Substituted metal carbonyls. Part 24. Heteropolymetallic oligomers [(OC)xM′(μ-L-L)M(CO)4(μ-L-L)M′(CO) x] and [(OC)5Mn-Mn(CO)4(μ-L-L)M(CO) 4(μ-L-L)(OC)4Mn-Mn(CO)5] [m = Cr, Mo or W; M′ = Cr, Mo, W (x = 5) or Fe (x = 4); L-L = Fe(C5H 4PPh2)...

Abstract

Full title: Substituted metal carbonyls. Part 24. Heteropolymetallic oligomers [(OC)xM′(μ-L-L)M(CO)4(μ-L-L)M′(CO) x] and [(OC)5Mn-Mn(CO)4(μ-L-L)M(CO) 4(μ-L-L)(OC)4Mn-Mn(CO)5] [m = Cr, Mo or W; M′ = Cr, Mo, W (x = 5) or Fe (x = 4); L-L = Fe(C5H 4PPh2)2 or Ph2P(CH2) mPPh2 (m = 2 or 3)], with metal carbonyl and diphosphine repeating units. A series of soluble oligomeric complexes of formulae [(OC) xM′(μ-L-L)M(CO)4(μ-L-L)M′(CO) x] [L-L = Fe(C5H4PPh2)2: M = Cr, M′ = Cr, Mo, W, Fe, or Mn2; M = Mo, M′ = Cr, Mo, Fe or Mn2; M = W, M′ = Cr or W. L-L = Ph2P(CH 2)mPPh2: M = Cr, M′ = Mo, m = 2 or 3. M′ = Cr, Mo, or W, x = 5; M′ = Fe, x = 4; M′ = Mn2, x = 9) has been isolated either as by-products in the syntheses of the bimetallics [(OC)xM′(μ-L-L)M(CO)x] or in a designed synthesis from cis-[M(CO)4(solv)2] (solv = solvent) (yields 1-18%). The repeating units are ferrocenyl or alkyl-chain diphosphine and metal carbonyl fragments and sometimes the oligomeric chains are supported by a M-M bond. The longest polymeric chain consists of seven metal atoms, Fe2MMn4. The linearity of the oligomeric propagation depends on the geometry of the central M(CO)4 unit, which is cis for Mo but trans for Cr or W. The geometrical preference is explained on steric and thermodynamic grounds, and the fluxionality of the five-co-ordinate intermediate. Nucleophilic attack by Me3NO on the bimetallics did not give oligomers through decarbonylation, but rather the phosphine oxide complexes [M(CO)5{Fe(C5H4PPh 2)(C5H4PPh2O)}] through dephosphination.