Reactions of Lithiated Diphosphanes R2P-P(SiMe3)Li (R = tBu and iPr) with [MeNacnacTiCl2·THF] and [MeNacnacTiCl3]. Formation and Structure of TitaniumIII and TitaniumIV β-Diketiminato Complexes Bearing the Side-on Phosphanylphosphido and Phosphanylphosphinidene Functionalities

Article abstract of DOI:10.1021/acs.inorgchem.6b01929

β-Diketiminate complexes of Ti^III-containing phosphanylphosphido ligands [^MeNacnacTi(Cl){η²-P(SiMe₃)-PR₂}] (^MeNacnac^- = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr₂C₆H₃) were prepared by reactions of [^MeNacnacTiCl₂·THF] with lithium derivatives of diphosphanes R₂P-P(SiMe₃)Li (R = tBu, iPr) in toluene solutions. Surprisingly, reactions of [^MeNacnacTiCl₂·THF] with R₂P-P(SiMe₃)Li in THF solutions led to Ti^IV complexes containing phosphanylphosphinidene ligands [^MeNacnacTi(Cl)(η²-P-PtBu₂)] via an autoredox path involving a migration of a nitrene NAr from the Nacnac skeleton to the Ti centers. Solid-state structures of [^MeNacnacTi(Cl){η²-P(SiMe₃)-PtBu₂}] (1a) and [^MeNacnacTi(Cl)(η²-P-PtBu₂)] (two isomers 2a1, 2a2) together with [^MeNacnacTi(Cl){η²-P(SiMe₃)-PiPr₂}] (1b) and [^MeNacnacTi(Cl)(η²-P-PiPr₂)] (2b) were established by the single-crystal X-ray diffraction and display clearly side-on geometry of the (Me₃Si)P-PR₂ and P-PR₂ moieties in the solid state. Phosphanylphosphinidene complexes [^MeNacnacTi(Cl)(η²-P-PR₂)] indicate that the ³¹P NMR resonances of phosphinidene P atoms appear at a very low field in solution and in the solid state.

Full text of DOI:10.1021/acs.inorgchem.6b01929

Article
pubs.acs.org/IC
Reactions of Lithiated Diphosphanes R2P−P(SiMe3)Li (R = tBu and iPr)
with [MeNacnacTiCl2·THF] and [MeNacnacTiCl3]. Formation and
Structure of TitaniumIII and TitaniumIV β‑Diketiminato Complexes
Bearing the Side-on Phosphanylphosphido and
Phosphanylphosphinidene Functionalities
Ł. Ponikiewski,* A. Ziołkowska, and J. Pikies
́
Department of Inorganic Chemistry, Chemical Faculty, Gdansk University of Technology, 11/12 Gabriela Narutowicza Str, 80-233
Gdansk, Poland
S
* Supporting Information
ABSTRACT: β-Diketiminate complexes of TiIII-containing
phosphanylphosphido ligands [MeNacnacTi(Cl){η2-P(SiMe3)-
PR2}] (MeNacnac− = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-
iPr2C6H3) were prepared by reactions of [MeNacnacTiCl2·
THF] with lithium derivatives of diphosphanes R2P−P(SiMe3)
Li (R = tBu, iPr) in toluene solutions. Surprisingly, reactions of
[MeNacnacTiCl2·THF] with R2P−P(SiMe3)Li in THF sol-
utions led to TiIV complexes containing phosphanylphosphi-
nidene ligands [MeNacnacTi(Cl)(η2-P-PtBu2)] via an autor-
edox path involving a migration of a nitrene NAr from the
Nacnac skeleton to the Ti centers. Solid-state structures of
[
[
M e NacnacTi(Cl){η2-P(SiMe3)-PtBu2 }] (1a) and
MeNacnacTi(Cl)(η2-P-PtBu2)] (two isomers 2a1, 2a2)
together with [MeNacnacTi(Cl){η2-P(SiMe3)-PiPr2}] (1b)
and [MeNacnacTi(Cl)(η2-P-PiPr2)] (2b) were established by the single-crystal X-ray diffraction and display clearly side-on
geometry of the (Me3Si)P−PR2 and P−PR2 moieties in the solid state. Phosphanylphosphinidene complexes [MeNacnacTi-
(Cl)(η2-P-PR2)] indicate that the 31P NMR resonances of phosphinidene P atoms appear at a very low field in solution and in
the solid state.
phosphinidene ligand.13 The reactions of R2P−P(SiMe3)Li
1. INTRODUCTION
with [Ind2ZrCl2] (Ind = C9H−7 ) and PMe2Ph do not yield
Stable phosphinidene complexes of transition metals have been
related phosphanylphosphinidene complexes but the phosphi-
intensively explored mainly because of their role as P−R
do derivatives [Ind2Zr(Cl){(Me3Si)P−PR2−κP1}] as the main
products.14 There is only one known phosphinidene complex
of hafnium [Cp2(PMe3)HfP−Mes*].15 Reactivity of
[Cp2HfCl2] was much lower than that of [Cp2ZrCl2], and
the main products of its reactions with tBu2P−P(SiMe3)Li were
monophosphido complexes [Cp2Hf(Cl){(Me3Si)P−
PR2−κP1}].16 The formation of phosphido and phosphinidene
complexes of titaniumIV with Cp spectator ligands via a
metathesis route (vide infra) is not possible due to oxidative
dimerization of phosphido groups and formation of titaniumIII
compounds.17−19 The reactions of tBu2P−P(SiMe3)Li with
[Cp2TiCl2] or with [CpCp*TiCl2] in the presence of tertiary
phosphines do not yield TiIV phosphanylphosphido and
phosphanylphosphinidene complexes but instead afforded
several TiIII compounds without phosphorus ligands.20 The
transfer reagents in synthetic organic chemistry.1 Nevertheless,
they are less studied than analogous nitrene complexes.2 The
stable phosphinidene complexes of these metals display evident
nucleophilic properties.3−6 The phosphinidene complexes of
tantalum stabilized by N3 N ligand (N3 N
=
(Me3SiNCH2CH2)3N) and phosphinidene complexes of
zirconium stabilized by Cp (η5-C5H5) ligands with bulky R
groups on the P-R ligand display phospha-Wittig reactivity and
have been thoroughly investigated by Schrock’s,7 Stephan’s and
Protasiewicz’s groups.1,8−13 Our group has studied the
metathesis reactions of R2P−P(SiMe3)Li with transition-metal
compounds bearing chloride ligands to introduce the
phosphanylphosphinidene moiety (R2P−P) into the resulting
complexes. The group 4 complexes with Cp ancillary ligands
display diverse reactivity that is metal-dependent. Thus,
[Cp2ZrCl2] reacts with tBu2P−P(SiMe3)Li in the presence of
PMe2Ph to yield [Cp2Zr(PPhMe2)(η1-P−PtBu2)]the only
complex of a transition metal with the terminal phosphanyl-
Received: August 12, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b01929
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Inorganic Chemistry
Article
slowly added to the solution of tBu2P−P(SiMe3)Li·2.5THF (0.449 g, 1
mmol) in 5 mL of toluene at −35 °C. After addition the reaction
mixture was stirred for 2 h at room temperature. The solvent was then
evaporated under reduced pressure, and a green solid residue was
extracted with 30 mL of pentane. The solution was filtered,
concentrated to 20 mL, and stored at +4 °C. After 2 h, light green
crystals of 1a were obtained (0.428 g, yield 60.4%). Anal. Calcd for
C42.5H74Cl1N2P2Ti1: C, 64.91; H, 9.48; N, 3.56. Found: C, 64.12; H,
9.33; N, 3.63%.
