Chemistry of the phosphorus-nitrogen ligands. Multiple isomeric transformations of the diphosphinohydrazine bearing 8-quinolyl substituent: P→C, P→N, and P→P migrations caused by different factors

Article abstract of DOI:10.1021/ic101410u

The reaction of 8-quinolylhydrazine with 2 equiv of Ph₂PCl in the presence of Et₃N gives 8-[(Ph₂P)₂NNH]-Quin (1) (Quin = quinolyl) in 84% yield. The heating of 1 at 130 °C for 1 h in toluene results in migration of the [Ph₂PNPPh₂] group to a carbon atom of the quinolyl fragment to form an isomer, 7-(Ph ₂P-N=PPh₂)-8-NH₂-Quin (2). The same migration is caused by the addition of LiN(SiMe₃)₂ to 1. On the contrary, lithiation of 1 with n-BuLi followed by the addition of ZnI ₂ (1:1) affords the aminoquinolyl-phosphazenide dinuclear complex [ZnI(8-Quin-NPPh₂dN-PPh₂)-κ³N,N,P] ₂ (4), which is a result of P→N migration. Compound 1 itself reacts with ZnI₂ in THF to form 4 and protonated molecule 1 · HI, which rearranges to the more stable iminobiphosphine salt (Ph ₂P-PPh₂dN-NH-Quin-8)3HI. Zinc iodide reacts with 2 equiv of the lithium salt of 1 without rearrangement, to form homoleptic aminoquinolyl zinc complex Zn[{(Ph₂P)₂NN-Quin-8}-κ²N, N]₂ (6). Solutions of 4 and 2 in dichloromethane show luminescence at 510 and 460 nm (quantum yields are 45% and 7%, respectively). DFT calculations were provided for possible isomers and their complexes.

Full text of DOI:10.1021/ic101410u

Inorg. Chem. 2010, 49, 9677–9682 9677
DOI: 10.1021/ic101410u
Chemistry of the Phosphorus-Nitrogen Ligands. Multiple Isomeric
Transformations of the Diphosphinohydrazine Bearing 8-Quinolyl Substituent:
PfC, PfN, and PfP Migrations Caused by Different Factors
Alexander N. Kornev,* Natalia V. Belina, Vyacheslav V. Sushev, Julia S. Panova, Olga V. Lukoyanova,
Sergey Y. Ketkov, Georgy K. Fukin, Mikhail A. Lopatin, and Gleb A. Abakumov
G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 Tropinin Street,
603950 Nizhny Novgorod, Russia
Received July 16, 2010
The reaction of 8-quinolylhydrazine with 2 equiv of Ph2PCl in the presence of Et3N gives 8-[(Ph2P)2NNH]-Quin (1)
(Quin = quinolyl) in 84% yield. The heating of 1 at 130 °C for 1 h in toluene results in migration of the [Ph2PNPPh2]
group to a carbon atom of the quinolyl fragment to form an isomer, 7-(Ph2P-NdPPh2)-8-NH2-Quin (2). The same
migration is caused by the addition of LiN(SiMe3)2 to 1. On the contrary, lithiation of 1 with n-BuLi followed by the
addition of ZnI2 (1:1) affords the aminoquinolyl-phosphazenide dinuclear complex [ZnI(8-Quin-NPPh2dN-PPh2)-
κ3N,N,P]2 (4), which is a result of PfN migration. Compound 1 itself reacts with ZnI2 in THF to form 4 and protonated
molecule 1 HI, which rearranges to the more stable iminobiphosphine salt (Ph2P-PPh2dN-NH-Quin-8) HI. Zinc
3
3
iodide reacts with 2 equiv of the lithium salt of 1 without rearrangement, to form homoleptic aminoquinolyl zinc complex
Zn[{(Ph2P)2NN-Quin-8}-κ2N,N]2 (6). Solutions of 4 and 2 in dichloromethane show luminescence at 510 and 460 nm
(quantum yields are 45% and 7%, respectively). DFT calculations were provided for possible isomers and their
complexes.
Introduction
and its modifications involving transition-metal centers,5
the major driving force of these reactions is the formation
of tetracoordinated phosphorus(V) species instead of P(III).
We have previously reported a migratory insertion of an
R2P group into the nitrogen-nitrogen bond of a phosphino-
hydrazide ligand, namely, R2P-NR-NR- f RNdPR2-
NR-, which in general occurred in the coordination sphere
of s, d, and f metals.6-10 This migration is a novel and useful
approach to the synthesis of phosphazenides and phosphi-
noamides. Here, we discuss the unique properties of the
diphosphinohydrazine 1 and diphosphinohydrazide ligand
bearing a quinolyl substituent. Depending on the reaction
conditions, these species demonstrate not only migration of
Compounds bearing a phosphorus-nitrogen bond have
attracted considerable attention both in heteroatom chemistry1
and as ligands for transition metals as well.2 A wide gradation in
phosphorus-nitrogen bond energies attributed to the PN com-
pounds of different types3 is an important circumstance which
makes possible template-like rearrangements and transforma-
tions of the phosphazane ligands in the coordination sphere of
transition metals. Like the Michaelis-Arbuzov rearrangement4
*To whom correspondence should be addressed. E-mail: akornev@
iomc.ras.ru.
