Reactivity of alpha phosphino enolate complexes of nickel(II) and palladium(II) toward electrophilic metal centers. Synthesis and crystal structures of the bimetallic palladium(II)-gold(I) complex (4a) and of the nickel(II)-cobalt(II) paramagnetic complex (5b) (see abstract)

Article abstract of DOI:10.1021/ic9513494

The chemoselective reactivity of metal-coordinated phosphino enolates has been studied by the reactions of cis-[Ni?{R′₂PCH?C(?O)R}₂] (R = Ph, p-C₆H₄Me, Me; R′ = Ph, ⁱPr, not all combinations) and [(C N)- Pd{Ph₂PCH?C(?O})Ph}] (C N = o-C₆H₄CH₂NMe₂, dmba or C₁₀H₈N, 8-mq) with different metal electrophiles. In the reaction of cis-[Ni{Ph₂PCH?C(?O)Ph}₂] (1a) with [PtCl₂(COD)] (COD = 1,5-cyclooctadiene), a transmetalation of the P,O ligands was observed, yielding the known complex cis-[Pt{Ph₂PCH?C-(?O)Ph}₂] (3). However, reaction of cis-[Ni{R′₂PCH?C(?O)R}₂] with anhydrous CoI₂ afforded the heterobinuclear complexes cis-[Ni{R′₂PCH?C(?O)R}₂]CoI₂ (5a, R = Ph, R' = Ph; 5b, R = p-C₆H₄Me, R' = Ph; 5c, R = Me, R' = Ph; 7, R = Ph, R' = ⁱPr) which contain the phosphino enolate ligand in an unusual chelating-bridging μ-η¹(O):η²(P,O) coordination mode in a nonplanar NiO₂Co unit. The magnetic properties of these complexes are discussed. The SHOP-type catalyst [Ni(Ph){Ph₂PCH?C(?O)Ph}(PPh₃)] also behaved as an oxygen-donor metalloligand toward CoI₂ to give a paramagnetic Co(II) complex. In contrast, reaction of [(C N)Pd{Ph₂PCH?C(?O)Ph}] with [Au(PPh₃)]⁺ occurred with formation of [(dmba)-Pd{Ph₂PCH(AuPPh₃)C(O)Ph}](BF₄) (4a) in which a C_enolate-Au bond has been formed while the P,O chelate has remained coordinated to palladium. This reaction generates a new stereogenic center, as also evidenced by ¹H NMR spectroscopy. The solid state structures of complexes 4a·1/2C₇H₈ and 5b·CH₂Cl₂ have been determined by single-crystal X-ray diffraction: 4a·1/2C₇H₈ crystallizes in the triclinic space group P1? with Z = 2 in a unit cell of dimensions a = 16.778(4) A?, b= 14.269(5) A?, c = 10.838(6) A?, α = 79.27(4)°, β= 71.59(3)°, and γ = 72.68(2)°; 5·CH₂Cl₂ crystallizes in the monoclinic space group P2₁ln with Z = 4 in a unit cell of dimensions a = 12.940(1) A?, b = 18.329(2) A?, c = 18.495(2) A?, and β= 91.627(8)°. The structures have been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least-squares methods on the basis of 7240 (4a·1/2C₇H₈) and 3644 (5b·CH₂Cl₂) observed reflections to R and R_w values of 0.0363 and 0.0406 (4a·1/ 2C₇H₈) and 0.040 and 0.038 (5b·CH₂Cl₂), respectively.

Full text of DOI:10.1021/ic9513494

5986
Inorg. Chem. 1996, 35, 5986-5994
Reactivity of r-Phosphino Enolate Complexes of Nickel(II) and Palladium(II) toward
Electrophilic Metal Centers. Synthesis and Crystal Structures of the Bimetallic
Palladium(II)-Gold(I) Complex [(dmba)Pd{Ph2PCH(AuPPh3)C(O)Ph}](BF4) and of the
Nickel(II)-Cobalt(II) Paramagnetic Complex cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)(p-C6H4CH3}2]CoI2
Jacques Andrieu,† Pierre Braunstein,*,† Marc Drillon,‡ Yves Dusausoy,§ Florent Ingold,†
Pierre Rabu,‡ Antonio Tiripicchio,| and Franco Ugozzoli|
Laboratoire de Chimie de Coordination, Associe´ au CNRS (URA 416), Universite´ Louis Pasteur,
4 rue Blaise Pascal, F-67070 Strasbourg Ce´dex, France, Groupe des Mate´riaux Inorganiques, IPCMS,
rue du Loess, 67037 Strasbourg Cedex, Laboratoire de Cristallographie et Mode´lisation des Mate´riaux
Mine´raux et Biologiques, Associe´ au CNRS (URA 809), Universite´ Henri Poincare´ Nancy 1, B.P. 239,
F-54506 Vandoeuvre-les-Nancy Ce´dex, France, and Dipartimento di Chimica Generale ed Inorganica,
Chimica Analitica, Chimica Fisica, Centro di Studio per la Strutturistica Diffrattometrica del CNR,
Universita` di Parma, Viale delle Scienze, I-43100 Parma, Italy
ReceiVed October 18, 1995X
The chemoselective reactivity of metal-coordinated phosphino enolates has been studied by the reactions of
i
cis-[Ni{R′2PCH ‚ ‚ C( ‚ ‚ O)R}2] (R ) Ph, p-C6H4Me, Me; R′ ) Ph, Pr, not all combinations) and [(C N)-
Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}] (C N ) o-C6H4CH2NMe2, dmba or C10H8N, 8-mq) with different metal electro-
philes. In the reaction of cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (1a) with [PtCl2(COD)] (COD ) 1,5-cyclooctadi-
ene), a transmetalation of the P,O ligands was observed, yielding the known complex cis-[Pt{Ph2PCH ‚ ‚ C-
( ‚ ‚ O)Ph}2] (3). However, reaction of cis-[Ni{R′2PCH ‚ ‚ C( ‚ ‚ O)R}2] with anhydrous CoI2 afforded the
heterobinuclear complexes cis-[Ni{R′2PCH ‚ ‚ C( ‚ ‚ O)R}2]CoI2 (5a, R ) Ph, R′ ) Ph; 5b, R ) p-C6H4Me,
i
R′ ) Ph; 5c, R ) Me, R′ ) Ph; 7, R ) Ph, R′ ) Pr) which contain the phosphino enolate ligand in an
unusual chelating-bridging µ-η1(O):η2(P,O) coordination mode in a nonplanar NiO2Co unit. The magnetic
properties of these complexes are discussed. The SHOP-type catalyst [Ni(Ph){Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}(PPh3)]
also behaved as an oxygen-donor metalloligand toward CoI2 to give a paramagnetic Co(II) complex. In con-
trast, reaction of [(C N)Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}] with [Au(PPh3)]+ occurred with formation of [(dmba)-
Pd{Ph2PCH(AuPPh3)C(O)Ph}](BF4) (4a) in which a Cenolate-Au bond has been formed while the P,O chelate
has remained coordinated to palladium. This reaction generates a new stereogenic center, as also evidenced by
1H NMR spectroscopy. The solid state structures of complexes 4a‚1/2C7H8 and 5b‚CH2Cl2 have been determined
by single-crystal X-ray diffraction: 4a‚1/2C7H8 crystallizes in the triclinic space group P1h with Z ) 2 in a unit
cell of dimensions a ) 16.778(4) Å, b ) 14.269(5) Å, c ) 10.838(6) Å, R ) 79.27(4)°, â ) 71.59(3)°, and γ
) 72.68(2)°; 5‚CH2Cl2 crystallizes in the monoclinic space group P21/n with Z ) 4 in a unit cell of dimensions
a ) 12.940(1) Å, b ) 18.329(2) Å, c ) 18.495(2) Å, and â ) 91.627(8)°. The structures have been solved from
diffractometer data by direct and Fourier methods and refined by full-matrix least-squares methods on the basis
of 7240 (4a‚1/2C7H8) and 3644 (5b‚CH2Cl2) observed reflections to R and Rw values of 0.0363 and 0.0406 (4a‚1/
2C7H8) and 0.040 and 0.038 (5b‚CH2Cl2), respectively.
Introduction
process is assigned a spectator role during catalysis,1 we have
shown previously that the reactivity of R-phosphino enolates
of the type [Ph2PCH ‚ ‚ C( ‚ ‚ O)R]- (R ) Ph, OEt, NPh2)2-5
Although the chelating R-phosphino enolate-type ligand
present in Ni-based homogeneous catalysts used in the SHOP
(1) (a) Keim, W. New J. Chem. 1987, 11, 531. (b) Klabunde, U.; Tulip,
T. H.; Roe, D. C.; Ittel, S. D. J. Organomet. Chem. 1987, 334, 141-
156. (c) Hirose, K.; Keim, W. J. Mol. Catal. 1992, 73, 271-276.
