A terminal nickel(II) anilide complex featuring an unsymmetrically substituted amido pincer ligand: Synthesis and reactivity

Article abstract of DOI:10.1039/c1dt10191a

This work describes preparation and reaction chemistry of a terminal nickel(ii) anilide complex supported by an unsymmetrically substituted diarylamido diphosphine ligand, [N(o-C₆H₄PPh ₂)(o-C₆H₄PⁱPr₂)] ^- ([Ph-PNP-ⁱPr]^-). Treatment of NiCl ₂(DME) with H[Ph-PNP-ⁱPr] in THF at room temperature produced [Ph-PNP-ⁱPr]NiCl as green crystals in 82% yield. Salt metathesis of [Ph-PNP-ⁱPr]NiCl with LiNHPh(THF) in THF at -35 °C generated cleanly [Ph-PNP-ⁱPr]NiNHPh as a greenish blue solid. The anilide complex deprotonates protic (e.g., PhOH and PhSH) and aprotic (e.g., trimethylsilylacetylene, phenylacetylene, and acetonitrile) acids in benzene at room temperature to give quantitatively [Ph-PNP-ⁱPr]NiX (X = OPh, SPh, CCSiMe₃, CCPh, CH₂CN). In addition, [Ph-PNP- ⁱPr]NiNHPh also behaves as a nucleophile to react with acetyl chloride to yield [Ph-PNP-ⁱPr]NiCl and N-phenylacetamide quantitatively. Carbonylation of [Ph-PNP-ⁱPr]NiNHPh with carbon monoxide affords cleanly the carbamoyl derivative [Ph-PNP-ⁱPr]Ni[C(O) NHPh]. The relative bond strengths of Ni-E in [Ph-PNP-ⁱPr]NiEPh (E = NH, O, S, CC) are assessed and discussed. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt10191a

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Pincers and other hemilabile ligands
Guest Editors Dr Bert Klein Gebbink and Gerard van Koten
Published in issue 35, 2011 of Dalton Transactions
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Articles in the issue include:
PERSPECTIVE:
Cleavage of unreactive bonds with pincer metal complexes
Martin Albrecht and Monika M. Lindner
Dalton Trans., 2011, DOI: 10.1039/C1DT10339C
ARTICLES:
Pincer Ru and Os complexes as efficient catalysts for racemization and deuteration of alcohols
Gianluca Bossi, Elisabetta Putignano, Pierluigi Rigo and Walter Baratta
Dalton Trans., 2011, DOI: 10.1039/C1DT10498E
Mechanistic analysis of trans C–N reductive elimination from a square-planar macrocyclic aryl-
copper(III) complex
Lauren M. Huffman and Shannon S. Stahl
Dalton Trans., 2011, DOI: 10.1039/C1DT10463B
CSC-pincer versus pseudo-pincer complexes of palladium(II): a comparative study on
complexation and catalytic activities of NHC complexes
Dan Yuan, Haoyun Tang, Linfei Xiao and Han Vinh Huynh
Dalton Trans., 2011, DOI: 10.1039/C1DT10269A
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PAPER
A terminal nickel(II) anilide complex featuring an unsymmetrically substituted
amido pincer ligand: synthesis and reactivity†
Lan-Chang Liang,*a Chun-Wei Li,a Pei-Ying Lee,a Chih-Hsiang Changa and Hon Man Leeb
Received 2nd February 2011, Accepted 5th May 2011
DOI: 10.1039/c1dt10191a
This work describes preparation and reaction chemistry of a terminal nickel(II) anilide complex
supported by an unsymmetrically substituted diarylamido diphosphine ligand,
[N(o-C6H4PPh2)(o-C6H4PiPr2)]- ([Ph-PNP-iPr]-). Treatment of NiCl2(DME) with H[Ph-PNP-iPr] in
THF at room temperature produced [Ph-PNP-iPr]NiCl as◦green crystals in 82% yield. Salt metathesis
of [Ph-PNP-iPr]NiCl with LiNHPh(THF) in THF at -35 C generated cleanly [Ph-PNP-iPr]NiNHPh
as a greenish blue solid. The anilide complex deprotonates protic (e.g., PhOH and PhSH) and aprotic
(e.g., trimethylsilylacetylene, phenylacetylene, and acetonitrile) acids in benzene at room temperature to
give quantitatively [Ph-PNP-iPr]NiX (X = OPh, SPh, C CSiMe3, C CPh, CH2CN). In addition,
[Ph-PNP-iPr]NiNHPh also behaves as a nucleophile to react with acetyl chloride to yield
[Ph-PNP-iPr]NiCl and N-phenylacetamide quantitatively. Carbonylation of [Ph-PNP-iPr]NiNHPh with
carbon monoxide affords cleanly the carbamoyl derivative [Ph-PNP-iPr]Ni[C(O)NHPh]. The relative
bond strengths of Ni–E in [Ph-PNP-iPr]NiEPh (E = NH, O, S, C C) are assessed and discussed.
iPr, Cy) complexes has been shown to be a function of the identity
Introduction
of their phosphorus substituents.19–22 We became interested in
Late transition metal amides are receiving increasing attention
unsymmetrically substituted pincer complexes due partly to the
due to their important roles as intermediates in a number of
recent discoveries of their unusual reactivity, particularly those
built on a lutidine or aryl skeleton.23–26 We report herein the
preparation and reactivity studies of a nickel anilide complex
containing an unsymmetrically substituted [N(o-C6H4PPh2)(o-
C6H4PiPr2)]- ([Ph-PNP-iPr]-) ligand, aiming to demonstrate its
divergent reactivity features as both a base and a nucleophile and
to assess the relative strengths of Ni–C and Ni–heteroatom bonds.
The incorporation of unsymmetric substituents in the derived
pincer complexes is beneficial in view of the assessment of their
solution structures by the magnitude of coupling constants arisen
between the two chemically inequivalent phosphorus donors in-
volved. Insights regarding the reactivity of [Ph-PNP-iPr]NiNHPh
are discussed.
biological and industrially relevant chemical transformations such
as catalytic hydroamination and C–N coupling reactions, etc.1–6
Understanding the nature and reactivity preferences of a non-
dative metal-amide bond is essential for the rational design of
catalytically active species. Due to the presence of inherent dp–
pp repulsion,6,7 late transition-metal amides are often relatively
destabilized and thus more reactive than their organometallic
analogues. Preparation and isolation of these species are therefore
valuable in view of the elucidation of their reactivity preferences.
