Heterobi- and Heterotrimetallic Transition Metal Complexes with Carbon-Rich Bridging Units

Abstract

The syntheses of heterobi-and heterotrimetallic complexes based on (2,2′-bipyridine-5-ylethynyl)ferrocene (3) are described. Complex 3 is accessible by the Pd(II)/Cu(I)-catalyzed Sonogashira crosscoupling of FcCtCH (1) (Fc ) (η 5 -C 5 H 4 )(η 5 -C 5 H 5 )Fe) with 5-bromo-2,2′-bipyridine (2). The complexation behavior of 3 was investigated. Treatment of 3 with (nbd)Mo(CO) 4 (4a) (nbd ) norbornadiene) at 25 °C, or refluxing 3 with Mn(CO) 5 Br (4b), (Me 2 S) 2 PtCl 2 (4c), and Ru(bipy) 2 Cl 2 ‚2H 2 O (4d) (bipy ) 2,2′bipyridine), respectively, gave the respective heterobimetallic complexes FcCtC-bipy 12) can be obtained by the subsequent reaction of 7 with Me 3 SiCtCH ( 9) and [Cu(NtCMe) 4 ]BF 4 (11), while [FcCtC-bipy{[Ti](µ-σ,π-CtCSiMe 3 ) 2 }M]X (14a: M ) Cu, X ) PF 6 ; 14b: M ) Ag, X ) ClO 4 ; [Ti] ) (η 5 -C 5 H 4 SiMe 3 ) 2 Ti) were formed by combining 3 with {[Ti](µ-σ,π-CtCSiMe 3 ) 2 }MX (13a: MX ) Cu(NtCMe)PF 6 , 13b: MX ) AgOClO 3 ). The identity of 3, 10, and 14a was confirmed by single-crystal X-ray structural studies. The main characteristic features of 3 and 10 are the almost eclipsed conformation of the ferrocene cyclopentadienyl rings, the linear C Cp -CtC-C bipy moieties, and the coplanarity of both the pyridine and the C 5 H 4 rings. The latter structural motif allows an optimal overlap between the π-orbitals of the cyclopentadienyl, ethynyl, and pyridyl rings. However, in 14a the bipy ligand is tilted by 96.9°toward the η 5 -C 5 H 4 unit, which most likely is attributable to cell-packing effects. The platinum atom in 10 is held in a somewhat distorted squareplanar surrounding. The chelated copper(I) ion in 14a possesses a pseudotetrahedral coordination geometry. Mononuclear 3 exhibits redox peaks in its cyclic voltammogram (E 0 ) 0.10 V, ∆E p ) 194 mV) for the Fe 2+ /Fe 3+ redox couple of the Fc unit and for the bipy ligand (E 0.1 ) -2.36 V, ∆E p ) 200 mV; E 0.2 ) -2.76 V, ∆E p ) 430 mV). Compounds 10, 12, 14a, and 14b additionally show electrode potentials attributed to the respective ML n building blocks.

Heterotrimetallic and heterotetrametallic transition metal complexes

“…5.1 ppm. The coordination of the bipyridine ligand to the respective metal atoms can be verified by the shift of the resonance signals of the bipyridine protons, i.e., due to the coordination of the bipyridine moiety to manganese the protons H6 and H6 0 , which are located next to the nitrogen atoms, are shifted from 8.42 (H6) and 8.64 ppm (H6 0 ) in 4a to 8.86 (H6) and 9.16 ppm (H6 0 ) in 14a [9,11]. Notable in the 1 H NMR spectra of 17 and 18, when compared with 15 and 16, is the highfield shift of the Me 3 SiC"C protons from ca.…”

2,2′-Bipyrimidine transition metal complexes: Synthesis, reaction chemistry and solid state structures

“…In the dimeric structures of 15a 0 and 15b 0 p-p contacts exist between the Pt(C"CFc) 2 agreement with similar organometallic or metal-organic building block systems [5,13]. Solely the cyclic voltammograms of 8a-8c were measured in tetrahydrofuran as solvent because all other complexes are very badly soluble in common organic solvents.…”

“…In the beginning of our work we selected as transition metal building block the heterobimetallic Ti-Ag organometallic p-tweezer molecule {[Ti](l-r,p-C"CSiMe 3 ) 2 }AgOTf ([Ti] = (g 5 -C 5 H 4 SiMe 3 ) 2 Ti, OTf = OSO 2 CF 3 ) (2) as starting material because we have experience in using such compounds for the preparation of multiheterometallic systems in which different metal atoms are bridged by carbon-rich organic and/or inorganic connecting moieties [5,6].…”

“…The appropriate metals are connected via carbon-rich organic groups including the 2,2 0 -bipyrimidine (bipym) connecting unit. Through the bipym connectivity planar molecules are formed with the Pt(II)-containing fragments [PtCl 2 ], [Pt(C"CR) 2 ] (R = SiMe 3 , Fc, Rc; Fc = (g 5 -C 5 H 4 )(g 5 -C 5 H 5 )Fe; Rc = (g 5 -C 5 H 4 )(g 5 From cyclic voltammetric studies it can be concluded that organometallic 8a-8c are in general easier to reduce than a non-coordinated free bipym molecule, explainable by the fact that a electron-withdrawing Lewis-acid is bonded to the bipym unit.…”

A first mixed heteropentametallic transition metal complex: Synthesis and characterisation

“…During the course of the reaction of 3 with 4, the m C"N absorption in 4 at 2283 cm À1 disappears. The bidentate coordination of the bipyridine ligand to copper(I) in 5 influences the frequency of the TiC"C vibration, whereby a week hypsochromic shift is observed [8].…”