ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .63. (BETA-AMINOVINYL)CARBENE COMPLEXES AND (ALKINYL)AMINOCARBENE COMPLEXES OF CHROMIUM AND TUNGSTEN - STEREOCHEMISTRY AND ISOMERIZATION

(Alkinyl)alkoxycarbene complexes L(n)M = C(OEt)-C- = CR 3 [L(n)M = Cr(CO)5, W(CO)5; R = Ph, nBu, SiMe3] react with primary amines H2NR1 4 (R1 = Me, iPr, allyl, CH2Ph, CHMePh) to give (beta-aminovinyl)carbene complexes L(n)M = C(OEt)-CH = CR-NHR1 (Z)-5 (by a Michael-type 3-addition) together with (alkinyl)aminocarbene complexes anti-6 (by a 1-aminolysis). The product ratio (Z)-5/anti-6 is strongly influenced by the reaction temperature: at 20-degrees-C (Z)-5 is obtained as the main product, while at -78-degrees-C mainly anti-6 is formed. Both reactions are stereospecifical; they yield 5 in the (Z), and 6 in the anti configuration only. An anti/syn isomerization is achieved by acidic treatment of anti-6i. The (alkinyl)aminocarbene complex 6a adds EtOH/EtO- albeit much slower than the (alkinyl)alkoxycarbene complex 3a. A NH2-Enamino carbene complexes (CO)5Cr = C(OEt)-CH = C(NH2)Ph [(Z)-8a] is obtained on addition of ammonia to 3a at 90-degrees-C.