Notably, the palladium catalyzed C–N bond forming reactions
have evolved as a powerful tool for organic synthesis.8–11 We are
currently exploring reaction chemistry involving metal complexes
containing o-phenylene-derived amido phosphine ligands.12–18 In
particular, the reactivity of [N(o-C6H4PR2)2]- ([R-PNP]-; R = Ph,
Results and discussion
aDepartment of Chemistry and Center for Nanoscience & Nanotechnology,
National Sun Yat-sen University, Kaohsiung, 80424, Taiwan. E-mail:
lcliang@mail.nsysu.edu.tw
Synthesis of the anilide complex
The reaction of NiCl2(DME)27 with H[Ph-PNP-iPr]20 in THF
at room temperature generated, after standard workup and
crystallization procedures, green crystals of [Ph-PNP-iPr]NiCl in
82% yield. Interestingly, the reaction is complete in 10 min and
the liberated HCl byproduct does not affect the production of
the desired chloride complex. Subsequent metathetical reaction of
[Ph-PNP-iPr]NiCl with LiNHPh(THF) in THF at -35 ◦C afforded
[Ph-PNP-iPr]NiNHPh as a greenish blue solid in 90% yield. These
bDepartment of Chemistry, National Changhua University of Education,
Changhua, 50058, Taiwan
† Electronic supplementary information (ESI) available: DFT geometry
optimized structures, bond distances, bond angles, and coordinates
of [Ph-PNP-iPr]NiEPh (E = NH, O, S, C C), energy changes for
protonolysis reactions involving these molecules, and contour plot of
HOMO of [Ph-PNP-iPr]NiNHPh. CCDC reference number 806151. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c1dt10191a
9004 | Dalton Trans., 2011, 40, 9004–9011
This journal is
The Royal Society of Chemistry 2011
©

compounds have been fully characterized by multi-nuclear NMR
spectroscopy (vide infra), combustion analysis, and in the case of
the chloride, by X-ray crystallography.
which undergoes reversible exchange with p-toluidine. The basic
strengths of these amido phosphine derived species thus follow
the order of [Ph-PNP-iPr]NiOtBu > [Ph-PNP-iPr]NiNHPh > [Ph-
PNP-iPr]NiOPh > [Ph-PNP-iPr]NiSPh, reminiscent of what was
found for [Ph-PNP]- counterparts.22 Attempts to prepare the tert-
butyl amide [Ph-PNP-iPr]NiNHtBu by either protonolysis of [Ph-
Reactivity studies of [Ph-PNP-iPr]NiNHPh
It has been documented that late transition-metal amides may,
in some cases, be strongly basic due to highly polarized M–N
bonds.1 The anilide complex [Ph-PNP-iPr]NiNHPh deprotonates
phenol and thiophenol readily in benzene solutions at room
temperature to yield quantitatively [Ph-PNP-iPr]NiEPh (E = O,
S) and aniline as evidenced by solution NMR studies. The
identity of the derived phenolate and thiophenolate complexes was
confirmed by independent preparation of these molecules from
salt metathesis of [Ph-PNP-iPr]NiCl with NaEPh. In contrast, the
anilide fails to convert to the tert-butoxide [Ph-PNP-iPr]NiOtBu
upon reaction with tert-butanol under similar conditions (1H and
31P NMR evidence). Instead, the tert-butoxide complex, prepared
by treating [Ph-PNP-iPr]NiCl with NaOtBu, reacts with aniline in
benzene at room temperature to give [Ph-PNP-iPr]NiNHPh and
tert-butanol quantitatively. Scheme 1 summarizes the protonolysis
reactions involving [Ph-PNP-iPr]NiOtBu, [Ph-PNP-iPr]NiNHPh,
[Ph-PNP-iPr]NiOPh and [Ph-PNP-iPr]NiSPh with appropriate
protic sources. We note that these reactions are essentially
irreversible or reversible but having an extremely large equilibrium
constant, as no protonolysis was found when reverse reactions
were attempted, even in the presence of an excess amount of appro-
priate protic sources at various temperatures. This phenomenon is
notably different from what was reported for Cp*Ni(PMe3)OTol,28
t
PNP-iPr]NiNHPh with BuNH2 or salt metathesis of [Ph-PNP-
iPr]NiCl with LiNHtBu were not successful. It is interesting to
note that both [Ph-PNP]NiNHtBu and [Ph-PNP]NiOtBu were
successfully synthesized by salt metathesis reactions whereas [iPr-
PNP]NiNHtBu and [iPr-PNP]NiOtBu were not.22 The successful
isolation of [Ph-PNP-iPr]NiOtBu but not [Ph-PNP-iPr]NiNHtBu
clearly emphasizes that the synthetic accessibility of complexes
containing these p-donor ligands is a function of the amido
phosphine ligands employed. The apparently higher stability of
aryl- than alkyl-derived M–OR and M–NHR complexes was also
found in other systems.1
Though [Ph-PNP-iPr]NiOtBu was not produced upon protonol-
ysis of [Ph-PNP-iPr]NiNHPh, addition of one equiv of tBuOD to
a C6D6 solution of [Ph-PNP-iPr]NiNHPh at room temperature
led to a decrease in NH integral by 33% in 1 h as indicated
by the 1H NMR spectrum. The 2H NMR spectrum of the
same reaction also shows the formation of [Ph-PNP-iPr]NiNDPh,
indicating clearly H/D exchange occurs between nickel-bound
anilide and tert-butanol. The exchange is reversible, as [Ph-
PNP-iPr]NiNDPh re-converts to [Ph-PNP-iPr]NiNHPh in the
presence of tBuOH. These results suggest the formation of a four-
membered, hydrogen-bonded intermediate I (Scheme 2) in this
exchange reaction, highlighting the strongly polarized nature of
the nickel–anilide bond in [Ph-PNP-iPr]NiNHPh. The production
of this hydrogen-bonded intermediate also implies that HOMO
of [Ph-PNP-iPr]NiNHPh resides at the terminal anilide ligand.
