Standard heats of formation and M–C bond energy terms for some homoleptic transition metal alkyls MR_n

Some highlights from the development and use of bulky monodentate ligands

“…For a long time it was widely thought that homoleptic, open shell transition alkyls or aryls were inherently unstable owing to weak metal-carbon bonds. There is thermochemical evidence to show that metalcarbon bonds are indeed weaker than metal-nitrogen or metal-oxygen bonds in related alkoxide and amide derivatives of Ti, Zr and Hf, but the M-C bonds are not inherently weak and have energies in the approximate range 40-80 kcal mol À1 for the alkyls M(CH 2 X) (M = Ti, Zr, Hf; X = Bu t , Ph or SiMe 3 ) [122]. In 1970, the view of transition metal-carbon bonds began to change at a rapid pace when it was shown almost simultaneously by Lappert [123] and Wilkinson [124] that the key to isolating stable homoleptic transition metal alkyls lay in their kinetic stabilization, i.e.…”

HfO2 and Hf1–xSixO2 Thin Films Grown by Metal‐Organic CVD Using Tetrakis(diethylamido)hafnium

“…The bond energy of Hf-NEt 2 agreed well with the experimental value (95 kcal mol -1 ). [43] The dissociation of the N-C 2 H 5 bond in the molecule requires less energy than that of the Hf-N bond. Ionic Hf-N bonds may react slightly with O 2 .…”

Zirconium and Hafnium: Introduction

“…26 Thermochemical data (not available for Group Ilia organometallics) show that for homoleptic compounds [ML W ] bond strengths (i) decrease with increasing group number, e.g. Hf > Ta > W, 30 30 We now turn to a brief comparison of the organometallic chemistry o f the Group I Va transition metals. The outstanding difference between Ti and its heavier congeners Zr and Hf is the relative stability of the M(III) complexes.…”