Synthesis of aminoiminophosphoranate complexes of palladium and platinum and X-ray diffractional investigation of the weak C-H ... Pd interactions affecting the geometry of the PdNPN metallacycles

Article abstract of DOI:10.1021/om900185r

New aminoiminophosphoranate (κ²-(N,N)-(NC ₆H₄i-Pr-p)₂PPh₂, NPN) complexes (NPN)Pd(PPh₃)Cl, (NPN)₂Pd, (NPN)Pt(η²- C₂H₄)Cl, and (NPN)Pt(PPh₃

Full text of DOI:10.1021/om900185r

Organometallics 2009, 28, 3021–3028
3021
Synthesis of Aminoiminophosphoranate Complexes of Palladium
and Platinum and X-ray Diffractional Investigation of the Weak
C-H · · · Pd Interactions Affecting the Geometry of the PdNPN
Metallacycles
Tat’yana A. Peganova, Anna V. Valyaeva, Alexander M. Kalsin,* Pavel V. Petrovskii,
Alexandra O. Borissova, Konstantin A. Lyssenko, and Nikolai A. Ustynyuk*
A. N. NesmeyanoV Institute of Organoelement Compounds, Russian Academy of Sciences,
28 VaViloV Street, GSP-1, B-334, 119991 Moscow, Russian Federation
ReceiVed March 10, 2009
New aminoiminophosphoranate (κ2-(N,N)-(NC6H4i-Pr-p)2PPh2, NPN) complexes (NPN)Pd(PPh3)Cl,
(NPN)2Pd, (NPN)Pt(η2-C2H4)Cl, and (NPN)Pt(PPh3)Cl were prepared in high yields from anionic [NPN]Li
and the corresponding transition metal chloride precursors. Reaction of (PhCN)2PdCl2 with aminoimi-
nophosphorane [NPN]H afforded bis-imino complex Pd{[NPN]H}2Cl2 in 82% yield. X-ray structures of
all palladium complexes were reported, and the specific weak interactions C-H · · · Pd were detected in
the crystals of both (NPN)Pd(PPh3)Cl (intramolecular) and (NPN)2Pd (intermolecular). The topological
analysis of electron density function F(r) within the AIM theory performed for (NPN)2Pd allowed us to
analyze the peculiarities of the chemical bonding of the NPN ligand and to estimate the energy of the
intermolecular C-H · · · Pd interaction as 0.8 kcal/mol. The plausible influence of these weak interactions
on the bending of the PdNPN metallacycle was discussed.
Chart 1
Introduction
During last 15-20 years the interest in complexes of
transition metals and lanthanides with chelating NNN (triaz-
enide), NCN (amidinate), and NPN (aminoiminophosphoranate)
ligands (Chart 1) has been growing considerably in light of their
versatile applications in homogeneous catalysis.1 Among these
types of compounds the coordination chemistry of amidinate
complexes has been mostly developed,2 whereas aminoimino-
phosphoranate complexes remain far less studied, though the
application of such systems as precatalysts for alkene cyclo-
propanation3 and polymerization4 is well recognized. Some
representative examples of aminoiminophosphoranate complexes
are known for metals of each row of the periodic table, but
systematic investigations of their structure and reactivity have
never been carried out. Particularly, scarce information is
available for NPN complexes of late transition metals: several
complexes of copper,3a-c,5 cobalt,6 and nickel4a,e,6 and only
single examples of ruthenium,7 palladium,4a and platinum8
compounds were reported.
Analysis of the aminoiminophosphoranate complexes
reported to date can provide some information on their
structural features: longer P-N bonds (average 1.60 Å)
compared to C-N bonds in amidinate complexes (average
1.33 Å) cause the increase of the natural bite angle N-M-N
(ca. 70° for aminoiminophosphoranate complexes vs ca. 64°
for amidinate). As a result, aminoiminophosphoranate ligands
are typically coordinated to the metal atom in chelate mode
(only one example of the bridging coordination was reported
* To whom correspondence should be addressed. E-mail: ustynyuk@
ineos.ac.ru, kalsin@ineos.ac.ru. Fax: +7-499-135-01-76.
(1) (a) Trost, B. M.; Van Vranken, D. L. Chem. ReV. 1996, 96, 395. (b)
Witt, M.; Roesky, H. W. Chem. ReV. 1994, 94, 1163. (c) Gibson, V. C.;
Spitzmesser, S. K. Chem. ReV. 2003, 103, 283.
(2) (a) Barker, J.; Kilner, M. Coord. Chem. ReV. 1994, 133, 219. (b)
Edelmann, F. T. Coord. Chem. ReV. 1994, 137, 403. (c) Nagashima, H.;
Kondo, H.; Hayashida, T.; Yamaguchi, Y.; Gondo, M.; Masuda, S.;
Miyazaki, K.; Matsubara, K.; Kirchner, K. Coord. Chem. ReV. 2003, 245,
177. (d) Kissounko, D. A.; Zabalov, M. V.; Brusova, G. P.; Lemenovskii,
D. A. Russ. Chem. ReV. 2006, 75, 351.
(3) (a) Straub, B. F.; Hofmann, P. Angew. Chem., Int. Ed. Engl. 2001,
40, 1288. (b) Straub, B. F.; Rominger, F.; Hofmann, P. Organometallics
2000, 19, 4305. (c) Shishkov, I. V.; Rominger, F.; Hofmann, P. Organo-
metallics 2009, 28, 1049. (d) Straub, B. F.; Gruber, I.; Rominger, F.;
Hofmann, P. J. Organomet. Chem. 2003, 684, 124.
(4) (a) Keim, W.; Appel, R.; Storeck, A.; Kru¨ger, C.; Goddard, R.
Angew. Chem., Int. Ed. Engl. 1981, 20, 116. (b) Mo¨hring, V. M.; Fink, G.
Angew. Chem., Int. Ed. Engl. 1985, 24, 1001. (c) Schubbe, R.; Angermund,
K.; Fink, G.; Goddard, R. Macromol. Chem. Phys. 1995, 196, 467. (d)
Vollmerhaus, R.; Shao, P.; Taylor, N. J.; Collins, S. Organometallics 1999,
18, 2731. (e) Stapleton, R. L.; Chai, J.; Taylor, N. J.; Collins, S.
Organometallics 2006, 25, 2514. (f) Tomaszewski, R.; Vollmerhaus, R.;
Al-Humydi, A.; Wang, Q.; Taylor, N. J.; Collins, S. Can. J. Chem. 2006,
84, 214. (g) Collins, S.; Ziegler, T. Organometallics 2007, 26, 6612.
