STRUCTURE AND REACTIVITY OF A TITANOCENE ETA-2-THIOFORMALDEHYDE TRIMETHYLPHOSPHINE COMPLEX

Bis(η5-cyclopentadienyl)titanium titanocene η2-thioformaldehyde trimethylphosphine (3) was prepared from titanocene methylidene trimethylphosphine and either sulfur-containing compounds (e.g., alkene sulfides, triphenylphosphine sulfide) or elemental sulfur. The product 3 crystallized in the orthorhombic system, in space group Pnma (No. 62), with a = 13.719 (3) Å, b = 12.384 (1) Å, c = 8.671 (1) Å, V = 1473.2 (6) Å3; Z = 4. The reaction with trans-styrene sulfide-d1 produced an equimolar mixture of trans- and cis-styrene-d1 as byproducts, suggesting a stepwise reaction. The formation of a six-membered ring from titanocene methylidene trimethylphosphine and trimethylene sulfide also supports the stepwise mechanism. A biradical mechanism is preferred in view of the biradical mechanism observed in the analogous reaction with styrene oxide. The complex 3 reacted with methyl iodide to produce the cationic titanocene η2-thiomethoxymethyl trimethylphosphine complex 5a, which crystallized with acetonitrile in the orthorhombic system, space group Pbca (No. 61) with a = 14.839 (2) Å, b = 15.184 (14) Å, c = 18.461 (3) Å, V = 4159.5 (14) Å3, Z = 8. Complexes 5b,c having a less coordinating anion such as BF4 or BPh4 were obtained, and complex 5c was converted to a trimethylphosphine-free complex by equilibration with copper(I) chloride. This cationic species (7c) does not catalyze the polymerization of ethylene or methyl vinyl ether in dichloromethane. © 1990, American Chemical Society. All rights reserved.