A simple synthetic access to the first ferrocenylene-bridged bisdiphosphenes Fe(C5H4−PP−R)2 is
reported. The unsaturated PP units require steric protection by adjacent substituents such as Dmp (2,6-dimesitylphenyl) and Tbt (2,4,6-tris[bis(trimethylsilyl)methyl]phenyl) and should be capable of conjugative
interaction with the central metallocene unit. The electronic situation in these molecules has been assessed
on the basis of DFT calculations. As a derivative of the Tbt-substituted bisdiphosphene with Tbt-PH2,
the resulting ferrocenylene-bridged bis-1,3-dihydrotriphosphane has been characterized by X-ray
crystallography
Connected by water: Water, which usually cleaves the PP bond in diphosphenes, can also be used for PP bond formation. This has been demonstrated for a metallocene‐bridged bisdiphosphene with both PP units in the proximity. The resulting ferrocenophane contains an H‐terminated linear P4 chain (see scheme) for which only a limited number of stereoisomers is observed owing to structural restraints.
A facile synthetic access to the homologous series of 1,1'-ferrocenylene bisdihalophosphanes Fc'(PX2)2 (X = F, Cl, Br, I; Fc' = 1,1'-ferrocenediyl = ferrocenylene = -C5H4FeC5H4-) is reported. The 31P NMR spectroscopic data of this series suggest a similar electronic interaction of the -PX(2) unit with the ferrocene system as in monofunctional ferrocenyldihalophosphanes. Crystal structures for Fc'(PCl2)2 and Fc'(PBr2)2 reveal that the nature of the halogen atom within the phosphane unit strongly influences the twist angle of the ferrocene system, while leaving the other structural parameters mostly unaffected. Based on these bisdihalophosphanes, a synthetic access to the first metallocene bridged bisphosphaalkene ((C5H4P=C(t-Bu)OTMS)2Fe) is reported in which the tert-butyl substituents provide sufficient steric pressure to control the E/Z isomeric ratio which leads to the almost exclusive formation of the most stable Z,Z isomer out of the three possible isomers.
The reaction of 2 equiv of LiSeCC-n-C(5)H(11) (1) with cis-PtCl(2)(Ph(3)P)(2) (2) gives a mixture of the cis and trans isomers of Pt(Ph(3)P)(2)(SeCC-n-C(5)H(11))(2) (3), which slowly isomerizes in CH(2)Cl(2) to the preferred trans form trans-3. The closely related cis-[Pt(dppf)(2)(SeCC-n-C(5)H(11))(2)] (4) (dppf = bis(diphenylphosphino)ferrocene) was prepared by a similar metathetical reaction using the platinum chloride complex of the chelating dppf to impose the cis geometry. The structures of the cis and trans complexes have been investigated in solution by heteronuclear NMR ((31)P, (77)Se, and (195)Pt) and, in the cases of trans-3 and 4, characterized in the solid state by single-crystal X-ray diffraction. Changing the coordination geometry from cis to trans induces significant changes in the structural and spectroscopic parameters, which do not comply with the previously anticipated donor-acceptor properties of selenolate ligands.
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