Mono-η-cycloheptatrienyltitanium chemistry: synthesis, molecular and electronic structures, and reactivity of the complexes [Ti(η-C₇H₇)L₂X](L = tertiary phosphine, O- or N-donor ligand; X = Cl or alkyl)

C–H bond activation through steric crowding of normally inert ligands in the sterically crowded gadolinium and yttrium (C 5 Me 5 ) 3 M complexes

“…(C 5 Me 5 ) 1Ϫ functions predominately as an ancillary spectator ligand that does not become involved in organometallic reaction pathways. One or two of these ligands are typically found in organometallic complexes, but not three because the cone angle of a (C 5 Me 5 ) 1Ϫ ligand was estimated to be as large as 142° (1), and, as a consequence, the formation of (C 5 Me 5 ) 3 M complexes was presumed to be impossible.…”

“…(C 5 Me 5 ) 2 Y(CH 2 C 6 H 5 ) (0.029 g, 86%) identified by 1 H NMR spectroscopy in C 6 D 12 (20). To further confirm the presence of (C 5 355 mmol) in 10 ml of toluene, the slurry changed from dark red to a bright orange and then back to a dark red.…”

Tris(polyalkylcyclopentadienyl) Complexes: The Elusive [(η5‐C5R5)2M(η1‐C5R5)] Structure and Trihapto Cyclopentadienyl Coordination Involving a Methyl Substituent

“…[1] Since the cone angle of (h 5 -C 5 Me 5 ) À had previously been estimated to be 1428, [2] or as large as 1718 [3] and 1888, [4] 3 ML 2 ] species (An = actinoide), [5] showed that the cone angle for (h 5 -C 5 Me 5 ) À could be reduced to 1208 by moving the ligand further away from the metal. In each of these complexes, the metal-C(h 5 -C 5 Me 5 ) distances are approximately 0.1 or more longer than any previously observed analogous distances.…”

Bis(cycloheptatrienyl) Derivatives of the First‐Row Transition Metals: Variable Hapticity of the Cycloheptatrienyl Ring

“…However, early work by Wilkinson and co-workers [17] suggested that reactions of tropylium salts with transitionmetal derivatives were rarely suitable for the preparation of η 7 -C 7 H 7 metal complexes. More recent studies on η 7 -C 7 H 7 -metal complexes suggest preferred formulations of such complexes as derivatives of the 10 π-electron trianion [18][19][20][21] C 7 H 7 3-, which has been generated in a metal-free form by the treatment of 1,4-cycloheptadiene with nBuLi. [22,23] Thus the metal formal oxidation states in the known mixed sandwich complexes (η 5 -C 5 H 5 )M(η 7 -C 7 H 7 ) (M = Ti, V, Cr) may be considered to be +4 in contrast to the formal zero metal oxidation states in the isoelectronic and isomeric dibenzenemetal complexes (η 6 -C 6 H 6 ) 2 M (M = Ti, V, Cr).…”