Making and breaking of P-P bonds with low-valent transition-metal complexes

Article abstract of DOI:10.1002/ejic.201001137

The 1:1 or 1:2 stoichiometric reaction of [Na₂(thf) ₄(P₄Mes₄)] (1; Mes = 2,4,6-Me₃C ₆H₂) with [{RhCl(cod)}₂] (cod = 1,5-cyclooctadiene) gave a mixture of compounds of which [Na(thf) ₃][Rh(P₃Mes₃)(cod)] (2) with a trimesityltriphosphane-1,3-diide ligand was structurally characterized. Density functional calculations on 2 confirmed the structural parameters obtained by X-ray diffraction studies. Shared electron number and natural bond orbital analyses indicated only weak interactions between Na and P, which were found to be even weaker than the Na-Rh interactions with covalent contribution. When an excess of 1 was used (3:1 or 4:1), 2 was also obtained as the major product together with small amounts of the side-products cyclo-P₆Mes ₆ (3) and [Na₃(Et₂O)(P₄Mes ₄)(PHMes)]_∞ (4). Compounds 3 and 4 were only characterized by single-crystal X-ray diffraction studies. Their formation indicates that the reaction includes the breaking and making of P-P bonds to give (P₃Mes₃)^2-, PHMes^-, and cyclo-P₆Mes₆, although the mechanism is unclear. Furthermore, the reaction of 1 with 2 equiv. of [AgCl(PPh₃) ₂] gave the tetranuclear compound [Ag₄(P ₆Mes₆)₂] (5) in which the novel (P ₆Mes₆)^2- ion also indicates degradation of the P₄ chain followed by P-P bond formation. Copyright

Full text of DOI:10.1002/ejic.201001137

FULL PAPER
DOI: 10.1002/ejic.201001137
Making and Breaking of P–P Bonds with Low-Valent Transition-Metal
Complexes
Santiago Gómez-Ruiz,[a] René Frank,[a,b] Beatriz Gallego,[a] Stefan Zahn,[b]
Barbara Kirchner,[b] and Evamarie Hey-Hawkins*[a]
Keywords: Metal–metal interactions / P ligands / Rhodium / Silver / Sodium
The 1:1 or 1:2 stoichiometric reaction of [Na2(thf)4(P4Mes4)]
(1; Mes = 2,4,6-Me3C6H2) with [{RhCl(cod)}2] (cod = 1,5-cy-
clooctadiene)gaveamixtureofcompoundsofwhich[Na(thf)3]-
[Rh(P3Mes3)(cod)] (2) with a trimesityltriphosphane-1,3-diide
ligand was structurally characterized. Density functional cal-
culations on 2 confirmed the structural parameters obtained
by X-ray diffraction studies. Shared electron number and
natural bond orbital analyses indicated only weak interac-
tions between Na and P, which were found to be even
weaker than the Na–Rh interactions with covalent contri-
bution. When an excess of 1 was used (3:1 or 4:1), 2 was also
obtained as the major product together with small amounts
of the side-products cyclo-P6Mes6 (3) and [Na3(Et2O)-
(P4Mes4)(PHMes)]ϱ (4). Compounds 3 and 4 were only char-
acterized by single-crystal X-ray diffraction studies. Their
formation indicates that the reaction includes the breaking
and making of P–P bonds to give (P3Mes3)2–, PHMes–, and
cyclo-P6Mes6, although the mechanism is unclear. Further-
more, the reaction of 1 with 2 equiv. of [AgCl(PPh3)2] gave
the tetranuclear compound [Ag4(P6Mes6)2] (5) in which the
novel (P6Mes6)2– ion also indicates degradation of the P4
chain followed by P–P bond formation.
anion by nickel(II) complexes in an intramolecular redox
reaction that gave (diaryldiphosphene)nickel(0) complexes,[2d]
whereas reductive P–P bond cleavage of tetraphenyltetra-
phosphane-1,4-diide by nickel(0) was observed to give the
mixed-metal (s-block/d-block) complexes [Na(Et2O)3][Na3-
Introduction
Alkali-metal oligophosphanediides M2(PnRn) (n = 2–4)[1]
are versatile starting materials in the preparation of phos-
phorus-rich main-group and transition-metal complexes.[2]
The chemistry of tetraaryltetraphosphane-1,4-diides
(P4R4)2– has proved to be as intriguing as that of alkali-
metal cyclo-oligophosphanides.[3] Thus, in addition to the
previously known group 4,[4] nickel,[5] and platinum[6] oligo-
phosphanide complexes, we have observed that the dianions
(P4R4)2– (R = Ph or Mes; Mes = 2,4,6-Me3C6H2) remain
intact in transmetallation reactions with late-transition-
metal halides such as [CuCl(PCyp3)2] (Cyp = cyclo-C5H9)
to give [Cu4(P4Ph4)2(PCyp3)3][2a] or with [PtCl2(L)2] to give
complexes of the type [Pt(P4Mes4)2(L)2] [(L)2 = cod, dppe;
L = CϵNtBu, and CϵNCy; cod = 1,5-cyclooctadiene,
dppe = Ph2PCH2CH2PPh2, and Cy = cyclo-C6H11].[2g] In
addition, in the reaction of Na2(P4Ph4) with [Cp*TaCl4]
(Cp* = C5Me5) tantalum was apparently reduced by the
dianion, and subsequent rearrangement and oxidative
addition gave the (phosphinidene)tantalum(V) complex
[Cp*Ta(Ph)(P6Ph5)].[2b] Furthermore, we observed oxida-
tive P–P bond cleavage of the (P4R4)2– (R = Ph, Mes) di-
(Et2O)2Ni3(μ-P2Ph2)2(P2Ph2)3]
and
[K(pmdeta)]2[Ni-
(P4Ph4)(P2Ph2)] with Ni–Na and Ni–K interactions, respec-
tively.[2f] The analogous protonated alkali-metal tetraaryl-
tetraphosphanides (P4HR4)– (R = Ph, Mes) also displayed
very interesting transmetallation reactions with rhodium(I)
and copper(I) salts, which led to phosphorus-rich complexes
such as [Rh(P4HMes4)(cod)] and [Cu4(P4Ph4)2(PH2Ph)2-
(PCyp3)2].[2e]
Herein we report the preparation of two novel metal
oligophosphanide complexes [Na(thf)3][Rh(P3Mes3)(cod)]
(2) with a trimesityltriphosphane-1,3-diide ligand and
[Ag4(P6Mes6)2] (5) containing two hexamesitylhexaphos-
phane-1,6-diide ligands. Compounds 2 and 5 were obtained
by the reaction of [Na2(thf)4(P4Mes4)] (1) with
[{RhCl(cod)}2] (1:1 or 2:1) and [AgCl(PPh3)2] (1:2), respec-
tively. In addition, the structural characterization of two
side-products obtained in addition to 2, namely, cyclo-
P6Mes6 (3) and [Na3(Et2O)(P4Mes4)(PHMes)]ϱ (4), is also
described.