(2) (a) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J.; Mitschler, A.
and Ricard, L. J. Am. Chem. Soc. 1981, 103, 5115-5125. (b)
Braunstein, P.; Matt, D.; Nobel, D. Chem. ReV. 1988, 88, 747-764.
† Universite´ Louis Pasteur.
‡ IPCMS.
§ Universite´ Henri Poincare´ Nancy 1.
| Universita` di Parma.
X Abstract published in AdVance ACS Abstracts, September 1, 1996.
S0020-1669(95)01349-8 CCC: $12.00 © 1996 American Chemical Society

R-Phosphino Enolate Complexes
Inorganic Chemistry, Vol. 35, No. 21, 1996 5987
Scheme 1
[(C N)Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}] (C N) 8-mq) instead of a
heterodinuclear complex (eq 2).7c Here we describe further
studies and report the crystal structures of Pd-Au and Ni-Co
complexes which illustrate a different chemoselectivity of the
enolate moiety. Note that cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2]
has been converted previously to an active ethylene homo-
polymerization catalyst by alkylation with trimethylaluminum.8
depends very much on the associated countercation. Whereas
palladium(II) complexes have been shown to readily react with
e.g. CO2,2 organic isocyanates,3 or activated alkynes such as
MeO2CsCtCsCO2Me4 by formation of a carbon-carbon bond,
the alkali metal salts for example are surprisingly unreactive
toward these heterocumulenes (Scheme 1). These observations
have been rationalized on the basis of favorable electronic
interactions involving the d8 metal center.6 Square-planar bis-
(phosphino enolate) complexes of Ni, Pd, and Pt have also been
prepared and shown to react with organic isocyanates or
MeO2CsCtCsCO2Me (reactivity order M ) Ni > Pd > Pt)
in a Michael-type addition resulting from nucleophilic attack
of the enolate carbon on the appropriate carbon of the organic
electrophile.4 In contrast, with reagents such as Ph2PCl or
PhPCl2, formation of a P-O bond occurs, leading e.g. to
complexes containing the phosphine, phosphinite ligand Ph2-
PCHdC(Ph)OPPh2.7 b-d In order to further evaluate the chemo-
selectivity of reactions involving these coordinated phosphino
enolate ligands, we decided to investigate reactions with elec-
trophilic metal reagents which could also provide an interesting
access to new heterometallic complexes. Thus, reaction of
Results
A transmetalation reaction of the anionic P,O chelate of the
type shown in eq 2 has now also been observed in the case of
Pt since reaction of 1a with [PtCl2(COD)] afforded the known
complex cis-[Pt{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (3)7c (details in the
Experimental Section) (eq 3). Transfer of the chelating ligand
from Ni to Pd or Pt obviously occurs under thermodynamic
control.
Synthesis and Structure of Pd(II)-Au(I) Complexes.
Reaction of the neutral complexes [(C N)Pd{Ph2PCH ‚ ‚ C-
( ‚ ‚ O)Ph}] with [Au(PPh3)]+ yielded complexes 4 in which
the gold atom is bonded to the former sp2 carbon of the enolate
which has become sp3 hybridized and chiral in 4 (eq 4).
[(C N)Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)OEt}] (C N) dimethylbenzyl-
amine (dmba) or 8-methylquinoleine (8-mq)) with [(C N)Pd-
(µ-Cl)]2 in a 2:1 molar ratio afforded a dinuclear complex in
which the phosphino enolate ligand has changed its coordination
mode from η2-P,O to µ-P,C (eq 1):2a However, reaction of cis-
[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] with [(C N)Pd(µ-Cl)]2 yielded
(3) (a) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel,
D. J. Chem. Soc., Chem. Commun. 1987, 488-490. (b) Bouaoud, S.-
E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel, D. Inorg. Chem.
1988, 27, 2279-2286. (c) Braunstein, P.; Nobel, D. Chem. ReV. 1989,
89, 1927-1945.
(4) (a) Balegroune, F. Braunstein, P.; Gomes Carneiro, T. M.; Grandjean,
D.; Matt, D. J. Chem. Soc., Chem. Commun. 1989, 582-583. (b)
Braunstein, P.; Gomes Carneiro, T. M.; Balegroune, F.; Grandjean,
D. Organometallics 1989, 8, 1737-1743.
(5) (a) Andrieu, J.; Braunstein, P.; Tiripicchio, A.; Ugozzoli, F. Inorg.
Chem. 1996, 35, 0000-0000. (b) Andrieu, J.; Braunstein, P.; Dusau-
soy, Y.; Ghermani, N. E. Inorg. Chem., in press.
(6) Veya, P.; Floriani, C.; Chiesi-Villa, A.; Guastini, C.; Dedieu, A.;
Ingold, F. and Braunstein, P. Organometallics 1993, 12, 4359-4367.
(7) (a) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel,
D. Inorg. Chem. 1986, 25, 3765-3770. (b) Braunstein, P.; Matt, D.;
Nobel, D.; Fischer, J. J. Chem. Soc., Chem. Commun. 1987, 1530-
1532. (c) Braunstein, P.; Matt, D.; Nobel, D.; Balegroune, F.; Bouaoud,
S.-E.; Grandjean, D.; Fischer, J. J. Chem. Soc., Dalton Trans. 1988,
353-361. (d) Balegroune, F.; Braunstein, P.; Grandjean, D.; Matt,
D.; Nobel, D. Inorg. Chem. 1988, 27, 3320-3325.
1
Accordingly, the H NMR spectrum of 4a contains a triplet
resonance at δ 5.23 for the PCH proton (2J(PPdH) ∼ J(PAuH)
3
) 8.2 Hz) and an ABX spin system for the NCH2 protons. Since
the keto functionality has been restored in this reaction, one
would anticipate to find in the IR spectrum a ν(CdO) absorption
around 1570 cm-1, as in the analoguous complex [(C N)Pd{Ph2-
PCH2C(O)Ph}]+ 7a (remember the isolobal analogy between Au-
(PPh3) and H). Instead, this absorption was found at 1510 cm-1
.
The larger mass and/or the electronic effect of the AuL
substituent could be responsible for this shift. Similar properties
have been found for 4b whose synthesis has been reported
(8) (a) Klabunde, U.; Mulhaupt, R.; Herskovitz, T; Janowicz, A. H;
Calabrese, J.; Ittel, S. D. J. Polym. Sci. 1987, 25, 1989-2003. (b)
Klabunde, U.; Ittel, S. D. J. Mol. Catal. 1987, 41, 123-134.

5988 Inorganic Chemistry, Vol. 35, No. 21, 1996
Andrieu et al.
(2.102(4) Å),9 probably as a result of the high trans influence
of the σ-bonded carbon C(3). The dimensions within the dmba
chelate are similar to those found for this ligand in other Pd(II)
complexes.10 Both chelating ligands form five-membered rings
with the metal atom, and the N-Pd-C(3) and O-Pd-P(1) bite
angles are 83.1(2) and 82.5(1)° respectively. These five-
membered rings have an envelope conformation with C(9) being
0.422(12) Å out of the mean plane passing through the Pd, C(3),
C(4), and N atoms, and the Pd atom being 0.591(2) Å out of
the mean plane through the P(1), C(1), C(2), and O atoms.
Because of the addition of the Au(PPh3) group on C(1), which
becomes sp3 hybridized, the values of the C(1)-C(2) and
C(2)-O bond distances, 1.435(6) and 1.260(7) Å, show, as
expected, a greater double bond character for the C-O bond
than in phosphino enolate-palladium complexes (see also below
the structure of 5b).3a,4a,7d The Au atom is almost linearly
coordinated by C(1) and P(2) [Au-C(1) ) 2.146(6) Å and Au-
P(2) ) 2.272(2) Å, C(1)-Au-P(2) ) 178.9(2)°]. The value
of the Au-C bond length is comparable to that found, 2.128-
(21) Å,11 in [Au2{µ-[CH(PPh3)]2CO}][ClO4]2, in which the Au
atom is also bound to a sp3-hybridized carbon atom adjacent to
a PPh3 and a CO group.
