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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.

The reaction between [Mo(NO)(Tp)I(2)] {Tp(-) = hydrotris(3,5-dimethylpyrazol-1-yl)borate} and 2,7-dihydroxynaphthalene affords, as its major product, the binuclear complex [Mo(NO)(Tp)(2,7-O(2)C(10)H(6))](2). The reaction appears to proceed under kinetic control so that shorter reaction times afford the syn-isomer (47% yield after 40 min) while longer reaction times allow the anti-isomer (43% yield after 48 h) to be obtained. The molecular structures of anti-[Mo(NO){HB(3,5-Me(2)C(3)HN(2))(3)}(2,7-O(2)C(10)H(6))](2).2CHCl(3).CH(2)Cl(2) (1)(,) syn-[Mo(NO){HB(3,5-Me(2)C(3)HN(2))(3)}(2,7-O(2)C(10)H(6))](2).0.67CHCl(3).2.7H(2)O (2) and syn-[Mo(NO){HB(3,5-Me(2)C(3)HN(2))(3)}(2,7-O(2)C(10)H(6))](2).3(CH(3))(2)CO (3) have been determined crystallographically: (1) C(50)H(56)B(2)N(14)O(6)Mo(2).2CHCl(3).CH(2)Cl(2), triclinic, space group P&onemacr;, a = 11.535(2) Å, b = 14.032(3) Å, c = 11.247(3) Å, alpha = 94.70(1) degrees, beta = 102.30(2) degrees, gamma = 110.31(2) degrees, Z = 1; (2) C(50)H(56)B(2)N(14)O(6)Mo(2).0.67CHCl(3).2.7H(2)O, monoclinic space group P2(1)/m, a = 23.770(7) Å, b = 26.600(10) Å, c = 11.334(4) Å, beta = 99.86(2) degrees, Z = 4; (3) C(50)H(56)B(2)N(14)O(6)Mo(2).3C(3)H(6)O, triclinic, space group P&onemacr;, a = 16.929(3) Å, b = 17.465(4) Å, c = 12.739(2) Å, alpha = 100.06(1) degrees, beta = 94.93(2) degrees, gamma = 114.13(1) degrees, Z = 2. In 1 each nitric oxide ligand is hydrogen bonded [C-H 0.98, H.O 2.26, C.O 3.13(2) Å, C-H.O 147 degrees } to a chloroform molecule which lies within a cavity in the molecule having as its base a bridging 2,7-naphthalenediyl fragment and as its sides a part of each HB(3,5-Me(2)C(3)HN(2))(3) ligand. No hydrogen bonding interactions with nitric oxide are apparent in the structures of 2 or 3.

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