Synthesis, Structure, and Reactivity of Tungsten Acetylide–Germylene Complexes

Abstract

The novel acetylide–germylene complexes Cp*(CO)2W(GePh2)(CCR) (7a, R = SiMe3; 7b, R = CMe3) were synthesized by the reactions of Cp*(CO)2W(NCMe)Me with Ph2HGeC≡CR (R = SiMe3, CMe3). X-ray crystal analysis of 7a revealed significantly increased germylene–tungsten and decreased germylene–acetylide interactions in comparison to the corresponding interactions in the previously reported acetylide–silylene complex Cp*(CO)2W(SiPh2)(CCSiMe3) (1). Complexes 7a,b reacted with acetone to give the six-membered cyclic vinylidene complexes Cp*(CO)2W═C═C(R)CMe2OGePh2 (8a, R = SiMe3; 8b, R = CMe3) by acetone insertion reaction, similar to the case of 1 affording Cp*(CO)2W═C═C(SiMe3)CMe2OSiPh2 (2). In the presence of 4-(dimethylamino)pyridine (DMAP), complexes 8a,b gave trans- and cis-DMAP-stabilized germylene acetylide complexes Cp*(CO)2W(GePh2·DMAP)(CCR) (trans- and cis-9a, R = SiMe3; trans- and cis-9b, R = CMe3) and acetone, showing a reactivity different from that of the silicon analogue 2. Complexes cis-9a,b were isolated as crystals from the reaction of 7a,b with DMAP and formed mixtures with trans-9a,b in solutions, respectively. A mixture of cis- and trans-9a reacted with acetone to form an equilibrium mixture with 8a and DMAP. The reactivity of 7a,b toward Me3COH was also investigated to reveal the formation of the vinylidene complexes Cp*(CO)2W{GePh2(OCMe3)}═C═CHR (10a, R = SiMe3; 10b, R = CMe3); 10a is equilibrated with 7a and Me3COH, whereas 10b is further converted to the carbyne complex Cp*(CO)2W≡CCH(CMe3){GePh2(OCMe3)} (11).