Phosphanyl-amino complexes of nickel(II): Synthesis and structure

Article abstract of DOI:10.1002/(SICI)1099-0682(199811)1998:11<1689::AID-EJIC1689>3.0.CO;2-E

New neutral pentacoordinate nickel(II) complexes of the type [NiCl₂(PR₃)(P^∩N)] [PR₃ = PMe₃, PMe₂Ph, PMePh₂; P^∩N = 2-(diphenylphosphanyl)aniline (P^∩NH_2<

Full text of DOI:10.1002/(SICI)1099-0682(199811)1998:11<1689::AID-EJIC1689>3.0.CO;2-E

FULL PAPER
Phosphanyl-Amino Complexes of Nickel(II): Synthesis and Structure
Laura Crociania, Francesco Tisatoa, Fiorenzo Refoscoa, Giuliano Bandoli*b, and Benedetto Corainc[°]
Istituto di Chimica e Tecnologia dei Materiali Avanzati, C. N. R.a,
C. so Stati Uniti, 4, I-35020 Padova, Italy
b
`
Dipartimento di Scienze Farmaceutiche, Universita di Padova ,
Via Marzolo 5, I-35131 Padova, Italy
Fax: (internat.) ϩ 39-49/8275345
Institut für Organische Chemie und Biochemie, TU Münchenc,
Lichtenbergstraße 4, D-85747 Garching, Germany
Received April 3, 1998
Keywords: Phosphanyl-amine / Nickel / Coordination chemistry / Pentacoordinate Ni complexes /
Tetracoordinate Ni complexes
New neutral pentacoordinate nickel(II) complexes of the type
[NiCl2(PR3)(PʝN)] [PR3 = PMe3, PMe2Ph, PMePh2; PʝN = 2-
(diphenylphosphanyl)aniline (PʝNH2), N-methyl-2-(diphen-
ylphosphanyl)aniline (PʝNHMe), N,N-dimethyl-2-(diphenyl-
phosphanyl)aniline (PʝNMe2)], as well as cationic tetra-
coordinate nickel(II) complexes of the type [NiCl(PR3)(PʝN)]+
have been synthesized and characterized both in the solid
state and in solution. Interesting X-ray structural data have
been collected for each class of compounds, which show,
inter alia, that the pentacoordinate neutral complexes can be
isolated in two different molecular forms, namely square-
pyramidal or bipyramidal-trigonal.
Introduction
tetradentate phosphanyl-amine behaves both as a ligand
and as a reducing agent towards [MO4]Ϫ (M ϭ Tc, Re)
to give hexacoordinate neutral oxo-MV phosphanyl-amido
complexes of the general formula [MO(dppd)X], X ϭ Cl,
OH, OMe, OEt, O2CCF3.
The synthesis of metal complexes stabilized by P∩N li-
gands and particularly phosphanyl-amines has attracted
considerable attention in recent years[1]. The ligands 2-(di-
phenylphosphanyl)pyridine and 2-(diphenylphosphanyl)an-
iline give rise to interesting examples. The first is known
to exhibit a very versatile coordination behavior towards
numerous transition metal centers[2], both in mono- and
polynuclear complexes. Remarkably, in these complexes it
acts as either a monodentate, a bidentate chelating, or a
bidentate bridging ligand. In its monodentate mode, the
phosphane ligating site normally exhibits the strongest
Similarly, P2N2 ligands such as N,NЈ-bis[2-(diphenylphos-
phanyl)phenyl]ethane-1,2-diamine and N,NЈ-bis[2-(diphen-
ylphosphanyl)phenyl]propane-1,3-diamine have been em-
ployed as efficient ligands for preparing unprecedented and
previously elusive copper(II) phosphane complexes[14]
.
These were subjected to X-ray structural analyses and were
found to be characterized by authentic thermodynamic sta-
bility that was not attributable to kinetic inertness[15]. The
finely balanced soft-hard character of the {P2N2} ligating
set has been proposed to play a major role in underlying
this important result.
bonding ability towards metal centers such as nickel(II)[3]
,
cobalt(I)[3], ruthenium(II)[4][5], rhodium(I)[4][6], and pal-
ladium(II)[4][7][8]. Conversely, the coordination chemistry of
2-(diphenylphosphanyl)aniline[9] has been widely investi-
gated because of its ability to behave as a bidentate chelat-
ing amino[10], amido[11], or imido[12] ligand. This behavior
has been further developed in the synthesis of new macro-
cyclic chelate compounds such as P2N2 ligands, which have
previously been tested in these laboratories[13]. In particu-
lar, the reactivity of the tetradentate ligand N,NЈ-bis[2-(di-
phenylphosphanyl)phenyl]propane-1,3-diamine, H2dppd,
toward technetium and rhenium has been investigated. This
The various properties of phosphanyl-amino ligands
prompted us to undertake a systematic study aimed at pre-
paring both neutral and cationic nickel(II) complexes of the
type shown in Scheme 1 and to evaluate the potential of
the cationic species as “SHOP”-type catalysts[16]
.
Scheme 1
[°]
Humboldt Stipendiat Ϫ on leave of absence from Dipartimento
di Chimica Ingegneria Chimica e Materiali, Via Vetoio Coppito
Due, I-67010 LЈAquila, Italy and from Centro di Studio sulla
`
`
Stabilita e Reattivita dei Composti di Coordinazione, CNR, c/o
Dipartimento di Chimica Inorganica Metallorganica e Anali-
In this paper, we report on the detailed development of
this project. Some of the results reported herein were antici-
pated in a preliminary report[17]
`
tica, Universita di Padova, via Marzolo 1, I-35131 Padova, Italy.
Supporting information for this article is available on the WWW
under http://www.wiley-vch.de/home/eurjic or from the author.
.
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ1948/98/1111Ϫ1689 $ 17.50ϩ.50/0
1689

L. Crociani, F. Tisato, F. Refosco, G. Bandoli, B. Corain
FULL PAPER
phanyl)aniline, P∩NHMe, and N,N-dimethyl-2-(diphenyl-
phosphanyl)aniline, P∩NMe2 (hereafter referred to as
P∩N), usually in MeCN solution, to give pentacoordinate
species of the type [NiCl2(PR3)(P∩N)] (Table 1).
