Two-, three-, and four-coordination at gold(I) supported by the bidentate selenium ligand [PH2P(Se)NP(Se)PH2]-

Article abstract of DOI:10.1021/ic010337h

Treatment of the gold(I) halide complexes LAuCl (L = PMe₃, PPh₃, CNC₆H₃Me₂-2,6) with K[Ph₂P(Se)NP(Se)Ph₂] provides the gold-selenium coordination compounds [{N(Ph₂PSe)₂-Se,Se′}AuL]. However, on standing for a number of days, the complex [{N(Ph₂PSe)₂-Se,Se′}AuPMe₃] gains a phosphine to provide the bis(phosphine) species [{N(Ph₂PSe)₂-Se,Se′}Au(PMe₃) ₂]. Treatment of the K[Ph₂P(Se)NP(Se)Ph₂] ligand with [(Ph₃PAu)₃O]BF₄ allows the isolation of [{N(Ph₂PSe)₂-Se,Se′}(AuPPh₃)2]BF ₄. Reaction of the complex [(dppm)(AuCl)₂] with AgSO₃CF₃ followed by addition of the ligand K[Ph₂P(Se)NP(Se)Ph₂] results in the formation of [{N(Ph₂PSe)₂Se,Se′}Au₂(dppm)]OSO ₂CF₃ and treatment of [(tht)AuCl] (tht= tetrahydrothiophene) with an equimolar quantity of K[Ph₂P(Se)NP(Se)Ph₂] affords the complex [{N(Ph₂PSe)₂-Se,Se′}₂Au₂]. The compounds [{N(Ph₂PSe)₂-Se,Se′} Au₂(dppm)]OSO₂CF₃, [{N(Ph₂PSe)₂-Se,Se′} AuPPh₃] and [{N(Ph₂PSe)₂-Se,Se′ Au(PMe₃)₂ have been investigated crystallographically. The results reveal that the metal centers are two-, three-, and four-coordinate, respectively. The cationic, eight-membered ring complex bearing the dppm ligand displays transannular aurophilic bonding and is further associated into dimers via intermolecular gold-selenium contacts. The six-membered rings in the other two structures have C₂-symmetrical twist conformations, however, the Au(I) coordination sphere in [N(PPh₂Se)₂]AuPPh₃ is not fully symmetrical. The Au-Se bond lengths increase dramatically as the coordination number of the metal atom becomes larger.

Full text of DOI:10.1021/ic010337h

4656
Inorg. Chem. 2001, 40, 4656-4661
Two-, Three-, and Four-Coordination at Gold(I) Supported by the Bidentate Selenium
Ligand [Ph2P(Se)NP(Se)Ph2]-
James D. E. T. Wilton-Ely, Annette Schier, and Hubert Schmidbaur*
Anorganisch-chemisches Institut, der Technischen Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching, Germany
ReceiVed March 27, 2001
Treatment of the gold(I) halide complexes LAuCl (L ) PMe3, PPh3, CNC6H3Me2-2,6) with K[Ph2P(Se)NP(Se)-
Ph2] provides the gold-selenium coordination compounds [{N(Ph2PSe)2-Se,Se′}AuL]. However, on standing for
a number of days, the complex [{N(Ph2PSe)2-Se,Se′}AuPMe3] gains a phosphine to provide the bis(phosphine)
species [{N(Ph2PSe)2-Se,Se′}Au(PMe3)2]. Treatment of the K[Ph2P(Se)NP(Se)Ph2] ligand with [(Ph3PAu)3O]-
BF4 allows the isolation of [{N(Ph2PSe)2-Se,Se′}(AuPPh3)2]BF4. Reaction of the complex [(dppm)(AuCl)2] with
AgSO3CF3 followed by addition of the ligand K[Ph2P(Se)NP(Se)Ph2] results in the formation of [{N(Ph2PSe)2-
Se,Se′}Au2(dppm)]OSO2CF3 and treatment of [(tht)AuCl] (tht ) tetrahydrothiophene) with an equimolar quantity
of K[Ph2P(Se)NP(Se)Ph2] affords the complex [{N(Ph2PSe)2-Se,Se′}2Au2]. The compounds [{N(Ph2PSe)2-Se,-
Se′}Au2(dppm)]OSO2CF3, [{N(Ph2PSe)2-Se,Se′}AuPPh3] and [{N(Ph2PSe)2-Se,Se′}Au(PMe3)2] have been inves-
tigated crystallographically. The results reveal that the metal centers are two-, three-, and four-coordinate,
respectively. The cationic, eight-membered ring complex bearing the dppm ligand displays transannular aurophilic
bonding and is further associated into dimers via intermolecular gold-selenium contacts. The six-membered
rings in the other two structures have C2-symmetrical twist conformations, however, the Au(I) coordination sphere
in [N(PPh2Se)2]AuPPh3 is not fully symmetrical. The Au-Se bond lengths increase dramatically as the coordination
number of the metal atom becomes larger.
Introduction
selenocyanate analogues [(Ph3P)AuSeCN] and [(dppm)(Au-
SeCN)2] were prepared in 1971.6 A gold(I) complex bearing
the biorelevant 1-selenoglucose ligand has also been synthe-
sized7 as have complexes of the selenium homologue of urea.8,9
Gold metal has a remarkable affinity for the heavy chalcogen
elements.1 This is particularly true for tellurium and leads to
the phenomenon that, next to gold and its alloys, gold tellurides
are the only binary gold minerals found in nature. The gold-
selenium solid-state chemistry is also rich in binary and polynary
systems2 which are of interest in the context of interfaces
between gold metal and gold alloys and II/VI or I/III/VI
semiconductors.