(5) (a) Straub, B. F.; Eisentra¨ger, F.; Hofmann, P. Chem. Commun. 1999,
2507. (b) Straub, B. F.; Rominger, F.; Hofmann, P. Chem. Commun. 2000,
1611. (c) Ackermann, H.; Bock, O.; Mu¨ller, U.; Dehnike, K. Z. Anorg.
Allg. Chem. 2000, 626, 1854.
(6) (a) Fenske, D.; Maczek, B.; Maczek, K. Z. Anorg. Allg. Chem. 1997,
623, 1113. (b) Boese, R.; Du¨ppmann, M.; Kuchen, W.; Peters, W. Z. Anorg.
Allg. Chem. 1998, 624, 837. (c) Fedotova, Y. V.; Kornev, A. N.; Sushev,
V V.; Kursky, Y. 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.
(7) Bailey, P. J.; Grant, K. J.; Parsons, S. Organometallics 1998, 17,
551.
(8) Scherer, O. J.; Nahrstedt, A. Angew. Chem., Int. Ed. Engl. 1979,
18, 234.
10.1021/om900185r CCC: $40.75
2009 American Chemical Society
Publication on Web 04/20/2009

3022 Organometallics, Vol. 28, No. 10, 2009
PeganoVa et al.
for [Cu{Ph2P(NSiMe3)2}]25c), which is in sharp contrast with
amidinate complexes of late transition metals. Amidinate ligands
Scheme 1
display either a chelating (for example for Ru complexes9a,b
)
or bridging mode of coordination (characteristic for Pd and Pt
complexes10), and even mixed mode in the case of dimeric
complex Pd2(dpb)4 (dpb ) N,N′-diphenylbenzamidinate), con-
taining two chelate and two bridging dpb ligands.10c It is also
noteworthy that the geometry of the MNCN metallacycle in
some chelating amidinate complexes is considerably nonplanar,
with the strongest bending up to ca. 50° (the dihedral angle
between NMN and NCN planes) observed for complexes having
additional π-coordination of the NCN ligand with the metal
atom.9 In contrast, the geometry of the MNPN metallacycle in
aminoiminophosphoranate complexes reported to date is usually
slightly nonplanar with the dihedral angle between NMN and
NPN planes rarely reaching ca. 15°.4e,6b,7,11 Several attempts
were made to explain the reason for such distortion for
complexes of alkaline earth metals (interaction of M2+ cations
with delocalized π-electron density of the NPN ligand11a),
zirconium (trans-annular influence of the substituents and great
strength of the crystal field11b), and ruthenium (partial contribu-
tion of the π-pseudoallyl bonding between NPN ligand and
metal7). All of these suggestions were based on the similarity
of the amidinate and aminoiminophosphoranate ligands, but the
contribution of delocalized π-electron density into the structure
of NPN ligands is rather doubtful and speculative.12
Results and Discussion
Diaminophosphonium salts [R2P(NHR′)2]+X- usually serve
as versatile starting compounds for the synthesis of NPN
complexes4e,6b,8 because their stepwise deprotonation leads
consecutively to the corresponding aminoiminophosphorane
R2P(NHR′)(NR′) and lithium aminoiminophosphoranate
[R2P(NR′)2]Li, which are direct precursors for creating an
aminoiminophosphoranate ligand framework.14 We have re-
ported recently a convenient method for the synthesis of the
di(arylamino)phosphonium salts based on direct aminolysis of
diphenyltrihalophosphorane with substituted anilines,15 thus
providing access to many NPN ligands with various electron-
withdrawing and electron-releasing properties. In this paper we
used diaminophosphonium salt [Ph2P(NHC6H4i-Pr-p)2]+Br- (1),
containing para-isopropyl groups, to increase the solubility of
the resulting aminoiminophosphoranate complexes. Deproto-
nation of 1 with 1 equiv of n-BuLi or Et3N leads smoothly to
the corresponding aminoiminophosphorane [Ph2P(NHC6H4i-Pr-
p)(NC6H4i-Pr-p)] (2) (Scheme 1).
Thus at present no systematic studies on electronic properties
of the NPN ligands and their complexes have been ac-
complished, which makes it impossible to unravel the factors
affecting the bending of the MNPN cycle and the influence of
the NPN ligand flexibility on catalytic properties of their
complexes. At the same time the ability of aminoiminophos-
phoranate ligands to stabilize coordinatively unsaturated species7,13
owing to their high σ- and π-donor properties5a is well
documented, demonstrating clearly the importance of further
investigations in this area.
In the 31P NMR the phosphorus resonance in 2 (-4.75 ppm)
is shifted downfield compared to that of diaminophosphonium
salt 1 (26.6 ppm). Analogously, all proton resonances in 2 are
downfield shifted (by 0.2-0.4 ppm compared to 1), obviously
due to the decrease of the positive charge at the phosphorus
atom. The full equivalency of the aryl substituents in 2 together
1
with the absence of a NH signal in the H NMR assumes that
fast proton exchange between amino- and imino-nitrogen atoms
occurs in solution at room temperature.16
Here we began a systematic study of electronic and structural
properties of aminoiminophosphoranate complexes of platinum
group metals. In this article we present the synthesis of novel
NPN complexes of palladium and platinum, the structural study
of three palladium complexes by X-ray diffraction and deter-
mination of the influence of the ligand environment on the extent
of distortion of the NPNM metallacycles. Square-planar com-
plexes of Pd(II) and Pt(II) are fully coordinatively saturated and
have a formal d8 electron configuration, meaning that the NPN
ligands in them act exclusively as 4 e donors, and therefore all
possible distortions of the MNPN fragments are produced only
by the nature of the auxiliary ligands.
Aminoiminophosphoranate complexes 4-8 were prepared by
the replacement of the chloride ligand in the transition metal
precursor with anionic lithium aminoiminophosphoranate 3,
generated in situ by deprotonation of 1 or 2 with an appropriate
quantity of n-BuLi.17
Reaction of [Ph2P(NC6H4i-Pr-p)2]-Li+ (3) with Zeise’s salt
dimer [Pt(η2-C2H4)Cl(µ-Cl)]2 leads to NPN platinum ethylene
complex 4 in high yield (Scheme 2). Importantly, the lithium
salt 3 should be prepared strictly from the pure aminoimino-
phosphorane 2, not from the diaminophosphonium salt 1. In
the latter case the presence of LiBr in the reaction mixture
caused the formation of the inseparable mixture of chloro- and
bromo-substituted platinum complexes 4 and 4′ (ratio 1:3).
The substitution of one of two chloride ligands in dimeric
complexes [M(PPh3)Cl(µ-Cl)]2 (M ) Pd, Pt) proceeds analo-
(9) (a) Yamaguchi, Y.; Nagashima, H. Organometallics 2000, 19, 725.
