AuIII binding to C5 of the model nucleobase 1,3-dimethyluracil (1,3-DimeU): Preparation and X-ray crystal structures of trans-K[Au(CN)2Cl(1,3-DimeU-)] and of two derivatives

Article abstract of DOI:10.1016/S0022-328X(97)00567-6

The reaction of trans-K[Au(CN)₂Cl₂] with 1,3-dimethyluracil (1,3-DimeU) gives trans-K[Au(CN)₂Cl(1,3-DimeU^--C⁵)] (1) which contains the 1,3-dimethyluracil-5-yl entity (1,3-DimeU^--C⁵) bound to Au^III. Complex 1 represents the first example of an X-ray structurally characterized organogold(III) complex of a nucleobase. Further reaction with purine model nucleobases (nb) such as 9-ethylguanine (9-EtGH), 9-methyladenine (9-MeA), and 1-methylcytosine (1-MeC) leads to mixed nucleobase complexes of type trans-[Au(CN)₂(1,3-DimeU^--C⁵)(nb)] (nb=9-MeA, 2a; nb=9-EtGH, 3a; nb=1-MeC, 4a) or to compounds containing the protonated purine base Hnb⁺ and [Au(CN)₂X(1,3-DimeU^--C⁵)]^- as a counter ion (X=Cl or CN), e.g. [9-MeAH][Au(CN)₂Cl(1,3-DimeU^--C ⁵)]·H₂O (2b) and [9-EtGH₂][Au(CN)₃(1,3-DimeU^--C⁵)] (3b). The crystal structures of 1, 2b, and 3b were determined. The C-bound nucleobase exerts a distinct trans-influence, as evident from long Au-Cl bonds in 1 and 2b (2.340(3) A and 2.358(6) A) and a long bond (2.082(7) A) between Au and the cyano ligand trans to 1,3-DimeU^- in 3b.

Full text of DOI:10.1016/S0022-328X(97)00567-6

Journal of Organometallic Chemistry 552 Ž1998. 127–134
III
Au binding to C5 of the model nucleobase 1,3-dimethyluracil
ž
/
1
,3-DimeU : Preparation and X-ray crystal structures of
y
w ž / ž
/x
trans-K Au CN Cl 1,3-DimeU and of two derivatives
2
F e´ lix Zamora , Ennio Zangrando , Michela Furlan , Lucio Randaccio b,),
a
b
b
a,1
Bernhard Lippert
a
Fachbereich Chemie, UniÕersit a¨ t Dortmund, Dortmund D-44221, Germany
Dipartimento di Scienze Chimiche, UniÕersit a` di Trieste, Trieste 34127, Italy
b
Received 23 June 1997; received in revised form 29 July 1997
Abstract
y
5
The reaction of trans-KwAuŽCN. Cl x with 1,3-dimethyluracil Ž1,3-DimeU. gives trans-KwAuŽCN. ClŽ1,3-DimeU –C .x Ž1. which
2
2
2
y
5
III
contains the 1,3-dimethyluracil-5-yl entity Ž1,3-DimeU –C . bound to Au . Complex 1 represents the first example of an X-ray
structurally characterized organogoldŽIII. complex of a nucleobase. Further reaction with purine model nucleobases Žnb. such as
9
-ethylguanine Ž9-EtGH., 9-methyladenine Ž9-MeA., and 1-methylcytosine Ž1-MeC. leads to mixed nucleobase complexes of type
y
5
trans-wAuŽCN. Ž1,3-DimeU –C .Žnb.x Žnbs9-MeA, 2a; nbs9-EtGH, 3a; nbs1-MeC, 4a. or to compounds containing the protonated
2
q
y
5
y
y
5
purine base Hnb and wAuŽCN. XŽ1,3-DimeU –C .x as a counter ion ŽXsCl or CN., e.g. w9-MeAHxwAuŽCN. ClŽ1,3-DimeU –C .xP
2
2
y
5
H O Ž2b. and w9-EtGH xwAuŽCN. Ž1,3-DimeU –C .x Ž3b.. The crystal structures of 1, 2b, and 3b were determined. The C-bound
2
2
3
nucleobase exerts a distinct trans-influence, as evident from long Au–Cl bonds in 1 and 2b Ž2.340Ž3. A˚ and 2.358Ž6. A˚ . and a long bond
Ž2.082Ž7. A˚ . between Au and the cyano ligand trans to 1,3-DimeUy in 3b. q 1998 Elsevier Science S.A.
Keywords: GoldŽIII.; Nucleobase; Uracil; Crystal structure
1
. Introduction
In the model nucleobase 1,3-dimethyluracil
meU
Ž
1,3-Di-
3
.
, the N position, which is a frequent binding site
in uracil nucleobases for metal ions, is blocked and
therefore unavailable Scheme 1 . Binding of light tran-
Ž
.
sition metal ions has been demonstrated to occur via the
4
exocyclic O position, however w1,2x, whereas the heavy
2
q
2q
transition metal ions Hg w3–6x and Pt w4x can also
5
bind to the C position with displacement of an aro-
matic proton. This reaction may involve initial binding
4
to O with the metal entity in an anti orientation
3
y
relative to N w4x. Similarly, reaction of wAuCl x with
4
5
this ligand takes place at C , followed by oxidative
Ž . w7x. Al-
dimerization to di 1,3-dimethyluracil–C ,C
X
5
5
Scheme 1.
5
though we were able to detect the C metalated species
1
by H NMR spectroscopy in solution and to character-
)
ize the oxidation product by X-ray crystallography, we
Corresponding author.
Also corresponding author.
1
y
were unable as yet to crystallize wAuCl3
Ž
1,3-DimeU –
0
022-328Xr98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.

