Chemistry of tungsten theocarbyne and thiocarbene complexes: Syntheses and structures of [HB(pz)3](CO)2(CS)W-Au(PR3) complexes, first examples of a semibridging CS ligand

Reaction of the carbyne complex HB(pz)(,3) (CO)(,2)W((TBOND)CSMe);with PEt(,3) gives HB(pz)(,3) (CO)(PEt(,3))W(C(O)CSMe), which upon;methylation with MeOSO(,2)F at the ketenyl O atom yields the unusual;acetylene complex HB(pz)(,3) (CO)(PEt(,3))W(MeOC(TBOND)CSMe)(\u27+). The;thiocarbene complex HB(pz)(,3) (CO)(,2)W (eta)(\u272)-CH(SMe) (\u27+) is prepared;by protonation of the carbyne carbon in HB(pz)(,3) (CO)(,2)W((TBOND)CSMe) with CF(,3)SO(,3)H. Nucleophiles add to the carbene carbon of HB(pz)(,3) - (CO)(,2)W (eta)(\u272)-CH(SMe) (\u27+), in which the (eta)(\u272)-CH(SMe) group is coordina- ted via both the C and S atoms. In the products of these reactions,;the C and S atoms remain coordinated. Thus, reactions of the car- bene compound with phosphorus donors, L (PPh(,3), PEt(,3), PPh(,2)H,;P(OMe)(,3)), give the carbene adducts HB(pz)(,3) (CO)(,2)W (eta)(\u272)-CH- (SMe)(L) (\u27+). The phosphonium proton in HB(pz)(,3) (CO)(,2)W ((eta)(\u272)-CH(SMe)(PPh(,2)H) (\u27+) is removed by NEt(,3) to give HB(pz)(,3) (CO)(,2)W- (eta)(\u272)-CH(SMe)(PPh(,2)) , whose structure was established by an X-ray;diffraction study. Mercaptides (SR(\u27-)) and the malonate anion react with the carbene compound to give air-stable adducts. With 4-dimethylaminopyridine, the carbene compound forms the air-stable;carbene adduct. With secondary amines (HNMe(,2), HNEt(,2)), the car- bene compound reacts quite differently and forms air-stable amino- carbyne complexes, HB(pz)(,3) (CO)(,2)W((TBOND)CNR(,2)). Reactions of the;carbene compound with primary amines (NH(,2)R; R = Me, Et, CH(,2)- CH(,2)OH, i-Pr, t-Bu, and tolyl) and NH(,3) also produce aminocarbyne compounds HB(pz)(,3) (CO)(,2)W((TBOND)CNHR), but they are in equilibrium;with their hydride-isocyanide tautomers HB(pz)(,3) (CO)(,2)(H)W(CNR) (R = Me, Et, CH(,2)CH(,2)OH, i-Pr, and t-Bu), the first examples of such a tautomerism;Reactions of HB(pz)(,3) (CO)(,2)W(CS)(\u27-) with ClAuPR(,3) (R = Ph or Me) yield the complexes HB(pz)(,3) (CO)(,2)(CS)W-Au(PR(,3)), which have a semibridging CO and a semibridging CS, the first examples of CS in this bonding mode. The much shorter Au-CS (2.162(7)(ANGSTROM)) than Au-CO(2.720(8)(ANGSTROM)) bond distance indicates a stronger semibridging interaction for CS than CO with the Au. The Au-CO distance is 0.174 (ANGSTROM) shorter in the PMe(,3) than the PPH(,3) derivative. This result, together with the short Au-CS bond distance, suggests the primary interaction between the semibridging CO and CS groups with Au is a donation of electron density from the Au to the CO and CS (pi)* orbitals