essential breakthrough in the chemistry of phosphinidene
complexes of TiIV was achieved by Mindiola and co-workers.
The use of sterically encumbered β-diketiminate ancillary
ligands21−24 or pincer PNP25 ligands and the oxidation of these
TiIII complexes with AgI salts25,26 afforded the formation of TiIV
phosphinidene complexes. At present we are investigating the
synthesis and reactivity of phosphanylphosphinidene complexes
of MoVI and WVI with ancillary imido ligands27−30 and FeII
complexes with β-diketiminate ancillary ligands.31 All the
resulting phosphanylphosphinidene complexes revealed the
side-on coordination for incoming R2P−P groups with little
phospha-Wittig character.29 Therefore, we extended our studies
to TiIII and TiIV complexes to determine the geometry of
resulting complexes and to obtain reagents with the expected
high phospha-Wittig reactivity. Herein we describe novel
synthetic routes to phosphanylphosphido TiIII and phospha-
nylphosphinidene TiIV complexes bearing β-diketiminate and
chlorido spectator ligands. [Ar]NC(Me)CHC(Me)N[Ar]
(MeNacnac−; Ar = 2,6-iPr2C6H3) was chosen as an ancillary
ligand because of its robust and “non-innocent” character and
because of its ability to stabilize reactive metal fragments.32,33
Moreover the very recent report of Bertrand and co-workers of
the synthesis and properties of a “bottle-able” phosphanylphos-
phinidene has allowed a direct comparison of the free and
ligated phosphanylphosphinidene. This species can be isolated
only because of the electronic stabilization by a phosphanyl
group bearing two nitrogen substituents and the steric
protection by the substituents on nitrogen atoms.34,35
2.3. Preparation of [MeNacnacTi(Cl){η2-P(SiMe3)-PiPr2}] 1b.
[
MeNacnacTiCl2·THF] (0.250 g, 0.411 mmol) in 5 mL of toluene was
added at −30 °C to a solution of iPr2P−P(SiMe3)Li·2.0THF (0.170 g,
0.457 mmol) in 5 mL of toluene. The mixture was then stirred for 2 h
at room temperature. The solvent was evaporated under reduced
pressure, and the green solid residue was dissolved in 30 mL of
pentane. The resulting solution was filtered and concentrated to 20
mL. After 1 h at +4 °C green crystals of 1b were obtained (0.193 g,
yield 65%). Anal. Calcd for C38H64ClN2P2Si1Ti: C, 63.19; H, 8.93; N,
3.88. Found: C, 63.20; H, 9.05; N, 3.79%.
2.4. Preparation of [MeNacnacTi(Cl)(η2-P-PtBu2)] 2a1 (Method
2) and Isolation of [{ArNC(Me)CHC(Me)}Ti(NAr){P(SiMe3)-
PtBu2}]−[Li(THF)4]+ 3a. [MeNacnacTiCl2·THF] (0.332 g, 0.561
mmol) in 5 mL of THF was added to a cold solution (−30 °C) of
tBu2P−P(SiMe3)Li·2.8THF (0.514 g, 1.123 mmol) in 5 mL of THF.
The solution was stirred at room temperature for 1 d. Then the
solvent was removed under reduced pressure, and the green-red oily
residue was extracted with 25 mL of pentane. The resulting solution
was filtered, concentrated to 5 mL, and stored at +4 °C. After 4 d the
green crystals of 2a1 were obtained (0.150 g, 39%). Anal. Calcd for
C37H59Cl1N2P2Ti1: C, 65.63; H, 8.78; N, 4.14. Found: C, 65.55; H,
8.92; N, 3.92. All NMR spectra for 2a1 compound are described in the
Section 2.1. The mother liquor remaining after separation of 2a1 was
concentrated to 2 mL. After several hours red oil separated and
crystallized a few days later yielding dark red crystals of 3a (0.086 g).
Anal. Calcd for C56H103TiN2P2O4SiLi: C, 66.38; H, 10.25; N, 2.76.
Found: C, 64.39; H, 9.49; N, 2.64%.
2. EXPERIMENTAL SECTION
Toluene and tetrahydrofuran (THF) were dried over Na/benzophe-
none and distilled under argon. Pentane was dried over Na/
benzophenone/diglyme and distilled under argon. All manipulations
were performed in flame-dried Schlenk-type glassware on a vacuum
2.5. Preparation of [MeNacnacTi(Cl)(η2-P-PtBu2)] 2a2. A
solution of tBu2P−P(SiMe3)Li·3THF (0.54 g, 1.143 mmol) in 5 mL
of THF was added dropwise to a solution of [MeNacnacTiCl2] (0.306
g, 0.572 mmol) in 5 mL of THF cooled to −40 °C. The mixture was
heated to room temperature and kept at this temperature for 2 d. Then
the solvent was evaporated under the reduced pressure, and the green-
yellow oily residue was extracted with pentane (20 mL). The resulting
solution was filtered, concentrated to 3 mL, and stored at −30 °C.
