Three- and four-coordinate gold(I) complexes of 3,6-bis(diphenylphosphino)pyridazine: Monomers, polymers, and a metallocryptand cage

Article abstract of DOI:10.1021/ic020601m

The slightly yellow polymeric complexes {Au₂Cl₂(P₂pz)₃}n, 1·6CHCl₃, (P₂pz is 3,6-bis(diphenylphosphino)pyridazine) and {[Au₂(P₂pz)₃](PF₆)₂}n, 2, are prepared by the stoichiometric reaction of AuCl(tht) (tht is tetrahydrothiophene) and P₂pz in either dichloromethane or dichloromethane/methanol, respectively. Addition of 2 equiv of AuCl(tht) to a dichloromethane solution of 1 equiv of P₂pz generates the simple (AuCl)₂(P₂pz) compound, 3. Compound 3 contains nearly linear P-Au-Cl units with intermolecular Au...Au separations of 3.570 A. Au₂l₂(P₂pz)₃, 4, is prepared by reacting excess Nal with 2 in a dichloromethane/methanol mixture. Characterization of 1, 2, and 4 by X-ray crystallography confirms the 2:3 gold/ligand ratio of all three complexes. The coordination polymer 1 maintains a high degree of solvation in the solid-state with three chloroform adducts hydrogen-bonded to the chloride ligand on each gold atom. These chloroform molecules are sandwiched between the two-dimensional polymeric sheets of 1. The crystal structure of 4 reveals an empty, iodide-capped metallocryptand cage with the tetrahedrally distorted gold atoms and the nitrogen atoms on the pyridazine rings directed away from the center of the cavity. No metal ion encapsulation was observed for complex 4. Complex 2 forms one-dimensional arrays of [Au₂(P₂pz)₂]²⁺ metallomacrocycles connected to each other by a third P₂pz ligand. The electronic absorption spectra (CH₂Cl₂) of 1-4 show broad, nearly featureless absorption bands that tail into the visible with π-π* bands at 296 nm and discernible shoulders at 314 nm for 2 and 334 nm for 3. Excitation into the low energy band of 2 produces only a modest emission in solution at 540 nm (λ_ex 468 nm) and 493 nm (λ_ex 403 nm). Under identical conditions, the P₂pz ligand also emits at 540 and 493 nm.

Full text of DOI:10.1021/ic020601m

Inorg. Chem. 2003, 42, 2141−2148
Three- and Four-Coordinate Gold(I) Complexes of
3,6-Bis(diphenylphosphino)pyridazine: Monomers, Polymers, and a
Metallocryptand Cage
Vincent J. Catalano,* Mark A. Malwitz, Stephen J. Horner, and John Vasquez
Department of Chemistry, UniVersity of NeVada, Reno, NeVada 89557
Received October 7, 2002
The slightly yellow polymeric complexes {Au2Cl2(P pz)3}n, 1‚6CHCl3, (P pz is 3,6-bis(diphenylphosphino)pyridazine)
2
2
and {[Au2(P pz)3](PF ) }n, 2, are prepared by the stoichiometric reaction of AuCl(tht) (tht is tetrahydrothiophene)
2
6 2
and P pz in either dichloromethane or dichloromethane/methanol, respectively. Addition of 2 equiv of AuCl(tht) to
2
a dichloromethane solution of 1 equiv of P pz generates the simple (AuCl)2(P pz) compound, 3. Compound 3
2
2
contains nearly linear P−Au−Cl units with intermolecular Au‚‚‚Au separations of 3.570 Å. Au2I2(P pz)3, 4, is prepared
2
by reacting excess NaI with 2 in a dichloromethane/methanol mixture. Characterization of 1, 2, and 4 by X-ray
crystallography confirms the 2:3 gold/ligand ratio of all three complexes. The coordination polymer 1 maintains a
high degree of solvation in the solid-state with three chloroform adducts hydrogen-bonded to the chloride ligand on
each gold atom. These chloroform molecules are sandwiched between the two-dimensional polymeric sheets of 1.
The crystal structure of 4 reveals an empty, iodide-capped metallocryptand cage with the tetrahedrally distorted
gold atoms and the nitrogen atoms on the pyridazine rings directed away from the center of the cavity. No metal
ion encapsulation was observed for complex 4. Complex 2 forms one-dimensional arrays of [Au2(P pz)2]2+
2
metallomacrocycles connected to each other by a third P pz ligand. The electronic absorption spectra (CH Cl2) of
2
2
1−4 show broad, nearly featureless absorption bands that tail into the visible with π−π* bands at 296 nm and
discernible shoulders at 314 nm for 2 and 334 nm for 3. Excitation into the low energy band of 2 produces only
a modest emission in solution at 540 nm (λex 468 nm) and 493 nm (λex 403 nm). Under identical conditions, the
P pz ligand also emits at 540 and 493 nm.
2
Introduction
and co-workers3 first used this approach in 1994 to suc-
cessfully bind a potassium ion into the center of the [Au2-
(P2nap)3]2+ metallocryptand cage (P2nap is 2,7-bis(diphen-
ylphosphino)-1,8-naphthyridine). We too, have been inter-
ested in the metal-metal interaction found within metallo-
cryptand cages (Scheme 1).4 By changing the ligand back-
bone of the metallocryptand, the internal cavity is altered,
and therefore, the intermetallic separations can be varied.
Toward this endeavor, a variety of multidentate phosphine
ligands have been employed including P2phen, P2bpy, and
The investigation of interactions between closed-shell,
heavy metal ions or atoms continues to attract attention.1
Employing multidentate ligands with specific geometric
arrangements and an affinity toward metal ions or atoms is
one approach to induce metal-metal interactions, and num-
erous examples of extended arrays of multimetallic com-
plexes have been produced.2 Alternatively, it is possible to
induce short metal-metal interactions through the encapsula-
tion of metal ions into the center of a metallocryptand. Che
* To whom correspondence should be addressed. E-mail: vjc@
unr.edu. Fax: (775) 784-6804.