The formation of [Ph-PNP-iPr]NiOPh and [Ph-PNP-iPr]NiSPh
instead of [Ph-PNP-iPr]NiOtBu upon protonolysis of [Ph-PNP-
iPr]NiNHPh is thus apparently governed by thermodynamic
reasons that involve the relative bond energies of Ni–X (X =
OtBu, NHPh, OPh, SPh) and H–X. On the basis of these
results, we suggest that the successful transformations of [Ph-
PNP-iPr]NiNHPh to [Ph-PNP-iPr]NiEPh (E = O, S) proceed by a
mechanism involving hydrogen atom transfer via an intermediate
conceptually similar to II as depicted in Scheme 2. A mechanistic
Scheme 1
Scheme 2
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9004–9011 | 9005
©

Table 1 Selected NMR data for [Ph-PNP-iPr]NiXa
alternative involving proton transfer should be less likely in view
of the formation of an ion pair {[Ph-PNP-iPr]Ni(NH2Ph)}{EPh}
in benzene. We note that the protonolysis solutions remain clear
and homogeneous throughout the reactions.
X
d31P (PiPr2, PPh2)
2JPP
dHa
3JPHa
Cl
39.8, 16.3
24.2, 2.8
33.5, 10.0
33.7, 6.9
38.2, 21.1
52.0, 28.8
50.1, 27.2
38.9, 27.5
42.8, 21.1
331
358
356
325
318
281
288
272
222
OtBu
NHPh
OPh
SPh
Mechanistically, the protonolysis may also proceed via an initial
+
Ni–N heterolysis to give cationic {[Ph-PNP-iPr]Ni} and anionic
-1.33
[PhNH]-. This possibility is rather low due to the considerably
rapid reaction rates observed for these protonolysis reactions con-
ducted in a non-polar medium. Crossover experiments involving
[Ph-PNP-iPr]NiNHPh with [Ph-PNP]NiCl22 or [iPr-PNP]NiCl22
in benzene at room temperature showed no anilide/chloride
exchange (Scheme 3). These observations certainly argue against
the involvement of an initial ionization pathway.
C
C
CSiMe3
CPh
CH2CN
C(O)NHPh
0.71
9.5, 11.5
a All spectra were recorded in C6D6 at room temperature, chemical shifts
in ppm, coupling constants in hertz.
NMR timescale, reminiscent of what was observed for previously
reported hydride and alkyl derivatives.20 The coupling constants
found for the two chemically inequivalent phosphorus donors
are all consistent with a meridional coordination mode7 for the
tridentate amido diphosphine ligand. Interestingly, the 2JPP values
of the anilide and other heteroatom-bound nickel complexes
(318–358 Hz) are notably larger than those of organonickel
derivatives (222–288 Hz),20 a consequence that is likely reflec-
tive of the more electron-deficient nature of the metal due to
higher electronegativity of the heteroatoms in the former. The
anilide complex shows a diagnostic signal at -1.33 ppm in
Scheme 3
1
the H NMR for NHPh, which moves downfield to 6.89 ppm
Though [Ph-PNP-iPr]NiOtBu is apparently more reactive than
[Ph-PNP-iPr]NiNHPh, we found that the latter complex is much
easier to be manipulated for reactivity exploration and thus chose
to examine further the reactivity preferences of this derivative. Its
reactions with extremely weak aprotic acids were also attempted.
Addition of trimethylsilylacetylene or phenylacetylene to benzene
solutions of [Ph-PNP-iPr]NiNHPh at room temperature produces
quantitatively the corresponding acetylide complexes as a red
solid. The anilide also deprotonates acetonitrile cleanly under
similar conditions to yield the cyanomethyl complex [Ph-PNP-
iPr]NiCH2CN. On the basis of these reactions, it is also interesting
to point out that these organonickel complexes appear not to react
appreciably with the liberated aniline.
In addition to its inherent basic nature, the anilide complex
is also a nucleophile. It reacts readily with acetyl chloride in
THF at room temperature to produce [Ph-PNP-iPr]NiCl and N-
phenylacetamide quantitatively on the basis of NMR and MS
studies. Introduction of CO (1 atm) to a benzene solution of [Ph-
PNP-iPr]NiNHPh at room temperature afforded the carbamoyl
complex [Ph-PNP-iPr]Ni[C(O)NHPh] as a red solid in 82%
yield. In [Ph-PNP-iPr]NiNHPh, the terminal Ni–N bond is thus
apparently more reactive than that associated with the PNP pincer
ligand. Though not unprecedented, carbon monoxide insertion
into a late transition metal–amide bond is uncommon.29,30 This
carbamoyl complex is thermally stable; neither decarbonylation
nor b-elimination was observed even at elevated temperatures
(110 ◦C, 4 days, 40 mM in benzene).
upon CO insertion. In principle, the Ha atoms in [Ph-PNP-
iPr]Ni(CH2CN) should be diastereotopic as what was found
for [Ph-PNP-iPr]NiEt and [Ph-PNP-iPr]Ni(n-hexyl).20 With the
cylindrical cyano substituent at the Ca atom, rapid rotation about
the Ni–C bond occurs readily and thus Ha atoms in [Ph-PNP-
iPr]Ni(CH2CN) become indistinguishable on the NMR timescale,
exhibiting a doublet of doublets resonance in the 1H NMR
spectrum due to coupling with two inequivalent phosphorus
donors.
X-Ray crystal structure of [Ph-PNP-iPr]NiCl
Fig. 1 depicts the X-ray structure of [Ph-PNP-iPr]NiCl. Consistent
with the solution NMR studies, the core geometry of [Ph-PNP-
iPr]NiCl is best described as distorted square planar with the
[Ph-PNP-iPr]- ligand being in a meridional coordination mode.
