Roger. Uhrhammer

Reactivity studies on bimetallic μ-malonyl complexes: cleavage and alkylation chemistry of the malonyl ligand

Abstract The bimetallic μ-malonyl complexes: {(η 5 -C 5 Me 5 (NO)(PPh 3 )Re[μ-(COCH 2 CO)-C 1 : C 3 ] Re(CO) 4 (Br)} − Li + ( 1 ), {(η 5 -C 5 Me 5 (NO)(PPh 3 )Re[μ-(COCH 2 CO)-C 1 : C 3 ]Re(CO) 4 (PMe 3 )} · Li + OSO 2 CF 3 − ( 2 ), and (η 5 -C 5 Me 5 )(NO)(PPh 3 ) Re[μ-COCH 2 CO)-C 1 ,O 3 :C 3 ]Re(CO) 4 ( 3 ) undergo carbon-carbon bond cleavage reactions of the malonyl ligand upon exposure to HCl. Deprotonation of (η 5 -C 5 Me 5 )Re(NO)PPh 3 (μ-η 1 ,η 2 -COCH 2 CO)Re(CO) 4 , ( 3 ), in THF solution and addition of CH 3 I leads to the C-alkylation product, (η 5 -C 5 Me 5 )Re(NO) PPh 3 )[μ-(COCH(CH 3 )CO)-C 1 ,O 3 :C 3 ]Re(CO) 4 ( 11 ), isolated as a single diastereomer (85% yield). Deprotonation of 11 and alkylation with CD 3 I leads to (η 5 -C 5 Me 5 )Re(NO)(PPh 3 )[μ-(COC(CH 3 )(CD 3 )CO)-C 1 ,O 3 :C 3 ]Re(CO) 4 ( 12 - d 3) with > 97% diastereoselectivity. Alkylation of the enolate anion derived from deprotonation of 11 with ethyl iodide led to isolation of (η 5 -C 5 Me 5 )(NO)(PPh 3 )Re{μ-[COCCH 3 =1cr,C(OCH 2 CH 3 )]- C 1 , O 3 : C 3 Re(CO) 4 ( 21 ) in 84% yield. Quenching of the enolate anion of 3 with excess ethyl iodide led to formation of an 11:89 mixture of (η 5 -C 5 Me 5 (NO)(PPh 3 )Re[μ-(COCHCH 2 CH 3 CO)- C 1 :C 3 , O 3 ]Re(CO) 4 ( 15 ) and(η 5 -C 5 Me 5 )(NO)(PPh 3 )Re[μ-(COCH=1cr; COCH 2 CH 3 )- C 1 , O 3 : C 3 ]Re(CO) 4 ( 16 ) in 87% combined yield. When the enolate anion of 3 was treated with allyl bromide, both C and O alkylation products (η 5 C 5 Me 5 )(NO)(PPh 3 )Re{μ-[COCH(CH 2 CH=1cr; CH2)CO]- C 1 : C 3 , O 1 Re(CO) 4 ( 17 ) and (η 5 -C 5 Me 5 )(NO)(PPh 3 )Re{μ-[COCH=1cr; C(OCH 2 CH=1cr; CH 2 )]- C 1 , O 3 : C 3 Re(CO) 4 ( 18 )were formed in a 32:68 ratio (84% combined yield). Alkylation with benzyl bromide gave (μ 5 C 5 Me 5 )(NO)(PPh 3 )Re[μ-(COCH=1cr; COCH 2 C 6 H 5 )- C 1 , O 3 : C 3 ]Re(CO) 4 ( 19 ) in 76% yield.

Conversion of a metallaenolate complex to a bimetallic μ-ketene complex : molecular structure of (η5-C5Me5)(NO)(PPh3)Re[μ-(COCH2)-C1:C2]Re(CO)4(PPh3)

Abstract Reaction of rhenaenolates [(η5-C5Me5)(NO)(PPh3Re(COCH2Li)] (2) and [Re(CO)4(PPh3)(OSO2CF3)] in THF at −78°C gave the μ-ketene complex [(η5-C5Me5) (NO)(PPh3)Re[μ-(COCH2)-C1:C2]Re(CO)4(PPh3)] (5). The structure of (5) was determined by single-crystal X-ray analysis.