Cyclodiphosphazane cis-{(o-MeOC6H4O)P(μ-NtBu)} 2 as a bridging bidentate ligand: Synthesis, structures of heterometallic complexes, and halogen exchange between Rh-Cl and Cu-X (X = Br, I)

Article abstract of DOI:10.1002/ejic.200700554

The mononuclear rhodium complexes of cyclodiphosphazane [(cod)RhCl{L-κP}] (1a) (L = cis-{(o-MeOC₆H₄0)P(μ- NtBu)}2) and frans-[Rh(CO)Cl{L-κP}₂] (1b) react in a 1:1 molar ratio with [AuCl(SMe₂)] to form the heteronuclear complexes [(cod)RhCl{μ-L-κP,κP}AuCl] (2) and trans-[Rh(CO)-C1{μ-L- κP,κP}₂(AUC1)2] (7), respectively, in quantitative yield. The reaction between la and CuCl afforded a tetranuclear complex [(cod)RhCl{μ-L-κP,κP)Cu(μ-Cl)]₂ (3). Under similar reaction conditions 1 reacts with 2 equiv. of CuX (X = Br, I) to produce the heteronuclear complexes [(cod)RhBr(μ-L-κP,κP}Cu(μ-Br)] ₂ (4) and [((cod)RhI(μ-L-κP,κP})2Cu(n-X)2Cu] (X ≈ 1:1 mixture of Cl and I disordered over both sites) (5), respectively, in which two molecules of 1a are bridged by the rhombic, disordered, mixed halide [Cu(μ-X)₂Cu] (5: X = Br; 6: X = Cl, I) unit. The crystal structures of 4 and 5 confirm the halogen exchange between the Rh-Cl and CuX (X = Br, I) moieties which leads to the formation of Rh-Br and Rh-I bonds. The heterodinuclear Rh^I/Pd^II complex [(cod)RhCl(μ-L- κP,κP)η³-C₃H₅)] (6) was synthesized by the reaction of 1a with [PdCl(η³-C ₃H₅)]₂ in a 2:1 ratio. Reaction of 1b with Cui leads to the formation of the tetranuclear complex [Rh(CO)I{μ-L-κP, κP)₂Cu(μ-I)]₂ (8) containing two terminal un-coordinated phosphorus(III) centers irrespective of reactant ratio and reaction conditions. Halogen exchange reaction which leads to the formation of the Rh-I bond was also observed during the preparation of complex 8. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700554

FULL PAPER
DOI: 10.1002/ejic.200700554
Cyclodiphosphazane cis-{(o-MeOC6H4O)P(µ-NtBu)}2 as a Bridging Bidentate
Ligand: Synthesis, Structures of Heterometallic Complexes, and Halogen
Exchange Between Rh–Cl and Cu–X (X = Br, I)
P. Chandrasekaran,[a] Joel T. Mague,[b] Ramalingam Venkateswaran,[a] and
Maravanji S. Balakrishna*[a]
Keywords: Heterometallic complexes / Cyclodiphosphazanes / P,N ligands / Halogen exchange / Rhodium
The mononuclear rhodium complexes of cyclodiphosphaz-
ane [(cod)RhCl{L-κP}] (1a) (L cis-{(o-MeOC6H4O)P(µ-
6: X = Cl, I) unit. The crystal structures of 4 and 5 confirm
the halogen exchange between the Rh–Cl and CuX (X = Br,
=
NtBu)}2) and trans-[Rh(CO)Cl{L-κP}2] (1b) react in a 1:1 mo- I) moieties which leads to the formation of Rh–Br and Rh–I
lar ratio with [AuCl(SMe2)] to form the heteronuclear com-
plexes [(cod)RhCl{µ-L-κP,κP}AuCl] (2) and trans-[Rh(CO)-
Cl{µ-L-κP,κP}2(AuCl)2] (7), respectively, in quantitative yield.
The reaction between 1a and CuCl afforded a tetranuclear
complex [(cod)RhCl{µ-L-κP,κP}Cu(µ-Cl)]2 (3). Under similar
reaction conditions 1 reacts with 2 equiv. of CuX (X = Br, I)
to produce the heteronuclear complexes [(cod)RhBr{µ-L-
κP,κP}Cu(µ-Br)]2 (4) and [((cod)RhI{µ-L-κP,κP})2Cu(µ-X)2Cu]
(X ≈ 1:1 mixture of Cl and I disordered over both sites) (5),
respectively, in which two molecules of 1a are bridged by the
rhombic, disordered, mixed halide [Cu(µ-X)2Cu] (5: X = Br;
bonds. The heterodinuclear RhI/PdII complex [(cod)RhCl{µ-
L-κP,κP}PdCl(η3-C3H5)] (6) was synthesized by the reaction
of 1a with [PdCl(η3-C3H5)]2 in a 2:1 ratio. Reaction of 1b with
CuI leads to the formation of the tetranuclear complex
[Rh(CO)I{µ-L-κP,κP}2Cu(µ-I)]2 (8) containing two terminal un-
coordinated phosphorus(III) centers irrespective of reactant
ratio and reaction conditions. Halogen exchange reaction
which leads to the formation of the Rh–I bond was also ob-
served during the preparation of complex 8.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
made easier by choosing robust bidentate ligands which can
perform as monodentate ligands under mild reaction condi-
tions to give mononuclear complexes containing one or two
free phosphorus(III) sites. These metalloligands containing
uncoordinated phosphorus(III) centers can be conveniently
treated with appropriate metal centers to form a variety of
heterometallic complexes. In this context, cyclodiphosphaz-
anes containing saturated four-membered P2N2 rings are
interesting since they often exhibit monodentate coordina-
tion with several metal reagents under mild reaction condi-
tions as shown in Scheme 1.[5,6] These mononuclear com-
plexes containing uncoordinated phosphorus centers can be
utilized to form heterometallic complexes. Such complexes
can be of importance in homogeneous catalysis to promote
Introduction
The cooperativity or synergism present in heterometallic
complexes gives remarkable chemical and biological prop-
erties compared to homonuclear complexes.[1] These hetero-
multinuclear complexes have applications in the formation
of new materials with useful physicochemical properties,[2]
and as polyfunctional catalysts for organic transforma-
tions.[3] The ligand design is important for the synthesis of
heteronuclear complexes because the dimensionality and
topology of the final structures are predominantly con-
trolled by the location of donor sites in the ligand and their
coordination preferences towards different metal centers.[4]
Several phosphane ligands have been utilized for the syn-
thesis of heterometallic complexes; however, in many cases
formation of homonuclear complexes was observed along
with the expected heterometallic complexes, due to the com-
petition between different metal centers for the coordina-
tion sites and also due to the symmetric nature of bis(phos-
phanes). Preparation of heterometallic complexes can be
[a] Phosphorus Laboratory, Department of Chemistry, Indian In-
stitute of Technology,
Bombay, Mumbai 400076, India
Fax: +91-22-2572-3480
E-mail: krishna@chem.iitb.ac.in
[b] Department of Chemistry, Tulane University,
New Orleans, Louisiana, LA 70118, USA
Scheme 1.
4988
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4988–4997

cis-{(o-MeOC6H4O)P(µ-NtBu)}2 as a Bridging Bidentate Ligand
more than one type of catalysis and also for exploring the spectrum which shows a single resonance at δ = 107.9 ppm.
