Synthesis and structural characterisation of Pd(ii) and Pt(ii) complexes with a flexible, ferrocene-based P,S-donor amidophosphine ligand

Abstract

1′-Diphenylphosphino-1-{[(2-(methylthio)ethyl)amino]carbonyl}ferrocene (1), accessible via amidation of 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) with 2-(methylthio)ethylamine, reacts with [PdCl₂(cod)] (cod = cycloocta-1,5-diene) at a 1 : 1 metal-to-ligand ratio to give trans-[PdCl₂(1-κ²P,S)] (trans-2) as the sole product. A similar reaction with [PtCl₂(cod)] affords a mixture of cis- and trans-[PtCl₂(1-κ²P,S)] (cis- and trans-3), which can be separated by fractional crystallisation. Complexation reactions performed with 2 equiv. of the ligand are less selective, yielding mixtures of the expected bis-phosphine complexes (i.e., trans-[PdCl₂(1-κP)₂], or a mixture of cis- and trans-[PtCl₂(1-κP)₂]) with the respective monophosphine complexes. The structures of 1, trans-2, cis-3 and trans-3 determined by X-ray diffraction demonstrate the ability of the title ligand to act as a flexible cis- or trans-P,S-chelate donor (the ligand bite angles are 174.03(2)/173.05(2)° for trans-2/3 and 92.86(2)° for cis-3).