Capital One Financial Corp. has agreed to acquire fintech startup Brex in a deal valued at $5.15 billion, expanding the bank’s push into technology-driven corporate finance and payments. Under the terms of the agreement, Capital One will pay 50% in cash and 50% in stock for Brex, the companies said on Thursday. The acquisition would fold one of Silicon Valley’s best-known financial technology firms into Capital One’s commercial banking and payments business. Capital One founder and CEO Richard Fairbank ...