(3) Uang, R.-H.; Chan, C.-K.; Peng, S.-M.; Che, C.-M. J. Chem. Soc.,
Chem. Commun. 1994, 2561-2562.
(1) Gade, L. H. Angew. Chem., Int. Ed. 2001, 40, 3573-3575.
(2) (a) Crespo, O.; Fernandez, E. J.; Jones, P. G.; Laguna, A.; Lopez-de-
Luzuriaga, J. M.; Mendia, A.; Monge, M.; Olmos, E. J. Chem. Soc.,
Chem. Commun. 1998, 2233. (b) Wang, S.; Garzo´n, G.; King, C.;
Wang, J.-C.; Fackler, J. P., Jr. Inorg. Chem. 1989, 28, 4623. (c) Wang,
S.; Fackler, J. P., Jr.; King, C.; Wang, J. C. J. Am. Chem. Soc. 1988,
110, 3308.
(4) (a) Catalano, V. J.; Malwitz, M. A.; Noll, B. C. J. Chem. Soc., Chem.
Commun. 2001, 581-582. (b) Catalano, V. J.; Bennett, B. L.; Noll,
B. C. J. Chem. Soc., Chem. Commun. 2000, 1413-1414. (c) Catalano,
V. J.; Bennett, B. L.; Yson, R.; Noll, B. C. J. Am. Chem. Soc. 2000,
121, 10056-10062. (d) Catalano, V. J.; Bennett, B. L.; Kar, H. M.;
Noll, B. C. J. Am. Chem. Soc. 1999, 121, 10235-10236. (e) Catalano,
V. J.; Kar, H. M.; Bennett, B. L. Inorg. Chem. 2000, 39, 121-127.
10.1021/ic020601m CCC: $25.00 © 2003 American Chemical Society
Published on Web 02/25/2003
Inorganic Chemistry, Vol. 42, No. 6, 2003 2141

Catalano et al.
Scheme 1
phino)pyridazine) would coordinate to gold(I) in a polymeric
fashion or whether it would form a metallocryptand. Interest-
ingly, it does both, and here we report the formation of two
polymeric complexes of Au(I), their interconversion, and
their conversion to an empty metallocryptand.
Results
According to Scheme 2, the two-dimensional polymer
{Au2Cl2(P2pz)3}n, 1‚6CHCl3, was prepared by reacting 1
equiv of AuCl(tht) (tht is tetrahydrothiophene) with 1.5 equiv
of P2pz in chloroform giving a pale yellow solution. Also
seen in Scheme 2 is the one-dimensional polymeric complex
{[Au2(P2pz)3](PF6)2}n, 2, prepared by reacting 1 with excess
NH4PF6 in a 1:1 dichloromethane/methanol mixture. The
simple digold complex (AuCl)2(P2pz), 3, is formed by the
reaction of 2 equiv of AuCl(tht) with 1 equiv of P2pz giving
rise to a sharp singlet in the 31P{1H} NMR spectrum at 33.0
ppm. Additionally, 1 can be formed by the reaction of 3 with
2 equiv of P2pz in chloroform or by the reaction of 2 with
Et4NCl in chloroform. All reactions to form 1 produce
31P{1H} NMR spectra that show a broad resonance at 23.6
ppm, indicative of a dynamic process, and two smaller
resonances at 20.2 and 19.8 ppm, identified as the diphos-
phine oxide and monophosphine oxide comprising only 5%
of the total spectrum. Moreover, the macrocyclic polymer,
2, may be formed by reacting 3 with NH4PF6 and 2 equiv
of P2pz in a dichloromethane/methanol mixture or directly
by reacting 1 equiv of AuCl(tht) with 1.5 equiv of P2pz with
excess NH4PF6 in the same solvent. Similar to the for-
mation of 1, reactions to form 2 also give rise to a broad
31P{1H} NMR resonance indicative of a dynamic process
(41.1 ppm for the phosphorus atoms of the P2pz ligand
and a heptet at -142.7 ppm for the phosphorus atom of the
P2nap where P2phen is 2,9-bis(diphenylphosphino)-1,10-
phenanthroline and P2bpy is 6,6′-bis(diphenylphosphino)-
2,2′-bipyridine.4 During these studies, we have never ob-
served polymer formation even though there are numerous
examples of coordination polymers using late transition
metals and multidentate ligands.5
The importance of metal containing polymers for new
materials is quite extensive,6 and Au(I) based polymers are
of particular importance due to their unique photophysical
properties.7,8 Often complexes with inter- or intramolecular
Au(I)‚‚‚Au(I) interactions are intensely luminescent, and
perturbations of these interactions can form the basis of a
luminescent sensor.9 The ability to form polymeric complexes
is often dictated by the geometry of the multidentate ligand.
A large number of ligands, particularly multidentate phos-
phine ligands, have been designed to hold gold atoms in close
proximity to each other. Because gold(I) complexes are
known to adopt a variety of coordination modes, including
two-, three-, or four-coordinate, it was of interest to see if
the tetradentate P2pz ligand (P2pz is 3,6-bis(diphenylphos-
(5) (a) Moulton, B.; Zaworotko, M. J. Chem. ReV. 2001, 101, 1629-
1658. (b) Swiegers, G. F.; Malefetse, T. J. Chem. ReV. 2000, 100,
3483-3587.
