Ruthenium complexes comprising paracyclophane and carbonyl ligands, and their use as catalyst

A ruthenium complex of formula (1a), (1b), (1c) or (1d):

• [Ru Hal2 L CO S] (1a)
• [Ru2 Hal4 L2 (CO)2] (1b)
• [Ru2 Hal4 L2 CO] (1c)
• [Ru Hal2 L (CO)2] (1d)
• wherein:
• Hal is a halogen ligand,
• L is a substituted or unsubstituted paracyclophane ligand of formula (2):
• wherein X1 and X2 are linking groups comprising between 2 to 4 carbon atoms,
• each Y1, Y2, Y3 and Y4 are independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl,
• each Z1, Z2 and Z3 are the same or different and are substituting groups that optionally contain functional groups,
• a, b, c, d, e and f are the integers 0 or 1 and a+b+c+d+e+f=0 to 6;
• CO is a carbonyl ligand;
• and
• S is a solvent ligand.