5
The dinuclear species [(Ph3PAu)2SePh]SbF6 and [(Ph3-
PAu)2Se]9 were reported at the beginning of the past decade
and the latter has recently proved to be an excellent precursor
for the preparation of aurated hypervalent selenium compounds.
Though the complexes [(Ph3PAu)3Se]Cl10 and [(Ph3PAu)4Se]-
(OTf)211 had previously been prepared using other methods, the
complex [(Ph3PAu)2Se] provided routes to all members of the
homoleptic series [(Ph3PAu)nSe](OTf)n-2 (n ) 3-6).12 This
work also incorporated the use of a bisphosphine precursor
[(dppf)Au2]Se, as well as theoretical calculations on the species
prepared.
Another topical area of gold-selenium chemistry is the use
of gold chalcogen compounds in chemotherapy.3
Though by no means as developed as the corresponding sulfur
chemistry, gold(I) compounds of selenium have therefore
received some recent attention. Probably due to the lack of
commercially available selenol compounds, the number of
known selenolate complexes grew slowly. A triethylphos-
phinegold(I) complex of a glucose residue reminiscent of
auranofin4 was patented in 1983 but it was only later that the
complexes [(Ph3P)AuSeR] (R ) organyl), [(dppm)(AuSePh)2]
were reported.5 As part of a study of pseudohalide ligands, the
Phosphineselenide ligands have been used to ligate gold in a
number of examples of the form [Ph3PSeAuR] (R ) organ-
yl),13,14 [(Ph3PSe)Au(PPh3)]SbF6 and [(Ph3PSe)2Au]SbF6.15 The
(5) Jones, P. G.; Thoene, C. Chem. Ber. 1990, 123, 1975; Eikens, W.;
Kienitz, C.; Jones, P. G.; Thoene, C. J. Chem. Soc., Dalton Trans.
1994, 83.
(1) Smith, D. M.; Roof, L. C.; Ansari, M. A.; McConnachie, J. M.;
Bollinger, J. C.; Pell, M. A.; Salm, R. J.; Ibers, J. A. Inorg. Chem.
1996, 35, 4999. Ansari, M. A.; Bollinger, J. C.; Ibers, J. A. J. Am.
Chem. Soc. 1993, 115, 3838. For further examples, see: Fackler, J.
P., Jr.; van Zyl, W.; Prihoda, B. A. In Gold - Progress in Chemistry,
Biochemistry and Technology; Schmidbaur, H., Ed.; John Wiley &
Sons: Chichester, 1999.
(2) Yang, Y.; Ibers, J. A. J. Solid State Chem. 1999, 147, 366. Salm, R.
J.; Misetic, A.; Ibers, J. A. Inorg. Chim. Acta 1995, 240, 239.
(3) Shaw, C. F., III. In Gold - Progress in Chemistry, Biochemistry and
Technology; Schmidbaur, H., Ed.; John Wiley & Sons: Chichester,
1999.
(6) Burmeister, J. L.; DeStefano, N. J. Inorg. Chem. 1971, 10, 998.
(7) Pill, T.; Breu, W.; Wagner, H.; Beck, W. Chem. Ber. 1991, 124, 713.
(8) Eikens, W.; Jones, P. G.; Lautner, J.; Thoene, C. Z. Naturforsch. 1994,
49b, 21.
(9) Jones, P. G.; Thoene, C. Chem. Ber. 1991, 124, 2725.
(10) Schmidbaur, H.; Franke, R.; Eberlein, J. Chem.-Ztg. 1975, 99, 91.
(11) Canales, S.; Crespo, O.; Gimeno, M. C.; Laguna, A.; Jones, P. G.
Chem. Commun. 1999, 679.
(12) Canales, S.; Crespo, O.; Gimeno, M. C.; Jones, P. G.; Laguna, A.;
Mendizabal, F. Organometallics, 2000, 19, 4985.
(13) Ahmad, S.; Akhtar, M. N.; Isab, A. A.; Al-Arfaj, A. R.; Hussain, M.
S. J. Coord. Chem., 2000, 51, 225.
(4) Stockel, R. F.; Dumas, P. E. Japanese patent, JP 58192893.
(14) Jones, P. G.; Thoene, C. Chem.-Ztg. 1991, 115, 366.
