Cycloheptatrienyl ligand

Reduction of ZrCl4 with Na/Hg at < -10 °C in the presence of cycloheptatriene gives Zr(i76-C7H8)2 it exhibits a non-parallel arrangement of the cycloheptatrienyl ligands (18-A-VIII) and can be used to prepare a series of zero- and monovalent 16-e zirconium complexes such as Zr(rf-CjH-,)(rf-CjH,)(PMe3), Zi(rf-0,H7)-(tmeda)Cl, and others.72... 

The complex has crystallographically imposed C2h symmetry and the cycloheptatrienyl ligands are planar to... 

A variety of organometallic, ir complexes are now known, in which both TT-cyclopentadienyl and ir-cycloheptatrienyl ligands are bonded simultaneously to the same transition metal, providing a series of unique mixed sandwich complexes. The first of these, x-cyclopentadienyl-x-cyclo-heptatrienyl-vanadium (XXXI), was described by King and Stone (153)... 

Reactions of anionic metal complexes with halide-bridged dimers can also be used to form a bond between two different metal atoms. Reaetion of (/j -C7H7)Fe(CO)3 with Mn2(CO)gBr2 gives ()j -C7H7)MnFe(CO)6 in which the cycloheptatrienyl ligand coordinates as a diolefin to manganese and as an allyl toward iron . 

The cycloheptatrienyl ligand has variously been assigned charges of +1, -1, and -3. See the text for a discussion of the merit of these values. 

Nucleophilic attack on coordinated unsaturated hydrocarbons is one of the fundamental and particularly well studied reactions in Organometallic Chemistry. The addition of carbonylme-tallates instead of common nucleophiles provides a directed synthesis of hydrocarbon bridged complexes. Carbonylmetallates (particularly Re(CO)5", Os(CO)4 ") add to 7C-bonded olefin, acetylene, allyl, diene, trimethylenemethane, dienyl, benzene, triene and cycloheptatrienyl ligands in cationic complexes and give hydrocarbon bridged bi- and trimetallic, homo- or he-teronuclear complexes [1]. 

The following nucleophiles may also be added to cycloheptatrienyl ligands phosphines, phosphites, derivatives of aromatic hydrocarbons, or other complexes " [equations (11.21)-(11.23)]. 

---