2,3-Bis(diarylphosphanyl)-1,4-diazadienes: P,P Coordination of Pd II, PtII and a Nickelacyclopentanone with Subsequent Formation of Quinoxalines by a Ring-Closure Reaction at the Periphery

Article abstract of DOI:10.1002/ejic.200300350

The solid-state structures of several 2,3-bis(phosphanyl)-1,4-diazadiene ligands of the general formula RN= C(PPh₂)-C(PPh₂)=NR (B: R = 4-tolyl; C: R = 4-tert-butylphenyl; D: R = mesityl) were determined by single-crystal X-ray diffraction. The ligands B and C are nonplanar and lie between the (E) and the (Z) form (N=C-C=N is 99.5° in B, 94.0° in C, and 128.2° in D). In the presence of air, B is oxidized to its corresponding phosphane oxide. Reaction of D with elemental sulfur yields the corresponding phosphane sulfide. Furthermore, ligand C reacts with [PtCl ₂(cod)] and [PdCl₂(CH₃CN)₂] to form mononuclear complexes (1 and 2, respectively) in which the two P atoms are bound to the metal center. X-ray structural analysis showed that in both complexes the 1,4-diazadiene functionality at the periphery had undergone a ring-closure reaction with one of the aromatic N-substituents thus resulting in a quinoxaline ring. The bulkier ligand D reacts with [PdCl₂(CH ₃CN)₂] to form the mononuclear complex 3. In the solid state, the two phosphorus atoms are coordinated to the metal center in a five-membered chelate ring. In contrast to 1 or 2, a cyclohexadiene system is formed as result of a cycloaddition reaction of one aromatic N-substituent with the 1,4-diazadiene system. The nickel complex [Ni(tmeda)(C₂H ₄COO)] reacts with D by displacement of tmeda to form a mononuclear complex 4a with P,P coordination. A subsequent ring-closure reaction (cyclo-addition) at the periphery does not occur in 4a. If the ligand is sterically less demanding (B or C), a cycloaddition between the 1,4-diazadiene system and one aromatic substituent takes place in the nickel complex to form complexes of the type 5 containing a quinoxaline ring. This reaction could be monitored by ³¹P NMR spectroscopy for ligand C. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300350

FULL PAPER
2,3-Bis(diarylphosphanyl)-1,4-diazadienes: P,P Coordination of PdII, PtII
and a Nickelacyclopentanone with Subsequent Formation of Quinoxalines by a
Ring-Closure Reaction at the Periphery
Dirk Walther,*[a] Stefan Liesicke,[a] Reinald Fischer,[a] Helmar Görls,[a] Jennie Weston,[b] and
Ariadna Batista[b]
Keywords: Chelates / Cycloadditions / Metallacycles / N,P ligands / Transition metals
The solid-state structures of several 2,3-bis(phosphanyl)-1,4-
diazadiene ligands of the general formula RN=
C(PPh2)−C(PPh2)=NR (B: R = 4-tolyl; C: R = 4-tert-bu-
tylphenyl; D: R = mesityl) were determined by single-crystal
uclear complex 3. In the solid state, the two phosphorus
atoms are coordinated to the metal center in a five-mem-
bered chelate ring. In contrast to 1 or 2, a cyclohexadiene
system is formed as result of a cycloaddition reaction of one
X-ray diffraction. The ligands B and C are nonplanar and lie aromatic N-substituent with the 1,4-diazadiene system. The
between the (E) and the (Z) form (N=C−C=N is 99.5° in B, nickel complex [Ni(tmeda)(C2H4COO)] reacts with D by dis-
94.0° in C, and 128.2° in D). In the presence of air, B is oxid- placement of tmeda to form a mononuclear complex 4a with
ized to its corresponding phosphane oxide. Reaction of D P,P coordination. A subsequent ring-closure reaction (cyclo-
with elemental sulfur yields the corresponding phosphane
sulfide. Furthermore, ligand C reacts with [PtCl2(cod)] and
[PdCl2(CH3CN)2] to form mononuclear complexes (1 and 2,
respectively) in which the two P atoms are bound to the metal
center. X-ray structural analysis showed that in both com-
plexes the 1,4-diazadiene functionality at the periphery had
undergone a ring-closure reaction with one of the aromatic
N-substituents thus resulting in a quinoxaline ring. The bulk-
addition) at the periphery does not occur in 4a. If the ligand
is sterically less demanding (B or C), a cycloaddition between
the 1,4-diazadiene system and one aromatic substituent
takes place in the nickel complex to form complexes of the
type 5 containing a quinoxaline ring. This reaction could be
monitored by 31P NMR spectroscopy for ligand C.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
ier ligand D reacts with [PdCl2(CH3CN)2] to form the monon- Germany, 2003)
Introduction
rise to a rich complex chemistry. Some of these chelating
ligands chelate by P,P complexation with nickel() bromide
and then subsequently undergo a rather unusual ring-
closure reaction at the periphery of the ligand to form a
quinoxaline.[17] This opens a simple route for the synthesis
of bis(diphenylphosphanyl)ethylenes containing a quinoxa-
line backbone. Continuing with our investigations, we now
report an alternative synthesis for obtaining these ligands.
We have further investigated their structural and electronic
properties as well as their behavior towards oxygen and sul-
fur. In order to gain a deeper understanding of their coordi-
nation behavior, as well as their interesting peripheral ring-
closure reaction, we have extended the palette of metal frag-
ments employed to include PdII and PtII as well as an
organometallic derivative of NiII.
2,3-Bis(phosphanyl)-1,4-diazadienes contain perhaps the
two most important chelating functionalities, a conjugated
1,4-diazadiene and a 1,2-bis(phosphanyl)ethane, within the
same ligand. Both of these structural units are known to
form stable five-membered metal chelate ring systems which
have general importance in organometallic and coordi-
nation chemistry. Numerous catalysts for homogeneous re-
actions are, for example, based on these chelate
complexes.[1Ϫ16]
In an initial communication, we reported a synthetic pro-
cedure for obtaining hitherto unknown 2,3-bis(diarylphos-
phanyl)-1,4-diazadienes.[17] These are the first experimen-
tally accessible representatives that unify the two func-
tionalities mentioned above. As one would expect, they re-
act readily with NiII, CuI, and Mo0 fragments thus giving
Results and Discussion
[a]
Institut für Anorganische und Analytische Chemie der
Synthesis of the Bis(diarylphosphanyl)-1,4-diazadienes
A؊D
Friedrich-Schiller-Universität Jena,
07743 Jena, Germany
[b]
Institut für Organische Chemie und Makromolekulare Chemie
der Friedrich-Schiller-Universität Jena,
07743 Jena, Germany
In analogy to the previously reported 2,3-bis(diarylphos-
phanyl)-1,4-diazadienes BϪD,[17] we succeeded in preparing
Eur. J. Inorg. Chem. 2003, 4321Ϫ4331
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D. Walther, S. Liesicke, R. Fischer, H. Görls, J. Weston, A. Batista
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Scheme 1
the 2,3-bis(diphenylphosphanyl)-1,4-diphenyl-1,4-diazadi- chloroform. All of these ligands possess the same structural
ene (A) in 40% yield from sodium diphenylphosphide and motif in the solid state. As a representative example, Fig-
the corresponding imidoyl chloride in THF (Scheme 1).
ure 1 illustrates the molecular structure of compound D,
This new ligand has one singlet 31P{1H} resonance (δ ϭ which co-crystallizes with 1 equiv. of CHCl3. Selected geo-
4.7 ppm) in the same spectral region as the 31P NMR sig- metrical parameters can be found in the figure caption.
1
nals of ligands BϪD. The H and 13C NMR spectra of A
are very simple, typical for a symmetrical structure in solu-
tion, and are directly comparable with those reported for
the ligands BϪD.[17]
An alternative route to D is the reaction of the corre-
sponding imidoyl chloride with diphenyl(trimethyl-
silyl)phosphane (Scheme 2).
This preparative route leads to pure D in a much higher
yield (64%) without the time-consuming necessity of pu-
rifying the raw material. The reaction mixture for this
alternative route contained, in addition to D, a small
amount of the hitherto unknown 2-(diphenylphosphanyl)-
1,4-dimesityl-1,4-diazabutadiene (G) which could be iso-
lated as yellow crystals and fully characterized by NMR
spectroscopy and X-ray diffraction analysis.