1
28
F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
5.x . Starting from trans-KwAu
y
Ž
.
Cl x instead of
AuCN; n CN 2231 cmy1
was filtered off
Ž .
C
CN
had formed
and the filtrate was then cooled to 48C. Colorless crys-
tals that formed were filtered off and dried in air 20%
Ž
Found: C, 20.9; H, 1.4; N, 12.2. Calc. for
2
2
NawAuCl x, however, we have now isolated and struc-
turally characterized the first Au complexes contain-
4
III
Ž
.
.
ing a C-bound nucleobase, trans-KwAu
Ž
CN.2Cl
2Cl 1,3-DimeU –
CN. Ž1,3-DimeU –C
Ž
1,3-Di-
y
5
y
meU –C
.
x
Ž
1
.
, w9-MeAHxwAu
Ž
CN
.
Ž
C H N O ClKAu: C, 20.8; H, 1.3; N, 12.1 .
.
8 7 4 2
5
y
5
y
5
C
Ž
.
.
x
Ž
2b
. In addition, the mixed nucleobase complexes
.
, and w9-EtGH xwAu
Ž
.
x
trans-wAu
2a
with 9-MeA
adjusted to ca. 4 with HNO3
formed was filtered off, washed with water, and dried in
air 47% Found: C, 28.7; H, 3.4; N, 21.5. Calc for
C H N O Au: C, 28.4; H, 3.4; N, 21.3
Ž
CN. Ž1,3-DimeU –C .Ž9-MeA
.x Ø 3H O
2
3
2
2
3
3b
trans-wAu
trans-wAu
Ž
.
. Complex 1
Ž
0.3 mmol in 2 cm water
.
was mixed
y
5
Ž
Ž
CN. Ž1,3-DimeU –C .Ž9-MeA
.
x
Ž
2a
3a
.
and
were
Ž
0.3 mmol
.
and the pH of the solution was
1 N . The solid that
2
y
5
CN. Ž1,3-DimeU –C .Ž9-EtGH
.
x
Ž
.
Ž
.
2
obtained, but due to their poor solubility in water, these
complexes could not be isolated as single crystals. The
described compounds extend the short list of X-ray
structurally characterized examples of Au nucleobase
coordination compounds w8–11x.
Ž
.
. Ž
.
.
1
4
20
9
5
III
y
5
w9-MeAHxwAu
2b . Compound 2b was prepared by reacting 1
mmol in 1 cm water
ca. 1 adjusted with 1 M HCl
was left at 258C overnight. The colorless crystals that
had formed were filtered off and dried in air 82%
Ž
Found: C, 28.8; H, 2.9; N, 21.7. Calc for
1,3-DimeU –C
ŽCN.2 ClŽ .x Ø H O
2
Ž
.
Ž
0.1
at pH
.
. The solution obtained
3
.
with 9-MeA 0.1 mmol
Ž .
Ž
2
. Experimental details
Ž
.
.
2
.1. Preparations
C H N O ClAu: C, 28.4; H, 2.9; N, 21.3 .
.
1
4
17
9
3
y
5
trans-KwAu
w13x, and 8-deutero-9-methyladenine w14x were prepared
as previously described; 1,3-dimethyluracil 1,3-Di-
meU and 9-ethylguanine 9-EtGH were of commercial
sources.
Ž
CN
.
Cl x w12x, 9-methyladenine
Ž
9-MeA
.
trans-wAu
Ž
CN. Ž1,3-DimeU –C .Ž9-EtGH
.
x Ø H O
2
2
2
2
y
5
Ž
3a
.
and w9-EtGH xwAu
Ž
CN. Ž1,3-DimeU –C
.
x
Ž
3b
.
.
2
3
Ž
Complex 3a was obtained by the method used for 2a
.
Ž
.
Ž
Ž
62%
Found: C, 31.1; H, 2.9; N, 22.0. Calc for
. After filtra-
.
, however, with 9-EtGH instead of 9-MeA.
y
5
trans-KwAu
Ž
CN. 2 Cl
0.3 mmol in 6 cm water
were mixed and the solution
Ž
1,3-DimeU – C
.
x
Ž
1
.
.
C H N O Au: C, 30.8; H, 3.1; N, 21.5
.
15
18
9
4
3
KwAu
Ž
CN
.
Cl x
Ž
.
and 1,3-Di-
pH 1.9
tion of 3a, the solution was cooled at 48C overnight.
The crystals of 3b that had formed were then filtered off
2
2
meU
Ž
0.3 mmol
.
Ž
.
allowed to react for 20 d at 258C. The yellow solid that
and dried in air
Ž
11%
.
.
Ž
Found: C, 31.2; H, 2.8; N, 22.3.
Table 1
Summary of crystal data, data collection parameters and refinements of compounds 1, 2b, and 3b
1
2b
3b
Formula
M
C H AuKClO N
462.69
C14 H17 AuClO N
591.77
C16 H17 AuO N
10
594.35
8
7
2
4
3
9
3
Crystal system
Space group
a Ž A˚ .
Orthorhombic
Pna21
14.068Ž7.
11.199Ž4.
7.720Ž2.
Monoclinic
Monoclinic
P2 rn
P2 rn
1
1
7.155Ž3.
9.852Ž4.
b Ž A˚ .
15.129Ž4.
17.671Ž8.
91.21Ž2.
1912Ž1.
2.06
7.9068Ž7.
25.81Ž1.
98.13Ž2.
1990Ž1.
1.98
c Ž A˚ .
b Ž8.
3
U Ž A˚ .
1216.3Ž8.
2.53
Dcalc Žg cmy3
.
Z
4
4
4
y1
m ŽMoK a. Žcm
FŽ000.
.
126.33
856
78.55
1136
74.19
1144
2
umax Ž8.