After one week, green crystals (plates) of 2a2 were separated (0.032 g,
yield 5.4%). Anal. Calcd for C37H59ClN2P2Ti: C, 65.63; H, 8.78; N,
4.14. Found: C, 65.54; H, 8.88; N, 3.95%.
1
line. 31P, 13C, and H spectra in solution were recorded on Bruker
AV300 MHz and Bruker AV400 MHz (external standard tetrame-
1
thylsilane for H, 13C; 85% H3PO4 for 31P). Literature methods were
used to prepare tBu2P−P(SiMe3)Li·nTHF,36 iPr2P−P(SiMe3)Li·
nTHF,37 [NacnacTiCl2·THF],21 [NacnacTiCl2],38 and [Nacnac-
TiCl3].39 The yields of the reactions leading to phosphanylphosphi-
nidene complexes 2a1, 2a2, and 2b are calculated in comparison to
amount of used [MeNacnacTiCl2·THF].
2.1. Preparation of [MeNacnacTi(Cl)(η2-P-PtBu2)] 2a1 (Method
1). A suspension of [MeNacnacTiCl3] (0.200 g, 0.349 mmol) in 5 mL
of THF was slowly added to the solution of tBu2P−P(SiMe3)Li·2.5
THF (0.303 g, 0.694 mmol) in 5 mL of THF at −35 °C. After 20 h at
room temperature THF was removed from the green-brown solution,
and pentane was added to the solid product. The resulting solution
was filtrated, and the filtrate was concentrated. After 2 d homogeneous
green crystals were isolated. For the crystals the unit cell was
investigated by the X-ray method and characterized as 2a1 complex
(0.078 g, yield 33%). NMR data for 2a1: 1H NMR (C6D6) δ 7.04 (m,
6H, C6H3), 4.64 (s, 1H, γ-CH), 3.76 (sept. 2H, J = 6.72 Hz, CHMe2),
3.18 (sept. 2H, J = 6.72 Hz, CHMe2), 1.57 (d, 6H, CHMe2, J = 6.72
Hz), 1.32 (s, 6H, C(Me)CHC(Me)), 1.317 (d, 6H, CHMe2, J = 6.72
Hz), 1.04 (d, 18H, tBu, JP−H = 14.67 Hz), 0.98 (d, 6H, J = 6.72 Hz,
CHMe), 0.96 (d, 6H, J = 6.72 Hz, CHMe2); 13C NMR (C6D6) δ
166.27 (C(Me)CHC(Me)), 142.71 (s, i-C6H3), 141.61 (s, o-C6H3),
127.00 (s, p-C6H3), 124.64 (s, m-C6H3), 124.00 (s, m-C6H3), 96.86
(C(Me)CHC(Me)), 40.04 (PCMe3), 32.45 (d, J = 5.87, Me3CP),
29.25 (CHMe2), 28.32 (CHMe2), 26.02 (CHMe2), 25.14 (CHMe2),
24.31 (C(Me)CHC(Me)), 24.29 (CHMe2), 23.61 (CHMe2); 31P
NMR (C6D6) 843.8 (d, P-PtBu2, JP−P = 457.76 Hz), 143.6 (d, P-PtBu2,
JP−P = 457.76 Hz).
2.6. Preparation of [MeNacnacTi(Cl)(η2-P-PiPr2)] 2b.
[
MeNacnacTiCl2·THF] (0.182 g, 0.309 mmol) in 5 mL of THF was
added dropwise to a solution of iPr2P−P(SiMe3)Li·2.0THF (0.230 g,
0.618 mmol) in 5 mL of THF cooled to −30 °C. The mixture was
then stirred overnight at room temperature. The solvent was
evaporated under reduced pressure; the oily residue was dissolved in
pentane, and the resulting solution was filtered. The filtrate was
concentrated to 2 mL and stored at −30 °C. After 6 d, dark green
crystals of 2b were separated (0.138 g, yield 35%). Anal. Calcd for
C57H55ClN2P2Ti: C, 64.76; H, 8.54; N, 4.32. Found: C, 64.74; H, 8.57;
N, 4.30%. 1H NMR (C6D6) δ 7.14 (m, 6H, C6H3), 4.67 (s, 1H, γ-CH),
3.96 (sept. 2H, J = 6.72 Hz, CHMe2), 3.12 (sept. 2H, J = 6.72 Hz,
CHMe2), 1.88 (m, 2 H, PCHMe2), 1.60 (d, 6H, J = 6.72 Hz, CHMe2),
1.42 (d, 6H, J = 6.72 Hz, CHMe23), 1.41 (s, 6H, C(Me)CHC(Me)),
3
1.29 (dd, 6H, JPCCH = 16.14 Hz, JHCCH = 7.09, PCHMe3), 1.09 (d,
6H, J = 6.72 Hz, CHMe2), 1.08 (d, 6H, J = 6.72 Hz, CHMe2), 0.92 (dd,
3
3
6H, JPCCH = 16.14 Hz, JHCCH = 7.09, PCHMe2); 13C NMR 166.28
(C(Me)CHC(Me)), 142.82 (s, i-C6H3), 141.42 (s, o-C6H3), 127.09 (s,
p-C6H3), 124.67 (s, m-C6H3), 124.05 (s, m-C6H3), 96.10 (C(Me)
CHC(Me)), 29.77 (d, JP−C = 7.89 Hz, PCHMe2), 29.08 (CHMe2),
28.13 (CHMe2), 26.16 (CHMe2), 24.71 (CHMe2), 24.43 (C(Me)-
CHC(Me)), 24.11 (CHMe2), 23.55 (CHMe2), 22.52 (PCHMe2),
2.2. Preparation of [MeNacnacTi(Cl){η2-P(SiMe3)-PtBu2}] 1a.
[
MeNacnacTiCl2·THF] (0.547 g, 0.9 mmol) in 5 mL of toluene was
B
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Scheme 1. Reaction of [MeNacnacTiCl3] with tBu2P−P(SiMe3)Li in Toluene
Scheme 2. Reaction of [MeNacnacTiCl3] with R2P−P(SiMe3)Li in THF
Scheme 3. Reaction of [MeNacnacTiCl2·THF] with 1 equiv of R2P−P(SiMe3)Li·nTHF in Toluene (R = tBu, iPr)
21.54 (PCHMe2); 31P NMR (C6D6) 823.8 (d, P-PtBu2, JP−P = 443.23
40
P(SiMe3)−P(SiMe3)−PtBu2 were detected, which points to
the dimerization of tBu2P−P(SiMe3) groups. Additionally
signals of tBu2PH, tBu2P−P(SiMe3)H and probably of
tBu2P−PH2 were found. These products support a radical
mechanism of the dimerization. The crystallization from
pentane solution resulted in separation of [MeNacnacTiCl2] as
a red solid, even if the run was conducted at −30 °C (Scheme
1).
