EXTRACTING ABSOLUTE TITANIUM-ALKYL AND TITANIUM-HYDRIDE BOND ENTHALPIES FROM RELATIVE D(TIR(H)) IN (SILOX)(2)((BU3SINH)-BU-T)TIR - ELECTRONEGATIVITY AND ECT MODELS

Relative D(Ti-R)(rel) have been measured previously for (silox)(2)((Bu 3SiNH)-Bu-t)TiR (1-R), Pauling and Matcha equations of D(MR) that cont ain elements of electronegativity, D(MM), D(HH) and D(RH) were used to estimate absolute D(TiR) in 1 with minimal success. The electronegati vity approaches need a variety of substituents with a wide spread in c hi(R), hence examination of 1-H and I-R are heavily and incorrectly we ighted by D(TiH)-D(TiR). Absolute D(TiR) generated in this manner appr oach those of related systems only when chi(Ti) = 2.9, a value shown t o be irrational, Drago's ECT parameters were used in the hope that the three parameter fit would compensate for inadequacies in electronegat ivity-based methods. The limited set of alkyl parameters available, an d a lack of distinguishing parameters that can significantly different iate one alkyl from another, render this potentially useful method imp recise. (C) 1998 Elsevier Science S.A.