FORMATION OF ETA ²-BONDED LACTONE COMPLEXES AND EIGHT-MEMBERED RING METALLACYCLES WITH KETENE GROUPS BY THE INSERTION OF ACETYLENES INTO CARBON-MOLYBDENUM AND-TUNGSTEN SIGMA BONDS; MOLECULAR AND CRYSTAL STRUCTURES OF CARBONYL (ETA -CYCLOPENTADIENYL)(3-5-ETA -2,3-DIHYDRO-3,4,5-TRIMETHYL-2-OXO-3-FURYL)(T-BUTYL ISOCYANIDE) MOLYBDENUM AND CARBONYL-(ETA -CYCLOPENTADIENYL)(3-4:5-6-ETA -2,3,4,5-TETRAMETHYL-6-OXO-1-TRIFLUORO-METHYLHEXA-1,3,5-TRIENYLOXO)(MO LYBDENUM)GREEN M; NYATHI JZ; SCOTT C et al.1978; J. CHEM. SOC., DALTON TRANS.; GBR; DA. 1978; NO 9; PP. 1067-1080; BIBL. 46 REF.Article