Results and Discussion
A general overview of the scope of the synthetic results
is given in Scheme 2. The compounds are obtained upon
substitution of one monodentate phosphane by the biden-
tate one, which chelates the metal through both the P and
N atoms.
The same reaction, carried out in CH2Cl2 in the pres-
ence of KPF6 as a scavenger of one ClϪ ligand per Ni
atom, successfully leads to tetracoordinated species of the
type [NiCl(PR3)(P∩N)]ϩ (Table 1), except in the case of
P∩NH2. The action of this tertiary phosphanyl-primary
amine on [NiCl2(PR3)2] (PR3 ϭ PMe2Ph and PMePh2)
leads to the bis-bidentate species [Ni(P∩NH2)2]2ϩ[18], and/
or to the mononuclear phosphorane-imino complex
[NiCl(PMe3)(P∩NP)]ϩ[19], [P∩NP ϭ N-(trimethylphos-
phoranyl)-2-(diphenylphosphanyl)aniline], when PMe3 is
incorporated into the starting material as a mono-ter-
tiary phosphane.
Scheme 2
The formation of the pentacoordinate [NiCl2(PR3)(P∩N)]
complexes is achieved under stoichiometric conditions in a
homogeneous phase after a few hours of reaction time at
room temperature. The products can be isolated as analyti-
cally pure species either upon spontaneous precipitation or
after the addition of Et2O. All these compounds are rather
unstable in solution when exposed to air. Nevertheless, they
can be recrystallized from e.g. CH2Cl2 (see Experimental
Section) and their MeCN solutions provide conductivity
[NiCl2(PR3)2] complexes react readily with 2-(diphenyl- measurements consistent with non-conducting species
phosphanyl)aniline, P∩NH2, N-methyl-2-(diphenylphos- (Table 1).
Table 1. Selected synthetic and physicochemical data of [NiCl2(PR3)(P∩N)] and [NiCl(PR3)(P∩N)]ϩ[a] complexes
[d]
Complex Color
Crystal
µeff [BM] ΛM[c] [ΩϪ1
νNϪH δNϪH
[cmϪ1 [d]
1H NMR δ[e]
P{1H } NMR δ[e] λmax[f] [nm] in
λmax
[nm] in
structure[b]
cm2molϪ1
]
]
solution
the solid state
2
3
Blue
Blue
n.d.
spy
1.3
n.c.[g]
Paramagnetic solu-
tions, signals from
ϩ18.0 to Ϫ2.0
485, 570, 725
380, 600, 800
[h]
[l]
Diam.
n.c.[g]
νas[i] 3236 m, νs
1.78 (s, 6 H), 2.67 Ϫ5.2 (br s, 1P),
475, 610 sh
475, 630 sh
490 sh, 620
550, 690 sh
3134 m, δ 1602 m (m, 2 H),
6.33Ϫ8.38
38.6
(br s, 1P)
(m, 19 H)
Paramagnetic solu-
4·0.5
MeCN
Blue
n.d.
tb
0.7
3.4
n.c.[g]
n.c.[g]
180
3241 s
3262 s
3191 m
tions, signals from
ϩ18.0 to Ϫ2.0
Paramagnetic solu-
tions, signals from
ϩ18.0 to Ϫ1.0
1.23 (s, 9 H), 2.87 Ϫ144 (sept,1 P), 265 (4.49), 290
(d, 3 H), 4.85 (m, Ϫ9.8 (dd, 1 P), sh, 430 (2.89)
1 H), 7.20Ϫ7.95
6·C6H6
Green
430, 610 sh, 1055 400 sh, 620,
1050
9
Yellow sp
Diam.[h]
Diam.[h]
Diam.[h]
Diam.[h]
430
445
450
445
42.5 (d, 1 P)
(m, 14 H)
10
11
Yellow n.d.
190
158
171
1.26 (d, 9 H), 3.19 Ϫ144 (sept, 1 P), 240 (4.16), 270
(s, 6 H), Ϫ9.51 (d, 1 P), sh, 435 (2.76)
7.12Ϫ8.15 (m, 14 38.1 (d, 1 P)
H)
Red-
orange
n.d
3229 m
3251 m
1.64 (s, 6 H), 2.04 Ϫ144 (sept, 1 P), 295 (4.06), 322
(d, 3 H), 4.94 (m, 1.30 (m, 1 P), (4.05), 430 (2.76)
1 H), 7.12Ϫ8.15
48.0 (m, 1 P)
(m, 19 H)
13·C6H6 Yellow sp
2.01 (d, 3 H), 2.33 Ϫ146 (sept, 1 P), 275 (4.08), 310
(s, 3 H), 6.91 (d, 1 P), 37.6 (4.02), 435 (2.81)
7.10Ϫ7.84 (m, 24 (d, 1 P)
H)
Ϫ
[a] PF6 salts. Ϫ [b] X-ray authenticated: n.d. ϭ not determined; spy ϭ square-pyramidal; tb ϭ trigonal-bipyramidal; sp ϭ square-pla-
nar. Ϫ [c] In MeCN. Ϫ [d] KBr plates. Ϫ [e] CDCl3 for 2, 3, 4 ·0.5 MeCN, and 6·C6H6; CD2Cl2 for 9, 10, 11, and 13·C6H6. Ϫ [f] The
data refer to solutions in CH2Cl2, ca. 10Ϫ2  for 2, 3, 4 ·0.5 MeCN, and 6·C6H6 and 10Ϫ3Ϫ10Ϫ5  for 9, 10, 11, and 13·C6H6; lg ε va-
[i]
lues in parentheses. Ϫ [g] n.c. ϭ non-conducting. Ϫ [h] Diam. ϭ diamagnetic. Ϫ
ν
ϭ ν asymmetric. Ϫ [l] νs ϭ ν symmetric.
as
1690
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697

Phosphanyl-Amino Complexes of Nickel(II)
FULL PAPER
The formation of the tetracoordinate [NiCl(PR3)(P∩N)]ϩ netic species are subject to fluxional behavior at room tem-
complexes can also be readily achieved under essentially perature in CDCl3 solution, since the 31P{1H} spectra exhi-
stoichiometric conditions, by removal of KCl, concen- bit broad signals that lack the multiplicity that would be
tration of the reaction solution, and addition of Et2O. Cat- expected given the presence of two magnetically non-equiv-
ionic complexes [NiCl(PR3)(P∩N)]ϩ can be readily recrys- alent phosphorus donors in the coordination sphere.
tallized from suitable solvent mixtures, such as CH2Cl2/
EtOH/Et2O or CH2Cl2/EtOH/C6H6.
