Crucial influence of the intramolecular hydrogen bond on the coordination mode of RC(S)NHP(S)(OiPr)2 in homoleptic complexes with Ni II

Article abstract of DOI:10.1002/ejic.201200890

Reaction of the deprotonated N-thiophosphorylated thioureas RC(S)NHP(S)(OiPr)₂ [R = EtNH (HL^I), iPrNH (HL ^II), Et₂N (HL^III), 2,5-Me₂C ₆H₃NH (HL^IV), 4-Me₂NC ₆H₄NH (HL^V)] with Ni^II leads to complexes of the formula [NiL^I-V₂]. The molecular structures of the complexes in the solid were elucidated by single-crystal X-ray diffraction analysis. In the complexes, the metal atom is found to be in a square-planar trans-N₂S₂ ([NiL^II,IV ₂]) environment formed by the C=S sulfur atoms and the P-N nitrogen atoms, or in a square-planar trans-S₂S′₂ ([NiL ^I,III₂]) environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands. Reaction of deprotonated N-thiophosphorylated thiourea HL^V with NiCl₂ leads to violet [Ni(L-1,3-N,S)₂] or dark violet [Ni(L-1,5-S,S′) ₂]·(CH₃)₂C=O crystals that were isolated by recrystallization from a mixture of CH₂Cl₂ or acetone, respectively, and n-hexane. DFT calculations confirmed that the [Ni(L ^I,II,IV,V-N,S)₂] conformers are more stable (by 5-7 kcal/mol) than [Ni(L^I,II,IV,V-S,S′)₂], whereas [Ni(L^III-N,S)₂] is less stable (by 7-9 kcal/mol) than [Ni(L^III-S,S′)₂]. The main reason for higher stability of the 1,3-N,S versus 1,5-S,S′ isomers is the formation of intramolecular N-H...S=P hydrogen bonds. The same hydrogen bonds are impossible in complex [NiL^III₂]. In solution, complex [NiL^III₂] has revealed an exclusively 1,5-S,S′ coordination, whereas compounds [NiL^I,II,IV,V₂] reveal at least two isomers in the ¹H and ³¹P{¹H} NMR spectra. The major species is assigned to the 1,3-N,S-coordinated isomer, and the minor signals are assigned to the 1,5-S,S′ isomer, which was confirmed by UV/Vis spectroscopic results. The electrochemical measurements reveal reversible one-electron reduction and irreversible oxidations both assigned to ligand-centred processes. Ligand-based oxidation processes agree well with TD-DFT results. Reaction of deprotonated RC(S)NHP(S)(OiPr)₂ [R = EtNH (HL^I), iPrNH (HL^II), Et₂N (HL^III), 2,5-Me₂C₆H₃NH (HL^IV), 4-Me ₂NC₆H₄NH (HL^V)] with Ni^II leads to [NiL^I-V₂]. The metal atom is found to be in a square-planar trans-N₂S₂ ([NiL^II,IV ₂]) or in a square-planar trans-S₂S′₂ ([NiL^I,III₂]) environment. Reaction of L^V with Ni^II leads to [Ni(L-1,3-N,S)₂] or [Ni(L-1,5-S,S′) ₂]·(CH₃)₂C=O crystals. Copyright

Full text of DOI:10.1002/ejic.201200890

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DOI:10.1002/ejic.201200890
Crucial Influence of the Intramolecular Hydrogen Bond on
the Coordination Mode of RC(S)NHP(S)(OiPr)2 in
Homoleptic Complexes with NiII
Maria G. Babashkina,*[a] Damir A. Safin,[a] Monika Srebro,[b]
Piotr Kubisiak,[b] Mariusz P. Mitoraj,*[b] Michael Bolte,[c] and
Yann Garcia[a]
Keywords: Coordination modes / Nickel / Thioureas / Density functional calculations / X-ray diffraction
Reaction of the deprotonated N-thiophosphorylated thio-
ureas RC(S)NHP(S)(OiPr)2 [R = EtNH (HLI), iPrNH (HLII),
Et2N (HLIII), 2,5-Me2C6H3NH (HLIV), 4-Me2NC6H4NH
(HLV)] with NiII leads to complexes of the formula [NiLI–V2].
The molecular structures of the complexes in the solid were
elucidated by single-crystal X-ray diffraction analysis. In the
complexes, the metal atom is found to be in a square-planar
trans-N2S2 ([NiLII,IV2]) environment formed by the C=S sulfur
atoms and the P–N nitrogen atoms, or in a square-planar
trans-S2SЈ2 ([NiLI,III2]) environment formed by the C=S and
P=S sulfur atoms of two deprotonated ligands. Reaction of
deprotonated N-thiophosphorylated thiourea HLV with NiCl2
leads to violet [Ni(L-1,3-N,S)2] or dark violet [Ni(L-1,5-S,SЈ)2]·
(CH3)2C=O crystals that were isolated by recrystallization
from a mixture of CH2Cl2 or acetone, respectively, and n-
N,S)2] conformers are more stable (by 5–7 kcal/mol) than [Ni-
(LI,II,IV,V-S,SЈ)2], whereas [Ni(LIII-N,S)2] is less stable (by 7–
9 kcal/mol) than [Ni(LIII-S,SЈ)2]. The main reason for higher
stability of the 1,3-N,S versus 1,5-S,SЈ isomers is the forma-
tion of intramolecular N–H···S=P hydrogen bonds. The same
hydrogen bonds are impossible in complex [NiLIII2]. In solu-
tion, complex [NiLIII2] has revealed an exclusively 1,5-S,SЈ
coordination, whereas compounds [NiLI,II,IV,V2] reveal at le-
ast two isomers in the 1H and 31P{1H} NMR spectra. The
major species is assigned to the 1,3-N,S-coordinated isomer,
and the minor signals are assigned to the 1,5-S,SЈ isomer,
which was confirmed by UV/Vis spectroscopic results. The
electrochemical measurements reveal reversible one-elec-
tron reduction and irreversible oxidations both assigned to
ligand-centred processes. Ligand-based oxidation processes
agree well with TD-DFT results.
hexane. DFT calculations confirmed that the [Ni(LI,II,IV,V
-
The synthesis and complexation properties of N-(thio)-
phosphorylated thioamides and thioureas RC(S)NHP-
(X)(ORЈ)2 (NTT; X = O, S), which are asymmetrical ana-
logues of IDPs, AAs and ATUs, have been extensively
studied,[3] but there is still limited information about struc-
tures of NiII complexes with NTT. In previous contri-
butions we have also studied the structures of NiII com-
plexes with NTT (X = O) ligands and demonstrated that
their square-planar complexes with NiII exhibit either a 1,3-
N,S or 1,5-O,S coordination mode. It was established that
intramolecular hydrogen bonds N–H···O=P are a necessary
condition for the formation of 1,3-N,S isomers for R =
PhNH, p-MeOC6H4NH, p-BrC6H4NH, iPrNH, tBuNH,
cyclo-C6H11NH, 1-AdNH and (4Ј-benzo-15-crown-5)NH;[4]
whereas 1,5-O,S coordination takes place when hydrogen
bonding in the coordinated anionic ligands is not possible
(R = Et2N, morpholino).[4b] Moreover, N-phosphorylated
thioamides RC(S)NHP(O)(OiPr)2 (R = p-BrC6H4, Ph[5])
form distorted octahedral complexes with NiII, in which
two deprotonated ligands are coordinated through the sulf-
ur and oxygen atoms of the C=S and P=O groups, respec-
tively, and two neutral forms of the ligands are bonded
through the oxygen atoms of the P=O groups. Furthermore,
Introduction
In the literature there is a number of NiII complexes with
the chalcogenated imidodiphosphinate ligands R2P(X)-
NP(Y)RЈ2 (IDP; X, Y = O, S, Se, Te)[1] and acylthioamides
RC(S)NC(X)RЈ (AA; X = O, S) or aroylthioureas R2NC(S)-
NC(X)RЈ (ATU; X = O, S).[2] These complexes are of great
interest owing to their structural versatility (square-planar,
octahedral, tetrahedral). However, the chelate backbones of
the IDP, AA and ATU ligands are coordinated towards the
NiII cation through the donor X and Y atoms.
