MIGRATORY INSERTION OF A PHOSPHORUS LIGAND INTO A TRANSITION METAL-ALKYL BOND

Treatment of Cp(CO)(R(1))Fe{PN(Me)CH(2)CH(2)NMe(OR(2))} (R(1) = R(2) = Me, 1a; R(1) = Me, R(2) = Et, 2a; R(1) = CH(2)Ph; R(2) = Me, 3a) with BF3 . OEt(2) and then with PPh(3) yields [Cp(CO)(PPh(3))Fe{PN(Me)CH(2)CH(2)NMe(R(1))}](+) (R(1) = Me, 1b; R(1) = CH(2)Ph 3b). The reaction proceeds via the formation of a cationic phosphenium complex, [Cp(CO)(R(1))Fe{PN(Me)CH(2)CH(2)NMe}](+) by the abstraction of an OR group as an anion from a phosphorus atom, and then migratory insertion of the phosphenium ligand into the iron-alkyl bond takes place to give [Cp(CO)-(BF(2)OR(2))Fe{PN(Me)CH(2)CH(2)NMe(R(1))}](+), which is characterized by spectroscopic data. The cationic complex readily reacts with PPh(3) to give the final product. A eta(5)-C(5)Me(5) derivative of 1a and a monoamino-substituted phosphite complex Cp(CO)(Me)Fe{PN(Me)CH2CH2O-(OMe)} show the same reactivity. The reaction of silyl complexes Cp(CO)(SiMe(3))Fe-{PN(Me)CH(2)CH(2)NMe(OR)} (R = Me, Et) with BE(3) . OEt(2) affords a phosphenium complex [Cp(CO)(SiMe(3))Fe{PN(Me)CH(2)CH(2)NMe}](+), which does not show the migratory insertion into an iron-silyl bond. Iron complexes Cp(CO)(CH(2)OMe)Fe{PN(Me)CH(2)CH(2)NMe(OR)} (R = Me, 9a; R = Et, 10a) having an alkoxy group both on a carbon and on a phosphorus react with BF3 . OEt(2) and then with PPh(3) to give [Cp(CO)(CH(2)PPh(3))Fe{PN(Me)CH(2)CH(2)NMe(OR)}](+) (R = Me, 9e; R = Et, 10e). The results prove that the OME in the CH(2)OMe ligand is selectively abstracted to give the methylidene complex which is trapped with PPh(3) to give a phosphine ylide complex. Complexes 1b . BF4 and 10e . BF4 have been characterized by X-ray diffraction (crystal data for 1b . BF4, monoclinic, P2(1)/n, a = 9.099(1) Angstrom, b = 13.727 (2) Angstrom, c = 23.134 (5) Angstrom, beta = 91.48 (1)degrees, Z = 4, R = 0.063; for 10e . BF4, orthorhombic, Pcab, a = 18.033(6) Angstrom, b = 24.619 (6) Angstrom, c 14.501 (4) Angstrom, Z = 8, R = 0.059).