Four-Coordinate Gold(I), Silver(I), and Copper(I) Complexes with a Large-Span Chiral Ditertiary Phosphine Ligand

Article abstract of DOI:10.1021/ic980385a

The ligand L = Ph₂PCH₂CHEtOPPh₂ (R,S) with two chemically different donor sites and a center of chirality in the middle of the loop connecting the phosphorus atoms has been chosen for the preparation of a series of gold(I), silver(I), and copper(I) complexes. The ligand-to-metal ratio was allowed to vary between 2:1, 1:1, and 1:2. The 1:1 complexes [LAuX]₂ with X = Cl, Br, I, and SCN have been found to be components of solution equilibria (in di- or trichloromethane) of various cyclic dinuclear isomers involving also several complexes generated in ligand redistribution processes. However, single crystals (X = Cl, Br) obtained from these solutions are composed solely of centrosymmetrical dimers where the two metal atoms are part of 12-membered rings and are bridged transannularly by two halogen atoms. By symmetry, the metal bridging by the two ligands L follows a head-to-tail pattern and involves a pair of enantiomers of L. The silver compound [LAgClO₄]₂ has an analogous structure with the silver atoms attaining coordination number 4 by perchlorate bridging. The copper complex [LCuCl]₂ is a tricyclic binuclear compound where each copper atom is chelated by an individual ligand L and doubly halogen bridged with the second metal atom. The 2:1 complex [L₂Au]Cl is assigned a bis-chelated structure with the tetracoordinated metal atom as a spiro center of two six-membered rings. The solution ³¹P NMR spectra show the presence of various stereoisomers which are readily identified via the strong couplings mediated by the metal center. Only small J(P, P') values would be expected for P-P' coupling along the ligand PCCOP' loops. The spectrum of the dinuclear 1:2 complex L(AuCl)₂ features only two singlet ³¹P resonances.

Full text of DOI:10.1021/ic980385a

Inorg. Chem. 1998, 37, 4353-4359
4353
Four-Coordinate Gold(I), Silver(I), and Copper(I) Complexes with a Large-Span Chiral
Ditertiary Phosphine Ligand
Angela Bayler, Annette Schier, and Hubert Schmidbaur*
Anorganisch-chemisches Institut der Technischen Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching, Germany
ReceiVed April 7, 1998
The ligand L ) Ph2PCH2CHEtOPPh2 (R,S) with two chemically different donor sites and a center of chirality in
the middle of the loop connecting the phosphorus atoms has been chosen for the preparation of a series of gold-
(I), silver(I), and copper(I) complexes. The ligand-to-metal ratio was allowed to vary between 2:1, 1:1, and 1:2.
The 1:1 complexes [LAuX]2 with X ) Cl, Br, I, and SCN have been found to be components of solution equilibria
(in di- or trichloromethane) of various cyclic dinuclear isomers involving also several complexes generated in
ligand redistribution processes. However, single crystals (X ) Cl, Br) obtained from these solutions are composed
solely of centrosymmetrical dimers where the two metal atoms are part of 12-membered rings and are bridged
transannularly by two halogen atoms. By symmetry, the metal bridging by the two ligands L follows a head-
to-tail pattern and involves a pair of enantiomers of L. The silver compound [LAgClO4]2 has an analogous
structure with the silver atoms attaining coordination number 4 by perchlorate bridging. The copper complex
[LCuCl]2 is a tricyclic binuclear compound where each copper atom is chelated by an individual ligand L and
doubly halogen bridged with the second metal atom. The 2:1 complex [L2Au]Cl is assigned a bis-chelated structure
with the tetracoordinated metal atom as a spiro center of two six-membered rings. The solution 31P NMR spectra
show the presence of various stereoisomers which are readily identified via the strong couplings mediated by the
metal center. Only small J(P, P′) values would be expected for P-P′ coupling along the ligand PCCOP′ loops.
The spectrum of the dinuclear 1:2 complex L(AuCl)2 features only two singlet 31P resonances.
Introduction
able interest because some of the salts show chemotherapeutic
potential for the treatment of arthritis, and also antitumor
The coordination chemistry of gold(I) is dominated by
complexes with coordination number two (CN 2) in a linear
geometry. The number of examples with higher coordination
numbers is growing only slowly, as illustrated by recent
reviews.1
The majority of these complexes is based on mono- or
polydentate tertiary phosphine ligands that are known to be the
most powerful ligands for gold(I).2 There is a limit to the
coordination of phosphines at gold(I) caused simply by steric
congestion in cations of the formula [Au(PR3)4]+ with its rather
small metal Au+ cation,3 and therefore this type of complex
can only be obtained with small phosphines PR3.4 The literature
still has no fully confirmed example, e.g., of a salt containing
the cation [Au(PPh3)4]+ with simple triphenylphosphine ligands,5
and it is only with bidentate tetraphenyldiphosphines, like Ph2-
PCH2CH2PPh2 (dppe), that clear-cut tetracoordination is reached
as in [Au(dppe)2]+.6 These compounds have attracted consider-
activity.7
Bis(diphenylphosphino)methane (dppm), with its smaller bite,
does not form a mononuclear, tetracoordinate complex with
gold(I), and binuclear species are formed instead.8 Ditertiary
phosphines with a larger ligand span have been investigated
repeatedly regarding their chelating or bridging properties for
gold(I),9 but very little is known about ligands where the donor
centers are bridged by loops other than simple polymethylene
chains -(CH2)n-.
The present report is a summary of the results of our recent
study of gold(I) complexes with a large-span, chiral diphosphine.
This work was initiated because the coordination chemistry of
gold(I) with chiral ligands is poorly developed even for
compounds with the standard CN 2.10 Stereoisomerism for
(7) (a) Berners-Price, S. J.; Colquhoun, L. A.; Healy, P. C.; Byriel, K.
A.; Hanna, J. V. J. Chem. Soc., Dalton Trans. 1992, 3357. (b) Berners-
Price, S. J.; Girard, G. R.; Hill, D. T.; Sutton, B. M.; Jarrett, P. S.;
Faucette, L. F.; Johnson, R. K.; Mirabelli, C. K.; Sadler, P. J. J. Med.
Chem. 1990, 33, 1386. (c) Berners-Price, S. J.; Jarrett, P. S.; Sadler,
P. J. Inorg. Chem. 1987, 26, 3074.
(1) Gimeno, M. C.; Laguna, A. Chem. ReV. 1997, 97, 511.
(2) Puddephatt, R. J. The Chemistry of Gold; Elsevier: Amsterdam, 1978;
p 51.
(3) (a) Bayler, A.; Schier, A.; Bowmaker, G. A.; Schmidbaur, H. J. Am.
Chem. Soc. 1996, 118, 7006. (b) Tripathi, U. M.; Bauer, A.;
Schmidbaur, H. J. Chem. Soc., Dalton Trans. 1997, 2865.
(4) (a) Elder, R. C.; Zeiher, E. H. K.; Onady, M.; Whitte, R. R. J. Chem.
Soc., Chem. Commun. 1981, 900. (b) Forward, J. M.; Assefa, Z.;
Staples, R. J.; Fackler, J. P., Jr. Inorg. Chem. 1996, 35, 16.
(5) Jones, P. G. J. Chem. Soc., Chem. Commun. 1980, 1031.
(6) (a) Berners-Price, S. J.; Mazid, M. A.; Sadler, P. J. J. Chem. Soc.,
Dalton Trans. 1984, 969. (b) Bates, P. A.; Waters, J. M. Inorg. Chim.
Acta 1984, 81, 151. (c) Harker, C. S. W.; Tiekink, E. R. T.;
Whitehouse, M. W. Inorg. Chim. Acta 1991, 181, 23.
(8) (a) Berners-Price, S. J.; Sadler, P. J. Inorg. Chem. 1986, 25, 3822. (b)
Schmidbaur, H.; Wohlleben, A.; Schubert, U.; Frank, A.; Huttner, G.
Chem. Ber. 1977, 110, 2751. (c) Shain, J.; Fackler, J. P., Jr. Inorg.
Chim. Acta 1987, 131, 157.
(9) (a) Berners-Price, S. J.; Sadler, P. J. Inorg. Chem. 1986, 25, 3822. (b)
Van Calcar, P. M.; Olmstead, M. M.; Balch, A. L. Inorg. Chem. 1997,
36, 5231. (c) Cooper, M. K.; Mitchell, L. E.; Hendrick, K.; McPartlin,
M.; Scott, A. Inorg. Chim. Acta 1984, 84, L9. (d) Schmidbaur, H.;
Bissinger, P.; Lachmann, J.; Steigelmann, O. Z. Naturforsch. 1992,
47B, 1711. (e) Van Calcar, P. M.; Olmstead, M. M.; Balch, A. L. J.
Chem. Soc., Chem. Commun. 1995, 1773.
S0020-1669(98)00385-1 CCC: $15.00 © 1998 American Chemical Society
Published on Web 07/30/1998

4354 Inorganic Chemistry, Vol. 37, No. 17, 1998
Bayler et al.
Scheme 1
tetracoordinate (tetrahedral) gold(I) was investigated for only
very few isolated cases in the past.11
at ambient temperature. High yields of crystalline products were
obtained for all three stoichiometries (Scheme 1).
The 1:1 complexes of gold(I) bromide, iodide, and thiocyanate
were synthesized from bromo(tetrahydrothiophene)gold(I) and
equimolar quantities of the ligand L or by anion metathesis using
KI or KSCN, respectively, in a two-phase system (H2O/CH2-
Cl2).
The analogous 1:1 complexes with AgCl, AgBr, AgClO4, and
CuCl can be synthesized by treating slurries of these salts in
dichloromethane (AgCl, AgBr), tetrahydrofuran (AgClO4), or
dichloromethane/acetonitrile (CuCl) with the ligand L.
NMR Spectra and Solution Structures. The 1:2 complex
L(AuCl)2 (2) is a colorless solid which dissolves readily in
chloroform. The 31P NMR spectrum of the solution shows two
singlet resonances for the two different ends of the ligand, but
only one of these is shifted strongly to lower field (by ∆δ 44.2
ppm) as compared to the parent ligand, while the other is
displaced by only 2.3 ppm. There is no NMR evidence for the
presence of isomers and a simple structure with both phosphorus
atoms coordinated to an AuCl unit is proposed, analogous to
the findings for 1:2 complexes of dppm, dppe, and their
homologues.9
By contrast, the solution of the 1:1 complex with AuCl
(“LAuCl”) in chloroform shows a very complex 31P{1H} NMR
spectrum which is indicative of the existence of various isomers
(Scheme 1) and ligand redistribution products. The signals are
all broad at room temperature, and upon cooling there is
extensive splitting into various sets of multiplets, suggesting
ligand exchange equilibria.
Preparation and Properties of the Complexes
The bidentate ligand L (Scheme 1) chosen for the present
investigation was selected as an example where (a) the two
phosphorus donor centers are chemically inequivalent (one is a
tertiary phosphine, the other is a phosphinite) and (b) the loop
connecting these donor centers features a carbon-based center
of chirality.
Unsymmetrical bisphosphorus ligands with chemically dif-
ferent phosphorus atoms are of considerable interest because
they allow a detailed investigation of coordination compounds
of these ligands by 31P NMR spectroscopy.12
The racemic ligand L is prepared (in 78% yield) from the
reaction of potassium diphenylphosphide and 1,2-epoxybutane,
followed by treatment with equivalent quantities of chlorodiphe-
nylphosphine in tetrahydrofuran starting at -78 °C and reaching
ambient temperature toward the end of the synthesis. The
racemic mixture is obtained as a colorless liquid which can be
used without further purification. Its identity and purity were
confirmed by NMR spectra.