The two phosphorus donors are trans-disposed with the P(2)–
Ni(1)–P(1) angle of 167.88(7)◦, which is sharper than that of [Ph-
PNP-iPr]NiH (174.15(3)◦)20 but comparable to that of [Ph-PNP-
iPr]Ni(n-hexyl) (165.65(9)◦),20 consistent with the steric repulsion
1
arising from these formally anionic h -ligands. Though bearing
different substituents at the phosphorus donors, the two Ni–P
distances in [Ph-PNP-iPr]NiCl are virtually identical. The two
o-phenylene rings are tilted with respect to the coordination
plane so as to accommodate simultaneously two fused five-
membered chelating rings and to minimize the steric repulsion
between two CH moieties ortho to the amido nitrogen donor. The
˚
Ni–N distance of 1.888(5) A is comparably shorter than those
Solution NMR studies
i
i
˚
of [Ph-PNP- Pr]NiH (1.924(2) A) and [Ph-PNP- Pr]Ni(n-hexyl)
(1.961(6) A),20 consistent with the anticipated trans influence order
˚
Table 1 summarizes selected NMR data for all derived complexes.
In general, these compounds display solution Cs symmetry on the
of Cl < H < alkyl.
9006 | Dalton Trans., 2011, 40, 9004–9011
This journal is
The Royal Society of Chemistry 2011
©

over Ni–N, is reminiscent of what was found in Cp*Ni(PMe3)X
derivatives.28 Interestingly, the bond strength difference between
M–NHPh and M–C CPh estimated herein is similar to that
acquired in studies employing Cp*Ru(PMe3)2X.31 DFT analysis
also confirms that HOMO of [Ph-PNP-iPr]NiNHPh is primarily
composed of the pp orbitals of the terminal anilide ligand (see
ESI†), consistent with what is deduced from the reversible H/D
exchange reaction depicted in Scheme 2.
Conclusions
We have prepared a nickel(II) anilide complex of an unsymmet-
rically substituted PNP pincer ligand. Its divergent reactivity
features in reactions with protic and aprotic acids and electrophiles
are demonstrated. In particular, a series of p-donor ligated nickel
complexes and organonickel derivatives are prepared. Of note
is its highly basic strength, able to deprotonate extremely weak
aprotic acids such as acetonitrile, and its high nucleophilicity to
undergo CO insertion. Interestingly, a deuterium labeling study
involving [Ph-PNP-iPr]NiNHPh and tBuOD revealed a reversible
H/D exchange in spite of no production of [Ph-PNP-iPr]NiOtBu.
The thermodynamic preferences regarding protonolysis of [Ph-
PNP-iPr]NiEPh (E = NH, O, S, C C) were also elucidated by
DFT computations. The Ni–N bond is relatively destabilized in
comparison with Ni–O, Ni–S and Ni–C C.
Fig. 1 Molecular structure of [Ph-PNP-iPr]NiCl with thermal ellip-
soids drawn at the 35% probability level. The asymmetric unit cell
contains two independent molecules and two unbound toluenes; only
one [Ph-PNP-iPr]NiCl is shown for clarity. Selected bond distances
◦
˚
(A) and angles ( ): Cl(1)–Ni(1) 2.1691(18), N(1)–Ni(1) 1.888(5), Ni(1)–
P(2) 2.1871(18), Ni(1)–P(1) 2.1877(18); N(1)–Ni(1)–Cl(1) 178.33(16),
N(1)–Ni(1)–P(2) 85.06(15), Cl(1)–Ni(1)–P(2) 95.50(7), N(1)–Ni(1)–P(1)
85.42(15), Cl(1)–Ni(1)–P(1) 94.23(7), P(2)–Ni(1)–P(1) 167.88(7).
Density functional theory (DFT) studies
It has been well-documented1,28,31–33 that the relative bond dis-
sociation energies of LnM–X and LnM–Y may be assessed by
equilibrium constants of reversible exchange reactions of the
general type:
Experimental
General procedures
LnM–X + H–Y ꢀ LnM–Y + H–X,
Unless otherwise specified, all experiments were performed under
nitrogen using standard Schlenk or glovebox techniques. All sol-
vents were reagent grade or better and purified by standard meth-
ods. Compounds NiCl2(DME),27 H[Ph-PNP-iPr],20 NaOPh,22 and
NaSPh22 were prepared according to the procedures reported
previously. LiNHPh(THF) was prepared by lithiation of aniline
with one equiv. of n-BuLi in THF followed by evaporation of
the reaction mixture. All other chemicals were obtained from
commercial vendors and used as received. The NMR spectra
were recorded on Varian Unity or Bruker AV instruments.
Chemical shifts (d) are listed as parts per million downfield
using the known H–X and H–Y bond energies.34 Given the dif-
ficulty of equilibrium constant determination of the protonolysis
reactions described herein, we chose to employ DFT computa-
tions to probe the bond energy differences between [Ph-PNP-
iPr]NiNHPh, [Ph-PNP-iPr]NiOPh, [Ph-PNP-iPr]NiSPh and [Ph-
PNP-iPr]NiC CPh. As summarized in Table 2, DFT studies
showed that these reactions are exothermic, with extremely
large computed Keq values, consistent with what is observed
experimentally. More importantly, the Ni–OPh, Ni–SPh, and Ni–
C
CPh bond strengths are all stronger than Ni–NHPh. These
1
results are also consistent with the acidity of aniline vs. phenol,
thiophenol and phenylacetylene.35 The trend that the Ni–S bond
is thermodynamically favored over Ni–O, which is in turn favored
from tetramethylsilane and coupling constants (J) in hertz. H
NMR spectra are referenced using the residual solvent peak at
d 7.16 for C6D6. 13C NMR spectra are referenced using the
Table 2 Relative bond energies of [Ph-PNP-iPr]NiEPh (E = NH, O, S, C C)
DHa/kcal mol-1
Keq
rel D(Ni–E)/kcal mol-1
b
E
NH
O
S
0
1
0
7.2
11.8
47.5
-10.2
-17.9
-6.11
3.2 ¥ 107
1.8 ¥ 1013
1.9 ¥ 105
C
C
a Calculated by DFT. b Estimated from DG values (see ESI†) calculated by DFT.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9004–9011 | 9007
©

residual solvent peak at d 128.39 for C6D6. The assignment of
the carbon atoms is based on the DEPT 13C NMR spectroscopy.
31P NMR spectra are referenced externally using 85% H3PO4 at
d 0. Routine coupling constants are not listed. All NMR spectra
were recorded at room temperature in specified solvents unless
otherwise noted. Elemental analysis was performed on a Heraeus
CHN–O Rapid analyzer. With multiple attempts, we were unable
to obtain satisfactory analysis for some complexes reported herein
due likely to incomplete combustion of samples examined.