[a] Institut für Anorganische Chemie, Universität Leipzig,
Johannisallee 29, 04103 Leipzig, Germany
Fax: +49-341-9739319
Results and Discussion
Reactions of [Na2(thf)4(P4Mes4)] (1) with [{RhCl(cod)}2] in
Ratios of 1:1 and 2:1
E-mail: hey@rz.uni-leipzig.de
[b] Wilhelm-Ostwald Institut für Physikalische und Theoretische
Chemie, Universität Leipzig,
Linnestr. 2, 04103 Leipzig, Germany
[Na(thf)3][Rh(P3Mes3)(cod)] (2) was obtained as the
major product in the mixtures obtained from the reaction
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201001137.
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E. Hey-Hawkins et al.
FULL PAPER
Scheme 1.
of 1 or 2 equiv. of [Na2(thf)4(P4Mes4)] (1) with 1 equiv. of discussed. The rhodium atom is coordinated in a distorted
[{RhCl(cod)}2] (Scheme 1). Crystals of 2 were obtained square-planar geometry by an η4-cod ligand and a chelating
from thf in low yield and were always contaminated with (P3Mes3)2– ligand, which coordinates through the two ter-
[Rh(P4HMes4)(cod)] and [Rh2(μ-P2HMes2)(μ-PHMes)- minal phosphorus atoms (P1 and P3, Figure 1). The Rh1–
(cod)2],[2e] which were also observed in the reaction mix- P1 and Rh1–P3 bond lengths in
2 [232.9(2) and
tures by 31P NMR spectroscopy. The ratio of 2, 231.5(1) pm] are similar to those observed in [Rh(P4-
[Rh(P4HMes4)(cod)], and [Rh2(μ-P2HMes2)(μ-PHMes)- HMes4)(cod)][2e] and [Rh{cyclo-(P5tBu4)}(PPh3)2].[3b] One
(cod)2][2e] in the mixtures depended on the stoichiometry. of the two negative charges of the trimesityltriphosphane-
The amounts of the side-products were higher in the 1:1 1,3-diide ligand is counterbalanced by the sodium cation
reaction than in the 2:1 reaction.
Na1, which interacts with the terminal phosphorus atoms
Compound 2 was characterized by 1H and 31P{1H} of the P3 chain [Na1–P1 315.7(2), Na1–P3 299.9(2) pm] and
NMR spectroscopy; characterization by 13C{1H} NMR presumably with the rhodium atom [Na1–Rh1
spectroscopy was thwarted by severe overlap with the sig- 310.5(2) pm]. The shorter Na1–P3 bond is in the range of
nals of [Rh(P4HMes4)(cod)] and [Rh2(μ-P2HMes2)(μ- those previously reported for sodium phosphanides,[1h,1i]
PHMes)(cod)2].[2e] The 31P{1H} NMR spectra of 2 in C6D6, whereas the Na1–P1 bond is somewhat longer and indicates
[D8]thf, or C7D8 exhibit two broad signals at δ = –30 (PAAЈ
)
a weaker Na–P interaction (Table 1). Furthermore, Na1 is
and –46 (PB) ppm both at room (C6D6, [D8]thf, or C7D8) coordinated by three thf molecules resulting in an unusual
and low temperature (–80 °C in [D8]thf or C7D8), which five-coordinate geometry.[7]
indicates that the Na–P interaction is retained in solu-
tion.[1g,1i]
In reference to the short Na–Rh distance of 310.5(2) pm,
an extensive literature search has shown that contacts be-
Complex 2 crystallizes as orange plates in the triclinic tween Rh and alkali metals are extremely rare,[8] and up to
¯
space group P1 with two almost identical independent mo- now short Rh···Li interactions with distances of 256.3,
lecules in the asymmetric unit of which only one will be 261.3, and 264.4 pm have only been described by Andersen
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Making and Breaking of P–P Bonds
Table 1. Selected bond lengths [pm] and angles [°] for 2–5.
2
3
4
5
Rh1–Na1
Rh1–P1
Rh1–P3
Ag1–P1
Ag1–P3
Ag1–P3B
Na1–P1
Na1–P3
Na1–P4A
Na2–P2
Na2–P4
Na2–P5
Na3–P1
Na3–P3
Na3–P5A
P1–P2
310.5(2)
232.9(2)
231.5(1)
256.3(2)
248.0(2)
250.1(2)
315.7(2)
299.9(2)
278.37(9)
281.80(9)
308.48(8)
295.95(8)
282.86(8)
295.15(8)
305.77(8)
288.79(8)
218.05(6)
222.0(2)
221.4(2)
223.0(1)
223.2(1)
225.7(3)
P1–P3
P1–P3A
P2–P2A
P2–P3
215.3(3)
221.3(4)
223.09(6)
P2A–P3
P3–P4
P5–H1p
222.7(2)
218.26(6)
133(2)
Figure 1. Solid-state molecular structure of 2 (hydrogen atoms have
been omitted for clarity).
