Synthesis and coordination behaviour of a protic phosphinoferrocene amidine

Abstract

A phosphinoferrocene amidine Ph2PfcN=CHNHiPr (1; fc = ferrocene-1,1'-diyl) has been synthesised and analysed as a new P,N-hybrid donor in Group 10 metal complexes. Thus, reactions with metal dichloride precursors produced tetrahedral and paramagnetic [NiCl2(1-κ2P,N)] and square-planar diamagnetic [MCl2(1-κ2P,N)] (M = Pd, Pt) and [PdCl(Me)(1-κ2P,N)]. The Pd(II) complex [MCl2(1-κ2P,N)] was further converted to chloride-bridged dimers [Pd2(μ-Cl)2(1-κ2P,N)2][BARF]2 and [(μ-Cl){PdCl(1-κ2P,N)}2][BF4] (BARF = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) through reactions with halide scavengers. In solution, the former compound exists in equilibrium with monopalladium species featuring an Fe‒Pd bond , [PdCl(1--κ3Fe,P,N)][BARF]. The interaction of 1 with [Pd(MeCN)4][BF4] and triphenylphosphine produced analogous κ3 complexes [Pd(PPh3)(1-κ3Fe,P,N)]X (X = BF4 and, after anion exchange, also PF6). Eventually, the compound family was expanded by a Pd(0) complex, [Pd(η2-ma)(1-κ2P,N)], containing a π-coordinated maleic anhydride. With the exception of the nonisolable [PdCl(1-κ3Fe,P,N)][BARF], all reported compounds were fully structurally characterised via a combination of elemental analysis, spectroscopic methods (ESI MS and NMR), and single-crystal X-ray diffraction analysis. Attempts to prepare complexes with a deprotonated terminal NH group failed. Nonetheless, the NH group plays a role in the structure-stabilising moiety, forming intramolecular NH···Cl hydrogen bonds with chloride ligands.