The addition of the ambiphilic compound (Me 2 PCH 2 AlMe 2 ) 2 (1) to Cp*RhMe 2 (DMSO) (DMSO ) dimethylsulfoxide) (2) gives Cp*RhMe 2 (PMe 2 CH 2 AlMe 2 ‚DMSO) (3‚DMSO). The addition of Lewis acids (LA) such as La(dbm) 3 (dbm ) dibenzoylmethane) and AlMe 3 to a solution of complex 3‚DMSO gives a competition reaction that results in the formation of LA‚DMSO and Cp*RhMe 2 (PMe 2 CH 2 AlMe 2 ) (3). When heated to 40 °C, complex 3 ionizes to a putative zwitterionic species, Cp*Rh + Me(PMe 2 CH 2 AlMe 3 -) (3′), which is converted to [Cp*Rh(Me)(µ 2 -η 2 -Me 2 PCH 2 )] 2 (4) irreversibly. Spin saturation transfer experiments demonstrated that the rate of the methyl abstraction by the alane moiety was 0.76 ( 0.09 s -1 , while the rate of abstraction of the methyl in Cp*RhMe 2 (PMe 3 ) by AlMe 3 was 0.10 ( 0.02 s -1 . The zwitterionic species 3′ could be trapped in solution by addition of PMe 3 to afford both Cp*Rh + Me(PMe 3 )(Me 2 -PCH 2 AlMe 3 -) ( 5) and [Cp*Rh + Me(PMe 3 )(Me 2 PCH 2 AlMe 2 )]AlMe 4 -(6). When compound 1 was added to complex 3′, the formation of the zwitterionic complex Cp*Rh + Me(η 2 -Me 2 PCH 2 Al -Me 2 CH 2 PMe 2 ) (7) was observed.

Key indicators: single-crystal X-ray study; T = 183 K; mean (C-C) = 0.005 Å; R factor = 0.039; wR factor = 0.099; data-to-parameter ratio = 19.8.In the title complex, [Rh(CH 3 ) 2 (C 10 H 15 )(C 12 H 10 OS)], the Rh III atom is in a distorted tetrahedral coordination environment, coordinated by an 5 -pentamethylcyclopentadienyl ring, two methyl groups and the S atom of the diphenyl sulfoxide ligand. The title compound is representative of a very small group of complexes in which the diphenyl sulfoxide ligand is coordinated via the S atom. ExperimentalCrystal data [Rh(CH 3 ) 2 (C 10 H 15 )(C 12 H 10 OS)] M r = 470.46 Orthorhombic, Pccn a = 14.4164 (15) Å b = 35.646 (4) Å c = 8.5214 (8) Å V = 4379.1 (8) Å 3 Z = 8 Mo K radiation = 0.89 mm À1 T = 183 (1) K 0.43 Â 0.33 Â 0.05 mm Data collection Bruker P4/SMART 1000 CCD areadetector diffractometer Absorption correction: multi-scan (SADABS; Sheldrick, 1997a) T min = 0.769, T max = 0.957 28282 measured reflections 4963 independent reflections 3473 reflections with I > 2(I) R int = 0.053