John A. Weaver

Crystal and molecular structure of di-µ-carbonyl-cis-µ-(1–5-η: 1′–5′-η-dicyclopentadienyldimethylsilane)bis(carbonyliron)(Fe–Fe)

Crystals of the title compound are monoclinic, space group P21/n, with Z= 4 in a unit cell of dimensions: a= 11·66, b= 13·27, c= 10·82 A, β= 105° 50′. The structure was determined from diffractometer data by the symbolic addition method and refined to R 0·072 for 1309 independent reflections. The silicon atom is tetra-hedrally σ bonded to two methyl groups and to two cyclopentadienyl rings; the latter are in turn each π-bonded to one iron atom. The two iron atoms are bonded to one another (2·51 A) and are also linked by two symmetrical carbonyl bridges; the four-membered ring so defined is non-planar, being folded along the Fe–Fe axis away from the C5 rings at an angle of ca. 160°. Each iron atom also carries one terminal carbonyl group, which makes the overall co-ordination approximately octahedral.The Si atom does not lie in the Fe2(CO)2(terminal) plane, nor are the cyclopentadienyl rings symmetrically related to it (though their centroids lie in it), and the overall symmetry of the molecule is only Cs(m). Reasons for this configuration are discussed. The Fe–C and C–O distances are as expected; the four Si–C distances relatively equal, mean 1·88 A.

Zinc(II) and cobalt(II) halide interactions with vitamin B1 and certain N-substituted thiazolium salts

Abstract The solid adducts isolated from the reactions of zinc and cobalt halides with derivatives of thiamine and certain other N -alkylthiazolium salts were characterized by i.r., electronic reflectance spectroscopy and magnetic susceptibility studies. The species appear to be complex salts without metal-sulfur or metal-nitrogen interaction.

The magnetic susceptibility of hemin 303-4.5 °K

Abstract The magnetic susceptibility of hemin has been measured from 303-4.5 °K. The magnetic moments are in agreement with the predictions of Harris at 273 and 4.5 °K, whereas the value at 4 °K is roughly 9% below the theoretical estimate. The hemin data do not fit the Griffith-Kotani equation, and the interpretation of susceptibility measurements using this equation has not been successful in determining the zero-field splitting parameter, D, for hemins.

Crystal and molecular structure of di-µ-dimethylstannylene-bis(carbonyl-π-cyclopentadienylcobalt): a metal ring compound

Crystals of the title compound are triclinic, space group P, with Z= 2 in a unit cell of dimensions a= 11·23(2), b= 11·10(2), c= 7·82(1)A, α= 95·7(2). β= 97·0(2), γ= 89·1(2)°. The structure was refined to R 0·085 for 1520 independent reflections measured on a diffractometer. There are two crystallographically distinct molecules in the unit cell, each located astride a centre of inversion; they show no significant differences in their molecular geometry but are differently oriented in the unit cell. Sn and Co atoms alternate around a planar four membered ring, the Sn atoms having only slightly distorted tetrahedral co-ordination, and Co having octahedral co-ordination if the cyclopentadienyl ring is assumed to occupy three sites. The idealised molecular symmetry is C2h(2/m), with the two-fold axis through the Sn atoms and the mirror through the Co atoms, the CO groups, and bisecting the cyclopentadienyl rings which lie mutually trans across the plane of the metal-atom ring. In the C5 ring, the carbon atom in the mirror plane is also diametrically opposite to the CO group attached to the same Co atom. Co–Sn [2·542(2)A] is significantly shorter than expected, but Co–C(CO), Co–C(π-C5H5), and C–O are ‘normal’; Sn–Co–Sn is 78°. The carbonyl groups occupy trans‘axial’ positions and are inclined slightly inwards; mean Sn–C 2·20(1)A, C–Sn–C only a little less than the tetrahedral value.