Syntheses for the diphosphadiboretane ((Pr2NBPH)-Pr-i)(2), the triphosphatriborinane ((Pr2NBPH)-Pr-i)(3), and the aminodiphosphanylborane (Pr2NB)-Pr-i(PH2)(2) are reported. Reaction of these ligands with Cr(CO)(5) . NMe(3) results in the formation of the complexes ((Pr2NBPH)-Pr-i)(2) . Cr(CO)(5) and (Pr2NB)-Pr-i(PH2)(2) . 2Cr(CO)(5). Molecular structure determinations for the diphosphadiboretane, the triphosphatriborinane, and the two coordination complexes have been completed by use of single crystal X-ray diffraction techniques : ((Pr2NBPH)-Pr-i)(2) (C6H15BNP) crystallizes in the monoclinic space group P2(1)/n with a = 7.7200(10) Angstrom, b = 10.514(2) Angstrom, c = 11.231(2) Angstrom, beta = 101.100(10)degrees, and Z = 4; ((Pr2NBPH)-Pr-i)(3) (C18H45B3N3P3) crystallizes in the monoclinic space group P2(1)/n with a = 20.217(16) Angstrom, b = 13.764(11) Angstrom, c = 20.494(16) Angstrom, beta = 104.40(5)degrees, and Z = 8; ((Pr2NBPH)-Pr-i)(2) . Cr(CO)(5) (C17H30B2N2O5P2Cr) crystallizes in the monoclinic space group P2(1)/n with a 11.284(3) Angstrom, b = 14.583(6) Angstrom, c = 16.515(4) Angstrom, beta = 105.97(2)degrees, and Z = 4; (Pr2NB)-Pr-i(PH2)(2) .[Cr(CO)(5)](2) (C16H18BNO10P2Cr2) crystallizes in the orthorhombic space group Fdd2 with a = 23.214(8) Angstrom, b = 11.914(5) Angstrom, c = 18.359(5) Angstrom, and Z = 8.