Structural and spectroscopic characterisation of linearly coordinated gold(I) tribenzylphosphane complexes

Article abstract of DOI:10.1002/ejic.200901209

The 1:1 tribenzylphosphane (PBn₃) complexes of gold(I)[(Bn ₃P)AuX] (X = Cl and Br) have been synthesised, and their structures were determined by single-crystal X-ray crystallography. The compounds are isomorphous, neutral molecules with linearly coordinated P-Au-X arrays. Each structure contains three independent [(Bn₃P)AuX] entities lying on the three threefold axes of space group P3c1. The mean bond lengths are Au-Cl 2.302(8), Au-P 2.227(11) A for the chloride and Au-Br 2.404(10), Au-P 2.229(4) A for the bromide. These contrast with the 1:1 adducts previously reported for copper(I), which take the form [Cu(PBn₃] ₂][CuX₂]. The 1:2 AuX.:PBn₃ compounds that have been synthesised are formulated as [Au(PBn₃)₂] X·nH₂O (X = Cl, n = 1 or 2; X = I and BF₄, n = O). Single-crystal X-ray structures show that linearly two-coordinate centrosymmetric [Au(PBn₃)₂]⁺ arrays are found in [Au(PBn₃)₂]Cl·H₂O and [Au(PBn ₃)₂]BF₄ with Au-P bond lengths of 2.2988(7) and 2.3016(7) A for the chloride and 2.2975(7) A for the tetrafluoroborate. v(AuX) bands in the far-IR spectra of [(Bn₃P)AuX] are assigned at: 320 and 227 cm^-1 for X = Cl and X = Br, respectively. The ³¹P CP MAS NMR spectra of [(Bn₃P)AuX] (X = Cl, Br) and [Au(PBn ₃)₂]X (X = Cl·H₂O, C1·2H ₂O,1, BF₄) are reported, and the observation of ₂J(PP) coupling in the spectrum of [Au(PBn₃) ₂]Cl· 2H₂O is consistent: with the presence in this complex of noncentrosymmetric cations in which the two phosphorus atoms are inequivalent.

Full text of DOI:10.1002/ejic.200901209

FULL PAPER
DOI: 10.1002/ejic.200901209
Structural and Spectroscopic Characterisation of Linearly Coordinated Gold(I)
Tribenzylphosphane Complexes
Eric W. Ainscough,*[a] Graham A. Bowmaker,*[b] Andrew M. Brodie,*[a]
Graham H. Freeman,[a] John V. Hanna,[c] Peter C. Healy,[d] Ward T. Robinson,[e]
Brian W. Skelton,[f] Mark E. Smith,[c] Alexandre N. Sobolev,[f] and Allan H. White[f]
Keywords: Gold / Phosphane ligands
The 1:1 tribenzylphosphane (PBn3) complexes of gold(I)-
[(Bn3P)AuX] (X = Cl and Br) have been synthesised, and their
structures were determined by single-crystal X-ray crystal-
lography. The compounds are isomorphous, neutral mole-
cules with linearly coordinated P–Au–X arrays. Each struc-
ture contains three independent [(Bn3P)AuX] entities lying
on the three threefold axes of space group P3c1. The mean
bond lengths are Au–Cl 2.302(8), Au–P 2.227(11) Å for the
chloride and Au–Br 2.404(10), Au–P 2.229(4) Å for the bro-
mide. These contrast with the 1:1 adducts previously re-
ported for copper(I), which take the form [Cu(PBn3)2][CuX2].
The 1:2 AuX:PBn3 compounds that have been synthesised
are formulated as [Au(PBn3)2]X·nH2O (X = Cl, n = 1 or 2; X
= I and BF4, n = 0). Single-crystal X-ray structures show that
linearly two-coordinate centrosymmetric [Au(PBn3)2]+ arrays
are found in [Au(PBn3)2]Cl·H2O and [Au(PBn3)2]BF4 with
Au–P bond lengths of 2.2988(7) and 2.3016(7) Å for the chlo-
ride and 2.2975(7) Å for the tetrafluoroborate. ν(AuX) bands
in the far-IR spectra of [(Bn3P)AuX] are assigned at 320 and
227 cm–1 for X = Cl and X = Br, respectively. The 31P CP MAS
NMR spectra of [(Bn3P)AuX] (X = Cl, Br) and [Au(PBn3)2]X
(X = Cl·H2O, Cl·2H2O, I, BF4) are reported, and the observa-
tion of 2J(PP) coupling in the spectrum of [Au(PBn3)2]Cl·
2H2O is consistent with the presence in this complex of
noncentrosymmetric cations in which the two phosphorus
atoms are inequivalent.
PCy3, 170, 9.7, PtBu3, 182, 11.40) shows that the introduc-
tion of the phenyl ring results in a steric bulk comparable
with secondary alkyl groups such as tricyclohexyl, but di-
minished basicity. Thus PBn3 may be considered to be a
bulky, relatively basic, alkylphosphane in which the pres-
ence of conformationally flexible phenyl groups would be
expected to influence the coordination chemistry. This has
been observed for complexes of both copper(I) and mer-
cury(II). With 1:1 adducts of copper(I) chloride and bro-
mide ligand disproportionation occurs, so that ionic com-
pounds of the form [Cu(PBn3)2][CuX2] are obtained in the
solid state with linear [Cu(PBn3)2]+ cations.[2,3] This con-
trasts with the situation for the corresponding adducts of
copper(I) and silver(I) halides with other tertiary phos-
phanes, which usually yield neutral [(R3P)CuX]n complexes
which are either tetrameric, dimeric or [(R3P)CuX] mono-
mers depending on the steric bulk of the PR3 ligands.[4]
Similarly, with mercury(II) [Hg(PBn3)2](BF4)2 contains
[Hg(PR3)2]2+ cations with linear P–Hg–P coordination, the
first example of a truly two-coordinate [Hg(PR3)2]2+ com-
plex.[5] The driving force for the formation of ionic adducts
with PBn3 has been ascribed to interligand “embraces”
within the linear two-coordinate cation,[2,3] such an em-
brace presumably preventing secondary coordination of the
Introduction
By comparison with triphenylphosphane (PPh3), less is
known about the coordination chemistry of tribenzylphos-
phane (PBn3). The insertion of methylene spacers between
the phosphorus atom and the phenyl rings in PBn3 alters
its physical properties in that it becomes a more bulky li-
gand than PPh3 with a Tolman cone angle of 165° com-
pared to 145° for PPh3, and it is also more basic, the pKa’s
of the conjugate acids being 2.7 and 6.0 (estimate), respec-
tively.[1] Further comparison of these properties with those
of alkylphosphanes (PEt3, cone angle, 137°, pKa, 8.69;
[a] Chemistry-Institute of Fundamental Sciences, Massey Univer-
sity,
Palmerston North 4442, New Zealand
Fax: +64-6-3505682
E-mail: e.ainscough@massey.ac.nz
a.brodie@massey.ac.nz
[b] Chemistry Department, University of Auckland,
Auckland 1142, New Zealand
Fax: +64-9-3737422
E-mail: g.bowmaker@auckland.ac.nz
[c] Department of Physics, University of Warwick,
Coventry CV4 7AL, UK
[d] School of Science, Griffith University,
Nathan 4311, Queensland, Australia
[e] Chemistry Department, University of Canterbury,
Christchurch 8140, New Zealand
[f] Chemistry M313, School of Biomedical, Biomolecular and
Chemical Sciences, University of Western Australia,
Crawley 6009, Western Australia, Australia
–
mercury to the BF4 counterions. Recently, the structure of
the complex [Au(PAd2Bn)2][AuCl2] (Ad = 1-adamantyl) has
been reported as the first example of an ionic form of a
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Linearly Coordinated Gold(I) Tribenzylphosphane Complexes
1:1 chlorophosphanegold(I) complex.[6] However, no single-
crystal X-ray structures have been reported for Au(I) com-
plexes of Bn3P itself.
