217826-09-0Relevant articles and documents
Reactions of (Trimethyltriazacyclononane)Rh(vinyl)3, - Rh(Z-propenyl)3, and - Rh(vinyl)2Me with protic acids. The relative migratory aptitude of methyl and vinyl groups to an (Ethylidene)Rh alkylidene carbon
Zhen, Hongshi,Wang, Chunming,Hu, Yonghan,Flood, Thomas C.
, p. 5397 - 5405 (1998)
Preparations of CnRh(CH=CH2)3, CnRh(Z-CH=CHMe)3, and CnRhMe(CH=CH2)2 (Cn = 1,4,7-trimethyl-1,4,7-triazacyclononane) are reported. An X-ray crystal structure determination of CnRh(CH=CH2)3 revealed C3 molecular symmetry with average lengths Rh-N, 2.25 ?; Rh-C, 2.00 ?; and C=C, 1.31 ?. Protonations of these compounds were carried out with HOTf (triflic acid, HOSO2CF3), [H(Et2O)2][BAr4] (BAr4 = (-)B[3,5-(CF3)2C6H3] 4), and HCl in organic solvents as well as with methanol as solvent and acid. CnRh(CH=CH2)3 gave [CnRh(CH=CH2)(η3-E-CH2CHCHMe)]X in isolated yields up to ca. 80%. Use of CD3OD as acid/solvent led to formation of [CnRh(CH=CH2)(η3-CH2CHCHCH2D)]X (X = (-)OCD3 assumed) as the only isotopomeric product, suggesting [CnRh(=CHCH2D)-(CH=CH2)2]+ as a probable intermediate. No Rh(=CH-CH3) functional group could be detected by NMR at -60 °C or above. Triflic acid protonation of CnRh(Z-CH=CHMe)3 generated [CnRh(Z-CH=CHMe)(η3-E,E-MeCHCHCHEt)], establishing that product formation is by alkenyl migration and not via an electrocyclic ring closure within the [Rh(=CHEt)(CH=CHMe)]+ moiety. Protonation of CnRhMe(CH=CH2)2 generated [CnRhMe(η3-CH2CHCHMe)]+ as the sole product (96% by NMR). Reaction of CnRh(CH=CH2)2Me in CD3OD generated [CnRhMe(η3-CH2CHCHCH2D)]+ as the sole isotopomer. Thus, the migratory competition established between methyl and vinyl groups for migration to the carbene carbon in proposed intermediate [CnRh(=CHMe)(CH=CH2)Me]+ is dominated by the vinyl group.