10.1021/ic010337h CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/26/2001

Bidentate Selenium Ligand
Inorganic Chemistry, Vol. 40, No. 18, 2001 4657
asymmetric ligand dppmSe has also been employed to form a
structurally characterized 10-membered ring system [(dppmSe)-
Scheme 1
16
Au2]ClO4 and as a supporting ligand for investigations into
nonconventional hydrogen-bonding systems.17
A number of selenium-bound, heteroleptic gold complexes
have been prepared using the mixed chalcogen ligand, 4,5-
diselenolate-1,3-dithiole-2-thione (dsit) such as the cyclic
example [(dsit)Au2(dppm)]. Interestingly, the use of a zinc
complex (NBu4)[Zn(dsit)] as ligand transfer agent was found
to be favorable to direct addition of the selenium ligand.18
The versatility of the dichalcogenoimidodiphosphinato anions
[R2P(E)NP(E)R2]- as ligands remained largely neglected for
many years after their synthesis by Schmidpeter in the 1960s.19
Recently, interest has been renewed in their coordination abilities
and they have found use in a number of diverse areas such as
catalysis,20 NMR shift reagents,21 and selective metal extract-
ants.22 Ligands with mixed chalcogen donors [R2P(O)NP(E)R2]-
(E ) S, Se) have also been prepared.23 The preparation by
Woollins and co-workers of the selenium analogue24 in 1995
has led to a sizable number of metal diselenoimidodiphosphinate
complexes being reported.24,25
Scheme 2
Gold has been shown to readily coordinate selenium species
in accordance with its “soft” nature and this potential was
touched upon in a recent report concerning the [R2P(Se)NP-
(Se)R2]- ligand.26
As part of an ongoing study of the coordination of sulfur
and selenium ligands at gold(I) centers, we present here an
investigation into the coordination chemistry of the diseleno-
imidodiphosphinate anion as a ligand for gold(I) mono- and
bisphosphine complexes. Compounds of the formula [{N(Ph2-
PSe)2-Se,Se′}AuL] (L ) PPh3, 1; PMe3, 2) were prepared along
with an isonitrile gold diselenoimidodiphosphinate species [{N-
(Ph2PSe)2-Se,Se′}AuCNC6H3Me2-2,6] (3) which was intended
to provide a phosphine-free example for comparison but proved
highly insoluble in common laboratory solvents. The oxonium
compound [(Ph3PAu)3O]BF4 was found to react with K[Ph2P-
(Se)NP(Se)Ph2] to provide the cationic complex [{N(Ph2PSe)2-
Se,Se′}(AuPPh3)2]BF4 (4). To investigate the possibility of ring
formation, two bimetallic examples were prepared. The complex
[{N(Ph2PSe)2-Se,Se′}Au2(dppm)]OSO2CF3 (5) yielded suitable
crystals for an X-ray diffraction study that confirmed its cyclic
nature. The second example [{N(Ph2PSe)2-Se,Se′}2Au2] (6), free
of auxiliary ligands, however, proved insoluble, probably due
to the formation of a polymeric structure (Scheme 2). The
structural studies reveal that the gold center in the [{N(Ph2-
PSe)2-Se,Se′}AuL] complexes [L ) PPh3 (1); (PMe3)2 (2a)] is
able to display different coordination numbers (3 or 4) depending
on the phosphine present. The ability of gold(I) to show higher
coordination numbers than that found in the usual linear species
has been the subject of a recent review.27 Probably owing to
steric crowding, no aurophilic interactions are observed in
complexes 1 and 2a, in contrast to the cyclic species [{N(Ph2-
PSe)2-Se,Se′}Au2(dppm)]OSO2CF3 (5) which has a transannular
gold-gold contact of 3.2687(4) Å and exhibits intermolecular
gold-selenium contacts.
(15) Jones, P. G.; Thoene, C. Inorg. Chim. Acta 1991, 181, 291.
(16) Schmidbaur, H.; Ebner von Eschenbach, J.; Kumberger, O.; Mu¨ller,
G. Chem. Ber. 1990, 123, 2261.
(17) Ahrens, B.; Jones, P. G. Z. Naturforsch. 1999, 54b, 1474. Jones, P.
G.; Ahrens, B. Chem. Commun. 1998, 2307.
(18) Cerrada, E.; Laguna, M. Can. J. Chem. 1998, 76, 1033. Cerrada, E.;
Laguna, M.; Sorolla, P. A. Polyhedron 1997, 17, 295.
(19) Schmidpeter, A.; Bohm, R.; Groeger, H. Angew. Chem., Int. Ed. Engl.
1964, 3, 704. Schmidpeter, A.; Stoll, K. Angew. Chem., Int. Ed. Engl.
1967, 6, 252. Schmidpeter, A.; Stoll, K. Angew. Chem., Int. Ed. Engl.
1968, 7, 549.
(20) Rudler, H.; Denise, B.; Ribeiro Gregorio, J.; Vaissermann, J. Chem.
Commun. 1997, 2299.
(21) Barkaoui, L.; Charrouf, M.; Rager, M.-N.; Denise, B.; Platzer, N.;
Rudler, H. Bull. Soc. Chim. Fr. 1997, 134, 167.
(22) Navra´til, O.; Herrmann, E.; Grossmann, G.; Telpy, J. Collect. Czech.
Chem. Commun. 1990, 55, 364.
(23) Smith, M. B.; Slawin, A. M. Z.; Woollins, J. D. J. Chem. Soc., Dalton
Trans. 1998, 1537. Slawin, A. M. Z.; Smith, M. B. New J. Chem.
1999, 23, 777.
Experimental Section
General Information. The experiments were carried out routinely
in air. NMR: JEOL GX 400 spectrometer using deuterated solvents
with the usual standards at 25°C. MS: Varian MAT311A instrument
(FAB, p-nitrobenzyl alcohol). The complexes [LAuCl] (L ) PMe3,
PPh3),28 [(dppm)(AuCl)2],28 [(2,6-C6H3Me2NC)AuCl],29 and [(Ph3-
(24) Bhattacharyya, P.; Slawin, A. M. Z.; Williams, D. J.; Woollins, J. D.
J. Chem. Soc., Dalton Trans. 1995, 2489.
(25) Rossi, R.; Marchi, A.; Marvelli, L.; Peruzzini, M.; Casellato, U.;
Graziani, R. J. Chem. Soc., Dalton Trans. 1992, 435. Rossi, R.; Marchi,
A.; Marvelli, L.; Magon, L.; Peruzzini, M.; Casellato, U.; Graziani,
R. J. Chem. Soc., Dalton Trans. 1993, 723. Bhattacharyya, P.;
Novosad, J.; Phillips, J.; Slawin, A. M. Z.; Williams, D. J.; Woollins,
J. D. J. Chem. Soc., Dalton Trans. 1995, 1607. Cea-Olivares, R.;
Novosad, J.; Woollins, J. D.; Slawin, A. M. Z.; Garcia-Montalvo, V.;
Espinosa-Perez, G.; Garcia y Garcia, P. J. Chem. Soc., Chem. Commun.
