Communication between Remote Moieties in Linear Ru–Ru–Ru Trimetallic Cyanide-Bridged Complexes

Abstract

In this article, we report the structural, spectroscopic, and electrochemical properties of the cyanide-bridged complex salts trans-[(NC)Ru(II)(L)4(μ-CN)Ru(II)(py)4Cl]PF6 and trans-[Ru(II)(L)4{(μ-CN)Ru(II)(py)4Cl}2](PF6)2 (L = pyridine or 4-methoxypyridine). The mixed-valence forms of these compounds show a variety of metal-to-metal charge-transfer bands, including one arising from charge transfer between the remote ruthenium units. The latter is more intense when L = 4-methoxypyridine and points to the role of the bridging ruthenium unit in promoting mixing between the dπ orbitals of the terminal fragments.

Phosphorus as Lone Pair Donor and Ligand Acceptor: A Paddlewheel with Ru←P Axis

“…Selected bond lengths [Å] and angles [°] for 2: Ru1-P1 2.1476(8), Ru1-N1 2.074(2), Ru1-N2 2.080(2), Ru1-N3 2.072(2), Ru1-N4 2.064(2), Ru1-O4 2.234(2), P1-O1 1.952(2), P1-O2 1.681(2), P1-O3 1.877(2), P1-C21 1.804(3), N1-Ru1-N3 177.7(1), N2-Ru1-N4 167.5(1), P1-Ru1-O4 175.76(6), O1-P1-O3 169.2(1), C21-P1-Ru1 147.3 (1). Selected bond lengths [Å] and angles [°] for 3: Ru1-P1 2.326(1), Ru1-N1 2.088(3), Ru1-N2 2.086(3), Ru1-N3 2.087(3), Ru1-N4 2.089(3), Ru1-C27 1.919(4), C27-O5 1.151(5), P1-O1 1.825(3), P1-O2 1.838(3), P1-O3 1.881(3), P1-O4 1.901(3), P1-C21 1.861(4), N1-Ru1-N3 169.85 (12), N2-Ru1-N4 169.57 (12), P1-Ru1-C27 177.10(13), O1-P1-O3 174.85(13), O2-P1-O4 172.78(13), C21-P1-Ru1 177.16 (13).…”

“…[PhP(μ-PyO) 2 2 3 RuCl 2 (PPh 3 )] [6] P-Ru /Å 2.1328(4) 2.1476 (8) 2.3261(10) Ru-P-C /°140.43 (6) 147.31(10) 177.16 (13) Although the longer Ru-P separation in 3 and the higher P coordination number might hint at (partial) cancelation of the Ru-P bond as the reason for this rather unusual 31 P NMR shift of a hexacoordinate P compound, the 2 J P,C coupling observed for the CO carbon in the 13 C NMR spectrum (267 Hz) is spectroscopic evidence of the Ru-P bond in 3. In order to gain deeper insights into the development of the Ru-P bond upon changing the P coordination number, NBO/NLMO calculations were performed for [PhP(μ-PyO) 2 RuCl 2 (PPh 3 )], [6] 2 and 3.…”

“…As expected, introduction of the strong π-acceptor CO trans to the Ru-P bond lowers the Ru→P backbonding in 3 (the energy of the competing Ru→C CO π-backbonding into the two CO π*-orbitals amounts to 56.4 kcal mol -1 ; Figure 4) 4 ] (E 1/2 = 0.67 V). [13] Complex 3 shows an irreversible oxidation, both in MeCN (E pc = 0.44 V) and in dichloromethane (E pc = 0.45 V), followed by decomposition to 2 and liberation of CO (Scheme 3). This loss of CO was concluded from observation of the CV trace of 2 in the second cycle (red curve in Figure 5).…”

“…C 27 H 21 N 4 O 5 PRu (613.52): calcd. C 52.86, H 3.45, N 9.13; found C 52.91, H 3.32, N 9.17. Supporting Information (see footnote on the first page of this article): 1 H, 13 C and 31 P NMR spectroscopic data, additional cyclic voltammetry data, and details of computational analyses.…”

Class III Delocalization in a Cyanide‐Bridged Trimetallic Mixed‐Valence Complex

“…[14,15] Another focus has been the characterization of higher nuclearity systems, [16] which also present challenging spectroscopy. [17][18][19] We have recently reported [18] the spectroscopy of two trimetallic cyanide-bridged mixed-valence complexes of formula trans-[Ru(L) 4 {(m-CN)Ru(py) 4 Cl} 2 ] 3+ (1 3+ , where L = pyridine and 2 3+ , where L = 4-methoxypyridine; Table 1). These systems exhibit two transitions in the near infrared (NIR) that correspond to a charge transfer from the central ruthenium(II) unit to the neighboring terminal {-Ru III (py) 4 Cl} fragment (MM'CT), and a charge transfer between the distant {-Ru(py) 4 Cl} fragments (MMCT).…”