The 16 electron cage phosphite complexes of the open titanocene Ti(2,4-C7H11)(2) can be prepared by direct interaction of the open titanocene with the cage phosphite, P(OCH2)(3)CR (C7H11 = dimethylpentadienyl; R = CH3, C2H5). Competitive equilibria studies involving the binding to Ti(2,4-C7H11)(2) by PMe(3) and the R = C2H5 cage phosphite lead to an estimation of Delta H = -16.3 +/- 0.9 kcal/mol and Delta S = -34.6 +/- 2.5 eu for the binding of the cage phosphite. The Delta H value greatly exceeds those of other open phosphites such as P(OMe)(3) and P(OEt)(3), indicating that these latter phosphites are not nearly so small as once believed. A structural study of the R = C2H5 complex has provided further insight into the differences between cage and noncage phosphites. The complex crystallized in the monoclinic space group P2(1)/n, with a = 9.261(3) Angstrom, b = 7.976(3) Angstrom, c = 27.196(6) Angstrom, beta 94.37(2)degrees, and V = 2002.8 Angstrom(3) for Z = 4.