SELECTIVE REACTIONS OF FUNCTIONALIZED RUTHENIUM(II) SIGMA-ALKYNYL COMPLEXES WITH DICOBALT OCTACARBONYL AND TETRACOBALT DODECACARBONYL - SYNTHESIS OF CYCLOPENTENONE DERIVATIVES VIA INTERMOLECULAR PAUSON-KHAND REACTIONS

Treatment of [Ru{C=CCPh2(C=CH)}(eta(5)-C9H7)(PPh3)(2)] (1) With [Co-2( CO)(8)] leads to the formation of the adduct 2)-eta(2)-C=CH)Co-2(CO)(6 )}(eta(5)-C9H7)(PPh3)(2)] (3) through the selective coordination of th e Co-2(CO)(6) fragment at the terminal alkyne group on 1. Similarly, t he enynyl complex [Ru{C=CCH=CH(C=CPh)}(eta(5)-C9H7)(PPh3)(2)] ((E,Z)-2 ), prepared via a Wittig reaction from [Ru{C=CCH2(PPh3)}(eta(5)-C9H7)( PPh3)(2)][PF6] (5) and phenylpropargyl aldehyde, also reacts with [Co- 2(CO)(8)] to yield selectively the adduct 2)-eta(2)-C=CPh)Co-2(CO)(6)} (eta(5)-C9H7(PPh3)(2)] ((E,Z)-6). Protonation of complexes 3 and (E,Z) -6 with HBF4 . Et2O affords the cationic vinylidene derivatives ta(2)- C=CH)Co-2(CO)(6)}(eta(5)-C9H7)(PP3)(2)][BF4] (4) and (2)-C=CPh)Co-2(CO )(6)}(eta(5)-C9H7)(PPh3)(2)][BF4] ((E,Z)-7), respectively. Dicobalt ad duct complexes 3 and (E,Z)-6 undergo Pauson-Khand cyclization processe s with strained cyclic alkenes (norbornadiene and norbornene) to affor d regioselectively the tricyclic cyclopentenone derivatives 8a,b, 9a,b , (E,Z)-10, and 11. (E,Z)-6 reacts with [Co-4(CO)(12)] to give an unpr ecedented ruthenium(II) vinylidene complex containing a tetranuclear ' 'butterfly'' type cobalt cluster (12), which has been characterized by X-ray diffraction.