Mono- and binuclear molybdenum and tungsten complexes containing asymmetric bridging ligands: effects of ligand conjugation and conformation on metal-metal interactions

• Published in: Inorganic chemistry Vol. 32; no. 10; pp. 2145 - 2155
• Main Authors: Das, Amitava, Jeffery, John C, Maher, John P, McCleverty, Jon A, Schatz, Erik, Ward, Michael D, Wollermann, Gerd
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-05-1993
• Subjects: 400400 - Electrochemistry; Carbonyl and nitrosyl compounds, and their complexes; Carbonyl and nitrosyl metals; CATIONS; CHARGED PARTICLES; CHEMICAL PREPARATION; CHEMICAL REACTIONS; CHEMISTRY; COMPLEXES; Condensed matter: structure, mechanical and thermal properties; ELECTROCHEMISTRY; ELECTRON SPIN RESONANCE; Exact sciences and technology; Inorganic chemistry and origins of life; Inorganic compounds; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IONS; LIGANDS; MAGNETIC RESONANCE; MOLECULAR STRUCTURE; MOLYBDENUM COMPLEXES; Physics; Preparations and properties; REDUCTION; RESONANCE; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; SYNTHESIS; TRANSITION ELEMENT COMPLEXES; TUNGSTEN COMPLEXES; Molecular structure; Nitrogen heterocycle; Molybdenum Nitrosyl Complexes; Organic ligand; Experimental study; X ray diffraction; Tungsten Nitrosyl Complexes; Cyclic voltammetry; Mu complex; Electrochemical properties; Transition metal Nitrosyl Complexes; Metal metal bond; Dinuclear complex; Boron Organic compounds; EPR spectrum; Monodentate ligand; Crystalline structure
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic00062a045

The authors have prepared the new monodentate ligands 4-(4-methoxyphenyl)pyridine, 1-(4-pyridyl)-2-(4-methoxyphenyl)ethene, 1-(4-pyridyl)-2-(3-methoxyphenyl)ethene, and 1-(3-pyridyl)-2-(4-methoxyphenyl)ethene (L[sup 5]-L[sup 8]); demethylation of the methoxy group in each case afforded the new bridging bidentate ligands HL[sup 1]-HL[sup 4], which contain one pyridyl and one phenolate donor. Attachment of a MoL*(NO)Cl [L* = hydrotris(3,5-dimethylpyrazolyl)borate] moiety to the pyridyl groups of L[sup 5]-L[sup 8] gave the 17-electron complexes [Mo(NO)L*ClL[prime]] (L[prime] = L[sup 5]-L[sup 8], complexes 5-8). Reaction of HL[sup 1]-HL[sup 4] with [M(NO)L*Cl[sub 2]] (M = Mo, W) afforded the mononuclear 16-electron complexes [M(NO)L*ClL[prime]] (M = Mo, L[prime] = L[sup 1]-L[sup 4], complexes 1-4; M = W, L[prime] = L[sup 1]-L[sup 4], complexes 13-16), in which the phenolate terminus of L[sup 1]-L[sup 4] is attached to the metal and the pyridyl group is pendant in each case. The pyridyl groups were N-methylated with CH[sub 3]I to afford [9][sup +]-[12][sup +] and [17][sup +]-[20][sup +], respectively. Alternatively, a second MoL*(NO)Cl could be attached to the pendant pyridyl groups of 1-4 to give the binuclear complexes [Mo(NO)L*Cl([mu]-L[prime])Mo(NO)L*Cl] (L[prime] = L[sup 1]-L[sup 4], complexes 21-24), which contain a 16-electron Mo center at the phenolate terminus and a 17-electron Mo center at the pyridyl terminus. Electrochemical studies showed that the anodic shift of the 16e-17e reduction due to N-methylation in [9][sup +]-[12][sup +] and [17][sup +]-[20][sup +] varies with the ligand in the order L[sup 1] > (L[sup 2] [approx] L[sup 4]) > L[sup 3]. 33 refs., 7 figs., 8 tabs.