INSERTION OF ALKYNES INTO MOLYBDENUM-PHOSPHINE AND MOLYBDENUM-CARBON BONDS - CRYSTAL-STRUCTURES OF THE ALKYNE-YLIDE COMPLEX H2PR3I-2,4,6)(2)(ETA(2)-CHC(TOL))(C(TOL)CHPMEPH2)] (TOL = C6H4ME-4) AND THE PHOSPHONIUM-ALKYLIDENE COMPLEX MOO(SC6H2PR3I-2,4,6)(3)-(=C(PH)CH=C(PH)CH2PME2PH)]

Treatment of [MoH(SC6H2R3-2,4,6)(3)(PMePh2)] 1a (R = Me or Pr-i) with HC=CR' (R'=Ph or C6H4Me-4) in tetrahydrofuran (thf)-MeOH gave the diam agnetic ylide complexes (SC6H2R3-2,4,6)(2){eta(2)-CHC(R')}-{C(R')CHPMe Ph2] 2, the source of the oxide ligand most probably being adventitiou s water. The crystal structure of one example, 2a (R' = C6H4Me-4, R = Pr-i), confirms their structure [Mo-O 1.69(2), Mo-C-yilde 2.12(3), Mo- C-alkyne 2.07(3) and 2.21(3) Mo-S 2.410(9) and 2.475(9), Ph2MeP-C 1.77 (3)Angstrom]. Treatment of [MoH(SC6H2-Pr-3(i)-2,4,6)(3)(PMe2Ph)(2)] 1b with HC=CPh under similar conditions gave the phosphonium-alkylidene complex [MoO(SC6H2Pr3i-2,4,6)(3){=C(Ph)CH=C(Ph)CH2PMe2Ph}] 3, whose cr ystal structure has been determined [Mo-O 1.691(3), Mo-C 1.990(5), Mo- S 2.424(1), 2.434(1) and 2.432(1), PhMe2P-C 1.808(6) Angstrom]. Spectr oscopic data for these complexes are discussed. Neither PhC=CPh nor Ph C=CMe reacted with 1b.