Octants collected
Number of measured reflections
Transmitted min, max
60
54
56
qh,qk,ql
2054
75.5, 100
1408
"h,qk,ql
4475
92.1, 99.9
2119
"h,qk,ql
5245
62.2, 99.9
3837
%
Number of independent reflections
w IG3s ŽI.x
Number of variables
R ŽFo.
153
254
271
0.026
0.029
1.37
0.043
0.049
1.25
0.041
0.048
1.53
Rw ŽFo.
Goodness of fit
Residuals Že A˚ y3
.
0.97, y1.10
1.46, y1.20
1.64, y1.77

F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
129
Calc for C H N O Au: C, 32.33; H, 2.89; N, 23.57
.
.
Table 3
1
6
17 10
3
Atomic coordinates of non-hydrogen atoms of 2b
Elemental analysis data are in better agreement if pres-
B Ž A˚ 2 .
0.14680Ž4. 0.21551Ž3. 3.109Ž8.
ence of one molecule of H O is assumed: C, 31.38; H,
Atom
x
y
z
2
3
.13; N, 22.88.
trans-wAu
Au
Cl
O2
O4
N1
N3
N7
N8
C1
C2
C3
C4
C5
C6
C7
C8
N1a
N3a
N6a
N7a
N9a
C2a
C4a
C5a
C6a
C8a
C9a
Ow
0.12320Ž8.
0.2093Ž8.
Ž
CN. Ž1,3-DimeU –C5.Ž1-MeC
y
.
x
Ž
4a
.
. The
0.2643Ž4.
y0.1917Ž7.
Ž .
0.2967Ž3.
0.0512Ž7.
7.4Ž1.
5.0Ž3.
2
y0.069Ž2.
compound was prepared on a NMR scale only and
identified by H NMR spectroscopy.
1
0.311 2
Ž .
0.0717 6
Ž .
4.9 3
Ž .
0.0459 7
y0.151Ž2.
y0.0818Ž9.
y0.0699Ž9.
0.236Ž1.
0.1297Ž8.
0.0602Ž7.
0.1669Ž9.
0.2645Ž9.
0.152Ž1.
0.0793Ž9.
0.009Ž1.
0.093Ž1.
4.8Ž3.
3.8Ž3.
5.0Ž3.
5.4Ž4.
7.4Ž5.
4.4Ž4.
5.1Ž4.
4.2Ž4.
3.9Ž3.
4.5Ž4.
3.6Ž3.
4.2Ž3.
3.2Ž2.
3.8Ž3.
4.7Ž3.
4.3Ž3.
3.3Ž2.
4.7Ž4.
3.4Ž3.
1
,3-Dimethyl-5-cyanouracil
was identified by mass spectrometry of an aged reaction
mixture of 1 and 1,3-DimeU in D O cf. text . Accord-
ing to H NMR spectroscopy, the solution contained a
single species: d 8.45
MS: mrz 165.1.
5
Ž1,3-Dime-5–CN–U. Ž .
0.124Ž2.
y0.254Ž2.
0.495Ž2.
y0.323Ž3.
y0.034Ž2.
0.243Ž2.
Ž
.
0.058Ž1.
2
1
y0.128Ž2.
y0.120Ž1.
y0.109Ž1.
0.009Ž1.
1H, s , 3,48 3H, s , 3.31 3H, s .
Ž . Ž . Ž .
0.170Ž2.
0.051Ž2.
0.040Ž1.
0.1528Ž9.
0.167Ž1.
2
.2. Instrumentation
y0.103Ž2.
y0.115Ž2.
0.363Ž2.
y0.008Ž2.
y0.007Ž1.
0.205Ž1.
0.1873Ž9.
0.2457Ž9.
0.4726Ž6.
0.4688Ž7.
0.4007Ž8.
0.3414Ž8.
0.3818Ž7.
0.493Ž1.
0.089Ž1.
Chemical analyses were performed by the University
of Dortmund Microanalytical Laboratory. IR spectra
KBr pellets were recorded on a Bruker IFS 113 v
0.1597Ž7.
0.0693Ž8.
0.1376Ž9.
y0.0242Ž9.
y0.0538Ž8.
0.136Ž1.
0.267Ž2.
Ž
.
1
y0.279Ž2.
y0.074Ž2.
0.217Ž2.
spectrometer. H NMR
on a Bruker AC200 instrument. Chemical shifts are
given in ppm and are referenced to internal TSP D O
and TMS
values taken from D O solutions. The mass spectrum of
200.13 MHz were measured
Ž .
0.171Ž2.
0.162Ž2.
Ž .
Ž .
0.070Ž2.
0.394Ž2.
0.398Ž2.
Ž
.
2
0.023Ž1.
0.4187Ž9.
)
DMSO-d6
Ž .
. pH denotes uncorrected pH
y0.018 2
y0.107 2
0.0390 9
Ž .
0.3918 8
Ž .
3.0 3
Ž .
Ž .
3.5 3
2
0.112 1
Ž .
0.4186 9
Ž .
5
was recorded on a WG Autospec instrument in D O
y0.078Ž1.
y0.096Ž1.
0.2230Ž7.
0.3379Ž9.
0.390Ž1.
0.0792Ž6.
4.1Ž3.
4.8Ž4.
4.7Ž3.
2
q
under EI conditions.
2
.3. X-ray crystallography
Ž
.
Isotropic equivalent displacement parameter defined as: 4r3
Ý Ý a a BŽi, j..
i
j
i
j
Suitable crystals for X-ray investigation of com-
pounds 1, 2b, and 3b were obtained according to the
above procedures. Details of crystal parameters, data
collection and refinements are summarized in Table 1.
