Synthesis of an Extremely Bent Acyclic Allene (A “Carbodicarbene”): A Strong Donor Ligand


  • We are grateful to the NSF (CHE 0518675) for financial support of this work, the NSERC for a postdoctoral fellowship (C.A.D.), and the ACS for a graduate fellowship (V.L.).


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Pushed to the limit: Pushing C[DOUBLE BOND]C π bonds to the breaking point by using a push–push substitution pattern forces allenes to bend (see structure; C light blue, N dark blue). An acyclic allene featuring a C[DOUBLE BOND]C[DOUBLE BOND]C bond angle of 134.8° has been isolated in which the typically sp-hybridized central carbon atom approaches a configuration that has two lone pairs of electrons, and acts as a very strong η1-donor ligand for transition metals.