(6) (a) Manners, I. J. Chem. Soc., Chem. Commun. 1999, 857-858. (b)
Blake, A. J.; Champress, N. R.; Hubberstey, P.; Li, W. S.; Withersby,
M. A.; Schroeder, M. Coord. Chem. ReV. 1999, 183, 117-138. (c)
Inorganic and Organometallic Polymers II: AdVanced Materials and
Intermediates; Wisian-Neilson, P., Allcock, H. R., Wynne, K. J., Eds.;
ACS Symposium Series 572; American Chemical Society: Washing-
ton, DC, 1994. (d) Inorganic and Organometallic Polymers; Zeldin,
M., Wynne, K. J., Allcock, H. R., Eds.; ACS Symposium Series 360;
American Chemical Society: Washington, DC, 1988. (e) Metal
Containing Polymeric Systems; Sheats, J. E., Carraher, C. E., Jr.,
Pittman, C. U., Jr., Eds.; Plenum: New York, 1985.
-
PF6 anion (1JF-P ) 704 Hz)). Further, the empty metallo-
cryptand complex Au2I2(P2pz)3, 4, can also be produced by
a variety of methods as shown in Scheme 2. Complex 4
forms by reacting 2 with excess NaI in a 2:1 dichlo-
romethane/methanol mixture, reacting 1 with excess NaI also
in a dichloromethane/methanol mixture, or by reacting 3
equiv of P2pz with 2 equiv of AuCl(tht) and excess NaI. All
of these reactions give rise to a variety of resonances in the
31P{1H} NMR spectrum with the largest resonance (compris-
ing 95% of the spectrum) at 15.3 ppm. Once crystallized,
compound 4 is insoluble in common organic solvents
including dimethyl sulfoxide, acetone, acetonitrile, dichlo-
romethane, chloroform, and methanol, and 31P{1H} NMR
spectra could not be obtained on the isolated product.
As indicated by the broad 31P{1H} NMR resonances, the
polymeric complexes 1 and 2 are dynamic in solution and
freely exchange ligand. This exchange process was explored
by 31P{1H} NMR spectroscopy by successive additions of
(7) Puddephatt, R. J. Coord. Chem. ReV. 2001, 216-217, 313-332.
(8) (a) Brandys, M.-C.; Puddephatt, R. J. J. Am. Chem. Soc. 2001, 123,
4839-4840. (b) Leznoff, D. B.; Xue, B.-Y.; Batchelor, R. J.; Einstein,
F. W. B.; Patrick, B. O. Inorg. Chem. 2001, 40, 6026-6034. (c)
Brandys, M.-C.; Puddephatt, R. J. J. Chem. Soc., Chem. Commun.
2001, 1280-1281. (d) Brandys, M.-C.; Jennings, M. C.; Puddephatt,
R. J. J. Chem. Soc., Dalton Trans. 2000, 4601-4606. (e) Ferna´ndez,
E. J.; Gimeno, M. C.; Laguna, A.; Lo´pez-de-Luzuriaga, J. M.; Menge,
M.; Pyykko¨, P.; Sundholm, D. J. Am. Chem. Soc. 2000, 122, 7287-
7293. (f) Hunks, W. J.; Jennings, M. C.; Puddephatt, R. J. Inorg. Chem.
1999, 38, 5930-5931. (g) Puddephatt, R. J. J. Chem. Soc., Chem.
Commun. 1998, 1055-1062. (h) Irwin, M. J.; Vittal, J. J.; Puddephatt,
R. J. Organometallics 1997, 16, 3541-3547. (i) Van Calcar, P. M.;
Olmstead, M. M.; Balch, A. L. Inorg. Chem. 1997, 36, 5231-5238.
(j) Irwin, M. J.; Jia, G.; Payne, N. C.; Puddephatt, R. J. Organome-
tallics 1996, 15, 51-57. (k) Irwin, M. J.; Vittal, J. J.; Yap, G. P. A.;
Puddephatt, R. J. J. Am. Chem. Soc. 1996, 118, 13101-13102. (l)
Tzeng, B.-C.; Cheung, K.-K.; Che, C.-M. J. Chem. Soc., Chem.
Commun. 1996, 1681-1682. (m) Van Calcar, P. M.; Olmstead, M.
M.; Balch, A. L. J. Chem. Soc., Chem. Commun. 1995, 1773-1774.
(n) Jia, G.; Payne, N. C.; Vittal, J. J.; Puddephatt, R. J. Organometallics
1993, 12, 4771-4778. (o) Jia, G.; Puddephatt, R. J.; Scott, J. D.; Vittal,
J. J. Organometallics 1993, 12, 3565-3574.
1
P2pz to AuCl(tht). Addition of /2 equiv of P2pz to 1 equiv
of AuCl(tht) produces a single sharp resonance at 33.0 ppm
that is attributed to the formation of Au2Cl2(P2pz), 3. Addition
1
of a second /2 equiv of P2pz causes the sharp resonance at
33.0 ppm to broaden slightly and diminish in intensity while
two other broad resonances are seen at 24.0 and 23.6 ppm.
(9) Mansour, M. A.; Connick, W. B.; Lachicotte, R. J.; Gysling, H. J.;
Eisenberg, R. J. Am. Chem. Soc. 1998, 120, 1329-1330.
1
Addition of yet another
/ equiv of P2pz significantly
2
2142 Inorganic Chemistry, Vol. 42, No. 6, 2003

Extended Structures of Au(I) Complexes
a
Scheme 2
a (i) 2/3AuCl(tht), CH2Cl2/CH3OH; (ii) NaI, CH2Cl2/CH3OH; (iii) 2AuCl(tht), CH2Cl2; (iv) 2P2pz, CHCl3; (v) 2P2pz, NH4PF6, CH2Cl2/CH3OH; (vi) Et4Cl,
CHCl3; (vii) CH2Cl2/CH3OH, NH4PF6.
simplifies the spectrum resulting in a broad resonance at 23.6
ppm assigned to complex 1 (comprising the majority of the
spectrum), along with two smaller sharp singlets, associated
with the mono- and diphosphine oxides. Subsequent additions
of 1/2 equiv of P2pz move the large broad resonance further
upfield toward that of the free ligand. No resonance was
observed for free ligand throughout the experiment, indicat-
ing that the ligand and the metal complex are involved in a
fast exchange process. Attempts to obtain low temperature
31P{1H} NMR spectroscopy data were thwarted by precipita-
tion of products from their corresponding solutions upon
cooling.
Crystals of 1 suitable for X-ray analysis formed upon
standing from a chloroform solution of 1. The complex
crystallizes in the rhombohedral space group R3h with the
AuCl unit oriented on a crystallographic 3-fold axis. Thus,
only one-third of the Au(I) coordination environment is
Figure 1. Thermal ellipsoid plot of 1 with hydrogen atoms omitted for
clarity. Only the asymmetric unit is numbered. The asymmetric unit contains
unique. A thermal ellipsoid drawing of 1 is shown in Figure
1 while selected bond distances and angles are presented in
Table 1. In complex 1, each gold(I) atom resides in a dis-
torted tetrahedral environment and is bound to three phos-
phorus atoms of three separate P2pz ligands and to one
chloride ligand. Because of the crystallographic symmetry,
the three Au-P distances of 1 are identical at 2.3683(6) Å.
These values are slightly shorter than those found in the
solvate-free, distorted tetrahedral AuCl(PPh3)3 complex
reported by Jones et al.,10 where the shortest Au-P distance
is 2.395(2) Å, and are closer to the values (2.3666(6)-
one-third of a Au-Cl unit and three-halves of a P2pz ligand.
2.3911(6) Å) found in the bis(solvate) form, AuCl-
(PPh3)3‚(CH2Cl2)2, reported by Schmidbaur and co-workers.11
However, the Au-Cl distance in 1 (2.7026(10) Å) shows
the opposite trend and is closer to the separation found in
solvent-free form of AuCl(PPh3)3 (2.710(2) Å) than the
corresponding separation in AuCl(PPh3)3‚(CH2Cl2)2 (2.7962-
(6) Å). The deviation from tetrahedral geometry can be seen
in the P-Au-P angles which are identical at 113.779(10)°
(10) Jones, P. G.; Sheldrick, G. M.; Muir, J. A.; Muir, M. M.; Pulgar, L.
(11) Hamel, A.; Schier, A.; Schmidbaur, H. Z. Naturforsch. 2002, 57b,
877-880.
B. J. Chem. Soc., Dalton Trans. 1982, 2123-2125.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2143

Catalano et al.
Figure 2. Structural drawing emphasizing the two-dimensional polymeric sheets of 1. The alternating “up and down” orientations of the Au-Cl units in
the polymer are shown along with the three chloroform solvate molecules per Au-Cl unit.
Table 1. Bond Lengths (Å) and Angles (deg) for 1
Au(1)-P(1)
Au(1)-Cl(1)
P(1)-C(1)
P(1)-C(3)
P(1)-C(9)
Au‚‚‚Au
2.3683(6)
2.7026(10)
1.826(2)
1.821(2)
1.811(2)
8.893
P(1)-Au(1)-P(1)#1
Au(1)-P(1)-C(9)
Au(1)-P(1)-C(3)
Au(1)-P(1)-C(1)
C(1)-P(1)-C(3)
C(1)-P(1)-C(9)
C(3)-P(1)-C(9)
113.779(10)
111.08(7)
125.09(7)
108.18(7)
100.79(9)
104.89(10)
104.79(9)
Figure 3. X-ray structural drawing of cationic portion of 2 showing only
one unit of the repeating polymeric structure with all but the ipso carbon
atom of the phenyl rings and hydrogen atoms omitted for clarity.
while the P-Au-Cl angles are 104.715(12)°. The Au(I)
center resides out of the plane formed by the three phos-
phorus atoms toward the Cl- ligand by 0.6015 Å. Com-
plex 1 shows no close Au‚‚‚Au interactions, and the closest
Au‚‚‚Au separation (8.893 Å) is between Au(I) atoms in the
same two-dimensional sheet. As shown in Figure 2, the AuCl
units alternate their orientation to each side of the polymeric
plane. Compound 1 shows a high degree of solvation in the
crystal structure with three chloroform solvates hydrogen
bonded to the chloride ligand of each gold atom. These
chloroform molecules are sandwiched between the polymer
sheets of 1 and comprise ∼30% by mass of this polymer.
Crystals of 2 suitable for X-ray diffraction analysis were
grown by the slow diffusion of benzene into a saturated 1,2-
dichloroethane solution of 2. The one-dimensional polymer
crystallizes in the triclinic space group P1h. Figure 3 shows
a thermal ellipsoid drawing of 2 with selected bond distances
and angles presented in Table 2. Complex 2 forms one-
dimensional arrays of [Au2(P2pz)2]2+ metallomacrocycles
connected to each other by a third P2pz ligand as presented
in Figure 4. The closest Au‚‚‚Au separation is long at 8.268
Å. The three-coordinate Au(1) center is nearly planar with
combined angles about the Au(1) center totaling 359.75°.
