Synthesis of a Molybdenum Hydrido(hydrogermylene) Complex and Its Conversion to a Germylyne Complex: Another Route through Dehydrogenation with Nitriles

Abstract

A molybdenum germylene complex having Mo−H and Ge−H bonds, Cp*(CO) 2 (H)MoGe(H){C(SiMe 3 ) 3 } (1), was synthesized by the reaction of a methyl molybdenum complex with a trihydrogermane and was converted to a germylyne complex, Cp*(CO) 2 MoGe{C(SiMe 3 ) 3 } (2), via dehydrogenation with aryl isocyanates under mild heating. A similar conversion from the same germylene complex into the germylyne complex also occurred using nitriles instead of isocyanates, while releasing imines via a Mo−Ge−N three-membered ring complex Cp*(CO) 2 Mo[κ 2 (N,Ge)Ge-(N CHR){C(SiMe 3 ) 3 }] (4, R = Me and aryl groups) as an intermediate. Formation of imines was confirmed by a trapping experiment with BPh 3 , which afforded a BPh 3 -imine adduct. In the case of aryl nitriles, the corresponding three-membered ring intermediates were converted into the germylyne complex efficiently by blue LED light irradiation. TD-DFT calculations on the three-membered-ring intermediate suggest that the role of the LED light is to induce CO ligand dissociation from the intermediate via a metal-to-ligand-charge-transfer (MLCT) transition.

Transition-metal Complexes with Triple Bonds to Si, Ge, Sn, and Pb and Relevant Complexes

“…20 The SC-XRD study revealed that both complexes 10a/b have very short MGe bonds and have linear geometries as indicated by their MGeC(substituent) angles (172173°). 20,21 Very recently, our group also found that similar dehydrogenation occurred using nitriles instead of arylisocyanates in the molybdenum system (Scheme 7). 21 In this case, three-memberedring intermediates Cp*(CO) 2 Mo[¬ 2 (N,Ge)-Ge(H)(N=CHR)(Tsi)] (12) were formed via CÔN hydrogermylation of nitriles and converted to germylyne complex 10b with releasing imines.…”

“…20,21 Very recently, our group also found that similar dehydrogenation occurred using nitriles instead of arylisocyanates in the molybdenum system (Scheme 7). 21 In this case, three-memberedring intermediates Cp*(CO) 2 Mo[¬ 2 (N,Ge)-Ge(H)(N=CHR)(Tsi)] (12) were formed via CÔN hydrogermylation of nitriles and converted to germylyne complex 10b with releasing imines. Notably, when arylnitriles were employed, the corresponding conversion was enhanced by LED light irradiation.…”

“…Thus, germylene complexes 9a/b, which were prepared by the reactions of Cp*M(CO) 3 Me and H 3 Ge{C(SiMe 3 ) 3 }, 17 were heated with arylisocyanate to give germylyne complexes 10a/b with release of ArNHCHO (Scheme 6). 20,21 Obviously, ArNCO acted as a hydrogen accepter during the reaction. Furthermore, in the case of a tungsten system, a five-membered-ring complex Cp*(CO) 2 W[¬ 2 (N,Ge)-GeH(OCH=NMes)(Tsi)] (11a) was isolated as an intermediate.…”

“…The29 Si NMR signal appears at 320.1 ppm in a very downfield, which is lower than those of Mo=Si double bonded complexes. Filippou's group also synthesized a cationic chromium silylyne complex [Cp*(CO) 2 CrÔSi(Sidipp)][A](21) [SIdipp = 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene] by the reaction of an NHC-silicon(II) dibromide with Li[CpMo(CO) 3 ] followed by bromide abstraction from the corresponding bromosilylene complex Cp*(CO) 2 Cr=SiBr(Sidipp) (Scheme 15) 29. Silylyne complex 21 is thermally stable up to 158°C.…”

Dehydrogenative Double C—H Bond Activation in a Germylene-Rhodium Complex

“…[1][2][3] In this regard, heavier tetrylenes (:ER2; E = Si, Ge, Sn, Pb) offer unique opportunities as single-site ambiphiles (σ-donating lone pair and empty p orbital), revealing unusual coordination modes and reactivity. [4][5][6][7][8][9][10][11][12] Moreover, they represent the prospects of new avenues for transition metal/P-element cooperation. [13][14][15][16][17][18][19][20][21][22][23][24][25] However, the coordination chemistry of tetrylenes remains considerably less explored than their lighter carbene congeners, in no little part due to reduced stability.…”