Hz), 118.4 (d, P-PtBu2, JP−P = 443.23 Hz).
2.7. Preparation of [MeNacnacTi(Cl)(η2-P-PtBu2)] 2a1 (Method
3). A solution of [iBu3PAgCl]4 (0.069 g, 0.05 mmol) in 1 mL of
toluene was added to a solution of 1a (0.150 g, 0.200 mmol) in 3 mL
of toluene cooled to −30 °C. Then the reaction mixture was stirred for
3 h at room temperature. The green solution turned green-brown. The
solvent was removed under vacuum. The solid product was dissolved
in 20 mL of pentane and filtered. The filtrate was concentrated to 2
mL and left at +4 °C. Dark green crystals of 2a1 were obtained after a
few hours (0.064 g, yield 49.23%).
According to the 31P NMR spectroscopic examination of the
reaction solutions, tBu2P−P(SiMe3)Li and iPr2P−P(SiMe3)Li
react with [MeNacnacTiCl3] in molar ratio 2:1 in THF yielding
phosphanylphosphinidene complexes [MeNacnacTi(Cl)(η2−P-
PtBu2)] (2a) and [MeNacnacTi(Cl)(η2-P-PiPr2)] (2b), respec-
tively (Scheme 2).
2.8. Preparation of [MeNacnacTi(Cl)(η2-P-PtBu2)] 2a1 (Method
3). A solution of iBu3PAgI (0.058 g, 0.033 mmol) in 2 mL of toluene
was added to a cold solution (−30 °C) of 1a (0.100 g, 0.133 mmol) in
3 mL of toluene. The mixture was stirred for 5 d at room temperature.
The green solution turned green-brown. The solvent was removed
under reduced pressure, and the solid product was dissolved in 30 mL
of pentane and filtered. The filtrate was evaporated to a small volume
and placed at −30 °C. Green crystals of 2a1 were obtained after 24 h
(0.038 g, yield 44.18%).
The yields of [MeNacnacTi(Cl)(η2-P-PtBu2)] were modest,
and the reproducibility was poor, because the runs shown in
Scheme 2 were accompanied by a dimerization of R2P−
P(SiMe3)2 moieties and formation of tBu2P−PH−P-
(SiMe3)−PtBu2 or iPr2P(1)−P(2)H−P(3)(SiMe3)−P(4)iPr2,
respectively. The identity of the latest compound was
established by comparison of its 31P NMR data: P(1) 1.70
ppm, P(2) −142.4 ppm, P(3) −177.4 ppm, P(4) 1.65 ppm,
3. RESULTS AND DISCUSSION
3.1. Reactivity of tBu2P−P(SiMe3)Li and iPr2P−P-
(SiMe3)Li with [MeNacnacTiCl3]. According to 31P NMR
spectroscopy the reaction of tBu2P−P(SiMe3)Li with
[MeNacnacTiCl3] in molar ratio 1:1 in toluene-d8 (NMR
tube) does not lead to the formation of a putative
phosphanylphosphido TiIV complex [MeNacnacTiCl2{η1-P-
(SiMe3)-PtBu2}] nor to [MeNacnacTi(Cl)(η2-P-PtBu2)] (2a).
In this run resonances of two diastereomers of tBu2P−
2
3
1JP(1)−P(2) 197.3 Hz, JP(1)−P(3) 120.3 Hz, JP(1)−P(4) 4.7 Hz,
2
1
1JP(2)−P(3) 243.5 Hz, JP(2)−P(4) 12.5 Hz, JP(2)‑H 184.0 Hz,
1JP(3)−P(4) 301.4 Hz, with the known data for tBu2P-PH-
P(SiMe3)-PtBu2.11 Additionally formations of R2P−P(SiMe3)-
H, R2P−P(SiMe3)−PR2, and R2P−PH−PR2 were observed. 2a
was isolated via crystallization from the pentane solution, which
C
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a
Scheme 4. Reaction of [MeNacnacTiCl2·THF] with tBu2P−P(SiMe3)Li in THF
a
Molar ratio ≈ 3:5.
Scheme 5. Reactions of [MeNacnacTi(Cl){η2-P(SiMe3)-PtBu2}] 1a with [iBu3PAgX] in Toluene
was however complicated due to the concomitant crystal-
lization of [MeNacnacTiCl2·THF]. The attempts to isolate 2b
failed. Thus, this way to introduce R2P−P functionalities
directly to titaniumIV center was not efficient, and the
introduction of Me3SiP−PtBu2 group was not possible at all.
3.2. Reactivity of tBu2P−P(SiMe3)Li and iPr2P−P-
(SiMe3)Li toward [MeNacnacTiCl2·THF]. To avoid oxidative
dimerization during the metathesis reactions involving
[MeNacnacTiCl3] the TiIII precursor [MeNacnacTiCl2·THF]
was used. The metathesis in toluene involving [MeNacnacTiCl2·
THF] and R2P−P(SiMe3)Li·nTHF in molar ratio 1:1 yielded
paramagnetic complexes [MeNacnacTi(Cl){η2-P(SiMe3)-
PtBu2}] (1a) and [MeNacnacTi(Cl){η2-P(SiMe3)-PiPr2}] (1b)
as green solids with good yields (Scheme 3).
denoted as 2a2, once isolated with low yield. The 31P NMR
spectroscopic examination of reaction solutions leading to 2a1
and 2a2 showed the same AX patterns 842.8 ppm, 143.6 ppm
(457.76 Hz; denoted as 2a), tBu2P−P(SiMe3)2 and tBu2P−
P(SiMe3)H. Isolated 2a1 and 2a2 are stable in solution, and in
toluene-d8 they displayed the same 31P NMR spectra (denoted
as 2a) and weak resonances of tBu2PH. Similarly reaction
solution of a run leading to 2b showed AX pattern 823.8 ppm,
118.4 ppm (443.23 Hz) together with weak signals of iPr2P−
P(SiMe3)2, iPr2P−P(SiMe3)H, and P(SiMe3)2H and not
identified AX pattern 642.9 ppm, 127.6 ppm (466.0 Hz). 2b
is stable in solution.