On the other hand, the 31P{1H} spectra of square-planar
cationic complexes indicate the existence of two types of
phosphorus donors; in fact, a double doublet pattern is
usually observed, the position of which is primarily deter-
mined by the nature of the mono-tertiary phosphane. In
addition, a septuplet centred at δ ϭ Ϫ144 establishes the
presence of the hexafluorophosphate counterion. The
methyl groups incorporated at the phosphorus and/or nitro-
gen donors are distinguishable on the basis of their chemi-
cal shifts and relative integrals in the proton spectra, which,
where appropriate, also show the coordinated amine pro-
tons at δ ϭ 4.90.
The ability of nickel(II) to give charged and neutral
pentacoordinate complexes is well-documented in the litera-
ture[20]. Thus, numerous high-spin distorted trigonal-bipy-
ramidal and square-pyramidal complexes are known, which
usually contain hard donor sites. Quite a few low-spin dis-
torted trigonal-bipyramidal complexes have also been de-
scribed and, conversely, they typically exhibit an overall soft
coordination sphere. To the best of our knowledge, only
four examples of pentacoordinate complexes with an
{NP2Cl2} donor set have been reported in the litera-
ture[17][21][22]; the data presented herein allow the possibility
of analyzing this coordination sphere, which is otherwise
only poorly documented. The geometry of complex 3 (vide
infra) is intermediate between square-pyramidal and trig-
onal-bipyramidal and this complex is diamagnetic. On the
other hand, complexes 5, 6·CH2Cl2, and 7 are trigonal-bi-
pyramidal and paramagnetic. Ligand sets high in the spec-
trochemical series are predicted[20] to give diamagnetic trig-
onal-bipyramidal complexes, but in our case the situation
is reversed. Apparently, the ligand field exerted by our li-
gand set is not large enough to produce a singlet funda-
mental electronic state. Moreover, complexes 2 and 4 are
characterized by magnetic moment values formally corre-
sponding to less than two unpaired electrons (Table 1),
which have previously been observed and discussed[23] in
terms of a thermally controlled equilibrium between singlet
and triplet states. However, the data collected prevent us
from invoking such an equilibrium as the sole factor re-
sponsible for the magnetic behavior of complexes 2 and 3.
The {NP2Cl} chromophore invariably produces square-
planar nickel(II) complexes for all the PR3 and P∩N ligands
employed, the structures of which have been validated by
single-crystal X-ray analyses. The spectra in the visible
range and the diamagnetism of all the complexes 9, 10, 11,
and 13·C6H6 are in accordance with this structure[20]. The
position of the d-d band at 430Ϫ450 nm (Table 1) indicates
that the {NP2Cl} chromophore is appreciably lower in the
spectrochemical series than e.g. {P2(CN)2}[24], for which
this band appears at ca. 350 nm. These bands are also ob-
served in solution (lg ε values are also reasonable) and the
conductivity figures are consistent with classical behavior
of these square-planar nickel complexes.
X-ray Structure Analysis
In the neutral complexes 3 (Figure 1) and 6·CH2Cl2 (Fig-
ure 2), the coordination around the NiII center is distorted
trigonal-bipyramidal with the two axial positions occupied
by the phosphorus atom of the monodentate phosphane
and by the nitrogen atom of the bidentate ligand (P∩NH2
in 3 and P∩NHMe in 6·CH2Cl2). The equatorial sites ac-
commodate the remaining phosphorus of the phosphanyla-
mine and the two Cl donors. The Ni atom is displaced from
˚
the equatorial plane in the direction of P(2), by 0.13 A in 3
∩
˚
and by 0.18 A in 6·CH2Cl2. The P N ligand mean plane
of 3 makes a dihedral angle of 94.6° with the equatorial
plane, while the corresponding angle in 6·CH2Cl2 is 67.5°.
The five-membered chelate ring, roughly planar in 3 (maxi-
˚
mum deviation of 0.05 A by the nitrogen atom; torsion
angles between Ϫ6.8° and ϩ9.3°), assumes an envelope (Cs)
conformation in 6·CH2Cl2, as shown by the deviation (0.29
˚
A) of the nitrogen atom and the torsion angle values (from
Ϫ30.5° to ϩ35.0°). Moreover, superposition of the two
˚
structures (Figure 3) gives a high r.m.s. value (0.56 A) when
the fitting is performed on the 12 atoms labelled in the per-
tinent figure. Based on these differences, the geometry of 3
could alternatively be described as distorted square-pyrami-
dal (Figure 4). In this description, the base could be re-
garded as comprising the P,N donors of the ligand, the P(2)
atom of the monodentate phosphane, and Cl(1). The Ni
˚
atom is displaced from the base by ϩ0.27 A in the direction
of Cl(2), but the deviations of the other donors are also
˚
˚
˚
dramatic [P(1) Ϫ0.31 A, N(1) ϩ0.35 A, Cl(1) Ϫ0.32 A and
˚
P(2) ϩ0.28 A]. Moreover, the trans angle P(1)ϪNiϪCl(1) is
Proton NMR spectra of the paramagnetic pentacoordi- only 148.29(6)°, while the cis angle P(1)ϪNiϪCl(2) is wid-
nate complexes in CDCl3 show signals spread over the ened to 110.82(6)°. In conclusion, the coordination ge-
range from δ ϭ ϩ20 to Ϫ14. Conversely, complexes 1 and ometry of 3 is intermediate between trigonal-bipyramidal
3, which retain the unsubstituted phosphanyl-amine and square-pyramidal and, accordingly, application of the
P∩NH2, are diamagnetic; their spectra allow the assignment τ index[25] gives a value of 0.46 (1.0 for trigonal-bipyrami-
of the coordinated phosphanyl-amine protons at δ ϭ 2.60 dal; 0.0 for square-pyramidal).