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Chem. 1999, 10(7), 529–537. (d) Stahl, L. Coord. Chem. Rev. 2000, 210, 203–
250. (f ) Nifantiev, E. E.; Grachev, M. K.; Burmistrov, S. Yu. Chem. Rev. 2000,
100, 3755–3799. (g) Bansal, R. K.; Heinicke, J. Chem. Rev. 2001, 101, 3549–
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(5) Brill, T. E.; Landon, S. J. Chem. Rev. 1984, 84, 577–585.
(6) Fedotova, Y. V.; Kornev, A. N.; Sushev, V. V.; Kursky, Yu. A.;
Mushtina, T. G.; Makarenko, N. P.; Fukin, G. K.; Abakumov, G. A.;
Zakharov, L. N.; Rheingold, A. L. J. Organomet. Chem. 2004, 689, 3060–
3074.
(7) Sushev, V. V.; Kornev, A. N.; Min’ko, Y. A.; Belina, N. V.; Kurskiy,
Yu. A.; Kuznetsova, O. V.; Fukin, G. K.; Baranov, E. V.; Cherkasov, V. K.;
Abakumov, G. A. J. Organomet. Chem. 2006, 691, 879–889.
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A. N.; Abakumov, G. A. Inorg. Chem. 2008, 47, 2608–2612.
(9) Kornev, A. N.; Belina, N. V.; Sushev, V. V.; Fukin, G. K.; Baranov,
(3) (a) Corbridge, D. E. C. Phosphorus. An Outline of its Chemistry
Biochemistry and Technology; Elsevier: Amsterdam, 1980. (b) Sudhakar,
P. V.; Lammertsma, K. J. Am. Chem. Soc. 1991, 113(6), 1899–1906. (c) Steiner,
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€
E. V.; Kurskiy, Y. A.; Poddelskii, A. I.; Abakumov, G. A.; Lonnecke, P.;
Hey-Hawkins, E. Inorg. Chem. 2009, 48, 5574–5583.
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r
2010 American Chemical Society
Published on Web 09/14/2010
pubs.acs.org/IC

9678 Inorganic Chemistry, Vol. 49, No. 20, 2010
Kornev et al.
Scheme 1. Isomeric Transformations of 1 and Its Metal Derivatives
Table 1. Crystal and Structure Refinement
1
2
4
6
empirical formula
fw
temp, K
C
527.52
100(2)
monoclinic
P2(1)/n
33H27N3P2
C33H27N3P2
527.52
100(2)
triclinic
P1
C76H74I2N6OP4Zn2
1595.83
100(2)
triclinic
P1
C87H73N6P4Zn
1391.76
100(2)
triclinic
P1
cryst syst
space group
unit cell dimensions
˚
a, A
9.3768(4)
10.0674(5)
11.7831(6)
12.5396(6)
96.9470(10)
112.7310(10)
98.9730(10)
1328.10(11)
2
12.3881(5)
12.4416(5)
12.9177(5)
107.3020(10)
114.3250(10)
94.7250(10)
1683.41(12)
1
12.2550(16)
17.405(2) A
17.594(2) A
80.360(3)
74.710(3)
89.626(3)
3566.0(8)
˚
b, A
28.0714(12)
10.5737(5)
90
100.8010(10)
90
2733.9(2)
˚
c, A
R, deg
β, deg
γ, deg
-3
˚
volume, A
Z
4
1.282
2
1.296
density (calcd), Mg/m3
abs coeff, mm-1
cryst size, mm3
reflns collected
independent reflns
abs correction
1.319
0.192
1.574
1.776
0.187
0.45 ꢀ 0.38 ꢀ 0.29
0.486
0.35 ꢀ 0.10 ꢀ 0.03
0.28 ꢀ 0.21 ꢀ 0.18
0.12 ꢀ 0.10 ꢀ 0.08
16973
8763
14357
28317
5638 [R(int) = 0.0158]
semiempirical
from equivalents
0.9479/0.9207
full-matrix
least-squares on F2
5638/0/451
R1 = 0.0350,
wR2 = 0.0911
R1 = 0.0380,
wR2 = 0.0929
0.383 and -0.209
5765 [R(int) = 0.0224]
semiempirical
from equivalents
0.9663/0.9482
full-matrix
6553 [R(int) = 0.0241]
semiempirical
from equivalents
0.8710/0.8152
full-matrix
12511 [R(int) = 0.1671]
semiempirical
from equivalents
0.9856/0.8483
full-matrix
Max./min transm
refinement method
least-squares on F2
5765/0/351
R1 = 0.0526,
wR2 = 0.1281
R1 = 0.0719,
wR2 = 0.1390
0.505 and -0.266
least-squares on F2
6553/7/394
R1 = 0.0413,
wR2 = 0.1111
R1 = 0.0528,
wR2 = 0.1169
1.517 and -1.120
least-squares on F2
12511/3/793
R1 = 0.0832,
wR2 = 0.1297n
R1 = 0.2119,
wR2 = 0.1673
0.799 and -0.662
data/restraints/params
R indices [I > 2σ(I)]
R indices (all data)
largest diff. peak
˚
and hole, e.A
-3
the Ph2P group into the N-N bond but also the migration of
the [Ph2PNPPh2] fragment to the nearest carbon atom of the
quinolyl substituent, and a reversible migration of the Ph2P
group from nitrogen to the phosphorus atom of another
Ph2P group (Scheme 1).
