A series of primary phosphine homoleptic complexes [ML(4)](n+)X(n) (1, M = Ni, n = 0; 2, M = Pd, n = 2, X = BF4; 3, M = Cu, n = 1, X = PF6; 4, M = Ag, n = 1, X = BF4; L = PH(2)Mes, Mes = 2,4,6-Me(3)C(6)H(2)] was prepared from mesitylphosphine and Ni(COD)(2), [Pd(NCMe)(4)]BF4](2), [Cu(NCMe)(4)]PF6, and AgBF4, respectively. Reactions of 1-4 with MeC(CH(2)PPh(2))(3) (triphos) or [P(CH(2)CH(2)PPh(2))(3)] (tetraphos) afforded the derivatives [M(’L]L](n+)X(n) (L’ = triphos; 6, M = Ni, n = 0; 7, M = Cu, n = 1, X = PF6; 8, M = Ag, n = 1, X = BF4; L’ = tetraphos; 9, M = Pd, n = 2, X = BF4). Addition of NOBF4 to 1 yielded the nitrosyl compound [NiL(3)(NO)]BF4, 5. The solution structure and dynamics of 1-9 were studied by P-31 NMR spectroscopy (including the first reported analyses of a 12-spin system for 1-2). Complexes 1, 3, 6, and 7 . solvent were characterized crystallographically. The structural and spectroscopic studies suggest that the coordination properties of L are dominated by its-relatively small cone angle and that the basicity of L is comparable to that of more commonly used tertiary phosphines.