The Au atom is displaced out of its phosphorus plane by
only 0.0687 Å. The P(1)-Au(1)-P(3), P(1)-Au(1)-P(5),
and P(3)-Au(1)-P(5) angles are 124.48(7)°, 114.77(7)°, and
Table 2. Bond Lengths (Å) and Angles (deg) for 2
Au(1)-P(1)
Au(1)-P(3)
Au(1)-P(5)
Au(2)-P(2)
Au(2)-P(4)
Au(2)-P(6)
Au‚‚‚Au
2.363(2)
2.347(2)
2.380(2)
2.369(2)
2.342(2)
2.3709(19)
8.268
P(1)-Au(1)-P(3)
P(1)-Au(1)-P(5)
P(3)-Au(1)-P(5)
P(2)-Au(2)-P(4)
P(2)-Au(2)-P(6)
P(4)-Au(2)-P(6)
Au(1)-P(1)-C(1)
Au(1)-P(3)-C(29)
Au(2)-P(2)-C(4)
Au(2)-P(4)-C(32)
124.48(7)
114.77(7)
120.50(7)
123.23(7)
114.18(7)
121.50(7)
117.2(2)
114.9(2)
119.8(3)
114.5(3)
120.50(7)°, respectively, with the largest angle corresponding
to the internal angle of the gold macrocycle. The three-
coordinate Au(2) center is slightly less planar and is displaced
out of its phosphorus plane by 0.1422 Å. The sum of the
angles around Au(2) total 358.91°. Similar to the angles
around Au(1), the P(2)-Au(2)-P(4), P(2)-Au(2)-P(6), and
P(4)-Au(2)-P(6) angles are 123.23(7)°, 114.18(7)°, and
121.50(7)°, respectively, with the largest angle again corre-
2144 Inorganic Chemistry, Vol. 42, No. 6, 2003

Extended Structures of Au(I) Complexes
Figure 4. Structural drawing of cationic portion of 2 emphasizing the polymeric nature of the complex. Each gold atom adopts a nearly trigonal planar
coordination environment with the gold atoms forming a “zigzag” pattern.
Figure 6. Thermal ellipsoid plot of 4 with hydrogen atoms and all but
the ipso carbon atoms on the phenyl rings omitted for clarity.
Figure 5. X-ray structural drawing of 3 looking down at the pyridazine
ring.
Au(1)-P(1) and Au(1)-Cl(1) separations of 2.2263(10)
and 2.2852(12) Å, respectively. The Au(1)-P(1)-C(1),
Table 3. Bond Lengths (Å) and Angles (deg) for 3
Au(1)-P(1)-C(3), and Au(1)-P(1)-C(9) angles are slightly
Au(1)-P(1)
Au(1)-Cl(1)
P(1)-C(1)
P(1)-C(3)
P(1)-C(9)
Au‚‚‚Au
2.2263(10)
2.2852(12)
1.825(4)
1.805(4)
1.811(4)
3.570
expanded from the ideal tetrahedral angles (109.5°) at
110.10(17)°, 112.87(12)°, and 117.74(13)°, respectively.
Yellow crystals of 4 were obtained by the slow diffusion
of diethyl ether into a dichloromethane solution of 4. Once
crystallized, complex 4 is no longer soluble in common
organic solvents. Complex 4 crystallizes in the hexagonal
P6(3)/m space group with the gold atom on a crystallographic
screw axis with only one-sixth of the molecule being
crystallographically unique. A thermal ellipsoid plot of 4 is
shown in Figure 6 with selected bond distances and angles
presented in Table 4. The structure shows an empty metal-
locryptand cage capped by two iodine atoms and two gold
atoms triply bridged by the P2pz ligand. The gold atoms
reside in distorted tetrahedral coordination environments with
P-Au-P and P-Au-I angles of 115.37(7)° and 102.62-
(9)°, respectively. The Au(1)-I(1) separation is 2.8726(19)
Å, and the Au-P separations are longer than those observed
in 1-3 at 2.417(4) Å. The nitrogen atoms in the pyridazine
rings are oriented slightly away from the cavity of the
metallocryptand cage preventing the nitrogen atom lone pairs
from penetrating the cage. The Au(I) atoms in 4 pucker away
from the cavity of the metallocryptand cage by 0.5280 Å,
P(1)-Au(1)-Cl(1)
Au(1)-P(1)-C(1)
Au(1)-P(1)-C(3)
Au(1)-P(1)-C(9)
C(1)-P(1)-C(3)
C(1)-P(1)-C(9)
C(3)-P(1)-C(9)
177.58(5)
111.10(17)
112.87(12)
117.74(13)
105.59(18)
103.26(19)
105.18(18)
sponding to the internal angle of the gold macrocycle. The
Au-P separations in 2 range from 2.342(2) to 2.380(2) Å
and are slightly shorter than those observed in 1.
X-ray quality crystals of complex 3 were formed by the
slow diffusion of tert-butylmethyl ether in to a chloroform
solution of 3. A thermal ellipsoid plot of 3 is presented in
Figure 5 with selected bond distances and angles in Table
3. The nearly colorless complex crystallizes in the monoclinic
space group C2/c with the middle of the pyridazine ring
residing on a crystallographic inversion center making only
one-half of the complex crystallographically unique. The
nearest intermolecular Au‚‚‚Au separation is 3.570 Å and is
considered only very weakly aurophilic.12 As in many other
structures containing Au‚‚‚Au interactions, the two inter-
molecular P-Au-Cl subunits are oriented nearly orthogonal
to each other. The intermolecular P-Au‚‚‚Au-P torsion
angle is 110.7°. The two-coordinate Au(I) atoms are nearly
linear with the angle P(1)-Au(1)-Cl(1) of 177.58(5)° and
(12) (a) Hamel, A.; Mitzel, N. W.; Schmidbaur, H. J. Am. Chem. Soc. 2001,
123, 5106-5107. (b) Magnko, L.; Schweizer, M.; Rauhut, G.; Schu¨tz,
M.; Stoll, H.; Werner, H.-J. Phys. Chem. Chem. Phys. 2002, 4, 1006-
1013. (c) Ferna´ndez, E. J.; Lo´pez-de-Luzuriaga, J. M.; Monge, M.;
Rodr´ıguez, M. A.; Crespo, O.; Gimeno, M. C.; Laguna, A.; Jones, P.