The reaction of tBu2P−P(SiMe3)Li with [MeNacnacTiCl2·
THF] in THF was also tested in molar ratio 1:1 to explain the
results of runs in THF (2:1). The only product was 2a isolated
as 2a1. In a run conducted in THF in molar ratio 2:1 in a bigger
scale, a paramagnetic TiIII complex 3a was isolated and as a red
solid structurally characterized. Thus, for this reaction the
stoichiometry presented in Scheme 4 was suggested.
Having considered that contraction of six-membered ring
{ArN-C(Me)−CH-C(Me)-NAr}Ti of 1a to five-membered
ring {ArN-C(Me)−CH-C(Me)}Ti of 3a and transfer of ArN
onto Ti atom (the transformation 1a → 3a) can be seen as 2e−
reduction,41−44 which was accompanied by the 1e− oxidation
1a → 2a (of two molecules), the reaction presented in Scheme
4 can be interpreted as an autoredox process.
The examination of stabilities of 1a and 1b in solvents of
different donor properties clearly revealed (31P NMR
spectrum) that 1a was relatively stable in toluene and
decomposed very slowly at room temperature yielding 2a,
tBu2PH, tBu2P−P(SiMe3)H, and tBu2P−P(SiMe3)2 together
with not identified compound (31P NMR spectrum: AX pattern
27.4 ppm and −104.3 ppm, 1JP−P 366.5 Hz). Differently 1a and
The 31P NMR spectroscopic examination of reaction
solutions indicated the presence of additional diamagnetic
compounds. A run leading to the isolation of 1a showed signals
of 2a, tBu2P−P(SiMe3)2, tBu2P−P(SiMe3)H, and small signals
of tBu2PH together with two unidentified AX patterns of low
intensity: (a) 81.3 ppm, −123.6 ppm (1JP−P 476.8 Hz); (b) 27.4
ppm, −100.3 ppm (1JP−P 366.8 Hz). 1a dissolved in toluene-d8
displayed weak resonance of 2a and a weak singlet of tBu2PH.
Similarly reaction solution from a run leading to 1b showed
signals of 2b, iPr2P−P(SiMe3)2, iPr2P−P(SiMe3)H, P-
(SiMe3)2H, and unidentified AX pattern 591.9 ppm, 125.8
ppm (470.1 Hz). 1b dissolved in toluene-d8 displayed weak
resonance of 2b, iPr2P−P(SiMe3)H and P(SiMe3)2H.
The reaction outcomes of [MeNacnacTiCl2·THF] with R2P−
P(SiMe3)Li·nTHF in molar ratio 1:2 in THF were quite
different, and diamagnetic TiIV complexes 2a and 2b were
isolated as green solids with good yields (Scheme 4).
[MeNacnacTi(Cl)(η2-P-PtBu2)] (2a) was isolated in two
forms, the main isomer denoted as 2a1 and second isomer
D
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1b were not stable in THF solution and rearranged even at low
temperature (−23 °C). 1b rearranged relatively rapidly at room
temperature yielding 2b (after one week the isolated yield ≈
37%). 1a rearranged slower with the formation of 2a (isolated
as 2a1, contaminated with 1a). Even after three weeks (0.19 M
1a in THF-d8) some amounts of 1a were observed in solution
(1H NMR broad signals). The evolution of a new AX pattern
(31P NMR, 64.6 and −244.4 ppm, 1JP−P = 357.5 Hz) parallel to
the formation of 2a was also observed, but this compound
decomposed within six weeks with a continuous growth of
signals of tBu2P−P(SiMe3)2. In conclusion, the stoichiometry
of the reaction of R2P−P(SiMe3)Li with [MeNacnacTiCl2·THF]
in THF should be considered as accordant to Scheme 4,
because the spontaneous transformations of 1 → 2 in THF
solution were significantly slower.
Considering the crucial role of redox processes in the
reactions of TiIII complexes 1a and 1b, the compounds of AgI as
external oxidants similar to oxidation by AgOTf or AgBPh4
reported by Mindiola and co-workers45−47 were tested.
Reactions of toluene solutions of 1a with [iBu3PAgX] (X =
Cl, I), molar ratio 1:1 at room temperature, led to formation of
a silver mirror concomitant with the formation of 2a isolated as
2a1 and iBu3P (Scheme 5). The 31P NMR spectroscopic
studies of reaction solutions of 1a with [iBu3PAgX] indicated
that [iBu3PAgI] has reacted much slower than [iBu3PAgCl],
and no traces of [MeNacnacTi(I)(η2-P-PtBu2)] were found.
This oxidation reaction represents a very nice entrance to
phosphanylphosphinidene complexes with NacnacTiIV center
(Scheme 5). It produces only one soluble and well-crystallizing
solid 2a [MeNacnacTi(Cl)(η2-P-PtBu2)] very easily and with a
high purity.
phosphinidene P atoms in these side-on bonded complexes are
unusually deshielded, a feature that until now was attributed to
complexes with terminal bent phosphinidene ligands. The
comparison with 31P NMR data of a recently reported “bottle-
able” phosphanylphosphinidene (δP1 = −200.4 ppm, δP2R2
=
1
80.2 ppm, JP−P = 884 Hz) has experienced an enormous
downfield shift, which seems however to be dependent on
electron deficiency on metal center. Thus, for complexes of
electron-rich late transition metal at low oxidation state Pt0 in
[(pTol3P)2Pt{η2-P1P2(NiPr2)2}] δP1 = −63.1 ppm, δP2
=
76.9 ppm, JPP = 662 Hz62 this downfield shift is relatively
small, but for electron-poor early transition metal in [{Ar-
(Np)N}3Nb(η2-P1P2tBu2)] (Np = neopentyl) δP1 = 405.5
1
ppm, δP2 = 80.6 ppm, and JPP = 425 Hz63 it is very significant
1
and for 2a δP1 = 843.8 ppm, δP2 = 143.6 ppm, and 1JPP = 457.76
Hz this downfield shift is already enormous.
3.3. X-ray Structural Analysis. The single crystals of 1a
and 1b suitable for X-ray diffraction were grown from the
saturated pentane solutions. 1a crystallizes with one molecule
of pentane in the unit cell in triclinic space group P1. The
̅
pentane molecule lies on the b axis and displays disorder
(occupancy 50:50, Figure S1 Supporting Information). 1a
reveals a five-coordinated titanium complex in a distorted
square pyramidal environment39,64 at the metal center, where
the chloride ion occupies an axial position (Figure 1). For
isostructural 1b see Supporting Information.
The 2b complex was also obtained successfully in the similar
1
reaction with [iBu3PAgCl], but in the H NMR spectrum the
paramagnetic signals were still presented.
