Stereoselectivity in the formation of metallomacrocycles from [Mo(NO){HB(3,5-Me2C3HN2)(3)}I-2] and ditopic proligands: The x-ray crystal structures of anti-[Mo(NO){HB(3,5-Me2C3HN2)(3)}{1,4-(OCH2)(2)C6H4}](2).4CHCl(3), syn-[Mo(NO){HB(3,5-Me2C3HN2)(3)}{1,4-(OCH2)(2)C6H4}](2).2CH(2)Cl(2), and anti-[Mo(NO){HB(3,5-Me2C3HN2)(3)}{(4-OC6H4)(2)CH2}](2).2CHCl(3).CH2Cl2

The reaction between the chelating ligand 1,2-(HOCH2)(2)C6H4 and [Mo(NO)(tp *)I-2] {tp* = HB(3,5-Me2C3HN2)(3)} in the presence of NEt3 affords the mono metallic complex [Mo(NO)(tp*){(OCH2)(2)C6H4}], 1. However, reactions involv ing the nonchelating ditopic proligands HE-EH {HE-EH = 1,4-(HOCH2)(2)C6H4, 1,3-(HOCH2)(2)C6H4, and 4,4'-(HOC6H4)(2)CH2} afford the binuclear metallocy clophanes Mo(NO)(tp*)(E-E)](2) as mixtures of syn- and anti-isomers. These binuclear complexes are formed under kinetic control so that syn-[Mo(NO)(tp *){1,4-(OCH2)(2)C6H4}](2), 2s, forms more rapidly than anti-[Mo(NO)(tp*){1, 4-(OCH2)(2)C6H4}](2), 2a, but in lower yield. Some kinetic control is also apparent in the formation of the syn- and anti-isomers of [Mo(NO)(tp*){4,4' -(OC6H4)(2)CH2}](2), 4, and [Mo(NO)(tp*){1,3-(OCH2)(2)C6H4}](2), 3, but in these cases the reaction is less stereoselective. The X-ray crystal structu res of three complexes were determined to establish their isomeric structur es: anti-[[Mo(NO){HB(3,5-Me2C3HN2)(3)}{1,4-(OCH2)(2)C6H4}](2).4CHCl(3), C46 H60B2Mo2N14O6.4CHCl(3), triclinic, space group P (1)over-bar, a = 11.967(3) Angstrom, b = 18.004(2) Angstrom, c = 8.740(2) Angstrom, alpha = 102.31(1) degrees, beta = 109.32(1)degrees, gamma = 82.08(1)degrees, Z = 1; syn-[Mo(N O){HB(3,5-Me2C3HN2)(3)}{1,4-(OCH2)(2)C6H4}](2), C46H60B2Mo2N14O6.2CH(2)Cl(2 ), monolinic, space group P2(1)/a, a = 16.576(3) Angstrom, b = 20.844(2) An gstrom, c = 17.024(2) Angstrom, beta = 109.32(1)degrees, Z = 4; anti-[Mo(NO ){HB(3,5-Me2C3HN2)(3)}{(4,4'-OC6H4)(2)CH2}](2), C56H64B2Mo2N14O6.2CHCl(3).C H2Cl2, triclinic, space group P (1)over-bar, a = 12.665(2) Angstrom, b = 13 .013(2) Angstrom, c = 11.894(2) Angstrom, alpha = 111.80(1)degrees, beta = 95.48(1)degrees, gamma = 94.78(2)degrees, Z = 1. All three structures are c haracterized by short Mo-O bond distances indicative of some Op(pi)-->Mod(p i) bonding. In the case of 2a evidence for weak hydrogen bonds between solv ating CHCl3 molecules and the alkoxide oxygens was found.