(b) Hayashida, T.; Yamaguchi, Y.; Kirchner, K.; Nagashima, H. Chem. Lett.
2001, 30, 954. (c) Terasawa, J.; Kondo, H.; Matsumoto, T.; Kirchner, K.;
Motoyama, Y.; Nagashima, H. Organometallics 2005, 24, 2713.
(10) (a) Singhal, A.; Jain, V. K.; Nethaji, M.; Samuelson, A. G.;
Jayaprakash, D.; Butcher, R. J. Polyhedron 1998, 17, 3531. (b) Edelmann,
F. T.; Ziegler, W.; Behrens, U. J. Organomet. Chem. 1992, 426, 261. (c)
Yao, C. L.; He, L. P.; Korp, J. D.; Bear, J. L. Inorg. Chem. 1988, 27, 4389.
(11) (a) Fleischer, R.; Stalke, D. Inorg. Chem. 1997, 36, 2413. (b)
Chernega, A. N.; Antipin, M.; Struchkov, Yu. T.; Boldeskul, I. E.; Shul’gin,
V. F.; Romanenko, V. D. Ukranian J. Chem. 1986, 52, 327. (c) Vollmerhaus,
R.; Tomaszewski, R.; Shao, P.; Taylor, N. J.; Wiacek, K. J.; Lewis, S. P.;
Al-Humydi, A.; Collins, S. Organometallics 2005, 24, 494.
(14) Du¨ppmann, M.; Kuchen, W.; Peters, W. Phosphorus, Sulfur, Silicon
Relat. Elem. 1997, 129, 53.
(15) Gusev, O. V.; Peganova, T. A.; Gonchar, A. V.; Petrovskii, P. V.;
Lyssenko, K. A.; Ustynyuk, N. A. Phosphorus, Sulfur, Silicon Relat. Elem.
2009, 184, 322.
(16) Scherer, O. J.; Klusmann, P. Z. Anorg. Allg. Chem. 1969, 370, 171.
(17) Separately, the reaction of 1 (δ 27.0 in CD3OD) and 2 (δ-9.0 in
C6D6) with n-BuLi in diethyl ether and benzene was monitored by 31P NMR
using 85% H3PO4 in D2O as an external standard. It completes in 1 h at
room temperature in diethyl ether or in 2 h at 50 °C in benzene to give 3
(δ 8.2 in Et2O and δ 24.0 in benzene). The registered chemical shifts for
3 correspond well to the reported lithium aminoiminophosphoranates,14 i.e.,
upfield shifted compared to diaminophosphonium salt 1 and downfield
shifted compared to aminoiminophosphorane 2.
(12) (a) Kocher, N.; Leusser, D.; Murso, A.; Stalke, D. Chem.sEur. J.
2004, 10, 3622. (b) Chaplin, A. B.; Harrison, A. J.; Dyson, P. J. Inorg.
Chem. 2005, 44, 8407.
(13) Scherer, O. J.; Kerth, J.; Sheldrick, W. S. Angew. Chem., Int. Ed.
Engl. 1984, 23, 156.

Aminoiminophosphoranate Complexes of Pd and Pt
Organometallics, Vol. 28, No. 10, 2009 3023
Scheme 2
substituents at the phosphorus atom and two different sets of
signals belonging to the coordinated and noncoordinated
nitrogen fragments. It is noteworthy that the signal of the NH
proton observed is broad probably due to the formation of
intramolecular hydrogen bonding with the chloride ligand.
X-ray Diffractional Study. Palladium complexes 5, 7, and
8 have been crystallographically characterized to provide
valuable structural information on the geometry of these
complexes in the solid state, particularly on correlation between
the geometry of the coordinated NPN ligand and the secondary
interactions with the co-ligands. The structures of complexes
5, 7, and 8 are shown in Figures 1-3, respectively; the main
bond lengths and angles are given in Table 3.
Scheme 3
In the crystal of 8 the palladium atom is bound to two chloride
ions and two monodentate aminoiminophosphorane ligands. In
crystalline 8 the molecule occupies a special position with the
inversion center coinciding with the palladium atom. The P-N
bonds in 8 significantly differ with pronounced elongation of
the uncoordinated one (1.597(2) vs 1.667(2) Å). The nitrogen
atoms in 8 are almost planar, with the N(1) atom being slightly
pyramidalizied (the sum of bond angles including N(1) is
357.1(2)°). The additional stabilization of complex 8 is attained
by the intramolecular N-H · · · Cl hydrogen bond (N(2) · · · Cl
3.138(2) Å, H(2N) · · · Cl(1) 2.17 Å, NHCl 152°), leading to the
formation of a six-membered cycle.
Scheme 4
In complexes 5 and 7 aminoiminophosphoranate serves as a
bidentante ligand (Figures 2 and 3, respectively). The Pd-N
bond lengths vary in the narrow range of 2.054(2)-2.0604(6)
Å, with the only exception of Pd(1)-N(2) (2.146(2) Å) in
complex 5. The latter increased value can be attributed to the
trans-effect of the PPh3 ligand. The interesting geometrical
feature of both complexes is the significant difference in the
nitrogen atoms’ configuration, one of the nitrogen atoms being
almost planar (∑N1 is 357.24(4)-359.9(1)°), while the other one
is significantly pyramidalized (∑N2 is 347.9(1)-350.57(4)°). In
the crystal of 7 the molecule is centrosymmetric; hence the
above variation of nitrogen atom configuration is not due to a
trans-effect. Furthermore, the degree of pyramidalization cannot
be related to the conjugation with the aryl substituent. Indeed,
in the crystal of 5 the maximum overlap of the electron lone
pair of the N atom with the π-system of the aryl group according
to the PNCC torsion angle is observed for the pyramidalized
N(2) (ca. 17°) atom rather than for the flat N(1) (ca. 50°).
Moreover, the P-N bond lengths in each complex are inde-
pendent of the nitrogen atom configuration and nature of the
trans-substituent in the case of 5.
gously, affording monomeric complexes 5 and 6 with a chelating
NPN ligand in more than 90% yield (Scheme 3).
This method can be efficiently applied to the preparation of
the bis-chelate NPN derivatives, which was demonstrated for
the palladium complex 7 (Scheme 4). It is noteworthy that
in the absence of base or on using a base of insufficient strength
(for example, Et3N instead of n-BuLi) aminoiminophsphorane
2 undergoes only monodentate coordination to the palladium
atom via the imine group and the bis-imino complex 8 was
isolated in 80% yield (Scheme 4). This compound cannot be
transformed to bis-chelate NPN complex 5 in the absence of
n-BuLi even at elevated temperatures. Its stability toward
deprotonation is probably caused by strong intramolecular
hydrogen bonding between amine protons and chloride ligands,
clearly shown in the solid state by X-ray diffraction (see below).
