Bis(tert‐butyldimethylsilyl)(2,6‐diisopropylphenyl)phosphane: the first structure of an organophosphane with two tert‐butyldimethylsilyl (TBDMS) substituents

The title compound, C₂₄H₄₇PSi₂, is the first organophosphane bearing two tert‐butyldimethylsilyl (TBDMS) groups to be crystallographically characterized, even though TBDMS is a very popular bulky silyl group. The structure is a considerably flattened trigonal pyramid, with the sum of the C/Si—P—C/Si angles being 333.35 (6)°, which can be attributed to the steric pressure from the three bulky groups. The P—Si distances 2.2605 (6) and 2.2631 (6) Å] are normal, while the P—C distance 1.8646 (12) Å] is long (outside the s.u. values) compared with related structures. The plane of the aryl ring approximately bisects the Si—P—Si angle, quite unlike the secondary (tert‐butyldimethylsilyl)(2,6‐diisopropylphenyl)phosphane bearing only one TBDMS group, in which the single Si atom is perpendicular to the aryl ring. The title structure conforms closely to that predicted from B3LYP/6‐31G(d) calculations, although the calculations overestimate the degree of planarity. The compound crystallizes centrosymmetrically in the space group P as isolated molecules.