2
catalytic activity of multimetallic systems.[7] As a continua- The gold-bound phosphorus center of 2 shows JPP and
tion of our work on transition metal chemistry of phospho- 3JRhP couplings of 30 and 5.5 Hz, respectively. The magni-
3
rus-based ligands and their catalytic applications,[8] we de- tude of JRhP is comparable with literature values,[10] while
1
scribe in this article the synthesis and molecular structures the rhodium-coordinated phosphorus atom shows a JRhP
2
of several heterometallic complexes of cyclodiphosphaz- coupling of 247 Hz along with JPP. However, compound
2
1
anes.
1a did not show any JPP coupling and the JRhP coupling
(229 Hz) was smaller than that of 2 (Table 1). The mass
spectrum of 2 exhibits a peak at m/z = 893.21 which corre-
sponds to the [M – Cl] ion (Figure 1).
Results and Discussion
Synthesis of Heterometallic Complexes
Table 1. 31P{1H} NMR spectroscopic data for complexes 1–7.
The rhodium(I) complex containing monocoordinated
cyclodiphosphazane, [(cod)RhCl{L-κP}] (1a), chosen for
the construction of heterometallic complexes was synthe-
sized by treating cis-{(o-MeOC6H4O)P(µ-NtBu)}2 (L) with
[Rh(cod)Cl]2 as described previously.[6] The reaction of 1a
with 1 equiv. of [AuCl(SMe2)] in dichloromethane at room
temperature affords the heterodimetallic RhI/AuI complex
2 in good yield as shown in Scheme 2. The 31P NMR spec-
trum of 2 consists of two sets of doublets of doublets cen-
tered at δ = 104.7 and 94.1 ppm, respectively, for Au-coor-
dinated and Rh-coordinated centers of the cyclodiphos-
phazane together with a low-intensity singlet at δ =
1
Compound δ(RhP) [ppm] JRhP [Hz] δ(MP) [ppm] (other J values [Hz])
1a
1b
2
102.8 (d)
112.5 (d)
94.1 (dd)
93.2 (d)
93.0 (d)
91.0 (d)
94.1 (dd)
104.8 (d)
229
187
247
227
236
259
240
219
131.7 (s)[a]
130.8 (s)[a]
3
104.7 (dd, 2JPP = 30, JRhP = 5.58)[b]
3
4
93.8 (br. s)[c]
92.3 (br. s)[c]
90.2 (br. s)[c]
5
6
7
2
130.6 (d, JPP = 37)[d]
106.8 (s)[b]
[a] M = lone pair. [b] M = Au. [c] M = Cu. [d] M = Pd.
The equimolar reaction of 1a with CuCl in CH3CN/
107.9 ppm attributable to the presence of a small amount of CH2Cl2 produces the tetranuclear, dimetallic complex 3.
[ClAu{(o-MeOC6H4O)P(µ-NtBu)}2AuCl].[9] The formation The 31P NMR spectrum of 3 exhibits a doublet at δ =
of the dinuclear complex may be due to the replacement of 93.2 ppm for the rhodium-coordinated phosphorus atom of
the RhCl(cod) moiety present in 2 by [AuCl(SMe2)] which the cyclodiphosphazane, while the signal due to the copper-
was used in slight excess quantity for the complete conver- coordinated phosphorus atom appears as a broad singlet at
sion of 1a into 2. In order to confirm this metathesis reac- δ = 93.8 ppm. Reaction of 2 equiv. of CuX (X = Br, I) with
tion between Au and Rh centers, we carried out an NMR- 1a leads to the formation of heterotetranuclear derivatives
tube reaction between [(cod)RhCl{L-κP}] (1a) and 2 equiv. [(cod)RhBr(µ-L-κP,κP)Cu(µ-Br)]2 (4) and [{(cod)RhI(µ-L-
of [AuCl(SMe2)] in CDCl3. We observed complete conver- κP,κP)}2Cu(µ-X)2Cu] (5), respectively. The rhombic [Cu(µ-
sion of 1a into dinuclear gold complex [ClAu{(o-MeO- X)2Cu] unit in complex 5 contains a ca. 1:1 mixture of Cl
C6H4O)P(µ-NtBu)}2AuCl] as indicated by its 31P NMR and I disordered over both sites as indicated by X-ray dif-
Scheme 2.
Eur. J. Inorg. Chem. 2007, 4988–4997
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4989

M. S. Balakrishna et al.
FULL PAPER
Figure 1. 31P{1H} NMR (161 MHz) spectrum of 1a and 2 in CDCl3.
fraction studies. Complexes 3–5 show a slight increase in the formation of Cu–P bonds. The formation of Rh–X (X
1
their JRhP values as the halide varies from chloride to io- = Br, I) through the halogen exchange between Rh–Cl and
1
dide (3: 227; 4: 236; 5: 259 Hz). Similar variations in JRhP CuX (X = Br, I) as well as the preference for CuI over CuCl
have been seen in complexes containing the [RhXP3] unit in coordination with phosphorus can be explained on the
depending on the nature of the anionic ligand X situated basis of the HSAB principle.[13]
cis to the phosphorus atom in question[11] although the
The reaction of 1a with [PdCl(η3-C3H5)]2 in dichloro-
range is smaller than observed here. However, the remain- methane in a 2:1 ratio produces the heterodinuclear com-
ing ligand set on Rh here is two C=C moieties which are plex [(cod)RhCl(µ-L-κP,κP)PdCl(η3-C3H5)] (6) in good
weaker σ-donors than the two P atoms in the other exam- yield. The 31P NMR spectrum of 6 exhibits a doublet cen-
1
ples and since the magnitude of JMP is sensitive to the s- tered at δ = 130.6 ppm with 2JPP = 37 Hz for the palladium-
orbital character in the M–P bond,[12] there should be more coordinated phosphorus atom, whereas the signal corre-
s-orbital character to share between Rh and X in the pres- sponding to the rhodium-coordinated phosphorus atom ap-
ent case. Thus, a larger variation in the s-orbital character pears as a doublet of doublets centered at δ = 94.1 ppm
2
of the Rh–P bond with the nature of the halide ligand (1JRhP = 240 Hz, JPP = 37 Hz). Compounds 2–6 are stable
might be expected. The X-ray crystal structure of 5 reveals solids and soluble in CH2Cl2, CHCl3, and THF.
the presence of an Rh–I bond instead of the Rh–Cl bond
The complex trans-[Rh(CO)Cl(L-κP)2] (1b)[6] containing
present in the starting complex as well as the presence of a two uncoordinated phosphorus centers from two trans-dis-
rhombic [Cu(µ-X)2Cu] unit which clearly contains a mix- posed cyclodiphosphazanes, when treated with 2 equiv. of
ture of chloride and iodide but because the unit sits on a [AuCl(SMe2)] in dichloromethane, afforded trinuclear com-
crystallographic center of symmetry, the two halides are dis- plex 7 in quantitative yield (Scheme 3). The 31P NMR spec-
ordered over the two bridging sites. This result was unex- trum of 7 consists of a singlet at δ = 106.8 ppm, which is
pected since CuI was used in the reaction and suggests that assigned to the gold-coordinated phosphorus centers. The
the halogen exchange reaction occurs between the Rh–Cl doublet appearing at δ = 104.8 ppm (1JPRh = 218 Hz) is due
bond present in 1a and CuI to form the Rh–I derivative to the rhodium-coordinated phosphorus centers. The IR
with concomitant formation of CuCl, which later coordi- spectrum of 7 shows νCO at 2019 cm–1.
nates to the uncoordinated phosphorus center of cyclodi-
The slow addition of 2 equiv. of copper(I) iodide dis-
phosphazane to produce a tetranuclear complex 5. This in- solved in acetonitrile to a dichloromethane solution of 1b
dicates that the halogen exchange reaction occurs prior to affords complex 8 containing two RhI and two CuI centers
4990
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4988–4997

cis-{(o-MeOC6H4O)P(µ-NtBu)}2 as a Bridging Bidentate Ligand
Scheme 3.