[a] Institute of Condensed Matter and Nanosciences,
MOST – Inorganic Chemistry,
Université Catholique de Louvain,
Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium
E-mail: maria.babashkina@ksu.ru
Homepage: www.uclouvain.be/262038.html
[b] Department of Theoretical Chemistry,
Faculty of Chemistry, Jagiellonian University,
R. Ingardena 3, 30-060 Kracow, Poland
E-mail: mitoraj@chemia.uj.edu.pl
[c] Institut für Anorganische Chemie,
J.-W.-Goethe-Universität,
60438 Frankfurt/Main, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201200890.
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the 1,3-N,S coordination of the NTT (X = O) ligands (Scheme 2). It is noteworthy that according to IR spec-
towards NiII allows octahedral complexes to be obtained troscopy the raw material [NiLV2] shows features of the 1,3-
by the reaction with additional donor ligands such as 2,2Ј- N,S-coordinated complex [Ni(LV-1,3-N,S)2].
bipyridine and 1,10-phenanthroline.[4e] It is important to
note that the situation for the coordination of NiII to the
NTT ligands is further complicated by the possibility to
form tetrahedrally configured complexes as recently de-
scribed for the complexes [Ni{R2NC(S)NP(S)(OiPr)2}2] (R
= Me, H), which in polar solvents exhibit features of a tet-
rahedral complex (colour, paramagnetism), whereas in apo-
lar solvents and in the solid state the complex has a trans
square-planar geometry. Both configurations clearly exhibit
a 1,5-S,SЈ coordination.[6] It should be noted that there are
no structurally characterized tetrahedrally configured NiII
complexes with the NTT ligands that have been reported so
far, whereas there are few examples of the NiII complexes
with the IDP ligands, which exhibit a tetrahedral NiS4 coor-
dination core in the solid state, established by single-crystal
X-ray analysis.[1a,1b,1d–1h] Furthermore, recently we reported
the first example of a 1,5,7-N,NЈ,S coordination of the de-
protonated chelate backbone in the square-planar NiII com-
plex [Ni{2-Py(6-Me)NHC(S)NP(S)(OiPr)2}2] (Py = pyr-
idine). No crystal structure could be obtained so far, but
from spectroscopic results it is clear that the 2-pyridyl func-
Scheme 1. Preparation of [NiLI–IV2].
tions are additionally coordinating in this octahedral com-
plex.[7] As a preliminary result we have also reported a first
success to induce the formation of a 1,3-N,S coordination
mode in the trans square-planar NiII complex with the di-
thio-containing NTT ligands.[8] Recently, we reported some
synthetic results presented here as a preliminary communi-
cation.[9]
In this work, we describe the synthesis of new NiII com-
plexes with N-thiophosphorylated thioureas RC(S)-
NHP(S)(OiPr)2 [R = EtNH (HLI), iPrNH (HLII), Et2N
(HLIII), 2,5-Me2C6H3NH (HLIV), 4-Me2NC6H4NH
(HLV)]. To obtain a complete picture of the electronic struc-
tures of the complexes we carried out DFT calculations on
the structures focusing on the energy difference between
[Ni(LI–V-N,S)2] and [Ni(LI–V-S,SЈ)2] conformers. Finally, we
investigated the molecular structures of the complexes in
solutions by multinuclear NMR spectroscopy and UV/Vis
absorption spectroscopy. The latter method, in combination
with electrochemical investigations (cyclic voltammetry)
should also allow us to shed light on the electronic proper-
ties of these complexes.
Scheme 2. Preparation of [NiLV2].
Results and Discussion
The IR spectra of complexes [NiLII,IV2] and [Ni(LV-1,3-
The raw materials [NiLI–V2] were prepared according to N,S)2] contain a band at 607, 618 and 616 cm–1 for the P=S
the following procedure: the corresponding ligand was de- group of the anionic forms LII,IV,V, respectively. This band
protonated in situ by using KOH, followed by reaction with is shifted to low frequencies in the spectra of complexes
NiCl2 (Schemes 1 and 2). The obtained dark violet solid [NiLI,III2] and [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O, and was ob-
materials are soluble in most polar solvents. Violet [Ni(LV- served at 562–594 cm–1. In the spectra there is a band at
1,3-N,S)2] or dark violet [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O 1506–1568 cm–1, which corresponds to the conjugated SCN
crystals were isolated by recrystallization from a 1:5 mixture fragment. In addition, there is a broad intense band arising
of CH2Cl2 or acetone, respectively, and n-hexane from the POC group at 972–982 cm–1. The IR spectra of
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[NiLI,II,IV,V2] contain the characteristic band for the alk-
ylNH or arylNH group at 3138–3369 cm–1. Furthermore,
the spectrum of the acetone solvate [Ni(LV-1,5-S,SЈ)2]·
(CH3)2C=O contains an intense band at 1702 cm–1 corre-
sponding to the C=O group.
The 31P{1H} NMR spectra of [NiLI,II,IV,V2] in CDCl3 are
rather complicated and contain two signals at δ = 50.7–50.9
and 53.6–54.3 ppm for [NiLI,IV2] and four signals at δ =
50.7–51.0, 53.5–54.4, 55.0–55.3 and 58.0–58.4 ppm for
[NiLII,V2]. The same was previously observed in the spectra
of the complexes [Ni{RNHC(S)NP(S)(OiPr)2}2] (R = tBu,
Ad, Ph, 2-MeC6H4, 2,6-Me2C6H3, 2,4,6-Me3C6H2) in
CD2Cl2 or CDCl3.[4d,8,10] The high-field signal corresponds
to the trans-1,5-S,SЈ coordination, whereas the second sig-
nal is typical for the trans-1,3-N,S coordination of the de-
protonated ligands.[4d,8,10] In view of the similar intensity
and line width of the two low-field signals in the spectra
of [NiLII,V2], they are diastereotopic and assigned to non-
equivalent ligand conformations (boat and chair) of the
same cis-1,5-S,SЈ complex isomer.[8] The 31P{1H} NMR
spectra of [NiLIII2] in CDCl3 contain a unique signal at δ =
42.1 ppm, which indicates the exclusive presence of diamag-
netic 1,5-S,SЈ-coordinated complex forms.[8]
Figure 2. Crystal structure of [NiLII2]. Thermal ellipsoids are drawn
at the 50% probability level (C = grey, N = blue, Ni = green, O
= red, P = orange, S = yellow). Hydrogen atoms are omitted for
clarity.
1
The H NMR spectra of [NiLI,II,IV,V2] contain two main
Figure 3. Crystal structure of [NiLIII2]. Thermal ellipsoids are
drawn at the 50% probability level (C = grey, N = blue, Ni = green,
O = red, P = orange, S = yellow). Hydrogen atoms are omitted for
sets of signals, which are clearly a result of two dominant
types of coordination, whereas there is only one set of sig-
nals in the spectra of complex [NiLIII2]. The signals of the clarity.
ethyl and isopropyl CH3 protons are at δ = 1.05–1.83 ppm,
whereas the aryl CH3 protons are at δ = 2.08–2.98 ppm.