A cursory study on the tribenzylphosphane complex,
[(Bn3P)AuCl] has been reported[7a] as well as the conversion
of [(Bn3P)AuX] (X = Cl, Br, I), upon reaction with AgBF4,
to cationic binuclear gold(I) complexes with formula
– [7b]
[{(Bn3P)Au}2X]+BF4 . The complex[(Bn3P)AuCl] (along
with similar compounds) has been evaluated for in vitro
cytotoxic potency against (e.g. B16 mouse melanoma cells)
and was found more cytotoxic than the triphenylphosphane
analogue due to its increased lipophilicity.[7c] In this con-
text, we extend our work with PBn3 to further study the
nature of the complexes formed by this ligand with some
gold(I) salts. The present report describes the synthesis and
structural characterisation of 1:1 AuX:PBn3 (X = Cl or Br)
as monomeric complexes [(Bn3P)AuX] and the syntheses of
1:2 complexes for X = Cl, I or BF4, all of which are ionic
[Au(PBn3)2]X and contain the linear coordinated [Au-
(PBn3)2]+ cation with a noncoordinated anion, character-
ised crystallographically for its X = Cl(·H2O), BF4 salts.
The far-IR and 31P CP MAS NMR spectra of all of these
new complexes are reported and discussed in relation to
their structure and bonding.
Results and Discussion
Synthesis
The reaction of [Bu4N][AuX2] (X = Cl, Br) with PBn3 in
a 1:1 molar ratio in warm N,NЈ-dimethylformamide yielded
the 1:1 complexes [(Bn3P)AuX], whereas for X = I, gold
metal was deposited with formation of the ligand oxide.
The 1:1 complex is not thus far accessible for the iodo spe-
cies and in this respect it parallels the chemistry of CuI with
PBn3.[3] When the molar ratio was 1:2 in thf [Au(PBn3)2]Cl·
2H2O was isolated which, interestingly, converted into the
monohydrate [Au(PBn3)2]Cl·H2O upon crystallisation from
dmf. In a similar way, [Au(PBn3)2]I was obtained from thf
and [Au(PBn3)2]BF4 from [Au(NCCH3)2]BF4 in acetoni-
trile. All the new compounds are moderately soluble in
common solvents such as dichloromethane and acetonitrile.
Crystal Structures
The results of the single-crystal X-ray structure determi-
nations on the AuX:PBn3 (1:1) (X = Cl or Br) adducts are
consistent with their formulation as neutral mononuclear
[(Bn3P)AuX] species. The two structures are isomorphous.
Although one molecule comprises the asymmetric unit of
the structure [Figure 1, (a)], it is made up of three indepen-
dent components, disposed with their linear PAuX arrays
on the three distinct crystallographic 3-axes of space group
P3c1. Bond lengths, along with those of related com-
pounds, are presented in Table 1.
Figure 1. (a) Molecule 1 of [(Bn3P)AuCl] (the other two molecules
and those of the isomorphous bromide analogue are similar); (b)
Cation 1 of [Au(PBn3)2]Cl·H2O (the other cation and that of the
BF4 salt are similar); (c) Unit cell contents of [Au(PBn3)2]Cl·H2O,
projected down the a axis.
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E. W. Ainscough, G. A. Bowmaker, A. M. Brodie et al.
FULL PAPER
Table 1. Au–P and Au–X bond lengths [Å] for [(R3P)AuX] (X = abundant cohorts, there is little point in attempting im-
Cl, Br or I; R = alkyl or aryl substituent) complexes.
provement by further augmentation with consequent exam-
ples. The manner in which the values adopted below origi-
nate is summarised in the associated references/footnotes,
for M,X = Cu,Cl;[9] Cu,Br;[10] Cu,I;[11] Ag,Cl;[12] Ag,Br;[13]
Ag,I;[14] Au,Cl;[15] Au,Br;[16] Au,I.[17] From these, we take as
baseline M–X bond length estimates (Å) in [XMX]– as:
Au–P
Au–X
PR3
X = Cl X = Br X = I X = Cl
X = Br X = I
[a]
PMe3
2.233(3) 2.242(7) 2.256(3) 2.306(4)
2.419(3) 2.583(1)
2.415(3)
2.415(3)
2.234(4) 2.235(5)
2.233(3) 2.228(6)
2.232(9)
2.310(4)
2.310(4)
2.305(8)
2.306(8)
2.309(3)
2.305(3)
2.293(3)
[b]
PEt3
Cu: Cl 2.09, Br 2.22, I 2.39
2.231(8)
[c]
PBn3
2.226(3) 2.232(3)
2.216(3) 2.229(3)
2.239(3) 2.225(3)
2.242(4) 2.247(2) 2.263(3) 2.279(5)
2.265(4)
2.239(2)
2.253(6)
2.235(3) 2.252(6) 2.254(5) 2.279(3)
2.240(4) 2.254(5) 2.265(4) 2.290(4)
2.236(4) 2.243(5) 2.261(4) 2.270(4)
2.410(1)
2.410(1)
2.393(2)
2.395(1) 2.551(1)
2.555(1)
Ag: Cl 2.33, Br 2.44, I 2.92 (?) (see ref.[14]
Au: Cl 2.27, Br 2.36, I 2.54
)
[d]
[e]
PCy3
noting the implication of a larger atomic radius for silver(I)
than gold(I) as described previously.[18] With an initial focus
on gold(I) as the metal atom in complexes of the form
[M(PR3)2]X and [(R3P)MX], an array of established struc-
PiPr3
PtBu3
PPh3
Potol3
2.284(3)
2.284(6)
[f]
[g]
2.407(2) 2.556(2)
2.411(2) 2.556(1)
[h]
2.388(2) 2.538(2) tural data is presented in Table 1 and 2, respectively; a da-
tum value for the Au–P distance in [Au(PPh3)2]+ is taken as
2.243(2)
2.281(3)
[i]
Pmes3
2.263(2) 2.279(3) 2.292(3) 2.272(2)
2.260(2) 2.288(4)
2.255(2)
2.393(2) 2.544(1)
2.31 Å.[19]
2.391(2)
2.272(3)
2.294(2)
[j]
Ptmpp3
Table 2. Bond lengths [Å] and angles [°] for [M(PR3)2]X (M = Cu,
Ag or Au) complexes.
[a] Ref.[39a–39c] [b] Ref.[39d] [c] Ref.[39e] [d] Ref.[39f,39g] [e] Ref.[39a] [f]
Ref.[39h] [g] Ref.[39i,39j] [h] Ref.[39k,39l] [i] Ref.[39m,39n] [j] Ref.[39o]
PR3
X
M–P
P–M–P
The structure of AuCl:PBn3 (1:2) is found to be ionic
and a monohydrate, comprised of [Au(PBn3)2]+ cations
[Figure 1, (b)] and chloride counterions. Again one formula
unit comprises the asymmetric unit of the structure, and
again this is made up of component fragments disposed
about crystallographic symmetry elements – in this case, a
pair of gold atoms lying on inversion centres, so that the
gold atom coordination environments are obligate linear
[Au–P are 2.3016(7) and 2.2988(7) Å]. The water molecule
and chloride ion, close to an inversion centre, form, with
their images, a centrosymmetric dimer [Cl···ClЈ 5.217(1);
O···OЈ 3.744(4); O···Cl, ClЈ 3.216(4), 3.206(3) Å] [Figure 1,
(c)]. The tetrafluoroborate is similarly ionic with one half
of the [Au(PBn3)2]BF4 formula unit comprising the asym-
metric unit of the structure. The gold atom again lies on a
crystallographic inversion centre with an obligate linear P–
Au–P coordination environment [Au–P 2.2975(7) Å]. The
anion is disposed with the boron atom lying on a crystallo-
graphic 2-axis (space group C2/c), the fluorine atoms being
disordered over sites of occupancy 0.5.