1996, 519. Cea-Olivares, R.; Garcia-Montalvo, J.; Novosad, J. D.;
Woollins, R. A.; Toscano, G.; Espinosa-Perez Chem. Ber. 1996, 129,
919.
30
PAu)3O]BF4 and the ligand K[Ph2P(Se)NP(Se)Ph2]24 were prepared
following literature procedures.
[{N(Ph2PSe)2-Se,Se′}AuPPh3] (1). An acetone solution (5 mL) of
K[Ph2P(Se)NP(Se)Ph2] (59 mg, 0.10 mmol) was added dropwise to a
(27) Gimeno, M. C.; Laguna, A. Chem. ReV. 1997, 97, 511.
(28) Schmidbaur, H.; Wohlleben, A.; Wagner, F.; Orama, O.; Huttner, G.
Chem. Ber., 1977, 110, 1748.
(26) Woollins, J. D.; Smith, M. B.; Slawin, A. M. Z. Polyhedron 1999,
18, 1135.
(29) Schneider, W.; Angermeier, K.; Sladek, A.; Schmidbaur, H. Z.
Naturforsch. 1996, 51b, 790.

4658 Inorganic Chemistry, Vol. 40, No. 18, 2001
Wilton-Ely et al.
Table 1. Crystal Data, Data Collection, and Structure Refinement of Compounds 1, 2a, and 5
1
2a
5‚CH2Cl2
empirical formula
M
crystal system
space group
a/Å
C42H35AuNP3Se2
1001.51
Triclinic
P1h
9.0980(1)
12.0153(2)
18.6794(3)
77.791(1)
79.768(1)
74.661(1)
1908.64(5)
1.743
C30H38AuNP4Se2
891.38
Orthorhombic
Fdd2
21.5152(2)
31.0765(6)
9.5041(1)
90
90
90
6354.6(2)
1.863
8
C51H44Au2Cl2F3NO3P4SSe2
1554.57
Triclinic
P1h
11.3563(4)
15.2646(4)
15.5717(5)
108.839(1)
91.216(1)
90.904(1)
2575.8(1)
2.004
b/Å
c/Å
R/deg
â/deg
γ/deg
U/Å3
F
calc/g cm-3
Z
2
2
µ(Mo KR)/cm-1
T/K
59.18
193
71.44
143
74.23
143
unique reflections
refined parameters
R1 [I > 2σ(I)]
wR2
11619
442
0.0409
0.0809
a ) 0.0177
b ) 7.60
0.873/-1.935
1701
173
0.0217
0.0556
a ) 0.0065
b ) 111.32
0.825/-1.768
9723
622
0.0449
0.0948
a ) 0.0353
b ) 11.28
1.672/-1.628
weighting schemea
σfin(max/min)/eÅ-3
a wR2) {[∑w(Fo2 - Fc2)2]/∑[w(Fo2)2]}1/2; w ) 1/[σ2(Fo2) + (ap)2 + bp]; p ) (Fo2 + 2Fc2)/3.
stirred solution of [Ph3PAuCl] (50 mg, 0.10 mmol) in dichloromethane
(15 mL). After stirring for 2 h, all solvent was removed and the crude
product dissolved in dichloromethane (20 mL) and filtered through
diatomaceous earth to remove KCl. After concentration of the solution
to ca. 10 mL, pentane (20 mL) was carefully added to precipitate a
colorless solid. This was washed with pentane (20 mL) and dried.
Yield: 79% (80 mg). MS (FAB) m/e ) 1001, 11% [M]+. 31P NMR
MS (FAB) m/e ) 1462, 58% [M]+; 1199, 16% [M - PPh3]+; 721,
57% [Au(PPh3)2]+; 460, 100% [AuPPh3]+. 31P NMR (CD2Cl2): 24.7
1
(s, PSe, JPSe ) 503.0 Hz), 35.3 (s, PPh3) ppm. H NMR (CD2Cl2):
7.55, 8.16 (m × 2, 50 H, C6H5) ppm. Anal. Calcd for C60H50Au2BF4-
NP4Se2.2CHCl3: C, 41.69; H, 2.93; N, 0.78%. Found: C, 41.62; H,
2.91; N, 0.73%.
[{N(Ph2PSe)2-Se,Se′}Au2(dppm)]OSO2CF3 (5). An ice-cooled
tetrahydrofuran solution (5 mL) of AgOSO2CF3 (61 mg, 0.24 mmol)
was added dropwise to a stirred tetrahydrofuran solution (10 mL) of
(dppm)(AuCl)2 (100 mg, 0.12 mmol) at 0°C. After 45 min. stirring,
this suspension was filtered into a solution of K[Ph2P(Se)NP(Se)Ph2]
(68 mg, 0.12 mmol) in tetrahydrofuran (5 mL), also at 0°C. The reaction
was stirred for 2 h and methanol added (15 mL). Reduction in solvent
volume caused the precipitation of a colorless solid. This was filtered,
washed with methanol (10 mL), pentane (10 mL) and dried. Yield:
70% (120 mg). MS (FAB) m/e ) 1326, 86% [M + 4H]+; 939, 7% [M
- (dppm)]+; 778, 2% [M - (N(Ph2PSe)2]+. 31P NMR (CD2Cl2): 24.4
1
(CD2Cl2): 25.4 (s, PPh2, JPSe ) 570.2 Hz), 37.5 (s, PPh3) ppm. H
NMR (CD2Cl2): 7.39, 7.97 (m × 2, 35 H, C6H5) ppm. Anal. Calcd for
C42H35AuNP3Se2: C, 50.32; H, 3.62; N, 1.40%. Found: C, 50.28; H,
3.43; N, 1.28%.
