Bis-Adducts of Substituted Phenylethynyl on a Ru₂(DMBA)₄ Core:  Effect of Donor/Acceptor Modifications

Abstract

The reactions between arylethynes (either BuLi activated or Et3N assisted) and Ru2(RDMBA)4X2, where RDMBA is either N,N ‘-dimethylbenzamidinate (R = H) or N,N ‘-dimethyl-m-methoxybenzamidinate (R = m-MeO) and X is either Cl- or NO3 -, resulted in the compounds Ru2(RDMBA)4(C⋮CC6H4Y)2 (Y = H (1a,b), 4-NO2 (2a,b), 4-CN (3a,b), 3-CN (4a,b), 4-NMe2 (5a,b); R = H (a), m-MeO (b)). The single-crystal X-ray diffraction study of 1b and 2a revealed the linear alignment of the arylethynyl ligands along the Ru−Ru vector. All of the compounds display two Ru-based one-electron processes, an oxidation and a reduction, and their electrode potentials correlate linearly with the Hammett constants of substituent Y. Compounds 5a,b display an additional pair of one-electron processes attributed to the oxidation of 4-NMe2 groups, on the basis of which an extensive electron delocalization along the metallayne backbone was inferred.

Bis‐alkynyl Diruthenium Compounds with Built‐in Electronic Asymmetry: Toward an Organometallic Aviram–Ratner Diode

“…Tables 2 and 3. It is clear from Tables 2 and 3 that the Ru À Ru bond lengths in all five compounds are within a narrow range of 2.4405(9)-2.4640(7) . These distances are similar to those previously reported for the [Ru 2 A C H T U N G T R E N N U N G (dmba) 4 A C H T U N G T R E N N U N G (CCY) 2 ]-type compounds (Y = Ar, Fc, SiR 3 , and CCSiR 3 ), [21,23,[25][26][27] and consistent with the existence of a Ru À Ru single bond. The Ca À Cb bond lengths in all compounds except 1 are very close to 1.20 , the value expected for a C C bond in metal acetyl-A C H T U N G T R E N N U N G ides.…”

“…[26,27] It was soon discovered that [Ru 2 A C H T U N G T R E N N U N G (dmba) 4 X 2 ] (X= NO 3 or BF 4 ) reacts with an unactivated alkyne HC CR in the presence of Et 3 N at room temperature and in an ambient atmosphere. [25,28] The use of unactivated alkyne proved to be advantageous in the high yield synthesis of compounds containing strong electrophilic functional groups, such as NO 2 and CN, and the insensitivity of the reaction toward air/ moisture enabled easy monitoring of reaction progress. However, the original protocol had shortcomings, including the use of terminal acetylenes in large excess (> 5 equiv) and extended reaction time (overnight).…”

“…This approach could be problematic for the preparation of compounds such as trans-[(4-NO 2 PhC C)Ru 2 A C H T U N G T R E N N U N G (dmba) 4 (C CPh-4-NMe 2 )] (6), because of the potential interaction between n-BuLi and the nitro group. [25] On the other hand, the weak base protocol is compatible with electrophilic functional groups and appears ideal for the synthesis of compound 6. Thus, the reaction between [Ru 2 A C H T U N G T R E N N U N G (dmba) 4 A C H T U N G T R E N N U N G (NO 3 ) 2 ] and a mixture of 4-Me 2 NC 6 H 4 CCH and 4-O 2 N-C 6 H 4 CCH in the presence of diethyl amine yielded three products as indicated in Scheme 1.…”

“…While the X-ray crystallographic studies revealed a minimal structural effect upon donor/acceptor substitution, voltammetric measure-methylbenzamidinate and Ar is phenyl bearing electron donor or acceptor substituent; the influence of these substituents on the electronic properties of these diruthenium species were investigated. [25] In this contribution, we describe the synthesis of both symmetric [Ru 2 A C H T U N G T R E N N U N G (dmba) 4 (4)(5)(6)(7), and the electronic asymmetry in the latter type of compounds that may render the function of single-molecule rectifier.…”

Conductivity Measurements of Paddlewheel Dimetal Complexes with Metal-Metal Multiple Bonds

“…These complexes were chosen for initial studies because they have a large difference in the metalmetal bond order and they are both robust and air stable. Following the initial synthesis of the paddlewheel complexes, the axial chlorides will be exchanged for labile ligands [5] and then replaced by a designed anchoring group [6], which contains a conjugated system [7] and can readily bind to coinage metal electrodes [8]. A schematic of the synthesis is shown in Fig.…”