4474
J. Am. Chem. SOC.1985, 107, 4474-4483
Transformation of a Tungsten(0) Alkyne to a Tungsten( 11) Alkyne via Vinylidene, Carbyne, and Ketenyl Ligands K. R. Birdwhistell, T. L. Tonker, and J. L. Templeton* Contribution from t h e W. R. Kenan, Jr., Laboratory, Department of Chemistry, University of N o r t h Carolina, Chapel Hill, N o r t h Carolina 27514. Received December 7 , 1984
Abstract: Rearrangement of the W(0) d6 $-alkyne c~mplexfac-(dppe)(OC),W(~~-PhC=CH) (dppe = Ph2PCH2CH2PPh2) yields a meridional tricarbonyl tungsten vinylidene complex, mer-(dppe)(OC),W-C=CHPh, which provides an M-C-C framework for further ligand-based transformations. Electrophilic addition a t the @-carbonof the vinylidene ligand generates a cationic tungsten carbyne, [mer-(dppe)(OC),WeCH2Ph] [BF,]. This carbyne cation undergoes carbon monoxide substitution by C1-, Br-, and I- and in the absence of added ligand thermal dissociation of CO allows isolation of the highly electrophilic [(dppe)(OC)2W=CCH2Ph] [BF,] complex. This reagent adds F to form a trans-FW=CCH2Ph unit in (dppe)( O C ) 2 F W e C H 2 P h and also adds neutral ligands to form cationic dicarbonyl derivatives, [ ( ~ ~ P ~ ) ( O C ) ~ L W = L C[BF,], H~P~] with L = PMe,, MeCOMe, and H20. Addition of dithiocarbamate salts (S2CNR2,R = Me or Et) to the electrophilic dicarbonyl cation initially forms a n TJ'-S,CNR~adduct which leads to a coupling of carbyne and carbon monoxide ligands to form an $-ketenyl complex upon chelation of the dithiocarbamate ligand. Addition of H+ or Me' to the electron-rich ketenyl oxygen of (S2CNMe2)(dppe)(OC)W(C,C-s2-OC=CCH2Ph) yields cationic tungsten(I1) alkyne complexes of the type [(S2CNMe2)(dppe)(OC)W(q2-ROC=CCH2Ph)][BF4] ( R = H, Me). The conversion from a d6 alkyne complex to a d4 alkoxyalkyne complex presented here combines electrophilic addition at ligand @-positions,effectively oxidizing the metal, with known carbyne-carbonyl coupling reactions. The (S2CNEt2)(dppe)(OC)W(C,C-~2-OC=CCH2Ph) complex has been structurally characterized: a = 10.910 ( 6 ) A, b = 19.303 (9) A, c = 9.513 (IO) A, a = 91.38 (7)', @ = 103.69 (7)', y = 100.51 (4)O, 2 = 2, daId = 1.55 g cm-,, space group Pi.
T h e facile conversion offac-(dppe)(OC),W(q2-HC2Ph) (dppe = P h 2 P C H 2 C H 2 P P h 2 )to mer-(dppe)(OC),W=C=CHPh (eq 1)' serves as a point of departure for t h e C2-based ligand transformations reported here. Molecular orbital studies indicate substantial charge localization at the j3 carbon of metal acetylides and metal vinylidenes2 and thus rationalize electrophilic addition reactions at t h e j3 position of these metal u-bound unsaturated organic m o i e t i e ~ . ~ . ~ 0 C
PhCeCH
I
c-w-co P'
.-co
I C
THF
.co
c7+c#
