A Digalla[1.1]ferrocenophane and Its Coordination Chemistry: Synthesis and Structure of [{Fe(η5-C5H4)2}2{GaMe}2] and of the Adducts [{Fe(η5-C5H4)2}2{GaMe(D)}2] (D = Monodentate Donor) and [{Fe(η5-C5H4)2}2{GaMe}2D] (D = Bidentate Donor)

Gentle warming of 1,1‘-bis(dimethylgallyl)ferrocene ( 1 ) leads to the formation of trimethylgallium and the thermolabile compound [{Fe(η 5 -C 5 H 4 ) 2 } 2 {GaMe} 2 ] ( 2 ), a [1.1]ferrocenophane featuring group 13 elements in bridging positions. While NMR data for 2 prove a dynamic structure in solution, X-ray data reveal an anti conformation of the ferrocenophane framework in the solid state. The anti conformation is maintained in the thermolabile adducts 2a − g, which are obtained from 2 and the donors diethyl ether ( 2a ), pyridine ( 2b ), pyrimidine ( 2c ), quinoxaline ( 2d ), DMSO ( 2e ), pyrazine ( 2f ), and dioxane ( 2g ), by donor-exchange reactions ( 2b − g ) or on gentle warming of the respective donor adducts of 1 . Rodlike polymers are formed either by interaction of 2 with bidentate donors ( 2f, g ) or by π-stacking effects of aromatic molecules acting as monodentate donors ( 2b − d ). Steric requirements inhibit the complex formation between 2 and the donor phenazine. A cyclic voltammogram of 2b in pyridine reveals two reversible oxidation steps at −314 and −114 mV, indicating only weak electron delocalization in the cationic species. The formation of 2 from 1 has been shown to be reversible and thus is an example of an application of “dynamic covalent chemistry” as synthetic strategy.