and of the methyl groups of the mono-tertiary phosphanes
In the cationic complexes 9 (Figure 5) and 13·MeOH
at δ ϭ 1.26 and 1.78 for 1 and 3, respectively. These diamag- (Figure 6), the coordination geometry around NiII can be
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697
1691

L. Crociani, F. Tisato, F. Refosco, G. Bandoli, B. Corain
FULL PAPER
Figure 1. ORTEP view of complex 3; hydrogen atoms are omitted
for clarity; the thermal ellipsoids are drawn at 40% probability
Figure 3. Superposition of geometries of 3 (—) and 6·CH2Cl2 (---
)
Figure 4. ORTEP view of complex 3 showing the square-pyramidal
geometry; hydrogen atoms are omitted for clarity; the thermal ellip-
soids are drawn at 40% probability
Figure 2. ORTEP view of complex 6·CH2Cl2; hydrogen atoms and
the CH2Cl2 molecule are omitted for clarity; the thermal ellipsoids
are drawn at 40% probability
MeOH. The conformation of the five-membered NiPCCN
described as square-planar, with the two phosphorus do- chelate ring results in a twist-envelope (C2) form (torsion
nors located in a mutual cis arrangement and the remaining angles between Ϫ14.2° and 13.2° in 9 and between Ϫ24.2°
two positions occupied by the secondary amine nitrogen of and 19.4° in 13·MeOH) and superposition of the two struc-
the bidentate P∩NHMe ligand and by the Cl donor. The tures (Figure 7) reveals only minor differences in the relative
nickel coordination spheres are distorted (Table 2) and the orientations of the phenyl rings, the r.m.s. value being 0.13
˚
four donor atoms deviate from the mean coordination A when the fitting is performed on the 11 atoms labelled in
˚
˚
plane by ±0.17 A in 9 and by ±0.10 A in 13·MeOH. The the pertinent figure.
P∩N ligand mean plane makes a dihedral angle with the
For each of the four complexes, the packing does not give
mean coordination plane of 18.8° in 9 and of 23.9° in 13 · rise to intermolecular contacts shorter than the sum of the
1692
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697

Phosphanyl-Amino Complexes of Nickel(II)
FULL PAPER
Figure 5. ORTEP view of complex 9; hydrogen atoms and the Figure 7. Superposition of geometries of 9 (—) and 13·MeOH
PF6Ϫ anion are omitted for clarity; the thermal ellipsoids are drawn
at 40% probability
(- - -)
Figure 6. ORTEP view of complex 13·MeOH; hydrogen atoms, the
˚
Table 2. Selected bond lengths [A] and angles [°] for 3, 6 · CH2Cl2,
Ϫ
PF6 anion and the MeOH molecule are omitted for clarity; the
9, and 13 · MeOH
thermal ellipsoids are drawn at 40% probability
3
6 · CH2Cl2
NiϪCl(1)
2.249(2)
2.565(2)
2.170(2)
2.189(2)
1.963(4)
99.78(6)
148.29(6)
87.5(1)
2.307(2)
2.298(2)
2.330(2)
2.380(2)
2.212(4)
144.59(6)
109.17(6)
84.8(1)
NiϪCl(2)
NiϪP(1)
NiϪP(2)
NiϪN(1)
Cl(1)ϪNiϪCl(2)
Cl(1)ϪNiϪP(1)
Cl(1)ϪNiϪN(1)
Cl(2)ϪNiϪP(2)
Cl(2)ϪNiϪP(1)
P(2)ϪNiϪN(1)
90.65(6)
110.82(6)
175.6(1)
92.24(6)
104.09(6)
177.6(1)
9
13·MeOH
NiϪCl
2.200(2)
2.137(1)
2.195(2)
1.987(4)
165.91(6)
89.53(6)
88.7(1)
2.177(2)
2.156(2)
2.204(2)
1.998(6)
171.36(9)
88.68(9)
87.9(1)
NiϪP(1)
NiϪP(2)
NiϪN(1)
ClϪNiϪP(1)
ClϪNiϪP(2)
Cl(1)ϪNiϪN(1)
P(1)ϪNiϪP(2)
P(1)ϪNiϪP(2)
P(2)ϪNiϪN(1)
95.87(6)
87.0(1)
98.05(8)
85.8(2)
174.8(1)
174.0(2)
van der Waals radii and there are no possibilities for hydro- erence” values retrieved from the Cambridge Structural Da-
gen bonding. The Ni(II)Ϫdonor atom bond lengths in the tabase (CSD)[26] reveals the following features. (i) The
∩
[NiCl2(PR3)(P∩N)] and [NiCl(PR3)(P N)]ϩ complexes Ni ϪCl distances (mean value of 2.196 A when c.n. ϭ 4,
II
˚
˚
merit some comment. Thus, the spread of their values and of 2.288 A with c.n. ϭ 5) are slightly shorter than the
(Table 3) might seem unexpectedly large (NiϪCl in the corresponding CSD values [2.22 (219 obs.) and 2.34 A (88
range 2.177Ϫ2.567 A; NiϪP 2.139Ϫ2.400 A and NiϪN obs.), respectively], but they confirm the finding that on go-
1.963Ϫ2.353 A), but this can be rationalized on the basis ing from c.n. 4 to 5 the distance increases. This trend also
˚
˚
˚
˚
of coordination number, c.n., and/or geometry arguments. holds for the NiϪP and NiϪN distances. The NiϪCl(2)
˚
In fact, comparison of the distances with the pertinent “ref- distance in 3 [2.567(2) A] represents an exception, being the
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697
1693

L. Crociani, F. Tisato, F. Refosco, G. Bandoli, B. Corain
FULL PAPER
Table 3. Selected structural data for [NiCl2(PR3)(P∩N)] and [NiCl(PR3)(P∩N)]PF6 complexes
Geometry[a] NiϪCl [A] NiϪPR3 [A] NiϪP [A]
NiϪN [A]
P∩Nbite [°] NiϪNϪCchelate Ref.[b]
[°]
˚
˚
˚
˚
[NiCl2(PMe2Ph)(P∩NMe2)]
tb
tb
2.276(2)
2.284(2)
2.298(2)
2.307(2)
2.288(3)
2.272(3)
2.249(2)
2.567(2)
2.217(2)
2.200(2)
2.177(2)
2.189(5)
2.372(2)
2.380(2)
2.400(5)
2.189(2)
2.290(2)
2.330(2)
2.310(3)
2.170(2)
2.353(4)
2.212(4)
2.325(8)
1.963(4)
77.9(1)
79.9(1)
78.7(2)
86.3(2)
109.2(5)
112.3(3)
108.5(5)
119.8(3)
5
[NiCl2(PMePh2)(P∩NHMe)]·CH2Cl2
6·CH2Cl2
[NiCl2(PMePh2)(P∩NMe2)]·0.5CH2Cl2 tb
[NiCl2(PMe2Ph)(P∩NH2)]
7
3
tb/spy
[NiCl(PMe3)(P∩NP)]PF6
sp
sp
2.192(2)
2.195(2)
2.177(2)
2.207(5)
2.159(3)
2.137(1)
2.156(2)
2.139(5)
2.011(7)
1.987(4)
1.998(6)
2.056(8)
83.1(2)
87.0(1)
85.8(2)
86.8(2)
113.8(5)
116.7(3)
115.2(5)
114.9(6)
8
9
[c]
[NiCl(PMe3)(P∩NHMe)]PF6
[NiCl(PMePh2)(P∩NHMe)]PF6·MeOH sp
13·MeOH
14
[NiCl(PMePh2)(P∩NMe2)]PF6
sp
[a] tb ϭ trigonal-bipyramidal; spy ϭ square-pyramidal; sp ϭ square-planar. Ϫ [b] 3, 6·CH2Cl2, 9, 13·MeOH in present work; 5 in ref.[21]
7 and 14 in ref.[17]; 8 in ref.[19]. Ϫ [c] P∩NP ϭ N-(trimethylphosphoranyl)-2-(diphenylphosphanyl)aniline.
