Dimerization, square-planar substitution

Amine adducts of Ni11 diphenyldithiophosphinate with substituted ethylenediamins have been prepared and characterized. A dimeric pentacoordinate structure was proposed for [Ni2(S2PPh2)4(tmeda)].91s One crystal structure of a square planar Ni11 complex (351) with an aminophosphonate ligand has been reported.916... 

Sulfur-based Cr coordination compounds include a series of dithiocarbamates of the type [Cr(S2CNR2)2] (R = Me, Et or R2 = C4H8), which are antiferromagnetically coupled. The diethyl-substituted compound is an S-bridged dimer, making chromium five-coordinate. Square-planar Cr coordinated by sulfur occurs in the violet [NEt4]2[Cr(S2C2H4)2]. Finally, Thiourea and its derivatives form adducts with Cr halides, which are similar to the adducts with O-donors mentioned above. 

Benzene formed from photolysis of the 1 1 complex is a cage-escape product from 3(Jul-CHO+ /Ph ). Benzene formed from the photolysis of the 2 1 complex is an in-cage product from 3((Jul-CHO)2 /Ph ). The formation of 2 1 complexes of amino-substituted ketones and iodonium salts has been suggested to account for the high photosensitivity of polymeric Mannich bases with iodonium salts [102]. Formation of 2 1 donor iodonium cation complexes has been rationalized by consideration of the crystal structures of diphenyliodonium halides, which crystallize as dimers with square planar iodine atoms with two bridging halide counterions [102,108]. 

The strong preference for cis substitution of pentacarbonyl halo rhenium(I) synthons has been exploited to prepare dimers and hetero dimers of 5,10-pyridyl derivatized porphyrins see compoimds 6-8 and Scheme 2 [13,17]. Related chemistry has been demonstrated with platinum(II) and palla-dium(ll) compounds where square planar coordination is used to an advantage [18]. In contrast to the square planar compoimds, the octahedral... 

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