The phosphorus and nitrogen atoms in the hydrazine frag-
ment adopt an almost coplanar arrangement; the sum of the
˚
angles around N(1) is 356.7°. The N(1)-N(2) (1.418(1) A) and
˚
P-N distances (1.723(1), 1.735(1) A) are in the typical range
found for diphenylphosphinohydrazines.6-10 The 31P{1H}
NMR spectrum of 1 exhibits a single resonance at δ 70.7 ppm.
Heating of toluene or pyridine solutions of 1 under a
vacuum at 130 °C for 1 h results in disappearance of this
signal, while two doublets arose at 44.5 and 27.3 ppm. The
observed coupling constant (JP,P = 104 Hz) is indicative of a
new structure, containing phosphoranato and phosphino
groups separated by the nitrogen atom. A strong and wide
absorption band at 1150 cm-1 in the IR spectrum is in
accordance with the presence of the PdN-P chain. Further
necessary information was obtained from an X-ray investi-
gation indicating formation of the isomeric product 2 (eq 2).
Results and Discussion
2,2-Bis(diphenylphosphino)-1-(quinolyl-8)-hydrazine (1)
was prepared by the reaction of 8-quinolylhydrazine with
two equivalents of chlorodiphenylphosphine in the presence
of Et3N (eq 1). It is a moisture- and air-resistant compound
that is not decomposed below 100 °C.
The structure of 1 was determined by X-ray analysis
(Supporting Information, Figure S1). Crystal data and some
details of the data collection and refinement for 1 are given in
Table 1.

Article
Inorganic Chemistry, Vol. 49, No. 20, 2010 9679
Figure 2. Molecular structure of [ZnI(8-Quin-NPPh2dN-PPh2)-κ3N,N,P]2
(4). Hydrogen atoms and Ph rings at phosphorus atoms are omitted for
clarity. Ellipsoids are drawn at 30% probability. Selected bond lengths
Figure 1. Molecular structure of 2. Hydrogen atoms other than at N(2)
are omitted for clarity. Ellipsoids are drawn at 30% probability. Selected
bond lengths [A] and angles [deg] for 2: P(1)-N(3) 1.561(2), P(1)-C(3)
˚
˚
[A] and angles [deg] for 2: Zn(1)-N(1) 1.987(2), Zn(1)-N(2) 2.079(2),
Zn(1)-P(1) 2.3765(8), Zn(1)-I(1) 2.5920(4), P(1)-N(3) 1.609(3),
P(2)-N(3) 1.560(3), P(2)-N(1A) 1.645(2); N(1)-Zn(1)-N(2) 83.19(9),
N(1)-Zn(1)-P(1) 125.42(7), N(2)-Zn(1)-P(1) 107.50(7), N(1)-
Zn(1)-I(1) 114.37(7), N(2)-Zn(1)-I(1) 102.01(7), P(1)-Zn(1)-I(1)
115.05(2), N(3)-P(1)-Zn(1) 123.2(1), P(2A)-N(1)-Zn(1) 127.8(1),
N(3)-P(2)-N(1A) 119.0(1), P(2)-N(3)-P(1) 150.4(2).
1.799(2), P(2)-N(3) 1.665(2), N(2)-C(2) 1.356(3), C(1)-C(6) 1.409(3),
C(1)-C(2) 1.451(3), C(2)-C(3) 1.400(3); N(3)-P(1)-C(3) 111.3(1),
P(1)-N(3)-P(2) 134.9(1), N(2)-C(2)-C(3) 123.8(2), N(2)-C(2)-C(1)
117.4(2).
Crystal data and some details of the data collection and
refinement for 2 are given in Table 1.
react at room temperature for one week. Over this period of
time, a yellow, crystalline precipitate formed.
