Heterobi- to heterotetrametallic transition metal complexes constructed from ferrocenecarboxylate and [{[Ti](μ-σ,π-C{triple bond, long}CSiMe3)2}M]+ units

Article abstract of DOI:10.1016/j.jorganchem.2007.06.059

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 [FcCH{double bond, long}CHCO₂Ag] (2b) (Fc = ferrocenyl, (η⁵-C₅H₄)Fe(η⁵-C₅H₅)) were obtained through deprotonation of the respective acids FcCO₂H (1a) and FcCH{double bond, long}CHCO₂H (1b) with NEt₃, followed by a reaction with [AgNO₃]. The heterotrimetallic complexes {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)₂}AgO₂CFc (4a) and {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)₂}AgO₂CCH{double bond, long}CHFc (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](C{triple bond, long}CSiMe₃)₂ (3). The related heterotrimetallic copper(I) complex {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)₂}CuO₂CFc (9a) was prepared via two synthetic routes. First, salt 2a was reacted with [(η²-Me₃SiC{triple bond, long}CSiMe₃)CuBr]₂ (10) to give the alkyne-stabilized copper(I) carboxylate [(η²-Me₃SiC{triple bond, long}CSiMe₃)(CuO₂CFc)₂]₂ (11). Subsequent reaction of 11 with four equivalents of 3 afforded 9a. Alternatively, 9a and its analogues {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)₂}CuO₂C-E-Fc (E = trans-CH{double bond, long}CH (9b), CH₂CH₂ (9c)), were prepared from acidolysis of the Cu-C_Me bond in {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)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-C{triple bond, long}CSiMe₃)₂}CuO₂CfcPPh₂M(CO)₅ (M = Cr (15a), Mo (15b), W (15c)). Reversing the reaction steps so that {[Ti](μ-σ,π-C{triple bond, long}CSiMe₃)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.