Figure 1. Solid-state structure of compound D; selected bond
˚
The Structure and Electronic Properties of Ligands A؊D
Single crystals of BϪD suitable for an X-ray diffraction
lengths [A] and bond angles [°]: C1ϪP1 1.874(2), C1ϪN1 1.280(2),
C1ϪC2 1.517(2), C2ϪP2 1.875(2), C2ϪN2 1.266(2); P1ϪC1ϪN1
119.5(1), P2ϪC2ϪN2 121.7(1), P1ϪC1ϪC2 125.4(1), N1ϪC1ϪC2
analysis could be grown from a solution in either toluene or 114.9(1), P2ϪC2ϪC1 124.7(1), N2ϪC2ϪC1 113.5(1)
Scheme 2
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2,3-Bis(diarylphosphanyl)-1,4-diazadienes
FULL PAPER
The central CϪC bond in D is a typical single bond
Table 1. Selected electronic properties of ligand D, calculated at the
B3LYP/6-31ϩG(d,p)//B3LYP/lanl2dz level of theory
˚
(1.517 A) and the CϪN bond lengths are typical of double
˚
bonds (1.280 and 1.266 A). The bulky PPh2 group results in
Atomic charge
Orbital
Occupancy
Energy [eV]
large PϪCϪC bond angles (125.4 and 124.7°); the NϪCϪC
angles (114.9 and 113.5°) are rather small due to the effect
of the lone pair on the nitrogen atom. Perhaps the most
unusual feature of ligand D is that, in spite of the 1,4 diaza-
butadiene unit, it is not planar and assumes a twisted (E)
conformation (the NϪCϪCϪN dihedral angle is 128.2°).
The twist angle is even larger in B (NϪCϪCϪN ϭ 99.5°)
and C (NϪCϪCϪN ϭ 94.0°), leading to an almost orthog-
onal conformation. A conformational search for D at the
B3LYP/lanl2dz level of theory confirmed that this non-
planar geometry is the global minimum (and the only stable
conformation on the hypersurface). All calculated geometri-
cal parameters agree quite satisfactorily with the solid-state
values. An NBO analysis for D showed that a residual de-
localization between the two CϭN double bonds is present
[πCϭNǞπ*CϭN ϭ 10.2 kcal/mol] in spite of the relatively
large twist angle.
The by-product 2-(diphenylphosphanyl)-1,4-dimesityl-
1,4-diazabutadiene (G, Scheme 2), which lacks the bulk of
a second PPh2 group, assumes a planar (E) conformation
in the solid state (not depicted; the NϪCϪCϪN torsion
angle is 158.8°). This prompted us to explore the rotational
process about the central CϪC bond in the absence of steric
hindrance (Figure 2).
qC
qN
qP
0.05
Ϫ0.46
ϩ0.76
nN
nP
1.82
1.80
Ϫ8.6
Ϫ7.7
case, a lone pair on the heteroatom functions as a donor
orbital to the metal ion. The NBO analysis of D (Table 1)
shows that the lone pair orbital on P lies significantly higher
in energy (Ϫ7.7 eV) than on N (Ϫ8.6 eV). This difference is
probably responsible for the observed preference of a P,P
coordination mode since the lone electron pair on P can
interact more effectively with low-lying unoccupied orbitals
on the metal ion.
Reactivity towards Oxygen and Sulfur
The ligands BϪD all decompose in the presence of water
and are oxidized by air to yield the corresponding phos-
phane oxides. We succeeded in isolating the phosphane ox-
ide E, resulting from the reaction of B with hydroperoxide
or with oxygen, as single crystals. Its solid-state structure
and relevant geometrical parameters can be found in Fig-
ure 3.
Figure 2. Torsional potential for rotation about the central CϪC
bond in a simple diphosphanyl-diazabutadiene, calculated at the
B3LYP/6-311ϩϩG(3df,3pd) level of theory
Figure 3. Solid-state structure of compound E; selected bond
˚
lengths [A] and bond angles [°]: P1ϪO1 1.484(2), P1ϪC1 1.857(3),
C1ϪN1 1.285(3), C1ϪC2 1.522(4), P2ϪO2 1.483(2), P2ϪC2
1.857(3), C2ϪN2 1.280(3); O1ϪP1ϪC1 112.1(1), O2ϪP2ϪC2
111.1(1), P1ϪC1ϪN1 113.0(2), P2ϪC2ϪN2 116.4(2), P1ϪC1ϪC2
The (E) conformation (PϪCϪCϪP ϭ 180°) is the only
stable minimum on the hypersurface of this bifunctional
chelating unit. The (Z) conformer is the transition structure
for rotation about the CϪC bond due to strong electronic
repulsions between the lone electron pairs on the nitrogen
115.9(2),
N1ϪC1ϪC2
130.9(3),
P2ϪC2ϪC1
115.9(2),
N2ϪC2ϪC1 127.2(3)
Ligand E also assumes a nonplanar conformation.
atom in this orientation. It is interesting that two inflection Rather than being almost orthogonal, the torsion angle
points occur in the rotational barrier at ca. 60 and 300°. In (NϪCϪCϪN ϭ 118.6°) is significantly shifted towards an
the neighborhood of these points, the repulsion between the (E) conformation (NϪCϪCϪN in B is 99.5°). This may
lone pairs of the nitrogen atoms is becoming quite weak possibly be due to the higher coordination number and thus
and a πCϭNǞπ*CϭN delocalization is beginning to appear. increased steric bulk of the phosphorus functionalities
This delocalization is responsible for the preferred (E) con- which force them to be (E) to each other.
formation. If bulky substituents on P are introduced, these
Adding elemental sulfur to a solution of D resulted in
inflection points are stabilized and become minima on the the formation of the corresponding disulfide F, which could
hypersurface at the expense of the planar (E) conformation. then be characterized by MS and NMR spectroscopy. In
There are several possibilities for the coordination of D the 31P{1H} NMR spectrum of F, a singlet at δ ϭ 34.9 ppm
to a metal ion (P,P, N,N and two P,N modes) but, as dis- (shifted downfield relative to D) was observed. In the 13C
cussed below, P,P coordination is generally favored. In each NMR spectrum at room temperature, all expected 11 sig-
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D. Walther, S. Liesicke, R. Fischer, H. Görls, J. Weston, A. Batista
FULL PAPER
nals were detected. Surprisingly, the resonance of the
PϪCϭN carbon atoms occurs at δ ϭ 159.3 ppm as a broad
signal, thus suggesting the presence of a hindered rotation
about the central PNCϪCNP single bond.
PdII and PtII Complexes of These Ligands
We observed in our initial investigation that a ring-clos-
ure reaction at the periphery of a metal-complexed 2,3-
bis(diarylphosphanyl)-1,4-diazadiene unit only occurred
when P,P coordination is present and only when the metal
ion was NiII.[17] Corresponding CuI or Mo(CO)4 complexes
did not promote this reaction. This fact prompted us to
investigate the coordination chemistry of the related d8 me-
tal ions PdII and PtII.
Ligand C reacts with [PtCl2(cod)] to yield the mononu- [A] and bond angles [°]: PtϪCl1 2.361(1), PtϪCl2 2.360(1), PtϪP1
clear complex 1 as the only product. The two phosphorus
atoms are nonequivalent as can be seen from two reso-
nances (δ ϭ 25.0 and 20.0 ppm) in the 31P{1H} spectrum
of 1. In addition, the 1H and 13C NMR spectra of 1 in
[D8]THF are in agreement with the unsymmetrical struc-
ture shown in Scheme 3.
