A New Concept for Chelate Ligands with Planar Chirality

The chiral donor substituted phosphaferrocene derivatives CpFe(3,4-Me 2 -2-R-C 4 HP) 6 (R = CH 2 CH 2 NMe 2 ), 7 (R = CH 2 NMe 2 ), and 8 (R = CH 2 OPPh 2 ) were synthesized as racemates starting from 2-formyl-3,4-dimethylphosphaferrocene. The P,N-ligand 6 reacted with [Cp*RuCl] 4 in THF to give the six-ring chelate complex Cp*RuCl( 6) (⋮ 10 ) which was characterized by single-crystal X-ray diffraction analysis. The complexation reaction was found to proceed diastereoselectively with respect to the newly created stereogenic center on the ruthenium atom. Under similar conditions, the reaction of ligand 7 with [Cp*RuCl] 4 did not lead to chelate formation. Instead, two isomers of the bis-P-coordinated complex Cp*RuCl( 7 ) 2 (⋮ 11 ) were observed by NMR spectroscopy. Reaction of the phosphinite ligand 8 with (PhCN) 2 PdCl 2 in toluene produced the six-ring chelate complex cis -PdCl 2 ( 8 ) (⋮ 12 ). The crystal structure of 12 has been determined.