Synthesis and characterization of a series of novel nickel(II)/nickel(I) complexes. Crystal structures of [NiCl2(dcpm)], [Ni(dcpm)2](NO3)2·2EtOH, [Ni2Cl2(μdcpm)2(μ-H)] and [Ni2(μ-PCy2)2(PCy2Me)2]; dcpm = bis(dicyclohexylphosphino)methane

Article abstract of DOI:10.1016/S0020-1693(99)00460-0

The complexes [(dcpm)NiCl₂] (1), [Ni2Cl₂(μ-dcpm)₂(μ-H)] (3), [Ni₂(μ-PCy₂)₂(PCy₂Me)₂] (4) and [Ni(dcpm)₂](NO₃)₂·2EtOH (2), dcpm = bis(dicyclohexylphosphino)methane, have been prepared and characterized by ³¹P, ¹H NMR (or EPR) as well as X-ray crystallography. The salt NiCl₂·6H₂O was found to react with dcpm to form the monomeric, four-coordinate, diamagnetic complex [(dcpm)NiCl₂] (1). Compound 1 was then reduced with (n)Bu₃SnH (or LiH with heating) in toluene at room temperature to form the air sensitive 'A-frame' complex [Ni₂Cl₂(μ-dcpm)₂(μ-H)] (3). The Ni-Ni bond distance for 3 was found to be 2.904(3) A? showing a lack of any Ni-Ni metal bonding. [Ni₂(μ-PCy₂)₂(PCy₂Me)₂] (4) was then formed by the reaction of 1 and excess LiH, heating to 90°C in an oil bath. [Ni₂Cl₂(μ-dcpm)₂(μ-H)] (3) was shown to be an intermediate in the synthesis of the bridging phosphido nickel complex. The Ni-Ni bond distance in 4 is 2.3910(8) A? corresponding to a single Ni-Ni metal bond. The reaction of Ni(NO₃)₂·6H₂O with dcpm in ethanol yields the square planar complex [Ni(dcpm)₂](NO₃)₂·2EtOH (2). (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00460-0

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 300–302 (2000) 200–205
Synthesis and characterization of a series of novel
nickel(II)/nickel(I) complexes. Crystal structures of [NiCl2(dcpm)],
[Ni(dcpm)2](NO3)2·2EtOH, [Ni2Cl2(m-dcpm)2(m-H)] and
[Ni2(m-PCy2)2(PCy2Me)2];
dcpm=bis(dicyclohexylphosphino)methane
Charles E. Kriley a,*, C. Joy Woolley a, Matthew K. Krepps a, Eric M. Popa b,
Phillip E. Fanwick b, Ian P. Rothwell c
a Department of Chemistry, 100 Campus Dri6e, Gro6e City College, Gro6e City, PA 16127, USA
b Department of Chemistry and Physics, Gyte Building, Purdue Uni6ersity Calumet, Hammond, IN 46323-2094, USA
c Department of Chemistry, 1393 Brown Building, Purdue Uni6ersity, West Lafayette, IN 47907-1393, USA
Received 27 August 1999; accepted 8 October 1999
Abstract
The complexes [(dcpm)NiCl2] (1), [Ni2Cl2(m-dcpm)2(m-H)] (3), [Ni2(m-PCy2)2(PCy2Me)2] (4) and [Ni(dcpm)2](NO3)2·2EtOH (2),
1
dcpm=bis(dicyclohexylphosphino)methane, have been prepared and characterized by 31P, H NMR (or EPR) as well as X-ray
crystallography. The salt NiCl2·6H2O was found to react with dcpm to form the monomeric, four-coordinate, diamagnetic
n
complex [(dcpm)NiCl2] (1). Compound 1 was then reduced with Bu3SnH (or LiH with heating) in toluene at room temperature
to form the air sensitive ‘A-frame’ complex [Ni2Cl2(m-dcpm)2(m-H)] (3). The NiꢀNi bond distance for 3 was found to be 2.904(3)
,
A showing a lack of any NiꢀNi metal bonding. [Ni2(m-PCy2)2(PCy2Me)2] (4) was then formed by the reaction of 1 and excess LiH,
heating to 90°C in an oil bath. [Ni2Cl2(m-dcpm)2(m-H)] (3) was shown to be an intermediate in the synthesis of the bridging
,
phosphido nickel complex. The NiꢀNi bond distance in 4 is 2.3910(8) A corresponding to a single NiꢀNi metal bond. The reaction
of Ni(NO3)2·6H2O with dcpm in ethanol yields the square planar complex [Ni(dcpm)2](NO3)2·2EtOH (2). © 2000 Elsevier Science
S.A. All rights reserved.
