Synthesis and reactivity of (silox)2R2WO (R = Cl, Me, Et, nPr and nBu; silox = OSitBu3) and (silox)2MO2 (M = Mo and W)

Abstract Addition of Na(silox) (silox = OSi t Bu 3 ) to Cl 4 WO afforded (silox) 2 Cl 2 WO ( 3 ), and subsequent alkylation with appropriate Grignard reagents yielded (silox) 2 R 2 WO ( 4 -R; R = Me, Et, n Pr, n Bu). 4 -R adopt distorted trigonal bipyramidal structures with axial silox groups, as implied by the X-ray crystal structure of 4 - n Bu. New metathetical procedures were utilized in the preparation of (silox) 2 M(O) 2 (M = Mo, 6 ; W, 7 ); the addition of Na(silox) to (DME)Cl 2 M(O) 2 (M = Mo, W) in THF afforded the dioxo species. None of the oxo complexes exhibited oxygen atom transfer (OAT) to PMe 3 . The thermolysis of 4 -Et and 4 - n Bu afforded olefin derivatives (silox) 2 (ole)WO ( 5 -ole; ole = C 2 H 4 , C 4 H 8 ) as the primary products. Thermal degradation of (silox) 2 (CD 3 CH 2 ) 2 WO ( 4 -CH 2 CD 3 ) revealed H/D-scrambling among α- and β-positions indicative of reversible β-H-elimination prior to alkane loss. A brief discussion of the lack of OAT is presented.