x - a highly reactive titanium hydride and an active species in the McMurry reaction

Article abstract of DOI:10.1016/0022-328X(94)80197-5

The complex reacts with catalytically-prepared solid magnesium hydride (MgH2^*) or dissolved magnesium hydride (MgH'2) with evolution of hydrogen to give a highly reactive titanium hydride, x (1).The well-known low valent titanium species, obtained by reduction of TiCl3 with LiAlH4, utilized in the McMurry reaction, has been shown to be 1.An X-ray absorption spectroscopy study (EXAFS) of 1 reveals that the Ti absorber is surrounded by O (from THF) and Cl atoms plus two types of Ti neighbors.Possible structural models for 1 compatible with the EXAFS results are proposed.Complex 1 is an active reagent for the coupling reaction of benzophenone to give tetraphenylethene.During the reaction hydrogen is liberated and the inorganic side product has been shown to be titanium(III) oxychloride; thus the McMurry reaction employing 1 as the reagent can be described by . On the basis of these results, a new interpretation of the mechanism for the McMurry reaction is presented.Complex 1 also undergoes a number of carbenoid type reactions, which may proceed via a "titanium carbenoid" intermediate 9a-c. Key words: Titanium; Hydride; Magnesium; EXAFS