G. Chem. Eur. J. 2000, 6, 636-644. (d) Ferna´ndez, E. J.; Lo´pez-de-
Luzuriaga, J. M.; Monge, M.; Rodr´ıguez, M. A.; Crespo, O.; Gimeno,
M. C.; Laguna, A.; Jones, P. G. Inorg. Chem. 1998, 37, 6002-6006.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2145

Catalano et al.
Table 4. Bond Lengths (Å) and Angles (deg) for 4
were then removed by rotary evaporation leaving 0.318 g (0.313
mmol) of 2 as a yellow solid (90%). Elemental Anal. Calcd
(C84H66Au2F12N6P8): C, 49.72; H, 3.28; N, 4.14. Found: C, 49.72;
Au(1)-P(1)
Au(1)-I(1)
P(1)-C(1)
P(1)-C(3)
P(1)-C(9)
Au‚‚‚Au
2.417(4)
2.8726(19)
1.855(14)
1.806(14)
1.781(14)
7.373
1
H, 3.48; N, 4.19. H NMR (500 MHz, CD2Cl2, 25 °C): δ ) 9.35
(m), 9.25 (m), 9.13 (m). 31P{1H} NMR (202.33 MHz, CD2Cl2, 25
1
°C): δ ) 41.1 (broad), -142.7 (hept, JF-P ) 704 Hz).
Preparation of (AuCl)2(P2pz), 3. A 25 mL Erlenmeyer flask
was charged with 10 mL of dichloromethane, 0.055 g of P2pz (0.122
mmol), and 0.081 g (0.252 mmol) of AuCl(tht). This mixture was
stirred for 2 h after which the solvent was removed by rotary
evaporation. The remaining tan solid was dissolved in a minimum
amount of dichloromethane and precipitated with diethyl ether to
afford 0.082 g (0.090 mmol) of 3 as a tan solid (73%). This solid
is easily crystallized by dissolving in a small volume of chloro-
carbon (CH2Cl2, CHCl3, or 1,2-C2H4Cl2) followed by precipitation
with diethyl ether. Elemental Anal. Calcd (C28H22Au2Cl2N2P2‚
1,2-C2H4Cl2): C, 35.60; H, 2.59; N, 2.77. Found: C, 35.70; H,
2.30; N, 2.94. 1H NMR (300 MHz, CDCl3, 25 °C): δ ) 7.90 (m),
7.65 (m), 7.46 (m). 31P{1H} NMR (121 MHz, CDCl3, 25 °C): δ
) 33.0 (s).
Preparation of Au2I2(P2pz)3, 4. A 25 mL Erlenmeyer flask was
charged with 0.141 g (0.139 mmol) of 2 and 10 mL of dichlo-
romethane. To this was added 0.208 g (1.39 mmol) of NaI in 5
mL of methanol. This mixture was stirred overnight, after which
the mixture was filtered through Celite, and the remaining yellow
solution was evaporated to dryness. The remaining yellowish solid
was dissolved in dichloromethane and filtered through Celite. The
remaining yellow solution was evaporated to dryness leaving 0.182
g (0.091 mmol) of 4 as a yellow solid (65%). 31P{1H} NMR (121
MHz, CD2Cl2/CD3OD, 25 °C): δ ) 15.3 (broad).
X-ray Crystallography. Crystal data for 1-4 are presented in
Table 5. Suitable crystals of 1, 2, and 3 were coated with light
petroleum oil, mounted on a glass fiber, and placed in the 91
K nitrogen cold stream of a Siemens SMART diffractometer
while a suitable crystal of 4 was coated with epoxy cement and
mounted on a Siemens P4 diffractometer. Unit cell parameters were
determined by least-squares analysis of 712 reflections for 1,
972 reflections for 2, and 940 reflections for 3. For 4, unit cell
parameters were determined by least-squares analysis of 25
reflections with 3.45° < θ < 12.35 °. A total of 10211 reflections
were collected in the range 1.9° < θ < 31.5°, yielding 5250 unique
reflections (Rint ) 0.008) for 1, while a total of 21205 reflections
were collected in the range 1.42 ° < θ < 27.5°, yielding 14331
unique reflections (Rint ) 0.053) for 2, and a total of 17523
reflections were collected in the range 1.9° < θ < 31.5°, yielding
4292 unique reflections (Rint ) 0.032) for 3. For 4, a total of 7120
reflections in the range 1.9° < θ < 25° were collected yielding
2855 unique data (Rint ) 0.11). The data were corrected for
absorption and Lorentz and polarization effects. Scattering factors
and corrections for anomalous dispersion were taken from a standard
source.15
P(1)-Au(1)-I(1)
Au(1)-P(1)-C(1)
Au(1)-P(1)-C(3)
Au(1)-P(1)-C(9)
C(1)-P(1)-C(3)
C(1)-P(1)-C(9)
C(3)-P(1)-C(9)
102.62(9)
107.5(5)
117.4(5)
119.8(5)
105.8(6)
103.3(7)
101.5(6)
and the intramolecular Au‚‚‚Au separation is long at 7.373
Å. Attempts to incarcerate Na+, Tl+, Pb2+, or Hg(0) into
the empty cage of 4 proved unsuccessful.