Keywords: Crystal structure complexes; Nickel complexes; Phosphine complexes; Dinuclear complexes
[NiX(L)2] (L=monodentate phosphines) complexes
was discovered by Schafer in 1979 when he synthesized
the first nickel(I) bridged phophido complex [Ni2(m-
SiMe3)(PR3)]2 (R=n-C4H9, C2H5, and CH3) from
(R3P)2NiCl2 and LiP(SiMe3)2 [4]. A crystal structure of
[Ni2(m-t-Bu2P)(PMe3)]2 was resolved by Atwood and
co-workers in 1982 and until the present time has
remained the only structurally characterized nickel
complex of this type [5].
Reaction of Ni(COD)2 (COD=cycloocta-1,5-diene)
with dppm, and phenyl isocyanide dichloride
(C6H5NCCl2) or thionyl chloride (SOCl2) has been
shown to result in an ‘A-frame’ complex of the type
[Ni2Cl2(m-dppm)2(m-L)] [6]. Bimetallic nickel complexes
1. Introduction
Over the past 40 years a large number of four-coordi-
nate nickel(II) phosphine complexes have been isolated
and characterized [1]. It was initially thought that, due
to steric strain, the bidentate phosphine dppm (bis-
diphenylphosphinomethane) would only act as
a
monodentate ligand [2]. Since that time nickel(II)
halides have been shown to react under controlled
conditions with dppm to yield the monomeric, four-
coordinate, low-spin chelated complexes [NiX2(dppm)],
where X is Cl, Br, or I [3]. Further reactivity of
* Corresponding author. Fax: +1-724-458 3855.
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 9 9 ) 0 0 4 6 0 - 0

C.E. Kriley et al. / Inorganica Chimica Acta 300–302 (2000) 200–205
201
of the general formula [Ni2X2(m-PP)2(m-L)] (X=halide,
PP=diphosphine, and L=SO, C=CH2, CNC6H5,
small Lewis bases) can adopt three distinct conforma-
tions: ‘mixed geometry’, ‘cradle’ and ‘A-frame’. Typi-
cally, ‘A-frame’ complexes contain square planar
symmetry around the nickel metal center. Unlike palla-
dium and platinum [7], only a small number ‘A-frame’
complexes of nickel have been structurally character-
ized [6].
Other factors that can be utilized in the study of
nickel-phosphine chemistry are the use of poorly coor-
dinating anions such as NO3−. The use of weakly
coordinating anions has led to the synthesis of nickel(0)
complexes containing two equivalents of a bidentate
phosphine such as dppm [8]. The [Ni(dppm)2] complex
has a tetrahedral coordination around Ni and is para-
magnetic in nature.
Through the catalytic hydrogenation of aryl-phos-
phine ligands, gram quantities of various mono-, di-,
and polydentate cyclohexyl phosphines have become
available to study [9]. Many of these were previously
either unavailable or difficult to chemically synthesize.
The availability of these novel phosphines, in particular
bis(dicyclohexylphosphino)methane (dcpm) [9] has pro-
vided the possibility of further development in the area
of dinuclear transition metal phosphine chemistry.
We report here the preparation, characterization and
reactivity of a series of nickel dcpm complexes.
2.1.2. [Ni(dcpm)2](NO3)2·2EtOH (2)
To 50 ml of a methanol solution of [Ni(NO3)2]·6H2O
(0.506 g, 1.74 mmol) was added 50 ml of a toluene
solution of dcpm (0.770 g, 1.88 mmol). An immediate
color change from green to yellow was observed upon
the addition of the dcpm–toluene solution. The solu-
tion was left to stir overnight under atmospheric pres-
sure. A yellow solid was obtained upon stripping off
the solvent. The yellow solid was then placed in a
minimal amount of ethanol and refluxed until com-
pletely dissolved. Small crystals of [Ni(dcpm)2]-
(NO3)2·2EtOH (2) were isolated after cooling the
ethanol solution overnight in a freezer (1.63 g, 46.6%).
