THE STRUCTURE OF TRANS-1,4-DIISOCYANOCYCLOHEXANE IN SOLUTION, IN THE SOLID-STATE, AND AS A LIGAND BRIDGING BULKY TUNGSTEN(II) COMPLEXES

The conformational structures of the bridging ligand trans-1,4-diisocy anocyclohexane were determined in solution, as a solid, and as a ligan d bridging bulky seven-coordinate tungsten(II) complexes. In solution CNC6H10NC exists as an equilibrium mixture of diaxial and diequatorial conformers, with the diequatorial conformer preferred in a 2 : 1 rati o. Infrared data indicate that the bulk solid does not consist of the diequatorial conformer, and a single-crystal study verifies that the d iaxial conformer is preferred in the solid state. The crystal data fou nd for CNC6H10 NC are: space group P2(1)/n, Z = 2, a = 5.996(1)Angstro m, b = 7.203(2) Angstrom, c = 8.972(3)Angstrom, beta = 96.89(2)degrees , and V = 384.7(2)Angstrom(3). C-13 NMR bandshape analysis provides a low activation barrier (40.7(4) kJ mol(-1)) in CH2Cl2 solution for dia xial-diequatorial conversion. In spite of the accessibility of both co nformers in solution, the ligand unexpectedly adopts the diaxial confo rmation in the bimetallic complex (Br-2(PEt(3))(2)(CO)(2)W)(2)CNC6H1ON C The crystal data found for (Br-2(PEt(3))(2)(CO)(2)W)(2)CNC6H1ONC are : space group Pca2(1), Z = 4, a = 17.162(5)Angstrom, b = 16.226(6)Angs trom, c = 18.233(3)Angstrom, and V = 5077.3(25)Angstrom(3).