136736-54-4Relevant articles and documents
Facile synthesis and stereochemistry of alkyne complexes of Cp2MH and Cp2MCH2CH2R (M = Nb, Ta)
Yasuda, Hajime,Yamamoto, Hitoshi,Arai, Takashi,Nakamura, Akira,Chen, Jie,Kai, Yasushi,Kasai, Nobutami
, p. 4058 - 4066 (2008/10/08)
Hydridoniobium-olefin complexes of type Cp2NbH(RCH=CH2) (R = H, CH3, C6H5) were found to readily react with propyne, 1-butyne, 2-butyne, and phenylacetylene under mild conditions to afford air-sensitive blue crystals of alkyl-alkyne complexes, Cp2NbCH2CH2R(alkyne), in high yield. Resulting complexes prefer the exo geometry in sharp contrast to the endo preference of the starting materials. An unusual α-agostic interaction was observed in the ethyl group of (C5H5)2NbCH2CH3(CH 3C=CCH3), which crystallizes in the orthorhombic space group P212121, with a = 12.930 (6) A?, b = 14.498 (7) A?, c = 7.590 (5) A?, and Z = 4. Bulky 1-alkynes such as 3,3-dimethyl-1-butyne, (trimethylsilyl)acetylene, and diphenylacetylene behave in a different manner and gave rise to the formation of hydridoniobocene complexes of the type Cp2NbH(alkyne) with exo geometry. (C6H5)2NbH[(CH3) 3CO≡CH] belongs to the monoclinic space group P21, with a ;= 6.037 (1) A?, b = 14.428 (3) A?, c = 8.218 (2) A?, β = 105.96 (1)°, and Z = 2. An analogous structure was found in (C5H5)2NbH[(CH3) 3SiC≡CH)], which crystallizes in the monoclinic space group P21, with a = 6.149 (4) A?, b = 14.727 (4) A?, c = 8.579 (5) A?, β = 104.78 (5)°, and Z = 2. The reaction of the alkene complexes with excess (CH3)3SiC≡CH and 1-phenyl-l-propyne afforded insertion products formulated by Cp2NbCH=CHR(CH≡CR). All the alkyne complexes were inert to CO, CO2, PR3, pyridine, and even carbonyl compounds. Cp2TaH(alkene) complexes also react with alkynes in a similar manner.
