Synthesis of a sulfido-capped triiron cluster with bridging phosphido ligands and its reactions with alkynes, phosphites and phosphines

Treatment of [Fe(CO)(5)] with Ph2P(SCMe3) at elevated temperature and press ure afforded, as the major product, the sulfur-capped trinuclear iron clust er [Fe-3(mu(3)-S)(mu-PPh2)(2)(mu-CO)(CO)(6)] 1, in which two Fe-Fe edges ar e bridged by phosphido groups and the other by a carbonyl group. Also isola ted in low yield from this reaction was the tetranuclear iron complex [{Fe- 2(mu-PPh2)(CO)(6)}(2)(mu(4)-S-2)] 2, which comprises two phosphido-sulfido- bridged diiron fragments linked by an S-S bond. In contrast it has been dem onstrated that the reaction of [Fe(CO)(5)] with Ph2P(SPh) gives the discret e dinuclear complex [Fe-2(mu-PPh2)(mu-SPh)(CO)(6)] in which a sulfur-carbon bond has been retained. The reaction of 1 with organo-phosphites and -phos phines results in preservation of the triiron core and monosubstitution of a carbonyl group to give [Fe-3(mu(3)-S)(mu-PPh2)(2)(mu-CO)(CO)(5)(L)] [L=P( OMe)(3) 3a, P(OPh)(3) 3b, PPhMe2 3c or PPh3 3d]. On reaction of 1 with term inal alkynes, RC=CH [R=Ph or CH2OH], degradation of the trinuclear framewor k results to give the metallacyclic-bridged bimetallic complexes [Fe-2(mu-P Ph2CHCRS)(mu-PPh2CHCR)(CO)(4)] [R=Ph 4a or CH2OH 4b] in which new sulfur-ca rbon and phosphorus-carbon bonds have formed. In addition, the phosphido-br idged species [Fe-2(mu-PPh2)(mu-PPh2CHCPhS)(CO)(5)] 5 is isolated as a mino r product from the reaction of 1 with PhC=CH. The structures of complexes 1 , 2, 3c and 4a have been determined by single crystal X-ray diffraction ana lysis and pathways are postulated for the formation of the various products .