Heterobi- to heterotetrametallic transition metal complexes constructed from ferrocenecarboxylate and [{[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}M]+ units

A series of copper(I) and silver(I) carboxylates received from various ferrocenecarboxylic acids was synthesized and used in the preparation of heterooligometallic Ti–Cu(Ag)–Fe complexes. The silver(I) salts [FcCO2Ag] (2a) and [FcCHdouble bond; length as m-dashCHCO2Ag] (2b) (Fc = ferrocenyl, (η5-C5H4)Fe(η5-C5H5)) were obtained through deprotonation of the respective acids FcCO2H (1a) and FcCHdouble bond; length as m-dashCHCO2H (1b) with NEt3, followed by a reaction with [AgNO3]. The heterotrimetallic complexes {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}AgO2CFc (4a) and {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}AgO2CCHdouble bond; length as m-dashCHFc (4b), where [Ti] denotes the (η5-C5H4SiMe3)2Ti unit, were obtained from the reaction of 2a and 2b with the organometallic π-tweezer compound [Ti](Ctriple bond; length of mdashCSiMe3)2 (3). The related heterotrimetallic copper(I) complex {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}CuO2CFc (9a) was prepared via two synthetic routes. First, salt 2a was reacted with [(η2-Me3SiCtriple bond; length of mdashCSiMe3)CuBr]2 (10) to give the alkyne-stabilized copper(I) carboxylate [(η2-Me3SiCtriple bond; length of mdashCSiMe3)(CuO2CFc)2]2 (11). Subsequent reaction of 11 with four equivalents of 3 afforded 9a. Alternatively, 9a and its analogues {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}CuO2C–E–Fc (E = trans-CHdouble bond; length as m-dashCH (9b), CH2CH2 (9c)), were prepared from acidolysis of the Cu–CMe bond in {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}CuMe (8) with acids 1a–1c. An analogous reaction between HO2CfcPPh2M(CO)5 (M = Cr (14a), Mo (14b), W (14c); fc = ferrocene-1,1′-diyl) and 8 at−30 °C gave the alkyne/ferrocene-bridged heterotetrametallic compounds {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}CuO2CfcPPh2M(CO)5 (M = Cr (15a), Mo (15b), W (15c)). Reversing the reaction steps so that {[Ti](μ-σ,π-Ctriple bond; length of mdashCSiMe3)2}CuO2CfcPPh2 (12) was prepared first and then reacted with M(CO)5(thf) (M = Cr (13a), Mo (13b), W (13a)) gave complicated reaction mixtures from which pure 15a–15c could not be isolated. The solid-state structures of 5, 7, 9a, and 11 have been corroborated by single-crystal X-ray structural studies and the electrochemical behavior of acids 1a–1c and of complexes 4a, 4b and 9a–9c was studied by cyclic voltammetry.