Pentamethylcyclopentadienyl halo- and alkyl-alkoxo tantalum(V) complexes. Crystal structure of [formula omitted

Abstract

Reaction of TaCp ∗Cl 4 with MOR (M  Li, Na) in different molar ratios gives halo alkoxides TaCp ∗ Cl n( OR) 4−n (n = 3: R  tBu 1; SiPh 3 2; 2,6- Me 2C 6H 3 3; n = 2: R = tBu 4; SiPh 3 5; 2,6- Me 2C 6H 3 6; n = 1: R = SiMe 3 7) in good yields. The alkylidene complex TaCp ∗(CH 2SiMe 3) 2(CHSiMe 3) is hydrolyzed in the presence of traces of water to give the oxo dialkyl derivative [TaCp ∗(Ch 2SiMe 3) 2O] n 8, and reacts with 1 equivalent of 2,6-Me 2C 6H 3NC affording a new η 2-iminoacyl compound TaCp ∗( Ch 2 SiMe 3) CHSiME 3){η 2- C(CH 2Sime 3) N(2,6- Me 2C 6H 3 )} 9. Reactions of TaCP ∗(CH 2SiMe 3) 2(CHSiMe 3) with 1 equivalent of C 6H 5OH and 4-MeC 6H 3(OH) 2 result in the formation of the alkyl phenoxo TaCp ∗(CH 2SiMe 3) 3(OC 6H 5) 10 and 4-methyl pyrocatecholate TaCp ∗(CH 2SiMe 3) 2(O 2C 6H 3Me) 11, whereas the relaxed reaction with 2,6-Me 2C 6H 3OH leads to the cyclic alkyl-alkoxo compound TaCp ∗( CH 2 SiMe 3) 2{η 2- O(2- CH 2-6- MeC 6 H 3)]} 12. All the complexe were characterized by IR and NMR ( 1H and 13C) spectroscopy. The crystal and molecular structure of 12 has been determined. Crystals of 12 are triclinic, space group P 1 − with Z = 2 in a unit cell of dimensions a = 9.151(5) A ̊ , b = 11.835(5) A ̊ , c = 14.045(4) A ̊ , α = 89.35(3)°, β = 72.34(3)° and γ = 88.51(4)°, V = 1449(1) A ̊ 3 . Final values of R = 0.025 and Rw = 0.0655 were obtained from 5547 reflections measured (5070, > 2 σ(1)).