Evidence for an intramolecular transition metal Arbuzov reaction

Abstract

Reaction of [CpCo(C3F7)(I)(L)], (L = PPh,Me (la), PPhMe, (lb), PMe, (lc), and PPh(OMe), (2)), with PPh(OMe), affords diastereomeric Co-and P-chiral metallophosphinates CpCo(C3F7)(L)(P(0)Ph(OMe)), 4a,b,c and 6, respectively. The solid state structure and relative configuration of the lower Rf diastereomeric phosphinate CpCo(C3F7)(PPh(0Me),)(P(O)Ph(OMe)), 6-2, was determined by X-ray diffraction. RR;SS-6-2 crystallizes in the triclinic system with space group PT(no. 2), with a = 12.928(4) A, b = 14.683(4) A, c = 7.666(2) A, a = 103.50(2)O, p = 101.31(3)", y = 109.50(2)", V = 1272.8(7) A3, Z = 2, and R = 0.036 (R,, = 0.030) for 2867 reflections with I > 3.00a(T). CpCo(C,F,)(I)(PPh(OMe),), 2, reacts with PPh,Me to yield the same Co-and P-chiral phosphinate products as obtained for the reaction of l a with PPh(OMe),, albeit with different optical yields. The product stereochemistry is not accounted for by the established mechanism for transition metal Arbuzov-like dealkylations, which requires formation of a common, ionic intermediate [CpCo(C3F7)(PPh,Me)(PPh(OMe),)]+, 3, via iodide substitution and subsequent nucleophilic attack at carbon. A parallel intramolecular dealkylation pathway is proposed to account for the results.

Thermal Chemistry of Cp*W(NO)(CH2CMe3)(H)(L) Complexes (L = Lewis Base)

“…Initial reductive elimination of CMe 4 from the cis form of the complex followed by the intramolecular oxidative addition of an O–Me bond to the tungsten center results in the formation of 16e Cp*W­(NO)­(Me)­(P­(O)­(OMe) 2 ) that then dimerizes so that the tungsten centers can attain the favored 18e configuration. Most interestingly, the product of this rearrangement is unlike those of previously reported Arbuzov rearrangements in that both the Me group and the resulting phosphonate ligand remain attached to the same metal center. − …”