their spectral IR and NMR behavior agreed with published
data.
are reported at the first time at which they were observed
although conceivably product could have been present at an
earlier time. The reaction conditions for the set of 1a, 2a–
9mxan, 1b, 2b–9mxan, 10% 1a :90% 1b, 10% 2a :90% 2b–
9mxan experiments at 37 ЊC is different from the others
reported in that the reaction is followeed in situ in the thermo-
statted NMR probe. Reactions were repeated in duplicate or
triplicate.
Preparation of cis-[Pt(NH3)2Cl4] 1b
In a round-bottom flask fitted with a water condenser, 1a
(0.5066 g, 1.7 mmol) was dissolved in 2 HCl (50 cm3) at room
temperature. The solution was filtered to remove undissolved
solid. Chlorine gas was bubbled into this solution for 6 min
(yellow solid formed in the solution after 5 min), followed by 30
min stirring, followed by 10 min of chlorine gas addition, finally
by 30 min stirring. After overnight refrigeration of the solution/
solid, 0.5536 g, 88%, of bright yellow solid was collected
(Found: H, 1.6; N, 7.6; Cl, 38.2. Calc. for Cl4H6N2Pt: H, 1.55;
N, 7.6; Cl, 38.5%).
Proton NMR measurements
The NMR measurements were performed using a Bruker 250
MHz spectrometer located in the Blue Hen NMR Complex at
University of Delaware, Newark, DE, on a GE 300 MHz
spectrometer located at Virginia Commonwealth University,
Richmond, VA, and on a Bruker WM 300 spectrometer at
Leiden University, the Netherlands.
Preparation of cis-[Pt(NH3)(cha)Cl2] 2a and cis-[Pt(NH3)(cha)-
Cl4] 2b
The compound cis-[Pt(NH3)(cha)Cl2] 2a was prepared by
Acknowledgements
literature methods.23
Support for the research has been received from the Petroleum
Research Fund, the William and Flora Hewlett Foundation of
Research Corporation and a National Science Foundation
Visiting Professorship for Women. The kind assistance of
Cees Erkelens and Fons Lefevre with operation of the 300
MHz NMR at Leiden University is gratefully acknowledged.
Colonial Metals, Inc. and Johnson Matthey are thanked for the
loan of platinum complexes.
Method 1 for cis-[Pt(NH3)(cha)Cl4]. Compound 2a (0.116 g,
0.30 mmol) was dissolved in 2 HCl (200 cm3) held at 70 ЊC.
After filtration, chlorine gas was bubbled into this solution
for six min as the solution became darker yellow in color. The
solution was allowed to cool with stirring, then evaporated
slowly to 20 cm3 with heat. After cooling, 0.052 g, 33% of bright
yellow solid, 2b was isolated. NMR [300 MHz, DCON(CD3)2,
standard SiMe4]: δH 1.10, 1.18, 1.23, 1.31, 1.43, 1.47, 1.56, 1.59,
1.69, 1.72 (8 H, m); 2.35, 2.39 (2 H, d); 3.07 (1 H, m, br); 5.82–
6.17 (5 H, spt) (Found: C, 15.8; H, 3.5; Cl, 31.4; N, 6.1. Calc. for
C6H16Cl4N2Pt: C, 15.9; H, 3.6; Cl, 31.3; N, 6.2%).
References
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Preparation of [Pt(dien)Cl]Cl 3a and mer-[Pt(dien)Cl3]Cl 3b
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Platinum complex–nucleobase reaction conditions
Saturated solutions of reactants were prepared by mixing
platinum complex (≈10 mg, 0.025 mmol) with 9-methylxanthine
(5 mg, 0.025 mmol) in D2O (0.5 cm3). In most cases this resulted
in incomplete dissolution of the platinum complexes. However,
platinum complex slowly dissolves during the reaction. In cases
where 9-methylxanthine is more soluble than the platinum
compounds, this procedure results in an excess of nucleobase.
Only in the case of [Pt(dien)Cl]Cl did the platinum complex
completely dissolve. For reactions run at 28 and 50 ЊC, reaction
mixtures were incubated in NMR tubes at the temperature
specified and spectra taken at various time intervals. Products
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3620
J. Chem. Soc., Dalton Trans., 1997, Pages 3615–3621
Roat, Rosette M.
