Polyhedron 18 (1999) 1401–1409 13 15 31 C, N and P NMR study of the disproportionation of cyanogold(I) 13 15 complexes: [R PAu C N] 3 1 * Anvarhusein A. Isab , M. Sakhawat Hussain , M. Naseem Akhtar, M.I.M. Wazeer, A. Rahman Al-Arfaj Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia Received 13 May 1998; accepted 9 December 1998 Abstract 13 15 1 13 15 2 The disproportionation of cyanogold(I) complexes of general formula [R PAu C N] forming [(R P) Au] and [Au( C N) ] ions 3 3 2 2 13 15 31 has been investigated using C, N and P NMR spectroscopy for a series of phosphines with R5cyclohexyl, i -propyl, Et, Me, 13 cyclohexyl / diphenyl, o-tolyl, p-tolyl, m-tolyl, p-tolyl/diphenyl, allyl/diphenyl, phenyl, tri(cyanoethyl) CEP, and 1-naphthyl. The C 13 15 13 13 15 NMR of the C N group in these complexes exhibited two distinct resonances, one due C in the starting [R PAu C N] complex and 3 13 15 2 31 31 13 15 the second in the [Au( C N) ] anion. The P NMR spectra revealed two P resonances due to [R PAu C N] complex, and the 2 3 1 15 13 15 13 15 2 [(R P) Au] cation. The N NMR revealed only an averaged resonance due to [R PAu C N] and [Au( C N) ] anion, except in the 3 2 3 2 13 15 13 15 1 13 15 2 31 13 cases of [Me PAu C N] and [Et PAu C N] where two resonances were observed. The coupling constants, J( C– N), J( P– C) 3 3 3 31 15 and J( P– N) were obtained for all complexes and the free energies of activation for ligand disproportionation were determined using 31 1 P– h Hj NMR band shape analysis.  1999 Elsevier Science Ltd. All rights reserved. Keywords: Disproportionation; Cyanogold(I) complexes; NMR of gold phosphine complexes 2 1. Introduction enters into the red blood cells in the form of [Au(CN) ] 2 has been a subject of several recent studies [11–15]. A 2 large formation constant [16] for [Au(CN) ] (log b 5 Gold(I) cyanide forms linear monomeric complexes of 2 2 36.6) is believed to drive the reaction in Eq. (1) in the the type [(R P)AuCN] where PR 5different tri(alkyl / 3 3 2 forward direction generating [Au(CN) ] anions which aryl)phosphines [1–3]. However, the tris(2-cyano- 2 ultimately enter the red blood cells. ethyl)phosphine (CEP), forms an ionic complex 1 2 In the present study, we have synthesized doubly labeled [(CEP) Au)] [Au(CN) ] , both in solution as well as in 2 2 13 15 [R PAu C N] complexes with R groups having different the solid state [4]. The formation of the ionic species was 3 steric and electronic requirements. The ligand disproportio- attributed [2,5,6] to disproportionation (Eq. (1)) of the 13 31 nation of these complexes was studied using C, P and ligand from the [R PAuCN] monomer initially formed in 3 15 N NMR spectroscopy. All relevant coupling constants solution. were determined and the free energy of activation for K eq 1 2 disproportionation of these complexes was determined 2[R PAuCN]á[(R P) Au] 1 [Au(CN) ] (1) 3 3 2 2 31 using proton decoupled P NMR band shape analysis. The ligand scrambling shown in Eq. (1) is quite important from the biological point of view [7]. Smokers treated with various anti-arthritic gold drugs are reported to have higher 2. Experimental concentrations of gold in their red blood cells as compared to nonsmokers [8–10]. The mechanism by which gold 2.1. Chemicals 13 15 K C N (99%) was obtained from Merck, Sharp and * Corresponding author. Dohme, Canada. Sodium NaAuCl .2H O, and R P ligands 4 2 3 E-mail address: sakhawat@kfupm.edu.sa (M.S. Hussain) 1 were obtained from Strem Chemical Co. CD OD was from Corresponding co-author. 3 E-mail address: aisab@kfupm.edu.sa (A.A. Isab) Fluka Chemical Co. 0277-5387 / 99 / $ – see front matter  1999 Elsevier Science Ltd. All rights reserved. PII: S0277-5387(98)00441-0