mL). The colour of the reaction mixture
became orange immediately. The solution was stirred at room
temperature under N2 for 3 h. The volatiles were removed under
vacuum, affording a red solid which was washed with diethyl ether
(2 Â 20 mL). The red powder obtained was dissolved in CH2Cl2
(30 mL). Petroleum ether (60 mL) was slowly layered onto the
solution, yielding red crystals of 2 CH2Cl2 (0.312 g, yield: 77%).
The NMR data of 2 revealed a tetrahedral-square planar equilib-
rium, which resulted in broad resonances due to the paramagne-
tism of the solution. The 1H NMR spectrum is reported in the
supplementary information, while no 31P NMR signals were ob-
served, even from saturated solutions (see main text). Selected IR
absorption: 1183(w), 1108(m), 1068(s), 1011(vs), 996(vs), 828(s),
742(s), 731(s), 697(vs). Anal. Calc. for C39H32O2P2Cl2NiÁCH2Cl2
(MW = 809.15): C, 59.37; H, 4.24. Found: C, 58.59; H, 4.40%.

C. Li et al. / Inorganica Chimica Acta 363 (2010) 4337–4345
4343
4.3. Synthesis of complex [PtCl2(1)] (4)
4.5. Synthesis of complex [FeCl2(1ox)] (6)
Solid [PtCl2(NCPh)2] (0.236 g, 0.50 mmol) was added to a solu-
tion of ligand 1 (0.298 g, 0.50 mmol) in CH2Cl2 (50 mL). The pale yel-
low reaction mixture was stirred at room temperature under N2 for
3 h. The volatiles were removed under vacuum, affording a pale yel-
low powder which was washed with diethyl ether (2 Â 20 mL). The
pale yellow solid obtained was dissolved in CH2Cl2 (20 mL) and pen-
tane (40 mL) was slowly layered onto the solution, yielding colour-
less crystals of 4Á2CH2Cl2 (0.324 g, yield: 63%). 1H NMR (CDCl3):
d = 3.90 (d, 4H 3J(31P,1H) = 9.2 Hz; CH2), 7.23–8.12 ppm (m, 28H;
aryls); 31P{1H} NMR (CDCl3): d = 96.1 ppm (s, with 195Pt satellites,
1J(31P,195Pt) = 4150 Hz); 13C{1H} NMR (CD2Cl2): d = 53.5 (s;
CH2CCH2), 70.4 (s; CH2), 120.4 (s; fluorene), 125.7 (s; fluorene),
127.7 (s; fluorene), 128.5 (virtual triplet, 3+5J(31P,13C) = 12.0 Hz,
2J(31P,31P) = 6.8 Hz; m-phenyls), 129.1 (s; fluorene), 132.2 (s; p-
phenyls), 132.2 (d, 1J(31P,13C) = 32.2 Hz; i-phenyls), 133.7 (virtual
triplet, 2+4J(31P,13C) = 11.6 Hz, 2J(31P,31P) = 6.8 Hz; o-phenyls),
140.8, (s; fluorene) 143.2 (s; fluorene). Anal. Calc. for C39H32O2P2
Cl2PtÁ2CH2Cl2 (MW = 1030.47): C, 47.79; H, 3.52. Found: C, 48.41;
H, 3.51%.
Anhydrous FeCl2 (0.063 g, 0.50 mmol) was added to a solution
of ligand 1 (0.297 g, 0.50 mmol) in THF (40 mL). The yellow reac-
tion mixture was stirred for 24 h at room temperature. The vola-
tiles were removed under vacuum affording a viscous yellow oil,
which was washed with ethyl ether (2 Â 30 mL). The yellow pow-
der obtained was dissolved in CH2Cl2 (10 mL). Pentane (20 mL) was
layered onto it, yielding yellow crystals of 6 after 3 days (0.203 g,
yield: 54%). The FT-IR spectrum of 6 is reported in the supporting
information. Selected IR absorptions:
m(P@O) 1191(vs), 1170(s,
sh). Anal. Calc. for C39H32O4Cl2P2Fe (MW = 753.37): C, 62.18; H,
4.28. Found: C, 62.16; H, 4.38%.
4.6. Synthesis of complex [CoCl2(1ox)] (7)
Anhydrous CoCl2 (0.065 g, 0.50 mmol) was added to a solution
of ligand 1 (0.297 g, 0.50 mmol) in THF (40 mL). The blue reaction
mixture was stirred for 24 h at room temperature. The volatiles
were removed under vacuum affording a blue solid, which was
washed with ethyl ether (2 Â 30 mL). The blue powder obtained
was dissolved in CH2Cl2 (20 mL). Pentane (40 mL) was layered onto
it, yielding blue crystals of 7 (0.280 g, yield: 74%). The FT-IR spec-
trum of 7 is reported in the supporting information. Selected IR
4.4. Synthesis of complex [Pd(l-Cl)(1)]2(OTf)2 (5Á2OTf)
A solution of AgOTf (0.051 g, 0.20 mmol) in MeCN (5 mL) was
added dropwise to a solution of complex 3 (0.154 g, 0.20 mmol)
in THF (30 mL). The colourless suspension was stirred for 1 h at
room temperature. The reaction mixture was filtered and the vol-
atiles removed under vacuum affording a yellow solid, which was
washed with diethyl ether (2 Â 20 mL). The yellow powder ob-
tained was dissolved in CHCl3 (10 mL). Pentane (20 mL) was lay-
ered onto the solution, affording yellow crystals of 5Á2OTfÁ2CHCl3
(0.113 g, yield (based on Pd) = 56%). 1H NMR (CDCl3): d = 4.5 (br,
8H; CH2), 7.30–8.10 ppm (m, 56H; aryls); 31P{1H} NMR (CDCl3):
d = 114.3 ppm (s); 13C{1H} NMR (CD2Cl2): d = 55.0 (t,
3J(31P,13C) = 5.7 Hz; CH2CCH2), 74.4 (s; CH2), 120.7 (s; fluorene),
126.2 (s; fluorene), 127.9 (s; fluorene), 129.1 (br; m-phenyls),
129.4 (s; fluorene), 132.5 (br; o-phenyls), 133.4 (s; p-phenyls),
133.8 (br; fluorene), 140.8 (s; fluorene). Anal. Calc. for
absorptions:
39H32O4P2Cl2Co (MW = 756.46): C, 61.92; H, 4.26. Found: C,
61.59; H, 4.25%.
m(P@O) 1189(vs), 1167(s, sh). Anal. Calc. for
C
4.7. Synthesis of complex [ZnCl2(1ox)] (8), observation of [ZnCl2(1)] (9)
Solid ZnCl2 (0.068 g, 0.50 mmol) was added to a solution of li-
gand 1 (0.297 g, 0.50 mmol) in CH2Cl2 (50 mL). The colourless mix-
ture was stirred for 24 h at room temperature. The volatiles were
removed under vacuum affording a white solid, which was washed
with diethyl ether (2 Â 30 mL) (0.362 g, yield: 95%). The powder
was dissolved in CH2Cl2 and diethyl ether was layered onto it,
yielding colourless crystals of 8. 1H NMR (CDCl3): d = 4.44 (d, 4H,
3J(H,31P) = 6.5 Hz; CH2); 7.3–8.0 ppm (m, 28H; aryls); 31P{1H}
NMR (CDCl3): d = 39.1 ppm; the poor solubility of 8 in chlorinated
solvents prevented the recording of 13C{1H} spectra. Anal. Calc. for
C80H64O10P4F6S2Cl2Pd2Á2CHCl3 (MW = 2009.87): C, 49.00; H, 3.31.
Found: C, 49.40; H, 3.77%.
Table 3
Collection and structure refinement data for 2ÁCH2Cl2, 3Á2CHCl3, 5Á2OTfÁ2CHCl3.
2ÁCH2Cl2
3Á2CHCl3
5ÁOTfÁ2(CHCl3)
Chemical formula
Formula mass
Crystal system
a (Å)
b (Å)
c (Å)
C
39H32Cl2NiO2P2ÁCH2Cl2
C39H32Cl2O2P2PdÁ2(CHCl3)
1010.62
Monoclinic
14.9987(7)
14.8495(3)
19.8687(8)
90.00
96.073(1)
90.00
4400.4(3)
173(2)
C78H64Cl2O4P4Pd2Á2(CF3O3S)Á2(CHCl3)
809.12
Monoclinic
14.9275(10)
15.1626(10)
19.404(2)
90.00
121.036(10)
90.00
3763.2(5)
173(2)
2009.75
Triclinic
15.9078(7)
16.0971(7)
19.9586(9)
86.327(2)
69.724(2)
61.915(2)
4199.2(3)
173(2)
a
(°)
b (°)
(°)
c
Unit cell volume (Å3)
Temperature (K)
ꢀ
Space group
P21/c
P21/c
P1
Number of formula units per unit cell (Z)
4
4
2
Absorption coefficient (
l
/mmÀ1
)
0.919
1.015
0.880
33 646
16 333
0.0599
0.0572
0.1227
0.1138
0.1418
1.032
Number of reflections measured
Number of independent reflections
Rint
22 487
9755
30 999
9605
0.0743
0.0517
0.1156
0.1072
0.1309
0.980
0.0535
0.0594
0.1532
0.1075
0.1772
1.047
Final R1 values (I > 2
r
(I))
r
Final wR(F2) values (I > 2
Final R1 values (all data)
(I))
Final wR (F2) values (all data)
Goodness of fit on F2

4344
C. Li et al. / Inorganica Chimica Acta 363 (2010) 4337–4345
Table 4
Collection and structure refinement data for 6, 7, 8 and 10.
