Synthesis and characterization of Co and Ni complexes stabilized by keto- and acetamide-derived P,O-type phosphine ligands

Article abstract of DOI:10.1039/b814284j

The coordination properties of the β-keto phosphine ligands R ₂PCH₂C(O)Ph (HL¹, R = i-Pr; HL², R = Ph), of the new acetamide-derived phosphine ligand (i-Pr)₂PNHC(O)Me (HL³) and of Ph_2<

Full text of DOI:10.1039/b814284j

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www.rsc.org/dalton | Dalton Transactions
Synthesis and characterization of Co and Ni complexes stabilized by keto-
and acetamide-derived P,O-type phosphine ligands†
Magno Agostinho,a,d Vitor Rosa,b Teresa Avile´s,b Richard Welterc and Pierre Braunstein*a
Received 18th August 2008, Accepted 24th September 2008
First published as an Advance Article on the web 2nd December 2008
DOI: 10.1039/b814284j
The coordination properties of the b-keto phosphine ligands R2PCH2C(O)Ph (HL1, R = i-Pr; HL2,
R = Ph), of the new acetamide-derived phosphine ligand (i-Pr)2PNHC(O)Me (HL3) and of
Ph2PNHC(O)Me (HL4) have been examined towards Ni(II) complexes. Comparisons are made between
systems in which the PCH2 function of the ketophosphine has been replaced with an isoelectronic PNH
group in amide-derived ligands, or the PCH functionality of phosphinoenolates with a PN group in
5
phosphinoiminolate complexes. Furthermore, ligands HL2 and HL4 reacted with [(h -C5H5)CoI2(CO)]
5
to afford the phosphine mono-adducts [(h -C5H5)CoI2{Ph2PCH2C(O)Ph}] (1) and
5
[(h -C5H5)CoI2{Ph2PNHC(O)Me}] (3), respectively, which upon reaction with excess NEt3 yielded the
5
phosphinoenolate complex [(h -C5H5)CoI{Ph2PCH···C(···O)Ph}] (2) and the phosphinoiminolate
5
complex [(h -C5H5)CoI{Ph2PN···C(···O)Me}] (4), respectively. The complexes
cis-[Ni{(i-Pr)2PN···C(···O)Me}2] (6) and cis-[Ni{Ph2PN···C(···O)Me}2] (7) were obtained similarly
from NiCl2 and HL3 and HL4, respectively, in the presence of a base. The phosphinoenolate complex
[Ni{(i-Pr)2PCH···C(···O)Ph}2] (5) exists in ethanol as a mixture of the cis and trans isomers, in contrast
to cis-[Ni{(Ph2PCH···C(···O)Ph}2], and the solid-state structure of the trans isomer of 5 was
established by X-ray diffraction. The structures of the ligand HL3 and of the complexes 1, 3 in
3·3/2CH2Cl2, 4, 6 and 7 have also been determined by X-ray diffraction and are compared with those
of related complexes. Complexes 4, 6 and 7 contain a five-membered heteroatomic metallocyclic moiety,
which is constituted by five different chemical elements. The structural consequences of the steric bulk
of the P substituents and of the electronic characteristics of the P,O chelates are discussed.
The monoanionic, enolate form obtained from the ketophos-
phine ligand Ph2PCH2C(O)Ph generally chelates the metal centre
Introduction
The synthesis of functional phosphine ligands of the P,O-type and
in a P,O mode but monodentate behaviour via the oxygen atom
their complexation to transition metals has been much investigated
has been observed with early transition metals, such as Ti(IV)
and Zr(IV).16 A few examples of bridging situations have also
been encountered, in homo- and heterometallic chemistry.3 The
replacement of the PCH2 group of such ketophosphines with
an isoelectronic PNH group in amide-derived ligands, or of the
PCH functionality of phosphinoenolates with a PN group in
iminolate phosphines, can bring about very interesting electronic
and geometric effects in their respective metal complexes.3,17–21
Here, we report the synthesis and characterization of Co(III)
and Ni(II) complexes containing the neutral b-ketophosphine
ligands (i-Pr)2PCH2C(O)Ph (HL1) and Ph2PCH2C(O)Ph (HL2)22
or the acetamide-derived phosphine ligand (i-Pr)2PNHC(O)Me
(HL3), prepared similarly to Ph2PNHC(O)Me (HL4),18 or the
deprotonated form of these ligands.
