Lead-based semiconductors are among the most explored compounds for the synthesis of colloidal nanomaterials, mainly due to the appealing optoelectronic properties demonstrated by lead halide perovskites in the UV-VIS and by lead chalcogenides in the IR spectral ranges. The mature research on both classes of materials has recently led to the exploration of systems where such properties can coexist and interact. One promising direction is that of heterostructures, which are composite materials formed by intimately connected domains of two different compounds. They are generally challenging to obtain, mostly because of the poor compatibility in terms of required synthetic conditions and crystal structures of the two materials. Another direction to investigate is represented by compounds that are chemically related to both lead halides and lead chalcogenides, namely the lead chalcohalides. These materials, with general formula PbaEbXc ,(E=S, Se, Te, X=F, Cl, Br) are expected to show intermediate properties in between those of lead halides and chalcogenides, and more importantly might feature the chemical and structural compatibility needed to interface with both. We pioneered the investigation of lead chalcohalides at the nanoscale, discovering additional colloidal nanocrystals (NCs): the new compounds are semiconductors with a band gap in between those of lead halide perovskites and of lead sulfide, were obtained in relatively mild reaction conditions and feature a remarkable chemical stability. Moreover, we achieved the synthesis of colloidal heterostructures formed by epitaxially connected domains of Pb₄S₃Br₂ sulfobromide and CsPbX₃ perovskite, thus demonstrating a synthetic and structural compatibility between lead halide perovskites and lead chalcohalides. Stability of the system is highly increased respect to CsPbX3 NCs We take advantage of the domains? compatibility and exploit CsPbCl₃ perovskite NCs as disposable and phase-selective epitaxial templates to drive the synthesis of lead sulfochloride NCs. As a result, we expand the family of lead chalcohalides with two new phases: Pb₃S₂Cl₂ and Pb₄S₃Cl₂.The perovskite domain is called a disposable template because, at a later stage, it can be etched from the heterostructures by exploiting the solubility of CsPbCl₃ in polar solvents, while leaving the Pb₄S₃Cl₂ domains intact. Hence, the full procedure delivered colloidally stable Pb₄S₃Cl₂ NCs that could not be obtained by direct synthesis due to the competitive nucleation. Our use of perovskite NCs as disposable and phase-selective epitaxial templates parallels that of reaction-directing groups in traditional organic chemistry and catalysis. Such an approach to a deterministic synthesis of NCs might be extended to other pairs of materials with known or predictable epitaxial relations, taking advantage of the vast library of already reported nanomaterials as starting templates. This approach could open new routes for the colloidal syntheses of materials which are now hindered by an excessive activation energy for the homogeneous nucleation, or by the competitive formation of undesired phases