Reactions of M(N-2,6-i-Pr2C6H3)(CHR)(CH2R‘)2 (M = Mo, W) Complexes with Alcohols To Give Olefin Metathesis Catalysts of the Type M(N-2,6-i-Pr2C6H3)(CHR)(CH2R‘)(OR‘ ‘)

The reaction between M(NAr)(CH-t-Bu)(CH2-t-Bu)2 (M = Mo, W, Ar = 2,6-i-Pr2C6H3) and various alcohols (1-adamantyl-OH, t-BuOH, ArOH, (CF3)2CHOH, (CF3)2MeCOH, CF3Me2COH, (CF3)3COH, C6F5OH) in pentane or toluene yields either complexes of the type M(NAr)(CH-t-Bu)(CH2-t-Bu)(OR), through direct addition of ROH across a Mo−C bond, or complexes of the type M(NAr)(CH2-t-Bu)3(OR), through direct addition of ROH across a MoC bond. The trineopentyl species appear to be formed when the alcohol has a relatively low pKa value. The outcome also can depend on whether the alcohol is employed neat or in benzene, and mixtures are observed in some circumstances. The conversion of M(NAr)(CH2-t-Bu)3(OR) into M(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) was shown to be unimolecular in several examples. Preliminary experiments have shown that M(NAr)(CH-t-Bu)(CH2-t-Bu)(OR) complexes are surprisingly active catalysts for various metathesis reactions, although conversion is sometimes limited by decomposition of intermediate alkylidenes to yield d...