The 1:1, 2:1, and 1:2 complexes of L with gold(I) chloride
are readily prepared by the reaction of appropriate amounts of
the ligand and chloro(dimethyl sulfide)gold(I) in tetrahydrofuran
(10) (a) Bayler, A.; Bowmaker, G. A.; Schmidbaur, H. Inorg. Chem. 1996,
35, 5959. (b) Bayler, A.; Bauer, A.; Schmidbaur, H. Z. Naturforsch.
1997, 52B, 1477. (c) Papathanasious, P.; Salem, G.; Waring, P.; Willis,
A. C. J. Chem. Soc., Dalton Trans. 1997, 3435.
(11) (a) Palmer, J. A. L.; Wild, S. B. Inorg. Chem. 1983, 22, 4054. (b)
Salem, G.; Schier, A.; Wild, S. B. Inorg. Chem. 1988, 27, 3029.
(12) Grim, S. O.; Briggs, W. L.; Barth, R. C.; Tolman, C. A.; Jesson, J. P.
Inorg. Chem. 1974, 13, 1095.
These equilibria include the products of ligand redistribution
such as [L2Au]Cl and L(AuCl)2 etc., and in fact the resonances
of L(AuCl)2 and [L2Au]Cl (above and below) have been
detected in the low-temperature spectrum of “LAuCl”.

Four-Coordinate Au(I), Ag(I), and Cu(I) Complexes
Inorganic Chemistry, Vol. 37, No. 17, 1998 4355
Chart 1. Stereoisomerism in the Annular Dinuclear 1:1 Complexes [LAuX]2 (X ) Cl, Br, I, SCN)
Single crystals of “LAuCl” could be grown, and their structure
has been determined in a X-ray diffraction study (below). From
this study it follows that the compound is a centrosymmetrical
dimer in the solid state containing the two L enantiomers
bridging the gold atoms in a head-to-tail fashion (3). This unit,
if persistent in solution, should therefore show only two 31P
NMR signals. Since many more resonances are actually
observed (also after dissolving the single crystals in chloroform),
one has to conclude that this form is undergoing fast ligand
scrambling in solution. For a 12-membered ring as present in
the crystal, four diastereomers can be drawn, which should
exhibit four sets of 31P NMR signals (Chart 1). As already
mentioned many more resonances are actually observed owing
to ligand redistribution, which has not been followed in detail.
The 1:1 complexes with AuBr, AuI, and AuSCN show similar
spectral properties, but fewer species are present in solution,
indicating less extensive ligand redistribution.
splittings of the phosphorus signals at low temperature, which
disappear at room temperature due to ligand scrambling. The
systems with X ) Cl, Br are complicated by ligand exchange
processes to give signal patterns similar to the gold(I) analogues.
In the case of the weakly coordinating anion ClO4- this ligand
redistribution is a slow process on the NMR time scale and the
low-temperature spectrum can be assigned solely to the cyclic
dinuclear complexes [LAgClO4]2 in head-to-tail (2JP,PO ) 168
1
1
107
107
Hz, J
) 490 Hz, J
) 543 Hz) and head-to-head
Ag,P
Ag,PO
1
1
107
107
( J Ag,P ) 512, J Ag,PO ) 547 Hz) constitution. The coupling
1
1
107
109
constants J Ag,P and J Ag,P are in the ratio of the gyromagnetic
1
107Ag,P
factors (1.15) of the two metal isotopes. The J
values
are also in good agreement with literature data reported for other
silver(I) derivatives with two tertiary phosphines coordinated
to the metal center.14 Signal splitting due to racemic and meso
diastereomers could not be observed for the AgClO4 complex.
The 31P{1H} NMR spectrum of the 1:1 complex with CuCl,
recorded immediately after dissolving single crystals in chlo-
roform, shows a reduced multiplet complexity. Only a pair of
broad doublets for the chemically inequivalent phosphorus atoms
appears in the room-temperature spectrum, consistent with a
structure as present in the crystal (below), with L chelating the
metal center. The observed splitting can be explained by P-P
coupling transmitted through the metal center (2JP,PO ) 153 Hz).
Broadening of the signals is caused presumably by 63/65Cu-
31P quadrupole relaxation, as generally observed for phosphine
complexes of copper(I) with low symmetry.15
In the low-temperature spectra of “LAuBr” and “LAuI” in
chloroform the resonances of the undissociated annular binuclear
complexes [LAuX]2 can be readily identified besides the minor
resonances for the ligand redistribution products [L2Au]X and
L(AuX)2. Head-to-tail coordination of the two ligands (3a, 3b)
gives rise to a pair of doublets for the phosphino and phosphinito
phosphorus atoms, respectively. The coupling constants 2JP,PO
2
) 346 Hz (X ) Br) and JP,PO ) 338 Hz (X ) I) are rather
large, as expected for linear two-coordinate gold(I) compounds.13
For the corresponding head-to-head isomers (4a, 4b), two
singlets appear in the 31P{1H} NMR spectrum and no coupling
between the phosphorus atoms through the ligand backbone can
be observed.
After several days additional peaks appear in the spectrum
of the solution owing to ligand redistribution processes. The
copper complex therefore appears to have a higher kinetic
stability compared to the corresponding gold and silver com-
plexes.
No further signal splitting indicating the existence of distinct
racemic and meso diastereomers could be observed down to
-60 °C.
The 2:1 Complex [L2Au]Cl. The reaction of two equivalents
of L with Me2SAuCl is proposed to give the bis-chelated
1
Owing to the presence of two spin /2 nuclei 107/109Ag, the
NMR spectra of the 1:1 silver complexes show additional
(14) Attar, S.; Alcock, N. W.; Bowmaker, G. A.; Frye, J. S.; Bearden, W.
H.; Nelson, J. H. Inorg. Chem. 1991, 30, 4166 and references therein.