For the purposes of comparison with potentially (linear)
two-coordinate LML arrays, containing M–X (X = halide)
and/or M–P bonds, it is useful to consider baseline dis-
tances for such species. For X = halide, X–M–X geometries,
especially the M–X distance(s), vary greatly in the abun-
dance with which they have been established, some such
species having an innate tendency to oligomerise, so that
for some there is a plethora, while others are accessible only
within unusual crystal lattice forms. Even for the former,
there is considerable divergence consequent on individual
lattice circumstances (see, in particular, outliers for Ag/Cl,
M = Cu
PBn3[a]
PBn3[b]
PBn3[c]
tmsp[d]
PF6
2.191(1)
2.205(3)
2.1955(14)
2.242(2)
180
180
180
[CuCl2]
[CuBr2]
BF4
M = Ag
PMe3[e]
[Au(C2Ph)2]
[Au(C2Ph)3]
2.368(5), 2.419(5)
2.392(3)
2.383(1)
2.461(6)
2.4409(9)
175.8(2)
177.1(1)
P(CH2CH2CN)3[f] NO3
tmsp[g]
tmsp[d]
tmpp[h]
tmpp[i]
PF6
BF4
179.80(6)
175.9(9), 179(1)
177.9(2)
178.5(2)
177.38(7)
[Ag5I7](ϱ|ϱ)
[Ag5I7(py)2]
[Ag5I6(quin)](ϱ|ϱ)
[(py)Ag(CN)2]
BF4
2.36(2)–2.40(2)
2.409(4), 2414(4)
2.411(6), 2.426(6)
2.417(2)
tmpp[j]
[PPh3][k]
2.4177(12), 2.4219(13) 156.65(4)[k]
M = Au
PMe3[l]
PBu3[m]
PCy3[n]
PCy3[n]
PAd2Bn[o]
PBn3[p]
Cl
BPh4
Cl
Br
[AuCl2]
Cl
2.304(1) (ϫ2)
2.310(3), 2.305(4)
2.318(1) (ϫ2)
175.4(1)
176.1(1)
180
178.4(1)
180
180
180
180
180
2.328(3), 2.305(3)
2.3348(9) (ϫ 2)
2.2988(7) (ϫ 2)
2.3016(7) (ϫ 2)
2.2975(8) (ϫ 2)
2.323(1), 2.321(1)
2.314(2), 2.309(2)
2.3525(10)
PBn3[p]
PtBu3[q]
PPh3[r]
tmsp[d]
BF4
Cl
PF6
BF4
177.4(1)
179.72(7)
[a] Ref.[40a] [b] Ref.[40b] [c] Ref.[40c] [d] Ref.[40d] [e] Ref.[40e] [f] Ref.[40f]
[g] Ref.[40g] [h] Ref.[40h] [i] Ref.[40i] [j] Ref.[40j] [k] Ref.[40k] [l] Ref.[40l]
[m] Ref.[40m] [n] Ref.[40n] [o] Ref.[40o] [p] Ref.[40p] [q] Ref.[40q] [r]
Ref.[40r]
Based on the above, the following trends in the bond
I), and there is some futility in attempting to define values lengths in [(Bn3P)AuX] are apparent:
to any precision better than 0.01 Å. For copper(I) and sil-
(1) Au–X are longer than the corresponding average val-
ver(I) the review of ref.[8] offers a compilation of structural ues in [AuX2]–, the phosphane ligand being a stronger σ-
data extant to that point, and, in the cases of the more donor than the halide ligand.[20] This holds for all of the
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Linearly Coordinated Gold(I) Tribenzylphosphane Complexes
results in Table 3, except that for [(tmpp)CuBr] [tmpp = the pair of ligands in the neutral complex. However, the
tris(2,4,6-trimethoxyphenyl)phosphane (2.177(1) Ͻ 2.22 Å); structural definition of species such as [(Bn3P)2Cu{(btz)-
see below].
BH2(btz)}] (btz = benzotriazolyl),[22] in which the smallest
of the coinage metal(I) species is found to lie in a trigonal
planar environment, with Cu–P only slightly increased over
the [Cu(PBn3)2]+ value [Cu–P 2.2380(5), 2.2463(6) Å, P–
Cu–P 139.23(2)°; Cu–N 2.021(2), N–Cu–P 112.56(5),
108.09(5)° [ΣCu 359.9°] is indicative of considerable flexibil-
ity in the situation.
Table 3. M–P and M–X bond lengths [Å] in [(R3P)MX] (M = Cu,
Au or Ag; X = Cl, Br or I).
PR3
Cu–P
Cu–Cl
Au–P
Au–Cl
Ag–P
Ag–Cl
tmsp
2.27
2.28[a,b]
2.30[d,e]
tmpp 2.177(1) 2.118(2)[c] 2.25
2.379(1) 2.342(1)[f]
PBn3
PPh3
2.23(1)
2.302(8)[g]
2.2280(10) 2.2882(10)[h]
Cu–P
Cu–Br
Au–P
Au–Br
Ag–P
Ag–Br
IR Spectra
tmsp 2.193(2) 2.225(1)[i] 2.28
2.39[c]
The mid-IR spectra mainly contain bands due to the co-
ordinated PBn3 ligand, and they are very similar for all of
the complexes. However, the spectra of the mono- and di-
hydrates of [Au(PBn3)2]Cl show some differences that con-
firm that these are distinct compounds. The spectra of these
compounds in the 4000–2500 cm–1 region, where the ν(OH)
and ν(CH) bands occur, are shown in Figure 2. While the
ν(CH) bands (3100–2800 cm–1) for the two complexes are
almost identical, the ν(OH) bands (3500–3200 cm–1) show
differences that are consistent with the different number of
water molecules present. The bands in the monohydrate
[Au(PBn3)2]Cl·H2O [Figure 2, (a)] are better resolved and
occur at higher wavenumber than those in the dihydrate
[Au(PBn3)2]Cl·2H2O [Figure 2, (b)]. These differences, sug-
gest a lesser degree of hydrogen bonding between the water
molecules in the monohydrate, in consequence of the
greater degree of separation of the water molecules in this
complex. The greater overall intensity of the ν(OH) bands
in the dihydrate is consistent with the greater number of
water molecules in this compound.
tmpp 2.197(3) 2.177(1)[c] 2.255(4)
2.413(2)[d]
2.404(10)[g]
2.4059(4)[h]
2.374(2) 2.448(1)[f]
PBn3
PPh3
2.229(4)
2.2366(8)
Cu–P
Cu–I
Au–P
Au–I
Ag–P
Ag–I
tmsp
2.292(3)
2.544(1)[b]
2.586(2)[d]
tmpp 2.188(4) 2.417(2)[j] 2.239(7)
PBn3
PPh3
2.2533(5)
2.5633(2)[h]
[a] Ref.[41a] [b] Ref.[41b] [c] Ref.[41c] [d] Ref.[41d] [e] Ref.[41e] [f] Ref.[41f]
[g] Ref.[41g] [h] Ref.[41h] [i] Ref.[41i] [j] Ref.[41j]
(2) Au–P are shorter than in [Au(PBn3)2]+. The reason
for this is the same as in (1). The corresponding relationship
is true for all cases in Table 1.
(3) Au–P increases from X = Cl to Br (to I). This is sensi-
ble because AuBr is expected to be a weaker σ-acceptor
than AuCl (etc.). This is true for all of the cases in Table 3
(except those for the adducts of tmpp: [(tmpp)CuX] [X =
Br, I; [2.188(4) Ͻ 2.197(3) Å]] and [(tmpp)AgX] [X = Cl,
Br; [2.374(2) Ͻ 2.379(1) Å]] – see below).
For those unidentate phosphane ligands, PR3, which
form 1:1 MX:PR3 adducts across all of M = Cu, Ag or Au
and X = Cl, Br or I, namely, tmpp, and trimesitylphos-
phane, (tmsp), M–P distances in the [M(PR3)2]+ cations
have been established for Cu, Au, Ag to the extent pre-
sented in the summary in Table 2.
These comparisons highlight the exceptional nature of
the tmpp complexes, which is probably due to the fact that
the methoxy oxygen atoms are involved to a small extent in
coordination to the metal, particularly in the Cu and Ag
cases. This, in turn, highlights a significant difference be-
tween the tmpp and PBn3 ligands, both of which have been
used to stabilise two-coordinate coinage metal complexes.