No EPR signal was detected but the 1H NMR was
found to contain contact shifted peaks. 1H NMR
(CDCl3, 300 MHz): l 3.1, 3.4, 8.6, and 9.1 (broad
contact shifted peaks), 0.5–2.5 (cyclohexyl), 4.5 (broad,
EtOH). 31P NMR (CDCl3, 300 MHz): l −23.472.
2.1.3. [Ni2Cl2(v-dcpm)2(v-H)] (3)
To a 50 ml toluene solution of [(dcpm)NiCl2] (1)
(0.20 g, 0.37 mmol) under nitrogen was added tri-
butyltin hydride (0.44 g, 1.51 mmol). A green solution
formed after stirring for approximately 12 h. Green
colored crystals were obtained by stripping the solution
to dryness and dissolving in a minimal amount of
hexane and placing the resulting solution in the freezer
overnight. It was also found that the desired product
could be prepared by reacting 1 with an excess of LiH
or NaH in toluene and heating the solution in an oil
bath until the solution turned green in color (approxi-
mately 4 h). The complex was found to be EPR active
showing a g value of 2.139 g at room temperature and
gꢀ=2.211 g and gÞ=2.071 g at T=113 K. Yield=
0.16 g (42%). Anal. Calc. for Ni2Cl2P4C50H93: C, 59.67;
H, 9.31; Cl, 7.05; P, 12.31. Found: C, 58.18; H, 9.60;
Cl, 6.86; P, 10.74%.
2. Experimental
2.1. General procedures
NMR spectra were recorded by using a Varian Gem-
ini 200 and 300 MHz spectrometer. EPR measurements
were obtained on a Bruker ESP 300E system with an
ER 4121 VT liquid-nitrogen variable-temperature con-
troller. The operating microwave frequency was 9.45
GHz.
2.1.4. [Ni2(v-PCy2)2(PCy2Me)2] (4)
To 50 ml of a toluene solution of [(dcpm)NiCl2] (1)
(0.20 g, 0.37 mmol) under nitrogen was added an excess
amount of LiH (0.045g, 5.66 mmol). The solution was
then heated in an oil bath at 90°C for 12 h, or until the
solution turned dark red in color. The solution was
then filtered and placed in the freezer. Red crystalline
2.1.1. Preparation of complexes [(dcpm)NiCl2] (1)
To 50 ml of a methanol solution of [NiCl2]·6H2O
(0.28 g, 1.18 mmol) was added 50 ml of a toluene
solution of dcpm (0.50 g, 1.22 mmol). An immediate
color change from green to dark orange was observed
upon the addition of the dcpm–toluene solution. The
solution was then stirred for 12 h. Concentration of the
resulting orange solution resulted in the formation of
large orange blocks of pure product 1 in high yield
1
blocks of 4 formed overnight. Yield=0.19 g (56%). H
NMR (C6D6, 300 MHz): l 2.1 (s, 3H, CH3), 0.8-2.8
(cyclohexyl). 31P NMR (C6D6, 300 MHz): l 23.569 (t,
PCy2, J=83.4 Hz), 111.816 (t, PCy2Me, J=83.4 Hz).