(15) Black, J. R.; Levason, W.; Spicer, M. D.; Webster, M. J. Chem. Soc.,
Dalton Trans. 1993, 3129 and references therein.
(13) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition Metal
Phosphine Complexes; Springer-Verlag: Berlin, 1979.

4356 Inorganic Chemistry, Vol. 37, No. 17, 1998
Bayler et al.
Chart 2. Stereoisomerism in the Tetrahedral Cation of
[L2Au]Cl
Figure 1. 31P {1H} NMR spectrum of [L2Au]Cl in CDCl3 at -60 °C.
(a) Phosphine region; (b) phosphinite region. The spectrum was
analyzed as overlapping spin systems for the distinct diastereomers 1a
(AA′XX′), 1b (BB′YY′), and 1c (ABXY).
tetracoordinated gold(I) species [L2Au]Cl (Scheme 1, 1), based
on the observation that the bis(phosphines) dppe and dppp also
form stable spiro complexes with gold(I) contained in two five-
or six-membered chelate rings.9a
as a representative example. Crystal data and other details are
summarized in Table 1. The molecular structure and the atomic
numbering are shown in Figure 2 with selected bond lengths
and angles in the figure caption.
Tetrahedral, bis-chelated complexes with unsymmetrical
bidentate ligands (with two chemically inequivalent phosphorus
atoms in the case of L) can exist as enantiomers with absolute
configurations ∆ and Λ.16 For the 2:1 complex of AuCl with
the chiral ligand L three pairs of enantiomers have to be
considered (∆(RR), Λ(SS); Λ(RR), ∆(SS); ∆(RS), Λ(RS))
(Chart 2). The spectra at the low-temperature limit indeed show
the expected three multiplets, the pattern of which could be
analyzed by computing the corresponding AA′XX′ (1a), BB′YY′
(1b), and ABXY (1c) spin systems (Figure 1). Upon warming,
coalescence is observed owing to increasingly rapid exchange
processes.
As e.g. shown for compounds 2-4 (above), P-P′ coupling
through the ligand backbone is very small and cannot be
resolved for the 1:2 and 1:1 complexes with L bridging two
metal centers. The observation of spin systems with large J(P,
P′) coupling constants, which lead to complex multiplet patterns
for the 2:1 compounds (Figure 1), can thus be taken as indicative
of the chelating nature of L, which gives rise to strong P-P′
coupling mediated by the metal center.
The two compounds, [LAuCl]2 and [LAuBr]2, crystallize in
the monoclinic space group P21/n with two formula units in
the unit cell. The lattices contain centrosymmetrical binuclear
molecules which feature a 12-membered ring with a transannular
double-bridging of the metal atoms by the halogen atoms. The
triatomic units P-Au-P are strongly bent [158.96(5)°] owing
to the coordination of the two halogen atoms. The two bromo
bridges are not symmetrical with distances at Au-Br 3.106(1)
and Au-Br′ 3.128(1) Å and the Au-Br-Au′ angles close to
rectangular [88.40(5)°].
As governed by the symmetry element of point group Ci the
two ligands in the molecule are a pair of enantiomers (R, S),
and each gold atom is coordinated to two different ends of the
ligands, i.e., Ph2PCH2 and Ph2PO. The sequence of the ligands
is thus head-to-tail. The crystallographical refinement of the
bridges as CH2 or O is not entirely conclusive because of the
minute differences in the R factors, and some minor disorder
has to be admitted, but these are not affecting the basic principle
of the structure. (As shown by NMR spectroscopy (above) some
isomerization through ligand redistribution also takes place in
solution.)
Solid State Structures. Single crystals of a quality accept-
able for X-ray diffraction studies could only be obtained for
the 1:1 complexes of the ligand with AuCl, AuBr, AgClO4, and
CuCl.
The two gold(I) halide complexes are isomorphous with only
minor differences in the individual molecular structures, and
therefore only the bromide [LAuBr]2 is discussed here in detail
The silver complex [LAgClO4]2 crystallizes in the triclinic
space group P1h with two formula units in the unit cell. The
asymmetric unit contains two halves of crystallographically
independent dimers, with the two other halves generated by
centers of inversion. One of the two molecules is shown in
Figure 3. The two molecules have very similar dimensions and
conformations as shown by the superposition presented in Figure
4.
(16) Ernst, R. E.; O’Connor, M. J.; Holm, R. H. J. Am. Chem. Soc. 1967,
89, 6104.

