Valeraldehyde and process for its preparation

A bidentate phosphine ligand of the formula

• 13
• wherein R1, R2, R3 and R4 are independently selected from the group consisting of hydrogen, fluorine, alkyl of 1 to 8 carbon atoms, alkoxy of 1 to 8 carbon atoms, acyloxy of an organic carboxylic acid of 1 to 8 carbon atoms, aryl of 6 to 18 carbon atoms, aryloxy of 6 to 18 carbon atoms, —CN, —CF3, —CHO, —SO3H, —SO3M, —SO3R, —SOR, —NH2, —NH-alkyl of 1 to 8 carbon atoms, —N-alkyl2 of 1 to 8 carbon atoms, —NHCO-alkyl, —N-(alkyl)-(CO-(alkyl) where the alkyl have 1 to 4 carbon atoms, —COO-alkyl of 1 to 8 carbon atoms, —CONH2, —CO-alkyl of 1 to 8 carbon atoms, —NHCOH, —NHCOO-alkyl of 1 to 4 carbon atoms, —CO-aryl of 1 to 8 carbon atoms, —COO-aryl of 1 to 8 carbon atoms, —CHCH—CO2-alkyl of 1 to 8 carbon atoms, —PO-(-aryl)2 of 1 to 8 carbon atoms, —PO-(alkyl2) of 1 to 4 carbon atoms;
• M is a cation selected from the group consisting of alkali metal ions, alkaline earth metal ions, —NR2H2, —NR3H, —NRH3, —NR4, —NH4, —PR2H2, —PR3H, —PRH3, —PR4 and —PH4;
• or R1, R2, R3 and R4, with one another, together form at least one aliphatic or aromatic ring of 5 to 20 carbon atoms;
• E is a bridge linking the two phosphorus atoms, where the number of atoms situated between the two phosphorus atoms is 2 and 6, selected from the group consisting of C, N, Si, S, 0, P, Fe and As;
• X is selected from the group consisting of —O—, —S—, —Si(Ra)2—, —Si(ORa)2—, —N(C(O)Ra)—, —N(Rb)—, —C(Rc)(Rc), —C(O)—, —N(SiRd)—, —P(Rd)—, P(O)(Rd)—, —C═C(Rc)(Rc)— and —P(ORd)— wherein
• Ra is alkyl of 1 to 8 carbon atoms,
• Rb is aryl of 6 to 18 carbon atoms,
• Rc is selected from the group consisting of hydrogen, alkyl of 1 to 8 carbon atoms, aryl of 6 to 18 carbon atoms, alkoxy of 1 to 8 carbon atoms, aryloxy of 6 to 18 carbon atoms, Ra(O)— and Rb(o);
• and
• Rd is one of Ra or Rb.