Primary and secondary phosphine piano-stool complexes of the type [eta~5-CpFeL_3]~+ (L=phenylphosphine,3,(alpha-methyl)vinylphosphine,4,allylphosphine,5,(2-methylpropenyl)phosphine,5b,allyl(phenyl)phosphine,6) are described.The alkenyl phosphine complexes,5 and 6,react by intramolecular hydrophosphination to give the corresponding [eta~5-CpFe]~+ complexes of 1,5,9-triphosphacyclododecane (12-aneP_3R_3,2,R=H),9 and 10 respectively.Alkylation of the secondary phosphines in 9 is achieved by hydrophosphinations with ethene to give the 12-aneP_3R_3 (R=Et) derivative 11.These complexes are also obtained by reaction of suitable [eta~5-CpFe]~+ containing precursor complexes with the corresponding free 12-aneP_3R_3 macrocycle as is the related [eta~5-Cp*Fe]~+ derivative,8.Direct substitution of acetonitrile in [Fe(CH_3CN)_6][BF_4]_2 by 12-aneP_3Et_3,leads to the macrocycle piano-stool complex,[(12-aneP_3Et_3)Fe(CH_3CN)_3][BF_4]_2,7.The crystal structures of selected primary phosphine,eta~5-Cp,eta~5-Cp* complexes and 7,allow a comparison of steric influences upon key macrocycle ring closure reactions and hence an insight into parameters required for the formation of smaller ring sizes by template based methods.
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