PENTACOORDINATED MOLECULES .89. HYDROGEN-BONDED CHAIN AND DIMER FORMATIONS OF SPIROCYCLIC TETRAOXYPHOSPHORANES POSSESSING PHOSPHORINANE CHAIR CONFORMATIONS

Oxidative-addition reactions of aminophenols with the monocyclic phosphite (Me2C3H4O2)P(O-Xyl), yielded new spirocyclic tetraoxyphosphoranes containing saturated six-membered rings, (Me2C3H4O2)(O2NC6H3ONH)P(O-Xyl) (1), (Me2C3H4O2)(C5H3NONH)P(O-Xyl) (2), and (Me2C3H4O2)(Me2C6H2ONH)P(O-Xyl) (4). Hydrogen bonding was introduced via N-H---X (X = O, N) interactions involving remote ring substituents to ascertain their influence as a structural determinant. X-ray analysis revealed phosphoranes in trigonal-bipyramidal geometries with rings situated in axial-equatorial sites. A hydrogen bonded chain structure was obtained for 1 with the phosphorinane ring in a chair conformation. For 2, a hydrogen-bonded dimer was found with the six-membered ring in a twisted or half-chair form. Reaction of 2-hydroxybenzyl alcohol with (Me2C3H4O2)P(O-Xyl) gave the phosphate formation (Me2C3H4O2)P(O)(O-Xyl) (3), confirmed by X-ray analysis with the ring in a chair conformation. Variable-temperature H-1 NMR spectroscopy showed fluxional molecules undergoing intramolecular ligand exchange via a TBP exchange intermediate with the six-membered ring located in diequatorial sites. Activation energies in the range 10.5-12.5 kcal/mol were obtained. The relevance of the results to pentaoxyphosphorane intermediates proposed in c-AMP enzyme reactions is cited. 1 crystallizes in the monoclinic space group P21/c with a = 8.1618 (9) angstrom, b = 20.240 (4) angstrom, c = 12.577 (1) angstrom, beta = 103.26 (1)-degrees, and Z = 4. 2 crystallizes in the monoclinic space group P21/n with a = 11.200 (2) angstrom, b = 27.347 (8) angstrom, c = 12.865 (3) angstrom, beta = 105.23 (2)-degrees, and Z = 8. 3 crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 7.253 (1) angstrom, b = 9.456 (2) angstrom, c = 20.510 (3) angstrom, and Z = 4. The final conventional unweighted residuals are 0.037 (1), 0.050 (2), and 0.035 (3).