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

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).