Ferrocenyl-substituted alkynes

The iminophosphine (134) with 1-alkynes gave various products of 1,1- or 1,2-additions. A new synthesis of diphosphenes (135) from aryldichlorophosphines and a tungsten complex has been described the tungsten complex catalysed an exchange between two diphosphenes to give the unsymmetric diphosphene. A ferrocenyl-substituted diphosphene (136) has been prepared which seems to represent a borderline case with respect to dimerisation thus the dimer (137) readily dissociates to (136) upon heating in xylene. 

Complexes of various donor-substituted alkynes, such as FcCH=CHC CPh with WTp COI Fc = ferrocenyl Tp" = hydridotris(3,5-dimethylpyrazolyl)borate, have been studied using powder SHG at 1,064 nm, but efficiencies were considerably less than that of urea the molecular NLO properties have not been studied. The isomers of (dppe)( 7 -C6o)M(CO)3 (M = Cr, Mo) show complex 2-scan (532, ns pulses) behavior which is not only due to electronic effects, but also due to excited-state processes. The inclusion complexes formed by several ( -ligand)Fe(CO)4 species with thiourea were subjected to the Kurtz-Perry powder technique, but none exceeded... 

The generation of a-ferrocenyl-P-silyl substituted vinyl cations of type 28 does not require superacidic conditions, they can be generated by protonation of l-ferrocenyl-2-trialkylsilyl alkynes with trifluoroacetic acid at room temperature. The SiR3-groups with larger alkyl substituents increase the lifetime of this type of carbocations. 

The a-aryl-p-triisopropylsilyl-substituted vinyl cations 1-3 are generated by protonation of the corresponding l-aryl-2-silyl-alkynes with superacids at low temperatures (Eq. 1). For die protonation of a-ferrocenyl-p-(triisopropyl)silylethyne to yield the l-ferrocenyl-2-(triisopropyl)silylvinyl cation 4 the weaker acid CF3COOH is sufficient (Eq. 2). 

When the alkynyl moiety is substituted with an alkyl group or a proton only, the corresponding benzoquinones were detected as products of thermolysis. But when R = Ph, OR, or MesSi, a mixture of both products was formed. Furthermore, the use of 4-alkynylcyclobutanones with electron-withdrawing substituents, like C02Et or CH=CHOMe, resulted in the formation of cyclopentediones as a sole product. These results can be explained by the mechanism presented in the scheme above. Intermediate 10 is favored over intermediate 8 when substituent R better stabilizes the adjacent radical site. A ferrocenyl group at the alkyne also provides a stabilization that favors the formation of cyclopentene-l,3-diones. ... 

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