The phosphinidene 31P resonance in solution was observed
for 2a and 2b at very low field, rather typical for complexes with
terminal “bent” phosphinidene ligands.14 The X-ray structures
of 2a1, 2a2, and 2b indicate in the solid state a side-on bonding
of R2PP moiety (see Section 3.3). To clear these problems
density functional theory (DFT) calculations to elucidate 31P
NMR spectra for complexes 2a1 and 2a2 were run.48−61 The
1
calculated δ and JP−P values for 2a1 787 ppm, 167 ppm, and
1JP−P = 393 Hz and for 2a2 725 ppm, 127 ppm, and 1JP−P = 423
Hz are relatively near to observed values for 2a in solution.
Additionally the solid-state 31P NMR spectrum of 2a1 displays
two resonances forming an AX pattern. The chemical shift of
one doublet (δ = 147.0 ppm, 1JPP = 447 Hz) is very close to the
value obtained for the tBu2P resonances of 2a in the solution
31P NMR spectrum. The second signal consists of a system of
side bands that spreads over the whole spectrum. The central
line, which denotes the isotropic chemical shift, cannot be
unambiguously established but is very probably located at δ ≈
600−900 ppm. A large shielding tensor anisotropy is
additionally supported by the data calculated for 2a1 and
2a2. Principal components of shielding tensor for phosphini-
dene P atom (2a1) are −1654.2, −211.4, and 296.9; for tBu2P
(2a1) they are 10.8, 92.3, and 186.1. This data set indicates a
very strong anisotropy for phosphinidene P atom (from 1918
ppm to −33 ppm) and the modest anisotropy for PtBu2 (from
253 to 78 ppm) that was observed for the solid-state 31P NMR
spectrum of 2a1. Thus, probably 2a1 and 2a2 do not adopt a
terminal geometry in solution but do adopt a side-on geometry
of tBu2P−P ligand both in solution and in the solid state. The
Figure 1. Molecular structure of [MeNacnacTi(Cl){η2-P(SiMe3)-
PtBu2}] (1a), hydrogen atoms omitted for clarity. Important bond
lengths (Å), bond angles (deg): Ti1−N1 2.069(4), Ti1−N2 2.088(4),
Ti1−Cl1 2.309(2), Ti1−P1 2.445(2), Ti1−P2 2.6759(18), P1−P2
2.125(2), P1−Si1 2.236(3); N1−Ti1−N2 88.94(16), N1−Ti1−Cl1
99.36(14), Cl1−Ti1−P1 128.52(7), Cl1−Ti1−P2 99.32(6), P1−Ti1−
P2 48.78(5), P2−P1−Si1 124.17(9), P2−P1−Ti1 71.28(7), Si1−P1−
Ti1 160.46(9). The sum of the angles around the P atoms: ∑P1 =
355.91, ∑P2 = 335.74.
1a contains the phosphanylphosphido ligand in a near side-
on geometry, Ti1−P1 2.445(2) Å, Ti1−P2 2.6759(18) Å. The
very short distance between two phosphorus atoms is 2.125(2)
Å, and it is shorter than in phosphanylphosphido complexes
with η1-coordination, that is, [Cp2Zr(Cl){P(SiMe3)-PiPr2-κP1}]
2.187 Å, [Cp2Hf(Cl){P(SiMe3)-PiPr2-κP1}] 2.185 Å, and
[Ind2Zr(Cl){P(SiMe3)-PiPr2-κP1}] 2.201 Å.14,16 The geometry
around P1 (∑P1 = 355.91°) is almost planar, and P2 (∑P2 =
335.74°) is more pyramidal. The Ti1−P1 distance of 2.445(2)
E
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Figure 2. Molecular structures of [MeNacnacTiCl(η2-P-PtBu2)], isomer 2a1 on the left, isomer 2a2 on the right side of the figure, hydrogen atoms
omitted for clarity. Important bond lengths (Å), bond angles (deg) for 2a1: N1−Ti1 2.0467(17), N2−Ti1 2.0774(17), P1−P2 2.1022(8), P1−Ti1
2.3160(7), P2−Ti1 2.5590(7), Cl1−Ti1 2.2894(7); P1−P2−Ti1 58.61(2), N1−Ti1−N2 92.80(7), P1−Ti1−P2 50.79(2), ∑P2 = 329.07; for 2a2:
Ti1−N1 2.034(7), Ti1−N2 2.072(8), Ti1−Cl1 2.329(3), Ti1−P1 2.334(3), Ti1−P2 2.523(3), P1−P2 2.112(4); N1−Ti1−N2 92.8(3), P1−Ti1−P2
51.36(10), P1−Ti1−P2 51.36(10).
Å is shorter than this seen in related complex [Cp2TiP-
(SiMe3)2] 2.467(1) Å,65 while the Ti1−P2 2.6759(18) Å is
comparable than those in complexes [(N2P2)TiMe2] 2.6215(6)
Å (N2P2 = tBuN−SiMe2N(CH2CH2PiPr2))66 and [Cp2Ti(κ2-
O,P-O-C6H4-PiPr2)] 2.7127(8) Å.67
The NCCCN unsaturated backbone of the ligand is almost
planar, with 0.0423(2) Å deviation from planarity; the titanium
atom is out of plane of the diamine ligand framework by
0.959(4) Å. The value of bond lengths of the N−C and C−C in
the backbone of the β-diketiminato ligand are between single
and double bond lengths. These results suggest the
delocalization of the double bonds of the ligand N1−C28
1.342(7) Å, C27−C28 1.382(8) Å, C26−C27 1.405(8) Å, N2−
C26 1.345(7) Å.
