Ladder structure of (( sup t BuCH sub 2 ) sub 2 TaN) sub 5 ter dot NH sub 3 ter dot 2C sub 7 H sub 8 and its relationship to cubic TaN

Ammonolysis of ({sup t}BuCH{sub 2}){sub 3}Ta{double bond}CH{sup t}Bu (1) at 20{degree}C produced an intermediate pentamer, (({sup t}BuCH{sub 2}){sub 2}TaN){sub 5} (2, {approximately} 40%); further reaction generated an orange precipitate. Thermolysis of the latter at 400{degree}C and then 820{degree}C produced cubic TaN (Fm3m, a = 4.300 (2) {angstrom}) at temperatures and pressures substantially below those of conventional nitriding procedures. Ammonolysis of ({sup t}BuCH{sub 2}){sub 2}Ta(NMe{sub 2}){sub 3} (3) provided an alternative (19%), route to 2. {sup 1}H, {sup 13}C, and {sup 15}N NMR spectra of 2 indicated C{sub 2v} symmetry, and x-ray crystallographic characterization of (({sup t}BuCH{sub 2}){sub 2} TaN){sub 5}{center dot}NH{sub 3}{center dot}2C{sub 7}H{sub 8} (2{center dot}NH{sub 3}{center dot}2C{sub 7}H{sub 8}) revealed a roughly planar ladder structure of alternating ({sup t}BuCH{sub 2}){sub 2}TaN units. The interior nitrogens adopt a T-shaped coordination geometry and an NH{sub 3} is weakly bound to an exterior Ta atom.