Crevice co-ordination: binding of a ligand molecule in a molecular crevice. Crystal and molecular structures of µ-oxo-µ-pyridine-µ-sulphido-bis[(OO′-di-isopropyl phosphorodithioato)oxo-molybdenum(V)] and µ-oxo-µ-pyridazine-µ-sulphido-bis[(OO′-di-isopropyl phosphorodithioato)oxomolybdenum(V)]

Abstract

Reaction of [{Mo(O)(X)}₂(O)(S)](1)(X =OO′-di-isopropyl phosphorodithioate) with various potential ligands L, in particular pyridine (py) and pyridazine (pydz), gives rise to 1:1 adducts. The crystal structures of two such adducts have been determined and are reported here, namely [{Mo(O)(X)}₂(O)(S)(py)](2) and [{Mo(O)(X)}₂(O)(S)(pydz)](3). Compound (2) is monoclinic, space group P2₁/a, with cell dimensions a= 17.200(10), b= 12.690(11), c= 15.448(9)Å, β= 110.0(2)°, and Z= 4. Compound (3) is monoclinic, space group P2₁/n, with a= 17.316(8), b= 14.560(11), c= 12.150(9)Å, β= 93.0(1),° and Z= 4. The structure for (2) has been refined to R 0.057 for 2 309 observed data and for (3) to R= 0.097 for 2 316 data. The two structures are similar in that the basic core of the parent compound (1) is maintained but there are major differences in the way in which the py and pydz are bonded to the metal atoms. In (2), the py molecule is weakly bonded to both molybdenum atoms through the nitrogen with Mo–N distances of 2.97(2) and 2.93(1)Å. The pyridine plane is approximately perpendicular to the Mo ⋯ Mo vector. In (3) the pydz is held parallel to this vector with each molybdenum being bonded to just one nitrogen [Mo–N 2.59(2) and 2.58(1)Å]. The preparative chemistry and i.r., u.v.–visible, and ³¹P n.m.r. spectra of the complexes are described.