Ag1–P3–Ag1C
82.33(7)
and co-workers in the compounds [Li(tmeda)][Rh(CH2- P1–Rh1–P3
74.91(3)
P1–Ag1–P3
123.94(8)
112.95(7)
112.54(6)
SiMe3)2(cod)] (tmeda = Me2NCH2CH2NMe2) and [Rh2-
P1–Ag1–P3B
(CH2SiMe3)4(cod)2(μ-Li)2].[8] Longer distances of about
P3–Ag1–P3B
288 pm were not considered as indicative of Rh–Li interac-
Na1–P1–Na3
105.83(2)
111.26(3)
tions by Cavell and co-workers for other related com-
plexes.[9] However, to the best of our knowledge no evidence
of Rh–Na interactions has been reported to date, and only
longer distances [320.9(2) and 331.9(2) pm] have been ob-
served in the sodium rhodate(III) complex Na[Rh(acac)2-
Na2–P5–Na3B
P1–Na1–P3
P1–Na1–P4A
P1–P2–P3
P1–P2–P2A
P1–P3–P2A
54.54(4)
79.14(5)
119.49(3)
100.20(2)
104.1(2)
104.8(2)
96.40(5)
102.60(5)
97.56(5)
Cl2]·H2O (acac = acetylacetonate),[10] probably due to pack- P1A–P2A–P3
P2–P1–P3
ing effects.
P2–P1–P3A
In this context, the structure of 2 was investigated with
P2–P3–P4
102.08(2)
the TURBOMOLE[11] suite. The calculations for 2 con-
firmed the structural parameters obtained by X-ray diffrac-
tion studies. A shared electron number (SEN) analysis was calculated for the two independent molecules of 2. The
applied to investigate the Rh···Na interaction (see the Sup- higher occupancy of the bonding NBO justifies the assump-
porting Information). The SEN can be correlated to the tion of Na–Rh interactions with a covalent contribution
covalent interaction between the investigated atoms. The (for further details, see the Supporting Information).
two almost identical crystallographically independent mole-
In addition, SEN studies on the Na–P bonds were car-
cules of 2 have SENs between Na and Rh of 0.35 and 0.37 ried out. The SENs range from 0.23 to 0.30 for the prede-
electrons. Because the clearly covalent Rh–P1 and Rh–P3 fined Na–P bonds and indicate weak interactions, weaker
interactions have values in the range of 0.55–0.59, covalency even than the Na–Rh interaction (SEN values of 0.35 and
between Na and Rh may be assumed on the basis of our 0.37). These results are consistent with those emerging from
calculations. Further proof of a partially covalent bond is the NBO analysis. Indeed, bonding Na–P orbitals were
provided by the natural bond orbital (NBO) analysis.
found in both individual molecules. However, the contri-
The NBO analysis showed a low occupancy of the 3s butions of Na to the NBOs were rather low, as indicated by
orbital of Na, which indicates that the ionicity of Na is less the polarization coefficients (cNa Ͻ 0.09). Thus, the elec-
than 100% and suggests a potential covalent contribution trons of these orbitals are highly localized at P, correspond-
from Na. A covalent bond between Na and Rh becomes ing to the P lone-pair of electrons. These results account
more likely when natural bond orbitals (NBOs), which are for the weak interactions between Na and P and suggest a
constructed as a linear combination of hybridized natural relatively high covalent contribution to the Na–Rh interac-
atomic orbitals of both atoms Na and Rh, are taken into tion, which is stronger than in the Na–P bonds (for further
account. The Na–Rh bond arises from an overlap of the 3s details, see the Supporting Information). To the best of our
and 5s orbitals of Na and Rh, respectively. Occupancies knowledge, no covalent bonds between Na and a transition
of the antibonding NBOs σ*Na–Rh of 0.07 and 0.09 were metal have been reported to date; however, by using SEN
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E. Hey-Hawkins et al.
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and NBO methods, other authors have observed metal– (cod)2][2e] as side-products, small amounts of cyclo-P6Mes6
metal bonds with covalent contributions that have been dis- (3) and [Na3(Et2O)(P4Mes4)(PHMes)]ϱ (4) were isolated.
cussed in a way similar to the Na–Rh bond found in 2.[12]
The formation of 2–4 indicates that the cleavage and forma-
tion of P–P bonds occurs in the course of the reaction to
give (P3Mes3)2–, PHMes–, and cyclo-P6Mes6 (3). Com-
pounds 3 and 4 could not be separated from 2 and were
only characterized by X-ray diffraction studies.
Reactions of [Na2(thf)4(P4Mes4)] (1) with [{RhCl(cod)}2] in
Ratios of 3:1 and 4:1
To obtain further insight into the mechanism of the for-
The compound cyclo-P6Mes6 (3) crystallizes in the mo-
mation of 2, the analogous reactions of 3 or 4 equiv. of 1 noclinic space group P2/c with half of the molecule located
with 1 equiv. of [{RhCl(cod)}2] were carried out. In ad- in the asymmetric unit and the other half generated by an
dition to the formation of 2 as the major product and inversion center. In addition, one half of a diethyl ether mo-
[Rh(P4HMes4)(cod)] and [Rh2(μ-P2HMes2)(μ-PHMes)- lecule was also located in the asymmetric unit with the oxy-
Figure 2. Solid-state molecular structure of 3 (hydrogen atoms have been omitted for clarity). Symmetry operations for A: –x, –y, –z.
Figure 3. Solid-state molecular structure of 4 (hydrogen atoms except at phosphorus atoms have been omitted for clarity). Symmetry
operations for A: –x + 1/2, y + 1/2, –z + 1/2; for B: x – 1/2, –y – 1/2, z – 1/2.
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Making and Breaking of P–P Bonds
Figure 4. Metallacycle formed by Na and P atoms. Symmetry operations for A: –x + 1/2, y + 1/2, –z + 1/2; for B: x – 1/2, –y – 1/2, z –
1/2.
gen atom located on a two-fold rotation axis. Like the C6
(1)
ring of cyclohexane, the P6 ring of 3 exhibits a chair confor-
mation in which the mesityl groups occupy equatorial posi-
This reaction represents the first preparation of a
tions (Figure 2). The P–P bond lengths of the ring differ
2–
P6Mes6 ligand, which, to the best of our knowledge, was
only slightly [with values between 222.7(2) and 223.2(1) pm]
previously unknown.
and are in the expected range,[13] whereas the endocyclic P–
P–P bond angles vary between 96.40(5) and 102.60(5)°.
