According to the data shown in Table 1, (3) has the same structure as the analogous cyclopentadienyl compound [4, ' ' 1 having no substituent in the five-membered ring. Complex (3) decomposes both thermally (ISOOC, 1 h) and photochemically (tetrahydrofuran, Hg high-pressure lamp, A > 300 nm) via carbonyl elimination to form (1) and the twofold carbonyl-bridged derivative (4). Maitlis et al. obtained (4) by heating (1) (80-85 "C/10-20 torr)[''; however, (4) does not form photochemically. Carbonylation of (4) under normal pressure essentially affords the starting material (1) along with very small amounts of (3).The carbonylrhodium compound (3) which in fact is inaccessible by thermal or photochemical (dimerizing) decarbonylation of (1) can readily be obtained by the protonation/ deprotonation sequence presented in this communication.Owing to the basic character of (1) and analogous metal-car-bony1 systems, their acid activation constitutes a clear-cut method for the facile construction of polynuclear complexes which can be obtained only with difficulty, in only low yields, or not at all by conventional methodsf61. Procedure['1(2): To a vigorously stirred solution of (1)Ix1 (294 mg, 1.0 mmol) in diethyl ether (20 ml) is added dropwise 54% HBF4 (ca. 0.2 ml) in the same solvent. Towards the end of acid addition, compound (2) deposits as a dark brown floccular precipitate which is quickly filtered off on a D3 frit, washed with ether (4 x 6 ml), and dried for 3 h in a high vacuum; yield 298 mg (92%).(3): Compound (2) (298 mg, 0.46 mmol) is treated with a saturated NaOCH3/CH30H solution (6 ml) in the dark at

No abstract

No abstract

No abstract

No abstract