The CH2, CHN and CHO protons are shown at δ = 3.21–
3.93, 3.91–3.99 and 4.62–5.09 ppm, respectively. The spec-
tra of [NiLI,II,IV,V2] contain two signals of the NH protons,
which are observed at δ = 5.58–5.79 and 8.97–9.03 ppm in
the spectra of the alkylNH-containing complexes [NiLI,II2],
and at δ = 7.34–7.44 and 10.63–10.76 ppm in the spectra of
the arylNH-containing complexes [NiLIV,V2]. The low-field
signals are presumably due to the formation of intramolecu-
lar hydrogen bonds of the type alkyl(aryl)N–H···S=P. The
spectra of [NiLIV,V2] contain the signals of the benzene ring Figure 4. Crystal structure of [NiLIV2]. Thermal ellipsoids are
drawn at the 50% probability level (C = grey, N = blue, Ni = green,
O = red, P = orange, S = yellow). Hydrogen atoms are omitted for
at δ = 6.52–7.30 ppm.
Crystals of the complexes were obtained by slow evapo-
clarity.
ration of the solvent from CH2Cl2/n-hexane or acetone/n-
hexane solution. The molecular structures are shown in
Figures 1, 2, 3, 4, 5 and 6, and the crystal and structure
Figure 1. Crystal structure of [NiLI2]. Thermal ellipsoids are drawn
at the 50% probability level (C = grey, N = blue, Ni = green, O
= red, P = orange, S = yellow). Hydrogen atoms are omitted for
clarity.
Figure 5. Crystal structure of [NiLV2]. Thermal ellipsoids are drawn
at the 50% probability level (C = grey, N = blue, Ni = green, O
= red, P = orange, S = yellow). Hydrogen atoms are omitted for
clarity.
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refinement data are given in the Experimental Section. Se- H···S=P type, which would have allowed the 1,3-N,S coor-
lected bond lengths and angles of the complexes are given dination mode of the corresponding ligand towards NiII.
in Table S1 in the Supporting Information.
The EtNH protons in [NiLI2] are also involved in intermo-
lecular hydrogen bonds of the type N–H···S=C (Table S2),
which leads to the formation of a polymeric chain in the
crystal. Thus, the NH hydrogen atom in [NiLI2] is also
blocked for the formation of the intramolecular N–H···S=P
hydrogen bonds. A closer inspection of the crystal struc-
tures revealed further H···X hydrogen bonds; however,
based on established criteria,[11] we consider them not to be
determining the crystal or molecular structures.
Dissolving the raw materials [NiLI–V2] in CH2Cl2 leads
to violet and greenish-blue solutions. The UV/Vis spectra
in CH2Cl2 are very similar in pairs [NiLI,II2], [NiLIII2] and
[NiLIV,V2] (Table S3 in the Supporting Information). In the
spectra of complexes [NiLI,II2], containing the alkylNH sub-
stituents, in the UV region two intense bands are discerni-
ble, one lying invariantly at 261–264 nm, the other around
Figure 6. Crystal structure of [NiLV2]·(CH3)2C=O. Thermal ellip-
soids are drawn at the 50% probability level (C = grey, N = blue,
Ni = green, O = red, P = orange, S = yellow). Hydrogen atoms
and (CH3)2C=O molecules are omitted for clarity.
Complexes [NiLI–III,V2] and [NiLV2]·(CH3)2C=O crys- 335 nm. For [NiLIV,V2], containing the arylNH substituents,
¯
tallize in the triclinic space group P1, whereas complex very similar absorption bands were observed; however, their
[NiLIV2] crystallizes in the monoclinic space group P21/c. energies (226–229 and 303–308 nm) deviate markedly from
Complex [NiLV2] contains four independent molecules in those of [NiLI,II2]. The spectrum of complex [NiLIII2], exhi-
the unit cell. The complexes show centrosymmetric struc- biting exclusively 1,5-S,SЈ coordination of the ligands in
tures. In the complexes, the metal atom is found to be in a solution, contains an absorption band at 246 nm ac-
square-planar trans-N2S2 ([NiLII,IV,V2]) environment formed companied by a shoulder at 265 nm. Furthermore, for com-
by the C=S sulfur atoms and the P–N nitrogen atoms, or in plexes [NiLIII2] and [NiLIV,V2] the band tails down to about
a square-planar trans-S2SЈ2 {[NiLI,III2] and [NiLV2]·(CH3)2- 435 and 335 nm, respectively, showing an additional shoul-
C=O} environment formed by the C=S and P=S sulfur der. Absorption bands for the free and protonated ligands
atoms of two deprotonated ligands (Figures 1–6). The four- RC(S)NHP(X)(OiPr)2 (X = O, S) are rather high in energy
abs
membered Ni–S–C–N metallocycles are planar in [Ni- (λ
Ͻ 250 nm), whereas the absorption bands of KLI–V
max
LII,IV,V2]. The six-membered Ni–S–C–N–P–S metallocycles were observed in the range 287–306 nm (ε = 175–
in complexes [NiLI,III2] and [NiLV2]·(CH3)2C=O have an 197 m–1 cm–1) and have been assigned to intraligand transi-
asymmetric boat form. The values of the intracyclic S–Ni– tions.[8b,12] Thus, the UV absorptions of the NiII complexes
N angles in the four-membered rings of [NiLII,IV,V2] fall in can be assigned to corresponding intraligand transitions (π–
the range of 74–75°, whereas the intracyclic S–Ni–S angles π* or n–π* type). The different behaviour of the complexes
in [NiLI,III
]
and [NiLV2]·(CH3)2C=O are about 99° might be explained by the presence of a mixture of 1,3-
2
(Table S1 in the Supporting Information). Inspection of the N,S and 1,5-S,SЈ isomers in the reaction product for
C=S and P–N bond lengths of [NiLII,IV,V2] indicates that [NiLI,II,IV,V
] (as evidenced from NMR spectroscopic
2
these bonds are best described as single bonds, whereas the measurements), whereas for complex [NiLIII2], the 1,5-S,SЈ
P=S distance indicates the presence of a double bond isomer was exclusively present. At the same time the dif-
(Table S1).[3] The lengthening of the C=S and shortening of ferent behaviour of complexes [NiLI,II2] and [NiLIV,V
]
2
the C–N bonds relative to those in NTT ligands are ob- might be explained by the different substituents (alkylNH
served upon [NiLI,III2] and [NiLV2]·(CH3)2C=O complex versus arylNH) at the thiocarbonyl group. In the visible re-
formation.[3] The same change, but to a smaller degree, has gion two absorption bands were essentially observed, one
been observed for the P–N and P=S bonds. The alkyl(aryl)- ranging from 515 to 532 and another that is rather invariant
NH protons in [NiLII,IV,V2] are involved in intramolecular at about 650 nm (Table S3). From the rather small extinc-
hydrogen bonds of the N–H···S=P type (Table S2 in the tion coefficients (ε = 103–257 m–1 cm–1) compared with
Supporting Information). Owing to their formation, a flat those of the bands in the UV region, the two long-wave-
syn,syn conformation of the N–C–N–P–S unit is favoured. length bands are assigned to ligand-field (d–d) transitions.
