Combinatorial screening of an in situ generated library of tungsten oxyhalide and imido complexes for olefin metathesis.

A series of substituted tungsten(VI) halides with general formula WECl4 (E = O or -NR (imido)) were screened via a high throughput study to identify potential new olefin metathesis catalysts. The tungsten species were treated with a series of aluminum alkyl activators and modifier ligands to generate active catalyst species in situ. Ring-opening metathesis polymerization (ROMP) of cyclooctene was used as a primary screen to identify potential metathesis catalysts and active catalysts were subjected to a secondary screen to evaluate tolerance toward polar functional groups.

(η(4)-Cyclo-octa-tetra-ene)(η(8)-cyclo-octa-tetra-ene)iodido-tantalum(V).

The title complex, [Ta(η(4)-C8H8)(η(8)-C8H8)I], lies across a crystallographic mirror plane that includes the Ta(V) atom and the iodide ligand. One cyclo-octa-tetra-ene (cot) ring is η(4)-coordinating and is bis-ected by the mirror plane. The fold angle between the plane of the coordinating butadiene portion and the middle plane of the ring is 27.

A total loss of innocence: double ortho-metallation of bis(triphenylphosphano)iminium cation, [N(PPh(3))(2)](+), by tris(eta-naphthalene)tantalate(1-).

For the first time [N(PPh(3))(2)](+), or [PPN](+), has been shown to undergo an irreversible reaction with a transition metal complex under ambient conditions and affords a product containing a unique structural motif in which two phenyl groups on one PPh(3) substituent of [PPN](+) are ortho-metallated, while the third phenyl ring is hydrogenated to provide a tantalum bound 1,3-cyclohexadiene group.