BEHAVIOR OF THE BIS(CHELATE) COMPLEX [RH(PO)2][BPH4] TOWARD ACYL HALIDES AND CARBON-MONOXIDE - INVESTIGATION OF A REVERSIBLE ALKYL MIGRATION

The bis(chelate) complex [Rh(P O)2][BPh4] (2; P O= eta2(O,P)-chelated (C6H11)2PCH2CH2OCH3 ligand) reacts with acyl chlorides RC(O)CI to give the acyl complexes [Rh(P O)2C(O)-RCI][BPh4] (4a-e; R = CH3 (a),C2H5 (b), i-C3H7 (c), Ph (d), C2H4Ph (e)). The structure of 4c, showing a distorted-octahedral configuration, was elucidated by an X-ray structural analysis. 4c crystallizes in the monoclinic space group P2/n with Z = 4. The cell dimensions are a = 21.881(4) angstrom, b = 10.303(2) angstrom, c = 26.516(5) angstrom, and beta = 100.91(3)-degrees. The reductive-elimination process of 4a proceeds via a reverse methyl migration to give Ga, followed by elimination of CH3Cl from 6a to form the carbonyl rhodium(I) complex [Rh(CO)(P approximately O)(P O)][BPh4] (8;P approximately O = eta1(P)-coordinated (C6H11)2PCH2CH20CH3 ligand). [ClRh(P approximately O)2(CO)] (9) is observed as the final product. Both Rh-O bonds in 2 are cleaved by 5-bar pressure of carbon monoxide, resulting in the formation of the tricarbonylrhodium(I) complex [Rh(P approximately O)2(CO)3][BPh4] (3). Upon bubbling argon through a CH2Cl2 solution of 3, [(OC)2Rh(P approximately O)2][BPh4] (cis-5 or trans-7) is favored compared to the monocarbonyl species 8.