China Vanke Co Ltd, the mainland's biggest property company by sales, said on Sunday it was terminating a key agreement to acquire a property development arm of Shenzhen Metro Group after it failed to get the approval of some of its major shareholders. Vanke is the subject of complex corporate power struggle with Chinese financial conglomerate Baoneng seeking to oust the management, having built up a 25 percent stake in Vanke. Fearing a hostile take-over attempt by Baoneng, Vanke announced in June it had agreed to buy the property unit of white knight Shenzhen Metro Group for $6.9 billion in shares, which would have made the state-owned subway operator its biggiest shareholder. Both Baoneng and China Resources Group, its two major shareholders, had said they would oppose the deal.