[1,3-Bis(1-methylethyl) benzenaminato](2-methyl-2-phenylpropylidene)bis(2-methyl-2-propanolato) molybdenum(1)1-4

[126949-65-3]  · C30H47MoNO2  · (MW 549.64)

(ring-closing metathesis,5 olefin metathesis,6 ring-opening metathesis polymerization7,8)

Physical Data: sublimes at high vacuum at 60 °C.

Solubility: soluble in common organic solvents.

Form Supplied in: orange-yellow solid.

Analysis of Reagent Purity: 1H NMR spectroscopy and by combustion analysis.

Preparative Methods: prepared in two steps from Mo(NAr)2(CHCMe2Ph)2.9

Purification: recrystallize from pentane at -40 °C or by sublimation under high vacuum at 60 °C, both under an inert atmosphere.

Handling, Storage, and Precautions: store below -30 °C under an inert atmosphere. Decomposes at elevated temperatures. Should be used under Schlenk line conditions or in a glove box.

Catalyst 1 or 2 is significantly less effective at carrying out olefin metathesis than the corresponding fluorinated analog 3 [where the alkoxide ligand is OC(CF3)2CH3]. The rate of olefin metathesis is slowed when electron-donating groups are present on the alkoxide ligand.9 Studies on ligand variation have been carried out.10

Ring-Closing Metathesis11-18

Complex 1 has been used for ring-closing metathesis5 of acyclic dienes. Optically enriched b-citronellene has been ring closed to give 3-methylcyclopentene without loss of any optical purity (1). The workers were then able to initiate ROMP with the same catalyst to give head-to-tail isotactic polymer.

Alkene Metathesis

Alkylidene 1 has been used to metathesize olefins, but the reaction takes days to come to equilibrium (2).6 This process is much more efficient with catalyst 3.

Ring-Opening Metathesis

Catalyst 3 [where the ligand = OCMe2(CF3)] has been used to ring-open cyclic imines (3).19

Ring-Opening Metathesis Polymerization (ROMP)20

Complex 2 will polymerize a variety of bicyclo[2.2.1]heptenes. The trifluoromethyl derivative 4 is polymerized to the trans syndiotactic polymer 5 (4).7 The stereochemistry of the polymer structure has also been investigated.21 2,3-Difunctionalized 7-oxanorbornenes, 7-oxanorbornenes,8 and the norbornene macromonomer22 have all been polymerized by either catalyst 1 or 2.

Functionalized redox-active polymers have been prepared23,24 using ROMP chemistry. Cyclobutene 6 has been polymerized to yield a polymer with interesting conformational properties (5).25 3,4-Disubstituted cyclobutenes have also been polymerized to give polymers with protic functionality.26

It has also been possible to incorporate interesting functionality into the polymers. Amino-ester functionalized have been prepared starting with the corresponding amino ester functionalized norbornene and alanine-derived homopolymers have also been prepared by ROMP chemistry with 1 (6).27 Polymer 9 is optically active and can be considered as an artificial peptide in which the amide backbone has been replaced by an all carbon system. Peptide functionalized norbornenes have also been polymerized by catalyst 1. Polymers based on peptides,27 antibiotics,28 nucleic acids,29 and carbohydrates30 have also been prepared using ROMP chemistry an metal alkylidenes. Deltacyclenes have also been polymerized by 1.31

Related Reagents.

[2,6-Bis(1-methylethyl)benzenaminato]bis(1,1,1,3,3,3-hexafluoro-2-methyl-2-propanolato (2-methyl-2-phenylpropylidene) molybdenum; [2,6-bis(1-methylethyl)benzenaminato]-bis(1,1,1,3,3,3-hexafluoro-2-methyl-2-propanolato (2,2-dimethylpropylidene) tungsten; Dimethyltitanocene; Tebbe reagent; Ruthenium(I); Ruthenium(II).

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Maarten Postema, Lei Liu & Shen Jie

Wayne State University, Detroit, Michigan, USA

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