The arylNH protons in [NiLV2]·(CH3)2C=O are also in- For a square-planar 3d8 system three bands [1A1gǞ1B1g
volved in hydrogen bonds (Table S2). The intermolecular (dx2–y2Ǟdxy), 1A1gǞ1B3g (dxzǞdxy) and 1A1gǞ1B1g
x2–y2
hydrogen bonds of the N–H···O=C type are formed be- (dz2Ǟdxy); assuming the orbital ordering: dxy Ͼ d
Ͼ dyz
tween the hydrogen atom of the NH group and the oxygen Ͼ dxz Ͼ dz2] are expected.[3a,6b,10a,13] However, comparison
atom of the acetone molecule, which is trapped during the with spectra of related complexes suggest that the third
crystallization. Owing to these intermolecular hydrogen band is hidden under the tail of the intense intraligand
bonds in the structure of [NiLV2]·(CH3)2C=O the NH hy- bands. It is thus interesting to note that the transition
drogen atom is blocked and, hence, is not suitable for the dx2–y2Ǟdxy strongly depends on substituent R, whereas the
formation of intramolecular hydrogen bonding of the N– transition dxzǞdxy is completely invariant.
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The assumption that complex [NiLIII2] is exclusively 1,5- S,SЈ isomer for [NiLIII2] is consistent with the experimental
S,SЈ-configured, whereas solutions of [NiLI,II,IV,V2] contain NMR and absorption UV/Vis spectroscopy results.
both 1,3-N,S as well as 1,5-S,SЈ isomers is strongly sup-
The DFT-based results on the preferred conformation
ported by the electronic spectra of the recently reported de- for complexes [Ni(LII,IV-1,3-N,S)2] are in line with the ob-
rivatives [Ni{RC(S)NHP(X)(OiPr)2}2] [X = S, R = H2N, served molecular structures from single-crystal X-ray crys-
MeNH, tBuNH, PhNH, Me2N, 2-MeC6H4NH, 2,6- tallography of the compounds obtained from reaction of
Me2C6H3NH, 2,4,6-Me3C6H2NH, 2-Py(6-Me)NH; X = O, deprotonated ligands LII,IV with NiII. However, whereas the
R = PhNH].[4a,6,7,8b,10]
trans-1,3-N,S conformer is preferred over the trans-1,5-S,SЈ
The electrochemistry of the raw materials [NiLI–V2] was configuration for [NiLI,III2] systems (Table S5), the 1,5-S,SЈ
measured by using cyclic voltammetry. The cyclic voltam- isomer has been crystallized. Here it is important to note
mograms of the complexes are quite similar (Table S4 in the that the DFT calculations refer to the complex unit (with
Supporting Information). However, the voltammograms of no surroundings), whereas stability in the crystal includes
complexes [NiLI,II,IV,V2] differ from that of [NiLIII2]. This is further energy increments such as intermolecular hydrogen
clearly due to the presence of a mixture of 1,3-N,S and 1,5- bonds and packing. Indeed, the complex units of [NiLI2]
S,SЈ isomers of the former complexes in CH2Cl2, whereas exhibit intermolecular N–H···S=C hydrogen bonds, which
the exclusively 1,5-S,SЈ isomer is observed for the latter is not the case for the remaining systems [NiLII,IV2]; the
complex (see the NMR spectroscopic data). A reversible energetically slightly disfavoured 1,5-S,SЈ isomer presum-
first one-electron reduction at around –1.50 V is followed ably has a better tendency to crystallize. The same probably
by a number of further irreversible reduction steps. This holds too for the recently reported derivatives [Ni{RC(S)-
first reduction wave is caused by a ligand-centred re- NHP(S)(OiPr)2}2] (R = H2N, MeNH, PhNH),[6b,8b,10a]
duction.[8b] On the oxidative side of the cyclic voltammog- which all have been found in the 1,5-S,SЈ isomeric form in
rams of [NiLI,II,IV,V2] the first wave occurs at around their crystal structures. It should be noted that the recently
+0.75 V (Ox 1) followed by a second at around +1.13 V reported complexes [Ni{RC(S)NHP(S)(OiPr)2}2] (R
=
(Ox 2). Measurements of complex [NiLIII2] reveals oxi- tBuNH, AdNH) have also been found to be 1,5-S,SЈ-coor-
dation processes that have very similar potentials (Ox 3), dinated, and no inter- or intramolecular hydrogen bonds
however at far lower potentials at –0.08 V (Ox 1). At 0.34 V have been found in the solid state.[4d,10b] This might be ex-
(Ox 2) there is seemingly an additional oxidation wave. The plained by the bulky tBu or Ad substituents, which proba-
oxidation is also attributed to a ligand-centred process since bly prevent the formation of the intramolecular hydrogen
the observed vast difference in oxidation potentials for the bonds. Moreover, blocking of the NH functions by hydro-
assumed isomers is too large to be attributed to a nickel- gen-bond formation with acetone molecules, as was found
centred oxidation NiII/NiIII. The assumption of a ligand- in the structure of complex [NiLV2]·(CH3)2C=O (see the X-
based oxidation is also in line with the absorption spec- ray results above), also leads to the formation of 1,5-S,SЈ
troscopy, which gave no evidence for a metal-to-ligand or isomeric forms. We have already indicated in a previous
ligand-to-metal charge transfer. Instead, rather low-energy study that the 1,5-S,SЈ isomer of [NiLV2]·(CH3)2C=O con-
intraligand transitions were observed alongside with low- tains an extra stabilization originating from the acetone mo-
lying d–d transitions. These observations appeared to be in lecule attached to the hydrogen atom of the NH group.[9]
line with the theoretical DFT and TD-DFT study, which We have found that the formation of one hydrogen bond,
will be presented hereafter.
(CH3)2C=O···H–N, adds extra stabilization in the 1,5-S,SЈ
To study the relative energy of the possible isomers system by 9.2 kcal/mol relative to the isolated [Ni(LV-1,5-
[Ni(LI–V-1,3-N,S)2] versus [Ni(LI–V-1,5-S,SЈ)2], as well as S,SЈ)2] complex (Figure 7 and Figure S3 in the Supporting
[NiLV2]·(CH3)2C=O, DFT/6-31++G** calculations were Information). Keeping in mind that two such hydrogen
performed at the B3LYP level, as implemented in the bonds can be present, it provides a total stabilization of
Gaussian 09 package.[14] We found the minima (confirmed 18.4 kcal/mol. Accordingly, it makes the 1,5-S,SЈ isomer
by the presence of all positive frequencies) on the potential- more stable (by 1.1 kcal/mol) than the trans-1,3-N,S system
energy surface (PES) for complexes [Ni(LI–V-1,3-N,S)2] ver- (Figure 7), which explains why the 1,5-S,SЈ isomer was pre-
sus [Ni(LI–V-1,5-S,SЈ)2] to exhibit the following conforma- dominantly observed in acetone.
tions: (i) trans-1,3-N,S, (ii) cis-1,3-N,S, (iii) trans-1,5-S,SЈ
From the results of DFT calculations we concluded that
and (iv) cis-1,5-S,SЈ. All structures with a cis configuration a crucial factor contributing to higher stability of the 1,3-
appeared to be less stable than those corresponding to the N,S isomers than 1,5-S,SЈ is the presence of an intramolecu-
trans isomers. For complexes [NiLI,II,IV,V2] the coordination lar hydrogen interaction in the former case. To shed some
in a trans-1,3-N,S fashion is much more preferred (by 5– light on the mechanism of such an intramolecular interac-
8 kcal/mol, depending on the system) over the trans-1,5- tion in the [Ni(LI–V-1,3-N,S)2] isomers, bonding between the
S,SЈ conformation, whereas the reverse trend was noted for amine-based group and the rest of the complex was charac-
complex [NiLIII2], that is, the trans-1,5-S,SЈ isomer is the terized based on the ETS-NOCV scheme[15] as implemented
most stable, by 9.9 kcal/mol (Table S5, part A, in the Sup- in the Amsterdam Density Functional (ADF) package, ver-
porting Information). The same trend is true when con- sion 2009.01.[16] The obtained results together with the divi-
sidering dispersion-corrected B3LYP-D3 and BLYP-D3 sion of molecules into two fragments are marked by black
functionals (Table S5, part B). Domination of the trans-1,5- loops in Figures 8 and 9. Numerical values from the ETS-
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Figure 7. Optimized structures of [Ni(LV-1,3-N,S)2], [Ni(LV-1,5-
S,SЈ)2], [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O and [Ni(LV-1,5-S,SЈ)2]·
[(CH3)2C=O]2 together with the relative energies calculated at the
DFT/B3LYP level of theory.