;
second longest distance ever reported in the literature[27]
.
donor set {NP2Cl2} and of their crystal structures. While
In the square-pyramidal description (Figure 4), this axial it is possible to assign a trigonal-bipyramidal structure to
elongation can be correlated with the electron density in the complex 6, in analogy to related compounds such as
dz2 orbital for the d8 ion, leading to a pronounced metalϪ- [NiCl2(PMe2Ph)(P∩NMe2)][21]
and
[NiCl2(PMePh2)-
halide electron-electron repulsion. (ii) The geometry seems (P∩NMe2)]·0.5 CH2Cl2[17], complex 3 has a structure inter-
to govern the NiϪP bond lengths. The corresponding mean mediate between trigonal-bipyramidal and square-pyrami-
values in the trigonal-bipyramidal complexes average 2.310 dal, which accounts for the very long NiϪCl distance.
˚
˚
A and 2.384 A for the chelating phosphane ligand and the
The cationic tetracoordinate species [NiCl(PR3)(P∩N)]ϩ
unidentate ligand axially bonded to NiII, respectively. The can be derived from the corresponding [NiCl2(PR3)2] pre-
magnitude of this “axial effect” (ca. 0.07 A) is consistent cursor only by the addition of KPF6 in order to remove
˚
with similar values encountered in the CSD file. In square- one ClϪ ligand per Ni atom. NMR spectra and crystal
planar complexes, the corresponding mean values are 2.148 structures indicate that these complexes consist of the cis-
˚
˚
A and 2.193 A and a parallel situation is presented by 3, P,P isomer. Comparison of some structural features such as
˚
˚
since values of 2.189 A and 2.170 A are observed. (iii) The the NiϪN, NiϪCl, and NiϪP bond lengths confirms the
NiIIϪN distances in cationic complexes with c.n. ϭ 4 (mean finding that on going from c.n. ϭ 4 to 5 the distances in-
value 2.01 A) are dramatically shorter than those in the crease. In particular, NiϪN is dramatically shorter than the
neutral complexes with c.n. ϭ 5 (mean value 2.30 A), but CSD reference value, but the paucity of literature data pre-
˚
˚
the paucity of literature data prevents us from making a vents us from making firm conclusions from this obser-
reliable comparison. In any case, the NiϪN(Csp2)H2 value vation.
˚
of 3 (1.963 A) conforms to those of the square-planar com-
Benedetto Corain is grateful to the Alexander von Humboldt
plexes. Similarly, the PϪNiϪN bite angle (86.3°) of 3
closely approaches the mean value (85.6°) found in the four
analogous complexes with c.n. 4, while it is compressed to
78.8° in those with c.n. ϭ 5. Finally, the NiϪNϪC angle
of the five-membered chelate ring averages 115.2° in com-
plexes with c.n. ϭ 4, while it is compressed to 110.0° when
the c.n. becomes 5.
Foundation for supporting his activities at TU München.
Experimental Section
General: All chemicals and solvents were of analytical grade and
were used as received unless otherwise stated. The starting
[NiCl2(PR3)2] (PR3 ϭ PMe3, PMe2Ph, PMePh2) complexes were
prepared according to the literature[28][29], as were the ligands
P∩NH2[9], P∩NHMe[9], and P∩NMe2[30]. Ϫ IR: Mattson 3030
Fourier-transform spectrometer. Ϫ UV/Vis in the solid state: Cary
5-E spectrophotometer (1200Ϫ220 nm), diffuse reflectance method.
Ϫ UV/Vis in solution: Cary 17D spectrophotometer (1200Ϫ220
nm), ca. 10Ϫ2  solutions in CH2Cl2 for the pentacoordinate com-
plexes in 0.1-cm cells and 10Ϫ3Ϫ10Ϫ5  solutions in CH2Cl2 for
square-planar and cationic complexes in 1-cm cells. Ϫ NMR:
Bruker AC-200 (200 MHz for 1H and 31P). For 1H NMR, CDCl3
or CD2Cl2 as solvent, TMS as internal standard; for 31P{1H}
NMR, CDCl3 or CD2Cl2 as solvent, 85% aqueous H3PO4 as exter-
nal standard. Ϫ Conductivity measurements: Amel conductimeter
Mod. 131, ca. 10Ϫ3  solutions in MeCN at 25°C. Ϫ Magnetic
susceptibility measurements: Cahn 2000 microbalance. Ϫ Elemen-
Conclusions
Phosphanyl-amines P∩NH2, P∩NHMe, P∩NMe2 exhibit
good coordination properties towards the nickel(II) center,
affording stable neutral pentacoordinate [NiCl2(PR3)(P∩N)]
and cationic tetracoordinate [NiCl(PR3)(P∩N)]ϩ complexes
starting from the corresponding [NiCl2(PR3)2] precursor.
The neutral pentacoordinate species [NiCl2(PR3)(P∩N)]
feature a rather unusual {NP2Cl2} donor set. Their be-
havior can be satisfactorily accounted for considering the
data collected in the course of this study. The range of mag-
netic moments they exhibit is unexpected in view of the tal analyses (C, H, N): Fisons EA 1108 elemental analyzer.