In the case of PBn3 this stabilisation is achieved by interac-
tion of the R groups of the two ligands with each other,
whereas in the case of tmpp it is through interaction of the
R groups with the metal ion.
Figure 2. IR spectra of (a) [Au(PBn3)2]Cl·H2O; (b) [Au(PBn3)2]-
Cl·2H2O in the 4000–2500 cm–1 region. The bands assigned to
ν(OH) modes are labelled with their wavenumbers.
While isolation of the 1:2 AuBF4:PBn3 adduct in its ionic
form is not surprising, the occurrence of the chloride in
that form rather, than, e.g. mononuclear [(Bn3P)2AuCl], is
unusual, given the precedents for [(Ph3P)2AuX] (X = Cl,
The far-IR spectra of [(Bn3P)AuX] (X = Cl, Br) are
Br, I)[21] and supports previous speculation concerning the shown in Figure 3. The ν(AuX) bands occur at 320 and
bestowal of some stability via the embracing concept arising 227 cm–1, respectively. These assignments are based on the
from the coordination of a pair of PBn3 ligands, even if strong halogen dependence of the frequencies and on as-
insufficient to result in ligand disproportionation of the 1:1 signments for analogous [LAuX] complexes with aliphatic
array; it may also be consequent on interference between or aromatic phosphane ligands L.[23–26] In the case of the
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E. W. Ainscough, G. A. Bowmaker, A. M. Brodie et al.
FULL PAPER
–
chloride complex the ν(AuCl) band overlaps with a ligand which is probably due to the ν4(T2) mode of BF4 . Most of
band at about 315 cm–1, but the relatively high intensity of the [Au(PBn3)2]+ bands in this region are due to the coordi-
the ν(AuCl) peak allows unambiguous assignment of this nated PBn3 ligand, but a ν(AuP) band might also occur in
band. The ν(AuX) wavenumbers are compared with those the region below 200 cm–1.[26] Weak bands at about
for a number of [(R3P)AuX] complexes in Table 4. The val- 180 cm–1 in the spectra of both [(Bn3P)AuX] (Figure 3) and
ues for [(Bn3P)AuX] lie between those for the correspond- [Au(PBn3)2]X (Figure 4) are in the right region to be so
ing PMe3 and PPh3 complexes. This type of complex pro- assigned, but the multiplicity of such bands in the case of
vides an opportunity to observe the trans-influence of the the [Au(PBn3)2]X complexes suggests that there is at least
ligand L on the ν(AuX) vibrational frequency, without some contribution from vibrations of the coordinated PBn3.
complications arising from the presence of other ligands in
the metal atom coordination sphere,[26] and the order PMe3
Ͼ PBn3 Ͼ PPh3 of trans-influence as reflected in the data
in Table 2 seems reasonable in relation to the expected
change in the inductive effect of the organic substituents in
the phosphane ligands and the effect of this on the σ-donor
basicity of the ligands. Although complicated by overlap
with the ligand band at 315 cm–1, the ν(AuCl) band in
[(Bn3P)AuCl] shows evidence of incompletely resolved split-
ting above 320 cm–1, which is probably due to the presence
of multiple inequivalent molecules in the crystal structure
(see above).
Figure 4. Far-IR spectra of [Au(PBn3)2]X, (a) X = Cl·2H2O; (b) X
= I, (c) X = BF4.
NMR Spectra
The 31P CP MAS spectra of [(Bn3P)AuX] (X = Cl, Br)
at 11.7 T are shown in Figure 5. The signals in both show
Figure 3. Far-IR spectra of [(Bn3P)AuX]; (a) X = Cl; (b) X = Br.
partially resolved splittings that are most likely due to the
presence of multiple inequivalent molecules in the crystal
structure (see above). The mean chemical shifts of the mul-
tiplets are 41 and 42 ppm, respectively. The increase in
chemical shift from the chloride to the bromide is consistent
Table 4. Wavenumbers [cm–1] of the ν(AuX) modes in some
[(R3P)AuX] complexes.
Complex
ν(AuCl)
ν(AuBr)
with, but rather lower than, those previously reported for
the corresponding PPh3 and PMe3 compounds.[23,27]
[(Bn3P)AuX][a]
[(Me3P)AuX][b]
[(Ph3P)AuX][c]
[(tmpp)AuX][d]
320
312
329
313
227
214
234
218
The 31P CP MAS spectra of [Au(PBn3)2]X (X = Cl·H2O,
Cl·2H2O, I, BF4) at 11.7 T are shown in Figure 6. The spec-
trum of the chloride monohydrate shows two well-resolved
signals, consistent with the presence of two distinct cations
in the asymmetric unit (see Crystal Structures above). The
[a] This work. [b] Ref.[23] [c] Ref.[25] [d] Ref.[24]
The far-IR spectra of [Au(PBn3)2]X, (X = Cl·2H2O, I, spectrum of the chloride dihydrate shows a well-resolved
BF4) are shown in Figure 4. The absence of any ν(AuX) multiplet structure that will be discussed further below. The
bands is consistent with the ionic structures determined chemical shifts for the four compounds are 60.9 (av.), 63.8
crystallographically for the X = Cl, BF4 salts and supports (av.), 59.0, 58.2 ppm, respectively. These are about 20 ppm
the proposed ionic formulation for the X = I case. All of higher than for the 1:1 complexes [(Bn3P)AuX], reflecting
the bands observed in these spectra are due to the [Au- the change in coordination environment from P–Au–X in
(PBn3)2]+ cation that each of them contains, with the pos- the 1:1 compounds to P–Au–P in the 1:2 compounds. The
sible exception of the band at 519 cm–1 in [Au(PBn3)2]BF4, fact that the chemical shifts for [Au(PBn3)2]Cl·2H2O and
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Linearly Coordinated Gold(I) Tribenzylphosphane Complexes
In the case of [Au(PBn3)2]Cl·2H2O a quartet signal is
observed [Figure 6, (b)]. We have considered two possible
explanations for this multiplet structure:
1
(a) Splitting due to J(31P-197Au) coupling. In a number
of cases in the past it has been shown that splitting due to
1J(31P-197Au) coupling can be observed in the MAS 31P
NMR spectra of gold(I) complexes containing phosphane
ligands.[23,27–29] The expected form of the MAS NMR spec-
trum of a spin I = 1/2 nucleus coupled to a quadrupolar
(I Ͼ 1/2) nucleus has been discussed by Menger and Vee-
man,[30] who showed that the form of the spectrum depends
on the parameters R = D/J (where D is the dipolar coupling
constant and J is the indirect or scalar coupling constant)
and K = –3χ/4I(2I – 1)Z (where χ is the quadrupole cou-
pling constant and Z the Zeeman interaction for the quad-
rupolar nucleus of spin I). In the case of 31P coupled to
197Au (I = 3/2), the parameter R is small, and an equally
Figure 5. 31P CP MAS spectra of [(Bn3P)AuX] at B = 11.7 T, (a)
X = Cl, (b) X = Br.
spaced four-line pattern [spacing = 1J(31P-197Au)] of the 31
P
spectrum is predicted for small K. This has been observed
in the 31P MAS NMR spectra of the compounds [Au-
(dppey)2]X [dppey = cis-1,2-bis(diphenylphosphanyl)eth-
ene; X = NO3 or PF6], where the near tetrahedral coordina-
tion of the Au is assumed to result in a 197Au quadrupole
coupling constant close to zero,[28] and hence corresponds
to K ≈ 0. For the opposite case of large K a doublet pattern
[Au(PBn3)2]I are very close to those of the corresponding
BF4 complex lends further support to the proposed ionic
structure of these compounds.