Figure 9. Black lines indicate the fragmentation used in the bond-
ing analysis (panel a). In panels b–d ETS-NOCV-based results [de-
formation densities Δρi and corresponding energies ΔEorb(i)] are
presented for the trans isomers of [Ni(L-1,3-N,S)2], [Ni(L-1,5-
S,SЈ)2] and [Ni(L-1,5-S,SЈ)2]·(CH3)2C=O, respectively. Red colour
of Δρi shows charge depletion, whereas blue is charge accumulation
upon bond formation. The contour value of 0.005 a.u. was used
for Δρ1, and 0.001 a.u. for Δρ2.
Figure 8. ETS-NOCV-based results [deformation densities Δρi and
corresponding energies ΔEorb(i)] are presented for the trans isomers
of [Ni(LI–IV-1,3-N,S)2]. Red colour of Δρi shows charge depletion,
whereas blue is charge accumulation upon bond formation. The
contour value of 0.005 a.u. was used for Δρ1, and 0.001 a.u. for
Δρ2.
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NOCV scheme are also gathered in Table S6 in the Sup-
porting Information.
In the case of [Ni(LI–V-1,3-N,S)2] isomers the total
strength of amine bonding decreases along the series
EtNH ≈ iPrNH Ͼ 2,5-Me2C6H3NH ϾϾ Et2N Ͼ 4-
Me2NC6H4NH (see ΔEtotal in Table S6 in the Supporting
Information). This trend is determined by the changes in
all bonding contributions (ΔEorb, ΔEelstat, ΔEPauli). More
specifically, the highest stabilization noted for EtNH- and
iPr-based derivatives is related to the most stabilizing con-
tributions stemming from the electronic (ΔEorb) and electro-
static (ΔEelstat) factors. Slightly lower stability of the 2,5-
Me2C6H3NH-based system (than EtNH and iPr) originates
from both the lower value of the repulsive Pauli term
(ΔEPauli), by 39.0–40.5 kcal/mol, as well as from the lower
stabilization arising from the electronic (by 23.8–24.4 kcal/
mol) and electrostatic (by 17.4–18.6 kcal/mol) contri-
butions. Finally, the weakest bonding (highest absolute
value of ΔEtotal) noted for 4-Me2NC6H4NH-containing
species results from the weakest electronic stabilization as
well as a relatively high repulsive Pauli contribution
(Table S6).
Figure 10. ETS energy-decomposition results characterizing the hy-
drogen bond formed between the [Ni(LV-1,5-S,SЈ)2] isomer (part A)
and the acetone molecule (part B).
tween the amine-containing fragment and the rest of the
complex is much weaker in the case of the [Ni(LV-1,5-
S,SЈ)2] system (ΔEtotal = –86.2 kcal/mol) than with the
Let us now characterize the origin of changes in the elec-
tronic contribution (ΔEorb) based on the ETS-NOCV
scheme. It is clear from Figure 8 that the highest absolute
values of ΔEorb that have been noted for the [Ni(LI,II-1,3-
N,S)2] complexes, containing electron-donating alkyl
groups, is related to the formation of the strongest
σ(HN–C) bonding (characterized by Δρ1). This leads to the
stabilization ΔEorb(1) = –494.1 kcal/mol for [Ni(LI-1,3-
N,S)2] and ΔEorb(1) = –493.1 kcal/mol for [Ni(LII-1,3-
N,S)2]. The weakest σ(HN–C) bonding [ΔEorb(1)
=
–464.3 kcal/mol, Figure 9b] within 1,3-N,S isomers, which
determines the lowest absolute value of total ΔEorb, is ob-
served for complex [Ni(LV-1,3-N,S)2]. This can be related to
the presence of the σ-electron-withdrawing p-NMe2 frag-
ment in the phenylene ring. Significantly less important is
the charge transfer described by the deformation density
channel Δρ2 [with the corresponding ΔEorb(2) values,
Table S6, Figures 8 and 9]. Qualitatively it characterizes the
formation of the π component of the N–C bond as well as
the intramolecular NH···S interaction in the case of [Ni-
(LI,II,IV,V-1,3-N,S)2] complexes. These charge transfers
correspond to |ΔEorb(2)| = 16.3–17.0 kcal/mol (depending
on the system). It can also be noticed that the intramolecu-
lar interaction originates from the donation of density from
the lone electron pair of the sulfur atom into the empty
σ*(N–H) orbital as well as density shift from the occupied
N–H orbital into a bonding region of HN···S (Figures 8
and 9). For the remaining [Ni(LIII-1,3-N,S)2] complex no
NH···S intramolecular bonding is present; hence, the charge
transfer characterized by Δρ2 leads to weaker stabilization,
ΔEorb(2) = –11.7 kcal/mol (Figure 8, Table S6).
To present a complete picture of the electronic structure
in the set of systems containing amine-based derivatives, we
will also recall below our recent findings[9] on complexes
Figure 11. Simulated TD-DFT/B3LYP spectrum of the [Ni(LV-1,5-
S,SЈ)2] complex in the gas phase (part A) together with the con-
tours of molecular orbitals (0.03 a.u.) involved in the dominant
[Ni(LV-1,5-S,SЈ)2],
[Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O
and
[Ni(LV-1,3-N,S)2] (Figure 9). It is clear that the bonding be- transitions (part B).
