2931.90.90.29 - Other

This HTS category, 2931.90.90.29, encompasses a residual classification for organo-inorganic compounds that do not fit into any more specific subcategories within the "Other organo-inorganic compounds" heading. It is intended for substances where an organic radical is directly linked to an inorganic element, and these compounds are not explicitly defined or listed elsewhere within Chapter 29. The classification hinges on the direct covalent or coordinate bond between organic and inorganic moieties, excluding salts or mixtures where such a direct linkage is absent.

To distinguish this category from its siblings, consider the specific examples provided. While 2931.90.90.21 covers dibutyltin oxide and 2931.90.90.25 covers tetrabutyltin, this "Other" category is for organo-tin compounds that are neither of these specific substances. For instance, it would capture organo-tin compounds that are not oxides or tetrabutyltin, or other organo-inorganic compounds that do not fall under the more specifically defined classifications for other elements like phosphorus, sulfur, halogens, or silicon.

As this is a leaf node, there are no further subcategories. Therefore, classification into 2931.90.90.29 requires careful examination to confirm that the compound is indeed an organo-inorganic compound that is not otherwise specifically classified and does not fall under any of the preceding, more particular subheadings within 2931.90.90. The key is the direct attachment of an organic group to an inorganic atom and the absence of a more specific classification.