Synthesis, Structure, and Magnetism of Heterobinuclear
Ni(II)-Co(II) Complexes. The reaction of complexes 1a-c
with 1 equiv of anhydrous cobalt(II) iodide in Et2O afforded
the air-stable adducts cis-[Ni{R′2PCH ‚ ‚ C( ‚ ‚ O)R}2]CoI2
(5a, R ) Ph; 5b, R ) p-C6H4Me; 5c, R ) Me) in good yield
(eq 5). In contrast to the reactions described in eqs 2 and 3, no
Figure 1. Crystal structure of complex [(dmba)Pd{Ph2PCH(AuPPh3)-
C(O)Ph}](BF4) in 4a‚1/2C7H8. The hydrogen atoms are not shown,
including that at C(1).
Table 1. Selected Bond Distances (Å) and Angles (deg) for
Complex 4a
Au-P(2)
Pd-P(1)
Pd-N
P(1)-C(1)
N-C(9)
C(4)-C(9)
2.272(2)
2.234(2)
2.127(5)
1.817(7)
1.481(15)
1.493(12)
Au-C(1)
Pd-O
Pd-C(3)
O-C(2)
C(1)-C(2)
2.146(6)
2.128(5)
1.990(7)
1.260(7)
1.435(6)
P(2)-Au-C(1)
O-Pd-N
178.9(2)
91.8(2)
82.5(1)
N-Pd-C(3)
83.1(2)
102.7(2)
99.3(2)
106.1(5)
111.9(4)
122.3(5)
116.4(5)
112.2(5)
120.3(7)
120.8(6)
P(1)-Pd-C(3)
Pd-P(1)-C(1)
Pd-N-C(9)
P(1)-Pd-O
Pd-O-C(2)
118.0(4)
104.7(3)
99.1(4)
121.3(5)
131.0(5)
117.7(8)
120.8(8)
108.4(7)
Au-C(1)-P(1)
Au-C(1)-C(2)
C(1)-C(2)-C(24)
Pd-C(3)-C(8)
C(3)-C(4)-C(9)
C(5)-C(4)-C(9)
N-C(9)-C(4)
P(1)-C(1)-C(2)
O-C(2)-C(1)
O-C(2)-C(24)
Pd-C(3)-C(4)
C(3)-C(4)-C(5)
C(3)-C(8)-C(7)
transmetalation was observed in this reaction. This should be
related to prior unsuccessful attempts to prepare a Co(II) bis-
(phosphino enolate) complex: octahedral fac- or mer-tris-
(phosphino enolate)-Co(III) complexes were isolated instead.12
The IR spectrum of 5a-c exhibits typical absorptions between
1568 and 1505 cm-1 associated with the [ν(C ‚ ‚ C) +
ν(C ‚ ‚ O)] vibrations of the phosphino enolate ligand. This
was taken as a strong indication that complexes 1a-c were
acting as chelating, oxygen donor metalloligands toward the
CoI2 unit. An X-ray diffraction study was carried out on 5b
(see below) in order to firmly establish the detailed structure of
these complexes. The bis(phosphino enolato)nickel complex
acts as a four-electron donor O,O chelate and the phosphino
before.6 The structure drawn for complexes 4 has now been
confirmed by an X-ray diffraction study on 4a.
Crystal Structure of the Pd(II)-Au(I) Complex 4a‚
1/2C7H8. A view of the molecular structure of this complex is
show in Figure 1, selected distances and angles are given in
Table 1. The palladium atom has a square planar coordination
involving the N and C(3) atoms of the chelating cyclometalated
dmba ligand and the P(1) and O atoms of the chelating
phosphino enolate ligand, the C(3) atom being trans with respect
to the O atom. The coordinated N, C(3), P(1) and O atoms
deviate from the mean plane through them by 0.105(5), -0.037-
(7), 0.009(2), and -0.017(4) Å, respectively, with the Pd atom
out of this plane by -0.014(2) Å. The bond distances to Pd
are in the normal range. The Pd-O distance of 2.128(5) Å is
(9) Braunstein, P.; Douce, L.; Fischer, J.; Craig, N. C.; Goetz-Grandmont,
G.; Matt, D. Inorg. Chim. Acta 1992, 194, 151-156.
(10) (a) Braunstein, P.; Matt, D.; Nobel, D.; Bouaoud, S.-E.; Grandjean,
D. J. Organomet. Chem. 1986, 301, 401-410. (b) Canty, A. J. In
ComprehensiVe Organometallic Chemistry, 2nd ed.; Abel, E. W.;
Stone, F. G. A.; Wilkinson, G., Eds.; Pergamon: Oxford, England,
1995; Vol. 9, Chapter 5, pp 1-72.
(11) Vicente, J.; Chicote, M.-T.; Saura-Llamas, I.; Jones, P. G.; Meyer-
Ba¨se, K.; Erdbru¨gger, C. F. Organometallics 1988, 7, 997-1006.
(12) Braunstein, P.; Kelly, D. G.; Tiripicchio, A.; Ugozzoli, F. Inorg. Chem.
1993, 32, 4845-4852.
slightly longer than in [cis-Pd{Ph2PCH2C(O)Ph}2][BF4][B2F7]

R-Phosphino Enolate Complexes
Inorganic Chemistry, Vol. 35, No. 21, 1996 5989
enolate ligand as a chelating-bridging µ-η1(O):η2(P,O), five-
electron donor ligand. These heterobinuclear complexes appear
to be the first examples where a phosphino enolate oxygen atom
bridges between two different transition metal atoms. We have
previously reported a related coordination mode in a Ru3
cluster.13 The present situation is however reminiscent of the
bonding found in recent phosphinophenolate complexes.14
Although numerous dinuclear complexes, with or without a
metal-metal bond, are known which contain a bridging alkoxy,
hydroxy or phenoxy oxygen,15-17 no Ni(II)-Co(II) complex
containing a bridging oxygen function appears to have been
described, with the exception of those already mentioned.14
However, bridging oxygen donor atoms are often found in
coordination complexes of more oxophilic metals, e.g. in
organolithium or -magnesium chemistry.18
The oxygen-cobalt dative bond is maintained in CH2Cl2
solution but it is labile in donor solvents such as EtOH,
acetonitrile or THF, where the precursors complexes 1a-c were
regenerated and could be separated from CoI2(solvent)n by
precipitation with EtOH (eq 5).
In contrast to the situation with 1a, no reaction was observed
between 5a and an activated alkyne such as MeO2CsCtCsCO2-
Me. Obviously, the coordination of the metal electrophile CoI2
has significantly decreased the nucleophilic character of the P,O
chelate compared with its precursor complex 1a.4
Attempts to form other bimetallic complexes by coordination
of 1a to other electrophilic metal complexes than CoI2, such as
anhydrous CoCl2, MnI2, NiBr2, NiCl2(Py)4, or [Ni(NCMe)6]-
[BF4]2, have so far been unsuccessful.
Crystal Structure of the Ni(II)-Co(II) Complex 5b‚
CH2Cl2. The crystal structure consists of discrete monomeric
molecular units separated by normal van der Waals contacts
and dichloromethane molecules of solvation. The molecular
structure of the complex is shown in Figure 2, and selected bond
lengths and angles are listed in Table 2. The planar coordination
geometry around the nickel atom is defined by the two P and
two O atoms of the two phosphino enolate ligands which are
in a mutual cis arrangement. The two P,O ligands have almost
identical geometries, bond lengths and angles. The five atoms
Ni, P(1), P(2), O(1), and O(2) are coplanar (distances from the
mean plane <0.05 Å) and the C(1), C(2), C(3), and C(4) carbon
atoms are, in first approximation, in this plane (distances <0.2
Å) but the Co atom is out of this plane by 1.058(1) Å. The
two Ni-P and the two Ni-O bond length values are respec-
tively 2.143(2), 2.156(2) Å and 1.932(5), 1.910(5) Å. The
bridging oxygen atoms O(1) and O(2) act as 2 electron donors
toward the Co atom. The coordination around the Co atom is
pseudotetrahedral, with an angle of 88.4(1)° between the planes
formed by Co, I(1), I(2) and Co, O(1), O(2). The NiO(1)O-
(2)Co unit is bent along the axis joining the oxygen atoms,
generating a dihedral angle of 148° between the NiO(1)O(2)
Figure 2. Crystal structure of cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)(p-C6H4-
CH3}2]CoI2‚CH2Cl2 (5b‚CH2Cl2).
