Chelate-stabilized alkoxopalladium(II) complexes with chiral phosphine-substituted carbohydrate ligands

Abstract

The reactions of chiral P,O-bidentate methyl 4,6-O-benzylidene-2-deoxy-2-(diphenylphosphino)-α-D-altropyranoside (HL¹) and methyl 4,6-O-benzylidene-3-deoxy-3-(diphenylphosphino)-α-D-altropyranoside (HL²) with [PdCl₂(cod)](cod = cycloocta-1,5-diene) or [PdCl₂(NCMe)₂] gave the complexes trans-[PdCl₂(HL)₂](L = L¹1a or L²1b). Complex 1b crystallizes in the tetragonal space group P4₁2₁2, with a= 12.326(2), c= 32.649(8)Å and Z= 4, R= 0.023 for 2502 reflections having I 3σ(I). The large deviation (14.6°) of the angle P–Pd–P′ from 180° may be ascribed to the overcrowding of the bulky phosphine ligands. Treatments of 1a and 1b with NaOMe in methanol gave the corresponding bis(alkoxo) complexes cis-[PdL₂]2a and 2b. The compounds have been characterized by infrared, Raman, ¹H, ¹³C and ³¹P NMR spectroscopy. The Pd–O absorption appears at 388 cm^–1 for 2a and 366 cm^–1 for 2b. The cis and trans geometries have been assigned by Raman spectroscopic studies.