Mechanism of alkyne conversion to carbyne by 14- or 16-electron Os(H)2ClL2X (L=PiPr3; X=OTf or B(C6H3(CF3)2)4)

Substituent Effect on the Reactions of OsCl2(PPh3)3 with o-Ethynylphenyl Carbonyl Compounds

“…The Os−C(alkyne) bond distances (2.117(12)−2.118(14) Å) are slightly shorter than those reported for osmium complexes with a two-electrondonating terminal alkyne ligand, for example, CpOsCl(η 2 -HCCC(OH)Ph 2 )(PiPr 3 ) (2.142(7), 2.163(6) Å), 10 [Os-(en) 2 (CH 2 CH 2 )(HCCH)](OTf) 2 (2.155(4) Å), 11 [Os-{CHC(PPh 3 )CH(OH)CCH}(NCS) 2 (PPh 3 ) 2 ] (2.154 (10) and 2.177(11) Å), 9l and [Os{CHC(PPh 3 )C(O)CCH}-(NCS) 2 (PPh 3 ) 2 ] (2.156(9) and 2.179(10) Å); 8d but they are slightly longer than those reported for osmium-alkyne complexes with a four-electron-donating terminal alkyne ligand, for example, [CpOs(η 2 -HCCC(OH)Ph 2 )(PiPr 3 )]-PF 6 (1.981 (8) and 1.992(9) Å), 10 [OsH(CCH 2 )(η 2 -HCCH)(PiPr 3 ) 2 ]BF 4 (2.022 (10) and 2.035(10) Å), 12 and [Os(H) 2 (OTf)(PiPr 3 ) 2 (η 2 -PhCCH)]OTf (1.994(6) and 2.007(5) Å). 13 The Os−O (2.057(8) Å for 3a, 2.045(3) Å for 3b) and CO (1.264( 16) Å for 3a, 1.270(7) Å for 3b) bond distances are comparable to those of reported osmiumacetone complexes. 14 The solid-state structures are supported by their solution NMR data.…”

“…For example, the 31 P{ 1 H} NMR spectrum of 3a showed a singlet peak at −14.2 ppm. The 13 15 ZnCl 2 , 16 Ag + , 17 and CuCl 18 but have not been isolated or detected. Furthermore, reactions of OsCl 2 (PPh 3 ) 3 with terminal alkynes usually give products derived from isomerization of the alkynes to give vinylidene complexes or nucleophilic attack of PPh 3 on the alkynes.…”

“…P{ 1 H} NMR (162 MHz, CD 2 Cl 2 ) δ −13.7 (s). 13 Synthesis of 4c. To a solution of OsCl 2 (PPh 3 ) 3 (750 mg, 0.71 mmol) in toluene (15 mL) was added N,N-diethyl-2-ethynylbenzamide (286 mg, 1.42 mmol).…”

“…Aldrich or Acros Chemical Co. and used as received unless otherwise specified. 1 H,13 C { 1 H}, and 31 P { 1 H} NMR spectra were recorded on a Bruker DPX 400 spectrometer at 400, 100, and 162 MHz, respectively. All signals were reported in δ with references to the residual solvent resonances of the deuterated solvents for proton and carbon chemical shifts, and to external 85% H 3 PO 4 for phosphorus chemical shifts.…”

“…H} NMR (162 MHz, CD 2 Cl 2 ): δ −14.2 (s) 13. C{ 1 H} NMR (100 MHz, CD 2 Cl 2 ): δ 175.8 (CHO), 133.8 (t, J = 5.2 Hz, o-or m-PPh 3 ), 130.7, 130.4, 130.3, 130.2, 130.1 (t, J = 23.2 Hz, ipso-PPh 3 ), 128.6 (p-PPh 3 ), 127.9, 126.7 (t, J = 4.9 Hz, o-or m-PPh 3 ), 125.7, 117.2 (CCH), 75.3 (CCH).…”