Four-Coordinate Au(I), Ag(I), and Cu(I) Complexes
Inorganic Chemistry, Vol. 37, No. 17, 1998 4357
Table 1. Crystal Data, Data Collection, and Structure Refinement
[LAuCl]2
[LAuBr]2
[LAuClO4]2‚1/2CH2Cl2
[LCuCl]2
crystal data
empirical formula
Mr
crystal system
space group
a (Å)
C56H56Au2Cl2O2P4
1295.72
monoclinic
P21/n
11.496(1)
17.818(1)
12.659(1)
90
98.20(1)
90
2566.5(5)
1.747
C56H56Au2Br2O2P4
1438.64
monoclinic
P21/n
11.503(1)
17.962(2)
12.727(1)
90
97.88(1)
90
2604.8(4)
1.834
C56.5H57Ag2Cl3O10P4
1341.99
triclinic
P1h
11.335(2)
12.881(1)
21.766(2)
94.89(1)
91.85(1)
113.33(1)
2899.9(6)
1.537
C56H56Cu2Cl2O2P4
1082.87
triclinic
P1h
9.315(1)
11.793(1)
13.010(1)
102.37(1)
103.51(1)
104.89(1)
1284.5(2)
1.400
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
F
calc (g cm-3
)
Z
2
2
2
1
F(000)
1320
59.80
1392
73.24
1362
9.80
560
10.98
µ(Mo KR) (cm-1
data collection
T (°C)
)
-74
ω
-74
ω-θ
-91
ω
-78
ω-θ
scan mode
hkl range
-14f14, 0f21, 0f15 0f14, 0f22, -16f16 -13f13, -15f15, 0f26 -11f11, -15f13, -16f16
sin(θ/λ)max (Å-1
)
0.62
5269
0.64
5919
0.62
11323
11323
9692
none
-
0.64
11311
5598 [Rint ) 0.0207]
5274
none
-
no. of measd reflcns
no. of unique reflcns
5037 [Rint ) 0.0189]
5648 [Rint ) 0.0289]
5605
ψ scans
0.45/0.99
no. of reflcns used for refinement 4993
abs corrn ψ scans
min/Tmax
refinement
no. of refined parameters
T
0.66/0.99
298
298
694
300
final R values [I > 2σ(I)]
R1a
0.0317
0.0642
0.0395
0.0920
0.0436
0.1035
0.0437
0.1178
wR2b
(shift/error)max
<0.001
1.303/-0.769
<0.001
2.256/-1.161
<0.001
0.763/-0743
<0.001
0.834/-0.776
Ffin(max/min) (e Å-3
)
2
2
a R ) ∑(||Fo| - |Fc||)/∑|Fo|. b wR2 ) {[∑w(Fo2 - Fc2)2]/∑[w(Fo )2]}1/2; w ) 1/[σ2(Fo ) + (ap)2 + bp]; p ) (Fo2 + 2Fc2)/3; a ) 0.0238 ([LAuCl]2),
0.0464 ([LAuBr]2), 0.0631 ([LAuClO4]2‚1/2CH2Cl2), 0.0801 ([LCuCl]2); b ) 5.89 ([LAuCl]2), 9.50 ([LAuBr]2), 0.31 ([LAuClO4]2‚1/2CH2Cl2), 0.59
([LCuCl]2).
Figure 3. Molecular structure of compound [LAuClO4]2 (ORTEP
drawing with 50% probability ellipsoids, H-atoms omitted for clarity).
Selected bond lengths (Å) and angles (deg): Ag1-P1, 2.401(1); Ag1-
P2, 2.408(1); Ag1-O11, 2.626(1); Ag1-O11′, 2.905(1); P1-Ag1-
P2, 157.13(4); Ag1-O11-Ag1′, 107.30(5).
Figure 2. Molecular structure of compound [LAuBr]2 (ORTEP
drawing with 50% probability ellipsoids, H-atoms omitted for clarity).
Selected bond lengths (Å) and angles (deg): Au-P1, 2.294(1); Au-
P2, 2.304(1); Au-Br, 3.106(1); Au-Br′, 3.128(1); P1-Au-P2, 158.96-
(5); Au-Br-Au′, 88.40(5).
P3-Ag2-P4, 157.63(5)°] are about the same as in the gold
compounds. There is again some crystallographic disorder (ring
folding and CH2/O substitution) in the ligand bridges, reminis-
cent of the ligand scrambling observed for solutions of the
compound by NMR spectroscopy.
Crystals of the copper(I) complex [LCuCl]2 (triclinic, space
group P1h, Z ) 1) also contain dinuclear complex molecules,
but the ligands L are chelating rather than bridging the metal
centers (Figure 5). The two ligands are related by a crystal-
lographic center of inversion and are thus enantiomers (R, S).
The copper atoms are bridged unsymmetrically by two chloride
Pairs of ligand enantiomers L (R, S) are bridging the two
metal atoms (head-to-tail) to give 12-membered rings with the
silver atoms connected transannularly and unsymmetrically by
perchlorate anions above and below the ring. Each perchlorate
anion is chelating one of the silver atoms and bridging the two
symmetry-related silver atoms via one oxygen atom, e.g. O11
bridging Ag1 and Ag1′. The 12-membered rings are more
heavily puckered than the gold heterocycles (above), but the
angles P-Ag-P at the silver atoms [P1-Ag1-P2, 157.13(4)°;

4358 Inorganic Chemistry, Vol. 37, No. 17, 1998
Bayler et al.
with nitrogen. Chloro(dimethyl sulfide)gold(I)19 and bromo(tetrahy-
drothiophene)gold(I) [(tht)AuBr]20 were prepared according to estab-
lished literature procedures.
NMR: JEOL JNM-GX 400 and JEOL JNM-LA 400 instruments;
1
CDCl3 as solvent and internal standard, converted to TMS for H and
13C{1H}; H3PO4 (85%) as external standard for 31P{1H}; spectra were
measured at room temperature or as otherwise noted. MS: Finnigan
MAT 90 (fast atom bombardment).
R/S-(1-Diphenylphosphinobut-2-yl)diphenylphosphinite (L). A
solution of potassium diphenylphosphide (5.0 mmol) in 30 mL of THF
is cooled to -78 °C and 1,2-epoxybutane (7.5 mmol, 650 µL) is added.
Upon warming to room temperature within 3 h the color of the reaction
mixture changes from intense orange to pale yellow. Chlorodiphe-
nylphosphine (5.0 mmol, 674 µL) is then added dropwise, and the
resulting turbid solution is stirred for 2 h at ambient temperature. The
solvent is removed under reduced pressure, and the residue is extracted
with diethyl ether (2 × 20 mL). The resulting colorless solution of L
in diethyl ether is stable at -30 °C and can be used for the following
reactions without further purification; yield 1.73 g (78%).
Figure 4. Superposition of the two independent molecules of [LAu-
ClO4]2.