1694 Eur. J. Inorg. Chem. 1998, 1689Ϫ1697

Phosphanyl-Amino Complexes of Nickel(II)
FULL PAPER
[ NiCl2( PMe3) ( P∩NMe2) ] (2): To a solution of 0.196 g of Yield: 0.195 g (70%). Crystals suitable for X-ray analysis were
[NiCl2(PMe3)2] (0.68 mmol) in 10 ml of MeCN was added 0.209 g grown by slow evaporation of the solvent from CH2Cl2 solutions.
of P∩NH2 (0.68 mmol). The blood-red solution immediately dark- Ϫ IR (KBr): ν˜ ϭ 3191 cmϪ1 m, 1583 m, 1462 m, 1104 w, 838 vs
1
ened and was stirred under dinitrogen at room temperature for 3 (PϪF), 557 s. Ϫ H NMR (CD2Cl2): δ ϭ 1.23 [s, 9 H, P(CH3)3],
3
h. The solution was then concentrated to a volume of 3 ml under
a flow of dinitrogen. A dark-blue powder precipitated, which was
2.87 (d, JHH ϭ 6 Hz, 3 H, NCH3), 4.85 (m, 1 H, NH), 7.20Ϫ7.95
(m, 14 arom. H). Ϫ 31P{1H} NMR (CD2Cl2): δ ϭ Ϫ144 (sept.,
collected by filtration, washed with 5 ml of Et2O, 5 ml of n-hexane JPF ϭ 711 Hz, 1 P, PF6Ϫ), Ϫ7.80 (m, 1 P, PMe3), 42.5 (m, 1 P,
and 0.5 ml of EtOH, and dried in vacuo. Yield: 0.140 g (40%). Ϫ
P∩NHMe). Ϫ C22H27ClF6NNiP3 (606.56): C 43.56, H 4.50, N
IR (KBr): ν˜ ϭ 3047 cmϪ1 s, 1580 m, 1481 m, 1437 s, 1094 s, 959 2.31; found C 43.42, H 4.16, N 2.16.
vs, 753 m, 514 m. Ϫ 1H NMR (CDCl3): Several signals in the
region δ ϭ ϩ18.0 to Ϫ2.0. Ϫ C23H29Cl2NNiP2 (483.01): calcd. C
54.05, H 5.73, N 2.74; found C 54.64, H 5.67, N 2.43.
[ NiCl( PMe3) ( P∩NMe2) ] PF6 (10): To a mixture of 0.082 g of
[NiCl2(PMe3)2] (0.29 mmol) and 0.074 g of KPF6 (0.40 mmol) in
10 ml of CH2Cl2 was added 0.089 g of P∩NH2 (0.25 mmol) and
the mixture was stirred at room temperature. The blood-red solu-
tion immediately turned orange-red. After 3 h, the mixture was
filtered and concentrated to a volume of 4 ml under a flow of
dinitrogen. Addition of 12 ml of Et2O caused the precipitation of
a yellow-orange solid, which was collected by filtration, washed
with H2O, and dried in vacuo. The solid was recrystallized from
CH2Cl2/EtOH/C6H6 (10:1:19) (20 ml). Yield: 0.121 g (67%). Ϫ IR
[ NiCl2( PMe2Ph) ( P∩NH2) ] (3): To a solution of 0.108 g of
[NiCl2(PMe2Ph)2] (0.27 mmol) in 10 ml of MeCN was added 0.075
g of P∩NH2 (0.27 mmol) and the mixture was stirred under dinitro-
gen at room temperature. The blood-red solution immediately
turned dark. After 5 min, a blue compound precipitated and after
15 min the solid was collected by filtration, washed several times
with MeCN, and dried in vacuo. Yield: 0.111 g (85%). Crystals
were grown by slow evaporation of the solvent from CH2Cl2 solu-
tions. Ϫ IR (KBr): ν˜ ϭ 3236 cmϪ1 m, 3179 m, 3093 s, 1555 m, 1478
m, 1433 s, 1095 m, 914 vs, 698 m, 512 m. Ϫ 1H NMR (CDCl3): δ ϭ
1.78 [s, 6 H, P(CH3)2], 2.67 (m, 2 H, NH2), 6.33Ϫ8.38 (m, 19 H,
aromatic). Ϫ 31P{1H} NMR (CDCl3): δ ϭ Ϫ5.2 (br. s, 1 P, PMe2),
38.6 (br., 1 P, P∩NH2). Ϫ C26H27Cl2NNiP2 (545.08): calcd. C
57.29, H 5.00, N 2.57; found C 57.17, H 5.37, N 2.57.
(KBr): ν ϭ 3070 cmϪ1 w, 1580 m, 1483 m, 1436 s, 1097 m, 836 vs
˜
(PϪF), 558 s. Ϫ 1H NMR (CD2Cl2): δ ϭ 1.26 [d, 9 H, JHP ϭ 12.5
2
Hz, P(CH3)3], 3.19 [s, 6 H, N(CH3)2], 7.12Ϫ8.15 (m, 14 H, aro-
matic). Ϫ 31P{1H} NMR (CD2Cl2): δ ϭ Ϫ144 (sept, 1 P, JPF
ϭ
713 Hz, PF6Ϫ), Ϫ9.51 (d, 1 P, JPP ϭ 107 Hz, PMe3), 38.1 (d, 1 P,
2JPP ϭ 107 Hz, P∩NMe2). Ϫ C23H29ClF6NNiP3 (620.59): calcd. C
44.51, H 4.71, N 2.26; found C 44.41, H 4.56, N 2.26.
2
[ NiCl( PMe2Ph) ( P∩NHMe) ] PF6 (11): To a mixture of 0.155 g
of [NiCl2(PMe2Ph)2] (0.38 mmol) and 0.138 g of KPF6 (0.75 mmol)
in 1 ml of CH2Cl2 was added 0.111 g of P∩NHMe (0.38 mmol)
and the mixture was stirred at room temperature. The blood-red
mixture slowly turned red-orange. After 3 h, the solution was fil-
tered and concentrated to a volume of 5 ml under a flow of dinitro-
gen. Addition of 15 ml of Et2O caused the precipitation of an or-
ange solid, which was collected by filtration, washed with H2O, and
dried in vacuo. The solid was recrystallized from CH2Cl2/EtOH/
C6H6 (7:1.5:19) (27.5 ml). Yield: 0.153 g (60%). Ϫ IR (KBr): ν˜ ϭ
3229 cmϪ1 m, 1584 m, 1506 m, 1437 s, 1102 m, 837 vs (PϪF), 557.