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[Ni(LV-1,3-N,S)2] isomer (Table S6). This is owing to lower lar orbitals involved in the dominant transitions are pre-
stabilization originating from the electronic (by 79.5 kcal/ sented in Figures 11 and 12 for [Ni(LV-1,5-S,SЈ)2] and
mol) and electrostatic (by 34.1 kcal/mol) factors. A lower [Ni(LV-1,3-N,S)2], respectively. These spectra were discussed
value of ΔEorb is, in turn, determined by weaker σ(HN–C) in our recent communication.[9] Only one conclusion from
bonding, ΔEorb(1) = –390.8 kcal/mol (Figure 9, Table S6). the theoretical data should be highlighted to compare it
The π component of the N–C bond, Δρ2, also drops signifi- with the experimental results; namely in the case of both
cantly, ΔEorb(2) = –9.3 kcal/mol, owing to a lack of intra- complexes, the dominant transitions involve predominantly
molecular interaction in the [Ni(LV-1,5-S,SЈ)2] system (Fig- intraligand charge transfers (HOMOǞLUMO+1; Fig-
ure 9c). As we go from [Ni(LV-1,5-S,SЈ)2] to the acetone- ures 11 and 12) with minor participation of the metal atom,
containing derivative, [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O, a no- which is fully consistent with the cyclic voltammetry re-
ticeable strengthening of the amine bonding is observed, sults.[9]
with ΔEtotal lower by 8.7 kcal/mol (Table S6). This is pre-
dominantly owing to the stronger σ(HN–C) and π(HN–C)
components, by ΔEorb(1) = –34.8 kcal/mol and by ΔEorb(2)
= –13.2 kcal/mol, respectively (Figure 9). Another impor-
Conclusion
tant factor is higher stabilization (by 38.4 kcal/mol) origi-
We have synthesized NiII complexes with N-thiophos-
nating from the electrostatic term. It should be pointed out phorylated thioureas RC(S)NHP(S)(OiPr)2 [R = EtNH
that when considering not one, but two acetone molecules, (HLI), iPrNH (HLII), Et2N (HLIII), 2,5-Me2C6H3NH
further stabilization of [Ni(LV-1,5-S,SЈ)2] is expected. In- (HLIV), 4-Me2NC6H4NH (HLV)]. Complex [NiLII2] is the
deed, as has been already mentioned, an inclusion of two first example of NiII complexes containing asymmetric
acetone molecules makes the [Ni(LV-1,5-S,SЈ)2]·[(CH3)2- NTT ligands with the alkylNH substituent, coordinating
C=O]2 system the most stable (Figure 7). Thus, it clearly the metal atom in a 1,3-N,S fashion in the crystal, whereas
shows an important role of the solvent (acetone species) for the derivatives [NiLI,III2] 1,5-S,SЈ coordination has been
environment in controlling the stability of the [Ni(LV-1,5- found. Complex [NiLIV2] was also found to be 1,3-N,S-co-
S,SЈ)2] complex. In addition, we found that the stabilization ordinated.
originating directly from the formation of hydrogen bonds
DFT-based calculations showed that the [Ni(LI,II,IV,V
-
in [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O is –5.7 kcal/mol (Fig- N,S)2] isomers are much more stable than the correspond-
ure 10). The major stabilizing force of the hydrogen-bond- ing [Ni(LI,II,IV,V-S,SЈ)2] conformers. This is owing to the for-
ing interaction is due to the electrostatic term (Figure 10).
mation of intramolecular N–H···S=P hydrogen bonds. The
To gain further insight into the nature of the electronic deformation density contributions obtained from the ETS-
spectra for the [Ni(LV-1,5-S,SЈ)2] and [Ni(LV-1,3-N,S)2] NOCV method revealed the presence of such an interac-
complexes, a time-dependent density functional method tion, which includes the transfer of electron density from
(TD-DFT) was applied, as implemented in the ADF pack- the lone electron pair of the S atom into the empty σ*-
age.[16] The simulated spectrum (at the DFT/B3LYP level of (N–H) orbital and from the occupied N–H orbital into a
theory) in the gas phase together with the selected molecu- bonding H···S region and the vicinity of the sulfur atom.
The thermodynamic stability of the 1,3-N,S coordination of
the investigated complexes is also evident from their behav-
iour in solution. Only for complex [NiLIII2] was the exclu-
sively 1,5-S,SЈ coordination found in 1H and 31P{1H} NMR
and UV/Vis spectra. In contrast to this, in solutions of
[NiLII,IV2], which crystallize in the 1,3-N,S isomeric form,
and [NiLI2], which crystallize in the 1,5-S,SЈ isomeric form,
spectroscopic evidence (NMR, UV/Vis) for a mixture of the
1,3-N,S and 1,5-S,SЈ isomer is found. Electrochemical mea-
surements in the rather nonpolar solvent CH2Cl2 reveal the
electronic properties only for the 1,5-S,SЈ-coordinated state
of [NiLIII2]. From the combination of absorption spec-
troscopy, electrochemistry and TD-DFT results we could
consistently conclude that the charge transfer is ligand-
centred.
Along with the [Ni(LV-1,3-N,S)2] complex we have also
synthesized its dithio-coordinated isomer [Ni(LV-1,5-S,SЈ)2]·
(CH3)2C=O. These compounds are the first example of NiII
complexes containing the same asymmetric NTT ligand
featuring an arylNH substituent at the thiocarbonyl group
and coordinating to the metal atom both in the 1,3-N,S
and 1,5-S,SЈ fashion in the solid state depending on the
crystallization conditions. Finally, comparing the energies
Figure 12. Simulated TD-DFT spectrum of the [Ni(LV-1,3-N,S)2]
system (part A) together with the contours of molecular orbitals
(0.03 a.u.) involved in the dominant transitions (part B).
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from DFT calculations for [Ni(LV-1,3-N,S)2], [Ni(LV-1,5-
S,SЈ)2] and [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O systems, it
should be pointed out that acetone species, by the forma-
tion of hydrogen bonds with the metal complex unit, makes
the [Ni(LV-1,5-S,SЈ)2]·(CH3)2C=O system the most stable;
accordingly, this conformer is crystallized from the acetone
solvent.
total bonding energy (ΔEtotal) between interacting fragments exhib-
iting the geometry as in the combined complex is divided into the
three components [Equation (2)]:
ΔEtotal = ΔEelstat + ΔEPauli + ΔEorb
(2)
The first term, ΔEelstat, corresponds to the classical electrostatic
interaction between the promoted fragments as they are brought to
their positions in the final complex. The second term, ΔEPauli, ac-
counts for the repulsive Pauli interaction between occupied orbitals
on the two fragments in the combined molecule. Finally, the last
stabilizing term, ΔEorb represents the interactions between the oc-
cupied molecular orbitals of one fragment with the unoccupied mo-
lecular orbitals of the other fragment as well as mixing of occupied
and virtual orbitals within the same fragment (inner-fragment po-
larization). This energy term may be linked to the electronic bond-
ing effect coming from the formation of a chemical bond. The three
last terms (ΔEelstat, ΔEPauli, ΔEorb) very often are combined into
the instantaneous interaction energy, ΔEint, as it describes the inter-
action between the fragments in the geometry of the complex.
The obtained NiII complexes are of great interest as sin-
gle-source precursors for Ni-containing nanomaterials as
was previously reported for the NiII complexes with the
IDP and NTT ligands.[1c,1e,17] Furthermore, we have also
established the crucial influence of the coordination mode
of the NTT ligands towards NiII for both the structure and
composition of the obtained nanomaterials.[17] Thus, the
dependence of the coordination mode of the NiII complexes
described herein on the appropriate solvent might be a cru-
cial driving force for the nanomaterials formation.
In the combined ETS-NOCV scheme the orbital interaction term
(ΔEorb) is expressed in terms of NOCVs eigenvalues (vk) as [Equa-
tion (3)]:
Experimental Section
Physical Measurements: Infrared spectra (Nujol) were recorded
with a Thermo Nicolet 380 FTIR spectrometer in the range 400–
3600 cm–1. NMR spectra were obtained with a Bruker Avance
300 MHz spectrometer at 25 °C. 1H and 31P{1H} NMR spectra
were recorded at 299.948 and 121.420 MHz, respectively. Chemical
shifts are reported with reference to SiMe4 (1H) and 85% H3PO4
(31P{1H}). UV/Vis/NIR spectra in 10–4–10–3 m solutions in CH2Cl2
were recorded with a Lambda-35 spectrometer in the range 200–
1000 nm. Cyclic voltammetry was carried out at a 100 mV/s scan
rate in 0.1 m nBu4NPF6 solutions by using a three-electrode config-
uration (glassy carbon electrode, Pt counter electrode, Ag/AgCl ref-
erence) and a Gamry Series G 750 potentiostat and function gener-
ator. The ferrocene/ferrocenium couple served as internal standard.
