Absolute configurations of organometallic compounds

Abstract

The structure and absolute configuration of the thioamido complex (-)s,s-($-CsH5)Mo(C0)$3C(CH3)NR with R' = (S)CH(CH,)(C,H,) have been determined by single-crystal X-ray diffraction. The substance crystallizes in the orthorhombic system; space group P212121 with cell constants of a = 8.314(l), b = 9.020(l), and c = 22.352(2) A, and 2 = 4 molecules/unit cell. The absolute configuration was determined using Bijvoet's method. Refinement of the data using the anomalous scattering contributions of MO and S yields a final R(F) = 0.036 for 2715 independent reflections having 1 > 3a(I). The distorted square pyramidal coordination of the MO atom is defined by two carbonyl carbons and the S and N atoms of the thioamido ligand occupying the four basal plane sites and the five carbons of the $-&Hs ligand in the axial position. The Mo-ligand distances and most of the bond lengths and angles within the ligands are normal and compare closely with those of recent structure determinations. However, the distances and angles within the thioacetamide ligand show, distinctly, the effect of chelate binding to the MO atom. In particular, the angles at the central thioacetamide c&bon differ markedly from those of free thioacetamide and monodentate, S-bound metal thioacetamido complexes. The MO atom is 1.041 a above the plane formed by the four basal ligands. The conformation of the (S)-cr-phenylethyl group with respect to the ligand plane, defined by the thio-For part IV see ref. 1. also part IL of the series Optically active transition metal compleses (Part XLVIII see ref. 2).

Cyclopentadienyl/Phenyl Attraction in CpM–L–E–Ph Compounds by CH/π Interactions

“…The thioamide derived from acetic acid with a ( S )-CH­(Me)­Ph substituent at the N atom gave the two diastereomers ( R Mo , S C )- and ( S Mo , S C )-[CpMo­(CO) 2 {SCMeNCH­(Me)­Ph}], which could be separated . The thermodynamically more stable diastereomer was characterized by X-ray crystallography (Scheme ) …”

“…23 The thermodynamically more stable diastereomer was characterized by X-ray crystallography (Scheme 3). 18 In contrast to the benzamidinato complexes, the thioamidato ligand in (R Mo ,S C )-/(S Mo ,S C )-[CpMo(CO) 2 {SCMeNCH(Me)-Ph}] is derived from acetic acid. Therefore, no H chir /π interactions in the ligand plane are possible.…”

Diverse Post-Metathesis Reactivities of Mixed Amido-Isothiocyanato Molybdenum Complexes

“…To the best of our knowledge, complexes of L 2 are unknown, although the unsymmetrical free thiourea SC­(HNSiMe 3 )­(NMe 2 ) has been reported . Nevertheless, coordination compounds of related ligands are known. , Notably, only low-oxidation state Group 6 metal centers (Mo II ) have been reported to accommodate κ 2 - N , S thioureato ligands, while three-membered N , S -chelated Mo V and Mo VI complexes can be found in a few examples with dithiocarbazate- and thiosemicarbazone-based multidentate donors …”

“…Consistent with the difference in oxidation states, the highly charged Mo VI in 3 effects shorter Mo–S and Mo–N bonds, and consequently a wider N–Mo–S angle (Table ), compared to its “softer” Mo II analogues (Mo–S ≈ 2.501(2)–2.514(1) Å; Mo–N ≈ 2.209(3)–2.231(2) Å; N–Mo–S ≈ 63°–64°) . Furthermore, comparison of monoanionic chelate L 2 in 3 (Table ) with dianionic L 1 revealed shorter N–C (i.e., higher multiple bond character) and longer C–S (higher single bond character) in the core scaffold of the latter, which reflects slightly diminished electronic delocalization.…”