1
is predicted with a spacing of about 1.65 times the J(31P-
197Au) coupling constant,[30,31] and this has been observed
in the linear two-coordinate complexes [(Ph3P)AuX] (X =
Cl, Br, I),[27] [(Me3P)AuX] (X = Cl, I)[23] and [(Me3P)2Au]-
X (X = Cl, Br).[32] In these cases the linear coordination of
the gold atom and the large quadrupole moment of the gold
nucleus results in a large 197Au quadrupole coupling con-
stant and hence a large value of K (estimated to be ≈ 34).[23]
However, this splitting is not found in all cases where it
might appear. Thus, it is not observed in the case of
[(tmpp)AuX],[24] despite the close similarity between these
and the corresponding PPh3 complexes or [(Cy3P)AuX].
Also, it is not observed in [(Me3P)AuBr] despite the fact
that the doublet splitting is clearly resolved in the corre-
sponding Cl and I compounds.[23] In [Au(PMe3)2]X the
doublet splitting is observed for X = Cl, Br but not for X
= I.[32] There are clearly very subtle structural effects that
influence the 197Au relaxation processes, which determine
whether the coupling is observed or not. In the present
study, the splitting observed in the spectrum of [Au-
(PBn3)2]Cl·2H2O is of the right magnitude to be attributed
to 1J(31P-197Au) coupling. The unequally spaced quartet
pattern is exactly what is expected in the transition from
the equally spaced quartet corresponding to K = 0 to the
doublet corresponding to large K.[30] The weighted average
separation between the two outermost partially collapsed
1
doublets is about 1100 Hz, corresponding to J(31P-197Au)
≈ 670 Hz. This is similar in magnitude to the values ob-
tained previously for [(Ph3P)AuX] (412–521 Hz),[27]
[(Me3P)AuX] (553–648 Hz)[23] and [Au(PMe3)2]X (ca.
340 Hz).[32]
2
(b) Splitting due to J(31P-31P) coupling between two in-
Figure 6. 31P CP MAS spectra of [Au(PBn3)2]X at B = 11.7 T; (a)
X = Cl·H2O; (b) X = Cl·2H2O; (c) X = I; (d) X = BF4.
equivalent phosphorus atoms. This would result in an AB
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E. W. Ainscough, G. A. Bowmaker, A. M. Brodie et al.
FULL PAPER
quartet pattern, and spectra of this kind have previously
been observed for [(Cy3P)2AuX] (X = Br, I).[33] In the case
of [Au(PBn3)2]Cl·2H2O this would imply the presence of
noncentrosymmetric [Au(PBn3)2]+ cations in the structure
in which the two phosphorus atoms are inequivalent, in
contrast to the case of [Au(PBn3)2]Cl·H2O, in which the two
phosphorus atoms in each of the two [Au(PBn3)2]+ ions in
the structure are equivalent (see Crystal Structures, above).
In order to distinguish between the above two possibil-
ities, the spectrum of [Au(PBn3)2]Cl·2H2O was run at two
different field strengths, 9.4 and 7.0 T, and the results are
shown as a frequency plot in Figure 7. The predicted
changes in the frequency plot spectra with the decrease in
field strength from 9.4 to 7.0 T (400 to 300 MHz proton
NMR frequency) are as follows:
Conclusions
Two-coordinate, tribenzylphosphane (PBn3) complexes
of gold(I), [(Bn3P)AuX] (X = Cl and Br), have been synthe-
sised. The compounds contain linear P–Au–X arrays, each
structure containing three independent [(Bn3P)AuX] enti-
ties lying on the three threefold axes of space group P3c1.
ν(AuX) bands in the far-IR spectra of [(Bn3P)AuX] are as-
signed at 320 and 227 cm–1 for X = Cl and X = Br, respec-
tively. In contrast, the 1:1 adducts previously characterised
for copper(I) take the form [Cu(PBn3)2][CuX2] and contain
linear P–M–P cationic and X–Cu–X anionic moieties.[2,3] In
this study, similar linear cations are found in the com-
pounds [Au(PBn3)2]X·nH2O (X = Cl, n = 1 or 2; X = I and
BF4, n = 0). The 31P CP MAS NMR spectra of all the new
compounds are reported and discussed. The spectrum of
the cationic monohydrate, [Au(PBn3)2]Cl·H2O, shows two
well-resolved signals consistent with the presence of two
distinct cations in the asymmetric unit, each with equivalent
phosphorus atoms. In contrast, the dihydrate, [Au(PBn3)2]-
Cl·2H2O, shows a well-resolved multiplet due to 2J(PP)
coupling, which indicates that the cations in this complex
are noncentrosymmetric with two inequivalent phosphorus
atoms.
(a) 1J(AuP) case: The K parameter will increase by a fac-
tor of 1.33, so the splitting between the outer doublets will
decrease while the separation of the doublet centres will re-
main unchanged.
2
(b) J(PP) case: The splitting of the outer doublets will
remain unchanged while the separation of the doublet
centres will decrease by a factor of 0.75. The intensity of
the inner relative to the outer lines will change from 1.8 to
2.3.
Experimental Section
Synthesis: Tetrahydrofuran (thf) was distilled from sodium/benzo-
phenone, dimethylformamide (dmf) was distilled from molecular
sieves and other solvents were dried by standard procedures. Tri-
benzylphosphane (PBn3) was prepared according to the method of
ref.[35] or obtained from Sigma Aldrich Co. Bis(acetonitrile)gold
tetrafluoroborate [Au(NCCH3)2]BF4 was prepared from gold pow-
der and NOBF4 by an adaptation of the method described in the
literature for the perchlorate salt[36a] while [Bu4N][AuX2] (X = Cl,
Br, I) were prepared according to literature methods.[36b] The 1:1
adducts with gold(I) chloride and bromide were prepared following
the method of ref.[7a], by the dissolution of millimolar quantities of
[Bu4N][AuX2] (X = Cl, Br) and PBn3 in 1:1 ratio in ca. 10 mL
warm dmf as described in detail below, well-formed crystals de-
positing on standing. With the iodide, tribenzylphosphane oxide
only was deposited and identified crystallographically, as described
in a footnote.[37] All reactions were carried out under dinitrogen.
Figure 7. 31P CP MAS spectra of [Au(PBn3)2]Cl·2H2O, (a) B =
9.4 T; (b) B = 7.0 T. The superimposed stick plots are the calculated
Chlorotribenzylphosphanegold(I) [(Bn3P)AuCl]:
A
mixture of
AB spectra for the two fields, with δA = 60.9, δB = 66.6, JAB
=
[Bu4N][AuCl2] (0.255 g, (0.5 mmol) and tribenzylphosphane
(0.152 g, 0.5 mmol) in 7.5 mL dimethylformamide was warmed to
60 °C under N2 with stirring for 15 min. Colourless crystals de-
posited on cooling to room temperature and were filtered and dried
under vacuum to give 0.12 g (45% yield). C21H21AuClP (536.79):
calcd. for C 46.99, H 3.94; found C 47.03, H 3.93.
292 Hz.
It is clear from Figure 7 that the results fit case (b) very
well, while the behaviour predicted for case (a) is not ob-
served at all. The superimposed stick plots are the calcu-
lated AB spectra for the two fields, with δA = 60.9, δB
=
Bromotribenzylphosphanegold(I) [(Bn3P)AuBr]: A warmed solution
of tribenzylphosphane (0.152 g, 0.5 mmol) in 3 mL of dmf was
66.6, JAB = 292 Hz. The coupling constant is of a similar
2
magnitude to J(PP) values found in similar systems, e.g.
slowly added, under N2, to
a warmed (60 °C) solution of
270 Hz in [(PCy3)2AuBr],[33] and ca. 300 Hz in
[Au2(Ph2P(CH2)2PEt2)2]Cl2.[34] The observation of 2J(PP)
coupling in [Au(PBn3)2]Cl·2H2O indicates that the cations
in this complex are noncentrosymmetric with two inequiva-
lent phosphorus atoms.
[Bu4N][AuBr2] (0.30 g, 0.5 mmol) in 2 mL of dmf. After 5 min stir-
ring at 60 °C the reaction mixture was cooled to room temperature.
