Mono- and di-nuclear complexes of ortho-palladated and -platinated 4,4′-dimethylazobenzene with bis(diphenylphosphino)methane. More data on transphobia

Abstract

Complexes [Pd(κ 2-R)(μ-Cl)] 2 [κ 2-R=κ 2- C,N′-C 6H 3(NNC 6H 4Me-4 ′)-2-Me-5 ( 1)] and [Pd(κ 1-R)Cl(κ 1-dppm)(κ 2-dppm)]TfO [dppm=bis(diphenylphosphino)methane ( 2)] have been used to prepare new palladium derivatives containing dppm. Thus, complex 1 reacts with one equivalent of dppm to afford [{Pd(κ 2-R)Cl} 2(μ-dppm)] ( 3) and with AgClO 4 and dppm (1:2:2 molar ratios) to give [Pd(κ 2-R)(κ 2-dppm)]ClO 4 ( 4· ClO 4). The triflate salt of this complex ( 4· TfO) reacts with PPh 3 to yield [Pd(κ 1-R)(PPh 3)(κ 2-dppm)]TfO ( 5). Dinuclear complexes were obtained by reacting 2, (i) with [AuCl(PPh 3)] or [AuCl(tht)] (tht=tetrahydrothiophene) (1:1, −60 °C) and (ii) with 1 (2:1) to give, respectively, [Pd(κ 1-R)Cl(μ-dppm) 2Au]TfO ( 6) and the A-frame complex [{Pd(κ 1-R)(μ-dppm)} 2(μ-Cl)]TfO ( 7). The latter decomposes in solution to give, among other products, [Pd(κ 2-R)(κ 2- P,O-dppmO)]TfO ( 8), containing the monoxide of dppm (dppmO). Complex 8 can be obtained by refluxing a toluene solution of 4· TfO under aerial conditions. The platinum complex trans-[Pt(κ 1-R)Cl(PPh 3) 2] reacts with an excess of dppm to give [Pt(κ 1-R)(κ 1-dppm)(κ 2-dppm)]Cl ( 10· Cl) which reacts with TlOTf to give 10· TfO. The crystal structures of complexes 3, 8 and 10· TfO have been determined by X-ray diffraction studies. The structure of complex 3 consists of a dimer formed by a dppm ligand bridging two Pd(κ 2-R)Cl units. The structure of the cation of complex 8 shows both the aryl and dppmO acting as chelating ligands with the O atom trans to the C atom. The structure of complex 10· TfO shows the κ 1-R ligand, one chelating and one monocoordinate dppm ligand.