The synthesis of stable heavier analogues of nitriles as monomeric tetrylene-phosphinidenes (Mes)TerEP(IDipp) (E = Ge, Sn; (Mes)Ter = 2,6-Mes(2)C(6)H(3), IDipp = C([N-(2,6-iPr(2)C(6)H(4))CH](2)) was achieved by taking advantage of NHC (N-heterocyclic carbene, here IDipp) coordination to the low-valent phosphorus center. Multiple bonding character of the E-P bonds was examined experimentally and computationally. Both germanium and tin compounds undergo [2+2] cyclo-addition with diphenylketene, whereas reaction of the tin derivative with tris(pentafluorophenyl)borane provided unique "push-pull" phosphastannene ((Mes)Ter)(Ar)Sn = P(IDipp) (Ar = C6F4[B(F)(C6F5)(2)]). Going further, we demonstrated the potential of tetrylene-phosphinidene complexes in catalytic hydroboration of carbonyl compounds.