Sam J. La Placa

On a nearly proton‐ordered structure for ice IX

Single‐crystal neutron diffraction shows that ice IX, the low‐temperature modification of ice III, has an almost completely proton‐ordered structure in which the ordered component contains two types of water molecules, type 1 in a site of no point symmetry, and type 2 on a twofold axis, each forming four hydrogen bonds in a three‐dimensional framework. The configuration of the water molecules is slightly but significantly altered from that of water vapor. Independent O–D distances, which do not differ significantly from one another, average 0.982± 0.003 A (corrected for thermal motion), and are increased by 0.012 A over the vapor value. The shift in O–D stretching frequency ν1 from vapor to ice IX corresponds to a slope dν1/dr≅ −20 000 cm−1. A−1, which agrees with the slope predicted from spectroscopic anharmonicity constants. D–O–D bond angles (104.7± 0.4°, 106.0± 0.2°) are not decreased from the vapor value (104.5°) despite the smaller O··· O··· O angles into which the water molecules donate protons (98...

A Short, Slightly Asymmetrical, Intramolecular Hydrogen Bond: A Neutron Diffraction Study of Bis(2‐amino‐2‐methyl‐3‐butanone Oximato)Nickel(II) Chloride Monohydrate {Ni(C5H11N2O)2H}+Cl−·H2O

A neutron diffraction study of bis(2‐amino‐2‐methyl‐3‐butanone oximato)nickel(II) chloride monohydrate {Ni(C5H11N2O)2H}+Cl−·H2O has provided a wealth of precise information concerning the short intramolecular hydrogen bond, the dynamics of rotating methyl groups, and the effects of intermolecular environment on potential functions. The intensities of 3500 single‐crystal reflections were measured at the Brookhaven High Flux Beam Reactor. These data were used in conjunction with the earlier x‐ray determination to locate all atoms including the 25 hydrogen atoms. After least squares refinement with anisotropic temperature factors, the agreement factor R = ΣΔ(F2) / ΣF02 was 0.055. The short intramolecular hydrogen bond O···O [2.420(3) A] is unique in that no bond symmetry is imposed by the space group, and it is slightly asymmetrical. The O–H bond lengths for the hydrogen bond are 1.242(5) and 1.187(5) A, and the O–H–O angle is 169.9(3)°. The potential apparently has a broad, flat, single minimum, shifted tow...

Molecular Structure of the Synthetic Molecular Oxygen Carrier O2IrCl(CO)(P[C6H5]3)2

The synthetic molecular oxygen carrier O2lrCl(CO)(P[C6H5]3)2, discovered by Vaska, has been characterized in a complete molecular structure determination. The structure surmised by Vaska from spectroscopic data has been confirmed and, in addition, definitive details on the attachment of molecular oxygen to iridium in this 1 : 1 reversible oxygen carrier have been obtained. The two oxygen atoms are equidistant from the metal atom, as in Griffiths model of the oxygen atoms in oxyhemoglobin. The O-O bond length of 1.30 � 0.03 � is intermediate between those characteristic of O2 (1.20 �) and O2-2 (1.48 �), and corresponds closely to O2-(1.28 �)

TRICYCLO(3,2,1,0(1,5))OCTAN, EIN 3,2,1-PROPELLAN, ′UMGEKEHRTE′ TETRAEDRISCHE GEOMETRIE AM BRUECKENKOPFKOHLENSTOFF, KRISTALL-, MOLEKULAR- UND ELEKTRONENSTRUKTUR VON 8,8-DICHLOR-TRICYCLO(3,2,1,0(1,5))OCTAN BEI -40 GRAD

Aus dem Bicyclohepten (I) entsteht in Pentan und in Gegenwart von Na-methanolat das tricyclische Dichlorid (II), das in Gegenwart von Diazomethan und Cu-chlorid in den Kohlenwasserstoff (III) ubergeht.

Structure of a Synthetic Molecular Oxygen Carrier

VASKA (1) has characterized a simple synthetic molecular oxygen carrier O2IrCl(CO)[P(C6H5)3]2 prepared by the addition of molecular oxygen to IrCI(CO)[P(C6H5)3]2 in benzene solution. This synthetic oxygen carrier, which is a reasonably stable crystalline solid, differs from most reported in the past in that there is but one molecule of oxygen per metal atom, as there is in oxyhemoglobin. The mode of attachment of oxygen to iridium in this cornpound is thus of interest both in itself and especially in relation to theories of the mode of attachment of molecular oxygen to the iron atom in oxyhemo — globin.