along with two uncoordinated PIII ends. Complex 8 crys-
tallizes from the mother liquor at room temperature and
the X-ray quality yellow crystals obtained are insoluble in
most organic solvents, thus preventing solution spectro-
scopic characterization. The IR spectrum of 8 shows a
strong νCO band at 2021 cm–1 which is slightly lower than
that of the parent compound 1b.[6] The analytical data for
8 indicate the formation of a 1:1 complex between 1b and
CuI, and also the presence of an Rh–I bond. The structure
of 8 was confirmed by low-temperature X-ray diffraction
studies. Surprisingly, only one of the two dangling phos-
phorus(III) centers of complex 1b coordinates to CuI with
the resulting dimetallic Rh/Cu complex dimerizing through
the formation of a rhombic [Cu(µ-I)2Cu] unit, leaving the
other phosphorus(III) center uncoordinated. Since phos-
phorus prefers the softer CuI for coordination over the
CuCl which is generated from the halogen exchange reac-
tion, we carried out the reaction between 1b and CuI in
a 1:3 ratio to force coordination of CuI to the heretofore
uncoordinated phosphorus atom in anticipation of the for-
mation of a heteronuclear metallopolymer containing rho-
dium(I) and [Cu(µ-I)2Cu] units bridged by the cyclodiphos-
phazane. However, we observed exclusive formation of
complex 8 in this reaction as well as under various other
conditions.
Figure 2. Molecular structure of 2. Ellipsoids are drawn at the 50%
probability level and H atoms and solvent molecules are omitted
for clarity.
[ClAu{(o-MeOC6H4O)P(µ-NtBu)}2AuCl], but this impurity
appears to have no effect on the derived structural param-
eters for 2. Previously, Krishnamurthy and co-workers have
reported[15] the crystal structure of a heterodimetallic Mo0/
W0 complex containing µ-cyclodiphosphazane, cis-[(p-Me-
C6H4O)P(µ-NPh)]2, which is the only structurally charac-
terized heterometallic complex of cyclodiphosphazanes to
date. The geometry around the gold center in complex 2 is
linear with a P2–Au–Cl2 angle of 178.36(3)°, whereas the
rhodium center is in a distorted square-planar environment.
The P1–Rh bond length is 2.2269(8) Å, which is consider-
ably shorter than that in the parent compound
1
[2.2439(9) Å]. The Rh–Cl and Rh–C bond lengths are al-
most equal in both the complexes [Rh–Cl 2.3605(5) Å for
1b, 2.3612(9) Å for 2]. The presence of a shorter Rh–P bond
in 2 is also reflected in its 31P NMR spectrum, which shows
1
a large JRhP coupling of 247 Hz, whereas that in complex
1 is 229 Hz. The Au–P2 bond length in 2 is 2.2084(8) Å,
which is comparable to that found in the mononuclear gold
complex [ClAu{(o-MeOC6H4O)P(µ-NtBu)}2] [2.210(1) Å].[9]
Assessment of these bond parameters suggests a stronger
metal–ligand interaction in the heterodimetallic complex 2
as compared to the homodimetallic complex. The exocyclic
phenyl substituents on the phosphorus centers are arranged
Molecular Structures of 2, 4, 5, 7, and 8
Molecular structures of complexes 2, 4, 5, 7, and 8 with in an exo,endo manner. The P2N2 ring present in 2 is un-
atom numbering schemes are shown in Figures 2, 3, 4, 5, evenly puckered (see Table 5) with the sum of the angles
and 6, respectively. Crystallographic information and the around N1 and N2 being 359.00(18)° and 355.46(12)°,
details of the structure determination are summarized in respectively. The crystal structure of 2 contains a molecule
Table 6. The pertinent bond lengths and bond angles are of dichloromethane in the lattice which forms a weak C–
listed in Tables 2, 3, and 4. A compilation of Cremer–Pople H···Cl hydrogen bond with the chlorido ligand on the rho-
puckering parameters[14] for the cyclodiphosphazane rings dium atom (C21–H31A···Cl1 153°; H31A···Cl1 2.56 Å
in 2, 4, 5, 7, and 8 appears in Table 5.
which is significantly less than the 2.88 Å average normal-
X-ray quality crystals of 2 were grown from a 1:1 solu- ized distance determined previously for this type of interac-
tion of CH2Cl2/Et2O at –30 °C. In complex 2, the cyclodi- tion[16]). The other hydrogen atom on this solvent molecule
phosphazane bridges the rhodium(I) and gold(I) moieties (H31B) makes a contact of less than the sum of the
in a cis fashion through P-coordination. As noted in the van der Waals radii with the chlorido ligand on the gold
previous section, the crystal used for the structure determi- atom (Cl2), but the C–H···Cl angle is too small for this to
nation proved to contain about 3.8% of cocrystallized be considered a hydrogen bond.
Eur. J. Inorg. Chem. 2007, 4988–4997
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4991

M. S. Balakrishna et al.
FULL PAPER
Figure 3. Molecular structure of 4. Ellipsoids are drawn at the 50% probability level and H atoms and substituents on N (except α-C)
are omitted for clarity.
Figure 4. Molecular structure of 5. Ellipsoids are drawn at the 50% probability level and H atoms and substituents on N (except α-C)
are omitted for clarity.
Figure 5. Molecular structure of 7. Ellipsoids are drawn at the 50% probability level and H atoms and substituents on N (except α-C)
are omitted for clarity.
4992
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4988–4997

cis-{(o-MeOC6H4O)P(µ-NtBu)}2 as a Bridging Bidentate Ligand
Table 3. Selected bond lengths [Å] and bond angles [°] for 4 and 5.
Bond lengths
Bond angles
Complex 4
Rh–P1
Rh–Br1
Rh–P1
Rh–Br1
Rh–C23
Rh–C26
Rh–C27
Rh–C30
Cu–P2
Br2–Cu
P1–O1
P2–O3
P1–N1
P1–N2
P2–N1
P2–N2
Cu···O4
Cu···Cui
2.243(2)
2.484(2)
2.243(2)
2.484(2)
2.153(6)
2.234(6)
2.261(6)
2.112(6)
2.154(2)
2.370(2)
1.630(4)
1.625(4)
1.685(5)
1.690(5)
1.706(5)
1.692(5)
2.691(4)
3.082
Br1–Rh–P1
Br1–Rh–C26
Br1–Rh–P1
Br1–Rh–C26
Br1–Rh–C27
P1–Rh–C23
P1–Rh–C30
C23–Rh–C26
Br2–Cu–P2
Cu–Br2–Cui
Br2–Cu–Br2i
P2–Cu···O4
Cu–P2–O3
P1–O1–C9
89.72(4)
91.45(18)
89.72(4)
91.45(18)
90.19(19)
93.11(16)
94.30(18)
81.0(2)
136.71(6)
80.50(4)
99.50(4)
79.87(12)
110.99(17)
128.1(4)
125.2(3)
96.5(3)
P2–O3–C16
P1–N1–P2
P1–N2–P2
N1–P1–N2
N1–P2–N2
96.8(3)
83.6(2)
82.9(2)
Complex 5
Rh–P1
Cu–P2
Rh–I2
Rh–C23
Rh–C24
Rh–C27
Rh–C28
Cu– (Cl,I1)
Cu– (Cli,I1i)
P1–N1
2.2318(9)
2.166(1)
2.6779(4)
2.256(3)
2.279(3)
2.122(3)
2.154(3)
2.4894(7)
2.4647(7)
1.691(3)
1.681(3)
1.694(3)
1.686(3)
3.033
P1–Rh–I2
88.30(2)
157.5(1)
167.4(1)
93.9(1)
94.8(1)
80.5(1)
Figure 6. Molecular structure of 8. Ellipsoids are drawn at the 50%
probability level and H atoms and substituents on N (except α-C)
are omitted for clarity.
