Syntheses of Variations of Stereogenic-at-Metal Imido Alkylidene Complexes of Molybdenum

Abstract

In this paper we describe the syntheses of several new stereogenic-at-metal imido alkylidene complexes of molybdenum, Mo(NR)(CHR′)(X)(Y), many of which had to be prepared through selective nucleophilic displacement reactions in imido alkylidene complexes. The reported compounds include Mo(NAd)(CHCMe2Ph)(MesPyr)2 (1a; MesPyr = 2-mesitylpyrrolide, Ad = 1-adamantyl), Mo(NAd)(CHCMe2Ph)(2-CNPyr)2 (1b; 2-CNPyr = 2-cyanopyrrolide), Mo(NAd)(CHCMe2Ph)(MesPyr)(OTPP) (2a; OTPP = 2,3,5,6-tetraphenylphenoxide), Mo(NAd)(CHCMe2Ph)(MesPyr)(OBr2Bitet) (2b; OBr2Bitet = (R)-3,3′-dibromo-2′-(tert-butyldimethylsilyloxy)-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl-2-olate), Mo(NAd)(CHCMe2Ph)(OHIPT)(2-Mespyr) (2c; HIPT = 2,6-(2,4,6-iPr3C6H2)2C6H3), Mo(NAd)(CHCMe2Ph)(OTf)(OHIPT) (3), Mo(NAd)(CHCMe2Ph)(OTf)(OHIPT)(PMe3) (3(PMe3)), Mo(NAd)(CHCMe2Ph)(2-CNPyr)(OHIPT) (4), Mo(NAd)(CHCMe2Ph)(OHIPT)(OCMe3) (5), Mo(NR)(CHCMe2Ph)(ORF6)(OHMT) (ORF6 = OCMe(CF3)2; HMT = 2,6-Mes2C6H3; R = 2,6-iPr2C6H3 (Ar, 6a), 2,6-Me2C6H3 (Ar′, 6b), 2-iPrC6H4 (AriPr, 6c), Ad (6d)), Mo(NR)(CHCMe2Ph)(ORF6)[N(H)HMT] (7a (R = Ar′) and 7b (R = AriPr)), and Mo(NAd)(CHCMe2Ph)(ORF6)(HMT) (8). X-ray structural studies were carried out on 1b, 2a–c, 3(PMe3), 4, 5, 6d, 7b, and 8. Compound 1b is an octamer in which two η1-pyrrolides are trans to one another at each metal center and cyano groups bind from neighboring Mo centers trans to the alkylidene and imido ligands.