CHEMISTRY OF CARBONYL-DERIVED LIGANDS - NUCLEOPHILIC-ATTACK ON ANIONIC ACETYLIDE CLUSTERS

The broad range of reactions of anionic ketenylidene clusters is reviewed. We then describe some chemistry of the triiron nonacarbonyl acetylide clusters (PPN)[Fe3(CO)9CCOR] (Ia,Ib), (a: R = CH2CH3; b: R = C(O)CH3; PPN = bis(triphenylphosphine)iminium (1 +), (Ph3P)2N+), which are derived from the iron ketenylidene (PPN)2[Fe3(CO)9CCO]. The ethoxyacetylide cluster Ia adds a single phosphine to form a phosphonium alkyne (PPN)[Fe3(CO)9PMePh2CCOEt] (II). In contrast, Ib reacts with loss of acetate anion to form an unusual phosphonium acetylide cluster [Fe3(CO)9CCPMePh2] (III), which is also formed cleanly by protonation of II with one equivalent of triflic acid, HSO3CF3. Implications of the formation of these products on bonding and mechanism are considered. Clusters II and III are spectroscopically characterized, and a single crystal X-ray structure determination of II and III are reported. (PPN)[Fe3(CO)9PMePh2CCOEt] (II) crystallizes in the triclinic space group P1; a 9.910(1); b 16.920(2); c 17.372(2) Å; α 74.83(1)°; β 84.65(1)°; γ 86.07(1)°; V 2796(1) Å3; Z = 2. [Fe3(CO)9CCPMePh2] (III) crystallizes with an orthorhombic lattice; space group Pbca; a 7.898(1); b 19.885(2); c 31.906(5) Å; V 5011(2) Å3; Z = 8. © 1990.