NMR spectroscopy data of complexes 4-8 are presented in
Tables 1 and 2. Complexes 4-6 contain equivalent phenyl
groups at the phosphorus atom and nonequivalent aryl substit-
uents at the nitrogen atoms, clearly indicating the presence of
a MNPN plane of symmetry. Characteristic satellite signals with
isotope 195Pt were observed in 31P and 13C NMR spectra of
platinum complexes 4 (2JP-Pt ) 252 Hz, 1JC-Pt ) 118 Hz) and
In both complexes 5 and 7 the PdNPN cycles deviate from
planarity. The bending of the PdNPN cycle, described by the
dihedral angle between Pd(1)N(1)N(2) and P(1)N(1)N(2) planes,
is equal to 23.4(1)° and 5.23(7)° in 5 and 7, respectively.
Although the nature of the bending of the MNPN metallacycle
in aminoiminophosphoranate complexes has not been specified
so far, the weak C-H · · · Pd intramolecular interactions appeared
to be responsible for this effect in 5.
2
6 (1JP-Pt ) 3996 Hz, JP-Pt ) 234 Hz). The presence of a η2-
Analysis of intramolecular interactions in complex 5 has
revealed the presence of two types of interactions, i.e.,
C(23)H(23) · · · Cl(1) (H · · · Cl 2.53 Å, CHCl 140°) and two
C-H · · · Pd (both H(42A) · · · Pd and H(6A) · · · Pd distances are
2.87 Å with the angles CHPd 118° and 130°, respectively). At
least C-H · · · Cl contacts may be rather strong, and according
to a recent investigation of the trimeric palladium complex, in
which similar intramolecular C-H · · · Cl contacts (H · · · Cl
∼2.72 Å, CHCl 112°) are present, their energies can be as much
coordinated ethylene ligand was confirmed by characteristic
broad singlets in the 1H (δ 4.06) and 13C (δ 64.4) NMR spectra,
demonstrating free rotation of the ligand at room temperature.
Similar observations (inequivalence of the N-substituents of the
NPN ligand and rotation of the η2-ethylene ligand) were found
earlier for platinum complex [(η2-C2H4)Pt{Me2P(NMe)2}Cl].8
Highly symmetric complex 7 displays in NMR spectra only
one type of phenyl and aryl rings. NMR spectra of bis-imino
complex 8 show the presence of two equivalent phenyl

3024 Organometallics, Vol. 28, No. 10, 2009
PeganoVa et al.
Table 1. 1H and 31P NMR Spectra of Complexes 4-8 (CDCl3, δ)a
1H NMR
complex
Ph
C6H4
Pri
L
31P NMR
4
7.87 (dd, J ) 11.8, J )
7.4, 4H, o-H) 7.62 (t, J
) 7.4, 2H, p-H) 7.48
(td, J ) 7.4, J ) 2.8,
4H, m-H)
7.74 (ddd, J ) 11.3, J )
7.7, J ) 1.4, 4H, o-H)
7.46 (td, J ) 7.5, J )
1.4, 2H, p-H) 7.34 (td,
J ) 7.7, J ) 2.7, 4H,
m-H)
7.77 (ddd, J ) 11.5, J )
7.7, J ) 1.3, 4H, o-H)
7.48 (td, J ) 7.5, J )
1.4, 2H, p-H) 7.36 (td,
J ) 7.5, J ) 2.7, 4H,
m-H)
6.96 (d, J ) 8.3, 2H)
6.88 (d, J ) 8.3, 2H)
6.83 (d, J ) 8.1, 2H)
6.54 (dd, J ) 8.1, J )
1.5, 2H)
6.98 (d, J ) 8.4, 2H)
6.80 (d, J ) 8.4, 2H)
6.18 (d, J ) 8.3, 4H)
6.17 (d, J ) 8.3, 4H)
2.72 (hept, J ) 6.9, 1H,
CH) 2.70 (hept, J )
6.8, 1H, CH) 1.11 (d, J
) 6.9, 6H, Me) 1.09
(d, J ) 6.8, 6H, Me)
2.68 (hept, J ) 6.8, 1H,
CH) 2.44 (hept, J )
6.8, 1H, CH) 1.09 (d, J
) 6.8, 6H, Me) 0.94
(d, J ) 6.8, 6H, Me)
3.82 (br s, 4H, C2H4)
73.7 (JPPt ) 252)
5
6
7.70 (ddd, J ) 11.6, J )
7.7, J ) 1.3, 6H, o-H)
7.32 (td, J ) 7.4, J )
1.4, 3H, p-H) 7.23 (td,
J ) 7.6, J ) 2.3, 6H,
m-H)
7.72 (ddd, J ) 11.6, J )
7.7, J ) 1.5, 6H, o-H)
7.28 (td, J ) 7.7, J )
1.4, 3H, p-H) 7.22 (td,
J ) 7.7, J ) 2.3, 6H,
m-H)
26.5 (s, PPh3) 57.5
(s, PPh2)
7.02 (dd, J ) 8.4, J )
1.3, 2H) 6.82 (d, J )
8.2, 2H) 6.26 (dd, J )
8.4, J ) 2.3, 2H) 6.17
(d, J ) 8.2, 2H)
2.69 (hept, J ) 6.8, 1H,
CH) 2.43 (hept, J )
6.8, 1H, CH) 1.09 (d, J
) 6.8, 6H, Me) 0.93
(d, J ) 6.8, 6H, Me)
2.6 (JPPt ) 3996, PPh3)
66.1 (JPPt ) 234, PPh2)
7b
8
8.17 (m, 8H, o-H) 7.07
(m, 12H, m-H + p-H)
7.15 (d, J ) 8.1, 8H)
6.71 (d, J ) 8.1, 8H)
2.59 (hept, J ) 6.9, 4H,
CH) 1.08 (d, J ) 6.9,
24H, Me)
2.72 (hept, J ) 6.7, 2H,
CH) 2.73 (hept, J )
6.7, 2H, CH) 1.17 (d, J
) 6.7, 12H, Me) 1.15
(d, J ) 6.7, 12H, Me)
54.0
26.4
7.81 (dd, J ) 12.6, J )
7.5, 8H, o-H) 7.41 (t, J
) 7.6, 4H, p-H) 7.24
(dd, J ) 7.6, J ) 3.5,
8H, m-H)
7.04 (d, J ) 8.3, 4H)
6.82 (d, J ) 8.5, 4H)
6.71 (d, J ) 8.3, 4H)
6.47 (d, J ) 8.5, 4H)
7.39 (br s., 2H, NH)
a J constants are given in Hz. b Spectra of 7 were registered in C6D6.
