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

The first representatives of phosphino(stibino)methanes R 2 PCH 2 Sb‐R′ 2 ( 3–5 ) with bulky alkyl or cycloalkyl groups R and R′ were prepared in two steps from Ph 3 SnCH 2 I via the isolated stannylated phosphanes Ph 3 SnCH 2 PR 2 ( 1, 2 ) as intermediates. X‐ray structural analysis of 5 (R = C 6 H 11 , R′ = t Bu) reveals that the lone pairs and the substituents R and R′ at phosphorus and antimony and the hydrogen atoms of the CH 2 bridge adopt staggered conformations. Treatment of [{C 8 H 12 RhCl} 2 ] with 3–5 affords the neutral compounds [Rh‐Cl(η 4 ‐C 8 H 12 )(κ‐ P ‐R 2 PCH 2 SbR′ 2 )] ( 6–8 ), of which 7 and 8 react with CH 3 MgI to give the corresponding methylrhodium derivatives [RhCH 3 (η 4 ‐C 8 H 12 )(κ‐ P ‐R 2 ‐PCH 2 SbR′ 2 )] ( 9, 10 ). Cationic complexes [Rh(η 4 ‐C 8 H 12 )(η 2 ‐ P,Sb ‐R 2 PCH 2 SbR′ 2 )]‐X (X = PF 6 : 11a, 12a, 13 ; X = BPh 4 : 11b, 12b ) containing the phosphino(stibino)methanes as chelating ligands were obtained either from [{C 8 H 12 RhCl} 2 ], R 2 PCH 2 SbR′ 2 and MX, or (for 13 ) from 8 and AgPF 6 . Compound 12a (R = i Pr, R′ = t Bu) was characterized by X‐ray crystallography. The PF 6 salts 11a, 12a , and 13 react with CH 2 N 2 by insertion of CH 2 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 BPh 4 salts 11b and 12b with H 2 gives the half‐sand‐wich‐type complexes [(η 6 ‐C 6 H 5 BPh 3 )Rh(κ 2 ‐ P,Sb ‐R 2 PCH 2 SbR′ 2 )] ( 17, 18 ), in which the tetraphenylborate is coordinated like a substituted arene to the metal center.