Synthesis of Racemic Aminoalkylferrocenyldichlorophosphanes and -dialkylphosphonites and Their Conversion to Primary Phosphanes

The dichlorophosphanyl-substituted ferrocene complexes 1-dichlorophosphanyl-2-N,N-dimethylaminomethyl-3-diphenylphosphanylferrocene
(2a) and 1-dichlorophosphanyl-2-N,N-dimethylaminomethyl-3,1′-bis(diphenylphosphanyl)ferrocene
(2b) have been prepared by the reaction of phosphorus
trichloride with the corresponding lithiated aminoalkylferrocene precursors.
The crystal structure of 2a reveals a short N···P
distance, which is suggestive of a weak N→P dative bond. Using
diethyl chlorophosphite instead of phosphorus trichloride as electrophile
gave 1-diethoxyphosphanyl-2-N,N-dimethylaminomethyl-3-diphenylphosphanylferrocene
(3a) and 1-diethoxyphosphanyl-2-N,N-dimethylaminomethyl-3,1′-bis(diphenylphosphanyl)ferrocene
(3b), respectively. The latter was converted to the corresponding
dimethoxy compound 4b by reaction with methanol. Crystal
structures of 3 and 4b have been determined.
Reduction of 2, 3, and 4b with
LiAlH4 or LiAlH4/SiMe3Cl yielded
the primary phosphanes 1-diphenylphosphanyl-2-N,N-dimethylaminomethyl-3-phosphanylferrocene (5a) and 1,1′-bis(diphenylphosphanyl)-2-N,N-dimethylaminomethyl-3-phosphanylferrocene (5b). The latter was also structurally characterized by X-ray diffraction.