Bi-, Tri-, and Tetranuclear Metallomacrocycles Constructed by Metal-Directed Reactions Involving Resorcinol or Hydroquinone or by Addition of Octahedral Metal Centers to Tetrahexylcalix[4]resorcinarene: X-ray Crystal Structure of syn,syn-[Mo{HB(3,5-Me(2)C(3)HN(2))(3)}(NO)(1,4-O(2)C(6)H(4))](3).

The reaction between [Mo(NO)(Tp)I(2)] [Tp(-) = hydrotris(pyrazol-1-yl)borate] and tetrahexylcalix[4]resorcinarene (resH(8)) affords a mixture of metalated macrocycles from which [{Mo(NO)(Tp)}(2)(resH(4))], [{Mo(NO)(Tp)}(3)(resH(2))], and [{Mo(NO)(Tp)}(4)(res)] can be isolated. In the solid state the tetrametalated compound can act as a host for CH(2)Cl(2) which forms a weak hydrogen bond to the oxygen of a coordinated nitric oxide: H.O1 2.47 Å, angle C-H.O1 161 degrees. Direct reaction of [Mo(NO)(Tp)I(2)] [Tp(-) = hydrotris(3,5-dimethylpyrazol-1-yl)borate] with resorcinol itself offers a route to the related resorcinol-based tetrametallomacrocycle [Mo(NO)(Tp)(1,3-O(2)C(6)H(4))](4). This reaction also produces the cyclic trimer [Mo(NO)(Tp)(1,3-O(2)C(6)H(4))](3) together with some cyclic dimer. A similar reaction involving 1,4-dihydroxybenzene and [M(NO)(Tp)I(2)] (M = Mo, W) also affords cyclic trimers and cyclic tetramers, but in this case, cyclic dimers are not formed. It has been possible to separate the single isomers syn,syn-[Mo(NO)(Tp)(1,4-O(2)C(6)H(4))](3), anti,syn-[M(NO)(Tp)(1,4-O(2)C(6)H(4))](3) (M = Mo, W), anti,syn-[Mo(NO)(Tp)(1,3-O(2)C(6)H(4))](3), and anti,syn,syn-[Mo(NO)(Tp)(1,3-O(2)C(6)H(4))](4). The crystal structure of syn,syn-[Mo(NO)(Tp)(1,4-O(2)C(6)H(4))](3) has been determined: C(63)H(78)B(3)Mo(3)N(21)O(9); monoclinic space group P2(1)/a; a = 16.269(10), b = 35.31(3), c = 16.056(10) Å; beta = 97.59(2) degrees; Z = 4. The coordination geometry at the molybdenum atoms is essentially octahedral. The trimer does not show 3-fold symmetry, the triangle of molybdenum atoms having two long edges, 8.485(3) and 8.703(3) Å, and one short edge of 7.886(3) Å. These distances are paralleled by the corresponding distances between the nitrosyl oxygen atoms, 6.177(12), 6.526(12), and 3.729(12) Å, respectively. The electrochemical properties of the metallomacrocycles reveal differing patterns of redox potentials depending upon the number and geometric arrangement of metal centers in the macrocyclic structure.