as 1.4-2.1 kcal/mol.18 Furthermore, the stabilizing role of the
above Pd · · · H contacts may be indirectly proved by the fact
that both phosphorus atoms (P(1) and P(2)) in 5 deviate by 0.42
and 0.20 Å from the Pd(1)Cl(1)N(1)N(2) plane toward the above
shortened contacts (Figure 2). The pyramidalization of the N(2)
in 5 can be then a secondary effect caused by the necessity to
decrease conjugation between an occupied π-orbital of N(2) and
the π-system of the aryl group to enhance the positive charge
at H(23A), to make the C-H · · · Cl interaction stronger. It is
noteworthy that similar C-H · · · Ni contacts of 2.81Å (angle
C-H-Ni is 121°) of the ortho-H of the triphenylphosphine
ligand were reported for the complex [Ni{PPh2(NSiMe3)2}Ph-
(PPh3)]; however such interaction alone did not induce signifi-
cant bending of the NiNPN plane (3.5°).4e
In the crystal of 7, instead of intramolecular C-H · · · Pd
contacts, there are two symmetrically equivalent intermolecular
Pd(1) · · · H(10A) interactions (Pd(1) · · · H(10A) 2.76 Å, C(10)-
H(10A)Pd 144°). These interactions do not affect much the
bending of the PdNPN cycle, perhaps because of the mutual
compensation (Figure 4).
in pincer palladium complexes18,19 and can be attributed to 4d-
orbitals of the palladium atom. Both the Pd-N bonds are “peak
to hole” type interactions; that is, the electron lone pairs of
nitrogen atoms are directed toward areas of the DED depletion
in the vicinity of the Pd(1) atom (Figure 5).
The topological analysis of the electron density function F(r)
within Bader’s “atoms in molecules” theory (AIM)20 revealed
that Pd-N bonds correspond to the intermediate type of
interactions; the values of the Laplacian of electron density
(32F(r) 10.0 e Å-5) in the corresponding critical points (3, -1)
are positive, while the local energy density (he(r)) is negative
(-0.0409 -0.0309 au). These values as well as those of F(r)
(0.70-0.73 e Å3) in the above critical points (3, -1) in 7 are
close to those recently observed for Pd-N bonds in the [LPdCl]3
trimers (L ) chiral secondary benzylamine).18
As expected, the P-N and P-C bonds in 7 correspond to a
shared type of interatomic interactions with negative values of
32F(r) in their corresponding critical points (3,-1). The values
of ellipticity (ε), which indicates the contribution of the π
component, for all the P-C and P-N bonds in 7, are similar
and close to zero (less than 0.10). They are comparable with ε
values for the N(2)-C(22) bond (0.09), but are significantly
smaller than ε for the N(1)-C(13) (0.2) one. Thus, we may
conclude that the double-bond character of the P-N bonds in
complex 7 is rather negligible, and therefore this bond is better
described as P+-N-, similarly to what was found experimentally
for the lithium picolyliminophosphoranate.12a
Complex 7 was chosen to analyze the peculiarities of
chemical bonding by performing a topological analysis of the
electron density function (F(r)). For the latter good-quality single
crystals were available, and therefore, an accurate determination
of the crystal structure was possible. We wish to note that such
an investigation for aminoiminophosphoranate complexes has
been performed for the first time.
The deformation electron density (DED) maps for the section
containing the metal atom are characterized by expected
features: the significant anisotropy of DED around palladium;
DED accumulation in the vicinity of the nitrogen atoms that
corresponds to their electron lone pairs and that on the covalent
P-N and C-N bonds (Figure 5). The observed DED distribu-
tion around palladium is rather similar to those recently observed
The atomic charges in complex 7 were obtained by integration
of the F(r) function over the atomic basins (Ω). It was found
that nitrogen atoms are characterized by rather high negative
values (-1.42 and -1.52 e). For comparison, the charges of
the nitrogen atom in the gadolinium-coordinated 1,10-phenan-
(19) Kozlov, V. A.; Aleksanyan, D. V.; Nelyubina, Yu. V.; Lyssenko,
K. A.; Gutsul, E. I.; Puntus, L. N.; Vasil’ev, A. A.; Petrovskii, P. V.; Odinets,
I. L. Organometallics 2008, 27, 4062.
(20) Bader, R. F. W. Atoms in Molecules. A Quantum Theory; Oxford:
Clarendron Press, 1990.
(18) Vatsadze, S. Z.; Medved’ko, A. V.; Zyk, N. V.; Maximov, A. L.;
Kurzeev, S. A.; Kazankov, G. M.; Lyssenko, K. A. Organometallics 2009,
28, 1027.

Aminoiminophosphoranate Complexes of Pd and Pt
Organometallics, Vol. 28, No. 10, 2009 3025
Figure 1. ORTEP drawing of 8 (thermal ellipsoids set at the 50%
probability level).
Figure 2. ORTEP drawing of 5 (thermal ellipsoids set at the 50%
probability level).
traline ligand are -1.12 to -0.94 e.21 The positive atomic charge
within the ligand is mainly located on the P(1) atom (1.74 e),
while that of the Pd(1) atom is very small (0.32 e) and is close
to that (0.65 e) observed for the palladium pincer complex in
which Pd is bound to two sulfur atoms, chlorine, and the carbon
atom of the aromatic ring.19
Among the intermolecular contacts in addition to numerous
weak H · · · H and C · · · H ones we can identify the above-
mentioned Pd · · · H interactions; the critical point search unam-
biguously revealed the presence of the latter.
These interactions are weak and characterized by a rather
small value of F(r) (0.038 e Å-3) in the critical point (3, -1).
The analysis of DED in their area revealed that hydrogen atoms
of the phenyl group are directed toward a maximum DED
corresponding to 4d-orbitals of the Pd(1) atom (Figure 6). The
interaction energy for these Pd · · · H contacts was estimated by
(21) Puntus, L. N.; Lyssenko, K. A.; Antipin, M. Yu.; Bu¨nzli, J.-C. G.
Inorg. Chem. 2008, 47, 11095.

3026 Organometallics, Vol. 28, No. 10, 2009
PeganoVa et al.
Figure 4. Fragment of crystal packing of 7 illustrating the formation
of intermolecular C-H · · · Pd contacts with the para-H atom of the
phenyl ring of the other molecule of 7.
Figure 3. ORTEP drawing of 7 (thermal ellipsoids set at the 50%
probability level).
