Reaction of the molecular cleft-containing triphosphazane C6H4N2[P(S)(NEt(2))(2)]2PCl (2) with LiBH4 yields the borane-coordinated triphosphazane hydride C6H4N2[P(S)(NEt(2))(2)]P-2(BH3)H (3). The complex is strongly associated; free hydride C6H4N2 [P(S)(NEt(2))(2)]2PH (4) can be obtained by treatment of 3 with tertiary amines. Complex 3 reacts with (norbomadiene)Mo(CO)(4) to form triphosphazane complexes {C6H4N2[P(S)(NEt(2))(2)]2PH}Mo(CO)(3) (5), {C6H4N2[P(S)(NEt(2))(2)]P-2(BH2)}Mo(CO)(4) (6), and {C6H4N2[P(S)(NEt(2))(2)]P-2(BH2)}Mo(CO)(5) (7). Under more vigorous conditions 2 and Mo(CO)(6) yield 5 and {C6H4N2[P(S)(NEt(2))(2)]2PH}Mo(CO)(4) (8). Compounds 3-8 were characterized by spectral data. X-ray analyses were performed on 6 and 7 : 6, monoclinic, P2(1)/c, a = 10.6350(10) Angstrom, b = 18.979(3) Angstrom, c = 18.204(3) Angstrom, beta = 91.750(10)degrees, V = 3672.6(9) Angstrom(3), Z = 4, R = 0.044, R(w) = 0.038; 7, triclinic, , a = 11.080(2) Angstrom, b = 11.253(3) Angstrom, c = 17.739(4) Angstrom, alpha = 94.86(2)degrees, beta = 104.57(2)degrees, gamma = 101.85(2)degrees, V = 2073.2(8) Angstrom(3), Z = 2, R = 0.040, R(w) = 0.047. Structures are compared, and the influence of the molecular cleft on reaction outcome and the involvement of the peripheral sulfur atoms in coordination are discussed.