A comparison of the coordination behaviour of R 2 PCH 2 BMe 2 (R = Me vs. Ph) ambiphilic ligands with late transition metals.

A new synthesis that avoids the use of Me 2 PH is reported for (Me 2 PCH 2 BMe 2 ) 2 , and this method was extended to the synthesis of (Ph 2 PCH 2 BMe 2 ) 2 . The ligand precursor (Me 2 PCH 2 BMe 2 ) 2 did not react with [{M(μ-Cl)(cod)} 2 ] (cod = 1,5-cyclooctadiene; M = Ir and Rh) or [PtCl 2 (cod)] at room temperature. However, after 12-48 hours at 65-70 °C, these reactions afforded (a) [Ir(cod)(μ-Cl)(Me 2 PCH 2 BMe 2 )] (1), (b) an equilibrium mixture of (Me 2 PCH 2 BMe 2 ) 2 , [{Rh(μ-Cl)(cod)} 2 ] and [Rh(cod)(μ-Cl)(Me 2 PCH 2 BMe 2 )] (2), and (c) cis -[Pt(μ-Cl) 2 (Me 2 PCH 2 BMe 2 ) 2 ] (3), respectively. By contrast, reactions between the phenyl-substituted analogue, (Ph 2 PCH 2 BMe 2 ) 2 , and [{M(μ-Cl)(cod)} 2 ] (cod = 1,5-cyclooctadiene; M = Ir and Rh) proceeded over the course of 1 hour at 20 °C to generate [M(cod)(μ-Cl)(Ph 2 PCH 2 BMe 2 )] (M = Ir (4) and Rh (5)), indicative of room temperature (Ph 2 PCH 2 BMe 2 ) 2 dissociation. Room temperature reactions of (Ph 2 PCH 2 BMe 2 ) 2 with [{Rh(μ-Cl)(coe) 2 } 2 ] (coe = cyclooctene) using a 1 : 1 or 3 : 1 stoichiometry also afforded [{Rh(coe)(μ-Cl)(Ph 2 PCH 2 BMe 2 )} 2 ] (6) or [RhCl(Ph 2 PCH 2 BMe 2 ) 3 ] (7), respectively, where the latter is a borane-appended analogue of Wilkinson's catalyst, and reactions of (Ph 2 PCH 2 BMe 2 ) 2 with [PtX 2 (cod)] (X = Cl or Me) yielded cis -[Pt(μ-Cl) 2 (Ph 2 PCH 2 BMe 2 ) 2 ] (8) and cis -[PtMe 2 (Ph 2 PCH 2 BMe 2 ) 2 ] (9). Compounds 1-9, (Me 2 PCH 2 BMe 2 ) 2 and (Ph 2 PCH 2 BMe 2 ) 2 were crystallographically characterized. In compounds 1-5 and 8, each chloride co-ligand is coordinated by the borane of an R 2 PCH 2 BMe 2 ligand. Additionally, in the solid state structure of 6, each bridging chloride ligand interacts weakly with a pendent borane, and in 7, the chloride ligand is tightly coordinated to the borane of one Ph 2 PCH 2 BMe 2 ligand and weakly coordinated to the borane of a second Ph 2 PCH 2 BMe 2 ligand. By contrast, both boranes in 9 (and one of the three boranes in 7) are non-coordinated.