P1–Rh–C23
P1–Rh–C24
P1–Rh–C27
P1–Rh–C28
C23–Rh–C28
C23–Rh–C24
P2–Cu–(Cl,I1)
P2–Cu–(Cli,I1i)
(Cl,I1)–Cu–(Cli,I1i)
Cu–(Cl,I1)–Cui
P1–N1–P2
Table 2. Selected bond lengths [Å] and bond angles [°] for 2.
35.1(1)
Bond lengths
Bond angles
130.59(4)
123.40(3)
103.79(2)
76.21(2)
96.2(2)
96.9(2)
82.9(1)
Rh–P1
Au–P2
Rh–Cl1
Au–Cl2
Rh–C23
Rh–C24
Rh–C27
Rh–C28
P1–N1
P1–N2
P2–N1
P2–N2
P1–O1
P2–O3
N1–C1
N2–C5
2.2269(8)
2.2084(8)
2.3612(9)
2.2868(8)
2.245(3)
2.254(3)
2.123(3)
2.128(3)
1.693(2)
1.704(3)
1.667(2)
1.673(3)
1.607(2)
1.607(2)
1.494(4)
1.496(4)
P1–Rh–Cl1
P2–Au–Cl2
P1–Rh–C23
P1–Rh–C24
P1–Rh–C27
P1–Rh–C28
C23–Rh–C28
C23–Rh–C24
P1–N1–P2
P1–N2–P2
N1–P1–N2
N1–P2–N2
P1–O1–C9
P2–O3–C16
P1–N1–C1
P2–N1–C1
88.91(3)
178.36(3)
164.7(1)
159.9(1)
91.52(9)
95.79(9)
81.6(1)
35.4(1)
96.2(1)
95.6(1)
82.8(1)
P1–N2
P2–N1
P2–N2
P1–N2–P2
N1–P1–N2
N1–P2–N2
Cu···Cui
82.6(1)
displacement parameters after which refinement of occu-
pancy factors converged at ca. 0.5 for each atom type. Cop-
per complexes containing mixed halide bridges are rare but
84.5(1)
127.7(2)
125.7(2)
131.32(20)
131.48(20)
in
a copper(I) complex containing a mixed halide
[Cu4Br2Cl2] unit of distorted cubane geometry a 50:50 oc-
cupancy of all bridging halide sites was used as the model
for refinement of the structure as we have done here. A
similar disorder model was used in refining the structures of
Crystals of 4 and 5 suitable for X-ray structure determi- a series of [Cu2Cl6–xBrx]2– (x = 0.70–4.78) salts.[17] Copper
nation were obtained by slow evaporation of dichlorometh- centers adopt a distorted trigonal-planar geometry in both
ane from respective 1:1 CH3CN/CH2Cl2 solutions at room the molecules 4 and 5. The bromo derivative 4 shows larger
temperature. The core structures of 4 and 5 consist of a P2–Cu–Br [136.71(6)°] and short Br–Cu–Bri angles
rhombic [Cu(µ-X)2Cu] [X = Br (4) and X = apparent equi- [99.50(4)°] compared with 5 [P2–Cu–Xi 130.59(4)°, X–Cu–
molar mixture of Cl and I (5)] unit bridging the two [(cod)- Xi 103.79(2)°]. In structure 4, the OMe groups present on
RhX] (X = Br, I) moieties through two cyclodiphosphaz- exocyclic phosphorus substituents show strong interaction
anes as shown in Figures 3 and 4, respectively. Because the with the copper center [Cu···O4 2.691(4) Å], and this inter-
[Cu(µ-X)2Cu] unit in 5 sits on a crystallographic center of action leads to the formation of a boat-shaped six-mem-
symmetry, the bridging chlorido and iodido ligands are nec- bered ring around each copper center. However, complex 5
essarily disordered, so it is not possible to say whether each does not show such Cu···O interactions. The rhodium cen-
molecule actually has a discrete [Cu(µ-Cl)(µ-I)Cu] unit at ters in 4 and 5 are located in the center of a distorted
its center or if a more random distribution of Cl and I is square-planar environment with the corners being occupied
present. The best model for refinement proved to be one in by iodido, phosphorus, and 1,5-cyclooctadiene ligands. The
which Cl and I were given the same atomic coordinates and Rh–P1 bond lengths in 4 and 5 are 2.243(1) and 2.232(1) Å,
Eur. J. Inorg. Chem. 2007, 4988–4997
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4993

M. S. Balakrishna et al.
FULL PAPER
Table 4. Selected bond lengths [Å] and bond angles [°] for 7 and 8. of the parent complex 1b. The geometry around the rho-
dium center is slightly distorted square-planar with cis
Bond lengths
Bond angles
angles varying from 88.80(2) (P1–Rh–Cl1) to 91.12(2)° (P1–
Rh–C1). The gold centers are dicoordinated and have a lin-
ear geometry with a P2–Au–Cl2 angle of 179.70(3)° which
is more linear than that in the monometallic complex of
the same ligand [176.83(2)°] but comparable with that in
Ph3PAuCl [179.63(2)°].[19] The Rh–P1 distance in 7 is
2.2687(7) Å, which is shorter than those in the parent com-
pound [1b: 2.2784(6), 2.2863(6) Å] – a situation comparable
to that in the RhI/AuI complex 2. The Au–P2 bond length
is 2.1968(7) Å which is slightly shorter than that in 3 but
much shorter than that in the mononuclear gold complex
of the same ligand, [AuCl({(o-MeOC6H4O)P(µ-NtBu)}2-
κP)].[11] The phenyl substituents on the phosphorus centers
are arranged in an exo,endo manner.
Crystals of 8 suitable for X-ray diffraction studies were
obtained from a CH2Cl2/CH3CN solution at room tem-
perature. The core structure of 8 consists of two trans-
Rh(P2N2)2 moieties that are bridged by a [Cu(µ-I)2Cu] unit
to form a heterometallic complex containing two RhI and
two CuI centers along with an uncoordinated PIII site at
each end. These two trans-Rh(P2N2)2 moieties are oriented
in a trans manner with respect to the plane of the rhombic
[Cu(µ-I)2Cu] unit and gives the molecule an overall S-shape.
