Stereospecific formation of face-shared bioctahedra and trioctahedra by oxidative displacement of carbon monoxide from the tetracarbonyltrichloromolybdate(1-) anion

Abstract

The reaction of MoCl62" or MoCl6" with Mo(CO)4Cl3~inCH2Cl2 results in the formation of Mo2Cl,3" and MoCl92", respectively. The temperature dependence of the magnetic moment of the latter is shown to be hi accord with the thermal equilibrium 5 = */2 4* S = 3/2, while its infrared spectrum can be readily assigned assuming a bioctahedral, D3h structure. It is easily reduced to Mo2C193_. The reaction of Mo2Cl92' with Mo(CO)4Cl3" leads to Mo3C1123" whose trinuclear structure was verified from conductivity measurements. Both the electronic and the infrared spectra are in accord with a linear, trioctahedral, face-shared structure (unlike Re3Cl123"). Magnetic moments in solution are in qualitative agreement with the thermal equilibrium 5 = '/2 & S = 3/2.

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]

“…The observed trend for the room temperature magnetic moments for the different [Mo 3 X 12 ] 3salts, i.e. 3.17 µ B for X ) I (PPh 4 + salt), 2.60 µ B for X ) Br (PPh 4 + salt), and 2.02 µ B for X ) Cl (for the previously reported NBu n 4 + salt) 37 can then be attributed to the increase of either or both intermolecular and intramolecular antiferromagnetic exchange interactions as the size of the halide ligands becomes smaller. The same trend was also observed by magnetic susceptibility 33 and by NMR methods 27 on halidebridged face-sharing bioctahedral complexes.…”

“…As stated in the Introduction, a salt of the corresponding chloro complex, [Mo 3 Cl 12 ] 3was reported several years ago by Wentworth. 37 This compound also shows only four stretching vibrations (rather than the expected six) in the Mo-Cl stretching region, probably because of accidental overlap. Following the detailed analysis offered for that trinuclear complex (for which a comparison with dinuclear [Mo 2 Cl 9 ] 3ion was possible), the two IR bands at higher frequency are assigned to the vibration of terminal bonds and those at lower frequency to bridging bonds.…”

“…36 About 20 years ago a related ion, [Mo 3 Cl 12 ] 3-, has also been described. 37 This was obtained by combining [Mo 2 Cl 9 ] 2and [MoCl 3 (CO) 4 ] -in a 1:1 ratio and was proposed to adopt a face-sharing trioctahedral structure on the basis of optical, magnetic, and conductivity studies. This structure is not related to a fragment of the MoCl 3 solid and an interesting question concerns the extent of metal-metal bonding along the supposed linear Mo 3 unit.…”

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.…”