Preparation, properties, and reactions of metal-containing heterocycles .95. Transition-metal-mediated cyclocotrimerization of selenophosphinites with activated alkynes

Selenophosphinito complexes (OC)(4)Mn(eta(2)-Se - PR1/2) (2a, b) [R(1)=cyc-Hex (a), tBu (b)] are formed by the reaction of BrMn(CO)(5) with the phosphane selenides R1/2HPSe (1a, b) in the presence of the auxiliary base Et(iPr)(2)N. According to an X-ray structural analysis, 2a crystallizes in the space group <P(1)over bar> with Z=2. The dimeric complex [(OC)(4)MN(mu-Se - PMe(2))](2) (4c) is not obtained in a straightforward way. Compound 4c is only obtained via the intermediate Br(OC)(4)Mn-Se - P(H)Me(2) (3c) by HBr elimination with nBuLi. Complex 3c is formed by replacement of carbon monoxide in BrMn((CO)(5) by Me(2)HPSe (1c). A dissociative equilibrium between [(OC)(4)Mn(mu-Se - PMe(2)](2), (4c) and the monomeric species (OC)(4)Mn(eta(2)-Se - PMe(2)) was not observed. The cyclocotrimerization of the >P - Se function with the activated alkynes ZC=CZ [Z=CO(2)R(2); R(2)=Me (d), Et (e), iPr (f), eye-Hex (g)] was successful only in the case of the cyclohexyl derivative 2a to give the selenaphosphamanganabicycloheptadienes 5d-g. An X-ray structural analysis proved that 5d crystallizes in the space group <P(1)over bar> with Z=2. Under CO pressure 5d was degraded to the selenophene 6.