The invention comprises 9,10-dihydroanthracene compounds having the formula-(A)-ZBy wherein -(A)- is a 9,10-dihydro-9,10-anthrylene diradical; Z is a tetravalent atom of Si, Sn, Pb or Ge; B is another diradical -(A)-, a monovalent C1 to C22 hydrocarbyl radical or a halogen atom; y is 0 to 3, except that when B is the diradical -(A)-, y is 1; the unsatisfied bond of the diradical -(A)- is joined to said atom Z, By Z-, hydrogen, a C1 to C8 alkyl radical or a C6-C10 aryl radical; and all unsatisfie bonds of said atom Z are bonded to a monovalent C1 to C22 hydrocarbyl radical or a halogen atom. The aforesaid 9,10-dihydroanthracene compounds may be prepared by reacting an alkali-metal adduct of anthracene, usubstituted or substituted at the 1-8 positions, by unreactive groupings such as C1-C8 alkyl radicals, with a halide of the formula RnZX4- n, wherein R is a hydrocarbyl radical and n is 0, 1, 2 or 3. The reaction may be carried out in an inert solvent such as saturated hydrocarbons, dialkyl ethers and cyclic ethers under anhydrous conditions in an inert atmosphere, under reflux provided that such a temperature does not lead to decomposition of the reactants or product. The alkali metal adducts, such as 9,10-dihydro-9,10disodio-anthrylene, may be prepared by reacting the alkali metal with the anthracene or a derivative thereof under conditions similar to those above. The 9,10-dihydroanthracene compound may be a homopolymer having repetitive monomeric units of the formula wherein R and R1 are C1 to C22 hydrocarbyl radicals or halogen atoms; such homopolymers may be formed by utilizing halides of the formula R2ZX2, RZX3 or ZX4 in the preparative reaction.ALSO:The invention comprises 9, 10-dihydroanthracene compounds having the formula -(A)-Z By wherein -(A)- is a 9, 10-dihydro9, 10-anthrylene diradical; Z is a tetravalent atom of Si, Sn, Pb or Ge; B is another diradical -(A)-, a monovalent C1 to C22 hydrocarbyl radical or a halogen atom; y is an integer from 0 to 3, except that when B is the diradical -(A)-, y is 1; the unsatisfied bond of the diradical -(A)- is joined to said atom Z, By Z-, hydrogen, a C1 to C8 alkyl radical or a C6-C10 aryl radical; and all unsatisfied bonds of said atom Z are bonded to a monovalent C1 to C22 hydrocarbyl radical or a halogen atom. The organometallic compounds of the invention are useful, in amounts ranging from 0.1-30 gm. per gallon, as additives to hydrocarbon fuels for controlling combustion chamber deposits and to improve storage stability. The lead anthracenyl derivatives can be used as additives to gasolines and to lubricatng oils and greases whilst the germanium derivatives are suitable as antiknock and antioxidant additives to gasolines. The dialkyl (9, 10-dihydro-9, 10-anthrylene) tin compounds can be used in amounts of 0.1-5% by weight to improve the oxidation stability of phenate containing hydrocarbon base stocks which are used, for example as crankcase lubricants in diesel engines. Those compounds in which a tin atom is bonded only to 9,10-dihydroanthrylene or other hydrocarbyl radicals, for example, R3Sn-A-SnR3 and A = SnR2 wherein R is a C1-C22 hydrocarbyl radical and similarly substituted polymers are useful in amount 0.01-20% by weight as stabilizers for transformer oils. The R3Si-A-SiR3 compounds and liquid silico anthracenyl polymers are useful per se as high temperature oils and hydraulic fluids and also as additives to hydrocarbon oils. Those silicon anthracenyl compounds in which unreacted halogen is bonded to silicon can be converted by methods similar to those used with other hydrocarbyl silicon halides to heat stable silicone oils and resins.ALSO:The invention comprises 9,10-dihydroanthracene compounds having the formula-(A)-ZBy wherein -(A)- is a 9,10-dihydro-9,10-anthrylene diradical; Z is a tetravalent atom of Si, Sn, Pb or Ge; B is another diradical -(A)-, a monovalent C1 to C22 hydrocarbyl radical or a halogen atom; y is an integer from 0 to 3, except that when B is the diradical -(A)-, y is 1; the unsatisfied bond of the diradical -(A)- is joined to said atom Z, ByZ-, hydrogen, a C1 to C8 alkyl radical or a C6-C10 aryl radical; and all unsatisfied bonds of said atom Z are bonded to a monovalent C1 to C22 hydrocarbyl radical or a halogen atom. The aforesaid 9,10-dihydro-anthracene compounds may be prepared by reacting an alkali-metal adduct of anthracene, unsubstituted or substituted at the 1-8 positions by unreactive groupings such as C1-C8 alkyl radicals, with a halide of the formula RnZX4- n wherein R is a hydrocarbyl radical and n is 0, 1, 2 or 3. The reaction may be carried out in an inert solvent such as saturated hydrocarbons, dialkyl ethers and cyclic ethers under anhydrous conditions in an inert atmosphere, under reflux provided that such a temperature does not lead to decomposition of the reactants or product. The alkali metal adducts, such as 9,10-dihydro-9,10-disodio-anthrylene, may be prepared by reacting the alkali metal with the anthracene or a derivative thereof under conditions similar to those above. The 9,10-dihydroanthracene compound may be a homopolymer have repetitive monomeric units of the formula wherein R and R1 are C1 to C22 hydrocarbyl radicals or halogen atoms, such homopolymers may be formed by utilizing halides of the formula R2ZX2, RZX3 or ZX4 in the preparative reaction.ALSO:The invention comprises, 9, 10-dihydroanthracene compounds having the formula -(A)-ZBy wherein -(A)- is a 9, 10-dihydro-9, 10-anthrylene diradical; Z is a tetravalent atom of Si, Sn, Pb or Ge; B is another diradical -(A)-, a monovalent C1 to C22 hydrocarbyl radical or a halogen atom; y is an integer from 0 to 3, except that when B is the diradical -(A)-, y is 1; the unsatisfied bond of the diradical -(A)- is joined to said atom Z, By Z-, hydrogen, a C1 to C8 alkyl radical or a C6-C10 aryl radical; and all unsatisfied bonds of said atom Z are bonded to a monovalent C1 to C22 hydrocarbyl radical or a halogen atom. Derivatives having a single halogen or other functional group bonded to a tin atom e.g. trihydrocarbyl tin halides, hydroxides, oxides and esters have biocidal, insecticidal, fungicidal and germicidal activity and can be used in an amount by weight of 1 ppm to 90% to combat mildew and other fungal growth on cellulose e.g. in pulp mills and may also be incorporated in paints for combatting marine growths and mildew. The dihydrocarbyl tin compounds and their amine adjuvants or derivatives thereof e.g. piperazine or dimethyl piperazine can be incorporated in poultry foods as anthelmintics and coccidiostats. Dibutyl-9, 10-dihydro-9, 10 anthrylene tin is, in an example, shown to be active against certain common soil fungi and to have a low phytotoxicity when spread in amounts as low as 10 lbs per acre as a 10% dust and when sprayed as a formulation of 1000 ppm to as low as 20 ppm, with acetone and emulsifier dispersed in water onto bean plants inoculated with powdery mildew fungus (Erysiphe polygoni).