Spiked-triangular arrangement

X-ray structural analysis reveals a jU4- j -C=CPh ligand about the triosmium framework with a platinum atom coordinated to one of the three osmium atoms in a spiked triangular arrangement (Fig. 22). 

The orange hydrido alkynyl complex [Ru3Pt(//-H) /i4- / -CHC( Bu ) (CO)9(dppe)] has a spiked triangular metal arrangement (6) whereas its red vinylidene isomer [Ru3Pt //4-/7 -C=C(H)(Bu ) (CO)9(dppe)] has a butterfly framework (4). Both complexes readily interconvert in solution, with 4 being the thermodynamically favored product. The hydrido alkynyl to vinylidene transformation involves the formal loss of two electrons donated by the ligands. 

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