Silylphosphines, structure

Tri-t-butylphenyl)(trimethylsilyl)phosphine (10a) and its t-butyldimethylsilyl analog (10b) were prepared from (2,4,6-tri-t-butylphenyl)phosphine33 (equation 76)3. Treatment of the silylphosphines 10a or 10b with n-butyllithium led to the formation of silylphosphides 11a and lib3, which were utilized for the reactions shown in Section V. (2,4,6-Tri-r-butylphenyl)(triphenylsilyl)phosphine and related compounds were also prepared starting from Mes PH i (equation 77) and their structures were analyzed27,89. 

Reaction of 10a with Mes P=C=0 afforded the adduct 12 (equation 78)90. It should be noted that compounds of the Mes P=C(OSiR3)PHMes type were converted to Mes P=C=PMes by addition of alkyllithiums90,91. Isophosphaethyne complexes were prepared using 10a as well as the related silylphosphines (equation 79)92. Stable cis-diphosphene was prepared from 10a and a dichloroaminophosphine, and its structure was analyzed by X-ray crystallography (equation 80)93. 

Silylphosphines, (R3Si)3P, are well known. On the basis of electronegativity (Table 1) they are weaker n acids than organophosphines. With the isolation of R2Si=PR compounds, an increased variety of structures is available. Six-membered silicon-phosphorus heterocycles (1) have been proposed as ligands for catalyst candidates, owing to the steric accessibility of the transition metal. 

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