during the last few years and their relevance to catalytic reactions
is well documented.1–8 With softer metal ions, P-coordination is
invariably observed, with or without interaction of the neutral
oxygen donor, in a chelating or, much more rarely, a bridging mode,
as found in some Fe–Cd complexes.9 In exceptional cases, the P,O
ligand interacts with the metal solely via the oxygen function, as in
Nb(V), Ta(V) and Mo(V) complexes of the acetamide-derived phos-
phine Ph2PNHC(O)Me.10 In addition to the possible occurrence
of hemilabile behaviour and enhanced catalytic reactivity,6 P,O or
P,N chelates can also lead to reactivity of their metal complexes
different from that observed with symmetrical P,P chelates.11–15
aLaboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177
CNRS), Universite´ Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg
Ce´dex, France
bREQUIMTE, Departamento de Qu´ımica, FCT, Universidade Nova de
Lisboa, 2829-516 Caparica, Portugal
Results and discussion
cLaboratoire DECOMET, Institut de Chimie (UMR 7177 CNRS), Univer-
site´ Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Ce´dex, France
Synthesis and characterization of the ligands
The ligands R2PCH2C(O)Ph (HL1, R = i-Pr; HL2, R = Ph) were
obtained in high yields by the previously reported procedure,1,22
which consists of the reaction of PhCOCH2Li with the correspond-
ing chlorophosphine in THF at low temperature (Scheme 1). In
contrast to HL2, which was obtained as a white solid,22 HL1 is an
dCurrent address: TCI Europe NV , Boerenveldseweg 6, Haven 1063, B-2070
Zwijndrecht, Belgium
† Electronic supplementary information (ESI) available: Additional details
concerning the crystal structures of complexes 1, 4, trans-5, 6 and 7. CCDC
reference numbers 698954–698960. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/b814284j
814 | Dalton Trans., 2009, 814–822
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observed for HL4,18 however, in that case the major tautomer in
CDCl3 solution was the acetamido form HL4 (60%). The suggested
tautomeric equilibrium is solvent dependent: in acetone-d6 the
acetamido forms HL3 and HL4 are favoured, HL4 is even the only
isomer observed. The 1H NMR signals for the CH3 protons of HL3
and HL3¢ occur at d 2.0 and 2.18 ppm, respectively (Table 1). The
13
3
=
C NMR signal of the HN–C O moiety in HL was observed at d
Scheme 1 Synthesis of ligands HL1 and HL2.
3¢
=
172.8 ppm and that of N C–OH in HL at d 177.3 ppm, the latter
showing a JPC coupling of 18.8 Hz. Two different signals were
2
orange liquid that can be exposed to air for short periods of time,
but is best kept under an inert atmosphere (see Experimental).1
In the 1H NMR spectrum of HL1, the PCH2 protons appear as
a doublet (Table 1) and the CH protons of the i-Pr substituents as
a septet of doublets (see Experimental), as in the related phosphi-
observed for the carbon atom of the methyl group, a doublet at d
21.8 (3JPC = 14.8 Hz) and a singlet at 22.7 ppm, corresponding each
to one of the tautomeric forms of the ligand (tentative assignment
in the Experimental).
The solid-state structure of HL3 has been determined by single-
crystal X-ray diffraction. An ORTEP view and a packing diagram
showing the unique hydrogen bond detected24 in this compound
(dH1–O: 2.37(3) A, N–H1–O: 161(3) ) are presented in Fig. 1 and 2,
respectively. The refined crystal structure clearly shows that only
the HL3 tautomer was present in the crystal. The H(1) hydrogen
is unambiguously observed by Fourier differences, whereas no
hydrogen atoms can be stabilized (from spatial position and
electronic density points of view) around the O atom (Fig. 1).
nooxazoline ligand (i-Pr)2PCH2(oxazoline).15 The 31P{ H} NMR
1
spectrum consists of a singlet at d 9.9 ppm and the characteristic
nCO absorption band appears in the IR spectrum at 1673 cm-1.
Comparative spectroscopic data are presented in Table 1.
◦
˚
The acetamido-phosphine (i-Pr)2PNHC(O)Me HL3 has been
synthesized by a similar procedure to that used for Ph2PNHC-
(O)Me (HL4),18 by condensation of N-trimethylsilylacetamide
with the corresponding chlorophosphine in toluene (Scheme 2).
Scheme 2 Synthesis of the ligands HL3 and HL4.
In contrast to HL1 and HL2, the 31P{ H} NMR (CDCl3)
1
Fig. 1 ORTEP view of ligand HL3 (hydrogen atoms have been omitted
for clarity, except H(1) on the nitrogen atom found by Fourier differences).
Displacement ellipsoids are drawn at 50% probability level.
spectrum of HL3 contains two signals at d 47.7 and 57.5 ppm
(ratio 20 : 80). This is explained by the existence of a tautomeric
equilibrium between the acetamido and the iminol forms HL3 and
3¢
=
HL , respectively (Scheme 2). The N C double bond having a
deshielding effect on the adjacent atoms, the 31P{ H} signal of HL3¢
1
Cobalt complexes
is expected to occur at lower field than that of HL3. We therefore
assign the signal at d 57.5 ppm (major tautomer, ca. 80%) to the
iminol form HL3¢. An equilibrium of this type has already been
5
The reaction between [(h -C5H5)CoI2(CO)] and Ph2PCH2C(O)Ph
(HL2) in toluene resulted in the cleavage of the Co–CO bond to
Table 1 Selected, comparative IR and NMR data for the ligands and complexes
NMRc
1
IR
1H
31P{ H}
HL1
1673b (s, nCO
1670a (s, nCO
1695a (s, nCO
—
)
)
)
3.11 (d, 2JPH = 1.3 Hz, 2H, PCH2)
9.9
-17.1
47.7
57.5
21.6
31.1
34.6
60.6
70.7
111.1
28.2
—
HL2
3.80 (s, 2H, PCH2)
HL3
2.00 (s, 3H, MeC( O)), 5.54 (br, 1H, NH)
=
HL3¢
2.18 (d, 4JPH = 2.7 Hz, MeC(OH)), 2.08 (br, 1H, OH)
HL4
1715b (s, nCO
—
)
)
2.13 (s, 3H, MeC( O)), 6.15 (br, 1H, NH)
=
HL4¢
2.30 (s, 3H, MeC(OH)), OH not observed
4.54 (d, 2JPH = 9.7 Hz, 2H, PCH2)
5.02 (s, 1H, PCH)
1
1671a (s, nCO
2
1518a (s, nCC + CO
)
3
1699a (s, nCO
)
1.20 (s, 3H, Me), 6.30 (d, 2JPH = 16.7 Hz, 1H, NH)
4
1487a (s, nCN + CO
1515a (s, nCC + CO
1517a (s, nCC + CO
)
)
)
2.19 (s, 3H, Me)
cis-Ni(L2)2
4.55 (s, 2H, PCH)
—
23
5
6
1519 (s, nCN + CO
)
1.26 (dd, 3JPH = 14.5 Hz, 3JHH = 7 Hz, 12H, Me i-Pr)
1.38 (dd, 3JPH = 17.1 Hz, 3JHH = 7.2 Hz, 12H, Me
i-Pr), 2.16 (s, MeCO)
115.9
7
1439a (s, nCN + CO
)
3.76 (d, 4JPH = 11.1 Hz, 6H, Me)
34.4
a In KBr. b In CH2Cl2, cm-1. c In CDCl3, ppm, J in Hz.