Figure 4. Solid-state structure of complex 1; selected bond lengths
˚
2.214(1), PtϪP2 2.206(1), P1ϪC1 1.795(6), C1ϪC2 1.342(8),
C1ϪN1 1.448(6), N1ϪC3 1.449(7), P2ϪC2 1.830(5), C2ϪN2
1.380(7), N2ϪC4 1.404(6), C4ϪC3 1.387(8), C4ϪC5 1.390(8),
C5ϪC6 1.390(8), C6ϪC7 1.392(8), C7ϪC8 1.391(8), C8ϪC3
1.399(7); Cl1ϪPtϪCl2 91.31(5), Cl1ϪPtϪP1 91.42(5), Cl1ϪPtϪP2
178.48(5), Cl2ϪPtϪP1 177.04(6),
P1ϪPtϪP2 87.48(5)
Cl2ϪPtϪP2 89.77(5),
For example, two different signals, each integrating to charge delocalization in the C1ϪC2ϪN2ϪC4 part of the
nine protons, were observed at δ ϭ 1.05 and 1.24 ppm for quinoxaline ring. Consequently, N1 is pyramidal and N2 is
the two tert-butyl groups. The NMR spectroscopic data planar. This difference may be explained by steric reasons:
suggest that 1 is the product of a ring-closure reaction be- N1 bears an aryl substituent in the neighborhood of the
tween the 1,4-diazadiene system at the periphery of the Ph2P group whereas N2 bears the much smaller hydrogen
complex with one tert-butylphenyl substituent of a nitrogen substituent.
atom yielding a quinoxaline system by subsequent tauto-
merization (Scheme 3).
Ligand C also reacts with [PdCl2(CH3CN)2] to form the
mononuclear complex 2 even if an excess of the palladium
Figure 4 shows the solid-state structure of 1, which con- compound was employed. Analogous to the Pt compound,
firms the existence of a mononuclear complex in which a the 31P{1H}spectrum show that the two phosphorus atoms
ring-closure reaction to form a quinoxaline ring has oc- are unsymmetrical (two doublets at
δ ϭ 43.5 and
curred. The coordination geometry of the platinum center 37.6 ppm). The 1H and 13C NMR spectra also indicate that
is square-planar with two cis-chloro ligands. The two phos- a ring-closure reaction has taken place (see Exp. Sect.).
phorus donor atoms form a five-membered chelate ring. Brown crystals of the palladium complex 2 could be iso-
Typical for this structure is the C1ϪC2 double bond (1.342 lated from THF. However, their quality was insufficient for
˚
A). As expected, the CϪC bond lengths in the peripheral the exact determination of bond lengths and bond angles
benzene ring are equivalent to each other within experimen- in the solid state. Only the structure motif of the planar
tal errors and correspond to typical CϪC bond lengths in complex containing a peripheral quinoxaline ring could be
aromatic systems. The C1ϪN1 and the C3ϪN1 bond unequivocally confirmed in the solid state.
lengths are those of typical single bonds [1.448(6), and
Ligand D contains, in contrast to C, methyl groups in
˚
1.449(7) A]. In contrast, the C2ϪN2 and C4ϪN2 bonds both ortho positions of the N substituents. This effectively
˚
[1.380(7), 1.404(6) A] are slightly shortened, indicating prevents tautomerization to form a benzene ring. Coordi-
Scheme 3
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2,3-Bis(diarylphosphanyl)-1,4-diazadienes
FULL PAPER
nation of a metal ion to both phosphorus atoms, followed [Ni{2,3-bis(diarylphosphanyl)-1,4-diazadiene}(C2H4COO)]
by a peripheral ring closure, must then stop at the cyclo- complex. If the ring closure is affected by the additional
hexadiene stage of the reaction.[17]
metal ligands, one would expect a different reactivity of this
Ligand D does indeed react with [PdCl2(CH3CN)2] in complex compared to the related NiBr2 complex, which un-
THF to form the mononuclear complex 3. 1H, 13C, and dergoes a fast ring-closure reaction.
31P{1H} NMR spectra are in complete agreement with a
Treatment of the nickelacycle with the bulk ligand D in
1,3-cyclohexadiene ring at the periphery of the metal com-
plex. The solid-state structure of 3 confirmed the presence
of the expected 1,3-cyclohexadiene ring with its typically
alternating bond lengths (Figure 5). The N1ϪC3 bond
a solution of DMF followed by removal of tmeda by distil-
lation in vacuo resulted in the expected organometallic
complex [Ni(D)(C2H4COO)] (4a; Scheme 4) which turned
out to be dark red. There are theoretically four possibilities
for the coordination of D to the nickelacyclic fragment in
this compound (P,P, N,N, and two P,N coordination
modes). NMR spectroscopic data show that both phos-
phorus donor atoms coordinate to the nickelacycle in a dif-
ferent chemical environment (double signal sets for the mes-
˚
length (1.300 A) is that of a double bond and therefore
much shorter than the corresponding bond length in the
˚
N1ϪC1 single bond of 1 (1.448 A). Bond lengths and
angles in the (P,P)Pd chelate ring are very similar to those
in 1.
1
ityl groups in the H NMR spectrum and two doublets at
δ ϭ 19.8 and 44.8 ppm in the 31P{1H} NMR spectrum of
4a). Isolation of single crystals of 4a from benzene and sub-
sequent X-ray diffraction analysis (Figure 6) showed that
both phosphorus atoms are coordinated to the nickel center
(square-planar P,P mode) in the solid state. In addition, an
oxygen and a carbon atom of the C2HC4COO moiety are
bound to the nickel center. The 1,4-diazadiene unit of D is
not involved in coordination. A ring-closure reaction of the
1,4-diazadiene and one mesityl substituent at the nitrogen
atom to yield a quinoxaline ring did not take place upon
coordination of the diphosphane unit to the nickelacycle.
The diazabutadiene unit in ligand D is not planar
(NϪCϪCϪN torsional angle is 52.4°) but is definitely
closer to a (Z) arrangement than to the twist-(E) confor-
mation of the free ligand D (NϪCϪCϪN ϭ 128.2°). Li-
gand bond lengths do not differ significantly between the
free ligand D and the coordinated complex 4a.
Figure 5. Solid-state structure of complex 3; selected bond lengths
˚
[A] and bond angles [°]: PdϪCl1 2.354(1), PdϪCl2 2.346(1),
PdϪP1 2.194(1), PdϪP2 2.227(1), P1ϪC1 1.789(5), C1ϪN1
1.394(7), C1ϪC2 1.350(7), N1ϪC3 1.300(7), C2ϪN2 1.386(7),
N2ϪC4 1.530(7), C4ϪC3 1.520(7), C4ϪC5 1.460(7), C5ϪC6
1.331(8), C6ϪC7 1.447(9), C7ϪC8 1.331(8), C8ϪC3 1.459(8);
Cl1ϪPdϪCl2 95.26(6), Cl1ϪPdϪP1 89.62(6), Cl1ϪPdϪP2
176.20(6), Cl2ϪPdϪP1 174.31(6), Cl2ϪPdϪP2 88.07(6),
P1ϪPdϪP2 87.14(5), P1ϪC1ϪN1 116.8(4), P2ϪC2ϪN2 125.0(4),
P1ϪC1ϪC2 120.9(4), P2ϪC2ϪC1 114.8(4), N1ϪC1ϪC2 122.0(5),
N2ϪC2ϪC1 120.1(5)
The less bulky ligand B also reacted with the nickelacycle
[Ni(tmeda)(C2H4COO)] to yield an orange chelate complex,
which could be isolated in good yields (54%) from dichloro-
methane as an adduct of the composition ‘‘[Ni(B)(C2H4-
COO)(CH2Cl2)]’’. Analogous to 4a, the 31P{1H} NMR
spectrum of this complex in CDCl3 shows a low-field shift
relative to the free ligand and indicates a P,P coordination
mode but, in this case, two sets of two doublets are observed
These results allow us to conclude that bromides and
chlorides of d8 systems (NiII, PdII, and PtII) generally favor
P,P coordination with 2,3-bis(phosphanyl)-1,4-diazadienes
over P,N or N,N coordination. The formation of a mono-
nuclear complex is then directly followed by an unusual
peripheral ring-closure reaction to form a quinoxaline de-
rivative, independent of the size of the metal ion.
2
2
at δ ϭ 28.3 [d, J(31P31P) ϭ 19.0 Hz], 39.0 [d, J(31P31P) ϭ
24.2 Hz], 46.1 [d, 2J(31P31P) ϭ 24.2 Hz], and 48.9 [d,
2J(31P31P) ϭ 19.0 Hz] ppm.
This is not compatible with the ‘‘open coordination
form’’ observed for 4a but can be rationalized by an unsym-
metrical chelate ring system formed by ring-closure reaction
between the 1,4-diazadiene unit and an aromatic N-sub-
stituent to form the regioisomers 5b/5bЈ (Scheme 4).
Reaction of These Ligands with a Nickelacycle
We then modified the metal fragment employed to find
out if the peripheral ring-closure reaction depends on the
nature of the additional ligand(s) coordinated to the metal
The 1H NMR spectroscopic data support this con-
1
ion. Our metal fragment of choice was the nickelacycle clusion. In the H NMR spectrum two sets of signals for
[Ni(tmeda)(C2H4COO)], which contains a doubly nega- the CH3 protons at δ ϭ 1.84, 1.91, 2.11, and 2.15 ppm were
tively charged 1-oxo-2-nickelacyclopentan-5-one chelate found whereas the CH2 protons of the metallacyclic ring
ring on one side of the square-planar complex. On the other appear as multiplets. The 13C{1H} NMR spectrum is very
side is the neutral chelating ligand N,N,NЈ,NЈ-tetramethyl- complicated due to the 31P coupling pattern of the 13C sig-
ethylenediamine (tmeda). Displacement of tmeda by either nals of the two very similar regioisomers. Therefore, not all
B, C, or D should result in the initial formation of an expected signals could be resolved (see Exp. Sect.).
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D. Walther, S. Liesicke, R. Fischer, H. Görls, J. Weston, A. Batista
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Scheme 4
The formation of a quinoxaline system at the periphery
When the closely related ligand C was treated with the
was confirmed by X-ray diffraction analysis. Figure 7 shows nickelacycle [Ni(tmeda)(C2H4COO)], an initial intermediate
the molecule structure of a single crystal of the regioisomer was formed which could be monitored by time-resolved
5b·CH2Cl2 grown from dichloromethane. Unfortunately, 31P{1H} NMR spectroscopy at 5 °C. The ‘‘open coordi-
the quality of the crystals was insufficient for satisfactory nation form’’, characterized by two doublets at δ ϭ 42.7
refinement of all parameters.
and 60.9 ppm, could be assigned to this intermediate
Ligand B thus behaves in a fundamentally different way [Ni(C)(C2H4COO)] (4c; Scheme 4).
to ligand D. This clearly demonstrates the subtle depen-
As the reaction progressed, two sets of two doublets ap-
dence of the ring-closure reaction upon ligand environment peared at δ ϭ 30.5/51.0 and 37.7/49.0 ppm and grew in
and identity in the metal complex. Both the nature of the intensity over time. The signals assigned to the ‘‘open form’’
metal and the coordination geometry of the complex intermediate 4c completely disappeared after 2 h at room
formed in the first step of the complex formation, and the temperature, and, except for a very small amount of the free
nature of the other ligands surrounding the metal center, ligand, only the two sets of two doublets were observed,
influence the subsequent cycloaddition reaction at the peri- which we concluded was the ‘‘quinoxaline form’’ 5c/5cЈ re-
phery.
sulting from the peripheral ring-closure reaction. A com-
4326
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Eur. J. Inorg. Chem. 2003, 4321Ϫ4331

2,3-Bis(diarylphosphanyl)-1,4-diazadienes
FULL PAPER
Experimental Section
General: 1H, 13C, and 31P{1H} NMR spectra were recorded at am-
bient temperature with a Bruker AC 200 MHz spectrometer unless
otherwise stated. All spectra were referenced to TMS or deuterated
solvent as an internal standard. FAB mass spectra were obtained
with a Finnigan MAT SSQ 710 system (2,4-dimethoxybenzyl al-
cohol as matrix), ESI mass spectra were recorded with a Finnigan
MAT, MAT 95 XL. IR measurements were carried out with a
PerkinϪElmer System 2000 FT-IR. All manipulations were carried
out by using Schlenk techniques under argon. Prior to use, tetra-
hydrofuran, diethyl ether, and toluene were dried with potassium
hydroxide and distilled from Na/benzophenone. [PtCl2(cod)] and
[PdCl2(CH3CN)2] (Aldrich) were used as received. Oxalic imidoyl
chlorides RϪNϭC(Cl)ϪC(Cl)ϭNϪR,[18,19] NaPPh2(dioxane) and
K(PPh2)(dioxane)n,[20] and the nickelacycle [Ni{(tmeda)-
C2H4COO}][21] were prepared according to the literature.
Figure 6. Solid -state structure of complex 4a; selected bond lengths
˚
[A] and bond angles [°]: NiϪP1 2.096(1), NiϪP2 2.170(1), NiϪO1
1.882(3), NiϪC1 1.952(4), C1ϪC2 1.526(6), C2ϪC3 1.512(6),
C3ϪO1 1.306(5), C3ϪO2 1.227(5), P1ϪC4 1.853(4), P2ϪC5
1.864(4), C4ϪC5 1.530(5), C4ϪN1 1.271(5), C5ϪN2 1.267(5);
P1ϪNiϪP2 90.30(4), P1ϪNiϪO1 170.55(9), P1ϪNiϪC1 88.6(1),
P2ϪNiϪO1 96.00(9), P2ϪNiϪC1 171.5(1), O1ϪNiϪC1 86.2(1),
P1ϪC4ϪN1 120.9(3), P2ϪC5ϪN2 133.4(3), P1ϪC4ϪC5 110.1(2),
P2ϪC5ϪC4 110.4(2), N1ϪC4ϪC5 128.9(3), N2ϪC5ϪC4 115.0(3)
Computational Methods: All calculations reported in this article
were performed using the Gaussian 98[22] program package using
the gradient-corrected B3LYP[23Ϫ25] density functional. Default
convergence criteria were used for all optimizations. The size of
ligand D limited optimizations and frequency calculations to the
lanl2dz basis set developed by Hay and Wadt[26] as implemented in
Gaussian 98. Atomic charges, orbital and hyperconjugative interac-
tion energies were obtained at the B3LYP/6-31ϩG(d,p)//B3LYP/
lanl2dz level using the natural bond orbital (NBO) analysis of Reed
et al.[27] as implemented in Gaussian 98. The torsional barrier of
diphosphanyl-diazabutadiene (Figure 2) was calculated using the
very large 6-311ϩϩG(3df,3pd) basis set.
Crystal Structure Determination: The intensity data for the com-
pounds were collected with a Nonius KappaCCD diffractometer,
using graphite-monochromated Mo-Kα radiation. Data were cor-
rected for Lorentz and polarization effects, and (only for 1) for
absorption effects.[28,29] The structures were solved by direct meth-
ods (SHELXS[30]) and refined by full-matrix least-squares tech-
niques against F2o (SHELXL-97[31]). For the molecules B, C, D, E,
and G, the hydrogen atoms were located by difference Fourier syn-
thesis and refined isotropically. All other hydrogen atoms were in-
cluded at calculated positions with fixed thermal parameters. All
non-hydrogen atoms were refined anisotropically.[4] Since the qual-
ity of the data of compounds 2 and 5c was too low, we will only
publish the conformation of 5b and the crystallographic data of 2
and 5b. We have not deposited the data in the Cambridge Crystallo-
graphic Data Centre. XP (SIEMENS Analytical X-ray Instruments,
Inc.) was used for structure representations.
Figure 7. Solid-state structural motif of complex 5b (the solvent
CH2Cl2 has been omitted for clarity)
Crystal Data for B:[32] C40H34N2P2, Mr ϭ 604.63 g·molϪ1, colour-
less prism, size 0.21 ϫ 0.18 ϫ 0.10 mm, monoclinic, space group
parison of the 31P NMR spectrum of the closely related
complex pair 5b/5bЈ completely supports this assignment.
There is no evidence for any other stable intermediate oc-
curring during the ring-closure reaction.
