COORDINATION-COMPLEXES DERIVED FROM TRIPHOSPHOXANE, TETRAPHOSPHOXANE, AND PENTAPHOSPHOXANE RINGS

Thermal reactions of hexacarbonylchromium and -tungsten with bis(diisopropylamino)phosphine oxide yielded the tetraphosphoxane complexes cis-M(CO)4[(i)Pr2NPO]4 as the major products. Spectral data and X-ray structural determination of the molybdenum analogue confirmed 1,5-coordination of statistical mixtures of the chair-boat (C(S)) and chair-chair (C2-upsilon) conformations of the P4O4 ring. Crystal data: monoclinic, A2/a; a = 18.992 (1), b = 11.306 (5), c = 19.368 (1) angstrom; beta = 98.63 (1)-degrees; V = 4111.6 (4) angstrom 3; Z = 4; final R(F) = 0.062, R(wF) = 0.057 for 2219 significant reflections and varying 204 parameters. Minor coproducts from the chromium reaction included Cr2(CO)8[(i)Pr2NPO]4, with a tetradentate P4O4 ring chelating both metals, as well as Cr2(CO)7[(i)Pr2NPO]5. The latter structure features a novel pentaphosphoxane P5O5 ring coordinated to one Cr(CO)3 and one Cr(CO)4 to form a bimetallic cage. Crystal data: monoclinic, P2(1)/c; a = 12.6554 (8), b = 17.639 (1), c = 23.670 (1) angstrom; beta = 101.82 (1)-degrees; V = 5171.7 (5) angstrom 3; Z = 4; final R(F) = 0.088, R(wF) = 0.081 for 4337 significant reflections and varying 491 parameters. Under milder reaction conditions with molybdenum hexacarbonyl, a triphosphoxane complex Mo(CO)5[(i)Pr2NPO]3 can be isolated. Crystal data: orthorhombic, Pbc2(1); a = 11.570 (2), b = 18.729 (5), c = 32.056 (3) angstrom; V = 6946.36 angstrom 3; Z = 8; final R(F) = 0.047, R(wF) = 0.048 for 3469 significant reflections and varying 685 parameters. This was converted readily by heating to the known Mo2(CO)8[(i)Pr2NPO]4 cage complex. Reactions of the parent [(i)Pr2NPO]3 triphosphoxane ring with Mo(CO)4(norbornadiene) afforded a 1:1 complex cis-Mo(CO)4-[(i)Pr2NPO]3 which also transformed into the same adamantanoid cage complex upon warming. With bis(benzonitrile)palladium dichloride, triphosphoxane gave a product characterized by spectral data and X-ray crystallography to be cis-PdCl2[(i)Pr2NPO]4 with a 1,5-coordinated tetraphosphoxane ring exclusively in the chair-chair (C2-upsilon) conformation. Crystal data: monoclinic C2/c; a = 19.980 (5), b = 11.0945 (10), c = 17.934 (9) angstrom; beta = 112.04 (3)-degrees; V = 3684.8 angstrom 3; Z = 4; final R(w) = 0.051 and R(wF) = 0.060 for 252 variables using 3246 significant reflections. A similar reaction with NiBr2.DME (DME = dimethoxyethane) yielded instead a 1,3-coordinated P4O4 complex NiBr2[(i)Pr2NPO]4. The parent [(i)Pr2NPO]4 ligand, stable below -20-degrees-C, can be liberated from this Ni complex by pyridine substitution. It reverts to the triphosphoxane compound upon warming to ambient temperature.