The methodology developed by Rorabacher et al.,[41 in which UV measurements are used to quantify Cu" complexation, is One Of the few methods that have been reported for determining stability constants of polythioether-metal com-

Ivteten Strukturverinderungen beim Ubergang von A nach B bereits angedeutet. So ist das PC,-Fragment in B signifikant in Richtung einer Envelope-Konformation verzerrt (Abweichung des PI-Atoms von der Ringebene C15-C2O-C2-C1 = 5 pm) und der Li-P1-Abstand auf 252pm verkurzt (258pm in A). Die ebenfalls zu beobachtende leichte Verkurzung der C1-C2 Bindung auf 139.4 pm (140.4 pm in A) ist in Einklang mit diesen Befunden. Die 01-P1-02-Ebene in 5 ist orthogonal zur PC,-Ringebene angeordnet; die Li * -* 0-Absthde (190-199 pm) entsprechen typischen Werten fur Ether-koordinierte Lithiumsalze. CIS C18 C17 a+ c1 c1 PI' w LI1 02

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The symmetrically hydrocarbon-bridged complexes (OC)5M-(CH2)n+1-X-(CH2)n+l-M(CO)5 [n = 1, X = 1,4-C6H4, M = Mn (2a), M = Re (3a); n = 2, X = 1,4-C6H4, M = Mn (2b), M = Re (3b); n = 1, X = 1,3-C6H4, M = Mn (5a), M = Re (6a); n = 2, X = 1,3-C6H4, M = Mn (5b), M = Re (6b); n = 1, X = 1,2-C6H4, M = Mn (8a), M = Re (9a); n = 2, X = 1,2-C6H4, M = Mn (8b), M = Re (9b)] are obtained by the reaction of the bistriflates X[(CH2)„-CH2-OSO2CF3]2 [X = 1,4-C6H4, n = 1 (la), n = 2 (lb); X = 1,3-C6H4, n = 1 (4a), n = 2 (4b); X = 1,2-C6H4, n = 1 (7a), n = 2 (7b)] with the carbonyl metalates [M(CO)5]- (M = Mn, Re) in THF and dimethyl ether, respectively. According to an X-ray structural analysis 8a crystallizes in the triclinic space group P1̅ with Ζ = 2. Depending on the solvent, the reaction of 7 a with [Mn(CO)5]~ affords also the cyclic carbene complex 10a. The behavior of the manganese compounds toward CO has been investigated exemplarily in the case of 8a and leads to the diacyl complex 1,2-C6H4[CH2CH2C(O)Mn(CO)5]2 (11). Upon reaction with Na2CO3/CH3OH 11 is converted to give the corresponding diester 1,2-C6H4[CH2CH2C(O)OCH3]2 (12).

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