Intramolecular thermolytic carbon-hydrogen activation processes. Solid-state structural characterization of a mononuclear .eta.6-Me4C5CH2 zirconium complex and a mechanistic study of its formation from (Me5C5)2Zr(C6H5)2

Abstract

The complex Cp'2Zr(C6Hs)2 (1, Cp' = 7j5-Me5C5) undergoes unimolecular thermolysis in solution ( * = 22.5 (3) kcal/mol, AS* = -11.8 (3) eu) to yield the ring-metalated complex Cp'Zr(C6H6) (Me4C5CH2) (2) and benzene. Complex 2 crystallizes in the monoclinic space group P2j/c with four molecules in a unit cell of dimensions o = 13.550 (2) Á, b = 9.651 (2) Á, c = 17.613 (3) A, and ß = 94.94 (1)°a t 0 °C. Least-squares refinement led to a value for the conventional R index (on F) of 0.043 for 2594 reflections having 2 < 55°and I > 3 ( )• The molecular structure of 2 consists of 7?6-Cp' and 7?6-Me4C5CH2 ligands in a distorted "bent sandwich" Cp'2ZrX2 configuration (/ring centroid-Zr-ring centroid = 143.6 (3)°) with the X groups being an unexceptional phenyl ligand (Zr-C = 2.285 (5) A) and a metalated cyclopentadienyl methyl group (Zr-C = 2.388 (7) A). The latter carbon atom is displaced 0.88 A (37°) from the C5 mean plane in the direction of the zirconium atom and is bonded to the C6 ring at a C-C distance of 1.468 (9) A. The zirconium atom

Different C−C Coupling Reactions of Permethyltitanocene and Permethylzirconocene with Disubstituted 1,3-Butadiynes

“…Cp*-mediated cleavage of Group 4 metal ± carbon bonds can also occur. [25,26] If this process works with metalScheme 1. Proposed reaction pathway for the formation of the complexes 3 ± 6.…”

“…These complexes are possibly formed in the first step, but being rather unstable, they are subsequently protonated and cleaved by Cp* ligands [25,26] for M Zr, R tBu and M Ti, R Ph, tBu, and so on, as shown in Scheme 1.…”

Catalytic thermal and photo-induced CH and CC activation reactions of alkanes with ansa amido functionalized half-sandwich complexes and methylalumoxane

“…Intramolecular non catalytic CH activation reactions at 120°C are known of several substituted cyclopentadienyl complexes of Zr [33,34].…”

Zirconium and Hafnium Permethylpentalene Compounds

“…The Zr−C(15) distance in 4 Zr is slightly longer than those found for ZrCp* 2 Ph 2 (2.311 Å) and ZrCp 2 Ph 2 (2.301 Å). 46,47 Since these examples are formally 16 e − complexes, the slight lengthening in 4 Zr can be attributed to increased steric crowding around the Zr center. The Pn* ligand in 4 Zr is considerably flatter and has longer M−Pn* cent.…”