AN UNUSUAL SANDWICH-TYPE NICKEL OXIDE-SILOXANOLATE COMPLEX ([PHSIO]6(MU-4-O)2(MU-3-O)4[NI8(MU-3-O)2](MU-3-O)4(MU-4-O)2[PHSIO]6).14N-BUOH.10H2O.2ME2CO - SYNTHESIS AND CRYSTAL-STRUCTURE

An X-ray crystal study of the nickel oxide-siloxanolate complex {[PhSiO]6(mu-4-O)2(mu-3-O)4[Ni8(mu-3-O)2](mu-3-O)4(mu-4-O)2[PhSiO]6}.14n-BuOH.10H2O.2MeCO (I or Ia without noncoordinating solvate molecules) having a cage structure has been carried out. The complex studied was prepared by the interaction of NiCl2 with the product of the reaction of phenylsilsesquioxane (PhSiO1.5)n with NaOH. The polynuclear cage-like centrosymmetric molecule Ia has a sandwich-type structure. The inner two-dimensional nickel oxide fragment Ni8O2(mu-O)12/2 = Ni8O8 is structurally identical to a fragment of the NiO crystal layer which is one Ni atom thick and parallel to the (111) plane. All Ni atoms have oxygen atoms in an octahedral coordination (oxide, silanolate, molecules of water, butanol and acetone). The O atoms of the nickel oxide layer have both trigonal pyramidal (mu-3-O) and distorted tetrahedral (mu-4-O) coordination. The nickel oxide layer is bonded by Ni-O-Si bridges through silanolate O atoms with two outer 12-membered hexasiloxane (SiO)6 cycles (sandwich ''caps'') with an almost ideal crown conformation. Some of the butanol and H2O crystallosolvate molecules do not coordinate the Ni atoms being included in the cavities between Ia molecules. The NiO bond lengths are 2.006-2.159 angstrom, while the average Si-O(Si) and Si-O(Ni) bond lengths are 1.637 and 1.618 angstrom, respectively.