Gold(I) complexes of neutral, anionic, and oxidized bis (diphenylphosphino)acetonitrile Sicelo V. Sithole a , Richard J. Staples b , Werner E. van Zyl a, ⁎ a School of Chemistry, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa b Department of Chemistry, Michigan State University, East Lansing, MI 48824–1322, USA abstract article info Article history: Received 9 September 2011 Accepted 21 October 2011 Available online 29 October 2011 Keywords: Gold(I) complexes bis(diphenylphosphino)acetonitrile Pentafluorophenyl Dinuclear X-ray crystal structures The ligand bis(diphenylphosphino)acetonitrile, (PPh 2 ) 2 CHCN, (“dppm-CN”), was prepared. The reaction be- tween dppm-CN and [Au(C 6 F 5 )(tht)] (tht = tetrahydrothiophene) (molar ratio 1:2) formed an open-ended dinuclear gold(I) complex [(AuC 6 F 5 ) 2 (dppm-CN)], 1. The crystal structure showed a linear disposition of di- mers with intramolecular Au···Au interactions between the dinuclear units, but despite two distinctly differ- ent distances between the gold centers, it is without intermolecular Au···Au interactions. Deprotonation of dppm-CN afforded the anion [(PPh 2 ) 2 CCN]¯ which reacted with [AuCl(tht)] (molar ratio 1:1) to form a neu- tral cyclic dinuclear gold(I) complex [Au 2 {(PPh 2 ) 2 CCN} 2 ], 2. Complex 2 could also be formed from mono- or bis(phosphine) gold(I) chloride complexes through the making and breaking of Au-P bonds. Reaction be- tween the oxidized, deprotonated form of the ligand, [(P(S)Ph 2 ) 2 CCN]¯, and [AuCl(PPh 3 )] (molar ratio 1:1) formed the neutral mononuclear complex [Au(PPh 3 )(P(S)Ph 2 ) 2 CCN] 3, with the [AuPPh 3 ] + fragment bonded to one sulfur atom and a large degree of electron delocalization across the S-P-C-P-S ring. Complexes 1–3 were all obtained in satisfactory yield (70-90%), and analyzed by single crystal X-ray studies, solution 1 H and 31 P NMR, IR, and elemental analyses. © 2011 Elsevier B.V. All rights reserved. Mono- and bis-tertiary phosphines are amongst the most utilized ligands in inorganic and organometallic chemistry [1] and have been studied in abundance in gold chemistry as well [2]. Within the bis(phos- phine) family, the single methylene-bridged derivative, Ph 2 PCH 2 PPh 2 (dppm) is an important ligand in metal coordination chemistry [3] and derivations thereof, most notably bis-(diphenylphosphino)amine, Ph 2 PNHPPh 2 (dppa), have been reviewed [4]. In general, interest into the study of these ligands stems from their use in homogeneous cataly- sis; in particular, the rich photochemistry that emanates from gold(I) complexes are an ongoing basis for investigation [5]. The bis(diphenylphosphino)acetonitrile, (PPh 2 ) 2 CHCN, (“dppm-CN”) ligand has been reported in the literature as the anion [(PPh 2 ) 2 CCN]¯ in a phosphorus-organic synthesis [6] and also as an anionic ligand in a se- ries of heterometallic Ru/Au and Mn/Au complexes [7]. More recently, this work was extended to the diphosphinoketenimine type ligand, (PPh 2 ) 2 C=C=NR [8]. Interest in the chemistry of dppm-CN was rejuvenated by Erker and co-workers who reported the facile preparation thereof [9], and developed diverse and fascinating aspects of its chemistry [10]. Perhaps the most interesting is the observed sharp increase in acidity when the H atom is replaced by a CN group on the bridging carbon atom of dppm [11]. We prepared dppm-CN from a slight modification of the above literature procedure [12] and recently reported the solid-state structures of the Group 11 complexes [Au 2 Cl 2 (dppm-CN)] and [Cu{P(O)Ph 2 ) 2 CCN} 2 ], using the dppm-CN ligand [13]. In continuing our interest in gold(I) complexes with P/S type ligands [14], we report on new gold(I) complexes of dppm-CN utilized as a neu- tral, anionic and oxidized ligand. The complex [(AuC 6 F 5 ) 2 (dppm-CN)], 1, was obtained in a CH 2 Cl 2 solution from the reaction between dppm-CN and [AuC 6 F 5 (tht)] (molar ratio 1:2) [15]. The solution 31 P NMR spectrum of 1 showed a singlet peak resonating at δ = 42.0 ppm for the two equivalent P atoms. In the solid-state, complex 1 formed an open-ended complex in a cis configuration and contains intramolecu- lar Au···Au interactions, see below. The crystal structure of 1 (triclinic) shows no packing resemblance to the previously reported structure (monoclinic) of the closely related [(AuC 6 F 5 ) 2 dppm] complex [16]. Al- though both complexes contain intramolecular Au···Au interactions in the solid-state, complex 1 additionally contains a crystal structure motif that is unorthodox and deserves comment: Dinuclear gold(I) com- plexes based on bis(phosphine) ligands fall into a number of observed structural motifs [17] as summarized in Chart 1: no Au···Au interaction A, intramolecular Au···Au interaction but without intermolecular Au···Au interaction B, 1-D polymeric chains C (all Au···Au distances approximately the same), and dimer type structures, D. Whereas D rep- resents discrete “face-on” dimers [18], complex 1 shows a different structural motif which can be described as “side-by-side” dimers along a linear chain, depicted by E. Complex 1 shows intramolecular Au···Au interactions are present at 3.0902(7) and 3.0809(6) Å, but each dinuclear Inorganic Chemistry Communications 15 (2012) 216–220 ⁎ Corresponding author. Tel.: + 27 31 260 3188; fax: + 27 31 260 3091. E-mail address: vanzylw@ukzn.ac.za (W.E. van Zyl). 1387-7003/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2011.10.030 Contents lists available at SciVerse ScienceDirect Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche