Coordination chemistry and structural rearrangements of the Me 2 PCH 2 AlMe 2 ambiphilic ligand.

Reaction of 2 equivalents of (Me 2 PCH 2 AlMe 2 ) 2 with [{RhCl(cod)} 2 ] (cod = 1,5-cyclooctadiene) afforded [{κ 2 P , P -(Me 3 Al)ClMeAl(CH 2 PMe 2 ) 2 }Rh(cod)] (1), which features a κ 2 -coordinated bis(phosphino)aluminate anion. In compound 1, an Al-Cl substituent bridges to a molecule of AlMe 3 , which could be removed in vacuo to provide [{κ 2 P , P -ClMeAl(CH 2 PMe 2 ) 2 }Rh(cod)] (2). By contrast, reaction of 1 equiv. of (Me 2 PCH 2 AlMe 2 ) 2 with [{RhCl(cod)} 2 ] yielded [Rh(cod)(μ-Cl)(Me 2 PCH 2 AlMe 2 )] (3) as the major product, where the phosphine donor of an intact Me 2 PCH 2 AlMe 2 ligand is coordinated to rhodium and a chloride ligand bridges between Rh and Al. [Rh(cod)(μ-Cl)(Me 2 PCH 2 AlClMe)] (3A) and 2 were also formed as minor products. The aforementioned reactions were carried out in benzene or toluene, whereas the 1 : 1 reaction of (Me 2 PCH 2 AlMe 2 ) 2 with [{RhCl(cod)} 2 ] in THF afforded [{Rh(μ-CH 2 PMe 2 )(cod)} 2 ] (4). Reactions of (Me 2 PCH 2 AlMe 2 ) 2 with iridium(I), gold(I) and platinum(II) precursors were also explored. A 1 : 1 reaction of (Me 2 PCH 2 AlMe 2 ) 2 with [{IrCl(cod)} 2 ] afforded [{κ 2 P , P -Cl 2 Al(CH 2 PMe 2 ) 2 }Ir(cod)] (5) as one of two major phosphine-containing products; unlike 3, this compound features two chlorine substituents on aluminium. For comparison, the rhodium analogue of 5, [{κ 2 P , P -Cl 2 Al(CH 2 PMe 2 ) 2 }Rh(cod)] (6), was also synthesized via the 1 : 1 reaction of {ClAl(CH 2 PMe 2 ) 2 } 2 with [{RhCl(cod)} 2 ]. Reactions of (Me 2 PCH 2 AlMe 2 ) 2 with [AuCl(CO)] or [PtCl 2 (cod)] also resulted in chloride-methyl group exchange between the transition metal and aluminium. However, these reactions generated free (Me 2 PCH 2 AlClMe) 2 accompanied by gold and ethane, or [PtMe 2 (cod)], respectively. Reaction of 1.5 equivalents of (Me 2 PCH 2 AlMe 2 ) 2 with [PtMe 2 (cod)] at 75 °C afforded zwitterionic [(PtMe{μ-κ 1 P :κ 2 P , P -MeAl(CH 2 PMe 2 ) 3 }) 2 ] (7) which features two tris(phosphino)aluminate anions bridging between PtMe units. Compounds 1-2, 3/3A, 4-7 and (Me 2 PCH 2 AlClMe) 2 were crystallographically characterized.