˚
C2, a ϭ 21.7489(8), b ϭ 6.3620(2), c ϭ 12.8609(6) A, β ϭ
3
˚
115.479(2)°, V ϭ 1606.4(1) A , T ϭ Ϫ90 °C, Z ϭ 2, ρcalcd. ϭ 1.250
g·cmϪ3, µ(Mo-Kα) ϭ 1.67 cmϪ1, F(000) ϭ 636, 4265 reflections in
h(Ϫ30/30),k(0/7),l(Ϫ18/18), measured in the range 3.22° Յ Θ Յ
30.54°, completeness to Θmax 95%, 2532 independent reflections,
Rint ϭ 0.029, 2233 reflections with Fo Ͼ 4σ(Fo), 267 parameters, 1
In order to separate the quinoxaline ligand from the nick-
elacycle, the reaction mixture was treated with a solution of
dimethylglyoxime in ethanol and aqueous ammonia. After
separation of bis(dimethylgyoximato)nickel(), thin white
needles of 4-(p-tert-butylphenyl)-9-tert-butyl-3,4-dihydro-3-
(diphenylphosphanyl)-1H-quinoxalin-2-one were isolated
from the mother liquor, and were identified by IR measure-
restraint, R1obs ϭ 0.038, wR2obs ϭ 0.083, R1all ϭ 0.048, wR2all
ϭ
0.087, GOOF ϭ 1.004, Flack parameter 0.1(1), largest difference
Ϫ3
˚
peak/hole 0.240/Ϫ0.199 e·A
.
Crystal Data for C:[32] C46H46N2P2, Mr ϭ 688.79 g·molϪ1, colour-
less prism, size 0.32 ϫ 0.30 ϫ 0.28 mm, orthorhombic, space group
1
ments, mass spectra, H, 13C, and 31P NMR spectra. The
˚
formation of this product can easily be explained by hy-
drolysis of the free 1,2-bis(diphenylphosphanyl)quinoxaline
according to Scheme 4.
Fdd2, a ϭ 31.3604(9), b ϭ 38.780(1), c ϭ 6.3478(2) A, V ϭ
3
7719.9(4) A , T ϭ Ϫ90 °C, Z ϭ 8, ρcalcd. ϭ 1.185 g·cmϪ3, µ(Mo-
˚
Kα) ϭ 1.47 cmϪ1, F(000) ϭ 2928, 9627 reflections in h(Ϫ43/
Eur. J. Inorg. Chem. 2003, 4321Ϫ4331
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4327

D. Walther, S. Liesicke, R. Fischer, H. Görls, J. Weston, A. Batista
FULL PAPER
44),k(Ϫ55/55),l(Ϫ9/0), measured in the range 3.34° Յ Θ Յ 30.49°,
completeness to Θmax 99.2%, 3155 independent reflections, Rint
Crystal Data for 3:[32] C44H42Cl2N2P2Pd·1.5C4H8O, Mr ϭ 946.19
g·molϪ1, yellow prism, size 0.18 ϫ 0.12 ϫ 0.10 mm, monoclinic,
ϭ
0.049, 2727 reflections with Fo Ͼ 4σ(Fo), 318 parameters, 1 re-
space group P21/n, a ϭ 14.4502(6), b ϭ 24.9850(10), c ϭ 14.6521(5)
3
straint, R1obs ϭ 0.047, wR2obs ϭ 0.090, R1all ϭ 0.061, wR2all ϭ 0.094, A, β ϭ 112.360(3)°, V ϭ 4892.2(3) A , T ϭ Ϫ90 °C, Z ϭ 4, ρcalcd. ϭ
˚
˚
GOOF ϭ 1.060, Flack parameter 0.07(9), largest difference peak/
1.285 g·cmϪ3, µ(Mo-Kα) ϭ 5.91 cmϪ1, F(000) ϭ 1960, 13135 reflec-
tions in h(Ϫ16/16),k(Ϫ28/28),l(Ϫ16/16), measured in the range
1.73° Յ Θ Յ 24.09°, completeness to Θmax 96.7%, 7502 indepen-
dent reflections, Rint ϭ 0.037, 4810 reflections with Fo Ͼ 4σ(Fo),
508 parameters, 8 restraints, R1obs ϭ 0.057, wR2obs ϭ 0.165, R1all ϭ
0.081, wR2all ϭ 0.177, GOOF ϭ 0.953, largest difference peak/hole
Ϫ3
˚
hole: 0.220/Ϫ0.278 e·A
.
Crystal Data for D:[32] C44H42N2P2·CHCl3, Mr ϭ 780.10 g·molϪ1
yellow prism, size 0.10 ϫ 0.10 ϫ 0.06 mm, triclinic, space group
,
˚
˚
¯
P1, a ϭ 10.9955(2), b ϭ 11.0908(4), c ϭ 18.6186(6) A, α ϭ
3
Ϫ3
˚
88.207(1), β ϭ 77.765(2), γ ϭ 65.120(2)°, V ϭ 2008.7(1) A , T ϭ
1.069/Ϫ0.475 e·A
.
Ϫ90 °C, Z ϭ 2, ρcalcd. ϭ 1.290 g·cmϪ3, µ(Mo-Kα) ϭ 3.42 cmϪ1
,
F(000) ϭ 816, 14121 reflections in h(Ϫ11/14),k(Ϫ14/13),l(Ϫ20/24),
measured in the range 2.03° Յ Θ Յ 27.48°, completeness to Θmax
98.3%, 9053 independent reflections, Rint ϭ 0.055, 6598 reflections
with Fo Ͼ 4σ(Fo), 641 parameters, 0 restraints, R1obs ϭ 0.047,
wR2obs ϭ 0.131, R1all ϭ 0.067, wR2all ϭ 0.140, GOOF ϭ 1.059, larg-
Crystal Data for 4a:[32] C47H46N2NiO2P2·0.5C6H6, Mr ϭ 830.56
g·molϪ1, red prism, size 0.10 ϫ 0.10 ϫ 0.08 mm, monoclinic, space
group P21/n, a ϭ 12.6055(3), b ϭ 16.4881(4), c ϭ 20.9493(6) A,
˚
3
˚
β ϭ 99.186(2)°, V ϭ 4298.3(2) A , T ϭ Ϫ90 °C, Z ϭ 4, ρcalcd.
ϭ
1.283 g·cmϪ3, µ(Mo-Kα) ϭ 5.68 cmϪ1, F(000) ϭ 1748, 45176 reflec-
tions in h(Ϫ15/16),k(Ϫ21/21),l(Ϫ22/27), measured in the range
2.39° Յ Θ Յ 27.42°, completeness to Θmax 98.6%, 9656 indepen-
dent reflections, Rint ϭ 0.115, 6543 reflections with Fo Ͼ 4σ(Fo),
499 parameters, 0 restraints, R1obs ϭ 0.069, wR2obs ϭ 0.162, R1all ϭ
0.114, wR2all ϭ 0.191, GOOF ϭ 1.055, largest difference peak/hole
Ϫ3
˚
est difference peak/hole 0.287/Ϫ0.461 e·A
.
Crystal Data for E:[32] C40H34N2O2P2, Mr ϭ 636.63 g·molϪ1, or-
ange prism, size 0.32 ϫ 0.20 ϫ 0.10 mm, monoclinic, space group
˚
P21/c, a ϭ 16.4345(5), b ϭ 12.3660(5), c ϭ 16.3540(4) A, β ϭ
3
˚
94.429(3)°, V ϭ 3313.68(19) A , T ϭ Ϫ90 °C, Z ϭ 4, ρcalcd. ϭ 1.276
g·cmϪ3, µ(Mo-Kα) ϭ 1.7 cmϪ1, F(000) ϭ 1336, 24310 reflections in
h(Ϫ18/20),k(Ϫ15/15),l(Ϫ20/20), measured in the range 3.16° Յ Θ
Յ 26.33°, completeness to Θmax 99.7%, 6730 independent reflec-
tions, Rint ϭ 0.128, 4229 reflections with Fo Ͼ 4σ(Fo), 551 param-
eters, 0 restraints, R1obs ϭ 0.061, wR2obs ϭ 0.115, R1all ϭ 0.119,
wR2all ϭ 0.134, GOOF ϭ 1.015, largest difference peak/hole 0.215/
Ϫ3
˚
1.412/Ϫ0.611 e·A
.