Diffraction data were collected at room temperature
on an Enraf-Nonius CAD4 diffractometer equipped with
graphite monochromator and MoK a radiation ls
.71069 A . Intensities of three standard reflections,
Ž
˚
.
0
measured during data collections, did not show any
decay for all compounds. Reflections having intensities
I)3s I were corrected for Lorentz-polarization fac-
tors and used in subsequent refinements. An absorption
correction, based on empirical c-scan, was applied to
all data.
Table 2
Atomic coordinates of non-hydrogen atoms of 1
Ž .
B Ž A˚ 2 .
Atom
x
y
z
Au
K
Cl
0.22860Ž2.
0.0487Ž2.
0.1914Ž3.
0.3531Ž7.
0.1285Ž6.
0.3861Ž7.
0.2444Ž6.
0.046Ž1.
0.4143Ž7.
0.477Ž1.
0.3292Ž8.
0.180Ž1.
0.2074Ž8.
0.2717Ž7.
0.3571Ž7.
0.1104Ž9.
0.3488Ž9.
0.25870Ž3.
0.0459Ž2.
0.4618Ž2.
0.500
2.033Ž5.
2.77Ž5.
4.30Ž7.
4.2Ž2.
2.9Ž2.
2.7Ž2.
2.5Ž2.
5.1Ž3.
3.0Ž2.
5.0Ž4.
2.8Ž2.
3.7Ž3.
2.1Ž2.
2.5Ž1.
2.4Ž2.
2.9Ž2.
2.4Ž2.
0.0676Ž4.
0.5224Ž8.
0.593Ž1.
0.385Ž1.
0.597Ž2.
0.478Ž1.
0.711Ž2.
0.309Ž2.
0.682Ž3.
0.559Ž2.
0.425Ž2.
0.448Ž1.
0.509Ž3.
0.569Ž2.
0.631Ž2.
0.374Ž2.
Structures were determined by conventional Patter-
son method and subsequent Fourier syntheses. The final
O2
O4
N1
N3
N7
N8
C1
C2
C3
C4
C5
C6
C7
C8
y0.2522Ž8.
0.0042Ž8.
y0.0561Ž8.
y0.1229Ž7.
0.187Ž1.
refinements on F were carried out with anisotropically
o
thermal parameters for all non-H atoms. Hydrogen atoms
Ž .
C–H bond distance 0.95 A˚
at calculated positions
were introduced in final cycles of refinements as fixed
0.344Ž1.
y0.081Ž2.
y0.1521Ž9.
y0.224Ž1.
y0.0088Ž9.
0.0847Ž7.
0.0599Ž9.
0.213Ž1.
contribution Bs1.3=Beq of their bonded atom . The
final weighting scheme was unit for all the compounds.
The refinement of the enantiomer of 1 gave Rs0.029
and Rws0.032, confirming the correct assignment of
the absolute configuration for this structure.
Ž
.
Atomic scattering factors and anomalous dispersion
0.310Ž1.
parameters were taken from Ref. w15x. All calculations
Isotropic equivalent displacement parameter defined as: Ž4r3.
Ý Ý a a BŽi, j..
were carried out on a m-VAX2000 computer using the
Enraf-Nonius MolEN package w16x. Final atomic coor-
i
j
i
j

1
30
F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
Table 4
Atomic coordinates of non-hydrogen atoms of 3b
is observed, which is of low intensity, and formation of
a yellow insoluble solid, identified by IR and elemental
B Ž A˚ 2 .
0.07025Ž4. 0.21590Ž1. 2.438Ž5.
0.030Ž1.
Atom
x
y
z
analysis as AuCN, has occurred. With very long reac-
)
0.09384Ž3.
0.6408Ž6.
0.1848Ž6.
0.5195Ž7.
0.4102Ž7.
0.6443Ž9.
0.5301Ž8.
0.418Ž1.
tion times
Ž
ca. 3 months, pH 1.4
.
5 remains as the
Au
O2
O4
N1
N3
C1
C2
C3
0.3570Ž3.
0.3305Ž3.
0.2816Ž3.
0.3447Ž3.
0.2603Ž5.
0.3289Ž3.
0.3980Ž4.
0.3139Ž3.
0.2643Ž2.
0.2462Ž4.
0.1611Ž3.
0.1289Ž4.
0.2716Ž3.
0.3026Ž3.
0.1675Ž2.
0.1460Ž4.
0.4949Ž3.
0.5582Ž3.
0.6255Ž3.
0.5508Ž3.
0.4310Ž3.
0.4666Ž4.
0.5773Ž3.
0.5030Ž4.
0.4805Ž3.
0.5086Ž4.
0.4233Ž4.
0.4799Ž7.
0.4670Ž9.
3.6Ž1.
3.8Ž1.
2.9Ž1.
2.6Ž1.
4.9Ž3.
2.8Ž2.
4.0Ž2.
2.5Ž1.
1.9Ž1.
3.4Ž2.
3.5Ž2.
5.0Ž2.
3.0Ž2.
3.9Ž2.
2.3Ž1.
5.4Ž2.
4.4Ž2.
2.9Ž1.
4.4Ž2.
4.0Ž2.
3.7Ž2.
5.9Ž2.
3.0Ž2.
3.5Ž2.
2.9Ž2.
3.1Ž2.
5.3Ž3.
11.9Ž6.
11.7Ž7.
only species in solution. By then, more AuCN has
precipitated. The new compound 5 was identified at that
point by mass spectrometry as 1,3-Dime-5–CN–U. Its
formation appears to be analogous to that of 1,3-di-
y0.080Ž1.
0.104Ž1.
y0.018Ž1.
0.162Ž2.
0.039Ž1.
y0.085Ž2.
y0.016Ž1.
0.058Ž1.
0.114Ž1.
y0.047Ž1.
y0.111Ž1.
