“…In this case, the measure of structural feature is to calculate the extent to which the Ge -O donor distance has changed from the van der Waals sum of 3.62 Å compared to the sum of the covalent radius of Ge and O, 1.96 Å . This method has successfully been used for cyclic silanes by Holmes et al7 Values of the percent trigonal bipyramidal character (% TBP) obtained in this manner are listed inTable 1.In the case of cyclic silanes investigated by Holmes et al, many compounds have % TBP values similar with those of 2 -4. However, if the central atom (Si) is substituted by halogens, the % TBP tends to be larger.…”