The deep green cubes of 2a1 were grown from a saturated
pentane solution and crystallized in the monoclinic space group
P21/c. This compound is similar to the five-coordinated
titanium complexes with a distorted square pyramidal environ-
ment of the metal center39,64 where the chloride ion occupies
an axial position (Figure 2).
respectively). The green plates of second isomer denoted as
2a2 from pentane solution were obtained only once. It
crystallizes in triclinic space group P1. In contrast to 2a1
̅
(Figure 2-2a1), the metal center of 2a2 adopts a pseudo-
trigonal-bipyramidal geometry with two nitrogen atoms of β-
diketiminato ligand and phosphanyl phosphorus atom in the
equatorial position. The axial position is occupied by one
chloride atom and phopshinidene phosphorus atom. The values
of Ti−P bond lengths (Ti1−P1 2.334(3) Å, Ti1−P2 2.523(3)
Å) indicate that the coordination of phosphanylphosphinidene
ligand to the metal center is near η2 (angle P2−P1−Ti1 =
68.93(12)°). The P1−P2 distances for both isomers are typical
for PP double bond in side-on geometry (2.1022(8) Å 2a1
and 2.112(4) 2a2).13 Similar structural properties were
described by Cummins and co-workers in the phosphanyl-
phosphinidene complexes of niobium and tungsten.63,73,74 The
NCCCN unsaturated backbones of the ligand are almost
planar, with 0.043(6) Å deviation from planarity in 2a1 and
0.044(5) Å in 2a2. The titanium atoms in both complexes are
out of planes of diimine ligand frameworks by 1.077(2) Å 2a1
and 0.872(2) Å 2a2.
The β-diketiminato ligand coordinates to the metal center
through two nitrogen atoms. The phosphanylphosphinidene
ligand coordinates side-on with Ti1−P1 = 2.3160(7) Å, Ti1−
P2 = 2.5590(7) Å, and P1−P2 2.1022(8) Å. The crystallo-
graphic structure shows that the distance Ti1−P1 lies in range
between single and double P−Ti bond, wherein the single bond
distance Ti−P is 2.564(2) Å in [Cp2Ti(PMe3)(η2-PCtBu)]68
and 2.503(2) Å in [Cp*Ti(κ2-PC(tBu)C(CH2))],69 while the
double bond TiP distance is 2.1644(7) Å in [tBuNacnacTi =
P(Trip) (Me)]24 and 2.1831(4) Å in [MeNacnacTi =
To clarify the charge distributions and bonding properties in
2a1 and 2a2 DFT calculations were performed.48−61 The
resulting molecular coordinates are well in accordance with X-
ray results (Figures S5 and S6, see Supporting Information).
2a1 and 2a2 have the same energy, and therefore it was
possible to obtain both isomers under similar crystallization
conditions. The rotation of a tBu2P−P moiety around an axis
near perpendicular to P−P bond must be of low energy. DFT
calculations have yielded following Mayer bond order (MBO)
values for 2a1: P1−P2 = 0.972; Ti1−P1 = 1.60; Ti1−P2 =
0.809. Similar MBO values were obtained for 2a2: P1−P2 =
0.948; Ti1−P1 = 1.57; Ti1−P2 = 0.872. Thus, according to
MBO values the P−P bonds in tBu2PP ligands are rather single
ones in both isomers. The Ti−P1 bond lengths and MBO
values indicate significant π-bonding contributions. It means
that tBu2PP group does display important properties of a
terminal tBu2PP moiety; however, it is side-on bonded, and the
P−P distance is short. The Hirshfeld population analysis for
2a1 yields negative charge at P1 (−0.159), which suggests some
23
t
PMes*(CH2 Bu)]. The bond distance Ti1−P2 is typical for
single bond between titanium and phosphorus atom. The angle
P2−P1−Ti1 = 70.60(2)° is a little wider than in the
prototypical η2-phosphanylphosphinidene compounds of plat-
inum [(tBu2PH)(Ph3P)Pt(η2-P-PtBu2)],70 [(EtPh2P)Pt(η2-P-
PtBu2)],71 [(dppe)Pt(η2-P-PtBu2)]72 (62.73°, 62°, and 61.88°,
respectively) described by Fritz and co-workers but is
comparable to the complexes of tungsten and molybdenum:
[(2,6-iPr2C6H3N)2(Cl)W(η2-tBu2PP)]Li·3DME29 and [(2,6-
iPr2C6H3N)2Mo(Cl)(η2-PPR2)]Li·3DME28 (69.13°, 69.08°
F
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ionic character of the P−P bond, positive at P2 (0.125) in
accord with donor properties of phosphanyl part of this ligand,
negative charges at N atoms (−0.128 and −0.138), and highly
positive charge at Ti atom (0.339). Scheme 6 shows the Lewis
structure of 2a according to DFT results.
Scheme 6. Lewis Structure of 2a
2b crystallizes in monoclinic space group P21/n. The X-ray
structure is shown in Figure 3.
Figure 4. Molecular structure of the anionic titanium-imido-
phosphanylphosphido complex 3a. H atoms and cation [Li(THF)4]+
are omitted for clarity (complete structure see Supporting
InformationFigure S4). Important bond lengths (Å), bond angles
(deg): N1−Ti1 1.986(3), N2−Ti1 1.736(4), Si1−P1 2.2342(18), P1−
P2 2.1799(17), P1−Ti1 2.4840(15), C16−Ti1 2.113(4); N2−Ti1−N1
114.57(16), N2−Ti1−C16 114.67(17), N1−Ti1−C16 85.86(16),
N2−Ti1−P1 114.79(12), N1−Ti1−P1 113.27(11), C16−Ti1−P1
110.37(15), Ti1−N2−C18 169.8(3). The sum of the angles around
the P atoms: ∑P1 = 344.14, ∑P2 = 319.01.
plexes.42−44,75 The C3N ligand of 3a displays η2-coordination
mode, although the Ti−C (ligand backbone) distances of 3a
(Ti1−C14 2.798(3) Å, Ti1−C15 2.763(2) Å) are shorter than
those in the C3N ligand (Ti−C = 2.981, 2.994, 2.892, and 2.928
Å).42,43 The central titanium atom deviates from the C3NTi
plane by 0.0703 Å. The lengths of C15−C16 1.340(6) Å in the
C3NTi ring are close to the corresponding values of double
bond lengths, whereas the C14−C15 1.487(6) Å lies in the
range of single bond lengths. The distance of N1−C14
1.387(5) Å is much longer than those reported in literature
(1.296−1.331 Å).42−44,75 P1−P2 is 2.1799(17) Å and might
suggest a partial double bond character of this bond. Similar
distances between P−P atom were observed in the
phosphanylphosphido complexes of zirconium and hafnium.16
Thus, the tBu2PP(SiMe3) moiety is terminally bonded to the
metal center. The relatively short distance Ti1−P1 2.4840(15)
Å is rather typical for TiIII phosphido complexes, see, for
example, [Cp2TiP(SiMe3)2] 2.467(1) Å,76 but it is slightly
shorter than that found in [{(C5Me4)-SiMe2-PCy}Ti(NMe2)]
2.505(3) Å.65 The geometry around P1 (∑P1 = 344.14°)
indicates significant extent of planarity, while the geometry
around P2 (∑P2 = 319.01°) is clearly pyramidal.
