A process for hydrogenating a substrate comprising a carbon-heteroatom double bond, the process comprising the step of reacting the substrate with hydrogen gas in the presence of a hydrogenation catalyst, wherein the hydrogenation catalyst is a complex of formula: wherein, R 1, R 2, R 3, R 4 and R 5 are each hydrogen, one of R 6 and R 7 is phenyl and the other of R 6 and R 7 is hydrogen, one of R 5 and R 9 is phenyl and the other of R 5 and R 9 is hydrogen, R 10 is a methyl, 2,4,6-trimethylphenyl, or 2,4,6-triisopropylphenyl group, A is -(CH 2) 3 - or -(CH 2) 4 -, and Hal is a halogen, wherein the substrate to be hydrogenated is a carbonyl of formula: wherein, R 50 and R 51 are each independently selected from the group consisting of hydrogen, an optionally substituted straight, branched or cyclic C 1-20 alkyl, an optionally substituted straight, branched or cyclic C 2-20 alkenyl, an optionally substituted C 2-20 alkynyl, an optionally substituted C 6-20 aryl, an optionally substituted straight, branched or cyclic C 1-20 heteroalkyl, an optionally substituted C 3-20 heteroaryl, -NR 60 R 61, -COR 60, -COOR 60, -CONR 60 R 61, an optionally substituted -C 1-20 -alkyl-COOR 60, an optionally substituted -C 1-20 -aklkyl-COR 60, an optionally substituted -C 1-20 -alkyl-CONR 60 R 61, optionally substituted -C 2-20 -alkynyl-C 6-20 -aryl and optionally substituted -C 2-20- alkynyl-C 1-20 -alkyl; or R 50 and R 51 are bound by an optionally substituted C 1-20 alkyl, an optionally substituted C 1-20 alkoxy or an optionally substituted C 2-20 alkenyl; or R 50 and R 51 are bound to form a 5, 6 or 7 membered ring by an optionally substituted -(CH 2) t -(ortho-C 5-6 -aryl)-(CH 2) u - chain, an optionally substituted -(CH 2) t -(ortho-C 5-6 -aryl)-Q-(CH 2) u - chain or an optionally substituted -(CH 2) t -(ortho-C 5-6 -heteroaryl)-(CH 2) u - chain, wherein t is an integer selected from 0 or 1, u is an integer selected from 2, 3 or 4, Q is selected from the group consisting of -O-, -N- and -SO 2 -, wherein the substituents are selected from the group consisting of one or more of straight, branched or cyclic C 1-20 alkyl, straight, branched or cyclic C 1-20 alkoxy, C 6-20 aryl, C 6-20 aryloxy, straight, branched or cyclic C 1-20 heteroalkyl, C 6-20 heteroaryl, straight or branched tri-C 1-20 -alkylsilyl-, -Hal, -OH, -CN, -NR 60 R 61, -COR 60, -COOR 60, -CONR 60 R 61 and -CF 3, wherein R 60 and R 61 are independently selected from the group consisting of hydrogen, straight, branched or cyclic C 1-20 alkyl, straight, branched or cyclic C 1-20 alkoxy, C 6-20 aryl, C 6-20 aryloxy and -OH. R 1, R 2, R 3, R 4 and R 5 are each hydrogen, one of R 6 and R 7 is phenyl and the other of R 6 and R 7 is hydrogen, one of R 5 and R 9 is phenyl and the other of R 5 and R 9 is hydrogen, R 10 is a methyl, 2,4,6-trimethylphenyl, or 2,4,6-triisopropylphenyl group, A is -(CH 2) 3 - or -(CH 2) 4 -, and Hal is a halogen, R 50 and R 51 are each independently selected from the group consisting of hydrogen, an optionally substituted straight, branched or cyclic C 1-20 alkyl, an optionally substituted straight, branched or cyclic C 2-20 alkenyl, an optionally substituted C 2-20 alkynyl, an optionally substituted C 6-20 aryl, an optionally substituted straight, branched or cyclic C 1-20 heteroalkyl, an optionally substituted C 3-20 heteroaryl, -NR 60 R 61, -COR 60, -COOR 60, -CONR 60 R 61, an optionally substituted -C 1-20 -alkyl-COOR 60, an optionally substituted -C 1-20 -aklkyl-COR 60, an optionally substituted -C 1-20 -alkyl-CONR 60 R 61, optionally substituted -C 2-20 -alkynyl-C 6-20 -aryl and optionally substituted -C 2-20- alkynyl-C 1-20 -alkyl; or R 50 and R 51 are bound by an optionally substituted C 1-20 alkyl, an optionally substituted C 1-20 alkoxy or an optionally substituted C 2-20 alkenyl; or R 50 and R 51 are bound to form a 5, 6 or 7 membered ring by an optionally substituted -(CH 2) t -(ortho-C 5-6 -aryl)-(CH 2) u - chain, an optionally substituted -(CH 2) t -(ortho-C 5-6 -aryl)-Q-(CH 2) u - chain or an optionally substituted -(CH 2) t -(ortho-C 5-6 -heteroaryl)-(CH 2) u - chain, wherein t is an integer selected from 0 or 1, u is an integer selected from 2, 3 or 4, Q is selected from the group consisting of -O-, -N- and -SO 2 -, wherein the substituents are selected from the group consisting of one or more of straight, branched or cyclic C 1-20 alkyl, straight, branched or cyclic C 1-20 alkoxy, C 6-20 aryl, C 6-20 aryloxy, straight, branched or cyclic C 1-20 heteroalkyl, C 6-20 heteroaryl, straight or branched tri-C 1-20 -alkylsilyl-, -Hal, -OH, -CN, -NR 60 R 61, -COR 60, -COOR 60, -CONR 60 R 61 and -CF 3, wherein R 60 and R 61 are independently selected from the group consisting of hydrogen, straight, branched or cyclic C 1-20 alkyl, straight, branched or cyclic C 1-20 alkoxy, C 6-20 aryl, C 6-20 aryloxy and -OH.