THE CRYSTAL STRUCTURES OF TETRAPHENYLANTIMONY ACETATE AND ITS

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Abstract
Tetraphenylantimony acetate is basically trigonal bipyramidal with an axial acetate group, but the structure is substantially distorted as a result of secondary Sb… O bonding with the formally non-bonded oxygen of the acetate group. A major feature of the distortion is an increase in one of the C-Sb-C equatorial angles to 152.6″ at the expense of the other two, which are close to 102.5″. Secondary bonding also leads to a reduction in the angle at the acetate bonded oxygen atom to 108.1°. Addition of a molecule of acetic acid gives Ph4SbOAc·HOAc with trigonal bipyramidal geometry about antimony, but secondary bonding is reduced to almost zero. The non-bonded oxygen of the acetate group forms a strong hydrogen bond (O… O 2.581 Å) to the acetic acid molecule but the cyclic structure suggested previously for this compound is not formed. Crystals of Ph4SbOAc·HOAc belong to the space group P21/n (a 8.077(4), b 17.189(6), c 16.095(6) Å, β 98.29(2)°) and those of Ph4SbOAc to the space group P21/c (a 16.261(6), b 10.312(5), c 17.423(6) A, B119.13(6)).