Compound 4 crystallizes in the monoclinic space group
P21/n. It consists of co-crystallized Na2(P4Mes4) and Na-
(Et2O)(PHMes), which also form the asymmetric unit. In
spite of minor differences, the overall structural arrange-
ment of the Na2(P4Mes4) core in 4 is similar to those ob-
served in analogous compounds.[1h] The central (P4Mes4)2–
dianion is in a syn arrangement with a P1–P2–P3–P4 tor-
sion angle of around 78.8°. The sodium cation Na1 has
an unusual three-coordinate environment (P1, P4, and the
oxygen atom of the diethyl ether molecule), whereas Na2
and Na3 have a distorted tetrahedral geometry with coordi-
nation by three phosphorus atoms and η2 coordination of
a mesityl group. Short Na–P distances are observed for Na2
and Na3 linked to the terminal and an internal phosphorus
atom of the P4 chain [Na3–P1 295.15(8), Na3–P3 305.77(8)
and Na2–P2 308.48(8), Na2–P4 295.95(8) pm], which indi-
cates a “quasicyclic structure”, as was previously observed
for alkali-metal tetramesityltetraphosphanediides.[1g,1h,2c]
These Na2P4 units are linked by PHMes– [bridging Na2 and
Na3B with short Na–P bonds of 282.86(8) and
288.79(8) pm] and Na(Et2O)+ [bridging P1 and P4A with
Na1–P bond lengths of 278.37(9) (P1) and 281.80(9) pm
(P4A)] resulting in a one-dimensional polymeric chain (Fig-
ure 3). Interestingly, P1–Na1–P4A–Na2A–P5A–Na3 form
an almost planar six-membered ring in which only Na3 de-
viates by about 86 pm from the other co-planar atoms (Fig-
ure 4).
As crystalline complex 5 is poorly soluble in polar and
nonpolar solvents, only very dilute solutions of 5 in C6D6
could be analyzed. The 31P{1H} NMR spectrum of 5 exhib-
its three broad multiplets at δ = –100.6, –14.3, and 0.7 ppm
at room temperature. The severe line-broadening, which
precluded numerical analysis of the coupling patterns, may
in part be due to the quadrupole moment of the silver nu-
clei. However, the presence of only these three signals in the
31P{1H} NMR spectrum and the H NMR spectrum indi-
1
cate that the molecular structure is also retained in solution.
Further analysis of this complex by ESI-MS was
thwarted by its poor solubility, and other ionization tech-
niques such as EI or CI led to severe fragmentation. How-
ever, the FAB mass spectrum showed a peak at m/z =
1331.6 of low relative intensity corresponding to the tetra-
nuclear compound with loss of one P6Mes6 ligand (see the
Exp. Sect.).
Crystals of 5 obtained from diethyl ether were systemati-
cally twinned, and crystallization from other solvents did
not lead to single crystals suitable for X-ray diffraction
studies. However, in spite of the relatively poor quality of
the crystals, the molecular structure of 5 was determined
without ambiguity.
¯
Complex 5 crystallizes in the tetragonal space group I42d
The asymmetric unit of 5 contains an AgP3Mes3 unit,
which, after application of an S4 axis, gives rise to the tetra-
nuclear complex [Ag4(P6Mes6)2] (5). Six highly disordered
diethyl ether molecules were also observed in the asymmet-
ric unit, only two of which could be satisfactorily refined;
the other four were removed by using the SQUEEZE pro-
gram implemented in PLATON.[14]
[Ag4(P6Mes6)2]
2–
In 5, two linear P6Mes6 ligands are bound by four
[Ag4(P6Mes6)2] (5) was obtained as the main product in phosphorus atoms (the most external ones P3 and P1) to
modest yield from the reaction of 1 equiv. of [Na2(thf)4- four silver(I) atoms, which are coordinated in a distorted
(P4Mes4)] (1) with 2 equiv. of [AgCl(PPh3)2] (Scheme 1). trigonal-planar fashion by three phosphorus atoms of two
Compound 5 was crystallized from diethyl ether and char- different P6 ligands (Figure 5). Interestingly, the 16-vertex
acterized by spectroscopic methods and single-crystal X-ray polyhedron consists of four five-membered rings in an enve-
diffraction studies.
lope conformation, formed by two silver atoms (e.g., Ag1
It seems that complex 5 is formed by a redox reaction and Ag1B) and three phosphorus atoms of two different P6
[Equation (1)] involving the formation of elemental silver, ligands (e.g., P1, P3A, and P3B), and four six-membered
which was detected in the black precipitate formed in the rings in a boat conformation, formed by five phosphorus
reaction.
atoms of a P6 ligand (e.g., P1, P2, P2A, P1A, and P3) and
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E. Hey-Hawkins et al.
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a silver atom (e.g., Ag1). Two six-membered rings are fused uct together with small amounts of the neutral hexaphos-
to give a bicyclic Ag2P6 fragment similar to bicyclo[2.2.2]- phane cyclo-P6Mes6 (3) and [Na3(Et2O)(P4Mes4)(PHMes)]ϱ
octane.
(4) as side-products indicating that the reaction may involve
cleavage of a P–P bond to give (P3Mes3)2– and PHMes–. In
addition, the formation of 3 may be possible by a rare cou-
pling of two P3 fragments. SEN and NBO analyses indi-
cated only weak Na–P interactions in 2, which are even
weaker than the Na–Rh interactions with a bond length of
310.5(2) pm.
Furthermore, the reaction of
1 with 2 equiv. of
[AgCl(PPh3)2] gave the tetranuclear compound [Ag4-
(P6Mes6)2] (5) in which the presence of (P6Mes6)2– indicates
a redox reaction with P–P bond cleavage and formation in-
volving the reduction of Ag+ to Ag0. Ag···Ag distances of
327.9(2) and 334.6(2) pm indicate argentophilic intramolec-
ular contacts in this compound.
Figure 5. Solid-state molecular structure of 5 (with the omission of
carbon and hydrogen atoms). Symmetry operations for A: –x, –y,
+z; for B: –y + 1/2, x + 1/2, –z + 1/2; for C: y + 1/2, –x + 1/2, –z
+ 1/2.
Experimental Section
The Ag–P bond lengths are between 248.0(2) and
256.3(2) pm, in the range of other reported Ag–P bonds,[3g]
whereas the P–P distances of the P6 ligand range from
215.3(3) (terminal P3 and P1A) to 225.7(3) pm and are also
in the expected range.[13] The (P6Mes6)2– dianion shows P3–
P1A–P2A–P2 and P1–P2–P2A–P1A torsion angles of
about 108.1 and 69.7°, respectively, and P–P–P angles of
about 104°. Silver(I) complexes often exhibit inter- or intra-
molecular Ag–Ag contacts (argentophilic interactions)[15]
with distances of less than the sum of the van der Waals
radii, which is 340 pm.[16] In 5, the four Ag atoms are sym-
metry-related by an S4 axis and thus are located on the
vertices of an imaginary tetrahedron (see Figure 6) with
Ag···Ag distances of 327.9(2) and 334.6(2) pm, which indi-
cate intramolecular contacts.