Compound reference
6
7
8
10
Chemical formula
Formula mass
Crystal system
a (Å)
C
39H32Cl2FeO4P2
C39H32Cl2CoO4P2
756.42
C39H32Cl2O4P2Zn
762.86
C27H25Cl2O3PZn
564.71
753.34
Orthorhombic
9.9473(3)
18.6615(8)
19.2969(8)
90.00
Orthorhombic
10.0142(10)
18.4845(11)
19.3294(10)
90.00
Orthorhombic
10.007(4)
18.579(4)
19.247(7)
90.00
Monoclinic
12.4850(4)
19.7120(8)
11.7270(4)
116.369(2)
2585.78(16)
173(2)
b (Å)
c (Å)
b (°)
Unit cell volume (Å3)
Temperature (K)
3582.1(2)
173(2)
3578.0(5)
173(2)
3578.4(2)
173(2)
Space group
Number of formula units per unit cell (Z)
Absorption coefficient (
P212121
4
0.700
P212121
4
0.758
P212121
4
0.965
P21/c
4
1.245
l
/mmÀ1
)
Number of reflections measured
Number of independent reflections
Rint
22 234
7032
15 796
6302
0.1010
0.0830
0.0926
0.1279
0.1012
1.098
7799
7799
0.0611
0.0456
0.0801
0.0875
0.0899
0.955
13 453
5093
0.0836
0.0479
0.1138
0.0832
0.1264
1.010
0.0593
0.0591
0.1415
0.0932
0.1529
1.038
Final R1 values (I > 2
r
(I))
r
Final wR(F2) values (I > 2
Final R1 values (all data)
(I))
Final wR (F2) values (all data)
Goodness of fit on F2
Flack parameter
0.05(3)
À0.02(2)
0.013(10)
C39H32O4P2Cl2Zn (MW = 762.91): C, 61.40; H, 4.23. Found: C, 61.58;
H, 4.47%. Selected IR absorptions: (P@O) 1187(vs), 1167(s, sh).
positions (0.97 Å aliphatic, 0.93 Å aromatic; SHELXS-97 procedures)
and refined riding on the corresponding parent atoms, except those
bound to the oxygen and phosphorus atoms in 10 which were
found in the Fo À Fc maps and refined isotropically.
m
When both reaction and crystallization procedures were per-
formed under argon, complex [ZnCl2(1)] (9) was obtained with a
spectroscopical 95% purity (impurities are 8 and the aforemen-
tioned monoxide, Scheme 5). Spectroscopic data for 9: 1H NMR
(CDCl3): d = 4.39 (triplet like m, 4H, simulated as ABX spin system
(A = B = H; X = P): 2J(A,B) = 5.8 Hz, 3J(A,31P) = 3.6 Hz, 3J(B,31P) =
1.0 Hz; CH2); 7.28–7.88 ppm (m, 28H; aryls); 31P{1H} NMR (CDCl3):
d = 91.2 ppm. 13C{1H} NMR (CD2Cl2): d = 55.2 (t, 3J(13C,31P) = 4.9 Hz;
CH2CCH2), 70.7 (s; CH2), 120.3 (s; fluorene), 126.3 (s; fluorene),
127.5 (s; fluorene), 128.9 (s; p-phenyl fluorene), 129.1 (virtual trip-
let, 3+5J(13C,31P) = 10.7 Hz; m-phenyls), 131.4 (virtual triplet,
2+4J(13C,31P) = 17.0 Hz; o-phenyls), 131.5 (d, 1J(13C,31P) = 25 Hz; i-
phenyls), 132.4 (s; fluorene), 140.6 (s; fluorene), 143.5 (s; fluorene).
The sensitivity of complex 9 prevented the obtention of satisfactory
elemental analyses.
Acknowledgement
This work was supported by the CNRS, the Ministère de l’Ens-
eignement Supérieur et de la Recherche and the Agence Nationale
de la Recherche (ANR-06-BLAN-410). We are grateful to SINOPEC
for supporting Mrs. C. Li.
Appendix A. Supplementary material
CCDC 773099, 773100, 773101, 773102, 773103, 773104 and
773105 contain the supplementary crystallographic data for
2ÁCH2Cl2, 3Á2CHCl2, 5Á2OTfÁ2CHCl3, 6, 7, 8 and 10. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplemen-
tary data associated with this article can be found, in the online
version, at doi:10.1016/j.ica.2010.06.007.
Spectroscopic data for 10: 1H NMR (CD2Cl2): d = 2.89 (br, 2H;
OH), 4.39 (s, 3H; A,B,B overlapped signals of two AB systems),
4.41 (m, 1H; A of one of the aforementioned AB systems, CH2),
7.10–7.95 (m, 18.5H; aryls and masked part of a PH doublet),
9.04 (part of the PH doublet) ppm; 31P{1H} NMR (CDCl3):
d = 31.1 ppm; 13C{1H} NMR (CD2Cl2): d = 57.3 (s; CH2CCH2), 66.4
(s; CH2), 71.0 (s; CH2) 120.0 (s; fluorene), 124.9 (s; fluorene),
127.2 (s; fluorene), 128.0 (s; fluorene), 129.2 (d, 3J(13C,31P) =
13.6 Hz; m-phenyl), 131.3 (d, 2J(13C,31P) = 12.3 Hz; o-phenyls),
131.4 (m; i-phenyls) 133.7 (s, p-phenyls), 131.5 (d, 1J(13C,31P) =
25 Hz; i-phenyls), 132.4 (s; fluorene), 140.6 (s; fluorene), 146.1
(s; fluorene).
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