Synthesis and Molecular Structure of the First Metal Complex of an Analogue of Guanine with Pd^II−C(8) Binding

Abstract

The reaction of cis-[PdCl2(PPh3)2] with 8-(methylthio)theophylline (HL) leads to the formation of trans-[PdCl(L)(PPh3)2], an N(7)−Pd-bonded complex, which under mild conditions converts into the mixed-ligand complex trans-[Pd(L‘)(L)(PPh3)2] (HL‘ is theophylline). Noteworthy, the latter represents the first example of a C(8)−Pd-bonded complex.

Synthesis and Crystal Structure of a New Sulfur-Palladium-Nitrogen Complex

“…The distance Pd1±Cl2 (232.2(2) pm) is somewhat longer than the distance Pd1±Cl1 (228.9 (1) [11]. The distances Pd1±S1 of 226.4(1) pm and Pd1±N1 of 203.2(4) pm are comparable to those found in other palladium-sulfur complexes [12,13]. One molecule of methanol is bound to the hydrazinic NH 2 -group via a hydrogen bridge (N2´´´O2 276.1(7) pm).…”

Studies on the coordination chemistry of methylated xanthines and their imidazolium salts. Part 1: benzyl derivatives

“…The acidic character is actually remarkable when the substituent on N(7) is a proton (theophylline, 1). This prediction of our model totally agrees with the experimental observations that have previously been reported [3,9], where theophylline can be easily deprotonated in presence of a basic late transition metal precursor or a late transition metal precursor in basic conditions, yielding N(7) coordinated species. The preferential coordination site at N(7), which has also been theoretically studied [3,61], has previously been proposed not only for theophylline derivatives but also for analogous molecules such as guanine and adenine.…”

“…both N (9) and N(7) have been substituted by a benzyl group) as a minor reaction byproduct that could be characterized. The 1,3-dimethyl-9,7-dibenzylxanthinium bromide (tphBz 2 Br, 1a 0 ) or other analog N(7) substituted species could be very interesting as potential carbene precursors, since a C (8) binding might be enhanced.…”

“…However, there are only a few reports of inorganic compounds with functionalized xanthines [9]. Among them, 8-alkyl-derivatives from theophylline [9] and N-methyl caffeine [10][11][12][13] have been reported.…”

“…Among them, 8-alkyl-derivatives from theophylline [9] and N-methyl caffeine [10][11][12][13] have been reported. To the best of our knowledge, none of those exist with C (8) or N(9)-substituted modified theobromine.…”