2.2. X-ray crystallography
1
(0.59 g, 94%). H NMR (CDCl3, 200 MHz): l 2.350 (s,
2H, CH2), 1.0–2.6 (cyclohexyl). 31P NMR (CDCl3, 300
MHz): l −32.469. Anal. Calc. for NiC32H54Cl2P2,
[(dcpm)NiCl2]·C7H8: C, 60.98; H, 8.64; Cl, 11.25; P,
9.83. Found: C, 61.71; H, 9.44; Cl, 11.28; P, 10.65%.
Preliminary examination and data collection were
performed with Cu Ka (structure 3) or Mo Ka (struc-
tures 1, 2, and 4) radiation on an Enraf–Nonius CAD4
computer controlled kappa axis diffractometer equip-

202
C.E. Kriley et al. / Inorganica Chimica Acta 300–302 (2000) 200–205
Table 2
,
Selected bond distances (A) and angles (°) for [NiCl2(dcpm)] (1)
Ni(1)ꢀCl(1)
Ni(1)ꢀCl(2)
P(1)ꢀC(B)
2.215(1)
2.204(1)
1.843(3)
Ni(1)ꢀP(1)
Ni(1)ꢀP(2)
P(2)ꢀC(B)
2.152(1)
2.142(1)
1.838(4)
Cl(1)ꢀNi(1)ꢀCl(2) 97.60(4)
Cl(1)ꢀNi(1)ꢀP(1) 95.93(4)
Cl(1)ꢀNi(1)ꢀP(2) 167.50(5)
Cl(2)ꢀNi(1)ꢀP(1) 163.34(4)
Ni(1)ꢀP(1)ꢀC(111)
Ni(1)ꢀP(1)ꢀC(121)
Ni(1)ꢀP(1)ꢀC(B)
Ni(1)ꢀP(2)ꢀC(211)
Ni(1)ꢀP(2)ꢀC(221)
Ni(1)ꢀP(2)ꢀC(B)
123.2(1)
111.6(2)
95.9(1)
114.7(1)
120.5(1)
96.4(1)
Cl(2)ꢀNi(1)ꢀP(2)
P(1)ꢀNi(1)ꢀP(2)
P(1)ꢀC(B)ꢀP(2)
92.20(4)
75.89(4)
91.7(2)
All calculations were performed on a VAX com-
puter. Refinement for structures 1, 3, 4 was carried
Fig. 1. Molecular structure of [(dcpm)NiCl2] (1).
out using
M
olEN [13], while refinement for structure 2
ped with a graphite crystal, incident beam monochroma-
tor. The crystallographic structure for [(dcpm)NiCl2] (1)
was solved using the Patterson–Heavy-atom method,
which revealed the position of the Ni atom. The remain-
ing atoms were located using DIRDIF [10] and succeeding
difference Fourier synthesis. The crystallographic struc-
ture for [Ni(dcpm)2](NO3)2·2EtOH (2) was solved using
the structure solution program PATTY in DIRDIF92 [11].
The remaining atoms were located with succeeding
difference Fourier synthesis. Hydrogen atoms were in-
cluded in the refinement but were restrained to ride on
the atom to which they were bonded. The crystallo-
graphic structures for [Ni2Cl2(m-dcpm)2(m-H)] (3) and
[Ni2(m-PCy2)2(PCy2Me)2] (4) were solved using the struc-
ture solution program SHELX-86 [12]. The remaining
atoms were located in succeeding difference Fourier
syntheses. Except as noted in the table of positional
parameters, hydrogen atoms were located and added to
the structure factor calculations but not refined.
was performed on an AlphaServer 2100 using SHELX
-
93 [14]. Crystallographic drawings were carried out
using the program ORTEP [15] and/or PLUTON [16].
Lorentz and polarization corrections were applied to
the data.
2.2.1. [(dcpm)NiCl2] (1)
The molecule can be seen to adopt a distorted square
planar geometry for the central NiCl2P2 core (Fig. 1).
Crystal data and data collection parameters are given in
Table 1. A listing of important bond distances and angles
is found in Table 2. The NiꢀP distances (average 2.147(5)
,
A) are typical for those found in related NiꢀP complexes
[17]. The P(1)ꢀNi(1)ꢀP(2) bite angle is 75.89(4)°, typical
for a square planar complex. The coordination around
the phosphorus atoms is a distorted tetrahedral while all
cyclohexyl groups are bonded in an equatorial manner
to the phosphorus atoms.
