Dynamic stereochemistry in the titanocene series with central and planar chirality. X-Ray structure and relative configuration of the racemic form (m.p. 186°C) of [(η 5-1-Me-2- iPrC 5H 3)(η 5-C 5H 5)Ti(2,6-Me 2C 6H 3O)Cl]

• Published in: Journal of organometallic chemistry Vol. 491; no. 1; pp. 31 - 39
• Main Authors: Besançon, Jack, Szymoniak, Jan, Moïse, Claude, Toupet, Loïc, Trimaille, Bernard
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.04.1995
• Subjects: Chirality; Titanium; Titanocene; X-ray diffraction; Titanium; X-ray diffraction; Titanocene; Chirality
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/0022-328X(94)05242-4

The dynamic stereochemistry of two substitution reactions [(i) and (ii)] for the thiocyanate and isocyanate complexes of titanocene has been reinvestigated. ▪(Cp = C 5H 5; Cp′ = 1-Me-2- iPrC 5H 3; Ar = 2,6-Me 2C 6H 3; X = NCO, NCS or Cl) The metathesis reaction (ii) has been shown to be chemoselective and stereospecific with inversion of the configuration at the titanium for X = NCO and retention for X = NCS. This stereochemical behaviour contrasts with that proposed previously, i.e. inversion of configurations for both X = NCO and X = NCS. The present result is unambiguously supported by the crystallographic structure of the racemic compound 1c′ (X = Cl, m.p. 186°C), which was chosen as the starting stereochemical reference. The complex 1c′ crystallizes in the monoclinic system, space group C c . Two well-characterized quasi-eclipsed and staggered conformational forms of the complex 1c′ are presented. According to Seebach's nomenclature, this structure corresponds to the u(Ti, p) configuration.