The rhodium centers are in distorted square-planar geome-
tries, whereas the copper centers are in trigonal-planar envi-
ronments. The Rh–P2 bond [2.288(2) Å] is shorter than the
Rh–P3 distance [2.302(2) Å] while the distance between the
two copper atoms (Cu···Cui) is 3.085 Å at 100 K, which in-
dicates the absence of metal–metal interactions in complex
8. This stands in contrast to the low-temperature structure
of (Cy3P)Cu(µ-I)2Cu(PCy3) in which the Cu···Cu separa-
tion is 2.893(2) Å.[20] Interestingly, the molecular structure
of 8 shows a weak interaction between the copper and io-
dine atoms to form two six-membered rings based on the
observation that the Cu···I2 distance is 3.262 Å, which is
distinctly shorter than the sum of the van der Waals radii
for the two atoms (3.38 Å).[21] There are no unusually short
intermolecular contacts apparent that would flex the mole-
cule so as to cause I2 to approach Cu more closely than a
van der Waals contact, but since the distance is much longer
than normal bonding distances [2.525(4)–2.640(2) Å],[22] it
is a weak attractive interaction at best. There also appears
Complex 7
Rh–P1
Rh–Cl1
Rh–C1
Au–P2
Au–Cl2
C1–O1
P1–N1
P1–N2
P2–N1
P2–N2
P1–O2
P2–O4
2.2687(7)
2.341(1)
1.841(4)
2.1968(7)
2.2720(7)
1.133(5)
1.699(2)
1.689(2)
1.671(2)
1.674(2)
1.608(2)
1.606(2)
P1–Rh–Cl1
P1–Rh–C1
P1–Rh–P1i
Cl1–Rh–C1
Au–P2–O4
P2–Au–Cl2
P1–N1–P2
P1–N2–P2
N1–P1–N2
N1–P2–N2
P1–O2–C10
P2–O4–C17
88.80(2)
91.12(2)
176.33(4)
176.6(1)
113.61(8)
179.70(3)
95.8(1)
96.1(1)
82.9(1)
84.2(1)
126.9(2)
125.4(2)
Complex 8
P2–Rh
P3–Rh
P1–Cu
Rh–I2
Rh–C45
Cu–I1
2.288(2)
2.302(2)
2.173(2)
2.6799(7)
1.832(7)
2.505(1)
2.564(1)
1.701(5)
1.701(5)
1.683(5)
1.686(5)
1.671(5)
1.685(5)
1.716(5)
1.725(6)
3.085
P2–Rh–C45
P3–Rh–C45
P2–Rh–I2
P3–Rh–I2
P2–Rh–P3
I2–Rh–C45
P1–Cu–I1
P1–Cu–Ii
91.0(2)
87.8(2)
88.19(4)
93.00(4)
178.25(6)
179.1(2)
128.95(6)
122.46(6)
105.01(3)
74.99(3)
95.9(3)
95.7(3)
82.6(3)
83.6(3)
97.7(7)
Cui–I1
P1–N1
P1–N2
P2–N1
P2–N2
P3–N3
P3–N4
P4–N3
P4–N4
Cu···Cui
Cu···I2
I1–Cu–Ii
Cu–I1–Cui
P1–N1–P2
P1–N2–P2
N1–P1–N2
N1–P2–N2
P3–N3–P4
P3–N4–P4
N3–P3–N4
N3–P4–N4
96.8(3)
83.1(3)
80.6(2)
3.262
Table 5. Cremer–Pople puckering parameters for the cyclodiphos-
phazane in 2, 5, 7, and 8.
Complex Q2 [Å]
Dihedral angle [°]
P1–N1–N2 vs. N1–P2–N2 P1–N1–P2 vs. P1–P2–N2
Dihedral angle [°]
2
5
7
8
0.106
–0.131
–0.111
0.167
170.3
168.2
169.8
164.8
166.2[b]
169.2
166.7
168.7
163.0
164.2[c]
0.155[a]
[a] For the P3–N3–P4–N4 ring. [b] Dihedral angle P3–N3–N4 vs.
P3–N4–P4. [c] Dihedral angle P3–N3–P4 vs. P3–P4–N4.
respectively, which is slightly shorter than that in the parent to be a distinct C–H···I hydrogen bond between the aro-
complex 1a. The Cu···Cui separation of 3.082(1) and matic hydrogen atom H27 and I1 (H27···I1 2.993 Å; C27–
3.057(1) Å, respectively, in complexes 4 and 5, indicate the H27···I1 156.05°) as the H27···I1 distance is less than the
absence of cuprophilicity.[18] The two rhodium moieties 3.15 Å mean H···I1 distance considered indicative of a C–
present in 4 and 5 are arranged in a trans disposition with H···I hydrogen bond.[16]
respect to the [Cu(µ-X)2Cu] plane; however, the molecules
maintain the cis disposition of substituents on the phospho-
rus atom with respect to the P2N2 plane as was found in
the molecular structure of 1a.
Conclusions
Single crystals of 7 were grown by slow diffusion of hex-
Several heterodi-, -tri-, and -tetrametallic complexes
ane into a dichloromethane solution of the complex at [CuI/RhI (3d/4d), PdII/RhI (4d/4d), and AuI/RhI (5d/4d)]
room temperature. Complex 7 contains two gold centers containing cyclodiphosphazanes are described. The selec-
bridged by rhodium-bound cyclodiphosphazanes to form a tive mono- and bidentate coordination modes exhibited by
trinuclear complex with a conformation very similar to that cyclodiphosphazane with a range of metal precursors gives
4994
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4988–4997

cis-{(o-MeOC6H4O)P(µ-NtBu)}2 as a Bridging Bidentate Ligand
0.128 mmol) and [(cod)RhCl{L-κP}] (1a) (44.9 mg, 0.064 mmol).
Yield: 74% (42.07 mg). M.p. 236–238 °C (dec). C60H88Br4Cu2N4-
O8P4Rh2 (1769.7): calcd. C 40.71, H 5.01, N 3.16; found C 40.94,
H 5.17, N 3.24. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.94–6.84
(m, 16 H, Ph), 5.78, 4.44 (m, 8 H, CH), 3.93 (s, 6 H, OMe), 3.82
a facile synthetic approach for construction of hetero-
metallic systems. The halogen exchange reaction was ob-
served for the first time between Rh–Cl and Cu–X (X = Br,
I) during the synthesis of CuI/RhI derivatives. Formation of
rhombic [Cu(µ-X)2Cu] units increases the nuclearity and
can be utilized for the synthesis of a series of heterometallic
coordination polymers. The work in this direction is cur-
rently underway in our laboratory.
(s, 6 H, OMe), 2.41–2.19 (m, 16 H, CH2), 1.55 (s, 36 H, tBu) ppm.
1
31P{1H} NMR (161.9 MHz, CDCl3, 25 °C): δ = 93.0 (d, JPRh
=
236 Hz, 2 P, RhP), 92.3 (br. s, 2 P, CuP) ppm.
Synthesis of [((cod)RhBr{µ-L-κP,κP})2Cu(µ-Cl,I)Cu] (5): The syn-
thesis was the same as that for 3, using copper(I) iodide (27.5 mg,
0.144 mmol) and [(cod)RhCl{L-κP}] (1a) (50.3 mg, 0.072 mmol).
Yield: 85% (57.10 mg). M.p. 224–226 °C (dec). C60H88ClCu2I3N4-
O8P4Rh2 (1866.3): calcd. C 38.61, H 4.75, N 3.00; found C 38.83,
H 4.81, N 3.07. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.98–6.87
(m, 16 H, Ph), 5.87, 4.67 (br. s, 8 H, CH), 3.82 (s, 6 H, OMe), 3.81
Experimental Section
General: All manipulations were performed under rigorously anaer-
obic conditions using high-vacuum manifolds and Schlenk tech-
niques. All the solvents were purified by conventional procedures
and freshly distilled and degassed prior to use.[23] Compounds cis-
{(o-MeOC6H4O)P(µ-NtBu)}2 (L), [(cod)RhCl{L-κP}] (1a), trans-
(s, 6 H, OMe), 2.47–2.01 (m, 16 H, CH2), 1.53 (s, 36 H, tBu) ppm.
1
31P{1H} NMR (161.9 MHz, CDCl3, 25 °C): δ = 91.0 (d, JPRh
=
259 Hz, 2 P, RhP), 90.2 (br. s, 2 P, CuP) ppm.
[Rh(CO)Cl{L-κP}2] (1b),[6] [AuCl(SMe2)],[24] CuX (X = Cl, Br)[25]
and [PdCl(η-C3H5)]2 were prepared according to published pro-
cedures. CuI was purchased from commercial sources and used as
received.