[{N(Ph2PSe)2-Se,Se′}AuPMe3] (2). An acetone solution (5 mL) of
K[Ph2P(Se)NP(Se)Ph2] (94 mg, 0.16 mmol) was added dropwise to a
stirred solution of [Me3PAuCl] (50 mg, 0.16 mmol) in dichloromethane
(15 mL). After stirring for 2 h, all solvent was removed and the crude
product dissolved in dichloromethane (20 mL) and filtered through
diatomaceous earth to remove KCl. After concentration of the solution
to ca. 10 mL, pentane (20 mL) was carefully added to precipitate a
colorless solid. This was washed with pentane (20 mL) and dried.
Yield: 80% (105 mg). MS (FAB) m/e ) 817, 8% [M]+, 273, 7%
1
(s, PSe, JPSe ) 499.0 Hz), 33.2 (s, dppm) ppm. H NMR (CD2Cl2):
3.43 (t, 2 H, CH2, JHP ) 11.25 Hz) 7.25, 7.41, 7.83 (m × 3, 40 H,
C6H5) ppm. Anal. Calcd for C50H42Au2F3NO3P4SSe2: C, 40.86; H, 2.88;
N, 0.95%. Found: C, 40.45; H, 2.73; N, 0.77%.
[AuPMe3]+. 31P NMR (CD2Cl2): -6.3 (s, PMe3), 26.3 (s, PPh2, JPSe
)
1
589.0 Hz) ppm. H NMR (CD2Cl2): 1.39 (d, 9 H, CH3, JHP ) 1.49
Hz), 7.37, 7.97, 8.02 (m × 3, 20 H, C6H5) ppm. Anal. Calcd for C27H29-
AuNP3Se2: C, 39.77; H, 3.59; N, 1.72%. Found: C, 39.92; H, 3.82;
N, 1.69%.
[{N(Ph2PSe)2-Se,Se′}2Au2] (6). An acetone solution (5 mL) of
K[Ph2P(Se)NP(Se)Ph2] (91 mg, 0.16 mmol) was added dropwise to a
stirred solution of [(tht)AuCl] (50 mg, 0.16 mmol) in dichloromethane
(15 mL) causing immediate precipitation of a colorless product. After
stirring for 2 h, all solvent was removed and the crude material washed
with water (30 mL) and filtered. The colorless product was washed
with water (20 mL) and pentane (20 mL) and dried. Yield: 69% (80
mg). NMR: Due to insolubility in all available deuterated solvents,
no NMR data could be obtained. Anal. Calcd for C48H40Au2N2P4-
Se4.CH2Cl2: C, 37.64; H, 2.71; N, 1.79%. Found: C, 37.35; H, 2.79;
N, 1.66%.
X-ray Crystallography. Specimens of suitable quality and size of
compounds 1, 2a, and 5 were mounted on the ends of quartz fibers in
F06206R oil and used for intensity data collection on a Nonius DIP2020
diffractometer, employing graphite-monochromated Mo KR radiation.
The structures were solved by a combination of direct methods
(SHELXS-97) and difference Fourier syntheses and refined by full
matrix least-squares calculations on F2 (SHELXL-97). The thermal
motion was treated anisotropically for all non-hydrogen atoms. All
hydrogen atoms were calculated and allowed to ride on their parent
atoms with fixed isotropic contributions. Further information on crystal
data, data collection and structure refinement are summarized in Table
1. Important interatomic distances and angles are shown in the
corresponding Figure Captions.
[{N(Ph2PSe)2-Se,Se′}Au(CNC6H3Me2-2,6)] (3). An acetone solution
(5 mL) of K[Ph2P(Se)NP(Se)Ph2] (80 mg, 0.14 mmol) was added
dropwise to a stirred solution of [(2,6-Me2C6H3NC)AuCl] (50 mg, 0.14
mmol) in dichloromethane (15 mL) causing immediate precipitation
of a colorless product. After stirring for 2 h, all solvent was removed
and the crude material washed with water (30 mL) and filtered. The
colorless product was washed with pentane (20 mL) and dried. Yield:
59% (71 mg). MS (FAB) m/e ) 740, 2% [M - CNC6H3Me2]+. IR
(Nujol/KBr plates): 2147 [ν(CN)] cm-1. NMR: Due to insolubility in
all available deuterated solvents, no NMR data could be obtained. Anal.
Calcd for C33H29AuN2P2Se2.2CH2Cl2: C, 40.41; H, 3.20; N, 2.69%.
Found: C, 40.68; H, 2.81; N, 2.18%.
[{N(Ph2PSe)2-Se,Se′}(AuPPh3)2]BF4 (4). A dichloromethane (20
mL) solution of [(Ph3PAu)3O]BF4 (100 mg, 0.068 mmol), K[Ph2P(Se)-
NP(Se)Ph2] (59 mg, 0.102 mmol) and NaBF4 (8 mg, 0.073 mmol) were
stirred for 2 h. The solution was filtered through diatomaceous earth
and the solvent volume of the filtrate reduced to ca. 5 mL. Diethyl
ether was then added to precipitate the colorless product which was
filtered, washed with diethyl ether (10 mL) and dried. Yield: 65%
(102 mg). The product was recrystallized from chloroform/diethyl ether.

