Optically active transition metal compounds.: 135.: Half-sandwich complexes [(η5-C5Me5)M(P-P′)Hal]X with chiral metal (Rh, Ir) and phosphorus atoms

Reaction of [(Cp*MHal)(2)](mu-Hal)(2)] (CP* = eta(5)-C5Me5; M = Rh, Ir; Hal = Cl, Br, I) with the unsymmetrical chelate phosphane P-P' (=P,P,P'-tris[(+)-9-phenyldeltacyclan-8-yl]-1,2-bis(phosphanyl)benzene) in the presence of the metathesis reagents NH4PF6, NaBF4, and NaBPh4 gave [Cp*M(P-P')Hal]X (X = PF6, BF4, BPh4; 1-9) in high yields. The P-P' ligand, easily accessible from norbornadiene and phenylacetylene in a highly enantioselective synthesis, contains three (+)-9-phenyldeltacyclan-8-yl substituents with a total of 24 homochiral asymmetric carbon atoms. The stereogenic metal center and the secondary phosphorus atom give rise to four diastereomers, all of which are formed in the synthesis of compounds 1-9. Crystallization of the diastereomer mixtures afforded 11 single crystals of compounds 1-9, which served to determine the absolute configurations at the metal atom and the secondary phosphorus atom. Surprisingly, all the compounds with the same configuration adopted almost identical conformations (types I-III). Moreover, compounds belonging to the same configuration series showed remarkably constant chemical shifts of their P-31{H-1} NMR signals. The (+)-Norphos complexes [Cp*M(Norphos)Cl]PF6 (M = Rh, Ir; Norphos = (2S,3S)-(+)-bis(diphenylphosphanyl)bicyclo[2.2.1]hept-5-ene; 10 and 11) were synthesized for comparison, which formed two diastereomers. On crystallization both the Rh and the Ir complexes crystallized as 1: 1 mixtures of diastereomers, differing in the metal configuration.