Kim như asen và antimon, và các kim loại như thủy ngân, chì, và tin-chiếm một vị trí tương tự như kim trong các hệ thống định kỳ tất cả có xu hướng hình thành liên kết cộng hóa trị ổn định với các nhóm hữu cơ. Một số cơ quan liên quan tin như kim đồng. Ngược lại, các kim loại như natri, kali, canxi, stronti, bari, thuộc nhóm 1 và nhóm 2 của hệ thống tuần hoàn, không hình thành các liên kết hóa trị với các nhóm hữu cơ. Các hợp chất được sử dụng như ví. | Q Organometallic Compounds BACKGROUND Metalloids such as arsenic and antimony and metals such as mercury lead and tin which occupy a similar location to metalloids in the periodic system all tend to form stable covalent bonds with organic groups. Some authorities regard tin as a metalloid. By contrast metals such as sodium potassium calcium strontium and barium which belong to groups 1 and 2 of the periodic system do not form covalent bonds with organic groups. The compounds used as examples here all possess covalent linkages between a metal and an organic group most commonly an alkyl group. The elements in question are mercury tin lead and arsenic all of which are appreciably toxic in their inorganic forms as well as in their organometallic forms. The attachment of the organic group to the metal can bring fundamental changes in its chemical properties and consequently in its environmental fate and toxic action. In particular the attachment of alkyl or other nonpolar groups to metals increases lipophilicity and thereby enhances movement into and across biological membranes storage in fat depots and adsorption by the colloids of soils and sediments. Thus the question of speciation is critical to understanding the ecotoxicology of these metals. In the first place organometallic compounds of mercury tin lead and arsenic have been produced commercially mainly for use as pesticides biocides or bactericides. Additionally methyl mercury and methyl arsenic are generated from their inorganic forms in the environment so residues of them may be both anthropogenic and natural in origin. Most of the following account will be devoted to organomer-cury and organotin compounds which have been extensively studied. Organolead and organoarsenic compounds have received less attention from an ecotoxicological point of view and will be dealt with only briefly. ORGANOMERCURY COMPOUNDS Origins and Chemical Properties A range of organomercury compounds have been produced .
