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New germanium containing tungsten carbyne complexes Ph 3 GeC≡W(CH 2 R) 3 (R = Bu t or SiMe 3 ) were synthesized by the reaction of the alkoxy derivative Ph 3 GeC≡W(OBu t ) 3 with alkyllithium reagents RCH 2 Li. The new compounds were isolated in individual form as crystals in 95 and 90% yields, respectively, and were characterized by elemental analysis, 1 H and 13 C NMR spectroscopy, and X ray diffraction. X ray diffraction study showed that the coordination environment of the W and Ge atoms in the Ph 3 GeC≡W(CH 2 Bu t ) 3 and Ph 3 GeC≡W(CH 2 SiMe 3 ) 3 complexes can be described as a distorted tetrahedron.Nowadays, olefin metathesis catalyzed by transition metal carbene complexes is widely used in organic syn thesis. 1-6 Metathesis of acetylenic hydrocarbons medi ated by transition metal carbyne complexes is much less well studied and is used to a lesser extent. 4-6 The tung sten carbyne complexes RC≡W(OR´) 3 (R and R´ = Alkyl or Aryl) are most efficient catalysts for metathesis of acety lenic hydrocarbons. 4 The catalytic activity of complexes was found 4 to be to a large extent determined by the nature of alkoxy groups. The influence of the nature of the substituent R bound to the carbyne carbon atom is much less well known. Recently, 7,8 we have synthesized the tungsten carbyne complexes Ph 3 EC≡W(OBu t ) 3 and Ph 2 E[C≡W(OBu t ) 3 ] 2 (E = Si, Ge, or Sn) containing organosilicon, germanium, and tin substituents at the carbyne carbon atom. The resulting carbyne complexes exhibit high catalytic activity in metathesis of hept 3 yne (as a test substrate). The catalytic activity of tin contain ing derivatives is substantially higher than that of silicon containing complexes, and the trinuclear complexes Ph 2 E[C≡W(OBu t ) 3 ] 2 are more efficient catalysts than the dinuclear complexes Ph 3 EC≡W(OBu t ) 3 . 9 In this connec tion, it was of interest to elucidate how the catalytic activ ity of silicon , germanium , and tin containing tungsten carbyne complexes changes when the alkoxy groups are replaced by other ligands, in particular, by alkyl groups.It is known that the tert butoxy groups in the tungsten carbyne complexes RC≡W(OBu t ) 3 (R = Alk or Ar) are readily replaced by alkyl groups in the reactions with alkyllithium compounds or Grignard reagents. 10 In the present study, we used this method for the replacement of the tert butoxy group in the germanium containing tung sten carbyne complex by the neopentyl and trimethyl silylmethyl substituents. Results and DiscussionIt was demonstrated that the tungsten triphenylgermyl carbyne complex Ph 3 GeC≡W(OBu t ) 3 (see Ref. 7) readily reacts with neopentyllithium and trimethylsilylmethyl lithium to give new alkyl containing carbyne complexes Ph 3 GeC≡W(CH 2 Bu t ) 3 and Ph 3 GeC≡W(CH 2 SiMe 3 ) 3 , re spectively (Scheme 1). Scheme 1Ph 3 GeC≡W(OBu t ) 3 + 3 RCH 2 Li Ph 3 GeC≡W(CH 2 R) 3 + 3Bu t OLi R = CMe 3 (1), SiMe 3 (2) Reaction conditions: diethyl ether, 0 °C.Both complexes were isolated in individual form as crystals in 95 and 90% yields, respectively. The 1 H ...