SYNTHESIS, STRUCTURE, AND REACTIVITY OF ETA-2-1,3-DIENE AND ENYNE COMPLEXES OF THE CHIRAL RHENIUM LEWIS-ACID [(ETA-5-C5H5)RE(NO)(PPH3)]- OZONOLYSIS WITHIN A METAL COORDINATION SPHERE( )

Reaction of [eta5-C5H5)Re(NO)(PPh3)(ClC6H5)]+BF4- (1) and trans-pipery lene at room temperature (RT) gives 5-C5H5)Re(NO)(PPh3)(eta2-H2C=CHCH= CHCH3)]+BF4-(2a; 72 %) as a 63:37 mixture of RS,SR/RR,SS diastereomers . At 95-degrees-C, (89-90):(11-10) mixtures are obtained (84-88 %). No linkage isomers with coordinated CH=CHCH3 moieties are observed. Reac tion of 1 and isoprene (RT) gives eta5-C5H5)Re(NO)(PPh3)(H2C=CHC(CH3)= CH2)]+BF4-90%) as a 65:15:7:13 mixture of isomers. At 95-degrees-C, 95 :2:1:2 mixtures are obtained (>99%). The major products have coordinat ed H2C-CH moieties ((RS,SR)/(RR,SS)-2b); the minor products have coord inated C(CH3)=CH2 moieties. Reactions of 1 or the corresponding dichlo romethane complex and vinylacetylene (RT) give (7-17):(9-35):(61-44):( 23-4) mixtures of the RS,SR and RR,SS diastereomers of alkene complex [(eta5-C5H5)Re(NO)(PPh3) (eta2-H2C=CHC=CH)]+BF4- and the sc and ac Re- (C=C) rotamers of alkyne complex [(eta5-C6H5)Re(NO)PPh3) (H2C=CH-eta2- C=CH)+BF4-. Ozonolyses of 2a and 2b cleave the free C=C moieties to gi ve alkene complexes of acrolein and methyl vinyl ketone (79-73%). The crystal structure of (RS,SR)-2a shows an s-trans diene conformation. O ther structural features of the preceding compounds are analyzed. Rati onales for the kinetic and thermodynamic binding selectivities are giv en.