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with a p–p interaction between them (see dashed line in Fig. 3).
Intermolecular interactions are given in the ESI.†
The treatment of 1 with excess triethylamine yielded the
5
phosphinoenolate complex [(h -C5H5)CoI(L2)] (2) as a dark solid
(Scheme 3). The IR spectrum confirmed the coordination of the
oxygen enolate to the metal center (nCC+CO = 1518 cm-1). The
1
31P{ H} NMR resonance of 2 at d 60.6 ppm is shifted 26 ppm
downfield to that for the corresponding phosphine complex 1.
5
The reaction between [(h -C5H5)CoI2(CO)] and the
(diphenylphosphino)acetamide ligand HL4 in toluene resulted in
Fig. 2 Crystal packing diagram of ligand HL3 showing the N–H ◊ ◊ ◊ O
hydrogen bonding. Symmetry code for equivalent positions: x, -y + 1/2,
z - 1/2. Dashed lines indicate the hydrogen bonds.
the cleavage of the Co–CO bond and afforded the P mono-aduct
5
complex [(h -C5H5)CoI2(HL4)] (3), as a dark purple crystalline
solid (Scheme 4).
5
afford the phosphine mono-adduct [(h -C5H5)CoI2(HL2)] (1), as a
dark blue solid (Scheme 3).
Scheme 4 Synthesis of complexes 3 and 4.
Its IR spectrum confirmed that the acetamide group was not
coordinated to the metal centre (nCO = 1699 cm-1 for 3 vs. 1715 cm-1
Scheme 3 Synthesis of complexes 1 and 2.
1
for the free ligand).18 The 31P{ H} NMR spectrum of 3 shows a
peak at d 70.7 ppm, which corresponds to a downfield shift of
49 ppm relative to the free ligand (d 21.6 ppm).18 The acetamide
NH proton was observed in the 1H NMR spectrum at d 6.30 ppm
and the methyl protons at d 1.20 ppm (Table 1). The solid-state
structure of 3 was determined by X-ray diffraction and an ORTEP
view is shown in Fig. 4 (selected distances and angles are given in
the caption).
The 31P{ H} NMR spectrum of 1 displays a resonance at
1
d 34.6 ppm, shifted ca. 52 ppm downfield of the free phosphine
(d -17.1 ppm),22 consistent with the coordination of the phos-
phorus to a cobalt centre.25 The methylene protons were observed
1
to be magnetically equivalent, giving rise to a doublet in the H
NMR spectrum (d = 4.54, 2JPH = 9.7, Table 1). The IR spectrum
confirmed that the carbonyl group of the ketophosphine was not
coordinated to the metal centre (nCO = 1671 cm-1 for 1 vs. 1670 cm-1
for the free ligand, Table 1).22 The solid-state structure of 1 was
determined by X-ray diffraction and an ORTEP view is shown in
Fig. 3 (selected distances and angles are given in the caption). The
˚
distance of 3.74(1) A between the centroids of the C(3)–C(8) and
C(9)–C(14) phenyl rings and the dihedral angle of 21(1)◦ between
the least-squares planes through these phenyl rings are consistent
Fig. 4 ORTEP view of a pseudo-dimer of complexes 3 in 3·3/2(CH2Cl2)
(the hydrogen atoms have been omitted for clarity). Displacement el-
lipsoids are drawn at 50% probability level. Symmetry operator * for
˚
equivalent positions: 2 - x, -1 - y, 1 - z. Selected distances (A) and
angles (◦): Co1–I1, 2.596(1), Co1–I2, 2.577(1), Co1–P1, 2.198(2), P1–N1,
1.71(1), N1–C1, 1.36(1), C1–O1, 1.22(1); I1–Co1–I2, 93.3(1), N1–P1–Co1,
109.8(2), C9–P1–C3, 106.2(3).
Two quasi-identical molecules of complex 3 crystallize in the
asymmetric unit. Only one of them is described (more information
concerning this crystal structure is available from the cif file given
in the ESI†). The dihedral angle between the least squares planes
through the phenyl rings C(3)–C(8) and C(9)–C(14) is 62(1)◦, a
Fig. 3 ORTEP view of complex 1 (the hydrogen atoms have been omitted
for clarity). Displacement ellipsoids are drawn at the 50% probability
◦
˚
level. Selected distances (A) and angles ( ): Co1–I1, 2.593(1), Co1–I2,
2.569(1), Co1–P1, 2.231(1), P1–C1, 1.85(1), C1–C2, 1.51(1), O1–C2,
1.21(1); P1–Co1–I2, 88.9(1), C1–P1–Co1, 114.4(1), C9–P1–C15, 105.6(1).
