NORBORNADIENE(BIPYRIDYL)MOLYBDENUM(II) COMPLEXES - SYNTHESIS, STRUCTURE AND REACTIVITY OF [MO(CO)(C7H8)(C(10)H(6)R(2)N(2))X(2)] (X=I, BR)

The reaction of [Mo(CO)(4)(C7H8)] (1) With I-2 gave the norbornadienem olybdenum(II) complex [Mo(CO)(2)(C7H8)I-2](n greater than or equal to 1) (2), which existed in an equilibrium of two isomeric forms. In acet onitrile, 2 reversibly formed the adduct [Mo(CO)(2)(C7H8)(NCCH3)I-2] ( 3), whereas on treatment with 2,2'-bipyridine or 4,4'-di-2,2'-tBu-bipy ridine, it gave stable 7-coordinated molybdenum(II) complexes, [Mo(CO) (C7H8)(C10H8N2)I-2] (4) and [Mo(CO)(C7H8)(C(10)H(6)tBu(2)N(2))I-2] (5) , in good yield. In similar reactions, the related dibromomolybdenun c ompounds [Mo(CO)(C7H8)(C10H8N2)Br-2] (6) and [Mo(CO)(C7H8)(C(10)H(6)tB u(2)N(2))Br-2] (7) were prepared by oxidation of 1 with two equivalent s of CuBr2. The X-ray structural analysis of 6 reveals that the geomet ry around the molybdenum atom is nearly perfectly pentagonal bipyramid al, with the CO and one of the bipyridyl rings perpendicular to the pl ane formed by the other ligands. The compounds 5 and 6 react with AgSb F6 by halogen abstraction to give cationic complexes, {[Mo(CO)(C7H8)(C 10H8N2)Br]SbF6}(n greater than or equal to 1) (8) and {[Mo(CO)(C7H8)(C (10)H(6)tBu(2)N(2))I]SbF6}(n greater than or equal to 1) (9): In aceto ne, 8 and 9 reversibly formed the adducts [Mo(CO)(C7H8)(C10H8 N-2)(ace tone)Br]SbF6 (8') and [Mo(CO)(C7H8)(C(10)H(6)tBu(2)N(2))(acetone)I]SbF 6 (9'); while on treatment with PMe(3), the stable monomeric complexes , [Mo(CO)(C7H8)(C10H8N2)(PMe(3))Br]SbF6 (10) and [Mo(CO)(C7H8)(C(10)H( 6)tBu(2)N(2))(PMe(3))I]SbF6 (11), were isolated in almost quantitative yield. In the presence of KBr, compound 8' reverted to the dibromo co mplex 6, whereas 9' reacted to produce a 1:1:2 mixture of 5, 7 and the bromo(iodo) complex [Mo(CO)(C7H8)(C(10)H6tBu(2)N(2))BrI] (12). The sa me mixture is available from the reaction of 5 with one equivalent of 7.