Table 1
Crystal data and data collection parameters
1
2
3
4
Formula
Formula weight
Space group
NiCl2P2C25H46
538.21
P21/c (no. 14)
Ni2P4O8N2C54H104
1150.76
P21/c (no. 14)
Ni2Cl2P4C50H93
1006.52
I41/a (no. 88)
Ni2P4C50H94
936.62
P21/n (no. 14)
Unit cell dimensions
,
a (A)
11.124(1)
12.5206(8)
19.783(2)
90
97.224(9)
90
2733.5(8)
4
1.308
10.493(3)
12.816(4)
21.548(4)
90
97.37(23)
90
2873(2)
2
1.330
22.387(3)
22.387(3)
20.742(3)
90
90
90
10395(4)
8
1.286
293
10.662(2)
22.057(4)
11.155(2)
90
96.39(1)
90
2607(1)
2
1.193
293
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
3
,
Z
Dcalc (g cm−3
Temperature (K)
)
293
296
,
,
,
,
Radiation (wavelength)
R
Rw
Mo Ka (0.71073 A)
0.044
0.056
Mo Ka (0.71073 A)
0.053
0.141
Cu Ka (1.54184 A)
0.055
0.060
Mo Ka (0.71073 A)
0.037
0.050

C.E. Kriley et al. / Inorganica Chimica Acta 300–302 (2000) 200–205
203
Fig. 2. Molecular structure of [Ni(dcpm)2](NO3)2·2EtOH (2).
Fig. 3. Molecular structure of [Ni2Cl2(m-dcpm)2(m-H)] (3).
Table 4
2.2.2. [Ni(dcpm)2](NO3)2·2EtOH (2)
,
Selected bond distances (A) and angles (°) for [Ni2Cl2(m-dcpm)2(m-H)]
(3)
The coordination around the Ni atom can best be
described as distorted square planar (Fig. 2). The
P(1)ꢀNiꢀP(2) bite angle of 73.51(4)° is close to what is
expected for a square planar, low spin, nickel d8 com-
plex. Crystal data and data collection parameters are
given in Table 1. A listing of important bond distances
and angles is found in Table 3. This is in contrast with
the previously determined structure of Ni(dcpm)2 [18],
which was determined to have a distorted tetrahedral
coordination around the nickel metal center. The coor-
dination around the phosphorus atoms is again dis-
torted tetrahedral while all cyclohexyl groups are
bonded in an equatorial manner to the phosphorus
atoms. The nitrate ion is extremely disordered, similar
to the nitrate ion found in the square planar complex
[Ni(Ph2CH2CH2PPh2)2](NO3)2 [19]. In contrast to
NiꢀNi
NiꢀCl
NiꢀP(1)
NiꢀP(2)
2.904(3)
2.268(4)
2.212(3)
2.213(3)
NiꢀH(1)
1.61(5)
1.84(1)
1.83(1)
93.8(1)
P(1)ꢀC(12)
P(2)ꢀC(12)
ClꢀNiꢀP(2)
NiꢀNiꢀCl
154.6(1)
87.7(1)
94.8(1)
26(4)
89.7(1)
166.1(2)
89.4(3)
ClꢀNiꢀH(1)
179(1)
NiꢀNiꢀP(1)
NiꢀNiꢀP(2)
NiꢀNiꢀH(1)
ClꢀNiꢀP(1)
P(1)ꢀNiꢀP(2)
P(1)ꢀNiꢀH(1)
NiꢀP(1)ꢀC(12)
NiꢀP(2)ꢀC(12)
P(1)ꢀC(12)ꢀP(2)
NiꢀH(1)ꢀNi
116.5(3)
114.5(3)
115.3(5)
128(8)
P(2)ꢀNiꢀH(1)
87(1)
[Ni(Ph2CH2CH2PPh2)2](NO3)2 our compound was
found to crystallize with 2 equiv. of ethanol in the final
structure.
