Toward highly metallized polymers: Synthesis and characterization of silicon-bridged [1]ferrocenophanes with pendent cluster substituents

The acetylide-substituted sila[1]ferrocenophanes [Fe(eta-C5H4)(2)Si(Me)CdropCR] (R = Ph (2a), Bu-n (2b)) reacted with [Co-2(CO)(8)], [{MoCP(CO)(2)}(2)], or [Ni(cod)(2)]/L selectively at the triple bond to give pendent organocobalt [Fe(eta-C5H4)(2)Si(Me){CO2(CO)(6)C2R}] (R = Ph (4a), Bu-n (4b)) or organomolybdenum [Fe(eta-C5H4)(2)Si(Me){Mo2Cp2(CO)(4)C2Ph}] (9) clusters or mononuclear organonickel [Fe(eta-C5H4)(2)Si(Me){Ni(L)C2Ph}] (L = dmpe (11), L = dppe (12)) complexes. The bis(acetylide)-substituted sila[1]ferrocenophanes [Fe(eta-C5H4)(2)Si(CdropCR)(2)] (R = Bu-n (6a), Ph (6b)) reacted with [Co-2(CO)(8)] in an analogous fashion, forming the novel pentametallic silicon-bridged [1]ferrocenophanes with two pendent cobalt clusters [Fe(eta-C5H4)(2)Si{Co-2-(CO)(6)C2R}(2)] (R = Bu-n (7a), R = Ph (7b)). Compound 7b subsequently underwent rapid hydrolytic ring-opening to yield an unusual, highly metallized silanol, [(eta-C5H5)Fe(eta-C5H4)Si(OH){Co-2(CO)(6)C2Ph}(2)] (8b). This reaction was found to be much slower for the hexynyl analogue (7a). The organonickel complexes (11 and 12) described in this work represent the first examples of mononuclear complexes prepared directly from an alkyne and [Ni(cod)(2)]. We postulate that steric factors prevent the addition of a second nickel fragment to the alkyne. The synthesis of a sila[1]ferrocenophane with a pendent platinum moiety was also attempted. However, reaction of 2a with [Pt(PEt3)(3)] instead gave the platinasila[2]-ferrocenophane [Fe(eta-C5H4)(2)Pt(PEt3)(2)Si(Me)CdropCPh] (15) via oxidative insertion of the platinum(0) fragment into a strained ipso-cyclopentadienyl carbon-silicon bond of the sila[1]ferrocenophane.