R-Group reversal of isomer stability for RuH(X)L2(CCHR)
s. Ru(X)L2(CCH2R): access to four-coordinate ruthenium carbenes and carbynes†
Abstract
NaOPh converts equimolar RuHClL2(C
CHR) (L = PPr3i and PCy3) first to
RuH(OPh)L2(
C
CHR), but then, only for R = H, these isomerize to the more stable carbynes Ru(OPh)L2(C–CH3); the
rate of isomerization is slowed considerably by THF. RuH(OPh)L2(
C
CHR) can also be synthesized by reaction of RuCl2L2[
CH(CH2R)]
with 2 NaOPh; again, only when R = H does the hydrido vinylidene isomerize to the carbyne. While phenoxide
converts RuCl2L2(
CHPh) to Ru(OPh)L2(CPh),
ia the observable intermediates RuCl2−n(OPh)nL2(
CHPh), alkoxides OBut and OAdamantyl
cause phosphine displacement to give the four-coordinate carbenes Ru(OR)2L(
CHPh). DFT (B3PW91) calculations show these d6 species have a traditional cis-divacant octahedral structure with trans OR groups.