,
Synthesis of [(cod)RhCl{µ-L-κP,κP}PdCl(η3-C3H5)] (6): A dichlo-
romethane solution (5 mL) of [PdCl(η3-C3H5)]2 (16.9 mg,
0.046 mmol) was added dropwise to a well-stirred dichloromethane
(10 mL) solution of [(cod)RhCl{L-κP}] (1a) (64.6 mg, 0.093 mmol)
at room temperature. The reaction mixture was stirred for 6 h,
concentrated to 5 mL under reduced pressure, diluted with
diethyl ether (5 mL) and stored at –30 °C for 1 d to give a yellow
crystalline solid (61.3 mg, 75%). M.p. 160–162 °C (dec).
C33H49Cl2N2O4P2PdRh (879.9): calcd. C 45.04, H 5.61, N 3.18;
found C 45.31, H 5.82, N 3.37. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 7.79–6.76 (m, 8 H, Ph), 5.60 (br. s, 1 H, allyl CH), 5.73,
4.32 (s, 4 H, cod CH), 4.66, 3.65 (m, 4 H, allyl CH2), 3.84 (s, 3 H,
OMe), 3.82 (s, 3 H, OMe), 2.46–2.25 (m, 8 H, CH2), 1.57 (s, 18 H,
tBu) ppm. 31P{1H} NMR (161.9 MHz, CDCl3, 25 °C): δ = 130.6
[26]
Instrumentation: 1H and 31P{1H} NMR (δ in ppm) spectra were
recorded with a Varian Mercury Plus spectrometer operating at the
appropriate frequencies using TMS and 85% H3PO4 as internal
and external references, respectively. IR spectra of KBr disks were
recorded with a Nicolet Impact 400 FT-IR instrument. Micro-
analyses were performed with a Carlo Erba Model 1112 elemental
analyzer. Mass spectrometry experiments were carried out with a
Waters Q-Tof micro-YA-105 instrument. Melting points were re-
corded in capillary tubes and are uncorrected.
Synthesis of [(cod)RhCl{µ-L-κP,κP}AuCl] (2): A dichloromethane
solution (5 mL) of [AuCl(SMe2)] (22.2 mg, 0.075 mmol) was added
dropwise to a well-stirred dichloromethane solution (7 mL) of
[(cod)RhCl{L-κP}] (1a) (52.5 mg, 0.075 mmol) at room tempera-
ture. The resulting yellow reaction mixture was stirred for 4 h. The
solution was concentrated to 5 mL under reduced pressure, diluted
with 5 mL of Et2O and stored at –30 °C for 1 d to give the product
as yellow crystals (62.4 mg, 89%). M.p. 222–224 °C (dec).
C30H44AuCl2N2O4P2Rh (929.4): calcd. C 38.76, H 4.77, N 3.01;
found C 38.50, H 4.74, N 3.22. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 7.78–6.79 (m, 8 H, Ph), 5.77, 4.33 (br. s, 4 H, CH), 3.85
(s, 3 H, OMe), 3.82 (s, 3 H, OMe), 2.49–2.24 (m, 8 H, CH2), 1.66
(s, 18 H, tBu) ppm. 31P{1H} NMR (161.9 MHz, CDCl3, 25 °C): δ
2
1
(d, JPP = 37 Hz, 1 P, PPd), 94.1 (dd, JPRh = 240 Hz, 1 P, PRh)
ppm.
Synthesis of trans-[Rh(CO)Cl{µ-L-κP,κP}2(AuCl)2] (7): To a sus-
pension of trans-[Rh(CO)Cl{L-κP}2] (1b) (100 mg, 0.093 mmol) in
acetonitrile (5 mL), a dichloromethane solution (10 mL) of [AuCl-
(SMe2)] (55.1 mg, 0.187 mmol) was added dropwise at room tem-
perature. The reaction mixture was stirred for 4 h, concentrated to
10 mL under reduced pressure, and diluted with hexane (5 mL).
Storing the resulting clear yellow solution overnight afforded a
crystalline product (132 mg, 93%). M.p. 236–238 °C.
C45H64Au2Cl3N4O9P4Rh (1532.1): calcd. C 35.27, H 4.21, N 3.65;
found C 35.02, H 4.10, N 3.88. IR (KBr disk): ν = 2019 [ν(CϵO)]
˜
2
3
cm–1. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 7.31–6.91 (m, 16 H,
Ph), 3.93 (s, 6 H, OMe), 3.91 (s, 6 H, OMe), 1.73 (s, 36 H, tBu)
ppm. 31P{1H} NMR (161.9 MHz, CDCl3, 25 °C): δ = 106.8 (s, 2
= 104.7 (dd, JPP = 30 Hz, JRhP = 5.58 Hz, 1 P, PAu), 94.1 (dd,
1JPRh = 247 Hz, 1 P, PRh) ppm. MS (EI): m/z = 893.21 [M – Cl].
Synthesis of [(cod)RhCl{µ-L-κP,κP}Cu(µ-Cl)]2 (3): Copper(I) chlo-
ride (4.5 mg, 0.045 mmol), dissolved in acetonitrile (5 mL), was
added dropwise to a well-stirred CH2Cl2 solution (10 mL) of
[(cod)RhCl{L-κP}] (1a) (31.1 mg, 0.045 mmol) at room tempera-
ture. The resulting yellow reaction mixture was stirred for 6 h. The
solution was concentrated to 5 mL under reduced pressure, diluted
with Et2O (5 mL) and stored at –30 °C for 1 d to afford yellow
crystals of the product (33.9 mg, 61%). M.p. 228–230 °C (dec).
C60H88Cl4Cu2N4O8P4Rh2 (1519.9): calcd. C 45.26, H 5.57, N 3.51;
found C 45.53, H 5.39, N 3.44. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 7.89–6.84 (m, 16 H, Ph), 5.72, 4.32 (s, 8 H, CH), 3.93
(s, 6 H, OMe), 3.81 (s, 6 H, OMe), 2.48–2.22 (m, 16 H, CH2), 1.57
(s, 36 H, tBu) ppm. 31P{1H} NMR (161.9 MHz, CDCl3, 25 °C): δ
1
P, PAu), 104.8 (d, JPRh = 218.5 Hz, 2 P, PRh) ppm.
Synthesis of [Rh(CO)I{µ-L-κP,κP}2Cu(µ-I)]2 (8): Copper(I) iodide
(0.019 g, 0.101 mmol) in CH3CN (5 mL) was added dropwise to a
well-stirred dichloromethane solution (10 mL) of trans-[Rh(CO)-
Cl{L-κP}2] (1b) (0.054 g, 0.051 mmol) at room temperature. The
reaction mixture was stirred for 6 h. Upon standing at room tem-
perature for 3 d, the yellow solution afforded compound 8 as dark
yellow crystals (47.5 mg, 69%). M.p. 248–250 °C (dec). C90H128
-
Cu2I4N8O18P8Rh2 (2698.3): calcd. 40.06, H 4.78, N 4.15; found C
40.38, H 4.42, N 4.27. IR (KBr disk): ν = 2021 [ν(CϵO)] cm–1.