Bidentate Selenium Ligand
Inorganic Chemistry, Vol. 40, No. 18, 2001 4659
Figure 1. Molecular structure of compound 1 (ORTEP drawing with
50% probability ellipsoids, H-atoms omitted for clarity). Selected bond
lengths [Å] and angles [deg]: Au1-P3 2.2786(9), Au1-Se1 2.5271(4),
Au1-Se2 2.6341(4), Se1-P1 2.1768(9), Se2-P2 2.169(1), P1-N1
1.600(3); P2-N1 1.596(3); P3-Au1-Se1 133.06(3), P3-Au1-Se2
114.24(3), Se2-Au1-Se1 112.69(1), Au1-Se1-P1 92.84(3), Se1-
P1-N1 117.9(1), P1-N1-P2 128.2(2), N1-P2-Se2 117.4(1), P2-
Se2-Au1 93.79(3).
Figure 3. Molecular structure of compound 2a (ORTEP drawing with
50% probability ellipsoids, H-atoms omitted for clarity). Selected bond
lengths [Å] and angles [deg]: Au1-P1/P1′ 2.333(2), Au1-Se1/Se1′
2.9230(7), Se1-P2 2.122(2), P2-N1 1.600(4); P1-Au1-P1′ 153.5(1),
P1-Au1-Se1 96.16(5), P1′-Au1-Se1 102.05(5), Se1-Au1-Se1′ 92.90-
(3), Au1-Se1-P2 108.88(5), Se1-P2-N1 120.6(3), P2-N1-P2′
135.0(7).
Figure 4. Side-on view of compound 2a showing twisted conforma-
tion.
Figure 2. Side-on view of compound 1 showing twisted conformation.
Treatment of the K[Ph2P(Se)NP(Se)Ph2] ligand with the oxonium
species [(Ph3PAu)3O]BF4 results in the isolation of [{N(Ph2PSe)2-Se,-
Se′}(AuPPh3)2]BF4 (4) in good yield (Scheme 1). A strong (58%)
molecular ion is observed at m/e ) 1462 in the FAB mass spectrum
for the cation in addition to diagnostic fragmentation of phosphine (m/e
) 1199) and a gold-phosphine unit (m/e ) 721).
Synthesis and Characterization of Complexes. Addition of an
acetone solution of K[Ph2P(Se)NP(Se)Ph2] to dichloromethane solutions
of the gold(I) halide complexes [LAuCl] (L ) PMe3, PPh3, CNC6H3-
Me2-2,6) provided the target complexes [{N(SePPh2)2-Se,Se′}AuL] as
crystalline products in good yield (Scheme 1). In addition to a singlet
at 37.5 ppm in the 31P NMR spectrum for the triphenylphosphine group,
the presence of the selenium ligand in the complex [{N(Ph2PSe)2-Se,-
Se′}AuPPh3] (1) was confirmed by a resonance at 25.4 ppm showing
In situ preparation of the complex [(dppm)(AuOSO2CF3)2] at low
temperature from [(dppm)(AuCl)2] and 2 equiv of AgOSO2CF3 was
followed by addition of K[Ph2P(Se)NP(Se)Ph2]. The resulting crystalline
product [{N(Ph2PSe)2-Se,Se′}Au2(dppm)]OSO2CF3 (5) shown in Scheme
2, gave rise to two resonances in the 31P NMR spectrum at 24.4 and
33.2 ppm, the former displaying a JPSe coupling of 499 Hz. A structural
study was undertaken and demonstrated that the complex formed was
indeed cyclic in nature, consisting of an eight-membered ring showing
a transannular gold-gold interaction of 3.2687(4) Å (Figures 5-7). It
is interesting to note that no ionization takes place to form the
homoleptic gold species [(dppm)2(Au)2]2+ and [{N(Ph2PSe)2-Se,-
Se′}2Au2], a tendency that has often been observed in other cases.31
The complex [{N(Ph2PSe)2-Se,Se′}2Au2] (6) with the same composition
as the neutral species above can, however, be prepared by reaction of
equimolar quantities of [(tht)AuCl] (tht ) tetrahydrothiophene) and
K[Ph2P(Se)NP(Se)Ph2]. The colorless product that precipitated im-
mediately on addition of the ligand, proved insoluble in all common
laboratory solvents including hot dimethylformamide. It is likely that
it adopts a polymeric structure in the solid state (Scheme 2).
a
31P-77Se coupling of 570 Hz. Similarly, the trimethylphosphine
analogue [{N(Ph2PSe)2-Se,Se′}AuPMe3] (2) gave rise to resonances at
26.3 (JPSe ) 589 Hz) and -6.3 ppm. The molecular mass pattern of
the ion observed for 2 at m/e ) 817 in the FAB mass spectrum
corresponded well to the calculated isotopic distribution. The xylyl-
isonitrile species [{N(Ph2PSe)2-Se,Se′}Au(CNC6H3Me2-2,6)] (3) proved
to be insufficiently soluble in common laboratory solvents to allow a
spectroscopic investigation but its composition was confirmed by
elemental analysis and FAB mass spectrometry. The isonitrile ligand
gave rise to a ν(CN) absorption at 2147 cm-1 in the solid-state infrared
spectrum.
