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

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.