General: All experiments were performed under dry argon by using
standard Schlenk techniques. The NMR spectra were recorded
with
a
Bruker Avance DRX 400 spectrometer. 1H NMR
(400.13 MHz): internal standard solvent, external standard TMS;
31P NMR (161.9 MHz): external standard 85% H3PO4. FAB mass
spectra were recorded with a MASPEC II spectrometer with 3-ni-
trobenzyl alcohol as matrix. EI-MS analyses were preformed with
a MASPEC II instrument [II32/A302] (m/z = 50–1000). ESI-MS
data were recorded with an FT-ICR MS Bruker Daltonics spec-
trometer (APEX II, 7 T, MASPEC II), and solutions of approxi-
mately 1 mg/mL of the compounds in dry thf/CH3CN (1:1) were
injected. IR spectra: KBr pellets were prepared in a nitrogen-filled
glove-box, and the spectra were recorded with a Perkin–Elmer Sys-
tem 2000 FTIR spectrometer in the range 400–4000 cm–1. All sol-
vents were purified by distillation, dried, saturated with argon, and
stored over
a
potassium mirror. [Na2(thf)4(P4Mes4)] (1),[1h]
[{RhCl(cod)}2],[17] and [AgCl(PPh3)2][18] were synthesized accord-
ing to literature procedures.
Synthesis of [Na(thf)3][Rh(P3Mes3)(cod)] (2): At –78 °C, a solution
of 1 (0.75 g, 0.80 mmol) in thf (30 mL) was carefully added drop-
wise to a solution of [{RhCl(cod)}2] (0.20 g, 0.40 mmol) in thf
(50 mL). The brown solution that formed was allowed to warm to
room temperature slowly over 2 h and then stirred for a further
2 h. The solvent was then removed under vacuum and the resulting
dark brown oil extracted with Et2O (2ϫ50 mL). The brown Et2O
solution was filtered and the solvent evaporated in vacuo. The re-
sulting brown solid was then recrystallized from thf (5 mL). A dark
orange crystalline solid formed at –28 °C over 1 week. Complex 2
was always obtained contaminated with [Rh(P4HMes4)(cod)] and
[Rh2(μ-P2HMes2)(μ-PHMes)(cod)2],[2e] and the signals in the 1H,
13C{1H,31P}, and 31P{1H} NMR spectra reported hereafter were
assigned by comparison with the spectra of the pure side-products.
Yield: 0.15 g (21%). 1H NMR (C6D6, 25 °C): δ = 1.41 (12 H), 3.56
(12 H) (thf), 2.18 (12 H), 2.49 (3 H), 2.86 (6 H), 3.44 (br. s, 6 H,
Me of Mes), 3.73 (2 H), 3.93 (1 H), 4.41 (br., 1 H, CH of cod),
6.46 (2 H), 6.96 (2 H), 7.06 (s, 2 H, aromatic CH of Mes) ppm
(signals of the CH2 groups of cod were obscured by the signals of
the methyl groups of mesityl). 13C{1H,31P} NMR ([D8]thf, 25 °C):
δ = 21.8, 21.9 (p-Me in Mes), 29.2, 30.0, 30.5, 31.2, 32.2 (s, o-Me
in Mes and CH2 of cod), 83.4, 86.0, 87.2, 87.8, 88.2, 94.1 (CH of
cod in 2 and impurities), 127.7, 127.8, 128.0, 128.5, 129.0, 129.1
Figure 6. Tetrahedron formed by the Ag atoms of 5 with Ag···Ag
distances [pm].
Conclusions
P–P bond-breaking and -making occur in the reactions
of [Na2(thf)4(P4Mes4)] (1) with [{RhCl(cod)}2] or
[AgCl(PPh3)2]. Thus, 1 reacted with [{RhCl(cod)}2] (1:1 or
2:1) to give a mixture of compounds from which [Na(thf)3]-
[Rh(P3Mes3)(cod)] (2) was isolated, whereas the reactions
with reagent ratios of 3:1 and 4:1 gave 2 as the major prod- (C-3,5 in Mes), 134.3, 134.9, 136.2, 137.3, 138.3, 138.8, 140.0,
744 Eur. J. Inorg. Chem. 2011, 739–747
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Making and Breaking of P–P Bonds
141.8, 143.1 (s, C-1,2,4,6 in Mes) ppm. 31P{1H} NMR (C6D6, Synthesis of [Ag4(P6Mes6)2] (5): At –78 °C and in the dark, a solu-
25 °C): δ = –30.3 (br., PAAЈ), –46.3 (br., P ) ppm. IR (KBr): ν =
tion of 1 (0.75 g, 0.80 mmol) in thf (50 mL) was carefully added
˜
B
3016 (m), 2958 (s), 2915 (s), 2871 (s), 2727 (w), 1722 (w), 1601 (m),
dropwise to a suspension of [AgCl(PPh3)2] (1.07 g, 1.60 mmol) in
1552 (w), 1455 (m), 1406 (w), 1375 (m), 1331 (w), 1289 (w), 1260 thf (50 mL). An orange solution formed that was allowed to warm
(m), 1176 (w), 1153 (w), 1096 (m), 1029 (s), 925 (w), 847 (s), 817 to room temperature slowly over 2 h and then stirred for a further
(m), 712 (w), 612 (m), 556 (m), 461 (w), 430 (w) cm–1. MS (EI): 6 h. The solvent was then removed under vacuum and the resulting
m/z (%) = 898.9 (0.8) [M + H]+, 795.0 (0.5) [M + H – cod]+, 335.1
(100) [Na(thf)2OPHMes]+. The elemental analysis data were not
satisfactory due to the contamination of 2 with [Rh(P4HMes4)-
(cod)] and [Rh2(μ-P2HMes2)(μ-PHMes)(cod)2].[2e] When using
equimolar amounts of 1 (0.75 g, 0.80 mmol) and [{RhCl(cod)}2]
(0.40 g, 0.80 mmol), the only significant difference was the pro-
portion of the side-products [Rh(P4HMes4)(cod)] and [Rh2(μ-
P2HMes2)(μ-PHMes)(cod)2][2e] in the reaction mixture, which was
higher than in the 2:1 reaction.