Single crystals of 1 were grown from a dichloromethane/diethyl ether
mixture and were found to be suitable for a structural study (Figures 1
and 2). The same crystallization process for complex 2 took consider-
ably longer (6 days) and yielded smaller single crystals. One of these
was used for a structural analysis which surprisingly revealed a four-
coordinate, bis(trimethylphosphine)gold center (complex 2a) shown in
Figures 3 and 4. The partial conversion to 2a is thought to arise from
a slow dissociation process in 2 to provide the additional phosphine
ligand. A dichloromethane solution of 2, stirred for a week, also yields
this bis(phosphine) species 2a in small amounts.
(30) Nesmeyanov, A. N.; Perevalova, E. G.; Struchkov, Yu. T.; Antipin,
M. Yu.; Grandberg, K. I.; Dyadchenko, V. P. J. Organomet. Chem.
1980, 201, 343.
(31) Bauer, A.; Schmidbaur, H. J. Chem. Soc., Dalton Trans. 1997, 1115.
Bauer, A.; Schmidbaur, H. J. Am. Chem. Soc. 1996, 118, 5324.

4660 Inorganic Chemistry, Vol. 40, No. 18, 2001
Wilton-Ely et al.
359.99°, but the two angles P3-Au1-Se differ quite signifi-
cantly [P3-Au1-Se1 133.06(3), P3-Au1-Se2 114.24(3)°] as
do the two pairs of Au-Se and P-Se bond lengths: Au1-Se1
2.5271(4)/ Au1-Se2 2.6341(4); P1-Se1 2.177(1)/P2-Se2
2.169(1) Å. In the structure of the analogous sulfur complex
[{N(Ph2PS)2-S, S′}AuPPh3], the Au-S distances differ by over
0.6 Å leading to pronounced asymmetry in the six-membered
ring.32 The data for 1 suggest that the bonding between gold
and selenium is weaker for Se2 than for Se1. By contrast the
two endocyclic angles N-P-Se are virtually identical [N1-
P1-Se1 117.9(1)°, N1-P2-Se2 117.5(1)°] and the bond
lengths N1-P1 1.600(3)/N1-P2 1.596(3) Å [at an angle P1-
N1-P2 128.3(2)°] are almost equidistant, showing that the
phosphazene unit of the bidentate ligand remains highly
symmetrical in its complex (1). It should be noted that these
results are in agreement with data published for a compound
where the Ph3P ligand is replaced by Ph2PNHP(O)Ph2.26 The
distortions at the three-coordinate gold atom in this reference
molecule are even greater, but this may be caused by an
extensive hydrogen-bonding network and by a different boatlike
conformation of the six-membered ring.
Figure 5. Dimeric units of compound 5 (ORTEP drawing with 50%
probability ellipsoids, H-atoms omitted for clarity). Au2B‚‚‚Se1A
3.447(1), Au1B‚‚‚Se1A 3.331(1) Å.
Crystals of complex 2a are orthorhombic, in space group
Fdd2, with Z ) 8 molecules in the unit cell. The crystallo-
graphically imposed symmetry of the individual molecules calls
for a 2-fold axis passing through the atoms N1 and Au1 (Figure
3). The six-membered ring has a twist conformation (Figure 4)
as encountered already for complex 1. The gold atom has a
coordination number of 4, however the geometry deviates very
strongly from the idealized tetrahedral symmetry. This is most
obvious from the large angle P1-Au1-P1′ 153.5(1)° which is
closer to 180° than to the 109° required for an undistorted
tetrahedron. The complex can therefore be described as a
combination of the linear [(Me3P)2Au]+ cation and the bidentate
[N(PPh2Se)2]- anion in which the approach of the latter causes
the distortion of the former. In this context it should be noted
that the two Au-Se contacts [2.9230(7) Å] are much longer
(in excess of 10%) than those in complex 1 indicating much
weaker interactions in 2a.
Figure 6. Side-on view along the axis of the two gold atoms for
compound 5.
It is not surprising that the P-Se bond lengths are shorter
[2.122(2) Å] for 2a than for 1, and that all endocyclic angles
are larger: P2-N1-P2′ 135.0(7), N1-P2-Se1 120.6(3)°. The
“natural” bite angle of the open phosphazene ligand is therefore
largely unaffected by the metal atom.
Figure 7. Molecular structure of compound 5 (ORTEP drawing with
50% probability ellipsoids, H-atoms omitted for clarity). Selected bond
lengths [Å] and angles [deg]: Au1-P3 2.265(2), Au1-Se1 2.4280(7)
Au1‚‚‚Au2 3.2687(4), Au2-P4 2.263(2), Au2-Se2 2.4209(8), Se1-
P1 2.201(2), Se2-P2 2.198(2), P1-N1 1.593(6), P2-N1 1.586(6), P3-
C1 1.817(7), P4-C1 1.819(8); Se1-Au1-P3 174.71(5), Au1-P3-
C1 112.9(2), C1-P4-Au2 113.9(2), P4-Au2-Se2 171.16(5), Au2-
Se2-P2 98.22(6), Se2-P2-N1 118.3(2), P2-N1-P1 135.4(4), N1-
P1-Se1 116.1(2), P1-Se1-Au1 97.76(5).
Crystals of complex 5 containing one molecule of solvent
CH2Cl2 are triclinic, of space group P1h, with Z ) 2 formula
units in the unit cell. The components are related by a center of
inversion. In the lattice, the cations are well separated from the
anions and from the solvent molecules, however the cations are
arranged in pairs with sub-van der Waals Au-Se contacts
(Figure 5). The monocations form eight-membered rings in
which a bis(diphenylphosphino)methane (dppm) and an imino-
bis(selenodiphenyldiphosphinate) ligand bridge two gold atoms
(Figures 6 and 7). The geometry of the ring approaches mirror
symmetry with the reference plane passing through N1 and C1.
