New palladacyclic complexes with pyridylphosphine ligands: crystal structures of [Pd(Azb)(Ph2POCH2Py-P,N)][PF6] and [Pd(Phpy)(Ph2PNHPy-P,N)][PF6]

The synthesis of palladacyclic derivatives with the hybrid pyridylphosphine ligands Py(CH2)OPPh2 (a) and PyNHPPh2 (b) in a neutral P,N-chelating coordination mode has been achieved. Treatment of selected chloride-bridged cyclometallated precursors [Pd(C∧N)(μ-Cl)]2 [C∧N = 2-pyridinin-phenyl Phpy, I-compounds; 7,8-benzoquinolyl Bzq, II-compounds; phenylazophenyl Azb, III-compounds or 2-(2-oxazolinyl)phenyl Phox, IV-compounds] with a or b in the presence of stoichiometric KPF6 gave the mononuclear derivatives Ia–IVa and Ib–IVb. The crystal structures of compounds [Pd(Azb)(Ph2POCH2Py-P,N)][PF6] (IIIa) and [Pd(Phpy)(Ph2PNHPy-P,N)][PF6] (Ib) have been determined. The new palladacyclopentadiene precursor [Pd{C4COOMe4}(CH3CN)2] (V) has been prepared starting from the polymeric complex [Pd{C4COOMe4}]n. Its usefulness in the preparation of new derivatives has been tested by means of the straightforward reaction with ligands (a) or (b) to give mononuclear compounds [Pd{C4(COOMe)4}(Ph2POCH2Py-P,N)] (Va) and [Pd{C4(COOMe)4}(Ph2PNHPy-P,N)] (Vb). The reactions of hydroxo-bridged precursors [Pd(C∧N)(μ-OH)]2 or [Pd2{C4(COOMe)4}2 (μ-OH)2][NBu4]2 with PyNHPPh2 afforded mononuclear complexes Ic–VcView the MathML source(PyNPPh2-=cligand) in which a less common anionic P,N-binding mode is forced as a result of ligand deprotonation. The new complexes were characterised by partial elemental analyses and spectroscopic methods (IR, FAB, 1H and 31P{1H} NMR).