dark orange oil extracted with Et2O (20 mL). The orange Et2O
solution was filtered and concentrated to ca. 5 mL. Orange crystals
formed at –28 °C over about 1 month. Once the crystals were iso-
lated, they were poorly soluble in solvents such as benzene, toluene,
diethyl ether, thf, n-hexane, n-pentane, dimethoxyethane, and diox-
1
ane. Yield: 0.090 g (17%); m.p. 233–235 °C (brown oil). H NMR
(C6D6, 25 °C): δ = 1.64 (6 H), 1.66 (6 H), 1.77 (6 H), 2.16 (6 H),
2.18 (6 H), 2.43 (6 H), 2.79 (6 H), 3.08 (6 H), 3.99 (s, 6 H, Me of
Mes), 6.17 (2 H), 6.23 (2 H), 6.32 (2 H), 6.49 (2 H), 6.85 (2 H),
7.08 (s, 2 H, aromatic CH of Mes) ppm. 13C{1H, 31P} NMR (C6D6,
25 °C): δ = 20.3, 20.4, 21.0, 22.9, 23.0, 24.0, 25.1, 28.3 (Me of Mes),
129.1, 129.5, 129.6 (C-3,5 in Mes), 133.7, 133.9, 134.0 (C-4 in Mes),
136.9, 137.7, 137.8 (C-1 in Mes), 143.8, 144.3, 144.7 (C-2,6 in Mes)
ppm. 31P{1H} NMR (C6D6, 25 °C): δ = –100.6 [br. m, appears as
br. sext, PAAЈ, J(P–P) = 230.0 Hz], –14.3 [br. m, appears as br. sext,
PBB’ J(P–P) = 228.4 Hz], 0.7 [br. m, appears as br. q, PCCЈ J(P–P)
Reaction of 1 with [{RhCl(cod)}2] in Ratios of 3:1 and 4:1: Crystalli-
zation of the Mixture of [Na(thf)3][Rh(P3Mes3)(cod)] (2), cyclo-
P6Mes6 (3), and [Na3(Et2O)(P4Mes4)(PHMes)]ϱ (4): At –78 °C, a
solution of 1 (1.13 g, 1.20 mmol) in thf (50 mL) was carefully added
dropwise to a solution of [{RhCl(cod)}2] (0.20 g, 0.40 mmol) in thf
(50 mL). The brown solution that formed was allowed to warm to
room temperature slowly over 2 h and then stirred for a further
2 h. The solvent was then removed under vacuum and the resulting
dark brown oil extracted with Et2O (2ϫ50 mL). The brown Et2O
solution was filtered and concentrated to ca. 5 mL. A crystalline
solid comprising colorless prisms of 3, yellow cubes of 4, and
orange plates of 2 formed at –28 °C over 1 week. A small amount
of the crystals obtained was transferred into perfluoro ether oil,
separated by hand under the microscope, and subjected to X-ray
diffraction. No significant differences were observed when using
the stoichiometry 4:1.
= 205.7 Hz] ppm. IR (KBr): ν = 3014 (m), 2958 (s), 2930 (m), 2867
˜
(s), 1626 (m), 1602 (m), 1549 (w), 1458 (s), 1373 (m), 1289 (w),
1261 (s), 1178 (w), 1145 (m), 1097 (s), 1021 (s), 917 (w), 847 (m),
804 (s), 745 (w), 711 (w), 709 (w), 607 (w), 549 (m), 473 (w), 446
(w), 404 (w) cm–1. MS (FAB): m/z (%) = 1331.6 (0.7) [M –
P6Mes6]+, 345.2 (100) [AgP2Mes2 – 4 Me – H]+. C108H132Ag4P12
(2233.36): C 58.08, H 5.96; found C 57.72, H 5.65.
Data Collection and Structural Refinement of 2–5: The data for 2–
5 were collected with a CCD Oxford Xcalibur S diffractometer
Table 2. Crystallographic data for 2–5.
2
3
4
5
Empirical formula
M
C47H69NaO3P3Rh
900.83
C58H76OP6
975.01
C49H66Na3OP5
894.84
C148H232Ag4O10P12
2974.46
T [K]
Crystal system
Space group
130(2)
130(2)
monoclinic
P2/c
130(2)
monoclinic
P21/n
130(2)
triclinic
tetragonal
¯
¯
P1
I42d
a [pm]
b [pm]
c [pm]
α [°]
1192.1(5)
1969.9(5)
2087.8(5)
70.537(5)
79.200(5)
80.798(5)
4.52(1)
1331.12(5)
852.68(3)
2454.24(7)
90
97.469(3)
90
1237.11(2)
1628.58(3)
2512.24(4)
90
96.223(2)
90
1895.90(1)
1895.90(1)
5054.71(8)
90
90
90
β [°]
γ [°]
V [nm3]
2.7620(2)
2
5.0317(2)
4
18.1688(3)
4
Z
4
Crystal size [mm]
ρcalcd. [Mgm–3]
F(000)
0.4ϫ0.18ϫ0.01
1.325
1904
0.30ϫ0.20ϫ0.10
1.172
1044
0.60ϫ0.20ϫ0.20
1.181
1904
0.60ϫ0.15ϫ0.05
1.087
6272
Absorption coefficient [mm–1]
hkl range
0.533
0.232
0.241
0.575
–15ՅhՅ14
–24ՅkՅ24
–26ՅlՅ26
53.46
–16ՅhՅ16
–10ՅkՅ10
–30ՅlՅ30
52.74
–16ՅhՅ16
–21ՅkՅ21
–33ՅlՅ33
56.56
–22ՅhՅ22
–20ՅkՅ22
–60ՅlՅ59
50.56
2θmax [°]
Reflections collected/unique
R(int)
Data/restraints/ parameters
Goodness of fit on F2
R1/wR2 [IϾ2σ(I)]
105139/19133
0.0690
19133/820/893
0.965
0.0415/0.0992
0.0787/0.1148
0.865/–1.138
–
59610/5655
0.0677
5655/0/292
1.035
0.0640/0.1998
0.0990/0.2220
0.937/–0.532
–
49467/12482
0.0443
12482/0/584
0.917
0.0351/0.0767
0.0752/0.0878
0.342/–0.224
–
69054/8185
0.1116
8185/16/291
1.178
0.0780/0.1882
0.0944/0.2032
1.271/–0.847
–0.05(6)
R1/wR2 (all data)
Largest difference peak/hole [eÅ–3]
Flack parameter
Eur. J. Inorg. Chem. 2011, 739–747
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
745

E. Hey-Hawkins et al.
FULL PAPER
Lönnecke, C. Jones, E. Hey-Hawkins, Eur. J. Inorg. Chem.