X-ray analysis of these crystals clearly showed the forma-
tion of a binuclear zinc complex 4 bearing a novel isomeric
ligand, which is a result of the migration and insertion of the
Ph2P group into the nitrogen-nitrogen bond (Figure 2, eq 3).
The molecular structure of 2 (Figure 1) has two different
˚
P-N bonds: P(1)-N(3) = 1.561(2) A of double bond char-
˚
acter and P(2)-N(3) = 1.665(2) A of single bond character.
The P(1)-N(3)-P(2) angle of 134.9(1)° is in the range typical
for iminophosphines.1a,11 Inspection of the NBO partial
charges in 1 (Supporting Information, Table S1) reveals that
the greatest negative charge is localized on the carbon atom in
position 7 of the quinolyl fragment, which makes it most
favorable for electrophilic attack. It is reasonable to propose
also that charge separation in the transition state (leading to
the [Ph2P-NdPPh2]þ cation and aminoquinolyl-anion) will
promote the electrophilic substitution of the hydrogen atom,
which migrates further to the amino-nitrogen to form 2
eventually.
Notably, the interaction of 1 with LiN(SiMe3)2 in a
toluene/ether solution at room temperature gave the lithium
salt of the isomeric product 2 quantitatively. The 31P NMR
spectrum of the product contains two doublets at 41.7 and
22.7 ppm with a coupling constant of 115 Hz. Workup of this
solution with water gave compound 2 according to the 31P
NMR and IR measurements.
Interestingly, n-BuLi did not cause rearrangement of 1.
The addition of one equivalent of n-BuLi to the toluene
solution of 1 causes precipitation of the lithium salt 3. The
THF solution of 3 exhibits a single resonance in the 31P{1H}
NMR spectrum upfield shifted (61.3 ppm) when compared
with the starting compound. The 31P NMR monitoring of the
solution indicated no dynamic processes during the next two
weeks. In comparing these two reactions, it is evident that a
dissociation equilibrium is possible in the reaction of 1 with
LiN(SiMe3)2, while the reaction with n-BuLi is an irreversible
process.
Both zinc atoms in the centrosymmetric dimer are sur-
rounded in a distorted tetrahedral fashion by two nitrogen
atoms of an aminoquinolyl group, one iodine atom, and one
phosphorus atom from the adjacent ligand. So, two parts of
the dimeric molecule are linked by normal coordination
˚
Zn-P bonds (2.3760(8) A). Chair-like 10-membered metal-
˚
locycle N4P4Zn2 contains two short PdN bonds (1.560(3) A)
˚
and four longer P-N bonds (two of 1.609(3) A and two of
˚
1.645(2) A, that is typical for P-N single bonds). Notably,
both aminoquinolyl ligand systems (including chelated zinc
atoms) are coplanar; the distance between the planes is 4.514
˚
˚
A, while the distance between Zn atoms is 5.77 A. The amido-
nitrogen atoms (N(1), N(1A)) demonstrate trigonal planar
geometry (sum of the angles of 359.51°). The imino-nitrogen
atoms (N(3), N(3A)) have an internal P-NdP angle of
150.4(2)°, which is notably larger than usually found for
similar compounds.11 It may be due to the increased steric
bulk of the dimeric unit. Chelated N-Zn-N angles
(83.19(9)°) in this structure are within the normal range ex-
pected for the related complexes.12 Compound 4 crystallized
Lithium salt 3 reacts with zinc iodide to form different
products depending on stoichiometry of the components.
The equimolar mixture of ZnI2 and 3 in THF was allowed to
(11) Lewis, G. R.; Dance, I. J. Chem. Soc., Dalton Trans. 2000, 299–306.

9680 Inorganic Chemistry, Vol. 49, No. 20, 2010
Kornev et al.
in the P1 space group with one equivalent of solvates Et2O
and c-hexane as part of the crystal lattice.
Recently, we have shown9 that the main factor, which
controls the P-N-N to NdP-N rearrangement, is the
charge at the hydrazido nitrogen. A strong negative charge
promotes elongation of the N-N bond and/or its cleavage.14
It is obvious that the mechanism of this rearrangement will be
different for alkaline and late transition metals since the last
ones usually have a strong PfM coordination bond together
with back-donation. It takes additional energy to destroy this
bond.15 Formation of the zinc dimer 4 requires about a week.
Tentatively, this reaction has two steps as minima. The first is
the N-N bond cleavage; the second step involves coupling of
the remaining particles in the zinc coordination sphere by the
novel P-N bond formation.
