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((CN)-N-boolean AND)(mu-Cl)](2) [(CN)-N-boolean AND=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 palladacyclopentachene 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{C-4(COOMe)(4)}(Ph2POCH2Py-P,N)] (Va) and [Pd{C-4(COOMe)(4)}(Ph2PNHPy-P,N)] (Vb). The reactions of hydroxo-bridged precursors [Pd-2((CN)-N-boolean AND)(mu-OH)](2) or [Pd-2{C-4(COOMe)(4)}(2) (mu-OH)(2)][NBu4](2) with PyNHPPh2 afforded mononuclear complexes Ic-Vc (PyNPPh2 = c ligand) 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, H-1 and P-31{H-1} NMR). (C) 2004 Elsevier B.V. All rights reserved.