Metallacarboranes in Catalysis. 2. Synthesis and Reactivity of Closo Icosahedral Bis(phosphine)hydridorhodacarboranes and the Crystal and Molecular Structures of Two Unusual closo-Phosphinerhodacarborane Complexes

Article abstract of DOI:10.1021/ja00322a038

A series of closo icosahedral rhodacarboranes bearing substituents at carbon has been synthesized by the reaction of <(PPh3)3RhCl> with the correspondingly C-substituted nido-carborane anions: from (1-) where R = R' = H; R = R' = D; R = H and R' = Ph, Me, and n-Bu; from (1-) where R = H, Ph, and Me; and from (1-).These closo icosahedral rhodacarboranes are catalytically active in alkene isomerization and hydrogenation reactions, among others.The B-D-B-bridge deuterated (1-) gave when reacted with <(PPh3)3RhCl>, establishing the regiospecific transfer of BHB hydrogen to Rh-H in the synthesis reaction.The complex is apparently transformed to by a polytopal rearrangement under mild conditions.The optically active catalyst was employed to hydrogenate ethyl α-phenylacrylate to give ethyl α-phenylpropionate in 3percent enantiomeric excess.In the absence of hydrogen this chiral catalyst reacted with certain esters of the acrylic type to yield alkyl chelates in which the alkene function of the ester had undergone migratory insertion into the Rh-H and the ester carbonyl oxygen became bound to Rh.One of these chelates, derived from the d-catalyst and n-butyl acrylate, was characterized crystallographically.The compound crystallizes in the space group P2₁2₁2₁ with unit cell parameters a = 24.578 (5) Angstroem, b = 12.543 (2) Angstroem, and c = 10.377 (2) Angstroem, four molecules per unit cell.The structure was solved by conventional heavy-atom methods and refined to a final value of R = 0.069, R_w = 0.080 (3159 reflections).The absolute configuration of the d-catalyst and the <1-nido-7-Me-7,8-B9C2H11>(1-), from which it was derived, was thus established.Reaction of the unsubstituted compounds and (L = PPh3) with more basic phosphines gave the corresponding L2 compounds with L = PEt3, PMe2Ph, and for the 3,1,2-isomer, L2 = Ph2PCH2CH2PPh2.Reaction of the unsubstituted 3,1,2-isomer (L = PPh3) with HCl in CHCl3 gave .The analogous chloro compound in which L = PMe2Ph was prepared by the reaction of the Rh-H species with CH2Cl2.Reaction of with HCl/CHCl3 produced the coordinatively unsaturated 16-electron species .This complex reacted with CO and ligands to produce coordinatively saturated adducts.A crystallographic study of the 16-electron 2,1,7-chloride was carried out.This compound crystallizes in the monoclinic system P2₁/n, a = 13.840 (5) Angstroem, b = 17.000 (7) Angstroem, c = 13.771 (6) Angstoem, and β = 118.98 (2) deg, four molecules of complex and...