Complex 4 is a reasonably air-stable, crystalline solid that
can be handled in the open laboratory for short periods of
time. The 31P{1H} NMR spectrum of 4 contains two reso-
nances at 23.8 (PIII) and 3.5 (PV) ppm, but the 2JP-P coupling
constant could not be resolved. The NBO charges of these
phosphorus atoms are þ1.17 e and þ2.13 e, respectively. Such
a large difference in charges is explained by the distinction
between the PIII and PV valent states. The natural charge on
the nitrogen atom of the P-N-Zn fragment is smaller than
that of the atom belonging to the P-N-P group, but the
difference is not so large (-1.17 e and -1.49 e, respectively).
It was found that dimer 4 may be synthesized in another
way, by the direct interaction of ZnI2 with diphosphino-
hydrazine 1. In this case, quinoline derivative 1 may provide a
HI abstraction (eq 4). 31P{1H} NMR monitoring of this
reaction revealed the formation of 4 (two singlets at 23.8 and
3.5 ppm), and a new product, showing two doublets at 49.4
and -19.5 ppm. Large coupling constant (JP,P = 266 Hz)
allowed us to propose the formation of a molecule, contain-
ing an iminobiphosphine fragment. It is known that the
protonation of diphosphinoamines attached to pyridine at
the ortho position quantitatively affords the corresponding
iminobiphosphine isomers.13 In our case, the formation of
proton-stabilized unit 5b (eqs 4 and 5) is energetically more
favorable by 3.3 kcal/mol than its isomer 5a according to the
DFT calculation (Supporting Information, Table S2).
The reaction of ZnI2 with 2 equiv of 3 produced the iodine-
free homoleptic compound 6 (eq 6).
Notably, that the color of the reaction mixture in this case
turned dark within a few hours.
Following removal of the solvent under a vacuum, extrac-
tion of the product with benzene, and crystallization at 10 °C,
affords dark-red crystals of 6 suitable for X-ray analysis. The
X-ray structure determination of 6 reveals the formation of
the bis(amidoquinolyl) zinc complex having distorted tetra-
hedral geometry (Figure 3). The rigid aminoquinolyl frame-
work of 6 prevents intramolecular coordination P f Zn. The
˚
Zn-P distances are in the range of 4.040-4.154 A.
˚
The N-N bonds in 6 (1.435(5) and 1.436(5) A) are ca. 0.02
˚
A longer than that in the starting compound 1. This is a small
elongation when compared to the known zinc hydrazide,
[EtZn(NHNMe2)]4, where the N-N bond distances are in
16
˚
the range of 1.447-1.464 A. The P-N bond distances
in 6 are slightly different (1.739(4), 1.703(4), 1.731(4), and
˚
1.714(4) A) and comparable to those within the starting
ligand. Compound 6 (and 3 as well) does not undergo further
rearrangement. Apparently, this is due to delocalization of
the negative charge of the hydrazido nitrogen over the five-
membered metallocycle and quinoline rings, which prevents
the N-N bond cleavage.
The 31P NMR spectrum of 6 demonstrates the equivalence
of all phosphorus atoms at room temperature in THF
solution, showing a single resonance at 43.5 ppm. The
crab-like structure of 6 has large chelate arms. The distance
between the phosphorus atoms of the different arms (P1 and
It is reasonably to propose that reactions 3 and 4 may give
mononuclear zinc complex together with the dimer 4. How-
ever, we could not detect or isolate the monomeric species.
DFT calculations showed that the dimerization process is
energetically favorable by 11.7 kcal (Supporting Informa-
tion, Table S3). Moreover, the formation of 4 may be a result
of low solubility of this compound.
˚
P3) is 4.93 A. This value is quite suitable for heterobimetallic
complex formation with metals of the fifth and sixth periods.
Solutions of 2 and 4 in methylene chloride or acetonitrile
glow yellow-green under visible light. Figure 4 demonstrates
emission of the solution of 4 in CH2Cl2 at 510 nm when
excited by 450 nm light. An excitation band at 380 nm is
observed upon monitoring the emission at 510 nm. The elec-
tronic absorption spectrum of this complex also shows a
peak at 380 nm, the experimental transition energy (3.26 eV)
(12) Malassa, A.; Koch, C.; Stein-Schaller, B.; Gorls, H.; Friedrich, M.;
Westerhausen, M. Inorg. Chim. Acta 2008, 361(5), 1405–1414.
(13) Fei, Z.; Biricik, N.; Zhao, D.; Scopelliti, R.; Dyson, P. J. Inorg. Chem.
2004, 43, 2228–2230.
(14) So, the lithium bisphosphinohydrazide, iPr2P-NMe-NLi-PiPr2, was
found to rearrange immediately under preparation in a THF solution into
iminophosphoranate LiNdPiPr2-NMe-PiPr2. At the same time, quite stable
ate-complex Li(DME)3][Li{(NPh-NPh-PiPr2)-κN}2] shows
elongated N-N bond compared to that of the starting compound, HNPh-
NPh-PiPr2.
a strongly
(15) Rearrangements of the Ni and Co phosphinohydrazides usually take
1-2 days at ambient conditions.