2004, 3277–3286; i) J. Geier, J. Harmer, H. Grützmacher, An-
gew. Chem. 2004, 116, 4185–4189; Angew. Chem. Int. Ed. 2004,
43, 4093–4097; j) M. Kaupp, A. Patrakov, R. Reviakine, O. L.
Malkina, Chem. Eur. J. 2005, 11, 2773–2782; k) R. Wolf, E.
Hey-Hawkins, Z. Anorg. Allg. Chem. 2006, 632, 727–734; l) D.
Stein, A. Dransfeld, M. Flock, H. Rüegger, H. Grützmacher,
Eur. J. Inorg. Chem. 2006, 4157–4167.
a) R. Wolf, E. Hey-Hawkins, Angew. Chem. 2005, 117, 6398–
6401; Angew. Chem. Int. Ed. 2005, 44, 6241–6244; b) R. Wolf,
E. Hey-Hawkins, Eur. J. Inorg. Chem. 2006, 1348–1351; c) R.
Wolf, S. Gómez-Ruiz, J. Reinhold, W. Böhlmann, E. Hey-Haw-
kins, Inorg. Chem. 2006, 45, 9107–9113; d) S. Gómez-Ruiz, E.
Hey-Hawkins, Dalton Trans. 2007, 5678–5683; e) S. Gómez-
Ruiz, R. Wolf, E. Hey-Hawkins, Dalton Trans. 2008, 1982–
1988; f) S. Gómez-Ruiz, S. Zahn, B. Kirchner, W. Böhlmann,
E. Hey-Hawkins, Chem. Eur. J. 2008, 14, 8980–8985; g) S.
Gómez-Ruiz, B. Gallego, E. Hey-Hawkins, Dalton Trans. 2009,
2915–2920.
a) A. Schisler, P. Lönnecke, U. Huniar, R. Ahlrichs, E. Hey-
Hawkins, Angew. Chem. 2001, 113, 4345–4348; Angew. Chem.
Int. Ed. 2001, 40, 4216–4219; b) A. Schisler, P. Lönnecke, E.
Hey-Hawkins, Inorg. Chem. 2005, 44, 461–464; c) S. Gómez-
Ruiz, A. Schisler, P. Lönnecke, E. Hey-Hawkins, Chem. Eur. J.
2007, 13, 7974–7982; d) S. Gómez-Ruiz, R. Wolf, S. Bauer, H.
Bittig, A. Schisler, P. Lönnecke, E. Hey-Hawkins, Chem. Eur.
J. 2008, 14, 4511–4520; e) R. Herrero, S. Gómez-Ruiz, J. Z.
Dávalos, E. Hey-Hawkins, C. R. Chim. 2010, 13, 1185–1190; f)
S. Gómez-Ruiz, E. Hey-Hawkins, New J. Chem. 2010, 34,
1525–1532; g) S. Gómez-Ruiz, E. Hey-Hawkins, Coord. Chem.
Rev. 2010, DOI: 10.1016/j.ccr.2010.11.020.
[λ(Mo-Kα) = 71.073 pm] by using ω- and φ-scan modes. Semi-em-
pirical equivalence absorption corrections were carried out with
SCALE3 ABSPACK,[19] and the structures were solved by direct
methods by using SHELXS-97.[20] Structure refinement was carried
out with SHELXL-97.[21] All non-hydrogen atoms were refined an-
isotropically. Hydrogen atoms were refined at idealized positions
by using the riding model. Table 2 lists the crystallographic data
for complexes 2–5. For 2, some carbon atoms of the thf molecules
were disordered and were refined over split positions with con-
strained geometry and fixed atomic displacement parameters
(SADI and EADP instructions). For 5, only two of the six diethyl
ether molecules found in the asymmetric unit could be satisfactorily
refined, and the other four were removed by using the program
SQUEEZE implemented in Platon.[14] CCDC-793271 (2), -793272
(3), -793273 (4), and -793274 (5) contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[2]
[3]
Calculations: All electronic structure calculations were carried out
with the TURBOMOLE suite.[11] The final optimized structure was
obtained by employing the BP86 density functional, and the resolu-
tion of identity approximation was used.[22] A TZVP basis set was
applied to all atoms. In the geometry optimization the convergence
criterion of the DFT energy and the magnitude of the gradient
vector were set to 10–8 Hartree and 10–4 Hartree/Bohr, respectively.
The SEN analysis was performed with the TURBOMOLE suite on
the basis of the precalculated wavefunctions. Gaussian 03[23] was
employed for the NBO analysis with the TZVP basis set and the
BP86 functional in which the recommended VWN-V-LDA corre-
lation was employed.[24] Thereby localized Lewis bonds and inter-
actions between bonds were sought for. When Gaussian 03 default
settings were employed, a number of second-order perturbation in-
teractions were indicated, but no Na–Rh single bond was assigned.
By predefinition of an Na–Rh single bond, however, covalent inter-
actions between both metal atoms could be supported. No clues to
a conceivable Na–Rh–P three-center bond were obtained. For fur-
ther details see the Supporting Information.
[4]
[5]
H. Köpf, R. Voigtländer, Chem. Ber. 1981, 114, 2731–2743.
R. A. Jones, M. H. Seeberger, B. R. Whittlesey, J. Am. Chem.
Soc. 1985, 107, 6424–6426.
D. Fenske, H. Schottmüller, Z. Anorg. Allg. Chem. 1998, 624,
443–451.
