FORMATION AND CHEMICAL-REACTIVITY OF METAL-CARBONYL-COMPLEXES CONTAINING PHOSPHORUS-BRIDGING CARBONYL GROUPS

Reactions of Na2Fe(CO)4 with sterically hindered R2NPCl2 derivatives (R2N = diisopropylamino, dicyclohexylamino, 2,2,6,6-tetramethylpiperidino) in diethyl ether solution result in migration of a carbonyl group from iron to phosphorus to give the air-stable P2Fe2 phosphorus-bridging carbonyl derivatives (R2NP)2COFe2(CO)6 in yields up to 35%. In addition, the corresponding P3Fe2 phosphorus-bridging carbonyl derivatives (R2NP)3COFe2(CO)6 are minor products of the reactions of Na2Fe(CO)4 with the same R2NPCl2 derivatives in tetrahydrofuran solution, the major products being the triphosphine complexes (R2NP)3Fe2(CO)6. The ketone-like reactivity of the phosphorus-bridging carbonyl group in (i-Pr2NP)2COFe2(CO)6 is indicated by its reactions with NaBH4 and with RLi (R = Me, n-Bu) to given the corresponding alcohols (i-Pr2NP)2C(R)(OH)Fe2(CO)6 (R = H, Me, n-Bu). Reduction of (i-Pr2NP)2COFe2(CO)6 with LiAlH4 gives a product of stoichiometry "(i-Pr2NP)2CH2Fe2(CO)6" shown by X-ray diffraction to be (i-Pr2NPCHPHN-i-Pr2)Fe2(CO)6, in which an FeP bond has broken and a new FeC bond has formed. Reduction of (i-Pr2NP)2COFe2(CO)6 with sodium amalgam in tetrahydrofuran results in cleavage of a diisopropylamino group to give the anion [i-Pr2NPCOPFe2(CO)6]-, which can be isolated as its bis(triphenylphosphine)iminium salt or converted to (i-Pr2N)(Me3Sn)P2COFe2(CO)6 or [(i-Pr2NP)(i-Pr2N)ClPP]Fe2(CO)6 by reaction with Me3SnCl or i-Pr2NPCl2, respectively. Reactions of (i-Pr2NP)2COFe2(CO)6 with the alcohols ROH (R = Me, Et) under relatively vigorous conditions or with HBr under relatively mild conditions result in expulsion of the phosphorus-bridging carbonyl group to give (i-Pr2NPOR)(i-Pr2NPH)Fe2(CO)6 or (i-Pr2NPBr)(HPBr)Fe2(CO)6, respectively. © 1990.