(d, JCP = 10.92, CH), 117.62 (d, JCP = 6.02, CH), 117.37 (d, JCP =
11.92, CH), 24.54 (d, JCP = 22.46, CHMe2), 19.01 (d, JCP = 36.40,
CHMe2), 18.01 (s, CHMe2). Anal. Calc. for C30H32ClNNiP2: C,
64.04; H, 5.73; N, 2.49. Found: C, 63.82; H, 5.72; N, 2.46%.
Synthesis of [Ph-PNP-iPr]NiNHPh
To a solid mixture of [Ph-PNP-iPr]NiCl (100 mg, 0.178 mmol) and
LiNHPh(THF) (30 mg, 0.178 mmol) was added THF (8 mL) at
◦
-35 C. The resulting greenish blue solution was stirred at room
temperature for 1 h. All volatiles were removed in vacuo. The solid
residue was dissolved in benzene (6 mL). The benzene solution was
filtered through a pad of Celite, which was further washed with
benzene (2 mL) until the washings became colorless. Evaporation
of the combined filtrate to dryness under reduced pressure afforded
the product as a greenish blue solid; yield 100 mg (90%). 1H NMR
(C6D6, 500 MHz) d 7.78 (m, 4, Ar), 7.59 (m, 2, Ar), 7.08 (t, 1, Ar),
7.02 (m, 6, Ar), 6.93 (m, 5, Ar), 6.84 (m, 2, Ar), 6.46 (t, 1, Ar), 6.38
(td, 2, Ar), 1.95 (m, 2, CHMe2), 1.22 (dd, 6, CHMe2), 1.01 (dd, 6,
X-Ray crystallography
Data for [Ph-PNP-iPr]NiCl were collected on a Bruker–Nonius
Kappa CCD diffractometer with graphite monochromated Mo-
Ka radiation (l = 0.7107 A). Structures were solved by direct
methods and refined by full matrix least squares procedures
against F2 using SHELXL-97.36 All full-weight non-hydrogen
atoms were refined anisotropically. All hydrogen atoms were
placed in calculated positions. Crystal data: C37H40ClNNiP2, M =
˚
1
CHMe2), -1.33 (s, 1, NH). 31P{ H} NMR (C6D6, 202.13 MHz) d
¯
654.80, triclinic, space group P1, a = 12.365(4), b = 15.097(5), c =
◦
1
˚
18.987(6) A, a = 110.914(5), b = 92.567(7), g = 91.650(6) , V =
33.54 (d, JPP = 356.07, PiPr2), 9.95 (d, JPP = 356.07, PPh2). 13C{ H}
3
-1
˚
3303.7(18) A , T = 200(2)K, Z = 4, m(Mo-Ka) = 0.792 mm , 33153
reflections measured, 13305 unique (Rint = 0.1485) which were used
in all calculations. Final R1 [I > 2s(I)] = 0.0616, wR2 [I > 2s(I)] =
0.1268, R1 (all data) = 0.1945, wR2 (all data) = 0.1795, GOF (on
F2) = 0.897, CCDC 806151.
NMR (C6D6, 125.5 MHz) d 163.77 (dd, JCP = 3.77 and 24.72, C),
163.23 (dd, JCP = 4.0 and 24.72, C), 159.64 (s, C), 134.43 (s, CH),
133.85 (d, JCP = 11.04, CH), 132.32 (d, JCP = 10.04, CH), 131.78 (s,
CH), 131.68 (dd, JCP = 2.76 and 40.29, C), 130.56 (d, JCP = 2.76,
CH), 129.14 (d, JCP = 10.04, CH), 128.98 (s, CH), 128.68 (s, CH),
124.05 (d, JCP = 45.75, C), 121.18 (d, JCP = 40.29, C), 118.48 (s,
CH), 117.67 (d, JCP = 10.04, CH), 117.60 (d, JCP = 12.80, CH),
117.35 (d, JCP = 5.52, CH), 116.77 (d, JCP = 11.92, CH), 111.26
DFT computations
The three-parameter hybrid of exact exchange and Becke’s
exchange energy functional37 and Lee–Yang–Parr’s gradient-
corrected correlation energy functional38 (B3LYP) were used. All
optimized structures were verified to be genuine minima on the
potential energy surface via vibrational frequency analysis. The
6-31G basis sets were used for C, H, O, N and the LANL2DZ
effective core potential plus basis functions for Ni, P, S.39 The
Gaussian09 suite of programs was applied in this study.40
(s, CH), 24.10 (dd, JCP = 1.88 and 20.96, CHMe2), 18.62 (d, JCP =
4.64, CHMe2), 17.74 (s, CHMe2). Anal. Calc. for C36H38N2NiP2:
C, 69.80; H, 6.19; N, 4.52. Found: C, 70.10; H, 6.42; N, 4.39%.
Deprotonation of phenol or thiophenol with [Ph-PNP-iPr]NiNHPh
To a C6D6 solution of [Ph-PNP-iPr]NiNHPh was added one
equivalent of PhEH (E = O, S) at room temperature. The reaction
mixture was transferred to a J. Young NMR tube and the
1
reaction was monitored by 1H and 31P{ H} NMR which showed
Synthesis of [Ph-PNP-iPr]NiCl
quantitative formation of [Ph-PNP-iPr]NiEPh and aniline in 1 h.
THF (2 mL) was added to a solid mixture of H[Ph-PNP-iPr]
(100 mg, 0.213 mmol) and NiCl2(DME) (59 mg, 0.213 mmol)
at room temperature. The reaction mixture was stirred at room
temperature for 10 min. All volatiles were removed in vacuo. The
solid residue was dissolved in a minimal amount of toluene (2 mL)
and pentane (◦20 drops) was layered on top. The solution was
cooled to -35 C to afford the product as green crystals suitable
for X-ray diffraction analysis; yield 98 mg (82%). 1H NMR (C6D6,
500 MHz) d 7.98 (m, 4, Ar), 7.62 (dd, 1, Ar), 7.53 (dd, 1, Ar), 7.07
(t, 1, Ar), 7.03 (m, 6, Ar), 6.95 (t, 1, Ar), 6.86 (m, 2, Ar), 6.43 (t,
1, Ar), 6.36 (t, 1, Ar), 2.20 (m, 2, CHMe2), 1.48 (dd, 6, CHMe2),
Synthesis of [Ph-PNP-iPr]NiOPh
To a solid mixture of [Ph-PNP-iPr]NiCl (100 mg, 0.178 mmol) and
NaOPh (21 mg, 0.178 mmol) was added THF (8 mL) at -35 ◦C.