Table 2. Selected Bond Distances (Å) and Angles (deg) for
a
5b‚CH2Cl2
Co-I(1)
Co-I(2)
Co-O(1)
Co-O(2)
Ni-P(1)
Ni-P(2)
Ni-O(1)
Ni-O(2)
P(1)-C(3)
P(2)-C(2)
2.545(1)
2.553(1)
2.036(5)
2.016(5)
2.143(2)
2.156(2)
1.932(5)
1.910(5)
1.769(8)
1.780(9)
O(1)-O(2)
O(1)-C(4)
O(2)-C(1)
C(1)-C(2)
C(3)-C(4)
P(1)-C(31)
P(1)-C(37)
P(2)-C(19)
P(2)-C(25)
2.553(7)
1.34(1)
1.34(1)
1.34(1)
1.35(1)
1.808(8)
1.813(9)
1.808(8)
1.815(9)
I(1)-Co-I(2)
I(1)-Co-O(1)
I(1)-Co-O(2)
I(2)-Co-O(1)
I(2)-Co-O(2)
O(1)-Co-O(2)
P(1)-Ni-P(2)
P(1)-Ni-O(1)
P(1)-Ni-O(2)
P(2)-Ni-O(1)
P(2)-Ni-O(2)
O(1)-Ni-O(2)
116.36(5)
122.2(1)
119.5(2)
106.4(1)
107.9(2)
78.1(2)
100.54(9)
87.9(2)
170.0(2)
171.1(2)
88.1(2)
Ni-P(1)-C(3)
Ni-P(2)-C(2)
Ni-O(1)-C(4)
Ni-O(2)-C(1)
Co-O(1)-Ni
98.0(3)
97.7(3)
118.2(5)
117.6(5)
91.3(2)
Co-O(2)-Ni
92.5(2)
Co-O(1)-C(4)
Co-O(2)-C(1)
P(1)-C(3)-C(4)
P(2)-C(2)-C(1)
O(1)-C(4)-C(3)
O(2)-C(1)-C(2)
134.4(5)
132.6(5)
116.5(6)
115.2(7)
119.4(7)
121.0(7)
83.3(2)
a Numbers in parentheses are estimated standard deviations in the
least significant digits.
and CoO(1)O(2) planes. The oxygen atoms O(1) and O(2) are
out of the planes (0.372(5), 0.388(5) Å) formed by Ni, Co, C(4)
and Ni, Co, C(1), respectively, and the angles Ni-O(1)-C(4)
and Ni-O(2)-C(1) (118.2(5)°, 117.6(5)°) are smaller than Co-
O(1)-C(4), and Co-O(2)-C(1) (134.4(5), 132.6(5)°). This
arrangement renders the enolate C ‚ ‚ C ‚ ‚ O system prochiral.
This contrasts with homobinuclear Co(II)-Co(II) complexes
containing a bridging phenoxy oxygen, where the Co(1)O2Co-
(2) network is planar.14 As for the Ni coordination, the two
chelating, bridging ligands introduce a strong distorsion of the
O-Co-O angle (78.1(2)°) which is accompanied by high values
for the I(1)-Co-O(1) and I(2)-Co-O(2) angles (122.2(1),
119.5(2)°). The bond lengths C(1)-C(2) (1.34(1) Å), C(3)-
C(4) (1.35(1) Å), and C(1)-O(2), C(4)-O(1) (1.34(1) Å) of
the enolate moiety are comparable with and similar to those in
1a,19 which is indicative of electron delocalization within the
system. The coordination of the cobalt(II) atom leads to a
lengthening of the Ni-O distances (1.910(5) and 1.932(5) Å
(13) Braunstein, P.; Coco Cea, S.; Bruce, M. I.; Skelton, B. W.; White, A.
H. J. Organomet. Chem. 1992, 423, C38-C42.
(14) (a) Dunbar, K. R. Comments Inorg. Chem. 1992, 13, 313-357. (b)
Dunbar, K. R.; Quilleve´re´, A. Organometallics 1993, 12, 618-620.
(15) Chang, Y.; Chen, Q.; Khan, M. I.; Salta, J.; Zubieta, J. J. Chem. Soc.,
Chem. Commun. 1993, 1872-1874.
(16) Lachicotte, R.; Kitaygorodskiy, A.; Hagen, K. S. J. Am. Chem. Soc.
1993, 115, 8883-8884.
(17) (a) Nanda, K. K.; Thompson, L. K.; Bridson, J. N.; Nag, K. J. Chem.
Soc., Chem. Commun. 1994, 1337-1338. (b) Jeffery, J. C.; Thornton,
P.; Ward, M. D. Inorg. Chem. 1994, 33, 3612-3615. (c) Krebs, B.;
Schepers, K.; Bremer, B.; Henkel, G.; Mu¨ller-Warmuth, W.; Griesar,
K.; Haase, W. Inorg. Chem. 1994, 33, 1907-1914.
(18) (a) Seebach, D.; Amstutz, R.; Laube, T.; Schweizer, W. B.; Dunitz, J.
D. J. Am. Chem. Soc. 1985, 107, 5403-5409. (b) Williard, P. G.;
Salvino, J. J. Chem. Soc., Chem. Commun. 1986, 153-154.
(19) Qichen, H.; Minzhi, X.; Yanlong, Q.; Weihua, X.; Meicheng, S.;
Youqi, T. J. Organomet. Chem. 1985, 287, 419-426.

5990 Inorganic Chemistry, Vol. 35, No. 21, 1996
Andrieu et al.
in 5b vs 1.857(14) and 1.877(11) Å in 1a) and to the closing of
the O(1)-Ni-O(2) angle from 86.9° in 1a to 83.3(2)°. This is
compensated by the high value of the opposite angle P(1)-
Ni-P(2) (100.54(9)°). The molecular conformation of the
phenyl groups of the phosphines is governed by a face to face
arrangement with van der Waals interactions. The mean
distance between the two pseudoparallel (16.8°) planes C(25)‚‚‚C-
(30) and C(37)‚‚‚C(42) is 3.35 Å and that between the two
planes (5.5°) C(19)‚‚‚C(24) and C(31)‚‚‚C(36) is 3.36 Å. The
tolyl planes have nearly the same orientation (29.1(4)°, 20.7-
(5)°) with respect to the Ni, P(1), P(2), O(1), O(2) plane.
Scheme 2
Isomerization Reactions of the r-Phosphino Enolate Ni-
(II) Complexes by Coordination to CoI2. The bis(phosphino
enolate) complexes of Ni(II) can adopt a trans-arrangement of
the phosphorus atoms when bulky substituents are present on
phosphorus. For example, in trans-[Ni{R′2PCH ‚ ‚ C( ‚ ‚ O)-
t
R}2] (R ) Ph, Bu) only the trans isomer was observed for R′
t
i
) Bu.20 However, with R′ ) Pr, we have observed the
formation of a mixture of the cis- and trans-isomers of [Ni-
{iPr2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (6) in a ca. 1:1 ratio determined
by integration of the 1H NMR PCH signals and of the 31P{1H}
NMR resonances (eq 6). Isomers trans-6 and cis-6 were
31P{1H} NMR monitoring showed a decrease of the intensity
of the singlet at δ 39.3, which was progressively replaced by
an AB pattern at δ 57.4 and 29.8 with a 2J(PP) of 304 Hz. This
is typical for a trans arrangement of chemically different P
atoms. It is interesting to note that this transformation has not
been observed with complexes 5, which contain a PPh2 group
in place of the more electron donor PiPr2 substituent. In order
to shed some light on this transformation, we exposed complex
7 to different solvents (THF, acetonitrile) and iodine-containing
reagents, such as [NMe4]I and I2. Only in the latter case was
a similar behavior observed. We therefore suggest that some
I2 is liberated by decomposition that would oxidize cis-6 to form
a square-planar Ni(II) complex. In view of independent
observations that iodine can indeed react with metal-coordinated
phosphino enolate complexes to form complexes containing the
new ligand Ph2PCH(I)C(O)Ph,5b we suggest in the present case
characterized by a singlet in the 31P{1H} NMR spectrum, at δ
1
50.0 and 39.3, respectively. The broad signals in H NMR at
δ 4.37 and 4.19 corresponding to the PCH proton could not be
assigned to a given isomer. The IR spectrum (KBr pellet) of
trans-6 and cis-6 shows only one absorption band at 1517 cm-1
for the [ν(C ‚ ‚ C) + ν(C ‚ ‚ O)] vibration. The formation of
both cis- and trans-6 can be explained by two opposite effects:
the steric effect favors the trans-arrangement while the electronic
effect favors the cis-arrangement (trans-influence of the donor
atoms). The fact that these isomers were always present in
solution suggested the existence of an equilibrium (see below).
