The Chloromethylgermyl Complexes (η5-C5H5)M(CO)nGeR2CH2Cl [M = Fe (n = 2), Mo, W (n = 3)]: Rearrangements, Transformations to 1-Germa-3-metallacyclobutanes (η5-C5H4)M(CO)nCH2GeR2, and their Ring-Opening Polymerizations

The reactions between the transition metal−carbonylate salts [(η5-C5H5)M(CO)n]−Na+ (M = Fe (n = 2), Mo, W (n = 3)) and ClCH2GeR2Cl result in the high-yield formation of (η5-C5H5)M(CO)nGeR2CH2Cl (M = Fe, R = Me (1), n-Bu (2); M = Mo, R = Me (3), R = n-Bu (4); M = W, R = Me (5), R = n-Bu (6)). Complexes 1, 2, 5, and 6 are transformed into the isomers (η5-C5H5)M(CO)nCH2GeR2Cl (1a, 2a, 5a, and 6a) thermally and/or photochemically. Treatment of either type of complex and the Mo complexes 3 and 4 with lithium diisopropylamide results in the formation of the metallacycles (η5-C5H4)M(CO)nCH2GeR2 (7−12). The metallacycles of Mo and W (9 and 11) are crystalline complexes, and single-crystal X-ray analysis reveals a degree of ring strain. However, these complexes cannot be ring-opened, in contrast to the corresponding Fe complexes (7 and 8), which readily form new polymeric materials [(η5-C5H4)Fe(CO)2CH2GeR2]n.