Catalyst and process for the production of aldehydes by hydroformylation of olefinically unsaturated compounds

A catalyst comprising rhodium and a compound of the formula (I)

• in which
• m is a number from 1 to 1000;
• x is a number from 0 to 4;
• W is a group of the formulae —CH2—CH2—, —CH(CH3)CH2— or —CH2CH(CH3)—;
• R is hydrogen, a straight-chain or branched C1-C5-alkyl radical;
• or a group of the formulae
• where
• a, b, c, d and e independently of one another are a number from 0 to 1000, at least one of the numbers a, b, c, d and e being greater than 0;
• R5, R6, R7, R8 and R9 are identical or different and are hydrogen, C1-C5-alkyl or a group of the formula
• R1 and R2 are identical or different and are a straight-chain, branched or cyclic C1-C30-alkyl radical or C6-C10-aryl radical, which is unsubstituted or substituted by from one to five C1-C3-alkyl radicals, or R1 and R2 together with the trivalent P atom form a dibenzophospholyl of the formula
• or a 3,4-dimethylphospholyl of the formula
• and
• L is C1-C5-alkyl, C1-C5-alkoxy, NO2, NR3R4, where R3 and R4 independently of one another are hydrogen or C1-C4-alkyl, or L is Cl or OH.