“…Expanded-ring NHCs, derived from six- and seven-membered cyclic amidinium salts, have been shown to increase the stability of other reactive metal species. − Recently, Whittlesey et al reported that (6Mes)copper(I) hydride (6Mes = 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) proved too unstable to isolate but could be trapped efficiently with alkynes or ketones . We now report the synthesis of [(6Dipp)CuH] 2 ( 3a ) and [(7Dipp)CuH] 2 ( 3b ) (6Dipp = 1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; 7Dipp =1,3-bis(2,6-diisopropylphenyl)-4,5,6,7-tetrahydro-1,3-diazepin-2-ylidene).…”