Showing papers by "Thomas F. Koetzle published in 1976"

X-ray and neutron diffraction studies on HW/sub 2/(CO)/sub 8/(NO)(P(OCH/sub 3/)/sub 3/). A compound with a slightly asymmetric hydrogen bridge bond

Abstract: The molecular structure of HW/sub 2/(CO)/sub 8/(NO)(P(OCH/sub 3/)/sub 3/), prepared by treating HW/sub 2/(CO)/sub 9/(NO) with trimethyl phosphite, was studied with x-ray and neutron diffraction techniques. The presence of the bulky P(OCH/sub 3/)/sub 3/ ligand eliminated the packing disorder problems which occurred in the earlier neutron diffraction analysis of HW/sub 2/(CO)/sub 9/(NO), and allowed the detailed geometry of the WHW region to be examined closely for possible asymmetric features. The structure of HW/sub 2/(CO)/sub 8/(NO)(P(OCH/sub 3/)/sub 3/) consists of W(CO)/sub 5/ and W(CO)/sub 3/(NO)(P(OCH/sub 3/)/sub 3/) fragments joined by a single WHW three-center bond. The nitrosyl ligand was located at an axial position, thereby confirming earlier results on HW/sub 2/(CO)/sub 9/(NO). In the present neutron diffraction study the WHW bond was found to be slightly asymmetric, the difference between the two W--H distances being 0.035 (10) A. The hydrogen atom is closer to the W(CO)/sub 5/ group than to the W(CO)/sub 3/(NO)(P(OCH/sub 3/)/sub 3/) group, as expected since the W(CO)/sub 5/ unit is the more electron-deficient half of the molecule. The rest of the structure is very similar to that of HW/sub 2/(CO)/sub 9/(NO). The molecule has a bent backbone with staggered equatorial ligands, and the hydrogen atom is significantlymore » removed from the point of intersection of the axial W--C and W--N vectors. Crystallographic details for HW/sub 2/(CO)/sub 8/(NO)(P(OCH/sub 3/)/sub 3/): unit cell P anti l; a = 10.012 (7), b = 11.261 (8), c = 9.062 (6) A; a = 90.84 (5), ..beta.. = 90.52 (6), ..gamma.. = 76.35 (4)/sup 0/; V = 992.7 A/sup 3/, Z = 2.« less