Preparation of tetranuclear heterometallic clusters by condensation of tungsten acetylides [W(CO)3(C≡CR) (η-C5H5)] with acetylide clusters [WRu2(CO)8(C≡CR)L] (L = η-C5H5 or η-C5Me5, R = Ph or C6H4F-p). Crystal structures of [W2Ru2...