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value very close to that found in complex 1. A p–p intermolecular
interaction is observed between the two cyclopentadienyl rings
˚
C(15)–C(19) with a distance between the centroids of 3.31(1) A.
This situation allows us to describe this crystal structure as that
of pseudo-dimers, as shown in Fig. 4. These pseudo-dimers are
connected to each other by some CH–p interactions and numerous
van der Waals contacts but no classical hydrogen bond has been
found in this structure.
Treatment of 3 with excess triethylamine yielded the chelated
5
phosphinoiminolate complex [(h -C5H5)CoI(L4)] (4) as a dark
solid (Scheme 4). The IR spectrum confirmed that the oxygen
atom was now coordinated to the metal centre (nCN+CO = 1487 cm-1,
Table 1). The solid state structure of 4 was also determined by X-
ray diffraction and an ORTEP view of its molecular structure is
shown in Fig. 5 (selected distances and angles are given in the
caption).
Scheme 5 Synthesis of complex 5 and solution equilibrium between the
cis and trans isomers.
ORTEP view is shown in Fig. 6 and selected bond distances and
angles are given in the caption.
Fig. 5 ORTEP view of complex 4 (hydrogen atoms omitted for clarity).
Displacement ellipsoids are drawn at 50% probability level. Selected
◦
˚
distances (A) and angles ( ): Co1–I1, 2.572(1), Co1–O1, 1.924(2), Co1–P1,
2.190(1), P1–N1, 1.676(2), N1–C1, 1.32(1), C1–O1, 1.29(1); O1–Co1–P1,
82.6(1), I1–Co1–P1, 94.45(2), N1–P1–Co1, 102.2(1), C9–P1–C3, 102.1(2).
Fig. 6 ORTEP view of complex trans-5 (the hydrogen atoms have
been omitted for clarity). Displacement ellipsoids are drawn at the 50%
probability level. Symmetry code f◦or equivalent positions *: -x, 2 - y, -z.
˚
The crystal structure confirms that a five-membered het-
eroatomic ring has been formed which contains five different
chemical elements. This ring is almost planar with a maximum
Selected distances (A) and angles ( ): Ni1–O1, 1.850(1), Ni1–P1, 2.199(1),
P1–C3, 1.769(2), C2–C3, 1.354(3), C2–O1, 1.32(1), C2–C1, 1.49(1), P1–C4,
1.836(2), P1–C5, 1.841(2); O1–Ni1–P1, 87.0(1); O1–Ni1–O1*, 180.0(1),
C3–P1–Ni1, 97.9(1), C2–O1–Ni1, 119.4(2), O1–C2–C3, 123.0(2).
˚
deviation out of the ring of 0.03 A for Co(1) and P(1). Additional
structural information is provided in the ESI.†
The crystal structure clearly reveals the square planar coordi-
nation environment of the nickel centre, which lies on the crystal-
lographic inversion centre. The five-membered heteroatomic ring
Ni(1)–P(1)–C(3)–C(2)–O(1) is almost planar, with a maximum
Nickel complexes
Complex [Ni(L1)2] (5) was obtained from HL1 as a mixture of
the cis and trans isomers, which are in equilibrium in solution
(Scheme 5).26
˚
deviation out of the least-squares plane of +0.31(1) A and -0.30(1)
˚
A for Ni(1) and P(1), respectively. Other structural data are given
The formation of both isomers can be explained by opposite
steric and electronic effects, the former favouring the trans-
arrangement and the latter a cis-arrangement owing to the
de-stabilizing effect on each other of two mutually trans soft
phosphorus donor atoms.27,28 The cis isomer has been shown to
be a precursor to heterometallic complexes when acting as an
O,O-chelate toward Co(II) ions.26 Slow diffusion of hexane into
a CH2Cl2 solution of the isomers afforded crystals suitable for
X-diffraction, which revealed to be those of the trans-5 isomer. An
in the ESI.†
In contrast to the equilibrium found with 5, the t-Bu-substituted
analogue [Ni{(t-Bu2PCH···C(···O)Ph}2] was observed only as the
trans isomer, but no crystal structure was reported,29 whereas
the phenyl derivative [Ni{(Ph2PCH···C(···O)Ph}2] forms the cis
isomer.23,30 The latter was also obtained by reacting the ylide
Ph3PCHC(O)Ph with [Ni(COD)2] in the presence of AsPh3.30
The complex [Ni{(Ph2PCH···C(···O)Ph}2] corresponds to the
deactivated form of SHOP-type catalysts but can be converted
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to an active ethylene homo-polymerization catalyst by alkylation
with trimethylaluminum.31,32
plane of +0.027(1) and -0.026(2) for Ni(1) and O(1), respectively
(some CH–p interactions are provided in the ESI†).
The reaction of HL3 with NiCl2·6H2O in ethanol followed by
the addition of NaOEt afforded cis-[Ni(L3)2] (6) (Scheme 6). Its
IR spectrum confirmed that the oxygen atom was coordinated to
The reaction of HL4 with NiCl2 in methanol, in the presence
1
of NaOMe, afforded cis-[Ni(L4)2] (7) (Scheme 7). Its 31P{ H}
NMR resonance is shifted ca. 13 ppm downfield of that of the
free ligand (d 21.6 ppm).18 The IR spectrum confirmed that the
1
the metal centre (nCN+CO = 1519 cm-1, Table 1). The 31P{ H} NMR
spectrum displayed a single resonance at d = 115.9 ppm, indicating
the presence of only one isomer. As expected, the CH3 protons of
the i-Pr substituents of the phosphorus appear as two doublets of
doublets. The multiplet assigned to the i-PrCH was not sufficiently
well resolved to allow a determination of the JHH and JPH
coupling constants. A crystal structure determination established
the cis geometry of 6, although steric effects were expected to
favour a trans-arrangement. Electronic effects favouring the cis-
arrangement appear in this case to be dominant.28,33
iminolate oxygen atom is coordinated to the metal centre (nCN+CO
=
1439 cm-1, Table 1).
