SYNTHESIS OF THE W=W TRIPLY BONDED DIMERS [W2(ETA-C5H4R)2X4] (X = CL, R = ME OR PR(I) - X = BR, R = PR(I)) AND X-RAY CRYSTAL-STRUCTURES OF [W(ETA-C5H4PR(I))CL4] AND [W2(ETA-C5H4PR(I))2CL4] - Green, M; Hubert, J; Mountford, P (1990)