Colourless crystals deposited on cooling and were filtered and
dried under vacuum to give 0.063 g (22% yield). C21H21AuBrP
(581.24): calcd. C 43.40, H 3.64; found C 43.45, H 3.70.
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Linearly Coordinated Gold(I) Tribenzylphosphane Complexes
Bis(tribenzylphosphane)gold(I) Chloride Dihydrate [Au(PBn3)2]Cl·
2H2O: A mixture of [Bu4N][AuCl2] (0.128 g, 0.25 mmol) and tri-
benzylphosphane (0.155 g, 0.51 mmol) in 5 mL tetrahydrofuran
was warmed to 60 °C under N2 with stirring for 5 min. The product
precipitated on cooling to room temperature and was filtered and
dried under vacuum to give 0.195 g of a colourless solid (93%
yield). C42H46AuClO2P2 (877.19): calcd. C 57.51, H 5.29; found C
57.43, H 5.27. Mp 233–235 °C (decomp.).
merging to N unique [Rint cited] after ЈempiricalЈ/multiscan absorp-
tion correction (proprietary software), No with I Ͼ 4σ(I) being con-
sidered ЈobservedЈ; all data were used in the full-matrix least-
squares refinements on F2, refining anisotropic displacement pa-
rameter forms for the non-hydrogen atoms, hydrogen atom treat-
ment following a ЈridingЈ model. Neutral atom complex scattering
factors were employed within the context of the SHELXL 97 pro-
gram.[38] Friedel data were retained distinct and xabs refined where
appropriate. Pertinent results are given in the Tables and Figures,
the latter showing 50% probability amplitude displacement ellip-
soids for the non-hydrogen atoms, hydrogen atoms (where shown)
having arbitrary radii of 0.1 Å. See Table 5. CCDC-617832,
-617833, -696892 and -696893 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Bis(tribenzylphosphane)gold(I) Chloride Monohydrate [Au(PBn3)2]-
Cl·H2O: Pentane was diffused into a solution containing 30 mg of
[Au(PBn3)2]Cl·2H2O dissolved in 8 mL dimethylformamide to give
X-ray quality crystals of a colourless product. C42H44AuClOP2
(859.17): calcd. C 58.71, H 5.16; found C 58.63, H 5.14.
Bis(tribenzylphosphane)gold(I) Iodide [Au(PBn3)2]I: A mixture of
[Bu4N][AuI2] (0.173 g, 0.25 mmol) and tribenzylphosphane
(0.155 g, 0.51 mmol) and 5 mL tetrahydrofuran was warmed to
60 °C under N2 with stirring for 5 min. The product precipitated
on cooling to room temperature and was filtered to give a colour-
less solid which was recrystallised from nitromethane and dried un-
der vacuum to give 0.08 g of a white crystalline powder (34%).
C42H42 AuIP2 (932.61): calcd. C 54.09, H 4.54: found C 54.06, H
4.64.
Infrared Spectroscopy: IR spectra were recorded at 4 cm–1 resolution
on dry powders using a Perkin–Elmer Spectrum 400 FT-IR spec-
trometer equipped with a Universal ATR sampling accessory. Far-
infrared spectra were recorded at 4 cm–1 resolution with a Nicolet
8700 FTIR spectrometer on samples suspended in Polythene disks.
NMR Spectroscopy: 31P Cross-polarisation, magic-angle-spinning
(CPMAS) NMR spectroscopic data were acquired at 7.0, 9.4 and
11.7 T on Varian Infinity Plus-300, Bruker DSX-400 and Bruker
Avance III-500 spectrometers operating at 31P frequencies of
121.47, 161.92 and 202.41 MHz, respectively. All spectra were ob-
tained with conventional cross-polarisation (CP) methods and a
MAS frequency of ca. 10 kHz using a Bruker 4 mm double-air-
Bis(tribenzylphosphane)gold(I) Tetrafluoroborate [Au(PBn3)2]BF4: A
solution of bis(acetonitrile)gold tetrafluoroborate (0.12 g,
0.355 mmol) in 40 mL acetonitrile was added to tribenzylphos-
phane (0.216 g, 0.708 mmol) and the reaction mixture refluxed un-
der N2 for 1.5 h. The resulting white solid was recrystallised from
dmf and dried under vacuum to give 0.20 g of off-white crystals
(63%). C42H42AuBF4P2 (892.51): calcd. C 56.52, H 4.74; found C
56.48, H 4.69.
1
bearing probe. The typical pulse parameters employed were: a H
π/2 pulse time of 3.5 µs, a Hartmann–Hahn contact period of
10 ms, a recycle delay of 20 s and a 1H decoupling field strength
during acquisition of ca. 80 kHz. All data were referenced to 85%
H3PO4 via an external reference of (NH4)(H2PO4) (δ = 1.0 ppm),
which was also used to set the Hartmann–Hahn match condition.
Structure Determinations: Full spheres of ЈlowЈ-temperature CCD
area-detector diffractometer data were measured (monochromatic
Mo-Kα radiation, λ = 0.71073 Å) yielding Ntotal reflections, these
Table 5. Crystal and refinement data for the complexes.
Compound
[(Bn3P)AuCl]
[(Bn3P)AuBr]
[Au(PBn3)2]Cl·H2O
[Au(PBn3)2]BF4
Empirical formula
M [Da]
T [K]
Crystal system
Space group
a (Å)
b [Å]
c [Å]
α [°]
β [°]
C21H21AuClP
536.76
100(2)
trigonal[a]
P3c1 (No. 158)
13.926(1)
13.926(1)
17.239(3)
90
90
120
2895.3(6)
6
7.8
C21H21AuBrP
581.22
170(2)
C42H44AuClOP2
859.13
203(2)
C42H42AuBF4P2
892.47
200(2)
monoclinic
C2/c (No. 15)
14.1316(2)
13.4801(1)
19.4918(1)
90
92.814(2)
90
3708.62(6)
4
4.1
1.598
54
10234
4004 [0.021]
3301
trigonal[a]
P3c1 (No. 158)
13.9414(4)
13.9414(4)
17.6558(5)
90
triclinic
¯
P1(No. 2)
9.8244(1)
12.9542(1)
15.8826(2)
84.133(1)
72.441(1)
71.549(1)
1828.04(4)
2
4.2
1.561
55
17359
90
120
2971.9(1)
6
9.5
1.949
68
66499
7245 [0.034]
4961
γ [°]
V [Å3]
Z
µ [Mo-Kα] [mm–1]
ρcalcd. [gcm–3]
2θmax. [°]
Ntotal
1.847
74
110703
9661 [0.056]
4357
N [Rint
No
]
7898 [0.022]
6246
R1
0.028
0.066
–0.045(8)
0.96
0.026
0.064
0.047(10)
1.00
0.022
0.045
n/a
1.05
0.022
0.044
n/a
1.10
wR2
xabs.
S
[a] The cell dimensions are remarkably similar to those of the hexagonal setting of the 1:1 CuBr:PBn3 adduct [a = 13.829(1), c =
3
[2]
¯
17.429(2) Å, V = 2887 Å at 298 K] which takes the form [Cu(PBn3)2][CuBr2] in space group R3.
Eur. J. Inorg. Chem. 2010, 2044–2053
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E. W. Ainscough, G. A. Bowmaker, A. M. Brodie et al.
FULL PAPER
[15] (Au,Cl) a) G. Helgesson, S. Jagner, Acta Chem. Scand., Ser. A
1987, 41, 556 [2.280(8) Å]; b) P. Braunstein, A. Müller, H.
Bögge, Inorg. Chem. 1986, 25, 2104 [2.257(4) Å]; c) Md. A.
Hossain, D. R. Powell, K. Bowman-James, Acta Crystallogr.,
Sect. E 2003, 59, m57 [2.2643(5) Å]; we adopt 2.27 Å.
[16] (Au,Br) a) A. C. Fabretti, A. Giusti, W. Malavasi, J. Chem.
Soc., Dalton Trans. 1990, 3091 [2.358(2), 2.420(1) Å]; b) P. T.
Beurskens, H. J. A. Blaauw, J. A. Cras, J. J. Steggerda, Inorg.
