A Tetranuclear Butterfly Cluster of Molybdenum, [PPh4]2[Mo4I11]

Abstract

Bis (tetraphenylphosphonium) undecaiodotetramolybdate, 2[PPh4]+[Mo,I11] 2-, was obtained by treating [Mo2(MeCN)8] 4+ with PPN+I -in dichloromethane. The four Mo atoms of the anion adopt a 'butterfly' arrangement which can be viewed as a portion of an octahedron with two missing mutually cis vertices. Ten of the eleven I atoms are located at the vertices of a cube in which the ideal octahedron would be inscribed; two of them cap the two triangular faces of the Mo4 buttefly, four bridge the edges and four are terminally coordinated to the metal atoms. The eleventh I atom bridges the two 'wing-tip' metal atoms. The metal-metal distances for four edges of the butterfly wings are in the range 2.533 (3)-2.547 (3) ,A,, whereas the 'hinge' edge is slightly longer [2.688 (3) A,] and the separation between the two wing tips is 3.051 (3) ~. CommentOctahalodimolybdate tetraanions, [Mo2X8] 4-, are known for X = C1 (Brencic & Cotton, 1969) and Br (Brencic, Dobcnik & Segedin, 1974) but have never been reported for X = I. The above complexes were prepared by interaction of the acetate complex Mo2(OOCCH3)4 or the sulfate complex (NH4)4Mo2(SO4)4.2H20 with aqueous HX solutions. On the other hand, the analogous interaction between Mo2(OOCCH3)4 and HI affords, after treatment with ["Bu4N]I, the salt [nBu4N]2[MO4Ill] (Glicksman & Walton, 1978). There are, however, numerous dimeric complexes of the Mo2X4L,4 type where X = I (Cotton & Walton, 1982) and the hexaiodo complexes [Cat]2[MOEI6(H20)2] (Cat = pyH ÷, picH*) are also known (Brencic & Segedin, 1978;Brencic & Golic, 1977 (Stensvad, Helland, Babich, Jacobson & McCarley, 1978) and another with the [AsPh4] ÷ counterion (Cotton & Poli, 1988), but neither was reported in full. We report here the full details of the structure of the tetraphenylphosphonium salt, [PPhn]2[Mo4I~I], which is not isomorphous with the previously described [AsPh4] ÷ salt and does not have the twinning problems encountered in that case.The compound crystallizes in the centrosymmetric space group P1 with both cations and the dianion in general positions. The two independent tetraphenylphosphonium cations are similar to each other. The average P--C bond lengths for the two ions are 1.78 (2) and 1.82 (3)/~. The values of the C--P--C angles are all very close to the expected tetrahedral value, being in the range 107-112 ° with averages of 109.7(10) and 109.5 (20) ° for the two ions. Other features of these cations are normal and do not merit further discussion.A view of the [Mo4I]]] 2-anion is shown in Fig. 1. The I atoms have been labeled according to the number of the Mo atom(s) to which they are bonded. For instance, 1(23) is bonded to atoms Mo(2) and Mo(3), etc. I atoms with one-digit numbers are thus terminal ligands, those with two-digit numbers are doubly bridging and those with three-digit numbers are triply bridging. The best geometical description of this ion is based on the geometry of the well known family of octahedral clusters [Mo6X8] 4+, as described for the tetra-n-butylammonium salt of t...

Molybdenum Iodides – from Obscurity to Bright Luminescence

“…The metal-metal distances for four edges of the "butterfly" wings are in the range 2.533(3)-2.547(3) Å, whereas the "hinge" edge is slightly longer, 2.688(3) Å, and the separation between the two wing tips is 3.051(3) Å. [55] For tungsten, only oxidized analogue of [Mo 4 I 11 ] 2-, [W 4 I 11 ] -, has been reported. It forms a part of the structure of crystalline W 4 I 13 , produced in the reaction between W(CO) 6 and iodine at 165°C in 9 % yield.…”

“…The coordination geometry around the Mo atoms is completed with terminal I atoms, to give the [Mo 4 (µ 3 ‐I) 2 (µ 2 ‐I) 5 I 4 ] 2– anion. The metal–metal distances for four edges of the “butterfly” wings are in the range 2.533(3)‐2.547(3) Å, whereas the “hinge” edge is slightly longer, 2.688(3) Å, and the separation between the two wing tips is 3.051(3) Å …”

W4Br10 Cluster Intermediates in the Solid State Nucleation of W6Br12

“…Halide ligands of octahedral clusters are often divided into face‐capping or edge‐capping types but their coexistence in one compound appears quite unusual. However, there are other tetrahedral clusters (obtained by solution chemistry) like [Mo 4 I 11 ] 2– ,17 where this type of coexistence has been reported. When considering the connectivity of clusters by terminal bromide ligands we can express the structure of W 4 Br 10 as W 4 (μ 3 ‐Br)(μ 2 ‐Br) 6 Br(Br) 4/2 , having one terminal and four bridging bromide ligands, with the relevant interatomic distances given in Table 3.…”

“…Related tetrahedral cluster species exhibit a varying number of electrons in metal–metal bonding states, having 12 electrons in W 4 Cl(O)(O i Pr) 9 22 and (Et 3 PH)[W 4 O 3 Cl 7 (PEt 3 ) 3 ],23 14 electrons in W 4 I 13 ,24 and 15 electrons in (PPh 4 ) 2 Mo 4 I 11 17…”

The First Molybdenum Oxo‐iodide Cluster – [Mo4OI12]2–

“…The structure of the butterfly cluster 1 can be derived from formal oxidative addition of “O” + “I” to the distorted tetrahedral Mo 4 core found in (Ph 4 P) 2 [Mo 4 (μ 3 ‐I) 2 (μ 2 ‐I) 5 I 4 ] ( 2 ), as well as in its Bu 4 N + and Ph 4 As + analogues , . This leads to formal oxidation of Mo +2.25 to Mo +3 , which is accompanied by opening up of one of the Mo–Mo edges [that corresponds to the longest Mo–Mo bond of 3.051(3) Å in 2 ] to accommodate the capping O 2– ligand, and of one of the μ 2 ‐I bridges via insertion of an iodine atom: “Mo 2 (μ 2 ‐I)” + “I” = 2”MoI t ”.…”