A bridging side-on allenylidene dimolybdenum complex without carbonyl stabilization

The bis(nitrile) complex [Mo2Cp2(mu-SMe)(3)(NCCH3)(2)]( BF4) (1) reacts with HCtCCPh(2)(OH) to give the mu-alkyne product [Mo2Cp2(mu-SMe)(3) {HC CCPh2(OH)}](BF4) (2). Sequential treatment with triethylamine and tetrafluoroboric acid converts 2 almost quantitatively, Via the mu-alkynyl derivative 3, into [Mo2Cp2(mu-SMe)(3)(mu-eta(1):eta(2)-C=C=CPh2)] (BF4) (4), the first example of a dinuclear mu-eta(1):eta(2)- allenylidene species without carbonyl ligands.