Crystal Data for 5b: C43H38N2NiO2P2·2CH2Cl2, Mr ϭ 904.70
g·molϪ1, prism, size 0.20 ϫ 0.18 ϫ 0.12 mm, monoclinic, space
˚
group P21/c, a ϭ 8.8883(3), b ϭ 26.1761(9), c ϭ 19.3778(6) A, β ϭ
3
˚
95.384(2)°, V ϭ 4488.6(3) A , T ϭ Ϫ90 °C, Z ϭ 4, ρcalcd. ϭ 1.391
g·cmϪ3, µ(Mo-Kα) ϭ 8.4 cmϪ1, F(000) ϭ 1936, 16022 reflections
in h(Ϫ11/11),k(Ϫ33/31),l(Ϫ25/25), measured in the range 2.89°
Յ Θ Յ 27.46°, completeness to Θmax 93.9%, 9655 independent re-
flections, Rint ϭ 0.101.
Ϫ3
˚
Ϫ0.344 e·A
.
Crystal Data for G:[32] C32H33N2P, Mr ϭ 476.57 g·molϪ1, orange
¯
prism, size 0.20 ϫ 0.18 ϫ 0.12 mm, triclinic, space group P1, a ϭ
˚
11.3416(6), b ϭ 11.7240(5), c ϭ 12.1736(7) A, α ϭ 116.217(3), β ϭ
3
˚
103.457(2), γ ϭ 95.600(3)°, V ϭ 1374.6(1) A , T ϭ Ϫ90 °C, Z ϭ
2, ρcalcd. ϭ 1.151 g·cmϪ3, µ(Mo-Kα) ϭ 1.22 cmϪ1, F(000) ϭ 508,
9420 reflections in h(Ϫ11/14),k(Ϫ15/12),l(Ϫ15/14), measured in the
range 2.01° Յ Θ Յ 27.49°, completeness to Θmax 97.3%, 6133 inde-
pendent reflections, Rint ϭ 0.030, 4556 reflections with Fo Ͼ 4σ(Fo),
448 parameters, 0 restraints, R1obs ϭ 0.060, wR2obs ϭ 0.116, R1all ϭ
0.091, wR2all ϭ 0.128, GOOF ϭ 1.049, largest difference peak/hole
Preparation of the Ligands
Ph؊N؍C(PPh2)؊C(PPh2)؍N؊Ph (Ligand A): A solution of
NaPPh2 (7.17 mmol 15% excess) in 10 mL of cold THF (Ϫ78 °C)
was added dropwise to a solution of diphenyloxalylimidoyl chloride
(0.9 g, 3.24 mmol) in 50 mL of THF at Ϫ78 °C. The reaction mix-
ture was then allowed to warm to room temperature. After remov-
ing the solvent in vacuo and recrystallization from toluene 0.75 g
(40%) of A was isolated as a light yellow powder. 1H NMR
([D8]THF, 25 °C, 200 MHz): δ ϭ 7.04 (m, CH-phenyl) ppm.
31P{1H} NMR ([D8]THF, 25 °C, 81 MHz): δ ϭ 4.59 (s) ppm. MS
(CI): 577 (basic peak [M ϩ1]ϩ (C38H30N2P2 ϩ Hϩ), 499 ([M ϩ1]ϩ
Ϫ3
˚
0.208/Ϫ0.277 e·A
.
Crystal Data for 1:[32] C46H46Cl2N2P2Pt·2C4H8O, Mr ϭ 1098.99
g·molϪ1, yellow prism, size 0.20 ϫ 0.18 ϫ 0.10 mm, monoclinic,
space group P21/n, a ϭ 18.5552(9), b ϭ 14.0777(6), c ϭ 21.6152(7)
3
˚
˚
A, β ϭ 104.845(2)°, V ϭ 5457.7(4) A , T ϭ Ϫ90 °C, Z ϭ 4, ρcalcd. ϭ
1.337 g·cmϪ3, µ(Mo-Kα) ϭ 27.66 cmϪ1, semiempirical,[2] trans(min)
0.507, trans(max) 0.849, F(000) ϭ 2232, 21216 reflections in h(Ϫ24/
24),k(Ϫ18/17),l(Ϫ26/25), measured in the range 1.84° Յ Θ Յ
27.55°, completeness to Θmax 95.7%, 12062 independent reflections,
Rint ϭ 0.060, 6529 reflections with Fo Ͼ 4σ(Fo), 563 parameters, 0
Ϫ C6H6, 3%), 409 ([M ϩ1]ϩ Ϫ C12H12N, 3%), 393 ([M ϩ1]ϩ
C12H9P, 16%), 288 ([M ϩ1]ϩ Ϫ C19H16NP, 37%), 185 ([M ϩ1]ϩ
C26H21N2P, 15%).
Ϫ
Ϫ
Mes؊N؍C(PPh2)؊C(PPh2)؍N؊Mes·CHCl3 [D(CHCl3)]
restraints, R1obs ϭ 0.044, wR2obs ϭ 0.101, R1all ϭ 0.095, wR2all
ϭ
a) From Mes؊N؍CCl؊CCl؍N؊Mes and KPPh2: A solution of
dimesityloxalylimidoyl chloride (2.7 g, 7.5 mmol) and Pd(OAc)2
(85 mg, 0.038 mmol) in 100 mL of toluene was cooled to Ϫ40 °C
0.109, GOOF ϭ 0.886, largest difference peak/hole 1.120/Ϫ0.853
Ϫ3
˚
e·A
.
Crystal Data for 2: C46H46Cl2N2P2Pd·3C4H8O, Mr ϭ 1082.40 in a three-necked flask equipped with a stirrer and a dropping
g·molϪ1, brown prism, size 0.18 ϫ 0.12 ϫ 0.10 mm, monoclinic,
space group P21/n, a ϭ 18.5913(3), b ϭ 14.0835(4), c ϭ 21.5903(6)
funnel. Over 1 h, a solution of KPPh2 (15.0 mmol) in 42 mL of
dioxane/THF (1:1) was added. The color of the solution turned
3
˚
˚
A, β ϭ 104.930(1)°, V ϭ 5462.2(2) A , T ϭ Ϫ90 °C, Z ϭ 4, ρcalcd. ϭ from yellow to dark red. The dry-ice bath was then removed and
1.316 g·cmϪ3, µ(Mo-Kα) ϭ 5.41 cmϪ1, F(000) ϭ 2264, 20954 reflec-
the reaction mixture was kept at room temperature overnight. The
tions in h(Ϫ23/24),k(Ϫ17/18),l(Ϫ28/28), measured in the range precipitated KCl was then filtered off. The solvent was removed in
1.84° Յ Θ Յ 27.49°, completeness to Θmax 99.2%, 12444 indepen-
dent reflections, Rint ϭ 0.077.
vacuo and the residue dissolved in hexane. The mixture was then
filtered through Celite and the filtrate concentrated to dryness. The
4328
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2003, 4321Ϫ4331

2,3-Bis(diarylphosphanyl)-1,4-diazadienes
FULL PAPER
residue is a slowly crystallizing oil. Recrystallization from chloro-
(CDCl3, 200.13 MHz, 298 K): δ ϭ 1.74 (s, 12 H, o-CH3), 1.97 (s, 6
form/hexane gave 3.96 g (80%) of D(CHCl3) as yellow crystals. H, p-CH3), 6.20 (s, 4 H, m-H), 1.74 (s, 12 H, o-CH3), 7.17 (m, 8
M.p. 170 °C. C45H43N2P2Cl3 (780.1): calcd. C 69.28, H 5.56, Cl
H, m-H), 7.24 (m, 4 H, p-H), 7.81 (m, 8 H, o-H) ppm. 13C{1H}
1
13.63, N 3.59; found C 69.97, H 5.67, Cl 13.18, N 3.55. H NMR NMR (CDCl3, 50.32 MHz, 298 K): δ ϭ 19.0 (o-CH3), 20.3 (p-
(CDCl3, 200.13 MHz, 298 K): δ ϭ 1.42 (s, 12 H, o-CH3), 2.17 (s, 6 CH3), 123.5 (o-C), 127.8 (m, o-CH), 129.1 (i-C), 130.5 (p-CH),
H, p-CH3), 6.45 (s, 4 H, m-H, Mes), 7.19Ϫ7.21 (m, 12 H, Ph), 131.5 (m, m-CH), 132.4 (p-C), 133.2 (m-CH), 142.5 (m, i-C), 159.3
7.50Ϫ7.54 (m, 8 H, Ph) ppm. 13C{1H} NMR (CDCl3, 50.32 MHz,
[br., t, J ഠ 29 Hz, (NϭCϪP)2] ppm. 31P{1H} NMR (CDCl3,
298 K): δ ϭ 17.7 [t, J(13C31P) ϭ 2.5 Hz, CH3), 20.6 (CH3), 124.4 81.01 MHz, 298 K): δ ϭ 34.9 (s) ppm. MS m/z ϭ 725 [Mϩ ϩ H].