Scheme 7 Synthesis of complex 7.
The solid-state structure of 7 was determined by single-crystal
X-ray diffraction, an ORTEP view of its molecular structure is
shown in Fig. 8 and selected distances and angles are given in the
caption.
Scheme 6 Synthesis of complex 6.
An ORTEP view of cis-[Ni(L3)2] (6) is shown in Fig. 7 and
selected distances and angles are given in the caption. The nickel
atom is in a square-planar coordination environment and lies
on the crystallographic twofold axis (space group C2/c). The
five-membered heteroatomic ring Ni(1)–O(1)–C(2)–N(1)–P(1) is
almost planar with a maximum deviation out of the least-squares
Fig. 8 ORTEP view of complex 7 (the hydrogen atoms have been omitted
for clarity). Displacement ellipsoids are drawn at the 50% probability level.
Symmetry code for equivalent positions *: 1 - x, y, 1/2 - z. Selected
◦
˚
distances (A) and angles ( ): Ni1–O1, 1.891(1); Ni1–P1, 2.153(1), P1–C3,
1.816(2); P1–C9, 1.805(2); P1–N1, 1.686(2); C2–O1, 1.299(2); C1–C2,
1.497(3); C2–N1, 1.313(3); P1–Ni1–P1*, 105.2(1); O1–Ni1–O1*, 87.8(1);
P1–Ni1–O1, 171.3(1); C2–O1–Ni1, 118.0(1); O1–C2–C1, 125.0(2).
The nickel atom has a square planar coordination and lies on the
crystallographic twofold axis. The five-membered heteroatomic
ring Ni(1)–O(1)–C(2)–N(1)–P(1) is almost planar with a maxi-
mum deviation out of the least-squares plane of +0.065(1) and
-0.071(1) for Ni(1) and P(1), respectively. Three significant CH–p
interactions (and their equivalents by symmetry operators) have
been identified in the crystal packing and are given in Table 2.
Fig. 7 ORTEP view of complex 6 (hydrogen atoms omitted for clarity).
Displacement ellipsoids are drawn at the 50% probability level. Sym-
metry code for equivalent positions *: -x + 2, y, -z + 3/2. Selected
◦
˚
distances (A) and angles ( ): Ni1–O1, 1.887(2), Ni1–P1, 2.175(1), P1–C3,
1.831(2), P1–C6, 1.841(2), P1–N1 1.690(2), C1–O1, 1.291(2), C1–C2,
1.502(3), C1–N1, 1.302(3); P1–Ni1–P1* 109.4(1), O1–Ni1–O1*, 85.2(1),
P1–Ni1–O1, 166.2(1), C1–O1–Ni1, 118.5(1), O1–C1–N1, 125.7(2).
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Table 2 Significant CH–p interactions in cis-[Ni(L4)2] (7)
X–H ◊ ◊ ◊ Centroid/◦
˚
X–H
→Ring
[Equiv. position]
H ◊ ◊ ◊ Centroid/A
C(4)–H(4)
C(6)–H(6)
C(12)–H(12)
C(9)/C(14)
Ni(1)/P(1)
C(3)/C(8)
[1 - x, y, 1/2 - z]
[1/2 + x, -1/2 + y, z]
[-1/2 + x, -1/2 + y, z]
2.954
2.848
2.860
113.23
159.57
136.78
[(h -C5H5)CoI2(CO)]35 and [Ni{(i-Pr)2PCH···C(···O)Ph}2] (5).26
5
Conclusion
Other chemicals were commercially available and used as received.
We have performed a comparative study of the coordination
properties of neutral functional phosphine ligands containing a
ketone or an amide function and of the corresponding anionic P,O
ligands obtained by deprotonation of the CH2 or the NH group in
a-position to the P donor, respectively. We have also examined the
steric influence of the P substituents, phenyl or isopropyl, on the
structure of the resulting complexes. The known b-ketophosphine
ligands R2PCH2C(O)Ph (HL1, R = i-Pr; HL2, R = Ph) and the new
acetamide-derived phosphine ligand (i-Pr)2PNHC(O)Me (HL3),
prepared similarly to Ph2PNHC(O)Me (HL4) allowed systematic
comparisons to be made. Ligands HL2 and HL4 reacted with the
Preparation and spectroscopic data for (i-Pr)2PCH2C(O)Ph (HL1)
Ligand HL1 was prepared similarly to Ph2PCH2C(O)Ph (HL2),22
but starting from acetophenone and (i-Pr)2PCl, and was obtained
as a clear orange liquid. Additional analytical data to those
1
initially reported:1 IR (CH2Cl2) n/cm-1: 1673 (s, nCO) cm-1. H
NMR (300.13 MHz, CDCl3, room temp.) d/ppm: 1.08 [dd, 3JPH
=
=
=
3
3
5.7 Hz, JHH = 7.1 Hz, 6H, (CH(CH3)(CH3))2], 1.12 [dd, JPH
3.3 Hz, 3JHH = 7.1 Hz, 6H, (CH(CH3)(CH3))2], 1.83 [septd, 2JPH
1.0 Hz, 3JHH = 7.1 Hz, 2H, (CH(CH3)2)2], 3.11 (d, 2JPH = 1.3 Hz,
5
cobalt cyclopentadienyl complex [(h -C5H5)CoI2(CO)] to afford
5
2H, PCH2), 7.40–7.55 (complex m, 3H, aromatic), 7.91–8.02 (m,
the phosphine mono-adducts [(h -C5H5)CoI2{Ph2PCH2C(O)Ph}]
1
2H, aromatic). 13C{ H} (CDCl3, room temp.) d/ppm: 18.8 [d,
5
(1) and [(h -C5H5)CoI2{Ph2PNHC(O)Me}] (3), respectively.
