Pulsed field gradient spin-echo (PGSE) measurements on (a) four arsine complexes of Pd(II), PdCl 2 L 2 (L ) AsMe x Ph 3-x (x ) 3-0)), (b) three different ferrocene phosphine dendrimers, and (c) a selection of other organometallic complexes of differing molecular weight, are demonstrated to provide a practical alternative to classical methods used in organometallic chemistry for estimating molecular size. PGSE measurements make use of translational and not rotational properties of molecules and will be especially valuable where one cannot isolate an unknown complex and/or where a side product is of especial interest, since one can measure several components of the mixture simultaneously.