Elemental analyses were performed with a Thermoquest Flash EA
1112 Analyzer from CE Instruments.
M/2
TS
TS
ΔEorb
=
ΔEorb(k) =
νk[–F
= +F ]
k,k,
(3)
͚
͚
k = 1
–k,–k,
k
TS
in which F
are diagonal Kohn–Sham matrix elements defined
k,k,
over NOCV with respect to the transition state (TS) density (at the
midpoint between density of the molecule and the sum of fragment
densities). The above components ΔEorb(k) provide the energetic
estimation of Δρk that may be related to the importance of a par-
ticular electron flow channel for the bonding between the consid-
ered molecular fragments. ETS-NOCV analysis was performed
based on the Amsterdam Density Functional (ADF) package in
which this scheme was implemented.
Synthesis of [NLI–V2]: A suspension of HLI–V (3 mmol; 0.85, 0.90,
0.94, 1.08, 1.13 or 1.17 g) in aqueous MeOH (10 mL) was mixed
with an aqueous MeOH solution of KOH (3.3 mmol, 0.18 g). An
aqueous MeOH (10 mL) solution of NiCl2 (1.9 mmol, 0.25 g) was
added dropwise under vigorous stirring to the resulting potassium
salt. The mixture was stirred at room temperature for a further 3 h
and left overnight. The resulting complex was extracted with
CH2Cl2, the combined organic phases were washed with water and
dried with anhydrous MgSO4. The solvent was then removed under
vacuum. Dark violet crystals were isolated by recrystallization from
a 1:3:8 mixture of CH2Cl2/acetone/n-hexane.
DFT Calculations: We have applied in DFT-based geometry opti-
mizations the hybrid exchange-correlation functional B3LYP[18]
and the 6-31++G** basis set as implemented in the Gaussian 09
package.[19,14] In addition, for the selected complexes dispersion-
corrected B3LYP-D3 and BLYP-D3 XC functionals were used
based on the ADF package (TZP basis set for all elements).[16]
Deformation density contributions of the ETS-NOCV method
were plotted based on the ADF-GUI interface.[20]
ETS-NOCV Bonding Analysis: Historically, the natural orbitals for
chemical valence (NOCV) have been derived from the Nalewajski–
Mrozek valence theory as eigenvectors that diagonalize the defor-
mation density matrix. It was shown that the natural orbitals for
chemical valence pairs (ψ–k,ψk) decompose the differential density
(Δρ) into NOCV contributions (Δρk) [Equation (1)]:
Complex [NiLI ]: Yield 0.211 g (81%). IR: ν = 562 (P=S), 977
˜
2
(POC), 1568 (SCN), 3369 (NH) cm–1. H NMR: δ = 1.08 (t, JH,H
1
3
= 7.2 Hz, CH3, Et), 1.17 (t, 3JH,H = 7.2 Hz, CH3, Et), 1.31 (d, 3JH,H
= 6.1 Hz, CH3, iPr), 1.65 (d, JH,H = 6.2 Hz, CH3, iPr), 3.21–3.36
(m, CH2, Et), 4.62 (dsept, JPOCH = 10.6, JH,H = 6.1 Hz, OCH),
3
3
3
4.84–5.09 (m, OCH), 5.58–5.79 (m, alkylNH), 9.03 (br. s, alkylNH)
M/2
M/2
ppm. 31P{1H} NMR:
δ = 50.7 (1 P), 54.3 (5.6 P) ppm.
Δρ(r) =
νk[–ψ2–k(r) + ψ2k(r)] =
Δρ(r)
(1)
͚
͚
k = 1
k = 1
C18H40N4NiO4P2S4 (625.42): calcd. C 34.57, H 6.45, N 8.96; found
C 34.69, H 6.41, N 8.92.
in which νk and M stand for the NOCV eigenvalues and the number
of basis functions, respectively. Visual inspection of deformation
density plots (Δρk) helps to attribute symmetry and the direction
of the charge flow. In addition, these pictures are enriched by pro-
viding the energetic estimations, ΔEorb(k), for each Δρk within the
ETS-NOCV scheme. The exact formula that links ETS and the
NOCV method will be given in the next paragraph, after we briefly
present the basic concept of the ETS scheme. In this method the
Complex [NiLII ]: Yield 0.248 g (91%). IR: ν = 607 (P=S), 972
˜
2
(POC), 1557 (SCN), 3172 (NH) cm–1. 1H NMR: δ = 1.08 (d, 3JH,H
3
= 6.5 Hz, CH3, iPrN), 1.19 (d, JH,H = 6.6 Hz, CH3, iPrN), 1.31
3
3
(d, JH,H = 6.1 Hz, CH3, iPrO), 1.39 (d, JH,H = 6.2 Hz, CH3,
iPrO), 1.47 (d, 3JH,H = 6.1 Hz, CH3, iPrO), 1.65 (d, 3JH,H = 6.1 Hz,
CH3, iPrO), 3.91 (dsept, 3JHNCH = 8.4, 3JH,H = 6.5 Hz, NCH), 3.99
(sept, 3JHNCH = 3JH,H = 6.6 Hz, NCH), 4.63 (dsept, 3JPOCH = 10.5,
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3JH,H = 6.1 Hz, OCH), 4.95 (dsept, 3JPOCH = 10.2, 3JH,H = 6.2 Hz,
OCH), 5.60 (t, 4JPNCNH = 3JH,H = 7.6 Hz, alkylNH), 8.97 (d, 3JH,H
= 8.3 Hz, alkylNH) ppm. 31P{1H} NMR: δ = 51.0 (2.2 P), 54.4 (11
P), 55.3 (1 P), 58.0 (1 P) ppm. C20H44N4NiO4P2S4 (653.47): calcd.
C 36.76, H 6.79, N 8.57; found C 36.68, H 6.83, N 8.60.
reflections: 27312 collected, 6045 unique, Rint = 0.0181, R1(all) =
0.0226, wR2(all) = 0.0557.
Crystal Data for [NiLIV2]: C30H48N4NiO4P2S4, Mr = 777.61 g/mol,
monoclinic, space group P21/c,
21.2495(10) Å, 8.9596(5) Å,
a
β
=
=
10.1475(5) Å,
103.275(3)°,
b
V
=
=
c
=
1880.33(17) Å3, Z = 2, ρ = 1.373 gcm–3, μ(Mo-Kα) = 0.862 mm–1,
reflections: 33524 collected, 6794 unique, Rint = 0.052, R1(all) =
0.0374, wR2(all) = 0.0862.
Complex [NiLIII ]: Yield 0.275 g (97%). IR: ν = 563 (P=S), 978
˜
2
(POC), 1506 (SCN) cm–1. H NMR: δ = 1.05 (t, JH,H = 7.1 Hz, 6
1
3
3
3
H, CH3, Et), 1.26 (t, JH,H = 7.0 Hz, 6 H, CH3, Et), 1.40 (d, JH,H
3
= 6.2 Hz, 12 H, CH3, iPr), 1.49 (d, JH,H = 6.2 Hz, 12 H, CH3,
Crystal Data for [NiLV2]: C30H50N6NiO5P2S4, Mr = 807.65 g/mol,
iPr), 3.53 (q, 3JH,H = 7.0 Hz, 4 H, CH2, Et), 3.93 (q, 3JH,H = 7.1 Hz,
¯
triclinic, space group P1, a = 15.0369(5) Å, b = 17.5722(6) Å, c =
3
3
4 H, CH2, Et), 4.97 (dsept, JPOCH = 10.2, JH,H = 6.1 Hz, 4 H,
OCH) ppm. 31P{1H} NMR: δ = 42.1 ppm. C22H48N4NiO4P2S4
(681.53): calcd. C 38.77, H 7.10, N 8.22; found C 38.84, H 7.03, N
8.14.
