The chemical reaction dynamics of silylidyne (SiH; X-2 Pi) with acetylene (C2H2; X-1 Sigma(+)(g)) were studied exploiting the crossed molecular beam approach, and compared with previous studies on D1-silylidyne with acetylene. The reaction is initiated by a barrierless addition of silylidyne to one or both carbons of acetylene leading to 1-sila-1-propene-1,3-diylidene and/or the cyclic 1-silacyclopropenyl with the former isomerizing to the latter. 1-Silacyclopropenyl eventually loses atomic hydrogen yielding silacyclopropenylidene (c-SiC2H2) in an overall exoergic reaction (experiment: -14.7 +/- 8.5 kJ mol (1); theory: -13 +/- 3 kJ mol (1)). The enthalpy of formation for silacyclopropenylidene is determined to be 421.4 +/- 9.3 kJ mol (1). (C) 2016 Elsevier B.V. All rights reserved.