(C), 128.1 (CH), 128.1 [d, J(13C31P) ϭ 8.3 Hz, CH], 128.8 (CH),
132.8 (C), 133.8 [br., d, J(13C31P) ϭ 10.5 Hz, C], 135.2 [br., d,
J(13C31P) ϭ 23.4 Hz, C], 145.3 [br., d, J(13C31P) ϭ 9.3 Hz, C], 175.2
[dd, J(13C31P) ϭ 58.1, J(13C31P) ϭ 4.5 Hz, C] ppm. 31P{1H} NMR
(CDCl3, 81.01 MHz, 298 K): δ ϭ 9.0 (s) ppm. MS (EI): m/z ϭ
660 [Mϩ], 330 [Mϩ/2]. G was separated by column chromatography
(Florisil, hexane, toluene) as the most nonpolar compound from
the residue of the mother liquor. Yield: 0.18 g (5%) of yellow crys-
tals. The yield can be increased up to 44% by addition of HPPh2
before KPPh2. 1H NMR (CDCl3, 200.13 MHz, 298 K): δ ϭ 1.55
(s, 6 H, o-CH3), 2.02 (s, 6 H, o-CH3), 2.14 (s, 3 H, p-CH3), 2.17 (s,
3 H, p-CH3), 6.65 (s, 2 H, m-H), 6.73 (s, 2 H, m-H), 7.34Ϫ7.64
(m, 11 H, Ph, ϭCHϪ) ppm. 13C{1H} NMR (CDCl3, 50.32 MHz,
298 K): δ ϭ 17.5 (CH3), 17.6 (CH3), 20.6 (CH3), 124.4 [d,
J(13C31P) ϭ 1.8 Hz, C], 126.7 (C), 128.4 [d, J(13C31P) ϭ 18.8 Hz,
CH], 128.4 (m-CH, Mes), 128.6 (m-CH, Mes), 129.1 (CH), 132.7
(C), 133.8 (C), 134.4 [d, J(13C31P) ϭ 6.6 Hz, C], 135.0 (CH), 135.2
(CH), 135.1 [d, J(13C31P) ϭ 20.1 Hz, C], 157.5 [d, J(13C31P) ϭ
23.4 Hz, C], 175.5 [d, J(13C31P) ϭ 14.2 Hz, C] ppm. 31P{1H} NMR
(CDCl3, 81.01 MHz, 298 K): δ ϭ 2.4 (s) ppm. 31P{1H} NMR
(C6D6, 81.01 MHz, 298 K): δ ϭ 5.7 (s) ppm. MS (EI): m/z ϭ 446
[Mϩ], 330 [Ph2PCNMesϩ], 146 [MesNCHϩ].
Complex 1 [PdCl2(C46H46N2P2)]: A solution of C (0.873 mmol,
0.601 g) in 25 mL of THF was added dropwise to a solution of
[PdCl2(CH3CN)2] (0.873 mmol, 0.226 g) in 25 mL of THF whilst
stirring. Shortly after warming the solution up to 60 °C, complex
1 precipitated almost quantitatively. After filtration, the compound
was dried in vacuo at room temperature. It is only very slightly
soluble in organic solvents. C50H54Cl2N2OP2Pd [1(THF)] (938.26):
calcd. C 64.01, H 5.80, N 2.99; found C 63.25, 62.94, H 6.24, 5.98,
1
N 2.89. H NMR ([D8]THF, 25 °C, 200 MHz): δ ϭ 1.06, 1.15 (s,
18 H, CH3-tBu), 6.79Ϫ7.67 (m, 28 H, Ph) ppm. 31P{1H} NMR
([D8]THF, 25 °C, 81 MHz): δ ϭ 37.67 (d), 43.54 (d) ppm.
Complex 2 [PtCl2(C46H46N2P2)]: A solution of B (0.32 mmol) in
10 mL of THF was added to [PtCl2(cod)] (0.32 mmol, 0.12 g), dis-
solved in 10 mL of THF. Shortly after warming the solution up to
60 °C, complex
2 crystallized in more than 95% yield.
C50H54Cl2N2OP2Pt [2(THF)] (954.82): calcd. C 58.48, H 5.30, N
1
2.73; found C 58.44, H 5.61, 5.44, N 2.65. H NMR ([D8]THF, 27
°C, 200 MHz): δ ϭ 1.11, 1.15 (s, 18 H,CH3), 6.38Ϫ8.01 (m, 25 H,
Ph and NH); 31P{1H} NMR ([D8]THF, 27 °C, 81 MHz): δ ϭ Ϫ1.49
(d), 4.38 (d), 20.16 (d, J ϭ 12 Hz), 25.05 (d, J ϭ 13 Hz), 41.82 (d),
45.80 (d) ppm. MS (DEI): 953 [Mϩ ϭ C46H46N2P2Cl2Pt], 918 [Mϩ
Ϫ Cl], 784 [Mϩ Ϫ C10H13Cl], 696 [Mϩ Ϫ C12H11PCl2].
b) From Mes؊N؍CCl؊CCl؍N؊Mes and Me3Si؊PPh2: A mix-
ture of dimesityloxalylimidoyl chloride (2.25 g, 6.23 mmol) and di-
phenyl(trimethylsilyl)phosphane (3.25 g, 12.58 mmol) was held at
100 °C in a water bath for 12 h. Trimethylsilyl chloride was then
distilled off the reaction mixture, which became more and more
solid. The residue was then extracted with n-hexane. Yield: 2.63 g
(64%) of D as yellow crystals. M.p. 170 °C.
Complex 3 [PdCl2(C44H42N2P2)]: A solution of 1.17 mmol of D in
20 mL of THF was added dropwise to a solution of [PdCl2(aceton-
itrile)2] (1.17 mmol, 0.292 g) in 25 mL of THF whilst stirring at
room temperature. The complex precipitated after a short time in
almost quantitative yield. After filtration, the product was washed
with cold THF and dried in vacuo. C48H50Cl2N2OP2Pd [3(THF)]
(910.21): calcd. C 63.34, H 5.53, N 3.08; found C 63.37, H 6.06, N
Phosphane Oxide E by Oxidation of B: A solution of B in THF
was treated with an equimolar amount of hydrogen peroxide at
room temperature and a few milligrams of CuSO4 were added.
After 6 h, the solvent was removed and the residue was treated
with chloroform. The organic phase was separated and dried with
NaSO4. After removing the solvent, a yellow product was isolated.
White single crystals of E were obtained from THF at Ϫ20 °C.
Similarly, the oxidation can also be carried out with air in the pres-
ence of a copper salt. MS (EI): m/z ϭ 636 [Mϩ ϭ C40H34N2O2P2],
402 [(Ph2PO)2], 318 [Mϩ/2], 201 [Ph2PO]. 31P{1H} NMR (CDCl3,
1
3.12. H NMR ([D8]THF, 27 °C, 200 MHz): δ ϭ 0.89, 0.99, 1.46,
1.59; 1.89, 2.17 (s, each 3 H, CH3), 5.13, 5.97 (s, each 1 H, olefin-
H), 6.08, 6.70 (s, each 1 H, mesityl-CH), 7.06Ϫ8.30 (m, 20 H, Ph),
31P{1H} NMR ([D6]DMSO, 25 °C, 81 MHz): δ ϭ 46.86 (d, J ϭ
46 Hz), 53.63 (d,
J ϭ 46 Hz) ppm. MS (EI): m/z ϭ 802
[C44H42N2P2ClPd ϭ Mϩ Ϫ Cl].