24.6552(8) Å, α = 89.796(2), β = 73.261(2), γ = 72.496(2)°, V =
5925.1(3) Å3, Z = 6, ρ = 1.358 gcm–3, μ(Mo-Kα) = 0.824 mm–1,
reflections: 111312 collected, 21625 unique, Rint = 0.0785, R1(all)
= 0.0983, wR2(all) = 0.1213.
Complex [NiLIV ]: Yield 0.263 g (81%). IR: ν = 618 (P=S), 979
Crystal Data for [NiLV2]·(CH3)2C=O: C33H56N6NiO5P2S4, Mr
=
˜
2
(POC), 1545 (SCN), 3138 (NH) cm–1. 1H NMR: δ = 1.18–1.83 (m,
24 H, CH3, iPr), 2.08–2.46 (m, 12 H, CH3, Me), 4.68 (br. s, 2 H,
OCH), 4.94 (br. s, 2 H, OCH), 6.70–7.21 (m, 4 H, m-H + p-H,
C6H3), 7.30 (s, 2 H, o-H, C6H3), 7.44 (br. s, 1 H, arylNH), 10.63
(br. s, 1 H, arylNH) ppm. 31P{1H} NMR: δ = 50.9 (1 P), 53.6 (3.8
P) ppm. C30H48N4NiO4P2S4 (777.61): calcd. C 46.34, H 6.22, N
7.20; found C 46.42, H 6.17, N 7.23.
¯
865.73 g/mol, triclinic, space group P1, a = 9.4301(7) Å, b =
9.4986(7) Å, c = 12.5942(9) Å, α = 105.235(2), β = 101.467(2), γ =
93.622(2)°, V = 1058.75(13) Å3, Z = 1, ρ = 1.358 gcm–3, μ(Mo-
Kα) = 0.776 mm–1, reflections: 27589 collected, 7652 unique, Rint
0.0167, R1(all) = 0.0379, wR2(all) = 0.0834.
=
CCDC-805253 ([NiLI2]), 805252 ([NiLII2]), 805251 ([NiLIII2]),
805249 ([NiLIV2]), 814216 ([NiLV2]) and 805250 {[NiLV2]·(CH3)2-
C=O} contain the supplementary crystallographic data for this pa-
per. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
Complex [NiLV ]: Yield 0.273 g (81%). IR: ν = 594 (P=S), 974
˜
2
(POC), 1515 (SCN), 3323 (NH) cm–1. 1H NMR: δ = 1.22–1.78 (m,
24 H, CH3, iPr), 2.90 (s, 6 H, CH3, Me), 2.94 (s, 6 H, CH3, Me),
4.68 (br. s, 2 H, OCH), 4.98 (br. s, 2 H, OCH), 6.52–6.76 (m, 4 H,
3
o-H, C6H4), 7.20 (d, JH,H = 8.1 Hz, 4 H, m-H, C6H4), 7.34 (br. s,
Supporting Information (see footnote on the first page of this arti-
cle): Selected bond lengths and bond angles (Table S1), selected
hydrogen bond lengths and bond angles (Table S2), UV/Vis absorp-
tion data (Table S3), selected electrochemical data (Table S4), rela-
tive energies (Table S5) and ETS-NOCV energy decomposition re-
sults (Table S6) for complexes [NiLI–V2].
1 H, arylNH), 10.76 (br. s, 1 H, arylNH) ppm. 31P{1H} NMR: δ
= 50.7 (2.6 P), 53.5 (5 P), 55.0 (1 P), 58.4 (1 P) ppm. C30H50N6Ni-
O4P2S4 (807.64): calcd. C 44.62, H 6.24, N 10.41; found C 44.71,
H 6.28, N 10.36.
Crystal Structure Determinations: The X-ray data were collected
with a STOE IPDS-II diffractometer with graphite-monochro-
matized Mo-Kα radiation generated by a fine-focus X-ray tube op-
erated at 50 kV and 40 mA. The reflections of the images were
indexed, integrated and scaled by using the X-Area data reduction
package.[21] Data were corrected for absorption by using the PLA-
TON program.[22] The structures were solved by direct methods
using the SHELXS-97 program[23] and refined first isotropically
and then anisotropically using SHELXL-97.[23] Hydrogen atoms
were revealed from Δρ maps, and those bonded to C were refined
by using appropriate riding models. H atoms bonded to N were
freely refined. Figures were generated by using the program Mer-
cury.[24]
Acknowledgments
M. P. M. acknowledges financial support from the Polish Ministry
of Science and Higher Education (“Outstanding Young Research-
ers” scholarship and T-subsidy). M. S. acknowledges financial sup-
port from the Foundation for Polish Science (“START” scholar-
ship). We are also grateful to ACK CYFRONET – Krakow, to the
Laboratory of Parallel Computing of the Institute of Computer
Science AGH for the computer time and to the Fonds National
de la Recherche Scientifique (F.R.S.-FNRS), Belgium for financial
support as well as a post-doctoral position to D. A. S.
Crystal Data for [NiLI2]: C18H40N4NiO4P2S4, Mr = 625.43 g/mol,
¯
triclinic, space group P1, a = 8.8957(3) Å, b = 8.9910(3) Å, c =
[1] For examples, see: a) R. Rösler, C. Silvestru, G. Espinosa-
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9.8312(4) Å, α = 94.872(1)°, β = 92.095(1)°, γ = 111.354(1)°, V =
727.75(5) Å3, Z = 1, ρ = 1.427 gcm–3, μ(Mo-Kα) = 1.094 mm–1,
reflections: 15501 collected, 4191 unique, Rint = 0.018, R1(all) =
0.0214, wR2(all) = 0.0594.
Crystal Data for [NiLII2]: C20H44N4NiO4P2S4, Mr = 653.48 g/mol,
¯
triclinic, space group P1, a = 8.81660(10) Å, b = 9.81210(10) Å, c
10.7912(2) Å, 103.5394(7)°, 107.5586(6)°,
=
α
=
β
=
γ =
102.1174(7)°, V = 824.72(2) Å3, Z = 1, ρ = 1.316 gcm–3, μ(Mo-
Kα) = 0.968 mm–1, reflections: 19504 collected, 4795 unique, Rint
0.0224, R1(all) = 0.0395, wR2(all) = 0.0910.
=
Crystal Data for [NiLIII2]: C22H48N4NiO4P2S4, Mr = 681.53 g/mol,
¯
triclinic, space group P1, a = 9.0381(6) Å, b = 9.5374(6) Å, c =
9.7949(6) Å, α = 91.109(2)°, β = 90.152(2)°, γ = 97.145(3)°, V =
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837.60(9) Å3, Z = 1, ρ = 1.351 gcm–3, μ(Mo-Kα) = 0.956 mm–1,
Eur. J. Inorg. Chem. 2013, 545–555
554
© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
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Received: August 2, 2012
Published Online: December 11, 2012
Eur. J. Inorg. Chem. 2013, 545–555
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim