Formation of cyclopentadienyl and ruthenacyclopentadienyl derivatives through ynenyl-diyne and ynenyl-alkyne couplings onto a triruthenium cluster core

The compound [Ru-3(mu -H)(mu (3)-eta (2)-ampy)(CO)(9)] (1: Hampy = 2-amino- 6-methylpyridine) reacts with diynes RC4R in THF at reflux temperature to g ive the ynenyl derivatives [Ru-3(mu (3)-eta (2)-ampy)(mu-eta (3)-RC equival ent to CC=CHR)(mu -CO)(2)-(CO)(6)] (2: R = CH2OPh; 3: R = Ph). These produc ts contain a 1,4-disubstituted butynen-3-yl ligand attached to two rutheniu m atoms. The compound [Ru-3(mu-eta (2)-ampy){mu (3)-eta (6)-PhCC5(C equival ent to CPh)-HPh2}(CO)(7)] (4), which contains an eta (5)-cyclopentadienyl r ing and a bridging carbene fragment. has also been obtained from the reacti on of 1 with diphenylbutadiyne. This compound arises from a remarkable [3+2 ] cycloaddition reaction of a preformed 1,4-diphenylbutynen-4-yl ligand wit h a triple bond of a second diphenylbutadiyne molecule. The reactivity of t he ynenyl derivatives 2 and 3 with diynes and alkynes has been studied. In all cases. compounds of the general formula [Ru-3(mu-eta (2)-ampy){mu (3)-e ta (5)-C(=CHR)-C=CRCR1=CR2}(CO)(7)] (5-17) have been obtained. They all con tain a ruthenacyclopentadienyl fragment formed by coupling of the coordinat ed ynenyl ligand of 2 (R = CH2OPh) or 3 (R = Ph) with a triple bond of the new reagent (the CR1=CR2 fragment results from the incoming diyne or alkyne reagent). While most of the products derived from 2 have the alkenyl C=CHR fragment with a Z configuration (R cis to Ru), all the compounds obtained from 3 have this fragment with an E configuration. Except 2 and 3, all the cluster complexes described in this article have a five-electron donor ampy ligand attached to only two metal atoms, a coordination mode unprecedented in cluster chemistry.