0.195Ž1.
0.269Ž1.
0.079Ž1.
0.079Ž1.
0.169Ž1.
0.127Ž1.
0.074Ž1.
0.197Ž1.
0.311Ž1.
0.318Ž2.
0.134Ž1.
0.248Ž1.
0.245Ž1.
0.179Ž1.
0.354Ž2.
0.386Ž3.
0.259Ž3.
y
methyl-5-chlorouracil from AuCl4 and 1,3-DimeU w7x.
The minor resonance at d 7.38 most likely is due to
0.2833Ž8.
0.2780Ž7.
0.3959Ž8.
0.1796Ž9.
0.2312Ž9.
0.0154Ž8.
y
C4
C5
C6
C7
N7
C8
N8
C9
a Cl
wAu
-DimeU –C .ŽOD
hydrolysis product of 1, hence trans-
y
5
Ž
CN. Ž1,3-DimeU –C .ŽOD2 .x r trans-wAuŽCN. Ž1,
2 2
5
y
y
3
.
x , since its intensity increases at
the expense of the d 7.51 resonance with AgNO3
added.
y0.0309Ž8.
y0.0939Ž8.
y0.189Ž1.
0.3203Ž6.
N9
O6a
N1a
N2a
N3a
N7a
N9a
C2a
C4a
C5a
C6a
C8a
C9a
C10a
0.1834Ž7.
0.0612Ž8.
y0.0523Ž7.
0.0543Ž8.
y0.1308Ž8.
0.0616Ž8.
y0.0331Ž8.
0.0841Ž8.
0.2074Ž9.
y0.076Ž1.
y0.269Ž2.
y0.358Ž3.
Isotropic equivalent displacement parameter defined as: Ž4r3.
Ý Ý a a BŽi, j..
i
j
i
j
dinates and equivalent isotropic thermal parameters are
given in Tables 2–4. Further details on the crystal
structure analyses may be obtained from E.Z. on re-
quest.
3
3
3
. Results and discussion
.1. Formation of complexes
.1.1. Formation of 1
When the reaction between trans-KwAu
Ž
CN.2Cl x
2
1
and 1,3-DimeU is followed by H NMR spectroscopy
)
Ž
pH 1.9, D O, 1:1 ratio
.
, formation of several water
2
soluble compounds is observed. Within 1 day of reac-
tion
Ž
Fig. 1a
.
6
a new singlet at d 7.51, upfield shifted
from the H
Ž
.
doublet of 1,3-DimeU, is observed. This
y
new resonance is assigned to H 6 of the 1,3-DimeU
Ž .
ligand of compound 1. The chemical shift of this reso-
nance is in agreement with similar Au–C uracil com-
pounds observed before w7x. Within ca. 20 days of
reaction Fig. 1a–d compound 1 represents the main
product. At this stage, another singlet at d 8.45 due to 5
Ž
.
Fig. 1. Reaction between trans-KwAuŽCN. Cl x and 1,3-DimeU as
2
2
Ž
.
1
followed by H NMR spectroscopy Žlow field section only; D O;
2
)
pH 1.9..

F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
131
Complex 1 was isolated in crystalline form on a
After isolation of 3a, a second species was obtained
preparative scale and characterized by X-ray analysis
in low yield from the filtrate and characterized by X-ray
y
5
Ž
vide infra
spectrum of 1 shows the most significant changes in the
bands due to n C5O and n C5C : relative to the free
base, these very intense bands are shifted to lower
.
. As compared to free 1,3-DimeU, the IR
analysis as w9-EtGH xwAu
Ž
CN. Ž1,3-DimeU –C
.
x 3b.
2
3
1
)
The H NMR spectrum of this compound
0.8
guanine, w9-EtGH x , and H
Ž
D O, pH
2
Ž
.
Ž
.
.
shows signals corresponding to protonated 9-ethyl-
q
y
Ž
6
.
of 1,3-DimeU in the
. Formation of 3b cannot be
rationalized at present. We rule out the possibility that
CN
the starting compound KwAu Cl x was contami-
CN
nated with KwAu Clx, however, considering the
simplicity of the IR spectrum of the starting material 1
2
y1
energies
Ž
1692 and 1623 cm
.
. The two intense and
expected range d 7.58, s
Ž .
y1
sharp bands at 755 and 815 cm
replaced by a weaker band at 766 cm . The weak
of 1,3-DimeU are
y1
Ž
.
2
2
y1
absorption at 2170 cm
is assigned to n
Ž
C[N
.
. The
Ž
.
3
changes observed for the uracil modes are very similar
5
y1
to those described previously for mercury binding to C
of 1,3-DimeU w4x.
Ž
single, sharp absorption at 2189 cm
.
.
y
3
.1.4. Reaction of 1 with 1-MeC
The addition of 1-MeC to a solution of 1
–5, 1:1 ratio leads to the formation of the neutral
D O, pH)
2
Ž
3
.1.2. Reaction of 1 with 9-MeA
Reaction of 1 with 9-MeA H O, pH 4–5, 1:1 ratio
gives the neutral complex trans-wAu
4
.
Ž
.
2
y
complex trans-wAu
Ž
CN. Ž1,3-DimeU .Ž1-MeC
.
x 4a.
Ž
CN. Ž1,3-
2
2
1
y
5
The H NMR spectrum of 4a
Ž
DMSO-d6
.
shows reso-
DimeU –C .Ž9-MeA
soluble but dissolves in DMSO and DMF. The H NMR
spectrum of 2a DMSO-d displays a singlet due to
of 1,3-DimeU at d 7.46 and a relatively broad
resonance at d 8.37. The latter is assigned to both H
and H of 9-MeA, since upon use of 8-deuterated
-MeA, the integral of this signal decreases by 50%. A
.x 2a. This compound is not water
1
nances at d 8.83 and d 8.63 corresponding to ex-
changeable protons of the amino group of 1-MeC and
Ž
.
