WESCO International Inc., a provider of electrical, industrial and communications MRO and OEM products, construction materials, advanced supply chain management and logistics services, and Anixter International Inc., a global distributor of network and security solutions, electrical and electronic solutions and utility power solutions, announced that their boards of directors have unanimously approved a definitive merger agreement under which WESCO will acquire Anixter in a transaction valued at approximately $4.5 billion.