[6]
[7]
For further examples, see: a) T. Akitsu, Y. Hiroshima, S. Ko-
morita, Y. Kushi, Bull. Chem. Soc. Jpn. 2001, 74, 507–508; b)
Y. Yokota, R. A. Jacobson, B. C. Logsdon, S. Ringrose, A. T.
Setterdahl, J. G. Verkade, Polyhedron 1999, 18, 2519–2532; c)
J. A. Balanta-Díaz, M. Moya-Cabrera, V. Jancik, L. W. Pineda-
Cedeño, R. A. Toscano, R. Cea-Olivares, Inorg. Chem. 2009,
48, 2518–2525; d) M. Mehring, D. Mansfeld, S. Paalasmaa, M.
Schürmann, Chem. Eur. J. 2006, 12, 1767–1781; e) A. Caselli,
E. Solari, R. Scopelliti, C. Floriani, J. Am. Chem. Soc. 1999,
121, 8296–8305; f) L. Shen, Z. M. Jing, Acta Crystallogr., Sect.
C 2002, 58, m591–m592; g) E. E. Baeva, A. V. Virovets, E. V.
Peresypkina, L. B. Serezhkina, Russ. J. Inorg. Chem. 2006, 51,
220–228.
Supporting Information (see footnote on the first page of this arti-
cle): Full details of the calculation of 2 and a complete picture of
the molecular structure of 5.
Acknowledgments
Support from the Alexander von Humboldt Stiftung (Humboldt
Fellowship for S. G.-R.), the Junta de Comunidades de Castilla-
La Mancha (postdoctoral fellowship for B. G.) and the Deutsche
Forschungsgemeinschaft (He1376/22-2) and a generous donation
of RhCl3 from Umicore AG & Co KG are gratefully acknowl-
edged. We thank Dr. P. Lönnecke for his assistance with the X-ray
structure determinations and Dr. R. Wolf for invaluable advice. We
also like to thank R. Oehme for the mass spectrometric measure-
ments and her invaluable advice in the interpretation of the mass
spectra.
[8]
M. A. Kulzick, R. A. Andersen, E. L. Muetterties, V. W. Day,
J. Organomet. Chem. 1987, 336, 221–236.
M. Fang, N. D. Jones, R. Lukowski, J. Tjathas, M. J. Ferguson,
R. G. Cavell, Angew. Chem. Int. Ed. 2006, 45, 3097–3101.
N. V. Podberezskaya, G. V. Romanenko, S. P. Khranenko, A. V.
Belyaev, J. Struct. Chem. 1997, 38, 744–749.
R. Ahlrichs, M. Bär, M. Häser, H. Horn, C. Kölmel, Chem.
Phys. Lett. 1989, 162, 165–169.
a) S. G. Minasian, J. L. Krinsky, V. A. Williams, J. Arnold, J.
Am. Chem. Soc. 2008, 130, 10086–10087; b) P. L. Arnold, S. T.
Liddle, J. McMaster, C. Jones, D. P. Mills, J. Am. Chem. Soc.
2007, 129, 5360–5361.
[9]
[10]
[11]
[12]
[13]
a) M. Baudler, K. Glinka, Coord. Chem. Rev. 1993, 93, 1623–
[1] a) K. Issleib, K. Krech, Chem. Ber. 1965, 98, 2545–2550; b) K.
Issleib, E. Fluck, Z. Anorg. Allg. Chem. 1965, 339, 274–280; c)
K. Issleib, K. Krech, Chem. Ber. 1966, 99, 1310–1315; d) K.
Issleib, M. Hoffmann, Chem. Ber. 1966, 99, 1320–1324; e) K.
Issleib, Ch. Rockstroh, I. Duchek, E. Fluck, Z. Anorg. Allg.
Chem. 1968, 360, 77–87; f) K. Issleib, K. Krech, J. Prakt.
Chem. 1969, 311, 463–471; g) J. Geier, H. Rüegger, M. Wörle,
H. Grützmacher, Angew. Chem. 2003, 113, 4081–4084; Angew.
Chem. Int. Ed. 2003, 42, 3951–3954; h) R. Wolf, A. Schisler, P.
1667; b) J. J. Daly, J. Chem. Soc. 1964, 6147–6165.
[14]
[15]
A. L. Spek, Acta Crystallogr., Sect. D 2009, 65, 148–155.
For example, see: a) Q.-M. Wang, T. C. W. Mak, J. Am. Chem.
Soc. 2001, 123, 7594–7600; b) C.-M. Che, M.-C. Tse, M. C. W.
Chan, K.-K. Cheung, D. L. Phillips, K.-H. Leung, J. Am.
Chem. Soc. 2000, 122, 2464–2468; c) M. A. Omary, T. R. Webb,
Z. Assefa, G. E. Shankle, H. H. Patterson, Inorg. Chem. 1998,
37, 1380–1386; d) A. A. Mohamed, L. M. Pérez, J. P.
746
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 739–747

Making and Breaking of P–P Bonds
Fackler Jr., Inorg. Chim. Acta 2005, 358, 1657–1662; e) M. P.
Carranza, B. R. Manzano, F. A. Jalón, A. M. Rodríguez, L.
Santos, M. Moreno, Inorg. Chem. 2010, 49, 3828–3835.
[16] A. Bondi, J. Phys. Chem. 1964, 68, 441–451.
[17] G. Giordano, R. H. Crabtree, Inorg. Synth. 1990, 28, 88–90.
[18] P. G. Jones, G. M. Sheldrick, J. A. Muir, M. M. Muir, L. B.
Pulgar, J. Chem. Soc., Dalton Trans. 1982, 2123–2125.
[19] Empirical absorption correction, CrysAlis – Software package,
Oxford Diffraction Ltd., Oxford, 2006.
[20] G. M. Sheldrick, SHELXS-97, Program for Crystal Structure
Solution, University of Göttingen, Göttingen, 1997.
[21] G. M. Sheldrick, SHELXL-97, Program for the Refinement of
Crystal Structures, University of Göttingen, Göttingen, 1997.
[22] a) E. J. Baerends, E. D. Ellis, P. Ros, Chem. Phys. 1973, 2, 41–
51; b) B. I. Dunlap, J. W. D. Connolly, J. R. Sabin, J. Chem.
Phys. 1979, 71, 3396–3402.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R.
Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morok-
uma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzew-
ski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K.
Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V.
Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B.
Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, re-
vision D.01, Gaussian, Inc., Wallingford, CT, 2004.
[24]
A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88,
899–926.
[23] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T.
Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Received: October 25, 2010
Published Online: January 12, 2011
Eur. J. Inorg. Chem. 2011, 739–747
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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