Cyclic Hydroborate Complexes of Metallocenes II: Reactivity of (&mgr;-H)(2)(BC(5)H(10))(2) and Its Cyclic Derivative, [H(2)BC(5)H(10)](-); Synthesis of (eta(5)-C(5)H(5))(2)MCl(&mgr;-H)(2)BC(5)H(10) (M = Zr, Hf).

Reactions of the organodiborane (&mgr;-H)(2)(BC(5)H(10))(2), 1, with the Lewis bases, N(CH(3))(3), P(CH(3))(3), NH(3), and H(-), produced the cyclic adducts LHBC(5)H(10) (L = N(CH(3))(3), P(CH(3))(3), NH(3), H(-)) through symmetrical cleavage of the hydrogen bridge system. The salt [(NH(3))(2)BC(5)H(10)][H(2)BC(5)H(10)] was produced through unsymmetrical cleavage of the hydrogen bridge system. An improved, synthesis of the anion H(2)BC(5)H(10), 3, is described. It can function as a hydride transfer reducing agent in its reactions with BH(3)THF and 4-tert-butylcyclohexanone. In its reactions with (eta(5)-C(5)H(5))(2)MCl(2) it serves as a chelating agent to produce (eta(5)-C(5)H(5))(2)MCl(&mgr;-H)(2)BC(5)H(10) (M = Zr, 4; Hf, 5). The molecular structures of 1 and 4 are reported here. Crystal data for 1: space group P&onemacr;, a = 6.415(3) Å, b = 9.260(4) Å, c =10.291(5) Å, alpha = 114.53(4) degrees, beta = 104.25(4) degrees, gamma = 90.01(4) degrees, Z = 2. Crystal data for 4: space group P2(1)/c, a = 12.584(2) Å, b = 9.511(1) Å, c = 12.813(2) Å, beta = 100.26(1) degrees, Z = 4.