The electronic absorption spectra (CH2Cl2) of 1-4 show
broad, nearly featureless absorption bands that tail into the
visible with π to π* bands at 296 nm and discernible
shoulders at 314 nm for 2 and 334 nm for 3. Excitation into
the low energy band of 2 produces only a modest emission
in solution at 540 nm (λex 468 nm) and 493 nm (λex 403
nm). Under identical conditions, the P2pz ligand also emits
at 540 and 493 nm. In the gas phase, the polymeric
complexes disintegrate into their respective components, and
no fragment larger than [Au2(P2pz)2]2+ could be identified.
Experimental Section
All solvents were purified with a Grubbs apparatus.13 P2pz3 and
AuCl(tht)14 were prepared from literature procedures. 1H chemical
shifts are reported relative to TMS, and 31P{1H} chemical shifts
are reported relative to 85% H3PO4. Combustion analysis was
performed by Desert Analytics, Tucson, AZ. UV-vis spectra were
obtained using a Hewlett-Packard 8453 diode array spectrometer
(1 cm path-length cells). Emission data were recorded using a Spex
Fluoromax steady-state fluorimeter.
Preparation of {Au2Cl2(P2pz)3‚6CHCl3}n, 1‚6CHCl3. A 25 mL
Erlenmeyer flask was charged with 0.167 g (0.520 mmol) of AuCl-
(tht) in 5 mL of dichloromethane followed by 0.350 g (0.780 mmol)
of P2pz in 5 mL of dichloromethane. After stirring for 15 min, a
white precipitate formed. At this point, 1.5 mL of methanol was
added dissolving the precipitate. This mixture was then stirred for
2 h forming a yellow solution. The solvent was removed by rotary
evaporation, and the remaining yellow solid was redissolved in
chloroform and filtered through Celite. Pale yellow crystals of 1
(0.363 g, 0.401 mmol) precipitated from the chloroform solution
upon standing overnight (77%). Elemental Anal. Calcd (C90H72-
Au2Cl20N6P6): C, 42.78; H, 2.87; N, 3.33. Found: C, 42.72; H,
2.91; N, 3.33. 1H NMR (500 MHz, CDCl3, 25 °C): δ ) 7.52 (m),
7.30 (m), 7.14 (m). 31P{1H} NMR (202.33 MHz, CDCl3, 25 °C):
δ ) 23.6 (broad).
Calculations were performed using the Siemens SHELXTL
Version 5.10 system of programs refining on F2. The structures
were solved by direct methods. In complexes 1 and 3, the pyridazine
ring incorporates a crystallographic symmetry element rendering
the carbon and nitrogen atoms attached to the ipso carbon atom
equivalent. These two positions are indistinguishable and therefore
modeled as 50% nitrogen and 50% carbon each. In 2 and 4, the
nitrogen atom positions were determined by inspection and
comparison of the respective anisotropic thermal parameters.
Preparation of {[Au2(P2pz)3](PF6)2}n, 2. A 25 mL Erlenmeyer
flask was charged with 0.317 g (0.350 mmol) of 1. To this was
added 0.570 g (3.50 mmol) of NH4PF6 in 5 mL of methanol. This
mixture was allowed to stir for 30 min after which the vola-
tiles were removed using a rotary evaporator. The remaining yel-
low white solid was dissolved in 25 mL of dichloromethane and
filtered through Celite leaving a yellow solution. The volatiles
(13) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmer, F. J. Organometallics 1996, 15, 1518-1520.
(14) Uson, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85-91.
(15) International Tables for X-ray Crystallography; Kynoch Press: Bir-
mingham, England, 1974; Vol. 4.
2146 Inorganic Chemistry, Vol. 42, No. 6, 2003

Extended Structures of Au(I) Complexes
Table 5. Crystallographic Data for 1-4
2‚2.25C6H6‚
0.75(1,2-C2H4Cl2)
1‚6CHCl3
3
4‚CH2Cl2
formula
fw
C90H72Au2Cl20N6P6
420.04
C
101H85Au2Cl2F12N6P8
C28H20Au2Cl2N2P2
911.23
C85H66Au2Cl2I2N6P6
2075.89
2251.42
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
space group
Z
15.253(2)
15.253(2)
36.565(7)
90
90
120
7368(2)
R3h
18
16.233(2)
16.303(2)
20.110(3)
95.600(4)
102.745(3)
112.860(2)
4682.5(11)
P1h
17.2902(13)
13.3536(9)
11.7382(9)
90
103.322(3)
90
2637.3(3)
C2/c
4
13.6458(12)
13.6458(12)
29.446(6)
90
90
120
4748.5(11)
P63/m
2
2
D
calcd, g/cm3
1.704
1.597
2.295
1.452
crystal size, mm3
µ (Mo KR), mm-1
λ, Å
0.30 × 0.22 × 0.21
0.24 × 0.20 × 0.10
0.14 × 0.18 × 0.08
0.14 × 0.42 × 0.44
3.673
3.383
3.934
11.459
0.71073
91(2)
0.71073
91(2)
0.71073
91(2)
0.71073
298(2)
temp, K
transm factors
R1, wR2 (I g σ(I))
0.40-0.51
0.0243, 0.0604
0.50-0.73
0.0523, 0.1342
0.23-0.46
0.0269, 0.0616
0.53-0.95
0.0706, 0.1742
Complex 2 contains two and one-quarter benzene solvates and three-
fourths of a dichloroethane solvate straddling a symmetry element.
In 4, the unit cell contains a slightly disordered dichloromethane
solvate. There are no unusual contacts between any of these moi-
eties, and simple models of the disorder provided satisfactory
refinements.
the empty metallocryptand cage complex, all of which have
a Au/P2pz ratio of 2:3. Interestingly, once the empty cage
complex forms, the dynamic nature of the gold-phosphine
coordination is stopped suggesting that the polymeric
complexes are the kinetic products while the cage complex
is the thermodynamic product.
