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] [sbnd]P [dbnd]SiR 2

Abstract

A way to the first transition-metal-substituted (fluorosilyl)phosphanes (R 2Si(F)P(H) M) and a P-ferrio phosphasilene (R 2Si P M) is reported. The bulkily substituted metal phosphido complexes [Is 2Si(F)P(H) M] 1a–c (M = (C 5H 5)Fe(CO) 2, (C 5Me 5)Fe(CO) 2, (C 5Me 5)Ni(PPh 3); 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, N iPr 2) to give the desired P-lithium phosphanide precursors 3a–c; instead, nucleophilic M P bond cleavage was observed. Thus, thermolabile [Is 2Si(F)P[Li(thf) 3] Fe(CO) 2(C 5H 5)] 3a was prepared via the tin/lithium exchange reaction starting from [Is 2Si(F)P(SnMe 3) Fe(CO) 2(C 5H 5)] 6a and nBuLi in THF. Thermolysis of 3a in hexane affords, upon LiF elimination, [Is 2Si P Fe(CO) 2(C 5H 5)] 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 [Is 2Si(F)P(H) SiMe(R)Fe(CO) 2(C 5H 5)] 8a (R = Me) and 8b (R = tBu) were prepared and the crystal structure of 8b was elucidated. These compounds and their P-SnMe 3 derivatives could not be transformed into phosphasilene derivatives.