Synthesis of alkyne complexes of the type Ta(.eta.5-C5Me5)(alkyne)Cl2 and crystal structure of (.eta.5-pentamethylcyclopentadienyl)(diphenylacetylene)dichlorotantalum

Synthesis, characterisation, and molecular and electronic structure of CpMoCl2(R1CCR2) (R1, R2 = Ph, Et, Me): a new class of half-sandwich 17-electron molybdenum(III) organometallics

“…The angle θ between the Mo-C(6)-C(7) plane and the plane defined by Mo, CNT (center of gravity of the Cp ring), and the midpoint of the C(6)-C(7) vector is 85.61°. This tilting away from the ideal parallel conformation (θ = 90°) is less pronounced relative to the previously reported W(III) complex (η 5 -C5Me4Bu t )WCl2(MeC≡CMe) (θ = 77.16°) 24 and slightly more relative to Cp*TaCl2(PhC≡CPh) (θ = 87.27°) 36 and (η 5 -C5H4Me)NbCl2(ArC≡CAr) (Ar = C6H4CH3-4, θ = 86.40°). 37 Table 2 collects relevant bond distances and angles, in comparison with those of the above mentioned Nb analogue (η 5 -C5H4Me)NbCl2(ArC≡CAr) 38 and of geometry optimised HC≡CH model compounds (vide infra).…”

Mononuclearη2(4e)-Bonded Phosphaalkyne Complexes; Selective Formation of a 1,2-Diphosphacyclobutadiene Tantalum Complex

“…We reasoned that a comparison of the structural data for the two complexes would provide an insight into the nature of the bond between the metal center and the phosphaalkyne. In this study we focused on the report that the well‐characterized (NMR, X‐ray) d 2 complex [TaCl 2 ( η 5 ‐C 5 Me 5 ){ η 2 (4e)‐PhC 2 Ph}]3 can be synthesized by reaction of PhC≡CPh with the labile complex [TaCl 2 ( η 5 ‐C 5 Me 5 )(CO) 2 (thf)] 4. This suggested that the tantalum dicarbonyl complex might also react with t BuC≡P to form a novel η 2 (4e)‐bonded phosphaalkyne complex.…”

Niobium and Tantalum

“…Alkenes (typically styrene or cyclooctene) are readily displaced f r o m Cp*Ta(r| 2 -alkene)X 2 (X = Cl or Br) to afford Cp*Ta(ROCR)Cl 2 (ROCR = PhOCPh, PhOCH, MeOCMe, EtOCEt, or HOCH). 418 It is interesting that none o f these complexes reacts with excess alkyne to f o r m metallacyclopentadienes. The alkoxide derivatives Cp*Ta(PhOCPh)(0Me)Cl and Cp*Ta(PhOCPh)(0Me) 2 are available f r o m Cp*Ta(PhOCPh)Cl 2 and NaOMe.…”

“…The alkoxide derivatives Cp*Ta(PhOCPh)(0Me)Cl and Cp*Ta(PhOCPh)(0Me) 2 are available f r o m Cp*Ta(PhOCPh)Cl 2 and NaOMe. 418 When Cp*Ta(TMS)Cl 3 is refluxed in benzene in the presence o f alkyne, reductive elimination o f TMS-C1 occurs and the d 2 adducts Cp*Ta(ROCR)Cl 2 (ROCR = PhOCPh, HOCPh, MeOCMe, or TMS-OC-TMS) are available. 212 Perhaps the most intriguing reaction to give rise to cyclopentadienyl alkyne complexes is the cycloaddition sequence involving the tantalum alkylidyne complex [Cl 2 (DME)Ta(|Li-CBu t )] 2 [Zn((a-Cl) 2 ] (23).…”