We then studied the coordination properties of 6 toward CoI2.
the formation of trans-[Ni(I){iPr2PCH ‚ ‚ C( ‚ ‚ O)Ph}{iPr2-
PCH(I)C(O)Ph}]. This is also consistent with the observation
in the 1H NMR spectrum of two resonances at δ 4.30 and 3.56
for the CH protons.
In view of the donor character of the enolate oxygen atoms
in complexes 5 and 6 and of the possible use of Lewis acidic
alkylating agents such as AlMe3 to transform 1a into an active
olefin polymerization catalyst,8 we examined the reaction be-
Under the conditions described for complexes 1a-c, the
reaction of 6 with anhydrous CoI2 led to the heterobinuclear
tween the SHOP-type catalyst [Ni(Ph){Ph2PCH ‚ ‚ C( ‚ ‚ O)-
Ph}(PPh3)]1 and CoI2. Under the conditions used for the
synthesis of complexes 5 or 7, but using only 0.5 equiv CoI2,
we obtained after extraction with CH2Cl2 a green solid. The
reaction was not complete, and a pure complex could not be
isolated. However, a new paramagnetic complex had formed,
as indicated by 1H and 31P{1H} NMR spectroscopy: 1H
chemical shifts are observed in the range 29.6 to -37.2 ppm
and a signal at -96.5 ppm is found in 31P{1H} NMR. A greater
lability or instability of this complex compared to 5 or 7 would
obviously result from the lack of chelating effect.
NMR Spectroscopic Studies of Paramagnetic Complexes
5b. The magnetic properties of heteropolymetallic systems
containing bridging atoms or groups are of interest for biologists
and bioinorganic chemists investigating the structure and the
role of polymetallic active sites in biological processes, and for
physicists and physical inorganic chemists who study new
magnetic materials. It has generally been found that the overall
complex cis-[Ni{iPr2PCH ‚ ‚ C( ‚ ‚ O)Ph}2]CoI2 (7) in 76%
yield (Scheme 2). The 31P{1H} NMR spectrum of the reaction
mixture showed only the presence of complex 7. The disap-
pearence of trans-6 therefore confirms that both isomers were
in equilibrium in solution and that coordination of CoI2
completely shifted the equilibrium toward the formation of 7.
When 7 was dissolved in donor solvents such as THF, the 31P-
{1H} NMR spectrum showed only one signal at δ 39.3 which
corresponds to cis-6 (Scheme 2) which is therefore the kinetic
isomer. Unfortunately, cis-6 and the CoI2(S)n formed could not
be separated due to similar solubility properties and to the
progressive transformation of cis-6 in the reaction mixture. Thus,
(20) Moulton, C. J.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1980, 299-
301.

R-Phosphino Enolate Complexes
Inorganic Chemistry, Vol. 35, No. 21, 1996 5991
Figure 3. 1H NMR spectrum of 5b in CD2Cl2 at 298 K.
Table 3. 1H NMR Data (at 298 K, in CD2Cl2) for 5ba
Figure 4. Experimental curves of 5a (in CD2Cl2) [δi (ppm) ) f(1/T)].
1
Table 4. Variable-Temperature H NMR Spectrum of 5a in CD2Cl2
P(C6H5)2
(a) H (b) Ho or m (c) Hm or o (d) Hp (e) Mep (f) Hm (g) Ho
δ (ppm) 30.04 14.16 10.17 9.56 -5.88 -8.04 -39.53
-C6H4Me
enolate
-P(C6H5)2
-C-C6H5
enolate
T (K) (a) H (b) Ho or m (c) Hm or o (d) Hp (e) Hp (f) Hm (g) Ho
298 30.35
278 30.99
266 31.39
255 31.67
237 31.91
14.14
14.88
15.58
16.35
17.69
10.17
10.47
10.76
9.54 -1.36 -8.01 -39.48
9.77 -2.22 -9.39 -43.55
9.98 -3.05 -10.71 -47.41
a Other peaks at δ 7.20, 5.32, and 2.29 were attributed to crystal-
lization solvents.
11.07 10.21 -3.98 -12.17 -51.68
11.60 10.63 -5.63 -14.69 -59.05
properties are not just the sum of the magnetic properties of
each individual ion, but rather they result from both the nature
and the magnitude of the interactions between the metal ions
within the molecular unit.21
In complex 5b, the presence of the paramagnetic center leads
in 1H NMR spectroscopy to chemical shifts in the range δ -39.5
to 30.0 ppm at room temperature (Figure 3). This also explains
the 31P{1H} NMR spectrum of 5b which exhibits a singlet at
-102.5 ppm. However, complex 5b does not exhibit any EPR
signal even when cooled down to 40 K. The availability of
NMR spectra for the paramagnetic species suggests that the
unpaired electron is rather localized on the cobalt(II) atom and
not fully delocalized over the P,O ligands. As shown by the
crystal structure of complex 5b (Figure 2), the bridging oxygen
atom of the P,O chelate has a pyramidal environment. This
arrangement could lead to a weak overlap of magnetic orbitals
as well as to some electron delocalization between the two metal
centers. The 1H NMR spectrum shows four well-resolved
downfield signals (a-d) in addition to three other more upfield
shifted (e-g), as shown in Figure 3. The assignment of these
signals given in Table 3 was confirmed by their respective
intensities and by analogy with the 1H NMR spectra of 5a and
5c. The presence of a paramagnetic center leads to a very
different chemical shift for the aromatic protons of the -C6H5
(5a) and the ortho-and meta protons of the C6H4Me (5b) groups.
A similar observation has previously been made in a heterobi-
nuclear Fe(II)-Co(II) complex containing a bridging phenolate.22a
The chemical shift of the enolate proton (a) indicates some
delocalization of the unpaired electron between the bridging
enolate and the cobalt(II) atom. The broad peak assigned to
the ortho proton (g) could be due to through-space dipolar
interaction with the near cobalt(II), as found in mononuclear
Co(II) complexes.22b
Figure 5. Temperature dependence of the øT product for complex 5c.
The full line represents the theoretical curve for isolated cobalt(II)
centers.
In a magnetic field, a heterobinuclear complex of type 5 will
exhibit two different magnetic moments: the induced moment
of the diamagnetic fragment 1 which is opposed by the magnetic
moment of the paramagnetic Co(II) fragment. When the
temperature decreases, the paramagnetism cancels more and
more the diamagnetism, and leads to the accentuation of the
chemical shifts observed on the 1H NMR spectrum of 5a. These
experimental curves show that the chemical shift of the ortho
proton (g) is the most affected (Table 4). This observation
suggests that the influence of the paramagnetic center is more
important through space than through the enolate bridge. This
is confirmed when the phenyl group (containing the protons
e-g) in complex 5a is replaced by a methyl substituent which
has a chemical shift at δ -83.8 ppm in 5c.
Magnetic Properties of the Ni-Co Complexes. The
temperature-dependent magnetic behavior of the above com-
pounds have been measured by means of a SQUID magnetom-
eter (Me´tronique) and a DSM8 susceptometer (Manics), in the
temperature range 2-300 K and applied fields 0-20 kOe.
Compounds 5a,c and 7 show a similar behavior, illustrated in
Figure 5 for 5c. The øT product decreases regularly from room
temperature down to 50 K, then more sharply upon cooling
toward a non-zero value (∼1.5 emu‚K‚mol-1) for T ) 2 K. In
We then investigated the variable-temperature 1H NMR
spectrum of 5a, in the range +25 °C [1/T ) 3.35 × 10-3 (K-1)]
to -35 °C [4.20 × 10-3 (K-1)] (Figure 4). When the
temperature decreased, all signals were shifted and an accentua-
tion of the chemical shifts was observed, which was a
consequence of the total magnetic susceptibilty (øm) variation.
(21) (a) Kahn, O. Struct. Bonding 1987, 68, 89-167. (b) Kahn, O.
Molecular Magnetism; VCH: Weinheim, Germany, 1994.
(22) (a) Wang, Z.; Holman, T. R.; Que, J.; Jr. Magn. Reson. Chem. 1993,
31, S78-S84. (b) Moratal, J. M.; Salgado, J.; Donaire, A.; Jime´nez,
H. R.; Castelles, J. Inorg. Chem. 1993, 32, 3587-3588.

5992 Inorganic Chemistry, Vol. 35, No. 21, 1996
Andrieu et al.
lattices.23-25 It has been shown, in particular, that zero-field
splitting is typically on the order of 10-20 K, and that a change
in sign of D occurs for a Cl-Co-Cl angle close to 109.50°.