The resulting dark red solution was stirred at room temperature
for 1 h. All volatiles were removed in vacuo. The solid residue was
dissolved in benzene (6 mL). The benzene solution was filtered
through a pad of Celite, which was further washed with benzene
(2 mL) until the washings became colorless. Evaporation of the
combined filtrate to dryness under reduced pressure afforded the
product as a red solid; yield 100 mg (90%). 1H NMR (C6D6,
500 MHz) d 7.82 (m, 4, Ar), 7.53 (dd, 1, Ar), 7.47 (dd, 1, Ar),
7.30 (d, 2, Ar), 7.13 (t, 1, Ar), 7.00 (m, 5, Ar), 6.96 (m, 2, Ar), 6.86
(m, 4, Ar), 6.51 (t, 1, Ar), 6.43 (t, 1, Ar), 6.37 (t, 1, Ar), 2.03 (m,
1
1.15 (dd, 6, CHMe2). 31P{ H} NMR (C6D6, 202.31 MHz) d 39.78
1
(d, JPP = 330.78, PiPr2), 16.32 (d, JPP = 330.78, PPh2). 13C{ H}
NMR (C6D6, 125.5 MHz) d 163.94 (dd, JCP = 3.77, JCP = 22.46,
C), 163.67 (dd, JCP = 2.76, JCP = 26.98, C), 135.08 (s, CH), 134.26
1
(d, JCP = 11.04, CH), 132.39 (d, JCP = 28.87, CH), 131.78 (d, JCP
=
2, CHMe2), 1.34 (dd, 6, CHMe2), 1.11 (dd, 6, CHMe2). 31P{ H}
1.88, CH), 130.98 (d, JCP = 41.67, C), 130.86 (d, JCP = 2.38, CH),
129.25 (d, JCP = 10.04, CH), 128.68 (s, CH), 123.65 (d, JCP = 48.95,
C), 121.11 (d, JCP = 38.40, C), 118.23 (d, JCP = 6.40, CH), 117.86
NMR (C6D6, 202.13 MHz) d 33.70 (d, JPP = 325.31, PiPr2), 6.91 (d,
1
JPP = 325.31, PPh2). 13C{ H} NMR (C6D6, 125.5 MHz) d 168.16
(s, ipso-OPh), 163.79 (dd, JCP = 3.76 and 21.59, C), 163.47 (dd,
9008 | Dalton Trans., 2011, 40, 9004–9011
This journal is
The Royal Society of Chemistry 2011
©

JCP = 2.76 and 25.60, C), 134.61 (s, CH), 134.09 (d, JCP = 11.42,
CH), 132.35 (d, JCP = 21.96, CH), 131.73 (d, JCP = 1.76, CH),
131.27 (dd, JCP = 2.26 and 39.78, C), 130.66 (d, JCP = 2.38, CH),
129.12 (d, JCP = 10.04, CH), 128.97 (s, CH), 128.68 (s, CH), 123.18
3.14 and 33.38, C), 132.14 (s, CH), 131.35 (dd, JCP = 1.76 and
10.92, CH), 130.52 (d, JCP = 2.26, CH), 129.02 (d, JCP = 9.54, CH),
128.68 (s, CH), 125.83 (dd, JCP = 2.26 and 47.56, C), 121.41 (d,
JCP = 37.90, C), 118.06 (d, JCP = 10.17, CH), 117.77 (d, JCP = 5.90,
CH), 117.71 (d, JCP = 1.88, CH), 116.60 (d, JCP = 5.90, CH), 68.20
(d, JCP = 2.76, OCMe3), 35.50 (s, OCMe3), 24.27 (d, JCP = 21.46,
CHMe2), 19.32 (d, JCP = 4.02, CHMe2), 17.93 (s, CHMe2). Anal.
Calc. for C34H41NNiOP2: C, 68.00; H, 6.88; N, 2.33. Found: C,
67.77; H, 6.27; N, 2.27%.
(dd, JCP = 1.38 and 48.95, C), 121.91 (s, CH), 120.60 (dd, JCP
1.38 and 40.79, C), 118.13 (d, JCP = 10.17, CH), 117.93 (d, JCP
=
=
6.78, CH), 117.53 (d, JCP = 6.02, CH), 117.41 (d, JCP = 11.42, CH),
114.22 (s, CH), 23.89 (d, JCP = 19.70, CHMe2), 18.48 (d, JCP
=
4.14, CHMe2), 17.64 (s, CHMe2). Anal. Calc. for C36H37NNiOP2:
C, 69.70; H, 6.01; N, 2.26. Found: C, 69.59; H, 6.01; N, 2.20%.
Synthesis of [Ph-PNP-iPr]NiC CSiMe3
Synthesis of [Ph-PNP-iPr]NiSPh
Trimethylsilylacetylene (6 mg, 0.057 mmol) was added to a
solution of [Ph-PNP-iPr]NiNHPh (35 mg, 0.057 mmol) in benzene
(2 mL) at room temperature. The red reaction solution was stirred
at room temperature for 20 h and evaporated to dryness under
reduced pressure, affording the product as a red solid; yield 30 mg
(84%). 1H NMR (C6D6, 500 MHz) d 7.99 (ddd, 4, Ar), 7.76 (dd,
1, Ar), 7.68 (dd, 1, Ar), 7.15 (m, 2, Ar), 7.07 (m, 6, Ar), 6.95 (m, 2,
Ar), 6.50 (t, 1, Ar), 6.42 (t, 1, Ar), 2.30 (m, 2, CHMe2), 1.45 (dd, 6,
To a solid mixture of [Ph-PNP-iPr]NiCl (100 mg, 0.178 mmol) and
NaSPh (23 mg, 0.178 mmol) was added THF (4 mL) at -35 C.