Ligand Exchange Reaction of [Ni(C2H4COO)(tmeda)] with B, C,
and D
81.01 MHz, 298 K):
δ ϭ
23.56 ppm. 1H NMR (CDCl3,
[Ni{Mes؊N؍C(PPh2)؊C(PPh2)؍N؊Mes}(C2H4COO)]
[Ni(tmeda)(C2H4COO)] (1.05 g, 4.26 mmol) and
(4a):
(2.82 g,
200.13 MHz, 298 K): δ ϭ 2.14 (s, 6 H, p-CH3), 6.62. 6.78 (AAЈBBЈ,
8 H, CH-tolyl), 7.24Ϫ7.70 (m, phenyl, solvent) ppm.
D
4.26 mmol) in 20 mL of DMF were stirred for 20 min. During this
time, the solution (initially light green) turned dark red. The vol-
atile part of the reaction mixture was then removed at 50 °C in
vacuo. The residue was washed with diethyl ether, extracted with
Phosphane Sulfide F by Oxidation of D with Sulfur: A solution of
D(CHCl3) (1.01 g, 1.30 mmol) in toluene was treated with sulfur
(85 mg, 2.65 mmol) and stirred at room temperature for 24 h. The
solution slowly turned dark red. The signal of D in the 31P{1H} benzene and crystallized at 5 °C by addition of diethyl ether. Yield
NMR spectrum of the reaction mixture disappeared and a new
signal at δ ϭ 33.8 ppm appeared. The solvent was removed in va-
cuo. Recrystallization of the crude product from diethyl ether gave
0.60 g of MesϪNϭC[P(S)Ph2]ϪC[P(S)Ph2]ϭNϪMes (F) (63.6%)
as dark red thin plates. M.p. 242Ϫ243 °C. C44H42N2P2S2 (724.8):
calcd. C 72.90, H 5.84, N 3.86, S 8.85; found C 72.55, H 6.08, N
1.22 g (33.5%) red crystals of 4a(C6H6)0.5.
1H NMR (CDCl3,
200.13 MHz, 298 K): δ ϭ 0.91 (m, 2 H, NiϪCH2), 1.33 (s, 6 H,
CH3), 1.37 (s, 6 H, o-CH3), 1.74 (s, 3 H, p-CH3), 2.10 (s, 3 H, p-
CH3), 2.10 (m, 2 H, COO-CH2), 5.67 (s, 2 H, CH Mes), 6.56 (s, 2
H, CH Mes), 7.20Ϫ7.64 (m, 20 H, Ph) ppm. 31P{1H} NMR
(CDCl3, 81.01 MHz, 298 K): δ ϭ 19.8 [br. d, 2J(31P31P) ϭ 19.3 Hz],
2
3.83, S 8.43. IR (nujol mull): ν(CϭN) ϭ 1640 cmϪ1
.
1H NMR
44.8 [br. d, J(31P31P) ϭ 19.3 Hz] ppm.
Eur. J. Inorg. Chem. 2003, 4321Ϫ4331
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4329

D. Walther, S. Liesicke, R. Fischer, H. Görls, J. Weston, A. Batista
FULL PAPER
Preparation of [Ni(C40H34N2P2)(C2H4COO)] (5b/5bЈ): A mixture of
Acknowledgments
[Ni(tmeda)(C2H4COO)] (0.76 g, 3.08 mmol) and
B (1.85 g,
3.08 mmol) in 20 mL of THF was warmed up until both com-
pounds dissolved. A few minutes later, an orange-colored com-
pound precipitated. Recrystallization from dichloromethane gave
1.36 g (54%) of 5b/5bЈ(CH2Cl2) as orange crystals. This compound
loses dichloromethane very easily in vacuo. C43H38N2NiO2P2
(735.4): calcd. C 70.22, H 5.21, N 3.81; found C 69.83, H 5.61, N
3.74. IR (nujol): ν(CϭO) ϭ 1606 cmϪ1 (s), ν(NϪH) ϭ 3140 cmϪ1
(w). 1H NMR (CDCl3, 200.13 MHz, 298 K): δ ϭ 0.70 (m, 2 H,
CH2-Ni), 1.84 (s, 3 H, CH3), 1.91 (s, 3 H, CH3), 2.11 (s, 3 H, CH3),
2.15 (s, 3 H, CH3), 2.20 (m, 2 H, CH2ϪCOO) ppm. 13C{1H} NMR
(CDCl3, 50.32 MHz, 298 K): δ ϭ 20.6 (CH3), 20.8 (CH3); CH: δ ϭ
128.2 [d, J(13C31P) ϭ 2.4 Hz], 128.2 [d, J(13C31P) ϭ 2.4 Hz], 129.3
[d, J(13C31P) ϭ 4.9 Hz], 129.4 [d, J(13C31P) ϭ 4.9 Hz], 129.5 (s),
129.9 [d, J(13C31P) ϭ 2.4 Hz], 130.4 (s), 132.5 [d, J(13C31P) ϭ
We are grateful to the Deutsche Forschungsgemeinschaft and the
Fonds der Chemische Industrie for supporting this research.
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J(13C31P) ϭ 5.9 Hz]; C: δ ϭ 113.4 (s), 113.6 (s), 117.7 (s), 119.6 (s),
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(s), 139.8 (s), 142.0 (s) ppm. 31P{1H} NMR (CDCl3, 81.01 MHz,
298 K): δ ϭ 28.3 [d, 2J(31P31P) ϭ 19.0 Hz], 39.0 [d, 2J(31P31P) ϭ
24.2 Hz], 46.1 [d, 2J(31P31P) ϭ 24.2 Hz], 48.9 [d, 2J(31P31P) ϭ
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In situ Preparation of 5c/5cЈ and Reaction with Dimethylglyoxime
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dissolved and the color of the solution changed from light green
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[Ni(C46H46N2P2)(C2H4COO)] was monitored by 31P{1H} NMR
spectroscopy. 31P{1H} NMR (C6D6/THF, 81.01 MHz, 298 K):
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4623Ϫ4624.
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C(PPh2)ϭNϪPh-p-tBu}(C2H4COO)]: 31P{1H} NMR (C6D6/THF,
81.01 MHz, 298 K): δ ϭ 42.7 [d, 2J(31P31P) ϭ 23.0 Hz], 60.9 [d,
2J(31P31P) ϭ 23.0 Hz] ppm.
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(165 mg, 1.42 mmol in 20 mL of methanol), followed by 10 drops
of concentrated aqueous ammonia, were added dropwise to a solu-
tion of [Ni(C46H46N2P2)(C2H4COO)] (0.70 mmol in 5 mL THF).
Red bis(dimethylglyoximato)nickel() precipitated from the reac-
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dryness in a rotary condenser and the residue recrystallized from
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1
1663 cmϪ1. H NMR (CDCl3, 200.13 MHz, 298 K): δ ϭ 1.18 (s, 9
H, tBu), 1.35 (s, 9 H, tBu), 6.70 (s, 1 H), 7.14Ϫ7.70 (m, 16 H), 8.00
(br., 1 H) ppm. 13C{1H} NMR (CDCl3, 50.32 MHz, 298 K): δ ϭ
30.8 (tBu), 30.9 (tBu), 34.8 (C, tBu), 35.2 (C, tBu), 112.0 (CH),
121.2 (CH), 127.0 (C), 127.3 [d, J(31P13C) ϭ 42.3 Hz], 127.8 (CH),
128.3 [d, J(31P13C) ϭ 5.5 Hz, CH], 128.9 (CH), 129.7 (CH), 132.0
(CH), 132.2 [d, J(31P13C) ϭ 9.7 Hz], 132.6 (CH), 133.5 (C), 134.5
(C), 134.7 (CH), 152.3 (C), 154.0 (C) ppm. 31P{1H} NMR (CDCl3,
81.01 MHz, 298 K): δ ϭ 0.0 (br) ppm. MS (CI) (m/z): 519 [M Ϫ
1]ϩ.
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4330
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 4321Ϫ4331

2,3-Bis(diarylphosphanyl)-1,4-diazadienes
FULL PAPER
G. M. Sheldrick, SHELXL-97, Release 97-2, University of
Göttingen, Germany, 1997.
CCDC-202223 (B), -202224 (C), -202225 (D), -202226 (E),
-202227 (G), -202228 (1), -202229 (3) and -202230 (4a) contain
the supplementary crystallographic data for this paper. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
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ϩ
44-1223/336-033; E-mail:
Received June 6, 2003
Early View Article
Published Online October 10, 2003
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Eur. J. Inorg. Chem. 2003, 4321Ϫ4331
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4331