˜
X-ray Crystallography: Crystals of 2, 4, 5, 7, and 8 were mounted
in a CryoLoop with a drop of Paratone oil and placed in the cold
nitrogen stream of the Kryoflex attachment of the Bruker APEX
CCD diffractometer (Table 6). For each, a full sphere of data was
collected using a protocol of 400 scans in ω (0.5° per scan) at φ =
1
= 93.8 (br. s, 2 P, CuP), 93.2 (d, JPRh = 227 Hz, 2 P, RhP) ppm.
Synthesis of [(cod)RhBr{µ-L-κP,κP}Cu(µ-Br)]2 (4): The synthesis
was the same as that for 3, using copper(I) bromide (18.4 mg,
Eur. J. Inorg. Chem. 2007, 4988–4997
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4995

M. S. Balakrishna et al.
FULL PAPER
Table 6. Crystallographic parameters and refinement details for complexes 2, 4, 5, 7, and 8.
2·CH2Cl2
4
5
7
8
Empirical formula
C31H46AuCl4N2O4P2Rh C60H88Br4Cu2N4O8P4Rh2 C60H88ClCu2I3N4O8P4Rh2 C45H64Au2Cl3N4O9P4Rh C90H128Cu2I4N8O18P8Rh2
Formula mass
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
γ [°]
V [Å3]
Z
1023.61
monoclinic
P21/c
11.161(1)
17.253(2)
19.776(2)
90
100.281(1)
90
3746.9(6)
4
1769.76
triclinic
P1
1866.27
monoclinic
P21/c
10.7191(8)
18.665(1)
17.017(1)
90
91.675(1)
90
3403.1(4)
4
1532.08
orthorhombic
Pnma
13.642(1)
29.323(3)
15.236(1)
90
90
90
6094.6(9)
4
1.670
2698.29
triclinic
P1
¯
¯
9.863(1)
10.319(1)
18.877(2)
91.670(1)
98.434(1)
114.655(1)
1718.3(3)
1
12.119(1)
15.336(2)
16.499(2)
106.365(1)
103.718(1)
104.491(1)
2687.8(5)
1
ρcalcd. [gcm–3
]
1.815
4.758
2015
1.710
3.554
888
1.812
2.641
1834
1.667
2.024
2696
µ(Mo-Kα) [mm–1
F(000)
]
5.355
2992
Crystal size [mm]
T [K]
0.10ϫ0.15ϫ0.18
100
0.05ϫ0.15ϫ0.19
100
0.15ϫ0.17ϫ0.20
100
0.09ϫ0.17ϫ0.17
100
0.17ϫ0.13ϫ0.06
100
θ range [°]
2.1–28.3
65502
9318 (Rint = 0.041)
0.0269
2.2–28.2
29820
8357 (Rint = 0.051)
0.0558
0.1602
1.03
2.2–28.3
59384
8484 (Rint = 0.035)
0.0381
0.1056
0.97
1.4–28.3
52609
7582 (Rint = 0.037)
0.0255
0.0615
1.04
1.4–28.3
23883
12230 (Rint = 0.025)
0.0635
0.1926
1.04
Total no. reflns.
No. of indep. reflns.
[a]
R1
[b]
wR2
0.0636
Goodness-of-fit on F2 1.05
2
2
[a] R = Σ||Fo| – |Fc||/Σ|Fo|. [b] wR2 = {[Σw(Fo – Fc )/Σw(Fo2)2]}1/2
.
0, 90, and 180° plus 800 scans in φ (0.45° per scan at ω = –30 and
210° for 2, 4, and 5) and one of 606 scans in ω (0.3° per scan) at
φ = 0, 120, and 240° for 7 and 8 using the SMART software pack-
age.[27] The raw data were reduced to F2 values using the SAINT+
software[28] and global refinements of unit cell parameters em-
ploying 8555–9267 reflections chosen from the full data set were
performed. Multiple measurements of equivalent reflections pro-
vided the basis for empirical absorption correction as well as a
correction for any crystal deterioration during the data collection
(SADABS[29]). The structures were solved by direct methods and
refined by full-matrix least-squares procedures using the
SHELXTL program package.[30] Hydrogen atoms were placed in
calculated positions [C–H 0.95 Å (aromatic rings) or 0.98 Å
(methyl groups)] and included as riding contributions with iso-
tropic displacement parameters 1.2 (aromatic rings) or 1.5 (methyl
groups) times those of the attached non-hydrogen atoms. Near the
end of the refinement of the structure of 2, two significant peaks
were observed in a difference map near the rhodium atom which
formed a linear unit with P1. These were treated as the second
Au and Cl atoms of the [ClAu{(o-MeOC6H4O)P(µ-NtBu)}2AuCl]
impurity which had been identified by NMR spectroscopy in the
original sample and which presumably had cocrystallized with 2.
Addition of these to the model significantly improved the refine-
ment and resulted in a refined occupancy of the digold complex
impurity of 0.038. CCDC-642038 (2), -642039 (4), -642040 (5),
-642041 (7), and -642042 (8) contain the supplementary crystallo-
graphic data for this paper. This can be obtained free of charge
from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
LEQSF(2002-03)-ENH-TR-67 for the purchase of a Bruker APEX
CCD diffractometer and the Chemistry Department of Tulane
University for support of the X-ray laboratory.
[1] a) N. Wheatley, P. Kalck, Chem. Rev. 1999, 99, 3379–3419; b)
C. E. Plecnik, S. Liu, S. G. Shore, Acc. Chem. Res. 2003, 36,
499–508; c) M. Sakamoto, K. Manseki, H. Okawa, Coord.
Chem. Rev. 2001, 219–221, 379–414; d) H. B. Gray, B. G.
Malmstrom, Biochemistry 1989, 28, 7499–7505.
[2] a) R. E. P. Winpenny, Chem. Soc. Rev. 1998, 27, 447–452; b) J.
Costes, F. Dahan, J. G. Tojal, Chem. Eur. J. 2002, 8, 5430–5434;
c) Y. Yang, L. McElwee-White, Dalton Trans. 2004, 2352–2356;
d) J. L. Dempsey, A. J. Esswein, D. R. Manke, J. Rosenthal,
J. D. Soper, D. G. Nocera, Inorg. Chem. 2005, 44, 6879–6892.
[3] a) M. Shibasaki, N. Yoshikawa, Chem. Rev. 2002, 102, 2187–
2209; b) P. A. Shapley, N. Zhang, J. L. Allen, D. H. Pool, H. C.
Liang, J. Am. Chem. Soc. 2000, 122, 1079–1091; c) G. J. Mat-
are, M. E. Tess, Y. Yang, K. A. Abboud, L. McElwee-White,
Organometallics 2002, 21, 711–716.
[4] a) H. Han, M. Elsmaili, S. A. Johnson, Inorg. Chem. 2006, 45,
7435–7445; b) M. Gagliardo, G. Rodriguez, H. H. Dam, M.
Lutz, A. L. Spek, R. W. A. Havenith, P. Coppo, L. D. Cola, F.
Hartl, G. P. M. vanKlink, G. vanKoten, Inorg. Chem. 2006, 45,
2143–2155; c) Y. Yang, K. A. Abboud, L. McElwee-White,
Dalton Trans. 2003, 4288–4296; d) A. H. Eisenberg, M. V. Ov-
chinnikov, C. A. Mirkin, J. Am. Chem. Soc. 2003, 125, 2836–
2837.
[5] a) M. S. Balakrishna, V. S. Reddy, S. S. Krishnamurthy, J. F.
Nixon, J. C. T. R. B. Laurent, Coord. Chem. Rev. 1994, 129, 1–
90; b) M. S. Balakrishna, S. S. Krishnamurthy, J. Organomet.
Chem. 1992, 424, 243–251; c) J. C. T. R. B. Laurent, P. B.
