Method of making an immobilized tungsten catalyst comprising or consisting of (≡SiO) x W(=O)(=CR 1 R 2)(R 3 or R 4) 2-x z, wherein each of R 1 and R 2 is independently R, -OR, -SR, -N 2, -OC R, -SOR, - SO 2 R, -SO 2 N 2, -C N 2, -NRC R, or -NRSO 2 R; each R is independently hydrogen or an optionally substituted group selected from C 1-20 aliphatic, C 1-20 heteroaliphatic having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl, ferrocene, a 3-7 membered saturated or partially unsaturated carbocyclic ring, an 8-10 membered bicyclic saturated, partially unsaturated or aryl ring, a 5-6 membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 4-7 membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 7-10 membered bicyclic saturated or partially unsaturated heterocyclic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or: two R groups on the same nitrogen atom are taken together with the nitrogen to form an optionally substituted 3-12 membered saturated, partially unsaturated, or aryl ring having 0-5 additional heteroatoms not including the same nitrogen atom independently selected from nitrogen, oxygen, or sulfur; R 3 and R 4 have independently the same meaning as R 1 and R 2; or tris(C 1-20 alkyl)silyl, tris(C 1-20 alkyl)silyloxy, tris(C 1-20 alkoxy)silyl, tris(C 1-20 alkoxy)silyloxy, tris(aryl)silyl, tris(aryl)silyloxy, tris(aryloxy)silyl, or tris(aryloxy)silyloxy; and wherein x = 1 or 2; z = 0, 1 or 2 or a number between 0 and 2; and L is a neutral ligand; comprising at least the following step (i): (i) reacting silica (SiO 2) with a tungsten oxo alkylidene complex comprising or consisting of (R 3)(R 4)W(=O)(=CR 1 R 2) y, wherein y = 0, 1, or 2, wherein L, R 1, R 2, R 3 and R 4 have the meaning as defined above, and wherein R 3 and R 4 additionally may independently have the meaning of halogen, preferably of CI. two R groups on the same nitrogen atom are taken together with the nitrogen to form an optionally substituted 3-12 membered saturated, partially unsaturated, or aryl ring having 0-5 additional heteroatoms not including the same nitrogen atom independently selected from nitrogen, oxygen, or sulfur; R 3 and R 4 have independently the same meaning as R 1 and R 2; or tris(C 1-20 alkyl)silyl, tris(C 1-20 alkyl)silyloxy, tris(C 1-20 alkoxy)silyl, tris(C 1-20 alkoxy)silyloxy, tris(aryl)silyl, tris(aryl)silyloxy, tris(aryloxy)silyl, or tris(aryloxy)silyloxy; and wherein x = 1 or 2; z = 0, 1 or 2 or a number between 0 and 2; and L is a neutral ligand; comprising at least the following step (i): (i) reacting silica (SiO 2) with a tungsten oxo alkylidene complex comprising or consisting of (R 3)(R 4)W(=O)(=CR 1 R 2) y, wherein y = 0, 1, or 2, wherein L, R 1, R 2, R 3 and R 4 have the meaning as defined above, and wherein R 3 and R 4 additionally may independently have the meaning of halogen, preferably of CI. (i) reacting silica (SiO 2) with a tungsten oxo alkylidene complex comprising or consisting of (R 3)(R 4)W(=O)(=CR 1 R 2) y, wherein y = 0, 1, or 2, wherein L, R 1, R 2, R 3 and R 4 have the meaning as defined above, and wherein R 3 and R 4 additionally may independently have the meaning of halogen, preferably of CI.