Coupling of Alkynyl Ligands at a Quadruply Bonded Molybdenum Dimer

Abstract

The complex [Mo2(C≡CSiMe3)3(μ,η2:η2-HC≡CSiMe3){μ,η1-CC(SiMe3)-η2-C⋮CSiMe3}(μ-dmpm)2][Li(dme)] ([1][Li(dme)]; dmpm = 1,2-bis(dimethylphosphino)methane, dme = 1,2-dimethoxyethane) was prepared in 32% yield from the reaction between Mo2Cl4(dmpm)2, LiCCSiMe3, and HCCSiMe3 in dme. A single-crystal X-ray diffraction study of [1][Li(dme)0.5(OEt2)0.5] revealed that 1 contains an alkynylvinylidene ligand derived from the head-to-tail coupling of two alkynyl ligands.

Structural Dichotomy in Six-Coordinate d0 Complexes: Trigonal Prismatic (tBu3SiC⋮C)6Ta- and Octahedral (tBu3SiC⋮C)6M2- (M = Zr, Hf)

“…; M = Ti, Zr, Hf), , few cases of an early transition metal bound to more than two alkynyl ligands are known (e.g., {Li(TMEDA) 2 }[V(C⋮CPh) 4 ](tmeda)). , Since homoleptic hydrocarbyls have historically been considered critical synthetic targets, the paucity of relevant early metal examples may be construed as a testament to the reactivity of the alkynyl functional group. Side reactions, such as insertion of the Cα⋮Cβ unit, external RC⋮C - attack at Cα or Cβ, , and dinuclear reductive elimination − may interfere with standard metathetical routes and terminal alkynyl stability.…”

Synthesis, spectroscopy and electrochemistry of tetrakis(μ-N,N ′-diarylformamidinato)di(phenylethynyl)diruthenium(III) †,‡

“…5,6 In contrast, there are few examples of metal-metal bonded dinuclear compounds bearing alkynyl groups, notably those of diruthenium 7,8 and dirhodium 9 with one or two axial phenylacetylides, and M 2 (PR 3 ) 4 (CCR) 4 (M = Mo or W) where the alkynyl groups co-ordinate at the equatorial positions. 10 Therefore, much remains to be explored concerning the nature of interactions between the alkynyl and the dinuclear core, i.e. what role alkynyl plays in determining the co-ordination geometry and electronic structures of the dinuclear core, how the dinuclear core activates the alkynyl, and the possible chemical transformation therein.…”

“…Contributions a (%) N p π (42), C m p π (58) Ru d xy(10), N p π (42), C m p π (47) N p π (41), C m p π (57) Ru d xy (72), N p π (28) Ru (dsp) σ (76), C α p σ (19), N (sp) σ (4) Ru d π (87), C β p π (10) Ru d xy (83), C m p π (17) Ru d π (82), C β p π (14) N p π (100) N p π (96) ) σ (54), N (sp) σ (12), C σ p σ (20), C β p (10) N p π (42), C m p π (58) N p π (43), C m p π (49) N p π (42), C m p π (57) N p π (40), C m p π (54) Ru d xz (41), p z (36) Ru d x 2 Ϫ y 2 (70) Ru d yz (84), d xy (3), C β p π (10) Ru d x 2 Ϫ y 2 (73), d xz (8) Ru d z 2 (15), d xz (61) Ru d z 2 (28), d xz (29), d x 2 Ϫ y 2 (9) Ru d yz (70) N p π (90) a C α , C β and C m are the α, β carbons of acetylide and methine carbon of formamidinate, respectively.…”

The nature of the normal modes of [Mo2(CN)8]4−

“…1 Following this publication, the Hopkins group reported 11 the molecular structures and vibrational spectra of quadruply metal-metal bonded dimetallotetrayne compounds of the type M 2 (C᎐ ᎐ ᎐ CR) 4 (PMe 3 ) 4 (M = Mo or W). [16][17][18][19][20][21] Like [Mo 2 (CN) 8 ] 4Ϫ , the compound Mo 2 (C᎐ ᎐ ᎐ CSiMe 3 ) 4 (PMe 3 ) 4 was found to exhibit a three-band pattern (397, 362, 254 cm Ϫ1 ) in the resonance-Raman spectrum upon 1 (δ → δ*) excitation. The resonance-Raman spectra of isotopomeric derivatives ( 13 C᎐ ᎐ ᎐ 13 CSiMe 3 , C᎐ ᎐ ᎐ CSiMe 3 -d 9 ) display wavenumber shifts and changes in intensities of all three bands relative to those of their naturalabundance counterparts, which strongly imply that the three modes giving rise to these bands are of mixed parentage.…”