Table 3. Main Geometrical Parameters of Complexes 5, 7, and 8
5
7
8
Pd(1)-N(1)
Pd(1)-N(2)
P(1)-N(1)
P(1)-N(2)
N(1)-C
2.055(2)
2.146(2)
1.631(2)
1.636(2)
1.394(3)
1.425(3)
97.4(1)
2.0604(6)
2.062(6)
2.054(2)
n/a
1.6223 (6)
1.6208(6)
1.3972(8)
1.4074(8)
97.15 (3)
72.30 (2)
5.23(7)
1.597(2)
1.667(2)
1.430(3)
1.417(3)
111.35 (2)
n/a
N(2)-C
N(1)P(1)N(2)
N(1)Pd(1)N(2)
NPN/NPdN
71.51 (8)
23.4(1)
n/a
∑
∑
359.9(1)
347.9(1)
357.24(4)
350.57(4)
357.1(2)
359.8
N1
N2
means of Espinosa’s correlation scheme,22 which according to
various theoretical23 and experimental24 investigations allows
estimating the energy (Econt) for closed-shell interactions with
rather high accuracy. The energy of the Pd · · · H interactions in
7 is equal to 0.8 kcal/mol, which is comparable with that for
the Ru · · · H contacts recently located in the crystal of
rutenocene.25 Although the Pd · · · H interactions are extremely
weak, we have to mention that the energy of two of them, as
observed in the case of 5, reaches ca. 1.5 kcal/mol and even ca.
3.5 kcal/mol taking into account the energy of the C-H · · · Cl
interaction, which can be more than sufficient to stabilize the
nonplanar conformation of the palladacycle.
Figure 5. Deformation electron density distribution in the plane of
the PdNN cycle of 7. The contours are drawn with 0.1 e Å-3
interval; the nonpositive contours are dashed.
Conclusion
In this work we have synthesized new complexes of palladium
and platinum with the aminoiminophosphoranate ligand belong-
ing to the type of compounds poorly described in the literature.
Complexes of palladium with aminoiminophosphorane and
chelating aminoiminophosphoranate ligands were investigated
by X-ray diffraction. It was proposed for the first time that weak
intra- and intermolecular interactions such as C-H · · · Pd can
play an important role in the deviation of MNPN metallacycles
from planarity. The experimental determination of deformational
electron density for bis-chelate palladium complex 7 revealed
low contribution of π-bonding in the P-N bonds, indicating
potential conformational flexibility of the NPN ligand. Also the
energy of the intermolecular interactions C-H · · · Pd in
(NPN)2Pd (7) was estimated to be 0.8 kcal/mol. The experi-
mentally determined high negative charges on the nitrogen atoms
and nonbonding character of their p-orbitals allow one to
consider aminoiminophosphoranates as electronically and con-
formationally tunable ligands for organometallic catalysis.
Additional studies to clarify the influence of electronic and steric
(22) (a) Espinosa, E.; Molins, E.; Lecomte, C. Chem. Phys. Lett. 1998,
285, 170. (b) Espinosa, E.; Alkorta, I.; Rozas, I.; Elguero, J.; Molins, E.
Chem. Phys. Lett. 2001, 336, 457.
(23) (a) Pidko, E. A.; Xu, J.; Mojet, B. L.; Lefferts, L.; Subbotina, I. R.;
Kazansky, V. B.; van Santen, R. A. J. Phys. Chem. B 2006, 110, 22618.
(b) Pidko, E. A.; van Santen, R. A. Chem. Phys. Chem. 2006, 7, 1657.
(24) (a) Lyssenko, K. A.; Nelyubina, Yu. V.; Kostyanovsky, R. G.;
Antipin, M. Yu. Chem. Phys. Chem. 2006, 7, 2453. (b) Lyssenko, K. A.;
Korlyukov, A. A.; Golovanov, D. G.; Ketkov, S. Yu.; Antipin, M. Yu. J.
Phys. Chem. A 2006, 110, 6545. (c) Lyssenko, K. A.; Korlyukov, A. A.;
Antipin, M. Yu. MendeleeV Commun. 2005, 90. (d) Glukhov, I. V.;
Lyssenko, K. A.; Korlyukov, A. A.; Antipin, M. Yu. Faraday Discuss. 2007,
135, 203. (e) Lyssenko, K. A.; Antipin, M. Yu. Russ. Chem. Bull. 2006,
55, 1.
(25) Borissova, A. O.; Antipin, M. Yu.; Perekalin, D. S.; Lyssenko, K. A.
Cryst. Eng. Commun. 2008, 10, 827.

Aminoiminophosphoranate Complexes of Pd and Pt
Organometallics, Vol. 28, No. 10, 2009 3027
and 4′ (75%) according to 1H NMR data. 1H NMR (C6D6) δ: 1.07
(d, J ) 6.9 Hz, 6H, CHMe2), 1.10 (d, J ) 6.8 Hz, 6H, CHMe2),
2.60 (sept, J ) 6.9 Hz, 1H, CHMe2); 2.66 (sept, J ) 6.8 Hz, 1H,
CHMe2), 4.06 (br s, 4H, C2H4), 6.70 (d, J ) 7.0 Hz, 2H, C6H4i-
Pr); 6.81 (d, J ) 8.0 Hz, 2H, C6H4i-Pr); 7.01 (m, 6H, m-H and
p-H, Ph); 7.09 (d, J ) 6.7 Hz, 2H, C6H4i-Pr); 7.54 (d, J ) 7.8 Hz,
2H, i-C6H4Pr); 7.83 (dd, J ) 7.3 Hz, J ) 4.4 Hz, 4H, o-H, Ph). 31
P
NMR (C6D6) δ: 72.59 (s, JPt-P) 236.5 Hz); 72.98 (s, JPt-P) 243.4
Hz).
Synthesis of [Pt{Ph2P(NC6H4i-Pr-p)2}(η2-C2H4)Cl] (4). To a
solution of 2 (0.45 g, 1.0 mmol) in benzene (60 mL) was added a
1.40 M solution of n-BuLi in hexane (0.80 mL, 1.12 mmol), and
the reaction mixture was allowed to stir for 2 h at 50 °C. Then
solid [Pt(η2-C2H4)(µ-Cl)Cl]2 (0.30 g, 0.50 mmol) was added to the
solution, and the reaction mixture was stirred at 50 °C for 2 h. The
reaction mixture was cooled to room temperature and filtered.
The filtrate was evaporated to dryness, and the crude product was
purified by recrystallization from hot hexane, affording 0.59 g (83%)
of 4 as a yellow solid. Anal. Calcd for C32H36ClN2PPt: C, 54.12;
H, 5.07; N, 3.94. Found: C, 54.09; H, 5.11; N, 3.75.