6
3
y
doublets due to H6
of 1-MeC. The H
ligand is normal
Ž
6
d 7.93, J 7.5 Hz
.
and H5
Ž
d 6.04
.
H 6
Ž .
y
Ž
.
resonances of the 1,3-DimeU
d 7.39, s . The three N-methyl reso-
nances of the two ligands occur between d 3.21 and d
2
Ž .
Ž
.
8
Ž .
9
3
3
.39. The 1-MeC resonances are consistent with N
third signal, at d 8.90, disappears after addition of D O,
2
metal binding.
and is therefore assigned to the amino group of the
No reaction was observed between 1 and 1-methyl-
9
-MeA. The large downfield shift of this resonance
relative to the free ligand 9-MeA in the same solvent wd
–H . . . O hydrogen bond-
)
thymine
Ž
1:1, D O, pH 2–9
.
. Considering our previ-
2
3
III
ous findings of N metalated Au complexes of uracil
7
.19x is consistent with N
Ž
6
.
4
Ž .
y
and thymine ligands w9,11x, this result was unexpected.
ing between 9-MeA and 1,3-DimeU , as previously
seen in mixed thymine,adenine complexes w17,18x. Since
3
3
.2. Crystal structures
7
only the N linkage isomer is capable of forming this
y
5
1
.2.1. trans-K Au CN Cl 1,3-DimeU –C 1
)] ( )
[
(
)
(
intramolecular H bond, yet not the N linkage isomer,
2
y
III
w
Ž
.
Ž
The crystal is built up by Au CN Cl 1,3-DimeU –
Au coordination to the adenine nucleobase must be
2
5
y
q
7
.
x
w x
C
anions and K cations. The ORTEP 19 drawing
through N .
of the anion, together with the atom numbering scheme
is shown in Fig. 2. Coordination bond lengths and
angles for this and other structures are given in Table 5.
If the reaction is carried out at a pH below ca. 1
y
Ž
HCl, 1 M , protonation of 9-MeA andror excess Cl
.
III
prevents binding of Au and instead crystals of w9-
y
5
MeAHxwAu
Ž
CN.2Cl
Ž
1,3-DimeU –C
.
x 2b are formed
1
in quantitative yield. The H NMR spectrum of 2b
D O, pD 1.2 is consistent with the presence of proto-
Ž
.
2
nated 9-MeA.
3
.1.3. Reaction of 1 with 9-EtGH
Upon reaction of 1 with 9-EtGH
Ž
H O, pH 4–5, 1:1
2
ratio
. the neutral compound trans-wAuŽCN. Ž1,3-Di-
2
5
1
y
meU –C .Ž9-EtGH
.
x 3a is formed. According to H
DMSO-d , 1,3-DimeU and 9-
NMR spectroscopy
Ž
.
6
EtGH are present in 3a in a 1:1-ratio. Gold binding to
7
N of 9-EtGH is concluded from a considerable down-
field shift of the H
relative to free 9-EtGH and the presence of N
1.32 and of the N H2 resonance at d 6.95. The
signal at d 7.43 is assigned to H
Ž
8
.
guanine resonance
Ž
q1.0 ppm
.
1
Ž .
H at d
1
2
Ž .
y
6 of 1,3-DimeU . We
Ž .
have previously isolated a related mercury compound
with this coordination pattern w5x.
Fig. 2. An ORTEP drawing and atom numbering scheme of the anion
of 1 Ž50% probability thermal ellipsoids..

1
32
F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
Table 5
very distorted pentagonal bipyramid. Three coordinating
oxygens pertain to carboxyl and four nitrogen atoms to
cyano groups of different complex units.
Coordination bond lengths Ž A˚ . and angles Ž8. and dihedral angles a
Ž8. between the coordination and the 1,3-DimeUy plane
1
2b
3b
Au–X
2.340Ž3.
2.042Ž8.
2.01Ž1.
2.04Ž1.
172.4Ž6.
91.4Ž4.
86.8Ž3.
89.2Ž5.
92.4Ž5.
177.8Ž5.
53.6Ž3.
2.358Ž6.
2.082Ž7.
2.053Ž6.
1.98Ž1.
1.989Ž9.
179.2Ž3.
91.2Ž3.
90.8Ž3.
89.0Ž3.
89.1Ž3.
177.2Ž3.
53.9Ž2.
y
5
3
.2.2. trans-[Au(CN) Cl(1,3-DimeU – C )][9-
2
Au–CŽ5.
2.02Ž2.
1.97Ž1.
1.99Ž2.
175.6Ž5.
91.9Ž5.
87.5Ž5.
90.5Ž6.
90.1Ž6.
179.1Ž7.
57.8Ž4.
Au–CŽ7.
MeAH]6H O (2b)
2
Au–CŽ8.
y
The crystal contains Au CN Cl 1,3-DimeU –
w
Ž
.
Ž
2
X–Au–CŽ5.
X–Au–CŽ7.
X–Au–CŽ8.
CŽ5.–Au–CŽ7.
CŽ5.–Au–CŽ8.
CŽ7.–Au–CŽ8.
