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

A way to the first transition-metal-substituted (fluorosilyl)phosphane s (R2Si(F)P(H)-M) and a P-ferrio phosphasilene (R2Si=P-M) is reported. The bulkily substituted metal phosphido complexes [Is(2)Si(F)P(H)-M] 1a-c (M=(C5H5)Fe(CO)(2), (C5Me5)Fe(CO)(2), (C5Me5)Ni(PPh3); Is=2,4,6-t riisopropylphenyl) were prepared in good yields (68-76%) by salt conde nsation reactions of the corresponding (fluorosilyl)phosphanide 2 with metal bromides. They were characterized by means of NMR and LR spectr oscopy and, with the exception of 1a, by X-ray structure analyses. The y do not react with RLi bases (R=Bu-n, Bu-t, (NPr2)-Pr-i) to give the desired P-lithium phosphanide precursors 3a-c; instead, nucleophilic M -P bond cleavage was observed. Thus, thermolabile [Is(2)Si(F)P[Li(thf) (3)]-Fe(CO)(2)(C5H5)] 3a was prepared via the tin/lithium exchange rea ction starting from [Is(2)Si(F)P(SnMe3)-Fe(CO)(2)(C5H5)] 6a and (BuLi) -Bu-n in THF. Thermolysis of 3a in hexane affords, upon LiF eliminatio n, [Is(2)Si=P-Fe(CO)(2)(C5H5)] 7. Although 3a and 7 could not be isola ted, their structures were unambiguously proven by characteristic P-31 and Si-29 NMR data and the composition of 7 was established by high r esolution mass spectrometry. Furthermore, the ferriosilyl phosphanes [ Is(2)Si(F)P(H)-SiMe(R)Fe(CO)(2)(C5H5)] 8a (R=Me) and 8b (R=Bu-t) were prepared and the crystal structure of 8b was elucidated. These compoun ds and their P-SnMe3 derivatives could not be transformed into phospha silene derivatives.