2
2JPC = 10.5 Hz, (CH(CH3)(CH3))2], 19.6 [d, JPC = 15.5 Hz,
No chelation of the neutral P,O ligands was observed
but the treatment of these complexes with excess NEt3
yielded the chelated phosphinoenolate and phosphinoiminolate
1
(CH(CH3)(CH3))2], 24.1 [d, JPC = 15.3 Hz, (CH(CH3)2)2], 34.6
1
(d, JPC = 29.8 Hz, PCH2), 128.3–137.0 (aromatics), 199.5 [d,
1
2JPC = 8.2 Hz, C(O)]. 31P{ H} NMR (CDCl3, room temp.) d/ppm:
5
5
complexes [(h -C5H5)CoI{Ph2PCH···C(···O)Ph}] (2) and [(h -
C5H5) CoI{Ph2PN···C(···O)Me}] (4), respectively. The chelate
ring of the latter contains five different chemical elements.
Both HL3 and HL4 reacted with NiCl2 in the presence of
base to give the cis isomers of the square-planar phosphinoimi-
nolate complexes cis-[Ni{(i-Pr)2PN···C(···O)Me}2] (6) and cis-
[Ni{Ph2PN···C(···O)Me}2] (7), respectively. In contrast, the phos-
phinoenolate complex [Ni{(i-Pr)2PCH···C(···O)Ph}2] (5) exists
in solution as a mixture of cis and trans isomers and a crystal
structure of the trans isomer was determined by X-ray diffraction.
Previous work has shown that transition metal complexes
containing a phosphino-enolate or iminolate function react
with electrophilic metal centres at the Cenolate or Niminolate atoms,
respectively, leading to heterometallic complexes and unique
coordination polymers.3,20,21 The complexes reported in this work,
therefore represent interesting candidates to extend such studies.
9.9 (s).
Preparation and spectroscopic data for (i-Pr)2PNHC(O)Ph (HL3)
P(i-Pr)2C1 (0.882 g, 5.78 mmol) was added to a solution of
MeC(O)NHSiMe3 (0.759 g, 5.78 mmol) in toluene (20 mL), and
the mixture was placed under vacuum for 30 s, before being heated
to 60 ◦C. The mixture was placed under vacuum for 10 s every 5 min
in order to eliminate SiClMe3, which was formed. After 30 min, the
solution was allowed to cool to ambient temperature. The solvent
was then evaporated under reduced pressure and the residue thus
obtained was dried under vacuum overnight. A crystalline material
with a melting point clos◦e to room temperature was obtained,
keeping this material at 5 C overnight afforded suitable crystals
for X-ray diffraction. Overall yield: 0.700 g (69%). HL3 is soluble in
most common organic solvents (including petroleum ether) and
therefore it was difficult to purify, however, the crude product
could be used for metal complexation and the resulting complexes
Experimental
1
were easier to purify. IR (KBr) n/cm-1: 1695 (s, nCO). H NMR
1
1
1
3
3
The H, 13C{ H} and 31P{ H} NMR spectra were recorded at
300.13, 75.48 and 121.49 MHz, respectively, on a FT Bruker
AC300 Avance 300 instrument, unless otherwise stated. Coupling
constants are given in absolute values. IR spectra, in the range
4000–400 cm-1, were recorded on a Bruker IFS66FT or a Perkin
Elmer 1600 Series FTIR. Elemental analyses were performed by
the Service de Microanalyse, Universite´ Louis Pasteur (Stras-
bourg, France). All reactions were carried out under purified N2,
using Schlenk techniques, and the solvents were freshly distilled
under nitrogen prior to use. The ligands HL2,22 and HL4,18,34 were
prepared according to literature procedures, as were the complexes
(CDCl3, room temp.) d/ppm: 1.02 [dd, JPH = 0.9 Hz, JHH
=
=
=
3
3
7.0 Hz, 6H, (CH(CH3)(CH3))2], 1.07 [dd, JPH = 4.2 Hz, JHH
7.0 Hz, 6H, (CH(CH3)(CH3))2], 1.72 [septd, 2JPH = 2.4 Hz, 3JHH
=
7.0 Hz, 2H, (CH(CH3)2)2], 2.00 [s, CH3C( O)], 2.08 (br, OH),
4
2.18 [d, JPH = 2.7 Hz, CH3C(OH)], 5.54 (br, NH), see text.
