R-Group reversal of isomer stability for RuH(X)L-2(CCHR) vs. Ru(X)L-2(CCH2R): access to four-coordinate ruthenium carbenes and carbynes

NaOPh converts equimolar RuHClL2(=C=CHR) (L=PPr3i and PCy3) first to RuH(OP h)L-2(=C=CHR), but then, only for R=H, these isomerize to the more stable c arbynes Ru(OPh)L-2(C-CH3); the rate of isomerization is slowed considerably by THF. RuH(OPh)L-2(=C=CHR) can also be synthesized by reaction of RuCl2L2 [=CH(CH2R)] with 2 NaOPh; again, only when R=H does the hydride vinylidene isomerize to the carbyne. While phenoxide converts RuCl2L2(=CHPh) to Ru(OPh )L-2(CPh), via the observable intermediates RuCl2-n(OPh)(n)L-2(=CHPh), alko xides OBut and OAdamantyl cause phosphine displacement to give the fear-coo rdinate carbenes Ru(OR)(2)L(=CHPh), DFT (B3PW91) calculations show these d( 6) species have a traditional cis-divacant octahedral structure with trans OR groups.