Anionic Halomolybdate(III) Chemistry. Tetrahydrofuran Loss from [MoX₃Y(THF)₂]^-(X, Y = Cl, Br, I), Preparation and Properties of [Mo₃X₁₂]^3-(X = Br, I), and Crystal Structure of the Edge-Sharing Trioctahedral [PPh₄]₃[Mo₃I₁₂]

Abstract

By interaction of MoX(3)(THF)(3) with [Cat]X in THF, the salts [Cat][MoX(4)(THF)(2)] have been synthesized [X = I, Cat = PPh(4), NBu(4), NPr(4), (Ph(3)P)(2)N; X = Br, Cat = NBu(4), PPh(4) (Ph(3)P)(2)N]. Mixed-halide species [MoX(3)Y(THF)(2)](-) (X, Y = Cl, Br, I) have also been generated in solution and investigated by (1)H-NMR. When the tetraiodo, tetrabromo, and mixed bromoiodo salts are dissolved in CH(2)Cl(2), clean loss of all coordinated THF is observed by (1)H-NMR. On the other hand, [MoCl(4)(THF)(2)](-) loses only 1.5 THF/Mo. The salts [Cat](3)[Mo(3)X(12)] (X = Br, I) have been isolated from [Cat][MoX(4)(THF)(2)] or by running the reaction between MoX(3)(THF)(3) and [Cat]X directly in CH(2)Cl(2). The crystal structure of [PPh(4)](3)[Mo(3)I(12)] exhibits a linear face-sharing trioctahedron for the trianion: triclinic, space group P&onemacr;; a = 11.385(2), b = 12.697(3), c = 16.849(2) Å; alpha = 76.65(2), beta = 71.967(12), gamma = 84.56(2) degrees; Z = 1; 431 parameters and 3957 data with I > 2sigma(I). The metal-metal distance is 3.258(2) Å. Structural and magnetic data are consistent with the presence of a metal-metal sigma bond order of (1)/(2) and with the remaining 7 electrons being located in 7 substantially nonbonding orbitals. The ground state of the molecule is predicted to be subject to a Jahn-Teller distortion, which is experimentally apparent from the nature of the thermal ellipsoid of the central Mo atom. The [Mo(3)X(12)](3)(-) ions reacts with phosphines (PMe(3), dppe) to form products of lower nuclearity by rupture of the bridging Mo-X bonds.

The Radical Trap in Atom Transfer Radical Polymerization Need Not Be Thermodynamically Stable. A Study of the MoX3(PMe3)3 Catalysts

“…The identity of the products of these reactions as iodophosphosnium salts, see Equation 4, was confirmed by an X-ray determination of the product of the diiodine oxidation. The [MoI 4 (PMe 3 ) 2 ]complex was previously isolated as a PPh 4 + salt [36] and reported as showing a 1 H NMR resonance δ -41. ) is in the expected range for 1:1 salts (75-95 .…”

Molybdenum Iodides – from Obscurity to Bright Luminescence

“…The [Mo 3 I 12 ] 3– ion reacts with phosphanes (PMe 3 , dppe) to form products of lower nuclearity. With PMe 3 (six‐fold excess), formation of a mixture of [Mo 2 I 7 (PMe 3 ) 2 ] – , mer ‐[MoI 3 (PMe 3 ) 3 ] and trans ‐[MoI 4 (PMe 3 ) 2 ] – was detected by 1 H NMR, while with dppe the reaction products were [MoI 4 (dppe)] – and [Mo 2 I 6 (dppe) 2 ] . In fact, [Mo 2 I 7 (PMe 3 ) 2 ] – with face sharing bioctahedral structure, plus three bridging iodides and a combination of two I – and one PMe 3 ligand at each Mo, can be accessed in various ways, either by oxidation of [Mo 2 I 4 (PMe 3 ) 4 ] with I 2 in toluene (as Me 3 PH + salt), or by treatment of [MoI 3 (THF) 3 ] with PMe 3 in the presence of Me 4 N + .…”

“…The all‐halide capped 9 e analogue of the hydride cluster, [Mo 3 (µ 3 ‐X)(µ 3 ‐I)(µ‐I) 3 I 6 ] 2– (the capping position X is statistically occupied by Cl/I), was obtained in an attempt to recrystallize (Ph 3 P) 3 [Mo 3 I 12 ] from a CH 2 Cl 2 /pentane mixture, it is formed by formal loss of an I – ligand: [Mo 3 I 12 ] 3– = [Mo 3 I 11 ] 2– + I – , and halide scrambling with the solvent. Excess of Ph 4 PI suppresses this reaction . This transformation between a linear Mo 3 chain (as a fragment in MoI 3 ) into a triangle (as a face of the octahedron in MoI 2 ) may constitute the first step in the clusters build‐up when MoI 3 is decomposed with the formation of MoI 2 (Scheme , right side) Tetranuclear clusters are represented by a distorted tetrahedral Mo 4 cluster found in various [Mo 4 I 11 ] 2– salts (Figure ).…”

Redox‐Dependent Metal−Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling

“…More recently, multi‐configurational SCF (CASSCF) approaches have been applied to the problem, revealing the importance of a correct treatment of the multi‐configurational nature of the problem . Much of the early work in this field focused on clusters containing only two transition metal centers, but careful synthetic work has extended the chemistry of face‐shared octahedral chains to trimetallic systems . The first fully characterized trinuclear complex based on the face‐sharing architecture was [Ru 3 Cl 12 ] 4− , with a 16‐electron ([Ru 3 ] 8+ ) core and a Ru−Ru bond length of 2.805(1) Å .…”

“…[2] Given the importanceo ft he electron-electron repulsion termi nd etermining the degree of delocalization,i tc omes as no surprise that the description of metal-metal bonds in theseb ridged systemsr epresents as ubstantialc hallenge to theory.H offmann and co-workerss et out the symmetry-related aspects of the problem using extended Hückel theory, [3] buts ubsequent studies using density functional theory have revealed just how sensitive the problem is to the choice of exchange functional. [6][7][8][9][10][11] The first fully characterizedt rinuclear complex based on the face-sharing architecture was[ Ru 3 Cl 12 ] 4À ,w ith a1 6-electron ([Ru 3 ] 8 + ) core and aR u ÀRu bond length of 2.805 (1) . [4] More recently,m ulti-configurational SCF (CASSCF) approaches have been applied to the problem,r evealing the importance of ac orrect treatment of the multi-configurational natureo fthe problem.…”