Synthesis and X-ray Structural Study on the Complexes of Silver(I) Halide with Tricyclohexylephosphine, Diphenyl-(2,4,6-trimethoxy)phenylphosphine, Phenyl-2,4,6-trimethoxyphenyl phosphine, and Tris(2,4,6-trimethoxy)phenylphosphine

Abstract

A diverse array of structures for the complexes of silver(I) halide with triphenylphosphine (PPh3) has been studied. The complexes may be described as being of the type [AgX(PPh3)n] (X = Cl, Br or I). The value of n varies in the range of 1–3. This also indicates that the stoichiometry of the complexes is in the range of 1–3. The complex with stoichiometry 1:1 is a tetramer. There are two structural types of tetramer reported, termed cubane and step or chair. The cubane structure has been reported for [AgX(PPh3)]4 (X = Cl, Br or I), while the step structure has only been reported for [AgI(PPh3)]4. The complex with stoichiometry 1:2 may be a monomer or a dimer. The monomer has a quasi trigonal planar structural type and has only been reported for [AgBr(PPh3)2]. The dimer has been reported for [(PPh3)2Ag(μ‐X)2Ag(PPh3)2] (X = Cl or Br) with silver atom in the distorted tetrahedral environment. The complex with stoichiometry 1:3 has a distorted tetrahedral structural type and has been reported for [AgX(PPh3)3] (X = Cl, Br or I). Changing PPh3 with more hindered ligand such as tricyclohexylephosphine (Pcy3) or derivative of PPh3 such as diphenyl‐2,4,6‐trimethoxy(phenyl)phosphine (dpmp), phenyl‐bis{2,4,6‐trimethoxy(phenyl)} phosphine (pdmp), or tris{2,4,6‐trimethoxy(phenyl)}phosphine (tmpp) may give complexes with various structural types but with lower range of stoichiometry. Synthesis and X‐ray structural study of these complexes has been done with the results summarized below. Silver(I) halide and Pcy3 give complexes with stoichiometry 1:1 and 1:2. The complex with stoichiometry 1:1 is a dimer or cubane. The dimer is observed for [(Pcy3)Ag(μ‐X)2Ag(Pcy3)] (X = Cl or Br). The unusual dimer is observed for [(Pcy3)Ag(μ‐I)2(μ‐py)Ag(Pcy3)] where the pyridine ligand is bonded to two silver atoms. The cubane is observed for [AgI(Pcy3)]4. The complex with stoichiometry 1:2 has a quasi trigonal planar structural type and has been observed for [AgX(Pcy3)2] (X = Cl, Br, I). Silver(I) halide and dpmp give complexes with stoichiometry 1:1 and 1:2. The complex with stoichiometry 1:1 is a dimer and has been observed for [(dpmp)Ag(μ‐X)2Ag(dpmp)] (X = Cl, Br or I). The complex with stoichiometry 1:2 has a quasi trigonal planar structural type and has been observed for [AgX(dpmp)2] (X = Cl, Br, I). Silver(I) halide and pdmp also give complexes with stoichiometry 1:1 and 1:2. The complex with stoichiometry 1:1 is a dimer and has been observed for [(pdmp)Ag(μ‐X)2Ag(pdmp)] (X = Cl, Br or I). The complex with stoichiometry 1:2 has a quasi trigonal planar structural type and has been observed for [AgX(pdmp)2] (X = Cl, Br, I). Silver(I) halide and tmmp only give complexes with stoichiometry 1:1. This complex is a monomer and has been observed for [AgX(tmpp)] (X = Cl or Br). In this complex the silver atom is in a quasi linear environment. Based on the bond lengths between silver and phosphorous atoms in the complexes obtained, it can be concluded that bulky ligands tend to give complexes with lower range of stoichiometry. In addition, the bulkier the ligand the longer the bond length between the silver and phosphorous atoms.