Phosphine coordinated copper(I)-N-heterocyclic carbene complexes have emerged as an efficient material in catalysis and light-emitting applications. In this study, a gentle and sustainable approach to the copper(I)-carbene phosphine complexes is reported through an efficient C=Se activation protocol. The complexes [(Py^NHC)Cu(PPh3)2]X, X=BF4 (1), ClO4 (2), PF6 (3) and OTf (4); Py^NHC=3-isopropyl-1-(pyridin-2-yl)-imidazol-2-ylidene, and [(Py^NHC)Cu(PPh3)(X)], X=Br (5) and I (6) have been synthesized by treating 1-isopropyl-3-(pyridin-2-yl)-imidazole-2-selone with corresponding copper(I) precursors and triphenylphosphine. In this synthetic strategy, N-heterocyclic carbene gets transferred from N-heterocyclic selone through a C=Se bond cleavage reaction to form copper(I) complexes within five minutes at room temperature. In addition, the mechanism responsible for the C=Se bond cleavage reaction has been fully investigated. These reactions are not sensitive to moisture and oxygen. © 2023 Wiley-VCH GmbH.