Copper miner Teck Resources has rejected a sweetened bid from Glencore and made changes to a proposed restructuring plan to allow for an earlier full separation of its metals and coal divisions. Glencore has offered Teck’s shareholders 24 percent of the combined metals group and up to $8.2bn in cash for those who may not want exposure to thermal coal, which is the most polluting fossil fuel. It had initially not offered a cash option. Glencore’s play for the Vancouver-based miner comes amid a rising wave of buyout offers for mines and…