Nitrosylation of either [M(N,N)(CO)(4)] or [Mo(H(2)CPz’(2))(CO)(2) (No)I], with NO+BF4- in MeOH, afforded readily [M(N,N)(Co)(2)(NO)(MeOH)]BF4 (M = Mo, (N,N) = H(2)CPz(2) (1), H(2)CPz’(2) (2); M = W, (N,N) = H(2)CPz(2) (3), H(2)CPz’(2) (4); PZ = pyrazol-1-yl; Pz’ = 3,5-dimethylpyrazol-1-yl). 2 reacted with py to form [Mo(H(2)CPz’(2))-(CO)(2)(NO)(py)]BF4 (5). Chloride, bromide, iodide, azide, nitrate, thiocyanide, acetate, and cyanide reacted with 2 in MeOH to form [Mo(H(2)CPz’(2))(CO)(2)(NO)L] (L(-) = Cl- (6), Br- (7), I- (8), N-3(-) (9), NO3- (10), SCN- (11), MeCO(2)(-) (12), CN- (14)). Alternatively, 7 could also be prepared from reaction of [Mo(H(2)CPz’(2))(CO)(2)Br-2] with NaNO2, n-Bu(4)NNO(2), or AgNO2 in CH2Cl2 but with a low yield. In the presence of Cl-, Br-, and I- in MeOH, 5 was transformed back into 6, 7, and 8, respectively. 2 reacted with a 0.5 equiv of KCN or with 1 equiv of 14 in MeOH to form [{Mo(H(2)CPz’(2))(CO)(2)(CO)(2)(NO)}(2)(mu-CN)] (13). Both spectral data for 1-14 and X-ray crystallographic structures of 9, 10, and 12 support that 1-4 and 6-14 are similar in geometry around the Mo center with the monodentate ligand (MeOH or L(-)) trans to NO while cis to H(2)CPz’(2) and that 5 may have two conformations with py cis to H(2)CPz’(2) but either trans or cis to NO. 2 reacted with excess PR(3) in CH(2)CL(2) to form [Mo(H(2)CPz’(2))(CO)(NO)(PR(3))(2)]BF4 (R = Ph (15), OMe (16), Me (17)). The spectral data for 15-17 and the X-ray crystallographic structure of 17 showed that two phosphine ligands in 15-17 are trans to each other while cis to H(2)CPz’(2). 2 reacted with excess bidentate ligand (L,L) in MeOH to form [Mo(L,L)(2)(CO)(NO)]BF4 ((L,L) = bpy (18), phen (19), Me(2)bpy (20), dppm(21)). However, when the solvent was changed to CH2Cl2, several products including 22 were formed. Both H-1 and P-31 NMR spectral data showed that 18-21 an isostructural with two (L,L) ligands cis to each other. 2 reacted with dithiocarbamate anion (S,S)(-) in MeCN to form orange-red and yellow products. The orange-red [Mo(S,S)(CO)(2)(NO)](2) ((S,S)(-) = Et(2)NCS(2)(-) (22), Me(2)NCS(2)(-) (23), C4H8NCS2- (24)) as a major product was isolated. As supported by the X-ray crystallographic structure of 22, 22-24 are dimeric with the six-electron (S,S)(-) Ligand bonded in a mu,eta(2)-fashion. The distance of 3.474(3) Angstrom between two S atoms and that of 3.773(1) Angstrom between two Mo atoms is compatible with no S-S or Mo-Mo bond. The nitrosyl groups are trans to the bridging sulfur atoms while cis to carbonyls. Structural data : 9, a = 11.9868(19) Angstrom, b = 10.7998(10) Angstrom, c = 14.723(3) Angstrom, beta = 113.995(13)degrees, P2(1)/c; 10, a = 12.993(4) Angstrom, b = 9.497(3) Angstrom, c = 15.090(5) Angstrom, beta = 105.49(3)degrees, P2(1)/c; 12, a = 8.854(7) Angstrom, b = 11. 904(7) Angstrom, c = 18.238(7) Angstrom, alpha = 88.06(3)degrees, beta = 97.65(1)degrees, gamma = 80.83(5)degrees, P $($) over bar$$ 1; 17, a = 16.637(3) Angstrom, b = 12.379(3) Angstrom, c = 14.6574(20) Angstrom, beta = 103.284(14)degrees, P2(1)/c; 22, a = 15.597(4) Angstrom, b = 12.026(3) Angstrom, c = 13.511(3) Angstrom, beta = 104.271(19)degrees, C2/c.펀$