Mono- and Bis(dibenzotetramethyltetraaza[14]annulene) Complexes of Group IV Metals, Including the Structure of the Lithium Derivative of the Macrocyclic Ligand

The deprotonation of tmtaaH2 by LiBu or LiMe gave a red solid, which upon recrystallization from DME was isolated as crystals suitable for X-ray analysis, [(tmtaa)2Li4(DME)3] (2). The lithium derivative was used in situ for the synthesis of [(tmtaa)Ti(Cl)] (3), [(tmtaa)Ti(Cl)2]-C6H6 (4), and [(tmtaa)M(Cl)2]-2THF (M = Zr, 5; M = Hf, 6). The structure of 2 shows a very pronounced bent cavity derived from the saddle-shape conformation of the ligand where the moiety is located. All these complexes should be considered as interesting starting materials for novel early transition metal organometallic chemistry. The reaction of MC14(THF)2 with 2 equiv of [(tmtaa)Li21] and the reaction of [(tmtaa)M(Cl)2] with [(tmtaa)Li2] both led to the formation of sandwich complexes [(tmtaa)2M] (M = Ti, 7; = Zr, 8; M = Hf, 9), in which the metal achieves a cubic-type octacoordination (through bonding to the eight nitrogen donor atoms, in two staggered N4 units). The first NMR study on [(tmtaa)M] diamagnetic complexes is reported. Crystallographic details are as follows: 2, space group PI, triclinic, a = 14.433 (2) Å, b = 17.319 (3) Å, c = 11.961 (2) Å, a = 94.76 (2)°, β = 101.24 (2)°, γ = 104.22 (2)°, Z = 2, and R = 0.070 for 7201 independent observed reflections; 3, space group C2/m, monoclinic, a = 34.239 (7) Å, b = 10.101 (2) Å, c = 18.403 (3) Å, α = γ = 90°, β = 100.96 (2)°, Z = 8, and R = 0.059 for 1822 independent observed reflections; 5, space group PI, triclinic, a = 12.437 (3) Å, b = 15.414 (4) Å, c = 9.337 (2) Å, a = 95.42 (3)°, ² = 109.16 (3)°, γ = 111.47 (3)γ, Z = 2, and R = 0.044 for 3601 independent observed reflections; 8, space group P21/n, monoclinic, a = 11.604 (5) Å, b = 19.073 (3) Å, c = 19.220 (3) Å, α = γ = 90°, β = 91.34 (2)°, Z = 4, and R = 0.049 for 3764 independent observed reflections.