Syntheses of 'Phosphine-Free' Molybdenum Oxo Alkylidene Complexes through Addition of Water to Alkylidyne Complexes

Addition of 1 equiv of water to Mo­(CArp)­(ORF9)3 (Arp = p-methoxyphenyl; ORF9 = OC­(CF3)3) in the presence of 5% NEt3 (vs Mo) in THF led to the formation of Mo­(O)­(CHArp)­(ORF9)2(THF)2 in good yield. Mo­(O)­(CHArp)­(ORF9)2(THF)2 reacts with 2 equiv of LiOHMT (OHMT = O-2,6-mesityl2C6H3) at room temperature to yield Mo­(O)­(CHArp)­(OHMT)2 and with 2 equiv of NaOTPP (OTPP = 2,3,5,6-tetraphenylphenoxide) to yield Mo­(O)­(CHArp)­(OTPP)2. In the presence of TMEDA (2.5 equiv), Mo­(CR)­(ORF9)3 (R = Arp, mesityl, or t-Bu) reacts with 1 equiv of water to yield Mo­(O)­(CHR)­(ORF9)2(TMEDA) complexes, from which (when R = t-Bu) TMEDA is readily displaced by 2,2′-bipyridyl to give Mo­(O)­(CH-t-Bu)­(ORF9)2(bipy). Mo­(O)­(CH-t-Bu)­(ORF9)2(bipy) was converted into Mo­(O)­(CH-t-Bu)­Cl2(bipy) readily, from which Mo­(O)­(CH-t-Bu)­Cl­(OHMT)­(3-Brpy) (3-Brpy = 3-bromopyridine) and Mo­(O)­(CH-t-Bu)­Cl­(OHIPT)­(3-Brpy) (OHIPT = O-2,6-(2,4,6-i-Pr3C6H2)2C6H3) were prepared. X-ray studies were carried out on Mo­(O)­(CHArp)­(ORF9)2(THF)2, Mo­(O)­(CH-t-Bu)­(ORF9)2(TMEDA), Mo­(O)­(CHArp)­(OTPP)2, Mo­(O)­(CH-t-Bu)­Cl­(OHMT)­(3-Brpy), and Mo­(O)­(CH-t-Bu)­Cl­(OHIPT)­(3-Brpy).