Hitchcock, J. F. Nixon, J. Organomet. Chem. 1983, 249, 243–
254.
Acknowledgments
[6] a) P. Chandrasekaran, J. T. Mague, M. S. Balakrishna, Organo-
metallics 2005, 24, 3780–3783; b) P. Chandrasekaran, J. T.
Mague, M. S. Balakrishna, Inorg. Chem. 2005, 44, 7925–7932;
c) P. Chandrasekaran, J. T. Mague, M. S. Balakrishna, Inorg.
Chem. 2006, 45, 6678–6683; d) P. Chandrasekaran, J. T. Mague,
M. S. Balakrishna, Inorg. Chem. 2006, 45, 5893–5897; e) P.
We are grateful to the Department of Science and Technology
(DST), New Delhi for funding. P. C. thanks the Council of Scien-
tific and Industrial Research (CSIR) for a Research Fellowship.
J. T. M. thanks the Louisiana Board of Regents through grant
4996
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 4988–4997

cis-{(o-MeOC6H4O)P(µ-NtBu)}2 as a Bridging Bidentate Ligand
Chandrasekaran, J. T. Mague, M. S. Balakrishna, Dalton
Trans. 2007, 2957–2962.
[13] R. G. Pearson, J. Am. Chem. Soc. 1963, 85, 3533–3543.
[14] D. Cremer, J. Pople, J. Am. Chem. Soc. 1975, 97, 1354–1358.
[15] V. S. Reddy, S. S. Krishnamurthy, M. Nethaji, J. Chem. Soc.
Dalton Trans. 1994, 2661–2667.
[16] L. Brammer, E. A. Bruton, P. Sherwood, Cryst. Growth Des.
2001, 1, 277–290.
[17] a) M. Haakansson, S. Jagner, E. Clot, O. Eisenstein, Inorg.
Chem. 1992, 31, 5389–5394; b) R. D. Willett, R. Butcher, C. P.
Landee, B. Twamley, Polyhedron 2005, 24, 2222–2231.
[18] P. Pyykko, Chem. Rev. 1997, 97, 597–636.
[19] N. C. Baenziger, W. E. Bennett, D. M. Soboroff, Acta Crys-
tallogr., Sect. B 1976, 32, 962–963.
[20] G. L. Soloveichik, O. Eisenstein, J. T. Poulton, W. E. Streib,
J. C. Huffman, K. G. Caulton, Inorg. Chem. 1992, 31, 3306–
3312.
[21] A. Bondi, J. Phys. Chem. 1964, 68, 441–451.
[22] G. A. Bowmaker, S. E. Boyd, J. V. Hanna, R. D. Hart, P. C.
Healy, B. W. Skelton, A. H. White, J. Chem. Soc. Dalton Trans.
2002, 2722–2730.
[23] W. L. F. Armarego, D. D. Perrin, Purification of Laboratory
Chemicals, 4th ed., Butterworth-Heinemann, Linacre House,
Jordan Hill, Oxford, U. K., 1996.
[24] M. Brandys, M. C. Jennings, R. J. Puddephatt, J. Chem. Soc.
Dalton Trans. 2000, 4601–4606.
[25] B. S. Furniss, A. J. Hannaford, P. W. G. Smith, A. R. Tatchell,
Vogel’s Textbook of Practical Organic Chemistry, 5th ed.,
ELBS, England, 1989.
[7] a) S. Ogo, R. Kabe, K. Uehara, B. Kure, T. Nishimura, S. C.
Menon, R. Harada, S. Fukuzumi, Y. Higuchi, T. Ohhara, T.
Tamada, R. Kuroki, Science 2007, 316, 585–587; b) M. A. F.
Hernandez-Gruel, J. J. Perez-Torrente, M. A. Ciriano, A. B.
Rivas, F. J. Lahoz, I. T. Dobrinovitch, L. A. Oro, Organometal-
lics 2003, 22, 1237–1249; c) J. Choudhury, S. Podder, S. Roy, J.
Am. Chem. Soc. 2005, 127, 6162–6163; d) T. Hosokawa, M.
Takano, S. Murahashi, H. Ozaki, Y. Kitagawa, K. Sakaguchi,
Y. Katsube, J. Chem. Soc. Chem. Commun. 1994, 1433–1434;
e) D. Drommi, F. Nicolo, C. A. Arena, G. Bruno, F. Faraone,
R. Gobetto, Inorg. Chim. Acta 1994, 221, 109–116; f) E. K.
Van Den Beuken, B. L. Feringa, Tetrahedron 1998, 54, 12985–
13011; g) P. A. Robles-Dutenhefner, E. M. Moura, G. J. Gama,
H. G. L. Siebald, E. V. Gusevskaya, J. Mol. Catal. A 2000, 164,
39–47; h) H. Kato, H. Seino, Y. Mizobe, M. Hidai, J. Chem.
Soc. Dalton Trans. 2002, 1494–1499.
[8] a) B. Punji, J. T. Mague, M. S. Balakrishna, Inorg. Chem. 2006,
45, 9454–9464; b) B. Punji, J. T. Mague, M. S. Balakrishna,
Dalton Trans. 2006, 1322–1330; c) S. Priya, M. S. Balakrishna,
J. T. Mague, S. M. Mobin, Inorg. Chem. 2003, 42, 1272–1281;
d) S. Priya, M. S. Balakrishna, J. T. Mague, J. Organomet.
Chem. 2003, 679, 116–124; e) M. S. Balakrishna, R. Panda,
J. T. Mague, Inorg. Chem. 2001, 40, 5620–5625; f) R. Venkates-
waran, J. T. Mague, M. S. Balakrishna, Inorg. Chem. 2007, 46,
808–817; g) R. Venkateswaran, S. M. Mobin, M. S. Balak-
rishna, Eur. J. Inorg. Chem. 2007, 1930–1938.
[9] P. Chandrasekaran, J. T. Mague, M. S. Balakrishna, unpub-
lished results.
[10] a) A. M. Z. Slawin, M. B. Smith, J. D. Woollins, J. Chem. Soc.
Dalton Trans. 1996, 1283–1293; b) A. M. Z. Slawin, M. B.
Smith, J. D. Woollins, J. Chem. Soc. Dalton Trans. 1996, 4575–
4581.
[11] a) G. G. Christoph, P. Blum, W.-C. Liu, A. Elia, D. W. Meek,
Inorg. Chem. 1979, 18, 894–897; b) T. H. Brown, P. J. Green, J.
Am. Chem. Soc. 1970, 92, 2359–2362.
[12] J. G. Verkade, J. A. Mosbo in Phosphorus-31 NMR Spec-
troscopy in Stereochemical Analysis (Eds.: J. G. Verkade, L. D.
Quin), VCH Publishers, Inc., Deerfield Beach, FL, USA, 1987,
p. 425–464.
[26] Y. Tatsuno, T. Yoshida, S. Otsuka, Inorg. Synth. 1990, 28, 342–
345.
[27] SMART, version 5.625, Bruker-AXS, Madison, WI, 2000.
[28] SAINT+, version 6.35A, Bruker-AXS, Madison, WI, 2002.
[29] G. M. Sheldrick, SADABS, version 2.05, University of
Göttingen, Germany, 2002.
[30] a) SHELXTL, version 6.10, Bruker-AXS, Madison, WI, 2000;
b) G. M. Sheldrick, SHELXS97 and SHELXL97, University
of Göttingen, Germany, 1997.
Received: May 25, 2007
Published Online: September 12, 2007
Eur. J. Inorg. Chem. 2007, 4988–4997
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4997