“…The uncomplexed conjugated diene in the complexes is more reactive towards Diels-Alder addition with dimethyl acetylenedicarboxylate than it is in the f r e e hydrocarbon. 13 The thermal reaction of 7,7-dimethoxy-5,6-dimethylenebicyclo[2.2.1]hept-2-ene with [Ru(CO) 3 (l,5-cod)] under CO is reported to give, among other products, a n exo-[R\x (CO) 4 ] complex, but in the light o f related iron chemistry, it seems more likely to be the chelate [O, rj 2 ] tricarbonyl complex (7). 14 14 and [M(CO) 4 (TJ-C 2 H 2 )] 15 are higher for osmium than for ruthenium, consistent with IR, NMR and chemical evidence for a stronger metal-ligand interaction with the heavier element, and are also greater for the alkyne complexes than for the C 2 H 4 complexes.…”