3
1H NMR: δ 0.80 (t, JH,H ) 7.3 Hz, 3H) CH3; 1.62-1.83 (m, 2H)
2
2
CH2-CH3; 2.27 (dd, JH,H ) 13.8 Hz, JH,P ) 7.5 Hz, 1H), 2.53 (dd,
2JH,H ) 13.8 Hz, 2JH,P ) 5.9 Hz, 1H) CH2-P; 3.89 (m, 1H) CH; 7.15-
7.70 (m, 20 H) arene H. 13C{1H} NMR: δ 9.7 (s) CH3; 30.1 (dd, 3JC,P
) 4.6 Hz, 3JC,P′ ) 7.7 Hz) CH2-CH3; 35.8 (dd, 1JC,P ) 15.3 Hz, 3JC,P′
2
2
) 5.4 Hz) CH2-P; 80.6 (dd, JC,P ) 20.0 Hz, JC,P′ ) 17.7 Hz) CH;
128.7-133.4 (m) C2/3/4/5/6; 139.1 (d, 1JC,P ) 13.8 Hz), 139.4 (d, 1JC,P
)
13.0 Hz) C1-P; 143.4 (d, 1JC,P′ ) 16.9 Hz), 143.5 (d, 1JC,P′ ) 17.7 Hz)
C1-PO. 31P{1H} NMR: δ -23.2 (d, 4JP,PO ) 7.0 Hz) Ph2P-R; 107.4
4
(d, JP,PO ) 7.0 Hz) Ph2P-OR.
L(AuCl)2. The phosphine L (93 mg, 0.21 mmol) and Me2SAuCl
(124 mg, 0.42 mmol) are dissolved in 10 mL of THF to give a colorless
solution, which is stirred for 1 h at ambient temperature. Addition of
pentane leads to precipitation of the white product, which is filtered
off, washed with pentane, and dried in a vacuum to yield 173 mg (90%).
3
1H NMR: δ 0.77 (t, JH,H ) 7.3 Hz, 3H) CH3; 1.75-1.87 (m, 2H)
2
2
3
CH2-CH3; 2.78 (ddd, JH,H ) 13.8 Hz, JH,P ) 11.0 Hz, JH,H ) 6.3
Hz, 1H), 3.17 (ddd, 2JH,H ) 13.8 Hz, 2JH,P ) 11.3 Hz, 3JH,H ) 5.5 Hz,
1H) CH2-P; 4.51 (m, 1H) CH; 7.30-7.82 (m, 20 H) arene H. 13C-
Figure 5. Molecular structure of compound [LCuCl]2 (ORTEP drawing
with 50% probability ellipsoids, H-atoms omitted for clarity). Selected
bond lengths (Å) and angles (deg): Cu-P1, 2.2455(7); Cu-P2, 2.2186-
(8); Cu-Cl, 2.3055(8); Cu-Cl′, 2.4218(7); P1-Cu-P2, 103.10(3);
Cu-Cl-Cu′, 79.54(2); Cl-Cu-Cl′, 100.46(2).
{1H} NMR: δ 9.1 (s) CH3; 29.4 (dd, JC,P ) 6.6 Hz, JC,P′ ) 4.5 Hz)
3
3
1
3
CH2-CH3; 33.8 (dd, JC,P ) 36.4 Hz, JC,P′ ) 5.4 Hz) CH2-P; 80.2
(s) CH; 128.0-128.9 (m) C1; 129.0-129.8 (m) C3/5; 131.9-133.5 (m)
C2/4/6.
31P{1H} NMR: δ 21.0 (s) Ph2P-R; 109.7 (s) Ph2P-OR.
anions [Cu-Cl, 2.3055(8) Å; Cu-Cl′, 2.4218(7) Å] with large
angles at Cu/Cu′ [100.46(2)°] and small angles at Cl/Cl′ [79.54-
(2)°]. Each copper atom is thus a spiro center for a six- and a
four-membered ring.17
L2AuCl. To a solution of L (413 mg, 0.94 mmol) in 20 mL of
THF is added Me2SAuCl (138 mg, 0.47 mmol) at room temperature,
and the resulting clear solution is stirred for 1 h. Upon addition of
pentane a pale yellow precipitate is obtained, which is filtered off and
dried in a vacuum; yield 430 mg (82%). 1H NMR: δ 0.75 (t, b, 3H)
CH3; 1.6-1.8 (m, b, 2H) CH2-CH3; 2.4 (m, b, 1H), 2.8 (m, b, 1H)
CH2-P; 3.5 (m, b, 1H) CH; 6.8-7.8 (m, 20 H) arene H. 31P{1H}
NMR: δ -5 (m, b) Ph2P-R; 113 (m, b) Ph2P-OR. MS (FAB), m/z:
1081.9 (100) [L2Au]+, 639.5 (57) [LAu]+.
[LAuCl]2. L (648 mg, 1.46 mmol) is dissolved in 20 mL of THF
and Me2SAuCl (431 mg, 1.46 mmol) is added. After stirring for 1 h
at room temperature the solution is evaporated to dryness. Recrystal-
lization of the residue from dichloromethane/pentane affords the product
as colorless crystals suitable for X-ray diffraction; yield 620 mg (63%).
31P{1H} NMR, [L2AuCl]: δ -5 (m, b) Ph2P-R; 113 (m, b) Ph2P-
OR. [L(AuCl)2]: δ 21.0 (s, b) Ph2P-R; 109.7 (s, b) Ph2P-OR. MS
(FAB), m/z: 1313.7 (28) [L2Au237Cl]+, 1311.7 (52) [L2Au235Cl]+,
1080.9 (22) [L2Au]+, 871.9 (30) [LAu237Cl]+, 869.9 (77) [LAu235Cl]+,
638.2 (100) [LAu]+.
This structure (Figure 5) reflects the preference of copper(I)
for fully tetrahedral coordination as opposed to silver(I) and in
particular to gold(I) where linear two-coordination is more
common. Because of the small covalent radius of copper(I),
the transannular Cu---Cu′ contact [3.0255(6) Å] is not expected
to contribute significantly to the bonding in the four-membered
ring, while Ag---Ag and Au---Au contacts of this order of
magnitude would have to be taken as sub-van der Waals
distances.18 However, the distances in [LAgClO4]2 and [LAuCl]2
above are well beyond this critical range.
