A “new” Frank-van de Merwe growth mode of Ag has been achieved using a macromolecular N-heterocyclic carbene-Ag(I) (NHC-Ag) complex. This polymer NHC-Ag acts as both a metal precursor and a capping ligand in the seed-mediated growth of Ag on gold nanorods (AuNRs). The newly deposited Ag nanospheres de-wet the lateral surface of AuNRs due to the strong capping of NHC-Ag motif, resulting in phase separated Au-Ag nanostructures with a contact angle of ~ 120°. Remarkably, this growth mode is also applicable to even homometallic systems, enabling the formation of Ag "islands" on Ag-coated AuNRs. This design principle opens alternative pathways to design colloidal nanoparticles with specific and otherwise challenging anisotropic nanostructures.