(16) Redshaw, C.; Elsegood, M. R. J. Chem. Commun. 2006, 523–525.

Article
Inorganic Chemistry, Vol. 49, No. 20, 2010 9681
Experimental Session
General Remarks. Solvents were purified following standard
methods.17 Toluene and c-hexane were thoroughly dried and
distilled over sodium prior to use. Diethyl ether and THF were
dried and distilled over Na/benzophenone. 8-Quinolylhydra-
zine was synthesized according to a known method.18
Chlorodiphenylphosphine and zinc iodide were purchased
from Sigma-Aldrich Chemical Co. and used as received. All
manipulations were performed in a vacuum or under an argon
atmosphere using standard Schlenk techniques. NMR spectra
were recorded in CDCl3 or C6D6 solutions using a Bruker DPX-
200 spectrometer. Absorption and photoluminescence spectra
of 2 and 4 were recorded on a Perkin-Elmer Lambda UV-vis
spectrometer at 25 °C. Infrared spectra were recorded on a
Perkin-Elmer 577 spectrometer from 4000 to 400 cm-1 in nujol
or on a Perkin-Elmer FT-IR Spectrometer System 2000 as KBr
mulls.
Computational Details. DFT calculations performed in this
work were carried out at the B3LYP/6-31G(d) level of theory
with the Gaussian 03 package (supporting general information).
The optimized geometries of the compounds 1, 2, 4, 5a, 5b, and 6
correspond to energy minima, as indicated by frequency com-
putations. For the geometry optimization of 1, 2, 4, and 6, we
used the full structure without simplification and the B3LYP/6-
31G(d) level of theory. The structure corresponds to an energy
minimum.
Figure 3. Molecular structure of Zn[{(Ph2P)2NN-Quin-8}-κ2N,N]2 (6).
Hydrogen atoms and Ph rings at phosphorus atoms are omitted for
˚
clarity. Ellipsoids are drawn at30%probability. Selectedbondlengths [A]
and angles [deg] for 6: N(1)-N(3) 1.436(5), N(4)-N(6) 1.435(5), Zn(1)-
N(4) 1.954(4), Zn(1)-N(1) 1.961(4), Zn(1)-N(5) 2.077(4), Zn(1)-N(2)
2.083(4), P(1)-N(3) 1.739(4), P(2)-N(3) 1.703(4), P(3)-N(6) 1.731(4),
P(4)-N(6) 1.714(4); N(4)-Zn(1)-N(1) 139.7(2), N(4)-Zn(1)-N(5)
83.0(2), N(1)-Zn(1)-N(5) 128.3(2), N(4)-Zn(1)-N(2) 121.5(2), N(1)-
Zn(1)-N(2) 82.2(2), N(5)-Zn(1)-N(2) 99.0(2), N(1)-N(3)-P(2)
119.8(3), N(1)-N(3)-P(1) 115.2(3), P(2)-N(3)-P(1) 125.0(2), N(4)-
N(6)-P(4) 122.0(3), N(4)-N(6)-P(3) 114.9(3), P(4)-N(6)-P(3)
123.1(2).
X-Ray Crystallography. The X-ray diffraction data of 1, 2, 4,
and 6 were collected on a SMART APEX diffractometer
(graphite-monochromated, Mo KR radiation, j-ω-scan tech-
˚
nique, λ = 0.71073 A). The intensity data were integrated by the
SAINT program.19 SADABS20 was used to perform area-
detector scaling and absorption corrections. The structures were
solved by direct methods and were refined on F2 using all
reflections with the SHELXTL package.21 All non-hydrogen
atoms were refined anisotropically. All H atoms in 1 were found
from Fourier syntheses of electron density and were refined
isotropically, whereas in 2, 4, and 6 they are located in calcula-
tion positions and were refined isotropically in the rigid model.
Details of crystallographic, collection, and refinement data for
all compounds are shown in the Table 1.
CCDC 780260 (1), 780261 (2), 780262 (4), and 780263 (6)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge at www.ccdc.cam.ac.
uk/const/retrieving.html from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, U.K.; fax:
(internat.) þ44-1223/336-033; e-mail: deposit@ccdc.cam.ac.uk.
