The molybdenum iodide cluster anion undecaiodotetramolybdate(2-). A new cluster type structurally related to the octaiodohexamolybdenum(4+) octahedral cluster

Abstract

Crystalline ((n-Bu)/sub 4/N)/sub 2/Mo/sub 4/I/sub 11/ has been prepared in high yield. Synthesis is described elsewhere. From data obtained at -75/sup 0/C with MoK ..cap alpha..-radiation, the cell parameters are a = 19.99(3), b = 12.49(3), c = 23.67(2)A; ..cap alpha.. = 89.89(6), ..beta.. = 105.80(5), and ..gamma.. = 90.27(8)A; z = 4, P/sub 1//sup -/. The structure is described from two perspectives. (1) It is viewed as a severely distorted tetrahedral cluster of molybdenum atoms bridged on two faces by triply bridging iodine atoms, and on five edges by doubly bridging iodine atoms. The coordination sphere of each Mo atom is completed by one bond attached to a terminal I atom so that each metal atom attains the coordination number 8- by bonding to five I atoms and three Mo atoms. The anion has approximate C/sub 2v/ symmetry. Bond lengths and bond angles are included. (2) The structure may also be considered to be a fragment of the octahedral cluster Mo/sub 6/X/sub 8//sup 4 +/ by removing two adjacent Mo atoms from the Mo/sub 6/ octahedron and one I atom from the I/sub 8/ cube. The I atom remaining on the cube edge adjacent to the positions of themore » two removed Mo atoms is then shifted to the midpoint of that edge, and becomes the unique atom which bridges the long Mo-Mo bond. Bond lengths are compared with compounds which exhibit similar structure.« less