Synthesis and coordination of hybrid phosphinoferrocenes with extended donor pendants.

Combining a phosphinoferrocene fragment with extended multidonor moieties affords novel, flexible multidonor pro-ligands. This contribution describes the synthesis of two structurally similar functional phosphines, Ph 2 PfcNHC(O)CH 2 PPh 2 (1) and Ph 2 PfcNHCH 2 CH 2 PPh 2 (2, fc = ferrocene-1,1'-diyl), and their coordination behaviour towards Pd(II). The former amidophosphine reacts with [PdCl 2 (MeCN) 2 ] to produce the chelate complex [PdCl 2 (1-κ 2 P , P ')] as a mixture of cis and trans isomers, which convert into bis-chelate [PdCl 2 (Ph 2 PfcNC(O)CH 2 PPh 2 -κ 3 P , P ', N )] upon reacting with a strong base (KO t -Bu). In contrast, the more flexible and more basic phosphinoamine 2 directly forms the cationic bis-chelate complex [PdCl(2-κ 3 P , P ', N )]Cl via spontaneous self-ionisation. Subsequent halogen abstraction with Ag[SbF 6 ] results either in counter ion exchange to give [PdCl(2-κ 3 P , P ', N )][SbF 6 ] or in the formation of a structurally unique complex [PdCl(2-κ 4 Fe , P , P ', N )][SbF 6 ] 2 with an Fe → Pd dative interaction, depending on the amount of silver(I) salt used (1 or 2 equiv.).