Synthesis of (fluorosilyl) phosphido iron and nickel complexes and ferriosilyl-substituted (fluorosilyl) phosphanes and evidence for the formation of a metallo phosphasilene of the type [M]-P=SiR2

Article abstract of DOI:10.1016/S0022-328X(96)06483-2

A way to the first transition-metal-substituted (fluorosilyl)phosphanes (R₂Si(F)P(H)-M) and a P-ferrio phosphasilene (R₂Si=P-M) is reported. The bulkily substituted metal phosphido complexes [Is₂Si(F)P(H)-M] 1a-c (M = (C₅H₅)Fe(CO)₂, (C₅Me₅)Fe(CO)₂, (C₅Me₅)Ni(PPh₃); Is = 2,4,6-triisopropylphenyl) were prepared in good yields (68-76%) by salt condensation reactions of the corresponding (fluorosilyl)phosphanide 2 with metal bromides. They were characterized by means of NMR and IR spectroscopy and, with the exception of 1a, by X-ray structure analyses. They do not react with RLi bases (R = ⁿBu, ^tBu, NⁱPr₂) to give the desired P-lithium phosphanide precursors 3a-c; instead, nucleophilic M-P bond cleavage was observed. Thus, thermolabile [Is₂Si(F)P[Li(thf)₃]-Fe(CO)₂(C₅H₅)] 3a was prepared via the tin/lithium exchange reaction starting from [Is₂Si(F)P(SnMe₃)-Fe(CO)₂(C₅H₅)] 6a and ⁿBuLi in THF. Thermolysis of 3a in hexane affords, upon LiF elimination, [Is₂Si=P-Fe(CO)₂(C₅H₅)] 7. Although 3a and 7 could not be isolated, their structures were unambiguously proven by characteristic ³¹P and ²⁹Si NMR data and the composition of 7 was established by high resolution mass spectrometry. Furthermore, the ferriosilyl phosphanes [Is₂Si(F)P(H)-SiMe(R)Fe(CO)₂(C₅H₅)] 8a (R = Me) and 8b (R =^tBu) were prepared and the crystal structure of 8b was elucidated. These compounds and their P-SnMe₃ derivatives could not be transformed into phosphasilene derivatives.