Nitrosation of 2-chlorophenyl acetonitrile with t-butylnitrite under basic conditions (Meyer reaction) resulted in a high-yield preparation of the first substituted arylcyanoxime, 2-chlorophenyl(oximino)acetonitrile, H(2Cl–PhCO) (HL). The obtained cyanoxime is readily deprotonated in solution by metal hydroxides or carbonates with the formation of yellow sodium, tetrabutylammonium, thallium(I) and silver(I) derivatives. The crystal structure of the Tl(I) complex was determined. Thallium(I) salt (TlL) crystallizes in the monoclinic space group P2₁ n with a = 3.8382(7), b = 11.0065(18), c = 20.901(4) Å, and β = 92.447(3)°, V = 882.2(3) ų, Z = 4; T = 193 K (Mo Kα radiation). The structure was solved by direct methods to a final R of 0.0689 (wR2 = 0.1650) for I > 2σ(I). The crystal structure of the complex is a one-dimensional coordination polymer that consists of centrosymmetric [TlL]₂ dimers in which Tl₂O₂ rhombohedra are connected to each other at 90.72°. The crystal structure of TlL is an interesting example of the ruffled metal-organic network composed of Tl–O–Tl–O zigzag chains with close (3.838 Å) intermetallic distances comparable to those in metallic thallium (3.42 Å). The cyanoxime anion bridges metal centers and acts as a tridentate ligand where oxygen atoms of the oxime group bond to three different Tl(I) cations with three different bond lengths.