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.

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The carbamoyl ferrate Li[Fe{C(O)NiPr2}(CO)4] reacts in diethyl ether with Br2PPh3, I2PPh3, or I2 followed by triphenylphosphine to provide the complexes [Fe(η2-OCNiPr2)X(CO)2(PPh3)] [X = I trans to PPh3 (1a); Br (1b) two isomers], each of which feature dihapto-C,O carbamoyl coordination. The reactions of 1a or 1b with AgBF4 in the presence of CO provide [Fe(η2-OCNiPr2)(CO)3(PPh3)]BF4 (2a·BF4), one carbonyl ligand of which is labile and readily replaced by I-, Br-, or PPh3 to provide 1a, 1b, or [Fe{η2-OCNiPr2}(CO)2(PPh3)2]BF4 (2b·BF4). The reaction of 1a with dppe leads to a separable mixture of the salt [Fe{η2-OCNiPr2}(CO)2(dppe)]I (3·I) and [Fe{η2-OCNiPr2}I(CO)(dppe)] (4). Successive treatment of Li[Fe{C(O)NiPr2}(CO)4] with ClSnPh3 and PPh3 provides the stannyl complex [Fe(η2-OCNiPr2)(SnPh3)(CO)2(PPh3)] (1d). Treating 1d with iodine leads to Sn−Fe rather than Sn−C cleavage and formation of 1a. In all the above transformations the integrity of the dihapto carbamoyl coordination is ultimately retained. The crystal structures of 1d and 2b·PF6 are reported.

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