Spectroscopic Properties and Electronic Structure of the Cycloheptatrienyl Molybdenum Alkynyl Complexes [Mo(C≡CR)(Ph₂PCH₂CH₂PPh₂)(η-C₇H₇)]ⁿ⁺(n= 0 or 1; R =^{But, Fc, CO₂Me, or C₆H₄-4-X, X = NH₂, OMe, Me, H, CHO, CO₂Me)}

Abstract

A series of molybdenum alkynyl complexes [Mo(CCR)(dppe)(η-C7H7)] featuring a range of alkynyl substituents R with varying electron-donating and -withdrawing properties have been prepared. Oxidation of representative members of the series to the corresponding 17-electron radical cations has been achieved through both chemical oxidation and in situ spectroelectrochemical methods. The largely metal-centered character of the HOMO in this class of compounds has been established through a combination of experimental measurements (IR, UV−vis−NIR, EPR spectroscopies) and DFT-based calculations and rationalized in terms of the stabilization of the metal d xy , d yz , d xz , and dx2-y2 through π- and δ-interactions with the C7H7 ring and concomitant destablization of the dz2 orbital.

Electron‐Rich Iron/Ruthenium Arylalkynyl Complexes for Third‐Order Nonlinear Optics: Redox‐Switching between Three States

“…The main discrepancies are found in the metal-phosphorus bonds and the CC triple bonds (0.03-0.04 ); these deviations are often seen with systems studied at the equivalent level of theory. [28] The Fe À C C angle is 170.28 in the crystal structure, a small angle that is not reproduced in the geometry optimization (179.18) and can be attributed to packing forces. The mono-oxidized state 3-H + can be described as a Fe III /Ru II complex, consistent with the X-ray structure obtained for that compound (Figure 2).…”

Polynuclear carbon-rich organometallic complexes: clarification of the role of the bridging ligand in the redox properties

“…42 The largely metal-centred character of the HOMO in this class of compounds has been established through a combination of experimental measurements (IR, UV-vis-NIR, EPR spectroscopies) and DFT calculations. This was rationalized in term of a strong d-interaction between molybdenum and the C 7 H 7 ligand not present in the Ru(h 5 -C 5 Me 5 )s y s t e m .T h e calculated Mulliken spin density is found to be of 1.1 e -on the Mo atom of the oxidized complexes 4-H + .…”

Electronic structure and spectroscopy of the cycloheptatrienyl molybdenum halide complexes [MoBrL2(η-C7H7)]+ (L2= 2CO, n= 0; L2= 2,2′-bipyridyl, n= 0 or 1)

“…The MLCT transitions observed for complexes 1[PF 6 ] and 2 do involve the cycloheptatrienyl ligand as an acceptor group but it is probably an oversimplification to attribute this property to a formal positive charge on the ligand. However a trinegative charge for the C 7 H 7 ligand (as generally proposed for mixed sandwich systems of the type [M(η-C 5 H 5 )(η-C 7 H 7 )], [1b]) resulting in the assignment of a Mo(IV), d 2 configuration also does not seem to be consistent with the reactivity of some Mo(C 7 H 7 ) half-sandwich systems which can promote alkyne to vinylidene isomerisation typical of a d 6 or d 4 metal centre [18,33]. One useful approach may be the assignment of a covalent bond classification [22] which is intimately linked with the contribution of the δ-interaction to the metal-cycloheptatrienyl bond (see ref.…”

“…The importance of metal-ring δ-interactions in the electronic structure of cycloheptatrienyl metal-sandwich complexes is well established [2-4, 8, 15] but very little attention has been given to the extension of this principle to half-sandwich systems [16] such as [ML 3 (η-C 7 H 7 )] n+ where potentially the impact on the tripodal L 3 ligand set could be even more pronounced. In this context, a recent series of investigations on half-sandwich vinylidene [Mo(C=CHR)(dppe)(η-C 7 H 7 )] + [17] (dppe = Ph 2 PCH 2 CH 2 PPh 2 ) and carbon chain complexes [Mo{(C≡C) x -C≡CR)L 2 (η-C 7 H 7 )] n+ (n = 0 or 1; x = 0 or 1, L 2 = dppe; x = 1, L 2 = bpy) [18,19], has demonstrated a re-ordering of the d-orbital manifold arising from metal-ring δ-bonding, leading to a metal-centred HOMO with significant d z 2…”

“…character. This in turn is reflected in the novel structural and redox chemistry of these systems [18][19][20][21].…”