Thus, for Cs3CoCl5, characterized by bond angles ranging
between 107.2 and 110.6°, D is negative while it is positive for
2-
Cs2CoCl4 exhibiting more distorted CoCl4 units. A direct
4-
comparison of our results with those of CoO2I2 species is
tricky, due to the presence of two I- ligands in the coordination
sphere of the metal ion. Indeed, the bond lengths differ
drastically, since they range from 2.016, 2.036 Å (Co-O bonds)
to 2.545, 2.553 Å (Co-I bonds), while in the chlorides they
are of the order of 2.25 Å. Furthermore, the O-Co-O bond
angle is very small (∼78°) while the I-Co-I counter-angle is
large (∼116°) compared with the bond angles of symmetrical
units. As a result, the local symmetry is lowered to C2V,
promoting a large zero-field splitting which allows to explain
the magnetic properties in the frame of a molecular model.
Figure 6. Temperature dependence of the øT product for complex
5b. The different variations show the influence of sample aging.
Discussion
turn, compound 5b exhibits a different øT variation (Figure 6),
since a large bump is observed around 30 K, the height of which
depends on the sample aging. Magnetization measurements,
performed at different temperatures up to 300 K, show that a
ferromagnetic component is superimposed to the classical linear
variation, due likely to the presence of a small amount of metal
impurity. Assuming that cobalt metal particles are responsible
for this behavior (considering the stability of the precursors 1
and the lability of the OfCo dative bonds), we obtain from
the magnetization results an estimate of 0.02% of metal impurity.
The behavior observed for the other compounds could be the
signature of magnetic exchange interactions between the metal
ions. In fact, nickel(II) in square planar geometry is nonmag-
netic, so that the results can only be explained by considering
cobalt(II) ions in distorted tetrahedral surrounding. Previous
work reported in the literature shows that a zero-field splitting
The reaction of cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (1) with
PtCl2(COD) has yielded cis-[Pt{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (3)
as a result of a transmetalation reaction of the anionic P,O
chelate which may be initiated by nucleophilic attack of the
enolate carbon onto the other metal center. This observation
suggests that the reaction is under thermodynamic control; bonds
to platinum are generally more stable than to nickel. This is
consistent with the reactivity trends of cis-[M{Ph2PCH ‚ ‚ C-
( ‚ ‚ O)Ph}2] (M ) Ni > Pd > Pt) toward activated alkynes
which occurred by carbon(enolate)-carbon coupling and metal-
oxygen bond dissociation and were complete after 12 h for M
) Ni and 72 h for M ) Pt.4 In a similar way, the enolate moiety
of [(dmba)Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}] behaves as a C-nu-
cleophile toward [(C N)Pd(µ-Cl)]2 or [Au(PPh3)]+, affording
in the latter case complex 4a which was structurally character-
4
of the A2 ground-term generally occurs for cobalt(II) in such
an environment, which is usually rather large.23-26 This splitting
(D)27 is related to the energy of the excited configurations
ized. However, the reactions between cis-[Ni{R′2PCH ‚ ‚ C-
4
4E and B2, giving the effective doublets Sz ) |(1/2 or Sz )
|(3/2 as low-lying spin states, and thus inducing a temperature-
( ‚ ‚ O)R}2] and anhydrous CoI2 afforded the heterobinuclear
Ni-Co complexes 5a-c and 7 in which the nickel complex acts
as a 4 electron donor toward the cobalt ion. It is interesting
that the chelating behavior of 1a via its oxygen atoms has been
previously observed in its reaction with AlMe3 which afforded
the ethylene polymerization catalyst formulated as A.8 The
dependent magnetic moment. In Cs2CoCl4,23 the zero-field
24
splitting stabilizes the |(1/2 state, while in Cs3CoCl5
the
|(3/2 state is lower. In both cases, the magnetic susceptibility,
given in the Appendix, depends strongly on D at low temper-
ature (for kT/D < 1). This model allows a very good description
of the øT) f(T) data for compound 5c (Figure 5), using the
parameters D ) 39.9 K, which stabilizes the spin doublet
|(1/2 , g| ) 2.72, g ) 2.34, and øvv ) 1.52 × 10-3 emu/mol.
Correlations between structural findings and magnetic proper-
2-
ties have been reported for the CoCl4 ion in close-packed
(23) McElearney, J. N.; Merchant, S.; Shankle, G. E.; Carlin, R. L. J. Chem.
Phys. 1977, 66, 450.
(24) Wielinga, R. F.; Blo¨te, H. W. J.; Roest J. W.; Huiskamp, W. J. Physica
1967, 34, 223.
(25) Algra, H. A.; de Jongh, L. J.; Blo¨te, H. W. J.; Huiskamp, W. J.; Carlin,
R. L. Physica 1976, B82, 239.
(26) McElearney, J. N.; Shankle, G. E.; Schwartz, R. W.; Carlin, R. L. J.
Chem. Phys. 1972, 56, 3755.
(27) We define as D the splitting of the 4A2 ground term resulting from
the mixing with the 4B2 and 4E excited configurations. The suscep-
tibilities parallel and perpendicular to the z axis are then given by
SHOP-type catalyst [Ni(Ph){Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}(PPh3)]
was also shown to behave as an oxygen-donor metalloligand
toward CoI2. A reasonable structural formulation for this
trinuclear complex would be that of a tetrahedral Co(II) com-
plex containing two monodentatate oxygen-donor nickel com-
øz ) Ng2µB2/4kT(1 + 9 exp(-D/kT))/(1 + exp(-D/kT)) + ø0
øx ) Ng2µB2/kT(1 + exp(-D/kT))-1
+
3Ng2µB2 tanh(D/2kT)/2D + ø1
plex molecules as in CoI2[Ni(Ph){Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}-
(PPh3)]2. The ability of the oxygen atom in [Ni(Ph){Ph2-
where ø0 and ø are second-order Zeeman contributions related to
1
the excited states 4B2 and 4E, respectively. The average susceptibility
1
is deduced from ø ) /3(øz + 2øx).

R-Phosphino Enolate Complexes
Inorganic Chemistry, Vol. 35, No. 21, 1996 5993
were obtained from dry ethanol at -25 °C (13.0 g, 43%): mp 86 °C.
PCH ‚ ‚ C( ‚ ‚ O)Ph}(PPh3)] to donate an unused electron pair
1
IR (KBr): ν(CO) 1671 vs. H NMR (CDCl3): δ 7.9-7.2 (m, 14 H,
aromatic), 3.79 (s, 2 H, PCH2), 2.40 (s, 3 H, CH3). 31P{1H} NMR
(CDCl3): δ -16.66 (s). Anal. Calcd for C21H19OP (M ) 318.36):
C, 79.23; H, 6.02. Found: C, 79.57; H, 6.11.
to an unsaturated metal center has been previously observed in
the homodinuclear complex [Ni(Ph){Ph2PCH ‚ ‚ C( ‚ ‚ O)-
Ph}]2 (B), which forms in the absence of an external donor
ligand.8 These addition reactions show the significant O-basicity
of the P,O chelate in its metal complexes. Obviously, the
control of the chemospecificity of the coordinated ligand [Ph2-
PCH ‚ ‚ C( ‚ ‚ O)Ph]- toward metal electrophiles depends
upon the nature of both the metal complex containing the P,O
chelate and the metal electrophile, which may allow a fine-
tuning of stoichiometric or catalytic reactivity.
The reversible coordination of CoI2 in the Ni(II)-Co(II)
heterobinuclear species 5 leads to the possibility of isomerizing
the R-phosphino enolate nickel(II) complexes from the trans-
to the cis-isomer. In the case of complex 7, dissociation in
donor solvents with liberation of cis-6 and progressive de-
cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)(p-C6H4CH3}2] (1b). A mixture of
NiCl2‚6H2O (0.400 g, 1.68 mmol) and Ph2PCH2C(O)(p-C6H4CH3)
(1.070 g, 3.37 mmol) was stirred in EtOH (20 mL). A red suspension
was formed, and after further stirring for 1 h, a solution of NaOEt
(prepared from 0.135 g of Na and 10 mL of EtOH) was slowly added.
After being stirred for 1 h, the orange suspension was cooled to 0 °C
and filtered. The orange residue was washed with cold EtOH (10 mL),
dried in Vacuo, and used without further purification (1.117 g, 95%).
IR (KBr): ν(CsC) + ν(CsO) 1524 s. 1H NMR (CD2Cl2): δ 7.78-
7.11 (m, 14 H, aromatic), 4.53 (s, 2 H, PCH), 2.37 (s, 6 H, CH3). 31P-
{1H} NMR (CDCl3): δ 28.4 (s). Anal. Calcd for C42H36NiO2P2 (M
) 693.37): C, 72.76; H, 5.23. Found: C, 72.61; H, 5.07.