Table 3
2.2.3. [Ni2Cl2(v-dcpm)2(v-H)] (3)
,
Selected bond distances (A) and angles (°) for [Ni(C25H46P2)2]-
(NO3)2·2CH3CH2OH] (2)
The structure of [Ni2Cl2(m-dcpm)2(m-H)] (3) can be
seen in Fig. 3. Crystal data and data collection parame-
ters are given in Table 1. A listing of important bond
distances and angles is found in Table 4. Few examples
of Ni ‘A-frame’ complexes have been structurally char-
acterized. Currently only three such structures have
been determined [6,21], this complex constituting the
fourth example of this class and the only Ni hydride
‘A-frame’ complex known. The NiꢀH bond distance
NiꢀP(2)
NiꢀP(2)
NiꢀP(1)
2.2836(11)
2.2836(11)
2.3095(13)
NiꢀP(1)
P(1)ꢀC(B)
P(2)ꢀC(B)
2.3095(13)
1.831(4)
1.827(4)
P(2)ꢀNiꢀP(2)
P(2)ꢀNiꢀP(1)
P(2)ꢀNiꢀP(1)
P(2)ꢀNiꢀP(1)
P(2)ꢀNiꢀP(1)
P(1)ꢀNiꢀP(1)
C(B)ꢀP(1)ꢀC(111)
C(B)ꢀP(1)ꢀC(121)
179.9990(10) C(B)ꢀP(1)ꢀNi
93.80(14)
121.14(14)
116.22(14)
107.1(2)
73.51(4)
106.49(4)
106.48(4)
73.51(4)
C(111)ꢀP(1)ꢀNi
C(121)ꢀP(1)ꢀNi
C(B)ꢀP(2)ꢀC(221)
C(B)ꢀP(2)ꢀC(211)
104.1(2)
179.9980(10) C(221)ꢀP(2)ꢀC(211) 106.1(2)
106.3(2)
109.1(2)
,
was found to be 1.61(5) A. The NiꢀNi distance of
C(B)ꢀP(2)ꢀNi
C(221)ꢀP(2)ꢀNi
C(211)ꢀP(2)ꢀNi
94.75(13)
121.20(14)
120.60(14)
,
2.904(3) A shows the absence of any NiꢀNi bonding.
The coordination around the phosphorus atoms is a
distorted tetrahedral while all cyclohexyl groups are
C(111)ꢀP(1)ꢀC(121) 108.3(2)

204
C.E. Kriley et al. / Inorganica Chimica Acta 300–302 (2000) 200–205
bonded in an equatorial manner to the phosphorus
atoms.
6H2O to form the corresponding Ni(II) complexes
(Figs. 1 and 2). In the case of [NiCl2]·6H2O the ex-
pected complex, [(dcpm)NiCl2] (1), was formed in high
yield, giving a diamagnetic, distorted square planar
geometry around the NiP2Cl2 core (Scheme 1). The
structure is indicative of a nickel d8, +2 oxidation state
with C26 symmetry. All four of the complexes prepared
in this study were found to contain phosphines resting
in a tetrahedral environment, with the cyclohexanes
being bound in an equatorial manner. The
[Ni(NO3)2]·6H2O also reacts quantitatively with dcpm
in ethanol forming [Ni(dcpm)2](NO3)2·2EtOH (Scheme
2). The NiP4 core having a square planar geometry and
a D4h symmetry in the solid state. The 1H NMR is
characteristic of a paramagnetic, contact shifted NMR
suggesting the possibility of a square planar/tetrahedral
structure in solution. Again the nickel d8 metal center
has a +2 oxidation state.
2.2.4. [Ni2(v-PCy2)2(PCy2Me)2] (4)
The structure of [Ni2(m-PCy2)2(PCy2Me)2] (4) can be
seen in Fig. 4. Crystal data and data collection parame-
ters are given in Table 1. A listing of important bond
distances and angles is found in Table 5. The
P(1)ꢀNi(1)ꢀP(2) bond angle of 122.50° giving a trigonal
planar coordination around nickel. A NiꢀNi bond dis-
,
tance of 2.3910(8) A is indicative of a single NiꢀNi
metal bond. The symmetry of the molecule is D2h with
coplanar Ni and P atoms and a linear arrangement of
P(1)ꢀNi(1)ꢀNi(1)ꢀP(1). The coordination around the
phosphorus atoms is a distorted tetrahedral while all
cyclohexyl groups are bonded in an equatorial manner
to the phosphorus atoms.
A study of the reactivity of [(dcpm)NiCl2] (1) was
then undertaken. It was found that by reacting 1 with
nBu3SnH (or LiH and heating for 4 h) in toluene a
green, paramagnetic complex could be isolated,
[Ni2Cl2(m-dcpm)2(m-H)] (3) (Scheme 1). The X-ray crys-
tal structure of 3 shows that the dcpm ligand bonds in
a bridging manner (Fig. 3) and that the coordination
around each of the Ni metal centers (NiP2HCl) is
approximately square planar. The product is currently
the only example of a nickel ‘A-frame’ complex with a
bridging hydride in the apex position. The NiꢀNi bond
3. Results and discussion
As has been previously shown with dppm, dcpm was
found to react with [NiCl2]·6H2O as well as [Ni(NO3)2]·
,
distance of 2.904(3) A shows the absence of any NiꢀNi
bonding as can be seen in Table 6. The paramagnetic
structure gives an EPR signal with a g value of 2.139 g
at room temperature and gꢀ=2.211 g and gÞ=2.071 g
at T=113 K. Compound 3 has been found to react
Fig. 4. Molecular structure of [Ni2(m-PCy2)2(PCy2Me)2] (4).
