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Under aprotic conditions, Cr(CO) 5 CNCCl 3 ( 1 ) reacts with triphenylphosphine in the presence of aromatic aldehydes or ketones to give the α-chloroalkenylisocyanide complexes cis ( Z )- and trans ( E )-Cr(CO) 5 CNCCl CRR′ {R = H, R′ = 4-C 6 H 4 F ( 7 ), 4-C 6 H 4 -CH C(Cl)NCCr(CO) 5 ( 8 )} and Cr(CO) 5 CNCCl CR 2 {CR 2 = fluorenylidene ( 9 )}. Two further representatives of this class of compounds, Cr(CO) 5 CNCCl CCl 2 ( 10 ) and Cr(CO) 5 CN–CCl CCl-NCCr(CO) 5 ( 11 ), have been obtained in low yields by reduction of 1 with zinc. Reactions with pyrrolidine of the isomeric mixtures 7 and 8 afford the alkylideneamino(pyrrolidino)carbene complexes 13 and 14 . An X-ray study of 13 shows the two π-systems within the amino(imino)carbene ligand to be approximately orthogonal to one another. With tris(dimethylamino)phosphine in the place of triphenylphosphine, complex 1 , 9-fluorenone plus a secondary amine combine to the 4-amino-Δ 3 -oxazolin-2-ylidene chromium complexes 17 and 19 , the latter of which has been protonated, alkylated and subject to an X-ray structure analysis. Reasons for the different modes of reaction in the system 1 /PR 3 /RR′C O are discussed and compared with the “dependence on the metal” of reactions in the system L n MCN–CH–PPh 3 /RR′C O {L n M = (OC) 5 Cr, (OC) 5 W versus Cl(Ph 3 P) 2 Pt + }. |
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