◦
The resulting dark yellowish green solution was stirred at room
temperature for 1 h. All volatiles were removed in vacuo. The solid
residue was dissolved in benzene (6 mL). The benzene solution was
filtered through a pad of Celite, which was further washed with
benzene (2 mL) until the washings became colorless. Evaporation
of the combined filtrate to dryness under reduced pressure afforded
1
CHMe2), 1.08 (dd, 6, CHMe2), 0.16 (s, 9, SiMe3). 31P{ H} NMR
1
the product as a yellowish green solid; yield 100 mg (88%). H
(C6D6, 202.31 MHz) d 52.04 (d, JPP = 281.21, PiPr2), 28.77 (d,
1
NMR (C6D6, 500 MHz) d 7.98 (m, 1, Ar), 7.78 (m, 4, Ar), 7.66
(dd, 2, Ar), 7.63 (m, 1, Ar), 7.59 (dd, 1, Ar), 6.89–7.03 (m, 10,
Ar), 6.71 (m, 1, Ar), 6.65 (t, 1, Ar), 6.46 (t, 1, Ar), 6.36 (t, 1, Ar),
2.21 (m, 2, CHMe2), 1.43 (dd, 6, CHMe2), 1.15 (dd, 6, CHMe2).
JPP = 281.21, PPh2). 13C{ H} NMR (C6D6, 125.5 MHz) d 163.58
(dd, JCP = 16.94, JCP = 3.64, C), 163.38 (dd, JCP = 21.46, JCP
=
3.64, C), 135.40 (s, CH), 134.52 (d, JCP = 11.04, CH), 132.78 (s,
NiC CSiMe3), 132.70 (s, CH), 132.47 (d, JCP = 1.76, CH), 131.96
(d, JCP = 1.76, CH), 131.92 (dd, JCP = 47.57, JCP = 1.38, C), 130.71
1
31P{ H} NMR (C6D6, 202.31 MHz) d 38.24 (d, JPP = 318.03, PiPr2),
1
21.09 (d, JPP = 318.03, PPh2). 13C{ H} NMR (C6D6, 125.5 MHz)
(d, JCP = 2.39, CH), 128.96 (d, JCP = 10.54, CH), 123.84 (d, JCP =
d 163.54 (dd, JCP = 21.08, JCP = 3.64, C), 162.79 (dd, JCP = 24.72,
JCP = 2.76, C), 145.60 (vt, JCP = 5.02, C), 134.55 (s, CH), 134.16
44.36, C), 121.61 (d, JCP = 36.14, C), 120.38 (vt, JCP = 40.47,
NiC CSiMe3), 117.70 (d, JCP = 6.40, CH), 117.21 (d, JCP = 5.90,
CH), 116.79 (d, JCP = 11.04, CH), 116.33 (d, JCP = 12.30, CH),
24.98 (dd, JCP = 25.23, JCP = 1.88, CHMe2), 19.20 (d, JCP = 3.77,
CHMe2), 18.27 (d, JCP = 1.26, CHMe2), 1.71 (s, SiMe3). Anal. Calc.
for (C35H41NNiP2Si)(C6H6)0.8: C, 69.58; H, 6.72; N, 2.04. Found:
C, 69.53; H, 6.83; N, 2.06%.
(d, JCP = 10.04, CH), 132.33 (d, JCP = 12.80, CH), 131.81 (d, JCP
=
7.28, CH), 131.01 (dd, JCP = 41.16, JCP = 2.76, C), 130.83 (s, CH),
130.50 (d, JCP = 1.76, CH), 129.25 (d, JCP = 10.17, CH),128.86
(d, JCP = 10.04, CH), 127.82 (s, CH), 126.03 (d, JCP = 46.69, C),
122.99 (s, CH), 121.65 (d, JCP = 38.40, C), 117.89 (d, JCP = 6.40,
CH), 117.40 (d, JCP = 5.52, CH), 117.31 (d, JCP = 4.52, CH), 116.69
(d, JCP = 11.80, CH), 24.80 (d, JCP = 23.85, CHMe2), 19.02 (d, JCP
3.64, CHMe2), 18.06 (s, CHMe2). Anal. Calc. for C36H37NNiP2S:
=
Synthesis of [Ph-PNP-iPr]NiC CPh
C, 67.94; H, 5.86; N, 2.20. Found: C, 67.73; H, 5.96; N, 2.12%.
Phenylacetylene (18 mg, 0.176 mmol) was added to a solution of
[Ph-PNP-iPr]NiNHPh (109 mg, 0.176 mmol) in benzene (4 mL) at
room temperature. The red reaction solution was stirred at room
temperature for 20 h and evaporated to dryness under reduced
pressure, affording the product as a red solid; yield 100 mg (90%).
1H NMR (C6D6, 500 MHz) d 8.02 (m, 4, Ar), 7.80 (dd, 1, Ar),
7.72 (dd, 1, Ar), 7.25 (d, 2, Ar), 7.19 (t, 1, Ar), 7.03 (m, 9, Ar),
6.98 (m, 2, Ar), 6.92 (t, 2, Ar), 6.53 (t, 1, Ar), 6.44 (t, 1, Ar),
2.32 (m, 2, CHMe2), 1.48 (dd, 6, CHMe2), 1.11 (dd, 6, CHMe2).
Synthesis of [Ph-PNP-iPr]NiOtBu
To a solid mixture of [Ph-PNP-iPr]NiCl (50 mg, 0.0889 mmol)
and ◦NaOtBu (8.5 mg, 0.0889 mmol) was added THF (4 mL) at
-35 C. The resulting dark greenish blue solution was stirred at
room temperature for 10 min. All volatiles were removed in vacuo.
The solid residue was dissolved in benzene (6 mL). The benzene
solution was filtered through a pad of Celite, which was further
washed with benzene (2 mL) until the washings became colorless.
