Reactions of chloro(triphenylphosphine)gold(I) and [µ-l,2-bis(diphenylphosphine)ethane]-bis[bromogold(I)] with oxopurine bases. Molecular and crystal structure and bonding of (theophyllinato)(triphenylphosphine)gold(I)

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Abstract
The interaction of chloro(triphenylphosphine)gold(I) and [µ-1,2-bis(diphenylphosphine)ethane]bis[bromogold(I)] with oxopurine derivatives under basic conditions has been investigated. The resulting complexes, [Au(PPh33)L][{Au(PPh3)}2(µ-L)], [LAu(µ-dppe)AuL], and [Au(µ-dppe)-(µ-L)Au][L = purine anion, dppe = 1,2-bis(diphenylphosphine)ethane], containing one or two N-bonded gold(I) phosphine groups were characterized by means of 1H and 13C n.m.r. and i.r. spectroscopy. The crystal structure of the complex (theophyllinato)(triphenylphosphine)-gold(I) was determined by X-ray crystallography. The compound is triclinic, space group P, with a= 9.061(2), b= 9.762(4), c= 13.588(4)Å, α= 71.30(2), β= 87.20(2), γ= 86.10(2)°, and Z= 2. The structure was refined anisotropically to R= 0.039 and R′= 0.044, on the basis of 5 150 observed reflections. The crystal contains discrete [Au(PPh3) L] molecules (L = theophyllinate anion) with no unusually close intermolecular contacts. The co-ordination of the gold atom is almost linear, P–Au–N(7) 176.1(2)° gold–nitrogen and gold–phosphorus bond distances of 2.047(7) and 2.231(2)Å respectively. Other bond lengths and bond angles are normal. The Au ⋯ O(6) distance of 3.317(6)Å indicates that there is no significant gold–carbonyl bonding.