Spectroscopic Properties and Electronic Structure of the Cycloheptatrienyl Molybdenum Alkynyl Complexes [Mo(C≡CR)(Ph₂PCH₂CH₂PPh₂)(η-C₇H₇)]^<i>n</i>+(<i>n</i>= 0 or 1; R =<sup />Bu^t, 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, dxz, and d_x2-y2 through π- and δ-interactions with the C7H7 ring and concomitant destablization of the dz2 orbital.