The syntheses of five cationic iridium(I) complexes, containing the bidentate ligands bis-(1-pyrazolyl)methane (BPM) and bis(3,5-dimethyl-1-pyrazolyl)methane (dmBPM), {[Ir(BPM)-4 ) -} (3), and {[Ir(dmBPM)(CO) 2 ] + (BPh 4 ) -} (5), are reported. The complexes were characterized by NMR spectroscopy, and the solid-state structure of {[Ir-(BPM)(CO) 2 ] + (BPh 4 ) -} (3) was determined by single-crystal X-ray crystallographic analysis. The complexes {[Ir(BPM)(CO) 2 ] + (BPh 4 ) -} (3) and {[Ir(dmBPM)(CO) 2 ] + (BPh 4 ) -} (5) are effective catalysts for the alcoholysis of a range of alcohols and hydrosilanes, including secondary and tertiary hydrosilanes, under mild conditions.

A suite of 1H-detected, gradient-enhanced experiments is presented for the measurement of small 1H−15N and 13C−15N coupling constants in small organic compounds, where no protons are directly bound to the nitrogens. The experiments are based on modified HMQC pulse sequences and a novel gradient supported half-filter element. The experiments were applied to obtain a complete set of coupling constants in tris(1-pyrazolyl)methane (1), where 6% of the aromatic ring systems were doubly enriched with 15N. The absolute sign of the 1H−1H, 1H−15N, 13C−15N, and 15N−15N coupling constants was determined by relating them to the sign of a one-bond 1H−13C coupling constant. The experiments also yield multiple bond 13C/12C isotope effects on the 15N chemical shifts. The 1H−15N and 13C−15N coupling constants in 1 are non-uniform, with some of the short-range coupling constants smaller than the longer range coupling constants. In contrast, all one-bond 13C/12C isotope effects on the 15N chemical shifts were observed to be significantly larger than the isotope effects mediated via two or more bonds. The one-bond isotope effect thus provides a valuable tool for assigning 15N resonances in cases where coupling constant data yield ambiguous results.

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