Alkynes allenyl complexes, reaction with

The dominant isomerization pathway for the trimeric allenyl clusters [M3H(CO)9(/Li3-i7, V> 7 I C =C=CHR)] is via a thermal 1,2-hydrogen migration to afford the 1,3-dimetalloallyl clusters [M3H(CO)9(/H3-i7, t7, t7 -RCCHCR)] (53c). Reaction of alkynes and dienes with metal carbonyls M3(C0)2 (M = Ru, Os) often occurs with C-H activation adjacent to the unsaturated carbon-carbon bond (54) however, the final products isolated are often of the 1,3-dimetalloallyl type, the intermediate allenyl complex formed being thermodynamically unstable under the reaction conditions necessary to initiate C-H activation. 

Cydoaddition reactions of allenylidene ligands with alkynes have also been described. Thus, heating a toluene solution of the neutral osmium complex 43 in the presence of dimethylacetylenedicarboxylate leads selectively to the allenyl-vinyli-dene 4S (Scheme 2.18) [31c[. The formal insertion of the alkyne into the Co =Cp... 

Zwitterionic rhodium(I) complex, Rh (CODX -CfiHsBPtn), is also found to be an efficient catalyst for the silylformylation of 1-alkynes at 40 °C and 40 atm of CO in CH2C12 (equation 125) although no reaction occurs with internal alkynes327. However, silylhydroformylation takes place when the reaction is carried out under hydroformylation conditions, i.e. in the presence of CO and H2 (CO/H2 = 1/1), to give (E)-2-silylmethyl-2-alkenals (319) in 54-92% isolated yields (equation 128). The intermediacy of 7r-allenyl-Rh species is proposed to account for the formation of 31 9327. When 4-acetoxy-l-butyne and 4-(p-tosyloxy)-l-butyne are used as the substrates, saturated silylhydroformylation products are obtained327. 

A new type of triaryl phosphine-functionalized imidazolium salt containing cations such as (6) has been prepared. Palladium complexes of (6) generated in situ have been used successfully in Heck-type reactions of aryl halides with acrylates and of 4-bromotoluene with styrene derivatives.34 The first Heck-type reaction of aryl halides with allenes has been reported. 1,3-Double arylations were observed with 3-substituted-l,2-allenyl sulfones, while 1-monoarylation was favoured with 3,3-disubstituted-l,2-allenyl sulfones.35 It has been shown that the a-arylation of methane-sulfonamides (7) may be achieved using palladium catalysis reaction proceeds through the sulfonamide enolates.36 It is also reported that palladium cross-coupling of alkynes with /V - (3 - i odophe n y I an i I i ncs) may lead to the formation of substituted carbazoles.37... 

The unsaturated hydride Mn2(li-H)2(CO)6(lt-dppm) reacts with RCMHH (R = H, Ph, Bu , COOMe) to form either hydrido-alkenyls Mn2(M.-H)(ji2. n. l -CR=CH2XCO)6(ii-dppm) (R = H, Ph), or alkenylidene species 2(tt-H)(il2,tl3,Ti2-CR=CHBuO(CO)6(M.- pm) and (OC)3Mn(ji-dppm) (i-C=CHCOOMe Mn(CO)3. The photochemical reactions of Mn2(CO)8(p.-dppm) with alkynes results in vinylidene complexes. 35 The photochemical reaction between Mn2(CO)io and MeCsCNEt2 affords the ynamine complex 86. This isomeiizes into an aminoallene complex on warming. 36 The corresponding riienium complex Re2(CXD)8(p.-MeC2NMe2) is transformed into three complexes on thermolysis these are the (dimethylamino)allenyl Re2(CO)7(p-T 3-... 

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