5
y
C
.
x anions, 9-MeAH cations and crystallization water
molecules. Fig. 3 provides the molecular structures of
the ions, together with the labelling scheme. The geom-
etry of the anion is very similar to that of 1, within the
experimental errors Table 5 . The 1,3-DimeU ring,
planar within "0.05 A, makes an angle of 57.8 4 8 with
y
Ž
˚
.
a
Ž .
the mean coordination plane. The protonated purine
Ž .
base is planar within "0.02 2
A˚ . The recent statistical
ŽXsCl in 1 and 2b,sCŽ9. in 3b..
analysis of the geometries of neutral and N1 protonated
adenine w24x indicates that on protonation the main
III
5
Au is bound to the nucleobase through C and the
geometrical variations between the two species consist
square planar coordination is completed by Cl, trans to
C , and two trans cyano groups. The coordination
geometry about Au presents a slightly tetrahedral
in a lengthening of the N 1 –C 2 distance, a shortening
Ž . Ž .
5
of the C
–N
angles involving N
Ž
1
2
.
–C
–N
Ž
6
3
.
bond as well as in a widening of the
III
C
Ž
2
.
Ž
.
Ž
.
angle and a narrowing of the other
5
Ž .
and Cl are displaced by q0.06 A˚ and
distortion: C
Ž .
by y0.06 A˚ out of their mean plane,
and C 8
Ž
1
.
. Within the limits of the accuracy
C
Ž
7
.
reached in the refinement of 2b, the geometry of the
cation seems to be closer to that reported for the
protonated form in most respects.
A network of H bonds involves the anions, cations
and water molecules. Specifically, the H bond between
˚
˚
whereas Au is displaced by q0.085 A. The 1,3-Di-
y
meU ligand is planar within "0.04 A and its mean
plane makes a dihedral angle, a, of 53.7 8 with the
mean coordination plane. The Au–C and the mean
A˚ , respec-
Au–CN distances are 2.042 and 2.03
A˚ is signifi-
tively. The Au–Cl distance of 2.340
A˚ re-
cantly longer than the mean value of 2.280
3
Ž .
5
Ž .
Ž
8
.
1
Ž .
O
0
Ž
2
.
and N
.5yz is 2.94
two short with N
A˚
2.68 and O4
at 1qx, qy, qz
A˚
2.94
Ž
6a
.
of the unit at y0.5yx, y0.5qy,
A˚ , whereas Ow makes four contacts,
1a at 0.5qx, 0.5yy, y0.5qz
A˚
2.75 and two long, with N
A˚
Ž .
2.91 and O 2 at yx, yy, yz
3
Ž .
2
Ž .
2
Ž .
Ž
.
y
ported in wAuCl x w20x and than those of about 2.270
A, reported in Au complexes having weak trans-in-
fluencing donors, such as Cl and N w21–23x. The com-
parison indicates the strong trans-influence exerted by
the C-bound uracil ligand. Recently, new complexes of
the type wAu Cl Lx, where L is a chelate ligand con-
sisting of a phenyl group C-bonded to Au and bearing a
N-donor substituent such as oxazoline andror dimeth-
ylaminomethyl, have been reported w24x. In these com-
plexes, the Au–Cl distances, trans to a C-sp atom,
vary from 2.353
significantly from that here reported. This effect has
been also observed in Pt complexes where Cl is trans
to a 1,3-DimeU –C w4x. In fact, in the latter, the Pt–Cl
distance is found to be 2.40
than the mean values of 2.304
Pt–Cl distances in wPtCl3Ž9-MeGH2
methylguaninium
w25x.
The internal bond lengths and angles in 1,3-DimeU
reflects, within the experimental errors, the trend re-
ported for uracil and thymine in a statistical survey of
4
Ž
Ž
2
.
.
Ž
Ž
2
2
.
.
7
Ž .
III
˚
Ž
Ž
.
.
Ž
Ž
2
.
.
.
III
y
5
3.2.3. [Au(CN) (1,3-DimeU –C )][9-EtGH ] (3b)
2
3
2
y
Crystals of 3b contain wAu
Ž
CN. Ž1,3-DimeU –C5.xy
2
3
anions and protonated 9-EtGH bases. A perspective
view of the compound, together with the atom number-
2
III
ing scheme is shown in Fig. 4. The Au coordination
Ž
3
.
to 2.369
Ž
3
.
A˚ and do not differ
geometry is essentially square planar, the four donor
˚
carbon atoms being coplanar within "0.02 A, while Au
II
˚
is displaced by 0.01 A from their mean plane. The
y
5
y
˚
1,3-DimeU ligand, planar within "0.02 A, makes a
dihedral angle of 53.9 8 with the coordination plane.
Ž
1
.
Ž
A˚ , significantly longer
A˚ of the two trans
2
Ž .
4
.
The geometry of this ligand appears to be determined
with a better accuracy than those of 1 and 2b. Compari-
son of internal bond lengths and angles with the corre-
sponding average values reported by Clowney et al. w26x
for the neutral 1,3-DimeU suggests that significant vari-
ations are a lengthening of N 1 –C 6 and of
Ž . Ž .
. Ž0.05 A˚
.
x
Ž
9-MeGH s9-
2
.
y
nucleobases w26x. The influence of the bonding through
C
Ž
5
.
1
–C
–C
Ž
6
2
. Ž0.04 A˚
distances and a shortening of the
. Ž0.06 A˚
.
one, with respect to the neutral
.
5
C
on the geometry of the ligand, if any, cannot be
N
Ž
.
Ž
detected
Ž
see structure 3b
.
.
form. Correspondingly, a narrowing of the C 1 –N 1 –
Ž . Ž .
q
The K ion has seven nearest neighbors with dis-
A˚ , making a
tances varying from 2.658 to 3.17
C
Ž
6
. Ž5.98
.
and of N
Ž
2
1
.
–C
Ž
1
6
.
–C
–C
Ž
6
5
. Ž6.78
.
angles and a
one are ob-
Ž
9
.
Ž
1
.
widening of the C
Ž
.
–N
Ž
.
Ž
. Ž3.58.