Synthesis of [Pd{Ph2P(NC6H4i-Pr-p)2}(PPh3)Cl] (5). To a
solution of 2 (0.45 g, 1.0 mmol) in benzene (50 mL) was added a
1.98 M solution of n-BuLi in hexane (0.60 mL, 1.10 mmol), and
the reaction mixture was then stirred at 50 °C for 2 h. The solution
was cooled to room temperature, and solid [Pd(PPh3)(µ-Cl)(Cl)]2
(0.44 g, 0.50 mmol) was added. The reaction mixture was stirred
overnight at 20 °C and then filtered; the filtrate was concentrated
to 3 mL and precipitated with 30 mL of hexane. The product was
purified by recrystallization from benzene/hexane, affording 0.78 g
(91%) of 5 as red solid. Anal. Calcd for C48H47ClN2P2Pd: C, 67.36;
H, 5.50; N, 3.27. Found: C, 67.02; H, 5.45; N, 3.17.
Synthesis of [Pt{Ph2P(NC6H4i-Pr-p)2}(PPh3)Cl] (6). To a
solution of 2 (0.27 g, 0.60 mmol) in benzene (30 mL) was added
a 1.98 M solution of n-BuLi in hexane (0.33 mL, 0.65 mmol), and
the reaction mixture was heated at 50 °C for 2 h. The solution was
cooled to room temperature, and solid [Pt(PPh3)(µ-Cl)(Cl)]2 (0.32
g, 0.30 mmol) was added. The reaction mixture was refluxed for
4 h, cooled to room temperature, and filtered. The filtrate was
concentrated to 3 mL and precipitated with 30 mL of hexane. The
product was purified by recrystallization from benzene/hexane,
affording 0.41 g (72%) of 6 as a yellow solid. Anal. Calcd for
C48H47ClN2P2Pt: C, 61.05; H, 4.98; N, 2.97. Found: C, 61.08; H,
5.10; N, 2.86.
Synthesis of [Pd{Ph2P(NC6H4i-Pr-p)2}2] (7). To a suspension
of the phosphonium salt 1 (0.53 g, 1.0 mmol) in Et2O (50 mL)
was added at 20 °C a solution of n-BuLi in hexane (1.45 M, 1.7
mL, 2.5 mmol), and the reaction mixture was stirred for 1.5 h. Then,
a solid of [PdCl2(PhCN)2] (0.19 g, 0.50 mmol) was added, and the
reaction mixture was stirred overnight. The solvent was removed
in Vacuo and the residue was extracted with benzene (3 × 20 mL).
The filtered extract was evaporated to dryness; the product was
purified by recrystallization from hot hexane, affording 0.30 g (60%)
of 7 as red solid. Anal. Calcd for C60H64N4P2Pd: C, 71.39; H, 6.35;
N, 5.55. Found: C, 71.24; H, 6.26; N, 5.61.
Figure 6. 3D distribution of the DED within the C-H · · · PdN4
fragment. Isosurface of the DED equal to 0.40 e A-3 is shown in
red.
properties of aminoiminophosphoranate ligands on the structure
of NPN complexes and their relationship to the catalytic
behavior of the NPN complexes are now in progress.
Experimental Details
All manipulations were carried out using standard Schlenk
techniques under an atmosphere of dry argon. Solvents were purified
1
by standard methods and distilled prior to use. H, 31P, and 13C
NMR spectra were obtained on a Bruker AMX-400 spectrometer
and referenced to the residual signals of the deuterated solvent (1H
and 13C) and to 85% H3PO4 (31P, external standard). Elemental
analyses were performed on a Carlo Erba 1106 CHN analyzer. The
following compounds were prepared according to described meth-
ods: [(η2-C2H4)PtCl(µ-Cl)]2,26 [(Ph3P)PdCl(µ-Cl)]2,27 [(Ph3P)PtCl(µ-
Cl)]2,28 [(PhCN)2PdCl2],29 Ph2P(NHC6H4i-Pr-p)2Br (1).15
Synthesis of Ph2P(NHC6H4i-Pr-p)(NC6H4i-Pr-p) (2). (a) To a
suspension of the diaminophosphonium salt 1 (6.3 g, 11.8 mmol)
in Et2O (200 mL) was added at 20 °C a 1.45 M solution of n-BuLi
in hexane (9.8 mL, 14.2 mmol), and the reaction mixture was stirred
for 2 h. The solvent was removed in Vacuo, and the residue was
extracted with C6H6 (60 mL). The extract was filtered and
concentrated to 20 mL, and the product was precipitated with 50
mL of hexane and dried, affording 5.0 g (94%) of 2 as a white
solid. Anal. Calcd for C30H33N2P: C, 79.62; H, 7.35; N, 6.19. Found:
1
C, 79.39; H, 7.38; N, 6.17. H NMR (CDCl3) δ: 1.17 (d, 12H,
CHMe2, J ) 6.9 Hz); 2.77 (sept, 2H, CHMe2, J ) 6.9 Hz); 6.96 (s,
8H, C6H4Pri); 7.45 (m, 6H, m-H + p-H, Ph); 7.94 (dd, 4H, o-H,
Ph, J ) 12.4 Hz, J ) 6.9 Hz). 31P NMR δ: -4.75 (CDCl3), -9.0
(C6D6).
(b) Analogously, reaction of 1 (0.53 g, 1.0 mmol) with NEt3
(0.11 g, 1.1 mmol) in benzene afforded 0.38 g (84%) of 2.
Synthesis of [Pt{Ph2P(NC6H4i-Pr-p)2}(η2-C2H4)X] (4, X )
Cl; 4′, X ) Br). To a suspension of 1 (1.07 g, 2.0 mmol) in Et2O
(80 mL) was added a 1.40 M solution of n-BuLi in hexane (3.3
mL, 4.6 mmol), and the reaction mixture was stirred at 20 °C for
1.5 h. Then solid [Pt(η2-C2H4)(µ-Cl)Cl]2 (0.59 g, 1.0 mmol) was
added and the reaction mixture was stirred overnight. The solvent
was removed in Vacuo and the residue was extracted with C6H6 (3
× 20 mL). The filtered benzene extract was concentrated until the
product started to crystallize and was precipitated with 50 mL of
hexane to give 0.70 g of a yellow solid, which consisted of 4 (25%)
Synthesis of [Pd{Ph2P(NHC6H4i-Pr-p)(NC6H4i-Pr-p)}2Cl2] (8).
