New palladacyclic complexes with pyridylphosphine ligands: crystal structures of [Pd(Azb)(Ph 2POCH 2Py-P,N)][PF 6] and [Pd(Phpy)(Ph 2PNHPy-P,N)][PF 6

Abstract

The synthesis of palladacyclic derivatives with the hybrid pyridylphosphine ligands Py(CH 2)OPPh 2 ( a) and PyNHPPh 2 ( 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 KPF 6 gave the mononuclear derivatives Ia– IVa and Ib– IVb. The crystal structures of compounds [Pd(Azb)(Ph 2POCH 2Py-P,N)][PF 6] ( IIIa) and [Pd(Phpy)(Ph 2PNHPy-P,N)][PF 6] ( Ib) have been determined. The new palladacyclopentadiene precursor [Pd{C 4COOMe 4}(CH 3CN) 2] ( V) has been prepared starting from the polymeric complex [Pd{C 4COOMe 4}] 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}(Ph 2POCH 2Py-P,N)] ( Va) and [Pd{C 4(COOMe) 4}(Ph 2PNHPy-P,N)] ( Vb). The reactions of hydroxo-bridged precursors [Pd(C ∧N)(μ-OH)] 2 or [Pd 2{C 4(COOMe) 4} 2 (μ-OH) 2][NBu 4] 2 with PyNHPPh 2 afforded mononuclear complexes Ic– Vc ( PyNPPh 2 - = 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, 1H and 31P{ 1H} NMR).