Evaporation of the combined filtrate to dryness under reduced
pressure afforded the product as a dark greenish blue solid; yield
50 mg (94%). 1H NMR (C6D6, 500 MHz) d 8.01 (td, 4, Ar), 7.48
(dd, 1, Ar), 7.32 (dd, 1, Ar), 7.09 (m, 6, Ar), 7.00 (td, 2, Ar), 6.82
(t, 1, Ar), 6.73 (t, 1, Ar), 6.37 (m, 2, Ar), 2.25 (m, 2, CHMe2), 1.65
1
31P{ H} NMR (C6D6, 202.31 MHz) d 50.11 (d, JPP = 287.88, PiPr2),
1
27.16 (d, JPP = 287.88, PPh2). 13C{ H} NMR (C6D6, 125.5 MHz)
d 163.65 (dd, JCP = 22.47, JCP = 3.77, C), 163.46 (dd, JCP = 26.48,
JCP = 2.76, C), 135.33 (s, CH), 134.43 (d, JCP = 10.54, CH), 132.76
(s, CH), 132.51 (s, CH), 132.00 (d, JCP = 1.26, CH), 131.96 (d, JCP
=
47.57, C), 131.29 (s, CH), 130.76 (d, JCP = 1.76, CH), 129.78 (s,
C), 129.12 (d, JCP = 10.04, CH), 128.92 (s, CH), 126.09 (d, JCP
1.76, C), 125.66 (s, CH), 123.95 (d, JCP = 44.93, C), 121.65 (d, JCP
=
=
1
(dd, 6, CHMe2), 1.32 (dd, 6, CHMe2), 1.15 (s, 9, OCMe3). 31P{ H}
NMR (C6D6, 202.13 MHz) d 24.15 (d, JPP = 358.49, PiPr2), 2.83 (d,
36.14, C), 117.76 (d, JCP = 6.40, CH), 117.33 (d, JCP = 5.90, CH),
116.90 (d, JCP = 11.42, CH), 116.30 (d, JCP = 11.80, CH), 96.80 (vt,
JCP = 42.98, NiC CPh), 24.99 (d, JCP = 24.72, CHMe2), 19.23 (d,
JCP = 3.64, CHMe2), 18.32 (s, CHMe2).
1
JPP = 358.49, PPh2). 13C{ H} NMR (C6D6, 125.5 MHz) d 164.32
(dd, JCP = 4.14 and 21.46, C), 162.74 (dd, JCP = 2.64 and 24.22,
C), 134.80 (d, JCP = 10.92, CH), 134.54 (s, CH), 133.08 (dd, JCP
=
This journal is The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9004–9011 | 9009
©

Synthesis of [Ph-PNP-iPr]NiCH2CN
Acknowledgements
Acetonitrile (4 mg, 0.097 mmol) was added to a solution of [Ph-
PNP-iPr]NiNHPh (60 mg, 0.097 mmol) in benzene (5 mL) at
room temperature. The reaction solution was heated to 80 ◦C for
21 h and evaporated to dryness under reduced pressure, affording
We thank the National Science Council of Taiwan for financial
support (NSC 99-2113-M-110-003-MY3 and 99-2119-M-110-
002), Professor Ching-Han Hu (NCUE) for informative sugges-
tions on DFT, and the National Center for High-performance
Computing (NCHC) for computer time and facilities. Insightful
comments from the reviewers are also acknowledged.
1
the product as a red solid; yield 50 mg (90%). H NMR (C6D6,
500 MHz) d 7.76 (m, 4, Ar), 7.61 (dd, 1, Ar), 7.54 (dd, 1, Ar), 7.05
(m, 6, Ar), 6.91 (m, 4, Ar), 6.47 (t, 1, Ar), 6.36 (t, 1, Ar), 2.25 (m, 2,
CHMe2), 1.34 (dd, 6, CHMe2), 0.98 (dd, 6, CHMe2), 0.71 (dd, 2,
1
3JHP = 9.5 and 11.5, NiCH2). 31P{ H} NMR (C6D6, 202.31 MHz) d
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1
38.92 (d, JPP = 272.11, PiPr2), 27.52 (d, JPP = 272.11, PPh2). 13C{ H}
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Reaction of [Ph-PNP-iPr]Ni(NHPh) with acetyl chloride
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1
solid; yield 52 mg (82%). H NMR (C6D6, 500 MHz) d 7.82 (m,
5, Ar), 7.72 (dd, 1, J = 4.5 and 8.5, Ar), 7.32 (d, 2, J = 8.0, Ar),
7.18 (m, 2, J = 8.5, Ar), 7.05 (m, 5, Ar), 6.98 (m, 6, Ar), 6.89 (s,
1, NH), 6.78 (t, 1, J = 7.5, Ar), 6.54 (t, 1, J = 7.5, Ar), 6.43 (t, 1,
J = 7.5, Ar), 2.25 (m, 2, CHMe2), 1.28 (dd, 6, J = 7.0 and 16.5,
1
CHMe2), 1.01 (dd, 6, J = 7.5 and 15.0, CHMe2). 31P{ H} NMR
2
(C6D6, 202.31 MHz) d 42.84 (d, JPP = 222.34, PiPr2), 21.13 (d,
1
2JPP = 222.34, PPh2). 13C{ H} NMR (C6D6, 125.5 MHz) d 195.70
2
(t, JCP = 26.98, C O), 163.00 (dd, JCP = 3.77 and 20.206, C),
162.78 (dd, JCP = 3.26 and 24.22, C), 139.78 (s, C), 135.09 (s, CH),
134.05 (d, JCP = 11.42, CH), 132.68 (s, CH), 132.38 (d, JCP = 44.80,
C), 131.91 (d, JCP = 1.38, CH), 130.67 (d, JCP = 1.76, CH), 129.43
(s, CH), 129.34 (d, JCP = 1.38, CH), 128.68 (s, CH), 123.49 (d,
JCP = 48.07, C), 122.57 (s, CH), 120.99 (d, JCP = 38.40, C), 118.38
(s, CH), 117.27 (d, JCP = 9.66, CH), 117.08 (d, JCP = 10.04, CH),
117.03 (d, JCP = 10.92, CH), 115.45 (d, JCP = 10.92, CH), 23.65
(d, JCP = 24.22, CHMe2), 18.94 (d, JCP = 4.14, CHMe2), 17.60 (s,
CHMe2). Anal. Calc. for C37H38N2NiOP2: C, 68.65; H, 5.92; N,
4.33. Found: C, 68.31; H, 5.89; N, 4.30%.
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