Experimental Section
All experiments were carried out under dry, purified nitrogen.
Solvents were dried, distilled and stored over molecular sieves in a
nitrogen atmosphere. Glassware was oven-dried, evacuated, and filled
[LAuBr]2. L (110 mg, 0.25 mmol) and (tht)AuBr (91 mg, 0.25
mmol) are dissolved in 10 mL of CH2Cl2 to give a colorless solution,
which is stirred for 1 h at ambient temperature. Careful layering of
the solution with hexane induces precipitation of the product as colorless
crystals suitable for X-ray diffraction; yield 142 mg (79%). 31P{1H}
NMR (-60 °C): [LAuBr]2: δ 31.9 (d, 2JP,PO ) 346 Hz) Ph2P-R; 128.9
(17) (a) Townsend, J. M.; Blount, J. F.; Sun, R. C.; Zawoiski, S.; Valentine,
D., Jr. J. Org. Chem. 1980, 45, 2995. (b) Lobkovskii, E. B.; Antipin,
M. Yu.; Makharv, V. D.; Borisov, A. P.; Semenenko, K. N.; Struchkov,
Y. T. Koord. Khim. 1981, 7, 141. (c) Wang, H.-E.; Liu, S.-T.; Lee,
G.-H.; Cheng, M.-C.; Peng, S.-M. J. Chin. Chem. Soc. (Taipei) 1991,
38, 565. (d) Baker, R. T.; Calabrese, J. C.; Westcott, S. A. J.
Organomet. Chem. 1995, 498, 109.
(19) Dash, K. C.; Schmidbaur, H. Chem. Ber. 1973, 106, 1221.
(20) Ahrland, S.; Dreisch, K.; Nore´n, B.; Oskarsson, A. Mater. Chem. Phys.
1993, 35, 281.
(18) Schmidbaur, H. Chem. Soc. ReV. 1995, 24, 391.

Four-Coordinate Au(I), Ag(I), and Cu(I) Complexes
Inorganic Chemistry, Vol. 37, No. 17, 1998 4359
2
1
1
109
107
(d, JP,PO ) 346 Hz) Ph2P-OR. 32.0 (s) Ph2P-R; 126.5 (s) Ph2P-
) 168 Hz, J Ag,P ) 490 Hz, J Ag,P ) 563 Hz) Ph2P-R; 115.8 (2dd,
2 1 1
107 109
OR. [L(AuBr)2]: δ 23.3 (s) Ph2P-R; 112.2 (s) Ph2P-OR. [L2AuBr]
data are very similiar to those of [L2AuCl]. MS (FAB), m/z: 1358.3
(27) [L2Au2Br]+, 1080.3 (26) [L2Au]+, 916.4 (31) [LAu281Br]+, 914.4
(31) [LAu279Br]+, 638.6 (48) [LAu]+. Anal. Calcd for C56H56P4O2-
Au2Br2 (1438.77): C, 46.75; H, 3.92; Au, 27.4. Found: C, 46.46; H,
3.89; Au, 28.1.
[LAuI]2. A 10 mL amount of an aqueous solution of KI (1.0 g,
excess) is added to a solution of [LAuCl]2 (135 mg, 0.2 mmol) in 10
mL of CH2Cl2. The resulting two-phase system is stirred vigorously
for 5 h. The aqueous layer is separated and washed with 10 mL of
CH2Cl2. The dichloromethane extracts are combined and dried with
MgSO4, and the solvent is evaporated in a vacuum to leave a white
crystalline product. Crystals obtained from dichloromethane/pentane
were not suitable for X-ray diffraction; yield 254 mg (83%). 31P{1H}
NMR, [LAuI]2: δ 29.2 (d, JP,PO ) 338 Hz) Ph2P-R; 126.5 (d, JP,PO
) 338 Hz) Ph2P-OR. 28.5 (s) Ph2P-R; 111.4 (s) Ph2P-OR.
[L(AuI)2]: δ 24.9 (s) Ph2P-R; 113.9 (s) Ph2P-OR. MS (FAB), m/z:
1404.3 (3) [L2Au2I]+, 1080.3 (2) [L2Au]+, 962.2 (5) [LAu2I]+, 638.6
(4) [LAu]+. Anal. Calcd for C56H56P4O2Au2I2 (1532.77): C, 43.88;
H, 3.68; Au, 25.7. Found: C, 43.64; H, 3.53; Au, 26.3.
JP,PO ) 168 Hz, J
) 543 Hz, J
) 622 Hz) Ph2P-OR.
Ag,PO
Ag,PO
1
1
109
107
5.4 (2d, J
) 512 Hz, J
) 587 Hz) Ph2P-R; 116.0 (2d,
Ag,P
Ag,P
1
1
109
107
J
) 547 Hz, J
) 628 Hz) Ph2P-OR. MS (FAB), m/z:
Ag,PO
Ag,PO
1197.6 (16) [L2Ag2ClO4]+, 993.0 (9) [L2109Ag]+, 991.0 (10) [L2107Ag]+,
550.3 (95) [L109Ag]+, 548.3 (100) [L107Ag]. Anal. Calcd for
C56H56P4O10Cl2Ag2 (1299.60): C, 51.76; H, 4.34; Ag, 16.6. Found:
C, 51 65; H, 4.09; Ag, 16.4.
[LCuCl]2. CuCl (43 mg, 0.43 mmol) is added to a solution of L
(183 mg, 0.43 mmol) in 20 mL of dichloromethane/acetonitrile (1:1)
and the resulting suspension is stirred for 22 h at room temperature.
The turbid solution is filtered and the volatiles are removed from the
filtrate in a vacuum. Recrystallization of the residue from dichlo-
romethane/diethyl ether affords the product as colorless crystals suitable
for X-ray diffraction; yield 151 mg (65%). 31P{1H} NMR: δ -23.0
(d, b, 2JP,P ) 153 Hz) Ph2P-R; 92.0 (d, b, 2JP,P ) 153 Hz) Ph2P-OR.
