‘User-friendly’ primary phosphines and an arsine: synthesis and characterization of new air-stable ligands incorporating the ferrocenyl group

Reaction of FcCH2CH2P(O)(OH)2 or FcCH2P(O)(OH)(OEt) [Fc=Fe(η5-C5H4)(η5-C5H5)] with excess CH2N2 followed by reduction with Me3SiCl–LiAlH4 gives the air-stable primary phosphines FcCH2CH2PH2 and the previously reported analogue FcCH2PH2 in high yields. Reduction of 1,1′-Fc′[CH2P(O)(OEt)2] [Fc′=Fe(η5-C5H4)2] and 1,2-Fc″[CH2P(O)(OEt)2] [Fc″=Fe(η5-C5H5)(η5-C5H3)] similarly gives the new primary phosphines 1,1′-Fc′(CH2PH2)2 and 1,2-Fc″(CH2PH2)2, respectively. The arsine FcCH2CH2AsH2, which is also air-stable, has been prepared by reduction of the arsonic acid FcCH2CH2As(O)(OH)2 using Zn/HCl. An X-ray structure has been carried out on the arsine, which is only the second structure determination of a free primary arsine. The molybdenum carbonyl complex [1,2-Fc″(CH2PH2)2Mo(CO)4] was prepared by reaction of the phosphine with [Mo(CO)4(pip)2] (pip=piperidine), and characterized by a preliminary X-ray structure determination. However, the same reaction of 1,1′-Fc′(CH2PH2)2 with [Mo(CO)4(pip)2] gave [1,1′-Fc′(CH2PH2)2Mo(CO)4] and the dimer [1,1′-Fc′(CH2PH2)2Mo(CO)4]2, characterized by electrospray mass spectrometry. 1,1′-Fc′[CH2PH2Mo(CO)5]2 and 1,2-Fc″[CH2PH2Mo(CO)5]2 were likewise prepared from the phosphines and excess [Mo(CO)5(THF)].