Synthesis, isomerism and supramolecular chemistry of diphenylmethanimine complexes of the coinage metals

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Abstract
The reactions of [AuCl(SMe 2 )] or [AuBr(C 4 H 8 S)] with 1 equivalent of diphenylmethanimine led to the formation of the complexes [AuCl(Ph 2 CNH)] 1a, [Au(Ph 2 CNH) 2 ][AuCl 2 ] 1b and [Au(Ph 2 CNH) 2 ][AuBr 2 ] 2, respectively. Treatment of 1a, 1b with KI in the two-phase system dichloromethane–water induced a redox process to give Au 0 and [Au(Ph 2 CNH) 2 ][I 3 ] 3. The same result was obtained when AuI and Ph 2 CNH were allowed to react under anhydrous and oxygen-free conditions. Copper(I) iodide reacted with an excess of Ph 2 CNH with formation of the complex [CuI(Ph 2 CNH)] 4. Bis(diphenylmethanimine) complexes of gold, [Au(Ph 2 CNH) 2 ]BF 4 5, and silver, [Ag(Ph 2 CNH) 2 ]BF 4 6, were prepared by the reaction of 2 equivalents of the ketimine and [Au(PhCN) 2 ]BF 4 or AgBF 4 in dichloromethane or tetrahydrofuran solutions, respectively. The crystal structures of the complexes 1a, 1b, 2, 3, 5 and 6 have been determined. The (Ph 2 CNH)AuCl units of compound 1a form infinite zigzag chains via weak Au · · · Au contacts [3.3633(5) Å]. In 1b two AuCl 2 - anions and two (Ph 2 CNH) 2 Au + cations form a tetranuclear Z-type unit with Au · · · Au contacts of 3.1944(5) [Au(1) · · · Au(2)], 3.604(1) [Au(1) · · · Au(2′)] and 3.392(1)Å [Au(1) · · · Au(1 ′)]. The N–H · · · Cl geometry suggests hydrogen bonding between the hydrogen and chlorine atoms of neighbouring ions. The bromine compound 2 is isostructural to the chloride 1b with slightly longer Au · · · Au distances. Compound 3 shows bis(diphenylmethanimine)gold(I) cations and triiodide anions with no anomalies in the packing and in bond distances and angles. The geometry of the silver(I) and gold(I) complexes 5 and 6 are quite similar except for the observation that the Au–N bond is 0.11 Å shorter than the Ag–N bond, which suggests that two-co-ordinate gold(I) is indeed smaller than two-co-ordinate silver(I) in systems with nitrogen-containing ligands, as previously observed for phosphine complexes.

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