[ NiCl2( PMe2Ph) ( P∩NHMe) ] (4): To a solution of 0.100 g of
[NiCl2(PMe2Ph)2] (0.25 mmol) in 5 ml of MeCN was added 0.073
g of P∩NHMe (0.25 mmol) and the mixture was stirred under dini-
trogen at room temperature. After 30 min, a blue compound pre-
cipitated and after 3 h the solid was collected by filtration, washed
twice with 6 ml of n-hexane, and dried in vacuo. Yield: 0.065 g
(44%). Ϫ IR (KBr): ν˜ ϭ 3246 cmϪ1 w, 3051 s, 2247 w, 1580 m,
1
1481 m, 1435 s, 1098 s, 913 s, 742 m, 487 s. Ϫ H NMR (CDCl3):
Several signals in the region
27H29Cl2NNiP2 ·0.5 CH3CN (579.64): calcd. C 58.02, H 5.31, N
3.62; found C 57.75, H 5.06, N 3.64.
δ ϭ ϩ18.0 to Ϫ2.0. Ϫ
C
Ϫ
1H NMR (CD2Cl2): δ ϭ 1.64 [s, 6 H, P(CH3)2], 2.96 (d, 3 H,
3JHH ϭ 6 Hz, NCH3), 4.94 (m, 1 H, NH), 6.90Ϫ8.04 (m, 19 H,
[ NiCl2( PMePh2) ( P∩NHMe) ] (6): To a blood-red solution of
0.101 g of [NiCl2(PMePh2)2] (0.19 mmol) in 10 ml of MeCN and
0.5 ml of CH2Cl2 was added 0.055 g of P∩NHMe (0.19 mmol). The
red solution immediately turned brown. After stirring under dini-
trogen at room temperature for 3 h, the solution was concentrated
to dryness under reduced pressure. The residue was washed with
0.4 ml of MeCN and 0.4 ml of CH2Cl2, and then redissolved in 10
ml of CH2Cl2 and 1.5 ml of C6H6. Addition of 23 ml of Et2O
caused the precipitation of a green solid, which was collected by
filtration, washed with 5 ml of Et2O, and dried in vacuo. Yield:
0.080 g (60%). Crystals were grown by slow evaporation of the
solvent from CH2Cl2 solutions. Ϫ IR (KBr): ν˜ ϭ 3262 cmϪ1 w,
aromatic). Ϫ 31P{1H} NMR (CD2Cl2): δ ϭ Ϫ144 (sept, 1 P, JPF
ϭ
713 Hz, PF6Ϫ), 1.30 (m, 1 P, PMe2Ph), 48.0 (m, 1 P, P∩NHMe).
Ϫ C27H29ClF6NNiP3 (668.63): calcd. C 48.55, H 4.38, N 2.10;
found C 48.71, H 4.38, N 2.03.
[ NiCl( PMePh2) ( P∩NHMe) ] PF6 (13): To a mixture of 0.132 g
of [NiCl2(PMePh2)2] (0.25 mmol) and 0.092 g of KPF6 (0.50 mmol)
in 10 ml of CH2Cl2 was added 0.073 g of P∩NHMe (0.25 mmol)
and the mixture was stirred at room temperature. The blood-red
mixture immediately turned red-orange. After 3 h, the solution was
filtered and concentrated to a volume of 4 ml under a flow of dini-
trogen. Addition of 16 ml of Et2O caused the formation of a red-
orange oil, which was separated by decantation. After dissolution
of the oil in 7 ml of CH2Cl2, 18 ml of C6H6 was added and upon
stirring an orange-yellow solid precipitated. This solid was col-
lected by filtration, washed with H2O, dried in vacuo, and recrys-
1
1580 m, 1471 s, 1434 s, 1099 m, 885 s, 685 vs, 502 s. Ϫ H NMR
(CDCl3): Several signals in the region δ ϭ ϩ18.0 to Ϫ1.0. Ϫ
C32H31Cl2NNiP2 ·C6H6 (699.3): calcd. C 65.26, H 5.34, N 2.00;
found C 65.38, H 5.44, N 1.74.
[ NiCl( PMe3) ( P∩NHMe) ] PF6 (9): To a mixture of 0.131 g of tallized from CH2Cl2/EtOH/C6H6 (6:1.5:17) (24.5 ml). Yield: 0.112
[NiCl2(PMe3)2] (0.46 mmol) and 0.117 g of KPF6 (0.64 mmol) in g (60%). Crystals were grown from CH2Cl2/MeOH/C6H6/Et2O
10 ml of CH2Cl2 was added 0.134 g of P∩NHMe (0.46 mmol) un- solutions. Ϫ IR (KBr): ν˜ ϭ 3251 cmϪ1 m, 1581 m, 1436 s, 1099 w,
der stirring. The blood-red mixture immediately turned dark-red.
After 3 h, a yellow solid had been deposited, which was filtered
off, washed with 2 ml of H2O, recrystallized from a 1:2 MeCN/
840 vs (PϪF), 557 s. Ϫ 1H NMR (CDCl3): δ ϭ 2.01 (d, 3 H, 3JHP ϭ
13 Hz, PCH3), 2.33 (s, 3 H, NCH3), 7.10Ϫ7.84 (m, 26 H, aromatic).
Ϫ
31P{1H} NMR (CDCl3): δ ϭ Ϫ146 (sept., 1 P, JPF ϭ 713 Hz,
Et2O solution (30 ml), and dried in vacuo. The filtrate was concen- PF6Ϫ), 6.91 (d, 1 P, JPP ϭ 83 Hz, PMe2Ph), 37.6 (d, 1 P, JPP
ϭ
2
2
trated to dryness under reduced pressure and the residue was 83 Hz, P∩NHMe). Ϫ C32H31ClF6NNiP3 ·C6H6 (808.82): calcd. C
recrystallized as above, giving a second crop of the yellow solid.
56.08, H 4.59, N 1.72; found C 56.99, H 4.55, N 1.65.
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697
1695

L. Crociani, F. Tisato, F. Refosco, G. Bandoli, B. Corain
FULL PAPER
X-ray Crystal Structure Determinations: Many of the details of
the structure analyses carried out on complexes 3, 6·CH2Cl2, 9,
and 13·MeOH are listed in Table 4.
partially occupied sites with occupancies of ca. 0.7, 0.2, and 0.1,
but efforts to refine these values were not successful and hence this
matter was not pursued further. The PF6Ϫ anion of 9 was modelled
Table 4. Crystallographic details for complexes 3, 6 · CH2Cl2, 9, and 13·MeOH
3
6·CH2Cl2
9
13·MeOH
formula
C26H27Cl2NNiP2
monoclinic
P21/n, (No.14)
11.937(5)
13.348(4)
15.575(4)
90
C33H33Cl4NNiP2
triclinic
C22H27ClF6NNiP3
monoclinic
P21/n, (No.14)
11.856(3)
13.669(4)
16.575(5)
90
C33H35ClF6NNiOP3
triclinic
cryst. system
space group
¯
¯
P1 (No.2)
P1 (No.2)
˚
a [A]
9.763(4)
10.002(3)
18.115(9)
77.89(3)
77.85(3)
87.36(3)
1691(1)
2
10.008(1)
13.395(2)
14.598(2)
101.50(1)
105.02(1)
104.56(1)
1745.5(3)
2
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
92.37(3)
90
96.54(2)
90
V [A3]
2479(1)
2669(1)
˚
Z
4
4
Dcalcd [Mg/m3]
1.460
1.251
1.510
1.444
µ [mmϪ1
F(000)
]
1.142
1.008
1.061
0.825
1128
728
1240
784
cryst. size [mm]
Θ range [°]
indep. refl.
0.20 ϫ 0.30 ϫ 0.20
2.3Ϫ25.0
4387
0.15 ϫ 0.10 ϫ 0.20
2.6Ϫ22.5
4429
0.25 ϫ 0.25 ϫ 0.25
2.5Ϫ22.5
3500
0.15 ϫ 0.15 ϫ 0.15
2.2Ϫ21.5
4013
refl. with I > 2σ(I)
no. of parameters
R1[a], wR2 [b] [I > 2σ(I)]
R1, wR2 (all data)
GooF on F2
2633
215
3295
385
2956
289
2798
414
0.043, 0.106
0.082, 0.121
0.745
0.041, 0.112
0.062, 0.123
0.987
0.045, 0.158
0.054, 0.163
1.509
0.055, 0.139
0.094, 0.165
1.182
max/min. resid. dens. [eAϪ3
]
0.90, Ϫ0.48
0.0000(6)
0.53, Ϫ0.49
Ϫ
0.87, Ϫ0.84
0.0039(11)
0.69, Ϫ0.46
0.0000(11)
˚
extinction coeff. Fc*[ c]
2
[a] R ϭ ΣʈFo͉ Ϫ ͉Fcʈ/Σ͉Fo͉. Ϫ [b] wR2 ϭ [Σw(Fo Ϫ Fc2)2/Σ(w͉Fo͉2)]1/2. Ϫ [c] Fc* ϭ kFc[1 ϩ (0.001 ϫ Fc2λ3/sin2Θ)]Ϫ1/4
.
using partial F atom occupancies, such that the central P atom had
two 100%, four 66% and four 33% occupied F atoms around it.
Crystallographic measurements were made at 293 K with a Sie-
mens Nicolet R3m/V four-circle diffractometer using graphite-
monochromated Mo-Kα radiation (λ ϭ 0.71073 A) (ωϪ2Θ scan
This model still gave rather high thermal parameters (ca. 0.10 A2
˚
˚
for all atoms), but resulted in an overall improvement in the struc-
ture. Finally, the MeOH molecule of 13·MeOH was located in a
disordered position and was included at half occupancy.
technique). The unit cell was determined by the automatic indexing
of 50 centered reflections at 2Θ > 21°. The rather poor quality of
crystals of 13·MeOH was manifested in broad scan-widths during
initial search routines with the diffractometer and the diffracting
ability of the sample dropped with increasing Bragg angle; much
of the higher angle data collected were deemed to be weak. As a
consequence, the data collection for 13·MeOH was restricted to
2Θ ϭ 43°. Corrections for Lorentz polarization effects and extinc-
tion were applied in all cases, while an empirical absorption correc-
tion, based on ψ scans for six reflections at χ ഠ 90°, was applied
only for compounds 3 and 13·MeOH (minimum and maximum
transmission factors 0.63Ϫ0.87 and 0.49Ϫ0.68 for 3 and 13·MeOH,
respectively). In fact, for 6·CH2Cl2 and 9, azimuthal scan data pro-
ved such correction to be unnecessary. The structures were solved
by Patterson methods and refined by full-matrix least-squares
methods on F2 using the SHELXTL/PC[31] and SHELXL-93[32]
suites of programs. Atomic scattering factors and anomalous dis-
persion parameters were taken from ref.[33]. Non-hydrogen atoms
were assigned anisotropic thermal parameters, with the exception
of the disordered atoms of 6·CH2Cl2, 9, and 13·MeOH. The hy-
drogen atoms were constrained to ride on the atom to which they
were attached. The isotropic thermal parameters for the methyl H
atoms were refined with 1.5 times, and for all phenyl H atoms with
1.2 times the Ueq value of the corresponding atom. On the contrary,
the hydrogen atoms attached to nitrogen atoms were located in the
final difference maps, but were not included in the refinement. Dur-
ing the refinement procedure it became apparent that the CH2Cl2
Selected bond lengths and angles are listed in Table 2.
Further details of the crystal structure determination can be or-
dered from the Fachinformationszentrum Karlsruhe, D-76344 Egg-
enstein-Leopoldshafen, Germany, on quoting the depository num-
bers CSD-408520 (3), -408521 (6·CH2Cl2), -408522 (9), -408523
(13·MeOH).
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`
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Ϫ
molecule in 6·CH2Cl2, the PF6 anion in 9, and the MeOH mol-
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6·CH2Cl2 was found to be severely disordered into a number of
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1696
Eur. J. Inorg. Chem. 1998, 1689Ϫ1697

Phosphanyl-Amino Complexes of Nickel(II)
FULL PAPER
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