Toward Highly Metallized Polymers: Synthesis and Characterization of Silicon-Bridged [1]Ferrocenophanes with Pendent Cluster Substituents

The acetylide-substituted sila[1]ferrocenophanes [Fe(η-C 5 H 4 ) 2 Si(Me)C⋮CR] (R = Ph ( 2a ), n Bu ( 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(η-C 5 H 4 ) 2 Si(Me){Co 2 (CO) 6 C 2 R}] (R = Ph ( 4a ), n Bu ( 4b )) or organomolybdenum [Fe(η-C 5 H 4 ) 2 Si(Me){Mo 2 Cp 2 (CO) 4 C 2 Ph}] ( 9 ) clusters or mononuclear organonickel [Fe(η-C 5 H 4 ) 2 Si(Me){Ni(L)C 2 Ph}] (L = dmpe ( 11 ), L = dppe ( 12 )) complexes. The bis(acetylide)-substituted sila[1]ferrocenophanes [Fe(η-C 5 H 4 ) 2 Si(C⋮CR) 2 ] (R = n Bu ( 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(η-C 5 H 4 ) 2 Si{Co 2 (CO) 6 C 2 R} 2 ] (R = n Bu ( 7a ), R = Ph ( 7b )). Compound 7b subsequently underwent rapid hydrolytic ring-opening to yield an unusual, highly metallized silanol, [(η-C 5 H 5 )Fe(η-C 5 H 4 )Si(OH){Co 2 (CO) 6 C 2 Ph} 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(PEt 3 ) 3 ] instead gave the platinasila[2]ferrocenophane [Fe(η-C 5 H 4 ) 2 Pt(PEt 3 ) 2 Si(Me)C⋮CPh] ( 15 ) via oxidative insertion of the platinum(0) fragment into a strained ipso -cyclopentadienyl carbon−silicon bond of the sila[1]ferrocenophane.