Chem. 1968, 7, 805 [2.349(5) Å]; c) Ref.[15b] gives 2.376(3) Å;
we adopt 2.36 Å.
Acknowledgments
We thank Dr A. K. Burrell for preliminary crystallographic assist-
ance and the Massey University Research Fund for support. The
Bruker Avance III-500 used in this research was obtained through
Birmingham Science City: Innovative Uses for Advanced Materials
in the Modern World (West Midlands Centre for Advanced Materi-
als Project 2), with support from Advantage West Midlands
(AWM) and part funded by the European Regional Development
Fund (ERDF).
[17] a) (Au,I) Ref.[15a] gives 2.530(2), 2.540(2) Å; b) R. J. Staples, S.
Wang, J. P. Fackler Jr, Acta Crystallogr., Sect. C 1994, 50, 1580
[2.536(1), 2.538(1) Å]; c) Ref.[15b] gives 2.529(1) Å; we adopt
2.54 Å.
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A. Z. Rubezhov, Mendeleev Commun. 1991, 1, 22 [2.314(3) Å];
c) J.-C. Wang, Y. Wang, Acta Crystallogr., Sect. C 1993, 49,
131 [2.290(2), 2.300(2) Å at 298 K; P–Ag–P here 161.23(9)°]; d)
R. J. Staples, C. King, M. N. I. Khan, R. E. P. Winpenny, J. P.
Fackler Jr, Acta Crystallogr., Sect. C 1993, 49, 472 [2.314(2),
2.309(2) Å; 2.312(4), 2.311(2) Å at 295 K]; e) J.-C. Wang, Acta
Crystallogr., Sect. C 1996, 52, 611 [2.321(3), 2.322(3) Å at
298 K]. We adopt 2.31 Å.
[6] U. Monkowius, M. Zabel, H. Yersin, Inorg. Chem. Commun.
2008, 11, 409.
[7] a) C. A. McAuliffe, R. V. Parish, P. D. Randall, J. Chem. Soc.,
Dalton Trans. 1979, 1730; b) A. Bayler, A. Bauer, H. Schmid-
baur, Chem. Ber./Recueil 1997, 130, 115; c) C. K. Mirabell,
R. K. Johnson, D. T. Hill, L. F. Faucette, G. R. Girard, G. Y.
Kuo, C. M. Sung, S. T. Crooke, J. Med. Chem. 1986, 29, 218.
[8] S. Jagner, G. Helgesson, Adv. Inorg. Chem. 1991, 37, 1.
[9] (Cu,Cl) From those values of Table 1 of ref.[8] with s.u. values
better than 0.003 Å, 2.09 Å would seem a reasonable value to
adopt.
[20]
[21]
G. A. Bowmaker, Adv. Spectrosc. 1987, 14, 1.
G. A. Bowmaker, J. C. Dyason, P. C. Healy, L. M. Engelhardt,
C. Pakawatchai, A. H. White, J. Chem. Soc., Dalton Trans.
1987, 1089.
[22]
[23]
G. G. Lobbia, M. Pellei, C. Pettinari, C. Santini, N. Somers,
A. H. White, Inorg. Chim. Acta 2002, 333, 100.
K. Angermair, G. A. Bowmaker, E. N. de Silva, P. C. Healy,
B. E. Jones, H. Schmidbaur, J. Chem. Soc., Dalton Trans. 1996,
3121 (see also the Erratum: p. 3897).
[10] (Cu,Br) cf. ref.[8], we adopt 2.22 Å.
[11] (Cu,I) a) N. P. Rath, E. M. Holt, J. Chem. Soc., Chem. Com-
mun. 1986, 311 [2.394(2), 2.383(1) Å]; b) C. Di Nicola, Effendy,
F. Fazaroh, C. Pettinari, B. W. Skelton, N. Somers, A. H.
White, Inorg. Chim. Acta 2005, 358, 720 [2.388(2), 2.380(2) Å];
c) M. Amirnasr, A. D. Khalaji, L. R. Falvello, Inorg. Chim.
Acta 2006, 359, 713 [2.4178(5), 2.4340(6) Å]. We use 2.39 Å as
an appropriate value.
[12] (Ag,Cl) a) G. Helgesson, S. Jagner, Inorg. Chem. 1991, 30, 2574
[2.328(2), 2.330(2) Å]; b) G. Exarchos, S. C. Nyburg, S. D. Rob-
inson, Polyhedron 1998, 17, 1257 [2.304(1), 2.306(4) Å]; c)
A. A. D. Tulloch, A. A. Danopoulos, G. J. Tizzard, S. J. Coles,
M. B. Hursthouse, R. S. Hay-Motherwell, W. B. Motherwell,
Chem. Commun. 2001, 1270 [2.342(14), 2.372(12) Å; Cl–Ag–Cl
164.1(1)°]; d) the isolated species in P. de Frémont, N. M. Scott,
E. D. Stevens, T. Ramnial, O. C. Lightbody, C. L. B. Macdon-
ald, J. A. C. Clyburne, C. D. Abernethy, S. P. Nolan, Organo-
metallics 2005, 24, 6301 gives 2.534(5) Å, which seem strangely
high. We adopt 2.33 Å.
[13] (Ag,Br) a) J. A. Cras, J. H. Noordik, P. T. Beurskens, A. M.
Verhoeven, J. Cryst. Mol. Struct. 1971, 1, 155 [2.450(5) Å]; b)
S. K. Schneider, W. A. Herrmann, E. Herdtweck, Z. Anorg.
Allg. Chem. 2003, 629, 2363 [2.4261(7) Å]. We adopt 2.44 Å.
[14] (Ag,I) A. D. Khalaji, R. Welter, Inorg. Chim. Acta 2006, 359,
4403 [2.9244(5) Å]. The value 2.9244(5) Å for Ag–I is for the
single compound [Cu(Phca2en)2][AgI2], seemingly the only one
to date that has been shown to contain discrete [AgI2]– species.
However, the [AgI2]– anions in the crystal structure are associ-
ated with some of the phenyl rings in the cations, producing a
one-dimensional network of [Cu(Phca2en)2][AgI2] components.
This interaction possibly weakens and lengthens the Ag–I
bonds. Extrapolation from data for the other [MX2]– species
suggests an Ag–I bond length of ca. 2.61 Å might be expected.
[24]
L.-J. Baker, R. C. Bott, G. A. Bowmaker, P. C. Healy, B. W.
Skelton, P. Schwerdtfeger, A. H. White, J. Chem. Soc., Dalton
Trans. 1995, 1341.
[25]
[26]
A. G. Jones, D. B. Powell, Spectrochim. Acta Sect. A 1974, 30,
563.
G. A. Bowmaker, Spectroscopic Methods in Gold Chemistry,
chapter in: Gold: Progress in Chemistry, Biochemistry and Tech-
nology (Ed.: H. Schmidbaur), John Wiley & Sons, 1999.
a) P. F. Barron, L. M. Engelhardt, P. C. Healy, J. Oddy, A. H.
White, Aust. J. Chem. 1987, 40, 1545 {[(Ph3P)AuX], X = Cl,
Br, I}; b) See Ref.[23] [(Me3P)AuBr].
[27]
[28]
[29]
S. J. Berners-Price, L. A. Colquhoun, P. C. Healy, K. A. Byriel,
J. V. Hanna, J. Chem. Soc., Dalton Trans. 1992, 3357.
P. C. Healy, B. T. Loughrey, G. A. Bowmaker, J. V. Hanna, Dal-
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[30]
[31]
[32]
E. M. Menger, W. S. Veeman, J. Magn. Reson. 1982, 46, 257.
A. C. Olivieri, Solid State Nucl. Magn. Reson. 1992, 1, 345.
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[33]
G. A. Bowmaker, C. L. Brown, R. D. Hart, P. C. Healy, C. E. F.
Rickard, A. H. White, J. Chem. Soc., Dalton Trans. 1999, 881.
