Novel Titanium−Cobalt Complexes Formed by Reductive Cleavage of a Co−Co Bond in Co₂(CO)₈ by Titanocene tert-Butoxides:  Synthesis, Characterization, and Mechanistic Aspects for Metal−Metal Bond Recombination

Abstract

Reactions of titanium(III) complexes (η5-C5R5)2TiOtBu (R = H (1), Me (4)) with Co2(CO)8 are found to be efficient methods to synthesize Ti−Co heterobimetallic complexes. A Ti−Co3 complex, (η5-C5H5)2Ti(OtBu)(μ4-OC)Co(CO)9 (3), was formed from 1 and Co2(CO)8, whereas a Ti−Co bimetallic complex, (η5-C5Me5)2Ti(OtBu)(μ-OC)Co(CO)3 (5), was obtained by the reaction of 4 with Co2(CO)8. In both cases, the reaction was complete within 5 min. The products were completely characterized by NMR, IR, and X-ray crystallography. Complex 3 contains a quadruply bridging CO group, the oxygen terminus of which is connected to the Ti moiety, whereas the carbon terminus is bound to three Co atoms in the Co3(CO)9 moiety. In contrast, complex 5 is dinuclear, and its Ti atom is connected to the Co(CO)3 group by an isocarbonyl bridge. A η5-C5H5 analogue of 5, [(η5-C5H5)2Ti(OtBu)(μ-OC)Co(CO)3] (6), was formed at the initial stage of the reaction of 1 with Co2(CO)8 in toluene. This dinuclear complex 6 was isolated from a reaction medium of a 5:1 mixture of 1 and Co2(CO)8, being characterized by spectroscopy. As further evidence for the formation of the Ti−Co heterobimetallic complex, reaction of 6 with THF gave the Ti−Co complex [(η5-C5H5)2Ti(OtBu)(η-THF)]+[Co(CO)4]- (7), which was completely characterized by spectroscopy, crystallography, and elemental analysis. Thermal decomposition of 6 produced a mixture of 3 and 1, whereas treatment of 6 with Co2(CO)8 gave 3; this is good evidence for the intermediacy of 6 in the formation of 3 from 1 with Co2(CO)8.

Tetrairon Cluster Cp3Fe4(CO)4(C5H4PPh2) as a P–O Chelating Agent to Bind Palladium(II) and Copper(I) Ions through Phosphine and μ3-Carbonyl Groups

“…The 31 P{ 1 H} NMR spectrum shows a sharp singlet at δ 38.8, which is 58 ppm downfield of the signal for the free ligand 1 . The 13 C{ 1 H} NMR spectrum presents two carbonyl resonances at δ 339.8 and 284.5, with the former deshielded signal correlating to an η 2 ,μ 4 -CO group. − Overall, the spectral data indicate only one geometric isomer is produced for 2 .…”

“…A variety of bridging coordination modes for CO range from the simple μ-CO fashion to the complex μ 4 ,η 2 -CO linkage . Two bonding features of μ 4 ,η 2 -CO, I and II , were previously characterized in coordination to a butterfly M 4 framework, while the coordination mode III has the oxygen atom linked to oxophilic early transition metals . The bonding mode IV is attractive, since the cluster framework appends a strongly coordinating phosphine group and a weakly coordinating η 2 -carbonyl group that can portray hemilabile coordination properties to alter the activity of the bound metal centers and may find an application in homogeneous catalytic systems …”

Multicomponent Mechanochemical Synthesis of Cyclopentadienyl Titanium tert-Butoxy Halides, CpxTiXy(OtBu)4–(x+y) (x, y = 1, 2; X = Cl, Br)

“…Compound 3 is not affected by the disorder problems in 1 and 2 and interpretation of its structural features is more straightforward (Figure ). The molecule has the same pseudotetrahedral geometry displayed by 1 and 2 , but 3 can probably be compared most directly with the [Cp 2 Ti­(O t Bu)­(thf)] + cation; the Ti–O bond of 1.806(4) Å and Ti–O–C angle of 166.9(3)° of the latter differ by 0.02 Å and 5.6°, respectively, from that of 3 . Comparisons are also possible with the structure of Cp 2 TiCl­(OEt), which has been suggested as representing a sterically unencumbered Cp 2 TiCl­(OR) complex .…”

Reactions of early–late heterobimetallics with oxiranes: New examples for cooperative reactivity

“…conditions of Method E), however, the complexes (Cp) 2 M E Cl 2 (M E = Ti, Zr) are known to transform easily into M E (III) species when reduced by metals like zinc or magnesium. Recently, the titanium(III) complexes, (Cp) 2 TiO t Bu (5a) and (Cp * ) 2 TiO t Bu (5b), have been shown to undergo reaction with Co 2 (CO) 8 [17]. The heterobimetallic product isolated in the case of 5b, (Cp * ) 2 Ti(O t Bu)(l-OC)Co(CO) 3 (6), contains a titanium atom connected to cobalt by an isocarbonyl bridge.…”

“…Refs. [11,13,17,21,22]). A nucleophilic attack of tetracarbonyl cobaltate on the sterically more accessible carbon of the oxirane ring results in the formation of 1 through ring opening and CO insertion.…”