Synthesis. 2,2-(Diphenylphosphino)-1-(quinolyl-8)-hydrazine (1)
and Its Lithium Salt (3). A solution of chlorodiphenylphosphine
(4.41 g, 20.0 mmol) in 20.0 mL of THF was added dropwise
to a mixture of 8-quinolylhydrazine (1.59 g, 10.0 mmol) and
Et3N (2.53 g, 25.0 mmol) in the same solvent. The mixture was
stirred for 24 h at 20 °C and then filtered. The solvent was
removed in a vacuum and replaced with toluene. Next, the solu-
tion was concentrated to 10.0 mL. Keeping the mixture over-
night at 10 °C yielded large pale yellow crystals of 1. Yield: 4.96 g
(94%). Anal. calcd for C33H27N3P2, %: C, 75.13; H, 5.16; P,
11.74. Found, %: C, 75.20; H, 5.11; P, 11.70. 1H NMR (CDCl3,
300 K) δ (ppm): 8.63 (dd, 1H, 3JHH = 4.0 Hz, 4JHH = 1.8 Hz),
7.98 (dd, 1H, 3JHH = 8.3, 4JHH = 1.8 Hz); 6.4-7.8 (m, 24H, Ph
and quinolyl protons), 8.33 (s, broad, 1H, NH). 31P{1H} NMR
Figure 4. Electronic absorption (dotted green), emission (red), and
excitation (blue) (monitored at 510 nm) spectra of 4 in CH2Cl2 at 298 °C.
agreeing well with thecalculatedHOMO-LUMO gap (3.48 eV).
The distribution of the electron density corresponding to the
HOMO and LUMO (Supporting Information, Figure S2)
suggests that the transition observed is associated with the
electron density transfer from the iodine atoms and the nitro-
gen atoms of the 10-membered metallacycle to the quinoline
fragment. The quantum yield of luminescence calculated
relative to rhodamine 6G is 45%. It is worth mentioning
that the mononuclear zinc complex 6 demonstrates no emis-
sion both in the solid state and in solution, while the spectral
properties of 2 are similar to those of 8-aminoquinoline:
maxima of excitation and emission are observed at 370 and
460 nm, respectively, in CH2Cl2 solution (Supporting Infor-
mation, Figure S3); however, the quantum yield of lumines-
cence is much lower (7%).
(17) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon: Oxford, 1980.
(18) (a) Dewar, M. J. S. J. Chem. Soc. 1944, 615–619. (b) Krasavin, I. A.;
Parusnikov, B. V.; Dziomko, V. M. 8-Quinolylhydrazine and its hydrochloride. In
Preparation of chemical reagents (In Russian); Moscow, 1963; Vol. 7, pp 5-7.
(19) SAINTPlus Data Reduction and Correction Program, v. 6.02a; Bruker
AXS: Madison, WI, 2000.
(20) Sheldrick, G. M. SADABS, v.2.01; Bruker AXS: Madison, WI, 1998.
(21) Sheldrick, G. M. SHELXTL, v. 6.12; Bruker AXS: Madison, WI, 2000.

9682 Inorganic Chemistry, Vol. 49, No. 20, 2010
Kornev et al.
(CDCl3, 300 K), δ (ppm): 70.7. IR (nujol), ν/cm-1: 3295ww,
1577m, 1505m, 1112s broad, 900m, 882w, 817m, 794w, 741s,
694s, 670w, 638w, 616w, 600w, 535w, 493m.
The lithium salt of 1, viz. 3, was prepared by the addition of an
equivalent of n-BuLi (1.0 M solution in hexane) to a toluene
solution of 1. Orange crystals of the lithium salt 3 formed
quickly were filtered and dissolved in THF. 31P{1H} NMR
(THF, 300 K): δ 61.3 ppm.
of 4 suitable for X-ray diffraction were grown from the mixture
of solvents: CH2Cl2/Et2O/C6H12 in a ratio of 3:1:1 respectively.
Interaction of 3 with ZnI2 in a Ratio of 2:1. A solution of ZnI2
(0.64 g, 2.0 mmol) in 10 mL of THF was added to a solution of
3 (2.11 g, 4.0 mmol) in 20 mL of the same solvent. The solution
was stirred at room temperature for 3 h, over which time the
solution turned dark red. Following removal of the solvent
under a vacuum, the product was extracted with benzene, and
the resulting solution was concentrated until crystalline material
began precipitating. The solution was cooled to 10 °C, resulting
in the formation of dark-red crystals (2.20 g, 79% yield). Anal.
Calcd for C66H52N6P4Zn(C6H6)3.5 (6), %: C, 75.08; H, 5.29; N,
6.04. Found, %: C, 74.97; H, 5.33; N, 5.95. 31P{1H} NMR
(THF, 300 K), δ (ppm): 71.1 (s, broad). IR (nujol), ν/cm-1: 1571m,
1324m, 1278w, 1232w, 1180w, 1150w, 1114w, 1090m, 1020m, 899s,
816m, 795m, 741s, 698s, 680s, 496m.
Thermal Rearrangement of 1. A solution of 1 (1.00 g) in
toluene (10 mL) was heated under a vacuum for 1 h at 130 °C.