Table 5
,
Selected bond distances (A) and angles (°) for Ni2(m-PCy2)2-
(PCy2Me)2 (4)
Ni(1)ꢀNi(1)
Ni(1)ꢀP(1)
2.3910(8)
2.1586(9)
Ni(1)ꢀP(2)
Ni(1)ꢀP(2)
2.1708(9)
2.1778(9)
Scheme 1.
Ni(1)ꢀNi(1)ꢀP(1)
Ni(1)ꢀNi(1)ꢀP(2)
Ni(1)ꢀNi(1)ꢀP(2)
P(1)ꢀNi(1)ꢀP(2)
P(1)ꢀNi(1)ꢀP(2)
P(2)ꢀNi(1)ꢀP(2)
Ni(1)ꢀP(1)ꢀC(111) 116.1(1)
Ni(1)ꢀP(1)ꢀC(121) 114.9(1)
Ni(1)ꢀP(1)ꢀC(131) 117.7(1)
179.05(3)
56.78(3)
56.50(3)
122.50(4)
124.20(3)
113.29(3)
C(111)ꢀP(1)ꢀC(121) 103.3(2)
C(111)ꢀP(1)ꢀC(131) 100.8(2)
C(121)ꢀP(1)ꢀC(131) 101.8(2)
Ni(1)ꢀP(2)ꢀNi(1)
Ni(1)ꢀP(2)ꢀC(221)
Ni(1)ꢀP(2)ꢀC(211)
Ni(1)ꢀP(2)ꢀC(211)
Ni(1)ꢀP(2)ꢀC(221)
66.71(3)
122.9(1)
120.5(1)
121.8(1)
121.1(1)
C(211)ꢀP(2)ꢀC(221) 102.4(1)
Scheme 2.

C.E. Kriley et al. / Inorganica Chimica Acta 300–302 (2000) 200–205
205
Table 6
NiꢀNi bond lengths for selected nickel compounds a
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Reference
NiꢀNi metallic radii
2.492
[Ni2(mdcpm)2Cl2(mH)]
[Ni2(mdppm)2(NCS)2(mCꢁCH2)]
[Ni2(mdcpm)2Cl2(mSO)]
[Ni2(mdppm)2Cl2(mCNC6H5)]
[{Ni(dippe)}2(mH)2][BPh4]
[Ni2(dcpp)2(mH)2]
2.904(3)
284.0(4)
3.308(1)
2.917(4)
2.316(5) b
2.441(1) b
2.438(1) b
2.375(3) b
2.559(2) b
2.3910(8) b
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Heating [Ni2Cl2(m-dcpm)2(m-H)] (3), for approxi-
mately 12 h, yields the red complex [Ni2(m-
PCy2)2(PCy2Me)2] (4) (Scheme 1). The desired complex
can also be obtained from heating 1 with LiH in an oil
bath for 12 h at approximately 90°C . A NiꢀNi bond
,
distance of 2.3910(8) A is indicative of a single NiꢀNi
metal bond (Table 6). The linear PꢀNiꢀNiꢀP bonding
gives a D2h symmetry. Further reactivity of the complex
has yet to be investigated.
4. Supplementary material
Crystal data and data collection parameters are con-
tained in Table 1. Crystallographic data for the struc-
tural analyses have been deposited with the Cambridge
Crystallographic Data Center, CCDC nos. 133445 (1),
133446 (2), 133447 (3), and 133448 (4). Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
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1EZ
[fax
+44-1223-336033]
or
e-mail
de-
posit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk.
Acknowledgements
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We thank the Department of Energy, Grove City
College and the Purdue Research Foundation for sup-
port of this research. Special thanks to Steve Boone,
Central Missouri State University, for his technical
advice.
.