F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
133
Fig. 3. An ORTEP drawing and atom numbering scheme of complex anion and 9-MeAH cation of 2b.
served. The Au–C
significantly different from those found in 1 and 2b
Table 5 . The values of the two cis Au–CN distances
A˚ are very similar and close to
of 1.98 and 1.899
5 distance of 2.053 6
Ž . Ž .
A˚ is not
the mean values of 1.98 2 and 2.03 1
Ž . Ž .
A˚ found in 1
and 2b, respectively, and do not differ significantly
A˚ found in the
from the mean value of 2.007
wAuŽCN.4 x anion w27x. The Au–CN bond length, trans
Ž
.
1
7
Ž .
y
Ž
.
Ž
9
.
Fig. 4. An ORTEP drawing and atom numbering scheme of compound 3b.

1
34
F. Zamora et al.rJournal of Organometallic Chemistry 552 (1998) 127–134
5
7
Ž .
A˚ and its lengthening confirms the
w2x M. Goodgame, K.W. Johns, Inorg. Chim. Acta 30 Ž1978. L335.
to C , is 2.082
strong trans influence exerted by the s-bonded C . It is
worthwhile to note that the C –N bond distance of
A˚ appears significantly shorter than the C
.02
and C –N distances, being 1.15 and 1.14
A, respectively, and than those found in 1 and 2b,
A˚ . Analogously, in
which range from 1.10 to 1.15
w27x, the mean bond length is
A˚ . Unfortunately, we were not able to find in
5
w3x L. Skulski, A. Kujawa, T.M. Kujawa, Bull. Pol. Acad. Sci.
Chem. 35 Ž1987. 499.
Ž
9
.
9
Ž .
w4x M. Hopp, A. Erxleben, I. Rombeck, B. Lippert, Inorg. Chem. 35
¨
1
N
˚
Ž
1
.
7 –
Ž .
1
Ž1996. 397.
Ž
7
.
Ž
8
.
Ž
8
.
Ž
1
.
Ž
.
w5x F. Zamora, M. Sabat, B. Lippert, Inorg. Chem. 35 Ž1996. 4858.
w6x F. Zamora, M. Kunsman, M. Sabat, B. Lippert, Inorg. Chem. 36
Ž1997. 1583.
Ž
2
.
1
Ž .
w7x F. Zamora, B. Fischer, P. Amo-Ochoa, A. Schimanski, B.
y
the anion wAu
CN
Ž . x
4
Lippert, to be submitted.
1
.126
9
Ž .
w8x M.S. Holowczak, M.D. Stancl, G.W. Wong, J. Am. Chem. Soc.
the literature accurate structural determinations of square
planar complexes, containing cyano groups trans to a
s-bonded C atom. The observation that a lengthening of
the Au–CN bond leads to a simultaneous shortening of
the C–N one is in agreement with expectations.
107 Ž1985. 5789.
w9x W. Micklitz, B. Lippert, G. Muller, P. Mikulcik, J. Riede, Inorg.
¨
Chim. Acta 165 Ž1989. 57.
w10x E. Colacio Rodriguez, J. Ruiz Sanchez, J. de Dios Lopez
Gonzalez, J.M. Salas-Peregrin, M.J. Olivier, M. Quiros, A.L.
Beauchamp, Inorg. Chim. Acta 171 Ž1990. 151.
The internal bond lengths and angles of the 9-EtGH2
cation agree, within the experimental errors, with the
mean values reported by Taylor and Kennard w28x as
w11x B. Fischer, E.C. Fusch, S. Poschmann, G. Oswald, G.
Tr o¨ tscher-Kaus, B. Lippert, to be submitted.
w12x M. Becka, J. Hornov ´a , J. Haring, Z. Anal. Chem. 214 Ž1965.
4
08.
well as with those reported for wAuCl xw9-EtGH x w20x.
4
2
w
3 G. Kr u¨ ger, Z. Physiol. Chem. 80 1893 434.
x Ž .
1
A network of H bonds, based on O
Ž
2
.
. . . N
Ž
1a. Ž1y
w14x R. Beyerle-Pfn ¨u r, B. Lippert, Inorg. Chim. Acta 66 Ž1982. 141.
x, yy, 1yz
.
, O
7a. Ž0.5yx, y0.5qy, y0.5yz
A˚ , respectively, con-
, 2.82 and 2.86
Ž
4
.
. . . N
Ž
2a. Žyx, yy, 1yz
.
and
w15x International Tables for X-ray Crystallography, Vol. 4, Kynoch
N
Ž
7
.
. . . N
Ž
9
.
contacts
Press, Birmingham, 1994.
w16x C.K. Fair, MolEN. An Interactive Intelligent System for Crystal
of 2.875
Ž
.
Ž
1
.
1
Ž .
Structure Analysis. Enraf-Nonius, Delft, The Netherlands, 1990.
nects the anions and cations. The latter H bond is a
Ž .
further support to the N 7a protonation in the free base.
w17x O. Krizanovic, M. Sabat, R. Beyerle-Pfnur, B. Lippert, J. Am.
¨
Chem. Soc. 115 Ž1993. 5538.
w18x A. Schreiber, M.S. Luth, A. Erxleben, E.C. Fusch, B. Lippert, J.
¨
Am. Chem. Soc. 118 Ž1996. 4124.
Acknowledgements
w19x C.K. Johnson, ORTEP, Report ORNL-3794, Oak Ridge Na-
tional Laboratory, Oak Ridge, TN, 1965.
This work was supported by the Deutsche
Forschungsgemeinschaft DFG , the Fonds der Chemis-
chen Industrie FCI , and Ministero della Ricerca Scien-
tifica e Tecnologica MURST , Rome and Consiglio
Nazionale delle Ricerche CNR . This research was part
of COST D1 and HCM programs. We thank A. Schi-
w2
x
Ž
.
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