New bis(silyl)cyclopentadienidoniobium and -tantalum complexes: X-ray crystal structures of [NbCp boolean AND Cl-4] and [NbCp boolean AND Cl-4(CNAr)] [Cp boolean AND = eta(5)-C5H3(SiClMe2)(SiMe3); Ar = 2,6-Me2C6H3]

摘要

The [bis(silyl) cyclopentadienido]tetrachloroniobium and -tantalum complexes [MCp boolean AND Cl-4] [Cp boolean AND=eta(5)-C5H3(SiCIMe2)-(SiMe3); M = Nb 3, Ta 4] were synthesized by reaction of the pentachlorides MCl5 with C5H3(SiCIMe2)(SiMe3)2 (1). Although the Lewis acidity of tetrachloro complexes 3 and 4 is lower than that of the pentahalides, two adducts [M{eta(5)-C5H3(SiClMe2)(SiMe3)}Cl-4(CNAr)] (Ar = 2,6-Me2C6H3; M = Nb 5, Ta 6) have been isolated by reaction with ArNC. Complexes 3 and 4 react with tert-butylamine or lithium amides to afford the dichloroimido and amidochloroimido complexes [M{eta(5)-C5H3(SiClMe2)(SiMe3)}Cl-2(NR)] (R = tBu, M = Nb 7, Ta 8; R = Me, M = Nb 9) and [Ta{eta(5)-C5H3(SiClMe2)(SiMe3)}-Cl(NHtBu)(NtBu)] (10), respectively. In addition, 7 and 8 can be prepared by treatment of the pentachlorides with [C5H3(SiMe(2)NHtBu)(SiMe3)(2)] (2) by elimination of 1. The tetrachloro compound 3 reacts with four equivalents of tBuNH(2) to give the constrained-geometry derivative [Nb{eta(5)-C5H3(SiMe(2)NtBu-kappa N)(SiMe3))Cl(NtBu)] (11), whereas the treatment of toluene solutions of 3 and 4 with H2NCH2CH2NH2 in the presence of triethylamine leads to the trichloro complexes [M{eta(5)-C5H3(SiMe2NCH2CH2NH2-kappa N-2,N)(SiMe3)}Cl-3] (M = Nb 12, Ta 13). All the reported complexes were studied by IR and NMR spectroscopy and the molecular structures of complexes 3 and 5 were determined by X-ray diffraction methods.