C-13 NMR SHIFTS OF BRIDGING HYDROCARBYLS DERIVED FROM THE ADDITION OF NUCLEOPHILES TO COMPLEXED ORGANIC-LIGANDS IN DINUCLEAR AND POLYNUCLEAR COMPLEXES

C-13 NMR data for a range of iron group dinuclear hydrocarbyl fragments derived from nucleophilic addition to mu-2-eta-2-acetylides and other complexed organic ligands are presented. For mu-2-vinylidenes C(alpha) resonances lie in the range 292.2-297.2 ppm, while C(beta) resonances have chemical shifts of 113.3-145.31 ppm. For mu-2-alkylidene complexes the electron rich C(alpha) lies in the range 28.8-74.95 ppm with C(beta) shifts of 196.0-215.3 ppm. Two carbon-bridged complexes include phenethylidene complexes with C(alpha) resonances in the range 202.0-249.7 ppm and C(beta) resonances between 31.0-44.9 ppm. Zwitterionic parallel acetylene complexes have different ranges depending on the nucleophile. Those derived from phosphites have C(alpha) in the range 78.2-110.0 ppm and C(beta) 191.3-216.4 ppm, while those derived from isocyanides have C(alpha) at 59.7-91.8 ppm and C(beta) at 211.5-241.2 ppm. Allenyl chemical shifts have a wide range but one generally in the order moving upfield delta-C(beta) > delta-C(alpha) > delta-C(gamma) The nucleophilic adducts of the allenyl complex Ru2(CO)6(mu-eta-1,eta-2-H2 C=C=CPh)(mu-PPh2) are dimetallacyclopentane and dimetallacyclopentene derivatives which give three C-13 chemical shifts in the range 33.4-122.7 ppm for C(alpha), 184.2-207.4 ppm for C(beta) and 0.4-7.7 ppm for C(gamma). For two carbon-bridged derivatives, the more carbene-like carbon atom has a downfield chemical shift and couples more strongly to a phosphido bridge phosphorus atom. The C-13 chemical shifts and C-13-P-31 coupling constants for these bridging zwitter-ionic hydrocarbyls provide a powerful spectroscopic probe of structure and bonding.