A method of replacing a hydroxyl group on an aryl or heteroaryl compound with a fluorine atom, the method comprising contacting a compound of Formula: with a Cp-Ru-(aryl or heteroaryl)-complex in the presence of a fluorine source under conditions sufficient to fluorinate the phenol compound, thereby providing a fluorinated (aryl or heteroaryl) compound, wherein, in Formula: R 1 and R 2 are independently selected from the group consisting of C1-30, preferably C1-20 aliphatic, aromatic, heteroaliphatic or heteroaromatic hydrocarbons, each of which is optionally substituted with at least one substituent selected from C1-20 straight chain, branched or cyclic alkyl, alkenyl, alkynyl, aryl, heteroaryl, each being optionally further substituted by one or more heteroatoms, or heteroatoms, R 3 and R 4 are independently selected from the group consisting of C1-30, preferably C1-20 aliphatic, aromatic, heteroaliphatic or heteroaromatic hydrocarbons, each of which is optionally substituted with at least one substituent selected from C1-20 straight chain, branched or cyclic alkyl, alkenyl, alkynyl, aryl, heteroaryl, each being optionally further substituted by one or more heteroatoms, or heteroatoms, or R 3 and R 4 together form a C4-20 hydrocarbon ring which may be saturated or unsaturated aliphatic, aromatic, heteroaliphatic or heteroaromatic, each of which is optionally substituted with at least one substituent selected from C1-20 straight chain, branched or cyclic alkyl, alkenyl, alkynyl, aryl, heteroaryl, each being optionally further substituted by one or more heteroatoms, or heteroatoms, and X being an anion; and L being a leaving group, wherein the Ru phenol complex is a Ru complex with a C5 to C30, preferably C5 to C20 aromatic or heteroaromatic mono- to polycyclic ring system having at least one aromatic or heteroaromatic ring with one hydroxyl group on said ring, said ring system optionally being further substituted with straight chain, branched or cyclic alkyl, alkenyl or alkynyl having 1 to 20 carbon atoms, or heteroatoms being selected from halogen, N, O or S, each being optionally further substituted or each being optionally part of a aliphatic or aromatic ring system, and at least one further ligand preferably selected from cyclopentadienyl, optionally being further substituted by one or more heteroatoms or preferably by C1-6 alkyl, optionally being further substituted with halogen. R 1 and R 2 are independently selected from the group consisting of C1-30, preferably C1-20 aliphatic, aromatic, heteroaliphatic or heteroaromatic hydrocarbons, each of which is optionally substituted with at least one substituent selected from C1-20 straight chain, branched or cyclic alkyl, alkenyl, alkynyl, aryl, heteroaryl, each being optionally further substituted by one or more heteroatoms, or heteroatoms, R 3 and R 4 are independently selected from the group consisting of C1-30, preferably C1-20 aliphatic, aromatic, heteroaliphatic or heteroaromatic hydrocarbons, each of which is optionally substituted with at least one substituent selected from C1-20 straight chain, branched or cyclic alkyl, alkenyl, alkynyl, aryl, heteroaryl, each being optionally further substituted by one or more heteroatoms, or heteroatoms, or R 3 and R 4 together form a C4-20 hydrocarbon ring which may be saturated or unsaturated aliphatic, aromatic, heteroaliphatic or heteroaromatic, each of which is optionally substituted with at least one substituent selected from C1-20 straight chain, branched or cyclic alkyl, alkenyl, alkynyl, aryl, heteroaryl, each being optionally further substituted by one or more heteroatoms, or heteroatoms, and X being an anion; and L being a leaving group, wherein the Ru phenol complex is a Ru complex with a C5 to C30, preferably C5 to C20 aromatic or heteroaromatic mono- to polycyclic ring system having at least one aromatic or heteroaromatic ring with one hydroxyl group on said ring, said ring system optionally being further substituted with straight chain, branched or cyclic alkyl, alkenyl or alkynyl having 1 to 20 carbon atoms, or heteroatoms being selected from halogen, N, O or S, each being optionally further substituted or each being optionally part of a aliphatic or aromatic ring system, and at least one further ligand preferably selected from cyclopentadienyl, optionally being further substituted by one or more heteroatoms or preferably by C1-6 alkyl, optionally being further substituted with halogen.