Ring‐Closing Metathesis of (η⁵‐Alkenylcyclopentadienyl)(alkenylphosphine)manganese(I) Dicarbonyl Complexes

Abstract

-(w-alkenyl)cyclopentadienyl](w-alkenylphosphine)manganese(I) dicarbonyl complexes were examined.T he RCM reactionb etween an h 5 -allyl-or an h 5 -vinyl-cyclopentadienyll iganda nd an allyldiphenylphosphine ligand in the manganese coordination spheresg ave the corresponding cyclized products in good to excellent yields.T he X-ray analyses of the two cyclized productsr evealed the structural differences between the C 3 -a nd the C 4 -bridged complexes.T he RCM reactions of the o-bromo-substituted manganese complexesw ere also operative andt he cyclized products were obtainedinexcellent yields of > 95%. Thepreferential formation of the C 4 -bridged species over the C 3 -bridged analogues in the RCM of the manganese complexes was confirmed by an intramolecular competitiveR CM experiment with the [h 5 -1-(methallyl)-2-(2-propenyl)cyclopentadienyl](allyldiphenylphosphine)manganese(I) dicarbonyl complex.

Kinetic Resolution of Planar-Chiral (η5-Bromocyclopentadienyl)manganese(I) Complexes by Molybdenum-Catalyzed Asymmetric Ring-Closing Metathesis

“…In this article, we have examined an extension of the ARCM method to the kinetic resolution of racemic planar-chiral cymantrene derivatives. The substrates employed in this study are rac -[η 5 -1-(ω-alkenyl)-2-bromo­cyclo­pentadienyl]­(methallyldi­phenylphosphine)­manganese­(I) dicarbonyl complexes ( rac - 1 ) . The structural motifs in RCM products 2 can be regarded as a hybrid of those in ferrocenes A and (π-arene)-chromium complexes C , whose ARCM preparations were reported previously. , The “bromo”-cyclopentadienide moieties in 2 can be easily converted to various functional groups by standard organic transformations with retention of the planar-chirality; thus the planar-chiral manganese complexes prepared in this report are considered versatile precursors to various planar-chiral cymantrene derivatives.…”

Enantioselective Preparation of Planar‐Chiral Transition Metal Complexes by Asymmetric Olefin‐Metathesis Reactions in Metal Coordination Spheres

“…, The ring-closing metathesis of (η 5 -alkenylcyclopentadienyl) Mn(CO) 2 (allylphosphine) using Grubbs-II catalyst afforded the corresponding bridged species C in high yields (Scheme 2, (3)). [18] The structural motifs in C can be regarded as a hybrid of those in bridged ferrocenes A (M = Fe) and bridged (η 6arene)chromium complexes B (see, Scheme 2), whose enantioselective extensions were developed by us previously (see, sections 3 and 4). The ARCM kinetic resolution of racemic planar-chiral manganese complexes rac-19 proceeds in the presence of (S)-Mo5 (Scheme 15).…”

“…[16c] Later, the RCM protocols were extended to the preparation of bridged (η 6 -arene)chromium(0) carbonyl complexes B (Scheme 2, ( 2)) [17] and (η 5 -cyclopentadienyl)manganese(I) carbonyl complexes C (Scheme 2, (3)). [18] In these cases, the olefin metathesis reactions took place between a coordinating allylphosphine and an η 6 -alkenylarene ligand or an η 5alkenylcyclopentadienyl ligand. The RCM method was found to be effective in preparing the η 5 -dihydroindenyl derivatives Professor Masamichi Ogasawara completed his Ph.D. at the University of Tokyo under the supervision of Prof. Masahiko Saburi in 1994.…”

“…Later, the RCM protocols were extended to the preparation of bridged (η 6 ‐arene)chromium(0) carbonyl complexes B (Scheme 2, (2)) [17] and (η 5 ‐cyclopentadienyl)manganese(I) carbonyl complexes C (Scheme 2, (3)) [18] . In these cases, the olefin metathesis reactions took place between a coordinating allylphosphine and an η 6 ‐alkenylarene ligand or an η 5 ‐alkenylcyclopentadienyl ligand.…”

Competition between Ring-Closing Migratory Insertion Polymerization and Monomer Cyclization

“…The synthesis of organometallic ring molecules has been explored for possible new functions derived from the metal elements. − Nonlinear metal coordination geometries are an advantage for the cyclization. Cyclopentadienyl (Cp) metal carbonyl complexes bearing a pendant phosphorus have a piano-stool coordination geometry and can undergo an intramolecular phosphorus–metal coordination producing ring molecules. , In addition to the small rings, cyclic macromolecular structures have also been made via metal coordination, but the resultant metal-coordinated structures are usually rigid without viscoelastic properties characteristic of polymer materials.…”