Absolute configurations of organometallic compounds. Part 6. The crystal structure and absolute configuration of (–)578-carbonyl(η-cyclopentadienyl){[(S)-methyl(1-phenylethyl)amino]diphenylphosphine}-nitrosylmolybdenum

Abstract

A structural analysis of the title compound has been carried out giving a final R of 0.043. Comparison of the observed and calculated parameters of the Bijvoet pairs has allowed the absolute configuration to be determined as R at the MO atom and S at the asymmetric carbon atom. The substance crystallizes in space group P2₁2₁2₁ with unit-cell constants of a= 12.612(1), b= 13.856(2), c= 14.174(2)Å, and Z= 4. There is no crystallographic disorder between the CO and NO groups [MO–C(O) and MO–N(O) 1.940(14) and 1.809(10)Å]. The compound shows the first example of chirality at a metal centre being determined by the difference between the similar ligands CO and NO, and the first example of the class of compounds [Mo(η-C₅H₅)L¹L²L³](‘three-legged’ piano stools) whose structure has been determined, the bond lengths being similar, but not the same, as those of the class [Mo(η-C₅H₅)L¹L²L³L⁴](‘four-legged’ piano stools).