‚‚
‚‚
Formation of cis-[Pt{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (3) from 1a. A
mixture of 1a (0.100 g, 0.15 mmol) and [PtCl2(COD)] (0.058 g, 0.015
mmol) was stirred in THF (10 mL) at 40 °C. After a few minutes, a
white suspension was formed which was further stirred for 0.5 h at
room temperature. The solvent was removed in Vacuo. The white
residue was extracted with CH2Cl2 (10 mL), filtered, and concentrated
in Vacuo. Addition of pentane afforded air-stable white needles.
composition led to a byproduct formulated as trans-[Ni(I)-
{iPr2PCH ‚ ‚ C( ‚ ‚ O)Ph}{iPr2PCH(I)C(O)Ph}]. The magnet-
ic properties of the paramagnetic Ni-Co bimetallic complexes
5 have been presented and discussed above. They could be
explained by a molecular model involving distorted Co(II) d7
centers, without invoking intermolecular interactions. The latter
also appeared unlikely in view of the packing in the solid state
and the similar behavior of complexes 5a-c, indicating that
the phenyl, p-tolyl, or methyl substituent, respectively, does not
provide communication between the isolated molecules. How-
ever, the slight structural modifications that may result from
this replacement could certainly influence slightly the coordina-
tion geometry about the Co(II) centersin particular the value
of the O(1)-Co-O(2) anglesand therefore explain magnetic
differences within this family of complexes. This will require
further structural/magnetic investigations.
1
Product 3 (0.080 g, 66%) was characterized by comparison of its H
NMR and 31P NMR data with those of an authentic sample.7c
[(dmba)Pd{Ph2PCH(AuPPh3)C(O)Ph}](BF4) (4a). To a stirred
solution of [AuCl(PPh3)] (0.495 g, 1.00 mmol) in THF (100 mL) was
added solid AgBF4 (0.200 g, 1.00 mmol). After being stirred for 0.5
h, the reaction mixture was filtered. To the filtrate was added [(dmba)-
Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}] (0.548 g, 1.00 mmol) and the solution
was stirred for 2 h. The resulting solution was concentrated and
addition of hexane afforded a white powder, which was washed with
toluene and dried in Vacuo. With the exclusion of light, a recrystal-
lization from toluene/CH2Cl2/hexane afforded white crystals character-
ized as complex 4a‚0.5C7H8 (0.729 g, 77%). IR (KBr): ν(CO) 1581
w, 1506 s, ν(BF4) 1101 s, 1084 vs, 1024 sh. IR (CD2Cl2): ν(CO)
1510 s. 1H NMR (CD2Cl2): δ 8.23-6.73 (m, 34 H, aromatic), 5.23
Experimental Section
Reagents and Physical Measurements. All reactions were per-
2
5
(t, 1 H, PCH, J(PPdH) ) J(PAuH) ) 8.2 Hz), 4.23 (dd, 1 H, CHAN,
formed in Schlenk-type flasks under nitrogen. Solvents were purified
2
part A of an ABX spin system (A ) B ) H, X ) P), J(AB) ) 14.1
1
and dried under nitrogen by conventional methods. The H and 31P-
Hz, J(AX) ) 2.3 Hz), 4.01 (dd, 1 H, CHBN, part B of an ABX spin
4
{1H} NMR spectra were recorded at 300.13 and 121.5 MHz, respec-
tively, on a FT Bruker AC 300 instrument. IR spectra were recorded
in the 4000-400-cm-1 range on a Bruker IFS66 FT spectrometer.
Syntheses. The ligands Ph2PCH2C(O)Ph and iPr2PCH2C(O)Ph and
system, J(AB) ) 14.1 Hz, J(BX) < 2.04 Hz), 3.05 (d, 3 H, MeAN,
4J(PH) ) 2.06 Hz), 2.98 (d, 3 H, MeBN, 4J(PH) ) 2.04 Hz). 31P{1H}
NMR (C6D6/CD2Cl2): δ 39.08 (s, 1 P), 39.06 (s, 1 P). Anal. Calcd
for C47H44AuBF4NOP2Pd‚0.5C7H8 (M ) 1090.99 + 46.06): C, 53.34;
H, 4.25; N, 1.23. Found: C, 53.21; H, 4.24; N, 1.26. FAB mass
2
4
the complexes [PtCl2(COD)], cis-[M{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (1a,
M ) Ni; 3, M ) Pt), cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Me}2] (1c),
[(dmba)Pd{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}] (2a), [(8-mq)Pd{Ph2PCH ‚ ‚ C-
spectrum m/e 1002 (M - 2 H - BF4), 544 (M - 2 H - BF4
-
AuPPh3).
cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Ph}2]CoI2 (5a). A mixture of com-
( ‚ ‚ O)Ph}] (2b), and [(8-mq)Pd{Ph2PCH(AuPPh3)(C(O)Ph}](BF4)
(4b) were prepared according to published procedures.6,7,28-30
plex 1a (0.300 g, 0.45 mmol) and anhydrous CoI2 (0.140 g, 0.45 mmol)
was stirred for 3 h in Et2O (20 mL). The green precipitate was filtered,
washed with Et2O (10 mL), and dried in Vacuo. The crude product
was dissolved in a 1:1 mixture of toluene/CH2Cl2 (1:1) (20 mL), and
the solution was filtered and then concentrated in Vacuo. On being
cooled to -23 °C, the solution afforded dark green, air-stable crystals
of 5a‚0.25C7H8 (0.365 g, 80%). IR (KBr): ν(C ‚ ‚ C) + ν(C ‚ ‚ O)
1551 vs, 1524 sh. 31P{1H} NMR (CD2Cl2, 298 K): δ -105.1 (s). Anal.
Calcd for C40H32CoI2NiO2P2‚0.25C7H8 (M ) 978.00 + 23.03): C,
50.09; H, 3.42. Found: C, 50.00; H, 3.27. FAB mass spectrum: m/e
978 (5%, M), 850 (60%, M - I), 793 (15%, M + 2H - Co - I), 665
(100%, M - CoI2), 362 (40%, M+ - 2I).
Ph2PCH2C(O)(p-C6H4CH3). A hexane solution (1.60 mol‚L-1) of
nBuLi (60 mL, 0.096 mmol) was added dropwise at -70 °C to a solution
of diisopropylamine (13.5 mL, 0.096 mmol) in THF (30 mL). After
the mixture was stirred for 0.5 h, a solution of p-tolylacetophenone
(12.7 mL, 0.095 mmol) in THF (20 mL) was added dropwise at -70
°C. After further stirring for 2.5 h, a solution of Ph2PCl (17 mL, 0.095
mmol) in THF (30 mL) was added dropwise at -70 °C. The mixture
was stirred overnight with a slow increase in temperature from -70
°C to room temperature. The solvent was removed in Vacuo. The
crude product was dissolved in toluene (100 mL). The colorless
solution was filtered and concentrated, and addition of pentane afforded
a white powder, which was filtered and dried in Vacuo. White crystals
cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)(p-C6H4CH3}2]CoI2 (5b). Following
(28) Drew, D.; Doyle, J. R. Inorg. Synth. 1990, 28, 346-351.
(29) Braunstein, P.; Matt, D.; Nobel, D.; Balegroune, F.; Bouaoud, S. E.;
Grandjean, D. Fischer, J. J. Chem. Soc., Dalton Trans. 1988, 353-
361.
(30) Georgiev, E. M.; tom Dieck, H.; Fendesak, G.; Hahn, G.; Petrov, G.;
Kirilov, M. J. Chem. Soc., Dalton Trans. 1992, 1311-1315.
the procedure described for 5a, but starting from 1b (0.400 g, 0.43
mmol) and CoI2 (0.135 g, 0.43 mmol), 5b‚0.25C7H8 was obtained as
green crystals (0.580 g, 73%), which were suitable for X-ray analysis.
IR (KBr): ν(CsC) + ν(CsO) 1548 s, 1505 s. 31P{1H} NMR (CD2-
Cl2, 298 K): δ -102.5 (s). Anal. Calcd for C42H36CoI2NiO2P2‚0.25C7H8
‚‚
‚‚

5994 Inorganic Chemistry, Vol. 35, No. 21, 1996
Andrieu et al.