MS (FAB), m/z: 1047.7 (6) [L2Cu2Cl]+, 947.7 (31) [L2Cu]+, 605.2
(42) [LCu2Cl]+, 540.2 (34) [LCuCl]+, 505.3 (100) [LCu]+. Anal. Calcd
for C56H56P4O2Cu2Cl2 (1082.96): C, 62.11; H, 5.21. Found: C, 61.45;
H, 5.50.
2
2
Crystal Structure Determinations. Specimens of suitable quality
and size were mounted in glass capillaries and used for measurements
of precise cell constants and intensity data collection on an Enraf Nonius
CAD4 diffractometer (Mo KR radiation, λ(Mo KR) ) 0.710 73 Å).
During data collection, three standard reflections were measured
periodically as a general check of crystal and instrument stability. No
significant changes were observed. Lp correction was applied. The
structures were solved by Patterson and direct methods ([LCuCl]2),
respectively (SHELXS-86), and completed by full-matrix least-squares
techniques against F2 (SHELXL-93). The thermal motion of all non-
hydrogen atoms was treated anisotropically, except for those of the
CH3CH2 unit of [LCuCl]2, which was disordered and refined isotro-
pically in split positions (50:50). Due to very large thermal parameters
of the solvent CH2Cl2 in the lattice of [LAgClO4]2, its occupancy was
lowered to 50%. All structures suffered from a disorder in the bridging
atoms, were the assignment of CH2 and O was not entirely conclusive.
Attempts to resolve this disorder were not successful. All hydrogen
atoms were placed in idealized calculated positions and allowed to ride
on their corresponding carbon atoms with fixed isotropic contributions
(Uiso(fix) ) 1.5Ueq of the attached C atom). 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.
[LAuSCN]2. The procedure given above for [LAuI]2 was followed,
using 1.0 g of KSCN and 135 mg (0.2 mmol) of [LAuCl]2. The product
is obtained as a yellow crystalline solid; yield 240 mg (86%). 31P{1H}
NMR, [L2AuSCN]: data similar to [L2AuCl]. [L(AuSCN)2]: δ 27.6
(s, b) Ph2P-R; 117.4 (s, b) Ph2P-OR. MS (FAB), m/z: 1337.4 (40)
[L2Au2SCN]+, 1081.9 (52) [L2Au]+, 894.5 (74) [LAu2SCN]+, 639.4
(100) [LAu]+. Anal. Calcd for C56H56P4O2Au2S2N2 (1395.13): C,
49.93; H, 4.05; S, 4.6; N, 2.01. Found: C, 48.26; H, 4.16; S, 5.2; N,
2.05.
[LAgCl]2. AgCl (67 mg, 0.47 mmol) is suspended in a solution of
L (207 mg, 0.47 mmol) in 15 mL of CH2Cl2, and the mixture is stirred
for 18 h with protection against incandescent light at room temperature.
The resulting clear solution is concentrated under vacuum and layered
with pentane to precipitate the product as colorless crystals, which are
filtered off, washed with pentane, and dried in a vacuum; yield 195
mg (71%). 31P{1H} NMR: δ -3 (b) Ph2P-R; 114 (b) Ph2P-OR. MS
(FAB), m/z: 1423.7 (4) [L2Ag4Cl3]+, 1279.6 (7) [L2Ag3Cl2]+, 1135.6
(4) [L2Ag2Cl]+, 993.7 (27) [L2109Ag]+, 991.7 (25) [L2107Ag]+, 693.1
(50) [LAg2Cl]+, 551.1 (92) [L109Ag]+, 549.1 (100) [L107Ag]+. Anal.
Calcd for C56H56P4O2Ag2Cl2 (1171.60): C, 57.41; H, 4.82; Ag, 18.41.
Found: C, 57.07; H, 4.81; Ag, 17.7.
[LAgBr]2. The procedure given above was followed using 66 mg
(0.35 mmol) of AgBr and 149 mg (0.35 mmol) of L; yield 150 mg
(68%). 31P{1H} NMR: δ -5 (b) Ph2P-R; 112 (b) Ph2P-OR. MS
(FAB), m/z: 1369.7 (3) [L2Ag3Br2]+, 1181.7 (8) [L2Ag2Br]+, 993.7
(16) [L2109Ag]+, 991.7 (16) [L2107Ag]+, 737.2 (60) [LAg2Br]+, 551.2
(91) [L109Ag]+, 549.1 (100) [L107Ag]+. Anal. Calcd for C56H56P4O2-
Ag2Br2 (1260.50): C, 53.36; H, 4.48. Found: C, 52.61; H, 4.46.
[LAgClO4]2. A solution of AgClO4 (106 mg, 0.51 mmol) in 5 mL
of THF and a solution of L (227 mg, 0.51 mmol) in 10 mL of THF are
mixed and stirred for 1 h at ambient temperature. After a few minutes,
precipitation of a pale yellow product begins, which is completed by
the addition of 20 mL of hexane. The product is filtered off, washed
with hexane, and dried in a vacuum. Colorless crystals suitable for
X-ray diffraction were obtained by layering a dichloromethane solution
with pentane; yield 203 mg (61%). 31P{1H} NMR: δ 3.4 (2dd, 2JP,PO
Acknowledgment. This work was supported by the Deutsche
Forschungsgemeinschaft, the Fonds der Chemischen Industrie,
andsthrough the donation of chemicalssby Degussa AG and
Heraeus GmbH. The authors thank Mr. J. Riede for establishing
the X-ray data sets.
Supporting Information Available: Tables of data collection and
refinement parameters, atomic coordinates, and thermal parameters
including hydrogens, complete bond distances and angles, and aniso-
tropic displacement parameters (20 pages). Ordering information is
given on any current masthead page.
IC980385A