The resulting solution was cooled to room temperature and then
kept overnight at 0 °C. Pale yellow crystals of 2 were filtered and
dried in a vacuum. Yield: 0.90 g (90%). Anal. Calcd for C33H27-
N3P2,%: C, 75.13; H, 5.16; P, 11.74. Found, %: C, 75.08; H,
5.19; P, 11.67. 1H NMR (CDCl3, 300 K) δ (ppm): 8.76 (dd, 1H,
3JHH = 4.2 Hz, 4JHH = 1.7 Hz; 8.00 (dd, 1H, 3JHH = 8.3 Hz,
4JHH = 1.7 Hz); 7.9-6.8 (m, 25H, Ph, quinolyl and NH2
protons). 31P{1H} NMR (CDCl3, 300 K), δ (ppm): 44.5 (d, JP,P
=
Conclusion
104 Hz), 27.3 (d, JP,P = 104 Hz). Note, 2 reacts with CDCl3 for a
:
3435m, 3226m (NH2), 1601w, 1577m, 1150 (PdN-P, s, wide),
1107sh, 1026w, 997w, 861w, 825m, 797w, 733sh, 720s, 695s,
635m, 534m.
In summary, we report the unique properties of diphos-
phinohydrazide ligand (1) bearing an 8-quinolyl substituent,
which demonstrates three types of isomeric transformations.
These are (1) migration of the [Ph2PNPPh2] block to the
nearest carbon atom of the quinolyl fragment under heating
or under the action of LiN(SiMe3)2, (2) migration of the Ph2P
group to another one to form iminodiphosphine upon
protonation of 1, and (3) migration and insertion of a Ph2P
group into the N-N bond proceeding in the Zn(II) coordi-
nation sphere. The last transformation gave binuclear zinc
complex 4 eventually, which shows strong electronic emission
in CH2Cl2 solution at 510 nm (j = 0.45). Compound 2 may
be considered as a new ligand, bearing two chelate rings of
different functionality, that may be useful for the design of
heterobimetallic complexes.
few days to give a mixture of products. IR (nujol), ν/cm-1
Interaction of 1 with (Me3Si)2NLi in a Ratio of 1:1. A solution
of (Me3Si)2NLi (0.50 g, 3.0 mmol) in 10 mL of toluene was
added to a solution of 1 (1.58 g, 3.0 mmol) in 10 mL of the same
solvent. After the mixture was kept at room temperature for 3 h,
0.5 mL of Et2O was charged into the system via syringe, and the
crystallization was initiated. The mixture was left undisturbed
for a few hours, and bright yellow crystals formed. 31P{1H}
NMR (THF, 300 K), δ (ppm): 41.7 (d, JP,P = 115 Hz), 22.7 (d,
J
P,P = 115 Hz). IR(nujol), ν/cm-1: 3438w, 3333w, 1583 m, 1530 m,
1496 m, 1400 m, 1300 m, 1260 m, 1240 m, 1110s, 1060s, 870 m,
800 m, 740s, 695s, 645 m. Note that using THF in this reaction is
not possible since the equilibrium in this case is shifted to the red
lithium salt 3.
Acknowledgment. This work was supported by The
Russian President’s program “Leading Scientific Schools”
(No. 4182.2008.3). We thank Dr. O. V. Kouznetsova and
N. M. Khamaletdinova for IR measurements.
Interaction of 3 with ZnI2 in a Ratio of 1:1. A solution of ZnI2
(0.67 g, 2.1 mmol) in 10 mL of THF was added to a solution of 3
(2.0 mmol, prepared from 1.05 g of 1 and 2.0 mL of 1.0 M
n-BuLi) in 15 mL of the same solvent at -20 °C. The reaction
mixture was stirred for 6 h and then concentrated to 10 mL.
Allowing the mixture to set at room temperature for a week
afforded the product as yellow fine crystals. Yield: 0.72 g (50%).
Anal. Calcd for C66H52I2N6P4Zn2 (4): C, 55.14; H, 3.65; I, 17.65;
N, 5.85. Found, %: C, 55.20; H, 3.69; N, 5.93. 31P{1H} NMR
Supporting Information Available: Crystallographic informa-
tion for 1, 2, 4, and 6 in CIF format; molecular structure,
selected bond lengths and angles, and NBO charges for 1;
HOMO and LUMO view for 4; electronic emission and excita-
tion spectra of 2; and B3LYP calculated structures of the
protonated molecules 5a and 5b. This material is available free
of charge via the Internet at http://pubs.acs.org.
(CH2Cl2), 300 K), δ (ppm): 23.8 (s), 3.5 (s). IR (nujol), ν/cm-1
:
1576w, 1500w, 1313m, 1297m, 1260s, 1192w, 1131s, 963m,
870m, 822m, 777m, 746m, 697m, 548m, 530m. Single crystals