Table 5. Crystallographic Data for Compounds 4a‚1/2C7H8 and 5b‚CH2Cl2
4a‚1/2C7H8
5b‚CH2Cl2
mol formula
mol wt
cryst system
space group
radiattion
a, Å
[C47H43AuNOP2Pd][BF4]‚1/2C7H8
C40H36NiCoI2P2O2‚CH2Cl2
1136.05
triclinic
P1h
1066.3
monoclinic
P21/n
graphite-monochromated (Mo-KR, λ ) 0.71073 Å)
16.778(4)
14.269(5)
10.838(6)
79.27(4)
71.59(3)
72.68(2)
2338(2)
2
12.940(1)
18.329(2)
18.495(2)
b, Å
c, Å
R, deg
â, deg
91.627(8)
γ, deg
V, Å3
4384.8(8)
4
1.617
Z
d
calcd, g cm-3
1.614
F(000)
1122
36.4
3-26
9681
7240 [I > 2σ(I)]
0.0363
0.0406
2100
24.9
2-23
6079
3644 [I > 6σ(I)]
0.040
0.038
µ(Mo KR), cm-1
θ range, deg
no. of unique tot. data
no. of unique obsd data
Ra
b
Rw
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑w(Fo)2]1/2
.
(M ) 1006.11 + 23.03): C, 51.03; H, 3.72. Found: C, 50.80; H,
and Fourier methods and refined by full-matrix least-squares methods,
first with isotropic thermal parameters and then with anisotropic thermal
parameters for all the non-hydrogen atoms excepting the carbon atoms
of the toluene molecule of solvation of 4a‚1/2C7H8. The toluene
molecule, lying on an inversion center, was found disordered with the
methyl group distributed in two centrosymmetrically related positions.
All hydrogen atoms (excepting those of the toluene molecule) were
placed at their geometrically calculated positions and refined “riding”
on the corresponding carbon atoms. The final cycles of refinement
were carried out on the basis of 567 (4a‚1/2C7H8) and 479 (5b‚CH2-
Cl2) variables. The highest remaining peak in the final difference map
was equivalent to about 1.1 (4a‚1/2C7H8) and 0.8 (5b‚CH2Cl2) e/Å3. In
the final cycles of refinement a weighting scheme w ) K[σ2(Fo) +
3.83.
cis-[Ni{Ph2PCH ‚ ‚ C( ‚ ‚ O)Me}2]CoI2 (5c). Following the pro-
cedure described for 5a, but starting from 1c (0.200 g, 0.37 mmol)
and CoI2 (0.116 g, 0.37 mmol), 5c‚0.25C7H8 was obtained as a green
‚‚
‚‚
crystalline powder (0.140 g, 43%). IR (KBr): ν(CsC) + ν(CsO)
1568 s. 1H NMR (CD2Cl2, 298 K): δ 49.99 (s, 2 H, CHP), 15.34 (s,
8 Hm or o, Ph2P), 10.45 (s, 8 Ho or m, Ph2P), 9.75 (s, 4 Hp, Ph2P), -83.86
(s, 6 H, CH3). 31P{1H} NMR (CD2Cl2, 298 K): δ -78.4 (s). Anal.
Calcd for C30H28CoI2NiO2P2‚0.25C7H8 (M ) 853.89 + 23.03): C,
43.48; H, 3.45. Found: C, 43.17; H, 3.50.
cis- and trans-[Ni{iPr2PCH ‚ ‚ C( ‚ ‚ O)Ph}2] (6). Following the
2
gFo ]-1 was used; at convergence the K and g values were 1.129 and
i
procedure described for 1b, but starting from the ligand Pr2PCH2C-
0.00095 (4a‚1/2C7H8), and 0.038 and 0.00034 (5b‚CH2Cl2) respectively.
The analytical scattering factors, corrected for the real and imaginary
parts of anomalous dispersion, were taken from ref 32. All calculations
were carried out using the SHELX-76 and SHELXS-86 systems of
crystallographic computer programs.33 The final atomic coordinates
for the non hydrogen atoms are given in Tables S-II (4a‚1/2C7H8) and
S-III (5b‚CH2Cl2). The atomic coordinates of the hydrogen atoms are
given in Tables S-II (4a‚1/2C7H8) and S-III (5b‚CH2Cl2), the thermal
parameters are given in Tables S-IV (4a‚1/2C7H8) and S-V (5b‚CH2-
Cl2).
(O)Ph (3.03 g, 12.82 mmol) and NiCl2‚6H2O (1.523 g, 6.41 mmol),
6 was obtained as orange-red crystals (2.05 g, 61%). IR (KBr):
ν(C ‚ ‚ C) + ν(C ‚ ‚ O) 1517 vs. Both isomers cis-6 and trans-6 were
present in a ca. 1:1 ratio in CDCl3. 1H NMR (CDCl3): δ 7.92-7.26
(m, 10 H, aromatic), 4.37 (s, 2 H, PCH, cis or trans isomer), 4.19 (s,
2 H, PCH, trans or cis isomer), 2.21 (m, 4 H, CH(CH3)2), 2.06 (m, 4
H, CH(CH3)2), 1.57-1.29 (m, 24 H, CH(CH3)2). 31P{1H} NMR
(CDCl3): δ 50.0 (s, 2 P, trans isomer) and 39.3 (s, 2 P, cis isomer).
Anal. Calcd for C28H40NiO2P2 (M ) 529.25): C, 63.55; H, 7.62.
Found: C, 63.67; H, 7.64.
Acknowledgment. We thank the Centre National de la
Recherche Scientifique (Paris) for financial support, the Min-
iste`re de l’Enseignement Supe´rieur et de la Recherche for a
Ph.D. grant to J.A and F.I. and the Consiglio Nazionale delle
Ricerche (Rome) for financial supports. Y.D. is grateful to J.
Hubsch and L. Montesi for preliminary magnetic measurements
performed at the Service Commun de Magne´tisme de l’Universite´
Henri Poincare´ Nancy I, and M.D and P.R are also grateful to
R. Poinssot (IPCMS) for magnetic measurements.
Supporting Information Available: Crystallographic data (Table
S-I), atomic coordinates for the non hydrogen atoms (Tables S-II (4a‚1/
2C7H8) and S-III (5b‚CH2Cl2)), atomic coordinates of the hydrogen
atoms (Tables S-IV (4a‚1/2C7H8) and S-V (5b‚CH2Cl2)), thermal
parameters (Tables S-VI (4a‚1/2C7H8) and S-VII (5b‚CH2Cl2)) and
complete bond distances and angles (Tables S-VIII (4a‚1/2C7H8) and
S-IX (5b‚CH2Cl2)) (19 pages). Ordering information is given on any
current masthead page.
cis-[Ni{iPr2PCH ‚ ‚ C( ‚ ‚ O)Ph}2]CoI2 (7). Following the proce-
dure described for 5a, but starting from 6 (0.200 g, 0.377 mmol) and
anhydrous CoI2 (0.118 g, 0.377 mmol), 7 was obtained as a green
‚‚
‚‚
crystalline powder (0.240 g, 76%). IR (KBr): ν(CsC) + ν(CsO)
1
1559 vs. H NMR (CD2Cl2, 298 K): δ 52.05 (s, 2 H, CHP), 9.64 (s,
2 H, CH(CH3)2), 9.33 (s, 12 H, CH(CH3)2), 5.33 (s, 2 H, CH(CH3)2),
5.12 (s, 12 H, CH(CH3)2), -0.60 (s, 2 Hp, C6H4), -8.91 (s, 4 Hm,
C6H4), -46.00 (s, 4 Ho, C6H4). 31P{1H} NMR (CD2Cl2, 298 K): δ
-54.7 (s). Anal. Calcd for C28H40CoI2NiO2P2 (M ) 841.99): C, 39.94;
H, 4.79. Found: C, 40.32; H, 4.66.
Crystal Structure Determinations for Compounds 4a‚1/2C7H8 and
5b‚CH2Cl2. The crystallographic data for both compounds are sum-
marized in Table 5. Data were collected at room temperature (25 °C)
on a Philips PW 1100 (4a‚1/2C7H8) and on a Enraf Nonius CAD4
diffractometer (5b‚CH2Cl2). One standard reflection was monitored
every 100 measurements; no significant decay was noticed over the
time of data collection. Intensities were corrected for the Lorentz-
polarization effect and an empirical absorption correction was applied
after isotropic convergence.31,32 The structures were solved by direct
IC9513494
(33) SDP Structure Determination Package; Enraf Nonius: Delft, The
Netherlands, 1977. Sheldrick, G. M. SHELX-76 Program for crystal
structure determination, University of Cambridge, England, 1976;
SHELXS-86 Program for the solution of crystal structures, University
of Go¨ttingen, 1986.
(31) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(32) International Tables for X-Ray Crystallography; Kynoch Press:
Birmingham, England, 1974; Vol. IV.