13C{ H} (CDCl3, room temp.) d/ppm: 16.9 [d, JPC = 7.8 Hz,
1
2
2
(CH(CH3)(CH3))2], 18.3 [d, JPC = 19.8 Hz, (CH(CH3)(CH3))2],
3
=
21.8 [d, JPC = 14.8 Hz, CH3C(OH)], 22.7 [s, CH3C( O)N], 25.9
[d, 1JPC = 12.1 Hz, (CH(CH3)2)2], 172.8 [s, C(O)], 177.3 [d, 2JPC
=
18.8 Hz, NC(OH)]. 31P{ H} NMR (CDCl3, room temp.) d/ppm:
1
47.7 (s, minor isomer 20% HL3), 57.5 (s, major isomer 80%, HL3¢).
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Dalton Trans., 2009, 814–822 | 819
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Preparation and spectroscopic data for
111.1 (s). Anal. calcd for C18H19CoINOP: C 46.27, H 3.68, N 2.84.
Found: C, 46.00 H, 3.90, N 2.60.
[(g5-C5H5)CoI2{Ph2PCH2C(O)Ph}] (1)
5
The complex [(h -C5H5)CoI2(CO)] (0.750 g, 1.85 mmol) was
Preparation and spectroscopic data for
cis-[Ni(i-Pr)2PN···C(···O)Me}2 (6)
suspended in toluene (50 mL) and HL2 (0.560 g, 1.84 mmol) was
added. The reaction mixture was stirred at room temperature for
1 h. The solvent was then evaporated under reduced pressure
affording a dark blue residue. The latter was washed with
diethylether (5 mL) and pentane (2 ¥ 10 mL) and dried under
vacuum (dark blue powder, 1.16 g, 92%). IR (KBr) n/cm-1:
A mixture of NiCl2·6H2O (0.200 g, 0.85 mmol) and HL3 (0.300 g,
1.71 mmol) was dissolved in ethanol (20 mL) to give a dark green
solution. After it was stirred for 1 h, a solution of NaOEt (prepared
from 0.040 g of Na and 10 mL of ethanol) was slowly added
(20 min) and the colour changed to light green-yellow. After
further stirring for 1 h, the colour of the solution changed to
yellow-orange. The solvent was removed under reduced pressure
and the orange solid was extracted with dry toluene to give an
orange solution, which was filtered in order to remove NaCl, and
pentane was added. The mixture was left in the fridge overnight to
give compound 6 as yellow crystals (0.210 g, 0.515 mmol, 60%). IR
n/cm-1: 1519 (s, nCN+CO). 1H NMR (CDCl3, room temp.) d/ppm:
1.26 (dd, 3JPH = 14.5 Hz, 3JHH = 7 Hz, 12H, (CH(CH3)(CH3))2),
1
1671 (s, nCO). H NMR (CDCl3, room temp.) d/ppm: 4.54 (d,
2JPH = 9.7 Hz, 2H, PCH2), 5.06 (s, 5H, C5H5), 7.17 (t, J =
7.6 Hz, 2H, aromatic), 7.31–7.45 (complex m, 7H, aromatic),
7.57 (d, J = 7.6 Hz, 2H, aromatic), 8.07 (t, J = 8.9 Hz, 4H,
1
aromatic). 31P{ H} NMR (CDCl3, room temp.) d/ppm: 34.6 (s).
Anal. calcd for C25H22CoI2OP: C 44.02, H 3.25. Found: C 44.30,
H 3.30.
Preparation and spectroscopic data for
1.38 (dd, 3JPH = 17.1 Hz, 3JHH = 7.2 Hz, 12H, (CH(CH3)(CH3))2,
[(g5-C5H5)CoI{Ph2PCH···C(···O)Ph}] (2)
1.97–2.07 (m, 4H, i-PrCH), 2.16 (s, 6H, MeC N). 31P{ H} NMR
1
=
To a solution of complex 1 (0.124 g, 0.18 mmol) in toluene
(20 mL) was added excess NEt3 (1.00 mL, 7.12 mmol). The
reaction mixture was stirred at room temperature for 1 h. The
solution was then filtered through dry Celite and the solvent
evaporated under reduced pressure. The residue was washed
with diethylether (5 mL) and pentane (2 ¥ 10 mL) and dried
under vacuum overnight. Complex 2 was obtained as a black
solid (0.074 g, 73%). IR (KBr) n/cm-1: 1518 (s, nCC+CO). 1H
NMR (CDCl3, room temp.) d/ppm: 5.02 (s, 1H, PCH), 5.16 (s,
5H, C5H5), 7.26–7.29 (m, 2H, aromatic), 7.44–7.52 (complex m,
7H, aromatic), 7.63–7.73 (m, 4H, aromatic), 7.82–7.88 (m, 2H,
(121.49 MHz, CDCl3, room temp.) d/ppm: 115.9 (s). Anal. calcd
for C16H34N2NiO2P2·1/2H2O: C 46.18, H 8.48, N 6.73. Found: C
46.16, H 8.32, N 6.53.
Preparation and spectroscopic data for
cis-[Ni{Ph2PN···C(···O)Me}2] (7)
NaOMe (0.030 g, 0.564 mmol) was dissolved in the minimum
amount of methanol and a solution of HL4 (0.135 g, 0.555 mmol)
in dichloromethane (15 mL) was added. Anhydrous NiCl2 (0.036 g,
0.278 mmol) was then added and the yellow solution thus obtained
was stirred at ambient temperature for 48 h. After removal of the
solvent under reduced pressure, the yellow residue was treated with
toluene, and the solution was filtered in order to remove NaCl.
