Scandium, Yttrium, and Lanthanum Benzyl and Alkynyl Complexes with the N-(2-Pyrrolidin-1-ylethyl)-1,4-diazepan-6-amido Ligand: Synthesis, Characterization, and Z-Selective Catalytic Linear Dimerization of Phenylacetylenes
摘要:
1,4,6-Trimethyl-N-(2-pyrrolidin-1-ylethyl)-1,4-diazepan-6-amine (HL) reacts with M(CH2Ph)(3)(THF)(3) to give the dibenzyl complexes (L)M(CH2Ph)(2) (M = SC, 1; M = Y, 2; M = La, 3). Compounds 1, 2, and 3 can be converted to their corresponding cationic monobenzyl species [(L)M(CH2Ph)](+) (M = Sc, Y and La) by reaction with [PhNMe2H][B(C6F5)(4)]. Reaction of (L)Sc(CH2Ph)(2) with 2 equiv of phenylacetylene affords the monomeric dialkynyl complex (L)Sc(C CPh)(2) (4), while reactions of (L)M(CH2Ph)(2) (M = Y and La) give the dimeric dialkynyl complexes [(L)M(C CPh)(mu-C CPh)](2) (M = Y, 5; M = La, 6). The neutral complexes (2, 3, 5, and 6) and the cationic monobenzyl species [(L)M(CH2Ph)](+) (M = Y and La) are catalysts for the Z-selective linear head-to-head dimerization of phenylacetylenes. The cationic yttrium and the neutral lanthanum systems are the most effective catalysts in the series. The related scandium species show poor activity and selectivity.
Highly Efficient Regio- and Stereoselective Dimerization of (Hetero)aromatic Terminal Alkynes by Organo Rare-Earth Metal Catalysts
作者:Shaozhong Ge、Victor F. Quiroga Norambuena、Bart Hessen
DOI:10.1021/om700893f
日期:2007.12.1
4-diazepan-6-amine), activated by [PhNMe2H][B(C6F5)4], catalytically dimerizes a range of (hetero)aromatic alkynes to Z-enynes with 100% selectivity and high rates. Catalyst turnovers up to 2000 were readily achieved in preparative scale (5–10 mmol) reactions. For comparison, the related E-enynes were produced with a permethyl lanthanocene catalyst.