Figure 3. Molecular structure of [NacnacTiCl(η2-P-PiPr2)] (2b),
hydrogen atoms omitted for clarity. Important bond lengths (Å), bond
angles (deg): N1−Ti1 2.0389(18), N2−Ti1 2.0411(18), P1−P2
2.1038(8), P1−Ti1 2.3182(7), P2−Ti1 2.4933(7), Cl1−Ti1
2.2786(7); P1−P2−Ti1 59.86(2), N1−Ti1−N2 92.43(7), P1−Ti1−
P2 51.70(2). The sum of the angles around the P atoms: ∑P2 =
328.84.
Coordination and environment on the metal center is the
same as in 2a1 and 2a2; however, in 2b it was found that the
location of phosphanylphosphinidene ligand is between related
locations in 2a1 and 2a2. It may be caused by the different
steric hindrance of substituents on the phosphorus atom (in
this case iPr groups). It additionally supports that the
phosphanylphosphinidene group can easily rotate along an
axis perpendicular to P1−P2 bond. The P1−P2 distance
2.1038(8) Å is short and is comparable to those in the
structures 2a1 and 2a2.
Reaction of [MeNacnacTiCl2·THF] with R2P−P(SiMe3)Li in
molar ratio 1:2 yielded also red crystals denoted as 3a. The X-
4. CONCLUSIONS
ray study showed that 3a crystallizes in the space group P1 with
Reactions of [MeNacnacTiCl2·THF] with R2P−P(SiMe3)Li·
nTHF in toluene (molar ratio 1:1) have yielded related TiIII
complexes [MeNacnacTi(Cl){η2-P(SiMe3)-PR2}] (1a, R = tBu;
1b, R = iPr) with (Me3Si)P-PR2 group bonded side-on to the
TiIII centers. Reactions of [MeNacnacTiCl2·THF] with R2P−
P(SiMe3)Li in THF (molar ratio ≈ 2:1) have yielded related
phosphanylphosphinidene TiIV complexes [MeNacnacTiCl(η2-
P-PR2)] (2a1 and 2a2, R = tBu; 2b, R = iPr) with P-PR2 group
also bonded side-on to the TiIV centers. The reaction between
[MeNacnacTiCl2·THF] and R2P−P(SiMe3)Li yielding 2a is a
̅
a distorted tetrahedral geometry at the metal center. Two
structurally similar independent molecules were found in the
unit cell of 3a. The molecular structure of anionic part of
complex 3a is depicted in Figure 4. Complete ionic complex,
together with THF-coordinated lithium counterion, is
presented in Supporting Information (see Figure S4).
Complex 3a features a four-coordinated titanium center. The
molecule of 3a has a nearly linear Ti1N2−C18 alignment
169.8(3)° similar to those reported for imido com-
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2e− autoredox process connected with the contraction of
MeNacnac moiety and transfer of a nitrene Ar−N onto Ti atom
with concomitant oxidation of two molecules of 1a to 2a.
Moreover the phosphanylphosphido complexes 1a and 1b are
not stable in THF solution and transform spontaneously into
2a and 2b. The best entrance to the TiIV complexes
[MeNacnacTiCl(η2-P-PR2)] is the preparation of the related
TiIII complexes [MeNacnacTi(Cl){η2-P(SiMe3)-PR2}] (1) fol-
lowed by their oxidation with [iBu3PAgCl]. It reacts with 1
yielding 2, iBu3P, Me3SiCl, and Ag.
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ASSOCIATED CONTENT
* Supporting Information
■
S
.The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b01929.
X-ray crystallographic information (CIF)
1H and 31P and 31P(H) NMR spectra, solid-state 31P
NMR spectra, molecular structure of 1a, 1b, and 3a,
comparison of molecular structure of 2a1 and 2a2 (X-ray
and optimization in the Amsterdam program) (PDF)
checkCIF/PLATON report (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: lukasz.ponikiewski@pg.gda.pl.
■
(13) Pikies, J.; Baum, E.; Matern, E.; Chojnacki, J.; Grubba, R.;
Robaszkiewicz, A. A new synthetic entry to phosphinophosphinidene
complexes. Synthesis and structural characterisation of the first side-on
bonded and the first terminally bonded phosphinophosphinidene
zirconium complexes [μ-(1,2:2-η-tBu2PP){Zr(Cl)Cp2}2] and [{Zr-
(PPhMe2)Cp2}(η1-P−PtBu2)]. Chem. Commun. 2004, 2478−2479.
(14) Łapczuk-Krygier, A.; Baranowska, K.; Ponikiewski, L.; Matern,
E.; Pikies, J. π-Indenyl substituted zirconium compounds containing
terminal bonded phosphanylphosphido ligands [Ind2Zr(Cl){(Me3Si)-
P−PR2-κP1}]. Synthesis, X-ray analysis and NMR studies. Inorg. Chim.
Acta 2012, 387, 361−365.
ORCID
Ł. Ponikiewski: 0000-0002-5037-1956
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Funding
National Science Centre; Grant Harmonia, No. 2012/06/M/
ST5/00472; Poland.
(15) Termaten, A. T. New developments towards stable transition metal
phosphinidene complexes; Vrije Universiteit Amsterdam: The Nether-
lands, 2004.
Notes
́
(16) Grubba, R.; Wisniewska, A.; Baranowska, K.; Matern, E.; Pikies,
The authors declare no competing financial interest.
J. General route for the synthesis of terminal phosphanylphosphido
complexes of Zr(IV) and Hf(IV): Structural investigations of the first
zirconium complex with a phosphanylphosphido ligand. Polyhedron
2011, 30, 1238−1243.
ACKNOWLEDGMENTS
■
J.P. thanks the National Science Centre (Grant Harmonia, No.
2012/06/M/ST5/00472) for financial support. Ł.P. thanks the
Deutscher Akademischer Austauschdienst (No. A/14/05583)
for two months of financial support. The authors thank
Karlsruhe Nano Micro Facility KIT Karlsruhe for X-ray single
crystal measurements, S. Stahl for the solid-state NMR
measurements, and M. Zauliczny for the theoretical calcu-
lations. Ł.P. thanks Prof. D. Fenske for help and friendly
atmosphere in Karlsruhe.
(17) Payne, R.; Hachgenei, J.; Fritz, G.; Fenske, D. Synthesis and
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