SYNTHESIS AND REACTIVITY OF NEW DIBORYLPHOSPHANES

The reactions of (i-Bu2N)2BP(H)Li.DME and (i-Pr2N)[(Me3Si)2N]BP(H)Li-D ME with (tmp)BCl2 (tmp = 2,2,6,6-tetramethylpiperidino) and (Me3Si)2NB Cl2 result in the formation of diborylphosphanes (tmp)B(Cl)P(H)B(Ni-Bu 2)2 (12), (tmp)B(Cl)P(H)B(N-i-Pr2)[N(SiMe3)2] (14), (Me3Si)2NB(Cl)P(H) B(N-i-Bu2)2 (13), and (Me3-Si)2NB(Cl)P(H)B(N-i-Pr2)[N(SiMe3)2] (15). T he diverse dehydrohalogenation chemistry of these species was studied. Combination of 12 and 13 with t-BuLi leads to formation of 1,3-dibory lated diphosphadiboretanes, [(i-Bu2N)2BPB(tmp)]2 (16) and {(i-Bu2N)2BP B[N(SiMe3)2]}2 (17), while reaction of 14 with t-BuLi leads unexpected ly to a monoborylated diphosphadiboretane [(Me3Si)2N](i-Pr2N)BPB(tmp)P (H)B(tmp). Another reaction pathway is found in the reactions of 15 an d [(Me3Si)2N]B(Cl)P(H)B(N-i-Pr2)2 With t-BuLi that produce acyclic dip hosphatriboretanes (Me3Si)2NB{P(H)B(N-i-Pr2)[N(SiMe3)2]}2 (19) and (Me 3Si)2NB[P(H)B(N-i-Pr2)]2 (20). The molecular structures of 19, 20, and [(i-Pr2N)(Cl)BPB(N-i-Pr2)]2(21) were determined by single-crystal X-r ay diffraction techniques with MoKalpha radiation (lambda = 0.71073 an gstrom): 19, C30H84B3N5P2Si6, crystallized in the triclinic space grou p P1BAR with a = 13.933(3) angstrom, b = 18.630(2) A, c = 20.367(3) an gstrom, a = 87.06(1)-degrees, beta = 80.79(1)-degrees, gamma = 88.96(2 )-degrees, and Z = 4; 20, C30H76B3N5P2Si2, crystallized in the monocli nic space group P2(1)/c with a = 13.169(4) A, b - 9.570(l) A, c = 35.2 41(7) angstrom, beta = 100.13(2)-degrees, and Z = 4; 21 crystallized i n the monoclinic space group P2(1)/n with a = 10.745(2) angstrom, b = 8.347(1) angstrom, c = 20.364(4) angstrom, beta = 99.90(2)-degrees, an d Z = 4. The structural features of these compounds are discussed in r elation to structures of diborylphosphanes reported previously.