The two gold atoms are two-coordinate, but the angles Se1-
Au1-P3 174.71(5)° and Se2-Au2-P4 171.16(5)° deviate
significantly from linearity. The bending of the two angles
allows a mutual approach of the two metal atoms to give a
transannular Au- -Au equilibrium distance of 3.2687(4) Å
representing an aurophilic contact. The two Au-Se distances
[Au1-Se1 2.4280(7), Au2-Se2 2.4209(8) Å] are the shortest
observed for the three compounds (1, 2a and 5) and, conversely,
The luminescence properties of some of the compounds detailed
above are currently under investigation.
Crystal and Molecular Structures
Crystals of complex 1 are triclinic, of space group P1h, with
Z ) 2 molecules related by a center of inversion in the unit
cell. The individual molecule has no crystallographically
imposed symmetry but, neglecting the orientation of the phenyl
groups, the geometry of the skeleton approaches quite closely
the requirements of point group C2 (Figure 1). The quasi-2-
fold axis passes through the atoms N, Au1, and P3. The six-
membered ring is in a twist conformation (Figure 2). The gold
atom is planar three-coordinate with a bond angles sum of
(32) Haiduc, I.; Fischer, A.; Edelmann, F. T. ReV. Roum. Chim. 2000, 44,
805.

Bidentate Selenium Ligand
Inorganic Chemistry, Vol. 40, No. 18, 2001 4661
atoms of the dichloromethane molecule [C3-H3B‚‚‚O1 144.5°;
C3-H3B 0.990 Å, O1-H3B 2.485 Å, C3‚‚‚O1 3.341 Å].
Interactions of this kind have been noted recently by Jones and
Ahrens in a number of gold(I) and silver(I) complexes.17
Anisotropic thermal parameters and tables of interatomic
distances and angles have been deposited with the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK. The data are available on request on quoting CCDS-
167314-167316.
Conclusion
Figure 8. Hydrogen bonding between the cations, anions and solvent
molecules in the structure of 5.CH2Cl2 (ORTEP drawing with 50%
probability ellipsoids, phenyl-H-atoms omitted for clarity). C1-H1B‚‚‚
O2: C1-H1B 0.990, H1B‚‚‚O2 2.272, C1‚‚‚O2 3.182 Å, C1-H1B‚‚‚
O2 152.2°; C3-H3B‚‚‚O1: C3-H3B 0.990, H3B‚‚‚O1 2.485, C3‚‚‚
O1 3.341 Å, C3-H3B‚‚‚O1 144.5°.
The structural chemistry of the three complexes leads to the
conclusion that coordinative bonding of the diselenide ligand
to gold(I) strongly depends on the coordination number of the
metal atom. With an increase in coordination number of gold-
(I) from 2 to 4 the Au-Se distances increase drastically. Already
in complex 1 with three-coordinate gold atoms, the bonding to
the second selenium atom is weaker than to the other, while in
complex 2a, containing a tetracoordinate gold atom, both
selenium atoms are attached only very weakly. It is therefore
only in complex 5 with two-coordinate gold(I) that Au-Se
contacts can attain the optimum conditions for coordinative
bonding. In the quasi-linear coordination geometry, the gold
atoms can establish closed-shell interactions with Au and Se
centers which are virtually absent in species with higher
coordination numbers.
the P-Se distances are the longest [P1-Se1 2.201(2), P2-Se2
2.198(2) Å]. Variations in the endocyclic angles of the diselenide
ligand in 5 as compared to 2a are small. The data for compound
5 are in good agreement with results published for the dication
[{Ph2PCH2P(Se)Ph2}2Au2]2+ which also features a strain-free
ten-membered ring with transannular aurophilic bonding.16
In the tetranuclear dimers of the cations in complex 5, one
of the two selenium atoms (Se1) of each monomer approaches
the pair of gold atoms of the neighboring monomer (Figure 5).
The two resulting triangles Au1-Au2-Se1′/Au1′-Au2′-Se
[with edges of Au1-Au2 3.2687(4), Au1′-Se1 3.331(1) and
Au2′-Se1 3.447(1) Å] are again related by inversion symmetry.
The long intercationic contacts signify that the bonding forces
between the two components are weak.
Two other types of weak interactions were also detected: (a)
between the cation and the anion and (b) between the anion
and the solvent molecule (Figure 8). One of the two methylene
hydrogen atoms of the dppm ligand (H1B) appears to be
engaged in a bond to the oxygen atom O2 of the triflate anion
[C1-H1B‚‚‚O2 152.2°; C1-H1B 0.990 Å, O2‚‚‚H1B 2.272 Å,
C1‚‚‚O2 3.182 Å], while a second oxygen atom of this anion
(O1) forms a hydrogen bridge to one of the methylene hydrogen
Acknowledgment. Support of this work by the Deutsche
Forschungsgemeinschaft, the Volkswagenstiftung, the Alexander
von Humboldt Stiftung (J.D.E.T.W.-E.), and by the Fonds der
Chemischen Industrie is gratefully acknowledged. The authors
are also indebted to Degussa AG and Heraeus GmbH for the
donation of chemicals.
Supporting Information Available: Details of crystal data, data
collection, and structure refinement and tables of atomic coordinates,
isotropic and anisotropic thermal parameters, and all bond lengths and
angles. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC010337H