Unusual cleavage of phosphaalkynes triple bond in the coordination sphere of transition metals.

The reaction of RCP (R = Me, tBu, iPr) with Co2(CO)8 and Fe2(CO)9 under mild conditions led to unpredictable fragmentations of the CP triple bond and subsequent formation of clusters with a dimeric Co3E (E = P and RC) and an Fe3P(CR) core, respectively.

Isomerization, Ring Expansion, and Ring Contraction of 1,3-Diphosphete Complexes.

Reactions between the 1,3-diphosphete complex [Cp'''Co(η4 -P2 C2 tBu2 )] (1) and Ag[Al{OC(CF3 )3 }4 ] (Ag[pftb]) were carried out under different conditions. In CH2 Cl2 , the unprecedented 1,2-diphosphete isomerization product [Ag2 {Cp'''Co(µ,η4 :η1 :η1 -1,2-P2 C2 tBu2 )}2 {Cp'''Co(µ,η4 :η1 -1,2-P2 C2 tBu2 )}2 ]⋅2[pftb] (2) could be isolated. In diffusion experiments of 1 in n-hexane with Ag[pftb] in CH2 Cl2 , the triphosphacobaltocenium complex [Cp'''Co(η5 -P3 C2 tBu2 )][pftb] (4) and the phosphirenylium complex [Cp'''Co(η3 -PC2 tBu2 )][pftb] (5) were obtained, showing a ring expansion and a ring contraction, respectively, under mild conditions. Moreover, addition of pyridine to the Ag complex 2 led to the new 1,2-diphosphete complex [Cp'''Co(η4 -1,2-P2 C2 tBu2 )] (3). Compound 3 is also formed by thermolysis of 1, making it a promising method for this type of isomerization. 1,2-Diphosphete complexes like 3 are thermodynamically more stable but also synthetically more elusive than their 1,3-isomer counterparts.

Homoleptic Phosphaalkyne Complexes of Silver(I).

By employing silver salts with a weakly coordinating anion Ag[A] ([A]=[FAl{OC12 F15 }3 ], [Al{OC(CF3 )3 }4 ]), two phosphaalkynes could be coordinated side-on to a bare silver(I) center to form the unprecedented homoleptic complexes [Ag(η2 -P≡CtBu)2 ][FAl{OC12 F15 }3 ] (1) and [Ag(η2 -P≡CtBu)2 ][Al{OC(CF3 )3 }4 ] (2). DFT calculations show that the perpendicular arrangement in 1 is the minimum energy structure of the coordination of the two phosphaalkynes to a silver atom, whereas for 2 a unique square-planar coordination mode of the phosphaalkynes at Ag+ was found. Reactions with donor molecules yield the trigonally planar coordinated silver salts [((CH3 )2 CO)Ag(η2 -P≡CtBu)2 ][FAl{OC12 F15 }3 ] (3) and [(C7 H8 )2 Ag(η2 -P≡CtBu)][FAl{OC12 F15 }3 ] (4). All of the compounds were comprehensively characterized in solution and in the solid state.