Synthesis, X-ray structure and reactivity of μ-(CF3COO)2-[Mo(N-2,6-i-Pr2-C6H3)(CHCMe2Ph)(OOCCF3)(Et2O)]2, the first Bis(trifluoroacetate) derivative of a Schrock catalyst

Reaction of Mo(N-2,6-i-Pr2-C6H3)(CHCMe2C6H5)(OSO2CF3)(DME) (DME = 1,2-dimethoxyethane) with 2 equiv. of CF3COOK yields μ-(CF3COO)2-[Mo(N-2,6-i-Pr2-C6H3)(CHCMe2Ph)(OOCCF3)(Et2O)]2 (1). Compound 1 crystallizes in the orthorhombic space group Pna21 with a = 17.2485(3), b = 17.0336(3), c = 25.4031(5) Å, α = β = γ = 90°, V = 7463.5(2) Å3, Z = 4. In contrast to alkoxide based Schrock type initiators, 1 is virtually inactive in numerous metathesis reactions including ring-closing metathesis (RCM) and homo metathesis reactions, the cyclopolymerization of 1,6-heptadiynes, and even ring-opening metathesis polymerization (ROMP) of norborn-2-ene. However, addition of quinuclidine results in the in situ formation of 1a (Mo(N-2,6-i-Pr2-C6H3)(CHCMe2C6H5)(OOCCF3)2(quinuclidine) which displays moderate activity in ROMP, cyclopolymerization of 1,6-heptadiynes and RCM. Theoretical investigations carried out on the B3LYP/LACVP∗ level provide substantial explanation for these findings.