First Synthesis and Structural Characterization of Neutral Chelatedsyn-Facial Bimetallic (η5-Cyclohexadienyl)benzylidene Complexes from Tetracarbonyl[2-{(η6-phenyl)tricarbonylchromium(0)-ĸC2′}pyridine-ĸN]manganese(I) Derivatives

Abstract

Reaction of tetracarbonyl[2‐{(η6‐phenyl)tricarbonylchromium‐ĸC2′}pyridine‐ĸN]manganese(I), 2a, with phenyllithium quantitatively affords an acylmanganese anion 3a that can be isolated and spectroscopically characterized. In‐situ O‐alkylation of the latter anion by means of MeOSO2CF3 at low temperature, yields a new neutral syn‐facial heterobimetallic analog 4a of (η5‐cyclohexadienyl)benzylidene complexes. The treatment of bimetallic carbonyl complexes of 3‐methyl, 2‐phenyl‐pyridine and 2‐phenyl‐quinoline, 2b and 2c, with PhLi and subsequently with MeOSO2CF3 affords deep purple crystalline products 4b and 4c that have been structurally characterized by X‐ray diffraction analyses. The molecular structures of 4b and 4c display, among other features, an overall helical shape with a pronounced π‐stacking of the aromatic groups and a weak interaction between the chromium and the manganese centeredunits.

Polynuclear Organometallic Helices by Means of Novel Coupling Reactions of Cyclomanganated Complexes with Aryl-Substituted Diazoalkanes: Syntheses of New Manganospiralenes and Appended (η5-fluoren-9-yl)M(CO)3 Complexes (M = Mn, Re)

“…The two metals face each other: the Cr atom occupies one of the equatorial positions of the pseudo-octahedron centered at the Mn atom. The Cr−Mn distance of 3.047(2) Å is characteristic of a weak intermetal interaction and remains in the range of previously reported data . An interplanar angle of 37° and the C10−C19 distance of 2.896(3) Å characterize the overlap of one phenyl ring and the pyridyl ring.…”

The Cr−Mn Interaction in syn-Facial [Tricarbonyl(benzyl)chromium]manganesetricarbonyl Complexes: A Non-Covalent Metal−Metal Bond

“…It is seen that, with respect to the PBE data, the BP86 vibrations are systematically shifted to lower wave numbers. Nonetheless, both methods predict that the bathochromic shift of the ν 1 CO vibration of 10b [−11 cm −1 (BP86), −13 cm −1 (PBE)] as well as the hypsochromic shift of the ν 3 CO vibration of 10a [+12 cm −1 (BP86), +12 cm −1 (PBE)] are in excellent agreement with the experimental values measured for syn - 6a (−10 cm −1 and +10 cm −1 , respectively) …”

“…For complexes containing the C 3 v symmetric M(CO) 3 units, the IR spectrum displays two intense bands (an A 1 and a degenerate E) for the vibrations of the CO ligands . Because of the lower symmetry of the M(CO) 3 units, the E band of 10a and 10b is separated into two distinct absorptions (ν 1 and ν 2 in Table ). , The experimental IR spectra of the syn -facial Cr−Mn complexes measured in CH 2 Cl 2 typically show four different signals whose pattern is consistent with the overlap of two A 1 + E vibration modes of the fac -Cr(CO) 3 and fac -Mn(CO) 3 units. , However, the IR-spectrum of syn - 14 in the solid state shows six absorptions, that is, two A 1 bands and two sets of E-bands with lifted degeneracy . A similar pattern was also obtained for the calculated IR-spectrum of syn - 10 .…”

Organometallic Helices: The Mechanism of Formation of “Metallospiralenes”

“…The 13 C signals of the carbonyl ligands connected to the manganese(I) atom were detected at values of chemical shift that suggested that the chelated Mn(CO) 3 moiety was not located in the vicinity of the Cr(CO) 3 group but was rather engaged in the η 2 coordination of one of the two phenyl groups attached to the benzylic carbon. Indeed, in syn -facial bimetallic complexesor Cr/Mn-spiralenesthe Mn(CO) 3 fragment generates three distinct 13 C NMR signals at approximately δ = 230, 229, and 220 ppm,5b while in chelated η 3 -benzylic complexesor Mn-spiralenesthe resonances related to Mn(CO) 3 appear at δ = 230, 221, and 220 ppm 5a. Our hypothesis for a non- syn -facial bimetallic structure was further supported by the IR spectrum of 17 that displayed a fac -Mn(CO) 3 - related stretching A-mode vibration band at 2004 cm -1 , while it usually appears in syn -facial heterobimetallic complexes 5−10 cm -1 higher at around 2010−2015 cm -1 5b…”

“…Indeed, in syn -facial bimetallic complexesor Cr/Mn-spiralenesthe Mn(CO) 3 fragment generates three distinct 13 C NMR signals at approximately δ = 230, 229, and 220 ppm,5b while in chelated η 3 -benzylic complexesor Mn-spiralenesthe resonances related to Mn(CO) 3 appear at δ = 230, 221, and 220 ppm 5a. Our hypothesis for a non- syn -facial bimetallic structure was further supported by the IR spectrum of 17 that displayed a fac -Mn(CO) 3 - related stretching A-mode vibration band at 2004 cm -1 , while it usually appears in syn -facial heterobimetallic complexes 5−10 cm -1 higher at around 2010−2015 cm -1 5b …”