Tellurium interatomic distance

Tellurium has only one crystalline form and this is composed of a network of spiral chains similar to those in hexagonal Se (Fig. 16.1c and d). Although the intra-chain Te-Te distance of 284 pm and the c dimension of the crystal (593 pm) are both substantially greater than for Scjt (as expected), nevertheless the closest interatomic distance between chains is almost identical for the 2 elements (Te Te 350 pm). Accordingly the elements form a continuous range of solid solutions in which there is a random... 

Under normal conditions an atom in elemental tellurium has coordination number 2 + 4. It has been known for a long time that pressure causes the interatomic distances to approximate each other until finally every tellurium atom has six equidistant neighboring atoms at 297 pm the structure (now called Te-IV) corresponds to /3-polonium. However, before this is attained, two other modifications (Te-II and Te-III) that are out of the ordinary appear at 4 GPa and 7 GPa. Te-II contains parallel, linear chains that are mutually shifted in such a way that each Te atom has, in addition to its two neighboring atoms within the chain... 

From elemental sulfur to selenium and tellurium, intermolecular interactions (,secondary bonds, soft-soft interactions) play an increasing role. According to N. W. Alcock,1 the term secondary bond describes interatomic distances longer than covalent single bonds but shorter than van der Waals interatomic distances.1 In many cases secondary bonds can also be described as coordinative Lewis base - Lewis acid or charge transfer (donor-acceptor) types of interactions. 

The symmetric and asymmetric C—stretching frequency decreases as one goes down the column from oxygen to tellurium while the interatomic distances increase. This implies a decrease in the force constants and a corresponding increase of the mean amplitudes of vibration. The C—O bond is thus more rigid than the C—Te bond. The force constants for the C=C is found to increase in... 

Two examples (from our own work) illustrate intramolecular secondary interactions. Thus, in triphenyltellurium(IV) tetraphenyldithioimidodiphosphinate, Ph3Te [SPh2PNPPh2S] , 27, the tellurium-sulfur interatomic distances, 3.264 and 3.451 A, are significantly longer than the sum of the covalent radii (2.443 A) but significantly shorter than the sum of the van der Waals radii (3.86 A) [56], In bis(diphenyldithiophosphinato)ditellurium(I), Te2(S2PPh2)2, 28, there are two types of tellurium-sulfur interaction - normal covalent, i.e. primary bonds (Te-S 2.471 and 2.493 A) and secondary bonds (Te- -S 2.989 and 3.066 A) [57]. 

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