US EPA

4837030 

Journal Article 

Cycloaddition and C-H Activation Reactions of a Tantalum Alkylidyne 

Ramirez-Contreras, R; Bhuvanesh, N; Ozerov, OV 

2015 

1 

Organometallics
ISSN: 0276-7333
EISSN: 1520-6041 

34 

7 

1143-1146 

10.1021/acs.organomet.5b00205 

WOS:000353005600002 

The alkylidyne complex (C5Me5)Ta(=CPh)(PMe3)(2)Cl (1) was first reported by Schrock in 1978, but little if any follow-up work on 1 or other group 5 metal alkylidynes has been reported. This work discloses two avenues of reactivity of 1. Treatment of 1 with 3-hexyne resulted in the formation of a tantalacyclobutadiene. Abstraction of chloride from 1 led to a mixture of products that included isomers of [(C5Me5)Ta(-CHPh)(CH2PMe2)(PMe3)](+) (4), in which a CH bond of a PMe3 ligand was added across the Ta C bond. The CH activation was found to be reversible, and the equilibrium mixture functioned as an equivalent of a cationic Ta alkylidyne in reaction with 3-hexyne, producing a cationic tantalacyclobutadiene (6). Compounds 4 and 6 were structurally characterized in the solid state by XRD methods, with 6 being the first structurally characterized metallacyclobutadiene in group 5.