S. J. Berners-Price, P. J. Sadler, Inorg. Chem. 1986, 25, 3822.
R. C. Hinton, F. G. Mann, J. Chem. Soc. 1959, 2835.
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[34]
[35]
[36]
[37]
H. N. de Armas, H. Pérez, O. M. Peeters, N. M. Blaton, C. J.
De Ranter, J. M. López, Acta Crystallogr., Sect. C 2000, 56,
2052
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 2044–2053

Linearly Coordinated Gold(I) Tribenzylphosphane Complexes
e98. This reference describes the molecule (Bn3PO) as disposed
on a crystallographic 3-axis in rhombohedral space group R3
(C34, #146), a = 16.685(2), c = 5.468(1) Å, V = 1318 Å3 (hexag-
onal setting) at T = 293 K. In our determination, initially at
ca. 153 K, the cell was found to be doubled in the same space
group: C21H21OP, M = 320.4, a = 16.431(3), c = 10.923(2) Å,
V = 2554 Å3. Dc (Z = 6) = 1.250 gcm–3. µMo = 0.16 mm–1;
D. M. Soboroff, Acta Crystallogr., Sect. B 1976, 32, 962 (X =
Cl); j) Ref. [27a] (X = Br, I); k) C. S. W. Harker, E. R. T. Tiekink,
Acta Crystallogr., Sect. C 1990, 46, 1546 (X = Cl); l) R. C.
Bott, P. C. Healy, G. Smith, Aust. J. Chem. 2004, 57, 213 (X =
Cl, Br, I); m) E. C. Alyea, G. Ferguson, J. F. Gallagher, J. Mal-
ito, Acta Crystallogr., Sect. C 1993, 49, 1473 (X = Cl); n) (X
= Cl, Br, I): R. C. Bott, G. A. Bowmaker, R. W. Buckley, P. C.
Healy, M. C. S. Perera, Aust. J. Chem. 2000, 53, 175; o) E. C.
Alyea, G. Ferguson, S. Kannan, Polyhedron 2000, 19, 2211.
specimen: 0.40ϫ0.40ϫ0.14 mm; ЈTЈmin/max = 0.80. 2θmax
=
60°; Nt = 10082, N = 2887 (Rint = 0.039), No = 2373; R1 =
0.038, wR2 = 0.085; S = 0.98. xabs = 0.01(9). [At ca. 300 K,
the cell was restored to the literature form: a = 16.680(2), c =
5.465(1) Å, V = 1317 Å3.] At ca. 153 K P–O, C are 1.497(2),
1.820(2); 1.494(2), 1.819(2) Å; O–P–C, C–P–C 114.34(6),
104.20(7); 115.13(6), 103.27(7)° for the two independent mole-
cules; CCDC-617831. In exploring the Cambridge Data Base
for other related systems, we noticed that [Bn3SnCl] also ap-
peared to be isomorphous (S. W. Ng, Acta Crystallogr., Sect.
C 1997, 53, 56), space group R3, a = 16.942(1), c = 5.9187(4) Å,
V = 1471 Å3, at 298 K. A readily available specimen was kindly
supplied by Dr. Bruce James of Latrobe University and a sim-
ilar doubling found at 100 K: C21H21ClSn, M = 427.5. a =
16.760(2), c = 11.6620(10) Å, V = 2837 Å3. Dc (Z = 6) =
[40]
a) E. W. Ainscough, A. M. Brodie, A. K. Burrell, J. V. Hanna,
P. C. Healy, J. M. Waters, Inorg. Chem. 1999, 38, 201; b) Ref.[3]
;
c) Ref.[2]; d) Ref.[18c]; e) O. Schuster, U. Monkowius, H. Schmid-
baur, R. S. Ray, S. Krüger, N. Rösch, Organometallics 2006,
25, 1004; f) C. W. Liu, H. Pan, J. P. Fackler Jr, G. Wu, R. E.
Wasylishen, M. Shang, J. Chem. Soc., Dalton Trans. 1995,
3691; g) E. C. Alyea, G. Ferguson, A. Somogyvari, Inorg.
Chem. 1982, 21, 1369; h) L.-J. Baker, G. A. Bowmaker, Effendy,
B. W. Skelton, A. H. White, Aust. J. Chem. 1992, 45, 1909; i)
G. A. Bowmaker, Effendy, B. W. Skelton, N. Somers, A. H.
White, Inorg. Chim. Acta 2005, 358, 4307; j) G. A. Bowmaker,
Effendy, J. C. Reid, C. E. F. Rickard, B. W. Skelton, A. H.
White, J. Chem. Soc., Dalton Trans. 1998, 2139; k) Analysts
may wish to exclude this system from consideration on the
grounds that the P–Ag–P angle is excessively bent, presumably
due to incipient anion coordination (R. E. Bachmann, D. F.
Andretta, Inorg. Chem. 1998, 37, 5657); l) Ref.[39a]; m) R. J.
Staples, J. P. Fackler Jr, M. N. I. Khan, R. E. P. Winpenny,
1.501 gcm–3.
µMo
=
1.49 mm–1;
specimen:
0.33ϫ0.13ϫ0.12 mm; ЈTЈmin./max. = 0.69. 2θmax. = 75°; Nt =
22896, N = 6058 (Rint. = 0.028), No = 3785; R1 = 0.028, wR2
= 0.078; S = 0.99. xabs. = 0.04(3). Sn–C, Cl are 2.149(3),
2.4000(12); 2.141(2), 2.3923(12) Å, C–Sn–Cl, C–Sn–C
100.96(8), 116.47(5); 102.87(7), 115.19(2)° for the two indepen-
dent molecules; CCDC-617830.
Acta Crystallogr., Sect. C 1994, 50, 191; n) Ref.[33]; o) Ref.[6]
;
p) this work; q) E. Zeller, A. Schier, H. Schmidbaur, Z. Natur-
forsch., Teil B 1994, 49, 1243; r) Ref.[19d]
[38] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[39] a) K. Angermaier, E. Zeller, H. Schmidbaur, J. Organomet.
Chem. 1994, 472, 371 (X = Cl); b) Ref.[23] (X = Br); c) S. Ahr-
land, K. Dreisch, B. Norén, A. Oskårsson, Acta Chem. Scand.,
Ser. A 1987, 41, 173 (X = I); d) E. R. T. Tiekink, Acta Crys-
tallogr., Sect. C 1989, 45, 1233; e) this work, mean values: Au–
P,X 2.227(11), 2.302(8) (X = Cl); 2.229(4), 2.404(10) (X = Br);
f) J. A. Muir, M. M. Muir, L. B. Pulgar, P. G. Jones, G. M. Shel-
drick, Acta Crystallogr., Sect. C 1985, 41, 1174 (X = Cl); g)
R. C. Bott, G. A. Bowmaker, R. W. Buckley, P. C. Healy,
M. C. S. Perera, Aust. J. Chem. 1999, 52, 271 (X = Br, I); h)
H. Schmidbaur, B. Brachthäuser, O. Steigelmann, H. Beruda,
Chem. Ber. 1992, 125, 2705; i) N. C. Baenzinger, W. E. Bennett,
[41] a) Ref.[39m]; b) Ref.[39n]; c) G. A. Bowmaker, J. D. Cotton, P. C.
Healy, J. D. Kildea, S. bin Silong, B. W. Skelton, A. H. White,
Inorg. Chem. 1989, 28, 1462; d) Ref.[24]; e) Ref.[39o]; f) L.-J.
Baker, G. A. Bowmaker, D. Camp, Effendy, P. C. Healy, H.
Schmidbaur, O. Steigelmann, A. H. White, Inorg. Chem. 1992,
31, 3656; g) this work, mean values (see Table 2); h) Effendy,
P. C. Healy, B. W. Skelton, A. H. White, unpublished work; i)
E. C. Alyea, G. Ferguson, J. Malito, B. L. Ruhl, Inorg. Chem.
1985, 24, 3720; j) Ref.[4]
Received: February 15, 2010
Published Online: March 30, 2010
Eur. J. Inorg. Chem. 2010, 2044–2053
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2053