In previous studies with P2phen, there was a noticeable
lack of polymer formation. This may be due, in part, to the
rapid uptake of a guest metal ion which appears to “turn-
off” ligand substitution around the three-coordinate Au(I)
center. For example, the addition of excess Na+ to Au(I)
and P2phen produces the Na+ encapsulated metallocryptand,
[Au2Na(P2phen)3]+, but in the reaction of Au(I), Na+, and
P2pz no encapsulation was observed.4d This is peculiar
because the lone pairs of electrons on the nitrogen atoms
in P2phen do not participate in the binding of Na+ ion in
[Au2Na(P2phen)3](PF6)3;4d however, in the P2nap analogue,
[Au2Na(P2nap)3](PF6)3,4e the lone pair of electrons on the
nitrogen atoms is essential for Na+ binding to occur. In both
Discussion
The coordination chemistry of P2pz is relatively unexplored
with only four other reports16-19 of this ligand. A silver(I)
metallocryptand, similar to 4, was recently reported in which
the five-coordinate silver(I) atoms are capped by nitrate
anions and coordinated to three bridging P2pz ligands.18
Although Ag(I) has a tendency to adopt a linear two-
coordinate geometry, multiple coordination modes are not
uncommon, and the metallocryptand structural motif has been
observed in other silver(I) complexes utilizing P2phen4e or
bis(diphenylphosphino)acetylene as the triply bridging ligand
backbone and either triflate or nitrate anions as capping
molecules.19 Complex 4 is less elongated than the afore-
mentioned silver(I) complex.18 The nearest Au‚‚‚Au separa-
tion is through the empty cage at 7.373 Å, while the
corresponding Ag‚‚‚Ag separation, also through the empty
cage, is longer at 7.543 Å. This increased elongation of the
silver(I) cage complex also results in an increased puckering
of the metal atoms away from the phosphine plane. The gold
atoms in 4 are only 0.5280 Å out of the phosphine plane
while in the analogous silver(I) complex they are 0.673 and
0.646 Å.18 Additionally, a polymeric complex containing
Ag(I) and P2pz has been reported.7 It should not be surprising
that the Au(I) analogue also forms polymers. However, it is
somewhat unusual to find multiple structural motifs for the
same stoichiometric composition as illustrated by the isola-
tion of the one- and two-dimensional polymers along with
cases, no polymer formation occurred, although in the former
the system is dynamic and exists as an equilibrium mix-
ture of the coordinated metallocryptate, empty metalloc-
ryptand, and metallomacrocycle with two ligands. In the case
of P2pz, the lone pair of electrons on the nitrogen atoms could
provide a template for a guest metal coordination, yet no
binding of metal ions was observed. Attempts to add auro-
philic metal ions or metals (Tl+, Hg(0)) that are known to
bind to Au(I) centers in the absence of stabilizing ligand
interactions4a,d also failed. One explanation for this be-
havior may be related to the relative positions of the
phosphorus lone pairs of electrons on P2pz versus P2phen
or P2nap. Their outward orientation would seem to prohibit
small-cage formation. The metallocryptand formed with
P2pz has Au‚‚‚Au separations that are far too large to
(16) Zhang, Z. Z.; Wang, H.-K.; Shen, Y.-J.; Wang, H.-G.; Wang, R.-J. J.
Organomet. Chem. 1990, 381, 45-52.
(17) Kuang, S.-M.; Zhang L-M.; Zhang, Z.-Z.; Wu, B.-M.; Mak, T. C.
W. Chem. Commun. 1998, 581-582.
(18) Kuang, S.-M.; Zhang L-M.; Zhang, Z.-Z.; Wu, B.-M.; Mak, T. C.
W. Inorg. Chim. Acta 1999, 284, 278-283.
(19) Lozano, E.; Nieuwenhuyzen, M.; James, S. L. Chem. Eur. J. 2001, 7,
2644-2651.
Inorganic Chemistry, Vol. 42, No. 6, 2003 2147

Catalano et al.
2
facilitate guest binding, and the filled dz orbital of the
interaction of the nitrogen lone pairs with the guest metal is
not critical, and the outward orientation of the nitrogen lone
pairs on P2pz may not be an issue. The key to forming an
encapsulated species may, therefore, be finding an appropri-
ate template mechanism to first arrange the ligands around
the guest metal of interest before the capping metal is added.
We are currently working toward this goal.
gold(I) atoms cannot effectively penetrate the cavity to help
immobilize a metal or metal ion within the cage through
noncovalent interactions. Furthermore, the internal lone pairs
on the nitrogen atoms of P2pz are also outwardly directed,
significantly reducing their ability to stabilize an incarcerated
metal ion. It is interesting to speculate whether there is
enough flexibility in the P-C bond to distort the Au(I)-
P2pz coordination environment enough to allow guest bind-
ing. Molecular modeling suggests that in the absence of an
axial ligands (I- in the case of 4) simple twisting of the
trigonally coordinated [AuP3]+-centers relative to each other
significantly reduces the Au‚‚‚Au separation and provides a
means to form a suitably sized metallocryptand to encapsu-
late a metal or metal ion. As demonstrated by the successful
preparation of metallocryptands using P2bpy and P2phen, the
Acknowledgment is made to the National Science Foun-
dation (CHE-0091180) and to the donors of the Petroleum
Research Fund, administered by the American Chemical
Society for their generous financial support of this research.
Supporting Information Available: Complete X-ray crystal-
lographic data for 1-4 (CIF format). This material is available free
of charge via the Internet at http://pubs.acs.org.
IC020601M
2148 Inorganic Chemistry, Vol. 42, No. 6, 2003