A solution of [PdCl2(PhCN)2] (0.19 g, 0.50 mmol) in benzene (30
mL) was added dropwise to a solution of Ph2P(NHC6H4Pri-
p)(NC6H4i-Pr-p) (0.45 g, 1.0 mmol) in benzene (50 mL) and stirred
at 20 °C overnight. The solvent was removed in Vacuo, and the
residue was washed with methanol (3 × 5 mL) and dried to give
0.44 g (82%) of 8 as red solid. Anal. Calcd for C60H66Cl2N4P2Pd:
C, 66.57; H, 6.10; N, 5.18. Found: C, 66.64; H, 6.28; N, 5.11.
X-ray Crystal Structure Determination. Single crystals of 5,
7, and 8 were obtained by slow diffusion of hexane to a solution
of the complex in dichloromethane (5, 8) or in benzene (7).
Diffraction data for 5 and 8 were taken using a Bruker SMART
1000 CCD diffractometer [λ(Mo KR) ) 0.71072 Å, ω-scans] and
(26) Chatt, J.; Searle, M. L.; Liu, C. F.; Wymore, C. E. Inorg. Synth.
1957, 5, 210.
(27) Chatt, J.; Venanzi, L. M. J. Chem. Soc. 1957, 2351.
(28) Goodfellow, R. J.; Venanzi, L. M. J. Chem. Soc. 1965, 7533.
(29) Doyle, J. R.; Slade, P. E.; Jonassen, H. B. Inorg. Synth. 1960, 6,
218.

3028 Organometallics, Vol. 28, No. 10, 2009
PeganoVa et al.
Table 4. Crystal Data and Structure Refinement Parameters for 5,
7, and 8
with the core and valence electron density derived from wave
functions fitted to a relativistic Dirac-Fock solution. Before the
refinement the C-H bond distances were normalized to ideal values
of 1.08 Å according to neutron data. The level of multipole
expansion was hexadecapole for metal atom and octupole for all
other non-hydrogen atoms. The refinement was carried out against
F and converged to R ) 0.0241, Rw ) 0.0267, and GOF ) 0.8695
(for 22 727 merged reflections with I > 3σ(I)). All bonded pairs
of atoms in the ligand satisfy the Hirshfeld rigid-bond criteria, while
the difference of the mean square displacement amplitude for Pd-N
was 1710-4 Å2).34 The potential energy density V(r) was evaluated
through the Kirzhnits approximation for the kinetic energy density
function g(r).35 Accordingly, the g(r) function is described as (3/
10)(3π2)2/3[F(r)]5/3 + (1/72)|3F(r)|2/F(r) + 1/632F(r), which in
conjunction with the virial theorem (2g(r) + V(r) ) 1/432F(r))20
leads to the expression for V(r) and makes it possible to estimate
the electron energy density he(r). The total electron density function
was positive everywhere, and the maxima of residual electron
density for observed reflections with sin θ/λ > 0.7 were located in
the vicinity of nuclei and were not more than 0.35 e Å-3. Analysis
of topology of the F(r) function was carried out using the WinXPRO
program package.36
5
7
8
formula
T, K
C48H47ClN2P2Pd C60H64N4P2Pd
C60H66Cl2N4P2Pd
298
120
100
fw
855.67
triclinic
P1, 2(1)
1009.49
triclinic
P1, 1(0.5)
1082.41
monoclinic
P21/n
9.363(2)
22.507(5)
13.716(2)
90
98.309(7)
90
2860.2(10)
1128,1.257
cryst syst
space group, Z (Z′)
a (Å)
b (Å)
c (Å)
R (deg)
(deg)
γ (deg)
V (Å3)
j
j
10.314(4)
12.219(4)
18.221(7)
94.734(6)
94.295(7)
114.159(6)
2073.0(13)
884, 1.371
9.3444(2)
11.5954(2)
12.9651(2)
85.553(1)
70.253(1)
79.469(1)
1299.72(4)
528, 1.290
F(000), Dcalc
(g cm-1
)
µ (cm-1
)
6.25
58
22 931
4.61
100
79 234
5.14
56
19 621
2θmax (deg)
reflns measd
indep reflns (Rint
obsd reflns
[I > 2σ(I)]
final R(Fhkl): R1
wR2
)
10 876 (0.0246) 25 522 (0.0314) 6848 (0.0395)
8564
22940
4234
0.0423
0.1035
0.0333
0.0822
0.0456
0.1023
GOF
1.080
0.776/-0.464
0.978
1.504/-0.961
1.028
0.480/-0.299
∆Fmax, ∆Fmin (e Å-3
)
for 7 using a Bruker SMART APEX II CCD diffractometer [λ(Mo
KR) ) 0.71072 Å, ω-scans] (see Table 4). The substantial
redundancy in data allows empirical absorption correction to be
applied using multiple measurements of equivalent reflections with
the SADABS Bruker program.30 The structures were solved by
direct methods and refined by the full-matrix least-squares technique
against F2 in the anisotropic-isotropic approximation. The hydrogen
atoms of the N-H group were located from the Fourier density
synthesis and refined with a riding model, while the positions of
the rest of the hydrogen atoms were calculated from the geometrical
point of view. The analysis of Fourier density synthesis has revealed
that one of the isopropyl groups in 8 is disordered by two positions
with equal occupancies. All calculations were performed using the
SHELXTL software.31 Crystal data and structure refinement
parameters for 5, 7, and 8 are given in Table 4.
Acknowledgment. The authors thank the Russian Foun-
dation for Basic Research (grant nos. 08-03-00086, 09-03-
00603) and the International Science and Technology Center
(grant ISTC G-1361) for financial support.
Supporting Information Available: CIF files for complexes 5,
7, and 8. X-ray data for 5, 7, and 8 have been also deposited with
the Cambridge Crystallographic Data Centre as supplementary
publication numbers CCDC 721726-721728. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM900185R
(33) Volkov, A.; Macchi, P.; Farrugia, L. J.; Gatti, C.; Mallinson, P.;
Richter, T.; Koritsanszky, T. XD2006, A Computer Program Package for
Multipole Refinement, Topological Analysis of Charge Densities and
Evaluation of Intermolecular Energies from Experimental and Theoretical
Structure Factors, 2006.
The multipole refinement of 7 was carried out within the
Hansen-Coppens formalism32 using the XD program package33
(30) Sheldrick, G. M. SADABS; University of Go¨ttingen, 1996.
(31) SHELXTL, version 6.1; Bruker AXS Inc.: Madison, WI, 2005.
(32) Hansen, N. K.; Coppens, P. Acta Crystallogr. 1978, A34, 909.
(34) Hirshfeld, F. L. Acta Crystallogr. 1976, A32, 239.
(35) Kirzhnits., D. A. SoV. Phys. JETP 1957, 5, 54.
(36) Stash, A.; Tsirelson, V. J. Appl. Crystallogr. 2002, 35, 371.