The toluene was then evaporated under reduced pressure and the
complex washed with cold petroleum ether (0.132 g, 0.243 mmol,
87%). IR (KBr) n/cm-1: 1439 (s, nCN+CO). 1H NMR (CDCl3, room
1
aromatic). 31P{ H} NMR (CDCl3, room temp.) d/ppm: 60.6 (s).
Anal. calcd for C25H21CoIOP: C 54.18, H 3.82. Found: C 53.89,
H 3.97.
Preparation and spectroscopic data for
[(g5-C5H5)CoI2{Ph2PNHC(O)Me}] (3)
4
temp.) d/ppm: 3.76 (d, JPH = 11.1 Hz, 6H, CH3), 7.42–7.56
(complex m, 6H, aromatic), 7.77–7.85 (m, 4H, aromatic). 31P{ H}
1
Complex 3 was obtained using a similar procedure to that
5
described above for 1, starting from [(h -C5H5)CoI2(CO)] (0.120 g,
NMR (CDCl3, room temp.) d/ppm: 34.4 (s). Anal. calcd for
C28H26N2NiO2P2: C 61.92, H 4.82, N 5.16. Found: C 62.11, H
4.95, N 4.99.
0.30 mmol) and HL4 (0.073 g, 0.30 mmol). It was obtained as a
dark purple crystalline solid (0.151 g, 81%). IR (KBr) n/cm-1: 1699
(s, nCO). 1H NMR (CDCl3, room temp.) d/ppm: 1.20 (s, 3H, CH3),
2
5.08 (s, 5H, C5H5), 6.30 (d, JPH = 16.7 Hz, 1H, NH), 7.47–7.57
Crystal structure determinations
(complex m, 6H, aromatic), 8.07–8.16 (complex m, 4H, aromatic).
Crystals of HL3 suitable for X-ray diffraction were obtained by
placing a Schlenk tube with the ligand at 5 ◦C overnight. Crystals
of 1, 3·3/2(CH2Cl2), 4, 5 and 7 were obtained by slow diffusion
of hexane into a CH2Cl2 solution of the respective complex at
1
31P{ H} NMR (CDCl3, room temp.) d/ppm: 70.7 (s). Anal. calcd
for C19H19CoI2NOP: C 36.74, H 3.08, N 2.26. Found: C 36.84, H
3.10, N 2.20.
5
◦C. Crystals of 6 were obtained from a mixture of toluene–
Preparation and spectroscopic data for
pentane at -25 ◦C overnight. Diffraction data were collected
[(g5-C5H5)CoI{Ph2PN···C(···O)Me}] (4)
on a Kappa CCD diffractometer using graphite-monochromated
˚
Complex 4 was obtained using a similar procedure to that
described above for 2, starting from 3 (0.176 g, 0.28 mmol) and
NEt3 (1.00 mL, 7.12 mmol). It was obtained has a dark purple
solid (0.113 g, 81%). IR (KBr) n/cm-1: 1487 (s, nCN+CO). 1H NMR
MoKa radiation (l = 0.71073 A) (Table 3). Data were collected
using phi-scans and the structures were solved by direct methods
using the SHELXL-97 software,36–38 and the refinement was per-
formed by full-matrix least squares on F2. The absorption was not
corrected. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were generated according to stereochemistry and
refined using a riding model in SHELXL-97.
5
(CDCl3, room temp.) d/ppm: 2.19 (s, 3H, CH3), 5.09 (s, 5H, h -
C5H5), 7.45–7.55 (complex m, 8H, aromatic), 7.93–8.01 (complex
1
m, 2H, aromatic). 31P{ H} NMR (CDCl3, room temp.) d/ppm:
820 | Dalton Trans., 2009, 814–822
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Dalton Trans., 2009, 814–822 | 821
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14 M. Agostinho and P. Braunstein, Chem. Commun., 2007, 58–60.
Acknowledgements
15 M. Agostinho and P. Braunstein, C. R. Chimie, 2007, 10, 666–676.
16 C. Mattheis, P. Braunstein and A. Fischer, J. Chem. Soc., Dalton Trans.,
2001, 800.
We thank Dr Andre´ DeCian (ULP Strasbourg) for his contribu-
tion to the crystal structure determinations, Dr Xavier Morise
for discussions, and Jonathan Kirsch and Anne Degre´mont
(LCC) for their experimental contribution. We are also grateful
to the European Commission (Palladium Network HPRN-CT-
2002-00196), the Centre National de la Recherche Scientifique
(France), the Ministe`re de la Recherche (Paris), and the CPU
(France) and CRUP (Portugal) (Portuguese-French Integrated
Action-2006, N◦ F-27/07) for financial support. We also thank
the Fundac¸a˜o para a Cieˆncia e Tecnologia, Portugal, for funding
(Project PTDC/QUI/66440/2006) and for a doctoral fellowship
to V.R. (SFRH/BD/13777/2003).
17 T. Q. Ly, A. M. Z. Slawin and J. D. Woollins, Polyhedron, 1999, 18,
1761–1766.
18 P. Braunstein, C. Frison, X. Morise and R. D. Adams, J. Chem. Soc.,
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19 P. Bhattacharyya, T. Q. Ly, A. M. Z. Slawin and D. J. Woollins,
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20 P. Braunstein, C. Frison, N. Oberbeckmann-Winter, X. Morise, A.
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21 N. Oberbeckmann-Winter, P. Braunstein and R. Welter,
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22 S. E. Bouaoud, P. Braunstein, D. Grandjean, D. Matt and D. Nobel,
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822 | Dalton Trans., 2009, 814–822
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©