The First Peralkylated Phosphino(stibino)methanes and Their Organometallic Rhodium Complexes

The first representatives of phosphino(stibino)methanes R2PCH2Sb‐R′2 (3–5) with bulky alkyl or cycloalkyl groups R and R′ were prepared in two steps from Ph3SnCH2I via the isolated stannylated phosphanes Ph3SnCH2PR2 (1, 2) as intermediates. X‐ray structural analysis of 5 (R = C6H11, R′ = tBu) reveals that the lone pairs and the substituents R and R′ at phosphorus and antimony and the hydrogen atoms of the CH2 bridge adopt staggered conformations. Treatment of [{C8H12RhCl}2] with 3–5 affords the neutral compounds [Rh‐Cl(η4‐C8H12)(κ‐P‐R2PCH2SbR′2)] (6–8), of which 7 and 8 react with CH3MgI to give the corresponding methylrhodium derivatives [RhCH3(η4‐C8H12)(κ‐P‐R2‐PCH2SbR′2)] (9, 10). Cationic complexes [Rh(η4‐C8H12)(η2‐P,Sb‐R2PCH2SbR′2)]‐X (X = PF6: 11a, 12a, 13; X = BPh4: 11b, 12b) containing the phosphino(stibino)methanes as chelating ligands were obtained either from [{C8H12RhCl}2], R2PCH2SbR′2 and MX, or (for 13) from 8 and AgPF6. Compound 12a (R = iPr, R′ = tBu) was characterized by X‐ray crystallography. The PF6 salts 11a, 12a, and 13 react with CH2N2 by insertion of CH2 into the Rh–Sb bond to yield the complexes 14–16, the first examples of transition‐metal compounds with Sb ylides as ligands. Treatment of BPh4 salts 11b and 12b with H2 gives the half‐sand‐wich‐type complexes [(η6‐C6H5BPh3)Rh(κ2‐P,Sb‐R2PCH2SbR′2)] (17, 18), in which the tetraphenylborate is coordinated like a substituted arene to the metal center.